Effects of Fildes enrichment on antibiotic susceptibility testing of Haemophilus influenzae in the Autobac

The results of this investigation showed that the Autobac could be used to determine the susceptibility of Haemophilus influenzae to ampicillin, chloramphenicol, and tetracycline when eugonic broth was supplemented with 1.5% Fildes enrichment. An excellent correlation was obtained between the susceptibilities as determined by the agar dilution minimal inhibitory concentration method and the Autobac. For ampicillin all H. influenzae isolates with minimal inhibitory concentrations of </=1 mug/ml had light scattering indexes of >/=0.60. Those isolates with minimal inhibitory concentrations of >/=4 mug/ml had light scattering indexes of </=0.49. For chloramphenicol and tetracycline all isolates had minimal inhibitory concentrations of </=1 mug/ml and light scattering indexes of >/=0.71.

Positron ranges obtained from biomedically important positron-emitting radionuclides

Positron ranges were obtained experimentally for several nuclides used in scintigraphic imaging. The nuclides examined were 13C, 13N, 15O, 18F, 68Ga, and 82Rb. The results are discussed with respect to the ultimate spatial resolution obrained in a scintigraphic image.

A novel diazonium-sulfhydryl reaction in the inactivation of yeast alcohol dehydrogenase by diazotized 3-aminopyridine adenine dinucleotide

Diazotized 3-aminopyridine adenine dinucleotide has been found to modify four sulfhydryl groups per molecule of enzyme during the complete inactivation of yeast alcohol dehydrogenase. The reaction of sulfhydryl groups was indicated by titration studies with 5,5-dithiobis(2-nitrobenzoic acid) as well as isolation and quantitation of the cysteinyl derivative released by acid hydrolysis of the modified enzyme. The cysteinyl derivative was identified as S-(3-pyridyl)cysteine. Authentic S-(3-pyridyl)cystein was synthesized and structurally characterized for these studies. Diazonium-sulfhydryl reactions were demonstrated for a number of diazonium derivatives with cysteine, homocysteine, glutathione, and mercaptoethanol at 0-4 degrees and neutral pH. Second order rate constants were determined in reactions of these sulfhydryl compounds with diazotized 1-methyl-3-aminopyridinium chloride, diazotized 3-aminopyridine adenine dinucleotide, and diazotized 3-aminopyridine adenine dinucleotide phosphate.