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Biomedical subjects

J D Fraser

Publications and source records attributed to J D Fraser.

69 records · Page 4Linked to original sources
PubMed1987

Molecular cloning of matrix Gla protein: implications for substrate recognition by the vitamin K-dependent gamma-carboxylase.

Matrix Gla protein (MGP), a low molecular weight protein found in bone, dentin, and cartilage, contains 5 residues of the vitamin K-dependent amino acid gamma-carboxyglutamic acid (Gla). We have used antibodies raised against MGP and oligonucleotide probes to screen a lambda gt11 cDNA library constructed from the rat osteosarcoma cells (line ROS 17/2) that had been pretreated with 1 alpha,25-dihydroxyvitamin D3. By sequencing several cloned cDNAs, we established a 523-base-pair sequence that predicts an 84-residue mature MGP and a 19-residue hydrophobic signal peptide. The 84-residue mature rat MGP predicted from the cDNA sequence has an additional 5 residues at its C terminus (-Arg-Arg-Gly-Ala-Lys) not seen in the sequence of MGP isolated from bovine bone. The structure of rat MGP provides insight into the mechanisms by which the vitamin K-dependent gamma-carboxylase recognizes substrate. The present studies show that MGP, unlike other vitamin K-dependent proteins, lacks a propeptide. The absence of an MGP propeptide demonstrates that gamma-carboxylation and secretion of vitamin K-dependent proteins need not be linked to the presence of a propeptide or to its proteolytic removal. The propeptides of other vitamin K-dependent proteins are structurally homologous, and there is evidence that this homologous propeptide domain is important to substrate recognition by the gamma-carboxylase. Mature MGP has a sequence segment (residues 15-30) that is homologous to the propeptide of other vitamin K-dependent proteins and probably serves the same role in gamma-carboxylase recognition. Rat MGP also has a second sequence that has recently been identified in all known vitamin K-dependent vertebrate proteins, the invariant unit Glu-Xaa-Xaa-Xaa-Glu-Xaa-Cys (EXXXEXC). Since the glutamic residues in this unit are sites of gamma-carboxylation, it has been suggested that the EXXXEXC unit could allow the gamma-carboxylase to discriminate between substrate and product. The demonstration that two structures common to vitamin K-dependent proteins, the homologous propeptides domain and the invariant EXXXEXC unit, are in mature MGP indicates that des-gamma-carboxy-MGP should be an excellent in vitro gamma-carboxylase substrate for analysis of mechanisms involved in substrate recognition and product dissociation.

Amino Acid Sequence↗
PubMed1986

The complete primary structure of the T-cell receptor genes from an alloreactive cytotoxic human T-lymphocyte clone.

The complete primary structure of the cDNAs encoding the alpha and beta chains of the T-lymphocyte receptor for antigen from a human alloreactive, cytotoxic T-cell clone, L17, is presented. Sequence analysis of these genes reveals that both are related to immunoglobulins and are composed of variable, diversity (at least in the case of the Ti beta clone), joining, and constant region sequences. Comparison of the sequence of the alpha-chain cDNA to that of previously sequenced mouse and human alpha cDNAs suggests the presence of human T-cell receptor alpha D-region sequences. Southern blot analysis confirms the finding that these cDNAs represent the functional receptor genes expressed by the L17 cytotoxic T-cell clone. The availability of these full-length T-cell receptor cDNA clones from a human T-lymphocyte clone of known antigen specificity should allow an analysis of the relationship between T-cell receptor structure and function.

Amino Acid Sequence↗
PubMed1984

Mitogenic proteinases from human leukocytes.

Serine proteinase activity has been identified in purified human lymphocyte membranes, and the corresponding enzymes have been isolated from human leukocyte extracts by affinity chromatography. The localization of these enzymes on lymphocyte and granulocyte membranes has been immunochemically demonstrated. Mitogenic activity towards human lymphocytes has been demonstrated for these enzymes, and anti proteinase antibodies inhibit the growth of transformed lymphocytes. The proteinases are similar in many properties to enzymes previously isolated from human leukocytes, and reported to be involved in a wide variety of leukocyte functions.

Cell Division↗
PubMed1984

Membrane proteinases from normal and neoplastic tissues in man and the rat.

Plasma membranes were purified from rat liver, muscle and sarcoma tissues and from human liver and hepatoma tissues. The plasma membranes all contained DFP-sensitive, neutral proteolytic activity. Plasma membranes from all normal tissues contained a single DFP-binding protein of apparent molecular weight 68,000. Only the plasma membranes from tumour tissue contained a plasminogen activator; the DFP-binding proteins from these membranes were more diverse than those from the normal samples. The rat liver plasma membrane proteinase was purified. It was a labile enzyme sensitive to inhibition by DFP and by calcium ions, and with a broad substrate specificity. A similar protein was the sole DFP-binding protein in rat liver microsomes. This and the properties of the enzyme suggested a possible role in the processing and secretion of newly-synthesized protein.

Animals↗
PubMed1983

Cyclophosphamide pretreatment in tumor cryotherapy: a comparison with alternative drugs.

The method of Turk and Lagrange for modulating immune responses in favor of the cell-mediated effector arm by using single high doses of cyclophosphamide 3 days before antigen has previously been shown to cause decreased rates of local tumor recurrence when adapted as an adjunctive therapy to cryosurgery in a murine model. This series of experiments compares cyclophosphamide, azathioprine, and methotrexate against cryosurgery alone in the same therapeutic protocol. Only cyclophosphamide gave enhanced numbers of cures; azathioprine caused an increase in metastases arising concurrently with local tumor recrudescence.

Animals↗
PubMed1978

Treatment of early breast cancer.

The early follow-up of patients treated by simple mastectomy alone or simple mastectomy combined with radical radiotherapy is presented. Both groups were well matched for age, menopausal status, duration of symptoms, size of tumour, and lymph-node involvement. There was no significant difference in survival of patients in the two groups at three years, but local recurrence was significantly more frequent (28%) in the mastectomy-alone patients. Early survival was not adversely affected by radiotherapy.

Age Factors↗
PubMed1978

Host responses to cryoablation of normal kidney and liver tissue.

Following cryoablation of one kidney in Strain-2 guinea-pigs, the viable opposite kidney was assessed by functional, histological and immunopathological techniques for evidence of immunologically mediated damage. The autoantibody content of postoperative sera was also examined. Control operations involved ligation, surgical nephrectomy and the production of hepatic cryolesions. The results indicate that autoantibody production and glomerular deposition of immune complexes can occur and may cause abnormal passage of hippuran through the kidney. There is no evidence for autoallergy against highly tissue-specific determinants; the specificity, strength and time course of the reactions obtained was dependent on the site of the lesion, whether or not freezing was accompanied by ligation.

Animals↗