Biomedical subjects
Publications and source records attributed to C Lacombe.
The authors, nurses who run a day program out of Centre hospitalier Ste-Thérèse de Shawinigan to help friends or families of schizophrenic patients, explore what makes the service so successful. Called Centre Info-Famille-Contact-Schizo, it was the brainstorm of psychiatrist Dr. Pierre Lalonde, who maintains that such families need information and support; after all, they are true allies of the patient.
A method for rapid purification of bacterial cardiolipin is presented. The cardiolipin level was first increased by suspending Bacillus subtilis cells in a buffer containing an uncoupling agent. At least 90% of the phosphatidylglycerol molecules were rapidly converted into cardiolipin. In sporulating strains, the accumulated cardiolipin appeared to be unextractable by conventional phospholipid extraction procedures. Sporulating bacteria were therefore treated first by a classical technique in order to eliminate lipids other than cardiolipin; a second extraction in a highly acidic medium then allowed us to quantitatively extract the remaining cardiolipin. Besides simplicity and rapidity, this method has the advantage of yielding cardiolipin in a nearly pure form from a relatively low number of bacteria.
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The characterization of two abnormal human haemoglobins by fast atom bombardment (FAB) mapping is presented. The first variant, called 'R', exhibits a tryptic FAB map identical to that of normal haemoglobin. However, using Staphylococcus protease V8, a peptide containing the carboxyl end of the beta-chain exhibits a mass shift down to 300 mass units. This clearly indicates the deletion of the two last amino acids of the beta-chain. The second variant, called 'Grenoble', is due to two different modifications of the beta-chain. The location of the Pro----Ser exchange on peptide T5 is achieved by the collisionally activated dissociation mass analyzed ion kinetic energy spectra of the corresponding [MH]+ ion. The m/z value of that peptide indicated a supplementary acid----amide modification, which was located by amino acid sequencing using chemical methods. This work concludes with the necessity of using complementary methods for achieving rapid determinations of abnormal proteins with minute amounts.
Ten healthy subjects performed two exercise sessions similar to an endurance training session for average athletes (1 cycling exercise at 85% of the maximal heart rate on a Monark cycle ergometer). In the first session, the subjects were not allowed to drink during exercise. During the second session, the same subjects performed the same exercise as during the first session but they drank a beverage volume equal to the weight loss induced by the first exercise session to verify the hypothesis that the compensation of sweat loss by drinking could attenuate the exercise-induced blood viscosity increase. Both protocols (with and without drinking) induced a significant increase of hematocrit and plasma viscosity. The whole blood viscosity increased at all shear rates but this increase was significant only for the exercise protocol without drinking. Blood thixotropic property, erythrocyte deformability, and erythrocyte aggregability remained unchanged after both exercise protocols. Hemoconcentration explained the increase of hematocrit and plasma viscosity. Hemoconcentration was probably the consequence of a filtration process through capillary leakage in addition to sweat loss, which could explain the partial effect of drinking in our study.
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Erythropoietin (Epo)-producing cells were identified in the murine hypoxic kidney by in situ hybridization. Profound anemia was induced in order to greatly increase Epo production. This resulted in high levels of Epo mRNA in the kidney. 35S-labeled DNA fragments of the murine Epo gene were used as probes for in situ hybridization. Control experiments conducted in parallel included kidneys of nonanemic mice, RNase-treated hypoxic kidney sections, and 35S-labeled non-Epo-related DNA. The Epo probe gave a specific hybridization signal in the hypoxic kidney in the cortex and to a lesser extent in the outer medulla. Glomerular and tubular cells were not labeled. All positive cells were identified as peritubular cells. Using immunofluorescence, we showed that cells with the same topography contained Factor VIII-related antigen. These data demonstrated that peritubular cells, most likely endothelial cells, constitute the major site of Epo production in the murine hypoxic kidney.
Hb J-Cordoba [alpha 2A beta 2(95)(FG2)Lys----Met], is one of the few hemoglobin variants discovered in Argentina. The structure and functional abnormalities are described. Hb J-Cordoba exhibits a slightly increased oxygen affinity, low cooperativity, and normal interaction with heterotropic cofactors.
During a routine hematological investigation of a child from Tunis, a silent hemoglobin variant was discovered by isoelectric-focusing. This variant was not detectable by conventional electrophoretic methods, had normal stability, expression, and oxygen affinity, and did not produce any clinical symptoms. This new variant beta 124(H2)Pro----Ser was named Hb Tunis.
A 26-year-old French woman born in Saverne (France) was found to have Heinz body hemolytic anemia. Isoelectrofocusing showed the presence of an abnormal band amounting to 35% of the total hemoglobin concentration, suggesting a beta variant. Structural analysis of the abnormal beta chain showed an elongated C-terminal segment. Histidine 143 is replaced by a proline and the C-terminal sequence is identical to the corresponding segment of Hb Cranston. This new variant, named Hb Saverne, has beta chains composed of 156 amino acid residues. Studies of its functional properties showed that Hb Saverne is an unstable, high affinity variant with low cooperativity.
Plasmatic proteins, namely fibrinogen and globulins, play a major role in red blood cell (RBC) aggregation which is accountable for the three-dimensional structure of blood. Consequently, blood rheological properties linked to this structure must be modified when the protein plasma content changes. This paper gives results and related comments on thixotropic properties of RBC suspensions (0.45 hematocrit) in isotonic solutions containing various amount of fibrinogen to which albumin is added. Thixotropic behavior of these RBC suspensions is studied with a low inertia coaxial cylinders viscometer at a shear rate step of Y = 1 s-1. Rheograms are interpreted in term of thixotropy coefficient. The main conclusion is that albumin improves RBC disaggregability of whole blood, resulting probably from a competitive effect between fibrinogen and albumin in the RBC aggregation process.
The Hemorheometer has been adapted to allow the recording of the flow rate during the filtration process. For newtonian fluids, the flow rate variation versus time through the pores is well approximated by Poiseuille's law. For dilute red blood cell suspensions, the same analysis can be applied by introducing the concept of "apparent filtration viscosity" which is higher than the usual viscosity measured by Couette viscometry. The apparent filtration viscosity parameter is related to the deformations undergone by red blood cells as they pass through the narrow pores. Apparent filtration viscosity can be used to obtain a precise determination of the erythrocyte deformability. Measurements performed, for a given blood sample, with pores of different diameters (5 microns, 8 microns and 12 microns) show that the error on the value of apparent filtration viscosity is less than 3%. As a result, the sensitivity of the filtration method allows to discriminate among normal blood samples. High concentrations of erythrocytes or leucocytes are found to modify the apparent filtration viscosity. These factors are apparent in the recorded filtration curves. Their effects on filtration measurements can be easily estimated.
The aim of this study was to determine the red blood cell (RBC) disaggregability dependence upon the RBC shape. The study concentrated on stored blood during bank storage and on suspensions of artificially induced echinocytes. Measurements was performed in autologous plasma of hematocrit 0.45 and at constant plasmatic content. Rheological studies using stationary viscometry, nonstationary viscometry and rheoscopy were made in order to assess different stages of the disaggregability process. Whatever the method of measurement used, the morphological interpretation of the results reveal that beyond 75% of echinocytes within the sample, the disaggregation process is altered. The shear stresses required to dissociate the echinocyte aggregates are significantly higher than those required to disaggregate normal RBC rouleaux.
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The effect of dietary restriction (half of the control ration) on VLDL turnover was investigated in cholesterol-fed rabbits. Rabbits on standard, cholesterol and restricted cholesterol diets were injected with homologous 125I-labelled VLDL. Accompanying the amplification of hypercholesterolemia, additional disturbances of VLDL turnover were observed when cholesterol feeding was associated with dietary restriction. Cholesterol-fed rabbits with normal caloric ration exhibited delayed clearance of 125I-labelled apolipoprotein B component of VLDL compared to control rabbits. This was markedly accentuated in underfed rabbits, indicating further down-regulation of apolipoprotein B,E receptors in these animals. Furthermore, a reduced proportion of radiolabelled apolipoprotein B was converted from VLDL to intermediate-density lipoprotein (IDL) and LDL in both groups receiving cholesterol-rich diets. Thus, the combination of further impairment in plasma clearance of VLDL and the poor conversion into IDL and LDL could account for the massive increase of beta-VLDL in underfed animals on cholesterol-rich diets.
Adult male rats were fed for 7 wk either a low fat diet (3% fat) or a high fat-cholesterol diet (20% fat, 0.5% cholesterol) containing 7% wheat germ or not. Body weights and food intakes were unchanged by adding wheat germ to the control low fat or high fat diets. Adding wheat germ to the high fat-cholesterol diet significantly increased high density lipoprotein (HDL) cholesterol and the HDL-serum cholesterol ratio and lowered the very low density lipoprotein (VLDL) triglycerides. Thus the lipoprotein pattern was comparable to that obtained with the low fat diet, but the VLDL lipid composition remained altered. At the same time, triglyceride and cholesterol accumulation in the liver and the triglyceride content in skin were significantly decreased. When wheat germ was added to the low fat diet, cholesterol and triglycerides were not significantly modified. No adaptative change in lipase and colipase contents was observed in the pancreas of rats fed the wheat germ-supplemented diets, whereas the high fat diet increased these values. The results show a beneficial effect of wheat germ added to a high fat-cholesterol diet on the lipid status of rats; the implicated mechanisms are yet to be elucidated.
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