BRAIN RECOVERY FROM ESSENTIAL FATTY ACID DEFICIENCY IN DEVELOPING RATS 1

Abstract— Rats were supplied from before birth with an essential fatty acid (EFA) deficient, a control, or an EFA deficient-control combination diet for various periods up to 6 months. It was found that EFA deficiency resulted in brain weights decreased in comparison with control values throughout development. The brain weight/body weight relationship, however, expressed by Donaldson's equation was generally maintained in animals fed either totally deficient or control diets. Animals deficient even during the brain's most actively growing period were able to recover completely on restoration of the control diet for a sufficiently long period. Fatty acid alterations in brain ethanolamine phosphoglyceride (EPG) during EFA deficiency were extensive. Acids of the ω6 family (18:2, 20:2, 20:3, 20:4, 22:3, 22:4 but not 22:5) were reduced from control figures. In the w9 family 20:3 and 22:3 were especially elevated whereas 22:6 ω3 levels were similar to those of the controls, finally decreasing only after a lengthy period of EFA deprivation. Mean unsaturation contents, as expressed by the proposed unsaturation index notation (Ul_mol) agreed closely in EPG fatty acids of deficient and control rats at a particular age. On substitution of the control for the deficient diet the ω6 family rebounded in a manner such that values for 20:4, 22:4, and 22:5 exceeded comparable figures in control animals. Concomitantly the ω9 family receded below control levels, and ω3 acids remained or returned to normal. This overadjustment in ω6 and ω9 families continued even after a prolonged period on the control diet.     

Early ethanolamine phospholipid translocation marks stress-induced apoptotic cell death in oligodendroglial cells

The consequences of H(2)O(2)/Fe(2+)-induced oxidative stress on translocation of ethanolamine phosphoglyceride (EPG) and serine phosphoglyceride (SPG) were studied in an oligodendroglia-like cell line (OLN 93) following 3 days of supplementation with 0.1 mM docosahexaenoic acid (DHA) and a series of polar head group precursors, including N-monomethyl- and N,N-dimethylethanolamine at millimolar concentrations. Added DHA was predominantly esterified in EPG species and those cells enriched in DHA showed enhanced sensitivity to oxidative stress and eventually died by apoptosis. Co-supplements with ethanolamine and DHA resulted in a rapid, but transient, EPG translocation with a maximum at 30 min following stress, as characterized by a trinitrobenzenesulfonic acid reagent. There was no significant translocation of SPG as evidenced by annexin V binding. Unlike SPG, which is usually irreversibly translocated to subserve as a tag for phagocytosis, EPG acted as a signaling molecule with biphasic kinetic characteristics. N-Monomethyl- and N,N-dimethylethanolamine supplements reduced EPG synthesis, prevented its externalization and rescued cells from apoptotic death. Following stress, the fatty acid profile of the externalized EPG showed marked losses in polyunsaturated fatty acids and aldehydes compared with the remaining intracellular EPG. Prevention of EPG species selective translocation to the outer membrane leaflet by altering phospholipid asymmetry may be important in the mechanism of rescue from cell death.     

Fatty acid composition, eicosanoid production and permeability in skin tissues of rainbow trout (Oncorhynchus mykiss) fed a control or an essential fatty acid deficient diet

Rainbow trout (Oncorhynchus mykiss) were fed either a control diet containing fish oil or an essential fatty acid (EFA) deficient diet containing only hydrogenated coconut oil and palmitic acid as lipid source (93.4% saturated fatty acids) for 14 weeks and the fatty acid compositions of individual phospholipid classes from skin and opercular membrane (OM) determined. The permeability of skin and OM to water and the production of eicosanoids in skin and gills challenged with the Ca²⁺ ionophore A23187 were also measured. Phospholipid (PL) fatty acid compositions were substantially modified in EFA-deficient fish, with increased saturated fatty acids and decreased polyunsaturated fatty acids (PUFA), especially arachidonic acid (AA) and eicosapentaenoic acid (EPA), while docosahexaenoic acid (DHA) was largely retained. The onset of EFA deficiency was shown by the appearance of n-9 PUFA, particularly 20:3n-9. The main effects of EFA deficiency on phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were to increase saturated fatty acids and monoenes, especially 16:1 and 18:1, and to decrease EPA and DHA. The content of DHA in phosphatidylserine (PS) was high in control animals (40% in skin and 35% in opercular membrane) and was mostly retained in EFA deficient animals. Arachidonic acid (AA) was the most abundant PUFA esterified to phosphatidylinositol (PI) and was significantly reduced in EFA deficient animals (from 31% to 13% in skin), where a large amount of 20:3n-9 (9% in skin) was also present. Influxes and effluxes of water through skin and opercular membrane were measured in vitro. No differences were detected between rainbow trout fed the control or the EFA deficient diet. 12-Hydroxyeicosatetraenoic acid (12-HETE), 12-hydroxyeicosapentaenoic acid (12-HEPE) and 14-hydroxydocosahexaenoic acid (14-HDHE) could not be detected in skin from control or EFA deficient fish. There was no difference between control and EFA deficient trout in the levels of leukotriene C₄ (LTC₄) and leukotriene C₅ (LTC₅) in skin cells challenged with the calcium ionophore A23187, and of prostaglandin F_2α (PGF_2α), 12-HETE and 12-HEPE in gill cells challenged similarly. Prostaglandin F_3α (PGF_3α) production by ionophore stimulated gill cells was significantly reduced in fish fed the EFA-deficient diet. 14-HDHE produced by gill cells was 3.3 fold higher in EFA deficient fish compared to controls.     

Dietary gangliosides increase the content and molecular percentage of ether phospholipids containing 20:4n-6 and 22:6n-3 in weanling rat intestine

This study was conducted to determine whether dietary ganglioside (GG) increases the content of ether phospholipids (EPL) in intestinal mucosa. Weanling Sprague-Dawley rats were fed a semipurified diet consisting of 20% fat as a control diet. Two experimental diets were formulated by adding either 0.1% (w/w fat) GGs (GG diet) or 1.0% (w/w fat) sphingomyelin (SM diet) to the control diet. Fatty acid methyl esters from the alkenylacyl, alkylacyl and diacyl subclasses of phospholipids were measured to determine total and molecular percentage of EPL comprising the choline phosphoglyceride (CPG) and ethanolamine phosphoglyceride (EPG) fraction. Animals fed the GG diet significantly increased total EPL content both in CPG (by 36%) and in EPG (by 66%), and the molecular percentage of EPL in CPG (by 76%) and in EPG (by 59%) compared to animals fed the control diet. Dietary GG-induced increase in EPL resulted in a higher level of polyunsaturated fatty acids (PUFA) specifically in 20:4n-6 and 22:6n-3 compared to control animals, leading to a decrease in the ratio of saturated fatty acids (SFA) to PUFA both in CPG and in EPG. Feeding animals the SM diet showed a higher level of EPL than control animals with a concomitant increase in 22:6n-3 in EPL. The present data demonstrate that dietary GG increases the content and composition of EPL containing PUFA in the weanling rat intestine.     

Steady-state haemoglobin level in sickle cell anaemia increases with an increase in erythrocyte membrane n-3 fatty acids

The aim of the study was to investigate, whether (a) patients with homozygous sickle cell disease (SCD, HbSS) have abnormal blood fatty acids; (b) the abnormality, if it exists, affects all the plasma and erythrocyte lipids or it is restricted to a particular lipid moiety; (c) there is an association between levels of membrane n-3 or n-6 long-chain polyunsaturated fatty acids (LCPUFA) and the degree of anaemia. Fatty acids of erythrocyte choline (CPG), serine (SPG) and ethanolamine (EPG) phosphoglycerides and sphingomyelin (SPM); and plasma CPG, triglycerides and cholesterol esters of 43 steady-state HbSS patients and 43 ethnically matched, healthy, HbAA controls were analysed. The levels of the n-6 LCPUFA, arachidonic (AA), adrenic and docosapentaenoic acids in erythrocyte CPG (P<0.001) and EPG (P<0.01) were higher in the patients compared with the controls. In contrast, the proportions of eicosapentaenoic acid (EPA) in CPG and EPG (P<0.001) and docosahexaenoic acid (DHA) and total n-3 metabolites in CPG (P<0.001) were lower in the patients. The steady-state haemoglobin level of the patients correlated with erythrocyte DHA (r=0.55, P<0.01), EPA (r=0.38, P<0.05) and total n-3 metabolites (r=0.51, P<0.001) in CPG. Also, it correlated with erythrocyte EPA (r=0.64, P<0.01) and total n-3 metabolites (r=0.42, P<0.01) in EPG. The study revealed an imbalance between n-3 and n-6 LCPUFA in erythrocyte and plasma lipid moieties of the HbSS group. Furthermore, it suggested that correction of the imbalance by supplementation with EPA and DHA could ameliorate anaemia in the patients. This observation is consistent with the results of pilot studies, which demonstrated that treatment with n-3 fatty acids confers clinical benefit to sickle cell patients.     

Polar Head Group Decarboxylation and Methylation of Phospholipids: An Alternate Route for Phosphatidylcholine Formation in Cultured Neuronal Cells

Decarboxylation of phosphatidylserine (SPG) and methionine-dependent, stepwise methylation of phosphatidylethanolamine (EPG) to form phosphatidylcholine (CPG) were examined in monolayer cultures of rat cerebral cells. Ethanolamine, monomethylaminoethanol, or dimethylaminoethanol nitrogenous bases (N-bases) added to culture medium at millimolar level result each in synthesis of the corresponding phospholipid via a de novo pathway at initial rates of 0.18, 0.30, and 0.36 nmol/h/micrograms DNA, respectively. Addition of methyl-labeled methionine to culture medium at tracer levels or at millimolar concentration enabled measurements of the rates of phospholipid methylation from EPG phosphatidylmonomethylaminoethanol (Me1EPG) and phosphatidyldimethylaminoethanol (Me2EPG) precursors. At tracer doses, the rates of methylation from the above respective phospholipids are 0.45, 1.17, and 1.70 pmol/h/micrograms DNA. At 1 mM methionine, synthesis of CPG proceeds from [14C]EPG or [14C]Me2EPG at initial rates of 8 and 17 pmol/h/micrograms DNA, respectively. Although the latter phospholipid analog can be generated from its monomethyl precursor, methylation of EPG does not result in the accumulation of Me2EPG, suggesting two segregated and metabolically distinct pathways. In the presence of N-bases, of the total [3H]serine incorporated into cellular phospholipids 30-36.5% of labelled SPG is converted into decarboxylation products. The decarboxylation and methylation routes contribute a significant portion of choline from endogenous sources, most likely through conversion of SPG.     

EFFECTS OF ESSENTIAL FATTY ACID DEFICIENCY ON MYELIN AND VARIOUS SUBCELLULAR STRUCTURES IN RAT BRAIN

Abstract— Essential fatty acid deficiency initiated in rats prior to birth and continued for 140 days after birth affects the fatty acid composition of ethanolamine phosphoglyceride of brain subcellular fractions (myelin, microsomes, mitochondria and synaptosomes). It was confirmed that the fatty acid composition of the same phospholipid class differs considerably among the various subcellular fractions: myelin has the highest concentration of long-chain monoenes, while in the other fractions saturates and polyenes predominate. In EFA deficiency it was found that (1) trienes are elevated and tetraenes decreased in all fractions, (2) the triene/tetraene ratio, which is considered a biochemical index of essential fatty acid deficiency, is highest in myelin and lowest in the synaptosomal fraction, and (3) in all fractions there is a shift towards more unsaturated members of the same fatty acid family.     

Changes in fatty acid composition of human brain myelin lipids during maturation

Abstract— The variation with age of the fatty acid composition of the major lipids in human brain myelin was compared with that of cerebral white matter from the same region. The myelin was isolated from the semiovale centre of the cerebrum of 27 subjects neonatal to old aged. The phospholipid, cholesterol and galactolipid concentrations were determined in all the samples, as were the proportions of the major phospholipid classes. The proportions of cholesterol and especially of the galactolipids increased in myelin during the first 6 months, and in cerebral white matter up to 2 years. During this period the individual phospholipids also varied substantially. Serine phosphoglycerides and especially sphingomyelins increased, and choline phosphoglycerides decreased. The fatty acid patterns of ethanolamine phosphoglycerides (EPG) and sphingomyelins underwent the largest changes. The proportions of saturated fatty acids in EPG diminished rapidly, and there was an increase of monoenoic acids. Fatty acids of the linoleic acid series showed a peak between 4 and 12 months, after which time their proportion slowly diminished to old age. The major fatty acid of this series was docosatetraenoic acid, 22:4 (n-6), which constituted more than 25% of total fatty acids at the maximum level. The fatty acid changes were larger in cerebral white matter, but from 2 years of age the EPG fatty acid pattern in myelin was similar to that in white matter. The fatty acid changes in serine and choline phosphoglycerides of myelin with maturation were much less striking than in EPG but of a similar type. In myelin sphingomyelin the proportion of saturated long-chain fatty acids, C₁₆-C₂₂, diminished, while that of monoenoic acids increased and continued to do so up to old age. From 2 years of age the fatty acid patterns in myelin and cerebral white matter were quite similar. Also the fatty acid patterns of cerebrosides and sulphatides in cerebral white matter and myelin were the same except for the first 2 months of life. The same fatty acid changes occurred in cerebrosides and sulphatides as in the sphingomyelins, i.e. increased proportions of unsaturated (monoenoic) acids. The proportions of 24:1 and 24h:1 and of the odd-numbered fatty acids 25:1 and 23h:1 continued to increase to old age. The variations of the individual lipid fatty acid patterns were small except in the youngest age classes, in which the variations were presumably ascribable to the difficulty in determining the gestational age.     

Protein deficiency and age related alterations in rat peritoneal macrophage lipids

The effects of dietary protein restriction and age on the thioglycollate elicited peritoneal macrophage lipid constituents were studied. Impact of subtle changes in lipid components on macrophage functions have been assessed. Lipid profiles of macrophages recovered from rats fed 20 and 4% protein diets and stock diet fed rats (0 and 3 wk) were comparable qualitatively. Quantitative analysis however revealed significant decrease in phospholipids (30–40%) and consequent elevation of cholesterol/phospholipid molar ratios in the protein depleted and young rats (0 wk), compared to the protein fed groups. The protein deficient and the young rats also exhibited accumulation of certain neutral lipids and reduction in triglycerides. Analysis of fatty acid methyl esters of macrophage phospholipids revealed the predominance of long chain polyunsaturated fatty acids even when oleic (C_18:1) and linoleic (C_18:2) formed the bulk of unsaturated fatty acids in the diet. However, the long chain poly unsaturated fatty acid content, particularly the docosahexaenoic acid (C_22:6n-3) was greatly reduced in the protein depleted and 0 wk rats. Observed changes in the long chain polyunsaturated fatty acids of macrophage phospholipids may be of physiological significance as they modulate the immunological functions of the cell.     

Evidence for a structurally specific role of essential polyunsaturated fatty acids depending on their peculiar double-bond distribution in biomembranes

ESR spectrometry with 5-, 7-, 10-, and 12-doxylstearate probes and a combined index considering separately the double-bond numbers of essential and nonessential fatty acids were used to investigate the structural role of the double bonds of polyunsaturated fatty esters in membrane phosphoglycerides. Purified brush border membrane vesicles were prepared from the jejunum of piglets receiving either high (HLA) or low (LLA) dietary levels of linoleic acid (18:2 n-6). In the LLA as compared to the HLA group, there were no significant modifications of (a) the relative contents of cholesterol, phospholipid, and protein and of (b) the phosphoglyceride class distribution, contrasting with very large changes in the fatty acid compositions of each phosphoglyceride. These changes were characterized by an increase in nonessential monoene and triene (18:1 n-9 and 20:3 n-9) and a decrease in essential diene (18:2 n-6) in LLA- as compared to HLA-fed piglets. The essential tetraene 20:4 n-6 remained rather constant despite an overall nonsignificant increase in the LLA group. The total double-bond number (TDBn) was not significantly affected, contrasting with the variations in the double-bond numbers of essential and nonessential fatty acids (DBn(EFA) and DBn(nonEFA), respectively). The combined DBn(EFA)/DBn(nonEFA) index was 1.7-3.3 times lower in LLA than in HLA membrane phospholipids. It was concluded that the diet was able to affect the double-bond distribution in the upper and inner half-parts of the membrane leaflet without changing the total number of double bonds.(ABSTRACT TRUNCATED AT 250 WORDS)     

Primary open-angle glaucoma patients have reduced levels of blood docosahexaenoic and eicosapentaenoic acids

The aetiology of primary open-angle glaucoma (POAG), which is the commonest cause of non-remediable blindness and visual impairment, is not well understood. Nevertheless, increased intraocular pressure, and vascular factors such as ocular blood flow deficits are thought to be risk factors. There is evidence of decreased optic nerve blood velocity and increased red blood cell aggregability in POAG. These factors are influenced by fatty acids. We have investigated if glaucoma patients have abnormal blood fatty acid composition. Patients with POAG (n=10) and their healthy siblings (n=8) were enrolled. Compared with their healthy siblings, the glaucoma patients had reduced eicosapentaenoic (EPA, P<0.01), and docosahexaenoic (DHA, P<0.05) fatty acids and total omega3 long-chain polyunsaturated fatty acids (LCPUFA) (P<0.05) in red cell choline phosphoglycerides (CPG); decreased EPA (P<0.05) in ethanolamine phosphoglycerides (EPG); lower EPA (P<0.05) and total omega3 LCPUFA (P<0.05) in serine phosphoglycerides (SPG). Similarly, they had reduced EPA, DHA and total omega3 LCPUFA in plasma CPG (P<0.005) and triglycerides (P<0.05). These findings may be significant, since EPA and DHA could modulate impaired systemic microcirculation and ocular blood flow and optic neuropathy, which are the main physiological changes associated with glaucoma.     

Incorporation of acetyl-CoA generated from peroxisomal β-oxidation into ethanolamine plasmalogen of rat liver

We have reported that peroxisomal β-oxidation has an anabolic function, supplying acetyl-CoA for biosynthesis of bile acids and phospholipids. Here we deal with its role in the biosynthesis of the subclasses of ethanolamine- and choline-containing phosphoglycerides (EPG, CPG, respectively). Rats were fed for 2 weeks on chow containing 0.25% clofibrate, which inhibits cholesterol and bile acid biosyntheses, but stimulates peroxisomal β-oxidation. [1-¹⁴C]Lignoceric acid, which is exclusively degraded by peroxisomal β-oxidation to acetyl-CoA, was intravenously injected, and 3 h later the rats were killed. The EPG-rich and CPG-rich fractions were prepared from the liver. When they were treated with phospholipase A₂, the radioactivity was predominantly recovered in the 1-radyl group. The radioactivity in EPG was easily dissociated with HCl vapor, and the lipid containing radioactivity was found to be a fatty aldehyde mixture consisting of steary aldehyde (approx. 58%) palmityl aldehyde (approx. 40%) and oleyl aldehyde (approx. 2%). Thus, in the case of EPG, acetyl-CoA from peroxisomal β-oxidation is incorporated mainly into the 1-alkenyl group of ethanolamine plasmalogen. The radioactivity in CPG, however, was found in fatty alcohol (formed from fatty acid), but not in alkylglycerol after reduction of the fraction with Vitride. Thus, in the case of CPG, acetyl-CoA from peroxisomal β-oxidation is exclusively incorporated into the 1-acyl group of diacyl glycerophosphocholine, but not into the 1-alkyl group. The above results were supported by the results of phospholipase C treatment. The above data indicate that peroxisomal β-oxidation plays a role in supplying acetyl-CoA for 1-alkenyl group of plasmalogen-type phospholipid, but this channel may open only to synthesis of EPG, and almost not to CPG.     

Fatty chains of alkenylacyl, alkylacyl and diacyl phospholipids in sea urchin spermatozoa.

1. Alkenylacyl, alkylacyl and diacyl phospholipids were analyzed in the spermatozoa of the sea urchin, Hemicentrotus pulcherrimus. 2. Choline phosphoglycerides (CPG) contained alkylacyl component (19%) in addition to the diacyl component (81%), and alkenylacyl analog was present in a trace amount. The ethanolamine phosphoglycerides (EPG) contained alkenylacyl (51%), alkylacyl (2%) and diacyl (47%) components and the serine phosphoglycerides (SPG), alkylacyl (9%) and diacyl (91%) derivatives. 3. Analysis by gas-liquid chromatography indicated that the fatty chain at the 1-position in alkenylacyl, alkylacyl and diacyl compounds of CPG, EPG and SPG was mainly composed of saturated and monoenoic types (16:0, 18:0, 18:1 and 20:1). In contrast, considerable amounts of polyunsaturated types (20:4 and 20:5) were noted at the 2-position.     

Characterization of a Novel Phospholipase A2 Activity in Human Brain

Abstract: Phospholipases A₂ (PLA₂) are a family of enzymes that catalyze the removal of fatty acid residues from phosphoglycerides. The enzyme is postulated to be involved in several human brain disorders, although little is known regarding the status of PLA₂ activity in human CNS. We therefore have characterized some aspects of the PLA₂ activity present in the temporal cortex of human brain. More PLA₂ activity was found in the membrane (particulate) fraction than in the cytosolic fraction. The enzyme could be solubilized from particulate material using 1 M potassium chloride, and was capable of hydrolyzing choline phosphoglyceride (CPG) and ethanolamine phosphoglyceride (EPG), with a preference (approximately eightfold) for EPG over CPG. When the solubilized particulate enzyme was subjected to gel filtration chromatography, PLA₂ activity eluted in a high molecular mass fraction (∼180 kDa). PLA₂ activity was weakly stimulated by dithiothreitol, strongly stimulated by millimolar concentrations of calcium ions, and inhibited by brief heat treatment at 57°C, bromophenacyl bromide, the arachidonic acid derivative AACOCF₃, γ-linolenoyl amide, and N -methyl γ-linolenoyl amide. Thus, whereas the human brain enzyme(s) characterized in our study displays some of the characteristics of previously characterized PLA₂s, it differs in several key features.     

Comparative studies of the responses of two strains of rats to an essential fatty acid deficient diet

A comparative study of two strains of rats to an EFA deficient diet was conducted. Parameters of insulin status in BHE and Sprague-Dawley rats were measured. No differences in growth were observed. The strains differed in their hepatic and adipose tissue response to insulin stimulation of glucose oxidation and conversion to fatty acids. Hepatic tissue from EFA deficient BHE rats converted more glucose to fatty acid under the influence of insulin than their controls while diet had no effect on glucose oxidation. Hepatic tissue from EFA deficient Sprague-Dawley rats oxidized more glucose than their controls but diet did not affect fatty acid synthesis. A reverse of these strain and diet differences was observed in adipose tissue. These results suggest that the genetic heritage of the rat may determine the type of response to EFA deficiency.     

Variations in the Lipid Compositions and in the Lipid Molecular Species of Lipomyces starkeyi Cultivated in the Glucose Sufficient and the Glucose Deficient Media

The lipid compositions, fatty acid compositions, positional distributions of fatty acids in glycerides, and molecular species of phospholipids of L. starkeyi, cultured in the glucose sufficient and the glucose deficient media were compared.

Under the glucose sufficient condition, the triglyceride content increased, accompanied by the remarkable increase of C_16:0–C_18:1–C_18:0. The phospholipid content also increased with the variations of the compositions of molecular species in phosphatidylethanolamine and phosphatidylcholine.

Under the glucose deficient condition, the triglyceride content remarkably decreased, especially in C_18:1–C_18:1–C_18:1. The compositions of phospholipid molecular species were considerably different from those of the glucose sufficient condition.     

Further studies on the lipid metabolism of the normal and vitamin B12-deficient chick embryo

1. The triglyceride, cholesterol ester and total phospholipid fractions were isolated from the livers and yolk sacs of normal and vitamin B₁₂-deficient chick embryos after 13, 15, 17, 19 and 21 days of incubation, and the fatty acid compositions were determined. 2. At all stages of incubation, the concentration of cholesterol ester in the livers of the normal embryos were greater, and on days 15 and 17 the concentrations of triglyceride were considerably less, than the corresponding concentrations in the livers of the deficient embryos. 3. Between day 13 and day 21 of incubation the concentration of oleic acid in the liver triglycerides of the normal embryos increased, whereas the concentrations of palmitic acid and docosahexaenoic acid decreased. Vitamin B₁₂ deficiency resulted in higher concentrations of palmitic acid in the liver triglycerides on days 15, 17 and 19, higher concentrations of C₁₈ polyunsaturated acids on days 13 and 15 and lower concentrations of oleic acid on days 13, 15, 17 and 19. 4. At all stages of development, cholesterol oleate accounted for almost 80% of the total liver cholesterol esters in both normal and deficient embryos. 5. As development of the normal embryos progressed, the concentrations of palmitic acid and arachidonic acid in the liver phospholipid decreased, whereas the concentrations of stearic acid and docosahexaenoic acid increased. Vitamin B₁₂ deficiency resulted in markedly higher concentrations of stearic acid and palmitic acid and markedly lower concentrations of arachidonic acid and docosahexaenoic acid in the liver phospholipids. 6. Vitamin B₁₂ deficiency did not influence the fatty acid composition of the triglyceride, cholesterol ester and phospholipid fractions either in the yolks of fertile unincubated eggs or in the yolks obtained from eggs that had been incubated for 13, 15, 17, 19 and 21 days.     

Effect of cholesterol deficiency on the composition of phospholipids and fatty acids of the housefly, Musca domestica

The housefly larvae were grown in the aseptic diet containing 0.56 μmole cholesterol/g wet weight of diet (control) and 0.05 μmole cholesterol/g wet weight of diet (deficient). The effects of cholesterol deficiency upon the phospholipid composition and fatty acids of the total phospholipid and triglyceride fractions from the lipid extract of the various larval tissues, whole larva, and in both sexes of adults 4 days after eclosion were examined. The total sterol and phospholipid contents (expressed relative to the wet weight of the insect) of the control and deficient insects at the larval and adult stages were analysed and molar ratios compared. The results suggest that cholesterol deficiency reduced the free sterol content of the larvae and adult insects to approximately 25% of the content of the control insects. However, cholesterol deficiency did not effect the phospholipid content during larval and adult stages when compared to that of control insects. Though the larvae reared on the cholesterol deficient diets did not show a profound alteration in the phospholipid composition, a marked increase in the ratio of phosphatidylcholine to phosphatidylethanolamine of the larval fat body and composite gut fraction were noticed. The cholesterol deficiency induced significant changes in the fatty acid composition of the phospholipid fraction of the insect. The ratio of unsaturated fatty acids to saturated fatty acids of the phospholipid fractions decreased significantly due to cholesterol deficiency in the whole larvae and in both sexes of adult flies. The data indicates that cholesterol deficient insects compensated for the lack of cholesterol by increasing saturated fatty acids preferentially in the phospholipid fraction of the lipids for the maintenance of proper membrane fluidity.     

Fatty acid and lipid analysis of the house cricket,Acheta domesticus

The fatty acid content and composition of the house cricket Acheta domesticus have been investigated in entire insects at different developmental stages and in selected organs of male and female adults. We have also determined the fatty acid composition of the various lipid classes within extracts of the organs of adult female insects. Fatty acids were analysed by capillary gas chromatography or mass spectrometry as their methyl esters (FAMEs) after direct transesterification of insect material or separated lipid classes.The major esterified fatty acids in all extracts were palmitate (C_16:0), stearate (C_18:0), oleate (C_18:1) and linoleate (C_18:2). Levels of esterified fatty acid varied considerably between organs but the fatty acid compositions showed only small variations. The levels of polyunsaturated fatty acids of the C₁₈ series were considerably higher in phospholipid fractions than in other lipid classes. Triacylglycerols formed the major lipid class in ovaries, fat-body and newly-laid eggs, whereas diacylglycerols and phospholipid predominate in the haemolymph. Triacylglycerols, phospholipids, diacylglycerols and free fatty acids were all found in significant amounts in the gut tissue.     

Studies on essential fatty acid deficiency. Effect of the deficiency on the lipids in liver mitochondria and oxidative phosphorylation

1. Dietary deficiency of essential fatty acids results in a twofold increase in the neutral lipid content of liver mitochondria as compared with the corresponding value for stock-fed rats. 2. Deficiency produces changes in the pattern of the constituent fatty acids of the main phospholipid fractions of liver mitochondria which are similar to those previously reported for the lipids of whole liver. There is a fall in the content of C_18:2 acid and to a smaller extent of C_20:4 acid associated with a rise of C_16:1, C_18:1 and C_20:3 acids. 3. Deficiency results in small decreases in the phosphorylation quotients of liver mitochondria during oxidation of succinate and pyruvate, but the values lie within the range reported for normal mitochondria. Mitochondrial respiration with succinate is decreased as a result of deficiency but no change was observed with pyruvate as substrate.