Major gangliosides in normal and pathological human thyroids

The major gangliosides of human thyroids were extracted, purified and then analyzed by gas-liquid chromatography. In normal thyroid, GM3 and GD3 represented about 80% of lipid-bound sialic acid. GM3 contained more than 50% of long-chain fatty acids, whereas GD3 contained mostly short ones. 4D hydroxy sphinganine represented 20% of long-chain base content in both cases. In pathological thyroids (Graves' disease, cancer, toxic adenoma), GM3 represented about 60% of lipid-bound sialic acid; its fatty acid content was mostly short chain fatty acids, as in normal GD3. 4D hydroxy sphinganine proportion was decreased.     

Isolation and characterization of major gangliosides from frog liver

Four major gangliosides isolated from frog liver were characterized by compositional analysis involving GLC and GC-MS, methylation analysis, chromium trioxide oxidation, and enzymatic hydrolysis. The results revealed that the most major ganglioside in the tissue was GM4 containing N-acetylneuraminic acid and the others were GM4 containing N-glycolylneuraminic acid, GD1a, and a fucosyl ganglioside which was tentatively assigned to be alpha-galactosyl alpha-fucosyl GM1. This is the first report describing the presence of GM4 containing N-glycolylneuraminic acid. The fatty acids in both GM4 were mainly alpha-hydroxylated, and those in the fucosyl ganglioside were exclusively nonhydroxy fatty acids. The GD1a contained both nonhydroxy and alpha-hydroxy fatty acids in a ratio of about 3:2. The predominant species were 22:0, 23:0, 24:0, and 24:1 in both species of the fatty acids. The long-chain bases of these four gangliosides consisted of C18-sphingosine and C18-phytosphingosine together with significant amounts of C16 to C19 dihydroxy and trihydroxy bases with iso and anteiso structures.     

Omega oxidation of fatty acids and the pathway of 3-hydroxybutyric acid formation

Pathways followed by the carbons of long chain fatty acids in their conversion to 3-hydroxybutyric acid were traced and the contribution of ω-oxidation to fatty acid oxidation was determined in the cellular environment where ketone body formation occurs. 1-¹⁴C-, 2-¹⁴C-, and ω-¹⁴C-labeled fatty acids were injected into alloxan-induced diabetic rats in ketosis. 3-Hydroxybutyric acid was isolated from their urines and degraded. About 1.2 to 1.4 times as much ¹⁴C was found in carbon 1 as carbon 3 of 3-hydroxybutyric acid when the 1-¹⁴C-labeled fatty acids were injected and in carbon 2 as carbon 4 when the 2-¹⁴C-labeled fatty acids were injected. There was about 4 times as much incorporation into carbon 4 as carbon 2 of 3-hydroxybutyric acid formed from the ω-¹⁴C-labeled fatty acids. This means that 50% or more of the fatty acids were oxidized, so that the terminal two carbons of the fatty acids were converted to acetoacetyl-CoA without acetyl-CoA as an intermediate. Incorporation of ¹⁴C into carbons 1 and 2 of the hydroxybutyric acid reflects the distribution of ¹⁴C in acetyl-CoA. Incorporation into carbon 1 was very small when the ω-¹⁴C-labeled fatty acids were substrate. This means that ω-oxidation of fatty acids makes, at most, a small contribution to the formation of the acetyl-CoA pool from which acetoacetate is derived.     

The glycosphingolipid receptor for Vibrio trachuri in the red sea bream intestine is a GM4 ganglioside which contains 2-hydroxy fatty acids

Three major glycosphingolipids (tentatively designated IGL-1, 2, and 3) were isolated from the intestine of red sea bream (Pagrus major) and were subjected to a TLC-overlay assay with (35)S-labeled Vibrio trachuri which causes vibriosis of fish. The bacteria adhered to IGL-2, which was determined to be a GM4 ganglioside (NeuAcalpha2-3Galbeta1-ceramide). The fatty acid portion of IGL-2 was composed of 2-hydroxy C22:0, C24:0, and C24:1, in addition to the non-hydroxy C16:0 and C18:0, while the sphingoid base was composed exclusively of sphingenine (d18:1). Among glycosphingolipids tested, V. trachuri adhered to GM4 the most strongly followed by adherence to GM3 and GalCer, but the bacteria did not adhere to GM1a, GM2, LacCer, or GlcCer. V. trachuri was found to aggregate with the erythrocytes coated with GM4, but not with those coated with GM1a or GM2, thus indicating that specific adhesion occurs on intact cells. Interestingly, the dynamics for adhesion of V. trachuri to glycosphingolipids was defined by the structure of not only the sugar moiety but also the ceramide moiety, since the bacteria adhered to GM4 which contained 2-hydroxy fatty acids much more strongly than to that which contained non-hydroxy fatty acids.     

Tissue-specific expression of GM3(NeuGc) and GD3(NeuGc) in epithelial cells of the small intestine of strains of inbred rats. Absence of NeuGc in intestine and presence in kidney gangliosides of brown Norway and spontaneously hypertensive rats

The ganglioside composition of the epithelial cells of the small intestine was investigated in 15 strains of inbred rats. Most of these strains had GM3 as the only detectable ganglioside. In addition to GM3, small amounts of GD3 were found in four strains, AVN, BN, DA, and LE. The fatty acid content of the ceramide portion was composed of a large, although variable, percentage of 2-hydroxy fatty acids. The sphingoid base was always C18-4D-hydroxysphinganine. The highly prominent sialic acid was N-glycolylneuraminic acid (NeuGc) in most strains. However in two strains, Brown Norway (BN) and spontaneously hypertensive rats (SHR), NeuAc was the only sialic acid of the gangliosides of the intestinal epithelium. The analysis of the ganglioside composition of the epithelium of the small intestine of the first generation hybrids of SHR with DA and BN, respectively, demonstrated that the expressions of GM3 (NeuGc) and GD3 were genetically transmitted as dominant traits and that BN and SHR were likely to carry the same deficient gene that led to the expression of GM3(NeuAc) instead of GM3(NeuGc) in the small intestine. For comparison, the sialic acid composition of kidney gangliosides was analyzed in some strains. 21-23% of the kidney gangliosides was GM3(NeuGc) in all tested strains, including BN and SHR. Therefore, the ganglioside composition of the intestinal epithelium could vary in the rat species, and the defect of N-glycolylneuraminic acid was not only strain-specific but also occurred in a tissue-specific way among strains of inbred rats.     

Characterization of neutral sphingolipids and gangliosides from chicken liver

The neutral sphingolipids and gangliosides were isolated from 62- and 63-day-old chicken livers and characterized. The total concentration of neutral sphingolipids was 59 nmol/g of liver, and that of gangliosides was 330 nmol/g of liver. The major neutral sphingolipids were free ceramide, galactosylceramide, glucosylceramide, lactosylceramide, galabiosylceramide, and Forssman glycolipid. Galactosylceramide was the most abundant and free ceramide was the second most abundant. The major gangliosides were sialosylgalactosylceramide (GM4) and sialosyllactosylceramide (GM3), each of which contained only N-acetylneuraminic acid as a sialic acid. Sphingosine (d18:1) was a major long-chain base in all the sphingolipids. Considerable amounts of 2-hydroxy fatty acids were present in free ceramide, galactosylceramide, and GM4.     

Isolation and characterization of acidic glycosphingolipids from the gill of the Pacific Salmon (Oncorhynchus keta): A novel hybrid-type ganglioside with isoglobo- and neolacto-Series

Monosialosyl gangliosides and sulfoglycolipids in the gill of pacific salmon, Oncorhynchus keta, have been prepared by solvent extraction and DEAE-Sephadex column chromatography. Acidic glycolipid bands (M1-M13) detected by thin layer chromatography were separated by Iatrobeads column chromatography and 13 components were characterized by TLC, compositional analysis, methylation analysis, chemical and enzymatic degradation, liquid secondary ion mass spectrometry and (1)H nuclear magnetic resonance spectroscopy. In addition to the acidic glycolipids with known structures (SM4s, SM3, GM3, LM1, GM1b and V(3)alphaFuc,IV(3)betaGalNAc-GM1a), two fractions (M11 and M13) of unknown monosialosyl gangliosides with TLC mobility slower than GM1a were isolated and characterized as having the following structure with a hybrid of isoglobo- and neolacto-series. [formula: see text] Analysis of fatty acid indicated predominance of C24:1 fatty acid in the upper band (M11) and shorter chain saturated fatty acids in the lower band (M13). The tissue concentrations of M11 and M13 were 1.15 and 0.96 mumol/kg wet weight, respectively.     

Effects of Brefeldin A on Galactosphingolipid Synthesis in an Immortalized Schwann Cell Line: Evidence for Different Intracellular Locations of Galactosylceramide Sulfotransferase and Ceramide Galactosyltransferase Activities

Abstract: Brefeldin A (BFA) has been used extensively to study the intracellular transport and processing of proteins and sphingolipids because of its dramatic alteration of the structural and functional organization of the Golgi. We have examined the effect of BFA on the synthesis of galactosylceramide sulfate (SGalCer) and its immediate precursor galactosylceramide (GalCer) in an immortalized Schwann cell line (S16) to determine the intracellular sites of synthesis of these two related glycolipids. During a 6-h labeling period, a dose-dependent inhibition of [³⁵S]sulfate incorporation into SGalCer was observed with 95% inhibition occurring at 0.5 µg/ml BFA. Labeling of newly synthesized galactosphingolipids with [³H]-palmitic acid for 6 h in the presence of BFA resulted in increased incorporation of label into GalCer containing nonhydroxy fatty acids (NFA-GalCer) to 162% of control values, whereas labeling of GalCer containing 2-hydroxy fatty acids (HFA-GalCer) was reduced to 63% of control. After 24 h, these values were at 366 and 91%, respectively. These results indicate that at least some of the HFA-GalCer was initially synthesized at a location distal to the BFA block and separate from the site of NFA-GalCer synthesis. Examination of [³H]palmitic acid incorporation into free ceramides showed an increase of 133 and 161% for hydroxy and nonhydroxy fatty acid ceramides, respectively, in cells treated for 6 h with BFA in comparison with levels found in untreated control cells, indicating that BFA did not block fatty acid 2-hydroxylation or the formation of HFA ceramide. Incorporation of [³H]palmitic acid into glucosylceramide and GM3 was increased over control levels whereas labeling of GM2 was inhibited, consistent with what has been reported previously for the effect of BFA on these glycolipids in other cell types. These results suggest that there are at least two separate intracellular sites for the galactosylation of HFA and NFA ceramide, respectively, which can be distinguished by their sensitivity to BFA. Our results also indicate that the site of GalCer sulfation is not redistributed to the endoplasmic reticulum in the presence of BFA and therefore may be localized to the distal Golgi or trans-Golgi network.     

Preparation of Alexa Fluor 350-conjugated nonradioactive or 3H-labeled GM1 ganglioside derivatives with different ceramides

Alexa Fluor 350 hydrazide (AF) was coupled to the aldehyde group at C-6 of terminal galactose of oxidized GM1 gangliosides containing different fatty acid residues (GM1s). The AF-GM1 hydrazones obtained were reduced with NaBH₄ or [³H]NaBH₄ and purified by high-performance thin layer chromatography (HPTLC) and high-performance liquid chromatography (HPLC). Final yields of AF-GM1s exceeded 30%, purity was better than 97%, and radiochemical purity of ³H-labeled AF-GM1s was more than 94.5%. Structures of AF-GM1s were confirmed by electrospray ionization-mass spectrometry (ESI-MS). When added to HL-60 cell culture media, more than 81.6 or 78.9% of the AF-[³H]GM1s were taken up by cells in a bovine serum albumin- or trypsin-resistant manner, respectively. Approximately 70% of the AF-[³H]GM1s were recovered in HL-60 total plasma membrane fraction.     

Incorporation and distribution of dihomo-γ-linolenic acid, arachidonic acid, and eicosapentaenoic acid in cultured human keratinocytes

Human keratinocytes in culture were labelled with ¹⁴C-dihomo-γ-linolenic acid, ¹⁴C-arachidonic acid or ¹⁴C-eicosapentaenoic acid. All three eicosanoid precursor fatty acids were effectively incorporated into the cells. In phospholipids most of the radioactivity was recovered, in neural lipids a substantial amount, and as free unesterifed fatty acids only a minor amount. The most of the radioactivity was found in phosphatidylethanolamine which was also the major phospholipid as measured by phosphorous assay. The incorporation of dihomo-γ-linolenic acid and arachidonic acid into lipid subfractions was essentially similar. Eicosapentaenoic acid was, however, much less effectively incorporated into phosphatidylinositol + phosphatidylserine and, correspondingly, more effectively into triacylglycerosl as compared to the two other precursor fatty acids. Once incorporated, the distribution of all three precursor fatty acids was relatively stable, and only minor amounts of fatty acids were released into the culture medium during short term culture (two days). Our study demonstrates that eicosanoid precursor fatty acids are avidly taken up by human keratinocytes and esterified into membrane lipids. The clinical implication of this finding is that dietary manipulations might be employed to cause changes in the fatty acid composition of keratinocytes.     

The Polyunsaturated Fatty Acids Arachidonic Acid and Docosahexaenoic Acid Induce Mouse Dendritic Cells Maturation but Reduce T-Cell Responses In Vitro

Long-chain polyunsaturated fatty acids (PUFAs) might regulate T-cell activation and lineage commitment. Here, we measured the effects of omega-3 (n-3), n-6 and n-9 fatty acids on the interaction between dendritic cells (DCs) and naïve T cells. Spleen DCs from BALB/c mice were cultured in vitro with ovalbumin (OVA) with 50 μM fatty acids; α-linolenic acid, arachidonic acid (AA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), linoleic acid or oleic acid and thereafter OVA-specific DO11.10 T cells were added to the cultures. Fatty acids were taken up by the DCs, as shown by gas chromatography analysis. After culture with arachidonic acid or DHA CD11c⁺ CD11b⁺ and CD11c⁺ CD11b^neg DCs expressed more CD40, CD80, CD83, CD86 and PDL-1, while IA^d remained unchanged. However, fewer T cells co-cultured with these DCs proliferated (CellTrace Violet^low) and expressed CD69 or CD25, while more were necrotic (7AAD⁺). We noted an increased proportion of T cells with a regulatory T cell (Treg) phenotype, i.e., when gating on CD4⁺ FoxP3⁺ CTLA-4⁺, CD4⁺ FoxP3⁺ Helios⁺ or CD4⁺ FoxP3⁺ PD-1⁺, in co-cultures with arachidonic acid- or DHA-primed DCs relative to control cultures. The proportion of putative Tregs was inversely correlated to T-cell proliferation, indicating a suppressive function of these cells. With arachidonic acid DCs produced higher levels of prostaglandin E₂ while T cells produced lower amounts of IL-10 and IFNγ. In conclusion arachidonic acid and DHA induced up-regulation of activation markers on DCs. However arachidonic acid- and DHA-primed DCs reduced T-cell proliferation and increased the proportion of T cells expressing FoxP3, indicating that these fatty acids can promote induction of regulatory T cells.     

Isolation and characterization of gangliosides from pig lymphocytes

Two major gangliosides from pig spleen lymphocytes, accounting for 57% of the total lipid-bound sialic acids, were isolated and purified to homogeneity by column chromatography on DEAE-Sephadex and silica gel. They were identified as GM3 (II3Neu5GcLacCer), and GD3 (II3(Neu5Gc)2LacCer), by thin-layer chromatography in comparison with standards and by analysis of the constituent sugars. The major fatty acids of these gangliosides were stearic acid and myristic acid, respectively. In addition to these gangliosides, GD2 and bands comigrating on thin-layer chromatography with authentic GM2, GM1, GD1a and GD1b were found. These compounds also occur in pig peripheral blood lymphocytes, where, however, GD3 represents about 70% of the total lipid-bound sialic acid.     

TR4 promotes fatty acid synthesis in 3T3-L1 adipocytes by activation of pyruvate carboxylase expression

We show that testicular orphan nuclear receptor 4 (TR4) increases the expression of pyruvate carboxylase (PC) gene in 3T3-L1 adipocytes by direct binding to a TR4 responsive element in the murine PC promoter. While TR4 overexpression increased PC activity, oxaloacetate (OAA) and glycerol levels with enhanced incorporation of ¹⁴C from ¹⁴C-pyruvate into fatty acids in 3T3-L1 adipocytes, PC knockdown by short interfering RNA (siRNA) or inhibition of PC activity by phenylacetic acid (PAA) abolished TR4-enhanced fatty acid synthesis. Moreover, TR4 microRNA reduced PC expression with decreased fatty acid synthesis in 3T3-L1 adipocytes, suggesting that TR4-mediated enhancement of fatty acid synthesis in adipocytes requires increased expression of PC gene.     

Biosynthesis of polyunsaturated fatty acids by the australian field cricket,Teleogryllus commodus

Aspects of testicular fatty acid biochemistry from the Australian field cricket, Teleogryllus commodus, are reported. Over 10% of the phospholipid fatty acids were C20 polyunsaturated fatty acids (PUFAs), with nearly 6% arachidonic acid (20:4). The testes and ovaries accumulated a large proportion of label from radioactive arachidonic acid that was injected into the hemocoel (about 30%). Specificity in the uptake was shown by comparison to a similar study with labelled stearic acid, in which only 1.5% of the radioactivity was taken up by testes. Sixty percent of the radioactivity taken up by testes from [³H]20:4 was incorporated into phospholipids and 30% into triacylglycerols. Fat body of males and females incorporated 27% of the [³H]20:4 into phospholipids and 68% (males) or 55% (females) into triacylglcyerols. Radioactivity from [1-¹⁴C]acetate was incorporated into testicular linoleic acid and eicosatrienoic acid, but not eicosatetraenoic acid, suggesting the de novo biosynthesis of both 18:2 and a C20 PUFA by this species. Label from injected [U-¹⁴C]linoleic acid was recovered mostly as linoleic acid, with a small portion of the recovered radioactivity in eicosatrienoic acid, but not eicosatetraenoic acid. Very little label from injected linoleic acid occurred as monounsaturated or saturated fatty acids, indicating only slight, if any, β-oxidation of 18:2 to acetate and subsequent lipid synthesis.     

Phospholipid metabolism of stimulated lymphocytes: Preferential incorporation of polyunsaturated fatty acids into plasma membrane phospholipid upon stimulation with concanavalin A

Rabbit thymocytes were isolated and incubated for various lengths of time with concanavalin A. The cultures were pulsed for the last 12.5 min of incubation with equimolar mixtures of radioactively labelled fatty acids, either [³H]arachidonate and [¹⁴C]oleate or [³H]arachidonate and [¹⁴C]palmitate, and the uptake of each fatty acid into phospholipid of plasma membrane was determined. Upon binding of the mitogen, the fatty acids were incorporated at an increased rate with a new steady state being reached between 12.5 and 42.5 min after stimulation. Initially after 12.5 min, when the two fatty acids were added together, no preferential incorporation of the polyunsaturated fatty acid arachidonate was seen compared to the saturated or monounsaturated ones, palmitate or oleate. However shortly thereafter arachidonate, when compared to palmitate or oleate, started to be preferentially incorporated into plasma membrane phospholipid so that by 4 h after activation, only arachidonate was incorporated at an increased rate: the uptake of palmitate and oleate had reverted to that of unstimulated cells. In contrast, when palmitate or oleate were added alone, after 4 h of activation incorporation was increased similar to that of arachidonate, suggesting that all long chain fatty acids compete for the same activated enzyme(s). A detailed analysis of incorporation into phospholipid species showed that all fatty acids were taken up with the highest rate into phosphatidylcholine. After activation, fatty acid incorporation was increased by approx. 50% for phosphatidylcholine: the highest stimulation rates were observed with phosphatidylinositol (3–7-fold) and phosphatidylethanolamine (2–3-fold). The data suggest that shortly after stimulation with mitogens, the membrane phospholipids start to change by replacing saturated and monounsaturated fatty acids by polyunsaturated ones, thus creating a new membrane.     

Improvement of 5-aminolevulinic acid production by Rubrivivax benzoatilyticus PS-5 with self-flocculation by co-fermentation of precursors and volatile fatty acids under pH-controlled conditions

Photosynthetic bacteria are known to utilize volatile fatty acids as a carbon source for growth and product formation. In this study, a new isolate, Rubrivivax benzoatilyticus PS-5, possessing self-flocculation properties, was cultivated in modified glutamate-malate (GM) medium containing glutamate and malate as carbon sources. The effect of acetic acid, propionic acid and butyric acid (at 1–4 g L^?1) as co-substrates and 7.5 mM glycine, 10 mM succinic acid as precursors for 5-aminolevulinic acid (ALA) production from R. benzoatilyticus PS-5 was investigated. Among the volatile fatty acids tested, acetic acid was preferred to butyric acid and propionic acid, with the optimum concentrations of 3 g L^?1, 1 g L^?1 and 3 g L^?1, respectively. The highest ALA production was 169.71 μM, 162.16 μM and 46.18 μM, respectively, while the highest productivity was 2.57 μM h^?1, 2.25 μM h^?1 and 0.96 μM h^?1, respectively. The precursor was consumed completely (100 %) while the assimilation of the acetic acid and butyric acid was 62.50 % and 48.65 %, respectively. Supplementation of propionic acid (at 1–4 g l^?1) had a negative effect on growth and ALA production. To increase production efficiency, the pH-control strategy (at pH 6.0–8.0) during fermentation was tested. The optimum pH was 7.0, giving the maximum ALA production of 286.18 μM and a productivity of 3.97 μM h^?1. These values were 1.68-fold and 1.54-fold higher, respectively, than those under uncontrolled pH conditions.     

Metabolism of tween-Fatty Acid esters by cultured soybean cells : kinetics of incorporation into lipids, subsequent turnover, and associated changes in endogenous Fatty Acid synthesis

Uptake of Tween-fatty acid esters and incorporation of the fatty acids into lipids by soybean (Glycine max [L.] Merr.) suspension cultures was investigated, together with subsequent turnover of the incorporated fatty acids and associated changes in endogenous fatty acid synthesis. Tween uptake was saturable, and fatty acids were rapidly transferred from Tweens to all acylated lipids. Patterns of incorporation into glycerolipids were similar in cells treated with Tweens carrying [1-¹⁴C]-fatty acids and in cells treated with [1-¹⁴C]acetate, indicating that exogenous fatty acids were used for glycerolipid synthesis essentially as if they had been made by the cell. In Tween-treated cells neutral lipids (which include Tweens) initially accounted for the majority of lipid radioactivity. Radioactivity was then rapidly transferred to glycerolipids. A transient pool of free fatty acids accounting for up to 10% of lipid radioactivity was observed. This was consistent with the hypothesis that fatty acids are transferred from Tweens to lipids by deacylation of the Tweens, creating a pool of free fatty acids which are then used for lipid synthesis. Sterols were only slightly labeled in cells treated with Tweens, but accounted for nearly 50% of lipid radioactivity in cells treated with acetate. This suggested very little degradation and reutilization of the radioactive fatty acids in cells treated with Tweens. In cells treated with either [1-¹⁴C]acetate or Tween-[1-¹⁴C]-18:1, 70% of the initial fatty acid radioactivity remained in fatty acids after a 100 hour chase. By contrast, fatty acids not normally present disappeared more rapidly, suggesting differential treatment of such fatty acids compared with those normally present. Cells which had incorporated large amounts of exogenous fatty acids altered fatty acid synthesis in three distinct ways: (a) amounts of [1-¹⁴C]acetate incorporated into fatty acids were reduced; (b) cells incorporating exogenous unsaturated fatty acids increased the proportion of [1-¹⁴C]acetate partitioned into saturated fatty acids, while the converse was true of cells which had incorporated exogenous saturated fatty acids; (c) desaturation of 18:1 to 18:2 and 18:3 was reduced in cells which had incorporated unsaturated fatty acids. These results suggest that Tween-fatty acid esters will be useful for supplying fatty acids to cells for a variety of studies related to fatty acid or membrane metabolism.     

Hormone selective lipase activation in the isolated rabbit heart

The synthesis and release of PGs by the isolated perfused rabbit heart upon bradykinin stimulation results from lipase stimulation which liberates arachidonic acid for PG biosynthesis. The [¹⁴C]-labelled fatty acids, arachidonate, linoleate, and oleate, when infused into the heart preparation, were efficiently incorporated into the phospholipid pool in the heart, mostly in the 2-position of phosphatidylcholine. On the other hand, [¹⁴C]-palmitate was esterified into both the 1- and the 2-position. Bradykinin released bioassayable PG when injected into the rabbit hearts regardless of which fatty acid label was incorporated into the phospholipid pool. However, only [¹⁴C]-arachidonic acid (but not [¹⁴C]-linoleate, oleate or palmitate) was liberated from the variously labelled hearts upon hormone stimulation. This selective bradykinin effect on fatty acid release suggests that hormone stimulation either activates a specific lipase that distinguishes different fatty acids in the 2-position or activates lipase which is selectively compartmented with arachidonate-containing phospholipids. Ischemia, on the other hand, appeared to non-specifically stimulate tissue lipases, resulting in a non-selective release of oleic as well as arachidonic acid. A disproportionally large release of arachidonic acid was observed accompanying a relatively small PG (10:1 arachidonate: PG ratio) production during ischemia, as compared to bradykinin (3:1 ratio), suggesting distinct mechanisms for PG biosynthesis induced by bradykinin and ischemia.This work was supported by NIH grants: SCOR-HL-17646, HE-14397, HL-20787, and Experimental Pathology training grant (WH) 5 TO1 GM00897-16. Address correspondence to Dr. Philip Needleman, Department of Pharmacology, Washington University Medical School, St. Louis, Missouri 63110.     

Prenatal and postnatal transfer of fatty acids from mother to pup in the hooded seal

Unlike most mammals, hooded seal (Cystophora cristata) pups are born with a substantial layer of adipose tissue. Subsequently, during the brief lactation period of only 4 days, fasting mothers mobilize enormous amounts of lipid from blubber and secrete milk (60% fat) at rates of 10 kg·day^-1. Pups gain 7 kg·day^-1 due primarily to the deposition of fat in blubber. We measured blubber content and fatty acid composition of blubber and milk in hooded seal mother-pup pairs at birth and over the 4-day lactation period to examine the nature and source of fetal lipids, the incorporation of maternal blubber fatty acids into milk lipid, and patterns of fatty acid deposition in suckling young. The fatty acid composition of the blubber of the newborn was notably different from that of its mother. Fetal deposition was likely due to a combination of both fetal synthesis and direct placental transfer of maternal circulating fatty acids. The blubber of the newborn was characterized by high levels (>90% of total fatty acids) of saturated and monounsaturated fatty acids of primarily endogenous origin. In particular, the fetus appeared to have high Δ-9 desaturase activity as evidenced by the large amounts of 14:1n-5 (4.2%) and 16:1n-7 (37.0%) in newborn blubber compared to maternal blubber (0.2% and 14.1%, respectively). Nevertheless, essential and long-chain polyunsaturated fatty acids of the n-3 and n-6 families, which could only have originated by direct transfer from the mother, comprised>7% of pup blubber fatty acids and indicated greater rates of placental transfer than found in humans. In hooded seal mothers, rapid lipid transfer during the brief lactation period appeared to be facilitated by direct incorporation of mobilized fatty acids into milk. Although some differences in proportions of specific fatty acids were found between milk and maternal blubber, most of these differences declined over the course of lactation. However, selective mobilization of 20:5n-3 from maternal blubber into milk was apparent throughout lactation and resulted in elevated levels in pup blubber at weaning compared to maternal blubber. Ingested fatty acids were deposited directly and without modification into the blubber of pups, and by 4 days the fatty acid composition of pup blubber was virtually identical to that of the milk consumed.