Biomedical subjects

A S Yee

Publications and source records attributed to A S Yee.

27 records · Page 2Linked to original sources

PubMed1988

Transactivation by the adenovirus E1A gene.

The 289aa product of the adenovirus E1A gene mediates the transcriptional activation of the set of early viral genes as well as several cellular genes. The E1A protein is not a DNA binding protein but, rather, acts indirectly to achieve the activation. The process of viral gene activation involves the use of cellular transcription factors, and in at least one case, in vivo assays have demonstrated a stimulation of stable promoter complex formation as a function of the E1A gene product. Analysis of transcription factors in nuclear extracts has identified a cellular factor, termed E2F, with specificity for the viral E2 promoter. The concentration of this factor increases as a result of the action of E1A. This increase in DNA binding activity does not require protein synthesis, thus indicating an E1A-mediated modification of a pre-existing factor. The E2F factor has been purified to homogeneity and is a polypeptide of 54,000 molecular weight. Analysis of an additional viral promoter, the E4 promoter, has identified a protein that interacts with sequences critical for transcription. This factor, termed E4F, is also increased as a function of the E1A product. The E4F factor has also been purified to homogeneity and has a molecular weight of 50,000. Therefore, the coordinate control of transcription by the E1A gene product involves the activation of multiple promoter specific factors.

Adenoviridae↗

PubMed1987

Promoter interaction of the E1A-inducible factor E2F and its potential role in the formation of a multi-component complex.

The precise binding site in the adenovirus E2 promoter for the E1A-inducible factor E2F was determined. DNase footprinting revealed two distinct regions of protection which spanned sequences from -33 to -49 and from -53 to -71. Chemical modifications of DNA further delineated nucleotides involved in DNA-protein contacts in each binding region. The E2F binding sites are clearly distinct from the binding site for another E2 promoter binding factor, located at -68 to -80, previously described by SivaRaman et al. [(1986) Proc. Natl. Acad. Sci. USA, 83, 5914-5918]. As determined by DNase footprinting using crude nuclear extracts, both factors were present in extracts of Ad5-infected cells and were found to bind simultaneously to their respective sites on the promoter. In contrast, E2F was not evident in extracts of uninfected cells, whereas there was no difference in the -68 to -80 footprint as a function of the extract. Thus, although multiple factors interact with the E2 promoter, only the E2F factor is unique to the infected extract. The implications of the formation of a multi-factor promoter complex as a possible mechanism of transcriptional regulation are discussed.

Adenovirus Early Proteins↗

PubMed1987

Digoxin levels in prehospital sudden-death syndrome.

Digitalis toxicity is common and has been associated with ventricular dysrhythmias. Digoxin levels in patients who suffer prehospital sudden death have never been studied. This study measured digoxin levels in a population of sudden-death patients. During the 15-week study period, 252 patients in cardiac arrest were seen by an urban paramedic system. During daytime hours, paramedics were requested to obtain a blood sample from sudden-death patients; the samples were subsequently analyzed for digoxin by means of radioimmunoassay. Thirty-nine patients had measured digoxin levels drawn; 28 (71.8%) were in the therapeutic range (0.5-2.1 ng/mL), and four (10.2%) were in the toxic range (greater than 2.1 ng/mL). The patients with toxic dogoxin levels and those with nontoxic levels had similar resuscitation rates (50.0% vs. 34.3%, P = NS), but none were found in ventricular fibrillation. Emergency medical services personnel should consider digoxin toxicity as a potential etiology of arrest.

Aged↗

PubMed1986

Thiol-group modification of Torpedo californica acetylcholine receptor: subunit localization and effects on function.

The effects of thiol-group modifications on acetylcholine receptor (ACHR) function were measured with purified ACHR reconstituted into asolectin vesicles. N-Phenylmaleimide (NPM) was used to modify sulfhydryl groups on ACHR in the absence of any prior reduction of dithiothreitol, so that only the functional relevance of free sulfhydryls was examined. Modification by NPM led to the inhibition of ion-channel activity without a detectable effect on ligand binding. The ion flux inhibition by NPM primarily affected channel activation, since the initial rates of activation were decreased over a wide range of carbamylcholine concentrations. The [3H]NPM subunit labeling pattern of ACHR (a multisubunit membrane protein with alpha 2 beta gamma delta stoichiometry) revealed that there was preferential labeling of the gamma subunit. At high NPM concentrations, the number of sulfhydryl groups on the gamma subunit that could be modified with NPM was approximately two. Detergent was required during labeling for functionally relevant thiol-group modifications, and most of the label was protected from protease digestion in the reconstituted membranes. These results are consistent with the presence of the NPM modification in a bilayer and/or cytoplasmic domain.

Animals↗

PubMed1985

Effects of carboxymethylation by a purified Torpedo californica methylase on the functional properties of the acetylcholine receptor in reconstituted membranes.

The functional effects of carboxymethylation of Torpedo californica acetylcholine receptor by an endogenous Torpedo methylase were examined. Both the receptor and the methylase were purified to increase the level of methylation and the sensitivity of the functional assays. The methylase catalyzed the carboxymethylation of all four receptor subunits (alpha, beta, gamma, delta) with preferential labeling of the alpha and gamma subunits. For all the reactions, S-adenosylmethionine was used as the methyl donor. Functional effects of methylation were assessed by measuring ligand binding and ligand-activated ion permeability responses in reconstituted membranes containing purified acetylcholine receptors. Methylation of receptor to a level of 20 mol% had no significant effect on agonist or antagonist binding nor did methylation affect the transition from low-to-high affinity binding triggered by agonists. In contrast, 20% methylation led to a 20% reduction in the agonist-stimulated flux of cations across the receptor-containing membranes. The results suggest that methylation inhibits the ion permeability control properties of acetylcholine receptors.

Animals↗

PubMed1984

Accuracy and usefulness of a breath alcohol analyzer.

We evaluated the accuracy of a hand-held breath alcohol analyzer in the rapid determination of blood alcohol levels in the emergency patient with suspected ethanol intoxication. The Alco -Sensor III breath alcohol analyzer was used to measure alcohol levels in orally and nasally obtained end-expiratory breath samples in 55 patients. These levels were compared to directly measured blood alcohol levels. The patients were categorized into cooperative and uncooperative groups. The mean oral breath alcohol level obtained was 0.187 +/- 0.100 g/dL (range, 0.000 to 0.419) while the mean serum level was 0.217 +/- 0.113 g/dL (range, 0.00 to 400). The overall correlation between these two methods of measuring blood alcohol level was strong (r = .879, P less than .001). In cooperative patients the correlation was even stronger (r = .963, P less than .001), while in uncooperative patients the correlation was less but still significant (r = .723, P = .001). Nasally obtained samples correlated well with blood levels in cooperative patients (r = .874, P less than .001), but the correlation was less strong in uncooperative persons (r = .694, P = .003). Our study indicates that the Alco -Sensor III breath alcohol analyzer is sufficiently accurate to be of use in rapidly assessing blood alcohol levels, even when a patient is unable to cooperate fully.

Alcoholic Intoxication↗

PubMed1982

Myasthenia Gravis.

Explore the source record for details and available documents.

Cholinesterase Inhibitors↗

PubMed1981

Proximal saphenous vein cutdown.

An anatomical review and venesection technique for the proximal greater saphenous vein is described. It is recommended as an additional intravenous approach for rapid volume resuscitation in the patient with profound hypovolemic shock.

Humans↗

PubMed1981

Magnesium: physiology, clinical disorders, and therapy.

Magnesium imbalance is clinically significant. It is common, treatable, and frequently overlooked. We review the literature describing magnesium deficit and excess syndromes and formulate specific treatment protocols.

Acute Kidney Injury↗