Races and hosts of Pseudomonas syringae pv. tomato in Serbia

During the past few years, frequent appearance of bacterial speck of tomatoes was recorded in several tomato-growing regions in Serbia. A three-year survey of tomato fields in Serbia (2002-2004) resulted in the isolation of numerous bacterial strains, with 30 representative strains selected for further analyses. Based on the results of pathogenicity, biochemical, and physiological tests, all strains isolated from diseased tomato plants were identified as P. syringae pv. tomato. The identity of strains was confirmed by the polymerase chain reaction (PCR), since PCR products of expected size (650 bp) specific for coronatine-producing strains of P. syringae pv. tomato were amplified from all tested strains. Study of the host range of P. syringae pv. tomato strains originating from Serbia confirmed tomato as the sole host. The reaction of tomato differential cultivar Ontario 7710 showed that the Serbian strains belonged to races 0 and 1 of P. syringae pv. tomato

Neural network prediction of the gas chromatographic separation of polycyclic aromatic hydrocarbons

This paper describes the application of artificial neural networks (ANNs) method to the modeling of 13 polycyclic aromatic hydrocarbons (PAHs)retentionsin temperature - programmed gas chromatography.The ANN method used resulted in relatively good agreement (RMStesting = 0.018) between the measured and the predicted retention times for 13 PAHs. Somewhat higher discrepancy in prediction was observed for the late – eluted PAHs at lower temperature ramps.Physical chemistry 2004 : 7th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 21-23 September 200

Idiopatski i sekundarni stečeni megakolon kod pasa udruženi su sa smanjenom vip-inervacijom u oštećenom kolonu

It is well established that megacolon in carnivores, including both cats and dogs, is a common finding. Megacolon occurs more often in the cat that the dog. Based on current data idiopathic megacolon is a common cause of constipation in cats (62% of constipated cats are affected by diopathic megacolon). There is no evidence of idiopathic megacolon in dogs and publications about this disease in this species is very scarce. We investigated the enteric nervous system in the dilated portion (DP) of the colon in dogs with idiopathic aquired (n=7) or secondary aquired megacolon (n=21) and compared the results with a normal colon in control dogs (n=3). Colonic sections of surgical specimens were investigated by conventional and immunohistochemical methods, including pan-neuronal markers (NSE, synaptophisin, and neurofilament) and VIP, as well as S-100 protein for detection of ganglionic glial cells. Compared to controls, the two megacolon groups showed no changes of density of enteric neurons in both submucosal and myenteric nervous plexuses in DP of the colon and of enteric glial cells. However, compared to controls and dogs with secondary megacolon, there was a significant decrease in the density of NFP-ir nerve fibers in the longitudinal muscle layer in dogs with idiopathic acquired megacolon. In addition, dogs with idiopathic megacolon display decreased VIP-ir in the myenteric plexus and lamina propria mucosae, and absence of VIP-ir neurons in the submucosal plexus of DP of the colon. Similar alterations, although of lesser severity, may be found in dogs with secondary aquired megacolon. We consider that both idiopathic and secondary aquired megacolon might occur on the basis of a dysplastic changes of VIP-ir enteric neurons.Poznato je da se magakolon javlja kod mesojeda, uključujući mačke i pse, pri čemu je ovo oboljenje daleko učestalije kod mačaka. Na osnovu dosadašnjih saznanja, idiopatski megakolon je čest uzročnik konstipacije kod mačaka i 62% mačaka sa konstipacijom ima idiopatski megakolon. Istovremeno, podaci o psima sa idiopatskim megakolonom veoma su oskudni. U ovom radu je proučavan enterični nervni sistem u dilatiranom delu kolona kod 7 pasa sa idiopatskim megakolonom i 21 psa sa sekundarnim stečenim megakolonom, a rezultati su upoređeni sa normalnim kolonom kod 3 kontrolne zdrave životinje. Tkivni preseci kolona bojeni su klasičnim histološkim i imunohistohemijskim metodama, pri čemu su primenjeni pan-neuronski markeri (NSE, sinaptofizin i neurofilament) i VIP, kao i S-100 protein za detekciju glijalnih ćelija u enteričnim ganglijama. Nisu otkrivene razlike u gustini enteričnih neurona u submukoznom i mijenteričnom pleksusu kod životinja sa megakolonom, kao ni razlike u gustini glijalnih ćelija enteričnih ganglija, u odnosu na kontrolnu grupu životinja. Međutim, u odnosu na kontrolnu grupu, kod životinja sa idiopatskim megakolonom dokazana je smanjena VIP-imunoreaktivnost (ir) u mienteričnom pleksusu i krznu mukoze, kao i kompletno odsustvo VIP-ir neurona u submukoznom pleksusu dilatiranog dela kolona. Slične promene, ali u manjem stepenu, postojale su kod pasa sa sekundarnim stečenim megakolonom. Može da se zaključi da u patogenezi idiopatskog i sekundarnog stečenog megakolona značajnu ulogu imaju displastične promene u VIP-ergičkim neuronima enteričkog nervnog sistema

Uticaj pentobarbitala i pentilenetetrazola na nivo azot oksida u frontalnom korteksu pacova

Levels of nitric oxide (NO) in the rats frontal cortex were continuously monitored before and after intraperitoneal administration of an antiepileptic drug-pentobarbital (20 and 40 mg/kg) or convulsant drug - pentylenetetrazol (50 mg/kg). Pentobarbital decreased the levels of NO in a dose dependent manner However, NO levels had a tendency to increase following the administration of pentylenetetrazol. It is suggested that central NO participates in the modulation of neuronal excitability, supporting the idea that NO is an important excitatory factor involved in the regulation of seizure susceptibility. Also, our results on anaesthetized rats suggests that endogenous NO may be involved in the mechanism of action of antiepileptic and analeptic drugs and this further suggest that NO levels in the human brain may decrease during antiepileptic therapy and increase during epileptic attacks or administration of excitatory drugs. The aim of the present study was to determine the possible role of NO levels in the brain during neuronal excitability and seizures.Nivo azot oksida (NO) u frontalnom korteksu pacova meren je kontinuirano kako pre, tako i nakon intraperitonealne primene antiepileptika pentobarbitala (u dozi od 20 i 40 mg/kg) ili konvulzivnog agensa pentilenetetrazola (u dozi od 50 mg/kg). Rezultati ovih eksperimenta su ukazali da pentobarbital smanjuje nivo NO u frontalnom korteksu pacova, dok koncentracija NO ima tendeciju rasta nakon primene pentilenetetrazola. Osim toga, dokazano je da endogeni NO ima važnu ekscitatornu ulogu u centralnim mehanizmima nastanka epilepsije. Takođe, naši rezultati su ukazali da kod anestetisanih životinja endogeni nivo NO ima uticaja na dejstvo kako antikonvulzivnih, tako i prokonvulzivnih lekova. Nivo NO u mozgu pacova je bio snižen tokom terapije antiepilepticima, a povišen tokom epileptičkih napada ili primene lekova iz grupe centralnih stimulansa

Mean field approximation of two coupled populations of excitable units

The analysis on stability and bifurcations in the macroscopic dynamics exhibited by the system of two coupled large populations comprised of $N$ stochastic excitable units each is performed by studying an approximate system, obtained by replacing each population with the corresponding mean-field model. In the exact system, one has the units within an ensemble communicating via the time-delayed linear couplings, whereas the inter-ensemble terms involve the nonlinear time-delayed interaction mediated by the appropriate global variables. The aim is to demonstrate that the bifurcations affecting the stability of the stationary state of the original system, governed by a set of 4N stochastic delay-differential equations for the microscopic dynamics, can accurately be reproduced by a flow containing just four deterministic delay-differential equations which describe the evolution of the mean-field based variables. In particular, the considered issues include determining the parameter domains where the stationary state is stable, the scenarios for the onset and the time-delay induced suppression of the collective mode, as well as the parameter domains admitting bistability between the equilibrium and the oscillatory state. We show how analytically tractable bifurcations occurring in the approximate model can be used to identify the characteristic mechanisms by which the stationary state is destabilized under different system configurations, like those with symmetrical or asymmetrical inter-population couplings.Comment: 5 figure

Dynamics of FitzHugh-Nagumo excitable systems with delayed coupling

Small lattices of $N$ nearest neighbor coupled excitable FitzHugh-Nagumo systems, with time-delayed coupling are studied, and compared with systems of FitzHugh-Nagumo oscillators with the same delayed coupling. Bifurcations of equilibria in N=2 case are studied analytically, and it is then numerically confirmed that the same bifurcations are relevant for the dynamics in the case $N>2$. Bifurcations found include inverse and direct Hopf and fold limit cycle bifurcations. Typical dynamics for different small time-lags and coupling intensities could be excitable with a single globally stable equilibrium, asymptotic oscillatory with symmetric limit cycle, bi-stable with stable equilibrium and a symmetric limit cycle, and again coherent oscillatory but non-symmetric and phase-shifted. For an intermediate range of time-lags inverse sub-critical Hopf and fold limit cycle bifurcations lead to the phenomenon of oscillator death. The phenomenon does not occur in the case of FitzHugh-Nagumo oscillators with the same type of coupling.Comment: accepted by Phys.Rev.

Analytical methods for arsenic speciation analysis

Arsenic exists in the form of various chemical species differing in their physicochemical behaviour, toxicity, bioavailability and biotransformation. The determination of arsenic species is an important issue for environmental, clinical and food chemistry. However, differentiation of these species is a quite complex analytical task. Numerous speciation procedures have been studied that include electrochemical, chromatographic, spectrometric and hyphenated techniques. This review presents the relevant research in the field of arsenic speciation analysis with novel applications and significant advances. Stability of arsenic species and each of the analytical steps (sample collection, storage, preservation, extraction) of the arsenic speciation methods is particularly evaluated. Analytical validation and performance of these Methods are also reviewed

Anomalous Microwave Emission from the HII region RCW175

We present evidence for anomalous microwave emission in the RCW175 \hii region. Motivated by 33 GHz 13\arcmin resolution data from the Very Small Array (VSA), we observed RCW175 at 31 GHz with the Cosmic Background Imager (CBI) at a resolution of 4\arcmin. The region consists of two distinct components, G29.0-0.6 and G29.1-0.7, which are detected at high signal-to-noise ratio. The integrated flux density is $5.97\pm0.30$ Jy at 31 GHz, in good agreement with the VSA. The 31 GHz flux density is $3.28\pm0.38$ Jy ($8.6\sigma$) above the expected value from optically thin free-free emission based on lower frequency radio data and thermal dust constrained by IRAS and WMAP data. Conventional emission mechanisms such as optically thick emission from ultracompact \hii regions cannot easily account for this excess. We interpret the excess as evidence for electric dipole emission from small spinning dust grains, which does provide an adequate fit to the data.Comment: 5 pages, 2 figures, submmited to ApJ Letter

Ambient air particles: The use of ion chromatography and multivariate techniques in the analysis of water-soluble substances

Seventeen water-soluble substances (of sodium, ammonium, potassium, magnesium, calcium, formate, methanesulfonate, glyoxylate, chloride, nitrite, nitrate, glutarate, succinate, malate, malonate, sulfate and oxalate) in 94 samples of particle matter in the ambient air, collected over ten months, in a suburb of Belgrade (Serbia), were determined by ion chromatography. To apportion the sources of the air pollution, the log-transformed data were processed by applying multivariate techniques. Principal component and factor analysis identified three main factors controlling the data variability: stationary combustion processes with the highest loadings of oxalate, malonate and malate; landfill emission and secondary inorganic aerosol characterized by high levels of ammonium, nitrate and sulfate; a contribution of mineral dust composed of magnesium, calcium and chloride. The hierarchical cluster analysis pointed out a differentiation of the samples into five groups belonging to different variables inputs. For the classification of ambient air samples using nine selected ions, the recognition ability of linear discriminant analysis, k-nearest neighbors, and soft independent modeling of class analogy were 87.0, 94.6, and 97.8 %, respectively. Time-series analysis showed that the traffic emission is more pronounced in winter in contrast to the mineral dust influence, while the effect of waste combustion exhibits no trend