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Biomedical subjects

M Tsuboi

Publications and source records attributed to M Tsuboi.

At least 217 records · Page 12Linked to original sources
PubMed1982

Hydrogen exchange kinetics of nucleic acids. Double and triple helices with Hoogsteen-type basepairs.

The kinetics of hydrogen-tritium exchange reaction have been followed by a Sephadex technique of a double-helical poly(ribo-2-methylthio-adenylic acid) . poly(ribouridylic acid) complex with the Hoogsteen-type basepair. Only one hydrogen in every 2-methylthio-adenine . uracil basepair has been found to exchange at a measurably slow rate, 0.023 s-1 (at 0 degrees C), which is, however, much greater than that for a double-helix with the Watson-Crick type A . U pair. The kinetics of hydrogen-tritium exchange were also examined by triple-helical poly(rU) . poly(rA) . poly(rU) which involves both the Watson-Crick and Hoogsteen basepairings. Here, three hydrogens in every U . A. U base triplet have been found to exchange at a relatively slow rate, 0.0116 s-1 (at 0 degrees C). The kinetics of hydrogen-deuterium exchange reactions of these polynucleotide helices have also been followed by a stopped-flow ultraviolet absorption spectrophotometry at various temperatures. On the basis of these experimental results, the mechanism of the hydrogen exchange reactions in these helical polynucleotides was discussed. In the triple helix, the rate-determining process of the slow exchange of the three (one uracil-imide and two adenine-amino) hydrogens is considered to be the opening of the Watson-Crick part of the U. A. U triplet. This opening is considered to take place only after the opening of the Hoogsteen part of the triplet.

Base Composition↗
PubMed1982

Kinetics of binding reactions of an antibody molecule with haptens on a membrane surface.

Direct measurement has been made of the reaction rate of binding of a bivalent antibody and fluorescent haptens, which were covalently bound on a model membrane surface, by a method of stopped-flow fluorometry. The result was interpreted as indicating that the reaction takes place in two steps: (i) binding of a hapten with one of the two antigen-combining sites of an antibody molecule, and (ii) binding of another hapten with the other site of the antibody molecule in question. The rate of the second step was found to depend on the fluidity of the membrane.

Antigen-Antibody Reactions↗
PubMed1982

Lifetime of tyrosine fluorescence in nucleosome core particles.

The fluorescence intensity and fluorescence lifetime of the tyrosine residues in calf thymus nucleosome core particles have been determined as functions of the ionic strength of the solvent. For interpreting the results, in the first approximation, the 30 tyrosine residues involved in the particle are classified into two groups. About 12 belong to class I; they are distributed in the protein core with an average distance of 2.0 nm from its center. In the intact particle (in 20 mM to 0.4 M salt solution), a Förster-type energy transfer is considered to take place from these class-I tyrosine residues to the DNA bases, but this no longer occurs on elevating the salt concentration to about 1.4 m. The remaining tyrosine residues (about 18, called class II) are considered to be involved in hydrogen bonds or in some other intramolecular interactions in the intact core particles, so that their fluorescence is completely quenched. On elevating the salt concentration to 2.0 M, this quenching is partially removed. Implications of these dynamic and static quenching are discussed in terms of the structure of the core particle.

Animals↗
PubMed1982

Micro-environment of the H3-H3 contact region of a nucleosome core particle, as revealed by a lifetime measurement of a fluorescent probe.

A sample of fluorescently-labeled nucleosome core particles was prepared by combining N-(3-pyrene)-maleimide to each of the two cysteine residues of the two H3 histones in the chicken erythrocyte nucleosome core particle, by a method previously reported by Zama et al. (Nucl. Acids Res. 5, 3881 (1978)). The fluorescence spectra and fluorescence lifetime of the sample in solvents with various Na+ concentrations have been examined. Three different types of micro-environment of the fluorescent probe have been found: (i) emits a pyrene dimer fluorescence at 460 nm, (ii) emits a pyrene monomer fluorescence with a long (75-65 ns) lifetime, and (iii) emits a pyrene monomer fluorescence with a short (5-15 ns) lifetime. The manner of dislocation of the two H3 subunits from each other in each of the solutions with different salt concentrations was discussed.

Animals↗
PubMed1982

A study of esterase--its application to biotransformation of midecamycin derivatives.

Esterases of intestinal mucosa and liver from human and rat were used to study the biotransformation of midecamycin derivatives. In the in vitro experiment with rat esterases, the 4"-acyl derivatives were more easily hydrolyzed than the 9-acyl derivatives. Among the 9-acyl esters, the highest hydrolytic activity was observed with butyrate. In the in vivo experiment, when the rats were administered with the derivatives of 4"-depropionylmidecamycin (M1) orally, comparatively more 9-acyl metabolites were excreted in the urine, but the amount of the 4"-acyl metabolites was very small. In the in vitro experiment with human esterases, the 9-acyl esters were hydrolyzed more easily than the 4"-acyl esters. Among the 9-acyl esters of M1, the highest hydrolytic activity was observed with butyrate. When the 9-acyl esters were administered to humans, the n-butyl ester was hydrolyzed faster than the acetyl ester. When the 9,4"-diacetyl ester was administered to humans, comparatively more 4"-acyl metabolites were excreted in the urine. These results suggest that the experiment with the use of these esterases is useful to estimate the biotransformation of midecamycin derivatives.

Animals↗
PubMed1982

[Laboratory and clinical studies of cefmetazole in serious infection by Staphylococcus (author's transl)].

Cefmetazole (CMZ) is an antibiotic agent belonging to the cephamycin group, which is resistant to beta-lactamase and has a broad antibacterial spectrum covering from Gram-negative to -positive organisms. Although this agent has been proved to have an antibacterial activity against Staphylococcus spp., it has not been used for treatment of the infections caused by the organism. Thus, 62 strains of S. aureus isolated clinically were compared for their sensitivity to CMZ, cefoxitin (CFX), cefuroxime (CXM), cefazolin (CEZ), and ampicillin (ABPC). In addition, 5 children suffering from septicemia due to S. aureus were treated with CMZ 158 mg/kg at a mean daily dose for a mean period of 14 days. The dose was used after dividing into 3 and 4 equal parts in 1 and 4 children, respectively. One old patient with septicemia was given 2,000 mg of CMZ twice daily for 4 days and once daily for subsequent 3 days. Another child with bacterial meningitis was treated with 50 mg/kg of CMZ 4 times daily for 63 days. The drug was given intravenous injection by one-shot or drip infusion in all cases under observation of clinical effects, bacteriological effects and side effects. The MIC of CMZ against S. aureus at inoculum sizes of 10(6) and 10(8) cells/ml was 1.56 mcg/ml in 72.6 and 56.5% of the strains, respectively. When 5 drugs were compared on the basis of the MIC to which the largest number of strains were sensitive, CEZ was most active, and CMZ was ranked in the next place and similar to CXM in activity. However, when the whole range of the MIC was considered, CMZ was more excellent than CXM, its MIC was lower than those of CEZ, CFX and ABPC in a greater number of strains. It was considered from the results that the serum level of CMZ was effective against 100 and 93.5% of strains at an inoculum size of 10(6) cells/ml and against 100 and 83.9% of strains at an inoculum size of 10(8) cells/ml until 4 and 6 hours after a one-shot intravenous injection of 50 mg/kg of Moni-trol I standard, respectively in the children. Thus, CMZ is expected to manifest a sufficient effect on septicemia caused by S. aureus in children who receive a one-shot intravenous injection of 50 mg/kg of it 4 times daily. Treatment with CMZ was clinically evaluated to be excellent in 3, good in 3 and poor in none of 6 patients with septicemia due to S. aureus, and fair in the 1 with Staphylococcal meningitis. The bacteriological result was excellent, since the causal organisms were eradicated in all cases. With regard to side effects, abnormal eosinophilia was found in 2 cases, but it was no ascribable to this drug in 1 of them. GOT showed an abnormal rise in 1 case and both GOT and GPT in 1, although they were considered not to be related to this drug in either case. It is considered from these results that CMZ is a valuable drug in treatment of septicemia due to S. aureus.

Aged↗
PubMed1981

Fourier transform infrared absorption studies on the sulfhydryl groups in heavy meromyosin.

Infrared absorptions of heavy meromyosin solutions were studied in the frequency range of 2600 cm-1 to 1800 cm-1 with a Fourier transform infrared spectrophotometer. An absorption band characteristic of the stretching vibration of sulfhydryl groups was found at about 2565 cm-1. By comparison with the infrared absorption spectrum of a cysteine solution, the absorption band of sulfhydryl groups in heavy meromyosin showed that the absorption intensity is much stronger, the absorption peak shifts to a lower wavenumber and the width of the absorption band is much broadened. These results indicate that the sulfhydryl groups in heavy meromyosin are strongly hydrogen-bound. The additions of ATP and ADP increased the absorption intensity of the absorption band, suggesting the that hydrogen-bonded structure involving the sulfhydryl groups becomes more strengthened on the binding of ATP and ADP. This indicates that myosin heads change conformation around the sulfhydryl groups during ATP hydrolysis.

Adenosine Diphosphate↗
PubMed1981

Sporulation of products of protoplast fusion without regeneration in Saccharomyces cerevisiae.

In Saccharomyces cerevisiae, diploid strains which are respiratory deficient (e.g., rho-) or are homozygous for the mating-type locus (i.e., either a/a or alpha/alpha) are unable to sporulate. In order to induce sporulation in these nonsporulating strains, the technique of protoplast fusion mediated by polyethylene glycol was adopted. In this study, the products of protoplast fusion were induced to sporulate without reversion to normal cells. Protoplasts from a respiratory-deficient diploid strain were mixed with those from a respiratory-competent haploid one carrying mitochondrial drug resistance markers, treated with 30% polyethylene glycol-4000 and 25 mM CaCl2, and incubated in 0.1 M potassium acetate containing 0.8 M sorbitol as an osmotic stabilizer. After two days' incubation, asci with three to eight spores were formed at a frequency of 1 x 10(-3) to 2 x 10(-4). Sporulation was also observed in products of fusion between an a/a diploid and alpha haploid strains and between an alpha/alpha diploid and a haploid strains. The analysis of the genotypes of spores revealed that when fusion products were cultured under conditions for sporulation, karyogamy did not take place, diploid nuclei underwent meiosis, and both diploid and haploid nuclei were able to develop into spores.

Cell Division↗
PubMed1981

Evaluation of the drug-induced morphological differentiation of rat glioma cells (C-6) from the aspects of S-100 protein level and con A binding pattern.

The intracellular content of the nervous system specific protein S-100 began to increase with 4 days latency following the morphological differentiation of cultured rat glioma cells (C-6) with 1 mM dibutyryl cyclic AMP (dbcAMP), rising to approximately 10-fold over the control level at 15 days after the treatment. The concanavalin A (Con A) binding pattern on the external cell surface of C-6 cells exposed to dbcAMP appeared as a smooth layer of 40-60 nm thickness whereas that of control cells was irregularly thick and patchy. The correlation between morphological and biochemical changes of C-6 cells after dbcAMP treatment is discussed in relation to the mechanism controlling the differentiation of glioma cells.

Animals↗