PubMed Health⌕ Search

Biomedical subjects

A N Lebedev

Publications and source records attributed to A N Lebedev.

At least 19 recordsLinked to original sources
PubMed1995

Forehead skin microcirculation during tilt table testing and lower body negative pressure.

Noninvasive skin microcirculation measurements based on a new Near Infrared sensor technique (NIR/Fa. Silicon Sensor GmbH; Berlin) were embeded in a tilt table experiment for simulation of acute effects of weightlessness (HDT -6 degrees) and active standing with the Russian Tschibis-LBNP device. The phenomenon of orthostatic intolerance depends on complex interactions among functional characteristics of central and peripheral cardiovascular control. The purpose of this study was to assess the blood volume and flow motion changes as well as pulsatile spectral pattern during orthostatic and antiorthostatic stress.

Adult↗
PubMed1993

[The dynamics of the electroencephalogram indices in pilots with acute hypoxia].

In experimental conditions the authors have modelled the state of acute hypoxia in pilots with disorders of high psychic functions. In the result of these researches it was found out that the changes of peak frequency of alpha rhythm anticipated the slow delta and theta rhythms. This EEG characteristic feature could be used for the development of a device which would control these states in pilots.

Acute Disease↗
PubMed1989

[Deletion-insertion mapping of the region non-essential for functioning of the beta-subunit of Escherichia coli RNA polymerase].

A plasmid has been constructed containing the gene of beta-subunit of RNA polymerase of Escherichia coli under control of the PR promoter of bacteriophage lambda. PR promoter may be induced by heating up to 42 degrees C. In frame insertions of different sequences between 989 and 990 or 1010 and 1011 codons of the rpoB gene do not inactivate the beta-subunit function. Deletions in the region of 1011-1027 codons result in inactivation of beta-subunit. We localized antigene determinant of monoclonal anti-beta-antibodies which do not inactivate RNA polymerase in vitro. The borders of non-essential region of beta-subunit were accurately determined.

Bacteriophage lambda↗
PubMed1988

[Mapping of the regions participating in the replication, maintenance and mobilization of the R-plasmid pBS222 with a wide circle of bacterial hosts].

The analysis of the deletion derivative of pBS359 obtained as a result of sodium bisulphite mutagenesis and of recombinant derivatives pBS361-pBS363 permitted to map genes of the broad-host-range pBS222 plasmid which participate in replication, maintenance and mobilization. These genes are localized within the coordinates 0.2 to 2.5 kb in the region including a unique HindIII restriction site on the pBS222 physical map. Possible participation of the in vitro synthesized polypeptides in providing functions of cosmopolitanism and mobilization is being considered. Putative molecular-genetic structure of pBS222 and the presence of active recombination points are discussed, as well as the merits of the employed method for obtaining derivatives. The derivatives obtained and recombinant plasmids belong to the smallest plasmids which may be inherited in various gram-negative bacteria.

Bacteria↗
PubMed1987

[Design of a hybrid gene coding for the leader sequence of Bacillus amyloliquefaciens alpha-amylase and for human proinsulin].

The chemically synthesized structure gene of human proinsulin was cloned in E. coli on the secretory vector containing regulatory elements of the Bacillus amyloliquefaciens alpha-amylase gene. The proinsulin gene was inserted by the EcoRI site located immediately after the DNA area encoding the alpha-amylase signal peptide. The E. coli cells transformed by such a plasmid produced hybrid protein consisting of the alpha-amylase signal peptide, five amino acid residues after the gene mating and human proinsulin. For accurate mating of the alpha-amylase gene leader sequence and proinsulin gene directed mutagenesis was performed on the filiform phage M13 mp9 with synthetic oligonucleotide. The hybrid gene was transferred to the vector molecule capable of replicating in Bacillus subtilis. It was shown that in the cells of both E. coli and B. subtilis there is synthesized protein interacting by the radio-immunological data with antibodies to porcine insulin, a large portion of immunologically active protein being detected in the periplasmic space of E. coli cells and in the culture fluid of B. subtilis cells which was indicative of proinsulin secretion directed by the alpha-amilase regulatory elements.

Amino Acid Sequence↗
PubMed1983

Monoclonal antibodies inhibiting RNA polymerase from Escherichia coli.

Monoclonal hybridoma antibodies directed against RNA polymerase from E. coli have been obtained. Only a few have been found to inhibit the enzyme activity. Antibodies produced by two clones, PYN-1 and PYN-2, inhibit RNA polymerase at the stage of RNA chain elongation. The PYN-1 antibodies react with the beta'-subunit of the enzyme. The PYN-2 antibodies react with the beta-subunit and with its 130 kDa amber fragment.

Antibodies, Monoclonal↗
PubMed1981

Antigenic variability of bacterial RNA polymerases.

Radioimmunoassay analysis of enteric and some other Gram-negative bacteria has shown that the antigenic structure of the RNA polymerase alpha subunit is more conserved than that of the beta and beta' subunits. Since anti-alpha antibodies do not affect RNA polymerase activity, the constraints which determine the low variability of the antigenic structure of the alpha subunit are not directly related to its functional role. The antigenic determinants of the alpha subunit located on the surface of the RNA polymerase molecule are more conserved than those involved in contacts with other subunits; an opposite tendency characterizes the beta subunit. The range of variability of the antigenic determinants buried inside the RNA polymerase molecule suggests that the subunits are attached to each other rather loosely. Immunological comparison of RNA polymerases provides a simple method for reconstructing bacterial genealogies. The genealogy of the bacteria examined is essentially in agreement with phylogenetic trees based on 16S and 5S rRNA sequence characterization. This argues against extensive interspecific transfer of genes coding for components of the transcription and translation apparatus.

Bacillaceae↗
PubMed1981

[Cloning and the expression of the DNA promotor fragments of Bacillus thuringiensis in Escherichia coli cells].

The promoter-containing fragments of Bacillus thuringiensis subsp. galleria 69-6 DNA have been cloned on the pGA24 vector in Escherichia coli cells. The recombinant plasmids make cells resistant to tetracycline in a wide range. The level of tetracycline-resistance does not depend on the length of a foreign insertion. New polypeptides are synthesized on the template of the recombinant plasmids in vitro. The data point out the presence in Bac. thuringiensis DNA of many genes which are able to express in E. coli cells.

Bacillus thuringiensis↗
PubMed1979

[Clinical diagnosis of neurinomas of Gasser's ganglion].

The first symptoms of the disease encountered in 30 patients were paresthesia, constant dull headaches and a feeling of numbness of the face or its half. Eventually weakness, atrophia of the masticatory muscles, a drop or absence of the corneal reflexes and cerebral and focal symptoms super vened (the symptoms depended upon the direction of the neurinoma growth). Signs of hypertension were seen in 17 cases. There was also a protein-cell dissociation: 0.5--7% of protein in pleocytosis 6/3--68/3. The craniograms showed a destruction of the ground of the middle cranial cavity in 24 cases, while in 23 cases there was a destruction of the pyramidal apex. Antiographic studies demonstrated a displacement of the carotid siphon medially (18 cases), forward (8 cases) or behind (5 cases). The tumor vascular network was detected in 5 patients. The diagnosis of neurinomas of Gasser's node requires a comprehensive summarization of the clinical and x-ray findings.

Adult↗
PubMed1978

[Positive ventriculographic signs of cerebral hemisphere glioma extension into the ventricular system].

A positive ventriculography with fatty and water soluble contrast substances (myodil, conray, dinner - x, amipaque) was performed in 87 patients with gliomas of the frontal lobe 36 cases), temporal (22 cases) and parietal (29 cases) lobes. Gliomas of the frontal and temporal lobes penetrating into the cavity of the lateral ventricles from an "amputation" of the anterior or inferior horn. Gliomas of the parietal lobe penetrated into the upper--outer wall of the triangle of the lateral ventricle and creates a defect of filling around which a certain "plication" develops. A common symptom of glioma penetration into the brain ventricles is its tuberous polycyclicity, an uneveness of the edges of the ventricles. The author describes some diagnostical signs of a penetrating glioma into the corpus callosum and subcortical nodes.

Adult↗
PubMed1975

[An x-ray and histologic study of calcifications of tumors of the subcortical ganglia of the brain].

X-ray and histological studies of 138 patients with tumors of subcortical nodes displayed signs of hypertension in 86.3% of the cases (119 cases). Calcified foci on the craniograms were found in 29 cases (21%) and in histological findings - in 48 cases (34.6%). Petrified foci in benign glial tumors were located between the tumor cells, perivascularly and in the tissue of the perifocal zone of the tumor. In malignant tumors the petrified foci were mainly in the area of necrosis, in microcysts and hemmorrhagical foci. According to the pattern of calcification on the x-ray it was impossible to determine the histological type of the tumor or the degree of malignancy. The volume of calcification on the craniograms do not correspond to the volume and configuration of the intracranial tumor.

Adolescent↗