Results 271 to 280 of about 267,539 (298)
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Trends in Cognitive Sciences, 2002
Evidence is accumulating that in many species, males deliver more sperm to some females and fewer to others depending on how valuable they perceive the copulation. Do humans have any control over the number of sperm they ejaculate?
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Evidence is accumulating that in many species, males deliver more sperm to some females and fewer to others depending on how valuable they perceive the copulation. Do humans have any control over the number of sperm they ejaculate?
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Archives of Andrology, 2000
Available data on dry and hydrated nuclear volume of mammalian spermatozoa indicate that available volume is clearly insufficient to contain sperm chromatin packed in nucleosome-like structures. Therefore, sperm DNA-protein complexes must be packed differently than somatic DNA-protein complexes.
G, Fuentes-Mascorro +2 more
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Available data on dry and hydrated nuclear volume of mammalian spermatozoa indicate that available volume is clearly insufficient to contain sperm chromatin packed in nucleosome-like structures. Therefore, sperm DNA-protein complexes must be packed differently than somatic DNA-protein complexes.
G, Fuentes-Mascorro +2 more
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Reviews of Reproduction, 1999
Communication between spermatozoa and egg before contact by chemotaxis appears to be prevalent throughout the animal kingdom. In non-mammalian species, sperm chemotaxis to factors secreted from the egg is well documented. In mammals, sperm chemotaxis to follicular factors in vitro has been established in humans and mice.
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Communication between spermatozoa and egg before contact by chemotaxis appears to be prevalent throughout the animal kingdom. In non-mammalian species, sperm chemotaxis to factors secreted from the egg is well documented. In mammals, sperm chemotaxis to follicular factors in vitro has been established in humans and mice.
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Sperm competition games: sperm selection by females
Journal of Theoretical Biology, 2003We analyse a co-evolutionary sexual conflict game, in which males compete for fertilizations (sperm competition) and females operate sperm selection against unfavourable ejaculates (cryptic female choice). For simplicity, each female mates with two males per reproductive event, and the competing ejaculates are of two types, favourable (having high ...
M A, Ball, G A, Parker
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Sperm competition influences sperm size in mammals
Proceedings of the Royal Society of London. Series B: Biological Sciences, 1991Among mammals sperm competition leads to selection for increased sperm numbers but it is not known whether it also leads to changes in sperm size. Two contrasting theoretical predictions have been made. The first hypothesis relies on the assumption that there is a trade-off between sperm numbers and sperm size and predicts that, in species confronting ...
M, Gomendio, E R, Roldan
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Early sperm-egg interaction after sperm microinjection
Reproduction, Fertility and Development, 1994The early events of sperm-egg interaction occurring 1-3 h after multiple sperm injection into the perivitelline space (PVS) and after direct injection into the ooplasm of human oocytes are reported. The sperm acrosome reaction occurred in the PVS but was not detected within the ooplasm.
A H, Sathananthan +5 more
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Sperm centriole disfunction and sperm immotility
Molecular and Cellular Endocrinology, 2000The two main causes of complete or nearly complete asthenozoospermia are necrozoospermia (presence of only non-viable spermatozoa) and the different ultrastructural abnormalities of spermatozoa. Ultrastructural alterations may affect also the function of the sperm centrosome, which can result in impaired motility.
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Sperm size and sperm competition in birds
Proceedings of the Royal Society of London. Series B: Biological Sciences, 1992In a sample of 20 species of North American passerine birds we found no relation between sperm size and mating system like that previously reported in mammals (Gomendio & Roldan (Proc. R. Soc. Lond. B 243, 181 (1991)). Instead, we found a positive correlation between sperm length and the length of female sperm storage tubules (SSTS) and a negative ...
J V, Briskie, R, Montgomerie
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Sperm‐sperm associations in the loris epididymis
Gamete Research, 1987AbstractIn a few mammals, the passage of maturing spermatozoa through the epididymis is characterized by development of persistent associations between one or more neighboring cells over the acrosomal region. The converse situation is described here in the loris, Nycticebus coucang, a prosimian primate.
D M, Phillips, J M, Bedford
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Sperm competition games: sperm size and sperm number under adult control
Proceedings of the Royal Society of London. Series B: Biological Sciences, 1993Evolutionary games of sperm competition in which two males mate with the same female have previously considered sperm size to be fixed at some (small) constant level. Although male gametes in multicellular organisms are typically small compared with ova, they vary greatly both between and within groups, and sperm size sometimes correlates with the ...
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