Reaction of rats to the effect of hyperbaric oxygenation after preliminary adaptation to hypoxia

Preliminary adaptation of rats to hypoxia in the regimen exceeding the resistance to many stress agents not only produced no protective effect in response to the action of increased oxygen pressure (IOP) up to 6 kg/cm2, but, on the contrary, decreased the organism resistance. Thus, the time of occurrence of convulsions in the adapted rats was shortened, particularly when IOP acted 24 or 48 hours after the termination of training to hypoxia; this effect was somewhat weaker in experiments conducted in 3 to 4 days. Reactions became completely normal one month after the termination of training to hypoxia. Possible causes of the phenomena detected are discussed.     

Antioxidant status in humans after exposure to hyperbaric oxygen.

Hyperbaric oxygen (HBO) treatment (i.e., exposure to 100% oxygen at a pressure of 2.5 atmosphere absolute (ATA) for a total of 3 x 20 min periods) of human subjects induced DNA damage in the alkaline comet assay with leukocytes and protected against the DNA damaging effects of subsequent in vivo HBO exposures. Furthermore, blood taken 24 h after the first HBO was well protected against the in vitro induction of genotoxic effects by hydrogen peroxide. To investigate the mechanisms which led to this apparent adaptive response, we determined the antioxidant status of blood from subjects before and after HBO. We did not find differences in the plasma concentrations of the antioxidant vitamins A, C and E after HBO treatment. HBO had also no effect on the 'antioxidant power' of the plasma as measured with the FRAP-assay or on the concentration of reduced glutathione determined in the plasma or in lymphocytes. Red cell concentrate activities of superoxide dismutase, catalase, glutathione peroxidase were not influenced by HBO. In contrast, synthesis of the heat shock protein HSP70 which has been implicated to play an important role in cellular protection against oxidative stress, was significantly induced in lymphocytes after a single HBO treatment. To investigate whether intake of antioxidants may protect against HBO-induced DNA damage, we supplemented subjects with vitamin E (800 mg for 7 days) or with N-acetylcysteine (400 mg, 1 h before the HBO treatment). However, these supplementations did not influence the induction of DNA damage by HBO.     

Potentiating the regional effect of hyperbaric oxygenation in Raynaud's phenomenon]

A usual method of hyperbaric oxygenation is insufficiently effective at the late stages of Raynaud's phenomenon. A new "chamber-in-chamber" method of HBO permits essentially improving the results at these stages. Two versions of the new method should be used, each for its own indications. Intermittent pneumo-compression without rarefaction in the small chamber is good for "functional" Raynaud's phenomenon, whereas in "organic" Raynaud's phenomenon both intermittent compression and rarefaction are necessary.     

Erythrocyte antioxidant enzymes in multiple sclerosis and the effect of hyperbaric oxygen

The activities of catalase, glutathione peroxidase, and glutathione reductase, were not significantly different from normal whereas that of superoxide dismutase was decreased (P<0.05) in erythrocytes from patients with multiple sclerosis. Assay of the lipid peroxidation product, malondialdehyde, after incubation of erythrocytes with 10 mM H₂O₂ under carefully controlled conditions (peroxide stress test) demonstrated that MS erythrocytes are significantly (P<0.001) less susceptible to H₂O₂-induced lipid peroxidation in vitro. This finding suggests that the level of an endogenous antioxidant, possibly vitamin E, may be elevated in MS red cells. After treatment with hyperbaric O₂, the activity of MS erythrocyte catalase is significantly (P<0.01) elevated by 2–6-fold.     

The role of antioxidant nutrients in preventing hyperbaric oxygen damage to the retina

Vitamin E and selenium play essential roles in preventing in vivo lipid peroxidation and free radical damage. Hyperbaric oxygen (HBO) treatment adversely affected the electroretinograms (ERGs) of rats fed a diet deficient in both vitamin E and selenium (the basal or B diet) or a diet deficient in vitamin E alone (B + Se diet). After 4 weeks of HBO treatment (3.0 ATA or 100% oxygen, 1.5 hours per day, 5 day/week) rats fed the B diet deficient in vitamin E and selenium for 6 weeks showed decreased (p less than 0.05) a-wave amplitudes, 85 +/- 9 microvolts (microV), n = 11, compared with a-waves recorded (150 +/- 10 microV, n = 21) for age matched rats fed an identical diet for 6 weeks but not treated with HBO. After 15 weeks of HBO treatment, rats fed the B + Se diet deficient in vitamin E alone showed decreased (p less than 0.01) a-wave (61 +/- 9 microV, n = 4) and b-wave (253 +/- 23 microV, n = 4) amplitudes compared with a-wave (115 +/- 7 microV, n = 4) and b-wave amplitudes (450 +/- 35 microV, n = 4) for age matched rats fed the same diet but not treated with HBO. Decreased a- or b-wave amplitudes provide evidence of retinal damage. Rats fed a diet supplemented with vitamin E and selenium or vitamin E alone showed no decreases in either a- or b-wave amplitudes after 15 weeks of HBO treatment.     

微量注射抗TGFβ—1抗体对爪蟾发育的影响

In order to testify the function of the TGF beta related protein, we microinjected the antibodies against the TGF beta-1 to one blastomere of two-cell stage embryos. Dosages of antibodies injected were 24-36 ng, 12 -18 ng, 6-9 ng and 1.5-2.25 ng. Malformed embryos with exposed yolk mass were produced. They were designated as YE-1, YE-2 and YE-3 according to the degree of malformation which was found to be related to the dosage of antibodies injected to the blastomere. These malformed embryos could normally develop to blastula, but the yolk mass was exposed on the injection half during gastrulation. In the group with the highest dosage, the most seriously affected embryos belong to the YE-1. For most of them, no muscle tissue could be found from head to tail in the injection half, the development of mesoderm seemed to be thoroughly inhibited. YE-2 was the group with decreased dosage, small block of muscle tissue was usually observed in the injection half. YE-3 was the least affected group with the injection half containing blocks of muscle tissue similar to that of the non-injection half. The different groups of malformations seemed to be related to the degree and range of interference on gastrulation. In the group with highest dosage, the gastrulation of the entire injection half seemed to be prohibited, and YE-1 was produced. In the groups with lower dosages, only part of injection half was interfered, and YE-3 v and YE-3 d were resulted. From the results mentioned above, we concluded that TGF beta-related protein are not only present in the early embryos of Xenopus laevis, but also may be concerned with mesoderm induction.     

The effect of trifluoperazine on maturation of Xenopus laevis oocytes

Full grown Xenopus oocytes were incubated with trifluoperazine (TFP) or injected with TFP. Incubation of oocytes in TFP resulted in normal-appearing meiotic maturation, as judged by the presence of the white spot and the absence of the germinal vesicle. Cortical granule breakdown in TFP-incubated oocytes was not normal. Abnormal cortical granule breakdown was also observed when progesterone-maturated oocytes were activated in the presence of TFP. Oocytes microinjected with TFP and incubated with progesterone appeared to mature in a normal manner, as judged by the absence of the germinal vesicle; these underwent cortical granule breakdown following activation, but frequently lacked the white spot. Oocytes microinjected with TFP did not mature in the absence of progesterone. We conclude that incubation, although not microinjection, of oocytes with TFP induces essentially normal resumption of meiotic maturation.     

The effect of hyperbaric oxygenation on rat somatic and generative cells

The effect of higher oxygen pressures (0.3 MPa, 5 sessions 1 h each daily) on induction of chromosomal aberrations in somatic cells and germinal tissues of rat males has been studied. Appearance of aberrations in bone marrow cells after HBO was recorded for 3 months, in cells of eye cornea epithelium--during 3 weeks after the end of sessions. Chromosome rearrangements in the first meiotic division were detected only 90 days after sessions. HBO affects neither functional nor morphological conditions of gonads and induces no dominant lethals. It is suggested that mutagenesis in bone marrow cells is an adaptive process, preventing mutagenic consequences of HBO in the cells of germinal tissue.     

Response of antioxidant enzymes to intermittent and continuous hyperbaric oxygen

Rats and guinea pigs were exposed to O2 at 2.8 ATA (HBO) delivered either continuously or intermittently (repeated cycles of 10 min of 100% O2 followed by 2.5 min of air). The O2 time required to produce convulsions and death was increased significantly in both species by intermittency. To determine whether changes in brain and lung superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSHPx) correlated with the observed tolerance, enzyme activities were measured after short or long HBO exposures. For each exposure duration, one group received continuous and one intermittent HBO; O2 times were matched. HBO had marked effects on these enzymes: lung SOD increased (guinea pigs 47%, rats 88%) and CAT and GSHPx activities decreased (33%) in brain and lung. No differences were seen in lung GSHPx or brain CAT in rats or brain SOD in either species. In guinea pigs, but less so in rats, the observed changes in activity were usually modulated by intermittency. Increases in hematocrit, organ protein, and lung DNA, which may also reflect ongoing oxidative damage, were also slowed with intermittency in guinea pigs. Intermittency benefited both species by postponing gross symptoms of toxicity, but its modulation of changes in enzyme activities and other biochemical variables was more pronounced in guinea pigs than in rats, suggesting that there are additional mechanisms for tolerance.     

The effect of hyperbaric oxygen treatment on aspiration pneumonia

We have studied whether hyperbaric oxygen (HBO) prevents different pulmonary aspiration materials-induced lung injury in rats. The experiments were designed in 60 Sprague-Dawley rats, ranging in weight from 250 to 300 g, randomly allotted into one of six groups (n = 10): saline control, Biosorb Energy Plus (BIO), hydrochloric acid (HCl), saline + HBO treated, BIO + HBO treated, and HCl + HBO treated. Saline, BIO, HCl were injected into the lungs in a volume of 2 ml/kg. A total of seven HBO sessions were performed at 2,4 atm 100% oxygen for 90 min at 6-h intervals. Seven days later, rats were sacrificed, and both lungs in all groups were examined biochemically and histopathologically. Our findings show that HBO inhibits the inflammatory response reducing significantly (P < 0.05) peribronchial inflammatory cell infiltration, alveolar septal infiltration, alveolar edema, alveolar exudate, alveolar histiocytes, interstitial fibrosis, granuloma, and necrosis formation in different pulmonary aspiration models. Pulmonar aspiration significantly increased the tissue HP content, malondialdehyde (MDA) levels and decreased (P < 0.05) the antioxidant enzyme (SOD, GSH-Px) activities. HBO treatment significantly (P < 0.05) decreased the elevated tissue HP content, and MDA levels and prevented inhibition of SOD, and GSH-Px (P < 0.05) enzymes in the tissues. Furthermore, there is a significant reduction in the activity of inducible nitric oxide synthase, TUNEL and arise in the expression of surfactant protein D in lung tissue of different pulmonary aspiration models with HBO therapy. It was concluded that HBO treatment might be beneficial in lung injury, therefore, shows potential for clinical use.     

The effect of hyperbaric oxygen on metabolism of the GABA shunt

Abstract— —The GABA-α-ketoglutarate transaminase pathway provides, in the brain, an alternative route for the conversion of α-ketoglutarate to succinate. In vitro experiments with rat brain homogenates and either [¹⁴C]GABA or [¹⁴C]α-ketoglutarate showed the percentage metabolism via the transaminase pathway to be about 17 per cent in air and 10 per cent oxygen at high pressure. Since the transaminase shunt was more sensitive to hyperbaric oxygen than the direct pathway, these results do not support the hypothesis of an alternative route operating under conditions of oxygen poisoning.