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PubMed1989

Patterns of steroid hormone effects on electrical and molecular events in hypothalamic neurons.

Hypothalamic neurons with nuclear receptors for steroid hormones provide opportunities to relate individual biosynthetic and electrical changes to hormone-driven behaviors. Successful work with female rodent reproductive behavior has proven that it is possible to define a neural circuit for a vertebrate behavior. In contrast to what might be expected from an invertebrate system, results from several approaches to neuronal gene expression show the complexity of hypothalamic control, even over this simple mammalian behavior. This is not a 1 hormone-1 gene-1 behavior system. Neither is there just one mode of hormonal induction. Certain steroid hormone effects can multiply each other, showing how a clear endocrine signal could be discerned among other variations in neural activity.

Animals↗
PubMed2004

Comparative distribution of estrogen receptor alpha and beta immunoreactivities in the forebrain and the midbrain of the female guinea pig.

Estrogen plays an important role in regulating gonadotropin secretion and reproductive behavior. The estrogen receptor alpha (ERalpha) was believed to be the only receptor which mediated the actions of the hormone until the identification of a novel ER called ERbeta. In the present study, the map of ERalpha immunoreactive (IR) neurons was compared with the distribution pattern of ERbeta-IR neurons in the forebrain and midbrain of ovariectomized guinea pigs using immunocytochemistry. The immunoreactivities appeared to be mainly nuclear in their subcellular distribution. Both ERalpha- and ERbeta-like immunoreactivities were highly expressed in the bed nucleus of the stria terminalis and the ventrolateral hypothalamic nucleus but were found to be differentially expressed in discrete subregions of the amygdaloid complex. A large number of intensely labeled ERalpha cells were observed throughout the rostrocaudal extent of the preoptic region, whereas only a few ERbeta-IR neurons were found in the periventricular preoptic nucleus bordering the third ventricle or scattered in the medial preoptic area. In contrast, only ERalpha-immunoreactivity was seen in the septum, and in the magnocellular supraoptic, paraventricular, arcuate, and premammillary nuclei. In the midbrain, neurons containing ERalpha were observed throughout the rostrocaudal extent of the gray matter, whereas ERbeta was only detected within the dorsal raphe nucleus. These observations provide evidence of a distinct neuroanatomical pattern for the two subtypes of the ER which may have different roles in regulating behavior and the neuroendocrine mechanisms of reproduction. Species similarities and differences in the distributions of ERalpha and ERbeta immunoreactivities are discussed.

Animals↗
PubMed1998

The health consequences of adolescent sexual and fertility behavior in sub-Saharan Africa.

This article reviews the literature on health consequences of adolescent sexual behavior and child-bearing in sub-Saharan Africa, and the social and cultural context in which they occur. It suggests that, in addressing the most serious health sequelae, sexual intercourse that occurs in early marriage and premaritally must both be considered. Some limitations of the data are noted. Despite the excess risk to which adolescents are exposed, due both to custom and age-related vulnerability, differences between health effects among adult and adolescent women are often differences in degree. They are attributable to behavioral, social, and biological causes, exist in traditional and nontraditional settings, in union and out of union, and are exacerbated by declining ages at menarche, pressures of HIV/AIDS and STDs, and a dearth of appropriate services-especially for young people. Some current interventions are discussed, and the need for policy as well as medical intervention is stressed.

Adolescent↗
PubMed1992

Risk factors for adolescent sexual behavior, fertility, and sexually transmitted diseases.

Current understanding of the risk factors related to adolescent initiation of sexual activity, use of contraception, pregnancy, and STDs is examined. From recent research on adolescent fertility, findings that have particular relevance to school health or reflect new understandings of adolescent sexuality are summarized. In selected cases, prevention programs that build directly on an understanding of these risk factors are cited.

Adolescent↗
PubMed1992

Teen contraception in the 1990s.

Basic information about appropriate contraceptive methods for teen-agers is provided. Methods most commonly used will be reviewed and an overview of alternative methods available for use in special subgroups will be provided.

Adolescent↗
PubMed1988

Fertility and child spacing among the urban poor in a third world city: the case of Calcutta, India.

The author examines the fertility behavior of the urban poor in India. "On the basis of data from 180 slum households in Calcutta, India, the paper indicates that in a situation where material and social conditions are comparable, cultural and demographic variables play a major role in influencing reproductive behavior. In this case study, caste and family type are shown to have a significant effect on the numbers of surviving children. As regards child spacing, the woman's age is of paramount importance."

Age Factors↗
PubMed1996

Primary care management of adolescent sexual behavior.

Adolescents continue to engage in sexual behaviors that place them at risk for sexually transmitted diseases, including HIV, and pregnancy. Recent advances in the prevention and management of sexually transmitted diseases and pregnancy may eventually lead to fewer negative consequences associated with adolescent sexual behavior. This paper discusses scientific and technologic advances in the management of adolescent sexual behavior such as the use of DNA amplification tests to detect genital chlamydial infection and the new female-controlled contraceptives.

Adolescent↗
PubMed2000

Empirical assessments of social networks, fertility and family planning programs: nonlinearities and their implications.

Empirical studies of the diffusion of modern methods of family planning have increasingly incorporated social interaction within nonlinear models such as logits. But they have not considered the full implications of these nonlinear specifications. This paper considers the implications of using nonlinear models in empirical analyses of the impact of family programs, modulated by social interaction, on reproductive behavior. Three implications of nonlinear models, in comparison with linear models, are developed. 1) With nonlinear models, there may be both low and high contraceptive-use equilibria (i.e., the ultimate level of use of modern family planning that a population can be expected to reach after the effects of a sustained change in a family planning program have worked through the population) rather than just one equilibrium as in linear models. If there are multiple equilibria, then one striking and important result is that a transitory large program effort may move a community from sustained low- to high-level contraceptive use. 2) With nonlinear models, the extent to which a social interaction multiplies program efforts depends on whether the community is at a low or high level of contraceptive use rather than being independent of the level of contraceptive use as in linear models. 3) With nonlinear models, intensified social interaction can retard or enhance the diffusion of family planning, in contrast to only enhancing diffusion as within linear models. To clarify these implications, for comparison a simple and more transparent linear model is also discussed. Illustrative estimates are presented of simple linear and nonlinear models for rural Kenya that demonstrate that some of these effects may be considerable.

Contraception↗
PubMed1997

The pattern of changing trends and the regional differences in the sex ratio at birth: evidence from Korea and Jilin Province, China.

"The main purpose of this study is to develop explanations for the pattern of recently changing trends and regional differences in the sex ratio at birth in Korea and for Koreans in Jilin Province and Yanbian Autonomous Prefecture, China.... The findings suggest that, since the mid-1980s, sex ratios at birth have risen remarkably in Korea.... This paper also highlights the recent increase in the sex ratio at birth for the Korean population in China, residing in urban areas densely populated with Koreans. As the key forces behind the regional differences in sex ratios at birth, the effects of son-selective reproductive behaviors, which in turn, are affected by the community characteristics, are stressed."

Asia↗
PubMedDate not supplied

Age differences between sexual partners in the United States.

CONTEXT: Researchers have examined the age of partners of young women at first intercourse and of young women who have given birth, but little is known about the age of partners of young women in current sexual relationships or young women who have had an abortion. METHODS: Data from the 1995 National Survey of Family Growth (NSFG) were used to examine age differences between women and their current partner and women's use of contraceptives at last intercourse, by marital status and by the age difference between women and their partner. Data from the NSFG and the 1994-1995 Alan Guttmacher Institute Abortion Patient Survey, with supplemental information from other sources, were used to estimate 1994 pregnancy rates for women by their age and marital status, according to the age difference between the women and their partner. RESULTS: Among all sexually active women aged 15-44, 10% had a partner who was three or more years younger, 52% a partner who was within two years of their age, 20% a partner who was 3-5 years older, and 18% a partner who was six or more years older. In contrast, 64% of sexually active women aged 15-17 had a partner within two years of their age, 29% a partner who was 3-5 years older, and 7% a partner who was six or more years older. Among women younger than 18, the pregnancy rate among those with a partner who was six or more years older was 3.7 times as high as the rate among those whose partner was no more than two years older. Among women younger than 18 who became pregnant, those with a partner who was six or more years older were less likely to have an unintended pregnancy (70%) or to terminate an unintended pregnancy (21%) than were those whose partner was no more than two years older (82% and 49%, respectively). Among women younger than 18 who were at risk of unintended pregnancy, 66% of those who had a partner who was six or more years older had practiced contraception at last sex, compared with 78% of those with a partner within two years of their own age. Young women who were Catholic and those who had first had sex with their partner within a relatively committed relationship were less likely to be involved with a man who was six or more years older than were young women who were Protestants and those who first had sex with their partner when they were dating, friends or had just met. Young women who had ever been forced to have sex were twice as likely as those who had not to have a partner who was 3-5 years older. CONCLUSION: Although the proportion of 15-17-year-old women who have a much older partner is small, these adolescents are of concern because of their low rate of contraceptive use and their relatively high rates of pregnancy and birth. Research is needed to determine why some young women have relationships with an older man, and how their partner's characteristics affect their reproductive behavior.

Abortion, Induced↗
PubMedDate not supplied

Knowledge and attitudes toward Tay-Sachs disease among a college student population.

To assess the feasibility of screening the single Jewish population for Tay-Sachs disease (TSD), a questionnaire examining the knowledge of and attitudes toward TSD and genetic screening was sent to 348 Yale University Jewish undergraduates. Of those students responding (63 percent), 78 percent were able to answer general genetic questions correctly while only 1.9 percent could answer specific Tay-Sachs questions correctly. A majority of the students (93.9 percent) indicated some concern about being a carrier for TSD, believed that carrier status would affect future social and reproductive behavior, and expressed an interest in having TS carrier status determined while still single (77.4 percent). Strong correlations were found between knowledge and attitudes, but no significant differences appeared between male and female respondents. In addition to leading to improvements in Tay-Sachs screening programs, the observations have led to suggestions that may be generalized to other genetic screening programs.

Adult↗
PubMed1993

Sexual activity and plasma levels of sex steroids in the aspic viper Vipera aspis L. (Reptilia, Viperidae).

Reproductive behavior and associated sexual activity was studied in individual male and female Vipera aspis over a 3-year period in western France in an attempt to correlate mating behavior with blood levels of gonadal sex steroids. Males had higher average levels of both testosterone (T) and 5 alpha-dihydrotestosterone (DHT) than females. Levels of progesterone (P) did not differ significantly between the two sexes but estradiol-17 beta (E2) concentrations were significantly higher in females during the season of mating. Spring mating behavior and copulation in males was associated with significantly increased levels of T and DHT, compared with postmating males; and a similar, but not significant trend, was evident with autumnal mating. The only statistically significant hormonal difference detected in males showing no sexual activity in autumn, was an elevated level of E2 at 0.52 +/- 0.20 ng/ml compared with 0.09 +/- 0.03 ng/ml in spring-breeding males (P = 0.05). Estrus in females is associated with increased levels of all four steroids but significant only for E2 and DHT. Levels of P were significantly reduced in females displaying seasonal anestrous in the spring immediately following reproduction. Females not displaying estrus in either spring or autumn had significantly lower plasma DHT and E2. Although mating behavior in males is associated statistically with elevated levels of T and DHT, a tight correlation is not obvious at the individual level, suggesting that increased concentrations of androgens are a necessary, but not sufficient, condition for mating. The data from V. aspis suggest that, as in a number of other reptilian species, high circulating levels of androgens function to "condition" or "organize" sexual behavior in males which may be displayed at some later time, well after actual levels have fallen, thus engendering the impression that reproductive behavior may be temporally dissociated from essential hormonal stimuli.

Animals↗
PubMed2000

Social signals influence hormones independently of calling behavior in the treefrog (Hyla cinerea).

Social signals play an important role in regulating hormone-behavior relationships. In anurans (frogs and toads), acoustic signals are an essential aspect of reproductive behavior; however, the physiological consequences of receiving social signals has remained largely undescribed. Each night for 5, 10, or 20 days, we presented acoustically isolated male treefrogs with a conspecific mating chorus, an array of tones, or no sound. We recorded calling rate of individuals throughout the experiment and collected blood before and after treatment. Days of stimulus exposure had no effect on any dependent measure. Acoustic treatment influenced steroid levels; testosterone, dihydrotestosterone, and corticosterone increased only in the group exposed to the chorus. Chorus-exposed males also showed an increase in stimulus-evoked calling. We found no correlation between androgens and calling within each treatment group. In addition, noncallers in the chorus group had higher levels of androgens than males in the tone or no sound groups. Further, chorus-exposed males with zero, low, or high rate of calling had similar levels of androgens. These data indicate that social signals increase circulating androgens independently of calling behavior. Elevated corticosterone associated with chorus reception did not inhibit calling behavior, and corticosterone showed no correlation with androgen levels.

Animals↗
PubMed1992

Effects of sexual experience, season, and mating stimuli on endocrine concentrations in the adult ram.

Two behavioral trials were conducted to determine the endocrine response of cortisol (C), luteinizing hormone (LH), testosterone (T), prolactin (PRL), and growth hormone (GH) in adult rams during exposure to estrous ewes during the breeding and nonbreeding seasons. One-half of the rams in each season were sexually experienced (SE) and the remainder were sexually inexperienced (SI). All SE rams (100%) achieved at least one ejaculation, but only 33% (summer) and 67% (fall) SI rams achieved ejaculation. In the fall, mean C, T, and GH concentrations were elevated (P less than .001) compared to values measured in the summer, whereas LH and PRL levels were higher (P less than .01) in the summer. Overall levels of C, LH, T, and PRL were higher (P less than .05) in SE rams than in SI rams. Mean GH concentration was higher (P less than .10) in SI than in SE rams during restricted and complete access to estrous ewes. In general, LH, PRL, and GH responses were similar during restricted and complete access to females for both SE and SI rams. Cortisol levels were higher (P less than .06) during periods of mating and T levels were higher (P less than .001) during periods where activity was limited to courtship behavior (nasogenital investigation). Correlations of hormones to reproductive behaviors indicated that mounting and intromission were associated with elevations in C and PRL, whereas elevated LH and T tended to be associated with courtship behaviors. Correlations between GH and behaviors were inconsistent. However, there was an increased coincidence between time of female exposure and hormonal response that occurred in the fall; brief exposure to estrous ewes resulted in increases in concentrations of all hormones examined. The most consistent response was observed in sexually experienced rams during restricted access to females during the breeding season. These results provide new information on the effects of season and level of sexual experience upon hormonal and behavioral characteristics of the ram during mating activity.

Animals↗