Uptake and effect of praziquantel and the major human oxidative metabolite, 4-hydroxypraziquantel, by Schistosoma japonicum

After exposure to praziquantel in vitro at a concentration of 1 microgram/ml for 0.5-2 hr, amounts of praziquantel in Schistosoma japonicum varied from 2.1 +/- 1.2 to 3.7 +/- 1.6 ng/male worm and 1.3 +/- 1.2 to 2.2 +/- 1.5 ng/female worm during the time studied. At 30 micrograms/ml, praziquantel amounts were 11-33-fold higher. However, within 2 hr after removal from a medium containing 30 micrograms/ml praziquantel, 95% of the drug was released from the parasites. When S. japonicum worm pairs were incubated in vitro with 1, 10, and 30 micrograms/ml of 4-hydroxypraziquantel, the major human oxidative metabolite of praziquantel, 0.2 +/- 0.2, 3.8 +/- 1.3, and 7.4 +/- 1.3 ng/worm pair, respectively, were found after a 2-hr incubation. 15-30-fold lower than corresponding worm pair amounts of praziquantel. In vivo, when 4- or 5-wk S. japonicum-infected mice were treated orally with praziquantel (300 mg/kg), peak concentrations of praziquantel in plasma determined by high pressure liquid chromatography were 14.7 +/- 1.5 micrograms/ml (4-wk infection) and 16.7 +/- 2.8 micrograms/ml (5-wk infection) 15 min after treatment. Corresponding in vivo worm praziquantel amounts were 1.8 +/- 0.4 ng/male worm and 2.4 +/- 1.1 ng/female worm, respectively, in the 4-wk infection and 4.6 +/- 1.6 ng/male worm and 5.6 +/- 1.2 ng/female worm in the 5-wk infection. Peak plasma concentrations of 4-hydroxypraziquantel were similar but corresponding in vivo worm amounts were 1-20-fold lower, depending on the time after drug administration.(ABSTRACT TRUNCATED AT 250 WORDS)     

Enemy at the Gates: Interaction-Specific Stomatal Responses to Pathogenic Challenge

Stomata regulate gas exchange and their closure in response to pathogens may, in some cases, contribute to resistance. However, in the cereal mildew and rust systems, stomatal closure follows establishment of compatible infections. In incompatible systems, expression of major (R) gene controlled hypersensitive responses (HR), causes drastic, permanent stomatal dysfunction: stomata become locked open following powdery mildew attack and locked shut following rust attack. Thus, stomatal locking can be a hitherto unsuspected negative consequence of R gene resistance that carries a physiological cost affecting plant performance.Key Words: stomata, rust, mildew, hypersensitive response, stomatal lock-up     

The high-resolution NMR structure of the R21A Spc-SH3:P41 complex: Understanding the determinants of binding affinity by comparison with Abl-SH3

Background  

SH3 domains are small protein modules of 60–85 amino acids that bind to short proline-rich sequences with moderate-to-low affinity and specificity. Interactions with SH3 domains play a crucial role in regulation of many cellular processes (some are related to cancer and AIDS) and have thus been interesting targets in drug design. The decapeptide APSYSPPPPP (p41) binds with relatively high affinity to the SH3 domain of the Abl tyrosine kinase (Abl-SH3), while it has a 100 times lower affinity for the α-spectrin SH3 domain (Spc-SH3).     

Ester derivatives of annulated tetrahydroazocines: a new class of selective acetylcholinesterase inhibitors

A series of ester derivatives of annulated tetrahydroazocines, namely 2,3,6,11-tetrahydro-1H-azocino[4,5-b]indoles (5-10), 2,3,6,7-tetrahydro-1H-azocino[5,4-b]indoles (11-14), and 4,7,8,9-tetrahydro-1H-pyrrolo[2,3-d]azocines (15-18), synthesized through an efficient 6-->8 membered ring expansion procedure, were investigated for their acetylcholinesterase (AChE) inhibitory activities. Most of the compounds acted as AChE inhibitors in vitro, with IC(50) values ranging from 5 to 40 microM. The most potent compounds 11 and 15, both as racemic mixtures, proved selective toward AChE, exhibiting selectivity ratios versus butyrylcholinesterase (BuChE) of ca. 15 and more than 20, respectively. Structure-activity studies highlighted, among other factors, lipophilicity as a property modulating the AChE inhibition potency, as shown by a reasonable parabolic correlation between pIC(50) and experimental 1-octanol/water partition coefficient (logP), which described the prevailing behavior of the examined compounds (r(2)=0.665). Molecular docking simulations using the X-ray crystal structure of AChE from Torpedo californica suggested possible binding modes of the tetrahydroazocine ester derivatives 11 and 15.     

Species delimitation of the liquorice tribe (Leguminosae: Glycyrrhizeae) based on phylogenomic and machine learning analyses

The liquorice tribe Glycyrrhizeae is a leguminous herbaceous group of plants comprised of the genera Glycyrrhiza and Glycyrrhizopsis. Some Glycyrrhiza taxa contain glycyrrhizin, a pharmacologically significant sweet substance that also has applications in crafting industrial materials. Here, we utilized an expanded taxon sampling of Glycyrrhizeae to reconstruct the phylogenetic relationships in the tribe based on genome skimming data, including whole chloroplast genomes, nuclear ribosomal DNA, and low-copy nuclear DNA. We also launched machine learning analysis (MLA) for one species pair with controversial taxonomic boundary. The integrated results indicated Glycyrrhizopsis should be split from Glycyrrhiza, while the former genus Meristotropis should be treated as part of Glycyrrhiza. Glycyrrhizopsis includes two species, Glycyrrhizopsis asymmetrica and Glycyrrhizopsis flavescens, and we recognize 13 species in Glycyrrhiza: Glycyrrhiza acanthocarpa, Glycyrrhiza astragalina, Glycyrrhiza bucharica, Glycyrrhiza echinata, Glycyrrhiza foetida, Glycyrrhiza glabra, Glycyrrhiza gontscharovii, Glycyrrhiza lepidota, Glycyrrhiza macedonica, Glycyrrhiza pallidiflora, Glycyrrhiza squamulosa, Glycyrrhiza triphylla, and Glycyrrhiza yunnanensis. We propose a broader G. glabra that includes former Glycyrrhiza aspera, G. glabra s.s., Glycyrrhiza inflata, and Glycyrrhiza uralensis, and represents the glycyrrhizin-contained medicinal group. Our ancestral state inferences show the ancestor of Glycyrrhiza lacked glycyrrhizin, and the presence of glycyrrhizin evolved twice within Glycyrrhiza during the last one million years. Our integrative phylogenomics-MLA study not only provides new insights into long-standing taxonomic controversies of Glycyrrhizeae, but also represents a useful approach for future taxonomic studies on other plant taxa.     

Rearrangements of integral membrane components during in vitro aging of sheep erythrocyte membranes

In vitro aged sheep erythrocytes and sheep erythrocyte ghosts spontaneously release vesicles that consist of long protrusions affixed to flattened headlike structures. The intramembranous particles seen on the protoplasmic face of freeze fracture electron micrographs of vesicle protrusions are arranged in paired particle rows. On the equivalent fracture face of headlike structures, the particle density is low; if particles are present, they are clustered along the rim of the flattened headlike structure and at the junction with the protrusion. The released vesicles are depleted of the intramembranous particles seen on the exoplasmic face of ghost but retain almost exclusively particles of the protoplasmic face. Correspondingly, the exoplasmic face of ghosts that have released vesicles reveals a 28 percent higher density of intramembranous particles than that of fresh ghosts. Purified vesicles are depleted of spectrin but retain integral membrane proteins, with one of an apparent mol wt of 160,000 accounting for nearly 50 percent of the total protein (Lutz, H.U.,R. Barber, and R.F. McGuire. 1976. J. Biol. Chem. 251:3500-3510). When vesicles are modified with the cleavable cross-linking reagent [(35)S]dithiobis (succinimidyl propionate)at 0 degrees C, the 160,000 mol wt protein is rapidly converted to disulfide-linked dimers and higher oligomers. Exposure of intact ghosts to the reagent in the same way fails to yield equivalent polymers. A comparison of the morphological and biochemical aspects of ghosts and vesicles suggest that a marked rearrangement of membrane proteins accompanies the supramolecular redistribution of intramembranous particles during spontaneous vesiculation. The results also suggest that the paired particles of the protoplasmic face of vesicle protrusions are arranged in paired helices and contain the 160,000 mol wt protein as dimers.     

Stoichiometry and compartmentation of NADH metabolism in Saccharomyces cerevisiae

In Saccharomyces cerevisiae, reduction of NAD(+) to NADH occurs in dissimilatory as well as in assimilatory reactions. This review discusses mechanisms for reoxidation of NADH in this yeast, with special emphasis on the metabolic compartmentation that occurs as a consequence of the impermeability of the mitochondrial inner membrane for NADH and NAD(+). At least five mechanisms of NADH reoxidation exist in S. cerevisiae. These are: (1) alcoholic fermentation; (2) glycerol production; (3) respiration of cytosolic NADH via external mitochondrial NADH dehydrogenases; (4) respiration of cytosolic NADH via the glycerol-3-phosphate shuttle; and (5) oxidation of intramitochondrial NADH via a mitochondrial 'internal' NADH dehydrogenase. Furthermore, in vivo evidence indicates that NADH redox equivalents can be shuttled across the mitochondrial inner membrane by an ethanol-acetaldehyde shuttle. Several other redox-shuttle mechanisms might occur in S. cerevisiae, including a malate-oxaloacetate shuttle, a malate-aspartate shuttle and a malate-pyruvate shuttle. Although key enzymes and transporters for these shuttles are present, there is as yet no consistent evidence for their in vivo activity. Activity of several other shuttles, including the malate-citrate and fatty acid shuttles, can be ruled out based on the absence of key enzymes or transporters. Quantitative physiological analysis of defined mutants has been important in identifying several parallel pathways for reoxidation of cytosolic and intramitochondrial NADH. The major challenge that lies ahead is to elucidate the physiological function of parallel pathways for NADH oxidation in wild-type cells, both under steady-state and transient-state conditions. This requires the development of techniques for accurate measurement of intracellular metabolite concentrations in separate metabolic compartments.