Feedback Inhibition of Key Glycolytic Enzymes in Liver: Action of Free Fatty Acids

G. Weber, H. J. H. Convery, M. A. Lea, N. B. Stamm
1966 Science  
5) that lacks tyrosinase activity can develop protoperithecia under certain conditions. Two wild strains of N. crassa, 5297a and 74A, and a mutant (ty-1) lacking tyrosinase activity were used. Westergaard and Mitchell's (1) crossing-media was used for maximum protoperithecial formation. However, the density of the hyphal growth on this medium prevented suitable photography of individual, developing protoperithecia. In contrast, they were readily discernible when the culture was initially grown
more » ... as initially grown in Petri plates on strips of sterile (autoclaved) Visking dialysis membrane cut to 4 by 1.5 cm and placed on top of Westergaard and Mitchell's medium for 4 to 6 days-that is, until protoperithecial development had been initiated. Subsequently, they were transferred to Petri plates containing 1.2 percent Bacto-agar. This procedure restricts hyphal growth sufficiently to permit accurate observation of the development and differentiation of individual protoperithecia on the agar, adjacent to the membrane, unobscured by heavy hyphal growth. Under these conditions, the protoperithecia are morphologically indistinguishable from those developing on Westergaard and Mitchell's medium under usual conditions and are normal as evidenced by mature perithecial formation and subsequent ascospore formation after fertilization. In the wild type, about 76 hours after its transfer to the Bacto-agar, the developing protoperithecia were initially recognized by the extension of a hyphal filament to form a loop (Fig. 1 a) . The incipient protoperithecia usually, but not invariably, occur within a halo-like zone, and occasionally development appears to be preceded by the deposition of a granular material. Subsequently, the hyphal loop extends to form numerous coils (Fig. 1, b and c) that become closely packed. The early protoperithecium then darkens, and hyphal filaments grow out from the organelle (Fig. Id) . The entire process takes about 12 to 18 hours. Normally, on Westergaard and Mitchell's medium, the first protoperithecia begin to develop about 36 hours after inoculation at 250C. Full development of a protoprithecium on Wes7ter-SCIENCE, VOL. 154
doi:10.1126/science.154.3754.1357 pmid:4288679 fatcat:54g36kvkhvdang2igib4pqbq4a