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Respiratory deficient cell lines are being increasingly used to elucidate the role of mitochondria and to understand the pathophysiology of mitochondrial genetic disease. We have investigated the oxygen consumption rates and oxygen concentration in wild-type (WT) and mitochondrial DNA (mtDNA) depleted (rho(0)) Molt-4 cells. Wild-type Molt-4 cells have moderate oxygen consumption rates, which were significantly reduced in the rho(0) cells. PCMB (p-chloromercurobenzoate) inhibited the oxygen consumption rates in both WT and rho(0) cells, whereas potassium cyanide decreased the oxygen consumption rates only in WT Molt-4 cells. Menadione sodium bisulfite (MSB) increased the oxygen consumption rates in both cell lines, whereas CCCP (carbonyl cyanide m-chlorophenylhydrazone) stimulated the oxygen consumption rates only in WT Molt-4 cells. Superoxide radical adducts were observed in both WT and rho(0) cells when stimulated with MSB. The formation of this adduct was inhibited by PCMB but not by potassium cyanide. These results suggest that the reactive oxygen species (ROS) induced by MSB were at least in part produced via a mitochondrial independent pathway. An oxygen gradient between the extra- and intracellular compartments was observed in WT Molt-4 cells, which further increased when cells were stimulated by CCCP and MSB. The results are consistent with our earlier findings suggesting that such oxygen gradients may be a general phenomenon found in most or all cell systems under appropriate conditions.

We report a case of a functional adenoma with excess black pigment deposition and myelolipoma in the same adrenal gland in a 58-year-old woman. The patient presented with gastrointestinal bleeding, and after being diagnosed with colonic diverticulosis, underwent a total colectomy. An abdominal computerized tomographic (CT) scan during her work-up showed a right adrenal mass consistent with myelolipoma. Postoperatively, the patient was diagnosed with Cushing's syndrome and underwent a right adrenalectomy. The adrenalectomy specimen consisted of a dark brown and golden-yellow adrenal adenoma, myelolipoma, and atrophic adrenal gland. Immunostains indicated that the dark brown adenoma component was responsible for the patient's hypercortisolism. Co-occurrence of a functional black adenoma and a well-developed myelolipoma has not been reported in the literature. We describe the significant findings of this case, together with a review of the literature.