| pheo- | 1. Prefix denoting the same substituents on a phorbin or phorbide (porphyrin) residue as are present in chlorophyll, excluding any ester residues and Mg. 2. Combining form meaning gray, dark-coloured. Origin: G. Phaios, dusky (05 Mar 2000) |
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| pheochrome | Synonym: chromaffin. 2. Staining darkly with chromic salts. Origin: G. Phaios, dusky, + chroma, colour (05 Mar 2000) |
| pheochrome cell | Former term for enteroendocrine cell. Synonym: pheochromocyte. (05 Mar 2000) |
| pheochromoblast | A primitive chromaffin cell which, with sympathetoblasts, enters into the formation of the adrenal gland. Origin: G. Phaios, dusky, + chroma, colour, + blastos, germ (05 Mar 2000) |
| pheochromoblastoma | <tumour> Obsolete term for pheochromocytoma. (05 Mar 2000) |
| pheochromocyte | A chromaffin cell of a sympathetic paraganglion, medulla of an adrenal gland, or of a pheochromocytoma. Synonym: pheochrome cell. Origin: pheochrome + G. Kytos, cell (05 Mar 2000) |
| pheochromocytoma | <oncology, tumour> A tumour of the adrenal gland which produces catecholamines (noradrenaline and adrenaline). Although the tumour is usually benign it produces hypertension, pounding headaches, tachycardia, palpitations, apprehension, facial flushing, nausea and vomiting. A diagnosis can be made using a urine test which measures the quantity of adrenaline byproducts. Adrenal tumours may be detected by CT, MRI or a nuclear scan of the adrenal glands. (15 Oct 1997) |
| pheomelanin | A type of melanin found in red hair; it contains sulfur and is alkali-soluble; elevated levels are found in the rufous type of oculocutaneous albinism. Compare: eumelanin. Origin: G. Phaios, dusky, + melos (melan-), black (05 Mar 2000) |
| pheomelanogenesis | The formation of pheomelanin by living cells. (05 Mar 2000) |
| pheomelanosome | A spherical melanosome of pheomelanin in red hair. (05 Mar 2000) |
| pheophytins | Chlorophylls from which the magnesium has been removed by treatment with weak acid. (12 Dec 1998) |