Search PubMed⌕ Search

Biomedical subjects

M Okamura

Publications and source records attributed to M Okamura.

At least 145 records · Page 8Linked to original sources
PubMed1981

Spectral evidence for a rapidly formed structural intermediate in the refolding kinetics of hen egg-white lysozyme.

For investigation of the conformation of the unfolded species and its role in the refolding kinetics, refolding kinetic measurements were made on hen egg-white lysozyme by using the stopped-flow method at 25 degrees C in the four sets of initial and final folding condition: (1) 4 M guanidinium chloride (GdmCl) and 0.5 M GdmCl; (2) 40% acetic acid (HOAc) and 5% HOAc; (3) 4 M GdmCl and 0.5 M GdmCl-5% HOAc; (4) 40% HOAc and 0.5 M GdmCl-5% HOAc. The kinetic results as measured by absorbance at three wavelengths, 301, 292, 250 nm, agreed with each other and indicated strict biphasic behavior without exception. The kinetic parameters were determined only by the final refolding conditions. The spectral properties of the unfolded species at the end of stopped-flow mixing were investigated by comparing the total kinetic amplitude with the difference between the static absorbance of the native molecule in the final refolding conditions and that of the unfolded molecule in the initial unfolding conditions. The solvent effect was considered in the comparison. It was concluded that the unfolded species assumed a new transient conformation in the mixing process and that the transformation was completed within the mixing time.

Egg White↗
PubMed1981

A specific method for determination of total ascorbic acids in urine by the alpha,alpha'- dipyridyl method.

Application ot the alpha,alpha'- dipyridyl method for determination of ascorbic acid in urine is described. The urine sample was acidified with trichloracetic acid and shaken with activated carbon to remove interfering substances. The acid filtrate was first neutralized (pH 7.0) by adding Na2HPO4. The dehydroascorbic acid was then reduced back to ascorbic acid by incubation with dithiothreitol. After removal of the excess dithiothreitol with N-ethylmaleimide, ascorbic acid was determined by measuring the reduction of ferric ion. The ferrous ion produced was coupled to alpha,alpha'-dipyridyl in the presence of H3PO4. Ferrous ion in urine samples, which theoretically interferes with the method, was removed by a combination of Na2HPO4 and H3PO4.

2,2'-Dipyridyl↗
PubMed1981

Significance of C-reactive protein elevation in the pretreatment stage of systemic lupus erythematosus.

The significance of C-reactive protein (CRP) elevation in patients with systemic lupus erythematosus (SLE) in the pretreatment stage was assessed with reference to other laboratory data obtained simultaneously. Sixteen of 31 cases were CRP-positive, and the CR-positive group contained significantly more cases with urinary cellular casts and with a high anti-DNA antibody titer, compared with the CRP-negative group. We suggest that CRP in patients with SLE, as measured at the time of the first consultation, reflects the severity of the disease. This includes those cases complicated by nephropathy.

Adolescent↗
PubMed1980

An improved method for determination of L-ascorbic acid and L-dehydroascorbic acid in blood plasma.

Various conditions for reducing L-dehydroascorbic acid were studied, using dithiothreitol. This led to an improved method for the separate determination of L-ascorbic acid and L-dehydroascorbic acid in blood plasma. The content of ascorbic acid was determined by an alpha,alpha'-dipyridyl method (A). Dehydroascorbic acid was reduced to ascorbic acid by incubation with dithiothreitol at room temperature for 10 min at pH 6.5 to 8.0. After removing the excess dithiothreitol with N-ethylmaleimide, total ascorbic acids, i.e. reduced plus original, were determined by the alpha,alpha'-dipyridyl method (B). The amount of dehydroascorbic acid could then be calculated from these results (B minus A).

2,2'-Dipyridyl↗
PubMed1979

Uptake of L-ascorbic acid and L-dehydroascorbic acid by human erythrocytes and HeLa cells.

Uptake of AsA and DAsA by human cells, i.e., erythrocytes and HeLa cells, was examined in vitro. AsA was taken up very slowly, but DAsA was taken up very rapidly by erythrocytes to establish equilibrium after 1 minute. Uptake of the vitamins by HeLa cells was similar to that by erythrocytes, except there was an uptake of DAsA that reached saturation after 5 minutes. The DAsA taken up was reduced in part to AsA and the concentrations of DAsA inside and outside the cells became almost equal. GSH was responsible for this reduction. Although DAsA was evidently a more permeant form than AsA in the case of human cells, the relevance of this to the uptake of vitamin C by the tissues in vivo remains uncertain.

Ascorbic Acid↗