Effect of heme on Bacteroides distasonis catalase and aerotolerance.

Parallel increases in intracellular catalase activity and resistance to extracellular H2O2 and to hyperbaric O2 toxicity were observed when Bacteroides distasonis VPI 4243 (ATCC 8503, type strain) was grown in either complex or defined medium containing graded amounts of hemin. Virtually all of the cells with high catalase activity (greater than 200 U/mg) remained viable upon exposure at 37 degrees C to 100-lb/in2 O2 on agar surfaces for 1 h, whereas low-catalase cells (less than 10 U/mg) lost 1.2 log units of viable cells during that treatment. Upon exposure to 500 microM H2O2, high-catalase cells lost 0.4 log units of the initial viable colonies during the same period in which low-catalase cells lost 3 log units of viable cells. The superoxide dismutase activity was the same in each test culture. These data support the role of intracellular catalase in protecting B. distasonis from oxidative damage resulting from hyperbaric oxygenation or H2O2 exposure. Catalase activity elicited by adding hemin to cells grown previously in medium lacking hemin was inhibited only 40% by prior incubation of the cells with chloramphenicol (30 micrograms/ml) and only 22% with rifampin (5 micrograms/ml). A model which is consistent with these data involves the production of an apocatalase in cells grown in low-hemin medium. Addition of hemin to the cells would result in a rapid chloramphenicolor rifampin-insensitive stimulation of catalase activity followed by further de novo biosynthesis of catalase.

Continuous speech recognition in MR imaging reporting: advantages, disadvantages, and impact.

OBJECTIVE: Our objective was to describe our experience with a commercially available continuous speech recognition system, highlighting the advantages, disadvantages, and costs compared with those of conventional transcription for MR imaging reports. MATERIALS AND METHODS: Data from 5072 reports generated in our MR imaging section during a 9-month period after the implementation of a commercial continuous speech recognition system were compared with 4552 reports produced during the same period 1 year earlier. Information pertaining to the use of continuous speech recognition, report turnaround time, word recognition rate, report appearance, and equipment costs was collected. RESULTS: After its system installation, continuous speech recognition was used to dictate 81.8% of all reports. The mean report turnaround time decreased from 87.8 to 43.6 hr, and report availability at 24 hr increased from 10.5% to 62.5%. The system was found to have an average word recognition accuracy of 92.7% for spontaneous dictation. Mean report length declined from 95 to 60 words, with an increase in spacing errors from 0.3 to 8.0 per 1000 words and a decrease in spelling errors from 3.0 to 0.8 per 1000 words. Initial hardware and software costs were approximately $10,000, compared with a yearly cost of $12,000 for human transcription. CONCLUSION: Although the technology is still evolving and was evaluated in its earliest implementation stages, continuous speech recognition nonetheless markedly improved report turnaround time and proved cost-effective.