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Biomedical subjects

M Sakamoto

Publications and source records attributed to M Sakamoto.

At least 829 records · Page 46Linked to original sources
PubMed1980

Light-scattering studies of cation-stimulated filament assembly of newborn rat epidermal keratin.

Effects of CaCl2 on in vitro polymerization of keratin extracted from cornified cells of newborn rat were investigated by means of light-scattering and supramolecular structures. Elongation and parallel assembly of filaments occurred with addition of CaCl2 to dialyzed keratin solutions and was detected by an increase in light-scattering intensity. Nonfibrous aggregates which occurred in higher buffer concentrations and in lower pH were also recorded as intensity increased. MgCl2, ZnCl2, and GdCl3 demonstrated similar effects, but NaCl and KCl showed no effect.

Animals↗
PubMed1980

Low frequency dielectric relaxation and light scattering under AC electric field of DNA solutions.

Low frequency dielectric relaxation of aqueous DNA was measured in a frequency range from 0.1 Hz to 30 kHz. Agreement was found between dielectric relaxation time and rotational one estimated from reduced viscosity for dilute solutions of DNA. The low frequency relaxation is thus ascribed to rotation of the major axis of DNA chains elongated by electrostatic repulsion between charges on the chain. A quasi-permanent dipole moment of DNA estimated from the dielectric increment is well explained by the fluctuation of dissociation of DNA. The above conclusion was confirmed for DNA samples of various molecular weights and for solutions in water ethanol mixtures. Effects of binding of salts and dyes are also interpreted in terms of the same mechanism. Light scattering of aqueous DNA under a.c. electric field supports the above conclusion.

Animals↗
PubMed1980

Thermostability of chromatin and variations in chromosomal proteins isolated under different ionic conditions.

Chromatin was prepared from calf thymus by three different methods differing in the ionic composition of the solutions used. The contents of histones and nonhistones per DNA unit were dependent on the preparative method utilized. Variations in protein content were analyzed by SDS-polyacrylamide gel electrophoresis. Although the amount of all histones varied with the isolation method, the abundance of H1 histone in chromatin was the most sensitive to the presence of magnesium ions during the isolation procedure. The variation in protein content effects the thermal denaturation profiles of chromatin. The amount of low-temperature melting chromatin is most sensitive to the preparation method used. Additionally, a very high-temperature denaturation step, designated delta, is detected for chromatin prepared in the absence of magnesium.

Animals↗
PubMed1980

Cytotaxin production by comedonal bacteria (Propionibacterium acnes, Propionibacterium granulosum and Staphylococcus epidermidis).

The potential role of different species of comedonal bacteria as chemotactic stimuli in the inflammatory phase of acne vulgaris was investigated by comparing 12 strains of Staphylococcus epidermidis, 11 strains of Propionibacterium acnes, and 5 strains of P. granulosum for production of cytotaxin in vitro. Results indicated that not only were there marked differences in cytotaxin production between different strains of the same species grown under identical growth conditons, but there were often significant differences in cytotaxin activity of the same strain grown in different media. This finding is discussed in relation to development of inflammation in quiescent comedones in acne vulgaris.

Acne Vulgaris↗
PubMed1980

Effects of trace elements in polymerization of keratin proteins and destruction of the filaments by processing techniques for electron microscopy.

Keratin extracted from keratinized cells of newborn rats polymerizes into filaments in vitro and this polymerization has been shown to be greatly stimulated by addition of divalent cations. In this study we investigated the optimum conditions for filament formation by use of CaCl2, ZnCl2, and GdCl3, a trivalent lanthanide. It was found that a concentration about 10 times higher was required for elongation and formation of wider filaments with CaCl2 when compared with that for ZnCl2, GdCl3 caused enhanced polymerization with an even lower concentration. Effects of fixation(s) and other processing techniques used for routine electron microscopy on the polymerized keratin filaments were also examined by electron microscopy and SDS polyacrylamide gel electrophoresis. Degradation of keratin protein was detected in various steps involved in handling of the keratin filaments. These results indicate that ultrastructural studies of keratin in epidermal cells in situ may be improved by re-evaluation of presently used experimental procedures.

Animals↗
PubMed1980

PS-6 and PS-7, new beta-lactam antibiotics. In vitro and in vivo evaluation.

Biological properties of two new beta-lactam antibiotics, PS-6 and PS-7, containing the carbapenem nucleus were studied. The in vitro activities of PS-6 and PS-7 were tested against clinical isolates of Gram-positive and Gram-negative bacteria in comparison with those of cefazolin, ampicillin and PS-5. In general, the antibacterial spectra of PS-6 and PS-7 were similar to that of PS-5. PS-7 was slightly less active than PS-5 and ABPC against Staphylococcus aureus. Clinical isolates of Gram-negative bacteria were found to be 2- to 8-fold more resistant to PS-6 than to PS-5, while PS-7 was 2-fold more active than PS-5 against Enterobacter, Klebsiella, Proteus, Serratia and Escherichia coli. The therapeutic effect of PS-6 seemed slightly less than that of PS-5 in an experimental infection with Staph. aureus Smith in mice.

Ampicillin↗
PubMed1980

Chemical modification of deltamycins. I. 4''-O-acyl analogs of deltamycins.

Using 4''-O-deacyldeltamycin as a starting material, various 4''-O-acyl derivatives were chemically synthesized by the following scheme: 2'-O-acetylation leads to 4''-O-acylation leads to 2'-O-deacetylation. 4''-O-Deacyldeltamycin is produced during the fermentation of deltamycin producing organisms or can be prepared by the biological deacylation of the deltamycins. 4''-O-Phenylacetyl-4''-O-deacyldeltamycin (PAD) showed good activity against various bacteria and mycoplasma. Among para-substituted PAD derivatives, NPAD (p-nitrophenylacetyl-) and SPAD (p-methylsulfonylphenylacetyl-) showed increased potency as compared to PAD against certain bacteria. The PAD was evaluated by in vivo experiments for plasma levels in mice and dogs and curative activity on the infected mice with Staphylococcus aureus Smith by subcutaneous or oral administration.

Administration, Oral↗
PubMed1980

PS-5 inhibition of a beta-lactamase from Proteus vulgaris.

Inhibition of Proteus vulgaris beta-lactamase by a new beta-lactam antibiotic, PS-5 was studied kinetically. There were two stages of inhibition. In the early stage, PS-5 inhibited the beta-lactamase by formation of a Michaelis-complex, and showed a competitive inhibition pattern with Ki-value of 0.22 microM (substrate, cephaloridine). After the formation of a Michaelis-complex between PS-5 and the enzyme, PS-5 showed a characteristic progressive inhibition pattern with time. Maximum inactivation was obtained after several minutes of preincubation of the enzyme with PS-5; as hydrolysis of PS-5 progressed, the enzyme activity was gradually recovered. Reactivation by an excess of substrate (cephaloridine) was not substantially realized in the presence of PS-5. PS-5 was very slowly hydrolyzed by the enzyme, showing a triphasic pattern in its reaction curve.

Anti-Bacterial Agents↗
PubMed1979

The occurrence of calicivirus in infants with acute gastroenteritis.

Calicivirus was detected in 8 (1.2%) of 647 hospitalized patients during a survey of acute gastroenteritis in infants and young children, conducted between December 1974 and September 1977. Morphologically calicivirus was approximately 30 nm in diameter with an easily recognizable staining "star of David" configuration. Its buoyant density in cesium chloride was 1.38-1.40 gm/ml. The serologic response to calicivirus by immune electron microscopy (IEM) was demonstrated only in paired sera from patients who shed the virus in their stools. The results suggest that calicivirus might be a cause of acute gastroenteritis in infants and young children.

Acute Disease↗