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M D Bick

Publications and source records attributed to M D Bick.

27 records · Page 2Linked to original sources
PubMed1973

Bromodeoxyuridine dependence--a new mutation in mammalian cells.

When cells of a Syrian hamster melanoma were grown in increasing concentrations of bromodeoxyuridine (BrdU), lines of mutant cells able to grow well at high concentrations of BrdU were isolated. The mutant cells were characterized by BrdU dependence. In the absence of BrdU, the cells grew very poorly. The requirement for BrdU was specific for both the bromine and the deoxy sugar. The mutant cells incorporated BrdU into the DNA, replacing about 50% of the thymine residues with bromouracil. The reason for the BrdU dependence is not known.

Aminopterin↗
PubMed1973

Molecular nature of mammalian cell DNA in alkaline sucrose gradients.

Mammalian cell DNA that exhibited anomalous sedimentation in alkaline sucrose gradients was examined directly by electron microscopy. Its appearance was that of duplex DNA. In addition, some duplex DNA was observed under conditions in which the sedimentation anomaly was no longer apparent. Persistence of double-stranded DNA under denaturing conditions suggests caution in the interpretation of changes in the molecular weight or conformation of DNA based solely on analysis of sedimentation profiles.

Animals↗
PubMed1971

Leucyl transfer RNA synthetase changes during soybean cotyledon senescence.

Previous work has shown the complement of leucyl transfer RNA (tRNA(Leu)) isoaccepting species present in soybean cotyledons to change during cotyledon senescence. Of the six tRNA(Leu) species resolved by Freon-column chromatography, the capacity of species 1-4 to accept leucine is decreased between 5 and 21 days of age. Parallel changes in tRNA(Leu) synthetase activity are reported here during the same time period. There is a reduction in the capacity of the synthetase from 21-day-old cotyledons to aminoacylate tRNA(Leu) 1-4, while the capacity to charge tRNA(Leu) 5-6 remains high. When tRNA(Leu) derived from 5-day-old cotyledons is maximally charged with the 21-day synthetase, the subsequent addition of synthetase from 5-day-old cotyledons promotes additional charging, primarily of species 1-4. These results suggest the presence of tRNA(Leu) "subspecies" within the individual peaks resolved on a Freon column, differing in synthetase specificity.

Carbon Isotopes↗
PubMedDate not supplied

Age-related changes in a spontaneously reassociating fraction of mouse DNA.

Rapidly reassociating fractions have been isolated from mouse brain and liver nuclear DNA by hydroxyapatite fractionation of sonicated and denatured preparations incubated at a Cot of 1. When prepared by thermal denaturation, a subfraction of this DNA, representing approximately 0.6% of liver and brain DNA, has been shown to spontaneously reassociate at Cot 10(-5). This fraction increases 3-fold in DNA from old animals. When prepared by alkaline denaturation or treated with pronase, no age-related increase is observed, suggesting the presence of an alkali-labile stabilizing protein component in DNA from old cells. A portion of this fraction is observed by electron microscopy under denaturing conditions to consists of looped hairpin structures in DNA from old, but not from yound or mature animals. These structures are not seen after pronase treatment.

Aging↗