Differences between drosophila melanogaster and its sibling species D. simulans in sensitivity to acridine orange treatment

Larvae and adults of D. melanogaster and D. simulans were fed with acridine orange, in order to test sensitivity differences between the species. Our results show that, of the two species, D. simulans is more resistant in the larval stages, and D. melanogaster is more resistant in the adult stage. Furthermore, adult males of both species are more sensitive than adult females.     

Towards a science of the individual: the Aristotelian search for scientific knowledge of individual entities

This article seeks to take a step towards recognizing that science can deal with the concrete and individual as well as the universal. I shall concentrate on some of Aristotle’s texts, as there is a long tradition going back to Aristotle, according to which science deals only with the universal, although his work also contains texts of a very different tenor. He tries to improve the process of definition as an attempt to bring science closer to the concrete, but ends up realizing that there are some unreachable limits. There is, however, a second Aristotelian approach to the problem in Metaphysica M 10, a passage which takes scientific rapprochement to the individual further by introducing a distinction between science in potential and science in act. The former is universal, but the latter deals with individual substances and processes. Aristotle himself acknowledges here that in one sense science is universal and in another it is not, a position that raises important ontological and epistemological problems. Some suggestions are also offered concerning the kind of truth applicable to science in act, that is, practical truth.     

DNA repair is limiting for haematopoietic stem cells during ageing

Accumulation of DNA damage leading to adult stem cell exhaustion has been proposed to be a principal mechanism of ageing. Here we address this question by taking advantage of the highly specific role of DNA ligase IV in the repair of DNA double-strand breaks by non-homologous end-joining, and by the discovery of a unique mouse strain with a hypomorphic Lig4(Y288C) mutation. The Lig4(Y288C) mouse, identified by means of a mutagenesis screening programme, is a mouse model for human LIG4 syndrome, showing immunodeficiency and growth retardation. Diminished DNA double-strand break repair in the Lig4(Y288C) strain causes a progressive loss of haematopoietic stem cells and bone marrow cellularity during ageing, and severely impairs stem cell function in tissue culture and transplantation. The sensitivity of haematopoietic stem cells to non-homologous end-joining deficiency is therefore a key determinant of their ability to maintain themselves against physiological stress over time and to withstand culture and transplantation.     

Comparing peripheral glial cell differentiation in <Emphasis Type="Italic">Drosophila</Emphasis> and vertebrates

In all complex organisms, the peripheral nerves ensure the portage of information from the periphery to central computing and back again. Axons are in part amazingly long and are accompanied by several different glial cell types. These peripheral glial cells ensure electrical conductance, most likely nuture the long axon, and establish and maintain a barrier towards extracellular body fluids. Recent work has revealed a surprisingly similar organization of peripheral nerves of vertebrates and Drosophila. Thus, the genetic dissection of glial differentiation in Drosophila may also advance our understanding of basic principles underlying the development of peripheral nerves in vertebrates.     

Bootstrap Replacement to Validate the Influence of the Economic Cycle on the Structure and the Accuracy Level of Business Failure Prediction Models

The aim of this study was to answer the question of how the economic cycle affects the stability and efficiency of business failure prediction models, using bootstrap replacement method for validation. We analyse 2228 Spanish small and medium‐sized enterprises for the period 2001–2009, and divide it into three different phases of the economic cycle (growth, crisis, recession). We find that the structure and the ability of business failure prediction models are different according to the economic cycle. These findings are relevant for the debate on the most suitable financial ratios when developing business failure prediction models and to pose their accuracy level in these prediction models. Copyright © 2015 John Wiley & Sons, Ltd.     

The social wasps (Hymenoptera: Vespidae: Polistinae) of a fragment of Atlantic Forest in southern Bahia,Brazil

The Atlantic Forest is one of the most threatened ecosystems in Brazil, with only 22% of its original coverage remaining. Despite around 900 species of Polistinae being described worldwide and their being widely distributed in the Neotropical region, they are still poorly known in northeastern Brazil, especially in Atlantic Forest. The aim of this work was a survey of social wasps in three fragments of Atlantic Forest with differences in the level of regeneration and in the physiognomy, performed at Michelin Ecological Reserve (located in Igrapiúna, southern Bahia State, Brazil) and employing three methodologies – attractive solution, Malaise trap and light trap ‘Luiz de Queiroz’ – for 12 months in transects. A total of 1066 specimens, belonging to 29 species from nine genera, were collected in the reserve. Epiponini was the richest tribe (23 species) followed by Mischocyttarini (five species) and Polistini (one species). The Malaise trap was not efficient during the night, having a deficit of 5110 hours; the only nocturnal genus, Apoica, was collected with a light trap – an attractive solution that was more efficient. Once it was left for 12 discontinuous days (72 hours), showing that more than one methodology is desirable for wasp surveys. Latitudinal analysis comparing the study area with other areas grouped the Michelin Ecological Reserve with areas in southeastern Brazil, which may be related to a lack of standardization in collecting methods. This study presented the highest richness in this region.     

Self-organized patchiness in asthma as a prelude to catastrophic shifts

Asthma is a common disease affecting an increasing number of children throughout the world. In asthma, pulmonary airways narrow in response to contraction of surrounding smooth muscle. The precise nature of functional changes during an acute asthma attack is unclear. The tree structure of the pulmonary airways has been linked to complex behaviour in sudden airway narrowing and avalanche-like reopening. Here we present experimental evidence that bronchoconstriction leads to patchiness in lung ventilation, as well as a computational model that provides interpretation of the experimental data. Using positron emission tomography, we observe that bronchoconstricted asthmatics develop regions of poorly ventilated lung. Using the computational model we show that, even for uniform smooth muscle activation of a symmetric bronchial tree, the presence of minimal heterogeneity breaks the symmetry and leads to large clusters of poorly ventilated lung units. These clusters are generated by interaction of short- and long-range feedback mechanisms, which lead to catastrophic shifts similar to those linked to self-organized patchiness in nature. This work might have implications for the treatment of asthma, and might provide a model for studying diseases of other distributed organs.