Inhibition of Photosynthetic Oxygen Evolution in Thylakoids by Cyanide

Cyanide inhibition of oxygen evolution from isolated chloroplastswas accomplished by altering the thylakoid membrane properties(in addition to charge-screening) by high concentrations ofMg²⁺. The divalent cation facilitated the approach of the cyanideligand (pK = 9.4) to the water-splitting site. The additionof the divalent cation ionophore, A23187 [GenBank] , in the presence ofMg²⁺ enhanced the expression of cyanide inhibition of photosystemII-mediated O₂-evolution. Furthermore, electron transport partialreactions allowed the identification of the site of cyanideaction as being between the site of Tris-inhibition of electrontransport and the site of diphenylcarbazide donation on theoxidizing side of PS II. (Received October 25, 1982; Accepted December 29, 1982)     

MRI Findings of Otic and Sinus Barotrauma in Patients with Carbon Monoxide Poisoning during Hyperbaric Oxygen Therapy

Background and Purpose

To study the MRI findings of otic and sinus barotrauma in patients with carbon monoxide(CO) poisoning during hyperbaric oxygen (HBO) therapy and examine the discrepancies of otic and sinus abnormalities on MRI between barotrauma and acute otitis media with effusion.

Materials and Methods

Eighty patients with CO-poisoning diagnosed with otic and sinus barotrauma after HBO therapy were recruited. Brain MRI was performed to predict delayed encephalopathy. Over the same period, 88 patients with acute otitis media with effusion on MRI served as control. The abnormalities of the middle ear and paranasal sinuses on MRI were noted and were compared between groups. Nine patients with barotrauma were followed up by MRI.

Results

In the barotrauma group, 92.5% of patients had bilateral middle ear abnormalities on MRI, and 60% of patients had both middle ear cavity and mastoid cavity abnormalities on MRI in both ears. Both rates were higher than those in the control group (p = 0.000). In the two groups, most abnormalities on MRI were observed in the mastoid cavity. The rate of sinus abnormalities of barotrauma was 66.3%, which was higher than the 50% in the control group (p = 0.033). In the nine patients with barotrauma followed up by MRI, the otic barotrauma and sinus abnormalities had worsened in 2 patients and 5 patients, respectively.

Conclusion

MRI is able to depict the abnormalities of otic and sinus barotrauma in patients with CO-poisoning during HBO therapy and to differentiate these from acute otitis media with effusion.     

Oxygen Therapy for Spontaneous Pneumothorax

The rate of absorption of gas from a pneumothorax was studied in 12 patients breathing air and in 10 patients breathing air and a high concentration of oxygen alternately. The mean rate of absorption while breathing air was the same in both groups of patients. In the second group the rate consistently increased during periods of oxygen therapy and decreased again on breathing air. The mean rate of absorption increased fourfold during periods of oxygen therapy. This increase was most pronounced in patients with a large pneumothorax.