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Biomedical subjects

H Ohshima

Publications and source records attributed to H Ohshima.

At least 343 records · Page 19Linked to original sources
PubMed1980

A hexokinase from fish liver with wide specificity for nucleotides as phosphoryl donor.

The liver of rainbow trout contains two hexokinases (ATP:D-hexose 6-phosphotransferase, EC 2.7.1.1) designated C and D from the elution pattern in DEAE-cellulose column chromatography. Hexokinase D has been purified about 50-fold from the liver of rainbow trout by chromatography with DEAE-cellulose and Sephadex G-200, and by isoelectric focusing. The properties of hexokinase D were similar to those of mammalian hexokinase III with respect to the Km values for ATP and glucose and the substrate inhibition by glucose at high concentration. However, the enzyme showed a wide specificity for nucleotides as the phosphoryl donor. Although it has been reported that the only effective nucleotide as the phosphoryl donor for hexokinase from various origin in ATP, and that ADP, a reaction product, inhibits the enzyme, hexokinase D from the rainbow-trout liver was found to be able to form glucose 6-phosphate (Glc-6-P) from glucose and various nucleotides such as ATP, ADP, CTP, GTP, UTP and UDP. The reaction products from ADP and glucose, Glc-6-P and AMP, were identified by chromatography on ion-exchange resin column and paper. The enzyme D was not inhibited by ADP but was strongly inhibited by AMP, which is a reaction product from ADP.

Animals↗
PubMed1980

Occurrence, formation and precursors of N-nitroso compounds in the Japanese diet.

A survey has been made of volatile nitrosamines in 123 fermented foods. These included salt-fermented vegetables, soy sauce, "miso", Japanese "sake" and other fermentation products. No appreciable amount, or only trace quantities, of NDMA and NPYR were detected in vinegar, "sake", wines and whiskies, while minute quantities of NDMA were detected in 31 out of 33 beer samples, where the levels ranged from traces to 13.8 micrograms/l, with an average of 5.1 micrograms/l. The nitrosamine content of salt-dried fish apparently increased when these products were broiled in a city gas range. A method for the determination of N-alkylureas in foods has been developed. A total of 57 food samples, both uncooked and broiled in a gas range or fried, were analysed. No alkylureas could be detected in these samples.

Animals↗
PubMed1979

Gas chromatographic separation of hydroxylated N-nitrosamines.

Derivatives of six hydroxylated N-nitrosamines were prepared by acylation, trifluoroacylation, trimethylsilylation and methylation, and the volatilities and sensitivities of these derivatives on gas chromatographic detection were compared. All six nitrosamines were successfully derivatized by either acylation or trimethylsilylation. The acylated derivatives were easy to prepare; in addition, acylation was more specific than trimethylsilylation for the reaction with hydroxyl groups in the molecule.

Acylation↗
PubMed1978

Mechanism of N-nitrosodimethylamine formation from trimethylamine and trimethylaminoxide.

The kinetics of nitrosation of trimethylamine (TMA) and trimethylaminoxide (TMAO) to give N-nitrosodimethylamine (NDMA) have been studied. The nitrosation rates of TMA and TMAO, when determined at 100 degrees C in sealed tubes, showed maximum values at about pH 3, while at temperatures lower than 75 degrees C the pH dependence of the nitrosation of these compounds was similar to that observed with alkylamides. The initial rate of NDMA formation from TMAO determined at pH 3.0 and 25 degrees C was found to be proportional to the TMAO and nitrite concentrations, not to the square of the nitrite concentration. In contrast, the rates of NDMA formation from TMA and TMAO when reacted at pH 3.0 and 100 degrees C in sealed tubes were found to be proportional to the square and the cube, respectively, of the nitrite concentration. These results strongly suggest that the NDMA formation at higher temperatures involves the oxidative cleavage of tertiary amines to produce secondary amines (dimethylamine, DMA) which may react with nitrite to form NDMA. On the other hand, at lower temperatures, NDMA may be formed from TMA or TMAO by a pathway not involving DMA.

Chemical Phenomena↗
PubMed1978

Occurrence of methylguanidine and agmatine in foods.

Methylguanidine (MG), a precursor of carcinogenic methylnitrosocyanamide and methylnitrosourea, has long been considered to occur widely in fresh beef and various fish muscles in fairly high concentrations. Agmatine (AG) has been reported to be easily nitrosated to give a potent mutagen under acidic conditions. A survey has been conducted on the MG and AG contents of various fresh and processed foods. The present study reveals that no appreciable amount, or only trace amounts, of MG could be detected in fresh beef, pork, chicken and various fish and shellfish. In addition, almost the same low levels of MG were detected in various processed foods, except in the case of smoked-dried fish products, where the MG values ranged from 18 to 178 mg/kg. Relatively high concentrations of AG, ranging from 40 to 200 mg/kg, could be detected in fresh abalone and top-shell muscles, while fairly high concentrations of AG could be detected in some processed foods. A dried squid product, in particular, was found to contain as high as 650 mg/kg of AG.

Agmatine↗
PubMed1977

Gas chromatographic determination of methylguanidine, guanidine and agmatine as their hexafluoroacetyletonates.

Seven derivatives of each of methylguanidine, guanidine and agmatine have been prepared, and the specificity and volatility of their gas chromatographic detection have been studied. The hexafluoroacetylacetonates have been found to be the most specific for the three guanidines, and are highly sensitive to alkali flame ionization and electron-capture detections. These derivatives are also fairly resistant to hydrolysis occurring in the derivatization process.

Agmatine↗
PubMedDate not supplied

Cultured epithelial autografting on meshed skin graft scars: evaluation of skin elasticity.

Many patients with meshed skin graft scars complain of the scars' unsightly appearance and hardness. Since 1989 we have shaved away meshed skin graft scars and then resurfaced the area with autologous cultured epithelium in nine patients. This method improved the disfigurement of meshed skin graft scars, with minimal sacrifice of normal donor skin. Furthermore, autologous cultured epithelium grafted areas had high skin elasticity compared with meshed skin graft scars, as measured with a noninvasive suction device.

Adolescent↗
PubMedDate not supplied

Clinical significance of "cannibalism" in urinary cytology of bladder cancer.

OBJECTIVE: To investigate the cytologic characteristics and clinical significance of "cannibalism" (cytophagocytosis), a characteristic histologic finding associated with malignancy, found in urinary cytology samples during the diagnosis of bladder cancer. STUDY DESIGN: The subjects were 252 patients with bladder cancer initially treated from 1981 to 1991. For their pretreatment urine samples, membrane filtration was performed to determine the presence and amount of cannibalism, a tumor cell within a tumor cell. The urinary cytologic findings were then correlated with the histologic findings of primary bladder cancer. RESULTS: Only cells from urinary cytology-positive specimens demonstrated cannibalism. The positive rate of cannibalism was significantly higher in grade 3 (25%) than grade 1 (0%) or 2 (8%) superficial papillary cancer (P < .01) and also higher in muscle-invading bladder cancer (57%) than grade 3 superficial papillary cancer (P < .01). The rate did not differ significantly between muscle-invading cancer and superficial nonpapillary cancer (44%). In 198 patients with superficial bladder cancer, progression was observed in 19 (10%) during a mean follow-up of 72 months. All of them showed positive urinary cytology results in pretreatment samples, and among the patients with positive urinary cytology, the progression rate was significantly higher when cannibalism was present than when it was absent (38% vs. 17%, P < .05). Moreover, in high grade cases, cannibalism had significant predictive value for progression. By multivariate analysis, cannibalism was an independent factor for prediction of progression, as were tumor grade and stage. CONCLUSION: Cannibalism in urinary cytology appears to be an indicator of both the anaplastic grade and invasiveness of transitional cell carcinoma of the bladder. Furthermore, cannibalism may provide a reliable predictor of progression of superficial bladder cancer.

Biopsy↗
PubMedDate not supplied

Transfer of protons from bulk solution to the surface of poly(L-lactide) microcapsules.

Excessive proton transfer from bulk solution to the surface of poly(L-lactide) microcapsules was observed. In acidic solutions of pH less than 3.0, the zeta potential of the microcapsules became slightly positive, although poly(L-lactide) has only carbonyl groups and alcoholic hydroxyl groups which can be charged. In an NMR study, the signal of the water protons shifted towards a higher applied field with increasing interaction of water with the poly(L-lactide) microcapsule surface when the microcapsules were dispersed at low concentrations (up to 4 x 10(-3) per cent). In solutions of pH 3.2-7.6, the observed values of the zeta potential were in good accordance with theoretical values calculated assuming that the charged groups distribute uniformly in the microcapsule wall. In this pH range, the average density of charged groups in the wall was estimated to be 0.04 M. The average volume occupied by one polymer unit (one poly(L-lactide) molecule) in the microcapsule membrane was estimated to be (35 A)3, suggesting a rather tight polymer network in the poly(L-lactide) microcapsule membrane.

Drug Compounding↗
PubMedDate not supplied

Mechanism of hydrolytic degradation of poly(L-lactide) microcapsules: effects of pH, ionic strength and buffer concentration.

The hydrolytic degradation rate of poly(L-lactide) molecules constituting the microcapsule membrane was estimated at different pH, ionic strength and buffer concentration. Poly(L-lactide) microcapsules were observed to be hydrolytically degraded rapidly in a strongly alkaline solution to lactic acid as the final product. The degradation was accelerated when the poly(L-lactide) microcapsules were immersed in solutions of high ionic strength. The effect of pH and ionic strength of the bulk solution is interpreted in terms of the electric potential distribution in the membrane. It is suggested that the concentration of OH- in the membrane has an important role in the hydrolysis of poly(L-lactide) microcapsules, when the microcapsules are dispersed in solutions where the zeta potential of the microcapsules is negative. On the other hand, when the zeta potential is positive, the concentration of H+ in the membrane has a predominant effect on the degradation. The degradation was also found to be affected by the salt concentration in buffered solutions, suggesting that the cleavage reaction of the polymer ester bonds is accelerated by conversion of the acidic degradation products into neutral salts.

Buffers↗
PubMedDate not supplied

Electrophoretic study of the degradation properties of poly(L-lactide) microcapsules.

The degree of degradation of poly(L-lactide) microcapsules was measured as a function of the time elapsed in solutions of different pH values. To determine how the distribution of poly(L-lactide) molecules in the microcapsule membrane changes during degradation, poly(L-lactide) microcapsules, at various stages of the degradation process in various solutions, were sampled and redispersed in pH 7.6 buffer solutions of different ionic strengths and their zeta potentials determined. In the early stages of the process, the zeta potential became more negative as time elapsed. Analysis of the ionic strength dependence of the surface potential on the basis of a simple model shows that hydrolytic scission of ester bonds in the polymer chains takes place preferentially at the microcapsule membrane surface creating negative charges localized at the membrane/solution interface. In the later stages of the degradation process, the zeta potential again became less negative. This suggests that liberation of degraded segments takes place in the later stages.

Capsules↗
PubMedDate not supplied

Electrostatic interaction of microcapsules with guinea-pig polymorphonuclear leucocytes.

Electrostatic interaction of microcapsules with guinea-pig polymorphonuclear leucocytes was investigated at different ionic strengths of the medium through measurements of the degree of phagocytosis by the cells of microcapsules. At any ionic strength, the interaction exhibited a maximum when the surface potential of microcapsules was equal to that of the leucocytes to make phagocytosis of microcapsules by the cells minimum. The experimental findings were analyzed by a novel model for the electrostatic interaction between ion-penetrable membranes. In this analysis, it was assumed that the leucocytes have an area (or areas) which permits cations to partition much more into the membrane than anions on their surface to reduce the electric potential of the area.

Animals↗
PubMedDate not supplied

Potential distribution across a plasma protein-coated poly(L-lactide) microcapsule surface.

A model is presented for the potential distribution across a protein-coated microcapsule membrane. The adsorbed protein layer is assumed to be divided into three sub-layers. The outer sub-layer is rich in positive fixed charges and the medium sub-layer in negative fixed charges, while the inner sub-layer may be either charged or uncharged. Also, the microcapsule membrane is negatively charged. The ionic partition coefficients into the inner sub-layer are less than unity, while those into the other sub-layers are unity. This model explains well the accelerated degradation of poly(L-lactide) microcapsules with an adsorbed protein layer onto their surface (Makino et al., 1987 c).

Blood Proteins↗
PubMedDate not supplied

Interaction of poly(L-lysine-alt-terephthalic acid) microcapsules with fibrinogen.

Interaction of poly(L-lysine-alt-terephthalic acid) microcapsules with fibrinogen was investigated by measuring the degree of microcapsule disintegration, fibrinogen adsorption to microcapsules, and the zeta potential of microcapsules as a function of fibrinogen concentration in phosphate buffer solutions of pH 7.4 at different ionic strengths. A minimum concentration was found to exist for fibrinogen to cause disintegration of the microcapsules at any ionic strength, and at this fibrinogen concentration the fibrinogen adsorption levelled off and the zeta potential exhibited an abrupt change. Increases in the ionic strength of the medium and the surface hydrophobicity of microcapsules produced an increase in the degree of microcapsule disintegration by fibrinogen. These findings were interpreted as showing that the interaction of the microcapsules with the protein is not of an ionic nature but of a hydrophobic nature.

Capsules↗
PubMedDate not supplied

Freezing behaviour of microencapsulated water.

The freezing behaviour of water in polyurea microcapsules was studied through DSC (differential scanning calorimetry) and ESR (electron spin resonance) measurements under a non-equilibrium condition to show that supercooling of water becomes more noticeable with decreasing droplet size of the liquid. Thermodynamics of small systems was found applicable to analyse the experimental findings, even though the process of water freezing in the microcapsules was not of an equilibrium nature.

Calorimetry, Differential Scanning↗