Correlation between a DNA restriction fragment length polymorphism and C4A6 protein

The fourth component of complement (C4) in man, is coded for by two separate but closely linked loci (C4A and C4B) within the major histocompatibility region (MHC), on the short arm of chromosome 6. Like class I and II loci of this region, the C4 genes are highly polymorphic with more than 30 alleles, including null alleles, assigned to the two loci. This extensive polymorphism, based mainly on electrophoretic mobility, provides a useful marker for studies of disease susceptibility. Several disorders, including systemic lupus erythematosus and type I diabetes, show associations with C4 phenotypes. We have used the technique of Southern with a C4 specific probe to examine the genomic DNA of individuals typed for C4 by protein electrophoresis. We have identified 10.7 and 3.8 kilobase (kb) BglII restriction fragments in each of 9 unrelated individuals with a C4A6 allele, and in none of 22 unrelated individuals in whom this allele was not expressed. This clear correlation of restriction fragment length polymorphism with C4 phenotype provides a precise basis for analysis of C4 polymorphism. It is likely to be of value in clinical investigations of autoimmune disease.     

Similar meltwater contributions to glacial sea level changes from Antarctic and northern ice sheets

The period between 75,000 and 20,000 years ago was characterized by high variability in climate and sea level. Southern Ocean records of ice-rafted debris suggest a significant contribution to the sea level changes from melt water of Antarctic origin, in addition to likely contributions from northern ice sheets, but the relative volumes of melt water from northern and southern sources have yet to be established. Here we simulate the first-order impact of a range of relative meltwater releases from the two polar regions on the distribution of marine oxygen isotopes, using an intermediate complexity model. By comparing our simulations with oxygen isotope data from sediment cores, we infer that the contributions from Antarctica and the northern ice sheets to the documented sea level rises between 65,000 and 35,000 years ago were approximately equal, each accounting for a rise of about 15 m. The reductions in Antarctic ice volume implied by our analysis are comparable to that inferred previously for the Antarctic contribution to meltwater pulse 1A (refs 16, 17), which occurred about 14,200 years ago, during the last deglaciation.     

Kranz anatomy is not essential for terrestrial C4 plant photosynthesis.

An important adaptation to CO2-limited photosynthesis in cyanobacteria, algae and some plants was development of CO2-concentrating mechanisms (CCM). Evolution of a CCM occurred many times in flowering plants, beginning at least 15-20 million years ago, in response to atmospheric CO2 reduction, climate change, geological trends, and evolutionary diversification of species. In plants, this is achieved through a biochemical inorganic carbon pump called C4 photosynthesis, discovered 35 years ago. C4 photosynthesis is advantageous when limitations on carbon acquisition are imposed by high temperature, drought and saline conditions. It has been thought that a specialized leaf anatomy, composed of two, distinctive photosynthetic cell types (Kranz anatomy), is required for C4 photosynthesis. We provide evidence that C4 photosynthesis can function within a single photosynthetic cell in terrestrial plants. Borszczowia aralocaspica (Chenopodiaceae) has the photosynthetic features of C4 plants, yet lacks Kranz anatomy. This species accomplishes C4 photosynthesis through spatial compartmentation of photosynthetic enzymes, and by separation of two types of chloroplasts and other organelles in distinct positions within the chlorenchyma cell cytoplasm.     

Comment on “On linking climate to Chinese dynastic change: Spatial and temporal variations of monsoonal rain”

An article by Zhang et al. questions the interpretation of our oxygen isotope record from Wanxiang Cave and the sediment titanium record from Lake Huguang Maar, and the possible linkage between climate change and Chinese culture. In response, we explain that their approach lacks logical rigor and their major argument is broadly consistent with, rather than contradictory to our original conclusions. We also note that climate-culture relationships similar to those that we observe in China have been observed for other cultures around the world.     

Does noble metal modification improve the photocatalytic activity of BiOCl?

Noble metal-surface-deposited BiOCl photocatalysts were prepared through photo-deposition and used for photodecomposition of Rhodamine B(RhB).The received materials were characterised using X-ray photoemission spectroscopy(XPS),UV-vis diffuse reflectance spectroscopy(UV-vis DRS),and X-ray diffraction(XRD) to understand the influence of surface deposited noble metals.The results showed that the noble metal species on the surface of BiOCl are in metallic state,which also brought about enhanced light absorption in broad UV-vis region due to plasmonic effects induced by the surfacedeposited noble metal species.All the samples showed good activity in photodecomposition of RhB under UV-light irradiation,but only Ag/BiOCl was more active than bulk BiOCl.The mechanism of the different reactivity of these noble-metal modified BiOCl was tentatively proposed based on the band structure and the interactions between noble metals and the BiOCl.     

The experimental induction of pseudogamy in early mouse embryos

Zusammenfassung Nach Behandlung von Mäusesperma mit ultraviolettem Licht oder Röntgenstrahlen wurden bei vielen dreieinhalb Tage alten Embryonen von der Norm abweichende Chromosomensätze gefunden. Verschiedene waren haploid oder nahezu haploid; diese vermutlich durch Gynogenese entstandenen Embryonen waren gewöhnlich in ihrer Entwicklung zurückgeblichen. Behandlung der Spermatozoen mit Trypaflavin oder Toluidinblau führte zu ähnlich verzögerter Entwicklung, aber ohne klar beobachtbare Abnormalitäten des Chromosomensatzes. Es wird eine Theorie der gynogenetischen und androgenetischen Entwicklung von Mausembryonen aufgestellt, und und mit ähnlichen Entwicklungstypen bei Amphibien verglichen.