Big sperm not necessarily fastest
Children with heart defects may someday receive perfectly-matched new heart valves built using stem cells from their umbilical cord blood, according to research presented at the American Heart Association’s Scientific Sessions 2008. When infants are born with malfunctioning heart valves that can’t be surgically repaired, they rely on replacements from animal tissue, compatible human organ
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Contrary to common scientific belief, the length of a sperm’s tail does not always determine how fast it can swim.
Research published in the open access journal BMC Evolutionary Biology has shown that in the counter-intuitive microscopic world in which sperm operate, streamlining and longer tails don’t always provide a speed advantage.
Stuart Humphries, from the University of Sheffield, and collaborators from the University of Western Australia have critically evaluated the evidence linking sperm shape to swimming speed. He said, “It seems clear that some assumptions regarding the physics of sperm locomotion have hampered our progress in understanding the processes mediating sperm competition. It is commonly believed that selection for increased sperm performance will favor the evolution of longer, and therefore faster swimming, sperm. In fact, the relative lengths of a sperm’s constituent parts, rather than their absolute lengths, are likely to be the target of selection.”
Small size and low swimming speeds mean that, in hydrodynamic terms, sperm operate in a very different regime from the one that we are used to. At this microscopic scale, although a longer tail does allow a sperm to generate more thrust, the drag created by a sperm’s head is often enough to counteract any such gains. According to Humphries, “We suggest that, irrespective of whether tail length, total length or head length is used, any attempts to correlate a single measure of length to speed are likely to be futile. We argue that accounting for the balance between drag from the head and thrust from the tail will allow us to extend our understanding of the link between sperm form and function.”
These findings imply that, contrary to current thinking, one cannot attribute the evolution of longer sperm to any competitive advantage that length alone gives them.
Scientists have developed a ground-breaking method for testing the quality of a sperm before it is used in IVF and increase the chances of conception. Researchers at the University of Edinburgh, funded by the EPSRC (Engineering and Physical Sciences Research Council), have created a way of chemically ‘fingerprinting’ individual sperm to give an indication of
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Reports from Taiwan say the sperm taken from a man with testicular cancer 13 years ago has been successfully used to impregnate his wife. The man was diagnosed with testicular cancer when he was 23, and sperm was taken and frozen before chemotherapy was used to treat the cancer as it was expected to render
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According to recent research whether men are likely to father a boy or a girl is determined by a “fatherhood gene”. Scientists believe the fatherhood gene which is inherited from both a man’s parents, comes in one of three variations and affects the number of sperm carrying male or female chromosomes. The British scientists say
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A Newcastle University study involving thousands of families is helping prospective parents work out whether they are likely to have sons or daughters. The work by Corry Gellatly, a research scientist at the university, has shown that men inherit a tendency to have more sons or more daughters from their parents. This means that a
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“Young men undergoing treatment for cancer often want to know how the disease and its treatment affect their chances of fathering healthy children. Our large-scale study shows that there is a slightly higher risk of deformities, but the actual risk of having a child with deformities is nevertheless extremely low. I think this is good
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