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Biomedical subjects

N Matthews

Publications and source records attributed to N Matthews.

At least 55 records · Page 3Linked to original sources
PubMed1991

Smoking, humoral immunity, and ulcerative colitis.

Since ulcerative colitis predominantly affects non-smokers and ex-smokers we have examined the possibility that smoking modifies the humoral immune response to an antigenic challenge from the gut lumen. Gut lavage was used in healthy subjects and patients with ulcerative colitis, including both smokers and non-smokers. Antibodies in the intestinal fluid to Escherichia coli (five pooled serotypes), Candida albicans, gliadin, ovalbumin, and beta lactoglobulin were measured by ELISA to determine specific antibody concentrations of IgG, IgA, and IgM classes. Total IgG, IgA, and IgM were also measured in intestinal secretions and serum. In addition, circulating antibody concentrations of IgG, IgA, and IgM to three gut commensals - E coli (five pooled serotypes) C albicans, and Poroteus mirabilis were measured. There was a significant reduction in the IgA concentration in intestinal fluid of smokers with ulcerative colitis compared with healthy non-smoking controls. No other significant differences were found between the groups. Overall, these data are not consistent with the idea that smoking suppresses immune responses in the gut and suggest that the effect of smoking in colitis is mediated by another mechanism.

Adult↗
PubMed1990

Differential augmentation by recombinant human tumor necrosis factor-alpha of neutrophil responses to particulate zymosan and glucan.

Zymosan (Z) and its major insoluble carbohydrate component beta-linked glucan activate human neutrophils (PMN) through a trypsin-sensitive recognition mechanism. This mechanism is believed to involve the PMN CR3R. Both Z and glucan generated dose and time-dependent release of the secondary lysosomal granule marker vitamin B12 binding protein, leukotriene B4 (LTB4) and superoxide from PMN and were phagocytosed with similar dose-dependent kinetics. The PMN superoxide and LTB4 responses to glucan; however, were consistently greater than those to the same doses of Z. The phagocytosis of both particles was significantly reduced after partial digestion with beta-laminarinase but not beta-glucosidase or alpha-mannosidase suggesting a recognition mechanism dependent on intact beta-1,3-glucosidic bonds in both particles. TNF-alpha (rhTNF-alpha) promoted a time- and dose-dependent increase in the expression of PMN CR3 up to 60 min. The increased expression of CR3 was paralleled by the release of the secondary lysosomal granule marker vitamin B12-binding protein. This granule contains a population of CR3R in its boundary membrane and it is the fusion of this membrane with the plasma membrane that may represent the mechanism by which CR3 expression is increased. Preincubation of PMN with 10(-9)M rhTNF-alpha augmented phagocytosis, LTB4, and superoxide generation by PMN in response to activation by Z. In contrast, none of the responses to glucan was significantly increased after incubation with rhTNF-alpha. These differences suggest a lack of absolute homology between the recognition mechanisms for zymosan and glucan and that there is a component of the recognition mechanism for zymosan that is independent of that for glucan and is up-regulated after rhTNF-alpha pretreatment.

Glucans↗
PubMed1990

Tumour cells which develop resistance to cytolysis by tumour necrosis factor have a different glycoform of a 105-kDa glycoprotein and lose the capacity to invade and metastasize.

A plastic-adherent variant of human myelomonocytic leukaemia cells (U937) is highly susceptible to direct TNF cytolysis in vitro. Previously, we found that a subline selected for resistance to TNF cytolysis (U937/R) was much less motile and more plastic-adherent than the parental line. In the present study we show that U937 and U937/R cells have different glycoforms of a 105-kDa cell-surface glycoprotein. This protein is predominantly N-glycosylated and has the physicochemical properties of the LAMP-I glycoprotein. In nude mice, U937 cells are highly malignant whereas U937/R cells form a benign, encapsulated tumour. Therefore, possession of a different glycoform of the 105-kDa glycoprotein by U937/R cells correlates not only with loss of TNF susceptibility but also with reduced invasiveness and metastasis.

Cell Line↗
PubMed1990

Agents which modify colonial morphology of tumor cells also affect acid vesicle function and fibronectin deposition in the extracellular matrix.

The tumor cell line U937A is motile, weakly plastic-adherent and forms large, loosely packed colonies in vitro and is invasive and metastatic in vivo. U937A/R, a mutant selected for resistance to killing by tumor necrosis factor (TNF), is less motile, more adherent and forms small, tightly packed colonies and is not invasive or metastatic. U937A and U937A/R also have differing cytoplasmic distributions of acid vesicles, and unlike U937A, U937A/R fails to deposit fibronectin into its extracellular matrix. In this study we have sought reagents that could convert "loose" U937A cells into the nonmetastatic, "tight" colonial phenotype. Six effective reagents were found: wheat germ agglutinin, phytohemagglutinin-L, dexamethasone, chloroquine, promethazine, and monensin. All 6 reagents caused swelling and/or redistribution of acid vesicles but phytohemagglutinin-L, dexamethasone, and monensin also reduced fibronectin deposition in the extracellular matrix. Therefore, these agents probably reduce motility by interference with recycling of cell surface receptors through acid vesicles and also in some cases by altering the extracellular matrix.

Cell Movement↗
PubMed1990

Colonial morphology of tumour cells and susceptibility to cytolysis by tumour necrosis factor. The role of cellular fibronectin deposition in the extracellular matrix.

The tumour cell lines U937A and L929 form large, loosely packed colonies in vitro and can be killed by the cytokine tumour necrosis factor (TNF). In contrast, their TNF-resistant mutants U937A/R and L929/R form tightly packed colonies. Since cells which form loose colonies have increased metastatic potential it is important to understand the factors governing colonial morphology. To this end, we have compared the extracellular matrices (ECMs) of the 'loose' lines, U937A and L929 with their 'tight' mutants. By immunofluorescence, a polyvalent anti-U937A serum revealed a fibrillar network in the ECMs of the 'loose' lines which was absent in the 'tight'. On Western blotting of ECMs the antiserum detected an additional 300 kDa protein in the 'loose' lines which was subsequently shown to be cellular fibronectin. The four lines secreted comparable amounts of fibronectin and this was qualitatively indistinguishable between 'loose' and 'tight' cells by peptide mapping or lectin binding. It is concluded that the differences in colonial morphology are due to the 'tight' mutants' inability to incorporate fibronectin into the ECM.

Autoradiography↗
PubMed1990

The selective augmentation by recombinant human tumour necrosis factor-alpha of neutrophil responses to pathogenic Escherichia coli.

Endotoxin release may amplify the neutrophil (PMN) responses to bacterial infection through the release of monocyte-derived tumour necrosis factor (TNF). The present study was designed to assess the effect of recombinant human TNF-alpha (rhTNF-alpha) on the in vitro response of human PMN to two defined strains of pathogenic Escherichia coli. In the absence of rhTNF-alpha, a P-fimbriate strain caused significant release of the PMN secondary granule marker vitamin B12-binding protein (B12 BP), and a low level of release of leukotriene B4 (LTB4). Type 1-fimbriate strain 504, however, stimulated the release of the primary granule marker myeloperoxidase (MPO) and PMN chemiluminescence (CL), in addition to B12 BP and LTB4 release. Following rhTNF-alpha (10(-9) M) pretreatment, the release of LTB4 by PMN stimulated with the P-fimbriate strain was synergistically augmented, while B12 BP and MPO release were additively increased. In contrast, rhTNF-alpha did not significantly affect any of the responses by the type 1-fimbriate strain. These results suggest selectivity in the priming of PMN by rhTNF-alpha and confirm the independence of PMN responses to phagocytic stimuli.

Cells, Cultured↗
PubMed1990

Zymosan-induced leukotriene B4 generation by human neutrophils is augmented by rhTNF-alpha but not chemotactic peptide.

Tumour necrosis factor (TNF) is a mediator of inflammation that has been shown to enhance neutrophil responses to soluble and particulate stimuli. The release of leukotriene B4 (LTB4) by human neutrophils stimulated by unopsonized zymosan was measured in the presence or absence of recombinant human TNF-alpha (rhTNF-alpha) preincubation. There was a threefold increase in the LTB4 response at an optimal TNF concentration of 10(-9) M and an optimal preincubation time of 10-20 min. A similar time and dose dependency was observed for CR3 receptor expression and for the release of the secondary lysosomal granule marker, vitamin B12-binding protein. In contrast, the chemotactic peptide formyl-methionyl-leucyl-phenylalanine (FMLP), although stimulating an increase in both CR3 receptor number and in particle phagocytosis, failed to induce an increase in LTB4 release in response to zymosan. In addition, the present study demonstrated that, unlike FMLP, the exocytotic mechanism for secondary granule release by rhTNF-alpha functioned in the absence of a rise in cytosolic free calcium. Furthermore, it was independent of changes in cyclic nucleotide concentrations and did not require an intact cytoskeleton. Thus the capacity of rhTNF-alpha to amplify the neutrophil response to zymosan through the CR3 receptor appears to be related to the amplification of post-membrane events as well as to an increase in the number of functionally active receptors.

Antigens, CD↗
PubMed1989

Development of tumour cell resistance to tumour necrosis factor does not confer resistance to cytotoxic drugs.

Tumour necrosis factor (TNF) is a protein product of macrophages with potential anti-cancer activity. As with other anti-cancer agents, tumour cells can develop resistance to the cytotoxic effects of TNF. The aim of his study was to see whether development of resistance to TNF resulted in a concomitant resistance to other anti-cancer agents, in particular those associated with multidrug resistance. Three TNF-susceptible tumour cell lines (L929, U937 and RK13) and their TNF-resistant sublines were compared for susceptibility in vitro to several cytotoxic drugs. The TNF-resistant sublines were not significantly more resistant to these drugs. In addition, an L929 subline selected for resistance to actinomycin D retained its susceptibility to TNF. These observations show that tumour cell resistance to TNF develops independently of resistance to cytotoxic drugs.

Animals↗
PubMed1989

Relationship between tumour cell morphology, gap junctions and susceptibility to cytolysis by tumour necrosis factor.

Tumour necrosis factor (TNF) is directly cytolytic to certain tumour cell lines in vitro, although TNF-resistant variants can be selected from these susceptible lines by exposure to TNF. While studying TNF-susceptible L929 cells and their resistant variant, L929/R, we noted that within L929 colonies the cells were widely spaced whereas they were closely packed in L929/R colonies. L929/R cells also adhered more strongly to plastic and differed from L929 in cell shape. Similar observations were made with TNF susceptible and resistant variants of two other cell lines (RK13 and a plastic adherent U937 subline). The tendency of resistant cells to grow closely together suggests the possibility of inter-cell communication for the TNF resistant state. However, like L929 and U937, L929/R and U937/R did not communicate by gap junctions and we could find no evidence of extracellular mediators of TNF resistance. Rather the differences in colonial morphology, cell shape and plastic adherence may be secondary to an underlying mechanism which defines TNF susceptibility/resistance.

Animals↗
PubMed1989

Chemical synthesis, expression and product assessment of a gene coding for biologically active human tumour necrosis factor alpha.

A gene encoding human tumour necrosis factor alpha (TNF-alpha) has been chemically synthesized, cloned and expressed to yield a biologically active protein in Escherichia coli. The 480-bp gene was assembled by enzymic ligation of 32 oligonucleotides, cloned directly into M13mp18 for sequence verification and expressed in the broad host range high-level expression vector pMMB66EHST. Expressed recombinant TNF-alpha was shown to have the correct molecular weight, processed N-terminal sequence, antibody cross-reactivity and tumour cell killing activity. The expression product of the synthetic gene has been purified to homogeneity by a two-step ion-exchange procedure and the purified material shown to be active.

Amino Acid Sequence↗
PubMed1989

Tumour necrosis factor activity in joint fluids from rheumatoid arthritis patients.

Although tumour necrosis factor (TNF) was first studied as an anti-cancer agent it is now recognized as a potent mediator of inflammation and could potentially play a role in rheumatoid arthritis. In this study TNF activity has been sought in fluids from arthritic joints. TNF was assayed by a well established bioassay which depends upon cytolysis of particular tumour cell lines and which has a limit of detection of c. 25 pg/ml. Of the 92 joint fluids tested (70 rheumatoid and 22 others) only three had demonstrable TNF activity. Despite this, joint fluid cells from all 14 patients tested (12 rheumatoid and two others) had the ability to synthesize TNF on stimulation in vitro. Subsequently it was shown that joint fluids contain a macromolecule which inhibits TNF activity in cytolytic assays and which may mask low levels of TNF activity in joint fluids.

Arthritis↗
PubMed1989

Photographic and spectroscopic correlations of human cataracts.

Intracapsular cataracts obtained within 3 h after surgical extraction were photographed with the CCRG technique and immediately subjected to fluorescence spectroscopy followed by 31P- and 13C-nuclear magnetic resonance (NMR) spectroscopy. Fluorescence spectroscopy demonstrates an excellent correlation between nontryptophan fluorescence intensities and lens color. An interesting correlation was also observed between the degree of light scatter as determined by the 290-nm excitation peak for intrinsic lens tryptophan fluorescence and the CCRG (photographic) appearance of these cataractous lenses. Based on 100 cataracts analyzed, there is a strong correlation between this kind of light scattering measurement and the type and degree of lens opacification. A similar correlation is evident with the 31P-NMR organophosphate profiles in the lenses in which the sugar phosphate levels are elevated only in diabetic patients with cataracts ('diabetic cataracts'). Aside from fluorescence and 31P-NMR spectroscopy, selected lenses were also incubated with 5.5 nM 13C-glucose as soon as they were obtained, and the foregoing spectroscopy was performed, followed by 13C-NMR analyses to detect and monitor for sorbitol accumulation in young versus old normal lenses and in diabetic cataracts. These studies clearly demonstrate a direct correlation between nontryptophan-fluorescent chromophore levels, light scattering (determined by tryptophan excitation peaks), lens age and cataract type. In addition, the organophosphate profiles clearly delineate the diabetic cataracts, and the 13C-NMR spectra correlate well with the age-related decrease in aldose reductase activity.

Aged↗
PubMed1989

A case of hereditary combined deficiency of complement components C6 and C7 in man.

Immunological investigation of a patient presenting with candidiasis and toxoplasmosis revealed a combined deficiency of C6 and C7. Deficiency of C6 was total, but small amounts (less than 1 microgram/ml) of apparently normal C7 were present in the serum. All family members (three sibs and both parents) were heterozygous for the combined deficiency. This is only the second reported case of combined homozygous deficiency of the closely linked and immunochemically similar proteins C6 and C7, and only the third kindred in which this defect has been demonstrated.

Adult↗
PubMed1988

Antibodies to influenza A in a cluster of children with juvenile chronic arthritis.

In this study of 41 patients with progressive juvenile chronic arthritis (JCA), born between 1946 and 1970, it was noticed that 14 were born in the same year (1963). The possibility of a common environmental factor was therefore investigated. Records showed that an epidemic of influenza A H2N2 was present in that year, and the study shows that JCA patients born in 1963 still have a higher level of antibody to influenza A H2N2 than JCA patients born in other years or age-matched controls. This elevation is not seen in a survey of three control viruses. Since this group developed their clinical JCA after the appearance of influenza A H3N2 in 1977, it is suggested that these patients developed a progressive arthropathy because they had been pre-sensitized to influenza A by contact with an earlier strain when in utero.

Adolescent↗
PubMed1988

Involvement of phospholipase A2 activation in tumour cell killing by tumour necrosis factor.

Earlier studies have indicated a possible role for arachidonate metabolism in the direct cytolysis of tumour cells by tumour necrosis factor (TNF) in vitro. In this study, the involvement of arachidonate metabolism has been investigated further with the following results: (i) Cytolysis of human U937 tumour cells by recombinant TNF was reduced by dexamethasone and quinacrine, agents which inhibit phospholipase A2. (ii) U937 and L929 cells, which are susceptible to TNF cytolysis, released arachidonic acid and its metabolites within 5 hr of TNF challenge, before cell death was apparent. In contrast, U937/R and L929/R, which are resistant to the cytolytic effects of TNF, did not release arachidonate products on TNF challenge. (iii) rTNF cytolysis of U937 cells was not reduced by inhibitors of the cyclo-oxygenase and lipo-oxygenase pathways of arachidonic acid metabolism. Cytolysis was reduced, however, by inhibitors of the arachidonate metabolic pathway involving cytochrome P450-dependent reductase, but only at reagent concentrations that also inhibited phospholipase A2 activity. Overall, these observations indicate a role for phospholipase A2 but not for arachidonic acid or its metabolites in the direct cytolysis of tumour cell lines by TNF.

4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyraz↗
PubMed1987

Measurement of antibodies to Candida albicans as a screening test for humoral immunodeficiency.

In screening for defects in humoral immunity, as well as measuring serum immunoglobulins it is advisable to have some measure of antibody production, e.g., immunising with a test antigen and measuring the antibody response some days later. However, this delay may be inconvenient and requires a second blood sample. An alternative is to test for antibody to a widespread commensal organism to which the patient must have been repeatedly exposed. The measurement of antibody to E. coli by haemagglutination has been previously used for this purpose. We report here that an equally good and simpler alternative is to measure antibodies to the commensal Candida albicans by immunofluorescence. Using a polyvalent conjugate, all 114 blood donors tested had antibody titres greater than 8 to C. albicans; similar responses were noted in 20 children (aged 6 months-16 years) without recurrent infections. In contrast, anti-candida responses were low or absent as expected in patients with hypogammaglobulinaemia but also in some patients with other immunodeficiency diseases. Overall candida immunofluorescence closely paralleled E. coli haemagglutination.

Antibodies, Fungal↗