Sympathetic influence on alveolar surface activity in hyperventilated dog

Hyperventilating IPPB, defined as intermittent positive-pressure breathing with a frequency of 32 beats/min and inspiratory pressure of 30 cmH2O, was administered for 14 h to open-chested anesthetized dogs in which nerves to one bronchus were operatively blocked. In the nerve-intact lungs, the lung stability index calculated from the pressure-volume relationship decreased with the duration of the hyperventilating IPPB (correlation coefficient r = -0.66, P less than 0.001), and atelectasis and hemorrhage appeared. In the nerve-blocked lungs, the index did not decrease during the 14 h of hyperventilating IPPB, and the appearance was almost normal. After pharmacologic sympathetic block with phenoxybenzamine, the lung stability index of both the operatively nerve-blocked lung and the nerve-intact lung was not decreased by hyperventilating IPPB. From these findings, we conclude that sympathetic block can protect pulmonary surface activity from the adverse effects of hyperventilating IPPB.

Partial purification and characterization of L-lactate dehydrogenase isozymes from sweet potato roots

Lactate dehydrogenase [L-lactate: NAD oxidoreductase, EC 1.1.1.27] was isolated from sweet potato root tissues. Two species of the enzyme (isozymes I and II) were separated by DE-52 cellulose column chromatography from healthy, cut, and black-rot diseased tissues. Isozymes I and II were purified from healthy and diseased tissues, respectively. Reduction of pyruvate by NADH with either isozyme I or II was inhibited by pyruvate at high concentrations, by NAD+ and by several mononucleotides. Isozyme I was inhibited by a lower concentration of adenine nucleotide than isozyme II, and Km for pyruvate was increased markedly at acidic pH in the case of isozyme I, but only slightly in the case of isozyme II. The molecular weights of both isozymes were determined to be 150,000 and they were found to be charge isomers by polyacrylamide gel electrophoresis. The enzyme activity increased in response to infection by black-rot fungus but decreased in response to cutting.

Macromolecular synthesis after a nutritional shift-up of Bacillus subtilis

Effects of amino acids of macromolecular synthesis in Bacillus subtilis were studied. Two mutants, CRK4001 and NIG45, that were selected as slow growers in rich media were proved to be useful to analyse early events occurring after addition of amino acids to exponentially growing cells in a glucose-salts medium (nutritional shift-up). In a wild type strain, the rate of stable RNA (sRNA: essentially ribosomal RNA) synthesis increased 2.3 fold shortly after the shift-up to the rate characteristic of the post-shift steady state growth. In contrast,sRNA synthesis in the mutant strains responded to the shift-up in two steps. Thus, shortly after the shift the rate of sRNA synthesis increased 2.2 fold as in the wild type but this increased level was maintained temporarily for 60 min and suddenly decreased to the post-shift steady state rate (1.4 fold increase). On the other hand, rates of DNA synthesis increased some 30 min after the shift directly to the post-shift steady state rates in all strains. Ratios of an origin to a terminus marker (purA/metB) began to increase exponentially to reach maximum values at 60 min after the shift, indicating that initiation of DNA replication occurred at frequencies characteristic of respective post-shift growth rates soon after the shift. These results revealed that the initial increase in the rate of sRNA synthesis and the frequency of initation of DNA replication after nutritional shift are not related to each other and are independently affected by amino acids. In concert with these findings, the increase in sRNA synthesis was not affected by inhibition of DNA synthesis for the first 60 min after the shift, while it was completely prevented by puromycin and choramphenicol. Protein synthesis for 10 min after the shift was sufficient to fully change the sRNA synthesis rate by amino acids.