Ultrastructure and elemental composition of dormant and germinating Diplodia maydis spores.

The ultrastructure of Diplodia maydis spores was studied in thin sections with a transmission electron microscope. Storage vacuoles were evenly distributed in the two cells. Some of the vacuoles that contained a dense osmiophilic sphere(s) were surrounded by a membrane, and had membranous aggregates around their periphery. The sport wall was composed of an electron-dense layer and an electron-translucent layer. An inner cytoplasmic membrane was present. Dormant and germinating spores were studied with scanning electron microscopy and also with a Si (Li) energy-dispersive X-ray analyzer. The dormant spore was ovate and usually two-celled with a central septum. Germination proceeded via a germ tube from the side of one end of the cell. Of several methods for preparation of specimens for X-ray analysis studied, freeze-dried spores mounted on carbon stubs and then further carbon coated gave the best results. X-ray analyses revealed that spore populations contained large amounts of Si, P, Cl, and K, smaller amounts of S and Ca, and trace amounts of Mg and Al. Analyses of single spores revealed high K and Cl and low P and Mg at one end of the cell with concomitant low K and Cl and high P and Mg in the central portion and other end of the cell. In two-celled germinating spores, high K and Cl occurred in the end of the nongerminating spore cell, whereas the germinating cell contained high P and Mg and low K and Cl. X-ray image maps revealed that K and Cl were located together at one end of the spore.     

Analysis of distributions of mutants in clones of plant-cell aggregates

Summary The organization of plant cells (or any other genetic elements, such as organelles) into aggregates modifies the expected distribution of mutants in clones. The reason for the modification, and its effect on the use of the Luria-Delbrück fluctuation test, are discussed. The Luria-Delbriick test was used to show that the trait for chlorate resistance in cultured rose-cell aggregates appeared spontaneously and in the absence of chlorate ion.     

Olfactory event-related potentials in young and elderly adults: evaluation of tracking task versus eyes open/closed recording.

The purpose of the present study was to evaluate olfactory event-related potentials (OERPs) elicited by amyl acetate from subjects performing a visuomotor tracking task compared with the no-task conditions of eyes open and eyes closed. Task condition did not produce any reliable effects for any amplitude measure. Task type weakly influenced only P2 latency. Elder adults evinced smaller P2 and N1/P2 amplitudes and longer N1 and P2 latencies than young adults. The results suggest that tracking task performance is not necessary to obtain robust OERPs from normal subjects of a wide age range.     

Kinetics of hydrolysis of endocytosed substrates by mammalian cultured cells: early introduction of lysosomal enzymes into the endocytic pathway

The kinetics of exposure of endocytosed material to two lysosomal enzymes were determined for a number of cultured cell lines using fluorogenic substrates. Hydrolysis of endocytosed substrates for cathepsin B and acid phosphatase was observed to begin within 3-10 min of substrate addition and to proceed linearly for up to 60 min thereafter. Hydrolysis of the cathepsin B substrate was not affected by inhibition of protein synthesis with cycloheximide, indicating that the enzymes present in early endosomes are not exclusively newly synthesized. As had been observed previously for a cathepsin B substrate (Roederer, M., Bowser, R., and Murphy, R. F., J. Cell. Physiol., 131:200-209, 1987), hydrolysis of the acid phosphatase substrate was not blocked at temperatures below 20 degrees C. The results suggest that the endosome is the primary site of initial exposure of endocytosed material to hydrolytic enzymes.     

Evaporative temperature and moisture control in a rocking reactor for solid substrate fermentation

Summary In the solid substrate fermentation of cooked yellow corn grits with Rhizopus oligosporus in a rocking drum fermenter, temperature was controlled by blowing air through the substrate, forcing water evaporation. The rate of evaporation was controlled by the relative humidity of the air, according to the rate of heat generation during fermentation. Moisture content was maintained constant by spraying cold water on the substrate regulated by the water balance equation of the system. Both controls were operated by computer programs. The rocking motion in the reactor allowed even distribution of air and water in the substrate without disturbing the growing mycelia.