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Biomedical subjects

E Simpson

Publications and source records attributed to E Simpson.

At least 73 records · Page 4Linked to original sources
PubMed1990

Prevention of insulin-dependent diabetes mellitus in non-obese diabetic mice by transgenes encoding modified I-A beta-chain or normal I-E alpha-chain.

Insulin-dependent diabetes mellitus (IDDM) is a disease with an autoimmune aetiology. The inbred non-obese diabetic (NOD) mouse strain provides a good animal model of the human disease and genetic analysis suggests that, as in man, at least one of the several genes controlling the development of IDDM is linked to the major histocompatibility complex. The NOD mouse does not express I-E owing to a deletion in the promoter region of the I-E alpha-chain gene, and the sequence of NOD I-A beta-chain in the first external domain is unique with His 56 and Ser 57 replacing Pro and Asp, respectively, at these positions. There has been considerable interest in the role amino acid 57 might have in conferring susceptibility to autoimmune diseases, including IDDM. The presence of a charged residue (such as Asp) at this position might affect the conformation of the peptide binding groove. But it could be assumed that Pro 56 gives rise to a different conformation of I-A beta-chain than does His 56. We therefore constructed transgenic NOD mice in which the transgene encoded a modified A beta nod with Pro 56, and studied its effect on the development of IDDM in this mouse strain. Previous studies have suggested that NOD mice expressing I-E as a result of the introduction of an I-E alpha-chain (E alpha) transgene are protected from the development of insulitis and hence IDDM. To explore further the protective effect of this molecule we constructed a second class of transgenic NOD mouse carrying an E alpha d transgene. Both transgenes protected the mice from IDDM, but this was not associated with a complete deletion of any T cells expressing commonly used T-cell receptor V beta genes.

Animals↗
PubMed1990

Characterization of the anticoagulant activities from a Brazilian arrow poison.

A recent report indicated that an arrow poison used by the native Indians of Rondonia, Brazil, to kill small animals was associated with profuse bleeding. The arrow poison was prepared from the bark of a tree, known locally as Tike-Uba. We have obtained bark and sap specimens from this tree and have characterized a potent anticoagulant activity in both the crude bark and sap samples as well as in more highly purified preparations. An aqueous extract of the bark significantly prolongs both prothrombin times and activated partial thromboplastin times in plasma based assays. Further fractionation of the bark extract and sap by molecular weight indicated that all of the anticoagulant activity could be isolated in a molecular weight fraction of equal to or greater than 30,000 daltons. The anticoagulant activity was also further purified by C-18 reverse phase chromatography. When highly purified preparations of the anticoagulant activity from the Tike-Uba tree were examined in specific blood coagulation enzyme assays utilizing chromogenic substrates, the highest inhibitory potency was found versus thrombin, followed by factor Xa. These studies establish the presence of a compound(s) in a Brazilian arrow poison, which potently disrupts mammalian blood clotting, and which may account for some of the observed toxicities associated with the arrows.

Amino Acids↗
PubMed1990

Restriction fragment length polymorphisms in the major histocompatibility complex of the non-obese diabetic mouse.

The inbred non-obese diabetic (NOD) mouse is a spontaneous model for insulin-dependent diabetes mellitus (IDDM). As in man and BB rats, IDDM in the NOD mouse has an autoimmune aetiology. The disease is controlled by several genes, one of which, Idd-1, has been mapped to the major histocompatibility complex (MHC) on chromosome 17. However, Idd-1 has not yet been identified. To facilitate the identification of Idd-1 we have further analysed the MHC region for restriction fragment length polymorphisms and we find that the NOD mouse has a distinct haplotype: H-2K1nod Kd A beta nod A alpha d E beta nod TNF-alpha beta. In addition, the NOD mouse shows some similarities with the H-2b haplotype in the Q region, in that either the Q7 or the Q9 gene seems to be like that in the b-haplotype and that the Qa2 antigen is expressed, while other parts of this region are distinct from the b- as well as the d- haplotype. In contrast, the sister strain, the non-obese normal (NON) mouse, derived from the same cataract-prone line of mice as the NOD mouse, has an MHC Class I region indistinguishable from the b-haplotype, but the MHC Class II region is distinct from the NOD mouse as well as the b-, d- and k-haplotype.

Animals↗
PubMed1990

The involvement of Ly2+ T cells in beta cell destruction.

The non-obese diabetic (NOD) mouse is considered to be a good model of human Type I diabetes mellitus. Both sexes develop insulitis starting at about 6 weeks of age, and onset of diabetes follows at about 30 weeks in females, but later and much less frequently in males. In some mice (but not all) infiltration of the islets leads to selective destruction of insulin-producing beta cells, which is marked by clinically overt diabetes and is thought to be an autoimmune response mediated by T cells. Both L3T4+ and Ly2+ cells have been implicated in the destructive process and we have used an in vivo transfer system, together with histological studies on the pancreas, to demonstrate the essential role played by Ly2+ T cells in the destruction of beta cells in diabetic mice.

Animals↗
PubMed1990

Canadian therapists' priorities for clinical research: a Delphi study.

Clinically relevant physical therapy research questions were developed by a Delphi technique among 55 teaching hospital physical therapists. The Delphi technique used in this study involved three rounds of questionnaires that included characteristics of anonymity, feedback, ranking with statistical scoring, and use of informed respondents. Fifty-eight initial research questions were narrowed to 11 according to their potential benefit for the patient, for the practice of physical therapy, and for decreasing health care costs. A literature review revealed that each of the 11 questions were as yet unanswered. The use of the survey results to guide and plan for clinical research in physical therapy is discussed.

Canada↗
PubMed1989

A glycophospholipid anchor is required for Qa-2-mediated T cell activation.

A number of lymphocyte surface proteins are anchored in the cell membrane by glycophosphatidyl inositol (known as GPI) linkages instead of hydrophobic protein domains. Treatment of mouse T lymphocytes with antibodies specific for two such proteins, Thy-1 and Ly-6, are known to induce proliferation. We have found that antibodies specific for Qa-2, a GPI-anchored class I histocompatibility antigen, can also activate mouse T cells. To determine whether the GPI-anchor is important for this pathway of cell activation, we produced transgenic mice expressing either normal GPI-anchored Qa-2, or Qa-2 molecules with a membrane-spanning protein domain derived from H-2. Our studies show that only lymphocytes from transgenic mice carrying GPI-anchored forms of Qa-2 can be activated in vitro by Qa-2-specific antibodies. We also show that transgenic mouse T cells expressing a GPI-anchored form of H-2Db can be activated by anti-H-2Db antibodies. These results strongly indicate that the GPI-anchor is critical for this pathway of T cell activation.

Animals↗
PubMed1989

Antistasin, a leech-derived inhibitor of factor Xa. Kinetic analysis of enzyme inhibition and identification of the reactive site.

Antistasin is a 119-amino acid protein isolated from the salivary glands of the Mexican leech Haementeria officinalis. The determination of the primary structure of antistasin revealed that the protein is highly disulfide-bonded with a 2-fold internal homology. Antistasin exhibits a potent anticoagulant activity purportedly due to the selective inhibition of Factor Xa (Tuszinsky, G. P., Gasic, T. B., and Gasic, G. J. (1987) J. Biol. chem. 262, 9718-9723). In the present study a detailed kinetic analysis of the inhibitory interaction between antistasin and Factor Xa was performed. In addition, the specificity of antistasin was examined by testing its ability to inhibit a variety of serine proteinases. Utilizing purified antistasin and a tripetidyl p-nitroanilide substrate, antistasin was shown to act as a reversible inhibitor of Factor Xa which exhibits slow-tight binding kinetics. Antistasin reacts stoichiometrically with Factor Xa with inhibition displaying a mixed, primarily competitive type. The inhibition is partial in the presence of Ca2+ and becomes complete in the absence of Ca2+. The estimated dissociation constant for the enzyme-inhibitor complex is between 0.31 and 0.62 nM. After binding to Factor Xa, antistasin is cleaved at a single site to yield a modified inhibitor. Automated gas-phase sequence analysis of the modified inhibitor indicates the arginine residue at position 34 in antistasin occupies the P1 position of the reactive site. These data indicate that the leech has evolved a highly selective and potent inhibitor of coagulation Factor Xa that shares several mechanistic similarities with other serine proteinase inhibitors.

Amino Acid Sequence↗
PubMed1989

Isolation and structural characterization of a potent inhibitor of coagulation factor Xa from the leech Haementeria ghilianii.

The present work reports the discovery and characterization of an anticoagulant protein in the salivary gland of the giant bloodsucking leech, H. ghilianii, which is a specific and potent inhibitor of coagulation factor Xa. The inhibitor, purified to homogeneity, displayed subnanomolar inhibition of bovine factor Xa and had a molecular weight of approximately 15,000 as deduced by denaturing SDS-PAGE. The amino acid sequence of the first 43 residues of the H. ghilianii derived inhibitor displayed a striking homology to antistasin, the recently described subnanomolar inhibitor of factor Xa isolated from the Mexican leech, H. officinalis. Antisera prepared to antistasin cross-reacted with the H. ghilianii protein in Western Blot analysis. These data indicate that the giant Amazonian leech, H. ghilianii, and the smaller Mexican leech, H. officinalis, have similar proteins which disrupt the normal hemostatic clotting mechanisms in their mammalian host's blood.

Amino Acid Sequence↗
PubMed1989

Florid radiological appearance of megakaryoblastic leukaemia--an aid to earlier diagnosis.

Accurate diagnosis of leukaemia is essential to enable appropriate treatment. The diagnosis is made by cytological and cytochemical techniques but radiology may, however, serve a very useful role in first suggesting a diagnosis. We present here four cases of megakaryoblastic leukaemia (AML FAB classification M7), three of which have strikingly similar unusual radiological changes. A review of the literature suggests this condition has previously been diagnosed as acute or malignant myelofibrosis, and the megakaryoblastic nature of the disease was not recognised. The presence of these radiological features may therefore prompt specific immunocytochemical testing, in a disease that is otherwise difficult to diagnose early.

Bone and Bones↗
PubMed1989

Minor transplantation antigens: their role in shaping the T cell repertoire.

Minor transplantation, or histocompatibility (H), antigens are the targets of host-versus-graft (hvg) and graft-versus-host (gvh) reactions that occur when organs or tissues are exchanged between members of the same species who, although genetically not identical, are matched for their major histocompatibility complex (MHC) encoded transplantation antigens. Genes encoding minor H antigens map outside the MHC, on a number of different chromosomes. Whilst gvh and hvg reactions against individual minor H antigens are relatively weak, certainly in comparison with such reactions against MHC antigens, the presence of multiple minor H differences (the situation encountered in man) gives rise to very vigorous reactions that can endanger the survival of graft or host, or both. This is the pathological role of minor H antigens and, indeed, it was this role which was first designated to the MHC antigens, before their physiological role as guidance molecules for T lymphocytes was discovered. Recently, a potential physiological role for minor H antigens has been uncovered by the finding that the presence of certain minor H alleles in mice leads to removal in the thymus (negative selection) of all those T cells expressing a particular T cell receptor (TCR) gene. Such cells therefore never reach the periphery, where they might otherwise give rise to autoimmune reactions. The T cell repertoire is thus moulded by at least some minor H antigens, which may therefore be regarded as non-MHC immune response genes. Furthermore, T cell receptor usage by T cells specific for allogeneic minor H antigens appears not to be representative of T cell receptor usage in the peripheral pool.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Quantitative computed tomography reflects vertebral fracture morbidity in osteopenic patients.

We studied the relationship between spontaneous vertebral compression fractures and lumbar vertebral trabecular bone density in 69 consecutive patients with suspected osteopenia. Seven had biopsy-confirmed osteomalacia. The remaining 62 were divided into three groups: group 1--asymptomatic patients suspected of having osteopenia on plain films, but with no vertebral compression fractures (N = 24); group II--those with one to five vertebral compression fractures (N = 16); and group III--those with six or more vertebral compression fractures (N = 22). A quantitative computed tomographic (QCT) scan of the lumbar spine was performed on all patients. Patients in group I had QCT values of 94 +/- 23 mg/cm3 (mean +/- SE); those in group II had QCT values of 66 +/- 28 mg/cm3; and those in group III had values of 34 +/- 28 mg/cm3. There were significant differences among all groups (P less than .001), although there was considerable overlap of individuals among the groups. There was no significant difference between the mean QCT value of patients with one compression fracture and the value of those with between two and five compression fractures. Patients with biopsy-proven osteomalacia had higher vertebral trabecular bone density than patients with osteoporosis and compression fractures. Our study provides evidence suggesting a strong inverse relationship between QCT-measured vertebral bone density and the presence of vertebral compression fractures in a group of osteopenic patients.

Absorptiometry, Photon↗
PubMed1989

Mapping minor H genes.

The manner in which minor histocompatibility (H) antigens have been defined in mouse and man, in vivo and in vitro, is considered. Chromosomal mapping of minor H genes using T-cell clones is illustrated, with particular reference to the H-Y antigen gene, using the sex-reversing translocation Sxr of mouse and the Sxr' mutation derived from it. A number of minor H antigen-specific T-cell clones restricted by class I or class II major histocompatibility complex (MHC) molecules are described, together with information about their phenotypes and T-cell receptor usage.

Animals↗
PubMed1988

The amino acid sequence of antistasin. A potent inhibitor of factor Xa reveals a repeated internal structure.

Antistasin is a 15-kDa protein from the salivary glands of the Mexican leech, Haementeria officinalis, which manifests anticoagulant activity by inhibiting factor Xa. Previous work demonstrating the presence of this activity in salivary gland extracts and its partial purification has been reported (Tuszynski, G. P., Gasic, T. B, and Gasic, G.J. (1987) J. Biol. Chem. 262, 9718-9723). The present study includes further purification to homogeneity of antistasin and its subsequent fragmentation and complete amino acid sequence determination. The protein, which possesses 119 amino acid residues, is blocked at its amino terminus by the presence of a pyroglutamic acid residue and has an unusually high cysteine content, with 20 cysteine residues. The primary structure of antistasin shows no homology to hirudin, a 65-residue anticoagulant protein from the medicinal leech, Hirudo medicinalis. Of great interest is the finding of significant internal homology within antistasin where a 2-fold internal repeated structure is observed. At least four isoforms of antistasin have been identified in leech salivary gland extracts by high performance liquid chromatography analysis, and partial amino acid sequence analysis of these isoforms indicates they differ by 1 or 2 amino acid residues.

Amino Acid Sequence↗
PubMed1988

Identification of novel proteins synthesized in bone cells by antibody screening of a cDNA expression library.

Novel proteins synthesize predominantly in bone have been identified by antibody screening of bone cell cDNA expression libraries. Two unique cDNAs were identified whose structures do not match any known nucleic acid or protein sequence in the NIH computer bank. The first cDNA clone, BP-I, encoded a mRNA of 2300 bases in size which was expressed at high levels in 17/2.8 rat osteosarcoma cells, rat calvarial bone cells and placenta. A second clone, BP-II, encoded a mRNA of 1500 bases which was expressed at high levels in 17/2.8 osteosarcoma cells and in salivary gland. Expression of both mRNAs in osteosarcoma cells was modulated by the calciotropic hormone, vitamin D. Southern blot analyses indicated that the two cDNAs represented distinct, single copy genes in the rat genome. These novel gene products may serve as potential new markers to study bone turnover in metabolic bone disease.

Amino Acid Sequence↗
PubMed1988

Rearrangement of T-cell receptor and immunoglobulin heavy chain genes in childhood acute mixed lineage leukaemia.

Rearrangement of the beta and gamma chain genes of the TCR gene complex and of the Ig heavy chain genes were examined in three cases of childhood acute mixed lineage leukaemia. Blast cells, classified morphologically as acute lymphoblastic leukaemia (ALL) in one child and acute non-lymphocytic leukaemia (ANLL) in the other two, all co-expressed markers associated with both T (CD7, TdT) and myeloid (CD33) cells. Cytogenetic analysis detected abnormalities associated with myeloid leukaemia. Immunoglobulin heavy chain genes were not rearranged in two patients but a novel rearrangement was seen in the third. No rearrangement of the beta or gamma chains of the T-cell receptor complex were seen. Acute mixed lineage leukaemia may thus arise from a pluripotent precursor cell capable of both lymphoid and myeloid differentiation.

Antigens, Differentiation↗