Lower Levels Of Phosphatidylcholine Research Articles

Lipidomic Analyses Reveal Specific Alterations of Phosphatidylcholine in Dystrophic Mdx Muscle.

In Duchenne muscular dystrophy (DMD), lack of dystrophin increases the permeability of myofiber plasma membranes to ions and larger macromolecules, disrupting calcium signaling and leading to progressive muscle wasting. Although the biological origin and meaning are unclear, alterations of phosphatidylcholine (PC) are reported in affected skeletal muscles of patients with DMD that may include higher levels of fatty acid (FA) 18:1 chains and lower levels of FA 18:2 chains, possibly reflected in relatively high levels of PC 34:1 (with 16:0_18:1 chain sets) and low levels of PC 34:2 (with 16:0_18:2 chain sets). Similar PC alterations have been reported to occur in the mdx mouse model of DMD. However, altered ratios of PC 34:1 to PC 34:2 have been variably reported, and we also observed that PC 34:2 levels were nearly equally elevated as PC 34:1 in the affected mdx muscles. We hypothesized that experimental factors that often varied between studies; including muscle types sampled, mouse ages, and mouse diets; may strongly impact the PC alterations detected in dystrophic muscle of mdx mice, especially the PC 34:1 to PC 34:2 ratios. In order to test our hypothesis, we performed comprehensive lipidomic analyses of PC and phosphatidylethanolamine (PE) in several muscles (extensor digitorum longus, gastrocnemius, and soleus) and determined the mdx-specific alterations. The alterations in PC 34:1 and PC 34:2 were closely monitored from the neonate period to the adult, and also in mice raised on several diets that varied in their fats. PC 34:1 was naturally high in neonate’s muscle and decreased until age ∼3-weeks (disease onset age), and thereafter remained low in WT muscles but was higher in regenerated mdx muscles. Among the muscle types, soleus showed a distinctive phospholipid pattern with early and diminished mdx alterations. Diet was a major factor to impact PC 34:1/PC 34:2 ratios because mdx-specific alterations of PC 34:2 but not PC 34:1 were strictly dependent on diet. Our study identifies high PC 34:1 as a consistent biochemical feature of regenerated mdx-muscle and indicates nutritional approaches are also effective to modify the phospholipid compositions.

Metabonomics Study on Serum Characteristic Metabolites of Psoriasis Vulgaris Patients With Blood-Stasis Syndrome.

Psoriasis is a chronic, refractory, systemic inflammatory skin disease. Traditional Chinese medicine (TCM) shows unique advantage in the treatment of psoriasis based on syndrome differentiation. An untargeted high-throughput metabonomics method based on liquid chromatography coupled to mass spectrometry was applied to study the serum metabolic characteristics in different TCM syndrome types in patients with psoriasis vulgaris (PV), and to discover potential serum biomarkers for its pathogenesis on the endogenous metabolite differentiation basis. The serum metabolic profiles of 45 healthy controls and 124 patients with PV (50 in the blood-stasis group, 30 in the blood-heat group, and 44 in the blood-dryness group) were acquired. The raw spectrometric data were processed using multivariate statistical analysis, and 14 biomarkers related to TCM syndrome differentiation and psoriasis types were screened and identified. The blood-stasis syndrome group showed abnormal lipid metabolism, which was characterized by a low level of phosphatidylcholine (PC) and a high level of lysophosphatidylcholine (LPC). We propose that platelet-activating factor can be applied as a potential biomarker in clinical diagnosis and differentiation of PV with blood-stasis syndrome. The difference in the serum metabolites among PV types with different TCM syndromes and healthy control group illustrated the objective material basis in TCM syndrome differentiation and classification of psoriasis.

Revealing Further Insights on Chilling Injury of Postharvest Bananas by Untargeted Lipidomics.

Chilling injury is especially prominent in postharvest bananas stored at low temperature below 13 °C. To elucidate better the relationship between cell membrane lipids and chilling injury, an untargeted lipidomics approach using ultra-performance liquid chromatography–mass spectrometry was conducted. Banana fruit were stored at 6 °C for 0 (control) and 4 days and then sampled for lipid analysis. After 4 days of storage, banana peel exhibited a marked chilling injury symptom. Furthermore, 45 lipid compounds, including glycerophospholipids, saccharolipids, and glycerolipids, were identified with significant changes in peel tissues of bananas stored for 4 days compared with the control fruit. In addition, higher ratio of digalactosyldiacylglycerol (DGDG) to monogalactosyldiacylglycerol (MGDG) and higher levels of phosphatidic acid (PA) and saturated fatty acids but lower levels of phosphatidylcholine (PC), phosphatidylethanolamine (PE), and unsaturated fatty acids were observed in banana fruit with chilling injury in contrast to the control fruit. Meanwhile, higher activities of phospholipase D (PLD) and lipoxygenase (LOX) were associated with significantly upregulated gene expressions of MaPLD1 and MaLOX2 and higher malondialdehyde (MDA) content in chilling injury-related bananas. In conclusion, our study indicated that membrane lipid degradation resulted from reduced PC and PE, but accumulated PA, while membrane lipid peroxidation resulted from the elevated saturation of fatty acids, resulting in membrane damage which subsequently accelerated the chilling injury occurrence of banana fruit during storage at low temperature.

NMR-Based Lipidomic Analysis of Red Blood Cells Membranes in Type 2 Diabetes

Changes in the composition of red blood cells membranes may lead to in an altered blood rheological pattern. Experimental studies suggest that hyperglycemia affects red cell rheology via direct effects on the membrane, including alterations of the lipid membrane bilayer composition and microviscosity and changes in membrane Na+/K+ ATP-ase function. We aimed to investigatate the 1H NMR-based lipid profile of RBC membranes in type 2 diabetic patients and compare it to that of nondiabetic subjects. Blood samples from 25 nondiabetic and 15 diabetic individuals were collected after an overnight fast. The groups were matched for age, sex and conventional lipid parameters. RBC were lysed and their lipid content was extracted according to a standard procedure. The lipid profile of membranes was recorded on Bruker DRX-500 NMR Spectrometer and analyzed by multivariate data techniques. The NMR-based lipidomic analysis showed that diabetic patients presented a significantly different lipid profile in RBC membranes compared to that recorded in nondiabetic individuals. RBC membranes from patients with diabetes were characterized by altered fatty acid pattern e.g., higher saturated and lower unsaturated fatty acid levels and lower concentrations of omega-3 fatty acids, mainly docosahexaenoic acid. In addition, lower levels of phosphatidylcholine and phosphatidylethanolamine, and higher levels of sphingomyelin and cholesterol were observed in diabetic patients compared to nondiabetic individuals. In conclusion, the lipid composition of RBC membranes in the diabetic state is significantly altered. These disturbances may be involved in the pathogenesis of the microvascular complications of diabetes through the disruption of tissue delivery of oxygen. Additionally, the increased cholesterol content of red cell membranes that reach the lipid core of the atherosclerotic plaques through the vasa vasorum may lead to core expansion, decrease their stability and make them prone to rupture. Disclosure C. Kostara: None. E. Bairaktari: None. M. Elisaf: None. V. Tsimihodimos: None.

Cholesterol-Independent SREBP-1 Maturation Is Linked to ARF1 Inactivation.

Lipogenesis requires coordinated expression of genes for fatty acid, phospholipid, and triglyceride synthesis. Transcription factors, such as SREBP-1 (Sterol regulatory element binding protein), may be activated in response to feedback mechanisms linking gene activation to levels of metabolites in the pathways. SREBPs can be regulated in response tomembrane cholesterol and we also found that low levels of phosphatidylcholine (a methylated phospholipid) led to SBP-1/SREBP-1 maturation in C.elegans or mammalian models. To identify additional regulatory components, we performed a targeted RNAi screen in C.elegans, finding that both lpin-1/Lipin 1 (which converts phosphatidic acid to diacylglycerol) and arf-1.2/ARF1 (a GTPase regulating Golgi function) were important for low-PC activation of SBP-1/SREBP-1. Mechanistically linking the major hits of our screen, we find that limiting PCsynthesis or LPIN1 knockdown in mammalian cells reduces the levels of active GTP-bound ARF1. Thus, changes in distinct lipid ratios may converge on ARF1 to increase SBP-1/SREBP-1 activity.

Components of the cytosolic and released virtosomes from stimulated and non-stimulated human lymphocytes

Abstract aimThis work intends to analyse the structure and the composition of virtosomes and their role. BackgroundVirtosomes are newly synthesized DNA-RNA-lipoprotein complexes released from living cells in a regulated and energy-dependent manner. MethodsVirtosome fractions were isolated by ultracentrifugation from human lymphocytes cytoplasm and from culture medium before and after stimulation with phitoemoagglutinin (PHA). The composition in DNA, RNA, protein and lipids was determined. The virtosomes present in the culture medium were put in contact with lymphocytes. ResultsVirtosome fractions released from non-stimulated lymphocytes are shown to reduce replication of stimulated lymphocytes and those from stimulated lymphocytes to increase multiplication of non-stimulated lymphocytes. Biochemical analyses of the virtosomal complexes have shown that those from stimulated lymphocytes have five proteins that are absent from non-stimulated virtosome fractions. A comparison of the cytosolic versus released virtosome fractions from non-stimulated lymphocytes indicated that there is a greater percentage of phospholipids in the released virtosomes with a corresponding decrease in the percentage of protein. ConclusionAlthough there is a presence of cholesterol in the virtosomes, the low levels of phosphatidylcholine and cholesterol, together with the low ratios of cholesterol: phospholipids leads to a confirmation of the apparent lack of a limiting membrane around the virtosomes. General significanceVirtosomes are structural particles formed in the cytoplasm, released from the cells and capable to be transferred in other cells influencing their behaviour.

Impaired liver regeneration in Ldlr−/− mice is associated with an altered hepatic profile of cytokines, growth factors, and lipids

It is widely recognized that in the early stages of liver regeneration after partial hepatectomy, the hepatocytes accumulate a significant amount of lipids. The functional meaning of this transient steatosis and its effect on hepatocellular proliferation are not well defined. In addition, the basic mechanisms of this lipid accumulation are not well understood although some studies suggest the participation of the Low Density Lipoprotein Receptor (Ldlr). To address these questions, we studied the process of liver regeneration in Ldlr null mice and wild type mice following partial hepatectomy. Ldlr deficiency was associated with a significant decrease in serum albumin concentration, during early stages of liver regeneration, and a delayed hepatic regeneration. Remnant livers of Ldlr(-)(/)(-) showed a time-shifted expression of interleukin-6 (IL6) and a defective activation of tumor necrosis factor-α (TNFα) and hepatocyte growth factor (HGF) expression in early phases of liver regeneration. Unexpectedly, Ldlr(-)(/)(-) showed no significant differences in the content of lipid droplets after partial hepatectomy compared to wild type mice. However, lipidomic analysis of the regenerating liver from Ldlr(-)(/)(-) revealed a lipid profile compatible with liver quiescence: high content of cholesterol esters and ceramide, and low levels of phosphatidylcholine. Ldlr deficiency is associated with significant changes in the hepatic lipidome that affect cytokine-growth factor signaling and impair liver regeneration. These results suggest that the analysis of the hepatic lipidome may help predict the success of liver regeneration in the clinical environment, specifically in the context of pre-existing liver steatosis.

Effects of dietary levels and ratio of phosphatidylcholine and phosphatidylinositol on the growth, survival and deformity levels of Atlantic cod larvae and early juveniles

Effects of two weaning diets that differed in phospholipid (PL) classes on growth, survival and deformities of cod larvae and early juveniles were evaluated. Cod larvae were fed rotifers until 21 days post hatch (dph) and then weaning onto dry diet started. One group of larvae were fed a control diet with low levels of phosphatidylcholine (PC), PE and phosphatidylinositol (PI) and the other group of larvae were fed with an experimental diet containing higher levels of PC, PE and PI. Larvae fed with the control diet were significantly smaller than larvae fed with the experimental diet at the end of the experiment. Swim bladder abnormalities were significantly higher in larvae fed with control diet at 35 dph than the larvae fed with experimental diet; however, no significant difference was evident at 42 dph. Vertebral deformities were significantly higher in larvae fed with control diet and scoliosis was significantly different between the treatments. Survival was also significantly higher in the experimental group. Our results indicate that dietary levels of PL, PC and PI may affect the cod larval growth, survival and deformities. More detail studies are needed to find out the optimal levels of these important PL classes in larval cod diets.

Anti-inflammatory Effects of Phosphatidylcholine

We recently showed that mucus from patients with ulcerative colitis, a chronic inflammatory disorder of the colon, is characterized by a low level of phosphatidylcholine (PC) while clinical studies reveal that therapeutic addition of PC using slow release preparations is beneficial. The positive role of PC in this disease is still elusive. Here we tested the hypothesis that exogenous application of PC has anti-inflammatory properties using three model systems. First, human Caco-2 cells were treated with tumor necrosis factor-alpha (TNF-alpha) to induce a pro-inflammatory response via activation of NF-kappaB. Second, latex bead phagosomes were analyzed for their ability to assemble actin in vitro, a process linked to pro-inflammatory signaling and correlating with the growth versus killing of mycobacteria in macrophages. The third system used was the rapid assembly of plasma membrane actin in macrophages in response to sphingosine 1-phosphate. TNF-alpha induced a pro-inflammatory response in Caco-2 cells, including 1) assembly of plasma membrane actin; 2) activation of both MAPKs ERK and p38; 3) transport of NF-kappaB subunits to the nucleus; and 4) subsequent up-regulation of the synthesis of pro-inflammatory gene products. Exogenous addition of most PCs tested significantly inhibited these processes. Other phospholipids like sphingomyelin or phosphatidylethanolamine showed no effects in these assays. PC also inhibited latex bead phagosome actin assembly, the killing of Mycobacterium tuberculosis in macrophages, and the sphingosine 1-phosphate-induced actin assembly in macrophages. TNF-alpha induces the activation of signaling molecules and the reorganization of the actin cytoskeleton in human intestinal cells. Exogenous application of PC blocks pro-inflammatory signaling in Caco-2 cells, in phagosomes in vitro and facilitates intracellular survival of mycobacteria. We provide further evidence that actin assembly by membranes is part of the pro-inflammatory response. Collectively, these results provide a molecular foundation for the clinical studies showing a beneficial effect of PC therapy in ulcerative colitis.

Phosphatidylcholine levels in Bradyrhizobium japonicum membranes are critical for an efficient symbiosis with the soybean host plant

Phosphatidylcholine (PC), the major membrane phospholipid in eukaryotes, is found in only some bacteria including members of the family Rhizobiaceae. For this reason, it has long been speculated that rhizobial PC might be required for a successful interaction of rhizobia with their legume host plants in order to allow the formation of nitrogen-fixing root nodules. A major pathway for PC formation in prokaryotes involves a threefold methylation of the precursor phosphatidylethanolamine (PE). Here, we report on the isolation of a Bradyrhizobium japonicum gene (pmtA) encoding the phospholipid N-methyltransferase PmtA. Upon expression of the bradyrhizobial pmtA gene in Escherichia coli, predominantly monomethylphosphatidylethanolamine was formed from PE. PmtA-deficient B. japonicum mutants still produced low levels of PC by a second methylation pathway. The amount of PC formed in such mutants (6% of total phospholipids) was greatly decreased compared with the wild type (52% of total phospholipids). Root nodules of soybean plants infected with B. japonicum pmtA mutants showed a nitrogen fixation activity of only 18% of the wild-type level. The interior colour of the nodules was beige instead of red, suggesting decreased amounts of leghaemoglobin. Moreover, ultrastructure analysis of these nodules demonstrated a greatly reduced number of bacteroids within infected plant cells. These data suggest that the biosynthesis of wild-type amounts of PC are required to allow for an efficient symbiotic interaction of B. japonicum with its soybean host plant.

Surfactant levels after reversible tracheal occlusion and prenatal steroids in experimental diaphragmatic hernia

In normal lungs, fetal tracheal occlusion (TO) induces lung growth but decreases the number of type II cells; this is remedied if TO is released (TR) before delivery. In the current study, the effects of TO with or without TR on pulmonary structure and surfactant were assessed in the ovine model in which lung hypoplasia was induced by creation of a diaphragmatic hernia (CDH). A left-sided CDH was created in fetal lambs at 80 days gestation; TO was done at 108 days; and TR at 129 days. All ewes were given 1 dose of glucocorticoids at 135 days. At 136 days, the fetus was delivered. Lung weight to body weight ratio, mean terminal bronchiole density, type II cell density, bronchoalveolar lavage fluid (BAL) phosphatidylcholine (PC), BAL surfactant protein A (SP-A) and B (SP-B), and lung tissue SP-A and SP-B were assessed in CDH, CDH with TO, CDH with TO and TR, and controls. CDH lungs were hypoplastic and structurally immature, but had increased type II cell density. TO with or without TR caused lung growth with normalization of lung parenchymal architecture and type II cell density. Although the BAL SP-A and BAL SP-B were similar in all 4 groups, the BAL PC was low in CDH with or without TO or TR. Also, lung tissue SP-B levels were low in CDH with or without TO or TR. However, lung tissue SP-A levels were normal in CDH, but low in CDH with TO with or without TR. Despite the finding that lung morphology was improved in CDH with TO with or without TR animals, surfactant content and composition remained abnormal. Although surfactant secreted early by the fetus into alveolar spaces contained normal levels of BAL SP-A and BAL SP-B, the low levels of BAL PC and low lung tissue stores of SP-B indicate that these experimental lambs may experience respiratory insufficiency soon after birth. This implies that prophylactic surfactant at birth might be beneficial for CDH.

Distinct alterations in phospholipid metabolism in brains of apolipoprotein E-deficient mice

Apolipoprotein E (ApoE) is the major brain lipoprotein and plays an important role in lipid transport. ApoE-deficient mice whose apoE gene has been knocked out have distinct cognitive and neurochemical deficits, and their recovery from brain injury is impaired. In the present study we examined the possibility that the neuronal derangements of apoE-deficient mice are related to impairments in their phospholipid metabolism. This was performed by comparison of the phospholipid, fatty acid, and cholesterol compositions of distinct membranal brain fractions of apoE-deficient and control mice. Analysis of the microsomal membrane fraction P(3) revealed that, in apoE-deficient mice, these membranes contain significantly lower levels of phosphatidylcholine (PC) than those of control mice. This effect was specific to PC and thus resulted in a twofold decrease of the PC to phosphatidylethanolamine (PE) ratio in apoE-deficient mice compared to the corresponding control ratio. In contrast, the cholesterol levels of the microsomal membranes of the two mice were similar, and the fatty acid composition of their PC was unchanged. There were, however, changes in the fatty acid composition of PE and phosphatidylserine (PS), which resulted in a lower ratio of polyunsaturated to saturated fatty acids in PE and in a higher ratio in apoE-deficient mice compared to the corresponding control values. These effects were specific to the microsomal fraction P(3) and were not observed with the brain subcellular membrane fraction P(2), which is composed mainly of plasma and mitochondrial membranes and whose phospholipid, fatty acid, and cholesterol levels were similar in apoE-deficient and control mice. These findings show that apoE deficiency results in specific and intracellular compartment-dependent changes in phospholipid metabolism, which may play an important role in mediating the neuronal effects of apoE.

Regional lipid composition in the rat brain.

The lipid composition of the brain is of great importance to its metabolism and function. Although much research has been done on regional brain lipid composition, studies usually suffer from limited brain regions or from limited lipids analyzed. We modified a previously described method for the separation of brain phospholipids and glycolipids, improving the separation and sensitivity of the method. Using this modified method, we measured the lipid composition of the frontal and entorhinal cortices, the hippocampus, basal ganglia, cerebellum, and medulla oblongata of five rats under nitrous oxide analgesia. Total lipid content was highest (p < 0.05) in the medulla oblongata (111.0 +/- 6.0 mg/g wet brain, X +/- SD) followed by the hippocampus (72.6 +/- 2.8), cerebellum (62.7 +/- 4.6), basal ganglia (62.6 +/- 1.5), frontal cortex (57.7 +/- 2.1), and entorhinal cortex (53.3 +/- 1.9). The areas with higher total lipid content (p < 0.05) also had higher percentages of cerebrosides (18.6 +/- 2.2 in the medulla oblongata vs 8.3 +/- 1.2 in the frontal cortex) and 40 to 50% lower levels of phosphatidylcholine and phosphatidylinositol. The relation between the ratio of cerebrosides plus sulfatides to phosphatidylcholine and the total lipid content indicates that differences in brain lipid composition between regions are attributable to their relative gray/white matter content.

Phosphatidylcholine and phosphatidylethanolamine enhance the activity of the mammalian mitochondrial endonuclease in vitro.

The purified endonuclease of bovine heart mitochondria extensively degrades a variety of DNA templates in vitro but shows a remarkably strong preference to nick within one specific evolutionarily conserved sequence block of 12 consecutive guanine residues which resides just upstream from the heavy strand origin of mitochondrial DNA replication (Low, R. L., Cummings, O. W., and King, T. C. (1987) J. Biol. Chem. 262, 16164-16170). If the enzyme serves to provide an important nicking function at this site in vivo, then mitochondrial factors likely exist which further enhance the enzyme's recognition of this locus and prevent cleavage at other less favored sites. In this study, we report that specific membrane phospholipids appear to exert such effects in vitro. In standard endonuclease assays, low levels of phosphatidylcholine or phosphatidylethanolamine (0.5 mM) stimulate the purified enzyme activity 10-20-fold. However, at moderate levels (20-40 mM), these phospholipids largely inhibit widespread degradation of duplex DNA while still allowing site-specific nicking at the conserved guanine target in the mitochondrial genome. These findings suggest that an interaction of the endonuclease with major lipid components of the inner membrane could be an important determinant of the enzyme's specificity for mitochondrial DNA.

Characterization of secretory granular membranes from rat parotid gland: analysis of membrane lipid composition and fluidity.

Membrane phospholipid compositions of a secretory granule-rich fraction (SG) from rat parotid glands were analyzed and compared with those of a microsomal fraction (Ms) and homogenates. Remarkable differences were concentrated in their phospholipid composition rather than their side-chain composition. SG had significantly higher levels of lysophospholipids (lyso-PL, 8.3 %) and phosphatidylethanolamine (PE, 30.5 %), whereas it had lower levels of phosphatidylcholine (PC. 40.3%) and phosphatidylserine (PS, 2.4%) than those of Ms. Although these phospholipids showed a characteristic side-chain composition depending on each phospholipid class, few differences among the three fractions were found in individual phospholipid side-chain compositions. Only PE from SG was relatively poor in the alkenyl chain, especially the octadec-1'-enyl chain, and concomitantly rich in octadecanoyl chain compared with PE from Ms. The side-chain compositions of total phospholipids from SG, Ms and homogenates were nearly similar to one another. Furthermore, ESR analysis demonstrated that fluidity of hydrophilic region of liposomes prepared by the phospholipids which were extracted from individual fractions, increase in the order of Ms<homogenates<SG. On the contrary, there were no differences in the fluidity of their hydrophobic regions.These results suggest that the granular membranes have a characteristic phospholipid profile, which affects the physical property of granular membranes.

Fetal surfactant in rhesus iso-immunisation

SummaryThe phospholipid composition of amniotic fluid samples from 29 normal patients and 40 patients with rhesus haemolytic disease was studied at 26–36 weeks pregnant. Lower levels of phosphatidylcholine (PC) were found in cases of severe rhesus disease between 34 and 36 weeks when ‘early’ surfactant normally appears in most pregnancies. Phosphatidylinositol (PI) and phosphatidylglycerol (PG) concentrations did not differ from values in normal pregnancy.The effect of treatment for the rhesus disease (plasmapheresis, steroids alone or steroids with intra-uterine transfusion) was studied in a smaller group of patients. We were unable to demonstrate any striking effect of treatment on amniotic fluid surfactant phospholipid levels.

Properties of membrane phospholipids and their fatty acyl compositions of secretory granules from rat parotid gland

A secretory granular fraction isolated from rat parotid glands was remarkably different from a microsomal fraction in its phospholipid composition. It had higher levels of lysophospholipids (8%) and phosphatidylethanolamine (31%), while there were lower levels of phosphatidylcholine (40%) and phosphatidylserine (2.1%) than the microsomal fraction. However, fatty acid compositions of individual phospholipid classes from the two subfractions were found to be nearly similar to each other. ESR analysis demonstrated that extracted phospholipids from the secretory granular fraction were more fluid than those from microsomes. The relevance of these observations to physiological function of secretory granules is discussed.

A comparison of platelet monoamine oxidase activity and phosphatidylserine content between chronic paranoid schizophrenics and normal controls

Mitochondrial monoamine oxidase (MAO), type B, has been implicated in the etiology of schizophrenia. We have found the phospholipid, phosphatidylserine (PS) to be a highly specific inhibitor of MAO-B, which has led us to postulate that the PS-MAO interaction might offer a basis for the lower MAO levels observed in platelets from certain schizophrenic populations. In this study we compared platelet MAO activity with phospholipid composition in a group of normals and chronic paranoid schizophrenics. The phospholipids in platelets and erythrocytes were extracted and separated by high-performance liquid chromatography into major classes phosphatidylcholine (PC), phosphatidylethanolamine, lysophosphatidylethanolamine, phosphatidylinositol and PS. The paranoid subjects showed statistically significantly lower MAO activity as well as higher mean levels of PS and lower levels of PC in both platelets and erythrocytes, consistent with our hypothesis. The Ca 2+-stimulated synthesis of serine-lipid in platelets was also monitored by incorporation of radioisotope into lipid extracts from 14C-labelled serine substrate, and no significant differences were found between subjects groups with respect to this parameter.

Phenobarbital induction of cytochrome P-450 and UDP-glucuronosyltransferase in rabbit liver plasma membranes.

The presence of cytochrome P-450 and UDP-glucuronosyltransferase was confirmed in rabbit liver plasma membranes. Their levels, expressed as amount or activity/mg protein, were 25 and 40% respectively of those found in hepatic microsomes. Both enzymes were induced by phenobarbital treatment of the animals: administration of the barbiturate for 4 days, produced a 150% increase in the cytochrome P-450 content and in the specific activity of UDP-glucuronosyltransferase. As compared with the microsomal enzymes, the plasma membrane enzymes were localized in a lipid environment characterized by high levels of cholesterol and sphingomyelin and a low level of phosphatidylcholine. Treatment with phenobarbital for 4 days also caused a significant increase of phosphatidylcholine and phosphatidylethanolamine content in plasma membranes.

Changes in fatty acid composition of phospholipids and triglycerides of Musca domestica resulting from choline deficiency

The fatty acid composition of the phospholipids and triglycerides extracted from housefly larvae reared on diets containing no added fatty acids but containing differing concentrations of choline has been determined. Reducing the choline content of the diet resulted in a graded reduction of the percentage of phosphatidylcholine present in the phospholipids of the larvae. This was accompanied by changes in the fatty acid composition, choline deficiency causing an increased utilization of 16-C rather than 18-C acids by the phospholipids. Changes in the fatty acid composition of the triglyceride fraction were also observed but these were associated with insects containing very low levels of phosphatidylcholine. Examination of the fatty acids in the different classes of phospholipids showed that the major change resulting from choline deficiency was in the fatty acids of the phosphatidylethanolamine fraction—the phospholipid which increased as the phosphatidylcholine decreased. Although the fatty acid composition of the different classes of phospholipids was not completely fixed, some preferential utilization of certain fatty acids by certain classes was observed, in both larval and adult insects. The fatty acid composition of the phospholipids extracted from larval gut, muscle, fat body, cuticle, trachea, nervous tissue, and haemolymph was determined. Changes resulting from choline deficiency similar to those seen in the whole larva were observed in all tissues except the nervous tissue. The effect of rearing larvae at temperatures between 24 and 35°C resulted in only minor changes in the fatty acid composition of both phospholipid and triglyceride fractions but the difference due to choline deficiency was observed at all temperatures. The possibility that the observed changes in the fatty acids of the phospholipids are compensatory to the changes in the proportion of the choline to the ethanolamine phospholipids is discussed.