Electrophysiological and morphological characterization of dentate astrocytes in the hippocampus

We studied electrophysiological and morphological properties of astrocytes in the dentate gyrus of the rat hippocampus in slices. Intracellular application of Lucifer yellow revealed two types of morphology: one with a long process extruding from the cell body, and the other with numerous short processes surrounding the cell body. Their electrophysiological properties were either passive, that is, no detectable voltage-dependent conductance, or complex, with Na+/K+ currents similar to those reported in the Ammon's horn astrocytes. We did not find any morphological correlate to the types of electrophysiological profile or dye coupling. Chelation of cytoplasmic calcium ([Ca2+]i) by BAPTA increased the incidence of detecting a low Na+) conductance and transient outward K+ currents. However, an inwardly rectifying K+ current (Kir), a hallmark of differentiated CA1/3 astrocytes, was not a representative K+-current in the complex dentate astrocytes, suggesting that these astrocytes could retain an immature form of K-currents. Dentate astrocytes may possess a distinct current profile that is different from those in CA1/3 Ammon's horn.     

Nested core collections maximizing genetic diversity in Arabidopsis thaliana

The successful exploitation of natural genetic diversity requires a basic knowledge of the extent of the variation present in a species. To study natural variation in Arabidopsis thaliana, we defined nested core collections maximizing the diversity present among a worldwide set of 265 accessions. The core collections were generated based on DNA sequence data from a limited number of fragments evenly distributed in the genome and were shown to successfully capture the molecular diversity in other loci as well as the morphological diversity. The core collections are available to the scientific community and thus provide an important resource for the study of genetic variation and its functional consequences in Arabidopsis. Moreover, this strategy can be used in other species to provide a rational framework for undertaking diversity surveys, including single nucleotide polymorphism (SNP) discovery and phenotyping, allowing the utilization of genetic variation for the study of complex traits.     

Student test scores are improved in a virtual learning environment

This study evaluates the effectiveness of delivering the core curriculum of an introductory neuroscience course using a software application referred to as a virtual learning interface (VLI). The performance of students in a virtual learning environment (VLE) is compared with that of students in a conventional lecture hall in which the same lecturer presented the same material. This study was not designed to determine whether grades are improved by augmenting a lecture with other information. The VLI takes advantage of audio, video, animation, and text in a multimedia computer environment. Our results indicate that raw average scores on weekly examinations were 14 percentage points higher for students in the VLE compared with those for students in a conventional lecture hall setting. Moreover, normalized test scores were over 5 points higher for students in the VLE. This analysis suggest that a core curriculum can be effectively presented to students using the VLE, thereby making it possible for faculty to spend less class time relaying facts and more time engaging students in discussion of scientific theory.     

Cyclophilin D Deficiency Rescues Axonal Mitochondrial Transport in Alzheimer’s Neurons

Normal axonal mitochondrial transport and function is essential for the maintenance of synaptic function. Abnormal mitochondrial motility and mitochondrial dysfunction within axons are critical for amyloid β (Aβ)-induced synaptic stress and the loss of synapses relevant to the pathogenesis of Alzheimer’s disease (AD). However, the mechanisms controlling axonal mitochondrial function and transport alterations in AD remain elusive. Here, we report an unexplored role of cyclophilin D (CypD)-dependent mitochondrial permeability transition pore (mPTP) in Aβ-impaired axonal mitochondrial trafficking. Depletion of CypD significantly protects axonal mitochondrial motility and dynamics from Aβ toxicity as shown by increased axonal mitochondrial density and distribution and improved bidirectional transport of axonal mitochondria. Notably, blockade of mPTP by genetic deletion of CypD suppresses Aβ-mediated activation of the p38 mitogen-activated protein kinase signaling pathway, reverses axonal mitochondrial abnormalities, improves synaptic function, and attenuates loss of synapse, suggesting a role of CypD-dependent signaling in Aβ-induced alterations in axonal mitochondrial trafficking. The potential mechanisms of the protective effects of lacking CypD on Aβ-induced abnormal mitochondrial transport in axon are increased axonal calcium buffer capability, diminished reactive oxygen species (ROS), and suppressing downstream signal transduction P38 activation. These findings provide new insights into CypD-dependent mitochondrial mPTP and signaling on mitochondrial trafficking in axons and synaptic degeneration in an environment enriched for Aβ.     

Crimes Against Nature: Kincest,Cosmology, and Conservation in Southwest China

ABSTRACT

The post-Mao era (1976–present) has seen a number of great changes in China. Two of these – the revival of religion and the emergence of a nascent, but powerful environmental movement – have come together in a unique way in the revitalisation of dongba religion among the Naxi nationality (pop. 300,000) of northwest Yunnan and southwest Sichuan provinces. This paper examines the relations between indigenous Naxi and outside tourists (mainly Han from other parts of China) through multiple lenses, including traditional Naxi cosmologies and theories of kinship and hospitality, as well as contemporary ideas concerning tourism development and environmental protection. The aim is to show that: (1) Naxi theories of alterity occur at multiple levels simultaneously – gods/demons vs. humans, kin vs. non-kin, native vs. stranger, host vs. guest, etc. – but that a unified logic underlies the relations, transactions, and interpenetration of these groups and (2) this logic is a productive force in its own right, that is, capable of harnessing new situations to it, even as it itself evolves as novel meanings are engendered in the process of intentional action. In all of this, one figure stands out: the dongba, a traditional shaman-priest viewed as a kind of mediator or facilitator in interactions and exchanges involving a wide range of human and non-human subjects.     

Experimental and genetic analysis of root development inArabidopsis thaliana

The cellular organisation of theArabidopsis thaliana root is remarkably regular. A fate map of the primary root and root meristem that predicts the developmental destinies of cells within the embryonic root primordium has been constructed. Nevertheless, laser ablation experiments demonstrate that root meristem cells develop according to position and not according to lineage. Mutational analysis has identified genes required for cell specification in the radial as well as in the apical-basal dimension. The corresponding gene functions appear to be necessary during embryogenesis for the formation of a correctly patterned primary root. H Lambers Section editor