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Biomedical subjects

V S Chadwick

Publications and source records attributed to V S Chadwick.

At least 37 records · Page 2Linked to original sources
PubMed1990

The effect of some anti-inflammatory agents on elastase release from neutrophils in-vitro.

In view of the potential role of released polymorphonuclear leucocyte elastase in causing tissue damage, the effect of commonly used anti-inflammatory drugs on elastase release from neutrophils has been studied in-vitro. Elastase release from neutrophils exposed to the synthetic bacterial cell wall peptide N-formyl-L-methionyl-L-leucyl-L-phenylalanine (10(-6) M) was quantitated using a radiometric immunoassay and a functional assay of elastase. Prednisolone and non-steroidal anti-inflammatory drugs inhibited elastase release at concentrations from 0.1 mM-0.1 nM. No inhibition by sulphosalicylic acid, D-penicillamine or chloroquine sulphate was observed. The clinical relevance of these findings is discussed.

Adult↗
PubMed1990

Measurements of unsaturated vitamin B12-binding capacity and myeloperoxidase as indices of severity of acute inflammation in serial colonoscopy biopsy specimens from patients with inflammatory bowel disease.

Measurements of tissue content of myeloperoxidase, a constituent of neutrophil azurophil granules and of unsaturated vitamin B12-binding protein from neutrophil-specific granules, have been used to assess intestinal inflammation. This paper reports results of a prospective evaluation of such measurements in serial colonoscopy biopsy specimens from patients with inflammatory bowel disease. Histologic grading of acute inflammation was based on perceived numbers of neutrophil polymorphs in sections from an immediately adjacent biopsy specimen. The mean + 2 SD range for unsaturated vitamin B12-binding protein activity in homogenates of histologically normal specimens was 62 pg mg protein-1. Values increased progressively up to 900 pg mg-1 protein in the most severely inflamed specimens. Unsaturated vitamin B12-binding protein measurements generally distinguished among histologic grades of inflammation, whereas myeloperoxidase activities failed to do this, probably because substantial myeloperoxidase activity was found in uninflamed colonic mucosa, suggesting a non-neutrophil source for this enzyme.

Acute Disease↗
PubMed1989

Partial purification and characterization of a formylmethionine deformylase from rat small intestine.

A formylmethionine deformylase from rat small-intestinal mucosa has been isolated, characterized and partially purified. The enzyme catalyses the release of equimolar amounts of formate and the free amino acid. The deformylase was active against formylmethionine (Km 7.1 mM) and formylnorleucine, but showed reduced activity against formyl-leucine. It was inactive against a range of other polar and nonpolar formyl-amino acids and against formyl di- and tri-peptides. The Mr of the native enzyme was between 45,000 and 66,000, as determined by h.p.l.c. gel permeation. Further purification of the enzyme either by h.p.l.c. ion-exchange chromatography and concanavalin A-Sepharose or by isoelectric focusing yielded a preparation with one predominant band of Mr 50,000 on SDS/polyacrylamide-gel electrophoresis. Bacteria in the intestine present the host with substantial amounts of formylmethionine (fMet) from proteinase and carboxypeptidase digestion of bacterial formyl-peptides in the intestinal lumen. fMet (0.01-1.0 mM) inhibited translation of a test RNA from brome mosaic virus in vitro, indicating that it could have adverse effects on cellular metabolism. Gut epithelial fMet deformylase may be required for deformylation of this exogenous (bacterial) and also endogenous (mitochondrial) fMet.

Amidohydrolases↗
PubMed1989

Bacterial chemotactic oligopeptides and the intestinal mucosal barrier.

Intestinal absorption and enterohepatic circulation of N-formyl-methionyl-leucyl-125I-tyrosine, a bioactive synthetic analog of the bacterial chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine has been investigated in the rat. In ileum and proximal and distal colon, dithiothreitol, which increases mucosal permeability, increased peptide absorption and biliary recovery fourfold, 70-fold, and 20-fold over control values, respectively. When dithiothreitol was combined with d-l-benzyl succinate, a potent inhibitor of intestinal carboxypeptidase, absorption and biliary recovery from ileal loops increased markedly to 40-fold over control, whereas there was no further increase in absorption from colon loops. There was a strong correlation between biliary N-formyl-methionyl-leucyl-125I-tyrosine recovery and intestinal absorption of 51Cr-ethylenediaminetetraacetate, a marker of passive mucosal permeability (r = 0.97). We conclude that in the ileum both enzymic degradation and restricted mucosal permeability contribute to the intestinal barrier to luminal bacterial formyl oligopeptides. In the colon, however, enzymic mechanisms are less active and restricted mucosal permeability is the major factor. Abnormalities of the intestinal mucosal barrier to proinflammatory bacterial peptides could play a role in inflammatory disorders of the gut.

Animals↗
PubMed1988

Enterohepatic circulation of bacterial chemotactic peptide in rats with experimental colitis.

The association of hepatobiliary disorders with colonic inflammation is well recognized. Although the pathophysiology is obscure, increased permeation of toxic bacterial products across the inflamed gut to the portal circulation might be one mechanism. Potentially toxic metabolites include N-formylated chemotactic peptides that are produced by several species of intestinal bacteria and can be detected in colonic fluid in vivo. To investigate the metabolic fate of one of these low molecular weight proinflammatory peptides, N-formyl L-methionine L-leucine 125I-L-tyrosine was introduced into colon loops of healthy rats (n = 10) and rats with experimental colitis (n = 15) induced by rectal instillation of 15% (vol/vol) acetic acid. Gut, liver, and blood radioactivity were monitored by external gamma-counting and radioactivity in bile was measured by biliary catheter drainage into a well counter. Bile was processed by high-performance liquid chromatography to determine the amount of intact, bioactive peptide excreted over 3 h. After colonic instillation of 1 nmol of peptide, the mean (+/- SEM) biliary excretion of intact peptide was 6.4 +/- 2.0 pmol in normal rats and 49.0 +/- 20 pmol in rats with colitis (p less than 0.01). An enterohepatic circulation of synthetic N-formyl L-methionine L-leucine L-tyrosine has been demonstrated in the rat. Experimental colitis was associated with an eightfold increase in biliary excretion of this proinflammatory bacterial peptide. Proinflammatory bacterial peptides synthesized by colonic bacteria could be important in the pathophysiology of colon inflammation and its frequently associated hepatobiliary complications.

Acetates↗
PubMed1988

Involvement of M1 cholinergic receptors and enteric nerves in the spasmogenic activity of bacterial N-formyl oligopeptides on guinea-pig ileum.

Bacterial N-formyl-methionyl oligopeptides are spasmogenic for guinea-pig ileum in vitro but the mechanism of this effect is not understood. To investigate this phenomenon further, we have determined pA2 values (the negative logarithm of the concentration of an antagonist reducing a double-dose agonist response to a single-dose response) for a number of potential antagonists of N-formyl-met-leu-phe (F-met-leu-phe) using histamine, acetylcholine, 5HT and substance P as control agonists. Atropine, pirenzepine and tetrodotoxin were potent inhibitors of F-met-leu-phe induced contraction (pA2's 8.4, 8.0 and 7.9, respectively) suggesting involvement of neural and cholinergic pathways in the response. Sulphasalazine, known to block the F-met-leu-phe receptor on neutrophil leucocytes, was also a potent inhibitor. Tachyphylaxis induced by either 5HT, or substance P, did not diminish the response to F-met-leu-phe, suggesting that these potential mediators were not involved. These studies indicate that bacterially synthesized formyl-methionyl oligopeptides bind to cells bearing receptors in guinea-pig ileum and produce muscle contraction via enteric cholinergic (M1) neural pathways.

Animals↗
PubMed1988

Production of peptides inducing chemotaxis and lysosomal enzyme release in human neutrophils by intestinal bacteria in vitro and in vivo.

Low molecular weight (Mr 200-1500) N-formylated peptides that stimulate many leucocyte functions, including chemotaxis and lysosomal enzyme release, have previously been isolated from Escherichia coli cultures. We have used high-performance liquid chromatography and bioassay techniques to study production of such peptides by intestinal bacteria in vitro and their activity in intestinal luminal contents, obtained by in vivo dialysis methods. Bioactivity was detected in culture supernatants of all 11 species of bacteria so far investigated, was resistant to digestion with aminopeptidase, but was destroyed by carboxypeptidase, confirming that bioactive moieties were amino-terminal-blocked peptides. By similar isolation procedures, pronase-sensitive bioactive factors have been demonstrated in human rectal dialysates from normal subjects and patients with Crohn's disease. In the patients, bioactivity in dialysates was not observed after treatment with broad-spectrum poorly absorbed antibiotics. The gut may be a reservoir or source of bacterial peptides that could promote an inflammatory response should they cross the 'mucosal barrier'.

Bacteria↗
PubMed1987

Erosive gastritis and gastrointestinal bleeding in a female runner. Prevention of the bleeding and healing of the gastritis with H2-receptor antagonists.

A 33-yr-old female runner presented with upper gastrointestinal symptoms and iron deficiency anemia. She was found to have erosive gastritis that was present when she exercised and which was associated with symptoms. Gastrointestinal blood loss during exercise periods was confirmed by measuring fecal blood loss using 51Cr-labeled red cells. Symptoms, gastritis, and blood loss disappeared with cessation of running or with H2-receptor antagonist therapy.

Adult↗
PubMed1986

Circulating human leucocyte elastase in rheumatoid arthritis.

Elastase-inhibitor complex (EIC) levels were determined in EDTA-plasma samples of 40 patients with connective tissue disease by a double antibody immuno-assay technique. In active rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), EIC levels were significantly higher than in the normal controls (P less than 10(-8) and fell on remission. The mean EIC level in active RA was significantly greater than in inactive disease (P = 0.0001) but there was no statistically significant difference between the EIC levels in the acute and inactive disease states in SLE (P = 0.49). In active RA, there was a positive correlation between EIC levels and white blood cell count (WBC) but not with erythrocyte sedimentation rate (ESR). In SLE there was no significant correlation between EIC levels and ESR or WBC. EIC measurement may be useful in the objective assessment of activity in RA.

Arthritis, Rheumatoid↗
PubMed1986

Indium-111-labeled autologous leukocyte scanning in gastrointestinal graft versus host disease (GVHD).

The technique of scanning with indium-111 autologous leukocytes has been used to assess gastrointestinal graft-versus-host disease (GVHD) following allogenic marrow transplantation. In patients with active disease, abdominal scans showed extensive abnormal localization in the bowel, while in those whose disease was quiescent after responding to treatment, scans showed localized ileocecal involvement. Rectal histology showed excellent agreement with scanning in the diagnosis of GVHD, but in three of six cases with active disease underestimated disease severity. Indium-111 leukocyte scanning is a useful noninvasive technique for the diagnosis and assessment of gut GVHD.

Acute Disease↗
PubMed1986

The cored sponge model of in vivo leucocyte chemotaxis.

A method has been developed for the in vivo measurement of leucocyte chemotaxis in response to the bacterial chemotactic peptide F-met-leu-phe (FMLP). Polyurethane sponges were pre-treated with FMLP and implanted subcutaneously in rats and after a suitable interval removed for determination of leucocyte influx. In vivo concentration gradients of chemotactic factors within intact sponges were shallow and leucocyte accumulation unsatisfactory. Accordingly a cored sponge model was developed in which the cylindrical core only was treated with chemotactic factor and the sponge reassembled prior to subcutaneous implantation. Steep concentration gradients were established within the outer sponge matrix with marked effects on leucocyte accumulation, permitting studies of the time course of in vivo chemotaxis. With cored sponges test to control cell number ratios were maximal at 4 hours using both free and albumin-bound FMLP. This model of in vivo chemotaxis may prove useful in several areas of inflammation research.

Animals↗
PubMed1986

Indium 111-granulocyte scanning in the assessment of disease extent and disease activity in inflammatory bowel disease. A comparison with colonoscopy, histology, and fecal indium 111-granulocyte excretion.

Indium 111-leukocyte scanning has recently been introduced as a new method for imaging inflammatory bowel disease. The technique has recently been made more specific for acute inflammation by labeling a pure granulocyte fraction rather than the conventional mixed leukocyte preparation. We now report a prospective study comparing 111In-granulocyte scanning with endoscopy, histology, and fecal 111In-granulocyte excretion for the assessment of disease extent and severity in colonic inflammatory bowel disease. In 52 patients with Crohn's disease or ulcerative colitis, disease extent and severity were assessed macroscopically, histologically, or by scanning using a numerical grading system. Excellent correlations were found between both endoscopy and histology and 111In scans [r = 0.90 (endoscopy) and r = 0.90 (histology) for extent; r = 0.86 and r = 0.91 for disease activity]. Severity graded by scanning also showed a close correlation with fecal 111In-granulocyte excretion (r = 0.90). Indium 111-granulocyte scans are a rapid, accurate, noninvasive means of assessing both disease extent and severity of colonic involvement in inflammatory bowel disease.

Biopsy↗