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Biomedical subjects

I Ivanov

Publications and source records attributed to I Ivanov.

At least 19 recordsLinked to original sources
PubMed1992

Effect of tandemly repeated AGG triplets on the translation of CAT-mRNA in E. coli.

It has been shown that tandems of rare arginine codons AGG have a strong inhibitory effect on translation of mRNA in E. coli [5]. This has been explained by the rate-limiting interaction of these codons with the less abundant tRNA(AGG) [6]. In this study tandemly repeated AGG triplets were introduced into the chloramphenicol acetyltransferase (CAT) gene either upstream of the initiation ATG codon or downstream of it (both in frame and out of frame) and the expression of the modified genes was investigated. We report that the addition of AGG clusters resulted in a substantial inhibitory effect on CAT gene expression independently of their localization in mRNA. This inhibitory effect is explained by a competition of the tandem AGGAGG with the natural Shine-Dalgarno (SD) sequence (consensus AAGGAGGU) for the 3'-end of the 16S small ribosomal RNA (rRNA).

Amino Acid Sequence↗
PubMed1992

A stable line of turkey bone marrow cells transformed by the myelocytomatosis virus strain MC31. Ultrastructural characteristics and localization of the DNA replication sites.

Attempts were made to characterize cells of the LSTC-SF2 line by scanning electron microscopy and transmission electron microscopy on the ultrastructural level. The virus-transformed cells are of oval, slightly elongated shape with an undulating surface. The cell nucleus is well outlined, poor in heterochromatin but with a strongly developed nucleolus. The cytoplasm is not rich in organelles except for an abundance of mitochondria with dense granules that are often found in them. With high-resolution autoradiography the DNA synthesis sites were identified mainly in proximity to the nuclear membrane and in the perinuclear spaces. The cells under study can be regarded as immature forms of the blood series and most likely as precursors of cells of the granulocyte or monocyte series.

Animals↗
PubMed1992

Microtubules and regulation of granulosa cell steroidogenesis by porcine granulosa cell conditioned medium.

Possible involvement of microtubules in the regulation of granulosa cell steroidogenesis by large follicle granulosa cell conditioned media (LGCCM) was assessed by monitoring the effect of agents that alter the cytoplasmic microtubule-tubulin equilibrium. The changes in microtubule organization and cell shape were examined by immunohistochemical procedure and morphometric analysis. Progesterone production stimulated by LGCCM was reduced by colchicine (agent that polymerizes microtubules) in a dose-dependent manner. In contrast, LGCCM stimulated progesterone secretion was significantly decreased by microtubule stabilizing agent (taxol: 1-10 microM). Cultured granulosa cells with a flattened appearance and projections after 24 h of incubation assumed a spherical configuration and were devoid of cytoplasmic processes when cultured with these agents. LGCCM stimulated GCs showed a reduction in the perimeter as compared with controls, although some cytoplasmic processes were observed. These findings suggest the involvement of microtubules in the regulation of cultured granulosa cell progesterone production by LGCCM, possibly through an effect on subcellular organelle distribution by altering the morphology of granulosa cells.

Animals↗
PubMed1991

Secretion of oligomeric Val8-human calcitonin by Saccharomyces cerevisiae.

Monomeric human calcitonin (hCT) gene and oligomeric hCT genes composed of two, three or four head-to-tail linked monomers were fused in-frame to the yeast alpha-factor leader coding sequence wild-type and fragile mutant Saccharomyces cerevisiae strains were transformed with the constructed plasmids and the yield of recombinant protein secreted into the culture medium was measured. The yeast cells secreted equal (molar) amounts of all of the hCT variants. The recombinant proteins remained stable in the growth medium for at least 3 days. The fragile cells secreted about 30% more hCT as compared to the wild-type yeast cells.

Amino Acid Sequence↗
PubMed1990

Construction of a Co1E1 plasmid bearing inducible high-copy-number phenotype.

In order to construct plasmids bearing inducible high-copy-number phenotype, the cloning plasmid pBR322 was modified as follows: a DNA fragment containing a strong synthetic promoter (P1), synthetic lac operator (O1), DNA sequence corresponding to the RNAI/RNAII region of the Co1E1 replicon and the CAT gene transcription terminator was substituted for the 29 bp EcoRI/HindIII DNA fragment. Two types of plasmids were constructed in this way, differing in the orientation of the RNAI/RNAII fragment. Depending on the orientation these plasmids coded for RNA molecules representing either RNAI or RNAII domains. It was found that when RNAII molecules were overproduced the plasmid copy number was about 4 times higher than that of pBR322 and only negligible change in the plasmid copy-number value was observed upon overproduction of RNAI molecules.

Bacteriocin Plasmids↗
PubMed1990

Avian bone-derived cell line infected with osteopetrosis virus pts-56.

Cell culture derived from embryonal turkey bone was infected with osteopetrosis virus pts-56. After 13 passages the morphology of the infected cells was changed and later a cell line was established. Some features of this cell line are described and compared with a non-infected cell culture.

Alkaline Phosphatase↗
PubMed1990

Stable line of turkey bone marrow cells transformed by the myelocytomatosis virus strain MC31.

A stable bone marrow-derived cell line LSTC-SF2, producing transforming avian acute leukaemia virus, was established. The cell line has been maintained in culture for over 4 years, and 450 passages can be frozen and easily recovered in viable form. The cells grow rapidly in monolayers with multilayer clumps, have low serum requirements, display specific morphology, form colonies in semisolid medium and release transforming MC31 virus. A helper virus was also detected by the reverse transcriptase assay.

Animals↗
PubMed1978

"Maturation" of DNA duplexes.

Reassociation of typical single-copy DNAs, like E. coli DNA, even when performed at relatively low temperatures, results in the formation of perfect duplexes with thermal stability very close to that of the native DNA. In contrast, duplexes of mouse repeated DNA as well as duplexes of Streptomyces DNA prepared under the same conditions, show a low thermal stability and undergo post-reassociation changes upon prolonged incubation. These changes, called "maturation" of the DNA duplexes, result in increasing of their thermal stability. Some of the factors affecting the rate of "maturation" are studied. The implication of the "maturation" process in reassociation analysis and in characterization of the heterogeneity of DNA is discussed.

Animals↗
PubMed1977

[Epizootiology of foot rot in sheep].

Investigations were carried out on the outbreak and spread of foot rot in sheep as well as on the ways of its restriction and eradication. It was found that the disease had been introduced with the import of breeding animals, its further spread being associated with the activity of the Breeding Centers for pedigree animals. The diseased animals have been 25 per cent, on an average, for the whole country, and the economic losses, as expressed in production parameters, have amounted to: produce of animal origin--20 per cent; culling of animals--15 per cent; mortality--1 per cent. Best in the group treatment of the affected animals prove: the dipping in a 5--10 per cent solution of formalin or a 20 per cent solution of copper sulfate, combined with the respective surgical and orthopedic handling and the disinfection of premises. The individual parenteral treatment and the local application of antibiotics and chemotherapeutics have proved suitable and successful in the cases of moderate spread of the disease. The eradication of foot rot can be achieved only via the planned and complex application of pertinent measures.

Animals↗
PubMed1976

[Products of the interaction of ethazole with mustard oils].

Synthesized were nonsymmetrical N1N1--replaced products of thiocarbamide containing residual alkyl- and arylsinapic oils and the sulfonamide ethasole, in order to study their pharmacologic activity. The synthesis was performed through heating the components up to the point of weak boiling in an ethanol medium. The obtained nine new N1N1--thiocarbamide products were identified in terms of their melting point and sulfur analysis. Tentative microbiologic testing showed that the newly obtained compounds produce bacteriostatic and bactericidal effects.

Anti-Infective Agents↗