IMPROVED CONDITIONS FOR CULTURE OF BIOSYNTHETICALLY ACTIVE COCKROACH CORPORA ALLATA

Currently, short-term culture of insect corpora allata is most often p erformed in TC199. We now show that L-15B, a medium widely used in art hropod tissue culture, is superior to TC199 for both short and long-te rm culture of cockroach corpora allata. In 3-h and 48-h incubations, j uvenile hormone biosynthesis by corpora allata from Diploptera punctat a was significantly higher in L-15B than in TC199. In addition, in bot h media, corpora allata activity was significantly improved by flotati on of glands at the medium surface. Characteristics of L-15B responsib le for its superiority were examined by comparison of gland activities in several TC199 formulations that had been modified in different way s to be more similar to L-15B. Adjusting the osmotic pressure of TC199 (288 mOsm/l) to near that of L-15B (362 mOsm/l) and D. punctata hemol ymph (360 mOsm/l) significantly improved gland activity during the sec ond 12 h of a 36-h incubation. Increasing the concentrations of amino acids, sugars, and organic acids in TC199 to the same levels as in L-1 5B significantly improved gland activity during both the second and th ird 12-h intervals of a 36-h incubation. These results suggest that L- 15B is superior to TC199 because L-15B is isoosmotic with D. punctata hemolymph and because L-15B, like cockroach hemolymph, contains a high level of organic constituents. It is therefore more appropriate to us e L-15B than TC199 for shortterm in vitro assays of juvenile hormone b iosynthesis and for extended corpora allata culture.