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Biomedical subjects

A V Popov

Publications and source records attributed to A V Popov.

At least 37 records · Page 2Linked to original sources
PubMed2001

[Brain central regions in courtship sound production in Drosophila melanogaster].

There are debates about the function of the two main central brain structures of insects--mushroom bodies and the central complex--in the control of motor co-ordination and triggering of different behaviour programs including sound production. To throw additional light onto this problem we analysed the parameters of the love song produced by 5-day old males courting for 5 minutes a fertilised CS female at 25 degrees C, in two wild-type strains of Drosophila melanogaster (Berlin and CS), hydroxyurea (HU)-treated flies (chemical ablation of the mushroom bodies) two mushroom body mutants (mbm1 and mud1), two central complex mutants (ccbKS127 and cexKS181) and a mutant cxbN71 with defects both in the mushroom bodies and in the central complex. It was found that the love song of HU-treated flies devoid of the mushroom bodies is very similar to that of wild-type flies. In mbm1 and mud1 the main parameters of the song (interpulse interval, IPI, and train duration) are slightly shifted from those of wild type but the sharpness of tuning of the pulse oscillator is the same. The flies of all these strains are equal to wild-type strains in mating success (% of copulations with virgins in 10-min test). On the contrary, the songs of the central complex mutants differ from those of wild-type flies. First of all, the sharpness of tuning of the pulse oscillator is destroyed,--the IPIs become highly variable. The pulses often are much longer and polycyclic as in well known cacophony mutant. The mean duration of pulse trains is much shorter. The males of the mutant cexKS181 usually court violently, but in most cases abnormal sounds are produced. Both cexKS181 and ccbKS127 males are much less successful in matings in comparison to wild-type flies. One can conclude that the central complex plays probably a very important role in the control of singing, whereas the mushroom bodies are practically not involved in this function.

Animals↗
PubMed2000

Study of cosmic rays and light flashes on board Space Station MIR: the SilEye experiment.

The SilEye experiment aims to study the cause and processes related to the anomalous Light Flashes (LF) perceived by astronauts in orbit and their relation with Cosmic Rays. These observations will be also useful in the study of the long duration manned space flight environment. Two PC-driven silicon detector telescopes have been built and placed aboard Space Station MIR. SilEye-1 was launched in 1995 and provided particles track and LF information; the data gathered indicate a linear dependence of FLF(Hz) ( 4 2) 10(3) 5.3 1.7 10(4) Fpart(Hz) if South Atlantic Anomaly fluxes are not included. Even though higher statistic is required, this is an indication that heavy ion interactions with the eye are the main LF cause. To improve quality and quantity of measurements, a second apparatus, SilEye-2, was placed on MIR in 1997, and started work from August 1998. This instrument provides energetic information, which allows nuclear identification in selected energy ranges; we present preliminary measurements of the radiation field inside MIR performed with SilEye-2 detector in June 1998.

Cosmic Radiation↗
PubMed2000

[Functional interrelations between suprachiasmatic nuclei and the hippocampus during elaboration and recovery of time conditioning in rats].

In hippocampectomised rats or in rats subjected to hippocampectomy combined with destruction of the hypothalamic suprachiasmatic nuclei, time conditioning could not be elaborated. The lesion of the suprachiasmatic nucleus alone, however, accelerated elaboration of the conditioned reflex. In denucleated rats, the hippocampectomy did not affect the time of a previous conditioning recovery.

Acoustic Stimulation↗
PubMed2000

[Modeling heterochromatin regions in transgenic mice].

Transgenic mice carrying bovine satellite DNA IV were obtained. The size of the transgene integrated into the mouse genome was approximately 390 kb (about 100 transgene copies) as determined by a semiquantitative PCR. Restriction analysis with isoschizomeric restrictases HpaII and MspI, showed that the alien DNA was methylated. In the genome of a transgenic founder male, two integration sites for satellite DNA IV were revealed by in situ hybridization and in situ PCR. These sites are situated on two different chromosomes: in pericentromeric heterochromatin and within a chromosomal arm. In transgenic mice, de novo formation of heterochromatin regions (C-block and the CMA3 disk within the centromeric heterochromatin of another chromosome) was revealed by C-banding and staining with chromomycin A3. This formation is not characteristic of mice, because their chromosomes normally contain no interstitial C-blocks or sequences intensely stained by chromomycin A3.

Animals↗
PubMed1999

Antibody repertoires of four- and five-feature translocus mice carrying human immunoglobulin heavy chain and kappa and lambda light chain yeast artificial chromosomes.

We have produced mice that carry the human Ig heavy (IgH) and both kappa and lambda light chain transloci in a background in which the endogenous IgH and kappa loci have been inactivated. The B lymphocyte population in these translocus mice is restored to about one-third of normal levels, with preferential (3:1) expression of human lambda over human kappa. Human IgM is found in the serum at levels between 50 and 400 microg/ml and is elevated following immunization. This primary human Ab repertoire is sufficient to yield diverse Ag-specific responses as judged by analysis of mAbs. The use of DH and J segments is similar to that seen in human B cells, with an analogous pattern of N nucleotide insertion. Maturation of the response is accompanied by somatic hypermutation, which is particularly effective in the light chain transloci. These mice therefore allow the production of Ag-specific repertoires of both IgM,kappa and IgM,lambda Abs and should prove useful for the production of human mAbs for clinical use.

Animals↗
PubMed1999

Dominance of intrinsic genetic factors in shaping the human immunoglobulin Vlambda repertoire.

The expressed human immunoglobulin Vlambda repertoire demonstrates a strong bias in the use of individual Vlambda segments. Mechanisms that underlie such biases can be divided into two categories: intrinsic genetic processes that lead to the preferential rearrangement and/or expression of certain segments; and selection following light chain expression. Here, we have used two approaches to investigate the factors that shape the human Vlambda repertoire. Firstly, we characterised 136 Vlambda rearrangements (59 productive and 77 non-productive) amplified from the human genomic DNA of peripheral blood cells. Secondly, we analysed Vlambda segment use in a library of 2000 cDNA clones from a transgenic mouse containing a 380 kb region (including 15 functional Vlambda segments) from the human immunoglobulin lambda locus. By hybridisation and sequencing we found that the patterns of use of human Vlambda segments in the transgenic mouse were similar to those found in the expressed human peripheral blood repertoire and in productive and non-productive genomic DNA rearrangements. These data indicate the importance of intrinsic genetic factors in shaping the human Vlambda repertoire and highlight the remarkable conservation of the molecular mechanisms involved in the production of the antibody repertoire in mouse and man. Therefore, transgenic mice represent a good model for analysis of the human antibody repertoire and for the production of human antibodies.

Animals↗
PubMed1999

A human immunoglobulin lambda locus is similarly well expressed in mice and humans.

Transgenic mice carrying a 380-kb region of the human immunoglobulin (Ig) lambda light (L) chain locus in germline configuration were created. The introduced translocus on a yeast artificial chromosome (YAC) accommodates the most proximal Iglambda variable region (V) gene cluster, including 15 Vlambda genes that contribute to >60% of lambda L chains in humans, all Jlambda-Clambda segments, and the 3' enhancer. HuIglambdaYAC mice were bred with animals in which mouse Igkappa production was silenced by gene targeting. In the kappa-/- background, human Iglambda was expressed by approximately 84% of splenic B cells. A striking result was that human Iglambda was also produced at high levels in mice with normal kappa locus. Analysis of bone marrow cells showed that human Iglambda and mouse Igkappa were expressed at similar levels throughout B cell development, suggesting that the Iglambda translocus and the endogenous kappa locus rearrange independently and with equal efficiency at the same developmental stage. This is further supported by the finding that in hybridomas expressing human Iglambda the endogenous L chain loci were in germline configuration. The presence of somatic hypermutation in the human Vlambda genes indicated that the Iglambda-expressing cells function normally. The finding that human lambda genes can be utilized with similar efficiency in mice and humans implies that L chain expression is critically dependent on the configuration of the locus.

Animals↗
PubMed1999

Age-dependent changes in memory and mushroom bodies in the Drosophila mutant vermilion deficient in the kynurenine pathway of tryptophan metabolism.

Evolutionary conservation of homologous genes that cause related phenotypes in humans and Drosophila help to unravel genes implicated in polygenic human diseases. Among them are neurodegenerative disorders, such as Huntington, Parkinson, Alzheimer and HIV-induced diseases. They are characterized by a late onset disturbances of memory, changes in volumetric indices of the brain structures involved in memory formation, synaptic and glial pathology, and altered content of the intermediates of the kynurenine pathway, the endogenous modulators of the NMDA receptors. This pathway in conserved in insects, rodents and humans. We, therefore, studied the effects of aberrant tryptophan metabolism on memory, brain plasticity, synaptic and glial immunoreactivity in the Drosophila mutants vermilion (no kynurenines) and cinnabar (excess of neuroprotective kynurenic acid) over the life time. The mutant vermilion demonstrated gradual decline of 3-th memory performance and complete memory failure on the 28th day of life in a paradigm of conditioned courtship suppression. A drastic increase in the volume of the calyces of the mushroom bodies, and a decay in immunochemical staining of this brain structure with antibodies to synaptic protein csp and glia, precede the age-dependent memory defect and develop from the 12th day of adult life.

Aging↗
PubMed1999

[The detection of transgenic animals using a polymerase chain reaction in situ].

The technique for detecting both foreign and host specific DNA sequences inside nuclei and chromosomes of single cells of transgenic mice with the help of polymerase chain reaction (PCR) in situ is described. The mouse preimplantation and postimplantation embryonic and adult cells were studied. The methodology is described in detail with particular attention to the optimization of composition of reaction mixture, kind of fixation and preliminary denaturation of target DNA. The reaction takes only several hours and needs no sophisticated equipment.

Animals↗
PubMed1997

Yeast colony size reflects YAC copy number.

A novel strategy for separation of co-cloned YACs was developed. For this, yeast cells were grown under non-selective conditions to allow the mitotic loss of multiple YACs. Yeast colonies of different size appear on 'drop-out' selection plates with small clones consistently containing a single-copy YAC. Different auxotrophic marker genes can be used to separate co-cloned YACs or reduce their copy number, which is essential for most YAC-modification procedures.

Blotting, Southern↗
PubMed1997

Rapid induction of B-cell lymphomas in mice carrying a human IgH/c-mycYAC.

Activation of the c-myc proto-oncogene by one of the immunoglobulin (Ig) loci after chromosomal translocation is a consistent feature of Burkitt's lymphoma. Different subtypes of this tumor vary in the molecular architecture of the translocation region. In most cases there are no known regulatory elements of the Ig locus neighboring the oncogene and this considerably obscures the mechanism of its deregulation. In order to assess possible oncogene activation signals, we produced an experimental translocation region by insertion of a c-myc gene about 50 kb from the IgH intron enhancer in a yeast artificial chromosome (YAC) containing a 220 kb region of the human Ig heavy chain (IgH) locus. Single copy integration of this YAC into the genome of mouse embryonic stem (ES) cells was achieved by spheroplast fusion. Chimeric mice derived from these ES cells developed monoclonal B-cell lymphomas expressing surface IgM by 8-16 weeks of age. The IgH/c-myc translocus showed different V(h)DJ(H) rearrangement in almost all tumors without any alterations of the distance between c-myc and the IgH intron enhancer. This mouse model can be used for the in vivo analysis of c-myc deregulation and the tumor formation capacity of the IgH locus in aberrant rearrangements.

Animals↗
PubMed1997

[Reconstructive plastic surgery of the esophagus in children].

The article presents the authors' experiences with reconstructive-plastic operations of the esophagus in children. The esophagoplasty was performed in 60 patients with congenital and acquired diseases. Among the congenital diseases are esophageal atresia, short esophagus and Barrett's esophagus, the acquired diseases include postburn scarry injuries. The optimum method of creation of the artificial esophagus are described. Of great significance are thought to be angiosurgical and microsurgical methods of cutting out the intestinal transplants. Cases of free autotransplantation of the intestinal segments for the substitution of the injured esophagus are described. Positive results were obtained in most cases.

Adolescent↗
PubMed1997

[Plasmosorption in combined therapy of psoriasis].

Combined therapy with plasmosorption has been performed in 22 patients aged 18-65 years suffering from different variants of psoriasis diagnosed 5 to 24 years before. Stable remission was achieved in 16 patients who exhibited normalization of peripheral blood characteristics including total protein and protein plasma fractions, lowering of CIC and middle molecular peptides concentration. The response was also obtained in severe psoriasis (psoriatic erythrodermia and arthropathic psoriasis). 11 patients remained in remission for at least 1 year. Due to plasmosorption the hospital stay of the patients reduced. Plasmosorption promoted detoxication, recovery of hepatic protein-synthetizing function, enhancement of plasma albumin detoxication ability.

Adolescent↗
PubMed1996

Assembly and extension of yeast artificial chromosomes to build up a large locus.

For the assembly of a large human locus, overlapping regions on yeast artificial chromosomes (YACs) and cosmids were linked up using their regions of homology. By site-specific recombination a YAC of 410 kb was created accommodating the major part of the human lambda light chain locus in authentic configuration with 28 variable (V) genes, all joining (J) segments, all constant (C) genes and the downstream enhancer. A contiguous region was first constructed from three overlapping cosmids. Each of these was linearized at unique sites in the vectors and YAC arms were ligated to the 5' and 3' ends. After cells of Saccharomyces cerevisiae were transformed with the three cosmids, YACs of 120 kb were obtained which contained the reassembled 3' J-C region in authentic configuration. The assembled YAC was further extended by mitotic recombination with a YAC containing a 280-kb region of the C-proximal part of the V gene cluster with a 15-kb 3' overlap. For this, a simple three-way selection procedure was developed involving the integration of different selectable marker genes at specific sites in the left and right YAC arms. Rare recombination events between two overlapping YACs could be identified in yeast clones able to grow in lysine- and adenine-deficient medium in the presence of 5-fluoro-orotic acid which is toxic for yeast cells containing a YAC with a functional URA3 gene. This approach made it possible to assemble and extend large YACs from an unlimited number of smaller overlapping YACs by positive-negative selection.

Chromosomes, Artificial, Yeast↗
PubMed1996

Dominant expression of a 1.3 Mb human Ig kappa locus replacing mouse light chain production.

Expression studies of multigene families, such as the immunoglobulin (Ig) loci, are difficult because of their large size and the necessity to introduce germline configured regions into an animal. Antibody diversity from Ig gene miniloci is limited by the number of variable (V) region genes and the need for distal regulatory elements to control expression. Here, we show germline transfer into mice of a 1300 kb human Ig kappa light chain locus on a yeast artificial chromosome that resulted in early DNA rearrangement and highly efficient human light chain expression. The human locus was assembled from a 300 kb authentic region using contig extension by addition of cosmid multimers to supplement the variable gene cluster. This resulted in the addition of about 100 V region genes in germline configuration from different families. In transgenic animals with Ig kappa disruption, this large human kappa locus replaced the endogenous locus, and subsequent down-regulation of Ig lambda light chain contribution led to a dominant expression of the rearranged human genes. Contrary to expectation, rather than providing a solely selective advantage for ensuring repertoire formation controlled by the sheer number of introduced genes, the lambda/kappa ratio in serum appears to be the result of competition for early surface Ig expression maintained in the developing B cell.-Zou, X., Xian, J., Davies, N. P., Popov, A. V., Brüggemann, M. Dominant expression of a 1.3 Mb human Ig kappa locus replacing mouse light chain production.

Animals↗