Biological characterization of human brain natriuretic peptide (BNP) and rat BNP: species-specific actions of BNP

We examined the diuretic-natriuretic activities of rat BNP and human BNP in anesthetized rats in vivo and their vasorelaxant activities for rat thoracic aorta and porcine coronary artery in vitro. Rat BNP was almost equipotent to rat ANP in diuresis and natriuresis with relative potencies of 1.6 and 2.5, respectively, while human BNP exerted no significant activity. Rat ANP, rat BNP and human BNP relaxed PGF2 alpha-contracted rat aortic strips with IC50 values of 0.62, 0.64 and 12.1 nM, respectively, while they relaxed PGF2 alpha-contracted porcine coronary arteries with IC50 values of 0.04, 1.10 and 0.02 nM, respectively. These results strongly suggest that the biological action of BNP is species-specific.     

Effects of angiotensin I-converting enzyme inhibitor, SQ 14225, in nomal men.

Effects of an orally active angiotensin I-converting enzyme inhibitor, SQ 14225, on the actions of angiotensin I (AI) infused intravenously for 120 to 390 min were studied in 5 normal men. When 20 ng/kg/min of AI infusion was started immediately after a single oral administration of 100 mg of SQ 14225, a significant rise in blood pressure (BP) was observed for the first 15 min, but BP began to fall from 17 min and returned to the pretreatment level at 45 min. This BP level continued at least to 120 min and in one subject to 180 min. In this subject BP began to rise again from 185 min and reached the level of 15 min at 390 min. Plasma AI level increased gradually from 45 min. At 15 min plasma renin activity (PRA) decreased and plasma aldosterone (PA) increased, but then PRA began to increase and PA began to decrease. At 120 min the values of PRA and PA were similar to the pretreatment values. In one subject plasma AI and PRA began to decrease and PA began to increase after 120 or 180 min. On the other hand, in the 5 men sole AI infusion caused a continued BP rise, PRA decrease and PA increase, and sole SQ 14225 administration caused increases in plasma AI and PRA and a decrease in PA but no BP change. From these results it was concluded that complete blockade and partial inhibition of AI conversion by 100 mg of oral SQ 14225 lasted for about 2.5 and 6.5 hr, respectively and that BP rise, PRA suppression and aldosterone stimulation after AI infusion were entirely due to the actions of angiotensin II converted from AI.     

Change in permeability of liposomes caused by methylmercury and inorganic mercury

The effects of two mercurial compounds, methylmercury and inorganic mercury, on lipids were examined by measuring permeability change of lipid bilayer, liposome. Both decrease in the cholesterol content and increase in the content of unsaturated fatty acid moieties in the lipid bilayers, augmented to susceptibility of the liposomes to the mercurial compounds. Inorganic mercury and methylmercury disrupted the lipid membrane to essentially the same extent. The influence on the permeability seems to be specific for mercury compounds. The significant increase in the permeability of some liposomal preparation noted even at the mercurial concentration of 10(-7) M strongly suggests that lipid in biomembrane could be one of the primary targets of these toxic substances.     

Incorporation of methionine by a soluble enzyme system from Escherichia coli

A soluble fraction from Escherichia coli B was found to incorporate methionine into 95°C CCl₃COOH-insoluble fraction. The incorporation required methionyl-tRNA synthetase, methionine tRNA, ATP, Mg²⁺ and bovine milk casein. The casein could be replaced by arginylated bovine serum albumin and arginylated bovine α-lactalbumin. A mixture of 19 amino acids other than methionine and GTP had no effect on the incorporation. KCl was rather inhibitory. Puromycin, RNase A and trypsin inhibited the incorporation, while DNase I did not. The soluble fraction also incorporated the methionyl moiety of methionyl-tRNA. This incorporation was not affected by the addition of free methionine.     

Radioimmunoassay for 11-deoxycortisol using iodine-labeled tracer.

A simple and sensitive radioimmunoassay for 11-deoxycortisol was developed. The antiserum produced in rabbits by immunizing with a complex of 11-deoxycortisol-3-oxime and bovine serum albumin (BSA) has little cross-reactivity with other endogenous steroids. The immunoassay procedure requires only one-step ethanol denaturation of binding proteins in plasma and extraction by an organic solvent can be omitted. Furthermore, use of 125I-labeled tracer significantly simplify the counting procedure. The method is sensitive enough to detect 1 microng/100 ml of 11-deoxycortisol. Plasma 11-deoxycortisol levels measured by this method after the administration of a single dose of metyrapone ranged from 5.0 to 19.2 microng/100 ml, whereas they were 0 to 4.0 microng/100 ml in hypopituitary patients. It is concluded that this simple method is useful for the routine assay of plasma 11-deoxycortisol as a parameter of the metyrapone tests.     

Recognition of rat liver and kidney nuclear T3 receptors by an antibody against c-erb A peptide

It has been reported that c-erb A encodes nuclear T3 receptors (NT3R). Based on the sequence of c-erb A cDNA, we synthesized a polypeptide consisting of 15 amino acids, the sequence of which has high homology between c-erb A alpha 1 and beta. The antibody against this c-erb A peptide not only immunoprecipitated rat liver and kidney NT3R but also inhibited T3 binding to NT3R. In a displacement study, the inhibition of [125I]T3-binding by the antibody was parallel to that by T3 in terms of the concentration of the competitor added in the incubation mixture. Scatchard analysis revealed that the antibody decreased the value for the association constant in a dose dependent manner. The antibody did not bind T3 itself. The results show that the antibody against c-erb A peptide recognizes rat liver and kidney NT3R and that the sequence encoding this peptide, the closest carboxyl-terminal of c-erb A may be critical or at least closely related to the hormone binding.     

CLE2 regulates light-dependent carbohydrate metabolism in Arabidopsis shoots

Plant Molecular Biology - This study focused on the role of CLE1-CLE7 peptides as environmental mediators and indicated that root-induced CLE2 functions systemically in light-dependent carbohydrate...     

Studies on Kojic Acid and its Related γ-Pyrone Compounds

The Mannich reaction of kojic acid in both acidic and basic media was studied. Mono-Mannich derivatives (substitution at position 6) were obtained; the reactivity in basic medium was found to be somewhat greater than in acidic medium. Reduction of the Mannich derivatives with zinc dust and acetic acid gave a 6-methyl kojic acid (6-methyl-5-hydroxy-2-hydroxymethyl-γ-pyrone).

Mono-Mannich base of pyromeconic acid was also prepared in a manner similar to that of kojic acid. From this Mannich base, maltol (2-methyl-3-hydroxy-γ-pyrone) was obtained by the reduction with zinc dust and acetic acid.