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Biomedical subjects

M Hiroi

Publications and source records attributed to M Hiroi.

At least 163 records · Page 9Linked to original sources
PubMed1985

Effects of aphidicolin and alpha-amanitin on visualization of acridine orange binding to DNA in rat astrocytoma C6 cells.

The purpose of this study was to examine effects of aphidicolin and alpha-amanitin on visualization of acridine orange (AO) binding to DNA in rat astrocytoma C6 cells and to discuss briefly the significance of AO chromatin interaction products. Aphidicolin inhibited DNA synthesis but percentage of AO positive cells was approximately 60% of that of the untreated control cells. alpha-Amanitin caused a slight inhibition of RNA synthesis and 3H-uridine incorporation in the treated cells was about 64% of that of the untreated cells, whereas a distinct decrease of the number of AO positive cell nuclei was observed. The results suggest that activity of RNA polymerase II and mRNA synthesis is mainly concerned in visualization of AO chromatin interaction products.

Acridine Orange↗
PubMed1984

Distribution pattern of DNA template activity in the developing cerebellar cortex in rats and its alteration after transplacental administration of ethylnitrosourea.

The ultracytochemical acridine orange(AO) method has been employed to demonstrate DNA template activity in the developing cerebellar cortex in rats and its alteration after transplacental administration of ethylnitrosourea (ENU). Electron microscopic studies revealed that AO binds to DNA exclusively within the active extended euchromatin portion of the cell nucleus of the proliferating external granular layer. No or only a few AO reaction products were visible in the non-proliferating cell nuclei of the internal granular layer and of Purkinje cells. With increasing cellular differentiation of granule cells in the cerebellar cortex the number of AO positive cells as well as the number of AO reaction products per cell showed a progressive decrease. A single i.p. injection of 50 mg/kg of ENU in rats on day 15 to 21 of gestation resulted in occasional cell damage to the proliferating external granule cells of developing cerebellar cortex at 4 and 7 days after birth. Damaged cells of the external granular layer were found to have no or only a small number of AO reaction products in their nuclei. In further development from 14 to 28 days the cerebellar cortex of offspring from ENU-treated mother showed no abnormality and exhibited no definite alteration in distribution pattern of AO reaction products.

Acridine Orange↗
PubMed1984

Electron microscopic localization of acridine orange binding to DNA within various human brain tumor cells.

The ultracytochemical acridine orange (AO) method has been employed to demonstrate DNA template activity within untreated human brain tumors. A total of 16 biopsies from brain tumors removed for frozen section examination were investigated. Ultrastructural examination revealed that AO binds to DNA exclusively within the extended euchromatin portion of the cell nucleus of brain tumors. The percentage of AO positive cells varied from 6.0 to 48.6% in various types of brain tumors. A few AO reaction products were visible in the nuclei of the endothelial cells and in the pericytes of the capillaries within neoplastic tissue. The present results suggested that untreated human brain tumors exhibit de-repression of DNA template normally repressed in the adult state. This altered DNA templates may be related to abnormal cell proliferation and differentiation diverted from the normal state.

Acridine Orange↗
PubMed1984

Electron microscopic localization of acridine orange binding to DNA within rat astrocytoma C6 cells.

Combination of autoradiography and ultracytochemical acridine orange method in rat astrocytoma C6 cells is described. Electron microscopic examination revealed that AO binds to DNA exclusively within the euchromatin portion of the cell nucleus. X-ray microanalysis showed that AO reaction products contain lead, uranium, and osmium. These heavy metals seem to contribute to electron density of the AO reaction products. The percentage of AO positive cells was 51.8 +/- 1.9%, whereas average labeling index of C6 cells incubated with 3H-thymidine for 30 minutes was 25.6 +/- 1.7%. About 82% of 3H-thymidine-labeled cell nuclei were AO positive and the remaining 18% were free of AO reaction products. On the other hand, about 27% of AO positive cells were not labeled with 3H-thymidine. However, most of C6 cell nuclei with active 3H-uridine incorporation showed AO chromatin reaction products. The results suggest that visualization of AO chromatin reaction products might be related to RNA synthesis rather than DNA synthesis in the cell nuclei.

Acridine Orange↗
PubMed1983

Lack of inhibitory effect of exogenous prolactin on ovarian responsiveness to gonadotropins in the rat.

Attempts were made to elucidate the possible antigonadotropic action of PRL at the ovarian level. Immature female rats of Wistar strain were injected subcutaneously with PMS (5-10 i.u.) at 0900 h on day 23 of age, followed an intraperitoneal injection of HCG (5-10 i.u.) at 1400 h on day 25. In all animals treated with PMS-HCG, ova were found in the oviducts when examined at 0900 h on day 26 of age. Rat PRL was administered either at various doses (1.0-20 micrograms/day) in the morning (0800 h) between day 23-25 or at 5 micrograms/day for 10 days prior to HCG injection. The ability of exogenous gonadotropins to induce ovulation and weight gain of the ovary were not affected by this PRL treatment. In animals injected with PMS, significant rises in serum estradiol-17 beta levels were observed 48 h later. This PMS-induced increase in the estrogen concentration was also not affected by the treatment with various doses of PRL. From these results, it seems likely that exogenously administered PRL may be unable to suppress the ovarian responsiveness to gonadotropins by direct action on the ovary.

Animals↗
PubMed1983

An acute increase in serum prolactin does not modify gonadotropin release in female rats.

Attempts were made to find out whether hyperprolactinemia has an effect on the hypothalamo-pituitary response to estrogen feedback and LHRH stimulation. Adult female rats of Wistar strain were ovariectomized and received subcutaneous injection of 20 micrograms estradiol benzoate (EB) 3-4 weeks later (day-0). A second injection of 20 micrograms EB, when administered at noon on day-3, induced a highly significant increase in serum LH (p less than 0.001 vs. basal values), but not FSH, estimated at 1800 h on the same day. This EB-promoted LH release was not altered by pretreatment with rat PRL (5 micrograms/day), which was administered subcutaneously daily in the morning (1100 h) between day-1 and day-3. No statistical difference in the serum LH concentration was found when compared with the values for the control animals pretreated with 0.9% saline alone. Serum gonadotropins 15 min after LHRH administration (100 ng/100 g BW) in 32-day-old female rats were not statistically different between the animals pretreated with 5 micrograms PRL, which was given subcutaneously daily (at 0800 h) for 3 days, and the controls pretreated with 0.9% saline. These results suggest that an acute increase in serum PRL may not exert a negative effect on the gonadotropin release induced by estrogen feedback and LHRH stimulation.

Animals↗
PubMed1983

Maturation of negative and positive estrogen feedback in the prepubertal female rat.

The development of estrogen feedback system on gonadotropin release during sexual maturation in female rats was studied. Animals (Wistar strain rats) were divided into 6 groups according to their ages; 10, 15, 20, 25, 30, and 35 days. Both LH and FSH levels in serum increased significantly in response to ovariectomy in all age-groups studied when measured one week postoperatively, though in the rats aged 10-15 days the increase in FSH following castration was only slight. In rats older than 25 days, the postcastration gonadotropin rise, calculated as a percent increase from the basal figure, decreased gradually with increasing age. Ovariectomized rats injected with estradiol benzoate (EB, 5 micrograms/100 g BW) showed significantly lower levels of both LH and FSH than those in castrated controls. However, the inhibitory action of EB on postcastration gonadotropin output was found to be relatively less effective in rats older than 25 days. Ovariectomized rats primed with EB were again injected with a 2nd dose of EB (5 micrograms/100 g BW) at noon 3 days after priming. The 2nd EB injection induced a significant rise in LH 6 h later in 30- and 35-day-old, though not in younger, animals. On the other hand, the FSH response to EB was markedly enhanced during days 15-25 of age. These results indicate that the estrogen negative feedback action on gonadotropin release is already operating in female rats at a very early age, and that the brain sensitivity to estrogen decreases slightly during the late prepubertal phase.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1982

[Evaluation of hypothalamic-pituitary function in amenorrheic women by utilizing the combined clomiphene-GnRH test (author's transl)].

Hypothalamic-pituitary function in 62 women with amenorrhea syndrome was evaluated by comparing the response of gonadotropin to GnRH stimulation before and after clomiphene treatment. Each woman was initially tested with an intramuscular injection of 100 microgram GnRH, and then ingested 150 mg of clomiphene daily for 5 consecutive days followed by GnRH test. Fourteen out of 29 patients with 1st grade amenorrhea showed increased baseline LH, FSH and estradiol, and slightly decreased net responses of LH to GnRH after clomiphene administration, indicating that positive and negative estrogen feedback for gonadotropin release is functioning. In contrast, 8 patients with 2nd grade amenorrhea (17 cases) showed an increase in LH net responses after Clomid treatment. In 5 patients, however, clomiphene induced the increase in baseline LH and FSH values and the decrease in the LH release in response to GnRH as seen in the 1st grade amenorrheic patients. These 5 patients ovulated on that clomiphene dosage. One patient with PCO also had a barely significant decrease in LH responses to GnRH following clomiphene administration, with slightly increased baseline gonadotropins. With one exception, all the 5 patients with primary amenorrhea showed no or poor LH responses to GnRH. Following clomiphene administration, no change in either baseline gonadotropine levels or pituitary responsiveness to GnRH was observed in 4 patients, suggesting that a hypothalamic-pituitary defect appeared most likely to be present. The two patients with streak gonad had significantly high responses to GnRH injection and further increase in the responses following clomiphene administration, accompanied by a slightly decreased baseline gonadotropin levels. On the other hand, in hyperprolactinemic amenorrhea syndrome individual response to GnRH before and after clomiphene use was quite variable. It is likely that this group includes the patients with various pathologic states of the hypothalamic-pituitary system. Thus, syndrome and in diagnosing the degree and the site of the defect.

Adolescent↗
PubMed1980

[A simplified method for measuring the binding capacity of sex hormone-binding globulin in human serum and its clinical application (author's transl)].

A simple and reliable method for determining the binding capacity of the sex hormone-binding globulin (SHBG-BC) in human serum is described. The principle of this method is to saturate the SHBG binding sites with dihydrotestosterone (DHT) and measure the amount of SHBG-bound steroid. Endogenous steroids are initially removed from the serum samples by adsorption on dextran-coated charcoal. The samples are subsequently equilibrated with a mixture of known amount of tritium-labeled and unlabeled DHT. The unbound steroid is removed by dextran-coated charcoal incubated at 4 degrees C, and the mass of bound DHT is determined from the known specific activity of the added steroid. The intraassay and interassay coefficient of variation of this assay method is less than 6.2% and 7.5%, respectively. Forty serum samples can be assayed in duplicate in a working day. The mean values of SHBG-BC, expressed as microgram DHT bound per 100ml serum, were 1.56 +/- 0.33 (SD) in 6 adult men aged 20 approximately 40 and 2.05 +/- 0.75 in 37 adult women aged 20 approximately 36. Higher levels (1.75 +/- 0.40) were found in 10 older men aged 65 approximately 80. In contrast, SHBG-BC (1.80 +/- 0.30) in postmenopausal women (ages 52 approximately to 62) was lower than that in the reproductive age group of women. No significant variations in SHBG-BC were observed during the normal menstrual cycle. The levels of SHBG-BC rose progressively in pregnancy to 9 approximately 10 times those in the normal non-pregnant women. In 4 women with polycystic ovarian disease and 2 hirsute women, SHBG-BC levels were lower (means: 1.63 and 0.75, respectively), while patients with 1st and 2nd grade amenorrhea showed levels similar to those in the reproductive women.

Adult↗