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Biomedical subjects

M Munemura

Publications and source records attributed to M Munemura.

At least 19 recordsLinked to original sources
PubMed1989

Chronic estrogen treatment promotes a functional uncoupling of the D2 dopamine receptor in rat anterior pituitary gland.

The effect of chronic estrogen treatment on the anterior pituitary D2 dopamine receptor was studied by treating rats with diethylstilbestrol (DES) over a 6-week period. DES treatment resulted in an increase in anterior pituitary weight and PRL content and serum PRL levels compared to those in sham-treated controls. The status of the anterior pituitary D2 dopamine receptor was evaluated using both radioligand binding and adenylate cyclase assays. [125I]N-(p-aminophenethyl)spiroperidol [( 125I]NAPS), a derivative of the D2-selective antagonist spiperone, was used to quantitate D2 receptors. Saturation analysis of [125I]NAPS binding indicated that DES treatment had no effect on the affinity or maximum binding capacity of the radioligand for the D2 receptor. Competition analysis with unlabeled D2 antagonists for [125I]NAPS binding also indicated that DES treatment did not affect antagonist interactions with the receptor. In contrast, the interactions of agonists with the D2 receptors from DES-treated rats were modified, as assessed through [125I]NAPS competition analysis. Using control tissue, agonist competition curves revealed both high and low affinity agonist binding states of the receptor. In the presence of guanine nucleotides, the high affinity agonist binding state is abolished, reflecting coupling of the receptor with a guanine nucleotide regulatory (G) protein. In DES-treated tissue, agonist competition curves indicated the presence of only low affinity agonist binding, with minimal effects of guanine nucleotides, suggesting uncoupling of receptor-G-protein interactions. The functionality of the D2 receptor was further assessed by examining dopaminergic inhibition of vasoactive intestinal peptide-stimulated adenylate cyclase activity. Although DES treatment resulted in a reduction of vasoactive intestinal peptide-stimulated enzyme activity itself, the ability of dopaminergic agonists to inhibit this activity was reduced by about 50%. These results suggest that estrogen is capable of attenuating the functional coupling of the D2 receptor with its biochemical effector system in the anterior pituitary gland.

Adenylyl Cyclases↗
PubMed1986

The effects of A23187 and phorbol ester on the phosphorylation of proteins in rat anterior pituitary cells.

The effects of A23187 and 12-O-tetradecanoyl-phorbol-13-acetate (TPA) on the phosphorylation of proteins in normal rat anterior pituitary cells were compared. A23187 rapidly activated the phosphorylation of at least 5 proteins (45, 47, 53, 54 and 58 kDa), which reached the maximal level in 2-10 min, and decreased gradually thereafter. In contrast, TPA activated the phosphorylation of at least 6 proteins (45, 62, 64, 72, 76 and 82 kDa), which were mostly distinguished from those activated by A23187. TPA-induced response was elicited more slowly, reached a plateau after about 10 min, and was sustained thereafter. These results suggest that the protein phosphorylation stimulated by A23187 and TPA is conducted by different mechanisms.

Animals↗
PubMed1985

[The effects of dopamine on the release of immunoreactive beta-endorphin-like peptide from the dispersed cells of the rat neurointermediate lobe].

The intermediate lobe of the rat pituitary gland is a homogeneous population of cells which synthesize and secrete various peptides related to ACTH and lipotropin derived from a common precursor, proopiomelanocortin. Catecholamine beta-receptor (beta-adrenoceptor) and dopamine receptor which are present in the intact cells of the intermediate lobe, remain functional in the enzymatically dispersed cells. In this study we investigated the mechanism by which beta-endorphin is released from the dispersed cells of the neurointermediate lobe of the rat pituitary gland. 1-Isoproterenol stimulated the release of immunoreactive beta-endorphin-like peptide (IR-beta-Ep) and the accumulation of adenosine 3', 5'-monophosphate (cAMP). On the other hand, dopaminergic drugs, apomorphine, bromocriptine, dopamine, lergotrile and lisuride, decreased the rate of release of IR-beta-Ep. Dopamine also inhibited the stimulatory effects of 1-isoproterenol on the release of IR-beta-Ep and cAMP accumulation. Dopamine antagonists, fluphenazine and sulpiride, diminished the inhibitory effects of dopamine on the release of IR-beta-Ep and cAMP accumulation which were stimulated by 1-isoproterenol. it has been reported that cholera toxin enhanced the release of IR-beta-Ep and the accumulation of cAMP in the rat neurointermediate lobe. After preincubation in the incubation medium containing 30 nM cholera toxin for 2 hours, the cells (CT cells) showed spontaneous release of IR-beta-Ep and cAMP accumulation. 1-Isoproterenol had no effect on the release of IR-beta-Ep and cAMP accumulation in CT cells. Dopamine, however, inhibited both the release of IR-beta-Ep from CT cells and cAMP accumulation in CT cells. These results suggest that dopamine may be involved in the regulatory mechanism of IR-beta-Ep release from the dispersed cells of the rat neurointermediate lobe.

Animals↗
PubMed1985

Involvement of calcium in the release of immunoreactive beta-endorphin-like peptide from dispersed cells of the neurointermediate lobe of the rat pituitary gland.

The presence of Ca2+ in the incubation medium was required for stimulation of the release of the immunoreactive beta-endorphin-like peptide (IR-beta-EP) from the dispersed cells of the neurointermediate lobe of rat pituitary gland by adenosine 3',5'-monophosphate (cAMP) analogs, a phosphodiesterase inhibitor, L-isoproterenol, cholera toxin and forskolin. The basal release observed in the absence of the stimulants was also dependent on the addition of Ca2+. A calcium antagonist (verapamil) inhibited the effects of the stimulants. A calcium ionophore (A23187) enhanced the release of IR-beta-EP, but did not stimulate the formation of cAMP. These findings suggest that Ca2+ has the essential role in the release of beta-endorphin from the neurointermediate lobe of rat pituitary gland.

1-Methyl-3-isobutylxanthine↗
PubMed1985

In vivo and in vitro studies on the production of placental proteins (human chorionic gonadotropin, human placental lactogen, and pregnancy-specific beta 1-glycoprotein) in an adrenal choriocarcinoma.

The ectopic production of placental proteins (human chorionic gonadotropin [hCG], human placental lactogen, and pregnancy-specific beta 1-glycoprotein) by an adrenal choriocarcinoma was investigated experimentally in vivo and in vitro. By an immunohistochemical method, the choriocarcinoma tissues obtained from the right adrenalectomy were found to react with hCG, human placental lactogen, and pregnancy-specific beta 1-glycoprotein antibodies. The concentrations of hCG-beta, human placental lactogen, and pregnancy-specific beta 1-glycoprotein in the tumor fluid were 1480, 100, and 47 ng/mL, respectively. On incubation of the tumor slices in vitro, the concentration of hCG-beta in the incubation medium increased markedly with time. Serial sections of the removed uterus and right ovary did not reveal any primary trophoblastic lesions. The present tumor responded well to double chemotherapy with actinomycin D and methotrexate, resulting in a decrease of the level of serum hCG-beta to less than 10 ng/mL after four courses of the chemotherapy.

Adrenal Gland Neoplasms↗
PubMed1984

[The effects of cholera toxin in the release of beta-endorphin from the dispersed cells of the rat neurointermediate lobe].

The intermediate lobe cells of pituitary gland synthesize and secrete bioactive peptides derived from proopiomelanocortin. In the present study, we investigated the effects of cholera toxin on the release of beta-endorphin (beta-Ep) from dispersed-intermediate lobe cells of rats. Cholera toxin added into culture medium, enhanced the intracellular accumulation of adenosine 3', 5'-monophosphate (cAMP) and the release of beta-endorphin like immunoreactive substance (beta-END-LIS). A positive dose-response relationship existed between the concentration of cholera toxin and the release of beta-END-LIS or the accumulation of cAMP. Maximal response was obtained with approximately 3 X 10(-10) M (in beta-END-LIS release) and 1 X 10(-9) M (in cAMP accumulation) concentration of cholera toxin. Incubation with cholera toxin (3 X 10(-8) M) resulted in a significant rise of cAMP accumulation after 20-30 min, and a 2-2.5 fold increase of beta-END-LIS release occurred after 60 min in comparison with nontreated cells. cAMP analog and phosphodiesterase inhibitor also increased the beta-END-LIS release). These results suggested the close relationship between cAMP accumulation and its biological effect (i.e. beta-END-LIS release).

Animals↗
PubMed1984

Endocrine studies on ovarian androblastomas (Sertoli-Leydig tumors).

Endocrine studies were made on 4 women with ovarian Sertoli-Leydig cell tumors of varying degrees of differentiation. Clinically, all 4 patients showed evidence of increased androgen production, manifested by either hirsutism or virilization. The calculated ratios of steroid hormones between the affected ovarian venous values and peripheral values for testosterone (T), androstenedione (A), and dehydroepiandrosterone (DHEA) in 3 patients, were 1.4-18.6, 4.2-24.4, and 3.7-10.0, respectively. The peripheral levels of the hormones before salpingo-oophorectomy in all the patients were T: 0.97-45.0 ng/ml; A: 2.92-114.0 ng/ml; and DHEA: 13.0-20.9 ng/ml. In the 3 juvenile patients, elevated basal levels of LH and normal or subnormal levels of FSH (high LH:FSH ratio) were found. In a 12-year-old patient with 1,900 g tumor composed predominantly of Sertoli cells with lipid storage, the peripheral serum levels of T and estradiol (E2) were 114 ng/ml and 1890 pg/ml, respectively. The present data suggest that: 1) androblastomas have a biosynthetic capacity for androgen, estrogen, or both in which both the delta 5 and delta 4 pathways are involved, and 2) little correlation exists between the endocrine function and cellular composition of the tumors or their degree of differentiation.

17-Hydroxycorticosteroids↗
PubMed1984

Massive edema of the ovary associated with hydrothorax and ascites.

A 29-year-old woman with massive edema of the ovary which was grossly mistaken for neoplasia because it was associated with large volumes of both pleural effusion and ascites is described. The ovarian mass measured 10 X 10 X 8 cm and weighed 850 g. Total hysterectomy and bilateral salpingo-oophorectomy were performed. Microscopically, the ovary consisted of diffusely edematous stroma enveloping nests of hyperplastic theca cells or showing a loose myxomatous contexture. However, no endocrine activity of the ovary was demonstrated on the basis of laboratory endocrine values obtained by radioimmunoassay techniques.

Adult↗
PubMed1984

[Endocrine profile and electron microscopic study of ovarian androblastoma].

The endocrine profile of a 23-year-old woman with an androblastoma of the right ovary and the results of electron microscopic observation of the tumor are presented. The calculated ratio of testosterone in testosterone intraoperative peripheral vein blood, right ovarian vein blood, and right ovarian tumor fluid was 1:1.4:4.0. The peripheral levels of hormones before right salpingo-oophorectomy were testosterone, 6.26 ng/ml; dehydroepiandrosterone, 17.80 ng/ml; androstenedione, 1.61 ng/ml; and cortisol, 16.5 micrograms/ml, and the corresponding levels at 14 days after surgery were 0.50 ng/ml; 13.80 ng/ml; 1.27 ng/ml; and 15.2 micrograms/ml, respectively. The tumor was responsive to hCG, resulting in a marked increase in the serum concentrations of testosterone, androstenedione, and dehydroepiandrosterone (3.7 times, 5.3 times, and 2.4 times, respectively). Preoperatively, an elevated basal level of luteinizing hormone (LH) and a normal basal level of follicle-stimulating hormone (FSH) (high LH:FSH ratio, 6.6) were found. The electron microscopic findings for the tumor revealed Leydig cells, Sertoli cells, transitional cells with features of both Sertoli cells and Leydig cells, and dark cells. The dark cells had features similar to dark cells of normal ovarian stroma.

Adult↗
PubMed1983

Calmodulin and Ca2+- and calmodulin-dependent protein kinase in rat anterior pituitary gland.

Calmodulin and Ca2+- and calmodulin-dependent protein kinase were identified in the rat anterior pituitary gland. The concentration of calmodulin was 1.18 +/- 0.11 microgram/mg protein (n = 7) in the cytosol fraction. The calmodulin of the anterior pituitary gland co-migrated with brain calmodulin on sodium dodecyl sulfate polyacrylamide gel electrophoresis. The Ka value of the partially purified enzyme for Ca2+ was 3.3 microM in the presence of 0.30 microM calmodulin. Trifluoperazine and chlorpromazine, calmodulin-interacting agents, inhibited enzyme activity, with Ki values of 1.3 and 2.6 X 10(-5) M, respectively. The enzyme was resolved into two peaks of activity, with sedimentation coefficients of 5.5 S and 16.5 S, by sucrose density gradient centrifugation. At least nine proteins were phosphorylated by the enzyme in a Ca2+- and calmodulin-dependent manner. In light of these results, the possibility that calmodulin and the calmodulin-activatable protein kinase system are involved in the mediation of the Ca2+ effect on hormone release from the anterior pituitary gland must be given consideration.

Animals↗
PubMed1983

[Immunochemotherapy of recurrent and advanced uterine and ovarian cancer using cisplatin].

A combination immunochemotherapy regimen containing cisplatin (20 mg, days 1-5), peplomycin (20 mg, days 2, 9, 16), +/- vinblastine (5 mg, days 1, 2), and picibanil (3-5 KE/week) was performed in twelve patients with advanced or recurrent uterine and ovarian cancers under intravenous hyperalimentation (IVH), except one patient receiving peplomycin by a continuous infusion method using IVH bag (10 mg/day for 5 days). This regimen was repeated every three weeks. Five (71.4%) of seven evaluable patients showed partial response. No patients yielded the complete disappearance of disease. No severe and lethal pulmonary or renal dysfunction occurred and all was well tolerated. In a regimen without vinblastine, myelosuppression, especially thrombocytopenia, occurred later compared to the regimen including vinblastine.

Adenocarcinoma↗