Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Reproductive Behavior”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,765 records · Page 98Linked to original sources
PubMed2006

Equilibriumizing all food chain chaos through reproductive efficiency.

The intraspecific interference of a top-predator is incorporated into a classical mathematical model for three-trophic food chains. All chaos types known to the classical model are shown to exist for this comprehensive model. It is further demonstrated that if the top-predator reproduces at high efficiency, then all chaotic dynamics will change to a stable coexisting equilibrium, a novel property not found in the classical model. This finding gives a mechanistic explanation to the question of why food chain chaos is rare in the field. It also suggests that high reproductive efficiency of top-predators tends to stabilize food chains.

Animals↗
PubMed1986

Teenage pregnancy: a multiracial sociologic problem.

Teenage pregnancy is not an epidemic in the United States. Because this is an emotional topic that receives high-decibel publicity in the press and on television, we wish to present the most recent factual information available on the subject and a more balanced perspective of the problem for physicians and other health professionals who care for women at the youngest age of the reproductive spectrum. Pregnancy during adolescence is a multiethnic sociologic problem that crosses all socioeconomic, ethnic, cultural, and geographic boundaries. Pregnancies in teenagers are decreasing (except in teenagers under age 15), not accelerating. New approaches for premature adolescent pregnancy and childbearing focus on adolescent peer pressure for behavior modification, prevention of pregnancy at a younger age, continuation of secondary education, and job training for both adolescent fathers and mothers.

Adolescent↗
PubMed1988

Determinants of menstrual bleeding patterns among women using natural and hormonal methods of contraception. I. Regional variations.

Records of the occurrence of vaginal bleeding were obtained from women using either a natural method of contraception or one of four types of hormonal contraceptive. The relationships between their bleeding patterns and a number of demographic variables were examined, with the aim of identifying subgroups of women who, if they used a particular hormonal method of contraception, would be likely to suffer more or less disruption to their bleeding pattern than the 'norm'. Within contraceptive method, bleeding patterns were more closely related to the women's geographical region of residence than to any other factor. Some of the differences between regions were consistent across contraceptive methods. European women tended to have more bleeding/spotting days than women in other regions; Latin American women had relatively short episodes and long bleeding-free intervals, whether they were using the ovulation method, combined pills or a vaginal ring. Other differences were method-specific. Women using combined pills in India or Pakistan had fewer spotting episodes than women using the same method elsewhere; those using progestogen-only pills had more. Regional variations in bleeding patterns were particularly marked among women using DMPA, and increased over time: by their fourth injection interval, 25% of European women had amenorrhea, as compared with 72% of subjects in North Africa. These findings need to be confirmed by carefully controlled studies of menstrual bleeding patterns and their acceptability in various ethnic groups. The results would be valuable in counselling new contraceptive acceptors, and could eventually guide the choice of methods for introduction into national family planning programmes.

Administration, Intravaginal↗
PubMed1999

The circadian timing system and reproduction in mammals.

Circadian systems in a wide variety of organisms all appear to include three basic components: 1) biological oscillators that maintain a self-sustained circadian periodicity in the absence of environmental time cues; 2) input pathways that convey environmental information, especially light cues, that can entrain the circadian oscillations to local time; and 3) output pathways that drive overt circadian rhythms, such as the rhythms of locomotor activity and a variety of endocrine rhythms. In mammals, the circadian system is employed in the regulation of reproductive physiology and behavior in two very important ways. 1) In some species, there is a strong circadian component in the timing of ovulation and reproductive behavior, ensuring that these events will occur at a time when the animal is most likely to encounter a potential mate. 2) Many mammals exhibit seasonal reproductive rhythms that are largely under photoperiod regulation; in these species, the circadian system and the pineal gland are crucial components of the mechanism that is used to measure day length. The rhythm of pineal melatonin secretion is driven by a neural pathway that includes the circadian oscillator(s) in the suprachiasmatic nuclei. Melatonin is secreted at night in all mammals, and the duration of each nocturnal episode of melatonin secretion is inversely related to day length. The pineal melatonin rhythm appears to serve as an internal signal that represents day length and that is capable of regulating a variety of seasonal variations in physiology and behavior.

Animals↗
PubMed1984

Problems of adolescent sex.

Four issues concerning adolescent sexuality are reviewed--the counselling needs of teenagers, the risks of Sexually Transmitted Diseases, the controversy over contraception for adolescents, and the consequences of pregnancy in adolescence--in terms of their effect on the adolescent as an individual, and on the community of which he/she belongs. The need for services specifically designed for adolescents is stressed, demonstrating that many of the "problems" of adolescent sex can be successfully addressed through comprehensively planned and executed programmes.

Adolescent↗
PubMed1999

Reflections on two decades of research on teen sexual behavior and pregnancy.

During the past 20 years, both researchers and program developers made great progress in their efforts to reduce adolescent unprotected sex and prevent teen pregnancy. Research studies are now more likely to employ experimental designs with random assignments, to have large sample sizes with adequate statistical power, to measure actual sexual and contraceptive behaviors, to measure longer term effects, to employ proper statistical methods, and to report results in an unbiased manner. As a result of this body of research, large advances have occurred in our understanding of: 1) the incidence of teen pregnancy, and its consequences; 2) the effects of improving adolescent knowledge, increasing access to contraception, and improving parent/child communication; and 3) the characteristics of effective programs. The on-going evaluation of sex and HIV education programs coupled with creativity and perseverance on the part of program developers led to two groups of effective programs--sex and HIV education programs that reduce sexual risk-taking behavior, and youth development programs that reduce teen-age pregnancy and childbearing.

Adolescent↗
PubMed2006

Vasotocin and mesotocin stimulate the biosynthesis of neurosteroids in the frog brain.

The neurohypophysial nonapeptides vasopressin (VP) and oxytocin (OT) modulate a broad range of cognitive and social activities. Notably, in amphibians, vasotocin (VT), the ortholog of mammalian VP, plays a crucial role in the control of sexual behaviors. Because several neurosteroids also regulate reproduction-related behaviors, we investigated the possible effect of VT and the OT ortholog mesotocin (MT) in the control of neurosteroid production. Double immunohistochemical labeling of frog brain sections revealed the presence of VT/MT-positive fibers in close proximity of neurons expressing the steroidogenic enzymes 3beta-hydroxysteroid dehydrogenase/delta5-delta4 isomerase (3beta-HSD) and cytochrome P450 17alpha-hydroxylase/c17, 20-lyase (P450(C17)). High concentrations of VT and MT receptor mRNAs were observed in diencephalic nuclei containing the 3beta-HSD and P450(C17) neuronal populations. Exposure of frog hypothalamic explants to graded concentrations of VT or MT produced a dose-dependent increase in the formation of progesterone, 17-hydroxypregnenolone, 17-hydroxyprogesterone, and dehydroepiandrosterone. The stimulatory effect of VT and MT on neurosteroid biosynthesis was mimicked by VP and OT, as well as by a selective V1b receptor agonist, whereas V2 and OT receptor agonists had no effect. VT-induced neurosteroid production was completely suppressed by selective V1a receptor antagonists and was not affected by V2 and OT receptor antagonists. Concurrently, the effect of MT on neurosteroidogenesis was markedly attenuated by selective OT and V1a receptor antagonists but not by a V2 antagonist. The present study provides the first evidence for a regulatory effect of VT and MT on neurosteroid biosynthesis. These data suggest that neurosteroids may mediate some of the behavioral actions of VT and MT.

Animals↗
PubMed2004

Social chemosignals from breastfeeding women increase sexual motivation.

Human pheromones, a type of social chemosignal, modulate endocrine function by regulating the timing of ovulation. In animals, pheromones not only regulate ovulation but also female reproductive motivation and behavior. There is no extant evidence that humans produce social chemosignals that affect human sexual motivation or reproductive behavior as occurs in other mammals. Here, we demonstrate that natural compounds collected from lactating women and their breastfeeding infants increased the sexual motivation of other women, measured as sexual desire and fantasies. Moreover, the manifestation of increased sexual motivation was different in women with a regular sexual partner. Those with a partner experienced enhanced sexual desire, whereas those without one had more sexual fantasies. These results are consistent with previous pheromonal effects on endocrine function, and warrant further study of these social chemosignals as candidates for pheromonal processes, including their effects on other aspects of motivation and behavior.

Adolescent↗
PubMed1999

Ejaculatory abnormalities in mice lacking the gene for endothelial nitric oxide synthase (eNOS-/-).

Nitric oxide (NO) has been established as a neurotransmitter in both the central and peripheral nervous systems. Three isoforms of its synthetic enzyme, NO synthase (NOS), have been identified: 1) in the endothelial lining of blood vessels (eNOS), 2) an inducible form found in macrophages (iNOS), and 3) in neurons (nNOS). Previous studies using pharmacological agents that block all three isoforms of NOS have revealed that NO mediates several aspects of reproductive physiology and behavior, including anomalies in male sexual behavior and erectile function. To determine the specific contribution of the endothelial isoform of NOS in male reproductive behavior, we studied mice missing the gene for only eNOS (eNOS-/-). Wild-type (WT) and eNOS-/- animals were placed with an estrous WT female and observed for 45 min. Both WT and eNOS-/- mice displayed equivalent motivation to mount the stimulus female. However, eNOS-/- mice exhibited striking anomalies in ejaculatory function. A higher percentage of eNOS-/- than WT mice ejaculated during the testing period (p < 0.001). This increased propensity to ejaculate was apparently due to reduced stimulation required to elicit ejaculation; eNOS-/- mice required significantly fewer mounts (p < 0.003) and intromissions (p < 0.001) to ejaculate compared to WT mice. Taken together, these results suggest that NO synthesized by eNOS may be involved in ejaculatory physiology, but not sexual motivation.

Animals↗