Adaptative mechanism of the equilibrative nucleoside transporter 1 (ENT-1) and blood adenosine levels in elite freedivers.

PURPOSE: Long static or intense dynamic apnoea-like high-altitude exposure is inducing hypoxia. Adenosine is known to participate to the adaptive response to hypoxia leading to the control of heart rate, blood pressure and vasodilation. Extracellular adenosine level is controlled through the equilibrative nucleoside transporter 1 (ENT-1) and the enzyme adenosine deaminase (ADA). The aim of this study was to determine the control of adenosine blood level (ABL) via ENT-1 and ADA during apnoea-induced hypoxia in elite freedivers was similar to high-altitude adaptation. METHODS: Ten freediver champions and ten controls were studied. Biological (e.g. ENT-1, ADA, ABL, PaO2, PaCO2 and pH) and cardiovascular (e.g. heart rate, arterial pressure) parameters were measured at rest and after a submaximal dry static apnoea. RESULTS: In freedivers, ABL was higher than in control participants in basal condition and increased more in response to apnoea. Also, freedivers showed an ADA increased in response to apnoea. Finally, ENT-1 level and function were reduced for the free divers. CONCLUSION: Our results suggest in freedivers the presence of an adaptive mechanism similar to the one observed in human exposed to chronic hypoxia induced by high-altitude environment.

Residual sleepiness in obstructive sleep apnoea: phenotype and related symptoms.

The characteristics of residual excessive sleepiness (RES), defined by an Epworth score >10 in adequately treated apnoeic patients, are unknown. 40 apnoeic patients, with (n = 20) and without (n = 20) RES, and 20 healthy controls underwent clinical interviews, cognitive and biological tests, polysomnography, a multiple sleep latency test, and 24-h sleep monitoring. The marked subjective sleepiness in the RES group (mean ± sd score 16.4 ± 3) contrasted with moderately abnormal objective measures of sleepiness (90% of patients with RES had daytime sleep latencies >8 min). Compared with patients without RES, the patients with RES had more fatigue, lower stage N3 percentages, more periodic leg movements (without arousals), lower mean sleep latencies and longer daytime sleep periods. Most neuropsychological dimensions (morning headaches, memory complaints, spatial memory, inattention, apathy, depression, anxiety and lack of self-confidence) were not different between patients with and without RES, but gradually altered from controls to apnoeic patients without and then with RES. RES in apnoeic patients differs markedly from sleepiness in central hypersomnia. The association between RES, periodic leg movements, apathy and depressive mood parallels the post-hypoxic lesions in noradrenaline, dopamine and serotonin systems in animals exposed to intermittent hypoxia.

Incidence and management of malignant digestive endocrine tumours in a well defined French population.

BACKGROUND AND AIMS: Little is known about the epidemiology of malignant digestive endocrine tumours. The aim of this study was to report on their incidence and management in a well defined population. METHODS: Data were obtained from the population based Digestive Cancer Registry of Burgundy (France) over a 24 year period. Incidence rates were calculated by sex, age groups, and period of diagnosis. Treatment and stage at diagnosis were also investigated. Prognosis was determined using crude and relative survival rates. A multivariate relative survival analysis was performed. RESULTS: Between 1976 and 1999, 229 cases were recorded. Age standardised incidence rates were 0.76/100,000 for men and 0.50/100,000 for women. They increased over time in both sexes. The resectability rate was 74.1%. Among recorded cases, 26.6% did not extend beyond the organ, 20% had lymph node metastases, and 53.3% had visceral metastases or were unresectable. There was no improvement in the resection rate or in the stage at diagnosis over the study period. The overall relative survival rate was 66.9% at one year, 50.4% at five years, and 40.6% at 10 years. Stage at diagnosis, age at diagnosis, and subsite were independent significant prognostic factors. CONCLUSIONS: Although their incidence is increasing, malignant digestive endocrine tumours remain a rare cancer, representing 1% of digestive cancers. Stage at diagnosis and prognosis at a population level are worse than those reported in hospital series. In the short term, new therapeutic possibilities represent the best way to improve their prognosis.

PDGF-D, a new protease-activated growth factor.

Platelet-derived growth factor (PDGF) has been directly implicated in developmental and physiological processes, as well as in human cancer, fibrotic diseases and arteriosclerosis. The PDGF family currently consists of at least three gene products, PDGF-A, PDGF-B and PDGF-C, which selectively signal through two PDGF receptors (PDGFRs) to regulate diverse cellular functions. After two decades of searching, PDGF-A and B were the only ligands identified for PDGFRs. Recently, however, database mining has resulted in the discovery of a third member of the PDGF family, PDGF-C, a functional analogue of PDGF-A that requires proteolytic activation. PDGF-A and PDGF-C selectively activate PDGFR-alpha, whereas PDGF-B activates both PDGFR-alpha and PDGFR-beta. Here we identify and characterize a new member of the PDGF family, PDGF D, which also requires proteolytic activation. Recombinant, purified PDGF-D induces DNA synthesis and growth in cells expressing PDGFRs. In cells expressing individual PDGFRs, PDGF-D binds to and activates PDGFR-beta but not PDGFR-alpha. However, in cells expressing both PDGFRs, PDGF-D activates both receptors. This indicates that PDGFR-alpha activation may result from PDGFR-alpha/beta heterodimerization.

T-STAR/ETOILE: a novel relative of SAM68 that interacts with an RNA-binding protein implicated in spermatogenesis.

RBM is an RNA-binding protein encoded on the Y chromosome in mammals and is expressed only in the nuclei of male germ cells. Genetic evidence from infertile men implicates it in spermatogenesis, but its function is unknown. Of a number of potential partners for RBM identified by a yeast two-hybrid screen with testis cDNA, the most frequent isolates encoded a novel RNA-binding protein, termed T-STAR, that is closely related to SAM68, an Src-associated protein of unknown function. The mouse homologue was also cloned and designated étoile. It mapped to chromosome 15, while T-STAR mapped to the syntenic region on human chromosome 8. T-STAR/étoile is expressed primarily in the testis; in rat germ cells, the expression of both T-STAR/étoile and SAM68 is regulated during meiosis. Transfection of T-STAR/étoile fused with green fluorescent protein into HeLa cells caused an accumulation of protein in a novel compartment of the nucleus, adjacent to the nucleolus but distinct from the peri-nucleolar compartment. RBM and other hnRNP G family members are candidate downstream targets for regulation by T-STAR/ETOILE and SAM68.

STAR, a gene family involved in signal transduction and activation of RNA.

A new subfamily of KH-domain-containing RNA-binding proteins is encoded by genes that are conserved from yeast to humans. Mutations with interesting developmental phenotypes have been identified in Caenorhabditis elegans, Drosophila and mouse. It is hypothesized that these bifunctional proteins provide a rich source of interesting molecular information about development and define a new cellular pathway that links signal transduction directly to RNA metabolism.

Non-homologous recombination within the major histocompatibility complex creates a transcribed hybrid sequence.

The P5-1 cDNA clone maps to the human MHC class I region (Vernet et al. 1993a). In this paper, we show that the P5-1 cDNA represents a chimeric transcript in which the first exon of an MHC class I gene has been spliced to an unrelated sequence. The corresponding gene P5-1 is composed of the 5' sequence of an MHC class I gene including the promoter region, the first exon, and the half of the first intron fused to an unrelated intron, followed by a large exon. Furthermore, the non-class I part of P5-1 is present within the MHC class I region in multiple copies, defining the P5 family. Another member of the P5 family is fused to a class I gene, although by a type of rearrangement different from P5-1. These two fusion events between members of HLA class I and P5 families reflect the existence of a duplication unit including two class I genes and a P5 sequence. These data shed light on the MHC class I evolution and on the creation and evolution of new genes.

Localization of the OTF3 gene within the human MHC class I region by physical and meiotic mapping.

OTF3 (octamer transcription factor 3) is a transcription factor containing a POU-specific domain and a homeodomain that could play a role in early development. In situ hybridization and pairwise linkage analysis showed that OTF3 gene maps close to the human MHC (major histocompatibility complex). In this paper, we define its localization within the MHC, around 100 kb telomeric to HLA-C, using a combination of physical and genetic analyses.

Structure and evolution of a member of a new subfamily of GTP-binding proteins mapping to the human MHC class I region.

A gene coding for a putative GTP-binding protein, MMR1, has been localized on band C of the murine Chr 17 within or close to the MHC (Denizot et al. 1992). Its human homolog, HSR1, localized to the human MHC class I region, is described in this paper. Its sequence, compared with MMR1, shows that the conceptual proteins encoded by these genes are highly homologous and have thus been subjected to high constraints during evolution. Furthermore, a detailed databank search with HSR1 leads to the characterization of a new subfamily of GTP-binding proteins, of which HSR1 and MMR1 are the only eukaryotic members. The precise localization of HSR1 within the human MHC class I region is also presented.

Evolutionary study of multigenic families mapping close to the human MHC class I region.

During a search for novel coding sequences within the human MHC class I region (chromosome 6p21.3), we found an exon (named B30-2) coding for a 166-amino-acid peptide which is very similar to the C-terminal domain of several coding sequences: human 52-kD Sjögren's syndrome nuclear antigen A/Ro (SS-A/Ro) and ret finger protein (RFP), Xenopus nuclear factor 7 (XNF7), and bovine butyrophilin. The first three of these proteins share similarities over the whole length of the molecule whereas butyrophilin is similar in the C-terminal domain. The N-terminal domain of butyrophilin is similar to rat myelin/oligodendrocyte glycoprotein (MOG) and chicken B blood group system (B-G) protein. These domains are components of a new subfamily of the immunoglobulin superfamily (IgSF). Butyrophilin is thus a mosaic protein composed of the MOG/B-G Ig-like domain and the C-terminal domain of 52-kD SS-A/Ro, RFP, and XNF7 (B30-2-like domain). Moreover, in situ hybridization shows that RFP, butyrophilin, and MOG map to the human chromosome 6p21.3-6p22 region and are thus close to the MHC class I genes. It is therefore possible that the butyrophilin gene is the product of an exon shuffling event which occurred between ancestors of the RFP and MOG genes. To our knowledge, this is the first example of the colocalization of a chimeric gene and its putative progenitors. Finally, regulatory protein T-lymphocyte 1 (Rpt-1) shares similarities with the N-terminal halves of RFP, 52-kD SS-A/Ro, and XNF7, but not with the B30-2-like domain. We show that the ancestral Rpt-1 gene evolved by overprinting.

A novel coding sequence belonging to a new multicopy gene family mapping within the human MHC class I region.

The human major histocompatibility complex (MHC) region is a genomic region spanning about 4000 kilobases (kb) including the class I, class II, and class III subregions. The class I subregion is larger than the two others but with fewer genes described to date. It includes a) classical human leucocyte antigen (HLA) class I genes (HLA-A, HLA-B, HLA-C) which are highly polymorphic and encode products presenting the endogenous antigenic peptides to the T-cell receptors, and b) non-classical class I genes (HLA-E, HLA-F, HLA-G) whose function is still unknown. In this study, we describe the first coding sequence which is not structurally related to the class I genes, although it is localized within the MHC class I region. This novel gene, P5-1, belongs to a multiple copy family, all members of which map within the MHC. Although the P5-1 sequence showed no similarity to sequences in different databanks, its transcription, which is restricted to lymphoid tissues, argues for an immunological function of its product.

YAC-assisted cloning of a putative G-protein mapping to the MHC class I region.

We report the successful use of whole yeast artificial chromosomes (YACs) as probes for direct positional cloning of novel expressed sequences in a given genomic fragment. The class I region of the human major histocompatibility complex, in particular the chromosomal fragment spanning the HLA-E locus, was investigated. The screening of a cDNA library with a 210-kb-long YAC clone led to the identification of a new gene, positionally conserved in the major histocompatibility complex of the mouse genome and encoding a putative GTP binding protein. Although its precise function remains unknown, the interspecies conservation of both sequence and map position suggests a regulatory or functional link with the histocompatibility cluster.

Class I-specific antibodies inhibit proliferation in primary but not secondary mouse T cell responses.

Murine T and B splenocytes were incubated with antibodies that recognize CD3 or surface IgM. These antibodies induced proliferation of their respective target cells. Once stimulated via their receptors, the proliferation of both CD4+ and CD8+ T but not B lymphocytes was inhibited by class I-specific antibodies or their monovalent Fab' fragments. The inhibition of proliferation was dependent on the site on class I molecules recognized by the antibodies used, with the alpha 1/alpha 2 domains of H-2K molecules representing the major site for inhibition. Only soluble antibody-mediated proliferation could be inhibited by class I-directed antibodies; proliferation induced by CD3-specific antibody immobilized on plastic was not inhibited. Primary allogeneic MLR was also inhibited by class I-specific antibodies. In contrast, neither secondary allogeneic MLR, secondary Ag-specific responses, nor proliferation of CTL clones or tumor cell lines were inhibited by class I-specific antibodies. These results suggest a role for class I molecules in regulation of TCR/CD3- but not surface IgM-mediated cell signaling, which depends on the form of stimulation and the stage of differentiation of T cells.

A continuous restriction map from HLA-E to HLA-F. Structural comparison between different HLA-A haplotypes.

The class I region of the human major histocompatibility complex contains genes encoding the classical transplantation antigens (HLA-A, B, and C), at least three new class I genes (HLA-E, F, and G) and many class I pseudogenes (including HLA-H). By pulse field gel electrophoresis and using five rare cutter enzymes, we have constructed a precise and continuous map of 1200 kilobases (kb) around HLA-A. The blots were hybridized with HLA-A, E, and F-specific probes and with new probes derived from yeast artificial chromosomes and cosmids of the class I region. We have compared the genomic organization of the same 1200 kb in three homozygous lymphoblastoid cell lines corresponding to three different HLA haplotypes (A3, A24, and A31). The differences in size observed may have been caused by insertions and deletions and may prove valuable in understanding the evolution of the HLA chromosomal region.