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L J Grady

Publications and source records attributed to L J Grady.

32 records · Page 2Linked to original sources
PubMed1977

Polyoma genome transcription in transformed mouse cells growing in culture and as tumors in syngeneic mice.

The strands of the polyoma genome coding for early and late viral RNA were separated by means of asymmetric cRNA synthesized under high salt conditions by Escherichia coli RNA polymerase. Each strand was then employed in RNA-DNA hybridization experiments to determine the degree to which it is transcribed in transformed cells under several conditions. Except for a concanavalin-A-selected revertant, approximately one-quarter of the early strand was expressed in all of the situations investigated. In contrast, while no significant late strand transcription was detected in transformed cells in culture, the tumors induced by these cells contained transcripts complementary to about 12% of this strand. The results are discussed in terms of current knowledge of the amount of the virus genome required to transform cells.

Animals↗
PubMed1977

Transcriptional complexity of vaccinia virus in vivo and in vitro.

The transcriptional complexity of vaccinia virus both in vivo and in vitro has been measured by using DNA:RNA hybridization with RNA in excess. In vivo, "early" or prereplicative RNA was found to saturate at 25% or one-half of the viral genome. "Late" or postreplicative RNA from infected HeLa cells saturated at 52% or essentially the entire genome. This well-regulated transcriptional pattern of the virus in vivo was not maintained in vitro. In a number of experiments a range of saturation values from 40 to 50% was obtained for in vitro synthesized RNA. The complexity of polyadenylated and non-polyadenylated RNA, as well as total purified 8 to 12S RNA released from the virus, was indistinguishable from purified high-molecular-weight virion-associated RNA with a sedimentation value of greater than 20S and equivalent to total in vitro synthesized RNA. No additional hybrid formation was observed in experiments in which total in vitro RNA and late in vivo RNA from infected HeLa cells were combined, suggesting that the virus does not transcribe in vitro DNA sequences that are not also transcribed during productive infection. Approximately 15% complementary RNA was detected when radiolabeled total in vitro RNA was allowed to reanneal with late in vivo RNA, while as much as 8% of the in vitro synthesized RNA was found to be complementary.

Cell-Free System↗
PubMed1976

Differences in transcription between transformed mouse cells in culture and the tumors that they produce in syngeneic mice.

RNA-DNA saturation hybridization experiments were used to determine the degree to which cellular DNA sequences are transcribed in cultured mouse cells transformed by polyoma virus and in tumors that develop after injection of these cells into syngeneic mice. A general, overall reduction in the proportion of the genome transcribed was found in tumors compared to the proportion in cultured transformed cells. When explants of the tumor cells were grown in culture, the level of transcription of both repetitive and nonrepetitive DNA returned to that observed in the original transformed cells.

Animals↗
PubMed1975

Transcription of the repetitive DNA sequences in polyoma-transformed and nontransformed mouse cells in culture.

RNA-DNA saturation hybridization experiments were used to estimate the extent of transcription of repetitive DNA sequences in polyoma-transformed and nontransformed mouse cells in culture. Measurements were made with RNA from nontransformed cells in both the subconfluent and confluent stages of growth, transformed cells in normal growth medium, and transformed cells grown in medium containing 5-bromodeoxyuridine, 3 mu-g/ml, a treatment which reduces their tumorigenic potential. No differences were observed in the amount of repetitive DNA transcribed or in the families of sequences expressed, except in transformed cells grown in the presence of 5-bromodeoxyuridine, in which case the extent of transcription was reduced.

Animals↗
PubMed1971

Deoxyribonucleic acid hybridization analysis of the defective bacteriophage carried by strain 15 of Escherichia coli.

Evidence from several laboratories indicates that strain 15 of Escherichia coli is lysogenic for a defective phage. When lysates from induced cultures were centrifuged in CsCl, three bands were obtained. In order of decreasing density, these bands contained tailless particles, complete phages, and a second band of complete phages, in a ratio of 65.7:28.6:5.7. Reassociation rate measurements were used to establish that the molecular weights of the deoxyribonucleic acid (DNA) species from the phages in the first two bands are similar. A smaller genome is postulated in the complete phages from the minor band. Hybridization experiments revealed extensive homology between the DNA species from all three phage bands, thus suggesting that the complete and tailless particles are not different at the genetic level. The DNA from each phage band was also shown to hybridize almost completely with DNA from either E. coli 15T(-) or a reportedly cured derivative of 15T(-). In contrast, only about 25% of each phage DNA was able to react with DNA from E. coli strains B and K-12 C-600.

Base Sequence↗
PubMed1967

CsCl density gradient centrifugation studies of intact bacterial cells.

Cells of Escherichia coli have been successfully banded in CsCl density gradients and a portion of the population reclaimed in a viable state. Differentiation between two strains of this organism in a CsCl density gradient has been demonstrated also. Several studies were undertaken to see whether differences could be detected between two samples of cells of the same strain which had been subjected to different conditions. The results were as follows: (a) Introduction of a heavy label (5-bromouracil) into the DNA during a 90 minute period did not produce an observable change in cell density. (b) Removal of a required amino acid from the growth medium of an E. coli auxotroph resulted in an increase in both the density and heterogeneity of the cells. (c) Exposure of cells to 27 kr of gamma radiation, followed by a period during which portions of both DNA and RNA were lost, yielded two distinct bands, one at the normal position in the gradient and the other shifted to a lighter region.

Carbon Isotopes↗