No abstract

No abstract

The capability for discrimination of vibratory stimuli of the sole of the foot was tested on 12 subjects (6 men, 6 women). Two vibratory stimuli (sinusoidal impulse: frequency, 200 Hz; amplitude, 0.1 mm; duration, 2 sec) were applied at different sites to the sole of the foot. Subjects were asked whether they detected one or two vibratory sensations. The discrimination threshold was defined as the shortest distance at which two vibrations can be differentiated at repeated trials. In addition, the absolute threshold was measured by one plunger (sinusoidal vibration: frequency, 200 Hz; variable amplitude). The values of the absolute threshold (average value, 1.2 microns) were in accordance with the results of other authors. A decrease of discrimination capability was observed along the longitudinal axis of the foot from distal to proximal parts and was about 15 mm at the big toe and 34 mm at the heel. Discrimination at the medial longitudinal arch was inferior to that at the lateral longitudinal arch. This was also true for inverse vibration in which all subjects showed lower thresholds. No relationship was found with respect to thickness of the skin (measured by ultrasound), side of foot, or gender. Determining factors for vibratory threshold might be the density of the Pacinian corpuscles per cm2 as well as their peripheral and central representation. Anatomical or physical factors (e.g., thickness of the skin, impedance of the deeper tissue) can probably be disregarded.

No abstract

Force velocity relationships of isolated vascular smooth muscle preparations were examined in the tetanized rat portal--anterior mesenteric vein by means of afterloaded isotonic contractions. Lowering of the temperature from 37 degrees C to 25 degrees C caused an average decrease of the follwoing parameters: maximal velocity of shortening at zero load from 0.51 to 0.28 muscle length/sec; maximal rate of tension increase (dT/dt) from 847 to 362 dyn/sec; mechanical tension developed at the maximum of dT/dt from 43 to 34% of the peak force generation; constant b of Hill's equation from 0.18 to 0.09 muscle length/sec. The latency was prolonged from 0.33 to 0.56 sec, and the time-to-maximum of dT/dt from 0.9 to 1.6 sec. Between 27 degrees C and 37 degrees C the following Q10 values were calculated: for the maximal velocity of shortening at zero load 1.56; for the maximal rate of tension increase 1.88; for the latency 1.63. No distinct influence of temperature could be observed on the extent of isotonic shortening at zero load (3.69 muscle length at 37 degrees C), on the extent of peak force generation (1107 dyn at 37 degrees C), and on constant a of Hill's equation (0.35 at 37 degrees C). It is concluded that parameters of contraction velocity in vascular smooth muscle depend on temperature, whereas the extent of contraction is independent of temperature. These findings are discussed in connection with the theory of the sliding-filament mechanism.