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.

Oral progestin induces rapid, reversible suppression of ovarian activity in the cat.

The influence of oral progestin (altrenogest; ALT) on cat ovarian activity was studied using non-invasive fecal steroid monitoring. Queens were assigned to various ALT dosages: (1) 0mg/kg (control; n=5 cats); (2) 0.044 mg/kg (LOW; n=5); (3) 0.088 mg/kg (MID; n=6); or (4) 0.352 mg/kg (HIGH; n=6). Fecal estrogen and progestagen concentrations were quantified using enzyme immunoassays for 60 days before, 38 days during and 60 days after ALT treatment. Initiation of follicular activity was suppressed in all cats during progestin treatment, whereas controls continued to cycle normally. Females (n=6) with elevated fecal estrogens at treatment onset completed a normal follicular phase before returning to baseline and remained suppressed until treatment withdrawal. All cats receiving oral progestin re-initiated follicular activity after treatment, although MID cats experienced the most synchronized return (within 10-16 days). Mean baseline fecal estrogens and progestagens were higher (P<0.05) after treatment in HIGH, but not in LOW or MID cats compared to pre-treatment values. The results demonstrate that: (1) oral progestin rapidly suppresses initiation of follicular activity in the cat, but does not influence a follicular phase that exists before treatment initiation; and (2) queens return to normal follicular activity after progestin withdrawal. This study provides foundational information for research aimed at using progestin priming to improve ovarian response in felids scheduled for ovulation induction and assisted breeding.

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.

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.

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.

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.

5 Beta-reductase activity in the brain and cloacal gland of male and female embryos in the Japanese quail (Coturnix coturnix japonica).

Testosterone metabolism was studied by an in-vitro technique in the brain and cloacal gland of young male and female quail at different ages ranging from 7 days of incubation to 2 days after hatching. Very active metabolism, leading almost exclusively to the production of 5 beta-reduced compounds, was observed. 5 beta-Reductase activity remained high throughout the incubation period in the hypothalamus, decreased around the time of hatching in the cerebellum and decreased progressively between days 7 and 15 of incubation in the cloacal gland. These changes could be involved in the control of sexual differentiation: the high 5 beta-reductase in the brain possibly protects males from being behaviourally demasculinized by their endogenous testosterone while the decreasing 5 beta-reductase in the cloacal gland would progressively permit the masculinization of that structure.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Sertoli cell tumors in Japanese quail.

Testicles were collected from 33 male Japanese quails older than 3 years. Three of these quails (9.1%) had one or two large neoplastic testicles. These testicles were 2-5 times normal size, round, and firm, with cystic spaces of various sizes. Microscopically, there was marked intratubular Sertoli cell proliferation and various-sized cystic spaces filled with an eosinophilic vacuolated fluid. Microscopic changes in all neoplastic testicles were diagnostic for Sertoli cell tumors.

Effect of coccidiosis on reproductive maturation of male Japanese quail.

The effects of coccidiosis on reproductive development of male Japanese quail were examined. Male Japanese quail were exposed to high (5 x 10(5) sporulated oocysts/quail) or low (5 x 10(3) sporulated oocysts/quail) doses of Eimeria uzura at 16 or 30 days of age and sampled at 37 days. Quail given high doses of coccidia had reduced testes weight and lowered circulating concentrations of androgen compared with control males. Low doses of coccidia did not affect testes weight but did result in elevated plasma androgen levels. There were no differences in average testes weights by 51 days; however, plasma androgen was still reduced in most groups. To study the effects of coccidiosis on egg production, males exposed to high doses of coccidia at 16 (16H) or 30 (30H) days of age were mated with control females, and control males were mated with control or 16H females. The onset of laying was delayed for 5 days in the control male: 16H female group. During the first week of production, eggs from females bred to 30H males had lower fertility and hatchability than those bred to control or 16H males. By the third week of production, levels of fertility were similar. Apparently, exposure of quails to coccidiosis before sexual maturation might result in long-term effects on later reproductive capability.