Attitudes towards sex selection for non-medical reasons: a review

Early non-invasive fetal sexing is widely available over the Internet, leading to concerns about its possible use for sex selection. The aim of this review is to summarise the results of surveys describing lay attitudes towards sex selection for non-medical reasons to help address or inform such concerns. A search of electronic databases and key journals was supplemented by an Internet search and citation-tracking. Twenty-one quantitative studies were identified. Most were conducted in the US, with five recent studies in the UK and Germany. Most studies found that, overall, people were not in favour of sex selection. However, this varied from 94 to 18%. People may hold more negative attitudes when the method of sex selection is specified, particularly if this involves termination of pregnancy (TOP). Attitudes towards the general availability of sex selection are less negative than those towards personal use. Attitudes were consistently negative in German surveys. Little is known of such attitudes outside the US, the UK and Germany, and how such attitudes may change as new sex selection technologies become available. Studies of use of early non-invasive fetal sexing for sex selection for non-medical reasons are needed to assess the extent to which concerns about usage are justified and to assist in debates on how these might be most appropriately addressed. Copyright © 2006 John Wiley & Sons, Ltd.     

Prenatal sex diagnosis: Testosterone and fsh levels in mid-trimester amniotic fluids

We studied the validity of mid-trimester amniotic fluid testosterone and FSH in the diagnosis of fetal sex in abnormal fetuses and in twins. It was found that the testosterone/FSH ratio, but not the level of the individual hormones, was an excellent criterion for fetal sex diagnosis. In a control group of 32 female and 34 male fetuses, the testosterone/FSH ratio was diagnostic. In two cases the values were indeterminate and fetal sex could not be predicted, but there were no false diagnoses. The abnormalities of the fetuses were diagnosed by karyotype analyses or raised levels of α-fetoprotein. It was found that neither autosomal trisomies nor X-chromosome aneuploidy or neural tube defect interfered with the diagnostic value of the hormonal approach. The twin study included 14 pairs, three of whom were discordant for sex. In all twins the fetal sex diagnosis was appropriate. In co-twins of the same sex the hormone levels were very close to each other.     

北京市居家空气微生物粒径及分布特征研究

室内外空气微生物对人们健康的危害不仅与微生物的种类和浓度有关,而且还与微生物粒子的大小及粒径分布特征密切相关,并且不同粒径的空气微生物对人们健康影响的作用机制不同.在北京市不同方向选取31户有1～10岁儿童的家庭进行空气微生物取样,系统研究了室内家庭空气微生物粒径及分布特征.结果表明,室内空气细菌和真菌粒径分布特征不随家庭环境、季节特征、儿童性别、房屋结构的变化而变化,但空气细菌和真菌的粒径分布特征不同.总体上空气细菌和真菌粒径均呈对数正态分布,但空气细菌粒子百分比从Ⅰ级(>8.2μm)到Ⅴ级(1.0～2.0μm)逐渐增加,Ⅵ级(<1.0μm)细菌粒子百分比急剧下降,最高值出现在Ⅴ级,而空气真菌粒径百分比从Ⅰ级～Ⅳ级(2.0～3.5μm)逐渐增加,而后从Ⅳ级～Ⅵ级真菌粒径百分比急剧下降,最高值出现在Ⅳ级.不同优势真菌属的粒径分布也不相同,枝孢属、青霉属和曲霉属呈对数正态分布,最高值出现在Ⅳ级,而链格孢属为偏态分布,最高值出现在Ⅱ级(5.0～10.4μm).室内空气细菌的中值直径明显大于空气真菌,1 a中空气细菌和真菌春、夏、秋季的粒径明显大于冬季.     

Establishment of facultative sexuals

The existence of sex is one of the major unsolved problems in biology. We use computer simulations to model conditions in which sex may first become established. We develop an individual-based population model and show that a hypothetical facultative sex gene can fix, provided that the initial cost is low. It is demonstrated that the equilibrium fitness in the population increases with increasing population size and decreasing mutation rate. The probability of the establishment of the sex gene is found not to be directly related to the fitness difference between the asexual and sexual populations. This change in fitness on changing the parameters of the model is investigated.     

Seaweed sex pheromones and their degradation products frequently suppress amphipod feeding but rarely suppress sea urchin feeding

Summary. A diverse group of brown seaweeds produce bouquets of C₁₁ metabolites, some of which act as pheromones that cue gamete release or attract sperm to eggs following release. We demonstrate that these C₁₁ metabolites and their degradation products also frequently and strongly deter feeding by the herbivorous amphipod Ampithoe longimana, but rarely by the herbivorous sea urchin Arbacia punctulata. Across the range of concentrations tested, seven of twelve C₁₁ metabolites or mixtures that we tested deterred feeding by the amphipod, but only two of eleven deterred the sea urchin. For those compounds where we could rigorously contrast the magnitude of deterrence against the amphipod with the magnitude of deterrence against the urchin, the amphipod was deterred significantly more than the urchin by five of six metabolites. Thus, C₁₁ compounds were more frequently and more strongly deterrent to the amphipod than to the sea urchin. These findings for C₁₁ metabolites conflict with previous investigations, where other classes of seaweed chemical defenses have been shown to deter feeding by large mobile herbivores like urchins and fishes but to be relatively ineffective against mesograzers, especially the species of amphipod that we used here. Our results suggest that C₁₁ metabolites are unusual among the known seaweed chemical defenses in that they are especially effective against mesograzers, which often consume seaweed spores, zygotes, and juveniles. The high concentrations of C₁₁ metabolites in brown algal eggs could allow these defenses to be especially important in defending gametes, zygotes, or young sporelings from herbivorous mesograzers. Received 26 February 1998; accepted 9 April 1998.     

The sex in short supply for matings varies over small spatial scales in a katydid (Kawanaphilanartee, Orthoptera: Tettigoniidae)

In katydids such as Kawanaphilanartee, a female bias in the operational sex ratio (OSR) results in female competition for mates and male choice of mates. Previous work showed that the excess of sexually active females occurs when food availability is low, in part because less food increases the propensity of females to mate as they forage for the large edible spermatophores produced by males. In this study with K.nartee, a pollen-feeding species, we estimate natural variation in numbers of sexually active males and females by assessing male calling activity and the propensity of females to respond to experimental calling males. We found an excess of sexually active males at a site with many flowers and an excess of sexually active females at a site with few flowers about 900 m away. Between-site differences in gut masses of calling males were consistent with the hypothesis that pollen availability controls OSR. Finally, at a third site where flowers were at first scarce, we found that the initial excess in sexually active females changed to an excess of sexually active males after a clump of grass-trees flowered. The mean gut mass of all sampled males from this site increased after flowering. The large variation in OSR that we document for K. nartee highlights the importance of identifying the appropriate spatial and temporal scales over which OSRs are measured in studies of factors controlling sexual selection. Received: 13 May 1997 / Accepted after revision: 27 October 1997     

家蚕斑纹限性品种SC_1的RAPD差异DNA片段的克隆及其酶切图谱分析

利用RAPD技术对家蚕限性普斑品种SC1的雌雄体分别进行PCR扩增通过120种引物的筛选,得到1个雌体特异的RAPDDNA片段将该片段克隆到pUC19质粒,井进行了限制性内切酶图谱分析.     

Possible Extinction Vortex for a Population of Iberian Lynx on the Verge of Extirpation

Abstract: Theory suggests that demographic and genetic traits deteriorate (i.e., fitness and genetic diversity decrease) when populations become small, and that such deterioration could precipitate positive feedback loops called extinction vortices. We examined whether demographic attributes and genetic traits have changed over time in one of the 2 remaining small populations of the highly endangered Iberian lynx (Lynx pardinus) in Doñana, Spain. From 1983 to 2008, we recorded nontraumatic mortality rates, litter size, offspring survival, age at territory acquisition, and sex ratio. We combined these demographic attributes with measures of inbreeding and genetic diversity at neutral loci (microsatellites) and genes subjected to selection (major histocompatibility complex). Data on demographic traits were obtained through capture and radio tracking, checking dens during breeding, track surveys, and camera trapping. For genetic analyses, we obtained blood or tissue samples from captured or necropsied individuals or from museum specimens. Over time a female‐biased sex ratio developed, age of territory acquisition decreased, mean litter size decreased, and rates of nontraumatic mortality increased, but there were no significant changes in overall mortality rates, standardized individual heterozygosity declined steadily, and allelic diversity of exon 2 of class II major histocompatibility complex DRB genes remained constant (2 allelic variants present in all individuals analyzed). Changes in sex ratio and age of territory acquisition may have resulted from demographic stochasticity, whereas changes in litter size and nontraumatic mortality may be related to observed increases in inbreeding. Concomitant deterioration of both demographic attributes and genetic traits is consistent with an extinction vortex. The co‐occurrence, with or without interaction, of demographic and genetic deterioration may explain the lack of success of conservation efforts with the Doñana population of Iberian lynx.