Deciphering the mechanisms involving cenexin, ninein and centriolin in sperm maturation during epididymal transit in the domestic cat

The sperm centrosome is an essential organelle with a key role in organizing the sperm aster for proper syngamy and formation of the first mitotic spindle. The sperm cell acquires the functional capability during epididymal transit by incorporation of key factors. The objective of the study was to identify these key maturation proteins, such as ninein and centriolin as well as cenexin-a scaffold protein that serves to bind ninein and centriolin. Epididymal samples were dissected from 17 adult cat testes (>1 year old) and spermatozoa were extracted from the different regions, including rete testis, caput, corpus, cauda and vas deferens. Tissue samples and sperm cells were fixed separately in 4% paraformaldehyde before immunostaining with anticenexin, ninein or centriolin antibodies. Results showed that the proportion of sperm cells with cenexin localized at the centrosome progressively increased along the tract with the lowest percentage of stained cells in the testis (mean = 45%) and highest in the cauda (mean = 81%). Although not significant, the intensity of cenexin immunofluorescence in positive cells increased twofold from the testis to vas deferens. There was no significant difference in the proportion of sperm labelled with centriolin or ninein (ranges of 21%-26% and 33%-48% between segments, respectively) or the intensity (±58% and ±63% change as compared to testis, respectively). Cenexin may serve as a scaffold protein for centriolin and ninein, as the vast majority of spermatozoa only displayed colocalization of these proteins when cenexin was also present (mean = 85% and 91% colocalization, respectively). In summary, these results could be applied to future efforts to create an in vitro culture system capable of rescuing the impaired centrosome of an infertile male, with particular potential for wild felid conservation.

270 PROGRESSIVE INCORPORATION OF CENEXIN IS RELATED TO SPERM MATURATION DURING EPIDIDYMAL TRANSIT IN THE DOMESTIC CAT

The sperm centrosome is an essential organelle playing a key role just after penetration into the oocyte. It serves to organise the sperm aster, which is required for syngamy and formation of the first mitotic spindle. It is also associated with acquisition of motility during epididymal transit. Previously, we demonstrated that testicular spermatozoa exhibit reduced developmental potential after oocyte injection due to the presence of an immature centrosome [Comizzoli et al. 2006 Biol. Reprod. 75, 252–260]. Centrosome and flagellum maturation naturally occur during epididymal transit where secreted proteins impart changes on the sperm to acquire its functional properties. The objective of this study was to better understand centrosome and flagellum maturation and identify key proteins that could be used to artificially mature testicular spermatozoa. Specifically, we focused our effort on cenexin, a protein that has been reported to aid in maturation of the flagellum and somatic cell centrosome. Epididymides were dissected from adult cat testes (>1 yr old). Spermatozoa were then extracted from the different regions (caput, corpus, cauda, and vas deferens) by slicing with a scalpel blade in phosphate buffered saline at 37°C and processed separately. Control samples were also collected from the rete testis. After recording sperm motility and forward progressive movement (FPM, from 0 = immotile to 5 = fast and straight), cells were fixed in 4% paraformaldehyde and immunostained with anti-cenexin antibodies labelled with a fluorescent probe. The proportion of cells with cenexin at the location of the centrosome and the intensity of immunofluorescence were quantified (n = 8 and 4 testes, respectively). The same methods were followed for detection of cenexin in the tail portion (n = 4 testes). Statistical analyses were conducted using repeated-measures and treatments were further compared using either a protected Tukey's or F-test for orthogonal contrasts. The proportion of sperm with cenexin localised at the centrosome progressively increased along the tract with the lowest percentage of stained cells in the testis and highest proportion in the cauda (45 v. 81%, T28 = 4.65, P < 0.0001). Among the labelled sperm, the intensity of immunofluorescence also significantly increased from the testis to vas deferens (4.33 v. 8.57 mean grey value; T12 = 3.29, P < 0.0065). Both motility and FPM increased from the testis to cauda segment (0 v. 93%, F4,15 = 13.53, P < 0.0001 and 0 v. 3.8 FPM, F4,15 = 26.67, P < 0.0001); however, the proportion with cenexin in the tail (range, 20 to 36%) as well as the labelling intensity (range, 3.14 to 5.26 mean grey value) did not change (P > 0.05) along the tract. These results clearly indicate that cenexin may be associated with centrosome but not flagellum maturation. Epididymal epithelial cells and luminal fluid from each segment are being examined to better understand the source of cenexin secretion and its incorporation into spermatozoa. Results from these studies will aid in further understanding the physiology of sperm maturation during epididymal transit and increase male fertility preservation options.

Effects of xenoestrogens on the differentiation of behaviorally-relevant neural circuits

It has become increasingly clear that environmental chemicals have the capability of impacting endocrine function. Moreover, these endocrine disrupting chemicals (EDCs) have long term consequences on adult reproductive function, especially if exposure occurs during embryonic development thereby affecting sexual differentiation. Of the EDCs, most of the research has been conducted on the effects of estrogen active compounds. Although androgen active compounds are also present in the environment, much less information is available about their action. However, in the case of xenoestrogens, there is mounting evidence for long-term consequences of early exposure at a range of doses. In this review, we present data relative to two widely used animal models: the mouse and the Japanese quail. These two species long have been used to understand neural, neuroendocrine, and behavioral components of reproduction and are therefore optimal models to understand how these components are altered by precocious exposure to EDCs. In particular we discuss effects of bisphenol A and methoxychlor on the dopaminergic and noradrenergic systems in rodents and the impact of these alterations. In addition, the effects of embryonic exposure to diethylstilbestrol, genistein or ethylene,1,1-dichloro-2,2-bis(p-chlorophenyl) is reviewed relative to behavioral impairment and associated alterations in the sexually dimorphic parvocellular vasotocin system in quail. We point out how sexually dimorphic behaviors are particularly useful to verify adverse developmental consequences produced by chemicals with endocrine disrupting properties, by examining either reproductive or non-reproductive behaviors.

Neuroendocrine and immune characteristics of aging in avian species

Avian species show a remarkable diversity in lifespan. The differing lifespan patterns are found across a number of birds, in spite of higher body temperature and apparent increased metabolic rate. These characteristics make study of age-related changes of great interest, especially for understanding the biology of aging associated with surprisingly long lifespan in some birds. Our studies have focused on a short-lived avian model, the Japanese quail in order to describe reproductive aging and the neuroendocrine characteristics leading to reproductive senescence. Biomarkers of aging used in mammalian species include telomere length, oxidative damage, and selected metabolic indicators. These markers provide confirming evidence that the long-lived birds appear to age more slowly. A corollary area of interest is that of immune function and aging. Immune responses have been studied in selected wild birds and there has been a range of studies that have considered the effects of stress in wild and domestic species. Our laboratory studies have specifically tested response to immune challenge relative to aging in the quail model and these studies indicate that there is an age-related change in the qualitative aspects of the response. However, there are also intriguing differences in the ability of the aging quail to respond that differ from mammalian data. Finally, another approach to understanding aging is to attempt to develop or test strategies that may extend lifespan and presumably health. One area of great interest has been to consider the effect of calorie restriction, which is a treatment shown to extend lifespan in a variety of species. This approach is routinely used in domestic poultry as a means for extending reproductive function and enhancing health. Our data indicate that moderate calorie restriction has beneficial effects, and that physiological and endocrine responses reflect these benefits.

Reproductive aging in Japanese quail, Coturnix japonica is associated with changes in central opioid receptors

Quantitative in vitro autoradiography was used to measure specific mu and delta opioid receptor densities in regions of the Japanese quail, Coturnix japonica, brain that regulates reproductive endocrine and behavioral responses to determine the possible involvement of the opioid system in reproductive decline seen during aging. Densities were measured in selected brain regions of young sexually active (YAM), young photoregressed (YPM), old reproductively senescent (OIM) male, young active (YF), and old senescent female (OF) Japanese quail. Medial and lateral septum (SM, SL), medial preoptic area (POM), and n. intercollicularis (ICo) were of particular interest for reproductive responses. Similar to previous observations, mu and delta opioid receptors showed differential distributions in the areas measured. Some age-related changes were observed, with lower SM mu receptor densities in aged males (OIM) than females or young males (YAM). Densities of mu receptors in the POM and in other areas examined did not vary with sex or age. Similarly, OIM males had lower densities of delta receptors in the SM than young males (YAM and YPM); POM delta receptor densities were also low in OIM males compared to the YPM males, and YAM males were intermediate. Interestingly, photoregressed males (YPM) had higher SL delta receptor densities than any other group. Thus there were age-related differences detected in mu receptor densities among groups in the SM of OIM relative to other groups; and the mu and delta receptor densities did not differ in females with brain region. Additionally for delta receptors specifically, YF and OF did not differ from OIM for any brain region and similarly had lower densities of delta receptors compared to YAM males. These data provide support for regional differences in opioid receptor distribution and for age- and sex-related differences in delta opioid receptor densities. The direction of change presents an interesting dichotomy in that, compared to young active males, delta opioid receptor densities increased with loss of reproductive function in the YPM, whereas receptor densities decreased in the OIM. Plasma androgen levels were relatively low in both these groups compared to the young active males. This observation suggests that there is an age-related loss in the ability of this receptor system to respond to circulating and centrally produced steroid hormones in the POM and in some septal regions, compared to young animals that are responding to environmental cues. Furthermore, these data support an active role of the opioid peptide system in the inhibition of the reproductive axis in photoregression.

Can testosterone and corticosterone predict the rate of display of male sexual behaviour, development of secondary sexual characters and fertility potential in primary broiler breeders?

1. Genetic selection for growth to enhance production may be associated with stress and with modified physiological and behavioural phenotypes which depress male primary broiler breeder fertility. 2. We hypothesised that male serum testosterone (T) and corticosterone (C) concentrations might correlate with fertility, sexual behaviour, and testicular, comb and wattle size. 3. Cockerels from two genetic strains (A and B) of primary broiler breeder were penned individually with an average of 10 females across 5 age periods (30 to 51 weeks) to evaluate male fertility, behaviour, serum T and C, and comb, wattle and testicular dimensions. 4. Strain A males had higher T at age periods 2, 4 and 5 than Strain B. Both strains had basal concentrations of C, apart from an elevated concentration for Strain B in period 5. 5. Strain B had a weak but significant, positive correlation between sexual behaviour and T and C, while Strain A males with higher C had larger combs and wattles. 6. Neither T nor C correlated with fertility. We conclude that evaluation of these endocrine factors (quantifiable measurements with the potential to correlate with fertility) alone seems insufficient to predict male fertility potential in these strains of primary broiler breeder.

Short term suppression of follicular recruitment and spontaneous ovulation in the cat using levonorgestrel versus a GnRH antagonist

Suppression and subsequent rebound of ovarian activity using a progestin (levonorgestrel; Norplant) versus a GnRH antagonist (antide) was assessed in the domestic cat via fecal estradiol and progesterone metabolite analyses. Following an initial dose-response trial, queens were assigned to one of four treatments: (1) antide, two 6 mg/kg injections 15 days apart (n = 8 cats); (2) levonorgestrel, six silastic rods (36 mg levonorgestrel/rod) implanted for 30 days (n = 8); (3) control injections (n = 5); and (4) control implants (n = 5). Steroid metabolites were quantified from daily fecal samples for 90 days before, 30 days during, and 90 days after treatment. Antide and levonorgestrel inhibited estrous cyclicity in contrast to continued cyclicity in controls. Cats already at estradiol baseline in antide (n = 7) and levonorgestrel (n = 4) groups remained inhibited during treatment. In females with elevated estradiol levels at treatment onset (Day 0), a normal estradiol surge was completed before concentrations declined to baseline (approximately Days 5-7) and remained suppressed throughout the remaining treatment period. Additionally, 56% of treatment animals exhibited at least one spontaneous ovulation during the pre-treatment period, but no female ovulated during treatment with levonorgestrel or antide. Antide-treated cats exhibited lower (P < 0.05) baseline estradiol concentrations during treatment compared to pre- and post-treatment. In contrast, levonorgestrel induced elevations in baseline estradiol following treatment compared to pre- and during treatment intervals. Control females showed no change (P > 0.05) in baseline estradiol throughout the study period. All levonorgestrel and antide cats returned to estrus after treatment withdrawal. Results demonstrate that: (1) both antide and levonorgestrel are effective for inducing short-term suppression of follicular recruitment and ovulation in the cat; (2) inhibition is reversible; and (3) GnRH antagonists and progestins differentially regulate basal estradiol secretion. This study also confirmed a relatively high incidence of spontaneous ovulation in the cat, a species generally considered to be an induced ovulator.

Fluctuating asymmetry and growth as biomarkers for exposure to androgen disrupting chemicals in Japanese quail

The effects of embryonic exposure to androgen disrupting chemicals (ADCs) on growth and fluctuating asymmetry (FA) were determined in Japanese quail chicks. Embryos were exposed to an anti-androgenic chemical, 1,1,1-Trichloro-2,2-bis(p-chlorophenyl)ethane (p,p'-DDE) at 20 or 40 microg, or to an androgenic chemical, trenbolone acetate, at 5 or 50 microg on day one of incubation. Growth was measured by body weight and tarsus and culmen lengths from day of hatch until day 29. FA was measured as differences in right versus left lengths of the tarsus, radius, zygomatic process, and premaxilla in day old carcasses. No differences in FA were observed for either treatment. Embryonic exposure to DDE resulted in no significant differences in all measures of growth, although the same quail exhibited significant differences in immunological, reproductive, and behavioral measurements (reported elsewhere). Chicks exposed to trenbolone exhibited no differences in body weight or measures of FA at day of hatch, however, subsequent growth was inhibited. This study shows that although growth and FA are often used as measures of chemical stress experienced during embryonic development, they are not sensitive measures for exposure to these ADCs at these levels in Japanese quail.

Consequences of endocrine disrupting chemicals on reproductive endocrine function in birds: establishing reliable end points of exposure

It has been difficult to establish reliable indices of exposure to endocrine disrupting chemicals (EDCs) appropriate for a variety of avian species because of a vast array of reproductive strategies. Data from mammals, reptiles and fish provide insight on likely mechanisms of action for EDCs. However, many of the effects of EDCs are weaker than the actions of the native hormones, making it difficult to assess adverse effects in domestic and wild birds. It is clear that differential sensitivity to EDCs exists across species, due to the timing and mode of exposure, compound toxicity and age of the individual. Our studies on EDCs are conducted in the quail model system, with focus on reproductive endocrine, neuroendocrine and behavioral responses. Studies have included EDC exposure, either by egg injection or via diet. Results from egg injection studies showed the following: (1) estradiol administered by embryonic day 12 demasculinized male sexual behavior, altered hypothalamic neurotransmitters and reduced hen day production and fertility in a dose dependent fashion, (2) methoxychlor (MXC) or vinclozolin impaired male sexual behavior in adult quail and (3) DDE exposure impaired reproductive and immune related end points. Two-generation studies were conducted on Japanese and northern bobwhite quail with dietary methoxychlor (MXC) exposure (0, 5 and 10 ppm) beginning in adults (P1), continuing in their offspring (F1), with F2 offspring raised on control diet. MXC exposure impaired male sexual behavior, hypothalamic catecholamines and plasma steroid hormones. Moreover, MXC exposure had reproductive consequences observable at both the lower and higher doses of MXC in F1 and F2 generations. These data demonstrate that embryonic EDC exposure interferes with sexual differentiation of neural systems that direct reproduction.

Introduction: neurobiological impact of environmental estrogens

This paper provides an introduction to a special issue dedicated to the action of environmental estrogens on neural circuits and behavior. The problem of endocrine disrupting chemicals (EDCs), i.e. chemicals that have the capacity to interfere with the endocrine system, has gained increasing attention as it has become clear that these environmental contaminants may be active in humans, as well as in wildlife and domestic animal species. The majority of the early investigations were aimed at the discovery of the toxicological effects of the EDCs, but biomedical observations were among some of the first indications that estrogenic compounds may exert deleterious effects, even some time after exposure. The data derived from women exposed prenatally to diethylstilbesterol provided powerful evidence for long-term effects and endocrine disruption associated with selected compounds. The examination of wild animal populations exposed to industrial chemicals showed that the chemical exposure, though nonlethal, left the individual impaired or even incapable of reproducing. Among the multiple targets of the action of EDCs, several researches performed in recent years have investigated subtle modifications of the animal behaviors (reproductive, aggressive) that are likely to be related to alterations of specific neural pathways. We have, therefore, focused here on the behavioral studies as one of the more powerful tools to investigate EDCs effects on specific neural circuits.

Birds as long-lived animal models for the study of aging

Despite their high lifetime energy expenditures, most birds can be characterized as long-lived homeotherms with moderately slow aging. A growing body of research confirms the prediction that birds have special adaptations for preventing aging-related oxidative and glycoxidative damage. Nonetheless, biogerontologists have been slow to develop avian laboratory models. A number of domestic poultry and cage bird species represent either established or very promising animal models for studies of basic aging processes and their prevention, including degenerative neurobiological, behavioral and reproductive processes. Several kinds of birds have also been used in studies of cellular resistance to oxidative stressors in vitro. Results of preliminary studies on chickens and quail suggest that caloric restriction may extend the reproductive life span of hens, but its long-term effects on life span remain unstudied. Birds' innate anti-aging mechanisms may actually make them more suitable in some respects as models of longevity than short-lived laboratory rodents, and bird studies may ultimately reveal routes for therapeutic intervention in diseases of human aging and infertility.

Toxicity of lead-contaminated sediment to mute swans

Most ecotoxicological risk assessments of wildlife emphasize contaminant exposure through ingestion of food and water. However, the role of incidental ingestion of sediment-bound contaminants has not been adequately appreciated in these assessments. This study evaluates the toxicological consequences of contamination of sediments with metals from hard-rock mining and smelting activities. Lead-contaminated sediments collected from the Coeur d'Alene River Basin in Idaho were combined with either a commercial avian maintenance diet or ground rice and fed to captive mute swans (Cygnus olor) for 6 weeks. Experimental treatments consisted of maintenance or rice diets containing 0, 12 (no rice group), or 24% highly contaminated (3,950 microg/g lead) sediment or 24% reference (9.7 microg/g lead) sediment. Although none of the swans died, the group fed a rice diet containing 24% lead-contaminated sediment were the most severely affected, experiencing a 24% decrease in mean body weight, including three birds that became emaciated. All birds in this treatment group had nephrosis; abnormally dark, viscous bile; and significant (p <or= 0.05) reductions in hematocrit and hemoglobin concentrations compared to their pretreatment levels. This group also had the greatest mean concentrations of lead in blood (3.2 microg/g), brain (2.2 microg/g), and liver (8.5 microg/g). These birds had significant (alpha = 0.05) increases in mean plasma alanine aminotransferase activity, cholesterol, and uric acid concentrations and decreased plasma triglyceride concentrations compared to all other treatment groups. After 14 days of exposure, mean protoporphyrin concentrations increased substantially, and mean delta-aminolevulinic acid dehydratase activity decreased by more than 95% in all groups fed diets containing highly contaminated sediments. All swans fed diets that contained 24% lead-contaminated sediment had renal acid-fast intranuclear inclusion bodies, which are diagnostic of lead poisoning in waterfowl. Body weight and hematocrit and hemoglobin concentrations in swans on control (no sediment) and reference (uncontaminated) sediment diets remained unchanged. These data provide evidence that mute swans consuming environmentally relevant concentrations of Coeur d'Alene River Basin sediment developed severe sublethal lead poisoning. Furthermore, toxic effects were more pronounced when the birds were fed lead-contaminated sediment combined with rice, which closely resembles the diet of swans in the wild.

Cloning of a partial cDNA for Japanese quail thyroid-stimulating hormone and effects of methimazole on the thyroid and reproductive axes

The purposes of this study were to develop a probe for the detection of thyroid-stimulating hormone (TSH) beta subunit mRNA, to validate the usefulness of that probe in measuring TSH, and to use it to investigate the effects of thyroid suppression on TSH and the reproductive axis in Japanese quail. The objectives of experiment 1 were to isolate and characterize a partial cDNA for quail TSH and validate a riboprobe transcribed from this cDNA. This riboprobe was then used to assess changes in TSHbeta mRNA levels in Japanese quail. We isolated a cDNA of 168 bp with 94% identity to the corresponding sequence in chicken TSHbeta. The transcribed riboprobe was shown to be pituitary gland specific, and differences in TSHbeta mRNA levels were detectable with 2.5 microg of total RNA in Northern blot analysis. In experiment 2, our objective was to determine if thyroid inhibition would result in a detectable change in TSHbeta mRNA and alterations in the pituitary luteinizing hormone (LH) or indices of gonadal function. We used adult, reproductively active, male Japanese quail on a long-day photoperiod. Treatment with a goitrogen, methimazole (MMI), increased (P < 0.05) thyroid gland and liver weights and decreased (P < 0.05) serum thyroxine (T4) concentrations compared to control birds. We detected increased TSHbeta mRNA in the pituitaries of MMI-treated birds compared to controls. There was no effect of MMI treatment on the reproductive variables measured, including LHbeta mRNA levels, serum androgen and estradiol concentrations, gonad weight, or cloacal gland area. Therefore, it appears that thyroid axis inhibition and the consequent increase in TSHbeta mRNA did not have direct effects on reproductive axis function in male Japanese quail.

Hypothalamic indolamines during embryonic development and effects of steroid exposure

The serotonin system has been implicated in the modulation of endocrine and behavioral components of reproduction. In this study, we examined endogenous hypothalamic indolamines during sexual differentiation and long-term effects of exogenous steroids during this time. In Experiment 1, Japanese quail were studied during the last half of embryonic development and early post-hatch. Samples were taken at embryonic day 10 (E10), E12, E14, E16, hatch (day 0), and days 3 and 5, post-hatch. Hypothalamic indolamines, including serotonin (5-HT) and its metabolite, 5-hydroxy indole acetic acid (5-HIAA) were measured by HPLC-EC detection. Females had relatively higher hypothalamic 5-HT at E14 than males, with both sexes showing increasing levels thereafter. By day 5, post-hatch, hypothalamic 5-HT content was higher in males than in females. When turnover was estimated by comparing relative concentrations of 5-HT to 5-HIAA, males were significantly higher at E12 and E14 than females. These data suggest that there are stage specific changes in the serotonin system, as well as sexually dimorphic patterns in the ontogeny and activity of this system. In Experiment 2, we investigated the effects of embryonic steroid hormone treatment on the serotonin system and on male sexual behavior. Birds were treated with either estradiol benzoate (EB), testosterone propionate (TP) or sesame oil (vehicle control) at selected embryonic days (E10, E12, E14, E16, 0, D3, and D5). At 4 weeks post-hatch, birds were transferred to short photoperiod (16D:8L) for 3 weeks to prevent photostimulated reproductive development. At 7 weeks of age, males were implanted with a 20mm silastic capsule filled with testosterone and sexual behavior was tested 1 week later. Brains were collected from both males and females, and preoptic area (POA) indolamines were measured. Steroid treatment at E10 or E12 resulted in the loss of male sexual behavior. Moreover, males treated with EB or TP on E12 also had increased POA 5-HT content as adults, compared to control males. Females treated with EB on either E10 or E 12 also had higher POA 5-HT content than control or TP treated females. These data provide evidence for sexual dimorphism in the hypothalamic 5-HT system at specific stages during embryonic development. Moreover, males were sensitive to exogenous EB and TP on E12, whereas females appeared to be affected by EB only and appeared to be sensitive to steroid effects over a longer period of time in development. Moreover, exogenous steroids at E12 in males also correlated with impaired sexual behavioral. These data suggest that long-term effects of embryonic steroid exposure may be mediated in part through effects on the serotonin neurotransmitter system.

Effects of exogenous testosterone on testicular luteinizing hormone and follicle-stimulating hormone receptors during aging

During aging, the male Japanese quail exhibits a loss of fertility, increased morphological abnormalities in the testes, and a higher incidence of Sertoli cell tumors. Although there is a coincident loss of reproductive behavior, plasma androgen levels remain high until testicular regression occurs in association with senescence. The purpose of this study was to compare mean specific binding of chicken luteinizing hormone (LH) and follicle-stimulating hormone (FSH) as a measure of testicular receptors during identified stages during aging. Males were categorized according to age (young = 9 months, middle aged = 24 months, or old = 36+ months) and sexual behavior (active or inactive). Testicular samples were collected immediately after perfusion with 4% paraformaldehyde from the following groups: young active (n = 8), young photoregressed (n = 5), young photoregressed plus testosterone implant (n = 4), middle-aged active (n = 8), middle-aged inactive (n = 4), old inactive (n = 5), and old inactive plus testosterone implant (n = 6). A crude plasma membrane fraction was prepared from the testes of each bird and an aliquot deriving from 10 mg of testicular tissue was used for binding assay. Specific binding of labeled LH or FSH was expressed as percentage of total radioactive hormone. Results showed significant (P < 0.05) age-related decreases in both FSH and LH receptor numbers. The highest FSH binding was found in young and middle-aged active males, with low binding in old inactive males. Testicular LH binding decreased during aging, with a sharp decrease in middle-aged males, which was similar to old males. Testosterone implants weakly stimulated FSH and LH binding in old males. Both LH and FSH binding decreased in photoregressed young males. However, testosterone implants stimulated increased LH binding, but did not affect FSH binding in young photoregressed males. These results provide evidence for separate regulation of testicular LH and FSH receptors, with testosterone stimulation of LH receptor, but not FSH receptor number in young males. However, during aging there appears to be a loss of this response, potentially because of the reduced efficacy of testosterone stimulation, thereby implying a diminished capacity for response with aging.

Impact of vinclozolin on reproductive behavior and endocrinology in Japanese quail (Coturnix coturnix japonica)

The impact of endocrine-disrupting chemicals (EDCs) has been demonstrated in mammalian models, but less research is available for avian species. The effects of vinclozolin (VIN), an antiandrogenic fungicide, on sexual differentiation and maturation were investigated in Japanese quail (Coturnix coturnix japonica). On day 4 of incubation, embryos were exposed to no treatment, oil, or 25, 50, or 100 ppm of VIN. Endpoints measured included adult male reproductive behavior, hypothalamic gonadotropin-releasing hormone I (GnRH-I) content in hatchlings and adults, plasma steroid levels in hatchlings and adults, proctodeal gland growth during maturation, and relative testicular weight at seven weeks of age. Results showed that exposure to VIN significantly (p < 0.05) altered GnRH-I in male hatchlings, whereas GnRH-I levels in females remained unaffected. Although steroid levels were unaltered by any VIN treatment, the display of male reproductive behavior seemed delayed, with the number of mounts and the number of cloacal contacts being significantly (p < 0.05) lower in the VIN-treated males. This could have an extreme negative impact on wild avian species that are routinely exposed to similar EDCs.

Exceptional cellular resistance to oxidative damage in long-lived birds requires active gene expression

Previous studies indicated that renal tubular epithelial cells from some long-lived avian species exhibit robust and/or unique protective mechanisms against oxidative stress relative to murine cells. Here we extend these studies to investigate the response of primary embryonic fibroblast-like cells to oxidative challenge in long- and short-lived avian species (budgerigar, Melopsittacus undulatus, longevity up to 20 years, vs Japanese quail, Coturnix coturnix japonica, longevity up to 5 years) and short- and long-lived mammalian species (house mouse, Mus musculus, longevity up to 4 years vs humans, Homo sapiens, longevity up to 122 years). Under the conditions of our assay, the oxidative-damage resistance phenotype appears to be associated with exceptional longevity in avian species, but not in mammals. Furthermore, the extreme oxidative damage resistance phenotype observed in a long-lived bird requires active gene transcription and translation, suggesting that specific gene products may have evolved in long-lived birds to facilitate resistance to oxidative stress.

Neuroendocrine and behavioral implications of endocrine disrupting chemicals in quail

Studies in our laboratory have focused on endocrine, neuroendocrine, and behavioral components of reproduction in the Japanese quail. These studies considered various stages in the life cycle, including embryonic development, sexual maturation, adult reproductive function, and aging. A major focus of our research has been the role of neuroendocrine systems that appear to synchronize both endocrine and behavioral responses. These studies provide the basis for our more recent research on the impact of endocrine disrupting chemicals (EDCs) on reproductive function in the Japanese quail. These endocrine active chemicals include pesticides, herbicides, industrial products, and plant phytoestrogens. Many of these chemicals appear to mimic vertebrate steroids, often by interacting with steroid receptors. However, most EDCs have relatively weak biological activity compared to native steroid hormones. Therefore, it becomes important to understand the mode and mechanism of action of classes of these chemicals and sensitive stages in the life history of various species. Precocial birds, such as the Japanese quail, are likely to be sensitive to EDC effects during embryonic development, because sexual differentiation occurs during this period. Accordingly, adult quail may be less impacted by EDC exposure. Because there are a great many data available on normal development and reproductive function in this species, the Japanese quail provides an excellent model for examining the effects of EDCs. Thus, we have begun studies using a Japanese quail model system to study the effects of EDCs on reproductive endocrine and behavioral responses. In this review, we have two goals: first, to provide a summary of reproductive development and sexual differentiation in intact Japanese quail embryos, including ontogenetic patterns in steroid hormones in the embryonic and maturing quail. Second, we discuss some recent data from experiments in our laboratory in which EDCs have been tested in Japanese quail. The Japanese quail provides an excellent avian model for testing EDCs because this species has well-characterized reproductive endocrine and behavioral responses. Considerable research has been conducted in quail in which the effects of embryonic steroid exposure have been studied relative to reproductive behavior. Moreover, developmental processes have been studied extensively and include investigations of the reproductive axis, thyroid system, and stress and immune responses. We have conducted a number of studies, which have considered long-term neuroendocrine consequences as well as behavioral responses to steroids. Some of these studies have specifically tested the effects of embryonic steroid exposure on later reproductive function in a multigenerational context. A multigenerational exposure provides a basis for understanding potential exposure scenarios in the field. In addition, potential routes of exposure to EDCs for avian species are being considered, as well as differential effects due to stage of the life cycle at exposure to an EDC. The studies in our laboratory have used both diet and egg injection as modes of exposure for Japanese quail. In this way, birds were exposed to a specific dose of an EDC at a selected stage in development by injection. Alternatively, dietary exposure appears to be a primary route of exposure; therefore experimental exposure through the diet mimics potential field situations. Thus, experiments should consider a number of aspects of exposure when attempting to replicate field exposures to EDCs.

Steroid hormones during embryonic development in Japanese quail: plasma, gonadal, and adrenal levels

The purpose of this experiment was to measure plasma, gonad, and adrenal steroid hormones during embryonic and early posthatch development in Japanese quail. Blood plasma samples were collected from male and female Japanese quail embryos at 2-d intervals between Day 10 of incubation and Day 5 posthatch. Gonads and adrenal glands were collected from a separate set of embryos at the same ages. Concentrations of androgen (testosterone and 5alpha-dihydrotestosterone) and 17beta-estradiol (E2) were determined by RIA. Plasma androgen changed significantly (P < 0.001) with age in males and females, and there were significant differences (P < 0.001) between sexes in the hormonal patterns. Males had higher plasma androgen than females; conversely, females consistently had overall higher levels of estradiol than males. Adrenal gland steroid content remained relatively high and did not change significantly with age. In contrast, steroid content of gonads followed patterns similar to those observed for plasma levels. These results provide evidence for steroid hormone production by the gonads of both sexes, as well as for distinct differences in the patterns observed in the adrenal gland and gonads. These results provide evidence for gonadal regulation of changes in circulating hormone levels. Further, these hormonal patterns were associated with the timing of steroid-induced sexual differentiation in the Japanese quail, suggesting that plasma gonadal steroids are critical in sexual differentiation.

Comparison of Gonadal Hormone Levels in Turkey Embryos Incubated in Long-Term Shell-Less Culture and In Ovo

Changes in concentrations of 17beta-estradiol (E2) and androgenic hormones were measured in turkey embryos incubated in long-term, shell-less culture (ex ovo) and in ovo. Blood samples were obtained from both sets of embryos on Days 14, 16, 18, 20, and 22 and from embryos incubated in ovo on Days 24, 26, and 28. Ex ovo and in ovo embryos showed no differences in either hormone within sexes, with one exception. On Day 14 of incubation, the ex ovo females had higher (P < 0.05) E2 levels (55.6+/-5.1 pg/mL) than the in ovo females (32.2+/-2.3 pg/mL); however, this result might have been due to the small sample size (n = 3) for ex ovo females. No significant differences were found in androgen concentrations between sexes in ovo on Days 24, 26, and 28 of incubation. However, on Days 24, 26, and 28, in ovo females showed highly significant differences (P < 0.01) in E2 compared with males of the same age. These results indicate a similar developmental pattern for the endocrine system in ovo and ex ovo through Day 22 of incubation. Further, there were sex differences in E2 that are likely to be critical for sexual differentiation that emerges late in embryonic development.

Quail and other short-lived birds

Japanese quail are small galliforms that are migratory and generally live 2 to 3years in the wild. Although there is evidence for other environmental cues, they primarily respond to long daylength for regulation of reproduction. In contrast to the Common Tern, a long-lived sea bird that shows little evidence of reproductive aging, Japanese quail follow a well-defined process of aging with evidence of declining function in reproductive, metabolic, and sensory systems. Our studies focus on neuroendocrine changes associated with reproductive aging in the Japanese quail, with emphasis on the male in order to study both endocrine and behavioral components of reproduction and the process of reproductive aging.

Age-dependent changes in sperm production, semen quality, and testicular volume in the black-footed ferret (Mustela nigripes)

The black-footed ferret (Mustela nigripes), which was extirpated from its native North American prairie habitat during the 1980s, is being reintroduced to the wild because of a successful captive-breeding program. To enhance propagation, the reproductive biology of this endangered species is being studied intensively. The typical life span of the black-footed ferret is approximately 7 yr. Female fecundity declines after 3 yr of age, but the influence of age on male reproduction is unknown. In this study, testis volume, seminal traits, sperm morphology, and serum testosterone were compared in 116 males from 1 to 7 yr of age living in captivity. Results demonstrated that testes volume during the peak breeding season was similar (P > 0.05) among males 1 to 5 yr of age, reduced (P < 0.05) among males 6 yr of age, and further reduced (P < 0.05) among males 7 yr of age. Motile sperm/ejaculate was similar in males 1 to 6 yr of age but diminished (P < 0.05) in those 7 yr of age. Males at 6 and 7 yr of age produced fewer (P < 0.05) structurally normal sperm than younger counterparts; however, serum testosterone concentrations were not reduced (P > 0.05) in older males. Histological comparison of testicular/epididymal tissue from 5- and 7-yr-old black-footed ferrets confirmed that the interval between these two ages may represent a transitional period to reproductive senescence. In summary, functional reproductive capacity of male black-footed ferrets exceeds that of females by at least 2 yr. Testes and seminal quality are indistinguishable among males 1 to 5 yr of age, with progressive reproductive aging occurring thereafter.

Plasma 17beta-estradiol levels and ovarian interstitial cell structure in embryonic Japanese quail

Plasma concentrations of 17beta-estradiol (E2) and left ovarian histology were investigated by light and electron microscopy in female Japanese quail from Day 10 of embryonic development through Day 7, posthatch. Plasma E2 levels remained relatively constant (102 to 140 pg/mL) in the embryo followed by a sharp decrease posthatch (47 to 70 pg/mL). Beginning on Day 10 of incubation, cells in the medullary portion (medullary cell; MC) of the left ovaries exhibited ultrastructural evidence of steroidogenic capability. The MC had numerous lipid droplets in close proximity to the smooth endoplasmic reticulum (SER). Mitochondria were also observed in the vicinity of the lipid droplets and SER. On Days 10 and 12, the cristae of the inner mitochondrial membranes were of a lamellar configuration; the cristae of some mitochondria in MC had a tubular appearance by Day 14. These data document relative ontogenic changes in ovarian morphology and plasma E2 levels during the early developmental period in female Japanese quail. These data further support the role of this steroid in sexual differentiation.

Endocrine patterns during aging in the common tern (Sterna hirundo)

Blood samples were taken from breeding common terns (Sterna hirundo) of known age during two successive breeding seasons to determine if plasma concentrations of estradiol, progesterone, androgen, and luteinizing hormone (LH) reflect the process of aging. Males and females were trapped and sampled once between laying of the first and the second eggs in the clutch. The transient capture and sampling did not disrupt incubation or the timing of the subsequent oviposition. Ages ranged from 2 to 21 years, with most in the range 4-11 years. There was a strong inverse correlation (P < 0.0001) between age and laying date in both females and males, with older birds nesting earlier in the season. Plasma LH levels increased (P < 0.005) among mature (>5 year) females. Plasma progesterone and E2 were positively correlated with each other among mature females, but did not change in an age-dependent manner. In males, plasma progesterone levels showed no age-related changes. However, maturing (3-5 year) males showed increasing plasma androgen levels (P < 0.01); mature males showed no change with age. Plasma LH levels were correlated with androgen levels in both maturing and mature males. Plasma progesterone declined with age in maturing males (P < 0.001). These data provide evidence for changing endocrine status with age, but the patterns differ for younger individuals (</=5 year) and mature birds. It appears that in younger individuals, nesting experience and maturity of the pair affect reproductive performance and endocrine status. Individual variability was high for all hormones, possibly masking age-related changes. Only breeding individuals were sampled at all ages, although the proportion of the population that continues to reproduce may decline as the birds age. In summary, common terns continue to breed successfully until at least age 21 years and these individuals maintain relatively stable endocrine status during aging. Although there was some indication of declines in estradiol and androgens among the oldest birds (16-21 years), these declines were not statistically significant and were manifested in only a small fraction (<4%) of the breeding population.

An analysis of physiological mechanisms underlying the antigonadotropic action of intracranial prolactin in ring doves

Intracerebroventricular (ICV) injections of prolactin (PRL) exert potent antigonadal and antigonadotropic effects in ring doves (Streptopelia risoria) at doses that are insufficient to stimulate prolactin-dependent crop growth. To explore the physiological basis of these effects, we tested the ability of ICV-injected PRL to influence pituitary responsiveness to chicken gonadotropin-releasing hormone-I (cGnRH-I) and to alter GnRH content and concentration in the preoptic area (POA) and median eminence (ME). cGnRH-I-induced changes in plasma LH were monitored by radioimmunoassay (RIA) in photostimulated male doves after they received five daily ICV injections of ovine PRL (1 microg/2 microl) or saline vehicle. Although PRL treatment reduced basal plasma LH levels and testes weight, it did not reduce the amount or alter the pattern of LH released in response to a bolus injection of cGnRH-I. This suggests that ICV PRL does not suppress LH by reducing pituitary responsiveness to GnRH. In two subsequent studies, GnRH content (ng/region) and concentration (pg/microg protein) in the POA and ME were measured in male doves by RIA and by competitive enzyme immunoassay after 5 days of ICV PRL or vehicle treatment. Although ICV PRL reduced plasma LH levels in both studies, no significant PRL-induced alterations in GnRH content or concentration were apparent. In a final study, PRL-treated female doves had lower plasma LH levels than vehicle-treated control females at 12 and 24 h after a single ICV injection. GnRH content of the POA was also lower in PRL-treated females than in controls at 24 h. However, the two treatment groups did not differ in POA or ME GnRH content at earlier postinjection sampling intervals. Analysis of GnRH concentration data revealed no treatment group differences in either region at any sampling interval (1, 6, 12, or 24 h post-PRL injection). Collectively, these results are consistent with the idea that ICV-injected PRL acts at the level of the CNS to inhibit the reproductive system. However, the nature of the alterations involved remains to be clarified. Plausible hypotheses are (1) that ICV PRL suppresses the gonadal axis by influencing the activity of GnRH neurons at brain sites other than the POA or ME or (2) that PRL alters the synthesis, storage, degradation, and/or release of GnRH in the POA or ME, but the dynamic changes involved are not reflected in integrated, steady-state measures such as peptide content or concentration in tissue.

Regulation of sperm function by protein tyrosine phosphorylation in diverse wild felid species

Protein tyrosine phosphorylation is associated with sperm capacitation and the acrosome reaction in several mammalian species. Changes in phosphorylation of a 95-kDa protein in human, mouse, and domestic cat spermatozoa are known to be influenced by capacitation and exposure to zona pellucida (ZP) proteins. We previously reported diminished phosphorylation of 95- and 160-kDa proteins in spermatozoa from teratospermic cats, compared with normospermic domestic cats. To determine if these proteins and mechanisms are present in other species in the phenotypically diverse Felidae family, we examined the relationship between tyrosine-phosphorylated sperm proteins and sperm morphology in the leopard cat (approximately 65% normal sperm/ejaculate), tiger (approximately 65%), clouded leopard (approximately 15%), and cheetah (approximately 30%). Furthermore, we investigated the involvement of cyclic adenosine monophosphate (cAMP) in the regulation of sperm protein tyrosine phosphorylation. Specifically, we assessed the following: 1) presence of tyrosine-phosphorylated proteins in sperm extracts; 2) changes in protein tyrosine phosphorylation after sperm capacitation and swim-up separation; 3) impact of tyrosine kinase inhibition on leopard cat sperm protein phosphorylation and ZP penetration; and 4) involvement of a cAMP-dependent pathway in the regulation of protein tyrosine phosphorylation. Immunoblotting analysis with anti-phosphotyrosine antibody (PY20) indicated that a 95-kDa protein was present in all four species. Additional phosphorylated proteins were detected in the leopard cat (145- and 175-kDa proteins), tiger (185-kDa protein), clouded leopard (160- and 190-kDa proteins), and cheetah (115- and 155-kDa proteins). Sperm capacitation in vitro increased phosphorylation of one or more proteins in the leopard cat, tiger and clouded leopard, but not in the cheetah. Although swim-up separation increased the proportion of morphologically normal spermatozoa in the clouded leopard and cheetah, no changes were observed in phosphorylation of the 95-kDa sperm protein. Thus, phosphorylation of the 95-kDa protein appeared to be related to the condition of teratospermia. Exposing leopard cat spermatozoa to the tyrosine kinase inhibitor, tyrphostin, reduced (P < 0.05) phosphorylation of the 95- and 145-kDa proteins, as well as ZP penetration, without affecting sperm motility. Similarly, when spermatozoa were incubated in the presence of cAMP analogs or active and inactive stereoisomers of cAMP, phosphorylation of sperm proteins was either stimulated or inhibited. Together, these data suggest that protein tyrosine kinase mechanisms appear conserved within the family Felidae and are regulated by a cAMP/protein kinase A pathway.

Assessment of ejaculate quality and sperm characteristics in turkeys: sperm mobility phenotype is independent of time

Given a pool of genetically superior male turkeys, the subsequent selection of toms as semen donors for artificial insemination should be based upon criteria that are predictive of the tom's fertility and fecundity over the course of a production cycle. Recently, sperm mobility phenotype has been shown to correlate highly with fertility. Therefore, the objectives of this study were to determine: 1) whether sperm mobility phenotypes of individual toms were independent of time, and 2) the extent to which traditional semen quality variables changed as a function of time during the study interval. Sperm mobility phenotype was determined by objectively measuring the ability of sperm to penetrate 2% Accudenz solution at body temperature. During the initial assessments of a flock (n = 94), sperm mobility indexes (SMI) were significantly higher for the High Mobility Phenotype toms (56.61 +/-1.03% SMI) compared to the Low Mobility Phenotype (30.46+/-1.27% SMI, P < or = 0.0001) toms. Over the 5 mo of this study, the High Mobility Phenotype toms consistently had higher (P < or = 0.05) SMI values than the Low Mobility Phenotype toms, with SMI values similar to those of the initial screen. Ejaculate volume, concentration, and plasma membrane integrity showed no significant differences between phenotypes (P > or = 0.05). Sperm viability remained significantly lower (P < or = 0.05) over the course of this study for the High Mobility Phenotype toms than for the Low Mobility Phenotype toms. Because sperm mobility phenotype remained consistent through time, the Sperm Mobility Test provides a potentially important tool for selecting semen donors in turkeys.

Multiple forms of GnRH are released from perifused medial basal hypothalamic/preoptic area (MBH/POA) explants in birds

Both chicken gonadotropin-releasing hormones I and II (cGnRH I and II) were detected in abundant quantity by radioimmunoassay of extracts of Japanese quail medial basal hypothalamic/preoptic area (MBH/POA) fragments that included the median eminence (ME) region. However, in radioimmunoassayed extracts of Japanese quail ME alone, the concentration of cGnRH I greatly exceeded that of cGnRH II (approximately 450 pg/ME vs < 10 pg/ME). Likewise, cGnRH I and II were released into perifusates from quail an turkey MBH/POA explants maintained in short-term perifusion. Release of both forms occurred whether or not explants included the ME region, i.e., from quail POA explants did not include the ME or from turkey MBH/POA explants from which the ME region had been dissected out. This indicates that neuropeptides released from areas other than the ME can be a major source of neuropeptides detected in perifusates. Further, release of cGnRH I was altered following the addition of norepinephrine to perfusion media, whereas cGnRH II release was unaffected, again, whether or not explants included the ME. These results demonstrate that the release of neurohemoral substances from perifused explants cannot be assumed to represent regulated secretion from the ME.

Inhibition of domestic cat spermatozoa acrosome reaction and zona pellucida penetration by tyrosine kinase inhibitors

Spermatozoa from teratospermic domestic cats (> 60% morphologically abnormal spermatozoa per ejaculate) consistently exhibit lower levels of oocyte penetration in vitro than their normospermic (< 40% abnormal spermatozoa per ejaculate) counterparts. This could be caused by structural abnormalities or intracellular defects resulting in disruption of normal cellular functions. Spermatozoa from teratospermic cats also are compromised in the ability to capacitate and undergo the acrosome reaction (AR) in vitro. Further, we recently identified two tyrosine phosphorylated proteins (95- and 160-kDa) localized over the acrosome region in domestic cat spermatozoa. Phosphorylation of these proteins is reduced in teratospermic compared with normospermic ejaculates. To begin to understand the relationship between tyrosine phosphorylation and sperm function, we examined the effects of two protein tyrosine kinase inhibitors (tyrphostin RG-50864 and genistein) on (1) sperm motility; (2) protein tyrosine phosphorylation; (3) the ionophore A23187-induced AR; (4) the spontaneous and zona pellucida (ZP)-induced AR, and (5) the ability of spermatozoa from normospermic cats to penetrate conspecific ZP-intact oocytes. Over a wide range of concentrations, neither inhibitor affected sperm percentage motility during incubation (P > 0.05). Preincubation with either inhibitor reduced tyrosine phosphorylation of both (95- and 160-kDa) sperm proteins. Although both inhibitors blocked the ZP-induced AR, neither influenced the spontaneous AR nor the A23187-induced AR, suggesting that tyrosine phosphorylation may be involved in physiologic AR. No differences (P > 0.05) were observed in the ability of control or inhibitor-treated spermatozoa to bind to or penetrate the outer ZP layer. However, percentages of oocytes with treated spermatozoa in the inner ZP (tyrphostin, 8.7%; genistein, 20.4%) and perivitelline space (tyrphostin, 0%; genistein, 2.3%) were less (P < 0.001) than untreated controls (inner ZP, 62.7%; perivitelline space, 10.2%). These results (1) demonstrate that ZP-induced acrosomal exocytosis in domestic cat spermatozoa is regulated via a tyrosine kinase-dependent pathway and (2) suggest that defects in these signaling pathways may represent one of the causes for compromised sperm function in teratospermic males.

An analysis of sex and breeding stage differences in prolactin binding activity in brain and hypothalamic GnRH concentration in Wilson's phalarope, a sex role-reversed species

Wilson's Phalarope (Phalaropus tricolor) is a sex role-reversed species in which incubation of eggs and care of young is performed exclusively by the male. Plasma levels of prolactin (PRL), the hormone most associated with parental care in birds, are higher in incubating males than in nonincubating males or females. Conversely, plasma testosterone levels are reduced in males during incubation. In an attempt to characterize the physiological basis of this unusual parental care system we used quantitative film autoradiography and densitometry to measure the specific binding in vitro of 125I-ovine PRL to 12 brain regions in females, nonincubating males, and incubating males during the normal breeding season. We also measured hypothalamic chicken gonadotropin-releasing hormone I (cGnRH-I) in three brain areas in these same birds, as well as plasma levels of PRL and testosterone. Analysis revealed that cGnRH-I concentrations in the preoptic area and plasma testosterone levels were significantly lower in incubating males than in nonincubating males. Specific binding of 125I-ovine PRL was detected in choroid plexus and in several diencephalic brain regions of both sexes, with highest binding activity recorded in the dorsolateral thalamus, medial habenula, nucleus subrotundus, and preoptic area. When adjustments were made for the large number of comparisons performed, specific binding did not vary significantly by sex or breeding stage in any single brain region. However, average specific binding values in nonincubating males exceeded those of incubating males in 9 of the 11 PRL-sensitive regions examined. Increased occupancy of the receptor by endogenous PRL during incubation could have contributed to this result, since plasma PRL levels were elevated in incubating males. In addition, PRL binding activity in several of these brain regions tended to correlate negatively with plasma PRL. The two exceptions to this general pattern were the preoptic area and the lateral septum, where mean specific binding was 14-15% higher in incubating males than in nonincubating males. This raises the interesting possibility that PRL sensitivity is up-regulated during incubation in some regions of the male phalarope brain, such as the preoptic area and lateral septum, that have been implicated in PRL-modulated changes in behavior and reproductive activity during this breeding stage.

Neuroendocrine regulation of GnRH and behavior during aging in birds

Avian species exhibit a great variety of life-long patterns in reproduction. Japanese quail are relatively short lived and undergo an age-related loss of reproductive function, making this species an excellent model for the study of the basic biology of aging. Because individuals age at variable rates, sexual behavior has provided a useful index to assess reproductive status of individuals of the same chronological age. Further, exogenous testosterone restores sexual behavior in reproductively senescent male quail, thereby providing evidence for a continued ability of the system to respond. In addition, we have been studying hypothalamic neuroendocrine systems that regulate the endocrine as well as behavioral components of reproduction. Overall, our findings point to the hypothalamic neuroendocrine systems as the site of initial age-related alterations that contribute to the reproductive deterioration. Specifically, we studied adrenergic, opioid peptide, vasotocin, and aromatase systems to understand their relationship to the cGnRH-I system and their potential role in the deterioration of the cGnRH-I system during aging. Our findings provide evidence for qualitative and quantitative alterations in the aromatase enzyme system, which can be partially restored with exogenous testosterone. In addition, other neuronal systems, including the vasotocin system, decline with the loss of gonadal steroids and are restimulated with exogenous testosterone. We will synthesize the data relative to these neuroendocrine systems with attention to the effects of gonadal steroids on these systems during aging.

Developmental stages of primary oocytes in turkeys

Little is known about the growth and differentiation of the primary oocyte in the sexually mature chicken or turkey hen. In this study, primary oocytes from turkey hens in egg production were examined by light and electron microscopy. Based on oocyte and germinal vesicle (GV) diameters and organelle morphology and distribution, the sequential development of the primary oocyte was divided into five stages. No Balbiani body was observed in Stage I oocytes (< 80 microns in diameter). Pleomorphic mitochondria were localized around the GV and multivesicular bodies were scattered in the ooplasm. By Stage II (81 to 150 microns), the Balbiani body was observed adjacent to the GV. Pleomorphic mitochondria, macrobodies, and smooth endoplasmic reticulum (SER) were associated with the Balbiani body. Lipid droplets were predominantly localized to the periphery of the oocyte. The Balbiani body was partially dispersed by Stage III (151 to 350 microns) and associated organelles appeared in clusters in the ooplasm. Golgi and SER were observed immediately subjacent to the oolemma. Stage IV oocytes (351 to 500 microns) were characterized by the absence of the Balbiani body, a more centrally located GV, and the redistribution of the mitochondria to the periphery of the oocyte. Throughout the ooplasm was vesicular SER. By Stage V (501 to 800 microns), zonation of the organelles was completed with the mitochondrial ring immediately subjacent to the oolemma and a concentric layer of lipid droplets subjacent to the mitochondrial ring. The GV was in the periphery of the oocyte. Organelle and inclusion redistribution and organelle pleomorphism were presumed to be reflective of increasing metabolic and transport requirements of the growing oocyte in the mature turkey hen.

Compromised sperm protein phosphorylation after capacitation, swim-up, and zona pellucida exposure in teratospermic domestic cats

Tyrosine phosphorylated proteins recently have been found in mouse and human spermatozoa. Our objectives were to (1) determine if domestic cat spermatozoa also express tyrosine phosphorylated proteins, and (2) examine the changes in protein phosphorylation between normospermic and teratospermic domestic cats following sperm capacitation, swim-up separation and exposure to zona pellucida (ZP). Membranes from cat spermatozoa contained two phosphorylated proteins of molecular weights 160 kDa and 95 kDa (designated as p160 and p95) that immunoreacted with monoclonal antibodies to tyrosine phosphate. The p95 protein was distinct from sperm-specific hexokinase. Following capacitation, the extent of phosphorylation of p95 was increased (P < 0.05) 3-fold in normospermic cats compared to only 1.75-fold in teratospermic cats. Similarly, phosphorylation of p160 also increased (P < 0.05) 2.4-fold in normospermic compared to 1.84-fold in teratospermic cats. Although swim-up separation increased the percentage of normal spermatozoa in teratospermic ejaculates, phosphorylation of p95 in swim-up, aliquots was increased (P < 0.05) only 1.95-fold in teratospermic cats compared to 2.9-fold in normospermic counterparts. Likewise, phosphorylation of p160 was lower (P < 0.05) in teratospermic (1.5-fold) compared to normospermic cats (2.0-fold) cats. Phosphorylation also was influenced by exposure to cat ZP proteins (P < 0.05). Solubilized cat ZP bound to the sperm proteins of apparent molecular mass 120, 95, 50, 42, 30, 27, 23 and 20 kDa, suggesting a direct binding interaction between p95 and the ZP. Overall, these findings (1) indicate the presence of tyrosine phosphorylated proteins in the domestic cat spermatozoon that directly interact with homologous ZP glycoproteins; (2) demonstrate that cat sperm hexokinase is not phosphorylated on tyrosine residues; and (3) suggest that the diminished phosphorylation efficiency of sperm from teratospermic cats may result in a compromise in capacitation and the acrosome reaction.

Testosterone effects on vasotocinergic innervation of sexually dimorphic medial preoptic nucleus and lateral septum during aging in male quail

Vasotocin fibers are known to innervate regions important in the regulation of sexual behavior and neuroendocrine systems in quail. In this experiment, vasotocinergic innervation of the lateral septum and of the sexually dimorphic medial preoptic nucleus was studied during reproductive aging relative to sexual behavior or following testosterone (T). There were 4 groups of male Japanese quail (Coturnix japonica) studied: adult reproductive (6 month, n = 4), photoregressed adult (n = 5), old senescent (36 month, n = 4), and old testosterone-treated (n = 5). Immunocytochemistry for vasotocin (VT) was performed on serial sections and quantification of the density of VT-positive fibers was performed by image analysis. Results showed a highly significant decrease in VT-immunocytochemical staining in photoregressed and in old senescent males; whereas T-treatment in old males was associated with recovery of VT-immunocyto-chemical staining, comparable to the adult reproductive male. Previous experiments have shown that T treatment restimulates sexual behavior in senescent males similar to the recovery of sexual behavior in T-treated castrates. These results indicate that the VT system may be associated with the behavioral recovery observed in senescent T-treated males.

Effect of lactation on hypothalamic preproenkephalin gene expression

Enkephalin appears to modulate several aspects of reproductive function in female rats. The purpose of this study was to determine if lactation influences preproenkephalin gene expression in one or more hypothalamic nuclei known to be involved in maternal or reproductive behavior and prolactin secretion. Lactating rats were killed on day 3 (LAC 3) or day 10 (LAC 10) of lactation. Controls consisted of regular 4-day cycling rats that were killed on diestrous day 1, with 9 to 12 females per group. We used in situ hybridization histochemistry to assess preproenkephalin gene expression in individual cells in the medial preoptic nucleus, anterior, medial and posterior arcuate nucleus, magnocellular and parvocellular aspects of paraventricular nucleus, and ventromedial nucleus. Preproenkephalin mRNA in the anterior arcuate nucleus increased to reach significance (P < 0.05) at day 10 of lactation. Levels in the medial arcuate nucleus increased significantly (P < 0.001) by day 3 of lactation (LAC 3) and remained elevated on day 10 (LAC 10). No significant differences between lactating and control rats were detected in preproenkephalin mRNA levels in the posterior arcuate nucleus, medial preoptic nucleus or in the ventromedial nucleus. Substantial levels of preproenkephalin mRNA were found in the paraventricular nucleus, particularly in a limited region of the magnocellular portion. However, these levels did not change with lactation. These data provide evidence for differential regulation of the preproenkephalin gene during lactation. This change may contribute to lactational hyperprolactinemia and suppressed GnRH secretion, leading to reproductive acyclicity.

Mating alters gonadotropin-releasing hormone cell number and content

Female musk shrews (Suncus murinus) are induced ovulators, which lack a behavioral and ovarian estrous cycle. Females mate the first time they are introduced to a male, but a second or third mating, at least 24 h later, is usually required to induce ovulation. Because GnRH-immunoreactive (GnRH-ir) cell numbers increase during and after exposure to a male, we hypothesized that mating promotes synthesis of this important peptide. To test this hypothesis, we examined changes in GnRH-ir cell number and GnRH-ir content at select time points after mating and ovulation. One hour after mating, GnRH-ir cell numbers in olfactory-related regions of the forebrain were increased. By 15 h after mating, just before ovulation, GnRH-ir cell number and content were increased. Twenty-four hours after mating, GnRH-ir cell numbers in the tenia tecta and medial septum/diagonal band were lower in females that ovulated compared with females that did not ovulate. By 40 h postmating, females that ovulated had fewer GnRH-ir neurons and lower GnRH content in the entire brain than females that did not ovulate. In addition, we found significant negative correlations between plasma estradiol concentrations and both GnRH-ir cell numbers and content in the preoptic area of animals killed around the time of ovulation. Interestingly, significantly more GnRH-ir neurons and a greater content of GnRH peptide were observed in several forebrain nuclei of females that did not ovulate 40, compared to 24, h after mating. In contrast, numbers of GnRH-ir neurons in the midbrain declined 40 h postmating in ovulated females. These results suggest that mating stimulates activity in GnRH-ir neurons, and that ovulation is correlated with a decline in GnRH-ir cell number and content. In this species, mating can be used as an external trigger to activate GnRH neurons and examine the regulation and production of GnRH in heterogenic neuronal populations.

Co-localization of aromatase enzyme and estrogen receptor immunoreactivity in the preoptic area during reproductive aging

Immunoreactive aromatase enzyme (AROM-IR) was studied in the preoptic and septal ares of the male Japanese quail brain relative to the age-related decline in endocrine and behavioral components of reproduction. Additional analyses were conducted to determine if the co-localization of AROM-IR and estrogen receptor immunoreactivity (ER-IR) in the medial preoptic area change during aging. Young, sexually active, male quail (6 months of age) were compared to aged sexually active or inactive, male quail (36 months of age). Testis size decreased in old, sexually inactive males, similar to our previous observations. The numbers of AROM-IR neurons in the medial preoptic area (POM) and the lateral septum (LS) decreased significantly with aging and sexual activity. The number of cells that co-localized both AROM-IR and ER-IR did not differ with age. As a consequence of the age-related change in AROM-IR cells, the relative percentage of dual labelled (AROM-IR and ER-IR) and single labelled cells (AROM-IR) increased in aged males. These data provide histochemical evidence that alterations in the aromatase enzyme system in the medial preoptic area may underlie behavioral and endocrine events associated with reproductive aging.

Estradiol and androgen modulate chicken luteinizing hormone-releasing hormone-I release in vitro

Hypothalamic slices (1 mm) including medial basal hypothalamus and preoptic areas (MBH-POA) were taken from adult male Japanese quail, placed in a short-term perifusion system, and exposed to estradiol or androgen. Release of chicken LHRH-I (cLHRH-I) was measured by an enzyme immunoassay specific for cLHRH-I. In separate experiments, MBH-POA slices were exposed short-term to 5 alpha-dihydrotestosterone (5 alpha-DHT, 10(-7) M) and testosterone (T, 10(-7) M), and short- or long-term to 17 beta estradiol (E2, 10(-9) M). Release of both basal and stimulated cLHRH-I (15-min exposure to 10(-6) M norepinephrine [NE]) was monitored. Basal cLHRH-I release during perfusion was episodic throughout the experimental periods. During no treatment, there was a mean (+/- SEM) pulse interval of 21.27 +/- 1.03 min, pulse duration of 13.98 +/- 0.59 min, pulse duration of 13.98 +/- 0.59 min, pulse amplitude of 4.12 +/- 0.13 pg/5 min, and pulse frequency of 2.93 +/- 0.12/h. Mean cLHRH-I pulse amplitude significantly (p < 0.05) increased with challenge by NE to 25.03 +/- 3.09 pg/5 min. Short-term E2 exposure significantly (p < 0.01) potentiated NE-induced cLHRH-I release. Neither T nor 5 alpha-DHT affected baseline or NE-stimulated cLHRH-1 release. Pretreatment with E2 (10(-9) M) for 14 h in static culture before perifusion significantly (p < 0.05) reduced the NE-induced cLHRH-I release. These results suggest that a hypothalamic LHRH-I pulse-generating mechanism is located within the MBH-POA. Further, these data provide evidence for E2 modulation of cLHRH-I release, which varies with exposure.

LHRH-I release from quail hypothalamic slices measured by specific EIA

A competitive enzyme immunoassay (EIA) was developed for luteinizing hormone-releasing hormone (LHRH), which measures either mammalian luteinizing hormone-releasing hormone or chicken LHRH-I (cLHRH-I). There is negligible cross-reactivity with chicken LHRH-II. Assay sensitivity is 1 pg/ml and the intra- and interassay variation are 3.4 and 10.0%, respectively. The assay was validated for measuring cLHRH-I by parallelism and quantitative recovery. Using this EIA, cLHRH-I content was measured in microdissected samples of median eminence from mature quail and chickens. Mean cLHRH-I concentrations were 1.25 +/- 0.35 and 2.10 +/- 0.25 ng/mg protein in quail and chickens, respectively. In vitro release of cLHRH-I was studied by perifusion of quail medial basal hypothalamus-preoptic area (MBH-POA) slices. Challenge with increasing concentrations of K+ resulted in significant (P < 0.05) release of cLHRH-I. The release of cLHRH-I from MBH-POA slices was also measured in response to norepinephrine (NE), epinephrine (E), and isoproterenol (ISO). Chicken LHRH-I was released in a dose-dependent manner; maximal release occurred with 10(-7) M NE, 10(-8) M E, and 10(-7) M ISO. Tissue response was optimal for experimental manipulation 6-25 hr postcollection; thereafter, the response deteriorated until 60 hr postcollection. These data extend previous studies in birds by detailed characterization of responses to neurochemical challenge and description of optimal parameters for tissue response during perifusion.

Issues facing researchers

Agriculture research spans the spectrum from fundamental to applied research. Researchers in agricultural fields must compete successfully with scientists in their field of research for funding during a time of diminishing resources. In addition, there are pressures on agricultural researchers within their institutions and at the state and national levels that often differ from pressures on scientists in fields other than agriculture. In order to be successful, the poultry scientist must compete for funds, keep current in a rapidly advancing technological environment, and attempt to meet the needs of the poultry industry.

Induced oviposition of precalcified eggs following prostaglandin administration

In order to obtain fertilized ova from White Leghorn chickens in the early cleavage stages, a nonsurgical procedure using prostaglandins (PG) was developed to induce premature oviposition of uncalcified eggs. The experimental design consisted of two 5 x 5 factorial arrangements of treatments using combinations of 0, .5, 1, 2, and 3 micrograms of PGF2 alpha and PGE1 or PGF2 alpha and PGE2. Frequency of PG-induced oviposition was highest (100%) with 1 microgram of PGF2 alpha and 3 micrograms of PGE1 or PGE2. Induced oviposition frequency decreased at the higher (2 and 3 micrograms of each PG) dosages. In general, induction time decreased as PG levels were increased; the minimum induction time was observed with injection of 3 micrograms of PGF2 alpha with 2 or 3 micrograms of PGE1 (1.8 min). There was a significant interaction for frequency of induced oviposition between PGF2 alpha and PGE1 (P less than .05), but not between PGF2 alpha and PGE2. There was also a significant interaction between PGF2 alpha and PGE2 (P less than .01) for induction time, which was not observed with PGF2 alpha and PGE1. Oviposition could not be induced earlier than 5 to 5.5 h after the previous oviposition. Prostaglandin-induced oviposition provides an alternative to euthanasia, surgery, or manual expulsion for collection of precalcified eggs in the early cleavage stages.

Avian LHRH during embryonic development: measurement by competitive ELISA with a monoclonal antibody

A mouse monoclonal antibody directed against chicken Gln8-luteinizing hormone-releasing hormone (cLHRH-I) was developed and characterized. This antibody was used for the development of a competitive microtiter plate enzyme-linked immunosorbent assay for avian LHRH. The assay was validated for use with tissue and was used at a working range between 5 pg and 10 ng per sample. Using this procedure, cLHRH-I and II were assayed in whole brain extracts of Japanese Quail embryos. Samples were taken at regular intervals between Day 6 of incubation through Day 1 posthatch. There were 10 samples taken at each age with 2 replicates of the entire sampling regime. Data from males and females were pooled. LHRH concentrations were low, then rose to higher levels (15 pg/mg tissue) between Days 10 through 13 and decreased thereafter. These changes are likely to be correlated with the activation of the hypothalamic-pituitary-gonadal axis. This is particularly apparent in later embryonic development.

Behavioral and hormonal correlates of social dominance in stable and disrupted groups of male domestic fowl

An experiment was conducted to determine the behavioral and hormonal correlates of social dominance in stable and disrupted groups of male domestic fowl (Gallus domesticus). In addition, the relative importance of visual and auditory cues in the maintenance of dominance status in this species was assessed. Alpha roosters were removed from their six-bird home pens for 1 week, and placed in either (1) and adjacent pen in visual contact with penmates, (2) and adjacent pen where visual, but not auditory, contact was prevented, or (3) a different building where they were in visual and auditory isolation. Dominance rank, aggressive activity, and crowing frequency were intercorrelated during the premove period. There was a significant increase in both aggression and crowing among the males remaining in the home pen following removal of the alpha male, except in the treatment in which males were still in visual contact with the removed alpha, in which only aggression increased. Increases in crowing frequency were also noted in alpha males. High levels of aggression occurred when alpha males were returned except in those pens in which visual contact had been maintained. Visual cues thus appear to be more important than auditory cues alone with respect to the maintenance of dominant social status in roosters. There were no clear correlations between behavioral variables and plasma androgen or corticosterone levels in either the stable or disrupted flocks, and no consistent changes in the levels of these hormones as a result of experimental manipulation; several possible explanations for this finding are discussed.

Sex steroid levels in developing and adult male and female zebra finches (Poephila guttata)

Serum samples from male and female zebra finches ranging in age from 1 day before hatch to 54 days posthatch were assayed for 17 beta-estradiol (E), androgen, testosterone (T), or 5 alpha-dihydrotestosterone (DHT). Additional samples were assayed from intact and gonadectomized adults, gonadectomized adults with intraperitoneal implants of testosterone propionate (TP) or estradiol benzoate (EB), gonadectomized nestlings, and nestlings injected subcutaneously with EB. DHT levels of developing birds did not vary as a function of either sex or age. During development, average androgen and T levels were highest during the nestling period, prior to sexual maturation, and were higher in females than in males. Endogenous androgen levels of most subjects that were sampled repeatedly rose and then declined between 24 and 49 days. TP implants produced higher T levels in adult females than in adult males. Levels of E were higher in both sexes during the hatching period (Days -1 through 0) than during the nestling period (Days 2 through 14). A greater number of males than females had relatively high E levels on Days 12 and 14 and during the second week overall. There was no sex difference in levels of E in adults, and gonadectomized adults had markedly higher E levels than intact adults. Gonadectomized nestlings had the same androgen and E levels as intact nestlings of the same age; EB injected nestlings had elevated E levels. The present results indicate specific endocrine changes that mirror events crucial to sexual differentiation of endocrine and behavioral components of reproduction, and have important implications for models of sexual differentiation in zebra finches.

Circulating estradiol and the activation of male and female copulatory behavior in Japanese quail (Coturnix japonica)

Previous experiments using systemic and preoptic area (POA) hormone treatments have shown that aromatization of testosterone (T) to estrogen (E) is essential for activation of male-typical copulatory behavior in castrated male Japanese quail (Coturnix japonica). Two experiments were conducted to determine whether circulating estrogen levels characteristic of normal intact males are high enough to activate male-typical or female-typical copulatory behavior. In Experiment 1, blood samples were drawn every 4 hr from groups of sexually active male quail housed under a 16L:8D light-dark cycle, and assayed for estradiol (E2) concentration. The mean +/- SEM serum E2 was 54.2 +/- 3.6 pg/ml, and no daily cycle in serum E2 was seen. The males were then tested for sexual behavior; 88% mounted females, and 23% crouched when mounted by males. In Experiment 2, 51 males were castrated and implanted with Silastic tubes containing estradiol benzoate (EB) and/or cholesterol designed to produce five different levels of serum E2, then tested for male- and female-typical copulatory behavior and bled. The serum E2 in EB-implanted quail which mounted (253 +/- 30 pg/ml) was significantly higher than that of intact quail in Experiment 1, and only 10.2% of intact males had serum E2 as high as the minimum associated with mounting in EB-implanted males. These results show that serum E2 levels in intact males are not high enough to support male-typical copulation, and that aromatization in the POA to produce locally high E2 levels may be required. In addition, it was found that the threshold serum E2 to elevate receptivity significantly was 3.6 times the intact male level, and only slightly higher than serum E2 reported for intact females. Thus the lack of receptivity in intact males is probably due to insufficient circulating E2, and the male is not defeminized with respect to sensitivity to E2 for activation of receptivity.

Sexual differentiation of neuroendocrine systems and behavior

Differentiation of the reproductive system occurs in stages, with early development of the gonads and later differentiation of the brain. The physiological mechanisms that are involved in the sequence of events during sexual differentiation have not been clearly understood. However, recent technological advances have made understanding these mechanisms much more accessible. Many of these techniques have been used to elucidate the nature of steroid-induced effects on target tissues, hormonal and neuroendocrine interactions, and the molecular basis of these processes. This review will focus on the sequence of events and mechanisms associated with sexual differentiation of endocrine, morphological, and behavioral components of reproduction in the chicken and Japanese quail.

Reproductive behaviour in poultry: implications for artificial insemination technology

1. Reproductive ability requires both endocrine and behavioural components. 2. Most reproductive behaviour is dependent upon the presence of sufficient circulating concentrations of the gonadal steroids, which in turn are synthesised and secreted in individuals who are in good reproductive condition. Mating behaviour patterns are thus not only essential for reproduction, but can provide excellent indices of the reproductive ability of an individual. 3. A number of factors can suppress or enhance reproductive behaviour in poultry, including management practices, flock social interactions, environmental variables, stressors, and disease. 4. Aspects of the regulation of reproductive behaviour and the endocrine control of reproductive processes in the male and in the female are reviewed in this paper. 5. An understanding of the impact of social and environmental stressors on reproductive physiology and behaviour is extremely important, both in order to improve breeding efficiency in natural mating systems and to facilitate the most effective application of artificial insemination technology.