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Biomedical subjects

G Torpier

Publications and source records attributed to G Torpier.

At least 73 records · Page 4Linked to original sources
PubMed1984

Excretion of ecdysteroids by schistosomes as a marker of parasite infection.

Ecdysteroids produced by schistosomes are released in biological fluids of infected hosts. In the sera, the concentration of ecdysteroids correlates with the permissiveness of the host to schistosome infection and its detection is available in the absence of positive parasitological tests. In the urine, ecdysteroid concentration decreases markedly after chemotherapy. 20-Hydroxyecdysone and its epimer were identified in the urine of infected patients using mass spectrometry. These data demonstrate for the first time that ecdysteroids are released by organisms. Moreover, they are potent molecules of parasite infection and can be used for parasite diagnosis.

Adolescent↗
PubMed1984

Neutrophil-mediated killing of Dipetalonema viteae microfilariae: simultaneous presence of IgE, IgG antibodies and complement is required.

Neutrophils from the peripheral washings of normal rats in the presence of sera obtained from rats immune to circulating microfilariae adhered to and killed the microfilariae of Dipetalonema viteae in vitro within 16-24 hr. No significant adherence or cytotoxicity was mediated by sera collected from animals with a high microfilaraemia or from normal rats. Ultrastructural studies show that neutrophils, which are bigger than microfilariae, can easily internalize the small larvae resulting in the disintegration of the parasite. Immunoadsorption and inhibition experiments showed that the adherence-promoting activity resides both in IgG and IgE classes of antibody. However, the mere participation of these two antibodies is not sufficient to effect neutrophil adherence towards microfilariae, the presence of complement is also required. Samples of fresh immune rat serum (fIRS) depleted in alternative pathway components of complement by treatment with zymosan A failed to mediate cell adherence to the parasite. fIRS inactivated for the classical pathway of complement by the chelating agent EGTA partially retains its activity in mediating cytotoxicity to microfilariae. The striking antigenic specificity of D. viteae antibodies was shown by their ability to mediate cytotoxicity only to D. viteae but not towards Brugia malayi microfilariae.

Animals↗
PubMed1983

Ecdysone and 20 hydroxyecdysone: new hormones for the human parasite schistosoma mansoni.

The insect moulting hormones, ecdysone and 20 hydroxyecdysone, were detected by the combined use of radioimmunoassay and high performance liquid chromatography in the human parasite Schistosoma mansoni. On day 11 after infection only the ecdysone form is present, but, on day 40 after infection the ratio between ecdysone and 20 hydroxyecdysone changes with anatomic localization of the adult worms in mammalian host. In the eggs, the ratio of these two hormones is identical to the ratio found in sexually mature worms located in mesenteric veins. These data demonstrate for the first time that S. mansoni synthesizes the steroid hormones ecdysone and 20 OH ecdysone which are potent molecules in stimulating growth and vitello-genesis of this gonochoric trematode.

Aging↗
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

Involvement of immunoglobulin E in the secretory processes of alveolar macrophages from asthmatic patients.

Alveolar macrophages from nonatopic donors were passively sensitized with allergen-specific IgE antibody from the serum of asthmatic patients. A selective release of 4-8% of the lysosomal beta-glucuronidase of these cells occurred within 30 min of contact with the related allergen or with anti-human IgE antibody, in the absence of any mast or basophil cells. The cell reactivity was dependent on the interaction of macrophages with IgE, as shown by the disappearance of the allergen-induced enzyme release after heating or IgE-immune adsorption of the sensitizing serum, but not after IgG-adsorption. Alveolar macrophages from asthmatic patients behaved similarly to passively sensitized normal macrophages. Contact with the related allergen or with anti-IgE antibody induced the same percentage of enzyme release, demonstrating that these cells possess allergen-specific IgE bound on their surface. 18% of them formed rosettes with anti-IgE-coated sheep erythrocytes, and 15-22% with allergen-coated erythrocytes, but lost this property after preincubation with the specific allergen. The presence of IgE-specific receptors on the macrophage surface was demonstrated both at the ultrastructural level with immunoperoxidase labeling, and at low magnification by the formation of 15-18% rosettes with human IgE-coated erythrocytes. The formation of such rosettes was inhibited after incubation of alveolar phagocytes with aggregated myeloma IgE. On the basis of these observations, the participation of the alveolar macrophages in IgE-mediated pulmonary hypersensitivity must be considered. Its precise involvement requires, however, further investigations.

Adult↗
PubMed1982

Detection of ecdysteroids in the human trematode, Schistosoma mansoni.

Freeze fracture study of Schistosoma mansoni membrane differentiation enabled us to describe the characteristic features of the tegumental membrane complex at various stages of development of this parasite. The observation of a membrane exuviation during the 10-20 day period of infection of the definitive host led us to search for possible hormonal control. The development of an appropriate radioimmunoassay has allowed the detection of significant production of ecdysteroids in a human platyhelminth. This hormonal material undergoes level variation during the development of post-cercarial stages of S. mansoni and its precise chemical characterization is presently being investigated.

Animals↗
PubMed1982

Subgenomic mRNA in OK10 defective leukemia virus-transformed cells.

OK10, a defective leukemia virus, is produced as a defective particle by so-called nonproducer transformed quail fibroblasts. OK10 defective viral particles contain an 8-kilobases (kb)-long genomic RNA, lack any detectable reverse transcriptase activity, and are not infectious. We studied the genetic content of OK10 RNA extracted from both virions and infected cells. As shown by RNA-cDNA hybridizations in stringent conditions, about 77% (6.4 kb) of the OK10 8.0kb RNA was related to avian leukosis viruses in the three structural genes gag, pol, and env, as well as in the c region. The remainder of the OK10 genome-encoding capacity (</=1.6 kb) was homologous to the MC29-specific transforming sequence myc(m) and therefore has been named myc(o). EcoRI restriction analysis of the OK10 integrated proviral DNA with different probes indicated the presence of only one provirus in the OK10 QB5 clone, which agreed with the gene order: 5'-gag-Deltapol-myc(o)-Deltaenv-c- 3'. Heteroduplex molecules formed between the viral OK10 8.0-kb RNA and the 6.8-kb SacI DNA fragment of the Prague A strain of Rous sarcoma virus confirmed that structure and indicated that the myc(o) sequence formed a continuous RNA stretch of 1.4 to 1.6 kb long between Deltapol and Deltaenv. We also examined the myc(o)-containing mRNA's transcribed in OK10-transformed cells. OK10-transformed quail fibroblasts (OK10 QB5) transcribed two mRNA species of 8.0 and 3.6 kb containing the myc(o) sequence. The genetic content of the 3.6-kb species made it a possible maturation product of the genome size 8-kb species by splicing out the gag and pol sequences. In OK10-transformed bone marrow cells (OK10 BM), a stable bone marrow-derived cell line producing OK10, the myc(o) sequence was found in four RNA species of 11.0, 8.0, 7.0, and 3.6 kb. Again, the genetic content of these mRNA's indicated that (i) the 3.6-kb species could be spliced out of the 8.0-kb-genome size mRNA and (ii) the 11.0-kb-long mRNA could represent a read-through of the OK10 provirus, the corresponding maturation product being, then, a 7.0-kb mRNA. The 7.0- and 3.6- kb mRNA's both contained the myc(o) sequence, but no sequences related to the gag or pol gene. In conclusion, whereas the myc sequences have been generally thought to be expressed through a gag-onc fusion protein, as for MC29 and CMII viruses, our experiments indicate that they could also be expressed as a non-gag-related product made from a subgenomic mRNA in the OK10-transformed cells.

Animals↗
PubMed1981

Proteolytic cleavage of IgG bound to the Fc receptor of Schistosoma mansoni schistosomula.

After the binding of IgG to the surface Fc receptor of Schistosoma mansoni schistosomula, the Fab portions of IgG are cleaved and small peptides are liberated in the culture medium. At least two types of proteinase activities have been demonstrated in the secretory products of schistosomula. One is an endoprotease with trypsin-like activity, with an optimum pH of 7 and an optimum temperature of 45 degrees C. The other is a metalloaminopeptidase with an optimum pH of 7 and temperature of 37 degrees C.

Chymotrypsin↗
PubMed1979

Bromodeoxyuridine-induced reversion of transformed characteristics in BHK21 cells: changes at the plasma membrane level.

When BHK21 cells transformed by hamster sarcoma virus are grown in the presence of 5-Bromedeoxyuridine (BUdr), several in vitro properties of the transformed cells such as morphology, adhesiveness, and alignment, revert towards a state close to that of untransformed cells. We have studied plasma membrane changes associated with this phenotypic reversion by several different biochemical methods. Reversion is accompanied by a reappearance of Fibronectin, an increase in a membrane-associated protein of M.W. 100,000 which is increased in transformed cells and a decrease in Con A-agglutinability. On the other hand, several membrane changes associated with malignant transformation namely, the increase in an integral membrane protein M.W. 177,000, the higher rate of hexose uptake, the increase in high molecular weight surface glycopeptides and, to some extent, the increase in the density of intramembranous particles, did not revert under BUdr treatment. Thus, membrane properties of transformed cells may be dissociated into two main groups by BUdr treatment. In addition, the exposure and glycosylation of a growth-regulated membrane protein M.W. 160,000 was highly sensitive to BUdr.

Agglutination↗