Search

Ultrastructural studies of the hippocampus and the prefrontal cortex of rats were performed 7, 30, and 50 days after their damage by neurotoxicant trimethyltin chloride (TMT). Significant damage to neurons was observed in both brain structures. In the hippocampus, a large number of autophagosomes (0.9±0.1 per μm2) appeared in the soma of neurons, dendrites, and axons in 7 days after intoxication. In addition, we observed the appearance of hyperchromic neurons with abnormal structure of mitochondria. In the prefrontal cortex, damaged neurons also contained autophagosomes, but their number was significantly lower (0.3±0.1 per μm2). The number of autophagosomes decreased with increasing the time after TMT administration: 30 days after injection, the content of autophagosomes in the hippocampus was 0.10±0.01 per μm2, while in the prefrontal cortex, autophagosomes were no longer found. We hypothesized that autophagy in the hippocampus was not effective enough to prevent neuronal death caused by the neurotoxicant. [ABSTRACT FROM AUTHOR]

The deposition of beta-amyloid (Aβ) in the brain is detected in Alzheimer's disease and during ageing. Until now, ultrastructural studies of changes caused by Aβ in the dentate gyrus are very scarce. The effects of Aβ 1-42 injection into the CA1 field of rat hippocampus were studied by electron microscopy. In 2 weeks after injection of aggregated Aβ in low concentrations, destructive changes were seen in the structure of dentate gyrus cells, which consisted in a decrease in the number of dentate gyrus neurons and axo-dendritic synapses. These changes were accompanied by enlargement of the endoplasmic reticulum cisterns and widening of the active zones of synapses. Thus, injection of aggregated Aβ 1-42 into the hippocampus led to irreversible (a decrease in the number of neurons and axo-dendritic synapses, agglutination of synthetic vesicles) and adaptive changes (an increase in the sizes of endoplasmic reticulum cisterns and active zones of synapses) in dentate gyrus neurons aimed at the maintenance of functional activity of the nervous system. [ABSTRACT FROM AUTHOR]

The effect of the anti-inflammatory cytokine IL-10 on the ultrastructural distribution of AMPA receptor GluR1 subunit in CA1 field of cultured hippocampal slices was studied by using immunohistochemical technique. It was found that long-term posttetanic potentiation increased the content of GluR1 in the postsynaptic density of the axo-spinous synapse. Addition of IL-10 in concentrations of 1 and 10 ng/ml to the medium facilitated long-term posttetanic potentiation thereby changing the distribution of GluR1 in the spine: the number of receptors increased in the cytoplasm and decreased in the postsynaptic density. It is assumed that activation of neuronal IL-10 receptors affects the distribution of AMPA receptors in axo-spinous synapses of hippocampal field CA1 through interplay of intracellular signaling pathways, thereby participating in the mechanisms of synaptic plasticity under normal conditions. [ABSTRACT FROM AUTHOR]

Ultrastructure of the neuropil of the brain oculomotor nuclei was studied in mice after 30-day exposure to microgravity on Bion-M1 biosatellite and after 13-h exposure to Earth gravity. The number of axo-dendritic synapses in the neuropil of the oculomotor nucleus significantly decreased after the flight. Degenerated axon terminals containing conglomerates of presynaptic vesicles appeared. The number of synapses with high functional activity increased and the length of active zones of the axo-dendritic synapses significantly increased. The observed ultrastructural changes of the neuropil of the oculomotor nuclei of mice exposed to microgravity reflect the development of long-term deafferentation of the analyzed brain structures. These changes in the neuropil ultrastructure can determine the disturbances in the oculomotor system, e.g. development of atypical nystagmus under conditions of microgravity. [ABSTRACT FROM AUTHOR]

We performed ultrastructural study of cerebral cortex mitochondria in rats with different tolerance to oxygen deficiency (low resistant and highly resistant specimens). Low resistant rats were characterized by the prevalence of mitochondria with lightened matrix due to the nondense packing of cristae. By contrast, mitochondria of highly resistant animals had the dense packing of cristae. The structure of mitochondria underwent adaptive changes at 14-10% O in the inspired air. Under these conditions, structural characteristics of the cerebral cortex in hypoxia-sensitive rats resembled those in resistant animals. The decrease in O concentration to 8% was accompanied by ultrastructural signs of mitochondrial damage, which correlated with de-energization of the cell and dysfunction of adaptive signaling systems. Ultrastructural features of cerebral cortex mitochondria in animals with low and high tolerance to acute oxygen deficiency confirm the hypothesis that they are associated with two different 'functionaland-metabolic portraits'. [ABSTRACT FROM AUTHOR]

The intracellular localization and distribution of the ROMK protein in rat liver and heart was studied by the electron microscopy of ultrathin sections using the antibodies against the ROMK channel protein, one of the contenders for the role of mitochondrial ATP-dependent potassium channel. In rat heart and liver tissues, the ROMK protein is localized on the membranes of mitochondrial cristae but differently distributed in hepatocytes and cardiomyocytes. In hepatocytes, colloidal gold particles were rather evenly distributed on the membranes of mitochondrial cristae. In cardiomyocytes, the number of granules was considerably lower than in hepatocytes, and they were also localized on the membranes of mitochondrial cristae and confined only by the center of these organelles. [ABSTRACT FROM AUTHOR]

A technique for detection of staphylococcal enterotoxin A with sandwich enzyme-linked immunoassay (ELISA) was developed. Mouse monoclonal anti-SEA antibodies were used as capture antibodies and phage displayed anti-SEA scFv were used as detection antibodies. The limit of detection was 6-12.5 ng/mL for different pairs of antibodies. Some conditions of phage-displayed antibodies for storage in dissolved and lyophilized state were examined. It was shown the use of trehalose and arginine preserved the functional activity of phage-displayed antibodies. [ABSTRACT FROM AUTHOR]

The electron microscopic study of thin sections of rat liver and heart using commercial specific antibodies against KIR.6.2 and secondary antibodies conjugated with colloidal gold was performed. It was found that the gold-labeled protein is localized in mitochondria of cardiomyocytes and hepatocytes but not in rough and smooth endoplasmic reticulum of hepatic cells and myofibrils of myocardium. In rat heart and liver mitochondria, the gold label was mainly located in mitochondrial cristae and was not found in mitochondrial matrix and intermembrane space. The data indicate that in heart and liver mitochondria there exists a protein similar in structure to the channel-forming subunit of a cytoplasmic potassium channel, KIR6.2. This is also supported by the presence of common modulators of cytoplasmic and mitochondrial ATP-dependent potassium channels. A possible role of the protein as a subunit of the mitochondrial ATP-dependent potassium channel is discussed. [ABSTRACT FROM AUTHOR]

Immunogold labeling was used to identify serotoninergic synapses of the chemical and mixed types on the ventral dendrite (VD) of Mauthner neurons (MN) in goldfish. These had the characteristic feature that they contained several mitochondria in the bouton and, apart from an active zone (AZ), had an obligatory desmosome-like contact (DlC). The AZ of these synapses generally contacted unlabeled chemical crested synapses, which in turn interacted directly with the VD. These latter synapses had virtually no mitochondria and lacked a DlC, such that they could be identified as inhibitory. This 'two-level' organization of excitatory serotoninergic and inhibitory synapses appears to be directly related to the reciprocal mechanism regulating the functional activity of MN via the visual apparatus. [ABSTRACT FROM AUTHOR]

Morphological studies showed that daily intraperitoneal injections of dopamine in doses of 10 and 10 M down-regulates the general number of cells in the Ehrlich ascites carcinoma in 10 and 30 times and decreases their diameter by 27% and 59%, respectively (as compared to the control animals received physiological saline). According to ultrastructural data these injections were followed by the abnormal changes in microvilluses, forming the specifi c moiré fringes in cytosol, thickening of cortical layer, and a signifi cant increase in fi lament reticulum density (actin fi bers) in tumor cells of treatment group specimens. We concluded that the oncocytotoxic effect of dopamine was related to the induced polymerization of cytosol actin. [ABSTRACT FROM AUTHOR]

Viability, histology and ultrastructure of normal cells and cells of different degrees of malignancy after interaction with dopamine as well as the ability of these cells and isolated G-actin in model experiments to stain by Falck technique were studied. It is shown that dopamine, virtually having no effect on the viability of the 'normal' non-tumorigenic transformed cells, noticeably reduces cell viability of slightly tumorigenic cells, causes a significant reduction in viability of attachable cancerous cells and a very significant decrease in cell viability of cancerous cells growing in suspension. The intensity of fluorescence of the cytosol in cells treated with dopamine, has been very high and varied in different cultures, and that of isolated actin directly depended on its concentration. Common to all cell morphological feature of damage from the action of dopamine and the putative substrate of fluorescence was actodopamine filaments network strands (identified on the structure and size), which appears in the cytosol loci, where they were absent in control. The data show that dopamine can be used as an oncotherapeutic remedy and diagnostic tool interacting with G-actin as a cellular target. [ABSTRACT FROM AUTHOR]

The possibility to reveal globular (G-) actin in cell cytosole by means of microscopy has been studied. The applicability of this method was in particular evaluated for diagnostics of malignant cells, whose main pathocytological feature is an anomalously high content of G-actin in cytosol. The cells of a common origin but with different states of cytosolic actin were analyzed by means of cytochemical reaction for biogenic amines using Falck-Hillarp method after 40-h incubation of the cells in dopamine-containing cultivation medium. Mouse embryo cell line BALB/3T3, clone A31 with differentiated actin cytoskeleton were used as a control cell line. The same cells infected with pathogenic virus SV-40 (cell line 3T3B-SV40) exhibited a malignant phenotype; their cytosol mainly consisted of G-actin. Manifold increase in fluorescence intensity of cytosol and karyoplasms, the loci with the highest G-actin concentration, was revealed in malignant cells in comparison with their healthy prototype. Thus, it was shown that G-actin of malignant cells is a diagnostic target for dopamine, which, as it was earlier shown, penetrates into the cytosol, polymerizes G-actin, incorporating into the filaments as integral component in the 100:1 ratio, and thus fluorescently labels G-actin due to conversion into isoquinoline by reaction with formaldehyde. Besides, dopamine exhibited a strong cytotoxicity that considerably reduced the viability of malignant cells. The data suggest that the content of Gactin in cytosol of living cells can be quantitatively estimated by fluorescence intensity of cytosol following incubation of the cells in dopamine-containing medium. [ABSTRACT FROM AUTHOR]

BHK-21 cells were incubated in medium containing dopamine (DA) and catecholamine contents were then measured using the Falck cytochemical method. As compared with controls, significant increases were seen in the fluorescence of cells and these were proportional to the concentration and duration of exposure to DA and more marked in cells in suspension than in attached cells. Parallel electron microscopic studies showed that the increased fluorescence intensity of the cytoplasm correlated with the presence of dense networks of fibrils which were identified on the basis of morphological characteristics as microfilaments consisting of F-actin. Prior blockade of dopaminergic receptors with haloperidol did not alter the subsequent effects of DA on fluorescence intensity or cell ultrastructure. These data suggest that, in conditions of chronic exposure, DA can penetrate into the cytoplasm, inducing actin polymerization and becoming bound to the newly formed actin cytoskeleton. Structurally, this can be apparent as hypertrophy of the cytoskeleton and its derivatives, with significant influences on the overall structure of the cell. [ABSTRACT FROM AUTHOR]

The interaction of dopamine with model membranes, isolated G-actin, and living cells, such as Mauthner neurons and fibroblast-like BHK-21 cells has been studied. It was found that in vitro dopamine passes through the phospholipid membrane and directly polymerizes G-actin due to incorporation into threads as their integral part. In in vivo conditions, it penetrates inside the cell and induces the appearance of a network of actin filaments in loci rich in globular actin. The data suggest that there exists a mechanism of dopamine interaction with living cells, which is based on direct polymerization of cytosolic G-actin as its cellular target. The reorganization of the actin cytoskeleton leads to changes in the morphofunctional status of cells. [ABSTRACT FROM AUTHOR]

The localization in cell of the protein forming in BLM the ATP-dependent potassium-selective channels was studied. The electron-microscopic investigation of rat liver and heart tissue sections after their incubation with Abs against the studied protein and visualization of the protein with secondary Abs conjugated with colloid gold were carried out. The colloid gold particles were observed both in mitochondrial membranes and in membranes of endoplasmic and sarcoplasmic reticulum. In heart mitochondria these particles were significantly greater then in liver mitochondria. The detection of the channel-protein localization both in mitochondria and reticulum, as well as structural similarity between the mitochondrial channel and the precursor of calreticulin suggests that the channel protein belongs to the calreticulin family. The possible function of the studied protein as a channel subunit of the mitochondrial ATP-dependent potassium channel is discussed. [ABSTRACT FROM AUTHOR]

We studied the effects of dopamine added to culture medium on survival of floating or adherent BHK-21 cells differing by organization of actin cytoskeleton. The viability of floating cells more drastically decreased with increasing dopamine concentration and duration of exposure than that of adherent cells. The cells worse adhered to the substrate and formed a monolayer. The formed monolayer degrades, cell borders become blurred, cells, polygonal in the control, are rounded. Preliminary blockade of dopamine receptors with haloperidol, inessential for cell survival and morphology, does not prevent the destructive effect of dopamine on the cells. Ultrastructural study revealed increased density of filamentous actin threads in deep compartments of cell cytoplasm after dopamine treatment, this increase being more pronounced in cells grown in suspension. Bearing in mind the polymerizing effect of dopamine on globular actin in vitro and the fact that the content of this protein in floating cells is higher than in adherent cells, we can conclude that the decrease in viability of BHK-21 cells is caused by interaction of dopamine with cytoplasmic globular actin. [ABSTRACT FROM AUTHOR]

The ultrastructure of a suspension or of adhered BHK-21 cells exposed to dopamine has been studied. It was found that ultrastructural modifications were observed mainly in cellular regions enriched in actin, including in intercellular desmosome-like contacts, microvilli, and under the membrane cortical layer. Desmosome-like contacts are hypertrophied with increased electron density and fibrillar bridges that appear in specialized contacts. Microvilli fused with each other and with plasma membrane of neighboring cells or were split up and penetrated by fibrils. The cytoplasm is filled with randomly arranged F-actin filaments and has a blotchy appearance. The effect of dopamine is more pronounced in nonattached cells with undifferentiated actin cytoskeletons than in spread cells with stress fibers. The blockage of the D2 receptor with haloperidol does not affect the ultrastructure of BHK-21 or dopamine induced modifications. The data obtained suggest direct interactions between dopamine and the actin cytoskeleton. [ABSTRACT FROM AUTHOR]

Some approaches for the elaboration of the method for immunocytochemical detection of labile protein on sections prepared from maize ( Zea mays L.) seedling tissues are outlined. The effects of severe chemical reagents applied during tissue pretreatment (fixatives, inhibitors of endogenous enzymes, solutions blocking nonspecific antibody binding) on labile protein immunoreactivity in extracts were assessed in preliminary experiments. The procedure was elaborated with a triple control, which provided for the lowest background staining on plant tissue sections and the high level of antibody specific binding. [ABSTRACT FROM AUTHOR]

We examined changes in the ultrastructure of afferent mixed synapses on the membrane of Mauthner neurons (M cells) of the goldfish, which were related to two functional states, long-term potentiation (LTP) of the electrotonic response (a model form of the memory trace) and adaptation (resistivity to fatigue resulting from long-lasting motor training and considered a natural form of the memory trace manifested on the neuronal level). LTP was induced in medullary slices using high-frequency electrical stimulation of the afferent input. Adaptation was produced using natural vestibular stimulation (everyday motor training, which modified motor behavior of the fish and function of the M cell). It was supposed that if the LTP phenomenon is involved in the formation of natural memory, both the adaptation and the LTP states should be accompanied by similar specific structural modifications. Indeed, it was found that in both cases the number of fibrillar bridges in the gaps of desmosome-like contacts (DLC) in the mixed synapses on the M cell surface demonstrated an about twofold increase. These bridges are known to include actin filaments, which function as conductors of cationic signals; thus, the LTP-related increase in the density of bridges corresponds to increased efficacy of electrotonic coupling via mixed synapses. Such a structural correlate of LTP, which probably has the same functional significance in mixed synapses of the “adapted” M cells, allows us to suppose that LTP is a natural property of the nervous system. The LTP-type intensification of the relay function of mixed synapses, which corresponds to adaptation, is probably a compensatory rearrangement allowing M cells to maintain some balance of the synaptic influences and, at the same time, to remain in a stable and plastic state; this is necessary for stable functioning under changing environmental conditions. [ABSTRACT FROM AUTHOR]