[Normal childbirth: physiologic labor support and medical procedures. Guidelines of the French National Authority for Health (HAS) with the collaboration of the French College of Gynaecologists and Obstetricians (CNGOF) and the French College of Midwives (CNSF) -- Text of the Guidelines (short text)]

OBJECTIVE

The objective of these guidelines is to define for women at low obstetric risk modalities that respect the physiology of delivery and guarantee the quality and safety of maternal and newborn care.

METHODS

These guidelines were made by a consensus of experts based on an analysis of the scientific literature and the French and international recommendations available on the subject.

RESULTS

It is recommended to conduct a complete initial examination of the woman in labor at admission (consensus agreement). The labor will be monitored using a partogram that is a useful traceability tool (consensus agreement). A transvaginal examination may be offered every two to four hours during the first stage of labor and every hour during the second stage of labor or before if the patient requests it, or in case of a warning sign. It is recommended that if anesthesia is required, epidural or spinal anesthesia should be used to prevent bronchial inhalation (grade A). The consumption of clear fluids is permitted throughout labor in patients with a low risk of general anesthesia (grade B). It is recommended to carry out a "low dose" epidural analgesia that respects the experience of delivery (grade A). It is recommended to maintain the epidural analgesia through a woman's self-administration pump (grade A). It is recommended to give the woman the choice of continuous (by cardiotocography) or discontinuous (by cardiotocography or intermittent auscultation) monitoring if the conditions of maternity organization and the permanent availability of staff allow it and, after having informed the woman of the benefits and risks of each technique (consensus agreement). In the active phase of the first stage of labor, the dilation rate is considered abnormal if it is less than 1cm/4h between 5 and 7cm or less than 1cm/2h above 7cm (level of Evidence 2). It is then recommended to propose an amniotomy if the membranes are intact or an oxytocin administration if the membranes are already ruptured, and the uterine contractions considered insufficient (consensus agreement). It is recommended not to start expulsive efforts as soon as complete dilation is identified, but to let the presentation of the fetus drop (grade A). It is recommended to inform the gynecologist-obstetrician in case of nonprogression of the fetus after two hours of complete dilation with sufficient uterine dynamics (consensus agreement). It is recommended not to use abdominal expression (grade B). It is recommended to carry out preventive administration of oxytocin at 5 or 10 IU to prevent PPH after vaginal delivery (grade A). In the case of placental retention, it is recommended to perform a manual removal of the placenta (grade A). In the absence of bleeding, it should be performed 30minutes but not more than 60minutes after delivery (consensus agreement). It is recommended to assess at birth the breathing or screaming, and tone of the newborn to quickly determine if resuscitation is required (consensus agreement). If the parameters are satisfactory (breathing present, screaming frankly, and normal tonicity), it is recommended to propose to the mother that she immediately place the newborn skin-to-skin with her mother if she wishes, with a monitoring protocol (grade B). Delayed cord clamping is recommended beyond the first 30seconds in neonates, not requiring resuscitation (grade C). It is recommended that the first oral dose (2mg) of vitamin K (consensus agreement) be given systematically within two hours of birth.

CONCLUSION

These guidelines allow women at low obstetric risk to benefit from a better quality of care and optimal safety conditions while respecting the physiology of delivery.

Effects of clopidogrel and its inactive form, SR 25989, on plasma, liver and platelet lipids in the rat

The aim of the present study was to determine whether clopidogrel, one of the most potent antiplatelet compounds in vivo, could alter the lipid composition of plasma, liver tissue or platelet membranes in the rat. Animals treated (10 mg/kg per day for 7 days) with clopidogrel and its inactive analogue (R form, SR 25989) were compared with control animals. Neither compound altered plasma concentrations of triglycerides or free and esterified cholesterol, and no changes were observed in liver lipids. Clopidogrel treatment significantly lowered platelet cholesterol content and cholesterol to phospholipid ratio, while SR 25989 had comparatively smaller effects. Concerning platelet phospholipids, clopidogrel treatment reduced phosphatidylcholine(PC) but increased sphingomyelin (SP) content, whereas SR 25989 lowered PC and phosphatidylserine (PS) but raised phosphatidylethanolamine (PE) content. A significant increase in the arachidonic acid content of PE was observed only in the SR 25989 group. Clopidogrel and SR 25989 both induced an increase in the unsaturation level of platelet PC, accompanied by a decrease in the level of unsaturation in platelet SP, while a similar decrease was observed for phosphatidylinositol only in the clopidogrel group. These changes in platelet membrane composition in the clopidogrel group are probably unrelated to the antiaggregating properties of the drug, but could influence other platelet functions under long-term treatment.

Long-chain n-3 fatty acids specifically affect rat coagulation factors dependent on vitamin K: relation to peroxidative stress

Fatty acids of marine origin have been shown to affect blood coagulation in the rat. In an attempt to gain insight into the mechanisms of this phenomenon, we studied the effects of dietary linseed and fish oils on the liver antioxidant status and plasma coagulation parameters in rats on a time-course basis. Dietary enrichment in eicosapentaenoic and docosahexaenoic acids resulted in strong hypocoagulation after only 1 week and a concomitant increase in liver lipid peroxidation and tocopherolquinone content. Enrichment in linolenic acid induced similar increases in lipid peroxidation and tocopherol catabolism but negligible alteration of coagulation. A significant correlation between plasma factor II coagulant activity and liver tocopherolquinone was found in fish oil- but not in linseed oil-fed rats. Although ingestion of tocopherolquinone led to high levels of this compound in the liver, it had only marginal effects on coagulation factors. Thus, it seems unlikely that this vitamin E metabolite could be involved in the lowering of vitamin K-dependent clotting factors through inhibition of gamma-glutamylcarboxylase. Rather, our results indicate that the effects of the n-3 fatty acids of fish oil on vitamin K-dependent coagulation factors are specific and independent of liver tocopherolquinone levels.

Phospholipid composition in late infantile neuronal ceroid lipofuscinosis

BACKGROUND

Neuronal ceroid lipofuscinosis (NCL) is a relatively common group of inherited neurodegenerative disorders characterised by the accumulation of autofluorescent lipopigments (ceroid) similar to lipofuscin. Because of this property, studies have concentrated on fatty acid metabolism and lipid peroxidation.

METHODS

In the present study, the fatty acid composition of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) and the molecular species compositions of diacylglycerophosphocholine (diacyl GPC), diacylglycerophosphoethanolamine (diacyl GPE) and alkenylacyl GPE (plasmalogens) were investigated in cultured skin fibroblasts from three patients with a confirmed diagnosis of the late infantile form of the disease (LINCL, CLN2) and three healthy age-matched controls.

RESULTS

Relatively minor differences in the fatty acid compositions of PC and PE were observed between patients and controls. However, dimethyl acetals of plasmalogens were found to be 40% higher in the patients compared to in the controls. Control and LINCL fibroblasts displayed only slight differences in the molecular compositions of diacyl GPE and diacyl GPC. In contrast, compared with normal cells, LINCL fibroblasts had higher levels of alkenylacyl GPE species containing both 18 : 1 and polyunsaturated fatty acids, but lower levels of species with 16 : 0 or 18 : 0 in the sn-1 position.

CONCLUSION

The molecular composition of PC and PE subclasses in skin fibroblasts of healthy subjects and patients suffering from LINCL is here described for the first time. While few differences are noticeable in the fatty acid composition of PC and PE and the molecular species distribution of diacylGPC and diacylGPE, the alkenylacyl GPE (or ethanolamine plasmalogens) were found to differ significantly between patients and healthy controls.

Lipid composition of blood platelets and erythrocytes of southern elephant seal (Mirounga leonina) and antarctic fur seal (Arctocephalus gazella)

Erythrocyte and blood platelet phospholipid compositions were studied in three elephant seals and two fur seals, two species of marine mammals living in the Subantarctic region feeding on preys rich in (n-3) polyunsaturated fatty acids. Results were compared with those reported for related species and humans. In erythrocytes, the phospholipid (PL) and cholesterol (CHOL) contents were lower in pinnipeds than in humans. Phosphatidylcholine (PC) levels were higher in elephant seals than in fur seals, with a reverse trend for phosphatidylethanolamine (PE) and phosphatidylserine (PS). Both species had lower SM/PC ratios and PE plasmalogen concentrations than human. Erythrocytes were richer in (n-3) fatty acids (FA) in pinnipeds than in humans. In platelets, the PL content was lower and the CHOL content higher in elephant seals than in humans or in other phocid seal species studied to date. The SM/PC ratio was much higher than in other seal species or in man. In both species, the proportion of PE plasmalogens was higher in platelets than in erythrocytes. PL were more saturated in elephant seals than in fur seals. These results suggest that the erythrocytes and platelets of wild marine mammals may prove useful models to study the influence of dietary lipids on the structure and hemostatic function of these cells.

Lipid composition of erythrocytes and thrombocytes of a subantarctic seabird, the king penguin

Phospholipid (PL) compositions and fatty acid (FA) patterns of PL were determined in the erythrocytes and blood thrombocytes of a seabird, the king penguin, living in the subantarctic area and feeding on prey rich in n-3 polyunsaturated FA. Results were compared between birds in three different physiological states (breeding and molting adults, chicks) to those reported for other birds. In erythrocytes, the ratios of cholesterol to PL and of sphingomyelin to phosphatidylcholine (PC) were lower than in other birds. The PL distribution was similar to those previously reported in the hen and pigeon. In contrast to other birds, cardiolipin levels were unexpectedly high (4%). Very long chain n-3 FA were abundant (13-27%) in phosphatidylethanolamine (PE), phosphatidylserine and PC, probably in relation to the natural diet of these birds. Among n-3 FA, 22:6n-3 was the most abundant in all PL (2-20%), whereas the highest levels of arachidonic acid were observed in PE (14%). In thrombocytes, the PL distribution and FA composition of the main PL (PC, PE) differed from those of erythrocytes, and in particular, levels of n-3 FA (9-12%) were 1.5-2 times lower. The highest levels of arachidonic acid were found in phosphatidylinositol (24%). The lipid profile of penguin erythrocytes could contribute to the efficiency of blood circulation and oxygen delivery in microvascular beds, thus favoring diving capacity of these animals. Our observations do not support the hypothesis of a common origin of avian thrombocytes and erythrocytes.

Incorporation of exogenous lipids modulates insulin signaling in the hepatoma cell line, HepG2

The lipid content of cultured cells can be experimentally modified by supplementing the culture medium with specific lipids or by the use of phospholipases. In the case of the insulin receptor, these methods have contributed to a better understanding of lipid disorder-related diseases. Previously, our laboratory demonstrated that experimental modification of the cellular lipid composition of an insulin-sensitive rat hepatoma cell line (ZHC) resulted in an alteration in insulin receptor binding and biological action (Bruneau et al., Biochim. Biophys. Acta 928 (1987) 287-296/297-304). In this paper, we have examined the effects of lipid modification in another hepatoma cell line, HepG2. Exogenous linoleic acid (LA, n-6), eicosapentaenoic acid (EPA, n-3) or hemisuccinate of cholesterol (CHS) was added to HepG2 cells, to create a cellular model in which membrane composition was modified. In this model, we have shown that: (1) lipids were incorporated in treated HepG2 cells, but redistributed differently when compared to treated ZHC cells; (2) that insulin signaling events, such as insulin receptor autophosphorylation and the phosphorylation of the major insulin receptor substrate (IRS-1) were altered in response to the addition of membrane lipids or cholesterol derived components; and (3) different lipids affected insulin receptor signaling differently. We have also shown that the loss of insulin receptor autophosphorylation in CHS-treated cells can be correlated with a decreased sensitivity to insulin. Overall, the results suggest that the lipid environment of the insulin receptor may play an important role in insulin signal transduction.

Antithrombotic effects of (n-3) polyunsaturated fatty acids in rat models of arterial and venous thrombosis

The antithrombotic effects of dietary lipids were investigated in rat models of arterial and venous thrombosis. In the arterial model, thrombus formation was evaluated by determination of the occlusion time and the deposition of 111In-labeled platelets and 125I-labeled fibrinogen in a collagen-coated glass capillary inserted into an arterio-arterial shunt. Venous thrombosis was evaluated by measurement of the thrombus weight after administration of thromboplastin as a source of tissue factor and establishment of stasis in the vena cava. Diets were supplemented with saturated (SAT group) or (n-3) fatty acids, the latter being added either as MaxEPA oil (MaxEPA group), or as docosahexaenoic (DHA group) or eicosapentaenoic (EPA group) ethyl ester. Only the MaxEPA group displayed a prolonged occlusion time as compared with all other groups. Platelet accumulation, similar in the MaxEPA, EPA and DHA groups (13.3, 16.7 and 17.7 x 10(6) platelets/shunt, respectively), was significantly higher in the SAT group (25.3 x 10(6) platelets/shunt), while accumulation of fibrinogen-fibrin was similar whatever the group. There was a trend towards a lower venous thrombus weight in MaxEPA fed rats relative to those fed other diets. Our data indicate that the MaxEPA diet had antithrombotic effects in arterial and to a lesser extent venous thrombosis models, best attributed to its multiple targeting of platelets and coagulation.

Simultaneous determination of homologues of vitamin E and coenzyme Q and products of alpha-tocopherol oxidation

A sensitive procedure is described for the simultaneous determination of vitamin E and coenzyme Q homologues and alpha-tocopherol oxidation products using two-isocratic step high pressure liquid chromatography (HPLC) and electrochemical detection in the oxidative mode. Zinc-catalyzed reduction in a post-column reactor allows the detection of alpha-tocopherolquinone, epoxy-tocopherolquinone, and ubiquinones. This technique was used to quantify lipophilic antioxidants in the liver tissue of rats treated or not with alpha-tocopherolquinone and in a plant oil. Alpha-tocopherolquinone and its epoxide derivatives, formed from alpha-tocopherol during iron-catalyzed phospholipid peroxidation, were also determined in a liposome suspension. The high selectivity and sensitivity of the coulometric detection system enabled use of low oxidation potentials giving little baseline noise, while a fast isolation procedure and quantitative recoveries of all oxidized and reduced forms made it possible to measure a high ubiquinol/ubiquinone ratio in liver tissue. Administration of alpha-tocopherolquinone to rats did not alter the antioxidant status of the liver, despite strong accumulation of both this quinone and its reduced form, alpha-tocopherolhydroquinone. These results indicate the presence of an efficient reductase and suggest that it could contribute to the protection of cellular membranes from oxidative stress.

Nuclear sphingomyelin protects RNA from RNase action

Chromatin phospholipidic fraction, as previously demonstrated, shows the same localization as RNA inside the nuclei. DNase and RNase treatment of nuclei removed almost totally the DNA, 63% of RNA and caused a 50% loss of phospholipids. The aim of the present investigation is to study the fraction of RNase undigested nuclear RNA and its relationship with the phospholipids still present in the nuclei. Isolated hepatocyte nuclei were treated with Triton X-100 and digested with RNase and DNase. The undigested nuclear material contained proteins (98%) and a small amount of RNA (1.7%), DNA (0.4%) and phospholipids (0.18%). The analysis of phospholipids showed the presence of two components only, namely phosphatidylcholine and sphingomyelin. In the same complex, the activity of sphingomyelin synthase, phosphatidylcholine-dependent phospholipase C and neutral sphingomyelinase has been detected. Treatment of isolated RNA with neutral sphingomyelinase modified the RNA in RNase sensitive RNA, thus suggesting that the SM may represent a bridge between two RNA strands possibly regulating transcription.

Diets enriched in (n-3) fatty acids affect rat coagulation factors dependent on vitamin K

The effects of dietary lipids on haemostasis were investigated in rats fed high fat diets enriched in saturated fatty acids (SAT), oleic acid (OLEIC), MaxEPA oil (MaxEPA), eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) and results were compared to those for rats fed standard chow (ST). Coagulant activities of factor IIc and factor VII-Xc were reduced by about 70% in the MaxEPA group and 50% in the EPA and DHA groups relative to the OLEIC, SAT and ST groups. Liver vitamin K levels were five times lower in the experimental groups than in the ST group, which would indicate an effect of high fat diets on vitamin K metabolism. However, only (n-3) fatty acids prolonged the prothrombin time. These components could act at the post-translational modification level of vitamin K-dependent plasma clotting factors. The changes in haemostatic factors found in the MaxEPA group were counteracted by vitamin K supplementation.

cADP-ribose formation by blood platelets is not responsible for intracellular calcium mobilization

Human platelet CD38 is a multifunctional ectoenzyme catalysing the synthesis and hydrolysis of cADP-ribose (cADPR), a recently identified calcium-mobilizing agent that acts independently of D-myo-inositol 1,4,5-trisphosphate and is known to be expressed by human platelets. The present work shows that ADP-ribosyl cyclase activity is exclusively a membrane activity, of which the major part is located in plasma membranes and a small part in internal membranes. In broken cells, cyclase activity was insensitive to the presence of calcium and was not modulated by agonists such as thrombin or ADP, whereas in intact cells thrombin increased cADPR formation by 30%, an effect due to fusion of granules with the plasma membrane. In order to assess the role of cADPR as a calcium-mobilizing agent, vesicles were prepared from internal membranes and loaded with 45CaCl2. These vesicles were efficiently discharged by IP3 in a dose-dependent manner, but were not responsive to cADPR or ryanodine in the presence or absence of calmodulin. Thus cADPR is unlikely to play a role in intracellular calcium release in human blood platelets.

Dietary (n-3) and (n-6) polyunsaturated fatty acids rapidly modify fatty acid composition and insulin effects in rat adipocytes

The influence of dietary (n-3) compared with (n-6) polyunsatured fatty acids (PUFA) on the lipid composition and metabolism of adipocytes was evaluated in rats over a period of 1 week. Isocaloric diets comprised 16.3 g/100 g protein, 53.8 g/100 g carbohydrate and 21.4 g/100 g lipids, the latter containing either (n-3) PUFA (32.4 mol/100 mol) or (n-6) PUFA (37.8 mol/100 mol) but having identical contents of saturated, monounsaturated and total unsaturated fatty acids and identical polyunsaturated to saturated fatty acid ratios and double bond indexes. Despite comparable food intake, significantly smaller body weight increments and adipocyte size were observed in rats of the (n-3) diet group after feeding for 1 wk. Rats fed the (n-3) diet also had significantly lower concentrations of serum triglycerides, cholesterol and insulin compared with those fed the (n-6) diet, although levels of serum glucose and free fatty acids did not differ in the two dietary groups. In the (n-6) diet group, the (n-6) and (n-3) PUFA contents of plasma triglycerides, free fatty acids and phospholipids were 30-60% higher and 60-80% lower, respectively, than in the (n-3) diet group, whereas adipocyte plasma membrane phospholipids showed a significantly higher unsaturated to saturated fatty acid ratio and greater fluidity. Glycerol release in response to noradrenaline was significantly higher in the adipocytes of rats fed the (n-3) diet, whereas the antilipolytic effect of insulin generally did not differ in the two groups. Finally, insulin stimulated the transport of glucose and its incorporation into fatty acids to a lesser extent in adipocytes of (n-3) diet fed rats compared with (n-6) diet fed rats. This reduction in the metabolic effects of insulin in rats fed a (n-3) diet for 1 wk could be related to smaller numbers and a lower binding capacity of the insulin receptors on adipocytes and/or to a lesser degree of phosphorylation of the 95 kDa beta subunit of the receptor. In conclusion, dietary intake for 1 wk of (n-3) rather than (n-6) PUFA is sufficient to induce significant differences in the lipid composition and metabolic responses to insulin of rat adipocytes.

Radiolabeling of the lipids of chinese hamster ovary cells with the probe [3-(trifluoromethyl)-3-(m-[125I]iodophenyl)diazirine]

[125I]TID [3-(trifluoromethyl)-3-(m-[125I]iodophenyl)diazirine] is a commercially available, hydrophobic, photoactivatable, gamma-emitting reagent mostly used to label protein hydrophobic domains. It has also been used to radiolabel the phospholipids of lung surfactant (Gilliard et al., Anal. Biochem. 193, 310-315, 1991). Since a nonspecific, highly sensitive, lipid-labeling probe would be a very useful tool to investigate lipid-protein interactions in biological membranes, we characterized further the [125I]TID-labeling products of lipids from cultured Chinese hamster ovary cells (IR-CHO). After labeling of whole cells, TLC analysis followed by autoradiography enabled detection of sphingomyelin, phosphatidylcholine, phosphatidylinositol, phosphatidylserine, phosphatidylethanolamine, cardiolipin, diglycerides, cholesterol and its esters, and triglycerides. Analysis of the radioactivity associated with the saponification products of different lipids showed that [125I]TID was mostly (80%) extracted with the fatty acid moiety of the lipids whereas 20% remained associated with the hydrosoluble moiety. Similar radioactivity profiles were observed after labeling of whole cells or extracted and liposome-reconstituted lipids; the [125I]TID probe was able to diffuse in all intracellular organelles. Labeling was not equivalent between the different lipid classes, and it appeared that the amount of associated radioactivity correlated well with the degree of lipid unsaturation. This was confirmed by studying [125I]TID incorporation in phosphatidylcholines of different chain length and unsaturation. Taken together, our data demonstrate that [125I]TID can be used as a radiolabel for lipids in cultured cells. It is rapidly incorporated in the hydrophobic part of membranes, diffuses into all cellular compartments, and labels all lipid classes, including phospholipids, cholesterol, and glycerides, with a sensitivity in the nanomolar range.

Brown fat thermogenesis in rats fed high-fat diets enriched with n-3 polyunsaturated fatty acids

OBJECTIVE

To examine the possible involvement of an increase in diet-induced thermogenesis from brown adipose tissue (BAT) in the n-3 polyunsaturated fatty acids (n-3 PUFA) induced limitation of the development of white fat pads during high-fat feeding.

DESIGN

Rats fed for four weeks on a low-fat/high-carbohydrate diet (C group) or high-fat diet without n-3 PUFA (REF group), with eicosapentaenoic acid (EPA group), with docosahexaenoic acid (DHA group) or with a mixture of these two fatty acids (MIX group).

MEASUREMENTS

Epididymal and retroperitoneal fat pad mass, BAT composition, Guanosine 5'-diphosphate (GDP) binding and uncoupling protein (UCP) content were measured in the five groups of rats.

RESULTS

The masses of retroperitoneal and epididymal white fat pads were lower in the groups fed n-3 PUFA than in the C and REF groups. The total BAT GDP binding was 1.6 times higher in the MIX and EPA groups than in the REF group. The BAT from the EPA group presented an enrichment in mitochondria compared to the C and REF groups whereas the BAT from the DHA and REF groups presented a hyperplasia and an increase in thermogenic activity of the mitochondria compared to the C group. The higher thermogenic activity of BAT was observed in the MIX group and is due to hyperplasia and to an increase in thermogenic activity of mitochondria.

CONCLUSIONS

n-3 PUFA induce a marked stimulation of BAT thermogenic activity without changes in the UCP content compared to a high-fat diet without n-3 PUFA. The mixture of EPA and DHA has the more pronounced effect while EPA and DHA seem to act in synergy on BAT thermogenesis via different mechanisms.

Quantitative analysis of vitamin E, cholesterol and phospholipid fatty acids in a single aliquot of human platelets and cultured endothelial cells

A reliable procedure is described for the joint analysis of vitamin E (tocopherols), cholesterol and phospholipids in the same minute sample of human platelets and on human cultured endothelial cells. The whole procedure is based on the extraction of total lipids, thin-layer chromatography of all compounds of interest and microcolumn purification of tocopherols and cholesterol. The combined use of butyl hydroxytoluene and ascorbic acid in the purification steps allowed a complete recovery of the tocopherols analyzed, as well as of cholesterol by high-performance liquid chromatography. The detection of these lipids was performed with fluorometric, spectrophotometric and evaporative light-scattering detectors whose respective sensitivities were compared. The fatty acid composition of phospholipid classes from the same sample, separated on the same silica gel plate, was determined by gas-liquid chromatography. The whole procedure is rapid since it requires about 4 h to analyse tocopherols and cholesterol and to prepare methylated fatty acids, 28 samples being easily completed within one working day. The evaluation of the whole membrane antioxidant status requires as little as one 25 cm2 confluent culture flask (about 0.75 x 10(6) cells) for endothelial cells or two ml of blood (3 x 10(8) platelets).

The P2Y1 receptor is an ADP receptor antagonized by ATP and expressed in platelets and megakaryoblastic cells

The human P2Y1 purinoceptor has been expressed in Jurkat cells and the effects of HPLC purified nucleotides on calcium movements were measured. The most potent agonist was 2-methylthio-ADP followed by ADP. ATP, Sp-ATPalphaS and beta,gamma-methylene-ATP were competitive antagonists. Suramin and PPADS inhibited the effects of ADP. This pharmacological profile is the same as that of the so-called P2T purinoceptor responsible for platelet aggregation, which has not yet been identified. Using PCR we found the P2Y1 receptor to be present in blood platelets and megakaryoblastic cell lines. These data suggest that the P2Y1 receptor may be the elusive P2T receptor.

Food deprivation modifies fatty acid partitioning and beta-oxidation capacity in rat liver

The involvement of lipids under starvation conditions in the shift from the phase of protein sparing (phase II) to the phase of increased protein breakdown (phase III) has been investigated. Plasma and liver were sampled from fed and unfed rats at two distinct stages which were characterized according to the changes in specific loss in daily body mass and nitrogen excretion. In the two groups of food-deprived rats corresponding to phases II and III, the liver concentration of triglycerides (micromol/g) was significantly lower, that of cholesterol significantly higher and that of the other lipid classes was moderately affected compared with concentrations in fed rats. Hepatic phospholipids had significantly higher concentrations (mol/100 mol) of 22:6(n-3) in food-deprived rats than in fed rats. Triglycerides had significantly higher concentrations of stearic and arachidonic acids in livers of both groups of food-deprived rats compared with fed rats. The total activity of carnitine palmitoyl transferase [mmol/(min x liver)] was 48% higher in rats studied at the end of phase II than in fed rats but was similar in fed rats and in rats studied at the beginning of phase III. The total activity of fatty acyl-CoA oxidase was 73% lower only in rats studied at the beginning of phase III when compared with fed rats. Our results indicate that during food deprivation the change in the rate of protein utilization is associated with important qualitative and quantitative alterations of hepatic lipids and oxidative capacity of fatty acids. These modifications appear to be related to the change from a preferential use of lipids to a preferential utilization of proteins.

The selective mobilization of fatty acids is not based on their positional distribution in white-fat-cell triacylglycerols

Fatty acids have been shown to be selectively mobilized from rat white fat-cells, whatever the dietary manipulations. For convenience, fatty acids have been classified as being highly, weakly and moderately mobilizable. The aim of this study was to examine whether the selective mobilization of fatty acids can be explained, even partly, by their positional distribution in adipose-tissue triacylglycerols (TAG) via the known specificity of hormone-sensitive lipase for the sn-1 and sn-3 positions. Adipose tissue was dietarily manipulated in order to obtain a wide spectrum of fatty acids, including large amounts of either very-long-chain polyunsaturated fatty acids (VLC-PUFA) or very-long-chain monounsaturated fatty acids (VLC-MUFA). The determination of fatty acid distribution in adipose tissue TAG was based on random formation of 1,2-diacyl-rac-glycerols by Grignard degradation, followed by synthesis of phosphatidic acids and hydrolysis in the sn-2 position by phospholipase A2. Regardless of the fatty acid composition and location of fat depots, highly (e.g. 18:4n-3 and some of the VLC-PUFA) and weakly (e.g. VLC-MUFA) mobilizable fatty acids were located mainly in the outer (sn-1 and sn-3) positions of the glycerol moiety (79.5% and 92.5% on average, respectively). Other fatty acids, which are rather moderately mobilizable, were more randomly distributed. We conclude that the selective mobilization of white-fat-cell fatty acids is not based on their positional distribution in TAG.

Molecular species analysis of 1,2-diglycerides on phorbol ester stimulation of LA-N-1 neuroblastoma cells during proliferation and differentiation

1,2-Diacyl-sn-glycerol (DAG) is a product of cell activation that has emerged as an important intracellular messenger whose primary function appears to be the activation of protein kinase C. They originate by the activation of phospholipases, which hydrolyze different phospholipids depending on the external stimulus and the nature of the cells, leading to the production of different molecular species. In the present study the quantitative changes in the total mass and the molecular species of DAG formed on phorbol ester (12-O-tetradecanoyl-phorbol 13-acetate) stimulation were investigated in proliferating and retinoic acid (RA)-differentiated human LA-N-1 cells. The TPA treatment of both cell types elicited an increase in the total amount of DAG. The increase was biphasic; i.e., an initial peak at 2-5 min was followed by a sustained increase that persisted for > 30 min. The analysis of the molecular species of DAG and phospholipids showed that in proliferating LA-N-1 cells, the DAG increase corresponds to the production of mainly saturated/monounsaturated (16:0-18:1, 18:0-18:1) and saturated/saturated (16:0-16:0, 16:0-18:0) species, suggesting that they originate essentially from the hydrolysis of phosphatidylcholine. In contrast, RA-differentiated cells responded to TPA treatment by increasing the level of saturated/polyunsaturated (16:1-22:6, 18:0-22:6, 16:0-20:4, 18:0-20:4) and monounsaturated/monounsaturated (18:1-18:1) species, suggesting mainly a phosphatidylethanolamine origin. These findings indicate that the treatment of LA-N-1 cells with TPA generates different molecular species of DAG depending on their physiological state. These observations suggest in turn that different phospholipases are activated by TPA in proliferating and RA-differentiated cells.

Composition and structure of triacylglycerols in brown adipose tissue of rats fed fish oil

This study examines the incorporation of highly unsaturated n-3 fatty acids (HUFA) into triacylglycerols (TAG) of brown adipose tissue (BAT), and their effect on the positional distribution of saturated (SFA) and of unsaturated (UFA) 16- or 18-carbon fatty acids. To this end, rats were fed a fish oil diet for up to four weeks. The stereospecific analysis of TAG was based on generation of sn-1,2- and sn-2,3-acylglycerols by Grignard degradation, followed by synthesis of phosphatidic acid and specific hydrolysis with phospholipase A2. From the end of the first week of fish oil feeding, a steady-state in the fatty acid composition of TAG in BAT was reached. HUFA concentration increased 30-fold, mainly at the expense of n-9 UFA and of SFA. The amount of SFA decreased selectively at position 3, where these fatty acids were progressively replaced by n-3 HUFA. By contrast, the amount of UFA decreased at all positions, and their positional distribution was not affected. About 60% of HUFA was incorporated at position 3. Nearly twice as much 22:6n-3 was incorporated into TAG than had been previously observed in white adipose tissue (WAT) [Leray, C., Raclot, T., and Groscolas, R. (1993) Lipids 28, 279-284]. At the steady-state, the distribution of HUFA was characterized by high proportions of 22:6n-3 and 20:5n-3 in position 3. Moreover, in each position of TAG, a steady level was reached rapidly (within 1 wk).(ABSTRACT TRUNCATED AT 250 WORDS)

Rat liver chromatin phospholipids

To shed light on the question whether the phospholipids present in chromatin are native or are due to contamination from nuclear membranes, we labeled the phospholipids of isolated nuclei and determined the amount of phospholipids (PL) and PL fatty acid composition in nuclei and chromatin. The hepatocyte nuclei were isolated and radioiodinated by the lactoperoxidase method under saturating and nonsaturating conditions, and the radioactivity associated with chromatin extracted from these nuclei was monitored. Whereas 97% the label was recovered in the nuclear membranes, only 0.08-0.6% was found in chromatin. The PL present in chromatin were relative to the amounts present in the entire nuclei and calculated as percentage of total, phosphatidylethanolamine (10%), phosphatidylserine (22%), phosphatidylinositol (19%) phosphatidylcholine (14%), and sphingomyelin (35%). In sphingomyelin of chromatin-associated PL an enrichment in polyunsaturated fatty acids was seen. The data indicated that the PL found in isolated chromatin do not seem to be due to contamination from the nuclear membrane.

Lipid composition and structure of commercial parenteral emulsions

In order to study the influence of the phospholipid/triacylglycerol (PL/TG) ratio of parenteral emulsions on the distribution and the physico-chemical properties of their fat particles, commercial 10, 20 or 30% fat formulas were fractionated by centrifugation into an upper lipid cake (resuspended in aqueous glycerol) and a subnatant or mesophase, from which a PL-rich subfraction (d = 1.010-1.030 g/l) was purified by density gradient ultracentrifugation. Chemical and 31P-NMR analyses of these fractions indicated that at least two types of fat particles coexist in parenteral emulsions: (i) TG-rich particles (mean diameter: 330, 400, 470 nm in the 10, 20, 30% emulsion) which contain practically all the TG and esterified phytosterols of native emulsions, but only a fraction of their PL, unesterified cholesterol and phytosterols, and other minor lipids; (ii) PL-bilayer particles or liposomes (mean diameter: 80-100 nm) which are constituted with the remaining PL and relatively very small amounts of TG and other lipids. The higher the oil content of the emulsion, the lower the amount of these PL-rich particles, which represent the major particle population of the mesophase. Indeed, minute amounts of TG-rich particles (probably the smallest ones) are also present in the mesophase, even in the PL-rich subfraction which contains the bulk of liposomal PL. Since the PL-rich particles of the infused emulsion generate lipoprotein X-like particles, only the large TG-rich particles can be considered as true chylomicron counterparts.

Molecular species of choline and ethanolamine glycerophospholipids in rat brain myelin during development

The composition of the molecular species of various phospholipid subclasses was examined in myelin isolated from brain of 15-, 21- and 90-day-old rats. The molecular species of diacylglycerophosphocholine (PtdCho), diacylglycerophosphoethanolamine (PtdEtn) and plasmenyl-ethanolamine (PlsEtn) were quantified by high-performance liquid chromatography (HPLC) after phospholipase C treatment and dinitrobenzoyl derivatization. In rat brain myelin, each phospholipid subclass showed a specific pattern of molecular species that changed during development. PtdCho contained large amounts of saturated/monounsaturated and disaturated species and low amounts of saturated/polyunsaturated species. During brain development, the levels of saturated/monounsaturated molecular species increased whereas those of the disaturated and saturated/polyunsaturated species decreased. PtdEtn were characterized by their low levels of disaturated species and a high content of saturated/monounsaturated and saturated/polyunsaturated species, of which those containing fatty acids of the n-3 series decreased, whereas those containing fatty acids of the n-6 series did not change during brain development. The levels of saturated/monounsaturated species increased in PtdEtn. No disaturated molecular species could be detected in PlsEtn. This alkenylacyl subclass contained large amounts of saturated/polyunsaturated, saturated/monounsaturated and dimonounsaturated molecular species. During development, the levels of saturated/polyunsaturated molecular species decreased while those of the two others increased. The data indicated that myelin sheaths undergo phospholipid changes during brain development and maturation.

Positional distribution of n-3 fatty acids in triacylglycerols from rat adipose tissue during fish oil feeding

The present study was designed to investigate the metabolism of the n-3 polyunsaturated fatty acids (PUFA) in adipose tissue and its dependence upon dietary factors. Changes in the positional distribution of the fatty acids in triacylglycerols from retroperitoneal adipose tissue were studied as a function of time on rats fed for 4 wk a diet enriched with fish oil. The stereospecific analysis of triacylglycerols by Grignard degradation. This was followed by synthesis of rac-phosphatidic acids and treatment with phospholipase A2. In the triacylglycerols of the fish oil diet, 57% of the total n-3 fatty acids were in position 3, i.e., two-thirds of 20:5n-3 and 22:5n-3 were esterified in sn-3 position, whereas 22:6n-3 was equally distributed in positions 2 and 3. After 4 wk of feeding fish oil, the fatty acid composition of adipose tissue triacylglycerols reached a steady state. Half of the n-3 fatty acids were found in position 3, namely 75% of 22:5n-3, 50% of 20:5n-3 and 18:4n-3 and 45% of 22:6n-3, the latter being equally distributed in positions 2 and 3. This pattern of distribution resembled that found in triacylglycerols of the fish oil diet, except for a higher proportion of 20:5n-3 in adipose tissue in position 1 at the expense of position 3. Throughout the 4-wk period of fish oil feeding, the distribution pattern of minor n-3 fatty acids (18:4n-3 and 22:5n-3) in adipose tissue triacylglycerols remained unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of dibutyryl cyclic AMP and isoproterenol on 7 beta-hydroxycholesterol cytotoxicity and esterification in spontaneous transformed cell lines derived from astrocyte primary cultures

Incubation of spontaneous transformed cells derived from astrocyte primary cultures with 30 microM 7 beta-hydroxycholesterol (7 beta-OH-CH) which is lethal to the cells or with 150 microM isoproterenol reduces the intracellular level of cAMP (4- and 2-fold respectively). Treatment of the cultures with 0.5 mM dibutyryl (db)-cAMP and 7 beta-OH-CH increases 3-fold the intracellular level of cAMP and both, db-cAMP and isoproterenol, raise the lethal effect of 7 beta-OH-CH and its esterification on C-3-OH by naturally occurring fatty acids (metabolite). Kinetic studies of net steryl-3-esters hydrolysis revealed that db-cAMP and isoproterenol lower that of cholesteryl-3-esters (2-fold) whereas the opposite is found for the metabolite. These data demonstrate that (i) high cAMP intracellular levels modulate differently the net hydrolysis of cholesteryl-3-esters and metabolite, (ii) isoproterenol acts otherwise than cAMP on 7 beta-OH-CH esterification, (iii) the cytotoxicity of 7 beta-OH-CH is linked to its own esterification. The accumulation of metabolite subsequent to db-cAMP or isoproterenol treatment as a result of acyl-CoA:cholesterol acyl transferase activation is discussed.

Effect of 7 beta-hydroxycholesterol on astrocyte primary cultures and derived spontaneously transformed cell lines. Cytotoxicity and cholesterogenesis

The correlation between the lethal effect of 7 beta-hydroxycholesterol (7 beta-OH-CH) on spontaneously transformed cell lines derived from rat astrocyte primary cultures (normal cells) and de novo cholesterogenesis was investigated. Both 7 beta-OH-CH and 7-keto-CH were not cytotoxic on normal cells but 7 beta-OH-CH affected markedly the viability of the transformed cells. The use of [14C]acetate or [14C]mevalonate indicated that 7-keto-CH inhibits de novo cholesterogenesis upstream of 3-hydroxy-3-methylglutaryl CoA reductase (HMGR) in both cell types whereas 7 beta-OH-CH also inhibits downstream of HMGR. The accumulation of two radiolabelled products X1 and X2 between mevalonate and CH was found in unsaponifiable neutral lipids extracted from 7 beta-OH-CH treated transformed cells. HPLC and GC-MS revealed that X1 and X2 are not lanosterol and 24,25-epoxylanosterol, respectively. Incubation of the transformed cells with X1 and X2 did not affect their viability. Our data demonstrate that, under our experimental conditions, 7 beta-OH-CH cytotoxicity is not linked to the inhibition of de novo cholesterogenesis in cultured glial transformed cells.

Sensitive analysis of phospholipid molecular species by high-performance liquid chromatography using fluorescent naproxen derivatives of diacylglycerols

A sensitive high-performance liquid chromatographic (HPLC) method for the separation and determination of diacylglycerophospholipid and diacylglycerol (DAG) molecular species has been developed. Phospholipids are hydrolysed with phospholipase C and the resulting DAGs are reacted with naproxen chloride in the presence of 4-dimethylaminopyridine. The naproxen-DAGs were purified by thin-layer chromatography on silica gel G plates. Molecular species were separated using reversed-phase HPLC with isocratic elution and determined by measuring the absorbance at 230 nm or fluorescence at 352 nm (excitation at 332 nm). The method was applied to the determination of diacylglycerophosphoethanolamine in rat cerebrum and cerebellum. The molar absorption coefficient of the naproxen derivatives was 53,000 lmol-1 cm-1 at 230 nm, permitting the generation of linear concentration-dependent determinations down to less than 10 pmol. A ten-fold increase in sensitivity was obtained with a fluorescence detection system owing to the fluorescent properties of the proposed adduct.

Molecular species of choline and ethanolamine phospholipids in rat cerebellum during development

The molecular species composition of rat cerebellar phospholipid subclasses has been studied by HPLC after phospholipase C treatment and dinitrophenyl derivatization. During rat cerebellum development (3-90 days postpartum), cholinephosphoglycerides and ethanolamine phosphoglycerides represented approximately 80% of all phospholipids, with their relative amount changing after 1 month. Among ethanolamine phosphoglycerides, the molar ratio of diacylglycerophosphoethanolamine (diacylGPE) to alkenylacylGPE decreased from approximately 1.4 at 3 days to approximately 0.5 after 10 days. The phospholipids investigated contained up to 12 different molecular species. The rate of accumulation of the various molecular species of diacylglycerophosphocholine (diacylGPC), diacylGPE, and alkenylacylGPE during cerebellar development allowed a classification into three main groups. The overall increase of the molecular species of the first group (6-diacylGPC, 5-diacylGPE, and 4-alkenylacylGPE) was approximately 18-fold between 3 and 90 days, with a faster rate of accumulation between 3 and 30 days. Those of the second group (3-diacylGPC, 5-diacylGPE, and 5-akenylacylGPE) increased by approximately 45-fold during the same developmental period, at a slow rate before day 15 and a faster one thereafter. The molecular species of the third group (3-alkenylacylGPE) increased by greater than 250-fold between 3 and 90 days, at a very slow rate before day 21 and more quickly thereafter. The different rates of accumulation of the components of the three groups during cerebellar development suggest a preferential location of the first group in membranes of neuronal perikaryons, glial cells, and synaptosomal structures. Those of the second group appear to be located in both synaptosomal membranes and myelin sheets, and those of the third group can be considered as myelin markers.

In vitro synthesis and transbilayer movement of phosphatidylethanolamine molecules labelled with different fatty acids in chick brain microsomes

The transbilayer fatty acid distribution of diacylglycerophosphoethanolamine and the translocation of newly synthesized phosphatidylethanolamine molecules labelled with different fatty acids has been investigated in chick brain microsomes using trinitrobenzensulfonic acid. The determination of the fatty acid composition of diacylglycerophosphoethanolamine in both the outer and the inner leaflet of the microsomal vesicles revealed a similar distribution indicating that both leaflets share the same molecular species. The in vitro incorporation of radioactive fatty acids (16:0, 18:1 and 20:4(n-6] into ethanolamine phospholipids, known to be catalyzed by the lyosphosphatidylethanolamine acyl transferase, showed that the radioactive diacylglycerophosphoethanolamine molecules appeared first in the outer leaflet and were thereafter transferred to the inner leaflet. The apparent rate of translocation of the newly synthesized ethanolamine phospholipid molecules was the highest for those labelled with 16:0 and the lowest for those labelled with 20:4(n-6). The results indicate that the active site of the acyl-CoA:lysophosphatidylethanolamine acyltransferases is located on the outer leaflet of the microsomal vesicles and that the different newly synthesized molecular species of diacylglycerophosphoethanolamine may be translocated from the outer to the inner leaflet at different rates.

Effect of 7 beta-hydroxycholesterol on astrocyte primary cultures and derived spontaneously transformed cell lines: cytotoxicity and metabolism

The lethal effect of 7 beta-hydroxycholesterol (7 beta-OHC) on neonatal rat astrocyte primary cultures and spontaneously transformed cell lines derived from them was investigated. Confluent astrocyte primary cultures were not affected by 30 microM 7 beta-OHC over a period of 72 h. In contrast, spontaneously transformed cells were killed by 20 microM 7 beta-OHC within the first 48 h. Further studies indicated that the cell lines metabolized 7 beta-OHC to a product the polarity of which was less than that of 7 beta-OHC. The metabolite was identified as 7 beta-OHC esterified on C-3 by naturally occurring fatty acids. Incubation of the cell lines with 0.5 microM metabolite markedly affected the cells within 24 h. These observations suggest that the 7 beta-OHC metabolite is implicated in the mechanism of action of 7 beta-OHC cytotoxicity on spontaneously transformed cells.

Effect of exogenous gangliosides on the lipid composition of chick neurons in culture

When exogenous gangliosides are added to the growth medium of neuronal cell cultures they are inserted into their plasma membranes and are afterwards metabolized in the cytoplasmic interior. The action of exogenous gangliosides brings important morphological and biochemical changes to neurons in culture. The present report shows that the treatment with exogenous gangliosides of a primary culture of chick neurons modified the distribution of fatty acids in phosphatidylinositol (PI), mainly that of arachidonic acid and the fatty acids of the (n - 3) series without affecting the other phospholipids. The composition of neutral lipids did not change but their content was increased up to 2-3-fold depending upon the concentration of gangliosides. The change of the growth medium from one containing fetal calf serum to a chemically defined one reduced dramatically the content of free fatty acids while the addition of gangliosides raised this content to normal levels. The increase in the amount of diacylglycerol (DG) confirmed the finding that gangliosides stimulate phosphoinositide degradation. Finally the fatty acid composition of DG suggests indirectly that this compound might be produced also by degradation of phosphatidylcholine and not only of PI.

Topological distribution of choline phospholipid fatty acids in trout intestinal brush-border membrane

The transbilayer distribution of choline phospholipids in trout intestinal brush-border membrane has been investigated using phospholipase C (from Clostridium welchii). In the middle intestine, 84% of phosphatidylcholine (PC) and 60% of sphingomyelin (SP) are located in the outer membrane leaflet. In the posterior intestine, 89% of PC and 52% of SP are located in the outer membrane leaflet. The externally located PC molecular species are (n - 3) fatty acid-rich in both parts of the intestine. While the sphingomyelin molecular species containing 24:1(n - 9) are exclusively located in the outer leaflet in the middle intestine, those containing 14:0 are more abundant in the same leaflet but in the posterior intestine. This strongly asymmetric distribution of both choline phospholipids may have numerous consequences on the brush-border membrane characteristics.

Effects of eicosatetraynoic acid on membrane lipids of trout liver and intestine

After two months feeding either an (n-3) or an (n-6) fatty acid-rich diet, two groups of trout were switched to the (n-6) or the (n-3) fatty acid-rich diet, respectively. Half of each group was treated with 0.03% 5,8,11,14-eicosatetraynoic acid (ETYA) in the diet. Liver and intestinal brush border membrane lipids were analyzed. No effect was observed on their cholesterol content. ETYA induced an accumulation of 18:2(n-6), and it did not affect the 20:4(n-6) content but decreased the 22:5(n-6) content. ETYA induced an increase of 18:3(n-3) content in the brush border membrane and a decrease of the 22:6(n-3) content in the liver. Those results suggest that ETYA blocks mainly the delta 6-desaturase, which should have two different sites in the liver and one in the intestine.

Topological distribution of aminophospholipid fatty acids in trout intestinal brush-border membrane

The transbilayer distribution of aminophospholipids in trout intestinal brush-border membrane has been investigated using trinitrobenzene sulfonic acid (TNBS). In the middle intestine, phosphatidylethanolamine (PE) is symmetrically distributed between the two leaflets while 68% of the phosphatidylserine (PS) are located in the inner membrane leaflet. In the posterior intestine, 64% of the PE and 69% of the PS are located in the inner membrane leaflet. When asymmetrically distributed, the inner species of PE and PS have a higher content of 22:6(n-3) than the outer ones. This asymmetric distribution of docosahexaenoic acid in trout intestinal brush-border membrane might be related to the rod-like shape of the microvillus membrane and to its metabolism to hydroxylated derivatives.

Influence of lipid environment on insulin binding in cultured hepatoma cells

The influence of alterations of plasma membrane physico-chemical properties on insulin binding have been characterized in an insulin-sensitive rat hepatoma cell line adapted to grow for several generations in culture medium enriched with linoleic acid (18:2) or with 25-hydroxycholesterol. The cells took up 18:2 and 25-hydroxycholesterol added to the culture medium, without exhibiting any sign of intolerance or intoxication. These compounds respectively increased and decreased membrane fluidity at 37 degrees C. The cells demonstrated extensive changes in insulin binding parameters in response to experimental modifications of their membrane lipid composition. When determined at 4 degrees C, insulin receptors were present in the control cells at 136,000 sites/cell but this fell to 111,000 (P less than 0.05) in cells enriched in 18:2, and rose to 176,000 (P less than 0.001) in hydroxysterol-grown cells. According to a two-site model, the main effect of 18:2 was a significant increase of the number of high-affinity sites with a concomitant decrease of low-affinity sites. The hydroxysterol had the opposite effects on these parameters. The high-affinity insulin binding capacity of the hepatoma cells was affected by lipid supplementation in a similar way, whether it was determined at 4 degrees C or at 37 degrees C. Assuming a negative cooperativity model, 18:2 enhanced the degree of negative cooperativity among the sites, while 25-hydroxycholesterol reduced it. The time-course of insulin-induced receptor down-regulation was accelerated in the cells enriched in polyunsaturated fatty acids, but reduced in cells exposed to 25-hydroxycholesterol. These insulin-binding alterations cannot be directly related to modifications of cellular growth rate, receptor internalization or membrane fluidity per se, and are discussed as being more likely due to membrane lipid composition than to overall cell metabolism modifications.

Dietary modifications of phospholipid composition and biophysical properties of the brush border membrane along the trout intestine

Brush border membranes (BBM) are isolated from middle and posterior intestine of trout fed either an essential fatty acid-rich diet or a saturated one. The different phospholipid classes are separated, and their fatty acid composition is determined. Fluorescence anisotropy studies are performed using two lipid fluorophores, namely diphenylhexatriene (DPH) and trimethylamino-diphenylhexatriene (TMA-DPH). The results indicate that the usual parameters affecting the lipid fluidity such as the phospholipid:protein (PL:PROT), cholesterol:phospholipid (CHOL:PL), and sphingomyelin:phosphatidylcholine (SP:PC) ratios and the unsaturation of the acyl chains are sufficient to explain the fluidity values determined using DPH, but not those obtained with TMA-DPH as a probe. This fluorophore is assessed to be localized only in the external leaflet of the membrane. Hence, it will be affected by the composition of the major phospholipids of this leaflet, sphingomyelin and phosphatidylcholine.

Isolation and characterization of brush-border membrane from trout intestine. Regional differences

The isolation of brush-border membranes from trout enterocytes is described for both middle and posterior intestine. Both procedures are based on differential centrifugations combined with calcium precipitation. Classical marker enzymes are quantified and indicate a valuable purification of the membranes (13-18-fold). No difference appears when comparing the relative amounts of phospholipids, cholesterol and proteins in microvillus membranes isolated from either middle or posterior intestine. In contrast, the membranes isolated from middle intestine are more unsaturated than those from the posterior one, and their sphingomyelin/phosphatidylcholine ratio is lower. These differences are reflected by fluorescence anisotropy studies with diphenylhexatriene as lipid fluorophore which indicate a higher fluidity of the microvillus membranes from the middle intestine as compared with those from the posterior intestine. These results point out the importance of the fatty acyl chains and that of the relative amounts of phosphatidylcholine and sphingomyelin in controlling the fluidity of biological membranes in relation with their transport properties.

The effect of dietary lipids on the trout erythrocyte membrane

Rainbow trout were fed either a commercial diet or semi-purified diets containing 8% by weight of either cod liver oil, grape seed oil or hydrogenated coconut oil. Important changes in the fatty acid composition of erythrocyte membrane phospholipids were induced by these dietary fats. No changes were seen in the cholesterol/phospholipid ratio and in the cellular ATP level. Shape changes (crenation of cell margin and shrinkage) were only seen in trout fed hydrogenated coconut oil in connection with an accumulation of high amounts of (n-9) fatty acids including 20:3 (n-9) phospholipids. The compositional changes affect the stability of the erythrocyte membrane. An increased rate of osmotic hemolysis appeared to be associated with an increased unsaturated fatty acid content of the membranes.

Na transport and enzyme activities in the intestine of the freshwater and sea-water adapted trout (Salmo gairdnerii R.)

Unidirectional fluxes of Na+ obtained in perfused preparation and mucosal enzyme equipment (alkaline phosphatase, ouabain-sensitive Na+, K+-ATPase) have been determined in the middle and posterior intestine of freshwater (FW) and sea-water (SW) adapted trout. In FW, influxes and outfluxes were higher in the middle than in the posterior intestine, although net fluxes were similar. SW adaptation induced an increase of influxes and net fluxes mainly in the posterior intestine. SW adaptation decreased the alkaline phosphatase activity only in the posterior intestine. Na+,K+-ATPase activity was always higher in the middle than in the posterior intestine in FW and SW and increased in both parts by SW adaptation. Thus, it seems that SW adaptation of rainbow trout modifies Na intestinal absorption principally in its posterior part and in relation with the Na+, K+-ATPase activity.