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Search Results: 1 - 10 of 488776 matches for " M. V. Medvedev "
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Ultrastructural assessment of leiomyoma tissue and different layers of myometrium in patients with uterine leiomyoma during hypo- and hyperestrogenic states after different schemes of gonadotroping relising hormone agonists use
Medvedev M.V.
Морфолог?я , 2011,
Abstract: In study conducted ultrastructural analysis of cells and extracellular matrix of myoma tissue and different layers of myometrium in 35 patients with uterine leyomioma in long-term and short-term corre ction of hormonal status before surgery gosereline acetate. Study of ultrastructural characteristics we re performed on ultrathin sectio ns for transmission electron microscope. Studies have shown that the ultrastructural characteristics of uterine le yomioma were similar to those of unchanged myometrium. The most characteristic feature of uterine fibroids is excessive extracellular matrix elements, arranged randomly. Under the action of a-GnRH there were atrophic changes in myocytes, which in most cases do not lead to cell death and is reversible: reducing the size of myocytes in both myomatous tissue and in normal myometrium, two-fold reduction in myofilaments amount in unchanged myometrium and in uterine myoma. Under the influence of hyperestrogenemy, along with increasing size of the nucleus, endoplasmic reticulum elements and number of ribosom es the size of myocytes was likely to increase in both myoma tissue and myometrium; increased the ratio of condensed chromatin to uncondensed one (in simple fibroids – 1.7 times, in cellular fibroids – 2.1 times); increase in 1.5 times the number of myofilaments both in unchanged myometrium and in uterine myoma; increase in number of mitochondria and increase of their size in myomatous tissue only caused mainly by by intracellular edema. Elements of extracellu lar matrix do not depend on short-term action of hyperestrogeny and mid-term action of hypoestrogeny, bu t the synthesis of new fibers is reduc ed under action of artificial menopause.
Immunohistochemical evaluation of leiomyoma tissue and normal myometrium in patients with uter-ine leiomyoma during hypo- and hyperestrogenic conditions caused by of use of gonadotropin-releasing hormone ana-logues
Medvedev M.V.
Морфолог?я , 2012,
Abstract: In study immunohistochemical an alysis of markers of proliferation, apoptosis, extracellular ma trix degradation, angiogenesis and steroid hormone receptors in myomatous tissue and myometrium was conducted in 62 patients with uterine leiomyomas during long-term and short-term correction of hormonal status by gosere line acetate. Studies have shown that pseudocapsule of fibroids at immunohistochemical level is unchanged myometrium. For le iomyoma tissue compared to myometrium were characteristic greater expression of steroid hormone receptors and aromatase, inhibition of apoptosis, greater expression of angiogenic factors compared to unchanged myometrium. Under the action of GnRH-a direct and medi-ated by reduction of estradiol occurred molecular changes, which cover almost all parts of th e pathogenesis of fibroids and include inhibition of expression of estrogen receptor and aromat ase synthesis, enhancing of e xpression of progesterone recep-tors, inhibition of proliferation and angi ogenesis, accelerated degradation of ECM. Under the influence of hyperestrogeny caused by flare-up effect of GnRH-a and direct peripheral effect of GnRH analogs progression of uterine leiomyoma pro-vides increased sensitivity of uterine myocyt es to ischemia. Despite the obvious role of antiapoptotic factor bcl-2 in the pathogenesis of uterine fibroids, short- and long-term hormonal treatment with GnRH-a does not lead to significant changes in its expression.
Quantitative morphological assessment of state myomatous tissue and different layers of myometrium at patients with uterus leiomyoma at preoperative correction of the hormonal status by means of Zoladex
Medvedev M.V.
Морфолог?я , 2011,
Abstract: In research was spent mорmorphometric analysis of cellular, stromal and microvascular components of myomatous tissue and different layers of myometrium at 35 patients with uterus leiomyoma during long-term and short-term preoperative correction of the hormonal status by means of Zoladex . Studying of specific volume of microvessels and stroma, quantitative density of myocyte nuclei and a mitotic index of myocytes was spent on sections in the thickness by 1 microns, made of epoxy blocks. Researches have shown, that in the conditions of 3-month's medicamental menopause there is an authentic depression of specific volume of microvessels. In the conditions of the raised level of sexual steroids growth of contents of microvessels of myomatous nodes at the expense of dilating of arterioles and metarterioles lumen and thickening of their sides is observed. At simple myoma against a medicamental menopause the reduction of specific volume of stroma in myometriums submucous and vascular layers at that time in 1 week after introduction Zoladex the changes are not defined. In nodes of a cellular myoma in the conditions of long menopause it is observed more than double growth of relative contents of a stroma. In conditions hypohormonemia throughout 3 months there is depression of mitotic activity of nodal myocytes as a part of simple and cellular myoma. On the contrary, against hyperhormonemia in 1 week of Zoladex action essential is rising of a mitotic index of myocytes of cellular leiomyoma is observed.
Quantitative morphological assessment of microvascular network of leiomyoma tissue and the layers of myometrium in patients with uterine leiomyoma with hypo- and hyperestrogenic conditions induced by different schemes of gonadotroping relising hormone agonists therapy
Medvedev M.V.
Морфолог?я , 2011,
Abstract: Microvascular components of myomatous tissue and the layers of myometrium were evaluated using mорmorphometric analysis in 35 patients with uterine leiomyoma with long-term and short-term preoperative hormonal correction with Gosereline Acetate. Our results show that the microvessels density depends on morphological type of the fibroid, which in case of the cellular leiomyoma is 2.9 times greater compared to the regular one. The tissue is characterized by decreased vascularization of simple leiomyoma as compared to surrounding myometrium. In conditions of a drug-induced 3-month menopause density of microvessels was significantly decreased. In conditions of elevated levels of sex steroids amount of microvessels in fibrois tissue increases, with expanding of the lumen of arterioles and metarterioles and thickening of their walls. Hipoestrogenic condition contributes significantly to reduction of the average diameter of arterioles in the tissue of cellular and simple leiomyoma, which in some cases leads to complete obliteration of the vessels. Short-time hypere-strogenemia leads to a statistically significant increase in wall thickness of arterioles in fibroid tissue samples. Similar changes observed in vessels of pseudocapsula of women with cellular leiomyoma.
Collisionless Dissipative Nonlinear Alfven Waves: Nonlinear Steepening, Compressible Turbulence, and Particle Trapping
M. V. Medvedev
Physics , 1999, DOI: 10.1063/1.873471
Abstract: The magnetic energy of nonlinear Alfven waves in compressible plasmas may be ponderomotively coupled only to ion-acoustic quasi-modes which modulate the wave phase velocity and cause wave-front steepening. In the collisionless plasma with $\beta\not=0$, the dynamics of nonlinear Alfven wave is also affected by the resonant particle-wave interactions. Upon relatively rapid evolution (compared to the particle bounce time), the quasi-stationary wave structures, identical to the so called (Alfvenic) Rotational Discontinuities, form, the emergence and dynamics of which has not been previously understood. Collisionless (Landau) dissipation of nonlinear Alfven waves is also a plausible and natural mechanism of the solar wind heating. Considering a strong, compressible, Alfvenic turbulence as an ensemble of randomly interacting Alfvenic discontinuities and nonlinear waves, it is shown that there exist two distinct phases of turbulence. What phase realizes depends on whether this collisionless damping is strong enough to provide adequate energy sink at all scales and, thus, to support a steady-state cascade of the wave energy. In long-time asymptotics, however, the particle distribution function is affected by the wave magnetic fields. In this regime of nonlinear Landau damping, resonant particles are trapped in the quasi-stationary Alfvenic discontinuities, giving rise to a formation of a plateau on the distribution function and quenching collisionless damping. Using the virial theorem for trapped particles, it is analytically demonstrated that their effect on the nonlinear dynamics of such discontinuities is non-trivial and forces a significant departure of the theory from the conventional paradigm.
Properties of Particles Obeying Ambiguous Statistics
M. V. Medvedev
Physics , 1996, DOI: 10.1103/PhysRevLett.78.4147
Abstract: A new class of identical particles which may exhibit both Bose and Fermi statistics with respective probabilities $p_b$ and $p_f$ is introduced. Such an uncertainity may be either an intrinsic property of a particle or can be viewed as an ``experimental uncertainity''. Statistical equivalence of such particles and particles obeying parastatistics of infinite order is shown. Generalized statistical distributions are derived and statistical and thermodynamical properties of an ideal gas of the particles are investigated. The physical nature of such particles and the implications of this investigation for the statistics of extremal black holes are discussed.
The Photino Induced Distortion of the CMBR Blackbody Spectrum
M. V. Medvedev
Physics , 1998,
Abstract: It is shown that photon--photino inter-conversions (if exist) may result in a detectable CMBR spectrum distortion which amplitude depends on photino properties, such as its mass. An upper bound on the distortion parameter determined from the recent COBE-FIRAS data, hence, sets a lower bound on the photino mass, $m_{\tilde\gamma} \gtrsim 300 eV$.
Thermodynamics of photons in relativistic $e^+e^-γ$ plasmas
M. V. Medvedev
Physics , 1999, DOI: 10.1103/PhysRevE.59.R4766
Abstract: Thermodynamic and spectral properties of a photon gas in $e^+e^-\gamma$ plasmas are studied. The effect of a finite effective mass of a photon, associated with the plasma frequency cutoff, is self-consistently included. In the ultra-relativistic plasma, the photon spectrum turns out to be universal with the temperature normalized plasma frequency cutoff being a fundamental constant independent of plasma parameters. Such a universality does not hold in the non-relativistic plasma.
Whence particle acceleration
M. V. Medvedev,A. Spitkovsky
Physics , 2009,
Abstract: We discuss how the electrons in relativistic GRB shocks can reach near-equipartition in energy with the protons. We emphasize the non-Fermi origin of such acceleration. We argue that the dynamics of the electrons in the foreshock region and at the shock front plays an important role. We also demonstrate that PIC simulations can directly probe this physics in the regimes relevant to GRBs.
On Poynting-Flux-Driven Bubbles and Shocks Around Merging Neutron Star Binaries
M. V. Medvedev,A. Loeb
Physics , 2012, DOI: 10.1093/mnras/stt366
Abstract: Merging binaries of compact relativistic objects (neutron stars and black holes) are thought to be progenitors of short gamma-ray bursts and sources of gravitational waves, hence their study is of great importance for astrophysics. Because of the strong magnetic field of one or both binary members and high orbital frequencies, these binaries are strong sources of energy in the form of Poynting flux (e.g., magnetic-field-dominated outflows, relativistic leptonic winds, electromagnetic and plasma waves). The steady injection of energy by the binary forms a bubble (or a cavity) filled with matter with the relativistic equation of state, which pushes on the surrounding plasma and can drive a shock wave in it. Unlike the Sedov-von Neumann-Taylor blast wave solution for a point-like explosion, the shock wave here is continuously driven by the ever-increasing pressure inside the bubble. We calculate from the first principles the dynamics and evolution of the bubble and the shock surrounding it and predict that such systems can be observed as radio sources a few hours before and after the merger. At much later times, the shock is expected to settle onto the Sedov-von Neumann-Taylor solution, thus resembling an explosion.
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