The effects of septal lesions in rats on the hyperglycaemic response to stress, adrenal weight and water intake were investigated. Tested four times post-operatively at approximately weekly intervals, septal rats did not manifest significantly different resting blood glucose levels than control animals nor did they demonstrate an abnormal degree of hyperglycaemia following periods of unavoidable foot shock. No adrenal hypertrophy was evident in septal subjects compared to controls. Daily water intake was significantly higher among septals. The results concerning blood sugar levels and adrenal weights are taken as evidence that septal rage may not represent true hyperemotionality since certain appropriate physiological concomitants are absent. A second experiment investigated resistance to capture and handling and aspects of open field behaviour in septal and control rats following injections of chlorpromazine hydrochloride or saline. Septalectomized rats resisted handling and capture to a greater extent than controls, traversed fewer squares and demonstrated less rears in an open field, and had a greater tendency to leave a home cage and enter an open field. Chlorpromazine affected neither control nor septal subjects except to suppress the tendency of septal rats to leave a home cage and enter an open field. The behaviour of septal rats is discussed in terms of apparent emotionality. / Arts, Faculty of / Psychology, Department of / Graduate

Plicatic acid and 5-isopropyltropolone, which are found in the heartwood of western red cedar (Thuja plicata, Donn), are known chelators of copper. A study has been made of their effects on some aspects of copper metabolism in rats and mice. As a basis of comparison similar experiments were carried out using penicillamine (PEN), a chelating agent with wide clinical use. In the experiments the sodium salt of 5-isopropyltropolone (T-Na) and the potassium salt of plicatic acid (P-K) were used. When administered daily, P-K and PEN caused an increase in urinary and fecal excretion of copper in rats on a normal diet and an increase in the level of copper in the liver and kidney and a decreased level of copper in the heart and brain. The increased urinary excretion is much more marked with PEN than with P-K. T-Na administered daily had no effect on the excretion of copper in rats on a normal diet and causes a rise in copper content of liver and kidney and a lowering of copper content of heart and brain. It appears that the copper level elevation in kidney and liver caused by P-K and PEN is due to an increased utilization of the routes of excretion while the increased level due to T-Na is probably due to deposition in the cells. When these compounds are administered daily to copper-fed rats similar observations were made with the difference that in organs where copper levels are increased the increases are greater and in organs where copper levels are decreased the decreases are smaller. With T-Na there is one marked difference in that the copper level in the brain is increased. It is felt that this increase is due to a greater penetrating ability of the T-Na-copper chelate because of its lipid solubility. P-K and PEN have very little effect on the toxicity of a single large dose of copper. Earlier experiments with T-Na showed that when T-Na is given shortly after a single large dose of copper the toxicity is greatly increased. The explanation of this is very likely that T-Na increases the penetration of the copper into the CNS and it is here that the toxic effect is exerted. It is felt that this is due to a solubility factor, T-Na and its chelate being lipld-soluble and P-K, PEN and their chelates being water-soluble. When T-Na, P-K and PEN are given to rats in small daily doses over a long period, the atria from such rats exhibited a reduced chronotropic response to tyramine. If at the same time as the rats are being given the chelating agent, they are given excess copper in drinking water the tyramine response remains close to normal. In this regard T-Na possesses the most activity. These observations support the theory that chelating agents inhibit dopamine-β-hydroxylase by rendering copper inaccessible to the enzyme and that subsequent to this inhibition the biosynthesis of the catecholamines is inhibited at the dopamine stage preventing the formation of norepinephrine and epinephrine. As the levels of endogenous norepinephrine and epinephrine fall, the result is a reduced tyramine response. If T-Na, P-K, PEN and D-Na are given in a large single dose the inhibition of dopamine-β-hydroxylase is not evident while it appears that COMT may be being inhibited. / Medicine, Faculty of / Anesthesiology, Pharmacology and Therapeutics, Department of / Graduate

The properties of the deoxyribonuclease activity in the intestinal mucosa of the rat have been studied. Two DNases were found in a cell-free extract prepared by homogenizing the mucosal tissue in Krebs-Ringer phosphate buffer and then centrifuging the homogenate at 105,000 x g for 60 mins. Resolution and partial purification of these two enzymes were achieved by ion-exchange chromatography on DEAE-cellulose and partition on hydroxylapatite of the cell-free extract or an acetone powder preparation of the enzymes. One of the enzymes was identified as DNase I by its optimum pH (6.5 to 6.8), its requirements for bivalent metals and by its reaction to known DNase I inhibitors such as EDTA, citrate and arsenate. It was also found to be active toward native DNA, and, to a lesser degree, toward heated DNA. The second DNase was shown to be qualitatively different from DNase I. It has an acidic optimum pH (3.5-4.0), does not require activation by bivalent cations and is not inhibited by EDTA, citrate or arsenate. This second DNase activity is therefore of the DNase II type. The linkage specificity of the two enzymes was studied by isolating the products of the reaction and examining them with respect to chain length, base composition of the mononucleotides, relative frequencies of the dinucleotides and base frequencies at the ends of the oligonucleotides. The hydrolysis reaction was carried out under a variety of conditions. When Mg++ was used as the activating ion and native DNA as substrate, DNase I was found to show a preference for the linkages pApC, pApT and pGpT. But when Mn++ was the activator, or when heated DNA was used as substrate in the presence of Mg++, DNase I did not show any significant order of specificity. With regard to DNase II, the enzyme was found to attack native DNA preferentially at the ApCp, GpCp and GpTp bonds. The mechanism of metal activation of intestinal DNase I was also studied. Preliminary experiments showed that the enzyme was inhibited by high concentrations of both metals and DNA. In addition, optimal activation was found to depend on the molar ratio of metal ion to DNA phosphorus. These experiments suggested that the metal-DNA complex is probably the true substrate. Consequently, a rate equation in terms of the metallosubstrate concentration was developed based on the assumption that intestinal DNase I can combine individually and simultaneously with free metal, free DNA and the metal-DNA complex. Data obtained from initial velocity studies carried out at varying concentrations of metal and DNA fitted this rate equation well. On this basis, it was suggested that the enzyme, the metal activator and the DNA substrate combine to form a ternary complex which then dissociates to give the products. / Medicine, Faculty of / Biochemistry and Molecular Biology, Department of / Graduate

Gastric mucosal erosions were induced in the glandular stomach of rats by scalding. The incorporation of Thymidine-methyl³-H into desoxyribonucleic acid was used to determine changes in gastric epithelial cell proliferating ability. Total desoxyribonucleic acid per milligram of gastric tissue was also determined. Sampling was done at twenty-four hours, seven days, and fifteen days postburn. Eighty-nine point two percent of rats with a standard 26.5 ± 2% scald burn had developed gastric mucosal erosions by twenty-four hours postburn. Seventeen point eight percent of burned rats had erosions by seven days and the incidence rose to 46.4% by fifteen days postburn. Ten point three percent of control rats in all sampling periods developed erosions. The total desoxyribonucleic acid in the gastric samples did not change significantly in any treatment period nor was it changed by treatment. Uptake of thymidine-methyl³-H was depressed twenty-four hours postburn and renewed so through seven days postburn. The results at the fifteen day sampling were inconclusive. By light microscope, the gastric surface epithelium was lifted from the lamina propria and at times there was complete denudation of this cell layer. The rat is a satisfactory animal model for gross study of mucosal erosions to at least fifteen day postburn. Because of eschar cannibalization inducing variable secretory status, the rat model was not suitable for thymidine uptake studies past seven days postburn. / Surgery, Department of / Medicine, Faculty of / Graduate

Preferences were determined for rats as they explored three differentially complex visual stimuli over a series of trials. Early visual experiences were manipulated by differential enrichment periods in the first of two experiments in the study and by differential rearing conditions in the second experiment. Results were evaluated in terms of their support for the following predictions from the theory of Dember and Earl (1957): 1. When experience with stimuli differing in visual complexity leads to preferences for stimuli of different complexities, high-complexity experienced organisms will prefer more complex stimuli than low-complexity experienced organisms. 2. When shifts in preference between trials are expressed, the direction of such shifts will be towards increased complexity. 3. When rate and/or degree of shift in complexity preferences differ between groups receiving different levels of visual complexity experience, high-complexity exposed groups will show the faster and/or greater degree of shift to higher complexities. Support for these predictions was found. Suggestions for improvement of the Dember and Earl model and of the techniques for investigating it were discussed. / Arts, Faculty of / Psychology, Department of / Graduate

The aim of this study was to investigate the intra- and intermodal impact of different kinds of early sensory experience on the development of specific neural/perceptual systems. The manipulations of the rats' early experience involved a combination of early binocular deprivation through dark-rearing, somatosensory restriction through cauterization of mystacial vibrissae, and multimodal enrichment through rearing in a complex environment. Specific lesions to somatosensory (Parl) and visual (Oc2M) cortex in differentially reared animals were included in an attempt to gain further insight into the plasticity surrounding manipulations of early stimulation history. Five tasks were used to assess these effects of early rearing condition in combination with later cortical lesions. Behavioral assessment focused on the ability of the animals to encode, abstract, and remember specific relationships between stimuli within the deprived modality itself, their ability to do so with information presented in other modalities, and on the basic species specific behavior. The only effect found was a main effect for rearing condition. Basically, complex-reared rats were more competent on several of the behavioral tasks than were dark-reared rats. However, this result provided little behavioral support for ideas of modality interdependence. Dendritic proliferation is considered to be a general mechanism supporting behavioral change. The subsequent neuroanatomical assessment focused on dendritic branching of neurons in specific cortical areas thought to be most affected by early environmental manipulations. Animals that were raised in a complex environment, but had experienced early tactile restriction through cauterization of vibrissae, showed significantly more dendritic branching than animals from all other rearing conditions in all cortical areas measured. This finding is consistent with ideas of both intra- and intermodal compensation following damage to an early developing modality, as well as behavioral demand acting as a significant factor in determining the impact of early somatosensory restriction. It is reasonable to assume that anatomical changes should be manifested behaviorally. Suggestions for smaller, more restricted studies, that would be more effective in describing the behavioral impact of early manipulations of the environment, were outlined. / Arts, Faculty of / Psychology, Department of / Graduate

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

It is well established that the neurotransmitter serotonin participates in the control of sexual behaviour in the male rat. Recently, it has been found that serotonergic activity may either inhibit or facilitate sexual behaviour, depending on the subtypes of serotonin receptors involved. However, the participation of 5-HT2 receptors in the control of male rat copulation has received little experimental attention, and the published data are equivocal. In Experiments 1-4, it was established that the 5- HT2/1C agonist DCI inhibits sexual behaviour in male rats; this inhibition is effectively reversed by the antagonists ritanserin, pirenperone, and ketanserin. Comparison of these effects , with reference to the binding profiles of each drug, provided strong evidence that 5-HT2/1C receptors mediate an inhibitory influence on sexual behaviour in male rats. In addition, a tentative claim may be made that the effects of these drugs may be more attributable to 5-HT2 activity than 5-UT1C activity. ‘Wet dog shake’ behaviour in rats is known to be 5-HT2- dependent. Experiments 5—7 evaluated the novel proposition that the incidence of spontaneous wet dog shaking (WDS) by male rats in mating tests may provide a behavioural assay of concurrent 5—HT2 activity. WDS was found to be associated with copulatory inhibition in noncopulating males, compared to normal copulators, and this relationship was specific to mating situations. Activating 5-HT2/1C receptors with DOl simultaneously induced WDS and inhibited copulation. Thus, the incidence of spontaneous WDS in untreated males may reflect the function of a 5—HT2—mediated neural mechanism that tonically inhibits copulation in male rats. In Experiment 8, DOl microinjection in the nucleus raphe obscurus/inferior olivary complex also induced WDS and inhibited copulation. This suggests that the hypothesized 5- flT2-dependent inhibitory mechanism is vested in the ventromedial brainstem. Recent anatomical findings support this suggestion: cells in this region have bifurcating axons, projecting collaterally to both the medial preoptic area (implicated in sexual behaviour) and to the ventral cervical spinal cord (implicated in WDS). Overall, the results of the eight experiments provide strong evidence that 5-HT2 receptors mediate some of the inhibitory effects of serotonin on male rat sexual behaviour. / Arts, Faculty of / Psychology, Department of / Graduate

The purpose of this study was to examine the effects of Vitamin E deficiency and/or ionizing radiation on uterine ceroidogenesis, incisor depigmentation, serum Vitamin E, haemoglobin concentration, haematocrit, 2,3-DPG and adipose tissue fatty acid composition in rats. An attempt was also made to define the nature of ceroid and to examine its relationship to lipofuscin. Rats fed a Vitamin E deficient diet deposited increasing amounts of ceroid in the uterine musculature between 90 to 261 days after the imposition of the experimental diets. This pigment was found to be essentially similar to lipofuscin. Ionizing radiation did not have any apparent effect on the rate and degree of ceroidogenesis in Vitamin E deficient rats, althought it did cause a significant decrease in the serum Vitamin E levels of both Vitamin E deficient and supplemented animals. The serum Vitamin E of the deficient animals were significantly lower than those of the supplemented animals, irrespective of their radiation status. Vitamin E deficiency also caused a depigmentation of the maxillary incisors of the animals and had no effect on the haemoglobin concentration, haematocrit and 2,3-DPG levels of these rats. Finally, Vitamin E deficiency and ionizing radiation resulted in a decrease in the polyunsaturated fatty acid content of adipose tissues. / Education, Faculty of / Curriculum and Pedagogy (EDCP), 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.