Comparative histological and radiochemical studies of iodine metabolism in juvenile Oncorhynchus revealed good agreement between thyroid epithelial height and ability to convert I¹³¹ into protein-bound I¹³¹(PBI¹³¹). The ratio of I¹³¹ to PBl¹³¹ in plasma samples (Conversion Ratio) was considered superior to other thyroid assays reviewed. Peaks in thyroid activity and loss of I¹³¹ from the body occurred in sockeye and coho at the time of downstream migration, but in chum and pink only when postmigrants were retained in fresh water. In coho and sockeye these changes were transitory, in chum irreversible and in pink prolonged. On the above basis, thyroxine was assigned no specific role but a theory of smolt evolution was proposed and related to a phylogeny within the genus Oncorhynchus. / Science, Faculty of / Zoology, Department of / Graduate

The beaver (Castor canadensis Kuhl) is subjected to a widely fluctuating energy regime in the northern portion of its distribution. During the summer the animal has free access to an abundant food supply in the form of growing plant material, while during the winter the food supply is limited to a store of cached saplings. The working hypothesis of this study was that seasonal shifts occur in energy expenditure such that it is highest during the summer when an abundant food supply is readily available. In the Mackenzie Delta, Northwest Territories, growth was found to be rapid in the summer and absent in the winter. A winter weight loss characterized immature animals. Fat was deposited in the autumn, maintained during the winter and mobilized in the spring. Animals were lean during the summer. Thyroid gland weights were high in the summer and low in the winter. It was concluded from these data that metabolic energy expenditure is high during the summer and low during the winter. A consideration of possible extrinsic causes of this annual pattern and the finding that the beaver ceases to grow during the winter when on a constant ration made available ad libitum led to the conclusion that the pattern is an inherent property of the beaver at northern latitudes. The thyroid gland was hypothesized as the major effector of the annual pattern within the organism. Light intensity was hypothesized as the environmental factor that times the level of energy expenditure to environmental conditions. No major seasonal changes in thyroid activity, food intake or growth were observed in California beavers maintained under Vancouver climatic conditions and a constant ration made available ad libitum, but Arctic beavers maintained under the same conditions showed a growth cessation, a 40% reduction in food intake and a depression in thyroid activity during the winter. This is consistent with the conclusion that the annual metabolic pattern observed in northern beavers in the field is an inherent attribute. Manipulation of light conditions had no detectable effects on California beavers, but exposure of Arctic beavers to constant darkness resulted in a reduction of food intake to zero after 17 and 22 days, a weight loss and a complete muscular paralysis of unknown nature. No body temperature drop occurred. Exposure to constant incandescent light after 24 days of darkness returned these effects to normal. The thyroid hypothesis was questioned because food intake dropped to zero rather than to a low basal level during the depression. It was hypothesized that the muscular paralysis represents a peripheral control of activity that reduces winter activity to a minimum. Continued exposure of the Arctic beavers to light during the winter resulted in rapid growth and high food intake during that period. It was concluded that in nature decreasing light intensity in the autumn induces a metabolic depression in the northern beaver and increasing light intensity in the spring dispels it. / Science, Faculty of / Zoology, Department of / Graduate

This project was undertaken to obtain more information about the nature of the water-soluble metabolites formed by rat liver since these had been shown to differ from the normal conjugates found in other species and are influenced by the sex of the animal and also by compounds in the soluble fraction of the cell. A comparison was made between these products and those formed from estrogens by mushroom phenolase under similar conditions, and it was found that glutathione had the same effect as the soluble fraction of the cell in increasing the yield of water-soluble metabolites in the rat liver microsomal system. This tripeptide also competed effectively with protein-binding and proposals to account for this reaction have been put forward. A marked increase in the yield of water-soluble estrogen derivatives was also observed when glutathione was added to the phenolase system, and although a different mechanism may be involved, similar types of products were formed. A competitive reaction for protein-binding in the presence of glutathione was again demonstrated. Sulphydryl compounds such as cysteine, ergothionine, homocysteine and thiolhistidine had little or no effect in either of the two systems, and the reaction therefore appears to be specific for glutathione. Oxidized glutathione was ineffective in increasing the yield of water-soluble metabolites indicating that the sulphydryl group was involved, and N-ethylmaleimide was found to be strongly inhibitory. The effect of estrogen oxidation products on the in vitro inactivation of gonadotropins was also investigated. / Medicine, Faculty of / Biochemistry and Molecular Biology, Department of / Graduate

A method is described for the preparation of an everted rectal sac of the desert locust. Water and solute absorption by the rectum was determined by measuring changes in hemocoel fluid and rectal tissue. Initial absorption rates of Na, K, Cl, water and trans-rectal potential are comparable to those in vivo under similar conditions. After an initial transient period (1 hour), transport activity of the in vitro rectum remained in a steady state for at least 4- hours. The relationship between osmotic gradient and steady state rate of net water movement across the rectal wall was determined. Absorption of water is partially inhibited by anoxia, malonate (10־² M), dinitrophenol (10־³M), potassium cyanide (10־³ M) plus iodoacetate (10־³ M) and ouabain (10־³ M). Tissue ions and water are secreted into the hemocoel compartment when the rectal sac is incubated in isosmotic pure sucrose solution. Dependence of water movement on solute transport is indicated by the requirement of lumen ions for prolonged maintenance of water absorption. Effects of different ions (Na, K and Cl) in bathing media on absorption rate of water and ions, absorbate concentrations, trans-epithelial electro-potential differences, and tissue compositions were determined. Observed properties of water and solute movement in vitro are discussed and evaluated in relation to possible mechanisms for active absorption of water. Possible locations of transport sites are suggested in a hypothetical scheme based on the ultrastructure of rectal epithelium. / Science, Faculty of / Zoology, Department of / Graduate

The effects of an increase in body temperature per se on the lactate and pyruvate concentrations of the arterial blood, muscle venous blood, sagittal sinus blood, and cerebrospinal fluid were determined. Paralysed anesthetized dogs with near normal arterial pH and PC0(2) values were ventilated with a 50% 0(2), 50% N(2) mixture and heated to a temperature of 42°C and maintained at this temperature for a period of 2 hours. During hyperthermia a slight increase in lactate and pyruvate was observed in the arterial blood. However, this was not statistically significant. Also a slight increase in the concentration of these substances occurred in the muscle venous blood and sagittal sinus blood. This change, however, was parallel to that observed in the arterial blood. The lactate-pyruvate ratio of the arterial blood, muscle venous blood and sagittal sinus blood did not show any significant change and thus no increase in anaerobic processes was detected during the hyperthermic period. On the other hand the cerebrospinal fluid lactate and pyruvate increased significantly throughout the hyperthermic period but maintained a constant lactate-pyruvate ratio. The results indicate that the increase of lactate and pyruvate in the cerebrospinal fluid are a result of an increased rate of aerobic glycolysis. The fact that the increases observed in the cerebrospinal fluid lactate and pyruvate were not reflected in the cerebral venous blood indicates lactate and pyruvate may have difficulty in diffusing across the blood brain barrier and cerebral venous blood is thus a poor index of cerebral lactate and pyruvate changes. / Medicine, Faculty of / Cellular and Physiological Sciences, Department of / Graduate

Phosphatidylcholine metabolism was investigated in Nb 2 node rat lymphoma, a cell line which is dependant on prolactin for growth in culture. Treatment of stationary cultures with prolactin stimulated the incorporation of [Me-³H] choline into phosphatidylcholine (1.7-fold after 4 h) and its aqueous precursors, mainly phosphocholine (2-fold after 4 h and 3-fold after 10 h). These effects were blocked by cycloheximide. Pulse-chase studies demonstrated that the reaction catalyzed by CTP:phosphocholine cytidylyltransferase (EC 2.7.7.15) was rate-limiting for phosphatidylcholine synthesis in Nb 2 cells. The specific activity of choline kinase (EC 2.7.1.32) increased 1.9-fold after 4 h of prolactin treatment, in correspondence with the increase in choline incorporation mentioned above, and this was also blocked by cycloheximide. The activities of the other enzymes of phosphatidylcholine synthesis were unchanged. These results suggested that phosphatidylcholine biosynthesis was not altered in Nb 2 cells after prolactin treatment. However, phosphatidylcholine levels increased in prolactin treated-cells (1.4-fold after 16 h). Turnover of labeled phosphatidylcholine was reduced 3.4-fold in prolactin treated cells. Calculated turnover rates for phosphatidylcholine averaged 3.2-fold lower in prolactin treated cells whereas the synthetic rates were similar in prolactin treated and stationary cells. Thus, Nb 2 cells utilize a novel mechanism, inhibition of turnover, to regulate the cellular levels of phosphatidylcholine during growth / Medicine, Faculty of / Biochemistry and Molecular Biology, Department of / Graduate

Clobazam (CLBZ) is a 1,5-benzodiazepine with potent anticonvulsant activity. The metabolism of this drug was investigated in the rat and in vitro with the aid of stable isotope-labelled analogues and gas chromatography-mass spectroscopy (GCMS). Pentadeuteriophenyl CLBZ [²H₅]CLBZ was synthesized in essentially quantitative isotopic purity, and characterized by ¹H-NMR and GCMS. Of the five steps involved in the synthesis of [²H₅]CLBZ, the most susceptible to deuterium exchange was the nucleophilic substitution of 2,4-dichloronitrobenzene by aniline-d₇ to form N-(5-chloro-2-nitrophenyl)pentadeuteriophenylamine 18. In this step, the isotopic impurity aniline-2,3,4,5,-d₅ introduced protons from nitrogen into the ortho and para positions of the deuteriophenyl ring of 18. Phenol and catechol metabolites of CLBZ and N-desmethylclobazam (DMC) were synthesized according to the method used for [²H₅]CLBZ using 4-methoxyaniline and 3,4-dimethoxyaniline as starting materials. The methyl ether protecting group was well-suited for the synthetic procedure and was cleanly removed under mild conditions with BBr₃ to afford the phenols and catechols in good yield. The 0-methylated catechols of CLBZ and DMC were enzymatically synthesized from the catechol analogues of CLBZ and DMC using rat liver cytosol as a source of catechol O-methyltransferase (COMT) and S-adenosyl-L-methionine as the methyl donor. A meta/para O-methylation ratio of 2 was obtained from the CLBZ catechol. Condensation of formaldehyde with DMC catalyzed by K₂CO₃ produced a compound whose GCMS (EI) spectral properties were consistent with the carbinolamide, however, this compound could not be isolated because of its marginal stability. A major product for this reaction was 3-hydroxymethyl DMC which was characterized by ¹H-NMR and LCMS. Formaldehyde condensation catalyzed by KOH also afforded 3-hydroxymethyl DMC. Whether formaldehyde addition at the 3-position occurs as a kinetic product or whether it arises as a result of an equilibrium process subsequent to N-hydroxymethylation remains to be resolved. Rats were administered CLBZ:[²H₅]CLBZ as an approximate 50:50 mixture. Isotope shifts detected by GCMS allowed the following CLBZ metabolites to be identified. In bile, decreasing levels of 4'-hydroxy CLBZ, 4'-hydroxy DMC, O-methylated CLBZ catechols, 4'-hydroxy-3'-methoxy DMC and 3',4'-dihydroxy CLBZ appeared as both glucuronide and sulfate conjugates. In urine decreasing levels of the following sulfate conjugates were observed: 4'-hydroxy-3'-methoxy CLBZ, 4'-hydroxy CLBZ, 4'-hydroxy DMC and 3',4'-dihydroxy CLBZ. In bile, the glucuronides were predominant over the sulfates, whereas in urine only sulfate conjugates were detected. There was no detectable evidence of unconjugated CLBZ metabolites in bile or urine. As the biliary glucuronide and urinary sulfate, 3'-hydroxy-4'-methoxy CLBZ constituted ≤2 % of the O-methylated CLBZ catechols, whereas in bile, the sulfate conjugate of this metabolite constituted 30 %. One possible explanation for the higher levels of this metabolite as a biliary sulfate could be the low regiospecific methylation of dihydroxy CLBZ by COMT combined with arylsulfatase activity present in the kidney. Neither the CLBZ carbinolamide nor the N-hydroxy DMC (hydroxamic acid) was present in detectable levels in the conjugated or unconjugated fractions of bile or urine. Isotope effects in the metabolism of CLBZ and DMC in the rat were marginal for phenyl ring oxidation as measured for phenol metabolites (kH/kD =1.103 ± .090) and for catechols (kH/kD. = 1.088 ± .207). The metabolism of CLBZ and DMC in vitro was examined using control and phenobarbital-induced rat liver microsomes. CLBZ metabolism resulted in N-demethylation to DMC and phenyl ring hydroxylation at the 4'-position. There was no detectable evidence for the carbinolamide intermediate. Induction appeared to increase N-demethylation compared to phenyl ring hydroxylation. DMC was metabolized to 4'-hydroxy DMC with no detectable production of the hydroxamic acid. The isotope effect associated with CLBZ N-demethylation was determined by incubating an approximate 50:50 mixture of pentadeuteriophenyl CLBZ:trideuteriomethyl CLBZ with control and phenobarbital-induced rat liver microsomes. In this way, the source of DMC derived from demethylation ([²H₅]DMC) and dedeuteriomethylation (DMC) could be determined. The values of kH/kD, determined by protio/deuterio product ratios, were calculated at 3.65 ± 0.27 (n = 3) and 2.80 ± 0.16 (n = 4) for control and induced microsomes respectively. / Pharmaceutical Sciences, Faculty of / Graduate

Catherine Foy Walters / Typescript / M.S. Florida State College for Women 1934 / Includes bibliographical references

Includes bibliographical references (leaves 45-52). / The aim of this study is to test the hypothesis that, for similar durations of diagnosed diatetes (DM); black South Africans have less atherosclerosis as measured by Carotid Intima Media Thickness (CIMT) than non-black South Africans.

In contrast to the vast amount of active research and available knowledge on many aspects of protein-calorie malnutrition, surprisingly little attention has been focused on the skeletal effects of this syndrome. As early as the 1920's it was realised that the skeletal metabolism in protein-calorie malnutrition was deranged. Notwithstanding this, there is still to date inadequate understanding of the mechanisms by which these skeletal changes are brought about. This is partly due to the fact that the research workers were "victims of their times" in that the techniques utilised gave limited information and it has only been in the past decade or two that more sophisticated techniques have become available. (Evidence for this will be borne out in the following chapter where the literature is reviewed). It was with this in mind that the work presented in this thesis was undertaken. Part I of the thesis consists of a review of the literature, followed by a dissertation on the normal physiological concepts of calcium metabolism as well as a description of the calcium pools used in kinetic models. Part II includes all the chapters on the various experiments performed. Included in each chapter are the methods used, results obtained as well as a discourse relevant to that particular study, with special reference to similar experiments performed by other authors. Part III encompasses the integrated summary of the results and a discussion theorising the mechanisms involved in those changes. Finally, an appendix which deals with the statistical methods used for analyses, as well as details of those techniques which were used, but were established by other authors.