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Biomedical subjects

A Wada

Publications and source records attributed to A Wada.

At least 469 records · Page 26Linked to original sources
PubMed1983

Denaturant-gradient chromatography for the study of protein denaturation: principle and procedure.

The particle volume of a protein which represents the expansion of the molecular chain is a useful probe to measure its conformation change in solution. To study the details of the conformation transition, we will report a novel device to trace the particle-volume change against increasing denaturant concentration. According to the denaturant gradient in the eluant of high-performance gel-permeation chromatography, information concerning the elution volume of proteins in the course of denaturation can be successively accessed. When a protein is injected into a denaturant solution, its effective molecular volume increases by the unfolding of a native compact structure, and the elution peak goes forward to separate from that of the native protein. Typical elution patterns were computer-simulated in an extended algorithm of the plate theory. The kinetic feature of denaturation and the effect of the denaturant gradient are discussed. The denaturation schemes of lysozyme, cytochrome c, and phosphoglycerate kinase were studied.

Chromatography, Gel↗
PubMed1983

Theoretical and experimental studies on zone-interference chromatography as a new method for determining macromolecular kinetic constants.

Zone-interference chromatography is a new method for studying macromolecular interactions (S. Endo and A. Wada, Anal. Biochem. 124 (1982) 372). This method is a new style of affinity chromatography which requires no preparation of affinity-column materials but utilizes the velocity difference in a column between interacting molecular species. Using the stochastic theory on the behavior of solute molecules, both the association and the dissociation rate constants can be analytically obtained from the degree of deformation of elution patterns, i.e., the change of the first and second moments. In order to verify the present theory, computer simulation of elution profiles by the extended plate theory and a binding experiment between glutamate dehydrogenase and ADP have been carried out.

Adenosine Diphosphate↗
PubMed1983

Magnesium ion induced proton release as a probe for the polyelectrolytic structure of ribosomal RNAs and subunits.

E coli ribosomes and rRNA's released 20 to 50 protons upon jump of magnesium ion concentration from 1 mM to 20 mM. The Mg2+-induced proton release was measured separately for 16S rRNA, 23S rRNA, 30S subunit, and 50S subunit by a new spectrophotometric method that had a much better sensitivity than the pH-stat method. The proton release from the subunits and rRNA's were similar in the number of protons, the pH dependence that had a minimum at neutral pH, and the upward concaveness of the Scatchard plot. From these results, the main source of protons in ribosomal subunits was assigned to nucleotide bases of rRNA's that showed a downward pKa shift upon Mg2+-ion binding. The subunits and rRNA's, however, differed in the proton release. 16S rRNA released protons somewhat more effectively than 23S rRNA, while 30S subunit released protons 2 to 5 times more effectively than 50S subunit. The marked difference between the two subunits suggest that ionizable bases in 16S and 23S rRNA's are covered and their pKa values are shifted by ribosomal proteins to different extents. The association of 30S and 50S subunits induced little proton release, showing that few ionizable groups with pKa near neutral pH are involved in the association. E. coli tRNA and poly U also showed Mg2+-induced proton release. The amounts of protons released from rRNA's, tRNA, and poly U were roughly proportional to the amount of bases not hydrogen bonded. The Mg2+-induced proton release from the natural and synthetic RNA's can be explained by the electrostatic field effect of polyphosphate backbones on bases not hydrogen bonded, as proposed in a previous paper. It also reflects the conformational structure of each RNA molecule.

Escherichia coli↗
PubMed1983

Trifluoperazine inhibits 45Ca2+ uptake and catecholamine secretion and synthesis in adrenal medullary cells.

In isolated adrenal medullary cells, carbamylcholine and high K+ cause the calcium-dependent secretion of catecholamines with a simultaneous increase in the synthesis of 14C-catecholamines from [14C]tyrosine. In these cells, trifluoperazine, a selective antagonist of calmodulin, inhibited both the secretion and synthesis of catecholamines. The stimulatory effect of carbamylcholine was inhibited to a greater extent than that of high K+. The inhibitory effect of trifluoperazine on carbamylcholine-evoked secretion of catecholamines was not overcome by an increase in either carbamylcholine or calcium concentration, showing that inhibition by trifluoperazine occurs by a mechanism distinct from competitive antagonism at the cholinergic receptor and from direct inactivation of calcium channels. Doses of trifluoperazine that inhibited catecholamine secretion and synthesis also inhibited the uptake of radioactive calcium by the cells. These results suggest that trifluoperazine inhibits the secretion and synthesis of catecholamines mainly due to its inhibition of calcium uptake. Trifluoperazine seems to inhibit calcium uptake by uncoupling the linkage between calcium uptake by uncoupling the linkage between cholinergic receptor stimulation and calcium channel activation.

Adrenal Medulla↗
PubMed1983

An algorithm for the bonding-probability map of nucleic acid secondary structure.

We report a more efficient and well-defined algorithm for predicting a secondary structure of single-stranded nucleic acid from a primary nucleotide sequence. Using this algorithm, one- and two-dimensional bonding-probability maps of 5S rRNA of thermus thermophilus HB8 were calculated. These maps well express the stability of the secondary structure.

Chemical Phenomena↗
PubMed1982

alpha 2-Adrenergic receptors inhibit catecholamine secretion from bovine adrenal medulla.

Catecholamine secretion evoked by carbamylcholine from isolated bovine adrenal medullary cells was inhibited by alpha 2-agonist, clonidine, in a dose-dependent manner with IC50 value of 2.8 X 10(-5) M. [3H]Clonidine bound to adrenal medullary membranes with high affinity and saturable characteristics. These results suggest that alpha 2-adrenergic receptors which exist on adrenal medullary cells have inhibitory effect on the secretion of catecholamine from the cells.

Adrenal Medulla↗
PubMed1982

Salt-concentration dependence of thermal denaturation of restriction fragment DNAs from phi X174.

High-resolution differential melting curves of phi X174 Y1 and Y2 restriction fragment DNAs, for which the base sequences were known, were measured at various sodium ion concentrations ranging from 195 to 2.3 mM. The curves were resolved into component peaks, and the change in the melting temperature, the change in the area, and the change in the breadth of each peak with change in salt concentration were examined. The locations of the melting regions corresponding to the peaks in the melting curves were assigned based on theoretical calculations of melting curves and stability maps. It was found that as the salt concentration was decreased from the high to the intermediate range, the breadths of the peaks on the low-temperature side decreased whereas those on the high-temperature side remained almost constant, and also the separation between the peaks along the temperature axis increased. Changes in the positions of peaks relative to one another were interpreted in terms of the difference in the free energy increase between a loop state and an end-coil state as the salt concentration decreased.

Bacteriophage phi X 174↗
PubMed1982

Two cases of viral myocarditis and one case of viral pericarditis.

Two cases of myocarditis, who had suffered from ventricular extrasystole, leucocytosis and elevated serum enzyme for a long period died from congestive heart failure and/or arrhythmias. The biopsy specimens from the right ventricle in one of them showed a positive reaction against Coxsackie B virus (1, 3, 4 and 5) in the fluorescent antibody method. One case of virus pericarditis had 5 recurrences over a five-year period. He suffered from dyspnea, chest oppression and general fatigue at each recurrence. Cardiomegaly on a chest X-ray, electrocardiographic abnormalities, leucocytosis and elevated serum enzyme appeared. However, serum neutralizing antibody titers against Coxsackie B2 had not risen significantly except during the first attack. Interferon administration inhibited its recurrence successfully.

Adult↗
PubMed1982

Correlation between thermal stability maps and genetic maps of double-stranded DNAs.

The positional correlation of boundaries of cooperatively melting regions with boundaries of genes and with cleavage sites of restriction enzymes are statistically examined for phiX174, G4, fd, SV40, BKV, and polyoma DNAs. A statistically significant correlation does exist in the case of gene boundaries, but none is detected for cleavage sites.

Base Composition↗
PubMed1981

Quasielastic light scattering study of solutions of synthetic myosin filaments.

Autocorrelation functions of the intensity fluctuations of light quasielastically scattered from solutions of synthetic myosin filaments were measured by means of single photon counting. The angular distribution of the total scattering intensity was measured simultaneously, and a supplementary investigation of depolarized light scattering was also performed. The light scattering data were analyzed based on the length distributions of synthetic filaments observed under an electron microscope. The results showed that synthetic filaments in a solution behave essentially as rods. The hydrodynamic frictional coefficient of synthetic filaments, however, was shown to be about twice as high as would be expected if the filaments took a "concept' conformation. This strongly suggests the existence of certain projections which are widely spread from the filament backbone in a solution. The molecular weight of the synthetic filament was calculated using the observed values of the translational diffusion coefficient and the sedimentation coefficient. The number of myosin molecules per 14.3 nm repeat was shown to be six or greater, which suggests that synthetic filaments lack an effective width-limiting mechanism which is presumed in the native thick filament. Additions of Ca2+, Mg2+ and ATP, alone or in combination, have been shown to cause no notable changes in the light scattering profile of synthetic filaments.

Adenosine Triphosphate↗