PubMed Health⌕ Search

Biomedical subjects

M Alexandrov

Publications and source records attributed to M Alexandrov.

12 recordsLinked to original sources
PubMed2003

Photon undulatory non-linear conversion diagnostic method for caries detection: a pilot study.

OBJECTIVE: The objective of this study was to evaluate a new optical method - photon undulatory non-linear conversion (PNC)--for use in different stages of caries detection. BACKGROUND DATA: Caries should be considered an infectious disease managed by risk assessment, early detection, and preventive therapies, rather than simply "drilling and filling." MATERIAL AND METHODS: Fluorescence emission spectroscopy was performed in vitro on 90 extracted teeth, with intact occlusal surfaces. This system differs from the basic Diagnodent unit in its ability to distinguish between different tissue components with respect to their spectrums. Histological analysis served as the gold standard for verification. The teeth sections correspond to the specific point with the highest reading of the detector. The system was compared to visual inspection, probing, and x-ray methods. The system tested (helium-neon [He-Ne], lambda = 633 nm) has a fiber optic device that delivers radiation to the tooth and a spectrophotometer device that detects bacterial porphyrins fluorescence, allowing detection of caries, fillings, and calculus by simultaneous measurement of backscattering and fluorescence intensity. RESULTS: The system tested provides quantitatively reproducible measurements and detection even through sound enamel of more than 1 mm in thickness. CONCLUSION: The PNC method detects different stages of caries lesions in real time, and it exceeds x-rays in sensitivity, without any ionizing radiation. Preliminary results showed a high potential of using the PNC method in clinical practice (98% accuracy) in comparison to the other methods.

Dental Caries↗
PubMed1999

Fluorescent and electron-microscopy immunoassays employing polyclonal and monoclonal antibodies for detection of goose parvovirus infection.

Polyclonal antibodies (PAbs) raised in geese and eight mice hybridomas secreting monoclonal antibodies (MAbs) against the goose parvovirus (GPV) were prepared. They were used for development of immunofluorescence (IF) and immunoelectron-microscopic (IEM) techniques to demonstrate the GPV infection in infected organs and biological fluids. The GPV antigens were established by immunofluorescence within the nuclei and the cytoplasm of many infected cells of the chorioallantoic membrane of goose and Peckin duck embryos, liver and heart of mortally diseased goslings. By means of IEM it was possible to detect the GPV in native organ homogenate supernatants and allantoic fluids. All techniques used in the study could be successfully applied for rapid diagnosis of the GPV infection. The test systems on the basis of MAbs should, however, be preferred. By means of immunoblotting (IB) using PAbs and MAbs four viral proteins (VP) with MW 88, 77, 65 and 60 kDa were demonstrated. Contrary to the others the VP with MW 65 kDa was the most antigenically reactive though invisible in the SDS-PAGE and Coomassie-blue dye-stained preparations.

Animals↗
PubMed1999

A threshold level of gag expression is required for particle formation in rat cells transformed by avian retroviruses.

To test the hypothesis that the block of polyprotein precursor processing and particle formation in RSV-transformed mammalian cells is due to a low level of pr76gag expression, rat tumor cell lines with different amounts of precursor molecules were used. The wild-type forms of pr76gag have been expressed at a high level by use of SV40-based vector and thirty-two stable transfected cell clones were isolated. The gag protein expression was detected in the cell lysate by immunoblotting. Untransfected cells released no proteins that could be detected by immunoprecipitation with anti-RSV serum. Membrane-enclosed gag precursor-polyprotein molecules and infectious virus particles from different stably transfected clones have been found in the medium. Both immature and mature virions of type C morphology were directly detected by transmission electron microscopy. Surprisingly, virus-like particles of morphology similar to mature type C retroviruses were found enclosed within intracellular membranes in a stably transfected nonproducing clone.

Animals↗
PubMed1998

Electron-microscopic immunocytochemical study of the intracellular transport of the viral glycoproteins in ts1, a mutant of Moloney murine leukemia virus.

The transport and localization of env-proteins of ts1 virus (a paralytogenic temperature-sensitive mutant of Moloney murine leukemia virus) in infected cells of the TB cell line have been studied at the ultrastructural level. It was found that the envelope precursor polyprotein gPr80-env of ts1 was inefficiently transported out of the endoplasmic reticulum at the restrictive temperature. It was speculated that inefficient transport correlates with inefficient processing of gPr80env into gp70 and Prp15E and leads to paralytic disease.

Animals↗
PubMed1997

Detection and identification of the Newcastle disease virus infection by electron and immunoelectron microscopy.

Various electron microscopic (EM) and immunoelectron microscopic (IEM) techniques were used to demonstrate and identify the Newcastle disease virus (NDV) infection. By IEM, the number of virions in native allantoic fluids was increased 50-100 times in comparison with direct EM. The immunogold staining showed that a number of immunogold particles were specifically bound to the antigen determinants located on the virion surface and these results were much easier to interpret. The obtained results showed that the EM and IEM can be successfully employed for a precise and rapid detection of NDV as well as for identification of this infection among other viral or bacterial infections.

Animals↗
PubMed1996

Demonstration of rabbit haemorrhagic disease virus antigen by Staphylococcus protein A coagglutination test.

The Staphylococcus protein A coagglutination test (Sp A COAT) was developed for the diagnosis of rabbit haemorrhagic disease (RHD). Liver, spleen, lungs and kidneys from 176 rabbits dead from viral haemorrhagic disease as well as the same organs from 64 healthy animals were examined by Sp A COAT and haemaglutination test (HAT). The Sp A COAT was specific and considerably more simple to carry out than the HAT, which made it very useful for rapid identification of RHD.

Agglutination Tests↗
PubMed1996

Two tumor-associated membrane antigens defined by monoclonal antibodies in a transplantable sarcoma induced by Rous sarcoma virus in rat.

Two hybridoma clones have been produced by hybridization of murine myeloma cell line PAI and splenocytes from BALB/c mice immunized with cells from a transplantable sarcoma induced in rat by SR-RSV. The antibody produced by hybridoma clone 2C2 was of subclass IgG3 and recognized a cell surface antigen of 52 kD. It only cross-reacted with cells from SR-RSV-induced sarcoma in hamster, but not with cells from the chicken RSV-induced sarcoma, nor with a number of methylcholanthrene sarcomas and various other tumors of viral or other etiology developed in rats, mouse, hamsters or chickens. The antibody produced by hybridoma clone 5G2 was of subclass IgG2A and recognized an antigen of 28 kD which was located under the plasma membrane, particularly in the cell protrusions and microvilli. Cross-reactions were found with all sarcoma cells tested, indicating that this antigen might represent a common sarcoma antigen of comparatively low molecular mass.

Animals↗
PubMed1995

Characterization of the virions of mopyridone-sensitive wild strain and mopyridone-resistant mutant of influenza virus A(H3N2)

Some differences were established between mopyridone-sensitive (MCU-s) wild strain and mopyridone-resistant (MCU-r) mutant progenies of influenza virus A/Hong Kong/1/68 (H3N2). The virions of MCU-r mutant had a lower buoyant density in linear sucrose gradient as compared to those of MCU-s strain, and an increased ability of aggregation as well. HA content (HAU/micrograms protein) in the purified virions of MCU-r mutant was twice lower as compared to MCU-s strain. The surface glycoproteins of MCU-r mutant were solubilized by octylglucoside faster than those of MCU-s strain. No differences were found between MCU-r strain and MCU-s mutant-induced red blood cell lysis at acid pH, and mopyridone did not influence this phenomenon. MCU-r mutant showed a lower thermostability as compared with MCU-s strain, but similar UV-inactivation curves for both viruses were observed. The quantity of the purified HA-NA complex and M1 protein incorporated into multilamellar liposomes was greater in the case of MCU-s mutant. Electron microscopy examination of liposomes which contained M1 protein from MCU-r mutant manifested pleomorphism with unusual gigantic forms tending to aggregate, whereas MCU-s M1 protein-containing liposomes were uniform and did not form aggregates. No morphological differences were found between the two viruses in HA-NA complex containing liposomes. These data indicate changes in the protein-lipid interactions in MCU-r mutant virions. Amino acid analysis of M1 protein revealed significantly lower content of asparagine, glutamine and serine, and a higher one oof hisitidine in MCU-r mutant as compared to MCU-s wild strain.

Amino Acids↗
PubMed1993

Electron- and immunoelectron-microscopic investigation on the rabbit haemorrhagic disease virus.

Electron- and immunoelectron-microscopic methods were used for detection and investigation of rabbit haemorrhagic disease virus (RHDV). The observed virus particles were uncoated, with an icosahedral symmetry, with a 35-40 nm dia and capsids built up by 32 capsomers with a central hollow part and a 3.5-5 nm dia. Particles with empty capsids could also be seen among them. Single virions visible in 5-fold symmetry, exhibited 10 projections on the surface. Virions with a 33-34 nm dia and cup-shaped surface depressions were a rare finding. Some of these particles were indistinguishable from the caliciviruses, but in most of them the cup-shaped depressions were single or no more then 2-3 in number, localized predominantly unilaterally or asymmetrically. Particles 25-29 nm large with full or empty capsids without capsomers could also be seen. Most probably they were some immature forms in the process of development of the RHDV.

Animals↗
PubMed1992

Immunohistochemical localization of the rabbit haemorrhagic disease viral antigen.

Immunohistochemical investigations were carried out to determine organ and cellular localization of the rabbit haemorrhagic disease viral antigen (RHDVA). It was found in certain parenchymal liver cells near the interlobular septs and in some macrophages and pseudoeosinophils of all studied organs and blood. Whereas in morphologically preserved hepatocytes and macrophages the RHDVA accumulated in the nuclei, in cells with disintegrated nuclei it was distributed throughout the cytoplasm.

Animals↗