Molecular Pathogenesis and the Possible Role of Mitochondrial Heteroplasmy in Thoracic Aortic Aneurysm.

Thoracic aortic aneurysm (TAA) is a life-threatening condition associated with high mortality, in which the aortic wall is deformed due to congenital or age-associated pathological changes. The mechanisms of TAA development remain to be studied in detail, and are the subject of active research. In this review, we describe the morphological changes of the aortic wall in TAA. We outline the genetic disorders associated with aortic enlargement and discuss the potential role of mitochondrial pathology, in particular mitochondrial DNA heteroplasmy, in the disease pathogenesis.

Electronic band structure in n-type GaAs/AlGaAs wide quantum wells in tilted magnetic field.

Oscillations of the real component of AC conductivity [Formula: see text] in a magnetic field were measured in the n-AlGaAs/GaAs structure with a wide (75 nm) quantum well by contactless acoustic methods at [Formula: see text] mK. In a wide quantum well, the electronic band structure is associated with the two-subband electron spectrum, namely the symmetric (S) and antisymmetric (AS) subbands formed due to electrostatic repulsion of electrons. A change of the oscillations amplitude in tilted magnetic field observed in the experiments occurs due to crossings of Landau levels of different subbands (S and AS) at the Fermi level. The theory developed in this work shows that these crossings are caused by the difference in the cyclotron energies in the S and AS subbands induced by the in-plane magnetic field.

Linear magnetoresistance in the low-field limit in density-wave materials.

The magnetoresistance (MR) of a material is typically insensitive to reversing the applied field direction and varies quadratically with magnetic field in the low-field limit. Quantum effects, unusual topological band structures, and inhomogeneities that lead to wandering current paths can induce a cross-over from quadratic to linear MR with increasing magnetic field. Here we explore a series of metallic charge- and spin-density-wave systems that exhibit extremely large positive linear MR. By contrast to other linear MR mechanisms, this effect remains robust down to miniscule magnetic fields of tens of Oersted at low temperature. We frame an explanation of this phenomenon in a semiclassical narrative for a broad category of materials with partially gapped Fermi surfaces due to density waves.

Fractional Quantum Hall States in a Ge Quantum Well.

Measurements of the Hall and dissipative conductivity of a strained Ge quantum well on a SiGe/(001)Si substrate in the quantum Hall regime are reported. We analyze the results in terms of thermally activated quantum tunneling of carriers from one internal edge state to another across saddle points in the long-range impurity potential. This shows that the gaps for different filling fractions closely follow the dependence predicted by theory. We also find that the estimates of the separation of the edge states at the saddle are in line with the expectations of an electrostatic model in the lowest spin-polarized Landau level (LL), but not in the spin-reversed LL where the density of quasiparticle states is not high enough to accommodate the carriers required.

A facility for X-ray diffraction in magnetic fields up to 25 T and temperatures between 15 and 295 K.

A facility for X-ray diffraction has been developed at the National High Magnetic Field Laboratory. It brings diffraction capability to the 25 T Florida split coil magnet and implements temperature control in a range of 15-295 K using a cold finger helium cryostat. This instrument represents an alternative to pulsed magnetic field systems, and it exceeds the static magnetic fields currently available at synchrotron facilities. Magnetic field compatibility of an X-ray source and detectors with the sizable magnetic fringe fields emanating from the magnet constrained the design of the diffractometer.

Stand alone experimental setup for dc transport measurements.

Described is a system consisted of Keithley's current source Model 6221 and nanovoltmeter Model 2182A pairs. That pair was developed by Keithley for precise measurements of a sample's one electrical parameter by the dc current-reversal transport technique. Nonstandard synchronization method employed in the presented setup allows assembling several pairs together for low level electrical measurements of a sample's several parameters associated with the same current, thus expanding the applications of these devices. The equipment was tested by simultaneous measurements of such two parameters as transverse magnetoresistance and Hall voltage on the following materials: Si/SiGe, Ge:Mn; HgTe/HgCdTe, and InMnSb.

[Operator-constitutive mutation in the recA gene enhances radiation resistance of Escherichia coli].

Plasmid pUC19-recAoc carrying a mutant allele of the recA gene, which plays the key role in the control of the SOS repair system and homologous recombinational repair, causes a 1.5-fold increase in radiation resistance of Escherichia coli DeltarecA cells, as compared to the wild-type recA+ cells. The protective effect of this plasmid is drastically reduced in mutant lexA3 recADelta21 deficient in the LexA protein and in induction of the SOS regulon. Plasmid pUC19-recAoc effectively suppresses UV sensitivity of the DeltarecA mutant. Mutation recAo20 allows constitutive high-level synthesis of the RecA protein. This mutation impairs the SOS box in the operator site of the recA gene and enhances heterology of the dimer LexA binding site. These data confirm that high level of the RecA protein synthesis per se is not sufficient for the expression of gamma-inducible functions and that the derepression of lexA-dependent genes, other than recA gene, is necessary for the complete induction of the SOS repair system.

[The investigation of the composition of liquid radioactive waste].

In investigation the process of composition sediment of liquid unorganic radioactive waste, that are forming in cistern-selectors at PNPI RAS, it was discovered apart from great quantity of ions of different metals and radionuclides considerable maintenance of organic material (to 30% and more from volume of sediment) unknown origin. A supposition was made about its microbiological origin. Investigation shows, that the main microorganisms, setting this sediment, are the bacterious of Pseudomonas kind, capable of effectively bind in process of grow the radionuclide 90Sr, that confirms the potential posibility of using this microorganisms for bioremediation of liquid low radioactive wastes (LRW).

[Isolation and investigation of natural yeast strains resistant to heavy metal salts and radionuclides]. / Vydelenie i izuchenie prirodnykh shtammov drozhzhei, ustoichivykh k soliam tiazhelykh tetallov i radionuklidov.

The collection of yeasts (more than 2000 strains) from extreme natural environment of Kamchatka peninsular and Kuril Islands was created. 448 strains were selected for their resistance to salts of such heavy metals as Cu, Cd, Co and to high temperature (37-52 degrees C). 72% of strains appeared to be resistant to one or more selective factors. We obtained several strains able to grow on medium with 0.1 M/L nonradioactive strontium and (or) cesium. Four of this strains accumulated radioactive isotope 90Sr with 45-80% efficiency. Thus, we demonstrated that yeast strains from nature could be used for bioremediation of industrial waste solutions, polluted by radionuclides and salts of heavy metals.

[Proteins induction by cysteamine in Escherichia coli cells]. / Induktsiia tsisteaminom belkov v kletkakh Escherichia coli.

It was shown, what in presence of oxygen in broad interval time of treatment in E. coli cells was induced line proteins by cysteamine which are proteins SOS--repair system and heat--shock system. There are quantitative defined induction level RecA, GroEL and DnaK proteins which are members this systems. It was allowed to propose what radioprotective action of cysteamine in higher degree is defined by its characteristics as induction agent for stress systems of cells.

[Quantitative analysis of inducible systems of Escherichia coli and Bacillus subtilis using radioimmunological methods]. / Kolichestvennoe issledovanie indutsibel'nykh sistem kletok Escherichia coli i Bacillus subtilis radioimmunologicheskim metodom.

By RIA dot-blot method two main cell system, system SOS-repair and heat shock system, was showed possibility to receive as well qualitative as quantitative results influence of different induced agents. Was showed quantitative differences in initial levels enzymes of RecA and CroEL in different strains of E. coli, as well of principle possibility to using received antibody, which has high specific to this enzymes, for investigation reactions this systems in the other bacterial species, such as Bac. subtilis.

[Polymerase chain reaction with universal primers for studying genomes]. / Polimeraznaia tsepnaia reaktsiia s universal'nym praimerami dlia izucheniia genomov.

Universal primer ability of generating conservative and variable UP-PCR (universally primed polymerase chain reaction) species-specific patterns was analysed on bacteria to serve as an example. Also, two important properties of the UP-PCR patterns (species/primer DNA hybridization specificity) are characterized.

[Induction of the SOS-like system in Rec-mutants of Bacillus subtilis]. / Induktsiia SOS-podobnoi sistemy u Rec-mutantov Bacillus subtilis.

Influence of the recE1, recB2, recB3, recB19, recF15, recF18, recL16, recM13 and recM27 mutations of the induction of the SOS-like system component, i. e. the RecE protein of Bacillus subtilis was studied by RIA-dot-blot method in UV-irradiated or treated by nalidixic acid cells. These agents caused a significant increase in the wild type (rec+) cells but did not stimulate the RecE synthesis in the rec mutants tested. The two exceptions were recB2 and recF18 mutants treated by nalidixic acid. The tsi23 mutation caused thermoinduction of phi 105 bacteriophage in the rec+ genetic background while no prophage particles were induced in the recE, recF, recL, recM mutants. The data suggest that the genetic damage of several rec genes including recB, recE, recF, recL and recM can block induction of the SOS-like system of Bacillus subtilis.

[Repaired and unrepaired DNA damage induced by x-irradiation of nonproliferating rat hepatocytes]. / Repariruemye i nerepariruemye povrezhdeniia DNK, voznikaiushchie pri rentgenovskom obluchenii neproliferiruiushchikh gepatotsitov krys.

An effective system of repair of double-strand DNA breaks was found in the stock culture of rat hepatocytes by the method of elastoviscosimetry. The inhibitors of DNA resynthesis, hydroxyurea and arabinosyl cytosine, which transformed single-strand breaks into double-strand ones were used to estimate the level of spontaneous affection of the hepatocyte genome. With a reference to this level the authors have demonstrated that after a dose of 2 Gy and 6-24-hour repair, the additional number of lesions was registered. These lesions were shown to be incised by nucleases similar to those involved into the conventional repair process.

[Mutagenic effects of gamma-rays on plasmid DNA in Escherichia coli]. / Mutagennoe deistvie gamma-luchei na plazmidnuiu DNK Escherichia coli.

A purified and dried DNA of plasmid pKO482 (galK+) is 10 times more resistant to the inactivating action of 60Co-gamma-rays than that of lambda phage. gamma-Irradiation of the plasmid DNA induces forward mutations of galK, the frequency of which increases linearly with the dose. The efficiency of the mutagenic action of gamma-rays on the plasmid galK locus is 10(-12) per 1 rad and per 1 base pair. The mutagenic effect of gamma-radiation but slightly depends upon bacterial recA+ gene and upon the SOS-repair system induced by UV-irradiation of the recipient cells. It is assumed that the premutational lesions induced in the purified DNA by the direct effect of gamma-radiation are fixed into mutations by misreplication.

Induction by gamma irradiation of double-strand breaks of Escherichia coli chromosomes and their role in cell lethality.

Viscoelastometric measurements of DNA from gamma-irradiated bacteria were used to identify the induction of double-strand breaks ( DSBs ) in the chromosome of Escherichia coli. It is shown by means of inhibitors of repair endonucleases and different repair mutants that most DSBs in DNA of E. coli, gamma-irradiated in buffer, arise from enzymatic incision of primary gamma-damages; therefore, previous conclusions regarding DSB repair must be reconsidered. Based on these results, much of the reparable damage is single-strand breaks, and this damage can initiate formation of gaps and ultimately, when repair is insufficient, generation of enzymatically caused DSBs . After extensive repair, the first residual DSB in the E. coli chromosome is generated at approximately 160 Gray (Gy), which corresponds to the D37 dose. We propose that DSBs induced directly by gamma-irradiation are not repaired in wild-type strains. In a recently isolated gamma-resistant strain, E. coli Gamr444 , the dose required for observation of DSB after postirradiation incubation is 1,000 Gy, which corresponds to the D37 of the strain. The resistance is proposed to be due to an ability to repair genuine DSBs .

[Modification of DNA damage in rat hepatocytes following whole-body roentgen radiation using cysteamine and 8-bromocaffeine]. / Modifitsiruemost' povrezhdenii v DNK gepatotsitov krys posle obshchego rentgenovskogo oblucheniia s pomoshch'iu tsisteamina i 8-bromkofeina.

Using the elastoviscosimetric method it was shown that the level of residual DNA double-strand breaks in rat hepatocytes depended on conditions of total-body X-irradiation: it increased in the presence of a sensitizer, 8-bromocaffeine and decreased in the presence of a protector, cysteamine. This correlation confirms a major role of fixed DNA double-strand breaks in the formation of a lethal effect in a cell.

[Relation of double-stranded DNA breaks and their repair to cell death and recovery after methylnitrosourea exposure]. / Sviaz' dvukhnitel'nykh razryvov DNK i ikh reparatsii s gibel'iu i vosstanovleniem kletok posle vozdeistviia metilnitrozomocheviny.

The yield of DNA double-strand breaks (DSB) in the cells of mouse lymphosarcoma treated with nitrosomethylurea (NMU) was registered by means of elastoviscosimetry. It was shown that after short-term (7 min) treatment with NMU the lesions formed in DNA are efficiently repaired both in complete and conditioned media. After long-term (30 min) treatment DNA was only repaired in complete growth medium. The yield of the first fixed DSB after long-term NMU treatment correlated with the mean lethal dose D0. After short-term NMU treatment the first DSBs are registered in the dose range which is 4-fold higher than D0. The nature of lethal and potentially lethal lesions as well as the participation of various repair systems in the elimination of potentially lethal lesions are discussed.