Michael J.G. Farthing

Nature of the toxicity of cyclosporin A in the rat

Abstract The potent immunosuppressive agent Cyclosporin A (CyA) causes a spectrum of toxicological effects in rats, of which the most striking is weight loss. Pair-feeding experiments have shown that this is caused, in part, by a short period of anorexia. However, even when the food intake has become normal the rats receiving CyA fail to gain weight. That CyA at the doses used causes increased protein catabolism is also indicated by a fall in serum albumin and a marked rise in blood urea unaccompanied by a corresponding rise in creatinine. CyA is mildly and reversibly hepatotoxic and there is slight nephrotoxicity in the rat on the basis of histology and small elevations in creatinine.

Abnormal illness attitudes in patients with irritable bowel syndrome

The Illness Attitudes Scales (IAS) and the Beck Depression Inventory (BDI) were administered to 40 patients with irritable bowel syndrome (IBS) and these were compared with 35 patients with organic gastrointestinal (GI) disease, 37 depressed patients, and 40 healthy volunteers. The BDI score was found to be greater in the IBS patients than in either the patients with organic disease or healthy subjects. All the patient groups had abnormal IAS scores compared with the healthy group, but these were most marked among the IBS patients with elevated scores on six out of the eight subscales. Three of these were specific to the IBS patients: bodily preoccupation, hypochondriacal beliefs and disease phobia. The results of this study indicate that clinical IBS is associated with abnormal illness attitudes which are not simply a reflection of either an associated depression or of experiencing physical symptoms.

Small intestinal injury in a neonatal rat model of giardiasis is strain dependent

BACKGROUND & AIMSnThe factors that determine the severity of giardiasis are poorly understood. Host factors are important, but parasite virulence may also play a role. The aim of this study was to compare the apparent virulence of three genotypically different Giardia isolates (PO1, VNB3, and WB).nnnMETHODSnInfection rates, parasite loads, structural damage, disaccharidase activity, and water and electrolyte absorption were observed at 10 days after inoculation in a neonatal rat model of infection.nnnRESULTSnDNA fingerprinting showed differences between isolates studied. The infective rate varied between 67% and 100%. There were no differences in intestinal parasite load. Infection with strains PO1 and WB, but not with VNB3, was associated with a reduction in villus height. There was precocious expression of sucrase at 10 days after inoculation in all infected groups. Water absorption of a plasma electrolyte solution was decreased in VNB3-infected animals when compared with PO1- and WB-infected animals and controls. Water absorption and lactose hydrolysis were impaired during perfusion with a lactose-containing solution in all infected groups.nnnCONCLUSIONSnThree genotypically different Giardia isolates that infect neonatal rats with the same trophozoite load differ in their ability to cause functional mucosal damage. Infection with Giardia lamblia induced precocious expression of sucrase activity and impaired mucosal absorption.

Water, electrolyte, glucose, and glycine absorption in rat small intestinal transplants

Water, electrolyte, glucose, and glycine absorption were studied in vivo in successful rat small intestinal transplants. Isolated bowel loops were transplanted from F1 hybrids into parental strain Lewis rats. A 7-day course of cyclosporin A was given for immunosuppression. Absorption was studied using a steady-state perfusion technique at either 9 or 21 days after transplantation. Histologic examination showed there was villus shortening with time but no evidence of rejection. When perfused with isotonic saline, both allografts and controls secreted water. However, allografts and denervated controls secreted chloride, whereas innervated controls absorbed chloride (p less than 0.05). There was a marked reduction in water and sodium absorption from 30 mM glucose-saline in transplanted loops and denervated controls, whereas glucose absorption was relatively preserved in these groups at 9 days (p less than 0.01). These changes could not be accounted for by rejection or ischemia. These studies demonstrate that denervation may be a major limiting factor in intestinal transplantation.

Interrelationships between Helicobacter pylori infection, nonsteroidal antiinflammatory drugs and gastroduodenal disease. A prospective study in healthy volunteers.

Helicobacter pylori and nonsteroidal antiinflammatory drugs independently cause gastroduodenal mucosal injury but the relationship between them remains unclear. We have performed a double-blind, parallel-group, placebo-controlled prospective study in 77 healthy volunteers aged 19–35 years who were randomly allocated to indomethacin (N=15), one of three oxicams (piroxicam, chlortenoxicam, or CHF 1194;N=36), or placebo (N=26). Esophagogastroduodenoscopy was performed before and after four weeks of treatment and the mucosal appearances graded. Colonization withH. pylori was established at each endoscopy and gastrointestinal symptoms were assessed by daily diary card. Seven subjects (9%) were positive forH. pylori before treatment (one placebo, one indomethacin, and five an oxicam); theirH. pylori status remained unchanged. Two of 70H. pylori-negative subjects becameH. pylori-positive (2.9%), both of whom had received placebo. The endoscopic score deteriorated in 1/6 drug-treatedH. pylori-positive subjects and in 0/1 taking placebo. Of theH. pylori-negative subjects whose endoscopic score deteriorated, three (13%) were taking placebo, four (28.6%) indomethacin, and eight (25.8%) an oxicam. Upper gastrointestinal symptoms were reported in eight (30.8%) of the subjects taking placebo (one subject negative forH. pylori became positive), eight (53.3%) indomethacin (oneH. pylori-positive), and 10 (27.8%) an oxicam (oneH. pylori-positive). There were no statistically significant differences between theH. pylori-negative andH. pylori-positive groups whether on drug or placebo. These findings suggest thatH. pylori infection, at least in the short term, neither influences the propensity of nonsteroidal antiinflammatory drugs to produce macroscopic gastroduodenal mucosal injury nor does it effect the occurrence of upper gastrointestinal symptoms.

The use of 3,3',5,5'-tetramethylbenzidine as a peroxidase substrate in microplate enzyme-linked immunosorbent assay.

The assay conditions for the use of 3,3,5,5 tetramethylbenzidine (TMB) in microplate enzyme-linked immunosorbent assay are described. TMB is a safe (non-mutagenic) chromogen that is more sensitive than OPD as a substrate for horseradish peroxidase. We describe the optimum storage and assay conditions for this chromogen.

Increased energy expenditure in growing adolescents with Crohn's disease

Undernutrition is considered to have a central role in the pathogenesis of growth retardation in Crohns disease. This may occur as a consequence of inadequate food intake, increased energy expenditure, or both. Ten growing adolescents with inactive Crohns disease were assessed with respect to anthropometric parameters and resting energy expenditure, measured by indirect calorimetry during remission, repeated in relapse (N=5), and compared to that predicted from the Harris-Benedict formula. Mean energy intake was assessed with seven-day diaries in five patients and compared to recommended intake for age, sex, weight, and physical activity. Ten healthy, growing, age- and sex-matched adolescents served as controls. Nine patients with inactive Crohns disease, who had ceased growing, were matched for disease site and duration and acted as disease controls. Patients and disease controls had lower body mass index (19.2±0.6; 20.9±0.7) than healthy controls (23.7±0.6;P<0.001). Percent body fat was lower in patients (13.2±1.9%) compared to healthy controls (20.5±2.4%;P<0.05) but not to disease controls (17.0±2.6%). Patients had higher resting energy expenditure per kilogram of fat-free mass than disease or healthy controls (36.9±5.1; 32.9±2.6; 30.9±2.1 kcal;P<0.02). Measured resting energy expenditure in patients, but not in disease or healthy controls, was higher than the predicted (measured: predicted 1.15, 1.03, 0.9, respectively;P<0.03). Energy intake in patients was 97% of recommended intake but the measured ratio of energy intake/resting energy expenditure was lower than the predicted ratio (1.49 vs 1.71;P<0.05). During subsequent relapse in five patients resting energy expenditure was unchanged. In growing adolescents with inactive Crohns disease, there is increased energy expenditure that is not accompanied by an increase in energy intake. Relapse of disease does not appear to increase resting energy expenditure further but may “divert” energy from growth to disease activity. This suggests that nutritional therapy should be directed towards increasing caloric intake to maximize growth potential.

Characterization of endothelin (ET) receptors in the isolated gall bladder of the guinea‐pig: evidence for an additional ET receptor subtype

1 We have characterized the receptors mediating contractions induced by endothelin‐1 (ET‐1), ET‐2, ET‐3 and the ETB‐selective receptor agonists, sarafotoxin 6c (SX6c), IRL 1620, BQ‐3020, [Ala1,3,11,15]ET‐1 and ET (16–21) in strips of the isolated gall bladder of the guinea‐pig (GPGB). We used as antagonists BQ‐123 (ETA receptor selective) and PD 145065 (ETA/ETB receptor non‐selective). 2 ET‐1, ET‐2 and ET‐3 (10−10 M to 3 × 10−7 M) caused similar slowly‐developing concentration‐dependent contractions of the GPGB. Contractile effects induced by ET‐1, ET‐2 or ET‐3 (at 3 × 10−7 M) were also similar (230 ± 25, 241 ± 7 and 287 ± 37% of that to histamine at 5 × 10−6 M, n = 7, 6, 12, respectively). However, the threshold concentration for ET‐1 or ET‐2 was 10−1 M whereas it was 3 × 10−9 M for ET‐3. 3 SX6c (10−10 M to 3 × 10−7 M) also caused slowly‐developing concentration‐dependent contractions at a threshold concentration of 10−1 M (n = 16). However, the contraction caused by SX6c at 3 × 10−7 M was 116 ± 9% of that to histamine at 5 × 10−6 M, which was half of that induced by the same concentration of the ET isopeptides. The contraction induced by IRL 1620 at 3 × 10−7 M (n = 9) was 43 ± 9% of that to histamine at 5 × 10−6 M, which was one fifth of that produced by the same concentration of ET‐1. Contractions induced by BQ‐3020 or [Ala1,3,11,15]ET‐1 at 3 × 10−7 M were even less than those produced by IRL 1620. ET (16–21) was inactive up to 10−5 M. Addition of a concentration of 3 × 10−7 M of ET‐1 to tissues with developed contractions induced by the bolus addition of 3 × 10−7 M SX6c caused a further contraction of the GPGB to the level observed with ET‐1 alone at 3 × 10−7 M (n = 8). 4 BQ‐123 (10−5 M) did not affect the concentration‐response curve to ET‐1 and the contraction induced by 3 × 10−7 M was also not affected (n = 5; 239 ± 19% of histamine at 5 × 10−6 M). PD 145065 (10−5 M) shifted the ET‐1 concentration‐response curve to the right and the contraction induced by ET‐1 at 3 × 10−7 M was inhibited by 15% (n = 6; NS). A higher concentration of BQ‐123 (10−4 M) caused a significant shift to the right of the ET‐1 concentration‐response curve similar to that caused by PD 145065 (10−5 M) and caused a 24% (n = 6; NS) inhibition of the contractions induced by ET‐1 at 3 × 10−7 M. PD 145065 (10−4 M) abolished contractions induced by ET‐1 (up to 10−7 M) and inhibited the response to ET‐1 at 3 × 10−7 M by 52% (n = 4; P < 0.05). 5 Contractions induced by ET‐3 were more sensitive to inhibition by the antagonists. BQ‐123 (10−6, 10−5 or 10−4 M) inhibited responses to 3 × 10−7 M ET‐3 by 66, 71 and 83%, respectively (n = 5, 5, 3; P < 0.05). PD 145065 (10−6, 10−5 or 10−4 M) attenuated more strongly than did BQ‐123 the contractions induced by ET‐3. For instance, the contractions caused by ET‐3 at 3 × 10−7 M were decreased by 73 and 80% (n = 5, 5; P < 0.05) in the presence of PD 145065 (10−6 or 10−5 M, respectively). PD 145065 (10−4 M) completely abolished contractions to ET‐3 (n = 4; up to 3 × 10−7 M). 6 Contractions induced by SX6c, especially those observed at concentrations lower than 10−8 M, were attenuated by BQ‐123 (up to 10−4 M). PD 145065 (10−5 M) shifted to the right the concentration‐response curve to SX6c and inhibited by 38% (P < 0.05) the contractions induced by 3 × 10−7 M. However, the contractions induced by a bolus addition of a high concentration of SX6c (3 × 10−7 M) and the subsequent addition of an identical concentration of ET‐1 on top of SX6c were not affected by BQ‐123 (10−6 or 10−5 M). 7 These results suggest that ETB receptors are involved in the contractions induced by endothelins in the GPGB. However, SX6c and other selective ETB agonists produced only half or less than half of the contractile response induced by non‐selective agonists. In addition, the responses to ET‐1 but not to ET‐3, were insensitive to the antagonist action of BQ‐123 at 10−5 M whereas BQ‐123 or PD 145065 at 10−5 M strongly antagonized contractions induced by ET‐3. Finally, BQ‐123 at 10−4 M inhibited contractions to ET‐1 and SX6c. Thus, within the GPGB there may well be additional ET receptor(s) not conforming to the established ETA/ETB receptor subtype classification, as well as ETB receptors.

Acetate and citrate stimulate water and sodium absorption in the human jejunum.

Using a standard perfusion technique, the organic anions acetate (50 mmol/l) and citrate (5 mmol/l) have been shown to stimulate absorption of water and sodium from the human jejunum. These observations may support further the rationale for including acetate or citrate in oral rehydration solutions for the treatment of acute diarrhoeal disease in humans.

Albendazole chemotherapy for treatment of diarrhoea in patients with AIDS in Zambia: a randomised double blind controlled trial

Abstract Objective: To determine the value of short course, high dose albendazole chemotherapy in the treatment of persistent diarrhoea related to HIV in unselected patients in urban Zambia. Design: A randomised double blind placebo controlled trial of albendazole 800 mg twice daily for two weeks. Patients were monitored intensively for one month and followed for up to six months. Setting: Home care AIDS services in Lusaka and Ndola. Patients: 174 HIV seropositive patients with persistent diarrhoea (defined as loose but not bloody stools three or more times a day for three weeks or longer). No investigations were undertaken except HIV testing after counselling. Main outcome measures: Proportion of time periods during which diarrhoea was experienced after completion of treatment; proportion of patients with full remission after completion of treatment; mortality. Results: The patients taking albendazole had diarrhoea on 29% fewer days than those taking placebo (P<0.0001) in the two weeks after treatment. The benefit of albendazole was maintained over six months. In patients with a Karnofsky score of 50 to 70 (needing help with activities of daily living and unable to work, but not needing admission to hospital) diarrhoea was reduced by 50%. Remission was obtained in 26% of all patients who received albendazole (P=0.004 against 9% receiving placebo), and this difference was maintained over six months (log rank test, P=0.003). Albendazole had no effect on mortality. Minimal adverse effects were noted. Conclusions: For HIV infected Zambians with diarrhoea of more than three weeks duration albendazole offers substantial relief from symptoms and may be used empirically, without prior investigation. Key messages Enteric intracellular protozoa can be identified in most of these patients in hospital in Lusaka Albendazole (800 mg twice daily for two weeks) reduced the time with diarrhoea over six months The Karnofsky score, a simple clinical assessment, identified patients most likely to benefit Albendazole had no measurable effect on mortality