Search PubMed⌕ Search

Biomedical subjects

R A Stockley

Publications and source records attributed to R A Stockley.

At least 127 records · Page 7Linked to original sources
PubMed1990

Neutrophil activation--an important cause of tissue damage during liver allograft rejection?

Although neutrophils have been implicated as mediators of tissue damage in a variety of conditions, their role in graft rejection has not previously been studied. Peripheral neutrophil activation was assessed sequentially in 16 patients following liver transplantation by measuring the ability of neutrophils to respond to the chemotactic peptide FMLP, to release superoxide radicals, and to cause extracellular proteolysis. All three functions increased 1-2 days before episodes of acute rejection and only returned to normal after treatment with high-dose corticosteroids. Three patients who did not develop rejection showed no increase in neutrophil function. Lymphocytes isolated from patients with acute rejection produced factors that were both chemotactic for and capable of activating normal neutrophils. This study shows that neutrophil activation occurs during acute liver allograft rejection, possibly in response to lymphokine secretion, and suggests an important, and hitherto unrecognized, mechanism of graft damage during rejection.

Adult↗
PubMed1990

Effect of alpha-1-proteinase inhibitor on neutrophil chemotaxis.

Factors that modulate neutrophil migration into the lung are poorly understood. However, there is evidence that neutrophil activation by formylmethionylleucylphenylalanine (FMLP) depends upon a surface proteinase with chymotrypsin-like activity. This suggests that chymotrypsin inhibitors such as alpha-1-proteinase inhibitor (alpha 1PI) could modify neutrophil migration in response to FMLP. We have studied neutrophil chemotaxis using the multiple blind well assay system. This article presents evidence that alpha 1PI is an inhibitor of neutrophil migration in response to FMLP. The effect is related to the inhibitory function of the protein. Alpha-1-antichymotrypsin is more potent than alpha 1PI as an inhibitor of this movement, whereas antileukoprotease is less potent. The results suggest that a cell membrane-bound serine proteinase (perhaps cathepsin G) is necessary for the enhancement of cell movement after receptor binding of FMLP. Oxidized alpha 1PI or a 4,000-D peptide cleaved from alpha 1PI by porcine pancreatic elastase or human neutrophil elastase are capable of enhancing cell motility. The results suggest that alpha 1PI may play a role in cell migration into the lung during acute inflammatory process.

Animals↗
PubMed1990

Inhibition of human leukocyte elastase bound to elastin: relative ineffectiveness and two mechanisms of inhibitory activity.

Human leukocyte elastase (HLE) has been demonstrated on lung elastic fibers in areas of pulmonary emphysema. In vitro studies in our laboratory have shown that HLE-elastin complexes may be remarkably stable. We tested the possibility that elastin-bound HLE may retain catalytic activity in the presence of inhibitors that are effective against free HLE and found: (1) alpha-1-proteinase inhibitor (alpha 1PI), antileukoprotease (ALP), and eglin C inhibited free HLE on an approximately 1:1 molar basis, measured with either 3H-elastin or a synthetic peptide substrate; (2) the ability of each inhibitor to control catalytic activity of HLE when complexed with elastin was impaired (e.g., in a 24-h assay, a 70-fold molar excess of alpha 1PI gave only 93% inhibition of HLE); and (3) a chloromethyl ketone inhibitor of HLE gave qualitatively similar results, although at the low enzyme concentrations used it was a less effective inhibitor of free and elastin-bound enzyme than were the polypeptide inhibitors. Further, we found evidence for two distinct mechanisms of inhibition of elastin-bound HLE. alpha 1PI and eglin C prevented elastin solubilization largely by enhancing net dissociation of HLE from the complexes; enzyme remaining bound to the substrate retained essentially full activity. In contrast, ALP and the chloromethyl ketone prevented elastin solubilization by binding to the complexes and inhibiting the enzyme in situ. These results may have implications regarding progressive elastin solubilization in vivo and should stimulate further investigation of enzyme activity in heterogeneous systems in which one or more reactants are insoluble.

Elastin↗
PubMed1990

Elastase inhibitors of the respiratory tract.

Lung secretions contain several elastase inhibitors although alpha 1-antitrypsin (alpha 1AT) and antileukoprotease (ALP) are the major ones. Studies of lung alpha 1AT show that the inhibitor is usually partly inactive. In patients with established lung disease this is due to a combination of proteolytic degradation, complex with enzyme and oxidation at the active site. Studies in subjects with normal lungs demonstrate that the alpha 1AT is also partly inactivated although not by any of the recognised mechanisms. Furthermore no difference in function is found between current smokers and nonsmokers. ALP is largely an inhibitor of the major airways although it is still present in the lower airway secretions collected by lavage in healthy subjects. The proportions of alpha 1AT to ALP vary in patients with alpha 1AT deficiency (1:9), established emphysema (1:1) and subjects with healthy lungs (10:1). These differences affect the ability of the lavage fluids to inhibit neutrophil elastase during prolonged incubation with enzyme substrate. The results suggest that the relative concentrations of alpha 1AT and ALP, particularly in close proximity to lung substrates, may determine the degree of connective tissue destruction.

Bronchoalveolar Lavage Fluid↗
PubMed1989

Patterns of leukocyte chemotaxis to bile after liver transplantation.

The role of chemotactic factors in the recruitment of leukocytes to human liver allografts was assessed by studying the effect of bile from transplant recipients on the chemotaxis of cells from normal subjects. Bile samples taken 2-3 days before clinical rejection were more chemotactic for lymphocytes than samples taken during rejection (p less than 0.01), during stable graft function (p less than 0.001), and from nontransplant patients (p less than 0.007). During clinical rejection there was an increase in bile chemotactic activity for both monocytes and neutrophils compared with samples from stable patients (monocytes: p less than 0.001; neutrophils: p less than 0.001) and nontransplant patients (monocytes: p less than 0.001; neutrophils: p less than 0.001). In serial studies chemotactic activity for lymphocytes reached a peak 1-3 days before the onset of clinical rejection, whereas maximum chemotactic activity for monocytes and neutrophils occurred at the time of rejection, when lymphocyte chemotaxis was decreasing. These results suggest that chemotaxis may be important in the recruitment of inflammatory cells to liver allografts and that chemotactic factors for lymphocytes, which appear in bile before clinical rejection, may be critical in the pathogenesis of rejection.

Bile↗
PubMed1989

Effects of plasma, tumour necrosis factor, endotoxin and dexamethasone on extracellular proteolysis by neutrophils from healthy subjects and patients with emphysema.

1. Neutrophils from patients with chronic obstructive bronchitis and emphysema or age-matched control subjects were cultured on a substrate of 125I-fibronectin. The neutrophils from patients with lung disease digested significantly more fibronectin and released more elastase into the culture supernatant than did cells from control subjects. Preincubation of neutrophils from emphysematous patients with plasma from control subjects significantly inhibited fibronectin digestion by the patients' neutrophils by, on average, 10%. Preincubation of control subjects' neutrophils with plasma from emphysematous patients had no effect on fibronectin digestion. 2. Tumour necrosis factor increased fibronectin digestion in a dose-dependent manner when the cytokine was added to the adherent cells but not when preincubated with the polymorphonuclear leucocytes in suspension. Bacterial endotoxin in concentrations above 6 micrograms/ml significantly increased fibronectin digestion by neutrophils, but leukotriene B4, interferon-gamma and interleukin-1 alpha had no significant effects. 3. Dexamethasone inhibited fibronectin digestion by neutrophils in a dose-dependent manner, from 11% at 10(-10) mol/l to 68% at 10(-3) mol/l.

Aged↗
PubMed1989

Role of beta-lactamases in the response of pulmonary infections to amoxycillin/clavulanate.

Lung secretions from patients with bronchiectasis have been studied before and during treatment with amoxycillin/clavulanate (Augmentin 750 mg tds). beta-Lactamase activity was usually present in the sputum sol phase and originated from organisms not usually considered to be the major pathogen. The presence of beta-lactamase was related to inactivation of amoxycillin in the lung secretions. Extensive bacteriological investigation of the sputum before therapy showed several organisms to be present in each sample. Six of eight patients showed a good clinical and biochemical response to therapy with amoxycillin/clavulanate. This, however, could not be predicted or explained by the results of bacterial investigation although Haemophilus influenzae was eradicated in three of these responders. beta-Lactamase activity did not change during treatment, and this investigation thus failed to produce indirect evidence of penetration of clavulanate into the secretions.

Amoxicillin↗
PubMed1989

Activities and sources of beta-lactamase in sputum from patients with bronchiectasis.

beta-Lactamase activity was measured in secretions from patients with bronchiectasis. Of 28 sputum samples, 23 contained measurable amounts of activity; values were significantly higher (P less than 0.01) in purulent samples than in mucoid or mucopurulent samples. beta-Lactamase activity was usually present in saliva collected before and between sputum expectorations, although values for sputum were higher than for either group of saliva samples (P less than 0.025 and P less than 0.005, respectively). This difference suggests that at least part of sputum beta-lactamase activity originates in the bronchial tree. Detailed microbiological study of a further eight specimens (seven were beta-lactamase positive) led to the isolation of Haemophilus influenzae from six, although only two of these isolates were beta-lactamase positive. Several other beta-lactamase-producing organisms were also isolated, including Staphylococcus aureus (n = 3), Escherichia coli (n = 1), Proteus spp. (n = 1), and Bacteroides spp. (n = 3). Size-exclusion high-performance liquid chromatography of the sputum showed several peaks of beta-lactamase activity which usually coeluted in fractions similar to those of their beta-lactamase-positive isolates. Therefore, sources of sputum beta-lactamases are often bacteria not considered truly pathogenic or not isolated during routine bacteriological assessment. These observations should be considered when embarking on antimicrobial therapy in bronchiectatic patients and suggest that increased dosages of penicillins are indicated.

Albumins↗
PubMed1988

Effect of ambroxol of neutrophil chemotaxis in vitro.

Ambroxol hydrochloride has been shown to protect the lung from damage by polymorphonuclear leucocyte (PMN). In view of this observation we have studied the effect of Ambroxol on PMN chemotaxis using a variety of chemoattractants. The PMN response was inhibited 50-80% by preincubating the cells with concentrations of 10(-4) M Ambroxol. There was no evidence of PMN killing by the drug at concentration of 10(-3) M. The results suggest that Ambroxol my have a role in the management of patients whose chronic lung damage is due to excess PMN recruitment.

Ambroxol↗
PubMed1988

Neutrophil chemotaxis in bronchiectasis: a study of peripheral cells and lung secretions.

1. Some bronchiectatic patients persistently expectorate purulent secretions containing many polymorphonuclear leucocytes (PMN) and bacteria, suggesting ineffective microbial clearing from the lung. We have therefore studied several aspects of PMN recruitment to the lung by chemotaxis. 2. Circulating PMN from patients with bronchiectasis show a variable chemotactic response to the synthetic peptide N-formyl-L-methionyl-L-leucyl-L-phenylalanine. This is similar to the response of PMN from healthy controls and suggests that failure to clear microbial organisms is not due to defective chemotaxis as measured here. 3. Purulent sputum solphase demonstrates chemotactic activity against control PMN. This activity is greater (P less than 0.001) than that found with mucoid sputum solphase, which is consistent with the neutrophil content of the secretions in vivo. 4. Successful antibiotic therapy reduces the chemotactic activity of purulent sputum solphase from a median value of 183 (range 28-201) cells/high power field to 33.5 (range 0.7-64) cells/high power field (P less than 0.0025). This indicates that the chemotactic activity is largely associated with bacterial load.

Adult↗
PubMed1988

Evidence for lipid-associated serine proteases and metalloproteases in human bronchoalveolar lavage fluid.

1. We have investigated the nature of elastase activity in bronchoalveolar lavage samples from healthy cigarette smokers and subjects with emphysema. 2. Initial experiments with pure human leucocyte elastase showed this enzyme to be inhibited by high concentrations (greater than 10 mmol/l) of ethylenediaminetetra-acetate, indicating that results of previous studies of 'metalloelastase' activity in bronchoalveolar lavage were ambiguous. 3. We have nevertheless demonstrated the presence in bronchoalveolar lavage of an elastase with the characteristics of a metalloproteinase, although samples also contained a substantial amount of activity that was sensitive to serine proteinase inhibitors. 4. Fractionation of lavage fluid supernatant by size-exclusion chromatography demonstrated most of the elastase activity to be of molecular mass greater than 300 kDa. Treatment of samples with lipase or detergent caused a reduction in metalloelastase activity and the generation of lower-molecular-mass components (90-100 kDa and 40 kDa) which were predominantly serine elastases. This suggested that the enzymes were associated with lipid.

Adult↗