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Biomedical subjects

G Gachelin

Publications and source records attributed to G Gachelin.

At least 37 records · Page 2Linked to original sources
PubMed1997

A unique cDNA coding for subunits 8 and 6 of mitochondrial adenosine triphosphatase of the lancelet Branchiostoma lanceolatum, an ancestor of vertebrates.

A cDNA encoding subunits 8 and 6 of mitochondrial ATPase of the cephalochordate lancelet (Branchiostoma lanceolatum), a direct ancestor of vertebrates, has been cloned and sequenced. A unique transcript encodes the 8 and 6 subunits. In the course of isolation of the 5' end of the ATPase 8 subunit gene, we also determined the sequence of the 5' adjacent tRNA-Lys gene. The anticodon used by mitochondrial tRNA-Lys is TTT.

Adenosine Triphosphatases↗
PubMed1997

The main features of the craniate mitochondrial DNA between the ND1 and the COI genes were established in the common ancestor with the lancelet.

We have cloned the mitochondrial DNA fragment extending from tRNA-Leu to the cytochrome oxidase subunit 1 (COI) genes of Branchiostoma lanceolatum, Myxine glutinosa, Lampetra fluviatilis, and Scyliorhinus caniculus and have determined their respective gene sequences and organization. In all four species, this region contains the ND1 and ND2 genes and the genes coding eight tRNAs, namely, tRNA-Ile, -Gln, -Met, -Trp, -Ala, -Asn, -Cys, and -Tyr. The gene order is the same in the hagfish, lamprey and dogfish. In the lancelet, the location of the tRNA genes is slightly different. The mitochondrial code of Myxine, Lampetra, and Scyliorhinus is identical to that of vertebrates. The code used by the lancelet is the same with the exception of AGA (a stop codon in vertebrates), which codes for glycine in the lancelet. From the comparison of the four maps with already published ones for other species, we propose that the main features of the craniate mtDNA between the ND1 and COI genes were established in the common ancestor to cephalochordates and vertebrates more than 400 MYA. The origin of replication of the light-strand (Ori-L), usually located between the tRNA-Asn and tRNA-Cys genes in vertebrates, was not found in the lancelet, hagfish, or lamprey (Lampetra). In contrast, it was found in the dogfish. Thus the position of Ori-L was established for the first time in the common ancestor to the Chondrichthyes and Osteichthyes and remained present in all later-emerging vertebrates.

Animals↗
PubMed1996

Expansion of a recurrent V beta 5.3+ T-cell population in newly diagnosed and untreated HLA-DR2 multiple sclerosis patients.

We have used a PCR-based technology to study the V beta 5 and V beta 17 repertoire of T-cell populations in HLA-DR2 multiple sclerosis (MS) patients. We have found that the five MS DR2 patients studied present, at the moment of diagnosis and prior to any treatment, a marked expansion of a CD4+ T-cell population bearing V beta 5-J beta 1.4 beta chains. The sequences of the complementarity-determining region 3 of the expanded T cells are highly homologous. One shares structural features with that of the T cells infiltrating the central nervous system and of myelin basic protein-reactive T cells found in HLA-DR2 MS patients. An homologous sequence was not detectable in MS patients expressing DR alleles other than DR2. However, it is detectable but not expanded in healthy DR2 individuals. The possible mechanisms leading to its in vivo proliferation at the onset of MS are discussed.

Base Sequence↗
PubMed1996

The J beta segment of the T cell receptor contributes to the V beta-specific T cell expansion caused by staphylococcal enterotoxin B and Urtica dioica superantigens.

We have used a new polymerase chain reaction-based technique to analyze at the clonal level the CDR3 diversity and the J beta usage associated with the V beta-dependent T cell receptor (TCR) recognition of two superantigens: the staphylococcal enterotoxin B and the Urtica dioica agglutinin. Our results show that subset of J beta elements is preferentially expanded in a given V beta family, independently of the nature of the superantigen. By contrast, the CDR3 loop does not contribute significantly to the T cell expansion induced by the superantigens. We conclude that the J beta segment of the TCR beta chain, but not the CDR3 region, participates in superantigen binding, presumably by influencing the quaternary structure of the TCR beta chain.

Animals↗
PubMed1996

Urtica dioica agglutinin, a V beta 8.3-specific superantigen, prevents the development of the systemic lupus erythematosus-like pathology of MRL lpr/lpr mice.

The V beta 8.3-specific superantigenic lectin Urtica dioica agglutinin (UDA) was used to delete the V beta 8.3+ T cells in MRL lpr/lpr mice. In contrast to the systemic lupus erythematosus-like pathology which progresses with age in the phosphate-buffered saline-injected MRL lpr/lpr controls, UDA-treated animals did not develop overt clinical signs of lupus and nephritis. The pathogenic T cell clones thus reside within the V beta 8.3+ T cell population, which includes an expanded T cell clone described previously. Finally, UDA alters the production of autoantibodies in a sex-dependent manner.

Animals↗
PubMed1996

Presentation of antigens derived from microorganisms residing in host-cell vacuoles.

Antigens presented by major histocompatibility complex molecules have been classified into those presented by 'endogenous' and 'exogenous' pathways. Some microorganisms reside within host-cell vacuoles that appear to avoid both pathways. Novel presentation mechanisms are being unraveled for these microorganisms, and their antigens, rather than being just peptides, can also consist of lipids or DNA fragments.

Animals↗
PubMed1996

The pattern of production of cytokine mRNAs is markedly altered at the onset of multiple sclerosis.

Using two independent PCR-based quantification techniques, we have determined the levels of IL1 beta, IL2, IL4, IL6, IL10, IFN gamma and TNF alpha mRNA in multiple sclerosis patients at the moment of diagnosis of the disease and prior to any immunosuppressive treatment. These patients exhibit markedly reduced IL2 and IL10 mRNA expression accompanied by decreased levels of TNF alpha mRNA. Our results add to the evidence that IL10 plays a role in multiple sclerosis and suggest that decreased production of this interleukin allows the proliferation of autoreactive T cells at the onset of the disease.

Acute Disease↗
PubMed1995

Phosphorylation of the adenovirus E1A-associated 300 kDa protein in response to retinoic acid and E1A during the differentiation of F9 cells.

Transcription of the c-jun gene is up-regulated by either retinoic acid (RA) or adenovirus E1A during the differentiation of F9 cells. We show here that RA and E1A induce phosphorylation of the E1A-associated 300 kDa protein (p300) during the differentiation of F9 cells. The region of E1A that is required for interaction with cellular protein p300 overlaps with the region of E1A required for E1A to induce expression of the c-jun gene. Treatment of F9 cells with RA or infection of the cells by adenovirus led to a decrease in the electrophoretic mobility of p300. Phosphatase treatment of p300 from RA-treated or adenovirus-infected F9 cells reversed the changes in migration of p300, indicating that RA- and E1A-mediated changes in the mobility of p300 were due to phosphorylation. We also found factors, designated DRF1 and DRF2, that bound specifically to a sequence element that is necessary and sufficient for RA- and E1A-mediated up-regulation of the c-jun gene. The mobility of DRF complexes was changed by E1A or RA and the complexes were supershifted by addition of a polyclonal p300 antiserum. Moreover, overexpression of p300 resulted in an increase in the level of DRF1 complex. p300 fused to the DNA binding domain of the E2 protein of papilloma virus stimulated E2-dependent reporter activity in response to RA or E1A in F9 cells. Our results suggest that p300 is part of the DRF complexes, that it is differentially phosphorylated in undifferentiated versus differentiated cells and that it is likely involved in regulating transcription of the c-jun gene during F9 cell differentiation.

Adenovirus E1A Proteins↗
PubMed1995

Induction by adenovirus-5 E1A of the differentiation phenotype of F9 teratocarcinoma cells involves a conserved region (CR1) of E1A.

The effects of the E1A protein of adenovirus-5 on the differentiation program of F9 teratocarcinoma cells were examined by the stable introduction of plasmids that expressed wild-type or mutated forms of E1A. Constitutive expression of plasmids for most of the mutant E1As induced loss of expression of the cell-surface antigen SSEA-1 and the enhanced expression of genes specific for the differentiated phenotype of F9 cells, such as genes for laminin B1, tissue-type plasminogen activator (tPA) and type IV collagen, as well as the altered cell morphology that is associated with the differentiated state. However, such changes were not observed in the case of genes for mutant proteins from which a conserved region (CR1) of E1A had been deleted. Furthermore, no significant induction of expression of the c-jun gene or transactivation of the c-jun-CAT reporter gene were observed when the sequence that encodes CR1 of E1A had been deleted. A palindromic sequence element (DRE) of the c-jun promoter was essential for the E1A-mediated up-regulation of the c-jun gene. These results imply that CR1 is required for activation of the c-jun gene and that it is implicated in the growth arrest, expression of parietal endoderm-specific functions and the orderly differentiation of F9 cells.

Adenovirus E1A Proteins↗
PubMed1995

Cooperatively between an upstream TATA-like sequence and a CAA repeated element mediates E1A-dependent negative repression of the H-2Kb class I gene.

In primary rodent cells transformed by the E1A region of the highly oncogenic adenovirus type 12, repression of transcription mediated by the far upstream TATA-like element was observed only in conjunction with either possible juxtaposition of a CAA repeated element in the presence of E1A and was dependent upon the relative arrangement of both the TATA-like and CAA repeated motifs in both homologous and heterologous promoter constructs. A gel shift competition study demonstrated that the TATA-binding protein (TBP) or a TBP-like protein can bind to both the upstream TATA-like sequence and the regular TATA box on the H-2Kb basal promoter. Moreover, employing immunoselection and cyclic amplification and selection of targets (CASTing) methods with nuclear extracts derived from Ad12-E1A transformants, we have identified a high affinity binding site in the H-2Kb class I promoter for E1A-associated DNA-binding proteins. The sequences of the binding sites were identified and were found to contain both the upstream TATA-like motif and the CAA repeated motifs. Our results suggest that the TATA-like sequence in the far upstream region of the H-2Kb gene is one of the elements that is required for Ad12-E1A-mediated negative repression.

Adenovirus E1A Proteins↗
PubMed1995

T lymphocyte repertoire in Theiler's virus encephalomyelitis: the nonspecific infiltration of the central nervous system of infected SJL/J mice is associated with a selective local T cell expansion.

Theiler's virus causes, in the susceptible SJL/J mouse, a chronic demyelinating disease that resembles multiple sclerosis. Demyelination is at least in part immune mediated and coincides with the infiltration of the central nervous system by T lymphocytes. We analyzed the repertoire of the T cell receptor (TcR) beta-chain for each V beta-J beta combination, in spinal cord and spleen T cells of infected animals. All V beta families were detected in spinal cord as well as in spleen, as if the central nervous system were undiscriminantly invaded by T cells in the infected animals. Some T cells, defined by specific V beta-J beta combinations, were expanded in the spinal cord but not in the spleen, most probably because of an antigen-driven response. The TcR beta-chain repertoire of infiltrating T cells was the same at the onset of demyelination as when the disease was full-blown. These results provide the first description of the repertoire of the T cells which infiltrate the central nervous system during the course of this disease.

Animals↗
PubMed1995

Cancer risk among workers in biomedical research.

OBJECTIVE: This epidemiologic study was undertaken after a cluster of five cases of rare forms of cancer (bone sarcoma, non-Hodgkin's lymphoma) had been observed among biomedical research workers at the Pasteur Institute in Paris to ascertain whether their disease was connected with exposure during this research. METHODS: A mortality study included 3765 people who worked at the Pasteur Institute between 1971 and 1986 and were followed until the end of 1987. Within this cohort a nested case-referent study included 23 cases of cancer [non-Hodgkin's lymphoma (6), multiple myeloma (1), leukemia (3), pancreatic cancer (7), bone cancer (3), brain tumor (3)], and four referents per case, matched for gender and year of birth. RESULTS: Total mortality from cancer was less than expected, the standardized mortality ratio (SMR) being 72 for the men and 82 for the women. Among the women the proportion of pancreatic cancer cases was larger than expected [SMR 490, 95% confidence interval (95% CI) 158-1144], as was the number of brain cancer cases (SMR 239, 95% CI 48-696). Among the men, mortality from bone cancer was greater than expected (SMR 553, 95% CI 62-2006). In the nested case-referent study, more cases than referents had worked in the areas of molecular biology [odds ratio (OR) 7.1, 95% CI 1.5-33] and microbial genetics (OR 6.7, 95% CI 1.3-35). These cases especially included non-Hodgkin's lymphoma and bone cancer. Associated with this finding was the fact that more cases had used certain chemicals, including ethidium bromide, acrylamide, methylnitronitrosoguanidine and ethylmethanesulfonate, and radioactive compounds (essentially 32phosphorus). CONCLUSIONS: As the products used are potent genotoxicants, the present findings suggest that work in biomedical research might well involve an increased risk of certain types of cancer; this conclusion should be balanced by the fact that two of the five index cases were included in the mortality study and four in the nested case-referent study.

Academies and Institutes↗
PubMed1994

Role for MHC class I molecules in selecting and protecting high affinity peptides in the presence of proteases.

Ag fragments derived from the cytosol are transported into the endoplasmic reticulum (ER) lumen, where they bind to nascent MHC class I molecules. However, it is not known whether only high affinity peptides enter the ER, or whether ER proteases must trim longer precursor peptides down to optimal size. To evaluate the feasibility of proteolytic fine trimming in vitro, soluble Kd and Kb were preincubated with peptides that bind to Kd or Kb and the mixture was exposed to three different proteases. Class I protected allele-specific peptides against proteolysis, whereas the other peptides were degraded to the amino acid level. When a Kd/S11E (SYIPSAEYILE) complex was immunoprecipitated after incubation with carboxypeptidase, both S11E and the optimal sized S9I (SYIPSAEYI) were found to be specifically bound to Kd. However, only S91 was recovered if S11E, Kd and carboxypeptidase were mixed at the same time, and there was no fine-trimming of bound S11E if high protease concentrations and short proteolysis times were used, which suggests that trimming occurs only in the unbound state. The amount of peptide that immunoprecipitated with Kd increased after carboxypeptidase treatment of Kd/S11E, implying that the peptide affinity had increased. Kd also protected S9I against proteolysis by a lysed microsome preparation, demonstrating that class I could also protect high affinity peptides in vivo. These results suggest that class I participates in the selection of high affinity peptides in the ER, by sampling transported unbound peptides are degraded by ER proteases or efflux back to the cytosol.

Amino Acid Sequence↗
PubMed1994

The expansion of a CD4+ T cell population bearing a distinctive beta chain in MRL lpr/lpr mice suggests a role for the fas protein in peripheral T cell selection.

MRL lpr/lpr mice suffer from a systemic lupus erythematosus-like autoimmune disease. The lpr mutation impairs the normal transcription of the fas message, the product of which mediates apoptosis and presumably the proper selection of T cells. We have found an early expansion of CD4+ T cells bearing a distinctive V beta 8.3-D beta 1.1-J beta 1.1 T cell receptor beta chain in the periphery of MRL lpr/lpr mice, which was not detected in MRL +/+ mice nor in the thymus of MRL lpr/lpr mice. Thus, since thymic selection is normal in MRL lpr/lpr mice, we propose that the lpr mutation results in defective negative selection at the periphery.

Animals↗
PubMed1994

A novel pathway for retinoic acid-induced differentiation of F9 cells that is distinct from receptor-mediated trans-activation.

Retinoic acid (RA) has striking effects on vertebrate development and induces differentiation of several lines of cells including embryonal carcinoma F9 cells. It is generally accepted that the actions of RA are mediated by nuclear receptors for RA. However, we now provide evidence that F9 cells can differentiate in response to RA without trans-activation by nuclear receptors. Irreversible differentiation of F9 cells was induced by 18 h of exposure to RA with subsequent incubation in the absence of RA. This induction of differentiation was not blocked after inhibition of protein synthesis and mRNA synthesis during the 18-h treatment with RA, but the endogenous RA receptors failed to activate transcription from their target genes that contain the receptor-binding sequences. During the commitment to RA-induced differentiation, at least five sets of four phosphorylated proteins underwent changes in the absence of protein synthesis de novo. These results suggest that there is a novel pathway for the action of RA that is independent of nuclear receptor-mediated trans-activation.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1994

Major histocompatibility complex class I molecules and resistance against intracellular pathogens.

The immune system employs a temporal hierarchy of effector mechanisms to combat infections by intracellular pathogens. The nonspecific response is independent of MHC and can be activated rapidly, while the specific response is slower, more specific, and requires major histocompatibility complex (MHC) molecules. MHC-dependent responses have been characterized extensively in vitro for antigens presented by polymorphic MHC class Ia and class II proteins and recognized by T lymphocytes carrying alpha/beta T-cell receptors (TcR). Growing indirect evidence has implicated monomorphic MHC class Ib proteins and gamma/delta T lymphocytes in defense against bacterial infections, but the biochemical and immunological behavior of class Ib proteins and gamma/delta TcR has not been well characterized, and most hypotheses involving these proteins have relied on data obtained with polymorphic MHC proteins and alpha/beta TcR. An overview of studies describing bacterial infections in vivo suggests that, in many cases, MHC class I-dependent effector cells may not be indispensable for effective immune responses, exerting instead a modulatory effect during the course of infection. Furthermore, many class Ib proteins have probably specialized to present stress antigens and conserved microbial antigens, which may be recognized by gamma/delta T cells through an interaction that is qualitatively very different from alpha/beta TcR binding to class I and class II proteins.

Animals↗
PubMed1993

Negative regulation of the gene for H-2Kb class I antigen by adenovirus 12-E1A is mediated by a CAA repeated element.

Both positive and negative regulatory elements responsive to the product of the adenovirus type 12 E1A gene are located in the promoter region of the gene for mouse H-2Kbm1 major histocompatibility complex (MHC) class I antigen (1). We have analyzed the negative regulatory element that is affected by E1A and identified a target CAA repeated motif, CAA(A)CAAA, within -1725 to -1705 and -1591 to -1568 in a 316-bp sequence located in the far upstream region of H-2Kb promoter (-1837 to -1522; +1 refers to the cap site). The extent of cell surface expression of the MHC class 1 antigen was significantly decreased in the case of transfectants obtained by introducing an expression plasmid that included MHC class 1 cDNA with the CAA repeated element, as compared with that of a plasmid with mutated CAA repeats. We have also characterized the nuclear proteins that bind to this motif. The analysis of the effects of mutations during competition assays of in vivo and gel retardation competition assays demonstrated that the CAA repeated element is essential not only for E1A-dependent repression of transcription but also for the cell surface expression of the product of the mouse H-2Kb class I gene, presumably through nuclear proteins that specifically bind to it.

Adenovirus E1A Proteins↗