Prenatal development of the rat amygdaloid complex: an electron microscopic study.

The prenatal development of the rat amygdaloid complex was studied ultrastructurally day by day starting from the 12th embryonic day (ED12) until birth (ED22). In the earlier stages of embryogenesis, the nerve cells were observed to be of small size. A thin cytoplasmic ring rich in free ribosomes surrounded the oval nuclei. The nucleoli were prominent their number being two or more in a nucleus. The intercellular spaces were wide. A significant advance in the development of the nerve cells and the neuropil was detected in the period between ED15 and ED18. This advance was represented by an increase in the cytoplasmic volume, appearance and development Golgi zones, grouping of the free ribosomes into rosettes, appearance of single synaptic contacts, and a ramification of large-calibre nerve processes that continued during the later stages of the embryogenesis (ED19-ED22). By the end of the prenatal period the number of the synaptic contacts increased and well-developed synaptic apparatuses were observed. The development of the organelles in the perikarya was also advanced. Nissl bodies were found in some neurons. The number of enlarged Golgi zones and mitochondria increased.

[Acetylcholinesterase activity, choline acetyltransferase and GABA immunoreactivity in the ventral horn of the spinal cord of rats during chromatolysis]. / Activité acétylcholinestérasique, choline--acétyltransférase et GABA--immunoréactivité dans la corne antérieure de la moelle épinère du rat au cours de la chromatolyse.

A comparative study on the changes of the acetylcholinesterase activity (AChE) and of choline acetyltransferase (ChAT)- and GABA-like immunoreactivity (LI) has been performed in the ventral horn cells of the spinal cord of white rats 1, 2 and 3 weeks after transection of the right sciatic nerve. For the visualization of the AChE the method of Karnovsky and Roots (1964) was used. ChAT-LI was demonstrated by means of the avidin-biotin-peroxidase complex method (Hsu et al., 1981), whereas GABA-LI was localized using the PAP-method of Sternberger et al. (1970). In the control rats AChE-activity was observed on the cellular membrane, weaker in the cytoplasm of the perikarya and the proximal processes of the motoneurons; a pericellular localization of the reaction product was also established. ChAT-like immunoreactivity was mainly observed in the cytoplasm of the perikarya and the cellular processes, whereas GABA-like was most intensive in the nuclei of a number of motoneurons and in the more distal parts of their dendrites; the staining intensity of the perikaryal cytoplasm was weaker. During chromatolysis a progressive decrease of the staining intensity of the reactions for all the 3 substances was observed. In some neurons there was a total loss of the immunoreactivity. These results suggest that during chromatolysis: 1. the production of acetylcholine and GABA decreases; 2. the GABA which coexists within some cholinergic motoneurons may be expressed by these cells and 3. the AChE activity may also in the future be used as a marker of the cholinergic system of the anterior horn cells of the spinal cord.

Embryonic development of rat diaphragm. An electron-microscopic study.

Ultrastructural aspects of white Wistar rats diaphragm during part of its embryonic development (from the 13th embryonic day till birth) have been studied. The dominating structures observed in the period of the thirteenth embryonic day (ED 13) are undifferentiated cells, their cytoplasm being poor in organelles but rich in ribosomes. The close examination of these cells reveals that some of them possess a kind of thin filaments near their Golgi zones. At ED 14-15 clusters of myoblasts are readily detected (their cytoplasm containing a lot of glycogen granules and myofibrils, some of them even with Z-line material); contact sites between their cell membranes appear, somewhere forming specialized junctions; in this period the myoblasts start to fuse giving rise to the primary generation of myotubes. At ED 16-17 the quantity of myofilaments and glycogen granules increases alongside with the initiation of a basal-lamina formation; occasionally some oval, undifferentiated cells very similar to those viewed at ED 13 are found. At ED 18-19 the cytoplasm of the myotubes contains a lot of myofibrils and a well-developed endoplasmic reticulum; at some places the adjacent membranes still form deep interdigitations. At the end of the prenatal myogenesis (ED 20-21) most of the muscle cells are close to their mature morphological appearance--the sarcomers are well-organized and some nuclei present a peripheral localization; nevertheless, in this period new generations of myotubes can be also distinguished.

Ultrastructural changes in the anterior horn synapses of rat spinal cord under different locomotor conditions.

Ultrastructural changes in axodendritic synapses of the spinal cord ventral horn are studied in rats subjected to different locomotor conditions: immobilization, control and physical loading. Enhanced motor activity results in a reduction of the number of synaptic vesicles in the axon terminal, as well as flattening and diminution of their size. Other changes correlated with the different motor regimes are likewise established in the number of terminal ending's mitochondria, in "active zones", in subjunctional dense bodies, and in the bouton area. Data are treated by means of variation analysis. The significance of differences is established by "T"-criterion.

Cytochemical localization of adenosine triphosphatase and thiamine pyrophosphatase in the synapases of rat's cerebral cortex.

Ultrastructural distribution of adenosine triphosphatase and thiamine pyrophosphatase in synapses of rat's cerebral cortex was studied. Adenosine triphosphatase activity in some synaptic vesicles and mitochondria, on pre- and postsynaptic membranes, as well as in the postsynaptic thickening was established. The reaction specificity was proved by means of some controls: various concentrations of ouabain, NaF, NiCl2, cysteine, substrate free medium and non-specific substrates - cocarboxylase and beta-glycerophosphate. At the thiamine pyrophatase reaction, the enzyme positive product was found on the membrane of some clear synaptic vesicles, on the singl sacs of smooth endoplasmic reticulum in the axon terminal, and bouton cell membrane. Substrate free medium, addition of cystein and substitution of orininal substrate with adenosine triphosphate and beta-glycerophosphate as controls were used. The fine structure localization of both enzymes in synaptic structures suggests their important role in the synaptic function.

Ultrastructural changes in satellite cells after denervation and reinnervation of skeletal muscles.

Changes taking place in the satellite cells after denervation and reinnervation of skeletal muscles are studied. A certain degree of similarity and synchrony of the changes occurring in these cells and in the muscle fibers is established during the degenerative and regenerative processes. Formation of new satellite cells and fusion of the same with muscle cells is not observed. These findings are explained by the fact that postdenervation changes in the skeletal muscles are not so heavy as in their direct lesion when, according to literature data, the satellite cells participate directly in the reparative process.

[Ultrastructural changes in the connective tissue of skeletal muscles following denervation]. / Ul'trastrukturnye izmeneniia soedinitel'noi tkani myshts skeleta posle denervatsii

The ultrastructural changes found in the endomysium of rats after denervation of the diaphragm and m. plantaris were studied. Within the first week after crossing the peripheral nerve in the nedomysium there appeared an increased amount of neutrophils and monocytes as well as phagocytic material in the cytoplasm of histocytes. Activization of the cytoplasm of fibroblasts which manifested itself in the appearance of numerous vesicles and multiple free and bound ribosomes was detected by the end of the second and the beginning of the third weeks after denervation. At the same period eosinophils invaded the endomysium and became closely surrounded by numerous collagenic fibres. After reparation of neuromuscular synapses these changes disappeared. On the basis of these results and others founded in previous studies of denervated and reinnervated skeletal muscles the authors consider these changes in the endomysium appearing under the above experimental conditions to be manifestations of metabolic interrelations between the endomysium connective tissue and muscle fibres.

Ultrastructural changes in the muscle cells of denervated muscles of rat.

The ultrastructural changes taking place in the diaphragm and plantaris of rat are followed up from the 3rd hour to 24th week after section of the peripheral nerve. The latter is either sectioned, or crushed. It is found out that the initial changes, consisting in an increase of the number of ribosomes and certain degree of mitochondrial destruction, are observed as early as the first 24 hours after denervation. The postdenervational changes are traced up to the occurrence of reinnervation with restoration of the myoneural junctions. A description is ade of the changes in the various organelles of the muscle cell, and of the appearance of spheromembranous bodies, hellical complex and destruction of the contractile apparatus. Differences in the course of the post-denervational process in the diaphragm and plantaris are outlined. The results obtained are discussed and comparatively studied with literature data.