Renal function studies in normal and toxemic pregnant sheep

Renal blood and plasma flow, glomerular filtration rate (GFR) and maximal tubular transport of PAH (TmPAH) were measured in nonpregnant and twin-pregnant sheep. Twin-pregnant animals were studied during normal pregnancy as well as during ovine pregnancy toxemia artificially produced by starvation. All animals were surgically prepared with aortic, post caval and renal vein cannulas at least one week prior to experimentation. Total renal blood and plasma flow was found to be elevated during pregnancy, but if expressed on the basis of body weight no changes were noted. Starvation and the resultant development of hypoglycemia and hyperketonemia caused a 25-30% decline in renal blood and plasma flow. GFR in pregnant fed sheep (193 ml/min or 2.7 ml/kg.min) was significantly higher (P less than .001) than that of nonpregnant ewes (118 or 2.3 ml/kg min). During ovine pregnancy toxemia the GFR was significantly (P less than .001) diminished (142 ml/min or 2.0 ml/kg min). TmPAH also was significantly higher (179 mg/min or 2.5 mg/kg min) in pregnant animals when compared to nonpregnant ewes (98 mg/min or 1.9 mg/kg min.), but starvation had no effect on Tm PAH in pregnant sheep. It thus appears that a functional renal hypertrophy occurs during pregnancy which is similar to that which follows unilateral nephrectomy or renal disease. During ovine pregnancy toxemia the diminution of renal function probably results from the metabolic derangements and is thus not comparable to human preeclampsia.     

Miocene burrows of extinct bear dogs: indication of early denning behavior of large Mammalian carnivores

Partial skeletons of four species of extinct carnivores have been found in their dens excavated in the floodplain of an early Miocene ephemeral braided stream at Agate Fossil Beds National Monument, Nebraska. Bear dogs (Carnivora: Amphicyonidae) were the principal occupants; their den dimensions and body size are similar to those of living wolves and hyenas. Discovery of this predator community extends the record of denning behavior of large mammalian carnivores to the early Miocene, 20 million years ago.     

Biomarker evidence for photosynthesis during neoproterozoic glaciation

Laterally extensive black shales were deposited on the S?o Francisco craton in southeastern Brazil during low-latitude Neoproterozoic glaciation approximately 740 to 700 million years ago. These rocks contain up to 3.0 weight % organic carbon, which we interpret as representing the preserved record of abundant marine primary productivity from glacial times. Extractable biomarkers reflect a complex and productive microbial ecosystem, including both phototrophic bacteria and eukaryotes, living in a stratified ocean with thin or absent sea ice, oxic surface waters, and euxinic conditions within the photic zone. Such an environment provides important constraints for parts of the "Snowball Earth" hypothesis.     

Chiral symmetry breaking in sodium chlorate crystallizaton

Sodium chlorate (NaClO(3)) crystals are optically active although the molecules of the compound are not chiral. When crystallized from an aqueous solution while the solution is not stirred, statistically equal numbers of levo (L) and dextro (D) NaClO(3) crystals were found. When the solution was stirred, however, almost all of the NaClO(3) crystals (99.7 percent) in a particular sample had the same chirality, either levo or dextro. This result represents an experimental demonstration of chiral symmetry breaking or total spontaneous resolution on a macroscopic level brought about by autocatalysis and competition between L- and D-crystals.     

Cyclic variation and solar forcing of Holocene climate in the Alaskan subarctic

High-resolution analyses of lake sediment from southwestern Alaska reveal cyclic variations in climate and ecosystems during the Holocene. These variations occurred with periodicities similar to those of solar activity and appear to be coherent with time series of the cosmogenic nuclides 14C and 10Be as well as North Atlantic drift ice. Our results imply that small variations in solar irradiance induced pronounced cyclic changes in northern high-latitude environments. They also provide evidence that centennial-scale shifts in the Holocene climate were similar between the subpolar regions of the North Atlantic and North Pacific, possibly because of Sun-ocean-climate linkages.     

A selective inhibitor of eIF2alpha dephosphorylation protects cells from ER stress

Most protein phosphatases have little intrinsic substrate specificity, making selective pharmacological inhibition of specific dephosphorylation reactions a challenging problem. In a screen for small molecules that protect cells from endoplasmic reticulum (ER) stress, we identified salubrinal, a selective inhibitor of cellular complexes that dephosphorylate eukaryotic translation initiation factor 2 subunit alpha (eIF2alpha). Salubrinal also blocks eIF2alpha dephosphorylation mediated by a herpes simplex virus protein and inhibits viral replication. These results suggest that selective chemical inhibitors of eIF2alpha dephosphorylation may be useful in diseases involving ER stress or viral infection. More broadly, salubrinal demonstrates the feasibility of selective pharmacological targeting of cellular dephosphorylation events.     

Pioneer 10 jovian encounter: radiation dose and implications for biological lethality

In its recent Jupiter flyby Pioneer 10 passed through a belt of intense particulate radiation. The radiation dose on the outer surface of the spacecraft was at least 4.9 x 10(5) rads from electrons plus 2.9 x 10(6) rads from protons, sufficient to cause significant microbial decontamination. The radiation dose inside Pioneer 10, approximately 2.8 x 10(5) rads, was less likely to cause microbial decontamination but would be lethal to man and to most multicellular biological organisms.     

Late Archean biospheric oxygenation and atmospheric evolution

High-resolution geochemical analyses of organic-rich shale and carbonate through the 2500 million-year-old Mount McRae Shale in the Hamersley Basin of northwestern Australia record changes in both the oxidation state of the surface ocean and the atmospheric composition. The Mount McRae record of sulfur isotopes captures the widespread and possibly permanent activation of the oxidative sulfur cycle for perhaps the first time in Earth's history. The correlation of the time-series sulfur isotope signals in northwestern Australia with equivalent strata from South Africa suggests that changes in the exogenic sulfur cycle recorded in marine sediments were global in scope and were linked to atmospheric evolution. The data suggest that oxygenation of the surface ocean preceded pervasive and persistent atmospheric oxygenation by 50 million years or more.