Publications by authors named "Dmitry Kovalev"

20 Publications

  • Page 1 of 1

Phylogenetics of Bacillus anthracis isolates from Russia and bordering countries.

Infect Genet Evol 2021 May 4:104890. Epub 2021 May 4.

Federal Government Health Institution «Stavropol Plague Control Research Institute» of the Federal Service for Surveillance in the Sphere of Consumers Rights Protection and Human Welfare, 13-15 Sovetskaya Str, 355035 Stavropol, Russian Federation.

Anthrax is a concern for public health and veterinary medicine in Russia. The available phylogenetic data on isolates from Russia and neighboring CIS countries are clearly not enough to gain a better understanding of their position in the global phylogenetic population structure of this pathogen. In this study, we analyzed the genomes of 66 Bacillus anthracis strains, which were isolated between 1935 and 2019 from different sources in Russia, as well as in Ukraine, Azerbaijan, Georgia, Armenia and Moldova. Whole genome SNP analysis of genomes of 66 strains obtained in this study along with 222 B. anthracis genomes available in the GenBank database revealed 7242 SNPs used to construct a phylogenetic reconstruction with the method of Maximum Likelihood. Studied strains belong to 6 different genetic groups: A.Br.008(A.Br.008/009), A.Br.001(Ames), A.Br.014(A.Br.Aust94), A.Br.085(A.Br.001/002), A.Br.034(A.Br.005/006, Ancient A) and B.Br.002 (B.Br.001/002). Within the group A.Br.014(A.Br.Aust94) a subcluster A.Br.029 of strains isolated in Georgia, Armenia, Azerbaijan, Russia (Republic of Dagestan) and Turkey, named Caucasus-East Anatolia (CEA), was identified. In the subgroup A.Br.105(Tsiankovskii) the cluster A.Br.117 of strains from Russia, Ukraine and Slovakia are assigned, in the subgroup A.Br118 (STI) - cluster A.Br.123 with strains from Russia and Georgia and cluster A.Br.125 with strains from Republic of Dagestan. New subclusters B.Br.017("EUROPE") were identified in the B.Br.002(B.Br.001/002) cluster, represented by strains from the European part of Russia, as well as from South Korea and Finland. For 8 clusters and subclusters, the SNP markers were identified. The study confirmed a significant genetic diversity of the strains isolated in Russia and border countries and clarified their position in the phylogenetic structure of the global B. anthracis population. New genetic clusters A.Br.029 (CEA), A.Br.117, A.Br.123, A.Br.125, and B.Br.017 («EUROPE») were defined. 96 marker SNPs specific for these clusters were identified.
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http://dx.doi.org/10.1016/j.meegid.2021.104890DOI Listing
May 2021

Differential paraventricular nucleus activation and behavioral responses to social isolation in prairie voles following environmental enrichment with and without physical exercise.

Soc Neurosci 2021 May 5. Epub 2021 May 5.

Department of Psychology, Northern Illinois University, DeKalb, IL, 60115.

Social stressors produce neurobiological and emotional consequences in social species. Environmental interventions, such as environmental enrichment and exercise, may modulate physiological and behavioral stress responses. The present study investigated the benefits of environmental enrichment and exercise against social stress in the socially monogamous prairie vole. Female prairie voles remained paired with a sibling (control) or were isolated from a sibling for 4 weeks. The isolated groups were separated into isolated sedentary, isolated with environmental enrichment, and isolated with both enrichment and exercise conditions. Behaviors related to depression, anxiety, and sociality were investigated using the forced swim test (FST), elevated plus maze (EPM), and a social crowding stressor (SCS), respectively. cFos expression was evaluated in stress-related circuitry following the SCS. Both enrichment and enrichment with exercise protected against depression-relevant behaviors in the FST and social behavioral disruptions in the SCS, but only enrichment with exercise protected against anxiety-related behaviors in the EPM and altered cFos expression in the hypothalamic paraventricular nucleus in isolated prairie voles. Enrichment may alleviate emotion-related and social behaviors, however physical exercise may be an important component of environmental strategies for protecting against anxiety-related behaviors and reducing neural activation as a function of social stress.
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http://dx.doi.org/10.1080/17470919.2021.1926320DOI Listing
May 2021

Yersinia pestis strains isolated in natural plague foci of Caucasus and Transcaucasia in the context of the global evolution of species.

Genomics 2021 Apr 20;113(4):1952-1961. Epub 2021 Apr 20.

Stavropol Research Anti-Plague Institute, 355035 Stavropol, Russian Federation.

Background: Plague is a highly dangerous vector-borne infectious disease that has left a significant mark on history of humankind. There are 13 natural plague foci in the Caucasus, located on the territory of the Russian Federation, Azerbaijan, Armenia and Georgia. We performed whole-genome sequencing of Y. pestis strains, isolated in the natural foci of the Caucasus and Transcaucasia. Using the data of whole-genome SNP analysis and Bayesian phylogeny methods, we carried out an evolutionary-phylogeographic analysis of modern population of the plague pathogen in order to determine the phylogenetic relationships of Y. pestis strains from the Caucasus with the strains from other countries.

Results: We used 345 Y. pestis genomes to construct a global evolutionary phylogenetic reconstruction of species based on whole-genome SNP analysis. The genomes of 16 isolates were sequenced in this study, the remaining 329 genomes were obtained from the GenBank database. Analysis of the core genome revealed 3315 SNPs that allow differentiation of strains. The evolutionary phylogeographic analysis showed that the studied Y. pestis strains belong to the genetic lineages 0.PE2, 2.MED0, and 2.MED1. It was shown that the Y. pestis strains isolated on the territory of the East Caucasian high-mountain, the Transcaucasian high-mountain and the Priaraksinsky low-mountain plague foci belong to the most ancient of all existing genetic lineages - 0.PE2.

Conclusions: On the basis of the whole-genome SNP analysis of 345 Y. pestis strains, we describe the modern population structure of the plague pathogen and specify the place of the strains isolated in the natural foci of the Caucasus and Transcaucasia in the structure of the global population of Y. pestis. As a result of the retrospective evolutionary-phylogeographic analysis of the current population of the pathogen, we determined the probable time frame of the divergence of the genetic lineages of Y. pestis, as well as suggested the possible paths of the historical spread of the plague pathogen.
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http://dx.doi.org/10.1016/j.ygeno.2021.04.021DOI Listing
April 2021

Molecular genotyping of 15 B. anthracis strains isolated in Eastern Siberia and Far East.

Mol Phylogenet Evol 2021 Jun 18;159:107116. Epub 2021 Feb 18.

Stavropol Research Anti-Plague Institute, 355035 Stavropol, Russian Federation. Electronic address:

Bacillus anthracis is a pathogenic bacterium, which causes anthrax disease. The ability of this bacterium to form spores, which can be preserved in soil for decades and cause outbreaks later on, makes this pathogen a serious problem for veterinary and health services of many countries. Siberia is one of the most anthrax-influenced regions of Russia. In this research we report on the results of genotyping based on whole genome SNP analysis of 15 strains, isolated on the territory of Eastern Siberia and the Far East in 1956-2018. In this research, we sequenced 15 genomes of B. anthracis strains isolated from infected humans and animals, and from soil samples from the territory of Eastern Siberia and the Far East in the period from 1956 to 2018. We used genomic sequences obtained in this study and 219 B. anthracis genomes available in the international GenBank database to perform a comparative analysis. As a result we detected 6400 chromosomal SNPs which allowed to differentiate the studied strains. We built phylogenetic reconstruction of the global B. anthracis population based on the detected SNPs using the Maximum Likelihood Method and described genetic diversity of the strains isolated on the territory of Eastern Siberia and the Far East. Strains, isolated on this territory from 1956 to 2018 belong to 5 different genetic groups: "Ames", "STI", "Tsiankovskii", "Siberia" and "Asia". The greatest diversity of the strains is registered for two regions of the southern part of Eastern Siberia - Tyva and Buryatia. This research expands current understanding of genetic diversity of B. anthracis strains circulating on the territory of Russia.
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http://dx.doi.org/10.1016/j.ympev.2021.107116DOI Listing
June 2021

Single crystals of ferroelectric lithium niobate-tantalate LiNbTaO solid solutions for high-temperature sensor and actuator applications.

Acta Crystallogr B Struct Sci Cryst Eng Mater 2020 Dec 16;76(Pt 6):1071-1076. Epub 2020 Nov 16.

Universität Potsdam, Institut für Physik, Karl Liebknecht Str. 24-25, Potsdam, 14471, Germany.

Ferroelectric LiNbTaO solid solutions with various Nb/Ta ratio were grown from the melt by the Czochralski method. The exact composition of the grown crystals was determined by inductively coupled plasma atomic mass spectrometry. The dependence of the crystal composition on the composition of the initial melt was obtained and explained by a wide separation between the phase boundaries of the liquid and solid phases on the LiNbO-LiTaO phase diagram. Using high-resolution X-ray diffraction, the parameters a and c of a crystal unit cell were determined (LiNbTaO: a = 5.1574 Å and c = 13.8498 Å). Further, the Curie temperature T of the crystals was measured using the differential scanning calorimetry technique. T was found to depend on the composition of the crystals that allowed conditions for the monodomainization of the grown crystals to be defined (LiNbTaO: T = 1102°C; LiNbTaO: T = 794°C). Finally, the velocity of surface acoustic waves was determined by scanning electron microscopy and X-ray diffraction techniques (YZ-cut of a LiNbTaO crystal: V = 3440 m s).
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http://dx.doi.org/10.1107/S2052520620014390DOI Listing
December 2020

Diazapyrenes: interaction with nucleic acids and biological activity.

Chem Heterocycl Compd (N Y) 2020 Jul 17:1-20. Epub 2020 Jul 17.

North Caucasus Federal University, 1a Pushkina St, Stavropol, 355017 Russia.

The review summarizes data on the practical aspects of the interaction of nucleic acids with diazapyrene derivatives. The information on biological activity is given and the probable mechanisms underlying the action of diazapyrenes are analyzed. It contains 119 references.
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http://dx.doi.org/10.1007/s10593-020-02717-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7366485PMC
July 2020

Phylogenetic analysis of Bacillus anthracis strains from Western Siberia reveals a new genetic cluster in the global population of the species.

BMC Genomics 2019 Sep 2;20(1):692. Epub 2019 Sep 2.

Irkutsk Antiplague Research Institute of Siberia and Far East, Irkutsk, Russian Federation, , 664047.

Background: Anthrax is a zoonotic disease caused by the gram-positive bacterium Bacillus anthracis. The most anthrax-endemic regions of Russia are Siberia and North Caucasus. Previously, genotyping of Russian B.anthracis isolates was carried out using canSNP and MLVA data; these methods yield lower resolution results compared to whole genome SNP analysis (wgSNP). In this research, we have used wgSNP method for genotyping of 10 B.anthracis isolates, obtained during 1961-2016 in Russia on territory of Western Siberia.

Results: We have analyzed 185 B.anthracis genomes available in GenBank database and genomes of 10 isolates obtained in this study to determine the place of Russian isolates in the global phylogeny of B.anthracis. For the studied genomes we have detected 7203 SNPs, which were used for building a phylogenetic reconstruction with Maximum Likelihood Method. Results of the phylogenetic analysis indicate that Russian strains belong to three different genetic groups. Three strains belong to genetic group "Ames", two strains - to "STI" group. Five strains belong to the main genetic line B, and four of them form a subcluster, described for the first time, which we have named "Siberia".

Conclusions: In this study, the data on genetic diversity of B.anthracis strains on the territory of Western Siberia is presented for the first time. As a result of complex phylogenetic analysis, the place of these isolates was determined in the global phylogenetic structure of the B.anthracis population. We describe a new cluster in the main genetic line B for the first time.
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http://dx.doi.org/10.1186/s12864-019-6060-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6720099PMC
September 2019

Genotyping and phylogenetic location of one clinical isolate of Bacillus anthracis isolated from a human in Russia.

BMC Microbiol 2019 07 17;19(1):165. Epub 2019 Jul 17.

Stavropol State Agrarian University, Stavropol, 355017, Russian Federation.

Background: Anthrax is a zoonotic disease caused by the Gram-positive bacterium Bacillus anthracis. In Russia, there are more than 35 thousand anthrax stationary unfavourable sites. At the same time, there is very little published information about the isolates of B. anthracis from the territory of Russia. In this study, we report the use of whole genome sequencing (WGS) and bioinformatics analysis to characterize B. anthracis 81/1 strain isolated in Russia in 1969 from a person during an outbreak of the disease in the Stavropol region.

Results: We used 232 B. anthracis genomes, which are currently available in the GenBank database, to determine the place of the Russian isolate in the global phylogeny of B. anthracis. The studied strain was characterized by PCR-based genetic methods, such as Multiple-Locus Variable-Number Tandem Repeat Analysis (MLVA), canonical single nucleotide polymorphisms (canSNP), as well as the method of full-genomic analysis of nucleotide polymorphisms (wgSNP). The results indicate that the Russian B. anthracis 81/1 strain belongs to Trans-Eurasion (TEA) group, the most representative in the world.

Conclusions: In this study, the full genomic sequence of virulent B. anthracis strain from Russia was characterized for the first time. As a result of complex phylogenetic analysis, the place of this isolate was determined in the global phylogenetic structure of the B. anthracis population, expanding our knowledge of anthrax phylogeography in Russia.
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http://dx.doi.org/10.1186/s12866-019-1542-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6637652PMC
July 2019

Global evolution and phylogeography of Brucella melitensis strains.

BMC Genomics 2018 May 10;19(1):353. Epub 2018 May 10.

Stavropol Research Anti-Plague Institute, 13-15 Sovetskaya Street, 355035, Stavropol, Russia.

Background: Brucellosis is a bacterial zoonotic disease. Annually in the world more than 500,000 new cases of brucellosis in humans are registered. In this study, we propose an evolutionary model of the historical distribution of B. melitensis based on the full-genomic SNP analysis of 98 strains.

Results: We performed an analysis of the SNP of the complete genomes of 98 B. melitensis strains isolated in different geographical regions of the world to obtain relevant information on the population structure, genetic diversity and the evolution history of the species. Using genomic sequences of 21 strains of B. melitensis isolated in Russia and WGS data from the NCBI database, it was possible to identify five main genotypes and 13 species genotypes for analysis. Data analysis based on the Bayesian Phylogenetics and Phylogeography method allowed to determine the regions of geographical origin and the expected pathways of distribution of the main lines (genotypes and subgenotypes) of the pathogen.

Conclusions: Within the framework of our study, the model of global evolution and phylogeography of B. melitensis strains isolated in various regions of the planet was proposed for the first time. The sets of unique specific SNPs described in our study, for all identified genotypes and subgenotypes, can be used to develop new bacterial typing and identification systems for B. melitensis.
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http://dx.doi.org/10.1186/s12864-018-4762-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5946514PMC
May 2018

Indications for and results of axillary arterio-venous fistula in patients with a functionally single ventricle after cavopulmonary anastomosis†.

Eur J Cardiothorac Surg 2019 Mar;55(3):572-578

Department of Radiation Diagnostics, Bakulev National Medical Research Center for Cardiovascular Surgery, Ministry of Health of the Russian Federation, Moscow, Russia.

Objectives: This study aimed to investigate the indications for and the results of axillary arterio-venous fistula in patients with a functionally single ventricle at mid-term follow-up after bidirectional cavopulmonary connection.

Methods: From 2012 to 2017, 20 patients aged 21.1 ± 8.7 years (median 20.5) underwent axillary arterio-venous fistula after bidirectional cavopulmonary connection in our institution. The interval between bidirectional cavopulmonary connection and axillary arterio-venous fistula was 13.9 ± 7.2 years. The clinical and haemodynamic parameters of the patients were assessed before and after surgery.

Results: There was no in-hospital mortality. Paraesthesia of the arm persisted for 1-7 days. The mean arterial oxygen saturation increased from 72.4 ± 7.1% pre-surgery to 81.6 ± 5.5% (P < 0.001) after surgery, and was 83.8 ± 6.5% at discharge (P = 0.002 Wilcoxon matched pairs test). The haemoglobin, haematocrit, McGoon index and ejection fraction values did not change significantly. The speed and minute volume of the blood flow in the superior vena cava increased from from 21.1 ± 8.3 cm/s to 28.8 ± 14.9 cm/s (P < 0.001) and from 10.6 ± 3.7 ml/s to 12.5 ± 2.9 ml/s (P < 0.001), respectively. At the mid-term follow-up (1-5 years), 2 patients died from concomitant pathology. Stable improvement in the state and tolerance of physical activity was noted: before surgery, 17 patients were classified as New York Heart Association functional capacity (FC) III and 3 patients as FC IV; after surgery, 9 patients were FC II and 3 patients were FC III. One patient underwent a Fontan operation within 3 years.

Conclusions: Axillary arterio-venous fistula can be used as the stage of surgical treatment and a bridge to Fontan and/or heart transplantation for this category of patients.
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http://dx.doi.org/10.1093/ejcts/ezx484DOI Listing
March 2019

Associations Between Newly Discovered Polymorphisms of the CEBPD GENE LOCUS and Body Parameters in Sheep.

Anim Biotechnol 2016 Oct;27(4):217-22

a Faculty of Veterinary Medicine , Stavropol State Agrarian University , Stavropol , Russian Federation.

An understanding of what effects particular genes can have on body parameters in productive animals is particularly significant for the process of marker-assisted selection. The gene of transcriptional factor CCAAT/enhancer-binding protein delta (CEBPD gene) is involved in the process of growth in animals and is known to be a promising candidate for use as a genomic marker. The structure of the CEBPD gene locus was determined using NimbleGen sequencing technology (Roche, USA). The effect of polymorphisms, which were identified using the aforementioned technology, was investigated in 30 rams of the Manych Merino sheep breed. Twenty-two single nucleotide polymorphisms (SNP) were detected in the CEBPD gene locus. Significantly, two SNPs, namely, g.315T>G and g.327C>T, have been identified for the first time. It was demonstrated that the complex of linked SNPs, consisting of g.301A>T, g.426T>C, and g.1226T>C, had a negligible effect on body parameters in Manych Merino sheep. Animals with the heterozygous type of SNP g.1142C>T exhibited changes solely in the chest and croup width. The newly discovered SNP g.327C>T was proven to have a negative effect on live weight and body size (p < 0.05) in Manych Merino sheep. Sheep with the heterozygous type of g.562G>A and g.3112C>G SNP complex showed an increase in live weight and dimensions (p < 0.05) compared with those of wild homozygous type. Consequently, SNPs g.327C>T, g.562G>A, and g.3112C>G in the CEBPD gene locus can be successfully used as markers in sheep breeding. Future research will evaluate the influence of the aforementioned SNPs on slaughter indicators for sheep meat production.
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http://dx.doi.org/10.1080/10495398.2016.1168304DOI Listing
October 2016

Comparative genomic analysis of two isolates of Vibrio cholerae O1 Ogawa El Tor isolated during outbreak in Mariupol in 2011.

Infect Genet Evol 2016 10 29;44:471-478. Epub 2016 Jul 29.

Federal Budget Institute of Science Central Research Institute for Epidemiology, Moscow 111123, Russian Federation. Electronic address:

Cholera is a water-borne, severe enteric infection essentially caused by toxigenic strains of Vibrio cholera O1 and O139 serogroups. An outbreak of cholera was registered during May-July 2011 in Mariupol, Ukraine, with 33 cholera cases and 25 carriers of cholera. Following this outbreak, the toxigenic strain of V. cholerae 2011EL-301 was isolated from seawater in the recreation area of Taganrog city on the territory of Russia. The aim of our study was to understand genomic features of Mariupol isolates as well as to evaluate hypothesis about possible interconnection between the outbreak of cholera in Mariupol and the single case of isolation of V. cholerae from the Sea of Azov in Russia. Mariupol isolates were phenotypically characterized and subsequently subjected to whole genome sequencing procedure. Phylogenetic analysis based on high-quality SNPs of V. cholera O1 El Tor isolates of the 7th pandemic clade from different regions showed that clinical and environmental isolates from Mariupol outbreak were attributable to a unique phylogenetic clade within wave 3 of V. cholera O1 El Tor isolates and characterized by six clade-specific SNPs. Whereas Taganrog isolate belonged to distantly related clade which allows us to reject the hypothesis of transmission the outbreak strain of V. cholerae O1 from Ukraine to Russia in 2011. Mariupol isolates shared a common ancestor with Haiti\Nepal-4\India clade indicating that outbreak progenitor strain most likely originated in the South Asia region and later was introduced to Ukraine. Moreover, genomic data both based on hqSNPs and similarity of virulence-associated mobile genomic elements of Mariupol isolates suggests that environmental and clinical isolates are a part of joint outbreak which confirms the role of contaminated domestic sewage, as an element of the complex chain of infection spread during cholera outbreak. In general, the genome-wide comparative analysis of both genes and genomic regions of epidemiological importance indicates accessory of this isolates to 'new' clone of toxigenic multiple drug resistance atypical variant of V. cholerae O1 El Tor.
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http://dx.doi.org/10.1016/j.meegid.2016.07.039DOI Listing
October 2016

Repair of isolated partial anomalous pulmonary venous connection of the right upper pulmonary veins to the left vertical vein.

Interact Cardiovasc Thorac Surg 2016 09 21;23(3):501-2. Epub 2016 May 21.

Bakoulev Center for Cardiovascular Surgery, Moscow, Russia

The most common form of partial anomalous pulmonary venous connection is drainage of the right pulmonary veins to the superior vena cava. On the contrary, partial anomalous venous connection of right pulmonary veins to the left vertical vein is described in few reports. The goal of this publication is to present the case of diagnosis and surgical repair of this extremely rare pathology in a 19-year old female. Methods of preoperative examination included but were not limited to spiral computed tomography and angiocardiography. Intraoperative examination confirmed that the collector of right upper pulmonary veins was connected to the vertical vein that continued to the innominate vein and then to the superior vena cava draining into the right atrium. During surgical intervention, the vertical vein was transected in the area of connection to the innominate vein with the suturing of inlet area. The collector of the right upper pulmonary veins was then anastomosed with the left atrial appendage. Postoperative course was uneventful. In conclusion, isolated partial anomalous pulmonary venous connection of the right upper pulmonary veins to the left vertical vein is a very rare congenital defect. Existing modern techniques contribute to the precise and timely diagnosis of this anomaly.
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http://dx.doi.org/10.1093/icvts/ivw151DOI Listing
September 2016

Results of Fontan operation in patients with atrioventricular valve regurgitation.

Eur J Cardiothorac Surg 2015 Aug 18;48(2):308-14; discussion 314-5. Epub 2014 Dec 18.

Bakoulev Center for Cardiovascular Surgery, Moscow, Russia

Objectives: The influence of concomitant atrioventricular valve regurgitation on the results of Fontan operation remains disputable. The goal of this study was to compare early and late results of Fontan operation performed in patients with mild or moderate-to-severe atrioventricular valve regurgitation.

Methods: For retrospective analysis, patients with atrioventricular valve insufficiency assessed by echocardiography were divided into three groups based on the severity of regurgitation and its repair or non-repair during Fontan operation: Group 1: unrepaired regurgitation 1-2+ (n = 33); Group 2: unrepaired regurgitation 3-4+ (n = 11); Group 3: repaired regurgitation 3-4+ (n = 35). Actuarial survival was estimated by the Kaplan-Meier method, followed by the log-rank test to compare survival curves between groups.

Results: Hospital mortality rates in Groups 1 through 3 reached 3, 27 and 14%, respectively (P = 0.015, Group 1 vs Group 2). The frequency of non-lethal complications did not significantly differ between groups. However, patients from Group 2 required significantly more intensive inotropic support, longer mechanical ventilation and had larger pleural effusion. Predicted survival after Fontan operation was the worst in Group 2 (P = 0.016, Group 2 vs Group 1). The frequency of non-lethal late complications was also the highest in Group 2 (50 vs 17 or 11%); however, the difference did not reach statistical significance (P = 0.13 and 0.069, respectively). The severity of atrioventricular valve regurgitation during the follow-up did not significantly change when compared with discharge after the repair in Group 2 or Group 3 (P = 0.19 and 0.52, respectively), and significantly increased in Group 1 (P = 0.003). However, this increase did not have clinical significance during the reported period of follow-up.

Conclusions: If unrepaired, concomitant moderate-to-severe atrioventricular valve regurgitation significantly worsens the results of the Fontan procedure. Longer observation is needed to define the strategy in patients with mild atrioventricular valve regurgitation that remained unrepaired during Fontan operation.
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http://dx.doi.org/10.1093/ejcts/ezu489DOI Listing
August 2015

Porous silicon nanocrystals in a silica aerogel matrix.

Nanoscale Res Lett 2012 Jul 17;7(1):397. Epub 2012 Jul 17.

Department of Physics, University of Bath, Claverton Down, Bath, BA2 7AY, UK.

Silicon nanoparticles of three types (oxide-terminated silicon nanospheres, micron-sized hydrogen-terminated porous silicon grains and micron-size oxide-terminated porous silicon grains) were incorporated into silica aerogels at the gel preparation stage. Samples with a wide range of concentrations were prepared, resulting in aerogels that were translucent (but weakly coloured) through to completely opaque for visible light over sample thicknesses of several millimetres. The photoluminescence of these composite materials and of silica aerogel without silicon inclusions was studied in vacuum and in the presence of molecular oxygen in order to determine whether there is any evidence for non-radiative energy transfer from the silicon triplet exciton state to molecular oxygen adsorbed at the silicon surface. No sensitivity to oxygen was observed from the nanoparticles which had partially H-terminated surfaces before incorporation, and so we conclude that the silicon surface has become substantially oxidised. Finally, the FTIR and Raman scattering spectra of the composites were studied in order to establish the presence of crystalline silicon; by taking the ratio of intensities of the silicon and aerogel Raman bands, we were able to obtain a quantitative measure of the silicon nanoparticle concentration independent of the degree of optical attenuation.
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http://dx.doi.org/10.1186/1556-276X-7-397DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3475076PMC
July 2012

Nanosilicon in water as a source of hydrogen: size and pH matter.

Nanotechnology 2011 Jul 1;22(30):305402. Epub 2011 Jul 1.

Department of Physics, University of Bath, Bath, UK.

We report on the interaction of silicon nanocrystals with water/alcohol solutions which results in their complete oxidation, the hydrolysis of water and hydrogen generation in amounts close to the ideal scenario. Water acts as an oxidizer while alcohol is required for efficient wetting of nanosilicon. This process results in the formation of silicon-based alcogel which can be further transferred to aerogel.
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http://dx.doi.org/10.1088/0957-4484/22/30/305402DOI Listing
July 2011

Experience with bidirectional cavopulmonary anastomosis and modified Fontan operation in patients with single ventricle and concomitant visceral heterotaxy.

Interact Cardiovasc Thorac Surg 2011 Apr 13;12(4):563-8. Epub 2011 Jan 13.

Department of Congenital Heart Defects, Bakoulev Center for Cardiovascular Surgery, Moscow, Russia.

The object of our study was to analyze the results of bidirectional cavopulmonary anastomosis (BCPA) and modified Fontan operations (MFO) in patients with a functionally single ventricle and heterotaxy syndrome and to reveal risk factors for these surgical interventions. During 1983-2010, 681 patients underwent BCPA or MFO. Thirty-nine had heterotaxy syndrome. The median follow-up period after BCPA and MFO was nine and 1.5 years, respectively. Risk factors for lethal outcomes were determined by logistic regression analysis. Hospital mortality after BCPA and MFO was 7.9% and 12.5%, respectively and did not significantly differ from patients without heterotaxy. The most frequent hospital complications were heart failure, pleural effusions, and arrhythmias. Late mortality after BCPA and MFO was 8.7% and did not significantly differ from patients without heterotaxy. Late deaths were caused by congestive heart failure or pulmonary thromboembolism. The main non-lethal complication was arrhythmia. Patients have significantly improved their functional class at follow-up. The independent risk factor for lethal outcomes after BCPA and MFO was preoperative regurgitation at atrioventricular valves (P=0.012). BCPA and MFO in patients with a functionally single ventricle and heterotaxy syndrome allow to significantly improves their quality of life. Preoperative regurgitation at atrioventricular valves worsens surgical results.
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http://dx.doi.org/10.1510/icvts.2010.253567DOI Listing
April 2011

Silicon photonics: moving into the red.

Authors:
Dmitry Kovalev

Nat Nanotechnol 2010 Dec;5(12):827-8

Department of Physics, University of Bath, Bath BA27AY, UK.

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http://dx.doi.org/10.1038/nnano.2010.244DOI Listing
December 2010

Immediate results of bidirectional cavopulmonary anastomosis and Fontan operations in adults.

Interact Cardiovasc Thorac Surg 2011 Feb 25;12(2):141-5. Epub 2010 Nov 25.

Department of Congenital Heart Defects, Bakoulev Center for Cardiovascular Surgery, Moscow, Russia.

The purpose of this study is to analyze the immediate results of bidirectional cavopulmonary anastomosis (BCPA) and Fontan operations performed in adults, and to reveal the risk factors. During the years 1983-2010, 681 consecutive patients underwent BCPA or a Fontan operation. Fifty-three of 681 patients were more than 18 years of age. Twenty-nine adults underwent BCPA and 24 underwent a Fontan operation. Immediate results of surgical treatment were followed during the hospital period. The average number of exceeded 'operability' criteria by Choussat et al. [Choussat A, Fontan F, Besse P, Vallot F, Chauve A, Bricaud H. Selection criteria for Fontan procedure. In: Anderson RH, Shinebourne EA, editors. Pediatric Cardiology. Edinburgh: Churchhill Livingstone, 1977:559-566] was significantly higher in patients from the BCPA group compared to the Fontan group (1.3±0.8 vs. 0.9±0.7, P=0.034). Hospital mortality after BCPA in adults was 6.9% (2/29) and did not differ from children (7.1%, 19/268), P=0.634. Hospital mortality after Fontan operation in adults was 8.3% (2/24) and did not differ from children (11.9%, 43/360), P=0.419. The frequency of non-lethal hospital complications was higher in patients after a Fontan operation. Patients from the Fontan group more frequently developed arrhythmias and prolonged pleural effusions. Preoperative regurgitation at atrioventricular valves was an independent risk factor for hospital mortality and morbidity after a Fontan operation. BCPA and Fontan operations performed in adults are accompanied by good immediate results and considerably improves patients' condition.
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http://dx.doi.org/10.1510/icvts.2010.253484DOI Listing
February 2011