Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0001430 (adenoma)
 21,222 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Activin A stimulated synthesis and secretion of intact FSH in dispersed human FSH-secreting adenoma cells. Significant stimulation was observed after 24 hr. Activin A caused an increase in Ca2+ concentration ([Ca2+]i). This response occurred soon after the activin A action. These effects were blocked in Ca(2+)-deficient medium and by nitrendipine (5 microM). Somatostatin inhibited the activin A-induced intact FSH secretion and the [Ca2+]i response. These findings indicated that Ca2+ influx through voltage-gated Ca2+ channel was involved in the activin A induced synthesis and secretion of intact FSH.
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PMID:Effects of activin A and somatostatin on intact FSH secretion and intracellular Ca2+ concentration in human FSH-secreting pituitary adenoma cells. 134 12

Activin A is a homodimer of inhibin beta A subunits, and was first isolated from gonadal fluids on the basis of its ability to stimulate FSH secretion by rat pituitary cells in vitro. The beta A subunits of activin and their mRNAs have been found in many cell types, in several species and at different stages of development, suggesting that activin A has a wide range of diverse biological roles. Apart from the modulation of gonadotroph function, in-vitro studies have demonstrated inhibitory effects of activin A on GH synthesis, GH secretion and possibly somatotroph proliferation. We have therefore investigated the potential role of activin A in the pathophysiological regulation of GH secretion by human somatotrophinoma cells using in-vitro techniques. Cell cultures were established by enzyme dispersion of adenoma tissue obtained from six patients with acromegaly, and treated for 72 h with 0.01-10 nmol recombinant human activin A/l followed by a 2-h stimulation test with 10 nmol GH-releasing factor (GRF)/l. Medium was collected at 24, 48 and 72 h, as well as after GRF treatment, and GH concentrations were measured by immunoradiometric assay. Basal GH secretion from the cells of two tumours was significantly stimulated 12-63% above control values during treatment with 0.01-10 nmol activin A/l, whereas the peptide had no effect on GH release from cells of the remainder of the tumours. GRF significantly stimulated GH release from the cells of two different adenomas, and pretreatment with 0.01-1 nmol activin A/1 partially but significantly blocked GRF-stimulated GH release from the cells of one of these.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effects of recombinant human activin A on growth hormone secretion by human somatotrophinomas in vitro. 832 58

Inhibin alpha and beta A subunit messenger ribonucleic acid (mRNA) levels were measured quantitatively by reverse transcription-polymerase chain reaction (RT-PCR) in human pituitary adenomas. The inhibin alpha subunit mRNA levels were undetectably low in cultured adenoma tissues, but beta A mRNA were 0.383 +/- 0.074 in 3 GH adenomas, 0.672 +/- 0.140 in 3 prolactinomas and 0.957 +/- 0.414 molecules/cell in 3 non-functioning adenomas. The addition of 10(-8) M activin A decreased the beta A mRNA levels within 4 h in 1 of 3 GH adenomas, 2 of 3 prolactinomas and 2 of 3 non-functioning adenomas, though the decreases were not statistically significant. The results showed an abundance of beta A subunit mRNA compared with alpha subunit mRNA in all human pituitary adenomas and a local role for activin in its own production through inhibin beta A mRNA subunit expression.
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PMID:Inhibin alpha and beta A subunit messenger ribonucleic acids expression in human pituitary adenomas: studies by quantitative reverse transcription-polymerase chain reaction. 888 32

Inhibins and activins have been known to modify the secretion of various pituitary hormones. To study whether inhibins and activins are present in human pituitary tissues, immunohistochemical studies with antisera to activin A and inhibin alpha subunit were performed on 9 human pituitary adenoma tissue specimens and one sample of normal pituitary tissue adjacent to one adenoma. Activin immunoreactivities were demonstrated in the cytoplasms of one GH and one PRL and two non-functioning adenomas and one normal pituitary tissue, but they were negative in one PRL, one ACTH, one FSH and two non-functioning adenomas. Thus, the presence and absence of activin in the same type of adenoma in regard to hormone production, suggested that the difference in immunostaining simply reflected the difference in the activin concentration. In contrast to this, inhibin alpha subunit immunoreactivity was not found in any of the tissues studied. These data suggested a local synthesis of activin in the normal pituitary as well as various kinds of pituitary adenoma tissues and its local role in the human pituitary gland.
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PMID:Demonstration of activin in normal pituitary and in various human pituitary adenomas by immunohistochemistry. 893 May 32

Apoptosis seems to be the predominant type of active cell death in the liver (type I), while in other tissues cells may die via biochemically and morphologically different pathways (type II, type III). Active cell death is under the control of growth factors and death signals. In the liver, endogenous factors, such as transforming growth factor beta 1 (TGF-beta 1), activin A, CD95 ligand, and tumor necrosis factor (TNF) may be involved in induction of apoptosis. Release and action of these death factors seems to be triggered by exogenous signals such as withdrawal of hepato-mitogens, food restriction, etc. During stages of hepatocarcinogenesis, not only DNA synthesis but also apoptosis gradually increase from normal to preneoplastic to adenoma and carcinoma tissue. Also, in human carcinomas, birth and death rates of cells are several times higher than in surrounding liver. (Pre)neoplastic liver cells are more susceptible than normal hepatocytes to stimulation of cell replication and of cell death. Consequently, tumor promoters may act as survival factors, i.e., inhibit apoptosis preferentially in preneoplastic and even in malignant liver cells, thereby stimulating selective growth of (pre)neoplastic lesions. On the other hand, regimens favoring apoptosis and lowering cell replication may result in selective elimination of (pre)neoplastic cell clones from the liver. Finally, we have studied the first stage of carcinogenesis, namely the appearance of putatively initiated cells after a single dose of the genotoxic carcinogen N-nitrosomorpholine (NNM). Most of these cells were found to be eliminated by apoptosis, suggesting that initiation, at the organ level, can be reversed at least partially by preferential elimination of initiated cells. These events may be regulated by autocrine or paracrine actions of survival factors.
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PMID:Apoptosis in the liver and its role in hepatocarcinogenesis. 929 54

Activin A belongs to the transforming growth factor-beta superfamily that exerts a wide range of biologic activities on cellular proliferation and differentiation. Although it was suggested that gonadal tissue is the primary site of activin production, several extragonadal sources have subsequently been identified, including human thyrocytes. The goal of the present study was to evaluate serum activin A levels in a series of patients with different thyroid disorders during the active state of the diseases and after recovery. Serum activin A levels were evaluated in 60 healthy subjects (controls), 8 with multinodular nontoxic goiter (MNG), 30 hyperthyroid (15 with Graves' disease (GD), 12 with autonomous hyperfunctioning adenoma (ATA), and 3 with thyrotropin (TSH)-secreting pituitary adenoma, 16 hypothyroid (11 with Hashimoto's thyroiditis and 5 after total thyroidectomy), and 9 patients with resistance to thyroid hormone (RTH) by commercial enzyme-linked immunosorbent assay (ELISA) kit. Patients with GD and ATA showed activin A levels higher than those found in controls and similar to those observed in MNG (GD, 0.74 +/- 0.3 ng/mL; ATA, 0.86 +/- 0.4; and MNG; 1.0 +/- 0.2 vs. controls: 0.39 +/- 0.5, p < 0.001), while in patients with Hashimoto's thyroiditis, total thyroidectomy or RTH activin A levels were similar to those of controls. In conclusion, this study demonstrates that thyroid hyperplasia and hyperfunction result in increased levels of activin A, although the normal levels observed in thyroidectomized patients clearly demonstrate that the thyroid gland is not the predominant source of activin A in normal conditions. Because activin A may exert negative action on thyrocyte proliferation, it is conceivable that activin A hypersecretion in thyroid disorders might represent a counteracting mechanism.
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PMID:Serum activin A levels in different thyroid disorders. 1259 25

Activins are dimeric proteins of the transforming growth factor beta superfamily, which exhibit multiple functions in gonadal and extragonadal tissues. Expression of activin A, composed of two betaA subunits, has been shown in the thyroid, whereas there has been no study regarding activin B (betaBbetaB) in this gland. In other tissues, such as the gonads, pancreas, and adrenal cortex, expression of both activin betaA and activin betaB has been described. In this study, we detected activin betaB mRNA and protein expression using reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry in rat experimental goiter and in human thyroid, including multinodular goiter, follicular adenoma, papillary carcinoma, and follicular carcinoma. Activin betaA mRNA and protein expression was also investigated in rat and human thyroid tissue. The expression of both activin betaB and activin betaA was highest in rat methimazole-induced goiter and in human follicular adenoma, and papillary and follicular carcinomas when compared with multinodular goiter and normal thyroid tissue. The increased expression of activin betaB as well as activin betaA, observed in this study, suggests that activin B and activin A may be involved in the proliferative and neoplastic processes of the thyroid.
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PMID:Activin betaB expression in rat experimental goiter and human thyroid tumors. 1272 72