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Biomedical subjects

R Cartier

Publications and source records attributed to R Cartier.

153 records · Page 9Linked to original sources
PubMedDate not supplied

Blood volume regulating hormones, fluid and electrolyte modifications during 21 and 198-day space flights (Altair-MIR 1993).

During the Altair MIR '93 mission we studied several parameters involved in blood volume regulation. The experiment was done on two cosmonauts before (B-60, B-30), during (D6, D12, D18 for French and D7, D12, D17 for Russian) and after the flight (R+1, R+3 and R+7). Space flight durations were different for two cosmonauts: for the Russian the flight duration was 198 days and for the French 21 days. On board the MIR station only urinary (volume and electrolytes, atrial natriuretic peptide (ANP), cyclic guanosine monophosphate (cGMP) and catecholamines) and salivary (cGMP and cortisol) samples were collected, centrifuged and stored in freezer. Lithium was used as a tracer to know exactly the 24 h urine output (CNES urine collection Kit). Before and after flight, blood was drawn with an epicite needle and vacutainer system for hormonal assays (renin, antidiuretic hormone, cGMP, ANP and aldosterone) in two positions: after 30 min rest in upright seated position and after 90 min of supine position. Salivary samples were collected simultaneously. During flight a decrease of diuresis and ANP and an increase of osmolality were found. No modifications of hematocrit, but an increase of salivary cGMP and cortisol were also observed. The decrease of urinary ANP is in favor of hypovolemia as described in previous flights. The postflight examinations revealed changes in fluid-electrolyte metabolism which indicate a hypohydration status and a stimulation of hormonal system responsible for water and electrolyte retention in order to readapt to the normal gravity.

Aldosterone↗
PubMedDate not supplied

Large-displacement 3D structural analysis of an aortic valve model with nonlinear material properties.

Grafts used in aortic valve-sparing procedures should ideally not only reproduce the geometry of the natural aortic root but also its material properties. Indeed, a number of studies using the finite element method have shown the importance of the natural sinus shape of the root in the functioning of the normal aortic valve, and the relative increase in stresses due to the replacement of the valve by a stiffer synthetic graft. Because of the wide range in experimentally measured values of aortic wall and leaflet material properties, studies by different research groups have incorporated very different material properties in their models. The aim of the present study was to investigate the influence of material properties on aortic wall displacements, and to determine which material properties would most closely match reported experimental data. Two geometrically accurate 3D models corresponding to the closed and open valve configurations were created in Pro/Engineer CAD software. Loads corresponding to systolic and diastolic pressures were specified and large-displacement structural analyses were carried out using the ANSYS package. Results have indicated that the closest match to experiments using isotropic material properties occurred for a Young's modulus of about 2000 KPa. Nonlinear models based on experimental stress-strain curves have shown similar displacements, but altered strain distribution patterns and significantly lower stresses. These results suggest that an accurate comparison of potential new graft models would have to be made with natural aortic valve models incorporating nonlinear material behavior.

Aortic Valve↗
PubMedDate not supplied

[Hypocholesterolemias: causes and diagnosis].

Most of the hypocholesterolemias in adults and children are presented and the non-cardiovascular risk of low serum cholesterol (cancer, depressive illness.) is discussed. A good assessment of hypocholesterolemia is provided by usual laboratory lipid tests (total, HDL- and LDL-cholesterol, apolipoproteins B and A1) and completed by lipid assays of parents in case of familial diseases. The diagnosis of secondary hypocholesterolemias is easy in well-known causes (liver diseases, hyperthyroidism, digestive malabsorption) but less obvious in other cases (fever, traumatism, inflammatory disease); nevertheless, it is necessary to avoid expensive laboratory investigations which will be reserved for severe familial hypocholesterolemias (in order to improve the treatment and the knowledge of these rare diseases); however diagnosis fails in some well-tolerated familial cases.

Adult↗
PubMedDate not supplied

[Should blood samples be drawn on heparin-anticoagulant for lipid analysis?].

Lipid profile is often performed on heparinized-plasma because nothing in particular is explained in the technical data sheet about anticoagulant and because few data (mainly with EDTA anticoagulant) are available in literature. In order to evaluate heparinized-plasma vs serum differences, 50 normo- or hyperlipidemic samples were collected and assayed in 3 clinical laboratories in Lyon on Hitachi analysers with Roche Diagnostic reagents. Lipid values are lower in plasma than in serum; the average negative bias for cholesterol levels is 2 to 4,5% and for triglycerides about 3%, depending on the laboratory; the effect on HDL-cholesterol values is not significant. These results were confirmed by manual procedure on 28 samples with Roche Diagnostic reagent and two similar other reagents (Biomerieux and Randox). A negative bias of 4% on total cholesterol and triglycerides levels is not very important for clinical diagnosis but it is more serious for LDL-cholesterol estimated with Friedewald equation; LDL-cholesterol value needs accuracy because it is a therapeutic goal with statin therapy and an high negative bias (until 0,70 g/L in our results) is unacceptable; moreover, there is a real risk of providing false total cholesterol results. Therefore it is essential to collect blood for lipid profile without any anticoagulant.

Anticoagulants↗
PubMedDate not supplied

Cardiac troponin T and creatine kinase MB isoenzyme as biochemical markers of ischemia after heart preservation and transplantation.

An ischemic preservation period of less than 4 to 6 hours for the donor heart is considered safe in heart transplantation. To determine the severity of myocardial cell damage, we measured serum creatine kinase MB isoenzyme activity, creatine kinase MB isoenzyme mass concentration, and troponin T release in 14 patients during the first 48 hours after heart transplantation. All donors had normal cardiac function at echocardiographic evaluation. The heart was arrested with cold crystalloid cardioplegic solution and preserved in a hypothermic solution. All patients survived the first week after transplantation. Total ischemic time averaged 126 +/- 33 minutes (range 88 to 195 minutes). Maximal creatine kinase MB isoenzyme activity, creatine kinase MB isoenzyme mass concentration, and troponin T serum values after transplantation averaged 130 +/- 44 IU/L, 140 +/- 121 ng/ml, and 3.3 +/- 1.4 ng/ml, respectively. No significant correlation was found between ischemic time and peak levels of creatine kinase MB isoenzyme activity (r = 0.22), creatine kinase MB isoenzyme mass (r = 0.37) and troponin T (r = 0.12). A moderate correlation between ischemic time and the initial slope of time-activity curve of creatine kinase MB isoenzyme mass (r = 0.66, p = 0.01) and of troponin T release (r = 0.55, p = 0.03) was observed. Ischemic time and donor age were significantly related to creatine kinase MB isoenzyme mass (R2 = 0.61) and to troponin T (R2 = 0.47) initial release slopes. In conclusion, during a short period of ischemic preservation, myocardial cell damage appears to be mild and best reflected by the elevation and the time-activity curves of release of cardiac troponin T and creatine kinase MB isoenzyme mass.

Adult↗