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K Noma

Publications and source records attributed to K Noma.

At least 73 records · Page 4Linked to original sources
PubMed1987

Effects of estrogen and vanadate on the proliferation of newly established transformed mouse Leydig cell line in vitro.

A permanent cell line (B-1-A-2) derived from an estrogen-responsive mouse Leydig cell tumor (T 124958-R) was established in culture. Although this cell line showed estrogen-induced enhancement of cell proliferation in vitro, a moderately high concentration (10(-8) M) of estradiol was required to stimulate maximum growth. A whole cell binding assay revealed that the B-1-A-2 cells contained estrogen receptors with relatively low affinity for estradiol (Kd, 10(-9)-10(-8) M). This estrogen receptor was found to have a mol wt of 65,000. In addition, incubation of the cells with [32P]orthophosphate and subsequent purification revealed that the estrogen receptor is phosphorylated. This finding prompted us to study the effect of phosphatase inhibitors on cell proliferation. The inclusion of vanadate (25 microM) in the culture medium resulted in a significant increase in estrogen sensitivity, showing a maximal growth stimulatory effect of estradiol at concentrations of 10(-10)-10(-9) M. Simultaneously, the conversion of the low affinity to the high affinity receptor (Kd, 10(-10)-10(-9) M) was induced by treatment of cells with vanadate. These data suggest that estrogen directly stimulates the growth of B-1-A-2 cells in culture, and that the sensitivity to estrogen can be altered by modulating the estrogen receptor possibly via a phosphorylation-dephosphorylation mechanism.

Animals↗
PubMed1987

A case of von Recklinghausen's disease associated with pheochromocytoma and papillary carcinoma of the thyroid gland.

A 58-year-old woman was admitted to our hospital complaining of headache, dizziness and intermittent elevation of blood pressure. Multiple café-au-lait spots and neurofibromas had appeared on the back and the limbs since the age of 30 years. At the age of 54 years she underwent total thyroidectomy because of papillary carcinoma of the thyroid gland. On admission, the levels of plasma norepinephrine and epinephrine, urinary norepinephrine and normetanephrine were all within the normal range. However, urinary excretion of metanephrine was markedly increased to 1.49 +/- 0.45 (Mean +/- SD) mg/day and that of epinephrine was also slightly increased. The computed tomographic scans of the abdomen and the scintigraphy with 131I-metaiodobenzylguanidine revealed a tumor mass in the region of the right adrenal gland. The tumor was histologically confirmed to be pheochromocytoma at the operation. In her family history, her mother and one of her two sisters had von Recklinghausen's disease and another sister suffered from follicular carcinoma of the thyroid gland. As far as we know, this paper is the first report of a patient with von Recklinghausen's disease associated with both pheochromocytoma and non-medullary carcinoma of the thyroid gland, and her family.

Carcinoma, Papillary↗
PubMed1987

Demonstration of specific dopamine receptors on human pituitary adenomas.

Dopamine receptors on human pituitary adenoma membranes were characterized using [3H] spiperone as the radioligand. The specific [3H]spiperone binding sites on prolactin (PRL)-secreting adenoma membranes were recognized as a dopamine receptor, based upon the data showing high affinity binding, saturability, specificity, temperature dependence, and reversibility. All of 14 PRL-secreting adenomas had high affinity dopamine receptors, with a dissociation constant (Kd) of 0.85 +/- 0.11 nmol/l (mean +/- SEM) and a maximal binding capacity (Bmax) of 428 +/- 48.6 fmol/mg protein. Among 14 growth hormone (GH)-secreting adenomas examined, 8 (57%) had dopamine receptors with a Kd of 1.90 +/- 0.47 nmol/l and a Bmax of 131 +/- 36.9 fmol/mg protein. Furthermore, 15 of 24 (58%) nonsecreting pituitary adenomas also had dopamine receptors with a Kd of 1.86 +/- 0.37 nmol/l and a Bmax of 162 +/- 26.0 fmol/mg protein. These results indicate that some GH-secreting adenomas as well as some nonsecreting pituitary adenomas contain dopamine receptors. But their affinity and number of binding sites are significantly lower (P less than 0.05) and fewer (P less than 0.001) respectively, than those in PRL-secreting adenomas.

Adenoma↗
PubMed1986

Biochemical and immunological characterization of estrogen binding components in human neoplastic adrenocortical tissues.

The estrogen binding components in human adrenocortical tissues were examined. Two adrenocortical cancer cytosols were found to contain the binder with a relative low affinity (Kd 5 X 10(-9) M) for estradiol. The association of [3H]estradiol to these cytosols was inhibited by a large dose of unlabeled estrone, estradiol or estriol, but neither by diethylstilbestrol nor by dihydrotestosterone. Incubation of cultured cells derived from these cancers with [3H]estradiol also showed the presence of this low-affinity estradiol binder. The addition of bovine serum albumin into these cytosols surprisingly resulted in a marked increase in estradiol binding capacity in a concentration-dependent manner. This component sedimented at 5 S in the low salt sucrose density gradient. This binding ability was found to be heat-labile in the absence of estradiol, but preformation of complexes with estradiol markedly stabilized its binding ability against thermal inactivation. In addition, experiments using monoclonal antibodies to human estrogen receptor revealed that the estrogen binder from one adrenocortical cancer cytosol shared antigenic determinants with human estrogen receptor. These results suggest that the unique estrogen binder in some adrenocortical cancer has the characteristics similar to estrogen receptors in terms of thermal stability and immunological cross-reactivity to antibodies.

Adrenal Cortex Neoplasms↗
PubMed1985

Identification of immunoassayable estrogen receptor lacking hormone binding ability in tamoxifen-treated rat uterus.

Using two different monoclonal antibodies to human estrogen receptor (ER), the enzymeimmunoassay was performed. The values of ER contents in human breast cancer and untreated rat uteri obtained by this procedure were correlated well with those by [3H] estradiol binding assay. When estradiol was injected to immature rats, the enzymeimmunoassay showed the uterine receptor dynamic pattern similar to those analyzed by exchange assays. In contrast, tamoxifen administration induced the immunoassayable but nonsteroid binding form of ER. This ER-like antigen was the heat-labile molecule with the sedimentation constant of 7 S while ER in untreated rat uterine cytosol sedimented at 9 S. These results suggest the presence of unique molecular state of ER induced by tamoxifen.

Animals↗
PubMed1985

Multiple estrogen binding sites in malignant mouse Leydig cells and their role in cell proliferation.

Incubation of dispersed cells derived from an estrogen-responsive mouse Leydig cell tumor with [3H]estradiol in the presence or absence of unlabeled estradiol showed the existence of two types of binding components with high (Kd approximately 10(-9) M) and low (Kd approximately 1.5 X 10(-8) M) affinity respectively. The use of unlabeled diethylstilbestrol as a competitor, however, abolished the low-affinity binder, resulting in the demonstration of the high binding site. This diethylstilbestrol-suppressible binding site was exclusively located in the nuclear fraction, even without hormonal stimuli. A long (5-hr) exposure of these cells to estrogen caused the decrease in the number of nuclear estrogen binding sites, which was similar to so-called 'processing' of putative nuclear estrogen receptor. The direct stimulative effect of estrogen on the proliferation of these cells was demonstrated by measuring cell numbers as well as thymidine incorporation into DNA in the cultured condition. These results would indicate that estrogen directly exerts its effects on this malignant Leydig cell through this unique nuclear binding site.

Animals↗
PubMed1984

Estrogen induces secretary proteins in transformed mouse Leydig cell in vivo, but not in vitro.

The estrogen-induced proteins were analyzed in one of estrogen responsive mouse Leydig tumors. The incubation of cells freshly prepared from solid tumors with [35S] methionine resulted in the demonstration of estrogen-induced secretary protein with a molecular weight of 34,000. The additional minor estrogen-induced secretary protein (36,000) was also identified. An exposure of these cells to the culture condition for 48 hr caused the loss of their ability to synthesize these secretary proteins even in the presence of estrogen. In contrast, minced tumor tissue was observed to sustain the ability to synthesize these proteins at least for 48 hr. These results would suggest that some cellular arrangement is required for the synthesis of estrogen-induced proteins.

Animals↗
PubMed1984

Effects of tamoxifen on estrogen-induced enhancement or inhibition of tumor growth in mouse Leydig cell tumor lines.

In order to avoid the complex dual effects of estrogen and antiestrogen, the attempt was made to establish the tumor lines in which estrogens show either stimulatory or inhibitory property in terms of the tumor growth. The administration of estrogen to host mice bearing one of the mouse Leydig cell tumor lines, called T 124958-R, resulted in marked enhancement of the tumor growth even at pharmacological levels of estrogen. On the other hand, estrogenization of host mice almost completely inhibited the growth of the other tumor line (T 22137) without detectable stimulatory effects. The physiocochemical properties of the cytosol estrogen receptor in both sublines were found to be similar in relation to the affinity toward ligands, steroid specificity, sedimentation profile, and the dissociation rate kinetics. Using these tumor lines, the action mechanism of tamoxifen on the tumor growth was examined. Daily administration of this compound (30 micrograms/mouse) led to enhanced tumor growth in T 124958-R, while the growth of T 22137 was inhibited by the same procedure. In the combination experiments, tamoxifen was found to be unable to antagonize estrogen-induced enhancement or inhibition of the growth in these tumors. In addition, both tumors contained similar levels of the antiestrogen binding sites. These results suggest that tamoxifen modulated the tumor growth through its estrogenic potency.

Animals↗
PubMed1983

Chronic estrogen treatment causes an alteration in uterine estrogen receptor dynamics of rats.

Estrogen receptor content and dynamics in the uteri obtained from chronically estrogenized rats were analyzed. 12 day treatment with a subcutaneous implantation of a diethylstilbestrol pellet resulted in maximal stimulation of uteri with regard to wet tissue weight, DNA content, as well as progesterone receptor content without significant alteration of the estrogen receptor level. Estrogen receptor dynamics in just ovariectomized or ovariectomized and diethylstilbestrol-stimulated rats elicited by a single injection of estradiol were next examined using the exchange methods. The cytosol receptor content rapidly declined, with a small and temporary accumulation of the nuclear receptor in the uterus from rats continuously exposed to diethylstilbestrol during the preceding 12 days. A relatively rapid cytosol receptor replenishment was also observed in rats pretreated with diethylstilbestrol. This was accompanied by a rapid decrease in the nuclear receptor level to 70% of the preinjection value at 5 h after estradiol administration. These data are in contrast to findings on uteri of ovariectomized and nonestrogen-treated rats, in which a single injection of estradiol resulted in a prolonged nuclear receptor retention and a delayed cytosol receptor replenishment. Adrenalectomy did not result in a significant change of receptor dynamic patterns, suggesting that adrenal steroids do not play a role in the alteration of receptor dynamics elicited by continuous stimulation with diethylstilbestrol. These observations suggest that a continuous exposure of rat uteri to the estrogen causes an altered regulation of estrogen receptor dynamics by the homologous steroid compared to those in chronically estrogen-deprived rats.

Animals↗
PubMed1983

Characterization of a unique nuclear estrogen-binding component in an estrogen-responsive mouse Leydig cell tumor.

An estrogen-responsive mouse Leydig cell tumor line (Tumor 124958) has been shown to contain only a low-affinity binder for estradiol in the cytosol fraction. This differed from the putative estrogen receptor in terms of its hormone-binding specificity as well as affinity. In addition, the possibility that an estrogen receptor-like molecule exists in the nuclei even without hormonal stimuli was examined using purified nuclei. Scatchard plot analyses showed that these nuclei possessed a large amount of estrogen binder having a high affinity for estradiol and diethylstilbestrol. The content of this nuclear binding component was not diminished by using molybdate, a potent inhibitor for receptor activation, and in vitro incubation of collagenase-dispersed cells with estradiol did not cause significant increase in the number of nuclear binding sites when compared with the values obtained by direct incubation of isolated nuclei with estradiol. These results support the view that this nuclear estrogen binder is not due to artificial migration of the cytosol receptor into nuclei during homogenization. The characterization of this nuclear binding component under cell-free conditions revealed that its affinity for estradiol in Mg2+-containing buffer was temperature dependent (Kd 3 nM at 30 degrees and 12 nM at 0 degrees) without significant alteration in the number of maximum binding sites. Introduction of a chelating agent (ethylenediaminetetraacetate) into the buffer system abolished the temperature effect on the affinity, resulting in high affinity for estradiol at both low and high temperatures. These Mg2+ and temperature effects were reversible. In addition, when compared with putative nuclear estrogen receptors, this nuclear binding was observed to be relatively resistant to high salt or micrococcal nuclease treatments in relation to solubilization from nuclei. However, trypsin digestion was found to result in a marked decrease in the nuclear binding sites, indicating that this unique nuclear binding component contains a protein unit(s). These results suggest the possibility that this tumor line contains a unique unoccupied nuclear estrogen binder which might be able to transmit estrogen signals to tumor cell nuclei with regard to tumor growth.

Animals↗
PubMed1983

Steroid receptor forms and their interaction with cytoplasmic modulators.

The cytoplasmic modulator affecting steroid receptor functions was studied. The diminution in the concentration of the low molecular weight substances in the cytosol caused the increased interaction of hormone-receptor complexes with nuclei (a step termed activation). Furthermore, dialysis of rat uterine cytosol in the absence of estrogens subsequently followed by incubation with isolated nuclei resulted in the demonstration of an appearance of unoccupied nuclear receptor which was found to be 4S form. The addition of the dialyzable compound into rat uterine estrogen receptor system caused the suppression of temperature-dependent activation while the already-activated estrogen receptor was not affected by the small molecules in relation to its nuclear binding ability. These results may indicate that this small molecule, so-called the low molecular weight inhibitor, is capable of interacting with nonactivated receptor. In one of the estrogen-independent Leydig cell tumor lines, unique low-affinity estrogen binder with a mol. wt approximately 36,000 was identified. This binder did not show appreciable nuclear binding ability even after conventional heat activation. However, removal of the small molecules from this cytosol resulted in a marked increase in affinity for estrogens with a concomittant alteration of the mol. wt to approximately 70,000. These changes also paralleled a dramatic enhancement of nuclear binding ability. This small molecule might be different from the low molecular weight inhibitor suppressing receptor activation, since this tumor cytosol containing unique estrogen binder had much less inhibitory activity against receptor activation when compared with those in the other cytosol containing usual estrogen receptor systems. In adult rat urine cytosol, a new modulator was identified to recognize only activated estrogen receptor but not glucocorticoid receptor and to induce receptor aggregation with a concomittant loss of its nuclear binding ability. These reactions were accelerated by the presence of physiological or higher KCl concentration and exposure to a relatively high temperature (20-30 degrees C). Interestingly, this factor was not identified in the immature rat uteri or liver.

Adrenalectomy↗
PubMed1981

A modulator which converts activated estrogen receptor to a biologically inactive aggregated form.

The in vitro nuclear binding of rat uterine estrogen-receptor complexes has been studied. Heating cytosol from mature rat uterus at 25 C for various times in the presence of 0.15 M KCl resulted in a transient increase in nuclear binding activity, followed by irreversible loss of this activity. The molecular state of these complexes heated at 25 C in the presence of 0.15 M KCl was determined using Sephadex G-200 chromatography and sucrose density centrifugation at high ionic strength (0.4 M KCl). Gel filtration resulted in steroid-binding activity in the void volume. Sucrose density gradient analysis revealed a broad peak, ranging from approximately 5-20S. When cytosol was heated at 25 C in the presence of 10 mM molybdate to block the temperature-induced activation of receptor, nuclear binding ability was easily recovered by dialysis, while heating already activated estrogen receptor in the presence of 0.15 M KCl and 10 mM molybdate caused irreversible loss of nuclear binding ability. When cytosols prepared from immature rats (19-23 days old) were heated at 25 C in the presence of 0.15 M KCl, only a minimum loss of nuclear binding ability was shown. The radioactive peak in a high salt sucrose density gradient appeared almost exclusively in the 5S region. However, the addition of receptor-free mature uterine cytosol to estrogen-receptor complexes from immature rat uterus caused a marked loss of nuclear binding utility, with a resultant receptor aggregation, whereas rat liver cytosol had no effect on this reaction. Furthermore, heating liver glucocorticoid receptor did not cause a loss of nuclear binding ability even in the presence of receptor-free adult rat uterine cytosol. These observations suggest that there is a factor(s) in rat uterus which recognizes only activated estrogen receptor and induces receptor aggregation and a rapid loss of the nuclear binding ability of receptor in a KCl concentration- and temperature-dependent manner. Preliminary characterization indicates that this factor is macromolecular in nature and resistant to RNase and trypsin treatment, but labile at 100 C.

Animals↗