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Biomedical subjects

G P Davidson

Publications and source records attributed to G P Davidson.

At least 37 records · Page 2Linked to original sources
PubMed1999

Factors affecting the validity of the 13C-urea breath test for in vivo determination of Helicobacter pylori infection status in a mouse model.

BACKGROUND: The mouse model using a human isolate of Helicobacter pylori is being widely accepted as an economical means of studying gastric infection. A noninvasive monitoring method would be useful for repeated testing to establish the time course of infection and the efficacy of treatments. In this study, we describe factors that affected interpretation of 13C urea breath test results for the assessment of H. pylori infection status in this model. MATERIALS AND METHODS: Female C57B1/6 mice that underwent gavage with H. pylori or saline were breath-tested using 50 micrograms of 13C urea at intervals up to 2 months after inoculation. The generation of 13CO2 (excess delta 13CO2) by infected mice was compared to that of uninfected controls. The effects of diet, fasting, and coprophagy on the reliability of the 13C urea breath test were quantitated. RESULTS: Both commercial and synthetic mouse diets exhibited marked in vitro urease activity. A minimum fasting time of 13 hours prior to breath testing significantly reduced this dietary contribution to excess delta 13CO2 values. The coprophagic tendency of the mice caused spuriously high excess delta 13CO2 counts in the breath of both control and H. pylori-infected mice. CONCLUSIONS: Although the dietary contribution to spuriously high values of excess delta 13CO2 in mice breath-tested for H. pylori infection was reduced by fasting, the high nonspecific urease activity generated by coprophagy severely limited the reliability of the urea breath test in the assessment of H. pylori infection status.

Animals↗
PubMed1998

The sugar permeability test reflects disease activity in children and adolescents with inflammatory bowel disease.

OBJECTIVES: To investigate the relationship of intestinal permeability in children and adolescents with inflammatory bowel disease (IBD) to disease activity, disease extent, and response to therapy. STUDY DESIGN: Patients with new and established diagnoses of IBD (12 Crohn's disease [CD] and 18 ulcerative colitis [UC]) were studied. Intestinal permeability was evaluated by measuring with high-performance liquid chromatography 5-hour urinary excretion ratio of lactulose/L-rhamnose (L/Rh). RESULTS: In 8 of 9 patients with active CD, the L/Rh ratio was higher than the reference range (0.006 to 0.074, n = 36). In inactive CD (n = 3) the L/Rh ratio was within the reference range. In 6 of 7 patients with active extensive UC, the L/Rh ratio was elevated. In inactive extensive UC (n = 6) the normal permeability ratio was shown. In both active CD and active extensive UC, the frequency of elevated intestinal permeability was significantly greater than values in both inactive forms. The permeability ratio was normal in 4 of 5 patients with active left-sided colitis. In 5 of 7 patients (3 CD, 4 UC), repeat permeability values entered the reference range after acute phase therapy. Two patients with persistently elevated intestinal permeability (1 CD, 1 UC) had a disease flare-up within 6 months. CONCLUSIONS: Intestinal permeability is a marker of disease activity in CD and extensive UC. Serial permeability test may be useful in monitoring disease activity.

Adolescent↗
PubMed1998

Bowel dysfunction in cystic fibrosis: importance of breath testing.

OBJECTIVE: To investigate the prevalence of carbohydrate malabsorption and bacterial overgrowth in children with cystic fibrosis (CF) and abnormal stool pattern referred for breath hydrogen testing. METHODS: Results from 89 tests using lactose, sucrose and lactulose in 54 children with CF were compared with 5430 tests on children with non-CF-related stool abnormalities. RESULTS: Children with CF were more frequently unable to ferment lactulose to hydrogen (39% vs. 20%, P<0.03); they had significantly longer oro-caecal transit times (mean 99 vs. 68 min, P<0.0003); they had a higher incidence of bacterial overgrowth (32% vs. 7%, P<0.003) and sucrose malabsorption (47% vs. 14.5%, P<0.004); but they had no increase in lactose malabsorption (40% vs. 31%). Children with bacterial overgrowth in both groups had longer transit times (CF 123 min, non-CF 108 min) compared to the non-CF children without overgrowth (68 min) and reference normal children (69 min). CONCLUSIONS: Bacterial overgrowth and carbohydrate malabsorption, particularly of sucrose, should be considered when assessing children with CF and abnormal stool patterns.

Breath Tests↗
PubMed1997

Tandem balloon dilatation for childhood achalasia.

BACKGROUND: There are no previous reports of tandem balloon dilatation in childhood achalasia. OBJECTIVE: To report the treatment of four cases of paediatric achalasia using tandem balloon dilatation of the lower oesophageal sphincter. A review of the literature since 1986 was undertaken to compare outcomes of balloon dilatation and surgery. MATERIALS AND METHODS: A retrospective review of the patients diagnosed with this condition and treated at our institution over the past 6 years: all four patients were treated by balloon dilatation of the lower oesophageal sphincter using two or three balloons in tandem. The definition of technical success was demonstration of a waist at 1-1.5 atmospheres of inflation pressure followed by abolition of the waist at higher pressures. Where this was unable to be achieved using a single balloon, two or three balloons in tandem were used. RESULTS: No patient required oesophagomyotomy, and symptomatic control has been good to excellent in three of four patients. No significant side effects were encountered. CONCLUSIONS: Balloon dilatation and surgery have similar success rates in paediatric achalasia. Because of the low morbidity associated with balloon dilatation, the procedure should be considered as first line treatment of this condition. If the lower oesophageal sphincter is stretched insufficiently using a single balloon, tandem balloon dilatation should be utilised.

Catheterization↗
PubMed1996

Bowel habits of healthy Australian children aged 0-2 years.

OBJECTIVE: To define the bowel habits of healthy Australian children aged up to 2 years. METHODOLOGY: One hundred and forty children were recruited in six age categories with a minimum of 20 children per category. Data on bowel habit was recorded by parents daily for 1 week. RESULTS: Stool frequency decreased with age. Ninety-five per cent of infants 0-14 days passed more than two stools per day compared with 21% at age 13-24 months. Breastfed infants passed more frequent and looser stools than children fed infant formula and solids and also showed a wider variation in frequency. CONCLUSIONS: Mean stool frequency decreased with age as did the variation. This is a combined effect of age and feed type. These data can be used as a guide to the bowel habit of healthy Australian children.

Australia↗
PubMed1994

The nutritional management of acute diarrhea in young infants: effect of carbohydrate ingested.

To compare the efficacy of a low-lactose hydrolyzed milk formula, a lactose-free corn syrup-based milk formula, and a standard lactose-containing formula during refeeding after rehydration in infants with gastroenteritis, 135 patients older than 2 years were studied by randomized trial. Clearly demonstrated disadvantages in terms of early weight loss and longer duration of diarrhea were observed with the lactose-based formula compared with early weight gains on both the low-lactose formulae, and thus the lactose-containing formula was discontinued after 91 patients. The early weight loss with the lactose-containing formula was statistically significantly related to the degree of relative (rehydrated) underweight. The two low-lactose formulae were further compared in the remaining 44 patients. Early weight gain (48 h) was significantly greater with the lactose-hydrolyzed formula compared with the corn syrup-based formula, but no statistically significant differences were observed in duration of diarrhea, energy intake, treatment failures, or late weight gain. We conclude that the routine use of a low-lactose formula during refeeding after rehydration in infants with gastroenteritis may have some advantages in underweight infants and toddlers in whom it is important to prevent further weight loss.

Acute Disease↗
PubMed1994

Strain induced augmentation of upper oesophageal sphincter pressure in children.

The hypothesis that troublesome oesophagopharyngeal reflux arises from defective upper oesophageal sphincter response to straining has been evaluated in 53 children aged two to 81 months (median 13) referred with symptoms thought to be related to gastro-oesophageal reflux. Spontaneously occurring pharyngeal, upper oesophageal sphincter, oesophageal body, and gastric pressures were analysed after feeding. Inspiratory strain was the most common spontaneously occurring strain (172 episodes), defined as an oesophageal body inspiratory negative pressure dip at least twice the size of the normal inspiratory wave. Overall, during inspiratory strain, upper oesophageal sphincter pressure was significantly higher than before straining (p < 0.01) (5 v 27 mm Hg, p < 0.01). Sustained strains defined as increases in gastric and oesophageal body pressure for two to 20 seconds were also common (149 episodes) and when compared with just before straining, also augmented upper oesophageal sphincter pressure (60 v 39 mm Hg, p < 0.01). The vigour of straining, estimated as increase of gastric pressure, correlated significantly with the degree of augmentation of upper oesophageal sphincter pressure (p < 0.05). Children with and without evidence of troublesome oesophagopharyngeal reflux showed no difference in upper oesophageal sphincter response patterns to straining. Failure of augmentation of upper oesophageal sphincter tone in the face of strain induced increases of oesophageal body pressure is probably a secondary factor in the production of oesophagopharyngeal reflux in children.

Child↗
PubMed1993

Epidermolysis bullosa and severe ulcerative colitis in an infant.

An infant with epidermolysis bullosa simplex had diarrhea at 3 weeks of age; severe ulcerative colitis was subsequently diagnosed. Epidermolysis bullosa simplex has not been associated with gastrointestinal disease except for buccal ulceration.

Colitis, Ulcerative↗
PubMed1993

Effect of gastro-oesophageal reflux on upper oesophageal sphincter motility in children.

Motor events of the upper oesophageal sphincter associated with gastro-oesophageal reflux were evaluated in 53 symptomatic children (median age 13 months) who were studied recumbent and unsedated. Children were divided into four groups according to symptoms, and then into two groups according to the presence or absence of neurological deficit. No grouping had basal upper oesophageal sphincter pressure that differed significantly from any other. Oesophageal distention due to gastro-oesophageal reflux, which was recognisable as oesophageal common cavity episodes, was associated with augmentation of mean basal upper oesophageal sphincter pressure from 36.5 (SD 18) mm Hg to 48.5 (18) mm Hg (p < 0.0001), irrespective of whether gastro-oesophageal reflux caused oesophageal acidification. Abrupt relaxations of the upper oesophageal sphincter independent of swallowing and lasting up to three seconds occurred during 54% of common cavity episodes. Forty nine per cent of these relaxations occurred within four seconds after the onset of distention. The oesophageal distention caused by gastro-oesophageal reflux is a potent stimulus of transient upper oesophageal sphincter relaxations in children. These relaxations are a more likely explanation for oesophagopharyngeal reflux than defective basal upper oesophageal sphincter tone.

Child↗
PubMed1991

An assay for human chorionic gonadotrophin using the capillary fill immunosensor.

Recently there has been much research effort directed towards the development of immunosensors. Optical technologies are currently proving very attractive for the construction of such sensors. The fluorescence capillary fill device (FCFD) has been designed to fulfil these needs. The development of an assay for human chorionic gonadotrophin (hCG) in the FCFD for a variety of body fluids (whole blood, serum, urine and saliva) demonstrates the versatility and assay performance of the device.

Biosensing Techniques↗
PubMed1991

Sensitivity enhancement of optical immunosensors by the use of a surface plasmon resonance fluoroimmunoassay.

Optical immunosensors employing evanescent wave techniques have the potential to address the requirements of the 'alternative site' market; however, this potential has yet to be realised. The development of 'direct' sensors, such as those using surface plasmon resonance (SPR), has been hampered by problems of non-specific binding and poor sensitivity to small molecules. 'Indirect' sensors (for example, those employing a fluorescently labelled reagent) overcome many of the problems of direct sensors but require more sophisticated instrumentation because of the low light levels detected. In an attempt to combine the best features of the two techniques, an indirect SPR fluoroimmunoassay (SPRF) technique has been investigated. The surface field intensity enhancement produced by SPR is used to boost the emission from a fluorescently labelled immunoassay complex at a metal surface. The potential of the method is demonstrated by assaying for human Chorionic Gonadotrophin (hCG) in serum. Enhanced sensitivity over conventional total internal reflection fluorescence (TIRF) and SPR techniques was achieved.

Biosensing Techniques↗
PubMed1991

Monitoring of upper oesophageal sphincter pressure in children.

In children technical limitations of upper oesophageal sphincter manometry have restricted investigation to the pull through technique under sedation. In this study we have used an adapted sleeve manometric technique for upper oesophageal sphincter monitoring in unsedated children and determined the influence of the state of arousal on upper oesophageal sphincter pressure. Twenty six children aged 3 to 42 months (median 17.5 months), who were referred for evaluation of oesophageal motor function, were studied with dual sleeve manometric assemblies which monitored upper and lower oesophageal sphincter pressures simultaneously. Pharyngeal, oesophageal body, and gastric pressures were also monitored with seven perfused side holes. Recordings were made for four hours after a meal and were technically successful in 24 children. The child's state of arousal was scored every 12th minute as follows: (A) resting, eyes closed, (B) resting, eyes open, (C) moving but comfortable, (D) restless and uncomfortable, (E) crying. In 67% of the 12 minute samples the children showed good adaptation to the procedure (arousal states A to C). There was a highly significant difference in upper oesophageal sphincter pressure between each of the arousal states (p less than 0.0001), being lowest in category A at (mean (SD) 18.1 (10.3) mmHg and highest in category D 55.7 (13.2) mm Hg. Abrupt changes in the state of arousal were associated with equally abrupt changes in upper oesophageal sphincter pressure. The state of arousal of unsedated children has an important influence on upper oesophageal sphincter pressure. It is essential that this factor is controlled for in any studies of upper oesophageal sphincter tone in children. The sleeve technique is capable of monitoring upper oesophageal sphincter motility for prolonged periods in unsedated children.

Arousal↗
PubMed1990

Anal size in children: the influence of age, constipation, rectal examination and defaecation.

With the increase in the number of reported cases of child abuse it is important that medical practitioners should know the normal values for the size of the anus. Children aged 3 months to 15 years, attending a paediatric gastroenterology clinic for a routine examination, had a photographic record made of the anus 30 seconds after exposure of the anus as part of a standardised examination protocol. Anorectal disease, including Crohn's disease was present in eight children. Analysis of the 54 children without anorectal disease indicated that the anteroposterior diameter of the anus was less than 10.0 mm and the transverse diameter was less than or equal to 2.0 mm. Age, sex of the child, digital rectal examination, time since last defaecation and the capacity and contents of the rectum were unrelated to the size of the anus. In view of the difficulties which arise in suspected child abuse, medical practitioners should gain experience of the normal appearance and size of the anus. This can best be validated within a medicolegal framework if some form of standardised examination protocol is used. The key element of such an examination is not the position in which the child is examined but the time taken to observe the anus, to allow any dynamic changes to occur. An inspection time of 30 seconds in a cooperating conscious child is recommended.

Adolescent↗
PubMed1989

Passive immunisation of children with bovine colostrum containing antibodies to human rotavirus.

The efficacy of a 10-day course of bovine colostrum with high antibody titre against the four known human rotavirus serotypes in protecting children against rotavirus infection was examined in patients admitted to hospital. Children aged 3 to 15 months were blocked in pairs according to ward accommodation (ie, isolation or open area). Each block contained 1 treated and 1 control child. The allocation to treatment or control (an artificial infant formula) was randomised. 9 of 65 control children but none of 55 treated children acquired rotavirus infection during the treatment period (p less than 0.001). The importance of protecting against rotavirus infection was highlighted by the fact that parents of symptomatic rotavirus-positive children sought medical attention seven times more often than did parents of symptomatic rotavirus-negative children (p less than 0.05).

Administration, Oral↗