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At least 973 records · Page 54Linked to original sources
PubMed1990

[Value and limitations of transthoracic Doppler echocardiography in the diagnosis of thromboses of mechanical valve prosthesis. Report of 19 cases].

The diagnosis of thrombosis of a valvular prosthesis is difficult especially in cases of partial thrombosis. The authors report 19 cases of partial thrombosis of mainly (16 cases) mechanical valve prostheses confirmed by radioscopy and treated either by reoperation or fibrinolysis. Mitral Valve Prostheses: 14 cases (6 Björk, 7 SJM, 1 Carbomedics). All but one case showed significant prolongation of the pressure half time compared with the postoperative reference value. In one case, however, the functional parameters of the prosthesis were normal; the diagnosis was made from the finding of a mobile thrombus on the ventricular surface of the prosthesis. Aortic Valve Prostheses: 5 cases (3 Björk, 1 SJM, 1 Duromedics). Continuous wave Doppler showed significant increases in the velocity of transprosthetic blood flow with respect to the postoperative reference values. Accurate analysis of the mobile elements of the prostheses was usually impossible. These results show that transthoracic Doppler echocardiography remains an excellent method of study and surveillance of mechanical valve prostheses but the limitations of the technique should be familiar to all operators.

Aged↗
PubMed1990

[Effects of gamma-irradiation on the gonadal cells of Drosophila melanogaster under varying conditions of hybrid dysgenesis].

Comparative analysis was carried out with respect to the results of combined effects of gamma-irradiation and transposition of mobile elements in Drosophila, depending on the succession of their application. As turned out, introduction of the P and hobo elements into the M' line, prior to irradiation, resulted in decreased number of unfertilized eggs and reduced the proportion of flies killed at the larval and pupal stages. However, opposite effects were shown, when the P element was introduced following irradiation: the number of unfertilized eggs and that of the flies killed at the larval and pupal stages has significantly increased, as compared to the control. Interaction between the processes induced at the level of DNA repair both by gamma-irradiation and the P' elements' transposition is suggested.

Animals↗
PubMedDate not supplied

[The variability of the telomeric and of a number of internal regions of Drosophila chromosomes according to the intensity of hybridization in situ with labelled probes].

Cloned Drosophila DNA fragments containing telomere-specific sequences have been hybridized in situ. It is found that intensity of their hybridization with telomeres greatly varies in different nuclei of the same salivary gland. This phenomenon is also observed for internal sites where some mobile elements included in several DNA fragments under investigation are located. Within each nucleus different regions are hybridized non-uniformly as well. It is suggested that these phenomena can be explained by varying polytenization in telomeres and some internal chromosomal regions.

Animals↗
PubMed1990

[Superunstable systems in Drosophila melanogaster. Analysis of mutations in signed and cut loci].

The lines of the M'-cytotype characterized by a long-term instability (which was shown to be conditioned by transpositions of the new mobile element, Stalker) were hybridized with the P-line. This resulted in the appearance of a number of superunstable mutations at the yellow, white, singed, ocelliless and some other loci. The authors analyzed four independently obtained families of superunstable mutations at the singed locus. A wide spectrum of derivatives and high frequency of mutations were demonstrated, as well as the regularities of allelic transitions. Besides this, mutagenesis at the cut locus was observed in the chromosomes carrying sn mutations with frequency of 5.05 x 10(4). By means of the blot analysis it has been shown that most of ct mutations are intragenic deficiencies, ranging from 1.3 to 3 Kb, whose appearance is, conceivably, attributed to the inaccuracy of the insertion excision (the insertion is present but fails to alter the phenotype) at the cut locus of the chromosomes with the superunstable sn-alleles. In the lines with the sn- and ct-mutations the transpositions of the P-element and the Stalker were found, which indicates their involvement in mutagenesis. The authors discuss possible effects of inserting the complicated constructions, based on the combinations of P-element and the Stalker, on the induction of superinstability.

Alleles↗
PubMed1990

[Superunstable systems in Drosophila melanogaster: analysis of mutations in the ocelliless locus].

Six super-unstable mutations were obtained after crossing the M-cytotype strain of Drosophila melanogaster, where transpositions of the Stalker mobile element occur, with the pi 2 strain. One of these mutations appeared at the ocelliless locus. Detailed genetic analysis of this mutation and its numerous super-unstable derivatives was performed. Eleven allelic classes with different expression of the oc phenotype were isolated. The main features of super-instability at the ocelliless locus have been described and found to be common for all super-unstable systems obtained in our experiments. The role of the P element in the induction of super-instability is discussed.

Alleles↗
PubMed1987

The mitochondrial reading frame RF3 is a functional gene in Saccharomyces uvarum.

The yeast mitochondrial genome contains three reading frames, RF1, RF2, and RF3, which are related to the group I maturases, though they are not intronic sequences. In the Saccharomyces cerevisiae strain D273-10B/A, these reading frames are interrupted by G + C-rich sequences (GC clusters) which break the frames. In the present work we described a Saccharomyces uvarum strain which possesses a RF3 continuous sequence devoid of GC clusters. Moreover, our results strongly suggest that in the same strain RF2 and RF1 are also continuous sequences. As all three RFs belong to transcription units which are highly expressed, it is most reasonable to assume that RF1, RF2, and RF3 are functional genes. Furthermore, we have discovered a rule which seems to explain the transposition of GC clusters, considered as mobile elements, in the mitochondrial genome.

Base Sequence↗
PubMed1989

[Interaction of products of su(Hw) and su(f) genes with MDG4 region regulating its transcription suppresses mutations in Drosophila caused by insertion of this gene].

The mdg4 (gypsy) mobile element of Drosophila contains two closely situated regions binding to proteins from nuclear extracts. One of these is an imperfect palindrome having homology with the lac operator of Escherichia coli, the other contains a reiterated sequence (5'PyPuTCTGCATACTPyPy) homologous to the octamer which is the core of many enhancers and upstream promoter elements. The transient expression of deletion mutants has shown that these DNA regions are negative and positive regulators, respectively, of mdg4 transcription. As was demonstrated earlier, mutations induced by the presence of mdg4 at different loci are suppressed, owing to either repression or activation of mdg4 transcription in Drosophila lines carrying unlinked mutations in su(Hw) or su(f) genes. We have shown that binding to a negative regulator (silencer) is weakened in nuclear extracts isolated from cell lines carrying su(f) mutations which activate mdg4 transcription; therefore, the su(f) gene codes for a protein capable of mdg4 repression. Furthermore, binding to a positive regulator is weakened in nuclear extracts isolated from cell lines carrying su(Hw) gene mutations which decrease the level of mdg4 transcription; hence, the su(Hw) gene encodes a protein which activates mdg4 transcription.

Animals↗
PubMed1989

[Detection of new genes participating in the trans-regulation of locus yellow of MDG-4 in Drosophila melanogaster].

The aim of the present work was to obtain mutations in the genes involved in regulation of the yellow locus and mdg4. For this purpose, we searched for mutations changing phenotypic expression of the y(2) mutation induced by mdg4 insertion into the regulatory region of the yellow locus. Mutations have been obtained in the earlier described system of prolonged genome instability, sometimes combined with P-M hybrid dysgenesis. The mutation mod(mdg4) in a novel gene, modifier of mdg4, was detected which either enhanced or suppressed a phenotypic expression of several mutations induced by mdg4 insertion. We suggest that mod(mdg4) controls the expression of mdg4. In addition, the mutations in five loci located on the X chromosome have been found which enhanced the mutation phenotype of several y alleles induced by insertions of different mobile elements in the regulatory region of the latter. Possibly, the protein products of these genes designated as enhancers of yellow-1, 2, 3, 4 and 5 are directly or indirectly involved in control of the yellow locus expression.

Alleles↗
PubMed1988

[X-chromosome inversion in Drosophila melanogaster accompanied by a mosaic-type position effect: an analysis using cloned DNA fragments].

DNA fragments carrying the genes affected by position effect variegation in the In(1LR)pn2a chromosome were revealed. In situ hybridizations demonstrate preservation of specific DNA sequences in the polytene chromosome regions containing the inactivated genes. It was shown that both euchromatic-heterochromatic boundaries in the In(1LR)pn2a chromosome contain the mobile element B104 (roo).

Animals↗
PubMed1987

[Comparative analysis of the structure of incompatibility plasmids N, P and W].

Evolutionary relationships of the IncN plasmid R15 and other broad host range plasmids (IncN plasmids N3 and R46, IncP plasmids RP4 and R906, IncW plasmids Sa and R388) were studied by Southern blot hybridization technique. The IncN plasmids were shown to harbour homologous determinants for replication and conjugation. No homology was found between the rep and tra genes in R15 and in the IncW and IncP plasmids, respectively. The second rep region of the N3 plasmid is distinctive from the corresponding determinants in the IncN plasmids. Homology was demonstrated for the plasmid genes that mediate restriction and modification in R15 and N3, mercury resistance in R15 and R906, sulfanilamide resistance in R15, N3, R46, Sa, R388, and R906, streptomycin resistance in R15, R46 and Sa. The latter genes are different from the R906 SmR gene. In addition to the three known mobile elements in the plasmid R15, the fourth one (IS46) that is a part of the transposon Tn2353 was identified in this study. Besides, the third copy of this insertion sequence was found in the N3 plasmid.

Base Sequence↗
PubMed1979

General considerations of X-ray microanalysis of frozen hydrated tissue sections.

X-ray microanalysis of frozen hydrated sections can be applied for analysis of diffusible or highly mobile elements which might be displaced or lost when conventional preparatory techniques are used. Once frozen the specimen must be handled in such a way that it becomes vacuum compatible for subsequent analysis. Analysis cannot be accomplished without compartment recognition. Initial freezing can be considered successful if ice crystal damage does not exceed the dimension of the compartment to be analyzed. As compartment size decreases ice crystal artifacts become a significant problem. The application of special freezing methods including use of non-penetrating cryoprotectants is an important advance in freezing methodology for X-ray analysis. Cryosectioning is a fracturing process at low temperatures which can affect morphology and may affect analysis. An understanding of this process can aid in optimizing cryosectioning for use in preparing frozen hydrated and frozen dried section for X-ray microanalysis. Special equipment is necessary for both freeze dried as well as frozen hydrated specimen; while special transfer devices are necessary for frozen hydrated specimen transfer. Because of the design of cold stages special consideration for reducing extraneous background radiation is an intrinsic part of their application to biological X-ray analysis.

Animals↗
PubMedDate not supplied

[Genome instability and neoplasia].

Necessity of oncogene for the neoplastic cell transformation is substantiated. The oncogene may be introduced into the cell by a virus; be present in the cell from its formation but be repressed by products of regulatory genes; be arisen from separated DNA segments. The latter possibility is discussed in view of data on the presence of mobile elements and Sarc sequences in the cell genome.

Animals↗
PubMed1983

[Exact method for the measurement of the rotation of the humerus head in the shoulder joint using computed tomography].

An exact method of measuring the degree of inward-and outward rotation in the humero-scapular joint is demonstrated. The advantage of the use of computed tomography as compared with the clinical method of measurement is the accurate differentiation of the mobility of the individual parts of the arm's mobile elements with respect to the trunk and the documentation of the result. For inward rotation we have measured a mean value of 38 degrees on the right side and of 37 degrees on the left; the corresponding values for outward rotation were 37 and 41 degrees. In eleven patients who had undergone Bankart's operation we found the outward rotation of the arm in the shoulder joint decreased to a mean value of 15 degrees.

Anthropometry↗
PubMed1995

[Determinants of hybrid dysgenesis in the native population of Drosophila from Altai].

Localization of mobile elements P and hobo in the genomes of isofemale Drosophila lines obtained from a natural population from Biisk (Altai) was analyzed using in situ hybridization. The average copy number per genome was 27.1 for P and 22.0 for hobo. The highest number of P and hobo copies was recorded in the 3R and 21 chromosomes, respectively. The X chromosome contained the lowest number of hobo copies. For P, this relationship was not shown. Both transposons had preferential localization sites, or "hot spots", which partly coincided with intercalary heterochromatin regions. Correlation analysis of P and hobo copy number showed independent distribution of these hybrid dysgenesis determinants. The 1A site, which is thought to be associated with the P-cytotype expression, was not labelled in any line.

Animals↗
PubMed1995

The proximal aorta: a source of stroke.

The availability of the sophisticated imaging techniques of transoesophageal echocardiography and epiaortic ultrasound scanning have drawn attention to the ascending aorta and aortic arch as a potential source of embolic stroke. Several studies have shown an association between atheroma in this region and cerebral ischaemic events. Although aortic atheroma is associated with vascular disease in other arterial territories, two large controlled studies have shown it to be a risk factor for stroke, independently of other major risk factors such as carotid vascular disease, cardiac disease and hypertension. In observational and case-control studies, the risk of stroke is higher in the presence of certain echocardiographic appearances of atheromatous plaque--these include plaque thickness of > 4-5 mm, surface irregularity suggesting plaque ulceration and mobile elements suggesting superimposed thrombus. However, longitudinal studies are required to evaluate the prognostic significance of such findings. Several therapeutic options have been described or suggested in patients with and without stroke in whom aortic atheroma is demonstrated, but the optimal management of such patients is yet to be determined in prospective controlled trials.

Aorta, Thoracic↗
PubMed1994

The origins and consequences of genetic instability in prokaryotes.

The causes of genetic change include errors in replication and repair, transposition and recombination. Together, these processes generate a reservoir of genetic variants from which selection will amplify any changes which increase host fitness. Recombination, transposition and slippage during replication may all result in large-scale DNA rearrangements. Homologous and illegitimate recombination generate deletions, inversions, duplications and fusions. Intramolecular transposition can cause deletion or inversion of DNA sequences adjacent to the mobile element, while intermolecular movement may lead to fusion of donor and target replicons when transposition is replicative. Of crucial importance is how genetic variation affects the fitness of the host cell. For a neutral variant the probability of eventual fixation is small, but changes which increase host cell fitness pose a more serious problem because these cells will eventually dominate the culture. The most effective way to combat the proliferation of variant plasmid cloning vectors is to block the processes by which they arise. Cloning vectors should be "stress-tested" and DNA sequence analysis programs can be used to screen for sequence repetition which should be removed, as far as possible, from both vectors and cloned sequences. It is also important that vectors place modest metabolic demands on their hosts in order to minimise the potential increase in fitness associated with changes in plasmid structure.

Biotechnology↗
PubMed1993

[Genetic analysis of the interaction of mutations in two genes, controlling expression of MDG4].

Transcription of the retrovirus-like mobile element mdg4 (gypsy) in controlled by the protein product of the suppressor of Hairy wing which interacts with the mdg4 enhancer, and by the protein product of the mdg4 modifier which seems to interact with the su(Hw) protein. In the present work, we studied interaction of mod(mdg4) and su(Hw) mutations in phenotypic expression of mutations induced by mdg4 insertion. Different types of inhibitory effect of mdg4 enhancer on transcription of the target gene were detected. Most frequently, the inhibitory depends on the presence of the mod(mdg4) protein. On of the two acidic domains of su(Hw) protein may be removed without changing the effect. Additional removal of the leucine zipper domain strongly reduces the effect. The second type of inhibition depends of or decrease in the concentration of the mod(mdg4) protein. The su(Hw) protein should have both acidic domains in this case. Sometimes, the su(Hw) protein lacking the C-end acidic domain may activate transcription of a target gene, and this effect does not depend on the presence or absence of the mod(mdg4) protein. The effect may be increased by removal of leucine zipper. Binding of the mod(mdg4) protein to the su(Hw) protein does not depend of the C-end acidic domain and leucine zipper.

Animals↗
PubMed1996

[Molecular nature of the unstable white-starka allele].

In 1992, Bashkirov et al. described the case of occurrence in line C(1)RM, yw/0; Dp(1; 3) wvco/+ of a unique female with light, uniformly colored eyes. This trait was not inherited together with Dp(1; 3) wvco but was linked to the X chromosome. We denoted this new allele as white-starka (wstr). It proved to be unstable, demonstrating mutational transitions to other allelic states with frequencies of 10(-3) to 10(-5). Southern blot analysis showed that the wstr mutation was induced by an insertion of an unknown sequence with a length approximately evaluated by the authors in 1992 as 7 kb. Using a wider spectrum of restriction endonucleases and a prolonged gel running, we were able to estimate the size of this insertion more precisely. According to our data, in the case of wstr we are dealing with an insertion in the locus white of a sequence 15.1 kb long. As seen from our restriction map of the allele wstr, this insertion does not resemble retroposons with long terminal repeats, but is possibly similar to LINE mobile elements of Het-A and TART types, characteristic for heterochromatin.

Alleles↗