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PubMed2005

Signaling mechanisms in progesterone-neurotransmitter interactions.

Ovarian steroid hormones, estradiol and progesterone, modulate neuroendocrine functions in the CNS resulting in alterations in physiology in female mammals. Classical model of steroid hormone action assumes that these neural effects are predominantly mediated via their intracellular receptors functioning as "ligand-dependent" transcription factors in the steroid-sensitive neurons regulating genes and genomic networks with profound behavioral consequences. Steroid receptors are phosphoproteins and steroid hormone-dependent, receptor-mediated transcription is dependent on the state of phosphorylation of the cognate receptors and/or their co-regulator proteins. Studies from our laboratory have demonstrated that in addition to the steroid hormones, intracellular steroid receptors can be activated in a "ligand-independent" manner by neurotransmitters that can alter the dynamic equilibrium between neuronal phosphatases and kinases. Using biochemical and molecular approaches we have elucidated that the signaling cascade initiated by neurotransmitter, dopamine, converges with steroid hormone-initiated pathway to regulate neuroendocrine pathways associated with reproductive behavior. Signal transduction via protein phosphorylation is common to the molecular pathways through which steroid hormones and neurotransmitters mediate their physiological effects in the CNS involving a high degree of cross-talk and reinforcement among rapid, membrane-initiated pathways at the G-protein level and the classical intracellular signaling pathways at the transcriptional level in mammals. The molecular mechanisms, by which a multitude of signals converge with steroid receptors to delineate a genomic level of cross-talk, provide new avenues for understanding the role of steroid hormones in brain and behavior.

Animals↗
PubMed1995

Sexual differentiation of brain and behavior in quail and zebra finches: studies with a new aromatase inhibitor, R76713.

In many species of vertebrates, major sex differences affect reproductive behavior and endocrinology. Most of these differences do not result from a direct genomic action but develop following early exposure to a sexually differentiated endocrine milieu. In rodents, the female reproductive phenotype mostly develops in the absence of early steroid influence and male differentiation is imposed by the early action of testosterone, acting at least in part through its central conversion into estrogens or aromatization. This pattern of differentiation does not seem to be applicable to avian species. In Japanese quail (Coturnix japonica), injection of estrogens into male embryos causes a permanent loss of the capacity to display male-type copulatory behavior when exposed to testosterone in adulthood. Based on this experimental result, it was proposed that the male reproductive phenotype is "neutral" in birds (i.e. develops in the absence of endocrine influence) and that endogenous estradiol secreted by the ovary of the female embryo is responsible for the physiological demasculinization of females. This model could be recently confirmed. Females indeed display a higher level of circulating estrogens that males during the second part of their embyronic life. In addition, treatment of female embryos with the potent aromatase inhibitor, R76713 or racemic vorozole which suppresses the endogenous secretion of estrogens maintains in females the capacity to display the full range of male copulatory behaviors. The brain mechanisms that control this sexually differentiated behavior have not been identified so far but recent data suggest that they should primarily concern a sub-population of aromatase-immunoreactive neurons located in the lateral parts of the sexually dimorphic preoptic nucleus. The zebra finch (Taeniopygia guttata) exhibits a more complex, still partly unexplained, differentiation pattern. In this species, early treatment with exogenous estrogens produces a masculinization of singing behavior in females and a demasculinization of copulatory behavior in males.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2005

Alternative male mating behaviors dependent on relative body size in captive oval squid Sepioteuthis lessoniana (Cephalopoda, Loliginidae).

We observed the reproductive behavior of the oval squid Sepioteuthis lessoniana in captivity. The male used three different mating behaviors: male-parallel (MP), male-upturned (MU) and sneaking. Male competition over females frequently occurred before and during the female egg-laying period, and the outcome of most fights depended on male body size. Larger males guarded their partners from other males and performed MP mating during the egg-laying period of the paired females. In contrast, there was no pairing and mate guarding in MU mating and sneaking, which were adopted by smaller subordinate males as alternative tactics outside female egg-laying period and during the period, respectively. MP matings were 95% successful, but more than half of MU matings were unsuccessful. Higher mating success in MP mating was achieved through pairing, whereas males in MU mating were less successful because mating attempts without pair formation were often foiled by escape of the female. Sneaking was successful in all cases but occurred less frequently. Spermatophores were attached at the opening of the oviduct in MP mating, whereas they were attached around the female buccal membrane in MU mating and sneaking. Considering the route of egg transportation, higher fertilization success can be expected in MP mating because of the advantageous location of the attached spermatophores. Our results suggest that MP mating is used by larger, paired males during the female egg-laying period, and that MU mating and sneaking are alternative tactics adopted by smaller, subordinate males. These alternative mating behaviors would be conditional strategy dependent on relative body size, because some individual males displayed both MP and MU mating behaviors.

Aggression↗
PubMed2006

The many faces of progesterone: a role in adult and developing male brain.

In addition to its well documented action in female-typical behaviors, progesterone exerts an influence on the brain and behavior of males. This review will discuss the role of progesterone and its receptor in male-typical reproductive behaviors in adulthood and the role of progesterone and its receptor in neural development, in both sexual differentiation of the brain as well as in the development of "non-reproductive" functions. The seemingly inconsistent and contradictory results on progesterone in males that exist in the literature illustrate the complexity of progesterone's actions and illuminate the need for further research in this area. As progestin-containing contraceptives in men are currently being tested and progesterone administration to pregnant women and premature newborns increases, a better understanding of the role of this hormone in behavior and brain development becomes essential.

Animals↗
PubMed1983

Specificity of gonadal hormone modulation of cholinergic enzymes in the avian syrinx.

The effectiveness of testosterone (T) and metabolites to increase activity of cholinergic enzymes in the androgen-sensitive syrinx of male zebra finches was assessed. Administration of aromatizable (T and androstenedione) or non-aromatizable (androsterone) androgens to castrates increased total activity of acetylcholinesterase (AChE) in the syrinx. Estradiol was ineffective in altering AChE activity. Results, when compared with behavioral data from the birds, support the hypothesis that expression of male reproductive behaviors requires peripheral target organ activation by androgens and central target area activation by both androgens and estrogens.

Acetylcholinesterase↗
PubMed1994

Emergencies of the female reproductive tract.

Emergencies of the female reproductive tract are common in small animal practice. The veterinarian must be familiar with normal and abnormal reproductive behaviors, as well as medical and surgical options available. Emergencies of the reproductive tract can be life-threatening for both dam and off-spring, requiring rapid diagnosis and assessment as well as aggressive treatment. With effective management, most of these conditions warrant a good prognosis.

Animals↗
PubMed2001

Slow aging during insect reproductive diapause: why butterflies, grasshoppers and flies are like worms.

Diapause is a state of arrested development accompanied by physiology for somatic persistence. Diapause is common in many invertebrates and is familiar to biogerontology in the context of Caenorhabditis elegans dauer. Among insects, diapause may occur in embryos, larvae, pupae or adults. At the adult stage, reproductive diapause arrests development of oogenesis, vitellogenesis, accessory gland activity, and mating behavior. Reproductive diapause has been well studied in monarch butterflies, several grasshoppers, and several Diptera, including Drosophila and Phormia. In monarchs and in grasshoppers, reproductive diapause physiology has been experimentally induced by the surgical removal of the corpora allata, the source of adult juvenile hormone; allatectomy in each case was found to double adult longevity. Among Drosophila, the endemic D. triauraria of Japan, and D. littoralis of Finland over-winter as adults in reproductive diapause. How D. melanogaster winter is poorly understood, but reproductive diapause can be cued by cool temperature. In laboratory studies, the mortality rates of post-diapause D. melanogaster are similar to rates of newly enclosed, young flies. This implies that senescence during diapause is slow or negligible. Slow aging during the diapause period may involve elevated somatic stress resistance as well as reallocation of resources to somatic maintenance. Reproductive diapause in Drosophila is proximally controlled by down regulation of juvenile hormone, a phenotype that is also produced by mutants of the insulin-like receptor InR, homologue of C. elegans daf-2. We propose neuroendocrine control of reproductive diapause in D. melanogaster that includes phenotypic plasticity for rates of senescence.

Aging↗
PubMed2002

Estimating the spontaneous mutation rate of loss of sex in the human pathogenic fungus Cryptococcus neoformans.

Few events have evolutionary consequences as pervasive as changes in reproductive behavior. Among those changes, the loss of the ability to undergo sexual reproduction is probably the most profound. However, little is known about the rate of loss of sex. Here I describe an experimental system using the fungus Cryptococcus neoformans and provide the first empirical estimate of the spontaneous mutation rate of loss of sex in fungi. Two critical steps in sexual reproduction in C. neoformans were examined: mating and filamentation. Mating, the fusion of cells of opposite sexes, is a universal first step in eukaryotic sexual reproduction. In contrast, filamentation, a prerequisite process preceding meiosis and sexual spore development, is restricted to C. neoformans and a few other fungal species. After approximately 600 mitotic divisions under favorable asexual growth conditions, mean abilities for mating and filamentation decreased significantly by >67 and 24%, respectively. Similarly, though statistically not significant, the mean vegetative growth rates also decreased and among the mutation accumulation lines, the vegetative growth rates were negatively correlated to the mating ability. The estimated mutation rates to decreases in mating ability and filamentation were in excess of 0.0172 and 0.0036, respectively. The results show that C. neoformans can be a highly attractive model for analyses of reproductive system evolution in fungi.

Cryptococcus neoformans↗
PubMed1991

Laboratory biology of Ornithodoros (Alectorobius) puertoricensis (Acari: Argasidae).

The laboratory biology of Ornithodoros (Alectorobius) puertoricensis Fox was studied over a 2-yr period. Approximately 100-150 ticks were reared individually at each of four temperatures: 22, 27, 33, and 40 degrees C and 90-95% RH. The mean egg incubation periods at those temperatures were 20.3, 11.1, 7.3, and 6.1 d, respectively. The average larval feeding period was 5.8 +/- 1.5 d for 15,875 larvae that fed on guinea pigs. The development times for first to fourth nymphal instars were as follows: 11.7, 48.5, 75.1, and 92.1 d, respectively, at 22 degrees C; 5.8, 18.8, 38.0, and 36.0 d, respectively, at 27 degrees C; 4.2, 10.5, 14.9, and 38.1 d, respectively, at 33 degrees C; and 5.8, 10.7, 21.2, and 35.3 d, respectively, at 40 degrees C. Males usually eclosed after three or four molts, and females usually eclosed after four or five molts. Approximately 10% of all nymphs required more than one blood meal per instar at least once during development. Twenty pairs of adults were held at each of three temperatures (22, 27, and 33 degrees C) for a year to study reproductive behavior. The number of gonotrophic cycles per female per year was 6.9, 9.8, and 10.8 at 22, 27, and 33 degrees C, respectively. The mean duration of the gonotrophic cycle was 42.3 d at 22 degrees C, 25.5 d at 27 degrees C, and 20.5 d at 33 degrees C. Mean egg production per female per gonotrophic cycle was 151 at 22 degrees C, 117 at 27 degrees C, and 130 at 33 degrees C and was not affected by temperature. O. puertoricensis did not exhibit autogeny or parthenogenesis. Hyperparasitism was observed in immatures and adults.

Animals↗
PubMed1982

Inhibition of lordosis behavior in the female rat by intraventricular infusion of prolactin and by chronic hyperprolactinemia.

The role of prolactin (PRL) in the control of the lordosis reflex of female rats was investigated. In the initial series of experiments, the normal high level of sexual receptivity observed in the ovariectomized, estrogen-progesterone (E-P) primed female rat was suppressed by intraventricular infusion of 100 ng PRL. Mating behavior remained suppressed 2, 3, and 5 hours following a single infusion of PRL into the third ventricle. In contrast, infusions of either an equal volume of the solvent vehicle (saline) or 100 ng of adrenocorticotropic hormone (ACTH) were ineffective in modulating the level of mating behavior in hormone-primed female rats. In a second series of experiments, chronic hyperprolactinemia was induced by pituitary transplants under the renal capsule in intact, normal cycle diestrus rats (N=12). A significant decrement in E-P induced mating behavior was observed at 12 and 14 weeks posttransplantation but not at 4 weeks. Sham-operated animals (N=12) displayed the characteristic pattern of behavior normally observed under exogenous E-P therapy. In summary, transient exposure as well as chronic exposure to high levels of PRL can suppress mating behavior, thus suggesting a possible role for PRL in the mediation of reproductive behavior in the female rat.

Adrenocorticotropic Hormone↗
PubMed2005

Ovarian intrafollicular processes as a target for cigarette smoke components and selected environmental reproductive disruptors.

Steroidogenesis, expansion of oocyte-cumulus complex, and meiotic maturation of the oocyte represent intrafollicular processes taking important part in the background of successful fertilisation. The reproductive health of female could be affected by a number of endogenous as well as exogenous factors, such as exposure to agents from specific lifestyle habits, environmental pollutants with endocrine disrupting properties, or heavy metals. Published data indicate that exposure to chemicals may cause alterations in reproductive behavior and contribute to sub-fecundity, infertility, or ovarian failure. Female reproductive functions can be compromised by exposure to toxic chemicals at a variety of sites, including ovary or reproductive tract. Substantial harmful effects of cigarette smoke on fecundity and reproduction have become apparent but are not generally appreciated. The effects of cigarette smoke components (cadmium, nicotine, cotinine) absorbed into the organism on intrafollicular processes may thus in part explain the negative impact of smoking on female fertility. Moreover, it is now evident that a variety of man-made pollutants present in the environment are capable to disrupt normal endocrine function in many species. Examples of these "endocrine disrupters" include plasticizers, such as phthalates and bisphenol A. The effects of selected environmental chemicals on the processes of steroidogenesis, expansion of oocyte-cumulus complex, and meiotic maturation of the oocyte are summarized in the present paper and possible mechanisms of action of these agents are suggested. However, for complete understanding the mechanisms by which chemical agents from the environment can affect the intrafollicular processes, a lot of further investigation is needed.

Cell Nucleus↗
PubMed1995

Workshop on perinatal exposure to dioxin-like compounds. II. Reproductive effects.

This summary report focuses on current studies on reproductive effects reported at the workshop on Perinatal Exposure to Dioxin-like Compounds and supporting data noted in the discussion. Recent laboratory studies have suggested that altered development (e.g., low birth weight, spontaneous abortion, congenital malformation) and reproductive health (e.g., fertility, sex organ development, reproductive behavior) may be among the most sensitive end points when examining the effects of dioxinlike compounds. Thus, future research should target the reproductive health of both males and females exposed postnatally and prenatally. Studies in humans are needed and are on-going. In animal models, postnatal exposure to dioxin or dioxinlike compounds has been associated with abnormal spermatogenesis and abnormal testicular morphology and size in males and with reduced fertility and endometriosis in females. In utero exposure may also produce profound reproductive consequences in both males and females including delays in sexual maturation, abnormalities in development of sexual organs, and abnormal sexual behavior. The mechanism by which dioxin-like compounds cause reproductive effects is not well delineated.

Animals↗
PubMed2003

Vasotocin and reproductive functions of the domestic chicken.

The neurohypophyseal hormone arginine vasotocin (AVT) combines both antidiuretic and reproductive activities. In the domestic chicken AVT produces assimetric effects on the reproductive functions of males and females. AVT synthesized in magnocellular diencephalic neurons is released into circulation in a highly coordinated manner contributing to the peripheral control of oviposition in hens. Conversely, parvocellular AVT cells located in the limbic system (bed nucleus of stria terminalis (BST)) are quite different in their properties and, possible, functions. In domestic chickens these cells express AVT in a sexually dimorphic manner and are found solely in males. This sexually dimorphic part of the AVT system is sensitive to gonadal steroids. Experimental data demonstrated that AVT modulates different aspects of reproductive behavior including courtship vocalization and copulation. Sexual differentiation of these limbic vasotocinergic cells show striking correlation with sexual differentiation of masculine behavior. Evidences coming from physiological, anatomical and ethological studies suggest strong implication of the vasotocinergic system in the control of reproductive functions.

Animals↗
PubMed2002

Food deprivation inhibits estrous behavior in hormone-treated Syrian hamsters despite elevated estradiol levels.

Estradiol and progesterone (P) induce female mammalian reproductive behaviors, which are, in turn, sensitive to food availability. When ovariectomized, steroid-primed hamsters are food deprived for 48 h, estrous behavior is suppressed. While this suppression of estrous behavior may be due to alterations in neural steroid receptor levels, it is also possible that decreased levels of circulating estradiol could be involved in mediating this suppression. Ovariectomized Syrian hamsters given varying doses of estradiol benzoate (EB) and P were tested to determine whether increasing doses of sex steroids would overcome the suppressive effects of food deprivation on estrous behavior. As expected, lordosis duration decreased in food-deprived animals. Increasing the levels of EB, but not P, increased lordosis duration in the food-deprived animals so that animals who were given 20 microg of EB had lordosis durations significantly longer than food-deprived hamsters that received 1.5 microg and 2.5 microg EB. Following an injection of 2.5 microg of EB, food-deprived hamsters actually had higher circulating levels of estradiol than ad libitum-fed animals. Therefore, increasing circulating levels of estradiol can increase lordosis durations in fasted animals; however, the suppression of estrous behavior occurs despite increased circulating estradiol levels in ovariectomized, steroid-treated animals. The most parsimonious explanation for this phenomenon is a deprivation-induced reduction in neural responsiveness to estradiol.

Animals↗
PubMed2002

Time course of VMN lesion effects on lordosis and proceptive behavior in female hamsters.

Previous studies suggest that ultrasound production by female hamsters is better able than other reproductive behaviors to recover from an initial drop caused by damage to the ventromedial hypothalamus (VMN). At the same time, few studies have examined the time course of such lesion effects. To remedy this, female hamsters were observed before and after control operations or VMN lesions. The behaviors considered were ultrasound production, lordosis, approach, and vaginal marking. Ultrasound production, lordosis, and approach were affected by lesions, permitting the description of the time course of each of these effects. Only ultrasound rates showed evidence of recovery, which culminated in rates significantly above those observed preoperatively in the same animals. This suggests that ultrasound production is unusual in its response to VMN damage and that the underlying mechanism could be of interest in studies of the processes that determine recovery from brain damage.

Animals↗
PubMed1971

Geographic distribution and light-dependent behavior in Drosophila.

Drosophila species fall into three classes with respect to the effect of light on their reproductive behavior: Class I, species that mate equally well in light or darkness; Class II, those merely inhibited by darkness; Class III, species whose mating is blocked by darkness. Species in the three classes also differ in the extent of their geographic distribution, with Class I including widely distributed and cosmopolitan species and Class III those that are endemic. Class II species have an intermediate distribution pattern. The behavioral differences among species reflects the degree to which courtship information is locked-in on unique visual stimuli, as well as indicating differences in the underlying genetic architecture of flexible versus specialized forms. It may be anticipated that most species of Drosophila will be found light dependent. Similar organizational differences in other forms relying on visual courtship stimuli may be reflected in correlation between distribution and behavioral reliance on a single sensory input. Dependence on a single sensory input offers a unique variety of methods for biological control of species that requires a particular sensory system for information transfer.

Animals↗
PubMedDate not supplied

Oral (drinking water) two-generation reproductive toxicity study of bromodichloromethane (BDCM) in rats.

Bromodichloromethane (BDCM) was tested for reproductive toxicity in a two-generation study in CRL SD rats. Thirty rats/sex/ group/generation were continuously provided BDCM in drinking water at 0 (control carrier, reverse osmosis membrane-processed water), 50,150, and 450 ppm (0, 4.1 to 12.6, 11.6 to 40.2, and 29.5 to 109.0 mg/kg/day, respectively). Adult human intake approximates 0.8 microg/kg/day (0.0008 mg/kg/day). P and F1 rats were observed for general toxicity (viability, clinical signs, water and feed consumption, body weights, organ weights [also three weanling Fl and F2 pups/sex/litter], histopathology [10/sex, 0- and 450-ppm exposure groups]) and reproduction (mating, fertility, abortions, premature deliveries, durations of gestation, litter sizes, sex ratios, viabilities, maternal behaviors, reproductive organ weights [also three weanling Fl and F2 pups/sex/ litter], sperm parameters, and implantations. F1 rats were evaluated for age at vaginal patency or preputial separation. Ten P and F1 rats/sex from the 0- and 450-ppm exposure groups and rats at 50 and 150 ppm with reduced fertility were evaluated for histopathology (gross lesions, testes, intact epididymis, all F1 dams for number of primordial follicles). Developmental parameters in offspring included implantation and pup numbers, sexes, viabilities, body weights, gross external alterations, and reproductive parameters (Fl adults). Toxicologically important, statistically significant effects at 150 and/or 450 ppm included mortality and clinical signs associated with reduced absolute and relative water consumption, reduced body weights and weight gains, and reduced absolute and relative feed consumption (P and F1 rats). Significantly reduced body weights at 150 and 450 ppm were associated with reduced organ weights and increased organ weight ratios (% body and/or brain weight). Histopathology did not identify abnormalities. Small delays in sexual maturation (preputial separation, vaginal patency) and more Fl rats with prolonged diestrus were also attributable to severely reduced pup body weights. Mating, fertility, sperm parameters, and primordial ovarian follicular counts were unaffected. The no-observable-adverse-effect level (NOAEL) and the reproductive and developmental NOAELs for BDCM were at least 50 ppm (4.1 to 12.6 mg/kg/day), 5125 to 15,750 times the human adult exposure level, if delayed sexual maturational associated with severely reduced body weights is considered reproductive toxicity. If considered general toxicity, reproductive and developmental NOAELs for BDCM are greater than 450 ppm (29.5 to 109.0 mg/kg/day), or 36,875 to 136,250 times the human adult exposure level. Regardless, these data indicate that BDCM should not be identified as a risk to human reproductive performance or development of human conceptuses.

Administration, Oral↗