Influence of aflatoxin B1 on seed germination, seedling growth, chlorophyll and carotenoid contents of mustard (brassica juncea L. var. pusa bold) seeds

Five different concentrations (100, 250, 500, 1000 and 2000 μg/L of aflatoxin B₁ were found to be inhibitory to seed germination and seedling growth (root and shoot lengths) of mustard seeds (variety Pusa bold). These also lowered the levels of chlorophyll and carotenoids in the emerging leaves during seedling growth. The inhibitory effect was correlated with the concentration of applied toxin.     

The Cutting Balloon--a new technology?

The Cutting Balloon consists of a standard balloon dilatation catheter with four microtome-sharp blades that incise the plaque and minimize arterial wall trauma. It was used in 31 patients; nine had calcified arteries, ten had non-compliant lesions, three had in-stent restenosis and nine had aorto-ostial lesions. Seventeen lesions were predilated, 28 were post-dilated and 18 required stent implantation. The procedure was very effective in aorto-ostial lesions, non-compliant lesions that were not responsive to high-pressure balloon dilatation, and was partially successful in calcified arteries. It has a very specific niche in selected lesions.     

Confirmation of a gene for multiple sclerosis (MS) to chromosome region 19q13.3

To identify the chromosomal localizations of the multiple sclerosis (MS) genes, we conducted a genomewide linkage analysis using eighteen affected families. A MS gene is linked to markers located in the 19q13.3 region (multipoint lod-score = 2.1). Apolipoprotein E (ApoE) gene, located in this region, is an excellent candidate gene for MS because the ApoEe4 allele is acting as a severity allele in the disease.     

Substitution bias, rapid saturation, and the use of mtDNA for nematode systematics

Only relatively recently have researchers turned to molecular methods for nematode phylogeny reconstruction. Thus, we lack the extensive literature on evolutionary patterns and phylogenetic usefulness of different DNA regions for nematodes that exists for other taxa. Here, we examine the usefulness of mtDNA for nematode phylogeny reconstruction and provide data that can be used for a priori character weighting or for parameter specification in models of sequence evolution. We estimated the substitution pattern for the mitochondrial ND4 gene from intraspecific comparisons in four species of parasitic nematodes from the family Trichostrongylidae (38-50 sequences per species). The resulting pattern suggests a strong mutational bias toward A and T, and a lower transition/transversion ratio than is typically observed in other taxa. We also present information on the relative rates of substitution at first, second, and third codon positions and on relative rates of saturation of different types of substitutions in comparisons ranging from intraspecific to interordinal. Silent sites saturate extremely quickly, presumably owing to the substitution bias and, perhaps, to an accelerated mutation rate. Results emphasize the importance of using only the most closely related sequences in order to infer patterns of substitution accurately for nematodes or for other taxa having strongly composition-biased DNA. ND4 also shows high amino acid polymorphism at both the intra- and interspecific levels, and in higher level comparisons, there is evidence of saturation at variable amino acid sites. In general, we recommend using mtDNA coding genes only for phylogenetics of relatively closely related nematode species and, even then, using only nonsynonymous substitutions and the more conserved mitochondrial genes (e.g., cytochrome oxidases). On the other hand, the high substitution rate in genes such as ND4 should make them excellent for population genetics studies, identifying cryptic species, and resolving relationships among closely related congeners when other markers show insufficient variation.      

Mono- and bis-hydrazone of D-erythrose and 2,3-Dioxo-y-butyrolactone

Aryl-and benzoyl-hydrazones of 2,4-O benzylidene D-erythrose were prepared and acetylated. D-glycero-Tetrulose phenyl-and p-substitute-phenyl-osazones were acylated with acetyl chloride and benzoyl chloride to give the N-acyl-di-O-acyl derivatives, which, on boiling with acetic anhydride, afforded the 1-aryl-3-formylpyrazole N-acetylarylhydrazones. The bis(hydrazones) of 2,3-dioxo-y-butyrolactone are partially hydrolyzed with copper(II) chloride to give the 2-hydrazono-3-oxo-y-butyrolactones, which, on treatment with alkali, rearrange to give the 1-aryl-3-hydroxymethylpyrazoline-4,5-dione 4-arylhydrazones.     

A biophysical model for plant cell plate maturation based on the contribution of a spreading force

Plant cytokinesis, a fundamental process of plant life, involves de novo formation of a “cell plate” partitioning the cytoplasm of dividing cells. Cell plate formation is directed by orchestrated delivery, fusion of cytokinetic vesicles, and membrane maturation to form a nascent cell wall by timely deposition of polysaccharides. During cell plate maturation, the fragile membrane network transitions to a fenestrated sheet and finally a young cell wall. Here, we approximated cell plate sub-structures with testable shapes and adopted the Helfrich-free energy model for membranes, including a stabilizing and spreading force, to understand the transition from a vesicular network to a fenestrated sheet and mature cell plate. Regular cell plate development in the model was possible, with suitable bending modulus, for a two-dimensional late stage spreading force of 2–6 pN/nm, an osmotic pressure difference of 2–10 kPa, and spontaneous curvature between 0 and 0.04 nm⁻¹. With these conditions, stable membrane conformation sizes and morphologies emerged in concordance with stages of cell plate development. To reach a mature cell plate, our model required the late-stage onset of a spreading/stabilizing force coupled with a concurrent loss of spontaneous curvature. Absence of a spreading/stabilizing force predicts failure of maturation. The proposed model provides a framework to interrogate different players in late cytokinesis and potentially other membrane networks that undergo such transitions. Callose, is a polysaccharide that accumulates transiently during cell plate maturation. Callose-related observations were consistent with the proposed model’s concept, suggesting that it is one of the factors involved in establishing the spreading force.

The late-stage onset of an “areal” spreading and stabilizing force is essential for regular plant cell plate development and maturation.     

Investigation of the extracellular accessibility of the connecting loop between membrane domains I and II of the bradykinin B2 receptor.

In analogy to the structure of rhodopsin, the seven hydrophobic segments of G-protein-coupled receptors are supposed to form seven membrane-spanning alpha-helices. To analyze the topology of the bradykinin B2 receptor, we raised site-directed antibodies to peptides corresponding to the loop regions and the amino and carboxyl terminus of this receptor. We found that a segment with predicted intracellular orientation according to the rhodopsin model, the connecting loop between membrane domains I and II of the bradykinin B2 receptor, was accessible to site-directed antibodies on intact fibroblasts, A431 cells, or COS cells expressing human B2 receptors. Extracellular orientation of this loop was further confirmed by the substituted cysteine accessibility method which showed that exchange of cysteine 94 for serine on this loop by point mutagenesis suppressed the effect of thiol modification by a membrane impermeant maleimide. In addition, this segment seemed to be involved in B2 receptor activation, since (i) thiol modification of cysteine 94 partially suppressed B2 receptor activation, and (ii) site-directed antibodies to the connecting loop between membrane domains I and II were agonists. The agonistic activity of the antibodies was suppressed by the B2 antagonist HOE140 confirming the B2 specificity of the antibody-generated signal. The extracellular orientation of the connecting loop between membrane domains I and II suggests a topology of the B2 receptor different from rhodopsin, consisting of five (instead of seven) transmembrane domains and two hydrophobic segments with both ends facing the extracellular side.     

The mechanical basis of impaired esophageal emptying postfundoplication

Fundoplication (FP) efficacy is a trade-off between protection against reflux and postoperative dysphagia from the surgically altered mechanical balance within the esophagogastric segment. The purpose of the study was to contrast quantitatively the mechanical balance between normal and post-FP esophageal emptying. Physiological data were combined with mathematical models based on the laws of mechanics. Seven normal controls (NC) and seven post-FP patients underwent concurrent manometry and fluoroscopy. Temporal changes in geometry of the distal bolus cavity and hiatal canal, and cavity-driving pressure were quantified during emptying. Mathematical models were developed to couple cavity pressure to hiatal geometry and esophageal emptying and to determine cavity muscle tone. We found that the average length of the hiatal canal post-FP was twice that of NC; reduction of hiatal radius was not significant. All esophageal emptying events post-FP were incomplete (51% retention); there was no significant difference in the period of emptying between NC and post-FP, and average emptying rates were 40% lower post-FP. The model predicted three distinct phases during esophageal emptying: hiatal opening (phase I), a quasi-steady period (phase II), and final emptying (phase III). A rapid increase in muscle tone and driving pressure forced normal hiatal opening. Post-FP there was a severe impairment of cavity muscle tone causing deficient hiatal opening and flow and bolus retention. We conclude that impaired esophageal emptying post-FP follows from the inability of distal esophageal muscle to generate necessary tone rapidly. Immobilization of the intrinsic sphincter by the surgical procedure may contribute to this deficiency, impaired emptying, and possibly, dysphagia.