Identification of the APUD endocrine cells of rat fundic mucosa by means of combined amine fluorescence and electron microscopy.

Rat fundic mucosa contains numerous APUD endocrine cells that can take up 5-hydroxytryptophan (5-HTP) and decarboxylate it to 5-hydroxytryptamine (serotonin), detectable by its formaldehyde-induced yellow fluorescence. To identify these cells by electron microscopy, pieces of rat gastric mucosa were incubated with DL-5-HTP. Some specimens were fixed in 4% formaldehyde-0.5% glutaraldehyde, while others were frozen, freeze-dried, and exposed to paraformaldehyde vapors. Thick sections of the Epon-embedded specimens were examined and photographed by fluorescence microscopy, and fluorescing and nonfluorescing cells were identified by electron microscopy in serial thin sections. Control specimens, not incubated with 5-HTP, revealed fluorescence of only the mast cells and EC cells, which were abundant in the pylorus, but rare in fundic mucosa. Specimens incubated with 5-HTP also exhibited numerous yellow fluorescent endocrine cells in fundic mucosa, which cells were found to be the ECL cells; the A-like cells did not fluoresce. In pyloric mucosa, many G and D (D1) cells also exhibited weak or moderate fluorescence after 5-HTP incubation. Thus, this study supports the contention of previous radioautographic studies that the ECL, but not the A-like, cells are the APUD endocrine cells of rat fundic mucosa, that G and D cells also possess some APUD activity, and that EC cells represent the enterochromaffin cells, which normally synthesize and store demonstrable quantities of serotonin.

Catecholamine fluorescence and tissue culture morphology. Technics in the diagnosis of neuroblastoma.

Neuroblastoma is often confused histologically with other small round cell tumors such as Ewing's sarcoma, acute lymphocytic leukemia, lymphoma, and oat cell carcinoma, particularly at metastatic sites. Studies were performed to evaluate glyoxylic acid-induced catecholamine fluorescence as a rapid method for identifying neuroblastoma cells in biopsy specimens. The morphology of tumor explants in tissue culture was also evaluated for use as a diagnostic aid. Eighteen neuroblastomas were stained for catecholamines; 78% showed specific catecholamine fluorescence. Two ganglioneurons and a pheochromocytoma also showed positive catecholamine fluorescence. All 20 neuroblastomas placed in tissue culture demonstrated neurite outgrowth, a property that distinguishes neuroblastoma from other small round cell neoplasms. Seventeen nonneuroblastoma tumors displayed neither specific fluorescence nor neurite outgrowth. The ability of these two technics to identify neuroblastoma was compared with routine histology, urinary vanillylmandelic acid (VMA) spot tests, quantitative urinary VMA and catecholamine assays, and electron microscopy. Only electron microscopy was as sensitive as fluorescence and morphology in culture. The fluorescence method is rapid and simple and provides a valuable tumor marker when positive. Neurite outgrowth in cell culture and electron microscopy, although more time-consuming, were the most sensitive of all the diagnostic methods evaluated.