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Biomedical subjects

R S Criddle

Publications and source records attributed to R S Criddle.

At least 55 records · Page 3Linked to original sources
PubMed1976

Factors affecting petite induction and the recovery of respiratory competence in yeast cells exposed to ethidium bromide.

When growing cultures of S. cerevisiae are treated with high concentrations of ethidium bromide (greater than 50 mug/ml), three phases of petite induction may be observed: I. the majority of cells are rapidly converted to petite, II. subsequently a large proportion of cells recover the ability to form respiratory competent clones, and III. slow, irreversible conversion of all cells to petite. The extent of recovery of respiratory competence observed is dependent on the strain of S. cerevisiae employed and the temperature and the carbon source used in the growth medium. The effects of 100 mug/ml ethidium bromide are also produced by 10 mug/ml ethidium bromide in the presence of the detergent, sodium dodecyl sulphate, and recovery is also observed when cells are treated with 10 mug/ml ethidium bromide under starvation conditions. Genetic analysis of strain differences indicates that a number of nuclear genes influence petite induction by ethidium bromide. In one strain, S288C, petite induction by 100 mug/ml ethidium bromide is extremely slow under certain conditions. Mitochondria isolated from from S288C lack the ethidium bromide stimulated nuclease activity found in D243-4A, a strain which shows triphasic kinetics of petite formation. This enzyme may, therefore, be responsible for the initial phase of rapid petite formation.

Acriflavine↗
PubMed1976

Molecular and genetic events accompanying petite induction and recovery of respiratory competence induced by ethidium bromide.

The treatment of yeast cells with high levels of ethidium bromide causes a rapid induction of respiratory deficient mutants followed by a period of recovery to respiratory competence in 60 to 70% of the cells. Prolonged exposure then results in a final irreversible phase of petite formation. Sucrose gradient sedimentation analysis of 3H-adenine labelled mtDNA indicates that limited fragmentation (to about 16-18S) occurs during the initial phase of petite induction followed by a reassembly of the fragments during the period corresponding to the recovery of respiratory competence. The reassembly is associated with an ethidium bromide insensitive incorporation of 3H-adenine into mtDNA at a level consistent with repair synthesis. Genetic analyses, based on the transmission of five markers carried on the mtDNA of "repaired rho+" clones, suggests that reassembly occurs with a high degree of fidelity, though in two of a total of twenty five clones differences in marker transmission frequency were observed which could possibly reflect an altered gene order. In addition, a description is given of the marked changes in the suppressive nature of the treated cells and the temporary reduction in the capacity for marker transmission seen to accompany the transitory fragmentation of the mtDNA. The final phase of petite induction is an energy dependent degradation of the mtDNA to produce a rho degrees culture.

Adenine↗
PubMed1973

Characterization of deoxyribonucleic Acid species from castor bean endosperm: inability to detect a unique deoxyribonucleic Acid species associated with glyoxysomes.

Three DNA buoyant density species (nuclear, 1.692 g cm(-3); mitochondria 1.705 g cm(-3); and proplastid, 1.713 g cm(-3)) can be detected in extracts from castor bean endosperm. No other buoyant density species can be identified. DNA extracts from sucrose density gradient purified glyoxysomes exhibit varying amounts of each of the three identified DNAs but no other distinguishable DNA species. RNA synthesized in vitro by Escherichia coli RNA polymerase using purified castor bean nuclear DNA as a template, hybridizes equally well with its template and with the 1.692 g cm(-3) species from glyoxysome fractions. These results are discussed in terms of their relevance to microbody biogenesis.

Journal Article↗
PubMed1971

DNA-dependent RNA polymerase from yeast mitochondria.

The DNA-dependent RNA polymerase present in the mitochondria of Saccharomyces cerevisiae has been solubilized using a 0.5 M KCI solution, and the soluble enzyme has been purified. Two forms of mitochondrial enzyme were obtained; they differ in their template specificity and metal-ion dependency. The mitochondrial RNA polymerase also differs from enzyme obtained from the nucleus with respect to antibiotic sensitivity and template specificity. Only the nuclear enzyme is sensitive to alpha-amanitin inhibition. The relative activities of the isolated nuclear and mitochondrial polymerases toward their homologous DNAs are consistent with their in vivo functions. The possibilities of bacterial- and nuclear-enzyme contamination of the mitochondrial enzyme preparation have been ruled out. RNA polymerase activity in two petite mutants has been studied. Isolated mitochondria from a petite mutant with no detectable mitochondrial DNA has greatly diminished mitochondrial DNA-dependent RNA polymerase activity, while a petite mutant with only a small change in mitochondrial DNA base composition has normal amounts of enzyme.

Anti-Bacterial Agents↗