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Biomedical subjects

G P Raaphorst

Publications and source records attributed to G P Raaphorst.

At least 127 records · Page 7Linked to original sources
PubMed1981

The effect of hypo- and hypertonic NaCl solutions on cellular damage resulting from combined treatments of heat and X-rays.

The exposure of Chinese hamster V79 cells to 0.05 or 1.5 M NaCl immediately after combined treatment with heat and X-rays resulted in fixation of potentially lethal damage. The synergistic damage resulting from the interaction of heat and X-rays responded to anisotonic treatment like X-ray damage when heating was at 44.0 or 45.0 degrees C and like heat damage when heating was at 41.5 or 42.0 degrees C. When anisotonic treatment was given before heat plus X-ray exposure, sensitization occurred but the differences between heating at 42.0 and 45.0 degrees C were not as large. Incubation at 37 degrees C between heat and X-ray treatments or between X-ray and heat treatments resulted in recovery as manifested by a decrease in the fixation of damage by subsequent anisotonic treatment. Recovery was also observed when cells were incubated at 37 degrees C between the combined exposure to heat plus X-rays and the anisotonic treatment. These data imply that the lesions produced by heat plus X-ray treatments, which are susceptible to salt fixation, can be repaired.

Animals↗
PubMed1981

Nuclear magnetic resonance spin-lattice times of normal and transformed cultured mammalian cells and of normal and neoplastic animal tissues.

Proton spin-lattice relaxation times (T1) for normal tissues and cultured cells, and for neoplastic tissues and transformed culture cells, were measured. Increases in T1 of neoplastic tissue and normal tissues of mice with neoplasms were observed. No difference was found between T1 of normal 3T3 cells and of an SV40 viral transformed cell line. These data imply that changes in T1 of neoplastic tissue may not be due to intrinsic properties of cancerous cells but rather to physiological interaction of the neoplasm with its physiological environment. The measurement of several tissues of rat showed a good correlation between T1 and tissue water content, and addition of water by glass capillary increased T1 of samples. For samples in sealed NMR tubes, however, changes in T1 were incurred by boiling, freezing, or storage at various temperatures. These data imply that changes in T1 may be influenced by cellular water content as well as macromolecular conformation.

Adenocarcinoma↗
PubMed1979

Fixation of potentially lethal radiation damage by post-irradiation exposure of Chinese hamster cells to 0.5 M or 1.5 M NaCl solutions.

The effect of 0.05 M and 1.5 M NaCl treatments on CHO cells during and after irradiation has been examined. Treatment with either hypotonic or hypertonic salt solutions during and after irradiation resulted in the fixation of radiation damage which would otherwise not be expressed. The half time for fixation was 4 to 5 min, and the increased expression of the potentially lethal damage by anisotonic solutions was mainly characterized by large decreases in the shoulder of the survival curve, as well as by decreases in DO. Fixation of radiation damage at 37 degrees C occurred to a much greater extent for the hypertonic treatment than for the hypotonic treatment and was greater at 37 degrees C than at 20 degrees C. Although both the hypotonic and hypertonic treatments during and after irradiation reduced or eliminated the repair of sublethal and potentially lethal damage, treatment during irradiation only, radiosensitized the cells when the treatment was hypotonic, and radioprotected the cells when the treatment was hypertonic. These observations are discussed in relation to salt treatments and different temperatures altering competition between repair and fixation of potentially lethal lesions, the number of which depends on the particular salt treatment at the time of irradiation.

Animals↗
PubMed1979

The effects of various salt and sucrose solutions on the U.V.L. sensitivity of CHO cells.

The response of cultured CHO cells to U.V.L. irradiation during treatment with anisotonic solutions shows that treatment with hypotonic sucrose, NaCl or KCl solutions causes an increase in the cellular U.V.L. sensitivity, while exposure to hypertonic solutions causes a large decrease in U.V.L. sensitivity. Cells exposed to 1.8 M sucrose, NaCl or KCl solutions and given a U.V.L. dose of 252 erg/mm2 towards the end of the 20 min solution exposure time have survival levels which are respectively 228,26, and 23 times higher than the controls, i.e. cells irradiated in phosphate buffered saline. Cell volume data obtained using a Coulter counter, and nuclear area data of attached cells obtained using an optical microscope with a micrometer reticle, show that cell and nuclear size are related to U.V.L. sensitivity. That is, as cells shrink and the nuclear area decreases, the cells become more U.V.L.-resistant. During hypotonic treatment with 0.1 M NaCl, the cell volume, nuclear area and U.V.L. sensitivity increased in the first 2 to 4 min of exposure time, but at longer exposure times (greater than 3 to 4 min), cell volume, nuclear area and cellular U.V.L. sensitivity decreased. For 0.1 M KCl treatment the cells initially displayed a rapid increase in volume, nuclear area and U.V.L. sensitivity, but at the longer exposure times no decrease in cell and nuclear size were observed, and a slight increase in U.V.L. sensitivity occurred. Changes in U.V.L. sensitivity were related to changes in nuclear size and cell volume; however, calculations showed that during hypertonic treatment there is an ionic effect as well as an osmotic effect. That is, the cellular U.V.L. survival in equal hypertonic concentrations of NaCl or KCl was lower than in the same concentration of sucrose.

Animals↗