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Biomedical subjects

E Wells

Publications and source records attributed to E Wells.

46 records · Page 3Linked to original sources
PubMed1983

Tegument surface membranes of adult Schistosoma mansoni: development of a method for their isolation.

Several approaches to surface membrane stripping have been applied to the adult schistosome. Membrane removal was evaluated by the use of different extrinsic and intrinsic markers of which alkaline phosphatase proved to be the most reliable. After initial studies employing incubation of worms in buffer alone, Triton X-100 or freeze/thaw, the last method was chosen for development. The final method applies a single freeze/thaw step to adult worms in balanced salt solution followed by short bursts of agitation on a vortex mixer to release the tegument. Differential and density gradient steps subsequently yield a final membrane pellet enriched over 130 times in surface alkaline phosphatase. The method has been characterized during its development using electron microscopy and enzyme markers for contaminant worm fractions.

Alkaline Phosphatase↗
PubMed1983

Identification of exposed components on the surface of adult Schistosoma mansoni by lactoperoxidase-catalysed iodination.

Adult schistosomes have been labelled with 125I using the lactoperoxidase-catalysed technique modified to cause minimal worm damage. After surface membrane removal and characterization, at least 13 labelled proteins were identified together with a large amount of labelled glycolipids, free fatty acids and phospholipids, especially phosphatidyl ethanolamine. Cationised ferritin has been used to stimulate surface membrane turnover of iodinated worms and the shedding of covalently bound 125I-counts used as an index of turnover. Finally worms have been iodinated before and after stimulation of membrane turnover in chemically defined media and the patterns of labelled proteins were compared.

Alkaline Phosphatase↗
PubMed1983

Laboratory infection of primates with Ascaris suum to provide a model of allergic bronchoconstriction.

Wild-caught non-human primates are naturally sensitive to Ascaris antigen and provide a useful model for studying atopic asthma. The present study was carried out to determine the effect of experimentally infecting home-bred macaques with the nematode Ascaris suum and hence provide an alternative for the naturally occurring model. Following oral infection with the parasite the animals developed a blood eosinophilia and specific antibodies to purified Ascaris antigen. These antibodies appeared to be of the IgE class as they could be detected by a radiometric assay using a radiolabelled antibody to human IgE. However, on further investigation, using the passive cutaneous anaphylaxis test, two classes of antibody were found, a heat labile (56 degrees C) and a heat stable antibody. Lung lavage cells taken from monkeys infected with Ascaris suum were shown to include cells morphologically characteristic of mast cells and released histamine when challenged in vitro with Ascaris antigen. Hence this model of immediate hypersensitivity provides a simple alternative to the less accessible natural model.

Animals↗
PubMed1983

Ascaris-induced bronchoconstriction in primates experimentally infected with Ascaris suum ova.

Bronchial provocation with Ascaris allergen evoked bronchoconstriction in home-bred Macaca arctoides monkeys sensitized by experimental infection with embryonated Ascaris suum ova. Inhalation of Ascaris allergen by aerosol prior to infection produced no changes in lung function. In infected animals total lung resistance (RL) increased and dynamic lung compliance (Cdyn) decreased following Ascaris inhalation. The changes in lung function reached a peak, 2-5 min after allergen inhalation, lasted for approximately 30 min and were associated with increases in arterial plasma histamine levels and decreases in arterial Po2 levels. Reproducible changes in lung function were obtained when the monkeys were challenged at bi-weekly intervals and lung sensitivity to Ascaris was maintained for at least 6 months. Histamine produced similar changes in RL and Cdyn before and after infection. Ascaris-induced bronchoconstriction was reversed by the beta 2-stimulant, salbutamol, and was partially reversed by cholinergic blockade with atropine. The responses were not inhibited by antihistamines or sodium cromoglycate although a new anti-allergic agent, FPL 58668 (disodium salt), inhibited Ascaris-induced bronchoconstriction and the increase in plasma histamine levels seen after Ascaris inhalation. Ascaris-induced bronchoconstriction in experimentally infected monkeys provides an animal model demonstrating many of the characteristics of allergic asthma in man and does not require the use of wild-caught monkeys.

Airway Resistance↗
PubMed1982

The incidence and epidemiology of retinoblastoma in New Zealand: A 30-year survey.

One hundred cases of retinoblastoma were diagnosed in New Zealand-born children between 1948 and 1977 inclusive. Five patients had an affected parent, and of the remaining sporadic cases 25 had bilateral and 70 unilateral tumours. The frequency of retinoblastoma, 1 in 17,500 births, was similar to that reported for most other countries. There was no evidence of an increase in the incidence of all cases of sporadic retinoblastoma during the 30-year period studied, nor was there any significant fluctuation in their incidence with space and time. There was an excess of bilateral sporadic cases in the southern-most districts of New Zealand, but this was of marginal significance. There was no significance evidence for any environmental influence on the occurrence of retinoblastoma.

Age Factors↗
PubMed1980

The isolation of human-erythrocyte band-3 polypeptide labelled with a photosensitive hydrophobic probe.

To investigate the intramembranous domains of the major band-3 polypeptide, human erythrocyte membranes were labelled with 1-azido-4-[125I]iodobenzene. The anion-exchange protein has been isolated by a new procedure that decreases possible contamination by other integral membrane proteins of similar molecular weight. After chemical modification, the protein was subjected to proteolytic cleavage by several proteinases to yield a distinct pattern of peptides, a few of which contained radioactivity.

Anion Exchange Protein 1, Erythrocyte↗
PubMed1979

Use of photosensitive hydrophobic probes to label the membrane of the human erythrocyte.

Two photosensitive hydrophobic probes, azido [3H]benzene and 1-azido-4-iodo[3H]-benzene, have been compared for their effectiveness in labelling, selectively, the intramembranous domains of lipid and proteins. Both partition preferentially into the lipid bilayer and, upon irradiation, covalently attach to both phospholipids and membrane proteins; the more extrinsic polypeptides have a significantly lower specific radioactivity than that of the intrinsic species. Proteolytic experiments also reveal higher labelling of intramembranous regions of the proteins. Consistently, the iodinated form of the probe showed the greater preference for the non-polar phase and a higher degree of selectivity for labelling hydrophobic regions. The results also suggest that penetration through the annulus of tightly bound lipid surrounding integral proteins occurs readily.

Azides↗
PubMed1979

Labelling of the intramembranous region of the major sialoglycoprotein of human erythrocytes with a photosensitive hydrophobic probe.

Human erythrocyte membranes were incubated with the photosensitive hydrophobic reagent 1-azido-r-iodo[3H]benzene and the mixture was irradiated. The major sialoglycoprotein was then isolated and the labelled polypeptide subjected to proteolytic dissection. Characterization of the purified tryptic and chymotryptic peptides show that the probe is covalently attached only to the transmembrane region of the protein. This labelling pattern is discussed in relation to the use of such reagents for the identification of segments of membrane proteins exposed to the hydrophobic millieu of the membrane.

Amino Acid Sequence↗