Biomedical subjects

K C Vaughn

Publications and source records attributed to K C Vaughn.

22 records · Page 2Linked to original sources

PubMed1981

Cytochemical localization of photosystem II donor sites.

Tetramethylbenzidene, an artificial donor of electrons to the photosystem (PS) II reaction center, is oxidized to an osmiophilic polymer that allows for the localization of the donor site of PS II. Mesophyll chloroplasts of Sorghum bicolor (L.) Moench. contain 0.1-0.2 micron deposits only in the grana stacks and on the lumen side of the thylakoid. Agranal mature bundle sheath plastids (known to be devoid of PS II activity) show little deposition and the products appear randomly distributed along the lamellae. The cytochemical localization of PS II donor sites on the lumen side is consistent with flash photolysis and diaminobenzenesulfonic acid inactivation studies as well as the chemiosmotic theory for the generation of a proton gradient.

Benzidines↗

PubMed1981

Histochemical localization of nitrate reductase.

NADH-dependent nitrate reductase (E.C. 1.6.6.1) was ultrastructurally localized in norflurazon-treated and control soybean cotyledons [Glycine max (L.) Merr.] by a method based upon the increase in osmiophilia due to the formation of an azo dye. The reaction product was observed in small vesicles throughout the cytoplasm. An apparent transport of nitrite to the plastid, the site of nitrite reduction, may occur through fusion of the nitrite-containing vesicles with the chloroplast envelope. Plants grown in tungstate lacked nitrate reductase activity as measured by standard assay procedures, and showed no increase in osmiophilia, suggesting a degree of specificity of this cytochemical procedure.

Herbicides↗

PubMed1980

Ultrastructure and biochemistry of two mutants in Hosta (Liliaceae).

In a survey of several plastid chimeras of the genus Hosta two white mutants with C4--type ultrastructure were noted. Mesophyll plastids from the white tissue have an extensive system of peripheral reticula, characteristic of C4 plants, and macrograna or vesiculated thylakoids, characteristic of photosystem I deficient mutants. Microbodies were either absent or in low quantities in these cells. Bundle sheath plastids from the white sectors had a concentration of all organelles, with plastids of typical C4 bundle sheath ultrastructure and numerous, ornate mitochondria. Green restituted sectors of one of these mutants retained the ability to make peripheral reticulum yet had normal Hosta granal formation. Despite these changes the plants show a carbon fractionation like C3 plants. Possible reasons for these ultrastructural modifications are discussed.

Carbon↗

PubMed1980

An ultrastructural survey of plastome mutants of Hosta (Liliaceae).

In an ultrastructural survey of 82 plastome mutants of Hosta two general groups of mutants were distinguished: yellow to yellow-green photostable mutants, and pale green to white mutants that 'photobleach' during development. The yellow to yellow-green mutants had reduced granal stacking compared to the wild type plastid, and thylakoids were frequently dilated. In the photobleaching group, thylakoids were aggregated into a tight mass, known as a magnograna. During development, the thylakoids vesiculated to a great extent, with a subsequent photo-oxidation of the photosynthetic pigments. Peripheral reticula, invaginations of the chloroplast inner membrane, were found consistently in the photobleaching strains. Osmiophilic globules were increased in both number and size in these two groups and occasionally more extensive electron dense areas were noted in the plastids of the photobleaching group.

Chloroplasts↗