Release of carboxylating enzymes from maize and sugar cane leaf tissue during progressive grinding

Summary The release of chlorophyll, chloroplasts, o-diphenols, o-diphenol oxidase activity and carboxylating enzyme activity during the grinding of maize and sugar cane leaf tissue has been correlated with the breakage of different types of cell. Enzymes of the photosynthetic carbon reduction cycle were released in the grinding stage during which the bulk of the mesophyll tissue was disrupted and grana-containing chloroplasts released. Since the largest amount of phenol oxidase activity and of phenols was also released at this stage it is likely that the enzymes were partly inhibited by phenol oxidation products and, therefore, underestimated. PEP carboxylase is released earlier in the grinding process. It is concluded that the photosynthetic carbon reduction cycle enzymes studied are located in mesophyll cell chloroplasts and that the PEP carboxylase resides outside the chloroplasts, either in the cytoplasm of mesophyll cells or in colourless tissue. These results are discussed in relation to current theories regarding the assimilation and shuttling of carbon dioxide in leaves of tropical grasses.     

A combination rapid and standard method for identification of Candida albicans

A medium consisting of an aqueous extract of zein, lactose, and Tween 80 is used together with an overlay of 1 % Tween 80 and coverslipping to provide a combined rapid (germ tube) and standard (chlamydospore) method for diagnosis ofCandida albicans. The method is exquisitely sensitive for diagnosis ofC. albicans but lumps chlamydospore-producing strains ofC. tropicalis withC. albicans.     

ARTIFICIAL INTERSPECIFIC HYBRIDIZATION IN RUELLIA (ACANTHACEAE)

Observations were made on the morphology, seed fertility, pollen viability and meiotic configurations of 22 different interspecific hybrids of 12 North American taxa representative of 3 sections of Ruellia. The hybrids were classified as (1) fully vigorous and fertile; (2) vigorous but with reduced fertility; (3) reduced vigor and fertility; (4) weak and sterile. Hybrids showed meiotic irregularities in microsporogenesis: univalents, chains, precocious separation of bivalents, nondisjunction, and micronuclei were commonly observed. Interspecific pollinations within sect. Dipteracanthus resulted in fertile or partially sterile F₁ hybrids. Intersectional crosses produced partially or completely sterile hybrids or failed. Assuming that crossability is correlated with degree of evolutionary relationship, the parental species are interpreted in genecological terms to be grouped in polytypic ecospecies. Hybridization experiments doubtless would be of value in clarifying relationships in tropical and subtropical species of Ruellia.     

Susceptibility of insecticide-susceptible and wild house flies (Diptera: Muscidae) to abamectin on whitewashed and unpainted wood

Unpainted plywood panels treated with 0.1% abamectin (avermectin B1) provided greater than 90% control of house flies, Musca domestica L., susceptible to insecticides for 4 wk and greater than 70% control for 7 wk compared with 46-92% control observed with permethrin at the same time and rate of application. Efficacy of abamectin on whitewashed panels was similar to that observed on unpainted panels, whereas permethrin was ineffective on whitewashed panels at all rates tested (range, 0.001-0.1%) at all intervals after treatment. Bioassays of newly colonized house flies resistant to permethrin indicated that wild populations may be cross-resistant to abamectin.     

Crystal structure of plakalbumin, a proteolytically nicked form of ovalbumin. Its relationship to the structure of cleaved alpha-1-proteinase inhibitor

The crystal structure of plakalbumin, a proteolytically nicked form of ovalbumin, has been determined to a resolution of 2.8 A by the isomorphous replacement method and preliminary refinement. The structure closely resembles that of the cleaved form of alpha-1-proteinase inhibitor, with some important exceptions. The disposition of the new carboxyl chain terminus liberated by proteolysis is different with respect to the central beta-sheet A in the structures of these two molecules. In alpha-1-proteinase inhibitor, the new chain terminus inserts in beta-sheet A to add a middle strand to the sheet. In plakalbumin, this strand remains free near the site at which the cleavage occurs. A structural basis for this difference in behavior is proposed from the structures and sequences of these two molecules and other members of the serpin family. The structures and positions of the putative signal peptide of ovalbumin, the several post-translational modifications, and the relationship of the intron-exon patterns of plakalbumin and alpha-1-proteinase inhibitor to their protein structures are also described.