Senataxin, the ortholog of a yeast RNA helicase, is mutant in ataxia-ocular apraxia 2

Ataxia-ocular apraxia 2 (AOA2) was recently identified as a new autosomal recessive ataxia. We have now identified causative mutations in 15 families, which allows us to clinically define this entity by onset between 10 and 22 years, cerebellar atrophy, axonal sensorimotor neuropathy, oculomotor apraxia and elevated alpha-fetoprotein (AFP). Ten of the fifteen mutations cause premature termination of a large DEAxQ-box helicase, the human ortholog of yeast Sen1p, involved in RNA maturation and termination.     

2002-based national population projections for the United Kingdom and constituent countries

The 2002-based national population projections, carried out by the Government Actuary in consultation with the Registrars General, show the population of the United Kingdom rising from 59.2 million in 2002 to nearly 65 million by 2031. Longer-term projections suggest the population will peak around 2050 at over 65 million and then gradually start to fall. The population will become gradually older with the median age expected to rise from 38.2 years in 2002 to 43.3 years by 2031. In 2002, there were around 850 thousand (8 per cent) more children aged under 16, than people of state pensionable age. However, from 2007, the population of pensionable age is projected to exceed the number of children.     

Convergence across biomes to a common rain-use efficiency

Water availability limits plant growth and production in almost all terrestrial ecosystems. However, biomes differ substantially in sensitivity of aboveground net primary production (ANPP) to between-year variation in precipitation. Average rain-use efficiency (RUE; ANPP/precipitation) also varies between biomes, supposedly because of differences in vegetation structure and/or biogeochemical constraints. Here we show that RUE decreases across biomes as mean annual precipitation increases. However, during the driest years at each site, there is convergence to a common maximum RUE (RUE(max)) that is typical of arid ecosystems. RUE(max) was also identified by experimentally altering the degree of limitation by water and other resources. Thus, in years when water is most limiting, deserts, grasslands and forests all exhibit the same rate of biomass production per unit rainfall, despite differences in physiognomy and site-level RUE. Global climate models predict increased between-year variability in precipitation, more frequent extreme drought events, and changes in temperature. Forecasts of future ecosystem behaviour should take into account this convergent feature of terrestrial biomes.     

Synthesis and stereospecific synthesis of some alkyl-5-amino-1-glycofuranosyl imidazole-4-carboxylates related to intermediates in purine nucleotide de novo biosynthesis

Zusammenfassung 5-Amino-Glycofuranosylimidazol-Derivative wurden durch Kondensation der Isopropylidenglycofuranosylamine mit Äthyl-N-(Cyano-N-Äthoxycarbonylmethyl)formimidat oder durch Reaktion von Äthylformimidat-Hydrochlorid mit den Furanosylaminen, wozu Äthyl--amino--cyanoacetat hinzugefügt wurde, dargestellt. Bei den Ribose- und Mannosederivaten, wurden - und -Formen als Kristalle isoliert. Eine neue stereospezifische Synthese von Xylofuranosylaminoimidazol über ein Xyloseoxazolin wird beschrieben.     

Fifty years of United Kingdom national population projections: how accurate have they been?

This article considers the accuracy of the official national population projections made for the UK over the last fifty years The findings take account of the revision to population estimates following the 2001 Census and are largely similar to the findings of a previous review carried out after the 1991 Census. The total population has been projected reasonably accurately but this is largely a chance result of compensating errors in the assumptions of fertility, mortality and net migration. The largest differences between projected and actual populations are for the very young and the very old, while projections of the working age population have been comparatively accurate. Fertility and mortality errors have reduced in more recent projections, while migration errors have grown. However, this may simply reflect the volatility or stability of the respective time-series at the time the projections are made. Changes in estimates of the past and current size of the population (highlighted by the revisions made to population estimates following the 2001 Census) are also shown to play a part in explaining projection error.     

Clusters of iron-rich cells in the upper beak of pigeons are macrophages not magnetosensitive neurons

Understanding the molecular and cellular mechanisms that mediate magnetosensation in vertebrates is a formidable scientific problem. One hypothesis is that magnetic information is transduced into neuronal impulses by using a magnetite-based magnetoreceptor. Previous studies claim to have identified a magnetic sense system in the pigeon, common to avian species, which consists of magnetite-containing trigeminal afferents located at six specific loci in the rostral subepidermis of the beak. These studies have been widely accepted in the field and heavily relied upon by both behavioural biologists and physicists. Here we show that clusters of iron-rich cells in the rostro-medial upper beak of the pigeon Columbia livia are macrophages, not magnetosensitive neurons. Our systematic characterization of the pigeon upper beak identified iron-rich cells in the stratum laxum of the subepidermis, the basal region of the respiratory epithelium and the apex of feather follicles. Using a three-dimensional blueprint of the pigeon beak created by magnetic resonance imaging and computed tomography, we mapped the location of iron-rich cells, revealing unexpected variation in their distribution and number--an observation that is inconsistent with a role in magnetic sensation. Ultrastructure analysis of these cells, which are not unique to the beak, showed that their subcellular architecture includes ferritin-like granules, siderosomes, haemosiderin and filopodia, characteristics of iron-rich macrophages. Our conclusion that these cells are macrophages and not magnetosensitive neurons is supported by immunohistological studies showing co-localization with the antigen-presenting molecule major histocompatibility complex class II. Our work necessitates a renewed search for the true magnetite-dependent magnetoreceptor in birds.