98 research outputs found
Another deep dimming of the classical T Tauri star RW Aur A
Context. RW Aur A is a classical T Tauri star (CTTS) with an unusually rich
emission line spectrum. In 2014 the star faded by ~ 3 magnitudes in the V band
and went into a long-lasting minimum. In 2010 the star suffered from a similar
fading, although less deep. These events in RW Aur A are very unusual among the
CTTS, and have been attributed to occultations by passing dust clouds. Aims. We
want to find out if any spectral changes took place after the last fading of RW
Aur A with the intention to gather more information on the occulting body and
the cause of the phenomenon. Methods. We collected spectra of the two
components of RW Aur. Photometry was made before and during the minimum.
Results. The overall spectral signatures reflecting emission from accretion
flows from disk to star did not change after the fading. However, blue-shifted
absorption components related to the stellar wind had increased in strength in
certain resonance lines, and the profiles and strengths, but not fluxes, of
forbidden lines had become drastically different. Conclusions. The extinction
through the obscuring cloud is grey indicating the presence of large dust
grains. At the same time, there are no traces of related absorbing gas. The
cloud occults the star and the interior part of the stellar wind, but not the
wind/jet further out. The dimming in 2014 was not accompanied by changes in the
accretion flows at the stellar surface. There is evidence that the structure
and velocity pattern of the stellar wind did change significantly. The dimmings
could be related to passing condensations in a tidally disrupted disk, as
proposed earlier, but we also speculate that large dust grains have been
stirred up from the inclined disk into the line-of-sight through the
interaction with an enhanced wind.Comment: 5 pages, 5 figures, Accepted for publication in A&
Facing the wind of the pre-FUor V1331 Cyg
The mass outflows in T Tauri stars (TTS) are thought to be an effective
mechanism to remove angular momentum during the pre-main-sequence contraction
of a low-mass star. The most powerful winds are observed at the FUor stage of
stellar evolution. V1331 Cyg has been considered as a TTS at the pre-FUor
stage. We analyse high-resolution spectra of V1331 Cyg collected in 1998-2007
and 20-d series of spectra taken in 2012. For the first time the photospheric
spectrum of the star is detected and stellar parameters are derived: spectral
type G7-K0 IV, mass 2.8 Msun, radius 5 Rsun, vsini < 6 km/s. The photospheric
spectrum is highly veiled, but the amount of veiling is not the same in
different spectral lines, being lower in weak transitions and much higher in
strong transitions. The Fe II 5018, Mg I 5183, K I 7699 and some other lines of
metals are accompanied by a `shell' absorption at radial velocity of about -240
km/s. We show that these absorptions form in the post-shock gas in the jet,
i.e. the star is seen though its jet. The P Cyg profiles of H-alpha and H-beta
indicate the terminal wind velocity of about 500 km/s, which vary on
time-scales from several days to years. A model of the stellar wind is
developed to interpret the observations. The model is based on calculation of
hydrogen spectral lines using the radiative transfer code TORUS. The observed
H-alpha and H-beta line profiles and their variability can be well reproduced
with a stellar wind model, where the mass-loss rate and collimation (opening
angle) of the wind are variable. The changes of the opening angle may be
induced by small variability in magetization of the inner disc wind. The
mass-loss rate is found to vary within (6-11)x10^{-8} Msun/yr, with the
accretion rate of 2.0x10^{-6} Msun/yr.Comment: 11 pages, 12 figures; accepted for publication in MNRAS.
Typographical errors have been corrected after the proof stag
Early markers of pathological left ventricular remodeling in patients after ST-elevation myocardial infarction according to speckle-tracking echocardiography
Aim. To assess early predictors of pathological remodeling in patients after ST-elevation myocardial infarction (STEMI) using speckle-tracking echocardiography (STE).Material and methods. The study included 114 STEMI patients aged 52 (44; 58) years. A two-dimensional echocardiography was performed with the analysis of standard parameters and STE with an analysis of strain and rotational characteristics of the myocardium. In addition, brain natriuretic peptide and troponin-I concentration was determined. The development of pathological post-infarction remodeling within 12-month follow-up was assessed as an end point. Depending on the outcome, 2 groups were formed: group 1 — patients with pathological remodeling (PR), n=45 (39,5%), group 2 — patients without PR, n=69 (60,5%).Results. Early remodeling was detected in 24 (53,3%) people, mid-term — in 15 (33,4%), and late remodeling — in 6 (13,3%). In the PR group, heart failure (HF) was detected in 100% of patients, while in non-PR group, 23 (33,3%) patients had no signs of HF.In the early period of myocardial infarction, each of following indicators with high sensitivity and specificity predicts postinfarction pathological dilatation: global longitudinal strain (GLS) <11,7%, global circular strain (GCS) <12,4%, and a Twist decrease to 7,8o. A multivariate logistic regression model was created for the formation of pathological remodeling in patients with STEMI, which included GLS, global radial deformation (GRS), end-systolic volume index (ESVI), determined on days 7-9 of STEMI.Conclusion. GLS, GCS, and left ventricular Twist are independent highly sensitive and specific predictors of pathological remodeling. The following early predictors of postinfarction pathological dilatation have been established: reduced GLS in combination with higher GRS and left ventricular ESVI
Effect of vasopressin on the expression of genes for key enzymes of interstitial hyaluronan turnover and concentration ability in WAG rat kidneys
In mammals, arginine-vasopressin (AVP) is a major hormone involved in the regulation of renal water reabsorption, acting via an increase in the osmotic permeability of the collecting duct epithelium. The AVP-induced intracellular events include, as an essential step, the trafficking of the vesicles containing the water channels, aquaporin-2, to the apical plasma membrane of the collecting duct principal cells. The interstitium of the renal inner medulla contains abundant linear negatively charged glycosaminoglycan hyaluronan (HA), which affects the water flow depending on their polymeric state. Using real-time RT-PCR, we tested the assumption that the renal hyaluronan may be involved in the longterm vasopressin effect on water reabsorption. The expression of the genes encoding hyaluronan synthase-2 (Has2) and hyaluronidase-1, 2 (Hyal1, Hyal2) in the kidneys of Wistar Albino Glaxo (WAG) was studied. Has2 mRNA content was the highest in the kidney papilla of the hydrated rats. The V2 receptor-selective vasopressin analog dDAVP (100 μg/kg bw, ip, twice a day for 2 days) induced a considerable decrease in Has2 mRNA content in the papilla with less pronounced changes in the cortex. In contrast to Has2, dDAVP treatment caused a significant increase in Hyal1 and Hyal2 mRNA content in the renal papilla. There was a good fit between Hyal1 and Hyal2 transcriptional level and changes in hyaluronidase activity in the renal tissue. It was suggested that vasopressin is able to inhibit the synthesis of hyaluronan and concomitantly promotes its degradation in the renal papilla interstitium, thereby facilitating water flow between elements of the renal countercurrent system. The implications for this effect are discussed in the context of the literature data
New Indicators of Myocardial Work in Healthy Individuals
Aim. To study in healthy individuals the gender and age characteristics of left ventricular (LV) myocardial work indicators, their correlations with global LV deformity indicators and echocardiographic parameters characterizing LV systolic and diastolic functions.Materials and methods. 70 Healthy individuals (n=70; 34 men and 36 women; aged 39.3±8.9 years) were included in the study. The echocardiographic examination determined the standard parameters and indicators of myocardial work: global work efficiency (GWE), global constructive work (GCW), global wasted work (GWW), global myocardial work index (GWI); as well as the myocardium deformation characteristics: global longitudinal deformation (GLS), global radial deformation (GRS) and global circular deformation (GCS). Spearman's correlation coefficient was used to investigate the relationship between parameters. A correlation was considered weak at r≤0.3, moderate at 0.3<r<0.7, and strong at r≥0.7.Results. The average value of global work efficiency (GWE) in men was 97% (96; 98), in women – 98% (97; 98). Global constructive work (GCW) in men was 2343.8±350.4 mm Hg%, in women – 2362.2±343.8 mm Hg%. The average value of global wasted work (GWW) in men was 46 mm Hg% (27; 75), in women – 44 mm Hg% (33; 55.5). The global myocardial work index (GWI) in men was 2069.9±356.4 mm Hg%, in women – 2055.7±339.9 mm Hg%. No significant differences were found in the comparative analysis of performance indicators. The analysis of correlations found that the myocardial work indicators didn't have significant correlations with age. Ejection fraction was moderately correlated with GWI (r=0.45) and GCW (r=0.49). Global longitudinal strain was strongly correlated with GWI (r=0.77) and GCW (r=0.77). Global radial strain correlated moderately directly with GWI (r=0.4) and GCW (r=0.4). Global circular strain was moderately correlated with GCW (r=0.35). A strong negative correlation was found between the GWE indicator and the post systolic contraction index (PSI) (r=-0.85). At the same time, PSI and GWW had a strong positive correlation (r=0.85).Conclusion. Indicators of LV myocardial work in healthy individuals do not have gender differences. The efficiency of the work of the myocardium depends primarily on the deformation of the LV, while the constructive work is determined by the volume characteristics. The wasted work indicator depends on the number of segments that peak in the post-systolic period
Density streams in the disc winds of Classical T Tauri stars
Spectral and photometric variability of the Classical T Tauri stars RY Tau
and SU Aur from 2013 to 2022 is analyzed. We find that in SU Aur the H-alpha
line's flux at radial velocity RV = -50 +- 7 km/s varies with a period P = 255
+- 5 days. A similar effect previously discovered in RY Tau is confirmed with
these new data: P = 21.6 days at RV = -95 +- 5 km/s. In both stars, the radial
velocity of these variations, the period, and the mass of the star turn out to
be related by Kepler's law, suggesting structural features on the disc plane
orbiting at radii of 0.2 AU in RY Tau and 0.9 AU in SU Aur, respectively. Both
stars have a large inclination of the accretion disc to the line of sight - so
that the line of sight passes through the region of the disc wind. We propose
there is an azimuthal asymmetry in the disc wind, presumably in the form of
'density streams', caused by substructures of the accretion disc surface. These
streams cannot dissipate until they go beyond the Alfven surface in the disc's
magnetic field. These findings open up the possibility to learn about the
structure of the inner accretion disc of CTTS on scales less than 1 AU and to
reveal the orbital distances related to the planet's formation.Comment: 9 pages, 10 figure
ЗНАЧЕНИЕ РЕГИСТРАЦИИ ВЫЦВЕТАНИЯ ФОТОСЕНСИБИЛИЗАТОРА ДЛЯ ОЦЕНКИ МЕХАНИЗМА ДЕЙСТВИЯ ПРЕПАРАТОВ НА ФОТОИНДУЦИРОВАННЫЙ ГЕМОЛИЗ
The influence of three pharmaceutical preparations on photo-induced lysis (irradiation with light-emitting diode of 653 nm) of human erythrocytes in the presence of photosensitizer radachlorin and also on the quantum yield of radachlorin photobleaching was studied. Both processes are mediated by singlet oxygen generation and therefore can become a target for antioxidant or prooxidant regulation. The pyridine preparation mexidol (action principle – 3-hydroxy-6-methyl-2-ethylpyridine succinate) in concentration of 152 µM used as an antioxidant and a membrane protector and aminazine (action principle – chlorpromazine) in concentration of 70 µM many times accelerated manyfold the photo-induced hemolysis. However only mexidol increased the quantum yield of radachlorin photobleaching in many times. The obtained data showed the direct prooxidant action of mexidol, but not aminazine that accelerated a photo-induced hemolysis due to other mechanism. A pyridine preparation nicotinic acid tested in equimolar to mexidol concentration, failed to influence both the velocity of the photo-induced hemolysis and the quantum yield of radachlorin photobleaching. Our study shows the possible use of a photobleaching tests for detection of the direct prooxidant action.Исследовано влияние трех лекарственных препаратов на фотоиндуцированный лизис (облучение светодиодом 653 нм) взвеси эритроцитов человека в присутствии фотосенсибилизатора радахлорин, а также на квантовый выход фотовыцветания радахлорина. Оба процесса опосредованы генерацией активных форм кислорода, поэтому могут быть объектами регуляции антиоксидантами и прооксидантами. Используемый в качестве антиоксиданта и мембранопротектора пиридиновый препарат мексидол (действующее начало – 3-окси-6-метил-2-этилпиридина сукцинат) в концентрации 152 мкМ и аминазин (действующее начало – хлорпромазин) в концентрации 70 мкМ многократно ускоряли фотоиндуцированный гемолиз. При этом только мексидол в несколько раз увеличивал квантовый выход выцветания радахлорина. Полученные данные свидетельствуют о прямом прооксидантном действии мексидола, но не аминазина, который ускорял фотоиндуцированный гемолиз иным механизмом. Пиридиновый препарат никотиновая кислота, испытанный в эквимолярной мексидолу концентрации не оказывал влияния ни на скорость фотоиндуцированного гемолиза, ни на квантовый выход выцветания радахлорина. Проведенное исследование демонстрирует возможность использования регистрации фотовыцветания фотосенсибилизатора для выявления прооксидантов прямого действия
Therapeutic effect of all-trans-retinoic acid (at-RA) on an autoimmune nephritis experimental model: role of the VLA-4 integrin
BACKGROUND: Mercuric chloride (HgCl(2)) induces an autoimmune nephritis in the Brown Norway (BN) rats characterized by anti-glomerular basement membrane antibodies (anti-GBM Ab) deposition, proteinuria and a severe interstitial nephritis, all evident at day 13 of the disease. We assessed the effects of all-trans retinoic acid (at-RA) in this experimental model. At-RA is a vitamin A metabolite which has shown beneficial effects on several nephropathies, even though no clear targets for at-RA were provided. METHODS: We separated animals in four different experimental groups (HgCl(2), HgCl(2)+at-RA, at-RA and vehicle). From each animal we collected, at days 0 and 13, numerous biological samples: urine, to measure proteinuria by colorimetry; blood to determine VLA-4 expression by flow citometry; renal tissue to study the expression of VCAM-1 by Western blot, the presence of cellular infiltrates by immunohistochemistry, the IgG deposition by immunofluorescence, and the cytokines expression by RT-PCR. Additionally, adhesion assays to VCAM-1 were performed using K562 α4 transfectant cells. ANOVA tests were used for statistical significance estimation. RESULTS: We found that at-RA significantly decreased the serum levels of anti-GBM and consequently its deposition along the glomerular membrane. At-RA markedly reduced proteinuria as well as the number of cellular infiltrates in the renal interstitium, the levels of TNF-α and IL-1β cytokines and VCAM-1 expression in renal tissue. Moreover, we reported here for the first time in an in vivo model that at-RA reduced, to basal levels, the expression of VLA-4 (α4β1) integrin induced by mercury on peripheral blood leukocytes (PBLs). In addition, using K562 α4 stable transfectant cells, we found that at-RA inhibited VLA-4 dependent cell adhesion to VCAM-1. CONCLUSION: Here we demonstrate a therapeutic effect of at-RA on an autoimmune experimental nephritis model in rats. We report a significant reduction of the VLA-4 integrin expression on PBLs as well as the inhibition of the VLA4/VCAM1-dependent leukocyte adhesion by at-RA treatment. Thereby we point out the VLA-4 integrin as a target for at-RA in vivo
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