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Biomedical subjects

Y Okai

Publications and source records attributed to Y Okai.

At least 19 recordsLinked to original sources
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↗
PubMed1985

Dual functions of DNA synthesis inhibitory peptide in fetal calf serum.

A novel factor in fetal calf serum was found which showed the dual inhibitory effects on DNA synthesis of murine lymphocytes and some species of bacteria. The factor was purified by gel filtration, ion exchange and thin-layer chromatography and characterized to be a 1 kDa basic peptide. In addition, this factor is not nonspecific to inhibitors, thymidine or polyamines. The modes of action and the spectrum of target cells were analyzed and its biological significance is discussed.

Animals↗
PubMed1985

Large-molecular-weight thymocyte-activating factors in extracellular matrix of SV40-transformed human embryo fibroblasts.

It has been reported that the major thymocyte-activating factors at 10-15 kDa exist in the culture medium of SV40-transformed human embryo fibroblasts. However, these factors could not be detected in the extracellular matrix (ECM) from the same transformed cells, but the 30-40 kDa factors were found. They showed a similar lectin requirement, charge heterogeneity and Concanavalin A-binding property as compared with the factors reported previously. They were separated from fibroblast DNA synthetic activities in ECM and did not contain interleukin 2 activity. A possible relationship between 30-40 kDa factors in ECM and 10-15 kDa factors in the culture medium is discussed.

Biological Products↗
PubMed1984

A large-molecular-weight regulating factor for chromatin-dependent RNA polymerase II reactions in rat liver cytoplasm.

The author found a sugar-containing 70 KDa factor in rat liver nuclei as described in the previous report (1), which repressed RNA chain initiation by all classes of rat liver RNA polymerases and specifically stimulated chromatin-dependent RNA chain elongation catalyzed by RNA polymerase II. In this communication, the localization of this factor in rat hepatic cells was studied. In the cytoplasmic fraction, a large-molecular-weight regulating activity for chromatin-dependent RNA polymerase II reactions was observed and it was characterized to be a 250 KDa glycoprotein. This factor showed the same biological activity for chromatin-dependent RNA polymerase II reactions as that of the factor reported previously (1). Furthermore, this factor was converted to the 70 KDa factor by the action of exogenous or unknown endogenous protease(s). These results suggest that a conversion mechanism from cytoplasmic factor to nuclear factor for RNA polymerase II-dependent transcription exists.

Animals↗
PubMed1984

3T3 fibroblasts release a low-molecular-weight inhibitory peptide of lymphocyte DNA synthesis into serum-free culture medium.

3T3 fibroblasts release a novel factor into serum-free culture medium, which strongly suppressed concanavalin A-induced thymocyte DNA synthesis. This activity was highly purified by gel filtration, ion exchange and thin-layer chromatography and was characterized as a 1 kDa heat-stable peptide. Although this peptide suppressed lymphocyte DNA synthesis when added relatively early after lectin-stimulation, the cell viability was not changed significantly. The peptide considerably repressed DNA synthesis of some mammalian fibroblast cells, but malignant-transformed cells were not affected.

Animals↗
PubMed1984

T cell growth factors from adult T cell leukemia virus-transformed cell lines.

Some characteristics of T cell growth factors derived from adult T cell leukemia virus (ATLV)-transformed cell lines, MT 1 and MT 2 were analyzed. MT 1 cells release significant interleukin 2 (IL 2) activity into the culture medium, which showed the same elution pattern of gel filtration and isoelectric focusing of IL 2 from lectin-stimulated normal human lymphocytes. This activity was also detected in the cell extract of MT 1. In contrast, MT 2 cell line did not produce IL 2 activity, but non-IL 2 type growth factor was observed. The significance of these factors from MT cell lines is discussed from the viewpoint of 'autokine' in ATLV-transformed cells.

Adult↗