PubMed Health⌕ Search

Biomedical subjects

B Sato

Publications and source records attributed to B Sato.

At least 145 records · Page 8Linked to original sources
PubMed1982

Localization of delta 4-5 beta- and 5 alpha-reductases and 17 beta-ol-dehydrogenase in immature golden hamster testes.

Testes of 28- and 70-day-old golden hamsters were separated into seminiferus tubules and interstitial tissue by wet dissection. Homogenates of the tissues and subcellular fractions were incubated with [14C]androstenedione, and NADPH and enzyme activity (nanomoles per 100 mg protein/h) was estimated. In immature testes, the 5 beta-reductase activity was largely confined to the seminiferous tubules, while 5 alpha-reductase was localized in the interstitial tissue. The activity of 17 beta-ol-dehydrogenase was found to be equally distributed between tubules and interstitial tissue. Although the activities of 5 beta- and 5 alpha-reductases were approximately 10 times greater in immature than adult testes, the 17 beta-ol-dehydrogenase activity in adult testes was approximately 10 times that in immature testes. In the immature testes, most 5 alpha-reductase and 17 beta-ol-dehydrogenase were localized in microsomes, whereas 5 beta-reductase was wholly localized in cytosol. These results indicates that 5 beta-reduction of delta 4-3-ketosteroids takes place largely in cytosol of tubular cells, while 5 alpha-reduction occurs in microsomes of interstitial cells in the testis of the immature golden hamster.

17-Hydroxysteroid Dehydrogenases↗
PubMed1982

Biological characteristics and estrogen and progesterone receptors in mammary carcinoma induced in male Sprague-Dawley rats by a series of intragastric intubations of 7,12-dimethylbenz(a)anthracene.

Biological characteristics and estrogen (ER) and progesterone (PR) receptors were studied in male mammary carcinomas induced by 7,12-dimethylbenz(a)anthracene (DMBA) in male inbred Sprague-Dawley rats (MM). DMBA-induced carcinomas in females (MF) were used as controls. In 36 of 44 female rats given 20 mg DMBA once by gastric intubation at 50 days of age, MF with microscopic characteristics of cystic papillary adenocarcinoma developed 124 +/- 49 (S.D.) days after challenge. In all of the 42 male rats given 10 mg DMBA at 14-day intervals for 14 weeks starting from 28 days of age. MM with microscopic characteristics of medullary adenocarcinoma developed 106 +/- 21 days after the first intubation of DMBA. The growth of primary MM was unaffected by orchiectomy or estrogen. Eighty to 100% of the MM transplanted in the four groups could grow in intact female rats, ovariectomized female rats, intact male rats, and castrated male rats, while the transplanted MF could grow only in intact female rats. The histology of MM was unchanged in primary and transplanted tumors under various hormonal conditions. ER were present in almost all of the hormone-independent primary and transplanted MM, although the levels for cytosol ER in MM were significantly lower than those in MF. Injection of 10 micrograms 17 beta-estradiol induced marked synthesis of PR in primary and transplanted MM, even 24 and 48 hr after the 17 beta-estradiol injection. These findings show that MM are hormone independent but, like hormone-dependent female tumors, contain ER and estrogen-dependent PR.

9,10-Dimethyl-1,2-benzanthracene↗
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↗
PubMed1980

Relation of membrane property of microsomes to androgen biosynthesis.

Spin-labelled fatty acids I(12,3) and I(1,14) were incorporated into microsomal membrane of cryptorchid mouse testis and Leydig cell tumor as well as liver. The freedom of motion of spin of I(12,3) was more restricted in testis microsome than in liver. At the lower temperatures, the freedom of motion of spin in the tumor microsomes was similar to that in the testis, but at higher temperature (20-50 degrees C) was much greater. Plotting of the empirical parameter, h0/h-1, calculated by the spectra of I(1,14), against the reciprocal of the absolute temperature clearly showed two inflection points in both liver and testis microsomes, one at 19 decrees C and the other at 30 degrees C. On the other hand, tumor microsomes lacked these break points and permitted spin to move more freely. These results suggest that tumor microsomes contain the increased fluidity. The importance of membrane fluidity in relation to steroid biosynthesis was also discussed.

Androgens↗
PubMed1980

Formation of 5 beta- and 5 alpha-products as major C19-steroids from progesterone in vitro in immature golden hamster testes.

Testicular homogenates from 8- to 55-day-old golden hamsters were incubated with [3H]progesterone, [14C]-progesterone, [3H]5 beta-pregnane-3,20-dione, [14C]progesterone plus [3H]5 beta-pregnane-3,20-dione, and [14C]progesterone plus [3H]5 alpha-pregnane-3,20-dione and NADPH. After incubation, the radioactive products were separated and identified by column and paper chromatographies with derivative formation and recrystallization to constant specific activity. The major C21-17-hydroxysteroids and C19-steroids formed from progesterone by the testes of immature golden hamsters were 5 beta- and 5 alpha-steroids, such as 3 alpha,17-dihydroxy-5 beta-pregnan-20-one, etiocholanolone, 5 beta-androstane-3 alpha,17 beta-diol, 3 alpha,17-dihydroxy-5 alpha-pregnan-20-one, androsterone, and 5 alpha-androstane-3 alpha,17 beta-diol. Incubation studies with the testes of the immature hamsters showed that the 5 alpha-C19-steroids were produced from progesterone mainly through 5 alpha-C21-steroids such as 3 alpha,17-dihydroxy-5 alpha-pregnan-20-one, while the 5 beta-C19-steroids were formed through androstenedione and testosterone. The major steroids formed by the testes of suckling and adult animals were 17-hydroxy-4-pregnen-3,20-dione, androstenedione, and testosterone, and little or no 5 beta- and 5 alpha-steroids were produced. The present results demonstrate for the first time that 5 beta-C19-steroids are major C19-steroid products of the gonad.

Androgens↗
PubMed1980

Effect of molybdate on activation and stabilization of steroid receptors.

The effects of molybdate on activation and stability of glucocorticoid, androgen, and estrogen receptors were studied. The activation of steroid receptors by heating or dialysis was inhibited by molydate, but molybdate had no effect on the nuclear binding of previously activated steroid-receptor complexes. The inhibitory effect of molybdate on activation was concentration dependent and was reversed when molybdate was removed by dialysis or gel filtration on Sephadex G-25. The steroid-binding capacities of the unoccupied glucocorticoid and androgen receptors were markedly reduced by removal of a small molecular weight factor(s) from the cytosol by dialysis or gel filtration on Sephadex G-25, even at 0 C. Molybdate blocked both this loss of steroid-binding ability on dialysis and also the heat-induced destabilization of the receptors. The dialysate of rat liver cytosol and molybdate had synergistic effects in increasing the stability of the glucocorticoid receptor in the cytosol after gel filtration at 25 C. These findings suggest that activation and destabilization have a common mechanism which involves a small molecular weight component(s) and that molybdate has a specific inhibitory effect on this mechanism.

Animals↗
PubMed1980

Steroid receptors in osteoblasts.

Using the whole-cell incubation system at 37 degrees C, the specific bindings for 3H-dexamethasone, 3H-estradiol-17 beta, 3H-dihydrotestosterone and 3H-R5020 were measured in the purified, putative osteoblasts isolated from fetal rat calvaria by collagenase digestion. More than 90% of the purified cells contained intense alkaline phosphatase activity. The specific binding for 3H-dexamethasone with high affinity and low capacity was demonstrated in the isolated osteoblasts. Most of the binding was found in the nuclear fraction, indicating nucler binding of the 3H-dexamethasone-receptor complex. The apparent dissociation constant (Kd) for 3H-dexamethasone was estimated to be 3.3 x 10(-9)M and the number of binding sites was calculated to be 65 fmol/ml (4 x 10(6) cells) or 9,750 binding sites per cell. High salt: sucrose gradient analysis of nuclear extracts revealed a radioactive 4.0 S peak. These results indicate that the purified osteoblasts are among the target cells for glucocorticoids. On the other hand, the specific bindings for 3H-estradiol-17 beta and 3H-dihydrotestosterone were not detectable in the isolated osteoblasts, which suggests that estrogens and androgens act on osteoblasts only indirectly.

Animals↗
PubMed1979

The testicular estrogen receptor system in two strains of mice differing in susceptibility to estrogen-induced Leydig cell tumors.

Cytosol obtained from cryptorchid testes of tumor-susceptible BALB/c and resistant C3HBi (Z) mice both bound 17 beta-estradiol (E2) and diethylstilbestrol (DES) specifically. The dissociation constant (Kd) of this binding component (RE) for E2 was determined to approximate 5 x 10(-9) M. Gel filtration of cytosols resulted in a significant increase in the binding constant (Kd approximately 3 x 10(-10) M) with the majority of the complex migrating in the 7-8S area after sucrose gradient centrifugation. Incubation of either untreated or gel-filtered cytosol with [3H]DES resulted in considerable nonspecific binding appearing in the 4S region in a low salt sucrose gradient. This 4S binding of [3H]DES was not inhibited by the addition to the incubation mixtures of a 100-fold excess of either E2 or DES, while the lesser peak at 7-8S as well as the major 7-8S peak formed with E2 were inhibited by both. In vitro translocation of the cytosol RE to the nucleus was demonstrated in both mouse strains using either estrogen. Quantitation of the in vivo translocation, employing the exchange method after a single injection of 2.5 micrograms E2/mouse, revealed a rapid increase in cytoplasmic receptor content accompanied by a concomitant increase in nuclear receptor content. Greater nuclear receptor content was identified in nuclei from BALB/c mice than in those from Z animals 45 min after injection of E2. The binding behavior of E2-RE complexes to nuclei was studied by the KCl extraction method. The percent extracted from the nuclei in the Z strain was significantly greater than that in the BALB/c at all concentrations of KCl tested. Essentially 100% of the RE was extracted from nuclei of Z animals at 0.4 M KCl, while nuclei of BALB/c mice retained 35-40% even in 2 M KCl. Cross-over experiments in a cell-free system suggested that the difference in binding was due to differences in chromatins rather than in nuclear estrogen-receptor complexes. The greater nuclear receptor content and stronger binding of nuclear receptor to chromatin might explain why estrogen-induced phenomena, including neoplastic transformation occur to a much greater degree in the BALB/c strain than in the Z strain of the mouse.

Animals↗