The purpose of this study was to elucidate certain aspects of the control of bicarbonate reabsorption in the surface distal tubule of rats made acidotic by ammonium chloride treatment. During acute metabolic acidosis, the effects of sodium delivery, water reabsorption, inhibition of carbonic anhydrase, and addition of the anion channel blocker SITS were determined. In addition, bicarbonate reabsorption was assessed during recovery from metabolic acidosis. Studies during the acute phase of acidosis: Sprague-Dawley rats were made acidotic by ammonium chloride gavage and then prepared for micropuncture. It was hypothesized that distal tubule bicarbonate transport might have components dependent on direct or indirect Na/H exchange, water reabsorption, carbonic anhydrase activity and chloride conductance. To test these hypotheses surface distal tubules were then microperfused in vivo at 8 nl/min with 4 different isoosmotic, bicarbonate containing solutions. These solutions were designed to (1) provide an index of the increased bicarbonate reabsorption evident in this model and assess the effect of the following on bicarbonate reabsorption: (2) sodium replacement with choline; (3) sodium substitution augmented by pharmacologic means (amiloride); (4) inhibition of carbonic anhydrase by acetazolamide. At 8 nl/min, collection of fluid from tubules perfused with all 4 solutions revealed significant bicarbonate reabsorption. Net distal tubule bicarbonate reabsorption was significantly increased in acidotic animals. Perfusion of tubules with sodium free solutions did not decrease this brisk reabsorptive flux, nor did perfusion of sodium free solutions which also contained amiloride. However, perfusion of tubules with the carbonic anhydrase inhibitor DIAMOX significantly decreased bicarbonate reabsorption. This is the first in vivo demonstration of such an effect in the distal tubule of the acidotic rat when bicarbonate load was held constant. The effect of sodium replacement at high perfusion rate was also studied, but again was not found to significantly alter bicarbonate reabsorption, although more bicarbonate was found to be reabsorbed at 25 nl/min than at 8 nl/min. Since some reports have suggested that a chloride conductance may play a role in acidification by proton pumps, the effects of perfusion with a chloride channel blocker was studied. Paired collections at 25 nl/min, with and without SITS, revealed a significant inhibitory effect of SITS. Studies during recovery from metabolic acidosis: Animals allowed to recover from the acidosis exhibited a rebound metabolic alkalosis. It was hypothesized that distal tubule bicarbonate reabsorption might contribute to this apparent overshoot of blood bicarbonate concentration. Tubules perfused 44 hours post gavage exhibited significant bicarbonate reabsorption at 8, 15, and 25 nl/min, despite the concurrent metabolic alkalosis. These are the first reported in vivo data of distal tubule bicarbonate reabsorption during rebound metabolic alkalosis. It is concluded that bicarbonate reabsorption in distal tubules of acidotic rats perfused in vivo at 8 nl/min was not affected by reduced sodium delivery, or water movement, but is partly dependent on carbonic anhydrase activity and may also be partly dependent on chloride permeability. In addition, bicarbonate reabsorption continues during the recovery phase, despite the existence of systemic metabolic alkalosis.

This thesis attempts to elucidate the role of epinephrine and/or norepinephrine in the regulation of ventilation in teleosts while also considering the effects of other potential ventilatory modulators. The ventilatory responses to various external respiratory challenges were quantified and compared with those in fish pre-treated with adrenoceptor antagonists. The effects of experimental elevation of circulating catecholamines on gill ventilation volume (Vw) were assessed. During hypoxia, pre-treatment of fish with either $\alpha$- or $\beta$-adrenoceptor antagonists did not affect the ventilatory response of rainbow trout (Oncorhyncus mykiss) or Atlantic cod (Gadus morhua), regardless of the degree of hypoxia used and the corresponding effects on circulating catecholamine levels. Furthermore, since increases in Vw were observed under mild hypoxia or hypercapnia it is concluded that elevation of circulating catecholamines is not a prerequisite for hyperventilatory responses to these stimuli. Pre-treatment of trout with a $\beta$-adrenoceptor antagonist (propranolol) prior to exposure to external hypercapnia prevented a sustained hyperventilation despite the absence of significantly elevated catecholamines in the circulation. This revealed that catecholamines of non-humoral origin are involved in the hyperventilatory response to hypercapnia. It is unlikely, at least in trout, that catecholamines play a stimulatory role in the regulation of ventilation. Respiratory acidosis may play a role in the control of ventilation in this species since external hypercapnia prevented the hypoventilatory response normally associated with hyperoxia. (Abstract shortened by UMI.)

This thesis deals with some of the unknown issues in slow auditory evoked potentials (AEPs). Slow AEPs were recorded in 10 healthy reading subjects. A change in the frequency of the tonebursts elicited an additional negativity--the mismatch negativity (MMN). The amplitude and latency of MMN changed with the magnitude of frequency deviance between stimuli which was varied between 50 and 2000 Hz. The voltage distributions of the MMN and N1 were significantly different from that of the SP. The MMN and N1 had their maximal amplitudes in the fronto-central areas, whereas the maximal amplitude of the SP was recorded frontally. The topographic mapping and statistical analysis of voltage distribution of individual waves enabled us to recognize and differentiate between the possible generators of the MMN, N1 and SP. Both the MMN and N1 are generated in the auditory cortices. The SP is more complexed and may consist of more than one component. (Abstract shortened by UMI.)

No description available.

Ten (10) normal adult male subjects were asked to move a known weight, representing 15% of the maximal lifted weight, in both horizontal and vertical conditions at frequencies of 40 cycles/min and 60 cycles/min. Raw EMG signals from six (6) shoulder muscles were recorded and synchronized with the cinematographic data during three (3) trials of six (6) seconds each. The raw EMG signals of each muscle were full wave rectified and filtered at three (3) Hz. The LE EMG signals were normalized by time (% cycle) and by amplitude (% MVC), and for the analysis of variance, the normalized LE EMG signals were integrated (IN LE EMG). The average shoulder angular velocities, joint moments and moment powers were computed from cinematographical data. No significant difference were observed between both tasks for the supraspinatus, infraspinatus, and pectoralis major IN LE EMG data as well as for integrated normalized shoulder joint moment for the whole cycle of movement. IN LE EMG data from middle deltoid, anterior deltoid, and trapezius muscles were significantly higher (p 0.05) when performing the vertical displacement task for the whole cycle of movement. (Abstract shortened by UMI.)

Abstract Not Available.

No statistically significant difference between genders was observed. Among all the comparisons of the 30 second intervals within the 5 minute HRREC data, only two time periods were not statistically significant. One was early in recovery and one was late in recovery. Mean BLa went down every minute from 6.91 mMol at post 1 minute to 6.51 mMol at post 5 minute but this difference was not statistically significant. No statistically significant correlation were found to exist between HRREC and BLaREC. However, PEAKBLa following the test was correlated with HRREC measurements such that the following two trends were found. First, the correlation between PEAKBLa and the absolute HR values obtained at different time intervals during recovery became stronger with increasing time up to the 2nd minute of recovery and second, PEAKBLa was negatively correlated with 5 minute HRREC. PEAKBLa was negatively correlated with the HRREC obtained in the first two minutes of recovery but this relation became positive between the 2nd and 5th minute of recovery. (Abstract shortened by UMI.)

A group of male subjects (N = 8) were used to examine the effects of two selected rest intervals on total work volume and blood lactate during a maximal effort elbow flexion resistance exercise performed at a fixed relative resistance (70% IRM). The rest intervals were set at 30 seconds (R$\sb{30}$) and 180 seconds (R$\sb{180}$) and were based on the half and full recovery times respectively of the high energy creatine phosphate (CP) system. The exercise continued until a computerized light sensor system detected a movement speed decrease to a pre-determined level of fatigue. R$\sb{180}$ resulted in a significantly greater volume of work (247%) achieved without a statistically significant increase in blood lactate (10%) compared to R$\sb{30}$. It was concluded that a rest interval between repeats of elbow flexion exercise of 180 seconds versus 30 seconds significantly increased the ability to do work without a significant increase in the contribution of the anaerobic lactic system. (Abstract shortened by UMI.)

Gold thioglucose (GTG) leads to hypothalamic obesity in mice. The purpose of this study was to determine if hypersensitivity to corticosterone is present in mice with hypothalamic obesity. Mice were injected with either saline or GTG and sham-adrenalectomized or adrenalectomized (adx). The adx animals received cholesterol implants containing corticosterone. Certain abnormalities of GTG-mice, namely hyperphagia, increased white adipose tissue and brown adipose tissue (BAT) weights and hyperinsulinemia are normalized by adrenalectomy and returned in virtually full force at low levels of corticosterone. Other abnormalities like high body weight and reduced BAT mitochondrial GDP binding are not affected. BAT protein was not affected by adrenalectomy in either lean or obese animals and was reduced by corticosterone replacement in both. It is concluded that GTG-mice are hypersensitive to an action of corticosterone which plays an important role in the development of their obesity. However, some abnormalities, like the suppressed BAT thermogenesis, persist in the adx state and seem to be due to metabolic defects primarily caused by the GTG lesions that are not dependent on corticosterone. (Abstract shortened by UMI.)

In this study, the ductal heterogeneity in the rat ventral prostate was further investigated in terms of structural elements that make up the different cell types of the prostate as well as cell populations found along prostatic ducts. In addition, effects of androgens were analyzed in specific locations of the ductal-acinar network. The cytokeratin content of the prostate was characterized biochemically and by immunofluorescence and was used as a marker to monitor the behaviour of each cell type after androgen depletion. It was found that the cytokeratin content of basal and luminal epithelial cells are characteristic for each cell type and that these structural proteins constitute good markers for these cell types. Using antibodies specific for basal and luminal epithelial cells, the ratio basal to luminal epithelial cells was shown to vary along the prostatic duct as well as after castration, suggesting a preferential loss of luminal epithelial cells. Based on the observations of the cellular dynamics in the prostate of intact versus castrated rats, a model of regression is proposed. (Abstract shortened by UMI.)