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Biomedical subjects

E POLLARD

Publications and source records attributed to E POLLARD.

At least 19 recordsLinked to original sources
PubMed1965

DIFFUSION RATES IN DISRUPTED BACTERIAL CELLS.

The viscosity of the material resulting from squeezing Escherichia coli cells through an orifice in a French pressure cell has been shown to be very high and variable with temperature. Diffusion constants in this medium have been determined for sucrose, dextran, and beta galactosidase. The values found are: 1.07 x 10(-6)cm(2)/second for sucrose, 0.36 x 10(-6)cm(2)/second for dextran, and 0.025 x 10(-6)cm(2)/second for beta galactosidase. The results agree with the idea that there is much interstitial space available for diffusion of small molecules in the cell medium in spite of the high viscosity, but that large molecules will be transported less readily.

Bacteriological Techniques↗
PubMed1964

THE EFFECT OF TEMPERATURE ON THE FORMATION OF T1 AND T2R BACTERIOPHAGE.

A very rapid variation of yield of T1 and T2r bacteriophage in E. coli at slightly higher than normal temperatures has been observed. T1 phage will develop at 41.2 degrees C but not at 41.7 degrees C. By infecting cells grown on lactose and, therefore, induced to contain beta galactosidase, a technique which indicates when cells have become leaky was worked out. This method shows that at elevated temperatures the enzymatic attack on the cell wall continues to go at a faster rate, while completion of the phage goes more slowly. Thermal constants are given for the processes. Cells at higher temperature, grown on P(32) medium develop incomplete particles capable of combining with phage antibody. This suggests that the process affected by the early leakiness of the cells is the completion of the virus protein coat. Supplementing the medium with casamino acids, phosphate, and ATP causes the "rescue" of phage particles by aiding the formation of the coat. This can be achieved several minutes after the cells have become leaky and may form a useful system for the study of phage development in the presence of analogs.

Adenosine Triphosphate↗
PubMed1961

Localization of beta-galactosidase in cells of Escherichia coli by low voltage electron bombardment.

By using low voltage electrons to bombard dried cells of Escherichia coli, the inactivation of the enzyme beta-galactosidase as a function of depth of electron penetration has been studied. There is little inactivation for a penetration of 100 A, but considerable for a penetration of 300 A. An analysis of the data for six initial electron energies shows that there exist outer and inner bounds of the enzyme region which are approximately 300 and 700 A below the cell surface, respectively.

Electrons↗