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771.
772.
Sperm number is often a good predictor of success in sperm competition; however, it has become increasingly clear that, for
some species, variation in probability of paternity cannot be explained by sperm number alone. Intraspecific variation in
ejaculate characteristics, such as the number of viable sperm and sperm longevity, may play an equally important role in determining
fertilization success. Here, we assess variation among ejaculates in three factors that may contribute to fertilization success
(number of sperm per ejaculate, viability, and longevity), in a population of Peron’s tree frog (Litoria peronii). We detected large variation among males in the number of sperm per ejaculate and the proportion of viable sperm within
ejaculates, which could not be explained by variation in either male size or body condition. However, the proportion of viable
sperm released by males increased over the season. Finally, we assessed sperm longevity (proportion viable sperm determined
using a dual-fluorochrome vital dye) at two different temperatures. At 23°C, on average, 75% of sperm remained viable after
2 h, but there were significant differences amongst males with the percentage of viable sperm ranging from 43% to 95%. For
sperm incubated at 4°C, ejaculates varied fivefold in sperm longevity with some males having 50% viable sperm after 5 days.
Our data suggest that ejaculate characteristics (sperm number, viability, and longevity) vary widely in Peron’s tree frog
and may therefore play an important role in determining siring success both in the presence and absence of sperm competition.
We discuss the results in relation to selection on ejaculate traits via natural and sexual selection in this and other amphibians. 相似文献
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776.
The most common mutation in alpha-1-antitrypsin deficiency, conversion of a G to an A at base 9989 (PI-Z), was detected with the chemical cleavage of mismatch method, demonstrating the power of the method for prenatal diagnosis. Exon V of the gene was amplified using the polymerase chain reaction and heteroduplexes were formed to test for the presence of the mutation. The predicted C mismatch was readily detectable with hydroxylamine, and by making the probe from the chorionic villus sample it was possible to determine that the fetus was heterozygous, not homozygous, for the mutation. 相似文献
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Andrew D. Dorfmann Jeane Perszyk Patricia Robinson Susan H. Black Joseph D. Schulman 《黑龙江环境通报》1992,12(11):899-902
This paper reports eight cases of non-mosaic, rare, and typically lethal trisomies diagnosed in chorionic villi and not confirmed by amniocentesis. Four cases were 47,XX, + 16; two cases were 47,XX, +2; one was 47,XX, + 12; and one was 47,XY, +7. There have been no known complications in any of these gestations. These eight cases were found in a series of approximately 12 000 samples processed in our laboratory (0.07 per cent). We conclude that (1) rare non-mosaic trisomy not reflecting the fetal condition is an occasional source of diagnostic ambiguity in chorionic villus sampling; and (2) when encountered, a follow-up amniocentesis should be recommended to the patient to confirm or rule out the abnormality. We propose the term ‘confined placental abnormality’ to describe non-mosaic trisomies and other related abnormalities found only in chorionic tissue. 相似文献
779.
H. Brandenburg MD W. De Koning M. G. J. Jahoda Th. Stijnen M. A. J. De Ridder E. S. Sachs J. W. Wladimiroff 《黑龙江环境通报》1992,12(12):1031-1035
One hundred and fifty-one women of advanced maternal age who underwent genetic termination of pregnancy (TOP) were studied for their reproductive behaviour and the type of procedure for prenatal diagnosis in a subsequent pregnancy. A total of 59 women (39 per cent) had a further pregnancy. In all continuing pregnancies prenatal diagnosis was performed, of which 75 per cent consisted of chorionic villus sampling (CVS). Reproductive behaviour following a genetic termination was negatively correlated with maternal age and parity. Both reproductive behaviour and the choice to undergo a diagnostic procedure in the next pregnancy were independent of the type of diagnostic procedure in the previous affected pregnancy. 相似文献
780.
Thuli N. Mdluli Coleen H. Vogel 《Mitigation and Adaptation Strategies for Global Change》2010,15(3):205-222
South Africa faces several development challenges including those linked to climate change. Energy usage in South Africa, for example, is already constrained because of a range of development challenges (the dependence on cheap coal as a heating source; energy availability; access; affordability of alternative energy sources; and a range of health impacts, including air pollution). Notwithstanding calls for a transition to a low carbon economy, there have been few, recent assessments in South Africa of the costs associated with such a transition, particularly the social and economic costs for the poor who use energy in a variety of ways. In this paper we focus on trying to unravel some of the complex energy-use behaviour including understanding what drives consumers in resource-poor areas to choose and use persistently risky energy options. Analysis of qualitative data in two township areas, Doornkop and Kwaguqa, shows that township households, whether electrified or not, continue to burn coal. In both study areas, an estimated 80% of electrified households burn coal for space heating and cooking and also make use of multiple fuel sources for a range of activities. Although the major obstacles preventing people from discontinuing domestic coal combustion are poverty, the ready availability and social acceptability of coal together with other social customs cannot be underrated. This paper therefore highlights some of the persistent challenges associated with sustainable energy transitions in South Africa including implications for improved mitigation and adaptation for the energy sector in wider climate change efforts. 相似文献