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Biomedical subjects

C Bernard

Publications and source records attributed to C Bernard.

At least 163 records · Page 9Linked to original sources
PubMed1995

Pentoxifylline selectivity inhibits tumor necrosis factor synthesis in the arterial wall.

Pentoxifylline (PTX) has been reported to potentially inhibit tumor necrosis factor (TNF) synthesis by monocytes/macrophages. Because inflammatory processes involve both leukocytes and vascular cells, we tested the effects of PTX on TNF and interleukin-6 (IL-6) production by the vessel wall in response to lipopolysaccharide (LPS). Rings of rat thoracic aorta were incubated for 24 h in DMEM containing antibiotics and 1% fetal calf serum in the presence of 1 microgram/ml LPS. TNF and IL-6 were biologically assayed using L-M fibroblast cytotoxicity and B9 hybridoma cell proliferation, respectively. Maximal LPS-induced production of TNF and IL-6 by the aorta was 0.77 +/- 0.04 and 23.3 +/- 3.5 x 10(3) U/mg dry weight, respectively. The addition of PTX dose-dependently suppressed the production of TNF by 26 +/- 7%, 58 +/- 6%, and 85 +/- 9% at 10, 100, and 1,000 microM, respectively. This effect was selective for TNF, because the production of IL-6 was not affected by any dose of PTX, suggesting a selective gene regulation of TNF and IL-6 in vascular cells. These results may have clinical implications. PTX may be useful in vascular inflammatory diseases, in which serum TNF levels have been shown to be correlated with the severity of the disease.

Animals↗
PubMed1995

Increased production of tumor necrosis factor and interleukin-6 by arterial wall of aged rats.

Plasma cytokine levels are enhanced in aged animals and in elderly people. Vascular cells are known to be both targets and sources of cytokines. To investigate the effect of aging on vascular cytokine synthesis, we studied tumor necrosis factor (TNF), interleukin-6 (IL-6), and prostacyclin (PGI2) production by the arterial wall using organoid culture of aorta from 10- (n = 8) and 30-mo-old (n = 8) rats, after activation by lipopolysaccharide (LPS). Biological activity of TNF and IL-6 was measured in supernatant from incubated vessels. 6-Ketoprostaglandin F1 alpha (6-keto-PGF1 alpha), a stable metabolite of PGI2, a secondary inflammatory mediator, was measured using enzyme immunoassay. In the absence of LPS, TNF production was undetectable in most animals and was not significantly increased in the aged group. By contrast IL-6 and 6-keto-PGF1 alpha productions, in the absence of LPS, were significantly greater in 30- (8,140 +/- 1,350 U/micrograms DNA and 23.2 +/- 6.4 ng/micrograms DNA, respectively) than in 10-mo animals (3,060 +/- 350 U/micrograms DNA and 8.4 +/- 1.6 ng/micrograms DNA, P < 0.01 and P < 0.05, respectively). LPS-induced production of TNF, IL-6, and 6-keto-PGF1 alpha was significantly increased in old rats, being increased respectively by 3.2-, 3.5-, and 2.4-fold at 1 ng/ml LPS, compared with the production in young rats. Because TNF and IL-6 are capable of regulating vascular cell function such as proliferation protein synthesis and contractility, these cytokines might play a major role in age-related remodeling of arteries and age-related vascular diseases.

6-Ketoprostaglandin F1 alpha↗
PubMed1995

In vitro electrogenic K secretion in the frog semicircular canal: absence of effect of streptomycin.

In vitro, the frog semicircular canal secretes an endolymph-like fluid, i.e. a K-rich, positively polarized fluid. This electrogenic K secretion involved basolateral Na+, K(+)-ATPase and Na-K-Cl co-transporter and a luminal protein possessing sulfhydryl groups blocked by N-ethylmaleimide. Streptomycin, an ototoxic antibiotic, is known to block the non-specific mechano-dependent channels in the sensory cells of the ampulla of the semicircular canal. The aim of the present study was to investigate the possible effect of streptomycin on the K fluxes in the ampulla of the semicircular canal. The posterior frog semicircular canal was isolated and the lumen was filled with perilymph-like solution containing or not containing 0.5 mM streptomycin. The luminal K concentration and the transepithelial potential were measured and the unidirectional K fluxes calculated. The K influxes (into the lumen, pmoles/min/mm2) were 114 +/- 25.9 and 111 +/- 3.2 (mean +/- SE, n = 3) in the absence and presence of streptomycin, respectively. The transepithelial potential was not altered (4.0 +/- 1.08 mV versus 3.4 +/- 1.03 mV, n = 3). When ouabain (10(-3)M) was added to the basolateral solution together with luminal streptomycin, no further alteration occurred as compared with the effect of ouabain alone. These results suggest that in these conditions, the sensory organ does not have a major role in the endolymphatic K secretion in the ampulla of the frog semicircular canal.

Animals↗
PubMed1995

Release of peptide YY by neurotransmitters and gut hormones in the isolated, vascularly perfused rat colon.

BACKGROUND: Peptide YY (PYY) is promptly released from endocrine cells of the distal part of the gut after food intake. To test the possibility that hormones produced by the proximal small intestine or transmitters of the enteric nervous system may take part in the early phase of meal-induced PYY release, various regulatory peptides and neurotransmitters of the gut were administered intra-arterially in the isolated, vascularly perfused rat colon. METHODS: A colonic loop was perfused with a Krebs-Henseleit buffer containing 20% washed bovine erythrocytes via the superior mesenteric artery. The release of PYY in portal effluent was measured by radioimmunoassay. RESULTS: Cholecystokinin and secretin produced a small release of PYY. In contrast, infusion of gastric inhibitory polypeptide (GIP) over the concentration range 0.25-1 nM for 30 min produced a dose-dependent secretion of PYY with a maximal response at 800% above basal. Tetrodotoxin (TTX) did not modify the GIP-induced PYY release. Bethanechol (10(-5) M, 10(-4) M) produced a PYY release that was maximal at the end of the 30-min infusion period. The beta-adrenergic agonist isoproterenol (10(-7) M, 10(-6) M) caused a prompt release of PYY, followed by a sustained release at a lower value. Calcitonin gene-related peptide (CGRP) (5.10(-9) M and 5.10(-8) M) induced a PYY release with kinetics similar to that found for isoproterenol. Finally, bombesin (10(-9)-10(-7) M) provoked a dose-dependent release of PYY, consisting of an early peak followed by a sustained response. TTX did not modify the bethanechol-, isoproterenol-, CGRP-, and bombesin-induced PYY secretion. CONCLUSION: The hormonal peptide GIP and several transmitters of the nervous enteric system may mediate the release of PYY through the occupation of receptors possibly located at the surface of the colonic L-cells.

Animals↗
PubMed1995

Expression of EPSP/spike potentiation following low frequency and tetanic stimulation in the CA1 area of the rat hippocampus.

Low frequency stimulation (LFS, 1 Hz for 15 min) has been shown to produce an NMDA receptor dependent homosynaptic long-term depression (LTD) of synaptic potentials in the CA1 area of the rat hippocampus. Here we describe experiments aimed at characterizing EPSP/spike (E/S) coupling associated with this form of LTD. Our data show that following LFS neurons have a higher probability of synchronous discharge in response to a population EPSP of fixed slope (E/S potentiation). This E/S potentiation was not significantly enhanced by a tetanic stimulation. When the protocol was reversed, that is, starting with a tetanic stimulus, E/S potentiation was observed which was unaffected by a subsequent LFS. Saturating these synaptic responses to either a maximal or a minimal value produced similar effects on E/S coupling. E/S depression was never encountered. Finally, we found that the expression of E/S potentiation did not require the activation of NMDA receptors. These data suggest that at the level of a local neuronal network in the CA1 area, LFS is not a very powerful tool since the synaptic depression is associated with a potentiation of the population response of these neurons. Furthermore, the expression of E/S dissociation seems different from that of homosynaptic long-term potentiation and LTD.

2-Amino-5-phosphonovalerate↗
PubMed1995

Detection of human cytomegalovirus in female and male anogenital lesions with papillomavirus-associated dysplastic changes.

The aim of the study was to determine the presence of human papillomavirus (HPV) and cytomegalovirus (CMV) DNA in lesions from mucosal and keratinized cutaneous epithelium of the anogenital tract. One hundred ninety-eight women and 55 men with anogenital lesions were enrolled for the study. Biopsies were prepared for histological analysis and in situ hybridization using biotinylated probes. Potential oncogenic HPV were found in 15% of samples showing no outward signs of HPV infection or inflammation. They were detected in 40% of samples showing low grade squamous intra-epithelial lesions (SIL) and in 95 to 100% of lesions showing high-grade SIL. Cytomegalovirus DNA was detected twice as frequently in women as in men, and was preferentially associated with high-grade SIL. A significant relationship between high-risk HPVs and the presence of CMV was observed in the low-grade lesions. Our data suggest that the CMV genome in the host epithelial cells might act as a permissive factor upon which oncogenic HPV could interact over time to increase the frequency and severity of cervical, penile, and anal dysplasia.

Anus Neoplasms↗
PubMed1994

Lipases of the euphorbiaceae family: purification of a lipase from Euphorbia characias latex and structure-function relationships with the B chain of ricin.

A lipase from the latex of Euphorbia characias was purified using a method involving extraction with apolar solvent and adsorption chromatography on silica gel. The lipase (specific activity, 1500 international units/mg of protein) was eluted from silica gel complexes with a lipid. The main protein fraction, which had a molecular mass of 38 kDa, was inactive when dissociated from the lipid fraction. When the lipid and protein fractions were reassociated, 72% of the lipolytic activity was recovered. This lipolytic activity was inhibited by diethyl p-nitrophenyl phosphate, which was shown to bind the lipase with a molar ratio of 0.75. High specific activities (1000 international units/mg) were measured for the lipase of E. characias on lipid extracts rich in galactosyl diacylglycerols. The apolipase was sequenced up to residue 23. The B chain of ricin has a strong homology (43.5%) with that sequence and cross-reacted with antibodies raised against the purified lipase from E. characias. The activity of the B chain of ricin was comparable (54 international units/mg) to that of the apolipase of E. characias (100 international units/mg) mixed with the same lipid cofactor complex. The primary structure (residues 68-72) of the B chain of ricin contains the lipase consensus sequence Gly-Xaa-Ser-Xaa-Gly. Its reactivity with diethyl p-nitrophenyl phosphate indicates the presence of an activated serine that, in addition to its well-documented lectin activity for galactosides, suggests that the B chain of ricin may be a galactosyl diacylglycerol lipase, closely analogous to the lipase from E. characias.

Amino Acid Sequence↗
PubMed1994

Functional coupling between the cyclic adenosine monophosphate pathway and cholecystokinin secretion in RIN cells.

The cellular events associated with cAMP-dependent cholecystokinin (CCK) release were investigated with an X-ray induced rat pancreatic tumor cell line (RIN 1056 E). Forskolin dose-dependently stimulated the release of CCK. Agents that increase [Ca2+]i (thapsigargin, Bay K 8644, ionomycin) also stimulated the release of CCK. Conversely, absence of extracellular Ca2+ or cell treatment with various calcium channel blockers strongly reduced the forskolin-induced CCK release. Finally, the cAMP-kinase inhibitor H89, the calmodulin antagonist W7 and the Ca/calmodulin-dependent protein-kinase II inhibitor KN62 strongly inhibited the forskolin-evoked CCK secretion. We conclude that the release of CCK via a cAMP-dependent pathway is dependent on the activation of voltage-dependent calcium channels and may implicate protein kinase A, calmodulin and the Ca/calmodulin-dependent protein kinase II.

Adenoma, Islet Cell↗
PubMed1994

Recombinant single-chain antibody peptide conjugates expressed in Escherichia coli for the rapid diagnosis of HIV.

Recombinant single chain Fv (scFv) antibody fragments can form the basis of a rapid, whole-blood diagnostic assay. The scFv described in this study is derived from a monoclonal antibody which has a high affinity for glycophorin A, an abundant glycoprotein on the human red blood cell membrane surface. The prototype reagent built around the scFv was designed to detect, in whole blood samples, the presence of antibodies that have arisen through infection with a foreign organism such as human immunodeficiency virus. The scFv was composed of the antibody heavy-chain variable domain (Vh) joined by a 15 residue linker -(GGGGS)3- to the light-chain variable domain (V1) terminated by either a C-terminal octapeptide tail (FLAG) or a 35 amino acid segment from the gp41 surface glycoprotein of HIV-1. Constructs were cloned into a Escherichia coli expression vector, pHFA, and expressed in a soluble form into culture supernatant. The product retained anti-glycophorin activity which could be detected directly in culture supernatants by ELISA. Furthermore, the scFv-epitope fusion functioned efficiently in the whole blood agglutination assay and was able to distinguish between HIV-1 positive and negative sera.

Amino Acid Sequence↗
PubMed1994

Elevated temperature accelerates and amplifies the induction of nitric oxide synthesis in rat macrophages.

Evidence has accrued that nitric oxide (NO) is an effector molecule in cell-mediated immunity, and it is generally agreed that fever is beneficial to host defence. Therefore, the role of elevated temperature in the induction of NO synthesis was examined in rat peritoneal macrophages activated by lipopolysaccharide (LPS). When macrophages were incubated in vitro at 40 degrees C, the time between macrophage activation and the induction of NO synthesis, as assessed by nitrite accumulation in the medium, was shortened as compared with incubation at 37 degrees C, and nitrite accumulation was markedly enhanced by 2.6- and 1.8-fold after 6 and 9 h of LPS activation, respectively. These results suggest that elevated temperature may contribute to enhance host defence by accelerating and amplifying the induction of NO synthesis in macrophages.

Animals↗
PubMed1994

Model of local connectivity patterns in CA3 and CA1 areas of the hippocampus.

In this study we describe a model of connectivity linking the different neurons in the CA3 and CA1 areas of the young male rat hippocampus. The anatomical and electrophysiological values of the parameters used in the model were selected from the available literature. Each type of synapse was characterized by its spatial location on the dendritic tree, its weight, its probability of activation, and the ionotropic receptors involved. We have shown that the degree of convergence and divergence of inputs is highly dependent upon the type of neuron and its spatial location. The different gradients of connectivity we describe support the lamellar hypothesis from a functional point of view, even if the anatomical patterns seem diffuse. The analysis of the proportion of common afferents to a class of neurons further confirmed this point. It is suggested that the circuitry creates local coherence in terms of processing of information by establishing restricted areas where information is preferentially treated. The functional consequences and limitations of these findings are also discussed. This model is the first step in the development of a network model of the hippocampus with realistic architecture.

Afferent Pathways↗
PubMed1994

Detection of human papillomavirus by in situ polymerase chain reaction in paraffin-embedded cervical biopsies.

The efficiency of the in situ polymerase chain reaction (PCR) for the detection of human papillomavirus (HPV) DNA sequences in 20 cervical biopsies fixed with buffered formalin, paraffin-embedded and revealed negatively by conventional in situ hybridization (ISH) has been investigated. The biopsies were classified histologically into condylomata acuminata without dysplasia, cervical intraepithelial neoplasia and carcinoma in situ. Amplified HPV DNA was performed after an optimal proteolytic digestion using one pair of consensus oligonucleotide primers located in the L1 ORF of HPV 6 and ISH was carried out after the PCR assay with a cocktail of biotinylated HPV probes. Viral DNA was detected in 100% of high grade squamous intraepithelial lesions (SIL) and in 50 to 60% of low grade SIL. The high sensitivity of the in situ PCR applicable to paraffin-embedded archival biopsies facilitated the detection of cells poorly reactive by conventional ISH. In situ PCR appeared clearly an efficient tool to investigate HPV infection in tissue sections.

Base Sequence↗
PubMed1994

Synaptic integration of NMDA and non-NMDA receptors in large neuronal network models solved by means of differential equations.

Alpha functions are commonly used to describe different receptor channel kinetics (non-NMDA, GABAA and GABAB). In this paper we show that they may be represented as solutions to simple ordinary differential equations. This alternative method is compared with the commonly used direct summation of the alpha function conductances in a high-level neuronal circuit model. A parametric study shows that the differential equation method greatly speeds up the previous summation method. The forward Euler method used to solve this differential equation is shown to be accurate for this type of simulation. The modelling of NMDA receptor channel kinetics is also discussed.

Animals↗