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317 results on '"Acker, Helmut"'

108. CO2 Chemoreflex in Spinal Man

Author

Pokorski, M., Paulev, P.-E., Morikawa, T., Masuda, A., Takaishi, S., Ahn, B., Honda, Y., Acker, Helmut, editor, Trzebski, Andrzej, editor, and O’Regan, Ronan G., editor

Published
1990
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123. Effects of Hypoxia in Developing Swine

Author

Gootman, P. M., Gootman, N., Buckley, B. J., Peterson, B. J., Steele, A. M., Sica, A. L., Gandhi, M. R., Acker, Helmut, editor, Trzebski, Andrzej, editor, and O’Regan, Ronan G., editor

Published
1990
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145. NCB5OR Is a Novel Soluble NAD(P)H Reductase Localized in the Endoplasmic Reticulum.

Author

Hao Zhu, Larade, Kevin, Jackson, Timothy A., Jianxin Xie, Ladoux, Annie, Acker, Helmut, Berchner-Pfannschmidt, Utta, Fandrey, Joachim, Cross, Andrew R., Lukat-Rodgers, Gudrun S., Rodgers, Kenton R., and Bunn, H. Franklin

Subjects
*ENDOPLASMIC reticulum, *CYTOCHROME c, *ORGANELLES, *SUBCELLULAR fractionation, *RAMAN spectroscopy, *HEME
Abstract

The NAD(P)H cytochrome b5 oxidoreductase, Ncb5or (previously named b5+b5R), is widely expressed in human tissues and broadly distributed among the animal kingdom. NCB5OR is the first example of an animal flavohemoprotein containing cytochrome b5 and chrome b5 reductase cytodomains. We initially reported human NCB5OR to be a 487-residue soluble protein that reduces cytochrome c, methemoglobin, ferricyanide, and molecular oxygen in vitro. Bioinformatic analysis of genomic sequences suggested the presence of an upstream start codon. We confirm that endogenous NCB5OR indeed has additional NH2-terminal residues. By performing fractionation of subcellular organelles and confocal microscopy, we show that NCB5OR colocalizes with calreticulin, a marker for endoplasmic reticulum. Recombinant NCB5OR is soluble and has stoichiometric amounts of heme and flavin adenine dinucleotide. Resonance Raman spectroscopy of NCB5OR presents typical signatures of a six-coordinate low-spin heme similar to those found in other cytochrome b5 proteins. Kinetic measurements showed that full-length and truncated NCB5OR reduce cytochrome c actively in vitro. However, both full-length and truncated NCB5OR produce superoxide from oxygen with slow turnover rates: kcat = ∼0.05 and ∼1 s-1, respectively. The redox potential at the heme center of NCB5OR is -108 mV, as determined by potentiometric titrations. Taken together, these data suggest that endogenous NCB5OR is a soluble NAD(P)H reductase preferentially reducing substrate(s) rather than transferring electrons to molecular oxygen and therefore not an NAD(P)H oxidase for superoxide production. The subcellular localization and redox properties of NCB5OR provide important insights into the biology of NCB5OR and the phenotype of the Ncb5or-null mouse. [ABSTRACT FROM AUTHOR]

Published
2004
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146. Visualization of the three-dimensional organization of hypoxia-inducible factor-1.... and interacting cofactors in subnuclear structures.

Author

Berchner-Pfannschmidt, Utta, Wotzlaw, Christoph, Merten, Evelyne, Acker, Helmut, and Fandrey, Joachim

Subjects
*THREE-dimensional imaging in biology, *GENE expression, *THREE-dimensional imaging, *HYPOXEMIA, *PHYSIOLOGICAL effects of oxygen
Abstract

Cells need oxygen (O2) to meet their metabolic demands. Highly efficient systems of O2-sensing have evolved to initiate responses enabling cells to adapt their metabolism to reduced O2 availability. Of central importance is the activation of hypoxia-inducible factor-1 (HIF-1), a transcription factor complex that controls the expression of genes the products of which regulate glucose uptake and metabolism, vasotonus and angiogenesis, oxygen capacity of the blood as well as cell growth and death. Activation of HIF-1 requires the accumulation and nuclear translocation of the HIF-1α subunit, its dimerization with HIF-1β and the binding of co-activator proteins such as p300. In this study we investigated the three-dimensional (3D) distribution of HIF-1α within the nucleus and assigned its localization to known nuclear compartments. Using two-photon microscopy we determined the colocalization of HIF-1α and -β subunits within nuclear domains as well as overlaps between HIF-1α and p300. Our data provide information on the nuclear distribution of HIF-1α with respect to subnuclear domains that could serve as specific locations for hypoxia-induced gene expression. [ABSTRACT FROM AUTHOR]

Published
2004
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147. Radiation Studies with Spheroids

Author

Durand, R. E., Sutherland, R. M., Herfarth, Ch., editor, Senn, H. J., editor, Daum, M., editor, von Essen, C., editor, Diehl, V., editor, Hitzig, W., editor, Rajewsky, M. F., editor, Thomas, C., editor, Acker, Helmut, editor, Carlsson, Jörgen, editor, Durand, Ralph, editor, and Sutherland, Robert M., editor

Published
1984
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148. Growth and Cellular Characteristics of Multicell Spheroids

Author

Sutherland, R. M., Durand, R. E., Herfarth, Ch., editor, Senn, H. J., editor, Daum, M., editor, von Essen, C., editor, Diehl, V., editor, Hitzig, W., editor, Rajewsky, M. F., editor, Thomas, C., editor, Acker, Helmut, editor, Carlsson, Jörgen, editor, Durand, Ralph, editor, and Sutherland, Robert M., editor

Published
1984
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