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Biomedical subjects

J Edwards

Publications and source records attributed to J Edwards.

At least 307 records · Page 17Linked to original sources
PubMed1983

Conformational changes in Sindbis virus envelope proteins accompanying exposure to low pH.

The attachment of high multiplicities of Sindbis virus to tissue-cultured cells followed by brief treatment at low pH has been shown to produce cell fusion (fusion from without). In this report, experiments to determine the effects of low pH on the physical and biological properties of Sindbis virus are described. Exposure of purified Sindbis virions to mildly acidic conditions resulted in a rapid and irreversible alteration in particle density and sedimentation characteristics, followed by a slower loss of infectivity. Infectivity was not restored by a return to neutral pH; rather, the loss of virus infectivity seemed to be initiated by exposure to low pH but continued at neutral pH. The formation of a virus-cell complex in which virions were attached to the cell surface protected the particles from low-pH inactivation, although low pH could still expose virus functions responsible for cell fusion. Low pH was found to induce a conformational change in the E2 polypeptide of the intact virion. These results are discussed with respect to the process of Sindbis virus infection of tissue-cultured cells.

Animals↗
PubMed1982

Transcriptional initiation and processing of the small ribosomal RNA of yeast mitochondria.

We have identified the nucleotide at which transcription initiates on the yeast mitochondrial small (14 S) rRNA gene by sequencing of RNA labeled at the 5' initiating triphosphate with vaccinia virus guanylyltransferase [alpha-32P]GTP (in vitro capping reaction). Initiation occurs within the stem of a 12-base palindromic repeat. The initiation sequence has homology with the large (21 S) ribosomal RNA initiation sequence that has been previously determined. We have also sequenced the 5' and 3' ends of the mature 14 S rRNA after labeling with T4 polynucleotide kinase and RNA ligase, respectively. These sequences demonstrate that about 80 nucleotides are cleaved from the 5' end of a precursor to produce the mature 14 S rRNA. This cleavage is imprecise in that the processing occurs at one of five adjacent nucleotides 77 to 81 nucleotides downstream from the 5' initiation site. The 3' ends of this precursor and the mature 14 S rRNA are unique and identical.

Base Sequence↗
PubMed1982

Induced coding strategies and hemispheric differences in matching letter pairs.

The importance of task requirements in producing visual half-field asymmetries was investigated through manipulation of the criteria by which a central probe and a unilateral target letter were matched. Physical characteristics of the letters were emphasized (those made up of straight lines only vs those having at least one curved feature, e.g. F vs P). An interaction of visual field and type of judgment (match vs mismatch) was found for manual response time. Matching responses were faster to RVF than LVF probes and mismatches were faster to LVF than RVF probes. The significance of this interaction for models of hemispheric asymmetry is discussed.

Adult↗
PubMed1982

Monoclonal antibodies to the murine Ly-2.1 cell surface antigen.

Six monoclonal anti-Ly-2.1 antibodies are described that arose from a single fusion using the spleen from a 129/ReJ mouse immunized with CBA/H thymus cells. The specificity was determined from the strain distribution, and testing of congenic strains where all six monoclonal antibodies detected the Ly-2.1 alloantigen. Furthermore, the antibodies fall into two groups: Group I (four antibodies) detected the expected number of Ly-2+ thymocytes and peripheral T cells, whereas Group II (two antibodies) detected 10% fewer peripheral T cells. Functional studies demonstrated that the Ly-2.1 determinant detected by a Group I antibody (49-31.1) was presented on cytotoxic T cells (Ly-1+2+), on concanavalin A (Con A)-induced suppressor T cells (Ly-1-2+), but absent from helper T cells (Ly-1+2-). One antibody (49-11.1) precipitated a 68,000-75,000 mol.wt glycoprotein, which on reduction yielded 30,000 and 35,000 mol.wt moieties. Thus, by functional, genetic and biochemical criteria these antibodies detected the Ly-2.1 specificity. In addition, a monoclonal, noncytotoxic, IgGl, anti-Thy-1.2 antibody is described.

Animals↗
PubMed1981

Laser microsurgery in cell and developmental biology.

New applications of laser microbeam irradiation to cell and developmental biology include a new instrument with a tunable wavelength (217- to 800-nanometer) laser microbeam and a wide range of energies and exposure durations (down to 25 X 10(-12) second). Laser microbeams can be used for microirradiation of selected nucleolar genetic regions and for laser microdissection of mitotic and cytoplasmic organelles. They are also used to disrupt the developing neurosensory appendages of the cricket and the imaginal discs of Drosophila.

Animals↗
PubMed1981

Allergy in laboratory animal workers.

179 people working with small laboratory animals were studied by questionnaire, lung-function tests, skin tests with common allergen extracts and extracts of the serum and urine of five animal species, and serology. 49 people had symptoms related to animal contact, most commonly rhinitis but also asthma and skin rashes. Skin reactivity to animal extracts was related to symptoms, particularly asthma, but many people with rhinitis only had negative skin tests. Positive skin tests without symptoms were rare. 3 people had additional late skin reactions. Atopic individuals were no more likely than non-atopics to have animal-related symptoms but were more likely to have asthma. Gel diffusion revealed no precipitating antibodies, and no specific IgG was detected with the ELISA technique. Lung-function measurements were normal. Sensitisation to laboratory animals may involve heavy antigen exposure, so that relatively unreactive individuals can be affected. Exclusion of atopic individuals from work with laboratory animals will not eliminate the problem.

Animals↗
PubMed1981

Effects of chloroquine and cytochalasin B on the infection of cells by Sindbis virus and vesicular stomatitis virus.

The effects of cytochalasin B and chloroquine on the process of endocytosis of Sindbis virus particles and polystyrene spheres were determined by electron microscopy. The effects of these agents on the process of infection (attachment, penetration, and uncoating) of BHK-21 cells by Sindbis virus and vesicular stomatitis virus were also determined. Cytochalasin B completely blocked ingestion of Sindbis virus particles or latex spheres by BHK cells but had no effect on the ability of Sindbis virus or vesicular stomatitis virus to infect or replicate in BHK cells. Chloroquine did not inhibit the ingestion of either latex spheres or virus particles but greatly reduced the yields of virus produced. These data suggest that endocytosis is not essential for the infection of cultured cells by Sindbis virus or vesicular stomatitis virus.

Animals↗
PubMed1981

An investigation of operating theatre staff exposed to humidifier fever antigens.

Sixty staff working in a hospital operating theatre, where a case of humidifier fever had been identified, were studied together with 49 subjects working in other parts of the hospital. They each had a blood test for serology, a skin test, and a chest radiograph and completed a questionnaire. The theatre staff also had pulmonary function tests. The theatre humidifier was found to contain several organisms including amoebae and antigens cross-reacting highly with those implicated in previous outbreaks of humidifier fever. Of the 60 exposed subjects, 25 had developed antibodies, nine had probable symptoms of humidifier fever, and six possible symptoms. There was a strong association between symptoms and antibodies (p = 6 x 10(-5) by Fisher's exact test). The development of antibodies was also related to duration of exposure in the theatre (p less than 0.01 by X2 test for trend) and inversely to smoking (p = 0.0073 by Fisher's exact test) but not to history of atopy. Because of the presence of antigens and because certain biocides added were ineffective in controlling antigenic build-up the humidifier was switched off. Eight months later specific IgG levels in the theatre staff sera, estimated by an enzyme-linked immunosorbent assay technique, had fallen on average by 25%. Inhalation challenge with humidifier water was performed in eight subjects. Four subjects reacted to the challenge, including both those with antibodies and previous symptoms.

Air Conditioning↗
PubMed1981

International conference on byssinosis. Mechanisms of disease induction.

From this work and other published data there are at least three distinct compounds that have been shown to be capable of inducing symptoms of byssinosis. There is an aminopolysaccharide-protein complex in cotton plant bracts that acts by causing histamine release in the human lung and also causes necrosis of bronchiolar epithelium. There is endotoxin or endotoxin-like material present in cotton plant bracts that acts by a mechanism other than by causing histamine release. This can induce histologic features of chronic bronchitis over a period of time. There is a polyphenol compound whose action is unlikely to be via complement activation, even though higher titers of antibody to it are present in byssinotic compared with nonbyssinotic subjects. It is postulated that such a compound is held in the lungs by antibody and exerts its effect on the pulmonary vasculature, altering capillary resistance. It also produces pathologic change as might be expected from its ability to precipitate proteins and activate complement.

Alcohols↗
PubMed1980

Cooperative structural transition of PM2 DNA at high ionic strength and its dependence on DNA damages.

Pohl and Jovin have shown that poly(dG--dC) . poly (dG--dC) in solution undergoes a cooperative transition at 2.5 M NaCl at neutral pH. The two forms of the polymer are structurally different as indicated by a change in ethidium bromide intercalation and in circular dichroism (CD). Wang et al. and Davies and Zimmerman have suggested that the low salt form of the polymer might correspond to the B form of DNA (right-handed helix) and the high salt form to the Z form of DNA (left-handed helix). We describe here a salt-induced transition of supercoiled PM2 DNA from a form which passes through nitrocellulose filters to a form which is retained by these filters. The transition occurs between 2.5 and 3.5 M NaCl. The dependence of the apparent equilibrium constant on the salt concentration indicates a cooperative transition. Irradiation of DNA with UV light or alkylation with N-acetoxyacetylaminofluorene (AAAF) shifts the transition to lower salt concentrations. The transition can also be observed with linear DNA but requires a much higher salt concentration.

Acetoxyacetylaminofluorene↗