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S M Parkhurst

Publications and source records attributed to S M Parkhurst.

28 records · Page 2Linked to original sources
PubMed1988

The Drosophila su(Hw) gene, which controls the phenotypic effect of the gypsy transposable element, encodes a putative DNA-binding protein.

Homozygous mutations at the suppressor of Hairy-wing [su(Hw)] locus reverse the phenotype of gypsy-induced alleles in a number of genes located throughout the Drosophila genome. To understand the molecular basis of this phenomenon, the su(Hw) locus was isolated by chromosomal walking from a cloned homeo-box-containing sequence. The exact location of the gene was determined by Southern analysis of the DNA alterations associated with several su(Hw) alleles. A 9.5-kb KpnI-SalI fragment, where all the DNA changes associated with su(Hw) mutations were mapped, was able to rescue the su(Hw) mutant phenotype after P-element-mediated germ-line transformation. This DNA fragment encodes a 3.3-kb RNA that is expressed in all stages of Drosophila development; the size or abundance of this RNA is affected in several su(Hw) alleles tested. This transcript encodes a protein that contains a highly acidic region and 12 repeats of the 'Zn finger' domain characteristic of some DNA-binding and transcription-activating proteins, supporting the hypothesis that the su(Hw) locus might encode a transcription factor that plays a role in the expression of the gypsy element.

Alleles↗
PubMed1987

Developmental expression of Drosophila melanogaster retrovirus-like transposable elements.

We have determined the pattern of temporal expression of several Drosophila retrovirus-like transposable elements. Some of these elements can be grouped into classes whose members show a similar profile of developmental transcription. The members of the 412 class, which includes 412, mdg1, 17.6 and 3S18, are transcribed mainly in the early larval and pupal stages of development, with small differences among the various members. HMS Beagle and Springer constitute another class where RNA accumulation in the larval stages is higher than in pupae and the adult flies accumulate more RNA than any other stage of development. Finally, the transcription of other elements such as copia, 297 and B104 follows a specific and individual pattern distinct from those described above. These results suggest the existence of evolutionary relationships among different transposable elements in Drosophila and the involvement of different cellular genes in the control of their expression.

Animals↗
PubMed1986

Interactions among the gypsy transposable element and the yellow and the suppressor of hairy-wing loci in Drosophila melanogaster.

We cloned and characterized the yellow locus of Drosophila melanogaster. We also studied its transcription pattern in the suppressible allele y2, which is caused by the insertion of the transposable element gypsy, and the effect of mutations at the unlinked suppressor of Hairy-wing locus on the transcription of yellow RNAs. The gypsy element is transcribed in a temporal fashion that correlates with the pattern of expression of the yellow locus. We propose that the mutational effect of the gypsy element is due to developmentally specific transcriptional interference on yellow transcription. Mutations at the su(Hw) locus reverse this effect by altering the quantitative expression of gypsy.

Animals↗
PubMed1986

The Drosophila melanogaster gypsy transposable element encodes putative gene products homologous to retroviral proteins.

We determined the complete nucleotide sequence of the gypsy element present at the forked locus of Drosophila melanogaster in the f1 allele. The gypsy element shares more homology with vertebrate retroviruses than with the copia element of D. melanogaster or the Ty element of Saccharomyces cerevisiae, both in overall organization and at the DNA sequence level. This transposable element is 7,469 base pairs long and encodes three putative protein products. The long terminal repeats are 482 nucleotides long and contain transcription initiation and termination signals; sequences homologous to the polypurine tract and tRNA primer binding site of retroviruses are located adjacent to the long terminal repeats. The central region of the element contains three different open reading frames. The second one encodes a putative protein which shows extensive amino acid homology to retroviral proteins, including gag-specific protease, reverse transcriptase, and DNA endonuclease.

Amino Acid Sequence↗
PubMed1986

Mutations at the suppressor of forked locus increase the accumulation of gypsy-encoded transcripts in Drosophila melanogaster.

We studied the effect of mutations at the suppressor of forked [su(f)] locus in Drosophila melanogaster on the accumulation of transcripts encoded by the gypsy transposable element. Mutations at this locus do not affect the pattern of developmental expression of gypsy, but they cause an increase in the total amount of gypsy RNA present at different stages of development as compared with wild-type or su(f)/+ flies. These results suggest that the su(f)-encoded products acts as a negative regulator of gypsy expression.

Animals↗
PubMed1985

Different modes of ligand binding to the hepatic galactose/N-acetylgalactosamine lectin on the surface of rabbit hepatocytes.

A study of the binding of three different 125I-labeled, galactose-terminated ligands to the hepatic galactose/N-acetylgalactosamine-specific lectin found on the surface of rabbit hepatocytes revealed that the different ligands manifest different physical parameters of binding. Asialoorosomucoid (125I-ASOR) binding was best described as involving two independent classes of binding sites on rabbit hepatocytes, with 161 000 sites/cell with a dissociation constant of 0.44 nM and 292 000 sites/cell with a Kd of 9.7 nM. Asialotriantennary glycopeptide purified from human alpha-1 protease inhibitor and modified with tyrosine at the N-terminus to permit radioiodination (TRI) [Lee, Y. C., Townsend, R. R., Hardy, M. R., Lönngren, J., Arnarp, J., Haraldsson, M., & Lönn, H. (1983) J. Biol. Chem. 258, 199-202] was also found to bind to two apparent classes of binding sites but with different binding parameters: 292 000 sites/cell of Kd = 1.47 nM and 982 000 sites/cell of Kd = 25.3 nM. A synthetic ligand, alpha,beta-diaspartamide of tris[(beta-lactosyloxy)methyl](6-aminohexanamido)methane (di-tris-lac) containing six nonreducing galactose residues [Lee, R. T., Lin, P., & Lee, Y. C. (1984) Biochemistry 23, 4255-4261], was found to bind to 817 000 sites/cell of Kd = 0.63 nM and 1.23 X 10(6) sites/cell of Kd = 25.3 nM. Thus, there were many more total binding sites for TRI or di-tris-lac on the surface of rabbit hepatocytes than there were for asialoorosomucoid, although the dissociation constants were similar for all three ligands.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylgalactosamine↗
PubMed1985

Surveillance for the detection of nosocomial infections and the potential for nosocomial outbreaks. II. Development of a laboratory-based system.

We describe the development of a surveillance system that uses thresholds for detecting nosocomial infections and the potential for nosocomial outbreaks based on data from microbiology laboratory records at our hospital from 1980 to 1982. These records were monitored weekly to determine the number of positive isolates by the identity of the organism and by the site of the culture. A mean of 225 specimens was processed weekly, with 60 of these yielding bacteria or fungi. The average number of organisms isolated per positive culture was 1.46. Two methods of establishing thresholds were compared, one based on percentiles of ranked isolates, the other based on the mean plus intervals of standard error. The system using thresholds established by the standard error method was consistently more useful to highlight weeks for which there was high risk of a problem occurring in less time than were the surveillance techniques traditionally employed.

Colorado↗
PubMed1985

Forked, gypsys, and suppressors in Drosophila.

We have isolated DNA sequences defining the forked locus of Drosophila. All the alleles belonging to the right pseudoallelic series of M. M. Green map within a 5.4 kb DNA fragment that encodes four transcripts. These RNAs are only expressed in 2-4 day old pupae and their accumulation is affected by mutations at the forked locus. Also, homozygous mutations at the unlinked suppressor loci su(Hw) and su(f) cause the accumulation of these RNAs to return to the normal wild-type levels. The gypsy transposable element, which causes the mutant phenotype in the suppressible forked alleles, encodes a transcript that is maximally expressed in 2-3 day old pupae, the same time in development as transcription of the forked RNAs. We propose a model to explain the mutagenic effect of gypsy based on the influence of promoter elements in the long terminal repeats of the transposon on the transcription from other promoters located nearby.

Alleles↗
PubMed1984

Surveillance for the detection of nosocomial infections and the potential for nosocomial outbreaks. I. Microbiology culture surveillance is an effective method of detecting nosocomial infection.

A study was undertaken to determine the sensitivity and specificity of a laboratory-based surveillance system using numbers of positive cultures in our institution. A randomized retrospective review of 575 medical-surgical patient charts revealed 70 nosocomial infections in 41 patients. Review of microbiology records indicated positive cultures for 71%, cultures obtained but inadequate for 6%, no culture necessary for 7%, and no culture obtained for 16%. Patients over 60 years old were significantly more likely to have a nosocomial infection cultured than were younger patients (p less than 0.025). There was no significant difference in rate of nosocomial infections classified by clinical service, site of infection, or length of stay in the hospital. By randomly selecting 100 positive cultures and reviewing the charts of the affected patients, we found that 48% represented nosocomial infections. Thus laboratory-based surveillance was 84% sensitive and 48% specific for detecting nosocomial infections.

Adult↗