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J T Murai

Publications and source records attributed to J T Murai.

32 records · Page 2Linked to original sources
PubMed1984

Estrogen induction of progestophilins in rat estrogen-sensitive cells grown in media supplemented with sera from castrated rats and from rats bearing an alpha-fetoprotein-secreting hepatoma.

The purpose of this work was to study the effect of alpha-fetoprotein (AFP) over cell multiplication and the induction of an estradiol-17 beta (E2)-dependent marker, i.e., progestophilins in E-sensitive cells C2(9)RAP derived from a W/Fu rat pituitary tumor. These cells proliferate in isogeneic hosts under the influence of E2, while they proliferate in culture regardless of the presence of E2. C2(9)RAP cells were grown in medium supplemented with 10% horse serum. Progestophilin levels were measured 48 h after adding serum (20% horse, or castrated rat, or AFP-secreting tumor-bearing rat) and estrogen to the 10% horse serum-supplemented medium in which the cells were growing. Maximal induction of progestophilins was obtained at 3 X 10(-10) M E2 in cells grown in medium containing horse or castrated rat serum. In contrast, maximal induction of progestophilins required 3 X 10(-8) M E2 in cells grown in medium supplemented with the serum of Morris hepatoma 7777-bearing rats. This serum contained AFP levels comparable to those present at birth in the rat. 11-Methoxy-17 beta ethynylestradiol (R2858), a synthetic estrogen with little affinity for AFP, was also tested for its ability to induce progestophilins. The degree of maximal induction of progestophilins expressed as percentage of the respective control, was similar for all experimental groups, both with E2 and with R2858. In addition, we compared the free E2 levels in the culture medium with the progestophilin levels and the cell proliferation rate. We found that the progestophilin levels were maximal at free E2 concentrations above 11 pg E2/ml, whereas there was no correlation between the free E2 levels and the proliferation rate. Moreover, the proliferation rate of cells in medium supplemented with horse or castrated rat serum was maximal at concentrations of free E2 below 0.4 pg/ml; whereas cell proliferation was inhibited with hepatoma serum even at concentrations of free E2 of 44 pg/ml. We conclude that the effect of hepatoma serum on the E2 induction of progestophilins seems to be mediated by the effect of AFP on the availability of free estrogen, since it is abolished by the addition of both natural and synthetic estrogens. The inhibitory effect of hepatoma serum upon cell proliferation is not reversed by estrogens and thus seems to be mediated by mechanisms other than E2 trapping by AFP.

Animals↗
PubMed1982

Serum concentrations of total and non-protein-bound oestradiol in patients with breast cancer and in normal controls.

In premenopausal women with breast cancer, total serum oestradiol (E2) concentrations are normal but nonprotein-bound E2 concentration are significantly raised. This is not due to low sex-hormone-binding-globulin (SHBG) binding capacities which are within the normal range and is unlikely to be due to the small but significant decrease in albumin concentrations. In post-menopausal patients, both total and non-protein-bound E2 are significantly raised: this may be explained partially by lower SHBG binding capacities. In patients and controls there is a highly significant correlation between non-protein-bound E2 and SHBG but, for a given SHBG binding capacity, the patients have more non-bound E2 than controls. It is concluded that the breast in women with breast cancer may be exposed to elevated levels of biologically active E2 although the reasons for this remain obscure.

Adult↗
PubMed1982

Inhibition by 12-O-tetradecanoylphorbol-13-acetate of 17 beta-estradiol-induced initiation of DNA synthesis in rabbit endometrial cells in culture.

The initial effects of 12-O-tetradecanoylphorbol-13-acetate (TPA) and 17 beta-estradiol on initiation of DNA synthesis by primary cultures of estrogen-responsive rabbit uterine epithelial cells were determined by autoradiography after a [3H]thymidine pulse. In contrast to the stimulatory response produced by estradiol, TPA (1.6 x 10(-7) M) reduced the fraction of cells synthesizing DNA for up to 48 h. Cells synthesizing DNA at the time TPA was added were found to be less sensitive to its inhibitory effect, suggesting that TPA blocked the cells from entering the S phase of the cell cycle. The cells were unresponsive to estradiol during the TPA-induced inhibitory period, although TPA did not interfere with the binding of [3H]estradiol to the hormonal whole-cell receptors. The results indicted that TPA acted to reduce the fraction of cells initiating DNa synthesis by a mechanism that appears to be independent of estrogen involvement.

Animals↗
PubMed1979

Decrease of estrogen receptors induced by 17 beta-estradiol and progesterone in cultured rabbit endometrial cells.

A whole cell technique to measure estradiol receptors in cultured rabbit endometrial cells is described. The estradiol receptors measured appear to be composed of at least two components: one component has high affinity but low capacity, while the other component has low affinity but high capacity. Using the assay, the effects of estradiol and progesterone pretreatment were examined on the estradiol receptor levels. It was found that both of the hormones decreased the number of estrogen receptors in the cultured cells. The finding that estradiol decreased its own receptors was unexpected and its possible relevance is discussed.

Animals↗
PubMed1975

Altered distribution and excretion of N-1-methylnicotinamide in rats with Walker 256 carcinosarcoma.

Levels of nicotinamide and N-1-methylnicotinamide in serum, liver, and kidney as well as renal clearances and 24-hr urine levels of N-1-methylnicotinamide were compared in normal rats and rats bearing Walker 256 tumors. There was no significant difference between normal and tumor-bearing rats with regard to nicotinamide levels. With regard to N-1-methylnicotinamide, tumor-bearing rats had significantly lower serum and liver levels and significantly higher 24-hr urine levels and renal clearances. Walker 256 tumor tissue and liver and kidney from a normal and a tumor-bearing rat were separately examined for S-adenosylmethionine:nicotinamide methyltransferase activity. The specific activity in tumor tissue extract was greater than that in each liver extract, which, in turn, was much greater than the specific activity in each tissue (liver and kidney) from the tumor-bearing rat was equal to the specific activity in the corresponding tissue of the normal rat. S-adenosylmethionine:nicotinamide methyltransferase was obtained with 18-fold purification from a tissue extract of Walker 256 tumor. The enzyme activity required activation by thiols, and maximal activity was observed at pH 8.6. The Km's for the substrates, S-adenosylmethionine and nicotinamide, were 7.0 x 10--3 mM and 0.50 mM respectively. The Ki's for the products, S-adenosylhomocysteine and N-1-methylnicotinamide, were respectively, 25 x 10--3 mM and greater than 5 mM.

Animals↗
PubMedDate not supplied

Conversion of androgens to estrogens in the male squirrel monkey (Saimiri sciureas).

Many New World primates such as the squirrel monkey have extraordinarily high plasma levels of steroid hormones including cortisol, testosterone, progesterone and vitamin D3. While plasma estrogen levels in female squirrel monkeys apparently are approximately the same as those found in other species no information is available for males. The present results indicate that the plasma levels of estrone (E1), estradiol (E2), and E1 sulfate are approximately 10-fold higher than those found in men. Comparative in vitro studies of androgen metabolism in genital skin fibroblasts indicate that squirrel monkey cells have higher aromatase and lower 5-alpha-reductase activity than human cells. Estimation of aromatase activity in vivo by a radiometric assay indicates that the high plasma estrogens are derived by peripheral conversion from testicular and/or adrenal androgens.

Androgens↗
PubMedDate not supplied

Hormonal regulation of cultured rabbit endometrial cells.

A technique for culturing primary explants of rabbit endometrial cells in chemically defined medium has been developed. Diethylstilbestrol and natural estrogens were found to increase the rate of DNA initiation while progesterone had the opposite effect. Ultrastructural studies revealed that with estrogens, the cultures had the appearance of rapidly dividing cells having large euchromatic nuclei and prominent nucleoli, with aboundant free ribosomes in the cytoplasm. On the other hand, progesterone induced the formation of large multinucleated cells and also converted the cells to a more secretory type. When the cultures appear secretory, a protein called blastokinin (uteroglobin) is believed secreted. We have found that cultured cells synthesize blastokinin and progesterone is necessary for its continuous synthesis. The cultures were found to have receptors for the ovarian hormones and these receptors exhibited saturation kinetics. The dissociation constants for the receptors were also determined. A hypothetical model for the hormonal regulation of cell proliferation and differentiation is proposed.

Animals↗
PubMedDate not supplied

Human umbilical vessels and cultured umbilical vein endothelial and smooth muscle cells lack detectable protein and mRNA encoding estrogen receptors.

OBJECTIVE: To identify and characterize estrogen receptors in human umbilical vascular tissues and in cultured cells derived from the human umbilical vein. METHODS: Human umbilical vein endothelial (HUVE) and human umbilical vein smooth muscle (HUVSM) cells were isolated. Immunohistochemical, radioligand binding. Western immunoblotting, and reverse transcription-polymerase chain reaction (RT-PCR) methods were used to detect estrogen receptors in vascular tissues and in cells derived from the umbilical cord. RESULTS: Estrogen receptor protein was not detected in either umbilical vessel tissue or in isolated HUVE or HUVSM cells. Messenger RNAs for the classic estrogen receptor (alpha) and estrogen receptor beta isoforms also were undetectable by RT-PCR. CONCLUSION: These findings suggest that the effects of estradiol observed in this widely used vascular model are mediated by very low concentrations of receptors that evade standard methods of detection. Alternatively, this steroid may affect umbilical vascular cells through mechanisms that do not involve the classic genomic estrogen-receptor pathway.

Blotting, Western↗