COMPARATIVE ULTRASTRUCTURAL STUDY BETWEEN YOUNG
AND ADULT FORMS OP TRYPANOSOMA LEWISI
APPROVED»
It Ma j o^Profess or
Qfcgsu ii. Q J U Minor Professor
\ \J r _ _
Director of the Department of Biology
Dean of the Graduate School <
iV
Abdul-Salam, Jasem VI., Comparative Ultras true tural
Study Between Young and Adult Forms of Trypanosoma Lewisi.
Master of Science (Biology), August, 1973> 57 pp., 20 illus-
trations, bibliography, 51 titles.
The purpose of this study was to examine the ultra-
structure of both young (dividing form) and adult (stationary
form) of Trypanosoma lewisi. Changes observed between the
two forms of the organism were related directly to data ob-
tained from previous comparative biochemical studies conducted
on these forms of Trypanosoma lewisi. The overall subcellular
arrangement of both young and adult forms shares many char-
acteristics with other members of the genus Trypanosoma
which already have been studied. Definite changes in the
size of the nucleolus, mitochondria, arrangement of the
granular reticulum and Golgi complex were observed between
the two forms. The presence of a large nucleolus, vesicular
Golgi complex, conspicuous granular reticulum, and abundance
of smooth-walled vesicles throughout the cytoplasm of young
trypar.osorr.es indicated high secretory activity at this stage
of growth. Existence of long mitochondria in adult trypan-
osomes was a characteristic feature absent in young
trypanosomes. High respiratory quotients reported in adult
trypanosomes could be associated with the presence of large
and highly developed mitochondria. A marked increase in
the number of inclusion bodies located in the posterior end
of adult trypanosoraes was observed. The nature of these
bodies is still obscure. Previous ultrastruetural studies
of flagellae of several members of the genus Trypanosoma
indicated termination of central tubulars of the axoneme
in the kinetosomal region. This study clearly showed the
penetration of central tubulars of the axoneme deep in the
cytoplasmic matrix, surpassing both kinetosomal plates.
COMPARATIVE ULTRA5TRUCTURAL STUDY BETWEEN YOUNG
AND ADULT FORMS OF TRYPANOSOMA LEWISI
THESIS
Presented to the Graduate Council of the
North Texas State University in Partial
Fulfillments of the Requirements
For the Degree of
MASTER OF SCIENCE
3y
Jasem M. Abdul-Salam, B.A.
Denton, Texas
August, 1973
TABLE OF CONTENTS
Page
LIST OF ILLUSTRATIONS ii
INTRODUCTION ' 1
MATERIALS AND METHODS 9
RESULTS . 11
DISCUSSION 48
BIBLIOGRAPHY 53
LIST OP ILLUSTRATIONS
Figure Page
1.1 Light Microscopy, Trypanosoma lewisi, young form, Giernsa stained . . . . 19
1.2 Electron Photomicrograph, Trypanosoma lewisi, young form, overall view of the organism . 19
2.1 Light Microscopy, Trypanosoma lewisi, adult form, Giemsa stained . . . . . . 21
2.2 Electron Photomicrograph, Trypanosoma lewisi, overall view of the organism . . . . . . . 21
3. Electron Photomicrograph, Trypanosoma lewisi, young form, the anterior end of the organism . . . 23
4. Electron Photomicrograph. Trypanosoma lewisi, adult form, the anterior end of the" organism 23
5. Electron Photomicrograph, Trypanosoma lewisi, adult form, the flagellum and the sub-pellicular microtubular 25
6. Electron Photomicrograph, Trypanosoma lewisi, young form, flagellum-associated reticulum and sub-peilicular microtubulars 25
7. Electron Photomicrograph, Trypanosoma lewisi, young form, intra-flagellar structure . . 25
8. Electron Photomicrograph, Trypanosoma lewisi, young form, granular reticulum system ." . 27
9. Electron Photomicrograph, Trypanosoma lewisi, adult form, agranular reticulum system, sub-peilicular microtubulars, and mito-chondria 29
10. Electron Photomicrographt Trypanosoma lewisi, your^g form* bvsrall VIgV of organism . . . . 31
11. Electron Photomicrograph, Trypanosoma lewisi. adult form, agranular reticulum system with sac of secretion . . . . . . . . . . . 33
12. Electron Photomicrograph, Trypanosoma lewisi, . young form, anterior part of the organism during division 35
13. Electron Photomicrograph Trypanosoma lewisi, adult form, mitochondria and agranular reticulum . . . . . . . . . 37
14-. Electron Photomicrograph, Trypanosoma lewisi, young form, granular reticulum in the nucleus vicinity . . . . . . . . . 39
15. Electron Photomicrograph, Trypanosoma lewisi, adult form, posterior end of the organism. . 41
16. Electron Photomicrograph, Trypanosoma lewisi, adult form, mitochondria and "kinetoplast . . 43
17. Electron Photomicrograph, Trypanosoma lewisi, adult form, vacuole surrounded by agran-ular reticulum . . . . . . ^3
18. Electron Photomicrography, Trypanosoma lewisi, adult form, posterior end of the organism. . kj
19• Electron Photomicrograph, Trypanosoma lewisi, young form, posterior end of the organism. . 45
20. Electron Photomicrograph, Trypanosoma lewisi, young form, high magnification of the kinetoplast and flagellum emergence from the cell . 47
INTRODUCTION
Trypanosoma lewisi is a typical member of the genus
Trypanosoma. The name of the genus was proposed by Gruby
•in 18^3. During the long history of this genus there have
been many attempts to subdivide it into subgenera or create
new genera. This conflict in classification was the result
of the discovery of new species and development of new
methods in the determination of species. Attempts to add
new genera did not succeed because of the great similarity
in the morphology of all species under study, although they
were host-specific parasites. Pleomorphism throughout the
life cycle of these parasites introduced another obstacle
for taxonomists.
After a great deal of controversy Hoare (20) initiated
a new classification scheme, which is recognized by most of
the workers with this group of parasites. The new classifi-
cation is based on the division of the genus Trypanosoma
into two major divisions or sections. Some of the criteria
upon which this classification is based are phylogenetic
consideration and conventional diagnostic characters such
as morphology, method of reproduction in the vertebrate host,
the position and size of the kinetoplast, and biochemical
data. Section A, or Stercoraria, the name of this section
indicates the development of the organism in the vector is
completed in the posterior parte cf the digestive system, and
transmission is accomplished by fecal contamination. The
Stercoraria are divided into four subgenera r Metatrypanum,
Schizotrypanum, Endotrypanum, and Herpetosom. Trypanosoma
lewisi is classified under the subgenus Herpetosom, Morpho-
logical characteristics shared by the Sterocoraria are -
(1) presence of free flagellumj (2) large and not terminal
kinetoplast j (3) posterior end of the body is pointed. Sec-
tion B or Salivaria also is divided into four subgenera t
Dultonella, Nannomonas, Pycnomonos, and Trypanzoon, which
originally included "lewisi." The development of Salivaria
members is completed in the anterior parts of the vector's
digestive system. The parasite is transmitted to the host
by direct inoculation. Species under the Salivaria section
share these morphological characteristics t (1) free flagellura
not always present? (2) the kinetoplast is terminal or sub-
terminal; (3) the posterior end of the body is usually blunt.
It is important to mention that most of the pathogenic try-
panosomes are placed under the Salivaria section, such as
the famous African species, Trypanosoma gambiense and Trypan-
osoma rhodesiense.
Because of the cosmopolitan distribution of Trypanosoma
lewisi and its relative ease of maintenance in the laboratory,
it has teen the subject of numerous studies all over the
world, and especially in the United States. The natural life
cycle of Trypanoscnga lewis! is divided between '/..any species
of wild rats of the genus Rattus as the vertebrate host and
the common rat flea Fasciatus nosophyllus as the invertebrate
vector. The rat acquires the infection by ingesting contam-
inated. flea feces. After several hours the parasite appears
in the circulatory system as an extracellular parasite. The
first week of the infection marks a rapid reproduction by
longitudinal and multiple fission. Reproduction terminates
after the first week, and the growth curve reaches a plateau
for three days before the number of organisms decreases
sharply. It takes from ten days to several months for organ-
isms to disappear completely from the blood, leaving the host
immune to another infection. The second cycle of reproduc-
tion lasts about fiye days in the vector's digestive system.
The flea acquires the infection by feeding on the blood of
an infected rat. Within the epitheliae cells lining the
stomach of the vector, the parasite is transformed from the
trypanosomal stage to the crithidial stage during the repro-
duction. Crithidial forms migrate to the rectum of the flea,
where they become attached to the highly folded tissues. In
the rectum the crithidia transforms again to the trypanosomal
form, while undergoing longitudinal fission. The infective
forms, which are better known as metacyclic forms, are passed
out with the flea's feces. The parasite life cycle is
5; Hr'
continued if the contaminated fecal materials are ingested
by the vertebrate host.
As a typical member of the genus Trypanosoma, Trypanosoma
lewisi share the following morphological features with other
members of the genusi (1) a body flattened and elongated in
the trypanosomal stage and round in the crithidial stage?
(2) the nucleus is round or oval, found in the anterior part
of the body in the trypanosomal stage and in the middle of
the body in the crithidial stage? (3) a spherical, rod, or
disc-shaped kinetoplast located posterior to the nucleus in
the trypanosomal stage and anterior to the nucleus in the
crithidial stage; (^) a flageHum arising from the blepharo-
plast, which is located anterior to the kinetoplast? (5) in
the trypanosomal stage the flagellum runs along the border
of the cell membrane, forming an undulating membrane, and a
free anterior flagellum. Morphologically there are two dis-
tinct forms of the parasite in the blood stream of the host.
The young or dividing form is found from the first day of the
infection to the sixth day, while the adult form or stationary
form is found from the seventh day until the end of the in-
fection (^2). The young trypanosomes exhibit a variety of
sizes ranging from 10 to U0 microns, and are usually fat and
spindle-shaped. The adult forms are uniform in size 28 to
^0 microns, and are long and slender in shape.
In 192^, Taliaferro (42) described the immunological
reaction of a rat infevIwith Tv-;yT^nosoma lewj.si* A series
of immunological studies was conducted by the same author
( 3» -6), elucidating factors involved .in the mech-
anism and naming the reproduction-inhibitor ablastin. .Recent
immunological investigations by D'Alesandro (8, 9) indicate •
the presence of three separate stages associated with spe-
cific factors that help in the defense mechanism. First, a
reproduction-inhibiting antibody (ablastin)r second, a try-
panocidal antibody detected during the first crisis? and
third, a second trypanocidal antibody which terminates the
infection. Changes in the antigenic structures were divided
between the young and adult forms of the parasite (11, 12).
Numerous studies have been published on the biochemical
activity and composition of Trypanosoma lewisi throughout the
infection. Moulder (19^8), Ryley (1951)» Thurston (1938), and
Lincicome and Warsi (1966) are some of the pioneer investi-
gators in this area. Recently, Hibbard and Dusanic (18, 19)
conducted a very extensive study on the metabolism of Trypan-
osoma lewisi, conforming to most of the data obtained by the
previous investigators. Oxygen utilization was found to be O
52 aI and 100 jil Og consumed/10 trypanosomes per hour for
young and adult forms, respectively. The respiration quo-
tients were found to be 0.96 and 1.01 for young and adult
forms, respectively. The above data show 00/glucose ratios
of young trypanosomes significantly lower than the adult
forms. A comparative study between mitochondrial enzymes
of young and adult.forms of Trypanosoma lewisi (13) indi-
cates a significant difference in the level of isocitrate
dehydrogenases and ATP synthesizing systems.
Talioferro and Piz,zi, in i960 (^7), demonstrated the
rate of protein synthesis in Trypanosoma lewisi, Trypano-
soma equiperdum. and Trypanosoma cruzi, using labeled
precursors. The results indicate a high rate of incorpora-
tion by young forms of Trypanosoma lewisi, while the rate
is lower in the adult form. Amino acids analysis of
different species of trypanosomes by Williamson and Desowtiz
(1961) indicated a similarity between amino acids found in
these organisms, and other protein such as bovine albumin.
Data from the same experiment showed that Trypanosoma lewisi
contained only 0. -3 percent free amino acid while other
trypanosomes contained 2-3 percent free amino acid. Finally,
a quantitative and qualitative study on Trypanosoma lewisi
biochemical composition was conducted by Hibbard and Dusanic
(19)• Total amounts of protein for young and adult forms
were found to be 23.0 XIO"^ and 85.3 XIO"" g protein per
trypanosomes. The authors explained that the increase in the
percentage of protein per unit of dry weight during the in-
fection was due to decrease in the total dry weight of the
trypanosome rather than increase in protein synthesis. RNA
content was shown to be 12.59 X10 pg per young trypanosome,
-7
and 2.53 X10 p.g per adu.lt trypanosome. The above data in-
dicate a decrease in nucleic acid and protein synthesis in
the adult form. Similar results were obtained in biochemical
studies conducted on Trypanosoma lewisi (14).
Recently, electron microscopy has been utilized to reveal
fine structures of various members of Trypanosomatidae, Try-
panosoma cruzi, Trypanosoma lewisi. Trypanosoma equiperdum.
Trypanosoma conorrhini, Trypanosoma mega, Trypanosoma congo-
lense, Trypanosoma brucei, Trypanosoma gambiense, Trypanosoma
raiae, and Trypanosoma avium are some of the Trypanosomatidae
which have been subjects of numerous ultrastrueture studies
(1, 2, 3, 21, 29, 30, 35, 37, 38, 39, 40, 41, 49, 50, 51).
The study of the whole-mount specimens of Trypanosoma lewisi
was conducted by Kleinschmidt and Kinder in 1950 (22), just
a few years after the invention of this technique. In 1964,
Judge and Anderson published a brief study on the ultrastrue-
ture of thin sections of adult forms of Trypanosoma lewisi
(21). Later, in 19^5, Anderson and Ellis published a more
detailed study oh the adult form> devoted extensively to the
structure of the flags Hum, microtubules, and the kinetoplast
(2 ) .
The objective of this study is to investigate the ultra-
structure of young and adult forms of Trypanosoma lewisi.
The comparative .investigations will be based on previous
8
physiological, biochemical, and immunological differences
"that have already bser; -nstfiDi,'!.b§'tween "the "two forms#
Emphasis will be placed on the shape and size of the nucleus
and the nucleolus, changes in the endoplasmic reticulum,
Golgi complex, and inclusion bodies.
MATERIALS AND METHODS
Trypanosoma lewisi was maintained in the laboratory by-
weekly intraperitonial injection of uninfected white rats
with three drops of blood from seven-days-infected rat mixed
with three ml of saline solution. Infected rats were bled
by cardiac puncture three and ten days after the infection
to collect young and adult forms of the parasite. Organisms
were separated from red blood cells by differential centrifu-
gation methods.
The blood was centrifuged at 500 r.p.m. for five minutes
to isolate the organisms in the supernatant. The supernatant
was centrifuged again at 3000 r.p.m. for 30 minutes at 4° C.
After the second centrifugation procedure the organisms were
concentrated in a white pellet. During the isolation pro-
cedure the organisms were kept in an ice-bath.
Preparation for electron microscopy studies starts with
fixing the organisms in cold 1.5 percent solution of osmium
tetraoxide in vernal acetate buffer (pH 7.^-7«5) for* thirty
minutes at 4° C (3*0 • The fixative was aspirated and the
organisms were washed with vernal acetate buffer. The buffer
was removed and organisms were dehydrated in an ethanol
series and infiltrated with propylene oxide before embedding
in Spone 812. Sections were cut with a Sorval MT-2
10
ultramicrotome using glass knives. Sections were collected
on copper grids, and stained for three minutes with uranyl
acetate and five minutes with lead citrate. Sections were
observed by RCA EMU-3& electron microscope.
RESULTS
Examination by light microscopy reveals the external
morphology of young and adult forms of Trypanosoma lewisi
(Figures 1.1 and 2.1). Both forms of the organism are
spindle-shaped with a dark nucleus in the middle of the body
and a kinetoplast located in the posterior end of the organ-
ism. The flagellum emerges from the posterior end of the
body forming an undulating membrane by adhering to the pel-
licle as it proceeds to the anterior part of the body. The
organism's movement in the blood of the host is achieved by
rapid vibration of the flagellum and undulating movement
along the body, under the light microscope young and adult
forms of Trypanosoma lewisi are easily characterized on the
basis of external morphological differences. Young trypano-
somes exhibit a variety of shapes and sizes, mostly broad,
ranging from 15 to 25 microns in length. On the other hand,
adult trypanosomes are elongate, slender and uniform in size,
approximately 28 microns long.
In general, the ultrastrueture of both forms of Trypano-
soma lewisi have many basic characteristics shared with all
other members of genus Trypanosoma which have been studied
so far. There are several structural differences observed
between the two forms of Trypanosoma lewisi which could be
11
12
attributed to the growth stage of the trypanosome and possible
changes evoked by the host defense mechanisms throughout the
infection course. Those differences observed between the
two forms of Trypanosoma lewisi will be discussed in some
detail as we proceed in surveying the general ultrastrueture
of the organism.
Pellicle.--A unit membrane consisting of three layers
of membranous structure covers both the body and the flagellum
of the trypanosome (Figures 5 and 6). In a cross-section the
three membranous layers of the pellicle are seen as two dark
layers, osmiophillic in nature, with a low density layer in
between. Thin osmiophillic fibers cover the pellicle surface
of the flagellum and the body (Figure 5). This surface coat
is not well defined as is the case in other species of trypan-
osome s (H-9, 50).
Sub-pellicular microtubules. -—Beneath the pellicle of
the trypanosome lie highly organized microtubules arranged
in parallel lines extending longitudinally along the entire
length of the body (Figures 1, 2, 5, 6, and 9). This is a
unique feature observed in all other hemaflageHates. The
resolution of the electron micrograph does not allow the
examination of micrctubular sub-units, which are known to be
made up of ten to twelve tubules (2). The exact function of
sub-pellicular microtubules is not known, although several
proposals were adapted, such as contraction, coordination,
13
and support of the organism. At the site of the attachment
of the flagellum to the pellicle iour microtubules form a
unique association with cytoplasmic granular reticulum (Fig-
ures 5 and 6). This specialized organelle has been found
also in Trypanosoma vivax, Trypanosoma cruzi, Trypanosoma
brucei, and Trypanosoma congolense (^8). It has been proposed
that granular reticulum connected to microtubules may serve
as channels for transporting protein to the outside (48).
Nucleus.— The nucleus is surrounded by the usual double-
membrane structure with pores (Figures 1.2, 2.2, 3» and 4).
The outer membranous envelope in young trypanosomes is con-
tinuous with granular reticulum (Figure 1*0 . The nucleolus
(karyosome) consisting of two masses of electron dense material
is located in the middle of the nucleus. One of the main
differences between the two forms of Trypanosoma lewis.i is
the size of the nucleolus. Young trypanosomes are distin-
guished easily from adult trypanosomes by the presence of
dense and larger nucleoli (Figure 1.2).
FlaReHum.—The flagellum emerges from the posterior
end of the trypanosome in a close proximity to the kineto-
plast. At the point of the emergence from the body a flagellum
pocket is formed by inward invagination of the pellicle (Fig-
ure 20). In a. cross section the flagellum's axoneme consists
of the usual nine peripheral pairs of tubulars and two cen-
tral single tubulars (Figures 1.2 and 2.2). Each of the nine
peripheral tubulars consists of two tubulars fused together
with l a t e r a l arms extending, out of theiii in a clocKwise direc-
tion (Figure 5)• Along t he flagellar axoneme the paraxial
rod is seen as a dense granular structure (Figure 5)• In a
longitudinal section t h e paraxial rod has a lattice-like
appearance formed by filaments running in different directions
(Figure 7)• The kinetosome is located at the base of the
flagellum facing t he anterior portion of the kinetoplast.
It is made of two kinetosomal plates, shown in the electron
micrograph as two dense lines perpendicular to the axoneme
(Figure 20).
There is no evidence for a direct contact between the
base of the flagellum and the kinetoplast (Figure 19)• How-
ever, a dense cytoplasmic matrix appears to serve as a bridge
between the base of the flagellum and the anterior membrane
of the kinetoplast.
Kinetoplast.—The kinetoplast consists of two main re-
gions enclosed within the same double membrane. The anterior
portion of the kinetoplast is made up of disc-shaped osmio-
phillic tangles of fibers oriented in a longitudinal direction
with rays of thin fibers radiating toward the posterior part
(20). The posterior region of the kinetoplast exhibits a
typical mitochondrial appearance with cristae embedded in
an amorphous matrix. Mitochondrial-like portions of the adult
trypanosome's kinetoplast are elongated, extending toward the
15
anterior part of the body (Figures 16 and 18), while they are
rounded in young tryparvnor^es locatcd in The posterior end
of the body (Figure 19).
Cytoplasmic membrane systems.—Granular and agranular
membranes varying in their osmiophillic property are found
in the cytoplasm of both adult and young Trypanosoma lewisi.
In the cytoplasmic matrix of young trypanosomes two prominent
granular reticulum systems are found. The first one is found
in the nuclear region while the other is found in the poster-
ior end of the body near the kinetoplast (Figures 3» 1^» 15»
and 19). The granular system consists of several cisternae
arranged in a concentric fashion. Under high magnification
smooth-walled vesicles are seen attached to distal ends of
cisternae, with more vesicles of the same nature found free
in cytoplasm (Figure 8). Vesicles appear to be formed be-
tween the granular reticulum cisternae before they are pinched
off at the distal ends. Adult's granular reticulum does not
show the highly specific compact arrangement found in young
trypanosomes. They are either dispersed throughout the cyto-
plasm or found arranged in two to four rows of cisternae in
the periphery of the body (Figures 2.2, 5» and 9). Several
dense granulars are observed in the cytoplasm of young and
adult trypanosomes (Figures 1.1, 2.1, 11, and 19). The nature
and function of these granulars have been the subjects of
several studies, but so far there are no convincing
16
interpretations. Ormerod associated the appearance of gran-
ulars in different speuies of trypanosomes with host cell
immune reaction (32, 33)•
Inclusion bodies.—Inclusion bodies are observed exclu-
sively in the posterior ends of both young and adult trypanosomes
(Figures 10, 15, and 18). The number of inclusion bodies is
higher in the adult trypanosomes. Inclusion bodies of the
same nature have been reported in the same region of several
other species of trypanosomes. Those bodies are believed to
be the by-product of metabolic activity.
Agranular reticulum system termination in sacs of secre-
tion are observed in both forms of Trypanosoma lewisi (Figures
1.2, 3» and 11). Vacuoles are observed only in the adult form
of Trypanosoma lewisi (Figure 17).
The Golgi apparatus of adult trypanosomes shows the
classical lamellar arrangement found in the posterior end of
the organism (Figure 2.2), whereas the Golgi apparatus of
young trypanosomes consists of aggregates of small vesicles
found in the middle of the organism (Figures 1.2 and 10).
Mitochondria.—'Adult trypanosomes possess a long tubular
mitochondrion attached to the kinetoplast by a narrow tubular
structure (Figures 1, 16, and 18). In some cases the mito-
chondrion extends to the nuclear region terminating in a
large spherical mitochondrion (Figure *0 . Young trypanosomes,
on the contrary, possess smaller mitochondria which are
17
spherical in shape, with lateral growth (Figures 12 and 19).
There is no indication of a physical connection between,
young trypanosomes' mitochondria and the kinetoplast. Both
young and adult trypanosomes* mitochondria are surrounded
by double membranes with cristae embedded in an amorphous
matrix which is easily distinguished from the cytoplasmic
matrix by the absence of ribosomes.
18
Figure 1.1 Smear of young form of Trypanosoma lewisi.
Stained with Giemsa, light microscopy. X 1,400.
Figure 1.2 Trypanosoma lewisi. young form. Longitudinal
section showing nucleus (N) with its dense nu-
cleolus (nu), nuclear membrane (nm), pellicle
(P), granular reticulum (gr), sub-pellicular
microtubules (pm), vesicular Golgi complex (G),
cross section of a flagellum (F), mitochondria
(M), and angular reticulum (ar) attached to sac
of secretion (sar). Several dense granules are
seen scattered throughout the cytoplasm (g).
X 30,000.
19
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r rc-*%,: < " . . . • " * . • • - > , - -
::SS& '•:•; ^ ' ' ; * < ""jST ' ' „v ;2.?
20
Figure 2.1 Smear of adult form of Trypanosoma lewisi.
Stained with Giemsa, light microscopy. X 1,400.
Figure 2.2 Trypanosoma lewisi. adult form. Longitudinal
section showing the nucleus (n) with its
nucleolus (nu), nuclear membrane (nm), granular
reticulum (gr), elongated mitochondrion (M),
lamellar Golgi complex (G), pellicle (P), and
a cross section of a flagellum (F). X 42,000.
21
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22
Figure 3. Trypanosoma lewisi, young form. Longitudinal
section through the anterior end of the organism
showing granular reticulum (gr) and vesicular
Golgi complex (G) in the vicinity of the nucleus
(N). X 30,000.
Figure b. Trypanosoma lewisi, adult form. Longitudinal
section through the anterior end of the organism
showing a nucleus (N) with two nucleoli (nu) and
an elongated mitochondrion (M). X 22,000.
*- 'X .
f?-j-„- -r" '5
^ : f y
$ ' . * r , ' / ; >" J # ^ 7
ft /'„ *- -" - -
\ J 0 ^ - ' : 4 -
t ' ^*" *• » " "
s& y
' • •'•:" ' ' . € ; • .
v - % *V-,V- :>
;% ,
' ,-r-f'y. — ^ " ^ v
- • ; T |
; ; p Q i i § S
gg/i? a*-r ^ £"
» / - • . . ^ - V '
* 4 - &•<**
-- . - f v : - <r ^ z-, - y ' '
•*"*- J J ' i </--
1 > I V v / * ' - # • - '-4
'" - ' y t -
i >„<• - > - T . Isfe*.
5-''"V>rS&?
• 5 - v ^ % v 4 s - « *
m ^ - - •
~"4'^_ * f
- ? X \>*
V ' ' ' ' ^
\&>
: X
it-* •1:): -n
a^ te4>%Sy>is J^ fe , - % £ ^ k J £ ' '
' -l. * - ''1% vi - -Y '
2k
Figure 5- Trypanosoma lewisi, adult form. Oblique section
demonstrating clearly the "9 + 2" pattern of the
axoneme (ax), paraxial rod (pr), and lateral arms
(la) extending from the nine peripheral tubulars
(pt) in a clockwise direction. The sub-pellicular
microtubules (pm) are seen along the entire pellic-
ular membrane with granular reticulum (gr) in
close proximity touching only microtubules which
are located directly under the flagellum. A
desmosome-like attachment (d) connects the flagel-
lum to the pellicle (P). X 63,000.
Figure 6. Trypanosoma lewisi, young form. Cross section
showing a distinct association between granular
reticulum (gr) and only sub-pellicular microtubules
(pm) located under the flagellar attachment zone
(far). ^5,000.
Figure 7« Trypanosoma lewisi. young form. Longitudinal
section through several flagella showing the
lattice-like arrangement of the intra-flagellar
structure, (if). X ^5,000.
2 5
pr
. i o x
1 . \
1 . \
l ! ' Is V - ' %
; 'i * "... ,
\ 'r-i / •%S
'"V_ ! c t .
« »
k * •"•
• - . 5
1 1 1
. . f » m ;
• "' 'k Z "'f'^,-"-''-. Z*.. i * / • "' 'k Z "'f'^,-"-''-. Z*.. i r-, - v .
, — "-- * »>
'
V Vs- ^ ' .
. - - , -" .V
; f ^ ^ * -" ; 1 .
- / - V ^
r - , . "
i - C • 1
• ? " :"*' ^
' C S . .
W' 1 .
& - 4 W ' ^ H
M . . . " "-i, • ! ' V/Ac-> •-
'•'- ' J
^ _ - V
-- " ^ : s v
. ...
J * * 3 , ^ y i i " " -
s •• ' f t t \ « « I S ' !
„ y . • V. • '
k ^ J ™ - . . : - ? , k :,/ ^ ,-****
i
<*••* * * s- ^ ,
1 : H-4 F
: • # • ' 1
l a r j $
w > ^ J - £ 1
* " V : • = " .-.;5'' • * . . ' ' • * ' ' • ' V . ; *
y ^ y - ' > - » v > . . / > / U S* ' : . , - ' , . V;"v- >-. - . _ . .< V ?* ~ ' , V
^ - . f ^ . ^
i ' ; v . <- ' ' t „ " ,
1 I
, - ^ v - V '
• ? " ' / • • •
26
Figure 8. Trypanosoma iewisi, young form. Oblique section
demonstrating concentric arrangement of granular
reticulum (gr) with smooth-walled vesicles (sv)
secreted from the distal ends and more vesicles
of the same nature are free in the cytoplasm.
X 62,000.
O *7 ^ (
i ?*•>
Jr . %
V- $' ** gps# - , . . , ."Wft-.. '- • . w 1 ;>**-.*' j /-* - ,* -~**" /f""~ -"sT"'
- *'' - , "*< *V'* '• • "*; »- ' -"*** r ** cv -V-; ' "?'"i-V * - ? ' • " ' r >£?
1 'T '"-•:' " J * ' - **'
SfVjg •'• * - ;
rrf< :?•>....•% ^ -
» ? i ' * -_«;-• * "* i" v • „ , * " ?-'• '-»•• Si V-' 1
m m : & - * » ' • - • , 4 ' ; ;,: /.:- ••;** a^a:'*A:: - \ % • •' rv-.' . - i
.- *. ._ . ,• ^ . . - -• ^ Sj . . -c .; - 5 " 1* - J- _ . --v
fc?'% i < aV'i ^ ^ f.. > ,\ - - V;
rv m ^ , F : "';"-:4 *'
1 *' S¥ ' -*"-r" ' ;
• 1 i'"K' ;,. ./' * ' ' " :'" ' " ' "' " -*1' 'V'i' <-'. '='C ' /y-, • " " •- y % - . ••
-> '-}% ; :.i '
~1<J> -'r<
s ' *
^ - *
x'-- -
: " A-S^
^ "* rvv**-. . r> % f
> «. . "*-'
LJ .7 - *? : i v"- . •• - : •' ,- •*k\ - ".. ct-&$• * * -JV. t*." ^ r f : •-**--- '-^~hi*- >^-v±-y>- : .•"--•v,-. - -:•" - - , . - • -~z^\ ir- : •>< »•/ v ':- "" •- , " '5. r-r -v.--'-O -- J - ' ':;- - ' r-"%r '•>,«- •;. .-•••, v: • .-. "- ;r • •.. •- •- .:- -al . fejf'. -.• - -ii •-.••:• -•'& *:•
*>:•" %. -': *?>
• i-Xj.
A-A. -.i :-
8 S¥ "5..
' '"1- 1 ""I"-. ' "•;
| 'P>
-- -1>
28
Figure 9« Trypanosoma lewisi, adult form. Oblique section
showing granular reticulum (gr), tnitochondrium
(M), sub-pellicular microtubules (pm), flagellum
(F), irregular smooth-walled vesicles (iv).
Granular reticulum is attached to four sub-
pellicular microtubules located under the flagellar
attachment to the pellicle. X 62,000.
25
V . *-, *v . '- 'H' ' '• . . --
<•% ' *V-f j . *.*-i. s* > v^»._ -. t Vi - * ' % 5s
j> . -.
1 X ; - w
W l ; ^ !>' V > "t>;
I - - ; ^ a . -<- t r ' r .v
: j « r - - *
: }<S.
.» < * •«:•
: . % : . ? w & }
• '•• '' • ^ - v ^ v s W ' ' "
^ / . • ' " - v * s v * r *
' - %
- * - ; *,*,'*
# . si\ ^ - '/% "-. ' * - r * •&
X ?l
t r * i g
V =
r i v ^ \ V ', * " ; '4V- -t, ; - ; • - :'! Tv, c / ^ | K • • \
c \ V " <;•?.*>! 'ki, 5£J<
' '' r -jf^A-..
i k ."'
-
' v - : A- ^
; . n
'*^T '?r'
f ;"-
~<^' • \
: X
£ . v . i : ; H >-,;-•
- f t l ^ f,t- v --'.
* *-• "'"
! - • • . I V * , , J> ,• .
" . - ' V \ . :i % ---- ^
9 • / ••••', ' •-. " v '
•*•- - i *«•. -4
30
Figure 10. Trypanosoma lewisi, young form. Longitudinal
section showing five inclusion bodies (ib) lo-
cated in the posterior end of the organism in
close proximity to the flage Hum's emergence
from the cell. Other organelles seen in the
section are nucleus (N) with a dense and large
nucleolus (nu), nuclear membrane (rim), granular
reticulum (gr)» several dense and large gran-
ular s (g), vesicular Golgi complex (G),
mitochondrion (M), and smooth-walled vesicles
(sv). X 50,000.
s , • * *
^ s f f . / V , •rftm -
*r • '•** 'hr*
w , & .
' S f
f •. ' vl", - . --^'1 « _^s^" vS
' " **" V r> '" * *'%„
•:<i
W^MiM -v- , 1
>.
-,£K' - : " ^ '
*
, &"
H * -v ,% ^ *>* / ' - a •. -
: I
% , 1 * •J' V -.
;3;£<. ' i f '
"f
^ '
* /
\jr
fe. ~5S
I t
#Sf# r V ; :\ J?8*
. &"
«4
1 S!-'H-
\ • * - ' :L%i
/Mv-n * :- 4. v ! S b t ' S W ^ \£*.
32
Figure 11. Trypanosoma lewisi, adult form. Longitudinal
section showing a nucleus (N}» nucleolus (nu),
mitochondrium (M), agranular reticulum (ar)
terminating in sacs of secretion (sar) and sev-
eral dense granulars (g) varying in their
osmiophillic property are seen in the posterior
end of the organism. X 38,000.
33
? v-
-m #$%
KX&J-
r/Y4
?Kt'Wk£*. ,/t &£'•&%'• -*r?,y-' : • % - - ^ %' 'n imi % ^:f A i "' -•*•• >-,A. '
% ,~x - &
.« .. - Vvf,r: ' ' ^ - 7 ^ i# ""
%- \ '• %
y zt J? Y\$
£r ^ I . ,. i?: . ' . , { % - 1 ? * !
\A '"* *8gV - * '" V\ V
V * m's - y / /
A > *! j "•%»; *i> " *J V,
y*
Figure 12. Trypanosoma lewisi, young form. Gross section
through the anterior end of dividing organism
showing two nuclei (N) with nucleolus (nu) and
mitochondria (M). X 42,000.
35
3^- .£ssr
® 1 y - •* - ' " *'*
- v -*"' " ' ^
P " <' -fhi ' % 1 ' v * y- M
'-i. ? * • * z i ^ w -
s a g A ^ *4 v-W - > ^ ,*
. . . . , 3& &. ... •
v ^ £
- ^ •% •*. - M <* -
* * ' " " ' % # L 1 - 3?
2- -
- - J - r . -N l l t ' ^ t f Jf
X a 3 6 . , . ' " . - * • r
V " ' U
i ' f e
1 "-T.
I V / . : 4 * ' ; " * % -
>' ' W % * *
\ ^ - v %'* : j ... J 5 . " » „ ^ i ^ i s w Ji^SSEa&^SSaJa .
36
Figure 13• Trypanosoma lewisit adult form. Gross section
showing circular and bifurcated mitochondria
(M) and smooth membraned agranular reticulum
(ar). X 38,000.
3 7
r V i ;
. A 4 C 0>: £}%:
frv
- : ' v r 4 ' / J
J>:-Xy - ' v
£ • • - " * . • ' r - „ . •
*" - 4 x f " '-:4 '•&%
•%£-&rK-*y-:h - S - -.•?.• \ -• *'i i-
\
> : V - .
• : , " s | >
' > f
50.-^ f l * kM n
• ' B
f f | \ V - ' ^ C ' - i ! - - " I •
• ' ' • " • • " • - V ' - l i
: ' " ' s ;• ; •" : * . ; " - . 1
1 - V
,* j? •' •• V s . - : Mr -• :j >*'* - ' * • * * : < ' " : ' ' r •?. - ~ v r :
" V * y \ % \ ' 4 # : " V . - ' . . - ' i y •' • ? : 4 - V v
* • f - : 4 - |
l f > ! ' - m r ' - V
- \ \ ' % -f-l i;; / / J " ' - ' ." ••?.; ± r - t j -\ ?->• ' • ' -S - - J . i f / " V - - • • • . ' .'• - A . ' : •
••-%#*% - •/>.-
\ ; f &
r y . " <
? r 5
' V ^ ; s * ? • ;?
. .vr J
l l
\U
- '•«;•••' '"w
*•?
^ 4
m i ~k \ 1
's% jv
j . i
"
. 4 * /
; ;J.;V % ' ' t
- A s? , l !
. ' v - J
/ . J
, , i
38
Figure 14. Trypanosoma lewisi. young form. Oblique section
through the anterior end of the organism showing
granular reticulum (gr), mitochondrion (M),
nucleus (N), with large nucleolus (nu), and
nuclear pore (np). X 42,000.
3 9
e .
t o •' - < r - \ a
*\-',\ esv-^. _
i ^ ,
V' *1
W : .:'- r l l # 3 ^ ' - -',,• :•'-. * rl/;: "•'-.:'y: A -.i J | * j : i : " ' - v : ^ y % : . \ : g . , •^;-
* " W i %
^ A.. >
kO
Figure 15. Trypanosoma lewisi, young form. Oblique section
through the posterior end of the organism showing
the anterior portion of the kinetoplast (K), flag-
ellum (F), mitochondria (M), granular reticulum
(gr) smooth vesicles (sv), and inclusion bodies
(ib). X 30,000.
, J- ' V" ^ '
' / V - V - ' •
:"::U
- * ~ r -
\ r W -
. - f y : < 1
f . \ >
J 6
" = ; • • ' W $
%
f - k • >
H ;
-**-r >/ : : : & '
V > / -
' ; f " j V .
i M
- - o ' " '
' -
" ' : . -V
~:,-/
V ? , *
v
CCr'i r . / ;
_ 4 r -
- • ' & r : -
:
v-.
" -r '
% \ \
%> 4,\F
% y y — /
" O k ~ : 3 S . > . •
- v ,
K s k - s i f t n
1 4 ?
42
Figure 16, Trypanosoma lswisi, adult form. Oblique section
through the posterior end of the organism showing
a large mitochondrion (M) attached to the kinet-
oplast (K) by a mitochondrial canal. Several
dense granules (g) are seen in the same region.
X 17,000.
Figure 1?. Trypanosoma lewisi, adult form. Transverse sec-
tion through the middle of the organism showing
smooth tubule surrounding a vacuole. X 17,000.
Figure 18. Trypanosoma lewisi, adult form. Longitudinal
section through the posterior end of the organism
showing an elongated mitochondrion (M) extending
from the kinotoplast (K) to the anterior portion
of the cell. Numerous inclusion bodies are seen
in the posterior end. X 23,000.
•,>/" - >-• r ^''is£fm_.
_, *:WX&. - J?% ; " ' & S jS^x^ i% -
op;-, i-z.g.:'-- ..• - -• /-' •"' '" .-•^% ::;V" ;-** 4 ? "
r^n • w • *
1 ^ 1 ^v / -
5'.; • .;•• .. • •- r ,&*r J
ym>.
W'""' a
m^r-' \
m-m^< W-'
*5; r i. F" iWFl^ ^^ * #' r1*' ^ *-w,
" r / ^.=/ 4* % # *
;S 3
"?/ •%'
>lV t
^ %
&IC$
}'-"ri 8
f * . ? ^ vu,; I - u«-*>&&, - %. i 1 -5> "> M - .*' - .^: t<r'is
f. V \ ^^TeVi '-ft C% f.- ;: ->s
v" ®»-i'.-s"#f t g_ ¥ £V v s w» -iff - ^
i ^ y t i i y ^ : £*- IS? ^#-r '£.^-3
•."V ..-j, * * ".V '. , > -«>"~ *ij£~*~'/ <v
VU a. V- a"" > % • >
• ' v w-
'C\' "£&%: oJC ':$&*&!$•
/xi^T i '. -,v3
'* J V4 V-C;' r.t" . f
.-i'- --" "'' i^r
, -
- -f«' -'• -T
Jc0^ '
^ '
- "" ^ v
I-. 1 y *%"%S i*" : -i
- j m ^ , "*r - / ^
**
i&taaar-'--- r>*i ?r_ „ -«-j, -;ir,'*/'
'•<? '" "~£§t& - v5 '"I5/ \
t ' / : C r 3 • - ^r,
;
J -7 - % & *' $
Sti-itV-T ... . „
Ws>
Figure 19. Trypanosoma lewisi, young form. Oblique section
through the flagellar (F) origin and the kineto-
plast (K) (v/ith its dense fibers). Several
organelles are found in this region such as
mitochondria (M), granular reticulum (gr) and
several types of vesicles and granules scattered
throughout the cytoplasm (arrows). X 56,000.
Lb
- ; v - r * \ v
- <r fe
• , • • •
.A <&>
^-h% »tt-5
"V ; ; § P # ;
, ' V
;->r r •%
J N / * - ' v -' -t' -" '•<?% -J ''-n*ii" '
••-*? -w&mr 4 , *C ?- - '
T ; 4
- 0 : » f - - - . - v ' - . . ^ " - \ M / . V \ .
* - ' : • , v .
: : ? ; W * § V - V !
i ; " : " I ; ' ' I € m : : • < • * ' • • v ^ a
fe' - s*y ". • * n Ms-- . & ' - - 4 ^ ' : . $ v ^ \ • y - ¥ U i : - ^ '
W-:-^fr ^ * ' ,v *:•">& :-n\* i f f - ' V ' > • . ' ^ * * ? r ' • -*\ • * , - ; . 4
¥«• < - V -„ - - *••• " • -' a -15
-y • ; *- ^ k " K' v
r t r r - . - - v - : - v - ' W - ' . v
•A i<-'-
•k*- n , *; ' * '
J. 2 -' V " " •
y r ' - ; ' # 1 ;-•£ -
^ • ' ,
- W V \ 4 ™ 4 ; „ - J ' i / . ' ' / * r ' *'
% - * • : • ^ - ; ; . . ^ '
^ V.
K>i. .' — v
' -SrP -r ^ i1- ",".^
. U - :r
- V V/'^F * ' . J ' ^ ' --'>
, * v ' • - "•' ,- , j :
" ^ " " - v " - *.i r- -
s3z • ' T
f W W - . • s - 3 ^ •- •• •-*•' ' • I • > , f t f r ^ a '"
|r .. • r ' ..-
&
1 %- ; : •??>;: /
* 7 ; ^ 1 > V "
"S ' /'-? s. -r
JJ*$k
t 5 ' ' ' : ; " % ' V r r ^ .
* % m . . • -? -
y'"d£-^ -
I ^ - A
. - ' ^ v - ' ^ 1 , ; " . X / ; / ' - £
- - V ! ' \ -
:•• K ' •> o i "% - y \ " ' " - " v , .4
-., 4-$y^%-X- * : %,&-.• .
«i .4 . .. i-"? t - '. , \ . ; y A
...•• - . ,/ ^ ;,V."'.:-
'46
Figure 20. Trypanosoma lewisi, young form. Medial section
through the kinetoplast (K) and the flagellar
origin demonstrating detailed structures of both
organelles. The central flagellar tubulars (ct)
are seen extending beyond both kinetoplast plates
(KppKpg). Dense cytoplasmic matrix connect the
tubulars to the kinetoplast membrane. Several
other structures could be identified such as
flagellum pocket (fp), attachment zone (az) be-
tween the pellicle (P) and the flagellar membrane
(fm), and peripheral axoneme tubule (pt). The
kinetoplast (K) is divided into two distinct
parts, the anterior part which consists of a
tangle of dense fibers (kt) and the posterior
end which has a mitochondrial appearance with
cristae (cr). X 84,000.
li?
•fx _ , •X^
^ 't - .'j ~ '' v.:-- '
,f T:l:. * ' , ? ' : Y';,: J?
" f ar
six'
^ » " • fp
' ... * - •- -i: m& - ->•' .* "~*.J***?-Z'j- - *,- •
- ,,• %. . <", ^ . •- - P—*• .. :
*k j.: , • - - - ; •'•
V«
-*sf*y
:1
4: •* • - v~ -
. - v , s
' - .--Jit'" V - ;* * < - _*-a
fm
Pt kpi
kp2 ,*v f ~'~-W-i?<-. • Mr
• "" 'V K I T — g - — - ct *? S *
I ' ' #*• ' «
/ - > *3
lii «£%w\ .fi
•V 'I? ,} , ^
: / " " • *
v. - ?i'/ 4: p : -.
K
cn-*
ty-'cj . -*t.
•I-; ' / it '•-• >;•'' 1 ^ if#-: • • " -j f-ii y-v
•; !- ' '
^ y g -
i * :
-j. >
. . -
• T ' " -• \ • • • - - '
r
'j-'H - • i
DISCUSSION
In interpreting an electron micrograph there is always
the hazard of misrepresentation or distortion brought about
during the process of preparation of the organisms or tissues
for electron microscopy. During the course of this study,
micrographs obtained were constantly checked with results
from previous studies on other members of the genus Trypan-
osomatidae. The overall ultrastructure of both young and
adult forms of Trypanosoma lewisi shares several common
features with other trypanosomes, although some unique char-
acteristics have been observed.
The three-layered pellicle and sub-pellicular micro-
tubulars are characteristic features found in all other
species of trypanosomes. However, absence of a thick sur-
face coat on both young and adult forms of Trypanosoma lewisi
distinguishes them from other trypanosomes such as Trypano-
soma con^olense and Trypanosoma cruzi. Protective and
antigenic functions have been correlated with the presence
of a thick surface coat (50).
There is no evidence for the existence of a cytostome
in either form of Trypanosoma lewisi. Ultrastructure studies
on blood forms of Trypanosoma vivax, Trypanosoma congolense,
Trypanosoma equiperdum and Trypanosoma avium also indicated
4-9
the absence of cytostcme (1, 3» 50)» However, it has been
found in the posterior end of culture forms of '''gypanogoir;a
raiae, Trypanosoma mega, and Trypanosoma conorrhini (30, 35»
40}. The. presence of granular reticulum, mitochondria, dense
granulars, and vesicles in the vicinity of the flagellar
pocket suggests the involvement of this region in high meta-
bolic activity. With the absence of a cytostome in this
region I believe there is participation of the flagellar
pocket in cytostomal activity, as it has been suggested in
Trypanosoma congolense (50). Attachment of smooth-wall
vesicles to the flagellar pocket's pellicle is another evi-
dence supporting this hypothesis.
Specialized secretory cells in higher animals are char-
acterised by the existence of a conspicuous granular
reticulum system, where amino acids are assembled in long
chains of protein and elaborate Golgi apparatus, where pro-
tein is concentrated in compact vesicles after the addition
of carbohydrate moiety (6). Young forms of Trypanosoma lewisi
exhibit typical features found in higher animals' secretory
cells. Granular reticulum, vesicular Golgi apparatus, and
an abundance of smooth-walled vesicles are readily observed
throughout the cytoplasm of young trypanosomes. Change in
the Golgi apparatus from aggregates of vesicular complex in
young forms of Trypanosoma lewisi to a small lamellar complex
in adult forms, points out a sharp decrease in secretion
50
activity. The nature of the secreted materials is unknown,
although electron cytechemicai studios on Trypanosoma raiac
indicated the production of acid phosphate, a lysosomal
marker enzyme in the immediate vicinity of the Golgi appa-
ratus (35)«
The association of vesicles with the granular reticulum
in young forms of Trypanosoma lewisi exhibits a unique feature
which is not observed in adult trypanosomes. There is a
striking resemblance between granular reticulum found in
young trypanosomes and those found in Tetrahymena pyriformis
(10). Smooth-walled vesicles attached to distal ends of
Tetrahymena pyriformis' granular reticulum is associated with
fluid regulation by separating excess water from
Vickerma
agranular ret
tive and horro
An abundance
the cytoplasm,
n (50) connected the function of the complex
iculum attached to sacs of secretion with nutri-
onal production to be utilized inside the cell,
of such organelles in adult forms of Trypanosoma
lewisi suggests a shift in the nature of the secreted materials,
One of the new findings in this study is the penetration
of the central-tubulars of the axoneme deep into the cytoplas-
mic matrix. Previous studies on the flagellum structure of
several species of trypanosomes reported the termination of
the central tubulars in the kinetosomal zone. Presence of
the flagellum base in the middle of the flagellar pocket in-
creases the risk of damage caused by chemicals used during
51
fixation, dehydration, or embedding, In this study the period
of fixation was shortened to rc-cric3 the chance of damage
caused by osmium tetraoxide.
There is no evidence for the existence of filopodia in
either form of Trypanosoma lewisi. Recently, filopodia have
been observed in many species of trypanosomes (2*0. Several
functions have been associated with their presence, such as
antigen liberation, protection against antibodies, and attach-
ment (^9) •
D'Alesandro (9) linked differences between the two forms
of Trypanosoma lewisi in morphology, enzyme levels, rates of
protein and nucleic acid synthesis, and respiration, with the
indirect effect of ablastin, the reproduction inhibitory
antibody to trypanosoma. This study shows definite changes
in the overall ultrastructure, but I have not determined the
factor causing the transformation. The nature of inclusion
bodies and granulars found in the cytoplasm of both forms
of Trypanosoma lewisi cannot be resolved unless various elec-
tron cytochemical techniques are applied, such as those used
to localize acid phosphate in Trypanosoma gambiense (39)•
Finally, the results of this study coincide with data
obtained from comparative biochemical studies on young and
adult forms of Trypanosoma lewisii
1. Presence of large nucleoli in young trypanosomes
could be associated with high amounts of non-protein
nitrogen and RNA found in this form (19)•
52
2. Presence of a conspicuous granular reticulum and
an abundance cf vesiclcs in young trypanosomes
indicates high protein content in this form (19).
3. Glucose uptake and oxygen utilization have been
reported to be higher in adult trypanosomes (18).
This could be related directly to the presence of
more developed tubular mitochondria with numerous
cristae in these adult trypanosomes.
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