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Biomedical subjects

A J Simpson

Publications and source records attributed to A J Simpson.

At least 217 records · Page 12Linked to original sources
PubMed1982

Technetium sulfur colloid scintigraphy in the detection of lower gastrointestinal tract bleeding.

99mTc sulfur colloid scintigraphy is a technique which can be used to localize sites of lower gastrointestinal hemorrhage. Two reports of patients illustrate its use clinically. This procedure is non-invasive, relatively inexpensive, easily performed and has a high degree of sensitivity. The technique may, in some instances, replace angiography or endoscopy as the initial procedure used to diagnose the site of lower gastrointestinal bleeding or, more likely, serve as a complementary diagnostic modality.

Aged↗
PubMed1982

Macrophages as effector cells of protective immunity in murine schistosomiasis. III. Loss of susceptibility to macrophage-mediated killing during maturation of S. mansoni schistosomula from the skin to the lung stage.

Newly transformed skin-stage and lung-stage schistosomula were compared in terms of their susceptibility to killing mediated by activated mouse macrophages in vitro. Although skin-stage schistosomula were readily killed by macrophages activated as a consequence of either BCG or Schistosoma mansoni infection and used either as cell monolayers or in suspension, lung-stage larvae appeared to be totally resistant to this effector mechanism and survived normally when reinjected into mice. Resistance of schistosomula to in vitro damage by macrophages was evident as early as 18 hr after host infection and was complete in worms recovered at 42 hr. The insusceptibility of lung-stage larvae is apparently not due to a defect in effector cell-target contact, because the induction of extensive macrophage adherence to the worms by the addition of anti-mouse red blood cell antisera to the cultures had no effect on parasite viability. These findings provide additional support for the concept that schistosomula during their development to the lung stage undergo a generalized change affecting their susceptibility to a variety of different immunologic effector mechanisms.

Aging↗
PubMed1981

Properties of a series of tegumental membrane-bound phosphohydrolase activities of Schistosoma mansoni.

1. Incubation of Schistosoma mansoni for 5 min in a phosphate-buffered medium, pH 7.4, released tegumental material containing the following phosphohydrolase activities: alkaline phosphatase, 5'-nucleotidase, glycerol-2-phosphatase, glucose 6-phosphatase, phosphodiesterase and ATPase. 2. Maximum activity of these enzymes was measured at pH 9.5; however, the phosphodiesterase and ATPase activities were also appreciable at pH 7.0. 3. Solubilization of the released tegumental material in 1% Triton X-100 followed by gel filtration distinguished three peaks of enzyme activity: an ATPase (mol.wt. greater than 1000 000), a phosphodiesterase (mol.wt. 1 000 000) and an alkaline phosphomonoesterase with broad specificity (mol.wt. 232 000). 4. The ATPase activity was highly activated by 10 mM-Mg2+ or 1 mM-Ca2+ and was inhibited by chelating agents. Ouabain, Na+ and K+ had little effect on enzyme activity, whereas activity was increased by 50% in the presence of calmodulin. The phosphodiesterase activity was highest in the presence of 100 mM-Na+ or -K+, and 10 mM-Mg2+ or -Ca2+. Alkaline phosphatase activity was also stimulated by 100 mM-Na+ or -K+, and 10 mM-Mg2+; however Ca2+ inhibited at greater than 1 mM. 5. Surface iodination of parasites followed by detergent solubilization and gel filtration of the released tegumental membranes indicated that these enzymes were not accessible. A major surface component, apparent mol.wt. 80 000, was iodinated. 6. Rabbit anti-(mouse liver 5'-nucleotidase) antibodies did not inhibit the phosphohydrolase activities. However, an immunoglobulin G fraction from sera of mice chronically infected with S. mansoni partially inhibited alkaline phosphatase activity, but was without effect on the phosphodiesterase and ATPase activities. 7. The location of the enzymes in the double membrane of the tegument and their significance in host-parasite interactions is discussed.

Animals↗
PubMed1981

Glycosyl transferase activities are associated with the surface membrane in adult Schistosoma mansoni.

Incubation of live adult Schistosoma mansoni in a variety of media released tegumental material containing membrane bound alkaline phosphatase, mannosyl transferase and galactosyl transferase activities. Centrifugation of the tegumental material released by incubation of worms in phosphate-buffered saline in sucrose density gradients yielded a pellet and four fractions, two of which consisted mainly of surface membranes. The distribution of the enzymes in the gradient, espeically in the two surface membrane-containing subfractions was similar. Application of the "digitonin shift" technique showed that the membranes containing the enzyme reactivities were moved to an equal extent into a denser part of the sucrose gradient. Thus the enzymes are located on the same or similar cholesterol-containing membranes. It is concluded that the transferases, like the alkaline phosphatases, are located in the surface membranes of S. mansoni and the consequences of this location for the host-parasite interaction are discussed.

Alkaline Phosphatase↗
PubMed1981

Isolation and partial characterization of the tegumental outer membrane of adult Schistosoma mansoni.

Incubation of adult Schistosoma mansoni at 37 degrees C in chemically defined media caused the shedding of variable amounts of the parasite's tegument. In phosphate-buffered saline, pH 7.4, 37% of 125I-labelled wheat germ agglutinin which was attached to the schistosome surface was released within 5 min. When the released material was collected by centrifugation at 55 000 g for 1 h, the pellet was seen to consist of components of the parasite tegument and contained 1% of the parasite protein and 6.2% of the 5'-AMPase activity. By monitoring the release of the gut enzyme, haemoglobinase, it was shown that predominantly tegumental material was released under these conditions. The material released from the parasite was separated by discontinuous sucrose gradient centrifugation into 4 major fractions and it was shown that a material banding at low density was highly enriched in vesicles of parasite outer membrane. Major polypeptides of apparent molecular weights 135 000, 110 000, 90 000, 65 000, 47 000 and 40 000 and glycoproteins of apparent molecular weights 135 000, 120 000, 65 000, 63 000 and 30-40 000 were identified in this fraction. Comparison of the distribution of 5'-AMPase activity and the contents of each fraction as revealed by ultrastructural examination showed that this enzyme is a good marker for the tegumental outer membrane.

Animals↗
PubMed1980

The incorporation and utilization of radiolabelled lipids by adult Schistosoma mansoni in vitro.

Live adult Schistosoma mansoni, maintained in vitro were able to absorb and utilize radiolabelled arachidonic acid, linolenic acid, 3-sn-phosphatidylcholine, tripalmitylglycerol and cholesterol in the culture medium. Differential centrifugation demonstrated that all these lipids were incorporated into the parasite's various membrane structures. Analysis by thin-layer chromatography of the labelled compounds which resulted from incubation with the labelled lipids revealed that arachidonic acid, linolenic acid and fatty acids of tripalmitylglycerol and 3-sn-phosphatidylcholine were present largely as triacylglycerol with smaller amounts of labelled diacylglycerol, phospholipids and fatty acids. The labelled polar head group of 3-sn-phosphatidylcholine was cleaved from the molecule during incorporation, which suggested that hydrolysis of complex lipids is an integral part of the absorption mechanism. Cholesterol was not apparently altered during incorporation or further metabolized. It was also observed that arachidonic acid was incorporated more readily than the other lipids, however, no prostaglandin biosynthesis was detected.

Absorption↗
PubMed1980

Characterization of the exposed carbohydrates on the surface membrane of adult Schistosoma mansoni by analysis of lectin binding.

The surface architecture of adult male Schistosoma mansoni was explored using a range of lectins with differing carbohydrate specificites. Highest specific binding was achieved with concanavalin A and the agglutinin of molecular weight 60000 from Ricinus communis; the binding of wheat germ agglutinin was mostly non-specific. Small amounts of peanut agglutinin and soybean agglutinin binding were observed and the binding of these lectins was increased by pre-treating the parasite with neuraminidase. The fucose binding protein of Lotus tetragonolobus failed to bind. These results indicate that mannose and/or glucose, galactose, N-acetylglucosamine, N-acetyl-galactosamine and sialic acid are exposed on the surface of the adult male schistosome.

Acetylgalactosamine↗
PubMed1979

The radiology corner. Segmental lymphangiectasia of the small bowel.

A case of intestinal lymphangiectasia, limited to a small segment of jejunum, is reported. This finding reflects part of the spectrum of generalized dysplasia of the lymphatic system. A discussion of the pathogenesis, pathophysiology and roentgen features of intestinal lymphangiectasia as part of a systemic disorder is presented.

Adult↗
PubMed1975

Gastrointestinal manifestations of the muscular dystrophies.

Five patients with acute megacolon with varied types of progressive muscular dystrophy are presented. Dysfunction of smooth muscle among patients with muscular dystrophy is reviewed. The extra gastrointestinal roentgen features are summarized. Recognition of the diffuse smooth muscular involvement among patients with muscular dystrophy is stressed for proper diagnosis and patient management.

Adult↗
PubMed1974

Appearance of specific colostrum antibodies after clinical infection with Salmonella typhimurium.

Colostrum and serum antibodies to Salmonella typhimurium have been found in three patients after clinical gastrointestinal infection during pregnancy. High levels of colostrum IgA agglutinins were directed specifically against both the flagellar and somatic antigens of the infective organism. The levels of colostrum agglutinating activity exceeded those found in the patients sera, while control colostrum gave negative results.

Agglutination Tests↗