The membrane lipids of Halobacterium halobium

The lipid content of the cell membrane of Halobacterium halobium increased from about 15% to 21% during exponential growth of the organism. Total lipid phosphorus more than doubled during the growth cycle. The mixture of membrane lipids from stationary-phase organisms was similar to lipid mixtures from whole cells of other halobacteria inasmuch as 80% of the lipid phosphorus occurred in a diether analogue of phosphatidylglycerophosphate and an additional 7.5% occurred in the ether analogue of phosphatidylglycerol. The lipid mixture was more complex than those reported for other halophils, however, 12 components being recognized in the acetone-insoluble fraction and 17 in the acetone-soluble fraction. There were major changes in the proportions of some minor components of the acetone-insoluble fraction during a growth cycle. Three nitrogenous lipids were recognized in the acetone-insoluble fraction, but all were present in relatively low proportion. One, which was not a phospholipid, contained a bound peptide. Of the 17 acetonesoluble compounds, 15 were pigments. The major carotenoids were alpha- and beta-bacteriorubrin. The carotenoid pigments occurred at maximal concentration after 6-7 days' growth.     

Lipid composition of the isolated rat intestinal microvillus membrane

1. Rat intestinal microvillus plasma membranes were prepared from previously isolated brush borders and the lipid composition was analysed. 2. The molar ratio of cholesterol to phospholipid was greatest in the membranes and closely resembled that reported for myelin. 3. Unesterified cholesterol was the major neutral lipid. However, 30% of the neutral lipid fraction was accounted for by glycerides and fatty acid. 4. Five phospholipid components were identified and measured, including phosphatidylethanolamine, phosphatidylcholine, phosphatidylserine, sphingomyelin and lysophosphatidylcholine. Though phosphatidylethanolamine was the chief phospholipid, no plasmalogen was detected. 5. In contrast with other plasma membranes in the rat, the polar lipids of the microvillus membrane were rich in glycolipid. The cholesterol:polar lipid (phospholipid+glycolipid) ratio was about 1:3 for the microvillus membrane. Published data suggest that this ratio resembles that of the liver plasma membrane more closely than myelin or the erythrocyte membrane. 6. The fatty acid composition of membrane lipids was altered markedly by a single feeding of safflower oil. Membrane polar lipids did not contain significantly more saturated fatty acids than cellular polar lipids. Differences in the proportion of some fatty acids in membrane and cellular glycerides were noted. These differences may reflect the presence of specific membrane glycerides.     

Induction of lipid metabolic enzymes during the endoplasmic reticulum stress response in plants

The endoplasmic reticulum (ER) stress response is a signal transduction pathway activated by the perturbation of normal ER metabolism. We used the maize (Zea mays) floury-2 (fl2) mutant and soybean (Glycine max) suspension cultures treated with tunicamycin (Tm) to investigate the ER stress response as it relates to phospholipid metabolism in plants. Four key phospholipid biosynthetic enzymes, including DG kinase and phosphatidylinositol (PI) 4-phosphate 5-kinase were up-regulated in the fl2 mutant, specifically in protein body fractions where the mutation has its greatest effect. The third up-regulated enzyme, choline-phosphate cytidylyltransferase, was regulated by fl2 gene dosage and developmental signals. Elevated accumulation of the fourth enzyme, PI 4-kinase, was observed in the fl2 endosperm and soybean cells treated with Tm. The activation of these phospholipid biosynthetic enzymes was accompanied by alterations in membrane lipid synthesis and accumulation. The fl2 mutant exhibited increased PI content in protein body membranes at 18 d after pollination and more than 3-fold higher triacylglycerol accumulation in the endosperm by 36 d after pollination. Incorporation of radiolabeled acetate into phospholipids in soybean culture cells increased by about 30% with Tm treatment. The coordinated regulation of ER stress related proteins and multiple components of phospholipid biosynthesis is consistent with signaling through a common pathway. We postulate that the plant ER stress response has an important role in general plant metabolism, and more specifically in integrating the synthesis of protein and lipid reserves to allow proper seed formation.     

Phospholipids from Bacillus stearothermophilus

The lipids of Bacillus stearothermophilus strain 2184 were extracted with chloroform-methanol and separated into neutral lipid and three phospholipid fractions by chromatography on silicic acid columns. The phospholipids were identified by specific staining reactions on silicic acid-impregnated paper, by chromatography of alkaline and acid hydrolysis products, and by determination of acyl ester:glycerol:nitrogen:phosphorus molar ratios. The total extractable lipid was 8% of the dry weight of whole cells and consisted of 30 to 40% neutral lipid and 60 to 70% phospholipid. The phospholipid consisted of diphosphatidyl glycerol (23 to 42%), phosphatidyl glycerol (22 to 39%), and phosphatidyl ethanolamine (21 to 32%). The concentrations of diphosphatidyl glycerol and phosphatidyl glycerol were lower in 2-hr cells than in 4- and 8-hr cells. Whole cells were fractionated by sonic treatment and differential centrifugation. The total lipid content, expressed in per cent of dry weight of each fraction was: whole protoplasts, 10%; membrane fraction, 18%; 30,000 x g particulate fraction, 22%; and 105,000 x g particulate fraction, 26%. The relative phospholipid concentrations in each fraction were about the same. As had been previously reported, none of the phospholipid was stable to alkaline hydrolysis.     

The effect of phosphate deficiency on membrane phospholipid composition of bean (Phaseolus vulgaris L.) roots

Plasma membranes were isolated from roots of bean (Phaseolus vulgaris L.) plants cultured on phosphate sufficient or phosphate deficient medium. The phospholipid composition of plasma membranes was analyzed and compared with that of the microsomal fraction. Phosphate deficiency had no influence on lipid/protein ratio in microsomal as well as plasma membrane fraction. In phosphate deficient roots phospholipid content was lower in the plasma membrane, but did not change in the microsomal fraction. Phosphatidylcholine and phosphatidylethanolamine were two major phospholipids in plasmalemma and microsomal membranes (80 % of the total). After two weeks of phosphate starvation a considerable decrease (about 50 %) in phosphatidylcholine and phosphatidylethanolamine in microsomal membranes was observed. The decline in two major phospholipids was accompanied by an increase in phosphatidic acid and lysophosphatidylcholine content. The effect of alterations in plasma membrane phospholipids on membrane function e.g. nitrate uptake is discussed.     

Quantitative profiling of Arabidopsis polar glycerolipids in response to phosphorus starvation. Roles of phospholipases D zeta1 and D zeta2 in phosphatidylcholine hydrolysis and digalactosyldiacylglycerol accumulation in phosphorus-starved plants

Phosphorus is an essential macronutrient that often limits plant growth and development. Under phosphorus-limited conditions, plants undergo substantial alterations in membrane lipid composition to cope with phosphorus deficiency. To characterize the changes in lipid species and to identify enzymes involved in plant response to phosphorus starvation, 140 molecular species of polar glycerolipids were quantitatively profiled in rosettes and roots of wild-type Arabidopsis (Arabidopsis thaliana) and phospholipase D knockout mutants pld zeta1, pld zeta2, and pld zeta1 pld zeta2. In response to phosphorus starvation, the concentration of phospholipids was decreased and that of galactolipids was increased. Phospholipid lost in phosphorus-starved Arabidopsis rosettes was replaced by an equal amount of galactolipid. The concentration of phospholipid lost in roots was much greater than in rosettes. Disruption of both PLD zeta1 and PLD zeta2 function resulted in a smaller decrease in phosphatidylcholine and a smaller increase in digalactosyldiacylglycerol in phosphorus-starved roots. The results suggest that hydrolysis of phosphatidylcholine by PLD zetas during phosphorus starvation contributes to the supply of inorganic phosphorus for cell metabolism and diacylglycerol moieties for galactolipid synthesis.     

Thermal behavior and lipid composition of cauliflower plasma membranes in relation to ATPase activity and chilling sensitivity

A plasma-membrane fraction rich in ion-stimulated ATPase activity was isolated from cauliflower (Brassica oleracea L.) buds. The activity of the ATPase was dependent on Mg(2+) and stimulated 4-fold by K(+). The lipids of the membrane fraction contained 57% by weight of phospholipid, 16% glycolipid including sterol glycosides, and 27% neutral lipids. Sterols and sterol esters comprised 9% by weight of the total lipid fraction, and the m ratio of total sterol to phospholipid was 0.5. Fatty acid unsaturation of the membrane lipids was 75%. Arrhenius plots of the Mg(2+) and Mg(2+) + K(+) stimulated ATPase activity were biphasic with an increase in activation energy occurring below about 12 degrees C, a response typical of some membrane-associated enzymes of chilling-sensitive plants. No thermal transitions were detected in the membranes or membrane lipids between 0 and 30 degrees C using differential scanning calorimetry and electron spin resonance spectroscopy. This type of thermal behavior is typical of membranes of chilling-resistant plants. It was concluded that the low temperature increase in activation energy of the ion-stimulated, membrane-associated ATPase is an intrinsic property of the enzyme system and not the result of a transition in the bulk membrane lipid.     

Effects of in vitro treatment with ozone on the physical and chemical properties of membranes

Treatment of microsomal membranes from cotyledons of Phaseolus vulgaris with ozone raises the liquid-crystalline to gel lipid phase transition temperature and results in the formation of distinct domains of gel phase lipid in the membranes. Liposomes prepared from the total lipid extracts of ozone-treated membranes undergo phase separations just a few degrees below the transition temperature for intact membranes, indicating that the formation of gel phase lipids is largely attributable to ozone-induced alterations in the membrane lipids. Levels of unsaturated fatty acids as well as the sterol to phospholipid ratio are markedly reduced in the ozone-treated membranes, and the neutral lipid fraction from treated membranes shows, an increased propensity to induce the formation of gel phase phospholipid when incorporated into liposomes of egg phosphatidylcholine. Since gel phase phospholipid also forms in naturally senescing plant membranes and appears to be attributable to changes in the neutral lipid fraction, the effects of natural senescence and ozone on membranes have been compared.     

Patterns of furanocoumarin production and insect herbivory in a population of wild parsnip (Pastinaca sativa L.)

Summary Seasonal changes in the distribution and abundance of furanocoumarins in wild parsnip, Pastinaca sativa (Umbelliferae), were examined in a population of plants in Tompkins County, New York. Xanthotoxin, imperatorin and bergapten (linear furanocoumarins) occur in all above-ground parts of the plant; in addition, angelicin and sphondin (angular furanocoumarins) occur in umbels of some individuals. Total furanocoumarin content, as measured by percent dry weight, is greatest in reproductive parts, particularly buds and seeds; variation in concentrations between plants is greatest in vegetative structures (e.g., leaves).Within the plant, the distribution of furanocoumarins is significantly correlated with nitrogen, as opposed to biomass, allocation. In that nitrogen is often a factor limiting the plant growth, furanocoumarins appear to be allocated in proportion to plant tissue value; reproductive structures, obvious contributors to plant fitness, contain over ten times the amount of nitrogen and furanocoumarin contained in vegetative structures such as senescent leaves.Stepwise multiple regression analysis revealed that generalized insect herbivores tend to feed on plants or plant parts low in furanocoumarin content and, correspondingly, low in nitrogen content. Parsnip specialists, notably Depressaria pastinacella (Lepidoptera: Oecophoridae), feed exclusively on umbels, plant parts rich in nitrogen and furanocoumarins; furanocoumarin number and content in fact account for over 60% of the variance in number of umbel feeders. These patterns conform with previous determinations of the toxicological properties of furanocoumarins. Nitrogen is known to affect growth rate, fecundity, longevity and survivorship of insect herbivores; by tolerating or detoxifying furanocoumarins, D. pastinacella can consume plant tissues containing significantly greater amounts of nitrogen than tissues consumed by generalist feeders. That the presence of D. pastinacella on individual plants is correlated with the number of furanocoumarins present is consistent with the hypothesis that parsnip specialists use angular furanocoumarins as host recognition cues.     

Adaptive changes in lipid composition of rat liver plasma membrane during postnatal development following maternal ethanol ingestion

The fatty acid composition of constituent phospholipids and the cholesterol content of rat liver plasma membranes were determined subsequent to maternal alcohol ingestion during pregnancy and lactation. The alcoholic group was given a liquid Metrecal diet containing 37% ethanol-derived calories. The control group was pair-fed an isocaloric sucrose/Metrecal diet. Litters were killed for lipid analyses at days 5, 15 and 25 after birth. These studies revealed that the total phospholipid phosphorus was similar and increased significantly with age in both groups. Cholesterol also increased significantly with age in both groups but was greater in the alcoholic pups, resulting in a higher cholesterol/phospholipid molar ratio. While the phosphatidylethanolamine (PE) content increased with age in both groups, that of sphingomyelin decreased. Phosphatidylserine + phosphatidylinositol (PS + PI) was significantly higher in the control group at all ages studied. A consistent increase of C22:6 in phosphatidylcholine (PC), sphingomyelin, PS + PI and in the total phospholipid fraction from alcoholic pups was observed. Although other fatty acid changes were found in PC, PS + PI and sphingomyelin, PE was not affected. These results suggest that specific adaptive changes were induced in the liver plasma membrane lipids of the progeny from alcoholic rats.     

Isolation of purified brush-border membranes from rat jejunum containing a Ca2+-independent phospholipase A2 activity

A novel phospholipase activity was recognized in intact, rat jejunal brush-border membranes and its effect on membrane lipid composition was evaluated following various incubation protocols. Brush-border membranes were isolated from mucosal scrapings by a combination of existing techniques. A brush-border plus nuclei fraction was first prepared by homogenization and low-speed centrifugation in isotonic mannitol, in the presence of 5 mM EDTA. Brush-border membrane vesicles were isolated from this fraction by homogenization, followed by precipitation of the remaining undesired membranes with 10 mM CaCl2. Membranes were judged to be highly purified by marker enzyme content, protein profile, and electron microscopy. In total lipid extracts, prepared immediately following membrane isolation, the ethanolamine phosphatides were found to be the major phospholipid class, accounting for nearly 45% of the total lipid phosphorus. Storage of the intact membranes, at either room temperature or at -20 degrees C, but not at -70 degrees C, resulted in a gradual and progressive hydrolysis of phosphatidylethanolamine to lysophosphatidylethanolamine. Over 60% of the total ethanolamine phospholipid was converted to the lyso form during a 2 week storage period. Incubation of the intact membranes at 37 degrees C produced a similar effect in one hour. Only small amounts of other glycerophospholipids were degraded under these conditions. Hydrolysis was specific for the sn-2 position as more than 80% of the fatty acids in the lysophosphatidylethanolamine were found to be saturated. Substitution of MgCl2 for CaCl2 in the precipitation step did not block the hydrolysis. It was concluded that rat brush-border membranes contain a Ca2+-independent phospholipase A2 with a high substrate preference for phosphatidylethanolamine. The physiological significance of this enzyme is not known.     

Phase properties of senescing plant membranes. Role of the neutral lipids

Wide-angle X-ray diffraction studies have indicated that rough and smooth microsomal membranes from bean cotyledons acquire increasing proportions of gel phase lipid at physiological temperature as the tissue senesces. In addition, for both types of membrane the lipid phase transition temperature, defined as the highest temperature at which gel phase lipid can be detected, progressively rises with advancing senescence. Liposomes prepared from total lipid extracts of the membranes show a similar increase in transition temperature with age, indicating that separation of the polar lipids into distinct gel and liquid-crystalline domains is not attributable to peculiar protein-lipid interactions. Liposomes prepared from purified phospholipid fractions of the membranes show little change in transition temperature with age, indicating that the altered phase properties of the lipid do not reflect an increase in fatty acid saturation. However, the formation of gel phase lipid that occurs naturally during senescence can be stimulated by preparing liposomes from a mixture of the phospholipid fraction from young membrane and the neutral lipid fraction from old membrane. By adding the separated components of the neutral lipid fraction to purified phospholipid it was found that sterol esters and several unidentified lipids are able to raise the transition temperature of the polar lipids. Sterols have no effect on the phospholipid transition temperature. The data have been interpreted as indicating that several neutral lipids, which presumably increase in abundance with advancing senescence, induce a lateral phase separation of the polar lipids resulting in distinct gel and liquid-crystalline domains of lipid in the senescent membranes.     

Changes in fatty acid composition of rat liver and serum induced by distal small bowel resection

The serum lipid composition and the fatty-acid profiles of the major lipid fraction (triglycerides, esterified cholesterol, and phospholipid) of liver and serum were examined 6 weeks after both 50% and 75% distal small bowel resection (DSBR). Total serum lipid content did not modify after DSBR. Esterified cholesterol and phospholipid levels of the serum did not significantly change after the operation. However, a significant increase in both free cholesterol and triglyceride levels was observed after DSBR. Different fatty acid changes in the liver and serum lipid fractions were found after DSBR, with the greatest differences in the hepatic esterified cholesterol fraction. These results suggest that DSBR affects both the lipid composition and the fatty acid composition of major lipid fraction of liver and serum.     

Changes in membrane lipid components and antioxidant levels during natural ageing of seeds of Acer platanoides

Changes in membrane lipid components and cellular antioxidant systems were investigated through 7 years in seeds of Acer platanoides L. after storage in natural conditions, i.e. - 3°C and 10% water content. The loss of germination capacity in aged seeds was associated with increased solute leakage during imbibition, reduced content of phospholipids, especially phosphatidylcholine, and increased free fatty acid content. A marked decrease of unsaturated fatty acids in the phospholipid fraction was observed after one year of storage. Antioxidant potential in the lipid fraction and level of -SH groups decreased during storage. The results are consistent with the hypothesis that ageing in seeds is mediated by a free radical mechanism.     

Homeostasis of plasma membrane viscosity in fluctuating temperatures

Temperature has a direct effect at the cellular level on an organism. For instance, in the case of biomembranes, cooling causes lipids to lose entropy and pack closely together. Reducing temperature should, in the absence of other factors, increase the viscosity of a lipid membrane. We have investigated the effect of temperature variation on plasma membrane (PM) viscosity. We used dispersion tracking of photoactivated green fluorescent protein (GFP) and fluorescence recovery after photobleaching in wild-type and desaturase mutant Arabidopsis thaliana plants along with membrane lipid saturation analysis to monitor the effect of temperature and membrane lipid composition on PM viscosity. Plasma membrane viscosity in A. thaliana is negatively correlated with ambient temperature only under constant-temperature conditions. In the more natural environment of temperature cycles, plants actively manage PM viscosity to counteract the direct effects of temperature. Plasma membrane viscosity is regulated by altering the proportion of desaturated fatty acids. In cold conditions, cell membranes accumulate desaturated fatty acids, which decreases membrane viscosity and vice versa. Moreover, we show that control of fatty acid desaturase 2 (FAD2)-dependent lipid desaturation is essential for this homeostasis of membrane viscosity. Finally, a lack of FAD2 function results in aberrant temperature responses.     

Effects of paclobutrazol and chilling temperatures on lipids, antioxidants and ATPase activity of plasma membrane isolated from green bell pepper fruits

The effects of paclobutrazol treatment on plasma membrane lipid composition and ATPase activity of bell pepper fruit ( Capsicum annuum ) subjected to chilling temperatures were assessed. Application of the growth regulator paclobutrazol affected plant growth and fruit morphology. The plants were more compact and the fruits were less elongated than control fruits. There was about 60% more plasma membrane on a fresh weight basis from treated fruits. At harvest there was no difference in sterol to phospholipid ratio, or in phospholipid fatty acid composition of control compared with paclobutrazol treated fruit. However, plasma membrane ATPase acitivity of treated fruit was two times higher than that of control fruit. After storage at chilling temperature (2°C), the control fruit developed more chilling iniury, and had greater weight loss and a higher rate of K⁺ leakage than paclobulrazol treated fruit. Plasma membrane phospholipid content decreased and saturation of phospholipid fatty acids was higher than in control fruit. These two changes were largely absent in plasma membrane from treated fruit. At harvest antioxidant levels in the plasma membrane of paclobutrazol treated peppers were higher than in those of controls and changed little during storage, whereas levels in control fruit plasma membrane decreased 66%. ATPase activity increased and then decreased in control fruit held at low temperature, whereas in treated fruit activity was constant. The protective effect of paclobutrazol against chilling injury of pepper fruit may result from a combination of its effect on fruit morphology, and protection of the lipids against oxidative stress.     

l-Acylimidazoles with Broad-spectrum Fungicidal Activity

The membrane lipids of six higher plants that differ in salt tolerance were analyzed and compared. The root lipids increased in a ratio of glycolipid/phospholipid with increasing salt- tolerance. A similar increase in the ratio was observed with increasing external salinity when halophytic orach and salt-sensitive cucumber were exposed to varying salinity, although the latter plant was limited to only a little increase. Measurements of ion-transport rates with artificial lipid membranes revealed that the root lipids from a salt-resistant plant formed a more permeable membrane than those from a salt-sensitive species. It was found that the membrane permeability was related to the glycolipid/phospholipid ratio in the membrane lipids, where the glycolipids were stimulative and the phospholipids were repressive for ion-flow. These different effects of the two lipid classes may be attributed to their molecular species and head groups.     

Thermal regulation of the fatty acid composition of lipopolysaccharides and phospholipids of Proteus mirabilis.

The fatty acid composition of the lipid A moiety of the lipopolysaccharide and phospholipid fractions of Proteus mirabilis changed significantly on varying the growth temperature. A decrease in the growth temperature from 43 degrees C to 15 degrees C resulted in a decrease in the palmitic acid content of the lipopolysaccharide from 19.4% of total fatty acids at 43 degrees C to 1.4% at 15 degrees C, and by the appearance of an unsaturated fatty acid residue, hexadecenoic acid. Changes in the 3-hydroxy-myristic acid content of the lipid A were minimal. The decrease in the growth temperature also resulted in a decrease in the saturated fatty acid content of the phospholipid fraction, which was accompanied by an increase in their fluidity, as measured by the freedom of motion of spin-labeled fatty acids incorporated into dispersions made of the phospholipids. Nevertheless, the fluidity obtained with membrane phospholipids extracted from the cells grown at various temperatures were essentially the same when fluidity was determined at the growth temperature, supporting the hypothesis that variations in the fatty acid composition of membrane phospholipids serve to produce membranes having a constant fluidity at different temperatures of growth.     

Effect of paclobutrazol and chilling on leaf membrane lipids in cucumber seedlings

The effects of paclobutrazol on the leaf membrane lipid composition of seedlings of cucumber ( Cucumis sativus L. cv. Victory) subjected to chilling temperatures were assessed. At a non-injurious temperature (12.5°C), there was no difference in the polar lipid fatty acid composition or in the glycolipid, phospholipid or free sterol content of leaves from treated vs untreated seedlings, regardless of whether paclobutrazol was administered 1 or 7 days prior to analysis. In the latter case (7 days pretreatment), there were clear effects of the bioregulator on plant growth and morphology as well as on leaf chlorophyll content. At an injurious chilling temperature (5°C), desaturation of leaf polar lipid fatty acids was markedly reduced in both treated and untreated seedlings. Chilling at 5°C resulted in losses of fresh weight and membrane lipids in leaves of both groups of plants. These losses were either reversible or irreversible, depending upon the duration of chilling and of pretreatment with paclobutrazol. Seedlings pretreated with 10 μg ml⁻¹ paclobutrazol generally sustained less chilling injury than untreated controls, as judged by the extent of wilting, necrosis and desiccation. This correlated with reduced losses of leaf fresh Weight and membrane lipids.     

The mucosa of the small intestine: development of the cellular lipid composition during enterocyte differentiation and postnatal maturation

Alterations in lipids linked to intestinal maturation and enterocyte differentiation were reviewed. The 3 main lipid components of cell membranes, ie cholesterol, phospholipids and glycolipids, were examined. Cell phospholipid content increases from the crypts to the mid-villus, which accounts for membrane development and organelle growth in differentiating cells. Changes in the proportion of phospholipid polar head groups occur in brush border membrane during postnatal maturation of the small intestine. The possibility that phospholipid fatty acid composition in differentiating cells might be altered by dietary lipids is discussed. Cholesterol biosynthesis mainly occurs in crypt and lower villus cells whereas its absorption from luminal content and esterification into lipoproteins occur in upper villus mature cells. Cholesterol cell content increases in mature cells in comparison to immature cells on the one hand, and in the distal by comparison with proximal parts of the intestine on the other. Increasing cholesterol content is generally correlated with decreasing membrane fluidity, which in turn could modulate functional properties of the mucosa. Glycosphingolipids are mainly found in the brush border membrane, which contains 20-30% glycolipids by weight of total lipids. These components tend to reinforce the membrane stability and significantly contribute to the surface properties of epithelial cells. The latter undergo noticeable changes during cell differentiation and postnatal maturation. Significant changes in both the glycosidic and lipophilic parts of glycosphingolipid molecules occur in differentiating cells and are of possible importance in the process of mucosal maturation. It is possible that the addition of a terminal sialic acid (sialyltransferase activity) instead of a terminal galactose (galactosyltransferase) to an endogenous acceptor (lactosylceramide) could constitute an important event in the differentiation process, and may account for the increasing content of hematosides along the intestinal villus of rat. Alterations in lipid counterpart mainly consist of hydroxylation of fatty acids in hematosides during postnatal maturation or in glucosylceramides during cell differentiation. Collectively these intestinal lipid changes may contribute in part to the development of mucosal barrier, selective permeability and functional properties of the mature intestinal mucosa.