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Biomedical subjects

R W Davis

Publications and source records attributed to R W Davis.

At least 181 records · Page 10Linked to original sources
PubMed1985

Assessing offenders: dying for reprieve.

As is true for those who face death, the trauma of arrest and conviction for a crime and subsequent imprisonment takes the individual through a series of psychological stages, In the offender, these defenses are to some extent prescribed by the culture. The nature of and the person's adaptation to this process has not been previously recognized and argues for an assessment approach that emphasizes developmental rather than static formulations. Examination and treatment implications are discussed.

Journal Article↗
PubMed1984

Deletion of plasmid sequences during Saccharomyces cerevisiae transformation.

Saccharomyces cerevisiae was transformed with DNA by the lithium acetate method. Mutation of nonselected markers on the transforming vector was observed at a frequency several orders of magnitude higher than spontaneous mutation frequencies. These mutations were shown to be deletions. Linearization of the vector before transformation stimulated deletion formation.

Base Sequence↗
PubMed1984

Sequences that regulate the divergent GAL1-GAL10 promoter in Saccharomyces cerevisiae.

The GAL1 and GAL10 genes of Saccharomyces cerevisiae are divergently transcribed, with 606 base pairs of DNA separating their transcription initiation sites. These two genes are stringently coregulated: their expression is induced ca. 1,000-fold in cells growing on galactose and is repressed by growth on glucose. The nucleotide sequence of the region of DNA between these genes and the precise sites of transcription initiation are presented here. The most notable feature of the nucleotide sequence of this region is a 108-base-pair guanine-plus-cytosine-rich stretch of DNA located approximately in the middle of the region between GAL1 and GAL10. Analysis of the effects of mutations that alter the region between these two genes, constructed in vitro or selected in vivo, suggest that these guanine-plus-cytosine-rich sequences are required for the expression of both genes. The region of DNA between GAL1 and GAL10 is sufficient for regulation of expression of these genes: fusion of the region to the yeast HIS3 gene places HIS3 under GAL control.

Base Sequence↗
PubMed1983

Yeast RNA polymerase II genes: isolation with antibody probes.

Genes encoding yeast RNA polymerase II subunits were cloned. Efficient isolation of these genes was accomplished by probing a phage lambda gt11 recombinant DNA expression library with polyvalent antibodies directed against purified yeast RNA polymerase II. The identity of genes that specify the largest RNA polymerase II subunits, the 220,000- and 150,000-dalton polypeptides, was confirmed by competitive radioimmune assay. Both of these genes exist in single copy in the yeast Saccharomyces cerevisiae.

Cloning, Molecular↗
PubMed1983

Instability of dicentric plasmids in yeast.

Dicentric plasmids containing either two copies of centromere 4 or one copy of centromere 4 and one copy of centromere 3 in the yeast plasmid vector YRp17 were constructed in vitro and introduced into yeast cells by DNA transformation. The resulting colonies were heterogeneous for a mixed population of rearranged plasmids. The rearrangements always involved deletion of one or both centromere sequences originally present on the plasmid. Heterogeneity was due to the continued production of deleted plasmids from a pool of unrearranged dicentric plasmids maintained within some of the yeast cells in the colony. The RAD52 gene product is known to be required for the repair of DNA double-strand breaks in yeast. Transformation of rad52 mutant yeast cells with dicentric plasmids gave rearranged plasmids similar to those observed with RAD+ yeast cells, but the transformation frequency was only 5-10% compared to transformation with monocentric plasmids. Also, the ratio of unrearranged dicentric plasmid to deleted plasmids was greatly reduced in the rad52-transformed cells. These observations are consistent with a model in which centromeric DNA sequences can interact independently with the yeast cell spindle apparatus. Occasional movement of centromeres to opposite poles may result in mechanical breakage of plasmid sequences. Plasmids deleted for one or both centromere sequences can be obtained from these broken molecules and are resistant to further rearrangement.

Centromere↗
PubMed1983

Targeted selection of recombinant clones through gene dosage effects.

The availability of multicopy plasmid vectors for the yeast Saccharomyces cerevisiae allows the selective amplification of individual segments of the genome. Increased dosage of particular genes results in overproduction of specific gene products and thereby confers resistance to certain metabolic inhibitors. Advantage was taken of this fact to isolate recombinant clones that increase the activities of the enzymes UDP-N-acetylglucosamine-1-P transferase and 3-hydroxy-3-methylglutaryl-CoA reductase.

Cloning, Molecular↗
PubMed1983

Efficient isolation of genes by using antibody probes.

A sensitive and general technique has been devised for the dual purposes of cloning genes by using antibodies as probes and isolating unknown proteins encoded by cloned DNA. The method uses an expression vector, lambda gt11 (lac5 nin5 cI857 S100), that permits insertion of foreign DNA into the beta-galactosidase structural gene lacZ and promotes synthesis of hybrid proteins. Efficient screening of antigen-producing clones in lambda gt11 recombinant cDNA libraries is achieved through lysogeny of the phage library in hflA (high-frequency lysogeny) mutant cells of Escherichia coli; lysogens produce detectable quantities of antigen on induction, even when plated at high cell densities. The vector is also designed to facilitate the isolation of proteins specified by previously cloned gene sequences. Hybrid proteins encoded by recombinant phage accumulate in strains defective in protein degradation (lon mutants) in amounts amenable to large-scale purification. Antibodies produced against the portion of the hybrid encoded by foreign DNA could in turn be used to isolate the native polypeptide from eukaryotic cells.

Animals↗
PubMed1983

RNA from the yeast transposable element Ty1 has both ends in the direct repeats, a structure similar to retrovirus RNA.

The RNA homologous to the yeast transposable element Ty1 is one of the more abundant poly(A)+ RNAs in many strains of the yeast Saccharomyces cerevisiae. The 5' and 3' ends of Ty1 RNA have been determined from analysis of cDNA. The 5' end is 245 bases into the left delta sequence measured from the left side of the Ty1 element. The delta sequence is a direct repeat of about 340 base pairs present at each end of the Ty1 element. The Ty1 transcription includes 93-97 bases of the left delta sequence and continues through the entire internal portion of the element and through about 295 bases of the right delta sequence before reaching the 3' end located 38-46 bases from the right side of the right delta sequence. Because the delta sequences present at each end of a single Ty1 element have identical or very similar DNA sequences, these end points for Ty1 RNA raise several questions about the expression of Ty1 elements. First, what are the initiation and termination signals, because the Ty1 transcript must read through a DNA sequence that is identical to the 3' end at about 50 bases from the 5' end? Second, why is the direction of transcription of the Ty1 element opposite to that of genes that are overexpressed after the insertion of a Ty1 element? Third, because the Ty1 RNA itself has direct repeats of about 45 bases, a structure analogous to retrovirus RNAs, is the Ty1 RNA an intermediate in the transposition of Ty1?

Base Sequence↗
PubMed1983

Renal glomerular filtration rate and hepatic blood flow during voluntary diving in Weddell seals.

Renal and hepatic function were studied during voluntary dives in Weddell seals by measuring the clearance rate of inulin and indocyanine green (ICG). Inulin is cleared exclusively by the kidneys and measures renal glomerular filtration rate (GFR). ICG is cleared by the liver and is blood flow dependent at concentrations used. Studies were conducted from a portable hut with a trapdoor placed over an isolated hole in the sea ice near McMurdo Station, Antarctica. An intravertebral extradural catheter was inserted percutaneously under light anesthesia in subadult seals weighing 130-200 kg. When released into the ice hole, the seals made voluntary dives, but always had to return to breathe. Serial blood samples were taken after single injections of inulin and ICG and analyzed within 24 h. The mean half time (t 1/2) for inulin clearance while resting at the surface was 27.3 +/- 13.0 min (n = 43) and the mean t 1/2 for ICG clearance was 18.3 +/- 7.3 min (n = 23). The mean resting GFR was 3.6 ml X min-1 X kg-1 (range 3.2-3.9, n = 3). Inulin and ICG clearance rates did not change from resting levels during dives shorter than the seal's aerobic dive limit (ADL). Inulin clearance decreased over 90% during dives longer than the ADL, but there was no significant reduction in ICG clearance during dives lasting up to 23 min. It appears that normal renal GFR and hepatic blood flow continue during natural aerobic dives. During dives that exceed the ADL, GFR is reduced but hepatic blood flow may be maintained.

Animals↗
PubMed1982

Reversion of a promoter deletion in yeast.

Promoter function in yeast has been examined by obtaining revertants of a his3 promoter deletion in vivo. Events which provide a new promoter for the his3 gene include insertion of the transposable element Ty1, rearrangements of the plasmid vector, and chromosomal mutations. A role for dicentric chromosomes as a source of the plasmid rearrangements is discussed.

Base Sequence↗
PubMed1982

Diving depths and energy requirements of king penguins.

During 4- to 8-day periods at sea, half of 2595 dives of three king penguins were more than 50 meters and two dives exceeded 240 meters. The at-sea metabolic rate, estimated from the turnover of tritiated water, was 2.8 times the standard metabolic rate and requires about 2.5 kilograms of squid per day. Ten percent or less of the dives may result in prey capture.

Animals↗
PubMed1982

CPR with simultaneous compression and ventilation at high airway pressure in 4 animal models.

CPR with simultaneous chest compression and ventilation at high airway pressure (SCV-CPR) improves blood flow in some studies but not in others, perhaps because of differences in the animal models employed. To resolve such discrepancies, we compared SCV-CPR to standard CPR in 4 mechanically different canine models, using both small and large dogs and small and large compression pads. The 4 groups were: large dogs receiving chest compression through a large pad (model A), large dogs receiving chest compression through a small pad (model B), small dogs receiving chest compression through a large pad (model C), and small dogs receiving chest compression through a small pad (model D). Cardiac output (CO) during CPR was determined by a specially modified indicator dilution method. Models A, B, and C all had similar mean COs of 14 ml/min . kg body weight during standard CPR, and 27 ml/min . kg during SCV-CPR. However, in model D, there was no significant difference during standard vs. SCV-CPR, and the mean output was 33 ml/min . kg. We conclude that in models A, B, and C, little direct heart compression occurred and the higher intrathoracic pressure pulses produced by SCV-CPR improved blood flow. However it seems likely that there was effective cardiac compression in model D. In the absence of direct cardiac compression, SCV-CPR provides an alternative means of generating satisfactory flow in a mechanically appropriate animal model.

Animals↗