Effects of photoperiod and temperature on testicular and thyroid activity of the Japanese quail

Effect of immunization against OPN5 on the reproductive performance in Shan Partridge ducks under different photoperiods

Photoperiod is an important environmental factor that influences seasonal reproduction behavior in birds. Birds translate photoperiodic information into neuroendocrine signals through deep brain photoreceptors (DBPs). OPN5 has been considered candidate DBPs involved in regulating seasonal reproduction in birds. We found that OPN5 could mediate light to regulate the follicle development in ducks. In this study, we further verified the effect of OPN5 on follicular development in Shan Partridge ducks by immunizing against the extracellular domain (ECD) of OPN5. We investigated the specific regulatory mechanism of photoperiod mediated by OPN5 on the reproductive activity of ducks. The trial randomly divided 120 Shan Partridge ducks into 3 groups with different treatments: the immunization of OPN5 group was done at d0, d15, d30, and d40 with 1 mL of vaccine containing OPN5 protein (thus containing 1, 1, 0.5, and 0.5 mg of OPN5-KLH protein), and the control group (CS and CL groups) was injected at the same time with the same dose of OPN5-uncontained blank vaccine. The group of CS (900 lux), OPN5 (600 lux), and CL (600 lux) lasted for 40 d in 12 L:12 D photoperiods, respectively. Then, the groups of CS, OPN5, and CL subsequently received 12 L:12 D, 12 L:12 D, and 17 L:7 D light treatments for 33 d, respectively. The ducks were caged in 3 constant rooms with the same feeding conditions for each group, free water, and limited feeding (150 g per duck each day). Duck serum and tissue samples were collected at d 40, d 62, and d 73 (n = 12). It was found that before prolonged light, the group of immunization (group OPN5) and the group of strong light intensity (group CS) were higher than the group of CL in egg production. Subsequent to prolonged light, the group CL in egg production rose about the same as the group immunization, while the strong light group (group CS) was lower. Group OPN5 increased the ovarian index of ducks, and both the immunization of group OPN5 and group CL (extended light) increased the thickness of the granular layer and promoted the secretion of E2, P4, LH, and PRL hormones. Compared with group CS, group CL and OPN5 increased the mRNA level and protein expression of OPN5 in the hypothalamus on d 62 and d 73 (P < 0.05). The gene or protein expression patterns of GnRH, TRH, TSHβ, DIO2, THRβ, VIP, and PRL were positively correlated with OPN5, whereas the gene expression patterns of GnIH and DIO3 were negatively correlated with OPN5. The results showed that immunization against OPN5 could activate the corresponding transmembrane receptors to promote the expression of OPN5, up-regulate the expression of TSHβ and DIO2, and then regulate the HPG axis-related genes to facilitate the follicular development of Shan Partridge ducks. In addition, in this experiment, prolonging the photoperiod or enhancing the light intensity could also enhance follicle development, but the effect was not as significant as immunizing against OPN5. Our results will offer beneficial data and more supportive shreds of evidence in favor of elucidating the role of OPN5 in relation to photoperiods and reproduction.

Influence of photoperiod and exogenous melatonin on testis morpho-physiology of sexually mature guinea fowl (Numida meleagris)

The biological effects of simulated photoperiod and melatonin on the control of reproduction of guinea fowls (Numida meleagris) are not well understood. Herein, thirty (30) sexually mature guinea fowl cocks were randomly assigned to 1-6 groups (n = 5) and subjected to different photoperiodic regimes in the presence or absence of exogenous melatonin (Mel; 1 mg/kgBW/day, i/m) for eight weeks. Testes of the euthanized cocks were processed for gross morphology, histological, histochemical, and oxidative stress markers. Testosterone concentration was determined in serum samples using the enzyme-linked immunosorbent assay (ELISA) technique. We observed an increase in testicular size in the Mel and Non-Mel groups under long-day (LD) photoperiods, and in the Non-Mel group under short-day (SD) photoperiod. Conversely, the testicular size was drastically reduced in the Mel group for SD. Seminiferous tubules in the Mel and Non-Mel groups of the SD showed cytomorphological changes, including degenerated cells, focal vacuolations, and depletion of germinal epithelium. However, the germinal epithelium appeared to be complete and active in both the Mel and Non-Mel groups for the LD. In all groups, the testes showed positive staining for PAS with varying intensities. There was a significant difference in PAS-staining intensity between different photoperiodic regimes and exogenous melatonin. The study observed the interaction between photoperiods and exogenous melatonin on glutathione reductase (GSH), malondialdehyde (MDA), and serum testosterone. Overall, the results indicated that a long-day (LD) photoperiod, combined with exogenous melatonin, enhanced reproductive activity in male guinea fowl by increasing testicular size and serum testosterone concentration.

OPN5 Regulating Mechanism of Follicle Development Through the TSH-DIO2/DIO3 Pathway in Mountain Ducks Under Different Photoperiods

Abstract: Photoperiod is an important environmental factor that influence seasonal reproduction behavior in bird. Birds translates photoperiodic information into neuroendocrine signals through deep brain photoreceptors (DBPs). OPN5 has been considered as candidate DBPs involving in regulation of seasonal reproduction in birds. However, little is known about the effect of OPN5 in non-seasonal breeding birds. Thus, we pondered on whether OPN5 regulating follicular development through TSH-DIO2/DIO3 system responds to different photoperiods in non-seasonal laying ducks. As an ideal non-seasonal breeding bird, a total of 120 mountain ducks were randomly divided into three groups and treated respectively to a different photoperiod: group S (8 L:16D), group C (17 L:7D), and group L (24 L:0D). The ducks were caged in a fully enclosed shelter with the same feeding conditions for each group, free water and limited feeding (150 g per duck each day). Samples were collected from each group at d 0, d 5, d 8, d 20, and d 35 (n = 8). The ducks in 24 h photoperiod had the highest laying rate and the lowest feed-to-egg ratio, while the ducks in 8 h photoperiod had the lowest laying rate and the highest feed-to-egg ratio. Long-day photoperiod for 24 h significantly increased the ovarian index and GnRH, LH, E2, and P4 levels in serum; short-day photoperiod for 8 h increased testosterone levels in serum. Compared with 8 h photoperiod, long-day photoperiod significantly or highly significantly increased the mRNA level and protein expression of OPN5 in the hypothalamus of long-day photoperiod on d 35 (p &lt; 0.05). The gene or protein expression patterns of GnRH, TRH, TSHβ, DIO2, THRβ, VIP, and PRL were positively correlated with OPN5, whereas the gene expression patterns of GnIH and DI O 3 were negatively correlated with OPN5. The results revealed that OPN5 mediated the effect of light on follicular development through the TSH-DIO2/DIO3 pathway, the expression of OPN5 increased with light duration and improved the efficiency of the HPG axis to promote follicular development in mountain ducks.

Photoperiodic Changes in Both Hypothalamus Neurotransmitters and Circulating Gonadal Steroids Metabolomic Profiles in Relation to Seasonal Reproduction in Male Quail

Both hypothalamic neurotransmitters and serum steroid hormones are impacted by photoperiod and have effects on physiology and seasonal reproductive. However, the relationship between circulating gonadal steroids and hypothalamic neurotransmitters underlying different photoperiod is still unclear. To further understand the crosstalk of neurotransmitters and steroids in seasonal reproduction, metabolic changes of 27 neurotransmitters concentrated in hypothalamus tissues and 42 steroids hormones in serum were assessed during two artificial photoperiodic programs. The results showed that photoperiod induce testicular atrophy and recrudescence. In L-to-S groups, significantly decreased levels of testosterone concentration were found in serum (P < 0.001) and increased 11-Dehydrocorticosterone (P < 0.05); Testosterone were almost undetectable at SD_14d. In addition, the hypothalamus exhibited significantly increased arginine and 4-aminobutyric acid (GABA) concentration and decreased serotonin and epinephrine content (P < 0.01 or P < 0.05). Accordingly, serum testosterone and androstenedione became detectable at LD_3d in the S-to-L group and were markedly increase at LD_7d. Furthermore, Serum androstenedione showed a significant increase with long light expose (P < 0.01). Additionally, the hypothalamus exhibited both significantly increased L.Tryptophan and phenylalanine concentration, as well as decreased L-glutamine and L-glutamine.acid content (P < 0.01 or P < 0.05). Serotonin metabolism showed significant differences between L-to-S group and S-to-L group. Furthermore, in the correlation analysis, serum testosterone had a positive correlation with 5-Hydroxyindole-3-acetic acid (5-HIAA), while Androstenedione was significantly negative with L.Tryptophan in L-to-S (P < 0.05). However, in S-to-L group, serum testosterone showed strong negative correlation with both serotonin and 5-HIAA (P < 0.05), but positive correlation with L.Tryptophan (P < 0.01), while Androstenedione was significantly negative correlation with both serotonin (P < 0.05) and L-Glutamine (P < 0.01). Photoperiod also had significant effects on the mRNA expression. We found significant differences in gene expression patterns of both serotonin signaling and steroid biosynthesis, while MAOB, NR5A1, and 3β-HSD showed an opposite tendency between two groups. Taken together, our results revealed that circulating gonadal steroids and hypothalamic neurotransmitters were significantly impact quail’s seasonal reproduction. Circulating gonadal steroids have different effects on neurotransmitter at different photoperiodism, which may coordinately influence the seasonal reproduction of quails.

Photoperiodic Regulation of Reproduction in Vertebrates

Organisms use changes in photoperiod for seasonal reproduction to maximize the survival of their offspring. Birds have sophisticated seasonal mechanisms and are therefore excellent models for studying these phenomena. Birds perceive light via deep-brain photoreceptors and long day–induced thyroid-stimulating hormone (TSH, thyrotropin) in the pars tuberalis of the pituitary gland (PT), which cause local thyroid hormone activation within the mediobasal hypothalamus. The local bioactive thyroid hormone controls seasonal gonadotropin-releasing hormone secretion and subsequent gonadotropin secretion. In mammals, the eyes are believed to be the only photoreceptor organ, and nocturnal melatonin secretion triggers an endocrine signal that communicates information about the photoperiod to the PT to regulate TSH. In contrast, in Salmonidae fish the input pathway to the neuroendocrine output pathway appears to be localized in the saccus vasculosus. Thus, comparative analysis is an effective way to uncover the universality and diversity of fundamental traits in various organisms.

Seasonal Rhythms: The Role of Thyrotropin and Thyroid Hormones

BACKGROUND

Seasonal changes in various physiological events have been reported in humans, including metabolism, immune function, and mood. However, the molecular and endocrine basis of these seasonal changes remains unclear.

SUMMARY

Animals that breed seasonally, such as Japanese quail and the Siberian hamster, have sophisticated seasonal mechanisms, and hence they provide excellent opportunities to understand the underlying processes. Functional genomic analysis in quail uncovered the photoperiodic signal transduction pathway, which regulates avian seasonal reproduction: a long-day stimulus induces secretion of thyrotropin (TSH) from the pars tuberalis (PT) of the anterior pituitary gland. This PT-derived TSH locally activates thyroid hormone within the hypothalamus, which in turn induces gonadotropin-releasing hormone and then gonadotropin secretion, leading to gonadal growth.

CONCLUSIONS

Studies using TSH receptor-null mice confirmed the involvement of PT-derived TSH in mammalian seasonal reproduction. The pars distalis of the anterior pituitary gland is the major source of circulating TSH. Although the pars distalis and PT are in close proximity, tissue-specific glycosylation of circulating TSH alters its function to avoid cross talk.

Molecular and Neuroendocrine Mechanisms of Avian Seasonal Reproduction

Animals living outside tropical zones experience seasonal changes in the environment and accordingly, adapt their physiology and behavior in reproduction, molting, and migration. Subtropical birds are excellent models for the study of seasonal reproduction because of their rapid and dramatic response to changes in photoperiod. For example, testicular weight typically changes by more than a 100-fold. In birds, the eyes are not necessary for seasonal reproduction, and light is instead perceived by deep brain photoreceptors. Functional genomic analysis has revealed that long day (LD)-induced thyrotropin from the pars tuberalis of the pituitary gland causes local thyroid hormone (TH) activation within the mediobasal hypothalamus. This local bioactive TH, triiodothyronine (T₃), appears to regulate seasonal gonadotropin-releasing hormone (GnRH) secretion through morphological changes in neuro-glial interactions. GnRH, in turn, stimulates gonadotropin secretion and hence, gonadal development under LD conditions. In marked contrast, low temperatures accelerate short day (SD)-induced testicular regression in winter. Interestingly, low temperatures increase circulating levels of T₃ to support adaptive thermogenesis, but this induction of T₃ also triggers the apoptosis of germ cells by activating genes involved in metamorphosis. This apparent contradiction in the role of TH has recently been clarified. Central activation of TH during spring results in testicular growth, while peripheral activation of TH during winter regulates adaptive thermogenesis and testicular regression.

Comparative analysis reveals the underlying mechanism of vertebrate seasonal reproduction

Animals utilize photoperiodic changes as a calendar to regulate seasonal reproduction. Birds have highly sophisticated photoperiodic mechanisms and functional genomics analysis in quail uncovered the signal transduction pathway regulating avian seasonal reproduction. Birds detect light with deep brain photoreceptors. Long day (LD) stimulus induces secretion of thyroid-stimulating hormone (TSH) from the pars tuberalis (PT) of the pituitary gland. PT-derived TSH locally activates thyroid hormone (TH) in the hypothalamus, which induces gonadotropin-releasing hormone (GnRH) and hence gonadotropin secretion. However, during winter, low temperatures increase serum TH for adaptive thermogenesis, which accelerates germ cell apoptosis by activating the genes involved in metamorphosis. Therefore, TH has a dual role in the regulation of seasonal reproduction. Studies using TSH receptor knockout mice confirmed the involvement of PT-derived TSH in mammalian seasonal reproduction. In addition, studies in mice revealed that the tissue-specific glycosylation of TSH diversifies its function in the circulation to avoid crosstalk. In contrast to birds and mammals, one of the molecular machineries necessary for the seasonal reproduction of fish are localized in the saccus vasculosus from the photoreceptor to the neuroendocrine output. Thus, comparative analysis is a powerful tool to uncover the universality and diversity of fundamental properties in various organisms.

Low temperature-induced circulating triiodothyronine accelerates seasonal testicular regression

In temperate zones, animals restrict breeding to specific seasons to maximize the survival of their offspring. Birds have evolved highly sophisticated mechanisms of seasonal regulation, and their testicular mass can change 100-fold within a few weeks. Recent studies on Japanese quail revealed that seasonal gonadal development is regulated by central thyroid hormone activation within the hypothalamus, depending on the photoperiodic changes. By contrast, the mechanisms underlying seasonal testicular regression remain unclear. Here we show the effects of short day and low temperature on testicular regression in quail. Low temperature stimulus accelerated short day-induced testicular regression by shutting down the hypothalamus-pituitary-gonadal axis and inducing meiotic arrest and germ cell apoptosis. Induction of T3 coincided with the climax of testicular regression. Temporal gene expression analysis over the course of apoptosis revealed the suppression of LH response genes and activation of T3 response genes involved in amphibian metamorphosis within the testis. Daily ip administration of T3 mimicked the effects of low temperature stimulus on germ cell apoptosis and testicular mass. Although type 2 deiodinase, a thyroid hormone-activating enzyme, in the brown adipose tissue generates circulating T3 under low-temperature conditions in mammals, there is no distinct brown adipose tissue in birds. In birds, type 2 deiodinase is induced by low temperature exclusively in the liver, which appears to be caused by increased food consumption. We conclude that birds use low temperature-induced circulating T3 not only for adaptive thermoregulation but also to trigger apoptosis to accelerate seasonal testicular regression.

Seasonal variations of steroid hormones and triiodothyronine concentrations in migratory northern shovelers

Endogenous serum testosterone, estradiol, and triiodothyronine concentrations were measured in the northern shoveler (Anas clypeata, n = 20) during different stages of migratory condition at their wintering grounds to look at how these hormones may be linked to the development of migratory condition. These hormones were assayed by enzyme-linked immunosorbent assay (ELISA). The changes in hormones concentrations were parallel to each other and correspond to the increasing day lengths of spring. Furthermore, the northern shovelers showed a distinct seasonal cycle in serum concentrations of triiodothyronine, estradiol, and testosterone. It is suggested that these seasonal cycles in the northern shovelers are endogenously programmed and their entrainment to the environmental photoperiod ensures the occurrence of different physiological functions at temporally fixed time of the year. The results of this study offer a captive model of the seasonal changes in physiology and behavior that occur in the months preceding and including vernal migration of the northern shovelers.

Seasonal changes in the behavior and plasma titers of various hormones in barheaded geese, Anser indicus

A number of behavioral and physiological parameters including the circulating levels of 7 hormones were investigated in a free ranging population of barheaded geese in Seewiesen, W. Germany. Behavioral data were collected on the entire flock from which seasonal changes in the frequencies were determined. In addition, data on the behavior of individuals were obtained to aid in the comparison of seasonal changes in behavior and hormones. The resulting curves were used to examine whether the annual changes in the frequencies of various behaviors were related to changes in circulating hormonal concentrations. Lastly, the physiological data were discussed with regard to reproductive biology in birds.

The behavior of the Japanese or domestic quail Coturnix japonica

This paper reviews the literature pertaining to the behavior of the Japanese or domestic quail Coturnix japonica. Details are given of the classification, characteristics, domestication and the economic and research potential of the species. Further sections deal with sensation and perception (including taste and smell, vision and hearing), maintenance behavior (including feeding and drinking, dust bathing and thermoregulation), development and aging (including vocalization, filial imprinting, sexual imprinting, fear and avoidance responses, sexual maturation and aging), adult learning (including habituation, instrumental conditioning, Pavlovian conditioning and observational learning), photoperiodism, reproductive behavior (including courtship and mating, hormonal control and ontogeny of sexual differentiation, and male and female sexual behavior), parental behavior (including nest-site selection and nest building, incubation behavior and its hormonal control, and hen-chick relationships), and aggressive behavior and dominance (including agonistic behavior and the hormonal control of aggressive behavior).

Seasonal temperature and its influence on plasma corticosterone, triiodothyronine, thyroxine, plasma protein and packed cell volume in mature male chickens

1. The relationship between seasonal changes in environmental temperature and hematological parameters was investigated in mature, single comb white leghorn (SCWL) male chickens. 2. Samples of blood plasma, obtained monthly from two groups of birds over two separate 12 month periods, were analysed for corticosterone (CT), 3,5,3'-triiodothyronine (T3), thyroxine (T4), plasma protein (PP), and packed cell volume (PCV). 3. Statistical analyses revealed that blood plasma concentrations of T3 were significantly correlated negatively with monthly dry-bulb temperatures. 4. There were no consistent or significant relationships between monthly dry-bulb temperature and CT, T4, PP or PCV over the two 12 month periods. 5. The results of this study indicate that blood plasma concentrations of T3 are influenced by season of year in mature, male domestic fowl.

Termination of LH secretion in Japanese quail due to high- and low-temperature cycles and short daily photoperiods

Mature male Japanese quail were transferred from 16L:8D (19 degrees) to one of the following combinations of daily light-dark and temperature cycles, 8L:16D (12 hr, 19 degrees:12 hr, 9 degrees), 12L:12D (12 hr, 19 degrees:12 hr, 9 degrees) and 12L:12D (16 hr, 19 degrees:8 hr, 9 degrees). The low temperature is for the middle of the dark period in each treatment. In the control groups, birds were transferred to the same photoperiodic conditions as the experimental groups, but without changes in ambient temperature. Blood samples were collected every other day for 30 days and circulating levels of plasma LH were estimated by radioimmunoassay. Both the change in conditions from 16L:8D to 8L:16D with the temperature lowered for 12 hr and that from 16L:8D to 12L:12D with temperatures lowered in one case for 12 hr and in the other for 8 hr caused a lowering in plasma LH levels in all the birds to reproductively quiescent levels. The cloacal protrusion of all these birds regressed completely. In control groups, however, most if not all the birds remained in active breeding states although the levels of circulating LH decreased to basal breeding levels of 1-2 ng/ml. The results indicated that in addition to a change from long to short days an alternation of high and low temperatures was sufficient supplementary information in causing termination of LH secretion and inducing regression of the gonads and the accessory sex organs in this species.

Temperature modulation of photoperiodically induced LH secretion and its termination in Japanese quail (Coturnix coturnix japonica)

Long days induced LH release in photosensitive Japanese quail and ambient temperature did not affect this process. Temperature also did not affect the levels of circulating LH concentrations at the steady state of LH release on long days. On the other hand, low ambient temperature was required to reduce circulating LH to a nonbreeding level together with the change of the photoperiod from long to short days; the changes of the photoperiod without low ambient temperature induced a decrease of circulating LH only to a certain level (1-2 ng/ml) which could maintain reproductive activity. The results also indicated that there were three levels of circulating LH in quail which were tentatively designated as a nonbreeding level (less than 0.5 ng/ml), a basal breeding level (1-2 ng/ml), and a steady breeding level (ca. 4 ng/ml). By photostimulation, levels of circulating LH increased to the steady breeding level directly and gradually, or leveled off after overshooting it. Photoperiodic changes from long to short days under moderate temperature resulted in a decrease in circulating LH to the basal breeding level which, however, could keep the gonad and the accessory sex organs active. Photoperiodic changes under cold ambient temperature reduce circulating LH to the nonbreeding level at which the gonad and the accessory sex organs regressed completely. These results suggest that ambient temperature is involved in the mechanism controlling an annual reproductive cycle, especially at the termination of the reproductive activity, in Japanese quail.

Roles of age, body weight and composition in the initiation of sexual maturation of Japanese quail (Coturnix coturnix japonica)

1. The roles of chronological age, body weight and body composition in the initiation of sexual maturation of Japanese quail (Coturnix coturnix japonica) were investigated by imposing an inhibitory photoperiod (IP), and by the intramuscular injection of turkey growth hormone (GH) or antisera to turkey growth hormone (AGH). 2. Absence of sexual maturity in the IP treatment was accompanied by reduced testis and ovary-oviduct weights, and an increased breast muscle weight expressed as a proportion of body weight. 3. Antisera to turkey growth hormone (AGH) did not completely inhibit the metabolic activities of endogenous GH. 4. The roles of chronological age, body weight and body composition in the initiation of sexual maturity were inseparable.

Response surface of daily thyroid hormone rhythms in young chickens exposed to constant ambient temperature

Response surface models were developed by multiple regression techniques to describe daily rhythms of plasma thyroid hormones in young chickens during acclimation to a wide range of ambient temperatures (Ta). Seventy-two Leghorn cockerels were raised in six environmental chambers under a 12L:12D light/dark cycle. Beginning at 21 days of age, two replicate chambers provided Ta treatments of 10, 24, or 38 degrees. During Day 6 of acclimation, blood samples were obtained at 0800, 1200, 1600, 2000, 2400, and 0400 hr for thyroid hormone analyses. Plasma triiodothyronine (T3) levels showed a convex response to the experimental region (10 to 38 degrees, and 0800 to 0400 hr under a 12L:12D light/dark cycle), whereas the plasma thyroxine (T4) response surface was concave. In particular, heat exposure (38 degrees) depressed (P less than .01) plasma T3 levels (2.8 ng/ml) below those of birds held at 24 degrees (4.5 ng/ml), whereas elevated (p less than 0.05) T3 concentrations were found in the 10 degrees treatment (5.0 ng/ml). Plasma T3 levels rose gradually during photophase and slowly declined during scotophase. Plasma T4 concentrations followed an opposite pattern with the daily zenith in scotophase and the nadir during photophase. Plasma T4 levels were sharply elevated in birds maintained at 38 degrees, particularly during scotophase. Although Ta did not change the daily amplitude or circadian frequency of the plasma T3 rhythm, an increased frequency or ultradian rhythm of plasma T4 was observed in cold-acclimated birds. The counter-responses of T3 and T4 to heat exposure and phase of the light/dark cycle were best seen in the molar ratio of plasma T3/T4 levels. The average daily T3/T4 molar ratio for heat-exposed birds was 0.16 while the average T3/T4 ratio was higher (P less than 0.01) for the 10 degrees (0.46) and 24 degrees (0.41) treatments. The opposing responses of plasma T3 and T4 levels to a wide range of Ta and phase of the light/dark cycle support a major role for circulating T3 in metabolic adjustments that chickens make to changes in the photothermal environment.

Influence of 12 hours of sound stimuli on gonad development and plasma luteinizing hormone in Japanese quail (Coturnix coturnix japonica) exposed to 6 hours of daily light

Two experiments were conducted to determine the effects of sound stimulation on gonadal growth in male and female Japanese quail (Coturnix coturnix japonica) maintained under a photoperiod of 6 hr light and 18 hr dark (6L:18D) from 1 to 12 weeks of age (Experiment 1) or 1 to 14 weeks of age (Experiment 2). The quail were split into three sound environments as follows: 1) 12 hr of radio music (RS) beginning 1 hr before lights off; 2) 12 hr of vocalization from a breeding colony of quail (QV) beginning 1 hr before lights off; 3) no sound stimulation (NS). In Experiment 1, birds were killed at 8, 10, and 12 weeks of age and in Experiment 2, they were killed at 8, 10, 12, and 14 weeks of age. There were no significant differences in tests weights of the three groups at 8 and 10 wk of age (Experiment 1), but those of the RS and QV groups were larger (P less than or equal to .05) than those of the NS group at 12 weeks. Tests in the NS group appeared to grow between 8 and 10 weeks, then regress. There were no differences in testis weights at 8 and 10 weeks of age in Experiment 2. At 12 weeks, testes in the RS group were larger (P less than or equal to .05) than those of the other two groups and by 14 weeks testes of both sound stimulated groups were larger than the NS group and were also different from each other.(ABSTRACT TRUNCATED AT 250 WORDS)

Light-induced avian glaucoma as an animal model for human primary glaucoma

Glaucoma can be induced in domestic chicks at the will of the investigator, by the simple device of rearing the chicks under continuous light. This light-induced avian glaucoma (LIAG) is presented as an animal model system for human open-angle glaucoma. A number of morphological and physiological findings in LIAG are reviewed, and the LIAG system is compared with several other glaucoma model systems, in dogs, rabbits and monkeys. Intraocular pressure in LIAG has been demonstrated to be responsive to several anti-glaucoma drugs, and the system could be used for further drug testing. Thus it is suggested that LIAG may be especially useful in studies seeking to understand human glaucoma, and how to forestall it, or treat it. As well, a prolonged "pre-glaucoma" period is available to the investigator working with LIAG, during which a pathological course is already underway in the eye, but intraocular pressure has not yet gone up.

Seasonal changes in some plasma hormones in pigeons: diurnal variation under natural photoperiods with constant or seasonally changing ambient temperature

The diurnal variations of several plasma hormones and free fatty acids (FFA) were studied during periods in summer and winter for pigeons reared either outdoors or indoors. The latter were subjected to constant temperature and naturally varying photoperiods. A significant seasonal variation in the mean daily levels of triiodothyronine (T3), thyroxine (T4), corticosterone (B), lutropin (LH) and FFA was seen in the outdoor birds and in the T4 and B levels of indoor birds. The diurnal variation of hormone levels was generally more pronounced in winter in both groups. Cold ambient temperature significantly decreased the plasma LH level and potentiated the increasing effect of short photoperiod on plasma B level. Diurnal variation of plasma FFA level seems to be under the control of photoperiod, without any effects due to the ambient temperature. No significant correlation was found between FFA and GH concentrations.

Effect of cyclic sound cues on sexual development in nonphotostimulated Japanese quail

The influence of cyclic ambient sound stimuli on sexual development was studied in nonphotostimulated [6 hr light:18 hr dark (16L:18D)] Japanese quail (Coturnix coturnix japonica). The incidence of accelerated gonadal development was reduced when ambient daily sound stimuli were attenuated by the presence of a white noise mask in the animal quarters. In a second experiment nonphotostimulated (9L:15D) male quail showed a phase-dependent testicular response to a daily 3-hr radio broadcast presented at different portions of the day. The radio sound stimulus induced a higher incidence of accelerated gonadal development when presented 6 hr prior to the photophase than when presented either 3 hr prior to the photophase or when presented coincidently with the photophase onset. In a third experiment locomotion was monitored in nonphotostimulated quail (9L:15D) with a 3-hr radio sound stimulus presented 6 hr prior to photophase onset. The onset of a daily locomotor activity pattern was associated with radio sound in some individuals, but sound-induced locomotion was not consistently associated with sound-induced accelerated gonadal development.

Variations in the photoperiodic cloacal response of Japanese quail: association with testes weight and feather color

The size of the cloacal gland was found to be a reliable indicator of testicular activity of Japanese quail. Six experiments were performed to examine the effects of alternating long and short photoperiod on the size of the cloacal gland of male Japanese quail. Three types of photoperiodic cloacal responses were distinguished. Type I birds became refractory to short photoperiods after they had experienced 5 weeks or more of short days. They maintained large cloacal glands under subsequent condition of alternating long and short photoperiod. Type II birds were intermediate types I and III birds did not become refractory to short photoperiods after experiencing 5 weeks or more of short days. The cloacal glands responded to conditions of alternating long and short photoperiods with increases or decreases in size. Feather color on the throat was found to correspond to the type of cloacal response. Type I birds had brick-red throat feathers. Type II birds had white feathers intermingled with brick-red feathers. Type III had white throat feathers. The percentages of types I, II, and III observed in the experimental population was 67, 18, and 15%, respectively. Type III birds were used to study the effects of blinding on the cloacal response to short photoperiod. Five out of eight blinded type III birds did not lose the responsiveness to short photoperiod. These results are consistent with the view that extraocular photoreceptors participate in the photoperiodic gonadal response of Japanese quail.

Comparison of plasma thyroxine levels following short exposure to cold and TRH administration in intact and pituitary autografted quail (Coturnix coturnix japonica)

The thyrotropic functional abilities of ectopically transplanted anterior pituitaries were tested by subjecting quail bearing their adenohypophysis in juxtarenal position either to a short cold exposure or to an intravenous injection of TRH. Thyroxine was determined in plasma samples collected from 20 to 120 min after treatment. Intact birds exhibited increasing T4 levels up to a peak at 40 min, then decreasing slowly within 2 hr after either cold or TRH stimulation. Autografted birds exhibited significant although lower and delayed increase of plasma thyroxine following both stimuli.