Biomedical subjects

Ia Iu Komissarchik

Publications and source records attributed to Ia Iu Komissarchik.

At least 19 recordsLinked to original sources

PubMed2006

[Structural-functional organization of Golgi apparatus].

This review is dedicated to the structure and function of Golgi apparatus (GA). It summarizes contemporary data published in numerous experimental papers and in several reviews. Possible ways of intra-Golgi transport of proteins, existent models of structural and functional organization of Golgi organelle, as well as the issues of its biogenesis, posttranslational modification and sorting of proteins and lipids, and mechanisms of their trafficking are discussed. Special attention is paid to the role of coatomer proteins (COPI, COPII and clathrin), fusion proteins (SNAREs), and small GTPases (ARF, SARI) in the secretory pathway. In addition, the phenomena of ultrastructural alterations of GA due to various functional conditions and physiological stimuli are specifically accented. We included in this review our original data on a probable involvement of GA in water transport, and on the organization of atypical GA in microsporidia--intracellular parasitic protists.

Animals↗

PubMed2006

[The role of facilitated diffusion in glucose transport across the apical membrane of enterocytes].

In chronic experiments on Wistar rats, glucose and galactose absorption in the isolated loop of the small intestine considerably decreased in presence of both phloridzine am phloritine (inhibitors of the glucose transporters SGLT1 and GLUT2). The load of the isolated loop with glucose or galactose solutions scarcely influenced the absorption of 2-deoxi-D-glucose (substrate for GLUT2). According to the immunocytochemical analysis by means of confocal microscopy, after the load of the isolated loop with glucose (75 mM) the labels to GLUT2 and proteinkinase C (PKC betalI) were concentrated mainly in the apical part of the enterocytes, whereas after the load with the Ringer solution--in the basal part of the enterocytes. It was shown on the mathematical model that the part of the facilitated diffusion in the total glucose absorption was considerably lesser in comparison with the active transport mediated by SGLT1. Thus the findings support the hypothesis about a recruitment of the transporter GLUT2 into the apical membrane of the enterocytes and its involvement in glucose transfer across this membrane. However, under natural conditions, the active transport is the main mechanism of glucose absorption, whereas the facilitated diffusion plays a certain role only at high carbohydrate loads.

Animals↗

PubMed2006

[Structural-functional organization of Golgi apparatus].

This review is dedicated to the structure and function of Golgi apparatus (GA). It summarizes contemporary data published in numerous experimental papers and in several reviews. Possible ways of intra-Golgi transport of proteins, existent models of structural and functional organization of Golgi organelle, as well as the issues of its biogenesis, posttranslational modification and sorting of proteins and lipids, and mechanisms of their traffic-king are discussed. Special attention is paid to the role of coatomer proteins (COPI, COPII and clathrin), fusion proteins (SNAREs), and small GTPases (ARF, SARI) in the secretory pathway. In addition, the phenomena of ultrastructural alterations of GA due to various functional conditions and physiological stimuli are specifically accented. We included in this review our original data on a probable involvement of GA in water transport, and on the organization of atypical GA in microsporidia--intracellular parasitic protists.

Animals↗

PubMed2006

[Structural-functional analysis of diffusion in glucose absorption by rat small intestine enterocytes].

To elucidate mechanisms providing transport of sugars across intestinal epithelium, on taking into account the current hypotheses (active transport, participation of paracellular transport and passive component of transcellular transport), it was important to reveal structural changes of tight junctions and distribution of the carriers of facilitated diffusion of GLUT2 and protein kinase C during absorption of glucose. On using confocal and electron microscopy, ultrastructural and immunocytochemical studies of enterocytes after perfusion of isolated rat small intestine fragment with 75 mM glucose (chronic experiment) have shown: 1) fluorescent labels of transporter GLUT2 and PKCbetaII are located in the apical area of enterocytes situated at the upper half of the villus. Antibodies against GLUT2, conjugated with gold, are revealed at the microvilli or apical membrane and in the area of terminal network; 2) no ultrastructural changes of the tight junction are detected on ultrathin sections and freeze--fracture replics. At the same time, fluorescent and gold labels against actin are concentrated in the vicinity of the lateral membrane in the tight junction area. The results obtained can serve a confirmation of a hypothesis that at high glucose concentrations GLUT2 participates in its transfer across the apical membrane.

Animals↗

PubMed2004

[Immunocytochemical localization of vasopressin at its absorption by cells of rat small intestine].

Morpho-physiological characteristics of the transport of cyclic nonapeptide arginine vasopressin (AVP) across the rat intestinal epithelium was studied in experiments in vitro. A partial absorption of physiologically active AVP was followed when filling the isolated intestinal lumen by hormone solution. By methods of immunoelectron and immunofluorescence confocal microscopy, using polyclonal anti-AVP antibodies, cytoplasmic localization of AVP label was shown in enterocytes. The AVP label was also observed in the intercellular space in the basal area of epithelium. No label was revealed in the intercellular junctions, and no predominant label accumulation was found in any cytoplasmic structures of the epithelial cells. The obtained results are considered as evidence for the transcellular pathway of partial AVP absorption in rat small intestine.

Animals↗

PubMed2003

[Structural and functional analysis of glucose adsorption at high maltose concentrations in the rat small intestine in vivo].

To elucidate the mechanism of glucose absorption at high substrate concentrations, we studied structural and ultrastructural peculiarities of enterocytes arranged at different levels along the intestinal villus. The preparations were obtained from an isolated segment of the rat small intestine after its perfusion with maltose solutions with both low (25 mM) and high (100 mM) concentrations, respectively. Under conditions of chronic experiment at high substrate concentration, an enlargement of intercellular clefts, indicating glucose absorption, occurred in deeper areas of the villus. Besides, also in chronic experiment, we studied kinetics of maltose hydrolysis and derived glucose absorption in the isolated segment of the rat small intestine after its perfusion with maltose at superhigh (up to 200 mM) initial concentrations. Based on these data, a conclusion is made that active transport is the main mechanism of absorption of glucose derived from maltose hydrolysis, operating both at low disaccharide concentrations, and in the range of its superhigh (up to 200 mM) concentrations.

Animals↗

PubMed2002

[Microtubule dynamics in epithelial cells].

Microtubules (MTs) are necessary components of all eukaryotic cells. They fulfill various functions being involved in cell division, ciliar and flagellar beating, cell shape maintaining, organelle distribution in the cell, organization of other cytoskeletal elements. Dynamic features of MTs have been commonly studied in vitro or on undiffirentiated cultured cells by means of molecular and ultrastructural methods. It is generally accepted that the phenomenon of dynamic instability is the major mechanism of MT turnover in the cell. MTs radiate from the centrosome and take part in the distribution of cell organelles. In addition, epithelial, nerve, and skeletal muscle cells contain non-centrosomal MTs. A few hypothesis of their origin have been so far put forward. According to the capture-release hypothesis, MTs are first nucleated on the a centrosome, then release to be driven in various parts of the cell by molecular motors. Some alternative mechanisms of non-centrosomal MT formation are also proposed in literature. For example, the nucleation sites were reported not only in centrosomes but also in other parts of cells, such as the apical membranes of epithelial cells, the nuclear membrane of muscle cells, pigment granule aggregates of melanophores. On studying frog urinary bladder and large intestine epithelial cells the authors observed in these cells numerous non-centrosomal MTs. This makes epithelial cells, good models for analysing structural and dynamic features of non-centrosomal MTs in differentiated cells. For the urinary bladder the pool of specific granules may serve as MT organizing centers. Non-cenrosomal MTs of these cells have big diameters (35-38 nm) and form bundles oriented in the apical-basal axis of the cell. In addition, non-centrosomal MTs of these cells may participate in the transport of specific granules and giant vacuoles that appear under stimulated water flows through the cell.

Animals↗

PubMed2001

[Electron microscopic study of colonic epithelial cells from the grass frog Rana temporaria under different intensity of water absorption].

Three cell types have been revealed in the epithelium of the frog large intestine: granular, mitochondria-rich, and mucosal cells. Under a low water permeability (0.12 +/- 0.10 mkl/(min.cm2)) the distribution of intramembrane particles (IMP) in the apical cell membrane was the same as in the most cell plasma membranes studied with freeze-fracture method. Under rising osmotic permeability and water absorption (0.43 +/- 0.05 mkl/(min.cm2)) the IMP distribution did not change. In these conditions, the quantity of fusion sites between granule membranes and the apical membrane increased, and the intercellular spaces in basolateral epithelial region were diluted. A a low water permeability, in addition to usual microtubules, bundles of noncentrosomal microtubules with associated osmiophilic globules were revealed. A comparative analysis has been made of the present evidence and previously obtained data on the frog urinary bladder epithelium.

Animals↗

PubMed2000

[Ultrastructure and elemental composition of frog bladder granular epithelial cells in normal state and upon stimulation of water transport].

Changes in the frog urinary bladder granular cell ultrastructure were analysed in parallel with those in element composition of these cells after induction of water transport across the urinary bladder wall. Two ultrastructural (ultrathin section and freeze-fracture) methods were used in addition to two methods of object preparation for electron microprobe analysis--freeze-drying and freeze-substitution. It has been shown that arginin-vasotocin stimulation of osmotic water flow across the urinary bladder wall causes certain morphological changes in the granular cells: decrease in electron density of the cytoplasm, depolymerization of the apical submembrane layer of actin microfilaments, increase in the number of sites of specific granules and apical membrane fusion, emergency of intramembrane particle aggregates in the apical membrane P-face. The quantitative electron microprobe analysis made it possible to reveal a statistically significant increase in sodium and calcium concentration and fall in that of potassium and chlorine in granular cells after water transport stimulation. A concentration gradient of sodium and potassium ions was seen to appear along the apical-basal axis in the cytoplasm of granular cells. Possible association between the obvious morphological transformations in granular cells and changes in their elemental composition has been discussed, in addition to some regulatory significance of calcium concentration increase in granular cells after arginin-vasotocin-induced osmotic water transport.

Animals↗

PubMed1999

[Electron-microscopic and immunohistochemical study of the reorganization of the microtubule system in granular cells of frog urinary bladder after water transport induction].

Structural changes in organization of the microtubule system in granular cells of frog urinary bladder after water transport induction by vasopressin were studied by methods of electron microscopy and immunocytochemistry. It is shown that in steady-state conditions microtubules form a wide network equally distributed in the whole cytoplasm of granular cells. After vasopressin action, the amount of microtubules increases in the apical region of the cytoplasm. A predominant orientation of microtubules, perpendicular to the apical membrane direction, appears. A structural association of microtubules with specific granules and large vacuoles was observed. A supposition is advanced about association of the described microtubule system reorganization with the activation of vectorial intracellular transport occurring after transepithelial water transport induction.

Animals↗

PubMed1999

[Aquaporins of plasma membranes of epithelial cells].

The early 90s have brought us a discovery of a new class of membrane proteins--aquaporins with a function of transmembrane water channels. Being genetically closed proteins aquaporins are members of a large family of channel-forming proteins called MIPs (major intrinsic proteins). All aquaporins, except AQP4, are mercury-sensitive. Many aquaporins have been cloned and identified. Polyclonal antibodies grown against some of them promoted numerous studies of aquaporin localization and distribution in animal and plant tissues. Up to the present, 10 and 2 aquaporins have been described in mammalian and amphibian epithelial tissues, respectively. One of described aquaporins, AQP2, whose localization is confined to kidney collecting duct principal cells, has been found to be a hormone-depending water channel. The insertion of apical vesicles bearing AQP2 was shown to be regulated by vasopressin, meanwhile all other aquaporins are inserted into the plasma membrane constitutively. There is a vast evidence showing that the integrity of microtubules is necessary for both pathways of aquaporin insertion. AQP2 is important for normal kidney functioning and AQP2 mutations cause water-balance disorders. On the contrary, the AQP1 mutations are not accompanied by any evident clinical pathology. This review is focused on a discussion of the data so far available on aquaporin distribution in different animal tissues.

Animals↗

PubMed1998

[Current concept of structure and function of the Golgi apparatus. On the 100-anniversary of the discovery by Camillo Golgi].

The paper is a brief review of the current data on the structure and function of the Golgi apparatus since its discovery till the recent investigations, including the works published in 1997. Apart from reviewing the electron microscopy level of the structure of the Golgi apparatus, the data are considered on its molecular and supramolecular organization. The paper analyses critically the proposed mechanisms of the intracellular transport of proteins and their processing and modifications in the Golgi apparatus both in terms of the vesicular theory and in a model based on the gradual maturation of the cis-cistern and its transformation to the trans-cistern (i.e. its propagation from one pole to the other, a so-called "progression"). Experimental data are described, which disagree with the current models of the intracellular transport. Based on the literature and authors' own data, a modified model of the intracellular transport is proposed. This model eliminates, to a degree, the contradictions present in the models discussed above.

Cell Biology↗

PubMed1998

[Invasion of Escherichia coli A2 induces reorganization of actin microfilaments in Hep-2 cells].

Bacteria of spontaneously isolated non-pathogenic strain E. coli A2 have been previously shown to produce a new proteinase, referred to as protease ECP 32, which specifically cleaves actin (Khaitlina et al., 1988; Matveyev et al., 1996). Similar proteinase activity was found in revertants of Shigella flexneri L-forms. In this work immunofluorescence and electron microscopy were used to address a question of whether E. coli A2 can invade epithelial cells similarly as it has been demonstrated for Sh. flexneri. Infection of Hep-2 cells with E. coli A2 resulted in bacterial invasion of the cells followed by cytoskeleton reorganization. On one end of intracellular bacteria bundles of actin filaments resembling a comet-like tail were observed. Bacteria of referent strain CCM 5172, not producing protease ECP 32, were not taken up by the cells. These data suggest that protease ECP 32 may be involved in the process of bacterial invasion and cytoskeleton reorganization.

Actins↗

PubMed1997

[Structural rearrangements of microfilaments and granular cells of the frog bladder during induction of water transport: fluorescent microscopic, immunocytochemical and electron microscopic studies].

The structural reorganization of actin cytoskeleton of the frog urinary bladder granular cells, in the process of vasopressin-induced water transport, was studied by fluorescent and electron microscopy, and immunocytochemistry. A significant decrease in density of actin microfilament network under the apical membrane was observed after water transport stimulation. Microfilaments were associated with membranes of large vacuoles emerging in granular cells of vasopressin-treated urinary bladders. A supposition is advanced concerning functional heterogeneity of actin filaments in granular cells.

Actin Cytoskeleton↗

PubMed1997

[Analysis of rat enterocyte ultrastructure during glucose absorption].

Electronmicroscopic study of rat enterocytes under glucose load (10-40 mM) has shown some changes of their structure: aggregations of intramembrane particles of the apical membrane in the microvilli region, the dilitation of lateral intercellular spaces below tight junction, the condensation of actin near tight and intermediate junctions. The presence of these changes and almost absolute absence of destructions in tight junctions organization indicate that the main pathway of the isotonic fluid containing glucose across leaky epithelium of rat small intestine is a transcellular one.

Animals↗

PubMed1996

[The ultrastructural characteristics of the epithelial cells in the frog bladder under the action of vasopressin and in a vasopressin-independent increase in permeability for water].

In experiments on isolated frog urinary bladders it has been found that the low basal level of water permeability in the absence of arginine-vasopressin (AVP) could be significantly increased when the serosal solution was changed several times every 15 min for a fresh Ringer solution. The electron microscopic study of these cells by the freeze-fracture technique showed that the enhancement of water permeability by AVP-independent manner was related to the appearance of intramembranous particle aggregates in luminal membrane of granular cell, that are usually observed only under the action of AVP. The immunocytochemical experiments with monoclonal antibodies against actin revealed the similarity in intracellular actin distribution under the action of AVP and AVP-independent increase of water permeability.

Animals↗

PubMed1996

[An ultrastructural study of the apical cytoskeleton of the epithelial cells in the frog bladder with an ADH-dependent and an ADH-independent increase in osmotic permeability].

Immunocytochemical methods of electron and confocal microscopy were applied for studying the primembrane actin cytoskeleton in the frog urinary bladder granular cells, following the two actions: under the increased vasopressin-induced water permeability, and following autacoid removal by multiple changes of the Ringer solution around the serosa. In both cases similar changes have been revealed in the structure of the apical cytoskeleton and, in addition, a decrease in the density of its actin filament distribution was noticed.

Animals↗

PubMed1995

[A morphofunctional analysis of the changes in the Golgi apparatus in the epitheliocytes of the frog bladder under conditions of the vasopressin stimulation of water transport].

Structural and chemical peculiarities of the Golgi apparatus elements in granular cells of the normal frog urinary epithelium and under vasopressin stimulation of water transport have been studied with different electron microscopic methods: standard chemical fixation, prolonged osmification, freeze-substitution, freeze-fracture, immunocytochemistry, and electron-probe X-ray microanalysis. The structure of the main Golgi elements and its derivatives in normal cells and under the stimulation of water transport has been described. The association of microtubules with the Golgi cisternae was shown. Microtubules are supposed to participate in the support of integrity of the Golgi complex (in normal cells). Under stimulated water transport, depolymerization of microtubules seems to occur, resulting eventually in the Golgi fragmentation. Participation of some specific granules, that are the Golgi derivatives, in the increase of apical membrane water permeability has been shown as the insertion of water channels. Besides, under big water flows, the Golgi cis-cisternae were shown to participate in the formation of large vacuoles containing low potassium. A supposition is put forward that these vacuoles may perform an osmoregulative function in the cell, similar to that of contractile vacuoles of Protozoa.

Animals↗