New species of Protocedroxylon from the Upper Jurassic of British Columbia, Canada

Protocedroxylon macgregorii sp. nov., from Jurassic strata of British Columbia, Canada, is the first reported occurrence of this genus in North America. Protocedroxylon macgregorii combines the tracheal pitting of the araucarians with the crossfield pitting of modern genera of the Abietineae. This species is similar to the type species Protocedroxylon araucarioides . They differ in that P. araucarioides has tangential pitting, tracheid septations, and entirely uniseriate rays. These features are lacking in P. macgregorii with the exception of the rays, which are partially biseriate in the latter species. Protocedroxylon macgregorii has traumatic resin canals or cysts that have not been reported in P. araucarioides .     

Genetic variation of woodrats ( Neotoma cinerea ) and deer mice ( Peromyscus maniculatus ) on montane habitat islands in the Great Basin

Seventeen loci were examined for polymorphism in four populations of Neotoma cinerea and Peromyscus maniculatus on isolated mountain ranges in the Great Basin, one population of each in the Sierra Nevada, and one of each in the Rocky Mountains. All Peromyscus populations had higher levels of heterozygosity than syntopic Neotoma populations.     

Bats of the Colorado oil shale region

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Golden Eagle ( Aquila chrysaetos ) population ecology in eastern Utah

Golden Eagle population ecology was studied from 1982 to 1992 in eastern Utah where over 47% of 233 territories monitored during the study period were active. Golden Eagle use of four habitat types was compared. Talus territories were used less often than expected; valley, aspen-conifer, and pinyon-juniper territories were used as expected. Number of young produced per territory averaged 0.612 and was correlated with rabbit abundance. Observations on the impacts of coal mining at two locations are discussed.     

Natural variability of vegetation, soils, and physiography in the bristlecone pine forest of the Rocky Mountains

Pinus aristata Engelm. forest vegetation in Colorado was studied to determine vegetation composition and the relationship between vegetation and environment. Species percent cover, tree size class, and environmental variables were recorded for 49 plots. Previously collected data for 4 plots form New Mexico were included. Environmental variables included latitude, longitude, elevation, slope, aspect, topographic position, parent material, percent rock cover, mean rock size, litter depth, estimated plot age class, and evidence of anthropogenic disturbance. Soils were analyzed for texture, depth, and percent carbon and nitrogen. Pinus aristata foliage was analyzed for percent nitrogen and phosphorus. Direct and indirect gradient analyses (CANOCO) were used to determine environmental factors associated with community composition. Vegetation in P. aristata forests is influenced primarily by elevation and soil pH. Substrate, soil texture, topographic position, and geographic location are secondary factors. Six plant associations were identified using cluster analysis (listed in an elevational sequence from low to high): Pinus aristata/ Festuca arizonica Vasey, Pinus aristata / Festuca thurberi Vasey, Pinus aristata / Juniperus communis L., Pinus aristata / Vaccinium myrtilus L., Pinus aristata / Ribes montigenum McClatchie, and Pinus aristata / Trifolium dasyphyllum Torr. & Gray.     

New records for Monotropa hypopithys (Ericaceae) from Colorado

Monotropa hypopithys L., rarely collected in Colorado, was taken five times during 1984. Coupled with previous collections, it is now known from 10 Colorado counties. The cool, moist August of 1984 may have contributed to its apparent ubiquity.     

A viral microRNA functions as an orthologue of cellular miR-155

All metazoan eukaryotes express microRNAs (miRNAs), roughly 22-nucleotide regulatory RNAs that can repress the expression of messenger RNAs bearing complementary sequences. Several DNA viruses also express miRNAs in infected cells, suggesting a role in viral replication and pathogenesis. Although specific viral miRNAs have been shown to autoregulate viral mRNAs or downregulate cellular mRNAs, the function of most viral miRNAs remains unknown. Here we report that the miR-K12-11 miRNA encoded by Kaposi's-sarcoma-associated herpes virus (KSHV) shows significant homology to cellular miR-155, including the entire miRNA 'seed' region. Using a range of assays, we show that expression of physiological levels of miR-K12-11 or miR-155 results in the downregulation of an extensive set of common mRNA targets, including genes with known roles in cell growth regulation. Our findings indicate that viral miR-K12-11 functions as an orthologue of cellular miR-155 and probably evolved to exploit a pre-existing gene regulatory pathway in B cells. Moreover, the known aetiological role of miR-155 in B-cell transformation suggests that miR-K12-11 may contribute to the induction of KSHV-positive B-cell tumours in infected patients.     

Structure of the yeast polarity protein Sro7 reveals a SNARE regulatory mechanism

Polarized exocytosis requires coordination between the actin cytoskeleton and the exocytic machinery responsible for fusion of secretory vesicles at specific sites on the plasma membrane. Fusion requires formation of a complex between a vesicle-bound R-SNARE and plasma membrane Qa, Qb and Qc SNARE proteins. Proteins in the lethal giant larvae protein family, including lethal giant larvae and tomosyn in metazoans and Sro7 in yeast, interact with Q-SNAREs and are emerging as key regulators of polarized exocytosis. The crystal structure of Sro7 reveals two seven-bladed WD40 beta-propellers followed by a 60-residue-long 'tail', which is bound to the surface of the amino-terminal propeller. Deletion of the Sro7 tail enables binding to the Qbc SNARE region of Sec9 and this interaction inhibits SNARE complex assembly. The N-terminal domain of Sec9 provides a second, high-affinity Sro7 interaction that is unaffected by the tail. The results suggest that Sro7 acts as an allosteric regulator of exocytosis through interactions with factors that control the tail. Sequence alignments indicate that lethal giant larvae and tomosyn have a two-beta-propeller fold similar to that of Sro7, but only tomosyn appears to retain the regulatory tail.     

Quantification of actinide alpha-radiation damage in minerals and ceramics

There are large amounts of heavy alpha-emitters in nuclear waste and nuclear materials inventories stored in various sites around the world. These include plutonium and minor actinides such as americium and curium. In preparation for geological disposal there is consensus that actinides that have been separated from spent nuclear fuel should be immobilized within mineral-based ceramics rather than glass because of their superior aqueous durability and lower risk of accidental criticality. However, in the long term, the alpha-decay taking place in these ceramics will severely disrupt their crystalline structure and reduce their durability. A fundamental property in predicting cumulative radiation damage is the number of atoms permanently displaced per alpha-decay. At present, this number is estimated to be 1,000-2,000 atoms/alpha in zircon. Here we report nuclear magnetic resonance, spin-counting experiments that measure close to 5,000 atoms/alpha in radiation-damaged natural zircons. New radiological nuclear magnetic resonance measurements on highly radioactive, 239Pu zircon show damage similar to that caused by 238U and 232Th in mineral zircons at the same dose, indicating no significant effect of half-life or loading levels (dose rate). On the basis of these measurements, the initially crystalline structure of a 10 weight per cent 239Pu zircon would be amorphous after only 1,400 years in a geological repository (desired immobilization timescales are of the order of 250,000 years). These measurements establish a basis for assessing the long-term structural durability of actinide-containing ceramics in terms of an atomistic understanding of the fundamental damage event.     

Skew of mantle upwelling beneath the East Pacific Rise governs segmentation

Mantle upwelling is essential to the generation of new oceanic crust at mid-ocean ridges, and it is generally assumed that such upwelling is symmetric beneath active ridges. Here, however, we use seismic imaging to show that the isotropic and anisotropic structure of the mantle is rotated beneath the East Pacific Rise. The isotropic structure defines the pattern of magma delivery from the mantle to the crust. We find that the segmentation of the rise crest between transform faults correlates well with the distribution of mantle melt. The azimuth of seismic anisotropy constrains the direction of mantle flow, which is rotated nearly 10 degrees anticlockwise from the plate-spreading direction. The mismatch between the locus of mantle melt delivery and the morphologic ridge axis results in systematic differences between areas of on-axis and off-axis melt supply. We conclude that the skew of asthenospheric upwelling and transport governs segmentation of the East Pacific Rise and variations in the intensity of ridge crest processes.