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Helicobacter pylori* ; Helicobacter*

The present study investigated an effective method of eliciting medium and long latency cutaneous reflexes in normal human subjects. The effect of changes in stimulus conditions (number of pulse train, duration of electrical pulse and inter-stimulus interval) on cutaneous reflexes in the first dorsal interosseous muscle (FDI) following non-noxious electrical stimulation to the hand digits (digit 1 ; D1, digit 2 ; D2 and digit 5 ; D5) were investigated in seven healthy volunteers. Cutaneous reflexes were elicited while the subjects performed isolated isometric contraction of FDI (D2 abduction). Under all experimental conditions, the level of muscle contraction was set at 10% of the maximal EMG amplitude, which was determined during maximal voluntary contraction. Intensity of the electrical stimulation was set at 2.0 times the perceptual threshold under all experimental conditions.Although the amplitude of E2 (excitatory response, peak latency ∼60∼90 ms) was independent of the number of pulses (1, 2, 3, and 5 pulses, pulse frequency at 333 Hz), that of I1 (inhibitory response, ∼45∼60 ms), I2 (inhibitory response, ∼90∼120 ms) and E3 (excitatory response, ∼120∼180 ms) was significantly increased depending on the number of pulses (p<0.001). Amplitudes of E2 and I2 were significantly affected by the digit stimulated (p<0.01). For all four components of the cutaneous reflexes, there were no significant differences in magnitude even by alternating both the inter-stimulus interval (fixed at 1, 2 and 3 Hz and random between at 0.7 and 2 Hz) and the duration (0.1, 0.5 and 1 ms) of the electrical stimulation.These findings suggest that the susceptibility of responsible interneurons impinging on each reflex pathway to temporal summation of the test impulse differs depending on the digit stimulated. It is also likely that almost the same population of the cutaneous afferent fibers were activated by test stimulation with different durations as far as the same stimulus intensity was utilized. As a practical application, double or more pulses up to 3 Hz without causing pain is recommended to effectively evoke medium and long latency cutaneous reflexes in FDI, which would reduce possible effects arising from fatigue.

It has recently demonstrated that central fatigue during sustained maximal voluntary contraction (MVC) progresses faster in the presence of delayed onset muscle soreness due to eccentric contractions than in normal states (Endoh et al., 2005). However, it remains to be clarified whether these findings are related to muscle damage or muscle pain induced by eccentric contractions. The present study investigated which factor plays a more critical role in the earlier onset of central fatigue during sustained MVC with muscle pain induced by injecting hypertonic saline. Ten healthy male right-handed subjects (age, 21~32 yrs.) were asked to perform brief MVCs (~3 sec) before and after injection of isotonic saline (0.9%, 1.0 ml, ISO) or hypertonic saline (5.25%, 1.0 ml, HYP) into the left biceps brachii. The subjects then performed 1 min MVC (fatigue test) with isometric elbow flexion was done in ISO or HYP condition or intact control condition (CON). During these contractions, transcranial magnetic stimulation was delivered to the contralateral motor cortex to evaluate voluntary activation (VA), the motor evoked potential (MEP) and electromyographic (EMG) silent period (SP). Ratio of root mean square of the EMG and elbow flexion force (EMGrms/F) was also measured.The peak pain induced by the injection of HYP was significantly higher than that of ISO (p<0.01). There was no significant difference in either the maximum size of the M response or the twitch force between ISO and HYP (p>0.05). However, during the brief MVCs, both maximal force (p<0.01) and VA (p<0.05) for HYP were significantly decreased compared to those for ISO. During the fatigue test, although MVC, VA, MEP and SP were significantly altered (p<0.05~0.01), there was no significant difference among CON, ISO and HYP (p>0.05). There was no significant difference in EMGrms during the fatigue test (p>0.05).These results suggest that peripheral force-producing capacity remained intact after the injection of ISO and HYP during sustained MVC, and that progression of central fatigue during sustained MVC was less affected by the increased group III and IV afferent activity induced by HYP.

The present study investigated how resistance training affects behaviors related to central and peripheral fatigue during a sustained maximal voluntary contraction (MVC) . The subjects were well-trained (TR, n=8) and sedentary untrained (UT, n=6) males. The subjects were asked to repetitively perform 3 sets of MVC (elbow flexion) for 1 min with a rest interval of 1 min. Transcranial magnetic stimulation (TMS) was delivered to the contralateral motor cortex to evoke the motor evoked potential (MEP) and electromyographic (EMG) silent period (SP) after the MEP. Ratio of root mean square (RMS) of the EMG and elbow flexion force (RMS/F) was also calculated.
The time course of the decrease in elbow flexion force that was standardized with respect to the maximal value obtained at the beginning of the first MVC was almost identical in both TR and UT. At the end of the task, the elbow flexion force decreased to around 30 % of the initial value in both groups. Decrease in voluntary activation (VA) estimated by the increment of the force after TMS was significantly larger in UT (77.3%) than in TR (88.2%) at the end of the task. Although the increase in MEP during the first set was significantly greater in UT than in TR, elongation of SP was significantly larger in UT than in TR. Increase in RMS/F, which is a manifestation of peripheral fatigue, was significantly larger in TR than in UT.
These results suggest that decrease in MVC in UT and in TR is respectively more attributable to central and peripheral fatigue, and that inhibitory inputs to motor cortex were larger in UT than in TR. It is concluded that expression of central and peripheral fatigue is affected by resistance training.

An in vitro infection system of Trypanosoma cruzi and HeLa cells was used to measure the anti-T. cruzi activities of various calcium antagonists classified into dihydropyridines, diphenylalkylamines, and benzothiazepines and of allopurinol and benznidazole as medium and highly effective reference compounds, respectively. Six dihydropyridines (10 μM each), i. e. nifedipine, nicardipine, nimodipine, nisoldipine, nitrendipine, and amlodipine, decreased the rates of infection of HeLa cells from 11.7% (control) to 5.8, 0.9, 1.2, 3.6, 5.9, and 1.7%, respectively. Nicardipine and amlodipine were highly toxic to HeLa cells, causing detachment of cells from coverslips. Nimodipine was thus the most effective inhibitor tested against T. cruzi infection in HeLa cells. Verapamil and gallopamil (diphenylalkylamines), diltiazem and midazolam (benzothiazepines), and allopurinol (positive control) were less effective than nimodipine. IC₅₀ values, the concentrations of compounds that elicited a 50% reduction in the infection rates of HeLa cells, were 2.5, 2.6, 1.3, 2.1, and 1.7 μM for nicardipine, nimodipine, amlodipine, verapamil, and benznidazole, respectively, while the values for nifedipine, diltiazem, and allopurinol were much higher. Nicardipine, amlodipine, and verapamil again showed significant cytotoxicities to HeLa cells. When Swiss 3T3 fibroblasts replaced HeLa cells, nimodipine markedly lowered the host-cell-infection rate, with an IC₅₀ value of 8.3 nM. Thus, nimodipine is expected to be a highly effective anti-T. cruzi lead compound, with low cytotoxicity to mammalian cells. Structural formulas of nimodipine and nicardipine in relation to their low and high cytotoxicities, respectively, against HeLa cells are discussed.