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Biomedical subjects

H Okada

Publications and source records attributed to H Okada.

At least 1,279 records · Page 71Linked to original sources
PubMed1976

Role of calcium ions in the thermostability of thermolysin and Bacillus subtilis var. amylosacchariticus neutral protease.

The stabilizing effect of calcium ions on thermolysin and Bacillus subtilis var. amylosacchariticus neutral protease has been investigated. Calcium and zinc ions were removed from the proteases by gel filtration over Sephadex G-25 equilibrated with metal chelating agents. Using these enzymes with different metal content, heat inactivation kinetics were studied at various temperatures. Removal of calcium ions caused a sharp decrease in thermostability and diminished the values of the activation enthalpy (deltaH*) and entropy (deltaS*) for heat inactivation. There was little difference in stability between thermolysin containing 0.3 g-atom/mol and B. subtilis neutral protease containing 1.4 g-atoms/mol. Calcium binding isotherms of the proteases were obtained by equilibrium gel chromatography with various concentrations of free calcium ions. Thermolysin had four independent calcium binding sites with an identical intrinsic binding constant (K) of 2.0 X 10(4) M-1. B. subtilis neutral protease had four independent sites. The K value for three sites was 1.1 X 10(5) M-1 and the binding constant for the other site was 1.5 X 10(3) M-1. There was little difference in total free energy change for calcium binding between these proteases. From these results it is concluded that the stabilizing effect of calcium on these enzymes is almost equal, and the extra thermal stability of thermolysin is likely to come from its polypeptide chain structure.

Bacillus subtilis↗
PubMed1976

[Effects of synthetic sex steroids on the pituitary responsiveness to luteinizing hormone releasing hormone (LH-RH) (author's transl)].

Effects of short and long term administrations of an oral contraceptive preparation on the pituitary responses to the synthetic LH-RH were compared in the present experiment. Five normal cycling women were used as controls in the late proliferative phase. Five healty volunteers taking an oral contraceptive agent (1.0 mg norethindrone with 0.05 mg mestranol) for less than 10 cycles were served as short term group and other 4 women taking the same preparation for more than 40 cycles were studied as long term group. Volunteers in each group were kept fasting overnight and 5 ml of blood was drawn at 9 to 10 am on the day of experiment. Ten minutes after drawing blood, 200 mug synthetic LH-RH was injected subcutaneously in the late proliferative phase in the normal cycling women. According to the same procedure, women taking pills were administered LH-RH on the 7th to 12th day after the beginning of taking the first tablet in each cyle. Three ml of blood was taken at 15, 30, 60, 120 minutes and 24 hours, and serum LH and Fsh were determined by the double antibody radioimmunoassay. The 2nd IRP-HMG was used as the standard materials and expressed as mIU/ml of serum. Mean baseline serum LH and FSH concentrations were not suppressed in a short term administration of norethindrone-mestranol combination. Fifteen minutes after the subcutaneous injection of LH-RH, mean LH level was significantly elevated, and thereafter the level was not significantly changed as compared with that seen in the late proliferative phase of the cycle. Concerning the FSH response to LH-RH, a short term administration did not induce a significant rise. ...

Contraceptives, Oral↗
PubMed1976

Differential susceptibility of L cells in the exponential and stationary phases to cadmium chloride.

Comparative studies of the cellular toxicity and uptake of cadmium in L cells in the exponential and stationary phases were done. The LD50 of cadmium chloride to L cells in the exponential and stationary phases was 5.5 and 30.5 muM respectively and the cadmium content of L cells exposed to 5.4 muM cadmium chloride for 3.5 hr in the exponential and stationary phases was 0.123 and 0.065 mug/10(6) cells, respectively. These results suggest that the higher susceptibility of cells in the exponential phase to cadmium may be caused by an increased permeability of the cell membrane to cadmium.

Animals↗
PubMed1976

Kinetic analysis of hormone-induced mitoses in epithelial cells of mouse uterus and vagina.

The intracellular localization of 3H-estradiol-17beta and 3H-progesterone to the different types of cells in the mouse uterus was investigated using autoradiographic techniques. The kinetics of cell proliferation in the surface epithelium of the uterus and in the vaginal epithelium (basal layer) are analysed by means of cumulative labeling method and mitosis chase method using 3H-thymidine autoradiographic procedures. The results are as follows, (1) Epithelial cell population of the uterine lumen and basal cell population of the vaginal epithelium in the ovariectomized mouse are divided into a major subpopulation of GO cells and a minor subpopulation of proliferating cells. (2) Proliferative potencies of uterine surface epithelial cells and vaginal basal cells in the ovariectomized mouse are regulated by a steroid-independent mechanisms through which the proportion of the GO cell-compartment and Tc value of the proliferating cell-compartment are determined according to their age; as the castrated mouse grows older, Tc value becomes longer and the proportion of the Go cell-compartment becomes larger. (3) If the dose levels of estrogen administered exceed the threshold value, estrogen-dependent cell proliferation will be provoked by transferring the cells in the GO cell-compartment to the proliferating cell-compartment in all or none fashion, and by reducing the Tc value of proliferating cell to 1/2-1/3 of that in the castrated mouse. (4) It is suggested that proliferating cells in the uterine surface epithelium and in the vaginal epithelium turn the cell cycle at a constant Tc value during estrous cycle, and that the tissue growth during estrous cycle is dependent on the size of the proliferating cell-compartment but not on the Tc value. (5) The results obtained from autoradiography of tritiated steroids in the mouse uterus gave a supporting clue to the kinetic data.

Animals↗
PubMed1976

Effects of clomiphene citrate and progesterone on resting and proliferative cell-populations in resting and proliferative cell-populations in mouse uterine epithelium.

Resting cells (GO cells) of the uterine surface epithelium in castrated mice began to synthesize DNA with high synchrony from 10 hr after the injection of 50 ng of estradiol-17beta with or without 5.5 mug of clomiphene citrate. Highly synchronized DNA synthesis in GO cells elicited with estradiol was delayed approximately 5 hr when the simultaneous administration of 0.5 mg of progesterone was given. In GO cells of castrated mice which received 5.5 mug of clomiphene or 55 mug of clomiphene plus 50 ng of estradiol, DNA synthesis with partial synchrony began 15 hr after the injection. The effects of estradiol were completely suppressed by the administration of 55 mug of clomiphene. It is suggested that the inhibitory action of clomiphene may be due to the competitive blocking of estrogen binding, while progesterone suppresses the estrogen-induced DNA synthesis of the surface epithelium and transfers them to the GO cell-compartment.

Animals↗
PubMed1976

Histochemical studies on fatty acid in lymphocyte-mediated immune reaction.

Generation of fatty acids by cell-mediated immune reactions was demonstrated histochemically by Okamoto's method, which stains fatty acids and their alkaline earth salts red-brown. The red-brown deposits were observed more frequently on the mixed culture of immune lymph node cells of C3H/He and C57Bl/6 mice than on the culture of either of the pair alone. Similar evidence was observed in the reaction of immune lymph node cells with the corresponding allogeneic mouse tumour cells as well as on the immune lumphocytes of guinea-pig incubated in the presence of the soluble antigen PPD. In spite of the findings which indicated a possible generation of fatty acids in the immunological reaction of immune lymphocytes, we failed to demonstrate evidence of fatty acid generation in the ascites during rejection of allogeneic ascitic MM102 tumour cells, although accumulation of neutral lipid was evident. This unexpected contradicition was interpreted by finding that MM102 cells incubated with oleic acid did not contain fatty acid but did contain a remarkable amount of neutral lipid on histochemical examinations. This finding indicated that once generated, fatty acids would be converted to neutral lipid in the ascites where allogeneic tumour cells were rejected.

Animals↗