Carbon isotope evidence for the stepwise oxidation of the Proterozoic environment

The oxidation of the Earth's crust and the increase in atmospheric oxygen early in Earth history have been linked to the accumulation of reduced carbon in sedimentary rocks. Trends in the carbon isotope composition of sedimentary organic carbon and carbonate show that during the Proterozoic aeon (2.5-0.54 Gyr ago) the organic carbon reservoir grew in size, relative to the carbonate reservoir. This increase, and the concomitant release of oxidizing power in the environment, occurred mostly during episodes of global rifting and orogeny.     

A carbon isotope record of CO2 levels during the late Quaternary

Analyses of gases trapped in continental ice sheets have shown that the concentration of CO2 in the Earth's early atmosphere increased from 180 to 280 p.p.m. during the most recent glacial-interglacial transition. This change must have been driven by an increase in the concentration of CO2 dissolved in the mixed layer of the ocean. Biochemical and physiological factors associated with photosynthetic carbon fixation in this layer should lead to a relationship between concentrations of dissolved CO2 and the carbon isotopic composition of phytoplanktonic organic material, such that increased atmospheric CO2 should enhance the difference in 13C content between dissolved inorganic carbon and organic products of photosynthesis. Here we show that a signal related to atmospheric CO2 levels can be seen in the isotope record of a hemipelagic sediment core, which we can correlate with the CO2 record of the Vostok ice core. Calibration of the relationship between isotope fractionation and CO2 levels should permit the extrapolation of CO2 records to times earlier than those for which ice-core records are available.     

INTERMEDIUM-C, a modifier of lateral spikelet fertility in barley, is an ortholog of the maize domestication gene TEOSINTE BRANCHED 1

The domestication of cereals has involved common changes in morphological features, such as seed size, seed retention and modification of vegetative and inflorescence architecture that ultimately contributed to an increase in harvested yield. In barley, this process has resulted in two different cultivated types, two-rowed and six-rowed forms, both derived from the wild two-rowed ancestor, with archaeo-botanical evidence indicating the origin of six-rowed barley early in the domestication of the species, some 8,600-8,000 years ago. Variation at SIX-ROWED SPIKE 1 (VRS1) is sufficient to control this phenotype. However, phenotypes imposed by VRS1 alleles are modified by alleles at the INTERMEDIUM-C (INT-C) locus. Here we show that INT-C is an ortholog of the maize domestication gene TEOSINTE BRANCHED 1 (TB1) and identify 17 coding mutations in barley TB1 correlated with lateral spikelet fertility phenotypes.     

TRPV3 is a temperature-sensitive vanilloid receptor-like protein

Vanilloid receptor-1 (VR1, also known as TRPV1) is a thermosensitive, nonselective cation channel that is expressed by capsaicin-sensitive sensory afferents and is activated by noxious heat, acidic pH and the alkaloid irritant capsaicin. Although VR1 gene disruption results in a loss of capsaicin responses, it has minimal effects on thermal nociception. This and other experiments--such as those showing the existence of capsaicin-insensitive heat sensors in sensory neurons--suggest the existence of thermosensitive receptors distinct from VR1. Here we identify a member of the vanilloid receptor/TRP gene family, vanilloid receptor-like protein 3 (VRL3, also known as TRPV3), which is heat-sensitive but capsaicin-insensitive. VRL3 is coded for by a 2,370-base-pair open reading frame, transcribed from a gene adjacent to VR1, and is structurally homologous to VR1. VRL3 responds to noxious heat with a threshold of about 39 degrees C and is co-expressed in dorsal root ganglion neurons with VR1. Furthermore, when heterologously expressed, VRL3 is able to associate with VR1 and may modulate its responses. Hence, not only is VRL3 a thermosensitive ion channel but it may represent an additional vanilloid receptor subunit involved in the formation of heteromeric vanilloid receptor channels.     

The chemotherapeutic activity of selected fasciolicides against immatureFasciola hepatica in mice

Zusammenfassung Die Wirkung von vier faszioliziden Agentien (Rafoxanid, Oxyklozanid, Nitroxynil und Diamphenethid) wurde im Mäuseversuch verglichen. Alle vier Substanzen waren gegen unreifeFasciola hepatica wirksam und entfalteten ihre höchste Wirksamkeit gegen spätere unreife Stadien, mit Ausnahme von Diamphenethid, welches gegen die Frühstadien der unreifen Parasiten am stärksten war.     

The most infectious prion protein particles

Neurodegenerative diseases such as Alzheimer's, Parkinson's and the transmissible spongiform encephalopathies (TSEs) are characterized by abnormal protein deposits, often with large amyloid fibrils. However, questions have arisen as to whether such fibrils or smaller subfibrillar oligomers are the prime causes of disease. Abnormal deposits in TSEs are rich in PrP(res), a protease-resistant form of the PrP protein with the ability to convert the normal, protease-sensitive form of the protein (PrP(sen)) into PrP(res) (ref. 3). TSEs can be transmitted between organisms by an enigmatic agent (prion) that contains PrP(res) (refs 4 and 5). To evaluate systematically the relationship between infectivity, converting activity and the size of various PrP(res)-containing aggregates, PrP(res) was partially disaggregated, fractionated by size and analysed by light scattering and non-denaturing gel electrophoresis. Our analyses revealed that with respect to PrP content, infectivity and converting activity peaked markedly in 17-27-nm (300-600 kDa) particles, whereas these activities were substantially lower in large fibrils and virtually absent in oligomers of < or =5 PrP molecules. These results suggest that non-fibrillar particles, with masses equivalent to 14-28 PrP molecules, are the most efficient initiators of TSE disease.