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Biomedical subjects

I M Cesari

Publications and source records attributed to I M Cesari.

At least 37 records · Page 2Linked to original sources
PubMed1983

Schistosoma mansoni: surface membrane isolation by polycationic beads.

The Schistosoma mansoni surface membrane complex was isolated by binding polycationic beads to the worm surface in a sucrose- or sorbitol-acetate buffer, pH 5.0, at 4 C. The ratio of incorporation [3H]cholesterol/[14C]arachidonic acid was measured as well as the specific activities of the alkaline phosphatase (EC 3.1.3.1), Type I phosphodiesterase (EC 3.1.4.1), and Ca2+-adenosine triphosphatase (EC 3.6.1.3). The results indicated that membranes isolated on beads were of comparable or greater purity than membranes isolated by sucrose gradient centrifugation. The isolation procedure was rapid (30 min) and produced membrane fractions whose cytoplasmic surfaces were probably exposed.

Alkaline Phosphatase↗
PubMed1983

Enhancement of eosinophil effector function by soluble factors released by S. mansoni: role of proteases.

Schistosomulum-released products (SRP) have been shown to enhance both expression of rat and human eosinophil Fc receptors and IgG-dependent cytotoxicity. The present work provides additional evidence of the secretion of eosinophil-enhancing factors by schistosomula and other developmental stages of schistosomes, including adult worms. The heat lability, as well as the strong inhibition of the stimulating activity of SRP by the protease inhibitor Trasylol, suggest that thermolabile proteases secreted by the parasite are involved in this mechanism. The purification of the schistosome proteases by preparative isoelectric focusing and gel filtration demonstrated that neutral proteases able to hydrolyze the collagenase substrates Azocoll and Z-Gly-Pro-Leu-Gly-Pro are able to significantly enhance eosinophil effector functions. Purified Clostridium histolyticum collagenase was also able to mimic the enhancing effect of schistosome proteases, suggesting involvement of a collagenase-like activity of the enzymes in the eosinophil stimulation.

Animals↗
PubMed1983

Aminopeptidase activity in adult Schistosoma mansoni.

An aminopeptidase activity capable of hydrolysing leucine 4-nitroanilide and alanine 4-nitroanilide at pH 7.0 was detected in saponin-CaCl2 extracts and homogenates of adult Schistosoma mansoni. The extracts were also capable of acting on synthetic dipeptides at the same pH, preferentially hydrolysing peptide bonds following leucine, alanine, or proline N-terminal residues. Imide bonds were not hydrolysed. The hydrolysis of leucine 4-nitroanilide was apparently stimulated by thiols, strongly inhibited by 1 mM 4-chloromercuric benzene sulfonic acid, and partially inhibited by 1 mM 1,10-phenanthroline.

4-Chloromercuribenzenesulfonate↗
PubMed1982

Neutral protease activities at different developmental stages of Schistosoma mansoni in mammalian hosts.

Neutral protease activities of schistosomula, 20 day old and adult worms of S. mansoni have been studied. 1. The neutral enzymes of the three development stages are able to hydrolyse numerous natural and synthetic substrates. 2. The enzymes of homogenates and saponin CaC12 extracts show significant discrepancies in their specificities, optimum pH activities and in the effects of enzyme inhibitors. 3. A serine protease activity was specific for the schistosomula stage whereas thiol proteinases characterize the later stages of evolution. A metalloaminopeptidase activity was shown at all three stages. 4. Gel filtration chromatography and isoelectric focusing of an adult worm homogenate demonstrated the presence of at least 5 caseolytic and 4 azocollytic neutral activities. Three aminopeptidases, one of which exhibited iminopeptidase specificity were revealed by the same procedure.

Aminopeptidases↗
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

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↗
PubMed1973

Mouse lambda-chain sequences.

Amino-acid sequences of the variable regions of three lambda chains produced by plasmacytomas of BALB/c mice are compared. Two are almost certainly identical and one differs from these by three amino acids. These findings extend our earlier conclusion on the relative uniformity of sequences in this type of immunoglobulin light chain. With amino-acid sequence data on two additional lambda chains, eight mouse lambda chains studied to date are indistinguishable and four probably differ from these by one, two, or three amino acids.

Amino Acid Sequence↗
PubMed1969

Localization and properties of enzymes involved with electron transport activity in mycobacteria.

A study of the subcellular localization of the nicotinamide adenine dinucleotide (NADH)-3-(4, 3-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT) oxido-reductase systems in Mycobacterium was presented. Evidence based on starch gel electrophoresis and different responses of the subcellular fractions to heat inactivation suggested the existence of more than one enzyme responsible for the NADH-MTT oxido-reductase activity. One type of activity was found in the membrane-mesosome fraction which contained labile and electrophoretically non-migrating enzymes. Another type of activity was also detected in the soluble fraction which on starch gel electrophoresis exhibited 4 bands of activity, two of which showed heat resistance.

Cell Wall↗