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S Dolapchieva

Publications and source records attributed to S Dolapchieva.

At least 19 recordsLinked to original sources
PubMed2002

Expression of neural cell adhesion molecule (NCAM) in the peripheral nerve fibers demonstrated by postembedding immunogold method on ultrathin sections. A preliminary study.

The neural cell adhesion molecule, NCAM, is thought to be necessary for the interaction between neurons, axons and glial cells, axons and target structures, and for myelination. The NCAM localization in the peripheral nerves has been less well studied. The data have shown significant differences. In this study, the distribution of the NCAM immunoreactivity in the sciatic nerves of 10- and 15-day-old Wistar rats was examined on ultrathin sections by the immunogold postembedding method. The sections were immunotested with a polyclonal antibody (Santa Cruz Biotechnology) that recognizes rat NCAM. The antibody was visualized with donkey anti-goat IgG, conjugated to 6 nm colloidal gold. NCAM immuno-like activity was found on axoplasmic profiles of myelinated and nonmyelinated axons, at non-assembled myelin lamellae, and at axo-glial junctions of the paranodes. The compact myelin and the Schwann cell cytoplasm were immunonegative. The presence of some NCAM immunoactivity on the level of the noncompact myelin membranes, deprived of the major myelin protein Po, might be associated with the mechanism of their maintenance.

Aging↗
PubMed2001

Immunohistochemical localization of the neural cell adhesion molecule in the rat sciatic nerve.

The neural cell adhesion molecule (NCAM) has been widely studied in the early embryonal development of the nervous system. The data about NCAM distribution in the peripheral nerves during postnatal life are scant and some controversial. In the present study, the NCAM localization in the sciatic nerves of 15-day-old Wistar rats has been studied. Semi-thin sections of the nerves were immunotested with a polyclonal antibody (Santa Cruz Biotechnology) that recognizes rat NCAM. The antibody was visualized with donkey anti-goat IgG, conjugated to 12 nm colloidal gold, and silver amplification. In the myelinated nerve fibres, the immunoreactivity was associated with the axons, mainly with their plasma membrane, which was unstained in the nodes of Ranvier. The myelin sheaths and the myelinating Schwann cells were negative. The extracellular matrix and the bundles of non-myelinated nerve fibres were immunopositive.

Animals↗
PubMed2001

N- and R-cadherins expression in the rat sciatic nerve demonstrated by postembedding immunogold method on semi-thin sections.

The calcium-dependent adhesion molecules N- and R-cadherins take part in the morphogenesis of the nervous system. The data about their localization in the peripheral nerves postnatum are limited and somewhat controversial. In the present study, a new methodological approach to the immunohistochemical cadherin detection has been applied. The sciatic nerves of 10-day-old rats were immunotested on semi-thin Epon sections by anti-N- and R-cadherins polyclonal antibody and visualized by IgG conjugated to colloidal gold and silver amplification. In the myelinated nerve fibers, an immuno-like activity was associated with the axoplasm and axolemma, the surface of the myelinating Schwann cells and their extracellular matrix. The units of nonmyelinated fibres and their associated glial cells were also intensely immunostained. The myelin sheaths and the glial cytoplasm were immunonegative. The significance of the localization is discussed in regard to the possible role of N- and R-cadherins in the anatomical and functional compartmentation of peripheral nerves.

Animals↗
PubMed2000

Automatic image analysis of the postnatal growth of axons and myelin sheaths in the tibial and peroneal nerves of the rabbit.

The numerous morphometric studies on the myelinated fibers in the peripheral nerves have presented varying results. Only a few studies deal with the peripheral nerves from rabbits. In this work, a morphometric study was carried out on the tibial and peroneal nerves of new-born, 10-, 15-, 20-, 30-, 60-, 90- and 240-day-old rabbits. The bilateral proximal segments of both nerves were investigated. Negatives of semi-thin cross sections were used for myelinated fiber morphometric analysis, carried out by an OLYMPUS Video image analyser. Two morphometric parameters, the average axon diameter (AD) (the average length of Feret's diameters) and the specific width of the myelin sheaths (SWMS) (specifying the total width of the myelin sheath), were evaluated for every age group. In the tibial and peroneal nerves a bimodal distribution of the average AD appeared on the 20th day, and of the SWMS on the 10th day postnatum. A tight correlation was obtained when comparing mean AD (mAD) and mean SWMS (mSWMS) in new-born and 240-day-old rabbits. From birth to adulthood the mAD increased in both nerves by about 270% and the mSWMS by about 280%. The mAD/mSWMS ratio in both new-born and 8-month-old rabbits was found to be 4 in the tibial and 5 in the peroneal nerves. According to the available data, an approach to the measurement of AD as an average length of Feret's diameters and the measurement of the myelin thickness as a SWMS has not yet been employed. An extension of this methodological approach could help to understand the growth and myelinization of peripheral nerve fibers.

Animals↗
PubMed1997

On the mechanism of the transport through Golgi apparatus.

The application of an ultrastructural cytochemical method for K(+)-dependent paranitrophenylphosphatase (Na+, K(+)-ATPase) has revealed patterns of plasticity of the Golgi apparatus of neurons in the cerebral cortex of 15-day-old rats. The peripheral part of the cis-most cisterna, being usually reactive, deviates from its regular arrangement in the Golgi stack and contacts with adjacent profile of the granular endoplasmic reticulum or with the next cisterna. The findings prompt the hypothesis that active movements of the cis-cisternae may facilitate and accelerate the transport of nascent proteins to and through the Golgi apparatus. The question about the nature of the contacts between the pointed membrane-bound compartments remains open.

Animals↗
PubMed1996

Distribution of concanavalin A and wheat germ agglutinin binding sites in the rat peripheral nerve fibres revealed by lectin/glycoprotein-gold histochemistry.

The affinity of rat peripheral nerve fibres for concanavalin A (Con A) and wheat germ agglutinin (WGA) was tested in semi-thin sections of Epon-embedded material. A two-step post-embedding technique was used. As a first step, Con A and WGA were used in pure form. As a second step, peroxidase-gold (for Con A) and ovomucoid-gold (for WGA) complexes were applied. The lectin-binding sites, visualized by means of signal amplification with the photochemical silver reaction, were associated mainly with the myelin sheaths and the surfaces of Schwann cells.

Animals↗
PubMed1996

Developmental changes of K(+)-dependent para-nitrophenylphosphatase (Na(+)-K(+)-ATPase) distribution in the synaptic regions in the cerebral cortex of rats.

Using Mayahara's method, the distribution of K(+)-dependent p-nitrophenylphosphatase activity was examined electron microscopically in the synaptic regions of the cerebral cortex of 10, 15 and 60-day-old Wistar rats. The enzyme achieved gradually its characteristic localization and uniform distribution. The main developmental changes were associated with the establishment of the postsynaptic density's activity. The controls with ouabain revealed activity only on the postsynaptic densities.

4-Nitrophenylphosphatase↗
PubMed1995

Ultracytochemical localization of ouabain-sensitive K(+)-dependent paranitrophenylphosphatase in rat sciatic nerve fibers.

In order to reveal and characterize Na+,K(+)-ATPase distribution in axon-myelin-Schwann cell units of sciatic nerves of adult and 15 days old Wistar rats, the ultracytochemical lead-paranitrophenyl-phosphatase technique was used. The activity of K(+)-dependent paranitrophenylphosphatase, a component of Na+,K(+)-ATPase, was found on the cytoplasmic side of the axolemma and Schwann cell plasma membrane, as well as on the major dense lines of the myelin sheath. K(+)-paranitrophenylphosphatase activity was localized also at the axoplasmic profiles and at the Golgi apparatus of the Schwann cells. Ouabain inhibition made it possible to distinguish alpha 1 from alpha 2 and alpha 3 isoforms of Na+,K(+)-ATPase. The results suggest that the activity of the axolemma and myelin sheath is determined by alpha 2 and alpha 3 isozymes. The enzyme activity of the Schwann cell plasma membrane and Golgi complex was not visibly influenced by ouabain. These results suggest that the activity of these glial structures is determined mainly by alpha 1 isozyme.

4-Nitrophenylphosphatase↗
PubMed1995

Changes in the neuronal plasma membrane during synaptogenesis.

During synaptogenesis the plasma membrane of neurons undergoes considerable changes and large portions of it develop to synaptic membranes. This transformation is brought about by biochemical and morphological changes. The aim of the present investigation was to study by morphological methods the in vivo changes of some basic components of the neuronal membranes during the early postnatal period, when active synaptogenesis occurs. The cerebral cortex of Wistar rats was used for preparation of either growth cones (up to postnatal day 10) or synaptosomes (postnatal days 14-30). Our studies were focused on the changes occurring in integral membrane proteins and cholesterol domains, and in certain carbohydrate residues and anionic sites. In the first days after birth relatively few intramembranous particles are found in the plasma membranes of growth cones, few and small cholesterol domains, scarce lectin-binding and anionic sites. During the following days there is a clear tendency for increase of the number of all of the studied structures until the appearance of typical synaptic membranes. Throughout the studied developmental period the protein and the cholesterol molecules were found to occupy distinct membrane domains. The structure of the developing neuronal membrane, poor on proteins and cholesterol, and its maturation to the fully functional synaptic membrane is discussed.

Age Factors↗
PubMed1990

Anionic sites in the myelin sheath as shown by cationized ferritin.

The distribution of anionic sites in the myelin sheath of sciatic nerves of rabbits was studied using cationized ferritin. Ferritin molecules were observed on the cytoplasmic sides of the myelin lamellae stratified in paranodes and Schmidt-Lanterman clefts. In the compact myelin, ferritin molecules have not been found in the tissue sections. They have been observed on membranes of the myelin fraction. The significance of the localization of negatively charged groups on the cytoplasmic side of membranes is discussed.

Animals↗
PubMed1990

[Cytochemical localization of concanavalin A binding sites in the peripheral nerve axons of old rats].

Distribution of alpha-D-mannose and alpha-D-glucose residues of glycoconjugates in axons of sciatic nerves of 24-month old rats of Wistar strains was studied by concanavalin-A-ferritin conjugate. In some of axons there were cumulations of ferritin molecules in agglomerates of various size with polarization of the phenomenon at preserved integrity of myelin sheath. In other cases the concentration of a large number of lectin binding sites was established in the region of the degenerating part of myelin sheath, engrossed in the axon cylinder. The changes in the distribution of carbohydrate residues in the axoplasm of some of the fibers are discussed in connection with the occurring axonal atrophy in fibers of peripheral nerves of old rats.

Aging↗
PubMed1989

Cytochemical localization of ATPase in axon-myelin-Schwann cell complex type.

ATPase activity was studied in the structures of axon-myelin-Schwann cell complex of sciatic nerves of rabbits of pre-and postnatal development. Positive reaction was observed on the plasma membrane, mitochondria and endoplasmic reticulum of Schwann cells, on the intraperiod lines of the compact myelin, in the split myelin lamellae in the paranodal regions and Schmidt-Lanterman clefts, in segment of outermost lamellae split off from the interparanodal myelin, in the mesaxons, in the loose myelin lamellae in the earlier stages of myelinization, on the axolemma (periaxonal space) and axoplasm. The ATPase activity on the Schwannian plasmalemma, axolemma and myelin sheath surface was found to be heterogeneously distributed. An accumulated of reaction deposits at the origin of the outer mesaxon, at the axoglial contacts as well as at the terminal part of the myelin sheath was respectively observed. Alterations of the enzyme activity distribution in axon-myelin-Schwann cell complex during rabbit's development were found to be associated with the growing myelin sheath and its node-paranode. Using controls with ouabain an attempt was made the possibilities of Wachstein and Meisel's method to be shown and the place of alpha+ form of Na+, K+-ATPase in the axon-myelin-Schwann cell Complex to be establish.

Adenosine Triphosphatases↗
PubMed1989

[Degenerative changes of the myelin fibers of sciatic nerves in aged rats].

Ischiadic nerves of 24-month old rats were examined by electron-microscopic technique. It was established that a large part of myelin fibres had degenerative changes, manifested at various degree. Axonal cylinder was atrophied even to complete disappearance. Myelin fibres endured degeneration, ending with sequestration and fragmentation. In part of the involved fibres the myelin sheaths preserved their intactness, but collapsed due to atrophy of the axon.

Aging↗
PubMed1988

Ultrastructural cytochemical localization of 5'-nucleotidase activity in axon-myelin-Schwann cell complex.

5'-Nucleotidase activity has been localized at the ultrastructural level in the axon-myelin-Schwann cell complex. Sciatic nerves of rabbits of pre- and postnatal development were used. Positive reaction was found on the plasma membrane, basal lamina, cytoplasm, and finger-like processes of the Schwann cells; on the intraperiod lines of the compact myelin, on the surface of myelin sheath, in the split myelin lamellae in the paranodal regions and Schmidt-Lanterman clefts, in segments of outermost and innermost lamellae, split off from the interparanodal myelin, in the mesaxons (outer and inner), in the loose myelin lamellae in the earlier stages of myelinization; on the axolemma (especially in the nodal and paranodal segments), in the periaxonal space, axoplasm. The alterations of 5'-nucleotidase distribution were associated with the developing myelin sheath.

5'-Nucleotidase↗
PubMed1986

Localizations of ruthenium red positive material in rabbit peripheral nerves.

The penetration and distribution of ruthenium red in the axon-myelin-Schwann cell complex of developing rabbit peripheral nerve fibers are investigated. Ruthenium red positive material is established in the axoplasm, axolemma, periaxonal space, major dense lines and intraperiod lines of the compact myelin, mesaxons, split peripheral myelin lamellae, Schmidt-Lanterman and longitudinal incisures, paranodal loops and axo-glial contacts, Schwann cell cytoplasm and basal lamina, nodal extracellular matrix, desmosome-like structures, endoneural collagen. Some features of the distribution of the contrast material in the developing myelin sheath are described. Regional differences of the axolemma and of the Schwann cell cytoplasm and plasmalemma are established. The prevalence of glycoproteins or glycolipids in the ruthenium red stained material in its different localizations is discussed on the basis of trypsin and hyaluronidase digestion performed.

Aging↗