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Biomedical subjects

Y Okai

Publications and source records attributed to Y Okai.

At least 55 records · Page 3Linked to original sources
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↗
PubMed1984

Differential changes of tightly chromatin-bound RNA polymerase II in starved and cycloheximide-treated rat liver nuclei.

In order to investigate the physiological function of loosely and tightly chromatin-bound RNA polymerase II in vivo (1), the changes of these enzyme activities in cycloheximide-treated or starved rat liver nuclei were studied. Total nuclear mRNA synthesis activity in starved rats was considerably decreased, but that of cycloheximide-treated rats was not affected significantly. In starved rats, tightly bound enzyme activity was much more repressed as compared with that of loosely bound enzyme. On the other hand, cycloheximide-treated rats showed the reverse relationship. Thus, mRNA synthesis activity in hepatic nuclei seems to be dependent on the tightly bound RNA polymerase II activity. However, the difference of nuclear mRNA synthesis in both cases can not be explained by the change of chromatin-bound enzyme activity of Yu (2).

Animals↗
PubMed1984

Murine splenocytes release an inhibitory peptide of lymphocyte DNA synthesis into serum-free culture medium.

Murine splenocytes release a novel repressing activity of Concanavalin A-induced lymphocyte DNA synthesis. This activity was purified by gel filtration, ion exchange and thin layer chromatography. It was characterized to be a heat-stable peptide whose molecular weight was estimated to be about 1 000 daltons. The strong inhibition by this peptide was observed when added at early periods of the cell culture. This factor does not affect early RNA synthesis in lymphocytes, but nucleotide (UTP) incorporation at early periods was considerably decreased. In addition, although the factor inhibits drastically lymphocyte DNA synthesis, the cell viability is not changed significantly. These results suggest that the peptide suppresses the cell membrane function at early periods and specifically blocks the concomitant DNA synthesis.

Animals↗
PubMed1984

A novel factor for DNA-dependent RNA polymerase II in rat liver nuclei.

The author found, in rat liver nuclei, a novel factor which exhibited a strong inhibitory effect on RNA chain initiation by various classes of RNA polymerases (I, II and III) using an exogenous DNA template. The molecular weight of this factor was estimated to be 70 K daltons, and its activity was not affected by treatment with trypsin, RNase A, lipase C, alpha-amylase and heat. However, its activity was inactivated by a digestion of glycosidases. The molecule is shown to contain a considerable amount of sugars by physicochemical analysis. In addition, it is elucidated that the factor is not heparin which has a similar biological activity.

Animals↗
PubMed1984

A decrease of RNA synthesis during macrophage activation with lipopolysaccharide--an association with novel regulating factors.

RNA synthesis during macrophage activation with lipopolysaccharide (LPS) was analyzed in mice. The RNA synthesis of macrophages was considerably increased early after LPS stimulation, but drastically decreased at a later period. The decrease of RNA synthesis was observed in mouse strains responding to LPS such as BALB/c, ATL and ddY, but not in nonresponder strain, C3H/HeJ. Furthermore, the decrease of RNA synthesis occurred in both alpha-amanitin resistant and sensitive RNA polymerase reactions. However, RNA polymerases in nuclei were not changed significantly in LPS-treated macrophages, but the factors affecting RNA polymerase reactions were drastically changed. Amongst these factors, the stimulating factors were decreased and a novel repressing factor was remarkably increased. The factors were partially characterized and their significance in macrophage activation is discussed.

Animals↗
PubMed1984

Modulation of early mRNA synthesis in lectin-induced lymphocyte activation--an association with a possible factor.

Two phases of early mRNA synthesis were observed in lectin-induced lymphocyte activation. At 0-2 h, lectin-treated lymphocytes showed a considerable decrease in nuclear RNA polymerase II activity as compared with that of untreated cells and, at later periods, a reverse increase was observed. Such modulation of mRNA synthesis is not due to the change of RNA polymerase II, but a possible factor in nuclei. This factor represses RNA chain initiation and stimulates chromatin-dependent RNA elongation catalyzed by RNA polymerase II. It was characterized to be a 10-30 kDa sugar-containing molecule and the physiological significance of this factor is discussed from the viewpoint of the transcriptional regulation.

Animals↗
PubMed1983

Preferential recognition of DNA by dimeric RNA polymerase II. An electron microscopic study.

The forms of purified rat liver RNA polymerase II and their functions were analyzed by an electron microscopy. The author found that highly purified RNA polymerase II showed the following distinct two forms; dimeric and monomeric forms. Furthermore, the preferential binding to promotors of lambda dvl template by dimeric enzyme forms was observed. Finally, the role of dimeric RNA polymerase II on DNA template recognition was discussed.

Animals↗
PubMed1982

A simple solubilization method for loosely and tightly chromatin-bound RNA polymerase II from rat liver nuclei.

Rat liver chromatin-bound RNA polymerase II could be differentially solubilized into two distinct populations, loosely and tightly bound enzymes, by a simple method. By this method the recovery of the solubilized enzyme from the chromatin fraction could be increased considerably as compared with the procedure of Yu (1). The two chromatin-bound enzymes had different properties: (a) Loosely bound enzyme was easily extractable from chromatin with relatively mild ionic condition (0.5 M NaCl); the tightly bound enzyme had to be solubilized by more drastic conditions such as sonication or nuclease treatment. (b) Loosely bound enzyme could not efficiently transcribe the chromatin template, but the tightly bound enzyme was active toward the same template. The latter enzyme is involved in the tight complex with the RNA synthesis activating factors. (c) Cycloheximide treatment in vivo suggests that the two enzymes have different turn-over rates. Therefore, with this simple solubilization method the functionally different two chromatin-bound RNA polymerase II activities can be estimated.

Animals↗