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Biomedical subjects

A Loiseau

Publications and source records attributed to A Loiseau.

At least 55 records · Page 3Linked to original sources
PubMed1993

Transport of choline by Madin-Darby canine kidney cells.

Choline is an essential precursor for the synthesis of phosphatidylcholine, the most abundant phospholipid classes in renal cells, as well as for the synthesis of the osmolyte glycerophosphorylcholine. The characteristics of choline uptake in the renal epithelial cell line MDCK were investigated. In the range of physiological concentrations, choline entered MDCK cells, grown as a monolayer on solid support, via a specific sodium-independent transport system (apparent Km = 43 microM, apparent Vmax = 284 pmol/mg protein per 5 min). Cell ATP depletion, addition of KCl to the medium to reduce the cell membrane potential, and hemicholinium-3 (HC-3) inhibited choline uptake. Specific binding of [3H]HC-3 was detected on the apical membrane of cells grown on plastic dishes, whereas it occurred only on the basolateral domain of cells grown on permeant support. When growing cells on filter, choline uptake from the basolateral side was 10-times the apical uptake. This suggests that the choline carrier present at the apical domain of cells grown on solid support is either inactivated or no longer targeted to the apical but to the basolateral membrane of MDCK cells grown on filter.

Adenosine Triphosphate↗
PubMed1993

Replacing the (beta alpha)-unit 8 of E.coli TIM with its chicken homologue leads to a stable and active hybrid enzyme.

In order to investigate how structural modifications interfere with protein stability, we modified a (beta alpha)-unit in E.coli triosephosphate isomerase (TIM), a typical (beta alpha)-barrel protein, assuming that the pseudosymmetrical beta-barrel can be divided into eight successive loop/beta-strand/loop/alpha-helix motifs. We replaced the eighth (beta alpha)-unit of E.coli TIM with the corresponding chicken (beta alpha)-unit. The substitution, involving the replacement of 10 of the 23 residues of this (beta alpha)-unit, was evaluated first by modelling, then experimentally. Modelling by homology suggests how the amino acid replacements might be accommodated in the hybrid E.coli/chicken TIM (ETIM8CHI). Both natural and hybrid recombinant TIMs, overproduced in E.coli, were purified to homogeneity and characterized as to their stability and kinetics. Our kinetic studies show that the modification performed here leads to an active enzyme. The stability studies indicate that the stability of ETIM8CHI is comparable to that of the wild type TIM.

Amino Acid Sequence↗
PubMed1993

N-ethylmaleimide-inhibited electrogenic K+ secretion in the ampulla of the frog semicircular canal.

1. The mechanisms of K+ secretion into endolymph were studied on a preparation of isolated semicircular canal with different pharmacological inhibitors. Three periods of 5 or 30 min were performed, the first as control, the second in the presence of the drugs added to the apical or the basolateral bathing solution, and the third as recovery. Apical fluid was sampled at the beginning and the end of each period, transepithelial potential was recorded, Na+, K+, and Cl- concentrations, and K+ efflux, with 86Rb+ as a tracer, were measured and K+ fluxes were calculated. 2. When both sides of the epithelium were bathed with perilymph-like solution, the epithelium absorbed Na+, secreted K+, and generated a lumen positive potential. 3. The ATPases inhibitors, ouabain (10(-5) and 10(-3) M) and N-ethylmaleimide (10(-4) and 10(-3) M) inhibited the electrogenic K+ secretion when added to the basolateral fluid. N-ethylmaleimide (10(-3) M) applied to the apical fluid during a 5 min period decreased the K+ influx by 43% and the transepithelial potential by 66%. Other ATPase inhibitors, harmaline (10(-3) M), omeprazole (10(-4) M), vanadate (10(-4) M and 10(-3) M), N,N'-dicyclohexylcarbodiimide (DCC, 10(-5) M), 7-chloro-4-nitrobenz-2-oxa-1,3-diazole (NBD-Cl, 5 x 10(-6) M and 5 x 10(-5) M), and bafilomycin (10(-7) M) did not affect the K+ transport nor the transepithelial potential when they were added to the apical fluid. 4. The Na(+)-K(+)-Cl- co-transporter inhibitor, bumetanide, decreased both the transepithelial potential and the K+ transport when added to the basolateral solution but not to the apical one. At 10(-6) M, bumetanide maximally decreased the K+ influx by about 60%. 5. K+ channel blockers, quinine (10(-4) M), TEA (5 x 10(-3) M), added to the apical solution and barium (2 x 10(-3) M) added to either the apical or the basolateral solutions, did not affect the K+ transport and the transepithelial potential. 6. The carbonic anhydrase inhibitor acetazolamide (10(-3) M) added to both apical and basolateral solutions did not affect the K+ transport and the transepithelial potential. 7. It is concluded that, in the ampulla of the semicircular canal, a basolateral Na(+)-K(+)-Cl- co-transporter energized by the Na+, K(+)-ATPase was involved for 60% in the K+ secretion into endolymph. The electrogenic K+ transport would partly depend on a N-ethylmaleimide-sensitive protein possibly located at the apical plasma membrane or intracellularly.

Animals↗
PubMed1992

Changes in the electrochemical composition of cochlear fluids after intracisternal application of doxorubicin in the rat.

Since doxorubicin (Adriamycin) is known to bind on membranous negative surface charges, its effect on the electrochemical composition of the cochlear fluids was studied in rats. Doxorubicin was infused into the cerebrospinal fluid via the lateral cerebral ventricle. The endocochlear resting potential was recorded, and endolymph and perilymph of the scala vestibuli were collected from the basal cochlear turn before and 1, 2, and 4 h after the drug application. Na+, K+, and Cl- concentrations and osmolality of the endolymph and perilymph were measured in 1 nl aliquots. In perilymph, Cl- concentration increased 4 h after doxorubicin treatment to reach a concentration 8 mM higher than recorded initially. In endolymph, the endocochlear potential decreased by 5 mV/h while its K+ concentration and osmolality increased by about 3 mM/h and 4 mosmol/kg H2O per hour, respectively. These results suggest that the negative surface charges demonstrated on Reissner's membrane may play a role in the homeostasis of endolymph.

Animals↗
PubMed1992

A phosphoglycerate kinase-related gene conserved between Trypanosoma brucei and Crithidia fasciculata.

Trypanosoma brucei and Crithidia fasciculata both contain three different phosphoglycerate kinase (PGK) genes, A, B and C, in a tandem array. The genes B and C encode the major PGKs: the cytosolic and glycosomal PGKs, respectively. The PGK-A genes of both Trypanosomatid species encode open reading frames related to PGK, which have most active site residues conserved, but contain an insert of 80 amino acids at approximately position 80 of the 420 amino acids average PGK sequence. The deduced amino acid sequence of these inserts is conserved between T. brucei and C. fasciculata (48% positional identity), indicating its functional importance. Although we have not been able to demonstrate PGK activity in the PGK-A gene product, we consider it likely that this gene codes for a minor PGK with special function.

Amino Acid Sequence↗
PubMed1992

[Exercise tests in pneumology. C.R.E.D.O].

Exercise tests have proved very useful in numerous areas such as sports medicine, research, clinical medicine and rehabilitation to exercise and therapeutic trials. It is not always easy for a pneumologist to decide what sort of effort and which protocol to use. There is also the question of which parameter to use and the relationship between parameters and which are the most pertinent as a function of the aim of the research. Above all the exercise test should be adaptable in view of the diversity of the objectives. In routine pneumology the exercise test using a bicycle ergometer and a triangular type of protocol are recommended for numerous reasons. The usual parameters (ventilation, oxygen consumption, production of carbonic dioxide, cardiac rate and blood gases) and their derivatives all have a value in the domain of cardiorespiratory physiology. It is important in clinical practice not to give too great an emphasis to the exact relationship expressed as a function of the workload, because the cycloergometer is practically never calibrated or even checked by the user. Dyspnoea was the major symptom leading the patient to seek a consultation and it is of primary importance that all effort tests include an estimation of the sensation of breathlessness.

Blood Gas Analysis↗
PubMed1991

Calibration method for small animal indirect calorimeters.

A simple mini-butane burner or "artificial rat," for calibration of small animal indirect calorimeters (modified Benedict and Haldane systems), was developed. Substitution of this burner for a live animal at regular intervals in an experimental protocol provides a means by which whole system function can be verified without disturbing respirometer conditions. Heat production, degree of total combustion of butane, proportion of unburned butane, and the CO2 production (VCO2)-to-O2 consumption (VO2) ratio were determined in animal and burner experiments by direct measurement or were derived from mass equations. Burner security was also discussed. VCO2/VO2 obtained in calibration experiments using the Benedict system remained constant and was not significantly different from the expected value for total combustion of butane. Observation of a stabilization phase in the Haldane burner experiments illustrated the utility of calibration over the duration of a normal animal experiment. This miniburner gave highly reproducible results and simulated the daily VO2, VCO2, and heat production of an adult rat.

Animals↗
PubMed1991

Bronchoalveolar mast cells in normal farmers and subjects with farmer's lung. Diagnostic, prognostic, and physiologic significance.

To evaluate the specificity and significance of increased lavage mast cells in farmer's lung, we examined the lavage cell differentials of 89 farmers and 19 normal nonfarming control subjects. The farmers were divided into four groups: acute farmer's lung (n = 17), farmers with one or more prior episodes of farmer's lung who remained in daily contact with hay (n = 26) or quit farming (n = 14), and normal farmers (n = 36). A total of 14 of the subjects with prior episodes of farmer's lung and still farming and 15 normal farmers were evaluated twice at a 2-yr interval. The lavage mast cell numbers were significantly higher in acute farmer's lung (7.5 +/- 7.3 x 10(3)/ml, mean +/- SD) and ex-farmer's lung who were still farming (1.2 +/- 1.3 x 10(3)/ml) than in normal farmers (0.1 +/- 0.1 x 10(3)/ml) (p less than 0.01). A total of 8 of 14 exfarmer's lung patients who had quit farming and 18 of 36 normal farmers had an increased number of mast cells in lavage, but mast cell count never exceeded 0.5% of total recovered cells. In the acute farmer's lung and ex-farmer's lung-still farming groups, the mast cell count correlated with the lymphocyte count: r = 0.83 and r = 0.69 (p less than 0.001), respectively. In the two groups evaluated twice, mast cell numbers at the first study did not correlate with changes seen at the second study in chest roentgenogram and pulmonary functions. We conclude that an increase in lavage mast cells occurs commonly as a part of the immune response against thermophilic bacteria.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1991

Antigen-induced proliferative response of lavage and blood T lymphocytes. Comparison of cells from normal subjects and patients with sarcoidosis.

To evaluate the mechanisms responsible for anergy in sarcoid patients, we studied the ability of highly purified lavage and blood T lymphocytes from control subjects and patients with sarcoidosis to proliferate in response to recall antigens, and compared the results of antigen-induced lymphocyte proliferation with the clinical characteristics of the patients. Both blood and lavage T lymphocytes from all control subjects proliferated in response to purified protein derivative (PPD) and candida antigens, and no significant difference was observed comparing the proliferation of lymphocytes from the two sources. The antigen-induced proliferation of blood and lavage T lymphocytes from sarcoid patients was reduced compared with that of the corresponding cell populations from normal subjects (p less than 0.01 for PPD, Candida, and tetanus), and the proliferative response of sarcoid lavage lymphocytes was significantly lower than that of blood T lymphocytes from these patients. No evidence for inhibition of T lymphocyte proliferation by accessory cells (blood monocytes) or CD8+ T lymphocytes was observed, and the refractory state could not be overcome by adding exogenous recombinant human IL-2 or IL-4. An inverse correlation was observed between the PPD-induced proliferation of sarcoid lavage T lymphocytes and criteria associated with "active" disease, including lymphocytes/ml lavage fluid (p less than 0.003), 67Ga uptake (p less than 0.005), and serum angiotensin converting enzyme activity (p less than 0.005). Lavage lymphocytes from patients studied early in the course of the disease proliferated better than those from patients with more long-standing disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Size dependence of the end-systolic stress/volume ratio in humans: implications for the evaluation of myocardial contractile performance in pressure and volume overload.

The end-systolic stress/volume ratio is currently recognized as a relatively load-independent index of myocardial contractile performance, but its dependence on ventricular size may limit its value for interpatient comparisons. In this study, the relation between the end-systolic stress/volume ratio and left ventricular end-diastolic volume was angiographically analyzed in 104 patients with normal coronary angiograms. Eighteen patients had a normal ventricle, 24 had aortic stenosis, 18 had aortic regurgitation, 9 had mitral regurgitation and 35 had cardiomyopathy. An inverse relation between the end-systolic stress/volume ratio and left ventricular end-diastolic volume was demonstrated in the normal group (r = 0.72, p less than 0.001); subjects with a larger left ventricle had a reduced index but, presumably, the same degree of contractility as that of subjects with a smaller ventricle. Attempts to normalize values by using end-diastolic volume or body surface area were unsuccessful. A similar inverse relation was demonstrated in the aortic stenosis group (r = 0.48, p less than 0.05), probably because hypertrophy helps to keep wall stress normal or low despite progressive ventricular enlargement in these patients. The end-systolic stress/volume ratio was also inversely related to left ventricular chamber size in patients with volume overload due to aortic regurgitation (r = 0.80, p less than 0.001) and in those with cardiomyopathy (r = 0.84, p less than 0.001). However, at a given left ventricular end-diastolic volume, the end-systolic stress/volume ratio was higher in patients with aortic regurgitation than in those with cardiomyopathy, suggesting better contractile performance for a comparable degree of ventricular dilation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

A simple method for correcting single breath total lung capacity for underestimation.

The single breath method underestimates total lung capacity by comparison with the multiple breath method (TLCmb) because of inhomogeneity of ventilation distribution. This study proposes a simple correction for the single breath TLC (TLCsb), using inert gas phase III slope to account for the effects of uneven ventilation distribution. A model of a non-uniform lung ventilation was designed, composed of a serial dead space and two alveolar compartments arranged in parallel, whose relative ventilations were determined from the phase III plateau. Before correction TLCsb was 104-44% of TLCmb in 64 subjects (17 with diffuse interstitial disease, 42 with chronic obstructive pulmonary disease, and five healthy subjects). The limit of acceptability for the correction (TLCcorr) was determined from the 95% confidence interval of TLCsb/TLCmb in the healthy subjects. The correction resulted in a significant increase in TLCsb (p less than 0.004). TLCcorr remained under the limit of acceptability for only 12 patients with emphysema, and all 12 showed a large improvement in the TLC estimate. The presence of poorly ventilated zones during a single breath in these patients may explain this partial correction.

Adult↗
PubMed1990

The resistance to parathyroid hormone of fibroblasts from some patients with type Ib pseudohypoparathyroidism is reversible with dexamethasone.

Skin fibroblasts from some patients with pseudohypoparathyroidism type Ib (PHP-Ib) are resistant to PTH. To characterize the defect producing PTH resistance in these cells and determine whether the abnormality is potentially reversible, we evaluated the ability of fibroblasts from patients with PHP-Ib to produce cAMP in response to PTH both before and after exposure to dexamethasone, an agent known to increase PTH responsiveness in other cell types. Before dexamethasone treatment, fibroblasts from five of eight patients with PTH-Ib produced reduced amounts of cAMP in response to PTH (but not prostaglandin E1 and forskolin) compared to that of control cells (6.3 +/- 1.0 and 37.3 +/- 6.3 pmol cAMP/100 micrograms protein, respectively). Whereas dexamethasone pretreatment had no effect on cAMP production by control or PTH-responsive PHP-Ib fibroblasts, it resulted in a dose-dependent increase in PTH-induced cAMP production by PTH-resistant fibroblasts to normal levels in four of five cases. Studies evaluating the binding of radiolabeled PTH did not permit quantification of the small number of high affinity PTH receptors present on these cells. We conclude that PTH resistance in PHP-Ib patients with PTH-resistant fibroblasts results from an abnormality in the expression of or coupling to cyclase of high affinity PTH-receptor complexes. Because it is expressed in only some tissues and is reversible, the defect could be regulatory in nature.

Adult↗
PubMed1990

Beta-adrenergic receptor function is acutely altered in surgical patients.

Catecholamine-induced desensitization of beta-adrenergic receptors resulting in hyporesponsiveness to further stimulation has been frequently reported after an increase in endogenous catecholamines. To examine the possibility of beta-adrenoceptor desensitization due to intraoperative adrenergic activation (surgical stress), the alterations of human lymphocyte beta-adrenergic receptor density and affinity observed after anesthesia and surgery were studied using (-)125I-iodocyanopindolol binding in 19 patients undergoing noncardiac surgical procedures with general anesthesia (thiopental, fentanyl, and halothane or isoflurane). In 13 patients, repeated determinations of plasma levels of norepinephrine and epinephrine showed an increase during the surgical procedure (norepinephrine +60%; epinephrine +60%); this change was not observed in the remaining patients. A significant postoperative increase in receptor density (Bmax +25%) and a significant decrease of receptor affinity for isoproterenol (IC50 +22%) were found in the patients who experienced intraoperative adrenergic activation. By contrast, no significant change in beta-receptor density or affinity was found in the patients who had normal intraoperative adrenergic activation. In addition, heart rate responses to the postoperative changes in plasma catecholamines (an index of cardiac sensitivity to agonist) were significantly attenuated in patients who experienced both intraoperative adrenergic activation and a decrease in affinity of beta-receptor for agonist, suggesting hyporesponsiveness to beta stimulation. We conclude that beta-adrenergic receptors and, consequently, beta-adrenergic responsiveness might be altered by perioperative adrenergic activation in surgical patients.

Adult↗
PubMed1990

Shape change of the occlusion-pressure wave during exercise.

In conscious subjects, the occlusion pressure measured in the initial part of the inspiration (up to 200 ms) appears to be a valid index of output of the respiratory centres. To interpret any relative change in occlusion pressure, the shape of the occlusion-pressure wave must remain absolutely constant. The purpose of this study was to test the hypothesis that the shape of occlusion-pressure wave does not change during exercise. However, we found that the shape changed significantly during cycle incremental-load exercise in five healthy subjects and in 12 of 17 patients with chronic obstructive pulmonary disease. The major change appeared during the second half of the exercise and mainly during the last workloads. This study shows that it is necessary to take into consideration this form change to interpret any relative change in mechanical transforms of the inspiratory neural output such as pressure at 0.1 s (P0.1) and mean inspiratory flow (VT/TI) or their ratio. This finding confirms, in direct fashion, the expected form change from previous data in which P0.1 is thought to measure the rate of change in chest wall muscle pressure (Pmus) over a segment somewhat removed from the onset of neural inspiration.

Adult↗
PubMed1990

Beta-adrenergic receptor changes during coronary artery bypass grafting.

To evaluate whether the function of beta-adrenergic receptors, essential to the biologic activity of catecholamines, is altered during coronary artery bypass grafting, we measured, in 16 patients undergoing myocardial revascularization, the density and the affinity of lymphocyte beta-adrenergic receptors before anesthesia induction (control) and at the end of cardiopulmonary bypass. Variations in the density and affinity of beta-adrenergic receptors were determined in vitro. Repeated determinations of plasma epinephrine and norepinephrine concentrations were also performed. Overall, no significant modification was observed in mean density and affinity of beta-adrenergic receptors at the end of cardiopulmonary bypass when compared with control values. However, a significant decrease (p less than 0.05) in affinity for isoproterenol was found in the six patients who had high catecholamine levels during cardiopulmonary bypass. In contrast, no significant modification of beta-adrenoreceptor affinity for isoproterenol was observed in the 10 patients who did not have this degree of adrenergic activation. In addition, beta-adrenoreceptor affinity for isoproterenol was decreased in the three patients in whom intraaortic balloon pumping was mandatory after discontinuation of cardiopulmonary bypass. We suggest that this decreased affinity of lymphocyte beta-adrenergic receptors could be related, at least in part, to a sustained adrenergic activation occurring in some patients during cardiopulmonary bypass.

Anesthesia↗
PubMed1990

[A visual analog scale of exercise dyspnea].

We have adapted a visual analogue scale (VAS) to make repeated measurements of the sensation of dyspnoea during an exercise test on a bicycle ergometer. We tested the reproducibility of the development of the VAS as a function of work load and its sensitivity in detecting changes in the sensation of dyspnoea induced by the addition of an inspiratory resistance or by a trial of oxygen administration in 13 patients who were dyspnoeic on effort. The reproducibility was acceptable providing to perform a preliminary test and to eliminate the rare subjects who was incapable of performing the test (1/13). The method turned out to be equally sensitive as to the effect of inspiratory resistance for 8/12 patients and for the oxygen enrichment of inspired air for 8/9 patients. This scale thus provides a reproducible and sensitive estimation of the sensation of dyspnoea during effort and thus appears valuable in evaluating the subjective response in therapeutic trials in patients who are dyspnoeic on effort.

Aged↗