Characteristics of reactive oxygen species (ROS) production in isolated guinea-pig brain mitochondria respiring on aglycerophosphate (a-GP) were investigated and compared with those supported by succinate. Mitochondria established a membrane potential (DY m ) and released H 2 O 2 in parallel with an increase in NAD(P)H fluorescence in the presence of a-GP (5-40 mM). H 2 O 2 formation and the increase in NAD(P)H level were inhibited by rotenone, ADP or FCCP, respectively, being consistent with a reverse electron transfer (RET). The residual H 2 O 2 formation in the presence of FCCP was stimulated by myxothiazol in mitochondria supported by a-GP, but not by succinate. ROS under these conditions are most likely to be derived from a-GP-dehydrogenase. In addition, huge ROS formation could be provoked by antimycin in a-GP-supported mitochondria, which was prevented by myxothiazol, pointing to the generation of ROS at the quinol-oxidizing center (Q o ) site of complex III. FCCP further stimulated the production of ROS to the highest rate that we observed in this study. We suggest that the metabolism of a-GP leads to ROS generation primarily by complex I in RET, and in addition a significant ROS formation could be ascribed to a-GP-dehydrogenase in mammalian brain mitochondria. ROS generation by a-GP at complex III is evident only when this complex is inhibited by antimycin. Keywords: brain mitochondria, a-glycerophosphate, oxidative stress, reactive oxygen species, succinate. The main site of mitochondrial ROS production has been a topic of scientific debate, and mainly complex I and complex III of the respiratory chain have been the focus of investigations using isolated mitochondria respiring on either NADH-linked substrates or succinate (Boveris and Chance 1973;Cadenas et al. 1977;Turrens and Boveris 1980). Recently, a growing body of evidence has suggested that complex I is a more important source of ROS under normal and pathological conditions (Hansford et al. 1997;Barja 1999;Herrero and Barja 1999;Votyakova and Reynolds 2001;St Pierre et al. 2002), but depending upon the substrates and experimental conditions, different mechanisms might be responsible for ROS production in isolated mitochondria. Very recently a new ROS-forming site, the a-ketoglutarate dehydrogenase enzyme (a-KGDH) has been described (Bunik and Sievers 2002;Starkov et al. 2004b; Received 21 July, 2006; revised manuscript received September 4, 2006; accepted September 5, 2006. Address correspondence and reprint reqeusts to Prof. Vera Adam-Vizi MD, PhD, Department of Medical Biochemistry, Semmelweis University, Budapest, H-1444, P.O. Box 262, Hungary. E-mail: av@puskin.sote.huAbbreviations used: BCECF, 2¢,7¢-bis(carboxyethyl)-5,6-carboxyfluorescein; BSA, bovine serum albumin; a-GP, a-glycerophosphate; a-GPDH, a-glycerophosphate dehydrogenase; DY m , membrane potential; FCCP, carbonyl cyanide-p-trifluoromethoxyphenyl-hydrazon; pH m , pH in the mitochondrial matrix; Q o , quinol-oxidizing center; RCR, respiratory control ratio; RET, rever...

The most influential environmental drivers of macrofungal species composition were studied in managed, even-aged, mixed forests of Őrség National Park, Hungary. Functional groups of macrofungi were analyzed separately by non-metric multidimensional scaling and redundancy analysis exploring their relations to tree species composition, stand structure, soil/litter conditions, microclimate, landscape, and management history. Some evidence was given that macrofungi are related to drivers that are relatively easy to measure. It was found that woodinhabiting fungal species composition is driven primarily by the species composition of living trees, while substrate properties and microclimate play minor roles. The terricolous saprotrophic community was determined principally by a litter pH gradient involving tree species composition and soil/litter properties. Microclimate had no concordant effect. No obvious underlying gradients were detected on ectomycorrhizal fungal species composition; however, tree size and litter pH had significant effects. For each group, no clear responses to landscape or management history were detected.

Abstract. Spatial 3-D information on soil hydraulic properties for areas larger than plot scale is usually derived using indirect methods such as pedotransfer functions (PTFs) due to the lack of measured information on them. PTFs describe the relationship between the desired soil hydraulic parameter and easily available soil properties based on a soil hydraulic reference dataset. Soil hydraulic properties of a catchment or region can be calculated by applying PTFs on available soil maps. Our aim was to analyse the performance of (i) indirect (using PTFs) and (ii) direct (geostatistical) mapping methods to derive 3-D soil hydraulic properties. The study was performed on the Balaton catchment area in Hungary, where density of measured soil hydraulic data fulfils the requirements of geostatistical methods. Maps of saturated water content (0 cm matric potential), field capacity (−330 cm matric potential) and wilting point (−15 000 cm matric potential) for 0–30, 30–60 and 60–90 cm soil depth were prepared. PTFs were derived using the random forest method on the whole Hungarian soil hydraulic dataset, which includes soil chemical, physical, taxonomical and hydraulic properties of some 12 000 samples complemented with information on topography, climate, parent material, vegetation and land use. As a direct and thus geostatistical method, random forest combined with kriging (RFK) was applied to 359 soil profiles located in the Balaton catchment area. There were no significant differences between the direct and indirect methods in six out of nine maps having root-mean-square-error values between 0.052 and 0.074 cm3 cm−3, which is in accordance with the internationally accepted performance of hydraulic PTFs. The PTF-based mapping method performed significantly better than the RFK for the saturated water content at 30–60 and 60–90 cm soil depth; in the case of wilting point the RFK outperformed the PTFs at 60–90 cm depth. Differences between the PTF-based and RFK mapped values are less than 0.025 cm3 cm−3 for 65 %–86  % of the catchment. In RFK, the uncertainty of input environmental covariate layers is less influential on the mapped values, which is preferable. In the PTF-based method the uncertainty of mapping soil hydraulic properties is less computationally intensive. Detailed comparisons of maps derived from the PTF-based method and the RFK are presented in this paper.

It has been reported recently (Tretter et al., 2007b) that in isolated guinea pig brain mitochondria supported by alpha-glycerophosphate (alpha-GP) reactive oxygen species (ROS) are produced through the reverse electron transport (RET) in the respiratory chain and by alpha-glycerophosphate dehydrogenase (alpha-GPDH). We studied the effect of calcium on the generation of H(2)O(2) as measured by the Amplex Red fluorescent assay in this model. H(2)O(2) production in alpha-GP-supported mitochondria was increased significantly in the presence of 100, 250, and 500 nM Ca(2+), respectively. In addition, Ca(2+) enhanced the membrane potential, the rate of oxygen consumption, and the NAD(P)H autofluorescence in these mitochondria. Direct measurement of alpha-GPDH activity showed that Ca(2+) stimulated the enzyme by decreasing the Km for alpha-GP. In those mitochondria where RET was eliminated by the Complex I inhibitor rotenone (2 microM) or due to depolarization by ADP (1 mM), the rate of H(2)O(2) formation was smaller and the stimulation of H(2)O(2) generation by Ca(2+) was prevented partly, but the stimulatory effect of Ca(2+) was still significant. These data indicate that in alpha-GP-supported mitochondria activation of alpha-GPDH by Ca(2+) leads to an accelerated RET-mediated ROS generation as well as to a stimulated ROS production by alpha-GPDH.