Adv Exp Med Biol
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Chronic mountain sickness (CMS) is a poorly understood syndrome, characterized by hypoxemia and polycythemia and occurring in persons residing at high altitude. To better characterize the disorder, we have reviewed measurements in more than 750 men and 200 women living at altitude as published and as submitted by colleagues. In men, blood hemoglobin concentration (Hb) and arterial oxygen saturation (SaO2) related to altitude (r=0.72). ⋯ Pulmonary hypertension was related to chronic hypoxia, with an uncertain contribution from polycythemia. In CMS there were profound hypoxemia at night, decrease in cerebral blood flow, and loss of cerebral blood flow regulation, possibly causing the cerebral symptoms. We speculate that the relationship of Hb to SaO2 is more useful than of hemoglobin to altitude, that hypoventilation awake and asleep are the primary causes accentuating altitude-hypoxia, and that the brain is the primary target organ in the disorder.
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Opioids such as morphine are potent analgesic and addictive compounds. Chronic morphine use also induces immunomodulatory and immunosuppressive effects, as especially evident in HIV-infected patients. Morphine acts on the immune cells primarily through its binding to mu-opioid receptors on the plasma membrane. ⋯ The results of the competitive RT/PCR indicated that CEM x174 cells expressed KOR mRNA constitutively, in the order of femto-grams. Treatment of 10 microM of morphine resulted in the up-regulation of KOR gene expression 24 hr post-treatment. The observed morphine effect could be reversed by treating the cells with either naloxone (a KOR-partially selective antagonist) or nor-Binaltorphimine (a KOR-selective antagonist).
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Hyperbaric oxygen (HBO2) at approximately 3 atmospheres absolute (ATA) pressure is toxic to the mammalian CNS due to excessive O2 free radical production. No study has ever determined the effects of < or = 3 ATA of O2 on the membrane potential and firing rate of neurons in the mammalian brainstem. Likewise, no study has ever determined the effects of < or = 3 ATA pressure per se on brainstem neurons. ⋯ Three of 8 neurons depolarized by HBO2 were also depolarized by hyperbaric helium, usually with an additional change in Rin. We conclude that hydrostatic (helium) pressure and HBO2 independently increase excitability in certain solitary complex neurons. We hypothesize that these responses contribute, in part, to neural events that either precede or occur during CNS O2 toxicity.