Kiril Ichev

Localization of lectin binding sites on the rat intestinal microvillous membrane

The distribution of peroxidase labeled Asparagus Pea Lectin and Soybean Agglutinin on the rat intestinal microvillous membrane was studied. Controls were carried out to determine the reaction specifity . Some analogy was established between the distribution of the binding sites of both lectins. The reaction product was deposited mainly on the microvillous membrane of the crypt cells and the cells from the lower part of the intestinal villi, and to a lesser extent on the upper part of the latter. Electron dense material was seen on the upper part and chiefly on the tip of the microvilli. From the results of this study and on the basis of data from our previous studies it was proposed, that changes in the carbohydrate content of the microvillous membrane appear during the differentiation and maturation of the intestinal cells.

Concanavalin A binding sites on the intestinal microvillus membrane of rat

Concanavalin A binding sites on the intestinal microvillus membrane have been studied by means of Concanavalin A-horseradish peroxidase method. Several controls were carried out to demonstrate the specifity of this technique. Reaction product on the microvillus membrane of columnar cells on the upper bigger part of intestinal villi was found, while on the intestinal cells from the base of the villi and undifferentiated crypt cells no electron dense material was established. The results of the suggested method were discussed in relation with the literature data.

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.

Mistletoe lectin I binding sites on the synaptosomes of the rat cerebral cortex

By means of combined lectinological and immunological methods were demonstrated mistletoe lectin I binding sites on rat cerebral cortex synaptosomes. The mistletoe lectin I binds specifically D-galactose. Galactosyl residues were established on the junctional and nonjunctional synaptosomal membrane, on the synaptic vesicles, mitochondria and on myelin contamination. The relative number of mistletoe lectin I receptors per unit area of synaptosomal membrane was calculated.

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.

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.

Distribution of negative charges of rat brain synaptosomes established by means of protamine-ferritin conjugate

The negative electric charges on the synaptosomes from rat cerebral cortex were studied by means of protamine-ferritin conjugate. The synaptic vesicles in some synaptosomes were heavily labelled with the positively charged conjugate. The synaptosomal membranes including presynaptic and postsynaptic membranes were also stained but in a lesser degree. It was established that the major dense line and the intraperiod line of myelin contaminants were labelled, too.

Visualization of anionic sites using polyethyleneimine-metal complexes

17 Polyethyleneimine-metal complexes were synthesized and 3 of them were tested cytochemically for visualization of negative tissue charges. The demonstration of the anionic sites was carried out on rat cerebral cortex and on frog cutaneous pectoral muscle. As controls, neuraminidase digestion, methylation, and omission of osmium-postfixation were used. The osmiophilic properties of polyethyleneimine, polyethyleneimine salts, and polyethyleneimine-metal complexes were discussed.

Radioautographic study of leucine uptake and transmission of proteins by rat enterocytes following Concanavalin A binding.

The transport of labeled leucine and following protein synthesis has been investigated in rat enterocytes using quantitative electron microscope radioautography. The presented normal distribution of the label has been compared with the distribution of radioactivity after Concanavalin A treatment. It has been established that the transport of amino acid and subsequent newly synthesized proteins are delayed and confused after Concanavalin A binding.