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Biomedical subjects

Y Allard

Publications and source records attributed to Y Allard.

7 recordsLinked to original sources
PubMed1992

Effects of K+ channel blockers on the action potential of hypoxic rabbit myocardium.

1. In order to assess the role of different ionic currents in hypoxia-induced action potential shortening, we investigated the effects of blockers of voltage-dependent and ATP-sensitive K(+)-channel on the membrane potential of hypoxic rabbit hearts and papillary muscles. The response to blocking of the inward rectifier was studied at three external K+ concentration: 2.5, 5, and 7.5 mM. 2. Hypoxia produced a progressive decline in action potential duration (APD) that levelled off after 15 to 20 min. Steady state APD values at 25% and 95% repolarization (APD25 and APD95) were 26.0 +/- 1.9% and 42.2 +/- 2.4% of controls respectively. 3. Tetraethylammonium (TEA, 10 mM) delayed but did not reduce APD shortening at the steady state. 4. Blocking of IK1 with a mixture of 0.2 mM Ba2+ and 4 mM Cs+ lengthened APD in normoxia and prevented APD95 shortening in hypoxia. The APD25 shortening was significantly attenuated at all [K]o. 5. Glibenclamide (Glib, 30 microM) did not prevent APD shortening, but produced a progressive action potential (AP) lengthening after 15 min of hypoxia. Steady levels of 48 +/- 3.5% and 62 +/- 5.0% of controls for APD25 and APD95 respectively were reached after 45 min. 6. The relation between APD25 and pacing rate was determined in normoxic and hypoxic papillary muscles and the effects of 2 mM 4-aminopyridine (4-AP) were examined. Hypoxia attenuated the APD25 shortening currently observed when the stimulation rate was lowered from 1 to 0.1 Hz without altering the plateau reduction occurring at frequencies above 2 Hz. These effects were potentiated by 4-AP.7. Our data suggest that the accelerated AP repolarization in hypoxic rabbit myocardium represents a delicate balance of several outward currents: IKI, IK-ATP. and at least one yet unidentified current component rather insensitive to changes in [K]o and to K+ channel blockers.

Action Potentials↗
PubMed1991

A controlled trial of corticosteroid injections into facet joints for chronic low back pain.

BACKGROUND: Chronic low back pain is a common problem with many treatments, few of which have been rigorously evaluated. This randomized, placebo-controlled trial was designed to evaluate the efficacy of injections of corticosteroid into facet joints to treat chronic low back pain. METHODS: Patients with chronic low back pain who reported immediate relief of their pain after injections of local anesthetic into the facet joints between the fourth and fifth lumbar vertebrae and the fifth lumbar and first sacral vertebrae were randomly assigned to receive under fluoroscopic guidance injections of either methylprednisolone acetate (20 mg; n = 49) or isotonic saline (n = 48) in the same facet joints. Ninety-five patients were followed for six months and their condition assessed with scales of pain severity, back mobility, and limitation of function. RESULTS: After one month, none of the outcome measures evaluating pain, functional status, and back flexion differed clinically or statistically between the two study groups. Forty-two percent of the patients who received methylprednisolone and 33 percent of those who received placebo reported marked or very marked improvement (95 percent confidence interval for the difference, -11 to 28 percentage points; P = 0.53). The results were similar after three months. At the six-month evaluation, the patients treated with methylprednisolone reported more improvement, less pain on the visual-analogue scale, and less physical disability. The differences were reduced, however, when concurrent interventions were taken into account. Moreover, only 11 patients (22 percent) in the methylprednisolone group and 5 (10 percent) in the placebo group had sustained improvement from the first month to the sixth month (95 percent confidence interval for the difference, -2 to 26; P = 0.19). CONCLUSIONS: We conclude that injecting methylprednisolone acetate into the facet joints is of little value in the treatment of patients with chronic low back pain.

Adrenal Cortex Hormones↗
PubMed1986

Is the change in intracellular pH during fatigue large enough to be the main cause of fatigue?

The intracellular pH of frog sartorius muscles exposed to an extracellular pH 8.0 (25 mM HCO3-, 1% CO2) was 6.9-7.1. Following a fatiguing stimulation period (one tetanic contraction per second for 3 min), the intracellular pH was 6.5-6.7. When similar experiments were repeated with frog sartorius muscles exposed to pH 6.4 (2mM HCO3-, 1% CO2), the intracellular pH was 6.8-6.9 at rest and 6.3-6.4 following fatigue. So, in both experiments the intracellular pH decreased by 0.4-0.5 pH unit during fatigue. When the CO2 concentration of the bathing solution was increased from 1 to 30%, the intracellular pH of resting muscles decreased from 7.0 to 6.2-6.3. Although the effect of CO2 on the intracellular pH was greater than the fatigue effect, the decrease in tetanic force with CO2 was less than 40%, while during fatigue the tetanic force decreased by at least 70%. Therefore in frog sartorius muscle the decrease in tetanic force during fatigue exceeds the decrease that is expected from just a change in intracellular pH.

Animals↗
PubMedDate not supplied

[Gingival preparation].

For the general practitioner, the superficial periodontal structure is an obstacle when trying to gain access, control and visualization to juxta or infra gingival preparations. A temporary restoration will maintain and protect those limits and in many cases it is a very efficient procedure. Sometimes it is necessary to enhance the gingival preparation by sophisticated methods. There are many different technics available to the practitioner. In this article we will describe the technics with easy clinical use and those respecting the gingival tissue (mechanical, physico-chemical).

Dental Impression Technique↗
PubMedDate not supplied

[Hydro-alginates].

Hydro-alginates are a combination of reversible and irreversible hydrocolloids. These products are a material choice in fixed prosthodontics and removable partial denture due to their reliability and ease of use, depending on adequate utilization of the materials and on a perfect synchronization during the impression procedures.

Alginates↗