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Biomedical subjects

M Tamai

Publications and source records attributed to M Tamai.

At least 307 records · Page 17Linked to original sources
PubMed1983

Use of new synthetic substrates for assays of cathepsin L and cathepsin B.

Efficient methods were developed for synthesizing synthetic substrates for assays of cathepsin B and cathepsin L. Several 2-naphthylamide compounds with a blocked NH2-terminus, Suc-Tyr-Met-NA, beta-Ala-Tyr-Met-NA, and D-Leu-Tyr-Met-NA, were specific and sensitive substrates for cathepsin L and cathepsin B; they were not specific for cathepsin L only, because all of them were also hydrolyzed by cathepsin B. Some kinetic constants for the hydrolyses of these three synthetic substrates by cathepsin B and cathepsin L are given.

Animals↗
PubMed1983

Increase in histidine decarboxylase activity in mouse skin after application of tumor promoters.

The activity of histidine decarboxylase (HDC) increased by a factor of 10 after a single application of 12-O-tetradecanoylphorbol-13-acetate (TPA). The HDC-inducing activity of other phorbol esters paralleled their tumor-promoting activity. Application of some indole alkaloids, which have been shown to be a new class tumor promoter, also induced the increase in HDC activity. The cell type responsible for this increase was examined. First, pieces of the skin were separated into epidermis and dermis after application of TPA. In contrast with ornithine decarboxylase, the HDC activity increased in the dermis. Second, genetically mast cell-deficient W/Wv and Sl/Sld mice were used. Although most histamine in the dermis is in the mast cells, the increase in HDC activity in W/Wv mice was comparable to that in congenic +/+ mice. However, no significant increase in HDC activity was detected in the skin of the Sl/Sld mice. Histological examination revealed that the magnitude of inflammatory cell infiltration was much less in the skin of Sl/Sld mice than in the skin of +/+ or W/Wv mice. The increase in HDC activity and the inflammatory cell response in the skin of W/Wv mice were abolished by prior X-ray irradiation, and were restored by subsequent bone marrow transplantation. Thus, inflammatory cells may be responsible for at least a part of the increase in HDC activity after application of tumor promoters.

Acrylamides↗
PubMed1983

Intratumor chemoimmunotherapy with mitomycin C and BCG in C3H/He mice transplanted with MH134.

Experiments were performed to explore the influence of local chemoimmunotherapy by intratumoral administration of mitomycin C (MMC) and/or BCG on the survival rate, lymph-node metastasis, growth pattern of rechallenge tumor, and host immune function, using a host-tumor system consisting of C3H/He mice and syngeneic tumor MH134. Combined intratumoral regimens of MMC plus BCG yielded a significantly higher survival rate than those achieved with BCG or MMC alone. Furthermore, the incidence of metastatic involvement of regional lymph nodes was also remarkably reduced in the combined regimen group. The group given the combined MMC-BCG regimen also showed a marked suppression of the growth of rechallenge tumor after surgical removal of the primary tumor and showed a greater induction of tumor-specific immunity than that seen in the group given intratumoral BCG injection alone. Both the delayed-type hypersensitivity, as measured by the footpad swelling assay, and the antibody response in spleen lymphocytes, as estimated by the plaque-forming cell assay, were found to be substantially depressed following a systemic injection of MMC, whereas the intratumoral administration of MMC had little or no effect on these parameters.

Animals↗
PubMed1983

Effect of a protein-bound polysaccharide preparation, PS-K, on dimethyl hydrazine induction of intestinal tumors in rats.

The effect of a protein-bound polysaccharide preparation, PS-K, on the induction of intestinal tumors by dimethyl hydrazine (DMH) was assessed in Wistar rats. One hundred and fifty-one rats were randomly divided into two groups. Seventy-two rats were treated with DMH alone and 79 rats were treated with DMH and PS-K. All animals were subjected to a sequential autopsy and all lesions within the gastro-intestinal tract were examined macroscopically and histologically. Tumor incidence in the DMH plus PS-K-treated group was significantly lower than that in the group treated with DMH alone. The most interesting histological finding was marked lymphoid infiltration in and around the tumors of the rats in the PS-K-treated group. The number of circulating lymphocytes dropped below the control range in the 25th and 35th weeks for the group treated with DMH alone, but the drop in the PS-K-treated group was smaller. Delayed-type hypersensitivity reaction to purified protein derivative was well maintained in the PS-K-treated rats. The most interesting findings in these experiments were differences in the serum blocking activities and serum immunosuppressive substance in these two groups; they were markedly reduced in the PS-K-treated rats. The present results may be explained in terms of competitive action of PS-K against the immunosuppressive factor produced by a tumor-bearing host.

Animals↗
PubMed1982

L-trans-Epoxysuccinyl-leucylamido(4-guanidino)butane (E-64) and its analogues as inhibitors of cysteine proteinases including cathepsins B, H and L.

1. L-trans-Epoxysuccinyl-leucylamido(4-guanidino)butane (E-64) at a concentration of 0.5 mM had no effect on the serine proteinases plasma kallikrein and leucocyte elastase or the metalloproteinases thermolysin and clostridial collagenase. In contrast, 10 muM-E-64 rapidly inactivated the cysteine proteinases cathepsins B, H and L and papain (t0.5 = 0.1-17.3s). The streptococcal cysteine proteinase reacted much more slowly, and there was no irreversible inactivation of clostripain. The cysteine-dependent exopeptidase dipeptidyl peptidase I was very slowly inactivated by E-64. 2. the active-site-directed nature of the interaction of cathepsin B and papain with E-64 was established by protection of the enzyme in the presence of the reversible competitive inhibitor leupeptin and by the stereospecificity for inhibition by the L as opposed to the D compound. 3. It was shown that the rapid stoichiometric reaction of the cysteine proteinases related to papain can be used to determine the operational molarity of solutions of the enzymes and thus to calibrate rate assays. 4. The apparent second-order rate constants for the inactivation of human cathepsins B and H and rat cathepsin L by a series of structural analogues of E-64 are reported, and compared with those for some other active-site-directed inhibitors of cysteine proteinases. 5. L-trans-Epoxysuccinyl-leucylamido(3-methyl)butane (Ep-475) was found to inhibit cathepsins B and L more rapidly than E-64. 6. Fumaryl-leucylamido(3-methyl)butane (Dc-11) was 100-fold less reactive than the corresponding epoxide, but was nevertheless about as effective as iodoacetate.

Binding Sites↗
PubMed1982

In vitro studies on shedding and phagocytosis of rod outer segments in the rat retina: effect of oxygen concentration.

The processes of outer segment shedding and phagocytosis were found to be significantly enhanced in explants of rat retina and pigment epithelium (PE) newly placed in culture. The number of phagosomes reached a maximum at 2 hr of incubation and then rapidly decreased, as is observed in rats entrained in a normal light-dark schedule when the lights are turned on in the morning. This pattern was not qualitatively affected by the time of day the tissues were excised or by the presence of a high concentration of melatonin in the culture medium. The shedding peak in vitro was observed only when the retina-PE unit was incubated in an atmosphere composed of 45% oxygen, 5% CO2, and 50% air. When the atmosphere contained lower (95% air and 5% CO2) or higher (95% O2 and 5% CO2) oxygen, PE cells contained only a few scattered phagosomes. These functional differences may be caused by different arrangement of PE cell microvilli at a "moderate" (45%) O2 concentration vs. "low" or "high" O2 concentrations. A balanced O2 level thus appears to be critical for phagocytosis in explant culture.

Animals↗
PubMed1982

Effect of splenectomy on establishment of hematopoietic chimerism in nonirradiated mice.

When spleen cells (1.5 x 10(8)) from beige C57BL/6 (bgJ/bgJ, Chediak-Higashi syndrome) mice were injected into nonirradiated (C57BL/6 x CBA)F1 hybrid mice, the hematopoietic stem cells of the hybrid host were eradicated by graft-versus-host (GVH) reaction, and peripheral neutrophils of the host changed from normal type to beige type with giant sudanophilic granules in 20 days after the cell injection. Effect of splenectomy on the establishment of such hematopoietic chimerism was investigated. The splenectomy carried out either before or after the cell injection reduced the proportion of mice in which more than 90% of peripheral neutrophils became of beige type. Since the mortality of mice which received splenectomy at various days prior to or after the cell injection paralleled the proportion of establishment of chimerism, the splenectomy does not seem to affect directly the establishment of chimerism but indirectly through the modification of the intensity of GVH reaction.

Animals↗
PubMed1981

Papain inhibitions by optically active E-64 analogs.

Modification of E-64 focused on the terminal agmatine for practical use led to some potent analogs which were successfully obtained by a stereoselective synthesis using D-tartaric acid as a starting material. Ep-475 (id. E-64-c), in which the agmatine was replaced by 3-methyl-butylamine, was found to react with the essential SH of papain in accord with the decrease of activity. [3H]Ep-475 was irreversibly incorporated into papain in an equimolar ratio. None of the analogs showed any effect on thiol enzymes other than proteolytic ones.

Agmatine↗
PubMed1981

The effect of an in vivo-injected thiol protease inhibitor, E-64-c, on the calcium-induced degeneration of myofilaments.

The role of intracellular calcium-dependent proteinase(s) has been investigated in intact rat muscle. When calcium ions were introduced into intact muscle in vitro with ionophore A23187, Z-line loss and concomitant release of alpha-actinin into the medium were observed. The calcium-induced release of alpha-actinin was not diminished in the muscle with in vivo-injection of a thiol protease inhibitor, E-64-c. Intramuscular concentrations of E-64-c were also measured after pulse labeling with [3H]E-64-c followed by subcellular fractionation. Most of the inhibitor was localized in the cytosol, not in the lysosome. Therefore, we conclude that cytosolic as well as lysosomal proteinases in muscle are not inhibited by the in vivo labeling of the protease inhibitor (10 mg/kg).

Actinin↗
PubMed1981

Electroretinogram changes after fluorescein injection: a new method to evaluate blood-retinal barrier dysfunction.

When a retina with an impaired blood-retinal barrier (BRB) is illuminated with blue light (480 mm) after intravenous fluorescein (F) injection, photoreceptors are presumed to be stimulated not only by the original blue light but also by a green one (520 mm) that is emitted by the leaked F. In the present study, the value of the electroretinogram (ERG) was examined before, and up to 10 min after, F injection in normal subjects and diabetics without overt retinopathy. In normal subjects, the amplitude of the b-wave was affected by F injection and stayed within +5.0% /+- 11.8% at 2 min and -2.1% /+- 16.4% at 10 min (mean +/- S.D.) of those recorded before administration of the dye. In the diabetic patient without overt retinopathy, the ERG was enhanced by F injection and the values were significantly larger than those of normal subjects at 0.25 (p < 0.001). 1 (p < 0.05), 2 (p < 0.005), 3 (p < 0.005), and 10 (p < 0.01) min after injection. It may be concluded from these results that a comparison of the ERGs before and after F injection can be useful in demonstration of impairment or destruction of the inner and outer BRB.

Adult↗
PubMed1979

The early appearance of disc shedding in the rat retina.

Postnatal development of the processes of rod outer segment shedding and phagocytosis was examined in 10- to 50-day-old rats. The number of phagosomes increased gradually from a minimallevel in the second postnatal week to that of the adult at 4 weeks after birth. No differences were observed in animals raised under two different light intensities i.e., relatively bright (45 to 50 ft-cd) and very dim (0.3 to 0.5 ft-cd). A definite circadian rhythm was observed first in 15-day-old animals, indicating that this is an important internal control mechanism that is synchronized with eye opening and the initiation of visual function.

Animals↗