Thesis (doctoral)--University of Uppsala, 1982. / Includes bibliographical references (p. 31-39).

No description available.

No description available.

Chromaffin cells are a modified post-ganglionic sympathetic neuron, which synthesise and secrete catecholamines. The neoplastic transformation of chromaffin cells is demonstrated by the tumour phaeochromocytoma, a functional tumour that recapitulates the normal role of chromaffin cells by synthesising, storing and releasing excess catecholamines. Within this thesis we have explored several aspects of chromaffin cell and phaeochromocytoma tumour biology, including the specific expression of key sympathoadrenal markers such as the noradrenaline transporter (NAT), neuropeptide Y (NPY) and chromogranin A (CGA) in normal human and mouse chromaffin cells versus phaeochromocytomas of human and mouse origin. Catecholamine-mediated signalling in chromaffin cells is terminated by the sequestration of extracellular catecholamines back into the cell via the noradrenaline transporter (NAT). Following observations that within the rat adrenal medulla, NAT is expressed in PNMT-positive chromaffin cells we explored whether this pattern of expression is also present in the human adrenal medulla. While we successfully established that NAT and PNMT are co localised, we also found that all human adrenal chromaffin cells are PNMT-positive. In the rat, NAT is also observed within the cytoplasm and has been suggested to be associated with secretory vesicles, thus using the secretory vesicle marker, CGA, we demonstrate that NAT is associated with secretory vesicles. However, in contrast to our findings within the normal chromaffin cells, in situ NAT expression in human phaeochromocytoma tumour samples was distorted, with observed changes including the level and type of staining observed, and disruptions to the strict NAT-CGA association observed in the normal adrenal. Continuing our theme of NAT, we investigated if pre treating the phaeochromocytoma PC12 cell line with the chemotherapy drug cisplatin had an effect on the expression of NAT, to give an indication of the efficacy of this compound in the treatment of metastatic phaeochromocytoma with radiolabelled 131Iodometabenzylguanidine (131I-MIBG), a noradrenaline analogue which can be incorporated into phaeochromocytoma tumour cells though uptake through NAT. The premise of this study is derived from previous work in which neuroblastoma cells pre-treated with cisplatin were more responsive to (131I-MIBG) accumulation due to increased activity and expression of the transporter. Thus we treated PC12 cells for 24-hours in a range of cisplatin concentrations and measured the effect on NAT expression. However, unlike the findings in neuroblastoma cells, in our study, we did not observe an effect of cisplatin pretreatment on NAT activity or expression in PC12 cells. Upto 30% of phaeochromocytoma arise as apart of a hereditary syndrome. The von Hippel-Lindau (VHL) syndrome, due to germline mutations to the VHL gene, and Multiple Endocrine Neoplasia type 2 (MEN 2), due to germline mutations to the RET gene represent two examples of hereditable endocrine disorders where phaeochromocytoma is a presenting feature. Notable differences in clinical presentation and tumour biology have been identified in phaeochromocytomas from patients with VHL and MEN 2. These differences prompted us to explore whether these observations extend to the chromaffin granule constituents, NPY and CGA. Patients with MEN 2 disease have a greater incidence of hypertension than patients with VHL disease, MEN 2 are characterised by an adrenergic phenotype (produce predominantly-adrenaline), whereas VHL phaeochromocytomas are noradrenergic (produce predominantly-noradrenaline). Neuropeptide Y, which has powerful vasoactive properties capable of significantly elevating blood pressure, is stored and released with catecholamines and is thought to be associated with PNMT-positive chromaffin cells. Thus, we questioned whether the differences in the symptomatology between VHL and MEN 2 patients may be related to differences in NPY expression between the two groups, and whether any differences in NPY relate to adrenaline and/or PNMT content, or are linked to hereditary factors. Thus we compared tumour samples from four cohorts of patients: (i) adrenergic versus noradrenergic phenotype, (ii) hereditary versus no hereditary syndrome. Results demonstrated that although tumour NPY levels (mRNA and peptide) correlate with PNMT expression and/or adrenaline content, when NPY expression was compared between groups of patients (adrenergic vs noradrenergic; hereditary versus nonhereditary) difference in NPY levels were only significant between VHL and MEN 2 tumour and not between sporadic adrenergic and noradrenergic Immunohistochemistry also supported the above observations. Hence, we concluded that NPY expression in all groups of phaeochromocytoma examined in this study, this effect is not related to tumour biochemical phenotype but rather appears to be a specific unique trait of VHL phaeochromocytomas. Continuing our theme of the possible differential expression of chromaffin granule constituents between VHL and MEN 2 patients, we also investigated CGA levels in plasma and tumour samples. Given, VHL tumours possess less chromaffin granules than MEN 2 tumours, and CGA has been implicated as a key director of secretory vesicle biogenesis we investigated whether CGA was differentially expressed between VHL and MEN 2 tumours. We found CGA expression was significantly greater in MEN 2 tumours (mRNA; 3-fold, and protein; 20-fold), with western blot confirming this trend. We also found that plasma CGA was greater in MEN 2 patients but not significantly, consequently, we explored the co-variables tumour size and tumour secretory activity (measured by plasma catecholamine concentrations), which influence plasma CGA and found that tumour size and plasma CGA are related but there was no influence of genotype on this relationship. In contrast, plasma CGA was significantly related to tumour secretory activity and the effect of genotype on this relationship narrowly missed significance, but when we expressed plasma CGA as a ratio of plasma catecholamines, plasma CGA was 2-fold greater in MEN 2 patients than VHL patients. Thus despite the tendency of phaeochromocytomas from VHL disease to readily and continuously release their catecholamine stores, plasma CGA levels still appeared to be higher in MEN 2 patients. Finally, we examined whether the expression of NPY, Leu- enkephalin (Leu-Enk), NAT and the vesicular monoamine transporters type 1 and 2 (VMAT1 and VMAT2,), in normal mouse adrenal glands, and in histologically-confirmed adrenal phaeochromocytomas generated by injected nude mice with a phaeochromocytoma (MPC) cells line. The results of this study established that similar to the rat and human NAT expression is preferentially localised with PNMT within mouse chromaffin cells, while VMAT1 and NPY are found in both PNMT-negative and PNMT-positive cell populations, although expression of NPY was reduced in PNMT-negative cells. In contrast, both VMAT2 and Leu-Enk were found in PNMT-negative noradrenergic cells, and VMAT2 was present in all noradrenergic chromaffin cells while Leu-Enk was observed in a subpopulation of noradrenergic chromaffin cells. In contrast to the normal adrenal but similar to our findings in human phaeochromocytoma, the pattern of marker expression within adrenal phaeochromocytoma lesions of MPC-injected mice are severely disrupted related to both the level of expression of the respective markers, and association with PNMT within the tissue. Thus, the experimentally generated phaeochromocytoma mouse model provides a valuable tool in studying human phaeochromocytoma. The data presented in this thesis further validate the heterogeneity observed in many aspects of phaeochromocytoma tumour biology, including the expression several chromaffin cell markers such as NAT, NPY and CGA. The altered expression of these markers may contribute to the clinical picture of these tumours, particularly relating to hereditary phaeochromocytoma from VHL and MEN 2 disease.

Thesis (M.S.)--University of Nevada, Reno, 2005. / "May, 2005." Includes bibliographical references. Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2005]. 1 microfilm reel ; 35 mm. Online version available on the World Wide Web.

Thesis (M.S.)--Ohio State University, 2008. / Title from first page of PDF file. Non-Latin script record Includes bibliographical references (p. 27-32).

No description available.

This thesis describes metabolic changes occurring in chromaffin cells when secreting catecholamine (principally adrenaline), and the factors involved in maintaining the rate of secretion. In perfused pig adrenal glands, <sup>31</sup/>p nuclear magnetic resonance showed that nucleotide stored with catecholamine in the secretory vesicles (chromaffin granules) of the chromaffin cell was distinguishable from cytoplasmic nucleotide. Intragranular pH was 5.52 ± 0.15 (± SD, n=8) in ischaemic glands and rose (+ 0.22 ± 0.16 (± SD, n=6)) on recovery of cytoplasmic ATP during perfusion. This suggests that catecholamine accumulation by the granules is not driven by an ATP-generated pH gradient in intact tissue, as cytoplasmic ATP did not reduce intragranular pH. Perfused cortex-free ox adrenal medulla consumed 0.51 ± 0.19 (± SD, n=8) μmole 0₂/min/g wet weight after 210-230 minutes of perfusion, and this rose 30% during 4 minute O.lmM acetylcholine stimulations. This enhancement correlated with secretion but depended on the mode of stimulation, indicating that ATP consumption in secretion itself was an inadequate explanation. The proton-translocating Mg-ATPase of the chromaffin granule may hydrolyse ATP at its uncoupled rate on entering the plasma membrane during secretion by exocytosis. 1.4 ± 0.9 (± SD, n=12) moles of catecholamine were secreted per mole of enhanced oxygen consumption over 16 minutes. From this ratio, the oxygen consumption enhancement is shown to be much larger than that predicted from uncoupled proton pumping. Ouabain-sensitive oxygen consumption rose from < 6% to 18 ± 8% (± SD, n=4) during prolonged acetylcholine stimulation in the absence of calcium, suggesting that Na,K-ATPase was not responsible for all of the oxygen consumption enhancement. On continuous stimulation, secretion showed a biphasic decline in both pig and ox. A decline was also observed on intermittent stimulation. Cell death, potential-sensitive calcium gating and acetylcholine receptor desensitisation were only minor contributors. Little recovery occurred on resting the tissue for 2-3 hours between stimulations. The results are explained in terms of depletion of a pool of chromaffin granules adjacent to the plasma membrane.

Sphingomyelin (SM), a sphingolipid that is concentrated in the extracellular leaflet of the plasma membrane, can interact with cholesterol to form more ordered raft domains. The hydrolysis of SM by sphingomyelinase (SMase) generates ceramide and may redistribute cholesterol molecules to other less ordered domains. I employed carbon fibre amperometry to examine whether SM hydrolysis affected the kinetics of release of catecholamines from individual granules of rat chromaffin cells when exocytosis was triggered by elevated extracellular [K+]. Similar to cholesterol overload, SMase treatment selectively increased the proportion of stand-alone foot signals and the duration of the pre-spike foot signals; both effects could be reduced by extraction of cellular cholesterol. In contrast, the application of an exogenous ceramide did not mimic the effects of SMase. My results suggest that SMase treatment liberated cholesterol from lipid rafts to increase the persistence of the semi-stable fusion pore before the onset of rapid dilation.

Thesis (M.S.)--University of Nevada, Reno, 2006. / "December, 2006." Includes bibliographical references. Online version available on the World Wide Web.