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Biomedical subjects

A Vilensky

Publications and source records attributed to A Vilensky.

11 recordsLinked to original sources
PubMed1999

Reactivity of singlet oxygen with tryptophan residues and with melittin in liposome systems.

The reactivity of singlet oxygen, 1O2, with amino acids, polypeptides and proteins has been studied extensively in solution, in micelles and also in vesicles. Here we attempt to examine its reactivity with N-acetyltryptophan amide (NATA), with a tryptophan residue with a long aliphatic chain attached, Trp(CH2)16, and with melittin--a small membrane protein--in a solution containing liposomes. In such a heterogeneous system the sensitizer and/or the tryptophan residue can be located in the ambient D2O, in the liposome membrane or at the membrane-solution interface. The sensitizer meso-tetra(N-methyl-4 pyridyl)porphine tetratosylate (mTPTT) is located in the aqueous phase while hematoporphyrin (HP) is embedded in the membrane. The quenching of 1O2 by the tryptophan residues and by melittin in solution, when using either of the sensitizers, was compared with the data in the liposome-containing system. It was found that the location of the sensitizer and of the quencher in the liposome membrane or in the surrounding solution greatly affects the quenching rate constants of 1O2.

Kinetics↗
PubMed1986

Hidden risk in operating room. Micro-shock.

The risk of electrical micro-shock is recognised in patients undergoing cardiac catheterisation or connected to electronic equipment instruments. The work reported here investigates the possibility of injury by electrical micro-shock when monitoring the central venous pressure as commonly done during surgical procedures. The studies were done on dogs catheterised for the measurement of central venous pressure with the catheter advanced into the right ventricle. It was found that currents less than 500 micro-amperes caused interference with heart rhythm, and in some of the dogs ventricular fibrillation developed. In view of these findings it appears that greater consideration should be given to the risk of electrical micro-shock in patients in whom the central venous pressure is measured.

Animals↗
PubMed1984

Comprehensive fetal monitoring by microcomputer--a clinical approach.

An inexpensive microcomputer has been devised to analyze fetal heart signals and fetal activity which were simultaneously recorded. Digital techniques were used to provide quantitative analysis of each of these inputs, and the interrelations among them. A parallel graphical presentation of those inputs was also provided.

Computers↗
PubMed1981

Factors affecting sperm motility. VIII. Velocity and survival of human spermatozoa as related to temperatures above zero.

The effect of temperature on motility and survival of ejaculated human spermatozoa was investigated with the aid of the multiple exposure photography (MEP) method for objective sperm motility determination. Fresh specimens from healthy donors were analyzed while being heated or cooled gradually, or during their storage at various temperatures from 0 to 48 degrees C. Sperm velocity increased steadily from zero to 50.4 nm/sec between freezing point and body temperature. Thereafter, their activity dropped dramatically and total immobilization occurred at 45 degrees C. The induced immobilization was reversible providing exposure to those extreme temperatures was short enough to prevent permanent damage. Sperm survived up to 24-48 h when stored at 23 degrees C, while at body temperature, their survival in vitro was much shorter and rarely extended beyond 12 h. Their longevity was still shorter at higher or lower temperatures, especially when approaching 48 degrees C. With the aid of the combined supravital staining and MEP methods it was found that temperatures of extreme levels induced mainly immobilization rather than a spermicidic effect. The possible mechanism of thermal effect on sperm motility and some of its practical implications are discussed.

Cell Survival↗
PubMed1980

Factors affecting sperm motility. III. Influence of visible light and other electromagnetic radiations on human sperm velocity and survival.

Specimens of semen from fertile and infertile patients were exposed to different electromagnetic radiations, including visible light, ultraviolet (UV) light, x-rays, and high-frequency radio waves. Sperm motility was analyzed before, during, and after irradiation by the multiple exposure photography (MEP) method. No significant difference was found between controls and specimens exposed to various doses of visible and UV light and x-rays either immediately or several hours after exposure. In contrast to spermatozoa of other species that were reported to be adversely affected by visible and UV light and x-rays, human spermatozoa seem to be highly resistant to similar doses of these radiations. A deleterious influence was observed when high-frequency radio waves were applied to human spermatozoa. This may be attributed to an intracellular diathermic effect. The informative value of this study in relation to routine semen analyses and experimental studies in the physiology and comparative anatomy of spermatozoa is discussed.

Cell Survival↗