Background processes at the population level during succession in grasslands on sand

Two population characteristics, reproductive allocation (RA) and the intensity of photosynthesis, were investigated in the successional stages of the sandy grassland communities of the Great Hungarian Plain. Most of the species studied changed their allocational response as succession advanced. Compound path schemes, as casual models, were constructed and analysed for describing intra-individual effects (influence of assimilating organs and root mass of the plant sampled) as well as the phytosociological effects on RA. In pioneer stages, the high values of path coefficients show that the effect of assimilating organs is responsible for the variability of RA. It is also shown that annuals and perennials exhibit different behaviour as to the regulation of RA. It seems that-in terms of path analysis-the reproduction of annuals is influenced by internal factors only. In case of perennials, an external (namely phytosociological) regulation was also observed. It is suggested that successional stages play a role in regulating the photosynthetic intensity of both the dominant species and the whole plant assemblage.Abbreviations RA = Reproductive Allocation     

The hazards of DAPI photoconversion: effects of dye, mounting media and fixative, and how to minimize the problem

Immunocytochemistry is a powerful tool for detection and visualization of specific molecules in living or fixed cells, their localization and their relative abundance. One of the most commonly used fluorescent DNA dyes in immunocytochemistry applications is 4′,6-diamidino-2-phenylindole dihydrochloride, known as DAPI. DAPI binds strongly to DNA and is used extensively for visualizing cell nuclei. It is excited by UV light and emits characteristic blue fluorescence. Here, we report a phenomenon based on an apparent photoconversion of DAPI that results in detection of a DAPI signal using a standard filter set for detection of green emission due to blue excitation. When a sample stained with DAPI only was first imaged with the green filter set (FITC/GFP), only a weak cytoplasmic autofluorescence was observed. Next, we imaged the sample with a DAPI filter set, obtaining a strong nuclear DAPI signal as expected. Upon reimaging the same samples with a FITC/GFP filter set, robust nuclear fluorescence was observed. We conclude that excitation with UV results in a photoconversion of DAPI that leads to detection of DAPI due to excitation and emission in the FITC/GFP channel. This phenomenon can affect data interpretation and lead to false-positive results when used together with fluorochrome-labeled nuclear proteins detected with blue excitation and green emission. In order to avoid misinterpretations, extra precaution should be taken to prepare staining solutions with low DAPI concentration and DAPI (UV excitation) images should be acquired after all other higher wavelength images. Of various DNA dyes tested, Hoechst 33342 exhibited the lowest photoconversion while that for DAPI and Hoechst 33258 was much stronger. Different fixation methods did not substantially affect the strength of photoconversion. We also suggest avoiding the use of mounting medium with high glycerol concentrations since glycerol showed the strongest impact on photoconversion. This photoconversion effect cannot be avoided even when using narrow bandpass filter sets.     

Similarity between contemporary vegetation and plant remains in the surface sediment in Mediterranean lakes

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Low‐dose bisphenol A induces RIPK1‐mediated necroptosis in SH‐SY5Y cells: Effects on TNF‐α and acetylcholinesterase

Bisphenol A (BPA) is an endocrine disruptor chemical, which is commonly used in everyday products. Adverse effects of its exposure are reported even at picomolar doses. Effects of picomolar and nanomolar concentrations of BPA on cytotoxicity, nitric oxide (NO) levels, acetylcholinesterase (AChE) gene expression and activity, and tumor necrosis factor‐α (TNF‐α) and caspase‐8 levels were determined in SH‐SY5Y cells. The current study reveals that low‐dose BPA treatment induced cytotoxicity, NO, and caspase‐8 levels in SH‐SY5Y cells. We also evaluated the mechanism underlying BPA‐induced cell death. Ours is the first report that receptor‐interacting serine/threonine‐protein kinase 1–mediated necroptosis is induced by nanomolar BPA treatment in SH‐SY5Y cells. This effect is mediated by altered AChE and decreased TNF‐α levels, which result in an apoptosis‐necroptosis switch. Moreover, our study reveals that BPA is an activator of AChE.     

Ecophysiological responses of desiccation-tolerant cryptobiotic crusts

In our present studies, the recovery of photosynthetic activity after rehydration was demonstrated. We measured chlorophyll fluorescence, CO₂ gas exchange and the pigment composition in the previously long-term air-dried cryptogamic inselberg crusts collected from two tropical areas. The cryptobiotic crusts were collected from different localities on similar ecological and climatic conditions from extreme habitats of inselbergs (outcrops). These inselbergs are characterized by a dry microclimate and are covered by scarce soil. We found that the ecophysiological responses of both cryptogamic inselberg crusts showed an extremely high degree of desiccation-tolerance due to the fast and full recovery during rehydration. The photosynthetic activity of the cryptobiotic crusts were restored and regained within 15 and 40 min, respectively, after rehydration. Photosynthetic activity of the crusts was retained at all applied light intensities when enough water was available, however the degree of the recovery was different between the crusts. Photosynthetic pigment contents were strongly and positively correlated with water content. Our results indicated that tropical desiccation-tolerant cryptogamic crusts found on inselberg rock surfaces have CO₂ fixation ability in the range of cyanobacteria and lichens, suggesting that at a global scale they can assimilate CO₂ in a significant amount.     

Investigation of Oxidative Status of the 2-Furan-2-yl-1H-Benzimidazole in Rats

We investigated the influence of 2-furan-2-yl-1H-benzimidazole regarding vitamins A, E, C, selenium (Se), malondialdehyde (MDA), and glutathione peroxidase (GSH-Px) levels on rats. 2-Furan-2-yl-1H-benzimidazole was given to rats by subcutaneous injection every other day for a total of 22 injections. At the end of the experiment, Se levels were determined by using a fluorimetric method. Serum levels of vitamins A, E, C, and malondialdehyde (MDA) were determined by high-performance liquid chromatography. Glutathione peroxidase (GSH-Px) levels of erythrocytes were spectrophotometrically determined. Our experimental results showed that vitamins A, E, C, and Se levels were found generally lower than the control groups, while serum MDA level and GSH-Px activity flexibly increased, which is dependent on injection days. The observed decreases in vitamins A, E, C, and Se levels in the blood might be causally related to the increased amount of free radicals that are generated with 2-furan-2-yl-1H-benzimidazole injection. However, further investigations are needed to clarify the significance of this observation in respect with the 2-furan-2-yl-1H-benzimidazole injection.     

Comparison of ELISA with shell vial cell culture method for the detection of human rotavirus in fecal specimens

The aim of the study was to compare an enzyme immunoassay method with shell vial cell culture method for detection of rotavirus in fecal specimens. In addition, the correlation between laboratory results and clinical scores of patients with gastroenteritis was evaluated. A total of 219 fecal specimens from children (ages 3 weeks to 5 years) with acute gastroenteritis submitted to pediatric emergency room were evaluated by both ELISA and shell vial cell culture. A Vesikari score was used for assessing the severity of the illness. Among 219 stool samples tested, 107 (48.9%) were determined to be positive. Two specimens were positive by shell vial cell culture method while they were ELISA negative. According to these results the calculated sensitivity, specificity, PPV, and NPV of ELISA were 98.1%, 100%, 100%, and 98.2%, respectively. The mean severity score for the 107 episodes of rotavirus diarrhoea was 11.0 +/- 3.6 compared to 4.5 +/- 1.9 for the 112 episodes of non-rotavirus diarrhea in the same population. Our study indicates that ELISA, which is easier to perform, faster and cheaper than cell culture methods may be suitable for routine diagnosis of rotavirus infections. The severity of rotavirus positive gastroenteritis was significantly higher than that of rotavirus negative patients.     

Seasonal CO<Subscript>2</Subscript>-exchange variations of temperate semi-desert grassland in Hungary

CO₂ exchange components of a temperate semi-desert sand grassland ecosystem in Hungary were measured 21 times in 2000–2001 using a closed IRGA system. Stand CO₂ uptake and release, soil respiration rate (R _s), and micrometeorological values were determined with two types of closed system chambers to investigate the daily courses of gas exchange. The maximum CO₂ uptake and release were –3.240 and 1.903 mol m^–2 s^–1, respectively, indicating a relatively low carbon sequestration potential. The maximum and the minimum R _s were 1.470 and 0.226 mol(CO₂) m^–2 s^–1, respectively. Water shortage was probably more effective in decreasing photosynthetic rates than R _s, indicating water supply as the primary driving variable for the sink-source relations in this ecosystem type.