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PubMed2006

Sperm nuclear basic proteins of two closely related species of Scorpaeniform fish (Sebastes maliger, Sebastolobus sp.) with different sexual reproduction and the evolution of fish protamines.

In this paper, we present a review of sperm nuclear basic proteins (SNBPs) in teleost fish. The distribution of the three basic groups of SNBPs [histone (H)-type, protamine-like (PL)-type and protamine (P)-type], their evolution and possible relation to the mode of fertilization are described. In this regard, we have characterized the SNBPs from two closely related species of Scorpaeniform fish: internally fertilizing Sebastes maliger and externally fertilizing Sebastolobus sp., both in the family Scorpaenidae. Despite the different reproductive behavior of these two closely related rockfish species, in both instances the SNBP consists of protamines. However, there is a significant increase in the arginine content of the protamine in the internally fertilizing rockfish. The relevance of this observation is discussed within the context of the P-type SNBP in teleosts. The rapid evolution of teleost protamines, including those in rockfish, has also allowed us to obtain a molecular phylogeny for this group of bony fish that is almost indistinguishable from that currently available from the use of conventional anatomical/paleontological markers.

Amino Acid Sequence↗
PubMed1994

Gonadal steroid control of preprocholecystokinin mRNA expression in the limbic-hypothalamic circuit: comparison of adult with neonatal steroid treatments.

The neuropeptide cholecystokinin (CCK) is involved in the regulation of female, but not male, reproductive behavior. In both sexes, estrogen regulates the expression of CCK in adulthood within the bed nucleus of the stria terminalis and medial amygdaloid nucleus. These areas are parts of an interconnected limbic system-hypothalamic circuit, the development of which is influenced by estrogen during the early postnatal period. This is the same period during which central nervous system (CNS) expression of CCK is dramatically increased, suggesting that the male and female patterns of CCK expression may be the result of early postnatal exposure to estrogen. In the present experiment, the expression of preprocholecystokinin (pCCK) mRNA was determined by in situ hybridization with an isotopically labeled pCCK complementary RNA and emulsion autoradiography in animals whose neonatal and adult gonadal steroid levels had been manipulated. The number of pCCK-expressing cells in animals that were gonadectomized as adults was determined by neonatal estrogen, but stimulation with steroids in adulthood induced a similar number of pCCK-expressing cells in both sexes in the medial amygdala and bed nucleus of the stria terminalis. Neonatal treatment of females with estrogen or testosterone, followed by ovariectomy in adulthood, eliminated the sex difference in pCCK mRNA expression. Males treated neonatally with the aromatase inhibitor androstenedione (to block metabolism of testosterone to estrogen) and orchidectomized in adulthood had a level of pCCK mRNA expression that was similar to that of ovariectomized females. These data suggest that, during neonatal development, estrogen determines the constitutive expression of pCCK mRNA in the medial amygdala and bed nucleus of the stria terminalis, resulting in higher levels of pCCK mRNA expression in males than in females. However, exogenous gonadal steroids induce the same levels of pCCK mRNA expression in adult females, indicating that the levels of gonadal steroids and the patterns of their secretion are the predominant influences on the sexually dimorphic adult levels of pCCK mRNA expression.

Aging↗
PubMed2003

Estrogen alters excitability but not morphology of a sexually dimorphic neuromuscular system in adult rats.

In rats, motoneurons of the spinal nucleus of the bulbocavernosus (SNB) innervate the bulbocavernosus (BC) muscle, which surrounds the base of the penis. The SNB/BC is a sexually dimorphic, steroid-sensitive neuromuscular system, which is critically important in male reproductive behavior. Androgens are necessary for the development, morphology, and function of the SNB/BC system. However, estradiol (E) is also necessary for the development of the SNB/BC system, and E is capable of maintaining BC EMG activity in adulthood. In this study, we used electrophysiological and anatomical methods to examine estrogenic effects on BC EMG activity. We used a modified H-reflex testing method to investigate polysynaptic reflex characteristics in intact males, castrates, and castrates treated short term with estradiol benzoate (EB). Measures of EMG activity, response latency, and spike count were altered in castrates, but maintained in EB-treated castrates to the levels of intact males. Furthermore, estrogenic effects were found in EMG activity that could be isolated to the periphery of the SNB/BC system. BC NMJ size and muscle fiber area have been demonstrated to be hormone sensitive, and we examined these for possible correlates of E's effects on BC EMG activity. BC muscles of intact males, castrates, and short-term EB-treated castrates were fixed and stained with zinc iodide and osmium tetroxide. NMJ size and muscle fiber area did not differ between groups. Together, these data suggest that E treatment results in changes in the neuromuscular periphery that maintain BC EMG activity, but this effect cannot be accounted for by changes in NMJ size or muscle fiber area.

Animals↗
PubMed1990

The developing visual system and metamorphosis in the lamprey.

Metamorphosis of the sea lamprey, Petromyzon marinus, is a true metamorphosis. The larval lamprey is a filter-feeder who dwells in the silt of freshwater streams and the adult is an active predator found in large lakes or the sea. The transformation usually occurs in the fifth or sixth year of life. Enlargement of the eye has been long accepted as a distinctive indication of metamorphosis in the sea lamprey, but it had been thought that this was because eye development in the larva was arrested after the formation of only the small central region. Recent studies indicate that all of the retina begins its development in the larva and that ganglion, amacrine, and horizontal cells differentiate in the peripheral retina of the larva. Retinal development is arrested during the premetamorphic period, to be resumed during metamorphosis. Metamorphic contributions include the differentiation of photoreceptor and bipolar cells. With the early appearance of ganglion cells, retinal pathways to the thalamus and tectum are established in larvae, as is a centripetal pathway. Tectal development spans the larval period but a spurt in tectal growth and differentiation is correlated with the completion of the retinal circuitry late in metamorphosis. The metamorphic changes in retina and tectum complete the functional development of the visual system and provide for the adult lamprey's predatory and reproductive behavior.

Animals↗
PubMed1995

White-throated sparrow morphs that differ in song production rate also differ in the anatomy of some song-related brain areas.

White-throated sparrows are unusual among songbirds in that they occur in two color morphs, white-striped and tan-striped, determined by a chromosomal inversion and maintained by negative assortative mating. These differ in several reproductive behaviors, including amount of singing: white-striped males sing frequently, tan-striped females never sing, and tan-striped males and white-striped females sing an intermediate amount. The present study measures the volumes of several nuclei in the avian song system and relates these to color morph and to sex. We find that robustus archistristalis and the tracheosyringeal part of the hypoglossal nucleus, nuclei closely involved in song production, are larger in white-striped than in tan-striped birds. We also find morph differences for nuclei in the rostral division of the song system, nuclei believed to be less directly involved in song production. We find sex differences throughout the song system as has been reported in other songbirds. Relationships between structure and function in the song system are discussed.

Animals↗
PubMed1996

Sp4, a member of the Sp1-family of zinc finger transcription factors, is required for normal murine growth, viability, and male fertility.

We report the cloning, characterization, and targeting of an Sp1-related zinc finger transcription factor gene from the distal arm of mouse chromosome 12. This gene, previously identified in rats and humans and designated sp4, is homologous to the Drosophila buttonhead (btd) gene, which is expressed in the head region of developing flies. Similarly, in situ hybridizations show that sp4 is highly expressed in mouse embryos in the developing central nervous system (CNS). Expression of sp4 is seen as early as Day 9 of development, where transcripts are abundant in the posterior neuropore. Expression in later embryos is detected throughout the CNS as well as in other structures, including the nasal mucosa, the vomeronasal organ, the epithelium of the lung and intestinal tract, the testes, and the developing teeth. Northern blot analysis showed sp4 expression in the adult brain and other tissues. Gene targeting by homologous recombination was used to determine the role of sp4 during mouse development. Two-thirds of homozygous mutants die within the first few days after birth and those that survive are smaller than their wild-type littermates. While fertility of the female mutants appears normal, homozygous mutant males do not breed, despite having histologically intact testes containing mature sperm. sp4/sp4 mutant males fail to copulate, indicating that this gene is required for normal male reproductive behavior.

Amino Acid Sequence↗
PubMed2000

Phylogenetic species recognition and species concepts in fungi.

The operational species concept, i.e., the one used to recognize species, is contrasted to the theoretical species concept. A phylogenetic approach to recognize fungal species based on concordance of multiple gene genealogies is compared to those based on morphology and reproductive behavior. Examples where Phylogenetic Species Recognition has been applied to fungi are reviewed and concerns regarding Phylogenetic Species Recognition are discussed.

Evolution, Molecular↗
PubMed1994

Gender and seasonal differences in the adrenocortical response to ACTH challenge in an arctic passerine, Zonotrichia leucophrys gambelii.

We evaluated the adrenocortical response to acute stress in free-living Gambel's white-crowned sparrows (Zonotrichia leucophrys gambelii) using a standardized capture stress protocol in which five serial blood samples (70 microliters) were taken for measurement of plasma corticosterone (B) over the course of an hour of captivity (at 1, 5, 10, 30, and 60 min). In field-captured birds, male plasma B levels rose two to four times higher than those of females under capture stress during the breeding season, but were no different during winter (nonbreeding). We investigated the basis of this pattern by conducting dexamethasone (DEX) suppression tests on breeding and nonbreeding sparrows of both genders. This test involves pretreatment with subcutaneous DEX implants (a potent synthetic glucocorticoid) and challenge with intrajugular injections of either corticotropin (ACTH) or saline, followed by collection of a series of blood samples for evaluation of plasma B levels over a 2-hr period. ACTH injections in DEX-treated birds resulted in elevated B in both genders, with nonbreeding B profiles consistently lower than those of breeding birds. All DEX-treated, saline-injected birds, except breeding males, maintained low B levels for the entire 2-hr post-challenge period. This result indicates effective negative feedback by DEX on the hypothalamic-pituitary-adrenal axis, thus inhibiting endogenous B secretion. The apparent reduction in glucocorticoid feedback inhibition in breeding males may be related to an uncoupling of adrenal effects on reproductive behavior.

Adrenal Cortex↗
PubMed1996

Changes in Vitellogenin expression during captivity-induced stress in a tropical anole.

Tropical anoline lizards have been shown to undergo massive reproductive retrogression when held in captivity. The present study focused on the effects generated by captivity-induced stress on the hepatic expression of vitellogenin (Vtg), the precursor of the major egg yolk proteins, in Anolis pulchellus. Several hepatic dysfunctions accompanying the regression of the reproductive organs were detected when mature highly vitellogenic females were kept in captivity for long periods. These included decreased synthesis of Vtg to undetectable levels after 4 days of captivity concomitant with a large reduction in the levels of its cognate mRNA. In addition, a drastic reduction in Vtg plasma levels preceding the conspicuous cessation of follicular growth was observed. Results suggest the activation of a specific mechanism for rapid clearance of vitellogenic and other female-specific proteins from plasma. The effects of captivity, both in the liver and in the reproductive tract, were alleviated or even reversed by treatment with 17 Beta-estradiol. Hepatic protein synthesis increased threefold when animals were maintained under estrogen therapy during the captivity period. Also, the levels of Vtg mRNA and Vtg protein synthesis and plasma levels were similar or even higher to the observed in control vitellogenic females. Animals treated with 17 beta-estradiol after long-term captivity recovered the normal vitellogenic levels after 72 to 96 hr. Therefore, our results im this tropical anole strongly suggest that the stress effects upon reproductive behavior previously reported in anoline lizards results from suppression of the estrogen stimulus for the hepatic vitellogenic response.

Animals↗
PubMed1998

Aspects of GnRH neurobiology conserved across vertebrate forms.

The decapeptide gonadotropin-releasing hormone (GnRH) came into prominence because of its roles in releasing luteinizing hormone and follicle-stimulating hormone and promoting reproductive behavior. At least three aspects of GnRH neurobiology have features which may be universal among vertebrates. First, the GnRH neuronal migration from the olfactory placode into the basal forebrain appears to hold true for forms ranging from fish to humans. Second, for proper agonist activity in the anterior pituitary, GnRH must be released in a pulsatile fashion. Since GT-1 neuronal cell cultures can demonstrate pulsatile release, it must be concluded that GnRH neuronal networks themselves can manage this type of pulsatility. Using a neuronal mathematical model with "minimalist" assumptions, we demonstrated that a network of identical neurons can achieve this self-organizing property without the use of, or spontaneous appearance of, "pacemaker cells." Indeed, since many parameter combinations worked, and since no information about species identity or chemical cell type is provided to the model, this conclusion could apply across many vertebrate forms and, perhaps, even for other neuroendocrine cell types. Third, Fernald and colleagues (this issue of General and Comparative Endocrinology) have demonstrated remarkable effects of social context on GnRH expression in fish. Reviewed here are some data in musk shrews suggesting that behavioral and social stimuli can also modify GnRH neurons in mammals. Therefore, although GnRH neuronal mechanisms are adapted to meet species-typical variations in environment and physiology, some of the important features of this system appear to be widely conserved.

Animals↗
PubMed1996

Epidemiology of cervical cancer in Taiwan.

Because the prevalence of several risk factors for cervical cancer, including sexual behavior, reproductive patterns, contraceptive use, and cigarette smoking, has changed significantly over time among Taiwanese women, it is of interest to analyze the impact of these trends on the incidence and mortality rates for this cancer during the decades between 1970 and 1990. The number of deaths from cervical cancer was obtained from the Taiwan Provincial Department of Health during the period from 1974 to 1992. Data of all incident cervical cancer cases from 1979 through 1990 obtained from the Taiwan Cancer Registry were also used for the analyses. The trends in the age-adjusted and age-specific rates were examined. Age, period, and cohort effects on the incidence and mortality rates were also examined, using age-period-cohort (APC) models. The age-adjusted mortality rate has been increasing since the 1970s, particularly in both the youngest group (20-29 years) and the oldest group (65 years and over). While the age-adjusted incidence rate decreased from 1979 to 1990, and decreases were apparent across all broad age groups, nevertheless, the incidence of adenocarcinoma was moderating during the same time period. The APC models disclosed a decreasing cohort effect for the mortality and incidence rates among women born after 1936. Decreasing incidence rates after menopause were more consistent with a hormonal effect than a cohort effect. Declining trends in cervical cancer incidence may be related to the screening practices which may have counteracted the increasing prevalence of several risk factors, although poor survival influenced the incidence/mortality differentials for cervical cancer. Continued surveillance is warranted; however, attention might be directed to the trends in cervical adenocarcinoma.

Adult↗
PubMed1998

Effects of 17alpha-methyltestosterone on sexually dimorphic characters in the weakly discharging electric fish, Brienomyrus niger (Günther, 1866) (Mormyridae): electric organ discharge, ventral body wall indentation, and anal-Fin ray bone expansion.

Adult males of African weakly discharging electric fish (family: Mormyridae) are distinguished from juveniles and adult females by a dorsally directed indentation of the posterior ventral body wall and by massive bone expansion of the bases of a select number of anal-fin rays. These sexually dimorphic structures seem to facilitate the anal-fin reflex that is displayed during courtship when the male envelopes its anal fin around the female's to form a common spawning pouch. Expanded bone could provide additional surface for muscle attachment and thus assist in part with the courtship sequence. Based on the fact that the expression of the male sexually dimorphic electric organ discharge (EOD) is under androgen control, and that the female EOD can be masculinized through testosterone administration, we hypothesized that androgens should also drive anal-fin ray bone expansion in male mormyrids and equally effect male-like changes in treated juveniles and adult females. Exogenous androgen treatment (17alpha-methyltestosterone) of adult female Brienomyrus niger resulted in a male-like EOD, and male-typical structural transformations (body wall indentation and anal-fin ray bone expansion). Some of these changes were immediate and receded following hormone withdrawal (EOD), while others developed more slowly and were apparently permanent (indentation and bone formation). 17alpha-Methyltestosterone administration affected only those targets in females that are normally involved in the male's reproductive behavior, i.e., its courtship signal (EOD) and two morphological features (body-wall indentation and bone expansion). Rays of the dorsal or caudal fins were never affected.

Animals↗
PubMed1996

The influence of petrochemicals and stress on the immune system of seabirds.

There is increasing attention directed to the role of environmental pollutants in altering immune function. Only with the identification of the responsible environmental toxicants, and an understanding of their mechanisms of action, can we hope to treat immunotoxic injuries. This situation is exemplified by the exposure of wild birds to oil spills, the subsequent potential for direct toxicity from the oil, and the secondary toxicity of stress-induced immune modulation. Immunosuppressive mechanisms related to oil ingestion and handling stress are implicated in the morbidity and mortality of seabirds during care and following reentry into the wild. This does suggest that improvements in the treatment of these affected animals will enhance their survival and well-being. However, a survey of the literature shows that the implementation of better techniques are hampered by inadequate information on the immunological consequences of oil contact with seabirds. Marine oil pollution is a constant occurrence and will continue as long as oil and oil products are important commodities transported by sea routes. Among the numerous negative consequences of oil pollution are its effects on marine wildlife. There is much evidence that oil spills are responsible for massive seabird deaths. However, the constant, low level releases of petrochemicals probably contribute to the harmful effects of oil pollution on seabird populations. In an attempt to rectify the damage inflicted on seabirds by accidental oil discharge, rehabilitation centers are established for the cleaning and care of affected wildlife. Unfortunately, there is evidence that the ingestion of oil by preening and the handling stress undergone by birds in these centers lowers their ability to survive and reproduce following release to their native habitats. Although the reasons for this are unclear, there is the suggestion that both oil and handling will induce immunosuppressive mechanisms that ultimately predispose birds to infections and immune-mediated diseases, as well as reproductive, behavioral, and other problems. Thus, there are questions concerning the effectiveness of intervention measures currently being used in the rehabilitation of seabirds.

Animals↗
PubMed1994

Differentiation of hypothalamic GABAergic neurons in vitro: absence of effects of sex and gonadal steroids.

The inhibitory neurotransmitter gamma-aminobutyric acid (GABA) is involved in the control of sexually dimorphic brain functions, such as pituitary secretion and reproductive behavior. Hypothalamic GABAergic systems in vivo exhibit sexually dimorphic functional properties. Sexual dimorphisms in the rat brain are currently thought to be brought about by the organizational influence of gonadal steroids during the perinatal developmental period. The present study is concerned with the question of whether developing hypothalamic GABAergic neurons are primary targets of sex hormones. Since it is impossible to distinguish direct from indirect effects of experimental manipulations of the hormonal environment of the in vivo brain, sex-specific primary cultures raised from embryonic day 14 rat diencephalon and cultured for up to 8 days in vitro (DIV) were used as a model system. Effects of sex steroids were investigated on high affinity uptake of [3H]GABA. GABA transport was already mature at 3 DIV. [3H]GABA uptake was sensitive to inhibition by nipecotic acid and the transmitter was taken up by high affinity transport (Km = 15.2 microM). Immunocytochemical preparations demonstrated extensive networks of GABA-immunoreactive fibers at 8 DIV. Concomitantly with the outgrowth of neurites, there was a marked increase in maximum uptake velocity (Vmax). No differences could be detected regarding cell numbers or uptake kinetics between cultures from male and female donors. Neither cell numbers nor GABA uptake were affected by short- and long-term treatment with estradiol-17 beta or testosterone. It appears that hypothalamic GABAergic neurons in vitro do not develop sex differences in cell numbers or GABA transport.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Auditory input to a vocal nucleus in the frog Rana pipiens: hormonal and seasonal effects.

In Rana pipiens, single unit recordings from the pretrigeminal nucleus (pre-V), a nucleus involved in call production, demonstrated neurons that respond to auditory stimuli. Most of these neurons had V-shaped tuning curves, with best excitatory frequencies between 200-1400 Hz, thresholds between 31-87 dB SPL, latencies between 10-50 ms, and Q (10 dB) between 1.3-5.1. The number of pre-V neurons that responded to acoustic stimulation increased after gonadotropin injections, and appeared to increase during the breeding season. In addition, a small number of neurons with more complex response properties, such as W-shaped tuning curves or sensitivity to white noise but not to pure tones, appeared after hormone treatments. The hormonal and possible seasonal effects on pre-V auditory activity suggest that the auditory input to this vocal nucleus may play a role in reproductive behavior.

Animals↗
PubMed1984

Proteins synthesized in medial hypothalamus and transported to midbrain in estrogen-treated female rats.

Results on the anatomy of ventromedial hypothalamic outputs, together with the temporal aspects of electrophysiological studies, predict that for reproductive behavior control sex steroids alter hypothalamic protein synthesis and transport of proteins to the dorsal midbrain. We have studied labeled proteins arriving in the dorsal midbrain after local microinjection of tritiated amino acids to the ventromedial hypothalamus. Estrogen treated and control ovariectomized female rats are significantly different in this respect, and in particular some proteins appear to be synthesized or transported in greater amounts in the estrogen treated animals. Physical characterization of these proteins and comparisons under a variety of endocrine conditions will suggest whether their synthesis could be part of the mechanism by which ovarian steroids affect behavior.

Amino Acids↗
PubMed1979

Fine structure of the receptor-free epithelium in the vomeronasal organ of the rat.

The topography and distribution of the epithelia of the vomeronasal organ were investigated in the adult male rat. Special attention was given to the light and transmission electron microscopic structure of the area that is known to be free of receptor cells. In contrast to several brief descriptions in which many cell types have been reported, only one cell type is presently described in different functional phases. In the rat, this epithelium does not show the typical features of a respiratory or, in more general terms, non-sensory epithelium. The authors propose to call this epithelium as "receptor-free" rather than respiratory, non-sensory or ciliated. The importance of the vomeronasal organ in the maintenance of olfacto-endocrine mechanisms and reproductive behavior is discussed.

Animals↗
PubMed1993

Lifetime menstrual activity--indicator of breast cancer risk.

A case-control study of 67 cases of breast cancer and 157 controls was conducted to investigate the role of different behavioral, reproductive, and hormonal factors and to develop a unifying indicator of breast cancer risk. The results confirm previous reports of the influence of smoking on the risk of breast cancer. Age at menarche was found to be a risk factor among the premenopausal women. Late age at menopause was suggestive of an increase in risk. Long use of oral contraceptive or estrogen supplementation were risk-enhancing both pre- and postmenopausally. Lifetime duration of menstrual activity (LMA) combines age at menarche and menopause, parity, and lactation into a biologically plausible model. Our findings concerning LMA support its role as a determinant of breast cancer.

Adult↗