Mapping the Drosophila genome with yeast artificial chromosomes

The ability to clone large fragments of DNA in yeast artificial chromosomes (YAC's) has created the possibility of obtaining global physical maps of complex genomes. For this application to be feasible, most sequences in complex genomes must be able to be cloned in YAC's, and most clones must be genetically stable and colinear with the genomic sequences from which they originated (that is, not liable to undergo rearrangement). These requirements have been met with a YAC library containing DNA fragments from Drosophila melanogaster ranging in size up to several hundred kilobase pairs. Preliminary characterization of the Drosophila YAC library was carried out by in situ hybridization of random clones and analysis of clones containing known sequences. The results suggest that most euchromatic sequences can be cloned. The library also contains clones in which the inserted DNA is derived from the centromeric heterochromatin. The locations of 58 clones collectively representing about 8 percent of the euchromatic genome are presented.     

Galileo Gravity Results and the Internal Structure of Io

Doppler data generated with the Galileo spacecraft's radio carrier wave were used to measure Io's external gravitational field. The resulting triaxial field is consistent with the assumption that Io is in tidal and rotational equilibrium. The inescapable conclusion is that it has a large metallic core. If the core is a eutectic mixture of iron and iron sulfide, it comprises 20.2 ± 7.4 percent of the satellite's total mass with a radius that is about 52 percent of Io's mean radius of 1821.3 kilometers; if the core is pure iron, it comprises 10.5 ± 3.7 percent of the total mass with a radius of about 36 percent of the mean radius.     

Crystallization of NADP-specific isocitrate dehydrogenase

The first crystalline preparation of isocitrate dehydrogenase specific for nicotinamide adenine dinucleotide phosphate has been obtained with enzyme isolated from Escherichia coli. Scanning electron microscopy was employed to elucidate the structure of the crystals, which were found to exist as regular octahedrons ranging in size from 5 to 90 micrometers.     

Subdiffraction multicolor imaging of the nuclear periphery with 3D structured illumination microscopy

Fluorescence light microscopy allows multicolor visualization of cellular components with high specificity, but its utility has until recently been constrained by the intrinsic limit of spatial resolution. We applied three-dimensional structured illumination microscopy (3D-SIM) to circumvent this limit and to study the mammalian nucleus. By simultaneously imaging chromatin, nuclear lamina, and the nuclear pore complex (NPC), we observed several features that escape detection by conventional microscopy. We could resolve single NPCs that colocalized with channels in the lamin network and peripheral heterochromatin. We could differentially localize distinct NPC components and detect double-layered invaginations of the nuclear envelope in prophase as previously seen only by electron microscopy. Multicolor 3D-SIM opens new and facile possibilities to analyze subcellular structures beyond the diffraction limit of the emitted light.     

The double quasar 0957+561: a radio study at 6-centimeters wavelength

The optical double quasar 0957+561 has been interpreted as the gravitational double image of a single object. A radio map made with the Very Large Array of the National Radio Astronomy Observatory shows unresolved sources coincident With the optical images as well as a complex of related extended emission. Although the results cannot rule out the gravitational lens hypothesis, the complex radio structure is more easily interpreted as two separate quasars. The optical and radio properties of the two quasars are so similar that the two must have been formed at the same time with similar initial conditions.     

Relationships between microbial community structure and soil environmental conditions in a recently burned system

Most wildfires, even the most severe, burn at mixed intensities across a landscape, depending on local fuel loads, fuel moistures, and wind strength and direction. This heterogeneous patchwork of fire effects can influence the patterns of above- and belowground biotic recovery through altered environmental conditions, nutrient availability, and biotic sources for microbial and vegetative re-colonization. We quantified the effects of low- and high-severity fire 14 months post-burn on key environmental variables typically limiting to microbial activity. We characterized the soil microbial community structure through ester-linked fatty acid analysis (EL-FAME) and identified the soil environmental factors that best explain the pattern of microbial community profiles through canonical correspondence analysis (CCA). Low-severity burning caused no change in soil moisture, pH or temperature while high-severity burning caused an increase in soil moisture, temperature, and a decrease in pH levels, relative to the unburned sites. Soil respiration rates were significantly lower in both the low- and high-severity burn sites, relative to unburned sites, likely due to initial root and microbial death. Overall microbial biomass did not change with either low- or high-severity burning, but the microbial community ordination biplots showed separation of communities by fire, and slight separation by fire severity along three axes. This community separation was driven primarily by a decrease in fungal biomarkers (18:2ω6c, 18:3ω6c) with both low- and high-severity fire. Only 23% of the variation in the microbial community distribution could be explained by three environmental variables: soil pH, temperature, and carbon. These results suggest that the microbial communities in both the low- and high-severity burn sites are structurally different from the populations in the unburned sites.     

Anthropogenic trace elements and polycyclic aromatic hydrocarbon levels in sediment cores from two lakes in the Adirondack acid lake region

Sediment cores were taken from the remote Sagamore and Woods Lakes in New York State's Adirondack acid lake region and analyzed for 3 to 7 ring polycyclic aromatic hydrocarbons (PAHs) and Ag, Al, As, Be, Cd, Cr, Cu, Hg, Ni, Ph, Se, Sn, TI, V, and Zn. With the exception of perylene, all of the parental PAHs, e.g. those without sidechains, and several of the metals, Pb, As, and Cd, were found to be significantly increased in the sediments of both lakes compared to their natural integrated deposits (ng cm^?2) and their background concentrations (μg g^?1 or ng g^?1 dry wt). Although the concentrations were generally much higher in Woods Lake, the total anthropogenic integrated depositions were about the same in both lakes for most of the metals and the 3 to 4 ring PAHs. The prime source of most of the 3 to 7 ring PAHs and trace elements measured is ascribed to anthropogenic combustion. Anthropogenically derived materials decreased in concentration with depth to baseline levels in sediment layers estimated by¹³⁷Cs analyses to be ～30 yr old, while biogenic or crustal derived species remained constant or fluctuated with core depth.     

Effects of white-tailed deer on the native earthworm,Eisenoides carolinensis,in the southern Appalachian Mountains,USA

Research on earthworms in North America has focused on the effects of invasive earthworms, with few studies examining the ecology of native earthworm species. Deer have been shown to influence belowground processes through grazing, trampling, and fecal pellet deposition. We proposed that native earthworms in an oak-dominated forest in Virginia might benefit from increased organic matter provided by deer fecal material. We examined potential interactions between a common aboveground herbivore, the white-tailed deer (Odocoileus virginianus), and earthworms using laboratory and field experiments. In our laboratory experiment, we found that a native earthworm, Eisenoides carolinensis, and an invasive earthworm, Lumbricus terrestris both fared better in treatments with deer pellets compared with the treatment with leaf litter alone. In our field experiment, we used fences to exclude deer from six plots and left twelve plots unfenced to explore the effects of deer activity on earthworm biomass and density. We also examined the effects of deer on soil and vegetation characteristics. After three years, the amount of herbaceous cover was higher on fenced plots compared with unfenced plots. Although we found no other differences for vegetation and soil characteristics between fenced and unfenced plots, many of these variables were important as covariates in our models examining the effect of deer exclusion on earthworms, indicating plot-level (as opposed to treatment-level) variation in these variables. All identifiable earthworms were either E. carolinensis or Diplocardia spp. (both native species), with E. carolinensis making up 90% of the specimens. The total biomass of earthworms, as well as the biomass and density of adult and small juvenile earthworms, was greater on unfenced plots with deer activity compared with fenced plots. This study highlights the importance of above- and below-ground interactions in forest ecosystems by showing that E. carolinensis appears to benefit from the presence of deer and adds to our sparse knowledge of the ecology of this native earthworm.     

Identification of a nonsense mutation in feline ABCB1

The aim of this study was to sequence all exons of the ABCB1 (MDR1) gene in cats that had experienced adverse reactions to P‐glycoprotein substrate drugs (phenotyped cats). Eight phenotyped cats were included in the study consisting of eight cats that experienced central nervous system toxicosis after receiving ivermectin (n = 2), a combination product containing moxidectin and imidacloprid (n = 3), a combination product containing praziquantel and emodepside (n = 1) or selamectin (n = 2), and 1 cat that received the product containing praziquantel and emodepside but did not experience toxicity (n = 1). Fifteen exons contained polymorphisms and twelve exons showed no variation from the reference sequence. The most significant finding was a nonsense mutation (ABCB11930_1931del TC) in one of the ivermectin‐treated cats. This cat was homozygous for the deletion mutation. All of the other phenotyped cats were homozygous for the wild‐type allele. However, 14 missense mutations were identified in one or more phenotyped cats. ABCB11930_1931del TC was also identified in four nonphenotyped cats (one homozygous and three heterozygous for the mutant allele). Cats affected by ABCB11930_1931del TC would be expected to have a similar phenotype as dogs with the previously characterized ABCB1‐1Δ mutation.