Effects of Triton X-100 and Quillaya Saponin on the ex situ bioremediation of a chronically polychlorobiphenyl-contaminated soil

The possibility of enhancing the ex situ bioremediation of a chronically polychlorinated biphenyl (PCB)-contaminated soil by using Triton X-100 or Quillaya Saponin, a synthetic and a biogenic surfactant, respectively, was studied. The soil, which contained about 350 mg/kg of PCBs and indigenous aerobic bacteria capable of growing on biphenyl or on monochlorobenzoic acids, was amended with inorganic nutrients and biphenyl, saturated with water and treated in aerobic batch slurry- and fixed-phase reactors. Triton X-100 and Quillaya Saponin were added to the reactors at a final concentration of 10 g/l at the 42nd day of treatment, and at the 43rd and 100th day, respectively. Triton X-100 was not metabolised by the soil microflora and it exerted inhibitory effects on the indigenous bacteria. Quillaya Saponin, on the contrary, was readily metabolised by the soil microflora. Under slurry-phase conditions, Triton X-100 negatively influenced the soil bioremediation process by affecting the availability of the chlorobenzoic acid degrading indigenous bacteria, whereas Quillaya Saponin slightly enhanced the biological degradation and dechlorination of the soil PCBs. In the fixed-phase reactors, where both the surfactant availability and the mixing of the soil were lower, Triton X-100 did not exert inhibitory effects on the soil biomass and enhanced significantly the soil PCB depletion, whereas Quillaya Saponin did not influence the bioremediation process. Received: 28 April 1998 / Received last revision: 15 July 1998 / Accepted: 29 July 1998     

Estimated comparative integration hotspots identify different behaviors of retroviral gene transfer vectors

Integration of retroviral vectors in the human genome follows non random patterns that favor insertional deregulation of gene expression and may cause risks of insertional mutagenesis when used in clinical gene therapy. Understanding how viral vectors integrate into the human genome is a key issue in predicting these risks. We provide a new statistical method to compare retroviral integration patterns. We identified the positions where vectors derived from the Human Immunodeficiency Virus (HIV) and the Moloney Murine Leukemia Virus (MLV) show different integration behaviors in human hematopoietic progenitor cells. Non-parametric density estimation was used to identify candidate comparative hotspots, which were then tested and ranked. We found 100 significative comparative hotspots, distributed throughout the chromosomes. HIV hotspots were wider and contained more genes than MLV ones. A Gene Ontology analysis of HIV targets showed enrichment of genes involved in antigen processing and presentation, reflecting the high HIV integration frequency observed at the MHC locus on chromosome 6. Four histone modifications/variants had a different mean density in comparative hotspots (H2AZ, H3K4me1, H3K4me3, H3K9me1), while gene expression within the comparative hotspots did not differ from background. These findings suggest the existence of epigenetic or nuclear three-dimensional topology contexts guiding retroviral integration to specific chromosome areas.     

Mapping of Alternaria and Pleospora concentrations in Central Italy using meteorological forecast and neural network estimator

Airborne particles (pollens and fungal spores) are recognized as important causes of allergies and many other pathologies whose main symptoms are usually associated with respiratory problems. In addition, these particles seem to be responsible for clinical symptoms of oculorhinitis and bronchial asthma. Many authors showed how pollen and spore concentrations are critically linked to meteorological conditions, while other studies investigated the possibility to estimate these concentrations through meteorological parameters. So, many different approaches have been proposed, and one of the most sophisticated is based on the use of a complex artificial neural network architecture. Once the neural device is calibrated using simultaneous time series of observed meteorological parameters and airborne biological particles, it is straightforward to use the Neural Network to predict spore concentrations using operational Limited Area Meteorological Model. In a previous work, it has been shown that the MM5 meteorological model developed by National Center for Atmospheric Research and Pennsylvania State University can be coupled with the above-cited neural predictor to provide a good prediction of Alternaria and Pleospora spore in the location of L’Aquila (Central Italy). Following the same approach, this work aims to provide the mapping of spore concentration over a wide area covered by high-resolution meteorological prediction in Central Italy. The complex patterns of fungal spore concentrations in selected areas will be described, and the high temporal variability of such fields will be discussed as well. The possibility to infer useful information from the predicted pattern of spore concentrations is discussed, as an example it appears that for people suffering from allergy to fungal spores is more comfortable to spend summertime close to the east coast of Italian Peninsula respect to the west coast. A further step of this work may easily lead to an operational use of the model for supporting the clinical management of allergies and for establishing a preventive strategy in agriculture to avoid unsafe and useless pollution of atmosphere, crops and fields.     

A wavelet-based ECG delineation algorithm for 32-bit integer online processing

Background  

Since the first well-known electrocardiogram (ECG) delineator based on Wavelet Transform (WT) presented by Li et al. in 1995, a significant research effort has been devoted to the exploitation of this promising method. Its ability to reliably delineate the major waveform components (mono- or bi-phasic P wave, QRS, and mono- or bi-phasic T wave) would make it a suitable candidate for efficient online processing of ambulatory ECG signals. Unfortunately, previous implementations of this method adopt non-linear operators such as root mean square (RMS) or floating point algebra, which are computationally demanding.     

Substrate recognition drives the evolution of serine proteases

A method is introduced to identify amino acid residues that dictate the functional diversity acquired during evolution in a protein family. Using over 80 enzymes of the chymotrypsin family, we demonstrate that the general organization of the phylogenetic tree and its functional branch points are fully accounted for by a limited number of residues that cluster around the active site of the protein and define the contact region with the P1-P4 residues of substrate.     

Fibrin as a scaffold for cardiac tissue engineering

Fibrin is a natural biopolymer with many interesting properties, such as biocompatibility, bioresorbability, ease of processing, ability to be tailored to modify the conditions of polymerization, and potential for incorporation of both cells and cell mediators. Moreover, the fibrin network has a nanometric fibrous structure, mimicking extracellular matrix, and it can also be used in autologous applications. Therefore, fibrin has found many applications in tissue engineering, combined with cells, growth factors, or drugs. Because a major limitation of cardiac cell therapy is low cell engraftment, the use of biodegradable scaffolds for specific homing and in situ cell retention is desirable. Thus, fibrin-based injectable cardiac tissue engineering may enhance cell therapy efficacy. Fibrin-based biomaterials can also be used for engineering heart valves or cardiac patches. The aim of this review is to show cardiac bioengineering uses of fibrin, both as a cell delivery vehicle and as an implantable biomaterial.     

Structural dynamics of the mitochondrial ADP/ATP carrier revealed by molecular dynamics simulation studies

The mitochondrial adenosine diphosphate/adenosine triphosphate (ADP/ATP) carrier has been recently crystallized in complex with its specific inhibitor carboxyatractyloside (CATR). In the crystal structure, the six-transmembrane helix bundle that defines the nucleotide translocation pathway is closed on the matrix side due to sharp kinks in the odd-numbered helices. The closed conformation is further sealed by the loops protruding into the matrix that interact through an intricate network of charge-pairs. To gain insight into its structural dynamics we performed molecular dynamics (MD) simulation studies of the ADP/ATP carrier with and without its cocrystallized inhibitor. The two trajectories sampled a conformational space around two different configurations characterized by distinct salt-bridge networks with a significant shift from inter- to intrarepeat bonding on the matrix side in the absence of CATR. Analysis of the geometrical parameters defining the transmembrane helices showed that even-numbered helices can undergo a face rotation, whereas odd-numbered helices can undergo a change in the wobble angle with a conserved proline acting as molecular hinge. Our results provide new information on the dynamical properties of the ADP/ATP carrier and for the first time yield a detailed picture of a stable carrier conformation in absence of the inhibitor.