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E Joly

Publications and source records attributed to E Joly.

At least 37 records · Page 2Linked to original sources
PubMed2000

Effects of Ca(2+) channel activity on renal hemodynamics during acute attenuation of NO synthesis in the rat.

In cultured vascular muscle cells, nitric oxide (NO) has been shown to inhibit voltage-dependent Ca(2+) channels, which are involved in renal blood flow (RBF) autoregulation. Therefore, our purpose was to specify in vivo the effects of this interaction on RBF autoregulation. To do so, hemodynamics were investigated in anesthetized rats during Ca(2+) channel blockade before or after acute NO synthesis inhibition. Rats were treated intravenously with vehicle (n = 10), 0.3 mg/kg body wt N(G)-nitro-L-arginine-methyl ester (L-NAME; n = 7), 4.5 microg. kg body wt(-1). min(-1) nifedipine (n = 8) alone, or with nifedipine infused before (n = 8), after (n = 8), or coadministered with L-NAME (n = 10). Baseline renal vascular resistance (RVR) averaged 14.0 +/- 1.2 resistance units and did not change after vehicle. RVR increased or decreased significantly by 27 and 29% after L-NAME or nifedipine, respectively. Nifedipine reversed, but did not prevent, RVR increase after or coadministered with L-NAME. RBF autoregulation was maintained after L-NAME, but the autoregulatory pressure limit (P(A)) was significantly lowered by 15 mmHg. Nifedipine pretreatment or coadministration with L-NAME limited P(A) resetting or suppressed autoregulation at higher doses. Results were similar with verapamil. Intrarenal blockade of Ca(2+)-activated K(+) channels also prevented autoregulatory resetting by L-NAME (n = 8). These findings suggest NO inhibits voltage-dependent Ca(2+) channels and thereby modulates RBF autoregulatory efficiency.

Animals↗
PubMed1999

RT1-U: identification of a novel, active, class Ib alloantigen of the rat MHC.

In common with other mammalian species, the laboratory rat (Rattus norvegicus) expresses MHC class I molecules that have been categorized as either classical (class Ia) or nonclassical (class Ib). This distinction separates the class Ia molecules that play a conventional role in peptide Ag presentation to CD8 T cells from the others, whose function is unconventional or undefined. The class Ia molecules are encoded by the RT1-A region of the rat MHC, while the RT1-C/E/M region encodes up to 60 other class I genes or gene fragments, a number of which are known to be expressed (or to be expressible). Here we report upon novel MHC class Ib genes of the rat that we have expression cloned using new monoclonal alloantibodies and which we term RT1-U. The products detected by these Abs were readily identifiable by two-dimensional analysis of immunoprecipitates and were shown to be distinct from the class Ia products. Cellular studies of these molecules indicate that they function efficiently as targets for cytotoxic killing by appropriately raised polyclonal alloreactive CTL populations. The sequences of these class Ib genes group together in phylogenetic analysis, suggesting a unique locus or family. The combined serological, CTL, and sequence data all indicate that these products are genetically polymorphic.

Amino Acid Sequence↗
PubMed1998

An improved PCR-mutagenesis strategy for two-site mutagenesis or sequence swapping between related genes.

The QuikChangeTM protocol is one of the simplest and fastest methods for site-directed mutagenesis, but introduces mutations at only one site at a time, and requires two HPLC-purified complementary oligonucleotides. Here, we describe that this method can be used with non-overlapping oligonucleotides. By doing this, two separate sites can be mutagenised simultaneously, or money can be saved by using a second 'standard' oligonucleotide. By a further modification, we have also used the QuikChangeTM approach to exchange DNA sequences between closely related genes.

Amino Acid Substitution↗
PubMed1998

Efficient generation of major histocompatibility complex class I-peptide complexes using synthetic peptide libraries.

The use of synthetic random peptide libraries is a powerful technology for the study of many aspects of antigen presentation and peptide selection by major histocompatibility complex (MHC) molecules. Here we have used them in conjunction with a recombinant system to determine the peptide binding motifs of three classical class I MHC molecules of the laboratory rat: RT1-Aa, RT1-Au, and RT1-A1c. Described is a method for producing large amounts of soluble class I heavy and light chains in bacteria. Refolding RT1-Aa heavy chain (HC) with rat beta2-microglobulin (beta2m) in the presence of a specific peptide and the subsequent purification of the complex yielded conformationally correct material. This was assessed by gel chromatography, SDS-polyacrylamide gel electrophoresis, isoelectric focussing gel electrophoresis, enzyme-linked immunosorbent assay, and fluorescence-activated cell sorter analysis employing a previously unreported method utilizing a His-Tag affinity silica. By refolding RT1-Aa HC and rat beta2m around a random nonapeptide library and subjecting the resulting complex to acid elution of the bound peptides and pool sequencing, the peptide binding motif for this MHC class I molecule was determined. Results corresponded well with those previously determined from naturally bound peptides and in addition gave a clear and unambiguous signal for the C-terminal anchor residue. This method was then applied to determine the previously undescribed binding motifs for RT1-Au and RT1-A1c. For both molecules, the whole motif was confirmed from naturally bound peptides. We propose this method as an alternative way to obtain the whole class I MHC peptide motif, particularly when a specific antibody is unavailable and/or natural expression of the class I molecule of interest is low.

Animals↗
PubMed1998

Co-evolution of rat TAP transporters and MHC class I RT1-A molecules.

The genes for rat major histocompatibility complex (MHC) class I molecules are associated either with those for the A allele of the transporter associated with antigen processing (TAP-A), which can transport peptides with basic carboxy-terminal residues, or with those for TAP-B, which cannot [1-5]. To explore whether these associations have a functional basis, we compared the sequences of 13 rat MHC class la RT1-A cDNAs from nine MHC haplotypes. Of seven TAP-A- linked RT1-A molecules, six possess strongly acidic F pockets, and these bind a high proportion of peptides with basic carboxy-terminal residues. The F pockets of TAP-B-linked molecules, by contrast, were more basic. Furthermore, we identified six positions at the 'righthand end' of the peptide-binding groove, at which a majority of TAP-B-linked molecules diverge from the consensus sequence for class la molecules whereas, at these positions, all the TAP-A-linked molecules reflect the consensus sequence. Our results suggest that the linked rat class la and TAP genes have co-evolved to maximize the supply of appropriate peptides to the presenting molecules.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1998

Peptide length preferences for rat and mouse MHC class I molecules using random peptide libraries.

MHC class I molecules bind short peptides for presentation to CD8+ T cells. The determination of the three-dimensional structure of various MHC class I complexes has revealed that both ends of the peptide binding site are composed of polar residues conserved among all human and murine MHC class I sequences, which act to lock the ends of the peptide into the groove. In the rat, however, differences in these important residues occur, suggesting the possibility that certain rat MHC class I molecules may be able to bind and present longer peptides. Here we have studied the peptide length preferences of two rat MHC class Ia molecules expressed in the TAP2-deficient mouse cell line RMA-S: RT1-A1c, which carries unusual key residues at both ends of the groove, and RT1.Aa which carries the canonical residues. Temperature-dependent peptide stabilization assays were performed using synthetic random peptide libraries of different lengths (7-15 amino acids) and successful stabilization was determined by FACS analysis. Results for two naturally expressed mouse MHC class I molecules revealed different length preferences (H2-Kb, 8-13-mer and H2-Db, 9-15-mer peptides). The rat MHC class Ia molecule, RT1-Aa, revealed a preference for 9-15-mer peptides, whereas RT1-A1c showed a more stringent preference for 9-12-mer peptides, thereby ruling out the hypothesis that unusual residues in rat MHC molecules allow binding of longer peptides.

Animals↗
PubMed1998

Regulation of major histocompatibility complex and TAP gene products in preimplantation mouse stage embryos.

PROBLEM: To determine the ontogeny of major histocompatibility complex (MHC) expression and TAP products in mouse embryos. METHOD OF STUDY: mRNAs encoding MHC and associated molecules were identified by reverse transcriptase-polymerase chain reaction, and the protein products were localized by confocal microscopy. RESULTS: mRNAs encoding class Ia (H-2Db) and class Ib (Q7/9) were present in one-cell embryos, whereas beta 2-microglobulin (beta 2-m) transcripts were not detected until the two-cell stage. Transporter TAP1, but not TAP2, transcripts were detected only in blastocysts. H-2 class Ia (classical) protein was detected on the surface of two-cell embryos, H-2 class Ib (nonclassical) protein was detected on one-cell embryos, and beta 2-m transcripts were detected on eight-cell embryos; TAP1 protein was present at low levels in the cytoplasm from the one-cell stage onward, increasing in expression in blastocysts. CONCLUSIONS: In mice, MHC class I mRNAs encoding the heavy chain of H-2- and Q7/9-encoding Qa2 molecules are synthesized soon after conception prior to implantation. Similarly, the nonpolymorphic MHC class I-associated molecule beta 2-m also is expressed before implantation. TAP1, but not TAP2, is first detected at the blastocyst stage, thus preceding the onset of TAP2 in embryonic development.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

Positive and negative MHC class I recognition by rat NK cells.

The prompt rejection of transplanted allogeneic lymphocytes by rat NK cells in non-sensitized recipients (allogeneic lymphocyte cytotoxicity or ALC) is determined by MHC genes as well as by genes located in the NK complex. The same genetic control is found when NK alloreactivity is measured by an in vitro assay, and we have employed this assay to delineate the specificity of NK cells for the MHC. The MHC of the rat, RT1, contains class I genes situated on either side of the class II/class III region. The majority of these class I genes are located in the RT1.C region and expressed class I products usually behave as non-classical (class Ib) molecules. They do not serve as restriction elements for the vast majority of conventional alpha/beta T-cells, in contrast to those class I molecules encoded by one or more loci in the classical (class Ia) region, RT1.A. However, NK cells appear to recognize the products of either class I region. Immunogenetic studies suggest that NK cells are inhibited by RT1. A molecules, whereas RT1.C region molecules may have a dual role in regulating NK cytolytic activity, i.e. they either inhibit or activate natural killing. Based on these premises, a model is proposed in which identification of a target as self or non-self depends on different receptors for class I in single NK cells, interpreting coincident positive and negative signals from the various target class I molecules. The putative role of peptides presented by class I, the biological implications, and the evolution of the NK receptors and their ligands are discussed.

Animals↗
PubMed1996

The rat MHC haplotype RT1c expresses two classical class I molecules.

Cloning and characterization of classical MHC class I coding sequences of the laboratory rat Rattus norvegicus has been reported so far for only four haplotypes, RT1a, RT1(1), RT1n, and RT1u. In all four cases, only one RT1.A classical class I molecule was found. Here we report that, in contrast, the RT1c haplotype expresses two different classical class I molecules. Using recombinant rat strains, we find that allotypic serologic determinants carried by the two molecules map to the RT1.A region, and so we have named them RT1.A1c and RT1.A2c. Multiple clones of functional cDNAs for each of these two molecules were isolated using a recently developed PCR-based expression-cloning method. Using a panel of 20 RT1.Ac-reactive mAb, we find that six recognize RT1.A1c, seven recognize RT1.A2c, and seven recognize both. We also show that both molecules are recognized and distinguished by primary alloreactive cytotoxic T lymphocytes, and that they correspond to identifiable and distinct molecular species in cells that express RT1c naturally. These data all concur to demonstrate that the RT1.Ac region carries two different loci, each of which encodes a functional classical class I molecule.

Amino Acid Sequence↗
PubMed1996

The rat cim effect: TAP allele-dependent changes in a class I MHC anchor motif and evidence against C-terminal trimming of peptides in the ER.

Functional polymorphism in the rat peptide transporter associated with antigen processing (TAP) changes the peptide pool available for binding and presentation by a class I MHC allele, RT1.Aa. The peptide binding motif for RT1.Aa, determined by stabilization with synthetic peptides, included a strong preference for arginine at the peptide C terminus. Analysis of natural peptides bound to RT1.Aa by both pool sequencing and anhydrotrypsin chromatography revealed that TAP polymorphism determined the presence or absence of arginine as the peptide C-terminal residue. This result highlights the in vivo impact of TAP-peptide selectivity, and provides evidence against a high rate of generation of new C termini by protease activity in the endoplasmic reticulum.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

The distribution of Tap2 alleles among laboratory rat RT1 haplotypes.

We are reporting the cDNA sequences of Tap2 from two cima and two cimb rat strains. Comparison of the cDNA sequences shows that these alleles fall into two groups, which we refer to as Tap2-A and Tap2-B. We found that alleles from the Tap2-B group are more closely related to the mouse homologue than are Tap2-A alleles, and among the 48 nucleotides which differ between the Tap2-A and Tap2-B cDNAs, three affect restriction sites. We defined pairs of oligonucleotides which allow amplification of the regions bearing these restriction sites from genomic DNA or cDNA, and this technique has been successful for the genotyping of all of the 56 laboratory strains of Rattus norvegicus tested and for five cell lines tested so far. All 14 known RT1 standard haplotypes were tested, and 7 found to belong to the Tap2-B group, and 7 to Tap2-A. We also found that intron sizes among the alleles of the Tap2-B group fall into two subgroups, providing further insight into the phylogeny of these various haplotypes.

ATP Binding Cassette Transporter, Subfamily B, Mem↗