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Biomedical subjects

M Tisdale

Publications and source records attributed to M Tisdale.

48 records · Page 3Linked to original sources
PubMed1988

Structural studies of the acquired immunodeficiency syndrome virus reverse transcriptase.

The clinical success of zidovudine has established the human immunodeficiency virus (HIV) reverse transcriptase (RT) as a valid target for the design of drugs to treat acquired immunodeficiency syndrome. In order to facilitate structural studies of this enzyme, expression systems in Escherichia coli, which allow the production of large amounts of RT, have been established. Using this recombinant material the RT has been purified and crystallized. Crystallographic studies currently underway are aimed at elucidating the three-dimensional structure of HIV RT. The availability of a bacterial expression system has enabled structural/functional studies of the RT by site-directed mutagenesis. These studies have identified amino acid residues that are essential for activity of the enzyme and might be involved in substrate binding. It is hoped that structural information of this nature will allow the rational design of HIV RT inhibitors.

Antiviral Agents↗
PubMed1988

Characterization of human immunodeficiency virus type 1 reverse transcriptase by using monoclonal antibodies: role of the C terminus in antibody reactivity and enzyme function.

We describe the production of eight monoclonal antibodies reactive with human immunodeficiency virus type 1 reverse transcriptase (RT) by immunization of mice with purified recombinant RT. These antibodies were found to react with one or the other of two regions of the enzyme and were found to be useful in immunodeficiency purification of large amounts of the enzyme. One epitope located at the C terminus of the enzyme was of particular interest, since it was present in only the larger, 66-kilodalton (kDa) RT species and not its smaller, 51-kDa counterpart. To define this epitope, a series of mutants was made which synthesized C-terminally truncated RT. These mutants indicated that the same region of the enzyme, when deleted, both removed the C-terminal epitope and drastically reduced RT activity, indicating the importance of this region in the function of the enzyme; however, even the 51-kDa enzyme component had demonstrable activity.

Animals↗
PubMed1985

Inhibition of the growth of human coronavirus 229E by leupeptin.

The protease inhibitor leupeptin prevented multiplication of the human coronavirus strain 229E in cultures of MRC-C cells. The IC50 of leupeptin in plaque reduction tests was 0.4 micrograms/ml, whereas growth of host cells was unaffected by leupeptin at 50 micrograms/ml. Inhibition of plaque formation could be prevented by the addition of proteases to the overlay medium. In single-cycle growth experiments, leupeptin reduced virus yield only if added within 2 h of infection, indicating its action on an early stage of virus replication.

Cell Line↗
PubMed1984

Effect of dichloroflavan (BW683C) on the stability and uncoating of rhinovirus type 1B.

Dichloroflavan was found to stabilize rhinovirus 1B to inactivation by heat at 56 degrees C or by acid at pH 4.6 to 5.0. The effects of dichloroflavan, arildone and sodium dodecyl sulphate on uncoating of virus in M.HeLa cells were compared by examining the production of sub-viral particles separated on sucrose density gradients; the development of photoresistance by neutral red labelled virus. All three compounds significantly reduced but did not completely suppress the production of sub-viral particles. They also affected the uncoating of neutral red labelled virus, although dichloroflavan appeared to delay rather than prevent this process. A variant of rhinovirus 1B, isolated by growth in the presence of dichloroflavan, showed increased resistance to inhibition by arildone and SDS as well as dichloroflavan, suggesting a similar site of action for the three compounds.

Acetates↗
PubMed1983

Inhibition of an early stage of rhinovirus replication by dichloroflavan (BW683C).

The mechanism of action of a new anti-rhinovirus compound, dichloroflavan, was examined using a variety of techniques. Dichloroflavan was shown to bind to the highly sensitive rhinovirus type 1B (50% inhibitory concentration 0.007 microM) and at a much lower level to the insensitive rhinovirus type 4 (50% inhibitory concentration greater than 25 microM). Binding of the compound to rhinovirus 1B was accompanied by a reduction (about 0.5 log10 units) in virus infectivity which could be restored by treatment with chloroform. Maximum inhibition of virus yield (about 2 log10 units) occurred only when compound and virus were added together, but some inhibition (about 0.7 log10 units) occurred even when the compound was added near the end of a single cycle of replication. This late reduction in infectivity could be abolished by treating with chloroform, and was therefore caused by the compound binding to progeny virus. The compound did not interfere with adsorption of virus to cells, nor with uncoating of the viral RNA. However, little or no viral RNA and protein synthesis occurred in the presence of dichloroflavan provided that the compound was added with the virus. Addition of the compound after virus adsorption had no effect on either viral RNA or protein synthesis. These results indicate that dichloroflavan binds directly to rhinovirus 1B and appears to prevent virus replication at a point immediately after uncoating of the viral RNA.

Flavonoids↗
PubMed1977

The relative potencies of anti-influenza compounds.

The relative potencies of some standard anti-influenza compounds have been examined in vitro by plaque reduction in calf kidney cells, and in vivo by reduction in virus titers of the lungs of infected mice. Strains belonging to the four subtypes H0N1, H1N1, H2N2, and H3N2 were employed to compare the activity of amantadine hydrochloride and ribavirin. In vitro for all strains except A/NWS/OO(H0N1) amantadine hydrochloride was 3-4 times more active than ribavirin. In vivo with sensitive strains amantadine hydrochloride produced a plateau effect at higher dose levels, but at lower dose levels was marginally more active than ribavirin. The sensitivity of A/Hong Kong/1/68 (H3N2) to amantadine hydrochloride, rimantadine hydrochloride, cyclooctylamine, and ribavirin was also investigated. In vitro rimantadine hydrochloride was similar in activity to amantadine hydrochloride and ribavirin, but cyclooctylamine was considerably less active. In vivo cyclooctylamine was active only at 150 mg/kg/day, whereas rimantadine hydrochloride produced a plateau effect over a range of concentrations from 9,12-150 mg/kg/day.

Adamantane↗
PubMedDate not supplied

Monitoring of viral susceptibility: new challenges with the development of influenza NA inhibitors.

With the clinical development of anti-viral agents, monitoring for the continued susceptibility of wild-type strains has become important in disease management. Various methods have been used to monitor viral susceptibility; the advantages and disadvantages of which depend on the virus, the target and the scale of the research being undertaken. The plaque-reduction assay is valuable for measuring susceptibility of most viruses but is not ideal for large-scale monitoring. Yield-reduction, measuring specific virus antigens, and dye-uptake assays, measuring virus cytopathic effects, are more suitable for high-throughput requirements, but the IC(50) value (the concentration that inhibits 50% of virus) varies with the viral inoculum. Surveillance of influenza susceptibility to rimantadine/amantadine in the clinic has predominantly used EIA-based assays, since plaquing of influenza clinical isolates is variable. With development of the influenza NA inhibitors it became apparent that current cell-based assays were unsuitable for monitoring susceptibility to this new class of drugs. Variability may result from virus spread directly from cell to cell in culture by-passing the NA function. Furthermore, mutations selected in the HA, while not apparently contributing to phenotypic resistance in vivo, may result in cell-culture based resistance, and may mask NA resistance in cell culture by modifying receptor-binding specificity. One important distinction between NA inhibitors and other antiviral enzyme inhibitors is that both target enzyme and inhibitor work extracellularly. NA assays are therefore most representative of the in vivo situation for monitoring susceptibility, supported by HA sequencing. As the clinical use of NA inhibitors escalates, a major change will be required in approaches used to monitor susceptibility of influenza isolates in virology laboratories world-wide.

Antiviral Agents↗
PubMedDate not supplied

Personality pathology in bulimics versus controls.

The Millon Clinical Multiaxial Inventory (MCMI) was administered to 37 bulimic women, as well as 32 female general psychiatric outpatients and 30 normal women in order to assess contrasts in prevalence of various types of personality pathology among the three groups. Bulimic women displayed significantly greater pathology on scales measuring dependent and avoidant characteristics. However, they were not significantly different from female psychiatric outpatients with regard to most types of personality pathology. Results are discussed within the framework of previous literature on personality characteristics and disorders within the bulimic population.

Adolescent↗