Portal Pressure Regulation following Kupffer Cell Activation: Control of Prostaglandin Production by Heme Oxygenases

Background: Portal pressure (PP) results from the interplay ofvasoconstrictors and vasodilators. Recently, we have shown that Kupffercell (KC) activation increases PP. Aims: The role of the vasodilatingcompounds nitric oxide (NO) and carbon monoxide (CO) was studied. Thehypothesis of the present study was that these vasodilators counteractthe PP increase following KC activation. Methods: Livers of ratsweighing 180-200 g were isolated and perfused. KCs were activated byzymosan A (cell wall particles from yeast; 150 mu g/ml). The effects ofNO and guanylate cyclase (GC) were evaluated by the NO synthaseinhibitor N-G-nitro-L-arginine methylester (L-NAME; 0.3 m M, and the GCinhibitor 4H-8-bromo-1,2,4-oxadiazolo(3,4-d)benz(b)(1,4)oxazin-1-one(NS-2028, 1.0 mu M); the effects of the heme oxygenase (HO) derivedcompound CO were evaluated by direct administration of CO or inhibitionof HO by zinc protoporphyrin IX (ZnPP IX, 1.0 mu M). Results: Inisolated perfused rat livers, administration of L-NAME or NS-2028further raised PP increase following KC activation. This effect could bereduced by the cGMP analogue 8-Br-cGMP. Inhibition of HO caused markedamplification of PP increase in zymosan-treated organs. CO preventedthis PP increase cGMP independently. Interestingly, KC activation andsimultaneous inhibition of HO augmented the production of prostaglandinsD-2 and F-2 alpha and of thromboxane A(2). Accordingly, indomethacinblunted the increase of PP in zymosan/ZnPP-treated livers. Conclusions:NO restricts the initial PP increase after KC activation by GC-mediatedcGMP. CO from heme degradation limits the increase of PP after KCactivation eicosanoid dependently, but cGMP independently

Thermal Conversion of Guanylurea Dicyanamide into Graphitic Carbon Nitride via Prototype CNx Precursors

Guanylurea dicyanamide, [(H2N)C(-O)NHC(NH2)2][N(CN)2], has been synthesized by ion exchange reaction in aqueous solution and structurally characterized by single-crystal X-ray diffraction (C2/c, a = 2249.0(5) pm, b = 483.9(1) pm, c = 1382.4(3) pm, β = 99.49(3)°, V = 1483.8(5) × 106 pm3, T = 130 K). The thermal behavior of the molecular salt has been studied by thermal analysis, temperature-programmed X-ray powder diffraction, FTIR spectroscopy, and mass spectrometry between room temperature and 823 K. The results were interpreted on a molecular level in terms of a sequence of thermally induced addition, cyclization, and elimination reactions. As a consequence, melamine (2,4,6-triamino-1,3,5-triazine) is formed with concomitant loss of HNCO. Further condensation of melamine yields the prototypic CNx precursor melem (2,6,10-triamino-s-heptazine, C6N7(NH2)3), which alongside varying amounts of directly formed CNxHy material transforms into layered CNxHy phases without significant integration of oxygen into the core framework owing to the evaporation of HNCO. Thus, further evidence can be added to melamine and its condensation product melem acting as “key intermediates” in the synthetic pathway toward graphitic CNxHy materials, whose exact constitution is still a point at issue. Due to the characteristic formation process and hydrogen content a close relationship with the polymer melon is evident. In particular, the thermal transformation of guanylurea dicyanamide clearly demonstrates that the formation of volatile compounds such as HNCO during thermal decomposition may render a large variety of previously not considered molecular compounds suitable CNx precursors despite the presence of oxygen in the starting material

Conventional methods fail to measure cp(omega) of glass-forming liquids

The specific heat is frequency dependent in highly viscous liquids. By solving the full one-dimensional thermo-viscoelastic problem analytically it is shown that, because of thermal expansion and the fact that mechanical stresses relax on the same time scale as the enthalpy relaxes, the plane thermal-wave method does not measure the isobaric frequency-dependent specific heat c_p(omega). This method rather measures a "longitudinal" frequency-dependent specific heat, a quantity defined and detailed here that is in-between c_p(omega) and c_v(omega). This result means that no wide-frequency measurements of c_p(omega) on liquids approaching the calorimetric glass transition exist. We briefly discuss consequences for experiment

Thermal Diffusion and Quench Propagation in YBCO Pancake Coils Wound with ZnO-and Mylar Insulations

The thermal diffusion properties of several different kinds of YBCO insulations and the quench properties of pancake coils made using these insulations were studied. Insulations investigated include Nomex, Kapton, and Mylar, as well as insulations based on ZnO, Zn2GeO4, and ZnO-Cu. Initially, short stacks of YBCO conductors with interlayer insulation, epoxy, and a central heater strip were made and later measured for thermal conductivity in liquid nitrogen. Subsequently, three different pancake coils were made. The first two were smaller, each using one meter total of YBCO tape present as four turns around a G-10 former. One of these smaller coils used Mylar insulation co-wound with the YBCO tape, the other used YBCO tape onto which ZnO based insulation had been deposited. One larger coil was made which used 12 total meters of ZnO-insulated tape and had 45 turns. The results for all short sample and coil thermal conductivities were ~1-3 Wm-1K-1. Finally, quench propagation velocity measurements were performed on the coils (77 K, self field) by applying a DC current and then using a heater pulse to initiate a quench. Normal zone propagation velocity (NZP) values were obtained for the coils both in the radial direction and in the azimuthal direction. Radial NZP values (0.05-0.7 mm/s) were two orders of magnitude lower than axial values (~14-17 mm/s). Nevertheless, the quenches were generally seen to propagate radially within the coils, in the sense that any given layer in the coil is driven normal by the layer underneath it.Comment: 58 pages, 5 tables, 16 fig

A New Crocodylian from the Late Maastrichtian of Spain: Implications for the Initial Radiation of Crocodyloids

The earliest crocodylians are known primarily from the Late Cretaceous of North America and Europe. The representatives of Gavialoidea and Alligatoroidea are known in the Late Cretaceous of both continents, yet the biogeographic origins of Crocodyloidea are poorly understood. Up to now, only one representative of this clade has been known from the Late Cretaceous, the basal crocodyloid Prodiplocynodon from the Maastrichtian of North America.The fossil studied is a skull collected from sandstones in the lower part of the Tremp Formation, in Chron C30n, dated at -67.6 to 65.5 Ma (late Maastrichtian), in Arén (Huesca, Spain). It is located in a continuous section that contains the K/P boundary, in which the dinosaur faunas closest to the K/P boundary in Europe have been described, including Arenysaurus ardevoli and Blasisaurus canudoi. Phylogenetic analysis places the new taxon, Arenysuchus gascabadiolorum, at the base of Crocodyloidea.The new taxon is the oldest crocodyloid representative in Eurasia. Crocodyloidea had previously only been known from the Palaeogene onwards in this part of Laurasia. Phylogenetically, Arenysuchus gascabadiolorum is situated at the base of the first radiation of crocodyloids that occurred in the late Maastrichtian, shedding light on this part of the cladogram. The presence of basal crocodyloids at the end of the Cretaceous both in North America and Europe provides new evidence of the faunal exchange via the Thulean Land Bridge during the Maastrichtian