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Biomedical subjects

I Mason

Publications and source records attributed to I Mason.

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

Abnormalities of the electrogastrogram in functional gastrointestinal disorders.

OBJECTIVE: Cutaneous electrogastrography records gastric electrical activity and detects gastric arrhythmias. Abnormalities of the electrogastrogram have been described in a variety of disorders, but their specificity and their prevalence in patients with functional gastrointestinal disorders has not been reported. The aim of this study was to assess the specificity of electrogastrography as well as the prevalence and pattern of abnormalities in functional dyspepsia and irritable bowel syndrome. METHODS: Electrogastrography was performed in 170 patients with functional dyspepsia, 70 patients with irritable bowel syndrome, 20 patients with gastroesophageal reflux disease, and 30 asymptomatic controls. The abnormal electrogastrogram was defined as <70% normal electrical activity either before or after a test meal. RESULTS: The electrogastrogram was abnormal in 36% of patients with functional dyspepsia and in 25% with irritable bowel syndrome who complained of concurrent dyspepsia. The electrogastrogram was normal in 93% of asymptomatic controls, 90% of patients with gastroesophageal reflux, and 92% of patients with irritable bowel syndrome who did not complain of dyspepsia. As a group, functional dyspepsia patients had a greater degree of tachygastrias both before (p < 0.02) and after (p < 0.01) a test meal. The electrical frequency after the test meal was also more unstable (p < 0.003). CONCLUSIONS: The electrogastrogram is abnormal in approximately 36% of functional dyspepsia patients and has a specificity of approximately 93%. Electrogastrography defines a subgroup of patients with functional dyspepsia and electrical rhythm disturbance. In irritable bowel syndrome, the electrogastrogram is usually abnormal only if concurrent dyspepsia is present.

Adult↗
PubMed1999

Regeneration of isthmic tissue is the result of a specific and direct interaction between rhombomere 1 and midbrain.

The midbrain-hindbrain boundary, or isthmus, is the source of signals that are responsible for regional specification of both the midbrain and anterior hindbrain. Fibroblast growth factor 8 (Fgf8) is expressed specifically at the isthmus and there is now good evidence that it forms at least part of the patterning signal. In this study, we use Fgf8 as a marker for isthmic cells to examine how interactions between midbrain and hindbrain can regenerate isthmic tissue and, thereby, gain insight into the normal formation and/or maintenance of the isthmus. We show that Fgf8-expressing tissue with properties of the isthmic organiser is generated when midbrain and rhombomere 1 tissue are juxtaposed but not when midbrain contacts any other rhombomere. The use of chick/quail chimeras shows that the isthmic tissue is largely derived from rhombomere 1. In a few cases a small proportion of the Fgf8-positive cells were of midbrain origin but this appears to be the result of a local respecification to a hindbrain phenotype, a process mimicked by ectopic FGF8. Studies in vitro show that the induction of Fgf8 is the result of a direct planar interaction between the two tissues and involves a diffusible signal.

Animals↗
PubMed1999

Sequential roles for Fgf4, En1 and Fgf8 in specification and regionalisation of the midbrain.

Experiments involving tissue recombinations have implicated both early vertical and later planar signals in the specification and polarisation of the midbrain. Here we investigate the role of fibroblast growth factors in regulating these processes in the avian embryo. We show that Fgf4 is expressed in the notochord anterior to Hensen's node before transcripts for the earliest molecular marker of midbrain tissue in the avian embryo, En1, are detected. The presence of notochord is required for the expression of En1 in neural plate explants in vitro and FGF4 mimics this effect of notochord tissue. Subsequently, a second member of the fibroblast growth factor family, Fgf8, is expressed in the isthmus in a manner consistent with it providing a polarising signal for the developing midbrain. Using a retroviral vector to express En1 ectopically, we show that En1 can induce Fgf8 expression in midbrain and posterior diencephalon. Results of the introduction of FGF8 protein into the anterior midbrain or posterior diencephalon are consistent with it being at least part of the isthmic activity which can repolarise the former tissue and respecify the latter to a midbrain fate. However, the ability of FGF8 to induce expression of genes which have earlier onsets of expression than Fgf8 itself, namely En1 and Pax2, strongly suggests that the normal function of FGF8 is in maintaining patterns of gene expression in posterior midbrain. Finally, we provide evidence that FGF8 also provides mitogenic stimulation during avian midbrain development.

Animals↗
PubMed1998

Expression of Gbx-2 during early development of the chick embryo.

Gbx-2 is required for the normal development of the anterior hindbrain. Since much of our understanding of the normal development of this region derives from studies of avian embryos, we have determined the expression of Gbx-2 in chick embryos at stages relevant to the regionalization of the hindbrain. As the neural plate forms transcripts already have a clear anterior limit of expression and, subsequently, occupy a domain extending from the extreme posterior midbrain to the rhombomere 3/4 boundary. Subsequently, expression is restricted to the isthmus, a dorsal stripe of expression extending throughout the hindbrain in the ventricular region and the cells adjacent to rhombomere boundaries. Transcripts were also detected in pharyngeal endoderm, the otic placode and vesicle, pharyngeal arches and somites.

Animals↗
PubMed1998

The management of acid-related dyspepsia in general practice: a comparison of an omeprazole versus an antacid-alginate/ranitidine management strategy. Compete Research Group [corrected].

BACKGROUND: There is need for an evidence-based comparison of clinical management strategies to provide the rationale for selection of a particular therapeutic approach to treatment. Ideal dyspepsia treatment should quickly and conveniently alleviate patient symptoms whilst also minimizing the use of healthcare resources. AIM: To examine dyspepsia symptom relief over 16 weeks and compare an omeprazole clinical management strategy with a commonly used combination of antacid-alginate followed by H2-antagonist. METHODS: Seven hundred and twenty-five patients participated in this randomized, open, parallel group comparison over 16 weeks. Patients were randomized to receive either an omeprazole treatment strategy (363) consisting of omeprazole 10 mg stepping up to 20 mg and 40 mg as required, or an antacid-alginate/ranitidine treatment strategy (362) consisting of antacid-alginate 10 mL q.d.s. stepping up to ranitidine 150 mg b.d. and 150 mg q.d.s. as required. RESULTS: A greater proportion of patients receiving the omeprazole clinical management strategy had achieved the stringent health target of complete symptom relief (61 vs. 40%, P < 0.0001) at 16 weeks. Forty-six per cent of omeprazole-treated patients were symptom free after the first 10 mg step compared to only 17% in the antacid-alginate treated group (P = 0.0001). Total relief of heartburn, the most common symptom at entry, was achieved by more patients in the omeprazole treatment group than the antacid-alginate/ranitidine treatment group, 62 vs. 36%, respectively, at 4 weeks, and 81 vs. 60% at 16 weeks (P = 0.0001). CONCLUSION: Treatment with the omeprazole clinical management strategy was superior to the antacid-alginate/ranitidine management strategy in providing relief of acid-related dyspepsia symptoms after 16 weeks. In addition, the omeprazole treatment strategy involved fewer GP consultations and thus minimized the use of other healthcare resources.

Abdominal Pain↗
PubMed1998

The effect of cisapride on dyspepsia symptoms and the electrogastrogram in patients with non-ulcer dyspepsia.

BACKGROUND: The electrogastrogram (EGG), which records gastric myoelectrical activity, is abnormal in one-third of adult patients with non-ulcer dyspepsia (NUD). AIM: To observe the effects of cisapride on EGG in adults with NUD. METHODS: Twenty-seven NUD patients who had undergone a pre- and post-prandial EGG were entered into an open study. All patients completed a dyspepsia symptom questionnaire and were then treated with cisapride 10 mg t.d.s. The dyspepsia questionnaire was repeated in all those completing 4 weeks of treatment. Those with an initial abnormal EGG (< 70% of slow wave activity at 2-4 cycles per minute) had a repeat EGG at the end of the study. RESULTS: Treatment with cisapride was associated with a significant improvement in the post-prandial EGG (P = 0.007). After 4 weeks of treatment, 7 of 13 abnormal EGGs normalized. Symptom scores improved significantly in the 13 patients with an abnormal EGG who completed treatment (P < 0.0003), but not in NUD patients with a normal EGG (P = 0.48). CONCLUSION: In this open study, treatment of NUD with cisapride was associated with significant symptom improvement in patients with an abnormal pre-treatment EGG, but not those with a normal EGG, with a significant improvement of the post-prandial EGG.

Adult↗
PubMed1997

FGF-1 and FGF-7 induce distinct patterns of growth and differentiation in embryonic lung epithelium.

Fibroblast growth factors (FGFs) and receptors (FGFRs) are expressed in the developing lung and appear to be major regulators of lung growth and differentiation. By using mesenchyme-free lung epithelial cultures we show that FGF-1 (aFGF) and FGF-7 (KGF) produce different effects in the developing lung. FGF-1 stimulates epithelial proliferation that results in bud formation (branching), while FGF-7 promotes epithelial proliferation that leads to formation of cyst-like structures. In addition, FGF-7 stimulates epithelial differentiation, stimulating expression of SP-A and SP-B mRNA throughout the explant, and inducing formation of focal areas of highly differentiated cells. The FGF-1 effects on differentiation are limited to induction of surfactant protein SP-B mRNA at the tips of the explant. The FGF-induced patterns of growth appear to correlate with the distribution of epithelial FGFRs mRNAs; FGFR-2 IIIb (KGFR) is diffusely expressed in the day 11 lung epithelium, while FGFR-4 appears in distal but not in proximal sites. We propose that cyst-like structures may result from FGF-7 binding to the uniformly distributed FGFR-2-IIIb. Lung bud formation may be regulated by FGF-1 and/or other ligands binding to FGFR-2 and a distally located FGFR, such as FGFR-4, leading to an increasing binding and activation of FGFRs at the tips of the explant. Thus, in the embryonic lung epithelium, growth effects of FGFs appear to be dependent on location of FGFRs, while effects on differentiation are ligand-dependent.

Animals↗
PubMed1997

Two omeprazole-based Helicobacter pylori eradication regimens for the treatment of duodenal ulcer disease in general practice.

BACKGROUND: Helicobacter pylori is the main acquired factor in the pathogenesis of duodenal ulcer disease. METHODS: This multicentre study conducted in 32 general practice centres in the UK and Ireland was a double-blind, placebo-controlled, randomized, parallel-group comparison of triple therapy (n = 98: omeprazole 40 mg once daily and amoxycillin 1 g b.d. for 2 weeks, and metronidazole 400 mg t.d.s. for the first week) and dual therapy (n = 85: omeprazole 40 mg once daily and amoxycillin 1 g b.d. for 2 weeks, with placebo during the first week) for the eradication of H. pylori in patients with symptomatic duodenal ulcer disease. Patients who were successfully treated entered a follow-up phase for 12 months to assess symptomatic relapse and use of health-care resources. RESULTS: Eradication of H. pylori based on a second 13C-urea breath test was successful in 95% (95% confidence interval (CI) = 90-100%) of patients receiving omeprazole triple therapy and 53% (95% CI = 41-65%) of those receiving omeprazole dual therapy (P < 0.0001 between groups, all data available analysis). The all-patients-treated analysis gave eradication rates of 80 and 44% for omeprazole triple therapy and omeprazole dual therapy, respectively. Symptomatic relapse occurred in 16% (18/116) of the H. pylori-negative patients who entered the 12-month follow-up period, and there were significant reductions in the number of consultations, investigations and prescriptions relating to upper gastrointestinal symptoms compared with the 12 months prior to the eradication therapies (all P < 0.0001). The two treatment strategies were comparable in terms of the number of adverse events reported. CONCLUSIONS: Omeprazole triple therapy provides a highly effective treatment for the eradication of H. pylori infection in patients in general practice, with an adverse event profile similar to that seen with omeprazole dual therapy. The successful eradication of H. pylori with these omeprazole regimens results in a significant decrease in the use of health-care resources in the 12 months following treatment.

Adult↗
PubMed1997

Hirschsprung's disease: genetic mutations in mice and men.

Hirschsprung's disease is a neuronal dysplasia of the hindgut, characterised by a loss of neurones, which affects about 1 in 5000 live births. Genetic factors have been implicated in the aetiology of this disease in about 20% of cases and a dominant pattern of inheritance has been revealed in several families. The pathogenesis of the aganglionosis is often attributed to a failure of migration of neural crest cells, although this has not been proven. Recently, mutations in a developmentally regulated receptor tyrosine kinase gene, ret, and mutations in the endothelin receptor-B gene (ENDR-B) have both been linked to familial Hirschsprung's disease in humans. Moreover, certain mutant mouse strains--namely piebald lethal and lethal spotted--exhibit striking similarities to the human condition. The mutation which gives rise to piebald lethal has now been found to be in the ENDR-B gene, and the mutation associated with lethal spotted occurs in the gene for endothelin-3 (ET-3), a ligand for ENDR-B. Two transgenic mouse lines have been developed which also reflect the human disease: ret-k-, which has a loss of function mutation of the ret gene, and ENDR-B null. In addition, the introduction of a Lac-Z reporter gene into neural crest cells of aganglionic mice has made it possible to study directly the fate of enteric neuroblasts which are affected by "Hirschsprung's-like" mutations. Here, we review the possible roles of RET and endothelin in the normal development of the enteric nervous system, and the significance of their mutated forms in the pathogenesis of familial aganglionosis. This review focuses on recent advances in our understanding of the genetic basis of the lesions which have been implicated in congenital forms of Hirschsprung's disease. Disruption of these genes in the mouse, either by transgenic "knockout" approaches or in mutant mouse lines, offers the prospect of greater understanding of both the cellular and developmental bases of the human disease.

Animals↗
PubMed1996

Secretion and mitogenic activity of zebrafish FGF3 reveal intermediate properties relative to mouse and Xenopus homologues.

Zebrafish (Brachyodanio rerio) Fgf-3 cDNAs expressed in COS-1 cells give rise to the heterogeneous set of secreted proteins with relative molecular masses in the range of 29-30.5 kDa. These proteins associate strongly with the extracellular matrix but are quantitatively released into the culture medium in the presence of heparin (5 micrograms/ml). Extracellular zebrafish FGF3 (ZFGF3) also contains a smaller sized component that appears to result from an amino-terminal proteolytic cleavage. These properties are similar to those described for Xenopus FGF3 (XFGF3). Receptor binding experiments indicate that ZFGF3 has a higher affinity for the IIIb rather than the IIIc isoform of FGFR2; properties that are more reminiscent of the mouse than the Xenopus homologue. Consistent with the FGF receptor binding properties, ZFGF3 shows a restricted mitogenic potential and a reduced transforming activity on NIH3T3 cells compared to XFGF3. Hybrid proteins made between Xenopus and zebrafish FGF3 implicate the C-terminal region in determining the differences in receptor potential affinities, mitogenic potency and transforming activity. Thus, ZFGF3 shows the structural and secretory properties of XFGF3, but has biological properties more akin to those of the mouse homologue.

Amino Acid Sequence↗