The mycotoxin phomoxanthone A disturbs the form and function of the inner mitochondrial membrane.

Mitochondria are cellular organelles with crucial functions in the generation and distribution of ATP, the buffering of cytosolic Ca2+ and the initiation of apoptosis. Compounds that interfere with these functions are termed mitochondrial toxins, many of which are derived from microbes, such as antimycin A, oligomycin A, and ionomycin. Here, we identify the mycotoxin phomoxanthone A (PXA), derived from the endophytic fungus Phomopsis longicolla, as a mitochondrial toxin. We show that PXA elicits a strong release of Ca2+ from the mitochondria but not from the ER. In addition, PXA depolarises the mitochondria similarly to protonophoric uncouplers such as CCCP, yet unlike these, it does not increase but rather inhibits cellular respiration and electron transport chain activity. The respiration-dependent mitochondrial network structure rapidly collapses into fragments upon PXA treatment. Surprisingly, this fragmentation is independent from the canonical mitochondrial fission and fusion mediators DRP1 and OPA1, and exclusively affects the inner mitochondrial membrane, leading to cristae disruption, release of pro-apoptotic proteins, and apoptosis. Taken together, our results suggest that PXA is a mitochondrial toxin with a novel mode of action that might prove a useful tool for the study of mitochondrial ion homoeostasis and membrane dynamics

Investigating orphan cytochromes P450 from Mycobacterium tuberculosis : the search for potential drug targets

Tuberculosis (TB) is a disease that the World Health Organisation (WHO) regards as a global pandemic. There is a great need for new drugs to combat this threat. Drug resistant strains of the causative agent, Mycobacterium tuberculosis (Mtb), have increased the urgency of this quest for novel anti-mycobacterial medicines. Publication of the Mtb genome sequence revealed a large number of cytochrome P450 (CYP) enzymes [Cole, S. T. et al. 1998]. These mono-oxygenase enzymes have been studied for many years and are responsible for metabolic functions in every kingdom of life. Research on the Mtb P450s to date has highlighted several of them as having critcal roles within the organism. CYP121 and CYP128 have been implicated as essential through gene knockout studies. It has been demonstrated that CYP125 is not essential for viability. However, it is part of a gene cluster highly important for Mtb infectivity and virulence. Due to the prospective importance of P450s to Mtb, this group of enzymes is under investigation as a source of novel drug targets. CYP142 was discovered as a potential drug target after it was located to a gene cluster involved in cholesterol catabolism during Mtb dormancy. As part of this PhD project, it was demonstrated that CYP142 performs an almost identical role to that reported for CYP125. These enzymes both perform C27 hydroxylation and carboxylation of the cholesterol side chain. However, variations in the level of oxidation have been identified, dependent upon the redox system with which these P450s are associated. A crystal structure of CYP142 showing high similarity in active site architecture to CYP125 supports the physiological role of CYP142 in cholesterol catabolism. Combining this with in vitro data which demonstrates that CYP142 possesses high affinity for a range of azole anti-fungal agents [Ahmad, Z. et al. 2005, 2006] supports the suggestion that it is a candidate target for the next generation of anti-mycobacterial drugs. CYP144 was highlighted as being important during the latent phase of Mtb growth, a phase that is not targeted by any of the current antimycobacterials. Work performed as part of this PhD has shown that many characteristics of CYP144 are highly comparable to those reported for other MtbP450s. CYP144 shows high affinity and specificity towards many azole molecules. Econazole, clotrimazole and miconazole have repeatedly been shown to bind to MtbP450s, including CYP144 and CYP142, with high affinity and are excellent potential candidates as novel anti-mycobacterial agents. An N-terminally truncated form of CYP144, CYP144-T, has been investigated in the pursuit of a CYP144 crystal structure. It is hoped that this will enable the elucidation of a physiological role for CYP144. Both CYP142 and CYP144 have demonstrated biochemical and biophysical characteristics that contribute to our knowledge of P450 enzymes. This PhD has established that CYP142 exhibits an equilibrium between P450 and P420 species in its CO-bound, ferrous form. A conversion from P420, and stabilisation of P450, upon substrate binding was also demonstrated. CYP144 displays unusual azole coordination characteristics when examined by EPR and removal of the CYP144 gene from Mtb increased sensitivity of the strain to clotrimazole. Studies of these enzymes has advanced knowledge of P450 and Mtb redox chemistry, established roles for the MtbP450 cohort and identified the potential of anti-mycobacterial drugs and associated targets.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Der Einfluss unterschiedlicher Unterrichtsmodelle auf den Erwerb von mathematischen und kaufmännischen Kompetenzen im beruflichen Unterricht

Mit der Einführung des Lernfeldkonzepts ist die Verknüpfung von domänenspezifischen und domänenübergreifenden Kompetenzen im beruflichen Unterricht zum herrschenden Unterrichtsprinzip geworden. Diese Veränderung erfolgte, ohne dass es schon ausreichend elaborierte theoretische Erklärungsmodelle für ihre Zusammenhänge und daraus folgende didaktische Konzeptionen gab. Empirische Befunde bestätigen, dass gerade bei der Anwendung von mathematischen Kompetenzen im beruflichen Unterricht Probleme auftreten. Neben unzureichenden mathematischen Vorkenntnissen gelingt insbesondere eine Verknüpfung von mathematischen Inhalten mit komplexen kaufmännischen Handlungssituationen häufig nicht. [...] Es besteht deshalb Forschungsbedarf darüber, wie sich beruflicher Unterricht auf den Lernerfolg bei den mathematischen und kaufmännischen Kompetenzen auswirkt. Durch eine Untersuchung der Wirkungen von Unterricht können zum einen Zusammenhänge beim Aufbau der unterschiedlichen Kompetenzen näher bestimmt werden. Zum anderen lassen sich didaktische Schlussfolgerungen für die Gestaltung von Unterricht ziehen, um mathematische und kaufmännische Kompetenzen besser zu fördern. (DIPF/Orig.

Trends in Biodiversity Research — A Bibliometric Assessment

Research on biodiversity has grown considerably during the last decades. The present study applies bibliometric methods to evaluate efforts in this field of study. We retrieved roughly 69,000 bibliographic records from the Web of Science database that matched the word biodiversity (and derivatives) in keywords, title or abstract. Article contributions and number of involved authors and journals increased exceptionally fast since the 1980s, when the term biodiversity was coined. But since the year 2008, a decelerated growth rate leads to an average rate of knowledge generation. Using the frequency of terms extracted from publication titles, we inferred that the community-level focus has increased in biodiversity studies, while molecular biodiversity is still not strongly represented. Climate-related topics are rapidly gaining importance in biodiversity research. The geographical imbalance between allocation of research efforts and distribution of biological diversity is apparent

A modular architecture for a driving simulator based on the FDMU approach

The present paper describes the development of a modular and easily configurable simulation platform for ground vehicles. This platform should be usable for the implementation of driving simulators employed both in training purposes and in vehicle components testing. In particular, the paper presents a first architectural model for the implementation of a simulation platform based on the Functional Digital Mock-Up (FDMU) approach. This platform will allow engineers to implement different kinds of simulators that integrate both physical and virtual components, thus achieving the possibility to quickly reconfigure the architecture depending on the hardware and software used and on specific test case needs. The platform has been tested by developing a case study that integrates a motion platform, some I/O devices and a simple dynamic ground vehicle model implemented in OpenModelica

Interactive semantic enrichment of 3D cultural heritage collections

Virtual Surrogates of Cultural Heritage (CH) objects are seriously being considered in professional activities such as conservation and preservation, exhibition planning, packing, and scholarly research, among many other activities. Although this is a very positive development, a bare 3D digital representation is insufficient and poor for fulfilling the full range of professional activities. In this paper, we present the first interactive semantic enrichment tool for 3D CH collections that is fully based on the CIDOC-CRM schema and that fully supports its sophisticated annotation model. The tool eases the user interaction, allowing inexperienced users without previous knowledge on semantic models or 3D modeling to employ it and to conceive it for the professional workflow on 3D annotations. We illustrate the capabilities of our tool in the context of the Saalburg fort, during Roman times (2nd century AD), for the protection of the Limes on the Taunus hills in Germany

LIS3D: Low-Cost 6DOF Laser Interaction for Outdoor Mixed Reality

This paper introduces a new low-cost, laser-based 6DOF interaction technology for outdoor mixed reality applications. It can be used in a variety of outdoor mixed reality scenarios for making 3D annotations or correctly placing 3D virtual content anywhere in the real world. In addition, it can also be used with virtual back-projection displays for scene navigation purposes. Applications can range from design review in the architecture domain to cultural heritage experiences on location. Previous laser-based interaction techniques only yielded 2D or 3D intersection coordinates of the laser beam with a real world object. The main contribution of our solution is that we are able to reconstruct the full pose of an area targeted by our laser device in relation to the user. In practice, this means that our device can be used to navigate any scene in 6DOF. Moreover, we can place any virtual object or any 3D annotation anywhere in a scene, so it correctly matches the user's perspective

LIS3D: Low-Cost 6DOF Laser Interaction for Outdoor Mixed Reality

This paper introduces a new low-cost, laser-based 6DOF interaction technology for outdoor mixed reality applications. It can be used in a variety of outdoor mixed reality scenarios for making 3D annotations or correctly placing 3D virtual content anywhere in the real world. In addition, it can also be used with virtual back-projection displays for scene navigation purposes. Applications can range from design review in the architecture domain to cultural heritage experiences on location. Previous laser-based interaction techniques only yielded 2D or 3D intersection coordinates of the laser beam with a real world object. The main contribution of our solution is that we are able to reconstruct the full pose of an area targeted by our laser device in relation to the user. In practice, this means that our device can be used to navigate any scene in 6DOF. Moreover, we can place any virtual object or any 3D annotation anywhere in a scene, so it correctly matches the user's perspective

In vitro functional analyses of arrhythmogenic right ventricular cardiomyopathy-associated desmoglein-2-missense variations

Gaertner A, Klauke B, Stork I, Niehaus K, Niemann G. In vitro functional analyses of arrhythmogenic right ventricular cardiomyopathy-associated desmoglein-2-missense variations. PloS one. 2012;7(10): e47097.BACKGROUND: Although numerous sequence variants in desmoglein-2 (DSG2) have been associated with arrhythmogenic right ventricular cardiomyopathy (ARVC), the functional impact of new sequence variations is difficult to estimate. METHODOLOGY/PRINCIPAL FINDINGS: To test the functional consequences of DSG2-variants, we established an expression system for the extracellular domain and the full-length DSG2 using the human cell line HT1080. We established new tools to investigate ARVC-associated DSG2 variations and compared wild-type proteins and proteins with one of the five selected variations (DSG2-p.R46Q, -p.D154E, -p.D187G, -p.K294E, -p.V392I) with respect to prodomain cleavage, adhesion properties and cellular localisation. CONCLUSIONS/SIGNIFICANCE: The ARVC-associated DSG2-p.R46Q variation was predicted to be probably damaging by bioinformatics tools and to concern a conserved proprotein convertase cleavage site. In this study an impaired prodomain cleavage and an influence on the DSG2-properties could be demonstrated for the R46Q-variant leading to the classification of the variant as a potential gain-of-function mutant. In contrast, the variants DSG2-p.K294E and -p.V392I, which have an arguable impact on ARVC pathogenesis and are predicted to be benign, did not show functional differences to the wild-type protein in our study. Notably, the variants DSG2-p.D154E and -p.D187G, which were predicted to be damaging by bioinformatics tools, had no detectable effects on the DSG2 protein properties in our study