Effects of replacing meat with soyabean in the diet on sex hormone concentrations in healthy adult males

A randomised crossover dietary intervention study was performed to evaluate the effects of replacing meat protein in the diet with a soyabean product, tofu, on blood concentrations of testosterone, dihydrotestosterone, androstanediol glucuronide, oestradiol, sex hormone-binding globulin (SHBG), and the free androgen index (total testosterone concentration/SHBG concentration x 100; FAI). Forty-two healthy adult males aged 35-62 years were studied. Diets were isoenergetic, with either 150 g lean meat or 290 g tofu daily providing an equivalent amount of macronutrients, with only the source of protein differing between the two diets. Each diet lasted for 4 weeks, with a 2-week interval between interventions. Fasting blood samples were taken between 07.00 and 09.30 hours. Urinary excretion of genistein and daidzein was significantly higher after the tofu diet (P

Physiological evidence for reproductive suppression in the introduced population of brown tree snakes (Boiga irregularis) on Guam

Introduced species are an increasingly pervasive problem. While studies on the ecology and behavior of these pests are numerous, there is relatively little known of their physiology, specifically their reproductive and stress physiology. One of the best documented introduced pest species is the brown tree snake, Boiga irregularis, which was introduced onto the Pacific island of Guam sometime around World War II. The snake is responsible for severely reducing Guam's native vertebrates. We captured free-living individuals throughout the year and measured plasma levels of stress and sex hormones in an effort to determine when they were breeding. These data were compared to reproductive cycles from a captive population originally collected from Guam. Free-living individuals had chronically elevated plasma levels of the stress hormone corticosterone and basal levels of sex steroids and a remarkably low proportion were reproductively active. These data coincide with evidence that the wild population may be in decline. Captive snakes, had low plasma levels of corticosterone with males displaying a peak in plasma testosterone levels during breeding. Furthermore, we compared body condition between the free-living and captive snakes from Guam and free-living individuals captured from their native range in Australia. Male and female free-living snakes from Guam exhibited significantly reduced body condition compared to free-living individuals from Australia. We suggest that during the study period, free-living brown tree snakes on Guam were living under stressful conditions, possibly due to overcrowding and overexploitation. of food resources, resulting in decreased body condition and suppressed reproduction. (C) 2004 Elsevier Ltd. All rights reserved.

Conditional deletion of hypothalamic Y2 receptors reverts gonadectomy-induced bone loss in adult mice

Reduction in levels of sex hormones at menopause in women is associated with two common, major outcomes, the accumulation of white adipose tissue, and the progressive loss of bone because of excess osteoclastic bone resorption exceeding osteoblastic bone formation. Current antiresorptive therapies can reduce osteoclastic activity but have only limited capacity to stimulate osteoblastic bone formation and restore lost skeletal mass. Likewise, the availability of effective pharmacological weight loss treatments is currently limited. Here we demonstrate that conditional deletion of hypothalamic neuropeptide Y2 receptors can prevent ongoing bone loss in sex hormone-deficient adult male and female mice. This benefit is attributable solely to activation of an anabolic osteoblastic bone formation response that counterbalances persistent elevation of bone resorption, suggesting the Y2-mediated anabolic pathway to be independent of sex hormones. Furthermore, the increase in fat mass that typically occurs after ovariectomy is prevented by germ line deletion of Y2 receptors, whereas in male mice body weight and fat mass were consistently lower than wild-type regardless of sex hormone status. Therefore, this study indicates a role for Y2 receptors in the accumulation of adipose tissue in the hypogonadal state and demonstrates that hypothalamic Y2 receptors constitutively restrain osteoblastic activity even in the absence of sex hormones. The increase in bone formation after release of this tonic inhibition suggests a promising new avenue for osteoporosis treatment.

Gonadotrophin and prolactin secretion in castrated male sheep following subcutaneous or intracranial treatment with testicular hormones

Interactions between testosterone, estradiol, and inhibin in the control of gonadotrophin secretion in males are poorly understood. Castrated rams were treated with steroid-free bovine follicular fluid (bFF), testosterone, or estradiol and for 7 d (2 x 2 x 2 factorial design). Given independently, none of the exogenous hormones affected follicle-stimulating hormone (FSH) concentrations, but the combination of one or both steroids with bFF reduced FSH secretion. Testosterone and estradiol reduced luteinizing hormone (LH) pulse frequency (there was no synergism), and bFF had no effect. Plasma prolactin concentrations were not affected by any treatment. To locate the central sites of steroid action, castrated rams were bilaterally implanted in the preoptic area (POA), ventromedial nucleus (VMH), or arcuate nucleus (ARC). These implants did not affect FSH or prolactin concentrations, or LH pulse amplitude. The frequency of the LH pulses was not affected by testosterone in any site. Estradiol located in the ARC, but not the POA or VMH, decreased LH pulse frequency. In summary, FSH secretion is controlled by synergistic interactions between inhibin and estradiol or testosterone, whereas GnRH/LH pulse frequency is controlled by testicular steroids. Estradiol acts partly, at least, in the ARC, but the central site of action, testosterone remains unknown.

Seeking SOCS and sex steroids

In seeking to explain why oral estrogen inhibits the GH-IGF-I axis, a recent study has unearthed a new way that steroid hormones can influence growth hormone action. This involves suppressors of cytokine signalling (SOCS), which offer a new level of understanding in signal control and crosstalk.

Using the level set method to model endogenous lava dome growth

Modeling volcanic phenomena is complicated by free-surfaces often supporting large rheological gradients. Analytical solutions and analogue models provide explanations for fundamental characteristics of lava flows. But more sophisticated models are needed, incorporating improved physics and rheology to capture realistic events. To advance our understanding of the flow dynamics of highly viscous lava in Peléean lava dome formation, axi-symmetrical Finite Element Method (FEM) models of generic endogenous dome growth have been developed. We use a novel technique, the level-set method, which tracks a moving interface, leaving the mesh unaltered. The model equations are formulated in an Eulerian framework. In this paper we test the quality of this technique in our numerical scheme by considering existing analytical and experimental models of lava dome growth which assume a constant Newtonian viscosity. We then compare our model against analytical solutions for real lava domes extruded on Soufrière, St. Vincent, W.I. in 1979 and Mount St. Helens, USA in October 1980 using an effective viscosity. The level-set method is found to be computationally light and robust enough to model the free-surface of a growing lava dome. Also, by modeling the extruded lava with a constant pressure head this naturally results in a drop in extrusion rate with increasing dome height, which can explain lava dome growth observables more appropriately than when using a fixed extrusion rate. From the modeling point of view, the level-set method will ultimately provide an opportunity to capture more of the physics while benefiting from the numerical robustness of regular grids.

Psychological distress among female sex workers

The prevalence and correlates of psychological distress were examined in a sample of 171 female sex workers in Queensland. It was found that 28 per cent were above the GHQ-28 threshold for mild psychiatric morbidity, a rate that is not appreciably different from that of women in the general community. The sample included only eight street sex workers, all of whom reported significant distress. Logistic regression analyses showed that a history of injecting drug use, an early age at leaving home and wanting to leave the sex industry were independent predictors of poor mental health. Distressed sex workers reported fewer sexual health examinations and less consistent condom use with their clients than those who were not distressed.

Biogenesis of sex pheromones in the female olive fruit-fly

A likely pathway to the sex pheromones of Bactrocera oleae (olive fruit-fly) is presented, based mainly on feeding experiments with deuterium labelled precursors.

Extended delayed recall of AVLT word lists: Effects of age and sex on adult performance

An extension of a previous study of age and sex effects on verbal recall (Geffen, Moar, O'Hanlon, lark, & Geffen, 1990) examined forgetting of words over extended delays. The AVLT was administered to 201 normal adults (99 males, 102 females) ranging in age between 20 and 59 years. Recall was tested at intervals of 30 minutes, 24 hours, and 7 days after acquisition. Testing of the latter two intervals was conducted by telephone (Experiment 1, N = 177). After 30 minutes there was no significant loss of the 10 to 11 words retained from five acquisition trials. However, an overall mean of about one word was forgotten after 1 day and a further word after 7 days. The oldest age group (50-59 years) acquired fewer words and forgot more words than the younger groups. Females of all age groups performed slightly better than males at acquisition, at retention, and at recall after longer delays. A second experiment showed that telephone testing at the longer delay intervals was equivalent to testing face to face. These results extend the use of the AVLT by assessing memory decay beyond the immediate testing period. Telephone follow-up is a convenient and economical method of testing delayed recall.

Rapid evolution towards equal sex ratios in a system with heterogamety

The equal sex ratios found in many species with heterogametic sex determination may be a consequence of selection for equality or the result of the Mendelian segregation of the two sex chromosomes. A lack of genetic variation in sex ratio in species with heterogamety has been the major obstacle in distinguishing between these two hypotheses. We overcome this obstacle by generating hybrids between two species of Drosophila. The resulting hybrid lines had biased sex ratios, allowing us to observe the evolution of sex ratio in replicate populations. Sex ratio converged towards 1:1 after 16 generations of natural selection. These changes in sex ratio were not due to differences in viability between the sexes and the loci underlying the variation in sex ratio were not sex-linked. Equal sex ratios may therefore be the result of natural selection as Fisher predicted.

Attachment style, assertive communication, and safer-sex behavior

This research tested the proposition that the effect of attachment security on safer-sex practice may be mediated by communication patterns. One hundred eighty-five undergraduate students completed questionnaire measures of attachment, assertiveness, and attitudes to communication about AIDS. Eight weeks later, they reported on their practice of safer sex in the period since the first testing session. Hierarchical regressions showed that at Step 1, anxiety about relationships (a measure of insecure attachment) was associated with less safer-sex practice, for all outcome measures. Attitudes to communication about AIDS added to the prediction of general reports of safer-sex practice: in line with the mediational model, anxiety about relationships became unimportant as a predictor when communication variables were included. Communication variables failed to add to the prediction of safer sex on the most recent encounter, and both anxiety about relationships and attitudes to communication about AIDS predicted condom use. Some gender differences in patterns of prediction were noted. The results are discussed in terms of attachment style and its links with the negotiation of sexual practice and relationship issues.

Effects of preferred hand and sex on the perception of tactile simultaneity

The effects of handedness, sex and the influence of hand placement in extrapersonal space on temporal information processing was investigated by measuring thresholds for perceiving the simultaneity of pairs of tactile stimuli. Simultaneity thresholds of preferred right handed and left handed university students with left hemisphere speech representation were compared using unimanual and bimanual stimulation at three hand placements (midline, lateral and crossed). In unimanual conditions two fingers of one hand were stimulated (single hemisphere), whereas in the bimanual conditions one finger of each hand was stimulated (cross hemispheres). Bimanual minus unimanual thresholds provided an estimate of interhemisphere transmission time (IHTT) regardless of hand placement. The effects of hemispace varied with the type of stimulation. With unimanual stimulation, overall thresholds were longer at the midline placement, however, with bimanual stimulation, thresholds were longer when the hands were spatially separated (crossed and/or uncrossed). Left handers' IHTTs were 8 ms faster than those of right handers. IHTTs in males were faster than females with hands placed in lateral (by 10.8 ms) or crossed (by 9.8 ms) but not midline positions. It was concluded that the cerebral hemispheres are equally capable of discriminating temporal intervals, but that the left hemisphere predominates when there is uncertainty about location of stimulation.