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

Serum TSH and corticosterone concentrations were measured in intact rats and in rats given TRH or exposed to short-term cold 3 h and 12 h after pretreatment with dexamethasone in various doses. Dexamethasone given 3 h before experiemtns significantly depressed both TRH- and cold-induced TSH responses at all dose levels. Dose of 25 pg/100 g body weight significantly depressed serum TSH concentration when given 3 h before the experiment. However, when given 12 h before the experiment the drug augmented TRH-induced TSH secretion, although the cold response was unaltered. In intact rats dexamethasone significantly depressed serum TSH concentration in doses of 250 and 500 mug/100 g body weight. In all experiments the steroid blocked ACTH secretion. These results support the view that the effect of dexamethasone on thyroid function is highly dependent on the time relations. A single large dose of dexamethasone has first an inhibitory effect at the pituitary level and then facilitates pituitary to TRH and at the same time inhibits secretion of TRH in response to cold.
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PMID:Effect of dexamethasone on the secretion of thyrotropin in the rat: dose and time relations. 16 68

The effect of temperature during preparation of rat adrenal quarters or isolated adrenal cell suspension on their response to ACTH was examined through a comparison of amounts of corticosterone produced after their incubation. The response to ACTH added in vitro was considerably higher when adrenal quarters and isolated adrenal cell suspension were prepared at room temperature (25 degree C) than when prepared at ice-cold. Endogenous steroidogenesis was not affected by the temperature. It seemed unlikely that this higher response to ACTH of adrenal quarters or isolated adrenal cell suspension prepared at room temperature was due to an activation of the cells. A possibility was discussed that cooling adrenal quarters or isolated adrenal cell suspension during the preparation may create an unphysiological state in some place to related the cell membrane.
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PMID:Effect of temperature during preparation of rat adrenal quarters and isolated cell suspension of their ACTH responsiveness. 16 70

Two distinct classes of mitochondria are described in the normal adrenal cortex of the Sprague Dawley CFY rat. Polyaminar mitochondria were frequently observed in the zona fasciculata and zona reticularis, particularly after ACTH stimulation of the cortex resulting from cold-stress exposure. It is uncertain whether such organelles are degenerating forms, or whether they have a specific functional role related to steroidogenesis in the normal cortical cell. In both normal and stressed adrenal cortices, protrusions of the outer membrane of mitochondria were evident, and were often seen penetrating lipid droplets. It is suggested that these protrusions may have some significance in the transport of cholesterol from the lipid droplet to the inner mitochondrial memrane 'desmolase complex', thus facilitating side-chain cleavage of cholesterol to pregnenolone.
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PMID:Mitochondrial structure in the rat adrenal cortex. 16 69

1. The effect of reserpine on hypothalamo-pituitary-adrenocortical (HPA) function in the rat was investigated by the use of direct and indirect indices of pituitary adrenocorticotrophic activity. 2. Administration of a single dose of the drug induced prolonged hypersecretion of corticotrophin (ACTH). 3. Corticotrophin release in response to the drug no longer occurred after repeated daily injections, indicating that some form of 'adaptation' occurred. 4. The increase in HPA activity normally caused by exposure to cold was prevented by reserpine once 'adaptation' to the drug had been produced. 5. Inhibition of stress-induced ACTH release was due neither to depletion of pituitary stores of the hormone, nor to a corticosteroid feedback effect.
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PMID:The effect of reserpine on hypothalamo-pituitary-adrenocortical function in the rat. 16 93

Rats treated with ACTH and hydrocortisone for 4 weeks were infused i.v. with noradrenaline or exposed to cold at -15 degrees C for 2 hours, and changes in the rectal temperature and plasma concentrations of NEFA, sugar, and lactate were observed. Rats received single injection of ACTH and hydrocortisone, warm- and cold-acclimated rats were used as controls. In ACTH- and hydrocortisone-treated rats, the noradrenaline infusion caused a significant elevation of the rectal temperature, but lowering of the rectal temperature induced by the acute cold exposure in these treated rats did not differ from the changes in control groups. Moreover, considerable differences were found between these treated rats and cold-acclimated ones in plasma concentrations of NEFA, sugar and lactate after noradrenaline infusion and acute cold exposure. From the results it was inferred that chronic treatment with ACTH and hydrocortisone did not produce similar adaptive metabolic alterations to those found in the course of cold acclimation.
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PMID:[Sensitivity to noradrenaline and cold tolerance of rats treated chronically with ACTH and adrenocortical hormone (author's transl)]. 16 34

The response and adaptation of the pituitary-adrenal system to chronic stresses was investigated. These included individual caging, confinement, and exposure to cold for varying periods of time. Studies were carried out demonstrating that during the period of adaptation when plasma corticosterone concentrations returned toward their prestress level despite continued exposure to the stressor, the animals responded to additional stimuli of ether for 1 min, a saline injection, or release from confinement with a faster increase (within 2.5 min) in plasma corticosterone than controls (10 min). This increased responsiveness was not limited to the adrenal since plasma ACTH showed a greater increase 2.5 min after ether in animals confined for 40 min than in nonconfined rats. It is concluded that during adaptation to a chronic stress the pituitary-adrenal system is not inhibited by the circulating steroid level but is actually hypersensitive to additional stimuli. Thus, chronic stress may cause an increased drive to the ACTH-secreting mechanism which compensates or overrides the cortical feedback.
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PMID:Increased rate of response of the pituitary-adrenal system in rats adapted to chronic stress. 17 68

In intact rats acclimated to 25 +/- 1 degrees C, acute exposure to cold resulted in simultaneous stimulation of TSH and ACTH secretion. The plasma TSH response to cold was identical at temperatures varying from +14 to -10 degrees C, whereas the adrenocortical response increased proportionally to the severity of cold. Acute stimulation of ACTH secretion by exposure to a stressful situation (electrical shocks) did not alter the TSH response to cold. Conversely, acute blockade of the pituitary-adrenocortical response by dexamethasone treatment did not enhance the TSH response to cold. Chronic stimulation of ACTH secretion resulting from adrenalectomy did not interfere with the TSH response during subsequent exposure to cold. However, a reduced adrenocortical response to cold was observed during chronic hypersecretion of TSH resulting from previous thyroidectomy. These findings do not support the hypothesis of an inverse relationship between TSH and ACTH secretions during acute cold exposure, but rather suggest that these secretions are independent.
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PMID:Interactions between the pituitary, thyroid and adrenal cortex during acute exposure to cold or to electric shocks in the rat. 17 86

1. The effect of either procaine penicillin or zinc bacitracin (25 mg active base/kg food) on the response of young birds to three different stressors - withdrawal of food for 18 h, exposure to cold for 24 h or treatment with ACTH- has been examined. 2. Neither antibiotic had any consistent effect on the stress responses. 3. It is concluded that neither penicillin nor bacitracin has any stress-ameliorating activity at least under the conditions of the test.
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PMID:Failure of procaine penicillin and zinc bacitracin to modify the response of the fowl to stressors. 17 72

The work reviewed here illustrates how a therapeutic procedure, exchange transfusion of newborn infants, may be used to gather information which is both of practical value to infants treated in this way and also of value in the study of human neonatal physiology. The scientific deductions that can be drawn are weakened by the uncontrolled nature of the subjects available for study but this problem can be mitigated by changing one variable at a time between two groups of clinically similar infants undergoing transfusion and paying attention only to large changes in whatever is measured. In this way it has been possible to show that the glucose of ACD blood stimulates insulin and GH secretion and that the stimulation of insulin secretion is less, and that of GH more, if the transfusion is performed via the umbilical artery rather than via the vein. Arterial transfusions may be more stressful than venous ones since they are associated with greater growth hormone, ACTH and glucocorticoid release. Citrate, the other additive in ACD blood, causes a fall in ionised plasma calcium levels resulting in a stimulation of PTH secretion and mobilisation of calcium and phosphorus. Transfusion with heparinised blood is therefore preferred by some because normoglycaemia is preserved during and for three hours after transfusion, whereas post-transfusion hypoglycaemia may occur after ACD transfusion. However, heparin transfusion causes a marked rise in plasma FFA levels which may interfere with the binding of bilirubin by albumin. In either type of transfusion the side-effects may be minimised by feeding the baby afterwards, as soon as practicable. Thyroid hormones are washed out of the infant during transfusion but normal thyroid balance is restored quickly afterwards. The temperature of the donor blood does have thermal effects on the baby but these are less than might be expected due to the rapid equilibration of donor blood temperature with that of the room. The metabolic consequences of transfusion with cold blood are less than might be anticipated due in part to the glucose infusion that is part of an ACD transfusion.
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PMID:Neonatal metabolism and endocrinology studied by exchange transfusion. 17 41

The response of intact and bursectomized chicks to stressful stimuli has been examined. The stressors imposed were: a. fast-acting ACTH adminstration; b. immersion in cold water; c. starvation. In Bursa-intact chicks the results were as follows: 1. Plasma corticosterone was increased by all stimuli. 2. Adrenal corticosterone was decreased by ACTH treatment while it was increased by immersion in cold water and by starvation. 3. Plasma glucose was increased by ACTH administration and cold water immersion and decreased by starvation of the birds. 4. Adrenal ascorbic acid concentration was not influenced by all stimuli. 5. Adrenal weights were found to be increased by ACTH and starvation treatments only. 6. Bursa weights were increased by ACTH administration. 7. A very low concentration of corticosterone was found in the Bursa of Fabricius. Bursectomized chicks differed from the intact ones in the following: 1. Plasma and adrenal corticosterone concentrations were not increased by starvation. 2. Plasma glucose increased moderately with ACTH administration. 3. Adrenal ascorbic acid was depleted by all stimuli but was not related to the corticosterone level in the adrenals and blood plasma.
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PMID:Effects of stress on the corticosterone content of the blood plasma and adrenal gland of intact and bursectomized Gallus domesticus. 18 May 4


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