Molecular species of phosphatidylcholine in abetalipoproteinemia: effect of lecithin:cholesterol acyltransferase and lysolecithin acyltransferase

In order to study the role of very low density lipoproteins (VLDL) and low density lipoproteins (LDL) in determining the molecular species composition of phosphatidylcholine (PC) and the specificity of lecithin:cholesterol acyltransferase (LCAT) in human plasma, we studied the PC species composition in plasma from abetalipoproteinemic (ABL) and control subjects before and after incubation at 37 degrees C. The ABL plasma contained significantly higher percentages of sn-2-18:1 species (16:0-18:1, 18:0-18:1, and 18:1-18:1) and lower percentages of sn-2-18:2 species (16:0-18:2, 18:0-18:2, and 18:1-18:2) as well as sn-2-20:4 species (16:0-20:4, 18:0-20:4, and 18:1-20:4). Similar abnormalities were found in the PC of ABL erythrocytes, while the PE of the erythrocytes was less affected. The relative contribution of various PC species towards LCAT reaction in ABL plasma was significantly different from that found in normal plasma. Thus, while 16:0-18:2 and 16:0-18:1 contributed, respectively, 43.8% and 15.9% of the total acyl groups used for cholesterol esterification in normal plasma, they contributed, respectively, 21.5% and 37.9% in ABL plasma. The relative contribution of 16:0-20:4 was also significantly lower in ABL plasma (4.7% vs. 9.0% in normal), while that of 16:0-16:0 was higher (6.4% vs. 0.5%). However, the selectivity factors of various species (percent contribution/percent concentration) were not significantly different between ABL and normal plasma, indicating that the substrate specificity of LCAT is not altered in the absence of VLDL and LDL. Incubation of ABL plasma in the presence of normal VLDL or LDL resulted in normalization of its molecular species composition and in the stimulation of its LCAT activity. Addition of LDL, but not VLDL, also resulted in the activation of lysolecithin acyltransferase (LAT) activity. The incorporation of [1-14C]palmitoyl lysoPC into various PC species in the presence of LDL was similar to that observed in normal plasma, with the 16:0-16:0 species having the highest specific activity. These results indicate that the absence of apoB-containing lipoproteins significantly affects the molecular species composition of plasma PC as well as its metabolism by LCAT and LAT reactions.     

Yellow leaf spot of cashew: A case of molybdenum deficiency

Summary Rooted cuttings ofSeverinia buxifolia were inoculated with the vesicular-arbuscular mycorrhizal (VAM) fungusGlomus intraradices or provided an inoculum filtrate (non-VAM plants) and grown in one of seven media combinations of fired montmorillonite clay (FMC) and Canadian peatmoss (CP) at ratios of 100%, 80%, 67%, 50%, 33%, 20%, or 0% FMC. Mycorrhizal infection increased with higher proportions of FMC, but the growth of both VAM and non-VAM plants was reduced with increased FMC amendment. The growth benefit (top and root fresh-dry weights) conferred by mycorrhizal infection was greater at higher levels of FMC in the media. Improved phosphorus uptake by inoculated severinia plants appeared at least partially responsible for increased growth compared to non-VAM plants under conditions of high soluble salts and pH associated with high FMC composition. Florida Agr. Expt. Sta. Journal Series No. 6319.     

Mitochondrial retrograde regulation in plants

Plant cells must react to a variety of adverse environmental conditions that they may experience on a regular basis. Part of this response centers around (1) ROS as damaging molecules and signaling molecules; (2) redox status, which can be influenced by ROS production; and (3) availability of metabolites. All of these are also likely to interface with changes in hormone levels [Desikan, R., Hancock, J., Neill, S., 2005. Reactive oxygen species as signalling molecules. In: Smirnoff, N. (ed.), Antioxidants and reactive oxygen species in plants. Blackwell Pub. Ltd., Oxford, pp. 169-196; Kwak, J.M., Nguyen, V., Schroeder, J.I., 2006. The role of reactive oxygen species in hormonal responses. Plant Physiol. 141, 323-329]. Each of these areas can be strongly influenced by changes in mitochondrial function. Such changes trigger altered nuclear gene expression by a poorly understood process of mitochondrial retrograde regulation (MRR), which is likely composed of several distinct signaling pathways. Much of what is known about plant MRR centers around the response to a dysfunctional mtETC and subsequent induction of genes encoding proteins involved in recovery of mitochondrial functions, such as AOX and alternative NAD(P)H dehydrogenases, and genes encoding enzymes aimed at regaining ROS level/redox homeostasis, such as glutathione transferases, catalases, ascorbate peroxidases and superoxide dismutases. However, as evidence of new and interesting targets of MRR emerge, this picture is likely to change and the complexity and importance of MRR in plant responses to stresses and the decision for cells to either recover or switch into programmed cell death mode is likely to become more apparent.     

A rapid and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the estimation of rivastigmine in human plasma

A rapid and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed and validated for the estimation of rivastigmine in human plasma. Rivastigmine was extracted from human plasma by using solid-phase extraction technique. Zolpidem was used as the internal standard. A Betabasic-8 column provided chromatographic separation of analytes followed by detection with mass spectrometry. The mass transition ion-pair was followed as m/z 251.20-->206.10, 86.20 for rivastigmine and m/z 308.10-->235.10 for zolpidem. The method involves a rapid solid-phase extraction from plasma, simple isocratic chromatographic conditions and mass spectrometric detection that enables detection at sub-nanogram levels. The proposed method has been validated for a linear range of 0.2-20.0 ng/ml with a correlation coefficient > or =0.9988. The intra-run and inter-run precision and accuracy were within 10.0%. The overall recoveries for rivastigmine and zolpidem were 86.28% and 87.57%, respectively. The total run time was 2.0 min. The developed method was applied for the determination of the pharmacokinetic parameters of rivastigmine following a single oral administration of a 3 mg rivastigmine capsule in 20 healthy male volunteers.