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R Brust

Publications and source records attributed to R Brust.

13 recordsLinked to original sources
PubMed1991

Manitoba virus, a new rhabdovirus isolated from Culex tarsalis mosquitoes collected in Manitoba, Canada.

A rhabdovirus, Mn 936-77, was isolated from a pool of two Culex tarsalis collected on August 16, 1977, from Morris, Manitoba. Isolate Mn 936-77 was not pathogenic for suckling Swiss white mice inoculated by the intracerebral route. The virus propagated in three vertebrate cell lines (Vero, primary chick embryo, mouse neuroblastoma), but apparently not in Aedes albopictus C6/36 cells. Isolate Mn 936-77 did not react by amplified enzyme-linked immunosorbant assay with 230 viruses of proven or possible arbovirus etiology or by immunofluorescence with 88 members of the family Rhabdoviridae. Isolate Mn 936-77 appears to be a newly discovered virus for which the name Manitoba virus is proposed.

Animals↗
PubMed1986

Viscosity of chromatin solutions increases with increasing ionic strength.

Increasing the ionic strength of rat liver chromatin solutions above 0.4 M causes increasing viscosity. This indicates transformation of the compact chromatin molecules to more elongated forms. In the range of 0.4-0.5 M ionic strength histone H1 is dissociating continuously from the chromatin and the quaternary structure chromatin unravels. At ionic strength higher than 0.5 M the viscosities of chromatin solutions are furthermore increasing due to structural deformation. Near 0.7 M ionic strength the core histones H2A and H2B begin to dissociate from the chromatin, and the opening of the nucleosome cores leads to increasing elongation of the chromatin molecules.

Animals↗
PubMed1985

Viscosity as an additional physico-chemical parameter for studying chromatin structure.

The viscosity values of chromatin in higher order structures, which range from 0.1 to 0.4 dl/g, are considerably lower than those of isolated DNA. These low values are consistent with other physico-chemical parameters, such as sedimentation and diffusion coefficients. When deducing molecular mass and compact shape of chromatin molecules in solvents of nearly physiological ionic strength, all these parameters are in general agreement. A decrease in ionic strength increases viscosity and decreases s-value. Both effects are consistent with a chromatin model postulating a very compact quaternary structure which unravels in low ionic environment to an unfolded but not completely extended tertiary structure.

Animals↗
PubMed1984

A magnetic viscometer for shear-sensitive macromolecules.

This paper is a report about a rotation-viscometer with a submerged rotor which has been developed for measuring the viscosity of biological macromolecules. The device avoids the effects of surface disturbance. The rotor is centered and height-balanced electromagnetically and is controlled by a light barrier. The driving force is a rotating electromagnetic field and rotor revolution periods are measured by an electronic timer controlled by a second ligh barrier. Shearing effects are negligible if very slow revolutions are pre-selected; thus, intrinsic viscosity values for DNA can be obtained by merely extrapolating the concentration dependence. In contrast to DNA, chromatin has a very low viscosity with almost no dependence on concentration. If the ionic strength of a chromatin solution is decreased, the viscosity increases due to structural unfolding.

Animals↗
PubMed1983

Cimetidine for recurrent ulcer after gastric surgery.

Seven of nine patients with ulcers recurring after a variety of gastric operations enjoyed loss of dyspeptic symptoms within 2 days of taking cimetidine, 1,200 mg/day for 6 weeks, and endoscopic confirmation of healing of the recurrent ulcer was established within 6 weeks of therapy. Once ulcer healing had been achieved in these seven patients, symptomatic remission persisted for over 19 months without maintenance therapy with cimetidine, and no complications suggestive of recurrent ulcerations occurred during this period in these seven patients. The eighth patient with a recurrent ulcer after vagotomy and pyloroplasty had symptoms suggestive of a gastric outlet obstruction in association with a bezoar and an elevated fasting serum gastrin concentration; cimetidine failed to heal the ulcer and a partial gastrectomy with Billroth I anastomosis was undertaken. The ninth patient lost his dyspeptic symptoms while on cimetidine, but 1 month after stopping therapy he succumbed to a massive hemorrhage; autopsy revealed a large pyloric channel ulcer. We suggest that cimetidine is helpful for the control of symptoms and the healing of recurrent ulcers after gastric surgery, but that endoscopy be repeated after an appropriate interval while such patients remain on cimetidine to assure that the disappearance of symptoms is truly associated with a lack of peptic ulceration. If the ulceration persists, we believe that cimetidine should be continued for a longer period.

Adult↗
PubMed1982

[Structural arrangement of chromatin (author's transl)].

Recent observations and hypotheses on the structure of chromatin are reviewed. Elementary "subunit" for higher structural orders is the nucleosome, consisting of a histone octamer and doublehelical DNA wrapped around it. During the last years details of the nucleosomal structure could be deduced down to a resolution of 2 nm. In the chromatin fiber, built up by (mono-)nucleosomes, the superhelical DNA has a tertiary structure, from which structures of still higher order (quaternary structure of DNA) can be formed. The correlation of these structures to the terms euchromatin and heterochromatin are discussed. Finally, some functional aspects, especially transcription and replication, are discussed in view of the new knowledge of chromatin structure.

Amino Acid Sequence↗
PubMed1981

Structural investigations on isolated chromatin of higher-order organisation.

Chromatin of a high structural order was prepared by a method avoiding drastic mechanical stress, as well as strong changes of the ionic strength, and was investigated by small-angle X-ray scattering. The results obtained support the idea that the quaternary structure of completely hydrated chromatin in solution is a solenoid with a diameter of about 32-34 nm. Gel chromatography of this chromatin yields solutions containing mainly quaternary structures with differing portions of tertiary structure. Decrease of the ionic strength results in an increase of loosening and unfolding of quaternary structures. Reconstitution by readjustment of the physiological ionic strength indicates slight differences between reconstituted and original higher-order structures.

Animals↗
PubMed1981

[A clinical study on the use of etomidate for induction and maintenance of anaesthesia (author's transl)].

The action of etomidate, a short-acting non-barbiturate hypnotic agent, was studied in three groups of patients. Used alone for induction it did not significantly alter either the pulse rate or the diastolic blood pressure. Systolic blood pressure fell slightly, but became stable after 2 minutes. The pH of the arterial blood was not significantly altered. pO2 and pCO2 showed changes indicative of respiratory depression during induction (group 1). Etomidate combined with fentanyl caused a moderate, significant fall in both diastolic and systolic blood pressure, but did not affect the pulse rate (group 2). In view of its inconsiderable haemodynamic effects etomidate can be regarded as a safe agent for induction. In doses of 10-20 micrograms/kilogramme bodyweight/minute infusions of etomidate (combined with fentanyl and muscle relaxants) provide adequate basal narcosis for most routine surgical operations. It cannot, however, be considered the anaesthetic of choice for major abdominal surgery which requires deep analgesia and full muscular relaxation (group 3).

Adult↗
PubMedDate not supplied

Soluble and insoluble rat liver chromatin is different in structure and protein composition.

Rat liver chromatin has been fractionated by different solubility in solvents of 155 mM ionic strength in soluble S and insoluble I-chromatin. Histone H1 content is lower in S as compared to I-chromatin. The HMG1/2 nonhistone proteins are observed in S-chromatin and in the nuclear pelleted residue from the chromatin isolation procedure, but no amount can be detected in I-chromatin. Thermal denaturation profiles and CD-spectra are different for S and I-chromatin indicating distinct interactions between DNA and proteins in the chromatin molecules. Both effects, differing protein content and distinct DNA-protein interactions, can be correlated with solubility and insolubility being the result of charge-charge interactions between chromatin molecules and ionic components of the solvent.

Animals↗
PubMedDate not supplied

Specific binding of calcium to soluble chromatin.

Equilibrium dialysis studies and sedimentation experiments with soluble rat liver chromatin and radioactive 45Ca support the hypothesis that there is a specific binding of Ca2+ to chromatin molecules. At low ionic strength the binding constant is about 12 l/mM indicating that more than half of the negative charges of the chromatin molecules are neutralized due to the binding of Ca2+ at appropriate concentrations. This effect possibly accounts for low concentration of Ca2+ and other divalent cations being effective in inducing compact higher order structures of chromatin. Monovalent cations are not specifically bound, but high concentrations cause unspecific shielding of the charges on the chromatin molecules and thus structural transformation. Even under these high salt conditions a specific binding of Ca2+ to chromatin occurs. The binding constant is, however, only 0.4 l/mM due to the lower effective concentration of the charged chromatin molecules which is reduced by unspecific neutralizing.

Animals↗