Automated total collection (ATC) of digesta from four steers fitted with duodenal re-entrant cannulas was compared with flow estimations based on Cr₂O₃and acid detergent lignin concentrations of ATC samples. In two successive periods, each steer was fed about 4 kg daily of an all-roughage or an 80% sorghum grain diet. Digesta samples were automatically taken and pooled every 2 hr, during 3- to 6-day collections. Sample aliquots, representing 4% of the digesta measured in each 2 hr were pooled to represent 24-hr digesta flow. Data of 2-hr samples were used to study diurnal flow patterns. Duodenal digesta and dry matter flow rates estimated by Cr₂O₃and lignin were greater by (TURN) 15% than flow rates measured by ATC. Mean recoveries of Cr₂O₃and lignin at the duodenum were 93 and 89%, respectively. Animals fed the roughage diet had about 55% greater digesta flow rates than when fed the concentrate diet (42 versus 65 l daily average by ATC). There appeared to be an interaction between diets and markers. Apparent ruminal dry matter digestibility calculated from direct measurements by ATC was 44% for the concentrate diet and 37% for the roughage diet. Rumen digestbility values based on Cr₂O₃and lignin were about 25% lower than the ATC values. Average coefficients of diurnal variation for digesta flow were 29% in the concentrate diet and 34% in the roughage diet. Estimations from Cr₂O₃and lignin based on 2-hr samples could either under- or overestimate digesta flow by 31 to 350% of the 24-hr flow based on ATC. Thus, special emphasis should be given to the problem of sampling procedures when using indicators and spot-sampling technique to estimate digesta flow. There was evidence of a 24-hr cycle for the whole digesta flow in the grain diet, with a period of low flow before the onset of the light hours. No consistent flow pattern could be identified in the roughage diet. Lignin concentration patterns in digesta were somewhat similar for both diets; however, Cr₂O₃patterns were different between diets. Digesta dry matter concentration followed a similar pattern to that of Cr₂O₃in the grain diet and to that of lignin in the roughage diet, suggesting that the flow patterns of solid phase components of digesta may also be differentially affected by the dietary concentrate: roughage ratio.

School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, 2017 / Snakes have often been proposed as ideal model organisms for studying digestive physiology. This is due to their easily–measureable and extreme changes in their digestive tracts in response to feeding, when compared to other vertebrates. Some species display extreme physiology regulation in response to feeding, a system known as digestive down-regulation. This regulation allows them to down-regulate their digestive tracts during their long fasting periods, which allows them to save energy. In response to feeding, they up-regulate their digestive tracts to a functional level, resulting in a significant increase in the size of the digestive organs during digestion. These changes have been found to be most noticeable in certain ambush foraging snakes. In contrast, actively foraging snakes appear to not display as extreme changes in response to feeding and keep their digestive tracts in a constant state of readiness. However it is not known if this pattern exists in all species and previous methods of classifying the digestive physiology have proven to be expensive, difficult and time consuming. My study aimed to investigate if museum specimens could be used as a cheap and quick method of classifying the characteristics of the digestive physiology within a species. I measured the dimensions of several organs from museum specimens from 13 species of southern African snakes, as well as recorded the relative size of the meal and month of capture. I compared measurements between postprandial and fasting individuals from each species as well as between individuals from each species with the same feeding state to assess whether they were able to down-regulate their digestive systems when not digesting. While the different foraging strategies appeared to be linked to differences in organ morphology, the presence of down-regulation was not clear-cut. No significant differences in organ size between feeding states were found within each species, and very few significant differences were found between species. Few correlations with organ size to meal size or seasonality were found. This suggests that the museum specimens are not suitable for determining digestive physiology in snakes, probably due to the poor quality of the specimens. I therefore recommend the use of freshly obtained samples as a suitable comparison rather than the use of museum specimens. / MT2017

Pancreatic cancer (PC) is the fourth leading cause of cancer death in Western societies. Despite significant progress in understanding the molecular pathology of PC and its precursor lesion: pancreatic intraepithelial neoplasia (PanIN), there remain no molecules with proven clinical utility. Affymetrix Genechipfi oligonucleotide microarrays were used to interrogate mRNA expression of PC and normal pancreas to identify molecular pathways dysregulated in PC. Analysis of these data identified altered expression of numerous components of the S100 Calcium Binding Protein Family, Retinoic Acid signalling pathway and the HOX transcriptional network in PC compared to normal pancreas. These pathways were assessed using immunohistochemistry (IHC) and in-situ hybridisation (ISH) in a cohort of patients with PC. Increased protein expression, of S100A2, S100A6 and S100P was observed in 43%, 60% and 48% of PC respectively. Expression of S100A2 was associated with a poor outcome (p = 0.009), whilst increased expression of S100A6 (p = 0.0008) and S100P (p = 0.0005) were associated with an improved outcome. Additionally, S100A2 expression was identified as an independent marker of outcome in resected tumours. Aberrant expression of retinoic acid signalling components was demonstrated in PC cell lines using semi-quantitative RT-PCR. ISH demonstrated expression of Retinoic Acid Induced 3 (RAI3), an orphan G protein coupled receptor normally expressed in the fetal lung, in 68% of PC, and this co-segregated with an improved overall survival (p = 0.026).Ectopic protein expression of HOXB2, a transcription factor normally expressed in the developing hindbrain and modulated by retinoic acid, was observed in 15% of early PanIN lesions and 38% of PC specimens. Expression of HOXB2 was associated with non-resectable tumours and was an independent predictor of poor survival in resected tumours. Suppression of HOXB2 protein expression using small interfering RNA, resulted in epithelioid trans-differentiation in the Panc-1 PC cell line, however no alteration in proliferation rates were observed compared to controls. This thesis has shown that transcript profiling and tissue validation has identified potential markers of early diagnosis and outcome in PC. Furthermore, pathways and molecules previously thought to be associated with normal human development have been implicated to play a role in the development and progression of PC. Further analyses of these markers will determine any potential role in future diagnostic and therapeutic strategies.