Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0009443 (cold)
 92,137 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. The role of thyroid hormone as a feed-back at the hypothalamic level in the control of thyrotrophin (TSH) secretion and release has been investigated by estimating the plasma and pituitary TSH levels following intrahypophysial and intrahypothalamic thyroid autotransplants.2. Thyroidectomized rats bearing thyroid autotransplants in the pituitary had a significantly lower (P < 0.001) plasma TSH than that of controls at 26 degrees C but not at 4 degrees C.3. Thyroidectomized rats bearing thyroid autotransplants in the supraoptic area showed a significantly lower (P < 0.001) level of plasma TSH and higher pituitary TSH at 4 degrees C but not at 26 degrees C.4. Study with both unilaterally and bilaterally thyroidectomized rats bearing thyroid autotransplants either in the pituitary or in the hypothalamus revealed that thyroxine feed-back operates at pituitary level in normal situations (26 degrees C) and there exists a feed-back through higher centres, specifically the TSR secreting area of the hypothalamus, in situations demanding higher thyroid function, as in cold exposure.
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PMID:Thyroxine feed-back on the regulation of thyrotropin [TSH] secretion. 564 87

The influence of thyroid hormone in thermogenesis of animals adapting to high altitude for different periods were studied in white rats. The adaptation to high altitude hypoxia decreased reaction of the organism to cold. The antithyroid injection of mercazolil potentiated the hypoxia action in cold thermogenesis and lowered sharply the body temperature stability in cooling. The analogous injection of triiodthyronine reduced the hypoxia influence on the thermogenesis and increased the contribution of the contractile heat production in the thermoregulative metabolism. The data suggest that one of the reasons of the low heat effect of the muscle contraction in adaptation to hypoxia may be the functional weakening of the thyroid gland.
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PMID:[Role of thyroid gland hormones in thermoregulatory reactions during adaptation to high altitude]. 616 65

The effects of substance P (SP), angiotensin II, oxotremorine and prostaglandin D2 (PG D2) on thyrotropin-releasing hormone (TRH) and thyrotropin (TSH) secretion in rats were studied. Either SP (100 micrograms/kg), angiotensin II (500 micrograms/kg), oxotremorine (1.0 mg/kg) or PGD2 (500 micrograms/kg) was injected intravenously or intraperitoneally, and the rats were serially decapitated. TRH, TSH and thyroid hormone were measured by means of a specific radioimmunoassay for each. The hypothalamic immunoreactive TRH (ir-TRH) contents were significantly increased by oxotremorine or SP and significantly decreased by angiotensin II, but no by PG D2. The plasma ir-TRH concentrations were significantly increased by angiotensin II, but not by oxotremorine, SP or PG D2. The plasma TSH levels were significantly increased by angiotensin II and significantly decreased by oxotremorine, SP or PG D2 in a dose-related manner. The plasma ir-TRH and TSH responses to cold were inhibited by oxotremorine, SP or PG D2, but enhanced by angiotensin II. The plasma TSH response to TRH was inhibited by SP, but enhanced by angiotensin II. The plasma TSH response to TRH did not differ from that of the control after PG D2 injection. In the haloperidol- or para-chlorophenylalanine (PCPA)-pretreated group, the inhibitory effect of PG D2 or oxotremorine on TSH release was prevented, while in the L-DOPA- or 5-hydroxytryptophan (5-HTP)-pretreated group, the inhibitory effect of SP on TSH release was prevented.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effects of substance P, angiotensin II, oxotremorine and prostaglandin D2 on thyrotropin secretion in rats. 620 27

Thyroid peroxidase in involved in several steps of the biosynthesis of thyroid hormone utilizing H2O2: peroxidation of iodide to iodine, iodination of thyroglobulin (Tg) and coupling reaction leading to T4 and T3 formation. The peroxidase enzyme appears to be an heme protein containing a protoporphyrin IX, with binding sites for both iodide and tyrosine. Although the peroxidase is present in numerous cellular structure, iodination activity occurs primarily if not only at all, at the apical cell border. Lack of peroxidase activity or abnormal peroxidase has been described in isolated cases of congenital goiter with organification defect and a positive perchlorate test. However no change in enzymatic activity has been found in patients with Pendred's syndrome as compared to normal tissue. The deficiency of hormone synthesis observed in various benign diffuse thyroid disorders in certainly not due to a lack of peroxidase activity. In treated hyperthyroid patients, a high cellular activity is observed, especially at the apical cell border. In euthyroid patients with diffuse sporadic goiter, an increase of peroxidase activity is also observed. However, the cytochemical localization of the enzyme in goitrous thyroid gland shows that the peroxidase activity is mostly visualized around numerous lipoid structures; being concentrated in this particular site, the enzyme might preferentially oxidize lipids and consequently be less available for hormone synthesis. In euthyroid hot nodule, the peroxidase activity is normal. In cold nodule, a discrepancy between iodide oxidation and protein iodination has been found, suggesting that iodide peroxidation and iodination of tyrosine residues of Tg are two relatively independent processes although thyroid peroxidase catalyses both reactions. In contrast with the benign pathological conditions, the peroxidase activity is lower than normal in thyroid cancerous tissue.
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PMID:[Peroxidase and human thyroid hormone synthesis disorders (author's transl)]. 626 13

This study is concerned with the characteristics of thyroid hormone binding to isolated hepatic nuclei from premetamorphic tadpoles. Conditions essential for nuclear stability and/or demonstration of saturable binding included 220-mosmol buffers containing 0.1 mM ZnCl2 and removal of most of the melanin granules; binding of T4 and T3 to melanin was significant, but unsaturable. Scatchard analysis of [125I]T3 binding to nuclei in the presence of increasing concentrations of T3 revealed the presence of two sets of saturable sites: a high affinity, low capacity set and a second set which had a lower affinity but approximately 4 times the capacity of the first set. Two sets of T4-binding sites were also detected. The data indicate that the two hormones bind to the same two sets of sites. Thus, both T3 and T4 completely displaced either [125I]T3 or [125I]T4 bound to saturable sites, although more T4 than T3 was required for 50% displacement of either hormone. Moreover, the presence of a partially saturating concentration of T4 in a displacement study of [125I]T3 by cold T3 resulted in decreased affinity of both sets of T3-binding sites. Both sets of sites have a higher affinity for T3 than for T4. It is postulated that the high affinity set of sites consists of hormone receptors.
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PMID:Binding of thyroid hormones to isolated hepatic nuclei from Rana catesbeiana tadpoles. 630 53

An assay procedure for thyroid hormone receptor activity which used nitrocellulose membrane filters was developed. Receptor proteins, extracted from washed rat liver nuclei with a 0.4 M NaCl solution, were incubated with 125I-labeled thyroid hormone (T3), and filtered on the cellulose ester membranes under suction at 2 degrees C. The filters were subsequently washed with cold buffer and counted for 125I radioactivity. The method allowed an accurate estimation of the receptor activity, satisfying a linear relationship between the activity and the receptor protein concentrations. The usefulness of this filter-binding method became evident when it was compared with the conventional procedure that employs Sephadex G-25 columns. For practical application to routine assays, various filtration conditions were examined, and a standard procedure was established. Using this technique, the isolated receptors were determined to possess an apparent Kd of 1.38 X 10(-10) M and a pH optimum of T3 binding at 8.2-8.4.
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PMID:Filter-binding assay procedure for thyroid hormone receptors. 631 96

Recent research has focused on developmental changes in thyroxine (T4) metabolism as well as hormonal and environmental interactions upon peripheral monodeiodination. Toward the end of incubation and the time of air space membrane perforation, concentrations of 3,3', 5'-triiodothyronine T3 increase more rapidly than T4, while reverse T3 (rT3) decreases. Administration of glucocorticoids or prolactin (hormones known to increase at the end of incubation) 2 to 3 days prior to air chamber perforation can induce this change in T4 metabolism. Attention has been focused on two major environmental factors that influence T4 concentrations in posthatch chicks. T4 disappearance rate and peripheral T4 conversion are adjusted during thermal acclimation. More T3 will be generated in cold-exposed chickens, and more rT3 will be produced at higher ambient temperatures. Peripheral T4 metabolism acts as an independent regulation pathway but accompanies changes in hypothalamo-thyroid activity. Changes in thyroid hormone levels following ambient temperature changes, therefore, are the result of a balance between central and peripheral control mechanisms, depending on age of the animal and degree and duration of the temperature change. In the hen, feeding also plays an important role in the regulation of the absolute levels and daily rhythms of plasma thyroid hormones. Fasting results in an increase in circulating T4 levels, but a decrease in T3 levels, owing to a lower 5'deiodinase activity, and also abolishes the circadian circulating T3 rhythm.
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PMID:Hormonal and environmental interactions on thyroid function in the chick embryo and posthatching chicken. 639 3

The status of TSH secretion in hypothalamic hypothyroidism was evaluated by using rats with anterior medial basal hypothalamic deafferentation as the experimental model of the disorder. In the deafferented rats, the basal serum thyroid hormone concentrations as well as that of TSH was significantly lower than normal and cold exposure failed to increase serum TSH, indicating they were in fact in a hypothalamic hypothyroid state. The minimum effective dose of TRH to elicit an increase in serum TSH was smaller in the deafferented rats than in the controls, whereas the response to the maximum dose of TRH was similar in both groups. Although the radioimmunoassayable TSH of the adenohypophysis was significantly decreased in the deafferented rats, it was qualitatively similar to that of the control rats, since the peak of TSH immunoreactivity was eluted at exactly the same position on the gel filtration column in the pituitaries from normal and deafferented rats. When the adenohypophysis was perifused in vitro with Krebs-Ringer solution buffered with Hepes, the minimum effective dose of TRH was similar in both cases. This finding suggests that the exposure to the perifusion medium completely devoid of thyroid and hypothalamic hormones erased the difference in sensitivity to TRH between the two groups as observed in vivo, although in vivo experiments on deafferented rats with normal thyroid hormone induced by exogenous thyroid hormone were not performed. Our results indicate that in hypothalamic hypothyroid rats: 1) the sensitivity but not the responsiveness of the thyrotroph to TRH is increased; and 2) the readily releasable fraction of pituitary TSH pool in response to exogenous TRH is increased. It is also suggested that the difference in the milieu between the pituitary of normal and deafferented rats in vivo is critically important for the latter to retain hypersensitivity to TRH.
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PMID:Increased sensitivity of the thyrotroph to thyrotropin-releasing hormones in rats with hypothalamic hypothyroidism. 641 26

The effects of vasoactive intestinal polypeptide (VIP) on the hypothalamic-pituitary-thyroid axis in rats were studied. VIP (250 micrograms kg-1) was injected i.v. and the rats were serially decapitated. Thyrotropin-releasing hormone (TRH), thyrotropin (TSH) and thyroid hormone were measured by radioimmunoassay. The hypothalamic immunoreactive TRH (ir-TRH) content significantly decreased after VIP injection, whereas its plasma concentration significantly increased. The plasma TSH level increased significantly in a dose-related manner with a zenith at 20 min after the injection. The plasma thyroid hormone level also increased significantly. The plasma ir-TRH and TSH responses to cold as well as the plasma TSH response to TRH were significantly enhanced by VIP. Naloxone partially blocked VIP induced TSH release. In 5-hydroxytryptophan pretreated group the stimulatory effect of VIP on TSH release was prevented, but not in that pretreated with para-chlorophenylalanine, L-DOPA or haloperidol. These drugs alone did not affect plasma TSH levels in terms of the dose used. The inactivation of TRH immunoreactivity by plasma or hypothalamus did not differ from that of the control. These findings suggest that VIP acts on the hypothalamus, pituitary and thyroid gland to stimulate TRH, TSH and thyroid hormone release, respectively, and that its effect may be at least partially modified by the serotonergic system and opioid peptides.
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PMID:Effects of vasoactive intestinal polypeptide on hypothalamic-pituitary-thyroid axis in rats. 643 Jun 73

The effects of beta-casomorphin on thyrotropin-releasing hormone (TRH) and thyrotropin (TSH) secretion in rats were studied. beta-casomorphin (300 micrograms/kg) was injected iv, and the rats were serially decapitated. TRH, TSH and thyroid hormone were measured by radioimmunoassay. The hypothalamic immunoreactive TRH (ir-TRH) contents increased significantly after beta-casomorphin injection, whereas its plasma concentrations tended to decrease, but not significantly. The plasma TSH levels decreased significantly in a dose-related manner with a nadir at 40 min. after the injection. The thyroid hormone levels showed no change. The plasma ir-TRH and TSH responses to cold were inhibited by beta-casomorphin, but the plasma TSH response to TRH was not. Naloxone partially blocked the inhibitory effect of beta-casomorphin on plasma TSH levels. In the haloperidol-pretreated group, the inhibitory effect of beta-casomorphin on plasma TSH levels was prevented, but not in the L-DOPA, para-chlorophenylalanine- or 5-hydroxytryptophan-pretreated group. These drugs alone did not affect plasma TSH levels in terms of the dose used. The findings suggest that beta-casomorphin acts at the hypothalamus to inhibit TRH release, and its effect are modified by a dopaminergic system.
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PMID:Beta-casomorphin inhibits thyrotropin secretion in rats. 644 29


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