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PubMed2005

Hormonal pleiotropy and the juvenile hormone regulation of Drosophila development and life history.

Understanding how traits are integrated at the organismal level remains a fundamental problem at the interface of developmental and evolutionary biology. Hormones, regulatory signaling molecules that coordinate multiple developmental and physiological processes, are major determinants underlying phenotypic integration. The probably best example for this is the lipid-like juvenile hormone (JH) in insects. Here we review the manifold effects of JH, the most versatile animal hormone, with an emphasis on the fruit fly Drosophila melanogaster, an organism amenable to both genetics and endocrinology. JH affects a remarkable number of processes and traits in Drosophila development and life history, including metamorphosis, behavior, reproduction, diapause, stress resistance and aging. While many molecular details underlying JH signaling remain unknown, we argue that studying "hormonal pleiotropy" offers intriguing insights into phenotypic integration and the mechanisms underlying life history evolution. In particular, we illustrate the role of JH as a key mediator of life history trade-offs.

Aging↗
PubMed2000

Estrogen receptors and aromatase activity in the hypothalamus of the female frog, Rana esculenta. Fluctuations throughout the reproductive cycle.

It is well known that certain actions of androgen are mediated through in situ aromatization to estrogen in neural target tissues. This study was undertaken to investigate androgen utilization in the hypothalamus of the female frog, Rana esculenta, through a quantification of estrogen receptors and aromatase activity during the reproductive cycle. 3H-estradiol-binding molecules were present in both the cytosol and the nuclear extract of the hypothalamus. These molecules bound specifically 3H-estradiol with high affinity (Kd 10(-10) M) and low capacity (cytosol: 1.2+/-0.4 fmol/mg protein; nuclear extract: 7.9+/-0.6 fmol/mg protein). Aromatase activity was detected in the microsomal fraction of the hypothalamus using a sensitive in vitro radiometric assay. Both aromatase activity and nuclear estrogen receptor binding fluctuated in synchrony throughout the reproductive cycle. Western blot analysis of aromatase protein revealed one immunoreactive band with a molecular weight of approximately 56 kDa. In contrast to aromatase enzyme activity, the relative levels of aromatase protein changed little during the reproductive cycle suggesting that post-translational mechanisms may be involved in regulating estrogen synthesis in the frog brain. A possible role for estrogens in the modulation of the reproductive behavior in this species is suggested.

Animals↗
PubMed1991

Comparative neuroanatomy of the sexually dimorphic hypothalamus in monogamous and polygamous voles.

In the present work we evaluated the degree of sexual dimorphism in two cell groups of the medial preoptic-anterior hypothalamus (MPOA-AH) in monogamous and polygamous voles. Quantitative determinations were made of volume, cell number, and cell density for the anteroventral-periventricular nucleus (AVPV) and the sexually dimorphic nucleus of the preoptic area (SDN-POA). Polygamous montane voles (Microtus montanus) had a greater degree of sexual dimorphism in both cell groups than did monogamous prairie voles (M. ochrogaster). Most notable was the complete absence of the AVPV in male montane voles; male montane voles also had a significantly larger SDN-POA volume than did females. The only sexual dimorphism in prairie voles was a greater cell density in the female AVPV. In addition, prairie voles had larger relative brain size than did montane voles. Comparative behavioral studies have revealed a correlation between the degree of sexual dimorphism in external morphology and mating system, i.e., polygamous species display greater levels of dimorphism than do monogamous species. The present results indicate that the effects of sexual selection can also be seen in those brain regions, like the hypothalamus, that underlie social and reproductive behavior. Moreover, these results support the hypothesis that neuroanatomic dimorphisms in the MPOA-AH may be related to sex differences in behavior.

Animals↗
PubMed2000

Cerebral hemisphere regulation of motivated behavior.

The goals of this article are to suggest a basic wiring diagram for the motor neural network that controls motivated behavior, and to provide a model for the organization of cerebral hemisphere inputs to this network. Cerebral projections mediate voluntary regulation of a behavior control column in the ventromedial upper brainstem that includes (from rostral to caudal) the medial preoptic, anterior hypothalamic, descending paraventricular, ventromedial, and premammillary nuclei, the mammillary body, and finally the substantia nigra and ventral tegmental area. The rostral segment of this column is involved in controlling ingestive (eating and drinking) and social (defensive and reproductive) behaviors, whereas the caudal segment is involved in controlling general exploratory or foraging behaviors (with locomotor and orienting components) that are required for obtaining any particular goal object. Virtually all parts of the cerebral hemispheres contribute to a triple descending projection - with cortical excitatory, striatal inhibitory, and pallidal disinhibitory components - to specific parts of the behavior control column. The functional dynamics of this circuitry remain to be established.

Amygdala↗
PubMed1988

F prostaglandins function as potent olfactory stimulants that comprise the postovulatory female sex pheromone in goldfish.

This study establishes that ovulated female goldfish release F type prostaglandins (PGFs) to the water where they stimulate male spawning behavior and comprise the goldfish postovulatory pheromone. We first demonstrated that ovulated and prostaglandin-injected female goldfish release immunoreactive PGFs to the water. Next, using electro-olfactogram recording (EOG), we determined that waterborne prostaglandins function as potent olfactory stimulants for mature male goldfish. Prostaglandin F2 alpha (PGF2 alpha) and its metabolite 15-keto-prostaglandin F2 alpha (15K-PGF2 alpha) were the most potent prostaglandins; the former had a detection threshold of 10(-10) M and the latter a detection threshold of 10(-12) M. Studies of prostaglandin-injected fish indicated that PGF metabolites are an important component of the pheromone. Cross-adaptation experiments using the EOG demonstrated that goldfish have separate olfactory receptor sites for PGF2 alpha and 15K-PGF2 alpha that are independent from those that detect other olfactory stimulants. Finally, we established that male goldfish exposed to low concentrations of waterborne PGFs exhibit reproductive behaviors similar to those elicited by exposure to the odor of ovulated fish. Together with our recent discovery that a steroidal maturational hormone functions as a preovulatory "priming" pheromone for goldfish, these findings suggest that hormones and their metabolites may commonly serve as reproductive pheromones in fish.

Animals↗
PubMed1993

Neurophysin-containing pathway from the paraventricular nucleus of the hypothalamus to a sexually dimorphic motor nucleus in lumbar spinal cord.

A model that has been widely used in the study of steroid sensitive neurons, the spinal nucleus of the bulbocavernosus (SNB) is a sexually dimorphic motor nucleus in the lower lumbar spinal cord that innervates the striated bulbocavernosus (BC) muscle. The BC is responsible for penile reflexes in the male rat, which are important in ensuring pregnancy in females. The characterization of afferents to the SNB aids in the understanding of the neural circuitry involved in reproductive behavior. We have recently identified the paraventricular nucleus (PVN) as a possible source of afferents to the SNB. Because the PVN is the major source of oxytocin/vasopressin within the central nervous system (CNS), the purpose of the present study was to examine and characterize a neurophysin (NP)-containing pathway from the PVN to the SNB. The results demonstrate that neurons of the lateral parvicellular subnucleus of PVN, which project to levels of spinal cord containing SNB motoneurons, contain NP, the coproduct of oxytocin and vasopressin. NP-containing fibers and putative terminals were found in the region of the SNB and appear to contact the soma and proximal dendrites of SNB motoneurons which were retrogradely identified as BC-innervating. Electrolytic lesions, which destroy the lateral parvicellular subnucleus of PVN, abolish NP-containing fibers in the region of the SNB, suggesting that the PVN is the source of these NP fibers. The results of this study indicate a NP-containing projection from the hypothalamus directly to SNB motoneurons. It is suggested that this pathway may play a role in the integration of penile reflexes with other aspects of male copulatory behavior that are under hypothalamic control.

Animals↗
PubMed2005

The effects of predator odors in mammalian prey species: a review of field and laboratory studies.

Prey species show specific adaptations that allow recognition, avoidance and defense against predators. For many mammalian species this includes sensitivity towards predator-derived odors. The typical sources of such odors include predator skin and fur, urine, feces and anal gland secretions. Avoidance of predator odors has been observed in many mammalian prey species including rats, mice, voles, deer, rabbits, gophers, hedgehogs, possums and sheep. Field and laboratory studies show that predator odors have distinctive behavioral effects which include (1) inhibition of activity, (2) suppression of non-defensive behaviors such as foraging, feeding and grooming, and (3) shifts to habitats or secure locations where such odors are not present. The repellent effect of predator odors in the field may sometimes be of practical use in the protection of crops and natural resources, although not all attempts at this have been successful. The failure of some studies to obtain repellent effects with predator odors may relate to (1) mismatches between the predator odors and prey species employed, (2) strain and individual differences in sensitivity to predator odors, and (3) the use of predator odors that have low efficacy. In this regard, a small number of recent studies have suggested that skin and fur-derived predator odors may have a more profound lasting effect on prey species than those derived from urine or feces. Predator odors can have powerful effects on the endocrine system including a suppression of testosterone and increased levels of stress hormones such as corticosterone and ACTH. Inhibitory effects of predator odors on reproductive behavior have been demonstrated, and these are particularly prevalent in female rodent species. Pregnant female rodents exposed to predator odors may give birth to smaller litters while exposure to predator odors during early life can hinder normal development. Recent research is starting to uncover the neural circuitry activated by predator odors, leading to hypotheses about how such activation leads to observable effects on reproduction, foraging and feeding.

Animals↗
PubMed1997

Gender-specific steroid metabolism in neural differentiation.

1. Both the neuroendocrine system and the brain mechanisms underlying gender-specific behavior are known to be organized by steroid sex hormones, androgen and estrogen, during specific sensitive phases of early fetal and perinatal development. The factors that control these phasic effects of the hormones on brain development are still not understood. Processes of masculinization and defeminization are thought to be involved in the sex differentiation of mammalian reproductive behavior. 2. The P450 aromatase, converting androgen to estrogen, is a key enzyme in the development of neural systems, and the activity of this enzyme is likely to be one of the factors determining brain sex differentiation. 3. We have examined the localization and regulation of brain aromatase using the mouse as a model. Measurement of testosterone conversion to estradiol-17 beta, using a sensitive radiometric 3H2O assay, indicates that estrogens are formed more actively in the male mouse brain than in the female during both the prenatal and the neonatal periods. In primary cell cultures of embryonic mouse hypothalamus there are sex differences in aromatase activity during early and late embryogenesis, with a higher capacity for estrogen formation in the male than the female. These sex differences are regionally specific in the brain, since on gender differences in aromatase activity are detectable in cortical cells. 4. Aromatase activity in the mouse brain is neuronal rather than glial. Using a specific antibody to the mouse aromatase, immunoreactivity is restricted to neuronal soma and neurites in hypothalamic cultures. There are more neurons containing expressed aromatase in the male hypothalamus than in the female. Therefore, gender-specific differences in embryonic aromatase activity are neuronal. 5. Testosterone increases aromatase activity specifically in hypothalamic neurons, but has no effect on cortical cells. The neuronal aromatase activity appears to be sensitive to the inductive effects of androgen only in the later stages of embryonic development. Androgen also increases the numbers of aromatase-immunoreactive neurons in the hypothalamus. 6. This work suggests that the embryonic male hypothalamus and other androgen target areas contain a network of neurons which has the capacity to provide estrogen for the sexual differentiation of brain mechanisms of behavior. The phasic activity of the key enzyme, aromatase, during development is influenced by androgen. What determines the developmental action of androgen and the other factors involved in the regulation and expression of this neuronal enzyme still have to be established.

Animals↗
PubMed2006

Mouse major urinary proteins trigger ovulation via the vomeronasal organ.

The major urinary proteins are a species-specific complex of proteins excreted by male mice that influence the reproductive behavior and the neuroendocrine condition of female mice through the olfactory system. The aim of this work is to determine their influence on ovulation. The major urinary proteins isolated from the urine of adult male mice were voided of bound odorants, dissolved at a physiological concentration in urine of prepubertal mice, and put on the nostril of reproductively cycling female mice housed in groups, the first day of estrus at 1100. The eggs shed in the oviducts were counted under dissection the morning of the second day of estrus. The results showed that 1) a single stimulus of the major urinary proteins increased ovulation nearly as much as the whole urine of male mice, 2) the effect was not elicited by male rat urine which contains different proteins, 3) a peptide with four residues of the amino-terminal sequence of the major urinary proteins stimulated ovulation, and 4) mice that had been isolated or had the vomeronasal organ (VNO) removed did not respond to the major urinary proteins and had a high spontaneous ovulation. The results suggest that the major urinary proteins activate the neuroendocrine system through the VNO and trigger ovulation.

Animals↗
PubMedDate not supplied

[Epidemiology of cancer of the breast in Mexico. Consequences of demography transition].

OBJECTIVE: Analyze the relation between reductions in fertility and the inverse en breast cancer mortality in the different states of Mexico for the period 1979-1994. MATERIALS AND METHODS: Fertility rates and beast cancer mortality rates were utilized to analyze the proposed relationship in the states of the country. Principal component analysis and classification analysis were then used in the confirmatory analysis of this relationship. RESULTS: There is an important decrease in fertility trends overall with regional differences: the northern states of Mexico have lowest then the southern states. These regional differences are inversely related to the observed differences in breast cancer mortality within the states: the northern states have levels of breast cancer mortality much higher than the southern states. CONCLUSIONS: The increase in mortality due to breast cancer and its relation to the decrease in fertility illustrates the importance that must be given to the preventive aspect of health services since in the near future Mexican women will exhibit reproductive behaviors similar to women in developed countries.

Adolescent↗
PubMed2006

Photoperiod-independent changes in immunoreactive brain gonadotropin-releasing hormone (GnRH) in a free-living, tropical bird.

Timing of seasonal reproduction in high latitude vertebrates is generally regulated by photoperiodic cues. Increasing day length in the spring is associated with changes in the brain that are responsible for mediating reproductive activities. A primary example of this is the increased content of gonadotropin-releasing hormone (GnRH) in the preoptic area of the hypothalamus in birds as they enter the spring breeding season. Increased GnRH activity stimulates the release of luteinizing hormone and follicle-stimulating hormone from the anterior pituitary. These gonadotropins induce growth of the gonads and release of sex steroids which act on the brain to mediate reproductive behaviors. By contrast, seasonal breeding in the tropics can occur in the absence of significant changes in photoperiod. To our knowledge, no studies have investigated whether seasonal breeding in free-living tropical vertebrates is associated with seasonal changes in the GnRH system. We studied two populations of rufous-collared sparrows (Zonotrichia capensis) at the equator, separated by only 25 km, but with asynchronous reproductive phenologies associated with local climate and independent of photoperiodic cues. We collected brains and measured GnRH immunoreactivity (GnRH-ir) during each population's breeding and non-breeding periods. Breeding males had larger, but not more, GnRH-ir cells than non-breeding birds. The plasticity of the GnRH system was associated with local climate, such that the two populations exhibited asynchronous changes in GnRH-ir despite experiencing identical photoperiod conditions. Our results demonstrate that tropical birds can exhibit neural changes similar to those exhibited in higher latitude birds. However, these tropical populations appear to be using supplementary cues (e.g., rainfall, temperature, food availability) in a similar way to higher latitude species using an initial predictive cue (photoperiod). These results raise questions about the evolution of reliance upon photoperiodism and the strength of reproductive responses to other environmental cues in congeners from higher latitudes. The ability to respond to a multitude of environmental cues might be part of the ancestral condition, and the subsequent obligate photoperiodism in high-latitude congeners could reflect a loss of flexibility in response to environmental signals.

Analysis of Variance↗
PubMed1986

Extrahypothalamic projection of luteinizing hormone-releasing hormone fibers in the brain of the toad, Bufo japonicus.

Extrahypothalamic projection of luteinizing hormone-releasing hormone (LHRH) fibers in the brain of the toad (Bufo japonicus) was examined immunohistochemically by the avidin-biotin-peroxidase complex (ABC) method. Immunoreactive LHRH perikarya are localized in the nuclei medialis septi and of the diagonal band of Broca. A part of the LHRH fibers are sent anteriad to the medial and dorsal pallia. Some fibers reach the olfactory bulb. Dorsocaudally, LHRH neurons in the medial septum project their fibers to the deep layers of the optic tectum and the posterior mesencephalon including the nucleus pretrigeminalis, which is considered to be a generator of mate calling behavior, via the habenular and posterior thalamic regions. In addition, LHRH fibers which run caudad through the dorsal infundibular region and then the mesencephalic reticular formation were widely distributed in both the gray and the white matter of the medulla oblongata. These findings suggest that LHRH acts as a neurotransmitter or a neuromodulator in the various neuronal circuitries for reproductive behavior in the central nervous system, because LHRH has been considered to be related to amphibian seasonal breeding, and many regions where the immunoreactive LHRH fibers were observed are the loci concerned with mating behavior.

Animals↗
PubMed1994

Behavioral and biological determinants of fecundability.

Our discussion has focused on a set of behavioral and physiological factors which influence fecundability. Some potentially important determinants are notable primarily because of their absence. Foremost among these determinants (as a group) are the male attributes. We have, by and large, ignored the links between male sexual behavior and hormonal profiles and the effects of hormones (or other factors) on sperm function. The fact that we have not reviewed them here does not imply that we believe that they are unimportant. Indeed, the effects of male factors may be particularly important because in some settings men are the predominant, if not the sole, decision-makers regarding reproductive behaviors including initiation of sexual intercourse and use of contraception. Also conspicuous by their absence are the effects of nutrition, consumption of alcohol, exercise, smoking, and behavioral and hormonal correlates of stress, all of which may affect fecundability. We have, though, reviewed a wide range of factors which contribute to fecundability and identified several points of potential interaction between the behavioral and biological determinants. We expect that our future understanding of these processes will be enhanced by empirical work and modeling efforts which also interact to draw upon the insights provided by each.

Behavior↗
PubMed1982

Behavior of rhesus monkeys during artificial menstrual cycles.

Daily subcutaneous injections of estradiol, progesterone, and testosterone were given to ovariectomized rhesus monkeys in amounts that imitated accurately the changing plasma levels of hormones in intact females with natural menstrual cycles. Because these cycles in ovariectomized, treated females were terminated by normal vaginal bleeding every 28 days and showed a mid-cycle gonadotropin surge, we termed them "artificial menstrual cycles." In dyadic mating tests, changes in the females' access times (lever pressing) for males, and in the males' ejaculatory performance, were closely similar during natural and artificial cycles, and there were well-marked behavioral rhythms. These rhythms were lost during 28-day control periods when ovariectomized females received injections of vehicle alone. Differences in ejaculatory performance during natural and artificial cycles could be accounted for by an order effect. It is concluded that the artificial cycle provides a valid and useful paradigm for a more detailed study of the neuroendocrine regulation of primate reproductive behavior.

Animals↗
PubMed1986

Age and infertility.

Direct evidence on age patterns of infecundity and sterility cannot be obtained from contemporary populations because such large fractions of couples use contraception or have been sterilized. Instead, historical data are exploited to yield upper bounds applicable to contemporary populations on the proportions sterile at each age. Examination of recent changes in sexual behavior that may increase infecundity indicates that sexually transmitted infections, the prime candidate for hypothesized rises in infertility, are unlikely to have added to infecundity to any great extent. These results imply that a woman in a monogamous union faces only moderate increases in the probability of becoming sterile (or infecund) until her late thirties. Nevertheless, it appears that recent changes in reproductive behavior were guaranteed to result in the perception that infecundity is on the rise.

Adolescent↗
PubMedDate not supplied

Geographic variation of breast cancer in Taiwan: international and migrant comparison.

BACKGROUND: Breast cancer is increasing rapidly in Taiwan. A geographic variation, international comparison and migrant study has become essential for the development of hypotheses to account for this. MATERIALS AND METHODS: Age-adjusted mortality rates of breast cancer patients from all precincts and townships of Taiwan were calculated for a geographic variation study, and summarized for an international comparison. Age-specific and adjusted incidence rates of breast cancer in Taipei City were used for a migrant study. RESULTS: Age-adjusted mortality from breast cancer was highest in the Taipei and lowest in aboriginal areas. Oriental countries have significantly lower mortality rates from breast cancer but the incidence of breast cancer among Chinese women, and the difference between younger and older age groups has increased together with the degree of westernization in residential areas. Chinese women were found to have lower incidence rates than white women of the same area. We concluded that diet, reproductive behavior, and hereditary factors are involved in the development of breast cancer.

Asian People↗
PubMed1997

An interspecific backcross of Lycopersicon esculentum x L. hirsutum: linkage analysis and a QTL study of sexual compatibility factors and floral traits.

A BC1 population of the self-compatible tomato Lycopersicon esculentum and its wild self-incompatible relative L. hirsutum f. typicum was used for restriction fragment length polymorphism linkage analysis and quantitative trait loci (QTL) mapping of reproductive behavior and floral traits. The self-incompatibility locus, S, on chromosome 1 harbored the only QTL for self-incompatibility indicating that the transition to self-compatibility in the lineage leading to the cultivated tomato was primarily the result of mutations at the S locus. Moreover, the major QTL controlling unilateral incongruity also mapped to the S locus, supporting the hypothesis that self-incompatibility and unilateral incongruity are not independent mechanisms. The mating behavior of near-isogenic lines carrying the L. hirsutum allele for the S locus on chromosome 1 in an otherwise L. esculentum background support these conclusions. The S locus region of chromosome 1 also harbors most major QTL for several floral traits important to pollination biology (e.g., number and size of flowers), suggesting a gene complex controlling both genetic and morphological mechanisms of reproduction control. Similar associations in other flowering plants suggest that such complex may have been conserved since early periods of plant evolution or else reflect a convergent evolutionary process.

Chromosome Mapping↗
PubMed2000

Functional connectivity among limbic brain areas: differential effects of incubation temperature and gonadal sex in the leopard gecko, Eublepharis macularius.

The neural basis of individual differences in behavior has been studied primarily by analyzing the properties of specific neural areas. However, because of the organization of the nervous system, it is also plausible that differences in behavior are mediated by differences in the interactivity or functional connectivity among brain nuclei in particular neural circuits. In the leopard gecko, Eublepharis macularius, the temperature of the egg during incubation not only determines gonadal sex, but also shapes the sociosexual behaviors, reproductive physiology, and hormone sensitivity of adult animals. In this study the effects of both incubation temperature and gonadal sex on functional connectivity among limbic brain areas were examined. Functional connectivity was assessed by analyzing covariance patterns in metabolic capacity, as revealed by quantitative cytochrome oxidase histochemistry. It was hypothesized that incubation temperature and gonadal sex affect the propensity to display aggressive or sexual behaviors by altering the functional connectivity within relevant neural circuits. The correlations of metabolic capacity between the anterior hypothalamus and both the septum and preoptic area were significant only in relatively aggressive individuals, suggesting that these circuits may regulate the phenotypic variation in aggressiveness caused by incubation temperature. The correlations between the ventromedial hypothalamus and both the dorsal ventricular ridge and septum were significant only in females, suggesting that these circuits may modulate female-typical sexual behaviors. Correlations among preoptic, hypothalamic and amygdalar areas tended to be distributed across both sexes, suggesting that there may be shared pathways underlying the expression of male-typical and female-typical behaviors.

Aggression↗