The cytochrome oxidase content of rat tissues was investigated, utilizing the accumulation of the free radical formed by the emzymatic, univalent oxidation of a stable, non-toxic substrate, N-phenyl- p-phenylenediamine ( p-aminodiphenylamine). This procedure eliminated the non-enzymatic coupling of the radical with α-naphthol, found in the classic Nadi reaction. Using homogenates, the following decreasing order of enzyme activity was found: heart, kidney, diaphragm, liver, rectus abdominis. A more sensitive assay was also developed, involving the reduction of cytochrome c by ascorbic acid, and using 2-( p-iodophenyl)-3-( p-nitrophenyl)-5-phenyl tetrazolium chloride to analyze unoxidized ascorbic acid. The same order of tissue activity was demonstrated. The cytochrome oxidase content of a tissue may be a reflection of its physiological role.
In the classic scimitar syndrome, a pulmonary vein draining all or part of the right lung enters the inferior vena cava. A variant is described with the same roentgenographic appearance, but with drainage of the anomalous pulmonary vein into both the inferior vena cava and the left atrium; the atrial septum was intact. This case, together with six others reported elsewhere, reminds us that the scimitar sign has both false positives and false negatives. Therefore, the diagnosis of scimitar syndrome cannot be made with certainty from a plain x-ray film.
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