This is a longitudinal study, having as its main purpose to determine the influence of environmental experience, specifically that of perceptual deprivation on problem-seeking behavior of rats. The effects of perceptual deprivation on exploratory behavior, and the distinctness of exploratory and problem-seeking behavior are also investigated. The subjects for the present study were sixty Sprague-Dawley albino rats. A three phase experimental procedure was utilized. In phase one pre-experimental measures were obtained from all subjects of their problem-seeking and exploratory behavior. Phase two, the experimental phase, consisted of dividing the animals into two groups and rearing them for thirty days in either a perceptually deprived or normal environment. During the third phase, all rats were post-tested on both the problem-seeking and exploratory measures. The major hypothesis tested states that the placement of animals in a perceptually deprived environment for a thirty day period will result in significant increases in both their problem-seeking and exploratory behaviors. Significant results were found and the hypothesis, therefore, was substantiated. A low but significant relationship was found to exist between problem-seeking and exploratory behavior indicating that the two behaviors do contain common elements. Eight minor hypotheses were also tested, attempting to determine the changes in exploratory or problem-seeking behavior of animals that have previously been divided into high or low groups according to either their problem-seeking or exploratory behavior and then reared in perceptually deprived or normal environments. Non-significant results were found in all but two cases. The results of the present investigation were interpreted in the light of the concept of optimal stimulation. Neurophysiological explanations were put forth indicating that the behavior changes due to the deprived rearing are dependent on neural changes, particularly in the reticular activating system.

Abstract not available.

It has been suggested that bombesin (BN)-like peptides may play a physiological role in the control of food intake. The working hypothesis behind the experiments presented in this dissertation was that if this family of peptides is involved in the mediation of satiety, then the availability of the peptide(s) and/or its receptors should change with feeding status. Thus, the specific objectives of this research were to elucidate the changes in the availability of central and peripheral BN-like peptides and their receptors during a meal. In our preliminary experiments, all rats were food deprived for a 12 hr period. Half the animals were then permitted to eat solid food until satiated (35 min). Techniques of Radioimmunoassay (RIA) and quantitative autoradiography (QAR) were employed to measure peptide and receptor levels respectively in several brain and gut sites. Our results indicated significant increases in BN-like peptide levels, specifically gastrin-releasing peptide (GRP) GRP1-27 and/or GRP18-27, in the hypothalamus, hippocampus, and antral region of the stomach after food ingestion. The autoradiography study indicated an effect of food intake on central, but not gastrointestinal, BN-like peptide receptors, but failed to identify specific loci where these differences were significant between feeding states. The objective of the next series of experiments was to elucidate the pattern and degree of change in the levels of BN-like peptides and their receptors at different timepoints during different feeding states. These experiments included four groups of animals: (1) Rats that were food deprived for a 12 hr period; (2) and then given access to food for either 10 min or (3) 35 min. The fourth group constituted of non-deprived controls (ad libitum fed). RIA of hypothalamic, hippocampal, and medullary (control) tissues replicated and extended our earlier findings and showed that, in relation to the ad libitum condition, hypothalamic BN-like peptide concentrations were reduced by fasting, while hippocampal levels were elevated by feeding. The autoradiographic studies of several central areas demonstrated decreased binding in the hypothalamus, fundus striatum, and nucleus accumbens of the postprandial animals, as compared to the food deprived group. In the next experiment, an attempt was made to identify whether the changes noted at the receptor level were related to changes in the receptor number or affinity. The saturation experiments did not reveal significant alterations in the KD and Bmax of BN-like peptide receptors in response to food intake. Thus, the mechanisms underlying these receptor changes were not successfully established. The rapid alterations in peptide and receptor levels may support the contention that BN-like peptides play a physiological role in the regulation of ingestive behavior.

Food consumption and growth of walleye, Stizostedion vitreum (Mitchill) and sauger, Stizostedion canadense (Smith) were compared. Both the species were caught in the Ottawa River during 1967 to 1972. Their daily feeding periods, feeding behavior, and movement were studied from spring to fall in the field. Growth of the walleye and sauger in the Ottawa River was the lowest recorded for any water of similar latitude. Slow growth was pronounced in fish older than three years. For example, the mean total lengths of six year old walleye and sauger were 40.2 cm and 29.4 cm respectively as compared to 49 cm (Balch, 1951) and 41 cm (Van Oosten, 1948) for walleye and sauger of the same age from the Great Lakes. Sauger consume demersal prey due to their sensitivity to light intensity. However, in the Ottawa, River, a lack of sufficient prey in demersal waters caused the sauger to com pete ineffectively for food with the walleye and non-Stizostedion predators in the littoral zone of the river. We observed that the emerald shiner (Notropis atherinoides) was the most abundant prey species in the littoral zone, accounting for more than 75% of the diet of the walleye and sauger. Yellow perch (Perca flavescens), also caught in the littoral zone, served as an important secondary food source during periods of low density of the emerald shiner. Daily food consumption of walleye in the river decreased from 4.3 to 3.0% of body weight in two to six year old fish. Daily food consumption of the sauger decreased from 3.3 to 2.9% of body weight in two to six year old fish. In the laboratory, two, three, and four year old walleye and sauger, when fed ad libitum, consumed more food per day (4-9% of body weight) than fish of the same age in the river. Approximately two thirds of the total walleye and sauger moving into the feeding area in the river were caught between sunset and midnight. Most of the remaining one third were caught before 3 a.m.. Daily food consumption and growth of the fish in the river indicated that both species must have fed every night during the growing season. Feeding activity of the walleye peaked in late July and coincided with the highest prey density. Feeding activity of the sauger peaked in August. In the laboratory, walleye and sauger differed very little with respect to food consumption, stomach and gut evacuation time, efficiency of food assimilation, and growth efficiency. Stomach evacuation at 19°C took an average of 18 hours, and food passed through the entire digestive tract in 48 hours. Ingested calories were assimilated with an efficiency of 92%. Food conversion efficiency for growth ranged between 13 and 15% for two and three year old fish fed at 4.0% of body weight and maintained at 19°C in the laboratory. Continued disruption of their habitat, e.g. dam construction and increased eutrophication, threatens the balance between the two species and may cause the disappearance of the sauger in the Ottawa River as it did in the St. Lawrence River. Only good fishery management practices can avert this situation.

The structure and function of mitochondria of cold-acclimated rats (+2°C) in comparison with those of control rats (+23°C) have been studied in relation to (A) uncoupling of oxidative phosphorylation, (B) protein synthesis, and (C) mitochondrial ultra structure, in an attempt to find the cause of extra heat production (non-shivering thermogenesis) which occurs during cold exposure. The dry mass, number and total protein content of mitochondria per gram of original fresh liver tissue was found to be reduced in cold-acclimated rats. Cold exposure also resulted in a decrease of the protein contents of the soluble and insoluble fractions of mitochondria. The reduction of dry mass per gram of original fresh liver tissue and the reduction of soluble and insoluble protein contents per gram of original fresh liver tissue seems to be due to the reduction of number of mitochondria since the dry mass per unit number of mitochondria was found to be more or less the same. Cold treatment also resulted in a decrease of the P:O ratio, owing to a higher uptake of oxygen and lower uptake of inorganic phosphate. Study on incorporation of uniformly labeled C14-amino acids into mitochondria) protein indicated that cold exposure induced a reduced accumulation of radioactivity in mitochondria) protein both in vitro and in vivo, this effect being more pronounced in the soluble protein fraction. Studies with the electron microscope revealed that a great number of mitochondria of cold-acclimated rats were larger than those of control rats, with more ruffled outer membrane and pale matrix. This enlargement of mitochondria of cold-acclimated rats could be due to swelling in vivo. The glycogen content of the liver cells was found to be higher in cold-acclimated rats than in control rats. It is concluded that cold exposure exerts its effect on mitochondrial protein synthesis, particularly the soluble fraction. This impaired protein synthesis with enlargement of mitochondria of cold-acclimated rats could be the reason for the swelling and the changes in the properties of the membrane, leading to the uncoupling of oxidative phosphorylation.

Abstract not available.

Carbonic anhydrase (CA) is an important enzyme that catalyzes the reversible hydration/dehydration reactions of CO2. In mammals, there are at least 15 isoforms of CA with diverse tissue distributions, widely varying kinetic properties and numerous physiological functions. The research reported in this thesis focused on the molecular characterization and physiological roles of two rainbow trout (Oncorhynchus mykiss) CA isoforms, the membrane-associated CAIV and a cytosolic form (tCAc). More specifically, I evaluated the roles of CAIV and tCAc in renal acidification and bicarbonate reabsorption at rest and during respiratory acidosis. In addition, the localization of these proteins within the kidney and gill was investigated, and the role of tCAc in branchial acid-base regulation was assessed. Using an array of techniques that included Northern analysis, Western analysis, real time RT-PCR, immunohistochemistry and in situ hybridization, I demonstrated that trout CAIV is specifically localized to renal tubule cells, whereas tCAc is widely distributed across different tissues such as gill, kidney and brain. (Abstract shortened by UMI.)

The aim of this thesis was to investigate the effects of nitric oxide (NO) on both basal and stimulus-evoked catecholamine secretion in rainbow trout (Oncorhynchus mykiss). Experiments were performed in vivo and in situ using an electrical field stimulation technique. Catecholamine secretion rates in situ were markedly reduced in response to electrical stimulation in the presence of the NO donor sodium nitroprusside (SNP; 5 X 10-3 M). This reduction was through the activation of soluble guanylyl cyclase (sGC) rather than via an acceleration of catecholamine degradation. Pre-treatment with the NO inhibitors 7-nitroindazole (10-4 M) and L-NAME (5 X 10-3 M) decreased NO production in response to electrical stimulation while increasing catecholamine secretion rates approximately 2-fold. Experimental evidence suggests that nNOS is the main isoform involved in the inhibition of catecholamine secretion. Following the repeated exposure of rainbow trout to hypoxia over 4 days in vivo, in situ preparations derived from these fish showed an approximately 2- and 1.8-fold increase in basal and stimulated NO levels, respectively, while catecholamine secretion rates were reduced by approximately 50%. Expression levels for the nNOS isoform in the head kidney and anterior posterior cardinal vein (PCV) suggests that this isoform is involved in the catecholamine response. In summary, nNOS appears to be the main isoform in producing NO under neuronal stimulation and that this NO decreases stimulus-evoked catecholamine secretion through the activation of sGC.

Body temperature variation affects most physiological processes in terrestrial ectotherms and, therefore, can have a large effect on fitness. I studied eastern milksnakes at the northern extreme of their range, in a thermally challenging environment. Because of the particular importance of thermoregulation in thermal extremes, I hypothesized that thermal quality would influence thermoregulation, behaviour and habitat selection. In chapter one, I demonstrated that when thermal quality decreased, milksnakes increased investment in thermoregulation, a result contrary to the central prediction of the cost-benefit model of thermoregulation. Because ecotherms obtain heat from their environment, I predicted that when thermal quality was low, milksnakes would bask more and select higher thermal habitat. Milksnakes did not alter their habitat use in response to thermal quality. They did, however, alter their behaviour and were seen basking more and concealed less when thermal quality was low. In chapter two, my main goal was to determine if thermal quality affected habitat selection at multiple scales. Supporting my prediction, thermal quality influenced habitat selection at both the home range scale and the location scale. At both scales, milksnakes selected high thermal quality habitats (rocky outcrops, fields, and edges) and avoided low thermal quality habitat (forest). At the microhabitat scale, milksnakes selected locations with open canopy and many rocks. As a secondary objective, I tested the ability of 4 m resolution IKONOS imagery to accurately quantify habitat selection at the scale of the locations used by each snake. Although not as accurate as traditional field methods, remote sensing showed promise in measuring habitat selection at that scale.

The aim of this thesis was to investigate respiratory plasticity in zebrafish (Danio rerio) confronted with long-term changes in water gas composition (hypoxia, hyperoxia or hypercapnia) either as embryos or adults. The ventilatory responses to acute changes in water gas composition (hypoxia, hypercapnia or cyanide) were assessed using a non-invasive technique (Altimiras and Larsen, 2000) to continuously monitor breathing frequency (f R) and relative breathing amplitude. The ventilatory response to acute hypoxia consisted of an increase in fR while the response to acute hypercapnia was an increase in relative breathing amplitude. (Abstract shortened by UMI.)