Search PubMed⌕ Search

Biomedical subjects

A Brown

Publications and source records attributed to A Brown.

At least 703 records · Page 39Linked to original sources
PubMed1968

Interference among group A arboviruses.

Interference among group A arboviruses is described which does not involve the mediation of interferon. Interference was observed only if the interfering virus had an advantage over the challenge virus, either in time or in multiplicity of infection. Adsorption, penetration, and uncoating of challenge virus did not appear to be inhibited, but the synthesis of infectious viral ribonucleic acid of the challenge virus was significantly retarded. It was shown with temperature-sensitive viruses or mutants that the replication of viral ribonucleic acid by the interfering virus was required to establish interference. A mechanism of interference based on a competition for replication sites or substrates is compared with other possible explanations.

Arboviruses↗
PubMed1968

Fractionation of Eastern equine encephalitis virus by density gradient centrifugation in CsCl.

When partially purified Eastern equine encephalitis (EEE) virus was centrifuged to equilibrium in CsCl, three virus specific bands were observed. A hemagglutinin was detected at a buoyant density of 1.18 g/cm(3). Infectious EEE virus banded in two positions; most of the virus banded at 1.20 g/cm(3) and a lesser amount banded at 1.22 to 1.23 g/cm(3). Analysis of radioactive profiles of CsCl-fractionated EEE virus labeled with either (32)PO(4) or (3)H-uridine suggested that the hemagglutinin was stripped from the intact EEE virion. The viral origin of the hemagglutinin was verified by inhibition with specific antiserum. Attempts to differentiate between infectious EEE virus of the different buoyant densities showed that the denser particle was neither a virus contaminant nor a density mutant. No evidence was obtained to indicate that the denser particle was an immature form of EEE virus. The two infectious EEE species obtained after CsCl fractionation were indistinguishable antigenically. Furthermore, unfractionated as well as CsCl-fractionated EEE virus sedimented at about 260S in sucrose gradients. These results together with the results of rebanding experiments suggested that the denser EEE species (1.23 g/cm(3)) results from a salt (CsCl)-induced alteration or breakdown of the EEE virion (1.20 g/cm(3)), and that it arises as the hemagglutinin is stripped from the surface of the EEE virion.

Arboviruses↗
PubMed1967

Temperature-sensitive steps in the biosynthesis of Venezuelan equine encephalitis virus.

In contrast to Eastern equine encephalitis virus, the replication of Venezuelan equine encephalitis (VEE) virus was strongly inhibited at 44 C in chick embryo cells. The inhibited steps were analyzed by shifting the incubating temperatures up or down, and by determining during the shifts the rate and extent of infectious ribonucleic acid (RNA) synthesis, intact virus synthesis, and formation of complement-fixing antigen or of antigen detectable by a direct fluorescent-antibody technique. The inhibition appeared to be due to two temperature-sensitive steps involved in the synthesis of VEE virus in chick embryo cells. The first step of inhibition at 44 C occurred early in virus replication and could be completely reversed simply by transferring cultures to 37 C. The inhibition appeared to take place at some point between the time when the virus entered the cell and was uncoated and the beginning of viral RNA synthesis. The second temperature-sensitive step in VEE virus synthesis was irreversible; it occurred at a point after the synthesis of viral RNA, and before the formation of virus protein measured as complement-fixing antigen or as antigen that could be stained with fluorescent antibody.

Animals↗
PubMedDate not supplied

Combined plasmid and peptide analysis of clinical and environmental Legionella pneumophila strains associated with a small cluster of Legionnaires' disease cases.

Plasmid and peptide analysis was used to characterize Legionella pneumophila strains isolated in the study of a small cluster of cases in hospitalized patients. The isolates from the Denver Veterans' Administration Medical Center could be clearly separated into three groups. Two of the three clinical isolates were found to be plasmidless, as were five of 19 environmental isolates. The patient isolates had plasmid and peptide profiles which were identical to the showerhead isolates to which each patient was exposed. Thus, the data suggest that the patients acquired their disease strains from environmental sites in their particular hospital wing, and that each wing of the building had its own unique flora of Legionella strains. The results also confirm the usefulness of using both these techniques when tracing transmission patterns of nosocomial disease.

Colorado↗
PubMedDate not supplied

Antigenic specificity of the antibody response in humans during legionellosis.

The antigenic specificity of the human immune response during legionellosis was studied. Twenty-two sera obtained from 12 individuals were studied using the Western-blot technique with antigens from various legionella. In five of six patients, the reactivity of their sera obtained at different times during legionellosis was qualitatively constant. In one patient, a new IgG antibody to a 50 Kdal bacterial antigen appeared between the 14th and 22nd day after infection. In every patient, the IgG and IgM responses differed. When the patient's serum was reacted with antigen prepared from the isolate obtained from that patient or from a closely related isolate, the antibody response appeared to be directed against broad antigenic bands.

Antibodies, Bacterial↗