Immunohistochemical demonstration of fibre type-specific isozymes of cytochrome c oxidase in human skeletal muscle

Summary The immunohistochemical reaction of monoclonal as well as polyclonal antibodies against cytochrome c oxidase (COX) subunits with serial sections of normal human skeletal muscle was investigated. The stronger reactivity of polyclonal antibodies to COX subunits II–III and VIIbc with type I as compared to type II fibres, correlated well with the higher histochemical reactivity of NADH dehydrogenase, succinate dehydrogenase and cytochrome c oxidase in type I fibres. In contrast an almost exclusive reaction of a monoclonal antibody against subunit IV with type I fibre and a preponderan reaction of a polyclonal antibody against subunits Vab with type II fibres was obtained. Antibodies against subuntis I, Vb and VIc did not reveal a fibre-type-specific reactivity. The data indicate in human muscle the occurrence of fibre type-specific isozymes of cytochrome c oxidase differing in subunits IV and Va or Vb.     

The structural nif genes of the cyanobacteria Gloeothece sp. and Calothrix sp. share homology with those of Anabaena sp., but the Gloeothece genes have a different arrangement.

Probes carrying the Anabaena sp. strain PCC 7120 nitrogenase reductase (nifH) and nitrogenase (nifK and nifD) genes were hybridized to Southern blots of DNA from the unicellular, aerobic nitrogen-fixing cyanobacterium Gloeothece sp. strain PCC 6909 and from the filamentous cyanobacterium Calothrix sp. strain PCC 7601. These data suggest that the Gloeothece sp. nif structural proteins must be similar to those of other diazotrophs and that the ability for aerobic nitrogen fixation does not reside in the nif protein complex. We also found that the nif structural genes of Gloeothece sp. are clustered, whereas those of Calothrix sp. are arranged more like those of Anabaena sp.     

The structure of cyanobacterial phycobilisomes: a model

Phycobilisomes, supramolecular complexes of water-soluble accessory pigments, serve as the major light-harvesting antennae in cyanobacteria and red algae. Regular arrays of these organelles are found on the surface of the thylakoid membranes of these organisms. In the present study, the hemi-discoidal phycobilisomes of several species of cyanobacteria were examined in thin sections of cells and by negative staining after isolation and fixation. Their fundamental structures were found to be the same. Isolated phycobilisomes possessed a triangular core assembled from three stacks of disc-shaped subunits. Each stack contained two discs which were 12 nm in diameter and 6–7 nm thick. Each of these discs was probably subdivided into halves 3–3.5 nm thick. Radiating from each of two sides of the triangular core were three rods 12 nm in diameter. Each rod consisted of stacks of 2 to 6 disc-shaped subunits 6 nm thick. These discs were subdivided into halves 3 nm thick.The average number of discs of 6 nm thickness forming the peripheral rods varied among the strains studied. For certain chromatically adapting strains, the average rod length was dependent upon the wavelength of light to which cells were exposed during growth. Analyses of phycobilisomes by spectroscopic techniques, polyacrylamide gel electrophoresis, and electron microscopy were compared. These analyses suggested that the triangular core was composed of allophycocyanin and that the peripheral rods contained phycocyanin and phycoerythrin (when present). A detailed model of the hemi-discoidal phycobilisome is proposed. This model can account for many aspects of phycobiliprotein assembly and energy transfer.Abbreviations PBS phycobilisome(s) - PBP phycobiliprotein(s) - AP allophycocyanin - PC phycocyanin - PE phycoerythrin - PEC phycoerythrocyanin - AP-B allophycocyanin B - C- cyanobacterial - R- rhodophytan - B- Bangiophycean - SDS sodium dodecyl sulfate - LPP Lyngbya-Plectonema-Phormidium group - Na-KPO₄ buffers NaH₂PO₄ titrated with a solution of KH₂PO₄ of equivalent molarity to a given pH     

UV-A irradiation induces a decrease in the mitochondrial respiratory activity of human NCTC 2544 keratinocytes

UV-A irradiation caused a dose-dependent decrease in cellular oxygen consumption (56%) and ATP content (65%) in human NCTC 2544 keratinocytes, one hour after treatment. This effect was partially reversed by maintaining the irradiated cells in normal culture conditions for 24h. Using malate/glutamate or succinate as substrates for mitochondrial electron transport, the oxygen uptake of digitoninpermeabilised cells was greatly inhibited following UV-A exposure. These results strongly suggest that UV-A irradiation affects the state 3 respiration of the mitochondria. However, under identical conditions, UV-A exposure did not reduce the mitochondrial transmembrane potential. The antioxidant, vitamin E inhibited UV-A-induced lipid peroxidation, but did not significantly prevent the UV-A-mediated changes in cellular respiration nor the decrease in ATP content, suggesting that these effects were not the result of UV-A dependent lipid peroxidation. UV-A irradiation also led to an increase in MnSOD gene expression 24 hours after treatment, indicating that the mitochondrial protection system was enhanced in response to UV-A treatment. These findings provide evidence that impairment of mitochondrial respiratory activity is one of the early results of UV-A irradiation for light doses much lower than the minimal erythemal dose.