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Biomedical subjects

R Okamoto

Publications and source records attributed to R Okamoto.

At least 271 records · Page 15Linked to original sources
PubMed1981

Studies on the effects of 3-acetyl-4"-isovaleryltylosin against multiple-drug resistant strains of Staphylococcus aureus.

The macrolide-resistance of multiple-drug resistant strains of Staphylococcus aureus was divided into two types; the decreased sensitivity of ribosomes (type I) and the decreased uptake (type II). Both types were resistant to erythromycin, tylosin and 3-acetyltylosin, and their resistance was not inducible. 3-Acetyl-4"-isovaleryltylosin inhibited the growth of both types. Protein synthesis on ribosomes of type I in vitro (S. aures MS-9610) was inhibited by 3-acetyl-4"-isovaleryltylosin, but little or no inhibition was seen with either tylosin or 3-acetyltylosin. Ribosomes of type II in vitro (S. aureus MS-8710) were sensitive to all macrolides. 3-Acetyl-4"-isovaleryltylosin accumulated about twice as much as 3-acetyltylosin in intact cell of type II.

Anti-Bacterial Agents↗
PubMed1981

Uterine estrogen receptor assayed by the controlled pore glass (CPG) method in adult rat after steroid administration.

The interaction of estrogen and androgen was studied at the estrogen receptor level of adult rat uterus by the in vivo experiment. Both the free and total estrogen receptor in the cytosol and nucleus were assayed by the controlled pore glass beads method [2]. Testosterone was given by daily injection for 5 days to the rats treated with estradiol dipropionate (long-acting estradiol) 3 or 5 days before. In the estradiol dipropionate-treated rats the plasma estradiol concentration remained at an extremely high level for 7 days and then decreased to 5-fold of that of proestrus control by the 14th day. There was no significant change in the uterine estrogen receptor of the adult rat with a high estradiol concentration induced by testosterone.

Animals↗
PubMed1980

[The effects of estradiol on uterine estrogen receptor and thymidine kinase in immature and spayed-adult rats (author's transl)].

Uterine estrogen receptor (ER) and thymidine kinase (TK) activity were investigated in response to an injection of estradiol (E2) (1.43microgram/100g body weight) in SD-strain immature female rats aged 21 days and spayed-adult rats aged 104 days (14 days after castration). In immature rats, uterine cytosol ER decreased abruptly after the injection of E2 and increased gradually from 4 hours later. On the other hand, nuclear ER increased rapidly and shaped a peak 1 hour after the injection of E2 and decreased gradually afterward. Uterine TK activity began to increase rapidly from 18 hours and shaped a peak 24 hours after the injection of E2 and was reduced to the same level as the controls 48 hours later. No differences in behavior of uterine cytosol and nuclear ER after the injection of E2 between immature and spayed-adult rats were noticed. Although uterine TK activity in immature rats was stimulated 30 times 24 hours after the injection of E2, that of spayed-adult rats increased by only twice. Uterine TK was separated into 3 fractions (A, B and C) by means of a DEAE-cellulose column chromatography. In immature rats, 95% of the great TK activity induced by E2 was involved in fraction A, which was not inhibited by dCTP. In contrast, uterine TK isozymes in spayed-adult rats were at fraction B and C, whose activities were inhibited by dCTP, without relation to the administration of E2. The molecular weight of fraction A was estimated to be approximately 125,000 and that of B was 100,000 by the method of gel filtration on a Sepharose CL-6B column. No differences in uterine ER levels between immature and spayed-adult rats were found, but E2-induced different TK isozymes seem to depend on the stage of uterine growth.

Animals↗
PubMed1980

Differences in the induction of thymidine kinase isozymes in estrogen-treated immature and adult rats.

Thymidine kinase activity in immature and castrated adult rat uterus has been examined in response to estrogen treatment. Following estrogen administration, it was found that immature uterine thymidine kinase activity was increased 30-fold after 24 h, but almost no effect was produced on castrated or non-castrated adult uterus. Uterine thymidine kinase activity was separated into three peaks (peak 1, 2 and 3) by means of DEAE-cellulose column chromatography. In response to estrogen, the thymidine kinase isozymes differed in adult and immature uteri. In immature uteri, marked and selective increase of the activity was found in peak I, whereas in adult only a slight increase in peak 2 activity was observed. The thymidine kinase activity in peak 1 and peak 2 were found to have different enzymatic properties and molecular weight, as determined by gel filtration of 125 000 for peak 1 and 100 000 for peak 2. From these results, it is suggested that estrogen induces specific thymidine kinase isozyme in immature uterus and that the isozyme may be involved in DNA synthesis. Such a induction mechanism seems to be lost during the development.

Animals↗
PubMed1980

PS-6 and PS-7, new beta-lactam antibiotics. Isolation, physicochemical properties and structures.

Antibiotics PS-6 and PS-7 which are shown to be 5R,6R-3-(2-acetamido)ethylthio-6-isopropyl-7-oxo-1-azabicyclo[3.2.0]hept-2-ene- 2-carboxylic acid and 5R,6R-3-(E)-(2-acetamido) vinylthio-6-ethyl-7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylic acid respectively, are new beta-lactam compounds isolated from fermentation broths of Streptomyces cremeus subsp. auratilis A271, S. fulvoviridis A933, S. olivaceus ATCC 31126 and S. flavogriseus NRRL 8139. Fermentation, isolation, physicochemical properties and structures of antibiotics PS-6 and PS-7 are described.

Anti-Bacterial Agents↗
PubMed1980

Biological properties of new acyl derivatives of tylosin.

The antibacterial activity of acyl derivatives of tylosin were examined in vitro and in vivo. The 4"-acyl group in the acylated tylosins enhanced the antibacterial activity and antimycoplasmal activity against some macrolide-resistant strains. The orally administered 3-acetyl-4" -isovaleryltylosin produced a higher blood level in mice and rabbits than tylosin and a good therapeutic effect on the infection of Staphylococcus aureus Smith in mice.

Administration, Oral↗
PubMed1979

[The behavior of 7, 12-dimethylbenz(a)anthracene (DMBA)-induced mammary tumors in rats during pregnancy and lactation and hormone levels in the pituitary and plasma (author's transl)].

In order to keep a long-term lactation in primiparous SD strain rats with DMBA-induced mammary tumors, 5 pups aged 5 to 10 days were exchanged every 10 days. FSH, LH and prolactin (PRL) in pituitary tissues and FSH, LH, PRL, estradiol (E2) and progesterone (PRG) in plasma were determined during pregnancy (1,2 and 3-week), at paturition (0 to 12 hours after parturition) and during lactation (1,2,3,4,5 and 6-week). Experimental rats were divided into 6 groups according to the lactating period (non-lactating 3,6,8,12 and 17-week). Blood samples were collected by cardiac puncture 1 hour after an intraperitoneal injection of urethane (150 mg/100 g body weight), and the pituitary gland was removed simultaneously. During pregnancy, plasma PRL was low in the first and second week. PRL, E2 and PRG were high in the third week, during which DMBA-induced mammary tumors began to proliferate. PRG in plasma in the third week was lower than that of the second week. After paturition, the tumors regressed and did not develop for three weeks of lactation, during which plasma PRL was high whereas E2 and PRG were low. The tumors began to proliferate again from the fifth week of lactation, during which E2 was high and the estrous cycle reappeared. The behavior of DMBA-induced mammary tumors in rats during pregnancy and lactation seems to be closely related to plasma estrogen levels.

9,10-Dimethyl-1,2-benzanthracene↗