Histochemical demonstration of glutamate dehydrogenase and phosphate-activated glutaminase activities in semithin sections of the rat retina

Summary The activities of the glutamate metabolizing enzymes phosphate-activated glutaminase (PAG) and glutamate dehydrogenase (Gldh) are demonstrated in semithin sections of the rat retina. Highest activities of both enzymes are found in the photoreceptor inner segments, PAG additionally in the outer plexiform layer and Gldh in the inner plexiform layer and in mueller glial cells. Although their non randomly distribution makes a role in neurotransmitter metabolism possible, their high activities in inner segments point towards the general problem of the functional interpretation of both molecules.     

Histochemical demonstration of glutamate dehydrogenase and phosphate-activated glutaminase activities in semithin sections of the rat retina.

The activities of the glutamate metabolizing enzymes phosphate-activated glutaminase (PAG) and glutamate dehydrogenase (Gldh) are demonstrated in semithin sections of the rat retina. Highest activities of both enzymes are found in the photoreceptor inner segments, PAG additionally in the outer plexiform layer and Gldh in the inner plexiform layer and in mueller glial cells. Although their non randomly distribution makes a role in neurotransmitter metabolism possible, their high activities in inner segments point towards the general problem of the functional interpretation of both molecules.     

Low-lying electronic states of carotenoids.

Four all-trans carotenoids, spheroidene, 3,4-dihydrospheroidene, 3,4,5,6-tetrahydrospheroidene, and 3,4,7,8-tetrahydrospheroidene, have been purified using HPLC techniques and analyzed using absorption, fluorescence and fluorescence excitation spectroscopy of room temperature solutions. This series of molecules, for which the extent of pi-electron conjugation decreases from 10 to seven carbon-carbon double bonds, exhibits a systematic crossover from S2----S0 (1(1)Bu----1(1)Ag) to S1----S0 (2(1)Ag----1(1)Ag) emission with decreasing chain length. Extrapolation of the S1----S0 transition energies indicates that the 2(1)Ag states of longer carotenoids have considerably lower energies than previously thought. The energies of the S1 states of spheroidenes and other long carotenoids are correlated with the S1 energies of their chlorophyll partners in antenna complexes of photosynthetic systems. Implications for energy transfer in photosynthetic antenna are discussed.     

Roaring rhythms in black howler monkeys (Alouatta pigra) of Belize

Roaring was recorded during 15-min intervals for 55 days from April 29 to July 14, 1981 in the area around Bermuda Landing, Belize. Roaring profiles were compiled to represent four three-week periods in which roaring was graphed against the time of day. Rates of roaring were also calculated for three troops. Results indicate a gradual change in the daily profile of roaring from dry to rainy season. The marked bimodality of roaring at dawn and dusk in the dry season changed to a more dampened bimodality with reduced dawn and dusk peaks and more roaring during the midday in the rainy season. This seems related to the decreased hours of sun and the amount of rain during the wet season. Additionally, literature on monkeys with long range vocalizations suggests that bimodal peaks in calling may be more prevalent in species which display territorial defense.