Nitric oxide-mediated inhibition of the ability of Rickettsia prowazekii to infect mouse fibroblasts and mouse macrophagelike cells.

The role of the nitric oxide synthase (NOS) pathway in inhibiting the ability of Rickettsia prowazekii to initially infect (invade) mouse cytokine-treated, fibroblastic L929 cells and macrophagelike RAW264.7 cells and the ability of nitric oxide (NO) to damage isolated rickettsiae were investigated. Substantial amounts of nitrite (a degradation product of NO) were produced and the initial rickettsial infection was suppressed in cultures of L929 cells treated with crude lymphokine preparations (LK) or with gamma interferon (IFN-gamma) plus tumor necrosis factor alpha (TNF-alpha) but not in L929 cell cultures treated with IFN-gamma alone or TNF-alpha alone. The NOS inhibitors N(G)-methyl-L-arginine and aminoguanidine both inhibited nitrite production and prevented the suppression of the initial rickettsial infection. Antibody-mediated neutralization of the IFN-gamma in the LK also inhibited both nitrite production and suppression of the initial rickettsial infection. Cultures of RAW264.7 cells treated with IFN-gamma plus lipopolysaccharide exhibited suppression of the initial rickettsial infection, and the suppression was relieved by aminoguanidine. Addition of oxyhemoglobin (a scavenger of extracellular NO) during the rickettsial infection alleviated the suppression of the initial rickettsial infection observed in appropriately treated L929 cells and RAW264.7 cells. In addition, the oxyhemoglobin restored the rickettsia-mediated, rapid killing of the treated RAW264.7 cells. Incubation of isolated rickettsiae with NO inhibited their ability to infect L929 and IFN-gamma-treated RAW264.7 cells and to rapidly kill IFN-gamma-treated RAW264.7 cells. In contrast, incubation of L929 cells with a solution that contained NO and/or degradation products of NO did not affect their ability to be infected by rickettsiae. The data are consistent with the hypothesis that NO released from appropriately stimulated potential host cells kills extracellular rickettsiae and thus prevents the rickettsiae from infecting the cells.

Hyperbaric oxygen for treatment of closed head injury.

Traumatic and vascular brain injuries consist of acute episodes followed by development of chronic components of varying magnitude and duration whose potentials for recovery differ. We discuss a case of closed head injury in which interventional hyperbaric oxygen (HBO) with single photon emission computed tomography were used as aids in determining the presence of recoverable neurons, to follow therapeutic progress, and to determine the end point of therapy. This case also shows the successful use of intensive HBO as a therapeutic modality.

Increased oxygen tensions influence subset composition of the cellular immune system in aged mice.

In acute and chronic experiments, each of eight groups of aged mice were assigned separately to different pressures of oxygen to which it was to be exposed. Lymphocytes from spleen, thymus, and peripheral blood were analyzed following oxygen exposure. Subset populations changed depending on the oxygen tension. Variable changes were observed in total numbers of lymphocytes, lymphocyte subsets, B cells, and macrophages depending on the organ studied and the oxygen pressure to which the mice were exposed. There were differences between acute and chronic exposure suggestive of adaptation to environmental stressors. The suggestion is made that the immune system has a reserve capacity that can be influenced by oxygen and, thereby, theoretically capable of being pharmacologically manipulated to assist patients with altered immune systems to promote defense mechanisms or, under certain circumstances, reduce autoimmunity. It is hypothesized that an underlying hypoxia may be involved in the age-associated decline in the immune system.

Hyperbaric oxygen limits infarct size in ischemic rabbit myocardium in vivo.

BACKGROUND: We explored the ability of increased oxygen pressure to modify necrosis in an open-chest rabbit model of myocardial ischemia and reperfusion. METHODS AND RESULTS: A branch of the left coronary artery was occluded for 30 minutes followed by 3 hours of reperfusion. Infarction was measured by triphenyl tetrazolium staining and expressed as a percentage of the ischemic zone. Untreated rabbits were ventilated with 100% oxygen at 1 atm absolute. Treatment animals were exposed to hyperbaric oxygen at 2.5 atm absolute. The 1.0-atm control hearts developed 41.5 +/- 4.6% infarction of the ischemic zone. Animals exposed to hyperbaric oxygen during ischemia only, reperfusion only, or ischemia and reperfusion had significantly smaller infarcts with respect to control animals (16.2 +/- 2.9%, 14.5 +/- 3.7%, and 9.8 +/- 2.7%, respectively; P < or = .01), indicating that they had been protected by the procedure. When hyperbaric oxygen was begun 30 minutes after the onset of reperfusion, no protection was seen (35.8 +/- 3.8%). CONCLUSIONS: We conclude that hyperbaric oxygen limits infarct size in the reperfused rabbit heart and that the effect can be achieved when hyperbaric oxygen is begun at reperfusion.

Increased oxygen tensions modulate the cellular composition of the adaptive immune system in BALB/c mice.

In acute and chronic experiments, each of eight groups of young mice were assigned separately to different pressures of oxygen to which it was to be exposed. Lymphocytes from spleen, thymus, and peripheral blood were analyzed following oxygen exposure. Subset populations changed depending on the oxygen tension. Blood lymphocyte populations reflected lymphocyte changes in thymus or spleen. Thus, a full understanding of the pharmacological effects of hyperbaric oxygen, requires a knowledge of simultaneous effects of increased oxygen pressures on the various compartments comprising the immune system.

Identification of hypometabolic areas in the brain using brain imaging and hyperbaric oxygen.

Current neurologic assessments consider idling neurons and ischemic penumbras to be metabolically lethargic and electrically nonfunctional or nonviable. Diagnosis, prognosis, and therapeutics of central nervous system dysfunctions require differentiation between viable and nonviable neurons. It is necessary to develop and document efficacious and safe techniques for reactivating idling neurons. The authors present a case study of a near drowning 12 years earlier. Areas of cortical hypometabolism were identified by using SPECT imaging in conjunction with hyperbaric oxygen therapy (HBOT). Delayed imaging after HBOT (1 hour, 1.5 atm abs) suggested viable but metabolically lethargic neurons. After HBOT (80 1-hour treatments, monoplace chamber, 1.5 atm abs), marked improvements in cognitive and motor functioning were demonstrated. The data support the hypothesis that idling neurons and ischemic penumbras, when given sufficient oxygen, are capable of reactivation. Thus, changes in tracer distribution after a single exposure to HBOT may be a good prognostic indicator of viable neurons. HBOT may be valuable not only in recovery from anoxic encephalopathy but also from other traumatic and nontraumatic dysfunctions of the central nervous system, including stroke. HBOT in conjunction with physical and rehabilitative therapy may help reactivated idling neurons to remain permanently active.

Reduction of rattlesnake-venom-induced myonecrosis in mice by hyperbaric oxygen therapy.

Hyperbaric oxygen therapy (HBOT) at 1, 2, and 2.75 atmospheres absolute (ATA) was used to treat rattlesnake (Crotalus atrox) venom-induced tissue damage and edema in thigh muscles of mice. Tissue damage was evaluated by double-blind histopathologic examination: tissue edema was determined by measuring tissue water content. A total of 10 intermittent exposures to oxygen over a period of 4 days at 2 and 2.75 ATA did not influence the resolution of venom-induced tissue edema, whereas tissue damage was significantly ameliorated as compared to air-treated envenomated controls. HBOT also promoted healing in the venom-injected mice as evidenced by the presence of regenerating muscle cells. It is concluded that HBOT may limit rattlesnake venom-induced myonecrosis and promote healing in a dose-response relationship without reducing venom-induced edema.

The etiology of multiple sclerosis: a new and extended vascular-ischemic model.

It is hypothesized that multiple sclerosis is a disease of the cerebro-vascular system. The basic defect is visualized as a wound in the CNS due to a focal hypertension of genetically susceptible vessels which results in vascular injury and the initiation of a series of biochemical and physiological events culminating in an ischemic hypoxia leading to demyelination and a secondary damaging process associated with the immune system.

The effect of allopurinol on oxygen-induced seizures in mice.

Prolonged exposure to hyperbaric oxygen causes central nervous system (CNS) oxygen toxicity manifested by grand mal seizures. The superoxide anion is believed to be a cause of tissue damage in CNS oxygen toxicity and it is proposed that xanthine oxidase activity is one of the prime sources of superoxide. Groups of mice were given equivalent doses of allopurinol, hypoxanthine, or saline, and exposed to five atmospheres absolute of oxygen. It was proposed that allopurinol, a xanthine oxidase inhibitor, would decrease the rate of superoxide formation thus delaying the onset of oxygen-induced seizures. It was further proposed that hypoxanthine would increase the rate of superoxide formation decreasing the preconvulsive latency. The data indicated that neither allopurinol nor hypoxanthine altered susceptibility to the CNS manifestations of oxygen toxicity. The results do not support the theory that xanthine oxidase is a prime source of superoxide anions in mouse brain.

Enhancement of cortical Na+,K+-ATPase by increased oxygen tensions: evidence of a new controlling mechanism.

This study describes the preliminary isolation of substances from beef brain cortex which are required to produce an oxygen-induced enhancing effect on Na, K-ATPase. Evidence is presented that at least 3 fractions--a heat stable, low molecular weight proteinaceous substance, a cholesterol rich, membranous component, and an as yet unidentified substance--are required to produce oxygen enhancement of Na, K-ATPase activity. These findings have specific ramifications in neurocellular physiology, especially as related to seizures.

The pectoralis major island flap for coverage in the upper extremity.

From July 1, 1978, to July 1, 1980, 26 patients required pedicle flap coverage for acute skin loss defects in the hand and upper extremity. Eighteen patients had groin or abdominal flap coverage, and the pectoralis major island flap (PMIF) was used in eight patients. The circumstances of injury were approximately the same in both groups, consisting of a gunshot wound or electrical injury in over half of the cases. The PMIF was selected more often in proximal and dorsal injuries of the forearm and wrist and in older patients. Two of 13 groin flaps sustained partial necrosis, but none of the abdominal or PMIF flaps necrosed. The principle advantages of the PMIF in these selected cases was fourfold: (1) an extremity placed in a less dependent, sling-like position, (2) mobility, (3) reliability, and (4) a complete inset into the defect. The chest wall donor site defect, however, must be given some consideration.

In vivo and in vitro induction of cytochrome P-450 synthesis in hyperoxia.

Exposure of dark- or light-adapted mice to 1--3 ATA oxygen for times ranging from 15 min to 4 h caused a progressive increase in P-450, which peaked and then decayed. The rate of decay appears to be independent of PO2. A linear, inverse relationship was noted between the PO2 in the range of 1--4 ATA and the duration of exposure needed to obtain maximum P-450 levels. Cytochrome P-450 was induced by hyperoxia in vitro in a suspension of hepatocytes, and this induction was prevented by inhibitors of transcription and translation and by disulfiram. Cytochrome P-450 induction is not a general phenomenon of stress, albeit physical restraint may decrease the level of P-450 induced. Induction was a specific effect of increased oxygen tensions and was not due to pressure per se. Neither equivalent pressures of compressed air in the in vivo experiments nor equivalent pressures of nitrogen in the in vitro experiments induced P-450. Induction in vivo was inhibited by disulfiram and metyrapone. Hyperoxia is the most rapid inducer of P-450 yet found, and this response may represent a protective mechanism against hyperoxia.

Interaction of increased pressures of oxygen and sulfonamides on the in vitro and in vivo growth of pathogenic bacteria.

The objective of these experiments was to determine whether synergism will occur between increased oxygen tensions and PABA-folic acid inhibitors in vitro and in vivo. Initial in vitro experiments indicated that PO2 greater than or equal to 2.2 ATA alone exerts marked growth-inhibitory (static) effects. Oxygen at 2.2 ATA decreased the minimal inhibitory concentrations (MIC) of sodium sulfisoxazole (NaS) fivefold and trimethoprim (TMP), a sulfonamide potentiator, twofold. At 3.2 ATA O2, there was a twenty-fivefold decrease in MIC of NaS and a tenfold decrease for TMP: cidal effects were also obtained. There is a PO2 dependent increase in effectiveness of the combination of NaS + TMP, including cidal effects, in situations where static effects were noted in absence of increased oxygen levels. Similar effects were not obtained with air pressure controls. In goldfish infected with Vibrio anquillarum, 3.2 ATA O2 in combination with NaS increased survival from 20% to 75%. Similar results were not obtained with air pressure controls. Trimethoprim was toxic to goldfish. We conclude that increased oxygen tensions synergize with NaS or TMP, or both, in vitro to decrease their MIC and to produce bactericidal effects where bacteriostatic effects are normally found: oxygen also synergizes with NaS in vivo to markedly increase survival of goldfish.

Pregnant mare serum and human chorionic gonadotropin stimulate ovarian delta5-3beta-hydroxysteroid dehydrogenase in aged mice.

Aged (12- to 14-month-old) estrous and diestrous C57BL mice exhibited lower histochemically demonstrable ovarian delta5-3beta-hydroxysteroid dehydrogenase (3beta-HSD) activity in thecal, luteal, and interstitial cells, and lower (P less than 0.01) ovarian 3beta-HSD concentration and total content than did young (3-month-old) estrous animals. Administration of pregnant mare serum (PMS, 10 IU subcutaneously), followed in 40 hours by human chorionic gonadotropin (HCG, 5 IU subcutaneously) or HCG (2 IU daily for 4 days) alone, restored luteal and interstitial 3beta-HSD in aged mice. Follicular, lutea, and interstitial 3beta-HSD activity was increased in aged mice by a single PMS injection (10 IU). The total ovarian dehydrogenase concentration was increased 100% in aged animals by PMS and/or HCG administration. Restoration of histochemically demonstrable ovarian 3beta-HSD and total enzyme content in aged mice by PMS and/or HCG indicates ovarian sensitivity to gonadotropin and subnormal tropic hormone stimulation of the ovary in situ.