Hormone Harmony

P.D. GUPTA

HORMONE HARMONY

P. D. Gupta

Publications & Information Directorate

Dr. K.S. Krishnan Marg

New Delhi 110 012

India

Hormone Harmony

P. D. Gupta

©Publications & Information Directorate First Edition : May 1993 Second Edition : January 1996 ISBN : 81-7236-065-7

Vistas in Biotechnology Series

Book No 3

Series Editor

Volume Editors

Cover Design

Illustrations

Production

Dr. Bal Phondke

Sudha Kannan & Sukanya Datta

Pradip Banerjee

Pradip Banerjee, Neeru Sharma, J.M.L. Luthra,

Sushila Vohra, Neeru Vijan and Malkhan Singh

Radhe Sham, Sudhir Chandra Mamgain, Tikha Ram

Gulab Singh, Rajbir Singh and S. Ramalingam

Designed, Printed and Published by

Publications & Information Directorate (CSIR)

under the project 'Dissemination of Biotechnology Information'

sponsored by Department of Biotechnology (Govt, of India)

FOREWORD

Hormones are organic substances produced in multicellular organ-isms - both plants and animals, that profoundly effect the cells in some distant tissues. Hormones regulate the basic cell biology in different ways - cell division, development and differentiation. A common denominator for these changes is the 'activation' of specific genes in the cell nucleus and synthesis of new proteins in the endoplasmic recticulum. Perception of the hormonal signal at the cell surface, leading to transcription, translation and synthesis of new proteins remains an exciting area of biology which is not well understood. Hormones are perceived by specific receptor proteins at the cell surface or within the cell. Some hormones pass through the cell membrane to combine with the intracellular recep-tor proteins to form a complex which enters, the nucleus. Other hormones do not enter the cell but the hormone-protein complex generates the 'second messenger'.

In both plants and animals a right balance between different hormones is essential for harmonious growth and development. Plant hormones include auxins, cytokinins and gibberellins. Excess production of these hormones leads to abnormal growth as is evident from studies on crown gall and hairy root diseases. The pathogenic bacterium, the causal organism for these diseases transfers its own genes governing auxin and cytokinin production into the host cell. The infected cell after transformation produces abnormal amount of these hormones, and keeps dividing and redividing leading to tumourous or hairy root growth.

In humans and other mammals hormones are mainly produced in specialised tissues, the endocrine glands. Anterior pituitary considered as the master gland secretes many hormones that affect other endocrine glands. Besides, female (oestrogen and progesterone) and male (testosterone) sex hormones, thyroid, parathyroid, adrenals and other glands produce hormones essen-tial for normal growth and development. Both higher and lower levels of these hormones effect human health and reproduction. At the same time, hormonal manipulation can be effectively used for contraception to avoid unwanted births.

Hormonal manipulation to increase the productivity of plants and animals is an important component of biotechnology. Growth factors can be used to enhance growth, milk or meat production or retard the growth of cancerous cells. Hormonal manipulation can enhance or retard senescence of leaves and control ripening of harvested fruits. There are innumerable biotechnological applica-tions of hormones and they are increasing rapidly.

The Publications & Information Directorate (PID) is bringing out a series of popular monographs on biotechnology as a part of the Project "Dissemination of Biotechnology Information" sponsored by the Department of Biotechnology, Government of India. The monographs would benefit school, college and university students and teachers as well as members of general public and create an awareness among them towards the newer developments in this field. PID, which is one of the premier institutions of its type within the country, engaged in dissemination of scientific information and science popularisation for more than twentyfive years, as also the authors of the various monographs who are all highly acclaimed for their scientific contributions have joined hands in this venture. I am confident that the readers would find the monographs infor-mative and enlightening and this will contribute to the development of the biotechnology within the country.

(C.R. BHATIA) Secretary

Department of Biotechnology Government of India

Sexual differentiation is the process that makes a man, a man and a woman, a woman. Of course, it is genetically controlled but is regulated by hormones. Machihembra (first, woman then man) or guevedoce syndrome and many such interest-ing matters and day-to-day vital processes are regulated by hormones. My purpose of writing this book is to share with the general readers my own excitement about these chemical messengers and how they influence animals, plants and even bacterial lives.

The use and misuse of hormones in contraception, sports, lie detection, growth, cancer diagnosis and treatment, metabolic diseases like diabetes, etc. induced biotechnologists to pro-duce hormones, which are required in large quantities and cannot be produced in laboratories, by "genetic engineering". A brief account of such methodologies is given in the last chapter.

Every attempt has been made to keep the language and facts in such a form that this book can also be read by those unfamiliar with the subject. I hope this book would be useful and interesting to those who are not exposed to hormones as a technical subject but are, of course, otherwise exposed in daily life to millimicro-quantities of these friendly messengers.

My inspiration and encouragement for writing popular science articles come from Prof. D. Balasubramanian's articles pub-lished in The Hindu' and elsewhere.

However, the idea of writing a book on hormones for general readers was germinating in my mind for a long time. For a variety of reasons, I was unable to undertake this work until I met Dr Bal Phondke who encouraged me to do so.

This book was thoroughly read by Shri G. Kranti Kumar, whose suggestions and comments have made it more read-able for those who are unfamiliar with the subject.

I have not had the opportunity of meeting those who looked after the various aspects of production of this book, starting from simplification of language to composing, art work and proof- reading, etc. and they all deserve my heartfelt thanks.

ACKNOWLEDGEMENT

DEDICATED TO my guru, the late Prof. Vishwa Nath, who gave me

my first lessons on Hormones.

The beginning ... 1

The factory ... 9

At work ... 20

Keeping balance ... 26

Male versus female ... 34

Productive performers ... 41

In harness ... 48

Off balance ... 65

Corporate venture ... 74

Glossary ... 80

ens saria in corpore sano', 'a sound mind in a sound body' is what man has always hoped for. Indeed the real measure of health is not in the absence of all

disease, but in the ability to function effectively within a given environment. And since environment keeps changing, good health is a process of continuous adaptation to the myriad microbes, irritants, pressures and problems which daily chal-lenge man.

When disease slaughtered millions the world over, ancient men readily looked for witches and wizards to blame. Where no witches and wizards were found, they began accepting the teachings of the ancient Greek doctor-philosophers, who believed that four elements — fire, air, water and earth —

The beginning

made up the universe and had their counterparts in the human body. These counterparts were the four 'humours' — blood, bile, phlegm and black bile. The balance of the four humours affected the psychological state of the individual. Thus people could be phlegmatic (or given to sloth), sanguine (or cheerful and optimistic), choleric (easily angered) or mel-ancholy. Illness, caused by an imbalance in the humours was treated by balancing the properties of the four elements. These were of course, ridiculous beliefs that were later re-placed by more rational ideas rooted in reality.

Modern physiology has evolved and much is now known about how the body functions. Claude Bernard, the Father of modern physiology advanced the 'Science of the Laws of Life'. In the second decade of the 20th century, Harvard's

2 HORMONE HARMONY

Sanguine

Phlegmatic

Choleric

Melancholy

THE BEGINNING

Claude Bernard — the Father of modern physiology

renowned Professor of Physiology, Walter B. Cannon, wrote a book called The Wisdom of the Body', where he described the constant adjustments the healthy body makes for survival.

The body's wisdom and its limits lies in the correct func-tioning of the cells of the body. All living things are made up of cells. Some are made up of just one cell. Others are composed of many cells. In multi-celled organisms, cells become specialized to perform distinct functions. A group of cells with similar structure and performing similar functions constitutes a tissue. Several types of tissues collectively form an organ, which carries out one (or more) specific activity. All organs are orchestrated for the smooth and efficient function* ing of the body. One such organ which exercises its control over the activities of the body, through its secretions, is the gland.

By definition, a gland is any organ that secretes some substance. The liver, for example, manufactures bile, and is therefore referred to as a gland. Basically, however, the body contains two types of glands. One type is the exocrine gland whose secretions are transported by way of ducts to other parts of the body. The second type is the endocrine gland, whose secretions are discharged directly into the blood stream without the benefit of ducts.

3

HORMONE HARMONY

These second type of g lands s e c r e t e sub-stances called hormones. The term hormone is de-rived from the Greek word hormaein, m e a n i n g to urge on or arouse to activ-ity. The word was first coined by the Greek phy-sician Hippocrates (about 460-377 BC) to descr ibe a 'vital principle' which he believed, is contained in certain body secretions and which generally enli-vens the body. Hormones

Hippocrates g r e ^ b Q d y , s c h e m i c a ,

messengers. Unlike nerve impulses which carry information in the form of electrical charges, hormones are synthesized and released in one part of the body and circulated in the blood to reach other organs known as targets. It is here that their effects are brought about.

Hormones determine the transition from one stage to another

Larva y Metamorphosis

Pupa

Moth

Egg

4

THE BEGINNING

Chemically, hormones are organic compounds. They are secreted both by plants and animals. Since higher animals are multicellular, the various physiological tasks are split up among distinct cell populations, tissues and organs which may be physically distant. Naturally, orchestrating the syn-chronized functioning of far flung organs is difficult unless there is a way to communicate the commands to the organs. This is facilitated by hormones that coordinate organ func-tions by establishing a common communication link. To-gether with the nervous system, hormones thus serve as major means of controlling the body's activities. While the nervous system enables the body to immediately adjust the internal processes in keeping with the changes that take place in the outside environment, the hormones regulate the continuing processes of longer duration. The responsibilities of hormones include the body's growth, sexual maturation and ability to reproduce. Hormones produced by insects control their entire life cycle, their secretion determining the transition from one stage to the other; from egg to larva to pupa and finally to the adult. Plant hormones serve to control and accelerate plant growth. They also govern flowering and fruition. Playing the role of chemical messengers, hormones help maintain a stable, constant internal environment. They exert an enormous influence over the way we feel and the way we react. They wield their power through their control over an intriguing and yet not fully explored province of the body — its internal chemistry.

The discovery of hormones and their role in the functioning of our body dates far back into the recorded history of man. Almost every ancient civilization had made and recorded its observations. The ancient Indian text of Ayurveda mentions the role of endocrines in detail. Several endocrine glands were known to the Alexandrians in the third century BC. Diabetes which is still very much a contemporary disease is caused by the deficiency of a pancreatic hormone, insulin. It was described by the Chinese in the first century AD. Thus

5

16 HORMONE HARMONY

even that far back in time ancients had known that a disturbed endocrine system meant a disaster for the body.

The fledgling science of endocrinology, as the science of study of hormones is called, was launched in 1902 by two British physiologists Ernest Starling and William Bayliss. They discovered and described the workings of secretin, a hormonal substance produced in the lining of the small intes-tine. As the years went on, physiologists found a number of other glands that secreted hormones. In 1915, Edward Calvin Kendall (1886-1972) of the Mayo foundation in Minnesota, USA, isolated from the thyroid, an iodine containing protein which behaved like a hormone, and named it thyroxine. Itwas found that the thyroid hormones aroused the cells of the body to activity and thus, controlled the overall rate of metabolism in the body.

Perhaps the best known hormone today is insulin. Its discovery was the culmination of a long chain of events. The most serious form of diabetes is diabetes mellitus. Mellitus comes from the Greek word for honey and refers to the fact that, in advanced stages of the disease, the urine has a sweet taste. In 1815, the French chemist Michel Eugene Cherreul was able to show that this sweetness is due to the presence of the simple sugar, glucose. Normally, glucose is precious to the body. It is burned to get energy. The wastage of glucose indicates that the body is not utilizing its food efficiently. In the nineteenth century, the German physiologists Joseph von Mering and Oscar Minkowski found that removal of the pan-creas in a dog produced a condition just like human diabetes. Attempts to extract the hormone from the pancreas at first failed miserably.

However, in 1921, Canadian physician Frederick Grant Banting (1891-1941), Charles Herbert Best (1899-1978) and John Macleod (1876-1935) succeeded in isolating insulin. Banting and Macleod received the 1923 Nobel Prize in Physi-ology or Medicine for this breakthrough. This was followed by

6

THE BEGINNING

Charles Herbert Best (left) and Frederick Grant Banting (right) succeeded in isolating insulin

the discovery of sex hormones by Adolf Butenandt, an achievement which earned him the Nobel Prize in 1930.

By systematically destroying each individual gland and then administering extracts of the missing glands to animals, scientists have unravelled the role of hormones in body functions. What has, however, been far more difficult to understand is how hormones do what they do.

18 HORMONE HARMONY

The mystery of the body's chemical messengers begins to unfold itself at their origin. The mystery lies in the tiny bits of tissues tucked away in the obscure corners of the body, the endocrine glands themselves.

he bits of tissues making up the hormone factories lie scattered about in the human body. The different facto-ries bear little similarity to each other in shape and size.

Common to both sexes and functioning throughout life are the pituitary glands at the base of the brain, the thyroid glands in the neck, the parathyroids behind the thyroids, the adrenals perched above the kidneys like miniature caps and the insulin making islets of Langerhans in the pancreas. The gonads or sex glands are of course specific to either the male or the female. The ovaries are found in the female and testes in the male. The placenta, which feeds the unborn child also be-haves like an endocrine organ, manufacturing special chemi-cals essential to successful pregnancy. Recent studies

The factory

indicate that the brain and the heart too act as endocrine organs. Indeed several organs which have never before been associated with the endocrine function, have now been iden-tified and appear to actively release hormones. The entire digestive tract, for example, releases several hormones aid-ing digestion.

The cells of the endocrine glands are provided with a rich supply of blood, through minute blood vessels. This enables the cells to pick up the requisite raw materials from the blood for the manufacture of hormone molecules. As and when the need arises, these molecules are discharged directly into the blood stream to be ferried across to the various cells of the body. The blood is a particularly good choice because it

10 HORMONE HARMONY

Glands are distributed all over the body

Thyroid gland Parathyroid glands

Pituitary gland

Thymus Adrenal gland

(Testes In males)

Ovary

THE FACTORY 11

Thyroxine controls the rate at which food is converted into energy

carries substances to every nook and corner of the body catering to the needs of each and every cell.

The endocrine gland most familiar to most of us is the thyroid. Located at the base of the neck, just below the Adam's apple, this gland can be felt from the outside. The hormone produced by thyroid is an iodine — protein com-pound called thyroxine. Thyroxine exercises control over the rate at which food is converted into energy in the millions of cells of the body. The thyroid was probably the first gland to be discovered. While several roles were attributed to the gland, including one which suggested that it lubricated and protected the vocal cords, it was not until 1859 that the real

12 HORMONE HARMONY

role of the thyroid was recognized. J.M. Schiff, a German anatomist discovered that animals whose thyroids were sur-gically removed became sluggish and showed evidence of stupor. In 1891, a British physiologist, G.R. Murray, prepared sheep thyroid extract that relieved similar symptoms in hu-man patients. Murray thus received history's accolade as the first man to cure a human endocrine disorder with a glandular extract from the thyroid gland. Subsequently, it became com-mon practice to treat glandular malfunctions with extracts of the healthy glands.

Besides regulating energy supply, the thyroid partners the parathyroids to regulate calcium levels in the body. Calcium is contained in our bones. From the bones calcium is drawn out for normal neuro-muscular activity for blood coagula-tion, to meet the needs of the growing baby in the womb and during lactation. Yet, excess of calcium in the blood can have disastrous consequences for the various organs and systems of the body. The twoway traffic between bone and blood is thus controlled by the two hormones, parathormone secreted by the parathyroids which withdraws calcium from bone and calcitonin secreted by the thyroids which inhibits excessive withdrawal.

Compared to the rather conspicuous presence of thyroids the numerous tiny islands of hormone producing cells of the pancreas seem hidden. They cannot be seen with the naked eye, but their importance cannot cannot be underestimated. They were first noticed by Paul Langerhans in 1869, and are called Islets of Langerhans in his honour. There are two types of cells in these cell-clusters. They are called alpha and beta cells. These pour their secretions into the blood. Alpha cells produce a hormone called glucagon; beta cells produce insulin. Between them, insulin and glucagon help to regulate the amount of sugar available to the cells for production of^ energy. Sugar is infact one of body's main fuels. As per the' body's requirements, insulin encourages the build-up of gly-cogen, our reserve food material. Glucagon on the other hand

THE FACTORY 13

The right balance

helps breakdown of glycogen to release energy. When the pancreas does not function properly, sugar is not utilized effectively and is instead passed out in the urine. The ancient Greeks named this disease Diabetes mellitus and ancient Indians called is Madhumeha. Madhu means honey, as does its Greek version mellitus.

If these tiny islets help provide energy for our day-to-day activities, the adrenal glands help us deal with crisis and critical situations. Each adrenal, one on each kidney, is infact, two endocrine glands in one. The central and the peripheral portions of each adrenal gland act as separate glands. The central part of the gland, called the adrenal medulla, releases hormones that are different from those released by the outer part — the adrenal cortex.

14 HORMONE HARMONY

The typical 'butterflies in the stomach' feeling when we are nervous or scared is brought about by the two hormones of the adrenal medulla, epinephrine and norepinephrine. They thus play an essential role in helping the body to respond to emergency situations. The two hormones sharpen the re-flexes and immediately put the body on guard. The typical sweating and pallor, dilated pupils, the rapid beating of the heart and the quick breathing alert the body either for fight or for flight! The hormones manufactured in the adrenal cortex were discovered comparatively recently. One class, called mineralocorticoids, helps the kidneys regulate the critical balance of salt and water content of body fluids inside and outside the cells. Another class, called glucocorticoids, influ-ences the body's ability to build up and break down proteins, repair damaged tissues and control inflammation. A third

Fight or Flight?

THE FACTORY 15

The tireless pump is also an endocrine gland class, called androgens, influences the appearance of sexual characteristics, such as the appearance of facial hair or deepening of voice in boys.

The kidneys themselves also act as endocrine organs. This role, however, has been overshadowed by their more obvious function as the main organs of excretion of the waste products of the body. The kidneys secrete at least three main hormones, namely renin, erythropoietin and urokinase. While renin exerts its influence on the production of a hormone secreted by the adrenals, erythropoietin regulates the pro-duction of red blood cells. Urokinase, an anti-clotting agent protects against the urinary tract becoming blocked by a blood clot.

The sex glands, ovaries in the female and testes in the male, secrete hormones which are structurally similar to those secreted by the adrenal cortex. The ovaries secrete oestrogen and progesterone. The testes secrete testosterone and androsterone. In women, the placenta which provides nutrition to the developing child, also secretes hormones necessary to sustain pregnancy.

16 HORMONE HARMONY

For centuries the heart has been assigned the role of a pump, pumping away throughout life, supplying the body with all vital ingredients to sustain life. Recent discoveries, how-ever, indicate that the heart is more than just a muscular organ pumping blood. The upper chambers of the heart — the atria secrete a hormone called atrial natriuretic factor that interacts with other hormones to fine-tune control of blood pressure and blood-volume.

The whole system of hormone production and use in the body is very complex and is often likened to an orchestra. The conductor or master manipulator of the 'endocrine orchestra' is the pituitary gland. Lying at the base of the brain and connected to it by a short stalk, the pituitary gland is divided into two parts. The front portion is called anterior pituitary, and the remaining portion referred to as posterior pituitary. The pituitary secretes many hormones which exert their influence by stimulating other endocrine glands to release their prod-ucts. These are called trophic, or stimulating hormones. Thus the thyroid — stimulating hormone triggers the release of thyroid hormone and the follicle stimulating hormone triggers

Hormone harmony is a result of orchestration between the glands

THE FACTORY 17

the release of hormones by the ovaries. Other hormones of the anterior pituitary exert their influence directly on the body tissues without the intervention of any target gland. One such hormne is the growth hormone, which acts on cells through-out the body to promote both growth in cell- size and replace-ment. The removal of the pituitary of an animal or its destruction by disease in a child causes cessation of growth, and excessive production of its hormone causes the child to become a giant. This shows how vital a role the pituitary plays.

It was initially thought that hormones are produced accord-ing to the needs of the body and once their function was over,

were immediate ly broken down. The first example that hormones are released by one gland and stored in an-other came with the discovery of the hormones of the poste-rior pituitary. The posterior part of the pituitary stores two important hormones — anti d iu re t i c h o r m o n e (ADH) which travels to the kidneys and helps to maintain a cor-rect fluid balance within me body, and oxytocin, which is produced during child-birth and helps the uterus to con-tract. These hormones are secreted by the hypothala-mus. This small lump of tissue at the base of the brain is, infact, the manager of the en-

l°n 9 anld. sh_°.rt ° f _ h ° r m o ^ d i f - tire orchestra - consisting

harmony. Mangal Singh and Gul Mohammed, India's tallest and

shortest men respectively, shake hands

not only of the endocrine sys-tem but of the closely associ-ated nervous system as well.

18 HORMONE HARMONY

The hypothalamus regulates the body's response to heat and cold, as also the metabolism of water, electrolytes, sugar and fat. It controls appetite, growth, activity of the heart, respira-tion, digestion and sleep; indeed all those functions of the body that are usually beyond conscious control. Many of these functions of the hypothalamus are performed by means of instructions issued to the endocrine glands through the medium of the pituitary gland. The hypothalamus discharges several 'releasing factors', which travel through minute cap-illaries to the pituitary. This signal activates the pituitary to release its hormones.

Thus, much like the athletes passing the baton on, in a relay race, the signal from the hypothalamus is passed on to the pituitary, from the pituitary to the specific gland and from the gland to the target cell. While human athletes run along a single specified track, the 'body' athletes are released from the glands and poured into the bloodstream. How a specific target cell recognises the specific hormone molecule, inter-prets precisely the message targeted only to it and carries out the instructions while all other cells remain indifferent to the message has been one of the mysteries biochemists are

Hypothalamus

Pass the signal on

Pituitary Specific gland

Target-ceil

THE FACTORY 19

attempting to unravel. This extraordinary power of hormones, to work with such clockwork precision is one of the major challenges of biochemistry.

ormones perform functions of vital importance to the body. The secret of their action must lie at least par-tially in their chemical structure. Considering the di-

verse functions they perform, hormones are equally varied in chemical structure.

Chemically, hormones fall into two basic categories. Some are proteins, while others are steroids. Of all the macromole-cules found in the cell, proteins are probably the most diverse. They are composed of long chains of amino acids which may be considered the building blocks. The function of a protein is determined by the type and distribution of these building blocks. The hormones of thfe pancreas and the anterior pituitary are proteins and those of the posterior pituitary are

At work

smaller chains of amino acids called peptides. The hormones of the thyroid and adrenal medulla are derivatives of the amino acids themselves.

Steroids on the other hand have a more complex chemical structure. They are made up of hydrogen and carbon ar-ranged in a system of rings. Steroids are secreted by the adrenal cortex, ovary and testes. Irrespective of their chemi-cal structure all hormones are active in very small amounts. In some cases, less than a millionth of a gram is enough for a task to be carried out.

Hormone producing glands pour their products into the blood stream, thus bringing them into contact with almost every cell in the body. But they do not activate every cell they encounter. It is as if the hormone's message is in 'code', and

T h e h o r m o n e - m e s s a g e is not mean t for every cel l

AT WORK 21

22 HORMONE HARMONY

only certain cells are able to decode it. Cells which can decode the message of a particular hormone are known as the 'target' cells of that particular hormone. Hormones do not even travel along specific routes to their target cells. They just reach their target cells by chance. But this is no ordinary 'hit and miss' trial run. Hormones very rarely miss their target. Even within the confines of the target cell they carry out their function with precision. How does this finely tuned hormonal orchestration function ?

Each cell in the body carries on its surface a specific address. This address is a tiny protein molecule called a receptor. The hormonal messenger hunts for precisely this 'address' before delivering the message. Thus, all target cells must have specific receptors which will recognize the hor-mone.

All those cells which respond to the same hormone prob-ably have the same kind of receptors. But this does not mean that they all respond in exactly the same way. Different cells have different responses. Nevertheless, their responses may well be geared to the same end result. How do hormones pass on the message and consequently induce a response from the cell ? Hormones exercise their control over the activity of the target cells by altering chemical reactions within the cells or by affecting the permeability of cell membranes.

It is gradually becoming clear that the essential action of hormones is upon enzymes — organic catalysts which are involved in virtually all vital reactions in the body.

The understanding of the exact reactions that take place in the cell under the influence of a hormone came with the discovery of a substance called cyclic adenosine monophos-phate (cyclic AMP), by Earl Wilbur Sutherland and Theodore Rail in 1960. Cyclic AMP is widely found in tissues and is known to have a pronounced effect on the activity of many enzymes and cell processes. It is formed by the action of an enzyme called adenyl cyclase on adenosine tri-phosphate

AT WORK 23

Hormone First messenger

Receptor

Cell membrane

A deny I cyclase

Cyclic AMP Second messenger

Hormone action

On target, everytime (ATP),-the major energy currency of a cell. Scientists believe that the locking of a hormone with the receptor protein, stimulates the formation of cyclic AMP. Cyclic AMP on its part acts as a 'second messenger' and activates a series of reactions within the cell. After binding with the receptor, the hormone receptor complex activates adenyl cyclase on the cell membrane. Adenyl cyclase immediately converts ATP to cyclic AMP. The cyclic AMP then initiates any number of cellular functions before it itself is destroyed. Functions such as activating enzymes in the cell, altering cell permeability, initiating synthesis of specific intracellular proteins, causing muscle contraction or relaxation are a few of its routine jobs. The types of effects that will occur inside the cell are deter-mined by the characteristic of the cell itself. Thus cyclic AMP produced by the presence of the hormone insulin, triggers

24 HORMONE HARMONY

cells to take up and use glucose, while the hormone glucagon, also made by the pancreas, causes glucose to be released by cells and build up in the blood to be 'burned-off' as energy-giving fuel for physical activity. Over the years, sev-eral other 'second messengers' have been discovered. Thus, more than one second messenger control mechanisms op-erate simultaneously in the same cell but function inde-pendently of each other.

But, this is not the only way in which a target cell may be made to respond, to a hormonal messenger. Hormones, specifically steroid hormones secreted by the adrenal cortex, the ovaries and the testes elicit a response in a different way. Being a small molecule they can diffuse through cell mem-brane unlike protein hormones. It was initially thought that they do not need receptors. However, in 1964 an Indian scientist Dr G. P. Talwar discovered steroid hormone recep-tors while studying steroid hormones and their functioning. Steroid hormones use calcium as second messengerfortheir quick effects. This was shown in 1990 by scientists at the Centre for Cellular and Molecular Biology (CCMB). The hor-mone-receptor complex itself triggers the synthesis of pro-teins in the target cells. These proteins function as enzymes and activate other functions.

In order to trigger protein synthesis, the hormone-receptor complex must interact with the genetic blue-print — DNA or Deoxyribose Nucleic Acid. In this complex molecule lie the instructions for synthesis of the protein requirements of a cell. The DNA does not synthesize all of the proteins all the time. Depending on cellular requirements, specific regions of DNA are switched on and required protein synthesized. Protein synthesis begins with the copying of the instructions from the DNA to a messenger. This messenger is a Ribose Nucleic Acid (RNA) which promotes the synthesis of proteins by directing the attachment of the appropriate amino acid in the required order. These proteins are churned out within the cell at factories called 'ribosomes'.

AT WORK 25

After they have done their work, the hormones are ren-dered inactive by the target cells themselves. They may be carried to the liver for deactivation, then broken down and either excreted or used to make new hormone molecules.

Hormones, released in very minute quantities act at the molecular level and do their job to perfection. However, should they be released in larger quantities or in too little amounts, cellular mechanisms and consequently the entire body system can go haywire. The body thus, needs to keep a perfect balance between the release and utilization of hormone molecules.

-DUTY SHEET

Mon

Tue

Wed

Thu

F r i

Sat

Sun

Sec A B C D E

O f f Duty

Of f Duty

Off Duty

Off Dutv

Off Duty

Off Duty

NO PRODUCTION

ur body generates two types of signals, one is electri-cal in nature, carried by nerves and normally flashed when immediate action is required. This type of mes-

sage may travel as fast as 100 metres per second. The second signal is slower and carried by hormones. Compared to nerves, hormones tend to act more slowly, and spin out their activity over a much longer time. However, for efficient control of the body, both the nervous and endocrine systems should work hand in hand. Many endocrine glands, through their hormones, affect the nervous system; similarly endo-crine glands are stimulated or inhibited by the products of nerve cells.

Since only very small amounts of hormones are needed to

Keeping balance

control most body processes it is essential to keep a strict vigil on the various factories churning out the hormone.

Initially it was thought that each hormone producing gland is independent and controls the production and release of its hormone(s) by itself, but research has shown that no gland works independently. They are all interdependent, like play-ers in a football team. This team is led by the pituitary gland and the hypothalamus. The two work together to control the production and release of hormones by other glands.

To control any team effectively, the manager and captain must be in close contact with their team as well as with each other. They must continuously monitor their team's perform-ance and ensure that every member works as part of the team. Generally speaking, it is the manager who monitors the

KEEPING BALANCE 27

Target gland

Products

Products

Products

f t p4ft-i I! I I I IC

Target gland

Products

Target gland

Synchronization is needed for hormone harmony

Pituitary Releasing factor \

Target gland

28 HORMONE HARMONY

team's performance and takes the decisions, but it is the captain who passes on these decisions to members of the team.

This is exactly how the hormonal control system works. The hypothalamus acts as the manager, monitoring hormone levels in the blood and the pituitary gland is the captain telling the other endocrine glands when to release their hormones, and when to stop.

When a particular hormone is needed, the hypothalamus sends a message to the pituitary gland by means of a releas-ing factor. Releasing factors have only recently been discov-ered, and very little is known about them. What is known, however, is that these releasing factors are liberated from nerve endings of the hypothalamus into the tiny blood vessels that lie between the hypothalamus and the pituitary and are carried to the anterior pituitary whose output of hormones they regulate.

The pituitary gland communicates with other endocrine glands by means of special 'trophic', meaning nourishing, hormones. These are produced in the anterior lobe of the pituitary gland and released, just like any other hormone, into the blood stream. They are thus transported throughout the body, to their target glands which include the thyroid, adrenals and gonads, where they stimulate hormone production.

The pituitary gland not only issues orders, but also re-sponds to the way those orders are carried out, boosting the output of trophic hormones when target glands lag behind in production, cutting back when their output is adequate. The body's endocrines are thus a self-regulating system. The trophic hormones act as signals and stimulate the target gland. The target gland steps up production of its own hor-mones which act on body cells. Rising levels of these hor-mones feed signals back to the hypothalamus, cutting production of trophic hormones. This is thus a feedback

KEEPING BALANCE 29

Thyroid hormone level indicator

Thyroid stimulating hormone (TSH)

Thyroid hormone

,Low thyroid -

A simple feedback system ensures the correct level of hormones

mechanism which keeps the production of these potent chemicals under tight control.

One of the simplest ways in which a hormone level is adjusted, is by 'switching off' the gland that produces it, when enough of the hormone has been released. Thus, when the thyroid gland is stimulated by thyroid stimulating hormone (TSH) from the pituitary, it produces thyroxine. Rising levels of thyroxine in the blood send signals to pituitary and less TSH is released and thyroxine output is controlled.

In some other cases, the hormone secretion is controlled by the substance whose level or function is being adjusted by that hormone. For example, when blood sugar levels rise, the beta cells of the pancreas increase the release of insulin,

Pituitaryi Thyroid

hormone

30 HORMONE HARMONY

which stimulates liver cells and other target cells to remove sugar from the blood for storage in the form of glycogen for future utilization. As blood sugar levels fall the beta cells reduce insulin secretion.

Yet another example of a little more complex kind is seen in the case of vitamin D which acts as a hormone. Vitamin D is synthesized by the skin under the influence of ultraviolet light. Vitamin D is by itself not a very effective compound. It is further processed in the liver and kidneys to an active form, and this form acts as a steroid hormone, and helps maintain calcium levels in blood. If calcium levels in blood are at the threshold level the processing of vitamin D in liver and kidney takes a longer time.

Maintaining a normal calcium balance

Vitamin D

Blood \ | with Vit D J

Normal blood

calcium level

Calcium i in bone

1 Releases / calcium |

\from bone\

PTH \ production K started J

( PTH \ [production] \ reduced J

Excess calcium excreted

Urine

KEEPING BALANCE 31

More complex feedback systems involve the coordination between the nervous and endocrine systems. The response of the healthy body to cold is a very complicated one. It is a perfect example of the way in which the hormones and the nervous system work in perpetual partnership.

The hypothalamus is the organ most closely concerned with the body's reaction to cold and heat. When the tempera-ture in the environment around us falls, the blood under the skin cools. When this cool blood mixes with the rest of the blood in the body, there is a minute drop in the temperature of the blood. When this blood reaches the brain, the tempera-ture change is detected by the hypothalamus. Immediately a signal is sent to the adrenal medulla. This time the signal is through a nerve. The adrenal gland responds by an increased production of its hormones, epinephrine and norepinephrine. The hormones constrict the blood vessels running under our skin, thus decreasing heat loss from the body surface. Simul-taneously, the hypothalamus secretes a releasing factor which stimulates the pituitary to release a thyroid stimulating hormone (TSH). TSH, in turn, stimulates increased output of thyroxine by the thyroid gland. Thyroxine increases the rate of cellular metabolism throughout the body. Thyroxine mobi-lizes glycogen from the liver which is broken down to generate heat. The thyroid gland, however, may take some time to reach new levels of thyroxine secretion. Thus, this job is carried out immediately by epinephrine and norepinephrine.

If there is a drastic drop in the outside temperature, shiv-ering begins. Here again, the hypothalamus acts by sending signals through nerve fibres to the muscles. Shivering gener-ates heat. During maximum shivering, body heat production can rise to as high as 4 to 5 times normal. Much like a heater along with its controlling thermostat, which produces more heat when the house gets too cool and less when the tem-perature goes up, the body too has its 'hypothalamic thermo-stat:

W a t e r , wa te r e v e r y w h e r e

74.5%

22%

82.7%

75.6%

83% r

32 HORMONE HARMONY

KEEPING BALANCE 33

The amount of water present in our body is also maintained by the joint efforts of the nervous and endocrine systems. Continuous monitoring of the amount of water in the body is done by two sets of specialized nerve cells. When the body has low water levels the hypothalamus has two options. It can either get more water or else, conserve the available water. An area in the hypothalamus called the 'thirst centre' creates a sensation of thirst, thus enabling the body to obtain more water.

Another area in the hypothalamus contains certain cells called osmoreceptors. When water levels in the body comes down, and the osmoreceptors detect it, they send signals to the posterior pituitary and stimulate it to secrete a hormone called antidiuretic hormone (ADH). This hormone is carried to the kidney. At the kidney where filtration of the body wastes takes place, ADH prevents too much of water from being passed out into the urine. The urine volume is decreased and concentrated urine is voided. By this means, the body retains as much water as is essential. The nervous system and the endocrine system are actually different sectors of one vast body-controlling organ system, each influencing the other and each dependent upon the functioning of the other for the maintenance of the body's total well-being.

f all the roles that the body's chemical regulators play, the most fascinating is in human genesis. The sperm fuses with the egg in a process called fertilization and

thus begins the journey through life. From conception to maturity, hormones play a vital role. They shape the growth of the child within the womb, nurture it during the transition from infancy to adolescence and bring about the transforma-tion from adolescence to adulthood.

The sperm and the egg carry information in the form of the genetic material, the chromosomes, which contain nearly all the information needed to construct a complete individual. The father's contribution to the offspring in the genetic mate-rial contained in the sperm determines the infant's sex at the

Male versus female

moment of conception.

All the cells of the human body, except the sperm and the egg, contain 46 chromosomes, arranged in the nucleus of a cell in 23 pairs. One of these pairs is associated with the individual's sex. In women, the members of this pair are identical with each other, both being the so-called X-chromo-some. In men, however the members of this pair are not identical. Male cells have only one X chromosome. The other is a very different type, known as Y. The sperm and the egg on the other hand, are different in their chromosomal numbers from all the other cells in the body. They contain only 23 chromosomes each. That is, instead of having a pair of each chromosomes they bear only one member of each pair. The egg contains one X chromosome. The sperm may contain

MALE VERSUS FEMALE 35

Male or female ?

either an X or a Y chromosome. Chance seems to determine whether the sperm that finally penetrates the egg is one that carries an X or a Y chromosome. If the chromosome is an X, a female has been conceived. If it is a Y, a male has been conceived.

Although the infant's sex is determined at the moment of conception, the reproduc-tive system does not begin to develop ..until the sec-ond month. Once it does, however, progress is so rapid that the differences between the sexes is un-m i s t a k a b l e . The sex glands develop in the sixth or seventh week and ap-pear on either side of the abdominal cavity as pairs of tissue similar in struc-ture in both sexes. By the ninth week, they differenti-ate into testes and ova-ries. The format ion of these primary sex organs 6 week foetus

Ovum Ovum

X Y

Sperm Sperm

XX

36 HORMONE HARMONY

sets the stage for the development of the rest of the structures that make up the reproductive system.

In pre-adolescent years, hormones play a major role in the growth of the child, through the growth hormone-somatotro-phin. This hormone is assisted by other hormones especially those secreted by the thyroid gland.

However, it is at the beginning of adolescence, the years of greatest growth, that developmental differences between girls and boys become most evident. The two major events that occur during this period are sexual maturation and accel-erated growth. Both are brought about by marked changes in hormonal secretion. This is the job of the hypothalamus which acts as the body's biological timer.

The hypothalamus signals the pituitary to take up a new role. The pituitary thereupon begins secreting two new trophic hormones. Surprisingly, they are the same in both sexes.

Pituitary•—

Hypothalamus

Progesterone and u

Oestrogen inhibition

-SH LH~

FSH

LH

_ Testosterone inhibition

Ovaries Testes

Female

Growing up


These hormones are the follicle-stimulating hormone (FSH) and luteinizing hormone (LH). They stimulate the gonads, which have been almost inactive since before birth. The activity of the adrenals also rises, and this is induced by the adrenocorticotrophic hormone of the pituitary.

At this point, the process diverges in the two sexes. In boys, both trophic hormones spark the growth of cells that produce the sperms. They also stimulate some other cells in the testes to produce the male sex hormone, testosterone. In girls, the process is different. Egg-cell production also requires the efforts of both trophic hormones, but the maturation of the eggs requires two hormones, oestrogen and progesterone which are secreted by the ovaries.

With such drastic changes in the internal cycle, there are equally noticeable changes in their appearance and behav-iour. Testosterone, the hormone secreted by the testes, stimulates the growth of facial hair, and causes changes in the voice box which cause deepening of the voice. In girls, the growth and development of breasts, uterus and ovaries come first. The hips broaden in preparation for child bearing. The two sexes also differ in the distribution of hair throughout the body. Hair growth and distribution is also hormone de-pendent.

The adrenals, are responsible for the production of andro-gens. These hormones influence hair growth and the distri-bution pattern characteristic to each sex. Growth of hair in the armpit and pubic region is very much influenced by even small amounts of androgen secreted by adrenal glands and, there-fore, hair in these regions of the body grows approximately in the same way in males and females. It is also true that all normal men have some oestrogen (female hormone) in their blood secreted by both adrenals and testes and that all women carry some androgen produced by adrenals and ovaries. Therefore, there is no sharp division between male and female type of hair growth. If you look through a hand lens you may find a slight hair growth on the face of a

38 HORMONE HARMONY

charming lady. There is considerable variability in hair growth in normal males and females. Just as a woman may have a large, medium or a small nose, so may she have a growth of facial hair varying from the obviously excessive to the unde-tectable.

Hair growth in areas typical of men such as face, upper pubic triangle, chest and ears requires a greater quantity of androgen to sustain growth. Since normal females do not produce large quantities of androgen, they do not show hair growth on these regions. The growth of hair on the scalp largely depends on the levels of oestrogens and, therefore, females have long hair on their scalps, whereas males who produce large quantities of androgen, may have dense growth of hair on their body and face but not on the scalp.

Other striking differences between the male and the female include immune responses and mental skills and these differ-ences are also believed to be modulated by hormones.


Design created by a girl Design created by a boy

Spatial skills differ in males and in females

40 HORMONE HARMONY

Females show increased immune activity as compared to males. Studies indicate that females have better linguistic skills while males are more gifted in tackling problem requiring spatial thought.

However, science has not yet discovered how the hypo-thalamus knows when the time for puberty has arrived. The process is thought to be connected with the general level of growth and development that the organism has achieved. Whatever the explanation, the hypothalamus at a certain time apparently becomes less sensitive to the sex hormones and ends its inhibition of the pituitary. Then the pituitary is free to release gonadotrophins. These, in turn, prod the sex glands into stepping up their output and the process of sexual maturation begins. These interlinked processes continue until the sex hormones in the blood-stream reach a level that can stimulate the hypothalamus, which thereupon calls a halt to further sexual changes. Thus the level of sexual development is stabilized. With clockwork precision, the infant grows into an adolescent,subsequently to an adult.

After the attainment of sexual maturity, the boy becomes a man, the girl a woman. The fusion of the sperm from the man and the egg from the woman can now recreate life.

he alterations in appearance that accompany adoles-cence are merely external evidence of internal proc-esses producing greater changes in the body than it has

experienced since birth—the attainment of puberty (or) sex-ual maturity being the most important of these changes.

In boys, the testes become larger and inside them, the tubules which manufacture sperm come to maturity. The sperms are manufactured in astronomical quantity. Nearly 300 million to 500 million sperms are released to meet each egg. The prostate gland develops and begins to secrete the seminal fluid.

In girls, the growth and development of breasts, uterus and ovaries come first. Shortly thereafter, the menstrual cycle

begins. Every 28 days or so, a woman's body prepares itself for nurturing a new life within itself. Except during pregnancy, this cyclic process repeats itself regularly for about 35 years after puberty.

The menstrual cycle is controlled by one of the body's most intricate feedback systems, in which four hormones enter and exit, advance and retreat. Each hormone presides over one step in the process and in addition triggers the next step.

The sequence begins with the secretion of the follicle stimulating hormone (FSH) by the pituitary. The ovaries con-tain an estimated 40,000 ova of which only 300 to 400 mature and are released during a woman's fertile years. Each matur-ing ovum in the ovary is enveloped by ovarian follicles. These follicles increase in size and some reach maturity, and

Productive performers

42 HORMONE HARMONY

Developing ovarian follicle

secrete the hormone oestrogen. The oestrogen cuts back the pituitary's production of FSH and sets it to making luteinizing hormone.

This triggers the follicle to release its ovum, a process called ovulation. Immediately after ovulation the cells lining the now empty follicle begin to proliferate and to fill the follicle, forming a temporary endocrine gland called the corpus luteum. This temporary gland, now under the influence of LH secretes progesterone and a little oestrogen.

Progesterone changes the pattern of the lining of the uterus, preparing the 'bed' for the fertilized ovum. The lining of uterine cells swell to store nutrients for the developing embryo. This, however, requires the concomitant action of another hormone oestradiol which is secreted by the ovary.

Developing follicle

26 days

Ovum Declining corpus luteum

PRODUCTIVE PERFORMERS 43

Anterior pituitary hormones

Period Clearer thinner slippery mucus -t h-

Secretions from the neck of the wonr 36.8° C

Basal body temperature n a y 12 14 16 20 24 28

.days Menstrual cycle

Levels of hormones from ovary

Blood vessels Period

Gland

Changes in the Oping of the womb_

Peak mucus thick; sticky

* mucus -

-utelnlzlng hormone , FSH - Follicle Emulating hormone »Oestrogen

• Progesterone

Development of ovum

Graafian follicles ovulation

Corpus luteum

44 HORMONE HARMONY

Progesterone helps the entry of the ovum into the uterus. It also cuts LH production.

After about a fortnight of progesterone action, if the ovum encounters the sperm, it is fertilized. If fertilization does not occur, production of both oestrogen and progesterone drops. This causes the uterine lining to slough away and permits FSH production to start, beginning the cycle once more. The sloughing away of the uterine lining is what is called men-struation or menarch. Menstruation can thus be regarded as a mechanism by which the uterine wall is periodically pre-pared for pregnancy.

If the egg is fertilized, however, a fifth hormone joins the cast and the plot changes. Upon fertilization, the fertilized ovum implants itself in the uterus, and continues to grow and mature for nine months. This growing embryo releases a hormone identical to the pituitary luteinizing hormone. This causes the corpus luteum to produce more oestrogen and progesterone. Progesterone prevents the release of any more ova from the ovaries and also prevents the shedding of the uterine lining.

During the growth of the embryo from a cluster of cells to a baby, the complexities of hormonal action reach a peak. Involved are the mother's endocrine system, the gradually maturing glands of the embryo and also the placenta.

By the third month of pregnancy, the corpus luteum in the ovary atrophies as the placenta takes over the job of supply-ing oestrogen and progesterone. In the foetus, oestrogen stimulates sexual development. In the mother, it prepares the breasts for nursing. Progesterone, serves as a semi-proc-essed material for the immature foetal adrenals, which con-vert it into adrenocortical hormones. It also promotes changes in the mother's uterus to accomodate the growing baby.

Synthesis and secretion of glucocorticoid hormones in-crease throughout pregnancy. These help in the availability of large amounts of glucose to the mother and the developing


Placenta : The life line

child. The thyroid gland enlarges during pregnancy and even doubles the production of thyroxine. The parathyroids also enlarge. This causes calcium absorption from the mother's bones. The calcium circulating in the mother's body is used by the foetus for calcification of its bones. The human placen-tal lactogen hormone released by the placenta promotes the growth of the embryo.

After nine months of pregnancy, the level of oestrogen in the mother's blood rises so high that it begins to counteract the effect of progesterone on the uterine muscles. Child birth is triggered by the placenta and the baby. Oestrogen,

j Syncytial cells

Villi

Foetal blood vessel

46 HORMONE HARMONY

produced by the placenta in large amounts before labour, helps in the enlargement of the vaginal opening. It also prepares the uterine muscles for labour. During labour, the baby's movements stretch the uterine muscles which in turn send nerve signals to the mother's brain. These signals trigger the immediate release of the hormone, oxytocin from the pituitary. This hormone causes contraction of the uterus, leading to more movements of the baby and the cycle repeats itself over and over again, gradually becoming faster and faster. Finally the infant is born.

The secretion of hormones by endocrine glands has to be re-scheduled after birth. Placental hormones vanish as the placenta is thrown out. The next essential step is the secretion of milk which requires an adequate amount of the mother's hormones. During pregnancy, the breasts are kept from

Effect of suckling

Prolactin Oxytocin Suckling stimulus

Hypothalamus

Oxytocin


producing milk by large amounts of oestrogen and progeste-rone. After the baby is born, the amount of these hormones decrease and prolactin, the hormone which stimulates milk production, takes over. Prolactin is a secretion of the anterior pituitary. Milk is secreted by the tiny cells of the sac-like glands in the mother. The flow of milk is controlled by both nerves and hormones. Nerve impulses arising from suckling by the baby are conveyed to the hypothalamus. The hypo-thalamus in turn sends messages to the pituitary for the secretion of two hormones oxytocin and prolactin. These hormones create a pressure on the glands to eject the milk through ducts present in the glands.

Thus, the perfect synchronization between the various hormones makes the event of a birth, a miracle in itself. This miracle of synchronization can, however, go haywire. This is when scientists take to the test tube to create life.

he marvellous mechanism of reproduction assures us that our body, with its complex structure and function serves a continuing purpose. There is, indeed, an in-

nate and deep-seated desire in all humans to leave behind 'a copy' to carry on the family name.

There are times, however, when a couple is unable to create a new being. If an apparently healthy couple is unable to have a child, it is because something has gone wrong in an otherwise perfectly synchronized chain of events leading to birth.

For pregnancy to occur a number of conditions must be fulfilled. The pituitary must regulate the function of the ovary, its production both of oestradiol and progesterone and of the

In harness

ova. Secondly, the ovum must be expelled from the ovary, be embraced by the fimbriae or the tasselled ends of the fallopian tubes leading to the uterus — and must be conducted gently to its meeting with the first of an approaching army of eager spermatozoa. The process of ovulation occurs usually at the middle of the menstrual cycle. The life of an ovum is probably not more than forty-eight hours and that of a spermatozoon is only two hours. Thirdly, the fertilized ovum must be embed-ded in the uterine wall. This can only occur when the uterus is normal and its lining properly prepared for the reception of the fertilized ovum by the flood of progesterone occurring at the time of ovulation. A proper endocrine balance is neces-sary to maintain the right conditions in the uterine walls in which the fertilized ovum may develop in the next nine

IN HARNESS 49

Female

Male

Fimbriae: Blockage

Uterus: Scarring Abnormal shape

Cervix:

Presence of antibodies

Vagina: Agglutination of sperm

Vas deferens: Inflammation Blockage: Infection Varicose veins

Urethra: Blockage Infection

Testicles: Low sperm production Sperms abnormal Undescended

Fertility problems can occur in any of the reproductive organs

Prostate-. • Infection

Epididymis: Blockage Infection

Penis: J-ack of ejaculation Retrograde ejaculation

Ovaries: Cysts

Fallopian tubes: Damaged

50 HORMONE HARMONY

months. But not all infertility problems arise because of com-plications in a women's body.

About one-third of all infertility problems are, however, due to faulty sperms. This could be due to inadequate sperm, no sperm in semen and sperm infected with bacteria. Some sperms lack a sense of direction and waltz around in one place instead of determinedly looking for the egg, sometimes the sperms may be abnormal. In women, on the other hand, blocking of the fallopian tubes, infection, fibroids or tumours in the uterus can lead to infertility.

Till about fifteen years ago there was little such couples could do except hope for a miracle. However, biotechnologi-cal procedures and an extensive study of the powers of hormones have now helped childless couples to conceive. As a culmination of a decade of hard work by Patrick Steptoe, gynaecologist and Robert Edwards, physiologist, the first test tube baby Louise Brown was born in England in July 1978.

A test tube baby despite what its name suggests is not 'grown' in a test tube. A test tube baby is a child born out of in vitro fertilization technique. This means that the fertilization of the egg by the sperm takes place outside the body, usually in a petridish. The term in vitro literally means 'in glass' and is in general applied to biological processes when they are experimentally made to occur in isolation from the whole organism. Since test tubes, petridishes and many scientific apparatus are indeed made of glass, the term has come to stay.

A novel technique called laparoscopy is used to recover eggs from the ovary. The woman is given anaesthesia and the abdominal wall is pierced with a slim needle through which gas is passed to distend the abdominal cavity. A small incision is then made just below the navel and the laparoscope is introduced. The laparoscope provides a clear view of the uterus, ovaries and the fallopian tubes. The doctor can thus see what exactly he is doing and can carry out minor surgery.

IN HARNESS 51

The next step is to recover eggs from the patient's ovaries. The laparoscope can be used together with a hollow needle to remove eggs from the ovaries of a woman.

Ini t ia l ly, a woman 's natural menstrual cycle was studied to decide when to recover the eggs. This was done by analyz-ing her urine. A sudden rise in luteinizing hormone was usually noted just be-fore ovulation. Now, hor-mones are used to stimu-late the ovary to produce

more eggs. This is known as superovulation. The powerful hormonal drugs used for the purpose include domiphene citrate (brand names Serophene and Clomid), human meno-pausal gonadotropin (Pergonal) and follicle stimulating hor-mone (Metrodin). These hormones are taken daily by injection for about 28 days and sometimes side-effects like hot flushes, nausea and mood swings are noted. Under normal conditions each ovary takes turns in releasing an egg every month. When both ovaries simultaneously release eggs which are fertilized by two different sperms, fraternal or non-identical twins result. But since the body believes in division of labour both ovaries usually share the work of ovulation by taking turn alternately.

Oncethe superovulatory process has succeeded, the eggs are retrieved through the vaginal route using a fine needle inserted with ultrasound guidance. Several eggs are taken out, because should any one be damaged there are spares to fall back on. Superovulation is necessary as an insurance

52 HORMONE HARMONY

Pregnancy

In vitro fertilization is a long drawn process

IN HARNESS 53

against failure. Physicians do not pin all their hopes on only one solitary ova but believe that there is safety (and success) in numbers.

The eggs are examined microscopically for any defects. These are then transferred to a dish containing fresh semen. The eggs and sperms take about 12-15 hours to fertilize. By 18 hours it becomes apparent if fertilization has taken place or not.

The fertilized cell called zygote is transferred to a special solution kept at body temperature. It is here that the zygote begins to divide. It is allowed to divide as it does within the mother. The next step is in determining the right stage in the mother's cycle when the developing embryo is to be placed in the uterus and discovering what hormones assist implan-tation. At precisely that stage when the developing embryo

54 HORMONE HARMONY

implants itself in the womb under natural conditions, artificial implantation is done.

The embryo is placed in the womb through a fine plastic tube inserted through the cervix and into the uterus. After years of refinement, today the success rate of implantation is as good as the natural rate. This process of fertilization is called ZIFT (Zygote Intra Fallopian Transfer).

GIFT (Gametes Intra Fallopian Transfer) is a variation, in the procedure, where fertilization takes place inside the body. Introduced in 1984, it is suitable for those women whose fallopian tubes are functional but who are unable to conceive for unexplained reasons. The eggs and the sperms, are placed in the fallopian tubes where they undergo fertilization and naturally move on unassisted to the uterus.

IN HARNESS 55

Apart from ZIFT and GIFT, another up and coming tech-nique is microfertilization. In this, a sperm is directly injected into an egg. Instead of using millions of sperms and letting one win the race to the egg, only one healthy sperm is directly injected into an egg. In yet another technique, a tiny hole is drilled into the outer wall of an egg without removal from the body. This helps the feeble sperm to enter the egg and effect fertilization. This is called Partial Zona Drilling and is usually carried out when the sperms are healthy but weak.

Helping childless couples conceive is not the only use of in vitro fertilization. It is also used extensively in the livestock industry to create animals with superior qualities. Techniques for inducing superovulation, in female animals that have exceptionally desirable features, and in vitro fertilization of these eggs and implantation of the embryos into animals of lower quality are commonly practiced.

56 HORMONE HARMONY

Superovulation means more profit

Perpetuation of desirable traits and building up a large flock of animals that show such traits is a natural tendency of all animal breeders. The racing enthusiasts have detailed pedi-gree charts of the horses and trace a winner's stamina and stride to its famous dam and sire. However, if the animal bred naturally, it could produce one, at best two offsprings (twins) every year. And in a lifetime it could leave behind only a handful of descendants. But its potential as a progenitor could be really utilized if the ova in its body could be collected, fertilized outside the body and then nurtured to term in the womb of surrogate mothers. The pedigree of the surrogate mothers does not matter as long as they are healthy and capable of carrying the foetus. These surrogate mothers are nothing more than living incubators for the highly prized test tube animals that spell profit for animal husbandry. Creating better livestock by manipulating their hormones has been in regular practice for years.

Induced superovulation has made it possible to breed more than twenty offsprings from one cow and a bull in a single reproduction cycle. The process is simple enough. The selected cow is made to superovulate and the ovaries are

IN HARNESS 57

s t r i pped of eggs . These eggs are fertil-ized by the sperm of the chosen bull. The fertilized eggs are im-planted, one each, into sur rogate mothers , which bear them to term. Biotechnological advances can even double this bonanza.

It is poss ib le to separate the two cells of the zygote when it is at the t w o - c e l l e d s tage . Essen t i a l l y mimicing the process by wh i ch i den t i ca l

twins result in nature, each cell can be expected to grow into a fully formed foetus to be born normally. Rac-ing enthusiasts have already created twin horses named Ques-tion and Answer using this process. Hormone manipulation can help ranchers too. Quite re-cently, there was pub-lic deba te over whe the r Eu ropean ranchers should be al-lowed to continue their practice of implanting steroid hormone pel-lets in the bull calves

Double trouble? Question and Answer, the twin horses created in the lab

Microinjecting foreign DNA into mouse ova

58 HORMONE HARMONY

being grown for meat. These hormone im-p lan ts speed up growth and the calves are bigger and ready for market much ear-lier than siblings with-out the g rowth ho rmone imp lan ts . These attempts to ma-n ipu la te ho rmones have usually had the motto 'more prof i t , qu ick ly ' . Ranchers want more bull calves which grow faster. In short they want quick turnover.

n . . , . , Transgenic mouse carrying rat GH gene is Biotechnology has l a r g e r than its normal sibling

now provided them with the tools for achieving this goal. It is now possible to manipulate the gene(s) responsible for the expression of growth hormones and experimentally at least, assure that a chosen animal grows faster. Animals into which foreign genes (or genes not normally present in the species in nature) have been introduced are termed transgenic. Transgenic animals manifest signs of the foreign gene(s) they carry.

Transgenic animals are produced by microinjection of foreign DNA into fertilized eggs. The injected embryos with their cargo of foreign gene(s) are implanted into the womb of a suitable female which carries it to term. However, not all the microinjections result in successful union of the introduced genes into host DNA. The failure rate, at present is quite high but the profits that can accrue from even one transgenic animal to begin with, has kept interest alive.

IN HARNESS 59

Many studies of transgenic animals have been concerned with attempts to increase growth or the efficiency of growth. The regulation of growth is, however, a complex process involving an interplay between circulating hormones, genetic potential and the nutritional and health status of the animal.

Not all animals have the potential to grow to a large size. Some, like mice, are genetically predetermined to remain small. Scientists wanted to see the effects of a GH gene taken from a much larger animal on mouse genotype. By incorpo-rating human or bovine GH genes in the genotype of mouse, they could create a much larger transgenic mouse which showed that the circulating 'foreign' GH had also done its work.

Dramatic spurt in growth has been shown by transgenic mice bearing bovine, rat or human growth hormone (GH) genes. Transgenic mice carrying rat GH gene have grown to double the size of their normal siblings. The strategy has been extended to commercially important species. It has been used to increase the growth rates of livestock, fish and poultry.

Transgenic pigs with bovine GH gene are'Teported to gain weight 23 per cent faster and to have an 18 per cent better feed efficiency. There has also been a significant reduction in the backfat thickness which means that the pork will be leaner. But transgenic pigs also suffer from ill health. Thus incorporation of the growth hormone genes has not been a rosy story throughout. Increasing the circulating GH concen-tration does not always lead to improved growth, at least not in chicken where circulating GH concentrations are invariably inversely related to growth. Inter-species transfer of GH genes has yielded variable results in livestock but good results have been recorded for fish. Initially, aquaculturists tried to feed fish with synthetic growth hormones. In trials these fish were found to gain weight up to twice as fast as normal. But the large scale production of the purified hormone was expensive and the fish did not always absorb it efficiently.

60 HORMONE HARMONY

Thomas Chen: revolutionizing aquaculture

Besides public wariness about cows injected with bovine growth hormone had convinced many scientists that there was no future in artificial hormone-fed fish. So aquaculturists moved to the next step.

They transferred into the fish cloned genes that boost the production of natural GH. A cloned gene is essentially the body's own gene. It was not a gene that has been borrowed from some other species. But, since multiple copies of the same gene are incorporated it makes a difference in the amount of circulating hormones. It is like having many times the recommended dosage of a drug. Thomas Chen and his colleagues at the University of Maryland's Center for Marine Biotechnology at Baltimore pioneered the technology in carp and rainbow trout. They injected a cloned GH gene into fish embryos a few hours after fertilization. About half the embryos survived the injection. An average of just under half of those

IN HARNESS 61

integrated the new gene into their DNA. The transgenic fish and their offspring both grew from 20 per cent to 46 per cent faster than ordinary specimens.

Chen and his colleagues are now trying to extend this growth enhancing technology to other commercial species, such as shellfish. Doing so means finding new techniques for getting foreign DNA into embryos. Shellfish embryos are very fragile and microinjection is too coarse a method for them.

Chen and two other scientists, Dennis Powers of Stanford University and Koji Iroue of Nippon Suisan Kaisha Ltd. (Ja-pan) are examining gentler means of getting foreign DNA into the embryos. Among the methods being tried is electropora-tion in which a brief electrical prtjlse makes the membrane of the embryo temporarily permeable. This allows the 'foreign gene' to cross into the nucleus where the chromosome cargo of the cell is present. Experiments boosting growth in animals have shown that growth control is a complicated process governed by a number of hormones acting on a background of genes that are yet unknown. The hormones that are rate-limiting for growth are not necessarily the same in every species.

Plants too secrete hormones which can be used to create plants in a test-tube. Plant hormones, like human hormones are also effective in minute concentrations at sites away from the tissues in which they are formed. They assist growth, flowering and fruition. Auxins, gibberellins, cytokinins and ethylene are typical examples of plant hormones. While aux-ins and gibberellins assist root and shoot elongation, ethylene helps in the ripening of fruits. Auxins play an additional role in seed germination and seedling growth.

Reproduction in plants begins with the seed which germi-nates and grows into a full-fledged plant. In multicellular plants, cells undergo many changes before they develop from a newly formed cell into a functional mature one. In the initial stages of growth, rapid cell division occurs leading to a cluster

62 HORMONE HARMONY

Roots, stems or fruits?

of identical generalized cells. Cell maturation involves devel-opment and specialization. Cells thus modify their appear-ance and physiological composition to carry out their tasks efficiently. Once tasks are assigned, only cells in certain specific apical areas such as root and stem tips still retain their ability to divide. Other tissues do not. These tissues, however, can be made to divide by manipulating the external milieu. Thus bits of shoots will develop roots at their lower ends and readily give rise to copies of the parent plant with a little careful coaxing. This careful coaxing is done with the help of plant hormones together with other nutrients, in a process called tissue culture.

B <3 A

PvtCoim here pur COIN HEWr por coin hei e

IN HARNESS 63

Specialization cannot be reversed

Plant tissues, from any part of the plant are grown on agar. Agar is a gelatinous substance obtained from red algae. It is a good culture medium for growing bacteria or plants in the laboratory. The tissues form a mass of undifferentiated cells called callus—a compact mass of small similar cells, where no part of the tree (stem, leaf or fruit) can be distinguished. When these cells are added to a medium containing nutrients, they begin to differentiate. Plant hormones such as auxins and cytokinins are added to stimulate the cells to divide.

STEfA SCHOOL-

LEAF SCHOOL.

ROOT SCHOOL

64 HORMONE HARMONY

A correct balance of hormones and chemicals can control the pathway of the growing tissue. Formation of roots is stimulated by auxins and shoots, by cytokinins.

Growing plants in this manner serves a dual purpose. The new plants obtained this way are identical to the parent plant. Thus large populations of plants with premium qualities can be created from specific plants having distinctive charac-teristics such as increased vigour, higher yields and better health status. These can then be multiplied all around the year within the laboratory and an unlimited number of superior plants produced.

The productive power of hormones has been scrutinized closely and scientists have indeed managed to manipulate it to human advantage.

he highly intricate and unimaginably complex human body works perfectly most of the time. However, the system may go haywire at times. A mess-up of the

body's chemical regulators can have disastrous conse-quences.

The most common and conspicuous of endocrine disor-ders is goitre, an ailment known from early times. It is men-tioned in the Atharva Veda in 1500 BC and even earlier in Ayurveda of Sushruta of about 1400 BC. Goitre is the enlarge-ment of the thyroid gland as a result of lack of iodine in the diet. Iodine is the essential raw material for the manufacture of thyroxine. Goitre is common in mountainous regions where soil lacks iodine. Addition of minute quantities of iodine in salt

Off balance

or drinking water helps prevention of the disease.

This however is not the only way thyroid gland malfunc-tions. Thyroid deficiency before birth leads to a condition called cretinism. Thyroxine is necessary for the development of the brain. A cretin is usually born a normal baby presumably because he has been able to use thyroxine from his mother's blood. After birth, his physical and mental developments are retarded. The characteristic appearance of the child includes coarse hair and skin, protruding tongue and pot belly. If treatment is begun within a few weeks of birth, the cretin may grow normally. Unfortunately, cretinism is difficult to recog-nize in the first few months and if treatment is delayed the patient may not quite catch up with normal children.

66 HORMONE HARMONY

Goitre prone areas

In yet another disorder of the thyroid, called Hashimoto's disease, the raw material constituents of the thyroid hormone escape into the blood. This provokes an antibody reaction, a protective reaction against foreign invaders. Part of this reac-tion is the invasion of the thyroid by white blood cells, which strangle the normal cells and cause a deficiency of thyroxine. This itself causes anaemia and consequently loss of energy and appetite, low body temperature, dry and puffy skin and dull mind.

On the other hand, over-activity of the thyroid causes Grave's disease. The patient becomes irritable and restless, there is increased metabolism, the heart is overactive and its disturbed rhythm may cause heart failure. Grave's disease is not any fault of the thyroid itself, but an abnormal stimulation of the thyroid. This stimulus is due to an excess of the normal thyroid-stimulating hormone from the pituitary.

OFF BALANCE 67

Cretinous infant before and after thyroid treatment

The abnormal functioning of the pituitary can often have startling results. The two extremes of human stature are gigantism and dwarfism as a result of too much or too little production of the growth hormone. An oversupply of pituitary

Grave's disease

68 HORMONE HARMONY

Apologies to Lewis Carroll

OFF BALANCE 69

growth hormone — hyperpituitarism, can result in two condi-tions: if it occurs during the growing years, the result is gigantism, which produces an individual of enormous propor-tions. In cases of this sort, excessive growth is usually con-centrated chiefly in the region of the head and lower extremities.

When it strikes a person whose overall growth has been completed, hyperpituitarism causes acromegaly. The chief symptom of this disease is the enlargement of various parts of the body, most notably the head, hands and feet accom-panied by lethargy and severe headaches. The right treat-ment can be by two methods. Surgical removal of the pituitary or the use of radiation to slow its activity.

The hyperactivity of one of the other essential endocrine glands which can cause havoc is the adrenals. The over-growth of the adrenal cortex causes excessive secretion of Cortisols. Cortisols cause the formation of fats and carbohy-drates at the expense of protein. There is thus a loss of muscle and increase of fat. The fat has a characteristic distribution over the trunk but not the limbs. The neck is heavy and face rounded. Bones and skin are both weakened. This condition is called Cushing's syndrome.

Conn's syndrome, on the other hand is caused by excess of aldosterone. This causes excessive fluid retention in the body. An imbalance in the ions in the body fluids impairs muscle function.

The third condition is a rare one, referred to as the adreno-genital syndrome. Here sex hormones are secreted in great excess and causes precocious sexual development with a tendency in either sex to develop male characteristics.

In contrast, the deficiency of the adrenals causes Ad-disons' disease. The disease was first described by Thomas Addison (1793-1860) in 1855, and is due to the failure of the cortical hormones. The symptoms include weakness, slow circulation and a weakened heart. Only about four people in

70 HORMONE HARMONY

Cushing's syndrome (left), after removal of adrenals (right)

a million develop Addison's disease today, and in three of them no cause can be found, their adrenals simply stop working.

Diabetes is a disease caused by the malfunctioning of the hormone insulin. The term diabetes refers to a whole group of diseases, all characterized by unusual thirst, and in conse-quence, an unusual output of urine. It is one of the few diseases to which the female is more subject than the male. Women diabetics outnumber men four to three. Ordinarily, the body stores most of its glucose in the liver in the form of glycogen keeping only a small quantity of glucose in the bloodstream to serve the immediate energy needs of the cell. Maintaining this level of glucose is insulin's job. In diabetics, glucose is not stored as glycogen. Instead, it accumulates in the blood. The excess glucose wastes away in the urine. Thus, diabetics constantly feel weak and tired.

Deficiency of insulin may be absolute, where pancreas do not produce sufficient insulin, or the patient may be unable to utilize insulin properly. These patients need injections of insulin to stay healthy.

OFF BALANCE 71

On the other hand, excess of insulin causes a condition called hypoglycemia. Increased levels of insulin remove glu-cose from the blood and store it away in the form of glycogen. So much so, that the brain, which has no reserve of glucose and relies on the constant supply from the blood is impaired. In excessive lowering of blood sugar, the patient may even lose consciousness. The less severe symptoms include un-easiness, hunger and sweating.

Disturbances in hormonal regulation cause abnormal dis-tribution of hair. These abnormalities are not very conspicu-ous in men and baldness is probably the only serious problem. However, in women these defects are of a more serious nature. The appearance of facial hair or beard in women is probably the most embarrassing. This is often due to the development of androgen producing tumours in the

Carbon di oxide

0 Fructose

**** Starch

+A Lactose

Enzymes

To lungs

Adrenalin, Cortisone raise glucose levels

Water

A. Glucose

« Galactose

•a Sucrose

Alimentary canal

Glucose stored as Blood stream glycogen

Protein made Into glucose

Cell

Excess glucose stored as fat

Glucose utilization by the body

Insulin reduces alucose levels

1Muscles

lOxygen

72 HORMONE HARMONY

adrenal gland. In older women, when the men-strual cycle comes to a stop, there are drastic variations in hormonal lev-els. The adrenals, at this time may also produce an-drogens which cause the appearance of a beard.

At times, women suffer-ing from breast cancer are treated with the male hor-mone, testosterone. This too causes increase in fa-cial hair. There has been at least one documented case where facial hair an-swered a maiden's prayer. Wilgefort, a princess of Portugal was about to be married to a suitor she did not love. She prayed to be

made unattractive. By a quirk of fate she developed an adrenal tumour which led to frontal baldness and growth of a beard. The wedding, predictably enough, did not take place and she devoted her life to religion. After death she was declared a saint and an effigy was installed in Westminister Abbey.

Effigy of St. Wilgefort

Lastly, there are increasing incidences of women suffering from uterine or ovarian cysts. This too, has been attributed to hormonal imbalances. While, there is no evidence yet that oestrogen perse causes cancer, the use of birth-control pills which are nothing but hormones, may be the cause of these cancers.

Scientists are working out appropriate measures to deal with patients suffering from hormones in excess. But, for

OFF BALANCE 73

those ailing from hormone-deficiency diseases, there seems to be tremendous hope. Indeed, the body's chemical regula-tors are now being churned out in factories outside the body and injected into the body in required amounts.

housands of years ago, the Chinese used the thyroid glands of animals to treat patients with thyroid defi-ciency. Infact, throughout history extracts of various

organs have been popular ingredients of medicines. The use of extracts to treat various malfunctions of the glands from which they originated, a procedure known as hormone re-placement therapy has indeed evolved over the years. The insulin injection that a diabetic receives today, to keep alive, is very different from what it would have been thousands of years ago. The advent of molecular biology, has revolution-ized the field of hormone therapy.

The British physiologist, G.R. Murray may have received history's accolade as the first man to use hormone replace-

Corporate venture

ment therapy but the credit for refining glandular extracts for safe administration, goes to Dr. Maurice Raben, a British physician.

In 1956, Raben began treatment of dwarfs with injections of the human growth hormone. Working in his laboratory at the Tufts New England Medical Center, Raben and his staff extracted the hormone from human pituitary glands obtained from the US and 15 other countries. They used an elaborate process called 'glacial acetic acid extraction method'. About four milligrams of growth hormone were derived from each gland. For a five-year treatment, for ten children, about 2,600 milligrams was needed, an amount that called for the proc-essing of 650 pituitaries. The supply, obviously was lamenta-

CORPORATE VENTURE 75

Amino acids 1 - alanine 2 • arginine 3 - asparagine 4 • aspartic acid 5 • cysteine 6 - glulamine 7 - glutamic acid 8 - glycine 9 • histidine 10 • isoleucine

C.H. Li dec iphe red the s t ruc tu re of t he g rowth h o r m o n e

bly low since pituitary could be obtained only from glands removed at death.

Similarly treatment of diabetes, by extracting insulin from human pancreas too hit a snag. Instead of extracting the hormones from dead humans, scientists thought it a better idea to isolate these hormones from animal sources. Purifi-cation techniques were standardized. Large scale produc-tion, especially of insulin from pancreas of pig and cattle was

11 • leucine 12 • lysine 13 - methionine 14 • phenylalanine 15 - proline 16 • serine 17 - threonine 18 - tryptophan 19 • tyrosine

20 • valine

76 HORMONE HARMONY

Molecular structure of insulin

adopted. However, while insulin performs the same function in pig and cattle, its structure differs from that of human insulin. Thus, the moment it was injected into humans, the alert defence cells of the body identified the injected insulin as alien and attacked and destroyed it. Thus animal extracts did not serve the purpose.

Simultaneous to these efforts, scientists were attempting to decipher the molecular structure of these hormones. The detailed structure of the human growth hormone was deci-phered by Professor C.H. Li, a Chinese — American Chemist. This chain like protein is composed of no less than 187 different amino acids.

The structure of insulin was elaborated by Frederick Sanger in 1953. It is made up of 51 amino acids in two chains linked up by disulphide bridges. Insulin was the first protein molecule to be deciphered and synthesized in the laboratory. Even though the chemical structure of some of these essen-tial hormones is now known their chemical synthesis in the factory is not cost effective.

Recombinant DNA technology promises a bright future for production of many hormones that are otherwise difficult to synthesize in the laboratory or require millions of glands

A-Choin

B-Choin

-COOH

-COOH

NH2

NH2


which produce the hormones, for extraction. Insulin and growth hormones are among the first ones to be produced by genetic engineering methods.

During the summer of 1978 two groups of researchers in USA, one in Massachusetts and one in California, were working feverishly to produce human insulin in the laboratory using recombinant DNA techniques. They hoped to coax a special laboratory strain of the bacterium Escherichia coli, commonly found in the intestines of man, to produce human insulin after suitably modifying it by the then new recombinant DNA technique.

DNA the substance of which genes are composed, con-tains the chemical record in which all genetic information is encoded. Recombinant DNA, popularly called gene slicing, is the process of taking pieces of the DNA of one organism and combining it with the DNA of another organism to produce a third; in this case it would involve taking the genetic material that codes for the production of insulin and joining it with the genetic material of bacteria. The bacteria carrying the newly incorporated gene could then make insulin. When the bacte-ria reproduced, more and more insulin would be manufac-tured. The bacteria thus would become virtually an insulin factory.

The same year scientists at Harvard Biological Laborato-ries, Cambridge and at Joslin Diabetes Foundation, Boston, succeeded in inducting bacteria to make rat proinsulin, the immediate precursor of rat insulin. But human insulin still eluded the scientists. By September 1978, Genetech Inc., and the City of Hope National Centre both in USA announced that they had indeed produced human insulin. This was the first time that recombinant DNA research had led to practical human applications. To produce human insulin in bacteria, researchers used E. coli as the insulin producing factory.

The common bacterium E. coli contains about 10,000 genes arrayed on a single circular DNA molecule. As the

78 HORMONE HARMONY

"A" chain genetic code "B" chain genetic code

DNA sequence

Plasmid

E.coli

Protein synthesis

Separation

Purification

insulin molecule

Turning E.coli into an insulin factory

bacterium grows, the DNA is duplicated so that each daughter cell, following cell division, receives a complete set of genes identical to those of its parent. In addition, the bacterium also harbours smaller circular DNA molecules called plasmids. These are replicated independently of the main DNA. They may contain as few as three or four genes or as many as a

"B" chain "A" chain "A"and "B" chains combined

S S I l S S


hundred. The plasmids serve as the vectors or carrier agents for recombinant DNA. To construct recombinant DNA mole-cules, the plasmid DNA vector, in this case called PBR322, is cut with a restriction endonuclease, an enzyme that recog-nizes particular sequences of nucleotides, the molecular building blocks of DNA.

The genes for the two amino acid chains of insulin are then attached to the vector plasmid. This newly constructed hybrid plasmid is introduced into E. coli. When the plasmid replicates in E. coli, so does its DNA passenger carrying the insulin gene. In the production of the hormone, researchers com-bined synthetic rather than natural genes for each of the two amino acid chains of insulin with the plasmid. Once inside the bacteria the genes were 'switched on' translating the code to produce the 'A' and 'B' protein chains of insulin. This gene combination could now churn out the insulin molecule. The separate chains were then joined to construct complete insu-lin molecules.

The production of hormones this way enables large scale production and high yields of the hormone. However, this method too, is not problem free. The clue to accurate activity of the hormone lies not only on the precise attachment of the amino acids, but also on the correct folding of the protein molecule. These problems have now been ironed out and insulin and growth hormone are now being produced in large quantities.

The most potent of substances synthesized by the body, hormones are crucial to life itself. Their precise and accurate functioning determines the internal rhythm of our body and our ability to stay in tune with the world.

Algae: A major division of the plant kingdom. Algae grow in damp conditions or in water. The plant body called a thallus may be made up of one or more cells but lacks detailed internal structure.

Bile: An alkaline fluid that helps in digestion and absorption of fat.

Blood coagulation: The solidification of blood which results in a clot. It is also called blood clotting. It is brought about by a series of reactions initiated by the breaking up of special blood cells called platelets.

Cloned: A clone is a group of individuals propagated from a single parent. The members of a clone have the same genetic makeup.

Catalyst: Any substance that affects the rate of a chemical reaction without itself being consumed in the course of the reaction. Cata-lysts are usually used to enhance the reaction rate. If used to retard the rate of a reaction, it is called a negative catalyst.

Ions: An electrically charged atom or group of atoms.

Inflammation: Local response to injury, infection or irritation. It is characterized by redness, swelling, heat and pain.

Lactation: The secretion of milk by female mammals.

Larva : The juvenile form in which some animals hatch out from eggs. Their mode of feeding is different from that of adults.

Metabolism: Biochemical processes occurring within an organism. It involves breaking down of organic compounds (catabolism) with liberation of energy and also building up of organic compounds (anabolism) using energy liberated by catabolism.

Pupa: State between larva and adult of certain insects in which locomotion and feeding cease but great developmental changes occur.

VISTAS IN BIOTECHNOLOGY

SUPERB synchronization characterizes the interplay of hor-mones in the body. The chemical mes-sengers enter and exit, advance and retreat like actors in a well choreo-graphed play. However, here, a missed cue might have disastrous conse-quences.

This lucidly written, profusely illus-trated book highlights the role of biotechnology in the production of hor-mones for therapeutic use. It also de-tails the manipulation of hormones for human profit and is a tribute to the finely tuned chemical orchestration that leads to hormone harmony.

About the Author After obtaining Ph.D. degree in 1968 from Panjab Uni-

versity, Chandigarh, Dr P.D. Gupta did his post doctoral training (1969-1970) at the University of Alberta, Canada He served as a Research Associate at the University of Pennsylvania. Returning to India, he worked at the All In-dia Institute of Medical Sciences, New Delhi. He went to the University of Alberta again in 1977 to establish a labo-ratory for neurotransmitter receptor work. After a short stay at Mahidol University, Bangkok, Thailand, Dr Gupta joined the Centre for Cellular & Molecular Biology, Hydera-bad, where he is still working. He has worked as visiting scientist at the Imperial Cancer Research Fund Labora-tory, London, the National Institute of Physiological Sci-ences, Okazaki, Japan, Tottori University, Yonago, Japan, and the Institute of Organic Chemistry & Biochemistry, Pra-gue, Czechoslovakia. He also visited many laboratories in Germany on a DAAD fellowship.

Dr Gupta is a Fellow of the Royal Microscopical Soci-ety, England and the National Academy of Sciences, In-dia. He is the Secretary of the Indian Society of Cell Biology.

Dr Gupta has published about 80 research papers. Hormone Harmony is his first popular science book.

ISBN : 8 1 - 7 2 3 6 - 0 6 5 - 7

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