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Biomedical subjects

A Knox

Publications and source records attributed to A Knox.

At least 37 records · Page 2Linked to original sources
PubMed1996

The effect of inhaled heparin on bronchial reactivity to sodium metabisulphite and methacholine in patients with asthma.

Inhaled heparin inhibits the early response to allergen and exercise-induced asthma, probably by inhibiting mast cell mediator release. Recent animal studies suggest that heparin might also inhibit cholinergic neurotransmission in asthma by restoring inhibitory M2 receptor function. We have tested the hypothesis that heparin inhibits neurally-mediated bronchoconstriction in asthma by examining the effect of inhaled heparin on bronchial reactivity to sodium metabisulphite. We also examined the effect of inhaled heparin on methacholine-induced bronchoconstriction to exclude a direct effect on airway smooth muscle. Eleven patients with mild asthma inhaled nebulized heparin (1,000 U.kg-1) or placebo (normal saline) in a randomized, double-blind fashion, 10 min before a challenge with sodium metabisulphite. Nine patients were also challenged with methacholine after the same dose of heparin or placebo. Inhaled heparin did not significantly change forced expiratory volume in one second (FEV1), nor did it alter the provocative dose of sodium metabisulphite or methacholine required to cause a 20% fall in FEV1 (PD20). Geometric mean sodium metabisulphite PD20 was 2.54 and 2.15 mumol after placebo and heparin, respectively (mean difference -0.24 doubling doses; 95% confidence interval (95% CI) -0.64-0.17). Geometric mean methacholine PD20 was 1.00 and 1.51 mumol after placebo and heparin, respectively (mean difference 0.6 doubling doses; 95% CI -0.25-1.5). Thus, heparin inhaled at doses sufficient to inhibit allergen and exercise-induced bronchoconstriction has no effect on the response to sodium metabisulphite and methacholine challenge in asthma. This argues against an inhibitory effect on neural pathways or airway smooth muscle.

Administration, Inhalation↗
PubMed1995

Production of PGE2 by bovine cultured airway smooth muscle cells: regulation by cAMP.

Prostaglandin E2 (PGE2) is thought to be an important inhibitory modulator of inflammatory processes in the airway. Previous studies have shown that it is produced by bovine cultured airway smooth muscle (ASM) cells in large quantities, but its regulation by second messengers has not been studied in this tissue. To determine whether PGE2 production by ASM might be an important action of beta-adrenoceptor agonists in asthma, the regulation of PGE2 production by adenosine 3',5'-cyclic monophosphate (cAMP) was assessed using dibutyryl cAMP (DBcAMP), forskolin, and albuterol. DBcAMP increased PGE2 production over a 24-h time course. Forskolin and albuterol both increased PGE2 production over control cells to similar levels after 24 h. Incubation of albuterol-treated cells with propranolol significantly (70%) reduced the stimulatory effect of albuterol on PGE2 production. Incubation of forskolin-treated cells with Rp-cAMP, a cAMP antagonist, inhibited the PGE2 response evoked by forskolin by 80%. Ro-20-1724, a selective inhibitor of type IV phosphodiesterase, stimulated PGE2 production (P = 0.02). Cycloheximide, a protein-synthesis inhibitor, did not inhibit the response to DBcAMP. The effects of DBcAMP were additive with the effects of bradykinin, a proinflammatory mediator known to increase PGE2 production (P < 0.05). These studies suggest that cAMP may play an important regulatory role in stimulating PGE2 production by ASM. This may be a novel beneficial action of beta-adrenoceptor agonists in asthma.

4-(3-Butoxy-4-methoxybenzyl)-2-imidazolidinone↗
PubMed1995

A comparison of the effects of inhaled furosemide and ethacrynic acid on sodium-metabisulfite-induced bronchoconstriction in subjects with asthma.

Inhaled furosemide prevents bronchoconstriction induced by a number of challenges in asthma. One approach to determine the mechanism underlying this protection has been to examine the effects of diuretics with different or overlapping pharmacologic effects. We have compared the effects of furosemide on sodium metabisulfite-induced bronchoconstriction with those of equivalent diuretic doses of ethacrynic acid, a loop diuretic that, unlike furosemide, does not interact directly with the membrane Na/K/Cl cotransporter protein or inhibit carbonic anhydrase. Eight subjects with mild asthma were studied on five occasions, receiving nebulized furosemide (20 and 40 mg), ethacrynic acid (25 and 50 mg), or placebo (normal saline) in random order and double-blind 10 min before a cumulative dose challenge with inhaled sodium metabisulfite. After placebo the geometric mean sodium metabisulfite PD20 was 7.9 mumol. Furosemide 20 mg and 40 mg increased the PD20 by a mean 1.1 (95% confidence interval, -0.2-2.4; p > 0.05) and 1.6 (0.4-2.9; p < 0.02) doubling doses to 17.1 and 24.7 mumol, respectively. After inhaled ethacrynic acid 25 mg and 50 mg, the geometric mean PD20 was increased by 0.9 (-0.4-2.2; p > 0.05) and 1.5 (0.2-2.8; p < 0.05) doubling doses to 14.5 and 22.4 mumol, respectively. Thus, equivalent diuretic doses of furosemide and ethacrynic acid have a similar inhibitory effect on sodium metabisulfite-induced bronchoconstriction in asthma. This suggests that interaction with the Na/K/Cl cotransporter protein, or carbonic anhydrase inhibition, is not relevant to the effects of furosemide in asthma.

Administration, Inhalation↗
PubMed1995

Effect of diuretics on allergen-induced contractions of passively sensitized human bronchi in vitro.

Inhaled furosemide has been shown to protect subjects with asthma from bronchoconstriction induced by a wide variety of stimuli, including allergen, but the mechanism of action is controversial. We have used an in vitro model of allergen-induced bronchoconstriction to examine the effects of furosemide and other ion transport inhibitors. Human bronchial rings were passively sensitized by incubation with serum from an atopic donor and were challenged with Dermatophagoides pteronyssinus. Allergen-challenged bronchial rings developed bronchoconstriction which was effectively inhibited by the cysteinyl-leukotriene antagonist ICI 198,615 (10(-7) M) and to a lesser extent by terfenadine (10(-5) M). Assessed over 60 min furosemide 10(-6), 10(-5), and 10(-4) M inhibited contractions by a mean (95% confidence interval [CI]) 7.9% (-23.5, 39.3%, p > 0.05), 44.2% (12.9, 75.2%, p < 0.01), and 86.9% (55.5, 118.3%, p < 0.001) respectively (n = 5). The same concentrations of bumetanide inhibited contractions by 21.5% (-8.4, 51.4%, p > 0.05), 13.6% (-16.3, 43.4%, p > 0.05) and 51.6% (21.7, 81.4%, p < 0.01) respectively (n = 5). The sodium transport inhibitor amiloride and the anion transport inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) were without effect (both 10(-4) M; n = 4). Furosemide increased PGE2 production by the bronchial rings by 134% (95% CI 53, 259%). Indomethacin (3 x 10(-6) M) blocked the furosemide-induced increase in PGE2 production and reduced the protection afforded by 10(-4) M furosemide against allergen-induced contractions from 67.9% to 34.7% (mean difference 33.2%; 95% CI 9.7, 56.6%; p < 0.01; n = 8).(ABSTRACT TRUNCATED AT 250 WORDS)

Allergens↗
PubMed1994

Dietary magnesium, lung function, wheezing, and airway hyperreactivity in a random adult population sample.

Magnesium is involved in a wide range of biological activities, including some that may protect against the development of asthma and chronic airflow obstruction. We tested the hypothesis that high dietary magnesium intake is associated with better lung function, and a reduced risk of airway hyper-reactivity and wheezing in a random sample of adults. In 2633 adults aged 18-70 sampled from the electoral register of an administrative area of Nottingham, UK, we measured dietary magnesium intake by semiquantitative food-frequency questionnaire, lung function as the 1-sec forced expiratory volume (FEV1), and atopy as the mean skin-prick test response to three common environmental allergens. We measured airway reactivity to methacholine in 2415 individuals, defining hyper-reactivity as a 20% fall in FEV1 after a cumulative dose of 12.25 mumol or less. Mean (SD) daily intake of magnesium was 380 (114) mg/day. After adjusting for age, sex, and height, and for the effects of atopy and smoking, a 100 mg/day higher magnesium intake was associated with a 27.7 (95% CI, 11.9-43.5) mL higher FEV1, and a reduction in the relative odds of hyper-reactivity by a ratio of 0.82 (0.72-0.93). The same incremental difference in magnesium intake was also associated with a reduction in the odds of self-reported wheeze within the past 12 months, adjusted for age, sex, smoking, atopy, and kilojoule intake, by a ratio of 0.85 (0.76-0.95). Dietary magnesium intake is independently related to lung function and the occurrence of airway hyper-reactivity and self-reported wheezing in the general population. Low magnesium intake may therefore be involved in the aetiology of asthma and chronic obstructive airways disease.

Adult↗
PubMed1994

Circulating levels of IgG1 and IgG4 anti-IgE antibodies and asthma severity.

In this paper, we have determined the levels of IgG1 and IgG4 anti-IgE in the sera of 66 asthma patients suffering from mild (n = 24), moderate (n = 23), or severe (n = 19) symptoms, and 20 nonatopic, healthy subjects. The study has revealed that although asthma patients have significantly elevated levels of IgG1 and IgG4 anti-IgE antibodies, the concentration of these autoantibodies is not related to the severity of asthma. This conclusion may be related to the known heterogeneity of autoanti-IgE antibodies in terms of their ability to trigger basophil histamine release.

Adolescent↗
PubMed1994

Production of PGE2 by bovine cultured airway smooth muscle cells and its inhibition by cyclo-oxygenase inhibitors.

1. Prostaglandin E2 (PGE2) is thought to be an important inhibitory modulator of inflammatory processes in the airway. It inhibits inflammatory cell function and cholinergic neurotransmission in vitro and roles have been postulated in vivo in refractoriness and in the mechanism of action of the diuretic agent, frusemide. 2. The production of PGE2 by bovine cultured airway smooth muscle cells has been studied under a range of conditions. The effects of cyclo-oxygenase inhibitors (flurbiprofen, indomethacin, acetyl salicylic acid) on serum-induced production of PGE2 were assessed over a range of concentrations (10(-7)-10(-4) M). 3. Serum-stimulated production of PGE2 in control wells ranged from 350 to 800 ng PGE2 ml-1 in cells from different animals. All three cyclo-oxygenase inhibitors inhibited PGE2 production with an order of potency, flurbiprofen > indomethacin > acetyl salicylic acid. Log IC50 values were -6.24 for flurbiprofen, -5.23 for indomethacin and -3.50 for acetyl salicylic acid. 4. PGE2 production was stimulated by arachidonic acid (10(-5) M) or addition of the proinflammatory mediator, bradykinin (10(-8)-10(-5) M). 5. Incubation of cells for 24 h with 5 bromo deoxyuridine (BRDU) (10(-4) M) to prevent DNA synthesis did not alter PGE2 production in response to serum, suggesting that it was not a function of proliferation per se. 6. Our study suggests that airway smooth muscle may be an important source of PGE2. Production of PGE2 may be a novel feedback mechanism whereby airway smooth muscle cells can negatively modulate airways inflammation. The differing potencies of the cyclo-oxygenase inhibitors may explain the contrasting effect of these drugs in recent studies in asthma.

Animals↗
PubMed1994

Airborne dissemination of Burkholderia (Pseudomonas) cepacia from adult patients with cystic fibrosis.

BACKGROUND: Burkholderia (Pseudomonas) cepacia is an increasingly important pathogen in patients with cystic fibrosis but it is unclear how it spreads from patient to patient. A study was undertaken to determine whether B cepacia could be recovered from room air occupied by colonised adult patients with cystic fibrosis. METHODS: Air samples were obtained consecutively from an enclosed room or isolation cubicle before, during, and after occupation by six patients on nine occasions using a surface air sampler incorporating contact plates with selective medium. Settle plates were also used and sputum from five patients was cultured. RESULTS: B cepacia was recovered from room air during occupation by five of six patients, the number of bacteria ranging from 1 to 158 cfu/m3 (mean 32 cfu/m3). The number of bacteria isolated was greater when patients were coughing. B cepacia persisted in room air on four occasions after the patient left the room, on one occasion for up to 45 minutes. CONCLUSIONS: The isolation of B cepacia from the air of rooms occupied by colonised patients suggests that dissemination might occur by aerosol as well as by direct physical contact with patients or contaminated environmental sites.

Adult↗
PubMed1994

Cross refractoriness between sodium metabisulphite and exercise induced asthma.

BACKGROUND: Exercise and inhaled sodium metabisulphite are thought to cause bronchoconstriction in asthma through different mechanisms. The response to both stimuli becomes refractory with repeat challenge. The mechanism of refractoriness is unclear, although depletion of mast cell derived mediators or neurotransmitters has been suggested. Recent studies suggest a common mechanism involving release of inhibitory prostaglandins. If this is true, exercise and sodium metabisulphite induced bronchoconstriction should show cross refractoriness. METHODS: Thirteen subjects with mild asthma and previously established exercise and sodium metabisulphite induced bronchoconstriction performed two sodium metabisulphite challenges (giving a single dose previously shown to cause a 20% fall in FEV1) on one study day, and two exercise tests on another. The second challenge proceeded after recovery (FEV1 > 95% baseline) from the first. Subjects then attended on two further occasions when an exercise test was performed after sodium metabisulphite and a sodium metabisulphite challenge after exercise. RESULTS: When expressed as the percentage reduction in the area under the change in percentage FEV1 curve over 20 minutes (AUC) the response to exercise was reduced by a mean 62.3% (95% CI 46.5% to 78.1%) following a first exercise challenge, and by 50.7% (95% CI 27.8% to 73.6%) following a sodium metabisulphite challenge. The response to a sodium metabisulphite challenge was reduced by a mean of 80.2% (95% CI 68.9% to 91.5%) when it followed a sodium metabisulphite challenge, and by 37.3% (95% CI 15.1% to 59.5%) following an exercise challenge. CONCLUSION: This study shows some cross refractoriness between exercise and sodium metabisulphite induced bronchoconstriction, in keeping with a partially shared mechanism of refractoriness.

Adolescent↗
PubMed1994

Dietary sodium intake and the risk of airway hyperreactivity in a random adult population.

BACKGROUND: High dietary sodium intake has been identified as a potential cause of asthma and airway hyperreactivity. This study was designed to test the hypothesis that dietary sodium intake is an independent determinant of the risk of hyperreactivity in the general population, and to assess the role of atopy in the association between these factors. METHODS: Airway reactivity to methacholine, atopy, 24 hour urinary sodium excretion, and self-reported smoking and symptom history were measured in a random sample of 1702 adults aged 18-70 from an administrative district of Nottingham. Hyperreactivity was defined as a PD20FEV1 of 12.25 mumol or less, and atopy was defined quantitatively as the mean allergen skin weal response to Dermatophagoides pteronyssinus, cat fur, and grass pollen, and categorically as the occurrence of any allergen response 1 mm or greater than the saline control. Multiple logistic regression analysis was used to estimate the independent relative odds of hyperreactivity, atopy, or symptoms in relation to sodium excretion in all 1702 subjects, and multiple linear regression to assess the independent relation between sodium excretion and mean allergen skin weal diameter, and the PD20 value amongst hyperreactive subjects. RESULTS: There was no relation between the relative odds of hyperreactivity to methacholine and 24 hour urinary sodium excretion, either before or after adjustment for age, smoking, allergen skin weal diameter, and sex, and similarly no relation if the analysis was restricted to men or women only. The relative odds of having at least one allergen skin test response 1 mm greater than the saline control were increased in relation to sodium excretion after adjustment for age, sex, and smoking by a ratio of 2.08 (95% CI 1.04 to 4.15) per log10 unit increase in sodium excretion, but there was no evidence of an association between sodium excretion and the occurrence of self-reported wheeze, hay fever, eczema, or asthma. There was no relation between 24 hour sodium excretion and the magnitude of the mean allergen skin weal response or the PD20 value. CONCLUSIONS: These findings do not support the hypothesis that a high dietary sodium intake is a risk factor for airway hyperreactivity or atopic disease in the general adult population.

Adolescent↗
PubMed1994

Factors influencing the occurrence of airway hyperreactivity in the general population: the importance of atopy and airway calibre.

The factors that determine the occurrence of airway hyperreactivity in the general population are not clearly understood. This study was designed to assess the independent effects of age, atopy, smoking and airway calibre. In a random sample of 2,415 adults aged 18-70 yrs we measured reactivity to methacholine as the dose provoking a 20% fall (PD20) in one-second forced expiratory volume (FEV1), atopy as the mean skin wheal response to three common environmental allergens, and airway calibre as the baseline FEV1 in absolute terms, as percent predicted (FEV1 % predicted) and as percent forced vital capacity (FEV1 % FVC). Hyperreactivity, defined as a PD20 < or = 12.25 mumol, was present in 314 (13%) of the sample, and before adjustment for FEV1 was more common in females (independent odds ratio (OR) = 2.05 (95% confidence interval 1.6-2.7)), current smokers (OR = 1.89 (1.3-2.6)), atopics (OR = 1.39 (1.3-1.5) per mm skin wheal), and in older age groups (OR for age 60-70 yrs relative to 18-29 yrs = 2.70 (1.7-4.3)). However, the odds of hyperreactivity were also strongly and independently related to absolute FEV1 (OR = 0.46 (0.27-0.77) per litre), FEV1 % predicted (OR = 0.96 (0.94-0.98) per percent), and FEV1 % FVC (OR = 0.92 (0.90-0.94) per percent; combined chi-square on 3 df = 312, p << 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Pharmacokinetic optimisation of inhaled steroid therapy in asthma.

The recognition that asthma has a large inflammatory component has led to the use of steroids in its treatment. The adverse systemic effects of the drugs have promoted the development of inhaled steroids with a high topical to systemic potency ratio. The 2 most widely used agents are beclomethasone dipropionate and budesonide. Budesonide has a longer plasma elimination half-life than beclomethasone dipropionate but a higher topical to systemic potency ratio. These agents have been shown to be equipotent with respect to their anti-asthma effects but budesonide may have a slightly more favourable adverse effect profile. At low dosages (up to 400 micrograms/day) these drugs are well tolerated. At higher dosages (> 1000 micrograms/day) adverse effects on bone metabolism and adrenal function have been noted. Other agents such a triamcinolone or flunisolide have no obvious advantages. We recommend that inhaled steroids should be prescribed at the lowest dose required to control symptoms, with the dose being increased or decreased in a stepwise manner in parallel with asthma severity.

Administration, Inhalation↗
PubMed1992

The effect of a five-month delay on children's and adults' eyewitness memory.

Child witnesses must endure a delay of around six months between observing or being the victim of an alleged offence and being required to give evidence in a criminal court. While the legal profession seem to believe that young children's memories are particularly sensitive to the passage of time, developmental psychology can offer little relevant data to support or refute this presumption. In the present study, children aged six and nine years and adults witnessed a staged event and were subsequently interviewed in the days following the event and/or five months later. Results indicate that while all witnesses forgot information over this period, the younger children (six years) recalled slightly less information than the older children and the adults. The total amount of incorrect information recalled did not increase over the same period. Two different interviewing techniques were used--cued recall vs. 'enhanced' recall--the latter incorporating some aspects of the cognitive interview procedure. No differences were found relating to the interview techniques employed. The results underline the importance of recording initial interviews with child witnesses wherever possible.

Adult↗
PubMed1991

Management of splenic trauma: a new CT-guided splenic injury grading system.

The aim of this study was to assess a newly developed computerized tomography (CT)-based splenic injury index in predicting the outcome of splenic injury. Twelve patients with isolated splenic injuries were studied. Splenic parenchymal injury was graded from 1 to 4 based on CT. The splenic injury index was obtained by multiplying the parenchymal score by the volume haemoperitoneum, which was measured on the CT scanner. The 12 patients with CT-proven splenic injuries had a mean injury index of 193.5 +/- 191 (mean +/- s.d.). The 3 patients who failed conservative management had a mean index of 475 +/- 50, compared with an index of 99.5 +/- 100 in the nine managed non-operatively (P less than 0.001). This new CT-based splenic injury index allows morphological assessment of splenic injury and may predict the outcome of splenic trauma.

Adolescent↗