Onset of puberty was observed in 12 bison bulls by the collection of semen at monthly intervals for 12 months beginning at 13 months of age. Onset of puberty was defined as the time in development when an ejaculate contained a minimum of 50x106 sperm showing at least 10% progressive motility. At each collection, data were recorded on body weight, semen quality, fecal testosterone concentration, and physical development. Semen was evaluated for gross motility, individual progressive motility, sperm morphology, sperm concentration and volume. From these data bison bulls attained onset of puberty at an average age of 16.5 months and an average body weight of 353 ± 52.8 kg. Age was the greatest determining factor for onset of puberty in this group of bulls. <p> Monthly abattoir collections of epididymal sperm (n=288) and testicular tissue (n=120) were evaluated to determine if bison bulls undergo seasonal changes in sperm production. Although epididymal sperm morphology did not give any indication of seasonal variation, the histological study of testicular tissue showed greater seminiferous tubule diameter (27.0 ± 4.3 ìm) during the breeding months (July, August and September) than during any other seasons. Semen collected at 4 different occasions during the year (June, November, January, and April) from live mature breeding bulls (n=21) was used to verify data collected from abattoir samples. Semen from mature bulls showed a significantly greater proportion of normal sperm in June than in November (73.8 ± 9.1%; 44.1 ± 24.3%), respectively. There was little improvement in sperm morphology at the January sampling but in April morphology improved to a level close to that observed in June. Fecal testosterone concentrations were highest in June (128.6 ± 67.4 ng/g) and lowest in April (48.5 ± 33.3 ng/g). Although there was no clear seasonal trend in sperm morphology from bulls sampled at the abattoir, mature bulls showed slight seasonal variations in semen quality.

Although there have been only a few etiological studies that have examined the development and maintenance of body image in males, research fairly consistently reports that exposure and presumed comparison to images of ideal male bodies increases body dissatisfaction. Social comparison provides individuals with a mechanism by which to evaluate their body appearance to those around them. When individuals compare their bodies to those of others, they are attempting to gauge their standing or status relative to those around them, the results of which have inherent status implications. There is increasing empirical evidence that suggests perceived increases in status result in increased testosterone levels, whereas testosterone decreases when status is perceived as having been diminished. Thus, the core of the present study: can the process of comparing the appearance of one’s body to that of others affect the testosterone levels, body satisfaction, and mood of males? To examine the above research questions, a two-part study was designed. A pilot study was conducted with 117 male undergraduates primarily to examine the psychometrics of measures to be used in the main study. The measures appeared psychometrically sound and were thus used in the main study. In the main study, 129 male undergraduates were exposed to photographs of one of three male body types (i.e., lean/muscular, skinny, average) to determine whether or not exposure to the different body types differentially affected participants’ testosterone levels, body satisfaction, and mood. Results indicate that testosterone levels decreased over the course of the experiment in each of the three groups; however, the body type to which participants were exposed did not differentially affect participants’ testosterone levels. Body dissatisfaction was greater among participants who viewed lean/muscular bodies than those who viewed average bodies. Lastly, mood was not differentially affected by viewing different types of male bodies. Implications and possible explanations for these results are discussed.

The diathesis-stress model focuses on the interaction between gene polymorphisms and negative environmental conditions (i.e., stressors); however, Belsky and Pluess (2009) recently proposed an alternative to diathesis-stress: the differential susceptibility hypothesis, which states that some individuals may be predisposed to be more adversely affected by negative environments but, also, to benefit more from positive environments. Nevertheless, the differential susceptibly hypothesis has not been rigorous tested. Thus, the purpose of this study was to test the differential susceptibility hypothesis by examining individual differences in men’s testosterone, behavioral, and psychological responses to social status as a function of the serotonin transporter promoter region polymorphism (5-HTTLPR), which was cited by Belsky and Pluess as a potential “plasticity gene” because one variant – the long (l) allele – appears to be associated with lower susceptibility/plasticity and another – the short allele (s) – appears to be associated with higher susceptibility/plasticity. In this study, groups of 3-4 male participants were allowed to socialize before being told that they were part of a larger initiative to create a student-run Honor Committee. They were asked to nominate one person to be the leader and one person to not be on the committee. Then, participants were told privately that everyone voted them to either (1) be the leader or (2) not be on the committee. Salivary hormone samples were collected at baseline and 20 minutes after vote feedback. In addition, after receiving the vote feedback, participants completed a series of dating anxiety and mate preference tasks and were given the option to examine an “actual honor violation” case either alone or as part of the committee. The results support the differential susceptibility hypothesis. In terms of testosterone response, ss individuals showed both greater reactivity and differential responses to vote feedback. Furthermore, the testosterone responses of ss individuals were moderated by basal cortisol, which is associated with approach/avoidance behavior (Kagan et al., 2003; Shoal, Giancola, & Kirillova, 2003). In addition, ss individuals’ decisions to work on the committee or work alone and responses to the mating tasks were dependent upon the vote feedback, whereas l-carriers’ decisions and responses were not. / text

Steroid hormones play an important role in modulating behavioral responses to various social stimuli. However, relatively little is known about how hormones respond to social stimuli and their modulation of subsequent behavior. Variation in the hormonal regulation of behavior across species has complicated the overall understanding of the hormone-behavior dynamic. In order to further elucidate the interplay of hormones and behavior in social situations, we exposed males of the monogamous convict cichlid Amatitliana nigrofasciata to three social stimuli: gravid female, intruder male and nonsocial neutral stimulus. We used a repeated exposure paradigm to create behavioral profiles and explore how sex steroid hormones respond to and regulate social behavior. Results show clear behavioral profiles in different social situations with 11-KT acting as the active androgen, increasing in response to social stimuli. Pharmacological manipulations using androgen and estrogen receptor agonists and antagonists exposed complex control over digging behavior based on social context, showed a unique decrease in aggressive behavior due to blocking the androgen receptors and a ubiquitous drug effect on vertical display. Results create well defined context-specific behavior profiles and extends our understanding of particular social behavior and how sex steroid hormones are involved in social situations and the behavioral response. / text

Synaptic dysfunction is a critical neuropathological feature prior to the formation of extracellular senile plaques and intracellular fibrillary tangles (NFTs) in Alzheimer’s disease (AD). The synapse loss and neurites impairment lead to synaptic dysfunction that can be induced by oligomeric Aβ. The administration of oligomeric Aβ reduced the pre-synaptic vesicle proteins and altered the cytoskeletal proteins. The synaptic vesicles (SVs) playing a crucial role to transport and recycle the SV proteins and neurotransmitters (NTs) in synaptic terminals. However, the uptake and release capabilities of SVs were also disrupted by oligomeric Aβ. The disruption of SVs recycling and neurites impairment attenuate neurotransmission that exacerbates the pathogenesis of AD. Therefore, any agents can maintain the SVs recycling and protect the neurites development that could be a therapeutic target for AD. Testosterone is a male sex steroid hormone, which is a potent therapeutic drug for neurodegenerative diseases. It has been found the neuroprotective effects for neuronal death, but the implication on synaptoprotection is still not clear. This study investigated the neuroprotective effects of testosterone from oligomeric Aβ-induced synaptic dysfunction in primary cultured hippocampal neurons. My study demonstrated that testosterone prevented Aβ-induced reduction of pre-synaptic proteins and shortening neurites. Also, testosterone could protect SVs recycling by increasing SVs unloading capability via estrogenic independent pathway. The findings reinforce the neuroprotective effects of testosterone. They are probably facilitating future development for using the concept of male sex hormone as therapy and the intervention of therapeutic drugs for AD patients. / published_or_final_version / Anatomy / Master / Master of Medical Sciences

No description available.

Two prospective investigations of periodicity of sexual behavior, well-being and testosterone (T) levels in women using and not using oral contraceptives (OCs) found no relationship between daily ratings of sexual desire and well-being across one pill and menstrual cycle. T, but not estradiol or progesterone, was positively correlated with sexual desire and sexual enjoyment in OC-users when T levels were below normal menstrual values. Other evidence suggested on association between post-ovulatory decreases in T and sexual desire in women. A bias to attend to sexual stimuli on a dichotic listening task was associated with sexual arousability in men. Moreover, task performance indicated T may enhance attention to relevant stimuli. While social variables are clearly important determinants of sexual behavior, these findings suggest a relationship between T and cognitive aspects of sexual behavior in young, healthy individuals.

Sex differences have been established in a number of behaviours, including aspects of cognition, aggression, and sexuality. Although there has been a considerable amount of research concerning the influence of estrogen on sexually dimorphic behaviours, there has been a dearth of investigations on the role of testosterone (T) in these behaviours in women. The studies presented here were undertaken to elucidate the role of T in sexually-dimorphic aspects of psychological functioning in women. In Study 1, users and non-users of oral contraceptives were tested with a battery of neuropsychological tests and questionnaires at two different phases of the menstrual cycle. Results showed that women with chronic low levels of free T induced by oral contraceptives demonstrated better verbal fluency and visuospatial memory performance and reported lower levels of verbal aggression than naturally-cycling women whose free T levels were within the normal female range. Furthermore, although self-ratings of hostility fluctuated across test sessions concomitant with changes in free T levels, performance on cognitive tests did not appear to be influenced by the fluctuations in T levels across the menstrual cycle. In Study 2, women with elevated free T levels due to polycystic ovary syndrome (PCOS) demonstrated worse verbal fluency, verbal memory, manual dexterity, and visuospatial working memory performance, but reported higher levels of anger than healthy, matched control women. Women with PCOS also reported lower levels of sexual cognition and arousal than healthy controls. In Study 3, women with PCOS were randomly assigned to receive 3 months of treatment with an anti-androgen or placebo. Anti-androgen treatment resulted in significant reductions in free T levels and in improvements in verbal fluency performance. Taken together, the results of these three studies suggest that T has a detrimental effect on aspects of cognitive functioning in women, particu

In chronic illnesses, such as prostate cancer, multiple health outcomes need to be considered. This project focused on two types of health outcomes: health-related quality of life (HRQoL) and cognitive function. The first aim was to investigate cognitive effects of pharmacological androgen-suppressing treatment. Numerous studies have shown cognitive performance to be associated with sex hormones. One of the main groups of drugs used for hormonal ablation in men with prostate cancer, the luteinising hormone releasing hormone (LHRH) agonists, has been associated with adverse cognitive effects in controlled studies in women and in case reports of female and male patients. However, there have been no published studies on the effect of LHRH agonists and other androgen-suppressing treatments on cognitive functioning in male patients. The second aim was to investigate the effect of treatments on HRQoL in men with prostate cancer. There are few randomised treatment studies of HRQoL in these patients. The third aim was to study additional predictors of HRQoL, examining stress and coping theory as a theoretical basis for understanding individual differences in HRQoL. The fourth aim was to examine patients’ subjective experiences of prostate cancer. To investigate these questions, 82 men with non-localised prostate cancer were randomly assigned to receive leuprorelin (LHRH agonist), goserelin (LHRH agonist), cyproterone (steroidal antiandrogen), or close clinical monitoring. These patients and 20 community volunteers matched for age, marital status, and general health undertook medical, psychosocial, and cognitive assessments before treatment and after 6 and 12 months of treatment. The main question for statistical analysis was whether dependent variables would show Group x Time interactions in the predicted directions. Compared with baseline assessments, men administered androgen suppression monotherapy performed worse in 3/12 tests of attention, memory, and executive function. Twenty-six percent of men randomised to active treatment demonstrated clinically significant decline in one or more cognitive tests at 6 months compared with baseline performance. By contrast, no community volunteers or patients randomised to close monitoring showed decline in test performance. Men on hormonal treatments reported impaired sexual function on treatment compared with baseline assessments. Men assigned to close monitoring and cyproterone treatment reported increased emotional distress over time. Groups did not differ in change in existential satisfaction, subjective cognitive function, physical symptoms, or social and role functioning. For individuals, hormonal treatments were more frequently associated with decreased physical, sexual, social and role functioning, but were also associated with improved HRQoL for some individuals. In hierarchical regression analysis, HRQoL was lower for men who had more comorbid illnesses, a history of neurological dysfunction, higher threat appraisals, or higher use of emotion-focused coping strategies. Coping strategies also showed some longitudinal associations with HRQoL, even when earlier levels of HRQoL had been taken into account. Subjective reports demonstrated that many patients viewed prostate cancer as a relatively manageable problem. Several patients said that other health problems affected them more than prostate cancer, whereas no patient said that prostate cancer was worse than other problems. Comments about the seriousness of prostate cancer were equally divided between patients who reported it as very serious (14.3% of patients) and those who saw it as a relatively minor problem (14.3%). Other patient observations were grouped into categories of personal responses to prostate cancer, health, and health research; life circumstances that were not directly associated with health; attributions about medication; and function prior to the study. The results demonstrated that pharmacological androgen suppression therapy was associated with impaired memory, attention, and executive function in male patients. Hormonal treatments and close monitoring had differential effects on patients’ HRQoL, particularly in terms of sexual function and emotional distress. HRQoL was also associated with appraisal and coping, to a greater extent than it was associated with medical variables, supporting the applicability of stress and coping theory for these patients. Observations from participants placed these findings in the context of participants’ concerns, demonstrating that issues such as cognitive and sexual function were relevant for these patients. These findings suggest that cognitive function should be given increased attention as a health outcome, not only in “neurological” disorders but also in other “non-neurological” conditions such as prostate cancer. They also support continued efforts to understand both beneficial and adverse effects of treatments for chronic illness on HRQoL and individual factors that affect health outcomes.

Thesis (M. Phil.)--University of Hong Kong, 2007. / Also available in print.