Science

Le site de Sheriden Pit dans l'Ohio apparait comme l'un des sites en grotte les plus important pour la connaissance de la l'ichtyofaune de l'Amerique du Nord. Le site est egalement un piege naturel pour une faune de mammiferes Pleistocene ainsi que pour des reptiles et quelques oiseaux. Les charbons ont permis de dater les couches superieures du site a 700 BP. Les AA etudient ici l'ichtyofaune de la cavite

“Clickers” have become common tools used to promote interactive engagement and enhanced learning in the undergraduate science classroom. While aspects of the technology have been previously identified as supporting effective interactive pedagogy, we have little ...

New specimens of Russellagus and Hesperolagomys (Mammalia, Lagomorpha, Ochotonidae), reexamination of type material, and new information from topotypic specimens provide a context for reassessment of these taxa. Hesperolagomys niobrarensis (new species) is described from a large sample from the late Barstovian (Miocene) of Nebraska. Cranial and dental characters of Hesperolagomys and Russellagus, including presence of a premolar foramen in the maxilla, place these genera within Family Ochotonidae. These taxa share characters including: rooted cheek teeth, talonids narrower than trigonids in lower molariform teeth and having an anterior projection, persistent crescentic valley in P4-M2, and p3 with deep buccal fold and slender trigonid. Hesperolagomys P3 is unique among North American lagomorphs. Hesperolagomys is smaller than Russellagus and has a deep, persistent lingual hypostria in P4-M2; Russellagus additionally differs from Hesperolagomys in having wider anterior projections of the talonid in lower molariform teeth and ventral border of posterior portion of horizontal ramus curves more strongly ventrad. The direction and magnitude of size changes in Russellagus vonhofi occur in apparent coordination with size changes in Hesperolagomys species in the Barstovian. Morphologic and taxonomic turnover in lagomorphs suggests dentally archaic forms (such as Russellagus and Hesperolagomys) may have been unable to develop hypselodont cheek teeth. I use a theoretical morphology and geometric model approach to investigate how the interaction of tooth shape and wear can cause occlusal size and shape changes in different types of hypsodont teeth, and potentially impose structural constraints on crown height. Modeled results of wear surface topography and dimensions closely correspond to observed patterns in P4s of Russellagus, Hesperolagomys, and lower incisors of the muskrat Ondatra. Model results on wear in theoretical tooth morphologies identify two major shape factors influencing wear: orientation of the wear surface ( incisor-like or cheek tooth-like ), and tooth curvature ( concentric or nonconcentric ). Modeled wear also suggests two geometric constraints on crown height. Potential tooth area limits crown height in some teeth with nonconcentric curvatures. Incomplete wear in any tooth can present severe constraints on increasing crown height, causing structurally untenable morphologies in very tall-crowned to hypselodont teeth

ABSTRACT The principal control on landscape evolution in the central Great Plains of the United States over the past 10 m.y is a contentious subject. New sedimentary data collected from Late Miocene Ogallala Group and Pliocene Broadwater Formation of the Nebraskan Great Plains demonstrates a twofold increase in the median grain size (from 20 mm to > 40 mm) exported from the Rocky Mountains across the Miocene-Pliocene boundary. Paleoslope reconstructions derived from these data support the tilting of the Miocene Ogallala Group after 6 Ma, but demonstrate that the transport slope of the lower part of the unconformably overlying Pliocene succession is identical to the present-day slope. These data allow us to constrain the timing of differential uplift in the Great Plains to between 6 and 3.7 m.y; the wavelength and short duration of this tilting are best explained by the initiation of localized dynamic topography. Our results also suggest a threefold to fourfold increase in specific stream power at this time, meaning that Pliocene rivers draining the central Rockies were considerably more competent than their Miocene predecessors. Incision during this period was not continuous. A significant episode of aggradation from 3.7 to 2.5 Ma is best explained by high rates of sediment supply relating to the warm, wet mid-Pliocene climate optimum. The modern pattern of incision on the Great Plains occurred from 2.5 Ma, and not from the end of the Miocene as is sometimes supposed, reflecting the onset of major Northern Hemisphere glaciation.

The adenosine A(2A) receptor (A(2A)R) plays an important role in the regulation of inflammatory and immune responses. Our previous work has demonstrated that A(2A)R agonists exhibit atheroprotective effects by increasing expression of reverse cholesterol transport proteins in cultured human macrophages. This study explores the impact of pharmacologic activation/inhibition and gene silencing of A(2A)R on cholesterol homeostasis in both THP-1 human monocytes/macrophages and primary human aortic endothelial cells (HAEC). THP-1 human monocytes/macrophages and HAEC exposed to the A(2A)R-specific agonist ATL313 exhibited upregulation of proteins responsible for cholesterol efflux: the ABCA1 and G1 transporters. Further, activation of A(2A)R led to upregulation of the cholesterol metabolizing enzyme P450 27-hydroxylase, accompanied by intracellular changes in level of oxysterols. We demonstrate that anti-atherogenic properties of A(2A)R activation are not limited to the regulation of lipid efflux in vasculature, but include protection from lipid overload in macrophages, particularly via suppression of the CD36 scavenger receptor. The reduced lipid accumulation manifests directly as a diminution in foam cell transformation. In THP-1 macrophages, either A(2A)R pharmacological blockade or gene silencing promote lipid accumulation and enhance foam cell transformation. Our pre-clinical data provides evidence suggesting that A(2A)R stimulation by ATL313 has the potential to be a viable therapeutic strategy for cardiovascular disease prevention, particularly in patients with elevated risk due to immune/inflammatory disorders.