Biomedical subjects

D Dorsett

Publications and source records attributed to D Dorsett.

28 records · Page 2Linked to original sources

PubMed1989

Ethnicity: post-traumatic stress disorder (PTSD) differences among black, white, and Hispanic veterans who differ in degrees of exposure to combat in Vietnam.

Clinical observations and empirical evidence suggest that, among Vietnam combat veterans, Blacks are more maladjusted than Whites (e.g., Parsons, 1985; Penk et al., 1985). The prediction that minority group status is associated with poorer post-war adjustment and higher rates of PTSD was examined among Vietnam combat veterans who were seeking treatment for addiction disorders. Adjustment scores among groups comparable in combat exposure were found to be similar for both Whites and Hispanics; Blacks, however, score significantly higher on both PTSD symptoms on MMPI scales. These findings indicate that ethnicity contributes importantly to PTSD in selected instances, but that minority group status alone does not account for observed differences. Additional research is indicated in which careful attention is given to the complicating and interacting role of addiction disorders in sampling.

Adaptation, Psychological↗

PubMed1989

Alteration of hsp82 gene expression by the gypsy transposon and suppressor genes in Drosophila melanogaster.

Several mutations in Drosophila result from insertion of the gypsy retrotransposon. Gypsy insertion mutagenesis and its modulation by allele-specific modifier genes were investigated by inserting gypsy or fragments of it into the intron of the Drosophila hsp82 heat shock gene. With gypsy in the parallel orientation, nearly all transcripts in transfected cells and transformed pupae were truncated in the 5' long terminal repeat (LTR). Truncation also occurred in or near the 3' LTR. The 5' LTR polyadenylation signal was strongly potentiated by a downstream 326-bp internal gypsy segment in either orientation. Anti-parallel gypsy reduced the amount of normal transcript to a much smaller extent, and a low level of truncation occurred within gypsy. No evidence was found for effects of the gypsy insertions on the hsp82 promoter. Mutations in the allelespecific modifier genes su(f) and su(w alpha) had effects on the amounts of readthrough transcripts consistent with their genetic behavior, whereas the effects of mutations in su(Hw) were only partly in accord with genetic expectations.

Animals↗

PubMed1988

Human immunodeficiency virus replication in human brain cells. Brief report.

Human immunodeficiency virus (HIV), the etiologic agent of AIDS, was found to infect and replicate in human brain cells. The extent of HIV replication was minimal in human brain-derived cells in comparison to T4 lymphoid cells. These results suggest that direct infection of glial/neuronal cells by HIV may contribute to the CNS dysfunction frequently observed in HIV infected individuals.

Brain↗

PubMed1987

Tooth loss in maintenance patients in a private periodontal practice.

A group of 162 maintenance patients, previously studied for compliance to suggested maintenance schedules, were surveyed for tooth loss over a 5-year period. The group was divided into those who complied to suggested maintenance schedules and those whose compliance was erratic. It was found that none of the patients who had complied to suggested maintenance schedules lost any teeth. In the erratic group, where all tooth loss occurred, it was found that the more often a patient presented for maintenance, the less likely he was to lose teeth. These findings are discussed in relation to current studies on efficacy of various therapies for periodontal diseases.

Dental Scaling↗

PubMed1985

Circular and linear simian virus 40 DNAs differ in recombination.

Linear forms of simian virus 40 (SV40) DNA, when added to transfection mixtures containing circular SV40 and phi X174 RFI DNAs, enhanced the frequency of SV40/phi X174 recombination, as measured by infectious center in situ plaque hybridization in monkey BSC-1 cells. The sequences required for the enhancement of recombination by linear DNA reside within the SV40 replication origin/regulatory region (nucleotides 5,171 to 5,243/0 to 128). Linearization of phi X174 RFI DNA did not increase the recombination frequency. The SV40/phi X174 recombinant structures arising from transfections supplemented with linear forms of origin-containing SV40 DNA contained phi X174 DNA sequences interspersed within tandem head-to-tail repeats derived from the recombination-enhancing linear DNA. Evidence is presented that the tandem repeats are not formed by homologous recombination and that linear forms of SV40 DNA must compete with circular SV40 DNA for the available T antigen to enhance recombination. We propose that the enhancement of recombination by linear SV40 DNA results from the entry of that DNA into a rolling circle type of replication pathway which generates highly recombinogenic intermediates.

Bacteriophage phi X 174↗

PubMed1985

Linear simian virus 40 DNA fragments exhibit a propensity for rolling-circle replication.

A linear simian virus 40 origin-containing DNA fragment replicated in monkey COS cells, generating tandemly repeated (head-to-tail) structures. Electron microscopy revealed circle-and-tail configurations characteristic of rolling-circle replication intermediates. Circularization of the same DNA before transfection led to a theta type of replication which generated supercoiled DNA molecules.

Animals↗

PubMed1982

A naturally occurring pyrimidodiazepine in Drosophila: chemical and spectral properties and relationship to drosopterin.

The structure of an intermediate, in drosopterin biosynthesis, as 6-acetylpyrimidodiazepine has been confirmed by high-resolution mass spectra, 13C NMR, chemical ionization mass spectra, and chemical properties. A trivial name of 6-acetylhomopterin is suggested and should replace the term "quench spot" used heretofore. The structure of drosopterin includes, in part, a pyrimidodiazepine, a compound that consists of a fused six- and seven-membered heterocyclic ring system. Earlier studies demonstrated that 6-acetylhomopterin strongly stimulated the enzymatic synthesis of drosopterin and related eye pigments by preparations from Drosophila. The occurrence in nature is quite limited for diazepines; drosopterin and homopterin are the first examples in eukaryotes.

Animals↗

PubMed1982

Biosynthesis, nonenzymatic synthesis, and purification of the intermediate in synthesis of sepiapterin in Drosophila.

The enzymatic conversion of the D-erythro-dihydroneopterin triphosphate [H2-neopterin-(P)3] to sepiapterin occurs via a nonphosphorylated intermediate as shown by others. We have developed a high-performance liquid chromatography assay for this intermediate and have found that the intermediate (X) and two related compounds (X1 and X2) can be formed nonenzymatically under certain conditions from H2-neopterin-(P)3. The reaction is catalyzed by tris(hydroxymethyl)aminomethane, dependent upon H2-neopterin-(P)3 concentration, significant at temperatures greater than 80 degrees C, and maximal between pH 8.5 and 9.5 (as determined at 25 degrees C). All three compounds were purified, and it was found that both X and X1 can serve as substrates for the enzymatic, NADPH-dependent synthesis of sepiapterin. From the kinetics of formation from H2-neopterin-(P)3 and the similarity of the ultraviolet spectra, it is clear that X, X1, and X2 are closely related compounds. None of the three compounds is reduced by NaBH4; only X1 is sensitive to periodate oxidation. All three can be oxidized with iodine to give rise to highly fluorescent compounds that in turn can be reduced by NaBH4 to give rise to the respective parent compounds. These latter observations indicate that X, X1, and X2 are dihydropterins. These results are discussed relative to the proposed structures for enzymatically produced X. The methods described for the nonenzymatic synthesis of X and its purification should allow preparation of large amounts of X for future study.

Drosophila↗

PubMed1982

Purification and biosynthesis of quench spot, a drosopterin precursor in Drosophila melanogaster.

Pteridine biosynthesis has been examined in extracts of the heads of Drosophila melanogaster by measuring the conversion of dihydroneopterin triphosphate to sepiapterin and the "drosopterins" (six eye pigments that are dipterin derivatives). These two products share a common first step in the production of an intermediate that is a branch point from which both products are formed. This first step can be catalyzed by sepiapterin synthase or by an enzyme found in particles that sediment at 600g. A substance named "quench spot" was found earlier to be at low levels in the purple mutants that were defective in drosopterin synthesis and to be restored to normal when a suppressor mutant, su(s)2, restored drosopterins in purple to normal levels. The sepia mutant is also deficient in the levels of both quench spot and drosopterins. In this report we propose that quench spot is a precursor of drosopterins, but not sepiapterin, and that it is formed from the sepiapterin synthase intermediate mentioned above. An additional precursor that is formed independently of the sepiapterin synthase pathway is also proposed that would react with quench spot to form drosopterins. These proposals are based on the following: (1) quench spot biosynthesis is observed in extracts of Drosophila heads in which [U-14C]dihydroneopterin triphosphate is the substrate; (2) Mg2+ is required for the synthesis of quench spot but either NADH or NADPH causes diminished incorporation of the label; (3) extracts from heads of a purple mutant (prbwcn) contain only 30% of the quench spot biosynthetic activity as compared to heads from wild type (Oregon-R); (4) quench spot has been purified from heads of wild-type Drosophila; (5) addition of quench spot stimulates the biosynthesis of drosopterins in an enzyme preparation from Oregon-R.

Animals↗

PubMed1979

Biosynthesis of "drosopterins" by an enzyme system from Drosophila melanogaster.

The red eye pigment of Drosophila melanogaster consists of six complex pteridines known as neodrosopterin, drosopterin, isodrosopterin, fraction e, and aurodrosopterins (2); these pigments are greatly reduced in the purple mutant. Conditions for biosynthesis of these "drosopterins" are described and compared with those for the synthesis of sepiapterin. The enzymes are contained in a soluble, pteridine-free extract obtained between 40 and 60% saturated ammonium sulfate. The results indicate that sepiapterin synthase consists of two enzymes, the first of which provides a precursor for "drosopterin" biosynthesis. The evidence is (1) the purple mutant, low in accumulated sepiapterin and "drosopterins", is known to have approximately 10% of the sepiapterin synthase activity of wild type; (2) unlabeled sepiapterin does not cause isotope dilution of "drosopterin" synthesis; (3) the 600g pellet prepared from a wild-type head homogenate contains "drosopterin" synthesizing activity and no sepiapterin synthase, yet a heat-labile factor in this fraction stimulates sepiapterin synthesis in the 100000g supernatant of wild-type or pr flies; (4) sepiapterin and "drosopterin" syntheses require Mg2+; (5) sepiapterin synthesis is stimulated by NADPH; "drosopterin" synthesis responds to either NADPH or NADH. Although "drosopterins" are complex pteridine-type pigments, we have demonstrated their biosynthesis by soluble enzymes. This allows us to consider investigation into the mechanism by which the amounts of these pigments are regulated.

Animals↗