Fossil evidence for an ancient divergence of lorises and galagos

Morphological, molecular, and biogeographic data bearing on early primate evolution suggest that the clade containing extant (or 'crown') strepsirrhine primates (lemurs, lorises and galagos) arose in Afro-Arabia during the early Palaeogene, but over a century of palaeontological exploration on that landmass has failed to uncover any conclusive support for that hypothesis. Here we describe the first demonstrable crown strepsirrhines from the Afro-Arabian Palaeogene--a galagid and a possible lorisid from the late middle Eocene of Egypt, the latter of which provides the earliest fossil evidence for the distinctive strepsirrhine toothcomb. These discoveries approximately double the previous temporal range of undoubted lorisiforms and lend the first strong palaeontological support to the hypothesis of an ancient Afro-Arabian origin for crown Strepsirrhini and an Eocene divergence of extant lorisiform families.     

Comparative analyses of multi-species sequences from targeted genomic regions

The systematic comparison of genomic sequences from different organisms represents a central focus of contemporary genome analysis. Comparative analyses of vertebrate sequences can identify coding and conserved non-coding regions, including regulatory elements, and provide insight into the forces that have rendered modern-day genomes. As a complement to whole-genome sequencing efforts, we are sequencing and comparing targeted genomic regions in multiple, evolutionarily diverse vertebrates. Here we report the generation and analysis of over 12 megabases (Mb) of sequence from 12 species, all derived from the genomic region orthologous to a segment of about 1.8 Mb on human chromosome 7 containing ten genes, including the gene mutated in cystic fibrosis. These sequences show conservation reflecting both functional constraints and the neutral mutational events that shaped this genomic region. In particular, we identify substantial numbers of conserved non-coding segments beyond those previously identified experimentally, most of which are not detectable by pair-wise sequence comparisons alone. Analysis of transposable element insertions highlights the variation in genome dynamics among these species and confirms the placement of rodents as a sister group to the primates.     

In pre-sterol carrier protein 2 (SCP2) in solution the leader peptide 1 – 20 is flexibly disordered, and residues 21 – 143 adopt the same globular fold as in mature SCP2

The preform of the rabbit sterol carrier protein 2 (pre-rSCP2) was cloned, the uniformly ¹⁵N-labelled protein expressed in Escherichia coli and studied by three-dimensional ¹⁵N-resolved nuclear magnetic resonance spectroscopy. In spite of its low solubility in aqueous solution of only ∼0.3 mM, sequential ¹⁵N and ¹H backbone resonance assignments were obtained for 105 out of the 143 residues. From comparison of the sequential and medium-range nuclear Overhauser effects (NOEs) in the two proteins, all regular secondary structures previously determined in mature human SCP2 (hSCP2) [Szyperski et al. (1993) FEBS Lett. 335: 18–26] were also identified in pre-rSCP2. Near-identity of the backbone ¹⁵N and ¹H chemical shifts and 1 : 1 correspondence of 24 long-range NOEs to backbone amide groups in the two proteins show that the residues 21 – 143 adopt the same globular fold in pre-rSCP2 and mature hSCP2. The N-terminal 20-residue leader peptide of pre-rSCP2 is flexibly disordered in solution and does not observably affect the conformation of the polypeptide segment 21 – 143. Received 11 May 1998; accepted 15 May 1998     

基于FPGA查阅表的面向结构的逻辑优化

介绍了基于现场可编程门阵列（ＦＰＧＡ）查阅表的逻辑优化准则．基于这一准则，讨论了几种重要的逻辑优化运算，例如抽取、分解、约数检查和简化，以按照目标工艺技术估算电路的价格．基于ＦＰＧＡ，利用我们的方法对查阅表进行逻辑优化，可以得到工艺映射中的良好出发点．以２５个基准试验例子为基础，我们的优化电路所需要的构造逻辑方块（ＣＬＢ）比利用ＭＩＳ－ＩＩ的优化电路的情形下少百分之十四，如果两者都利用ＭＩＳ－ｐｇａ顺序映射的话．此外，电路的级数也稍有改进．     

United Kingdom: The Science and Engineering Research Council (SERC): A Report on Research in the United Kingdom,France and Germany (W)

Science Policy News

United Kingdom: The Science and Engineering Research Council (SERC): A Report on Research in the United Kingdom, France and Germany (W)     

Carl du Prel (1839–1899): explorer of dreams, the soul, and the cosmos

Nineteenth-century spiritism was a blend of religious elements, the philosophy of mind, science and popular science and contacts with extraterrestrials were a commonplace phenomenon during spiritistic séances. Using the example of Carl du Prel (1839–1899) I show how his comprehensive mystic philosophy originated in a theory of extraterrestrial life. Carl du Prel used a Darwinian and monistic framework, theories of the unconscious and a Neo-Kantian epistemology to formulate a philosophy of astronomy and extraterrestrial life. He claimed that the mechanism of Darwinian selection is responsible for the distribution of stars and the orbits of the planets. In his speculations on the nature of extraterrestrial life he used the concept of organ projection to argue that technical solutions on earth will be realized organically on other planets and claimed that superior extraterrestrials have quantitatively and qualitatively different senses and thus different forms of intuition. A comparison with Camille Flammarion, spiritist and populariser of astronomy, demonstrates the contextual complexities of spiritism. In contrast to du Prel’s sober Neo-Kantian philosophical speculations, Flammarion was a late proponent of a French esoteric tradition that was rooted in romantic socialism, painted grand cosmological vistas and emphasized reincarnation. I put forward the hypothesis that current discourses on extraterrestrial life are affected by the spiritist tradition mainly through the ‘Golden Age’ science fiction literature of the 1940s and 50s and its successors. However, neither Carl du Prel nor Camille Flammarion contributed significantly to this tradition, which is mainly shaped by the psychical research of J. B. Rhine.     

Generation time and temporal scaling of bird population dynamics

Theoretical studies have shown that variation in density regulation strongly influences population dynamics, yet our understanding of factors influencing the strength of density dependence in natural populations still is limited. Consequently, few general hypotheses have been advanced to explain the large differences between species in the magnitude of population fluctuations. One reason for this is that the detection of density regulation in population time series is complicated by time lags induced by the life history of species that make it difficult to separate the relative contributions of intrinsic and extrinsic factors to the population dynamics. Here we use population time series for 23 bird species to estimate parameters of a stochastic density-dependent age-structured model. We show that both the strength of total density dependence in the life history and the magnitude of environmental stochasticity, including transient fluctuations in age structure, increase with generation time. These results indicate that the relationships between demographic and life-history traits in birds translate into distinct population dynamical patterns that are apparent only on a scale of generations.     

Mapping determinants of human gene expression by regional and genome-wide association

To study the genetic basis of natural variation in gene expression, we previously carried out genome-wide linkage analysis and mapped the determinants of approximately 1,000 expression phenotypes. In the present study, we carried out association analysis with dense sets of single-nucleotide polymorphism (SNP) markers from the International HapMap Project. For 374 phenotypes, the association study was performed with markers only from regions with strong linkage evidence; these regions all mapped close to the expressed gene. For a subset of 27 phenotypes, analysis of genome-wide association was performed with >770,000 markers. The association analysis with markers under the linkage peaks confirmed the linkage results and narrowed the candidate regulatory regions for many phenotypes with strong linkage evidence. The genome-wide association analysis yielded highly significant results that point to the same locations as the genome scans for about 50% of the phenotypes. For one candidate determinant, we carried out functional analyses and confirmed the variation in cis-acting regulatory activity. Our findings suggest that association studies with dense SNP maps will identify susceptibility loci or other determinants for some complex traits or diseases.     

Mapping the Hawaiian plume conduit with converted seismic waves

The volcanic edifice of the Hawaiian islands and seamounts, as well as the surrounding area of shallow sea floor known as the Hawaiian swell, are believed to result from the passage of the oceanic lithosphere over a mantle hotspot. Although geochemical and gravity observations indicate the existence of a mantle thermal plume beneath Hawaii, no direct seismic evidence for such a plume in the upper mantle has yet been found. Here we present an analysis of compressional-to-shear (P-to-S) converted seismic phases, recorded on seismograph stations on the Hawaiian islands, that indicate a zone of very low shear-wave velocity (< 4 km s(-1)) starting at 130-140 km depth beneath the central part of the island of Hawaii and extending deeper into the upper mantle. We also find that the upper-mantle transition zone (410-660 km depth) appears to be thinned by up to 40-50 km to the south-southwest of the island of Hawaii. We interpret these observations as localized effects of the Hawaiian plume conduit in the asthenosphere and mantle transition zone with excess temperature of approximately 300 degrees C. Large variations in the transition-zone thickness suggest a lower-mantle origin of the Hawaiian plume similar to the Iceland plume, but our results indicate a 100 degrees C higher temperature for the Hawaiian plume.     

Kinetics of BRCA1 regulation in response to UVC radiation

To investigate changes in BRCA1 following DNA damage, we exposed MCF-7 cells to increasing doses of ultraviolet C. We observed an increase in BRCA1 protein levels above 78 J/m². This increase was observed as early as 5 min after irradiation. BRCA1 levels were then observed to decrease after 2 h, consistent with the previously published data. By pretreating with cycloheximide prior to irradiation, we observed a decrease in the protein half-life, from 3.5 h to 53 min, suggesting that a decrease in protein half-life may cause the lower levels of BRCA1 after irradiation. We also observed an increase in BRCA1 mRNA within 15 min of irradiation, followed by a decrease after 4 h. These data suggest that newly translated protein may contribute to increases in BRCA1 protein levels. The very rapid changes in BRCA1 support its role as a sensor of DNA damage, as opposed to being a repair gene. Received 6 April 2000; received after revision 23 May 2000; accepted 23 May 2000