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Biomedical subjects

P Clerc

Publications and source records attributed to P Clerc.

At least 55 records · Page 3Linked to original sources
PubMed1988

Functional somatostatin receptors on a rat pancreatic acinar cell line.

Somatostatin receptors from a rat pancreatic acinar cell line, AR4-2J, were characterized biochemically, structurally, and functionally. Binding of 125I-[Tyr11]somatostatin to AR4-2J cells was saturable, exhibiting a single class of high-affinity binding sites (Kd = 0.55 +/- 0.06 nM) with a maximal binding capacity of 258 +/- 20 fmol/10(6) cells. Somatostatin receptor structure was analyzed by covalently cross-linking 125I-[Tyr11]somatostatin to its plasma membrane receptors. Gel electrophoresis and autoradiography of cross-linked proteins revealed a peptide (Mr 80,000) containing the somatostatin receptor. Somatostatin inhibited vasoactive intestinal peptide (VIP)-stimulated adenosine 3',5'-cyclic monophosphate (cAMP) formation in a dose-dependent manner. The concentration of somatostatin that caused half-maximal inhibition of cAMP formation (IC50 = 0.4 nM) was close to the receptor affinity for somatostatin. Pertussis toxin pretreatment of AR4-2J cells prevented somatostatin inhibition of VIP-stimulated cAMP formation as well as somatostatin binding. We conclude that AR4-2J cells exhibit functional somatostatin receptors that retain both specificity and affinity of the pancreatic acinar cell somatostatin receptors and act via the pertussis toxin-sensitive guanine nucleotide-binding protein Ni to inhibit adenylate cyclase.

Adenylyl Cyclases↗
PubMed1987

Localization of plasmid loci necessary for the entry of Shigella flexneri into HeLa cells, and characterization of one locus encoding four immunogenic polypeptides.

We have previously cloned a 44 kb fragment from the virulence plasmid of Shigella flexneri serotype 5 strain M90T which is capable of restoring invasiveness to an avirulent, plasmidless mutant. This report presents a genetic and physical analysis of Tn5 mutations in recombinant clone pHS4108. Tn5 mutagenesis allowed identification of at least five regions implicated in the entry phenotype. These regions were located on a 20 kb portion of pHS4108. Expression of the insertion mutants was studied by immunoblots using the serum of a convalescent monkey infected by S. flexneri 2a, which recognized four plasmid-associated polypeptides. We propose that the four immunogenic polypeptides, a, b, c, and d, are encoded an operon.

Chromosome Mapping↗
PubMed1987

Entry of Shigella flexneri into HeLa cells: evidence for directed phagocytosis involving actin polymerization and myosin accumulation.

The enteroinvasive bacterium Shigella flexneri expresses a plasmid-mediated capacity to penetrate into nonphagocytic cells. By using 7-nitrobenz-2-oxa-1,3-diazole-phallacidin (NBD-phallacidin), a fluorescent dye which specifically stains microfilaments, we observed condensations of filamentous actin underneath the plasma membrane of HeLa cells which interacted with the invasive isolate M90T. As demonstrated by indirect immunofluorescence with the antimyosin monoclonal antibody CC-212, myosin accumulated at the same sites. The entry process could be synchronized by using strain SC301, a pIL22 transformant of M90T. pIL22, a recombinant plasmid encoding the Escherichia coli afimbrial adhesin AFA I, rendered shigellae highly adherent to HeLa cells. Using such a system, we demonstrated that the occurrence of bacterial penetration and the appearance of structures brightly stained by NBD-phallacidin were simultaneous events. Such microfilamentous structures resulted from de novo polymerization of the monomeric actin pool in a DNase I inhibition assay, as shown by measurement of the monomeric versus total actin content of infected HeLa cells. These data provide direct evidence that the penetration of S. flexneri into HeLa cells occurs through a mechanism similar to phagocytosis by professional phagocytes.

Actin Cytoskeleton↗
PubMed1986

VIP regulation of a human pancreatic cancer cell line: Capan-1.

VIP and secretin control the secretory function of the normal pancreas. We analysed their regulatory functions in a human pancreatic cancer cell line: Capan-1. Saturation binding experiments with 125I-VIP showed the existence of one class of binding sites of very high affinity: KD 6.4 +/- 3.0 X 10(-11) M and a low Bmax: 12 fmoles/10(6) cells, in both intact cells and membrane preparations. This site has not yet been described in normal or tumorous digestive cells. Competition binding experiments let us characterize two more binding sites, KD: 2.1 +/- 0.7 X 10(-9) M and 5.0 +/- 0.6 X 10(-8) M and the corresponding Bmax: 120 and 500 fmoles/10(6) cells. These sites are similar to those found on cells of the digestive tract. Competition binding experiments gave the following IC50: 3.0 +/- 0.9 X 10(-9) M for VIP; 2 +/- 0.6 X 10(-6) M for PHI; and 1 +/- 0.7 X 10(-5) M for secretin. VIP elicited a cAMP rise, the half maximal response being obtained at 1.2 X 10(-10) M. Secretin induced a cAMP response but only for concentrations higher than 10(-8) M. VIP receptors were found to be modulated by two factors: cell ageing and cell density. Cells chronically treated with VIP showed a slight decrease of their proliferation; insulin exerted an opposite effect. It is concluded that at the difference of normal pancreatic cells, the present cell line lacks secretin-preferring receptors and acquires some of the properties of intestinal cells.

Binding, Competitive↗
PubMed1986

Multiplication of Shigella flexneri within HeLa cells: lysis of the phagocytic vacuole and plasmid-mediated contact hemolysis.

Virulent strains of Shigella flexneri invade HeLa cells with high efficiency. This crucial step in the pathogenic process is encoded by a 140-megadalton plasmid which induces phagocytosis of the bacteria by host cells. In this report we used pWR100, the virulence plasmid of S. flexneri serotype 5, and pHS4108, a 32-megadalton subclone of pWR100, to demonstrate that the plasmid is also responsible for rapid intracellular growth of the bacteria. The ability to replicate intracellularly was not correlated with induction of Shiga toxin. However, plasmid-mediated intracellular multiplication was strongly correlated with the ability of the bacteria to rapidly and efficiently lyse the phagocytic vacuole and replicate freely in the cytoplasm. Temperature-regulated plasmid-mediated contact hemolytic activity strongly correlated with both phagosomal membrane lysis and efficient intracellular multiplication. We propose this virulence plasmid-associated hemolysin to be an important factor in the invasion and proliferation of Shigella spp. in mammalian cells.

HeLa Cells↗
PubMed1986

[Radiographic aspect of enterocystoplasties using the Kock technic].

Normal radiologic images obtained during postoperative review examinations of patients with bladder epithelioma, treated by cystectomy and continent enterocystoplasty using the recently introduced Kock's technique, are described and a programme of radiologic follow up of these patients proposed.

Female↗
PubMed1985

[Unusual cause of digestive hemorrhage in chronic hemodialysis patients: splenic aneurysm with arteriovenous fistula].

A 45 years old woman, hemodialysed since 1981, with an history of Staphylococcal septicemia in may 1983, is admitted in emergency room in may 1984 for massive gastro intestinal bleeding. After oesogastro fibroscopy suspecting duodenal ulcer, because continuous and recurrent bleeding, a laparotomy find only symptoms of portal hypertension (ascites, venous dilatation on abdominal oesophagus and stomach). The ligation of this venous dilatations stop temporarily the gastro intestinal bleeding. But recurrence of this bleeding conduct to a celiac angiography discovering a splenic aneurysm with arterio venous fistula. The surgical treatment of this aneurysm can stop the gastro intestinal bleeding. Histopathologic observation of this aneurysm can suspect an infectious origin.

Arteriovenous Fistula↗
PubMed1984

Dopamine receptors in a human colonic cancer cell line (HT29). Some receptor-related biological effects of dopamine.

The presence of dopamine receptors in normal colonic cells has been postulated from physiological studies. The existence of such receptors in human colonic tumor cells and their role in tumor progression are still unknown. The aim of the present work was to characterize the dopaminergic receptors in a human colonic adenocarcinoma cell line (HT29) and to evaluate the effect of dopamine on cAMP, protein and DNA synthesis. The binding characteristics of 3H-dopamine on the tumor cells were rapid, reversible, specific, saturable and stereospecific. The first site characterized corresponds to a D3 subtype:KD 3.09 nM, insensitive to sulpiride, unrelated to adenylate cyclase. Competitive inhibitions of 3H-dopamine binding by different drugs showed the existence of a second binding site, D1, with an apparent affinity for dopamine of 6,700 nM. The rank order of potency of inhibitors of 3H-dopamine binding was: haloperidol greater than dopamine greater than cis flupenthixol greater than (+) butaclamol greater than (-) butaclamol greater than trans flupenthixol greater than isoproterenol greater than clonidine greater than prazosin. D3 binding sites are modulated with age, Bmax was 116 fmol/10(6) cells on the 5th day and decreased to 8.2 fmol/10(6) cells on the 15th day of culture. Cell culture in serum-deprived medium allowed an increase in the number of high-affinity receptor sites. D1 sites are coupled to adenylate cyclase as shown by a dose-dependent cAMP accumulation from 10(-8) M to 10(-5) M dopamine concentrations. Interacting with D1 sites, dopamine evokes an increase in protein synthesis with no modification of 3H thymidine incorporation. The present results indicate that the human colonic cancer cell line HT29 exhibits dopamine receptors and that stimulation may induce metabolic modifications in the tumor cells.

Binding, Competitive↗
PubMedDate not supplied

Plasmid-mediated contact haemolytic activity in Shigella species: correlation with penetration into HeLa cells.

The main feature of virulent strains of Shigella is their ability to invade eucaryotic cells. This phenotype is both plasmid-mediated and temperature-regulated. In the present report, we demonstrate a plasmid-mediated and temperature-regulated haemolytic activity in S. flexneri, S. dysenteriae and S. sonnei. Detection of this haemolytic activity requires centrifugation of suspensions containing bacteria and erythrocytes, followed by incubation of the pellets at 37 degrees C. No soluble intra- or extracellular haemolytic activity could be detected. Dose-effect and electron microscopic studies demonstrated that direct contact of several virulent bacteria per erythrocyte was critical for haemolysis to occur. However, no local morphological alteration of the erythrocyte membrane at the site of contact with bacteria could be detected. Intensity of this haemolytic activity was fully correlated with the efficiency of penetration within HeLa cells, suggesting a common mechanism for induction of phagocytosis and lysis of erythrocytes.

Animals↗