The gas exchange performance of the European blackberry (Rubus fruticosus agg.) and ecological traits for interpreting colonization in forest canopy gaps

Blackberry is a considerable weed in both antropogenous habitats and semi-natural vegetation, and this results in robust colonization in open sites. Our research investigated the carbon gain and water exchange performance of this species under ecologically contrasted forest gap conditions in temperate deciduous forests. We used a Kruskal–Wallis test to assess this species ecophysiological behaviour in response to the functional relevance of light environment, seasons and forest gap character. Our research also confirmed significant relationships between abundance, gap characteristics and light response measures. Light environment plays an essential role in the development of assimilation and water use efficiency. Seasonal variation affects transpiration, and forest type influences stomatal conductance. The amount of precipitation and canopy gap size is linked to the relative abundance of the species. These characteristics integrate with a nitrogen biomass trade-off across forest types. Measures of stomatal conductance and assimilation turned out to be the most significant functional variables including a gas exchange indicator for species abundance. Extended functional leaf phenology can promote successful colonization under adequate abiotic conditions. Our results conclude that environmental-related canopy gap size can be recommended for ecologically contrasted forest types, thus modulating the biomass production of the blackberry.     

Role of dopamine in the peripheral mechanisms of respiration control

Under clinical conditions, we studied the interaction between dopamine (DA) metabolism and hypoxia stimulationrelated ventilatory responses (HVR) before and after adaptation to periodical hypoxic episodes. Thirty-seven young and elder persons were tested; among elder tested subjects there were patients with Parkinson’s desease treated or not treated with DOPA-DA precursor-containing drugs (levoDOPA/carbiDOPA). We measured the HVR indices and DA and DOPA contents in the venous blood of tested persons before and after a 14-day-long hypoxic training. The highest indices of the ventilation sensitivity to hypoxia together with the lowest above-mentioned chemical indices were observed in young persons. An increase in the DA and DOPA levels in the venous blood were observed concurrently with suppression of the ventilation responses to hypoxic episodes. After a course of periodical hypoxic sessions, we observed in all groups opposite dynamics of DA and DOPA metabolism. An increase in the DA level in young persons and a trend toward its decrease in older healthy persons and parkinsonian patients was nevertheles accompanied by an HVR increase in all groups. Possible relations between the DA metabolism indices and peripheral mechanisms of respiratory control are discussed.     

Are steady-state temporal correlations between evoked stochastic releases of synaptic vesicles as informative as suggested?

Using a stochastic model, we found that the steady-state temporal correlation between synaptic responses evoked by successive presynaptic spikes under conditions of high-frequency repetitive stimulation (50–100 sec⁻¹) is always negative. Therefore, the sign of this correlation cannot be used as a criterion that allows one to distinguish the univesicular vs multivesicular modes of neurotransmitter release in an active zone or the univesicular releases with low vs high probabilities of vesicle release, as suggested earlier [7]. For lower stimulation frequencies (15–20 sec⁻¹), positive correlation between release events evoked by consecutive stimuli is observed only in those cases where the number of ready-releasable vesicles and the time constant of recovery from depression are sufficiently large. Neirofiziologiya/Neurophysiology, Vol. 38, Nos. 5/6, pp. 412–415, September–December, 2006.     

Nonuniformity of the chemical composition of a capillary discharge plasma

A steady-state distribution of the concentration of two ion species in a capillary discharge plasma is studied using MHD equations for a plasma with a spatially nonuniform, time-dependent chemical composition. In our case, the set of equations is significantly simplified because of the steady-state character and symmetry of the problem. Even with such simplification, however, some results could be obtained only by numerical integration. The factors affecting the distribution of heavy ions are studied. It is shown that the distribution of the heavy impurity over the discharge cross section can be much more nonuniform than the distribution of the main component (hydrogen). A simple criterion for such a nonuniformity is obtained.     

Quantifying the magnetic advantage in magnetotaxis

Magnetotactic bacteria are characterized by the production of magnetosomes, nanoscale particles of lipid bilayer encapsulated magnetite, that act to orient the bacteria in magnetic fields. These magnetosomes allow magneto-aerotaxis, which is the motion of the bacteria along a magnetic field and toward preferred concentrations of oxygen. Magneto-aerotaxis has been shown to direct the motion of these bacteria downward toward sediments and microaerobic environments favorable for growth. Herein, we compare the magneto-aerotaxis of wild-type, magnetic Magnetospirillum magneticum AMB-1 with a nonmagnetic mutant we have engineered. Using an applied magnetic field and an advancing oxygen gradient, we have quantified the magnetic advantage in magneto-aerotaxis as a more rapid migration to preferred oxygen levels. Magnetic, wild-type cells swimming in an applied magnetic field more quickly migrate away from the advancing oxygen than either wild-type cells in a zero field or the nonmagnetic cells in any field. We find that the responses of the magnetic and mutant strains are well described by a relatively simple analytical model, an analysis of which indicates that the key benefit of magnetotaxis is an enhancement of a bacterium's ability to detect oxygen, not an increase in its average speed moving away from high oxygen concentrations.     

Place de la tomographie par émission de positons (TEP) au [18F]FDG dans l’exploration des vascularites

[¹⁸F]fluorodeoxyglucose (¹⁸FDG) positron emission tomography (PET) is a noninvasive metabolic imaging modality that is well suited to the assessment of activity and extent of large vessel vasculitis, such as giant cell arteritis and Takayasu arteritis. PET could be more effective than magnetic resonance imaging in detecting the earliest stages of vascular wall inflammation. The visual grading of vascular [¹⁸F]FDG uptake makes it possible to discriminate arteritis from atherosclerosis, providing therefore high specificity. High sensitivity can be achieved provided scanning is performed during active inflammatory phase, preferably before starting corticosteroid treatment. Large scale prospective studies are needed to determine the exact value of PET imaging in assessing the large vessel vasculitis outcome and response to immunosuppressive treatment.     

Use of 3H and 14C double-labeled glucose to assess in vivo pathways of amino acid biosynthesis in Escherichia coli.

3H and 14C tracing data concerning amino acid biosynthetic pathways in Escherichia coli K12 are presented. Thirteen acidic and neutral amino acids were isolated from protein hydrolysates of wild type E. coli K12 grown aerobically or anaerobically in the presence of [U-14C]glucose together with [1-3H]glucose, [3-3H]glucose, [4-3H]glucose, or [6-3H]glucose. The observed 3H/14C counts of the amino acids were compared with the ratios expected on the basis of the input substrate specific activities and present understanding of biosynthetic pathways. For nine amino acids, serine, valine, leucine, threonine, isoleucine, glycine, glutamate, proline, and phenylalanine, the agreement between anticipated and observed specific activities was satisfactory. For the remaining four, methionine, alanine, aspartate, and (in cells labeled with [3-3H]glucose) tyrosine, the anticipated and observed specific activities differed markedly. For alanine, aspartate, and tyrosine, the differences are probably due to exchange of tritium in the course of biosynthesis; for methionine, it may be that there is a principle source of the methyl group other than carbon 3 of serine.     

Analysis of chromosomal polymorphism in barley (Hordeum vulgare L. ssp. vulgare) and between H. vulgare and H. chilense using three-color fluorescence in situ hybridization (FISH)

The aim of the present work was to study chromosomal polymorphism within cultivated barley (Hordeum vulgare ssp. vulgare) using three-color fluorescence in situ hybridization (FISH). The physical distribution of the most frequently used, highly repetitive DNA sequences (GAA)₇ specific for pericentromeric heterochromatic regions, the ribosomal DNA clone pTa71, specific for the 45S rDNA, and the barley-specific telomere-associated sequence HvT01, was investigated to reveal genetic diversity in metaphase spreads of ten barley genotypes with diverse geographical origin, growth habit and row number. A wild relative of barley, Hordeum chilense was also studied in order to compare the polymorphism between and within Hordeum species. Significant differences in the hybridization patterns of all three DNA probes could be detected between the two related species, but only probes pTa71 and HvT01 showed variation in the intensity and/or position of hybridization sites among genotypes of H. vulgare ssp. vulgare. The extent of polymorphism was less than that earlier reported for molecular markers and was restricted to the long chromosome arms, with differences between the chromosomes. 1H and 3H proved to be the most variable chromosomes and 4H and 6H the most conserved.     

Isolation of Bioactive Compounds from Pistacia integerrima with Promising Effects on Reverse Cancer Multidrug Resistance

Russian Journal of Bioorganic Chemistry - Pistacia integerrima grows in some areas of Pakistan and some other south Asian countries such as Afghanistan, India, Nepal, and Myanmar. It is an...     

Preconditioning decreases ischemia/reperfusion-induced peroxynitrite formation

The role for peroxynitrite (ONOO(-)) in the mechanism of preconditioning is not known. Therefore, we studied effects of preconditioning and subsequent ischemia/reperfusion on myocardial ONOO(-) formation in isolated rat hearts. Hearts were subjected to a preconditioning protocol (three intermittent periods of global ischemia/reperfusion of 5 min duration each) followed by a test ischemia/reperfusion (30 min global ischemia and 15 min reperfusion). When compared to nonpreconditioned controls, preceding preconditioning improved postischemic cardiac performance and significantly decreased test ischemia/reperfusion-induced formation of free nitrotyrosine measured in the perfusate as a marker for cardiac endogenous ONOO(-) formation. During preconditioning, however, the first period of ischemia/reperfusion increased nitrotyrosine formation, which was attenuated after the third period of ischemia/reperfusion. We conclude that classic preconditioning inhibits ischemia/reperfusion-induced cardiac formation of ONOO(-) and that subsequent periods of ischemia/reperfusion result in a gradual attenuation of ischemia/reperfusion-induced ONOO(-) generation. This mechanism might be involved in ischemic adaptation of the heart.