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Biomedical subjects

S Natori

Publications and source records attributed to S Natori.

At least 325 records · Page 18Linked to original sources
PubMed1982

Correlation between effects of 24 different cytochalasins on cellular structures and cellular events and those on actin in vitro.

To compare the effects of cytochalasins on the cellular level with those on the molecular level, 24 cytochalasins, 20 natural compounds and 4 derivatives, were used. The following effects were tested for each of 24 cytochalasins; (a) four high dose (2-20 muM) effects on the cellular level: rounding up of fibroblastic cells, contraction of actin cables, formation of hairy filaments containing actin, and inhibition of lymphocyte capping; (b) a low dose (0.2-2 muM) effect: inhibition of membrane ruffling; and (c) two in vitro effects: an inhibition of actin filament elongation (the high affinity effect [low dose effect] in vitro) and an effect on viscosity of actin filaments(the low affinity effect [high dose effect] in vitro). These results indicated that there are almost the same hierarchic orders of relative effectiveness of different cytochalasins between low and high dose effects and between cellular and molecular effects. From the data obtained with the 24 cytochalasins, we have calculated correlation coefficients of 0.87 and 0.79 between an effect in vivo, inhibition of capping, and an effect in vitro, inhibition of actin filament elongation, as well as between inhibition of capping and another effect in vitro, effect on viscosity of actin filaments, respectively. Furthermore, a correlation coefficient between the high affinity effect and the low affinity effect determined in vitro was calculated to be 0.90 from the data obtained in this study. The strong positive correlation among low and high dose effects in vivo and those in vitro suggests that most of the effects caused by a cytochalasin, irrespective of doses or affected phenomena, might be attributed to the interaction between the drug and the common target protein, actin. In the course of the immunofluorescence microscope study on cytochalasin-treated cells using actin antibody, we have found that aspochalasin D, a 10-isopropylcytochalasin, strongly induced the formation of rodlets containing actin in the cytoplasm of the treated fibroblasts. In contrast, the other cytochalasins, including cytochalasin B, cytochalasin C, cytochalasin D, and cytochalasin H, were found to induce the formation of nuclear rodlets. Both cytoplasmic and nuclear rodlets found in the cytochalasin-treated cells were similar in ultrastructures to those induced by 5 to 10 percent (vol/vol) dimethyl sulfoxide in the same type of cells.

Actins↗
PubMed1982

Tissue-specific distribution of DNA-binding nuclear proteins.

The DNA-binding capacity of nuclear proteins of mouse cells was examined by the protein-blotting method. Under conditions in which the lac repressor specifically binds to the lac operator, the DNA-binding nuclear proteins from different tissues showed a tissue-specific distribution, suggesting that the species and amounts of nuclear proteins with DNA binding activity differ in different tissues. When cloned eukaryotic genes were used for binding, eukaryotic DNA showed stronger binding than prokaryotic DNA. Competition experiments suggested that many nuclear proteins have different DNA binding properties from that of the prokaryotic repressor.

Animals↗
PubMed1982

Viscometric analysis of effects of cytochalasins on in vitro polymerization and depolymerization of microtubules.

Nineteen cytochalasins including 6 natural cytochalasins, 2 natural aspochalasins, 7 natural chaetoglobosins and 4 their acetates were investigated by viscometry to examine their effects on in vitro polymerization and depolymerization of microtubules. Cytochalasin A was proved as an only active cytochalasin, confirming the studies of Himes et al., and others showed very weak or no noticeable effects. This results indicate that a wide range of effects of cytochalasins are not related to interactions with microtubules.

Animals↗
PubMed1982

Induction of macrophage-mediated tumor lysis by an animal lectin, Sarcophaga peregrina agglutinin.

Several animal lectins, such as Sarcophaga peregrina agglutinin, Limulus polyhemus agglutinin, Helix pomatia agglutinin and Helix aspersa agglutinin, were tested for induction of tumor lysis mediated by macrophages. Among them, only S. peregrina agglutinin purified from the hemolymph of S. peregrina larvae lysed tumor cells in co-operation with macrophages from the peritoneal cavity of mice. S. peregrina agglutinin alone did not kill target tumor cells. Macrophages in the presence of this lectin could kill other syngeneic tumor cells. This lectin-dependent cytolysis by macrophages was inhibited by galactose, a sugar which is specifically recognized by S. peregrina agglutinin. These findings suggest that the animal lectin S. peregrina agglutinin is a ligand in macrophage-mediated cytolysis, inducing binding of effector macrophages to target cells which in turn triggers off lysis of the target cells.

Agglutinins↗
PubMed1981

A possible mechanism of induction of insect lectin.

Studies were made using antibody against a lectin induced in the hemolymph of Sarcophaga peregrina larvae on injury. The results suggested that the alpha subunit (Mr = 32,000) of the lectin is normally present in the hemolymph. On injury of the body wall, part of the alpha subunit seems to be converted to the beta subunit (Mr = 30,000), probably by partial proteolysis with a protease activated in response to the injury. As a result, an active lectin with the structure alpha 4 beta 2 is formed.

Animals↗
PubMed1981

Activation of latent ribonuclease in the fat-body of fleshfly (Sarcophaga peregrina) larvae on pupation.

A crude extract of the fat-bodies of third-instar larvae of Sarcophaga peregrina (fleshfly) was found to contain latent RNAase (ribonuclease) consisting of RNAase and inhibitor protein that is sensitive to p-chloromercuribenzoic acid. The RNAase activity in the crude extract of fat-bodies became detectable with time after puparium formation, indicating that the inhibitor is selectively inactivated and RNAase is released from the RNAase-inhibitor complex during metamorphosis.

Adipose Tissue↗
PubMed1981

Difference in phosphorylation of two factors stimulating RNA polymerase II of Ehrlich ascites tumor cells.

The structures of two protein factors, S-II and S-II', that specifically stimulate RNA polymerase II from Ehrlich ascites tumor cells were compared. The two proteins behaved differently on CM-cellulose chromatography and on isoelectric focusing, although they were shown to have common antigenicity. The following findings strongly suggest that S-II and S-II' have the same primary structure, but that S-II' is more extensively phosphorylated than S-II: (1)S-II an S-II' gave identical peptide maps when digested with various proteases. (2) S-II' that had been treated with alkaline phosphatases had the same mobility on sodium dodecyl sulfate-polyacrylamide gel as S-II, indicating that it could be converted to S-II by hydrolysis of its phosphate residues. (3) S-II' was phosphorylated more than S-II when Ehrlich ascites tumor cells were labeled in vivo with [32P]orthophosphate.

Alkaline Phosphatase↗
PubMed1981

Stimulation of messenger ribonucleic acid synthesis in isolated nuclei by a protein that stimulates RNA polymerase II.

A factor stimulating RNA polymerase II purified from Ehrlich ascites tumor cells was found to stimulate alpha-amanitin-sensitive RNA synthesis in nuclei isolated from spleen cells of anemic mice, though less than it stimulated purified RNA polymerase II. The fidelity of the resulting RNA synthesis was monitored by measuring the stimulation of globin mRNA synthesis. Globin mRNA was measured quantitatively by DNA-RNA hybridization by using plasmid DNA containing globin DNA sequences. Results showed that the synthesis of globin mRNA was enhanced in isolated nuclei in the presence of this factor coinciding with an increase of overall alpha-amanitin-sensitive RNA synthesis. Thus, it was concluded that an externally added factor did not stimulate random transcription but meaningful RNA synthesis in isolated nuclei.

Anemia↗
PubMed1981

Mutagenicities of 61 flavonoids and 11 related compounds.

The mutagenicities of 61 flavonoids (naturally occurring flavonoid aglycones and flavonal glycosides and synthetic flavonoids) and those of 11 compounds structurally related to flavonoids were tested with Salmonella typhimurium strains TA100 and TA98. Among the 22 flavone derivatives tested, only wogonin was strongly mutagenic, while five derivatives, apigenin triacetate, acacetin, chrysoeriol, pedalitin, and pedalitin tetraacetate, were only weakly mutagenic. Two bisflavonyl derivatives, neither of which has a 3-hydroxyl group, were not mutagenic. Of the 16 flavonol derivatives tested, all except 3-hydroxyflavone and the tetra- and penta-methyl ethers of quercetin were mutagenic. Of the five flavanone derivatives tested, only 7,4-dihydroxyflavanone was mutagenic, showing weak activity. Of the four flavanolol derivatives tested, hydrorobinetin and taxifolin were weakly mutagenic. Of the six isoflavone derivatives tested, tectorigenin was weakly mutagenic. Of the 11 compounds in the miscellaneous group structurally related to flavonoids, only isoliquiritigenin was mutagenic, showing weak activity. For the emergence of strong mutagenicity, the double bond between positions 2 and 3 and the hydroxyl group at position 3 are required, except in wogonin, which does not have a hydroxyl group at position 3 but is strongly mutagenic to TA100. The 3-O-acetyl ester of flavonol, quercetin, was mutagenic with S9 mix, but 3-O-methyl ethers were not. Six flavonol glycosides, three quercetin glycosides and three kaempferol glycosides were mutagenic after preincubation with "hesperidinase," a crude extract of Aspergillus niger. Of 66 flavonoid agylcones and compounds structurally related to flavonoids, quercetin was the strongest mutagen. The carcinogenicity of this compound should be clarified because it is ubiquitously found in vegetables.

Animals↗
PubMed1981

Carcinogenicity examination of quercetin and rutin in ACI rats.

Carcinogenicity of quercetin and rutin were examined in inbred ACI strain rats. Rats were given a diet containing 1% or 5% quercetin or 5% rutin for 540 days, or 10% quercetin and 10% rutin for 850 days. Rats in control groups were fed a normal basal diet. Most tumors found in experimental groups were also found in the corresponding control groups. Furthermore, there was no significant difference between the incidence of tumors in the experimental or control groups (P greater than 0.05). Thus, quercetin and rutin tested were not shown to be carcinogenic to ACI rats.

Animals↗
PubMed1981

Purification of a new protein stimulating RNA polymerase II from Ehrlich ascites tumor cells: comparison with proteins purified before.

A protein factor named S-I(b) that stimulates the activity of RNA polymerase II was purified from Ehrlich ascites tumors cells. The final preparation gave a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This protein has a molecular weight of 24,000 and is significantly smaller than S-II and S-II', stimulatory proteins of RNA polymerase II purified previously. However, S-I(b) cross-reacted with antibody against S-II and its peptide map obtained after radio-iodination was identical with that of S-II' (a phosphorylated form of S-II), indicating that S-I(b) and S-II share a common primary structure. S-I(b) is suggested not to be a degradation product of S-II produced during the purification process, and the structural relations between S-II and S-II' are discussed.

Animals↗
PubMed1981

Mycotoxin production by Chaetomium spp. and related fungi.

Screening for mycotoxin production by Chaetomium spp. and related fungi on rice culture was conducted by a combination of cytotoxicity tests using HeLa cells and thin-layer chromatography. Producers of sterigmatocystin, O-methylsterigmatocystin, chaetochromin, chaetocin, chetomin, cochliodinols, and mollicellin G were found and the taxonomic significance of these findings is discussed.

Anti-Bacterial Agents↗
PubMed1980

Purification of lectin induced in the hemolymph of Sarcophaga peregrina larvae on injury.

A lectin was purified from the hemolymph of Sarcophaga peregrina larvae, obtained after injury of their body wall. This lectin agglutinated sheep red blood cells markedly and the hemagglutinating activity was inhibited by galactose and lactose. The active lectin was found to have a molecular weight of 190,000 and to consist of four alpha subunits and two beta subunits, with molecular weights of 32,000 and 30,000, respectively. During the early pupal stage, similar hemagglutinating activity in the hemolymph increased to several times than in larval hemolymph. This activity was completely inhibited by the antibody prepared against the lectin purified from the hemolymph of injured larvae. Thus, the same protein having lectin activity is apparently induced under two different physiological conditions: injury of the body wall of larvae and during pupation. The biological significance of this lectin is discussed.

Animals↗