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Biomedical subjects

H Drouin

Publications and source records attributed to H Drouin.

11 recordsLinked to original sources
PubMed2003

Continuous passive motion following total knee arthroplasty.

BACKGROUND: Knee arthroplasty (KA) is a common intervention that can enhance the quality of life for patients with osteoarthritis (OA) and rheumatoid arthritis (RA). Post-surgery rehabilitation protocols often include continuous passive motion (CPM). However, CPM protocols vary considerably amongst institutions. OBJECTIVES: The purpose of the current meta-analysis is to evaluate the effectiveness of continuous passive motion following total knee arthroplasty. SEARCH STRATEGY: An electronic search of MEDLINE (1966 to 2002), EMBASE (1988 to 2002), CINAHL (1982 to 2002), HEALTH STAR (1991 to 1994) and CURRENT CONTENTS (1997 to 2002) was conducted to identify randomized controlled trials. SELECTION CRITERIA: Following an a priori protocol, only randomized controlled trials of CPM for the treatment of participants post KA were eligible. Subjects were 18 years of age or older and had a pre-surgery diagnosis of degenerative joint disease. Both the experimental and control groups received physiotherapy. In addition to the physiotherapy intervention, the experimental group received CPM. DATA COLLECTION AND ANALYSIS: Two reviewers independently selected trials for inclusion. Data were then extracted and the quality of the trial assessed using predetermined forms. Outcome measures of interest were: active and passive knee range of motion (ROM) length of hospital stay, pain, swelling and quadriceps strength. A fixed effects model was used throughout for continuous variables, except where heterogeneity existed; in which case, a random effects model was used. Results were analyzed as weighted mean differences (WMD) with 95% confidence intervals (CI). Standardized mean differences (SMD) were used when different scales were used to measure the same concept (e.g. pain). Dichotomous outcomes were presented as a relative risk. MAIN RESULTS: Fourteen trials were retained for analysis. Results favouring CPM were found for the main comparison of CPM combined with physiotherapy (PT) versus PT alone at end of treatment. For the primary outcomes of interest, CPM combined with PT was found to statistically significantly increase active knee flexion (WMD 4.30 degrees, 95% CI: 1.96, 6.63) and decrease length of stay (WMD -0.69 days, 95% CI: -1.35, -0.03). CPM was also found to decrease the need for post-operative manipulation (RR 0.12, 95% CI: 0.03, 0.53). CPM did not significantly improve passive knee flexion and passive or active knee extension. REVIEWER'S CONCLUSIONS: CPM combined with PT, may offer beneficial results compared to PT alone in the short term rehabilitation following total knee arthroplasty.

Arthroplasty, Replacement, Knee↗
PubMed1994

Intracellular action of spermine on neuronal Ca2+ and K+ currents.

Intra- and extracellular effects of the polyamine spermine on electrical activity and membrane currents of identified neurons in the abdominal ganglion of Aplysia californica were studied under current- and voltage-clamp conditions. Ionophoretic injection of spermine reduced the amplitude of action potentials and altered their time course as well as spontaneous discharge activity. Investigation of membrane currents showed that intracellular spermine suppressed the total outward current but increased the inward rectifier current. After separation of ion currents it was found that the voltage-activated, delayed K+ outward current and the Ca2+ inward current were reduced by intracellular spermine in a dose- and voltage-dependent manner. The block of the K+ current can be described by a voltage-dependent reaction, where one spermine molecule binds to one channel. The binding constant Kb, at zero voltage, and the effective valency, z delta, had values of 176/M and 0.41 for cell R-15, 223/M and 0.64 for cell L-11, and 137/M and 0.42 for cell L-3. Apparently, more than one spermine cation is needed to block one Ca2+ channel, since the coefficient n, which absorbs the molecularity and cooperativity of the reaction, had non-integral values between 1.34 and 2.22. The binding constant Kb and the effective valency z delta had values of 265/M and 0.64 for cell R-15, 82/M and 0.56 for cell L-4, and 263/M and 0.51 for cell L-6. Intracellular spermine also blocked the Ca(2+)-activated K+ current induced by ionophoretic Ca(2+)-injections, but increased the current at prolonged times after spermine injection.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1991

Reevaluation of hydropathy profiles of voltage-gated ionic channels.

A reevaluation of the secondary structure of Na, Ca and K channel proteins led to the following results. Only three segments (S1, S5 and S6) of each repeat are sufficiently hydrophobic to be predicted as transmembrane helices, if a window of 19 amino acids is used. Some of the S2 and S3 segments show higher hydrophobic values when calculated with the window of 9 amino acids and can be predicted as short helices. S4 segments are strongly hydrophilic and cannot be predicted as transmembrane helices. Some of the S2, S3 and S4 segments have an amphipathic character; however, these helices do not span a membrane. A model is proposed where 12 hydrophobic transmembrane helices surround 12 shorter helices, forming a hydrophilic pore. In addition, a unique pattern for S4 segments of voltage-gated channel proteins is defined.

Amino Acid Sequence↗
PubMed1984

On microelectrode ionophoresis.

An equation for ionophoresis in large tip microelectrodes is derived from Nernst-Planck equations for the general case of a completely dissociated electrolyte. The relation between the release of ions and the applied electric current is mainly determined by two parameters: the transference number of the ions under consideration and the diffusional leak of the microelectrode. Also it is shown how the release of ions is affected by the concentration of the electrolyte within the electrode and that of the external solution. The equation describes the ionophoretic release of polyvalent spermine. In addition, new equations for tip potential and for tip resistance are derived.

Iontophoresis↗
PubMed1980

Carticaine: action of the local anesthetic on myelinated nerve fibres.

Unlike other clinically used local anesthetics, carticaine contains a thiophene ring. Current voltage relations of peak sodium current INa and steady state potassium current IK were measured in voltage clamp experiments on the node of Ranvier of Rana esculenta. The dependence of the maximum sodium conductance on external concnetration of carticaine is described by an apparent dissociation constant KNa = 0.065 mM at pH = 7.3. An apparent dissociation constant KK = 0.147 mM at pH = 7.3 was calculated on the basis of the action of carticaine on the maximum potassium conductance. Similar to other amine local anesthetics, carticaine blocks sodium channels at a lower concentration than potassium channels, but lower concentrations of the thiophene derivative than of the benzene derivatives are needed to block the ionic channels. The partition coefficients in-octanol/Soerensen buffer at pH = 7.35 follow the sequence lidocaine (46) more than carticaine (17) more than procaine (2). Therefore, the action of these local anesthetics on sodium channels and potassium channels seems not to follow mere lipid solubility properties of the neutral drug. Increasing the pH from 6.3 to 8.3 favoured the neutral drug form and enhanced the block of both ionic channels but the relative reduction of the ionic currents was larger for potassium currents.

Animals↗
PubMed1978

Effects of the antituberculous agent ethambutol on myelinated nerve.

The action of the antituberculous agent ethambutol on the myelinated nerve was studied in two ways: (1) Resting and compound action potentials of the desheathed sciatic nerve were measured; (2) Na+ and K+ currents through the node of Ranvier were investigated by means of the voltage clamp. Reversible dose-dependent decreases of the compound action potential and of the conduction velocity were observed when ethambutol was applied in concentrations of 1--7 mM for 15 min; prolongation up to 60 min caused irreversible changes in membrane function and a decrease in Ca content. Ethambutol induced a hyperpolarizing change of the resting potential. When the nerve was depolarized in Ca2+-free solutions, ethambutol repolarized the nerve membrane. Ethambutol instantly reduced sodium and potassium currents through the nodal membrane. Presumably ethambutol acts primarily as a Ca2+ chelating cation on negative charges at the nerve membrane.

Action Potentials↗
PubMed1977

Monomeric methylmethacrylate (MMA) acts on the desheathed myelinated nerve and on the node of Ranvier.

The influence of monomeric methylmethacrylate (MMA) on resting and compound action potential of the isolated desheathed sciatic nerve of the frog (sucrose gap method) was determined. Above 10 mM there was a dose-dependent decrease of the compound action potential and a hyperpolarization of the membrane which was augmented with increasing MMA concentrations (4.1 mV +/- 0.2 S.E.M. after 50 mM MMA). The depolarization in low [Ca2+]0 solutions or with veratrine was reversed by MMA. The homologous ethyl, allyl and n-butyl esters were more effective than MMA, and the isobutyl ester less effective, whereas Na-methacrylate and methacrylamide showed no influence. Voltage clamp experiments on the node of Ranvier indicated that 50 mM MMA led to a decrease of the Na+ and K+ currents.

Action Potentials↗
PubMed1976

Kinetics of the slow variation of peak sodium current in the membrane of myelinated nerve following changes of holding potential or extracellular pH.

(1) Changes of the holding potential applied to the membrane of myelinated nerve fibres induced slow variations of the peak sodium current, which are super-imposed on the effect of sodium inactivation. (2) These slow variations are transitions between various steady levels of available sodium conductance. Their time course can be described by the function erfc (square root t/tau) where tau is the time and erfc the error function complement. The characteristic time tau lies in the range 2-4 min and depends on the membrane potential. (3) Changes of extracellular pH cause a rapid change of the peak sodium current followed by a slow variation as observed after changes of the holding potential. This slow variation can be prevented by applying simultaneously an appropriate change of the holding potential, e.g. the effect of changing pH from 7.3 to 5.3 is balanced by changing the potential from --70 to --55 mV. (4) The results are interpreted by postulating charged components diffusion slowly within the nodal membrane. Their transverse distribution controls the number of sodium channels available at a given membrane potential. The equivalence between change of pH and voltage is explained by assuming negative fixed charges at the outer surface of the membrane, which are protonated at low pH and thus affect the intrinsic membrane potential. (5) It is concluded that effects which are ascribed to the action of agents on individual sodium channels have to be corrected for variations in the number of available channels if these agents influence the intrinsic membrane potential, e.g. changes of extracellular pH.

Animals↗