Long-Term Responses of Mediterranean Mountain Forests to Climate Change,Fire and Human Activities in the Northern Apennines (Italy)

Ecosystems - Fagus sylvatica (beech) dominates the montane forests of the Apennines and builds old-growth high-conservation value stands. However, recent severe drought-induced diebacks raise...     

Unusual Role of the 3-OH Group of Oligosaccharide Substrates in the Mechanism of Bacillus 1,3-1,4-β-glucanase

Abstract

In the mechanism of retaining β-glycosidases, the 2-hydroxyl group of the substrate in the monosaccharyl unit involved in catalysis (subsite -1) is beleived to play an important role through hydrogen bonding interactions with protein residues that are optimized at the transition state. Commonly, removal of the 2-OH group of the substrate results in a 10–12 kcal·mol^-1 transition state destabilization. However, this effect seems not to be general as reported here for Bacillus 1,3-1,4-β-glucanase, a family 16 retaining endo-glycosidase. A p-nitrophenol 2-deosxy tetrasaccharide substrate was synthesized to probe the involvement of the 2-OH group in catalysis. Comparative kinetics with wild-type and subsite +1 mutants show that the 2-deoxy analog is a better substrate than the corresponding 2-hydroxy substrate. It is tentatively proposed that the 2-deoxy analog adopts a different conformation upon binding that compensates for the lack of the 2-OH substituent.     

Myeloperoxidase-mediated LDL oxidation and endothelial cell toxicity of oxidized LDL: attenuation by (−)-epicatechin

Recent data suggest an inverse epidemiological association between intake of flavanol-rich cocoa products and cardiac mortality. Potential beneficial effect of cocoa may be attributed to flavanol-mediated improvement of endothelial function, as well as to enhancement of bioavailability and bioactivity of nitric oxide in vivo. ( ? )-Epicatechin is one bioactive flavanol found in cocoa. This review deals with protective actions of ( ? )-epicatechin on two key processes in atherogenesis, oxidation of LDL and damage to endothelial cell by oxidized LDL (oxLDL), with emphasis on data from this laboratory. ( ? )-Epicatechin not only abrogates or attenuates LDL oxidation but also counteracts deleterious actions of oxLDL on vascular endothelial cells. These protective actions are only partially shared by other vasoprotective agents such as vitamins C and E or aspirin. Thus, ( ? )-epicatechin appears to be a pleiotropic protectant for both LDL and endothelial cells.     

Purification of Transferrin and Albumin from Mouse Ascites Fluid

Mouse ascites fluid, which is readily obtained when cell lines and hybridomas are maintained in host mice, is a convenient source of several plasma proteins. This paper describes procedures for the purification of albumin and transferrin from mouse ascites fluid. Mouse transferrin was prepared from a 50–75% ammonium sulfate fraction of mouse ascites fluid by CM- and DEAE-cellulose chromatography. Mouse albumin was obtained by the same purification route, but required an additional chromatography step on Cibacron Blue F3GA-agarose. Both proteins were shown to be homogeneous by polyacrylamide gel electrophoresis and Immunoelectrophoresis. Characterization, which included a determination of amino acid composition, partial N-terminal sequence, molecular weight and extinction coefficient, correlated well with known values reported for human transferrin and albumin. The purified mouse proteins may be useful for biochemical studies, antibody preparation, and as growth factors for hybridomas or other mouse cell lines maintained in culture.     

Hydrurus‐related golden algae (Chrysophyceae) cause yellow snow in polar summer snowfields

In polar regions, melting snow fields can be occupied by striking blooms of chrysophycean algae, which cause yellowish slush during summer. Samples were harvested at King George Island (South Shetland Islands, Maritime Antarctica) and at Spitsbergen (Svalbard archipelago, High Arctic). The populations live in an ecological niche, where water‐logged snow provides a cold and ephemeral ecosystem, possibly securing the survival of psychrophilic populations through the summer. A physiological adaptation to low temperatures was shown by photosynthesis measurements. The analysis of soluble carbohydrates showed the occurrence of glycerol and sugars, which may play a role in protection against intracellular freezing. Although both populations were made of unicells with Ochromonas‐alike morphology, investigation by molecular methods (18S rDNA sequencing) revealed unexpectedly a very close relationship to the mountain‐river dwelling Hydrurus foetidus (Villars) Trevisan. However, macroscopic thalli typical for the latter species were never found in snow, but are known from nearby localities, and harvested samples of snow algae exposed to dryness evolved a similar pervading, ‘fishy’ smell. Moreover, in both habitats tetrahedal zoospores with four elongate spikes were found, similar to what is known from Hydrurus. Our molecular results go along with earlier reports, where chrysophycean sequences of the same taxonomic affiliation were isolated from snow. This points to a distinct group of photoautotrophic, Hydrurus‐related chrysophytes, which are characteristic for long‐lasting, slowly melting snow packs in certain cold regions of the world.     

Bioconversion of Agave tequilana fructans by exo-inulinases from indigenous Aspergillus niger CH-A-2010 enhances ethanol production from raw Agave tequilana juice

Agave tequilana fructans are the source of fermentable sugars for the production of tequila. Fructans are processed by acid hydrolysis or by cooking in ovens at high temperature. Enzymatic hydrolysis is considered an alternative for the bioconversion of fructans. We previously described the isolation of Aspergillus niger CH-A-2010, an indigenous strain that produces extracellular inulinases. Here we evaluated the potential application of A. niger CH-A-2010 inulinases for the bioconversion of A. tequilana fructans, and its impact on the production of ethanol. Inulinases were analyzed by Western blotting and thin layer chromatography. Optimal pH and temperature conditions for inulinase activity were determined. The efficiency of A. niger CH-A-2010 inulinases was compared with commercial enzymes and with acid hydrolysis. The hydrolysates obtained were subsequently fermented by Saccharomyces cerevisiae to determine the efficiency of ethanol production. Results indicate that A. niger CH-A-2010 predominantly produces an exo-inulinase activity. Optimal inulinase activity occurred at pH 5.0 and 50 °C. Hydrolysis of raw agave juice by CH-A-2010 inulinases yielded 33.5 g/l reducing sugars, compared with 27.3 g/l by Fructozyme^® (Novozymes Corp, Bagsværd, Denmark) and 29.4 g/l by acid hydrolysis. After fermentation of hydrolysates, we observed that the conversion efficiency of sugars into ethanol was 97.5 % of the theoretical ethanol yield for enzymatically degraded agave juice, compared to 83.8 % for acid-hydrolyzed juice. These observations indicate that fructans from raw Agave tequilana juice can be efficiently hydrolyzed by using A. niger CH-A-2010 inulinases, and that this procedure impacts positively on the production of ethanol.     

Electron Microscopic,Genetic and Protein Expression Analyses of Helicobacter acinonychis Strains from a Bengal Tiger

Colonization by Helicobacter species is commonly noted in many mammals. These infections often remain unrecognized, but can cause severe health complications or more subtle host immune perturbations. The aim of this study was to isolate and characterize putative novel Helicobacter spp. from Bengal tigers in Thailand. Morphological investigation (Gram-staining and electron microscopy) and genetic studies (16SrRNA, 23SrRNA, flagellin, urease and prophage gene analyses, RAPD DNA fingerprinting and restriction fragment polymorphisms) as well as Western blotting were used to characterize the isolated Helicobacters. Electron microscopy revealed spiral-shaped bacteria, which varied in length (2.5–6 µm) and contained up to four monopolar sheathed flagella. The 16SrRNA, 23SrRNA, sequencing and protein expression analyses identified novel H. acinonychis isolates closely related to H. pylori. These Asian isolates are genetically very similar to H. acinonychis strains of other big cats (cheetahs, lions, lion-tiger hybrid and other tigers) from North America and Europe, which is remarkable in the context of the great genetic diversity among worldwide H. pylori strains. We also found by immunoblotting that the Bengal tiger isolates express UreaseA/B, flagellin, BabA adhesin, neutrophil-activating protein NapA, HtrA protease, γ-glutamyl-transpeptidase GGT, Slt lytic transglycosylase and two DNA transfer relaxase orthologs that were known from H. pylori, but not the cag pathogenicity island, nor CagA, VacA, SabA, DupA or OipA proteins. These results give fresh insights into H. acinonychis genetics and the expression of potential pathogenicity-associated factors and their possible pathophysiological relevance in related gastric infections.