RESUMEN
One of the most exciting questions about the human voice is how the vocal fold produces and modulates different sounds. One hypothesis to explain the wide range of movements found in the vocal fold is based on the variety of muscle fiber orientations in the thyroarytenoid (TA) muscle. The tongue (TO) muscle is considered the most complex structure in the body in terms of muscle fiber orientation and movements. Thus, possible similarities between these two muscles and their innervations, the recurrent laryngeal nerve (RLN) and hypoglossal nerve (XII), could explain the complex movements executed by the focal fold. Moreover, such studies help us to understand some microanatomical aspects of vocal fold reinnervation, based on XII-to-RLN anastomosis. Therefore, this study investigates the histological organization of TA and TO muscles and their innervations (n=12 subjects). The muscle fibers were classified into three categories according to their orientation (transverse, undefined, and longitudinal). To quantify the percentage of fibers in each category in the TA and TO, the shape coefficient (shape Z) was estimated. Qualitative analysis and estimation of fiber area and shape Z show that the histological organization of TA and TO muscle is similar. Both muscles present the same percentage of transversal (~72%), undefined (~15%), and longitudinal fibers (~10%). By contrast, the authors' analysis of the morphometric parameters of the RLN and XII shows that there is no correlation between these nerves. In conclusion, in humans, TA and TO muscles present similar histological organization and this finding could help to explain interesting questions about human phonation.
Asunto(s)
Nervio Hipogloso/anatomía & histología , Músculos Laríngeos/citología , Músculos Laríngeos/inervación , Fibras Musculares Esqueléticas/citología , Nervio Laríngeo Recurrente/anatomía & histología , Lengua/citología , Lengua/inervación , Adulto , Anciano , Anciano de 80 o más Años , Femenino , Humanos , Procesamiento de Imagen Asistido por Computador , Masculino , Persona de Mediana Edad , Coloración y EtiquetadoRESUMEN
Studies have suggested that neuronal loss in Parkinson's disease (PD) could be related to the pacemaker activity of the substantia nigra pars compacta generated by L-type Ca(v) 1.3 calcium channels, which progressively substitute voltage-dependent sodium channels in this region during aging. Besides this mechanism, which leads to increases in intracellular calcium, other factors are also known to play a role in dopaminergic cell death due to overproduction of reactive oxygen species. Thus, dihydropyridines, a class of calcium channel blockers, and resveratrol, a polyphenol that presents antioxidant properties, may represent therapeutic alternatives for the prevention of PD. In the present study, we tested the effects of the dihydropyridines, isradipine, nifedipine, and nimodipine and of resveratrol upon locomotor behavior in Drosophila melanogaster. As previously described, paraquat induced parkinsonian-like motor deficits. Moreover, none of the drugs tested were able to prevent the motor deficits produced by paraquat. Additionally, isradipine, nifedipine, resveratrol, and ethanol (vehicle), when used in isolation, induced motor deficits in flies. This study is the first demonstration that dyhidropyridines and resveratrol are unable to reverse the locomotor impairments induced by paraquat in Drosophila melanogaster.
Asunto(s)
Antioxidantes , Bloqueadores de los Canales de Calcio/administración & dosificación , Dihidropiridinas , Degeneración Nerviosa/inducido químicamente , Estilbenos , Animales , Antioxidantes/administración & dosificación , Antioxidantes/metabolismo , Antioxidantes/uso terapéutico , Bloqueadores de los Canales de Calcio/metabolismo , Bloqueadores de los Canales de Calcio/uso terapéutico , Canales de Calcio/efectos de los fármacos , Canales de Calcio/metabolismo , Dihidropiridinas/administración & dosificación , Dihidropiridinas/metabolismo , Dihidropiridinas/uso terapéutico , Modelos Animales de Enfermedad , Dopamina/metabolismo , Drosophila melanogaster/metabolismo , Degeneración Nerviosa/metabolismo , Paraquat , Trastornos Parkinsonianos/inducido químicamente , Trastornos Parkinsonianos/metabolismo , Resveratrol , Estilbenos/administración & dosificación , Estilbenos/metabolismo , Estilbenos/uso terapéutico , Sustancia Negra/citología , Sustancia Negra/efectos de los fármacos , Sustancia Negra/metabolismoRESUMEN
Histological studies of the human recurrent laryngeal nerves (RLNs) have described differences in fiber length and thickness between the right and left RLNs. This asymmetry is probably involved in the different times of arrival of the stimuli to the laryngeal musculature controlled by each nerve. Histological and structural differences between the right and left RLNs could explain the synchronicity of laryngeal musculature contraction despite the differing nerve lengths. The purpose of this investigation was to shed some light on this paradigm by obtaining estimates of some morphometric parameters, such as intraperineural area, intraperineural perimeter, fiber area, fiber perimeter, fiber density (number of fibers/mm(2)), and total number of fibers in the right and left RLN of humans. Thus, the right and left RLNs were studied in a total sample of eight human specimens obtained from necropsies. The nerves were analyzed using histology, and the morphometric parameters were measured using Image Pro Plus Software 4.1 (Media Cybernetics, Silver Spring, MD, USA). No statistical differences between the two RLNs were observed in the intraperineural area, intraperineural perimeter, density (number of fibers/mm(2)), and total number of fibers. However, the area and perimeter of fibers of the right RLN were statistically larger when compared with those of the left RLN--21% and 11%, respectively. In conclusion, we show that in humans, the area and perimeter of the right RLN are larger than those of the left RLN. This morphological finding is probably related to the different time of arrival of the stimulus to the laryngeal musculature.