Biomedical subjects
Publications and source records attributed to H Shimada.
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Recombinant plasmids which contain EcoRI fragments of tobacco chloroplast DNA carrying tRNA genes were constructed. Plasmids pTC211 and pTC293 contain the base sequences for tRNAAsn in their 1.4 and 1.1 Md EcoRI fragments, respectively. These two tRNA sequences are identical and are; 5'-TCCTCAGTAGCTCAGTGGTAGAGCGGTCGGCTGTTAACCGATTGGTCGTAGGTTCGAATCCTACTTGGGGAG-3'. Each tRNAAsn gene is located at about 0.9 kb apart from the distal end of each 5S rRNA gene and is coded for by the DNA strand opposite from that of the rRNA genes.
MCD was applied to ferric and ferrous low-spin complexes of cytochrome P-450 cam to elucidate the electronic states and the nature of the axial ligands of the heme in cytochrome P-450cam. (1) Low-spin complexes of ferric cytochrome P-450cam, produced either by ligation of external ligands such as pyridine and imidazole derivatives or by being freed of (-)-camphor, showed sinusoidal Soret and alpha-MCD bands. The magnitude ratio of the Soret vs. alpha-MCD bands was quite sensitive to the nature of axial ligands of the ferric low-spin complexes. The ratio (2.7) for the camphor-free form of cytochrome P-450cam, thus, was the smallest among those (2.7-9.0) for low-spin forms of cytochrome P-450cam and other corresponding low-spin hemoproteins (ratio 7.8-13.9). The ratio (4.2) for the alpha-picoline-bound form of cytochrome P-450cam, however, was the closest to that (2.7) for the camphor-free form of cytochrome P-450cam among those (4.2-9.0) for the external ligand-bound form of cytochrome P-450cam. The ratio for the 2-methylimidazole-bound form of cytochrome P-450cam was the smallest among those of cytochrome P-450cam bound with imidizole derivatives. Thus, among the nitrogen-bound low-spin forms, the low-spin form with a sterically hindered nitrogen ligand trans to the thiolate anion (-S-) most reproduced spectral characteristics of the native low-spin ferric form. Low-temperature absorption studies offered the same results. (2) It was found that MCD magnitudes of alpha-bands of ferrous low-spin complexes are intimately related to the electronic character of axial ligands. Thus, the CO, O2 and NO-bound forms of cytochrome P-450cam, which have two pi-type axial ligands, showed the smallest alpha-MCD bands ([theta]M = 5.2-7.5) among complexes, while ferrous cytochrome b5 and cytochrome c, which have two sigma-electron-donating axial ligands, showed the largest magnitude ([theta]M = 120-176). The data for the ferrous low-spin complexes of other hemoproteins so far available were well rationalized in consideration of the property of the axial ligands.
A simple specific and reproducible method for determination of plasminogen activator activity in rat ovaries has been developed by using the chromogenic substrate S-2251. The two steps of enzymatic reactions, i.e. activation of plasminogen and subsequent hydrolysis of the substrate was performed in one step incubation. A linear relationship was observed between the amount of chromogen produced and activator activity in the range of the optical density form 0.05 to 1.20 for 30 min's incubation. Endogenous activity of non-specific proteases, plasmin or plasmin inhibitors which might be contained in rat ovaries turned out not to interfere with the specificity of a standardized assay procedure. Reproducibility was firmly established with coefficient of variation not exceeding 10%. Using this method, a marked increase followed by a drastic decrease in the activator activity was shown with rat ovaries around the time of ovulation after the injection of human chorionic gonadotropin.
Infrared spectra for the carbon monoxide complex with myoglobin isolated as the oxygenyl species from bovine heart muscle were carefully examined in the C--O stretch region as either the pH or the temperature was varied. Deconvolutions of these spectra into bands of Gaussian shape suggest the presence of four bands near 1938(I), 1944(II), 1954(III), and 1965(IV) cm-1 with halfband widths of about 18, 9, 9, and 10 cm-1, respectively. The relative intensities of the four bands varied with changes in pH or temperature. 13C NMR spectra and other evidence indicate that the four C--O stretch bands arise from four discrete rapidly interconverting conformers: CI, CII, CIII, and CIV. Under conditions of physiological pH and temperature, the relative stabilities are CI approximately CII much greater than CIII approximately CIV. The delta H and delta S values for conformer interconversions are estimated to range from -8 to 34 kJ/mol and -27 to 87 J.mol-1 K-1, respectively; therefore the structures of the conformers may be expected to vary significantly. These findings provide evidence for a highly flexible, dynamic structure at the ligand-binding site of bovine myoglobin, even when ligands are bound.
The present study was undertaken in an attempt to clarify whether or not any relationship exists between the echocardiographic indices of cardiac function and the severity of progressive muscular dystrophy of the Duchenne type (PMD). A total of 75 patients with PMD was used for analysis. Among the echocardiographic parameters measured in the study, the maximal diastolic endocardial velocity (DEVM) and ejection fraction (EF) revealed a gradual decreasing tendency with increasing severity of the disorder. It can be concluded therefore that DEVM and EF may represent useful indices in the assessment of cardiac function in PMD.
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