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Biomedical subjects

Maria Dimitrova

Publications and source records attributed to Maria Dimitrova.

5 recordsLinked to original sources
PubMed2003

Hepatitis C virus IRES efficiency is unaffected by the genomic RNA 3'NTR even in the presence of viral structural or non-structural proteins.

Hepatitis C virus (HCV) translation is mediated by an IRES structure. Instead of a poly(A) tail, the 3' end of the genome contains a tripartite 3'NTR composed of a non-conserved region, a polypyrimidine tract and a highly conserved stretch of 98 nt, termed the 3'X region. Using a set of bicistronic recombinant DNA constructs expressing two reporter genes separated by the HCV IRES, it was determined whether the HCV 3'NTR sequence, in the presence or absence of HCV proteins, played a role in the efficiency of HCV IRES-dependent translation ex vivo. Bicistronic expression cassettes were transfected into hepatic and non-hepatic cell lines. These results show that neither the entire 3'NTR nor the 3'X sequence alters IRES-dependent translation efficiency, whatever the cell line tested. A potential effect of the 3'NTR on IRES-dependent translation in the presence of HCV proteins was investigated further. Neither non-structural nor structural HCV proteins had any effect on the efficiency of IRES in this system. In addition, in order to mimic HCV genome organization, monocistronic expression cassettes containing the IRES and a Core-DsRed fusion gene were constructed with or without the 3'NTR. In this context, no effect of the 3'NTR on IRES translation efficiency was observed, even in the presence of HCV proteins. These data demonstrate that HCV translation is not modulated by the viral genomic 3'NTR sequence, even in the presence of HCV structural or non-structural proteins.

3' Untranslated Regions↗
PubMed2003

Protein-protein interactions between hepatitis C virus nonstructural proteins.

Replication of the hepatitis C virus (HCV) genome has been proposed to take place close to the membrane of the endoplasmic reticulum in membrane-associated replicase complexes, as is the case with several other plus-strand RNA viruses, such as poliovirus and flaviviruses. The most obvious benefits of this property are the possibility of coupling functions residing in different polypeptidic chains and the sequestration of viral proteins and nucleic acids in a distinct cytoplasmic compartment with high local concentrations of viral components. Indeed, HCV nonstructural (NS) proteins were clearly colocalized in association with membranes derived from the endoplasmic reticulum. This observation, together with the demonstration of the existence of several physical interactions between HCV NS proteins, supports the idea of assembly of a highly ordered multisubunit protein complex(es) probably involved in the replication of the viral genome. The objective of this study, therefore, was to examine all potential interactions between HCV NS proteins which could result in the formation of a replication complex(es). We identified several interacting viral partners by using a glutathione S-transferase pull-down assay, by in vitro and ex vivo coimmunoprecipitation experiments in adenovirus-infected Huh-7 cells allowing the expression of HCV NS proteins, and, finally, by using the yeast two-hybrid system. In addition, by confocal laser scanning microscopy, NS proteins were clearly shown to colocalize when expressed together in Huh-7 cells. We have been able to demonstrate the existence of a complex network of interactions implicating all six NS proteins. Our observations confirm previously described associations and identify several novel homo- and heterodimerizations.

Dimerization↗
PubMedDate not supplied

Assessment of myocardial viability with (99m)Tc-sestamibi -gated SPET images in patients undergoing percutaneous transluminar coronary angioplasty.

The present study was designed to evaluate whether nitroglycerin administration preceding the injection of technetium-99m labelled metroxy-isobutyl-isonitryl ((99m)Tc-sestamibi), improves the detection of myocardial perfusion defect reversibility. Moreover, we assessed whether myocardium kinetics improved after the percutaneous transluminar coronary angioplasty (PTCA) study. The study population consisted of 12 patients, 8 males and 4 females, 48-73 years old (mean age: 60.41 years) with chronic stable angina, resting wall dyskinesia, and >/=50% stenosis or occlusion of at least one coronary artery, who were scheduled to undergo PTCA. A gamma-camera gated single photon emission tomography myocardial perfusion scintiscan was performed as a baseline study with (99m)Tc-sestamibi (GSPET-B) and another similar scintiscan after nitrate augmentation (GSPET-N) before PTCA and two to six months after PTCA (GSPET-R), to assess the extent of perfusion defects, contraction abnormalities and myocardial viability. Cedars QGS software was used for semi quantitative assessment and sum perfusion scores were calculated for each study. According to our results from the 174 hypoperfused segments studied by GSPET-B, 137 segments had tracer activity <50%. From the 137 segments with tracer activity of <50% only 51 (37%) remained unaltered after PTCA. Twenty-six of them (51%) were described as nonviable after the GSPET-N study and the remaining 25 were defined as viable. Our study demonstrated significant perfusion improvement after nitrate augmentation (mean sum perfusion score decreased from 34+/-9 in the baseline study (SBS) to 23+/-11 in the GSPECT-N study (SNS), P=0.04. There was no significant difference between SNS and mean sum perfusion score after revascularisation (SRS), 23+/-11 and 24+/-13 respectively (P=0.833). The specificity, sensitivity and accuracy of the perfusion improvement after PTCA, were calculated as: 52%, 85% and 76% respectively. The low specificity in our study could be due to performing GSPET-R in some patients, six months after PTCA; during this time restenoses may occur. Two of our patients whose perfusion and myocardial wall motion kinetics had worsened and also had clinical symptoms of pain and fatigue, were considered to have developed restenosis. In the present study, myocardial wall motion kinetics showed non-significant improvement of global ejection fraction (EF). EF increased from 43.9%+/-3.3% to 48.9% after nitrate augmentation (P=0.262) and to 47.2%+/-6.4% after revascularization (P=0.091). Myocardial wall motion hypokinesia showed significant improvement of severity scores in the GSPET-N study, as well as after PTCA revascularization (P<0.01). It is concluded that GSPET-N (99m)Tc-sestamibi imaging significantly improves the detection of defect reversibility. On the basis of our results, it appears appropriate to recommend GSPET-N (99m)Tc-sestamibi imaging only in patients with perfusion defects and tracer activity of <50%. In such cases it is recommended to perform GSPET not only for perfusion but also for a myocardial wall motion kinetic study. The follow up study to evaluate the result of PTCA is recommended to be performed within 2 months after PTCA, before restenosis may occur and 6 months after PTCA if restenosis is suspected.

Aged↗
PubMedDate not supplied

The brain scintiscan with iodine-123-ioflupane to diagnose early Parkinson's disease; seven months follow up. First results in Bulgaria.

The aim of this study was to evaluate the brain scintiscan images with (123)I-ioflupane for the diagnosis of patients with early Parkinson's disease (PD). Sixteen patients were studied, nine males and seven females, aged between 38-81 y (mean age: 64 y). All patients underwent thyroid blocking by oral administration of 120 mg potassium iodide before and 24 h after the intravenous (iv) injection of 110-185 MBq/70 kg patient's weight, of (123)I-ioflupane. To check the correct biodistribution of the radiopharmaceutical, whole-body scans were performed at 15 min and 2-3 h after the administration of the radiopharmaceutical. All patients underwent brain single photon emission tomography (SPET) scans on a SPET gamma-camera 3-5 h after (123)I-ioflupane administration. To compensate for scatter and to avoid artifacts, the filtering and reconstructing procedures of the images were performed individually for each patient. Brain SPET results were evaluated semi-quantitatively using different indices. The morphology of the nigrostriatum (NS) area was also examined visually. The (123)I-ioflupane uptake by the affected nigrostriatum (ANS) was compared to a similar area at the occipital (Occ) brain section and to a similar area at the opposite NS. When the value of ANS/Occ was within the confidence limit of 1.507-1.636 and the value of ANS/NNS was within the limit of 0.755-0.889, PD was diagnosed (P<0.05). Thirteen of our patients were diagnosed as having PD and were given l-DOPA treatment. In the remaining patients the diagnosis of PD was rejected due to normal scintigraphic and morphologic findings of the NS area. The interest of this article lies in the following: The correct distribution of the radiopharmaceutical was confirmed by whole body scintiscan. Parameters for better quality of imaging were individually selected for each patient. The morphology of the NS areas, as estimated visually by us, was in accord with the scintigraphic (123)I-ioflupane uptake. The diagnosis of PD was clinically confirmed after treatment with l-DOPA in a seven month follow up period. Results from the small number of cases studied showed: 93% sensitivity and maximum specificity for the diagnosis of PD.

Adult↗