The aim of the present study was to examine the effect of testosterone (T) and estradiol-17β (E₂), known as being produced in the theca cells, on the production of progesterone (P₄) by granulosa cells of the hen. When granulosa cells isolated from the largest preovulatory follicle (F₁) were incubated for 4 hr with increasing doses of ovine luteinizing hormone (oLH), T or E₂, P₄ production by granulosa cells was increased in a dose-dependent manner by oLH, but not by T or E₂. However, when F₁ granulosa cells cultured for 48 hr in a monolayer culture system were cultured for an additional 48 hr with increasing doses of oLH, T or E₂, not only oLH but also T stimulated P₄ production of granulosa cells in a dose-related manner while E₂ alone had no effect on P₄ production. In addition, when the time course of P₄ production by F₁ granulosa cells in response to oLH and T was examined for 48 hr during 48 to 96 hr of culture, P₄ production with oLH was found to be increased at 4 hr of culture, with the maximal level at 6 hr, while P₄ production with T increased significantly from 12 hr of culture, with the maximal response at 36 hr. Furthermore, when F₁ granulosa cells were precultured with E₂ for various times before 4 hr culture with oLH at 96 hr of culture, the increase in P₄ production in response to oLH was only found at a pretreatment time of more than 12 hr.
These results indicate that, in granulosa cells of the hen, T may have a direct stimulatory action over the long term on P₄ production, and E₂ in long-term action may enhance the sensitivity to LH for P4 production.

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This study was conducted to investigate the effects of non-steroidal aromatase inhibitor (AI, Fadrozole, Ciba-Geigy) on gonadal differentiation in the chicken. Fertilized eggs of single comb White Leghorn hens were injected with AI on day 5 of incubation. AI-treated eggs were incubated, hatched, and raised until 10 months of age. The genetic sex of the adult chickens was evaluated by Southern hybridization analysis of red blood cell lysate using ³²P-dCTP-labelled W-specific DNA probe. Groups were (1) hens without a sex-reversal effect, (2) sex-reversed hens, genetic females but phenotypic males, and (3) normal genetic males displaying no obvious changes in secondary sex characteristics. Hens without a sex reversal effect had normal ovarian follicles and a well-developed oviduct on the left side. Genetic males without sex-reversal effect had a pair of normal testes containing seminiferous tubules and interstitial cells. Numerous sperm were present in the seminiferous tubules. Sex-reversed females had retarded gonads on both sides. These gonads contained essentially the same cellular components as those of normal testes, however, the inside diameter of the seminiferous tubules was extremely small. Sex-reversed females had the secondary sex characteristics of the male and displayed mating behavior of normal cocks but had a developed oviduct as well. Plasma concentrations of testosterone and estradiol of the sex-reversed females showed intermediate levels between those of genetic and phenotypic females and males. The gonadal mRNA levels of P45017α-hydroxylase were higher in the genetic males than in phenotypic females and sex-reversed females. On the other hand, mRNA levels of P 450_aromatase were higher in the phenotypic females than the sex-reversed females and genetic males. These studies indicate that AI may cause reduction of mRNA expression of P450_aromatase and plasma levels of estradiol of sex-reversed females which are indirectly correlated with retarded development of the gonads.

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Plasma concentrations of arginine vasotocin (AVT), pituitary prolactin messenger RNA (PRL mRNA) and weights of ovary and oviduct were measured at different reproductive stages in the Chabo hens. Concentrations of plasma AVT dropped significantly at the laying stage but increased at 1-week of incubation stage and was sustained during the whole incubation period. The concentration decreased markedly at the brooding stage of rearing chicks. At the laying stage weights of ovary and oviduct were the highest while it remained at other stages. Pituitary PRL mRNA expression was high during the incubation period as previously observed in the Chabo hens. The present results may indicate the sustained level of plasma AVT is involved, at least in part, in the regulation of body water balance.

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Using ³H-melatonin, radioligand binding assays were performed on membrane fractions of the hypothalamic tissues involving preoptic area and median eminence area of laying and non-laying hens. The binding was found to be specific for melatonin. By Scatchard analysis of saturation data, the value of the equilibrium dissociation constant obtained was of the order of nM, and the maximum binding capacity was of the order of fmol per mg protein. Both values changed during an ovulatory cycle or during a 24-h day with a different pattern between the two areas and between the laying and non-laying hens. The results suggest that there exists melatonin receptor in both preoptic and median eminence areas of the hypothalamus of the hen, and that the aspect of action of melatonin through binding to its receptor may be different between the two areas of the hypothalamus and between laying and non-laying hen.

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Restriction endonuclease cleavage patterns of mitochondrial DNAs (mtDNAs) from four species of jungle fowl were examined. The sequence divergence between the various mtDNA haplotypes was estimated from the numbers of common and different restriction fragments. The sequence divergence between Gallus gallus and respectively, G. sonnerati, G. varius, and G. lafayettei was 0.9%, 10.5%, and 12.6%. Assuming that the rate of evolution of mtDNA is 3% per million years (Myr), we estimated that the divergence of mtDNA of G. gallus from that of G. sonnerati, G. varius, and G. lafayettei occurred 0.3 Myr, 3.5 Myr, and 4.5 Myr ago, respectively. These maternal phylogenetic relationships are in good agreement with those inferred from allozyme data and reported in the literature.

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In order to investigate the direct effects of thyroid hormones on steroidogenesis in avian ovary, quail granulosa cells were isolated from the three largest follicles and cultured with follicle stimulating hormone (FSH) at 41° Cin 5% CO₂ and 95% air. After 72 hr of culture, the cells were incubated with luteinizing hormone (LH) for 3 hr and the progesterone contents in the media were measured by radioimmunoassay. Addition of thyroid stimulating hormone (TSH), thyroxine (T₄), or triiodothyronine (T₃) during 72 hr of culture with FSH or during 3 hr of incubation with LH showed no significant effects on progesterone production. These results suggested that TSH, T₄, and T₃ might not affect the steroidogenesis of quail granulosa cells.

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This study was conducted to investigate the rate of raising, viability and growth rate of the Gifu Native Fowl. Results obtained are as follows.
(1) Rate of raising and viability
The average rate of raising during 20 weeks of age and viability after 20 weeks of age for male and female birds were approximately 92% and 90%, and 74% and 72%, respectively.
The viability of males hatched on February was higher than that of the birds hatched on March, May, June, September and December. On the other hand, females hatched on July were higher than that of birds hatched on January, April and August.
(2) Growth rate
Body weight of males or females is increased gradually till about 28 or 24 weeks of age. The mean values of body weight for males at 28 and 55 weeks of age were nearly 1, 140 and 1, 297 g, and 873 and 920 g for females at 24 and 55 weeks of age. No appreciable change was observed in the body weight after 55 weeks of age. However, summer season caused a slight decrease in the body weight for both sexes.

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This study was conducted to investigate the egg laying performance of the Gifu Native Fowl. Results obtained are as follows.
(1) Age at first egg production
The age at first laying for the females was about 174 days on an average, and 152 days for the birds hatched on December and 195 days for those hatched on June.
The Age at first egg was shown to be dependent upon the day length in their hatching periods. The difference in the day between the earliest and the latest layers was about 43 days.
(2) Body weight at first egg
The body weight at first laying was not related to their ages, showing that the body weight at first egg was approximately 927 g on an average.
(3) Egg weight at first egg
The egg weight at first laying was strictly related to the age, indicating that the average egg weight at first laying for the females hatched on July was approximately29 g, and 24 g for the those hatched on December.
(4) Number of eggs laid and pattern of egg production
The number of eggs laid was relatively associated with the age at first laying. The peak of egg production was observed on about 30 weeks of age.
A slight increase in egg production was found from late Winter to early Summer, showing that the females hatched on September, to February had the second peak in egg production until 79 weeks of age.
(5) Egg weight
The average egg weight at 30, 50 and 79 weeks of age were 32 g, 38 g and 39 g, respectively, showing 35 g on an average. The total egg weight was conversely related to the number of eggs laid.

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