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R W Davis

Publications and source records attributed to R W Davis.

283 records · Page 16Linked to original sources
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The use of proline as a nitrogen source causes hypersensitivity to, and allows more economical use of 5FOA in Saccharomyces cerevisiae.

The use of proline as a nitrogen source causes hypersensitivity to 5-fluoro-orotic acid (5FOA) and allows up to 40-fold less of this drug to be used to select for the loss of URA3 function in Saccharomyces cerevisiae. 5FOA hypersensitivity is presumably due to the absence of nitrogen catabolite repression when proline is substituted for (NH4)2SO4 as a nitrogen source. There are two constraints to the use of the proline-5FOA combination: (1) S288c genetic background strains are hypersensitive to 5FOA when grown in proline as a nitrogen source but at least one other genetic background is resistant to low levels of 5FOA under these conditions. (2) The addition of some nutritional supplements confers phenotypic resistance to the 5FOA-proline combination.

Culture Media↗
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Genes for the major protein antigens of the leprosy parasite Mycobacterium leprae.

Leprosy, a chronic infectious disease afflicting between 10 and 15 million people, is caused by the obligate intracellular parasite Mycobacterium leprae. Although M. leprae was the first identified bacterial pathogen of man, basic biochemical, immunological, diagnostic and therapeutic investigations have been severely limited because it remains one of the few human pathogens that have not been cultured in vitro. An M. leprae recombinant DNA expression library was constructed to provide a source of genes encoding proteins relevant for such studies. Monoclonal antibodies directed against M. leprae specific antigens have been used to isolate the genes encoding the five most immunogenic protein antigens of the leprosy bacillus. We report here that M. leprae specific epitopes recognized by all of 13 monoclonal antibodies tested were produced by recombinant phage in Escherichia coli.

Antibodies, Monoclonal↗
PubMedDate not supplied

Bent DNA at a yeast autonomously replicating sequence.

DNA fragments that show retarded electrophoretic mobility through polyacrylamide gels have been found in both prokaryotes and eukaryotes. In the case of kinetoplast DNA, evidence has been presented that the DNA is curved or 'bent'. Bent DNA has previously been found at the lambda and simian virus 40 (SV40) DNA replication origins. Here we show the existence of bent DNA at a yeast autonomously replicating sequence (ARS1), a putative replication origin. The bent DNA has been localized to a 40-55 base pair (bp) segment and contains six (A)3-5 stretches (that is, six poly(A) stretches, three to five nucleotides in length) phased approximately every 10.5 bp. This region contains a DNA binding site for a yeast protein factor. This site lies at the 3' end of the TRP1 gene, in a region devoid of nucleosomes, and is positioned 80 bp away from the ARS consensus sequence; removal of this region impairs ARS function in vivo. The bent DNA may be involved in transcription termination or the prevention of nucleosome assembly in this region.

Base Sequence↗
PubMedDate not supplied

Bioelectric potentials associated with the growing deer antler.

Bioelectric potentials associated with the developing deer antler throughout its growth cycle can be correlated with the rate of longitudinal bone growth. Electrodes were connected to a high input impediance microvoltmeter, and potentials on the surface of antlers of mature deer were measured during the antler growth cycle. The reference electrode was placed at the base of the antler, while the recording electrode was placed at the antler tip or along the antler shaft. Antler length measurements were made during the growth cycle and longitudinal growth rates were determined. Growth rates and bioelectric potentials were compared for three specified periods during the antler growth cycle. The most negative potential was recorded from the antler tip. Furthermore, electronegativity increased as the rate of growth in length increased and decreased as the rate of growth in length decreased. The potentials reached isopolarity at the end of antler growth.

Action Potentials↗