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Biomedical subjects

G Georgiev

Publications and source records attributed to G Georgiev.

At least 127 records · Page 7Linked to original sources
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Modulation of mts1 expression in mouse and human normal and tumor cells.

The mts1 gene, encoding small Ca(2+)-binding protein of the S100-family, is considered as a gene whose activity correlates with the manifestation of a metastatic phenotype of tumor cells. It was shown before that the mts1 is expressed not only in metastatic tumor cells but also in some normal tissues, namely in so-called "lymphoid" organs: spleen, thymus, bone marrow. In this work we analyzed in more detail the expression of mts1 in human and mouse hematopoietic cells and cell lines. A high level of mts1 RNA was observed in T-lymphocytes, neutrophils, monocytes/macrophages and in corresponding cell lines. Controversially, the mts1 gene was silent in B-lymphocytes as well as in myeloma and erythroleukemia cell lines. The possibility of modulating the mts1 gene expression by the action of different agents was demonstrated. Mitogens, such as lipopolysaccharides (LPS), interferon (IFN gamma), and concanavalin A (Con A), modulate the level of the mts1 gene expression in hematopoietic cells differently. Calcium ionophore, A23187, can also be regarded as a modulator of the mts1 gene expression, since its addition to the cells results in a substantial decrease of the mts1 RNA level. It was shown that the mts1 RNA's half-life is relatively long, more than 24 h. We therefore believe that calcium ionophore can activate some ribonucleases which degrade the mts1 RNA. Cycloheximide prevents the effect of A23187 and stabilizes the mts1 RNA, probably by blocking the synthesis of these nucleases. Thus, the obtained data indicate that the agents which are capable of changing the physiological status of the cells also modulate the mts1 gene expression.

Animals↗
PubMedDate not supplied

In vivo transfection and/or cross-priming of dendritic cells following DNA and adenoviral immunizations for immunotherapy of cancer--changes in peripheral mononuclear subsets and intracellular IL-4 and IFN-gamma lymphokine profile.

In order to provoke an immune response, a tumor vaccine should not only maximize antigen-specific signals, but should also provide the necessary "co-stimulatory" environment. One approach is to genetically manipulate tumor cells to either secrete lymphokines (GM-CSF, IL-12, IL-15) or express membrane bound molecules (CD80, CD86). Furthermore, patient dendritic cells can be loaded with tumor-associated antigens or peptides derived from them and used for immunotherapy. Genetic modification of dendritic cells can also lead to presentation of tumor-associated antigens. Transfection of dendritic cells with DNA encoding for such antigens can be done in vitro, but transfection efficiency has been uniformly low. Alternatively, dendritic cells can also be modulated directly in vivo either by "naked" DNA immunization or by injecting replication-deficient viral vectors that carry the tumor specific DNA. Naked DNA immunization offers several potential advantages over viral mediated transduction. Among these are the inexpensive production and the inherent safety of plasmid vectors, as well as the lack of immune responses against the carrier. The use of viral vectors enhances the immunogenicity of the vaccine due to the adjuvant properties of some of the viral products. Recent studies have suggested that the best strategy for achieving an intense immune response may be priming with naked DNA followed by boosting with a viral vector. We have successfully completed a phase I and phase II clinical trials on immunotherapy of prostate cancer using naked DNA and adenoviral immunizations against the prostate-specific membrane antigen (PSMA) and phase I clinical trial on colorectal cancer using naked DNA immunization against the carcinoembryonic antigen (CEA). The vaccination was tolerated well and no side effects have been observed so far. The therapy has proven to be effective in a number of patients treated solely by immunizations. The success of the treatment clearly depends on the stage of the disease proving to be most efficient in patients with minimal disease or no metastases. A panel of changes in the phenotype of peripheral blood lymphocytes and the expression of intra-T-cell lymphokines seems to correlate with clinical improvement.

Adenoviridae↗
PubMedDate not supplied

Activity and localization of NADH-dependant oxidoreductase (diaphorase) in boar spermatozoa.

Investigations were carried out into the activity and localization of NADH-dependant diaphorase in boar spermatozoa. Semen samples were collected from healthy boars, used in A.I. centers. The enzyme was extracted with distilled water and Triton X-100. Two forms of diaphorase were found-water-soluble and Triton X-100 soluble, showing low activity-0.36 U/ml and 0.26 U/ml. The enzyme was localized in the mitochondria, manifesting different intensities of reaction between sperm cells in the same ejaculate. It was found, that a part of the mitochondria and outer doublets showed positive reaction. It is suggested that the enzyme regulates the ratio between reduced and oxidized forms of NADH, takes part in the energy balance and possibly in the mechanism of sperm motility.

Animals↗