Medicina
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beta-lapachone (beta-lap) is a lipophilic o-naphthoquinone isolated from the bark of the lapacho tree. Initial observations proved its capability for inhibiting growth of Yoshida tumor and Walker 256 carcinosarcoma. beta-Lap redox-cycling in the presence of reductants and oxygen yields "reactive oxygen species" (ROS: O2-, OH and H2O2) which cytotoxicity led to assume its role in beta-lap activity in cells. beta-Lap inhibited DNA synthesis in Trypanosoma cruzi as well as topoisomerases I and II, poly(ADP-ribose) polymerase (PARP) in different cells. These enzymes are essential for maintaining DNA structure. beta-Lap inhibited growth of a large variety of tumor cells including epidermoid laringeal cancer, prostate, colon, ovary and breast cancer and also different types of leukemia cells. ⋯ These enzymes activity, as well as ROS production by beta-lap redox-cycling, would be essential for beta-lap cytotoxicity. Diaphorase and NAD(P)H-quinone reductase, which catalyse beta-lap redox-cycling and ROS production, seem to play an essential role in beta-lap activity. On these grounds, clinical applications of beta-lap have been suggested.
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The purpose of this article is to review the etiological and pathophysiological aspects of chronic severe hypoxemia (CSH) and to determine the indications of long-term oxygen therapy (LTOT). Three hypothesis are presented and analyzed: 1) CSH is harmful to the economy; 2) LTOT is therefore useful; 3) LTOT is not toxic and does not imply major risks than the benefits that it offers. ⋯ Chronic obstructive pulmonary disease is the most common cause of CSH; these patients have a poor prognosis associated to the hypoxemia and its effects, being a PaO2 below 60 mmHg one of the most precise factors of mortality. Patients selection criteria for LTOT different sources for home oxygen therapy, methods of administration and finally an update of LTOT situation in our country and abroad are discussed.