Biomedical subjects

J Morin

Publications and source records attributed to J Morin.

At least 19 recordsLinked to original sources

PubMed2003

Passive transfer of flt-3L-derived dendritic cells delays diabetes development in NOD mice and associates with early production of interleukin (IL)-4 and IL-10 in the spleen of recipient mice.

CD11c+/CD11b+dendritic cells (DC) with high levels of major histocompatibility complex (MHC) class II and co-stimulatory molecules have been derived from spleen cells cultured with granulocyte-macrophage colony stimulating factor (GM-CSF) + flt-3L + interleukin (IL)-6 (flt-3L-DC). Investigating in vivo the function of DC in non-obese diabetic mice (NOD), we showed that a single injection of this in vitro-derived subset of DC prevents the development of diabetes into prediabetic female mice. In contrast, DC derived from bone marrow cells cultured with GM-CSF + IL-4 [bone marrow (BM)-DC] induced no protection. Moreover, protection against diabetes following injection of flt-3L-DC was associated with IL-4 and IL-10 production in the spleen and the pancreatic lymph nodes of recipient mice, indicating that this DC population is able to polarize the immune response towards a Th2 pathway. As we shown previously, NOD BM-DC exhibit an enhanced capacity to produce IL-12p70 in response to lipopolysaccharide (LPS) and anti-CD40 stimulation compared to BM-DC from control mice. In contrast, NOD flt-3L-DC, as their control mouse counterpart, produced no IL-12p70 to these stimuli. Our findings show that a subset of DC, characterized by a mature phenotype and the absence of IL-12p70 production can be derived from NOD mouse spleen favouring IL-4 and IL-10 regulatory responses and protection from diabetes development.

Animals↗

PubMed2001

Avian orientation at steep angles of inclination: experiments with migratory white-crowned sparrows at the magnetic North Pole.

The Earth's magnetic field and celestial cues provide animals with compass information during migration. Inherited magnetic compass courses are selected based on the angle of inclination, making it difficult to orient in the near vertical fields found at high geomagnetic latitudes. Orientation cage experiments were performed at different sites in high Arctic Canada with adult and young white-crowned sparrows (Zonotrichia leucophrys gambelii) in order to investigate birds' ability to use the Earth's magnetic field and celestial cues for orientation in naturally very steep magnetic fields at and close to the magnetic North Pole. Experiments were performed during the natural period of migration at night in the local geomagnetic field under natural clear skies and under simulated total overcast conditions. The experimental birds failed to select a meaningful magnetic compass course under overcast conditions at the magnetic North Pole, but could do so in geomagnetic fields deviating less than 3 degrees from the vertical. Migratory orientation was successful at all sites when celestial cues were available.

Animals↗

PubMed2001

Three loci on mouse chromosome 6 influence onset and final incidence of type I diabetes in NOD.C3H congenic strains.

The development of insulin-dependent diabetes mellitus in both human and mouse is dependent on the interaction between genetic and environmental factors. The analysis of newly created NOD.C3H congenic strains for spontaneous and cyclophosphamide-induced diabetes has allowed the definition of three controlling genetic loci on mouse chromosome 6. A NOD-derived susceptibility allele at the Idd6 locus strongly influences the onset of diabetes in spontaneous diabetes. A NOD-derived resistance allele at the Idd19 locus affects the final diabetes incidence observed in both models, while a novel locus, provisionally termed Idd20, appears to control Idd19 in an epistatic manner. Decreased diabetes incidence is observed in CY-induced diabetes when Idd20 is homozygous for the C3H allele, while heterozygosity is associated with an increase in diabetes incidence. The Idd20, Idd19, and Idd6 candidate regions fall respectively within genetically defined intervals of 4, 7, and 4.5 cM on mouse chromosome 6. From our YAC contig, Idd6 would appear to localize within a ca. 1.5-Mb region on distal chromosome 6.

Age Factors↗

PubMed2001

Plasmid expression of a peptide that selectively blocks oncogenic ras-p21-induced oocyte maturation.

PURPOSE: We have previously found that a synthetic peptide corresponding to ras-p21 residues 96 110 (PNC2) selectively blocks oncogenic (Val 12-containing) ras-p21 protein-induced oocyte maturation. With a view to introducing this peptide into ras-transformed human cells to inhibit their proliferation, we synthesized an inducible plasmid that expressed this peptide sequence. Our purpose was to test this expression system in oocytes to determine if it was capable of causing selective inhibition of oncogenic ras-p21. METHODS: We injected this plasmid and a plasmid expressing a control peptide into oocytes either together with oncogenic p21 or in the presence of insulin (that induces maturation that is dependent on normal cellular ras-p21) in the presence and absence of the inducer isopropylthioglucose (IPTG). RESULTS: Microinjection of this plasmid into oocytes together with Val 12-p21 resulted in complete inhibition of maturation in the presence of inducer. Another plasmid encoding the sequence for the unrelated control peptide, X13, was unable to inhibit Val 12-p21-induced maturation. In contrast, PNC2 plasmid had no effect on the ability of insulin-activated normal cellular or wild-type ras-p21 to induce oocyte maturation, suggesting that it is selective for blocking the mitogenic effects of oncogenic (Val 12) ras p21. CONCLUSION: We conclude that the PNC2 plasmid selectively inhibits oncogenic ras-p21 and may therefore be highly effective in blocking proliferation of ras-induced cancer cells. Also, from the patterns of inhibition, by PNC2 and other ras- and raf-related peptides, of raf- and constitutively activated MEK-induced maturation, we conclude that PNC2 peptide inhibits oncogenic ras p21 downstream of raf.

Amino Acid Sequence↗

PubMed2001

[ A registry of ischaemic cardiopathies among active workers at Electricité de France-Gaz de France. Program development and first results].

BACKGROUND: The social security department of the French national electric and gas company has established an ischemic heart disease register among a population of about 140 000 employees based on sick leaves as well as deaths recorded with their medical cause. METHODS: History of the illness, medical tests and treatments were known retrospectively from the consulting physicians of the company. Acute coronary events recorded were: inaugural angina pectoris, myocardial infarction, sudden coronary death and fortuitous discovery of coronary disease. RESULTS: A first study conducted on employees during the 1993-1995 period showed infarction incidence age rates similar to those estimated from the French MONICA registers for France as a whole. Regional discrepancies were observed for myocardial infarction rates: Nord-Pas de Calais, Champagne-Ardennes, Lorraine, Franche-Comté and Limousin were at the most elevated risk (SIR=131, 155, 169, 125 and 178 resp). Large variations according to socio-economic status were observed. CONCLUSION: This register will permit studies on the links between socio-economic status at different professional career points and the occurrence of ischemic heart disease and the evaluation of the impact of psychosocial factors such as previous depressive disorders.

Absenteeism↗

PubMed2000

Glucose down-regulates the expression of the peroxisome proliferator-activated receptor-alpha gene in the pancreatic beta -cell.

To better understand the action of glucose on fatty acid metabolism in the beta-cell and the link between chronically elevated glucose or fatty acids and beta-cell decompensation in adipogenic diabetes, we investigated whether glucose regulates peroxisomal proliferator-activated receptor (PPAR) gene expression in the beta-cell. Islets or INS(832/13) beta-cells exposed to high glucose show a 60-80% reduction in PPARalpha mRNA expression. Oleate, either in the absence or presence of glucose, has no effect. The action of glucose is dose-dependent in the 6-20 mm range and maximal after 6 h. Glucose also causes quantitatively similar reductions in PPARalpha protein and DNA binding activity of this transcription factor. The effect of glucose is blocked by the glucokinase inhibitor mannoheptulose, is partially mimicked by 2-deoxyglucose, and is not blocked by the 3-O-methyl or the 6-deoxy analogues of the sugar that are not phosphorylated. Chronic elevated glucose reduces the expression levels of the PPAR target genes, uncoupling protein 2 and acyl-CoA oxidase, which are involved in fat oxidation and lipid detoxification. A 3-day exposure of INS-1 cells to elevated glucose results in a permanent rise in malonyl-CoA, the inhibition of fat oxidation, and the promotion of fatty acid esterification processes and causes elevated insulin secretion at low glucose. The results suggest that a reduction in PPARalpha gene expression together with a rise in malonyl-CoA plays a role in the coordinated adaptation of beta-cell glucose and lipid metabolism to hyperglycemia and may be implicated in the mechanism of beta-cell "glucolipotoxicity."

Animals↗

PubMed2000

RARbeta2 specificity in mediating RA inhibition of growth of lung cancer-derived cells.

Retinoic acid receptor beta is the retinoid receptor most frequently associated with the growth suppressive effects of retinoic acid in various epithelial tumor-derived cell lines. In particular, it has been shown that transfection of RARbeta2 in epidermoid lung tumor cells could reduce their in vitro growth rate in the presence of retinoic acid and in vivo tumorigenicity. However, the question remained as to the isoform specificity of this effect. To investigate this, we transfected RARalpha1, RARbeta1 and RARbeta2 into the epidermoid lung cancer cell line Calu-1 and assessed the in vitro growth capacities of the transfected cells. The expression of the fetal RARbeta1 or overexpression of the ubiquitous RARalpha1 isoforms could not mimick the growth suppressive effect of RARbeta2. In addition we analyzed the expression of another RAR isoform, alpha2, in many tumor-derived lines and conclude from its expression pattern that RARalpha2 is unlikely to be involved in retinoic acid growth suppression of lung cancer. Overall our data suggest that the suppressive effect of RARbeta2 is isoform specific.

Carcinoma, Small Cell↗

PubMed2000

RARbeta involvement in enhancement of lung tumor cell immunogenicity revealed by array analysis.

The retinoid receptors (RARs and RXRs) are mediators of the multiple effects of retinoic acid. Of these, the retinoic acid receptor beta2 (RARbeta2) has frequently been shown to be the principal mediator of the growth and tumor suppressive effects of retinoic acid; this gene is inactivated in many epithelial tumors and their derived cell lines. We have searched for genes that are regulated by this isoform and are potentially involved in tumor suppression. Using the Atlas human cDNA array I, we identified 27 genes (not counting RARbeta itself) that are regulated, directly or indirectly, by RARbeta2 when it is transfected into Calu-1, a lung tumor-derived line that does not normally express RARbeta. Several of the affected genes code for proteins whose functions would augment the process of apoptosis and/or the host's immune response. The latter group included ICAM-1 and MHC class I heavy chain, whose protein products play particularly important roles in the mounting of an effective anti-tumor response. We then confirmed by flow cytometry that the observed increases in message levels were reflected in increased cell surface protein levels for ICAM-1 and MHC class I in RARbeta2 transfectants of two RARbeta-deficient lines, Calu-1 and the epidermoid lung cancer-derived line SK-MES. Finally, we showed that RARbeta2 transfection of Calu-1 cells enhanced the heterologous CTL response in both the induction and the effector phases by up to threefold. These results support the hypothesis that down-regulation of these genes (and possibly others) in RARbeta-deficient tumor cells contributes to immune system evasion, and suggest a novel therapeutic approach for this disease.

Apoptosis↗

PubMed2000

Novel class of thiourea compounds that inhibit herpes simplex virus type 1 DNA cleavage and encapsidation: resistance maps to the UL6 gene.

In our search for novel inhibitors of herpes simplex virus type 1 (HSV-1), a new class of thiourea inhibitors was discovered. N-(4-[3-(5-Chloro-2,4-dimethoxyphenyl)-thioureido]-phenyl)-acetamide and its 2-fluoro-benzamide derivative inhibited HSV-1 replication. HSV-2, human cytomegalovirus, and varicella-zoster virus were inhibited to a lesser extent. The compounds acted late in the replication cycle by impairing both the cleavage of concatameric viral DNA into progeny genome length and the packaging of the DNA into capsids, indicative of a defect in the encapsidation process. To uncover the molecular target of the inhibition, resistant HSV-1 isolates were generated, and the mutation responsible for the resistance was mapped using marker transfer techniques. Each of three independent isolates had point mutations in the UL6 gene which resulted in independent single-amino-acid changes. One mutation was located in the N terminus of the protein (E121D), while two were located close together in the C terminus (A618V and Q621R). Each of these point mutations was sufficient to confer drug resistance when introduced into wild-type virus. The UL6 gene is one of the seven HSV-1 genes known to play a role in DNA packaging. This novel class of inhibitors has provided a new tool for dissection of HSV-1 encapsidation mechanisms and has uncovered a new viable target for the treatment of herpesviral diseases.

Animals↗

PubMed1999

Inhibition of influenza A virus replication by compounds interfering with the fusogenic function of the viral hemagglutinin.

Several compounds that specifically inhibited replication of the H1 and H2 subtypes of influenza virus type A were identified by screening a chemical library for antiviral activity. In single-cycle infections, the compounds inhibited virus-specific protein synthesis when added before or immediately after infection but were ineffective when added 30 min later, suggesting that an uncoating step was blocked. Sequencing of hemagglutinin (HA) genes of several independent mutant viruses resistant to the compounds revealed single amino acid changes that clustered in the stem region of the HA trimer in and near the HA2 fusion peptide. One of the compounds, an N-substituted piperidine, could be docked in a pocket in this region by computer-assisted molecular modeling. This compound blocked the fusogenic activity of HA, as evidenced by its inhibition of low-pH-induced cell-cell fusion in infected cell monolayers. An analog which was more effective than the parent compound in inhibiting virus replication was synthesized. It was also more effective in blocking other manifestations of the low-pH-induced conformational change in HA, including virus inactivation, virus-induced hemolysis of erythrocytes, and susceptibility of the HA to proteolytic degradation. Both compounds inhibited viral protein synthesis and replication more effectively in cells infected with a virus mutated in its M2 protein than with wild-type virus. The possible functional relationship between M2 and HA suggested by these results is discussed.

Amantadine↗

PubMed1998

Human lung parenchyma responds to contractile stimulation.

Tissue resistance increases after agonist challenge. Parenchymal contractile cells may be the responsible element. We investigated the viscoelastic properties of human parenchymal strips before and after challenge with acetylcholine (ACh) (10(-)3 M). Thirteen subpleural strips were oscillated in the organ bath, and measurements of resistance (R), elastance (E), and hysteresivity (eta) were obtained. After physiologic measurements, tissues were fixed for morphometric and immunohistochemical analysis. We quantitated the volume proportion of alveolar, airway, and blood vessel wall in individual strips. Smooth-muscle-specific actin was identified using a monoclonal antibody and the volume proportion of actin quantitated by point counting. After ACh, there was a significant increase in tension (2.6 +/- 0.6%), R (11.0 +/- 1.8%), E (4.3 +/- 0.7%), and eta (8.2 +/- 2.4%) (p < 0.002). Four strips contained no identifiable airways, yet in strips with and without airways there was no difference in the magnitude of the mechanical response or in the volume proportion of smooth-muscle-specific actin in the alveolar walls. We conclude that human lung parenchymal strips respond to ACh challenge with changes in dynamic mechanical behavior. Furthermore, small airways are not required for such a response to occur. This implicates a direct contractile response at the level of the alveolar wall and/or the alveolar duct.

Acetylcholine↗

PubMed1998

Expression of lumican in human lungs.

The collagen-elastin-proteoglycan (PG) matrix is the key constituent of lung parenchyma and plays a major role in the mechanical behavior of lung tissues. However, the exact composition of the PG matrix in lungs has not yet been fully determined. In the present study we report the expression of leucine-rich repeat PGs in adult human lungs. PG extraction was performed on peripheral lung tissue from patients undergoing therapeutic lung resections. The samples were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting using antipeptide antisera specific to human lumican, decorin, biglycan, and fibromodulin. Control experiments to verify antiserum reactivity were performed with an extract of adult human articular cartilage, which is known to contain all four PGs. In all lung extracts analyzed, a single component of molecular weight 65 to 90 kD was detected for lumican. Decorin, biglycan, and fibromodulin were either not detected or were barely detectable in the lung extracts, but were readily visualized in the cartilage samples. Immunohistochemistry showed that lumican was diffusely present in peripheral lung tissue, mainly in vessel walls. These results suggest that lumican is a major component of the PG matrix in adult human lungs.

Aged↗

PubMed1998

Rilmenidine normalizes fructose-induced insulin resistance and hypertension in rats.

OBJECTIVE: The aim of this study was to determine the effects of rilmenidine (an antihypertensive drug that lowers blood pressure by decreasing sympathetic outflow) in an animal model of hypertension associated with insulin resistance, i.e. rats fed on a high-fructose diet. DESIGN: Wistar rats were fed for 4 weeks either on a standard diet (S group) or on a high-fructose diet (F group; 34.5% fructose). In half of the rats in the F group, rilmenidine (1 mg/kg per day) was added to the drinking water for the last 2 weeks of the diet (FR group). RESULTS: Body weight gain was higher in the F than in the S rats (66+/-8g versus 45+/-8g, P< 0.05), but was prevented by rilmenidine treatment (32+/-2g). Arterial systolic blood pressure was increased in F rats (162+/-2 versus 155+/-2 mmHg, P< 0.05), rilmenidine reduced this value to normal (149+/-3 mmHg). Glucose tolerance, glucose turnover rate, and insulin secretion were not modified by the diet or by the drug. However, during a euglycemic hyperinsulinemic clamp, glucose utilization was lower (10+/-1 versus 14+/-1.5 mg/min per kg; P< 0.05) and hepatic glucose production higher (1+/-0.01 versus 0 mg/min per kg, P< 0.01) in F than in S rats. These changes in insulin action were totally abolished by rilmenidine. CONCLUSIONS: These data demonstrate that rilmenidine can ameliorate the deleterious effects of a high-fructose diet, i.e. weight gain, hypertension, and resistance to the effects of insulin.

Animals↗

PubMed1997

Induction of fatty acid synthase and S14 gene expression by glucose, xylitol and dihydroxyacetone in cultured rat hepatocytes is closely correlated with glucose 6-phosphate concentrations.

It is now well established that the transcription of several genes belonging to the glycolytic and lipogenic pathway is stimulated in the presence of a high glucose concentration in adipocytes and hepatocytes. We have previously proposed that glucose 6-phosphate could be the signal metabolite that transduces the glucose effect. This proposal has recently been challenged and both an intermediate of the pentose phosphate pathway, xylulose 5-phosphate, and metabolites of the later part of glycolysis (3-phosphoglycerate and phosphoenolpyruvate) have been proposed. To discriminate between these possibilities, we have measured concomitantly, in primary cultures of adult rat hepatocytes, the expression of the fatty acid synthase (FAS) and S14 genes and the concentration of glucose metabolites. We have used various substrates entering at different steps of the glycolytic pathway (glucose, dihydroxyacetone) and the pentose phosphate pathway (xylitol). When compared with 5 mM glucose, 25 mM glucose induces a marked increase in both S14 and FAS gene expression, detectable as early as 2 h and peaking at 6 h. Increasing concentrations (1-5 mM) of xylitol and dihydroxyacetone in the presence of 5 mM glucose are also able to induce S14 and FAS gene expression progressively. Among the various glucose metabolites measured, glucose 6-phosphate, in contrast with xylulose 5-phosphate and metabolites of the lower part of glycolysis, is the only one that shows a clear-cut parallelism between its concentration and the degree of S14 and FAS gene expression. We conclude that glucose 6-phosphate is the most likely signal metabolite for the glucose-induced transcription of this group of genes.

Aging↗

PubMed1997

Pioglitazone induces in vivo adipocyte differentiation in the obese Zucker fa/fa rat.

Thiazolidinediones are potent antidiabetic compounds, in both animal and human models, which act by enhancing peripheral sensitivity to insulin. Thiazolidinediones are high-affinity ligands for peroxisome proliferator-activated receptor-gamma, a key factor for adipocyte differentiation, and they are efficient promoters of adipocyte differentiation in vitro. Thus, it could be questioned whether a thiazolidinedione therapy aimed at improving insulin sensitivity would promote the recruitment of new adipocytes in vivo. To address this problem, we have studied the in vivo effect of pioglitazone on glucose metabolism and gene expression in the adipose tissue of an animal model of obesity with insulin resistance, the obese Zucker (fa/fa) rat. Pioglitazone markedly improves insulin action in the obese Zucker (fa/fa) rat, but doubles its weight gain after 4 weeks of treatment. The drug induces a large increase of glucose utilization in adipose tissue, where it stimulates the expression of genes involved in lipid metabolism such as the insulin-responsive GLUT, fatty acid synthase, and phosphoenolpyruvate carboxykinase genes, but decreases the expression of the ob gene. These changes are related to both an enhanced adipocyte differentiation, as shown by the large increase in the number of small adipocytes in the retroperitoneal fat pad, and a direct effect of pioglitazone on specific gene expression (phosphoenolpyruvate carboxykinase and ob genes) in mature adipocytes.

Adipocytes↗

PubMed1996

Structure of the human retinoic acid receptor beta 1 gene.

We report the isolation and characterization of genomic sequences coding for the 5' end of human retinoic acid receptor beta 1, a fetal RAR isoform which is also expressed in small cell lung cancers. Primer extension analysis revealed a principal transcription start site with a secondary site 23 bp further upstream in both SCLC and fetal tissues. The sequences isolated were CpG-rich between -60 and the 3' end of the first exon but there were no features like a TATA-box or an Inr element. In several important aspects, the human RAR beta 1 differs from its mouse counterpart. The 5'-UTR is 823 bp long and is encoded by four exons (vs two in the mouse giving a 477 bp UTR). The 5' end of the mouse cDNA has been mapped to a 67 bp CT repeat which is absent in our sequences. We were also unable to find evidence for a human isoform RAR beta 3 which is widely expressed in mouse tissues.

Animals↗

PubMed1996

Exogenous thymidine is preferentially incorporated into human cytomegalovirus DNA in infected human fibroblasts.

The effect of human cytomegalovirus infection on cellular DNA synthesis in human fibroblasts was measured by fluorometry and by incorporation of radiolabeled thymidine. The results show that although HCMV infection stimulates cellular DNA synthesis in both quiescent and serum-stimulated cells, radiolabeled thymidine is almost exclusively incorporated into viral DNA.

Cell Division↗

PubMed1996

[Effects of rilmenidine on rats made insulin resistant and hypertensive by a high fructose diet].

This study was aimed to determine the effects of rilmenidine, an hypertensive drug, in an animal model of hypertension associated with insulin resistance, i.e. rats fed on a high fructose diet. Wistar rats were fed during four weeks either on a standard diet (S) or on a high fructose diet (F, 34.5% de fructose). In half of the F groups, rilmenidine (1 mg/kg/day) was added to the drinking water during the two last weeks of the diet (FR). Arterial blood pressure as well as insulin efficiency were determined at the end of the four weeks. Body weight gain was higher in F than in S rats (66 +/- 8 g versus 45 +/- 8 g; p < 0.05), this was prevented by rilmenidine treatment (32 +/- 2 g). Arterial systolic blood pressure was increased in F rats (162 +/- 2 vs 155 +/- 2 mmHg; p < 0.05), rilmenidine brought this value back to normal (149 +/- 3 mmHg). During the euglycemic hyperinsulinemic clamp, glucose utilization was lower (10 +/- 1 vs 14 +/- 1.5 mg/min/kg; p < 0.05) and hepatic glucose production higher (1 +/- 0.01 vs 0 mg/min/kg; p < 0.01) in F than in S rats. These changes in insulin action were totally abolished by rilmenidine. These data demonstrate that rilmenidine can ameliorate the deleterious effects of a high fructose diet, i.e. weight gain, hypertension and resistance to the effects of insulin Rilmenidine could represent a potential therapeutic agent for the treatment of hypertension associated with metabolic disorders such as syndrom X and obesity.

Adrenergic alpha-Agonists↗