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Biomedical subjects

D Durand

Publications and source records attributed to D Durand.

At least 217 records · Page 12Linked to original sources
PubMed1992

[Male osteoporosis, an unrecognised etiology: moderate idiopathic proximal tubulopathy (MIPT)].

Routine renal tubular investigations in 8 osteoporotic men, in whom phosphorus/calcium balance studies were normal or almost normal revealed moderate phosphorus (PD) or bicarbonate (BD) diabetes possibly responsible for their decalcification. Osteoporosis affected the spine and lower limbs, resulting in clinical pictures of frequently recurrent spontaneous algodystrophy. Histomorphometric studies revealed an increase in surface areas of resorption, the diagnosis of PD being based upon the finding at several successive investigations, in the absence of any drug treatment, of a phosphorus clearance of greater than 20 ml/min and/or a phosphorus reabsorption level of less than 80%. Arterial HC03 levels of greater than 21 mEg/l and a fractional bicarbonate excretion (FBE) of greater than 15% enabled the diagnosis of bicarbonate diabetes (proximal tubular acidosis). These cases of PD and BD appeared to be secondary to proximal tubulopathies for which no known etiology was found.

Acidosis, Renal Tubular↗
PubMed1991

Suppression of spontaneous epileptiform activity with applied currents.

It has been well established that both applied and endogenous electric fields can modulate neuronal activity in various preparations. In this paper, we present the effects of applied currents on spontaneous epileptiform activity in the CA1 region of the rat hippocampus. A computer-controlled system was designed to detect the spontaneous abnormal activity and then apply current pulses of programmable amplitude with monopolar electrodes in the stratum pyramidale. The epileptiform activity was generated by subperfusion of the neural tissue with an elevated potassium artificial cerebrospinal fluid (CSF) solution. Extracellular recordings showed that the interictal bursts could be fully suppressed in 90% of the slices by subthreshold currents with an average amplitude of 12.5 microA. Intracellular recordings showed that the anodic currents generated hyperpolarization of the somatic membrane thereby suppressing neuronal firing. This inhibitory effect of applied current pulses is important for the understanding of electric field effects on abnormal neuronal activity and could be an effective means of preventing the spread of epileptiform activity.

Action Potentials↗
PubMed1991

[Early failure in kidney transplantation].

Parameters of early failure in kidney transplantation have been analyzed from 507 transplantations with transplant loss in the first month, selected among the 7541 cadaveric kidney transplantations performed in France between 1985 and 1989. These failures represent 6.7 percent of the population transplanted over this period of time, 68.6 percent of the failures that occurred in the first 3 months post-grafting, and 47 percent of the total number of the first year failures. Comparing patients with and without transplant failure in the first month, sex of the donor and the recipient, ABO group of the donor and the recipient, origin of the kidney, cold ischemia time, HLA compatibility, dialysis duration, number of previous transplantations, showed no influence on the occurrence of early failure. Three parameters appeared to be significant risk factors: donor's age less than 5 years, P = 0.00001; recipient's age less than 5 years, P = 0.05; pregraft immunization, P = 0.002. Furthermore, multifactorial analysis showed that the absence of HLA compatibilities between donor and recipient in hyperimmunized patients also has a significant influence on early graft loss. However, comparison of these same parameters in patients with transplant failure within the first month and between 2 and 12 months post-grafting revealed that the influence of these 4 significant parameters is longstanding and that none of them is specific of the precocity of graft loss.

Adolescent↗
PubMed1991

[The European experience of liver-kidney transplantation for primary hyperoxaluria type I. Prevention of recurrent intrarenal oxalate deposits].

Following simultaneous liver-kidney transplantation for primary hyperoxaluria type I, although the missing enzyme is provided by the liver transplant, there is a risk of recurrent calcium oxalate crystal formation in the implanted kidney. The necessary kidney protection methods are extrarenal blood purification, principally haemodialysis and haemofiltration, and an abundant diuresis ensured by copious fluid intakes together with prescription of diuretics. These therapeutic measures reduce the oxalate concentrations in both blood and urine. Oxalates are excreted in large amounts over a long period, owing to the formation of important tissue deposits during systemic oxalosis.

Follow-Up Studies↗
PubMed1991

Effects of ethanol on the excitability of hippocampal granule neurons.

The effects of low dose ethanol treatment on neuronal firing threshold were studied in dentate granule neurons using intracellular recording. A higher threshold for orthodromic activation and lower threshold for somatic activation were observed in 50 mM of ethanol, based on an examination of the excitatory postsynaptic potentials, strength duration and repetitive firing properties. Experiments involving blockade of glutamate-receptor subtypes suggest that an N-methyl-D-aspartate (NMDA) receptor mediated mechanism is implicated in this action of ethanol.

2-Amino-5-phosphonovalerate↗
PubMed1991

[Extrarenal purification techniques in acute kidney failure].

During the last few years much progress has been achieved in extrarenal blood purification, notably since continuous dialysis techniques have been developed. All forms of acute renal failure can now be treated specifically and safely. Conventional haemodialysis is still widely used, particularly when acute renal failure is of long duration or when it occurs in a context of renal disease. Continuous blood purification is in full development: it is relatively easy to perform, well tolerated in terms of haemodynamics and better than haemodialysis in modulating fluid subtraction. It has become the method of choice in high-risk patients, notably elderly people or subjects with multiple visceral impairment. These advances have made it possible to treat efficiently a greater number of patients, but the benefit obtained must be evaluated in relation to a prognosis which is still determined by the acute renal failure. When several organs are involved, the mortality rate is above sixty percent.

Acute Kidney Injury↗
PubMed1991

Electrical properties of axons within probst bundles of acallosal mice and callosi that have reformed upon glial-coated polymer implants.

Lesioning of the developing cerebral midline and corpus callosum of mice results in the formation of bilateral masses of axons known as Probst's longitudinal bundles. These ectopic axons were examined using an in vitro brain slice technique, and they were found to be functional and to have electrical properties that were similar to those of the unlesioned corpus callosum at a comparable age. When a nitrocellulose bridge is properly oriented at the site of the callosal lesion in neonates, the implant will support the migration of glia which, in turn, promote the redirection of callosal axons across the midline. These axons were also analyzed by in vitro brain slice techniques, and they were found to be functional and to have electrical properties that were similar to the unlesioned corpus callosum with respect to conduction velocity and chronaxie but dissimilar with respect to charge threshold and rheobase current.

Animals↗
PubMed1991

Effects of applied currents on epileptiform bursts in vitro.

In this study, results show that applied electric currents can be effective to control the neuronal bursting that characterizes epileptic activity. Recordings from the CA1 region of rat hippocampus treated with penicillin show that local inhibition of epileptiform bursts is possible by short anodic current pulses (50 ms duration) applied extracellularly. Inhibition was evidenced by a large reduction (greater than 90%) in the amplitude of field potential. Data collected from 20 slices with moderate field potentials (50-80% of maximum) showed that current needed for complete inhibition was on the order of 42 +/- 3 microA. Intracellular recordings in CA1 cells (n = 13) showed that the decrease in field potential amplitude was accompanied by suppression of intracellular neuronal firing caused by somatic hyperpolarization as measured by transmembrane potentials. The resulting hyperpolarization was on the order of 13 mv below resting potential for weakly epileptiform responses (less than 50% of maximum response), and 50 mv below resting potential for strongly epileptiform activity (greater than 50% of maximum response). These results reveal the existence of a stimulation window within which inhibition of neuronal elements can be achieved without simultaneous excitation.

Action Potentials↗
PubMed1991

Reconstruction of hippocampal granule cell electrophysiology by computer simulation.

A model of the hippocampal granule cells was created that closely approximated most of the measured intracellular responses from a neuron under a variety of stimulus conditions. This model suggests that: (1) A simple, four-conductance model can account for most of the intracellular behavior of these neurons. (2) The repolarization mechanism in granule cells may be different from that in squid axons. A weak potassium conductance may be present in hippocampal granule neurons, which simultaneously give rise to a small, passive depolarizing afterpotential. (3) The strength duration properties may assist in identifying the electronic and sodium channel properties with short stimulus pulse widths. (4) Repetitive firing responses are highly dependent on the cell's recent history of activation and the regulation of the slow potassium conductance and calcium dynamics. (5) The anodic break response is probably not a property of typical granule cells. Through thorough and precise comparison of experimental and model responses, computer simulations can help assembling channel information into verifiable models that accurately reproduce intracellular data.

Action Potentials↗
PubMed1991

The evolution of lymphadenopathy and hypergammaglobulinemia are evidence for early and sustained polyclonal B lymphocyte activation during human immunodeficiency virus infection.

To examine whether polyclonal activation of B lymphocytes as measured by hypergammaglobulinemia contributes to lymphadenopathy in human immunodeficiency virus (HIV) infection, correlates of adenopathy were examined in 240 homosexual men. Lymph node size was measured in 12 sites semiannually over 4 years. Both adenopathy and hyperglobulinemia developed within 1 year after seroconversion and persisted at high levels. Adenopathy declined near diagnosis of AIDS whereas serum IgG decreased 8-16 months after diagnosis. Adenopathy attributable to HIV occurred in all palpable node groups. By logistic regression, HIV-positive men were best discriminated from HIV-negative men by size of posterior cervical nodes and the number of sites with enlarged nodes. In a repeated measures model of covariance, adenopathy in HIV-positive men was associated with more CD4+ cells (P less than .002), elevated serum globulins (P less than .01), and lower platelet counts (P less than .05). Adenopathy declined over time (P less than .001) and with diagnosis of AIDS or AIDS-related complex (P less than .03). Thus, adenopathy and hypergammaglobulinemia are correlated and follow a similar course through various stages of HIV infection, suggesting that both are caused by polyclonal B cell activation.

AIDS-Related Complex↗
PubMed1991

Immunofluorescent deposits on the tubular basement membrane in human renal transplant.

In this retrospective study, the presence of tubular basement membrane (TBM) deposits of IgG and/or C3 was demonstrated in 41 renal transplants (out of 95 studied). The follow-up of these transplants varied from 9 to 19 years. The deposits were of 'linear' type in 9 cases (circulating anti-TBM antibodies were detected in 7 cases by radioimmunoassay tests and/or indirect immunofluorescence), 'granular' type in 22 cases and 'atypical' with linear and granular segments in 10 cases. Light microscopic diagnosis was acute rejection in 26 cases (33 biopsies) associated with deposits along the TBM:linear (6 cases), granular (13 cases) and atypical (7 cases). Chronic rejection present in 15 transplants (21 biopsies) was associated with linear (2 cases), granular (9 cases) and atypical (4 cases) deposits along the TBM. Electron microscopic study of renal tubules showed altered TBM with thickening, lamellation and splitting. Electron-dense deposits were not demonstrated in cases of linear deposits. A long-term follow-up study did not show any difference in survival of transplants presenting acute or chronic rejection associated or not with TBM deposits. If we consider the outcome of the transplants with TBM deposits, those with granular type seemed to have the poorest prognosis at long term, whatever the type of rejection. In the linear TBM deposits group, all the transplant nephrectomies which occurred (7 out of 9 cases) have been performed within 5 years.

Adolescent↗
PubMed1991

[Transport of amino acids in the splanchnic bed by blood plasma and blood in the preruminant calf].

Three preruminant calves were fitted with catheters in portal and hepatic veins and in a mesenteric artery. Two electromagnetic flowmeter probes were clipped around the portal vein and the hepatic artery. The calves were fed either a diet with a low (L) or a high (R) abomasal emptying rate for dietary proteins. Blood flow and free amino acid levels in plasma (P) and blood (S) were determined before the morning meal and during the following 7 h. In the portal vein, for most amino acids P/S ratios were correlated to the net amino acid balance of the digestive tract measured in plasma. By contrast in the hepatic vein, these ratios were mainly correlated to hepatic balance measured in whole blood. Correlations between digestive tract and hepatic balance calculated using either plasma or whole blood pool were different for some amino acids. This suggests that amino acid exchange between plasma and blood cells is low and absorbed amino acids are mainly transported to the liver by plasma, whereas whole blood rather than plasma is concerned in amino acid exchanges in the liver.

Amino Acids↗
PubMed1991

Intestinal lymph and plasma lipoproteins in the preruminant calf: partial resolution of particle heterogeneity in the 1.040-1.090 g/ml interval.

Our previous studies in the preruminant calf have provided evidence for the heterogeneity of lipoprotein particles in the 1.040-1.090 g/ml density interval in both plasma and postprandial intestinal lymph (Bauchart, D. et al., 1989. J. Lipid Res. 30: 1499-1514; and Laplaud, P. M. et al., 1990. J. Lipid Res. 31: 1781-1792). We therefore attempted to resolve this heterogeneity by use of heparin-Sepharose affinity chromatography. Experiments were performed on three calves; portal vein plasma and intestinal lymph were obtained simultaneously 10 h after a meal, i.e., at peak lipid absorption. In both fluids, the chromatographic profile presented three fractions, I, II, and III. Fraction I was characterized by the presence of cholesteryl ester-rich particles (approximately 35-37% of lipoprotein mass), which migrated electrophoretically as typical high density lipoproteins and exhibited Stokes diameters in the 130-160 A range; apoA-I was the predominant protein. In addition to this polypeptide, fraction II contained small amounts of a supplementary protein (Mr approximately 51,000), exhibiting heparin-binding properties. In the light of results reported in the literature, we suggest that this latter protein could correspond to beta 2 glycoprotein I. The chemical composition of each fraction II closely resembled that of the corresponding fraction I, while their electrophoretic migrations appeared slightly slower and their Stokes diameters slightly larger (155-165 A). Apart from the presence of small amounts of apoA-I, two high Mr proteins (Mr approx. 560,000 and 300,000) were typical of the apolipoprotein moiety of fractions III. The lower Mr form was present as a trace component only in fraction III originating from plasma; its proportion increased in lymph fraction III so as to approximately match that of the higher Mr (i.e., 560,000) protein. In both plasma and lymph, fraction III was electrophoretically heterogeneous, exhibiting a doublet of bands with migration and Stokes diameters (250 A) typical of low density lipoprotein particles. However, no evidence for the presence of a particle resembling lipoprotein[a] in fraction III could be obtained. In lymph only, fraction III contained a supplementary population of lipoproteins with migration intermediary between those of conventional low and high density lipoproteins and with Stokes diameters in the 190-200 A range. Other specific features of lymph fraction III included a sevenfold increase in its triglyceride content (8.5 +/- 3.4% vs. 1.2 +/- 1.1% in the corresponding fraction from plasma), to the detriment of cholesteryl esters, and a higher proportion of protein.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗