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

Long-term cold exposure (5-7 days) is known to induce concomitant increases in the levels of adrenomedullary tyrosine hydroxylase (TH) RNA, protein, and enzyme activity. In this report, we compare the time courses of these changes and investigate the effects of cold exposure on the levels of biopterin, the cofactor required for tyrosine hydroxylation. After only 1 h of cold exposure, TH mRNA abundance increased 71% compared with nonstressed controls. Increases in total cellular TH RNA levels were maximal (threefold over control values) within 3-6 h of cold exposure and remained elevated throughout the duration of the experiment (72 h). TH protein levels increased rapidly after 24 h of cold exposure and reached a maximal value threefold above that of controls at 48-72 h. Despite the relatively rapid and large elevations in TH RNA and protein content, only modest increases in TH activity were detected during the initial 48 h of cold exposure. Adrenomedullary biopterin increased rapidly after the onset of cold exposure, rising to a level approximately twofold that of the nonstressed controls at 24 h, and remained at this level throughout the duration of the stress period. Taken together, the results of this time course study indicate that cold-induced alterations in adrenal TH activity are mediated by multiple cellular control mechanisms, which may include pre- and posttranslational regulation. Our findings also suggest that cold stress-induced increases in the levels of the TH cofactor may represent another key event in the sympathoadrenal system's response to cold stress.
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PMID:Effects of cold exposure on rat adrenal tyrosine hydroxylase: an analysis of RNA, protein, enzyme activity, and cofactor levels. 169 Dec 81

An investigation was carried out regarding the mechanism of behavioral changes in mice elicited by cold stress. Cold stress was induced in adult male mice by restraining them from free action for 2 h at 4 degrees C. As the control test, mice were restrained from free action for 2 h at room temperature. The locomotor counts in cold-stressed mice were found to be lower than in controls. The counts in cold-stressed mice were increased by IP pretreatment with EDTA or alpha-methyltyrosine (tyrosine hydroxylase inhibitor), and were further decreased by IP pretreatment with CaCl2. On the other hand, serum calcium and brain calcium levels in cold-stressed mice were increased 15-30 min and 30 min, respectively, after restraint under cold temperatures, and returned to original levels 1 h after restraint. Also, the biochemical and immunohistochemical brain dopamine levels in cold-stressed mice were higher than in control mice. The increment of brain dopamine levels in the control mice was also observed by the administration of CaCl2. Furthermore, the ability of cold stress to enhance the dopamine level in mice brains was attenuated by IP pretreatment with alpha-methyltyrosine. In light of previous reports that central calcium activates catecholamine-synthesizing enzymes via a calmodulin-dependent system, it is suggested that cold stress enhances the brain calcium level, and then increased calcium enhances dopamine synthesis in the brain through a central calcium-dependent catecholamine synthesizing system. Subsequently, increased dopamine induces behavioral changes.
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PMID:Behavioral changes in cold-stressed mice related to a central calcium-dependent-catecholamine synthesizing system. 180 45

Chronic cold stress and chemical sympathectomy are known to increase the synthesis and release of catecholamines in the adrenal medulla. Chromaffin cells adapt to altered functional requirements by increasing the synthesis of tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine biosynthesis. In this study, we investigated the molecular genetic mechanisms underlying these changes in enzyme activity. Estimates of TH mRNA levels were obtained by RNA dot-blot analysis with a cloned TH cDNA hybridization probe. Exposure to cold produced a 4.3-fold increase in the relative abundance of adrenomedullary TH mRNA. Increases in TH mRNA levels (90%) also were observed in the brainstem of cold-stressed animals. The relative amount of TH synthesized in vitro in a rabbit reticulocyte cell-free system, programmed with adrenal poly(A)+RNA, increased 4.3 times in cold-stressed rats. Alteration in TH mRNA abundance appears to be specific, as we observed no significant difference in the levels of total RNA or poly(A)+RNA in this tissue. In addition, the relative abundance of adrenomedullary TH mRNA increased by 60% 4 days after systemic administration of the neurotoxin 6-hydroxydopamine. This increase was transient and disappeared 2 weeks after the lesion. Changes in TH mRNA levels after cold stress or sympathectomy were eliminated by denervation of the adrenal gland. These results indicate that alterations in the relative abundance of TH mRNA mediate changes in TH activity induced by chronic stress or sympathectomy, and that these changes require an intact sympathetic input.
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PMID:Molecular adaptations in catecholamine biosynthesis induced by cold stress and sympathectomy. 242 35

Cold stress is known to increase the synthesis and release of catecholamines in the sympathoadrenal system. Previously, we have demonstrated that cold exposure results in a 3- to 4-fold increase in adrenomedullary tyrosine hydroxylase (TH) activity, which is mediated by concomitant alterations in TH mRNA and protein levels. To further investigate the effects of stress on the expression of the catecholamine biosynthetic enzymes, we have isolated a rat cDNA clone encoding the epinephrine-synthesizing enzyme phenylethanolamine N-methyltransferase (PNMT). The cDNA clone is 905 nucleotides in length and contains a single open reading frame corresponding to 270 amino acids. The amino acid sequence predicted from this nearly full-length cDNA is 89% and 86% identical to that of bovine and human PNMT, respectively. Using the rat PNMT cDNA as a hybridization probe, we have measured the effects of cold stress on the relative abundance of adrenomedullary PNMT mRNA. Levels of PNMT protein were also estimated using an immunoblot analysis. As in the case of TH, cold exposure resulted in a rapid and prolonged increase in PNMT mRNA abundance, followed by concomitant increases in PNMT immunoreactivity. However, there appear to be quantitative and qualitative differences in the adaptive response of TH and PNMT to cold stress.
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PMID:Isolation of a rat adrenal cDNA clone encoding phenylethanolamine N-methyltransferase and cold-induced alterations in adrenal PNMT mRNA and protein. 257 95

Chronic hypotension and hypoglycemia are known to increase the capacity for catecholamine biosynthesis in the rat adrenal medulla by increasing the maximal velocity of the rate-limiting enzyme, tyrosine hydroxylase (TH). The present report indicates that the gradual increase in maximal TH activity is preceded by a more rapid increase in the affinity of TH for its pterin cofactor. These short-term alterations in adrenal TH activity are related to the severity of the stress, associated with parallel changes in catecholamine biosynthesis, and prevented by prior adrenal denervation. In contrast, cold exposure, which leads to comparable long-term increases in adrenal TH activity, does so without causing a prior activation of TH. However, adrenal TH is activated by acute cold exposure if the sympathetic nerves, that normally are stimulated during cold, are destroyed previously by 6-hydroxydopamine treatment. These and other observations suggest that alterations in adrenal TH activity vary according to the type and duration of physiological stress, and may be mediated by temporally distinct processes.
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PMID:Tyrosine hydroxylase activity and catecholamine biosynthesis in the adrenal medulla of rats during stress. 285 82

Rats were exposed to combined enforced swimming and cold stress in order to investigate the influence of the sedative compounds 2-(2-oxo-3-piperidyl)-1,2-benzisothiazoline-3-one-1,1-dioxide (supidimide), phenobarbital, and diazepam on stress-induced changes in cyclic adenosine 3',5'-phosphate (cAMP) and trans-synaptic induction of tyrosine hydroxylase (TH) in adrenal glands. Pretreatment with supidimide at greater than or equal to 150 mg/kg suppresses the early poststress rise in cAMP and the delayed TH induction. Phenobarbital at 75 mg/kg slightly inhibits the cAMP increase, but does not significantly interfere with TH induction. Diazepam already at 5 mg/kg completely blocks the stress-induced increase of cAMP, but leaves the TH induction unchanged at dosages up to 20 mg/kg. It is concluded that the stress-induced rise in adrenal cAMP and the trans-synaptic induction of TH are rather coincidental than causally related. Suppression of TH induction by supidimide appears to be a peculiarity of this compound not strictly related to its sedative potency.
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PMID:Influence of sedatives on stress-induced trans-synaptic induction of tyrosine hydroxylase. 285 22

Ornithine decarboxylase (ODC) and tyrosine hydroxylase (TH), the first enzymes in the polyamine and catecholamine biosynthetic pathways, respectively, are induced in the adrenal gland of the rat through the application of stressors or dopamine agonists. In the present work, following exposure of rats to cold, application of bodily restraint, or administration of apomorphine (APM), adrenal putrescine increased in proportion to the induction of ODC. Spermidine content increased by 60% after APM and about 30% after immobilization. Spermine was unaffected. To test whether the increases of ODC (and polyamines) are necessary to the slower and later induction of TH, induction of ODC in vivo was undertaken. alpha-Difluoromethylornithine (alpha-DFMO), an irreversible inhibitor of ODC, given orally or subcutaneously, almost completely abolished the induction of ODC by APM or immobilization, and inhibited the increase of putrescine in both cases, but did not affect spermidine after APM. Repeated administration of alpha-DFMO over several days did not affect the induction of adrenal TH. The results question whether increases of adrenal ODC activity and of putrescine are essential for the induction of TH in that gland.
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PMID:Effects of alpha-difluoromethylornithine on polyamine biosynthesis and tyrosine hydroxylase induction in the adrenal gland of the rat subjected to stress or apomorphine. 285 59

Subtotal destruction of central noradrenergic neurons with the neurotoxin, 6-hydroxydopamine, is known to increase tyrosine hydroxylase (TH) activity within surviving nerve terminals. The present report demonstrates a similar, dose-related elevation of TH activity in the adrenal medulla and sympathetic nerves after systemic 6-hydroxydopamine treatment. Two temporally distinct processes were observed in the sympathetic nerves: a rapid activation of TH, present during the first few days after the lesion, and a more gradual increase in maximal TH activity, most probably due to enzyme induction. In this regard, the stimulatory effect on catecholamine biosynthesis of cyclic AMP-dependent phosphorylation was attenuated substantially within cardiac sympathetic nerves 3 days after the lesion, but by 3 weeks the efficacy of cyclic AMP-dependent phosphorylation was restored completely. Similarly, the normal activation of cardiac TH activity elicited by insulin-induced hypoglycemia and cold stress was absent soon after 6-hydroxydopamine treatment, but returned 3 weeks later. These latter findings suggest that the adaptations within the sympathoadrenal system after subtotal sympathectomy can preclude further adaptations to stress.
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PMID:Tyrosine hydroxylase activity in the sympathoadrenal system under basal and stressful conditions: effect of 6-hydroxydopamine. 286 49

The effect of chronic stress on the levels of tyrosine hydroxylase (TH) RNA in rat adrenal gland was investigated by RNA-DNA hybridization using a cloned TH cDNA probe. Results of dot-blot hybridization experiments and northern analysis demonstrate that exposure of animals to cold for 1 week results in a 4-5-fold increase in the relative abundance of TH mRNA. This increase in TH mRNA level may underlie the increase in adrenal TH activity that is known to occur when rats are exposed to such cold stress.
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PMID:Effect of chronic cold exposure on tyrosine hydroxylase mRNA in rat adrenal gland. 286 19

Effects of hyper- and hypothyroidism on catecholamine (CA) metabolism in the brain, adrenal glands, liver, and brown adipose tissue (BAT) were studied in adult rats during cold acclimation. Hypothyroidism was induced by the administration of propylthiouracil (PTU) and hyperthyroidism by the injection of thyroxine (T4). After 2 weeks of treatment, they were exposed to cold (5 degrees C) and sacrificed after 1 or 4 weeks. Although the body weight gain of PTU-treated rats were markedly impaired, the body temperature was maintained within normal range. They had increased cerebral dopamine, adrenal CA and BAT norepinephrine (NE) contents, enhanced cerebral tyrosine hydroxylase and adrenal dopamine beta-hydroxylase (DBH) activities and elevated [3H]dihydroalprenolol (DHA) binding to liver plasma membranes (P less than 0.01 vs controls). T4-treated rats showed an increased brain and adrenal CA only after cold exposure. The BAT NE content, DHA binding to liver plasma membranes, and [3H]guanosine diphosphate binding to BAT mitochondria were reduced by 30 to 50% from control values after 4 weeks of cold exposure. These results indicate that during cold acclimation, thyroid hormone deficiency is associated with an accelerated CA synthesis and release, which results in an enhanced BAT thermogenesis, and the hyperthyroid state suppresses CA release, hepatic DHA binding, and BAT heat production. Thus, there is a close metabolic interrelationship between thyroid hormone and CA during exposure to cold. CA appears to ameliorate thyroid hormone excess or deficiency.
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PMID:Thyroid hormone-catecholamine interrelationship during cold acclimation in rats. Compensatory role of catecholamine for altered thyroid states. 287 53


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