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Query: UMLS:C0009443 (cold)
 92,137 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Male rats aged 6 weeks, 6 months, and 18 months were kept at 4 to 5 degrees C for 12 days and compared with age-matched controls at room temperature as to survival, weight change, food consumption, core body temperature, and several parameters of thyroid hormone economy. After 12 days in the cold, 14%, 50%, and 71% of 6-week-, 6-month-, and 18-month-old rats, respectively, were living. Weight declined in both older groups, though at a faster rate in the oldest. Increasing age did not affect serum T3, rT3, TSH, or the ability to convert T4 to T3 by 20% liver homogenate. Cold exposure, however, resulted in an increase in serum T3 and a decrease in T4 to T3 conversion by liver homogenate in a similar magnitude both in mature and early senescent rats.
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PMID:Effect of cold exposure on thyroid hormone in Fischer 344 rats of increasing age. 713 Jun 41

We investigated the characteristics of the monodeiodination of thyroxine to T3 and rT3 in human placentas which were obtained at normal delivery. The placentas were homogenized in a cold sucrose Tris-HCl buffer, pH 7.5. The microsomal fraction was incubated at 37 degrees C in air for 1 hr with 2 micrograms of T4 in the presence of 50mM DTT. The T3 and rT3 generated in the reaction mixture were extracted into cold ethanol and measured by RIA. Among the usal subcellular fractions of the placental homogenate, microsomes were the most potent in deiodinating T4 to rT3. In microsomes, production of rT3 increased with protein concentration, incubation temperature up to 37 degrees C, incubation time up to 120 min and T4 concentration up to 16 micrograms/tube. The production of rT3 from T4 was lost by prior heating of the microsomal fraction to 56 degrees C for 30 min. The net production rate of T4 to rT3 in the microsomal fraction was 17.9 ng/mg protein/micrograms T4/60 min at pH 7.5. RT3 production from T4 was maximal at pH 7.0. The production of T3 from T4 was negligible in the present system. Degradation of T3 in the placentas was rapid. Although the addition of anti-T3 antibody to the reaction mixture suppressed the degradation of T3, it had no effect on the net production of T3, suggesting that the obtained net T3 production rate had not been influenced by its degradation. Degradation of rT3 was negligible. These results indicate that the human placenta actively deiodinates T4 to rT3 enzymatically. This enzyme system might have some influence on the transplacental passage of the thyroid hormone from the mother to the fetus.
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PMID:[Monodeiodination of thyroxine to 3,3',5'-triiodothyronine in the human placenta]. 718 76

Measures prior to diagnosis and treatment already installed were assessed retrospectively in 8501 patients with suspect thyroid disease between the years 1976 and 1979. In 10.5% of these patients there were 11.2% misdiagnosis or wrong treatment. The most common misdiagnoses were hyperthyroidism in euthyroid patients (1.9%), hypothyroidism in euthyroidism (0.8%), non-recognition or non-aspiration of cold nodules (0.9%), missing a goitre (0.6%). Among diagnostic methods the radio-iodine test was reason for a wrong diagnosis most commonly (66%). The TRH-test proved to be least erroneous, technical reasons being the cause of the 9.6% of misdiagnoses. The most common mismanagements were due to lack of prophylaxis of recurrence after goitre operation (1.5%), external irradiation of the thyroid gland with radium or Roentgen rays (0.7%), and during thyroid hormone treatment of goitre (1.3%). Iatrogenic disease existed mainly as factitious hyperthyroidism (0.7%), non-treated hypothyroidism after treatment with radio-iodine of hyperthyroidism (0.1%), and as goitre recurrence due to lack of prophylaxis of recurrence (0.8% of all patients). As every 10th patient was subjected to misdiagnosis or mismanagement, shifting to endocrinological advisory centers may prevent future mismanagement of thyroid disorders.
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PMID:[Misdiagnoses and mismanagement in thyroid diseases (author's transl)]. 730 88

Creatine metabolism in cold-acclimated rats was studied with the aid of [1-14C] creatine as a tracer. Urinary creatine derived from muscle increased in the early stage of cold exposure, and creatine contents of all muscles studied were significantly lower in cold-acclimated rats than in controls. Increased urinary creatine derived from muscle and reduced creatine contents of all muscles were also observed in thyroid hormone, triiodothyronine (T3)-treated rats, while chronic treatment of noradrenaline did not affect urinary creatine derived from muscle and creatine contents of all muscles. Radioactive creatine uptake by skeletal muscle was significantly lower in cold-acclimated rats than in controls, while radioactive creatine uptake by heart and diaphragm of cold-acclimated rats was not different from that of controls. Chronic treatment of noradrenaline produced a similar change in radioactive creatine uptake by skeletal muscle, while the inhibitory effect of T3 on radioactive creatine uptake is not different among the different types of muscle, although the uptakes of radioactive creatine by all muscles studied were lower in T3-treated rats than in controls. These findings indicate that cold acclimation results in reduced creatine contents in all muscles and reduced uptake of creatine in skeletal muscle, possibly reflecting an enhanced ability of nonshivering thermogenesis in skeletal muscle induced by both thyroid hormones and noradrenaline.
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PMID:[Studies on the creatine metabolism in cold acclimation (author's transl)]. 740 28

This study examines the relation between whole body O2 requirements and lung growth. 6-week-old hamsters were exposed to cold (5 degrees C) or injected with thyroid hormone. These treatments elevated O2 consumption by 26% over a 28-day period. Both alveolar surface area and total lung air volume were increased by approximately 25% in each group. Morphometric data suggest that lung enlargement was due to an increase in the number or complexity, rather than size of individual alveolar units. Further elevating O2 demand by increasing thyroid dosage did not enhance lung size beyond the level observed with the lowest dose used. Depressing metabolic rate with an antithyroid drug for four weeks had no effect on lung structure (in this animal model). Results indicate that in hamsters, increased physiologic O2 demand may be met to a certain extent by augmentation of the pulmonary diffusing surface.
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PMID:Lung growth in response to altered metabolic demand in hamsters: influence of thyroid function and cold exposure. 744 19

Hypothyroidism in dogs should be diagnosed by integrating the history, clinical symptoms and thyroid hormone assay. Affected dogs have a slow onset of decreased activity, cold intolerance, and skin changes of thickening and mild hyperpigmentation. The hair coat becomes dry and coarse, and alopecia develops in friction areas. The non-specific clinico-pathological changes of a mild anaemia and hypercholesterolaemia do not occur consistently. The easiest and best documented thyroid hormone assay is serum thyroxine (T4). The most accurate diagnosis is made using either the thyrotropin (TSH) stimulation test or thyroid gland biopsy. The condition is controlled by thyroxine replacement therapy at a dose rate of 30--50 mcg/kg/day in 2 divided doses, for the life of the dog.
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PMID:The diagnosis and treatment of canine hypothyroidism. 745 58

Growth of capillaries in the heart occurs under physiological circumstances during endurance exercise training, exposure to high altitude and/or cold, and changes in cardiac metabolism or heart rate elicited by modification of thyroid hormone levels. Capillary growth in all these conditions can be linked with increased coronary blood flow, decreased heart rate, or both. This paper brings evidence that, although increased blood flow due to long-term administration of coronary vasodilators results in capillary growth, a long-term decrease in heart rate induced by electrical bradycardial pacing in rabbits and pigs, or by chronic administration of a bradycardic drug, alinidine, in rats, stimulates capillary growth with little or no change in coronary blood flow. Decreased heart rate results in increased capillary wall tension, increased end-diastolic volume and increased force of contraction, and thus stretch of the capillary wall. This could lead to release of various growth factors possibly stored in the capillary basement membrane. Correlation was found between capillary density (CD) and the levels of low molecular endothelial cell stimulating angiogenic factor (ESAF) both in rabbit and pig hearts with CD increased by pacing. There was no relation between expression of mRNA for basic fibroblast growth factor and CD in sham-operated and paced rabbit hearts. In contrast, mRNA for TGF beta was increased in paced hearts, and the possible role of this factor in the regulation of capillary growth induced by bradycardia is discussed.
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PMID:Factors involved in capillary growth in the heart. 749 56

The T3 thyroid hormone was shown to change the motor unit activity in the thermoregulatory tonus from 13 to 22/sec in intact rats to 9 to 11/sec in the hyperthyroid ones. This data corresponds to that obtained in rats adapted to cold and suggests participation of thyroid hormones in cold adaptation.
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PMID:[The effect of experimental hyperthyroidism on the thermoregulating activity of the motor units in rat skeletal muscles]. 758 65

Brown adipose tissue (BAT) thermogenesis is activated by the sympathetic nervous system. BAT responses to norepinephrine are blunted in hypothyroidism and are rapidly restored by thyroid hormone. We examined in rats the effects of thyroid hormone on BAT beta 1- and beta 2-adrenergic receptors (AR) expression and capacity to generate cAMP in response to adrenergic stimulation. Both are reduced in hypothyroidism. The reduction in cAMP generation is equal to or greater than that in beta 1,2-AR; it is the same whether cAMP production is stimulated with norepinephrine, selective beta 3-AR agonists, or forskolin; and it is not affected by the inhibition of phosphodiesterase. Both beta 1,2-AR and the capacity to generate cAMP were slowly corrected by thyroid hormone. T3 normalized beta 1,2-AR between 1 and 2 days, whereas the improvement in cAMP generation lagged 1 or 2 days behind. Within 2 days of acclimation of athyreotic rats at 30 C, the number of beta 1,2-AR reached the euthyroid level, whereas exposure to 4 C decreased these receptors. We reached the following conclusions: 1) BAT beta 1,2-AR and capacity to generate cAMP are reduced in hypothyroidism; 2) the latter, however, is not explained by the reduction in beta 1,2-AR, but, rather, reflects a fault at the postreceptor level; 3) the reduction in beta 1.2-AR number is largely caused by the cold stress derived from the low metabolic rate of the hypothyroid state; and 4) the slow restoration of both receptor number and capacity to generate cAMP after T3 are not consistent with these defects being a significant factor in the previously reported blunted uncoupling protein responses to adrenergic stimulation in hypothyroidism.
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PMID:Effects of thyroid hormone on norepinephrine signaling in brown adipose tissue. I. Beta 1- and beta 2-adrenergic receptors and cyclic adenosine 3',5'-monophosphate generation. 762 60

We have compared the levels of the integral plasma membrane glycoprotein CE9 (MRC OX-47) in different tissues of the rat and have ascertained that the levels of CE9 protein and mRNA in selected tissues and cells exhibit moderate increases in response to diverse stimuli of metabolic activation. When normalized on the basis of total protein, the level of CE9 detected in the different tissues was found to vary over a 50-fold range. In addition, the apparent molecular mass of CE9 was observed to vary from 40 kDa to 68 kDa as a consequence of tissue-specific glycosylation. The highest level of CE9 was detected in brown adipose tissue, where the protein was found to be localized to the plasma membranes of the adipocytes. The metabolic activation of brown adipose tissue that occurs upon exposure of rats to the cold was found to be accompanied by 3.0 +/- 0.4-fold and 1.7 +/- 0.2-fold increases in the levels of CE9 mRNA and protein respectively. An intermediate level of CE9 was detected in the liver, where the protein is known to be expressed within the basolateral domain of the hepatocyte plasma membrane. The metabolic activation of hepatocytes that occurs upon administration of thyroid hormone to euthyroid rats was found to be accompanied by 2.2 +/- 0.3-fold and 1.9 +/- 0.3-fold increases in the levels of CE9 mRNA and protein respectively. A low level of CE9 was detected in the lymphoid organs, such as thymus and spleen. The metabolic activation of isolated rat splenocytes that occurs upon concanavalin A-mediated blast transformation in culture was found to be accompanied by 2.1 +/- 0.2-fold and 1.6 +/- 0.2-fold increases in the levels of CE9 mRNA and protein respectively. On the basis of these and other observations, we suggest that the level, and possibly also the localization, of the integral plasma membrane glycoprotein CE9 may be correlated in a positive fashion with metabolic activity in a diverse array of cell types.
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PMID:Distribution of the integral plasma membrane glycoprotein CE9 (MRC OX-47) among rat tissues and its induction by diverse stimuli of metabolic activation. 765 13


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