Analysis of the DNA sequence and duplication history of human chromosome 15

Here we present a finished sequence of human chromosome 15, together with a high-quality gene catalogue. As chromosome 15 is one of seven human chromosomes with a high rate of segmental duplication, we have carried out a detailed analysis of the duplication structure of the chromosome. Segmental duplications in chromosome 15 are largely clustered in two regions, on proximal and distal 15q; the proximal region is notable because recombination among the segmental duplications can result in deletions causing Prader-Willi and Angelman syndromes. Sequence analysis shows that the proximal and distal regions of 15q share extensive ancient similarity. Using a simple approach, we have been able to reconstruct many of the events by which the current duplication structure arose. We find that most of the intrachromosomal duplications seem to share a common ancestry. Finally, we demonstrate that some remaining gaps in the genome sequence are probably due to structural polymorphisms between haplotypes; this may explain a significant fraction of the gaps remaining in the human genome.     

微波消解FI-HG-AAS法测定血清中的痕量硒

建立了一种测定血清样品中痕量硒的新方法。血清样品经微波消解,将Se（VI）还原为Se（IV）,用流动注射氢化物发生原子吸收分光光度法测定。在优化条件下,检测限Se的质量浓度为0.3 μg/L。测定两种标准参考物质的结果符合标准值。该法已用于测定产妇、新生儿和成人血清中的硒。     

Moderate cooling depresses the accumulation and the release of newly synthesized catecholamines in isolated canine saphenous veins

Summary Moderate cooling (from 37° to 24°C) depressed the formation of³H-dopamine and³H-norepinephrine from³H-tyrosine by isolated canine saphenous veins. Cooling reduced the evoked release ofnewly synthesized catecholamine to the same extent as tha of stored norepinephrine. Hence the augmentation by cold of the contractile response to sympathetic nerve stimulation observed in earlier work is not accompanied by an augmentated release of newly synthesized norepinephrine.Acknowledgments. This work was supported by grant HL 05883 from the National Institutes of Health. The authors want to thank F. Jordaens for his valuable technical assistance, J. Beckman for secretarial assistance and H. Hedrickson for preparing the illustrations.Recipient of training grant 80304 from the I.W.O.N.L.     

Cristallisation de l'α-amylase de pancréas

Summary In a series of 32 urinary calculi, examined with X-rays and microscope, 2 were found to consist of hydroxylapatite, 4 of whewellite, 4 of struvite and 15 of uric acid. 4 stones contained two minerals: apatite + brushite, apatite + whewellite and both hydrates of Ca-oxalate.     

DNA sequence and analysis of human chromosome 8

The International Human Genome Sequencing Consortium (IHGSC) recently completed a sequence of the human genome. As part of this project, we have focused on chromosome 8. Although some chromosomes exhibit extreme characteristics in terms of length, gene content, repeat content and fraction segmentally duplicated, chromosome 8 is distinctly typical in character, being very close to the genome median in each of these aspects. This work describes a finished sequence and gene catalogue for the chromosome, which represents just over 5% of the euchromatic human genome. A unique feature of the chromosome is a vast region of approximately 15 megabases on distal 8p that appears to have a strikingly high mutation rate, which has accelerated in the hominids relative to other sequenced mammals. This fast-evolving region contains a number of genes related to innate immunity and the nervous system, including loci that appear to be under positive selection--these include the major defensin (DEF) gene cluster and MCPH1, a gene that may have contributed to the evolution of expanded brain size in the great apes. The data from chromosome 8 should allow a better understanding of both normal and disease biology and genome evolution.     

Mössbauer and electron microscopy study of martensitic transformations in an Fe-Mn-Mo alloy

The kinetic, morphological, crystallographic, and magnetic characteristics of thermally induced martensites in Fe-13.4wt% Mn-5.2wt% Mo alloy were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Mössbauer spectroscopy. The experimental results reveal that two types of thermal-induced martensites, ? (hcp) and α′ (bcc) martensites, are formed in the as-quenched condition, and these transformations have athermal characters. Mo addition to the Fe-Mn alloy does not change the coexistence of ? and α′ martensites with the Mn content between 10wt% and 15wt%. Besides, Mössbauer spectra reveal a paramagnetic character with a singlet for the γ (fcc) austenite and ? martensite phases and a ferromagnetic character with a broad sextet for the α′ martensite phase. The volume fraction of α′ martensite forming in the quenched alloy is much more than that of the ? martensite.     

Dendrite growth increased by visual activity requires NMDA receptor and Rho GTPases

Previous studies suggest that neuronal activity may guide the development of synaptic connections in the central nervous system through mechanisms involving glutamate receptors and GTPase-dependent modulation of the actin cytoskeleton. Here we demonstrate by in vivo time-lapse imaging of optic tectal cells in Xenopus laevis tadpoles that enhanced visual activity driven by a light stimulus promotes dendritic arbor growth. The stimulus-induced dendritic arbor growth requires glutamate-receptor-mediated synaptic transmission, decreased RhoA activity and increased Rac and Cdc42 activity. The results delineate a role for Rho GTPases in the structural plasticity driven by visual stimulation in vivo.     

Alpha-neurexins couple Ca2+ channels to synaptic vesicle exocytosis

Synapses are specialized intercellular junctions in which cell adhesion molecules connect the presynaptic machinery for neurotransmitter release to the postsynaptic machinery for receptor signalling. Neurotransmitter release requires the presynaptic co-assembly of Ca2+ channels with the secretory apparatus, but little is known about how synaptic components are organized. Alpha-neurexins, a family of >1,000 presynaptic cell-surface proteins encoded by three genes, link the pre- and postsynaptic compartments of synapses by binding extracellularly to postsynaptic cell adhesion molecules and intracellularly to presynaptic PDZ domain proteins. Using triple-knockout mice, we show that alpha-neurexins are not required for synapse formation, but are essential for Ca2+-triggered neurotransmitter release. Neurotransmitter release is impaired because synaptic Ca2+ channel function is markedly reduced, although the number of cell-surface Ca2+ channels appears normal. These data suggest that alpha-neurexins organize presynaptic terminals by functionally coupling Ca2+ channels to the presynaptic machinery.