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Biomedical subjects

Y Okai

Publications and source records attributed to Y Okai.

At least 37 records · Page 2Linked to original sources
PubMed1996

Suppressive effects of chlorophyllin on mutagen-induced umu C gene expression in Salmonella typhimurium (TA 1535/pSK 1002) and tumor promoter-dependent ornithine decarboxylase induction in BALB/c 3T3 fibroblast cells.

The potentially protective role of chlorophyllin, the sodium and copper salt of chlorophyll a against the initiation and promotion stages in carcinogenesis was studied by in vitro short-term assays. Chlorophyllin showed a dose-dependent suppressive effect on 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indol (Trp-P-1)-induced umu C gene expression of Salmonella typhimurium (TA 1535/pSK 1002) in the presence of metabolizing enzyme mixture. The similar inhibitory effect of chlorophyllin was detected in mitomycin C (MMC)-dependent umu C gene expression in the absence of metabolizing enzyme mixture. Furthermore chlorophyllin also exhibited a dose-dependent inhibition on 12-O-tetradecanoyl-phorbol-13-acetate (TPA)-induced ornithine decarboxylase (ODC) activity of 3T3 fibroblast cells at the same concentrations. However, when chlorophyll a isolated from Japanese tea leaves was applied on the same assay systems as a comparative experiment, chlorophyll a showed much weaker activity compared with that of chlorophyllin. The significance of this finding is discussed from the viewpoint of the protective role of chlorophyllin against carcinogenesis.

3T3 Cells↗
PubMed1996

Possible immunomodulating activities of carotenoids in in vitro cell culture experiments.

Immunomodulating activities of beta-carotene and carotene-associated carotenoids such as canthaxanthin (beta, beta-carotene-4,4 dione) and astaxanthin (3,3'-dihydroxyl beta, beta-carotene 4,4-dione) were analyzed by in vitro cell culture experiments. (i) beta-Carotene, canthaxanthin and astaxanthin caused significant stimulatory effects on the cell proliferative response of spleen cells and thymocytes from BALB/c mice at the concentrations of 2 x 10(-8) to 10(-7) M, although they showed the activities different from each other. (ii) Astaxanthin exhibited the highest activity on the polyclonal antibody (immunoglobulin M and G) production of murine spleen cells at the concentrations of 2 x 10(-8) to 10(-7) M but beta-carotene did not cause a significant effect at a low concentration (2 x 10(-8) M) although stimulated at a high concentration (2 x 10(-7) M). Canthaxanthin expressed moderate activities at the same concentrations. (iii) All tested carotenoids significantly enhanced the release of interleukin-1 alpha and tumor necrosis factor-alpha from murine peritoneal adherent cells at the concentrations of 2 x 10(-8) to 10(-7) M and the ranks of cytokine-inducing activities were astaxanthin > canthaxanthin > beta-carotene. These results indicate that carotenoids such as beta-carotene, canthaxanthin and astaxanthin have possible immunomodulating activities to enhance the proliferation and functions of murine immunocompetent cells.

Adjuvants, Immunologic↗
PubMed1994

Suppressive effects of the extracts of Japanese edible seaweeds on mutagen-induced umu C gene expression in Salmonella typhimurium (TA 1535/pSK 1002) and tumor promotor-dependent ornithine decarboxylase induction in BALB/c 3T3 fibroblast cells.

Some of epidemiological data indicated that ubiquitous consumption of seaweeds in Japan may be a possible protective factor against some types of tumor. To analyse this problem, the authors studied the antimutagenic and antitumor promotion activities in methanol-soluble extracts of typical edible seaweeds which showed suppressive effects on 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indol (Trp-P-1)-induced umu C gene expression in SOS response of Salmonella typhimurium (TA 1535/pSK 1002) and 12-O-tetradecanoylphorbol-13-acetate (TPA)-dependent ornithine decarboxylase induction in BALB/c 3T3 fibroblast cells. Although eight varieties of edible seaweeds including chlorophyta, Phaenophyta and Rhodophyta showed significant antimutagenic and antipromotion activities, they expressed the activities different from each other. Among these seaweeds, Enteromorpha prolifera ('Sujiaonori' in Japanese) and Porphyra tenera ('Asakusanori') showed relatively strong suppressive activities in both antimutagenic and antipromotion assays compared with other seaweeds. These seaweeds contained considerable amounts of beta-carotene as a possible active principle with anticarcinogenic activity. This compound was partially associated with the antimutagenic activity in the seaweed extract, but did not contribute to the antipromotion activity of seaweed extract under our experimental conditions. These results strongly suggest that Japanese edible seaweeds have possible antimutagenic and antipromotion activities probably associated with antitumor activity.

3T3 Cells↗
PubMed1994

A possible immunomodulating activity of arbekacin (ABK), a newly synthesized antibiotic against methicillin-resistant Staphylococcus aureus (MRSA).

Arbekacin (ABK) is a newly developed aminoglycoside in Japan which can cause bactericidal effects on methicillin-resistant Staphylococcus aureus (MRSA). However, details of the mechanism on effective antibacterial activity of this drug in host patients has not been completely elucidated. We studied the modulating effects on some functional activities of immunocompetent cells in in vitro and in vivo mouse experimental systems. (i) ABK stimulated the phagocytic activity against S. aureus into mouse phagocytic cells in a dose-dependent manner. (ii) ABK enhanced oxygen radical generation with chemiluminescence in mouse phagocytic cells. (iii) ABK exhibited a stimulatory effect on interleukin 1 alpha release from mouse adherent cells. (iv) Injection with ABK into mice showed an adjuvant activity which stimulated antibody production against sheep red blood cells and S. aureus. These experimental results indicate the possibility that ABK has not only a direct antibacterial activity but also a modulating activity for immunocompetent cells to enhance host defense against S. aureus infection.

Adjuvants, Immunologic↗
PubMed1993

Differential regulation of carcinoembryonic antigen and biliary glycoprotein by gamma-interferon.

Carcinoembryonic antigen (CEA), biliary glycoprotein (BGP), and non-specific cross-reacting antigen (NCA) are three closely related cell surface glycoproteins induced by gamma-interferon (IFN-gamma) in colonic epithelial cells. Maximal induction of CEA by IFN-gamma and tumor necrosis factor alpha (TNF-alpha) in the colon carcinoma cell line HT-29 occurs at 5-6 days with maximal secreted levels at 14 ng/ml for IFN-gamma and 20 ng/ml for TNF-alpha. Cell viability was reduced to 67% of controls for TNF-alpha and to 36% for IFN-gamma. Dose-response curves showed maximal induction of CEA at 500 units/ml for TNF-alpha and at 200 units/ml for IFN-gamma. Combinations of the two lymphokines revealed that the CEA induction effects were additive and the cytotoxicity effects were synergistic. Northern blot analysis of HT-29 cells treated with IFN-gamma and probed with specific probes for BGP, CEA, and NCA showed a 2-fold increase in mRNA level for BGP, and a greater than 10-fold induction for CEA and NCA. Similar results were obtained for the SW403 cell line, but in the case of the LS174T cell line, CEA mRNA levels remained constant before and after IFN-gamma treatment, while BGP and NCA mRNA levels increased by 2-5-fold. Polymerase chain reaction analysis of the four alternatively spliced transcripts of BGP revealed no differential induction of one transcript over another by IFN-gamma. A comparison of the kinetics of induction of the mRNA levels for BGP and CEA by IFN-gamma in the HT29 cell line revealed a half-time of < 6 h for BGP and 48 h for CEA. The induction of CEA mRNA was completely inhibited with either cycloheximide (protein synthesis inhibitor) or actinomycin D (RNA synthesis inhibitor), but the induction of BGP mRNA was superinduced by cycloheximide. The difference in the kinetics of induction and effect of cycloheximide on CEA and BGP mRNAs suggest that the two genes are regulated differently in the same cell line. We conclude that the regulation occurs mainly at the posttranscriptional level for CEA and involves mRNA stability. BGP regulation may be more complex, involving transcriptional and posttranscriptional regulation, and more closely resembles the regulation of MHC class II mRNA by IFN-gamma in epithelial cells. The mRNA stability effects may be mediated by the dramatically different sequences present in the 3'-untranslated regions of CEA and BGP.

Antigens, CD↗
PubMed1993

Identification of heterogenous antimutagenic activities in the extract of edible brown seaweeds, Laminaria japonica (Makonbu) and Undaria pinnatifida (Wakame) by the umu gene expression system in Salmonella typhimurium (TA1535/pSK1002).

A significant antimutagenic activity was found in the hot water-soluble extract from a common edible brown alga, Laminaria japonica (Makonbu in Japanese) which showed suppressive effects on umu gene expression of the SOS response against DNA damage in Salmonella typhimurium (TA1535/pSK1002). The extract showed a drastic antimutagenic activity against 2-acetylaminofluorene (2-AAF)- or 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1)-induced mutagenesis which requires liver-metabolizing enzymes, whereas the same extract exhibited weak but significant inhibitory effects on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)- or furylfuramide (AF-2)-induced mutagenesis in the absence of liver-metabolizing enzymes. Among these antimutagenic activities, the minor activity was found in the polysaccharide fraction of the extract which showed roughly equal antimutagenic activities against all the mutagens tested. The major activity was detected in the nonpolysaccharide fraction which exhibited a relatively strong antimutagenic activity against 2-AAF- or Trp-P-1-induced mutagenesis but a weak activity against MNNG- or AF-2-induced mutagenesis. The nonpolysaccharide fraction was further separated into high- or low-molecular-weight fractions and the latter fraction showed a much stronger activity than the former fraction. In addition, similar antimutagenic activities were detected in polysaccharide and nonpolysaccharide fractions from the extract of the other edible brown alga, Undaria pinnatifida (Wakame in Japanese). These experimental results indicate that the hot water-soluble extract of Laminaria japonica or Undaria pinnatifida contains heterogenous antimutagenic activities against typical genotoxic substances. The significance of this finding is discussed from the viewpoint of the protection against genotoxic substances by traditional edible seaweeds in Japan.

Antimutagenic Agents↗
PubMed1991

Subpopulations of rat vascular smooth muscle cells as discriminated by calcium release mechanisms from internal stores.

Transsarcolemmal influx and release from the sarcoplasmic reticulum (SR) through specific Ca2+ channels are the two main pathways to elevate cytosolic Ca2+ (Ca2+i) in vascular smooth muscle cells (VSMCs). To elucidate intercellular distribution and function of the Ca2+ channel in SR in cultured VSMCs, we observed Ca2+i transients by digital two-dimensional imaging with a fluorescent Ca2+ indicator, fura-2, and found an alternative response to either caffeine or angiotensin II under the condition that selectively enabled Ca2+ release from SR. Caffeine (20 mM) increased the Ca2+i by 292 +/- 36% (mean +/- SEM) over the basal level in one third of the VSMC population (n = 19), while the remaining cells in the same observation field showed no or very weak response (110 +/- 4%). In contrast, after the treatment with caffeine plus ryanodine (30 microM), which inactivates the caffeine-sensitive channel, and with 1 mM Ca2+ chelator (EGTA) instead of Ca2+ in the incubation medium to block the CA2+ entry from outside, angiotensin II (10 nM) induced the Ca2+i elevation (287 +/- 26%) in previously caffeine-nonresponsive cells, although caffeine-responsive cells retained quiescence (112 +/- 2%). These responses did not differ when the order of the reagent application was reversed. These heterogeneities of VSMCs in the Ca2+i response to vasoactive substances indicate that VSMCs are functionally divided into subgroups with different Ca2+ channel predominance on SR, necessitating reevaluation of the previous studies obtained from multiple VSMCs.

Angiotensin II↗
PubMed1989

Effects of a purified cecropin D from a Chinese silk moth on growth, function and differentiation of murine hemopoietic cells.

The effects of cecropin D, a small basic peptide isolated from a Chinese oak silk moth, on the functions or differentiation of mammalian hemopoietic cells are described in the present paper. This peptide suppressed lectin-induced DNA synthesis of murine splenocytes in a dose-dependent manner without any significant cytotoxic effects. It also exhibited inhibitory effects on antibody production in lipopolysaccharide-stimulated lymphocytes and on colony formation of hemopoietic progenitor cells in plasma clots culture. These results indicate that cecropin D can regulate growth, function and differentiation of murine hemopoietic cells. The biological significance of this finding is discussed from the comparative immunological point of view.

Animals↗
PubMed1989

A human embryo fibroblast-derived peptide suppresses the zymosan-induced biochemical activation in human polymorphonuclear leukocytes.

Previously, a low-molecular-weight peptide was found in the serum-free culture media conditioned by a human embryo fibroblast cell strain (YH-1), which showed inhibitory effects on the proliferation and functions of B and T lymphocytes (Okai et al. (1987) Zool. Sci. 4, 99-105). In this paper, the inhibitory effect of this peptide on the functional activation in human polymorphonuclear leukocytes (PMNs) is documented. This peptide suppressed the opsonized zymosan-induced generation of chemiluminescence and superoxide anion and concomitant RNA synthesis. However, this peptide did not show significant cytotoxic effects on human PMNs as judged by a cytoplasmic enzyme-releasing assay. These results indicate that a fibroblast-derived peptide reported previously has a suppressive activity on the functional activation of human PMNs. The immunological significance of this finding is discussed.

Cell Survival↗
PubMed1989

Collagen-stimulated human platelet aggregation is mediated by endogenous calcium-activated neutral protease.

To clarify the physiological role of calcium-activated neutral protease (CANP) in human platelets, we loaded the platelets with a Ca2+ -sensitive fluorescent dye, fura-2, and measured the degree of aggregation, cytosolic calcium ion concentration [( Ca2+]i), and proteolysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). At physiological concentration of Ca2+ (1 mM) in the incubation medium, [Ca2+]i was below 0.5 microM and platelet aggregation was not shown. Ionomycin (0.15 microM) or collagen (50 micrograms/ml), but not ADP (10 microM), sharply enhanced the [Ca2+]i to near 1 microM and caused the aggregation. A calcium entry blocker, verapamil, completely abolished both the [Ca2+]i rise and the aggregation. NCO-700, a membrane permeable inhibitor against cysteine proteases (including CANP), dose-dependently blocked the aggregation but did not change the [Ca2+]i transient. SDS-PAGE revealed that filamin, talin, and 70 kDa protein were specifically degraded when platelets were aggregated by ionomycin or collagen and that the proteolysis was not observed when the aggregation was blocked by verapamil or NCO-700. These data provided evidence that Ca2+ entry exceeding 0.5 microM is essential, but not sufficient per se, and that activation of cysteine protease, most likely CANP, is involved in the platelet aggregation by collagen or calcium ionophore.

Blood Platelets↗
PubMed1989

Response of intracellular Ca2+ transients in cultured vascular smooth muscle cells to angiotensin II, vasopressin, acetylcholine and atrionatriuretic peptide.

Modulation of intracellular Ca2+ concentration [( Ca2+]i) is a signal for the contraction of vascular smooth muscle cells responding to vasoreactive substances. We prepared confluently cultured smooth muscle cells from rat aorta, loaded them with Ca2+ sensitive fluorescent dye, fura-2, and measured the [Ca2+]i transient by microscopic spectrofluorometry. The [Ca2+]i was distributed heterogeneously in cytosol. Angiotensin II (10 nM) transiently doubled the [Ca2+]i. It was also increased by arginine-vasopressin (10 nM), even after stimulation by angiotensin II was saturated. In contrast, acetylcholine (10 microM) or rat atrionatriuretic peptide (10 nM) did not change the [Ca2+]i in the same detecting field of the same cell, contradicting previous reports.

Acetylcholine↗
PubMed1988

Heterogeneous macrophage-activating factors from extracellular matrix of human embryo fibroblasts.

Previously, the author found a low-molecular-weight stimulating activity for macrophages in the extracellular matrix of a human embryo fibroblast cell strain. It showed stimulatory effects on the attachment ability of macrophages and their production of superoxide anion (-O2) and [3H]UTP incorporation (Zool. Sci. 3, (1986) 621-626). When the author further analyzed this activity, it was found to be associated with two different factors which could be separated by ion exchange chromatography. Their molecular weights were estimated to be about 5 kDa and 10 kDa by gel filtration chromatography; they are designated fibroblast-derived macrophage activating factor I and II (FMAF I and II). They were sensitive to trypsin, but resistant to heat and did not show significant colony stimulating factor and interferon activities. In addition, FMAF II exhibited much higher activity for granulocyte RNA synthesis than FMAF I. The properties of these factors are compared with other factors reported previously and the biological significance of the factors is discussed.

Cell Adhesion↗
PubMed1988

Identification of colony-forming activities of various hemopoietic cells in the serum-free culture medium of a human embryo fibroblast cell strain.

Ralph et al. reported that human cell lines for the production of colony stimulating factor cannot secrete the factor in serum-free media (Blood 68, 633-639, 1986). However, we found various colony-forming activities to be present in the serum-free culture medium of a human embryo fibroblast cell strain (YH-1). When a soy bean trypsin inhibitor was added to the serum-free media, semisolid cultures of mouse and human bone marrow cells exhibited a considerable degree of colony formation by macrophages and to a lesser extent by other cells. A difference in apparent molecular weights in macrophage colony-forming activities by YH-1 cells from serum-free and serum-containing cultures was observed. The physiological significance of these findings is discussed in terms of regulation of hemopoietic cell differentiation by human embryo fibroblasts.

Blood↗
PubMed1986

Different inducing activities for cytotoxic T cells by heterogeneous thymocyte-activating factors from SV40-transformed human embryo fibroblasts.

Thymocyte-activating factors are produced by human embryo fibroblasts and their production is enhanced by SV40-induced transformation (Okai, Gotoh and Yamashita, Immununol. Lett. (1985), 9, 153-159). The activities for thymocyte DNA synthesis in the culture medium from SV40-transformed cells are separated into the two fractions by a DEAE Sephadex A-25 column chromatography eluting at 150 and 500 mM NaCl. Each fraction contains the heterogeneous molecular weight activities as judged by a Sephadex G-100 column chromatography. In the fraction eluted at 150 mM NaCl, the inducing activities for cytotoxic T cells by the factors are dependent upon their molecular weights; the larger factors exhibit much higher cytotoxic activity than that of the smaller factors. In contrast, the heterogeneous molecular weight factors eluted at 500 mM NaCl do not show the remarkable difference of their biological activities. In addition, the inducing activities by thymocyte-activating factors are also dependent upon their charge properties. These different inducing activities for cytotoxic T cells by thymocyte-activating factors is discussed from the aspect of the immunological regulation.

Animals↗
PubMed1985

DNA synthesis inhibitory peptides in mammalian serum and insect hemolymph.

Similar inhibitory factors for DNA synthesis were found in fetal calf serum and a hemolymph of the moth, Bombyx mori. The factors were highly purified by gel filtration, ion exchange and thin layer chromatography and appeared to be heat-stable. They showed the same effects on some bacteria and mammalian cells. The significance of these DNA synthesis inhibitory 1 Kd peptides is discussed.

Animals↗
PubMed1985

An increase of the regulating factor for chromatin-dependent RNA polymerase II reactions in the tightly-bound chromatin fraction by glucocorticoid injection.

A sugar-containing factor for chromatin-dependent RNA polymerase II reactions exists in rat liver nuclei (1). In this communication the localization of this factor in cell nuclei was investigated. The major activity of the factor was observed in the nuclear soluble fraction whereas a minor activity was detected in the tightly-bound chromatin fraction, but not in the loosely bound chromatin fraction. The factor in the tightly-bound chromatin fraction was considerably increased by glucocorticoid injection, but not in other fractions.

Animals↗
PubMed1985

Thymocyte activating factors from SV40-transformed human embryo fibroblasts.

A novel factor was found in the medium conditioned by SV40-transformed human embryo fibroblasts, which stimulate concanavalin A-induced thymocyte DNA synthetic response. This activity was estimated to be 10-15 kD and divided into two activities by ion exchange chromatography. One of them is a protein molecule and the other is a glycoprotein. In addition, these activities are not derived from the growth factors reported previously such as interleukin 2 (Morgan, R., Ruscetti, F. and Gallo, R. C. (1976) Science 193, 1007-1008) and transforming growth factor (De Larco, J. E. and Todaro, G. J. (1978) Proc. Natl. Acad. Sci. U.S.A. 75, 4001-4005).

Animals↗