Band 2, Heft 3

Little is known about the extra- and intracellular stimuli inducing renal stem/progenitor cells to develop into three-dimensionally structured tubules. To study this specific development in a controlled environment, we used an advanced culture technique. Embryonic tissue derived from neonatal rabbit kidney was placed in a perfusion culture container at the interface of an artificial interstitium made of a polyester fleece. Culture was carried out in chemically defined Iscove’s Modified Dulbecco’s Medium (IMDM) for 13 days. Development of tubules was histochemically detected on cryosections labeled with Soybean Agglutinin (SBA). The experiments showed that aldosterone exerts a specific tubulogenic effect. Application of aldosterone (1 × 10−7 M) raised numerous SBA-labeled tubules, while in the absence of the steroid hormone the development of tubules was lacking. Specificity of hormone action was analyzed by the use of aldosterone antagonists. Administration of spironolactone (1 × 10−4 M) and canrenoate (1 × 10−5 M) completely inhibited the development of tubules. Finally, disrupting the intracellular molecular complex of the mineralocorticoid receptor (MR) and heat shock proteins by geldanamycin (2 μg/ml) prevented the development of tubules. Our results suggest that the tubulogenic effect induced by aldosterone is attributed to both hormone binding and an undisturbed intracellular response of the MR.

The effect of hydrogen peroxide on the activities of catalase and superoxide dismutase (SOD) in S. cerevisiae has been studied under different experimental conditions: various H2O2 concentrations, time exposures, yeast cell densities and media for stress induction. The yeast treatment with 0.25–0.50 mM H2O2 led to an increase in catalase activity by 2–3-fold. At the same time, hydrogen peroxide caused an elevation by 1.6-fold or no increase in SOD activity dependently on conditions used. This effect was cancelled by cycloheximide, an inhibitor of protein synthesis in eukaryotes. Weak elevation of catalase and SOD activities in cells treated with 0.25–0.50 mM H2O2 found in this study does not correspond to high level of synthesis of the respective enzyme molecules observed earlier by others. It is well known that exposure of microorganisms to low sublethal concentrations of hydrogen peroxide leads to the acquisition of cellular resistance to a subsequent lethal oxidative stress. Hence, it makes possible to suggest that S. cerevisiae cells treated with low sublethal doses of hydrogen peroxide accumulate non-active stress-protectant molecules of catalase and SOD to survive further lethal oxidant concentrations.

The CuZn superoxide dismutase (SOD1), a member of a group of isoenzymes involved in the scavenger of superoxide anions, is a dimeric carbohydrate free protein, mainly localized in the cytosol. The reactive oxygen species (ROS) are involved in many pathophysiological events correlated with mutagenesis, cancer, degenerative processes and aging. In the first part of this mini-review the well known role of SOD1 and ROS are briefly summarized. Following, a potential novel biological action that SOD1 could exert is described, based on the recent researches demonstrating the secretion of this enzyme in many cellular lines. Moreover, the role of impaired mutant SOD1 secretion, associated with cytoplasmic toxic inclusion, which occurs in familial amyotrophic lateral sclerosis (ALS), is summarized. In addition, a depolarization-dependent release of SOD1 in pituitary GH3 cells and in rat synaptosomes through a calcium and SNARE-dependent mechanism is reported.

An experimental set-up which enabled non-invasive, real-time reactive oxygen species (ROS) visualization on a whole plant level was constructed. In the test organism, Lemna minor L. (common duckweed), apoplastic and symplastic oxidative stress was evaluated by exposure to menadione (50 μM), menadione (50 μM) + ascorbate (100 μM) or neither for control. Menadione (50 μM) caused a statistically significant increase in H2DCFDA fluorescence in the apoplast after 60 minutes of exposure. The addition of ascorbate (100 μM) in the test medium significantly decreased apoplastic oxidative stress. 50 μM menadione caused an increase in symplastic H2DCFDA fluorescence in 57% of fronds. The exposure of L. minor plants to both menadione and ascorbate decreased the rate of fluorescence intensity accumulation in the symplast to control levels. The method has proven to be quick and straightforward and could be applied to a range of chemicals in various physiological and toxicological plant studies. The advantages of the set-up and different possible artefacts are discussed.

The low ethanol tolerance of thermophilic anaerobic bacteria, generally less than 2% (v/v) ethanol, is one of the main limiting factors for their potential use for second generation fuel ethanol production. In this work, the tolerance of thermophilic anaerobic bacterium Thermoanaerobacter BG1L1 to exogenously added ethanol was studied in a continuous immobilized reactor system at a growth temperature of 70°C. Ethanol tolerance was evaluated based on inhibition of fermentative performance e.g. inhibition of substrate conversion. At the highest ethanol concentration tested (8.3% v/v), the strain was able to convert 42% of the xylose initially present, indicating that this ethanol concentration is not the upper limit tolerated by the strain. Long-term strain adaptation to high ethanol concentrations (6–8.3%) resulted in an improvement of xylose conversion by 25% at an ethanol concentration of 5% v/v, which is the concentration required in practice for economically efficient product recovery. For all ethanol concentrations tested, relatively high and stable ethanol yields (0.40–0.42 g/g) were seen. The strain demonstrated a remarkable ethanol tolerance, which is the second highest displayed by thermophilic anaerobic bacteria known to the authors. This appears to be the first study of the ethanol tolerance of these microorganisms in a continuous immobilized reactor system.

Plasmids capable of horizontal transfer contribute to the adaptability of bacteria, as they may provide genes that enable their hosts to cope with different selective pressures. Only limited information is available on plasmids from Antarctic habitats, and up until now surveys have only used traditional methods of endogenous plasmid isolation. The method based on primer systems, designed on the basis of published sequences for plasmids from different incompatibility (Inc) groups, is appropriate to detect the replicon-specific regions of corresponding plasmids in cultured bacteria, or in total community DNA, which share sufficient DNA similarity with reference plasmids at the amplified regions. In this study, we applied broad-host-range plasmid-specific primers to DNA from microbial samples collected at six different locations in Northern Victoria Land (Antarctica). DNA preparations were used as targets for PCR (polymerase chain reaction) amplification with primers for the IncP (trfA2) and IncQ (oriV ) groups. PCR products were Southern blotted and hybridized with PCR-derived probes for trfA2 and oriV regions. This approach detected the occurrence of IncP-specific sequences in eight out of fifteen DNA samples, suggesting a gene-mobilizing capacity within the original habitats.

Secretion of periplasmic alkaline phosphatase (PhoA) encoded by the gene constituent of plasmids and the peculiar properties of cell envelope biogenesis in Escherichia coli strains with controlled synthesis of individual membrane phospholipids have been studied. Alkaline phosphatase secretion across the cytoplasmic membrane declines, while secretion into the culture medium intensifies under changed metabolism. The composition of anionic membrane phospholipids changes due to inactivation of the pgsA gene or regulation of its expression by environmental factor, as well as in the absence of the pssA gene which is responsible for the synthesis of the precursor for zwitter-ionic phospholipid — phosphatidylethanolamine. This correlates with intensified secretion of exopolysaccharides and lower content of lipopolysaccharide and lipoprotein which are responsible for barrier properties of the outer membrane. The results suggest a possible coupling of protein secretion with biogenesis of cell envelope components at a level of phospholipid metabolism.

The harmful effects of surfactants to the environment are well known. We were interested in investigating their potential toxicity in a pure culture of Acinetobacter junii, a phosphate (P)-accumulating bacterium. Results showed a high acute toxicity of sodium dodecyl sulfate (SDS) and hexadecyltrimethylammonium bromide (HDTMA) against A. junii. The estimated EC50 values of the HDTMA for the inhibition of CFUs in the pure culture of A. junii was 3.27 ± 1.12 × 10−7 mol L−1 and for the inhibition of the P-uptake rates 2.47 ± 0.51 × 10−6 mol L−1. For SDS, estimated EC50 values for the inhibition of CFUs in the pure culture of A. junii was 5.00 ± 2.95 × 10−6 mol L−1 and for the inhibition of the P-uptake rates 3.33 ± 0.96 × 10−4 mol L−1. The obtained EC50 values in the standardised yeast toxicity test using Saccharomyces cerevisiae were 3.03 ± 0.38 × 10−4 and 4.33 ± 0.32 × 10−5 mol L−1 for SDS and HDTMA, respectively. These results emphasized the need to control concentrations of surfactants entering the activated sludge system. The negative effects of these toxicants could greatly decrease populations of P-accumulating bacteria, as well as eukaryotic organisms, inhabiting activated sludge systems, which in turn could result in the decrease of the system efficiency.

In this study on the excretory apparatus of the Bufo bufo larvae, the ultrastructural features and the atrial natriuretic peptide (ANP)-system were examined using cytochemical and immunocytochemical methods. The early embryonic kidney, the pronephros, is replaced by a later stage, the mesonephros. The pronephros degenerates at the time of metamorphosis and the mesonephros becomes the functional kidney in the adult. Both these organs are targets for ANP, demonstrated by the presence of the specific receptors, indirectly highlighted by the cytochemical localization of the guanylate cyclase in the presence of exogenous atrial natriuretic peptide. This study concluded that the mesonephros produces ANP and thus clusters of cells containing ANP-like granules, positive to the anti-α ANP immunolocalization, were present along the mesonephric proximal tubule. The atrial natriuretic peptide system carries out an important osmoregulatory role in the excretory apparatus.

In this study, we analyzed the dynamic motor patterns of attack or defense and age hierarchy to investigate aggression in African mole-rats Cryptomys foxi and the house mouse Mus musculus. The objective is to verify if the social order of dominance is associated with age hierarchy within the social group. Using the resident-intruder experimental model, we created a series of dyadic encounters that comprised of a standard adult mouse or rat paired with groups of aggressive and hierarchically age-ranked small animals in a territorial aggression test. Our results indicate that though the adult animals displayed the highest level of aggression, indicating their dominant status, there was no age-related hierarchical formation in the expression of aggression. In the non-territorial aggression test in which rats or mice were grouped together, animals displayed low levels of aggression compared to the territorial test and no hierarchical age-related order. These results indicate that the magnitude of aggression expressed by animals in the social group, based on their motor patterns of attack and defense, seem to depend on individual competitive strategies in reaction to various environmental challenges and not necessarily on age hierarchy.