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Biomedical subjects

C Lacombe

Publications and source records attributed to C Lacombe.

At least 19 recordsLinked to original sources
PubMed1992

Desmopressin has no beneficial effect on excessive postoperative bleeding or blood product requirements associated with cardiopulmonary bypass.

Cardiopulmonary bypass during open-heart surgery is sometimes associated with excessive perioperative bleeding. Following a non-randomized study suggesting that desmopressin acetate (desmopressin) reduced blood product requirements in these patients, we conducted a double-blind, placebo-controlled randomized trial of desmopressin (0.3 micrograms/kg, i. v.) in 92 patients with overt bleeding and a prolonged bleeding time. Mean blood loss during the first 24 h post-treatment was similar in the desmopressin and placebo groups (582 vs 465 ml, respectively; p = 0.15). Red-cell (p = 0.76), fresh frozen plasma (r = 0.66) and platelet unit (p = 0.74) requirements were also similar. The haemostatic effect of desmopressin has been attributed to the release of von Willebrand factor (vWF) and a reduced bleeding time. In our study, vWF and factor VIII:C levels increased while the bleeding time decreased significantly at 90 min and 24 h in both groups and, although vWF and factor VIII:C levels were slightly higher in desmopressin-treated patients at 90 min, the difference was not significant. Thrombin-antithrombin III complex, fibrinogen degradation product and tissue plasminogen activator levels, reflecting activation of the coagulation and fibrinolytic systems, respectively, decreased uniformly in both groups. We conclude that desmopressin is not useful in reducing blood loss or blood product requirements in patients with excessive immediate postoperative bleeding.

Adolescent↗
PubMed1992

Erythropoietin induces the tyrosine phosphorylation of its own receptor in human erythropoietin-responsive cells.

Using the human erythropoietin-responsive hematopoietic cell line UT-7, we showed that erythropoietin (Epo) rapidly and specifically induced the tyrosine phosphorylation of its own receptor (M(r) 75,000) and increased the tyrosine phosphorylation of other proteins of M(r) 140,000, 120,000, 95,000, 60,000, 57,000, and 42,000. Neither granulocyte-macrophage colony-stimulating factor, interleukin 3, interleukin 6, nor the kit ligand induced the phosphorylation of the M(r) 75,000 receptor protein, although these growth factors induced the phosphorylation of other proteins. Cross-linking experiments using 125I-Epo indicated that the UT-7 cells expressed three Epo receptor subunits, of M(r) 100,000, 85,000, and 75,000, among which only the M(r) 75,000 subunit was tyrosine-phosphorylated following activation with Epo.

Blotting, Western↗
PubMed1992

Methodological pitfalls in serum IgG2 level measurements by immunoenzymatic assays with monoclonal antibodies.

Four anti-IgG2 monoclonal antibodies (Mabs) were evaluated for their reactivity with purified myeloma IgG2 of different light chain types and Gm allotypes in three distinct immunoenzymatic assays (ELISA). The reactivity of three Mabs with solid-phase antigens was similar whereas an anti-Fab antibody (clone HP 6114) predominantly bound IgG2 kappa. In competitive and immunometric (sandwich type) assays, the binding of the two anti-IgG2 Mabs (HP 6014 and HP 6114) reacting with epitopes located on the Fab fragment was strongly influenced by the light chain type of IgG2 and by other factors (probably including differences in the variable regions); the Mab HP 6114 reacted virtually only with IgG2 kappa whereas the Mab HP 6014 displayed a much stronger affinity for IgG2 lambda than for IgG2 kappa; for both anti-Fab Mabs, important differences were found in their binding to individual IgG2 proteins. In addition, the Mab HP 6014 seemed to show a slightly better affinity for IgG2 bearing the Gm(23) allotype. These results urge much caution in IgG2 level measurement, especially with commercial kits, most of which use the Mab 6014 as the single anti-IgG2 reagent.

Antibodies, Anti-Idiotypic↗
PubMed1992

Fate of exogenous and newly synthesized cholesterol in intestinal cell lines.

1. The current study was undertaken to test the existence of functionally distinct intracellular pools of cholesterol depending on the origin: neosynthesis or exogenous. 2. This was performed on two subpopulations, either differentiated or undifferentiated, of the HT29 cell line. 3. A parallel study was also carried out on Caco-2 cells. 4. First we checked the ability of differentiated HT29 cells to secrete lipids into the medium and found that lipid production was efficient but less so than in Caco-2 cells. 5. In contrast, undifferentiated HT29 cells were unable to secrete lipids into the medium. 6. Then we studied the fate of [14C]cholesterol incorporated into micellar preparations and of [14C]mevalonate in the different models. 7. The data obtained with labelled exogenous cholesterol show that it enters the membrane cholesterol pool as well as, for the differentiated models, the cholesteryl ester pool. 8. Similarly, labelled newly synthesized cholesterol could be used for membrane formation as well as for incorporation into cholesteryl esters. 9. Thus, in HT29 subpopulations as well as in Caco-2 cells, the results suggest the existence of a common pool of cholesterol whatever its origin.

Adenocarcinoma↗
PubMed1992

[Raynaud's phenomenon and blood viscosity].

Raynaud's phenomenon is mainly linked with cold provoked vasomotor perturbations, but also with rheological alterations since blood viscosity is enhanced by lowering temperature. Several methods are available for studying distal vascularization: peri-ungual capillaroscopy, digital plethysmography and laser-Doppler. Digital arteriography must be reserved to serious ischemia regarding the general anesthesia needed to avoid spasm. All these methods explore especially the vessel wall. Conservely, blood viscosity which has been developed for 25 years investigates the content of the vessel. Since 1965, numerous hemorheological studies pointed out the rheological disorders, especially those concerning plasma and blood viscosity. The most usual viscometry abnormalities revealed erythrocyte hyperaggregation, red cell hypodeformability, blood and plasmatic hyperviscosity. In a comparative study, 46 patients with Raynaud's phenomenon were studied: we performed peri-ungual capillaroscopy, plethysmography and viscosity measurements. The results demonstrated a link between capillaroscopy and thixotropy. Both investigations are never normal at the same time in connectivites and never abnormal at the same time in Raynaud's disease (primary Raynaud's phenomenon). In conclusion hemorheological studies showed nearly normal rheological parameters in Raynaud's disease, but abnormal rheological parameters in secondary Raynaud's phenomenon.

Adult↗
PubMed1991

Structure of the murine erythropoietin receptor complex. Characterization of the erythropoietin cross-linked proteins.

The structure of the murine erythropoietin receptor was studied using antibodies against the intracellular part of the cloned erythropoietin receptor chain. These antibodies precipitated erythropoietin-receptor complexes from Triton X-100-solubilized cells. When the complexes were cross-linked by disuccinimidyl suberate, the 85- and 100-kDa erythropoietin-cross-linked proteins previously described were immunoprecipitated. However, these proteins were not precipitated when the complexes were denatured and reduced before immunoprecipitation. Using 1-ethyl 3-(3-dimethylaminopropyl)carbodiimide, we observed erythropoietin cross-linking with a protein of 66 kDa in addition to the 100- and 85-kDa proteins. Only the 66-kDa erythropoietin-cross-linked protein was immunoprecipitated by anti-receptor antibodies after denaturation and reduction of the complex. Thus, our results suggest that the 85- and 100-kDa proteins previously evidenced by cross-linking are associated with the cloned chain of the receptor to form a multimeric complex but these proteins seem immunologically unrelated to the cloned chain. We observed that reducing the length of molecules able to cross-link amino groups decreased the efficiency of cross-linking with the 100-kDa protein and only the 85-kDa protein was cross-linked with erythropoietin using 1,5-difluoro-2,4-dinitrobenzene. These results suggest that the 85- and 100-kDa proteins occupate slightly different positions relative to the erythropoietin molecule bound to the receptor.

Animals↗
PubMed1991

Polycythemia and steroid overproduction in a gonadotropin-secreting seminoma of the testis.

While investigating the cause of mild polycythemia in a young man, a testicular seminoma was discovered with unusual and tumor-dependent features: an absolute polycythemia with high plasma erythropoietin (EPO) levels, an overproduction of estradiol and testosterone, and a dramatic Leydig cell hyperplasia surrounding the tumor tissue. The authors attempted to gain insight into the relationship between this testicular tumor and the hormonal overproduction, i.e., of EPO, estradiol, and testosterone. Their results favored the conclusion that the high EPO levels and the polycythemia were an indirect effect secondary to the steroid overproduction rather than a direct EPO-producing activity. Moreover, the steroid overproduction by the testis could be caused by a paracrine mechanism through human chorionic gonadotropin activity on the Leydig cells.

Adult↗
PubMed1991

Acyl-CoA: cholesterol acyltransferase in HT 29 cell subpopulations. Defect of activity in the undifferentiated cells.

The ACAT activity was studied on different subpopulations deriving from HT29 cells, a human colon carcinoma cell line. Grown on standard medium (25 mM glucose), about 95% of these cells are undifferentiated (G + cells). From this heterogeneous population, differentiated cells were selected by glucose deprivation and grown either on medium without glucose (G - cells) or in standard medium containing 25 mM glucose (G-Rev cells). The G- and G-Rev cells have the features of differentiated small intestine cells. The two types of differentiated cells (G- and G-Rev) exhibited similar ACAT activities and the kinetic characteristics of the enzyme were also similar. A time-course study showed increasing activity during the exponential phase and a decrease just after confluency. It was possible to stimulate the enzyme by micellar or lipoprotein cholesterol. In contrast, the ACAT activity was hardly detectable in undifferentiated G + cells. In addition, all the experimental conditions known to stimulate ACAT activity, and confirmed in the differentiated HT29 cells, were inefficient in the undifferentiated G + cells. Therefore, the different models derived from HT29 cells provide the opportunity to study cholesterol esterification as well as the consequences of its aberrances in intestinal cells.

Adenocarcinoma↗
PubMed1991

Multimeric structure of the membrane erythropoietin receptor of murine erythroleukemia cells (Friend cells). Cross-linking of erythropoietin with the spleen focus-forming virus envelope protein.

In erythroleukemia cells infected with the polycythemia strain of the Friend virus complex, erythropoietin could be cross-linked mainly to a protein of 63 kDa when using disuccinimidyl suberate. In contrast, erythropoietin in other erythroleukemia cells cross-linked to two proteins of 85 and 100 kDa. When native erythropoietin receptor complexes were immunoprecipitated, the 63-kDa erythropoietin-cross-linked protein could be precipitated both by antibodies directed against the intracellular part of the cloned chain of the erythropoietin receptor and by antibodies directed against the envelope proteins of the Friend virus. However, after denaturation of the complexes, the 63-kDa protein was only precipitated by antibodies directed against the envelope proteins of the Friend virus. Enzymatic deglycosylation confirmed that erythropoietin was cross-linked with the envelope protein of the defective virus and bidimensional diagonal gel electrophoresis analyses showed that some of the erythropoietin cross-linked envelope proteins were dimerized by disulfide bonds. Thus, the main erythropoietin-receptor complex in the plasma membrane of these cells consisted of a molecule of the cloned chain of the erythropoietin receptor noncovalently associated with one or two disulfide-bonded molecule(s) of the envelope protein of the defective virus. Moreover, our results also showed that the viral envelope protein associated with the cloned chain of the erythropoietin receptor at a site distinct from the erythropoietin binding site.

Animals↗
PubMed1991

Spleen focus-forming virus long terminal repeat insertional activation of the murine erythropoietin receptor gene in the T3Cl-2 friend leukemia cell line.

We have characterized the structure of the erythropoietin receptor gene promoter in normal murine erythroid tissues and in Friend-induced tumor cells. Using primer extension analysis, we identified two distinct transcriptional start sites, which were located 2 base pairs apart in anemic spleens, fetal liver, Friend-induced tumoral spleens, and mouse erythro-leukemia cells. In contrast, transcription was initiated 37 base pairs upstream of the normal cap sites in T3Cl-2, a Friend virus-induced murine erythroleukemia cell line. Also, the erythropoietin receptor mRNA in T3Cl-2 was overexpressed when compared with other erythroleukemia cell lines. We found that abnormal transcription occurring in T3Cl-2 cells resulted from an erythropoietin receptor gene alteration. Indeed, one erythropoietin receptor allele was rearranged by insertion of a spleen focus-forming virus long terminal repeat within the noncoding region of the first exon, 45 bases upstream of the ATG initiation codon and in the same 5'----3' orientation. The transcription of the rearranged allele was shown to be directed from the long terminal repeat promoter, leading to a long terminal repeat-erythropoietin receptor fusion transcript, whereas the normal erythropoietin receptor allele was weakly transcribed. Such altered receptor gene activation may provide a positive pressure in the development of tumorigenic erythroleukemia.

Animals↗
PubMed1991

[Venous insufficiency in the pregnant woman. Rheological correction by troxerutin].

We realized a double-blind randomized study in 26 pregnant with clinical symptoms of lower limbs venous insufficiency. Both groups were similar and received either (n = 12) troxerutine (4 g/day) or placebo (n = 14), during 30 days. Evaluation at J0 and J30 was both clinical and rheological by mean of Myrenne aggregometer. After blood shear rate of 600 s-1, two parameters were determined: M after roughly stopping shear rate, M1 after diminishing to shear rate of 3 s-1. Results exhibited steady values in patients receiving troxerutine while a significant increasing values in patients receiving placebo for the two parameters M and M1. That result in erythrocyte antiaggregating action of troxerutine, hence lowering viscosity action, in venous insufficiency during pregnancy.

Adult↗
PubMed1991

Plasma lipid lowering effects of wheat germ in hypercholesterolemic subjects.

The present study was performed to investigate the possible effects of wheat germ supplementation on lipid metabolism in humans. Ten free-living adult subjects participated in the study. None was obese or diabetic. They all presented an hypercholesterolemia (from 6.58 to 9.50 mM), associated in 6 over 10 cases to an hypertriglyceridemia (from 1.70 to 5.00 mM). The subjects were studied in three consecutive periods, during which they first were on their usual diet (first week), they then ingested a daily supplement of 30 g wheat germ (4 weeks) and then they returned to their usual basal diet (4 weeks follow-up). Dietary records were obtained for 7 and 3 consecutive days before and during wheat germ supplementation, respectively. Fasting blood samples were taken at the end of each period. After 4 weeks of wheat germ intake, glycemia did not change while total plasma cholesterol significantly decreased (paired Student's t test, p less than or equal to 0.05) from 7.80 to 7.15 mM. LDL and HDL cholesterol values did not show marked changes, but VLDL cholesterol significantly dropped by 40.6%. Thus, the plasma/HDL total cholesterol ratio was significantly lower. Apoprotein B and A1 decreased. In the hypertriglyceridemic subjects, this was accompanied by a significant reduction of plasma triglycerides (1.64 vs. 2.68 mM) and a marked drop of VLDL triglycerides (-51%). Taken as a whole, the present results obtained in humans are very close to those previously obtained in the rat and point out that wheat germ may play a beneficial role in the dietary management of hyperlipidemia.

Adult↗
PubMed1991

[Overview of erythropoietin].

Erythropoietin (Epo) is a glycoprotein that promotes the proliferation and differentiation of erythrocyte precursors. The major site of Epo production is the kidney and the liver is the main extra renal site of Epo production. Epo producing cells were identified by in situ hybridization, in the kidney, they are peritubular cells, most likely endothelial cells of the cortex and outer medulla; in the liver, they are mainly hepatocytes. The Epo secretion is stimulated by hypoxia, which is detected by an oxygen sensor. The Epo receptor is a multimeric protein, one chain which binds Epo has been cloned. However the structure of the Epo receptor is still puzzling, and one or more accessory chains remain to be identified. Since the clonage of the Epo gene, recombinant Epo has been available and allowed the treatment of patients with renal diseases with a constant efficacy.

Erythropoietin↗
PubMed1991

Erythropoietin: sites of synthesis and regulation of secretion.

Erythropoietin (Epo) is a glycoprotein that promotes the proliferation and differentiation of erythrocyte precursors. The major site of Epo production is the kidney, while the liver is the main extrarenal site of Epo production. Within these organs, the cells synthesizing Epo were identified by using in situ hybridization in hypoxic animals with an increased Epo mRNA expression. Epo-producing cells in the kidney were peritubular cells, most likely endothelial cells of the cortex and outer medulla. Glomerular and tubular cells were not labeled. In three patients with renal adenocarcinomas associated with polycythemia, in situ hybridization showed a strong labeling of the tumor cells. Epo secretion is stimulated by hypoxia, which is detected by an oxygen sensor located in the kidney. This oxygen sensor has been recently shown to be an heme protein. At the Epo gene level, studies to identify cis-acting DNA sequences, and trans-activation factors for inducible kidney and liver Epo expression are being pursued.

Animals↗
PubMed1991

[Hemorheologic effects following ergometric-controlled physical exercise].

In collaboration with the Laboratory of Physiology, the Unity of Biorheology realized hemorheological studies on healthy volunteers who performed four kinds of well-controlled exercises on a cycle ergometer. Blood was always collected just before exercise and just after exercise. Rheological measurements were performed (blood and plasma viscosities, blood thixotropy and blood viscoelasticity) as well as biological (plasma proteins) and biophysical (osmolarity, pH) measurements. In all the cases, results show the importance of a hemoconcentration and its hemorheology consequences.

Blood Viscosity↗
PubMed1990

Solubilization and hydrodynamic characteristics of the erythropoietin receptor. Evidence for a multimeric complex.

In order to study the erythropoietin receptor in its native state, we solubilized erythropoietin-receptor complexes from spleen cell membranes of mice infected with the anemia strain of Friend virus using mild detergents. Among 11 tested detergents, Triton X-100 and Lubrol PX were the most effective. Triton X-100 was therefore selected for this study. The solubilized complexes appeared to be well representative of the total membrane receptor population as indicated by cross-linking experiments and affinity measurements. The hydrodynamic characteristics of the complexes were determined by gel filtration chromatography and ultracentrifugation through sucrose gradients prepared with H2O or D2O. Although erythropoietin-receptor-detergent complexes exhibited some heterogeneity, we determined the following minimal hydrodynamic values: sedimentation coefficient (s20,w): 11.7 +/- 0.8 S, Stokes radius: 7.7 +/- 0.2 nm, partial specific volume: 0.774 +/- 0.017 ml/g, giving a molecular mass of 458 +/- 66 kDa. The contribution of the detergent was estimated to be 28% from the measured partial specific volume, giving an estimated molecular mass of 330 +/- 48 kDa for the erythropoietin-receptor complex. The minimal molecular mass value was significantly greater than those obtained by polyacrylamide gel electrophoresis under denaturing conditions, strongly suggesting that the erythropoietin receptors were present as multimeric complexes. The nature of these complexes is discussed. Beside this major component our results revealed the presence of higher-molecular-mass erythropoietin binding components. We also demonstrated that erythropoietin-receptor complexes could be precipitated with anti-erythropoietin antibodies. This property should greatly improve the purification of erythropoietin receptors.

Animals↗