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Biomedical subjects

K Koga

Publications and source records attributed to K Koga.

At least 307 records · Page 17Linked to original sources
PubMed1978

Nucleolar size in parallel with ribosomal RNA synthesis at diapause termination in the eggs of Bombyx mori.

The eggs of Bombyx mori, both in diapause and nondiapause, were subjected to cytological examination of nucleoli and measurement of RNA precursor incorporation (2 hours) into ribosomal RNA. In diapause eggs, the nucleoli were very small and the rate of ribosomal RNA synthesis was the lowest of the samples tested. Most cells in diapause possessed nuclei with one nucleolus. In contrast, the eggs activated from diapause by long chilling attained the largest size of nucleoli and the highest rate of ribosomal RNA synthesis. A significant proportion of the cell nuclei still had only one nucleolus at this stage. Three days after activation, the eggs exhibited intermediate levels in both the size of nucleoli and the rate of ribosomal RNA sythesis. At this stage, about half of the egg cell nuclei had two nucleoli.

Animals↗
PubMed1978

[Distribution, metabolism and excretion of toluene in mice (author's transl)].

Tissue distribution, metabolism and excretion of 14C-labeled toluene were investigated after a single intraperitoneal administration (290 microgram/kg) of the compound into mice. The highest radioactivity was detected in the adipose tissue, followed in descending order by the kidney, liver and lung. The lowest radioactivity was retained in brain tissue and the brain/blood concentration ratio was about 0.4 throughout. Radioactivity in the blood declined exponentially and the biological half-life was estimated to be 25 min. Radioactive materials detected at as early as 8 min in the kidney (78%) and liver (64%) proved to be non-volatile metabolites. On the contrary, 70% of radioactive materials in the brain and near 100% in the adipose tissue were found to be a volatie compound (probably unchanged toluene). The cumulative urinary excretion of radio-activity was 26.4% of the dose at 30 min and 73.8% at 18 hr, whereas the pulmonary or fecal excretion was negligibly small. Radioactive materials excreted in the urine were identified by paper and the thin-layer chromatography as hippuric acid (59%) and benzoylglucuronic acid (41%). These results show that toluene is metabolized rapidly and is excreted mainly in the urine. The relative importance of glucuronide formation in detoxication mechanisms was noted.

Animals↗
PubMed1978

Potentiation of toluene toxicity by hepatic enzyme inhibition in mice.

The toxicity of toluene was evaluated in male mice by the narcotic effects and lethality. The i.p. LD50 of toluene for male mice was calculated to be 1.15g/kg according to the method of Weil. Pretreatment with phenobarbital, produced a marked decrease in the number of sleep induced by a test dose (0.96 g/kg i.p.) of toluene. By contrast, pretreatment with a variety of hepatic enzyme inhibitors such as CCl4, SKF 525A, pyrazole and cyanamide was found to produce an increase in the number of sleep and death, accompanied with the prolongation of sleeping time. The present results suggest that the toxicity of toluene is enhanced by the inhibition of any step of metabolism.

Animals↗
PubMed1978

Protein-mediated transfer of DDT to adipose tissue.

The in vitro transfer of DDT through various media to rat adipose tissue was examined. About 15% of DDT was transferred through Krebs-Ringer solution to the tissue slices after 2-hr incubation at 37 degrees C. The addition of albumin accelerated the transfer of DDT proportionally to the concentrations up to 1.0%. Hemoglobin and gamma-globulin showed a lesser accelerating activity, but protamine, trypsin and pepsin showed little or no effect. When the Krebs-Ringer solution was replaced by triglyceride suspensions, only a small amount of DDT was taken up by the adipose tissue. Ffflux experiments revealed that the adipose tissue scarcely released DDT into albumin solution or triglyceride suspensions. The results suggest that lipid may play an important role as a storage site of DDT and that albumin may behave as a carrier system.

Adipose Tissue↗
PubMed1977

An ESR study of the Mn(II)-heavy meromyosin system.

The Mn(II)-heavy meromyosin system was studied by measuring the ESR spectrum of Mn(II). The temperature dependence of the line width parameter W(1, t) of a freshly prepared sample changes at around 7-10 degrees C, where W(1, t) is the reciprocal of the peak-to-peak height of the lowest magnetic field component of the hyperfine structure. It is shown that the change in the slope of W(1, t) at 7-10 degrees C is due to a change in the structure of Mn(II)-heavy meromyosin or a change in the interaction between Mn(II) and heavy meromyosin without ATP. This result is in accord with the recently reported observations that heavy meromysin ATPase activity showed different temperature dependence above and below 10 degrees C in the presence of Mn(II). The characteristics of the spectrum of the Mn(II)-heavy meromyosin system in the liquid state between 2 degrees C and 20 degrees C are compared with those of a frozen sample of Mn(II)-heavy meromyosin in a low temperature region (-50-0 degrees C) and with those of the lyophilized material. The forbidden transitions are observed, and hence the zero field splitting parameter can be obtained. It is 115 +/- 15 gauss at -50 degrees C, and decreases with increase of the temperature to 70 +/- 15 gauss at 20 degrees C.

Adenosine Triphosphate↗
PubMed1977

Isolation and characterization of malic enzyme from the pupa of Bombyx mori.

Malic enzyme, which requires NADP+ as a coenzyme, was isolated and purified from pupae of the silkworm, Bombyx mori. The purified enzyme appeared homogeneous and had a molecular weight of 195,000 on polyacrylamide gel electrophoresis. The optimum pH for the oxidative decarboxylation of malate, measured in terms of the increase of NADPH (MH activity) and CO2 (MC activity), was pH 7.5, while that for the decarboxylation of oxaloacetate measured in terms of the increase of CO2 (OC activity) was pH 4.6. Several differences between MH and OC activity were investigated.

Ammonium Sulfate↗
PubMed1977

Isolation and characterization of NADP+-specific isocitrate dehydrogenase from the pupa of Bombyx mori.

NADP+-specific isocitrate dehydrogenase was found in several tissues of the pupa of the silkworm, Bombyx mori. This enzyme was highly purified from the whole bodies of pupae. This is the first isolation of the enzyme from insect materials. The purified enzyme gave a single protein band on polyacrylamide gel electrophoresis. The reaction catalyzed by the purified enzyme was readily reversible. The pH optimum for the forward reaction (reduction of NADP+) was 7.8, and that for the reverse reaction (oxidation of NADPH) was 6.6. The enzyme had a molecular weight of 86,000 and was found to be composed of two identical subunits, which have a molecular weight of 44,000. The activity of the enzyme in the forward reaction was slightly inhibited by citrate, oxaloacetate, alpha-ketoglutarate, and others. Citrate stabilized the activity over a wide pH region.

Animals↗
PubMed1977

The mast cell and eosinophil in nasal secretion.

With an improvement of Hansel staining it became possible to identify mast cells, eosinophils and other cells in nasal smears. By this improved method 87% of children and 95% of adult patients who visited our allergy clinic proved to have mast cells in their nasal smears.

Adolescent↗
PubMed1976

Effect of periodate oxidation on the structure and properties of glucose oxidase.

In order to elucidate the molecular structure of glucose oxidase (beta-D-glucose: oxygen 1-oxidoreductase, EC 1.1.3.4) and the roles of its carbohydrate moiety, chemical, physiochemical and immunological experiments were performed with enzyme samples before and after periodate oxidation. Hydrodynamic parameters indicated that the native enzyme was a globular protein with values of 1.21 for the frictional ratio and 43 A for the Stokes radius. The enzyme contained about 12% carbohydrate by weight, of which the main component was mannose. The periodate treatment decreased the carbohydrate content to about 40% of its original value. Slight modifications were detected in the absorbance spectrum and the content of arginyl residue. However, no significant alteration was brought about by this treatment in the catalytic parameters, immunological reactivities of the gross structure, not in the secondary and quaternary structures of the protein moity. Thermal denaturation temperature (about 72.5 degrees C) and the enthalpy of denaturation (about 450 kcal/mol) were common to the native and the periodate-oxodozed enzymes. The native was found to be quite resistant to sodium dodecyl sulfate and fairly stable to urea and heating. The periodate-oxidized enzyme was also stable to heat treatment, but it showed a diminished stability when denaturing agents were present. Kinetic analyses of the thermal inactivation processes showed that the entropy of activation was greatly decreased by the denaturing agents, especially in the case of the periodate-oxidized enzyme. It is concluded that the carbohydrate moiety of the enzyme plays a role in increasing the stability of the protein moiety, but does not directly participate in the catalytic activity, the immunological reactivity, or in maintaining the conformation of the enzyme protein.

Amino Acids↗