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M Taga

Publications and source records attributed to M Taga.

At least 73 records · Page 4Linked to original sources
PubMed1989

Identification and partial characterization of mesenchyme-derived growth factor that stimulates proliferation and inhibits functional differentiation of mouse mammary epithelium in culture.

The effect of mesenchyme on both proliferation and differentiation of mammary epithelial cells was investigated in a primary cell culture system. Mammary cells cultured on collagen gel for 4 days produced casein in response to the synergistic action of insulin, cortisol, and prolactin. When mammary epithelial cells were co-cultured with fibroblasts derived from three different kinds of fetal mesenchymal tissues, casein production was suppressed. The addition of conditioned media obtained from cultures of these mesenchymal cells stimulated DNA synthesis and reduced casein synthesis in a dose-dependent fashion in the cultured mammary cells. Although such biological actions are similar to those of epidermal growth factor (EGF), the capability to compete with EGF for EGF receptor was not found in this conditioned medium. Sephadex G-200 column chromatography revealed that molecular weight of the peak which has these biological activities was around 100,000. These results indicate that fetal mesenchymal cells secrete a substance(s) which has a stimulatory effect on proliferation and an inhibitory effect on differentiation of mammary epithelial cells.

Animals↗
PubMed1987

Study of the growth factors for the mammary gland: epidermal growth factor and mesenchyme-derived growth factor.

The physiological importance of EGF in the development of the mouse mammary gland during pregnancy and in spontaneous mammary tumorigenesis has been documented by a series of experimental results presented herein. In our study, we have taken a variety of experimental approaches including radioimmunoassay of EGF in the submandibular gland and plasma, mammary gland organ/cell culture, EGF receptor assay, sialoadenectomy and treatment with EGF and EGF antibodies to assess the role of EGF in the mammary gland. In particular, studies employing sialoadenectomy and EGF replacement have provided valuable information concerning the function of EGF in the body. These studies are possible in the mouse system because the submandibular gland serves as a major source of circulating EGF and also because purified mouse EGF is available commercially. Our work on the biological, endocrinological, and physiological aspects of EGF in normal and neoplastic growth of the mammary gland should be useful for the study of the regulation of mammary gland growth at the molecular level as well as for clinical investigations of mammary tumors. Finally, our findings of a mammary growth factor in embryonic mesenchymal cultures suggest the possible involvement of paracrine growth factor(s) in mammary cell growth. Further progress in this area is needed for better understanding of the complex process of mammary gland growth and development.

Animals↗
PubMed1982

[Endocrinological analysis of hypothalamic primary amenorrhea (author's transl)].

Primary amenorrhea, in which serum concentrations of gonadotropins are low or normal, has been considered to be relatively rare. Recent analysis in our outpatient clinic revealed that the incidence of hypothalamic primary amenorrhea is higher than previously appreciated, comprising 26.7% of the total primary amenorrheas. Endocrinological functions of the hypothalamo-hypophyseo-ovarian axis in these patients were therefore investigated. Studies on gonadotropin secretion indicated that a disturbance in LH-RH secretion and a lack of estrogen positive feedback were principle features of this disease. In addition to the dysfunction of gonadotropin secretion, the control of PRL secretion was disturbed in this disease since there was a poor PRL response to chlorpromazine in spite of normal responsiveness to TRH. Thus, "isolated gonadotropin deficiency" hitherto used to describe this disease is not pertinent. Furthermore, these results suggest that PRL might be involved in the onset of puberty in humans. Clinically, the induction of ovulation with HMG (Human Menopausal Gonadotropin) is possible in hypothalamic primary amenorrhea, although the ovarian responsiveness to gonadotropin is poor. Therefore, an endocrinologically precise diagnosis of hypothalamic primary amenorrhea is important in the gynecological clinic because fertility has been considered to be almost impossible in primary amenorrhea.

Amenorrhea↗
PubMed1982

Synthesis and secretion of prolactin in the decidualized human endometrium unassociated with pregnancy in vitro.

The effect of the decidualization induced by the administration of sex steroid hormones on the human endometrial PRL contents and the mechanism of synthesis and secretion of PRL in this decidualized endometrium of non-pregnant women were investigated. The PRL contents increased in proportion to the degree of decidualization. In vitro secretion of PRL in decidualized human endometrium was inhibited by the protein synthesis inhibitors, while TRH, dopamine, and bromocriptine did not have any effects on PRL secretion in incubation experiments. These data suggest that the production and secretion of PRL in the human endometrium have no relation to the presence of conceptus, and furthermore, they are regulated by mechanism different from the pituitary PRL.

Cycloheximide↗
PubMed1982

Effects of sex steroid hormones on rat anterior pituitary LH-RH receptor.

In order to elucidate the mechanism of estrogen action at the anterior pituitary level, the effects of estradiol on the number of binding sites of LH-RH receptor in the anterior pituitary as well as its effects on the anterior pituitary responsiveness to LH-RH were studied in castrated adult female rats. Daily sc injections of 20 micrograms of 17 beta-estradiol for 2 and 4 days increased both LH-RH receptor levels and the responsiveness of the pituitary to LH-RH. This result indicates that estrogen modulates the sensitivity of the anterior pituitary to LH-RH by changing its LH-RH receptor.

Animals↗
PubMed1982

[Studies on the intercompartmental relationship of PRL secretion during human pregnancy--maternal, fetal, and amniotic fluid PRL--(author's transl)].

Although it is well established that PRL is present in the maternal serum, fetal serum, and amniotic fluid during human pregnancy, the precise interrelationship among those three compartments is unknown. In order to elucidate the intercompartmental relationship, several experiments were undertaken. Results are as follows: 2. The concentration of amniotic fluid PRL was different from that of maternal or fetal serum PRL during gestation. 2. There was no correlation between amniotic fluid and maternal or cord serum PRL at delivery. 3. Although bromocriptine suppressed the secretion of maternal serum PRL abruptly, the concentration of amniotic fluid PRL remained unchanged after the administration of bromocriptine at mid-gestation. 4. Analysis of molecular size of PRL by Sephadex G-100 column gel filtration revealed that the elution profiles of maternal serum PRL, fetal serum PRL, and amniotic fluid PRL differed from one another and furthermore, they were similar to those of adult pituitary PRL, fetal pituitary PRL, and decidual PRL, respectively. 5. PRL which was secreted from decidua could transfer to amniotic cavity across the fetal membrane. 6. Decidual PRL and amniotic fluid PRL have a biological activity. These results suggest that three compartments of PRL secretion during human pregnancy are independent each other and, furthermore, possible origin of amniotic fluid PRL is decidua.

Amniotic Fluid↗
PubMed1981

Stimulatory effect of chlorpromazine on prolactin secretion in anencephalic infants.

The effect of chlorpromazine on serum levels of PRL was studied in two anencephalic infants without identifiable hypothalamic tissue. After a single im injection of chlorpromazine, serum concentrations of PRL rose about 3-fold. This result indicates that chlorpromazine stimulates PRL release by directly acting on the pituitary gland in humans.

Anencephaly↗
PubMed1981

Effect of prolactin on the secretion of dehydroepiandrosterone (DHEA), its sulfate (DHEA-S), and cortisol by the human fetal adrenal in vitro.

The effect of prolactin on the secretions of dehydroepiandrosterone (DHEA) and its sulfate (DHEA-S) as well as that of cortisol were studied in vitro in order to investigate the possible regulatory role of prolactin on steroidogenesis of the human fetal adrenal at mid-gestational age. The addition of 0.5 microgram/ml of human prolactin to the incubation medium produced a significant (P less than 0.05) increase in DHEA, DHEA-S, and cortisol secretion. These results indicate that prolactin has a regulatory role in steroidogenesis in the human fetal adrenal at mid-gestation.

Adrenal Glands↗
PubMed1981

Synthesis of prolactin by human decidua in vitro.

Human decidua, chorion, amnion and placenta from the 1st., 2nd. and 3rd. trimesters of gestation were investigated for synthesis and secretion of prolactin by in vitro incubation of these tissue fragments in medium 199. Prolactin content in decidua was found to be significantly higher than that in chorion, amnion or placenta at any stages of gestation. During 6 hours of incubation, decidua secreted significantly more prolactin into medium than did chorion, amnion or placenta. The amount of prolactin secreted by decidua was significantly higher than the prolactin content in tissue before incubation. Decidua were also incubated in medium 199 with or without actinomycin-D (20-200 micrograms/ml), puromycin (200 micrograms/ml) or cycloheximide (100-200 micrograms/ml) for 12 hours. Both total prolactin secreted into medium and prolactin content in tissue after incubation were significantly lower than the control without inhibitor. Decidua of 2nd. trimester of gestation was noted to secrete more prolactin into medium than decidua of 1st. or 3rd. trimester of gestation. In further studies, 3H-leucine (200 muCi) was incubated for 12 hours with decidua (10 grams) from 2nd. trimester of gestation. The incorporated protein in medium or tissue was extracted, fractionated by gel filtration through Sephadex G-100 column and by 10% SDS-polyacrylamide gel electrophoresis. Peaks of 3H count and immunoreactive prolactin in gel slices were coincident with the peak of standard pituitary prolactin at gel slices' No. 31 (Rf = 0.62). These results demonstrate that prolactin is synthesized and secreted by human decidua, which is identical to human pituitary prolactin. The synthetic activity is most prominent in the decidua of the 2nd. trimester of pregnancy.

Amnion↗
PubMed1980

Effect of hypothalamic deafferentation on the distribution of luteinizing hormone-releasing hormone (LHRH) in the rat brain.

Anterior (AHD) and complete hypothalamic deafferentation (CHD) were performed in female rats to ascertain the origin of LHRH detected in the external layer of ME. Deafferented brains were serially sectioned in a cryostat in the frontal plane. LHRH activity in each section was determined by RIA. While AHD, using a knife with a small radius caused no change in the distribution of LHRH in the brain, AHD, using a knife with a large radius resulted in a significant decrease in LHRH content in the ARC-ME. CHD caused a more marked decrease in the ARC-ME LHRH than AHD. The decrease was more marked in the anterior and posterior portions of the ARC-ME than in the middle one. These effects of CHD on the distribution of LHRH in the ME were ascertained by immunohistochemical studies. In contrast, LHRH content in the POA showed no significant change after AHD and CHD. However, a few LHRH containing fibers were observed in the area lying just proximal to the cut by immunohistochemistry. These results strongly suggest that a part of the LHRH detected in the external layer of ME is derived from that synthesized outside the MBH, possibly in the POA and another part is derived from that synthesized inside the MBH, possibly in the ARC.

Afferent Pathways↗