Theoretical models are used to study pH-dependent equilibria of 2,4-diamino-5-phenylthiazole tautomer molecules in water. A complete screening of semiempirical SCF multiple minimums of hypersurfaces, corresponding to several solute-water supermolecules, has been made. Multiple minimum hypersurface searching confirms experimental NMR results indicating that the native diamine tautomer predominates in aqueous neutral and basic media. This tautomeric structure, protonated either in N3 and N4, also predominates in aqueous acid media with a minor presence of a protonated monoimine tautomer, in agreement with 1 H NMR results in D 2 O. High-level ab initio SCF MO of the main structures, where solvent reaction field effects are taken into account with a dielectric constant equivalent to that of water, predict a nonconjugated protonated monoimine tautomer in nonprotic solvents, according to 1 H NMR data in polar aprotic solvents. Calculated electron excitation patterns of hydrated species in water agreed with the experimental UV spectra at different pH values. The quantum chemical procedures for calculating total energies and frontier orbital eigenvalues in local minimum geometries of the relevant supermolecules provide an appropriate model for comparisons of theoretical results with experimental facts in the case of analytical voltametry. The frontier orbital eigenvalues of the most populated minimums discard the appearance of electroanalytic signals in the case of acidic samples because of the similarity of the predicted values for all protonated isomers and water. Experimental measurements confirm the oxidative character of electroanalytic signals.

Pepsinogen and HCl secretion in the amphibian stomach are performed by a single cell type, the oxyntopeptic cell. These functions were studied in gastric mucosae of toads (Bufo marinus) mounted in Ussing-type chambers. HCl and peptic activity of luminal fluid were measured by titration and proteolysis of albumin, respectively. Distribution of pepsinogen in the gastric mucosa was heterogeneous, activity being highest in the proximal part of the stomach. Zymogen granules in the oxyntopeptic cell were more abundant in the deeper cells of the glands and in the fundus. On stimulation, the granules were released into the lumen of the glands by exocytosis. Histamine, forskolin, or carbachol alone each induced an increase in HCl and pepsinogen secretion. Carbachol after maximal histamine or forskolin stimulation produced an extra increase in both secretions that was greater for pepsinogen response. Similarly, joint addition of carbachol and histamine was more potent than histamine alone for both parameters; however, the effect was greater on pepsinogen release. Pretreatment with cimetidine blocked HCl and pepsinogen responses to carbachol but did not affect responses to forskolin. Addition of omeprazole to forskolin-stimulated mucosae uncoupled the two secretions, inducing a total inhibition of HCl secretion with a slight reduction in pepsinogen secretion. Thus pepsinogen release, similar to HCl secretion, is sensitive to cAMP and Ca(2+)-dependent secretagogues. However, the action of Ca2+ would require the previous elevation of cAMP induced by the different secretagogues. In such a case, the increase in intracellular Ca2+ would result in a nonparallel activation of the two secretions.

The department of Antioquia, Colombia, lies in the northwestern corner of South America and provides a biogeographical link among divergent faunas, including Caribbean, Andean, Pacific and Amazonian. Information about the distribution of biodiversity in this area is of relevance for academic, practical and social purposes. This data paper describes the dataset containing all bird specimens deposited in the Colección de Ciencias Naturales del Museo Universitario de la Universidad de Antioquia (MUA). We curated all the information associated with the bird specimens, including the georeferences and taxonomy, and published the database through the Global Biodiversity Information Facility network. During this process we checked the species identification and existing georeferences and completed the information when possible. The collection holds 663 bird specimens collected between 1940 and 2011. Even though most specimens are from Antioquia (70%), the collection includes material from several other departments and one specimen from the United States. The collection holds specimens from three endemic and endangered species (Coeligena orina, Diglossa gloriossisima, and Hypopirrhus pyrohipogaster), and includes localities poorly represented in other collections. The information contained in the collection has been used for biodiversity modeling, conservation planning and management, and we expect to further facilitate these activities by making it publicly available.