Plasma Thyroid Hormone Levels Research Articles

Fasting increases the phosphorylation of AMPK and expression of sirtuin1 in muscle of adult male northern elephant seals ( Mirounga angustirostris )

Fasting typically suppresses thyroid hormone (TH)‐mediated cellular events and increases sirtuin 1 (SIRT1) activity. THs may regulate metabolism through nongenomic pathways and directly through activation of adenosine monophosphate‐activated protein kinase (AMPK). Adult male elephant seals (Mirounga angustirostris) are active, hypermetabolic, and normothermic during their annual breeding fast, which is characterized by stable TH levels. However, the contribution of TH to maintenance of their fasting metabolism is unknown. To investigate the fasting effects on cellular TH‐mediated events and its potential association with SIRT1 and AMPK, we quantified plasma TH levels, mRNA expressions of muscle SIRT1 and TH‐associated genes as well as the phosphorylation of AMPK in adult, male northern elephant seals (n = 10/fasting period) over 8 weeks of fasting (early vs. late). Deiodinase type I (DI1) expression increased twofold with fasting duration suggesting that the potential for TH‐mediated cellular signaling is increased. AMPK phosphorylation increased 61 ± 21% with fasting suggesting that cellular metabolism is increased. The mRNA expression of the TH transporter, monocarboxylate transporter 10 (MCT10), increased 2.4‐fold and the TH receptor (THrβ‐1) decreased 30‐fold suggesting that cellular uptake of T4 is increased, but its subsequent cellular effects such as activation of AMPK are likely nongenomic. The up‐regulation of SIRT1 mRNA expression (2.6‐fold) likely contributes to the nongenomic activation of AMPK by TH, which may be necessary to maintain the expression of PGC‐1α. These coordinated changes likely contribute to the up‐regulation of mitochondrial metabolism to support the energetic demands associated with prolonged fasting in adult seals.

Unraveling the different toxic effect of flufenoxuron on the thyroid endocrine system of the Mongolia racerunner (Eremias Argus) at different stages

Flufenoxuron is a widely used pesticide to inhibit the synthesis of chitin during insect development and its effect on the growth of lizards has been little addressed. The hypothalamus-pituitary-thyroid (HPT) axis plays an important role on the development of lizards. In this study, the lizards at different development stages (proliferation and resting stages) were exposed to flufenoxuron for 21 days. The plasma thyroid hormone levels, thyroid gland histopathology and expression profiles of thyroid hormone receptors (trα, trβ), deiodinases (dio1, dio2), and transthyretin (ttr) genes were measured to evaluated the toxic effect of flufenoxuron on the HPT axis at different stages. The flufenoxuron exposure showed more seriously effect on the triiodothyronine (T3) level at resting phase than that at proliferation stage. The follicle epithelium cell height in the thyroid was only significantly increased when the exposed male lizards were at proliferation stage. The alteration of HPT axis-related genes expression was gender and tissue dependent after flufenoxuron treatment. The lizards exposed to flufenoxuron showed that the trα, trβ, dio1, dio2, and ttr genes in the female liver were more sensitive at the proliferation stage than that at the resting stage. In the male brain, the expressions of trα, trβ, dio1, and dio2 gene were significant decreased at proliferation stage while significant increased at resting stage after flufenoxuron exposure. Therefore, the thyroid endocrine system of lizards could be affected by the flufenoxuron exposure and the different development stage should also be considered when study the toxic effect of contaminants on the lizards.

Plasma antioxidant capacity, sexual and thyroid hormones levels, sperm quantity and quality parameters in stressed male rats received nano-particle of selenium

Objective: To evaluate the effects of nano-particle of selenium (nSe) on plasma antioxidant capacity, sexual and thyroid hormones and spermatogenesis in male rats exposed to oxidative stress. Methods: Forty rats were randomly divided into four treatments with ten replicates. Treatment groups were: C, the control group received normal saline as gavage and injection (i.p.); OS, received tert-butyl hydroperoxide (0.2 mmol/kg body weight) for inducing oxidative stress; nSe, received nSe (0.3 mg/kg body weight) as gavage, and OS+nSe, received tert-butyl hydroperoxide and nSe. All groups were treated for 28 d and administrations were done each 48 h. Results: Oxidative stress decreased and gavage of nSe to stressed rats increased the antioxidant capacity and activities (P 0.05) between rats exposed to oxidative stress and those in the control group for sperm quantity and quality. Gavage of nSe to stressed rats had no effect (P>0.05) on the sperm parameters, except increased viability and progressive percentages. Conclusions: Nano-particle of Selenium administration in stressed rats could ameliorate the negative effects of oxidative stress on the antioxidant capacity and activities, but not on the quantity and quality parameters of sperm.

A validated LC-MS/MS method for thyroid hormone determination in sea lamprey (Petromyzon marinus) plasma, gill, kidney and liver.

A UPLC-MS/MS method was developed to provide a reproducible, sensitive and quantitative assay to determine thyroid hormones in sea lamprey tissues and plasma. l-Thyroxine (T4) and its two triiodo-thyronine isomers have been simultaneously quantified and validated for plasma, gill, liver, and kidney matrices. Multiple sample preparation techniques were investigated to achieve optimal sample matrix digestion and clean-up. Enzymatic digestion followed by protein precipitation was selected to process the samples. The developed method exhibited excellent linearity for all analytes with regression coefficients higher than 0.99 for concentrations ranged from 10 to 50,000pg/mL. The limit of detection (LOD) was under 1pg/mL while the limit of quantification (LOQ) was estimated as 10pg/mL. This method was validated according to the FDA guidance and applied to determine thyroid hormone levels in plasma, gill and kidney of sea lamprey exposed to a sex pheromone. With appropriate implementation and further validation, this method could be applied to tissues in other species including humans.

The physiological consequences of ingesting a toxic plant (Diplotaxis tenuifolia) influence subsequent foraging decisions by sheep (Ovis aries)

Toxins and nutrients interact and define herbivores' experiences with toxic plants. However, there are still open questions about the mechanisms by which nutrient-toxin interactions affect experience and as a consequence foraging decisions by consumers. This study provides a deeper insight into such mechanisms by using supplemental nutrients, a toxic plant typically avoided by herbivores (wild rocket; Diplotaxis tenuifolia), and a small ruminant (sheep; Ovis aries) as models. Thirty-six sheep were randomly assigned to four treatments (n=9) where animals consumed: wild rocket (“DT”), wild rocket followed by a protein supplement (“DT+P”), wild rocket followed by a protein supplement+a mineral supplement containing iodine and copper (“DT+P+M”), or alfalfa pellets in amounts that paired the ingestion of wild rocket by DT (“CTRL”). Towards the end of the phase of exposure (day 35), DT showed the lowest intake of wild rocket, as well as reduced levels of plasma thyroid hormones (T3 and T4), alanine aminotransferase, and a trend towards reduced hemoglobin relative to DT+P and DT+P+M. Total concentration of serum proteins and albumins were greater in sheep fed the protein supplements, which have probably elicited a protective effect on toxin ingestion. Foraging behavior was then evaluated in an experimental arena where animals could select among randomly distributed buckets containing a fixed amount of wild rocket or variable amounts of barley grain (a preferred food). Regardless of barley grain availability, DT showed lower intake and lower times spent eating wild rocket than DT+P and DT+P+M. Unexpectedly, CTRL (without previous experience with wild rocket) ingested amounts of wild rocket comparable to those observed by DT+P and DT+P+M. A negative feeding experience with wild rocket is needed for animals to display the typical pattern of aversion commonly observed in grazing conditions.

Effects of dietary prebiotic GroBiotic®-A on growth performance, plasma thyroid hormones and mucosal immunity of great sturgeon,Huso huso(Linnaeus, 1758)

Summary The present study was conducted to evaluate the effects of Grobiotic®-A, a commercial prebiotics, when administered in feed on the growth performance, plasma thyroid hormones and mucosal immunity of great sturgeon (Huso huso). The commercial prebiotic mixture was supplemented in the diets at four different levels (i.e. 0.0% as control, 0.5%, 1% and 2%, in three replicates, 20 fish per replicate) and fed to the fish for an 8-week period wherein 240 fish were cultured in 1,800-L fiberglass tanks that formed part of a flow-through system. Water temperature was maintained at 20.4 ± 1.5°C. Significant changes in growth performance parameters were observed, but only in those groups fed with 1% and 2% prebiotics. Specifically, marked improvements relative to the control group were observed in percentage weight gain, body weight gain, feed conversion ratio and specific growth rate in prebiotic-fed fish. The levels of plasma thyroid hormones, specifically thyroxine and thyroid stimulating hormones were significantly elevated in the group receiving 2% prebiotics. Activities of lysozyme and alkaline phosphatase in skin mucus were significantly enhanced in prebiotics-fed groups, particularly at an inclusion level of 1% and higher (2% group compared to the control). Inhibitory activity of the skin mucus against pathogens, particularly Streptococcus iniae and Yersinia ruckeri, was significantly improved following prebiotic feeding. Taken together, dietary inclusion of GroBiotic®-A promoted growth, modulated thyroid hormones, and enhanced mucosal immunity of H. huso. This prebiotic mixture has the potential for use in improving the growth performance and health status of farmed great sturgeon.

Associations between Repeated Measures of Maternal Urinary Phthalate Metabolites and Thyroid Hormone Parameters during Pregnancy.

Background:Maintaining thyroid homeostasis during pregnancy is essential for normal fetal growth and development. Growing evidence suggests that phthalates interfere with normal thyroid function. Few human studies have investigated the degree to which phthalates may affect thyroid hormone levels in particularly susceptible populations such as pregnant women.Objectives:We examined the associations between repeated measures of urinary phthalate metabolites and plasma thyroid hormone levels in samples collected at up to four time points per subject in pregnancy. Additionally, we investigated the potential windows of susceptibility to thyroid hormone disturbances related to study visit of sample collection.Methods:Data were obtained from pregnant women (n = 439) participating in a nested case–control study of preterm birth with 116 cases and 323 controls. We measured 9 phthalate metabolite concentrations in urine samples collected at up to four study visits per subject during pregnancy (median = 10, 18, 26, and 35 weeks of gestation, respectively). We also measured a panel of thyroid function markers in plasma collected at the same four time points per subject during pregnancy.Results:Although our results were generally null, in repeated measures analyses we observed that phthalate metabolites were largely inversely associated with thyrotropin and positively associated with free and total thyroid hormones. Cross-sectional analyses by study visit revealed that the magnitude and/or direction of these relationships varied by timing of exposure during gestation.Conclusions:These results support previous reports showing the potential for environmental phthalate exposure to alter circulating levels of thyroid hormones in pregnant women.Citation:Johns LE, Ferguson KK, McElrath TF, Mukherjee B, Meeker JD. 2016. Associations between repeated measures of maternal urinary phthalate metabolites and thyroid hormone parameters during pregnancy. Environ Health Perspect 124:1808–1815; http://dx.doi.org/10.1289/EHP170

Arterial Stiffness and Central Hemodynamics in Thyroidectomized Patients on Long-Term Substitution Therapy with Levothyroxine.

Long-term levothyroxine (LT4) therapy targeting thyrotropin (TSH) suppression in hypothyroid patients treated for thyroid cancer has been associated with increased arterial stiffness and increased cardiovascular mortality. However, most patients with hypothyroidism receive LT4 therapy targeting TSH in the reference range. The long-term vascular effects of this strategy have never been evaluated. Arterial stiffness and central hemodynamics were studied in 30 thyroidectomized patients (Mage = 54.5 ± 10.2 years; 80% female) on long-term (median = 11 years; range 3-41 years) LT4 replacement therapy targeting TSH in the reference range and 30 sex- and age-matched controls. Arterial stiffness was evaluated by carotid-femoral pulse wave velocity (PWV) and central hemodynamics by pulse wave analysis using the SphygmoCor system. TSH levels were comparable in patients and controls (median = 1.99 × 10(3) IU/L [range 0.24-5.64 × 10(3) IU/L] vs. median = 2.13 × 10(3) IU/L [range 0.59-5.63 × 10(3) IU/L]; p = 0.69), but patients had higher plasma thyroxine and lower plasma triiodothyronine levels than controls (median = 108 nmol/L [range 84-149 nmol/L] vs. 86 nmol/L [range 59-141 nmol/L]; p < 0.001 and median = 1.49 nmol/L [range 1.00-2.37 nmol/L] vs. 1.62 nmol/L [range 1.18-2.09 nmol/L]; p = 0.04, respectively). PWV was not significantly higher in patients compared to controls (8.2 ± 1.9 vs. 7.9 ± 1.9 m/s, p = 0.69). Similarly, no group differences were observed in central systolic/diastolic blood pressure (120 ± 16 mmHg vs. 119 ± 12 mmHg, p = 0.77; and 80 ± 11 mmHg vs. 80 ± 10 mmHg, p = 0.98, respectively), the augmentation index (28 ± 13% vs. 29 ± 8%, p = 0.72), or the pulse pressure amplification ratio (129 ± 17% vs. 124 ± 13%, p = 0.18). Despite subtle differences in plasma levels of thyroid hormones, long-term LT4 replacement therapy targeting TSH in the reference range does not seem to cause adverse effects on arterial stiffness and central hemodynamics.

Cardioprotective effects of lipoic acid, quercetin and resveratrol on oxidative stress related to thyroid hormone alterations in long-term obesity

This study investigated possible mechanisms for cardioprotective effects of lipoic acid (LA), quercetin (Q) and resveratrol (R) on oxidative stress related to thyroid hormone alterations in long-term obesity. Female C57BL/6 mice were fed on high-fat diet (HFD), HFD+LA, HFD+R, HFD+Q and normal diet for 26weeks. Body weight, blood pressure, thyroid hormones, oxidative stress markers, angiotensin converting enzyme (ACE), nitric oxide synthase (NOS) and ion pump activities were measured, and expression of cardiac genes was analyzed by real-time polymerase chain reaction. HFD induced marked increase (P<.05) in body weight, blood pressure and oxidative stress, while plasma triidothyronine levels reduced. ACE activity increased (P<.05) in HFD mice (0.69±0.225U/mg protein) compared with controls (0.28±0.114U/mg protein), HFD+LA (0.231±0.02U/mg protein) and HFD+Q (0.182±0.096U/mg protein) at 26weeks. Moreover, Na+/K+-ATPase and Ca2+-ATPase activities increased in HFD mice whereas NOS reduced. A 1.5-fold increase in TRα1 and reduction in expression of the deiodinase iodothyronine DIO1, threonine protein kinase and NOS3 as well as up-regulation of AT1α, ACE, ATP1B1, GSK3β and Cja1 genes also occurred in HFD mice. Conversely, LA, Q and R inhibited weight gain; reduced TRα1 expression as well as increased DIO1; reduced ACE activity and AT1α, ATP1B1 and Cja1 gene expression as well as inhibited GSK3β; increased total antioxidant capacity, GSH and catalase activity; and reduced blood pressure. In conclusion, LA, resveratrol and quercetin supplementation reduces obesity thereby restoring plasma thyroid hormone levels and attenuating oxidative stress in the heart and thus may have therapeutic potential in heart diseases.

Short Term, Low Dose Thyroxin Treatment of Euthyroid Patients with Type 2 Diabetes improves Peripheral Blood Flow and Overall Insulin Sensitivity

Purpose: Variation of plasma thyroid hormone levels influences insulin sensitivity and peripheral glucose disposal. High thyroxin dose administration to healthy humans induces insulin resistance, whereas moderate doses increase peripheral glucose disposal. An open-labeled, randomized and placebo-controlled intervention was performed in euthyroid type 2-diabetic patients, to examine the effect of a small thyroxin dose within the euthyroid range on postprandial forearm muscle glucose uptake, insulin sensitivity, in vitro glucose uptake and GLUT4 recruitment in the plasma membrane of monocytes. Methods: A meal was given to eleven euthyroid, treatment-naive, type-2 diabetic patients (aged 43 ± 3.8 yrs, BMI 27.48 ± 1.39 kg/m2, T3 119 ± 5.7 ng/dl, T4 8,13 ± 0.46 μg/dl, TSH 1.51 ± 0.14 μU/ml, FT4 1.272 ± 0.047 ng/dl) before and after administration of 50 μg of thyroxin once daily for 2 months. Similarly, a placebo was given to eleven age, sex and BMI-matched euthyroid, type-2 diabetic patients. Blood was drawn for 300 min from a forearm deep vein and the radial artery for measurements of glucose, insulin, and GLUT4 abundance in peripheral monocytes. Forearm blood flow (BF) was measured with strain-gauge-plethysmography. Forearm glucose-uptake, and insulin sensitivity were assessed. After the first meal-tolerance-test, daily treatment with 50 μg of thyroxin or placebo was initiated for a 2-month period. Then a second identical test was repeated. Results: TSH, glucose, insulin levels and HbA1c reduced significantly in the treatment group. Peak-baseline BF and Glucose-uptake (AUC0-300 min) increased significantly (1.685 ± 0.3 vs. 3.07 ± 0.15 ml/min per 100 cc tissue, p=0.0018) and (587 ± 68 vs. 1015 ± 131 μmol per 100 cc tissue, p=0.0051), respectively. All insulin-sensitivity indices improved post-treatment. Glucose uptake and GLUT4 abundance in monocytes also improved. The placebo group exhibited no change in all variables. Conclusion: Administration of small, subthyrotoxic doses of thyroxin to euthyroid diabetic patients improves peripheral glucose disposal, blood flow responses and overall insulin sensitivity. This could be of therapeutic importance by reducing the burden of hyperglycaemia and possibly the long term complications of diabetes.

Effect Of Organic Selenium And Iodine Supplementation On Selenium And Thyroid Hormones Status Of Lactating Ewes And Lambs

Abstract The aim of this research was to determine the influence of 56-days (from day 4 to day 60 post partum) of simultaneous supplementation of selenium (Se) and iodine (I) enriched Chlorella algae on blood and urine Se concentrations and thyroid hormone levels in ewes and lambs. The study included 18 Šumava sheep ewes and their lambs divided into three groups (CON, HSe, HSeI). Selenium and I content in the diet of ewes measured 0.2 and 0.7 mg (CON), 0.4 and 0.7 mg (HSe), 0.4 and 1.3 mg (HSeI) per kg of dry matter. During the experimental period a significantly higher blood serum Se concentration was determined in ewes of the HSeI group (P&lt; 0.001) and urine (P&lt; 0.01). A significantly higher (P&lt; 0.001) blood serum Se concentration was found also in lambs of the HSeI group. The highest Se concentration in the blood serum was recorded in ewes (128.0 μg/L) and lambs (74.2 μg/L) on the 26th day of the experiment. The results demonstrate a higher utilization of Se administered in the organic form accompanied by a higher intake of I applied also in the organic form. Plasma thyroid hormone levels in ewes were not explicitly affected by higher Se and I supplementation. A higher Se concentration in the lambs’ blood serum led to significantly higher (P&lt; 0.05) T3 levels up to 30 days post birth.

Neonatal Persistent Exposure to 6-Propyl-2-thiouracil, a Thyroid-Disrupting Chemical, Differentially Modulates Expression of Hepatic Catalase and C/EBP-β in Adult Rats.

Persistent exposure of rats to 6-propyl-2-thiouracil (PTU) from birth resulted in decreases in plasma thyroid hormone (TH) levels and hepatic expression of catalase and CCAAT enhancer binding protein β (C/EBP-β). Catalase promoter region (-185 to +52) that contains binding sites for C/EBP-β showed an augmentation in the methylation level along with a change in methylation pattern of CpG islands in response to PTU treatment. PTU withdrawal on 30 days of birth restored TH levels and C/EBP-β to control rats in adulthood. Although catalase expression was restored to some extent in adult rats in response to PTU withdrawal, a permanent change in its promoter CpG methylation pattern was recorded. The results suggest that downregulation of adult hepatic catalase gene in response to persistent neonatal PTU exposure may not solely be attributed to thyroid-disrupting properties of PTU. It is possible that besides thyroid-disrupting behavior, PTU may impair expression of hepatic catalase by altering methylation pattern of its promoter.

Assessment of thyroid hormones status and some adipocytokines among Egyptian obese children

Aim: Childhood obesity is one of the most serious public health problems facing the developed and increasingly, the developing world. In this study, we aimed to investigate the possible role of thyroid hormones and some adipokines in childhood obesity. Materials & methods: A total of 80 children were enrolled; 50 obese children and 30 non-obese of matched age and sex. Clinical, demographic characteristics and lipid profile levels were monitored. Plasma levels of thyroid hormones, leptin, IL-1α and TNF-α were measured in these subjects. Results: Dyslipidemia was evident in obese children relative to normal ones. Obese children exhibited a significant reduction in TSH and free- T4 levels. There was an increment in both leptin and IL-1α levels of obese children, however, their TNF-α level were significantly decreased. Conclusion: Alterations in thyroid hormones status, leptin, IL-1α and TNF-α are associated with obesity in Egyptian children.

Regulation of growth rate and developmental timing by Xenopus thyroid hormone receptor α.

Thyroid hormone (TH) is critical for vertebrate postembryonic development, a period around birth in mammals when plasma TH levels are high. Interestingly, TH receptors (TRs), especially TRα, are expressed prior to the synthesis and secretion of zygotic TH, suggesting the existence of unliganded TR during development. However, the role of unliganded TR during mammalian development has been difficult to study, in part due to the relatively weak phenotype of TR knockout mice. Amphibian metamorphosis resembles postembryonic development in mammals and is controlled by TH via TRs. Like in mammals, TRα gene is highly activated and is the major TR expressed prior to the synthesis of endogenous TH. By using TALEN (transcriptional activator like effector nucleases)-mediated gene editing approach, we and others have now shown that unliganded TRα has two independent functions during Xenopus premetamorphosis, i.e. inhibiting growth rate and slowing development. Furthermore, molecular and transgenic studies have shown that unliganded TRα accomplishes these via the recruitment of histone deacetylase (HDAC)-containing corepressor complexes to repress the expression of TH-inducible genes.

The Effect of a Mutation in the Thyroid Stimulating Hormone Receptor (TSHR) on Development, Behaviour and TH Levels in Domesticated Chickens.

The thyroid stimulating hormone receptor (TSHR) has been suggested to be a “domestication locus” in the chicken, due to a strong selective sweep over the gene found in domesticated chickens, differentiating them from their wild ancestor the Red Junglefowl (RJF). We investigated the effect of the mutation on development (incubation time), behaviour and thyroid hormone levels in intercross chickens homozygous for the mutation (d/d), wild type homozygotes (w/w) or heterozygotes (d/w). This allowed an assessment of the effect of genotype at this locus against a random mix of RJF and WL genotypes throughout the rest of the genome, controlling for family effects. The d/d genotype showed a longer incubation time, less fearful behaviours, lower number of aggressive behaviours and decreased levels of the thyroid hormone T4, in comparison to the w/w genotype. The difference between TSHR genotypes (d/d vs. w/w) in these respects mirrors the differences in development and behaviour between pure domesticated White Leghorns and pure RJF chickens. Higher individual T3 and T4 levels were associated with more aggression. Our study indicates that the TSHR mutation affects typical domestication traits, possibly through modifying plasma levels of thyroid hormones, and may therefore have been important during the evolution of the domestic chicken.

Dietary Inorganic Chromium in Summer-Exposed Buffalo Calves (Bubalus bubalis): Effects on Biomarkers of Heat Stress, Immune Status, and Endocrine Variables.

The aim of this study was to evaluate the effect of different levels of inorganic chromium (Cr) on heat stress, immune response, and hormonal variation in Murrah buffalo calves during the summer season. Twenty-four growing Murrah buffalo calves were randomly allocated into four treatments for a period of 120days. Feeding regimen was same in all the groups, except the buffalo calves in treatment groups were additionally supplemented with 0.5, 1.0, and 1.5mg of inorganic Cr/kg dry matter. Buffalo calves were monitored daily for physiological variables and dry matter intake (DMI) and fortnightly for body weight change. Blood samples were collected at day 0, 15, 30, 45, 60, 75, 90, 105, and 120 and analyzed for heat shock protein 70 (Hsp 70), lymphocyte proliferation, neutrophil phagocytic activity, immunoglobulin, ferric reducing antioxidant power (FRAP) assay, insulin, cortisol and thyroid hormones, and Cr levels. Dietary Cr supplementation did not have any effect on DMI, growth performance, and physiological variables. However, lymphocyte proliferation, neutrophil phagocytic activity, plasma immunoglobulin, FRAP value, and plasma Cr concentration increased significantly (P < 0.05) with increase in levels of Cr. Adding Cr to the diet of summer-exposed buffalo calves did not show any effect on plasma levels of thyroid hormone, while concentration of insulin, cortisol, and Hsp 70 decreased (P < 0.05). Supplementation of inorganic Cr to the diet of buffalo calves reared under high ambient temperature improved heat tolerance, immune status without affecting nutrient intake, and growth performance.

Seasonal variations in physio-biochemical profiles of Indian goats in the paradigm of hot and cold climate

To explore the heat and cold adaptation in Indian goats by the physiological, haematological, blood biochemical parameters and their seasonal variations, this study was conducted on heat- and cold-adapted Indian goats maintained in their natural habitat. Study was carried out in three different phases coincide with the three seasons (winter, spring and summer). The levels of physiological responses, that is rectal temperature, respiration rate and pulse rate, were observed to be significantly (p < 0.01) lower in heat-adapted breeds and higher in cold-adapted breeds, whereas the levels of Hb, PCV and TEC were significantly (p < 0.01) higher in cold-adapted goats. Significantly (p < 0.01) higher levels of plasma thyroid hormones (thyroxine and triiodothyronine) and plasma stress enzyme (AST and ALT) were also observed in cold-adapted goats. Significant (p < 0.01) seasonal variations in physiological responses, haematological and blood biochemical parameters in both heat- and cold-adapted breeds were reported in this study. Physiological responses, plasma enzymes and plasma cortisol levels significantly (p < 0.01) increased during summer in all the goat breeds. The levels of haematological parameters (Hb, PCV, TEC and TLC) and plasma thyroid hormones (thyroxine and triiodothyronine) decreased during summer. The changes in physiological parameters during summer due to heat stress were higher in cold-adapted goats whereas the levels of changes in these parameters during winter due to cold were higher in heat-adapted goats. High neutrophil/lymphocyte ratio during summer in cold-adapted breeds is an indicator of higher level of stress. Decrease in plasma electrolytes (Na and K) during summer also observed in cold-adapted breeds during summer. The variations in physiological, haematological, blood biochemical parameters in heat- and cold-adapted goats may be due to their adaptation to different environmental and geographical conditions essential for their survival.

Monocrotophos pesticide decreases the plasma levels of total 3,3',5-triiodo-l-thyronine and alters the expression of genes associated with the thyroidal axis in female goldfish (Carassius auratus).

Our recent study showed that monocrotophos (MCP) pesticide disrupted the hypothalamic-pituitary-thyroid (HPT) axis in male goldfish (Carassius auratus); however, the effects of MCP on the thyroid system in female goldfish are remain unclear. In the present study, plasma thyroid hormone (TH) and thyroid-stimulating hormone (TSH) levels were evaluated in female goldfish exposed to 0.01, 0.10, and 1.00 mg/L of 40% MCP-based pesticide for 21 days in a semi-static exposure system. Expression profiles of HPT axis-responsive genes, including transthyretin (ttr), deiodinases (d1, d2, and d3), tshβ, thyrotropin-releasing hormone (trh), and corticotrophin-releasing hormone (crh), were determined. The results indicated that MCP decreased the plasma levels of total 3,3′,5-triiodo-l-thyronine (TT3) and the ratio of TT3 to total 3,3′,5,5′-l-thyroxine (TT4), and induced alternative expression of TH-related genes. Exposure to 0.01 and 0.10 mg/L MCP pesticide resulted in the up-regulation of ttr mRNA. The reduction of plasma TT3 levels was partly attributed to an increase in the metabolism of T3 in the liver, as revealed by the highly elevated hepatic d1 and d3 mRNA levels in the MCP treatment groups, and the expression of hepatic d3 showed a negative correlation with the plasma TT3/TT4 levels in females. Moreover, the plasma TSH levels were lower in females exposed to 0.01 and 0.10 mg/L MCP pesticide, whereas the up-regulation of tshβ mRNA levels was compensated by the decreased plasma TT3 levels. These results indicated that MCP had the potential to influence several pathways of HPT axis homeostasis in female goldfish.

Caffeine Exposure During Late Chick Embryogenesis Alters Hatchability and Plasma Thyroid Hormone Levels

To evaluate the consequences of exposure to caffeine during the final week of embryogenesis, we treated chick embryos with caffeine (20 μmol/egg) on day 15 and examined them and the hatchlings' behavior. Of the control embryos, more than 85% hatched on day 21, whereas 75% of the caffeine-treated embryos hatched on day 20. The caffeine hatchlings did not have significant malformations. The caffeine hatchlings on day 20 showed a significantly decreased tissue weight (mg) of the telencephalon (391.7±7.5 vs. 451.8±4.6), optic lobe (139.6±2.1 vs. 157.9±4.9), cerebellum (106.9±2.4 vs. 126.8±3), and brain stem (171.4±4.1 vs. 203.1±7.5) compared to the controls on day 21. The weights did not reach the control levels during the experimental period. The hatchlings' behaviors were evaluated using the imprinting ability test (assessing recognition and memory) and social behavior tests (aggregation, belongingness, and vocalization activity). These were designed to examine their willingness to find each other and form a group. None of the behavior tests showed significant differences between the caffeine-treated and the control hatchlings. Marked elevation of the duodenum alkaline phosphatase activity and the plasma triiodothyronine level were observed before hatching during normal development. The caffeine-treated group showed the increase in parallel 1 day earlier. Since thyroid hormone is involved in brain and gut maturation during the final week of embryogenesis, it is suggested that caffeine exposure accelerated the elevation of the hormone, which affects the maturation of brain quality related to imprinting and behavior and necessary gut maturation in hatchlings.

Seasonal variation of metabolic thermogenesis in Eurasian tree sparrows (Passer montanus) over a latitudinal gradient.

Phenotypic flexibility of various morphological and physiological characters is widespread in animals. Resident endothermic animals of temperate climates provide a natural experiment in phenotypic flexibility. In this study, we took an integrative approach to assess seasonal and geographic influences on metabolism in Eurasian tree sparrows (Passer montanus). We measured resting metabolic rate (RMR), masses of internal organs, mitochondrial respiration capacities in liver and muscle, cytochrome C oxidase (COX) activities in liver and muscle, and circulating levels of plasma triiodothyronine (T3) and thyroxine (T4) in summer and winter sparrows at two sites from southeastern (Wenzhou) and northeastern (Qiqihar) China that differ in climate. Body masses of tree sparrows were significantly higher in winter than in summer at both sites but did not differ with latitude. RMRs of tree sparrows varied significantly with both latitude and season, with RMRs of Qiqihar birds being higher than those of Wenzhou birds and with RMRs being higher in winter than in summer. Consistently, dry masses of brain, lung, liver, gizzard, small intestine, rectum, and total digestive tract varied significantly with either latitude or season. State 4 respiration and COX activity in liver and muscle were remarkably higher in Qiqihar and increased significantly in winter. Circulating levels of plasma T3 also showed significant seasonal and latitudinal variation and was higher in Qiqihar in winter than in other groups. These data suggest that tree sparrows mainly coped with cold by enhancing thermogenic capacities through heightened activity of respiratory enzymes and higher levels of plasma thyroid hormones (T3). These results are consistent with a pronounced seasonal and latitudinal phenotypic flexibility mediated through physiological and biochemical adjustments in Eurasian tree sparrows.