Lipid composition of viral envelope of three strains of influenza virus - not all viruses are created equal

While differences in the rate of virus fusion and budding from the host cell membrane have been correlated with pathogenicity, no systematic study of the contribution of differences in viral envelope composition has previously been attempted. Using rigorous virus purification, marked differences between virions and host were observed. Over 125 phospholipid species have been quantitated for three strains of influenza (HKx31- H3N2, PR8- H1N1, and VN1203- H5N1) grown in eggs. The glycerophospholipid composition of purified virions differs from that of the host or that of typical mammalian cells. Phosphatidylcholine is the major component in most mammalian cell membranes, while in purified virions phosphatidylethanolamine dominates. Due to its effects on membrane curvature, it is likely that the variations in its content are important to viral processing during infection. This integrated method of virion isolation with systematic analysis of glycerophospholipids provides a tool for the assessment of species specific biomarkers of viral pathogenicity.

Application of an informatics-based decision-making framework and process to the assessment of radiation safety in nanotechnology

The National Council on Radiation Protection and Measurements (NCRP) established NCRP Scientific Committee 2-6 to develop a report on the current state of knowledge and guidance for radiation safety programs involved with nanotechnology. Nanotechnology is the understanding and control of matter at the nanoscale, at dimensions between ∼1 and 100 nm, where unique phenomena enable novel applications. While the full report is in preparation, this paper presents and applies an informatics-based decision-making framework and process through which the radiation protection community can anticipate that nano-enabled applications, processes, nanomaterials, and nanoparticles are likely to become present or are already present in radiation-related activities; recognize specific situations where environmental and worker safety, health, well-being, and productivity may be affected by nano-related activities; evaluate how radiation protection practices may need to be altered to improve protection; control information, interpretations, assumptions, and conclusions to implement scientifically sound decisions and actions; and confirm that desired protection outcomes have been achieved. This generally applicable framework and supporting process can be continuously applied to achieve health and safety at the convergence of nanotechnology and radiation-related activities.

Biomarkers of NAFLD progression: a lipidomics approach to an epidemic

The spectrum of nonalcoholic fatty liver disease (NAFLD) includes steatosis, nonalcoholic steatohepatitis (NASH), and cirrhosis. Recognition and timely diagnosis of these different stages, particularly NASH, is important for both potential reversibility and limitation of complications. Liver biopsy remains the clinical standard for definitive diagnosis. Diagnostic tools minimizing the need for invasive procedures or that add information to histologic data are important in novel management strategies for the growing epidemic of NAFLD. We describe an "omics" approach to detecting a reproducible signature of lipid metabolites, aqueous intracellular metabolites, SNPs, and mRNA transcripts in a double-blinded study of patients with different stages of NAFLD that involves profiling liver biopsies, plasma, and urine samples. Using linear discriminant analysis, a panel of 20 plasma metabolites that includes glycerophospholipids, sphingolipids, sterols, and various aqueous small molecular weight components involved in cellular metabolic pathways, can be used to differentiate between NASH and steatosis. This identification of differential biomolecular signatures has the potential to improve clinical diagnosis and facilitate therapeutic intervention of NAFLD.

The TMAO-Generating Enzyme Flavin Monooxygenase 3 Is a Central Regulator of Cholesterol Balance

Circulating levels of the gut microbe-derived metabolite trimethylamine-N-oxide (TMAO) have recently been linked to cardiovascular disease (CVD) risk. Here, we performed transcriptional profiling in mouse models of altered reverse cholesterol transport (RCT) and serendipitously identified the TMAO-generating enzyme flavin monooxygenase 3 (FMO3) as a powerful modifier of cholesterol metabolism and RCT. Knockdown of FMO3 in cholesterol-fed mice alters biliary lipid secretion, blunts intestinal cholesterol absorption, and limits the production of hepatic oxysterols and cholesteryl esters. Furthermore, FMO3 knockdown stimulates basal and liver X receptor (LXR)-stimulated macrophage RCT, thereby improving cholesterol balance. Conversely, FMO3 knockdown exacerbates hepatic endoplasmic reticulum (ER) stress and inflammation in part by decreasing hepatic oxysterol levels and subsequent LXR activation. FMO3 is thus identified as a central integrator of hepatic cholesterol and triacylglycerol metabolism, inflammation, and ER stress. These studies suggest that the gut microbiota-driven TMA/FMO3/TMAO pathway is a key regulator of lipid metabolism and inflammation.

Enhanced synthesis of saturated phospholipids is associated with ER stress and lipotoxicity in palmitate treated hepatic cells

High levels of saturated FAs (SFAs) are acutely toxic to a variety of cell types, including hepatocytes, and have been associated with diseases such as type 2 diabetes and nonalcoholic fatty liver disease. SFA accumulation has been previously shown to degrade endoplasmic reticulum (ER) function leading to other manifestations of the lipoapoptotic cascade. We hypothesized that dysfunctional phospholipid (PL) metabolism is an initiating factor in this ER stress response. Treatment of either primary hepatocytes or H4IIEC3 cells with the SFA palmitate resulted in dramatic dilation of the ER membrane, coinciding with other markers of organelle dysfunction. This was accompanied by increased de novo glycerolipid synthesis, significant elevation of dipalmitoyl phosphatidic acid, diacylglycerol, and total PL content in H4IIEC3 cells. Supplementation with oleate (OA) reversed these markers of palmitate (PA)-induced lipotoxicity. OA/PA cotreatment modulated the distribution of PA between lipid classes, increasing the flux toward triacylglycerols while reducing its incorporation into PLs. Similar trends were demonstrated in both primary hepatocytes and the H4IIEC3 hepatoma cell line. Overall, these findings suggest that modifying the FA composition of structural PLs can protect hepatocytes from PA-induced ER stress and associated lipotoxicity.

A phosphatidylinositol transfer protein integrates phosphoinositide signaling with lipid droplet metabolism to regulate a developmental program of nutrient stress-induced membrane biogenesis

Lipid droplet (LD) utilization is an important cellular activity that regulates energy balance and release of lipid second messengers. Because fatty acids exhibit both beneficial and toxic properties, their release from LDs must be controlled. Here we demonstrate that yeast Sfh3, an unusual Sec14-like phosphatidylinositol transfer protein, is an LD-associated protein that inhibits lipid mobilization from these particles. We further document a complex biochemical diversification of LDs during sporulation in which Sfh3 and select other LD proteins redistribute into discrete LD subpopulations. The data show that Sfh3 modulates the efficiency with which a neutral lipid hydrolase-rich LD subclass is consumed during biogenesis of specialized membrane envelopes that package replicated haploid meiotic genomes. These results present novel insights into the interface between phosphoinositide signaling and developmental regulation of LD metabolism and unveil meiosis-specific aspects of Sfh3 (and phosphoinositide) biology that are invisible to contemporary haploid-centric cell biological, proteomic, and functional genomics approaches.

Diacylglycerol kinase delta promotes lipogenesis

We have studied the relationship between diacylglycerol kinase delta (DGKδ) and lipogenesis. There is a marked increase in the expression of DGKδ during the differentiation of 3T3-L1 cells to adipocytes, as well as in the synthesis of neutral and polar lipids. When 3T3-L1 undifferentiated fibroblasts are transfected to express DGKδ, there is increased triglyceride synthesis without differentiation to adipocytes. Hence, expression of DGKδ promotes lipogenesis. Lipid synthesis is decreased in DGKδ knockout mouse embryo fibroblasts, especially for lipids with shorter acyl chains and limited unsaturation. This reduction occurs for both neutral and polar lipids. These findings suggest reduced de novo lipid synthesis. This is confirmed by measuring the incorporation of glycerol into polar and neutral lipids, which is higher in the wild type cells than in the DGKδ knockouts. In comparison, there was no change in lipid synthesis in DGKε knockout mouse embryo fibroblasts. We also demonstrate that the DGKδ knockout cells had a lower expression of acetyl-CoA carboxylase and fatty acid synthase as well as a lower degree of activation by phosphorylation of ATP citrate lyase. These three enzymes are involved in the synthesis of long chain fatty acids. Our results demonstrate that DGKδ markedly increases lipid synthesis, at least in part as a result of promoting the de novo synthesis of fatty acids.

The serine hydrolase ABHD6 Is a critical regulator of the metabolic syndrome

The serine hydrolase α/β hydrolase domain 6 (ABHD6) has recently been implicated as a key lipase for the endocannabinoid 2-arachidonylglycerol (2-AG) in the brain. However, the biochemical and physiological function for ABHD6 outside of the central nervous system has not been established. To address this, we utilized targeted antisense oligonucleotides (ASOs) to selectively knock down ABHD6 in peripheral tissues in order to identify in vivo substrates and understand ABHD6's role in energy metabolism. Here, we show that selective knockdown of ABHD6 in metabolic tissues protects mice from high-fat-diet-induced obesity, hepatic steatosis, and systemic insulin resistance. Using combined in vivo lipidomic identification and in vitro enzymology approaches, we show that ABHD6 can hydrolyze several lipid substrates, positioning ABHD6 at the interface of glycerophospholipid metabolism and lipid signal transduction. Collectively, these data suggest that ABHD6 inhibitors may serve as therapeutics for obesity, nonalcoholic fatty liver disease, and type II diabetes.

Regulation of phospholipase D activity and phosphatidic acid production after purinergic (P2Y6) receptor stimulation

Phosphatidic acid (PA) is a lipid second messenger located at the intersection of several lipid metabolism and cell signaling events including membrane trafficking, survival, and proliferation. Generation of signaling PA has long been primarily attributed to the activation of phospholipase D (PLD). PLD catalyzes the hydrolysis of phosphatidylcholine into PA. A variety of both receptor-tyrosine kinase and G-protein-coupled receptor stimulations have been shown to lead to PLD activation and PA generation. This study focuses on profiling the PA pool upon P2Y6 receptor signaling manipulation to determine the major PA producing enzymes. Here we show that PLD, although highly active, is not responsible for the majority of stable PA being produced upon UDP stimulation of the P2Y6 receptor and that PA levels are tightly regulated. By following PA flux in the cell we show that PLD is involved in an initial increase in PA upon receptor stimulation; however, when PLD is blocked, the cell compensates by increasing PA production from other sources. We further delineate the P2Y6 signaling pathway showing that phospholipase Cβ3 (PLCβ3), PLCδ1, DGKζ and PLD are all downstream of receptor activation. We also show that DGKζ is a novel negative regulator of PLD activity in this system that occurs through an inhibitory mechanism with PKCα. These results further define the downstream events resulting in PA production in the P2Y6 receptor signaling pathway.

Sum of the parts: mass spectrometry-based metabolomics

Metabolomics is a rapidly growing field of research used in the identification and quantification of the small molecule metabolites within an organism, thereby providing insights into cell metabolism and bioenergetics as well as processes important in clinical medicine, such as disposition of pharmaceutical compounds. It offers comprehensive information about thousands of low-molecular mass compounds (<1500 Da) that represent a wide range of pathways and intermediary metabolism. Because of its vast expansion in the past two decades, mass spectrometry has become an indispensable tool in "omic" analyses. The use of different ionization techniques such as the more traditional electrospray and matrix-assisted laser desorption, as well as recently popular desorption electrospray ionization, has allowed the analysis of a wide range of biomolecules (e.g., peptides, proteins, lipids, and sugars), and their imaging and analysis in the original sample environment in a workup free fashion. An overview of the current state of the methodology is given, as well as examples of application.

Regulated accumulation of desmosterol integrates macrophage lipid metabolism and inflammatory responses

Inflammation and macrophage foam cells are characteristic features of atherosclerotic lesions, but the mechanisms linking cholesterol accumulation to inflammation and LXR-dependent response pathways are poorly understood. To investigate this relationship, we utilized lipidomic and transcriptomic methods to evaluate the effect of diet and LDL receptor genotype on macrophage foam cell formation within the peritoneal cavities of mice. Foam cell formation was associated with significant changes in hundreds of lipid species and unexpected suppression, rather than activation, of inflammatory gene expression. We provide evidence that regulated accumulation of desmosterol underlies many of the homeostatic responses, including activation of LXR target genes, inhibition of SREBP target genes, selective reprogramming of fatty acid metabolism, and suppression of inflammatory-response genes, observed in macrophage foam cells. These observations suggest that macrophage activation in atherosclerotic lesions results from extrinsic, proinflammatory signals generated within the artery wall that suppress homeostatic and anti-inflammatory functions of desmosterol.

Long term myriocin treatment increases MRP1 transport activity

We investigated the effect of myriocin treatment, which extensively depletes sphingolipids from cells, on multidrug resistance-related protein 1 (MRP1) efflux activity in MRP1 expressing cells and isolated plasma membrane vesicles. Our data reveal that both short term (3 days) and long term (7 days) treatment effectively reduce the cellular sphingolipid content to the same level. Intriguingly, a two-fold increase in MRP1-mediated efflux activity was observed following long term treatment, while short term treatment had no impact. Very similar data were obtained with plasma membrane vesicles isolated from myriocin-treated cells. Exploiting the cell-free vesicle system, Michaelis-Menten analysis revealed that the intrinsic MRP1 activity remained unaltered; however, the fraction of active transporter molecules increased. We demonstrate that the latter effect is due to an enhanced recruitment of MRP1 into lipid raft fractions, thereby promoting MRP1 activity.

CGI-58/ABHD5-derived signaling lipids regulate systemic inflammation and insulin action

Mutations of comparative gene identification 58 (CGI-58) in humans cause Chanarin-Dorfman syndrome, a rare autosomal recessive disease in which excess triacylglycerol (TAG) accumulates in multiple tissues. CGI-58 recently has been ascribed two distinct biochemical activities, including coactivation of adipose triglyceride lipase and acylation of lysophosphatidic acid (LPA). It is noteworthy that both the substrate (LPA) and the product (phosphatidic acid) of the LPA acyltransferase reaction are well-known signaling lipids. Therefore, we hypothesized that CGI-58 is involved in generating lipid mediators that regulate TAG metabolism and insulin sensitivity. Here, we show that CGI-58 is required for the generation of signaling lipids in response to inflammatory stimuli and that lipid second messengers generated by CGI-58 play a critical role in maintaining the balance between inflammation and insulin action. Furthermore, we show that CGI-58 is necessary for maximal TH1 cytokine signaling in the liver. This novel role for CGI-58 in cytokine signaling may explain why diminished CGI-58 expression causes severe hepatic lipid accumulation yet paradoxically improves hepatic insulin action. Collectively, these findings establish that CGI-58 provides a novel source of signaling lipids. These findings contribute insight into the basic mechanisms linking TH1 cytokine signaling to nutrient metabolism.

Regional skeletal muscle remodeling and mitochondrial dysfunction in right ventricular heart failure

Exercise intolerance is a cardinal symptom of right ventricular heart failure (RV HF) and skeletal muscle adaptations play a role in this limitation. We determined regional remodeling of muscle structure and mitochondrial function in a rat model of RV HF induced by monocrotaline injection (MCT; 60 mg·kg(-1); n = 11). Serial sections of the plantaris were stained for fiber type, succinate dehydrogenase (SDH) activity and capillaries. Mitochondrial function was assessed in permeabilized fibers using respirometry, and isolated complex activity by blue native gel electrophoresis (BN PAGE). All measurements were compared with saline-injected control animals (CON; n = 12). Overall fiber cross-sectional area was smaller in MCT than CON: 1,843 ± 114 vs. 2,322 ± 120 μm(2) (P = 0.009). Capillary-to-fiber ratio was lower in MCT in the oxidative plantaris region (1.65 ± 0.09 vs. 1.93 ± 0.07; P = 0.03), but not in the glycolytic region. SDH activity (P = 0.048) and maximal respiratory rate (P = 0.012) were each ∼15% lower in all fibers in MCT. ADP sensitivity was reduced in both skeletal muscle regions in MCT (P = 0.032), but normalized by rotenone. A 20% lower complex I/IV activity in MCT was confirmed by BN PAGE. MCT-treatment was associated with lower mitochondrial volume density (lower SDH activity), quality (lower complex I activity), and fewer capillaries per fiber area in oxidative skeletal muscle. These features are consistent with structural and functional remodeling of the determinants of oxygen supply potential and utilization that may contribute to exercise intolerance and reduced quality of life in patients with RV HF.

Increased diacylglycerols characterize hepatic lipid changes in progression of human nonalcoholic fatty liver disease; comparison to a murine model

Background and Aims

The spectrum of nonalcoholic fatty liver disease (NAFLD) includes steatosis, nonalcoholic steatohepatitis (NASH), and progression to cirrhosis. While differences in liver lipids between disease states have been reported, precise composition of phospholipids and diacylglycerols (DAG) at a lipid species level has not been previously described. The goal of this study was to characterize changes in lipid species through progression of human NAFLD using advanced lipidomic technology and compare this with a murine model of early and advanced NAFLD.

Methods

Utilizing mass spectrometry lipidomics, over 250 phospholipid and diacylglycerol species (DAGs) were identified in normal and diseased human and murine liver extracts.

Results

Significant differences between phospholipid composition of normal and diseased livers were demonstrated, notably among DAG species, consistent with previous reports that DAG transferases are involved in the progression of NAFLD and liver fibrosis. In addition, a novel phospholipid species (ether linked phosphatidylinositol) was identified in human cirrhotic liver extracts.

Conclusions

Using parallel lipidomics analysis of murine and human liver tissues it was determined that mice maintained on a high-fat diet provide a reproducible model of NAFLD in regards to specificity of lipid species in the liver. These studies demonstrated that novel lipid species may serve as markers of advanced liver disease and importantly, marked increases in DAG species are a hallmark of NAFLD. Elevated DAGs may contribute to altered triglyceride, phosphatidylcholine (PC), and phosphatidylethanolamine (PE) levels characteristic of the disease and specific DAG species might be important lipid signaling molecules in the progression of NAFLD.

Quantitative analysis of glycerophospholipids by LC-MS: acquisition, data handling, and interpretation

As technology expands what it is possible to accurately measure, so too the challenges faced by modern mass spectrometry applications expand. A high level of accuracy in lipid quantitation across thousands of chemical species simultaneously is demanded. While relative changes in lipid amounts with varying conditions may provide initial insights or point to novel targets, there are many questions that require determination of lipid analyte absolute quantitation. Glycerophospholipids present a significant challenge in this regard, given the headgroup diversity, large number of possible acyl chain combinations, and vast range of ionization efficiency of species. Lipidomic output is being used more often not just for profiling of the masses of species, but also for highly-targeted flux-based measurements which put additional burdens on the quantitation pipeline. These first two challenges bring into sharp focus the need for a robust lipidomics workflow including deisotoping, differentiation from background noise, use of multiple internal standards per lipid class, and the use of a scriptable environment in order to create maximum user flexibility and maintain metadata on the parameters of the data analysis as it occurs. As lipidomics technology develops and delivers more output on a larger number of analytes, so must the sophistication of statistical post-processing also continue to advance. High-dimensional data analysis methods involving clustering, lipid pathway analysis, and false discovery rate limitation are becoming standard practices in a maturing field.

A mouse macrophage lipidome

We report the lipidomic response of the murine macrophage RAW cell line to Kdo(2)-lipid A, the active component of an inflammatory lipopolysaccharide functioning as a selective TLR4 agonist and compactin, a statin inhibitor of cholesterol biosynthesis. Analyses of lipid molecular species by dynamic quantitative mass spectrometry and concomitant transcriptomic measurements define the lipidome and demonstrate immediate responses in fatty acid metabolism represented by increases in eicosanoid synthesis and delayed responses characterized by sphingolipid and sterol biosynthesis. Lipid remodeling of glycerolipids, glycerophospholipids, and prenols also take place, indicating that activation of the innate immune system by inflammatory mediators leads to alterations in a majority of mammalian lipid categories, including unanticipated effects of a statin drug. Our studies provide a systems-level view of lipid metabolism and reveal significant connections between lipid and cell signaling and biochemical pathways that contribute to innate immune responses and to pharmacological perturbations.

Lipidomics reveals a remarkable diversity of lipids in human plasma

The focus of the present study was to define the human plasma lipidome and to establish novel analytical methodologies to quantify the large spectrum of plasma lipids. Partial lipid analysis is now a regular part of every patient's blood test and physicians readily and regularly prescribe drugs that alter the levels of major plasma lipids such as cholesterol and triglycerides. Plasma contains many thousands of distinct lipid molecular species that fall into six main categories including fatty acyls, glycerolipids, glycerophospholipids, sphingolipids, sterols, and prenols. The physiological contributions of these diverse lipids and how their levels change in response to therapy remain largely unknown. As a first step toward answering these questions, we provide herein an in-depth lipidomics analysis of a pooled human plasma obtained from healthy individuals after overnight fasting and with a gender balance and an ethnic distribution that is representative of the US population. In total, we quantitatively assessed the levels of over 500 distinct molecular species distributed among the main lipid categories. As more information is obtained regarding the roles of individual lipids in health and disease, it seems likely that future blood tests will include an ever increasing number of these lipid molecules.

Molecular species of phosphatidylinositol-cycle intermediates in the endoplasmic reticulum and plasma membrane

Phosphatidylinositol (PI) turnover is a process requiring both the plasma and ER membranes. We have determined the distribution of phosphatidic acid (PA) and PI and their acyl chain compositions in these two subcellular membranes using mass spectrometry. We assessed the role of PI cycling in determining the molecular species and quantity of these lipids by comparing the compositions of the two membranes isolated from embryonic fibroblasts obtained from diacylglycerol kinase epsilon (DGKepsilon) knockout (KO) and wild-type (WT) mice. In the KO cells, the conversion of arachidonoyl-rich DAG to PA is blocked by the absence of DGKepsilon, resulting in a reduction in the rate of PI cycling. The acyl chain composition is very similar for PI and PA in the endoplasmic reticulum (ER) versus plasma membrane (PM) and for WT versus KO. However, the acyl chain profile for PI is very different from that for PA. This indicates that DGKepsilon is not facilitating the direct transfer of a specific species of PA between the PM and the ER. Approximately 20% of the PA in the ER membrane has one short acyl chain of 14 or fewer carbons. These species of PA are not converted into PI but may play a role in stabilizing regions of high positive curvature in the ER. There are also PI species in both the ER and PM for which there is no detectable PA precursor, indicating that these species of PI are unlikely to arise via the PI cycle. We find that in the PM of KO cells the levels of PI and of PA are decreased approximately 3-fold in comparison with those in either the PM of WT cells or the ER of KO cells. The PI cycle is slowed in the KO cells; hence, the lipid intermediates of the PI cycle can no longer be interconverted and are depleted from the PI cycle by conversion to other species. There is less of an effect of the depletion in the ER where de novo synthesis of PA occurs in comparison with the PM.

Diacylglycerol kinase epsilon is selective for both acyl chains of phosphatidic acid or diacylglycerol

The phosphatidylinositol (PI) cycle mediates many cellular events by controlling the metabolism of many lipid second messengers. Diacylglycerol kinase epsilon (DGK epsilon) has an important role in this cycle. DGK epsilon is the only DGK isoform to show inhibition by its product phosphatidic acid (PA) as well as substrate specificity for sn-2 arachidonoyl-diacylglycerol (DAG). Here, we show that this inhibition and substrate specificity are both determined by selectivity for a combination of the sn-1 and sn-2 acyl chains of PA or DAG, respectively, preferring the most prevalent acyl chain composition of lipids involved specifically in the PI cycle, 1-stearoyl-2-arachidonoyl. Although the difference in rate for closely related lipid species is small, there is a significant enrichment of 1-stearoyl-2-arachidonoyl PI because of the cyclical nature of PI turnover. We also show that the inhibition of DGK epsilon by PA is competitive and that the deletion of the hydrophobic segment and cationic cluster of DGK epsilon does not affect its selectivity for the acyl chains of PA or DAG. Thus, this active site not only recognizes the lipid headgroup but also a combination of the two acyl chains in PA or DAG. We propose a mechanism of DGK epsilon regulation where its dual acyl chain selectivity is used to negatively regulate its enzymatic activity in a manner that ensures DGK epsilon remains committed to the PI turnover cycle. This novel mechanism of enzyme regulation within a signaling pathway could serve as a template for the regulation of enzymes in other pathways in the cell.

Lipidomics: a mass spectrometry based systems level analysis of cellular lipids

Lipidomics is a logical outcome of the history and traditions of lipid biochemistry and advances in mass spectrometry are at the heart of a renaissance in understanding the roles of lipids in cellular functions. Our desire to understand the complexity of lipids in biology has led to new techniques that allow us to identify over 1000 phospholipids in mammalian cell types and tissues. Improvements in chromatographic separation and mass spectrometry have positioned us to determine not only the lipid composition (i.e. parts list) of cells and tissues, but also address questions regarding lipid substrates and products that previously overwhelmed traditional analytical technologies. In the decade since lipidomics was conceived much of the efforts have been on new methodologies, development of computer programs to decipher the gigabytes of raw data, and struggling with the highly variable nature of biological systems where absolute quantities of a given metabolite may be less important than its relative change in concentration. It is clear that the technology is now sufficiently developed to address fundamental questions about the roles of lipids in cellular signaling and metabolic pathways.

Lipidomic profiling in mouse brain reveals differences between ages and genders, with smaller changes associated with alpha-synuclein genotype

Advances in lipidomics technology have facilitated the precise detection, identification and profiling of lipid species within tissues. Mass spectrometry allows for identification of lipids as a function of the total number of carbons and double bonds in their acyl chains. Such detailed descriptions of lipid composition can provide a basis for further investigation of cell signaling and metabolic pathways, both physiological and pathological. Here, we applied phospholipid profiling to mouse models relevant to Parkinson's disease, using mice that were transgenic for human alpha-synuclein (alphaSyn) or deleted of endogenous alphaSyn. Proposed functions of alphaSyn include phospholipid binding, regulation of membrane composition, and regulation of vesicular pools. We investigated whether alphaSyn gene dosage interacts with differences in phospholipid composition across brain regions or with age-related changes in brain phospholipid composition. The most dramatic phospholipid changes were observed in alphaSyn wild-type animals as a function of age and gender. alphaSyn genotype-specific changes were also observed in aged, but not young, mice. Our results provide a detailed and systematic characterization of brain phospholipid composition in mice and identify age-related changes relevant both to Parkinson's disease and to normal aging.

Spatial and temporal alterations of phospholipids determined by mass spectrometry during mouse embryo implantation

Molecular events involved in successful embryo implantation are not well understood. In this study, we used MALDI imaging mass spectrometry (IMS) technologies to characterize the spatial and temporal distribution of phospholipid species associated with mouse embryo implantation. Molecular images showing phospholipid distribution within implantation sites changed markedly between distinct cellular areas during days 4-8 of pregnancy. For example, by day 8, linoleate- and docosahexaenoate-containing phospholipids localized to regions destined to undergo cell death, whereas oleate-containing phospholipids localized to angiogenic regions. Arachidonate-containing phospholipids showed different segregation patterns depending on the lipid class, revealing a strong correlation of phosphatidylethanolamines and phosphatidylinositols with cytosolic phospholipase A(2alpha) and cyclooxygenase-2 during embryo implantation. LC-ESI-MS/MS was used to validate MALDI IMS phospholipid distribution patterns. Overall, molecular images revealed the dynamic complexity of lipid distributions in early pregnancy, signifying the importance of complex interplay of lipid molecules in uterine biology and implantation.

Dramatic differences in the roles in lipid metabolism of two isoforms of diacylglycerol kinase

Lipid species changes for SV40-transformed fibroblasts from wild-type or from diacylglycerol kinase-epsilon (DGKepsilon) or diacylglycerol kinase-alpha (DGKalpha) knockout mice were determined for glycerophospholipids, polyphosphatidylinositides (GPInsP n ) and diacylglycerol (DAG) using direct infusion mass spectrometry. Dramatic differences in arachidonate (20:4 fatty acid)-containing lipids were observed for multiple classes of glycerophospholipids and polyphosphatidylinositides between wild-type and DGKepsilon knockout cells. However, no difference was observed in either the amount or the acyl chain composition of DAG between DGKepsilon knockout and wild-type cells, suggesting that DGKepsilon catalyzed the phosphorylation of a minor fraction of the DAG in these cells. The differences in arachidonate content between the two cell lines were greatest for the GPInsP n lipids and lowest for DAG. These findings indicate that DGKepsilon plays a significant role in determining the enrichment of GPInsP n with 20:4 and that there is a pathway for the selective translocation of arachidonoyl phosphatidic acid from the plasma membrane to the endoplasmic reticulum. In contrast, no substantial difference was observed in the acyl chain composition of any class of glycerophospholipid or diacylglycerol between lipid extracts from fibroblasts from wild-type mice or from DGKalpha knockout mice. However, the cells from the DGKalpha knockout mice had a higher concentration of DAG, consistent with the lack of downregulation of the major fraction of DAG by DGKalpha, in contrast with DGKepsilon that is primarily responsible for enrichment of GPInsP n with arachidonoyl acyl chains.

Vasodilator effects of leptin on canine isolated mesenteric arteries and veins

1. Although leptin increases sympathetic nerve activity and blood pressure, its direct action on large arterial rings is to cause relaxation. However, it is the small resistance arteries and veins that are important in blood pressure control. The effects of leptin on these small vessels has not been reported previously in the canine and the effect of leptin on the capacitance vessels is not known. 2. In the present study, third- or fourth-order canine mesenteric arteries and veins were isolated and placed in a perfusion myograph and preconstricted with noradrenaline. The responses to graded concentrations of leptin were determined and the role of nitric oxide was assessed by administration of N(G)-nitro-l-arginine methyl ester (l-NAME), a blocker of nitric oxide synthase. 3. Leptin induced dose-related dilatations in both arterial and venous segments. The mean (+/-SEM) maximum increases in the diameter of the arteries and veins were 25.0 +/- 4.8 and 29.9 +/- 2.0% of the initial preconstriction, respectively. Relaxations of both arteries and veins were abolished by l-NAME or by endothelium denudation, although dilatations were still obtained to sodium nitroprusside, a nitric oxide donor. 4. These results indicate that leptin dilates canine small mesenteric arteries and veins by a mechanism involving endothelial release of nitric oxide. This observation may result in a decrease of peripheral resistance and venous return and, hence, counteract the leptin-induced neurally mediated vasoconstriction that has been reported previously.

Effects of dietary salt loading on the responses of isolated rat mesenteric arteries to leptin

BACKGROUND

Leptin induces relaxation of vascular smooth muscle through an endothelium-dependent release of nitric oxide (EDNO) and administration of a high-salt diet reduces the relaxation of vessels to EDNO. We would, therefore, predict that salt loading would reduce the leptin-induced dilatation. However, in salt-loaded animals the relaxation to acetylcholine is maintained through an endothelial-dependent hypopolarizing factor instead of EDNO. These experiments were, therefore, designed to examine whether in salt-loaded animals the response to leptin would be reduced or whether, as for acetylcholine, an alternative mechanism would be substituted.

METHODS

Weanling rats were given diets containing either 0.4% (n = 10) or 8% (n = 9) sodium chloride for 4 weeks. They were then killed and a length of second order mesenteric artery was mounted in a perfusion myograph with diameter changes measured using a microscope-video tracking system. The vessels were preconstricted with norepinephrine and then the effects of graded concentrations of leptin were determined.

RESULTS

In vessels from the low salt animals leptin caused a dose-dependent dilatation (maximum change 31.4% +/- 5.8% of the initial norepinephrine-induced constriction) but in the high salt animals the change was only 3.4% +/- 1.1%. The nitric oxide synthase blocker Nomega-nitro-L-arginine methyl ester (L-NAME) abolished the responses, although responses could still be obtained in vessels from both groups to the NO donor, sodium nitroprusside.

CONCLUSIONS

These results indicate that salt loading to rats almost completely abolishes the vasodilatation to leptin. This implies endothelial disruption and, unlike the response to acetylcholine, no other vasodilator mechanism is implicated. This could provide a link between high salt intake and hypertension because the known increase in sympathetic activity caused by leptin would not be countered by a direct vasorelaxation.

Shortcut to mycothiol analogues

[structure: see text] The synthesis of a simplified thioglycosidic analogue (2) of mycothiol (1) is described. Evaluation of 2 against mycothiol S-conjugate amidase from Mycobacterium tuberculosis reveals good specific activity (7500 nmol min(-)(1) mg-protein(-)(1), vs 14 200 for 1), indicating that 2 can serve as a starting point for antitubercular drug design.

Synthesis of alpha-GalNAc thioconjugates from an alpha-GalNAc mercaptan

A variety of functionalized thioglycosides and other derivatives (10-24) of 2-acetamido-2-deoxy-1-thio-alpha-D-galactopyranose have been prepared in good yields and with high anomeric purities by S-substitution reactions of the sulfide anion or sulfur-centered radical from mercaptan 6. Given the importance in nature of the alpha-GalNAc 1-O-linkage, and the greater chemical and biological stability of the corresponding 1-S-linkage, these thioconjugates may find application in studies of synthetic vaccines, enzyme inhibitors, glycomimetic scaffolds, and other complex carbohydrate systems.

Absence of reflex vascular responses from the intrapulmonary circulation in anaesthetised dogs

The aim of this investigation was to determine whether reflex cardiovascular responses were obtained to localised distension of the intrapulmonary arterial and venous circulations in a preparation in which the stimuli to other major reflexogenic areas were controlled and the lung was shown to possess reflex activity. Dogs were anaesthetised with -chloralose, artificially ventilated, the chests widely opened and a cardiopulmonary bypass established. The intrapulmonary region of the left lung was isolated and perfused through the left pulmonary artery and drained through cannulae in the left pulmonary veins via a Starling resistance. Intrapulmonary arterial and venous pressures were controlled by the rate of inflow of blood and the pressure applied to the Starling resistance. Pressures to the carotid, aortic and coronary baroreceptors and heart chambers were controlled. Responses of vascular resistance were assessed from changes in perfusion pressures to a vascularly isolated hind limb and to the remainder of the subdiaphragmatic circulation (flows constant). The reactivity of the preparation was demonstrated by observing decreases in vascular resistance to large step changes in carotid sinus pressure (systemic vascular resistance decreased by -40 +/- 5%), chemical stimulation of lung receptors by injection into the pulmonary circulation of veratridine or capsaicin (resistance decreased by -32 +/- 4%) and, in the four dogs tested, increasing pulmonary stroke volume to 450 ml (resistance decreased by -24 +/- 6%). However, despite this evidence that the lung was innervated, increases in intrapulmonary arterial pressure from 14 +/- 1 to 43 +/- 3 mmHg or in intrapulmonary venous pressure from 5 +/- 2 to 34 +/- 2 mmHg or both did not result in any consistent changes in systemic or limb vascular resistances. In two animals tested, however, there were marked decreases in efferent phrenic nerve activity. These results indicate that increases in pressure confined to the intrapulmonary arterial and venous circulations do not cause consistent reflex vascular responses, even though the preparation was shown to be reflexly active and the lung was shown to be innervated.

Reflex responses from the main pulmonary artery and bifurcation in anaesthetised dogs

This study was undertaken to determine the reflex cardiovascular and respiratory responses to discrete stimulation of pulmonary arterial baroreceptors using a preparation in which secondary modulation of responses from other reflexes was prevented. Dogs were anaesthetised with -chloralose, artificially ventilated, the chests widely opened and a cardiopulmonary bypass established. The main pulmonary arterial trunk, bifurcation and extrapulmonary arteries as far as the first lobar arteries on each side were vascularly isolated and perfused through the left pulmonary artery and drained via the right artery through a Starling resistance which controlled pulmonary arterial pressure. Pressures distending systemic baroreceptors and reflexogenic regions in the heart were controlled. Reflex vascular responses were assessed from changes in perfusion pressures to a vascularly isolated hind limb and to the remainder of the subdiaphragmatic systemic circulation, both of which were perfused at constant flows. Respiratory responses were assessed from recordings of efferent phrenic nerve activity. Increases in pulmonary arterial pressure consistently evoked increases in both perfusion pressures and in phrenic nerve activity. Both vascular and respiratory responses were obtained when pulmonary arterial pressure was increased to above about 30 mmHg. Responses increased at higher levels of pulmonary arterial pressures. In 13 dogs increases in pulmonary arterial pressure to 45 mmHg increased systemic perfusion pressure by 24 +/- 7 mmHg (mean +/- S.E.M.) from 162 +/- 11 mmHg. Setting carotid sinus pressure at different levels did not influence the vascular response to changes in pulmonary arterial pressure. The presence of a negative intrathoracic pressure of -20 mmHg resulted in larger vascular responses being obtained at lower levels of pulmonary arterial pressure. This indicates that the reflex may be more effective in the intact closed-chest animal. These results demonstrate that stimulation of pulmonary arterial baroreceptors evokes a pressor reflex and augments respiratory drive. This reflex is likely to be elicited in circumstances where pulmonary arterial pressure increases and the negative excursions of intrathoracic pressure become greater. They are likely, therefore, to be involved in the cardio-respiratory response to exercise as well as in pathological states such as pulmonary hypertension or restrictive or obstructive lung disease.

Reflex control of splanchnic blood volume in anaesthetized dogs

1. In chloralose-anaesthetized, artificially ventilated dogs, the splenic pedicle was tied and the carotid sinuses were vascularly isolated and perfused at controlled pressures. In Series 1 experiments, the hepatosplanchnic circulation was perfused through the abdominal aorta with a tie on the aorta separating it from the caudal circulation, which was perfused through the femoral arteries. The two circulations were drained from cannulae in the inferior vena cava and the femoral veins, with a tie on the inferior vena cava separating the two. In Series 2, the splanchnic circulation drained from the portal vein. In both series, inflows and outflows were measured and integrated to derive volume changes. Capacitance responses were assessed during constant flow, and capacitance plus passive responses were obtained during constant pressure perfusion. 2. In Series 1, an increase in carotid sinus pressure (from 8 to 26 kPa) during constant flow and constant pressure perfusion increased hepatosplanchnic volume by 2.5 and 5.7 ml (kg body weight)-1, respectively. The volume of the subdiaphragmatic circulation did not increase during constant flow, but during constant pressure it increased by 2.0 ml (kg body weight)-1. 3. In Series 2, increasing carotid pressure during constant flow and constant pressure increased the volume of the splanchnic circulation by 0.5 and 4.2 ml (kg body weight)-1, respectively. 4. These results confirm that carotid baroreceptor stimulation causes larger volume changes during constant pressure perfusion than during constant flow perfusion. Also, the active capacitance change in the splanchnic circulation is small in relation to the passive response. We propose that in dogs (following splenic ligation), the major active capacitance control is from the liver. However, large passive changes in splanchnic volume occur due to changes in flow.

Reflex vascular responses in the anesthetized dog to large rapid changes in carotid sinus pressure

This study examined reflex vascular responses to large rapid increases and decreases in carotid sinus pressure to determine whether delayed or inappropriate vascular responses might be obtained that, if they occurred in people, could lead to hypotension during exposure to rapidly alternating gravitational forces. In chloralose-anesthetized open-chest dogs, a perfusion circuit controlled carotid sinus and thoracic aortic pressures and blood flows to both the vascularly isolated abdominal circulation and a hindlimb (perfusion pressure changes denoted resistance). When carotid pressure was increased and decreased over the range of 60-180 mmHg, the resulting reflex vasodilatation occurred significantly more rapidly than the vasoconstriction (P < 0.001). In the abdominal vascular bed, time constants for vasodilatation and vasoconstriction were 4.2 +/- 0.5 and 7.5 +/- 1.0 s, respectively. Decreases in carotid pressure in pulses of 10-s duration or less failed to elicit maximal vasoconstriction, whereas increases in carotid pressure lasting as little as 5 s did elicit maximal vasodilatation. "Square-wave" alternations in carotid pressure with periods of 10 s or less (5 s high, 5 s low) resulted in attenuation of the vasoconstriction, and at a 4-s period, both vascular beds remained almost maximally vasodilated throughout. The failure of vascular resistance to follow carotid pressure changes was not due to a failure of the response of sympathetic efferent activity, since the time constants for the reduction and increase in discharge were much shorter at 0.56 +/- 0.13 and 0.43 +/- 0.10 s, respectively. These results indicate that rapid changes in carotid pressure could result in inappropriate vasodilatation and hypotension and might, in some circumstances, such as in pilots flying high-performance aircraft, predispose to syncope.

Blood mobilization from the liver of the anaesthetized dog

The abdominal circulation contains a high proportion of the total blood volume and this can change either passively in response to changes in vascular distending pressure or actively (termed a capacitance response) to changes in sympathetic nervous activity. The liver is the largest abdominal organ and this study was designed to evaluate its potential contribution to overall vascular capacitance and compliance. In chloralose anaesthetized dogs, the liver was vascularly isolated, perfused through the portal vein and hepatic artery at either constant pressures or constant flows and drained from the hepatic veins at constant pressure. Changes in vascular resistance were assessed from changes in inflow pressures or flows and hepatic blood volume was determined by differences between net inflow and outflow. During constant flow perfusion the change in hepatic volume (capacitance change) in response to supramaximal stimulation of sympathetic nerves at 16 Hz was (mean +/- S.E.M.) -2.40 +/- 0.61 ml (kg body weight)-1. This response was not significantly different during constant pressure perfusion. The changes in portal venous and hepatic arterial pressures during stimulation at constant flow perfusion were +0.67 +/- 0.13 and +4.92 +/- 0.67 kPa, respectively. The compliance of the liver, assessed as the change in volume to a change in hepatic venous pressure, was +5.44 +/- 0.18 ml kg-1 kPa-1. These results indicate that the liver has a major capacitance role, comparable to that of the canine spleen and, in addition, is highly compliant. No evidence was found to suggest that a sphincter on the hepatic outflow exists. Assuming similar responses occur in humans, who do not possess a large contractile spleen, the liver would be the most important controllable blood reservoir in the body.

Reflex vascular responses to alterations in abdominal arterial pressure and flow in anaesthetized dogs

The existence of abdominal arterial baroreceptors has long been controversial. Previously difficulties have been encountered in localizing a stimulus to abdominal arteries without affecting reflexogenic areas elsewhere. In these experiments, using anaesthetized dogs, the abdomen was vascularly isolated at the level of the diaphragm, perfused through the aorta, and drained from the inferior vena cava to a reservoir. Changes in abdominal arterial pressure were effected by changing the perfusion pump speed. During this procedure the flow back to the animal from the venous outflow reservoir was held constant. Increases and decreases in abdominal arterial pressure resulted, respectively, in decreases and increases in perfusion pressure to a vascularly isolated hind-limb and in some dogs also a forelimb. Responses were significantly larger when carotid sinus pressure was high (120-180 mmHg) than when it was low (60 mmHg). Responses were still obtained after cutting vagus, phrenic and splanchnic nerves, but were abolished by spinal cord lesion at T12. These experiments provide evidence for the existence of abdominal arterial baroreceptors. The afferent pathway for the reflex vasodilatation appears to run in the spinal cord.

Mechanisms responsible for changes in abdominal vascular volume during sympathetic nerve stimulation in anaesthetized dogs

This study was designed to determine the extent to which the decrease in volume of blood in the abdominal circulation in response to sympathetic stimulation was due to a passive effect of decreasing flow rather than active constriction of the capacitance vessels. In dogs anaesthetized with alpha-chloralose (100 mg kg-1 i.v.) the abdominal circulation was vascularly isolated and perfused either at constant flow or at constant pressure, and drained at constant pressure from the inferior vena cava. Changes in volume were determined by integration of the differences between inflow and outflow. Supramaximal stimulation of both splanchnic (sympathetic) nerves at 1 Hz decreased abdominal volume during constant pressure perfusion (active and passive components) by 3.04 +/- 0.58 ml kg-1 and at constant flow (active responses only) by 2.30 +/- 0.49 ml kg-1 (means +/- S.E.M.). The responses at 8 Hz were respectively 9.52 +/- 0.91 and 5.09 +/- 0.49 ml kg-1. The proportion of the responses calculated to be passive at 1 and 8 Hz was 23 +/- 6.3 and 45 +/- 5.1%, respectively. These responses were almost identical to those induced by changing inflow by increasing the pump speed. Following ligation of the splenic pedicle, the responses during both constant pressure and constant flow were reduced by similar amounts, indicating that only the active response was affected. After ligation of the splenic pedicle, the proportion of the response calculated to be passive at 1 and 8 Hz increased to 44 +/- 8.0 and 62 +/- 3.7% respectively. These results indicate the importance of passive volume change in affecting abdominal volume, particularly following ligation of the splenic circulation.

Reflex vascular responses to abdominal venous distension in the anesthetized dog

This was undertaken to determine whether distension of the subdiaphragmatic veins results in reflex vasoconstriction and interacts with the carotid baroreflex. In alpha-chloralose-anesthetized open-chest dogs, a perfusion circuit controlled carotid and thoracic aortic pressures, splanchnic and limb blood flows, and cardiopulmonary blood flows. At carotid sinus pressures below approximately 90 mmHg, increases in splanchnic pressure of 7 mmHg or more resulted in increases in vascular resistance in both the splanchnic and limb circulations; there was no response at higher carotid pressures. At high venous pressures, the average maximum gains of the carotid baroreflex for splanchnic and limb resistance responses were increased by 106 and 67%, respectively. The responses were not abolished by cutting the vagal or phrenic nerves but were prevented by cutting the splanchnic nerves and, for the limb, the sciatic and femoral nerves. These results suggest that splanchnic congestion, by causing vasoconstriction and augmentation of the carotid baroreflex, may be important in the maintenance of blood pressure during gravitational stress.

The effect of anticoagulant choice on apparent total antioxidant capacity using three different methods

We assessed total antioxidant capacity using three different methods, in plasma samples treated with either EDTA or heparin as anticoagulant, from 26 healthy subjects. Total antioxidant capacity was determined using an oxygen electrode (as the total peroxyl radical-trapping antioxidant parameter), by enhanced chemiluminescence, and by measurement of the antioxidant-mediated quenching of the absorbance of a radical cation. The choice of anticoagulant had a profound effect on antioxidant capacity with heparinized plasma giving consistently higher values than plasma anticoagulated with EDTA. Using the oxygen electrode the mean value was 786.5 +/- 171.5 mumol/L (heparin) compared to 681.4 +/- 160.4 mumol/L (EDTA, P < 0.01). The chemiluminescence technique gave a mean antioxidant capacity of 915.6 +/- 214.1 mumol/L in heparin samples and 714.4 +/- 195.4 mumol/L in EDTA samples (P < 0.0001). The absorbance quenching technique gave a mean value of 867.0 +/- 199.2 mumol/L (heparin) and 675.5 +/- 245.4 mumol/L (EDTA, P < 0.001). All methods tested showed comparable results for EDTA plasma, but the chemiluminescence technique gave higher apparent antioxidant capacity than either of the two techniques when heparin plasma was used. We suggest that either heparin is interacting to enhance antioxidant protection perhaps through release of superoxide dismutase, or the chelation of metal ions by EDTA is limiting the activity of antioxidant metalloenzymes. Consistency in the choice of anticoagulant is clearly extremely important.

The effect of propofol anaesthesia on free radical-induced lipid peroxidation in rat liver microsomes

In order to assess the in vivo significance of the free radical scavenging properties of propofol the effect of propofol anaesthesia on the sensitivity of rat liver microsomes to radical-induced lipid peroxidation has been examined. Microsome peroxidation was initiated with a combination of reduced nicotinamide adenine dinucleotide phosphate and ferric ions, and assessed by measuring the changes in oxygen tension in the microsome suspension. In comparison to animals receiving 10% intralipid, saline or midazolam, microsomes prepared from animals anaesthetized with propofol demonstrated a significantly increased resistance to lipid peroxidation. Thus, the median delay in onset of the maximum rate of oxygen consumption in animals receiving a bolus of propofol was 23.1 min (range 14.4-32.3), in comparison to delays in the animals receiving intralipid, saline or midazolam of 1.9 (0.5-4.1), 2.4 (2.0-3.7) and 3.0 (1.8-6.1) min respectively (P < 0.01 in each case, Mann Whitney U-test). More prolonged anaesthesia with either repeated boluses or an infusion of propofol also delayed the onset of lipid peroxidation (45.6 (27.2-60) and 18.3 (9.2-60) min respectively). We conclude that the free radical scavenging properties of propofol are biologically significant at anaesthetic doses.

The antioxidant potential of propofol (2,6-diisopropylphenol)

We have examined in vitro the antioxidant properties of 2,6-diisopropylphenol. In studies using electron spin resonance spectroscopy we have demonstrated that 2,6-diisopropylphenol acts as an antioxidant by reacting with free radicals to form a phenoxyl radical--a property common to all phenol-based free radical scavengers. In additional experiments, the antioxidant properties of the clinical formulation of 2,6-diisopropylphenol (propofol) have been measured using an assay of antioxidant potential. In these experiments, propofol, but not Intralipid, was found to exhibit significant antioxidant activity, such that in the range of propofol concentrations examined (10(-6)-10(-5) mol litre-1), each molecule of 2,6-diisopropylphenol was able to scavenge two radical species. We conclude that the free radical scavenging properties of 2,6-diisopropylphenol resemble those of the endogenous antioxidant alpha-tocopherol (vitamin E).

Direct detection of free radical generation in an in vivo model of acute lung injury

Electron spin resonance (ESR) spectroscopy has been used to provide direct evidence that free radical production occurs in an in vivo model of acute lung injury. Two experimental groups of rabbits were given the spin trap alpha-phenyl N-tert.-butyl nitrone (PBN), together with endotoxin in the test group, and saline in the control group. Both groups were subsequently briefly ventilated with air containing cigarette smoke. Plasma samples from the endotoxin pretreated group showed a sudden burst of radical formation, detected as PBN spin adduct, which peaked in the first ten minutes after smoke exposure. No signals were detected in the control group. Permeability of the alveolar capillary barrier of the lung, measured by the clearance of 99mTc-DTPA, demonstrated significantly greater damage following smoke in the endotoxin primed animals than in the controls. Temporal studies suggest that this increase in permeability occurred after a burst of radical production. These studies provide supportive evidence for the hypothesis that endotoxin promotes the accumulation of a population of primed white cells within the lung, which when triggered by cigarette smoke, are able to generate a burst of free radicals which produce tissue damage and acute lung injury.

Active and passive tactual recognition of form

Subjects (N = 30) actively touched forms with the preferred palm or were restricted to passive touch, where forms were either statically or sequentially pressed on the palm. Visual matches to tactual standards were made with unlimited stimulus exposure time. Active touch was superior to both forms of passive touch in recognition accuracy. The provision of sequential presentations and stimulus change failed to aid passive touch.