Effect of facilitation on side-to-side H reflex amplitude ratio.

Although voluntary facilitation is sometimes necessary to evoke the H reflex, relevant data is lacking on side-to-side amplitude ratios in facilitated condition. To determine the normal limits of H reflex amplitude ratio in facilitation and to assess it's clinical applicability, we performed FCR H reflex study in fifty asymptomatic subjects. The lower limit of the amplitude ratio that encompasses 97.5% of subjects in facilitation was 0.48. These data suggest H reflex amplitude ratio measured in facilitation without averaging is useful for the diagnosis of unilateral radiculopathy.

Quantification of the path of center of pressure (COP) using an F-scan in-shoe transducer.

By tracking the path of the center of pressure (COP) during the stance phase, the balance and pattern of progression can be determined. The path of COP is frequently used in clinical practice, although it is not quantified. In this study, an F-scan pressure sensitive insole system was used to quantify the path of COP. The COP of initial contact and the average during the stance phase corresponded to the center of the heel and to the center of the total plantar surface, respectively. The COP displacement corresponded to 83% of foot contact length and 18% of forefoot contact width. When the longitudinal axis of the insole was plotted as the Y-axis and the transverse axis of the insole as X-axis, the slopes of the COP coordinates during stance phase was 6 degrees inward. Velocities of the COP during each functional rocker action were even and 22-27 cm/s. The changes of quantified COP parameters according to the biomechanical alteration of the foot were confirmed by high-heeled gait.

Selective potentiation of GABA-mediated Cl- current by lanthanum ion in subtypes of cloned GABAA receptors.

The effect of lanthanum ion (La3+) on gamma-aminobutyric acid (GABA)-mediated Cl- currents was examined in the alpha 1 beta 2 or alpha 1 beta 2 gamma 2 subtype of GABAA receptors expressed in a human kidney cell line (A293), using a whole-cell configuration of patch-clamp techniques. La3+ dose-dependently stimulated the Cl- currents in the alpha 1 beta 2 gamma 2 subtype with an EC50 of 21.3 +/- 3.5 microM with a maximal potentiation of 240 +/- 16% as normalized to the GABA response at 5 microM. In the alpha 1 beta 2 subtype, however, the ion marginally potentiated GABA response, a maximal stimulation being less than 70% with an EC50 for La3+ near 200 microM. The stimulation of GABA response by La3+ in the alpha 1 beta 2 gamma 2 subtype was due to a decrease in the half maximal concentration for GABA and was more pronounced at the negative membrane potentials. This selectivity of La3+ toward the subtypes of GABAA receptors contrasts to that of Zn2+ which inhibits the currents in the alpha 1 beta 2, but not in the alpha 1 beta 2 gamma 2 subtype (Neuron, 5: (1990) 781-788). It appears that these polyvalent cations are useful in understanding the molecular basis for the functional diversity and in characterizing the molecular organization of native GABAA receptors.