University of Ljubljana

About: University of Ljubljana is a education organization based out in Ljubljana, Slovenia. It is known for research contribution in the topics: Population & Liquid crystal. The organization has 17210 authors who have published 47013 publications receiving 1082684 citations. The organization is also known as: Univerza v Ljubljani.

Electric properties of tissues

Abstract: 1. INTRODUCTIONThe electrical properties of biological tissues and cell sus-pensions have been of interest for over a century for manyreasons. They determine the pathways of current flowthrough the body and, thus, are very important in theanalysis of a wide range of biomedical applications such asfunctional electrical stimulation and the diagnosis andtreatment of various physiological conditions with weakelectric currents, radio-frequency hyperthermia, electro-cardiography, and body composition. On a more funda-mental level, knowledge of these electrical properties canlead to an understanding of the underlying basic biologicalprocesses. Indeed, biological impedance studies have longbeen important in electrophysiology and biophysics; one ofthe first demonstrations of the existence of the cell mem-brane was based on dielectric studies on cell suspensions(1).To analyze the response of a tissue to electric stimula-tion, we need data on the specific conductivities and rel-ative permittivities of the tissues or organs. A microscopicdescription of the response is complicated by the variety ofcell shapes and their distribution inside the tissue as wellas the different properties of the extracellular media.Therefore, a macroscopic approach is most often used tocharacterize field distributions in biological systems.Moreover, even on a macroscopic level, the electrical prop-erties are complicated. They can depend on the tissue ori-entation relative to the applied field (directionalanisotropy), the frequency of the applied field (the tissueis neither a perfect dielectric nor a perfect conductor), orthey can be time- and space-dependent (e.g., changes intissue conductivity during electropermeabilization).2. BIOLOGICAL MATERIALS IN AN ELECTRIC FIELDThe electrical properties of any material, including bio-logical tissue, can be broadly separated into two catego-ries: conducting and insulating. In a conductor, theelectric charges move freely in response to the applicationof an electric field, whereas in an insulator (dielectric), thecharges are fixed and not free to move. A more detaileddiscussion of the fundamental processes underlying theelectrical properties of tissue can be found in Foster andSchwan (2).If a conductor is placed in an electric field, charges willmove within the conductor until the interior field is zero.In the case of an insulator, no free charges exist, so netmigration of charge does not occur. In polar materials,however, the positive and negative charge centers in themolecules do not coincide. An electric dipole moment, p,issaid to exist. An applied field, E

A novel toxinotyping scheme and correlation of toxinotypes with serogroups of Clostridium difficile isolates.

Abstract: Two hundred nineteen Clostridium difficile isolates from 22 serogroups were screened for changes in the genes coding for toxin B (tcdB) and toxin A (tcdA). Parts of the toxin genes were amplified, and the PCR fragments were checked for length polymorphisms and cut with several restriction enzymes to monitor restriction fragment length polymorphisms (RFLPs). For 47 strains (21%), differences in the toxin genes were found compared to the toxin genes of reference strain VPI 10,463. Polymorphisms were usually observed in both toxin genes. RFLPs were more commonly found in the tcdB gene, in which a single restriction enzyme could give up to five different patterns. Restriction sites seemed to be less heterogeneous in the tcdA gene, in which for most enzymes only two different RFLPs were recognized. However, deletions were observed in tcdA, and four new types of shortened tcdA genes are described. According to the changes in their toxin genes, variant strains could be divided into 10 groups (toxinotypes I to X). A toxinotype was characterized by similar patterns of changes in the toxin genes and in other regions of the pathogenicity locus and also similar pulsed-field gel electrophoresis patterns. Variant toxinotypes were found in 9 of the 22 serogroups studied, and some toxinotypes were clearly associated with specific serogroups. Toxinotype VIII is characteristic for all strains of serogroup F. Other serogroups in which variant toxinotypes were commonly found are A1, A15, E, and X. Testing of variability in C. difficile toxin genes not only might be useful as a molecular typing system but also could have implications in diagnostics and pathogenesis.

Comparative genomics reveals high biological diversity and specific adaptations in the industrially and medically important fungal genus Aspergillus

Abstract: Background: The fungal genus Aspergillus is of critical importance to humankind. Species include those with industrial applications, important pathogens of humans, animals and crops, a source of potent carcinogenic contaminants of food, and an important genetic model. The genome sequences of eight aspergilli have already been explored to investigate aspects of fungal biology, raising questions about evolution and specialization within this genus. Results: We have generated genome sequences for ten novel, highly diverse Aspergillus species and compared these in detail to sister and more distant genera. Comparative studies of key aspects of fungal biology, including primary and secondary metabolism, stress response, biomass degradation, and signal transduction, revealed both conservation and diversity among the species. Observed genomic differences were validated with experimental studies. This revealed several highlights, such as the potential for sex in asexual species, organic acid production genes being a key feature of black aspergilli, alternative approaches for degrading plant biomass, and indications for the genetic basis of stress response. A genome-wide phylogenetic analysis demonstrated in detail the relationship of the newly genome sequenced species with other aspergilli. Conclusions: Many aspects of biological differences between fungal species cannot be explained by current knowledge obtained from genome sequences. The comparative genomics and experimental study, presented here, allows for the first time a genus-wide view of the biological diversity of the aspergilli and in many, but not all, cases linked genome differences to phenotype. Insights gained could be exploited for biotechnological and medical applications of fungi.

Eigenvector 1: An Optimal Correlation Space for Active Galactic Nuclei.

Abstract: We identify a correlation space involving optical and UV emission-line parameters as well as the soft X-ray spectral index that provides optimal discrimination between all principal classes of active galactic nuclei (AGNs). Most of the sources in our three high-quality data samples show a strong intercorrelation with narrow-line Seyfert 1 (NLSy1) galaxies and steep-spectrum radio galaxies occupying opposite extrema in the space. NLSy1 sources show a clear continuity with broader line sources, indicating that they are not a disjoint class of AGN as is sometimes suggested. We interpret the principal intercorrelation in the parameter space as being driven by the AGN luminosity-to-black hole mass ratio (L/M is proportional to the Eddington ratio). Source orientation no doubt also plays an important role, but it is not yet clear whether FWHM Hβ or C IV λ1549 line shift is the better indicator. We tentatively identify two radio-quiet populations: an almost pure radio-quiet population A, with FWHM ≤ 4000, and population B, which occupies the same parameter domain as the flat-spectrum radio-loud sources. A possible interpretation sees population A/NLSy1 as lower mass/high accretion rate sources and population B/radio-loud sources as the opposite.

International Guidelines for Management of Metastatic Breast Cancer: Can Metastatic Breast Cancer Be Cured?

Abstract: A distinctive subset of metastatic breast cancer (MBC) is oligometastatic disease, which is characterized by single or few detectable metastatic lesions. The existing treatment guidelines for patients with localized MBC include surgery, radiotherapy, and regional chemotherapy. The European School of Oncology-Metastatic Breast Cancer Task Force addressed the management of these patients in its first consensus recommendations published in 2007. The Task Force endorsed the possibility of a more aggressive and multidisciplinary approach for patients with oligometastatic disease, stressing also the need for clinical trials in this patient population. At the sixth European Breast Cancer Conference, held in Berlin in March 2008, the second public session on MBC guidelines addressed the controversial issue of whether MBC can be cured. In this commentary, we summarize the discussion and related recommendations regarding the available therapeutic options that are possibly associated with cure in these patients. In particular, data on local (surgery and radiotherapy) and chemotherapy options are discussed. Large retrospective series show an association between surgical removal of the primary tumor or of lung metastases and improved long-term outcome in patients with oligometastatic disease. In the absence of data from prospective randomized studies, removal of the primary tumor or isolated metastatic lesions may be an attractive therapeutic strategy in this subset of patients, offering rapid disease control and potential for survival benefit. Some improvement in outcome may also be achieved with optimization of systemic therapies, possibly in combination with optimal local treatment.