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Biomedical subjects

K Nagano

Publications and source records attributed to K Nagano.

At least 253 records · Page 14Linked to original sources
PubMed1980

Effect of polynucleotides and a basic protein on the condensation of phenylalanyl adenylate.

The effect of polyuridylate and of histone on the oligomerization of phenylalanyl adenylate was tested. Polyuridylate which pairs with adenine under suitable conditions showed no effect. Histone increased the rate of the polymerization whereas a neutral protein, albumin, had no effect. Simultaneous presence of nucleotides diminished the effect of histone. The implication of these results on the prebiotic polypeptide formation is discussed.

Adenosine Monophosphate↗
PubMed1980

Effect of reducing agents on the solubilization of renal sodium and potassium dependent ATPase with detergent.

A high concentration (0.5 M) of a reducing agent such as dithiothreitol or 2-mercaptoethanol inactivated both crude (microsomal) and purified preparations of Na+,K+-ATPase only in the presence of detergent. The concentration of SDS needed for inactivation by a reducing agent was low (around 0.3 mg/ml), and was similar to that required for activation in the absence of reduction. The subunits of the enzyme after inactivation with a reducing agent were not sedimented by centrifugation at 100,000 x g for 1 h. Electron microscopic observation of the inactivated enzyme revealed that membranous structures were dominant in the pellet obtained by centrifugation, whereas many particles were present in the supernatant. These results suggest that Na+,K+-ATPase was inactivated by reduction of disulfide bond(s) embedded within the lipid bilayer in the presence of detergent, and that the subunits of the resulting enzyme were no longer bound to the membrane.

Animals↗
PubMed1979

[Testicular atrophy of mice induced by ethylene glycol mono alkyl ethers (author's transl)].

Toxicities of ethylene glycol (EG) and 6 ethylene glycol mono alkyl ethers administered orally were studied. Mice were given various doses (62.5, 125, 250, 500, 1,000, 2,000 and 4,000 mg/kg body weight) of the compounds daily for 5 days/week, for 5 weeks. High doses of ethylene glycol mono methyl ether (EGM), ethylene glycol mono methyl ether acetate (EGMA), ethylene glycol mono ethyl ether (EGE) and ethylene glycol mono ethyl acetate (EGEA) produced marked testicular atrophy and leucopenia. Dose-responce relation was found in these effects. EGM was more effective than EGE, while ethylene glycol mono butyl ether and ethylene glycol mono phenyl ether had but slight effect and EG had no detectable action on testis and leucocytes. Toxic doses being expressed as mg/kg body weight, esterification seemed to weaken the atrophic action of EGM and EGE, but when expressed as mol/kg, significant difference was found neither between EGM and EGMA nor between EGE and EGEA. The mechanism of testicular atrophy induced by low ethylene glycol mono alkyl ethers is likely to be an inhibitory action on cell division.

Animals↗
PubMed1978

[Anatomical and biomechanical considerations for medullary nailing (author's transl)].

By using X-ray films of 390 adult femurs and 15 cadaveric femurs of Japanese origin, and by measuring successive cross-sections the authors have made morphological and statistical analyses of the shape of the femoral medullary canal. These studies suggest new dimensions for the diameter of the reamer and the amount of contact area between nail and inner cortex. Furthermore it was found that the physiological antecurvature of the femur on the lateral view does not correspond with the prebending of the OA-nail. The authors made some mechanical experiments on four types of nails which are widely used today. As a consequence of these studies, the authors developed a new elastic nail for trial (Okayama-nail). This new type of nail greatly increases the area of contact with the inner femoral cortex. Obviously this nail satisfies better all of Kuentscher's originally mentioned requirements an intramedullary nail.

Adolescent↗
PubMed1977

The origin of the protein synthesis mechanism.

The origin and development of the protein synthesis mechanism is considered in four successive steps. The genetic code is supposed to be controlled by the relative amount (availability) of various amino acids and nucleotides on the one hand, and utility on each amino acid in the polypeptide. on the other hand. Thus, more simple (inutile) and abundant amino acids tended to correspond to codons which were rich in the less frequent base species, G and C. Features of primitive tRNA in the discrimination of amino acid are discussed. Primitive tRNA is proposed to have a discriminator site for amino acid and, separated from it, an anticodon site for interaction with nucleotides. A hypothetical course of subdivision of various nucleic acid species is proposed. In the scheme, mRNA and ribosomal RNA (rRNA) were derived from more primitive insoluble RNA. DNA appeared in the late, not first, step of the development. Several other aspects of evolutionary development of the whole protein synthesis mechanism, e.g., role of the discriminator site on primitive tRNA, modification and subdivision of code catalogue into a more precise specification of amino acids, and possible primordial interactions between tRNA and tRNA-binding sites on insoluble rRNA, are discussed.

Amino Acyl-tRNA Synthetases↗
PubMed1977

A new nail-plate for treatment of fracture of the neck of the femur.

Operative treatment of fractures of the neck and trochanter of the femur does not always produce a satisfactory result. This is usually due to biomechanical problems with the available internal fixation methods. We studied the anatomy of the neck of the femur by roentgenograms and sectional specimens from 70 cadavers. In addition, various nail-plates were subjected to buckling tests and, by simultaneously attaching a strain-gauge, stress distribution was calculated. The results of these preliminary studies were then used to design a new nail-plate better than those available at present. Testing of this new nail-plate confirmed that it had a strength equal to that of the Holt nail-plate (the strongest of the available nail-plates).

Bone Nails↗
PubMed1976

Change in ATP-pyrophosphohydrolase activity during spherule formation of Physarum polycephalum.

The activity of Ca2+-dependent ATP pyrophosphohydrolase was found to fluctuate during spherule formation of the acellular slime mold Physarum polycephalum under starving incubation. The enzyme activity increased up to 16-fold at the 3rd day of the starvation, then decreased drastically to less than its original level. Column chromatography of the enzyme preparation suggested that the increase in the activity was due to de novo synthesis of a new isozyme. Cycloheximide inhibited the synthesis. The two isozymes were different in their Ca2+ sensitivity, the new one being less sensitive.

Adenosine Monophosphate↗
PubMed1975

A calcium ion-dependent atp pyrophosphohydrolase in Physarum polycephalum.

An activity of ATP Pyrophosphohydrolase (EC 3.6.1.8) was found in the soluble fraction of the plasmodium of Physarum polycephalum. The products of the enzyme reaction were inorganic pyrophosphate and 5'-AMP in equimolar quantities. The enzyme had a pronounced requirement for Ca2+ with high specificity. Mg-2+ was not an essential cofactor but stimulated the enzyme activity about 2.5-fold of the control. The enzyme hydrolyzed ITP, GTP and beta,gamma-methylene ATP at a limited rate. Among inhibitors tested, 3 mM caffeine reduced the activity to about 75% of the control. The enzyme had a broad pH optimum around pH=7.0 and the Km for ATP was 2.0 mM. An Arrhenius plot showed a break at about 18 degrees C and the calculated activation energies were 6.7 and 11.4 kcal/mol above and below the transition temperature, respectively. Disc electrophoresis in dodecyl sulfate and gel filtration on Sephadex -g-200 gave apparent molecular weights of 56 000 and 240 000, respectively, suggesting that the native enzyme was built up from 4 polypeptide chains. The possible role of the enzyme in vivo was discussed.

Adenosine Triphosphate↗
PubMed1975

The origin of the genetic code.

A new approach to the origin of the genetic code is proposed based on some regularities in the nucleotide distribution pattern of the code. The relative amounts of various amino acids in primitive proteins were possibly different from those in organisms living today. The primordial ratio was supposed to shift to the modern one guided by the action of primitive nucleotides. Each primitive tRNA had a discriminator site and, distinguished from it, an anticodon site. It also postulated that primordially each amino acid could correspond to a wide variety of codons. During the course of the evolutionary change, a selective mechanism worked among the protobionts so that less frequent nucleotides became associated with more abundant amino acids in the primordial conditions,thus finally leading to the present codon catalogue.

Amino Acids↗