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Biomedical subjects

D Durand

Publications and source records attributed to D Durand.

At least 199 records · Page 11Linked to original sources
PubMed1993

Effect of antiretroviral therapy on the cerebrospinal fluid of patients seropositive for the human immunodeficiency virus.

Elevated levels of beta 2-microglobulin and neopterin in cerebrospinal fluid (CSF) have been associated with neurologic complications of infection with the human immunodeficiency virus (HIV). The effect of zidovudine (ZDV) on these markers was assessed by studying the effect of ZDV treatment duration on CSF levels in a cohort of 145 HIV-positive men who were receiving ZDV. CSF beta 2-microglobulin and neopterin levels were significantly lower in those who had been taking ZDV for an intermediate period of time (46-365 days) than in those who had received ZDV either long term (> 365 days) or short term (1-45 days). CSF quinolinic acid levels were independent of duration of ZDV administration. A second CSF evaluation was available after 1 year for 54 HIV-positive men (19 of whom were also in the first cohort) and 11 HIV-negative controls. Patients who had started ZDV between lumbar punctures showed a significant decrease in CSF beta 2-microglobulin, but in those who had been receiving ZDV for > 1 year beta 2-microglobulin increased (p = 0.001). The effect was not observed with neopterin (p = 0.14). (Quinolinic acid levels were not studied longitudinally.) Finally, we observed that CSF levels of beta 2-microglobulin, neopterin, and quinolinic acid correlated strongly with each other in HIV-positive individuals (r = 0.7, p < 0.0001), even though ZDV might have different effects on these markers. In conclusion, we report that initiation of ZDV therapy is associated with a transient decrease in CSF levels of beta 2-microglobulin and neopterin.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

[Study of CD45 isoforms on T CD8 lymphocytes, in the peripheral blood and the graft in patients after kidney transplantation].

We report characterization of CD45 isoforms expressed by CD8+ lymphocytes in peripheral blood and in the graft of 40 kidney transplanted patients who underwent kidney biopsy on the basis of clinical signs suggesting rejection. Standard histological examination of the biopsy fragments and three-color cytofluorimetric analysis of lymphocytes extracted from the same fragments by mechanical and enzymatic treatment were performed simultaneously and compared to the peripheral blood lymphocytes. In 14/40 biopsies where lymphocyte extraction succeeded, the predominant subset was CD8 (CD4/CD8 mean ratio was 0.53). Almost all CD8+ cells were activated: among these CD8+ cells, 55 percent were HLA-DR+, and 68 percent CD45RO+, i.e. of a memory cell type with cytotoxic activity. This situation resembles the in vitro observation made during mitogenic stimulation of lymphocytes by phytohemagglutinin, OKT3 or CML ("culture mixte lymphocytaire"). Beside their evident interest for the diagnosis, these data could be useful for our understanding of the physiopathology of the rejection crisis.

Biopsy, Needle↗
PubMed1992

[The heart in chronic kidney failure patients].

Risk factors for heart disease in patients with chronic renal failure (CRF) are the same as in general population; moreover CRF and renal replacement therapies (dialysis, immunosuppressive drugs for kidney transplantation) induce further specific cardiac risks. In practice, the commonest heart diseases associated with CRF are coronary artery diseases, myocardiopathies from various aetiologies, valve diseases and arrhythmias. Uremic pericarditis are quite unusual nowadays. Advances in therapy authorize easier control of congestive heart failure, the major complication of heart disease in CRF patients. Furthermore, it was observed that correction of anemia with erythropoietin therapy or kidney transplantation can ameliorate or reverse partially some cardiac diseases.

Arrhythmias, Cardiac↗
PubMed1992

[Optimization of renal transplantation].

In 1990, 1,949 renal transplantations were performed in France, with a graft survival rate of 89% at one year and 70% at five years. To improve on these results it would be necessary to pursue a dynamic policy in all fields of transplantation: in view of the ever growing number of patients on the transplantation list, more kidneys should be collected; hyperimmunized recipients should undergo reinforced exchanges to have compatible kidneys; immunosuppression must be optimized: just a using cyclosporin and monoclonal antibodies has resulted in a significant advance, so should the discovery of new drugs, such as FK 506, or of more specific monoclonal antibodies, be a source of progress; the complications of immunosuppression must be controlled: prevention protocols and antiviral treatments have considerably reduced the incidence of viral infections. The emergence of malignant tumours directly related to the degree of immunosuppression can be prevented by a rational use of immunosuppressants and by systematic detection. All these advances make it possible to extend the indications of renal transplantation to subjects at risk, notably patients more than 60 years old, and diabetic patients who can successfully benefit from a dual kidney-pancreas transplantation.

France↗
PubMed1992

Effect of surface boundary on neuronal magnetic stimulation.

The effect of the surface boundary between free space and a conducting medium on the excitation properties of neurons by magnetic fields are analyzed. The electric field and the spatial derivative of the induced field generated by a coil mounted both parallel and perpendicular to the surface of a semi-infinite conducting medium were calculated using the method of images. An imaginary axon is located in the same relative position from the coil in both configurations and the excitation properties are compared. The calculations are expressed in terms of the activating function for the electrical stimulation of axons. The calculations indicate that the activating function for magnetic stimulation is biphasic as opposed to triphasic for electrical stimulation. The large spatial extent of the magnetically induced electric field compared to the electric field generated by point source electrode suggests a different mode of excitation for neuronal structures in the CNS. The field distribution have been verified experimentally and are important for the understanding of the mechanisms of magnetic stimulation of neural tissue.

Axons↗
PubMed1992

Estimation of electrotonic parameters of neurons using an inverse Fourier transform technique.

The objective of this paper is to estimate the passive electrotonic parameters of hippocampal granule cells. Accurate estimation of these parameters is important in understanding the information processing of neurons. A shunt cable model, where the somatic and dendritic time constants can be different, is used to describe the potential changes in the soma and along the dendritic tree. For this model, parameter values are estimated by nonlinear least-squares fitting of the model output to the voltage response of the stimulated cell to current pulses. The solutions are obtained in a two-step process: First, the sensitivity functions are derived from the Laplace transform solution of the theoretical model. Second, the time domain solutions are obtained numerically by an inverse FFT. A sensitivity analysis indicates that accurate estimates require the use of a short current pulse injected at the soma and the sampling of the voltage response close to the end of that pulse. This parameter estimation procedure has been tested on hippocampal granule cells. It yields accurate estimation of neural parameters and will be a useful tool for measuring passive properties of neurons.

Animals↗
PubMed1992

Modeling the effects of electric fields on nerve fibers: determination of excitation thresholds.

We have developed a method to predict excitation of axons based on the response of passive models. An expression describing the transmembrane potential induced in passive models to an applied electric field is presented. Two terms were found to drive the polarization of each node. The first was a source term described by the activating function at the node, and the other was an ohmic term resulting from redistribution of current from sources at other nodes. A total equivalent driving function including both terms was then defined. We found that the total equivalent driving function can be used to provide accurate predictions of excitation thresholds for any applied field. The method requires only knowledge of the intracellular strength-duration relationship of the axon, the passive step response of the axon to an intracellular current, and the values of the extracellular potentials. Excitation thresholds for any given applied field can then be calculated using a simple algebraic expression. This method eliminates the errors associated with use of the activating function alone, and greatly reduces the computation required to determine fiber response to applied extracellular fields.

Axons↗
PubMed1992

Pyruvate dehydrogenase activity is stimulated by growth hormone (GH) in human mononuclear cells: a new tool to measure GH responsiveness in man.

Human peripheral mononuclear cells (PMC) were used to examine the effects of hGH and insulin on the activity of the pyruvate dehydrogenase (PDH) complex. Incubation of PMC with 10(-7) mol/L hGH or insulin increased basal PDH activity. Hormonal effects were maximal (50-60% above control values) at 15 min. Later on, activation progressively decreased and was no longer detectable at 30 min. Total PDH activity was unaffected by hormonal treatment. PMC were subfractionated into lymphocytes and monocytes to assess the sensitivity of each cell types to the hormones. hGH significantly increased basal PDH activity in lymphocytes and monocytes (38% and 70% above control values, respectively), whereas insulin increased basal PDH activity only in monocytes (151% above control value). PMC from healthy subjects aged 1-45 yr were incubated for 15 min with 10(-7) mol/L hGH or insulin before PDH measurement. An increase of enzyme activity higher than 20% was observed in 26 patients out of 29 with hGH, and in 15 out of 18 with insulin. In conclusion, hGH is able to stimulate PDH activity of human mononuclear cells. This hormonal effect allows rapid evaluation of the cellular responsiveness of hGH in various pathophysiologic situations.

Adolescent↗
PubMed1992

The influence of parathyroid hormone-related protein on hepatic IGF-1 production.

Four young milk-fed calves were fitted with catheters chronically implanted in the mesenteric, portal and hepatic veins and in the hepatic artery. Electromagnetic blood flow probes in the portal vein and hepatic artery allowed continuous measurement of hepatic IGF-1 production. In accordance with a latin square design these calves received iv mesenteric infusion (for 60 min) of calcium (Ca, 0.125 mmol.kg body wt-1), the synthetic human parathyroid hormone-related protein (1-34) fragment (PTHrP, 1 nmol.kg body wt-1), the synthetic analogue [tyr]34-bovine PTH-(7-34) NH2 (2 nmol.kg body wt-1) and PTHrP (1 nmol.kg body wt-1) or solvent alone (1.2 ml.kg body wt-1). Hypercalcaemia observed following Ca infusion had no significant effect on hepatic IGF-1 production. PTHrP induced a slight but significant increase in plasma Ca and IGF-1 concentrations measured in the hepatic vein, without changing blood flows measured in the hepatic artery and portal vein. Thus PTHrP increased hepatic IGF-1 production (15.1 +/- 2.7 nmol.6 h-1.kg body wt-1 vs 4 +/- 1.3 nmol.6 h-1.kg body wt-1 in controls; p less than 0.05). These effects induced by PTHrP were inhibited by the synthetic analogue [tyr]34-bPTH-(7-34) NH2.

Animals↗
PubMed1992

[Micropolyarteritis].

Micropolyarteritis are defined as necrotizing inflammatory lesion of the wall of small vessels affecting different organs. A necrotizing crescentic glomerulonephritis without immuno-deposits is observed in the kidney, frequently involved in this microscopic form of systemic vasculitis. Micropolyarteritis are regrouped with Wegener's syndrome and isolated pauci-immune necrotizing crescentic glomerulonephritis as "ANCA-related vasculitis", whose diagnosis is assessed throw renal biopsy and prognosis dependent on immuno-suppressive treatment. Sixty-one patients treated in our nephrology department for a RPGN during these ten recent years have been retrospectively studied. Among them, twenty-five patients presented clinical and morphologic aspects compatible with the diagnosis of micropolyarteritis. We present their clinical aspects and evolution under treatment.

Antibodies, Antineutrophil Cytoplasmic↗
PubMed1992

Factors influencing the reaction of alpha 1-fetoprotein with concanavalin A and Lens culinaris agglutinin in crossed affinoimmunoelectrophoresis.

Concanavalin A (Con A) and lentil lectin (LCA) analysis of alpha-fetoprotein (AFP) glycosylation heterogeneity is used in a variety of clinical situations. We studied the influence of analytical conditions on the separation of AFP glycoforms by using lectin-crossed affinoimmunoelectrophoresis, regardless of the AFP concentration, which can vary over a wide range in biological fluids. We defined the optimal concentration of Con A (2 g/L) and LCA (0.35 g/L) in the first-dimension gel, together with the optimum antigen (AFP)/antibody ratio in the second-dimension gel. The presence of protein in the diluent used for AFP samples was found to change the shape of crossed affinoimmunoelectrophoresis patterns without changing the percentage composition of AFP fractions. The within-run CV was less than 4% for both lectins, and the between-run CV was less than 6.3%. The minimal quantity of AFP that provided a visible pattern with both lectins was 4 ng, corresponding to 50 microL of an 80 micrograms/L AFP sample. These technical conditions allow the cellular origin of AFP to be determined, regardless of the concentration in the sample. Typical AFP lectin patterns of secreting tumors are compared with fetal and cord serum AFP.

Amniotic Fluid↗
PubMed1992

Combined liver kidney transplantation in primary hyperoxaluria type I. Prevention of the recidive of calcium oxalate deposits in the renal graft.

We report the case of a 31-year-old patient who underwent combined liver and kidney transplantation for primary hyperoxaluria type I. Intensive hemodialysis was performed before the intervention and post-operatively in order to maintain plasma oxalate levels near the normal range. In spite of the correction of the liver enzyme deficiency, oxalate removal from the tissular stores led to prolonged hyperoxaluria, more longer than one year after the transplantation, as already reported. This increased urinary oxalate excretion exposes the renal graft to the risk of recurrence of calcium oxalate deposits and stone formation during a prolonged period. Hemodialysis in the postoperative period and fluid intake allowing a large urine volume might be able to decrease the concentration of urinary oxalate under the critical value of 300 mumol/l, at which supersaturation of urine in respect of calcium oxalate occurs.

Adult↗
PubMed1992

[Sustained-released verapamil and ambulatory recording of blood pressure in mild to moderate essential hypertension].

An open study in 25 patients evaluated the efficacy and safety of Isoptine S.R., in some cases associated with Aldactazine in mild to moderate essential hypertension. After a placebo period of 2 weeks, the patients received sustained release verapamil (240 mg/24 hours) in a single morning dose for 6 months. An increase in the dosage (360 mg/24 hours in two subdoses) could be made during the first month of treatment if the diastolic blood pressure remained greater than or equal to 95 mmHg. If the diastolic blood pressure persisted at these levels at the second monthly assessment, a tablet of Aldactazine was associated. The blood pressure was evaluated by means of conventional clinical determinations and 24-hour ambulatory recordings carried out at the time of inclusion and then after 3 and 6 months of treatment. From the first month of treatment, the casual blood pressure determinations in the supine and standing position fell highly significantly (p less than 0.0001), resulting in a mean reduction of 22.3 mmHg in the systolic blood pressure (-12.6%) and of 17.4 mmHg in the diastolic blood pressure (-17%). The ambulatory recordings of blood pressure also showed a significant reduction in the mean systolic blood pressure over 24 hours (p less than 0.05 at the 3rd month of treatment), in the mean diastolic blood pressure over 24 hours (p less than 0.01) and the mean pressure (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗