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PubMed2006

Influence of immunization against GnRH on reproductive cyclicity and estrous behavior in the mare.

The aim of this study was to evaluate the effect of active immunization against GnRH on ovarian activity, plasma progesterone and estradiol concentrations and on estrous behavior in adult mares. Eighteen cyclic mares were randomly divided into a treatment and control group. Nine mares were immunized twice with 2 mL (400 microg GnRH-protein conjugate) of a GnRH-vaccine (Improvac, CSL Limited, Australia) administered intramuscularly, 4 weeks apart. Control mares received the same amount of saline solution. Ovaries and uterus of all mares were examined weekly by ultrasonography from 3 weeks before to 60 weeks after first immunization. Thereafter, vaccinated mares were evaluated monthly until 100 weeks after first vaccination. In addition, mares were teased with a stallion for assessment of estrous behavior and blood was collected for progesterone, estradiol-17beta and GnRH antibody titer determination. Results demonstrate that vaccination against GnRH significantly (P<0.05) influenced all parameters, except estradiol-17beta concentration. All vaccinated mares ceased reproductive cyclicity (plasma progesterone <1 ng/mL, follicles <3 cm) within 8 weeks after the first injection and ovarian activity remained suppressed for a minimum of 23 weeks. Five mares resumed cyclicity (follicles >3 cm, progesterone >1 ng/mL) while three mares showed only follicular activity (follicles >3 cm) and one mare remained completely suppressed for the entire duration of the study. In spite of ovarian suppression, four mares expressed sporadic and one mare continuous estrous behavior. In conclusion, reproductive cyclicity in adult mares can be successfully suppressed by immunization against GnRH but the timing of resumption of cyclicity is highly variable and estrous behavior may occur in spite of ovarian suppression.

Animals↗
PubMed1999

Neural oxytocinergic systems as genomic targets for hormones and as modulators of hormone-dependent behaviors.

At the molecular level, estradiol turns on the gene for oxytocin in a subset of paraventricular hypothalamic neurons and turns on the gene for the oxytocin receptor in other limbic and hypothalamic cell groups. As a result, oxytocin deposition, whose signal is transduced both through G alpha (q/11) and Gi to stimulate phosphatidylinositol turnover, facilitates electrical activity in certain hypothalamic neurons. Consequently, affiliative behaviors including those closely associated with reproduction--mating behaviors and parental behaviors--are promoted. One important aspect of this effect is the preservation of instinctive behaviors associated with reproduction, in the face of disturbances due to mild stress.

Animals↗
PubMedDate not supplied

Changing behavior: a challenge for reproductive health awareness.

Social marketing applies commercial sector ideas to programs to change behavior. It involves a mindset that is customer-focused; a process that starts with customers and continually returns to them for validation; and concepts to make change happen. Customer behavior models guide strategy. One useful model is based on stages of change and four behavioral influences: perceived benefits, perceived costs, the influence of others, and perceived behavioral control.

Awareness↗
PubMed1983

A model of premarital coitus and contraceptive behavior among female adolescents.

At the most general level, I seek to model female adolescent sexual and contraceptive behavior in terms of the social context in which it occurs. Drawing on emerging theoretical literature pertaining to social exchange theory and changes in the social positions of women (and men) and also on existing substantive literature, I apply these notions to adolescent sexuality and contraceptive usage. The reviews of the literature reveal a number of inconsistencies among those factors (variables) advanced to explain both the prevalence and frequency of premarital coitus and contraceptive employment. Furthermore, as there is a paucity of well-developed theoretical models that might explain these inconsistencies, what is needed is an additional study that seeks to examine the net effects of those variables used in the literature to explain variations in female premarital coitus and contraceptive use. The present formulation is a two-stage causal model that can be used to estimate the impact of these variables on premarital coital behavior (stage 1) and subsequent contraceptive usage (stage 2). These models, and a concomitant set of hypotheses, take into account an array of the more significant sociological and social psychological variables as far as the prediction of the two phenomena in question are concerned. These models may be useful in guiding future research as they graphically display the relationships between these sets of variables within the context of a more general theory of human behavior.

Adolescent↗
PubMed2003

Allee effects, extinctions, and chaotic transients in simple population models.

Discrete time single species models with overcompensating density dependence and an Allee effect due to predator satiation and mating limitation are investigated. The models exhibit four behaviors: persistence for all initial population densities, bistability in which a population persists for intermediate initial densities and otherwise goes extinct, extinction for all initial densities, and essential extinction in which "almost every" initial density leads to extinction. For fast-growing populations, these models show populations can persist at high levels of predation even though lower levels of predation lead to essential extinction. Alternatively, increasing the predator's handling time, the population's carrying capacity, or the likelihood of mating success may lead to essential extinction. In each of these cases, the mechanism behind these disappearances are chaotic dynamics driving populations below a critical threshold determined by the Allee effect. These disappearances are proceeded by chaotic transients that are proven to be approximately exponentially distributed in length and highly sensitive to initial population densities.

Alleles↗
PubMed2003

Management of menstrual problems and contraception in adolescents with mental retardation: a medical, legal, and ethical review with new suggested guidelines.

The controversial history of the reproductive rights of the mentally retarded has led to the formulation of laws in the past century designed to protect women from forced sterilization. Significantly, however, in their official ethical guidelines, The American College of Obstetricians and Gynecologists states that "sterilization should not be denied to individuals simply because they also may be vulnerable to coercion" (Int J Gynaecol Obstet 1999; 65:317). Recent advances in medical and surgical methods of contraception and control of menstrual abnormalities have led to a re-evaluation of the management of adolescents with special needs. Physicians, the courts, parents, and caretakers need to be aware of the latest medical and surgical options available, the current applicable laws in each state if such exist, and the ethical guidelines to determine what treatment option is in the best interests of the patient. This review examines the history of the sterilization of the mentally retarded, the latest surgical and pharmacologic treatments available, and the current legal environment and proposes an algorithm to facilitate the management of menstrual hygiene and contraception.

Contraception↗
PubMed2002

Paternal care and male mate-attraction effort in the European starling is adjusted to clutch size.

In facultative polygynous birds with biparental care, a trade-off may occur between male parental care and attraction of additional mates. If there is a cost associated with reduced male parental care, the relative benefit of mate attraction may be predicted to decrease as the size of a male's clutch or brood increases. We tested this prediction in monogamous pairs of facultatively polygynous European starlings (Sturnus vulgaris). The larger the clutch, the more time the male spent incubating and the less time he spent attracting an additional female (i.e. singing near and carrying green nesting material into adjacent empty nest-boxes). Reduced paternal incubation resulted in lower overall incubation (the female did not compensate) and lower hatching success. Immediately after experimental reduction of clutches, males spent significantly less time incubating and more time singing and carrying greenery, and vice versa for experimentally enlarged clutches. Males with experimentally reduced clutches attracted a second female more often than males with experimentally enlarged clutches. This is the first study, to our knowledge, to provide experimental evidence for an adjustment of paternal care and male mate-attraction effort to clutch size. However, a trade-off between paternal nestling provisioning and mate attraction was not revealed, probably due to the absence of unpaired females by that time in the breeding season. Experiments showed that the relative contribution of the male and female to nestling provisioning was unrelated to brood size.

Animals↗
PubMed2002

Mate choice and imprinting in birds studied by cross-fostering in the wild.

Sexual-selection theories generally assume that mating preferences are heritable traits. However, there is substantial evidence that the rearing environment may be important for the development of mating preferences, indicating that they may be learnt, or modified by experience. The relative importance of such sexual imprinting across species remains largely unexplored. Here, we report results of a large-scale cross-fostering experiment in the wild in which nestling birds were raised by parents of a different species. We show that resulting sexual imprinting may have a negative effect on pairing success in one species (the great tit, Parus major), but not in two other species (the blue tit, P. caeruleus and the pied flycatcher, Ficedula hypoleuca). A remarkable variation thus seems to exist, even between species that are congeneric and have similar breeding ecologies. The cross-fostering resulted in heterospecific pairings between the two tit species (female blue tit breeding with male great tit), which has never, to our knowledge, been previously documented. However, the chicks fledging from these nests were all blue tit.

Animals↗
PubMed2001

High gene flow levels lead to gamete wastage in a desert spider system.

Field censuses, breeding experiments, and a quantitative model are used to obtain insight into the extent and consequences of genetic mixing between locally adapted populations of a desert spider. Typically, 9% of the matings of desert riparian spiders (non-aggressive phenotype) in native habitat involve an arid-land partner (aggressive phenotype). Mating was found to be random with respect to behavioral phenotype, but linearly related to both the rate of immigration and survival of immigrants from surrounding arid habitats in the riparian area. Genetic mixing between riparian and arid-land spiders produces offspring that exhibit lower rates of survival in riparian habitat. Two extreme behavioral phenotypes were also observed in the field studies: approximately 5% of the female spiders attacked all males they encountered while another 22% ran from all potential mates. Punnett square analyses of the potential genotypes produced by introgression between arid- and riparian-adapted spiders indicate that these extreme phenotypes appear in F2 generation hybrids and backcrosses. Because there is a costly wastage of gametes in the case of mixed phenotype mating, model results indicate that within three generations of the cessation of gene flow, the riparian population would be free of mixed genotypes and moving towards genetic differentiation.

Alleles↗