Ectopic development of skeletal muscle induced by subcutaneous transplant of rat satellite cells

The present study analyzes the ectopic development of the rat skeletal muscle originated from transplanted satellite cells. Satellite cells (10(6) cells) obtained from hindlimb muscles of newborn female 2BAW Wistar rats were injected subcutaneously into the dorsal area of adult male rats. After 3, 7, and 14 days, the transplanted tissues (N = 4-5) were processed for histochemical analysis of peripheral nerves, inactive X-chromosome and acetylcholinesterase. Nicotinic acetylcholine receptors (nAChRs) were also labeled with tetramethylrhodamine-labeled alpha-bungarotoxin. The development of ectopic muscles was successful in 86 percent of the implantation sites. By day 3, the transplanted cells were organized as multinucleated fibers containing multiple clusters of nAChRs (N = 2-4), resembling those from non-innervated cultured skeletal muscle fibers. After 7 days, the transplanted cells appeared as a highly vascularized tissue formed by bundles of fibers containing peripheral nuclei. The presence of X chromatin body indicated that subcutaneously developed fibers originated from female donor satellite cells. Differently from the extensor digitorum longus muscle of adult male rat (87.9 ± 1.0 æm; N = 213), the diameter of ectopic fibers (59.1 æm; N = 213) did not obey a Gaussian distribution and had a higher coefficient of variation. After 7 and 14 days, the organization of the nAChR clusters was similar to that of clusters from adult innervated extensor digitorum longus muscle. These findings indicate the histocompatibility of rats from 2BAW colony and that satellite cells transplanted into the subcutaneous space of adult animals are able to develop and fuse to form differentiated skeletal muscle fibers.

Distribution of the alfa2, alfa3, and alfa5 nicotinic acetylcholine receptor subunits in the chick brain

Nicotinic acetylcholine receptors (nAChRs) are ionotropic receptors comprised of alpha and beta subunits. These receptors are widely distributed in the central nervous system, and previous studies have revealed specific patterns of localization for some nAChR subunits in the vertebrate brain. In the present study we used immunohistochemical methods and monoclonal antibodies to localize the alpha2, alpha3, and alpha5 nAChR subunits in the chick mesencephalon and diencephalon. We observed a differential distribution of these three subunits in the chick brain, and showed that the somata and neuropil of many central structures contain the alpha5 nAChR subunit. The alpha2 and alpha3 subunits, on the other hand, exhibited a more restricted distribution than alpha5 and other subunits previously studied, namely alpha7, alpha8 and beta2. The patterns of distribution of the different nAChR subunits suggest that neurons in many brain structures may contain several subtypes of nAChRs and that in a few regions one particular subtype may determine the cholinergic nicotinic responses.

Modulación de la liberación del transmisor y de su interacción con el receptor en la unión neuro-muscular / Modulation of transmitter release and of its receptor interaction in the neuromuscular junction

La aparición reciente de técnicas de control de potencial en parches de membrana está permitiendo entender con mejor detalle el funcionamiento de los canales iónicos pre y post-sinápticos y su vinculación con la regulación del tamaño cuántico durante la liberación sincrónica (evocada) o asincrónica (espontánea) del neurotransmisor. La técnica de control de potencial en macroparches, aplicada a sistemas sinápticos adultos o en desarrollo tiene ventajas sobre otras técnicas para el registro de corrientes macroscopicas tal como, la producida durante un miniatura (corriente miniatura de placa terminal, cmpt) ya que los registros se hacen de una manera focalizada. De esta forma, se impide la contaminación de los eventos originados en lugares distantes, como cuando se registra en una área extensa de sitios de liberación de neurotransmisor. La regulación de la respuesta cuántica, es importante en el proceso de plasticidad sináptica en sistemas adultos y en desarrollo. Aquí, se analizarán algunos aspectos de la regulación pre y post-sináptica de la respuesta cuántica durante la liberación asincrónica del neurotransmisor y se hará énfasis en la unión neuromuscular "en desarrollo" del músculo caudal de renacuajos de anfibios