Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

For further investigating the mechanism of the known autoregulation of thyroid follicle growth and function by iodine, we tried to detect iodolactone (6-iodo-8,11,14-eicosatrienoic-delta-lactone) in isolated porcine thyroid follicles and investigated the effects of in vitro synthesized iodolactone on EGF induced thyroid cell proliferation as well as on TSH induced cycli AMP formation. In vitro synthesis of iodolactone was performed with lactoperoxidase catalyzed iodination of arachidonic acid. With gas chromatography-mass spectrometry a molecular mass of 391 m/z corresponding to the derivatization product of iodolactone was found. An ethanol/chloroform extract of isolated thyroid follicles preincubated with KI (10uM) and arachidonic acid (1uM) revealed an identical substrate. This indicates the ability of thyroid follicles to form iodolactone. Iodolactone (0.1-1.0 uM) dose-dependently inhibited EGF induced thyroid cell growth. This growth inhibiting effect of iodolactone was found to be 50-fold more pronounced than the inhibitory effect of KI (4 x 10(-5] on thyroid cell proliferation. In contrast to the effect of iodide, the inhibitory effect of iodolactone on thyroid cell growth could not be abolished by methimazole (1mM). The basal as well as TSH (0.5 U/l) induced cyclic AMP formation was not changed by iodolactone. These experiments suggest a physiological role of iodolactone as a mediator of the known inhibitory effect of iodide on thyroid growth.
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PMID:Evidence that thyroid growth autoregulation is mediated by an iodolactone. 216 2

Different phenomena under consideration, lymphocytic and macrophagic infiltration and increased thyrocyte class I and class II antigen expression, normally ascribed to autoimmune thyroid disease (Graves' disease; Hashimoto's thyroiditis) were frequently found in thyroid glands with autonomous nodules, too. Contrary, nodular formations in the vast majority of nodular goiters were not associated with these immunopathological findings. Furthermore, thyroid microsomal, anti-peroxidase and TSH-receptor antibodies although at low frequency rates, were only detected in cases of autonomous nodules but not in cases of nodular goiters. From these findings we conclude that the immune phenomenon observed in thyroid autonomy could not be a consequence of nodular formations but that at least in some cases of thyroid autonomy immunopathogenic mechanisms may play an important role. Based on the fact that class I hyper-expression was more common and that a stronger correlation of cell infiltration with increased class I than with increased class II expression on thyrocytes existed we propose, that if the initial event of the autoimmune process is indeed increased class II expression, this stimulus may more likely originate from increased non-thyrocyte class II positivity (for example dendritic or endothelial cells) than from thyrocyte class II positivity. But, if aberrant class II expression is not the initial stimulus, another candidate could be the increased thyrocyte class I expression observed, probably due to the action of interferon alpha and/or beta induced by any unknown stimulus (viruses?).
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PMID:Immunopathological findings and thyroid autoantibodies in thyroid autonomy. 220 77

The pars tuberalis (pt) of the adenohypophysis is unique in its close spatial relationship to the neurohemal contact area of the median eminence. The morphology of pt-specific secretory cells does not resemble cell types of the pars distalis (pd); the functional role of these cells within the endocrine system is still unknown. One group of young mature female Wistar rats received propylthiouracil (PTU), a second group thyroxine (T4) (10 mg/l each in drinking water) from about 3 weeks prior to the expected pregnancy and throughout the experiment. On gestation day 20, the fetuses were obtained by laparatomy. Serial sections from the rostral portion of the pt and from the pd were immunostained using the peroxidase-antiperoxidase method. TSH concentrations were determined by RIA in serum and pituitaries; T4 was measured in serum. An antiserum against rat (r) TSH revealed a moderate positive reaction of nearly all cells of the pt in the control group. In both experimental groups the pt-specific cells showed weak or no immunoreactivity. Sections of all groups were negative with anti(r)-LH, -GH, -PRL. In contrast to controls, only a few immature TSH-cells could be found in sections of the pd in the T4-group, while concentrations of TSH in blood and hypophysis were very low. TSH-cells in the PTU-group were enlarged and less intensely stained. TSH-concentrations were decreased in the hypophysis, blood levels were elevated. All sections of the pd-specific cell populations showed positive immunoreactions with anti-r)-LH, -GH, -PRL.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Changes in TSH-immunoreactivity in the pars tuberalis and pars distalis of the fetal rat hypophysis following maternal administration of propylthiouracil and thyroxine. 235 26

The effects of monensin on subcellular structure, release of thyroglobulin (TG) and peroxidase (PO) activity were investigated using primary cultures of thyroid cells obtained from patients with Basedow's disease (Basedow's cells). TG concentration in the culture medium was measured by a sandwich enzyme immunoassay and the amount of TG in cultured cells was measured with an identical sandwich enzyme immunoassay after lysis of the cells with Triton X-100. PO activity of cultured cells was measured by a biochemical method. Addition of TSH (10 mU/ml/day) to the culture medium increased the synthesis and release of TG. When monensin (1 micron/l) was added to the medium on the last day of a 3-day incubation with TSH, the Golgi complex showed vacuolative change ultrastructurally, and the amount of intracellular TG was increased, whereas the amount of TG in the culture medium and PO activity became lower than those in the control group. These results suggest that in cultured Basedow's cells, TG is secreted through the Golgi complex, and that the activity of PO is elevated after processing in the Golgi complex.
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PMID:Effects of monensin on subcellular structure, thyroglobulin secretion and peroxidase activity of cultured thyroid cells obtained from patients with hyperthyroidism. 236 Apr 57

Reversed-phase (RP) HPLC, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and gel permeation chromatography have been used to study the incorporation of 125I into bovine (b) TSH by the lactoperoxidase-catalyzed radioiodination procedure. Two preparations of [125I]bTSH were studied, being freshly iodinated bTSH and tracer purified from this preparation by the method of receptor adsorption. It is demonstrated with these methods that both the alpha- and beta-subunits of bTSH are labeled with 125I, and that the tracer purified by receptor adsorption retains this incorporation pattern. However, the implied theoretical specific activity of (at least) 2 I atoms per TSH molecule (or approximately 140 muCi/micrograms) suggested by this result was not achieved, with observed tracer specific activity being 30-60 muCi/micrograms, indicating that hormone molecules with varying extents of labeling must exist. Evidence to support this was provided by comparison of the MIT/DIT ratios for the 2 tracer preparations. Receptor adsorption decreased the MIT/DIT ratio from 75:25 in the freshly iodinated bTSH to 93:7, indicating the selection of particular iodinated species. Tryptic mapping by RP-HPLC was used to study both tracer preparations, and it is shown that at least 14 iodine-containing tryptic peptides may be resolved for each preparation, which is greater than the theoretical maximum of 13 peptides if every tyrosine was labeled and tryptic cleavage occurred at all possible lysine and arginine residues. Tracer heterogeneity was also studied by purification using RP-HPLC. Selection of peak fractions demonstrated that intact [125I]bTSH may be recovered from RP-HPLC which in TSH radioreceptor assay exhibit increased assay sensitivity, increased saturable binding, and decreased nonsaturable binding.
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PMID:Characterization and purification of iodinated bovine thyrotropin by high performance liquid chromatography. 242 94

The effect of six drugs on the uptake and organification of iodide by porcine thyroid cells stimulated with bovine TSH (10 miU/L) has been investigated. The drugs fall into two categories: the peroxidase inhibitors, methimazole (MMI), 2-thiouracil (2-TU) and 3-amino 1,2,4 triazole (3-ATA) and the ionic inhibitors, lithium chloride (LiCl), potassium perchlorate (KC10(4], and sodium iodide (NaI). All the drugs led to a dose-related inhibition of iodide metabolism. The most potent effect on iodide uptake was seen with NaI which inhibited this function by 20% even at 10(-8) mol/l. In contrast, the most potent effect on iodide organification was observed with methimazole which led to a 25% inhibition at 10(-8) mol/l. The concentrations of drug which gave rise to a 50% inhibition of iodide uptake were (mumol/l) 0.26 (NaI), 3.5 (KClO4), 9.7 (2-TU), 15 (MMI), 26 (3-ATA), and 1500 (LiCl). The comparable figures for organification were 0.13 (MMI), 0.18 (2-TU), 0.23 (NaI), 1.2 (3-ATA), 15 (KClO4) and 1300 (LiCl). We conclude that this in vitro system has considerable potential for the assessment of potency and possible bioassay of anti-thyroid drugs of varying structures and sites of action.
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PMID:Assessment of the biopotency of anti-thyroid drugs using porcine thyroid cells. 243 28

Intact anterior pituitary tissue and primary anterior pituitary cultures were stained with 1:30,000 anti-TRH and 1:10,000 anti-GnRH using the peroxidase antiperoxidase immunocytochemical technique. Stains applied to serial ultrathin sections of intact pituitaries showed that TRH immunoreactivity could be localized in secretory granules of thyrotropes, gonadotropes and corticotropes whereas GnRH immunoreactivity was found only in gonadotropes and corticotropes. Long-term primary pituitary cultures were studied to remove the anterior pituitary cells from hypothalamic influences. In these cell populations both TRH and GnRH immunoreactivity persisted. In addition, quantification of the stained cells at the light microscopic level demonstrated that the volume fraction of TRH and GnRH immunoreactive cells remained constant up to 3 weeks of culture. Studies of serial ultrathin sections through cells from these cultures showed TRH or GnRH localized in secretory granules of cells that contained LH and ACTH, but not TSH. Both liquid and solid phase immunoabsorption specificity controls were used to validate the immunocytochemical stains. These studies suggest that the pituitary TRH and GnRH immunoreactivities may not be completely of hypothalamic origin, but may also be endogenous to a subpopulation of unique multihormonal pituitary cells.
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PMID:Persistence of immunoreactive TRH and GnRH in long-term primary anterior pituitary cultures. 244 3

The presence of mAB lu-5, a panepithelial, monoclonal antibody was studied in human adenohypophyses and pituitary adenomas by immunohistochemistry using the avidinbiotin-peroxidase complex technique. In nontumorous adenohypophyses, only corticotrophs showed strong immunoreactivity, whereas other adenohypophysial cell types exhibited little or no staining. Positive immunostaining was observed in corticotrophs spreading to the posterior lobe, in cells of squamous nests located in the pars tuberalis and several cells lining pars intermedia cavities. The Crooke's hyaline material in the cytoplasm of corticotrophs was immunopositive. In adenomatous corticotrophs and cytoplasmic fibrous bodies of sparsely granulated adenomatous somatotrophs, distinct mAB lu-5 immunoreactivity was evident. GH-, PRL-, TSH-, FSH-, LH-, alpha-subunit-producing adenomas, null cell adenomas and oncocytomas showed no convincing staining. Immunopositivity in corticotroph adenomas was diffusely distributed in the cytoplasm and was not located in secretory granules, indicating that mAB lu-5 did not stain ACTH. Immunoreactivity with mAB lu-5 was not specific for pituitary corticotrophs, since the antibody stained nontumorous epithelial cells and epithelial tumor cells in other organs as well. It can be concluded that mAB lu-5 is a valuable immunocytochemical marker in pituitary related studies, especially in those pituitary adenomas in which immunostaining for ACTH is weak or equivocal; in these cases, it can confirm the diagnosis of corticotroph adenoma. The antibody yields similar results as keratin antisera. In our experience, however, it gives a stronger, more distinct immunopositivity with less nonspecific background staining.
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PMID:Identification of corticotrophs in the human pituitary with mAB lu-5, a novel immunocytochemical marker. 244 79

The effects of TSH on peroxidase activity (PO) and thyroglobulin (TG) production were investigated using primary cultures of thyroid cells obtained from patients with Basedow's disease (Basedow's cells). PO activity of cultured cells and TG concentration in the culture medium were measured by biochemical and sandwich enzyme immunoassays, respectively. The addition of TSH (10 mU/ml/day) to the medium did not increase the cell number but did increase the PO activity and TG concentration. It took more than 3 days for the PO activity of cells cultured with TSH (stimulated group) to reach a level twice that of cells cultured without TSH (control group), whereas 2 days of incubation with TSH was sufficient for increasing the TG concentration. When actinomycin D (AD) was added to the medium on the first day of 3-day incubation with TSH, the stimulatory effect of TSH on PO was completely blocked and the TG concentration was reduced to half that of the control group. AD given to the stimulated group on the last day of induction produced no inhibitory effect on the induction of PO activity by TSH, but reduced the TG concentration to almost half that in the stimulated group. An electron microscopic study of Basedow's cells cultured with AD and TSH failed to reveal any cytopathic change. The findings of the present study suggested that in cultured Basedow's cells TSH induces PO activity and TG production through the synthesis of new messenger RNA.
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PMID:Induction of peroxidase and thyroglobulin by TSH in cultured thyroid cells from patients with Basedow's disease and its inhibition by actinomycin D. 254 97

A rat thyroid peroxidase cDNA has been isolated from a FRTL-5 thyroid cell library and sequenced. The cDNA is 2776 base pairs long with an open reading frame of 770 amino acids. By comparison to full-length human thyroid peroxidase cDNA and based on its identification of a 3.2 kilobase mRNA in rat thyroid FRTL-5 cell Northern blots, the rat peroxidase cDNA appears to lack 400-500 base pairs at the 5'-end of the mRNA. It exhibits only a 74% nucleotide and 77% amino acid sequence similarity to human thyroid peroxidase cDNA within the total aligned sequences, although the predicted active site regions are highly conserved (greater than 90-100%). The cDNA has been used to map the thyroid peroxidase gene in mice to chromosome 12 and to compare thyroid peroxidase and thyroglobulin gene expression in FRTL-5 rat thyroid cells. Despite the fact TSH action in both cases is duplicated, and presumably mediated, by cAMP, TSH-induced increases in thyroid peroxidase and thyroglobulin mRNA levels differ. Differences exist with respect to hormone concentration and time. The ability of TSH to increase thyroglobulin, but not thyroid peroxidase mRNA levels, requires insulin, 5% serum, or insulin-like growth factor-I. Insulin or insulin-like growth factor-I alone can increase thyroglobulin mRNA levels as well as or better than TSH but have only a small effect on thyroid peroxidase mRNA levels by comparison to TSH. The ability of TSH to increase thyroglobulin gene expression is readily detected in nuclear run-on assays but not the ability of TSH to increase thyroid peroxidase gene expression. Cycloheximide inhibits TSH-increased thyroglobulin but not peroxidase mRNA levels. Finally, methimazole and phorbol 12-myristate 13-acetate show different effects on TSH-induced increases in thyroglobulin and thyroid peroxidase mRNA levels.
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PMID:Thyroid peroxidase: rat cDNA sequence, chromosomal localization in mouse, and regulation of gene expression by comparison to thyroglobulin in rat FRTL-5 cells. 269 80


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