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Fragments of Necturus maculosus liver, spleen and kidney were cultured at 25°C in 50% Minimal Essential Medium (MEM) or 50% Leibovitz L-15 Medium (L-15) for up to 49 days. The integrity of tissue structure was evaluated, hepatocyte cell and nuclear volumes were measured, the respiration rates of freshly-isolated and cultured liver fragments were determined, and the mitotic incidences in cultured liver, spleen and kidney were estimated. The addition of adrenalin caused a reduction in the glycogen content of liver cultures, and the subsequent addition of insulin resulted in a net increase in glycogen synthesis. Glycogen levels fell in fragments cultured in L-15, but rose in cultures in MEM. Arginase and ornithine transcarbamylase levels fell gradually throughout a 49-day culture period in L-15. Evidence presented supports the position that the survival of tissues in vitro is related to cell size and respiration rate. These experiments show that N. maculosus is a suitable donor of tissues for long-term organ culture studies on the maintenance and control of tissue-type specific structure and function., (Copyright © 1975 Wiley-Liss, Inc.)

Anuran amphibian metamorphosis is an immunologically interesting period. For the investigator, it provides an unusual opportunity for analyzing both humoral regulation of the immune response and the development and maintenance of self-tolerance. Some of the questions one can ask are: Why don't immunocompetent larvae destroy antigenically disparate adult cells as they differentiate within them during metamorphosis? Do the dramatic hormonal changes occurring during this period regulate immunological function? How do animals in metamorphosis protect themselves from their immunologically hostile environment?