Genetic variation in DPP6 is associated with susceptibility to amyotrophic lateral sclerosis

We identified a SNP in the DPP6 gene that is consistently strongly associated with susceptibility to amyotrophic lateral sclerosis (ALS) in different populations of European ancestry, with an overall P value of 5.04 x 10(-8) in 1,767 cases and 1,916 healthy controls and with an odds ratio of 1.30 (95% confidence interval (CI) of 1.18-1.43). Our finding is the first report of a genome-wide significant association with sporadic ALS and may be a target for future functional studies.     

Early life history of the sheepnose (Plethobasus cyphyus) (Mollusca: Bivalvia: Unionoida)

Managing a rare species can be improved with knowledge of its natural history. The sheepnose (Plethobasus cyphyus) is a freshwater mussel recently listed by the US as federally endangered. We used standard methods to study P. cyphyus brooding behaviour, host fishes in the laboratory and under natural conditions, and glochidial morphology. We monitored a population of P. cyphyus in the Chippewa River, WI during spring and summer 2007–2009 and 2011 and found brooding animals between mid-May and early August. Gravid individuals ranged between 5 and 27 yr (mean age ± 1 s.d. = 13 ± 4 yr). Plethobasus cyphyus brooded glochidia in outer gills, which varied in colour from red, orange, pink, cream, or white. We observed mature glochidia more commonly in individuals with cream or white gills and these glochidia were released in a clear, adhesive, mucus matrix. In laboratory trials we found several minnow and topminnow species (29 spp.) served as productive suitable native hosts. The mean number of juvenile mussels released per cyprinid per day was significantly higher for trials conducted at 22–25°C compared with those at 18–20°C, and 83% of trials conducted at 18–20°C using suitable host species produced no juveniles. Glochidia had a unique outline and shell morphometrics that distinguished P. cyphyus from seven other Chippewa River mussel species that produce similar sized glochidia. Using morphometrics we determined that mimic shiners (Notropis volucellus) were natural hosts for P. cyphyus, round pigtoe (Pleurobema sintoxia), and Wabash pigtoe (Fusconaia flava). Releasing mucus-bound glochidia has evolved in a variety of mussel species and may be more common than is currently realized. Our data show that P. cyphyus is a cyprinid host specialist, and propagation efforts for this species can be strengthened through improved access to mature glochidia by using females with cream-coloured gills and increased juvenile production through warmer fish holding temperatures.     

Complex patterns formed by motile cells of Escherichia coli

When chemotactic strains of the bacterium Escherichia coli are inoculated on semi-solid agar containing mixtures of amino acids or sugars, the cells swarm outwards in a series of concentric rings: they respond to spatial gradients of attractants generated by uptake and catabolism. Cells also drift up gradients generated artificially, for example by diffusion from the tip of a capillary tube or by mixing. Here we describe conditions under which cells aggregate in response to gradients of attractant which they excrete themselves. When cells are grown in semi-solid agar on intermediates of the tricarboxylic acid cycle, they form symmetrical arrays of spots or stripes that arise sequentially. When cells in a thin layer of liquid culture are exposed to these compounds, spots appear synchronously, more randomly arrayed. In either case, the patterns are stationary. The attractant is a chemical sensed by the aspartate receptor. Its excretion can be triggered by oxidative stress. As oxygen is limiting at high cell densities, aggregation might serve as a mechanism for collective defence.     

Phenotypic differences between alpha beta versus beta T-cell receptor transgenic mice undergoing negative selection

T-cell differentiation in the thymus is thought to involve a progression from the CD4-CD8- phenotype through CD4+CD8+ intermediates to mature CD4+ or CD8+ cells. There is evidence that during this process T cells bearing receptors potentially reactive to 'self' are deleted by a process termed 'negative selection' One example of this process occurs in mice carrying polymorphic Mls antigens, against which a detectable proportion of T cells are autoreactive. These mice show clonal deletion of thymic and peripheral T-cell subsets that express the autoreactive V beta 3 segment of the T-cell antigen receptor, but at most a two-fold depletion of thymic cells at the CD4+CD8+ stage. By contrast, transgenic mice bearing both alpha and beta chain genes encoding autoreactive receptors recognizing other ligands, show severe depletion of CD4+CD8+ thymocytes as well, suggesting that negative selection occurs much earlier. We report here the Mls 2a/3a mediated elimination of T cells expressing a transgene encoded V beta 3-segment, in T-cell receptor alpha/beta and beta-transgenic mice. Severe depletion of CD4+CD8+ thymocytes is seen only in the alpha/beta chain transgenic mice, whereas both strains delete mature V beta 3 bearing CD4+ and CD8+ T cells efficiently. We conclude that severe CD4+CD8+ thymocyte deletion in alpha/beta transgenic mice results from the premature expression of both receptor chains, and does not reflect a difference in the timing or mechanism of negative selection for Mls antigens as against the allo- and MHC class 1-restricted antigens used in the other studies.     

Classification and distribution ofFicus

Summary The classification of the genusFicus has changed considerably in the course of time and is still the subject of further research and discussion. The main subdivisions in the most recent classification by Corner¹² are presented together with the genera of pollinating fig wasps (Agaonidae) associated with them. These subdivisions are discussed and grouped according to morphological and functional traits, in particular in connection with the unique pollination system. Two main groups are recognized: one with only monoecious species and the other with predominantly (gyno)dioecious species. The former comprises two subgroups (Pharmacosycea andUrostigma) and the latter three, more profoundly different subgroups (Ficus, Sycidium andSycomorus). The neotropical representatives of the genus are discussed in somewhat more detail. In addition, the distribution of the genus is summarized for the three main regions of distribution; Africa, America, and Asia-Australasia. Finally the concordance between subdivisions ofFicus and those of the Agaonidae is briefly discussed.     

Escherichia coli swim on the right-hand side

The motion of peritrichously flagellated bacteria close to surfaces is relevant to understanding the early stages of biofilm formation and of pathogenic infection. This motion differs from the random-walk trajectories of cells in free solution. Individual Escherichia coli cells swim in clockwise, circular trajectories near planar glass surfaces. On a semi-solid agar substrate, cells differentiate into an elongated, hyperflagellated phenotype and migrate cooperatively over the surface, a phenomenon called swarming. We have developed a technique for observing isolated E. coli swarmer cells moving on an agar substrate and confined in shallow, oxidized poly(dimethylsiloxane) (PDMS) microchannels. Here we show that cells in these microchannels preferentially 'drive on the right', swimming preferentially along the right wall of the microchannel (viewed from behind the moving cell, with the agar on the bottom). We propose that when cells are confined between two interfaces--one an agar gel and the second PDMS--they swim closer to the agar surface than to the PDMS surface (and for much longer periods of time), leading to the preferential movement on the right of the microchannel. Thus, the choice of materials guides the motion of cells in microchannels.