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Biomedical subjects

P Mazur

Publications and source records attributed to P Mazur.

At least 91 records · Page 5Linked to original sources
PubMed1976

Survival of frozen-thawed human red cells as a function of cooling and warming velocities.

Human red cells were equilibrated for 30 min at 20degreesC in buffered saline containing 2 M glycerol and then frozen to --196degreesC at 0.27, 1.7, 59, 180, 480, 600, and 1300degreesC/min and warmed at 0.47, 1, 26, 160, and 550degreesC/min. Cells frozen at 600 and 1300degreesC/min responded in the classical fashion for cells containing intracellular ice; i.e., survivals were low when warming was slow (less than 10%), but increased progressively with increasing warming rate. The sensitivity to slow warming presumably reflects the recrystallization of intracellular ice. Cells frozen at 59 and 180degreesC/min yielded high survivals at all warming rates. This response is also consistent with the findings for other cells cooled just slowly enough to preclude intracellular ice. Cells frozen very slowly at 0.27 and 1.7degreesC/min, however, responded differently; survivals were considerably higher when warming was slow (0.47 or 1degreesC/min) than when it was 26, 160, or 550degreesC/min. This response is analogous to that observed recently by others in mouse embryos and in higher plant tissue-culture cells and to that observed for many years in higher plants. It also confirms previous observations of Meryman in human red cells. It may reflect osmotic shock from rapid dilution but, if so, the basis of the osmotic shock is uncertain.

Animals↗
PubMed1976

Survival of fetal rat pancreases frozen to -78 and -196 degrees.

Transplantation of pancreases may have clinical utility in the treatment of diabetes, for it has been shown that chemically induced diabetes in rats can be reversed by the transplantation of greater than or equal to four syngeneic fetal pancreases. Allogeneic transplants produce serious immunological problems, but the problems could be ameliorated if tissue-typed organs could be stored in the frozen state. Unfortunately, nearly all attempts to freeze organs have failed. Nevertheless, recent developments in the physical-chemical analysis of freezing injury and its successful application to the freezing of mammalian embryos encouraged us to attempt the freezing of 16 1/2- to 17 1/2-day intact fetal pancreases. The analysis indicated that to achieve success pancreases would have to be cooled less than 1 degree/min and diluted extremely slowly after thawing. Experiments with embryos and red cells indicated that high survivals might require high concentrations of protective solutes and slow warming. These predictions were accurate. After freezing to -78 or -196 degrees and thawing under optimal conditions, the fetal pancreases synthesized 80-100% as much protein as unfrozen controls and they yielded viable allografts. Optimal conditions included suspension in 2 M dimethylsulfoxide, freezing at 0.3 degrees/min, and slow dilution to preclude osmotic shock.

Animals↗
PubMed1976

Osmotic shrinkage as a factor in freezing injury in plant tissue cultures.

Haplopappus gracilis and Acer saccharum tissue culture cells are extremely sensitive to freezing injury, and exhibit a decrease in survival from 98% at -1 C to 4% at -3 C (Haplopappus) and 92% at -3 C to 13% at -5 C (Acer) when suspended in distilled H(2)O, seeded at -1 C, and then cooled by 0.1 C/minute. Similar results are obtained when cells are suspended in growth medium. The extent of shrinkage of cells during freezing can be duplicated by exposure of the cells to plasmolyzing solutions of nonpenetrating substances (Delta T(f) = 1.86 phivm). Solutions of sucrose and glycerol that produce extensive plasmolysis cause a decrease in survival within 3 to 5 minutes at room temperature, and the higher the molality to which the cell is exposed the greater the injury. Also, the rate of rehydration of the plasmolyzed cell and of the frozen cell affects its survival, with the slower rate being more beneficial. The close correlation between the decrease in survival at subzero temperatures and the decrease in survival when cells are placed in solutions having osmolalities, which could produce the same extent of shrinkage as these killing temperatures, suggests that this shrinkage is related to freezing injury in tissue culture cells.

Journal Article↗
PubMed1973

Visualization of freezing damage.

Freeze-cleaving can be used as a direct probe to examine the ultrastructural alterations of biological material due to freezing. We examined the thesis that at least two factors, which are oppositely dependent upon cooling velocity, determine the survival of cells subjected to freezing. According to this thesis, when cells are cooled at rates exceeding a critical velocity, a decrease in viability is caused by the presence of intracellular ice; but cells cooled at rates less than this critical velocity do not contain appreciable amounts of intracellular ice and are killed by prolonged exposure to a solution that is altered by the presence of ice. As a test of this hypothesis, we examined freeze-fractured replicas of the yeast Saccharomyces cerevisiae after suspensions had been cooled at rates ranging from 1.8 to 75,000 degrees C/min. Some of the frozen samples were cleaved and replicated immediately in order to minimize artifacts due to sample handling. Other samples were deeply etched or were rewarmed to -20 degrees C and recooled before replication. Yeast cells cooled at or above the rate necessary to preserve maximal viability ( approximately 7 degrees C/min) contained intracellular ice, whereas cells cooled below this rate showed no evidence of intracellular ice.

Cell Survival↗
PubMed1972

Survival of mouse embryos frozen to -196 degrees and -269 degrees C.

Mouse embryos survived freezing to -196 degrees C. Survival required slow cooling (0.3 degrees to 2 degrees C per minute) and slow warming (4 degrees to 25 degrees C per minute). Depending on the specific rates used, 50 to 70 percent of more than 2500 frozen and thawed early embryos developed into blastocysts in culture after storage at -196 degrees C for up to 8 days. When approximately 1000 of the survivors, including some frozen to -269 degrees C (4 degrees K), were transferred into foster mothers, 65 percent of the recipients became pregnant. More than 40 percent of the embryos in these pregnant mice gave rise to normal, living full-term fetuses or newborn mice.

Animals↗
PubMed1966

Effect of osmotic shock and low salt concentration on survival and density of bacteriophages T4B and T4Bo1.

Measurements of survival and buoyant densities of bacteriophages T4B, T4Bo(1), and T4D have demonstrated the following: (a) After suspension in a concentrated salt solution, T4B and T4D are sensitive both to osmotic shock and to subsequent exposure to low monovalent salt concentrations. (b) Sensitivity of T4B to dilution from a concentrated salt solution is dependent on dilution rate, that of T4D is less dependent, and that of T4Bo(1) is independent. (c) Sensitivity of all three phages to low salt concentrations depends on initial salt concentrations to a variable extent. (d) Density gradient profiles indicate that nearly half of osmotically shocked T4B retain their DNA. Similar analysis demonstrates that few, if any, T4Bo(1) lose DNA when subjected to a treatment causing 90% loss of infectivity. (e) The effective buoyant densities of T4B and T4Bo(1) depend significantly on the dilution treatments to which the phages are subjected prior to centrifugation in CsCl gradients. These data are explicable in terms of the different relative permeabilities of the phages to water and solutes, and of alterations in the counterion distribution surrounding the DNA within the phage heads.

Cesium↗