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Biomedical subjects

M A Morris

Publications and source records attributed to M A Morris.

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

Coeliac disease and Down syndrome: associations not due to genetic linkage on chromosome 21.

BACKGROUND: Individuals with Down syndrome have an increased prevalence of coeliac disease (CD). The HLA region accounts for only 30% of the heritability of CD, and segregation analyses have suggested the involvement of at least one other non-HLA gene. Distribution of known HLA susceptibility types in Down syndrome and normal populations are similar and do not explain the difference in disease frequency. This study tests the hypothesis that the association between these disorders is due to a susceptibility gene for coeliac disease being present on chromosome 21. METHODS: We studied 21 families multiply affected with CD, none of whom had Down syndrome. The typing information of six microsatellite markers across chromosome 21 was used to test linkage. RESULTS: Negative results from lod score and model-free linkage analysis were obtained, providing no support for genetic linkage of coeliac disease to chromosome 21 in this population. CONCLUSIONS: The high prevalence of coeliac disease in Down syndrome is not due to an increased copy number of a polymorphic susceptibility gene on chromosome 21.

Celiac Disease↗
PubMed1999

Molecular analysis of the ERGIC-53 gene in 35 families with combined factor V-factor VIII deficiency.

Combined factor V-factor VIII deficiency (F5F8D) is a rare, autosomal recessive coagulation disorder in which the levels of both coagulation factors V and VIII are diminished. The F5F8D locus was previously mapped to a 1-cM interval on chromosome 18q21. Mutations in a candidate gene in this region, ERGIC-53, were recently found to be associated with the coagulation defect in nine Jewish families. We performed single-strand conformation and sequence analysis of the ERGIC-53 gene in 35 F5F8D families of different ethnic origins. We identified 13 distinct mutations accounting for 52 of 70 mutant alleles. These were 3 splice site mutations, 6 insertions and deletions resulting in translational frameshifts, 3 nonsense codons, and elimination of the translation initiation codon. These mutations are predicted to result in synthesis of either a truncated protein product or no protein at all. This study revealed that F5F8D shows extensive allelic heterogeneity and all ERGIC-53 mutations resulting in F5F8D are "null." Approximately 26% of the mutations have not been identified, suggesting that lesions in regulatory elements or severe abnormalities within the introns may be responsible for the disease in these individuals. In two such families, ERGIC-53 protein was detectable at normal levels in patients' lymphocytes, raising the further possibility of defects at other genetic loci.

Algeria↗
PubMed1999

Isolation and characterization of the mouse Aire gene.

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) is a rare autosomal recessive disorder characterized by Addison's disease and/or hypoparathyroidism and/or chronic mucocutaneous candidiasis. Patients may also have other clinical symptoms both within and outside the endocrine system, mainly as a result of autoimmunity against organ-specific autoantigens. The gene for APECED has recently been identified and termed AIRE (for AutoImmune REgulator). APECED is a model of organ-specific autoimmunity and isolation and characterization of the homologous mouse gene, Aire, will provide tools for dissection of the mechanisms underlying this human disorder and defining molecular pathways involved in organ-specific autoimmunity. We have isolated and completely sequenced the mouse Aire gene which is split into 14 exons over 13 kb and encodes a predicted protein of 552 amino acids. The predicted mouse and human AIRE proteins are 71% identical and contain motifs suggestive of a transcriptional regulator. Additional conserved motifs are emerging in the AIRE/Aire proteins including a nuclear localization signal, an "ASS" domain, and a "SAND" domain. The human and mouse AIRE promoters have conserved sites for several thymus-specific transcription factors and others important in hematopoesis, consistent with its expression in rare cells of the thymus medulla, lymph nodes, and fetal liver. We have mapped mouse Aire to mouse chromosome 10 by FISH, to the same region as Pwp2 and Pfkl, confirming synteny to the corresponding region of human chromosome 21.

3' Untranslated Regions↗
PubMed1999

A testis-specific gene, TPTE, encodes a putative transmembrane tyrosine phosphatase and maps to the pericentromeric region of human chromosomes 21 and 13, and to chromosomes 15, 22, and Y.

To contribute to the creation of a transcription map of human chromosome 21 (HC21) and to the identification of genes that may be involved in the pathogenesis of Down syndrome, exon trapping was performed from HC21-specific cosmids covering the entire chromosome. More than 700 exons have been identified to date. One such exon, hmc01a06, maps to YAC 831B6 which contains marker D21Z1 (alphoid repeats) and had previously been localized to the pericentromeric region of HC21. Northern-blot analysis revealed a 2.5-kb mRNA species strongly and exclusively expressed in the testis. We cloned the corresponding full-length cDNA, which encodes a predicted polypeptide of 551 amino acids with at least two potential transmembrane domains and a tyrosine phosphatase motif. The cDNA has sequence homology to chicken tensin, bovine auxilin and rat cyclin-G associated kinase (GAK). The entire polypeptide sequence also has significant homology to tumor suppressor PTEN/MMAC1 protein. We termed this novel gene/protein TPTE (transmembrane phosphatase with tensin homology). Polymerase chain reaction amplification, fluorescent in situ hybridization, Southern-blot and sequence analysis using monochromosomal somatic cell hybrids showed that this gene has highly homologous copies on HC13, 15, 22, and Y, in addition to its HC21 copy or copies. The estimated minimum number of copies of the TPTE gene in the haploid human genome is 7 in male and 6 in female. Zoo-blot analysis showed that TPTE is conserved between humans and other species. The biological function of the TPTE gene is presently unknown; however, its expression pattern, sequence homologies, and the presence of a potential tyrosine phosphatase domain suggest that it may be involved in signal transduction pathways of the endocrine or spermatogenetic function of the testis. It is also unknown whether all copies of TPTE are functional or whether some are pseudogenes. TPTE is, to our knowledge, the gene located closest to the human centromeric sequences.

Amino Acid Sequence↗
PubMed1999

A proven case of materno-foetal transfusion determined by cytogenetic and DNA analysis.

We report a case of materno-foetal transfusion in a phenotypically normal male foetus after death in utero at the 35th week of gestation. We have used cytogenetic and polymerase chain reaction (PCR) microsatellite analysis to determine the presence of maternal cells in foetal blood collected by intracardiac puncture. In the intracardiac blood sample, maternal cells were estimated to comprise between 5 and 10% of nucleated foetal blood cells. When there is a suspicion of foetal genetic pathology, it is necessary to be aware that the foetal blood karyotype may be misrepresentative, as the analysed blood cells can indeed be of maternal origin.

Adult↗
PubMed1999

The 11 kb FGA deletion responsible for congenital afibrinogenaemia is mediated by a short direct repeat in the fibrinogen gene cluster.

Congenital afibrinogenaemia is an autosomal recessive disorder characterised by the complete absence of detectable fibrinogen. We previously identified the first known causative mutations for this disorder in a non-consanguineous Swiss family. The four affected male individuals (two brothers and their first two cousins) were shown to have homozygous deletions of approximately 11 kb of the fibrinogen alpha chain (FGA) gene. Haplotype data suggested that the deletions occurred on three distinct ancestral chromosomes, implying that the FGA region of the fibrinogen locus is susceptible to deletion by a common mechanism, but the sequences responsible for the recombination remained to be identified. Here, we report the detailed characterisation of the deletion by nucleotide sequence analysis of all three deletion junctions and comparison with normal sequences. We found that all three deletions were identical to the base-pair and probably resulted from non-homologous (illegitimate) recombination. The centromeric and telomeric deletion junctions featured both a 7 bp direct repeat, AACTTTT, situated in FGA intron 1 and in the FGA-FGB intergenic sequence and a number of inverted repeats which could be involved in the generation of secondary structures. Analysis with closely linked flanking polymorphic markers revealed the existence of at least two haplotypes, further suggesting independent origins of the deletions in this family.

Adult↗
PubMed1999

Common HLA alleles, rather than rare mutants, confer susceptibility to coeliac disease.

Coeliac Disease (CD) is a gluten sensitive enteropathy characterised by villous atrophy and crypt cell hyperplasia. It has a very strong HLA class II association to the DQ locus. The nature of the involvement of the DQ locus in the susceptibility to CD has been examined by tissue culture experiments, association and peptide binding studies. We examined the role of the DQ molecules in the pathogenesis from the perspective of a genetic family study. Using flanking microsatellite markers to the class II region of the MHC to establish the parental origin of the susceptibility DQ alleles, we have evidence suggesting that the HLA association is probably due to the necessity to have these DQ alleles in order to express CD and there is no support for the presence of a rare mutation within the DQ alleles nor any rare HLA-linked gene nearby in linkage disequilibrium with the DQ locus. This approach is applicable to other diseases demonstrating strong association with common alleles, and can be used to predict whether screening the region for rare mutations is likely to be worthwhile.

Alleles↗
PubMed1999

Phytoseiid mites on peppermint and effectiveness of Neoseiulus fallacis to control Tetranychus urticae (Acari: Phytoseiidae, Tetranychidae) in arid growing regions.

The humid-adapted species Neoseiulus fallacis (German) was the most common phytoseiid mite collected in either humid (> 100 cm annual rainfall) or arid (20-45 cm annual rainfall) mint growing regions of Washington, Oregon, Montana, Idaho, and California during 1991-1995. In experimental field plots, this predator gave excellent biological control of Tetranychus urticae Koch on mint grown under arid conditions in central Oregon when evaluated by an insecticide check method or by the caging of mites. N. fallacis is effective as a predator in arid areas probably because regular irrigation creates a humid environment in the canopy. The selective miticide propargite, when used in combination with predators, was effective at reducing high spider mite populations to below the treatment threshold faster than did N. fallacis alone.

Animals↗
PubMed1999

Deletion of the fibrinogen [correction of fibrogen] alpha-chain gene (FGA) causes congenital afibrogenemia.

Congenital afibrinogenemia is a rare autosomal recessive disorder characterized by the complete absence of detectable fibrinogen. Uncontrolled bleeding after birth from the umbilical cord is common, and spontaneous intracerebral bleeding and splenic rupture can occur throughout life. Patients respond well to fibrinogen replacement therapy, either prophylactically or on demand. Because the half-life of infused fibrinogen is essentially normal, the genetic defect is assumed to be at the level of synthesis, but no responsible locus has been identified. Preliminary studies using Southern blotting suggested that no gross structural changes of the fibrinogen genes were present in patients. We report the identification of causative mutations in a nonconsanguineous Swiss family with congenital afibrinogenemia. The four affected male individuals (two brothers and their two first cousins) have homozygous deletions of approximately 11 kb of the fibrinogen alpha-chain gene (FGA). Haplotype data suggest that these deletions occurred separately, on three distinct ancestral chromosomes, implying that the FGA region of the fibrinogen locus is susceptible to deletion by a common mechanism. Furthermore, our results demonstrate that humans, like mice, may be born without the capacity to synthesize functional fibrinogen.

Afibrinogenemia↗
PubMed1999

Family linkage study of the T-cell receptor genes in coeliac disease.

BACKGROUND: The susceptibility to coeliac disease is genetically determined by possession of certain HLA DQ alleles, together with a one or more non-HLA genes. The central role of the T-cell receptor in disease pathogenesis makes the T-cell receptor genes strong candidates as disease susceptibility genes, and previous studies had provided equivocal ambiguous results. METHODS: A pedigree based genetic linkage study was used to determine if any of the T-cell receptor genes have a role in the genetic aetiology of coeliac disease. Intragenic microsatellite markers were used to study T-cell receptor alpha, beta, and delta, while gamma was studied using two flanking microsatellites D7S484 and D7S629. RESULTS: Conventional linkage analysis was performed using the MLINK computer package. Model-free linkage analysis was performed using MFLINK. No evidence of linkage between coeliac disease and the T-cell receptor genes was found in these pedigrees. CONCLUSIONS: Mutations in the T-cell receptor genes are not implicated in the genetic aetiology of coeliac disease.

Base Sequence↗
PubMed1998

Complement opsonization is required for presentation of immune complexes by resting peripheral blood B cells.

Complement receptor 2 (CD21, CR2) is a B cell receptor for complement degradation products bound to Ag or immune complexes. The role of CD21 in mediating Ag presentation of soluble immune complexes by resting B cells was studied. Complement-coated immune complexes were formed by the incubation of influenza virus with serum from immune donors. These complexes bound to peripheral blood B cells in a complement-dependent manner. The binding required CD21 or, to a lesser extent, complement receptor 1 (CR1, CD35). B cells pulsed with immune complexes containing complement elicited a response from a panel of influenza-specific T cell clones, while those pulsed with immune complexes formed in the absence of complement did not. The expression of the early activation marker CD69 and the costimulatory molecule CD86 were not induced by CD21 ligation alone, suggesting that CD21-mediated Ag presentation occurs independently of B cell activation. Up-regulation of these markers required exposure to T cell factors elicited by the recognition of Ag derived from complement-containing immune complexes. These findings suggest that binding of Ag to CD21 enables Ag-nonspecific B cells to participate in the activation of Ag-specific T cells in a process that occurs independently of well-characterized B cell activation events.

Antigen Presentation↗
PubMed1998

Clinical reporting to primary care physicians leads to increased use and understanding of bone densitometry and affects the management of osteoporosis. A randomized trial.

BACKGROUND: A major barrier to wider use of bone densitometry has been a lack of reports that are comprehensible to primary care physicians. OBJECTIVE: To compare the effect of short technical reports and longer clinical reports on use, understanding, and acceptance of bone densitometry by primary care physicians and on management of osteoporosis. DESIGN: Randomized trial. SETTING: Osteoporosis center of a community teaching hospital. SUBJECTS: 57 primary care physicians ordering bone mineral density tests with dual x-ray absorptiometry. INTERVENTION: Physicians were randomly assigned to receive short technical reports or long clinical reports written by endocrinologists with access to clinical information. MEASUREMENTS: Physicians were interviewed by telephone after receiving at least two reports. RESULTS: Before being interviewed, physicians receiving short reports ordered a mean +/- SD of 0.72 +/- 0.71 tests per month; those receiving long reports ordered 1.30 +/- 1.21 tests per month (P = 0.002). At the first interview, 30% of physicians receiving short reports and 86% of those receiving long reports understood the bone mineral density definition of osteoporosis (P < 0.001). Receiving long reports led to more modifications in the pharmacologic treatment of osteoporosis by gynecologists (19% of patients whose reports were short and 61% of patients whose reports were long; P = 0.021) and less confusion about reports by all physicians (36% of physicians receiving short reports and 1% of those receiving long reports; P = 0.003). CONCLUSIONS: Clinical reporting of bone densitometry to primary care physicians increased use and understanding of bone densitometry, changed management of osteoporosis, and was well accepted. It may help achieve appropriate use of bone densitometry and may allow convenient dissemination of information on osteoporosis.

Absorptiometry, Photon↗
PubMed1998

Needle muscle biopsy in the investigation of neuromuscular disorders.

We have evaluated needle muscle biopsies in 220 patients with various neuromuscular disorders, using a method developed previously at Tuft's University. The method uses a 14-gauge needle propelled by an automatic device. An average of 3.5 samplings were taken per patient. Muscle samples were used for histological and molecular genetic analysis, and for the isolation of muscle satellite cells for in vitro cultures. The biopsy is well tolerated by the patients who never declined multiple samplings. Complications were few and minor, with no sequelae. In most cases the small size of the muscle specimen (ca. 15 mg per sampling) was sufficient to perform the various procedures and to yield a diagnosis. Specimens were considered insufficient for histological results in 9 patients (4%), due to technical artifacts or insufficient material. We now routinely use this method, which has several advantages over the surgical technique for most muscle biopsies.

Adolescent↗
PubMed1998

A pedigree-based linkage study of coeliac disease: failure to replicate previous positive findings.

Coeliac Disease (CD) is a gluten sensitive enteropathy characterised by villous atrophy and crypt cell hyperplasia. There is a tight HLA association between CD and the HLA DQ alleles DQA1*0501, DQB1*0201 (DQ2), arranged in either cis- or trans- configuration, are found in 98.9% of cases in Northern European populations and 80% in Greeks and Ashkenazi Jews resident in Israel. We have previously shown that the HLA alleles and CD do not co-segregate in families multiply affected with CD, suggesting that the HLA association is entirely due to the necessity to have these normal DQ alleles for CD to manifest, and that the main genetic predisposition lies at a locus other than the MHC. It is therefore possible to conduct genetic linkage studies in order to isolate the non HLA genes which predispose to CD. Recently a group conducted a genome screen for the non HLA genes in an affected sib-pair analysis and identified four non HLA loci with positive lod scores. We examined these loci using a pedigree based linkage study. Our pedigree sample consisted of a cohort of 21 families with 60 affected individuals and 125 unaffected family members. We used 11 microsatellite markers at the loci implicated and analysed the genotype data using both MLINK and MFLINK to detect linkage. The MLINK and MFLINK analyses did not provide any evidence to support the earlier findings, although the difficulties involved in analysing complex diseases mean that one cannot be certain that these regions do not harbour susceptibility loci, at least in some families.

Celiac Disease↗
PubMed1998

Effects of induced mast cell activation on prostaglandin E and metalloproteinase production by rheumatoid synovial tissue in vitro.

OBJECTIVE: To determine whether induced mast cell activation/degranulation in rheumatoid synovial explants modulates the production of prostaglandin E (PGE2), and the matrix metalloproteinases (MMPs) collagenase 1, gelatinase A, and stromelysin 1. METHODS: Synovial explant cultures were treated either with rabbit IgG anti-human IgE as a mast cell (MC) secretagogue or with non-immune rabbit IgG as controls. After 20 hours conditioned medium was assayed for the release of MC tryptase, PGE2, collagenase 1, gelatinase A, and stromelysin 1 using radioimmunoassay, enzyme linked immunosorbent assay, western blot, and zymogram techniques; tissue explants were examined immunohistologically for the relative distributions of MC tryptase, collagenase 1, and stromelysin 1. RESULTS: Over a 20 hour incubation period the MC secretagogue treated explants showed a significant increase in the quantities of released tryptase and PGE2 compared with controls. By contrast, the three MMPs showed variable values between experiments in response to MC activation; no reproducible trend of either an increased or decreased production of each MMP over control values was evident. Each MMP initially appeared as an inactive precursor form; collagenase 1 and stromelysin 1 were more effectively processed to active forms in the MC activated cultures. Immunolocalisation studies of MC activated explants showed that areas of extracellular tryptase were commonly associated with the local production of both collagenase 1 and stromelysin 1. CONCLUSION: MC degranulation induced artificially in rheumatoid synovial explant cultures consistently resulted in an increased production of PGE2 but had variable effects on the quantification of released collagenase 1, gelatinase A, and stromelysin 1. Such observations support the concept that activated synovial MCs within their native environment stimulate the production of non-MC derived PGE2 and may contribute to the regulation and processing of specific MMPs; both aspects represent important components of the inflammatory and degradative processes of the rheumatoid lesion.

Arthritis, Rheumatoid↗
PubMed1998

Mel 1a melatonin receptor expression is regulated by protein kinase C and an additional pathway addressed by the protein kinase C inhibitor Ro 31-8220 in ovine pars tuberalis cells.

The expression of the melatonin receptor is positively regulated by cAMP and negatively regulated by melatonin in the ovine pars tuberalis (PT). Furthermore, when PT cells are dispersed in primary culture, both messenger RNA (mRNA) and protein levels spontaneously increase through a process that can be blocked by melatonin, but does not involve cAMP. This suggests that other second messengers may be regulated by melatonin, which, in turn, regulates melatonin receptor mRNA and protein levels. In this study using ribonuclease protection assays, ligand binding, protein kinase C (PKC), and cAMP analysis, we demonstrate that the levels of Mel 1a mRNA and protein expression in ovine PT are reduced by phorbol 12-myristate 13-acetate in a cAMP-independent process. This is indicative of an inhibitory role for PKC in receptor regulation. Melatonin, however, does not act through PKC activation to reduce Mel 1a mRNA or protein levels. Basal PKC activity in PT cells can be inhibited by the PKC inhibitor Ro 31-8220, and this suggests that basal PKC activity may suppress Mel 1a receptor expression. Paradoxically, however, Ro 31-8220 also inhibits melatonin receptor mRNA and protein levels in PT cells by a cAMP-independent mechanism. This suggests that other undefined pathways must play an important role in the physiological self-regulation of Mel 1a receptor expression by melatonin.

Animals↗