Search PubMed⌕ Search

Biomedical subjects

J Dupont

Publications and source records attributed to J Dupont.

At least 55 records · Page 3Linked to original sources
PubMed1998

Effect of nutritional state on the formation of a complex involving insulin receptor IRS-1, the 52 kDa Src homology/collagen protein (Shc) isoform and phosphatidylinositol 3'-kinase activity.

The Src homology and collagen protein (Shc) is tyrosine phosphorylated in response to insulin; however, evidence for its interaction with insulin receptor (IR) in normal tissues is missing. Interactions between IR, Shc and regulatory subunits of the phosphatidylinositol 3'-kinase (PI 3'-kinase) were characterized in the present study in liver and muscles of chickens submitted to various nutritional states. A chicken liver Shc cDNA fragment encoding a 198 amino acid long fragment, including the phosphotyrosine binding domain was sequenced. It shows 89% homology with the corresponding human homologue. The amounts of the three Shc isoforms (66, 52 and 46 kDa) and Shc messenger were not altered by the nutritional state. Shc tyrosine phosphorylation was decreased by fasting in both liver and muscle. Importantly, Shc was immunoprecipitated by IR antibody (mostly the 52 kDa isoform) or by alphaIRS-1(mostly the 46 kDa isoform). IR-Shc association was decreased by fasting and restored by refeeding. In liver, alphaShc immunoprecipitated the three forms of regulatory subunits of PI 3'-kinase and a PI 3'-kinase activity which was decreased by fasting. In muscle, alphaShc immunoprecipitated only the p85 isoform; the associated PI 3'-kinase activity was not altered by the nutritional state. Conversely, in both tissues anti-p85 antibody precipitated only the 52 kDa Shc isoform. In liver, antibodies to insulin receptor substrate-1 (alphaIRS-1), Shc or IR immunoprecipitated the three regulatory subunits of PI 3'-kinase and an equal PI 3'-kinase activity, without any residual activity left in the supernatants, suggesting the presence of a large complex involving IR, IRS-1, Shc (mainly the 52 kDa isoform) and PI 3'-kinase activity. The presence of another complex containing IRS-1 and the 46 kDa Shc isoform, but no PI 3'-kinase activity, is suggested.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Cloning the chicken leptin gene.

Chicken is characterized by a relative insulin resistance and a physiological hyperglycemia (2g/L) and is also subjected to fattening. Fat deposits in chicken, as in mammals, are regulated by environmental and genetic factors. In mammals, leptin, an adipose cell-specific secreted protein has been characterized that is encoded by ob gene. Leptin regulates satiety through hypothalamic specific receptors, energy balance, energy efficiency and contributes to adaptation to starvation. The leptin gene has been characterized in various mammalian species, and the cloning and sequencing of the chicken leptin gene (ob gene) are reported. Using RT-PCR and primers flanking the coding region of the leptin gene selected from known mammalian sequences, we have successfully amplified a 600-bp fragment from chicken liver and adipose tissue total ARNs. The amplified fragment exhibits a similar size to that of the coding region of the mammalian leptin gene. The sequences of the coding region of chicken liver and adipose tissue are identical and presented 97%, 96% and 83% similarity to the mouse, rat and human sequences, respectively. Finally, this is the first report showing that leptin gene expression in chicken is not exclusively localized in adipose tissue but is also expressed in liver. The expression of leptin in liver may be associated with a key role of this organ in avian species in controlling lipogenesis.

Adipose Tissue↗
PubMed1998

Insulin receptor substrate 1 antisense expression in an hepatoma cell line reduces cell proliferation and induces overexpression of the Src homology 2 domain and collagen protein (SHC).

In mammalian cells, the insulin receptor substrate 1 protein (IRS-1) is a specific substrate for insulin and IGF-1 receptor tyrosine kinases which is involved in mediating metabolic and mitogenic actions of insulin and IGFs. In order to determine if IRS-1 is also essential in a chicken derived hepatoma cell line (LMH cells), IRS-1 gene has been invalidated in these cells. For this, we subcloned chicken IRS-1 gene in an antisense orientation into a mammalian expression vector driven by the cytomegalovirus early promoter. LMH cells were stably transfected with this construct or with the empty vector carrying only the neomycin resistance gene and selected for cIRS-1 expression. One subclone, C2, showed a complete repression of cIRS-1 expression at both protein and mRNA levels. Proliferation of C2 cells was dramatically reduced (54%) compared with Neo(r) cells. Furthermore this reduction was accompanied by a decrease in insulin-dependent [3H]thymidine incorporation, indicating a reduction in DNA synthesis. Insulin-dependent [U-14C]glucose incorporation into cellular lipids was also significantly reduced in C2 cell line suggesting an alteration in lipogenesis. In wild type LMH cells, SHC which is involved in Ras pathway, also served as a substrate for insulin receptor tyrosine kinase. In C2 cells, SHC expression, its association with the insulin receptor and its tyrosine phosphorylation were largely increased. Two forms of the regulatory subunit of PI 3-kinase were present: p85 and p55 forms. Furthermore, C2 cells displayed increased basal phosphatidylinositol (PI) 3'-kinase activity. This report demonstrates a role for cIRS-1 in the metabolic and mitogenic actions of insulin in LMH cells. However, the overexpression of cIRS-1 antisense did not completely abolish cell proliferation. This may be explained by the exacerbation of an alternative pathway that only partly compensate for the knocking out of cIRS-1 gene: the overexpression of SHC.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Systolic pressure variation as a guide to fluid therapy in patients with sepsis-induced hypotension.

BACKGROUND: Monitoring left ventricular preload is critical to achieve adequate fluid resuscitation in patients with hypotension and sepsis. This prospective study tested the correlation of the pulmonary artery occlusion pressure, the left ventricular end-diastolic area index measured by transesophageal echocardiography, the arterial systolic pressure variation (the difference between maximal and minimal systolic blood pressure values during one mechanical breath), and its delta down (dDown) component (= apneic - minimum systolic blood pressure) with the response of cardiac output to volume expansion during sepsis. METHODS: Preload parameters were measured at baseline and during graded volume expansion (increments of 500 ml) in 15 patients with sepsis-induced hypotension who required mechanical ventilation. Each volume-loading step (VLS) was classified as a responder (increase in stroke volume index > or = 15%) or a nonresponder. Successive VLSs were performed until a nonresponder VLS was obtained. RESULTS: Thirty-five VLSs (21 responders) were performed. Fluid loading caused an overall significant increase in pulmonary artery occlusion pressure and end-diastolic area index, and a significant decrease in systolic pressure variation and delta down (P < 0.01). There was a significant difference between responder and nonresponder VLSs in end-diastolic area index, systolic pressure variation, and dDown, but not in pulmonary artery occlusion pressure. Receiver-operator curve analysis showed that dDown was a more accurate indicator of the response of stroke volume index to volume loading than end-diastolic area index and pulmonary artery occlusion pressure. A dDown component of more than 5 mmHg indicated that the stroke volume index would increase in response to a subsequent fluid challenge (positive and negative predictive values: 95% and 93%, respectively). CONCLUSION: The dDown component of the systolic pressure variation is a sensitive indicator of the response of cardiac output to volume infusion in patient with sepsis-induced hypotension who require mechanical ventilation.

Aged↗
PubMed1998

Nutritional state regulates insulin receptor and IRS-1 phosphorylation and expression in chicken.

After insulin binding, insulin receptors (IR) phosphorylate the insulin receptor substrate 1 (IRS-1) on specific motifs and thereby initiate insulin action. The interaction between IR and IRS-1 and their expression were studied in vivo in two target tissues (muscle and liver) in chickens, a species that is insulin resistant. To induce extreme changes in plasma insulin levels, chickens were subjected to three different nutritional states (ad libitum fed, fasted for 48 h, and refed for 30 min after 48-h fast). Liver membrane IR number was significantly increased in fasted compared with fed chickens. This upregulation of IR number was concomitant with the an enhanced expression of IR mRNA as determined by reverse transcription-polymerase chain reaction. In leg muscle, IR mRNA was not altered by the nutritional state. Using specific antibodies directed toward human IR, anti-phosphotyrosines, or mouse IRS-1, we demonstrated that IR and IRS-1 are associated in vivo in liver and muscles. Tyrosine phosphorylation of liver IR and IRS-1 were significantly decreased by prolonged fasting and restored by 30-min refeeding. These alterations were not observed in muscle. Fasting increased IRS-1 mRNA expression in liver but not in muscle. These results are the first evidence showing that chicken liver and muscle express IRS-1. Therefore, the chicken insulin resistance is not accounted for by the lack of IRS-1. The differences observed for the regulation of IR and IRS-1 messengers and phosphorylation between liver and muscle in response to alterations of the nutritional state remain to be explained.

Animals↗
PubMed1997

Combination salvage chemotherapy with MIZE (ifosfamide-mesna, idarubicin and etoposide) for relapsing or refractory lymphoma.

In this study, 54 patients with relapsed or refractory non-Hodgkin's lymphoma (NHL) were treated in a phase II, multicentric trial with ifosfamide-mesna 1500 mg/m2 IV days 1-3, idarubicin 12 mg/m2 IV day 1 and etoposide 100 mg/m2 IV day 1-3 (MIZE). Overall response was 72%; complete response (CR) and partial response (PR) were 46% and 26% respectively. In Stage I-II pts CR was 59% and in Stage III-IV pts CR was 40.5%. Patients who relapsed from an initial CR had a 64% CR rate when treated with MIZE, in contrast to refractory disease's patients who only had 19% CR (p = 0.004). The group of pts that had an objective response (CR + PR) to front line therapy had a 2 year survival rate of 55% compared with none for refractory disease (p = 0.029) after salvage therapy. Median survival for the entire group was 17.5 months. Better survival was seen in pts who were asymptomatic with low levels of LDH, previous CR, non high-grade histology, and limited disease stage at relapse. Toxicity was mainly hematologic: 91.5% had neutropenia, (56.5% grade III-IV), and 9.5% died from infectious complications. Other clinical toxicities including cardiac toxicity were negligible. MIZE chemotherapy was effective in patients with relapsed and refractory lymphoma and showed limited clinical and cardiac toxicity. Myelosupression was the most frequent single toxicity.

Adult↗
PubMed1996

Retinal hemodynamics in retinitis pigmentosa.

PURPOSE: To investigate the retinal hemodynamic changes occurring in patients with retinitis pigmentosa (RP). METHODS: Bidirectional laser Doppler velocimetry and monochromatic fundus photography were used to determine retinal venous diameter (D), maximum erythrocyte velocity (Vmax), and volumetric blood flow (Q) in the major retinal veins of eight patients with RP and eight age-matched normal controls. The retinal vascular regulatory responses to hyperoxia, defined as the percent decreases in D (RD), Vmax (RVmax), and Q (RQ) at four to six minutes of breathing 100% oxygen, were determined in eight normal subjects and five RP patients. RESULTS: Average D, Vmax, and Q +/- S.D. in the largest retinal vein of each subject were 106 +/- 14 microns, 1.01 +/- 0.20 cm/sec, and 3.5 +/- 1.3 microliters/min, respectively, in RP patients, and 166 +/- 12 microns, 1.79 +/- 0.14 cm/sec, and 14.7 +/- 2.6 microliters/min, respectively, in normal subjects. This corresponded to significant decreases from normal of 36% in D, 44% in Vmax, and 76% in Q in RP patients (Wilcoxon's rank sum test, P < .001). Average total retinal volumetric blood flow rate was 8.2 +/- 2.9 microliters/min in RP patients and 37 +/- 4.9 microliters/min in normal subjects, corresponding to a significant decrease from normal of 78% (Wilcoxon's rank sum test, P < .001). In RP patients, the regulatory responses to hyperoxia (RD, RVmax, and RQ) were similar to those observed in normal subjects. RESULTS: Retinal blood flow is significantly decreased in patients with RP, probably as a result of vascular remodeling in response to reduced metabolic demand. The regulatory responses to hyperoxia are similar to those of normal subjects. Measurements of retinal blood flow may help assess the progression of the disease and the effects of treatment.

Adult↗
PubMed1996

Fatty acid-related functions.

The first recommendations for specific nutrient quantities that must be obtained to support health were made by the US Department of Agriculture before 1939. Hazel Stiebeling was the leader of this effort and the scientific background was published in the Yearbook of Agriculture. The recommendations clearly stated that food must be available to provide the nutrients to support health. The science of nutrition in the United States is engaged in the most thorough review and reexamination of the recommended dietary allowances in at least a generation of nutrition scientists. There is a new awareness of nutrition complexity and the likelihood of identification of new essential nutrients. This meeting was devoted to the search for functional endpoints to reach quantitative estimates of dietary substances needed to support a function. Included in that concept is determining a range of individual needs and identifying factors that alter these needs. We give the rationale for endpoints of fatty acid metabolism related to platelets and the risk of thrombosis, give the rationale for the recommendation for a new nutrient, and show the necessity for including nutrient interaction in the determination of needs for two nutrients.

Blood Platelets↗
PubMed1996

The duration of medium-chain triglyceride feeding determines brush border membrane lipid composition and hydrolase activity in newly weaned rats.

To better understand the effect of dietary fat on intestinal brush border (BB) membranes in the young animal, we compared the effect of dietary medium-chain triglycerides (MCT) with that of monounsaturated and saturated long-chain triglycerides (LCT) on jejunal brush border membrane lipid composition and hydrolase activity in newly weaned rats. Twenty-day-old rat pups were divided into three groups and were weaned to diets containing 14% MCT + 6% soybean oil, 18% olive oil + 2% soybean oil, or 14% tallow + 6% soybean oil, and fed for 40 h or for 33 d. The diets were isonitrogenous and contained similar amounts of cholesterol and polyunsaturated fatty acids. Within 40 h, the fatty acid compositions of the brush border membranes were significantly different among treatment groups. These differences were maintained in rats fed for 33 d. No medium-chain fatty acids, but significantly greater amounts of polyunsaturated fatty acids, especially 18:2(n-6) and 20:4(n-6), were found in the brush border membranes of rats fed the medium-chain triglyceride diet. The cholesterol and phospholipid concentrations in the membranes were highest in rats fed the medium-chain triglyceride diet for 33 d. Rats fed that diet for 40 h had generally higher leucine aminopeptidase, sucrase and maltase activities compared with rats fed the olive oil or tallow diets. However, after 33 d of feeding, the differences between dietary treatment groups disappeared. This study demonstrates that, in the newly weaned rat pup, dietary medium-chain triglycerides and long-chain triglycerides rapidly affect the fatty acid composition of the brush border membrane. However, the changes in the hydrolase activities associated with the changes in the lipid composition of the membranes are transient.

Aging↗
PubMed1996

Liver transplantation without the use of fresh frozen plasma.

In orthotopic liver transplantations (OLT), fresh frozen plasma (FFP) is classically used to normalize coagulation factor concentrations. In this study, 28 OLT were performed without the use of FFP. According to their preoperative factor V (FV) levels, two groups of patients were defined: Group 1 (13 patients, FV > 10% and < 60%) and Group 2 (15 patients, FV > 60%). Spontaneous evolution of coagulation factors, concentration, and bleeding were observed during OLT and up to 48 h after surgery. Total intraoperative bleeding was similar in both groups (3460 +/- 2700 mL and 3470 +/- 2110 mL in Groups 1 and 2, respectively). Levels of clotting factors were not different between groups after the anhepatic stage. The lowest values were noted after reperfusion. Thirty-six hours after surgery, all levels of clotting factors in both groups were more than 50%, with FV level increasing the most rapidly. Hematocrit from the subhepatic drainage liquid was 1.8% and less than 1% at 24 and 48 h, respectively, after surgery. No reintervention for bleeding was necessary. These results suggest that, in OLT, correct hemostasis can be assumed without FFP use when hyperfibrinolysis, platelet count, fibrinogen rate, and hemodynamic status are controlled.

Adult↗
PubMed1996

Rapid estimation of Escherichia coli in live marine bivalve shellfish using automated conductance measurement.

Conductance measurement for quantitative estimations of Escherichia coli in live bivalve shellfish was evaluated as an alternative to the conventional most probable number (MPN) method used in France. The sensitivity of the two techniques was comparable. A single regression line (r = -0.968, P < 10(-6)) between log10 MPN and detection time (DT) was used to estimate E. coli concentrations for all shellfish examined. Estimation accuracy was +/- 0.92 log unit. Repeatability was better for DT than the log10 of MPN estimations (average coefficients of variation 2.7 and 9.3%, respectively). The conductance signal was attributable to E. coli in 96% of cases, and only 0.7% of E. coli cultures failed to exhibit a signal within 20 h. The conductance method reduces analysis handling time and is much easier to use than the MPN method. Moreover, results can be obtained within 5-9 h compared to 3 d for the MPN method.

Animals↗
PubMed1994

Prenatal diagnosis of congenital adrenal hyperplasia due to 21-hydroxylase deficiency by allele-specific hybridization and Southern blot.

The feasibility and accuracy of gene-specific molecular genetic diagnosis for congenital adrenal hyperplasia due to 21-hydroxylase deficiency was studied in a group of 24 pregnancies at 25% risk of carrying an affected fetus. Chorionic villus sampling was performed at 9-10 weeks' gestation. Southern analysis and polymerase chain reaction, followed by allele-specific hybridization for a panel of nine known mutations, were performed for each family. Mutations were identified in 95% of chromosomes examined; the molecular diagnosis was accurate in 96% of infants as confirmed by postnatal examination. The most common mutation identified was an A-to-G transition at base 656 in the second intron, the result of an apparent gene conversion. In one family, there had been a de novo mutation in intron 2, which was detected in the proband, but not in the mother or in the fetus. We conclude that first trimester prenatal diagnosis of congenital adrenal hyperplasia due to 21-hydroxylase deficiency is feasible and accurate employing CYP21-specific probes.

Adrenal Hyperplasia, Congenital↗
PubMed1994

Molecular genetic prenatal diagnosis of congenital adrenal hyperplasia due to 21-hydroxylase deficiency by allele-specific hybridization.

The feasibility and accuracy of gene-specific molecular genetic diagnosis for congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency were studied in a group of 24 pregnancies at 25% risk of carrying an affected fetus. Chorionic villus sampling was performed in the majority of cases. Southern blot analysis was carried out to identify deletions or other gross rearrangements. In parallel, the polymerase chain reaction (PCR) was performed, followed by allele-specific oligonucleotide hybridization (ASO) for a panel of nine known mutations. Mutations were identified in 95% of the chromosomes examined. The molecular diagnosis was accurate in 23 of 24 infants. The most common mutation identified was an A-to-G transition in the second intron (52% of affected chromosomes), the result of an apparent gene conversion. One fetus carried homozygous deletion of CYP21, which accounted for 13% of all affected chromosomes. Other mutations identified included an 8-bp deletion in the third exon (22%); Ile172 to Asn, a nonconservative substitution, in the fourth exon (9%); and Gln318 to term, a nonsense mutation, in the eight exon (4%). No mutation was detected in CYP21 in 5% of obligate-affected chromosomes examined by these methods.

Adrenal Hyperplasia, Congenital↗
PubMed1994

Future directions for nutrient requirements--lipids.

Recent advances in instrumentation and methodologies are redefining the study of lipid nutrition by allowing probing for subtle responses to marginal variations in nutrients. Stable isotope labeling studies allow demonstration of chain elongation, desaturation, chain shortening and resynthesis in humans. Essential fatty acid deficiency affects membrane physicochemical properties and membrane-bound protein activity. Understanding of the molecular functions of dietary fat has progressed to conceptualization of complex competing and complementary interactions and signals. The physical properties of lipids--insolubility in water and amphipathic qualities--underlie their physiological function. These findings will lead to new biomarkers of health status.

Dietary Fats↗