Influence of long-term supplementation with α-linolenic acid on myocardial lipid peroxidation and antioxidative capacity in spontaneously hypertensive rats

The ischaemic vulnerability of the heart of spontaneously hypertensive rats (SHR) is enhanced after feeding an α-linolenic acid (LNA) enriched diet. Because oxygen radical-induced reactions (e.g. lipid peroxidation) are involved in the ischaemic damage, an increased susceptibility of the SHR heart to such damaging reactions might be the reason. As a sign of the enhanced susceptibility to lipid peroxidation of LNA-fed SHR, we found (measured as TBARS) higher plasma and heart lipid peroxide levels (3.84 ± 0.50 μmol/l vs 2.98 ± 0.78 μmol/l and 507 ± 127 nmol/g prot. vs 215 ± 80 nmol/g prot., respectively) after feeding LNA. Using Fe²⁺/Vit. C to induce lipid peroxidation in myocardial tissue homogenates, we demonstrated the enhanced susceptibility to lipid peroxidation of the LNA-fed SHR heart (68 ± 12 nmol/min × g prot. vs 40 ± 8 nmol/min × g prot.) also in vitro. The myocardial enrichment of n-3 polyunsaturated fatty acids (PUFA) resulting in a higher peroxidation index (Pl 227 vs. 170) and the loss in myocardial activities of the antioxidative enzymes (SOD: 76 ± 24 U × 10³/g prot. vs 235 ± 150 U × 10³/g prot.; GSH-Px: 32 ± 5 U/g prot. vs 110 ± 30 U/g prot.) by feeding LNA could be the cause of the increase in myocardial susceptibility to lipid peroxidation of PUFA supplemented SHR.     

Protection from nonfreezing cold injury by quinacrine, a phospholipase inhibitor

A recent study from our laboratory indicated additional tissue injury during rewarming of a cooled rabbit leg. Oxygen-derived free radicals were believed to play a role in such "rewarming injury." Since free radicals may attack membrane phospholipids, we analyzed the phospholipid composition in the leg tissue during cooling and rewarming. Our results indicated significant breakdown of membrane phospholipids, particularly phosphatidylcholine and phosphatidylethanolamine, with a corresponding accumulation of lysophosphatidylcholine and nonesterified fatty acids. Quinacrine, a phospholipase inhibitor, was able to preserve membrane phospholipids during rewarming of the cooled leg. Rewarming of cooled tissue was also accompanied by additional tissue injury, as evidenced by the increased release of lactic acid dehydrogenase and creatine kinase, as well as enhanced lipid peroxidation, as evidenced by increased malonaldehyde formation. Quinacrine reduced the release of these intracellular enzymes and decreased lipid peroxidation, suggesting its efficacy as a therapeutic agent against hypothermic injury.     

Lipid peroxidation and phospholipase A2 activity in liposomes composed of unsaturated phospholipids: a structural basis for enzyme activation

The effect of lipid peroxidation on membrane structure and phospholipase A2 activity was studied using liposomes composed of bovine liver phosphatidylcholine (PC) and phosphatidylethanolamine (PE). The phospholipids were mixed at set ratios and sonicated to yield small unilamellar vesicles. The liposome preparations were subjected to lipid peroxidation as induced by cumene hydroperoxide and hematin. Under these conditions, a sharp increase in lipid peroxidation was noted over a 30 min incubation period and was accompanied by loss of polyunsaturated fatty acids (PUFA). Liposomes enriched in PE were most extensively peroxidized with a preferred oxidation of this phospholipid. The extent of PC oxidation was also greater in liposomes containing the largest proportions of PE. Analysis of liposome anisotropy, via steady-state fluorescence polarization of diphenylhexatriene indicated that progressive increases in either PE content or the level of lipid peroxidation increased the apparent microviscosity of the vesicles. Moreover, lipid peroxidation increased anisotropy more effectively than variations in the ratios of PE vs. PC. Thus, peroxidation of 5-10% of the phospholipids produced the same anisotropy increase as a 20% increase in the ratio of PE vs. PC. Analysis of vesicle turbidity suggested that fusion was also more readily achieved through lipid peroxidation. When liposomes were incubated with 0.4 U/ml of snake venom phospholipase A2, a direct correlation was found between the degree of lipid peroxidation and the extent of phospholipid hydrolysis. The more unsaturated phospholipid, PE, was most extensively hydrolyzed following peroxidation. Increasing the proportion of PE also resulted in more extensive phospholipid hydrolysis. These findings indicate that lipid peroxidation produces a general increase in membrane viscosity which is associated with vesicle instability and enhanced phospholipase A2 attack. A structural basis for membrane phospholipase A2 activation as a consequence of lipid peroxidation is discussed in light of these findings.     

Differential incorporation of fatty acids into and peroxidative loss of fatty acids from phospholipids of human spermatozoa

Intact human sperm incorporated radiolabelled fatty acids into membrane phospholipids when incubated in medium containing bovine serum albumin as a fatty acid carrier. The polyunsturated fatty acids were preferentially incorporated into the plasmalogen fraction of phospholipid. Uptake was linear with time over 2 hr; at this time sufficient label was available to determine the loss of fatty acids under conditions of spontaneous lipid peroxidation. Loss of the various phospholipid types, the loss of the various fatty acids from these phospholipids, and the overall loss of fatty acids were all first order. The loss of saturated fatty acids was slow with first order rate constant k₁ = 0.003 hr^?1; for the polyunsaturated fatty acids, arachidonic and docosahexaenoic acids, k₁ = 0.145 and 0.162 hr^?1, respectively. The rate of loss of fatty acids from the various phospholipid types was dependent on the type, with loss from phosphatidylethanolamine being the most rapid. Among the phospholipid types, phosphatidylethanolamine was lost at the greatest rate. Analysis of fatty acid loss through oxidation products was determined for radiolabelled arachidonic acid. Under conditions of spontaneous lipid peroxidation at 37°C under air in the absence of albumin, free arachidonic acid was found in the medium, along with minor amounts of hydroxylated derivative. All the hydroperoxy fatty acid remained in the cells. In the presence of albumin, all the hydroperoxy fatty acid was found in the supernatant bound to albumin; none could be detected in the cells. Albumin is known as a very potent inhibitor of lipid peroxidation in sperm; its action may be explained, based on these results, as binding the damaging hydroperoxy fatty acids. These results also indicate that a phospholipase A₂ may act in peroxidative defense by excising a hydroperoxy acyl group from phospholipid and providing the hydroperoxy fatty acid product as substrate to glutathione peroxidase. This formulation targets hydroperoxy fatty acid as a key intermediate in peroxidative degradation. © 1995 wiley-Liss, Inc.     

Lipid order and composition of synaptic membranes in experimental diabetes mellitus

The effect of diabetes in rats on lipid composition and order of synaptosomal membranes (SM) was determined in streptozotocin-induced diabetic rats after 6 weeks of chronic hyperglycemia. The cholesterol content was slightly, but not significantly, higher in diabetic SM (0.287±0.042 vs. 0.209±0.061 mol/mg protein). The phospholipid concentration in diabetic SM was significantly increased (0.515±0.042 vs. 0.305±0.041 mol/mg protein;P<0.005). Neither the molar ratios of cholesterol to phospholipids in the SM nor the fatty acid composition of the SM was significantly altered with diabetes. Diabetes did not affect membrane order or the thermotropic transition temperature of the SM as determined fluorometrically. On the other hand, the SM of diabetic rats had significantly increased concentration of lipid peroxidation products, namely conjugated dienes (the calculated O.D./mol phospholipids was 11.56±1.83 in controls and 19.95 ±4.1 in diabetic ratsP<0.01). Despite the accumulation of lipid peroxidation byproducts in SM of diabetic rats the overall membrane order and the cholesterol to phospholipid molar ratio do not appear to be significantly altered.     

Lipid composition, phospholipid profile and fatty acid of rat caecal mucosa.

In this study, we examined the lipid composition of rat caecal mucosa, including the fatty acid composition of major phospholipid classes. Phospholipids accounted for 90% of the total lipid, with cholesterol, triacylglycerols, diacylglycerols, fatty acids and cholesterol ester making up the remainder. Therefore, a phospholipid to neutral lipid ration of 9:1 was found. Phosphatidylethanolamine was the predominant phospholipid, with phosphatidylcholine as the second most abundant phospholipid. Cardiolipin, phosphatidylserine, phosphatidylinositol and lysophosphatidylcholine were present in lesser amounts. Sphingomyelin and lysophosphatidylethanolamine were only detected in trace amounts. The major fatty acids present in both the lipid and all phospholipid fractions were palmitate, stearate, oleate, linoleate and arachidonate. Other fatty acids of chain length greater than C20 were only detected in phospholipid fraction and accounted for < 5% of the total fatty acids in this fraction. However, 11.10% of 22:6 (n-3) and 7.17% of 24:0 were detected in phosphatidylserine and lysophosphatidylcholine, respectively. The results are discussed in terms of their possible physiological significance.     

Inhibition of phospholipid hydrolysis by phospholipase A2 in microsomal and mitochondrial membranes subjected to lipid peroxidation

The rate of phospholipid hydrolysis in rat liver microsomal and mitochondrial membranes catalyzed by phospholipase A2 was shown to decrease after ascorbate + Fe2+-induced lipid peroxidation. The degree of inhibition was linearly dependent on the amount of lipid peroxidation products (malonyl dialdehyde) accumulated in the membrane. The decreased phospholipid hydrolysis rate in membranes after lipid peroxidation was registered using phospholipases A2 from two sources: porcine pancreas and bee venom. It was established that the inhibitory action of phospholipid peroxidation products was not linked with a direct effect on the enzyme and was not caused by depletion of phospholipase reaction substrates (as a result of lipid peroxidation). A possible role of lateral separation of oxidized and non-oxidized lipid phases in the mechanisms of inhibition of phospholipid hydrolysis by phospholipase A2 is discussed.     

THE COMPOSITION OF LIPIDS IN CEREBROSPINAL FLUID OF CHILDREN AND ADULTS

Abstract— The proportions of esterified cholesterol and phosphatidyl ethanolamine in lipids of cerebrospinal fluid (CSF) from children were found to be lower than the corresponcling values for adult CSF. The fatty acid patterns of the cholesterol ester, triglyceride + non-esterified fatty acids and phospholipid fractions all displayed low proportions of linoleate; palmitate and oleate were the principal acids present. The fatty acid composition of these lipid classes for CSF derived from children was similar to that from adult subjects. Degradation of CSF lecithin by snake-venom phospholipase A₂ revealed the saturated acids to be located predominantly in the 1-position with the unsaturated ones mainly in the 2-position.     

Changes in fatty acids of leaf polar lipids during chilling and post-chilling rewarming of Zea mays genotypes differing in response to chilling

Changes in fatty acids of leaf polar lipids: monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), sulfoquinosyldiacylglycerol (SQDG) and phosphatidylglycerol (PG) in maize seedlings of chiling-sensitive (CS) CM 7 and Co 151 lines and chilling-tolerant (CT) S 215 and EP 1 lines upon chilling for either 4 or 6 days in the dark and after rewarming for 4 days at original growth conditions were studied. The content of free fatty acids (FFA) in control leaves as well as alterations in the proportion of major fatty acids, unsaturation ratio (UR), double bond index (DBI) and changes in the proportion of heigh-temperature melting of both phosphatidylglycerol (htm-PG) and sulfoquinovosylglycerol (htm-SQDG) after chilling and rewarming of seedlings were estimated. FFA content in intact leaves was 2–3-fold higher in the chilling susceptible CM 7 line than in the other three inbreeds studied. After chilling for 6 days the level of FFA increased only in CM 7 and S 215 lines by about 30 %. Upon rewarming seedlings chilled for 6 days the level of FFA increased about two-fold in CS Co 151 line and CT EP 1 line and decreased in CS CM 7 line. Limited accumulation of FFAs during chilling and post-chilling rewarming of maize seedlings, did not correspond to the extent of polar lipid breakdown (Kaniuga et al. 1999b) probably due to the contribution of active oxidative systems to the peroxidation of fatty acids under these conditions. During rewarming seedlings chilled for 6 days major changes were observed in decrease of 18:3 and an increase of 16:0 in all four polar lipids studied with more pronounced changes in CS than CT lines. Similarly, in CS inbreeds a decrease in UR of fatty acids in MGDG, DGDG and SQDG after post-chilling rewarming was greater than in CT lines. Proportion of htm-fraction in both PG and SQDG increased after post-chilling rewarming in all four inbreeds, however to a lesser extent in CT than CS lines. A similar pattern of changes in DBI in CS and CT maize seedlings was observed in glycolipid and combine lipid classes. More extensive degradation of polar lipids in CS than CT maize inbreeds following galactolipase action in chloroplasts (Kaniuga et al. 1998) provides FFAs for initiation of peroxidation by LOX which is manifested by decrease of UR and DBI. This sequence of reactions during chilling and post-chilling rewarming appears to be a main route of fatty acids peroxidation responsible for secondary events involved in chilling injury. In addition, the extent of these changes differentiates CS and CT inbreeds. Contribution of esterified fatty acids in thylakoid lipids to direct peroxidation, may be of minor importance.     

The lipid composition and permeability to the triazole antifungal antibiotic ICI 153066 of serum-grown mycelial cultures of Candida albicans

The total lipid content of Candida albicans (serotype A: NCPF 3153) exponential-phase mycelial cultures grown in tissue-culture medium 199 (containing 10%, v/v, foetal calf serum) was 29.8 +/- 8 mg (g dry weight)-1 (mean +/- SD). The weight ratios of phospholipid to neutral lipid and phospholipid to non-esterified sterol were 2.6 +/- 0.4 and 24.9 +/- 0.5, respectively. The major phospholipid was phosphatidylcholine with smaller amounts of phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, phosphatidylglycerol and diphosphatidylglycerol; the most abundant fatty acids were palmitic, palmitoleic, oleic and linoleic acids. The major neutral lipids comprised esterified sterol, triacylglycerol and non-esterified fatty acid with a smaller amount of non-esterified sterol. The fatty acid compositions of the three fatty-acid-containing neutral lipids were distinct from each other and the phospholipids. Comparison with previous data on yeast cultures of C. albicans A grown in glucose broth shows that mycelial cultures have a larger lipid content, lower phospholipid to neutral lipid ratio and higher phospholipid to non-esterified sterol ratio. We now show that mycelial cultures were more permeable to a [14C]triazole antifungal antibiotic compared with exponentially growing yeast cultures of several azole-sensitive strains. Taken together these data are consistent with there being a relationship between the phospholipid/non-esterified sterol ratio of a culture and its ability to accumulate a triazole.     

Formation of N-(hexanoyl)ethanolamine, a novel phosphatidylethanolamine adduct, during the oxidation of erythrocyte membrane and low-density lipoprotein

The primary amino groups of biomolecules such as aminophospholipids, as well as proteins, are the potential targets of covalent modifications by lipid peroxidation products; however, little attention has been paid to the modification of aminophospholipids such as phosphatidylethanolamine (PE). The purpose of this study is to characterize the formation of a novel modified phospholipid, N-(hexanoyl)phosphatidylethanolamine (HEPE), in the reaction of PE with lipid hydroperoxides using mass spectrometric analyses. Upon reaction of egg PE with 13-hydroperoxyoctadecadienoic acid or other oxidized polyunsaturated fatty acids followed by phospholipase D-mediated hydrolysis, the formation of N-(hexanoyl)ethanolamine (HEEA), a head group of HEPE, was confirmed by isotope dilution liquid chromatography/tandem mass spectrometry. Moreover, increasing HEEA was detected in the hydrolysates of oxidized erythrocyte ghosts and low-density lipoprotein with their increasing lipid peroxidation levels. Collectively, these results suggest that the N-hexanoylated product of phospholipid, HEPE, can be generated during lipid peroxidation and may serve as one mechanism for the covalent modification of aminophospholipids in vivo.     

Piperine modulation of carcinogen induced oxidative stress in intestinal mucosa

The plasma-borne long-chain free fatty acids (FFA) enter skeletal muscle cells. Upon entering they are oxidized or esterified and a fraction remains free (non-esterified). The data on free fatty acids in skeletal muscles remain highly controversial. Furthermore, the composition of individual fatty acids in various lipid fractions including free fatty acids, monoglyceride and diglyceride in muscles has not been characterized. Also data on the composition of fatty acids esterified into muscle triglycerides and phospholipids are incomplete. The present study was undertaken to examine a composition of fatty acids in lipid fractions of different skeletal muscle types. For this purpose, samples of the rat soleus, red and white portions of gastrocnemius were excised, trimmed of visible fat and fascias and immediately frozen in liquid nitrogen. Samples were then pulverized and, lipids were extracted and fractionated by thin-layer chromatography. Individual long-chain fatty acids in different fractions were identified, characterized and quantitated by gas-liquid chromatography. FFA composition in the plasma was also determined. The total FFA content in the soleus, red and white gastrocnemius was 69.1 ± 10.8, 49.0 ± 13.6 and 22.7 ± 8.6 nmol/g, respectively. Palmitic and oleic acids were the major fatty acids in the muscles FFA fraction. Monoglyceride fraction of each muscle contained palmitic, stearic and linoleic acid as the major fatty acids, Diglyceride fraction contained mostly palmitic and oleic acid whereas triglyceride fraction mostly palmitic and linoleic acid.. The fraction of phospholipids was composed mostly of palmitic and linoleic acid but contained also considerable percentage of archidonic acid. Total plasma FFA/muscle FFA ratio depended on a muscle type and was: 2.4 in the soleus, 3.5 in the red and 7.4 in the white gastrocnemius. This assured transport of FFA to the myocytes. However, there were great differences in the ratio between particular FFA within the same muscle as well between the muscles. It indicates that individual FFA are either selectively transported from the plasma to the muscles or selectively used within the myocytes or both.     

The effect of calcium on phospholipid peroxidation

The effect of calcium ions on the peroxidation of ox-brain phospholipid liposomes in different free-radical catalysing systems has been assessed. Using thiobarbituric acid-reactivity (TBA) as a measure of lipid peroxidation, calcium ions both inhibited and enhanced peroxidation in the different systems.Changing the composition of the ox-brain phospholipid liposome with synthetic non TBA-reactive phosphatidylcholine, significantly altered its susceptibility to peroxidation both in the presence and absence of calcium ions.The results are discussed with reference to the possibility that calcium ions induce conformational changes in membrane phospholipids. Susceptibility to peroxidation is then influenced by a complex interrelationship between the qualitative lipid composition of the membrane, the pro-oxidant catalyst and the presence of calcium or other active ions.     

Detection of phospholipid peroxides in biological samples

Peroxidation of membrane lipids has been hypothesized to play a key role in various types of tissue degeneration and pathology. Lipid peroxides are formed when oxygen reacts with an unsaturated fatty acid chain. Virtually all of the unsaturated fatty acids in biological systems are bound by ester linkages in phospholipids or triglycerides. Phospholipid and triglyceride peroxides are primary products of lipid peroxidation and have rarely been measured. Most of the commonly used methods for detection of lipid peroxidation are based on detection of malondialdehyde or other chemical species that are derived from oxidized fatty acids. This review presents an overview of recently developed methods aimed at identifying and measuring oxidized phospholipids and triglycerides which are direct evidence of the occurrence of lipid peroxidation in vivo.     

Lipid Peroxides in the Free Radical Pathophysiology of Brain Diseases

1. Polyunsaturated fatty acids are essential for normal neural cell membrane functioning because many membrane properties, such as fluidity and permeability, are closely related to the presence of unsaturated and polyunsaturated side chains. Lipid peroxidation results in loss of membrane polyunsaturated fatty acids and oxidized phospholipids as polar species contributing to increased membrane rigidity.2. Polyunsaturated fatty acids are released from membrane phospholipids by a number of enzymic mechanisms involving the receptor-mediated stimulation of phospholipase A₂ and phospholipase C/diacylglycerol lipase pathways.3. The overstimulation of excitatory amino acid (EAA) receptors stimulates the activities of lipases and phospholipases, and this stimulation produces changes in membrane phospholipid composition, permeability, and fluidity, thus decreasing the integrity of plasma membranes.4. Alterations in properties of plasma membranes may be responsible for the degeneration of neurons seen in neurodegenerative diseases. Two major processes may be involved in neuronal injury caused by the overstimulation of EAA receptors. One is a large Ca²⁺ influx and the other is an accumulation of free radicals and lipid peroxides as a result of neural membrane phospholipid degradation. It is suggested that calcium and free radicals act in concert to induce neuronal injury in acute trauma (ischemia and spinal cord injury) and in neurodegenerative diseases.     

The degree of dietary fatty acid unsaturation affects torpor patterns and lipid composition of a hibernator

Diets rich in unsaturated and polyunsaturated fatty acids have a positive effect on mammalian torpor, whereas diets rich in saturated fatty acids have a negative effect. To determine whether the number of double bonds in dietary fatty acids are responsible for these alterations in torpor patterns, we investigated the effect of adding to the normal diet 5% pure fatty acids of identical chain length (C18) but a different number of double bonds (0, 1, or 2) on the pattern of hibernation of the yellow-pine chipmunk, Eutamias amoenus. The response of torpor bouts to a lowering of air temperature and the mean duration of torpor bouts at an air temperature of 0.5°C (stearic acid C18:0, 4.5±0.8 days, oleic acid C18:1, 8.6±0.5 days; linoleic acid C18:2, 8.5±0.7 days) differed among animals that were maintained on the three experimental diets. The mean minimum body temperatures (C18:0, +2.3±0.3°C; C18:1, +0.3±0.2°C; C18:2,-0.2±0.2°C), which torpid individuals defended by an increase in metabolic rate, and the metabolic rate of torpid animals also differed among diet groups. Moreover, diet-induced differences were observed in the composition of total lipid fatty acids from depot fat and the phospholipid fatty acids of cardiac mitochondria. For depot fat 7 of 13 and for heart mitochondria 7 of 14 of the identified fatty acids differed significantly among the three diet groups. Significant differences among diet groups were also observed for the sum of saturated, unsaturated and polyunsaturated fatty acids. These diet-induced alterations of body fatty acids were correlated with some of the diet-induced differences in variables of torpor. The results suggest that the degree of unsaturation of dietary fatty acids influences the composition of tissues and membranes which in turn may influence torpor patterns and thus survival of hibernation.Abbreviations bm body mass - T _a air temperature - T _b body temperature - FA fatty acid - MR metabolic rate - MUFA monounsaturated fatty acids - PUFA polyunsaturated fatty acids - VO₂ rate of oxygen consumption - SFA saturated fatty acids - UFA unsaturated fatty acids - UI unsaturation index - SNK Student-Newman-Keuls test     

Effects of chronic amiodarone treatment on cat myocardial phospholipid content and on in vitro phospholipid catabolism

Amiodarone is used extensively for the chronic treatment of life-threatening arrhythmias caused by ischemic heart disease. However, chronic therapy with this agent results in phospholipidosis in various tissues and it has been suggested that the inhibition of lysosomal phospholipase A by this drug contributes to this abnormality. Exogenous amiodarone has been shown to inhibit purified rat liver lysosomal phospholipase A₁, as well as acid phospholipase activities of alveolar macrophage homogenates and those of snake venom phospholipase A₂ and bacterial phospholipase C. The effects of drug treatment on heart have not been explored. The results described here demonstrate that amiodarone also significantly increases (37%, p < 0.001) phospholipid content in cat hearts. This increase is proportionately distributed to all major phospholipid classes, with the exception of sphingomyelin which appears to increase more than the others. In addition, the data also show that following amiodarone treatment, the endogenous drug levels in the heart were sufficient to reduce in vitro losses of membrane phospholipid at 37°C by inhibiting a variety of endogenous phospholipases at physiological (7.4), ischemic (6.2) and acidic (5.0) pH values. This protection is more pronounced at acidic pH values than at physiological pH. Endogenous amiodarone also affects myocardial phospholipase activities towards exogenous phosphatidylcholine and again the extent of inhibition is more at acidic pH. These results suggest that amiodarone induces phospholipidosis in the heart by inhibiting phospholipid catabolism and that its antiarrhythmic properties may reside in its ability to modulate alkaline, neutral and acid phospholipase activities in ischemia. To what extent amiodarone metabolites (desethylamiodarone and bis-desethylamiodarone) are involved in these actions remains to be determined.     

The lipid composition of flight muscle mitochondria isolated from the blowfly, Phormia regina.

The role of lipids in membrane structure and function was studied by measuring the major lipid classes in mitochondria isolated from flight muscle of the blowfly, Phormia regina. Approximately 98% of the total lipid is phospholipid. Neutral lipid constitutes the remaining 2% of the total. Phosphatidylethanolamine accounts for 55–60% of the phospholipid. A molecular ratio of 4:1:1 is found for phosphatidylethanolamine, phosphatidylcholine, and cardiolipin (diphosphatidylglycerol). The neutral lipids include cholesterol, about 20%, and quinone, 40–45% of the total. The free fatty acid content of the neutral lipid fraction is variable, apparently being generated by endogenous phospholipase activity. The fatty acids of the neutral and phospholipid classes are predominantly 14–18 carbon acids; long-chain fatty acids of 20 and 22 carbons are essentially absent. The neutral lipid fraction contains 43% saturated and 51% monoenoic fatty acids. More than 65% of the phospholipid fatty acids are unsaturated. The principal fatty acids are palmitic, palmitoleic, oleic, linoleic, and linolenic. No trace of α- or β-tocopherol is detected. As vitamin E is considered an important naturally occuring antioxidant that prevents lipid peroxidation, the apparent absence of α- and β-tocopherol in these mitochondria coupled with intense oxidative activity of the mitochondria leads to the suggestion that blowfly flight muscle mitochondria may be particularly susceptible to peroxidative damage.     

Protein and lipid utilization during fasting with shallow and deep hypothermia in the European hedgehog (Erinaceus europaeus)

We investigated whether the relative contributions of body protein and lipid reserves differ according to the level of energy expenditure in fasting animals. Protein and lipid utilization was therefore quantified and compared in hedgehogs which fasted with shallow and deep hypothermia, i.e. by exposure at 5 or 20 °C ambient temperature. Body composition was determined for every 150-g decrease in mass throughout the experiment, allowing the calculation of regression lines between body mass (independent variable, x) and body composition (dependent variable, y: water, protein, neutral lipids, phospholipids and cholesterol). There were highly significant (P<0.001) linear decreases in all body components with decreasing body mass in both groups of hedgehogs. Neutral lipids were the main component of the total body mass loss (54%) in fasted animals with shallow and deep hypothermia, percentages of water (26–30%) and protein (10–11%) being lower, and those of phospholipid and cholesterol negligible (<0.5%). In spite of different levels in energy expenditure (2.54 and 1.07 W·kg^-1 in shallow-and deep-hypothermal fasting hedgehogs, respectively), the energy sources were identical in both groups, neutral lipid being the main fuel (91–92%) and body protein accounting for the remainder (8–9%). Prolonged fasting with shallow and deep hypothermia were marked by low alaninemia and glycemia, while plasma free fatty acids and -hydroxybutyrate were elevated. These data therefore indicate that the relative contribution of lipid and protein is similar during prolonged fasting with shallow and deep hypothermia, i.e. there is no specific effect of deep hypothermia on body fuel utilization. The tolerance of a much longer fast in deep-hypothermal hedgehogs can simply be attributed to the lower rates of lipid and protein utilization as a result of the lower level of energy expenditure.Abbreviations bm body mass     

Characteristics of the early recovery period and the level of carbohydrate-lipid metabolic substrates after 24-hour immobilization hypothermia

The peculiarities of 24-hour hypothermia were studied in rats during immobilization and a 5-hour recovery period. The levels of glucose in blood and liver, glycogen in liver, skeletal muscles and heart, total lipids in liver and blood, nonesterified fatty acids in blood have shown that the speed of rewarming is limited both by the level of carbohydrate and lipid energy substrates.