THE EFFECTS OF FAR ULTRAVIOLET RADIATION ON RESPIRATION AND CATION ACCUMULATION BY ISOLATED MITOCHONDRIA OF PHASEOLUS VULGARIS

Functions of maternal mRNA as a cytoplasmic factor responsible for pole cell formation in Drosophila embryos

Injection of mRNA extracted from Drosophila cleavage embryos or mature oocytes restored pole cell-forming ability to embryos that had been deprived of this ability by uv irradiation. However, mRNA extracted from blastoderms did not show the restoration activity. Pole cells thus formed in uv-irradiated embryos bear similarities to normal pole cells both in their morphology and their ability to migrate to the gonadal rudiments. But this mRNA does not appear to be capable of rescuing uv-induced sterility, or inducing pole cells in the anterior polar region.

Cellular inactivation and mitotic recombination induced by ultraviolet radiation in aneuploid and euploid strains of Candida albicans

Prototrophic aneuploid and euploid derivatives of wild type Candida albicans strains 207 were produced by fusing protoplasts of complementing auxotrophs obtained from strain 207. Comparisons of cell survivals and incidences of mitotic recombinants occurring after ultraviolet irradiation (UV) of these strains indicate that (i) aneuploids are categorically less efficient than euploids for repair of pyrimidine dimers induced in DNA by UV and that (ii) such repair is enhanced by growing irradiated cells at 25 degrees C, on minimal medium or in the presence of ergosterol rather than at 37 degrees C, on amino acid enriched medium or medium unsupplemented with ergosterol. In addition, the comparisons establish than one cannot discriminate between strains of C. albicans which differ in cellular DNA contents or genomic constitutions on the basis of their UV survival curves.

Effect of gamma-radiation on the structure and function of yeast membrane

A decrease in the influx of several amino acids was observed following gamma-irradiation. At low dose (2.5 Gy), which does not affect cell survival, a stimulation in the uptake was visible; moreover, sulphydryl loss and lipid peroxidation were also evident. With further increase in the dose of radiation, a parallel increment in the loss of sulphydryl groups and production of malonaldehyde was observed. Radioprotectors like L-cysteine and dithiothreitol were shown to shield the radiation-induced loss of sulphydryl and damage to transport and survival. Reduced glutathione, on the other hand, exhibited protection at the level of sulphydryl damage only. N-ethylmaleimide, a well known hypoxic cell radiosensitizer, enhanced the radiosensitivity with respect to survival; it, however, had no effect on amino acid transport. Oxygen enhancement of radiation damage to transport and cell survival and the radioprotection by sodium formate under these circumstances, and more so by anoxia, were demonstrated. The results indicate that the manifestation of damage to membrane structure and function precedes any observable loss of survival.

Porphyrin-sensitized photodynamic damage of isolated rat liver mitochondria

The respiration rates and the respiratory control ratios of isolated rat liver mitochondria have been measured following exposure to 0--160 kJ/m2 of near-ultraviolet radiation (blacklight) in the presence of low concentrations of porphyrins (0.1--0.2 mumol/l). Depending on the light dose, the concentration and the type of porphyrin, the following sequence of reactions occurred: uncoupling and inhibition of oxidative phosphorylation, energy dissipation, inhibition of respiration and swelling and disruption of the mitochondria. The detrimental effects could not be elicited in the absence of oxygen, neither could they be elicited by porphyrins or light alone. At equimolar concentrations, the effectiveness of the porphyrins as photosensitizers were: deuteroporphyrin greater than protoporphyrin much greater than coproporphyrin greater than uroporphyrin. The results may be of importance to explain the skin lesions seen when porphyrins of different hydrophobicity accumulate in the skin.