Chikahiko Eguchi

ISOLATION OF A URINARY DIGITALIS-LIKE FACTOR INDISTINGUISHABLE FROM DIGOXIN

A digitalis-like factor has been purified to apparent homogeneity from human urine based on the inhibitory effect on [3H] ouabain binding to intact human erythrocytes. The purification scheme involved large scale adsorption followed by preparative, semipreparative and analytical high-performance liquid chromatography. The purified material showed a prominent digoxin-like immunoreactivity. The behaviour of the isolated substance was identical to that of authentic digoxin in three high-performance liquid chromatography and three thin-layer chromatography systems. Moreover, fast atom bombardment mass spectrum and proton nuclear magnetic resonance spectrum suggested that the purified material may be indistinguishable from digoxin.

Presence of digitalis-like factor in mammalian plasma

We attempted to purify a digitalis-like factor from volume expanded dog plasma using an inhibitory effect on the binding of [3H]ouabain to intact human erythrocytes to monitor digitalis-like activity. A highly polar [3H] ouabain displacing compound was purified to a high degree using a combination of chromatographic procedures including reverse phase and gel filtration high performance liquid chromatography. This compound, a reversible inhibitor of [3H]ouabain binding, closely resembles ouabain in its polarity and significantly increases during saline infusion. Its molecular weight was estimated to be 343Da. Moreover, similar compound was consistently detected in other mammalian plasma.

Purification and characterization of human urine-derived digitalis-like factor

We were able to purify a digitalis-like factor to apparent homogeneity from human urine based on the inhibitory effect on [3H]-ouabain binding to intact human erythrocytes. This ouabain displacing compound closely resembles ouabain in its polarity, molecular weight, non-peptidic nature and mode of action except for its UV absorbance spectrum. This compound sharing many biological activities of ouabain may be the endogenous ligand for the Na+, K+-ATPase and serve as a specific regulator of the sodium pump.

New amphoteric surfactants derived from lysine. I. Preparation and properties of Nε-acyllysine derivatives-acyllysine derivatives

New amphoteric surfactants were prepared from Nε-acyllysine which was obtained by the thermal dehydration of a higher fatty acid salt of lysine and was not soluble in water. Nα,Nα-dimethyl-Nε-acyllysine was prepared by the catalytic reductive condensation of Nε-acyllysine ester with formaldehyde in good yield. Nα,Nα,Nα-trimethyl-Nε-acyllysine was obtained from the reaction of Nα,Nα-dimethyl-Nε-acyllysine ester with methyl iodide. Confirmation of the structure of these derivatives was obtained by spectrometric and spectroscopic analyses.The solubility of Nε-acyllysine was improved significantly by the introduction of Nα-methyl groups. Physicochemical and surface active properties of the derivatives were investigated in terms of isoelectric points, dissolution temperatures, surface tensions, critical micelle concentrations (cmc), foaming properties and wetting powers. Nα,Nα,Nα-trimethyl-Nε-acyllysine had lower dissolution temperatures than Nα,Nα-dimethyl-Nε-acyllysine. The latter showed lower surface tensions than the former at cmc. Nα,Nα-dimethyl-Nε-lauroyllysine was best in wetting power and foaming property.

Existence of a polar digitalis-like factor in mammalian hypothalamus.

We were able to partially purify a polar digitalis-like factor from rat and bovine hypothalami based on the capacity to inhibit [3H]ouabain binding to intact human erythrocytes. This factor was characterized in reference to the digitalis-like factor that we have isolated and reported on. Hypothalamic factor shared digitalis-like activities and physicochemical properties with the one derived from human urine and mammalian plasma. These findings strongly suggest that a polar digitalis-like factor identical to the circulatory factor does exist in mammalian hypothalamus.

Expression of dystrophin on the cell surface membrane of intrafusal fibers of human skeletal muscle

SummaryWe examined the morphological expression of dystrophin in the intrafusal muscle fibers in skeletal muscle from normal human and Duchenne muscular dystrophy (DMD) patients, using antisera against the N-terminal and C-terminal regions of dystrophin. The intrafusal fibers of normal muscle express dystrophin on their cell surface membrane, but those of DMD muscle do not.

Novel peptides with orally active and long-lasting antihypertensive activity

A series of N-(P-substituted phosphinoyl)peptides were synthesized and their antihypertensive activities were tested in spontaneously hypertensive rats (SHR). Among them, N-(dibenzyloxyphosphinoyl)-L-Ala-L-Pro-L-Pro-OH showed the most potent and long-lasting antihypertensive activity in SHR when administered orally. Although the inhibitory activity of this peptide against the angiotensin-converting enzyme was about one-hundredth of that of Captopril, the antihypertensive activity in SHR was significantly higher and longer-lasting than that of Enalapril which has been reported to be the most potent agent among similar converting enzyme inhibitors.

Enzymatic Production of l-Tryptophan from l- and dl-5-Indolyl-methylhydantoin by Newly Isolated Bacterium

Bacteria which can hydrolyze dl-5-indolylmethylhydantoin to l-tryptophan were isolated from various soils. The dl-5-indolylmethylhydantoin-hydrolyzing enzymes were found to be inducible and intracellular. With intact cells, 50 mg/ml as wet base, of newly isolated bacterial strain T-523, 10 mg/ml of dl-5-indolylmethylhydantoin dissapeared and 7.4 mg/ml of l-tryptophan in a molar yield of 82% was produced after 35 hr incubation. Tryptophan produced was confirmed to be l-form regardless of the stereoisomer of the substrates used. A mechanism of asymmetric hydrolysis of dl -5-indolyImethylhydantoin was discussed.

Syntheses of Optically Active Amino Acids by the Combination of Chemical Methods and Microbial Techniques

The newly developed processes combining the advantages of chemical methods and microbial techniques brought about optically active amino acids (D- or L-) from racemic compounds. In all cases, the other isomer of substrates (L- or D-) that cannot be catalyzed by hydrolyzing enzymes were easily racemized under reaction conditions. Then, optically active amino acids were produced quantitatively from the racemic compounds.

Effects of human urine-derived digitalis-like factor on cultured renal tubular epithelial cells.

We purified a polar digitalis-like factor to apparent homogeneity from human urine using inhibition of 3H-ouabain binding to intact human erythrocytes to monitor digitalis-like activity. Since endogenous digitalis-like factor may act as a natriuretic hormone, we tested the binding characteristics of this urine-derived ouabain-displacing compound to the sodium pump in intact renal epithelial cells, in order to assess its potential physiological significance. Cultured canine and porcine epithelial cell lines, MDCK and LLC-PK1, had a high sodium pump density as estimated from 3H-ouabain binding sites. Human urine-derived ouabain-displacing compound showed a dose-related inhibition of 3H-ouabain binding to both of these cells, similar to the inhibition of unlabelled ouabain. These findings indicate that the ouabain-displacing compound is capable of acting on the sodium pump in intact renal epithelial cells and may be the circulating regulator of Na+,K+-ATPase.