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Biomedical subjects

J Picard

Publications and source records attributed to J Picard.

At least 37 records · Page 2Linked to original sources
PubMed1998

Role for PKC alpha and PKC epsilon in down-regulation of CFTR mRNA in a human epithelial liver cell line.

BACKGROUND/AIMS: In the liver, intrahepatic biliary cells are the sole site of expression of the cystic fibrosis transmembrane conductance regulator, the product of the cystic fibrosis gene. We examined the regulation of cystic fibrosis transmembrane conductance regulator gene expression by protein kinase C in the recently characterized human liver epithelial BC1 cell line which expresses, at early confluence, both biliary (cystic fibrosis transmembrane conductance regulator, cytokeratin 19) and hepatocytic (albumin) specific markers. METHODS: Expression of the cystic fibrosis transmembrane conductance regulator was examined at the mRNA level by Northern blot, reverse transcription-polymerase chain reaction and nuclear run-on assays and at the protein level by Western blotting. The functionality of this protein was tested by measurement of chloride efflux. Protein kinase C isotype expression and cytosol-to-membrane translocation were analysed by Western blotting. RESULTS: 1) Phorbol ester down-regulated cystic fibrosis transmembrane conductance regulator mRNA expression in a time- and dose-dependent manner through a post-transcriptional mechanism with concomitant inhibition of stimulated chloride efflux. 2) Phorbol ester also activated protein kinase C as indicated by the cytosol-to-membrane translocation of both protein kinase C alpha and epsilon the two major protein kinase C isotypes expressed by BC1 cells. 3) Further, maximal down-regulation of the cystic fibrosis transmembrane conductance regulator mRNA by the phorbol ester was inhibited by H7 and by GF 109203X, two known protein kinase C inhibitors. CONCLUSIONS: These findings provide the first evidence for phorbol ester-induced down-regulation of cystic fibrosis transmembrane conductance regulator mRNA expression in a human liver epithelial cell line and point to a role for the classical protein kinase C alpha and the novel protein kinase C epsilon in this process.

Cell Line↗
PubMed1998

Intrinsic differences in hearing performances between ears revealed by the asymmetrical shooting posture in the army.

Left ear noise-induced hearing losses are dominant in the army. The common explanation is the asymmetrical effect of the shooting posture. However, firm evidence to support this possibility is still lacking. In the French army shooters, eye preference rather than hand preference for shooting determines the side of shooting and hence the ear more exposed to noise. To test whether left-right asymmetry of hearing thresholds really relates to the shooting posture, we analyzed audiograms from 644 officers of the infantry and artillery branches. The interaural differences reached 7 dB for right-eyed subjects, and less, about 5 dB, for left-eyed subjects at 6-7 kHz, both with disadvantage for the left ear. In contrast, hearing thresholds of both groups in the low frequency range were significantly better for left ears. Our results suggest each ear has different intrinsic characteristics. The right cochlea might be a less sensitive but more robust sensor than the left cochlea, which might be a finer sensor but more sensitive to noise.

Adult↗
PubMed1997

Caffeine-induced disturbances of early neurogenesis in whole mouse embryo cultures.

In toto mouse embryos were cultivated at embryonic day 8.5 for 26 h with 105, 310 or 620 microM caffeine; 105-310 microM correspond to concentrations transferred by the placenta of heavy caffeine consumers. Failure of neural tube closure, excessive proliferation of neuroepithelial cells and premature evagination of telencephalic vesicles were present in 50% of treated embryos. When reaching the embryonic neural tube before neuronal migration, caffeine regionally modifies the schedule and/or rate of neural cell proliferation.

Abnormalities, Drug-Induced↗
PubMed1997

Chronic episodic diarrhoea associated with apparent intestinal colonisation by the yeasts Saccharomyces cerevisiae and Candida famata in a German shepherd dog.

A 3-year-old German shepherd dog was presented with a history of lifelong episodic diarrhoea. An adverse reaction to food was considered the most likely cause of the diarrhoea. The dog had received prolonged antibiotic therapy for most of its life as well as receiving probiotics containing the yeast Saccharomyces cerevisiae (syn. S. boulardi) for a year before referral. The probiotic was discontinued 2 months before to referral. Examination and culture of faecal samples identified yeast-like organisms, S. cerevisiae and Candida famata. S. cerevisiae has been isolated from humans in association with predisposing conditions such as prolonged sojourns in hospital, immunosuppression, broad-spectrum antibiotic therapy and prosthetic devices, but is regarded as non-pathogenic in humans and is rarely associated with disease in animals. C. famata has been isolated from animals, humans and the environment, but is regarded as a very rare pathogen. No evidence of immunosuppression was found in the dog. The presence of yeasts in the faecal isolates and the history of prolonged use of antibiotics and probiotics with a concurrent adverse reaction to food, suggest that conditions may have occurred within the bowel that made it possible for the yeasts to colonise parts of it. This has apparently not been reported before.

Animals↗
PubMed1996

VISAUDIO: a Windows software application for Bekesy audiogram analysis and hearing research.

A Windows software system has been designed to facilitate hearing research programs and decision aid for epidemiological surveys in a military context. VISAUDIO provides graphical displays of audiograms with the results of various processing (smoothing, pathological patterns detection and classification), audiograms with pathological patterns like scotoms and recruitments are described (number, impaired frequencies, severity of loss for scotoms). Classical French ORL indexes are calculated (Index 42 which is the French legal index in occupational medicine, PAM or Lafon's index, IPA from the French norm NF S31-013 and IRB, a new occupational medicine index). An audiometric pattern classification is done for each audiogram using discriminant factorial analysis. The program allows audiogram comparisons on the same screen. The processing and analysis results can also be copied to any Windows software package via a PC clipboard. This prototype software is to be tested in a quasi real-time audiological information system comprising audiogram acquisition, processing, analysis and storage in a database. VISAUDIO software functions are illustrated with examples of screen displays.

Adult↗
PubMed1996

Hyaluronic acid and dermatan sulfate are selectively stimulated by retinoic acid in irradiated and nonirradiated hairless mouse skin.

All-trans retinoic acid (RA) has been shown to enhance subepidermal repair in photoaged hairless mice. The current study assesses the effects of RA on the glycosaminoglycan (GAG) content in irradiated and nonirradiated mouse skin. Mice were exposed to ultraviolet B (UVB) for 10 wk, after which they were treated either with 0.05% RA or with an ethanolpolyethylene glycol 400 vehicle three times a week for 10 or 20 wk. When assessed at the end of 10 wk of UVB irradiation, the GAG content had doubled, without a change in the hyaluronic acid (HA) to dermatan sulfate (DS) ratio. When irradiation was discontinued, the GAG content decreased progressively until the end of the experimental period. This decline was totally inhibited by RA treatment and could be ascribed to a marked increase in hyaluronic acid (78%), whereas no significant change in DS was observed. In nonirradiated skin, however, topical RA increased GAG levels mainly by a pronounced increase in the content (50%) and the synthesis (40%) of DS. In untreated mice, the HA/DS ratio decreased significantly with age in both irradiated and nonirradiated mice. Interestingly, RA maintained this ratio only in animals exposed to UVB. In addition, there was a marked stimulation in the heparin content, up to approximately 20-fold, after irradiation, whereas the amount of heparin in both irradiated and nonirradiated skin increased about 2- to 3-fold with RA treatment. In summary, the alterations induced in HA and DS contents in irradiated and nonirradiated skin indicate the specificity of the RA-induced effects for the various GAGs.

Animals↗
PubMed1995

Aspartate at position 57 of nonobese diabetic I-Ag7 beta-chain diminishes the spontaneous incidence of insulin-dependent diabetes mellitus.

MHC class II genes have been shown to influence the development of the autoimmune disease insulin-dependent diabetes mellitus (IDDM) in the nonobese diabetic (NOD) mouse. In human IDDM it has been suggested that the presence of an aspartate at position 57 of the DQ beta-chain might be important in determining resistance to development of IDDM. The involvement of MHC class II genes in IDDM was investigated through the introduction of MHC encoding transgenes. We show that introduction of a mutated I-Ag7 Ab gene which encodes an aspartate at position 57 reduces the incidence of IDDM but does not prevent insulitis, sialadenitis, or the development of insulin and nuclear autoantibodies.

Amino Acid Sequence↗
PubMed1995

Overexpression of annexin V in cystic fibrosis epithelial cells from fetal trachea.

In this report, we investigated the expression of annexins I, II, V, and VI by Northern and Western blot analysis in four cell lines isolated from human fetal tracheae. Two cell lines were obtained from normal fetuses and the two others from fetuses with cystic fibrosis (CF). One CF fetus was heterozygous for the S549N and N1303K substitutions, whereas the other was homozygous for the delta F508 deletion. We found that the four annexins are always coexpressed. The expression of annexins I, II, and VI was the same in the four cell lines. In contrast, that of annexin V was significantly higher in CF than in normal cells. These observations demonstrate that annexins I, II, V, and VI are independently regulated in tracheal epithelial cell lines. Moreover, they suggest that the overexpressed annexin V, a Ca2+ channel, might profoundly modify Ca2+ transport across the membranes of CF cells.

Actins↗
PubMed1995

CFTR gene transfer corrects defective glycoconjugate secretion in human CF epithelial tracheal cells.

We demonstrate that in immortalized normal human tracheal epithelial cells (NT-1 and 56FHTE8o-) 14C-labeled glycoconjugate secretion may be regulated independently by agonists of the protein kinase A (PKA) and protein kinase C (PKC) signaling pathways. In contrast, in immortalized cystic fibrosis (CF) human tracheal epithelial cells (CFT-1 and CFT-2), regulation is defective for agonists specific for the PKA but not for the PKC pathway. To characterize the involvement of the cystic fibrosis transmembrane conductance regulator (CFTR) in regulated glycoconjugate secretion, we examined the effect of adenovirus-mediated gene transfer of CFTR to CF and control cells. Forty-eight hours after infection, at a multiplicity of infection of 50 plaque-forming units per cell, high levels of CFTR mRNA were detected by reverse transcription-polymerase chain reaction, and de novo synthesis of CFTR protein was demonstrated by immunoblotting. Gene transfer to CF cells restored defective adenosine 3',5'-cyclic monophosphate (cAMP)-dependent secretion not only of chloride but also of glycoconjugates. Taken together, these results argue for a role for CFTR in cAMP-mediated glycoconjugate secretion.

Adenoviridae↗
PubMed1994

Enterocytic differentiation of the human Caco-2 cell line is correlated with down-regulation of fibronectin and laminin.

Human intestinal Caco-2 cells were used to examine the expression of fibronectin (FN) and laminin (LN) during enterocytic differentiation. Combination of immunoprecipitation, Western and Northern blotting revealed that Caco-2 cells expressed a classical FN and a variant form of LN: besides B1 and B2 chains, LN contained a 350-kDa heavy chain instead of the 400-kDa A chain. Throughout Caco-2 cell differentiation, FN and LN synthesis decreased at both mRNA and protein levels. These data indicate that enterocytic differentiation involves both transcriptional and/or post-transcriptional down-regulation of FN and LN gene expression.

Cell Differentiation↗
PubMed1994

Insulin receptor mutation at tyrosines 1162 and 1163 alters both receptor serine phosphorylation and desensitization.

Chinese hamster ovary (CHO) cells expressing human insulin receptor (hIR) of the wild-type (CHO R) or hIR mutated at tyrosines 1162 and 1163 (CHO Y2) were compared for agonist-induced receptor phosphorylation of serine/threonine residues and receptor desensitization. Relative to CHO R cells, CHO Y2 cells exhibited a marked decrease in their response to insulin and 4 beta-phorbol 12 beta-myristate 13 alpha-acetate (PMA) for hIR phosphorylation on serine residues. Moreover, the tyr1162,1163 mutant hIR could not be normally phosphorylated by purified protein kinase C (PKC) in vitro. Finally, in contrast to CHO R cells, CHO Y2 cells were refractory to PMA-induced IR desensitization for subsequent activation by insulin of exogenous tyrosine kinase and glycogen synthesis. These results strongly suggest that the replacement of tyrosines 1162 and 1163 by phenylalanine residues changes the IR beta-subunit conformation and thus impedes phosphorylation of the IR at crucial serine residues and prevents PMA-induced desensitization. This supports the hypothesis that IR serine phosphorylation and desensitization are related.

Animals↗
PubMed1994

Insulin receptor autophosphorylation sites tyrosines 1162 and 1163 control both insulin-dependent and insulin-independent receptor internalization pathways.

We previously reported that Chinese hamster ovary (CHO) cell lines overexpressing mutated human insulin receptors (hIRs) in which the tyrosine residues 1162 and 1163 were replaced by phenylalanines (CHO-Y2) exhibited a marked defect in hormone-induced receptor internalization as compared to CHO transfectants overexpressing wild-type hIRs (CHO-R). These two cell lines are now used to compare the role of tyrosines 1162-1163 in basal and ligand-stimulated receptor internalization as well as in receptor turnover. We show here that (1) in CHO-Y2 cells, basal endocytosis, like insulin-induced internalization, was markedly altered despite normal receptor turnover and (2) in both CHO-R and CHO-Y2 cells, basal receptor endocytosis was altered by tunicamycin, an inhibitor of protein N-glycosylation, whereas insulin-induced internalization was not. These results support a role for tyrosines 1162-1163 of the IR beta-subunit major autophosphorylation domain in both basal and ligand-stimulated receptor endocytosis and provide evidence that the two processes follow distinct pathways.

Animals↗
PubMed1994

Phosphorylation of vimentin is an intermediate step in protein kinase C-mediated glycoconjugate secretion.

We have previously shown that fibroblasts from patients with cystic fibrosis (CF) display a higher response to 4 beta-phorbol 12-myristate 13-acetate (PMA) than control fibroblasts for stimulation of both protein kinase C (PKC) cytosol-to-membrane translocation and glycoconjugate secretion. In this study we took advantage of these cells with differential responsiveness to PMA to investigate the endogenous substrate(s) involved in PKC stimulation of glycoconjugate secretion after verification of cystic fibrosis transmembrane conductance regulator gene expression in control and CF fibroblasts. We show that a 57-kDa protein that was associated with cytoskeleton and was identified as vimentin by immunoblotting emerged as a good candidate for mediating PKC stimulation of glycoconjugate secretion. 1) Its phosphorylation by PMA was abolished by PKC inhibition or depletion. 2) In both control and CF fibroblasts, the PMA-induced increase in its phosphorylation preceded the phorbol ester stimulation of glycoconjugate secretion. 3) For both processes, the concentration-response curves were superimposable, with higher maximal levels for CF fibroblasts relative to controls. 4) PMA-stimulated 57-kDa protein phosphorylation, like PMA-stimulated glycoconjugate secretion, was significantly increased by Ca2+. 5) Increased PMA phosphorylation of the 57-kDa protein as a result of okadaic acid inhibition of intracellular phosphatases was reflected in increased PMA stimulation of glycoconjugate secretion. In conclusion, 1) PMA phosphorylation of a cytoskeletal 57-kDa protein, identified as vimentin, appears to be an intermediate step in PKC stimulation of constitutive glycoconjugate secretion in human skin fibroblasts; and 2) this process is impaired in CF disease.

Base Sequence↗
PubMed1994

Differences in both glycosylation and binding properties between rat and mouse liver prolactin receptors.

To investigate whether glycanic chains of prolactin receptors (PRL-R) play a role in hormone binding activity, comparison was made of rat and mouse liver solubilized receptors with respect to both their affinity for the hormone and their glycosylation properties. As compared with rat receptors, mouse receptors exhibited a 2-fold higher affinity for human growth hormone (hGH), the hormone being bound by both tissues with a lactogenic specificity. Along with this increased affinity, mouse receptors had a 2 lower M(r) relative to rat receptors (62 kDa versus 64 kDa as measured on hGH cross-linked receptors). These differences could be ascribed to different glycosylation properties of the receptors from the two species, as supported by the followings. 1) After treatment with endoglycosidase F (endo F), rat and mouse PRL-R no longer exhibited any difference in their M(r) (54 kDa for both cross-linked receptors). 2) Neuraminidase treatment increased by 37% the binding of hGH to mouse receptors, but was ineffective on the hormone-binding to rat receptors. Conversely, wheat germ agglutinin (WGA), another sialic acid specific probe, decreased hGH binding to rat receptors by 25%, but had no effect on this process for mouse ones. 3) Marked differences were observed in the recoveries of rat and mouse hormone-receptor (HR) complexes from ricin-1- (RCA1-), concanavalin A- (ConA-) and WGA-immobilized lectins. These differences were reduced (RCA1 and ConA) or abolished (WGA) after rat and mouse receptor desialylation by neuraminidase, a treatment which decreased the M(r) of both receptors by 2 kDa. Taken together, these results strongly suggest that the PRL-R from rat and mouse liver contain biantennary N-linked oligosaccharidic chains with distinct type of sialylation, which may account for their differential hormone-binding affinities.

Animals↗
PubMed1993

A malaria control trial using insecticide-treated bed nets and targeted chemoprophylaxis in a rural area of The Gambia, west Africa. 8. Cost-effectiveness of bed net impregnation alone or combined with chemoprophylaxis in preventing mortality and morbidity from malaria in Gambian children.

In The Gambia, insecticide impregnation of bed nets, used alone or combined with Maloprim, reduced morbidity and mortality from malaria amongst children between one and 4 years of age. Taking expenditure of both time and money by public authorities and village volunteers into account, the costs and cost-effectiveness of each intervention were estimated. Bed net impregnation alone and the combined strategy cost US $5.65 and US $7.49 per child-year protected respectively (1990 figures). Insecticide (and drugs) accounted for more than 80% of the costs of each intervention strategy. They were both highly cost-effective. Estimated costs per death and per clinical episode of malaria averted were US $188 and US $28 for bed net impregnation and $257 and $19 for impregnation combined with chemoprophylaxis. Estimated costs per healthy year of life saved, discounted at 3%, were US $7.90 and US $10.84.

Antimalarials↗
PubMed1993

Alterations of proteoglycans in ultraviolet-irradiated skin.

The effect of UVB exposure on the distribution and synthesis of dermal proteoglycans was measured in the skin of hairless mice. Two groups of mice were included: one was irradiated for 10 weeks; the other was kept as control. After intraperitoneal injection of sodium 35-S-sulfate, punch biopsies were taken for histology and proteoglycans were extracted from the remaining skin with 4 M guanidinium chloride, containing 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (0.5%, weight per volume). Following proteolytic digestion, the glycosaminoglycan constituents were isolated and analyzed by quantitative cellulose acetate electrophoresis and enzymatic digestibility. Under the influence of UVB radiation, newly synthesized proteoglycans measured by 35SO4 uptake increased as much as 60%. In addition, the irradiated skin had a higher average content of proteoglycan than had control skin (4981 micrograms vs 4134 micrograms/g dry weight). This could be ascribed to an increase in heparin (1400 vs 533 micrograms/g dry weight) and heparan sulfate (472 vs 367 micrograms/g dry weight), whereas no change in the concentration of hyaluronic acid (1243 vs 1372 micrograms/g dry weight) and dermatan sulfate (1866 vs 1863 micrograms/g dry weight) was observed. The irradiated animals also exhibited a marked increase in the synthesis of heparan sulfate and heparin (62% and 71%, respectively). These results demonstrate that chronic doses of UVB altered proteoglycan metabolism through both quantitative and qualitative changes.

Animals↗
PubMed1993

[Cellular expression of CFTR in cystic fibrosis: defective cyclic AMP-dependent regulation of glycoconjugate secretion in cystic fibrosis fetal tracheal epithelial cells transfected by SV40 large T oncogene].

Epithelial tracheal cells isolated from two fetuses with cystic fibrosis (CF) and non-CF fetus (control) were transfected with a plasmid vector recombined with the large T oncogene of SV40. All transfected cells expressed SV40 antigen and exhibited an epithelial morphology (junctional complex, cytokeratins). CFT cells retained the mutations of the CF gene, one heterozygous for the S549N/N1303K substitutions (CFT-1 cells), the other homozygous for the deletion delta F508 (CFT-2 cells). Accordingly, these CFT cells exhibited the defective beta-adrenergic regulation of chloride conductance. We compared the responsiveness of control (NT-1 cells) and CF cells (CFT-1 and CFT-2 cells) to agonists of the protein kinase A (PKA)-dependent pathway for stimulation of glycoconjugate secretion. We show that the isoproterenol (10(-5) M) and forskolin (10(-5) M) markedly increased the cAMP content and the PKA activity of all three cell lines. In contrast, these effectors produced an increase in glycoconjugate secretion in control cells, but not in CFT-1 and CFT-2 cells. In conclusion, our results indicate that CFT cells do not respond to agonists of the PKA-dependent pathway for stimulation of both glycoconjugate secretion and chloride transport, which suggests the involvement of CFTR in these two processes.

Cells, Cultured↗