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J F Wright

Publications and source records attributed to J F Wright.

18 recordsLinked to original sources
PubMed1992

Identification and partial characterization of a low affinity metal-binding site in the light chain of tetanus toxin.

Tetanus toxin was shown to contain a metal-binding site for zinc and copper. Equilibrium dialysis binding experiments using 65Zn indicated an association constant of 9-15 microM, with one zinc-binding site/toxin molecule. The zinc-binding site was localized to the toxin light chain as determined by binding of 65Zn to the light chain but not to the heavy chain after separation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and transfer to Immobilon membranes. Copper was an efficient inhibitor of 65Zn binding to tetanus toxin and caused two peptide bond cleavages in the toxin light chain in the presence of ascorbate. These metal-catalyzed oxidative cleavages were inhibited by the presence of zinc. Partial characterization of metal-catalyzed oxidative modifications of a peptide based on a putative metal-binding site (HELIH) in the toxin light chain was used to map the metal-binding site in the protein.

Amino Acid Sequence↗
PubMed1991

Proteolytic fragmentation of tetanus toxin by subcellular fractions of JY, a B lymphoblastoid cell line.

Proteolysis of 125I-labelled tetanus toxin by subcellular fractions from an Epstein-Barr-virus-transformed B lymphoblastoid cell line, JY, was investigated. Fractions enriched in lysosomes and plasma membranes cleaved the toxin molecule at several sites, with a pH optimum of 5.5. N-Terminal sequence analysis of Mr-81,000, -45,000 and -35,000 proteolytic fragments indicated cleavage of the Asp-460-Leu-461, Asp-872-Glu-873 and Ile-1013-Thr-1014 peptide bonds, all sites located within the heavy chain of the toxin molecule. Additional sites near the C-terminus of the heavy chain, giving rise to low-Mr peptides, were implicated. The toxin light chain was more resistant to proteolysis. A similar pattern of fragmentation was observed with tetanus toxin biosynthetically radiolabelled with 14C-labelled amino acids, showing that the proteolysis was not an artifact caused by iodination. The proteolytic activity was inhibited by the serine proteinase inhibitor di-isopropyl phosphorofluoridate, thiol-blocking proteinase inhibitors N-ethylmaleimide and iodoacetamide, and by EDTA. These results represent a preliminary characterization of the processing in vitro of tetanus toxin by an antigen-presenting cell line.

B-Lymphocytes↗
PubMed1991

Formation of covalent C3b-tetanus toxin complexes: a tool for the in vitro study of antigen presentation.

A novel method is described for the formation and purification of covalent complexes between the complement component C3b and an antigen (tetanus toxin, TT), using purified proteins in fluid phase. C3b is generated in situ by tryptic cleavage of C3 after co-precipitation of C3 and TT in the presence of polyethylene glycol. Various parameters were analysed to optimize complex formation; under conditions which minimized the formation of covalent C3b multimers, 30% and 8% respectively of C3b and TT were incorporated into covalent one-to-one complexes which were purified using gel filtration chromatography. The linkage was localized between the alpha' chain of C3b and either the H or L chain of TT; it required the in situ formation of C3b and was partially destroyed by 1 M hydroxylamine. Spontaneous dissociation of the complex could be partly avoided by HgCl2, a thiol reagent which inhibits the esterase-like activity of bound C3b. These findings suggest the involvement of the reactive carbonyl of nascent C3b with hydroxyl groups of TT. Such C3b-TT complexes provide a defined tool to analyse the influence of antigen-bound C3b on antigen addressing and intracellular processing by antigen-presenting cells.

Animals↗
PubMed1990

C1 binding by mouse IgM. The effect of abnormal glycosylation at position 402 resulting from a serine to asparagine exchange at residue 406 of the mu-chain.

We have previously shown that IgM-Asn406, a mutant IgM which has asparagine in place of the serine which is normally found at position 406, also has an abnormally glycosylated mu-chain and is defective in complement-dependent cytolysis. Here we show by analyzing cyanogen bromide fragments from normal and mutant mu-chains that the site of abnormal glycosylation is at the neighboring position, Asn402. The cytolytic defect was shown to be due to impaired C1 binding. At physiological ionic strength, the C1 binding defect was estimated to be 12-fold, which correlates well with the measured defect in cytolytic activity; also, the severity of the defect in C1 binding by the mutant protein decreases with decreasing ionic strength. Kinetic studies showed that the difference in affinities is due to a proportional difference in the association rate for C1q. By comparing IgM made in the presence and absence of deoxymannojirimycin, we show further that the defect in cytolytic activity derives mostly from the abnormal oligosaccharide.

Amino Acid Sequence↗
PubMed1990

Some unusual features of mycobacteriosis in the cichlid fish Oreochromis mossambicus.

Adult, aquarium-reared Oreochromis mossambicus (Tilapia mossambica), which were naturally infected with Mycobacterium marinum, displayed non-healing skin ulcers and other clinical signs considered to be typical of piscine mycobacteriosis. However, in addition, they frequently had melanotic foci in the skin and spleen, due to the presence of pigment cells surrounding the cutaneous and splenic inflammation. Such melanotic foci have never been reported in response to mycobacteriosis. All fish also have variable numbers of melanomacrophages which appeared to replace pancreatic acini. The relationship of the pancreatic melanomacrophages to the pathogenesis of mycobacteriosis is uncertain, but such lesions may have contributed to the chronic cachexia associated with this case.

Animals↗
PubMed1989

Chronic inflammatory cells with epithelial cell characteristics in teleost fishes.

Certain cells that participate in the chronic inflammatory response of teleost fishes have many features typical of epithelioid cells of mammals. Such features include high metabolic activity, frequent phagolysosomes, and cytoplasmic interdigitations between adjacent cells; however, the epithelioid granulomas formed in response to certain diseases in teleost fishes also have several features associated with epithelial cells. Cases of ulcerative mycosis or acid-fast bacterial infection in Atlantic menhaden (Brevoortia tyrannus), fungal infection in silver perch (Bairdiella chrysoura), and mycobacteriosis in Mozambique tilapia (Oreochromis mossambicus) had epithelioid cells that were joined together by well-formed desmosomes with tonofilaments. "Mature granulomas" of the ulcerative mycosis-infected menhaden stained positively for cytokeratin, a cytoskeletal protein that is considered to be highly specific for epithelial cells. The consistent presence of these heretofore unrecognized epithelial features suggest that they may be characteristic of certain types of cells participating in piscine chronic inflammation.

Animals↗
PubMed1988

A mitochondrial intergenic mutation affecting processing of specific yeast mitochondrial transcripts.

The mutation in the temperature-conditional mit- mutant h56, mapped previously to the var1 gene region of Saccharomyces cerevisiae mitochondrial DNA, results in a specific inhibition of var1 protein synthesis in cells incubated at the non-permissive temperature, 36 degrees C (1). We have now characterized the mutation present in mutant h56 by DNA sequencing and found it to be an A to T transversion located 109 nucleotides upstream of the var1 reading frame. Two spontaneous revertants of mutant h56 restore the parental strain sequence at residue -109, confirming that this single base change within the 5'-untranslated region of the var1 mRNA is responsible for defective synthesis of the var1 protein. A comparison of var1 transcripts in the parental and mutant strains has shown that the mutation specifically blocks formation of var1 mRNA at 36 degrees C and leads to accumulation of precursor transcripts. Expression of the oli1 gene, co-transcribed with the var1 gene in primary transcripts, is not affected. It is concluded that the mutation in mutant h56 alters the secondary structure of the precursor RNA, inhibiting an endonucleolytic cleavage required to generate the 5' end of var1 mRNA.

Base Sequence↗
PubMed1988

C1 binding by murine IgM. The effect of a Pro-to-Ser exchange at residue 436 of the mu-chain.

We have examined a defect in complement activation in a mutant trinitrophenyl-binding pentameric murine monoclonal IgM which has serine replacing the proline normally found at position 436 in the protein. The mutant protein showed equivalent hapten binding but a 100-fold decreased ability to initiate complement-dependent lysis of trinitrophenyl-coupled erythrocytes at physiological ionic strength (mu = 0.15). C4b deposition mediated by the mutant protein was impaired to a similar degree. C1 bound by the mutant protein showed C1s to C1-s conversion, suggesting normal activation. When measured at reduced ionic strength (mu = 0.06), the C1 and C1q binding affinity of the mutant protein was approximately one-half that of the wild type. However, the C1 binding affinity of the mutant protein showed a greater dependence upon ionic strength such that at physiological ionic strength we estimate a 50-fold lower C1 binding affinity for the mutant molecule. Kinetic studies suggested that this difference in affinity was largely attributable to differences in association rates. In addition, a fixed proportion of the mutant molecules showed no C1 binding. We conclude that the defect in complement activation occurs at the level of C1 binding. Our data support a role for the C mu 3 domain (residues 340-440) in C1 binding by IgM.

Complement Activating Enzymes↗
PubMed1988

Fibrous dysplasia of the spine.

Fibrous dysplasia affecting the spine is unusual. A further 11 cases are reported and the radiological features are described. The complications and difficulties with the diagnosis of this condition are discussed.

Fibrous Dysplasia of Bone↗
PubMed1988

Spinal cord compression caused by dual pathology: a close shave with Ockham's razor.

A case of spinal cord compression in an oncology patient is presented. The compression was caused by minimal expansion of a vertebral body involved by a metastatic deposit impinging on a previously asymptomatic lipomatous spinal cord tumour. Nuclear magnetic resonance imaging clearly demonstrated both the vertebral metastasis and the intramedullary and extramedullary components of the lipomatous tumour in a single noninvasive investigation.

Aged↗
PubMed1988

The aortic pole.

Explore the source record for details and available documents.

Abscess↗
PubMed1977

A comparison of cAMP phosphodiesterases in normal, malignant, and somatic cell hybrids.

Hybrids (PCM) between a malignant mouse lymphoma suspension cell line (P388F-36) and a normal Chinese hamster fibroblastic cell line (Ch23) have already been isolated in this laboratory. Investigations were carried out on the cAMP phospodiesterases of the parents and two of these hybrids--PCM2 and PCM3. PCM3 shows a rather unusual growth characteristic in that a considerable proportion of the cells exist at any one time either in suspension or only loosely attached to the substratum, the remaining cell population existing in a monolayer form. It was found that each cell line exhibited multiple forms of the enzyme with varying affinities for cAMP. Both parents, although different, contained high-, low-, and extra-high apparent Km forms of the enzyme. The hybrids exhibited characteristics of both parental systems but were different from each other. Neither hybrid exhibited a high-Km enzyme, but both exhibited two low-Km forms. There was also a slight variation between monolayer and suspension cells of PCM3 hybrid. An attempt has been made to explain these phenomena with respect to hybridization and the growth characteristics of the cells.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1975

Neoplastic and life-span effects of chronic exposure to tritium. II. Rats exposed in utero.

A study was conducted to determine the effects on neoplasia incidence and life-span of exposure in utero to a major environmental radionuclide. Sprague-Dawley rats were continuously exposed to tritiated water (HTO) from conception through birth in doses of 0, 1, 10, 50, and 100 muCi HTO/ml body water. HTO administration was terminated at birth. Calculated cumulative doses during gestation were approximately 0, 6.6, 66, 330, and 660 rads of total body irradiation. Under these exposure conditions, the two highest doses resulted in sterile offspring. Animals surviving through 30 days postnatally were defined as the study population and observed until their deaths. Intrauterine exposures to doses up to 66 rads had no significant effects on either sex with respect to life-span, overall neoplasia incidence, incidence rate, or onset of mammary fibroadenomas. Females exposed to 330 or 660 rads were sterile and had lower incidence rates of mammary fibroadenomass than did controls; at 660 rads females had a lower incidence of overall neoplasia and reduced mean life-spans. Sterile male offspring had reduced mean longevity after irradiation at 660 rads. Regardless of dose group, females had significantly higher incidences of neoplasia and longer life-spans than males.

Adenofibroma↗
PubMed1975

Neoplastic and life-span effects of chronic exposure to tritium. I. Effects on adult rats exposed during pregnancy.

Female Sprague-Dawley rats were continuously exposed to equilibrium levels of tritiated water (HTO) during pregnancy. The tritium activities were 1, 10, 50, and 100 muCi HTO/ml body water which provided cumulative, whole-body radiation doses of approximately 6.6, 66, 330, and 660 rads. Administration of the radioisotope was terminated at parturition. Throughout their life-spans and at autopsy, the dams showed an increased incidence of mammary fibroadenomas at exposure to 330 and 660 rads. Although the data for the incidence of malignant mammary neoplasms were consistent with a linear dose response, the small numbers of tumors preclude specific definition of the dose-response curve. Postexposure life-spans for dams chronically exposed to 66, 330, and 660 rads during pregnancy were reduced by 14, 24, and 22%, respectively. Accelerated aging was also demonstrated in these rats: The mean age for mammary fibroadenoma onset decreased with an increasing dose of radiation.

Adenofibroma↗