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Biomedical subjects

C Amiel

Publications and source records attributed to C Amiel.

At least 145 records · Page 8Linked to original sources
PubMed1981

Pharmacokinetics of gentamicin in perilymph and endolymph of the rat as determined by radioimmunoassay.

The kinetics of gentamicin in the inner ear fluids of the rat were studied with a sensitive radioimmunoassay. Continuous infusion over a broad range (7.5--150 micrograms/min) was used to obtain equilibrium. The lowest rate of infusion produced plasma concentrations after 45 min that were within the range of peak serum levels desirable in humans. The purity of perilymph and endolymph was ensured by measurement of sodium and potassium concentrations. The concentration of gentamicin in perilymph was linearly related to its concentration in plasma, which depended on the rate of infusion. After six days of constant infusion of gentamicin at 15 microgram/min, the concentrations in plasma, perilymph, and endolymph averaged 25.8, 5.1, and 1.2 micrograms/ml, respectively, for five of 11 rats. Gentamicin cleared from the perilymph with a half-life of 3 hr.

Animals↗
PubMed1981

Influence of parathyroid status of rats on renal tubular handling of adenosine 3'5'-monophosphate: a micropuncture study.

In order to correlate cyclic AMP handling by the nephron to the parathyroid status, clearance and micropuncture experiments were performed in rats with intact parathyroid glands, or immediately after parathyroidectomy, or six days after parathyroidectomy. In intact animals cyclic AMP urinary excretion was about twice the filtered load and the tubular addition of the nucleotide was achieved at the end of the accessible proximal tubule. In acutely parathyroidectomized rats cyclic AMP urinary excretion was not different from the filtered load and no proximal tubular addition was detected at the late accessible proximal tubule. In chronically parathyroidectomized animals urinary excretion of cyclic AMP was not different from the filtered load, nevertheless a proximal tubular addition of the nucleotide was observed, similar in magnitude to that of intact rats. The data afford a direct evidence that the convoluted proximal tubule is the major site of cyclic AMP tubular addition, confirm that this addition disappears immediately after parathyroidectomy, but indicate that it re-occurs in chronic parathyroidectomy.

Animals↗
PubMed1980

Localization of parathyroid-hormone-independent sodium bicarbonate inhibition of tubular phosphate reabsorption.

We investigated phosphate transport along superficial nephrons in two groups of acutely parathyroidectomized (APTX) rats. Animals of group 1 were infused with 0.5 M sodium chloride; and those of group 2, with 0.5 M sodium bicarbonate at the same rates. Compared to the sodium chloride infusion, the sodium bicarbonate infusion was associated with a significant increase in urinary excretion of phosphate: the fractional phosphate excretion was 2.3 +/- (SD) 1.3% in the sodium chloride group and 14.4 +/- 3.2% in the sodium bicarbonate group, P less than 0.01, whereas the fractional sodium excretion was identical, 7.4 +/- 0.60% and 7.5 +/- 0.50%. Micropuncture studies performed at the late accessible proximal and early accessible distal sites of the same superficial nephrons indicate that the reabsorptive capacity for phosphate (absolute reabsorption/absolute delivered phosphate per nephron segment) is decreased during sodium bicarbonate infusion in the convoluted proximal tubule as well as in the loop (segment located between late proximal and early distal accessible convolutions) and the terminal nephron. Such an effect is independent of both parathyroid hormone secretion and extracellular fluid volume expansion.

Animals↗
PubMed1979

[Recent data on the kidney tubule behavior of phosphorus, calcium and magnesium ions].

Information recently obtained about tubular renal handling of phosphorus calcium and magnesium ions deals with: 1. Localization of transport processes along the nephron; 2. Effects of several hormones on those transports, particularly parathyroid hormone and calcitonin, and localization of their receptor sites along the nephron; 3. Adaptation of phosphate tubular handling to its content in the diet; 4. Mechanisms of cellular transports.

Absorption↗
PubMed1976

Evidence for a parathyroid hormone-independent calcium modulation of phosphate transport along the nephron.

To disclose a parathyroid-independent calcium modulation of phosphate transport along the nephron, the effect of increasing plasma calcium concentration to subnormal levels in rats 6 days after parathyroidectomy (chronic PTX) was studied. Fractional phosphate reabsorption was significantly increased. The whole kidney response to calcium infusion was similar whether or not the thyroid gland was removed, which suggests that calcitonin is not involved. The micropuncture study indicated an increase in the reabsorptive capacity for phosphate (absolute reabsorption/absolute delivered phosphate per nephron segment) in the proximal tubule, the loop, and the terminal nephron when calcium was infused. Thus, the level of plasma calcium or some related factor affects the phosphate transport by the tubule independently of parathyroid hormone. With calcium infusion, the profile of phosphate reabsorption along the nephron became close to that of acutely parathyroidectomized rats, but with persisting differences. The level of plasma calcium concentration may partly account for the differences between the acute and the chronic steps of parathyroidectomy. The role of possible interferences between alterations of extracellular calcium concentration or some related factor and the adenylate cyclase-cyclic AMP system in such an action of calcium was evaluated. Cyclic AMP was infused so as to achieve a 10(-6) M plasma concentration. Combined infusions of calcium and cyclic AMP were also performed. The results are compatible with calcium inhibition of adenylate cyclase, although they do not rule out a direct action of calcium.

Animals↗
PubMed1976

Electrophoretic mobility of lymphocytes in new born.

T lymphocytes in normal new born at the 4th day after birth have an electrophoretic mobility of 1.04, quite slower than adult normal T lymphocytes (1.13), but the same of the EM of lymphoblasts of ALL (1.04).

Aging↗
PubMed1975

[Leukomalacia and subsequent brain status in relation to intensive neonatal care].

Leucomalacia or white matter necrosis is one of the major aspects of neonatal encephalopathies, especially in the premature baby. These necroses are found mainly in the deep periventricular white matter of the "semi-oval centre". Characteristically, they are ischaemic and their anatomical and histological progress is rapid: coagulation necrosis with rapid axonal fragmentation followed by polymorphic cellular reaction with glial cells and macrophages. Regeneration in the minor forms consists of glyosis process in severe forms; multiple cavities appear in a few weeks. Physiopathogenic hypotheses put forward are related to: 1 -- the very anatomic aite: special tissue and terminal arteries, 2 -- onset of myelinization process, 3 -- associated clinical and biological lesions such as hypoxia, acidosis and hypotention. These lesions are symptom-free during the neonatal period. One of us suggested in 1962 that these could be the anatomical basis of spastic monoplegia or diplegia (LITTLE's disease). All motor cerebral sequelae have disappeared since 10 years. This is particularly significant mainly in the case of spastic diplegia of the former premature baby under 2500 g. This decrease coincides with improvement in neonatal care, especially correction of hypoxia, acidosis and cardiovascular collapse. These findings seem to support the pathogenic hypotheses.

Brain Diseases↗
PubMed1974

[H+ ion balance].

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Acid-Base Equilibrium↗