Characteristics of Columbia spotted frog ( Rana luteiventris ) oviposition sites in northeastern Oregon, USA

Several western ranid frogs possess a unique strategy of breeding communally over a short temporal window and reusing oviposition sites between years. However, little is published on the characteristics of oviposition sites selected by these explosive breeders. The Columbia spotted frog ( Rana luteiventris ) is native to northwestern North America and is of conservation concern in the southern portions of its range. As part of a study examining relationships between livestock grazing and R. luteiventris habitat, we assessed characteristics of the species' oviposition sites in 25 fishless ponds in northeastern Oregon. Oviposition sites were generally in shallow water (<25 cm) close to shore and tended to be in the northeastern portion of ponds. Oviposition sites were found more frequently over heavily vegetated substrates and in areas of less substrate slope and shade than random points in littoral zones. We did not quantify temperature differences within ponds, but the patterns we documented are consistent with preferential use of warmer microhabitats for oviposition.     

Insertional mutagenesis identifies multiple networks of cooperating genes driving intestinal tumorigenesis

The evolution of colorectal cancer suggests the involvement of many genes. To identify new drivers of intestinal cancer, we performed insertional mutagenesis using the Sleeping Beauty transposon system in mice carrying germline or somatic Apc mutations. By analyzing common insertion sites (CISs) isolated from 446 tumors, we identified many hundreds of candidate cancer drivers. Comparison to human data sets suggested that 234 CIS-targeted genes are also dysregulated in human colorectal cancers. In addition, we found 183 CIS-containing genes that are candidate Wnt targets and showed that 20 CISs-containing genes are newly discovered modifiers of canonical Wnt signaling. We also identified mutations associated with a subset of tumors containing an expanded number of Paneth cells, a hallmark of deregulated Wnt signaling, and genes associated with more severe dysplasia included those encoding members of the FGF signaling cascade. Some 70 genes had co-occurrence of CIS pairs, clustering into 38 sub-networks that may regulate tumor development.     

In vivo continuous electrochemical determination of dopamine release in rat neostriatum]

Polarographic micro-electrodes (carbon fiber, o. d. 8 micron) implanted in the Rat caudate nucleus, allowed a practically continuous in vivo monitoring (one measurement every 5 sec.) of the extra-cellular concentration of dopamine released by striatal dopaminergic terminals. Administration of amphetamine produced a reproducible increase of the oxidation current. This effect was suppressed after the selective degeneration of the striatal dopaminergic terminals following the injection of 6-OHDA into the substantia nigra or after inhibition of the synthesis of the amine by alpha methyl-p-tyrosin. After 5 hrs. this drug produced a 70% decrease of the oxidation current.     

Propulsion of organelles isolated from Acanthamoeba along actin filaments by myosin-I

Eukaryotic cells are dependent on their ability to translocate membraneous elements about the cytoplasm. In many cells long translocations of organelles are associated with microtubules. In other cases, such as the rapid cytoplasmic streaming in some algae, organelles appear to be propelled along actin filaments. It has been assumed, but not proven, that myosin produces these movements. We have tested vesicles from another eukaryotic cell for their ability to move on the exposed actin bundles of Nitella as an indiction that actin-based organelle movements may be a general property of cells. We found that organelles from Acanthamoeba castellanii can move along Nitella actin filaments. Here, we report two different experiments indicating that the single-headed non-polymerizable myosin isozyme myosin-I is responsible for this organelle motility. First, monoclonal antibodies to myosin-I inhibit movement, but antibodies that inhibit double-headed myosin-II do not. Second, approximately 20% of the myosin-I in homogenates co-migrates with motile vesicles during Percoll density-gradient ultracentrifugation. This is the first indication of a role for myosin-I within the cell and supports the suggestion of Albanesi et al. that myosin-I moves vesicles in this way.     

The RCAF complex mediates chromatin assembly during DNA replication and repair

Chromatin assembly is a fundamental biological process that is essential for the replication and maintenance of the eukaryotic genome. In dividing cells, newly synthesized DNA is rapidly assembled into chromatin by the deposition of a tetramer of the histone proteins H3 and H4, followed by the deposition of two dimers of histones H2A and H2B to complete the nucleosome-the fundamental repeating unit of chromatin. Here we describe the identification, purification, cloning, and characterization of replication-coupling assembly factor (RCAF), a novel protein complex that facilitates the assembly of nucleosomes onto newly replicated DNA in vitro. RCAF comprises the Drosophila homologue of anti-silencing function 1 protein ASF1 and histones H3 and H4. The specific acetylation pattern of H3 and H4 in RCAF is identical to that of newly synthesized histones. Genetic analyses in Saccharomyces cerevisiae demonstrate that ASF1 is essential for normal cell cycle progression, and suggest that RCAF mediates chromatin assembly after DNA replication and the repair of double-strand DNA damage in vivo.     

N-trees as nestings: Complexity,similarity, and consensus

Interpreting a taxonomic tree as a set of objects leads to natural measures of complexity and similarity, and sets natural lower bounds on a consensus tree Interpretations differing as to the kind of objects constituting a tree lead to different measures and consensus Subset nesting is preferred over the clusters (strict consensus) and even the triads interpretations because of its superior expression of shared structure Algorithms for computing the complexity and similarity of trees, as well as a consensus index onto [0,1], are presented for this interpretation The full consensus is defined as the only tree which includes all the nestings shared in a profile of rival trees and whose clusters reflect only nestings shared in the profile The full consensus is proved to exist uniquely for each profile, and to equal the Adams consensusThe author is grateful for the many helpful comments on presentation from Frances McA Adams, William H E Day, and Christopher A Meacham