Electron Microscopy and Glycosaminoglycan Histochemistry of Cerebellar Stellate Neurons

The stellate neurons of the cerebellar molecular layer have been mostly studied by light and transmission electron microscopy (TEM). However, the freeze-fracture scanning electron microscopy (SEM) and glycosami noglycan histochemistry of these inhibitory microneurons have not been explored thus far. The freeze-etching technique, the freeze-fracture method for SEM and the conventional techniques for TEM were applied to cerebellar samples of Swiss albino mice and Arius spixii teleost fishes. In addition, Alcian Blue (AB) staining was applied to mouse cerebellar tissue in order to study glycosaminoglycan histochemistry. At the SEM level, the stellate neurons showed a short axonal plexus extending to the nearby secondary and tertiary Purkinje dendritic branches, and 2 to 4 conical dendrites receiving typical axo-dendritic synapses on their shafts. The fractured stellate neurons showed compact nuclear heterochromatin masses and the three dimensional interrelationship of ER and Golgi complex (Novikoff\u27s GERL complex). The surface of the scarce endoplasmic reticulum was observed as strands extending from the nuclear envelope to the inner surface of the plasma membrane. At the TEM level, axosomatic endings of parallel and climbing fibers were distinguished. The cytochemical study revealed a homogeneous alcianophylic cytoplasmic substance, sensitive to hyaluronidase. This was particularly evident around and within the nucleus. The AB results indicated the presence of hyaluronic acid. A complex neuropil formed by Purkinje cell spiny branches, bundles of parallel fibers, spine synapses and Bergmann astrocytic cytoplasm was seen adjacent to the stellate neurons

Three-Dimensional Morphology of Cerebellar Protoplasmic Islands and Proteoglycan Content of Mossy Fiber Glomerulus: A Scanning and Transmission Electron Microscope Study

The present review summarizes the outer and inner surface features of mossy fiber glomeruli in vertebrate cerebellar granular layer as seen by conventional scanning electron microscopy (SEM) and SEM freeze-fracture method. The intracortical trajectory of mossy fibers and their synaptic contacts with granule cell dendrites were traced by the slicing and freeze-fracture techniques revealing the radial distribution of granule cell dendrites around the central mossy rosette. The en passant nature of mossy fiber synaptic contacts and the participation of Golgi cell axonal ramifications were demonstrated. The results obtained were compared with available light and transmission electron microscopy data. The freeze-etching technique disclosed the true extension of glomerular neuroglial investment. The proteoglycan content of mossy fiber rosette has been also studied by Alcian Blue staining, enzymatic digestion with testicular hyaluronidase and neuraminidase and Os-DMEDA staining method resulting in the presence of an electron dense material at the mossy fiber axoplasmic matrix and some synaptic vesicles, pre-and postsynaptic densities and cleft substance. The axoplasmic material appears to be constituted by proteoglycans with hyaluronic acid or chondroitin sulphate in their composition. The possible role of proteoglycans in synaptic functions is also discussed. Scanning electron microscopy is a promising methodology for analysis of short intracortical circuits and for the study of complex multisynaptic arrangements

Scanning Electron Microscope, Freeze Etching and Glycosaminoglycan Cytochemical Studies of the Cerebellar Climbing Fiber System

Mouse and teleost fish cerebelli were processed by the freeze-fracture methods for scanning and transmission electron microscopy in order to study the three-dimensional morphology and intramembrane features of climbing fiber-Purkinje spine synapses. In addition, Alcian Blue and ruthenium chloride stainings were applied to mouse cerebellar tissue to investigate the polyanion composition of these excitatory synapses under the transmission electron microscope. In the granular layer, tendril and glomerular collaterals of climbing fibers were observed. In the molecular layer climbing fibers exhibited a characteristic crossing-over or arborescence pattern type of bifurcation, Scheibel\u27s collaterals and multiple thorn synapses with Purkinje spiny dendrites. At the synaptic active zones of climbing fiber-Purkinje spine synapses the freeze-etching replicas showed focal aggregates of intramembrane particles at the E and P faces of the pre-and past-synaptic membranes. Membrane protuberances and pits were also observed at the pre-synaptic membrane. Ultracytochemical study of the climbing fiber synaptic varicosities revealed an Alcian Blue and ruthenium chloride positive material which appeared at the axoplasm surrounding the synaptic vesicles, at the pre-and post-synaptic densities and in the synaptic cleft. The axoplasmic material was sensitive to testicular hyaluronidase, therefore it would correspond to glycosaminoglycans (hyaluronic acid and/or chondroitin sulphates), which have been earlier reported in other cerebellar excitatory systems as those of mossy fiber-granule cell and parallel fiber-Purkinje dendritic spine

Quality indicators in physical education teaching

La calidad de la enseñanza pasa por ideas preconcebidas sobre el propio concepto de calidad. La visión que tiene el legislador no tiene por qué ser igual que la que tienen los padres o los educadores. Para poder obtener información sobre la calidad en educación física, podemos situarnos en un proceso jerarquizado, desde el ministerio hasta la dirección del centro, en el que se utilizan indicadores que pueden exponerse ante la comunidad educativa. O bien puede realizarse un proceso interno, en el que los indicadores son propuestos por el profesorado, que se encuentra inmiscuido en el proceso de enseñanza aprendizaje. Los indicadores de resultados suelen ser los más habituales en el sistema jerarquizado, mientras que los de proceso suelen aplicarse en la evaluación interna de la calidad. El profesorado de educación física tiene la posibilidad de diseñar y aplicar indicadores que pueden demostrar la calidad de sus enseñanzas, siempre y cuando defina claramente los aspectos a los que pretende aplicar los indicadores.Quality in education revolves around preconceived idea on the very concept of quality itself. Legislators need not necessarily have the same vision as parents or educators. To obtain further information on quality in physical education we can place ourselves in a hierarchical process ranging from the government ministry to school management, where indicators are used and shared with the educational community. This could be an internal process, where the indicators are put forward by the teachers involved in the teaching/learning process. The indicators of results are usually commoner in the hierarchical system, whereas those from the process are usually applied in internal quality assessment. Physical education teachers are able to design and apply indicators that can demonstrate the quality of teaching, provided they clearly define the aspects to which they aim to apply the indicators

Investigació i millora de l’educació. Cap a una pràctica i política educativa basades en l’evidència

Lección Inaugural Curso Académico 2014-2015 | Lliçó Inaugural Curs Acadèmic 2014-201