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Biomedical subjects

Y Nosoh

Publications and source records attributed to Y Nosoh.

At least 55 records · Page 3Linked to original sources
PubMed1981

Sensitivity of anticancer agents of human gastric cancers transplanted into nude mice.

In the chemotherapy for gastric cancer, the most sensitive anticancer agent against individual tumors should be prescribed. The establishment of a sensitivity test using nude mice as an in vivo model is urgently awaited by clinicians and researchers alike. Seventy-three tumors derived from human gastric cancer were transplanted subcutaneously into nude mice and these mice were then treated intraperitoneally with anticancer agents. Mitomycin C (MMC), 5-fluorouracil (5-FU) and cyclophosphamide (CPM) were used. The doses given were 3 mg/kg of MMC, 75 mg/kg of 5-FU and 200 mg/kg of CPM. IN 52 of the 73 cancers, chemosensitivity was evaluated by the microscopic changes in the tumors. The rate of positive sensitivity against gastric cancer was 42.2% in MMC, 34.6% in 5-FU and 30.8% in CPM, respectively. The sensitivity of each agent tested by this method indicated a good correlation with the clinical therapeutic effects. Our results suggest the feasibility of evaluation of the sensitivity of various agents from the microscopic changes on tumors transplanted into nude mice.

Animals↗
PubMed1981

Effect of lipids on a membrane-bound NADH dehydrogenase from Bacillus caldotenax.

NADH dehydrogenase [EC 1.6.99.3] in membranes of Bacillus caldotenax was solubilized with sodium N-lauroylsarcosinate and purified 50-fold from membranes to 75-80% homogeneity, as judged by SDS-polyacrylamide gel electrophoresis. The enzyme was considered to be located on the electron transport chain and to be an FAD-containing protein. The molecular weight of the subunit was estimated to be 44,000. The enzyme (or the enzyme bound to the B. caldotenax membrane lipids) follows a ping-pong mechanism. The enzyme can oxidize NADH, but not NADPH, with 2,6-dichlorophenol indophenol, ferricyanide, menadione, and cytochrome c as electron acceptors. Membrane lipids or Triton X-100 stimulated the enzyme activity, except that with menadione. Lipids decreased the apparent affinity of electron acceptors and NADH to the enzyme, and increased the maximum velocity, except when menadione was used as the electron acceptor. Lipids partially protected the enzyme from thermal inactivation. The enzyme exhibited a continuous Arrhenius plot, while the lipids- or membrane-bound enzyme exhibited a discontinuous plot.

Bacillus↗
PubMed1980

Change in chemical composition of membrane of Bacillus caldotenax after shifting the growth temperature.

Membranes from Bacillus caldotenax contain neutral lipids and phospholipids such as phosphatidyl-ethanolamine, phosphatidyl glycerol and cardiolipin. Each of the lipids has almost the same fatty acid composition. When the growth temperature decreases, not only the fatty acid composition but also the lipid composition changes such that the membrane fluidity increases, and the composition of membrane-bound proteins also changes. On shifting the growth temperature from 65 degrees to 45 degress C, the bacterium grows immediately with a doubling time at 45 degrees C, but the compositions of proteins and lipids in membranes gradually change and reach the compositions typical of cells growing at 45 degrees C one doubling time after the temperature shift, respectively. It is concluded that the change in chemical composition of membrane of the bacterium on the temperature shift from 65 degrees to 45 degrees C is not prerequisite for growth at 45 degrees C.

Bacillus↗
PubMed1980

Purification and some properties of 6-phosphoglucose isomerase from Bacillus caldotenax.

6-Phosphoglucose isomerase [EC 5.3.1.9] was purified from Bacillus caldotenax. The isomerase shared many common properties with the isomerase from B. stearothermophilus, i.e, pH and temperature optima, thermostability, competitive inhibition by 6-phosphogluconate and Pi, and amino acid composition. The enzyme activity of the former, however, was lower than that of the latter. The molecular weight of the B. caldotenax isomerase was estimated to be 202,000-204,000 by gel filtration and electrophoresis of the enzyme cross-linked with dimethyl adipimidate (DMA). The enzyme was shown to consist of four subunits of equal molecular weight (50,600), and the four subunits were concluded to be identical based on the results of dansylation and cyanogen bromide cleavage of the enzyme. The interaction between the subunits were shown to be isologous by cross-linking with DMA.

Amino Acids↗
PubMed1979

Basis of thermostability in pig heart lactate dehydrogenase treated with O-methylisourea.

Acetamidination of pig heart lactate dehydrogenase (L-lactate:NAD+ oxidoreductase, EC 1.1.1.27) with ethyl acetimidate resulted in an increase of thermostability, and covalent bridge formation between pairs of lysine residues is observed. Guanidination with O-methylisourea of the enzyme also increases the thermostability, but such a bridge seems not to be formed. Increased thermostability of guanidinated enzyme is considered to be due to the shift of the pK values of the lysine residues from 10.5 to 12.5 after guanidination. Modification experiments with carbodiimide reveals that the enzyme contains 4.6 pairs of neighboring lysine and carboxyl residues per subunit, and amide bonding between 3.2 pairs results in an increase of thermostability. Guanidination of 4.6 Lys/subunit of the enzyme yields an enzyme derivative with considerably increased thermostability. Salt bridge formation between the 4.6 pairs of neighboring carboxyl and guanidinated lysine residues per subunit might make a major contribution to the increased thermostability of the guanidinated enzyme.

Animals↗
PubMed1979

Chemical modification of epsilon-amino groups in glutamine synthetase from Bacillus stearothermophilus with ethyl acetimidate.

The activity of glutamine synthetase [EC 6.3.2.1] from Bacillus stearothermophilus decreased slightly on modification with ethyl acetimidate. Acetamidination of 25--26 of the 2 epsilon-amino groups/subunit of the enzyme affected the maximum velocity, but not the Michaelis constant. The thermostability of the enzyme was considerably increased on acetamidination. Acetamidination of the enzyme did not affect the circular dichroism, the tryptophan fluorescence or the quenching effects of KI and acrylamide on the tryptophan emission. The fluorescence spectrum of p-toluidinylnaphthalene sulfonate bound to the enzyme changed on acetamidination.

Geobacillus stearothermophilus↗
PubMed1979

Cross-linking with diimidates of glutamine synthetase from Bacillus stearothermophilus.

Glutamine synthetase [EC 6.3.2.1] from Bacillus stearothermophilus was modified with diethyl malonimidate (DEM), dimethyl adipimidate (DMA), and dimethyl suberimidate (DMS). DMA modified most epsilon-amino groups. On modification with DMA, formation of 3 to 4 cross-links/subunit resulted in a large increase in thermostability. The activity, allosteric properties and fluorescence spectrum of the enzyme were not changed on cross-linking. The SDS-polyacrylamide gel electrophoretic profiles of DEM-, DMA-, and DMS-modified enzymes suggested that the interaction berween six subunits in each of the two hexagonal rings of the protein are heterologous and are different from those between the piled subunits on different rings.

Allosteric Regulation↗
PubMed1977

Acidostability of speroplasts prepared from Thiobacillus thiooxidans.

Thiobacillus thiooxidans was acidostable even in the absence of its respiratory substrate, elementary sulfur. This suggests that the acidostability of the bacterium was enery-independent. The organism was subjected to osmotic shock with 0.75 M sucrose at 0 degrees C and then treated with snail intestinal juice in the presence of 0.3 M sucrose. The decrease in the optical density of the sample thus prepared on dilution with deionized water and electron microscopic observation of the sample showed that spheroplasts were formed from the bacterium by this procedure. Spheroplasts were able to respire sulfur and their respiratory activity was acidostable. Spheroplasts, when treated with Nagase, proteolytic enzyme, lost their acidostability, and some protein components disappeared from the membrane fraction. This suggests that the acidostability of the bacterium may be related to protein conponents of the membrane.

Acidithiobacillus thiooxidans↗
PubMed1977

Effect of ADP on ATPASE from a strain of Bacillus stearothermophilus.

Bacillus stearothermophilus ATCC 12016 was unable to grow at temperatures below 40 degrees C. On incubating the bacteria at the temperatures, ATP in cells disappeared, ADP was accumulated and ATPase (EC 3.6.1.3) was inactivated. When the purified ATPase was incubated at the temperatures for 1 h with 0.17 mM ADP in the presence of MgCl2, the enzyme was completely inactivated. The inactivated enzyme was reactivated on dilution or dialysis or on warming at 65 degrees C. During the incubation of the enzyme sample, the absorbance spectrum of the enzyme changed. On further incubating the sample over 1.5 h, the second step of spectral change occurred together with the change of the circular dichrosim and the dissociation into a lower molecular weight species of the protein. When the enzyme was treated with ADP-MgCl2 at 65 degrees C, the inactivation and conformational change of the enzyme was not observed.

Adenosine Diphosphate↗
PubMed1977

ATP and acetylene-reducing activity of a sulfate-reducing bacterium.

A sulfate-reducing bacterium, a strain of Desulfovibrio vulgaris, when lactate or pyruvate was supplied as an electron and energy source, reduced acetylene only in the presence of sulfate. Acetylene reduction started after a lag of 1 h. H2 which acts as an electron and energy source for sulfate reduction was unable to reduce acetylene even in the presence of sulfate. It was suggested, from the measurements of the amounts of adenine nucleotides of the bacterium incubated under various conditions, that the bacterium is able to reduce acetylene at a high ATP level or a high ATP/ADP ratio.

Acetylene↗
PubMed1976

Effect of the pH of culture medium on the alkalophilicity of a species of Bacillus.

The amino acid incorporation and alpha-amino-isobutyric acid (AIB) uptake of an alkalophilic Bacillus grown at pH 8.2 (the pH 8-bacteria) were much less pH dependent (less alkalophilic) than those of the organisms grown at pH 10.0 (the pH 10-bacteria), respectively. The rate of AIB uptake of the pH 10-bacteria was almost the same as that of the pH 8-bacteria, while the rate of amino acid incorporation of the pH 10-bacteria was higher than that of the pH 8-bacteria in alkaline environments. The colloidal titration with clupein showed that the amount of negative charge on the pH 10-bacteria was greater than that of the pH 8-bacteria in alkaline environments. Considerable difference in protein composition was observed between the membranes of the pH 8- and 10-bacteria while no difference was observed in phospholipid composition.

Aminoisobutyric Acids↗
PubMed1976

Effect of temperature on the viability of Bacillus stearothermophilus.

One of the obligate thermophilic bacteria, Bacillus stearothermophilus, was unable to grow at temperatures below 35 degrees C. About 80% of the population in the bacterial culture died at the temperatures, and the same extent of loss in either of the activities of oxygen consumption or synthesis of protein or nucleic acid of the organisms was observed. With the progress of death of the organisms, reduced nicotinamide-adenine dinucleotide came to be oxidized by the organisms, enzymes such as fructose-1,6-diphosphate aldolase, when the organisms were washed with phosphate buffer, were leaked out of the organisms, and an increasing amount of ribonucleoprotein was released into the culture medium. The change of the membrane state was then suggested to be one of the possible causes for the death of the organisms at the temperatures.

Bacterial Proteins↗
PubMed1976

Some catalytic and molecular properties of threonine deaminase from Bacillus stearothermophilus.

Threonine deaminase [EC 4.2.1.16] was highly purified from Bacillus stearothermophilus. The enzyme exhibited maximum activity at 65 degrees and at pH 9.2--9.6. It was inactivated on dilution and on storage at 4 degrees, but was protected by egg albumin. The enzyme was labile at 65 degrees, but became stable in the presence of egg albumin and isoleucine at pH 7.0. The substrate saturation curve for the enzyme reaction at 40 or 65 degrees was hyperbolic, but in the presence of isoleucine, the curve became sigmoidal (n = 2). The enzyme was more sensitive to isoleucine at 40 degrees than at 65 degrees, while valine slightly inhibited the enzyme at both 40 and 65 degrees. Inhibition of the enzyme by isoleucine was antagonized by valine at 40 and 65 degrees. These properties were essentially similar to those of the enzymes from mesophilic and thermophilic bacteria. The enzyme existed in two forms with different molecular sizes, 1.5-5 X 10(6) and 2 X 10(5) daltons, at pH 7.0 and at temperatures below 40 degrees. The larger component disaggregated into the small one at pH 8.5 or above, at temperatures above 50 degrees or in the presence of isoleucine and valine.

Geobacillus stearothermophilus↗