Biomedical subjects

F Watanabe

Publications and source records attributed to F Watanabe.

At least 271 records · Page 15Linked to original sources

PubMed1983

Thermodynamics and kinetics of co-operative protein-nucleic acid binding. I. General aspects of analysis of data.

The process under consideration is the binding of a ligand to a linear polymer of equivalent subunits such that each bound molecule of ligand occupies n subunits. Interactions between bound ligand molecules are also considered. Some useful points regarding the evaluation of raw data without recourse to any specific binding mechanism are discussed first. For a treatment in terms of appropriate thermodynamic parameters a simple model is examined in greater detail. It assumes that interactions are limited to those between ligands bound to nearest-neighbour positions on the polymer. Exact expressions for some basic binding properties of this model at equilibrium are developed. The relations can be considerably simplified in the case of pronounced positive co-operativity which is frequently encountered in practice. Appropriate plots of the data to test the model and to evaluate its parameters are proposed. A simple but consistent kinetic scheme is also introduced. It allows calculation of relaxation times as they can be measured by means of special techniques.

Biopolymers↗

PubMed1983

Thermodynamics and kinetics of co-operative protein-nucleic acid binding. II. Studies on the binding between protamine and calf thymus DNA.

Unspecific binding of a protamine, namely fluorescein-labelled clupeine Z, to double-stranded calf thymus DNA was studied using fluorescence titration methods and chemical relaxation techniques. Both equilibrium and kinetic data have been analysed using general theoretical approaches discussed in the accompanying paper. The results agree well with the predictions made on the basis of a standard co-operative binding model. Basic parameters evaluated are the co-operative binding constant (K), the coefficient measuring co-operative interaction between nearest neighbours (q), the number of nucleotides occupied by one protamine molecule (n) and the rate constant of dissociation at the ends of bound ligand sequences (kD). Values obtained at 20 degrees C, pH 7.5 and 0.4 M-NaCl were K = 5.8 X 10(7) M-1, q = 1700, n = 20 and kD = 0.29 s-1. They have been found to be sensitive to the concentration of added salt (NaCl). This effect apparently reflects the essentially electrostatic nature of the binding process. The results can be satisfactorily described in terms of competitive binding of sodium ions.

Animals↗

PubMed1983

Decreased serum 19-nor-deoxycorticosterone (21-hydroxy-19-nor-4-pregnene-3, 20-dione) level in adrenal regeneration hypertensive rats.

An enzyme immunoassay of 19-nor-deoxycorticosterone in rat serum was established. The normal value of 19-nor-DOC in rat serum obtained from 9:00 am to 10:00 am was 148 +/- 30 ng/dl (mean +/- SE,n = 10). Serum levels of this steroid decreased in rats with adrenal regeneration hypertension during the course of the experiment up to 8 weeks, while systolic blood pressure rose progressively. We concluded that this mineralocorticoid is not involved at least as a circulating hormone in the pathogenesis of adrenal regeneration hypertension in rats.

Adrenal Glands↗

PubMed1983

Mutagenic activities of gentisin and isogentisin from Gentianae radix (Gentianaceae).

The mutagenic activities of 2 hydroxyxanthones, gentisin and isogentisin, obtained from the methanol extract of Gentianae radix (Gentianaceae) were investigated. The methanol extract of Gentianae radix, which showed mutagenicity in the Ames test in Salmonella typhimurium strain TA100 with S9 mix, was fractionated by column chromatography on Sephadex LH-20, and the fractions were purified by preparative TLC and column chromatography on polyamide. 2 mutagenic materials thus obtained, S1 and S2, each gave a single band on TLC. Identification of S1 and S2 was accomplished by comparing the analytical (mps, elementary analyses) and spectral (UV, IR, mass, NMR) results for S1 and S2 with literature data for gentisin and isogentisin. At doses below 10 micrograms, S1 (gentisin) and S2 (isogentisin) had similar specific mutagenic activities. At doses of over 10 to 50 micrograms, the mutagenic activities of S2 and S1 were 19.1 and 6.94 revertants per microgram respectively. This much lower activity of S1 than S2 may be a result of its poor solubility owing to the presence of the OMe group at C-3. The combined yield of S1 and S2 was about 76 mg (40 mg as S1 and 36 mg as S2), which accounted for 76% of the content of mutagenic compounds (100 mg) estimated roughly from the total mutagenic activity in the extract of the starting materials (100 g).

Animals↗

PubMed1983

Decrease in mitochondrial levels of adenine nucleotides and concomitant mitochondrial dysfunction in ischemic rat liver.

The process of mitochondrial dysfunction in ischemic rat liver was studied. A close correlation was found between decrease in the mitochondrial adenine nucleotide content and deterioration of oxidative phosphorylation capacity. The level of total adenine nucleotides, which was 15--20 nmol/mg protein in mitochondria isolated from normal liver, fell to 1--2 nmol/mg protein with concomitant loss of oxidative phosphorylation capacity after anoxic incubation in vitro or in vivo for 120 min. However, neither the permeability barrier to adenine nucleotides nor matrix enzymes were affected under these conditions. The loss of adenine nucleotides was ascribed to degradation of AMP to adenosine and then leakage of the latter. Conventional procedures for maintenance of oxidative phosphorylation capacity of isolated mitochondria, preservation in the cold and addition of ATP or a respiratory substrate under aerobic conditions, were very effective in maintaining the intramitochondrial levels of adenine nucleotides. Of the three species of adenine nucleotides, only AMP was ineffective in maintaining mitochondrial function; mitochondria containing more than 5 nmol of ATP plus ADP/mg protein exhibited normal activity of oxidative phosphorylation, but with less than 2 nmol they showed no activity.

Adenine Nucleotides↗

PubMed1983