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Biomedical subjects

M Rubinstein

Publications and source records attributed to M Rubinstein.

At least 253 records · Page 14Linked to original sources
PubMed1979

Long-term electrode implantation for recording cochlear electrical activity in guinea pigs.

Comparative measurements of the cochlear electrical activity over prolonged periods require long-term implantation of electrodes. During this time, changes in the electrode recording ability and/or impairment of the sound-conducting system, could erroneously be attributed to the experiment. To avoid this risk, an easy and reliable technique is described. The procedure uses the Fallopian canal as a route by which to approach the cochlear potentials' generators, while leaving the middle ear untouched.

Action Potentials↗
PubMed1978

Human leukocyte interferon purified to homogeneity.

One of the species of human interferon produced by incubation of leukocytes with Newcastle disease virus was purified to homogeneity. It exhibited one peak of activity coinciding with a single protein band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

Humans↗
PubMed1978

Binding assay for opioid peptides with neuroblastoma x glioma hybrid cells: specificity of the receptor site.

A sensitive and rapid radioreceptor assay has been developed to monitor opioid peptides in column effluents. It is based on competitive binding to NG 108-15 cells using [3H-Tyr]Leu-enkephalin as the displaced ligand. The specificity of binding to the cells of naturally occurring opioid peptides and synthetic analogs has been shown to be similar to that found with synaptic plasma membranes.

Animals↗
PubMed1978

Characterization of pro-opiocortin, a precursor to opioid peptides and corticotropin.

The high molecular weight (approximately 30,000) precursor to opioid activity (pro-opiocortin) previously detected in extracts of rat pituitary was digested with trypsin and the resulting peptide mixture was resolved by high-performance reverse-phase chromatography. A peak of opioid activity was eluted at the position of the nonapeptide beta-LPH (61-69), which was also the same fragment obtained by trypsin digestion of betas-lipotropin or beta-endorphin. This identified the protein as a precursor to the endorphins and Met-enkephalin. No activity was detected in the position corresponding to the Leu5 analog of betas-LPH (61-69), thus ruling out the possibility of a beta-lipotropin-like precursor to Leu-enkephalin in pituitary extracts. Pro-opiocortin and beta-lipotropin are present in rat pituitary extracts in comparable amounts, approximately 10 pmol/mg of tissue.

Adrenocorticotropic Hormone↗
PubMed1978

High molecular weight opioid-containing proteins in striatum.

Striatal extracts of guinea pigs, rats, and cattle were found to contain two large proteins (greater than 40,000 and greater than 100,000 daltons) that on treatment with trypsin yield opioid peptides differing chromatographically from the opioid nonapeptide generated by trypsin digestion of endorphins, beta-lipotropin, or pro-opiocortin. Furthermore, the large opioid proteins found in the pituitary do not appear to be present in the striatum. These and other findings indicate that the striatal enkephalins are produced via a pathway from the one deduced from studies on the pituitary.

Animals↗
PubMed1977

Selective covalent binding of methionyl-containing peptides and proteins to water insoluble polymeric reagent and their regeneration.

A polymeric reagent of the type P approximately NHCOCH2Cl (where P is Bio-Gel P-100) was prepared. This polymer covalently bound peptides and proteins specifically at methionine residues under acidic conditions in the presence of a small amount of sodium iodide. Treatment of the polymer-peptide conjugate with 2-mercaptoethanol resulted in essentially complete removal of the peptide with regeneration of intact methionyl residues. In an alternative way, the polymer was suspended for 2 h in boiling water. This treatment resulted in the conversion of the bound methionyl residues to homoserine residues and cleavage and liberation of the bound peptides. The polymeric reagent was successfully applied to the separation of methionyl peptides from peptide mixtures and for specific covalent binding of enzymes and biologically active proteins via their exposed methionyl residues, with the retention of their biological activity.

Acrylamides↗
PubMed1977

Isolation and characterization of the opioid peptides from rat pituitary: beta-endorphin.

beta-Endorphin was isolated from 200 rat pituitaries by means of high-performance column chromatography, using sensitive fluorometric methods and a radioreceptor assay for opioid activity. The beta-endorphin was characterized as to molecular weight, amino acid composition, and mapping of tryptic peptides by a new microtechnique. It was found that rat beta-endorphin is identical to camel and sheep beta-endorphin. Furthermore, alpha-endorphin, Met-enkephalin, a nonpeptide morphine-like compound (MLC), and an additional unidentified opioid compound were detected in the extract of rat pituitary.

Amino Acids↗
PubMed1977

Isolation and characterization of the opioid peptides from rat pituitary: beta-lipotropin.

Rat beta-lipotropin was isolated from 40 anterior pituitaries using high efficiency chromatography columns and sensitive fluorometric methods. The beta-lipotropin was characterized as to molecular weight, amino acid composition, and generation of opioid activity by trypsinization. Other opioid peptides, as well as a precursor to opioid peptides with a molecular weight larger than that of beta-lipotropin, were observed in this tissue.

Amino Acids↗
PubMed1977

Chronic cardiovascular pathology and hearing loss in the aged.

With the objective of studying a possible correlation between chronic cardiovascular disturbances and hearing loss in aged people, two groups were compared. The first was composed of apparently healthy subjects and the second, of subjects suffering from clinically evident chronic cardiovascular pathology. All the subjects were submitted to a pure tone audiometry, discrimination test, SISI test and TDT. The results showed a significant difference in pure tone threshold audiometry between the apparently healthy subjects and those presenting cardiovascular symptoms; the discrimination and the TDT were comparable in the two groups.

Aged↗
PubMed1976

Precise "one line" measurement of intracardiac electrograms.

Atrioventricular nodal (A-H) and infranodal (H-Q) conduction times were determined in 22 patients undergoing intracardiac electrophysiologic studies. These measurements were determined independently both on line from a digital oscilloscope and from paper recordings at a rate of 100 mm/sec. There was no significant difference and excellent correlation between mean A-H (91.39 +/- 29 versus 95.44 +/- 32 msec) and H-Q (53.48 +/- 14 versus 50.52 +/- 15 msec) intervals determined by these two methods. The digital oscilloscope enables virtually instantaneous highly accurate (+/- 1 msec) timing of intracardiac events and rapid and more efficient processing of data. Potential applications during electrophysiologic studies include precise monitoring of drug effects on atrioventricular conduction and refractoriness, on line analyses of complex rhythm disturbances, and ready storage of data for computer retrieval and analyses.

Arrhythmias, Cardiac↗
PubMed1975

Modulation of the enzymic activity of chicken pepsin by the covalent modification of its single -- SH group.

The single cysteinyl residue of chicken pepsin was modified with a wide spectrum of reagents to produce mixed disulfides or alkylated derivatives. All these derivatives showed enhanced catalytic activity towards the synthetic peptide Z-Ala-Ala-Phe-OPrP, where OPrP is the 3-(4-pyridyl)-propyl-1-oxy group. The overall catalytic constant kcat/Km for these derivatives was 4 -- 25-fold larger than that of the native enzyme. The activity of the enzyme towards denatured hemoglobin was slightly decreased (10--45%) by these modifications. When the mixed disulfide derivatives were treated with excess mercaptan, the sulfhydryl group was regenerated and activity reverted to that of the native enzyme. The --SH group of chicken pepsin reacted preferentially with reagents containing an aromatic group. The reaction was found to depend on the ionization of a single group, presumably the --SH itself, with a pKa = 7.5. The rate of reaction of the fully deprotonated species with various disulfides was 100--1000-fold smaller than that of the --SH group of glutathione. It is suggested that the groups attached covalently to the sulfhydryl also interact with other amino acid side chains in the protein thereby affecting the active center of chicken pepsin.

Amino Acids↗
PubMed1975

Reconstruction of upper cervical esophagus.

We describe a surgical technique for reconstruction of the upper cervical esophagus after a segment has been excised. The technique involves the downward rotation of a full thickness pharyngeal flap to close the defect. The flap is obtained from the posterior wall of the hypopharynx and oropharynx. We describe a case in which this technique was used.

Child↗