Effects of fires on vascular plant and microalgae communities of steppe ecosystems

The article is focused on a hypothesis verification: the higher plants, microalgae and cyanobacteria may be used in bioindication of steppe ecosystem restoration dynamics after fires. On the territory of the Askania Nova biosphere reserve (Ukraine) 4 stationary polygons were investigated: SP1 – steppe area which had not been exposed to fire for 20 years preceding our study, as well as areas where single fires occurred in 2001 (SP2), 2005 (SP3), and a site where fires occurred in 2001 and 2004 (SP4). The investigation revealed the dynamics of height and projected area of the higher vegetation according to seasons during two years (2010 and 2011), as well as abundance and biomass of microalgae and cyanoprokaryotes in the soil layer by the layer of the depth to 15 cm. It was found that the effects of pyrogenic load re-main evident for several years after the fires, manifesting in decrease of the height and projected area of herbage, the number and biomass of algae and cyanobacteria in the soil, especially to the depth of 5 cm. Multivariate general linear models were used to test the significance of the dependence of quantitative characteristics of vegetation, microalgae, and cyanoprokaryotes on environmental predictors (season, year, soil layer, and fire). In the model, 75.2% of the grass height variability and 91.6% of the grass projected area variability could be explained by the predictors under consideration. In the series SP1 → SP2 → SP3 → SP4 the grass height and projected area decreased. The differences in the projected area of the grass stand were most evident in spring. The model explained 89.1% of the variation in abundance and 91.6% of the variation in biomass of Bacillariophyceae. The abundance of Bacillariophyceae was greater in the upper soil layer than in the lower layer and decreased with depth. The abundance of this group of algae decreased in the series SP1 → SP2 → SP3 → SP4 at depths of 0–5 and 5–10 cm. Changes in abundances of Chlorophyta, Streptophyta, Heterokontophyta (Xanthophyceae and Eustigmatophyceae) equaling 47.6% could also be explained by the model. The abundance of this group of algae was greatest in the upper soil layer. In the upper soil layer, the maximum abundance of Chlorophyta, Streptophyta, and Heterokontophyta (Xanthophyceae and Eustigmatophyceae) was recorded for Polygon SP1 and the minimum for Polygon SP3. Within the model, 48.0% of the variation in biomass of Chlorophyta, Streptophyta, and Heterokontophyta (Xanthophyceae and Eustigmatophyceae) was explained by the environmental predictors. The biomass trend was cohe-rent with the population trend. A special feature was that there was a significant increase in biomass at 10–15 cm depth at Polygon SP3 compared to other polygons at this depth. The model was able to explain 61.8% of the variation in abundance and 66.7% of the variation in cyanobacteria biomass. The highest abundance of cyanobacteria was found in the upper soil layer of polygon SP1. Somewhat lower num-bers of cyanobacteria were at polygons SP2 and SP4, and the lowest were found in the upper soil layer at polygon SP3. In turn, the highest number of cyanobacteria was found particularly at this polygon in the 5–10 cm layer. The biomass in the 0–5 cm layer was coherent with the abundance pattern of this group. The research results confirmed that the quantitative characteristics of the higher vegetation (height and projected area) as well as of microalgae and cyanobacteria (abundance and biomass) may be used in bioindication of the dynamics of post-pyrogenic processes in steppe ecosystems

Interaction of nucleotide excision repair factors RPA and XPA with DNA containing bulky photoreactive groups imitating damages

Interaction of nucleotide excision repair factors-replication protein A (RPA) and Xeroderma pigmentosum complementing group A protein (XPA)-with DNA structures containing nucleotides with bulky photoreactive groups imitating damaged nucleotides was investigated. Efficiency of photoaffinity modification of two proteins by photoreactive DNAs varied depending on DNA structure and type of photoreactive group. The secondary structure of DNA and, first of all, the presence of extended single-stranded parts plays a key role in recognition by RPA. However, it was shown that RPA efficiently interacts with DNA duplex containing a bulky substituent at the 5′-end of a nick. XPA was shown to prefer the nicked DNA; however, this protein was cross-linked with approximately equal efficiency by single-stranded and double-stranded DNA containing a bulky substituent inside the strand. XPA seems to be sensitive not only to the structure of DNA double helix, but also to a bulky group incorporated into DNA. The mechanism of damage recognition in the process of nucleotide excision repair is discussed.</p

Interaction of nucleotide excision repair factors RPA and XPA with DNA containing bulky photoreactive groups imitating damages

Interaction of nucleotide excision repair factors-replication protein A (RPA) and Xeroderma pigmentosum complementing group A protein (XPA)-with DNA structures containing nucleotides with bulky photoreactive groups imitating damaged nucleotides was investigated. Efficiency of photoaffinity modification of two proteins by photoreactive DNAs varied depending on DNA structure and type of photoreactive group. The secondary structure of DNA and, first of all, the presence of extended single-stranded parts plays a key role in recognition by RPA. However, it was shown that RPA efficiently interacts with DNA duplex containing a bulky substituent at the 5′-end of a nick. XPA was shown to prefer the nicked DNA; however, this protein was cross-linked with approximately equal efficiency by single-stranded and double-stranded DNA containing a bulky substituent inside the strand. XPA seems to be sensitive not only to the structure of DNA double helix, but also to a bulky group incorporated into DNA. The mechanism of damage recognition in the process of nucleotide excision repair is discussed.</p

Combined myocardial perfusion scintigraphy and computed tomography: diagnostic and prognostic value in coronary artery disease

Modern imaging techniques occupy an important place in the diagnosis, selection of treatment and prognosis of patients with coronary artery disease. Hybrid imaging is a combination of two sets of diagnostic data that complement and enhance each other by comparing anatomical and functional characteristics. As a rule, hybrid imaging is synergistic, that is, more powerful, since the addition of new information leads to an increase in the sensitivity and specificity of each of the modalities separately.The review provides brief information on the diagnostic efficacy of myocardial perfusion scintigraphy (MPS), computerized tomography (CT) coronary angiography in comparison with invasive coronary angiography with fractional flow reserve. The diagnostic and prognostic significance of assessing calcium index with MPS, as well as CT coronary angiography combined with MPS in the diagnosis, risk stratification and prognosis of patients with coronary artery disease, is characterized in detail. A separate section is devoted to the importance of hybrid imaging in making decisions about myocardial revascularization

Impact of magnetic storms on the global TEC distribution

The study is focused on the analysis of total electron content (TEC) variations during six geomagnetic storms of different intensity: from Dstmin = −46&thinsp;nT to Dstmin = −223&thinsp;nT. The values of TEC deviations from its 27-day median value (δTEC) were calculated during the periods of the storms along three meridians: American, Euro-African and Asian-Australian. The following results were obtained. For the majority of the storms almost simultaneous occurrence of δTEC maximums was observed along all three meridians at the beginning of the storm. The transition from a weak storm to a superstorm (the increase of magnetic activity) almost does not affect the intensity of the δTEC maximum. The seasonal effect was most pronounced along the Asian-Australian meridian, less often along the Euro-African meridian and was not revealed along the American meridian. Sometimes the seasonal effect can penetrate to the opposite hemisphere. The character of average δTEC variations for the intense storms was confirmed by GOES satellite data. Though there are some common features of TEC variation revealed during each storm phase, in general no clear dependence of TEC responses on the storm phases was found: the effects were different during each storm at different locations. The behavior of the correlation coefficient (R) between δTEC values along the three meridians was analyzed for each storm. In general, R &gt; 0.5 between δTEC values averaged along each meridian. This result is new. The possible reasons for the exceptions (when R &lt; 0.5) were provided: the complexity of phenomena during the intense storms and discordance in local time of the geomagnetic storm beginning along different meridians. Notwithstanding the complex dependence of R on the intensity of magnetic disturbance, in general R decreased with the growth of storm intensity.</p

Association of impaired myocardial flow reserve with risk factors for cardiovascular diseases in patients with nonobstructive coronary artery disease

Aim. To reveal the association between disorders of myocardial blood flow and reserve, according to dynamic single photon emission computed tomography (SPECT), with risk factors for cardiovascular diseases (CVD) in patients with nonobstructive coronary artery disease (CAD).Material and methods. The study included patients with suspected stable nonobstructive (&lt;50%) CAD. Based on the survey data, anamnesis, out- and in-patient medical records, we analyzed main CVD risk factors. All patients underwent dynamic myocardial SPECT and analysis of blood lipid profile in vitro. Depending on myocardial flow reserve (MFR), two groups were formed: 1. With reduced MFR &lt;2,0 (rMFR); 2. With normal MFR ≥2,0 (nMFR).Results. The study included 47 patients divided into 2 following groups: the rMFR group consisted of 24 patients (15 men, age 56,3±9,1 years), the nMFR group — 23 patients (13 men, age 58,4±10,7 years). There was no significant difference in prevalence of CVD risk factors in groups. However, dyslipidemia was detected more often in rMFR patients (p=0,053): 58% vs 30%, respectively. In patients with rMFR, there were significantly higher levels of total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C). Correlation analysis revealed significant negative inverse relationships between MFR values with TC (ρ=-0,36, p=0,01) and LDL-C (ρ=-0,38, p=0,009). According to univariate logistic regression, significant predictors of reduced MFR were TC (odds ratio (OR), 2,32; 95% confidence interval (CI), 1,17-4,59; p=0,01) and LDL-C (OR, 2,16; 95% CI, 1,04-4,51; p=0,04). According to a stepwise multivariate logistic regression analysis, only TC was an independent predictor of a decrease in MFR (OR, 2,32; 95% CI, 1,17-4,59; p=0,02).Conclusion. MFR, determined by dynamic SPECT, is associated with TC and LDL-C levels. TC level is an independent predictor of a decrease in MFR

Coronary flow reserve in patients with heart failure with preserved ejection fraction

Aim. To study the parameters of myocardial blood flow (MBF) and coronary flow reserve (CFR) in patients with heart failure (HF) with preserved ejection fraction and evaluate their relationship with the severity of HF.Material and methods. The study included 47 patients (men, 68,7%) aged 65,0 (58,0; 72,0) years with left ventricular ejection fraction of 62 (56; 67)% and coronary artery stenosis &lt;50%. Serum levels of N-terminal pro-brain natriuretic peptide (NT-proBNP) were assessed by enzyme immunoassay. MBF and CFR values were assessed using cardiac single photon emission computed tomography.Results. Depending on NT-proBNP levels, the patients were divided into 2 groups (p&lt;0,001): the 1st group included (n=15) patients with NT-proBNP &lt;125 pg/ml (58,2 [41,6; 70,7] pg/ml), while in the 2nd group (n=32) — with NT-proBNP ≥125 pg/ml (511,4 [249,8; 1578,1] pg/ml). The group of patients with high NTproBNP levels was characterized by higher values (by 33,8%, p=0,0001) of resting MBF and reduced CFR (by 14,7%, p=0,001) compared with patients with normal NT-proBNP level: resting MBF — 0,65 (0,44; 0,79) vs 0,43 (0,30; 0,58) ml/min/g; CFR — 2,21 (1,52; 2,83) vs 2,59 (2,47; 3,05), respectively. At the same time, MBF at stress did not differ between the groups. The relationship of NTproBNP levels with global CFR (p=0,012; r=-0,339) and MBF at rest (p=0,012; r=0,322) was established. A stepwise decrease in global CFR was revealed depending on the NYHA class as follows (p&lt;0,001): 2,79 (2,52; 2,93); 1,8 (1,55; 2,08); 1,31 (1,23; 1,49) — for class I, II, and III, respectively.Conclusion. A decrease in CFR in patients with HF with preserved ejection fraction indicates impaired myocardial blood supply, which, in this group of patients, is associated with microcirculatory changes. At the same time, the severity of MBF alterations is closely related to HF severity

Comparative estimation of prognostic value of the models GRACE, TIMI, PURSUIT in risk stratification of coronary complications in patients with non-ST-elevation acute coronary syndrome

The aim of investigation was to held comparative analysis of prognostic value of different models of short-term and long-term cardiovascular risk estimation in patients with non-ST-elevation acute coronary syndrome (ACS). Material and methods. This prospective investigation included 150 patients with non-ST-elevation ACS. During observation estimation of risk complications development level was held with the help of prognostic models GRACE, TIMI, PURSUIT, comparative analysis of predictive possibilities of this models, was held. Results. According to the results of investigation model GRACE demonstrated the most high sensitivity (100%) in prediction of all cause mortality during in-hospital observation. The most high specificity (90%) was marked in prediction of unfavourable outcomes during 6-months observation. TIMI risk stratification model revealed the most high sensitivity (64%), specificity (77%) and predictive accuracy (67%) in prediction of death/myocardial infarction/ischemia during 1-year observation, showed maximal value of positive predictive accuracy during in-hospital period and 12 months of observation in compare with other models. PURSUIT model of cardiovascular risk estimation showed the highest specificity (91%), which was marked in prediction of death/myocardial infarction during next 12 months. High predictive accuracy of this model (91 %) related to death/myocardial infarction revealed during 6 months and was maintained during 1-year observation. Conclusion. All systems of risk stratification had high prognostic value, negative predictive accuracy, that is all of them were effective in prognosis of favourable events in patients with non-ST-elevation ACS. GRACE model of risk stratification had maximal sensitivity in prediction of death and death or myocardial infarction during hospitalization and 6-month or 1 -year dynamic observation. System of risk stratification TIMI showed maximal value of positive predictive accuracy during in-hospital period and dynamic observation. System of risk stratification PURSUIT demonstrated maximal specificity in prediction of in-hospital, 6-month and 1-year outcomes. Also this model had maximal predictive accuracy related to the prognosis of death and death/myocardial infarction during in-hospital period and 1-year observation.Цель исследования: провести сравнительный анализ прогностической ценности различных моделей оценки краткосрочного и долгосрочного коронарного риска у больных острым коронарным синдромом без стойких подъемов сегмента ST. Материалы и методы. В проспективное наблюдение включено 150 больных острым коронарным синдромом без стойких подъемов сегмента ST (ОКСБПБТ). В ходе наблюдения проводилась оценка уровня риска развития осложнений с применением прогностических моделей GRACE, TIMI, PURSUIT; проводился сравнительный анализ предиктивных возможностей используемых моделей. Результаты. Согласно полученным результатам наиболее высокая чувствительность модели GRACE (100%) отмечалась в предсказании смерти от всех причин в госпитальный период. Наиболее высокая специфичность (90%) отмечалась в прогнозировании летальных исходов в течение 6-месячного наблюдения. Система риск-стратификации TIMI продемонстрировала наиболее высокие показатели чувствительности (64%), специфичности (77%) и предиктивной точности (67%) в отношении предсказания смерти/ИМ/ишемии на период годового наблюдения; показала наибольшее значение (по сравнению с другими шкалами) положительной предсказующей точности и в период госпитализации, и в период 12-месячного наблюдения. Система оценки риска PURSUIT показала наиболее высокую специфичность (91 %), которая наблюдалась в отношении прогнозирования смерти/ИМ в течение последующих 12 месяцев. Высокая предиктивная точность данной модели (91%) в отношении смерти/ИМ отмечалась в период 6 месяцев и сохранялась на протяжении годового наблюдения.Заключение. Все системы риск-стратификации обладают высокой прогностической значимостью; отрицательной предиктивной точностью, т.е. хорошо прогнозируют благоприятные исходы больных OKCBnST. Модель риска GRACE обладает максимальной чувствительностью при прогнозировании смерти и смерти или ИМ в период госпитализации и на период 6-месячного и годового динамического наблюдения. Шкала TIMI показала наибольшее значение положительной предсказующей точности и в период госпитализации, и в период динамического наблюдения. Система оценки риска PURSUIT обладает наибольшей специфичностью в прогнозировании госпитальных, 6-месячных и годовых исходов. Вышеуказанная система обладает наибольшей предсказывающей точностью в отношении прогноза смерти и смерти/инфаркта миокарда на период госпитального и годового наблюдения