Role of thyroid and testicular hormones in the regulation of basal metabolic rate, gonad development, and body weight of spotted munia, Lonchura punctulata

Normal saline, L-thyroxine (L-T4, 0.5 micrograms/bird/day), and testosterone (100 micrograms/bird/day) were administered separately to intact, thyroidectomized, and castrated spotted munia over a 30-day period and the effects on basal metabolic rate (BMR), gonads, and body weight were recorded. Thyroidectomy and castration decreased the BMR. L-Thyroxine increased the BMR of intact and thyroidectomized but not of the castrated birds. Testosterone had no effect on BMR of either the intact or of the operated birds. L-Thyroxine and testosterone both had no effect on regressing gonads but inhibited thyroidectomy-induced testicular development. Body weight increased in intact, testosterone-treated birds, and in thyroidectomized and castrated spotted munia. L-Thyroxine inhibited body weight gain only in thyroidectomized birds. It is suggested that the physiological actions of L-T4 and testosterone depend on the gonadal status, thyroid activity, and nature of the thyroid-gonad relationship.     

Photoperiodic regulation of the male house sparrow song control system: gonadal dependent and independent mechanisms

The primary and secondary sexual characteristics of many species of passerine birds undergo dramatic seasonal variation in response to the change in the length of photoperiod. Among the many physiological processes that undergo seasonal changes, bird song and the song control system underlying it undergo similar seasonal variation in size and function. The mechanisms of this seasonal variation are largely unknown but are at least partially due to steroidal action from the gonads. The present study determined the relative roles played by the gonads and the photoperiodic timing system that controls gonadal development on song control nuclei in the brain of the male house sparrow, Passer domesticus. Sparrows maintained in short photoperiods (SD) possessed small regressed testes. Transfer to long photoperiods (LD) for 6 weeks evoked a dramatic increase in testes size, but, after 20 weeks under the same conditions (LDLD), testes completely collapsed. Song control nuclei HVC and RA were smaller in SD than in LD but regressed only moderately in LDLD. Castration of sparrows in SD reduced the amplitude of the seasonal variation but did not completely abolish it. The data support the view that the song control system of the house sparrow is regulated by the photoperiodic timing system independently of gonadal influence, but that the gonads augment seasonal regulation of song, presumably via steroidal hormone secretion.     

Thyroidectomy prevents the development of photorefractoriness and the associated rise in plasma prolactin in starlings

Intact and radiothyroidectomized male starlings were transferred from short (8-hr) to long (16-hr) day lengths and measurements made of testicular development and of plasma prolactin concentrations. In intact birds the testes reached full maturity within 3 weeks and regressed after 6 weeks of photostimulation, indicative of the development of photorefractoriness . Prolactin levels increased gradually, reaching maximal values (25.2 +/- 4.7 ng/ml compared with 1.2 +/- 0.2 ng/ml before photostimulation) at the time of testicular regression. Testicular growth was normal in the thyroidectomized birds, but in three of eight testes remained fully mature for at least 1 year, and prolactin remained low (below 2.0 ng/ml) during this entire time. The testes of the other five thyroidectomized birds did regress partially, accompanied by a corresponding increase in prolactin, although the testes subsequently regrew . Removal of the testes from thyroidectomized birds after 1 year on long days resulted in a marked rise in plasma FSH, indicating that these birds were indeed not photorefractory ; FSH levels in the refractory-intact starlings remained low after castration. These results confirm that the presence of an intact thyroid gland is essential for the development of photorefractoriness and for the release of prolactin which normally follows photostimulation.     

Thyroxine treatment facilitates prolactin secretion and induces a state of photorefractoriness in thyroidectomized starlings

Sexually immature male starlings were radiothyroidectomized while held under short day-lengths. They were then subjected to long (18-h) photoperiods and the testes developed rapidly and apparently normally to full maturity. As expected, thyroidectomy prevented an onset of photorefractoriness and after 140 days the testes were still fully developed (testicular width 6.5 +/- 0.8 mm). Half of the birds were then given thyroxine (0.011 mmol/l) in the drinking water for 14 days while the others were maintained as controls. At the end of this time the birds still had fully developed gonads (testicular width 7.8 +/- 0.3 mm) but after a further 14 days testicular regression began in the thyroxine-treated birds. The testes of all individuals in this group were fully regressed (width 1.8 +/- 0.1 mm) by 56 days after the end of thyroxine administration and moulting of the flight feathers had begun. No recrudescence of the gonads was subsequently noted in the next 2 months and the birds were apparently photorefractory. The short period of thyroxine treatment also caused a rapid and prolonged increase in plasma prolactin levels from 2.0 +/- 0.3 to 16.8 +/- 2.6 micrograms/l. No testicular regression or moulting was observed in the control birds and their plasma prolactin levels remained very low (below 4.0 micrograms/l) throughout the experiment. In thyroidectomized and castrated starlings held on 18-h daylengths, 14 daily injections of thyroxine (100 micrograms/bird per day) caused a rapid and permanent decrease in circulating FSH to basal levels (reached about 36 days after thyroxine treatment began, at which time the birds moulted). The treatment also caused a marked increase in plasma prolactin lasting for about 50 days.     

Light responses of thyroidectomized Common Myna Acridotheres tristis

Under normal day length, the gonads of thyroidectomized Common Myna, Acridotheres tristis, decreased and those of sham-operated Common Myna increased significantly. Long photoperiod (15L:9D) stimulated and short photoperiod (6L:18D) inhibited the development of gonad of sham-operated and thyroidectomized birds. It is suggested that, while thyroidectomy had an inhibitory influence, long photoperiod stimulated the hypothalamo-hypophyseal-gonadal axis of athyroidic birds.     

Thyroid-gonad and thyroid-body weight relationship in the red-vented bulbul, Molpastes cafer

Male and female gonads, but not the body weight, of the red-vented bulbul Molpastes cafer undergo an annual cycle of development. Gonads are small and inactive during winter and large and active during spring and early summer months. When during December (day length, 10.26L:13.34D) male birds were transferred to 9L:15D photoperiod, the gonads remained small and inactive, and when exposed to 15L:9D, the testes developed rapidly, reached a maximum, and then regressed. Exposure to 15L:9D during April (day length, 12.45:11.15D), however, produced no significant effect either on the size or on the rate of growth of the gonads. Thyroidectomy led to rapid collapse of the partially or fully developed testes irrespective of whether the birds were exposed to natural or long photoperiod. The body weight of the birds was not affected significantly either by day length or by thyroidectomy. It is suggested that while the thyroid is essential for sustaining the growth of the gonads and reproduction it has no significant influence on the body weight of the bird.     

The effects of testosterone propionate on secondary sexual characters and testes of house sparrows, Passer domesticus

Male house sparrows were captured in October and transferred to artificial short days of 8L 16D. Beginning on November 19th they were injected either with 0.4 mg testosterone propionate (group T) or with sesame oil only (group C) every other day. Within 24 days the androgen injections caused a change in the inner and outer surfaces of the bill from light brown to black (Figs. 1,2) and a pronounced enlargement of the glomus vesicles (Table 1). In group C bill coloration was unchanged compared with the start of the experiment. In contrast, therefore, to other recent findings the development of ornamental structures in Passer domesticus does not depend on gonadotropins. No significant differences were observed between the testes of the two groups which were all regressed and inactive.     

Binding of follicle-stimulating hormone by homogenates of testes of photostimulated white-crowned sparrows, Zonotrichia leucophrys gambelii.

Homogenates of testes of the white-crowned sparrow bind specifically with ¹²⁵I-labeled rat FSH (follicle-stimulating hormone). The binding is competitively inhibited by unlabeled rat FSH and PMSG (pregnant mare serum gonadotropin) but not by purified rat LH (luteinizing hormone). Crude gonadotropin preparations also inhibit binding but the rates of inhibition are fully explained by amounts of FSH in these preparations. The testes of photosensitive birds with resting testes were found to bind about 4 × 10^?15 moles of ¹²⁵I-labeled rat FSH per milligram of tissue. The binding per milligram of tissue decreases during photoperiodically induced testicular growth, although the total binding capacity increases during the first 3 weeks of photoperiodic stimulation. Thereafter it increases no further although the weight of the testes continues to increase rapidly. With further development, a specific and sensitive radioreceptor assay of avian FSH, using a testicular homogenate of the white-crowned sparrow as the receptor, may be possible.     

Seasonal changes in testicular size and in plasma follicle-stimulating hormone and prolactin concentrations in thyroidectomized male and thyroidectomized castrated starlings (Sturnus vulgaris)

Testicular size and plasma concentrations of FSH and prolactin were measured frequently in thyroidectomized male and thyroidectomized castrated starlings kept in outdoor aviaries during 1 year. In thyroidectomized males, testes increased from minimal to maximal size during March, remained large until June, and then decreased slowly during the next 6 months. Plasma FSH increased to a peak in April (126 micrograms/litre) and then declined slightly. Plasma FSH in thyroidectomized castrates was very high (360-760 micrograms/litre) and did not change significantly during the year. In both groups of birds, plasma prolactin concentration remained low (less than 5 micrograms/litre) and there was no molt. These results demonstrate that while thyroidectomy prevents the onset of photorefractoriness in starlings, short days nevertheless cause gonadal regression. However, this regression is not analogous to the short-day-induced gonadal regression shown by species, such as quail, which do not exhibit absolute photorefractoriness.     

Thyroidectomy and the termination of juvenile refractoriness in the red-legged partridge (Alectoris graeca chukar)

The role of thyroid hormones in the maintenance of juvenile refractoriness was studied in the red-legged partridge hybrid, Alectoris graeca chukar. Juvenile partridges, maintained on long (20L:4D) daylengths from hatch, were radiothyroidectomized at 6 1/2 weeks of age, and after 2 weeks were either held on long days or transferred to short (8L:16D) daylengths. Short-day thyroidectomized birds showed no evidence of gonadal growth 18 weeks after thyroidectomy, and neither did euthyroid controls on either short or long daylengths. Thyroidectomized birds held on long daylengths did show significant gonadal growth at this point. Further treatment with low levels of thyroxine (10 micrograms/bird) led to even greater testicular development in long-day thyroidectomized birds, but had no effect on the gonads of short-day thyroidectomized or euthyroid birds.     

Thyroid and gonadal regulation of hair growth during the seasonal molt in the male European badger, Meles meles L

In the male badger we showed that hair growth and molt are related to plasma testosterone and thyroxine cycles. We established the action of testosterone by castration and subcutaneous testosterone implants, and the action of thyroxine by thyroidectomy and dietary supplementation with thyroxine. The following groups of animals were studied: controls, thyroidectomized, thyroidectomized and thyroxine-treated, castrated, castrated and thyroxine-treated, thyroidectomized and castrated and thyroxine-treated, castrated and testosterone-implanted, and intact testosterone-implanted. In control animals, molt and hair growth occurred during the summer, with a maximum growth in autumn. Molt ended at the beginning of winter when the plasma testosterone level had started to rise, and began again after this level had started to decline. Both the start of molt and the period of maximum hair growth coincided with high thyroxine levels of about 20 ng/ml. Castration advanced molt and hair follicle activity, whereas testosterone implants delayed both molt and hair growth. In thyroidectomized badgers, neither hair growth nor seasonal molt was observed. However, when thyroxine levels were restored to 20 ng/ml or more by dietary T4 supplementation, molting was resumed in animals that had undergone either thyroidectomy or thyroidectomy plus castration. In those that underwent castration only, the molt was advanced leading to early hair growth further stimulated by the suppression of testosterone. Testosterone had an inhibitory effect on the molt--since testosterone implants in intact control animals delayed it by 4 weeks--but did not inhibit it completely. On the other hand, a T4-enriched diet advanced the date of the molt. However, the molt could not be induced, nor could hair follicle growth be reactivated, at all times during the annual cycle. Thus, in castrated animals. T4 enrichment of the diet in early January, at the end of the molt, caused follicle reactivation only toward the end of May, despite the lack of testosterone. This 18-week latency period from January to May might therefore constitute a "refractory period" in this species. The above findings show that the regulation of the seasonal molt and hair growth in the European badger involves both the thyroid and genital axes. This regulation is discussed in terms of joint control by the hypothalamus and pituitary governed, in turn, by an external factor--the photoperiod--considered to be the main synchronizer.     

Influences of thyroidectomy and thyroxine replacement on photoperiodically controlled reproduction in quail

The breeding season in quail ends when they become relatively refractory to long photoperiods. The processes underlying the development of this refractoriness are dependent upon the thyroid gland. Thyroidectomized male Japanese quail transferred from short (8 h light: 16 h darkness; 8L: 16D) to long (20L:4D) daily photoperiods mature their gonads and develop the androgen-dependent cloacal gland at rates only marginally slower than controls. However, when the birds are retransferred to short days thyroidectomized individuals do not show the rapid testicular regression and moult which occurs in controls under such conditions. The testes remain large for a long period, eventually decreasing in size slowly and irregularly. Once such thyroidectomized birds are transferred back to short days the administration of thyroxine has little effect upon the slow rate of gonadal regression but if the hormone is administered during the preceding period of long days normal regression does occur under short days, even though treatment has ceased. This suggests that a process dependent upon thyroid hormones takes place under long day-lengths that ensures the termination of reproduction when they are exposed either to short daylengths or to decreasing daylengths after the summer solstice. This view was substantiated by further experiments in which thyroidectomy was performed after the birds had been exposed to long daylengths. When transferred to 8L:16D normal testicular regression and moult occurred rapidly. Presumably the thyroid-dependent process had proceeded to an adequate extent in these quail before the thyroid glands were destroyed. Further support came from treating intact quail chronically with thyroxine. Its administration to quail on 20L:4D had no observable effect; the testes grew rapidly to maximal size and remained large. However, if the birds were given thyroxine under 12L:12D the gonads first developed to maximal size and then, after about 12 weeks of treatment, regressed spontaneously whether or not thyroxine was still being administered. It seems that thyroxine had made the quail so relatively refractory that 12L:12D was no longer sufficiently stimulatory to overcome the developing inhibition on the photoperiodic system. The results in quail are very reminiscent of the finding that the absolute photorefractoriness and spontaneous testicular regression which develops in starlings under long daylengths is thyroid dependent.(ABSTRACT TRUNCATED AT 400 WORDS)     

Role of thyroid in sexual and body weight cycles of the migratory redheaded bunting, Emberiza bruniceps

In the male redheaded bunting, Emberiza bruniceps, kept under natural lighting in northern India (Lat 25 degrees 18'N, Long 83 degrees 01'E), testicular growth began during March/April and full spermatogenesis was achieved in May/June; thereafter, the testes regressed and remained regressed for the rest of the year. Thyroidectomy between November and April partially suppressed photoinduced testicular growth in May/June, but did not prevent testicular regression in July. The extent to which thyroidectomy suppressed photoinduced testicular growth was directly related to the time elapsed between thyroidectomy and photostimulation. Thyroidectomy in mid-late May induced testicular regression, an effect which was reversed by daily im injection of 500-2000 ng thyroxine/bird/day/30 days. Thyroidectomy or treatment of intact or thyroidectomized birds between July and March when the testes were regressed had no immediate effect on testicular growth. Body weight which was about 24 g between December and March, increased to about 28 g during the breeding season. Thereafter, it decreased to 21-22 g between August and October. Thyroidectomy between November and May caused an immediate fall in body weight, an effect which was reversed by daily im injection of 500-2000 ng thyroxine/bird/day/30 days. Neither thyroidectomy nor thyroxine treatment prevented the seasonal fall in body weight in June and July nor affected body weight between August and October. It is suggested that in the male redheaded bunting, under natural lighting, thyroid hormones are necessary for the full development of the testes and an increase in body weight during the breeding season. However, thyroid hormones do not appear to be necessary for the development of photorefractoriness or for the seasonal decrease in body weight.     

Thyroid,gonad, and photoperiod in the hemopoiesis of the migratory red-headed bunting, Emberiza bruniceps

l-Thyroxine and thyroidectomy, separately or together had no significant influence on the gonadal activity and erythropoiesis of the migratory red-headed bunting maintained under natural photoperiod during January to March. But when exposed to 15L:09D, while there was no significant change in the activity of the testes and erythropoiesis of the thyroidectomized birds, significant increases occurred in those of the intact and l-thyroxine-treated intact and thyroidectomized birds. It is suggested that a long photoperiod acting by way of the thyroid and gonad enhances erythropoiesis which in turn helps the bird in meeting higher oxygen demand during migration and reproduction.     

Light, thyroid, gonad, and photorefractory state in the migratory redheaded bunting, Emberiza bruniceps

When exposed to constant long photoperiods the redheaded bunting, Emberiza bruniceps, was shown to become absolutely photorefractory and the condition was observed to be accelerated by thyroidectomy. Photoinduced gonadal growth was inhibited partially and the photoinduced increase in body weight was inhibited completely by thyroidectomy. Injection of thyroxine reversed the effects of thyroidectomy if administered during the nonbreeding photosensitive or breeding states, but had no effect in birds which had entered the photorefractory state. Gonadal growth was stimulated by pregnant mare serum gonadotrophin in intact and thyroidectomized photorefractory birds, suggesting that thyroidectomy does not lead to loss of response of the gonads to gonadotrophins but directly affects the secretion of gonadotrophins. Injection of prolactin increased the body weight of intact but not of thyroidectomized photorefractory birds, suggesting that metabolic photorefractoriness is due to a decreased secretion of prolactin and that the effects of T4 on body weight depend on its synergism with prolactin. It is suggested that thyroid hormone(s) may be part of the coupling mechanism(s) for body weight and gonad development cycles and that the beneficial role of thyroid hormones may consist in an increased threshold of the central nervous system control of neuroendocrine functions towards the negative feedback regulation of increased sex steroid levels.     

Recombinant human granulocyte colony-stimulating factor (rhG-CSF; filgrastim) treatment of clozapine-induced agranulocytosis

Abstract. After 10 weeks of treatment with clozapine, severe agranulocytosis was diagnosed in a 33-year-old female. The patient was treated with filgrastim (granulocyte colony-stimulating factor [G-CSF]) 5 μg kg^?1 day^?1. The neutrophil count was 0.234 × 10⁹ l^?1 on admission, with a further decrease the next day to < 0.050 × 10⁹ l^?1, and this complete agranulocytosis continued for 10 days. As no response was obtained after 1 week the dosage of filgrastim was increased to 10 μg kg^?1 day^?1 with immediate improvement. A rapid and pronounced leucocytosis developed with maximal value of neutrophil granulocytes (including immature forms) of 33.108 × 10⁹ l^?1 on day 12 after admission. The patient only had minor infectious complications during the neutropenic period. In conclusion, early treatment with filgrastim seems warranted in severe cases of clozapine-induced agranulocytosis. A dosage of 10 μg kg^?1 day^?1 can be recommended.     

The effects of testosterone propionate and gonadotropins on the bill pigmentation and testes of the house sparrow (Passer domesticus)

Sexually regressed winter house sparrows, Passer domesticus, were treated with exogenous testosterone propionate, luteinizing hormone (LH) or follicle-stimulating hormone (FSH) after first confirming they were no longer photorefractory. Controls at the start and end of the experiment in December had the pale brown beaks typically noted in this species during the early winter. Treatment with relatively large doses of exogenous androgen did not cause the bill to assume a darker coloration than would occur in the wild in early spring. Neither FSH nor LH given alone restored pigmentation. A combination of FSH and LH caused a complete darkening of the bill, and FSH injected in combination with testosterone propionate was also effective. Testosterone propionate exerted a spermatokinetic effect consistent with other reports in the literature. Testicular weight and spermatogenetic condition was most advanced in subjects given FSH plus LH injections.     

Pharmacological characterization of intracellular glucocorticoid receptors in nine tissues from house sparrow (Passer domesticus)

Glucocorticoid hormones play a key role in the stress response, but plasma concentrations vary based on physiological, environmental, or social parameters. However, hormone titers alone do not determine organismal response. To enhance our understanding of glucocorticoid actions we can examine ‘downstream’ factors in the organismal stress response, measuring glucocorticoid receptors across target tissues. Here, we characterized intracellular binding sites for CORT (corticosterone, the avian glucocorticoid) in house sparrow (Passer domesticus) brain, liver, skeletal muscle, spleen, fat, testes, ovary, kidney and skin. We used radioligand binding assays to identify total capacity, relative density and affinity for CORT of intracellular receptors in each tissue. Most evidence supported two binding sites similar to mammalian low-affinity glucocorticoid receptor (GR) and a high-affinity mineralocorticoid receptor (MR) for brain, liver, kidney and testes, and only a GR-like receptor for muscle, spleen, fat, ovary and skin. However, kidney data were somewhat more complicated, possibly hinting at a mineralocorticoid function for CORT and/or GR in birds. In all tissues, GR and MR affinities were close to published house sparrow values (K_d ∼ 6 nM for GR, and ∼0.2 nM for MR). Taken together, these data show that CORT receptor distribution appears to be as widespread in birds as it is in mammals, and suggest that independent regulation of peripheral receptors in different target tissues may play a role in CORT’s diverse physiological effects.     

Frontiers of hormone research,Vol. 8, ACTH and LPH in health and disease: Edited by Tj. B. van Wimersma Greidanus and L. H. Rees. S. Karger,basel, 1981. x + 210 pp., 25 figs., 14 tables,S Fr. 132.-DM 158.-, US $79.25

Extirpation of the thyroid gland and administration of l-thyroxine to the intact Indian garden lizard, Calotes versicolor, caused complete inhibition of spermatogenesis and growth of the testes and of the accessory sex organs throughout the year. When injected into the thyroidectomized lizards, l-thyroxine counteracted the effects of thyroidectomy.     

Seasonal changes in adrenocortical responses to acute stress in Eurasian tree sparrow (Passer montanus) on the Tibetan Plateau: comparison with house sparrow (P. domesticus) in North America and with the migratory P. domesticus in Qinghai Province

Seasonal modulation of the adrenocortical response to stress appears to be ubiquitous in arctic-breeding and temperate-zone-breeding birds, but has not been well investigated in alpine-breeding species at mid-latitude. We examined the adrenocortical response to acute stress (capture, handling and restraint) in populations of Eurasian tree sparrow (Passer montanus) among seasons and migratory house sparrow (P. domesticus bactrianus) in pre-breeding on the Qinghai-Xizang Plateau (the Tibetan Plateau). A population of house sparrow (Passer domesticus domesticus) was also sampled in lowland Phoenix, Arizona during breeding and wintering stages. In Eurasian tree sparrows, baseline corticosterone (CORT) does not differ among life history stages, but stress-induced CORT level (maximal CORT, total and corrected integrated CORT) is significantly higher in late breeding stage than those in early breeding and prebasic molt stages. In house sparrows, stress-induced CORT level does not differ between sites and life history stages, but baseline CORT is significantly lower in pre-breeding from Qinghai compared with those in breeding and wintering stages from Phoenix. Interestingly, both baseline CORT and maximal CORT do not differ between the populations of Eurasian tree sparrow and house sparrow in early/pre-breeding stage although tree sparrow is resident species whereas house sparrow is migratory in Qinghai. Our results suggest that the extreme environment of the Tibetan Plateau does not have significant effects on adrenocortical responses to acute stress in Eurasian tree sparrows and house sparrows, which may be a result of masking by human activities. These invasive human commensals may have a unique HPA axis response to different environments because they can take advantage of human food sources and shelter (i.e. buildings).