Exposure of an organism to a stressor results in a primary stress response. A part of this response involves the release of the catecholamines, epinephrine and norepinephrine, which exert their actions by binding to specific membrane binding sites or receptors termed adrenergic receptors or adrenoceptors. Two adrenoceptor types exist on hepatic membranes, and their occupation results in significant changes in the biochemistry of the hepatocyte. The distribution of $\alpha\sb1$- and $\beta\sb2$-adrenoceptors on hepatic membranes is known to be species specific, and also seasonally dependent in cardiac tissue. This study tests the hypothesis that $\alpha$- and $\beta$-adrenoceptor distribution can be modified by cortisol and long term temperature acclimation. Rainbow trout (Oncorhynchus mykiss) were injected with slow release hydrogenated coconut oil implants alone (sham) or containing cortisol for 10-14 days to elevate plasma cortisol levels. Hepatic membranes were purified on discontinuous sucrose gradients and $\alpha$- and $\beta$-adrenoceptors were assayed from sham and cortisol injected trout as well as non-injected (naive) trout. No significant differences were found between any of the experimental groups for either the affinity $\rm(K\sb{d})$ or receptor number $\rm(B\sb{max})$ values of both receptor types. Cortisol treatment resulted in no change in either hepatic membrane phospholipid composition or plasma glucose, although plasma lactate decreased in cortisol injected fish. Adrenoceptor function was tested by examining glycogenolysis in isolated hepatocytes from sham and cortisol injected rainbow trout. Epinephrine significantly stimulated glucose release in sham injected trout only. This effect was blocked by both $\alpha$- and $\beta$-antagonists. In addition, studies on trout acclimated to 5 and 20$\sp\circ$C did not demonstrate different receptor characteristics. These studies do not support the hypothesis that rainbow trout exposed to cortisol alter properties of hepatic adrenoceptors.

This retrospective study assessed the usefulness of a drop and a blunted systolic blood pressure (SBP) response to exercise testing as predictors of multiple or left main coronary artery disease (CAD) as defined by a 'Coronary Score' (CS). Three types of systolic BP response to exercise were used: (1) an increase by more than 20 mmHg (Group I, n = 107), (2) an increase by 20 mmHg or less (Group II, n = 84), and (3) a decrease of at least 10 mmHg (Group III, n = 45). The extent of CAD was significantly greater in groups II and III than in group I (group I, $6.7\pm6.9;$ group II, $9.3\pm7.1;$ group III, $11.7\pm8.5,$ p 0.05). However, the difference was not statistically different between groups II and III which reinforces the value of a blunted SBP response. Treatment outcome also differed between SBP groups. Seventy percent of patients in group I received medical therapy. Over 70% of those in groups II and III underwent coronary angioplasty (PTCA) or coronary bypass surgery (CABG). It was concluded that similarly to a drop in SBP, a blunted SBP response to treadmill exercise testing in patients with known or suspected CAD is a potential indicator of multiple or left main coronary artery disease.

An enzyme activity that reversibly inactivates adipose glycerolphosphate acyltransferase (GPAT) and diacylglycerol acyltransferase (DGAT), in vitro, in the presence of ATP, has been partially purified from adipose tissue with an apparent molecular weight of 68 kDa. The activity responsible for inactivation DGAT is associated with a kinase activity as determined by phosphate incorporation into microsomes and a tyrosine containing peptide. Major substrates of this kinase are two microsomal polypeptides of 53 and 69 kDa. Both DGAT inactivation and kinase activities assayed from the purified sample and the cytosol, have been found to be insensitive to the Ser/Thr kinase inhibitor H-7 while being sensitive to the inhibitors genistein and tyrphostin 25. A crude protein phosphatase preparation from the liver was capable of reversing the effects of both activities. The purified sample was also shown to inactivate GPAT in the presence of ATP. These results suggest that a protein tyrosine kinase, in concert with a protein tyrosine phosphatase, may regulate the activities of DGAT and GPAT by a phosphorylation-dephoshorylation mechanism.

The first goal of my thesis is to develop a double catheterization method allowing simultaneous infusion of labeled compounds and blood sampling, and to quantify glucose fluxes in resting rainbow trout by continuous infusion of 6-$\sp3$H-glucose (Chapter 2). The new cannulation technique consists of placing both sampling and infusing catheters in the dorsal aorta. Continuous isotope infusion results show that resting glucose turnover is 9.5 $\pm$ 0.8 $\mu$mol $\rm kg\sp{-1}\ min\sp{-1},$ a value 4 to 9 times higher than most rates measured with bolus injection technique. Consequently, the second goal is to quantify the accuracy of the continuous infusion technique in estimating glucose turnover rate. Trout are hepatectomizad and liver glucose production is artificially replaced by a pump infusing unlabelled glucose. Glucose flux measured with the continuous infusion technique using either plasma or whole blood is not significantly different from artificial pump glucose entry rate. Therefore, this result suggests that the bolus injection method widely used in previous trout studies strongly underestimates true glucose flux. Using the continuous infusion technique, my third goal is to investigate the effects of two environmental disturbances namely acute hypoxia and cold exposure, on the rates of glucose and NEFA (non-esterified fatty acids) turnover. My hypotheses are that: (1) during hypoxia, a fuel preference for carbohydrates would lead to an increase in glucose flux and a decrease in NEFA flux; (2) during cold exposure, both glucose and NEFA fluxes would decrease in proportion to metabolic rate depression. The results suggest that no fuel preference is occurring during cold exposure. However, while glucose concentration only shows a slight overall decrease, NEFA concentration increases by 30% after 100 minutes at 6$\sp\circ$C. (Abstract shortened by UMI.)

The purpose of this study was to examine the effects of selected exercise intensities on muscle protein degradation. On two occasions eight male trained subjects performed a bench press exercise: on one occasion each set consisted of 10 repetitions at 70% of 1RM; on the other occasion each set consisted of 5 repetitions at 85% of 1RM. Venous blood samples were drawn preceding, immediately following and 24 hours after each exercise sessions and analyzed for 3-methylhistidine and tyrosine. The results showed a significant decrease in the concentration of 3-methyhistidine immediately following exercise. There was a significant decrease in tyrosine following exercise at 85% 1RM when compared to baseline. There was not a significant difference found between the 70 and 85% of 1RM protocols for either 3-methylhistidine or tyrosine. The lack of difference between 70 and 85% of 1RM may have been due to similar motor unit recruitment patterns for the two intensities. The exact mechanisms responsible for decreased protein degradation following strength training exercise are presently unclear but may be the result of mechanical tension placed on the muscle fibre.

This thesis examined a variety of factors controlling the storage and release of the catecholamine hormones, adrenaline and noradrenaline, from chromaffin cells in teleost fish. In these fish, chromaffin cells line the walls of the posterior cardinal vein (PCV) in the anterior kidney region (head kidney). To examine the process of catecholamine release, an in situ saline-perfused PCV preparation first was developed and validated in the rainbow trout (Oncorhynchus mykiss). The levels of stored catecholamines were approximately 4X greater in trout than in eel, and trout chromaffin cells released greater quantities of catecholamines in response to both 60 mmol 1$\sp{-1}$ K$\sp+$ and carbachol administration, in situ. Thus trout chromaffin cells appear to exhibit a greater capacity to release catecholamines than do eel chromaffin cells which may explain the different plasma catecholamine levels during acute hypoxia. The proximate stimulus for catecholamine release in rainbow trout, during exposure to acute hypoxia, was examined by acclimating trout to either 5 or 15$\sp\circ$C in order to modify haemoglobin oxygen-affinity. At 15$\sp\circ$C, catecholamines were released into the circulation at a PaO$\sb2$ threshold of 34.5 torr while at 5$\sp\circ$C the threshold was 24.0 torr. Release thresholds, calculated on the basis of arterial blood oxygen-saturation were similar at both temperatures (approximately 60% Hb O$\sb2$-saturation). Thus the lowering of blood oxygen content, rather than PO$\sb2,$ appears to be the proximate stimulus causing catecholamine release in rainbow trout during acute hypoxia. In the rainbow trout, intra-arterial injections of serotonin in vivo caused an increase in both plasma adrenaline and noradrenaline levels. In situ, bolus injections of catecholamines which was attenuated by pre-treatment with the serotonergic receptor antagonist, methysergide but unaffected by hexamethonium. Thus serotonin is capable of causing the release of catecholamines by interacting with serotonergic receptors on the chromaffin cells. The effect of adrenocorticotropic hormone (ACTH), the normal secretagogue of cortisol, on catecholamine release, was investigated in the rainbow trout. Intra-arterial injections of ACTH, in vivo, caused an elevation of plasma adrenaline levels. In situ, adrenocorticotropic hormone (ACTH) caused the release of both catecholamines. ACTH-induced release was unaffected by pre-treatment with hexamethonium or methysergide but abolished in Ca$\sp{2+}$-free media. Injections of cortisol in situ did not elicit catecholamine release. ACTH, therefore, is capable of eliciting catecholamine secretion from the chromaffin cells in rainbow trout. (Abstract shortened by UMI.)

This research contrasted two methods for calculating the internal work of running. The methods are known as absolute work (also known as Winter's (1979) W$\sb{\rm wb}$ calculation) and absolute power. The study also examined whether or not there were differences in the amounts of internal work done by trained and untrained runners. The absolute work approach was believed to calculate internal work incorrectly. The absolute power approach, on the other hand, correctly computes internal work by taking the absolute power generated or absorbed at each joint and summing them across a movement cycle. Five trained and five untrained female runners were filmed, while running across a laboratory runway, by a cinecamera at 100 fps. Simultaneously, force plate data, for one step, were collected. The results showed absolute work values were three times the absolute power values. Furthermore, the results of the absolute work method were too large compared to the estimated physiological cost of running. Conversely, the absolute power method produced amounts of internal work that were too high but were much closer to the estimated physiological cost. There was no significant difference between work values of the two groups of runners, for the absolute power method. The correlations for the absolute power method were higher than those of the absolute work method. Based on the results, the absolute power method provided a more accurate estimate of locomotor cost of running.

Acetylcholinesterase (AChE) is responsible for the rapid hydrolysis of acetylcholine into acetic acid and choline thus allowing precise temporal control of muscle contraction. The expression of AChE in skeletal muscle is strongly influenced by both nerve-evoked electrical activity and trophic factors. In recent years however, several lines of evidence have emerged indicating that mechanical forces influence the growth and differentiation of a variety of tissues including cardiac and skeletal muscles. In the present study, we therefore tested the hypothesis that AChE expression is modulated by mechanical stimulation by using two distinct, yet complementary approaches. In a first series of experiments, primary cultures of myotubes were subjected to repeated cycles of stretch/relaxation. In a second series of experiments, we further tested our hypothesis in vivo by examining AChE expression in denervated rat hemidiaphragm muscle. Results from these studies indicate that in addition to neural activation and trophic factors, passive mechanical forces modulate the expression of AChE in skeletal muscle fibers. Since in tissue cultured myotubes tetrodotoxin did not prevent the increase in AChE expression, it appears that the effects of mechanical stimulation are independent of electrical activity and further indicates the use of an alternate signalling pathway: The results therefore show for the first time, that passive mechanical forces modulate expression of a synaptic protein in skeletal muscle fibers. As such, these results fit well with converging lines of evidence indicating that the imposition of a mechanical stimulus dramatically affects expression of several muscle genes encoding specialized contractile proteins. (Abstract shortened by UMI.)

Whole body calcium influx, branchial calcium efflux, and renal Ca$\sp{2+}$ excretion were measured in rainbow trout (Oncorhynchus mykiss) either exposed to environmental hypercapnia or infused intra-arterially with NaHCO$\sb3$. These experiments were performed to assess the potential impact on Ca$\sp{2+}$ balance of the changes in gill morphology that are known to accompany acid-base disturbances in this species. After 48 hours of environmental hypercapnia, gill filamental chloride cell fractional area was significantly reduced. Despite this reduction, and the presumed involvement of the chloride cell in calcium influx, whole body calcium influx was increased after 12 hours of hypercapnia and remained elevated for 48 hours. Branchial calcium efflux was unaltered during hypercapnia exposure, whereas renal Ca$\sp{2+}$ excretion was elevated over preflux values only at 6 hours of hypercapnia. Measurement of the kinetics of whole body calcium influx after 48 hours of hypercapnia revealed a significant increase in the maximal uptake rate of Ca$\sp{2+}$ yet the affinity constant of Ca$\sp{2+}$ uptake was unaffected. Measurements of high-affinity. Ca$\sp{2+}$-ATPase activities and ATP-dependent Ca$\sp{2+}$ transport of gill basolateral membrane vesicles revealed that the ATP-dependent Ca$\sp{2+}$ extrusion mechanism of the gills was not affected by hypercapnia. The results of this study clearly show that the reduced chloride cell surface area that accompanies hypercapnia in trout does not impair calcium homeostasis. Whole body Ca$\sp{2+}$ influx was significantly increased after 6 hours of NaHCO$\sb3$ infusion and remained elevated throughout the duration of the experiment. Branchial and renal Ca$\sp{2+}$ effluxes were largely unaffected by NaHCO$\sb3$ infusion. Plasma total Ca$\sp{2+}$ concentrations were significantly decreased after 6 hours of NaHCO$\sb3$ infusion and remained so until 48 hours. (Abstract shortened by UMI.)

This study compared the cardiovascular responses to the PWC 140, cold pressor test (CPT), and isometric hand grip (IHG), to evaluate the consistency in the blood pressure response among these physical stressors. Eighteen resting normotensive males were classified as either normotensive at exercise or exercise hypertensive on the basis of their blood pressure response to the first stage of the Canadian Aerobic Fitness Test (CAFT) for their age group. Subjects were administered a 6-min PWC 140 bicycle ergometer test, a 120 sec CPT (forearm and hand immersion), and a 120 sec IHG at 30% MVC. Systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), heart rate (HR), stroke volume (SV), cardiac output (CO), and ejection fraction (EF) were recorded every 5 seconds during a one min resting period, during exercise, and for 3 min post exercise using a Finapress 2000 BP monitor and BoMed bioimpedance cardiac monitor. The results of this study indicate that: (1) there were no significant differences between the two groups for the cardiovascular responses to the PWC 140, IHG, and CPT with the exception of a greater CO and SV in normotensives on the PWC 140, and a higher HR in exercise hypertensives on the CPT; (2) the exercise hypertensives had a greater rate of increase in SBP and DBP than the normotensives over the first 90 seconds of the CPT; (3) there was no consistent pattern in the individual responses to the CAFT, CPT, and IHG with respect to $\Delta$SBP. It was concluded that within the context of this study, the blood pressure responses to dynamic exercise, isometric exercise, and cold stress were not consistent among the subjects and tests.