The mechanism of intestinal absorption of phosphatidylcholine in rats

1. The mechanism of absorption of phosphatidylcholine was studied in rats by injecting into the intestine phosphatidylcholine specifically labelled either in the fatty acid or in the glycerol moiety or with (32)P, when considerable amounts of 1-acyl-lysophosphatidylcholine were found in the intestinal lumen. 2-([(14)C]Acyl)phosphatidylcholine gave markedly more radioactive unesterified fatty acids in the lumen, compared with the 1-([(14)C]acyl) derivative. Some of the radioactivity from either the fatty acid or the glycerol moiety of the injected phosphatidylcholine appeared in the mucosal triacylglycerols. 2. Injection of (32)P-labelled phosphatidylcholine or (32)P-labelled lysophosphatidylcholine led to the appearance of radioactive glycerylphosphorylcholine, glycerophosphate and P(i) in the mucosa. 3. Rat mucosa was found to contain a highly active glycerylphosphorylcholine diesterase. 4. It was concluded that the dietary phosphatidylcholine is hydrolysed in the intestinal lumen by the pancreatic phospholipase A to 1-acylglycerylphosphorylcholine, which on entering the mucosal cell is partly reacylated to phosphatidylcholine, and the rest is further hydrolysed to glycerylphosphorylcholine, glycerophosphate, glycerol and P(i). The fatty acids and glycerophosphate are then reassembled to give triacylglycerols via the Kennedy (1961) pathway.     

Diverse effects of essential (n−6 andn−3) fatty acids on cultured cells

Fatty acids (FAs) have long been recognized for their nutritional value in the absence of glucose, and as necessary components of cell membranes. However, FAs have other effects on cells that may be less familiar. Polyunsaturated FAs of dietary origin (n–6 andn–3) cannot be synthesized by mammals, and are termed essential because they are required for the optimal biologic function of specialized cells and tissues. However, they do not appear to be necessary for normal growth and metabolism of a variety of cells in culture. The essential fatty acids (EFAs) have received increased attention in recent years due to their presumed involvement in cardiovascular disorders and in cancers of the breast, pancreas, colon and prostate. Manyin vitro systems have emerged which either examine the role of EFAs in human disease directly, or utilize EFAs to mimic thein vivo cellular environment. The effects of EFAs on cells are both direct and indirect. As components of membrane phospholipids, and due to their varying structural and physical properties, EFAs can alter membrane fluidity, at least in the local environment, and affect any process that is mediated via the membrane. EFAs containing 20 carbons and at least three double bonds can be enzymatically converted to eicosanoid hormones, which play important roles in a variety of physiological and pathological processes. Alternatively, EFAs released into cells from phospholipids can act as second messengers that activate protein kinase C. Furthermore, susceptibility to oxidative damage increases with the degree of unsaturation, a complication that merits consideration because lipid peroxidation can lead to a variety of substances with toxic and mutagenic properties. The effects of EFAs on cultured cells are illustrated using the responses of normal and tumor human mammary epithelial cells. A thorough evaluation of EFA effects on commercially important cells could be used to advantage in the biotechnology industry by identifying EFA supplements that lead to improved cell growth and/or productivity.Abbreviations AA arachidonic acid (20 carbons: 4 double bonds,n–6) - BHA butylated hydroxyanisole - BHT butylated hydroxytoluene - cAMP cyclic adenosine monophosphate - CHO Chinese hamster ovary - DAG diacylglycerol - DGLNA dihomo--linolenic acid (203,n–6) - DHA docosahexaenoic acid (226,n–3) - EFA essential fatty acid - EGF epidermal growth factor - EGFR epidermal growth factor receptor - EPA eicosapentaenoic acid (205,n–3) - FA fatty acid - FBS fetal bovine serum - GLNA -linolenic acid (183,n–6) - LA linoleic acid (182,n–6) - LNA -linolenic acid (183,n–3) - LT leukotriene - MDA malondialdehyde - NAD nicotinamide adenine dinucleotide - NDGA nordihydroguaiaretic acid - OA oleic acid (181,n–9) - PG prostaglandin - PKC protein kinase C - PUFA polyunsaturated fatty acid - SFM serum-free medium - TX thromboxane     

YY1 controls Igκ repertoire and B‐cell development,and localizes with condensin on the Igκ locus

Conditional knock‐out (KO) of Polycomb Group (PcG) protein YY1 results in pro‐B cell arrest and reduced immunoglobulin locus contraction needed for distal variable gene rearrangement. The mechanisms that control these crucial functions are unknown. We deleted the 25 amino‐acid YY1 REPO domain necessary for YY1 PcG function, and used this mutant (YY1ΔREPO), to transduce bone marrow from YY1 conditional KO mice. While wild‐type YY1 rescued B‐cell development, YY1ΔREPO failed to rescue the B‐cell lineage yielding reduced numbers of B lineage cells. Although the IgH rearrangement pattern was normal, there was a selective impact at the Igκ locus that showed a dramatic skewing of the expressed Igκ repertoire. We found that the REPO domain interacts with proteins from the condensin and cohesin complexes, and that YY1, EZH2 and condensin proteins co‐localize at numerous sites across the Ig kappa locus. Knock‐down of a condensin subunit protein or YY1 reduced rearrangement of Igκ Vκ genes suggesting a direct role for YY1‐condensin complexes in Igκ locus structure and rearrangement.     

Synthesis,characterization and in vitro biological evaluation of some novel 1,3,5-triazine–Schiff base conjugates as potential antimycobacterial agents

A series of some novel 1,3,5-triazine–Schiff base conjugates (1–32) have been synthesized and evaluated for their in vitro antimycobacterial activity against Mycobacterium tuberculosis H37Rv using Alamar Blue assay and the activity expressed as the minimum inhibitory concentration (MIC) in μg/mL. Compounds 4 (4-Methoxy-6-methyl-N-(3,4,5-trimethoxybenzylidene)-1,3,5-triazin-2-amine), 11 (4-Methoxy-6-methyl-N-(2-hydroxy-3-bromo-5-chloro-benzylidene)-1,3,5-triazin-2-amine) and 24 (4-Methoxy-6-methyl-N-(1-(2,5-dihydroxyphenyl)ethylidene)-1,3,5-triazin-2-amine) exhibited a significant activity at 3.125, 6.25 and 6.25 μg/mL, respectively, when compared with the antitubercular drugs such as ethambutol (3.125 μg/mL), pyrazinamide (6.25 μg/mL) and streptomycin (6.25 μg/mL) and it could be a potential starting point to develop new lead compounds in the fight against Mycobacterium tuberculosis H37Rv.     

Automated Entire Thrombus Density Measurements for Robust and Comprehensive Thrombus Characterization in Patients with Acute Ischemic Stroke

Background and Purpose

In acute ischemic stroke (AIS) management, CT-based thrombus density has been associated with treatment success. However, currently used thrombus measurements are prone to inter-observer variability and oversimplify the heterogeneous thrombus composition. Our aim was first to introduce an automated method to assess the entire thrombus density and then to compare the measured entire thrombus density with respect to current standard manual measurements.

Materials and Method

In 135 AIS patients, the density distribution of the entire thrombus was determined. Density distributions were described using medians, interquartile ranges (IQR), kurtosis, and skewedness. Differences between the median of entire thrombus measurements and commonly applied manual measurements using 3 regions of interest were determined using linear regression.

Results

Density distributions varied considerably with medians ranging from 20.0 to 62.8 HU and IQRs ranging from 9.3 to 55.8 HU. The average median of the thrombus density distributions (43.5 ± 10.2 HU) was lower than the manual assessment (49.6 ± 8.0 HU) (p<0.05). The difference between manual measurements and median density of entire thrombus decreased with increasing density (r = 0.64; p<0.05), revealing relatively higher manual measurements for low density thrombi such that manual density measurement tend overestimates the real thrombus density.

Conclusions

Automatic measurements of the full thrombus expose a wide variety of thrombi density distribution, which is not grasped with currently used manual measurement. Furthermore, discrimination of low and high density thrombi is improved with the automated method.     

Trans unsaturated fatty acids are less oxidizable than cis unsaturated fatty acids and protect endogenous lipids from oxidation in lipoproteins and lipid bilayers

Epidemiological data suggest that dietary trans unsaturated fatty acids increase the risk of heart disease; however, the underlying mechanisms are unclear. In this study, we investigated one possible mechanism, namely, their effect on LDL oxidation. Supplementation of LDL with 10% 16:1 trans-cholesteryl ester (CE) inhibited the oxidation compared to that with 16:1 cis-CE. Total replacement of core lipids with 18:2 trans,trans-CE decreased the rate of LDL oxidation by 19% compared to replacement with 18:2 cis,cis-CE. When the surface phosphoglycerides were replaced with either 16:0-18:2 cis,cis-phosphatidylcholine (PC) or 16:0-18:2 trans,trans-PC, the latter was found to inhibit the rate and increase the lag time of oxidation to a greater extent than the former. To confirm these findings, we studied the oxidation of PC liposomes by assessing the formation of conjugated dienes or the degradation of a fluorescently labeled PC. By both methods, the 16:0-18:2 trans,trans-PC exhibited greater resistance to oxidation than the 16:0-18:2 cis,cis-PC. Eliminating the fluidity differences did not completely eliminate the differences in oxidation rates, suggesting that the trans double bond is inherently resistant to oxidation. The composition of the conjugated hydroperoxy products formed after oxidation differed markedly for the two 18:2 isomers. Supplementation of 16:0-18:2 cis,cis-PC liposomes with 20 mol % di16:1 trans-PC retarded oxidation rates to a greater extent than supplementation with di16:1 cis-PC. These studies show that dietary trans unsaturated fatty acids decrease the rate of lipid peroxidation, an effect that may mitigate the atherogenic effect of these fatty acids.     

Role of group IIa and group V secretory phospholipases A(2) in the metabolism of lipoproteins. Substrate specificities of the enzymes and the regulation of their activities by sphingomyelin

Although many isoforms of secretory phospholipases A(2) (sPLA(2)) are known to be secreted by various inflammatory cells, and are present in plasma, their role in lipoprotein metabolism is unknown. We studied the in vitro hydrolysis of lipoprotein phospholipids by group IIa and group V sPLA(2), two structurally related enzymes with differing phospholipid specificities. The group V sPLA(2) was about 30 times more efficient than the group IIa enzyme in the hydrolysis of lipoprotein phosphatidylcholine (PC), and both enzymes were more active on high density liporotein (HDL) than on low density lipoprotein (LDL). The lower activity on LDL appears to be due to the higher sphingomyelin (SPH) concentration in this lipoprotein. PC hydrolysis in lipoproteins was stimulated significantly by enzymatic depletion of their SPH. The hydrolysis of PC in liposomes was inhibited by the incorporation of SPH, and this inhibition was reversed by treatment with sphingomyelinase. The incorporation of ceramide, on the other hand, stimulated the sPLA(2) activity significantly. Unlike most sPLA(2), which show no fatty acid preference, group V sPLA(2) released disproportionately more linoleate, and less arachidonate from lipoproteins. These studies show that group V sPLA(2) is physiologically more important than group IIa enzyme in lipoprotein metabolism, that the sPLA(2) activities are regulated by sphingomyelin and ceramide, and that the pathological effects of sPLA(2) may not be mediated through stimulation of eicosanoid synthesis.     

Towards a framework for the evolutionary genomics of Kinetoplastids: what kind of data and how much?

The current status of kinetoplastids phylogeny and evolution is discussed in view of the recent progresses on genomics. Some ideas on a potential framework for the evolutionary genomics of kinetoplastids are presented.