Molecular cloning of the cDNA encoding the β subunit of thyrotropin and regulation of its gene expression by thyroid hormones in the goldfish, Carassius auratus

A cDNA encoding the subunit of thyrotropin (TSH) was isolated from a goldfish (Carassius auratus) pituitary gland cDNA library. By comparing the sequence with other teleost TSHs, a signal peptide of 19 amino acids and a mature hormone of 131 amino acids were predicted for goldfish TSH subunits. The resulting putative mature hormone of 131 amino acids had well-conserved cysteine positions and a putative N-linked glycosylation site; homology was 51–67% with TSHs from other teleosts, 38–43% with tetrapod TSHs, but only 27 and 29% with goldfish GTH-I and -II, respectively. We also examined the effects of thyroid hormones (TH) and thiourea (TU, an inhibitor of TH production) treatments on TSH and GTH subunit gene expressions in the goldfish pituitary gland. After thyroxine (T₄) treatment, circulating T₄ concentration increased and TSH mRNA level decreased. Supressing the amount of circulating T₄ and triiodothyronine (T₃) by TU treatment increased the TSH mRNA level. Moreover, T₄ replacement therapy (simultaneous treatment of both TU and T₄) caused a high level of circulating T₄ and a low level of circulating T₃, and a decrease in the TSH mRNA level. Thus, changing levels of circulating TH exert a negative feedback on the level of TSH subunit mRNA in goldfish in vivo. On the other hand, GTH subunit mRNA levels were not affected by changes in the levels of circulating TH.     

Stimulation of acetylcholinesterase activity by triiodothyronine in the brain of Singi fish,Heteropneustes fossilis (Bloch)

Three consecutive days of injections of triiodothyronine (T₃)(0.038, 0.075, 0.15 and 1.54 nmoles/g) significantly elevated the acetylcholinesterase (AchE) activity in the brain of Singi fish, Heteropneustes fossilis (Bloch). The higher doses of 0.075, 0.15 and 1.54 nmoles of T₃/g induced a greater increase in enzyme activity than 0.038 nmoles/g. A T₃ dose of 0.019 nmoles/g was found to be ineffective. The T₃ action on AchE activity was blocked by cycloheximide. Thiourea treatment for 30 days decreased the AchE activity below the control level. This reduced level of the enzyme activity was brought back even above the control level by T₃ injections. It is, therefore, suggested that thyroid hormone is involved in the sustenance of AchE activity in fish brain.     

Temporal changes in plasma thyroid hormone,growth hormone and free fatty acid concentrations,and hepatic 5′-monodeiodinase activity,lipid and protein content during chronic fasting and re-feeding in rainbow trout (Oncorhynchus mykiss)

Temporal changes in growth, plasma thyroid hormone, cortisol, growth hormone (GH) and non-esterified fatty acid (NEFA) concentrations, hepatic T₃ content and hepatic 5-monodeiodinase activity were measured in rainbow trout (Oncorhynchus mykiss) subjected to a sustained fast for up to eight weeks, and during a four-week re-feeding period. The purpose of the study was to examine aspects of the endocrine control of energy partitioning processes characteristic of short-term (acute; fasting) and long-term (chronic; starvation) food-deprivation states in fish, and to explore the role of the thyroid hormones, cortisol and GH in the energy repartitioning that takes place during an acute anabolic (re-feeding) state following chronic food deprivation.Differences in growth rate between fed and fasted groups were evident after two weeks, but significant weight loss by the fasted groups was not evident until between four and six weeks into the fast. Hepatosomatic indices (HSIs) were significantly reduced in the fasted fish within seven days, and as early as two days in one study; recovery of the HSI in fasted fish was evident within three days of re-feeding. Liver protein content (expressed as % wet weight) was consistently depressed in the fasted fish in only one of the three studies. Liver total lipid content (expressed as % wet weight) was depressed in the fasted fish within two days of food deprivation. Because of the rapid and sustained decrease in the HSI of fasted fish, the hepatic total protein and lipid reserves, when considered on a body weight basis, were markedly lowered within the first few days of the fast. Plasma GH concentrations exhibited a bi-modal pattern of change, with a transient fall in levels, followed by a sustained increase in fasted fish. The indicators of interrenal activity were suggestive of a depressed pituitary-interrenal axis in fasted animals; plasma cortisol levels were elevated to levels of fed animals within one day of re-feeding. The indicators of thyroid hormone economy (plasma thyroid hormone levels, liver triiodothyronine content, hepatic 5-monodeiodinase (MD) activity, thyroid epithelial cell height) were similarly indicative of a depressed pituitary-thyroid axis in fasted animals, with recovery to levels of the fed animals within one week. Despite the compensatory changes in accumulation of reserves (as indicated by a compensatory increase in HSI), there were no apparent compensatory changes in any of the endocrine parameters evident during the re-feeding period.     

菜籽粕对肉用仔鸡血清中甲状腺激素浓度和生产性能的影响

用放射免疫分析法研究了菜籽粕对肉用仔鸡血清中甲状腺激素(T_3和T_4)浓度的影响,考察了生产性能,比较研究了仔鸡性别对菜籽粕的不同反应。结果表明:1.12％菜籽粕使仔母鸡血清三碘甲腺原氨酸浓度均值显著降低(P<0.05),尤其在饲喂菜籽粕5周以内影响更大,而对仔公鸡没有显著影响;2.12％籽菜粕对仔鸡血清甲状腺素浓度无显著影响,但前期血清甲状腺素浓度略有增加,后期略为下降;3.12％菜籽粕使仔鸡前期增重减少,料肉比增加,但对后期生产性能没有显著不良影响;4.12％菜籽粕导致仔鸡甲状腺显著增大(P<0.05),而对肝重、肾重和脾重则无显著影响:5.12％菜籽粕组8周龄仔鸡血浆中未检出恶唑烷硫酮和异硫氰酸酯等毒素。     

低温和添加三碘甲状腺原氨酸致肉鸡肺动脉高压综合征的自由基变化

将 2 4 0羽AA商品肉鸡 ,随机分为A ,B ,C组 ,参试鸡 1～ 14日龄常规饲养 ,14日龄后A组鸡仍常规饲养 ,而B和C组的鸡舍温度按每日 1～ 2℃由 2 5℃逐步降至 12℃ ,同时C组日粮中按 1 5mg·kg-1的剂量添加三碘甲状腺原氨酸T3 以诱发PHS。结果显示 ,低温和添加T3 极显著地增加了肉鸡PHS发病率、血液PCV值及血浆、肺、心和肝组织的MDA值 ,显著增加了心脏指数RV/TV值 ,极显著降低了血浆、肺、心和肝组织的SOD值。表明低温和T3 已成功地诱发了肉鸡PHS ,其发病机制可能与肉鸡已产生了大量的自由基并发生了一系列的脂质过氧化链锁反应有关     

Epidemiology and diagnosis of subclinical iodine deficiency in crossbred cattle of Punjab.

OBJECTIVE: To determine the prevalence of iodine deficiency in crossbred cows (taurus x indicus) of Punjab and to assess the diagnostic value of the plasma concentrations of thyroid hormones, total cholesterol and free fatty acids in iodine deficiency. The efficacy of ethiodised oil, as a long-term supplement of iodine, was also evaluated. PROCEDURES: Base-line survey of iodine status was conducted by measuring plasma inorganic iodine (PII) concentration in 48 crossbred cows from 31 dairy units. Concentrations of plasma triiodothyronine (T3), thyroxine (T4), total cholesterol and free fatty acids were compared between iodine deficient and normal cows. Circulating T4 and T3 concentrations were also determined before and after injection of ethiodised oil in cows with low PII levels. RESULTS: The mean prevalence of iodine deficiency was 35.9% and showed considerable geographical variation from 0 to 86% within Punjab. Cardinal clinical signs of iodine deficiency were absent and basal plasma T3 and T4 concentrations and their ratio did not differ between deficient and control cows. Activity of circulating T4 and T4:T3 ratio increased in response to ethiodised oil injection and persisted beyond 70 days after injection. CONCLUSION: Asymptomatic iodine deficiency is prevalent in crossbred cows of Punjab and response to iodine supplementation is the most reliable index of thyroid dysfunction associated with iodine deprivation. The results of this study also support the view that injection of 1 mL of 78% ethiodised oil can prevent iodine deficiency for more than 70 days.     

牙鲆let-7基因的克隆与表达及其靶基因预测

let-7是时序发育过程中的重要调控因子,在促进幼体向成体转变过程中起着极其重要的作用.为探讨let-7对牙鲆(Paralichthys olivaceus)从幼体到成体转变的变态发育过程的影响,本实验对let-7进行了克隆与表达研究,并预测了其可能的靶基因.利用普通PCR技术从牙鲆中成功鉴定出let-7及其前体序列,...     

Effect of cortisol and triiodothyronine bath treatments on the digestive enzyme profile and growth of Catla catla larvae during ontogenic development

Digestive enzyme profile is a good indicator of the nutritional and health status of the fish. The present investigation aims to evaluate the effect of exogenous bath treatment of hormones, cortisol and triiodothyronine, on the digestive enzyme activities and growth of carp Catla catla (Ham.) during ontogenic development. Catla larvae (4 days old) were given bath treatment with cortisol (hydrocortisone, 0.2 mg L^?1), 3,5,3′‐triiodothyronine (T3, 2.5 mg L^?1) and a combination of cortisol and T3 for 30 min. Digestive enzyme profile was recorded on every third day and was continued for 30 days. Larvae were fed with live food for initial 14 days and then weaned to mix feeding of live food and prepared diet. Significantly (P < 0.05) higher amylase, total protease, trypsin, chymotrypsin, lipase, chitinase and chitinobiase activities were found in the hormone‐treated groups compared to the control one during ontogenic development. Among the treated groups, amylase activity was highest in cortisol‐treated larvae. Total protease, trypsin, chymotrypsin, lipase, chitinase and chitinobiase activities were significantly (P < 0.05) higher in larvae exposed at combined treatment of cortisol and T3 compared to the other two groups in most sampling days. Average length, weight and specific growth rate of treated larvae were higher compared to the control one. The combined bath treatment of cortisol and triiodothyronine influenced the digestive enzyme activities of catla larvae and thereby enhanced the growth at early developmental stage. This helps the larvae to overcome the problems associated with early developmental stage.     

Selenium supplementation changes glutathione peroxidase activity and thyroid hormone production in Senegalese sole (Solea senegalensis) larvae

Dietary selenium (Se) influences the glutathione peroxidase (GPx) activity and the thyroid hormone system in vertebrates, but these relations are poorly described in fish. The present study aimed to evaluate the effect of Se supplementation on Senegalese sole larvae, focusing on GPx activity and thyroid status. Two groups of larvae were fed on either control (C) or Se‐enriched live feed, from 2 days after hatch (DAH) until 34 DAH. Senegalese sole larvae fed Se‐enriched live feed significantly increased their whole‐body Se, compared to larvae from C group. The activity of GPx was higher in larvae from Se group, suggesting that the levels of this mineral were suboptimal in the control diet. TH levels were also higher in larvae fed Se‐enriched live feed, suggesting that Se may have a positive influence on the TH production in early life stages of marine fish larvae.     

玉米蛋白粉替代鱼粉对异育银鲫生长和甲状腺激素水平的影响

分别用0%(对照组)、4%、8%和12%玉米蛋白粉替代饲料中0%、33.33%、66.67%和100%的鱼粉配制4种等氮、等能的试验饲料,在室内循环养殖系统中饲养初始体质量为(13.68±1.77)g异育银鲫60d,研究玉米蛋白粉替代鱼粉对异育银鲫生长的影响,同时以15d为采样间隔研究鱼体血清中三碘甲腺原氨酸(T3)和甲状腺素(T4)含量的变化。结果表明:对照组与8%替代组的饲料系数无显著差异,且均显著低于4%和12%替代组;玉米蛋白粉对异育银鲫生长无显著影响;饲养30到60d对血清中T3含量无显著影响,而15d对照组血清中T3含量显著高于其余各替代组;30d时4%和8%替代组血清中T4含量与对照组无显著差异,而12%替代组显著低于对照组,而60d时与对照组无显著差异;60d时,各组鱼体的生长与T3、T4含量变化趋势相同。在本实验条件下,玉米蛋白粉在异育银鲫饲料中的适宜用量为4%～8%,对鱼粉的适宜替代量为33.33%～66.67%。