Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.11.1.7 (peroxidase)
 65,474 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The properties of TSH receptors in normal and pathological human thyroid tissues were studied. Highly purified bovine TSH after lactoperoxidase iodination retained full biological activity, as assessed by radioreceptor assay. Binding of bovine [125I]TSH to 1000 x g pellets of human thyroid homogenate was specific with respect to hormone and tissue. Total binding amounted to 50-60% of total radioactivity using 10 mg (wet weight) normal thyroid tissue. Nonspecific binding was only 6% of total radioactivity. Normal thyroid tissue contained two orders of binding sites, which were shown to be independent of each other by Hill plot analysis. The high affinity sites [equilibrium dissociation constant (Kd), 0.015-0.16 x 10-9 M] were present in concentrations of 1.05-9.30 pmol/mg protein and concentrations of low affinity sites (Kd, 1.2-2.4 x 10-9 M) were 35.9-213 pmol/mg. In all pathological thyroid tissue studied, two orders of binding sites were found with dissociation constants similar to those of normal tissues, but the number of binding sites was markedly reduced. Both orders of binding sites in solitary "cold" adenomas and only the low affinity sites in thyroid tissue from patients with Graves' disease were significantly reduced in number (P less than 0.01). There was a questionable decrease in high affinity sites in the Graves' tissue (P = 0.05). We have found the definite presence but a decreased number of binding sites in both orders of receptors in papillary and follicular carcinomas. There were few or no binding sites in medullary carcinoma.
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PMID:Thyrotropin receptors in normal and pathological human thyroid tissues. 4 70

Rat anterior pituitaries were cytologically studied following cultivation in organ culture, with and without the addition of hypothalamic and cortical extracts. Although five distinct cell types could be identified with classical stains in the uncultivated glands, the peroxidase-labeled antibody technique (using antibodies against STH, LTH, FSH, LH and TSH) showed that not all of the immune-specific cell types were being identified with the classical stains. This discrepancy was magnified following culture as chromophilic cells seen with classic stains decreased in number with an increase in culture time. The peroxidase technique, however, revealed that all cells remained constant in type and number regardless of time in culture. While the addition of either hypothalamic or cortical extract to the culture medium produced cytological alterations demonstrated by the classical dyes, the antibody technique showed no such alterations. Such a comparison of staining techniques emphasizes the hazards of relying solely on histological procedures to reveal the hormonal activity of the pituitary gland.
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PMID:Immunochemical staining of the rat adenohypophysis in organ culture. 4 77

The iodide-peroxidase activity of the thyroid gland remains, in hypophysectomized Rats maintained on a low iodine diet, below normal value. This result suggests that the early increase of peroxidase activity observed in control Rats maintained on a low iodine diet is TSH dependent.
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PMID:[Development of thyroid peroxidase activity during the early stage of iodine deficiency in the hypophysectomized rat]. 11 12

The initial step in TSH action reflects binding of the hormone to specific receptor sites on the plasma membrane. Such binding has been studied using plasma membranes, homogenates, isolated thyroid cells grown in culture, and thyroid slices. 3-H- and iodinated TSH preparations have been used; the latter have been prepared using both chloramine-T and lactoperoxidase. Some of the discrepancies reported in the literature might reflect the different thyroid and hormone preparations and the variable incubation conditions which have been used. In general, good correlation exists between binding of TSH and activation of adenylate cyclase in thyroid plasma membranes. Data is reviewed related to activation of protein kinase in intact thyroid cells by TSH. Although there is impressive evidence for cyclic AMP mediation of effects of TSH on the thyroid, some data that are inconsistent with this concept are considered, especially in relationship to 32-P incorporation into phospholipid. The role of cyclic GMP in thyroid function is discussed.
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PMID:Thyroid-stimulating hormone and cyclic adenosine 3',5'-monophosphate in the regulation of thyroid gland function. 16 59

A highly specific and sensitive radioreceptor assay for FSH has been developed, using partially purified plasma membranes from bovine testes. Highly purifed hFSH was radioiodinated by the lactoperoxidase method. The limit of detection of purified hFSH was 1 ng/ml on the basis of 2 times standard deviation of the zero value. The assay was applicable for measurements of FSH in serum; however, the sensitivity decreased slightly to 2.5 ng/ml. The precision of the assay was less than +/- 10% within-assays and +/- 15% between-assays as expressed by the coefficient of variation. The assay was highly specific for FSH of various species. Slight inhibition of uptake of 125I-hFSH was observed with LH and TSH; but no competition was seen with 10,000 ng/ml of insulin, prolactin, hGH, hCG, and subunits of LH. Purified hFSH (LER-1575C) was measured to be 200 times the potency of the reference FSH/LH (LER-907); and purified ovine FSH (LER-1491) and rat FSH (FSH-I-1) were estimated to be 35 times and 71 times that of oFSH-S-1 (NIH), respectively. The content of FSH in human pituitary was estimated to be 226.8 +/- 118.8 mIU/mg, and the index of discrimination (radioimmunoassay/radioreceptor assay) for pituitary FSH was demonstrated to be 1.71 +/- 0.49. For measurements of serum hFSH, the index of discrimination (radioimmunoassay/radioreceptor assay) was demonstrated to be 1.08 +/- 0.20.
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PMID:A radioreceptor assay for follicle-stimulating hormone. 16 91

Specific prolactin (PRL) binding activity of lactoperoxidase catalyzed 125I-labeled ovine-PRL was determined in a membrane-rich particulate fraction of pigeon crop sacs. Levels of TSH, LH or FSH as high as 1000 ng each were unable to displace the 125I-o-PRL bound to 600 mug of crop sac microsomal protein, whereas competitive displacement was achieved with as little as 0.5 ng unlabeled PRL. Ovine GH exhibited some cross reactivity when incubated in amounts greater than 500 ng, but this could be accounted for by its stated PRL contamination. Specific PRL binding activities were determined in juvenile and mature pigeons with unstimulated crop sacs, and parent pigeons with 'crop milk' and mature birds injected with PRL for 4 days. Crop sacs from juvenile birds contained approximately twice as much binding activity as crop sacs from mature pigeons. Parent and PRL injected pigeons, each with proliferated crop sac epithelium, exhibited 4-5 times as much specific PRL binding as the non-proliferated crops from juvenile or mature birds. These results show that the pigeon crop sac contains specific binding sites for PRL, and that the crop sac response to PRL is associated with an increase in PRL binding activity.
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PMID:Prolactin binding activity on the crop sacs of juvenile, mature, parent and prolactin-injected pigeons. 17 Nov 36

The thyroid gland of homozygous Gunn rats is moderately enlarged and displays a brownish-black discoloration. Light microscopic examination discloses that the follicular cells are filled with brown granules, which are shown, under the electron microscope, to be modified colloid droplets. Most of them possess a strong acid phosphatase and a mild peroxidase activity and contain a melanin-like pigment, according to histochemical analysis. In comparison with normal Wistar rats, Gunn rats possess significantly higher plasma thyroxine and lower triiodothyronine as well as an increased plasma TSH level. The soluble protein content of the thyroid is reduced in the Gunn rat, as is the total intrathyroid iodine content. The hyperthyroxinaemia of homozygous Gunn rats is due to a hereditary deficiency in hepatic glucuronyl transferase activity. The excess circulating thyroxine is of little functional importance because it is firmly bound to plasma proteins. But Gunn rats have a slight hypothyroid goitre for reasons not yet elucidated. The functional as well as morphological data at present available suggest a modified thyroid iodine metabolism and an altered composition of the thyroglobulin which may induce abnormalities in colloid proteolysis. The observed pigment may result from peroxidation of tyrosine. These alterations are probably independent of the sole enzymatic deficiency so far encountered in these animals and may probably be ascribed to a primary enzymatic defect in the thyroid gland itself.
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PMID:Pigmentation and dysfunction of Gunn rat thyroid: correlation between morphological and biochemical data. 17 74

The nature of the TSH receptor in adenoma and carcinoma of the thyroid gland was studied using a radioreceptor assay technique. A membrane fraction of tissue homogenate was obtained by discontinuous sucrose gradient ultracentrifugation, and 125I-TSH, labelled by a lactoperoxidase method, was purified with a receptor adsorption method. Both the capacities and the association constants of high affinity receptors (4 x 10(9) M-1) and of low affinity receptors (0.073 x 10(9) M-1) observed in the normal thyroid were almost identical to those of the thyroid of Graves' disease and those of thyroid adenoma. Although the two papillary carcinomas examined were found to have two kinds of TSH receptors, one of the carcinomas showed decreased association constants for both high affinity and low affinity receptors.
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PMID:Presence of TSH receptor in thyroid neoplasms. 17 43

Adenohypophysial primordia of rat embryos at 13 to 15 days gestation were cultured in Parker 199 synthetic medium for 2 to 11 days. At the end of the culture period their fine structure and the presence of immunoreactive trophic hormones using the peroxidase-labeled antibody technique were investigated. The degree of differentiation in the glands depends largely on the age of the embryos furnishing the explants. Cultured pituitaries explanted on the 13th day of gestation contain only ACTH-positive cells and about 15% of the cells are granular. The granules are 50-100 nm in diameter in some cells, while in other cells they range from 50 to 200 nm. In cultivated adenohypophysial primordia of embryos on the 15th day of intrauterine life ACTH, prolactin, LH and TSH cells are evident, but only the same two kinds of granular cells can be observed with the electron microscope. The extent of cytodifferentiation in the glands explanted on the 14th day of gestation is intermediate between the two other groups. The data suggest that the fetal rat pituitary has the capacity of self-differentiation but to a lesser extent than that of the in situ hypophysis.
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PMID:Cell differentiation of the fetal rat anterior pituitary in vitro. 18 70

The onset of hormone synthesis in the rat fetal pituitary gland was studied with the use of the peroxidase labelled antibody method. On the 16th day of fetal life, cells containing immunoreactive ACTH appeared in the primordial cell outgrowth of the Rathke's pouch. In some fetuses, also prolactin cells could be detected at the same developmental stage and these cells were present consistently on subsequent days. Differentiation of ACTH and prolactin cells was followed by onset of TSH, LH and GH synthesis on the 17th, 18th and 19th day of gestation, respectively.
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PMID:Functional differentiation of the fetal anterior pituitary cells in the rat. 18 42


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