Ultrastructural clarification of the peripherally located actin network in the myelinated axons / Aclaración ultraestructural de la red de actina localizada periféricamente en los axones mielinizados

SUMMARY: Despite the existence of a large amount of actin in the axons, the concentration F-actin was quite low in the myelinated axons and almost all the F-actin were located in the peripheries of the myelinated axons. Until now, the ultrastructural localization of F-actin has still not been reported in the myelinated axons, probably due to the lack of an appropriate detection method. In the present study, a phalloidin-based FITC-anti-FITC technique was adopted to investigate the subcellular localization of F-actin in the myelinated axons. By using this technique, F-actin is located in the outer and inner collars of myelinated cytoplasm surrounding the intermodal axon, the Schmidt-Lanterman incisures, the paranodal terminal loops and the nodal microvilli. In addition, the satellite cell envelope, which encapsulates the axonal initial segment of the peripheral sensory neuron, was also demonstrated as an F-actin-enriched structure. This study provided a hitherto unreported ultrastructural view of the F-actin in the myelinated axons, which may assist in understanding the unique organization of axonal actin cytoskeleton.

RESUMEN: A pesar de la existencia de una gran cantidad de actina en los axones, la concentración de F-actina era bastante baja en los axones mielinizados y casi la totalidad de F-actina se localizaba en las periferias de los axones mielinizados. A la fecha aún no se ha reportado la localización ultraestructural de F-actina en los axones mielinizados, probablemente debido a la falta de un método de detección apropiado. En el presente estudio, se adoptó una técnica FITC-anti-FITC basada en faloidina para investigar la localización subcelular de F-actina en los axones mielinizados. Mediante el uso de esta técnica, la F-actina se localiza en los collares externo e interno del citoplasma mielinizado que rodea el axón intermodal, a las incisiones de Schmidt-Lanterman,a las asas terminales paranodales y a las microvellosidades nodales. Además, la envoltura de la célula satélite, que encapsula el segmento axonal inicial de la neurona sensorial periférica, también se demostró como una estructura enriquecida con F-actina. Este estudio proporcionó una vista ultraestructural de la F-actina en los axones mielinizados, que puede ayudar a comprender la organización única del citoesqueleto de actina axonal.

Differential expression of alpha-smooth muscle actin and vascular endothelial growth factor in skin biopsy of patients with systemic sclerosis: a histological and immunohistochemical study

Vasculopathy is a hallmark of systemic sclerosis [SSc]. It contributes to many of its clinical manifestations and precedes fibrosis. The aim of this study was to investigate the expression of alpha-smooth muscle actin [alpha-SMA] in skin biopsy of patients with SSc and correlate it with other manifestations of vasculopathy, including those seen on fundus fluorescein angiography and tissue vascular endothelial growth factor [VEGF] expression. This study included 25 patients with SSc and 10 healthy individuals. Patients underwent full history taking and a clinical examination. All participants underwent fundus fluorescein angiography. Skin biopsy was examined by H and E staining, Mallory triple staining, and immunohistochemical staining for alpha-SMA and VEGF. Histological examination showed loss of dermal papillae, hypovascularity of the dermis, and subepidermal fibrosis. Immunohistochemical staining of the vessel wall in skin biopsy samples showed a statistically highly significant increase in VEGF and a highly significant decrease in alpha-SMA in patients as compared with controls. There was a highly significant positive correlation between VEGF and duration of illness, Raynaud's phenomenon, digital ulcers, disease activity score, and modified Rodnan Skin Score. As regards alpha-SMA, there was a highly significant negative correlation with Raynaud's phenomenon, disease activity score, modified Rodnan Skin Score, and VEGF, whereas there was a significant negative correlation with digital ulcers. The strongest correlation [r] for the duration of illness was found with alpha-SMA, followed by VEGF. alpha-SMA was found to be correlated to different manifestations of vasculopathy in SSc. It was found to be one of the early markers of vasculopathy among the other studied variables. Besides its diagnostic role in SSc vasculopathy, it could play a role in impaired vasculogenesis, making it a potential therapeutic target in the management of SSc

Actin cytoskeleton structure and its localization in gongronella butleri, mucor javanicus and absidia cylindrospora (mucorales-zygomycetes)

Mediante estudios de microscopia òptica de fluorescencia se describe y caracteriza la estructura, distribución y localización de la actina, en tres especies de hongos de la clase zygomycetes: absidia cylindrospora, gongronella butleri y mucor javanicus. La estructura de la actina fué analizada utilizándose el marcador fitc-phalloidina, especifico para actina, en muestras fijadas con formaldehido. En los resultados se observan diferencias en la estructura, distribución y localización de esta proteina en las especies analizadas. Filamentos , aglomerados, placas o aglomerados periféricos y gránulos, fueron las formas más comunes encontradas en los hongos, con prevalencia de los aglomerados observados en todos los citoplasma de las hifas. La tinción de actina en losápices de las hifas, solo se observó en mucor javanicus, esta diferencia en la estructura de la actina podría estar asociada a zonas de expansión de la pared celular de los hongos