Search PubMed⌕ Search

Biomedical subjects

T Oka

Publications and source records attributed to T Oka.

At least 1,333 records · Page 74Linked to original sources
PubMed1980

Influence of lithium on mammary tumor growth in vivo.

The possibility that lithium ions stimulate growth of mammary tumors in vivo has been suggested by their mitogenic action in vitro on normal and neoplastic mammary epithelium [8] and their clinical use as stimulators of neutrophil production in tumor-bearing patients treated with cytotoxic drugs [14,15]. Three experiments were performed to assess this possibility. Buffalo/N female rats received a single injection of N-nitrosomethylurea (NMU) at a dose known to produce mammary carcinomas in about 50% of animals under standard conditions. Under lithium treatment, the incidence of tumors did not increase significantly. Sprague-Dawley female rats treated with a single dose of 7,12-dimethylbenz[alpha] anthracene (DMBA), but showing no mammary tumors after 4 months, received lithium in their drinking water for 3 additional months. The number of late-appearing tumors was not increased by lithium treatment. Buffalo/N females with NMU-induced tumors were castrated, and the subsequent changes in tumor volume were compared in lithium-treated and control animals. The regression-regrowth curves were not altered by lithium treatment. These results are in contrast to the growth stimulatory capacity of lithium on mammary epithelium observed in vitro [8] and indicate it is very unlikely that lithium ions have an undesirable growth stimulatory action on primary mammary carcinomas in vivo.

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

Cyclic AMP as a negative regulator of hormonally induced lactogenesis in mouse mammary gland organ culture.

In organ cultures of mammary glands from mice in midpregnancy, addition of both insulin and prolactin induces a marked accumulation of alpha-lactalbumin, whereas the augmentation of casein synthesis requires the presence of insulin, prolactin, and cortisol. Addition of 0.5 mM dibutyryl cyclic AMP resulted in complete inhibition of alpha-lactalbumin accumulation and partial inhibition of casein synthesis. Furthermore, either cholera toxin at 0.1-1.0 microgram/ml (a stimulator of adenylate cyclase) or 3-isobutyl-1-methylxanthine (an inhibitor of phosphodiesterase) in combination with 2 mM cyclic AMP, produced a similar pattern of inhibition of alpha-lactalbumin and casein synthesis in cultured tissue. During culture of mammary explants in medium containing no hormone, or insulin alone, or insulin, prolactin, and cortisol, the tissue content of cyclic AMP decreased rapidly, reaching half the initial level in 24-48 hr. These results indicate that cyclic AMP plays "negative" regulatory function in hormonal induction of milk protein synthesis during the development of the mammary gland.

1-Methyl-3-isobutylxanthine↗
PubMed1980

Evidence for a naturally occurring anti-spermine antibody in normal rabbit serum.

Normal rabbit serum contains an IgG-like component(s) that binds spermine as well as other polyamines. This molecule(s) has the same physicochemical properties as anti-spermine antibody obtained from rabbits immunized with spermine-thyroglobulin conjugates. However, the polyamines-binding IgG-like molecule(s), unlike anti-spermine antibody, is incapable either of precipitating a spermine-bovine serum albumin complex or of binding to a spermine-Sepharose column. These results suggest the existence of a naturally occurring anti-polyamine antibody that may have defective antibody functions.

Animals↗
PubMed1980

Coupling between Cbz-Arg-OH and Leu-X catalyzed by trypsin and papain.

Trypsin [EC 3.4.21.4] and papain [EC 3.4.22.2] catalyzed the coupling between Cbz-Arg-OH and Leu-X (X=-NH2, -OEt, -OBut, or -NH) in solution. The optimum pH for synthesis by trypsin and by papain was 6.5-7.0 and 5.5, respectively. Papain possessed reactivity several times higher than that of trypsin. To shift the reaction toward synthesis, the concentration of amine components must be at least several times higher than that of the carboxyl component (Cbz-Arg-OH). The effect of the concentration of Leu-X depended upon the nature of X; higher concentrations were required in the following order: -NH2 > -OEt, -OBut > -NH. High concentrations of organic cosolvents were also significant for promoting the synthesis.

Arginine↗
PubMed1980

Peptide bond synthesis catalyzed by thermolysin.

The coupling between Cbz-Phe-OH and Leu-NH2 catalyzed by thermolysin was examined under various experimental conditions. The highest yield (ca. 80%) was obtained in the reaction mixture containing 0.05 M each of the carboxyl and amine components and 10 muM enzyme at pH 7 and 37 degrees C for 5 h. The reactivity was ca. 100 times higher than that of alpha-chymotrypsin. Amino acid derivatives or peptides were useful as amine components, though a hydrophobic or bulky amino acid residue was required at the N-terminal position. Strict stereospecificity was observed at this position. A hydrophobic or bulky amino acid residue occupying the C-terminal position of carboxyl components was also favorable for synthesis. The specificity requirements for synthesis were the same as those for hydrolysis.

Amino Acids↗
PubMed1980

Enkephalin receptor in the rabbit ileum.

The effects of the classical morphine-like compounds and opioid peptides on the electrically-induced contractions of the myenteric plexus-longitudinal muscle strip of the rabbit ileum were studied. The results indicate that the rabbit ileum contains the new type of opiate receptor, which is not sensitive to morphine but is sensitive to enkephalins, and provides evidence that the enkephalins may function as neurotransmitters in the intestine. The action of the enkephalins was antagonized by relatively high dose of naloxone.

Animals↗
PubMed1980

Immunochemotherapy of gastric cancer with levamisole.

In 156 cases of gastric cancer, levamisole (LMS) was administered at a daily dose of 150 mg for three consecutive days every other week. The administration was started 3 days before operation. This medication was repeated for more than one month. The survival rate up to two years after surgery was studied. The survival rate was not affected in patients with Stage I and II gastric cancer, but in patients with Stage III, the difference in the survival rate between the LMS group and the control group was significantly higher than that in the control group (p less than 0.05). In patients with Stage IV, the survival rate in the LMS group was higher than that in the control group although the difference was not significant. In patients of Stage III and IV, the effect of LMS on the survival rate was highest in cases with curative resection (p less than 0.01). In cases with noncurative resection, the difference between the LMS group and the control group was greatest (24.4%) 12 months after surgery but not significant (p less than 0.5), and also in cases without resection the difference between the two groups was greatest (20.3%) 12 months after surgery but not significant (p less than 0.2).

Adjuvants, Immunologic↗
PubMed1980

Inhibition of peptidoglycan transpeptidase by beta-lactam antibiotics: structure-activity relationships.

The inhibitory activities of representative beta-lactam compounds, such as penicillins G and N, cephalosporins C and G, clavulanic acid, nocardicin A and thienamycin against Escherichia coli KN-126 and Bacillus megaterium KM peptidoglycan transpeptidases were studied. Their modes of action against E. coli are discussed on the basis of the results and the published binding data for penicillin binding proteins. The effects of modifications at position 3 and 7 of the cephalosporin and those at alpha-carbon of the benzyl side-chain of cephalosporin G and penicillin G were studied. The introduction of an amino group at this position in cephalosporin G together with the removal of an acetoxy group from the acetoxymethyl group at position 3 reduced the inhibitory activity against E. coli transpeptidase considerably. The activity was restored by the replacement of the methyl group at position 3 of cephalexin with chlorine. The restoration was accompanied by about 15-fold increase in the lytic activity of cephachlor against E. coli.

Acyltransferases↗
PubMed1980

Three-dimensional observation of the temporomandibular joint disk in the rhesus monkey.

The three-dimensional ultrastructure of the TMJ disk of two normal rhesus monkeys was investigated using the SEM. The upper and under surface of the TMJ disk consists of a close network of delicate collagen fibrils. On the undersurface, they have an undulating configuration, with the elevations running in one direction. On the upper surface, irregular and gentle waves can be observed. The matrix of the TMJ disk is composed of two main parts: one is the collagen fibrils that run in a sagittal direction making up the central fibrous core, and the other consists of the collagen fibrils that enclose the fibrous core. The collagen fibrils running in a sagittal direction show a wavy, winding appearance, and these structures are more numerous on the side of the TMJ disk facing the condyle. It is concluded that the wavy, winding structure and undulated configuration of the collagen fibers results in an elastic quality, opposes stress, and functions to absorb shock.

Animals↗
PubMed1979

Sodium ions and the development of the inotropic action of ouabain in guinea-pig heart.

Factors that determine the interaction of ouabain with the positive inotropic receptor were examined in isolated perfused guinea-pig hearts. The hearts were exposed to ouabain during a perfusion with a modified Krebs-Henseleit solution. The interaction of ouabain with the inotropic receptors under those conditions was estimated by subsequently perfusing the heart with a regular Krebs-Henseleit solution and monitoring the resting and developed tension. Ouabain failed to cause an increase in the force of contraction when the cardiac tissue was exposed to this agent in the absence of Na+ and Ca2+ either in the presence of a low or high concentration of K+. The absence of Ca2+ or the lack of contraction was not responsible for the failure of ouabain to interact with the inotropic receptor, since the exposure of cardiac tissue to ouabain in a Ca,+-free medium containing Na+ resulted in a development of the positive inotropic effect. Thus, ouabain does not interact with its inotropic receptor in the absence of Na+. The properties of the ouabain-receptor interaction resemble those of ouabain binding to Na+, K+-ATPase. In addition, ouabain increases the mobility of superficially bound Ca2+.

Animals↗