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N S Ambartsumian

Publications and source records attributed to N S Ambartsumian.

At least 19 recordsLinked to original sources
PubMed1997

Expression of the metastasis-associated mts1 gene during mouse development.

The mts1 gene, a member of the S100 family, is specifically expressed in different metastatic tumor cell lines. After transfection in some nonmetastatic cell lines Mtsl can induce a metastatic phenotype. Mts1 protein can interact with non-muscle myosin, indicating that Mts1 plays a role in cell motility. In order to understand the function of this gene, we studied the expression of the mts1 mRNA and protein in vivo during mouse development. Both mRNA and protein were present in high concentrations from 12.5 to 18.5 days post coitum (dpc) in a variety of developing embryonic tissue of mesodermal origin. We found by double immunostaining with a macrophage-specific antibody that Mts1 protein was highly expressed in fetal macrophages throughout the embryonic mesenchyme and in macrophages colonizing developing lymphatic and non-lymphatic organs. Moreover, we found mts1 expression during differentiation and morphogenesis of mesenchymal tissues such as the mesenchyme surrounding the tips of digits, the mesenchyme underlying the epithelium of the bladder, and the mesenchyme between the primordia of the nasal capsule and the skin as well as in the developing dermal papilla of hair and tooth follicle. In developing bone, Mts1 was expressed in invasive mesenchymal cells and in osteoclasts. The results presented here suggest that Mtsl plays an important role in mouse development during differentiation and function of macrophages and might be involved in different processes associated with mesenchymal morphogenesis including mesenchymal-epithelial interaction, tissue remodeling, and invasion.

Animals↗
PubMed1997

[Extrachromosomal DNA spectrum of Bacillus thuringiensis Berliner and Bacillus sphaericus Meyer et Neide].

Analysis of the pattern of extrachromosomal DNA in different cultures of Bacillus thuringiensis and Bacillus sphaericus demonstrated a higher content of extrachromosomal DNA in B. thuringiensis than in B. sphaericus. The quantity and approximate molecular weights of the plasmids were determined. The assumption that the plasmid DNA content in B. thuringiensis strains is higher than in the other representatives of the genus Bacillus was confirmed.

Bacillus↗
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↗
PubMed1995

[Expression of a splice-variant of the mts1 gene in normal and tumorous human tissue].

Data on cloning of cDNA corresponding to human mts1 gene transcripts are presented. By comparing nucleotide sequences of the genomic DNA clone and cDNA of mts1, it was shown that human osteosarcoma OHS cells contain two alternative splice variants of mts1 transcripts. Alternative splicing occurs in the 5'-untranslated region of the mts1 pre-mRNA. Both splice variants, hu-mts1 and hu-mts1(var), demonstrate similar stability in the cells, and each contains one open reading frame for the MTS1 protein. However, the two types of transcripts are translated with different effectiveness. The level of transcription of mts1 splice variants in different normal and neoplastic tissues and cell lines varies significantly. The role of alternative splicing as the mechanism responsible for posttranscriptional regulation of mts1 gene expression is discussed.

Alternative Splicing↗
PubMed1994

Non-muscle myosin heavy chain as a possible target for protein encoded by metastasis-related mts-1 gene.

The mts-1 gene is associated with the expression of the metastatic phenotype of tumor cells. The protein product of the mts-1 gene belongs to the S100 family of Ca(2+)-binding proteins with unknown biochemical function. In the present work, monoclonal anti-Mts-1 antibodies were used to isolate and characterize Mts-1 protein possible targets. Mts-1 protein can be immunoprecipitated by both anti-Mts-1 and anti-myosin antibodies as a complex with myosin from lysates of different mouse and human cell lines. Precipitation of myosin by anti-Mts-1 antibodies is specific and depends on the presence of Mts-1 protein. Ca(2+)-dependent association between Mts-1 protein and the heavy chain of non-muscle myosin was demonstrated by blot overlay technique. Furthermore, association between myosin and Mts-1 was confirmed by sucrose gradient analysis. Finally, immunofluorescent staining of the mouse mammary adenocarcinoma cell line showed that Mts-1 protein is co-localized with the myosin complex. The data suggest that the target for Mts-1 protein is a heavy chain of non-muscle myosin.

Amino Acid Sequence↗
PubMed1987

Unstable visible mutations induced in Drosophila melanogaster by injections of oncogenic virus DNA into the polar plasm of early embryos.

When RSV DNA cloned in pBR 322 or DNA of simian adenovirus Sa7 (C8) is injected into the pole plasm of embryos of various Drosophila stocks, the progeny of 1-70% of the surviving flies display visible mutations. The mutagenesis is partially directed: the loci mutating due to retrovirus and adenovirus DNA do not overlap. The majority of resulting mutants are characterised by high instability: reversions and new mutations occur in them, which sometimes spread over the whole population ("explosive" instability). The injected sequences are revealed by dot-hybridization in the DNA of many mutant strains, but only rarely by Southern blotting procedures. The results show that the microinjection of oncovirus DNA into embryos is an approach for obtaining highly unstable strains even from wild-type stable Drosophila stocks without crosses with MR lines or the introduction of P elements. The sets of unstable mutations induced by oncovirus DNA is different from those in hybrid dysgenesis.

Adenoviridae↗
PubMed1987

[Detection of nucleotide sequences specific for retroviruses in Saccharomyces cells].

Restriction endonuclease cleavage analysis and blotting hybridization of nuclear DNA and RNA to cloned avian sarcoma and murine leukemia virus genes (pol, scr and abl) demonstrated the presence and expression in baker's yeast cells of retrovirus-specific sequences. The relationship exists between the pol-specific yeast sequences and Ty cloned fragments. The results obtained are discussed in the light of evolutionary role of retroviral genes in cell division control and transposition.

Base Sequence↗
PubMed1987

[Induction of unstable mutations in Drosophila melanogaster by microinjection of DNA from oncogenic viruses into the embryo polar plasma. II. Analysis of the role of injected DNA].

We have demonstrated that the mutagenic effect of oncovirus DNA injected into Drosophila embryos is of two-type locus specificity: the spectrum of mutations induced by the retroviral cDNA (RSV) changed in different recipient stocks and those induced by the adenoviral DNA (Sa7) did not differ in the stocks studied. The Sa7 DNA and the cDNA of RSV induce mutations in different groups of loci. Transpositions of the copia element were found in mutant lines obtained in both cases.

Adenoviridae↗
PubMedDate not supplied

[Transcription and expression in Escherichia coli of src gene cloned sequences of rous sarcoma virus].

Effective transcription of virus-specific sequences was shown in Escherichia coli cells that carry recombinant plasmids pPrC11 and psrcC with fragments of the Rous sarcoma virus (RSV) genome. Analysis of transcripts revealed several classes of RNA, one of which is probably transcribed from the structural part of the RSV src gene. Analysis of the primary structure of the region adjacent to the src RSV gene showed the existence of sequences similar to the bacterial promoters from which the src-specific RNAs can be transcribed. The synthesized RNA directs the translation of a functionally active protein product, that has tyrosine-specific phosphoproteinkinase activity.

Avian Sarcoma Viruses↗
PubMedDate not supplied

[Transfer of active oncogenes and promoters into the mouse cell genome].

Different cell DNA's (normal NIH 3T3 DNA; human osteosarcoma cell DNA; human malignant glioma cell DNA with amplified c-Ha-ras) were cotransfected onto NIH 3T3 cells with cloned long terminal repeat (LTR) sequences of Rous sarcoma virus. LTR RSV and normal NIH 3T3 DNA c-fos oncogen expression was detected in tumors induced in nude mice. In the same system human tumour cell DNA with amplified c-Ha-ras gene was used, that to the integration and amplification of LTP sequences with simultaneous maintenance of c-Ha-ras amplification. Nude mouse tumour DNA with integrated LTR sequences was active in successive rounds of transfection.

Animals↗