934 resultados para FEMALE-BIASED SEX RATIO


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We earlier described three lines of sex-reversed XY female mice deleted for sequences believed close to the testes-determining gene (Sry) on the Y chromosome short arm (Yp). The original sex-reversed females appeared among the offspring of XY males that carried the Yp duplication Sxr on their X chromosome. Earlier cytogenetic observations had suggested that the deletions resulted from asymmetrical meiotic recombination between the Y and the homologous Sxr region, but no direct evidence for this hypothesis was available. We have now analyzed the offspring of XSxr/Y males carrying an evolutionarily divergent Mus musculus domesticus Y chromosome, which permits detection and characterization of such recombination events. This analysis has enabled the derivation of a recombination map of Yp and Sxr, also demonstrating the orientation of Yp with respect to the Y centromere. The mapping data have established that Rbm, the murine homologue of a gene family cloned from the human Y chromosome, lies between Sry and the centromere. Analysis of two additional XY female lines shows that asymmetrical Yp-Sxr recombination leading to XY female sex reversal results in deletion of Rbm sequences. The deletions bring Sry closer to Y centromere, consistent with the hypothesis that position-effect inactivation of Sry is the basis for the sex reversal.

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Female moths often become depleted of sex pheromone after mating as the various components of virgin behavior are switched off. In examining a potential male contribution to these events in the corn earworm moth Helicoverpa zea, we have characterized a basic polypeptide from the tissues producing (accessory glands) and storing (duplex) the seminal fluids. The peptide evokes the depletion of sex pheromone when injected into virgin females. This pheromonostatic peptide (PSP) is 57 amino acids long and contains a single disulfide bridge. It is blocked at the N terminus with pyroglutamate and at the C terminus by amidation. As little as 23 ng of peptide evokes the near-complete depletion of pheromone in decapitated (neck-ligated) females that had been injected with pheromone biosynthesis-activating neuropeptide. Activity is approximately 15-fold less in intact virgins, showing that the head limits the expression of activity in these injected females. Females mated to surgically impaired males, capable of producing a spermatophore but not transferring spermatozoa or seminal fluids, are depleted of pheromone by injected peptide. Females whose abdominal nerve cords have been severed are not depleted of pheromone after mating. Thus, neural signals either descending or ascending via the nerve cord are required for the depletion of pheromone after mating. PSP, from the seminal fluids, may participate in this process by direct or indirect action on the glandular tissue; if so, it represents an unusual mechanism in insects for the regulation by seminal fluids of postmating reproductive behavior.

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The study of psychopathy is still in early stages with regard to gender differences. Historically, the majority of research has been conducted on male populations, resulting in a gender-biased construct that does not appear to be generalizable to female populations. This paper provides a review of the existing literature on psychopathy, as well as research on inherent gender differences (biology, chemistry, socialization, etc.). Connections between these bodies of research are supposed and suggestions for future study are provided.

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Illus. by F. Hayman.

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Mode of access: Internet.

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"This is not the kind of book that can usefully be taken through numerous editions, so with the issue of this edition it will finish its career."

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Thesis (Master's)--University of Washington, 2016-06

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We combine spatial data on home ranges of individuals and microsatellite markers to examine patterns of fine-scale spatial genetic structure and dispersal within a brush-tailed rock-wallaby (Petrogale penicillata) colony at Hurdle Creek Valley, Queensland. Brush-tailed rock-wallabies were once abundant and widespread throughout the rocky terrain of southeastern Australia; however, populations are nearly extinct in the south of their range and in decline elsewhere. We use pairwise relatedness measures and a recent multilocus spatial autocorrelation analysis to test the hypotheses that in this species, within-colony dispersal is male-biased and that female philopatry results in spatial clusters of related females within the colony. We provide clear evidence for strong female philopatry and male-biased dispersal within this rock-wallaby colony. There was a strong, significant negative correlation between pairwise relatedness and geographical distance of individual females along only 800 m of cliff line. Spatial genetic autocorrelation analyses showed significant positive correlation for females in close proximity to each other and revealed a genetic neighbourhood size of only 600 m for females. Our study is the first to report on the fine-scale spatial genetic structure within a rock-wallaby colony and we provide the first robust evidence for strong female philopatry and spatial clustering of related females within this taxon. We discuss the ecological and conservation implications of our findings for rock-wallabies, as well as the importance of fine-scale spatial genetic patterns in studies of dispersal behaviour.

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During mammalian sexual development, the SOX9 transcription factor up-regulates expression of the gene encoding anti-Mullerian hormone (AMH), but in chickens, Sox9 gene expression reportedly occurs after the onset of Amh expression. Here, we examined expression of the related gene Sox8 in chicken embryonic gonads during the sex-determining period. We found that cSox8 is expressed at similar levels in both sexes at embryonic day 6 and 7, and only at the anterior tip of the gonad, suggesting that SOX8 is not responsible for the sex-specific increase in cAmh gene expression at these stages. We also found that several other chicken Sox genes (cSox3, cSox4 and cSox11) are expressed in embryonic gonads, but at similar levels in both sexes. Our data suggest that the molecular mechanisms involved in the regulation of Amh genes of mouse and chicken are not conserved, despite similar patterns of Amh expression in both species.

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Background: Recent work has demonstrated that the lifetime suicide risk for patients with DSM IV Major Depression cannot mathematically approximate the accepted figure of 15%. Gender and age significantly affect both the prevalence of major depression and suicide risk, Methods: Gender and age stratified calculations were made on the entire population of the USA in 1994 using a mathematical algorithm. Sex specific corrections for under-reporting were incorporated into the design. Results: The lifetime suicide risks for men and women were 7% and 1%, respectively. The combined risk was 3.4%. The male:female ratio for suicide risk in major depression was 10:1 for youths under 25, and 5.6:1 for adults. Conclusions: Suicide in major depression is predominantly a male problem, although complacency towards female sufferers is to be avoided. Diagnosis of major depression is of limited help in predicting suicide risk compared to case specific factors. The male experience of depression that leads to suicide is often not identified as a legitimate medical complaint by either sufferers or professionals. Increasing help-accessing by males is a priority. Clinical implications: Patients with a history of hospitalisation; comorbidity, especially for substance abuse; and who are male, require greater vigilance for suicide risk. It may be that for males che threshold for diagnosing and treating major depression needs to be lowered. Limitations: This research is based on a mathematical algorithm to approximate a life-long longitudinal study that identifies community cases of depression. Our findings therefore rely on the validity of the statistics used. Extrapolation is limited to populations with an actual suicide rate of 17/100,000 or less and a lifetime prevalence of major depression of 17% or more. (C) 1999 Elsevier Science B.V. All rights reserved.