Loss of PTEN Facilitates Rosiglitazone-Mediated Enhancement of Platinum(IV) Complex LA-12-Induced Apoptosis in Colon Cancer Cells

We demonstrated for the first time an outstanding ability of rosiglitazone to mediate a profound enhancement of LA-12-induced apoptosis associated with activation of mitochondrial pathway in human colon cancer cells. This effect was preferentially observed in the G1 cell cycle phase, independent on p53 and PPARγ proteins, and accompanied with significant changes of selected Bcl-2 family protein levels. Further stimulation of cooperative synergic cytotoxic action of rosiglitazone and LA-12 was demonstrated in the cells deficient for PTEN, where mitochondrial apoptotic pathway was more stimulated and G1-phase-associated dying was reinforced. Our results suggest that combined treatment with rosiglitazone and LA-12 might be promising anticancer strategy in colon-derived tumours regardless of their p53 status, and also favourable in those defective in PTEN function.     

Chitinolytic enzymes from bacterium inhabiting human gastrointestinal tract -- critical parameters of protein isolation from anaerobic culture

The object of this study are chitinolytic enzymes produced by bacterium Clostridium paraputrificum J4 isolated from the gastrointestinal tract of a healthy human. In particular, we focus on the development of purification protocols, determination of properties of the enzymes and their activity profiles. The process of bacteria cultivation and isolation of chitinolytic complex of enzymes showing specific activities of endo-, exo-chitinase and N-acetyl-β-glucosaminidase was optimized. A range of various purification procedures were used such as ultrafiltration, precipitation, chromatographic separations (ion-exchange, size exclusion, chromatofocusing) in altered combinations. The optimal purification protocol comprises two or three steps. Individual samples were analyzed by SDS/PAGE electrophoresis and after renaturation their activity could be detected using zymograms. Mass spectroscopy peptide fragment analysis and MALDI analysis of the purest samples indicate presence of endochitinase B (molecular mass about 85 kDa) and of 60-kDa endo- and exochitinases.     

Proteinase inhibition and antioxidant activity of selected forage crops

The hypothesis of the possible therapeutic potential of selected species of forage crops is discussed. Extracts from genotypes of Anthyllis sp., Astragalus sp., Coronilla sp., Lotus sp., Medicago sp., Melilotus sp., Onobrychis sp. and Trifolium sp. were prepared and tested for proteinase inhibition and antioxidant activities. We found that Trifolium pratense accession POLKIE99-3 expressed the highest relative trypsin inhibition activity (80.0%) compared to standards. The highest thrombin inhibition activity (81.4%) was detected in the Medicago sativa old cultivar Hodoninka, whereas the highest relative urokinase inhibition activity (62.5%) was expressed by the local population Nitranka. Relatively high antioxidant properties of Trifolium sp. accessions, Trifolium pratense genetic resources SVKZAH98-40, were of interest. Results of this study confirmed that there are significant differences in proteinase inhibition and antioxidant activity among important selected agricultural crops. The present paper may also be the starting point of the research aimed for development of new functional food and nutraceuticals, and/or of the research focused on new secondary metabolites with potential as bioactive compounds.     

Uptake and incorporation of sialic acid by the tick Ixodes ricinus

We describe the detection of sialylated N-linked glycans in partially fed Ixodes ricinus tick females using matrix-assisted laser desorption/ionization time-of-flight/time-of-flight mass spectrometry. Sialylated glycans were detected in salivary glands as well as in tick guts and we propose the host origin of these structures. In addition, we mapped the transport of sialylated structures from the blood meal through the gut to the salivary glands using electron microscopy. Specific localization of sialylated glycans to basement membranes of salivary glands was observed. Finally, the influence of the sample preparation methods for electron microscopy on ultrastructure and immunogold labeling was evaluated.     

The effect of water stress during ontogeny of primary bean leaves on the light-induced stomatal opening

The increase in epidermal conductance of primary bean leaves started within 10 min after irradiation by 1200 μmol m⁻² s⁻¹ of darkened plants. The rate of stomatal opening increased toa maximum and then decreased till a steady-state value of epidermal conductance was reached. Stomata on the abaxial epidermis always started to open sooner and opened faster than stomata on adaxial epidermis. Both water stress and ageing of leaves delayed the beginning of opening and decreased the opening rate as well as the steady-state values of epidermal conductance.     

Photosynthesis of plant régénérants. Specificity ofin vitro conditions and plantlet response

Regenerants from tobacco(Nicotiana tabacum L. cv. White Burley) leaf segments cultivatedin vitro in vessels with solid agar medium under usual conditions (plantlets) grew under very low irradiance (I = 40 μxmol m?2 s?1), very high relative humidity (more than 90%) and decreased CO₂ concentration (c_a) during light period. In comparison with seedlings of a similar number of leaves and similar total leaf area grown in sand and nutrient solution, the plantlets had lower dry mass of shoots and roots per plant and thinner leaves almost without trichomes and epicuticular waxes. Due to a low transpiration rate under high relative humidity the water potential of plantlet leaves was higher than that of seedling leaves and the difference in water potential between leaves and medium was lowei. The rate of water loss from leaves detached from plantlets was considerably faster than that from seedlings under the same conditions (I = 110 μrnol m^?2; s^?1, temperature 30 °C, relative humidity 50 %). Net photosynthetie rates (P_n) of leaves of plantlets and seedlings measured under saturating I, natural ca and the leaf temperature 20 °C were similar, nevertheless the shape of curves relating Pn to c» indicated some differences in photosynthetie parameters(e.g. saturation of Pn under lower ca> higher CO2 compensation concentration in plantlets than in seedlings). Similarly compensation and saturating I were lower in plantlets than in seedlings. The shape of transpiration curves as well as the expressive linear phases of P_N(ca) and P_N(I) curves of plantlet leaves indicated ineffective stomatal control of gas exchance. These results were confirmed by microscopic observations of stomatal movementsin situ     

Fusarium oxysporum (Schlecht.) Snyd. et Hans. — A dominant fungus species on the root-surface of woody plant seedlings

Summary and conclusions The imperfect fungusFusarium oxysporum dominated the root surface of first-year seedlings of woody plants grown in the forest nursery in eany near Pardubice, Czechoslovakia. The second most frequent species wasCylindrocarpon radicicola whose relative frequency increased towards the end of the growing season. The morphological variability of isolated strains ofFusarium oxysporum was studied; notwithstanding their great variability they all fall within the range of this complex species. The ecological conditions for the occurrence ofFusarium oxysporum on the root surface and the saprophytic or parasitic relations between this fungus and the higher plants are discussed on the basis of personal observations and reports in the literature.