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Biomedical subjects

O L Miller

Publications and source records attributed to O L Miller.

At least 55 records · Page 3Linked to original sources
PubMed1977

Visualization of ribosomal ribonucleic acid synthesis in a ribonuclease III-Deficient strain of Escherichia coli.

Transmission electron microscopy was used to examine active ribosomal ribonucleic acid (rRNA) genes in two strains of Escherichia coli: N2077, deficient in the enzyme responsible for proper cleavage of the 16S sequence from the elongating nascent rRNA transcript; and N2076, functional in ribonuclease (RNase) III activity, yet otherwise isogenic to N2077. In the strain with wild-type RNase III, double gradients corresponding to a pattern of 16S-cleavage-23S transcription were observed. However, the RNase III-deficient strain exhibited a single ribosomal gradient of approximately the same length as the combined 16S-23S gradients of the wild-type strain. When the rRNA genes were somewhat loosely packed with RNA polymerases, a few of the nascent chains in the ribosomal matrixes of the RNase III-deficient strain were cleaved, but most appeared to be unprocessed. The completed, uncleaved transcripts originating from these gradients are believed to be 30S rRNA molecules recently characterized by biochemical probes.

DNA-Directed RNA Polymerases↗
PubMed1976

Ultrastructural patterns of RNA synthesis during early embryogenesis of Drosophila melanogaster.

Chromatin was obtained from Drosophila melanogaster during early embryogenesis and examined by transmission electron microscopy. Nuclear contents spread at progressive stages of syncytial development show a low level of only non-nuclear template activity, and very few RNP fibril gradients extending over 2mum in length are observed. At the cellular blastoderm stage, newly activated nucleolar genes appear during the early portion of the first true cell cycle. Variation in the lengths of incomplete rRNP gradients indicates that the activation of each rRNA gene is independently controlled. All rRNA loci, whether having complete or incomplete gradients, exhibit high densities of nascent transcripts per unit length, suggesting that the rate of chromatin transcription, rather than the RNA polymarase I pool size, limits rRNA synthesis on individual genes. No more than half the rRNA genes are derepressed at this stage indicating that total rRNA synthesis is regulated by the number of genes activated. Non-nucleolar RNP fibril gradients covering up to 8 mum of genome are also first observed at the cellular blastoderm stage. Most of these gradients are differentiated from the short gradient first seen during syncytial growth by a lower density of transcribing RNA polymerases.

Animals↗
PubMed1970

Visualization of bacterial genes in action.

The morphology of active structural and putative ribosomal RNA genes was observed by electron microscopy after lysis of fragile Escherichia coli cells. Conclusions drawn are: most of the chromosome is not genetically active at any one instant; translation is completely coupled with transcription; the 16S and 23S ribosomal RNA cistrons occur in tandem, in regions which are widely spaced on the chromosome.

Chromosomes, Bacterial↗
PubMed1970

Reinforcing self-help group activities of welfare recipients.

The attendance rates of welfare recipients at self-help group meetings was compared when supplementary reinforcement was given for attending and when it was not. Reinforcers included donated items, such as clothing and household goods, and information about welfare services. It was found that the attendance at meetings averaged three recipients per meeting without reinforcement and 15 recipients per meeting with reinforcement. There was evidence that attendance was associated with participation in other self-help activities. It was concluded that practical forms of reinforcement can be found to maintain the participation of severely disadvantaged populations in self-help groups.

Journal Article↗
PubMed1969

Visualization of nucleolar genes.

The presence of extrachromosomal nucleoli in amphibian oocytes has permitted isolation and electron microscopic observation of the genes coding for ribosomal RNA precursor molecules. Visualization of these genes is possible because many precursor molecules are simultaneously synthesized on each gene. Individual genes are separated by stretches of DNA that apparently are not transcribed at the time of synthesis of precursor rRNA in the extrachromosomal nucleoli.

Amphibians↗