Detecting Stress at the Whole-Ecosystem Level: The Case of a Mountain Lake (Lake Santo, Italy)

Detecting the early signs of stress is imperative for the conservation of natural ecosystems. They may, however, go unrecognized because ecosystems, when disturbed, may act as sinks that absorb the external impact without showing any evident changes. This seems to be the case for Lake Santo, a small water body located in a mountainous area of northern Italy. Tourism activity in this area began to develop in the early 1970s and grew continuously over the following 20 years. This activity caused a continually increasing nutrient load into the waters, but surprisingly the lake has remained oligo-mesotrophic, as it was before human pressure became a stressor to the lake. To anticipate possible severe damage to the ecosystem, we searched for early signs of stress by carrying out a retrospective analysis based on a whole-ecosystem approach using trophic flow networks. Ecosystem properties of the lake as calculated from network analysis for the disturbed (year 1991) and unimpacted (year 1973) configurations were compared, with the support of sensitivity analysis and statistical tests. We found evidence that in the period 1970–90 nutrient enrichment did change the course of normal development as the observed increase in system throughput was accompanied by a drop in the level of mutual organization of flows, which instead would be expected to increase during the natural progression of the ecosystem. The scenario that emerged from the comparison of system-level indices, cycling activity, trophic structure, and trophic efficiency indicates that the ecosystem has been subjected to stress. In particular, the type of disturbance corresponds to a quantitative definition of eutrophication.     

Sourdough bread made from wheat and nontoxic flours and started with selected lactobacilli is tolerated in celiac sprue patients

This work was aimed at producing a sourdough bread that is tolerated by celiac sprue (CS) patients. Selected sourdough lactobacilli had specialized peptidases capable of hydrolyzing Pro-rich peptides, including the 33-mer peptide, the most potent inducer of gut-derived human T-cell lines in CS patients. This epitope, the most important in CS, was hydrolyzed completely after treatment with cells and their cytoplasmic extracts (CE). A sourdough made from a mixture of wheat (30%) and nontoxic oat, millet, and buckwheat flours was started with lactobacilli. After 24 h of fermentation, wheat gliadins and low-molecular-mass, alcohol-soluble polypeptides were hydrolyzed almost totally. Proteins were extracted from sourdough and used to produce a peptic-tryptic digest for in vitro agglutination tests on K 562(S) subclone cells of human origin. The minimal agglutinating activity was ca. 250 times higher than that of doughs chemically acidified or started with baker's yeast. Two types of bread, containing ca. 2 g of gluten, were produced with baker's yeast or lactobacilli and CE and used for an in vivo double-blind acute challenge of CS patients. Thirteen of the 17 patients showed a marked alteration of intestinal permeability after ingestion of baker's yeast bread. When fed the sourdough bread, the same 13 patients had values for excreted rhamnose and lactulose that did not differ significantly from the baseline values. The other 4 of the 17 CS patients did not respond to gluten after ingesting the baker's yeast or sourdough bread. These results showed that a bread biotechnology that uses selected lactobacilli, nontoxic flours, and a long fermentation time is a novel tool for decreasing the level of gluten intolerance in humans.     

A nucleophilic catalysis step is involved in the hydrolysis of aryl phosphate monoesters by human CT acylphosphatase

Acylphosphatase, one of the smallest enzymes, is expressed in all organisms. It displays hydrolytic activity on acyl phosphates, nucleoside di- and triphosphates, aryl phosphate monoesters, and polynucleotides, with acyl phosphates being the most specific substrates in vitro. The mechanism of catalysis for human acylphosphatase (the organ-common type isoenzyme) was investigated using both aryl phosphate monoesters and acyl phosphates as substrates. The enzyme is able to catalyze phosphotransfer from p-nitrophenyl phosphate to glycerol (but not from benzoyl phosphate to glycerol), as well as the inorganic phosphate-H(2)18O oxygen exchange reaction in the absence of carboxylic acids or phenols. In short, our findings point to two different catalytic pathways for aryl phosphate monoesters and acyl phosphates. In particular, in the aryl phosphate monoester hydrolysis pathway, an enzyme-phosphate covalent intermediate is formed, whereas the hydrolysis of acyl phosphates seems a more simple process in which the Michaelis complex is attacked directly by a water molecule generating the reaction products. The formation of an enzyme-phosphate covalent complex is consistent with the experiments of isotope exchange and transphosphorylation from substrates to glycerol, as well as with the measurements of the Br?nsted free energy relationships using a panel of aryl phosphates with different structures. His-25 involvement in the formation of the enzyme-phosphate covalent complex during the hydrolysis of aryl phosphate monoesters finds significant confirmation in experiments performed with the H25Q mutated enzyme.     

Sequence-dependent DNA curvature and flexibility from scanning force microscopy images

This paper reports a study of the sequence-dependent DNA curvature and flexibility based on scanning force microscopy (SFM) images. We used a palindromic dimer of a 1878-bp pBR322 fragment and collected a large pool of SFM images. The curvature of each imaged chain was measured in modulus and direction. It was found that the ensemble curvature modulus does not allow the separation of static and dynamic contributions to the curvature, whereas the curvature, when its direction in the two dimensions is taken into account, permits the direct separation of the intrinsic curvature contributions static and dynamic contributions. The palindromic symmetry also acted as an internal gauge of the validity of the SFM images statistical analysis. DNA static curvature resulted in good agreement with the predicted sequence-dependent intrinsic curvature. Furthermore, DNA sequence-dependent flexibility was found to correlate with the occurrence of A.T-rich dinucleotide steps along the chain and, in general, with the normalized basepair stacking energy distribution.     

Fungal parasitism in freshwater calanoid population: ecological consequences and possible mechanisms involved in the infection process

This paper reports the results of a study on a zoosporic fungus (Saprolegniaceae) parasitizing populations of Eudiaptomus intermedius (Copepoda, Calanoida) in mountain lakes located in the Northern Apennines, Italy. The dynamics of this infectious process was previously described in one of the lakes of the study area. The virulence is particularly high at the end of the calanoid reproductive phase, when the fungal hyphae penetrate the host eggs provoking their degeneration. Here new data are presented and the phenology of the host–parasite interaction is comparatively analyzed in different years and in different sites. The occurrence of the parasite was assessed at a regional scale. Possible mechanisms involved in the pathogen dispersal and in the host recognition are proposed, and the ecological impact of the fungal parasitism on the calanoid populations is discussed.     

Recent ostracods (Crustacea,Ostracoda) found in lowland springs of the provinces of Piacenza and Parma (Northern Italy)

The “fontanili” are artificial aquatic ecosystems, typical of the lowland plains of Northern Italy, exploiting natural resurgences of deep groundwater. These habitats are characterized by low variation in hydrologic, hydrochemical and thermal conditions throughout the year. Proper management is required to prevent the spring clogging by biomass accumulation. In spite of their importance as refugia for endangered species, many springs were completely abandoned in the last years and several of them will disappear. We report the results of a study carried out in 2001 on 31 springs of the provinces of Piacenza and Parma, distributed in seven areas defined on hydrological and geological considerations. Physical and chemical variables and parameters of waters were measured and ostracod samples were collected. Most of the springs showed high nitrate concentration, due to a diffuse pollution of agricultural origin. Twelve ostracod species in four families were identified. Ostracod valves were analysed by scanning electron microscopy. Cypria ophtalmica was found in all the springs; other relatively common species were Cyclocypris laevis,Notodromas persica, and Prionocypris zenkeri.The maximum number of species per site was four. Cypridopsis vidua,P. zenkeri, and N. persicashowed a very localized distribution in the study area. The ostracod fauna of the “fontanili” was compared to other species assemblages found in spring habitats and to the available information on recent freshwater ostracods reported for Italy.     

Aeromonas Hydrophila and its Relation with Drinking Water Indicators of Microbiological Quality in Argentine

In Argentine, water municipal supplies disinfection is carried out by chlorine. We have isolated Aeromonas hydrophilafrom a chlorinated water supply in Buenos Aires that fulfilled Argentinean microbiological quality standards. It is an aquatic organism that could produce cytotoxins and enterotoxins associated with acute gastroenteritis and wound infections in human and hemorrhagic septicaemia of fish, reptiles and amphibians. The isolated strain produced protein bands at isoelectric point in the range of 4.6–5.3 lightly labile at 56°C and heat labile at 100°C non cholera antitoxin reactive in electrofocusing assay (IEF) and showed hemolytic activity thermolabile at 56°C and 100°C in 5% rabbit erythrocytes in phosphate buffered saline. A cytotoxic effect thermolabile at 56°C and 100°C and a cytotonic activity were demonstrated in Vero cell cultures. Survival assay of A. hydrophilaand indicator organisms would show no correlation between their contamination sources. Biofilms production could explain the persistence of this gram negative pathogen organism in chlorinated tap water. A water system supply maintenance program and pasteurisation may be performed in spite of water chlorination.     

Tetracycline affects abnormal properties of synthetic PrP peptides and PrP(Sc) in vitro

Prion diseases are characterized by the accumulation of altered forms of the prion protein (termed PrP(Sc)) in the brain. Unlike the normal protein, PrP(Sc) isoforms have a high content of beta-sheet secondary structure, are protease-resistant, and form insoluble aggregates and amyloid fibrils. Evidence indicates that they are responsible for neuropathological changes (i.e. nerve cell degeneration and glial cell activation) and transmissibility of the disease process. Here, we show that the antibiotic tetracycline: (i) binds to amyloid fibrils generated by synthetic peptides corresponding to residues 106-126 and 82-146 of human PrP; (ii) hinders assembly of these peptides into amyloid fibrils; (iii) reverts the protease resistance of PrP peptide aggregates and PrP(Sc) extracted from brain tissue of patients with Creutzfeldt-Jakob disease; (iv) prevents neuronal death and astrocyte proliferation induced by PrP peptides in vitro. NMR spectroscopy revealed several through-space interactions between aromatic protons of tetracycline and side-chain protons of Ala(117-119), Val(121-122) and Leu(125) of PrP 106-126. These properties make tetracycline a prototype of compounds with the potential of inactivating the pathogenic forms of PrP.     

Prophylaxis and treatment of bacterial infections: do we need new strategies?

Bacterial infections in patients with hematologic malignancies still represent a severe and life-treating problem. Several observational studies during the last decade have revealed that neutropenic patients with fever are a heterogeneous population with various differences regarding response to initial therapy, development of serious complications and mortality. The role of neutropenia as main risk factor for infections in hematologic patients and the definition of different level of risk related to neutrophils count and duration of neutropenia have been extensively studied and different categories of patients based on the risk of infection, mostly the condition of neutropenia, have been clearly defined. The strategies on antimicrobial therapy and supportive care in hematologic patients need to be continuously assessed, in fact new conditions favouring the occurrence of infectious complications in patients with hematologic malignancies have progressively emerged. The use of oral prophylactic antibiotics in neutropenic cancer patients is still a matter of debate. Before 2005, several trials showed how the prevention of infection can be extremely important in this setting of patients but none was conclusive. In 2005 two meta-analysis and two large randomized clinical trials gave new evidence that antibacterial prophylaxis can reduce in neutropenic patients several important outcomes including mortality. The use of the empiric antibacterial therapy represents the cornerstone of the antimicrobial strategies in the febrile neutropenic patients leading, over the span of 20 years, to a dramatic decrease of deaths: Actually beta-lactam monotherapy is commonly used for the empiric treatment of febrile neutropenia. Recently, large randomized clinical trials and meta-analysis showed that the addition of an aminoglycoside and/or a glycopeptides results in a more favourable outcome only in selected severe infections. The use of antibiotics should be prudent and safe also in neutropenic hematologic patients to prevent emergence of microbial resistance, to save costs, to reduce toxicity. For this reasons, according to the evidence, antibacterial prophylaxis should be restricted to high risk hematologic patients and empiric parenteral antibiotic monotherapy should be recommended in case of febrile neutropenia limiting the use of amynoglicosides and glycopeptides. In the next future, a major effort should be made to state in hematologic patients new risk factors which could more accurately define subgroups for targeted anti-infective strategies.