40 research outputs found
Synthesis and study of the antimicrobial activity of nifuroxazide derivatives
The number of infections caused by microorganisms that are resistant to antibiotics and synthetic antibacterial drugs is growing fast worldwide. This is one of the most important and urgent problems in health care. The main efforts of researchers around the world are focused on solving this issue. Nitrofurans represent one of the most effective classes of antibacterial drugs. We have synthesized 4 analogues of nifuroxazide – a well known nitrofuran antibiotic – and confirmed their structures by NMR, IR spectroscopy, and mass-spectrometry. All of the obtained compounds were studied for antimicrobial and antifungal activity. Activity against Escherichia coli, Staphylococcus aureus, Staphylococcus haemolyticus, and Pseudomonas aeruginosa was evaluated by the agar diffusion method. The synthesized compounds suppressed the growth of all the studied bacterial strains except Escherichia coli; the diameter of the inhibition zones ranged from 13.5 to 28 mm depending on the concentration of the tested compound and bacterial strain. One of the compounds studied in this project – the pyridine analogue of nifuroxazide – exceeded the activity of the standard (nifuroxazide) against the Staphylococcus aureus. The inhibitory activity of the synthesized compounds against the Candida albicans and Cryptococcus neoformans yeasts was determined using the microdilution method. The results were assessed according to the indicator color change. None of the studied compounds showed activity against these cultures. The obtained results confirm that substituted nifuroxazides have significant antimicrobial activity and, therefore, can be considered as promising candidates for developing new antibacterial drugs.The number of infections caused by microorganisms that are resistant to antibiotics and synthetic antibacterial drugs is growing fast worldwide. This is one of the most important and urgent problems in health care. The main efforts of researchers around the world are focused on solving this issue. Nitrofurans represent one of the most effective classes of antibacterial drugs. We have synthesized 4 analogues of nifuroxazide – a well known nitrofuran antibiotic – and confirmed their structures by NMR, IR spectroscopy, and mass-spectrometry. All of the obtained compounds were studied for antimicrobial and antifungal activity. Activity against Escherichia coli, Staphylococcus aureus, Staphylococcus haemolyticus, and Pseudomonas aeruginosa was evaluated by the agar diffusion method. The synthesized compounds suppressed the growth of all the studied bacterial strains except Escherichia coli; the diameter of the inhibition zones ranged from 13.5 to 28 mm depending on the concentration of the tested compound and bacterial strain. One of the compounds studied in this project – the pyridine analogue of nifuroxazide – exceeded the activity of the standard (nifuroxazide) against the Staphylococcus aureus. The inhibitory activity of the synthesized compounds against the Candida albicans and Cryptococcus neoformans yeasts was determined using the microdilution method. The results were assessed according to the indicator color change. None of the studied compounds showed activity against these cultures. The obtained results confirm that substituted nifuroxazides have significant antimicrobial activity and, therefore, can be considered as promising candidates for developing new antibacterial drugs
Does One Size Fit All? Drug Resistance and Standard Treatments: Results of Six Tuberculosis Programmes in Former Soviet Countries.
SETTING: After the collapse of the Soviet Union, countries in the region faced a dramatic increase in tuberculosis cases and the emergence of drug resistance. OBJECTIVE: To discuss the relevance of the DOTS strategy in settings with a high prevalence of drug resistance. DESIGN: Retrospective analysis of one-year treatment outcomes of short-course chemotherapy (SCC) and results of drug susceptibility testing (DST) surveys of six programmes located in the former Soviet Union: Kemerovo prison, Russia; Abkhasia, Georgia; Nagorno-Karabagh, Azerbaijan; Karakalpakstan, Uzbekistan; Dashoguz Velayat, Turkmenistan; and South Kazakhstan Oblast, Kazakhstan. Results are reported for new and previously treated smear-positive patients. RESULTS: Treatment outcomes of 3090 patients and DST results of 1383 patients were collected. Treatment success rates ranged between 87% and 61%, in Nagorno-Karabagh and Kemerovo, respectively, and failure rates between 7% and 23%. Any drug resistance ranged between 66% and 31% in the same programmes. MDR rates ranged between 28% in Karakalpakstan and Kemerovo prison and 4% in Nagorno-Karabagh. CONCLUSION: These results show the limits of SCC in settings with a high prevalence of drug resistance. They demonstrate that adapting treatment according to resistance patterns, access to reliable culture, DST and good quality second-line drugs are necessary
Radiation from a charge circulating inside a waveguide with dielectric filling
The emitted power of the radiation from a charged particle moving uniformly
on a circle inside a cylindrical waveguide is considered. The expressions for
the energy flux of the radiation passing through the waveguide cross-section
are derived for both TE and TM waves. The results of the numerical evaluation
are presented for the number of emitted quanta depending on the waveguide
radius, the radius of the charge rotation orbit and dielectric permittivity of
the filling medium. These results are compared with the corresponding
quantities for the synchrotron radiation in a homogeneous medium.Comment: 10 pages, Latex, four EPS figure
Operator algebras associated with multi-valued mappings
In the paper a new approach is proposed to construction of operator algebras generated by multi-valued mappings on a countable set. We present initial results, discuss the connection with known structures, outline further research directions. © 2014 Pleiades Publishing, Ltd
Synchrotron radiation from a charge moving along a helical orbit inside a dielectric cylinder
The radiation emitted by a charged particle moving along a helical orbit
inside a dielectric cylinder immersed into a homogeneous medium is
investigated. Expressions are derived for the electromagnetic potentials,
electric and magnetic fields, and for the spectral-angular distribution of
radiation in the exterior medium. It is shown that under the Cherenkov
condition for dielectric permittivity of the cylinder and the velocity of the
particle image on the cylinder surface, strong narrow peaks are present in the
angular distribution for the number of radiated quanta. At these peaks the
radiated energy exceeds the corresponding quantity for a homogeneous medium by
some orders of magnitude. The results of numerical calculations for the angular
distribution of radiated quanta are presented and they are compared with the
corresponding quantities for radiation in a homogeneous medium. The special
case of relativistic charged particle motion along the direction of the
cylinder axis with non-relativistic transverse velocity (helical undulator) is
considered in detail. Various regimes for the undulator parameter are
discussed. It is shown that the presence of the cylinder can increase
essentially the radiation intensity.Comment: 18 pages, 8 EPS figure
Electromagnetic field and radiation for a charge moving along a helical trajectory inside a waveguide with dielectric filling
We investigate the electromagnetic field generated by a point charge moving
along a helical trajectory inside a circular waveguide with conducting walls
filled by homogeneous dielectric. The parts corresponding to the radiation
field are separated and the formulae for the radiation intensity are derived
for both TE and TM waves. It is shown that the main part of the radiated quanta
is emitted in the form of the TE waves. Various limiting cases are considered.
The results of the numerical calculations show that the insertion of the
waveguide provides an additional mechanism for tuning the characteristics of
the emitted radiation by choosing the parameters of the waveguide and filling
medium.Comment: 17 pages, 9 figures, discussion, graphs, and references adde
Синтез и исследование противомикробной активности производных нифуроксазида
The number of infections caused by microorganisms that are resistant to antibiotics and synthetic antibacterial drugs is growing fast worldwide. This is one of the most important and urgent problems in health care. The main efforts of researchers around the world are focused on solving this issue. Nitrofurans represent one of the most effective classes of antibacterial drugs. We have synthesized 4 analogues of nifuroxazide – a well known nitrofuran antibiotic – and confirmed their structures by NMR, IR spectroscopy, and mass-spectrometry. All of the obtained compounds were studied for antimicrobial and antifungal activity. Activity against Escherichia coli, Staphylococcus aureus, Staphylococcus haemolyticus, and Pseudomonas aeruginosa was evaluated by the agar diffusion method. The synthesized compounds suppressed the growth of all the studied bacterial strains except Escherichia coli; the diameter of the inhibition zones ranged from 13.5 to 28 mm depending on the concentration of the tested compound and bacterial strain. One of the compounds studied in this project – the pyridine analogue of nifuroxazide – exceeded the activity of the standard (nifuroxazide) against the Staphylococcus aureus. The inhibitory activity of the synthesized compounds against the Candida albicans and Cryptococcus neoformans yeasts was determined using the microdilution method. The results were assessed according to the indicator color change. None of the studied compounds showed activity against these cultures. The obtained results confirm that substituted nifuroxazides have significant antimicrobial activity and, therefore, can be considered as promising candidates for developing new antibacterial drugs.В связи с постоянно растущим числом инфекций, вызываемых устойчивыми к синтетическим антибактериальным препаратам и антибиотикам микроорганизмами, основные усилия исследователей всего мира направлены на решение данной проблемы. Одним из самых эффективных среди антибактериальных препаратов является класс замещенных нитрофуранов. Синтезированы 4 аналога нифуроксазида (представителя нитрофуранового ряда), структура которых подтверждена с помощью ЯМР, ИК спектроскопии и масс-спектрометрии. Все полученные соединения изучены на противомикробную и противогрибковую активность. Активность по отношению к бактериям Escherichia coli, Staphylococcus aureus, Staphylococcus haemolyticus и Pseudomonas aeruginosa оценивали методом диффузии в агар. Полученные вещества подавляли рост всех исследованных штаммов бактерий, кроме Escherichia coli; диаметр зон ингибирования находился в пределах от 13.5 до 28 мм в зависимости от концентрации исследуемого вещества и штамма бактерий. Одно из изученных в этой работе соединений – пиридиновый аналог нифуроксазида – превзошло по активности стандарт (нифуроксазид) по отношению к Staphylococcus aureus и поэтому может считаться перспективным соединением для разработки новых антибактериальных средств. Определение ингибирующей активности синтезированных препаратов по отношению к дрожжевым грибам Candida albicans и Cryptococcus neoformans проводили с помощью метода последовательных разведений с оценкой эффекта по изменению окраски индикатора. Ни одно из полученных соединений не проявило активности в отношении данных культур. Полученные результаты подтверждают, что замещенные аналоги нифуроксазида обладают противомикробной активностью и являются перспективными кандидатами для разработки новых антибактериальных средств
Антимикробные пептиды и белки в биожидкостях человека
Antimicrobial peptides and proteins (AMPs) are endogenous compounds that have a direct antimicrobial effect on bacteria (e. g., by disrupting bacterial membranes), as well as on fungi and viruses. AMPs are the main component of the innate immunity of living organisms and are produced by both epithelial cells (skin cells, cells of respiratory tract, intestine, urinary and genital tracts) and cells of the immune system and are secreted into secretory fluids. AMPs can also act as chemoattractants for immunocompetent cells (neutrophils, monocytes, T lymphocytes, dendritic cells) in the inflammation site and affect the antigen presenting cells by modulating adaptive T cell immune responses. The representatives of the main 15 AMP classes, that we describe in this review, are the most studied group of the large pool of these compounds. We discuss their localization, expression, and concentration in various biofluids of humans under normal and pathological conditions.Антимикробные пептиды и белки (АМПБ) – это эндогенные соединения, оказывающие прямое противомикробное действие на бактерии, а также на грибы и вирусы. АМПБ являются основным компонентом врожденного иммунитета живых организмов и вырабатываются как эпителиальными клетками (клетки кожи, дыхательных путей, кишечника, мочевыводящих и половых путей), так и клетками иммунной системы, и выделяются в секреторные жидкости. Помимо антимикробной функции АМПБ могут выполнять роль хемоаттрактантов иммунокомпетентных клеток (нейтрофилы, моноциты, Т лимфоциты, дендритные клетки) в очаг воспаления. АМПБ оказывают влияние также на антигенпрезентирующие клетки, модулируя адаптивные T-клеточные иммунные ответы. Из большого количества описанных АМПБ наиболее изученными являются 15 основных классов, которые мы рассматриваем в данном обзоре, включая их локализацию, экспрессию и концентрацию в различных биожидкостях в норме и при патологии
Effective-Range Expansion of the Neutron-Deuteron Scattering Studied by a Quark-Model Nonlocal Gaussian Potential
The S-wave effective range parameters of the neutron-deuteron (nd) scattering
are derived in the Faddeev formalism, using a nonlocal Gaussian potential based
on the quark-model baryon-baryon interaction fss2. The spin-doublet low-energy
eigenphase shift is sufficiently attractive to reproduce predictions by the
AV18 plus Urbana three-nucleon force, yielding the observed value of the
doublet scattering length and the correct differential cross sections below the
deuteron breakup threshold. This conclusion is consistent with the previous
result for the triton binding energy, which is nearly reproduced by fss2
without reinforcing it with the three-nucleon force.Comment: 21 pages, 6 figures and 6 tables, submitted to Prog. Theor. Phy