Sex hormone-dependent brain maturation and sexual behaviour in rats.

In male and female rats the endogenous steroid and gonadotrophin secretion was inhibited by injecting high doses of chlormadinone acetate (CmAc) from day 14 to 24 of life, i. e. during the period of brain maturation. In adulthood the males treated prepubertally with CmAc exhibited reduced sexual activity and fertility, whereas the females did not differ from the controls. More complete sex hormone deficiency during brain maturation was achieved by castration on day 14 of life. Controls were castrated at normal puberty time (40--60 days). Both groups were then substituted with androgens or oestrogens. In the females castrated on day 14 no impairment of sexual behaviour was observed as compared to the later castrated controls. In contrast, the early castrated males showed delayed onset of mounting behaviour. At autopsy, the weights of their sex organs were found to be lower than in the controls despite equal testosterone replacement for several months. These findings speak in favour of a permanently diminished responsiveness to androgens in males having been exposed to more or less severe androgen deficiency during sex specific brain maturation. Hence, the maturation of a male hypothalamus as well as the differentiation appears to depend at least in part on the presence of androgens, whereas in females it runs without hormonal influence.     

A routine method for contrasting elastin at the ultrastructural level

A reliable, simple, and inexpensive method for ultrastructural investigation of elastin is described. This method uses uranyl acetate dissolved in absolute methanol, followed by an optional lead citrate counterstain. The procedure was tested on a number of animal and human tissues that had been fixed and processed differently.     

A new method for the routine spreading of DNA in protein-free conditions.

Electron microscopic studies of DNA are hampered by difficulties encountered with the spreading of DNA under protein-free conditions. The established and currently popular technique of spreading DNA on carbon membranes treated by glow discharge in an atmosphere of pentylamine is limited with regard to its reproducibility and the proper distribution of spread molecules on the surface of the membranes. A new, reliable, and highly reproducible technique using tri-L-(dimethylaminomethyl)phenol (DMP 30), a promotor factor for spreading circular DNA, linear DNA, and DNA-protein complexes, is described in this paper. Monolayers of DMP 30 are formed at the air-water interface by a microdiffusion procedure on droplets. DNA molecules that diffuse on this monolayer can easily be picked up on hydrophobic carbon membranes. This method, which is easy, reproducible, and fast, will facilitate electron microscopic studies of DNA-protein interactions.     

Stimulatory effect of a maize diet on sexual behaviour of male rats

Feeding rats for 4 days with a diet of maize, a staple which is deficient in tryptophan (TP), caused a depletion of brain 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) without affectin noradrenaline and dopamine content.Addition of TP (2 g/kg of diet) to the TP deficient diet resulted in increased brain 5-HT and 5-HIAA content.Isolated male rats consuming the maize diet, when brought together, showed markedly increased mounting activity, while rats on the maize diet supplemented with TP did not display such a behaviour.These data provide further evidence for the role of the 5-HT system in regulating the sexual behaviour of male rats.     

A routine method for the establishment of permanent growing lymphoblastoid cell lines

Summary Permanent lymphoblastoid cell lines are of great practical value in human clinical and experimental genetics. A detailed protocol for routine use is given for the establishment of lymphoblastoid lines from peripheral blood using Esptein-Barr virus and the immunosuppressivum Cyclosporin A. In addition, the biologic basis of this transformation system is briefly summarized.     

A revised method for the observation of conidiogenous structures in fungi

Preparation of fungal material for microscopical examination of their conidiogenous structures is described below. A modification to the existing methods used coupled with a sporulation medium has proved to be simple to use and successful for the induction of sporulation and subsequent examination of conidiogenous structures in a range of xylariaceous species and in endophytic fungi.     

Genetics of sexual behaviour in Drosophila

The analysis of genetics of behaviour within and between species provides important clues about the forces shaping the evolution of behavioural genes. In Drosophila, a number of key processes such as emergence from the pupal case, locomotor activity, feeding, olfaction and aspects of mating behaviour are under circadian regulation. Genes controlling sexual behaviour are likely to control species specific differences in courtship that are involved in reproductive isolation of closely related species. Courtship in Drosophila is characterized by a series of stereotyped behaviours that lead to copulation and more than 30 genes have been identified through mutations that affect one or more of these elements. Although curiosity about behavioural differences between the sexes undoubtedly predates recorded history, little efforts have been made to uncover the molecular basis of male and female courtship. The brain and nervous system functions that underlie sex-specific behaviour are of obvious importance to all animals including humans. To understand behaviour related to sex it is important to distinguish those aspects that are controlled genetically. The isolation and analysis of Drosophila mutants with altered sexual orientation lead to the identification of novel branches in the sex-determination cascade, which govern the sexually dimorphic development of the nervous system.     

Male-like sexual behaviour of female rats with unilateral lesions in the hypothalamic ventromedial nuclear region.

In castrated female rats treated with androgen or oestrogen a significant decrease of female sexual behaviour assocated with a significant increase of male sexual behaviour was induced by unilateral lesions of the hypothalamic ventromedial nucleus.     

Effect of rapid eye movement sleep deprivation on sexual behaviour of male rats

Rapid eye movement sleep deprivation for 3 to 4 days by the platform pedestal procedure produced an increase in sexual behaviour of male rats. The possible factors contributing towards the increase in sexual behaviour are discussed.     

A multilevel analysis of the determinants of high-risk sexual behaviour in sub-Saharan Africa

A number of authors have identified multiple concurrent sexual partnerships by both men and women to lie at the root of the HIV/AIDS epidemic in sub-Saharan Africa. This study applies multilevel models to Demographic and Health Survey data collected during 2003-2008 in 20 sub-Saharan African countries to examine the influence of social and cultural context on involvement with multiple sexual partnerships in the region, above and beyond the effects of individual characteristics. The findings provide support for the ecological argument that health behaviours are shaped and determined by societal conditions, in addition to the effects of individual and household characteristics. Involvement with multiple sex partners is most prevalent in societies in which sexual norms are widely permissive and where polygyny is common. Individual autonomy is substantial and attitudes towards sexuality are more liberal among men and women who live in communities in which sexual norms are widely permissive. Men and women who are most likely to have multiple sex partners in the sub-Saharan region are those who initiated sexual activity earlier and those who have the individual attributes (e.g. young age, urban residence, education, media exposure and working for cash and away from home) that bring to them more rights and/or decision-making autonomy, but not necessarily more financial resources and economic security (mostly among women). On the other hand, involvement with multiple partners is determined by cultural norms (i.e. permissive sexual norms) and social change (i.e. mass education, expansion of cash employment). The findings suggest a number of opportunities for more effective policy and programmatic responses to curb the prevalence of multiple partnerships in sub-Saharan Africa.     

A simplified routine method for determining carbohydrate fermentation by yeasts

The use of commercially available materials in a minimal medium contributes to the simplicity, reliability, and reproducibility of a method described to demonstrate carbohydrate fermentation reactions by yeasts. The medium consists of 1% yeast extract and 2% test carbohydrate in distilled water, dispensed in a modified Durham fermentation tube. Carbohydrate fermentation patterns can usually be obtained within a period of 7 days. The ability of yeasts to ferment carbohydrates is determined strictly on the basis of gas production from the substrate. The method proved reliable in reproducing established fermentation patterns for 112 different yeast strains representing 13 separate genera.

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Zusammenfassung Der Gebrauch von handelsüblichen Grundbestandteilen in einem geringen Medium trägt zu der Einfachheit, Zuverlässigkeit und Reproduzierbarkeit der beschriebenen Methode, um die Gärungsreaktionen der Karbohydrate durch Hefen zu veranschaulichen, bei. Das Medium besteht aus einem 1 prozent. Hefenauszug und aus einem 2 prozentigen Testkarbohydrat in destilliertem Wasser, die auf modifiziertes Durham Gärungsreagensglas verteilt sind. Das Karbohydrat-Gärungsmodell kann gewöhnlich innerhalb einer Periode von sieben Tagen erhalten werden. Die Fähigkeit von Hefen, Karbohydrate zu vergären, ist ausschließlich auf Grund der Gasentwicklung aus den Produkten bestimmt. Die Methode erwies sich zuverlässig in der Erzeugung festgestellter Gärungsmodelle aus 112 Hefen, die 13 verschiedene Gattungen darstellten.

     

A glycol methacrylate method for the routine histologic evaluation of rat inner ear

A method has been developed for the histologic evaluation of rat inner ear using glycol methacrylate (GMA) and steel knife sectioning. The necropsy, fixation, and histologic techniques described are not so complex and difficult as to preclude their routine use. The method is particularly useful in studies in which the entire inner ear of a large number of animals must be evaluated histologically.     

A shot in the dark: same-sex sexual behaviour in a deep-sea squid

Little is known about the reproductive habits of deep-living squids. Using remotely operated vehicles in the deep waters of the Monterey Submarine Canyon, we have found evidence of mating, i.e. implanted sperm packages, on similar body locations in males and females of the rarely seen mesopelagic squid Octopoteuthis deletron. Equivalent numbers of both sexes were found to have mated, indicating that male squid routinely and indiscriminately mate with both males and females. Most squid species are short-lived, semelparous (i.e. with a single, brief reproductive period) and promiscuous. In the deep, dark habitat where O. deletron lives, potential mates are few and far between. We suggest that same-sex mating behaviour by O. deletron is part of a reproductive strategy that maximizes success by inducing males to indiscriminately and swiftly inseminate every conspecific that they encounter.