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Biomedical subjects

M Okazaki

Publications and source records attributed to M Okazaki.

At least 19 recordsLinked to original sources
PubMed1979

Analysis of paramagnetic centers in X-ray-irradiated enamel, bone, and carbonate-containing hydroxyapatite by electron spin resonance spectroscopy.

Carbonate-containing hydroxyapatite, enamel, and bone were irradiated by an X-ray and investigated between 77 degrees and 350 degrees K by means of electron spin resonance (ESR) spectroscopy. The ESR spectrum of enamel irradiated at 77 degrees K in vacuum and observed at the same temperature was almost the same as that of the carbonate-containing hydroxyapatite. The temperature dependence of signal intensities confirms a spin-energy exchange between the mineral and organic constituents in bone, but in enamel no or very little spin-energy exchange between the mineral and organic constituents. Considerable similarity among the ESR spectra of enamel, bone, and carbonate-containing apatite was obtained after X-ray irradiation in air at 300 degrees K with both an X-band and a Q-band ESR spectrometer. The Q-band spectrum can be interpreted in terms of two paramagnetic species. One is identified as a CO3(3-) anion radical which has an axial symmetry with g factors of 2.0029 and 1.9972. The other species is found to be centered at g = 2.0019.

Animals↗
PubMed1979

[Oxygen contents and casting porosities in Ag alloys (author's transl)].

Although pure Ag has a large casting porosity near the sprue attachment, Ag-Zn and Ag-Cu alloys have small or no porosities. The casting porosities of Ag-Au alloys are similar to that of pure Ag. These experimental results were discussed using the calculated oxygen contents in molten state and the measured oxygen contents of castings, and related to the capacity for deoxidization of additive elements. In the present study the casting porosities in pure Ag and Ag-Au alloys are considered to be not shrinkage porosities, but porosities due to discharged oxygen gas. In spite of high oxygen contents of molten state and castings, the casting porosity was not observed in pure Cu. This may be due to the fact that the occluded oxygen atoms exist as copper oxide (Cu2O) in solid Cu.

Dental Alloys↗
PubMed1979

[Effects of oxythiamine and pyrithiamine on rat liver. --Biochemical and morphological changes in the thiamine deficient rat (author's transl)].

We studied biochemical changes in the rat liver in a thiamine (T) deficient state as induced by oxythiamine (OT), pyrithiamine (PT) and thiamine deficient diet (TDD) and simultaneously observed morphological changes under light and electron microscope. Severe loss of weight was observed in the OT treated rats fed on TDD (OTD) and such was frequently accompanied by a complete loss of righting reflex. Biochemical changes commonly found in T deficient groups were decrease in serum total protein, alkaline phosphatase activity and liver lipids, and increase in serum total cholesterol and transaminase activity. Microscopically, most of the liver cells were atrophied and necrosis was observed in the OTD group. Electron microscopically, ultrastructural changes revealed active Kupffer cells, microvilli and Golgi apparatus, and decrease in rough endoplasmic reticulum (rER) associated with increasing detached ribosomes and smooth ER. Abnormal nucleus and mitochondria were found in the OTD group. These results suggest that a T deficiency occurs readily and easily within a short time when a T antagonist, particularly OT, is used together with the TDD, while a much longer time is required to produce a T deficiency with only the TDD.

Animals↗
PubMed1978

Kinetics of enzymatic hydrolysis of cellulose: analytical description of a mechanistic model.

A generalized mechanistic model for the enzymatic hydrolysis of cellulose is developed and expressed mathematically. The model is based on Michaelis--Menten-type kinetics for concurrent random and endwise attack of the substrate involving end-product inhibitions and three types of enzymes: an endo-beta-1,4-glucanase, an exo-beta-1,4-glucanase, and beta-glucosidase. Basic parameters of the model which can explain synergistic and other effects observed experimentally are quantified and discussed. It is shown that cellulose degradation kinetics are expected to be strongly affected by the ratio of endo- to exocellulases in the reaction mixture as indicated by previous experimental data, and the substrate degree of polymerization, a factor not fully appreciated in previous studies, which appear to be overridingly important in many practical cases.

Cellulase↗
PubMed1978

[Effect of oxythiamine and pyrithiamine on rat brain--morphological changes in the thiamine deficient rat brain (author's transl)].

We observed under light and electron microscopes morphological changes in the brains of rats in a thiamine deficient state as induced by an oxythiamine, pyrithiamine and thiamine deficient diet (OT, PT and TDD). We simultaneously determined thiamine levels in the whole brain of rats. The rats were separated into six groups-normal control, OT or PT treated rats (OT or PT group), OT or PT treated rats fed a TDD (OTD or PTD group), rats fed a TDD (TDD group)-. Microscopically, there were symmetrically distributed lesions containing spongy reticulation mainly in the vestibular nucleus. Electron microscopically, we found more advanced lesions in the OTD and PTD groups than in the TDD group. These ultrastructural changes were seen in the vicinity of capillaries and such consisted of abnormal endothelial cells and pericytes, excrescence of microglias, swelling or vacuolation of astrocytes, nerve cells containing distorted organelle and myelin degeneration, besides extracellular edema. The thiamine level in the TDD group decreased to 56% that of control. No effect of OT on the thiamine level was observed either in case of ingestion of a regular diet or when TDD was given. On the other hand, the thiamine level decreased to 43% in the PT group and to 17-23 in PTD. These results suggest that encephalopathy caused by the OT or PT-induced thiamine deficiency has the same selective vulnerable site as does the TDD-induced deficiency, however cellular sensitivity may differ slightly with the various ultrastructural changes.

Animals↗
PubMed1977

Assimilation of liquid hydrocarbon by microorganisms. I. Mechanism of hydrocarbon uptake.

The uptake mechanism of liquid hydrocarbons of low solubility in water was investigated, using microorganisms with different affinities for liquid hydrocarbon. Microorganisms which could utilize hydrocarbon were much more adherent to hydrocarbon than those which could not. The adhesive force between Candida intermedia IFO 0761 and hydrocarbon was higher than that of Candida tropicalis ATCC 20336, though both could utilize hydrocarbon; The total hydrocarbon uptake from the drop and accommodation forms of hydrocarbons was much higher than that from dissolved hydrocarbon. The uptake rate of drop-form hydrocarbon was nearly equal to that of accommodation-form hydrocarbon for C. intermedia, but was lower for C. tropicalis which shows lower adhesion to hydrocarbon.

Adsorption↗
PubMed1977

Assimilation of liquid hydrocarbon by microorganisms. II. Growth kinetics.

The growth kinetics of a microorganism with high affinity for liquid hydrocarbon which has a low solubility in water was investigated for Candida intermedia IFO 0761 in our previous work. The microorganism contained a hydrocarbon pool in and/or on the cell. The transfer of water-soluble substrates to the cell was not the rate-limiting step in the growth of C. intermedia accompanied by clump formation with liquid hydrocarbon. The operating conditions necessary for the oxygen supply for the growth were adequate for the growth of C. intermedia on n-tetradecane. The saturation kinetics was valid for the specific growth rate of C. intermedia and specific concentration of hydrocarbon per unit cell mass; the specific growth rate was expressed by the following equation: (formula: see text).

Antifoaming Agents↗