The etiology of male homosexuality

Sexual Orientation in Twins: Evidence That Human Sexual Identity May Be Determined Five Days Following Fertilization

Human same-sex sexual attraction has been recorded from the beginning of written history. It remains a controversial topic, but recent theories favor prenatal influences. A paradox is the occurrence of same-sex orientation in twins in that there is a higher level of concordance in monozygous twins compared to that in dizygous twins or non-twin siblings. If sexual orientation was entirely genetically determined monozygous twins would be expected to have identical sexual inclinations. Monozygous twins have twice the incidence of sexual concordance in comparison to dizygous twins but a third of these pairs have different sexual identities. An explanation for this disparity may lie in the time an embryo splits to form two separate fetuses. If splitting occurs early in twin development each twin may develop his or her own sexual identity; splitting occurring later results in twins that have the same sexual dispositions. A possible process for such determination may be in the mitochondria, with universal maternal inheritance of a proportion of normal functioning but alternate mitochondria. Variation in the distribution of these mitochondria in neural precursor cells becomes a mechanism for the development of intrinsic sexual orientation and for the spectrum of human sexual inclinations. The timing of embryonic splitting may be determined from the examination of fetal membranes, and the concept of early fetal sexual orientation is open to support or disproval.

Cognitive-Behavioral Therapy for Depression in an Older Gay Man: A Clinical Case Study

Although strong evidence supports cognitive-behavioral therapy for late-life depression and depression in racial and ethnic minorities, there are no empirical studies on the treatment of depression in older sexual minorities. Three distinct literatures were tapped to create a depression treatment protocol for an older gay male. Interventions were deduced from the late-life depression literature, culturally adapted CBT protocols for racial minorities, and the emerging social and developmental psychological theories for lesbian, gay, and bisexual populations. Specific treatment interventions, processes, and outcomes are described to illustrate how these literatures may be used to provide more culturally appropriate and effective health care for the growing, older sexual minority population.

An immune hypothesis of sexual orientation

Sexual orientation is encoded within immune-cell subsets (ICS) of mucosal and epithelial tissues. Gender orientation may be encoded within other ICS. Many immune cells: recognize and react to H-Y and H-X antigens; and enact these perceptions and reactions in accord with the perceiver's and the perceived's MHC haplotype, XX or XY status, and immune-self recognition. Non-heterosexual orientations derive from excessive cross-priming, accompanied by clonal deletions, clonal expansions, anergy and tolerance. For at least some tissues, cross-priming sufficient to induce altered orientations may occur during critical periods of immunological development and can occur during fetal and infant development via maternal-fetal transfusion, placental pathology, and impaired maternal nutrient-status or via excessive peripheral apoptosis during postnatal illness. Mast cell interactions with neurons illustrate how mucosal perceptions can be transduced into neuronal signals that modulate CNS events. This hypothesis is testable by mixed-lymphocyte reactions in appropriate cell subsets. Dendritic-cell immunizations are a potential therapy.