PubMed Health⌕ Search

Biomedical subjects

D A Wright

Publications and source records attributed to D A Wright.

At least 19 recordsLinked to original sources
PubMed1998

Biotic factors modifying acute toxicity of aqueous cadmium to estuarine amphipod Leptocheirus plumulosus.

A 96-h exposure to aqueous cadmium (Cd) is the recommended reference toxicity test for 10-day sediment bioassays with the estuarine amphipod, Leptocheirus plumulosus (US EPA 1994). This water-only test was used to assess the influence of organism size, sex, and nutritional status on the sensitivity of laboratory-cultured L. plumulosus to Cd. In addition, the response of field-collected amphipods was compared to similarly sized laboratory animals to assess potential seasonal changes in Cd sensitivity. Lipid content of test organisms was measured in these seasonal experiments and those evaluating effects of nutritional status because of its potential as an indicator of physiological condition. LC50 values of laboratory animals size-sorted on nested 500-, 710-, and 1000-micron mesh sieves, increased with size class: 0.36, 0.65, and 0.88 mg Cd/L, respectively. Gravid females were less sensitive than males or mature females to aqueous Cd. Studies on the influence of the molt cycle on Cd toxicity indicated enhanced sensitivity of immediate postmolt animals that may explain some of the observed differences in Cd tolerance. Nutritional effects were investigated by comparing the sensitivity of fed and starved laboratory-reared amphipods. Starved juveniles and adults were significantly smaller than their fed counterparts and exhibited a 28-43% reduction in lipid content, respectively. However, comparison of LC50 values indicated no significant differences in sensitivity to Cd between starved and fed juveniles (0.23 vs 0.30 mg Cd/L) or adults (0.37 vs 0.52 mg Cd/L). Field-collected amphipods were typically more sensitive to Cd than laboratory animals, regardless of the season, although their lipid content varied, ranging from 6.6% in August to 13.7% in November. Results are discussed with respect to the use and interpretation of toxicity tests with this species.

Animals↗
PubMed1998

Potential retroviruses in plants: Tat1 is related to a group of Arabidopsis thaliana Ty3/gypsy retrotransposons that encode envelope-like proteins.

Tat1 was originally identified as an insertion near the Arabidopsis thaliana SAM1 gene. We provide evidence that Tat1 is a retrotransposon and that previously described insertions are solo long terminal repeats (LTRs) left behind after the deletion of coding regions of full-length elements. Three Tat1 insertions were characterized that have retrotransposon features, including a primer binding site complementary to an A. thaliana asparagine tRNA and an open reading frame (ORF) with approximately 44% amino acid sequence similarity to the gag protein of the Zea mays retrotransposon Zeon-1. Tat1 elements have large, polymorphic 3' noncoding regions that may contain transduced DNA sequences; a 477-base insertion in the 3' noncoding region of the Tat1-3 element contains part of a related retrotransposon and sequences similar to the nontranslated leader sequence of AT-P5C1, a gene for pyrroline-5-carboxylate reductase. Analysis of DNA sequences generated by the A. thaliana genome project identified 10 families of Ty3/gypsy retrotransposons, which share up to 51 and 62% amino-acid similarity to the ORFs of Tat1 and the A. thaliana Athila element, respectively. Phylogenetic analyses resolved the plant Ty3/gypsy elements into two lineages, one of which includes homologs of Tat1 and Athila. Four families of A. thaliana elements within the Tat/Athila lineage encode a conserved ORF after integrase at a position occupied by the envelope gene in retroviruses and in some insect Ty3/gypsy retrotransposons. Like retroviral envelope genes, this ORF encodes a transmembrane domain and, in some insertions, a putative secretory signal sequence. This suggests that Tat/Athila retrotransposons may produce enveloped virions and may be infectious.

Amino Acid Sequence↗
PubMed1997

Recovery of YAC-end sequences through complementation of an Escherichia coli pyrF mutation.

We have developed a genetic means to recover sequences from YAC-ends near the yeast selectable marker URA3. This strategy is based on the ability of URA3 to complement mutations in pyrF, an Escherichia coli gene required for pyrimidine biosynthesis. We have developed an E.coli strain with a non-reverting allele of pyrF that is also suitable for cloning (recA-, hsdR-). We demonstrate the utility of this complementation strategy to obtain right-end clones from three YACs containing Arabidopsis thaliana DNA.

Chromosomes, Artificial, Yeast↗
PubMed1997

CD30 induction of human immunodeficiency virus gene transcription is mediated by TRAF2.

CD30 is a member of the tumor necrosis factor receptor (TNFR) superfamily expressed on activated T and B lymphocytes and natural killer cells. Ligation of CD30 was previously shown to induce NF-kappaB activation and HIV expression in chronically infected T lymphocytes. In this study, we report that two members of the TNFR-associated factor (TRAF) family of proteins, TRAF1 and TRAF2, independently bind to the intracellular domain of CD30 (CD30IC). Transient overexpression of TRAF2, but not TRAF1, induced NF-kappaB activation and HIV-1-long terminal repeat-driven transcription in the T cell line, KT3. Moreover, dominant negative mutants consisting of the TRAF domain of TRAF1 and TRAF2 inhibited CD30 induction of NF-kappaB activation and HIV-1 transcription. These results suggest that CD30 ligation may enhance the expression of HIV via TRAF-2-mediated activation of NF-kappaB.

Cell Line↗
PubMed1997

Substance use in the US college-age population: differences according to educational status and living arrangement.

OBJECTIVES: Substance use in the college-age population is an important public health and educational concern. This study compared rates of use among college students and nonstudents, including high school dropouts, from a single data source representative of the nation. METHODS: Rates of use were estimated from the combined National Household Surveys on Drug Abuse from 1991 to 1993. Logistic regression models were used to test the effects of educational status and living arrangement. RESULTS: Educational status and living arrangement were found to be significant predictors of substance use. Rates of illicit drug and cigarette use were highest among high school dropouts, while current and heavy alcohol use were highest among college students who did not live with their parents. CONCLUSIONS: Substantial variation in substance use patterns within the college-age population suggests that overall rates of use for young adults should not be used to characterize specific subgroups of young adults. These data from a single source will thus help planners more clearly distinguish the service needs of the diverse subgroups within this population.

Adolescent↗
PubMed1996

Association of human fas (CD95) with a ubiquitin-conjugating enzyme (UBC-FAP).

A novel human ubiquitin conjugating enzyme (UBC) was found to associate with Fas (CD95). The mRNA for this UBC Fas-associated protein (FAP) was widely expressed in human tissues, and the protein was identified in several mammalian cell lines. UBC-FAP shows strong homology to two recently identified UBCs, Hus5 and Ubc9, which control yeast cell cycle progression. UBC-FAP, but not an active site mutant, complemented ubc9-1(ts) mutants. This suggests that UBC-FAP is a human homologue of Ubc9, possesses ubiquitin conjugating activity, and may play an important role in mammalian cell cycle regulation. A single amino acid substitution in the death domain of Fas that abolishes Fas-mediated apoptosis also abolished Fas association with UBC-FAP, suggesting that UBC-FAP may play a role in Fas signal transduction. The sequence of UBC-FAP is identical to that of HsUbc9, a UBC recently shown to interact with Rad51.

Animals↗
PubMed1996

Treatment of immune globulin-resistant Kawasaki disease with pulsed doses of corticosteroids.

We describe four children with Kawasaki disease resistant to treatment with intravenously administered immune globulin who were treated with high doses of methylprednisolone. All four patients apparently responded with normalization of symptoms, and none had significant progression of coronary artery abnormalities or adverse events. We recommend pulse methylprednisolone therapy (30 mg/kg per day) during a 1- to 3-day period for patients with Kawasaki disease who do not respond to intravenous immune globulin therapy or who have recrudescent disease after adequate therapy.

Child, Preschool↗
PubMed1996

Multiple non-LTR retrotransposons in the genome of Arabidopsis thaliana.

DNA sequence analysis near the Arabidopsis thaliana ABI3 gene revealed the presence of a non-LTR retrotransposon insertion that we have designated Ta11-1. This insertion is 6.2 kb in length and encodes two overlapping reading frames with similarity to non-LTR retrotransposon proteins, including reverse transcriptase. A polymerase chain reaction assay was developed based on conserved amino acid sequences shared between the Ta11-1 reverse transcriptase and those of non-LTR retrotransposons from other species. Seventeen additional A. thaliana reverse transcriptases were identified that range in nucleotide similarity from 48-88% (Ta12-Ta28). Phylogenetic analyses indicated that the A. thaliana sequences are more closely related to each other than to elements from other organisms, consistent with the vertical evolution of these sequences over most of their evolutionary history. One sequence, Ta17, is located in the mitochondrial genome. The remaining are nuclear and of low copy number among 17 diverse A. thaliana ecotypes tested, suggesting that they are not highly active in transposition. The paucity of retrotransposons and the small genome size of A. thaliana support the hypothesis that most repetitive sequences have been lost from the genome and that mechanisms may exist to prevent amplification of extant element families.

Amino Acid Sequence↗
PubMed1995

The Saccharomyces Ty5 retrotransposon family is associated with origins of DNA replication at the telomeres and the silent mating locus HMR.

We have characterized the genomic organization of the Ty5 retrotransposons among diverse strains of Saccharomyces cerevisiae and the related species Saccharomyces paradoxus. The S. cerevisiae strain S288C (or its derivatives) carries eight Ty5 insertions. Six of these are located near the telomeres, and five are found within 500 bp of autonomously replicating sequences present in the type X subtelomeric repeat. The remaining two S. cerevisiae elements are adjacent to the silent mating locus HMR and are located within 500 bp of the origin of replication present in the transcriptional silencer HMR-E. Although the S. cerevisiae Ty5 elements no longer appear capable of transposition, some strains of S. paradoxus have numerous Ty5 insertions, suggesting that transposition is occurring in this species. Most of these elements are adjacent to type X telomeric repeats, and regions flanking four of five characterized S. paradoxus insertions carry autonomously replicating sequences. The genomic organization of the Ty5 elements is in marked contrast to the other S. cerevisiae retrotransposon families (Ty1-4), which are typically located within 500 bp of tRNA genes. For Ty3, this association reflects an interaction between Ty3 and the RNA polymerase III transcription complex, which appears to direct integration [Chalker, D. L. & Sandmeyer, S. B. (1992) Genes Dev. 6, 117-128]. By analogy to Ty3, we predict that Ty5 target choice is specified by interactions with factors present at both the telomeres and HMR that are involved in DNA replication, transcription silencing, or the maintenance of the unique chromatin structure at these sites.

Base Sequence↗
PubMed1995

Functional expression of the renal organic cation transporter and P-glycoprotein in Xenopus laevis oocytes.

The hypothesis that P-glycoprotein (P-gp) mediates the renal secretion of organic cations was tested by functional expression of mRNAs in the Xenopus laevis oocyte system. Efflux of 2'-deoxytubercidin (dTub), a substrate for the renal organic cation transporter (OCT) but not for P-gp, was enhanced by injection of renal mRNA but not by injection of mRNA from P-gp-overexpressing cells (MDCK cells transduced with the cDNA for human MDR1). The functional capacity of the MDCK-MDR mRNA was established by its ability to reduce the steady-state uptake of a classical P-gp substrate, vinblastine. Thus, these data indicate OCT and P-gp to be distinct entities. The Xenopus oocyte system provides a functional approach to further characterize the OCT.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Physical fitness and cardiovascular disease risk factors in senior military officers.

Over a 5-year period (1986-1990), 1,223 male, senior military officers were tested to determine lipoprotein profiles, body composition (by densitometry), peak oxygen consumption (VO2 peak by graded, treadmill walking), and strength (one repetition maximum). Average (+/- SD) VO2 peak and body fat were 44.9 +/- 6.7 ml/kg x min and 24.4 +/- 5.1%, respectively. Although the average VO2 peak of these individuals is in the top 10-15% of this age group, nearly 39% are over-fat (by U.S. Army Regulation 600-9). Mean (+/- SD) total cholesterol, high-density lipoproteins, low-density lipoproteins, and triglycerides were 205 +/- 36, 50 +/- 12, 134 +/- 32, and 108 +/- 71 mg%, respectively. These results reflect an apparently healthy diet and lifestyle, which was strengthened, for the most part, when an average Framingham risk index (FRI) of approximately 2.3 was calculated. The low mean FRI for this group may possibly be attributed to lower total cholesterol and smoking rates than the average 45-year-old man in the Framingham study. The results of the testing indicate that this group generally has a high aerobic capacity, is normotensive, non-obese, and at low risk for the development of cardiovascular disease.

Adult↗
PubMed1993

Physical fitness and cardiovascular disease risk factors of female senior U.S. military officers and federal employees.

This study compared physical fitness and cardiovascular risk factors between military officers (N = 23) and civilians (N = 17). Subjects were women (average age 43 years) who attended the U.S. Army War College from 1986-1991. Officers had less body fat, higher aerobic capacity, lower resting heart rates, lower resting diastolic blood pressure, higher HDL, and marginally lower triglycerides. Female military officers appear to be more fit and have lower cardiovascular risk factors than their civilian counterparts.

Adult↗
PubMed1992

Embryonic expression and functional analysis of a Xenopus activin receptor.

We report the isolation and characterization of a Xenopus activin receptor (XAR1). The amino acid sequence of this protein shows extensive homology with a murine activin receptor. The mRNA is expressed maternally and is ubiquitously distributed during the early stages of embryogenesis. Consistent with a possible role in mesoderm induction and patterning, interference with the normal expression of the receptor by overexpression in the early embryo results in the formation of ectopic dorsal axial structures. During neurulation the XAR1 mRNA is expressed predominantly in the presumptive brain and spinal cord, suggesting an additional function for XAR1 in neurogenesis.

Activin Receptors↗