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Biomedical subjects

K Imai

Publications and source records attributed to K Imai.

At least 1,531 records · Page 85Linked to original sources
PubMed1978

Role of Bohr group salt bridges in cooperativity in hemoglobin.

Possible problems in measuring the first Adair constant, K1, from accurate oxygen equilibrium curves have been investigated. Of these only the presence of small amounts of CO-hemoglobin or hemoglobin dimers had a significant effect. The former can be eliminated by treatment with oxygen, the latter by measuring the concentration-dependence of K1 or working at high protein concentrations. K1 values have been measured for normal hemoglobin at pH 7 and 9, hemoglobin specifically reacted with cyanate at Val 1alpha (alphac2beta2) and des(His 146beta) hemoglobin at pH 7. K1 is equal to KT, the oxygen affinity of the T state of hemoglobin, for all these hemoglobins and was increased in all of them when compared to normal hemoglobin at pH 7. This shows that the breakage of the Bohr group salt bridges by increasing pH or specific modification changes KT. Hence the Bohr group salt bridges break on ligation of the T state and are partially responsible for the free energy of cooperativity.

Allosteric Regulation↗
PubMed1978

Liquid chromatographic determination of urinary dopamine and norepinephrine as fluorescamine derivatives.

Dopamine (DM) and norepinephrine (NE) with 3,4-dihydroxybenzylamine as internal standard in normal human urine were extracted with alumina, labeled with fluorescamine and determined fluorometrically by liquid chromatography. The method is simple and in the case of excretion of DM in urines of subjects receiving 1-dopa, even the alumina treatment was unnecessary. The C.V. of method was 4.3% and 4.5% for DM and NE, respectively. The mean contents of DM and NE in 7 normal urines were 182 and 35.5 ng/mg creatinine, respectively.

Buffers↗
PubMed1978

On the validity of the spectrophotometric determination of oxygen saturation of hemoglobin. The wavelength dependence of observed oxygen equilibrium parameter values.

Spectral changes of oxyhemoglobin induced by such anions as 2,3-diphosphoglycerate, inositol hexaphosphate, and Cl- may affect the validity of the spectrophotometric determination of oxygen saturation of hemoglobin. Therefore, the anion-induced difference spectra were extensively measured under a variety of conditions and accurate oxygen equilibrium curves were determined under representative conditions with detection at different wavelengths selected from peaks, troughs, and zero difference points of the difference spectra in the visible and Soret regions. Oxygen equilibrium parameters including the four Adair constants (i.e., equilibrium constants for four steps of oxygenation) estimated from the equilibrium curves did not show any dependence on wavelength within the limits of experimental error. These results indicate that anion-induced spectral changes do not invalidate the spectrophotometric determination of oxygen saturation and confirm the validity of the previous conclusions drawn in our series of studies on the effects of anions, pH and temperature on oxygen equilibrium parameters.

Diphosphoglyceric Acids↗
PubMed1978

Testosterone-induced focal myocarditis in rats. I. Morphological and biochemical studies with special reference to pathogenetical mechanism and species differences.

Focal myocarditis characterized by interstitial edema, round cell infiltration and fibrosis occurred in rats given a subcutaneous administration of testosterone propionate in a dose of 50 mg/kg for 30 consecutive days or longer. Biochemical analysis showed a two to five time increase of deoxycorticosterone and a moderate decrease of corticosterone in blood plasma of these rats as well as in those treated with 50 mg/kg of testosterone propionate for 15 days. It was also shown that myocarditis did not occur in adrenalectomized rats after administration of testosterone propionate 50 mg/kg for 30 days, while subcutaneous injections of deoxycorticosterone acetate in a dose of 15 mg/kg for 30 days invariably produced cardiac lesions in both adrenalectomized rats and sham-operated rats. Regarding species difference, administration of testosterone did not produced either a high blood level of deoxycorticosterone or focal myocarditis in guinea pigs or rabbits. From these results, it is concluded that focal myocarditis in rats after administration of large amounts of testosterone propionate is related to the elevation of deoxycorticosterone in blood plasma but not to the direct effects of testosterone propionate on the myocardium.

Adrenalectomy↗
PubMed1978

Testosterone-indued focal myocarditis in rats. II. Morphological and biochemical observations of the adrenal in relation to the pathogenetical mechanism of cardiac lesions.

Correlative morphological and biochemical studies were made on the adrenal of rats treated with daily subcutaneous injections of testosterone propionate in a dose of 50 mg/kg for 30 consecutive days. Histologically, there is a thinning of the zona fasciculata with a decrease of cell numbers, swelling of the cell body and the occurrence of large lipid droplets in the cytoplasm. Electron microscopic examination revealed swelling of mitochondria with reduction of cristae and hypertrophy of smooth-surfaced endoplasmic reticulum with cluster formation or whirl-like arrangement. In in vitro biochemical experiments, it was noted that conversion of deoxycorticosterone to corticosterone or 18-hydroxydeoxy-corticosterone was decreased to 45% of the control level in the testosterone-treated group.

Adrenal Cortex↗
PubMed1978

Cell contact to metal surface.

In order to observe cell contact with various metals, the pulp cells of human origin were grown on vacuum evaporated metal film in such tissue culture mediums as Medium 199 supplemented with 10% calf serum. Medium 199 (serum free), Hanks' balanced salt solution (serum free) and calcium and magnesium ions free balanced salt solution (serum free). Secondary electron images of the cells were observed. The following findings were recorded. 1) Differences of metal did not give any discernible effects in cell morphology, except cytotoxic metals which gave severe deteriorating effects to the cells. 2) Lack of serum appeared to give unfavourable effects to cell growth, but no decisive, positive evidences for cell contact were obtained. 3) The effect of calcium and magnesium ions on cell contact was not substantiated. Importance of accumulation of informations on cell to material contact was stressed in order to develop various biomaterials compatible to the cells. Further approaches to understand the phenomena in the subject were discussed.

Calcium↗
PubMed1978

Continuous-flow determination of bile acids in serum, and its clinical application.

We describe a highly sensitive and accurate automated continuous-flow method for determining bile acids in serum. The bile acids are first liberated from serum protein by dialysis at alkaline pH and then measured fluorometrically after the following enzymic reaction. Bile acids are converted to 3-oxo bile acids with 3alpha-hydroxysteroid dehydrogenase (EC 1.1.1.50) with concomitant reduction of NAD+ to NADH. The hydrogen in the generated NADH is transferred by diaphorase (EC 1.6.4.3) to resazurin to yield resorfin, the fluorophore. Only 100 microliter of serum is required and 40 determinations can be done per hour. The CV for 20 replicate determinations in serum with a mean bile acid concentration of 9.8 mumol/liter was 2.6%. The CV for day-to-day variation for another serum on 27 successive days was 3.0% (mean concentration, 10.0 mumol/liter). We applied this method to 826 sera from various diseases; 29% exceeded the upper limit of normal, 10 mumol/liter, and abnormally high values (greater than 20 mumol/liter) were almost exclusively limited to sera from hepatobiliary and enteric disorders.

3-Hydroxysteroid Dehydrogenases↗
PubMed1977

High-performance liquid chromatographic assay of rat-brain dopamine and norepinephrine.

A high-performance liquid chromatographic method for the assay of dopamine (DM) and norepinephrine (NE) in rat brain has been developed. 3,4-Dihydroxybenzylamine was added to the sample as an internal standard. The isolated amines and the internal standard were subjected to reaction with fluorescamine, separated liquid chromatographically on a glycol-type gel and determined fluorimetrically. The standard deviation of the method was +/-2.7% for DM and +/-5.3% for NE. The contents of DM and NE in rat brain, with or without administration of a tyrosine hydroxylase inhibitor, as measured by the proposed method were always lower than those obtained by the trihydroxyindole method.

Animals↗
PubMed1977

The hemoglobin-oxygen equilibrium associated with subunit dissociation.

The effect of oxygen-linked tetramer-dimer dissociation on oxygen equilibrium of hemoglobin was investigated by measuring the equilibrium curves over a wide range of protein concentration. A Hill scheme which takes the subunit dissociation into account describes well the overall concentration dependences of the oxygen pressure and slope of the Hill plot at half saturation. Values of dissociation constant for oxyhemoglobin estimated from the equilibrium data agree with the vaues measured by other methods for phosphate-free and diphosphoglycerate-added hemoglobin. The present results indicate that oxygen equilibrium properties are only slightly influenced bysubunit dissociation in the concentration range above 60 muM (as heme) at which most equilibrium experiments have been carried out.

Diphosphoglyceric Acids↗