Mitochondrial respiratory chain deficiency leads to overexpression of antioxidant enzymes.

U937 cell growth in the presence of either chloramphenicol or ethidium bromide rapidly leads to respiratory deficiency. The novel finding of this report is that this response is paralleled by a specific increase in Se-dependent and independent glutathione peroxidase activities as well as of glutathione peroxidase and heme oxygenase mRNAs. Under the same experimental conditions, catalase activity and catalase mRNA do not show appreciable changes. These results can be explained by an increased formation of H2O2 at the early times of development of respiratory deficiency followed by induction of antioxidant enzymes.

Laser modification to an x-ray collimator: an aid in positioning patients for neurosurgical and radiographic procedures.

In high-ambient-light levels such as are found in operating rooms, and at long target-to-patient distances, the cross lines and light field projected from conventional x-ray collimators are not easily visible and proper patient positioning is difficult. The collimators on two mutually perpendicular x-ray units have been modified by replacing the incandescent bulbs with lasers and adjusting the lasers to be coaxial with the x-ray beams. These modifications have been coupled with a third wall-mounted laser to facilitate patient positioning for stereotaxic thermal hypophysectomy. The use of the laser-modified collimators has resulted in considerable saving of time for the operating team and has markedly reduced patient anesthesia time. The laser-modified collimator has also been found useful in positioning patients for other radiographic procedures in the operating room and has virtually eliminated retakes due to malpositioning.