Hypoxic pulmonary vasoconstriction is enhanced by inhibition of the synthesis of an endothelium derived relaxing factor

Inhibition of the synthesis of endothelium derived relaxing factor by NG-monomethyl-L-arginine, a competitive inhibitor of the synthesis of nitric oxide from L-arginine, enhances hypoxic pulmonary vasoconstriction in pulmonary artery rings and isolated, Krebs albumin perfused rat lungs. L-arginine rapidly reduces hypoxic vasoconstriction, particularly in lungs treated with NG-monomethyl-L-arginine. Following administration of NG-monomethyl-L-arginine, bradykinin-induced vasodilatation is inhibited (p less than 0.01) and a bradykinin-induced vasoconstriction develops (p less than 0.001). NG-monomethyl-L-arginine does not significantly diminish acetylcholine-induced vasodilatation in the isolated lung. NG-monomethyl-L-arginine causes an endothelium-dependent vasoconstriction in pulmonary artery rings.     

Factors influencing chromatography of proteins on short alkylsilane-bonded large pore-size silicas

The separation of proteins by high-performance gradient chromatography on short alkylchain bonded silica was studied with respect to pore size, mobile-phase composition, and temperature. Selectivity could be increased in particular cases by varying temperature or eluate compositon. Recovery of late-eluting, hydrophobic proteins was found to increase with flow rate and gradient slope. Recovery was also shown to be dependent on eluate composition—decreasing with added salt. The applicability of reverse-phase chromatography to proteins as large as 150 kD was demonstrated by the separation of monoclonal immunoglobulin.     

Methanogenesis from Ethanol by Defined Mixed Continuous Cultures

Methanogenesis from ethanol by defined mixed continuous cultures was studied. Under sulfate-free conditions, a Desulfovibrio strain was used as the ethanol-degrading species producing acetic acid and hydrogen. In a two-membered mutualistic coculture, the hydrogen was converted to methane by a Methanobacterium sp. and pH was maintained at neutrality by the addition of alkali. Introduction of a third species, the acetate-utilizing Methanosarcina mazei, obviated the need for external pH control. Methanogenesis by the co-and triculture was studied at various dilution rates in the steady state. The mutualistic coculture performed like a composite single species, as predicted from the theory of mutualistic interactions. Coupling between the mutualistic coculture and the acetate-utilizing methanogen was less tight. Increasing the dilution rate destabilized the triculture; at low dilution rates, instability was soon recovered, but at higher dilution rates imbalance between the rates of production and removal of acetic acid led to a drop in pH. Flocs formed in the triculture. An annulus of the Methanobacterium sp. and Desulfovibrio sp. was retained around the Methanosarcina sp. by strands of material probably derived from the Methanosarcina sp.     

Novel variants in the KIT and PAX3 genes in horses with white‐spotted coat colour phenotypes

Variants in the EDNRB, KIT, MITF, PAX3 and TRPM1 genes are known to cause white spotting phenotypes in horses, which can range from the common white markings up to completely white horses. In this study, we investigated these candidate genes in 169 horses with white spotting phenotypes not explained by the previously described variants. We identified a novel missense variant, PAX3:p.Pro32Arg, in Appaloosa horses with a splashed white phenotype in addition to their leopard complex spotting patterns. We also found three novel variants in the KIT gene. The splice site variant c.1346+1G>A occurred in a Swiss Warmblood horse with a pronounced depigmentation phenotype. The missense variant p.Tyr441Cys was present in several part‐bred Arabians with sabino‐like depigmentation phenotypes. Finally, we provide evidence suggesting that the common and widely distributed KIT:p.Arg682His variant has a very subtle white‐increasing effect, which is much less pronounced than the effect of the other described KIT variants. We termed the new KIT variants W18–W20 to provide a simple and unambiguous nomenclature for future genetic testing applications.     

Variation in basal sprouting in co-occurring shrubs: implications for stand dynamics

Abstract. Sources of basal sprouting for five shrub species representing five plant families common to the Tamaulipan biotic province were quantified, following four intensities of top removal. Among undisturbed shrubs, Celtis pallida and Zanthoxylum fagara were somewhat arborescent, with one or two dominant primary stems per plant. Aloysia gratissima, Ziziphus obtusifolia and Schaefferia cuneifolia were fruticose in architecture, with more and smaller stems. Following top removal, each species exhibited a distinct regenerative hierarchy whereby shoot production following disturbance was primarily from structures immediately subtending the removed tissues, even though more distal tissues had the capacity for shoot production. Thus, removal of stems to a 5 cm residual increased the contribution of primary stems from stem bases, whereas stem removal to ground line typically induced regeneration from root crowns. Schaefferia, Zanthoxylum and Ziziphus were capable of producing shoots from root tissue, yet regeneration from roots was not stimulated until tissues were removed to below root crowns. Field observations indicate that most woody species in the subtropical thorn woodlands of southern Texas, USA, are highly persistent in the face of natural and anthropogenic disturbance, owing to their ability to regenerate vegetatively. Alternative sources of stem replacement contribute to the high resilience of these shrubs following disturbance and may help explain or predict patterns of secondary succession and plant persistence following various intensities of disturbance.