Heterogeneity in the myoglobin content of chicken heart Purkinje fibers

The myoglobin content of chicken myocardial cells was studied using indirect-immunoperoxidase histochemistry. While ordinary myocardial cells exhibited a homogeneous reaction pattern, the reactions for ventricular Purkinje fibers were remarkably heterogeneous. On the basis of the degree of staining, three types of cells, i.e., dark, intermediate, and clear, were distinguishable. In addition, the cytological heterogeneity of Purkinje cells was confirmed using conventional and immunological electron microscopy. The dark cells contained more myofibrils, mitochondria, and other organelles (e.g., ribosomes) than the clear cells.     

Analysis of photosystem II using particle II preparation III. Roles of cytochrome b559 with different redox potentials and plastocyanin in the photosynthetic electron transport system

1. Using the P-II preparation (photosystem II preparation),the functional sites for Cyt-b₅₅₉ with different redox potentialsand for plastocyanin in the non-cyclic electron transport chainof chloroplasts were investigated. 2. In the absence of plastocyanin, the P-II preparation showedno light-induced absorption changes in Cyt-b₅₅₉. However, uponthe addition of a sufficient amount of plastocyanin, remarkablephotooxidation of this cytochrome was observed at room temperature. 3. Parallel measurements of the light-induced absorption changesin both Cyt-b₅₅₉ and plastocyanin revealed a close relationshipbetween them, and indicated that Cyt-b₅₅₉ and plastocyanin arelocated in series on the main path of the electron transportchain involving two photoreactions in PS-II. 4. Difference spectra and action spectra for the light-inducedabsorption changes in Cyt-b₅₅₉ and plastocyanin offered additionalevidence in support of the above conclusion. 5. Analysis of the relationship between the activity of ferricyanideHill reaction and the contents of Cyt-b₅₅₉ of different redoxpotentials showed that both forms of Cyt-b₅₅₉ (i.e. high- andlow-potential forms) play important roles under physiologicalconditions, being on the main pathway of the electron transportchain connecting PS-II and PS-I. 6. To these findings it is possible to give reasonable explanationsbased on our scheme presented previously, which suggested thatPS-II contains not one but two different photoreactions. Thisscheme is much more elaborately supported by this study whichshows the functional sites for Cyt-b₅₅₉ with two different potentials. ¹This work has been supported by a Grant from the Ministry ofEducation (Grant No. 844004), which we gratefully acknowledge.Part of this report has been presented at the Gordon ResearchConference on Regulatory Mechanisms in Photosynthesis, at Tilton,N.H., U.S.A., Aug. 13–17, 1973. (Received June 20, 1974; )