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Biomedical subjects

D Durand

Publications and source records attributed to D Durand.

At least 307 records · Page 17Linked to original sources
PubMed1984

Impairment of long-term potentiation in rat hippocampus following chronic ethanol treatment.

The effect of chronic ethanol treatment on long-term potentiation (LTP), a possible substrate for memory, was studied in rats using the in vitro hippocampal slice preparation. Rats were provided ad libitum access to an ethanol-containing or control liquid diet. One group of animals received the diet for a total period of 9 months before testing, while a second group received the diet for 7 months and was allowed a 2 month ethanol-free period before testing. LTP was induced in the CA1 region by orthodromic stimulation of the stratum radiatum with 4 stimulus trains of 200 pulses each at 25, 50, 100 and 200 Hz separated by 10 min intervals. The number of slices with potentiation greater than 15% was significantly smaller in the ethanol-fed animals both before and following the 2 month withdrawal period. However, the average percent increase in the amplitude of the population spike was significantly decreased in the ethanol-fed animals when tested before withdrawal but no significant difference was detected following the 2 month withdrawal period, suggesting some recovery. The possible mechanisms mediating the chronic ethanol-induced depression of LTP are discussed.

Alcoholism↗
PubMed1984

Decreased neuronal inhibition in vitro after long-term administration of ethanol.

The pathophysiology of brain dysfunction was studied with an animal model of chronic alcoholism. Rats were fed a liquid diet with or without ethanol for 20 weeks and then the diet without ethanol for three more weeks. Hippocampal slices were prepared and intracellular recordings were obtained from dentate granule and CA1 cells. Significant depression of orthodromically elicited inhibitory postsynaptic potentials and postspike afterhyperpolarizations was observed in neurons from ethanol-exposed animals. No differences were observed in other active or passive membrane characteristics. These results suggest that a loss of neuronal inhibition could contribute to brain dysfunction in chronic alcoholism.

Action Potentials↗
PubMed1984

Immunofluorescence and ultrastructural localization of beta 2-microglobulin in human renal allografts.

The localization of beta 2-microglobulin (beta 2m) was studied in renal biopsies from 18 patients with pathological transplanted kidney using immunofluorescence and electron-immunohistochemical techniques; the renal biopsies of 4 cases with normal kidneys were used as controls. Using immunofluorescence, beta 2m was not observed in the normal kidneys, beta 2m was found in the glomeruli (7 cases) and the tubular epithelium (16 cases) of the transplanted kidneys. Using immunoelectron microscopy, some labelling of the normal kidneys was observed mainly along the cell coat of foot processes and in tubular-epithelial lysosomes. In the glomeruli of transplanted kidneys, particularly in cases of acute or chronic rejection, beta 2m was most frequently localized on the outer layer of the basement membrane and along the cell coat of foot processes. The brush border of the proximal tubules and the lysosomal structures were intensely labelled. Although immunoelectron-microscopy studies are unable to discriminate between the localization of beta 2m in normal and transplanted kidneys, these findings nevertheless suggest the glomerular filtration of beta 2m and its metabolism in the tubular epithelium.

Adolescent↗
PubMed1984

The somatic shunt cable model for neurons.

The derivation of the equations for an electrical model of nerve cells is presented. The model consists of an equivalent cylinder, a lumped somatic impedance, and a variable shunt at the soma. This shunt was introduced to take into account the fast voltage decays observed following the injections of current pulses in some motoneurons and hippocampal granule cells that could not be explained by existing models. The shunt can be interpreted either by penetration damage with the electrode or by a lower membrane specific resistance at the soma than in the dendrites. A solution of the model equations is presented that allows the estimation of the electrotonic length L, the membrane time constant tau m, the dendritic dominance ratio rho, and the shunt parameter epsilon, based only on the measurement of the first two coefficients and time constants in the multiexponential voltage response to injected current pulses.

Animals↗
PubMed1984

[Renal insufficiency after administration of captopril in renal artery stenosis with a single kidney or bilateral stenosis is not compulsory].

Acute renal failure has been reported during captopril therapy of hypertension due to renal artery stenosis with a single kidney or bilateral renal artery stenosis. Under low perfusion pressures inhibition of the renin-angiotensin system could disturb the autoregulation, decrease efferent arteriolar resistance and lead to a critical decrease in glomerular filtration. Renal function tests were repeated in a patient with hypertension due to 90 p. 100 renal artery stenosis with a single kidney, before and after captopril administration (sodium intake 100 mmol/24 h). (table; see text) Identical results have also been observed in a patient with bilateral renal artery stenosis. Both patients presented high risk renal haemodynamic states. The control of systemic blood pressure and the fall in filtration fraction were not associated with a critical, immediate or short term fall in glomerular filtration. The isolated administration of captopril is therefore not systematically contra-indicated in these two clinical situations.

Acute Kidney Injury↗
PubMed1983

Diabetes-induced variation in hepatic binding protein.

The total capacity of hepatocytes to bind asialoorosomucoid was measured on normal and streptozotocin diabetic rats. 4 days after the streptozotocin injection, a slight decrease of total receptor concentration was observed while a more marked reduction of cell surface receptor occurred. In animals sacrificed 11 days after the streptozotocin injection, the total capacity of hepatocytes to bind asialoorosomucoid was about 70% of the normal level.

Animals↗
PubMed1983

Pyridoxal 5'-phosphate deficiency in uremic undialyzed, hemodialyzed, and non-uremic kidney transplant patients.

In this study, we have investigated plasma pyridoxal 5'-phosphate (PLP) concentrations in undialyzed and dialyzed uremic patients and in kidney transplant subjects, using an enzymatic technique with thermal deproteinization to liberate PLP from plasma proteins. The specificity of the reaction indicates no interference with pyridoxal and only 3% interference with pyridoxamine phosphate. In 17 hemodialyzed patients, a deficiency of about 50% of plasma PLP concentration is found as compared to 25 healthy subjects (22.2 +/- 2.47 vs. 48.8 +/- 3.00 nmol . l-1), as mean +/- SEM). In seven undialyzed uremic patients with end-stage renal failure, the plasma PLP concentration is also decreased (29.3 +/- 1.74 nmol . l-1). The absence of PLP in plasma ultrafiltrates demonstrates that no loss of PLP occurs due to hemodialysis. The daily oral supplementation with 250-750 mg pyridoxal induces a supraphysiological increase in plasma PLP concentration in hemodialyzed as well as in undialyzed patients. In 116 non-uremic kidney transplant subjects, the mean plasma PLP concentration was 33.8 +/- 3.50 nmol . l-1). In 65% of these patients, a marked deficit (below 20 nmol . l-1) was observed. In conclusion, uremic patients have a deficient vitamin B6 state. Its correction with pyridoxal to restore physiological plasma PLP concentration necessitates oral supplementation with lower doses that those widely used at present. In kidney transplant patients a similar plasma PLP deficiency is observed in the absence of chronic renal failure.

Adult↗
PubMed1983

The influence of 1,25-dihydroxycholecalciferol on the mineral content of foetal guinea pigs.

The influence of 1,25-dihydroxycholecalciferol (0.05 microgram/kg bw/day, given I.M. for 10 days) on calcium transfer from dam to foetus and on foetal calcium and phosphate content was observed in 3 groups of 10 guinea pigs, one group on each of days 40, 50 and 66 of gestation. At 40 and 50 days of gestation, 1,25-dihydroxycholecalciferol increased the calcium and phosphate content of the foetus. 45Ca transfer from the dam to placenta (measured during a 30-90 min period) was higher in treated than in control animals.

Animals↗
PubMed1983

The effect of 1 alpha-hydroxycholecalciferol on the placental transfer of calcium and phosphate in sheep.

The calcium and phosphorus concentrations in foetal tissue or the placental transfer of 45Ca and 32P, or both, were studied in fifty-five control or 1 alpha-hydroxycholecalciferol (1 alpha-(OH)D3)-treated (0.1 micrograms/kg body-weight per d for 12 d) ewes between 77 and 140 d of gestation. Treatment resulted in a significant increase in the concentration of Ca and P in foetal tissues at all stages of gestation except at 140 d when, it is suggested, foetal mineralization may approach a maximum value. This increase in Ca and P concentration in foetal tissues was associated with an increased placental transfer of Ca, though at 111 and 120 d gestation this increase was not significant. P transfer, which was only measured at 140 d gestation, was also significantly higher in treated animals. The concentrations of Ca and P in both maternal and foetal plasma were increased significantly by the 1 alpha-(OH)D3 treatment. Whereas the concentration of Ca in the plasma of foetuses was always greater than in their dams, the concentration of plasma P in treated animals, unlike controls, was lower in foetuses than dams. This suggests that the increased placental transfer of P, unlike that of Ca, may be a passive rather than an active process.

Animals↗
PubMed1983

Electrotonic parameters of rat dentate granule cells measured using short current pulses and HRP staining.

The passive electrotonic parameters of nerve cells in the dentate gyrus of the rat were studied in vitro. Intracellular recordings from 30 granule cells and 3 pyramidal basket cells followed by intracellular injection of horseradish peroxidase (HRP), allowed calculations of input resistance (RN), membrane time constant (tau m), electrotonic length (L), ratio of dendritic to somatic conductance (rho), membrane specific capacitance and resistance (Rm, Cm), and specific axoplasmic resistance (Ri). The analysis of the voltage decays from long saturating (100 ms) and short (0.5 ms) current pulses showed that the short-pulse method gave better resolution for the measurement of the time constants and avoided some of the time-dependent nonlinearities but required larger currents than the long pulse. Morphological analysis of 49 branching points taken from the dendritic trees of granule cells showed that the branching power, n, is equal to 1.56 +/- 0.186 and was fairly constant throughout the tree. Given the fact that all dendrites have approximately the same length and number of branch points, the granule cell dendritic tree can be meaningfully collapsed into an equivalent cable. Moreover, electrophysiological data suggested that the cable had a "sealed" end or at least a high-impedance termination. Based on an equivalent cable model with a sealed end and a lumped soma impedance, a method was implemented to analyze the multiexponential decays from hyperpolarizing current pulses and to solve the equations of the model. This was done successfully in only 40% of the cells and yielded the following mean values for L = 1.13 and rho = 7.58. From the measurements of the soma surface area (S) and the equivalent cable diameter (D), the average specific membrane parameters were calculated: Rm = 2,726 alpha x cm2, Cm = 5.24 microF/cm2, Ri = 101 alpha x cm. The input resistance and time constant of the granule cells as measured from the short-pulse technique averaged to RN 58.57 M alpha and tau m = 16.21 ms. The failure of the model to fit 60% of the cells was interpreted to be due to the presence of a somatic shunt resulting from electrode injury, tonic synaptic activity, a lower somatic membrane specific resistance, or electronic coupling.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1983

Influence of streptozotocin-induced diabetes on growth hormone secretion in the rat.

The effects of streptozotocin-induced diabetes on pituitary growth hormone (GH) content and release from incubated pituitaries were investigated. Male rats were made diabetic by a single injection of streptozotocin (65 mg/kg) and sacrificed by decapitation 15 days later. Pituitary GH concentration was significantly reduced in streptozotocin diabetic rats as compared to that observed in control animals. The amount of GH released from hemipituitaries was also lower in diabetic rats than in controls. Kinetic characteristics of somatostatin (SRIF) inhibition of GH release were not affected by the treatment. These results suggest that the decrease in plasma GH observed by some investigators in streptozotocin diabetic rats is probably due to a deficiency in GH storage and/or synthesis rather than a change in the responsiveness of pituitary GH cells to SRIF.

Animals↗
PubMed1983

[Side effects induced by captopril. Comparison of a series of hypertensive patients with renal failure and a series with cardiac failure].

The first oral converting enzyme inhibitor, Captopril, has been used to treat hypertension and cardiac failure since 1978. Based on this two year experience, we studied the side-effects of this drug in 64 patients, a privileged series as it included 32 hypertensive patients with chronic renal failure and 32 patients with cardiac failure and normal renal function. After 16 months of treatment, we observed 19 p. 100 of skin complaints, 17 p. 100 disturbance of taste, 6 p. 100 oral problems, and one case of orthostatic hypotension. From the biological point of view: 20 p. 100 eosinophilia, 10 p. 100 hyperkalemia, 5 p. 100 antinuclear antibodies, 2 p. 100 renal failure, and one case of agranulocytosis. The group with renal failure had many more side effects due to a relative dosage (corrected for weight and renal function) which was three times as great. It would therefore appear to be essential to adapt the dosage in each individual case, a task which we have attempted using a formula which considerably reduced the incidence of side effects in our series: (formula; see text)

Captopril↗
PubMed1983

Radiologic features of a metastatic carcinoma to the ureter.

2 cases of metastasis to the ureter from carcinoma of the stomach are presented. The clinical and radiologic features are reviewed. Metastasis to the ureter is rare. A plea for vigorous evaluation and early detection of this entity is made.

Adenocarcinoma↗