Plasma secretin and gastrin responses to a meat meal and duodenal acidification in dogs

In five conscious dogs with gastric fistula and two duodenal cannulas, plasma RIA secretin and gastrin levels were determined in response to 1) infusion of 0.1 N HCl in the proximal duodenal cannula, 2) ingestion of a meal, and 3) intraduodenal infusion of 0.1 N HCl following ingestion of a meal. Significant increases in plasma RIA secretin levels occurred during duodenal acidification. However, no significant change occurred in the secretin levels after ingestion of a meal, whereas significant increase in plasma gastrin level was observed. Postprandial duodenal pH remained above 4.5 for 3 h.

Artifacts in ultracentrifugal estimation of aqueous fatty acid concentration

Ultracentrifugation for determination of isotropic concentrations of fatty acids is widely used. However, several artifacts, which would affect the isotropic concentration, could occur if care is not taken. These include sedimentation of micelles, incomplete flotation of unsolubilized oil, and uptake of labeled fatty acid by the walls of centrifuge tubes. The first artifact can be overcome by sampling large volumes from the ultracentrifuged sample, and the second by ultracentrifugation for long periods; a force-duration of 7.2 X 10(7) g-min is suitable. The third artifact cannot be eliminated but may be made constant if the duration of exposure of lipid mixtures to centrifuge tubes is kept constant.

Invitro formation of assimilatory reduced nicotinamide adenine dinucleotide phosphate: nitrate reductase from a Neurospora mutant and a component of molybdenum-enzymes

An active Neurospora-like assimilatory NADPH-nitrate reductase (EC 1.6.6.2), which can be formed in vitro by incubation of extracts of nitrate-induced Neurospora crassa mutant nit-1 with extracts of (a) certain other nonallelic nitrate reductase mutants, (b) uninduced wild type, or (c) xanthine oxidizing and liver aldehyde-oxidase systems was also formed by combination of the nit-1 extract with other acid-treated enzymes known to contain molybdenum. These molybdenum enzymes included (a) nitrogenase, or its molybdenum-iron protein, from Clostridium, Azotobacter, and soybeannodule bacteroids, (b) bovine liver sulfite oxidase, (c) respiratory formate-nitrate reductase from Escherichia coli, (d) NADH-nitrate reductase from foxtail grass (Setaria faberii), and (e) FADH(2)- and reduced methyl viologennitrate reductase preparations from certain Neurospora mutants. Several molybdenum-amino-acid complexes, as possible catalytic models of nitrogenase, were inactive (as were some previously tested 20 nonmolybdenum enzymes) in place of the acid-treated molybdenum-containing enzymes. The results imply the existence of a molybdenum-containing component shared by the known molybdenum-enzymes.

Loss of lipid to plastic tubing

14C-labeled oleic acid and (3)H-labeled monoether in a bile salt solution were perfused through three types of plastic tubing. Large proportions of lipid were lost to the walls of silicone rubber and polyvinyl chloride tubes. The major portion of the lipid lost was recoverable only when chloroform-methanol was perfused through the tubings. On the other hand, very little lipid was lost to the wall of polyethylene tubing. Polyethylene tubing should therefore be used in perfusion studies involving lipid-soluble compounds.