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Biomedical subjects

E Vassileva

Publications and source records attributed to E Vassileva.

11 recordsLinked to original sources
PubMed2003

Microembolic signals and carotid plaque morphology: a study of 71 patients with moderate or high grade carotid stenosis.

OBJECTIVES: To determine whether particular carotid plaque features on ultrasound are more likely to produce microembolic signals (MES). PATIENTS AND METHODS: We have reviewed 71 patients with moderate or high grade carotid stenosis established by ultrasound (30-99%). Plaque appearance was classified according to five subtypes. Transcranial monitoring of the middle cerebral arteries was performed on each patient. RESULTS: MES were more frequently encountered in patients with anechogenic/hypoechogenic plaques compared with isoechogenic/hyperechogenic lesions (P < 0.01). MES+ patients presented also more frequently an irregular surface of the plaque and more severe stenosis, however, the differences did not reach significance. There was no relationship between the presence of MES and a history of stroke or transient ischaemic attack (TIA). When considering the different above mentioned variables (logistic regression), only plaque morphology appeared to be a risk factor for the presence of MES. CONCLUSION: MES+ patients presented a significantly increased frequency of anechogenic/hypoechogenic plaques. As MES may be a marker of increased risk of stroke, the clinical significance of this particular association should be further investigated.

Aged↗
PubMed2001

Discussion of parameters associated with the determination of arsenic by electrothermal atomic absorption spectrometry in slurried environmental samples.

A slurry sampling-fast program procedure has been developed for the determination of arsenic in plants, soils and sediments by electrothermal atomic absorption spectrometry. Efficiencies of various single and mixed modifiers for thermal stabilization of arsenic and for a better removal of the matrix during pyrolysis step were compared. The influence of the slurry concentration, amounts of modifier and parameters of the pyrolysis step on the As integrated absorbance signals have been studied and a comparison between fast and conventional furnace programs was also made. The ultrasonic agitation of the slurry followed by a fast electrothermal program using an Ir/Mg modifier provides the most consistent performance in terms of precision and accuracy. The reliability of the whole procedure has been compared with results obtained after application of a wet digestion method with an HF step and validated by analyzing eleven certified reference materials. Arsenic detection and quantitation limits expressed on dry sample matter were about 30 and 100 micrograms kg-1, respectively.

Arsenic↗
PubMed2001

Advantages of the iridium permanent modifier in fast programs applied to trace-element analysis of plant samples by electrothermal atomic absorption spectrometry.

The application of a fast program combined with the advantages of the iridium permanent modifier is proposed for trace element analysis of plant samples by electrothermal atomic absorption spectrometry (ETAAS). For two volatile elements (Cd, Pb) and two mid-refractory elements (Cr, Ni) it was demonstrated that coating of the platform or of the tube atomization area with Ir is an efficient means of improving the accuracy and precision of results. A detailed study of interference from individual main matrix components and from composite plant matrices has confirmed the usefulness of the whole approach. The validity of the method has been confirmed by analysis of eight reference plant materials.

Iridium↗
PubMed2001

Application of high-surface-area ZrO2 in preconcentration and determination of 18 elements by on-line flow injection with inductively coupled plasma atomic emission spectrometry.

A flow-injection analysis (FIA) system incorporating a micro-column of ZrO2 has been used for the development of an on-line multi-element method for the simultaneous preconcentration and determination of Al, Bi, Cd, Co, Cr, Cu, Fe, Ga, In, Mn, Mo, Ni, Pb, Tl, V, Sb, Sn, and Zn by inductively coupled plasma atomic emission spectrometry (ICP-AES). The conditions for quantitative and reproducible preconcentration, elution, and subsequent on-line ICP-AES determination were established. A sample (pH 8) is pumped through the column at 3 mL min(-1) and sequentially eluted directly into the ICP-AES with 3 mol L(-1) HNO3. With a sample volume of 100 mL and an elution volume of 1 mL signal enhancement 100 times better than for conventional continuous aspirating systems was obtained for the elements studied. The reproducibility (RSD %) of the method at the 10 ng mL(-1) level in the eluate is acceptable - less than 8% for five replicates. Recoveries between 95.4% and 99.9% were obtained for the elements analysed. ZrO2, with a specific surface area of 57 m2 g(-1) and a capacity of approximately 5 mg g(-1) for the elements studied, was synthesized by hydrolysis of ZrCl4. The preconcentration system was evaluated for several simple synthetic matrices, standard water samples and synthetic seawater. The effect of foreign ions on the efficiency of preconcentration of the elements studied was investigated. The application of a micro-column filled with high-surface-area ZrO2 and flow injection inductively coupled plasma atomic emission spectrometry enables preconcentration and simultaneous determination of 18 elements at low concentrations (ng L(-1)) in different water samples.

Chlorides↗
PubMed1995

Changes in the neuronal plasma membrane during synaptogenesis.

During synaptogenesis the plasma membrane of neurons undergoes considerable changes and large portions of it develop to synaptic membranes. This transformation is brought about by biochemical and morphological changes. The aim of the present investigation was to study by morphological methods the in vivo changes of some basic components of the neuronal membranes during the early postnatal period, when active synaptogenesis occurs. The cerebral cortex of Wistar rats was used for preparation of either growth cones (up to postnatal day 10) or synaptosomes (postnatal days 14-30). Our studies were focused on the changes occurring in integral membrane proteins and cholesterol domains, and in certain carbohydrate residues and anionic sites. In the first days after birth relatively few intramembranous particles are found in the plasma membranes of growth cones, few and small cholesterol domains, scarce lectin-binding and anionic sites. During the following days there is a clear tendency for increase of the number of all of the studied structures until the appearance of typical synaptic membranes. Throughout the studied developmental period the protein and the cholesterol molecules were found to occupy distinct membrane domains. The structure of the developing neuronal membrane, poor on proteins and cholesterol, and its maturation to the fully functional synaptic membrane is discussed.

Age Factors↗
PubMed1994

Effect of some hydroxycoumarins on complement-mediated hemolysis in human serum.

Coumarin derivatives are known to possess antiinflammatory and antimetastatic properties due to their direct action on cells, predominantly on macrophages. In the present study the interactions between esculin, esculetin, fraxin, fraxetin, as well as their acetylated and methylated derivatives and non-cell system participating in inflammatory processes, comprised of serum complement proteins, were investigated in vitro. 7-Methylesculin, esculin 5Ac and esculetin 2Ac exhibited good inhibition on classical pathway (CP) activity and scoparone strongly reduced alternative pathway (AP) activity in normal human serum (NHS). Some of the hydroxycoumarins were able to enhance hemolysis. Seven derivatives were tested in C1 and C3 functional assays, as 7-methylesculin appeared to be the strongest inhibitor of both activities. Esculin (En) and scopoletin (St) altered the effect of other complement activators (heat aggregated IgG, suramin, and zymosan) when applied with them simultaneously in vitro.

Buffers↗
PubMed1992

Developmental changes of proteins and concanavalin A reactive glycoproteins in growth cones from rat forebrain.

Growth cones were isolated from the forebrains of 1, 5 and 9 days-old rats. The ultrastructural characterization of the obtained subcellular fractions reveals that two of them (GC1 and GC2) contain predominantly growth cones. It was found that the protein content of the membranes contained in these fractions increases 7.5 times, while in whole forebrain the increase is only 3 times, showing that during the studied developmental period there is a predominant protein enrichment of the specialized brain structures (e.g. growth cones). Electrophoretic studies show that there are characteristic changes of the Coomassie Brilliant Blue R250 staining and concanavalin A reactive protein profiles. Comparison of the protein patterns of growth cones to those of synaptosomes from mature forebrain reveal a number of bands, which appear to be characteristic for one of these structures. The possible roles of the developmentally controlled proteins in the processes of synaptogenesis is discussed.

Animals↗
PubMed1991

Morphological characteristics of the endocrine pancreas in alloxan diabetes after cyclosporin A administration.

Histological, immunocytochemical, morphometric and electron microscope studies were carried out on the pancreas of alloxan diabetic rats pretreated with cyclosporin A. High mortality, severe destruction of pancreatic B-cells and presence of sporadic mononuclear infiltrations in islets and around excretory ducts were observed. The results obtained show that cyclosporin A potentiates the toxic effect of alloxan on the pancreatic B-cells.

Animals↗
PubMedDate not supplied

Antiviral activity of some hydroxycoumarin derivatives.

Esculetin (6,7-dihydroxycoumarin) and its diacetate exhibited a marked inhibitory effect on Newcastle disease virus replication in cell cultures at concentrations of 36 microM and 62 microM, respectively. These compounds were selected from ten hydroxycoumarin derivatives through an in vitro antiviral screen involving viruses of the picorna-, orthomyxo-, paramyxo-, and herpes virus families.

Animals↗