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Biomedical subjects

D Bertrand

Publications and source records attributed to D Bertrand.

At least 217 records · Page 12Linked to original sources
PubMedDate not supplied

Development of electrical membrane properties in cultured avian neural crest.

In previous studies of the development of membrane excitability in vertebrate neurones, a calcium current has commonly been observed first, later replaced by a sodium current. We have now examined the development of membrane currents in explant cultures of mesencephalic neural crest cells from the quail embryo. Some of these cells constitute the precursors for the ciliary and trigeminal ganglia and in certain conditions can be characterized morphologically as neurones after only a few hours in culture. We report here that two membrane currents are present in neurones after 1 day in culture, a voltage-and time-dependent potassium current and a leakage current. On the second day in culture, voltage-dependent sodium and calcium currents can be detected. With time the sodium and calcium currents increase in magnitude and all four currents are present for at least 7 days in culture. This onset of electrical excitability differs from that described in other vertebrate neurones both in vitro and in vivo, but resembles the sequence observed in neurones of the developing grasshopper.

Action Potentials↗
PubMedDate not supplied

Electrophysiology: a method to investigate the functional properties of ligand-gated channels.

Ligand-gated channels (LGCs) play a fundamental role in the fast transmission of electrical activity from neuron to neuron and/or to effector cells. Studies of LGCs in isolation have become possible since the identification of genes coding for these membrane proteins together with the establishment of reconstitution techniques in host systems. Methods for electrophysiological investigations of LGCs reconstituted either in the Xenopus oocytes or stably tranfected in cell lines are discussed. Functional studies of reconstituted receptors enable fast determination of LGCs' pharmacological profiles and comparison of their physiological properties. Combination of molecular engineering with physiological measurements allows studies with unpreceeding resolution and it is now possible to examine at the amino-acid level the contribution of some residues in the formation of the ligand-binding site or the ionic channel domains.

Acetylcholine↗
PubMedDate not supplied

Synthesis and electrophysiological studies of a novel epibatidine analogue.

The new epibatidine analogue exo-2-(2-pyridyl)-7-azabicyclo[2.2.1]heptane (2PABH) was synthesised. Separation of enantiomers was performed on chiral HPLC chromatography in polar-organic phase mode at 0 degree C. Enantiomeric purity was greater than 99.8%ee for the (-)- and 90.5%ee for the (+)-enantiomer respectively. Optical rotation was determined to be [alpha]23D = +/- 13 degrees. Electrophysiological studies of 2PABH were carried out on alpha 4 beta 2, alpha 3 beta 4 and alpha 7 nAChR subtypes cloned from rat and reconstituted in Xenopus oocytes. Both enantiomers could not significantly activate the heteromeric subtypes. The homomeric alpha 7 nAChR displays a high sensitivity only towards (-)-2PABH. The EC50 for (-)-2PABH and ACh were determined (32.5 +/- 9.5 microM, 137.3 +/- 16.5 microM). (-)-2PABH was shown to be a partial agonist (80% of ACh). Thus the efficacy of 2PABH differs markedly from that of epibatidine. The intramolecular N-N-distance and the spatial pyridine nitrogen orientation play a central role in nAChR recognition.

Animals↗
PubMedDate not supplied

Outpatient satisfaction: validation of a French-language questionnaire: data quality and identification of associated factors.

OBJECTIVES: Following 1996 legislation requiring French hospitals to assess patient satisfaction, this study developed and validated a brief French-language multidimensional questionnaire designed to measure outpatient satisfaction with hospital visits and compared data quality for two patient-satisfaction survey methods. DESIGN: Authors developed a 19-item questionnaire following a strict procedure (identification of dimensions to explore, formulation, and selection of items). SETTING: Validation data were obtained from patients of six outpatient clinics in a teaching hospital. PARTICIPANTS: 586 consenting eligible patients were randomized to receive the questionnaire 2 weeks after their visit with one of two survey methods: a mailed self-administered questionnaire or a telephone interview. RESULTS: The response rate (79%) was not significantly different between the two survey methods. The risk of having one or more missing values was higher in the mail survey group (odds ratio, 1.65; 95% confidence interval, 1.03-2.63), but mail respondents were less likely to use the "extremely positive" response category. Principal component analysis identified four factors that accounted for 56% of the variance: interpersonal skills and information transfer, physical surroundings, convenience, and appointment delay. Patients' comments on open-ended questions validated the semantic content of the factorial construct. The internal consistency coefficient was greater than 0.70 for three of four subscales. Patient background characteristics accounted for less than 10% of the factorial score variance. Patient satisfaction was correlated with age, type of visit, and, to a lesser extent, gender and education level. CONCLUSION: This easily administered, multidimensional out-patient-satisfaction questionnaire provided encouraging preliminary psychometric characteristics.

Adolescent↗
PubMedDate not supplied

[Circulatory and respiratory repercussions to direct suspension laryngoscopy in the adult: value of a propofol-alfentanil combination].

The clinical effects of a propofol-alfentanil association were studied in fifteen patients ASA II (mean age 50.1 +/- 14.1) anaesthetized for E.N.T. endoscopy after informed consent. All the patients received an intramuscular premedication with 0.10 to 0.15 mg.kg-1 midazolam. Propofol 2.5 mg.kg-1 was injected in a peripheral venous line with alfentanil 10 micrograms.kg-1, followed by continuous automatic injection of propofol at a dose of 5 to 10 mg.kg.h-1 and alfentanil 5 micrograms.kg-1 given just before suspension. After induction and during maintenance of anaesthesia, the patients were allowed to breathe oxygen spontaneously O2 assisted when apneic. The following variables were studied before induction (to), after induction (t1), during suspension (t2) and when stopping the infusion (t3): haemodynamic parameters using an invasive method and blood gases. Statistical analysis was performed using the Student's test for paired samples. Surgical conditions and anaesthetic quality were good with early recovery of consciousness and return of all reflexes. After an initial period of cardio vascular depression, the haemodynamic parameters did not vary much during the anaesthesia and propofol-alfentanil appeared to limit considerably the hypertension due to laryngoscopy. However, there was a moderate degree of hypercapnia (p less than 0.001) in most patients, giving evidence of some respiratory depression and possibly a greater depth of anaesthesia than desirable. Indeed, the doses of alfentanil required seemed to be more important with propofol because of a probably interference between the two drugs; the doses of these drugs should therefore be modified according to the length of surgery.

Adult↗
PubMedDate not supplied

[Anesthesia in resections and anastomoses of the trachea].

Resections and end-to-end anastomosis have been effective in correcting localized tracheal strictures. Important clinical considerations are the precise preoperative assessment of the lesion, careful planning of anesthetic management and choice of the appropriate decision. Surgical procedures involving sharing of the air way between the anaesthetist and the surgeon impose special problems on the anaesthetist. On the one hand, the surgeon requires unrestricted access to the operating site and on the other, the anaesthetist must ensure adequate anaesthesia, oxygenation and carbon dioxide elimination, preferably without contamination of the lung fields. The more commonly employed technique is the use of a tracheal tube so that anaesthesia can be maintained using conventional IPPV. In our experience, the majority of strictures in adults can be managed as well, or better, by using a conventional endotracheal tube.

Adult↗