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Biomedical subjects

A Mironov

Publications and source records attributed to A Mironov.

At least 19 recordsLinked to original sources
PubMed2006

Cerebrospinal fluid dynamics between the intracranial and the subarachnoid space of the optic nerve. Is it always bidirectional?

CSF is thought to flow continuously from the site of production in the ventricles into interconnected spaces; i.e. cisterns and subarachnoid spaces (SASs). Since the SAS of the optic nerve is defined by a cul-de-sac anatomy, it is not evident how local CSF might recycle from that region to the general SAS. The concept of free communication of CSF has recently been challenged by the description of a concentration gradient of beta-trace protein, a lipocalin-like prostaglandin d-synthase (L-PGDS), between the spinal CSF and that in the SAS of the optic nerve, indicating diminished local clearance or local overproduction of L-PGDS here. In fact, computed cisternography with a contrast agent in three patients with idiopathic intracranial hypertension and asymmetric papilloedema demonstrate a lack of contrast-loaded CSF in the SAS of the optic nerve despite it being present in the intracranial SAS, thus suggesting compartmentation of the SAS of the optic nerve. The concept of an optic nerve compartment syndrome is further supported by a concentration gradient of brain-derived L-PGDS between the spinal CSF and the CSF from the optic nerve SAS in the same patients.

Adult↗
PubMed2003

[Cerebral metastasis in choriocarcinoma a case report].

Choriocarcinoma are malignant neoplastic tumors from the trophoblastic tissue with a tendency to early metastases. Beside pulmonary metastases there are often cerebral metastases, leading to intracerebral hemorrhage often responsible for the first clinical symptoms. In young women, symptoms like vaginal or pulmonary bleeding or neurologic disturbances shortly after a hydatiform mole or a normal pregnancy, accompanied by high levels of HCG in serum and CSF, choriocarcinoma should be considered. Choriocarcinoma are very sensitive to chemotherapy, which consists--depending on the stage of the disease--of a mono- or polychemotherapy. Cure rates are high, even in extended stages with cerebral metastases--as in the case described. Brain metastases with or without oncotic aneurysms can be rapidly controlled by immediate whole brain irradiation. Surgical interventions may be necessary in the case of life threatening bleedings. Levels of HCG in serum and cerebrospinal fluid are good markers to control the effect of therapy. But--as shown in this patient--levels of HCG in CSF may decrease protracted without affecting prognosis. Oncotic aneurysms are rarely reported and mostly detected post mortem. The presented case leads to a more optimistic attitude and demonstrates efficacy of immediately started radio- and chemotherapy.

Adult↗
PubMed2001

The GM130 and GRASP65 Golgi proteins cycle through and define a subdomain of the intermediate compartment.

Integrating the pleomorphic membranes of the intermediate compartment (IC) into the array of Golgi cisternae is a crucial step in membrane transport, but it is poorly understood. To gain insight into this step, we investigated the dynamics by which cis-Golgi matrix proteins such as GM130 and GRASP65 associate with, and incorporate, incoming IC elements. We found that GM130 and GRASP65 cycle via membranous tubules between the Golgi complex and a constellation of mobile structures that we call late IC stations. These stations are intermediate between the IC and the cis-Golgi in terms of composition, and they receive cargo from earlier IC elements and deliver it to the Golgi complex. Late IC elements are transient in nature and sensitive to fixatives; they are seen in only a fraction of fixed cells, whereas they are always visible in living cells. Finally, late IC stations undergo homotypic fusion and establish tubular connections between themselves and the Golgi. Overall, these features indicate that late IC stations mediate the transition between IC elements and the cis-Golgi face.

Animals↗
PubMed2001

Influence of the substitution of 3-vinyl by 3-formyl group on the photodynamic properties of chlorin P6: molecular, cellular and in vivo studies.

Molecular in vitro and in vivo properties of 3-devinyl-3-formylchlorin p6 (FCp6) were examined in order to characterize this derivative as a new prospective photosensitizer. The long-wavelength absorption maximum of FCp6 was 690-696 nm (depending on environment). FCp6 was found to bind readily to membranous structures and form complexes with some proteins. The dye was associated with the plasmalemma and distributed rather diffusely along the cytoplasm with ca a three-fold higher accumulation within mitochondria in A549 human adenocarcinoma cells. The spectral analysis revealed that the major part of FCp6 was bound to membranes within cells. The membrane-bound FCp6 was shown to generate singlet oxygen efficiently. The average cytoplasmic concentration of FCp6 in A549 cells achieved ca 80% of its extracellular concentration in complete medium. The dye was characterized by a very fast efflux (16-fold decrease in 2 h). The ex vivo analysis of FCp6 fluorescence in mice revealed that the maximal dye content in blood, tissues, organs and tumor was achieved in less than 1 h after injection, followed by a considerable (ca six-fold) decrease during the next 23 h and a long-term persistence at low level. A preferential accumulation of FCp6 in subcutaneously implanted Ehrlich carcinoma along with its higher retention level comparing to the surrounding skin and muscles were observed in mice treated with different dye doses. In vitro cytotoxic assays with A549 and Raji B-cell lymphoma cells as well as in vivo analyses using Ehrlich carcinoma in mice revealed the very low toxicity of FCp6 without light irradiation and the significant photodynamic activity of this compound.

Humans↗
PubMed1999

CtBP/BARS induces fission of Golgi membranes by acylating lysophosphatidic acid.

Membrane fission is essential in intracellular transport. Acyl-coenzyme As (acyl-CoAs) are important in lipid remodelling and are required for fission of COPI-coated vesicles. Here we show that CtBP/BARS, a protein that functions in the dynamics of Golgi tubules, is an essential component of the fission machinery operating at Golgi tubular networks, including Golgi compartments involved in protein transport and sorting. CtBP/BARS-induced fission was preceded by the formation of constricted sites in Golgi tubules, whose extreme curvature is likely to involve local changes in the membrane lipid composition. We find that CtBP/BARS uses acyl-CoA to selectively catalyse the acylation of lysophosphatidic acid to phosphatidic acid both in pure lipidic systems and in Golgi membranes, and that this reaction is essential for fission. Our results indicate a key role for lipid metabolic pathways in membrane fission.

Acyl Coenzyme A↗
PubMed1999

Starts of bacterial genes: estimating the reliability of computer predictions.

Exact mapping of gene starts is an important problem in the computer-assisted functional analysis of newly sequenced prokaryotic genomes. We describe an algorithm for finding ribosomal binding sites without a learning sample. This algorithm is particularly useful for analysis of genomes with little or no experimentally mapped genes. There is a clear correlation between the ribosomal binding site (RBS) properties of a given genome and the potential gene start prediction accuracy. This correlation is of considerable predictive power and may be useful for estimating the expected success of future genome analysis efforts. We also demonstrate that the RBS properties depend on the phylogenetic position of a genome.

Algorithms↗
PubMed1999

Molecular cloning and functional characterization of brefeldin A-ADP-ribosylated substrate. A novel protein involved in the maintenance of the Golgi structure.

Brefeldin A (BFA) is a fungal metabolite that disassembles the Golgi apparatus into tubular networks and causes the dissociation of coatomer proteins from Golgi membranes. We have previously shown that an additional effect of BFA is to stimulate the ADP-ribosylation of two cytosolic proteins of 38 and 50 kDa (brefeldin A-ADP-riboslyated substrate (BARS)) and that this effect greatly facilitates the Golgi-disassembling activity of the toxin. In this study, BARS has been purified from rat brain cytosol and microsequenced, and the BARS cDNA has been cloned. BARS shares high homology with two known proteins, C-terminal-binding protein 1 (CtBP1) and CtBP2. It is therefore a third member of the CtBP family. The role of BARS in Golgi disassembly by BFA was verified in permeabilized cells. In the presence of dialyzed cytosol that had been previously depleted of BARS or treated with an anti-BARS antibody, BFA potently disassembled the Golgi. However, in cytosol complemented with purified BARS, or even in control cytosols containing physiological levels of BARS, the action of BFA on Golgi disassembly was strongly inhibited. These results suggest that BARS exerts a negative control on Golgi tubulation, with important consequences for the structure and function of the Golgi complex.

ADP-Ribosylation Factors↗
PubMed1999

Platelet contribution to leukotriene production in inflammation: in vivo evidence in the rabbit.

The contribution of platelets to arachidonic acid transcellular metabolism may represent an important pathway of leukotriene (LT) production. The aim of this study was to investigate the role of platelets on LT production in an acute inflammatory model in the rabbit. Preliminary experiments showed that rabbit whole blood (5 ml) stimulated in vitro with the calcium ionophore A23187 produced LTB4 (52.7+/-13.9 ng) and the mixed 5,12-DiHETE (7.25+/-0.75 ng). In A23187-stimulated thrombocytopenic blood, LTB4 was significantly reduced to 19.5+/-8.6 ng and 5,12-DiHETE was undetectable. Peptido-LTs were undetectable in both conditions. In experiments using washed cells, addition of thrombin-activated platelets to fMLP-activated PMN resulted in the appearance of 5,12-DiHETE and in more than twofold increase of LTB4 synthesis. When 3H-arachidonic acid-labelled platelets were mixed with unlabelled PMN and challenged with fMLP and thrombin, radioactive LTB4 and 5,12-DiHETE were produced, indicating that platelet-derived arachidonic acid was utilized by PMN 5-lipoxygenase. Intravenous infusion of fMLP (2.5 nmol/kg/min) in the rabbit induced marked granulocytopenia, thrombocytopenia and increased TxB2 plasma concentrations within 3 min. Electron microscopy of lungs showed morphologically activated and aggregated platelets occluding the capillary lumen. Activation and recruitment of circulating cells was accompanied by the production of LTB4 (peak levels at 1 min: 30.0+/-9.5 ng/ml) and LTE4 (peak levels at 10 minutes: 77.8+/-11.6 ng/ml). The areas under the blood concentration-time curve (AUC, ng min/ml) corresponded to 812+/-182 and 3692+/-658 for LTB4 and LTE4, respectively. In immunologically thrombocytopenic rabbits, the AUC for LTB4 (86.0+/-23.0) and LTE4 (1165+/-542) were both significantly different from controls while in rabbits treated with an anti-leukocyte antiserum, both LTB4 and LTE4 were similar to controls. This experimental model provides in vivo evidence that platelets, involved in an acute inflammatory event contribute to the transcellular production of LTs.

Animals↗
PubMed1999

Role of brefeldin A-dependent ADP-ribosylation in the control of intracellular membrane transport.

The fungal toxin brefeldin A (BFA) dissociates coat proteins from Golgi membranes, causes the rapid disassembly of the Golgi complex and potently stimulates the ADP-ribosylation of two cytosolic proteins of 38 and 50 kDa. These proteins have been identified as the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and a novel guanine nucleotide binding protein (BARS-50), respectively. The role of ADP-ribosylation in mediating the effects of BFA on the structure and function of the Golgi complex was analyzed by several approaches including the use of selective pharmacological blockers of the reaction and the use of ADP-ribosylated cytosol and/or enriched preparations of the BFA-induced ADP-ribosylation substrates, GAPDH and BARS-50. A series of blockers of the BFA-dependent ADP-ribosylation reaction identified in our laboratory inhibited the effects of BFA on Golgi morphology and, with similar potency, the ADP-ribosylation of BARS-50 and GAPDH. In permeabilized RBL cells, the BFA-dependent disassembly of the Golgi complex required NAD+ and cytosol. Cytosol that had been previously ADP-ribosylated (namely, it contained ADP-ribosylated GAPDH and BARS-50), was instead sufficient to sustain the Golgi disassembly induced by BFA. Taken together, these results indicate that an ADP-ribosylation reaction is part of the mechanism of action of BFA and it might intervene in the control of the structure and function of the Golgi complex.

Adenosine Diphosphate Ribose↗
PubMed1999

Morphological features of regeneration of rabbit aortic endothelium after cryoinduced vascular damage.

Regeneration of endothelium after damage is an important factor, which limits the development of atherogenesis. This study examines the topographical characteristics of regenerating endothelial cells (EC) in rabbit aorta after de-endothelialization by cryodestruction. The effects of cloricromene on these processes were also studied. Vessels were harvested from 6-month-old NZW rabbits, 1 and 3 days after cryodestruction. The vessels were evaluated using scanning electron microscopy (SEM). One day after cryodestruction, there were defects in the endothelial monolayer in the zone of injury in saline treated animals. Large numbers of platelets and monocytes were observed in association with endothelium in the damaged zone. Three days after de-endothelialization the size of the area of the damage had decreased. On the surface of the new endothelial layer and below this defect, the number of adhering monocytes was increased, and many microdefects between endothelium could be seen. Administration of cloricromene for 1 or 3 days after damage reduced the number of endothelium-adherent platelets and monocytes, and microdefects in endothelium. The feature of endothelial repair in rabbits is a relatively large involvement of monocytes and platelets, which are visible below regenerated endothelium. Administration of cloricromene essentially restored re-endothelialization and significantly decreased the number of adherent monocytes and microdefects in the new endothelium.

Animals↗
PubMed1998

Combining diverse evidence for gene recognition in completely sequenced bacterial genomes.

Analysis of a newly sequenced bacterial genome starts with identification of protein-coding genes. Functional assignment of proteins requires the exact knowledge of protein N-termini. We present a new program ORPHEUS that identifies candidate genes and accurately predicts gene starts. The analysis starts with a database similarity search and identification of reliable gene fragments. The latter are used to derive statistical characteristics of protein-coding regions and ribosome-binding sites and to predict the complete set of genes in the analyzed genome. In a test on Bacillus subtilis and Escherichia coli genomes, the program correctly identified 93.3% (resp. 96.3%) of experimentally annotated genes longer than 100 codons described in the PIR-International database, and for these genes 96.3% (83.9%) of starts were predicted exactly. Furthermore, 98.9% (99.1%) of genes longer than 100 codons annotated in GenBank were found, and 92.9% (75.7%) of predicted starts coincided with the feature table description. Finally, for the complete gene complements of B.subtilis and E.coli , including genes shorter than 100 codons, gene prediction accuracy was 88.9 and 87.1%, respectively, with 94.2 and 76.7% starts coinciding with the existing annotation.

Algorithms↗
PubMed1998

A synthetic model of intra-Golgi traffic.

We present a hypothesis on the mechanisms used by cells to transport cargo through the secretory system. We propose that at least three basic processes coordinately participate in membrane traffic: cisternal maturation-progression, controlled cargo diffusion along transient membrane continuities between different compartments, and a mostly retrograde vesicle-mediated transport. A 'synthetic' model based on the combination of these mechanisms can explain both the progression of supramolecular aggregates through the secretory pathway and the fast intra-Golgi transport of conventional cargoes. Analysis of the existing literature shows that the available data are consistent with the proposed model.

Endoplasmic Reticulum↗
PubMed1998

Selective transvenous embolization of dural fistulas without occlusion of the dural sinus.

Two patients with dural arteriovenous fistulas (DAVFs) and unsuccessful transarterial embolizations were treated with a technique for selective transvenous embolization. A 5F catheter was advanced from a femoral vein access into the internal jugular bulb and a catheter was navigated through the sinus lumen into the involved cortical veins or the parasinusal venous draining channels of the DAVFs. The venous recipients at the nidal level of the DAVFs were occluded by fibered platinum coils. Complete angiographic cure was effected in both patients, with occlusion of the venous recipients and the nidus, although the sinus segments next to the nidus of the DAVFs remained patent. Placement of coils in a transsinusal route into the venous channel of a DAVF yet outside the sinus lumen can result in complete obliteration of the fistula without damage to the physiological function of the dural sinuses.

Aged↗
PubMed1998

Cryodamage of the vessel wall accelerates the development of atherosclerotic lesions in arterial vessels of Watanabe hyperlipidemic rabbits.

In the present study we developed an experimental model, resembling human atherosclerosis, by removing the endothelial layer in Watanabe heritable hyperlipidemic (WHHL) rabbits (10 months old) by application of cryodamage on the external surface of arterial vessels. In age-matched New Zealand white (NZW) rabbits, used as control, after two months following cryodamage, carotid artery and infrarenal segments of abdominal aorta did not show any particular change in the ultrastructure of vessel wall. In WHHL rabbits, two months after cryodamage, atherosclerotic lesions (fatty streaks and fibrous plaques) were observed in both arteries. Many lipid-laden endothelial cells, subendothelial foam cells and smooth muscle cells were found in cryodamaged areas. In some areas, the cap of plaques appeared to be thinned and ruptured. Increased number of collagen and elastic fibrils was also observed in atherosclerotic regions. We conclude that this simple technique on WHHL rabbits provides a model of atherosclerosis with a high degree of morphological similarity between the artificially-induced plaque and human atherosclerotic plaque.

Animals↗