Search PubMed⌕ Search

Biomedical subjects

J E Strickler

Publications and source records attributed to J E Strickler.

27 records · Page 2Linked to original sources
PubMed1982

Identification and partial characterization of plasma membrane polypeptides of Trypanosoma brucei.

A plasma membrane-enriched vesicle fraction has been prepared from Trypanosoma brucei by sonication and differential centrifugation on sucrose gradients. This fraction is enriched 5-fold in the plasma membrane marker enzymes adenyl cyclase (EC 4.6.1.1) and ouabain-inhibitable, (Na+ +K+)-dependent adenosine triphosphatase (EC 3.6.1.3). It is also enriched up to 14-fold in iodinated surface proteins, and up to 4-fold in (3H-mannose-labeled glycoproteins, of which the major variable surface coat glycoprotein is the main constituent. Proteins of the plasma membrane fraction and other subcellular fractions have been identified by electrophoretic analysis in sodium dodecyl sulfate-polyacrylamide gradient slab gels. Several high molecular weight surface glycopeptides have been selectively investigated and partially characterized by a combination of metabolic labeling with [3H]mannose, lactoperoxidase-catalyzed surface iodination, and affinity chromatography on Con A-Sepharose. In addition to the major variable surface coat glycoprotein (estimated Mr = 58000), there are several minor surface glycopeptides (Mr = 76000, 86000 and 92000-100000) which are apparent extrinsic membrane components, and two surface glycopeptides (Mr = 42000 and 130000) which are intrinsic membrane components.

Adenylyl Cyclases↗
PubMed1982

Trypanosoma brucei: effect of inhibition of N-linked glycosylation of the nearest neighbor analysis of the major variable surface coat glycoprotein.

As an assay for the surface deposition of newly synthesized major variable surface coat glycoprotein (VSCG) we have treated intact Trypanosoma brucei cells with the cleavable cross-linking reagent dithiobis-(succinimidyl propionate). Under appropriate conditions, surface VSCG is converted to oligomers of n not less than 8. The oligomeric protein, apparent molecular weight greater than 4 x 10(5), does not migrate more than 1 to 2 mm into a 3-15% linear polyacrylamide gradient gel containing 0.1% sodium dodecyl sulfate, hence the appearance of newly synthesized radiolabeled protein in the top 2 mm of the gel indicates the translocation of VSCG from the site of synthesis to the surface and the gross establishment of normal interactions among the molecules. In addition, purified VSCG treated with the cross-linking reagent yielded a dimeric product on gel electrophoresis. To examine the role of N-linked carbohydrate in the translocation of the protein and in intermolecular interactions we have allowed trypanosomes to incorporate L-[14C] serine into protein in the presence of the antibiotic tunicamycin. Our results show that N-linked carbohydrate is not essential to the transfer of VSCG to the cell surface nor does its absence interfere with gross intermolecular interactions in the short term. On the other hand N-linked carbohydrate does appear to play an essential role in dimer formation.

Animals↗
PubMed1980

Trypanosoma brucei brucei: inhibition of glycosylation of the major variable surface coat glycoprotein by tunicamycin.

Trypanosoma brucei brucei incorporates D-[3H]mannose into protein in vitro in a medium we describe here. The label appears entirely in glycoproteins with approximately 90% in the major variable surface coat glycoprotein (VSCG). Incorporation is linear for 60 min and usually continues for an additional 30 min although at a decreased rate. In the same medium incorporation of L-[14C]serine is linear for 90 min. Incorporation of [3H]mannose is completely inhibited by tunicamycin at concentrations above 100 ng/ml, indicating that the label is being added as part of an N-linked oligosaccharide. This is reflected by a 5% decrease in the apparent molecular weight of VSCG on sodium dodecyl sulfate/polyacrylamide gel electrophoresis. Cycloheximide inhibits incorporation of both mannose and serine, although the rates and extent of inhibition differ. Based on the effects of tunicamycin or cycloheximide on incorporation of either precursor, we suggest that N-linked glycosylation occurs subsequent to synthesis of the VSCG polypeptide.

Culture Media↗
PubMed1980

Detection and quantification of variant specific antigen in the plasma of rats and mice infected with Trypanosoma brucei brucei.

Variant specific antigen (VSA), the principal constituent of the surface coat of salivarian trypanosomes, was detected by gel immunoassays in the plasma of rats and mice infected with Trypanosoma brucei brucei. The quantity of VSA in plasma was measured in radial immunodiffusion tests using a monospecific antiserum and purified VSA as a standard. During the first peak of parasitemia, a statistically significant, linear relationship was determined between the number of parasites in the blood (in the range between 4 x 10(8) and 10(9)/ml) and the concentration of VSA in the plasma (28-320 microgram/ml). The VSA from parasites of the first peak was lost within 2 days of remission. Variant antigens of parasites constituting the second peak then began to appear in the plasma of infected rats. All plasma samples had been separated from parasites and blood cells within 15 min of blood collection. The pH of plasma was controlled with a buffered anticoagulant. No soluble parasite antigens, other than VSA, were detected in the plasma of infected hosts. The results of this study extend the observation that salivarian trypanosomes shed surface coat material during the course of infection. Thus, sloughed VSA may be the parasite product that has been hypothesized to cause the nonspecific lymphocyte proliferation, immunosuppression, and/or hypergammaglobulinemia which occur during African trypanosomiasis.

Animals↗
PubMed1975

Adenosine 3',5'-monophosphate in reproducing and differentiated trypanosomes.

Trypanosoma lewisi, a blood protozoan of rats, undergoes differentiation from a rapidly reproducing form to a nonreproducing form in response to the host antibody ablastin. Intracellular concentrations of adenosine 3',5'-monophosphate (cyclic AMP), which has been implicated in controlling reproduction in cultured mammalian cells, was measured in the two developmental forms of T. lewisi. The concentrations were significantly different, and the results support a hypothesis under which ablastin stimulates an increase in intracellular cyclic AMP.

Animals↗
PubMedDate not supplied

A protein kinase involved in the regulation of inflammatory cytokine biosynthesis.

Production of interleukin-1 and tumour necrosis factor from stimulated human monocytes is inhibited by a new series of pyridinyl-imidazole compounds. Using radiolabelled and radio-photoaffinity-labelled chemical probes, the target of these compounds was identified as a pair of closely related mitogen-activated protein kinase homologues, termed CSBPs. Binding of the pyridinyl-imidazole compounds inhibited CSBP kinase activity and could be directly correlated with their ability to inhibit cytokine production, suggesting that the CSBPs are critical for cytokine production.

Amino Acid Sequence↗