Biomedical subjects

C Minatel

Publications and source records attributed to C Minatel.

4 recordsLinked to original sources

PubMed2001

Postvibration depression of the H-reflex as a result of a dual mechanism: an experimental study in humans.

Changes in amplitude of the soleus H (S(H))-reflex and its neurographic correlates (P(1) and P(2) waves) after vibration of the soleus muscle have been evaluated as a function of mechanical stimulation frequency, duration of the conditioning train, and test stimulus intensity. Additional experiments aimed at assessing the nervous system mechanisms underlying the postvibration depression (PVD) have been performed. In particular, homonymous (S(HMR) or S(H)) versus heteronymous (S(HTR)) soleus response, evoked respectively by tibial nerve and femoral nerve electrical stimulation, the effectiveness of sub-H threshold tibial nerve conditioning volleys on the S(HTR), and the respective effects of a brief passive stretching of the quadriceps and soleus muscles on the recovery of both the S(HMR) and S(HTR) after vibration of the homologous muscle were investigated under suitable experimental conditions. It was found that PVD occurs in the absence of changes in amplitude of the P(1) wave and the S(HTR), is paralleled by a reduced effectiveness of tibial nerve-conditioning volleys on the S(HTR) and is shortened consistently by brief passive stretching of the homologous muscle. It follows that PVD may be the result of a long-lasting reduction of the transmitter release from Ia presynaptic terminals depending, at least in part, on a protracted postvibration Ia afferent discharge caused by spindles thixotropy. These findings may provide a better understanding of the pathophysiologic mechanisms underlying spasticity in humans.

Adult↗

PubMed1998

Presynaptic and postsynaptic mechanisms underlying H-reflex changes produced by a selective voluntary contraction.

Concurrent recordings of (i) the soleus H reflex and (ii) the underlying afferent (P1) and efferent (P2) neural volleys were performed during a protracted, moderate, isometric, voluntary contraction of the soleus (S) muscle, and the subsequent release period. Besides the expected enhancement of the H reflex, muscular contraction caused a significant reduction in the corresponding central delay (as extrapolated from variations of P1-P2 interval), while the opposite trend occurred during the release phase. Control experiments, based on (a) neural blockade below the stimulation site, (b) muscle stretching at the end of the muscular contraction, (c) changes in amplitude of homonymous and heteronymous S responses, and (d) variations in effectiveness of homonymous and heteronymous conditioning volleys on the S motoneuronal pool, showed that both voluntary contraction and the subsequent release period are associated with a reduced effectiveness of la afferents, while postsynaptic motoneuronal responsiveness is significantly modified only during the actual contraction time.

Adult↗

PubMed1997

Testing for pre-synaptic and post-synaptic changes in the soleus H reflex pathway following selective muscle vibration in humans.

Muscle vibration does not affect post-synaptic excitability of the corresponding motoneuronal pool, the concurrent depression of the monosynaptic reflex resulting from a pre-motoneuronal block of Ia spindle afferents. Indeed (1) both homonymous and heteronymous soleus responses (to electrical stimulation of the posterior tibial nerve (TN) and femoral nerve (FN), respectively) are clearly depressed during selective vibration of the homologous muscle (namely soleus (S) or quadriceps (Q)), but remain completely unchanged during vibration of the heterologous muscle (i.e. Q or S); (2) the effectiveness of facilitatory conditioning of FN and TN Ia afferents, respectively on the S motoneuronal pool is definitely reduced during vibration of the homologous muscle (namely Q and S).

Adult↗

PubMed1995

Lowering body temperature with a cooling suit as symptomatic treatment for thermosensitive multiple sclerosis patients.

A cooling system (Mark VII Microclimate System) was used to give six thermosensitive multiple sclerosis patients two 45-minute daily coolings for a period of one month. Before the first cooling, a baseline clinical and electrophysiological examination was performed. The same tests were repeated after the first application and after the thirtieth cooling day, thus providing information relating to acute and chronic efficacy. A clinical improvement was observed after both acute and, more unexpectedly, chronic cooling, whereas a significant improvement in central somatosensory conduction was recorded only under acute conditions. Our data suggest that cooling with this device leads to an improvement in some functional performances (mainly fatigue and strength) of about two hours' duration in thermosensitive patients.

Adult↗