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Questions and answers should be concise. We reserve the right to edit items for clarity and style. Include a daytime telephone number and email address if you have one. Restrict questions to scientific enquiries about everyday phenomena. The writers of answers published in the magazine will receive a cheque for £25 (or US$ equivalent). Reed Business Information Ltd reserves all rights to reuse question and answer material that has been submitted by readers in any medium or in any format. New Scientist retains total editorial control over the content of The Last Word. Send questions and answers to The Last Word, New Scientist, Lacon House, 84 Theobald’s Road, London WC1X 8NS, UK, by email to [email protected] or visit www.last-word.com (please include a postal address in order to receive payment for answers). To view unanswered questions visit the Last Word website at www.last-word.com/. THE LAST WORD A strange tail My two feline buddies bring me a never-ending supply of geckos. I frequently find tails and bodies separated, as tails can be shed for defence and regrown if escape is successful. However, I was surprised to find a lone tail that has two bifurcations (see photo). Can anyone explain this? n Of all the lizard families, geckos rely most heavily on autotomy of the tail. In most species, muscular contractions break the tail at a plane of weakness passing through the middle of a vertebra, rather than between vertebrae. This produces a clean break and little bleeding. A papilla of tail- growing tissue then forms in the break and develops into a replacement, although it is visibly different to the original. Internally ,the replacement spinal column is not formed of bony vertebrae, but a tube of cartilage. It is complicated to grow such an elaborate organ with its properly organised skin, muscles, nerves and blood vessels, so if anything interferes with that papilla, things go wrong. For example, the tissue-organising process can lose coherence and produce two tails or even more. Another outcome is possible and seems to have happened twice in this specimen: a tail might break only part way through, after which a new tail may grow from each lesion. By examining the skin, one can tell what has happened; if both tines of the fork look the same, two new tails had grown after autotomy, otherwise an extra tail must have emerged from a partial break. Jon Richfield Somerset West, South Africa Heartache Can heart muscles cramp in the way calf muscles do? If not, why not? n In cramp, the muscle filaments known as actin-myosin units within the muscle are stuck in full or hyper contraction, in a state of energy depletion that may be exacerbated by electrolyte disturbance. The normal rhythmic contraction of the heart muscle – a phase called systole – pumps blood out of the left ventricle to the body. A systolic spasm or cramp would kill you very quickly. However, the heart is more likely to suffer serious disturbance to its rhythm rather than cramp, such as ventricular fibrillation, or asystole – when cardiac electrical activity stops. But spasm of the smooth muscle of the coronary arteries can occur and cause a heart attack. In Queensland we have the world’s most venomous animal, Chironex fleckeri, a box jellyfish that lives along the coast and in the estuaries of Queensland. One of its toxic effects is to cause the heart to spasm in systole – it can kill you in minutes, and possibly in as little as 20 seconds. There is an antivenom but the chances of it working against a fatal dose are slim because you die before it can be injected. Immediate CPR should be attempted and I have seen it work in a marginal case. Vinegar inhibits further release of the toxin, and prudent bathers in “stinger” territory carry vinegar both to sprinkle on their fish and chips and, if necessary, to flush sticky tentacles from their skin. Bob McCrossin Cooroy, Queensland, Australia n Can the heart cramp like a calf muscle? Yes, if sustained muscle shortening is included in our definition of cramp. Such a contracture happens in severe metabolic inhibition, as in a heart attack. My group and I have shown this contracture depletes cells of their energy currency, adenosine triphosphate (ATP). We found this out by injecting a single heart-muscle cell with firefly luciferase, which releases light in the presence of ATP, while simultaneously watching the cell shorten – or cramp – in infrared laser light. (Thanks to the Biochemical Society, our paper is free at 1.usa.gov/Z4ZkX7). During the contracture, myosin converts the ATP to adenosine diphosphate (ADP) which then spreads to the next cell. ADP initiates the cell shortening so the injury process propagates from cell to cell. We can speculate that preventing ADP from passing through the pores in the junctions between cells could prevent the spread of injury. To do this, I would suggest applying cytoplasmic adenylate kinase to the pores. This enzyme rapidly converts ADP to ATP. The question is how to do it. Like all science, one question begets more. Peter Cobbold Emeritus professor of human anatomy and cell biology Corwen, Denbighshire, UK This week’s question PAINDROPS KEEP FALLING This morning it was raining so hard the drops were painful. What causes this? Is it drop size and the height from which they fall? Or is there another mechanism that increases the speed at which drops fall? The rain seemed to be coming down especially hard, and drops hitting the ground bounced high into the air. Paul Freyer Andover, Hampshire, UK “The heart can cramp, if we include any sustained muscle shortening in our definition of cramp” Last words past and present, plus questions, at last-word.com The new book out now: packed full of wit, knowledge and extraordinary discovery Available from booksellers and at newscientist.com/dolphins Will we ever speak dolphin?
