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Biomedical subjects

D Engelman

Publications and source records attributed to D Engelman.

5 recordsLinked to original sources
PubMed1995

Myocardial adaptation to ischemia by oxidative stress induced by endotoxin.

In this study, we examined the effects of oxidative stress adaptation on myocardial ischemic reperfusion injury. Oxidative stress was induced by injecting endotoxin (0.5 mg/kg) into the rat. After 24 h, rats were killed, hearts were isolated, and the effects of ischemia-reperfusion were studied using an isolated working heart preparation. The development of oxidative stress was examined by assessing malonaldehyde production in the heart. The antioxidant defense system was studied by estimating antioxidant enzyme activities and ascorbate- as well as thiol-dependent antioxidant reserve. The results of our study indicated that endotoxin induced oxidative stress within 1 h of treatment; the stress was reduced progressively and steadily up to 24 h. The antioxidant enzymes superoxide dismutase, catalase, glutathione (GSH) peroxidase, and GSH reductase were lowered up to 2 h and then increased. Both thiol- and ascorbate-dependent antioxidant reserve were enhanced, but the enhancement of the former was only transitory. After 24 h, endotoxin provided adequate protection to the heart from the ischemic-reperfusion injury, as evidenced by improved left ventricular function and aortic flow. Our results suggest that the induction of oxidative stress by endotoxin-induced adaptive modification of the antioxidant defense in the heart, thereby reducing ischemic-reperfusion injury.

Adaptation, Physiological↗
PubMed1983

Assignment of segments of the bacteriorhodopsin sequence to positions in the structural map.

Specific amino acid sequence segments have been assigned to locations in the structural map of bacteriorhodopsin using two-dimensional neutron diffraction data and a model building analysis. Models are constructed computationally by building specific regions of the amino acid sequence as alpha helices and then positioning the helices on axes indicated by the density map of Henderson and Unwin (Nature [Lond.]. 1975, 257:28-32). Neutron diffraction data were collected from samples of stacked, oriented "native" purple membranes as well as purple membranes containing different kinds of deuterated amino acids. Models differing in the assignments of helices to specific axes and in rotations of the helices about those axes were tested against the neutron data using a weighted residual factor to rank the models. This residual factor was calculated between observed and predicted intensity differences for pairs of data sets. Using this approach, a small set of related models has been found that predicts the observed intensity changes between five independent data sets. These models are inconsistent with the proposed locations of the retinal chromophore and the carboxyl terminus and with any of the previously proposed models for bacteriorhodopsin.

Amino Acid Sequence↗
PubMed1974

The lac repressor protein: molecular shape, subunit structure, and proposed model for operator interaction based on structural studies of microcrystals.

Electron microscopic and powder x-ray diffraction studies of small crystals of the lac repressor protein provide evidence on its molecular shape and subunit structure which in turn suggests a possible mode of repressor-operator interaction. The crystals are probably orthorhombic space group P222(1) with unit cell dimensions of a = 140, b = 91, c = 117 A. This tetrameric protein appears rather asymmetric, having approximate molecular dimensions of 140 A by 60 A by 45 A. The dumbbell shape of the projected molecular outline observed in the electron micrographs can be explained by assuming that the subunits are related by 222 symmetry and are placed at the corners of a plane rectangle. We propose a model for repressor-operator interaction in which the DNA binds to the repressor with its long axis aligned with that of the repressor and with its 2-fold axis coincident with a twofold axis of the repressor.

Bacterial Proteins↗