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Biomedical subjects

F E Leon-S

Publications and source records attributed to F E Leon-S.

At least 19 recordsLinked to original sources
PubMed1998

A re-evaluation of the mechanism of action of botulinum toxin on facial movement disorders in man.

Despite a lot of research aimed at clarifying the mechanism of action of botulinum toxin, mostly at supraspinal levels, a complete understanding of it is still elusive. However, recent investigations, including our own, allow us to suggest that, in facial muscles, the effects of botulinum toxin are not only in the neuromuscular junctions affecting the acetylcholine release but also modify the sensory inflow with subsequent changes on the muscle spindle-gammamotoneuron system.

Animals↗
PubMed1997

The effects of tobacco smoking on the short, middle, and long latency responses of the blink reflex in humans.

The three responses (R1, R2, and R3) of the electrically elicited blink reflex (BR) obtained in four normal human subjects were investigated before and after smoking both a filtered and an unfiltered cigarette. The changes observed in the BR were stronger and statistically more significant for the unfiltered than for the filtered cigarette, (p < 0.0001) and were more dramatic in R3 than R1 or R2. The action of nicotine on central pathways located at the interneuronal network of the brainstem, basal ganglia, and C fiber structures involved with this reflex seems to be the most likely mechanism for these findings.

Adult↗
PubMed1997

Discrepancy, coincidence or evidence in chronic idiopathic spastic paraparesis throughout the world. A meta-analysis on 2811 patients.

HTLV-I has been associated with a chronic idiopathic spastic paraparesis (CHISPA) in man; however, a complete understanding of this association is still debated. We selected the most comprehensible papers on this topic between 1985 and 1996, and found that 1261 out of 2811 patients (44.9%) reported, throughout the world, were HTLV-I positive. The mean age was 39.5 years and there was a female predominance of 1.9:1. These results do not exclude the causality of HTLV-I as a germen associated to CHISPA; however, other causes (e.g., toxic, immunosuppressors) must be considered as participating in the multistep neurodegeneration observed in CHISPA throughout the world.

Adolescent↗
PubMed1996

Multiple sclerosis and HTLV-I associated myelopathy/tropical spastic paraparesis are two distinct clinical entities.

Multiple sclerosis (MS) and HTLV-I associated myelopathy/tropical spastic paraparesis (HAM/TSP) can overlap in their clinical features and thereby cause difficulties for clinicians in relation to diagnosis and therapy. However, epidemiological biochemical, immunological, virological and radiological studies point to a number of significant differences. Recent comparative neurophysiological data, including blink reflex studies, obtained in these disorders, is briefly reviewed here and provides additional evidence of difference. The abnormal blink reflex in patients with MS consist of prolonged latencies and absences of R1 and R2 responses and are mainly due to demyelinating lesions around the pans. In contrast, in HAM/TSP the blink reflex abnormalities frequently include an unusual early response, R1k, which is probably a consequence of interneuronal hyperexcitability around the brainstem. Thus these findings provide further support for our contention that HAM/TSP and multiple sclerosis are distinctly different both as clinical entities and in their underlying pathomechanisms.

Adult↗
PubMed1995

Contralateral early blink reflex in patients with HTLV-I associated myelopathy/tropical spastic paraparesis.

Thirty-two Japanese patients with HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP) were studied by means of the electrically elicited blink reflex and three responses (R1, R2, R3) were registered. 69% of the patients displayed a uni- or bilateral crossed R1 response (R1k) as compared to 11% in the control group. A positive correlation between R1k and an exaggerated jaw jerk reflex was found in the patients. Central abnormalities of the nervous system with diminished presynaptic inhibition acting in the interneuronal input of the brainstem of HAM/TSP patients was the most likely cause. It could lead to the unmasking of crossed trigemino-facial pathway reflex which is present in the normal population from birth. These results strongly support the supraspinal involvement of the central nervous system (CNS) in HAM/TSP more than usually thought.

Action Potentials↗
PubMed1995

Clinical neurophysiological comparative study on HTLV-1 associated myelopathy/tropical spastic paraparesis.

In order to determine the neurophysiological characteristics of HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) throughout the world, we analyzed and compared the most common clinical neurophysiological studies (CNPS) performed in this entity from those places with a high prevalence and interesting regional differences were noted. African patients showed a noteworthy involvement of the peripheral nervous system (PNS). Chilean patients displayed a more circumscribed abnormality around the spinal cord. The migrants from the West Indies to England showed important visual, and somatosensory evoked potential (SSEP) alterations in the upper limbs (UL). Japanese patients also presented some involvement of the PNS, but their illness duration was less protracted than that observed in other countries. The differences found in visual pathways and PNS involvement among these groups were statistically significant (p < 0.05). Thus, this study shows not only a widespread subclinical involvement in both central and PNS in HAM/TSP, but also strongly supports the idea that the lesion distribution and progression of this disease are different among countries. Such differences could likely be due to the action of the so-called environmental co-factors present in each of these areas which should be promptly investigated.

Human T-lymphotropic virus 1↗