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PubMed2002

Social regulation of gonadotropin-releasing hormone.

Behavioral interactions among social animals can regulate both reproductive behavior and fertility. A prime example of socially regulated reproduction occurs in the cichlid fish Haplochromis burtoni, in which interactions between males dynamically regulate gonadal function throughout life. This plasticity is mediated by the brain, where neurons that contain the key reproductive regulatory peptide gonadotropin-releasing hormone (GnRH) change size reversibly depending on male social status. To understand how behavior controls the brain, we manipulated the social system of these fish, quantified their behavior and then assessed neural and physiological changes in the reproductive and stress axes. GnRH gene expression was assessed using molecular probes specific for the three GnRH forms in the brain of H. burtoni. We found that perception of social opportunity to increase status by a male leads to heightened aggressiveness, to increased expression of only one of the three GnRH forms and to increases in size of GnRH-containing neurons and of the gonads. The biological changes characteristic of social ascent happen faster than changes following social descent. Interestingly, behavioral changes show the reverse pattern: aggressive behaviors emerge more slowly in ascending animals than they disappear in descending animals. Although the gonads and GnRH neurons undergo similar changes in female H. burtoni, regulation occurs via endogenous rather than exogenous social signals. Our data show that recognition of social signals by males alters stress levels, which may contribute to the alteration in GnRH gene expression in particular neurons essential for the animal to perform in its new social status.

Aggression↗
PubMed1992

Time and sex in the male mouse: temporal regulation of infanticide and parental behavior.

Infanticide is a violent but successful reproductive strategy found in many mammals, particularly rodents. In male house mice (Mus domesticus and M. musculus), the act of ejaculation provides a reliable neural signal for timing the birth of their offspring. However, a unique chronobiological aspect of this phenomenon is the extraordinary temporal latency that can occur between the stimulus (coital ejaculation) and its adaptive neural response (male mice cease killing pups and behave parentally toward them instead). Specifically, the inhibition of infanticide is often time delayed for many days after a male ejaculates, but virtually always occurs before or around the time his own sired offspring would be born 18-20 days later. Furthermore, infanticide spontaneously reemerges 50-60 days after mating. In CF-1 stock male mice this entire behavioral sequence is synchronized with the female's reproductive cycle, and occurs even in the total absence of social cues or changes in pituitary or gonadal hormones after mating. When entrained and mated at 22 h (light:dark 11:11) or 27 h (light:dark 13.5:13.5) T-cycles, photoperiodic cues appeared to synchronize this dramatic shift in behavior, because a sudden transition from pup killing to parenting was matched with the number of light/dark cycles experienced after ejaculation rather than the amount of real time experienced, suggesting a circadian timing link. Housing in constant light accelerated the postmating transition to parenting, whereas constant dark significantly delayed the transition to parenting, but still occurred by 3 weeks after mating. Most males tend to oscillate between infanticide and parental behavior for several days before locking in to constant parenting, regardless of lighting conditions. Variation in the time delay between ejaculation and the inhibition of infanticide was consistent within young individuals (< 10 months of age), but in older males (> 18 months of age) the time interval between ejaculation and parenting was significantly prolonged and attenuated. Another unique aspect of this phenomenon is that variation among individuals in their timing and response to light cues is correlated with phenotypic variation in sex steroid exposure during late fetal development. So far, no simple physiological explanation can account for the neural mechanism triggered by ejaculation that coordinates these time-delayed behavioral changes toward pups.

Animals↗
PubMed1999

The Women and Infants Demonstration Project: an integrated approach to AIDS prevention and research.

The Women and Infants Demonstration Project is a multisite, behavioral intervention research effort funded by the Centers for Disease Control. The project is evaluating a theory-based, integrated intervention model to increase the use of condoms for prevention of both sexually transmitted diseases (STDs) and unintended pregnancy among women and their partners at risk of infection with HIV. The importance of utilizing carefully targeted, credible and persistent risk reduction interventions to effect lasting behavior change has become evident over the last ten years of the AIDS epidemic. The theory-based intervention components being evaluated in this intervention study involve one-on-one stage-tailored outreach; the development and distribution of community-tailored HIV prevention materials, called role-model stories; and the development of organizational and peer networking, all within a community mobilization framework. This article describes each of the intervention components being evaluated during this 5-year study. Such an intervention effort represents an important contribution in the design of community-level AIDS prevention intervention efforts which support individual-level behavioral changes by women at risk for HIV and other sexually transmitted infections.

Adolescent↗
PubMed1999

Chronic fenthion toxicity in laying hens.

White leghorn laying hens were exposed to weekly dermal applications of either 1 mg fenthion/kg (FEN; low dose) or 4 mg FEN/kg (high dose) for 24 w with the objective of evaluating chronic FEN toxicity. Four of 24 hens at the high dose exhibited transitory loss of proprioception, perching ability, and righting reflex after 8 to 16 w exposure. All hens receiving the high dose lost the ability or desire to jump from a box during the latter half of the FEN exposure period. Inhibition of serum cholinesterase and brain acetylcholinesterase was greater in the high-dose hens. Brain neuropathy target esterase was not inhibited. Behavioral changes were not correlated with changes in brain concentrations of enzymes or neurotransmitters or their metabolites. Muscle fiber abnormalities were more common in the high-dose hens. Muscle electrical activity was recorded electromyographically via telemetry. Fibrillation (denervation) potentials were absent, but amplitude times duration values for motor unit potentials of the peroneus longus muscle for 5 of the 6 4-w evaluation intervals were higher in the high-dose hens. This EMG response suggested presence of a mild neuropathy which was supported by results of ultrastructural examinations of the sciatic nerve. The low dose initially produced 8% stimulation of egg production while the high dose inhibited egg production 10% during the latter 16 w of the study and reduced body weight 8% during this period.

Acetylcholinesterase↗
PubMedDate not supplied

Androgens in human evolution. A new explanation of human evolution.

Human evolution consists of chronological changes in gene regulation of a continuous and relatively stable genome, activated by hormones, the production of which is intermittently affected by endogenous and exogenous forces. Periodic variations in the gonadal androgen, testosterone, and the adrenal androgen, dehydroepiandrosterone (DHEA), significantly participated in all hominid transformations. The hominid characteristics of early Australopithecines are primarily a result of increased testosterone. The first significant cold of the early Pleistocene resulted in an increase in DHEA that simultaneously produced Homo and the robust Australopithecines. Subsequent Pleistocene climatic changes and differential reproduction produced changes in DHEA and testosterone ratios that caused extinction of the robust Australopithecines and further changes and continuation of Homo. Changes in testosterone and DHEA produce allometric and behavioral changes that are identifiable and vigorous in modern populations.

Adolescent↗
PubMed1988

The ethics of safe sex.

Explore the source record for details and available documents.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Project Redirection: evaluation of a comprehensive program for disadvantaged teenage mothers.

An evaluation of Project Redirection, a two-year demonstration program designed to help pregnant teenagers and teenage mothers, shows that teenagers from a comparison group, who were not enrolled in the demonstration program, were significantly more likely than project participants to experience a repeat pregnancy after one year, but that after two years the difference was small and nonsignificant. Likewise, at 12 months into the program, the project participants proved more likely to be using contraceptives, but by 24 months the comparison group had caught up. After one year of participation, the project teenagers were more likely than the others either to be in school or to have graduated (56 and 49 percent, respectively). However, this differential also disappeared by 24 months. Nonetheless, even at that point, project teenagers who had dropped out prior to joining the program and those who had had a repeat pregnancy were more likely to be in school or to have completed school than were similar comparison teens. Project teenagers also were somewhat more likely to have held a job during the two-year period than were teenagers not enrolled in the program. All in all, the evaluation demonstrated that teenagers who participated in the project and remained in it for more than a year had consistently better outcomes in education, employment and repeat pregnancy than any other group had. Comparison teenagers who had never participated in any special program for pregnant teenagers, on the other hand, demonstrated consistently poorer outcomes than any other group.

Adolescent↗
PubMed1979

Effects of chronic lead ingestion on social development in infant rhesus monkeys.

The social behavior of infant rhesus monkeys during the first year of life was examined under a variety of lead (Pb) exposure conditions in four separate experiments. Daily ingestion of PB acetate in milk for one year elevated blood Pb levels to 30-100 microgram/dl, suppressed play, increased social clinging, and exacerbated the disruption of social behavior caused by changing the play environment midway through the year of observation. The presence of control monkeys in social test-groups reduced the magnitude of Pb-induced social behavior changes. In contrast to daily postnatal Pb exposure, chronic exposure to Pb during gestation had no measurable effect on postnatal social development, and acute, transient postnatal Pb exposure (producing blood Pb levels > 200 microgram/dl during month 2 of life) affected only the monkeys' response to the change in the plan environment. These data suggest that daily ingestion of Pb, and not a previously-acquired tissue burden, was responsible for the long-term changes in social development observed. The results are discussed in the general context of primate social development, which is thought to require adequate interactive play for appropriate social integration and reproductive behavior at maturity.

Aging↗
PubMed1982

The development of menstrual-related beliefs and behaviors during early adolescence.

Adolescent girls' menstrual-related beliefs and behaviors are examined from a developmental perspective. 2 studies, 1 cross-sectional and 1 longitudinal, were conducted. In the first, 639 girls in grades 5-6, 7-8, and 11-12 were seen. In the second, 46 pairs of girls were seen twice: all were premenarcheal at the first testing; at the second testing, one-half had begun to menstruate in the last few months and one-half were a matched premenarcheal comparison group. Girls answered questions on menstrual symptomatology, menstrual-related attitudes, and potential informational sources. 3 questions were asked in the present study: (1) What are the expectations for menstrual symptoms that girls hold prior to menstruation and when do these develop? (2) How do expectations for menstrual symptoms and beliefs relate to the actual experience of menarche? (3) What are the sources of information for menstruation and do they relate to subsequent menstrual-related behavior? First, as early as fifth grade, premenarcheal girls had clear expectations regarding menstrual symptoms; their expectation that cycle-related changes would occur paralleled the changes reported by adult and older adolescent women. Second, girls who had begun to menstruate reported experiencing less severe menstrual distress (less pain, water retention, negative affect, and behavioral changes, and more concentration) than the premenarcheal comparison group expected to experience. In addition, early symptom expectations were positively related to later-reported menstrual distress (pain, water retention, and behavioral change) in the changing-menarcheal-status group. Third, there were few changes in the amount learned from various sources as a function of menarcheal status. However, correlational analyses indicate that girls who learned more from male sources rated menstruation as more debilitating and negative than those girls who learned less from male sources. The importance of socialization in the emergence of menstrual distress and negative menstrual attitudes is discussed.

Adolescent↗
PubMed1993

AIDS in sub-Saharan Africa: the epidemiology of heterosexual transmission and the prospects for prevention.

As the epidemic of the acquired immunodeficiency syndrome (AIDS) in sub-Saharan Africa enters its second decade, much has been learned about the distribution and determinants of the disease and its causative agent, the human immunodeficiency virus (HIV). Over 6 million people, or 2.5% of the adult population, are thought to be infected with HIV. The distribution of HIV is largely determined by sexual behavior; as for other sexually transmitted diseases, the characteristics of sexual networks determine the extent and rate of spread of HIV. Female sex workers and their male clients are at high risk for HIV and have been important in initiating the epidemic in many African countries. The dynamics of HIV in the rest of the population are complex; men with multiple sexual partners are largely responsible for transmission of HIV to women in the general population. Other sexually transmitted diseases and lack of male circumcision may increase the probability of transmission of HIV during sexual intercourse and probably are partially responsible for the rapid diffusion of HIV in Africa. Interventions among high-risk groups are needed, but they must be accompanied by attempts to induce behavior change among men and women in the general population. Epidemiologic studies of the determinants of sexual behavior and sexual contact patterns, as well the design and evaluation of interventions, are urgently needed. Key areas for development are the study of behavioral exposures and outcomes, the evaluation of interventions, developing new methods for conducting interventions in resource-poor environments, and increasing the number of African scientists with the skills and resources to conduct epidemiologic studies.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Influence of tapeworm infection on the production of aggregation pheromone and defensive compounds in Tribolium castaneum.

Recent studies suggest that parasites affect host development, reproduction, and behavior through alterations of host hormones and pheromones, or other hormone-triggered biochemical events. We previously reported that Hymenolepis diminuta infection affects surface-seeking and cannibalism behaviors, and reduces male sperm precedence of Tribolium castaneum beetles. This study examined the quantitative effects of H. diminuta on the production of aggregation pheromone and 3 defensive compounds in male T. castaneum beetles, using 2 wild-caught, geographically distinct T. castaneum strains. For the c-Madison strain, infected beetles exhibited a 2- to 22-fold increase in defensive compounds; conversely, no changes were observed in strain c-Africa. Parasite infection did not significantly influence aggregation pheromone secretion in either strain. Because defensive compounds function as repellents or deterrents to other insects, parasite-induced increases in the secretion of defensive compounds may be a physiologic clue for the behavioral changes in infected T. castaneum beetles. Significant among-strain variation in defensive compound production seen in infected beetles suggests that caution is needed before generalizing about changes in volatile production and in host behavior induced by a parasite.

Analysis of Variance↗