Search PubMed⌕ Search

Biomedical subjects

T A Edwards

Publications and source records attributed to T A Edwards.

12 recordsLinked to original sources
PubMed2001

Structure of Pumilio reveals similarity between RNA and peptide binding motifs.

Translation regulation plays an essential role in the differentiation and development of animal cells. One well-studied case is the control of hunchback mRNA during early Drosophila embryogenesis by the trans-acting factors Pumilio, Nanos, and Brain Tumor. We report here a crystal structure of the critical region of Pumilio, the Puf domain, that organizes a multivalent repression complex on the 3' untranslated region of hunchback mRNA. The structure reveals an extended, rainbow shaped molecule, with tandem helical repeats that bear unexpected resemblance to the armadillo repeats in beta-catenin and the HEAT repeats in protein phosphatase 2A. Based on the structure and genetic experiments, we identify putative interaction surfaces for hunchback mRNA and the cofactors Nanos and Brain Tumor. This analysis suggests that similar features in helical repeat proteins are used to bind extended peptides and RNA.

Amino Acid Motifs↗
PubMed2000

Crystallization and characterization of Pumilo: a novel RNA binding protein.

Axis determination in early Drosophila embryos is controlled, in part, by regulation of translation of mRNAs transcribed in maternal cells during oogenesis. The Pumilio protein is essential in posterior determination, binding to hunchback mRNA in complex with Nanos to suppress hunchback translation. In order to understand the structural basis of RNA binding, Nanos recruitment, and translational control, we have crystallized a domain of the Drosophila Pumilio protein that binds RNA. The crystals belong to the space group P6(3) with unit cell dimensions of a = b = 94.5 A, c = 228.9 A, alpha = beta = 90 degrees, gamma = 120 degrees and diffract to 2.6 A with synchrotron radiation. We show that the purified protein actively binds RNA and is likely to have a novel RNA binding fold due to a very high content of alpha-helical secondary structure.

Animals↗
PubMed1993

Cannabinoids modulate potassium current in cultured hippocampal neurons.

Characterization of the newly discovered G-protein-coupled cannabinoid receptor in brain requires determination of its functional significance. The effects are reported of several potent cannabinoid analogs (CP 55,244, CP 55,940, levonantradol and WIN 55,212-2) on cultured neurons from hippocampus, a brain region that exhibits high cannabinoid receptor density. The electrophysiological effects of cannabinoids were determined by whole-cell patch clamp recordings of voltage-dependent potassium currents. The voltage dependence of the rapidly inactivating potassium A current (IA), characteristic of hippocampal neurons, was significantly altered in a concentration-dependent manner by cannabinoid analogs. Decreased inactivation, which led to an increased activation of IA near resting levels in these cells, was observed after brief local extracellular applications of cannabinoids. These actions were blocked by pertussis toxin. Cellular dialysis of GTP-gamma-S mimicked the actions of cannabinoids on IA while blocking further effects due to added cannabinoids. The rank order of potency of the cannabinoid analogs was similar to that observed with respect to binding at cannabinoid receptors in brain membranes. The concentration-related effectiveness of cannabinoid analogs in modulating IA was similar to their potency in stimulating low Km GTPase in cell membranes isolated from the cannabinoid receptor-rich dentate gyrus. These data support the conclusion that cannabinoid effects on IA are mediated through G-protein-coupled receptors. This cannabinoid-induced shift in the voltage dependence of IA could serve to counteract fast, transient, depolarizing events such as action potentials and synaptic currents in hippocampal neurons.

Action Potentials↗
PubMed1993

Cannabinoid receptors: G-protein-mediated signal transduction mechanisms.

The recent discovery and cloning of cannabinoid receptors has provided a major breakthrough in the understanding of the biochemical mechanisms of action of delta 9-tetrahydrocannibinol (delta 9-THC). Cannabinoid receptors are coupled to G-proteins and inhibit adenylyl cyclase in a variety of systems. In the brain, cannabinoid-inhibited adenylyl cyclase and the receptors are particularly prevalent in the cerebellum, where they are localized to cerebellar granule cells (Fig. 1). In these cells, cannabinoid receptors are co-localized with other Gi/o-linked receptors such as gamma-aminobutyric acid (GABAB) receptors, where they share common effector systems (adenylyl cyclase catalytic units) but not common G-proteins. This sharing of effectors leads to the phenomenon of receptor convergence, in which agonists of different receptor types can produce the same biological response in certain cells. In cultured hippocampal neurons, cannabinoids also act through G-proteins to increase potassium conductance. In these cells, the predominant electrophysiological response at relatively low (microM) concentrations of cannabinoids is mediated through a voltage-sensitive potassium A current (IA) (Fig. 1). The action of cannabinoid receptors in this system is to shift the voltage sensitivity of IA channels to higher voltage ranges, thus increasing K+ conductance at lower membrane potentials and decreasing the probability of multiple action potentials. When combined with data from other groups showing a cannabinoid receptor-mediated decrease in calcium conductance, along with the unique localization of cannabinoid receptors in the brain, it is clear that these receptor-effector combinations are well situated to mediate many of the well-known neurobiological effects of delta 9-THC.

Animals↗
PubMed1990

Health locus of control beliefs and alcohol-related factors that may influence treatment outcomes.

Treatment programs have based their treatment approach on the premise that alcoholics should exert internal control over situations and events that affect them. Since chronic alcohol use affects the health of an individual, Walston and Walston's Multidimensional Health Locus of Control Scale was administered to 47 alcoholics in a treatment program. The population reflected a higher belief that health status is more under their own control than under the control of chance or powerful others. However, the results indicated that recovering alcoholics with a more powerful other health orientation tended to maintain membership longer with Alcoholics Anonymous, would seek help sooner, would begin heavy drinking at a later age, and would attempt formal treatment more often.

Adolescent↗
PubMed1990

High school students' perceptions of nursing as a career choice.

Declining enrollments in nursing programs, coupled with the current shortage of practicing registered nurses, prompted this investigation of 306 high school students' beliefs about nurses and nursing. The study also identifies potential numbers of future nursing students from high school populations and their primary source of information about nursing. Using an investigator questionnaire, subjects responded to statements about educational requirements for registered nurses along with their working conditions, earning power, and social status. Findings reveal a projected continuing shortage of nurses based on the very small percentage of subjects even considering nursing as a career. Additional findings show that whereas some perceptions about nursing seem congruent with those of nurses themselves, other beliefs held by high school students are not consistent with the realities of professional nursing today. Results of this study can be used by nurse recruiters to correct misconceptions about nursing and to help high school students perceive the profession in a more positive way. Expanding the informational sources about nursing can facilitate the recruitment process.

Adolescent↗
PubMed1989

Transforming growth factor-beta causes partial inhibition of interleukin 1-stimulated cartilage degradation in vitro.

We show that purified human transforming growth factor-beta (1-10ng/ml) inhibits interleukin 1-stimulated loss of proteoglycan from cartilage in vitro. Inhibition is incomplete, as interleukin 1 retains the ability to cause a dose dependent stimulation of proteoglycan release in the presence of high levels of transforming growth factor-beta (100ng/ml) although both basal and interleukin 1-stimulated levels can be reduced by up to 50 per cent. This observation, together with its ability to stimulate proteoglycan synthesis and to stimulate proteinase inhibitor production, suggests a possible role for transforming growth factor-beta in limiting cartilage proteoglycan loss in inflammatory conditions such as rheumatoid arthritis.

Animals↗
PubMed1982

Diagnosis of gonorrhea using a genetic transformation test on mailed clinical specimens.

The genetic transformation test (GTT), a technique used for the detection of gonococcal DNA in clinical specimens, was compared with culture testing for the diagnosis of gonorrhea. At the De Kalb County Venereal Disease Clinic, Decatur, Ga., 454 cervical and 160 rectal specimens from women and 191 urethral specimens from men were collected in duplicate. One of each of the two specimens from each anatomic site was immediately plated on Martin-Lewis medium and incubated; the other specimen was mailed to Philadelphia for a GTT. Using culture results as a standard, the GTT had a specificity of 98.1% although some "false-positive" GTT results were probably a reflection of false-negative culture results. The sensitivity of the GTT was greater than 96% except when specimens were collected with Culturettes (Marion Laboratories, Kansas City, Mo.). In situations where Gram staining is not appropriate or where on-site culture facilities are not available, GTT may be the method of choice for the diagnosis of gonorrhea.

Biological Assay↗