2,175,853 research outputs found

    The male to female ratio at birth

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    The factors that influence the male to female ratio at birth are legion. Males are usually born in excess and stress decreases the ratio while wellbeing and good health tends to increase it. This paper reviews the multitudes of factors that have been implicated as affecting this ratio, from historical times to date.peer-reviewe

    Female Scent Signals Enhances Male Resistance to Influenza

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    Scent of receptive females as signal to reproduction stimulate male mice to olfactory search of a potential breeding partner^1, 2^. This searching behavior is coupled with infection risk due to bacterial contamination of the fecal and urine scent marks^4^. The theoretical consideration of host evolution under inevitable parasitic pressures, including helminthes, bacteria, virus etc., predicts adaptations that help protect against parasites associated with breeding^7^. In this study, we propose that acceptation of female signals by male mice leads to adaptive redistribution of immune defense directed to protection against respiratory infection risks. Our results reveal migration of macrophages and neutrophils to upper airways upon exposure to female odor stimulus resulting in increased resistance to influenza virus in male mice. Contrary to widely accepted immunosuppressive function of female sexual signals, our data provide the first demonstration of the adaptive immunological response to female odor stimulus through induction of nonspecific immune response in upper airways

    Influence of a knee brace intervention on perceived pain and patellofemoral loading in recreational athletes

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    Background: The current investigation aimed to investigate the effects of an intervention using knee bracing on pain symptoms and patellofemoral loading in male and female recreational athletes. Methods: Twenty participants (11 males & 9 females) with patellofemoral pain were provided with a knee brace which they wore for a period of 2 weeks. Lower extremity kinematics and patellofemoral loading were obtained during three sport specific tasks, jog, cut and single leg hop. In addition their self-reported knee pain scoreswere examined using the Knee injury and Osteoarthritis Outcome Score. Datawere collected before and after wearing the knee brace for 2 weeks. Findings: Significant reductions were found in the run and cut movements for peak patellofemoral force/pressure and in all movements for the peak knee abduction moment when wearing the brace. Significant improvements were also shown for Knee injury and Osteoarthritis Outcome Score subscale symptoms (pre: male= 70.27, female = 73.22 & post: male = 85.64, female = 82.44), pain (pre: male = 72.36, female = 78.89 & post: male = 85.73, female = 84.20), sport (pre: male = 60.18, female = 59.33 & post: male = 80.91, female =79.11), function and daily living (pre: male = 82.18, female = 86.00 & post: male = 88.91, female = 90.00) and quality of life (pre: male= 51.27, female= 54.89 & post: male= 69.36, female= 66.89). Interpretation:Male and female recreational athleteswho suffer frompatellofemoral pain can be advised to utilise knee bracing as a conservative method to reduce pain symptoms

    Evaluation of voice in female-to-male transsexuals

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    Male and female stem cells and sex reversal in Hydra polyps

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    Single interstitial stem cells of male polyps of Hydra magnipapillata give rise to clones that differentiate either male or female gametes. To test the sexual stability of these clones, stem cells were recloned. The results indicate that stem cells from female clones are stable in their sexual differentiation capacity; male stem cells, by comparison, switch sexual phenotype at the rate of 10-2 per cell per generation. As a result, female polyps contain only female stem cells; male polyps contain a mixture of male and female stem cells. A model is presented in which the sexual phenotype of Hydra polyps is controlled by (i) the switching rate of male and female stem cells and (ii) the repression of female differentiation by male stem cells

    Mating has opposite effects on male and female sexually selected cuticular hydrocarbons

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    In Drosophila serrata flies, there is female choice for male cuticular hydrocarbon (CHC) profiles and male choice for female CHC profiles. Furthermore, both males and females can alter their CHCs: when there is more opportunity for mating, males express combinations of CHCs preferred by females; however, females appear to change CHC profiles to avoid male harassment. In this study, I investigate the effect of number of matings (0–4) on male and female sexually selected CHCs. Mating caused males to express CHCs associated with higher male mating success. Thus, successfully mating males are likely to have increased future mating success. Conversely, females that mated more times expressed CHC profiles that were associated with lower female mating success. Females maximized their offspring production by mating more than once, but additional matings did not provide additional benefits. Furthermore, number of matings did not affect female survival. In total, these results suggest that females alter CHC expression to discourage male courtship when additional matings are not beneficial. In conclusion, plasticity in male and female CHC expression can both increase variance in male mating success and decrease variance in female mating success, driving the evolution of sexually selected chemical signals

    Differential expression of conserved germ line markers and delayed segregation of male and female primordial germ cells in a hermaphrodite, the leech helobdella.

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    In sexually reproducing animals, primordial germ cells (PGCs) are often set aside early in embryogenesis, a strategy that minimizes the risk of genomic damage associated with replication and mitosis during the cell cycle. Here, we have used germ line markers (piwi, vasa, and nanos) and microinjected cell lineage tracers to show that PGC specification in the leech genus Helobdella follows a different scenario: in this hermaphrodite, the male and female PGCs segregate from somatic lineages only after more than 20 rounds of zygotic mitosis; the male and female PGCs share the same (mesodermal) cell lineage for 19 rounds of zygotic mitosis. Moreover, while all three markers are expressed in both male and female reproductive tissues of the adult, they are expressed differentially between the male and female PGCs of the developing embryo: piwi and vasa are expressed preferentially in female PGCs at a time when nanos is expressed preferentially in male PGCs. A priori, the delayed segregation of male and female PGCs from somatic tissues and from one another increases the probability of mutations affecting both male and female PGCs of a given individual. We speculate that this suite of features, combined with a capacity for self-fertilization, may contribute to the dramatically rearranged genome of Helobdella robusta relative to other animals

    Different response to epidermal growth factor of hepatocytes in cultures isolated from male or female rat liver. Inhibitor effect of estrogen on binding and mitogenic effect of epidermal growth factor

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    Deoxyribonucleic acid (DNA) synthesis in hepatocytes isolated from the livers of male and female rats has been compared in monolayer culture. Plating efficiency, DNA and protein content, viability, and morphologic appearance were the same in cultures prepared with hepatocytes isolated from male or female rats. Epidermal growth factor (EGF)-induced DNA synthesis was significantly higher in hepatocytes from male rats than in hepatocytes from female rats. This was the case whether hepatocytes were isolated from normal or partially hepatectomized male or female rats. Hepatocytes isolated from regenerating liver synthesize more DNA than those isolated from normal liver in response to EGF. This increased response to EGF in hepatocytes derived from regenerating liver was relatively the same for male- and female-derived hepatocytes, but the magnitude of the response was considerably higher in male-derived hepatocytes. In contrast, in vivo DNA synthesis in the liver remnant after partial hepatectomy was similar in male and female rats if measured 24 h after the operation. A comparison of EGF binding to male- and female-derived hepatocytes maintained in primary culture indicated a lower number of high-affinity receptors for EGF in the female hepatocytes. The addition of estrogen to primary cultures of hepatocytes isolated from male rats inhibited EGF binding as well as EGF-induced DNA synthesis. Our studies show significant differences in DNA synthesis in response to EGF when male and female hepatocytes are compared in primary culture. The regenerative response after partial hepatectomy, on the other hand, was the same in male and female rats. Thus, our studies indicate that the sex of the donor rat is important when hepatocytes in culture are used for a variety of studies, such as hepatocyte metabolism, induction and control of DNA synthesis, and hepatocarcinogenesis. In addition, our results indicate that caution is advised when inferences are made from in vitro findings for in vivo conditions. © 1987

    Request Strategies Used by Five Street Dance Groups Leaders to Male and Female Members in the Meeting

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    This study entitled “Request Strategies Used by Five Street Dance Group Leaders to Their Male and Female Members in the Meetings” was conducted to know the influence of gender toward the request made by the leaders in the street dance groups' meetings. The writer observed five young male leaders of five different street dance groups in making request to the male and female members in the meeting. The writer used the theory from Trosborg (1995) to classify the request uttered by the leaders. He found that the leaders mostly used the same request strategy, which is direct strategy to both male and female members in the meetings. The result also showed that the leaders used more indirect strategies, such as mild hints to the female than the male members probably because the leaders tried to be more polite to the female members

    Reproductive isolation between two sympatric simultaneous hermaphroditic shrimp, Lysmata wurdemanni and L. boggessi

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    To investigate pre- and post-zygotic isolation between two sympatric and phylogenetically related species of Lysmata shrimp, two assays were conducted in the laboratory: (1) no specific mate choice where mating between the two species was ‘forced’; (2) specific mate choice or preference where a female had a choice between conspecific and heterospecifc males. Behavioural studies reveal that female L. wurdemanni accepted only conspecific male shrimp, whereas L. boggessi females would mate with an interspecific male if there was no conspecific male present. When males of both species were present, L. boggessi females always mated with the conspecific male. Male L. boggessi in general did not respond to the sex pheromones secreted by female L. wurdemanni and did not display any pre-copulatory behaviour to newly moulted female L. wurdemanni. On the other hand, some male L. wurdemanni responded to female L. boggessi. Although mating was successful between male L. wurdemanni and female L. boggessi, the resulting embryos lived at most for 10 days and failed to hatch. The results indicate that the two species are both pre-zygotically and post-zygotically isolated. Behavioural observation suggests that chemical cues are most likely responsible for pre-zygotic isolation
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