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Biomedical subjects

I Tasaki

Publications and source records attributed to I Tasaki.

At least 91 records · Page 5Linked to original sources
PubMed1978

Further studies of periodic miniature response in squid giant axons.

Electric responses of extremely small amplitudes (1-30 muV peak-to-peak) repeating with more-or-less definite periodicity could be induced by a variety of chemical stimulants applied to squid giant axons either extracellularly or intracellularly. The chemical stimulants studied include allethrin, aminopyridines, N-bromosuccinimide, dimethylamino-pyridine, glutaraldehyde, osmium tetroxide, parachloromercuribenzoate, rose bengal, scorpion venoms and veratridine. With several mild stimulants, it was possible to evoke periodic miniature responses unaccompanied by a fall in the resting membrane potential. The frequency of miniature responses could be lowered by intracellular injection of TEA (tetraethylammonium). These miniature responses could readily be suppressed by external application of TTX (tetrodotoxin). The miniature responses evoked by 4-aminopyrine were characterized by a large variation in the frequency of responses. Cross-linking of the membrane proteins with a dilute solution of glutaraldehyde produced miniature responses repeating at progressively falling frequencies. Analyses of the processes of production of miniature responses with these and other stimulants have clarified several aspects of the physicochemical properties of the excitable sites of the axon membrane.

Animals↗
PubMed1977

A study of conduction velocity in nonmyelinated nerve fibers.

By treating a nonmyelinated nerve fiber as a continuous cable consisting of three distinct zones (Resting, transitional, and excited), the following mathematical expression was derived: (formula: see text) where v is the conduction velocity, d the diameter of the fiber, R the resistance of the membrane of unit area at the peak of excitation, rho the resistivity of the medium inside the fiber, and C the capacity of membrane per unit area. The validity of this expression was demonstrated by using squid giant nerve fibers intracellularly perfused with dilute salt solutions. The relationship between these results and previous theories and experiments on conduction velocity is discussed.

Animals↗
PubMed1977

Evidence for the glia-neuron protein transfer hypothesis from intracellular perfusion studies of squid giant axons.

Incubation of intracellulary perfused squid giant axons in [3H]leucine demonstrated that newly synthesized proteins appeared in the perfusate after a 45-min lag period. The transfer of labeled proteins was shown to occur steadily over 8 h of incubation, in the presence of an intact axonal plasma membrane as evidenced by the ability of the perfused axon to conduct propagated action potentials over this time-period. Intracellularly perfused RNase did not affect this transfer, whereas extracellularly applied puromycin, which blocked de novo protein synthesis in the glial sheath, prevented the appearance of labeled proteins in the perfusate. The uptake of exogenous 14C-labeled bovine serum albumin (BSA) into the axon had entirely different kinetics than the endogenous glial labeled protein transfer process. The data provide support for the glia-neuron protein transfer hypothesis.

Animals↗
PubMed1977

Relation between liver amino acid-catabolizing enzymes and free amino acids of liver and plasma in adult cockerels fed diets containing graded levels of protein.

Activities of liver amino acid-catabolizing enzymes and liver and plasma free amino acid concentrations in adult cockerels fed diets containing 3% to 21% casein were determined 2 hours after a meal. Liver tryptophan pyrrolase activity and liver tryptophan increased with an increase in dietary casein level, but plasma tryptophan decreased with the increase dietary casein level. As the dietary casein level increased, liver lysine-ketoglutarate reductase activity decreased, but liver and plasma lysine increased proportionally, and the rate of increase was larger in the plasma than in the liver. Liver phenylalanine hydroxylase activity increased with the increase in dietary casein level from 3% to 12%, and thereafter remained unchanged. Reflecting the change of this enzyme, phenylalanine increased in the liver and decreased in the plasma with the increase in dietary casein level from 3% to 12%, and thereafter the rate of increase in liver phenylalanine became small and plasms phenylalanine increased. Liver tyrosine was not influenced by the dietary casein level, whereas plasma tyrosine increased sharply from 3% to 12%, and thereafter the rate of increase decreased. Thus, the difference between liver and plasma free amino acid responses might be due to the changes in the activities of liver amino acid-catabolizing enzymes.

Amino Acids↗
PubMed1977

Properties of excitable sites in the squid axon membrane as revealed by use of chemical stimulants and a spectrum analyzer.

Properties of the excitable sites in the squid axon membrane were studied by using various chemical stimulants and a real-time spectrum analyzer. Intact squid axons immersed in media with a reduced divalent cation concentration develop very small electric responses (1-30 micronV in amplitude) which repeat at more-or-less regular intervals. The frequency of repetition of these miniature responses falls when the temperature of the axon is lowered. Replacement of a small fraction of the external Na-ion with K-ion is a powerful means of generating miniature responses. Passage of an outwardly directed current through the axonal membrane also evokes miniature responses. This effect of an electric current is attributed to a transport of intracellular K-ion into the axonal membrane. The results of the effects of external application of the salts of Li-, Rb- and Cs-ion indicate that the ability of alkali metal ions to induce miniature response falls in the following order: K, Rb is greater than Cs is greater than Na is greater than Li.

Animals↗
PubMed1976

Studies of light emission, absorption and energy transfer in nerve membranes labelled with fluorescent probes.

Physicochemical properties of fluorescent membrane probes, 2-p-Cl-anilinonaphthalene-6-sulfonate (p-Cl-ANS), 2-p-Br-anilinonaphthalene-6-sulfonate (p-Br-ANS), merocyanine-540, methyl violet, etc., were examined because of the possibility of demonstrating resonance energy-transfer between probes. The emission psectra of p-Cl-ANS and p-Br-ANS and the absorption (or fluorescence excitation) spectra of Eastman Kodak merocyanine-540 (M-540) and other probes were found to be very sensitive to changes in the solvent polarity. The spectra of these probes incorporated in the nerve membrane were determined and compared with the corresponding spectra in various organic solvents and macromolecules. This comparison suggests that the polarity of the binding sites for p-Cl-ANS (and p-Br-ANS) in the membrane is high and that of M-540 is very low. The spectrum of the portion of p-Cl-ANS fluorescence contributing to production of optical responses (i.e., transient changes during action potentials) was determined. Both absorption responses and fluorescence responses were detected from M-540 in the nerve membrane. It was possible to demonstrate resonance transfer of electronic energy from p-Cl-ANS to M-540 incorporated in lysolecithin micelles and in crab nerves. During action potentials, the intensity of M-540 fluorescence excited by energy transfer was found to undergo transient changes. Based on these and other experimental findings, properties of the binding sites for these probes in the nerve membranes are discussed.

Anilino Naphthalenesulfonates↗
PubMed1976

Release of proteins from the inner surface of squid axon membrane labeled with tritiated N-ethylmaleimide.

Proteins in the inner surface of the squid axon membrane were labeled by intracellular perfusion of [3H]N-ethylmaleimide (NEM), which forms covalent bonds with free sulfhydryl groups. The excitability of the axon was unaffected by the [3H]NEM perfusion. After washout of the unbound label, the perfusate was monitored for the release of labeled proteins. Labeled proteins were released from the inner membrane surface by potassium depolarization of the axon only in the presence of external calcium ions. Replacement of the fluoride ion in the perfusion medium by various anions also caused labeled protein release. The order of effectiveness was SCN- greater than Br- greater than Cl- greater than F-. The extent of labeled protein release by the various anions was correlated with their effects on axonal excitability. The significance of these results is discussed.

Animals↗
PubMed1974

A tumour cell aggregation promoting substance from rat ascites hepatoma cells.

A substance capable of promoting tumour cell aggregation was released from rat ascites hepatoma cell (possibly from the cell surface) kept in Hanks' balanced salt solution (free of calcium and magnesium) in the cold, and then partially purified by chromatography with DEAE-Sephadex and gel filtration with Bio-gel. The thermostable substance seemed to be a glycoprotein and its molecular weight was about 72,000 when measured by gel filtration on Sephadex G-200. It had no proteolytic activity. The material was clearly effective for rat ascites hepatoma cells as well as SV40 transformed cells, but less effective for Chang's cells and apparently ineffective for normal rat liver cells and red blood cells. The action of this material was more potent than that of Jack bean concanavalin A when assayed for aggregation of SV40 transformed cells. Its effect was not influenced by concanavalin A inhibitors such as alpha-methyl-D-glucopyranoside, N-acetyl-D-glucosamine and D-glucose.

Animals↗