[Show abstract][Hide abstract] ABSTRACT: 1. We have compared the activities of the endothelin precursors (human big ET-1(1-38), porcine big ET-1(1-39), big ET-2(1-38) and big ET-3(1-41 amide) and their respective mature 21 amino acid peptides as contractors of isolated gallbladder strips of the guinea-pig. We have also used different protease inhibitors and/or epithelial cell removal to investigate the nature and the location of the endothelin-converting enzyme (ECE) activity responsible for the conversion of porcine big ET-1(1-39) in this isolated preparation. In addition, we have conducted binding studies to investigate whether porcine big ET-1(1-39) interacts directly with ET receptors. 2. ET-1, ET-2 and ET-3 were equipotent at causing 50% of the contractions of the isolated strips (22.9 +/- 6.8, 39.5 +/- 9.9 and 35.9 +/- 3.7 (x 10(-9) M), respectively), as estimated with contractions to 3 x 10(-7) M taken as 100%. Big ET-1(1-38) was equipotent to ET-1 while big ET-1(1-39) was one fifth as potent as ET-1, and big ET-2(1-38) was one fifth as potent as ET-2. Precursors of ET-1 and ET-2 induced similar contractions at 3 x 10(-7) M. Conversely, the contraction induced by big ET-3(1-41 amide) (3 x 10(-7) M) was only 14% of that induced by the same concentration of ET-3 (287 +/- 37% of 5 microM histamine). 3. The kinetics of the responses induced by single additions of 3 x 10(-7) M of the endothelin isopeptides were compared.(ABSTRACT TRUNCATED AT 250 WORDS)
British Journal of Pharmacology 01/2012; 114(7):1383-90. · 5.07 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The HIV epidemic in sub-Saharan Africa has had a major impact on infectious disease, and there is currently great interest in the impact of HIV on intestinal barrier function. A three year longitudinal cohort study in a shanty compound in Lusaka, Zambia, carried out before anti-retroviral therapy was widely available, was used to assess the impact of HIV on susceptibility to intestinal infectious disease. We measured the incidence and seasonality of intestinal infection and diarrhoea, aggregation of disease in susceptible individuals, clustering by co-habitation and genetic relatedness, and the disease-to-infection ratio.
Adults living in a small section of Misisi, Lusaka, were interviewed every two weeks to ascertain the incidence of diarrhoea. Monthly stool samples were analysed for selected pathogens. HIV status and CD4 count were determined annually.
HIV seroprevalence was 31% and the prevalence of immunosuppression (CD4 count 200 cells/microL or less) was 10%. Diarrhoea incidence was 1.1 episodes per year and the Incidence Rate Ratio for HIV infection was 2.4 (95%CI 1.7-3.3; p < 0.001). The disease-to-infection ratio was increased at all stages of HIV infection. Aggregation of diarrhoea in susceptible individuals was observed irrespective of immunosuppression, but there was little evidence of clustering by co-habitation or genetic relatedness. There was no evidence of aggregation of asymptomatic infections.
HIV has an impact on intestinal infection at all stages, with an increased disease-to-infection ratio. The aggregation of disease in susceptible individuals irrespective of CD4 count suggests that this phenomenon is not a function of cell mediated immunity.
[Show abstract][Hide abstract] ABSTRACT: Adults with acquired immune deficiency syndrome and persistent diarrhoea in Zambia have intestinal infection, predominantly protozoa.
To search for treatment which can be offered with minimal investigation, we carried out a double-blind, randomized-controlled trial of nitazoxanide (a drug with a range of activity against parasites and bacteria).
Patients with diarrhoea of 1 month duration or longer were randomized to receive nitazoxanide (1000 mg twice daily) or placebo for 2 weeks. End-points were clinical response, parasitological clearance and mortality.
Two hundred and seven adults were randomized; 42 died during the study. The primary assessment of efficacy was made after 17 days. Clinical response was observed in 56 (75%) of 75 patients receiving nitazoxanide and 45 (58%) of 77 patients receiving placebo (P = 0.03). The rate of improvement was markedly higher in patients with CD4 counts under 50 cells/microL receiving nitazoxanide (P = 0.007). The benefit was largely restricted to the period when the drug was being administered. No difference was seen in parasitological clearance between the two groups. Mortality was 19% by 4 weeks of follow-up and did not differ with treatment allocation.
Nitazoxanide given orally for 14 days was associated with clinical improvement in Zambian acquired immune deficiency syndrome patients with diarrhoea, especially those with very low CD4 counts.
[Show abstract][Hide abstract] ABSTRACT: To determine the response of the small intestinal mucosa to environmental conditions, we studied changes in mucosal architecture and function in a longitudinal cohort study in African adults. Over three consecutive years, 238 adults submitted monthly stool samples for parasitologic and bacteriologic analysis and underwent an annual endoscopic jejunal biopsy for mucosal morphometry. Absorption and permeability assays were performed on the same day as the enteroscopy. Variation in mucosal architecture and function was correlated with environmental factors and stool microbiology. The whole cohort had structural and functional evidence of tropical enteropathy, but structure and function were only weakly correlated. There were marked changes over time, and seasonal variation was observed in villous height (16%), xylose recovery (16%), and permeability (28%). Asymptomatic intestinal infections were common. Enteropathy was more severe in participants with Citrobacter rodentium or hookworm ova in the stool sample taken one month before the investigations were performed.
The American journal of tropical medicine and hygiene 05/2004; 70(4):412-9. · 2.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Identification of patients likely to experience high levels of discomfort during unsedated gastroscopy would be useful as these patients could be prospectively targeted for sedation. We prospectively assessed patient and endoscopic variables in subjects attending for endoscopy in order to identify factors associated with patients' experience of the unsedated examination.
We studied 508 patients attending for routine diagnostic gastroscopy. Clinical and endoscopic data were collected and patients completed a two-part questionnaire assessing their anxiety with, and experience of, the procedure.
Thirty-nine subjects failed to complete the initial unsedated endoscopy. Failure to tolerate endoscopy was associated with younger age (P = 0.002) and examination with a standard-bore (> or = 9.0 mm) endoscope (P = 0.004). High levels of patient discomfort during the procedure were associated with younger age (P < 0.001), high levels of pre-endoscopic anxiety (P < 0.001), high levels of pre-endoscopic discomfort due to throat spray (P = 0.02) and examination with a standard-bore endoscope (P < 0.001). Preference for sedation during future examinations was related to female gender (P = 0.02), young age (P = 0.02), high levels of apprehension (P < 0.001), the examining doctor (P = 0.002) and use of a standard-bore endoscope (P < 0.001).
Discrete clinical characteristics and endoscopic variables are associated with patients' experience of unsedated endoscopy. Further work might result in an algorithm for identifying patients who would benefit from sedation prior to gastroscopy.
Scandinavian Journal of Gastroenterology 01/2002; 36(12):1352-7. · 2.33 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Delayed puberty is a frequent complication of inflammatory bowel disease. The precise etiological mechanisms are not known. In this study, we wanted to determine the relative contribution of undernutrition and inflammation to delayed puberty and the effect of inflammation on the reproductive axis. Puberty was assessed in rats with 2,4,6-trinitrobenzenesulfonic acid induced-colitis, healthy controls, and animals pair fed to match the food intake of the colitic group. The response to testosterone administration was assessed in colitic rats. We found that induction of colitis was associated with hypophagia and reduced weight gain, and undernutrition in healthy females (i.e., pair fed) resulted in a delay in the onset (by 4.8 days, P < 0.001) and progression of puberty (normal estrous cycles in 42%, P = 0.04) compared with controls. However, puberty was further delayed in the colitic group (1.4 days after pair fed) with the absence of normal estrous cycling in all rats. In males, the onset of puberty was also delayed, and weights of accessory sex organs were reduced compared with pair-fed controls. Plasma testosterone concentrations were low, and gonadotropin concentrations were normal in colitic rats. Testosterone treatment normalized puberty in male rats with colitis. In conclusion, in rats with experimental colitis, inflammation appears to potentiate the effect of undernutrition on puberty. The weights of secondary sex organs and the onset of puberty were normalized by testosterone treatment.
[Show abstract][Hide abstract] ABSTRACT: Tropical enteropathy is widespread throughout the tropics, but its pathogenesis is unknown. T-cell activation has been demonstrated to result in enteropathy in vitro and in animal models, and occurs in untreated patients with coeliac disease. We have therefore examined the hypothesis that T-cell activation is important in the pathogenesis of tropical enteropathy.
Healthy black Zambian subjects were compared with black and white South Africans. Quantitative microscopy was conducted on distal duodenal biopsies. Mucosal T-cell activation was quantitated by dual colour immunofluorescence staining for CD3 plus CD69 or HLA-DR. Crypt proliferation was measured by direct counting of Feulgen-stained mitotic figures, and systemic immune activation by assay of serum tumour necrosis factor alpha (TNF-alpha).
Villous height was reduced (P = 0.0004), crypt depth increased (P < 0.0001), and mitoses per crypt increased (P = 0.014) in black Zambians compared with black and white South Africans. Mucosal thickness was similar. Intraepithelial lymphocyte count was increased in the black groups compared with whites (P = 0.03). CD3+CD69+ (P = 0.0007) and CD3+HLA-DR+ (P < 0.0001) expression was increased in black Zambians compared with black and white South Africans. Serum TNF-alpha was similar in all groups.
Tropical enteropathy is associated with mucosal T-cell activation and crypt hyperplasia. Tropical enteropathy occurs in the absence of malnutrition, diarrhoea or systemic illness.
European Journal of Gastroenterology & Hepatology 10/2001; 13(10):1175-81. · 1.92 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Esophageal disease research is impeded by a paucity of nonmalignant cell lines. Furthermore, culture of primary esophageal cells is difficult because of a lack of cell adhesion and contamination. The aim of this study was to develop a short-term culture method to facilitate cell physiologic studies by using primary esophageal cells.
By using a cytology brush, squamous and Barrett's epithelial cells were obtained from the esophagus of patients undergoing upper endoscopy. Cells were brushed onto chamber slides and allowed to adhere to the surface. Primary culture media was then added and cells were maintained at 37 degrees C for up to 72 hours. Cell yield and viability were calculated after trypan blue staining. For cell physiologic studies, cells were loaded with pH-sensitive dye BCECF-AM and intracellular pH measured on a dual excitation fluorescence microscope after an ammonium chloride prepulse. At the end of the physiologic experiments, cells were fixed in methanol and acetone and the cell type was verified with cytokeratin immunocytochemistry.
Viable human esophageal cells were maintained in culture for up to 72 hours. The cells extruded trypan blue, and BCECF-AM was cleaved to BCECF by an intact cell membrane and permitted intracellular pH measurements. The epithelial cell origin of the cells was confirmed by cytokeratin staining. There was no contamination over the culture period and no overgrowth by lymphocytes or fibroblasts.
This novel adaptation of brush cytology technique enables short-term culture of esophageal cells for in vitro studies. This rapid, simple primary culture technique is suitable for endoscopy and does not require the immediate, time-consuming laboratory techniques.
[Show abstract][Hide abstract] ABSTRACT: We have previously demonstrated a strong relationship between low serum retinol concentration and mortality in Zambian AIDS patients with diarrhoea, but were unable to detect any benefit from oral micronutrient supplementation.
To test the hypothesis that this is related to impaired availability of vitamin A, we analysed serum retinol concentration changes over 6 h following oral mega-dose therapy (60, 120 or 180 mg retinol).
Twenty-four men without diarrhoea, 15 adults with persistent diarrhoea and 11 children (six girls, five boys) with persistent diarrhoea were studied.
Men with persistent diarrhoea had lower baseline serum retinol concentrations (median 0.39 micromol/L, interquartile range 0.21-0.56) than controls (median 1.16 micromol/L, interquartile range 0.84-1.47; P=0.0003). After 60 mg retinol, the rise in serum retinol in HIV seropositive controls (median 0.63 micromol/L, interquartile range 0.35-0.77) did not differ significantly from that observed in HIV seronegative controls (median 0.35 micromol/L, interquartile range - 0.04-0.56; P=0.20). Increasing the dose to 120 mg or 180 mg retinol did not enhance the increase in serum retinol concentration. The increase in serum retinol was less in adults with persistent diarrhoea (median 0.25 micromol/L, interquartile range 0.04-0.35) and in children (median 0.11 micromol/L, interquartile range 0.04-0.46) than in men without diarrhoea (median 0.44 micromol/L, interquartile range 0.26-0.74; P=0.03). Adults and children with diarrhoea had greater losses of retinol in urine over a 24-h period than controls, but less than 1% of the ingested dose was excreted.
These results suggest that persistent diarrhoea in this population is associated with reduced bioavailability of retinol. Further work is required to determine the metabolic fate of therapeutic doses of retinol and to determine appropriate replacement strategies for HIV infected individuals.
[Show abstract][Hide abstract] ABSTRACT: The role of mucosal T-cell activation in HIV-associated enteropathy is uncertain. Twenty Zambian patients with AIDS and chronic diarrhea were studied, as were nine controls. Distal duodenal biopsies were taken at endoscopy. Morphometric analysis and dual color immunofluorescence staining were performed. Villous height was reduced [177 (118-228) vs 305 (244-358) microm P = 0.002] and crypt depth increased [220 (164-202) vs 194 (164-202) microm P = 0.008] in AIDS patients compared to controls. CD3+CD4+ T cells were reduced in AIDS patients compared to controls [12.9 (5.7-25.2) vs 47.6 (33.4-65.5)% P = 0.04]. There was no significant difference in expression of CD8, CD25, CD69, HML-1, or HLA-DR on T cells between the AIDS patients and controls, with the exception of CD3+HML-1+ cells, which were increased in AIDS patients (P = 0.05). Small intestinal T-cell activation was similar between AIDS patients and controls. We conclude, therefore, that this mechanism is not likely to be important in the pathogenesis of HIV-associated enteropathy.
Digestive Diseases and Sciences 06/2001; 46(5):1133-8. · 2.26 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Upper gastrointestinal endoscopy is performed without sedation in many countries. Unsedated patients experience more discomfort during endoscopy than sedated patients, but few studies have examined factors which could be modified to minimize discomfort during the procedure. We assessed the effect of endoscope diameter on patient discomfort during unsedated transoral gastroscopy.
A total of 322 patients attending for unsedated endoscopy were examined using an endoscope of diameter either 6.0 mm or 9.8 mm. Patients completed a two-part questionnaire assessing tolerance of the procedure and discomfort during it.
There was failure to complete the initial unsedated endoscopy in three of 163 patients in the 6.0 mm group and 14 of 159 in the 9.8 mm group (P = 0.009). Patients in the 6.0 mm group reported less discomfort both during endoscope insertion (P < 0.0001) and during the remainder of the procedure (P < 0.0001). 14% of patients in the 6.0 mm group indicated that they would request sedation if a further endoscopy were necessary, compared with 31% in the 9.8 mm group (P = 0.0005).
Ultrathin endoscopes may have a role in clinical practice if randomized comparative studies with standard-bore instruments confirm that they do not compromise diagnostic quality.
[Show abstract][Hide abstract] ABSTRACT: Hemolysins have been found to possess a variety of functions in bacteria, including a role in virulence. Helicobacter pylori demonstrates hemolytic activity when cultured on unlysed blood agar plates which is increased under iron-limiting conditions. However, the role of an H. pylori hemolysin in virulence is unclear. Scrutiny of the H. pylori 26695 genome sequence suggests the presence of at least two distinct hemolysins, HP1086 and HP1490, in this strain. Previous studies have shown that the in vitro hemolytic activity of H. pylori is reduced when it is coincubated with dextran 5000, suggesting the presence of a pore-forming cytolysin. HP1086 has homology to pore-forming cytolysins (TlyA) from other bacterial species, and the introduction of the cloned H. pylori tlyA gene into a nonhemolytic Escherichia coli strain conferred hemolytic activity. An H. pylori tlyA defined mutant showed reduced in vitro hemolytic activity, which appears to be due to pore formation, as the hemolytic activity of the wild-type strain is reduced to the same level as the tlyA mutant by the addition of dextran 5000. The mutant also showed reduced adhesion to human gastric adenocarcinoma cells and failed to colonize the gastric mucosa of mice. These data clearly suggest a role in virulence for H. pylori TlyA, contrary to the suggestion that hemolytic activity is an in vitro phenomenon for this pathogen.
Infection and Immunity 04/2001; 69(3):1697-703. · 4.07 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Neuropeptide Y (NPY) is thought to play a crucial role in the normal hypothalamic response to starvation. After a period of food restriction, increased release of NPY induces hunger and hyperphagia, and helps to restore body weight to its set point. Persistent anorexia in rats with experimental colitis implies failure of this adaptive feeding response. In vivo NPY release and regional hypothalamic NPY concentrations were measured in rats with trinitrobenzenesulphonic acid (TNBS)-induced colitis, healthy controls and animals pair-fed to match the food intake of the colitic group. Food intake in the colitic group was assessed after administration of NPY and two other potent orexigenic peptides: melanin-concentrating hormone (MCH) and hypocretin (orexin-A). Food intake was decreased by 30-80% below control values for 5 days in the colitic rats. In both the pair-fed and colitic groups, release of NPY in the paraventricular nucleus was significantly increased compared with free-feeding controls. Intraventricular or intrahypothalamic administration of NPY, MCH or hypocretin elicited a feeding response in healthy controls, but not in the colitic group. In summary, animals with TNBS-colitis and anorexia show an appropriate increase in hypothalamic NPYergic activity. However, the failure of NPY and other orexigenic peptides to increase feeding in the colitic group indicates suppression of feeding, either by inhibition of a common downstream hypothalamic neuronal pathway or by induction of one or more potent anorexigenic agents.
[Show abstract][Hide abstract] ABSTRACT: Knowledge of sedation trends for upper gastrointestinal endoscopy is important for health service planning, particularly in view of rapidly increasing demands on endoscopy services. However, no data are available on sedation trends in Britain over the past 10 years.
To determine sedation use for routine gastroscopy in a single endoscopy unit between 1989 and 1998.
This was a retrospective study of 9795 consecutive adults (mean age 56 years, range 18-100 years; 4512 females) who had undergone a gastroscopy between 1989 and 1998. Clinical, pharmacological and endoscopic data were retrieved from a computerized database.
Over the 10-year study period, the sedation rate remained constant for patients undergoing therapeutic endoscopy (P=0.99) and those undergoing in-patient diagnostic examinations (P=0.63). In contrast, the sedation rate for out-patient diagnostic endoscopy decreased by 54%, from a high of 70% in 1990 to 32% in 1998 (P < 0.0001). Logistic regression analysis showed that the decline in sedation use was greater in females (P < 0.0001) than males and in procedures performed by non-consultant compared to consultant staff (P=0.01).
If our results form part of a national trend, they will have important implications for cardiopulmonary monitoring strategies, recovery room practices and for complication rates due to the use of sedation for upper gastrointestinal endoscopy.
[Show abstract][Hide abstract] ABSTRACT: Interferon (IFN)-gamma plays an important role in the immunologic control of infection by the protozoan enteropathogen Cryptosporidium parvum. We tested the hypothesis that IFN-gamma may directly inhibit infection of enterocytes by this pathogen.
HT-29, Caco-2, and H4 human enterocyte cell lines were grown in monolayers and incubated with IFN-gamma before exposure with C. parvum. IFN-gamma receptor expression in the cell lines was determined by Western blot analysis.
IFN-gamma inhibited C. parvum infection of both HT-29 and Caco-2 cells but not H4 cells. Response to IFN-gamma was related to the expression of the IFN-gamma receptor in the respective cell lines. The effect of IFN-gamma was partially reversed by inhibition of the JAK/STAT signaling pathway. IFN-gamma mediated its action by at least 2 mechanisms: (1) inhibition of parasite invasion and (2) by modification of intracellular Fe(2+) concentration. No role for tryptophan starvation or nitric oxide synthase activity was found. TNF-alpha and IL-1beta also had anti-C. parvum activity but had no synergistic effect with IFN-gamma.
IFN-gamma directly induces enterocyte resistance against C. parvum infection; this observation may have important consequences for our understanding of the mucosal immune response to invasive pathogens.
[Show abstract][Hide abstract] ABSTRACT: Epidemiological evidence has clearly shown a highly significant relationship between Helicobacter pylori infection and the development of duodenal ulcer and distal gastric adenocarcinoma. Despite H. pylori being a common aetiological factor for both disorders, the two disease phenotypes are virtually mutually exclusive. This indicates that the host response to infection has a pivotal role in determining outcome; these disease phenotypes relate to the effect of infection on gastric acid secretion, duodenal ulcer being closely related to sustained acid secretion whereas gastric cancer follows gastric atrophy and impaired gastric acid secretion. Cancer at the oesophageal junction and that associated with Barrett's oesophagus is now the most rapidly increasing tumour in the gastrointestinal tract. The challenge for the next millennium, therefore, is to try and develop methods for identifying patients at risk of developing oesophagogastric cancer. A common feature in the pathogenesis of both gastric and oesophageal adenocarcinoma is inflammation presenting clinically as gastritis and oesophagitis. The pathway from gastritis to gastric atrophy, dysplasia and carcinoma is thought to be a multi-step process, probably triggered by free radicals within the gastric epithelium and increased exposure to luminal carcinogens. However, it has been unclear as to which aspect of the host response determines whether an individual will move along the neoplasia pathway. Recent work has shown that qualitative aspects of the immune environment in the stomach may account for a substantial part of the phenotypic divergence following H. pylori infection. Interleukin-1 beta polymorphisms relate closely to the propensity for an individual to develop distal gastric cancer and maybe useful for predicting risk in family members. In Barrett's oesophagus, we have recently shown that the immune environment may also be important in determining whether an individual will develop cancer. Although we did not find that Barrett's oesophagus was a profoundly inflammatory condition (unlike esophagitis in the squamous epithelium), where there was evidence of inflammation it was qualitatively different from that of oesophagitis in that a Th-2 response with increased expression of IL-4 predominated in Barrett's, whereas a Th-1 proinflammatory response characterised oesophagitis in squamous epithelium. It seems likely that the specific immune environment within Barrett's metaplasia may be an important driver towards dysplasia and carcinoma. Thus, the immune environment in the stomach and esophagus may be critical in determining whether an individual is at risk of developing neoplastic complications of H. pylori infection and gastroesophageal reflux. Identification of the genetic factors which underpin these responses may ultimately result in development of methods to identify individuals at high risk.
Journal of Physiology-Paris 01/2001; 95(1-6):423-7. · 0.82 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: HIV-related diarrhoea is an important cause of morbidity and mortality in HIV infection. Cytomegalovirus is a well-established cause of diarrhoea, but the role of other enteric viruses is less clear and will be discussed here. The clinical manifestations, disease mechanisms, diagnostic techniques and current treatments for the management of these infections are reviewed.