Members of opposite sex mutually regulate gonadal recrudescence in the lizard Calotes versicolor Agamidae).

Adult males and females of the seasonally breeding lizard Calotes versicolor were subjected to various social situations under semi-natural conditions to explain the role of socio-sexual factors in gonadal recrudescence. They were grouped as: (i) males and females, (ii) males and females separated by a wire mesh, (iii) same sex groups of males or females, (iv) castrated males with intact females and (v) ovariectomized (OvX) females with intact males from postbreeding to breeding phase. Specimens collected from the wild during breeding season served as the control group. Plasma sex steroid levels (testosterone in male and 17b-estradiol in female), spermatogenetic activity and vitellogenesis were the criteria to judge gonadal recrudescence. In intact males and females that were kept together, gonadal recrudescence and plasma sex steroids levels were comparable to those in wild-caught individuals. Gonadal recrudescence was at its least in all male and all female groups, and plasma sex steroids were at basal levels. Association with OvX females initiated testicular recrudescence but spermatogenetic activity progressed only up to the spermatid stage while males separated from females by wire mesh showed spermatogenetic activity for a shorter period. Females grouped with castrated males and those separated from males by wire mesh produced vitellogenic follicles. However, the total number and diameter of vitellogenic follicles, and plasma estradiol levels were lower than in the females grouped with intact males. The findings indicate that association with members of the opposite sex with progressively rising titers of sex steroids is crucial in both initiating and sustaining gonadal recrudescence in the lizard. Thus, members of the opposite sex mutually regulate gonadal recrudescence in the C. versicolor.

Pattern of plasma sex steroid hormone levels during reproductive cycles of male and female tropical lizard, Calotes versicolor.

Annual changes in gonadal activity and plasma sex steroid hormone levels in male and female Calotes versicolor [plasma testosterone (T) levels in males and 17 beta-estradiol (E(2)) and progesterone (P) levels in females] are described. In females both plasma E(2) (32.80 +/- 12.91 pg/ml) and P (1.72 +/- 0.79 ng/ml) levels are at their low levels during the postbreeding season when the gonads are regressed. With the onset of recruitment of vitellogenic follicles, E(2) levels begin to rise, reaching peak values (1306.00 +/- 407.01 pg/ml) when the follicles are preovulatory. During this time, plasma levels of P are low. Plasma E(2) levels decline (285.60 +/- 143.0 pg/ml) soon after ovulation, and circulating concentrations of P begin to rise, reaching peak value (19.24 +/- 10.03 ng/ml), during eggshell formation. In gravid females, at mid-gestation, the same pattern of E(2) secretion is found when a second set of follicles undergoes vitellogenesis. However, P levels remain low from mid-gestation (4.06 +/- 2.17 ng/ml) until oviposition. These findings suggest that high P levels are not needed for oviductal egg retention during late gestation and that low levels of P may facilitate growth of a new batch of vitellogenic follicles. In males, plasma levels of T are correlated with the spermatogenetic activity that accompanies breeding.

Effect of sex steroids on gonadal differentiation and sex reversal in the frog, Rana curtipes.

The bicolored frog, Rana curtipes, is endemic to Western Ghats of Southern India, having a prolonged larval life. In this species, gonadal differentiation is of the semidifferentiated type. The gonads initially differentiate into ovaries in all the individuals at Gosner stage 25. Later, in genetic males, the oocytes degenerate and testicular differentiation occurs at stages 30-31. Exposure of R. curtipes tadpoles to 50 microg/L of testosterone (T) or estradiol-17beta (E(2)) during stages 24-26 or 29-32 did not affect gonadal sex differentiation and proportion of males and females at metamorphosis. In all the groups, the sex ratio was almost 1:1 as in the controls. Likewise, exposure of tadpoles to low concentration of steroids (12.5 microg/L T or E(2)) throughout larval development was ineffective in altering the sex ratio or the gonadal sex differentiation. On the other hand, exposure to higher concentrations of steroids (25 and 50 microg/L) throughout the larval development (stages 25-45) significantly skewed the sex ratio toward the male or female direction, depending upon the sex steroid used. Thus, exposure to T or E(2) throughout the larval period could produce 93% males or 79% females, respectively, indicating the ability of these steroids to cause sex reversal. This study shows a possible absence of a "critical stage" that is sensitive to sex steroids for gonadal sex reversal in this frog.

Plasma progesterone levels and luteal activity during gestation and prolonged oviductal egg retention in a tropical lizard, Calotes versicolor.

Plasma progesterone (P) levels and luteal and adrenal activities were studied during normal gestation and unusual prolonged period of oviductal egg retention in a polyautochronic, multiclutched lizard, Calotes versicolor. The normal gestation period (approximately 15 days) was categorized into four stages: stage I--a few hours following ovulation, stage II--eggs with shell and embryo at primitive streak, stage III--embryonic stages 16-20, and stage IV--prior to ovipostion (stages 26-27). The gravid lizards maintained in captivity retained eggs in their oviducts for 45 days. Plasma P levels were low in stage I, increased significantly during stage II, declined in stage III, and reached their lowest in stage IV of gestation. 3Beta-hydroxysteroid dehydrogenase (3beta-HSDH) activity was greater in lutein cells at stage II and was present in traces in stage IV gestation. Interestingly, plasma P titers that were high in lizards with eggs retained longer though the corpora lutea (CL) showed a trace 3beta-HSDH activity. However, 3beta-HSDH activity was greater in the adrenocortical cells in these lizards than that in lizards during a normal gestation period. The present study on C. versicolor shows that the CL remains active and secretes P only during the early part of the gestation. The drop in P level during the later part of gestation might facilitate growth of a second set of vitellogenic follicles. During unfavorable conditions when the lizards are forced to retain eggs in the oviduct, the adrenal glands seem to secrete progesterone to help in egg retention and in inhibition of oviposition.

Pattern of gonadal sex differentiation, development, and onset of steroidogenesis in the frog, Rana curtipes.

Histomorphological changes and steroidogenic potential of the gonads during sexual differentiation and development were studied in Rana curtipes from tadpole stage 25 (Gosner) until maturity. In stage 25 tadpoles of smaller snout-vent length (SVL; 4-5 mm) the gonads were indifferent, containing a few somatic and germ cells, whereas in larger tadpoles (SVL > 7 mm) gonads were differentiated into ovaries with a central lumen. Onset of meiosis was seen in these ovaries. At stage 26, diplotene and first growth phase oocytes were found. With advancement in developmental stage and after metamorphosis the ovaries progressively enlarged due to increase in number and size of oocytes. Vitellogenesis began in the ovary of 4-month-old frogs. Females attained maturity 6 months after metamorphosis. The frogs showed amplexus and one frog spawned. Onset of testicular formation seen at stage 31 was associated with the degeneration of oocytes and infiltration of darkly stained somatic cells in the central region. By stage 35 all oocytes degenerated, leaving behind a large number of somatic and germ cells interspersed with each other. At stage 38, formation of seminiferous tubules enclosing spermatogonia and pre-Sertoli cells was seen. Initiation of meiosis was evident at metamorphic climax. Cysts of elongated spermatids associated with Sertoli cells were seen in 45-day-old frogs. Histochemically, delta(5)-3 beta-hydroxysteroid dehydrogenase activity was localized in the ooplasm, follicular cells, and interstitium of the ovary from stage 28 onward. The enzyme activity in the testis appeared in 45-day-old froglets. In R. curtipes gonadal differentiation is a semidifferentiated type since gonads initially differentiate into ovaries, and later, in the prospective males, the ovaries degenerate and transform into testes. The males attain maturity much earlier than the females. In R. curtipes gonadal sex differentiation precedes the onset of gonadal steroidogenesis.

GnRH but not warm temperature induces recrudescence of quiescent testes in the tropical lizard Calotes versicolor (Daud.) during postbreeding phase.

The effects of temperature and various doses of GnRH on testicular recrudescence were studied in Calotes versicolor during the postbreeding (December-January) resting phase. Adult lizards (n = 51) were segregated into seven groups. Group I served as the initial control. Groups II, III, and IV were maintained at room temperature (23 +/- 1 degrees, range 17.5-25.5 degrees ) and natural photoperiod (12.25 h light:11.35 h dark). Groups V, VI, and VII were maintained at 30 +/- 1 degrees in an environmental chamber with 12 h light:12 h dark. Groups II and V received 0.2 ml saline, groups III and VI received 0.1 microgram GnRH/0.2 ml saline, and groups IV and VII received 0.5 microgram GnRH/0.2 ml saline on alternate days for 30 days. In the two groups that received 0.5 microgram GnRH, there was a significant increase in the diameter of the seminiferous tubules and Leydig cell nuclei, 3beta-HSDH activity in Leydig cells, and plasma testosterone level compared to those in other groups. There was no evidence of testicular recrudescence in lizards exposed to room/high temperatures treated with saline or 0.1 microgram GnRH. This study of C. versicolor shows that during the resting phase, high temperature per se does not stimulate testicular recrudescence, whereas 0.5 microgram GnRH does so. Also, the findings suggest that either higher brain centers regulating hypothalamus or hypothalamus itself become dormant, causing testicular inactivity (inactivation of hypophysial-testicular axis) during the postbreeding resting phase.

Immunocytochemical localization of androgen receptor in the comb, uropygial gland, testis, and epididymis in the domestic chicken.

Nuclear, but not cytoplasmic androgen receptors (AR), were localized immunocytochemically in the comb, uropygial (preen) gland, testis, and epididymis of juvenile and adult cockerels. Androgen receptor immunoreactivity (AR-ir) was seen in the comb, in the stratum germinativum of the epidermis and in fibromucoid cells in the dermis in juvenile and adult cockerels. AR-ir was observed in the glandular epithelial (sebum-producing) cells lining the peripheral and middle sections of the tubules in the uropygial gland. AR-ir was not detected in innermost part of the tubules which conduct the sebum to the surface of the skin. AR-ir labeling was not observed in the uropygial gland of juveniles. In the testis, AR-ir was seen in the Leydig cells, in adults but not juveniles. The epithelial cells lining the tubules in the epididymis contained AR-ir in both juveniles and adults.

Fat body ovarian relationship in the garden lizard, Calotes versicolor (Daud.).

Abdominal fat body mass of Calotes versicolor showed annual changes that were universal related to the changes in ovarian somatic (GSI) and hepatosomatic (HSI) indices. Fat bodies were absent in late breeding phase (June-August). Thirty day fatectomy (FBX) during prebreeding phase significantly reduced GSI, HSI, and total number of extrastromal follicles; also, recruitment of vitellogenic follicles was arrested and ateretic follicles increased. The FBX during postbreeding phase had no such effect, whereas in 30 day ovariectomised (OvX) lizards in prebreeding phase fat body mass significantly increased but HSI decreased. However, in lizards in prebreeding phase, E2 caused a significant decrease in fat body mass and an increase in HSI, while during the postbreeding phase there was a significant increase in HSI but the fat bodies were not affected. The above findings suggest that the development of the first clutch of vitellogenic follicles in the lizard utilises lipids stored in the fat bodies and that the growth of the subsequent clutches of vitellogenic follicles is met through the intake of food, which is abundant in the latter part of the breeding phase. The fat bodies are not needed for the growth of previtellogenic follicles. The fact that lipolytic action of E2 occurs only during the breeding phase suggests that responsiveness of the fat bodies to the steroid is related to the reproductive phase and that during postbreeding phase of the lizard they become refractory to E2.

Effect of LH, FSH, LH + FSH and homoplastic pituitary extract on developing testis and epididymis of pigeon Columba livia.

Ovine LH is needed for differentiation of juvenile Leydig cells and for their maintenance and steroidogenic potential, while FSH is necessary for Sertoli cell activity and spermatogonial multiplication suggesting that LH is steroidogenic hormone and FSH is gametogenic in the developing pigeon, C. livia. Homoplastic pituitary extract is more potent than ovine LH + FSH in stimulating gametogenic and endocrine components of the developing testis.