Altered xanthophyll compositions adversely affect chlorophyll accumulation and nonphotochemical quenching in Arabidopsis mutants

Collectively, the xanthophyll class of carotenoids perform a variety of critical roles in light harvesting antenna assembly and function. The xanthophyll composition of higher plant photosystems (lutein, violaxanthin, and neoxanthin) is remarkably conserved, suggesting important functional roles for each. We have taken a molecular genetic approach in Arabidopsis toward defining the respective roles of individual xanthophylls in vivo by using a series of mutant lines that selectively eliminate and substitute a range of xanthophylls. The mutations, lut1 and lut2 (lut = lutein deficient), disrupt lutein biosynthesis. In lut2, lutein is replaced mainly by a stoichiometric increase in violaxanthin and antheraxanthin. A third mutant, aba1, accumulates normal levels of lutein and substitutes zeaxanthin for violaxanthin and neoxanthin. The lut2aba1 double mutant completely lacks lutein, violaxanthin, and neoxanthin and instead accumulates zeaxanthin. All mutants were viable in soil and had chlorophyll a/b ratios ranging from 2.9 to 3.5 and near wild-type rates of photosynthesis. However, mutants accumulating zeaxanthin exhibited a delayed greening virescent phenotype, which was most severe and often lethal when zeaxanthin was the only xanthophyll present. Chlorophyll fluorescence quenching kinetics indicated that both zeaxanthin and lutein contribute to nonphotochemical quenching; specifically, lutein contributes, directly or indirectly, to the rapid rise of nonphotochemical quenching. The results suggest that the normal complement of xanthophylls, while not essential, is required for optimal assembly and function of the light harvesting antenna in higher plants.     

Three-dimensional Doppler velocimetry of flow jets

A closed-form solution is derived of the Doppler equation for the magnitude and angle to the three-dimensional velocity vector. The resultant solution is more general than previous formulations and, since it is based on multiple conventional transmit-receive Doppler probes, it can be readily applied by adapting existing Doppler units. Turntable experiments demonstrated that the three-dimensional angle-independent theory correctly predicted velocity within average 32% over a 26.°-range of Doppler angles. Experiments with a flow phantom showed general agreement with the angle-independent theory in the more demanding setting of an actual flow stream. Experiments utilizing a jet stream which modeled the clinically important conditions that exist in stenotic vessels, valvular abnormalities, and septal defects within 1.4-3.8% of the actual velocity, over an 18° range of Doppler angles     

Effects of ethanol administration on components of the ubiquitin proteolytic pathway in rat liver

Hepatic protein accumulation during ethanol administration may result partly from an ethanol-elicited decline in hepatic protein degradation, which we have previously shown. We conducted the current studies to examine the effects of ethanol administration on the levels of hepatic ubiquitin, an 8.5-kd protein which is an important mediator of extralysosomal protein catabolism. Rats were pair-fed liquid diets containing either ethanol (36% of calories) or isocaloric maltose-dextrin for 1 to 5 weeks. Ubiquitin was immunochemically quantified by competitive enzyme-linked immunosorbent assay (ELISA) in crude cytosol fractions from whole liver and in 12,000g supernatants of hepatocyte lysates. Ubiquitin levels in hepatic cytosol fractions of ethanol-fed rats exceeded those of controls by about 30%. Isolated hepatocytes from ethanol-fed animals also showed a 40% to 75% elevation of ubiquitin above that in cells of pair-fed controls and this difference exceeded the relative rise in hepatocellular protein. In hepatocyte lysates subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting, we detected monomeric ubiquitin and higher molecular mass ubiquitin-protein conjugates. However, the immunoblot analyses revealed no quantitative changes in the level of either free or conjugated ubiquitin. The ubiquitin conjugating activity of crude and diethyl aminoethyl-fractionated liver cytosols of ethanol-fed rats had equal capacities to those from controls in catalyzing the formation of ubiquitin-protein conjugates. Our findings indicate that chronic ethanol consumption increased the level of immunoreactive ubiquitin in rat liver. This may have resulted from enhanced ubiquitin production because of an ethanol-elicited stress response and/or decreased catabolism of ubiquitin and its conjugates. Our findings also provide no indication that the ethanol-elicited reduction in hepatic proteolysis is because of a ubiquitin-mediated mechanisms.     

Microwave Rejection Networks

This is an extension of the Bridged-T infinite rejection network idea transformed into microwave concepts. These devices achieve approximately 100db of attenuation with skirt attenuations approximately 5db. The tuning range between 1 KMc and 10 KMc is continuously covered with 4 units at present. Work is continuing to reduce the number of units to 2. Design parameters, performance curves, and application to MILSTD 826 will be discussed.