No description available.

Acute pancreatitis remains a challenging disease because of incomplete understanding of its pathobiology and the absence of an effective specific therapy. To address these difficulties, experimental animal models are indispensable. Recent research has identified the key role of fatty acid ethyl esters in the pathogenesis of alcohol-induced acute pancreatitis, but to date there is no satisfactory experimental model. Since cell signalling abnormalities, including excessive intracellular release of calcium and/or reactive oxygen species (ROS) and induction of the mitochondrial permeability transition pore (MPTP) have been demonstrated to play a pivotal role in acute pancreatitis, targeting these pathways could either prevent this disease completely or ameliorate its severity. Such therapies require preliminary assessment in experimental models. A novel acute alcoholic pancreatitis model (F AEE-AP) was established by two concomitant administrations of ethanol (1.35 g/kg) and palmitoleic acid (80 or 150 mg/kg) at 1 h apart. 4-methylpyrazole, a non-oxidative ethanol metabolism pathway inhibitor, significantly increased the necrosis histopathological score of the pancreas, whereas 3-benzyl-6-chloro-2- pyrone, a F AEE synthase inhibitor, significantly decreased the severity of FAEE-AP. Bis-(4-nitrophenol) phosphate, an FAEE hydrolase inhibitor, did not show any significant protective effect against F AEE-AP. The inositol trisphosphate receptor inhibitor caffeine and its metabolites were investigated in mice with acute pancreatitis induced by either 7 or 12 injection of caerulein (50 ug/kg/h; CER-AP) or by infusion of 50 III taurolithocholic acid 3-sulphate (TLC-S, 3 mM; TLCS-AP). Caffeine (25 mg/kg/h) significantly reduced severity markers of pancreatitis in both CER-AP and TLCS-AP, an effect that might be due to inhibition of inositol triphosphate receptor, attenuation of endoplasmic reticulum stress and/or phosphodiesterase inhibition. The caffeine metabolites theophylline and paraxanthine however did not appear to be protective against CER-AP. Manipulation of ROS by menadione (an oxidant inducer), 2,4-dimethoxy- 2-methylnaphthalene (a non-cycling analogue of menadione) and n- acetyl cysteine (an antioxidant) in both CER-AP and TLCS-AP provided paradoxical results. Cyclophilin D knockout mice, which are resistant to formation of the MPTP, had significantly reduced histopathological scores and severity markers tested compared to wild type mice in FAEE-AP. The cyclophilin D inhibitor cyc1osporine A (l0 mg/kg) did not show a significantly protective effect in CER-AP, while its non-immunosuppressive analogue D-3-methyl-Ala-4-ethyl-Val-CyA (Debio-025, 10-100 mg/kg) significantly reduced histopathological scores and severity marker of CER-AP with the most marked effect at 10 mg/kg. These data suggest that inhibition of cytosolic and mitochondrial calcium overload could be effective strategies in the prophylaxis and/or treatment of acute pancreatitis.

The clinical management of severe acute pancreatitis has improved significantly in the last decade, mainly due to advances in supportive critical care. However, it still poses formidable problems to the clinician, due to lack of uniformity in early disease definition, absence of disease specific treatment and paucity of evidence base for management of complications. This thesis attempts to address these problems using inter-related studies based on clinical (cohort study and randomised control trial), experimental and data-analysis methodologies.

No description available.

Both acute (AP) and chronic (CP) pancreatitis are complex diseases, with a number of aetiologies and complex pathogeneses. A number of contributing factors are assessed here. Genetic studies were performed looking at a high activity polymorphism of the alcohol metabolising enzyme cytochrome P450 2E l. Assessing a role in alcohol abuse and end organ disease; alcohol abusers (n= 239) and controls (n= 208) were studied. A significantly lower number of alcohol consumers (2.1 %) had the polymorphism than controls (5.8%); p= 0.049, Fisher's exact test. Any association with end organ disease could not be further elucidated due to the rarity of the polymorphism in this population. In another genetic study, looking at a polymorphism in interleukin-1a, no associations were found with CP; of note no associations were found with genotypes implicated in AP. A double-blind, placebo controlled crossover trial of a leukotriene receptor antagonist in chronic pancreatitis revealed no benefit. Studies of production of arachidonic acid metabolites leukotriene E4 (LTE4), prostaglandin E2 (PGE2) and (a known marker of mast cell activation) prostaglandin D2 (11β-PGF2a) were performed. Analysis looked at both acute (n= 19) and chronic pancreatitis (n= 19), employing age and sex matched controls. The LTE4 studies did not reveal any significant difference in levels. PGE2 levels were not different between CP patients and controls while they were significantly higher in AP than controls; p= 0.006, independent samples t-test. The variation appeared most marked for mild disease; one way ANOVA p= 0.024 and direct comparison of patients with mild disease and their matched controls; p= 0.011. The 11β-PGF2a study conversely showed no difference in AP but significantly higher levels in CP in comparison to their matched controls; p= 0.001, Mann Whitney U test. Based on a previous pilot study in CP and a difference in variance of LTE4 in AP in the above study, a genetic study of the known functional polymorphism in the gene of leukotriene C4 synthase (the first dedicated enzyme in the formation of the cysteinyl leukotrienes) was performed. Controls totalled 108 subjects; AP 238 (mild= 169 patients; severe= 69) and CP 57 subjects; no difference in the genotype or allele frequencies were found. In summary: A possible role for a functional polymorphism in cytochrome P450 2E1 (not previously examined in patient groups) in protection against alcoholism has been identified. Perhaps analogous to the protection associated with high activity forms of alcohol dehydrogenase and low activity forms of aldehyde dehydrogenase. PGE2 is elevated in acute pancreatitis in humans consistent with the majority of the data in animals. Again consistent with the bulk of animal data this appears to be most marked in mild disease, possibly indicating a protective, and therefore potentially therapeutic, role. 11β-PGF2a, a metabolite of PGD2 and marker of mast cell activation, is elevated in chronic but not acute pancreatitis. This implicates mast cells in chronic pancreatitis and would be consistent with their known role in fibrosis and tissue remodelling and suggests a possible therapeutic target.

No description available.

The hazardous technique of endoscopic manometry precludes the investigation of "normal volunteers" required to advance our knowledge of the physiology and pathophysiology of the sphincter of Oddi, a suitable animal model is required. Large and small animal models have been proposed, as yet no one model has been accepted as being representative of the human sphincter of Oddi. Furthermore no animal model of sphincter of Oddi dysfunction has been developed. In this thesis a porcine animal model of sphincter of Oddi function has been developed. The importance of selecting the appropriate anaesthetic agent, enflurane, has been proven. The effect of cholecystectomy on the porcine sphincter of Oddi is shown to have no overall significant effect on sphincter motility when compared to a sham laparotomy group. However, two of the seven pigs after cholecystectomy showed a paradoxical rise in sphincter basal pressure after cholecystokinin infusion, these animal may represent porcine sphincter of Oddi dysfunction. Although substance P is found throughout the intestinal tract including the sphincter of Oddi of man and pig its action was hitherto unknown. In this thesis exogenous substance P was shown to stimulate the sphincter of Oddi in vivo. In this thesis the first development in sphincter of Oddi manometry catheter design in nearly twenty years is presented. A superior nine 3 lumen catheter has been evaluated in porcine model and subsequently used to assess sphincter of Oddi asymmetry in man. Two retrospective studies are reported in this thesis; an audit of the largest U. K. series, and a study assessing the relationship of sphincter of Oddi motility and duodenal activity. Tachyoddia dissociated from the duodenal migrating motor complex was associated with a raised sphincter of Oddi basal pressure and may be a part of sphincter of Oddi dysfunction.

Sustained, toxic elevations of pancreatic acinar cell cytosolic free calcium ion concentration ([Ca2+]C), such as those observed with supramaximal secretagogue stimulation (CCK) are implicated in acute pancreatitis. However, Cholecystokinin (CCK) has been thought to act only indirectly on human pancreatic acinar cells via vagal nerve stimulation, rather than by direct CCK receptor activation as observed in rodent pancreatic acinar cells. However, in the series of experiments presented here using human pancreatic acinar cells, CCK at physiological concentrations (1-20 pM) elicited rapid, robust, oscillatory rises of the cytosolic Ca2+ ion concentration ([Ca2+]C), showing apical to basal progression in acinar cells, in the presence of atropine and tetrodotoxin. The [Ca2+]C rises were followed by increases in mitochondrial ATP production and secretion, concluding that CCK acts directly on acinar cells in the human pancreas. The earliest pathological mechanisms, such as sustained, toxic elevations of the acinar cytosolic free calcium ion concentration ([Ca2+]C), incriminated in experimental pancreatitis have been previously demonstrated by non-oxidative metabolites of ethanol (FAEE’s), as well as bile salts, at supramaximal concentrations. However, in the clinical situation such hyperstimulation is unlikely to occur. To simulate a more clinically relevant stimulus, pancreatic acinar cells were stimulated with lower doses of FAEE’s and/or bile salts in combination with physiological doses of secretagogues - a process which may precipitate pancreatitis clinically. Illustrated here, the toxic transformation of secretagogue induced physiological Ca2+ signalling occurs with the perfusion of low doses of TLCS and POAEE resulting in cell injury. The intracellular second messengers implicated are IP3, cADPR and NAADP with the IP3 receptor channel pivotal with both toxins. However, as previously demonstrated with supramaximal concentrations of POAEE, if supplementary ATP is added to the intracellular milieu, cellular injury is avoided with continued extrusion of large quantities of Ca2+ from the cytosol indicating functional Ca2+ ATPase pumps. This is not observed in cells which do not receive supplementary ATP. The toxic sustained Ca2+ elevation is also be prevented by the removal of external Ca2+ or blockade of IP3 receptor using caffeine and cell injury is again avoided. Therefore, it may be concluded, that it is the large, sustained toxic [Ca2+]c load which impairs mitochondrial function and ATP production leading to Ca2+ATPase pump failure and ultimately cell death. Lowering sustained intracellular [Ca2+]c by blockade of IP3 receptor channels may reduce cell injury in clinical acute pancreatitis.

Bibliography: leaves x-xxii / xvii, 285, xxii leaves : / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (M.D.)--University of Adelaide, 1987

Erratum inserted on front fly leaf. / Bibliography: p. 283-315. / xiv, 315 p., [3] leaves of plates : ill. (one col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / To establish whether altered sulphation in cystic fibrosis could be demonstrated in different experimental systems, by focusing on glycosaminoglycans. The second aim was to establish the molecular basis for such a phenomenon. / Thesis (Ph.D.)--University of Adelaide, Dept. of Paediatrics, 1995