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Biomedical subjects

D Stuart

Publications and source records attributed to D Stuart.

At least 73 records · Page 4Linked to original sources
PubMed1991

The target DNA sequence for resolution of poxvirus replicative intermediates is an active late promoter.

The linear double-stranded genomes of poxviruses such as Shope fibroma virus (SFV) replicate autonomously within the cytoplasm of infected cells, and it is believed that all of the replication functions are virally encoded. During DNA replication the incompletely base-paired terminal hairpin loops of the viral genome transiently exist in the form of inverted repeat replicative intermediates. These inverted repeat structures form the target for telomere resolution events that include sequence-specific cleavage and directed strand exchange to form the hairpin termini of progeny virus genomes. The terminal sequence domain which forms the telomere resolution target (TRT) shares considerable sequence similarity with viral late promoters. In this study we demonstrate that the TRT of SFV is capable of functioning as a strong viral promoter late in infection. A spectrum of TRT mutations affects telomere resolution and late transcription in a strictly concordant fashion, suggesting that the two activities may be inextricably linked. Further support for this concept comes from the demonstration that a late SFV promoter sequence designated cryptic TRT, which differs substantially from the native TRT in terms of sequence, can support telomere resolution when placed in the correct spatial context. The proposed model for telomere resolution invokes directed unwinding of the TRT double helix by a transcription initiation complex and processing of the resulting secondary structure by viral late-gene products.

Animals↗
PubMed1990

Structural and serological evidence for a novel mechanism of antigenic variation in foot-and-mouth disease virus.

Changes resulting in altered antigenic properties of viruses nearly always occur on their surface and have been attributed to the substitution of residues directly involved in binding antibody. To investigate the mechanism of antigenic variation in foot-and-mouth disease virus (FMDV), variants that escape neutralization by a monoclonal antibody have been compared crystallographically and serologically with parental virus. FMDVs form one of the four genera of the Picornaviridae. The unenveloped icosahedral shell comprises 60 copies each of four structural proteins VP1-4. Representatives from each of the genera have similar overall structure, but differences in the external features. For example, human rhinovirus has a pronounced 'canyon' that is proposed to contain the cell attachment site, whereas elements of the attachment site for FMDV, which involves the G-H loop (residues 134-160) and C-terminus (200-213) of VP1, are exposed on the surface. Moreover, this G-H loop, which is a major antigenic site of FMDV, forms a prominent, highly accessible protrusion, a feature not seen in other picornaviruses. It is this loop that is perturbed in the variant viruses that we have studied. The amino acid mutations characterizing the variants are not at positions directly involved in antibody binding, but result in far-reaching perturbations of the surface structure of the virus. Thus, this virus seems to use a novel escape mechanism whereby an induced conformational change in a major antigenic loop destroys the integrity of the epitope.

Antibodies, Monoclonal↗
PubMed1990

The structure of foot-and-mouth disease virus: implications for its physical and biological properties.

The structure of foot-and-mouth disease virus has been solved at a resolution of 2.9 A by X-ray diffraction techniques. The overall structural organisation of the particle is similar to that seen in other picornaviruses but there are several unique features. Many of these help to explain its characteristic physical and biological properties. In particular the canyon or pit found at the surface of other picornaviruses is lacking, which has important implications for cell attachment and the process of infection. Also there are 60 large disordered protrusions at the surface corresponding to the major antigenic site. This disorder is of particular interest in relation to the striking ability of linear synthetic peptides to induce protective immunity against foot-and-mouth disease.

Animals↗
PubMed1989

The three-dimensional structure of foot-and-mouth disease virus at 2.9 A resolution.

The structure of foot-and-mouth disease virus has been determined at close to atomic resolution by X-ray diffraction without experimental phase information. The virus shows similarities with other picornaviruses but also several unique features. The canyon or pit found in other picornaviruses is absent; this has important implications for cell attachment. The most immunogenic portion of the capsid, which acts as a potent peptide vaccine, forms a disordered protrusion on the virus surface.

Algorithms↗
PubMed1988

High levels of genetic recombination among cotransfected plasmid DNAs in poxvirus-infected mammalian cells.

The frequency of recombination between transfected plasmid DNAs was measured by using cultured cells infected with a variety of poxviruses. Plasmid derivatives of pBR322 containing XhoI linker insertion mutations in the tetracycline gene were used to assess recombination frequencies in rabbit cells infected with the leporipoxviruses Shope fibroma virus and myxoma virus and the orthopoxvirus vaccinia virus. Recombination frequencies were calculated by Southern blotting, which detects novel plasmid restriction fragments generated by genetic recombination, and by a plasmid rescue procedure in which the reconstruction of an intact tetracycline gene in the transfected rabbit cell was monitored by transformation back into Escherichia coli. The highest recombination frequencies were measured in cells infected with Shope fibroma virus and myxoma virus, and a minimum recombination frequency of at least one recombination event per 7 kilobases was calculated within 24 h posttransfection under these conditions. The deduced recombination frequency in vaccinia virus-infected cells was at least fivefold lower and was not detectable in mock-infected cells, suggesting that the induced recombination activity detected by these methods was under viral control. The results of kinetic studies, analysis with methylation-sensitive restriction enzymes, and the use of phosphonoacetic acid, a specific inhibitor of poxvirus DNA polymerase, indicated that recombination between transfecting DNAs occurred concomitantly with DNA replication but that the two processes could be partially uncoupled. We conclude that the dramatic expansion of recombination activities in the cytoplasm of poxvirus-infected cells is virus specific and offers a good model system with which to analyze the mechanism of recombination in a eucaryotic environment.

Animals↗
PubMed1987

Crystallization and preliminary X-ray diffraction analysis of foot-and-mouth disease virus.

Foot-and-mouth disease virus has been crystallized with the objectives of (1) determining the composition and conformation of the major immunogenic site(s) and (2) comparing its structure with those of the related polio, rhino and Mengo viruses, representing the other three genera of the picornaviruses. Most of the work has been done with virus strain O1BFS 1860, which crystallized as small rhombic dodecahedra of maximum dimension 0.3 mm. Virus recovered from crystals was infectious, and was indistinguishable from native virus both in protein composition and buoyant density. The stability of the crystals in the X-ray beam was comparable with that of other picornavirus crystals and they diffracted to a resolution of better than 2.3 A. Initial analysis of the X-ray diffraction data shows the virus to be positioned on a point of 23 symmetry in a close-packed array so that examples of all the icosahedral symmetry elements, except the 5-fold axes, are expressed crystallographically. The cell dimensions are a = b = c = 345 A, alpha = beta = gamma = 90 degrees, with a space group of I23. The diameter of the virus particle is 300 A. Despite the small size of the crystals, diffraction data have been collected to a reasonable resolution using a synchrotron source. Phasing of the diffraction data will be attempted using the methods of molecular replacement.

Aphthovirus↗
PubMed1987

AIDS in psychiatry.

Explore the source record for details and available documents.

Acquired Immunodeficiency Syndrome↗
PubMed1986

Beta-endorphin attenuates the serum cortisol response to exogenous adrenocorticotropin.

Controversy surrounds the issue of whether beta-endorphin affects adrenal steroidogenesis. Recent work has both supported and refuted the claim that beta-endorphin stimulates a rise in serum aldosterone. We investigated the role of beta-endorphin in adrenal steroidogenesis by examining its potential modulation of the response of serum cortisol to exogenous ACTH (Cosyntropin). Four of five normal men received: 1) synthetic beta-endorphin (1 microgram/kg X min) for 30 min, followed by a bolus dose of 0.2 micrograms ACTH; 2) beta-endorphin (100 micrograms, iv), followed by 0.2 micrograms ACTH iv; 3) 0.2 micrograms ACTH iv; and 4) beta-endorphin (100 micrograms iv) alone. The integrated cortisol response to exogenous ACTH, calculated as the area under the cortisol response curve, was significantly less when the ACTH infusion was preceded by the 30-min beta-endorphin infusion than when administered alone [163 +/- 50 (SE) microgram/dl X min vs. 282 +/- 51 micrograms/dl X min, respectively; P less than 0.01]. By contrast, there was no difference between the integrated cortisol response to exogenous ACTH alone and exogenous ACTH after the bolus dose of beta-endorphin (282 +/- 51 vs. 293 +/- 39 micrograms/dl X min, respectively). Beta-Endorphin (30-min infusion or 100-micrograms bolus dose alone) caused no change in serum aldosterone, dehydroepiandrosterone, or PRA. Serum PRL levels, however, were raised significantly (P less than 0.05) by the 30-min infusion of beta-endorphin. The infusion and bolus doses of beta-endorphin raised plasma beta-endorphin levels to over 100,000 pg/ml and 5,000 pg/ml, respectively. We conclude that very high plasma levels of beta-endorphin may influence the response of cortisol to ACTH through a direct effect on the adrenal cortex. However, even in disease states such as Addison's and Nelson's diseases, such levels of plasma beta-endorphin are not known to be achieved.

Adrenocorticotropic Hormone↗