Growth of cultured rabbit renal tubular cells does not require exogenous glutamine.
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Animals↗
Biomedical subjects
C Gauthier
Publications and source records attributed to C Gauthier.
Rabbit pancreatic acini express CFTR as a cAMP-activated chloride efflux pathway.
Cystic fibrosis transmembrane conductance regulator (CFTR) is responsible for adenosine 3',5'-cyclic monophosphate (cAMP)-activated chloride transport in epithelial cells. Isolated rabbit pancreatic acini possess a cAMP-activated chloride efflux mechanism distinct from zymogen granule secretion. To determine whether CFTR is expressed in acini, we used polymerase chain reaction (PCR) to amplify a 480-base pair (bp) sequence from reverse-transcribed rabbit acinar RNA. The PCR product was consistent with a 480-bp band amplified in T84 cells, and its sequence was > 90% homologous to human CFTR. CFTR antibody M3A7 recognized a 180- and a 160-kDa protein from acinar membranes consistent with bands seen in Chinese hamster ovary (CHO) cells transfected with CFTR. To determine if CFTR was responsible for the cAMP-activated chloride efflux previously demonstrated in pancreatic acini, we incubated acinar cells for 20 h with 1.75 microM CFTR antisense or sense oligodeoxynucleotide. Chloride efflux, in response to 8-bromoadenosine 3',5'-cyclic monophosphate and phorbol ester but not to calcium ionophore, was selectively inhibited by CFTR antisense oligodeoxynucleotide. Antisense oligodeoxynucleotide did not inhibit acinar amylase secretion. These findings indicate that isolated pancreatic acini can be used for future studies of CFTR expression and function.
Amylases↗
Protein endocytosis by a kidney tubule suspension: metabolic requirements.
Endocytosis in the renal tubular cell is a permanent process serving the role of saving nitrogen from plasma peptides that are continuously cleared away by kidney glomerulus. Since small proteins appear in urine after strenuous exercise, it was hypothesized that renal ischemia impairs the tubular endocytic reabsorption of proteins. The aim of this paper is to describe a simple in vitro model of renal endocytosis and to use it in studies of endocytic metabolic requirements. The results show that rabbit renal proximal tubules in suspension are able to take up 125I-lysozyme, as well as RITC-lactalbumin. The fluorescent protein was taken up only by the ends of the everted tubule fragments, and accumulated into intracellular vesicles, demonstrating the luminal pathway of endocytosis. The amount of 125I-lysozyme taken up was equivalent to that taken up by isolated perfused tubules (Nielsen et al. (1986) Am. J. Physiol. 251, F822-F830). Anoxia decreased 12-fold the intracellular accumulation of 125I-lysozyme; however, the time-course of inhibition shows that only the late steps of endocytic accumulation are energy-dependent. Substrate deprivation studies suggest a specific role of glucose to sustain endocytosis. Lastly, renal uptake of 125I-lysozyme was shown to be strongly depressed by chloroquine, an alkalinizing agent of endosomes and lysosomes. We conclude that (1) renal tubules in suspension are a satisfactory model for endocytic studies in kidney; (2) suppressing oxygen and substrate supplies to kidney impairs endocytic tubular reabsorption of proteins.
Alanine↗
Endomyocardial biopsies: a new approach for studying the electrical and mechanical properties of human ventricular myocardium.
The novel endomyocardial biopsy approach described here could facilitate the study of some human pathologies for which tissue specimens are currently unavailable. Electrical and mechanical characteristics such as rat responses, effect of extracellular calcium concentration changes and beta-adrenergic tone were similar to those determined for other human ventricular tissues, indicating that endomyocardial biopsies are suitable for physiological studies. This new source of cardiac tissues should facilitate the investigation of cellular mechanisms involved in the development of previously inaccessible human diseases.
Action Potentials↗
Haemolyzed samples: responsibility of short catheters.
The haemolysis of blood samples is a source of error in the electrolytic and enzymatic determination in clinical biochemistry. This circumstance seems dependent on the material used for the venepuncture. In this study we compared three kinds of material in 350 patients who were sampled in the emergency department. This randomized study compared the haemolysis of blood samples collected with stainless steel needles and short catheters, either Teflon FEP (Cathlon Critikon) or polyurethane Vialon (Insyte Becton-Dickinson). Quantification of hemolysis was performed by assay of the optical density of plasma haemoglobin. Results were analysed, after verification of the randomization, by one-way analysis of variance by ranks. This study demonstrated a highly significant relation between occurrence of haemolysis and the sampling material, used according to its technical obligations. Haemolysis occurred frequently when short catheters were used in 42% and 55% of cases with the Teflon and Vialon catheters, respectively. Haemolysis was much less frequent with stainless steel needles (12%). This difference was even more marked for haemoglobin levels above 1.5 milligrams of plasma, where the incidence was 4.2%, 9% and 30%, respectively, for the stainless steel needles, the Teflon catheter and the Vialon catheter. This study induced our emergency department to take more blood samples with a needle, even if an infusion was to be given subsequently, or to take them using a Teflon catheter.
Adolescent↗
[Diagnosis of orthostatic hypotension. Value of the head-up tilt test. 110 cases].
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Humans↗
[Association of disseminated lupus erythematosus and Hashimoto's thyroiditis. 2 new cases].
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Aged↗
Early after/depolarizations and triggered activity: mechanisms and autonomic regulation.
An early after/depolarization (EAD) is an abnormality of the repolarization process of an action potential which causes an interruption or a retardation of normal repolarization. Two types were described: phase 3 EADs occur at a takeoff potential of approximately-60 mV and phase 2 EADs occur at the end of a prolonged plateau at a takeoff potential of between-10 and-30 mV. EADs can result from an increase in inward current, a reduction of outward current or both. EADs show cycle-length dependence: as cycle length increases and repolarization lengthens, EADs occur, and their magnitude increases, at a critical cycle length, can trigger the action potential of these EADs. The autonomic nervous system can also modulate EADs and trigger activity. In cesium-intoxicated Purkinje fibers, beta-adrenergic stimulation increases EAD magnitude and the occurrence of triggered activity. Cholinergic stimulation decreases EAD magnitude and suppresses triggered activity occurring after beta-adrenergic stimulation. Alpha 1-adrenergic stimulation has no effect on phase 3 EADs but induces phase 2 EADs. In normal Tyrode's solution (0 cesium), phenylephrine prolongs action potential and induces EADs. This effect seems to depend on alpha 1 A stimulation. These electrogenic abnormalities are supposed to be responsible for long QT and torsades de pointes. As our experimental data have shown that both the rate of stimulation and the autonomic nervous system could modulate EADs and trigger activity, we can speculate on the therapeutic implications of such modulations and the role of pacing as well as alpha- and beta-adrenergic antagonists.
Animals↗
Antisense oligodeoxynucleotide to the cystic fibrosis transmembrane conductance regulator inhibits cyclic AMP-activated but not calcium-activated cell volume reduction in a human pancreatic duct cell line.
Cystic fibrosis (CF) is characterized by a defect in cAMP-regulated chloride channels in epithelial cells. The CF gene product CF transmembrane conductance regulator (CFTR) is expressed in the apical membrane of pancreatic duct cells, and mutant CFTR accounts for the pathology in the CF pancreas. PANC 1, a pancreatic duct cell line, has not been considered a good model for studying CFTR and pancreatic chloride transport because CFTR mRNA and protein are undetectable using standard methods. Using electronic cell sizing and cell volume reduction under isotonic conditions, PANC 1 cells were found to possess both cAMP and calcium-activated chloride conductances. Using CFTR antisense oligodeoxynucleotides, the cAMP-activated conductance could be specifically inhibited in a concentration- and time-dependent manner. These findings demonstrate that PANC 1 cells express CFTR and a CFTR-independent calcium-activated chloride channel. With electronic cell sizing and CFTR antisense oligodeoxynucleotides, PANC 1 cells can provide an ideal system for the study of pancreatic duct cell physiology and pathophysiology with respect to the role of CFTR in the pancreas. These findings also suggest that antisense oligodeoxynucleotides may provide a more sensitive yet highly specific means of detecting low levels of expression of CFTR than currently available.
8-Bromo Cyclic Adenosine Monophosphate↗
Forskolin effects on slow inward current and phasic tension of frog atrial fibres: modulation by adenosine and phosphodiesterase inhibitors.
The effects of forskolin, which is known as a direct activator of adenylate cyclase were studied on the slow inward calcium current (Isi) and phasic tension of frog atrial fibres. Forskolin induced a dose-dependent positive inotropic effect related to an increase in the slow inward calcium current. These effects, which were not reproduced by 1,9-dideoxyforskolin, seemed to result from an activation of adenylate cyclase. The action of forskolin was antagonized by adenosine and potentiated by phosphodiesterase inhibitors with the following order of potency: rolipram greater than theophylline greater than dipyridamole; M & B 22,948 was without influence. This study suggests that adenosine and rolipram might be suitable tools for studying the implication of cAMP in the modulation of contraction in frog atrium.
Adenosine↗
Synthesis and characterization of a d(ApG) platinated nonanucleotide duplex.
The nonamer 5'd(CTCAGCCTC) 3' 1 has been reacted with cis-diamminediaquaplatinum(II) in water at pH 4.2. The major reaction product was shown by enzymatic digestion and 1H NMR to be the d(ApG)cis-Pt(NH3)2 chelate [cis-Pt(NH3)2[d(CTCAGCCTC)-N7(4),N7(5)]] 1-Pt. When mixed with its complementary strand 2, 1-Pt forms a B DNA type duplex 3-Pt with a Tm of 35 degrees C (versus 58 degrees C for the unplatinated duplex). The NMR study of the exchangeable protons of 3-Pt revealed that the helix distortion is localized on the CA*G*-CTG moiety (the asterisks indicating the platinum chelation sites) with a strong perturbation of the A*(4)T(15) base pair related to a large tilt of A*(4).
Base Composition↗
[Arrhythmogenic effects of sultopride chlorhydrate: clinical and cellular electrophysiological correlation].
This study was designed following the first documented case of torsades de pointes induced by sultopride hydrochloride, a substituted benzamide neuroleptic drug. The patient, a 48 year-old woman with no known cardiovascular disease, had been treated for several years with this drug. She was admitted for severe bronchospasm requiring artificial ventilation. Twenty-one hours after her admission, she developed several episodes of torsades de pointes, which were successfully treated with magnesium sulphate. At that time, the QT interval was 500 ms for a heart rate of 108 b.min-1 (QTc of 668 ms, and theoretical QTc 370 ms). On the fourth day, QTc was 548 ms and theoretical QTc 370 ms. The sultopride was stopped on the fifth day. Two days later, QTc was 397 ms. Six months later, there was no recurrence. Several cases of TdP or sudden death have been reported in patients receiving neuroleptic drugs. The effects of sultopride hydrochloride were therefore tested on isolated ferret Purkinje fibres, using the microelectrode technique. Three concentrations of the drug (D1, D2, D3) were tested, as well as normal Tyrode solution. Maximum diastolic potentials (Vmax) were -88.37 +/- 0.89 mV (control), -89.08 +/- 1.20 mV (D1), -90.00 +/- 1.06 mV (D2), and -90.14 +/- 1.20 mV (D3). Vmax was not affected by sultopride during pacing at 1,000 ms of cycle length. The duration of the action potential increased with the drug concentration. There was no early after-depolarisation (EAD) during control, and 7 out of 9 fibers had EAD and 3 out of 9 triggered activity in D3. The solvent (benzyl alcohol) did not modify the action potential.(ABSTRACT TRUNCATED AT 250 WORDS)
Action Potentials↗
Cyclic nucleotide phosphodiesterases from frog atrial fibers: isolation and drug sensitivities.
The cyclic nucleotide phosphodiesterase (PDE) forms present in frog atrial fibers were isolated and characterized by their drug sensitivities. DEAE-sephacel chromatography of cytosolic PDE activity resolved three major PDE forms: peak A hydrolyzed both adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5'-cyclic monophosphate (cGMP) and was activated by calcium-calmodulin (PDE I); peak B also hydrolyzed both cAMP and cGMP but was activated by 5 microM cGMP (PDE II); peak C specifically hydrolyzed cAMP (PDE IV). Rolipram specifically inhibited PDE IV (Ki = 1.1 microM), whereas dipyridamole potently inhibited both PDE II (Ki = 4.6 microM) and PDE IV (Ki = 0.8 microM). Atrial fiber PDE I was preferentially inhibited by zaprinast (Ki = 10 microM). 3-Isobutyl-1-methyl xanthine (IBMX) and theophylline inhibited nonspecifically all three different enzymes. The positive inotropic drug CI 930 only inhibited the different isolated atrial PDE forms at concentrations greater than 200 microM. However, under assay conditions for which PDE IV was specifically inhibited (presence of 100 microM rolipram), an IC50 of 17 microM for CI 930 was observed on the remaining 26% cAMP hydrolytic activity of peak C (which could represent a cGMP-inhibited PDE form: PDE III). The same PDE forms were also found in frog ventricle. The major difference between frog atrial fiber (and ventricular tissue) PDEs and mammalian cardiac PDEs is that the main cytosolic cAMP-specific hydrolytic activity in frog heart is due to PDE IV rather than PDE III. Rolipram, dipyridamole, and zaprinast might be useful tools to investigate the participation of cAMP in frog atrial contraction (unpublished observations).
1-Methyl-3-isobutylxanthine↗
[Comparative epidemiological characteristics of a homogeneous series of acute common pneumopathies seen in a general hospital center (GHC)].
Between 1979 and 1989, 108 cases of community acquired pneumonia in non-immunodepressed subjects were admitted to hospital to a specialist chest department. The patient's characteristics were as follows: mean age = 56 (range 14-91), 44 women and 64 men. The causal agent was isolated in 44 cases (40%) of which 4 cases were viral (9% of 44 cases) and 12 were Legionella (27%), pneumococci (SP) 11 cases (25%), Mycoplasma pneumoniae (MP) 8 cases (18%), and Chlamydia 8 cases. The microbacteriological criteria for diagnosis were as follows: significant seroconversion for viruses, MP, Chlamydia, Legionella, bacteriological isolation on blood cultures, and pleural liquid for SP. In 64 cases the bacteriological diagnosis was not established. In this series we note as follows: 1) There did not appear to be any seasonal peak in relation to bacteria isolated, contrary to previous reports, in particular for Legionella. On the other hand viruses occur notably in February and March. 2) Chlamydia were more frequent in individuals living in rural areas; 7 cases out of 8. Whereas amongst the 108 patients 55 were from the country and 34 from the city (16 from institutions and 3 uncertain). In conclusion, if the level of bacteriological identification (IMB) appears weaker than in previous reference series: 51-65%, the diagnostic yield clearly improved in our experience achieving results nearer to the best achievable: 54% of IMB from 48 cases which were recruited between 1985-1989.(ABSTRACT TRUNCATED AT 250 WORDS)
Adolescent↗
Lobbying for research and academic medicine.
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Budgets↗
Prevalence of superficial fibrillary lines of the cornea in contact lens wearers and nonwearers.
Superficial corneal epithelial striations described as fibrillary lines have been documented as a common finding in normal and keratoconic eyes. We first noticed these fine white structures in both soft and rigid contact lens wearers. This prompted us to investigate whether the prevalence of these lines was greater in contact lens wearers than in non-lens wearers. Our results indicated that although the lines were more frequently observed in lens wearers (35.7% of 42 patients) than in the controls (19.0% of 42 patients), the difference was not statistically significant (p = 0.0867, chi 2 analysis). We speculate that lens wear makes fibrillary lines more visible but is not responsible for their presence.
Adult↗
Theophylline effects on phasic tension and slow inward current of isolated frog atrial fibres: influence on the action of isoprenaline.
The action of theophylline on phasic tension and slow inward current (Isi) was investigated on isolated voltaged-clamped frog atrial fibres. The action of theophylline was both dose- and time-dependent; the most effective dose was 2.10(-3)M. Theophylline induced a rapid positive inotropic effect which cannot be attributed to a beta-adrenoceptor stimulation or to an adenosine antagonism; this effect was closely related to an increase in slow inward current (Isi), probably due to an inhibition of phosphodiesterase activity and a subsequent increase in cAMP content. The decline of the positive inotropic effect of theophylline was discussed in terms of additional effects of the drug. Theophylline, consistently with its phosphodiesterase inhibitory action, was shown to potentiate the effects of isoprenaline on phasic tension and Isi; however no potentiation was observed after reserpine-induced depletion of endogenous catecholamines. It might be thought that non-specific effects of reserpine on some steps of cardiac excitation-contraction coupling counteract the effects of theophylline.
Adenosine Deaminase↗
Cyclic AMP-sensitive chloride efflux in rabbit pancreatic acini.
We studied chloride efflux from isolated rabbit pancreatic acini in suspension, by loading with 36Cl to steady state and rapidly washing acini by filtration to determine 36Cl cpm/micrograms DNA remaining. Linear loss of acinar chloride occurred over 5 min (k = 0.038 +/- 0.008 min-1, n = 5). Forskolin (5 x 10(-5) M) increased the rate of chloride efflux (k = 0.100 +/- 0.016 min-1, n = 5, p less than 0.001) 2.6-fold. At 5 min, forskolin increased acinar cAMP levels (1065 +/- 254 versus 7 +/- 2 pmol/mL, n = 5, p less than 0.005) and percentage of chloride efflux (37.4 +/- 2.3 versus 26.0 +/- 2.2%, n = 13, p less than 0.005). The chloride channel inhibitor anthracene-9-carboxylic acid (10(-3) M) had no effect on chloride loss from acini exposed to vehicle (30.9 +/- 1.9 versus 29.9 +/- 2.3%, n = 4), but completely inhibited forskolin-stimulated efflux at 5 min (40.0 +/- 2.4 versus 29.3 +/- 2.4%, n = 5, p less than 0.005). Manipulation of extracellular calcium concentration demonstrated that chloride efflux was not coupled to zymogen granule amylase release. Secretin (10(-7) M) increased acinar cAMP levels (68 +/- 22 versus 7 +/- 2 pmol/mL, n = 5, p less than 0.05) and significantly increased the loss of chloride from acini (34.9 +/- 1.4 versus 26.1 +/- 1.7%, n = 7, p less than 0.005) without affecting amylase release. Secretagogue-stimulated amylase release by cholecystokinin octapeptide (10(-8) M) and carbamylcholine (10(-5) M), did not increase chloride efflux at 5 min.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗