Substitution Of Fatty Acids Research Articles

Diets enriched in unsaturated fatty acids enhance apolipoprotein A-I catabolism but do not affect either its production or hepatic mRNA abundance in cynomolgus monkeys

To determine the mechanisms whereby dietary fatty acids influence high density lipoprotein (HDL) cholesterol and apolipoprotein (apo) A-I concentrations, ten cynomolgus monkeys were fed each of three experimental diets enriched in saturated (SAT), monounsaturated (MONO), or polyunsaturated (POLY) fatty acids in a crossover design consisting of three 13-week periods, with each animal serving as its own control. Each diet contained 30% of energy as fat with 0.22 mg cholesterol/kcal and differed solely by the isocaloric substitution of fatty acids as 18% of total energy calories. The replacement of dietary saturated fatty acids with either monounsaturated or polyunsaturated fatty acids, respectively, resulted in significant reductions of plasma total cholesterol ( − 17%; − 30%), HDL cholesterol ( − 32%; − 41%), and apo A-I (− 37%; − 44%) concentrations, while no significant differences were noted in. plasma lipid or apo A-I concentrations when the MONO and POLY phases were compared. Although the MONO and POLY diets were similar in their effects on plasma lipids and apolipoproteins, the HDL of monkeys fed the POLY diet, as compared with either the SAT or the MONO diets, contained more cholesteryl ester and phospholipid but less total protein, resulting in a significantly lower total lipid to protein constituent ratio. Metabolic experiments revealed that the significantly lower plasma apo A-I concentrations observed during both the MONO and POLY phases relative to SAT were directly attributable to enhanced HDL apo A-I catabolism. Conversely, neither HDL apo A-I production rates nor hepatic apo A-I mRNA concentrations were significantly affected by dietary fatty acid perturbation in this study. Taken together, these data indicate that fractional catabolic rate is the predominant mechanism by which dietary fatty acids differentially modulate circulating concentrations of HDL apo A-1 in this species when all other dietary variables are held constant.

Effects of dietary fat saturation on plasma lipoprotein(a) and hepatic apolipoprotein(a) mRNA concentrations in cynomolgus monkeys

Plasma lipoprotein(a) (Lp(a)) concentration is an independent risk factor for the development of premature coronary artery disease. Although the majority of available data indicates that circulating Lp(a) levels are under strict genetic regulation, there is some evidence that this parameter may be subject to dietary modification as well. The effects of dietary fat saturation on plasma Lp(a) levels and hepatic apolipoprotein(a) (apo(a)) mRNA abundance were examined in ten unrelated cynomolgus monkeys which were fed each of three experimental diets enriched in saturated (SAT), monounsaturated (MONO), or polyunsaturated (POLY) fatty acids in a crossover design consisting of three 13-week periods. Each diet contained 30% of calories as fat with 0.1% dietary cholesterol by weight and differed solely by the isocaloric substitution of fatty acids as 60% of total fat calories. The mean Lp(a) level for these animals during the SAT diet (13.4 ± 2.4 mg/dl) was significantly greater as compared with those observed during the MONO (8.6 ± 2.2 mg/dl, P < 0.0003) and POLY (9.3 ± 2.1 mg/dl, P < 0.002) diets, while the difference noted between the MONO and POLY diets was nonsignificant. Hepatic apo(a) mRNA abundance was decreased in these animals during the MONO diet relative to both the SAT and POLY diets, with only the difference between the SAT and MONO diets achieving statistical significance ( P < 0.02). Our data demonstrate that the substitution of dietary SATs with either MONOs or POLYs result in significant reductions of Lp(a) levels in these monkeys. However, only the MONO diet significantly decreased hepatic apo(a) mRNA levels relative to the SAT diet, suggesting that dietary MONOs and POLYs may differ in the manner by which they regulate plasma Lp(a) levels.

Inhibition of the human leukocyte endopeptidases elastase and cathepsin G and of porcine pancreatic elastase by N-oleoyl derivatives of heparin

N-oleoyl-heparin derivatives differing in their oleic acid and sulfate contents were synthesized and studied for their abilities to inhibit human leukocyte elastase (HLE), human leukocyte cathepsin G (CatG) and porcine pancreatic elastase (PPE) at pH 8.0, ionic strength 0.05 M and 37°. Heparin (Hep) as well as N-oleoyl-heparins behaved as tight-binding, hyperbolic noncompetitive inhibitors of HLE ( K iHep = 75 pM) and CatG ( K i Hep < 25 pM). The main driving force for the interaction between enzymes and glycosaminoglycans was electrostatic in nature. Under the condition [enzyme] ⪢ K i , the stoichiometries of the interaction with Hep were 1:2 (Hep:HLE) and 1:4 (Hep:CatG). Coupling one oleic acid residue to three disaccharide units of partially N-desulfated Hep, Ol 1:3 Hep, lowered HLE inhibition ( K i = 0.3 nM) and the stoichiometry of binding was reduced to 1:1. Re-N-sulfation of a similar derivative, OI 1:5 Hep(SO 4), containing one fatty acid residue for five disaccharide units, led to a substance with similar HLE inhibitory characteristics as Hep ( K i = 92 pM) and stoichiometry 1:2. 01 1:5Hep(SO 4) was also a more efficient inhibitor of CatG ( K i < 33 pM) than O1 1:3Hep ( K i = 9.5 nM). The residual activities of N-oleoyl-Hep complexes with CatG were much lower than the corresponding activities in the presence of Hep. While oleate and Hep could not inhibit PPE, N-oleoyl-Hep, independently of fatty acid substitution and sulfate content, could inhibit this enzyme with K i , ⋍ 60 nM and low residual activity. The efficient endopeptidase inhibitory characteristics of N-oleoyl-Hep derivatives, together with their non-anticoagulant properties and their capacity to interact with elastin, may be therapeutically useful in connective tissue degenerative diseases.

Satisfactory separation and MS-MS spectrometry of six surfactins isolated from Bacillus subtilis natto.

We optimized HPLC conditions for the first time to achieve satisfactory separation of six surfactins, two of which were novel, isolated from Bacillus subtilis natto. Peptide sequences were analyzed by sophisticated MS-MS analysis, performed with a pair of two surfactins with different fatty acid substitutions. Fragment peaks were divided into two series; one was a series of the ions which carried fatty acid, and thus were characterized by the fatty acid mass difference, and the other was a series of the ions which consisted of pure peptide and thus showed a superimposable pattern between a pair of surfactins.

Omega-3 and omega-6 PUFA's have different effects on the phospholipid fatty acid composition of rat myocardial muscle when added to a saturated fatty acid dietary supplement

Changes in the type of dietary lipid intake can alter the fatty acid composition of cardiac membrane phospholipids. Generally these changes reflect the fatty acid composition of the diet, but important metabolic alterations also occur. These metabolic alterations between fatty acids are influence by competition for common metabolic pathways of conversion. However, the efficacy of omega-3 PUFA's is much greater than that of omega-6 PUFA's as a relatively small amount of fish oil added to a diet rich in saturated animal fats was most effective in changing membrane composition. Conversely almost total substitution of saturated fatty acids by omega-6 PUFA's was required to significantly alter cardiac membrane fatty acid profiles. These results agree with the difference in physiological efficacies of omega-3 and omega-6 PUFA's noted previously, and strengthen the view that dietary lipids can influence cardiac function via changes in membrane fatty acid composition.

Omega-3 PUFA's reduce the vulnerability of the rat heart to ischaemic arrhythmia in the presence of a high intake of saturated animal fat

The effect of dietary lipids upon the development of cardiac arrhythmias has been studied in an animal model of Sudden Cardiac Death. Ischaemic arrhythmia in mature male rats was induced by occlusion of the coronary artery. After 44 weeks of feeding various lipid modified diets, it was demonstrated that complete substitution of omega-6 polyunsaturated fatty acids (PUFA's) for saturated animal fat produced great benefits in cardiac function; as the number of ventricular premature beats (VPB), and the incidence (%) and severity (duration in seconds) of both ventricular tachycardia (VT) and ventricular fibrillation (VF) were markedly reduced. However, when mixed diets containing additional saturated fat (SF) plus either sunflower seed oil (SSO) rich in omega-6 PUFA or fish oil (FO) containing omega-3 PUFA's were compared, it was apparent that the inclusion of a relatively small proportion of omega-3 PUFA's in the diet was of great benefit as no VF was recorded in this group, whereas a similar proportion of omega-6 PUFA added to a saturated fatty acid rich diet was without significant effect. As the mixed SF/PUFA diets were constructed to contain essentially similar proportions of both saturated and monounsaturated fatty acids, but with contrasting amounts of either omega-6 or omega-3 PUFA's, the benefits observed by the inclusion of omega-3 PUFA's in the diet were direct and not due to coincidental changes in other fatty acid components of the diets.

Chromatographic separations of sucrose monostearate structural isomers

High-performance liquid chromatography (HPLC), thin-layer chromatography (TLC) and gas—liquid chromatography (GLC) methods are described for separating sucrose monostearate isomers. The HPLC procedure provides baseline separation of purified monoester isomers into three main peaks at room temperature, and completely separates monoesters with different acyl chain lengths (C 14, C 16, C 18). The TLC method separates up to six of the eight possible positional monostearate isomers, which can be further differentiated by specific color development with a visualizing agent. The GLC technique used resolves monoesters with different acyl chain lengths, and partially separates monostearate isomers. Isomers collected from HPLC were subjected to treatment with invertase, then resolved and detected by TLC to determine fatty acid substitution patterns on the sucrose molecule.

Endotoxic lipid A interaction with human platelets. Structure-function analysis of lipid A homologs obtained from Salmonella minnesota Re595 lipopolysaccharide.

We previously reported that human blood platelets are directly stimulated by endotoxic Lipid A via the protein kinase C pathway (Grabarek, J., Timmons, S., and Hawiger, J. (1988) J. Clin. Invest. 82, 964-971). To study the relationship between the molecular structure of Lipid A and its ability to activate human platelets, we used Lipid A homologs derived from Salmonella minnesota Re595 lipopolysaccharide. Preparations of Lipid A are heterogeneous in regard to the degree of substitution of fatty acids which result in multiple homologs. These were separated by thin-layer chromatography and characterized by fast atom bombardment spectroscopy and related techniques (Johnson R. S., Her, G.-R., Grabarek, J., Hawiger, J., and Reinhold, V. N. (1990) J. Biol. Chem. 265, 8108-8116). The homologs of monophosphoryl Lipid A (MLA) present in fractions TLC-8 (heptaacyl MLA ion, m/z 1953), TLC-7 (three hexaacyl species with predominant MLA ion m/z 1715), and TLC-6 (four pentaacyl homologs with predominant MLA ion, m/z 1505) induced secretion of [14C]serotonin and aggregation of platelets. Lipid A homologs in fractions TLC-5 (three tetraacyl MLA ions, m/z 1323, 1307, and 1279), TLC-4 (one major triacyl MLA ion, m/z 1097), TLC-3 (tetraacyl MLA ion, m/z 1278), TLC-2 (a diphosphoryl hexaacyl Lipid A ion, m/z 1795, and several ions of low abundance), and TLC-1 (two ions, m/z 1097 and 666) were not active in regard to human platelet aggregation and [14C]serotonin secretion. The most active homolog was heptaacyl MLA ion, m/z 1953, present in TLC-8, while homologs present in TLC-7 and TLC-6 were 5 and 10 times less active, respectively. Rapid phosphorylation of a human platelet protein of Mr 40,000-47,000 (P47), a substrate for protein kinase C activation, preceded secretion of serotonin when platelets were triggered by the most active heptaacyl MLA ion, m/z 1953. These events were time-dependent, with half-maximal response of phosphorylation of P47 at 30 s and [14C]serotonin secretion at 45 s. A marked difference in the degree of phosphorylation of P47 was observed with heptaacyl MLA homolog present in TLC-8 inducing complete phosphorylation (97%), whereas less acylated Lipid A homologs present in TLC-1 caused marginal phosphorylation (20%). These results indicate that the degree of acylation of monophosphoryl Lipid A determines its functional properties toward human platelets in regard to secretion of [14C]serotonin, aggregation, and activation of protein kinase C.(ABSTRACT TRUNCATED AT 400 WORDS)

Unusual fatty acid substitution in lipids and lipopolysaccharides of Helicobacter pylori

Cellular fatty acids, phospholipid fatty acids, and lipopolysaccharide fatty acids of four strains of Helicobacter pylori were analyzed by gas-liquid chromatography. The presence of myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, 19-carbon cyclopropane fatty acid, beta-hydroxypalmitic acid, and beta-hydroxystearic acid was confirmed. In phospholipids, myristic acid and 19-carbon cyclopropane fatty acid were the major fatty acids. Hydroxy fatty acids and unsaturated fatty acids were not detected or occurred only in small amounts. The major fatty acids of lipopolysaccharides were stearic acid, beta-hydroxypalmitic acid, and beta-hydroxystearic acid. Unsaturated fatty acids and 19-carbon cyclopropane fatty acid were not found. The unusual compositions of H. pylori phospholipid and lipopolysaccharide fatty acids may have important implications for the taxonomy, physicochemical membrane properties, and biological activity of lipopolysaccharides.

Endotoxic induction of prostaglandin release from macrophages by nontoxic lipid A analogs synthesized chemically

The ability of synthetic lipid A analogs to induce prostaglandin synthesis in macrophages was compared with that of native lipopolysaccharide. The synthetic preparations comprised monomeric or dimeric derivatives of D-glucosamine with different patterns of substitution by phosphate and tetradecanoic, (R)-3-hydroxytetradecanoic, and (R)-3-tetradecanoyloxytetradecanoic acid. All of these preparations are structurally distinct from native lipid A (principally regarding the position of fatty acid substitution) and hence have been previously shown to be endotoxically inactive in many biological tests. It was found that many of these synthetic samples exhibit strong activity in inducing prostaglandin E2 and prostaglandin F2 alpha, with some of them having activity comparable to that of lipopolysaccharide. Experiments with macrophages of C3H/HeJ mice enabled us to differentiate between endotoxin-specific (in the case of dimeric preparations) and endotoxin-nonspecific (for monomeric preparations) mechanisms for the induction of prostaglandins. These results indicate that there is a difference in the mechanism of induction of prostaglandin synthesis between monomeric lipid A's and dimeric or native lipid A structures.

Chemical composition of a lipopolysaccharide from Legionella pneumophila.

Lipopolysaccharide isolated from Legionella pneumophila (Phil. 1) was examined for chemical composition. The polysaccharide split off by mild acid hydrolysis contained rhamnose, mannose, glucose, quinovosamine, glucosamine and 2-keto-3-deoxyoctonate, in molar proportions 1.6:1.8:1.0:1.5:4.1:2.7. Heptoses were absent and glucose was probably mainly phosphorylated. The carbohydrate backbone of the lipid A part consisted of glucosamine, quinovosamine and glycerol, in the molar ratios 3.9:1.0:3.4, with glycerol as a phosphorylated moiety. A complex fatty acid substitution pattern comprising eight O-ester-linked, exclusively nonhydroxylated acids, and nineteen amide-linked, exclusively 3-hydroxylated acids was revealed. Both straight- and branched (iso and anteiso) carbon chains occurred. The major hydroxy fatty acid was 3-hydroxy-12-methyltridecanoic acid and six others were of a chain-length above 20 carbon atoms, with 3-hydroxy-20-methyldocosanoic acid as the longest. Two dihydroxy fatty acids, 2,3-dihydroxy-12-methyltridecanoic and 2,3-dihydroxytetradecanoic acids, were also detected. These results suggest that L. pneumophila contains a rather complex and unusual lipopolysaccharide structure of considerable biological and chemotaxonomic interest.

Chemical studies on the lipopolysaccharide of Rhizobium meliloti 10406 and its lipid A region

The structure of the lipopolysaccharide from Rhizobium meliloti 10406, a derivative of the wild-type strain MVII-1, was examined. The compositional analysis of its polysaccharide moiety demonstrated lack of heptose(s), but high contents in glucose, galacturonic acid and 2-keto-3-deoxy-octonate (dOclA) as characteristic features. The lipid A moiety consisted of a β-1,6 linked glucosamine disaccharide carrying ester (at C-4′) and glycosidically (at C-1) linked phosphate residues, both present exclusively as monoester phosphates but not as phosphodiesters. Ester- and amidelinked 3-hydroxy fatty acids were mostly present as non-3-O-acylated residues. Laser desorption mass spectrometry (LD-MS) revealed heterogeneity in the fatty acid substitution, as was also indicated by the non-stoichiometric ratios obtained by quantitative fatty acid analysis. The predominating lipid A structure contained at the reducing glucosamine residue ester-linked 3-hydroxy-tetradecanoic acid (3-OH-14:0) and amide-linked 3-OH-18:0, or 3-OH-18:1, respectively. The distal (non-reducing) glucosamine carried ester-bound the recently discovered 27-hydroxyoctacosanoic acid and 3-OH-14:0 and, as amide-linked fatty acid, mostly 3-hydroxy-stearic acid (3-OH-18:0).

Synthesis and Properties of Alkyl Glycoside and Stachyose Fatty Acid Polyesters

AbstractA solvent‐free interesterification procedure was used to synthesize alkyl giycoside fatty acid polyesters: methyl glucoside polyesters, methyl galactoside polyesters, octyl glucoside polyesters, and tetrasaccharide fatty acid polyester, stachyose polyester. To obtain high yields, the hydroxyl groups on alkyl glycosides and stachyose were first protected by acetylation, and thereafter interesterified with fatty acid methyl esters (FAME) of long chain fatty acids to yield saccharide polyesters. Spectral analysis indicated excellent substitution of fatty acids onto the saccharide moiety. Quantitative C‐13 NMR spectroscopic data calculation of the degree of substitution on the saccharide acetates and the saccharide fatty acid polyesters were obtained using chromium acetyl acetonate. Studies of the physical properties of the polyesters indicated that the alkyl glycosides and stachyose polyesters were not markedly different from sucrose polyesters (SPE) or triglycerides.In vitro lipolysis indicated no evidence of hydrolysis, suggesting potential use of alkyl giycoside and stachyose fatty acid polyesters as low calorie oils.

Fish again for dinner! The role of fish and other dietary oils in the therapy of skin disease

Adequate levels of polyunsaturated fatty acids are necessary for the normal functioning of most mammalian cells, both to provide fluidity to the cell membrane lipid bilayer and to function as precursors for the synthesis of the regulatory eicosanoids, prostaglandins, and leukotrienes. The omega-6 class of polyunsaturated fatty acids, such as linoleic and arachidonic acids, are of special importance as precursors for eicosanoid synthesis. The skin is a particularly good organ in which to study the effects of polyunsaturated fatty acids metabolism, inasmuch as either deficiencies of specific PUFA or overproduction of polyunsaturated fatty acids—derived prostaglandin and leukotriene result in specific, clinically recognizable cutaneous diseases. To help understand the pathogenesis of these diseases, polyunsaturated fatty acids metabolism is reviewed here, with emphasis on clinical manifestations of both deficiency syndromes and overproduction of proinflammatory eicosanoids. A rationale is presented for a therapeutic approach to inflammatory disease by dietary manipulation and substitution of omega-6 fatty acids by the unique omega- 3 class of polyunsaturated fatty acids found in fish. Evidence for the efficacy of fish oil in the therapy of specific inflammatory diseases is reviewed, as are the caveats regarding its therapeutic use. Dietary manipulations, specifically fish oil additives, appear to hold promise as therapeutic tools for cutaneous diseases.

Plasma cholesterol responsiveness to saturated fatty acids

The variability in responsiveness to saturated fatty acids has not been studied systematically. For this reason data from three dietary studies carried out in our laboratory were pooled and used to evaluate how individuals vary in their responses in plasma concentrations of total cholesterol and low-density-lipoprotein cholesterol to the substitution of saturated fatty acids for unsaturated fatty acids. The data showed a marked variability in response. Some patients demonstrated a striking rise in cholesterol levels whereas others had more modest increases. This finding points to the need for further investigation on this issue.

Drugs or Diet

Early observations that the regular use of aspirin (acetylsalicylic acid, ASA), a nonsteroidal anti-inflammatory agent, seemed to protect against myocardial infarction and reduce platelet aggregation made this substance the most frequently used drug in large clinical trials. The objectives of these studies were to reduce thromboembolic complications in arterial cardiovascular diseases (prevention of myocardial infarction in unstable angina, secondary prevention of acute myocardial infarction, and increased patency of aortocoronary bypass grafts) and to reduce platelet deposition on artificial surfaces (artificial heart valves and hemodialysis shunts). Despite the recent synthesis of more selective inhibitors of arachidonic acid metabolism in blood platelets, and a multitude of questions concerning optimal dose, schedule, and mode of action that still remain open, ASA continues to be the most frequently used drug in arterial vascular disorders. Because of the frequent and potentially serious side effects of aspirin, mainly on the gastrointestinal tract, less toxic ways of inhibiting eicosanoid metabolism in blood platelets are attracting more and more interest. Among these, the alimentary substitution of omega-3 fatty acids for a competitive inhibition of the omega-6-arachidonic acid metabolism seems the most promising. Results with fish-oil diet raise the question of whether substitution of polyunsaturated lipid acids influence only platelet metabolism, or whether the action of "anti-platelet" drugs or diet in cardiovascular disorders is mediated primarily by leukocytes or monocytes. This new dietary principle, which possibly corrects only a poor alimentary habit of civilization, could open simple and adequate ways for even a primary prophylaxis of vascular disease by diet alone or, at least for therapeutic aims, in combination with drugs.

A fish oil diet retards experimental amyloidosis, modulates lymphocyte function, and decreases macrophage arachidonate metabolism in mice.

Several recent reports have shown that diets in which the only source of fat was fish oil can modify the course of diseases with an inflammatory or immune component. In these experiments we examined the effect of a fish oil diet on experimental amyloidosis in mice. In most azocasein-treated mice, amyloid deposits were found in the spleen, varying from a trace to wide and contiguous perifollicular bands. The spleens of mice receiving fish oil had significantly less amyloid than did spleens of mice fed corn oil. A marked increase in spontaneous blastogenesis that occurred in azocasein-treated mice on corn oil was suppressed in azocasein-treated mice on fish oil. Substitution of the unsaturated fatty acids of corn oil with those of fish oil was also found to modify the prostaglandin profile of macrophages. This altered profile may change cellular immune function and/or enhance the processing of serum amyloid A to retard the induction of secondary amyloidosis in mice.

The effect of sn-2 fatty acid substitution on phospholipase C enzyme activities

The human monocyte cell line U937 expresses phospholipase A2 and phospholipase C activities and produces eicosanoids. The phospholipase C (PLC) activity exhibits substrate preference for phosphatidyl-choline (PC), rather than phosphatidylinositol or phosphatidylethanolamine. In order to characterize the PLC activity found in these cells, the effects of substitution of the sn-2 fatty acid on this activity were examined. PC substrates with palmitic acid (PC-2P), oleic acid (PC-2O), arachidonic acid (PC-2A) and linoleic acid (PC-2L) at the sn-2 position were used. The sn-1 fatty acid was palmitic acid. PC-2L and PC-2A with the longer-chain less-saturated fatty acids linoleic acid and arachidonic acid esterified at sn-2 were found to be better substrates for PLC activity than PC-2P or PC-2O in these cells. This preference was maintained even when substrate phospholipid was solubilized in non-ionic, anionic, cationic and zwitterionic amphiphiles. Furthermore, when a 500-fold excess of 1,2-diolein or 1,2-dipalmitin was added to the reaction, the specificity of the PLC activity for PC-2A and PC-2L remained unchanged. When similar experiments were performed with phosphatidylinositol as a substrate, we did not observe any effect when the sn-2 position was altered. These data show that the fatty acid constituent at the sn-2 position affects the observed PLC activity when phosphatidylcholine, but not phosphatidylinositol, is used as a substrate by these cells.

Comparison of N-acyl phosphatidylethanolamines with different N-acyl groups as activators of glucocerebrosidase in various forms of Gaucher's disease

The acidic phospholipid requirement of the predominant particulate β-glucosidase of mammalian spleen and liver was investigated using a series of N-acyl derivatives of dioleoyl phosphatidylethanolamine (PE). The PE, a neutral phospholipid, was converted to an acidic lipid, ( N-acyl)-phosphatidylethanolamine (NAPE) by acylation of the amino group with different fatty acyl chains. Lysosomal β-glucosidases from rat liver and spleens of controls and patients with various types of Gaucher's disease were solubilized and delipidated by extraction with sodium cholate and 1-butanol. All members of the NAPE series tested were effective activators of the delipidated rat liver β-glucosidase, and the stimulatory power of the NAPE family increased with increasing chain length of the fatty acid substitution. In contrast, dioleoyl-PE had no effect on β-glucosidase activity. A heat-stable factor (HSF) purified from the spleen of a patient with Gaucher's disease significantly increased the sensitivity of the rat liver β-glucosidase to all of the NAPE derivatives. The maximum stimulation achieved in the presence of HSF was independent of N-acyl chain length. Compared to the potent activator, phosphatidylserine (PS), ( N-acetyl)-PE and ( N-linoleoyl)-PE were half as effective as activators of β-glucosidase from control human spleen. PS stimulated the β-glucosidase of type 1 nonneurologic Gaucher's disease, but none of the NAPE compounds activated it. Neither PS nor any of the ( N-acyl)-PE compounds could activate a delipidated preparation of β-glucosidase obtained from the spleen of a neurologic case. These results indicate that although the presence of a net negative charge on a phospholipid confers upon it an ability to reconstitute β-glucosidase activity to the normal, nonmutant enzyme, it is insufficient to permit differentiation of the various types of Gaucher's disease.

Effect of Membrane Fatty Acid Substitution and Temperature on Repair of Sublethal Damage in Mammalian Cells

Repair of sublethal radiation damage (SLD) has been investigated as a function of temperature in mouse fibroblast LM cells with different membrane lipid composition. Rigidification or fluidization of the cellular membranes was accomplished by incorporation of myristic acid and arachidonic acid, respectively, in the phospholipids of the membranes. The SLD repair after radiation was essentially the same for the cells with the more rigid (saturated fatty acid) membranes and the cells with the more fluid (polyunsaturated fatty acid) membranes. This observation was made for repair at 37 degrees C as well as for repair at hypothermic temperatures. Incorporation of polyunsaturated fatty acid protected the cells against hypothermic death. These experiments demonstrate that although membranes are likely targets for cell killing by low temperature treatments, membrane lipids are probably not involved in the repair of sublethal radiation damage. It must be concluded that neither the degree of polyunsaturation of the lipids nor the degree of fluidity of the membrane is important for radiation-induced killing of mammalian cells.