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J Schrevel

Publications and source records attributed to J Schrevel.

17 recordsLinked to original sources
PubMed1992

Purification and characterization of a new 120 kDa alkaline proteinase of Trypanosoma cruzi.

A new alkaline proteinase activity was identified in cell-free extracts of Trypanosoma cruzi epimastigotes on the basis of its ability to hydrolyze the fluorogenic substrate N-Z-Gly-Gly-Arg-AMC. The optimal activity was at pH 8.0. After a three step-chromatography procedure using two anionic columns (DEAE-Sepharose and Mono Q) and a chromatofocusing column (Mono P), the proteolytic activity was associated with a single 120 kDa protein and was called Tc 120 proteinase. The molecular mass of the proteinase was confirmed by direct visualization of the proteolytic activity using a fluorometric assay on SDS-PAGE. The Tc 120 proteinase which also cleaves N-Z-Arg-AMC, N-Z-Phe-Arg-AMC and N-glutaryl-Gly-Arg-AMC substrates, is a cysteine-type proteinase with an unusual low sensitivity to E-64.

Amino Acid Sequence↗
PubMed1992

Endogenous superoxide dismutase activity in two Babesia species.

Babesia hylomysci and B. divergens were studied for superoxide dismutase (SOD) activity by enzyme assay and isoelectric focusing (IEF). In the two Babesia species, parasite-associated SOD is cyanide-insensitive and inhibited by H2O2, indicating that iron is the cofactor metal. Measurements of SOD activity from purified parasites show that the SOD activity detected in Babesia is, for the main part, due to an endogenous enzyme.

Animals↗
PubMed1992

Unexplained in-vitro fertilization failure: implication of acrosomes with a small reacting region, as revealed by a monoclonal antibody.

To determine the acrosomal characteristics related to in-vitro fertilization (IVF) outcome, spermatozoa from 50 men whose wives had resorted to IVF have been studied by indirect immunofluorescence microscopy with anti-human pro-acrosin monoclonal antibody 4D4 (mAb 4D4), prior to and after incubation in a capacitating medium. The antibody labelled only the acrosomal principal region (APR), revealing its shape (i.e. normal, small or amorphous) and its status (i.e. unreacted, partially or totally reacted). The IVF outcome distinguished: (i) spermatozoa which were able to fertilize at least one oocyte in vitro (group I; n = 25) and (ii) spermatozoa which failed to fertilize any oocyte in vitro (group II; n = 25). The semen characteristics of the two sperm groups, including the acrosome morphology, were similar according to conventional analysis. The mAb 4D4 detected in both the whole and the swim-up sperm cell fractions a lower percentage of normal APR in group II (< 50% for 10 patients in group II versus one patient from group I), which was related to a higher percentage of small APR. Moreover, after 21 h incubation, group II had a lower acrosomal loss index. The spermatozoa of five patients of this infertile group II did not undergo acrosomal modification whereas spermatozoa of all group I patients underwent the acrosomal reaction. The data showed that the relationship between acrosomal anomalies and IVF failure is mainly due to an increased incidence of acrosomes with a reduced size of the region involved in the acrosome reaction. Immunodiagnosis of this acrosomal region by means of mAb 4D4 is informative for IVF outcome.

Acrosin↗
PubMed1992

Babesia divergens vaccine.

A vaccine strategy against Babesia divergens bovine babesiosis was successfully developed after perfecting of an efficient in vitro culture. Crude supernatants and purified fractions were able to induce a vaccine protection in gerbils against B. divergens infection. More, supernatants induced an effective vaccine protection in cattle. The role of B. divergens exoantigens of 17, 37, 46, 70 and 90 kDa in the development of the immune response was clearly demonstrated in gerbils, cattle, and man.

Animals↗
PubMed1991

Cytological and immunological responses to Babesia divergens in different hosts: ox, gerbil, man.

A continuous in vitro culture system for Babesia divergens was initiated from a human isolate. It was maintained through 305 subcultures for 3 years using a low concentration of serum and a low haematocrit, with no decrease in the initial virulence. This in vitro system enabled the routine culture of all human and bovine B. divergens isolates thus far tested, with a mean parasitaemia level of 30%-40%. Different cytological aspects observed in the same isolate by optical and electron microscopy were described in parasitized ox, gerbil and human erythrocytes. The sequence of B. divergens antibody responses was determined in man and ox, enabling the precise identification of major B. divergens antigens as candidates for vaccines.

Animals↗
PubMed1991

Lipid traffic between high density lipoproteins and Plasmodium falciparum-infected red blood cells.

Several intraerythrocytic growth cycles of Plasmodium falciparum could be achieved in vitro using a serum free medium supplemented only with a human high density lipoprotein (HDL) fraction (d = 1.063-1.210). The parasitemia obtained was similar to that in standard culture medium containing human serum. The parasite development was incomplete with the low density lipoprotein (LDL) fraction and did not occur with the VLDL fraction. The lipid traffic from HDL to the infected erythrocytes was demonstrated by pulse labeling experiments using HDL loaded with either fluorescent NBD-phosphatidylcholine (NBD-PC) or radioactive [3H]palmitoyl-PC. At 37 degrees C, the lipid probes rapidly accumulated in the infected cells. After incubation in HDL medium containing labeled PC, a subsequent incubation in medium with either an excess of native HDL or 20% human serum induced the disappearance of the label from the erythrocyte plasma membrane but not from the intraerythrocytic parasite. Internalization of lipids did not occur at 4 degrees C. The mechanism involved a unidirectional flux of lipids but no endocytosis. The absence of labeling of P. falciparum, with HDL previously [125I]iodinated on their apolipoproteins or with antibodies against the apolipoproteins AI and AII by immunofluorescence and immunoblotting, confirmed that no endocytosis of the HDL was involved. A possible pathway of lipid transport could be a membrane flux since fluorescence videomicroscopy showed numerous organelles labeled with NBD-PC moving between the erythrocyte and the parasitophorous membranes. TLC analysis showed that a partial conversion of the PC to phosphatidylethanolamine was observed in P. falciparum-infected red cells after pulse with [3H]palmitoyl-PC-HDL. The intensity of the lipid traffic was stage dependent with a maximum at the trophozoite and young schizont stages (38th h of the erythrocyte life cycle). We conclude that the HDL fraction appears to be a major lipid source for Plasmodium growth.

Animals↗
PubMed1991

Analysis of immune responses of different hosts to Babesia divergens isolates from different geographic areas and capacity of culture-derived exoantigens to induce efficient cross-protection.

The immunoprecipitation of [35S]methionine-radiolabelled antigens from different Babesia divergens isolates by using bovine, gerbil, and human immune sera has shown that many B. divergens proteins contain epitopes shared between isolates. The cross-protective capacity of culture-derived soluble immunogens from the B. divergens Rouen 1987 isolate was tested against different B. divergens isolates. Results showed complete protection against the 7107b French isolate and substantial protection against the Weybridge 8843 English isolate (80% protection) and the Munich 87 German isolate (60% protection). In order to explain these vaccination results and to assess both the common and variable antigenicity of B. divergens, the antigenic patterns of the challenge isolates (Rouen 1987, 7107b, Weybridge 8843, and Munich 87) were compared by immunoprecipitation, using gerbil antisera raised against the Rouen 1987 vaccine isolate. Differences in the antigenic patterns and in the cross-protection of gerbils in these heterologous challenges were examined by studying the virulence and the antigenic status of each isolate.

Animals↗
PubMed1991

Human acrosome biogenesis: immunodetection of proacrosin in primary spermatocytes and of its partitioning pattern during meiosis.

Proacrosin biosynthesis timing during human spermatogenesis has been studied using the monoclonal antibody 4D4 (mAb 4D4). Frozen and paraffin-embedded sections of testicular biopsies were labelled by standard indirect immunofluorescence and avidin-biotin immunoperoxidase procedures. The labelling specificity was checked by immunochemistry assays on unrelated tissues and by western blotting of testis extracts showing that only the 50-55 x 10(3) Mr proacrosin was recognized by mAb 4D4. Proacrosin was first observed in the Golgi region of midpachytene primary spermatocytes. In late pachytene primary spermatocytes, proacrosin was observed in two regions located at opposite nuclear poles. During the subsequent steps of the first meiotic division, the two bodies containing proacrosin were located: (i) on opposite sides of the equatorial plate during metaphase; (ii) along the microtubular spindle during anaphase; and (iii) close to each chromosomal aggregate during telophase. Two bodies containing proacrosin were still observed in interphasic secondary spermatocytes. The single labelled area observed in early spermatids was found to increase considerably in size during spermiogenesis. Anomalies of proacrosin scattering were observed in patients with Golgi complex partitioning failure. These data reveal proacrosin biosynthesis during diploid and haploid phases of human spermatogenesis and the proacrosin partitioning pattern during meiosis.

Acrosin↗
PubMed1991

Isolation and characterization of a soluble antigen complex of Plasmodium falciparum with pyrogenic properties.

A soluble antigen complex, previously designated antigen no. 7 (Ag7) on the basis of the pattern obtained by crossed immunoelectrophoresis of culture supernatants of P. falciparum, was isolated by affinity chromatography. It was shown to be synthesized at the schizont stage of the parasite growth cycle and to be located on the surface of the schizonts. Antibodies to Ag7 did not inhibit the growth of the parasite in vitro. Ag7 is recognized by immune human sera from many parts of the world and it stimulated the production of specific antibody in mice when incorporated into immune-stimulating complex (ISCOM) structures. It also specifically stimulated in vitro proliferation of lymphocytes from clinically immune adults. That it induced the secretion of interleukin 1 by human monocytes and was pyrogenic in rabbits was of particular interest. Thus Ag7 has endotoxin-like properties which make it a possible candidate for an antitoxic malaria vaccine.

Animals↗
PubMed1991

Identification and localization of a soluble antigen, Ag2, of 136 kDa from Plasmodium falciparum in vitro cultures.

The soluble antigens, antigen 2 (Ag2) and antigen 6 (Ag6), were copurified from supernatants of P. falciparum in vitro cultures by affinity chromatography and Fast Protein Liquid Chromatography. Rabbit antibodies to Ag2 were raised and characterized by crossed immunoelectrophoresis. Ag2 appeared as a duplet with molecular masses of 136 and 120 kDa when tested by immunoblotting. Immunoprecipitation experiments on Triton X-100 extracted antigens from synchronized cultures showed that the antigen was synthesized in the schizont stage. Ag2 was located near the surface of schizonts in the parasitophorous vacuole and in clefts in the infected erythrocyte cytoplasma as shown by immunogold electron microscopy.

Adult↗
PubMed1990

Isoprenoid metabolism in Plasmodium falciparum during the intraerythrocytic phase of malaria.

Products of the isoprenoid metabolism were identified upon incubations of extracts from Plasmodium falciparum infected red blood cells with [14C] mevalonate. Uninfected erythrocytes and wild type yeast Saccharomyces cerevisiae extracts were used as controls. In parasitized red blood cells as well as in yeast extracts, mevalonate was converted into the biosynthetic isoprenoid precursors of sterol pathway until farnesyl pyrophosphate. In contrast, no mevalonate conversion was observed in uninfected erythrocyte extracts. The isoprenoid metabolism appeared stage-dependent as shown by the increase of radiolabelled farnesyl pyrophosphate amount at the beginning of the schizogonic phase (30-36 hours).

Acetates↗
PubMed1990

Biochemical characterization, localization and immunostimulating properties of a soluble glycoprotein, Ag1, isolated from in vitro cultures of Plasmodium falciparum.

The soluble amphiphilic glycoprotein, Ag1 (gp60), purified from supernatants of in vitro cultures of Plasmodium falciparum has a molecular mass of 60 kDa and did not exhibit size variation in the different P. falciparum isolates tested by immunoblotting. Ag1 was shown to interact with the lectin Erythrina christagalli agglutinin, which is specific for carbohydrates bearing beta-D-galactose(1-4)-D-N-acetylglucosamine. Indirect immunofluorescence studies showed that Ag1 is located on the surface of trophozoites and schizonts but not on the surface of merozoites. Ag1 is recognized by human immune sera from six different malaria-endemic regions. Ag1 induces in vitro proliferation of lymphocytes from malaria-immune individuals in an antigen-specific manner.

Animals↗
PubMed1990

Identification of major Babesia divergens polypeptides that induce protection against homologous challenge in gerbils.

[35S]methionine-radiolabeled proteins from the Babesia divergens Rouen 1987 isolate were immunoprecipitated with immune sera from three potential hosts: human, ox, and gerbil. The results showed a constant humoral response against major babesial antigens. Similarly, immunoprecipitation of radiolabeled in vitro culture supernatant demonstrated that the exoantigens of 37, 46, 70, and 90 kDA were the immunodominant polypeptides, whatever the host. The effects of vaccination with concentrated supernatant from B. divergens Rouen 1987 in vitro cultures (30 to 40% parasitemia) were examined in gerbils inoculated with the homologous B. divergens isolate. Gerbils having received two or three injections of a whole vaccine dose (1.5 ml of parasitized culture supernatant equivalent [PCSE]) or of a 1:5 diluted vaccine dose (0.3 ml of PCSE) showed 100% survival after intraperitoneal challenge with 10(6) B. divergens-infected gerbil erythrocytes. Moreover, two or three injections of a 1:25 diluted vaccine dose (0.06 ml of PCSE) or 9% NaCl or 1.5 ml of unparasitized culture supernatant equivalent resulted in a mortality rate of 80 to 90% of the infected gerbils. Immunoprecipitation and immunofluorescence assays performed with antisera from vaccinated and control gerbils demonstrated that a single vaccine injection induced a humoral response, which increased slightly after the second or third injection. After challenge, antibody levels increased significantly, although the immunoprecipitation did not display any modification of Babesia antigen patterns.

Animals↗
PubMed1978

Formation and growth of gap junctions in mouse myocardium during ontogenesis: a freeze-cleave study.

The freeze-cleave technique demonstrates the presence of gap junctions at early stages of mouse cardiac muscle ontogenesis. The formation and growth of these junctions were studied at 4 stages of development: 10, 14, 18 days post-coitum (dpc) and at the adult stage. The diverse aspects of the gap junctions are interpreted as different steps in their formation. The first indication of this formation seems to be the presence of linear arrays of 9-nm particles on PF faces. At one end of these arrays a small aggregate of particles appears which acts as nucleation site and grows by incorporating individual gap particles and/or linear arrays. Nexuses with arms and/or central particle-free zones would represent intermediate steps in the formation of junctions. The largest nexuses could be formed by fusion of smaller ones and/or by accretion of gap particles. Analysis of the size distribution of gap junctions shows their growth during their development. At 10 dpc the surface area (S) of nexuses ranges from 0.1 to 3 x 10(-2) micrometer2, at 14 dpc from 0.1 to 15 x 10(-2) micrometer2, at 18 dpc from 0.1 to 26 x 10(-2) micrometer2, and at the adult stage from 0.1 to 54 x 10(-2) micrometer2. The percentage of large nexuses (Sgreater than 0.5 x 10(-2) micrometer2) steadily increases from 10 dpc to the adult stage. Fixation by glutaraldehyde before glycerol infiltration does not induce any modification in the size distribution of adult heart gap junctions.

Animals↗
PubMed1975

[A functional flagella with a 6 + 0 pattern].

The male gamete of the Gregarine Lecudina tuzetae has been studied with transmission electron microscopy and microcinematography. It is characterized by a flagellar axoneme of 6 + 0 pattern, a reduction of the chondriome, and the abundance of storage polysaccharide or lipid bodies. The movements of the flagella are of the undulating type and they are performed in the three dimensions of space. They are very slow, with a cycle time of about 2s. The structure of the axoneme components are similar to those of flagella with a 9 + 2 pattern. Each doublet has overall dimensions of 350 x 220 A; the space between the adjacent doublets is about 160 A. The A subfiber bears arms like dynein arms. The diameter of the axoneme is about 1,000 A. The basal body consists of a cylinder of dense material 2,500 A long and 1,300-1,400 A in diameter; a microtubule 200 A in diameter is present in the axis. This study shows that a 6 + 0 pattern can generate a flagellar movement. The mechanism of the flagellar movement of the male gamete of L. tuzetae does not require the presence of central microtubules and it would include molecular interactions of the dynein-tubulin type between the adjacent peripheric doublets. The slowness of the movements is discussed in terms of the axoneme's structure and its energy supply. Finally, the phylogenetic significance of this flagella is examined on the basis of the morphopoietic potentialities of the centriolar structures.

Animals↗