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C Chouchkov

Publications and source records attributed to C Chouchkov.

At least 19 recordsLinked to original sources
PubMed2004

Specificity of membrane specializations in mechanoreceptors of birds--A freeze-etching study.

The detailed knowledge of the molecular process of mechanotransduction is still an unsolved question. The investigation of the intramembranous structure of the cutaneous mechanoreceptors may play an important role in elucidating this problem. In this relation, Herbst sensory corpuscles in ducks were studied for the first time using the freeze-etching and thin sectioning techniques. Herbst corpuscles have the basic structural components valid for most of the encapsulated mechanoreceptors in mammals: a capsule made of perineural cells, a lamellar complex of modified Schwann cells, surrounding the non-myelinated part of the receptor nerve fiber and its ending. Freeze-etching replicas reveal that the plasmalemmae of the capsule cells, modified Schwann cells and axolemmae of parts of the nerve fiber differ in both density and pattern of distribution of intramembranous particles (IMPs) as well as IMP size. On all the plasmalemmae the IMP density is higher on the P-face (2000-3300 microm(-2)) than the respective E-face (800-1500 microm(-2)). The axolemma of the ending of the receptor nerve fiber expresses higher density of IMPs than its shaft. The mean IMP size for all the plasmalemmae varies between 5.5 and 7.5 nm. Many tight junctions occur between the capsule cells. These results indicate that the non-myelinated axolemma as well as the plasmalemmae of other components of Herbst corpuscles are specialized in terms of content and distribution of IMPs. The IMPs may represent various kinds of mechanosensitive channel proteins or related membrane-bound proteins participating in the process of mechanotransduction.

Animals↗
PubMed2003

Localization and distribution of laminin in the basal lamina of certain mechanoreceptors--an immunogold study.

The applied immunogold cytochemical technique in investigating the cytologic distribution of the laminin (LAM) molecule in the capsulated Pacinian and Herbst mechanoreceptors shows the presence of LAM around most elements of the receptor structures. The LAM immunoreactivity (LAM-IR) is best expressed in the vicinity of the perineural capsule cells of both receptor types, where it is primarily concentrated around the perinuclear regions as well as the cytoplasmic lamellae. Such a localization overlaps with the already known ultrastructural localization of a basal lamina (BL) around these cells. Laminin immunoreactivity is less well expressed around the modified Schwann cells. Even in these cells, however, there is an apparent immunoreaction around the cytoplasmic lamellae regardless of the lamellar location. In both receptor types, there is no LAM-IR in the cells of the subcapsular space. Of particular significance we consider the localization of gold particles (respectively the presence of a BL) between the innermost lamellae of the modified Schwann cells and the non-myelinated part of the receptor nerve fiber and their endings, as well as around the axoplasmic protrusions of the nerve endings. We discuss the role of the BL and LAM in the investigated rapidly adapting mechanoreceptors and their trophic influence upon the sensory regions. We also assume the arresting and selective effect of these membranes in building up the ion channels of the axolemma which probably has a certain importance in mechanotransduction.

Animals↗
PubMed1999

Morphological study of mast cell localization in the wall of the proximal tubule in the domestic swine kidney.

Morphological studies to localize mast cells in the wall of the convoluted and straight parts of the proximal tubules of the domestic swine kidney were performed. Kidney perfusion was carried out in 8-month-old pigs and semi-thin and ultrathin sections were prepared after a routine treatment. A light microscopic study showed that mast cells were not frequently found. Most were localized in the wall of the proximal convoluted tubule, while in the proximal straight tubule wall they were fewer in number. Most of the mast cells were oval in shape, their size being typical for this species, and the granules were reddish in colour. Three types of granule containing an evenly distributed granular-fibrous substance were found by TEM examination: the first type had a single electron-optically dense belt under the membrane; the second showed optically empty spaces between the substance and the cell membrane; the granules from the third type had two parallel dense belts below the granular membrane and were the smallest in size. Some of the granules of the first type were connected with the granular endoplasmic reticulum. A very narrow intercellular area and single desmosome-like junctions were found between the mast cells and the epithelial cells. Protrusions of plasmalemma and granules outside the cells were not established. On the basis of these results and data from the scientific literature, a comparative analysis was carried out. This showed certain differences between the results obtained and previous findings on the morphology of domestic swine mast cells and granules.

Animals↗
PubMed1998

GABA- and glutamate-immunoreactivity in sensory ganglia of cat: a quantitative analysis.

Several amino acids may function as neurotransmitters in the nervous system. The potential role of glutamate (Glu) and aspartate in excitatory responses was demonstrated and it was established that GABA and glycine act as inhibitory agents. The present study aimed at investigating the availability of Glu and GABA in certain feline sensory ganglia, i.e. the trigeminal (TrG), nodose and dorsal root ganglia (DRG). A significant part of the neurons were GABA-positive (19.5% to 23.5%). These were large-sized neurons as well as small- to medium-sized ones. The intensity of immunostaining varied from weak to strong. GABA-containing neuronal fibres were seen in the neuropil and some of them surrounded unstained ganglionic cells. The Glu-immunoreactive (IR) neuronal perikarya in all the investigated ganglia were 63.6% to 66.4%. The majority of positive cells were small- to medium-sized, but large primary sensory neurons were also seen. There was no difference between the intensity of the reaction in the primary sensory and small neurons. Glu-IR neuronal fibres were seen in close apposition to immunopositive as well as immunonegative neurons. In conclusion, in the TrG, nodose and DRG, GABA and glutamate are involved in neurotransmission. There is a significant number of GABAergic neurons in the investigated sensory ganglia of the cat. The difference in the expression of these amino acids suggests that they can act not only as neurotransmitters but also as modulators of sensory information.

Animals↗
PubMed1997

Immunocytochemical localization of the neurons in the superior mesenteric ganglion innervating the small intestine of the cat.

Retrograde tracing was used to determine the localization of neuronal perikarya and fibres in the feline superior mesenteric ganglion (SMG), projecting to the small intestine. In the distal part of the ileum, a retrograde neuronal tracer Fast Blue (FB) was injected and after approximately thirty five to forty days the animals were killed by perfusion. The SMG were removed and the neuropeptide contents of the neurons, projecting to the distal ileum, were determined by means of immunofluorescence with antisera to neuropeptide Y (NPY), calcitonin gene-related peptide (CGRP), substance P (SP), somatostatin (SOM), and vasoactive intestinal polypeptide (VIP). Neurons innervating the small intestine were located in the upper part of the SMG and all of them were NPY-immunopositive. The group of CGRP-immunoreactive (IR) cells was less numerous (73.33%). Probably the FB-labeled fibres, containing the same neuropeptides, arise from these perikarya. SP- or VIP-immunopositive neuronal processes were found to surround immunonegative ganglionic cells but their origin is not in the ganglion. Only single FB-marked cells were VIP-immunopositive. SP- and SOM-immunoreactive amounted respectively to 2.28% and 3.01% of all the neuronal population, but only a few of these cells were FB-labelled.

Amidines↗
PubMed1990

Cytochemical localization of 5'-nucleotidase activity in the nodose ganglion of the rabbit.

5'-nucleotidase (5'N) activity was histochemically examined in the rabbit nodose ganglion at light and electron microscopic levels. Under the light microscope, the 5'N activity was clearly demonstrated on the satellite cells and their processes surrounding neurons. No deposits of reaction product were observed within the perikarya of the ganglion cells and at intracellular sites in the glial cells. Electron microscopically, the reaction product of enzyme activity was located in both neuronal and satellite cell membranes, usually on the external surface. The glial cells exhibit the enzyme activity more extensively than the neurons. The presence of membrane-bound 5'N activity on the external aspect of the plasma membranes supports earlier findings that the functional role of the enzyme in the primary sensory neurons is related to processes of intracellular communication.

5'-Nucleotidase↗
PubMed1990

Localization of somatostatin-like immunoreactive fibres in the trigeminal principal sensory nucleus of the cat.

The location and distribution of nerve fibres and terminals displaying somatostatin-(SOM)-like immunoreactivity (LI) has been examined in cat trigeminal principal sensory nucleus (Vp) using the peroxidase-antiperoxidase technique. The varicose SOM-LI nerve fibres form a fine network in the Vp. SOM-positive terminals are distributed throughout Vp but they are particularly abundant in the ventral subdivision of the nucleus (Vpv). The labelled terminals make predominantly asymmetric axodendritic synaptic contacts. SOM-LI terminals only rarely form symmetrical synapses with non-reactive neuronal elements and are also present free in the neuropil. No SOM-LI perikarya are detected in the Vp. The results of the present study suggest that the majority, if not all, of SOM-LI fibres in the Vp are probably of primary afferent origin and may be involved in relaying trigeminal sensation to neuron located in this brain area.

Animals↗
PubMed1988

Serotonin-like immunoreactivity in the cat trigeminal ganglion.

The immunohistochemical distribution of serotonin-like immunoreactivity (SER-LI) has been established in networks of fine nerve fibers which arborize and wind profusely between non-immunoreactive sensory neurons in the cat trigeminal ganglion. Some of the varicose nerve fibers surround occasional non-immunoreactive sensory neurons like a woven basket. None of the sensory neurons display SER-LI. An extrinsic origin of intraganglionic fine nerve fibers has been suggested.

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

[Methods for long-term storage of anatomical demonstration objects].

2 methods for longterm conservation of anatomical objects have been described. The former concerns the use of methylmethacrylate (the plastic material) for embedding of anatomical objects into different forms. The 2nd method uses the same plastic material for impregnation of anatomical objects. The authentic anatomical models produced by the both methods possess very good demonstrative features. They are solid and cheap.

Methylmethacrylate↗
PubMed1983

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.

Animals↗
PubMed1980

Ruthenium red staining material in Herbst and Grandry sensory corpuscles.

The penetration and distribution of ruthenium red into Herbst and Grandry sensory corpuscles has been investigated. Ruthenium red positive substances have been localized in all intercellular spaces including the collagen fibrils, basement membranes and predominately the outer leaflet of the plasmalemmae including the axolemma. Some of the numerous pinocytotic and coated vesicles of the receptor cell layers have been heavily loaded with the dye. Sometimes, the intracytoplasmic and intraaxoplasmic penetration of ruthenium red has been observed. In these cases, the dye deposits have been restricted to the elements of smooth endoplasmic reticulum, mitochondria and microtubules.

Animals↗
PubMed1980

[Evolution of encapsulated sensory nerve endings in the hairless part of the lips of mammals].

The simple cylindrical end-bulb is the unique type of encapsulated receptors of the hairless part of the lips in Rodentia, Carnivora and Ruminantia. For the first time, more complex sensory structures have been established in Apes. Having regard to the terminal nerve arborization, three types of sensory corpuscles can be differentiated. The 1st one is the transitional type between the simple end bulb and more complicated receptors in Primates. The terminal nerve fibres are very thick and simply convoluted. The 2nd type comprises thick nerve coils surrounded by intermingled thin nerve branches. The 3rd type contains mainly thin nerve branches which form twisty configuration. Meissner's corpuscles have been proved only in Primates - Apes and Man. The results give strong evidence that the complex structure of apes sensory corpuscles is an quantitative evolutionary improvement. The man encapsulated receptors do not differ substantially from apes corpuscles. In other words, the man evolution does not present so significant evolutionary leap as the apes do.

Animals↗
PubMed1979

Degeneration and regeneration of some mechanoreceptors. An ultrastructural study. III. Ultrastructure of reinnervated Herbst corpuscles.

The ultrastructure of reinnervated Herbst corpuscles shows that the regenerating nerve branches appear in the inner zone of the receptors at the end of the first month after nerve crush. The nerve branches are accompanied by the Schwann receptor cells. Two periods of regeneration can be established. During the first period the changes reflect mainly the quantitative relations between the regenerating nerve branches and the Schwann receptor cells, whereas during the second period the intracytoplasmic and intraaxoplasmic renewal of the organelles take place. The final regeneration of the receptors finishes at the end of the fifth month after nerve crush and one month later after nerve transection. Also, after transection the number of reinnervated receptors is less encountered.

Animals↗
PubMed1979

Degeneration and regeneration of some mechanoreceptors. An ultrastructural study. IV. Ultrastructure of reinnervated Pacinian corpuscles.

The first signs of reinnervation of the Pacinian corpuscles have been established at the middle of the second month after nerve crush. The regenerative process pass through two periods. During the first period the progressive increase of the Schwann receptor cells has been observed parallel to the reduction of the regenerating nerve branches. During the second period the reorganization and renewal of the regenerated organelles takes place. Some organelles as dense core vesicles, coated vesicles and microtubules of the receptor nerve fibre show noticeable dynamics. The regeneration has been established only in the preexisting after denervation capsulated remnants of the receptors. After nerve transection the regeneration is prolonged one month later and the less of quantity reinnervated receptors have been observed.

Animals↗
PubMed1979

Degeneration and regeneration of some mechanoreceptors. An ultrastructural study. I. Ultrastructure of denervated Herbst corpusles.

The degenerative changes in the HERBST corpusles have been investigated at ultrastructural level during the 3rd h to 1 year after nerve section. The earliest changes have been established in the nerve ending followed by the remaining nonmyelinated and myelinated portion of the receptor nerve fibre. The changes reflect the retrograde character of the degenerative process. The receptor cell elements pass through the stage of activation followed by their destruction and elimination. The Schwann receptor cells fullfill the pagocytotic role in the elimination of the axonal debris, after that they have been also completely eliminated. Their places are occupied by the activated fibroblasts and developed collagen fibrils. One part of the perineural cells persist a long time after denervation and they preserve the common although modified receptor configuration.

Animals↗