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Biomedical subjects

H F BLUM

Publications and source records attributed to H F BLUM.

At least 37 records · Page 2Linked to original sources
PubMed1954

Photodynamic hemolysis at low temperatures.

It is shown that photodynamic hemolysis may occur at -79 degrees C. if the erythrocytes are suspended in a solution containing 70 per cent glycerol which prevents hemolysis by freezing; but that there is no hemolysis under the same conditions at -210 degrees C. At the higher temperature the viscosity of the solution is still low enough to permit appreciable movement of molecules, whereas at the lower temperature the molecules must be virtually immobile. The findings are compatible with the idea that the dye molecule acts in a cycle, bringing about successive oxidations by O(2) molecules, as has been shown for photodynamic hemolysis at room temperature. The assumption of a combination between dye, O(2), and substrate does not explain photosensitized hemolysis in the semi-solid state. The mechanism of photosensitized oxidation by O(2) is discussed.

Cold Temperature↗
PubMed1954

A comparison of five effects of ultraviolet light on the Arbacia egg.

The demonstration of five different effects of ultraviolet radiation on the sea urchin's egg indicates that more than one basic photochemical process goes on there. Photorecovery is observed in only one of these. The need for caution in interpreting such effects is obvious. Evidence for a different mechanism for the timing of cleavage in eggs activated by ultraviolet radiation as compared to normally fertilized eggs is presented. The bearing of these studies on survival curves for microorganisms is discussed.

Animals↗
PubMed1954

Ultraviolet light and the mitotic cycle in the sea urchin's egg.

The effect of ultraviolet light in delaying certain events in the cell division cycle has been examined. The time to fusion of the egg and sperm nucleus is not affected by doses of ultraviolet that cause considerable delay in other parts of the cycle. The principal delay occurs before anaphase. Between anaphase and cleavage there is only slight delay. The "refractory period" during which the radiation does not delay the immediate cycle of cell division, does not seem to represent complete refractoriness of the mitotic cycle to interference during this period.

Animals↗
PubMed1951

The loci of action of ultraviolet and x-radiation and of photorecovery in the egg and sperm of the sea urchin Arbacia punctulata.

Various experiments are described which show the locus of action of ultraviolet radiation and of x-ray in delaying cell division of the fertilized egg of Arbacia punctulata to be in the nucleus. Photorecovery following ultraviolet radiation has its locus in the egg cytoplasm. Analogy is drawn with the action of ultraviolet radiation and photorecovery on the E. coli-bacteriophage system, and certain suggestions are made regarding a common mechanism. Photorecovery after x-ray exposure could not be demonstrated.

Animals↗
PubMed1950

Delay of cleavage of the Arbacia egg by ultraviolet radiation.

While our data do not permit us to state the exact locus or mode of action of ultraviolet radiation in the Arbacia egg, certain general conclusions may be reached. The amount of delay of cleavage of these eggs is determined by two principal factors: (1) The extent of an effect, resulting from photochemical action induced by ultraviolet radiation, which is reversible in a biological sense, the reversibility not being directly dependent upon the process of cell division. (2) The sensitivity of the cell division process to the effects of the ultraviolet-induced photochemical reaction. This factor varies with the stage of cell division, the cell being insensitive during a period corresponding to most of mitosis. It seems likely that these findings may apply to cell division in general, but, since the quantitative relationships observed must, in this case, reflect the integration of two semi-independent factors, the over-all picture may appear quite different for different kinds of cells.

Animals↗
PubMed1950

Time relationships in the cleavage of the normal fertilized egg of Arbacia punctulata.

Quantitative data are presented indicating the extent of variability in the time of cleavage of normal fertilized eggs of Arbacia punctulata. It is a pleasure to acknowledge the valuable suggestions and criticisms of Professor Arthur K. Parpart during the course of the experiments described in this and the preceding paper, and those of Professor Douglas A. Marsland and Professor M. J. Kopac at the final manuscript stage.

Animals↗
PubMed1950

The accelerating action of illumination in recovery of Arbacia eggs from exposure to ultraviolet radiation.

Light of wave lengths 0.30micro to 0.50micro, accelerates return of the cleavage rate of Arbacia eggs to normal, after delay by exposure to ultraviolet radiation (wave lengths 0.238micro to 0.31micro). Recovery is apparently complete. Wave lengths 0.30micro to 0.50micro have no effect on the cleavage rate of normal eggs, nor does such illumination previous to dosage with ultraviolet radiation influence subsequent recovery. Acceleration of recovery of the egg occurs before fertilization as well as after. The effects of ultraviolet radiation and recovery therefrom are essentially the same in nucleated "white halves" as in the intact eggs. This phenomenon in the Arbacia egg seems basically comparable to photoreactivation of bacteria and fungi.

Animals↗