The cathartic colon: pathological findings and radiological/pathological correlation

Cathartic colon has been described radiologically, but the pathological characteristics have not been reported. The authors describe a case in which radiological/pathological correlation was possible, with emphasis on the pathology of the colon. The disease simulates chronic ulcerative colitis radiologically and pathologically.

Interrelation between glycosidic torsion, sugar pucker, and backbone conformation in 5'-beta-nucleotides. A 1H and 31P fast Fourier transform nuclear magnetic resonance investigation of the conformation of 8-aza-5'-beta-adenosine monophosphate and 8-aza-5'-beta-guanosine monophosphate

Hydrogen-1 and phosphorus-31 nuclear magnetic resonance spectra of 5'-AMP, 5'-GMP, 8-aza-5'-GMP, adenosine, 8-aza-adenosine, and guanosine were obtained at biological pH values at a concentration sufficiently low to obtain information regarding their intramolecular solution conformation. The spectra were analyzed by computer simulation. It is shown that all of the above nucleosides and nucleotides have a flexible molecular framework in aqueous solution, 5'-AMP and 5'-GMP showing preference for anti(2-E in equilibrium 3-E)gg-g'g' conformations and the 8-aza analogs showing preference for (syn in equilibrium anti)-(2E in equilibrium 3-E) - g/t-g'g' conformations. In addition, aza substitution causes increase in 3-E sugar populations and in the populations of g'/t' conformers. It is argued that in the 8-aza analogs repulsive electrostatic interactions would prevail between --N (see article) at the 8 position and the negatively charged phosphate group, if the molecule existed in the anti-gg orientation. Such electrostatic repulsions can be relieved by rotating the C(4')--C(5') bond from gg to g/t orientations as well as by torsional variation about the glycosidic linkage from anti to syn conformation. Rotation from anti to syn orientation, for steric and electrostatic reasons, necessitates a simultaneous rotation about the C(4')--C(5') bond from gg to g/t conformation. The observation that the 8-aza substitution in 5'-beta-purine nucleotides cause a depopulation of gg and anti conformers with corresponding increase in the population of g/t and syn orientation seems to support the above thesis. The finding that rotational variation about a bond such as C(4')--C(5') is accompanied by torsional variation about C(5')--O(5') and the glycosidic bonds, as well as changes in the endocyclic torsion angles of the ribose moiety, gives important insight into the engineering of nucleic acid components: even though they in general prefer certain conformations, there is enough flexibility present in their molecular framework, that the entire system can undergo conformational adjustment in response to a perturbation. A conformational basis for the antileukemic effects of 8-aza purines is proposed.

Pharmacological characterization of cardiac histamine receptors: sensitivity to H1-and H2-receptor agonists and antagonists

In the isolated guinea pig heart, histamine H1-receptor antagonists inhibit the histamine-induced negative dromotropic effect, but not the positive inotropic and chronotropic effects (Levi and Kuye, 1974, European J. Pharmacol. 27, 330). Burimamide, the H2-receptor antagonist, inhibits the positive chronotropic effect of histamine (Black et al., 1972, Nature 236, 385). In this study, the hypothesis that H1- and H2-receptors selectively mediate the various cardiac effects of histamine was tested: (a) by investigating the inhibition of cardiac histamine effects by burimamide; (b) by studying the cardiac effects of 2-methylhistamine (an H1-agonist) and 4-methylhistamine (an H2-agonist). Burimamide, as a function of concentration, inhibited the positive inotropic and chronotropic effects of histamine, whereas it attenuated the negative dromotropic effect of histamine at the higher concentration only. 4-Methylhistamine caused dose-dependent positive inotropic and chronotropic but not negative dromotropic effects; conversely, with 2-methylhistamine the negative dromotropic effect prevailed. Sinus tachycardia and slowing of atrioventricular conduction were also obtained in the guinea pig in vivo by the i.v. administration of histamine. Burimamide selectively antagonized the positive chronotropic effect, whereas promethazine (an H1-antagonist) selectively inhibited the negative dromotropic effect. These results substantiate the hypothesis that H2-receptors mediate the histamine-induced increase in rate and contractility, whereas H1-receptors mediate the slowing of atrioventricular conduction.

Sweet taste of water induced by artichoke (Cynara scolymus)

Exposure of the tongue to artichoke can make water taste sweet. Two major active components of artichoke are the salts of chlorogenic acid and cynarin. The sweetening of substances by temporarily modifying the tongue, rather than by adding a substance sweet in itself, may provide an alternative to currently used nonnutritive sweeteners.