Biosynthesis of modified peptidoglycan precursors by vancomycin-resistant Enterococcus faecium

In the presence of bacitracin, vancomycin-resistant Enterococcus faecium (vanA phenotype) accumulate UDP-N-acetylmuramyl(UDP-Mur-NAc)-tetrapeptide and a UDP-MurNAc-depsipentapeptide containing lactate substituted for the carboxy-terminal-D-alanine residue. In an in vitro peptidoglycan polymerization assay, the modified precursors function and confer resistance to vancomycin.     

GM1 Ganglioside: In Vivo and In Vitro Trophic Actions on Central Neurotransmitter Systems

Abstract: There is now substantial evidence that GM1 ganglioside is effective in partially correcting the consequences of neuroinjury in a number of in vivo and in vitro model systems. Although the molecular mechanism(s) and the substrates for the neurotrophic activity of the gangliosides are not fully understood, the published experimental work suggests that GM1 has antineurotoxic, neuroprotective, and neurorestorative effects on various central neurotransmitter systems. This review focuses attention on studies reporting that GM1 restores neuronal integrity and function in the brain of lesioned young as well as aged animals. Critical analysis of these studies can provide guidance for future ganglioside research and may point to novel approaches for treating neuroinjury and a variety of degenerative conditions, including aging.     

The effect of catecholamines and prostaglandins upon human and rat erythrocytes.

Both human and rat erythrocytes respond to low doses (10(-11)--10(-9) M) of L-isoproterenol and L-epinephrine with an increased degree of hypotonic hemolysis and a decreased rate of filtration through standardized paper filters. The receptors in both cell types have many of the characteristics of beta-receptors for catecholamines. However, hormone-receptor interaction in the human cell does not lead to an increase in intracellular cyclic AMP concentration, but in the rat cell, hormone-receptor interaction does lead to a significant increase in cyclic AMP content. Thus, catecholamine-beta-receptor interaction, at least in the human red cell, leads to a change in red cell properties which are not mediated by adenylate cyclase activation. Likewise, prostaglandin E2, at 10(-12)--10(-10) M, causes are increased degree of hypotonic hemolysis and a decreased rate of filtration through standardized paper filters, but it also does not increase the cycliC AMP content of the human erythrocyte but does increase that of the rat erythrocyte. Nevertheless, exogenous cyclic AMP, when added at a concentration of 10(-8) M to washed human erythrocytes, increases the degree of hypotonic hemolysis. Conversely, prostaglandin E1, at 10(-12)--10(-10) M, causes a decreased degree of hypotonic hemolysis and an increased rate of filtration through a standard filter. Both prostaglandin E2 and the catecholamines decrease the size of a rapidly exchangeable calcium pool, and prostaglandin E1 increases it.     

Will intra‐specific differences in transpiration efficiency in wheat be maintained in a high CO2 world? A FACE study

This study evaluates whether the target breeding trait of superior leaf level transpiration efficiency is still appropriate under increasing carbon dioxide levels of a future climate using a semi‐arid cropping system as a model. Specifically, we investigated whether physiological traits governing leaf level transpiration efficiency, such as net assimilation rates (A_net), stomatal conductance (g_s) or stomatal sensitivity were affected differently between two Triticum aestivum L. cultivars differing in transpiration efficiency (cv. Drysdale, superior; cv. Hartog, low). Plants were grown under Free Air Carbon dioxide Enrichment (FACE, approximately 550 µmol mol^?1 or ambient CO₂ concentrations (approximately 390 µmol mol^?1). Mean A_net (approximately 15% increase) and g_s (approximately 25% decrease) were less affected by elevated [CO₂] than previously found in FACE‐grown wheat (approximately 25% increase and approximately 32% decrease, respectively), potentially reflecting growth in a dry‐land cropping system. In contrast to previous FACE studies, analyses of the Ball et al. model revealed an elevated [CO₂] effect on the slope of the linear regression by 12% indicating a decrease in stomatal sensitivity to the combination of [CO₂], photosynthesis rate and humidity. Differences between cultivars indicated greater transpiration efficiency for Drysdale with growth under elevated [CO₂] potentially increasing the response of this trait. This knowledge adds valuable information for crop germplasm improvement for future climates.     

The isolation and characterization of mouse liver glyoxalase I.

The purification of glyoxalase I (S-lactoyl-glutathione methylglyoxal-lyase (isomerizing) EC 4.4.1.5) from DBA/1J mouse liver employing ion exchange and affinity chromatography is described. The enzyme was purified 1140-fold and it exhibits a specific activity of 2200 units/mg of protein. The activity was determined to be homogeneous by sedimentation velocity and sedimentation equilibrium ultracentrifugation and by polyacrylamide electrophoresis. The molecular weight is approimately 43 000 and the sedimentation coefficient is 3.4 S. Kinetic data are consistent with a one-substrate (hemimercaptal) reaction mechanism but do not rule out alternate branches at low substrate and free glutathione concentrations.     

Time-dependent botulinum neurotoxin serotype A metalloprotease inhibitors

Botulinum neurotoxins (BoNTs) are the most lethal of biological substances, and are categorized as class A biothreat agents by the Centers for Disease Control and Prevention. There are currently no drugs to treat the deadly flaccid paralysis resulting from BoNT intoxication. Among the seven BoNT serotypes, the development of therapeutics to counter BoNT/A is a priority (due to its long half-life in the neuronal cytosol and its ease of production). In this regard, the BoNT/A enzyme light chain (LC) component, a zinc metalloprotease responsible for the intracellular cleavage of synaptosomal-associated protein of 25 kDa, is a desirable target for developing post-BoNT/A intoxication rescue therapeutics. In an earlier study, we reported the high throughput screening of a library containing 70,000 compounds, and uncovered a novel class of benzimidazole acrylonitrile-based BoNT/A LC inhibitors. Herein, we present both structure–activity relationships and a proposed mechanism of action for this novel inhibitor chemotype.     

Surface-templated fibril growth of peptide fragments from the shaft domain of the adenovirus fibre protein

Here we present a study of five analogues of a fragment from the shaft domain of the adenovirus fibre protein that readily form fibrils under a range of conditions. Using atomic force microscopy the fibrillisation of these peptides at the liquid/solid interface utilizing ordered crystalline substrates has been investigated. Our results demonstrate that the assembly pathway at the liquid/solid interface enables only the formation of truncated fibrillar structures, which align along the substrate's underlying atomic lattice during growth. Furthermore, that the concentration and volume of solution applied can be used to directly control the density of fibrillar coverage at the surface.     

Molecular analysis of a novel family of complex glycoinositolphosphoryl ceramides from Cryptococcus neoformans: structural differences between encapsulated and acapsular yeast forms

Complex glycoinositolphosphoryl ceramides (GIPCs) have been purified from a pathogenic encapsulated wild-type (WT) strain of Cryptococcus neoformans var. neoformans and from an acapsular mutant (Cap67). The structures of the GIPCs were determined by a combination of tandem mass spectrometry, nuclear magnetic resonance spectroscopy, methylation analysis, gas chromatography-mass spectrometry, and chemical degradation. The main GIPC from the WT strain had the structure Manp(alpha1-3)[Xylp(beta1-2)] Manp(alpha1-4)Galp(beta1-6)Manp(alpha1-2)Ins-1-phosphoryl ceramide (GIPC A), whereas the compounds from the acapsular mutant were more heterogeneous in their glycan chains, and variants with Manp(alpha1-6) (GIPC B), Manp(alpha1-6) Manp(alpha1-6) (GIPC C), and Manp(alpha1-2)Manp(alpha1-6)Manp(alpha1-6) (GIPC D) substituents linked to the nonreducing terminal mannose residue found in the WT GIPC A were abundant. The ceramide moieties of C. neoformans GIPCs were composed of a C(18) phytosphingosine long-chain base mainly N-acylated with 2-hydroxy-tetracosanoic acid in the WT GIPC while in the acapsular Cap67 mutant GIPCs, as well as 2-hydroxy-tetracosanoic acid, the unusual 2,3-dihydroxy-tetracosanoic acid was characterized. In addition, structural analysis revealed that the amount of GIPC in the WT cells was fourfold less of that in the acapsular mutant.