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Report of the experimental UV absorbance behavior of the supercritical ethane-pyrazine system, the quantum-chemically determined structures for pyrazine and ethanes, the computed transition energies, predictions of the supercritical ethane densities and a two-dimensional computational probe of the pyrazine-ethane potential surface is illustrated. The combination of experiment and computation allows prediction of supercritical ethane bulk densities at which the pyrazine primary solvation shell contains an average of one, two, three, and four ethane molecules.

A new and improved synthesis cis,syn-o,o'-dibenzene was developed to obtain cis,syn-o,o'-dibenzene in larger amounts with improved purity. The formation of excited benzene in its singlet state in the photolysis of o,o'-dibenzenes, during the detection of benzene fluorescence, shows that these upconversions can also occur efficiently in the singlet manifold.

A new efficient anti-o,o'-dibenzene preparation has been prepared in three stages from cis-3,5-cyclohexadiene-1,2-diol. This enabled an extensive exploration of the chemistry of anti-dibenzenes. The thermal reversion of anti-o,o'-dibenzene to benzene was studied in three different solvents.

Research was conducted to show that ammonia profoundly inhibits cyclic nucleotide-regulated Cl- secretion in model human T84 intestinal epithelia but does not impair the secretory response to the Ca2+ agonist carbachol. The dichotomy was explored using transepithelial transport, fura 2/fluorescence and radioisotropic efflux techniques. Results show that the secretory response to the Ca2+-adenosinetriphosphatase inhibitor thapsigargin is unaffected by ammonia suggesting that an increase in intracellular Ca2+ stimulates secretory pathways insensitive to ammonia.

The Cl- secretory apparatus of T84 cell lines were analyzed after the administration of cytochalasin D, latrunculin A and jasplakinolide to determine the effects of cytochalasin D on cytoskeletal microfilaments. Adenosine 3',5'- cyclic monophosphate-mediated short-circuit current and basolateral Na-K-2Cl cotransport were inhibited in T84 cell lines by jasplakinolide. Furthermore, jasplakinolide enhanced actin stabilization while cytochalasin D mediated the disassembly of the cytoskeleton by activating Na-K-2Cl cotransport.

Song, Jaekyung Cecilia, Bruce J. Hrnjez, Omid C. Farokhzad, and Jeffrey B. Matthews. PKC-[Epsilon] regulates basolateral endocytosis in human T84 intestinal epithelia: role of F-actin and MARCKS. Am. J. Physiol. 277 (Cell Physiol. 46): C1239-C1249, 1999.--Protein kinase C (PKC) and the actin cytoskeleton are critical effectors of membrane trafficking in mammalian cells. In polarized epithelia, the role of these factors in endocytic events at either the apical or basolateral membrane is poorly defined. In the present study, phorbol 12-myristate 13-acetate (PMA) and other activators of PKC selectively enhanced basolateral but not apical fluid-phase endocytosis in human T84 intestinal epithelia. Stimulation of basolateral endocytosis was blocked by the conventional and novel PKC inhibitor Go-6850, but not the conventional PKC inhibitor Go-6976, and correlated with translocation of the novel PKC isoform PKC-[Epsilon]. PMA treatment induced remodeling of basolateral F-actin. The actin disassembler cytochalasin D stimulated basolateral endocytosis and enhanced stimulation of endocytosis by PMA, whereas PMA-stimulated endocytosis was blocked by the F-actin stabilizers phalloidin and jasplakinolide. PMA induced membrane-to-cytosol redistribution of the F-actin cross-linking protein myristoylated alanine-rich C kinase substrate (MARCKS). Cytochalasin D also induced MARCKS translocation and enhanced PMA-stimulated translocation of MARCKS. A myristoylated peptide corresponding to the phosphorylation site domain of MARCKS inhibited both MARCKS translocation and PMA stimulation of endocytosis. MARCKS translocation was inhibited by Go-6850 but not Go-6976. The results suggest that a novel PKC isoform, likely PKC-[Epsilon], stimulates basolateral endocytosis in model epithelia by a mechanism that involves F-actin and MARCKS. cytoskeleton; microfilaments; pinocytosis; protein kinase C isoforms; cell polarity; carbachol; diacylglycerol

Hrnjez, Bruce J., Jaekyung C. Song, Madhu Prasad, Julio M. Mayol, and Jeffrey B. Matthews. Ammonia blockade of intestinal epithelial [K.sup.+] conductance. Am. J. Physiol. 277 (Gastrointest. Liver Physiol. 40): G521-G532, 1999.--Ammonia profoundly inhibits cAMP-dependent [Cl.sup.-] secretion in model T84 human intestinal crypt epithelia. Because colonic lumen concentrations of ammonia are high (10-70 mM), ammonia may be a novel regulator of secretory diarrheal responsiveness. We defined the target of ammonia action by structure-function analysis with a series of primary amines (ammonia, methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, and octylamine) that vary principally in size and lipid solubilities. The amine concentrations required for 50% inhibition of C[1.sup.-] secretion in intact monolayers and 50% inhibition of outward [K.sup.+] current ([I.sub.K]) in apically permeabilized monolayers vs. the logs of the respective amine partition coefficients give two plots that are strikingly similar in character. Half-maximal inhibition of short-circuit current ([I.sub.sc]) by ammonia was seen at 6 mM and for [I.sub.K] at 4 mM; half-maximal inhibition for octylamine was 0.24 mM and 0.19 mM for [I.sub.sc] and [I.sub.K], respectively. The preferentially water-soluble hydrophilic amines (ammonia, methylamine, ethylamine) increase in blocking ability with decreasing size and lipophilicity. Conversely, the preferentially lipid-soluble hydrophobic (propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine) amines increase in blocking ability with increasing size and lipophilicity. Ammonia does not affect isolated apical [Cl.sup.-] conductance; amine-induced changes in cytosolic and endosomal pH do not correlate with secretory inhibition. We propose that ammonia in its protonated ammonium form [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] inhibits cAMP-dependent [Cl.sup.-] secretion in T84 monolayers by blocking basolateral [K.sup.+] channels. ammonia; chloride; diarrhea; T84 cells; pH