Seasonal changes in serum thyroid hormone levels of the feral brown bullhead, Ictalurus nebulosus Lesueur

Seasonal changes in serum L-thyroxine (T4) and triiodo-L-thyronine (T3) concentrations were measured in a feral population of brown bullheads, Ictalurus nebulosus . Serum T4 was elevated in mid April concomitant with the onset of gonadal recrudescence and the increase in ambient temperatures from the winter level. Thereafter, serum T4 levels were constant throughout the late spring and summer (except for a significant lowering in levels associated with the spawning and early postspawning period), declining to a low overwintering level by mid December. Serum T3 levels increased in April, and apart from a significant decrease in July associated with the postspawning period, rose progressively until August, after which levels declined progressively to reach overwintering levels again by mid December. Between mid April and mid May serum T4/T3 ratios fell from the high values found in fish during the winter months. Apart from variations associated with the fluctuations of T4 and T3 concentrations in the spawning and early postspawning periods, serum T4/T3 ratios remained at a low level throughout the summer and early autumn months, and rose again in October to the overwintering levels. The circannual cycles are discussed in relation to the possible role of the thyroid hormone in gonadal maturation and metabolism in this species.     

Effect of sex and age on serum aldosterone and thyroid hormones in the laboratory rat

Serum levels of aldosterone, tri-iodo thyronine (T3) and thyroxine (T4) were measured in male and female rats aged 3 months, 12 months, and 18 months. Female rats were found to have higher aldosterone and T3 levels, and lower T4 level than the male. No age-related change was observed in serum aldosterone in either sex. In contrast, serum T4 were found to decrease with age in both sexes while serum T3 showed an age-associated diminution in the male only. Serum testosterone was also measured in the male rats and was found to decline with age.     

Insolation effect on vitamin D supply in children during sanatorium treatment

Serum 25/OH/D3 levels were determined in 58 children aged 5-7 years staying from April 1 to September 30 1981 in Ko?obrzeg in a sanatorium. A comparison of isolation conditions in that time period with the serum values of 25/OH/D3 showed that the supply of vitamin D was sufficient only in the period from June to September. In the remaining months no correlation was observed between the values of solar radiation and vitamin D levels. During the study and for three months before it exogenous vitamin D administration was stopped.     

Simultaneous observations of iodothyronine content in the thyroid gland, serum and thyroxine 5'- and 5-monodeiodinase activity in liver, during the neonatal period of the pig

Serum T4 and rT3 were high at about 4-12 h after birth, then they decreased to a nadir on day 3 (rT3) and day 7 (T4). Serum T3 concentration fell immediately after birth but then increased to a relatively stable level during the next 2-6 weeks, then fell after weaning. Reciprocal concentration profiles of T4, T3 and rT3 in the thyroid were found. The thyroidal iodothyronine content increased significantly after weaning. In the liver, 5'-monodeiodinating activity, low after birth, rose until day 3 and then decreased concomitantly with T3 in serum. The 5-monodeiodinating activity, high at birth, fell to a nadir at about 3 weeks. No changes in 5- and 5'-deiodinase activity after 3 weeks were observed. Opposite to the variations in absolute content, the iodothyronine relative proportion in thyroid tissue was practically unchanged until weaning time (6 weeks), when they rose. Serum T3/T4 and rT3/T4 ratios increased with age until weaning. The post-weaned pigs had T3/T4 and rT3/T4 ratios about two times smaller than 6-weeks-old pigs. Serum rT3/T3, high after birth, decreased with age. Summarizing, the results indicate that neither changes in the thyroid iodothyronine content nor in the liver T4-monodeiodinating activity can solely account for variations in serum TH during the early neonatal period in the pig. It is suggested that the rapid variations in serum TH levels can reflect changes in the thyroidal secretory activity in preferential T3 secretion and/or blood disappearance rates.     

Blood levels of cyclic AMP, thyroxine, uric acid, certain metabolites and electrolytes under heat-stress and dehydration in the pigeon.

The effect of heat stress and dehydration on certain blood parameters were studied in the pigeon. Pigeons exposed to heat-stress and dehydration showed higher haematocrit values. Serum cyclic AMP levels, both with and without corrections made for difference in haematocrit, showed a more than two-fold increase in heat-stressed and dehydrated pigeons. Serum triglyceride level (before and after correction for haematocrit difference) in the experimental birds dropped to less than half that in the control birds. Total serum thyroxine (T4) did not show significant change in the experimentals (either with or without correction for haematocrit), although bound T4 and T3 index showed a statistically significant drop in the experimental group, after the correction for haematocrit. Total serum protein and albumin values after correction for haematocrit difference showed significant decreases in experimental birds. In pigeons exposed to heat-stress and dehydration, serum sodium increased while potassium dropped (with and without haematocrit correction). Heat stress and dehydration did not have any significant effect on serum levels of total cholesterol, uric acid, sodium, potassium, calcium and magnesium.     

Serum concentrations of 3, 3'-diiodothyronine, 3', 5'-diiodothyronine, and 3, 5-diiodothyronine in altered thyroid states

To investigate the thyroid hormone metabolism in altered states of thyroid function, serum concentrations of 3, 3'-diiodothyronine (3, 3'-T2), 3', 5'-T2 and 3, 5-T2 as well as T4, T3 and rT3 were determined by specific radioimmunoassays in 17 hyperthyroid and 10 hypothyroid patients, before and during the treatment. Serum T4, T3, rT3, 3, 3'-T2 and 3', 5'-T2 concentrations were all higher in the hyperthyroid patients than in age-matched controls and decreased to the normal ranges within 3 to 4 months following treatment with antithyroid drugs. In the hypothyroid patients, these iodothyronine concentrations were lower than in age-matched controls and returned to the normal ranges after 2 to 3 months treatment with T4. In contrast, serum 3, 5-T2 concentrations in hyperthyroid patients (mean +/- SE : 4.0 +/- 0.5 ng/dl) were not significantly different from those in controls (3.9 +/ 0.4 ng/dl), although they tended to decrease in 3 of 6 patients after the antithyroid drug therapy. Serum 3, 5-T2 levels in the hypothyroid patients (3.8 +/- 0.6 ng/dl) were also within the normal range and showed no significant change following the T4 replacement therapy. However, serum 3, 5-T2 as well as 3, 3'T2 concentrations rose significantly with a marked rise in serum T3 following T3 administration, 75 micrograms/day for 7 days, in Graves' patients in euthyroid state.(ABSTRACT TRUNCATED AT 250 WORDS)     

Long-term treatment of postmenopausal osteoporosis with active vitamin D3, 1-alpha-hydroxycholecalciferol (1 alpha-OHD3) and 1, 24 Dihydroxycholecalciferol (1, 24(OH)2D3)

The effects of active vitamin D3 analogues on radial mineral content (RMC) in postmenopausal osteoporosis were examined. Seventy eight subjects with postmenopausal osteoporosis were divided into 5 groups; Group 1 (n = 23) as the control group and Group 2 (n = 27), Group 3 (n = 8), Group 4 (n = 9) and Group 5 (n = 11) which were given 1 microgram of 1, 24(R) (OH)2D3 per day, 1 microgram of 1, 24(S)(OH)2D3 per day, 0.5 and 1 microgram of 1 alpha-OHD3 per day for 6 to 24 months, respectively. After 3-months administration of these drugs, RMC values were significantly increased in Groups 2 (102.8 +/- 1.8%), 4 (103.9 +/- 3.3%) and 5 (114.2 +/- 3.6%), when compared with the controls (97.9 +/- 2.4%). RMC in Group 3 (97.9 +/- 2.4%) was not significantly different from the control value. The administration of 1 alpha-OHD3 caused in increase in RMC in a dose-related manner. A rapid decrease in RMC was observed after withdrawal of the treatment in Groups 2, 4, and 5. A subsequent increase in RMC was observed after re-administration of 1 alpha-OHD3 and 1, 24(R)(OH)2D3. Serum Ca levels were increased in the group treated with 1, 24(R)(OH)2D3 and were decreased after the discontinuation of 1 alpha-OHD3 administration. Serum A1-P activity was decreased by treatment with 1 alpha-OHD3 (1 microgram per day) and a subsequent increase was observed in both groups treated with 1, 24(R)(OH)2D3 and 1 alpha-OHD3. Serum PTH levels were decreased by the administration of 1, 24(R)(OH)2D3 and 1 alpha-OHD3. In the group treated with 1 microgram of 1 alpha-OHD3 per day, hypercalcemia (2 out of 11 cases and these patients took calcium tablets) and an increase in BUN (1 out of 2 hypercalcemic patients) were observed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Induction of hepatic mitochondrial alpha-glycerophosphate dehydrogenase by L-triiodothyronine in Singi fish (Heteropneustes fossilis Bloch)

A single injection of L-triiodothyronine (T3) in different doses (0.25, 0.5, 5, 20 and 50 micrograms/g) increased the hepatic mitochondrial cytochrome-linked alpha-glycerophosphate dehydrogenase (alpha-GPD) activity and mitochondrial protein content of Singi fish, as observed on the 3rd day. A non-linear dose-response relationship with respect to enzyme activity was observed with different doses of T3. A low dose of 0.1 micrograms of T3 per g failed to cause any change in alpha-GPD activity and mitochondrial protein content of the liver. The enhancement of alpha-GPD activity over the control level with a low and a high dose of T3, viz., 0.5 and 5 micrograms/g, was followed from the 1st to the 7th day, when it was found that enzyme activity reached the maximum level on the 3rd day and then gradually declined to the control value on the 7th day. The percentage increase in enzyme activity with 5 micrograms/g was higher than that with 0.5 microgram/g from the 2nd to 5th day. Compared to the control, these two doses of T3 caused an increase in alpha-GPD activity from the 1st to the 6th day. Cycloheximide inhibited the T3-induced increase in alpha-GPD activity, mitochondrial and total protein content of liver. Immersion of Singi fishes in thiourea-containing (1 mg/ml) medium for 30 days showed a fall in hepatic alpha-GPD activity in comparison to the euthyroid control. A single injection of T3 (0.5 microgram/g) to the hypothyroid fish recovered alpha-GPD activity to more than the euthyroid control level. An increase in mitochondrial protein content in the T3-injected hypothyroid fish has been observed. DNA content of the fish liver remained unchanged in every experimental condition. The results thus showed the significant responsiveness of the fish liver to thyroid hormone.     

The effects of age, season and geographic region on thyroid hormones in Steller sea lions (Eumetopias jubatus)

The purpose of this study was to investigate thyroid hormone concentrations, thyroxine (T4) and triiodothyronine (T3), in order to determine basal levels in Steller sea lions of different ages and over seasons. Serum concentrations of total T4 were highest in Steller sea lions followed by total T3 concentrations. Concentrations of free T4 and free T3 were three to four orders of magnitude lower. Concentrations for all four thyroid hormone measurements tended to a lower level as animals matured beyond the neonatal stage. When thyroid hormones from captive sea lions were evaluated across seasons, all thyroid hormones were highest in the July to September period. When compared across the geographic range, animals in southeast Alaska tended to have lower thyroid hormone levels, while the Steller sea lions west of Prince William Sound and animals from the Russian Far East had significantly higher concentrations. Significant inter-annual differences in concentrations were also observed across the geographic range. With an understanding of the basic changes in thyroid hormone concentrations, changes in plane of nutrition or life history states (i.e. fasting, pregnancy or lactation) can now be evaluated for their effect on the overall health of this endangered species.     

Circadian and circannual changes in the testicular function of adult rhesus monkeys

The endocrine and gametogenic status of the testes were studied in 9 healthy adult rhesus monkeys of proven fertility throughout a one-year period. Testosterone levels were estimated by radioimmunoassay in blood samples collected at 4 h intervals over a 24 h period once a month. Semen samples and testicular biopsies were also examined once a month. A well-defined circandian rhythm was evident in serum levels of testosterone. The rhythmicity was less pronounced in February and September. The 24 h mean levels of serum testosterone were high between the months of August to March and low in the months of May to July. All animals did not uniformly respond to electro-ejaculation in April and May. Semen volume and total number of spermatozoa were maximal between September and March and least from April to August. Testicular biopsies indicated that all stages of spermatogenesis were evident between September and March and the spermatogenic activity was less evident between April and August. The contents of Sertoli cells showed a seasonal cyclicity; they were laden with lipid droplets during April to August when spermatogenesis was quiescent and vacuolated during September to March when spermatogenesis was active. These studies indicate that the testing of contraceptive drugs needs to be restricted to months of September to March in male rhesus monkeys otherwise, it is possible that the naturally occurring reproductive quiscence may be attributed to the effect of the drug being tested. The data accrued from the present studies also provide quantitative information on circulating levels of testosterone which could be used as a reference background while evaluating the contraceptive drug-effects in male rhesus monkeys.     

Levels of T4, T3 and cortisol in the blood serum of the European bison (Bison bonasus) in the winter period

1. In the blood of 56 European bison, the levels of T4, T3, and the ratio of T3:T4 and cortisol were studied. 2. Between December and March, the T4 level changed from about 53 to 83 ng/ml of blood serum but in April it increased to 90 ng/ml. 3. The level of T3 in this period was 0.817-1.475 ng/ml and in April it was 2.40-3.40 ng/ml. 4. The ratio of T3:T4 was 0.015-0.024 and in April it increased to 0.027-0.052. 5. The level of cortisol changed from 1.00 to 6.70 ng/ml and in April it was from 1.00 to 14.00 ng/ml.     

The impact of seasonal alteration in the lipid composition of broodstock diets on egg quality in the European sea bass

Groups of European sea bass Dicentrarchus labrax L., broodstock were fed two pelleted, lipid-enriched diets [maize oil, low essential fatty acid (EFA) or fish oil, high EFA]. Those fed the high EFA diet for 12 months or only during vitellogenesis (September to February) with the low EFA diet fed for the remaining 6 months, showed improved egg quality and higher hatching rates when compared to two groups fed the high EFA diet during either previtel-logenesis (February to September) or the spawning period (February to April). The higher quality eggs contained higher levels of total n-3 fatty acids, including increased levels of both docosahexaenoic acid (DHA) and eicosapaentaenoic acid (EPA). High levels of triacylglycerol (TAG) were linked with the poorer quality eggs from those groups fed the low EFA diet during the period of vitellogenesis. The present work identifies vitellogenesis as the period in the maturation during which EFA are incorporated most effectively into the developing oocytes.     

Seasonal changes in the content of lipids,fatty acids,and pigments in brown alga <Emphasis Type="Italic">Costaria costata</Emphasis>

We compared the content of total lipids, particular lipid classes, fatty acids (FAs), and pigments in the brown alga Costaria costata [Turn.] Saund (Laminariaceae) in different seasons: during algal active life (April–June) and in the beginning of their degradation (the end of July). Lipids comprised only a small part of algal extractable compounds (10.9–13.4%). Their higher content was observed in May, in the period of alga preparation to sporogenesis. Polar lipids, glyceroglycolipids (GL) and phospholipids (PL), comprised a great part of total lipids in spring months and June, whereas neutral lipids, in July. GL predominated in polar lipids in spring and summer. The highest content of GL was observed in May and PL in April. Storage lipids comprised a great part of lipids in July. The content of sterols was the highest in April and May. In summer months, the content of sterols decreased and remained on unchanged level until thallus degradation. Polyunsaturated FAs (PUFAs) comprised the most part of FAs. Their highest content was observed in April. The main part of PUFAs were those of ω-3 series. In July, the level of these PUFA decreased substantially. The levels of ω-6 PUFAs were approximately similar in spring and summer months. The lowest content of monounsaturated FAs was detected in April; in May and July; the relative content of these FAs increased sharply. We also detected seasonal changes in the content of pigments and the ratios between them.     

Blood levels of thyroid hormones and certain metabolites in relation to moult in the harp seal (Phoca groenlandica)

1. Changes in blood levels of thyroxine (T4), triiodothyronine (T3), free fatty acids (FFA), glucose, pyruvic acid and lactic acid in the harp seal during moult, were studied. 2. Serum levels of both T4 and T3 showed significant increase in the moult phase from that in the pre-moult phase. While T4 level continued to remain high during the early and late post-moult phases, T3 level dropped in the latter two phases to the same low pre-moult level. 3. The T3/T4 ratio was significantly higher during the pre-moult phase than that in all the other phases. It is suggested that the high pre-moult T3/T4 ratio marks the initiation of moult. 4. There were no significant changes in the levels of the metabolites studied except that of FFA which was highest in the moult phase indicating the hormonal basis of lipid mobilization.     

Testicular development and serum sex steroid profiles during the annual sexual cycle of the male sturgeon hybrid the bester

Testicular development in the adult male F₁ sturgeon hybrid, the bester ( Huso huso L. female x Acipenser ruthenus L. male), was examined monthly in relation to serum sex steroid levels. Spermatogenesis lasted for 1 year, with meiosis generally starting in September and spermiogenesis in November, although there was considerable variation in testicular developmental stages between fish sampled monthly. Testicular development continued, slowly, during the winter months until April. Fish did not exhibit spontaneous spermiation, and phagocytotic activity of Sertoli cells became prominent from May onwards. Androgen levels increased during Spermatogenesis and remained high throughout the pre-spermiation period. In the degeneration stage, 11-ketotestosterone concentrations declined to low levels, while testoster- one levels remained high. The serum concentration of 17,20β-dihydroxy-4-pregnen-3-one was low throughout the reproductive cycle. Based on these results, it is suggested that the time appropriate for induction of final maturation would be from November–December to April when the testes are in the late stage of development.     

Seasonal changes in thyroid-gonadal interactions in the edible dormouse,Glis glis

Summary This study was conducted to determine changes in thyroid-gonadal interaction in the edible dormouse during the phase of the annual cycle that corresponds to the end of the breeding season (from June to September). We evaluated intra-hypothalamic luteinizing hormone-releasing hormone (LHRH) content, and plasma concentrations of luteinizing hormone (LH), testosterone, thyroid-stimulating hormone (TSH) and thyroxine (T4) in three groups of dormice: (1) controls; (2) dormice receiving sufficient T4 supplementation to maintain June levels in control animals until September, thus counteracting the seasonal reduction of T4 that normally begins in July; and (3) thyroidectomized dormice. The effect of thyroidectomy was only detectable in June, when plasma T4 concentration in the control group was maximal, and consisted of a significant decrease in plasma testosterone levels. This provides strong support for the hypothesis that thyroid function positively influences gonadal function during the breeding season. The T4 supplementation resulted in a decrease in hypothalamic LHRH concentration, suggesting that an increased LHRH release led to the observed stimulated hypophyseal secretion of LH in June and September and the increased circulating testosterone levels in September. There was no detectable effect in July and August. These results show that thyroid axis activation of the hypothalamic-pituitary-gonadal system is only possible during certain phases of the annual cycle, particularly evidenced here during the breeding season. They also reinforce our conclusions drawn from the thyroidectomy results. Conversely, the summer testicular regression which normally occurs after the breeding season is no longer controlled by plasma T4 levels. Even though the sensitivity of the gonadal axis to the thyroid axis appears to reappear at the end of the summer, results of previous studies indicate that this resumption is only temporary.Abbreviations LH luteinizing hormone - LHRH luteinizing hormone-releasing hormone - RIA radioimmunoassay - T4 thyroxine - TSH thyroid-stimulating hormone     

Effect of graded doses of tri-iodothyronine on ventricular myosin ATPase activity and isomyosin profile in young and old rats.

Ventricular myosin ATPase activity, V1 isomyosin content and serum T3 (tri-iodothyronine) values decrease with age in male Fischer 344 rats. To determine if the age decrement in ATPase activity and V1 isomyosin content are caused by decreased T3 levels or an age-related decrease in V1 isomyosin induction by T3, 3-, 12- and 24-month-old male Fischer 344 rats were given constant T3 infusions by osmotic minipump. Rats at all ages were given 0.75, 5 and 15 micrograms(/100 g per 24 h) doses of T3, whereas 12- and 24-month-old rats were given an additional 0.4 microgram dose. In control rats, T3 levels decreased from 97 +/- 2.7 at 3 months to 75 +/- 4.7 ng/100 ml at 24 months. Likewise, Ca2+-activated myosin ATPase activity decreased from 1.04 +/- 0.05 to 0.68 +/- 0.05 mumol of Pi/min per mg of protein, and the relative proportion of V1 of isomyosin decreased from 90 +/- 4.0 to 26 +/- 2.0%. The lowest (0.4 microgram) T3 dose, which was sufficient to restore T3 levels in 24-month-old animals to 3-month control values, abolished the age decrement in myosin ATPase activity and markedly increased the proportion of V1 isomyosin present in the ventricle. These findings indicate that the senescent ventricle responds readily to small doses of T3 and strongly suggest that the age decrement in serum T3 levels is sufficient to contribute to the age-related decrease in myosin ATPase activity and V1 isomyosin content. Since these parameters correlate with ventricular contractility, the age decrement in T3 levels may also contribute to the decreased ventricular contractility and cardiac output observed in senescent rats.     

Thyroxine-induced changes of hepatic glucose-6-phosphatase activity and glycogen, protein, RNA and DNA contents in the rat

Thyroxine (T4) in a dose of 0.1 microgram per g body weight caused in the rat a significant increase in hepatic glucose-6-phosphatase activity, while a reduction of this enzyme activity was observed after 1 microgram of T4 per g. The hepatic glycogen content was found to be depleted and a marked elevation in protein, RNA and DNA contents were observed after both doses of T4.     

Circadian and circannual rhythms of LH, FSH, testosterone (T), prolactin, cortisol, T3 and T4 in plasma of mature, male white-tailed deer

Circadian and circannual rhythm of plasma LH, FSH, testosterone (T), prolactin, cortisol, triiodothyronine (T3) and thyroxine (T4) were investigated in two mature male white-tailed deer. No circadian rhythms were detected. Seasonal levels of LH and FSH were reached in September and October; troughs occur in May and June. Maximal T values were detected in November and December (the time of the rut); minimal levels occur between February and July. Prolactin peaked in May and June; minimal levels were detected between October and February. T3 exhibited two maxima; the first in the May-June period, the second in the September-October period. T4 showed no recognizable circannual rhythm. Cortisol levels were found to be much higher during cold months (December-April) than during the rest of the year. The least variable circadian levels were that of FSH and prolactin, with LH, T4, T3, cortisol and testosterone following in descending order. Cannulation stress might have some effect on the levels of testosterone, LH and cortisol. Correlation between LH and testosterone levels were detected mainly during sexually active periods.     

Comparison between the thyrotropin response to thyrotropin-releasing hormone in summer and that in winter in normal subjects.

A comparison was made between the thyrotropin (TSH) response to 500 microgram thyrotropin-releasing hormone (TRH) in summer and that in winter in ten healthy normal adults living in Supporo. The serum resin triiodothyronine (T3) uptake (RT3U), thyroxine (T4) and T3 levels were also measured. While the TSH response to TRH in summer was similar to that in winter, serum T3 concentration and free T3 index were significantly higher in winter than in summer, associated with the similar values in RT3U and T4 levels in serum. Independently measured 86 specimens (43 in summer and 43 in winter) from normal adults living in the same district also showed a significant increase in serum free T3 index as well as a slight elevation of serum T3 concentration in winter but not in serum T4 level. These results indicate that the primary change in cold winter would be the stimulation of peripheral conversion of T4 to T3 rather than the activation of hypothalamo-pituitary-thyroid axis. The relevance of this interpretation was discussed.