Errors in subtractions: judged and observed frequencies.

In a first study 10 adults, aged 24-44 years, solved all 105 subtraction problems in the form M - N = , where 0 < or = M < or = 13, 0 < or = N < or = 13 and N < or = M. Each participant solved every problem 10 times and in total there were 10 500 answers. Answers, response latencies and errors were registered. Retrospective verbal reports were also given, indicating how a solution was reached: (1) via a (conscious) reconstructive cognitive process or (2) via an (unconscious) reproductive (retrieval) process. The participants made 291 errors (2.8%) when solving the subtractions in study 1. The rate of self-correction was very high, 92%. In a second study 27 undergraduate students estimated overall error rates, including self-corrected errors for the 105 subtraction problems used in the first study. Judged and actual error rates were compared. The participants systematically underestimated error rates for error prone problems and overestimated error rates for error free problems. The participants were fairly accurate when they predicted problems that were most error prone, with a hit rate of 0.67 for the (18) problems predicted as the most error prone ones. In contrast, predictions of which problems were error free were very poor with a hit rate of only 0.20 of the problems predicted as error free really having no errors in study 1. The correlation between judged error rates and frequencies for actually made errors was 0.69 for answers belonging to reconstructive solutions. In contrast, there was no significant correlation between judged and actual error rates at all for retrieved solutions, possibly reflecting the inaccessibility to consciousness of quick retrieval processes.

Asbestos fibers induce release of collagenase by human polymorphonuclear leukocytes.

The asbestos fibers chrysotile and crocidolite cause a dose-dependent release of specific granule collagenase by human polymorphonuclear leukocytes (PMNL). Release of azurophil granule elastase was induced by the asbestos fibers at higher concentrations, suggesting that asbestos fibers primarily cause the release of specific granule contents of human PMNL. Wollastonite, a fibrous silicate mineral, causes a weaker collagenase release and no elastase release. The collagenase was released in inactive, latent form. Carboxymethyl cellulose (CMC), an agent known to blunt chrysotile-induced hemolysis and production of reactive oxygen metabolites by human PMNL, specifically inhibits chrysotile-induced release of collagenase. Chrysotile asbestos was found to bind the PMNL serine proteinase cathepsin G. A role of collagenase release, production of reactive oxygen metabolites and cathepsin G binding by chrysotile for the perpetuation of the asbestos-induced alveolitis is suggested.

Effect of two particle surface-modifying agents, polyvinylpyridine-N-oxide and carboxymethylcellulose, on the quartz and asbestos mineral fiber-induced production of reactive oxygen metabolites by human polymorphonuclear leukocytes.

We studied the capacity of quartz and asbestos fibers to induce the generation of reactive oxygen metabolites in human polymorphonuclear leukocytes (PMNs) with a chemiluminescence (CL) assay. On an equal weight basis, the particulates induced CL in the following order of magnitude: chrysotile, quartz greater than amosite, crocidolite, greater than anthophyllite, wollastonite. The intensity of CL correlated positively with the Alcian blue (a cationic dye) binding capacity of the particles. Polyvinylpyridine-N-oxide (0.5 microgram/ml) inhibited completely the CL induced by quartz but had little effect on the CL induced by asbestos fibers. Carboxymethylcellulose (1.0 microgram/ml), however, reduced the CL caused by chrysotile asbestos but had no effect on the CL induced by the other particulates. Our results suggest that in addition to length and diameter, the effect of quartz and asbestos fibers on inflammatory cells will depend on surface characteristics, including the charge of the particles.

IgG and IgA enhance the chrysotile-induced production of reactive oxygen metabolites by human polymorphonuclear leucocytes.

Chrysotile asbestos fibres induce a rapid generation of reactive oxygen metabolites by human polymorphonuclear leucocytes (PMNL) in vitro. This effect was markedly enhanced by the presence of 10-200 micrograms/ml of human gammaglobulin, purified polyclonal IgG, and monoclonal IgG and IgA myeloma proteins. Purified monoclonal IgD, IgM, kappa light chain proteins, and secretory IgA inhibited this chrysotile-induced response. No enhancing effect of IgG was observed when quartz dust or opsonized zymosan were used as stimulators of PMNL metabolism. The enhancing effect of IgG was shown to depend on opsonization of the asbestos fibre. We suggest that the IgG and IgA potentiating effect on the asbestos fibre-induced production of tissue-damaging reactive oxygen metabolites by inflammatory cells is dependent on a particle-specific binding of immunoglobulin to the fibre surface, with subsequent Fc receptor-mediated effects on cells. Such an interaction between certain immunoglobulins and asbestos may explain a number of in vivo phenomena in which immunological responses (hypergammaglobulinemia, circulating immune complexes, etc.) have been shown to relate to the progression of pulmonary asbestosis. The differences between various immunoglobulin classes and monoclonal immunoglobulins could represent an individual inflammation-modulating mechanism in the development of acute or chronic pulmonary asbestosis.

Quartz-dust-induced production of reactive oxygen metabolites by human granulocytes.

We studied the effect of quartz on the production of reactive oxygen species by human polymorphonuclear leukocytes (PMN) in vitro by a chemiluminescence (CL) assay. Quartz caused a rapid dose-dependent CL response in the cells. Diamond dust used as an inert control did not stimulate the production of reactive oxygen metabolite by PMN. The quartz-induced activation of oxygen metabolism was also demonstrated by measuring oxygen consumption, nitroblue tetrazolium reduction, and superoxide and hydrogen peroxide production by PMN. Poly-vinyl-pyridine N-oxide (a quartz surface modifying agent) completely abolished the quartz-induced response, but had no effect on opsonized zymosan-induced CL response of PMN. The effect of N-acetylcysteine (a known antioxidant) was inhibitory to the CL formation induced by both quartz and opsonized zymosan. Our results are in agreement with the hypothesis that quartz-induced production of reactive oxygen metabolites is a possible mechanism by which quartz dust produces chronic inflammation and tissue injury of the lung. Agents interfering with the generation of reactive oxygen metabolites may provide a rationale for treatment of mineral-dust-induced pulmonary disease.

Titanium dioxide induced chemiluminescence of human polymorphonuclear leukocytes.

The ability of different titanium dioxides (TiO2) to induce production of reactive oxygen metabolites by human polymorphonuclear leukocytes was studied. Pure rutile or anatase preparations show only a weak chemiluminescent response. Surface-modified TiO2 causes a strong chemiluminescent response with a biphasic configuration resembling that of quartz. Sonication of the dust suspensions resulted in a strong enhancement of the chemiluminescent response, with each dust preparation showing approximately equal maximal activity. However, coated TiO2 still exhibited a different mode of cell activation. The chemiluminescence-inducing activity of the different TiO2 studied did not correlate with their hemolytic activity. As polyvinyl-pyridin-N-oxide (PVPNO) inhibits the chemiluminescence induced by coated TiO2 samples, it seems that both particle size and surface structure determine the mode and intensity of activation of human PMNL by TiO2. The results point out the need for in vivo testing and comparison of different TiO2 preparations.

Production of reactive oxygen metabolites induced by asbestos fibres in human polymorphonuclear leucocytes.

The ability of quartz and various asbestos fibres to induce the production of reactive oxygen metabolites in human polymorphonuclear leucocytes was assessed. A chemiluminescence assay showed that the activation of polymorphonuclear leucocytes was induced in the following order of effect: quartz; chrysotile A; crocidolite; chrysotile B; amosite; and anthophyllite. Only slight chemiluminescence was produced by cells exposed to wollastonites and titanium dioxide. A positive correlation was seen between production of chemiluminescence and red cell haemolysis. Our results suggest that the potential of various environmental particles and mineral fibres to induce inflammation, fibrosis, and cancer of the lung could be related to their ability to induce inflammatory cells to produce reactive oxygen metabolites.