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PubMed1990

Modes of estrus induction as a factor in studies of the reproductive behavior of rodents.

The choice of a mode of estrus for use in studies related to reproductive processes often is made arbitrarily. Females may be in hormone-induced estrus (HIE), cycling estrus (CE), male-induced estrus (MIE), or postpartum estrus (PPE). Although mode of estrus affects various aspects of copulatory behavior in different species in different ways, males mating with PPE females generally require more intromissions to reach ejaculation than with females in HIE or CE; males mating with females in CE generally attain more ejaculations than with PPE females. The duration of receptivity generally is shorter in PPE than in CE. Females in CE and PPE have different stimulus thresholds for pregnancy initiation, with the direction of the difference varying with the species. Among the other phenomena affected by mode of estrus are sperm competition, mate choice, and the Bruce effect. Because mode of estrus can be an important determinant of results, selection of a mode of estrus for any experiment should not be simply a matter of convenience. Further study of effects of mode of estrus is warranted.

Animals↗
PubMedDate not supplied

The sexual and reproductive behavior of American women, 1982-1988.

Comparison of 1988 data from the National Survey of Family Growth with 1982 data reveals that the proportion of U.S. women who have had sexual intercourse rose slightly, from 86 percent to 89 percent. Among teenagers, the proportion sexually active rose from 47 percent to 53 percent; most of the change is attributable to increases occurring among white and nonpoor teenagers, thus narrowing racial and income differences. Among women aged 15-44 in 1988 who have ever had intercourse, 67 percent reported that they had had two or more sexual partners in their lifetime. The proportion was highest among women aged 20-34 (about 70 percent), but 58 percent of sexually active teenage women reported having had two or more sexual partners. About 67 percent of women of reproductive age in 1988 were exposed to the risk of unintended pregnancy, up from 63 percent in 1982. Among these women, 35 percent rely on contraceptive sterilization to prevent pregnancy and 55 percent use reversible methods, while 10 percent use no method. Poor women are much more likely than nonpoor women to be using no method of contraception (15 vs. eight percent); among poor teenagers, this proportion reaches 25 percent. The level of contraceptive use at first intercourse among teenage women improved substantially between 1982 and 1988, however, rising from 48 percent to 65 percent. During 1984-1988, almost four in 10 births and almost six in 10 pregnancies among American women were unintended; most of these were mistimed, but 12 percent of births were unwanted ever.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Correlation between immunoreactive vasotocin in optic tectum and seasonal changes in reproductive behaviors of male rough-skinned newts.

Previous studies have shown that intracranial administration of the amphibian neuropeptide arginine vasotocin (AVT) to male rough-skinned newts (Taricha granulosa) can stimulate masculine sexual behaviors. The present study was conducted to determine whether concentrations of endogenous AVT in specific brain areas are correlated with seasonal changes in sexual behavior. Immunoreactive (ir) AVT was measured in the dorsal preoptic area and in the optic tectum throughout the course of the reproductive cycle. In the optic tectum, irAVT levels were low throughout the summer, fall, and winter, but rose over fivefold in the spring when sexual behaviors are most prevalent in male newts. In contrast, irAVT levels in the dorsal preoptic area were high in the summer, but declined in the fall and fluctuated widely during the winter and spring. Thus, there are site-specific changes in irAVT concentrations in the brain of male newts during the seasonal reproductive cycle. The finding that irAVT concentrations in the optic tectum are seasonally correlated with newt sexual behaviors provides further evidence that AVT in this brain area may be important in the expression of sexual behavior.

Animals↗
PubMedDate not supplied

Assessing the reproductive behavior of on- and off-reservation American Indian females: characteristics of two groups in Montana.

Only limited fertility and general reproductive health data exist on American Indians. Using data from the 1987 Montana American Indian Health Risk Assessment, we found that the fertility of American Indians in Great Falls and on the Blackfeet Reservation was similar to blacks in the U.S. and relatively high when compared with fertility of whites in the United States. The influence of the direct determinants of fertility (nuptiality, contraceptive use, and lactation) was very different for the populations examined in this study. Great Falls American Indians and the U.S. black population were similar regarding age at first sexual intercourse (very young), breastfeeding (low prevalence and short duration), planning status of pregnancies (high unplanned), and contraceptive use (only moderate use). In contrast, Blackfeet women on the reservation and the U.S. white population married relatively late, had very high contraceptive use, used effective methods of contraception, and had moderately high levels of breastfeeding. However, Blackfeet fertility was much higher than that of whites. Three interrelated reasons are suggested as possible explanations. Blackfeet couples either wanted high fertility, were relatively poor users of family planning methods, or used less effective methods until they had exceeded their desired family size after which time they turned to sterilization. These finds raise numerous questions concerning the social and economic factors that may account for these group similarities and differences. Further studies with much larger data sets are needed to address these issues adequately.

Adolescent↗
PubMed1986

Prenatal stress disrupts reproductive behavior and physiology in offspring.

Prenatal maternal stress has been related to neonatal activity and irritability in both lower animals and humans in documented research for at least the past 30 years. Contemporary animal research demonstrates that prenatal stress feminizes and demasculinizes the sexual behavior of males and reduces fertility and fecundity in females, producing estrous cycle disorders, spontaneous abortions, or vaginal hemorrhaging and high neonatal mortality. Mechanisms of stress are being sought in the maternal-fetal blood exchange, hormonal alterations in the hypothalamus-pituitary-gonads and adrenals, and in brain catecholamines. Contemporary human research demonstrates that negative maternal attitudes toward pregnancy are related to high incidences of congenital abnormalities and infant deaths. Severe psychosocial stress is related to high incidences of neonatal deaths and neurological impairments in infants, and a high incidence of psychiatric disorders in adulthood. Data derived from both animal and human research may help explain the etiology and mechanisms of prenatal-stress-induced reproductive dysfunctions as well as some forms of human psychopathology.

Animals↗
PubMed1988

The effects of an aromatization inhibitor on the reproductive behavior of male zebra finches.

Recent evidence indicates that aromatizable androgens are more effective than nonaromatizable androgens in restoring normal levels of sexual behavior in castrated male zebra finches (Poephila guttata). To determine whether the efficacy of treatment with aromatizable androgens, is in part due to their conversion to estrogens, castrated male finches were treated with androstenedione (AE), an aromatizable androgen, and their sexual and aggressive behavior was compared with that of castrates treated with AE plus 1,4,6-androstatriene-3,17-dione (ATD), an aromatization inhibitor. Males treated with AE + ATD showed less courtship activity and less copulatory behavior than AE-treated males, and were unlikely to have nests. Estradiol (E), when given concurrently with AE + ATD, reversed the inhibitory effects of ATD and restored levels of courtship and copulation to those observed in AE-treated males. Only AE- and AE + ATD + E-treated males displayed aggressive behaviors, but the frequency of such behaviors was so low that there were no significant differences across groups. These data affirm the importance of estrogen in the control of reproductive activities in male zebra finches and indicate that aromatization may be an obligatory step for maintaining normal levels of sexual and aggressive behavior.

Aggression↗