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Biomedical subjects

S Nishi

Publications and source records attributed to S Nishi.

At least 19 recordsLinked to original sources
PubMed1979

Characteristics of fast excitatory postsynaptic current in bullfrog sympathetic ganglion cells. Effects of membrane potential, temperature and Ca ions.

The membrane current underlying the fast excitatory postsynaptic potential (EPSC) of bullfrog sympathetic ganglion cells was studied. The relationship between the EPSC amplitude and membrane potential was linear at negative levels of membrane potential, but deviated from the linearity toward a smaller amplitude at positive levels. The falling phase of EPSC almost followed a single exponential decay. The half-decay time (HDT) of EPSC's increased exponentially with an increase in the negativity of membrane potential. The rise time (RT) was also prolonged slightly with membrane hyperpolarization. Lowering of temperature decreased the EPSC amplitude, lengthened markedly the HDT and increased the slope relating the logarithm of the HDT to membrane potential. Neostigmine (1 x 10(-5) M) prolonged both the RT and HDT. A decrease in Ca2+ concentration caused a marked reduction in the EPSC amplitude, and a slight shortening in the RT and HDT. An increase in Ca2+ concentration significantly prolonged the RT and HDT without altering the slope of the relationship between the HDT and membrane potential, while the amplitude of EPSC was increased slightly. The HDT was independent of EPSC amplitude. It is suggested that the mechanism responsible for closing the ion channels of the nicotinic receptor at the subsynaptic membrane is regulated by membrane potential. The possible mechanisms of the action of Ca2+ on the decay phase of EPSC were discussed.

Animals↗
PubMed1979

In vitro synthesis of murine pre-alpha-fetoprotein.

Murine alpha-fetoprotein was synthesized in a wheat germ cell-free system in the presence of radioactive amino acids under the direction of alpha-fetoprotein messenger RNA isolated from mouse yolk sacs. The radiolabeled alpha-fetoprotein was isolated by immunoabsorption, and the amino acid residues at the NH2 terminus were determined by radioactive sequencing techniques. In a comparison to the NH2-terminal sequence of circulating alpha-fetoprotein, the in vitro-synthesized alpha-fetoprotein was found to contain an extra peptide 20 amino acids long linked at the NH2 terminus, the sequence of which is: (formula: see text). The molecular size, the hydrophobic nature, and the other properties of the peptide are consistent with the "leader" or "signal" piece found in the precursors of many other secretory proteins. This suggests that alpha-fetoprotein, the synthesis of which is limited primarily to fetal development, is produced in the form of the precursor as are secretory proteins in the adult tissues.

Amino Acid Sequence↗
PubMed1978

Studies on Epstein-Barr virus-related antigens. III. Purification of the virus-determined nuclear antigen (EBNA) from non-producer Raji cells.

The purification of Epstein-Barr virus-determined nuclear antigen (EBNA) was attempted on the basis of its biochemical and physicochemical properties and its immunological specificity, assayed by the indirect single radial immunodiffusion test and anti-complement immunofluorescence absorption test. When non-producer Raji cell extract was subjected to 20--60% saturated ammonium sulfate fractionation, followed by DNA-cellulose chromatography and immunoadsorbent chromatography, EBNA was purified more than 3,000 times with a 8% yield. Such purified protein was composed of three polypeptides with molecular weights of 100,000 +/- 5,000, 70,000 +/- 5,000 and 50,000 daltons, respectively, on SDS-polyacrylamide gel electrophoresis. Similar purification was achieved by heating the extract at 70 degrees C for 10 min, instead of ammonium sulfate fractionation, followed by DNA-cellulose chromatography and immunoadsorbent chromatography. This final preparation consisted almost exclusively of 100,000 +/- 5,000 daltons polypeptide, 50,000 polypeptide, and the 70,000 +/- 5,000 polypeptide passing through the adsorbent column. These findings suggest that EBNA is probably a molecular complex of three smaller subunits of heat-stable 100,000 +/- 5,000 and 50,000 daltons and heat-labile 70,000 +/- 5,000 daltons polypeptides, respectively.

Ammonium Sulfate↗
PubMed1978

Sympathetically induced atrial tachycardia. Successful treatment by left stellate ganglion block.

An unusual type of atrial tachycardia was observed in a 52-year-old woman. The tachycardia occurred only when the patient kept the left upper limb in the lateral and horizontal position. Propranolol, atropine sulfate, carotid sinus massage and ocular compression were not effective in terminating or preventing the arrhythmia. Left stellate ganglion block has stopped the tachycardia for at least two years. The atrial tachycardia in this patient was thought to be caused by mechanical stimulation of the left stellate ganglion resulting in pacemaker shifting, as has been demonstrated in the canine heart.

Action Potentials↗
PubMed1978

Characterization and ionic basis of GABA-induced depolarizations recorded in vitro from cat primary afferent neurones.

1. Responses of single cells in the isolated cat spinal ganglion to GABA applied by superfusion or by iontophoresis were recorded using intracellular micro-electrodes. 2. Of the twelve structurally related compounds investigated, GABA was the most effective in its ability to produce a depolarization of the cell membrane. 3. Studies determining concentration-response relationships indicate that two to three molecules of GABA are required to combine with the GABA receptor for activation. 4. Bicuculline and picrotoxin, each act in a non-competitive manner to antagonize the GABA-induced membrane current. 5. The equilibrium potential for iontophoretically induced GABA depolarizations (EGABA) was found to be -23.5 plus or minys 6.1 mV. EGABA was independent upon [cl-]o, but independent of [Na+]o, [K+], or [Ca2+]o. 6. Intracellular injection of twenty antions (Br-, I-, NO2-, NO3-, ClO4-, SCN-, Bf4-, HS-, OCN-, ClO3-, BrO3-, F-, HCO2-, HSO3-, HCO3-, CH3CO2-, SO42-, C6H5O73-) indicated that the activated GABA receptor membrane was permeable to those anions whose hydrated diameter is no larger than that of ClO-3. 7. Restoration of the GABA depolarization to its control level after augmentation by Cl- injection had a mean time constant of 27.8 plus or minus 2.6 min. Picrotoxin did not alter this value. 8. When foreign anions were exchanged for Cl- in the perfusion solution, the ten anaions smaller or equal to ClO3-, decreased the GABA depolarization by 50-90% and increased its time course 1.5-2.0 x control. The only exception having a small radius was Br- which augmented the amplitude 10-30%. 9. The ten anions larger than ClO3- produced a biphasic effect, i.e. an initial augmentation followed by a marked (up to 100%) depression of the response. Experiments with CH3COO-, CH3SO4-, or HOCH2CH2SO3-, indicated that this depression was non-competitive.

Aminobutyrates↗
PubMed1977

Studies on Epstein-Barr virus-related antigens. II. Biochemical properties of soluble antigen in Raji Burkitt lymphoma cells.

Biochemical properties of Epstein-Barr virus (EBV)-related soluble antigen in non-producer Raji Burkitt lymphoblastoid cells, assayed by the indirect single radial immunodiffusion (ISRD) test, were investigated. The soluble ISRD antigen retained activity even after exposure to a temperature of 80 degrees C. The antigen was precipitated in 40% saturated ammonium sulfate and ISRD activity was recovered from the precipitate when reconstituted into a solution. Isoelectric focusing and crossed immunoelectrophoretic analyses revealed that the esoelectric point of the ISRD antigen is pH 4.8 with an electrophoretic mobility similar to that of serum alpha-globulin. With Sephadex G-200 or Sepharose 6B gel filtration, ISRD activity was obtained as a single peak which corresponded to the activity absorbing anti-complement immunofluorescence. The molecular weight of the present EBV-related soluble antigen was estimated to be 220,000-2408000 daltons.

Antigens, Viral↗
PubMed1977

Myocardial ultrastructural changes in Kugelberg-Welander syndrome.

Electron microscopical study of a biopsied specimen of myocardium from a patient with the Kugelberg-Welander syndrome revealed myocardial degeneration, including preferential loss of myosin filaments and abnormalities in the Z bands. Leptomeric fibrils were also observed in the cardiac muscle cell; there does not appear to be a previous report of the finding of such fibrils in human myocardium.

Adult↗