xix, 207 leaves : ill., diagrs., graphs, tables, photo. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.1980)--The Dept. of Animal Physiology, University of Adelaide

The gastric morphology of the white-tailed rat M. albicaudatus - was described in detail. The bilocular hemiglandular stomach consists of a papillated corpus, non-glandular PGP and glandular antrum. The antrum contains cardiac, fundic and PJ loric glands (suggesting limited glandular reduction during gastric evolution) while the FCE and PGP are lined with orthokeratin. The corpal papillae, which increase surface area for microbial attachment, have undergone a different type of keratinisation called physiological hyperkeratosis. Streptococci, Lactobacilli and unidentified anaerobic bacilli (which colonise papillary microhabitats) are autochthonous in the stomach of M. albicaudatus but P. vulgaris and Ps. flourescens are probably autochthonous. Early gastric development is innate but the rapid development of PB into papillae between 15 and 17 days suggests the presence of allogenic growth stimuli: possibly mechanical abrasion by solid food, low chalone concentration in the papillary basal cells and the influence of the APB. Stimulation by VFA presence, however, is unlikely due to the low concentration of these acids in the stomach (Summary, p. 225)

Despite the extensive work done on the neural consequences of tactile restriction very little is known about the behavioural consequences of this manipulation. In the present investigation, an assessment was made of the effects of early, long-term tactile restriction by bilateral removal of the mystacial vibrissae on the subsequent somatosensory capacities of rats (i.e. the intramodal consequences) as well as its effects on visual and spatial capacities (i.e. the intermodal consequences). As well, rearing environment (enriched vs. normal) and type of surgery (vibrissae removal by cauterization of follicles or by plucking) were examined to determine specific factors that might influence the effect of early, long-term vibrissae removal. Five tasks were used to assess these effects. The first two tasks assessed the intermodal consequences of vibrissae removal. Visual competence was assessed by measuring the habituation of orientation to repeated visual stimuli and the dishabituation to subtle changes in these stimuli. A version of the Morris (1981) water maze was used to assess the rats' spatial abilities. The results of these two tasks revealed limited evidence for intermodal effects. In terms of habituation to visual orientation, rats that had had their vibrissae removed by cauterization and were subsequently reared with daily access to an enriched environment required more trials to habituate to the presentation of repeated visual stimuli. As well, these rats were the only group to dishabituate to a subtle change in the stimuli. No effect of vibrissae removal was found in the spatial task, and environmental enrichment during development enhanced performance on this task, apparently through increased attention to distal cues by rats reared in this condition. The remaining three tasks assessed the motoric and somatosensory effects of tactile restriction. No effect was found on the performance of the Puzzle Latch Box test in which the rats were required to manipulate various latches to obtain a food reward. As well, no significant effect was observed in reactions to the tying of pieces of wire to the rats' wrists. However, early, long-term vibrissae removal (by cauterization of follicles or by plucking) attenuated orientation to contacts of the mystacial pad itself. This effect was dissociated from tactile reactivity; all rats exhibited eye-flinch responses to taps on this area. These results suggest that early, long-term tactile restriction has significant behavioural consequences for the somatosensory system as well as the visual system. These data also provide limited evidence for theories of modality interdependence as well as yielding basic information concerning the role of the mystacial vibrisse in the behaviour of the rat. / Arts, Faculty of / Psychology, Department of / Graduate

A study was made of the renal and cardiovascular responses of rats to the chronic intravenous administration of bacterial endotoxin. Endotoxin (E coli; 026: B6) was infused intravenously at the rate of 10 μg/h for a period of 4-6 days by means of subcutaneously implanted osmotic mini-pumps. The chronic endotoxemia resulted in a large fall in the renal output of sodium, a decrease in urine osmolality and an increase in potassium output. Aldosterone concentration in plasma was not changed. The renal retention of sodium was associated with an increased plasma volume, sodium space and total body exchangeable sodium. A study of renal function using clearance methods showed that the above changes occurred in the absence of statistically significant changes in glomerular filtration rate, renal plasma flow or filtration fraction. Measurements of renal medullary plasma flow by means of an isotope accumulation method indicated that no significant redistribution of intrarenal blood flow had occurred which might account for either the retention of sodium or the impaired renal concentrating ability. An investigation of cardiovascular function showed that rats with chronic endotoxemia had a significantly increased cardiac output as measured by the reference sample technique using radio-labelled plastic microspheres. These animals also had an increased stroke volume, bradycardia, hypotension and a decreased total peripheral resistance. The renal fraction of the cardiac output was significantly reduced but total renal blood flow was unchanged. The fractional distribution of nutritional blood flow to the kidney, as measured with ⁸⁶RbCl, was not significantly changed. Because of theoretical, but possible, sources of error inherent in the use of microspheres to measure cardiac output an attempt was made to confirm the above data using an alternative method. Measurement of cardiac output using the direct Fick method did not disclose a significant difference in cardiac output. Measurements were also made of the circulating half-life of endotoxin in plasma using ⁵¹Cr-labelled endotoxin. There was a very large increase in the rate of plasma clearance of endotoxin in rats subjected to chronic endotoxemia but no change in the fractional uptake of endotoxin by selected organs. It is suggested that the observed changes in renal function were secondary to the hemodynamic effects of endotoxin rather than to direct nephrotoxic effects. / Medicine, Faculty of / Cellular and Physiological Sciences, Department of / Graduate

This study has examined the expression of the glutathione S-transferases (GSH S-T) in fetal rat livers in order to provide more information about the role played by this important group of enzymes in the fetus. The study commenced with an examination of the subunit composition of adult and fetal rat liver GSH S-T using affinity chromatography followed by polyacrylamide gel electrophoresis in sodium dodecyl sulphate. Adult livers contained four major GSH S-T subunits. An additional and previously unidentified subunit was detected in fetal livers. This subunit, which differed from that found in rat placenta, had a Mᵣ of approximately 25 500. Densitometric measurements suggest that the newly detected subunit accounts for as much as 26% of the GSH S-T in fetal livers. The novel fetal isoenzyme comprising this subunit was purified using a combination of affinity chromatography, carboxymethyl-cellulose column chromatography and chromatofocusing. The six major basic rat liver GSH S-T were purified for reference and comparative purposes. The fetal isoenzyme is composed of two non-identical subunits, namely, subunit Yc (Mᵣ 28 000) and the fetal subunit referred to as 'Yfetus'· The enzyme which I have termed GSH S-transferase Yc Y fetus has an isoelectric point of approximately 8.65 and has GSH S-T activity towards a number of substrates. Significantly, the fetal isoenzyme has one of the highest glutathione peroxidase activities yet described for the purified rat liver GSH S-T towards the model substrate, cumene hydroperoxide. Kinetic studies reveal that the fetal isoenzyme has a catalytic efficiency for the peroxide substrate which is four fold higher than that of the adult rat liver isoenzyme, GSH S-T YcYc. The in vitro effect of the GSH S-T substrate and teratogen, acrolein, on this fetal isoenzyme was investigated and compared with acrolein's effect on some of the adult rat liver GSH S-T isoenzymes in the standard 1-chloro-2,4-dinitrobenzene assay. Surprisingly, acrolein was identified as a non-competitive inhibitor of the GSH S-T. Exposure to acrolein in various guises could therefore result in inhibition of the fetal isoenzyme and its subsequent failure in inhibiting lipid peroxidation. Inhibitor studies were performed to look at the effect of acrolein, as well as other substrate and non-substrate ligands, on the glutathione peroxidase activity of GSH S-T YcY fetus and YcYc. The glutathione peroxidase activity of the fetal isoenzyme was far less susceptible to acrolein inhibition than the YcYc isoenzyme and the fetal isoenzyme was found to retain significant glutathione peroxidase activity despite saturating concentrations of non-substrate ligand. This study suggests that the fetal isoenzyme serves a specific function in protecting fetuses against the possible teratogenic effects of organic peroxides.

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