The etiology of clinical depression is unknown, but thought to be related to an impairment in brain transmission of monoamines. Depression is treated with antidepressant drugs which, regardless of classification, ultimately result in increased efficacy of aminergic transmission. Tricyclic antidepressants are known to inhibit the presynaptic uptake of amines. [3H]Imipramine, the prototype tricyclic antidepressant and a potential biological marker in depression, binds to both high- and a low-affinity sites in the brain. The high-affinity binding of [3H]imipramine to its binding site on the serotonin (5-HT) neuronal transporter has been shown to be a sodium-dependent process. However, that of [3H]paroxetine, a novel and selective 5-HT uptake inhibitor, has not yet been investigated. Because of a discrepancy between the onset of uptake-blocking effect and alleviation of depressive symptoms, the blockage of uptake is probably not the only pharmacological action of antidepressants underlying their clinical effect. Recent studies have reported decreases in beta-adrenoceptor and 5-HT2 receptor numbers following long-term treatment with antidepressants, and suggested that an adaptive change in amine receptors may be more relevent for the clinical effect. However, not all 5-HT uptake inhibitors elicit this downregulation. Recent research has thus centred on elucidating changes in the signal transduction apparatus of aminergic neurons. The 5-HT2 receptor in the brain is coupled to the phosphoinositide turnover cascade and protein kinase C (PKC) activity. The subcellular distribution of PKC following chronic antidepressant treatment has not yet been investigated. This study was undertaken (1) To compare the sodium dependence of [3H]paroxetine binding and [3H]5-HT uptake in rat diencephalon in order to confirm whether paroxetine binds to the 5-HT recognition site on the transporter, and (2) to investigate the effects of both acute and chronic antidepressant treatment on PKC location and activity (both basal and 5-HT2 receptor agonist (DOI)-challenged) in rat cortex and hippocampus. Results indicate that, antidepressant drugs induce differing but significant effects on PKC activity in the subcellular fractions of neurons both after acute and chronic treatment. These changes in PKC activity may alter transduction of cellular signals evoked by the binding of 5-HT to receptors. (Abstract shortened by UMI.)

Abstract not available.

This thesis examines the pharmacological basis for the traditional phytomedicinal uses of Zanthoxylum americanum Mill. (Rutaceae). The antifungal activity of six crude extracts was evaluated against 11 clinically relevant pathogenic fungi including Candida albicans and Cryptococcus neoformans. All extracts demonstrated light-activated antimicrobial action and broad spectrum of activities against at least eight fungal species. A positive correlation was observed between total furanocoumarin content and antifungal activity (r2 = 0.88, P < 0.001). Antiviral activity towards Herpes simplex virus type-1 was linked to various phytochemical constituents, including three isolated pyranocoumarins suitable for authentication and standardization of commercial raw materials. Anti-HSV activity was significantly enhanced with light treatment (L), for phytochemical fractions rich in polyphenols (+L, MIC = 9.4; -L, MIC > 500) or pyranocoumarins (+L, MIC = 31; -L, MIC > 500), but not in the case of furanocoumarins (+L, MIC = 62; -L, MIC = 94). Phytochemical profiles and average content for phenolic acids and flavonoids contributing to antiviral activity of Z. americanum were reported here for the first time.

The present studies tested the hypothesis that 17beta-estradiol (E2) downregulates ACE and AT1R in several tissues important to cardiovascular regulation, including the brain and heart, and that this downregulation attenuates the progression of LV dysfunction following myocardial infarction (MI). In Experiment 1, female Wistar rats were randomized into one of four groups: (1) sham-ovariectomized (OVX); (2) OVX+vehicle (veh); (3) OVX+E2 replacement at physiological levels and (4) OVX+high E2. Five weeks following OVX, ACE and ATIR were increased 15-90% in the heart, several cardiovascular nuclei of the brain, kidney, abdominal aorta, adrenal and lung. These increases were prevented in all cases by E2 replacement at physiological levels and in most cases reversed to decreases by high E2. In Experiment 2, age-matched female Wistar rats underwent 1 of 3 treatments: no surgery (ovary-intact), OVX+veh treatment for two weeks, or OVX+high E2 treatment for two weeks. (Abstract shortened by UMI.)

The mammalian D1-like dopaminergic receptors are composed of two subtypes, D1R (or D1A) and D5R (or D1B), which belong to the large family of heptahelical G protein-coupled receptors (GPCRs). D1R and D5R receptors have been characterized pharmacologically via their ability to couple to Galphas and activate AC. Against the high overall amino acid sequence homology of the two D1-like dopaminergic receptors, the divergent primary structure of the extracellular loops, as well as discrete residues within the exofacial end of the transmembrane (TM) regions provide new targets for the assessment of structure-activity relationships represented by D1R and D5R. While residues within the second extracellular loop (EL2) of a number of GPCRs have been the subject of site-directed mutagenesis, a broader understanding of the structure-activity role of EL2 as a whole has yet to be formed. In the present study, chimeric proteins have been engineered to swap the EL2 of D1R and D5R receptors, both with and without the exchange of the divergent amino acid in the exofacial end of TM4. (Abstract shortened by UMI.)

Resistance to traditional modes of cancer therapy is a major obstacle facing cancer patients. The untreated HCT116 cell line was subcloned and each clone was assessed for its response to several drugs and X-radiation. One clone HCT116-K was resistant to cisplatin/etoposide/topotecan but sensitive to XR while another HCT116-2 was sensitive to cisplatin but resistant to XR. HCT116-10, a clone that responded to drugs and radiation in a manner similar to parental HCT116 cells was used as a control clone. Comparing gene expression between HCT116-K, or HCT116-2, vs. HCT116-10, we were able to identify several genes whose expressions were altered in clones that were resistant/sensitive to various insults. Each identified gene's expression was then examined in a panel of HCT116 clones to determine whether the expression observed in the resistant/sensitive clone was outside the normal expression distribution within the population. One gene APM2 was significantly upregulated in HCT116-K. Upon follow-up, APM2, was found to promote cisplatin resistance when overexpressed in sensitive HCT116 clones. Furthermore, silencing APM2, using sequence specific siRNAs, in a panel of cell lines encompassing all combinations of p53 status and MMR proficiency (HCT116-K, HCT116, SW620, MCF7, PC-3, and OV2008) resulted in sensitization regardless of these two factors. In addition, silencing APM2 stably, using shRNAs, also resulted in the sensitization of cells to cisplatin. More importantly, cisplatin inhibited the growth of APM2 silenced tumour xenografts (HCT116-K or OV2008 cells) significantly better than it inhibited the growth of xenografts carrying non-targeting control shRNAs. Additionally, APM2 was found to be localized to the cytoplasm and membrane. Further investigation revealed that HCT1 16 cells secrete APM2 to the extracellular space representing a possible mechanism by which APM2 promotes cellular resistance to cisplatin, by binding to and carrying cisplatin out of the cell. These findings represent a novel strategy that could be exploited to overcome cisplatin resistance in patients regardless of p53 status or ability to perform MMR.

Melatonin, or N-acetyl-5-methoxytryptamine, is an interesting neurohormone that governs the body's circadian rhythm, and is synthesized predominantly in the retina and the pineal gland, a small pea-sized gland in the centre of the brain. Since melatonin is found in low concentrations in almost all tissue, many have speculated that its biological function may include detoxification protection, but little is actually known. In the United States and other countries, such speculation has lead to a growing interest and popularity in melatonin as an over-the-counter nutritional supplement, but the lack of research and clinical trials has led to a federal ban on the sale of this neurohormone in Canada. In this thesis, our research was to investigate some molecular properties of melatonin to further the knowledge of this popular and controversial indoleamine. Examination of the photophysical and photochemical properties of melatonin have shed some light on its role in the retina, while oxygen uptake experiments have exposed some of the misconceptions regarding its antioxidant activity. (Abstract shortened by UMI.)

The present work summarizes the results of a study done by Dr Claude Bernard on the effect of the natural lignan, dillapiol, on multidrug resistance phenotypes. In a tissue culture system, dillapiol was selectively toxic to hamster drug-resistant B30 cells; this same compound was substantially less toxic to the drug-sensitive AUXB1 cell line. The so-called collateral sensitivity of drug-resistant tumor cells to an otherwise benign lignan compound makes dillapiol an ideal candidate for an adjuvant in chemotherapy. Examination of the toxicity of dillapiol revealed no negative effects with respect to weight changes or behavior of the rats, no deaths, and no abnormalities of the brain, liver, heart, kidney and lungs. Moreover, a drug-fate study using $\sp $C-radiolabeled dillapiol showed that the lignan is available to the liver, kidney and gut and is excreted almost entirely via the urine. A novel synthesis of dillapiol which allows the incorporation of $\sp $C radioactivity in the final product is also discussed. The preparation of several dillapiol derivatives from either the intermediates of the dillapiol synthesis or from the modification of dillapiol itself is presented. (Abstract shortened by UMI.)

The phosphorylation of proteins on tyrosine residues by tyrosine kinases has been suggested to contribute to signalling processes that lead to smooth muscle contraction. The aim of the current study was to further determine the role of tyrosine kinase in the contraction of rat vascular smooth muscle. The specific objectives included (i) studying the effect of tyrosine kinase inhibitors on vascular contraction induced by noradrenaline (NA), potassium chloride (KCl) and neuropeptide V (NPY); (ii) studying the effect of sodium orthovanadate on contraction; (iii) studying the role of endothelium dependence in contraction; as well as (iv) studying the role of L-type Ca$\sp{2+}$ channels in the tyrosine kinase-related response. The effects of NPY, nifedipine, sodium orthovanadate and various tyrosine kinase inhibitors were tested in intact ring segments of rat mesenteric and tail arteries. The present studies illustrate that tyrosine kinase plays an important role in signal transduction stimulated by agonists in vascular smooth muscle. (Abstract shortened by UMI.)

No description available.