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Biomedical subjects

M Okazaki

Publications and source records attributed to M Okazaki.

At least 559 records · Page 31Linked to original sources
PubMed1982

Carbonate apatites from aqueous and non-aqueous media studied by ESR, IR, and X-ray diffraction: effect of NH4+ ions on crystallographic parameters.

Carbonate-containing apatites prepared from aqueous and non-aqueous media were investigated by ESR, IR, and X-ray diffraction. A typical asymmetric signal at g = 2.0, which many workers have observed in irradiated calcified tissues, is interpreted in terms of CO3(3)- and Co-2 and the trapped electron center, The CO3(3)- and CO2- ions originated from the carbonate which substitutes for the phosphate ion in the apatite crystalline structure. From the comparison of the data between the carbonate apatites prepared under the presence of Na+ and NH4+ ions, it is suggested that NH4+ ions contribute to the crystallographic parameters, either by substituting in the structure or by suppressing the CO3 incorporation into the structure, or by both. The production of the CO2- radical ion could be accounted for based on the concept of hydrogen bond between the oxygen atom of CO2(3)- and the hydrogen atom of NH4+.

Apatites↗
PubMed1982

Estimation of solidification time during casting by use of a heat transfer model.

Time-dependent temperature profiles in dental casting molds were analyzed by an unsteady heat conduction model. The thermal conductivity and initial temperature of the mold greatly affected the heat transfer in the mold. The thermal conductivities of gypsum- and phosphate-bonded investments at high temperatures were accurately measured by means of the hot wire method. From the data obtained, the solidification times of Ag, Ag alloy, and Co-Cr alloy were calculated and compared with the experimental results.

Chemical Phenomena↗
PubMed1982

Electron spin resonance study of sound and carious enamel.

The present electron spin resonance (ESR) study aimed to investigate chemical alterations in enamel apatite associated with carious attacks. Enamel blocks were cut from sound areas and natural white spot lesions of human molar teeth and then X-irradiated at room temperature in air. Q-band ESR analysis of these samples showed the presence of two stable signals in the spectra recorded at room temperature. One of them has been identified at CO3-(3) centers, which originate from the carbonate ion substituting in the apatite lattice. The other signal is tentatively identified as O- defects in the hexad axis of apatite lattice. A comparison of the spectra between sound and carious samples demonstrated that the intensity ratios between the O- and the g parallel component of CO3-(3), R = O-/CO3-(3) (g parallel), are significantly higher in the carious samples than in the sound ones. This suggests that enamel apatite in the white spot lesions may have less carbonate ions in the crystal lattice, or have a higher producibility of the O- defects in its hexad axis. The observed alterations in enamel apatite may well be accounted for by remineralization playing a major role in the formation of white spot lesions, because this acid-dissolution study using irradiated enamel blocks showed that the R values do not increase but decrease in a simple process of demineralization.

Dental Caries↗
PubMed1982

[Microvascular architecture of human tumors transplanted in nude mice--its relationship to sensitivity to antineoplastic agents].

Microangiographic study was performed with ten human tumors serially transplanted into nude mice to clarify the role of tumor vessels on the chemosensitivity of the human tumors. Five gastric carcinomas, two colon carcinomas, one breast carcinoma, one cholangiocarcinoma, and one hemangiopericytoma were used for the experiments. Seven tumors revealed hypervascular network of vessels, whereas hypovascular patterns of tumor vessels were observed in the other three tumors. It was found that the histologically differentiated tumors were hypervascular and undifferentiated tumors were hypovascular, with statistically significant differences (p less than 0.05). Each tumor possessed the vascular network similar to human tumors originated from the same organs. No discernible changes of microangiographic features were noticed by serial transfers. As the chemosensitivities of these tumors depended mainly on their original tissues, these chemosensitivities could not be explained only by tumor vascularities or drug transferences. However, in the tumors with similar chemosensitive spectra, less susceptible tumors were observed to possess the irregular vascular networks in comparison with sensitive strains. From these considerations, tumor vessels were thought to have some role on vascular flow and drug transference which affected chemosensitivity of human tumors.

Animals↗
PubMed1981

High-performance aqueous gel permeation chromatography of serum lipoproteins: selective detection of cholesterol by enzymatic reaction.

A rapid method for the quantitation of cholesterol in each lipoprotein fraction has been developed which utilizes high-performance aqueous gel permeation chromatography followed by enzymatic reaction using reaction-type high-performance chromatography. Cholesterol in serum lipoproteins eluted from the column could be sensitively and selectively detected by the absorbance at 550 nm following the enzymatic reaction. The sensitivity of the detection for cholesterol measured by A550 was compared with that for protein measured by A280 using the standard lipoprotein fractions: low-density lipoprotein (LDL) and high-density lipoproteins (HDL2 and HDL3). The effects of changing the flow-rate and lengthening the column on the resolution of LDL and HDL were examined. Analyses of serum protein and cholesterol were performed with this method for human and animal subjects.

Animals↗
PubMed1981

Rapid method for the quantitation of cholesterol in human serum lipoproteins by high performance liquid chromatography.

A simple and rapid method for the quantitation of cholesterol in human serum lipoproteins (VLDL, LDL, HDL2, and HDL3) was developed (1). The content of cholesterol in each lipoprotein fraction was determined by means of a commercial enzymatic reaction kit after separation by high performance liquid chromatography with gel permeation columns. The quantitation of cholesterol could be performed with only 10-20 mu l of serum in less than 50 min by measuring A550 after passing the mixed eluate and enzyme solution through an on-line reactor system of a high-speed chemical derivatization liquid chromatograph. The precision, reproducibility and sensitivity of the quantitation of cholesterol with this method were acceptable, and the values of HDL-cholesterol determined by this method correlated well with those found by the heparin-manganese chloride precipitation method (r=0.958, n=93).

Cholesterol↗
PubMed1981

Fractionation of human serum lipoproteins by high performance liquid chromatography. I.

Immunologically pure lipoprotein fractions of human serum were subjected to high performance liquid chromatography (HPLC) on a combination system of aqueous gel permeation columns. Each lipoprotein fraction appeared at a distinct elution volume as a single homogeneous peak. Elution was carried out with 0.1 M Tris-HCl buffer solution, pH 7.4, or 0.15 M NaCl solution and no significant differences in elution volume and elution pattern were found. The lipoprotein mixtures (total lipoprotein fraction d less than 1.210) of healthy and pathological subjects were subjected to HPLC and showed characteristic elution patterns which could be of diagnostic significance.

Cholesterol↗
PubMed1981

The laser-Raman spectroscopic studies on human enamel and precipitated carbonate-containing apatites.

Laser-Raman spectra of synthetic apatites containing from zero to 12.4 wt% carbonate ions and enamel apatite are reported. Special attention is paid to the correlation between the intensities of the carbonate, phosphate, and hydroxyl modes and the carbonate content in the apatites. The data presented here indicate that most of the CO2-3 incorporated in the apatite lattice substitutes for PO3-4 and suggest that a small amount of CO2-3 might be located in the OH- position.

Apatites↗
PubMed1981

Solubility and crystallinity in relation to fluoride content of fluoridated hydroxyapatites.

Fluoridated hydroxyapatites were synthesized at 80 degrees C (pH 7.4) to study their crystallinity and solubility in relation to fluoride content. The crystallinity of fluoridated hydroxyapatities increased initially, then decreased, and finally increased again with the degree of fluoridation, whereas the decrease in relative solubility of fluoridated hydroxyapatites at 25 degrees C (pH 4.0) was proportional to the logarithm of the fluoride content.

Crystallography↗
PubMed1981

High-voltage electron microscopy of radiation damages in octacalcium phosphate.

The present high-voltage electron microscopic study showed two types of radiation damages in OCP. The first type commenced with the formation of voids, which later grew and coalesced along the c-axis. The second type was characterized by the appearance of paired and concentric strain fields and the subsequent formation of dislocations. The origin of the strain fields is attributed tentatively to a precipitation of a second phase in the crystal.

Calcium Phosphates↗
PubMed1981

Organic-bound chromium in enamel, dentin, and bone studied by electron spin resonance.

The present ESR investigation shows clearly that chromium is potentially present in the calcified tissues. With the use of the hydrazine-deproteinated procedure, it is suggested that chromium is associated with the organic constituent of the calcified tissues. The fact that the unheated tissues disclosed no chromium signal indicates either that the potentially present chromium is not paramagnetic, or that it is still paramagnetic, but the chromium signal cannot be detected because of a short relaxation time due to strong interaction with the organic materials.

Animals↗
PubMed1981

Dissolution rate behavior of fluoridated apatite pellets.

The dissolution rate of synthetic fluoridated apatite pellets with various fluoride content was measured in acetate buffer solution at pH 4.0. The dissolution rate decreased with degree of fluoridation. The rate decreased greatly at low fluoride levels. The experimental data were analyzed by means of a diffusion-controlled model and compared with the solubility data. This model showed that the initial dissolution rate is greatly affected by both the solubility and the overall mass transfer resistance. Overall mass transfer resistance is affected by fluoride content.

Apatites↗
PubMed1981

[Effect of oxythiamine and pyrithiamine on thiamine levels in the blood, liver and urine of rats (author's transl)].

Thiamine (T) deficient state and various functional and morphological changes in rat liver were induced, after several days, with T antagonists, oxythiamine (OT) or pyrithiamine (PT), and a thiamine deficient diet (TDD). The relationship between the extent of liver damage and T levels in blood, liver and urine were studied in OT treated rats fed a TDD (OTD group). PT treated rats fed a TDD (PTD group), OT treated rats (OT group), PT treated rats (PT group) and rats fed a TDD (TDD group). The T levels in blood and liver of OT group, PT group, OTD group, PTD group and TDD group were 89% and 91%, 76% and 88%, 25% and 14%, 33% and 16%, 24% and 15% compared with the data in the control group, respectively. Effects of OT or PT on T levels were not remarkable in some cases, and such may be due to the duration time of T antagonists, which was considered to be 3-15 hours in PT treated rats, and 0-18 hours in PT treated rats, as assessed by urinary T measurements. Treatment of T antagonist twice daily is recommended to obtain a definite T deficient state. Our results suggest that the extent of liver damage is related to the T levels in tissue.

Animals↗