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L Walter

Publications and source records attributed to L Walter.

At least 19 recordsLinked to original sources
PubMed2001

Physical map and expression profile of genes of the telomeric class I gene region of the rat MHC.

The rat is an important model for studying organ graft rejection and susceptibility to certain complex diseases. The MHC, the RT1 complex, plays a decisive role in controlling these traits. We have cloned the telomeric class I region of the RT1 complex, RT1-C/E/M, of the BN inbred rat strain in a contig of overlapping P1-derived artificial chromosome clones encompassing approximately 2 Mb, and present a physical map of this MHC region. Forty-five class I exon 4-hybridizing BAM:HI fragments were detected, including the previously known rat class I genes RT1-E, RT-BM1, RT1-N, RT1-M2, RT1-M3, and RT1-M4. Twenty-six non-class I genes known to map to the corresponding part of the human and mouse MHC were tested and could be fine mapped in the RT1-C/E/M region at orthologous position. Four previously known microsatellite markers were fine mapped in the RT1-C/E/M region and found to occur in multiple copies. In addition, a new, single-copy polymorphic microsatellite has been defined. The expression profiles of several class I genes and the 26 non-class I genes were determined in 13 different tissues and exhibited restricted patterns in most cases. The data provide further molecular information on the MHC for analyzing disease susceptibility and underline the usefulness of the rat model.

Animals↗
PubMed2001

The major histocompatibility complex of the rat (Rattus norvegicus).

This review of the RT1 complex, the major histocompatibility complex (MHC) of the rat, focuses on genetic, genomic, evolutionary, and functional aspects at the molecular level. The class I, class II, and framework genes are listed. The physical map of the RT1 complex as revealed by analysis of clonal contigs is compared with the human and mouse MHC, and the degree of orthologous relationship is outlined. Elucidation of the RT1 complex provides important information for using the rat as a model of experimental transplantation and complex diseases.

Animals↗
PubMed2001

Genomic analysis of MIC genes in rhesus macaques.

MIC genes map to the major histocompatibility complex (MHC) and are distantly related to MHC class I genes. Recently, MICA/MICB-like genes have been described in nonhuman primates. In Macaca mulatta, three MICA/B-like genes could be identified: Mamu-MIC1, Mamu-MIC2, and Mamu-MIC3. We show here the isolation and characterization of rhesus macaque cosmid clones which carry the Mamu-MIC2 and Mamu-MIC3 genes. Neither the MIC2- and MIC3-coding sequences nor respective flanking sequences can be aligned unambiguously to either the human HLA-MICA or -MICB subregions, although MIC2 was found at a similar distance to the BAT1 gene as known for MICB in human. Thus, the characteristics allowing for a classification of primate MIC genes as being of the MICA or MICB types appear to have evolved after the separation of humans and rhesus monkeys from a common ancestor. Furthermore, also Mamu-MICD-containing cosmids could be isolated. In contrast to Mamu-MIC2 and Mamu-MIC3, the Mamu-MICD gene and its flanking sequences are highly conserved and orthologous to the human MICD subregion.

Animals↗
PubMed2001

Genomic and funtional aspects of the rat MHC, the RT1 complex.

The major histocompatibility complex (MHC) plays a central role in controlling immune responsiveness, susceptibility to certain diseases and histo-incompatibility. A physical map of the complete rat MHC, the RTI complex, is presented based on a PAC clonal contig (RT1n haplotype). Expression profiling of various tissues of different inbred strains has been carried out for genes of the RT1-C/E/M region, and different types of variability of expression are shown. As an example of single gene analysis, the RT1-linked heat shock-inducible heat shock genes Hsp70-1 and Hsp70-2 have been studied. It is demonstrated that their gene products are able to increase lysability of target cells by cytotoxic T lymphocytes.

Animals↗
PubMed2000

Three classes of ubiquinone analogs regulate the mitochondrial permeability transition pore through a common site.

To identify the structural features required for regulation of the mitochondrial permeability transition pore (PTP) by ubiquinone analogs (Fontaine, E., Ichas, F., and Bernardi, P. (1998) J. Biol. Chem. 40, 25734-25740), we have carried out an analysis with quinone structural variants. We show that three functional classes can be defined: (i) PTP inhibitors (ubiquinone 0, decylubiquinone, ubiquinone 10, 2,3-dimethyl-6-decyl-1,4-benzoquinone, and 2,3,5-trimethyl-6-geranyl-1,4-benzoquinone); (ii) PTP inducers (2,3-dimethoxy-5-methyl-6-(10-hydroxydecyl)-1,4-benzoquinone and 2,5-dihydroxy-6-undecyl-1,4-benzoquinone); and (iii) PTP-inactive quinones that counteract the effects of both inhibitors and inducers (ubiquinone 5 and 2,3,5-trimethyl-6-(3-hydroxyisoamyl)-1,4-benzoquinone) . The structure-function correlation indicates that minor modifications in the isoprenoid side chain can turn an inhibitor into an activator, and that the methoxy groups are not essential for the effects of quinones on the PTP. Since the ubiquinone analogs used in this study have a similar midpoint potential and decrease mitochondrial production of reactive oxygen species to the same extent, these results support the hypothesis that quinones modulate the PTP through a common binding site rather than through oxidation-reduction reactions. Occupancy of this site can modulate the PTP open-closed transitions, possibly through secondary changes of the PTP Ca(2+) binding affinity.

Animals↗
PubMed2000

Heat shock protein 70 is able to prevent heat shock-induced resistance of target cells to CTL.

Heat shock or transfection with heat shock protein 70 (Hsp70) genes has been shown to protect tumor cell lines against immune mechanisms of cytotoxicity. We have reported previously that heat shock confers resistance to CTL in the rat myeloma cell line Y3 that is Hsp70 defective. Evidence is now presented that Hsp70 is able to prevent the induction of the resistant phenotype. In Con A-stimulated lymphocytes and in lymphocyte x Y3 somatic cell hybrid clones a severe, non-Hsp70-inducing heat shock elicits resistance to CTL in contrast to a heat shock that results in Hsp70 expression. Thus, Hsp70 expression appears to be negatively associated with the development of resistance. Furthermore, loading of Y3 cells with recombinant Hsp70 protein before heat shock is able to prevent resistance. Because apoptosis induced in Y3 cells by heat shock is not affected, Hsp70 appears to interfere selectively with the CTL-induced lethal pathway that is found to be calcium but not caspase dependent. It is suggested that after heat shock Hsp70 enhances the CTL-induced apoptotic pathway by chaperoning certain proteins in the target cell that are involved in the execution of cell death. Thus, although shown to confer protection against many cytotoxic mechanisms, Hsp70 does not appear to be generally cytoprotective. This observation could also be of relevance when interpreting the effectiveness of tumor immunity.

Animals↗
PubMed2000

Physical mapping and evolution of the centromeric class I gene-containing region of the rat MHC.

We physically mapped the centromeric part of the BN rat MHC (RT1n haplotype) in a contig of overlapping P1-derived artificial chromosome (PAC) clones encompassing about 300 kb. The following genes were identified and ordered as: (Syngap, Hset, Daxx, Bing1)-Tapbp-Rgl2-Ke2-Bing4-B3galt4- Rps18-Sacm2l-RT1-A1-RT1-A2-RT1-A3-Ring1-Ring2-++ +Ke4-Rxrb-Col11a2-RT1-Hb-Ring3-RT1-DMb. Thus, in contrast to other RT1 haplotypes, RT1n contains three class I genes, RT1-A1, RT1-A2, and RT1-A3, mapping between the Sacm2l and Ring1 genes. Comparisons of the sequences flanking the Sacm2L and Ring1 genes in rat, human, and mouse suggest that the class I gene-containing region was inserted between these genes in rat and mouse at a similar position. Thus, this insertion is likely to have occurred in a common ancestor of these rodents, although the presence of a site particularly permissive for insertions cannot be excluded.

Animals↗
PubMed1999

Enhanced susceptibility to cytotoxic T lymphocytes without increase of MHC class I antigen expression after conditional overexpression of heat shock protein 70 in target cells.

Antigenic peptides have been found associated with heat shock proteins (HSP) including cytoplasmic HSP70 and heat shock cognate protein 70 as well as the endoplasmic reticulum-resident glucose-regulated protein 94. Recently, HSP70 transfection has been reported to increase MHC class I cell surface expression and antigen presentation on mouse melanoma B16 cells (Wells et al., Int. Immunol. 1998. 10: 609). To analyze the effect of HSP70 on MHC class I cell surface expression and lysability of target cells we transfected a human melanoma cell line with the rat Hsp70-1 gene using the Tet-On system for conditional overexpression of HSP70. Induction of HSP70 did not increase cell surface expression of HLA class I molecules in general or individual HLA-A and B antigens in particular. Nonetheless, induction of HSP70 enhanced susceptibility of these cells to lysis by allospecific CTL. The same effect was observed using an HLA-A2-restricted tyrosinase-specific CTL clone after pulsing the tyrosinase-negative target cells with the specific peptide. Thus, HSP70 induction can increase killing by CTL without affecting MHC class I cell surface expression or antigen processing. This effect of HSP70 appears to be different from the commonly found protection exerted by HSP70 against stress like heat shock, and might be mediated by improving CTL-induced apoptosis.

Animals↗
PubMed1998

Identification of a novel highly conserved gene in the centromeric part of the major histocompatibility complex.

A novel highly conserved gene designated Sacm2l alias Are1) has been identified and fine mapped in the centromeric part of the major histocompatibility complex in rat, human, and mouse. Sacm2l is closely linked to the ribosomal protein S18 gene Rps18 with a distance of about 450 bp between the respective translational start points. Numerous Sacm2l-homologous EST sequences can be identified in the database. Northern blot experiments of rat Sacm2l revealed a transcript of 3 kb in each organ tested, and by RT-PCR differentially spliced products could be detected in testis RNA. The deduced amino acid sequence of the rat Sacm2l gene shows a putative coiled-coil region and significant homology to a putative Caenorhabditis elegans protein and the yeast SAC2 protein.

Amino Acid Sequence↗
PubMed1998

Analysis of the 5'-flanking regions of the MHC-linked Hsp70-2 and Hsp70-3 genes of the rat.

We have analyzed the genomic interval between the MHC-linked heat shock protein 70 (Hsp70) genes Hsp70-2 and Hsp70-3 in the rat. The distance between the transcription start sites of both genes which are organized in a head-to-head orientation is 604 bp. Unlike Hsp70-2 the 5'untranslated region of Hsp70-3 is interrupted by an intron of about 3.9 kb. The Hsp70-3 promoter lacks a TATA box and heat shock elements, but contains two CRE elements, one Sp1-GC and two PuF binding sites. Analysis of the Hsp70-2 promoter by CAT assays reveals positive and negative regulatory elements extending into the Hsp70-3 gene.

Animals↗
PubMed1998

Isolation and molecular characterization of the rat MR1 homologue, a non-MHC-linked class I-related gene.

We isolated and analyzed a new rat gene which is homologous to the recently described human major histocompatibility complex class I-related gene MR1. The deduced amino acid sequence of the rat Mr1 gene shows conserved cysteine residues typical of class I genes as well as conserved beta2-microglobulin and CD8 contact sites. Analysis of partial DNA sequences and restriction fragment length polymorphism patterns of several inbred rat strains indicate that Mr1 is not polymorphic. Mr1 is a single-copy gene, which could be mapped to rat chromosome 13 by co-segregation analysis of Mr1 and a microsatellite marker in the renin (Ren) gene in double-backcross hybrids. The recombination frequency between both genes was determined to be 14.7% (4.9-31.1, 95% confidence limits). Expression analysis revealed various Mr1 transcripts in each organ tested and occurrence of alternative splicing.

Amino Acid Sequence↗
PubMed1998

The determinants of fat intake in a multi-ethnic New Zealand population. Fletcher Challenge--University of Auckland Heart and Health Study Management Committee.

BACKGROUND: The New Zealand diet is high in total and saturated fat and this is likely to be contributing to the increasing prevalence of obesity and relatively high rates of coronary heart disease in New Zealand. The identification of subgroups with a high-fat intake will enable nutrition-related public health strategies to be better targeted. METHODS: Subjects from two surveys were included in the study: 7574 employees from a large multinational workforce survey and 2447 people aged 35-84 years selected from a stratified random sample of the electoral roll in central Auckland. Fat and saturated fat intake were assessed by short questionnaire which gave a dietary fat habits (DFH) score and supplemented by a six-item food frequency questionnaire. RESULTS: The DFH scores were higher in males than in females at all ages, and there was an inverse relationship with age which was stronger for males. Age-adjusted scores showed significantly higher DFH scores for Maori than for Europeans. Lower socioeconomic status was associated with higher DFH scores in males. Current smoking and heavy drinking (in males) were associated with significantly higher DFH scores after controlling for socioeconomic status. The results of the limited food frequency questionnaire supported the trends in DFH scores. CONCLUSIONS: The subgroups with high total and saturated fat intakes which should be a priority for public health action are young and middle-aged males, Maori and lower socioeconomic status males. The clustering of high-fat intake with smoking and heavy drinking should be considered when developing preventative strategies.

Adult↗