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Biomedical subjects

K Ichev

Publications and source records attributed to K Ichev.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1989

[Light microscopic and ultrastructural study of the lower olivary complex in the pigeon (Columba livia)].

The normal morphology of neurones and neuropile of the inferior olivary complex (LOC) in a pigeon (Columbia livia) was investigated by a light and electron microscope. The light microscopic analysis on the basis of the histological techniques of Vissl, Gldgi-Rio Hortega showed that olivary neurons had moderate mean dimensions and moderately branched dendrite tree, but single neurons with a model for dendrite branches were encountered similar to the second type of neurons in mammals. Axo-somatic synapses and synapses on the primary dendrites were comparatively small in number, observed by the electron microscope. Complex synaptic connections, similar to those of the mammals, were observed in the neuropile of LOC together with axo-dendrite synapses. The central part of glomerulo-like connections consisted of two-three dendrite profiles, connected sometimes with desmosomelike contacts. The presented results show that the morphological characteristics of olivary neurons of a pigeon are similar to those of mammals, although they are not so complex.

Animals↗
PubMed1989

[Morphology of glial cells in the lower olivary complex of the pigeon (Columba livia). I. Astrocytes].

The morphologic peculiarities of astrocytes in the lower olivary complex (LOC of a pigeon were examined at light and electron microscopic level. Usage of histological technique established the presence of three varieties: fibrous, real protoplasmic and covered type of astrocytes. In LOC of a pigeon most of astrocytes, observed by the electron microscope, possessed in their cytoplasm bunches of filaments, which passed and proceeded along side to astrocytic arborizations parallelly. Other type of arborizations were the so-called astrocytic plates, which were frequently arranged at layers and embraced the elements of the neuropappila under the form of capsules. Multiple desmosomo-like and gap junctions were encountered between adjoining astrocytic membranes. Heterogenous astro-oligodendrocytic gap junctions were observed as well. The functional significance of these glial cells and their probable role in neuronal metabolism is discussed on the basis of a comparative analysis of the structural and ultrastructural characteristics of astrocytes in LOC of a pigeon and in various species of mammals.

Animals↗
PubMed1989

[Morphology of glial cells in the lower olivary complex of the pigeon (Columba livia). II. Oligodendrocytes].

The morphologic peculiarities of oligodendrocytes in the lower olivary complex (LOC) of a pigeon were examined at light and electron microscopy level. The analysis on the basis of the applied histological techniques (staining with cresyl-violet and silver impregnation according to Goldgi-Rio Hortega) showed that oligodendrocytes were small rounded cells with nuclei stained more darkly than those of astrocytes. Oligodendrocytic arborizations were thin, slightly ramified and small in number. The predominant number of oligodendrocytes were of median type in LOC of a pigeon, observed by the electron microscope. The nuclei of oligodendrocytes were dense, seen by the electron microscope, in comparison with those of the astrocytes. The cytoplasm contained abundance of short and median cysternae of granulated endoplasmic reticulum, microtubules, but there were no microfilaments. Gap junctions contacts of the type astro-oligodendrocytes were found on the surface of cellular membrane. Oligodendrocytes were located in the perineuronal position, connected with myelinated nervous fibers or were situated freely among the elements of the neuropila. The functional significance of these glial cells and their probable role in neuronal metabolism is discussed on the basis of the comparative analysis of the morphologic characteristics of oligodendrocytes in LOC of a pigeon and those of mamals. The present work is a part of our observations on the structure of LOC in phylogenic aspect.

Animals↗
PubMed1989

Structure of the plasmalemma of human spermatozoa after treatment with antispermatozoa serum and concanavalin A.

Human ejaculated spermatozoa were treated with antispermatozoa serum as well as with the same serum and concanavalin. A. At both experimental conditions clusters of intramembranous particles both on P-face and on E-face in the acrosomal and postacrosomal regions were seen. The clusters were with different form and size and were built up from different number of intramembranous particles. Large areas with single particles or in some cases devoid of these particles were found out.

Autoantibodies↗
PubMed1989

Soybean agglutinin-binding sites on the human sperm surface.

Some differences in the distribution of lectin-binding sites on the surface of the plasma membrane of acrosomal and postacrosomal regions and tail of ejaculated human spermatozoa were demonstrated by means of horseradish peroxidase labeled soybean agglutinin. The acrosomal region was more densely coated with labeled lectin in comparison with the postacrosomal region. Hapten inhibition with N-acetyl-D-galactosamine was used as control.

Binding Sites↗
PubMed1988

Demonstration of negative tissue charges by means of polyethyleneimine-metal complexes.

Three polyethyleneimine-metal complexes were synthesized and cytochemically tested for demonstration of negatively charged sites. For this purpose rat cerebral cortex synaptosomes were used. It was established that both types of polyethyleneimine-copper complexes labeled the synaptosomal membrane and synaptic vesicles with electron-dense granules, whereas the polyethyleneimine-lead complex marked the anionic sites with amorphous electron-dense material.

Animals↗
PubMed1988

A method for demonstration of lectin-binding sites using a blood group substance A/ferritin conjugate.

A new technique for demonstration of lectin-binding sites is proposed. At the 1st step of the method, the lectin binds the respective monosaccharide constituent of the glycoconjugate and at the 2nd step, the blood-group substance A-ferritin conjugate is used as a marker. The following lectins were tested: wheat germ agglutinin, soybean agglutinin, mistletoe lectin I, and concanavalin A. Human red blood cells were used as material. By means of control experiments, the specificity of the proposed technique was proved.

ABO Blood-Group System↗
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↗
PubMed1987

On the concanavalin A positive layer on the skeletal muscle fibre.

The localization and distribution of mannosyl and glucosyl residues on the extrajunctional sarcolemma of skeletal muscle fibres of frog, rat and new-born rat was studied by means of concanavalin A labelled with FITC and ferritin-concanavalin A conjugate. A strong fluorescent layer surrounding the muscle fibres was found out. Ultrastructurally concanavalin A binding sites were established on the outer surface of muscle cell membrane, on the basal lamina, on the space between them, as well as on the reticular lamina, which ensheeted the muscle fibre. The width of the concanavalin A positive layer was 0.3 to 0.7 micron. On the basis of intensity of the fluorescence, some differences in the content of mannosyl and glycosyl residues during ontogeny as well between both species was admitted.

Animals↗
PubMed1987

Localization of newly synthesized protein precursors of basement membrane in the embryonic central nervous system as revealed by radioautography.

Using light- and electron microscope radioautography, the dynamics of newly synthesized protein precursors taking part in elaboration of brain basement membrane have been examined. The data presented give evidence that all cell types (endothelial, pericytal, and astroglial cells) surrounding the brain basement membrane contribute to its composition. A quantitative uptake analysis of 3H-proline indicates a progressive decline in the amount of labeled precursor in the examined cell types with a corresponding increase in deposition of the label at the presumptive basement membrane. The endothelial cells plays the main role in the membrane elaboration followed by pericyte and astrocyte which participate at lesser but equal degree in this synthesis.

Animals↗
PubMed1987

Changes of localization of lectin-binding sites on the intestinal epithelial cell surface membrane during differentiation of the columnar intestinal cells.

Light and electron microscopically localizations of Concanavalin A, Soybean Agglutinin, and Asparagus Pea Lectin-binding sites on the intestinal microvillous membrane were studied by means of horseradish peroxidase labelled lectins. The distribution of the lectin-binding sites was composed with the cell differentiation from the crypts to the tip of the intestinal villi. The visualization of lectin receptors in the mucin vesicles in the goblet cells was established as well. The controls for the determination of the specificity of reactions were carried out.

Animals↗
PubMed1986

A method for the fine-structural demonstration of lectin receptors.

A new two-step method using an Fc-fragment/ferritin conjugate as a marker for the visualization of lectin-binding sites on neuronal and other cell membranes is described. In this study of rat synaptosomes, three lectins were tested: concanavalin A, mistletoe lectin I and wheat germ agglutinin. The specificity of the method was proved by control experiments.

Animals↗
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↗