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R J Parmer

Publications and source records attributed to R J Parmer.

75 records · Page 5Linked to original sources
PubMed1986

A cloned chromogranin A (CgA) cDNA detects a 2.3Kb mRNA in diverse neuroendocrine tissues.

CgA is a 72Kd protein of unknown function that is present in many neuroendocrine tissues and co-secreted with their resident hormones. We prepared a cDNA library to the mRNA from CgA-producing human medullary thyroid carcinoma (MTC) cells in the expression vector lambda gt11. The library was screened with a panel of one polyclonal and two monoclonal antibodies to CgA. The specificity of the antibodies for CgA was demonstrated by immunoassay, immunohistology, and immunoprecipitation of the in vitro translation products of mRNA from CgA-producing tissues. A chromogenic second antibody identified five immunoreactive clones. Their cDNA inserts were isolated after EcoRI digestion and agarose gel electrophoresis. These cDNAs were 32P-labelled and used as probes in Northern hybridization studies. An mRNA of approximately 2.3Kb was detected with the cDNA probes in human cell lines from MTC and lung cancers that were shown to produce CgA and in human pheochromocytoma and bovine adrenal medulla tissue. To confirm its identity, one of the putative CgA cDNAs was subcloned into a plasmid and was used to hybridization-arrest the in vitro translation of CgA mRNA. These studies demonstrate the cloning of cDNAs which hybridize with CgA mRNA from diverse neuroendocrine tissues.

Adrenal Medulla↗
PubMed1985

Enkephalins in pheochromocytoma: studies in a rat model.

Enkephalins, endogenous opioid pentapeptides which are found in high concentration in normal chromaffin tissue, may play a role in blood pressure regulation. We therefore examined the presence and actions of enkephalins in pheochromocytoma in a rat model. Transplantable norepinephrine-rich tumors, which gave rise to significant blood pressure elevations, contained measurable immunoreactive enkephalins as determined by specific radioimmunoassays for leucine-enkephalin and methionine-enkephalin. Enkephalin immunoreactivity paralleled the enkephalin assay standard curves and was not abolished by boiling or by protease inhibitors (EDTA, PMSF). Authenticity of the immunoreactive enkephalins was confirmed by reverse-phase high pressure liquid chromatography. The amount of enkephalin immunoreactivity present initially in these tumors was greatly augmented by the prohormone activators trypsin or trypsin plus carboxypeptidase B, suggesting that most of the immunoreactive enkephalin was present in higher molecular weight precursor form. Enkephalin determinations on human pheochromocytoma and catecholamine measurements in both rat and human pheochromocytoma, demonstrated certain similarities and differences in enkephalin and catecholamine content between rat and human tumors. Total tumor enkephalins correlated (r = 0.91, p less than 0.05) with total tumor catecholamines in rat pheochromocytoma, suggesting co-regulation of synthesis of these 2 chromaffin tissue substances. Physiologic studies, in which intravenous leucine-enkephalin and the opioid antagonist nalaxone were administered to pheochromocytoma-implanted rats and sham-operated controls, failed to uncover an opioid peptide influence upon blood pressure in this animal model of pheochromocytoma.

Adrenal Gland Neoplasms↗