Relationship of lithogenesis and oxidative damage in experimental nephrolithiasis

Introduction: Modern literature indicates that tissue damage in the kidneys is an important factor in the formation of urinary stones. It is recognized that the deposits of calcium salts are capable of inducing tissue reactions in the epithelium of the distal tubules and collecting tubules, particularly activating the process of free radical oxidation. Material and Methods: The morphological study of 60 rat kidneys with experimental oxalate nephrolithiasis was conducted. To identify the calcium deposited, silver impregnation by von Kossas method was used. Using immunohistochemistry, the expression of the severity indices of oxidative damage (malondialdehyde - MDA) and antioxidant defenses (mitochondrial superoxide dismutase - SOD-2) were determined. Results: After 3 weeks of the nephrolithiasis modeling in the epithelium of the collecting tubules, in the interstitium of the medulla substance, in the lumen of collecting tubules numerous calcium deposits were found (mean 21.4±3.40 in the field of view). The average size of the deposits was observed to be 16.510.60 mm. In 10% relatively large microlites (up to 30-35 pm) were found with obturation of the lumen of the collecting tubules. Noted decreased expression (1+) of SOD-2 in epitheliocytes. The weakening expression of the antioxidant enzyme was accompanied by a statistically significant elevation of lipid peroxidation products (2+).With using of a-tocopherol in the experiment, a much smaller intensity of histopathological kidney restructuring was determined. The moderate amount (up to 17.612.39 in the field of view) of calcium compounds were small, averaging 5.4010.28 mm in size. Large compounds of calcium, obturation clearance tubules and collecting tubules, or inlays their epithelium were not detected. Immunohistochemical study of the rat kidney during treatment with a-tocopherol showed moderate (2 i) expression of the SOD-2 in epitheliocytes of the collecting tubules, comparable to the intact group and significantly (12.5%) higher than in animals with an experimental model oxalate nephrolithiasis. The intensity of the expression of MDA was similar to that in the intact group and significantly lower in animals with the experimental oxalate nephrolithiasis. Conclusion: During the simulation of the experimental oxalate nephrolithiasis in the rat kidney, marked morphological signs of oxidative damage activation in the tissues and cells and a weakening of the enzymatic antioxidant defense system, accompanied by an acceleration lithogenesis were noted. The usage of antioxidants has beneficial effects on the renal morphologic reorganization, as it reduces the degree of oxidative damage to the cells and tissues, while it helps to reduce the number and size of the calcium deposits formed

The Afterglow of GRB 990123 and a Dense Medium

Recent observations show that the temporal decay of the R-band afterglow from GRB 990123 steepened about 2.5 days after the burst. We here propose a possible explanation for such a steepening: a shock expanding in a dense medium has undergone the transition from a relativistic phase to a nonrelativistic phase. We find that this model is consistent with the observations if the medium density is about $3\times 10^6 {\rm cm}^{-3}$. By fitting our model to the observed optical and X-ray afterglow quantitatively, we further infer the electron and magnetic energy fractions of the shocked medium and find these two parameters are about 0.1 and $2\times 10^{-8}$ respectively. The former parameter is near the equipartition value while the latter is about six orders of magnitude smaller than inferred from the GRB 970508 afterglow. We also discuss possibilities that the dense medium can be produced.Comment: 12 pages, LaTeX, published in ApJ Letter

Cyclic brightening in the short-period WZ Sge-type cataclysmic variable SDSS J080434.20+510349.2

We have observed a new cataclysmic variable (CV) SDSS J080434.20+510349.2 and study the origin of a long-term variability found in its light curve. Multi-longitude time-resolved photometric observations were carried out to analyze the uncommon behavior also found recently in two newly discovered CVs. This study of SDSS J080434.20+510349.2 mainly concerns the understanding of the nature of the observed double-humped light curve and its relation to a cyclic brightening occurring during quiescence. The observations were obtained early in 2007, when the object was at about V~17.1, 0.4 mag brighter than the pre-outburst magnitude. The light curve shows a sinusoidal variability with an amplitude of about 0.07 mag and a periodicity of 42.48 min, which is half of the orbital period of the system. In addition, we have observed two "mini-outbursts" of the system up to 0.6 mag, with a duration of about 4 days each. The "mini-outburst" had a symmetric profile and repeated in about 32 days. Subsequent monitoring of the system shows a cyclical behaviour of such "mini-outbursts" with a similar recurrence period. The origin of the double-humped light curve and the periodic brightening is discussed in the light of the evolutionary state of SDSS J080434.20+510349.2.Comment: 7 pages, 6 figures, Accepted by A&A, typos added, figure correcte

Environment and Energy Injection Effects in GRB Afterglows

In a recent paper (Dai & Lu 1999), we have proposed a simple model in which the steepening in the light curve of the R-band afterglow of the gamma-ray burst (GRB) 990123 is caused by the adiabatic shock which has evolved from an ultrarelativistic phase to a nonrelativistic phase in a dense medium. We find that such a model is quite consistent with observations if the medium density is about $3\times 10^6 {\rm cm}^{-3}$. Here we discuss this model in more details. In particular, we investigate the effects of synchrotron self absorption and energy injection. A shock in a dense medium becomes nonrelativistic rapidly after a short relativistic phase. The afterglow from the shock at the nonrelativistic stage decays more rapidly than at the relativistic stage. Since some models for GRB energy sources predict that a strongly magnetic millisecond pulsar may be born during the formation of GRB, we discuss the effect of such a pulsar on the evolution of the nonrelativistic shock through magnetic dipole radiation. We find that after the energy which the shock obtains from the pulsar is much more than the initial energy of the shock, the afterglow decay will flatten significantly. When the pulsar energy input effect disappears, the decay will steepen again. These features are in excellent agreement with the afterglows of GRB 980519, GRB 990510 and GRB 980326. Furthermore, our model fits very well all the observational data of GRB 980519 including the last two detections.Comment: 21 pages, LaTeX, accepted for publication in ApJ, one paragraph adde

Subaru optical observations of the old pulsar PSR B0950+08

We report the B band optical observations of an old (17.5 Myr) radiopulsar PSR B0950+08 obtained with the Suprime-Cam at the Subaru telescope. We detected a faint object, B=27.07(16). Within our astrometrical accuracy it coincides with the radio position of the pulsar and with the object detected earlier by Pavlov et al. (1996) in UV with the HST/FOC/F130LP. The positional coincidence and spectral properties of the object suggest that it is the optical counterpart of PSR B0950+08. Its flux in the B band is two times higher than one would expect from the suggested earlier Rayleigh-Jeans interpretation of the only available HST observations in the adjacent F130LP band. Based on the B and F130LP photometry of the suggested counterpart and on the available X-ray data we argue in favour of nonthermal origin of the broad-band optical spectrum of PSR B0950+08, as it is observed for the optical emission of the younger, middle-aged pulsars PSR B0656+14 and Geminga. At the same time, the optical efficiency of PSR B0950+08, estimated from its spin-down power and the detected optical flux, is by several orders of magnitude higher than for these pulsars, and comparable with that for the much younger and more energetic Crab pulsar. We cannot exclude the presence of a compact, about 1'', faint pulsar nebula around PSR B0950+08, elongated perpendicular to the vector of its proper motion, unless it is not a projection of a faint extended object on the pulsar position.Comment: 8 pages, LaTeX, aa.cls style, 5 PS figures, submitted to A&A. Image is available in FITS format at http://www.ioffe.rssi.ru/astro/NSG/obs/0950-subar

Subaru optical observations of the two middle-aged pulsars PSR B0656+14 and Geminga

We carried out a deep subarcsecond BRI imaging of the two middle-aged pulsars to establish their properties in the optical range. Both pulsars are detected at >10 sigma level. Geminga is for the first time reliably detected in the I band with a magnitude of 25.10+/-0.14. We also reanalyze archival ESO/NTT and HST broadband data and find that some published fluxes for Geminga were estimated inaccurately. The resulting dereddened broadband spectra of both pulsars are remarkably similar to each other and show significant flux increases towards the far-UV and near-IR, and a wide flux excess in V-I bands. This suggests a multicomponent structure of the optical emission. The nonthermal power law component of the pulsar magnetospheric origin dominates in the most part of the optical range. For PSR B0656+14 it is compatible with a low energy extension of the power law tail seen in hard X-rays. For Geminga the respective extension overshoots by a factor of 100 the nonthermal optical flux, which has a less steep spectral slope than in X-rays. This implies a spectral break at a photon energy of about 1 keV. The flux increases towards the far-UV are compatible with contributions of the Rayleigh-Jeans parts of the blackbody components from whole surfaces of the neutron stars dominating in soft X-rays. The V-I excess, which is most significant for PSR B0656+14, suggests a third spectral component of still unidentified origin. Faint, a few arcseconds in size nebulae extended perpendicular to the proper motion directions of the pulsars, are seen around both objects in our deepest I band images. They can be optical counterparts of the bow-shock head of Geminga and of the tentative pulsar wind nebula of PSR B0656+14 observed in X-rays.Comment: 15 pages, 8 figures, A&A, accepted. For higher resolution images see http://www.ioffe.ru/astro/NSG/obs/map

Intriguing X-ray and optical variations of the gamma Cas analog HD45314

A growing number of Be and Oe stars, named the gamma Cas stars, are known for their unusually hard and intense X-ray emission. This emission could either trace accretion by a compact companion or magnetic interaction between the star and its decretion disk. To test these scenarios, we carried out a detailed optical monitoring of HD45314, the hottest member of the class of gamma Cas stars, along with dedicated X-ray observations on specific dates. High-resolution optical spectra were taken to monitor the emission lines formed in the disk, while X-ray spectroscopy was obtained at epochs when the optical spectrum of the Oe star was displaying peculiar properties. Over the last four years, HD45314 has entered a phase of spectacular variations. The optical emission lines have undergone important morphology and intensity changes including transitions between single- and multiple-peaked emission lines as well as shell events, and phases of (partial) disk dissipation. Photometric variations are found to be anti-correlated with the equivalent width of the H-alpha emission. Whilst the star preserved its hard and bright X-ray emission during the shell phase, the X-ray spectrum during the phase of (partial) disk dissipation was significantly softer and weaker. The observed behaviour of HD45314 suggests a direct association between the level of X-ray emission and the amount of material simultaneously present in the Oe disk as expected in the magnetic star-disk interaction scenario.Comment: Accepted for publication in A&

Glycoprotein Ib activation by thrombin stimulates the energy metabolism in human platelets

<div><p>Thrombin-induced platelet activation requires substantial amounts of ATP. However, the specific contribution of each ATP-generating pathway <i>i</i>.<i>e</i>., oxidative phosphorylation (OxPhos) versus glycolysis and the biochemical mechanisms involved in the thrombin-induced activation of energy metabolism remain unclear. Here we report an integral analysis on the role of both energy pathways in human platelets activated by several agonists, and the signal transducing mechanisms associated with such activation. We found that thrombin, Trap-6, arachidonic acid, collagen, A23187, epinephrine and ADP significantly increased glycolytic flux (3–38 times <i>vs</i>. non-activated platelets) whereas ristocetin was ineffective. OxPhos (33 times) and mitochondrial transmembrane potential (88%) were increased only by thrombin. OxPhos was the main source of ATP in thrombin-activated platelets, whereas in platelets activated by any of the other agonists, glycolysis was the principal ATP supplier. In order to establish the biochemical mechanisms involved in the thrombin-induced OxPhos activation in platelets, several signaling pathways associated with mitochondrial activation were analyzed. Wortmannin and LY294002 (PI3K/Akt pathway inhibitors), ristocetin and heparin (GPIb inhibitors) as well as resveratrol, ATP (calcium-release inhibitors) and PP1 (Tyr-phosphorylation inhibitor) prevented the thrombin-induced platelet activation. These results suggest that thrombin activates OxPhos and glycolysis through GPIb-dependent signaling involving PI3K and Akt activation, calcium mobilization and protein phosphorylation.</p></div

Spectroscopy of the massive interacting binary UU Cassiopeiae

Context. The eclipsing close binary UU Cas is an interacting massive double-periodic system with a gainer star partly hidden in an accretion disk. Aims. In order to study the physics of the accretion process in greater detail, along with the structure and dynamics of the circumstellar matter in the system, we supplement our previous results obtained from photometry with an analysis of the spectra of UU Cas. Methods. We collected all available spectra used in previous publications on UU Cas and we acquired new ones. The method of disentangling was applied to this set of spectra spanning the years 2008 2021. The orbital parameters were disentangled and a fit of the separated component spectra by synthetic ones has been used to determine the physical parameters of the component stars. We compared the results to models of the evolution of interacting binaries. Results. We found that in addition to the dominant role of the donor star and a weak contribution of the gainer, the line profiles are strongly influenced by the circumstellar matter. The absorption lines reveal a presence of a disk wind emanating above the orbital plane. The variability of Hα emission yields evidence of changes in the structure of the circumstellar matter on a timescale of several orbital periods. © ESO 2022.Grantová Agentura České Republiky, GA ČR: 22-34467S; Fondo Nacional de Desarrollo Científico y Tecnológico, FONDECYT: 1190621, ANID PIA/BASAL FB210003, AP08856419, IN102120; Bulgarian National Science Fund, BNSF: DN 18/13-12.12.2017; Ministry of Education and Science of the Russian Federation, Minobrnauka: 075-15-2020-780, 780-10, FEUZ-2020-0030; Ministry of Education and Science of the Republic of Kazakhstan; Ministarstvo Prosvete, Nauke i Tehnološkog Razvoja, MPNTR: 21202285, 451-03-68/2020-14/200002; Centro de Astrofísica y Tecnologías Afines, CATA: PFB–06/2007The authors highly appreciate valuable comments and suggestions by the referee Herman Hensberge, which helped to improve this paper. We acknowledge the allotment of observing time at San Pedro Mártir observatory, UNAM, Baja California, Mexico. We are also indebted to Drs. Gyula Szabó and his colleagues for obtaining the GAO spectra, Zlatan Zvetanov for the APO spectra, and Brankica Kubátová, Petr Kabáth and other colleagues from AI for the AIO spectra. P. Hadrava was supported by project RVO 67985815, M. Cabezas also by GAČR 22-34467S. G. Djurašević, J. Petrović and M. I. Jurkovic acknowledge the financial support from the Ministry of Education, Science and Technological Development of the Republic of Serbia through contract No. 451-03-68/2020-14/200002. J. Garcés acknowledges support by ANID project 21202285. S. Yu. Gorda was supported in part by the Ministry of Science and Higher Education of the Russian Federation (projects no. FEUZ-2020-0030 and no. 075-15-2020-780, contract 780-10). H. Markov acknowledges the support by Bulgarian National Science Fund under contract DN 18/13-12.12.2017. R. E. Mennickent acknowledges support by BASAL Centro de Astrofísica y Tecnologías Afines (CATA) PFB–06/2007, FONDECYT 1190621 and the grant ANID PIA/BASAL FB210003. S. Zharikov acknowledges PAPIIT grants IN102120 and grant no. AP08856419 of the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan.Acknowledgements. The authors highly appreciate valuable comments and suggestions by the referee Herman Hensberge, which helped to improve this paper. We acknowledge the allotment of observing time at San Pedro Mártir observatory, UNAM, Baja California, Mexico. We are also indebted to Drs. Gyula Szabó and his colleagues for obtaining the GAO spectra, Zlatan Zvetanov for the APO spectra, and Brankica Kubátová, Petr Kabáth and other colleagues from AI for the AIO spectra. P. Hadrava was supported by project RVO 67985815, M. Cabezas also by GACˇ R 22-34467S. G. Djurašević, J. Petrović and M. I. Jurkovic acknowledge the financial support from the Ministry of Education, Science and Technological Development of the Republic of Serbia through contract No. 451-03-68/2020-14/200002. J. Garcés acknowledges support by ANID project 21202285. S. Yu. Gorda was supported in part by the Ministry of Science and Higher Education of the Russian Federation (projects no. FEUZ-2020-0030 and no. 075-15-2020-780, contract 780-10). H. Markov acknowledges the support by Bulgarian National Science Fund under contract DN 18/13-12.12.2017. R. E. Mennickent acknowledges support by BASAL Centro de Astrofísica y Tecnologías Afines (CATA) PFB–06/2007, FONDECYT 1190621 and the grant ANID PIA/BASAL FB210003. S. Zharikov acknowledges PAPIIT grants IN102120 and grant no. AP08856419 of the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan.IRAF is distributed by the National Optical Astronomy Observatories, operated by the Association of Universities for Research in Astronomy, Inc., under contract to the National Science Foundation of the United States