Search PubMed⌕ Search

Biomedical subjects

G Georgiev

Publications and source records attributed to G Georgiev.

At least 37 records · Page 2Linked to original sources
PubMed1999

Inhibitory effects of freeze-dried milk fermented by selected Lactobacillus bulgaricus strains on carcinogenesis induced by 1,2-dimethylhydrazine in rats and by diethylnitrosamine in hamsters.

Fermented milk products might be used for cancer chemoprevention due to their putative anticarcinogenic and antitumor activities. The diet was supplemented with freeze-dried milk fermented by Lactobacillus bulgaricus strain LBB.B 144 (product FFM.B 144) added throughout the experiment at doses of 1.3 g and 2.5 g per rat, 5 times a week starting 3 weeks before the first carcinogen injection. This treatment significantly inhibited, by 26.2-28.6% and by 34.2%, the total intestinal carcinogenesis induced by 1,2-dimethylhydrazine (DMH, 21 mg/kg, s.c., once per week for 20 weeks) in male and female BD6 rats, respectively. FFM.B144 decreased the tumor incidence and multiplicity in large bowel, caecum, and duodenum. Protective effects were better expressed in female animals, with exception of that observed in duodenum. Supplementation of diet with freeze-dried milk fermented by Lactobacillus bulgaricus strain LBB.B5 (product FFM.B5) inhibited DMH-induced carcinogenesis only in the large bowel, but had no significant protective effect when all intestinal tumors were taken into account. However, both freeze-dried products favorably shifted the differentiation of large bowel tumors by increasing the proportion of benign and highly differentiated malignant tumors and decreasing in parallel the number of poorly differentiated carcinomas without influencing the tumor size. A lower number of cases with visible mesenterial metastasis was also observed in FFM-treated rats. In addition, both FFM.B 144 and FFM.B5 significantly inhibited, by 26-33%, the induction in the same rats of ear-duct tumors. FFM.B144 but not FFM.B5 was also effective in inhibiting the tracheal carcinogenesis induced in Syrian golden hamsters by diethylnitrosamine (DEN, 100 mg/kg, two s.c. injections), the protective effect being better expressed in female animals. The anticarcinogenic potential of some fermented milk products might be exploited in chemoprevention of cancer in humans.

1,2-Dimethylhydrazine↗
PubMed1999

Calculating the force tension at horizontal pressure of teeth and different degree of decomposition of parodontium.

The aim of this study was to analyze the relationship of decomposition of parodontium at applied horizontal pressure on teeth. A model tooth has been constructed which allows quick and precise calculating of force tensions. The results have shown that increased force tensions lead to the destruction of the parodontium and can be used for planning of prosthetic constructions.

Biomechanical Phenomena↗
PubMed1998

Metastasis-associated Mts1 (S100A4) protein modulates protein kinase C phosphorylation of the heavy chain of nonmuscle myosin.

Mts1 protein (S100A4 according to a new classification) has been implicated in the formation of the metastatic phenotype via regulation of cell motility and invasiveness. Previously we have demonstrated that Mts1 protein interacted with the heavy chain of nonmuscle myosin in a calcium-dependent manner. To elucidate the role of the Mts1-myosin interaction, we mapped the Mts1-binding region on the myosin heavy chain molecule. We prepared proteolytically digested platelet myosin and a series of overlapped myosin heavy chain protein fragments and used them in a blot overlay with Mts1 protein. Here we report that the Mts1-binding site is located within a 29-amino acid region, at the C-terminal end of the myosin heavy chain (between 1909-1937 amino acids). Two-dimensional phosphopeptide analysis showed that Mts1 protein inhibits protein kinase C phosphorylation of the platelet myosin heavy chain at Ser-1917. We hypothesize that Mts1 protein regulates cytoskeletal dynamics of the metastatic cells through modulation of the myosin phosphorylation by protein kinase C in calcium-dependent fashion.

Binding Sites↗
PubMed1997

A kappaB-related binding site is an integral part of the mts1 gene composite enhancer element located in the first intron of the gene.

The transcription of the mts1 gene correlates with the metastatic potential of mouse adenocarcinomas. Here we describe strong enhancer whose location coincides with the DNase I hypersensitivity area in the first intron of the mts1 gene. The investigation of the transcriptional activity of a series of plasmids bearing deletions in the first intron sequences revealed that the observed enhancer has a composite structure. The enhancer activity is partially formed by the kappaB-related element: GGGGTTTTTCCAC. This sequence element was able to form several sequence-specific complexes with nuclear proteins extracted from both Mts1-expressing CSML100 and Mts1-non-expressing CSML0 adenocarcinoma cells. Two of these complexes were identified as NF-kappaB/Rel-specific p50.p50 homo- and p50.p65 heterodimers. The third complex was formed by the 200-kDa protein. Even though the synthetic kappaB-responsible promoter was active in mouse adenocarcinoma cells, a mutation preventing NF-kappaB binding had no effect on the mts1 natural enhancer activity. On the contrary, the mutation in the kappaB-related element, which abolished the binding of the 200-kDa protein, led to the functional inactivation of this site in the mts1 first intron. The mts1 kappaB-like element activated transcription from its own mts1 gene promoter, as well as from the heterologous promoter in both CSML0 and CSML100 cells. However, in vivo occupancy of this site was observed only in Mts1-expressing CSML100 cells, suggesting the involvement of the described element in positive control of mts1 transcription.

Adenocarcinoma↗
PubMed1996

Metastasis of mammary carcinomas in GRS/A hybrid mice transgenic for the mts1 gene.

Transgenic mice, carrying the mts1 gene, one of the genes involved in the acquisition of the metastatic phenotype, were generated. The mts1 gene was placed under the control of the mouse mammary tumor virus (MMTV) long terminal repeat (LTR) promoter leading to overexpression in the lactating mammary gland of transgenic animals. Animals bearing the transgene appear phenotypically normal. Animals of two transgenic lines (Tg463 and Tg507) were crossed with the GRS/A mice. The GRS/A strain is characterized by high incidence of mammary tumors which rarely metastasize. 40% of the tumor bearing hybrid GRS/A mts1 females were found to develop secondary tumors in the lungs. The Mts1 protein was detected in the transgene primary tumor cells as well as in the corresponding metastases. Nontransgenic littermates expressed the Mts1 protein only in the stromal cells surrounding the tumor but not in the tumor cells by itself. Taken together these observations indicate that overexpression of the mts1 gene in the mouse mammary carcinoma cells gives rise to more aggressive tumors which are able to metastasize.

Animals↗
PubMed1996

Unusual chromosome aberration, t(13;14)(q32;q32.3), in a case of essential thrombocythemia with extreme thrombocytosis.

A case of essential thrombocythemia (ET) with extreme thrombocytosis in a 70-year-old male patient is described. The cytogenetic analysis revealed a pathologic clone with the following previously unreported, unusual karyotype: 46,XY,t(13;14)(q32:q32.3) and pericentric inversion of chromosome 9. The possible association of t(13;14) with the high platelet count is discussed.

Aged↗
PubMed1996

Effect of mts1 (S100A4) expression on the progression of human breast cancer cells.

The mts1 (S100A4) gene, encoding a Ca(2+)-binding protein of the S-100 subfamily, is involved in the control of tumor metastasis in some murine tumor cell lines. To further analyze its role, we transfected hormone-responsive human breast cancer MCF-7 cells with the mts1 gene under the control of a strong constitutive promoter. All of the 3 tested clones (MCF-7/mts1) producing Mts1 protein acquired an ability for hormone-independent growth in nude mice. Tumors derived from mts1 transfectants revealed local invasiveness into surrounding muscle and adipose tissues and metastasized to regional lymph nodes and lungs, characteristics which are rarely observed with parental MCF-7 cells. Electron-microscopic analysis of MCF-7/mts1 cells demonstrated structural changes in anchoring junctions, particularly in intermediate filament attachment site (desmosomes). The mts1-transfected clones expressed estrogen receptor, and their growth in tissue culture was both estrogen- and anti-estrogen responsive. Changes in regulation of the estrogen-dependent proteins progesterone receptor and cathepsin D were observed in some of the transfected clones. Our results indicate that mts1 expression in human breast cancer cells induces several changes characteristic of malignant phenotype and tumor progression.

Animals↗
PubMed1996

Activation of mts1 transcription by insertion of a retrovirus-like IAP element.

The mechanism of activation of mestatasis-associated mts1 gene transcription in the mouse myelomonocytic leukaemia WEHI-3 cell line is described. Northern blot analysis showed that WEHi-3 cells expressed two types of mts1-specific mRNA: standard (550 nt) and additional (about 800 nt). The steady-state expression level of the 800-nt RNA was isolated and sequence analysis showed that it contained a 357-bp fragment represented by long terminal repeat (LTR) sequences and a 5' untranslated region of the gag gene of the intracisternal A-particle (IAP) element. The chimeric IAP::mts1 800-nt mRNA is initiated from the 5' LTR promoter. The rearranged and normal loci of mts1 were cloned and partially sequenced. The results suggested that the insertion of the IAP sequences into the first intron of mts1 brings the gene under control of the strong IAP promoter. The additional chimeric 800-nt IAP::mts1 RNA transcript was the result of a splicing event linking IAP sequences with the coding part of mts1. We suggest that the chimeric IAP::mts1 RNA is capable of producing a functional Mts1 protein.

Animals↗
PubMed1995

Characterization of two splice variants of metastasis-associated human mts1 gene.

The mts1 gene is one of the genes specifically expressed in mouse metastatic tumors and tumor cell lines. In this paper, we present data on cloning and sequencing of two variants of human mts1 cDNAs (hu-mts1 and hu-mts1 (var)), as well as of the corresponding region in the human genome. Comparison of the genomic sequence with the sequence of the mts1 cDNAs demonstrates presence of two alternatively spliced variants of the mts1 in the human osteosarcoma cell line (OHS). The alternative splicing occurs within the 5'-untranslated region (UTR) of human mts1 pre-mRNA. Both splice variants, hu-mts1 and hu-mts1 (var), retain similar stability in the cells, contain one open reading frame coding for the MTS1 protein and differ only slightly in their translational capacity. The splice variants demonstrate dramatic variations in the level of expression in different human tissues and in human tumor cell lines. Although we have not revealed substantial differences in the mode of action of the two splice variants in the cells, the observed tissue specificity of expression supports the notion that it plays an important role in determining the activity of mts1 in different tissues.

Alternative Splicing↗
PubMed1995

Transcriptional regulation of the mts1 gene in human lymphoma cells: the role of DNA-methylation.

The transcription of the mts1 gene putatively involved in the control of tumor metastasis was studied in three human lymphoma cell lines: MOLT-4, CEM and Jurkat. The level of the mts1 gene transcription is high in MOLT-4 cells, lower in CEM cells and hardly detectable in Jurkat cells. This correlates with the hypomethylation of DNA in the first exon and the first intron of the mts1 gene in the analyzed culture cells. This area was also found to be undermethylated in human peripheral blood cells--macrophages, neutrophils and lymphocytes where the mts 1 gene is highly expressed. 5-Azadeoxycytidine (AzadC)--an inhibitor of the eukaryotic DNA-methylase--significantly induces the expression of the mts1 gene in CEM and Jurkat cells and has little effect on mts1 gene transcription in MOLT-4 cells. The drug does not influence mts1 transcription in cultivated peripheral blood lymphocytes. These data indicate the possible involvement of the methylation of the first exon/first intron sequences in the transcriptional repression of the mts1 gene. The finding of two DNAaseI hypersensitivity sites (DHSs) mapped in the first intron of the mts1 gene supports this suggestion.

Azacitidine↗
PubMed1995

[Blood autotransfusion in vascular surgery (predeposited blood)].

The study covers 100 patients, candidates both anamnestically and clinically for autologous blood transfusion. Practically elective patients for reconstructive vascular surgery are concerned. The amount of predonated blood (500 or 1000 ml) depends on the type of operation. A number of indices are followed up: Hb alterations--baseline and after 500 and 1000 ml blood predeposition, Ht alterations--baseline and after 1000 ml blood predeposition, as well as changes in blood protein level following 1000 ml blood predonated. Also, an assessment is made of coagulation factors before and after 1000 ml blood predonation, as well as the optimal longevity of blood storage in refrigerator (the so-called "blood aging"), expressed by K+ levels is stored blood. The studies are carried out in the clinic of vascular surgery of the St. Catherine over the period 1991-1992. As shown by the results autohemotransfusion is a safe, practical and effective procedure, accomplished in one or two stages--only 500 ml blood predonated with 2-3 days interval until operation, and 1000 ml blood predonated in two stages--2-3 days between first and second exfusion, and 3-4 days between the latter and operation. Autohemotransfusion is well tolerated and useful when properly indicated.

Blood Donors↗
PubMed1995

Denture implants.

Explore the source record for details and available documents.

Dental Implants↗
PubMed1992

Monoclonal antibodies directed to the O antigen of Salmonella serogroup E cross-react with lipopolysaccharides of Salmonella serogroups C, F and S.

Four murine hybridoma clones secreting monoclonal antibodies (mAb) directed against lipopolysaccharide (LPS) antigen of S. newington, serogroup E1, were obtained after a fusion of spleen cells of mice immunized with formaldehyde-killed bacteria and mouse myeloma cells of the X63-Ag8.653 line. Antigen binding properties and specificity of the mAb were studied in bacterial agglutination tests, passive hemolysis and its inhibition, passive hemagglutination tests, passive hemolysis and its inhibition, passive hemagglutination and immunoenzyme tests (ELISA and immunoblotting). Three of the mAb (24E6, 29E1 and 45F6) were agglutinating and were active in all tests used, while mAb 31H12 did not agglutinate bacteria but revealed a high reactivity in the immunoenzyme reactions. It was found that the mAb reacted with LPS and Salmonella strains from serogroup E (E1, E2, E3 and E4) as well as from serogroups C (C1 and C4), F and S thus showing that the O3 antigen possesses more than one epitope, one of which is represented on the LPS antigens of the serovars from the cross-reacting groups mentioned. According to the known chemical the most probable recognized epitope consists of mannose with beta-linkage to the next monosaccharide residue in the LPS chain.

Antibodies, Bacterial↗
PubMed1992

[Activation of lipid peroxidation and changes in vitamin E contents in the lungs under oxidative stress].

The lipid peroxidation (LPO) of the lung tissue and the bronchoalveolar lavage in rats under the influence of immobilization has been investigated. The effects accompanying the development of oxidative stress in animals--an increase in the content of conjugated dienes and fluorescent LPO products in biological objects and a strong decrease in the content of vitamin E in the lung tissue were registered.

Animals↗
PubMed1990

Characterization of NAD(P)H diaphorase from boar spermatozoa using specific monoclonal antibodies.

1. After immunization of BALB/c mouse, four monoclonal antibodies against soluble NADH diaphorase from ejaculated boar spermatozoa were produced and characterized. The monoclonal antibodies were designated as follows Mab 1F2, Mab 4E2, Mab 5B8, Mab 5D8. 2. These monoclonal antibodies react with other enzyme forms-sedimentary NADH and NADPH and soluble NADPH and inhibit (although not completely) their activity. It is supposed that different forms of the enzyme share some common epitopes. 3. Treatment of ejaculated boar semen with 2O-methylcholanthrene causes an increase of the activity of the soluble diaphorase form only. 4. These results lead to the assumption that the sperm diaphorase is a dynamic enzyme system consisting of four immunologically similar isoenzymes although their functions are different.

Animals↗