Gravitational microlensing by low-mass objects in the globular cluster M22.

Gravitational microlensing offers a means of determining directly the masses of objects ranging from planets to stars, provided that the distances and motions of the lenses and sources can be determined. A globular cluster observed against the dense stellar field of the Galactic bulge presents ideal conditions for such observations because the probability of lensing is high and the distances and kinematics of the lenses and sources are well constrained. The abundance of low-mass objects in a globular cluster is of particular interest, because it may be representative of the very early stages of star formation in the Universe, and therefore indicative of the amount of dark baryonic matter in such clusters. Here we report a microlensing event associated with the globular cluster M22. We determine the mass of the lens to be 0.13(+0.03)(-0.02) solar masses. We have also detected six events that are unresolved in time. If these are also microlensing events, they imply that a non-negligible fraction of the cluster mass resides in the form of free-floating planetary-mass objects.     

Localization of a susceptibility locus for schizophrenia on chromosome 5

Schizophrenia is a common disorder with a life time prevalence of approximately 1 per cent. The illness often develops in young adults, who were previously normal, and is characterized by a constellation of symptoms including hallucinations and delusions (psychotic symptoms) and symptoms such as severely inappropriate emotional responses, a disorder of thinking and concentration, erratic behaviour as well as social and occupational deterioration. A considerable proportion of the variance in the liability to develop schizophrenia may be genetic, but segregation analysis, to establish a mode of transmission, has not produced a consistent result. One of these studies was carried out in Iceland and made use of the large family size and extensive geneaological information present in that country. Here we demonstrate genetic linkage of two DNA polymorphisms on the long arm of human chromosome 5 to schizophrenia in seven British and Icelandic families with multiple affected members. The results indicate the existence of a gene locus with a dominant schizophrenia-susceptibility allele. Inheritance of the allele in the families studied suggests that it may also predispose to psychiatric conditions such as schizophrenia spectrum disorders and a variety of other disorders. This report provides the first strong evidence for the involvement of a single gene in the causation of schizophrenia.     

Subcellular distribution of catecholamines and enzymes in human neuroblastoma

Résumé Dans 18 cas de neuroblastome humain la noradrénaline (NA) et la dopamine--hydroxylase présentent des profils de distribution intracellulaire identiques, suggérant un stockage dans la même particule. Le contenu en NA de ces particules n'est pas inférieur à celui des particules du nerf splénique; on peut en conclure qu'un stockage défectueux de NA dans les cas de neuroblastome est peu probable.

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The authors are grateful to Prof.F. Derom (Surgical Clinic, University of Ghent Medical School), Prof.R. Eeckels and Prof.E. Eggermont (Paediatric Clinic, University of Leuven Medical School), Prof.A. Lacquet and Prof.J. Gruwez (Surgical Clinic, University of Leuven Medical School), Dr.G. Delalieux, Dr.F. Delange, Dr.P. De Mol, Dr.R. Denis, Dr.R. Maurus and Dr.J. Otten (Paediatric Clinic, University of Brussels Medical School) and Dr.W. Mattheiem (Surgical Clinic, Jules Bordet Institute, Brussels) for making the tumors available to them.     

Structure of the Sec13/31 COPII coat cage

Endomembranes of eukaryotic cells are dynamic structures that are in continuous communication through the activity of specialized cellular machineries, such as the coat protein complex II (COPII), which mediates cargo export from the endoplasmic reticulum (ER). COPII consists of the Sar1 GTPase, Sec23 and Sec24 (Sec23/24), where Sec23 is a Sar1-specific GTPase-activating protein and Sec24 functions in cargo selection, and Sec13 and Sec31 (Sec13/31), which has a structural role. Whereas recent results have shown that Sec23/24 and Sec13/31 can self-assemble to form COPII cage-like particles, we now show that Sec13/31 can self-assemble to form minimal cages in the absence of Sec23/24. We present a three-dimensional reconstruction of these Sec13/31 cages at 30 A resolution using cryo-electron microscopy and single particle analysis. These results reveal a novel cuboctahedron geometry with the potential to form a flexible lattice and to generate a diverse range of containers. Our data are consistent with a model for COPII coat complex assembly in which Sec23/24 has a non-structural role as a multivalent ligand localizing the self-assembly of Sec13/31 to form a cage lattice driving ER cargo export.     

Complex SNP-related sequence variation in segmental genome duplications

There is uncertainty about the true nature of predicted single-nucleotide polymorphisms (SNPs) in segmental duplications (duplicons) and whether these markers genuinely exist at increased density as indicated in public databases. We explored these issues by genotyping 157 predicted SNPs in duplicons and control regions in normal diploid genomes and fully homozygous complete hydatidiform moles. Our data identified many true SNPs in duplicon regions and few paralogous sequence variants. Twenty-eight percent of the polymorphic duplicon sequences we tested involved multisite variation, a new type of polymorphism representing the sum of the signals from many individual duplicon copies that vary in sequence content due to duplication, deletion or gene conversion. Multisite variations can masquerade as normal SNPs when genotyped. Given that duplicons comprise at least 5% of the genome and many are yet to be annotated in the genome draft, effective strategies to identify multisite variation must be established and deployed.     

Differential alterations in branched-chain amino acid decarboxylation in liver of hypophysectomized rats.

Valine decarboxylation was significantly increased and leucine decarboxylation was significantly decreased in rat liver slices following hypophysectomy. In both normal and hypophysectomized rats decarboxylation of leucine exceeded that of valine in slices whereas the reverse was observed with the respective keto acids and mitochondria.     

Lymphatic metastasis of transplantable animal neoplasms

Résumé L'injection de 5 millions de cellules tumorales RD3 dans la patte du rat, fait apparaître des dépôts métastasique sous forme de ganglions lymphatiques poplitétaux. L'examen histologique détaillé montre qu'ils sont vraies métastases. Des résultats pareils sont apparus dans 2 autres tumeurs qui étaient histologiquement malignes, mais non dans celles qui étaient bénignes. Cette technique semble convenir à étude de la métastase lymphatique.