Lysosomen ung lysosomale Enzyme im Zentralnervensystem der Ratte

Pre- and postnatal development of the primary visual cortex of the common marmoset. II. Formation, remodelling, and elimination of synapses as overlapping processes

During ontogenesis changes in the numerical density of synapses are usually assumed to depend essentially on variations in the formation of synapses. Only the final adjustment to adult synapse densities is thought to include the elimination of synapses in some brain regions of certain species. Here, we focus attention on quantitative aspects of synapse elimination throughout development of area 17 of marmoset monkeys (Callithrix jacchus). Mature synapses, various precursor forms, and indicators of lysosomal degradation of synapses were quantitatively analysed by electron microscopy and morphometric methods. A total number of about 135 x 10(9) synapses was calculated for area 17 in each adult hemisphere corresponding to a volume density of 600 x 10(6) synapses/mm3. At 3 months of age, the respective values were 508 x 10(9)/area and 1,159 x 10(6)/mm3, while at birth these values were 69 x 10(9)/area and 328 x 10(6)/mm3. Consequently, at least three out of four synapses are eliminated between 3 months and adulthood. However, the real number of synapses being eliminated during development is probably much larger if the time course of lysosomal degradation is additionally taken into account. The frequency of lysosomes in presynaptic endings is highest before net-elimination of synapses occurs, i.e., between 1 and 3 months. This suggests that lysosomal degradation is not directly responsible for the majority of synapses removed during ontogenesis but apparently represents a second mechanism for synapse remodelling and elimination. Thus, it appears from this study that remodelling and elimination of synapses are quantitatively as important as their formation, and accompany synaptogenesis from its very onset onwards.

Cytochemical localization of acid phosphatase and adenosine triphosphatase in some avian mechanoreceptors

Ultrastructural distribution of acid phosphatase and adenosine triphosphatase was studied in the receptor elements of HERBST and GRANDRY sensory corpuscles. Acid phosphatase activity was established in the elements of smooth and rough endoplasmic reticulum of perineural capsule cells, as well as in the secondary lysosomes of all cell types. Particular interest was paid on the activity of myelin-like dense bodies and some clear core vesicles belonging to the axoplasm of receptor nerve fibres. Adenosine triphosphatase activity was established on the membranes of receptor structures and pinocytotic vesicles. More deposits of electron dense material were localized on the axolemma of the non-myelinated portions of the receptor nerve fibres. The functional significance and importance of the both enzymes in the receptor structures was discussed.

On the histochemistry of N-acetyl-beta-D-glucosaminidase in rat central nervous system

The optimal conditions for histochemical demonstration of NAG activity in the cerebrum, diencephalon, midbrain, cerebellum, medulla oblangata, and spinal cord were studied in a series of 37 Wistar rats of either sex. The following more important results were obtained: Each CNS zone required a definite methodlogical approach. Optimal fixation for most structures was achieved after 2 h treatment with formol-calcium and subsequent immersion of tissue blocks in formol-calcium 0,88 M saccharose. By this fixation technique it was possible to preserve high enzyme activity and good tissue structure. Only for the large pyramidal cells of the cerebral cortex the method of Holt provided optimal fixation. Formol-calcium-saccharose mixture and pure 0,88 M saccharose produced the opposide osmotic effect on nervous tissue previously fixed with formol-calcium: the former induced tissue shrinkage, the latter edema. The use of hexazonium p-rosaniline coupler prompted preliminary alcohol treatment of sections and introduction of 0.1 M acetate buffer in the incubation solution. Acetate buffer concentrations lower than 0.2 M diminished the diffuse cytoplasmic coloration and permitted a clear-cut demonstration of the lysosomal reaction. Ample information on the distribution of NAG activity in the CNS was obtained by using fast garnet GBC coupler and 0.1 M citrate buffer. Manganese chloride in a 0.2 mM concentration activates the reaction. The distribution of NAG reaction product in the cells of the different sections of the CNS was studied. The distribution of NAG reaction product in the cells of the different sections of the CNS was studied. The neurons, glial cells, and blood vessels showed positive reaction. Strongest activity was reported for the neurons of the supraoptic and paraventricular necleus, the epithelial cells of the chorioid plexus, nucleus ruber of the mesencephalon, and the vascular wall pericytes.