High sensitivity negative ion GC-MS method for detection of desaturated and chain-elongated products of deuterated linoleic and linolenic acids

A sensitive negative chemical ionization (NCI) gas chromatography-mass spectrometry (GC-MS) method for the detection of pentafluorobenzyl (PFB) esters of deuterated fatty acids is described. Deuterated linoleic [18:2n-6 2H4-9,10,12,13] and linolenic [18:3n-3 2H5-17,17,18,18,18] acids were converted to chain-elongated and desaturated products during incubations with homogenates prepared from rat liver. The extracted fatty acids were derivatized with pentafluorobenzyl bromide and analyzed in the negative ion mode by GC-MS. The detection limit of the PFB esters in NCI using selected ion monitoring was below 10 femtograms. In general, detection of the PFB derivatives using the negative ion mode was more than three orders of magnitude more sensitive than using a positive chemical ionization (PCI) method with methyl ester derivatives. The PFB esters of the 2H4-18:2n-6 metabolites eluted with their unlabeled analogues, whereas the PFB esters of the 2H5-18:3n-3 metabolites were resolved from the unlabeled compounds on polar capillary FFAP columns. Isotope ratios of the 2H4-18:2n-6 metabolites were used to quantify the deuterated compounds from standard dilution curves generated from the ion abundances of the unlabeled fatty acids. The 2H5-18:3n-3 metabolites were quantified similarly using 18:3n-3. This method is feasible for the study of the in vivo metabolism of deuterated essential fatty acids in whole animals.

Egg yolk as a source of long-chain polyunsaturated fatty acids in infant feeding

In this paper we compare the fatty acid content of egg yolks from hens fed four different feeds as a source of docosahexaenoic acid to supplement infant formula. Greek eggs contain more docosahexaenoic acid (DHA, 22:6 omega 3) and less linoleic acid (LA, 18:2 omega 6) and alpha-linolenic acid (LNA, 18:3 omega 3) than do fish-meal or flax eggs. Two to three grams of Greek egg yolk may provide an adequate amount of DHA and arachidonic acid for a preterm neonate. Mean intake of breast milk at age 1 mo provides 250 mg long-chain omega 3 fatty acids. This amount can be obtained from less than 1 yolk of a Greek egg (0.94), greater than 1 yolk of flax eggs (1.6) and fish-meal eggs (1.4), or 8.3 yolks of supermarket eggs. With proper manipulation of the hens' diets, eggs could be produced with fatty acid composition similar to that of Greek eggs.

Cardiotoxicity evaluation in patients treated with a mitoxantrone combination as adjuvant chemotherapy for breast cancer

Indices of cardiac function were measured in 49 women who received adjuvant treatment for stage II breast cancer. The combination chemotherapy consisted of six monthly courses of cyclophosphamide, 500 mg/m2, mitoxantrone, 10 mg/m2 and fluorouracil, 500 mg/m2 (CNF). Left ventricular function was assessed by echocardiography, systolic time intervals and nuclear angiography. The values of the echocardiographic left ventricular end diastolic diameter (Dd) and end systolic diameter (Ds), and those of the index of preejection period (PEPI) and the ratio of the preejection period to left ventricular ejection time (PEP/LVET), determined in 41 patients before chemotherapy, at midcourse and after chemotherapy by echocardiography and systolic time intervals (STI), showed a slight but significant increase. All these values remained within normal limits. Resting nuclear angiography, performed before and after treatment, showed a decrease in LVEF by 10% or more in four patients; the postchemotherapy values remained within the normal range in all cases. In conclusion, adjuvant treatment of breast cancer patients with 6 cycles of the CNF combination, as judged by its effect on the measured indices, does not appear to be cardiotoxic.

Brain microvessel 12-hydroxyeicosatetraenoic acid is the (S) enantiomer and is lipoxygenase derived

12-Hydroxyeicosatetraenoic acid (12-HETE) production from arachidonic acid by cerebral microvessels isolated from perfused adult murine brain was reduced by the lipoxygenase inhibitors baicalein, esculetin, gossypol, nordihydroguaiaretic acid, and quercetin. Except for quercetin and gossypol, the IC50 did not exceed 10 microM. Each inhibitor, except baicalein, also decreased microvessel prostaglandin production when present in concentrations above their IC50 value for 12-HETE. In contrast, inhibitors of the cytochrome P450 monooxygenase system, clotrimazole, metyrapone, and proadifen (SKF-525A), had little effect on microvessel 12-HETE production. Chiral phase HPLC analysis revealed that only the (S) enantiomer of 12-HETE was formed. The major microvessel metabolite of eicosapentaenoic acid co-eluted with 12-hydroxyeicosapentaenoic acid (12-HEPE) on reverse-phase HPLC and the (S) enantiomer of 12-HEPE on chiral phase HPLC. Furthermore, like 12-HETE, 12-HEPE production was blocked by lipoxygenase inhibitors. These studies demonstrate that brain microvessels produce only the (S) enantiomeric 12-hydroxy derivatives of both arachidonic acid and eicosapentaenoic acid by the action of a lipoxygenase that can be selectively inhibited by baicalein. Since arachidonic acid and eicosapentaenoic acid are available to cerebral blood vessels in certain pathological settings, these 12-hydroxy acid lipoxygenase products may mediate some of the cerebrovascular dysfunction that occurs following stroke, brain trauma, or seizures.

Ethanol inhalation and dietary n-6, n-3, and n-9 fatty acids in the rat: effect on platelet and aortic fatty acid composition

The effects of 18-carbon n-6, n-3, and n-9 fatty acid diets and ethanol exposure on the fatty acyl composition of platelets and vascular tissue were examined. An experimental design was devised to control the dietary content of 18-carbon fatty acids. The levels of 18:3n6, 18:3n3 and 18:1n9 were varied by a formulation of dietary oils which contained similar proportions of 18:2n6. Male Sprague-Dawley rats were fed a purified diet containing 11% by weight of either borage oil (BOR) rich in 18:3n6, linseed/safflower oil (LSO) rich in 18:3n3, or sesame oil (SES) rich in 18:1n9 for 7 weeks and exposed to ethanol vapors by means of inhalation for the final 6 days of the dietary regimen. Moderate blood ethanol levels of 118 +/- 6.6 mg/dl were obtained. Total lipids were extracted from platelets and aortae, and the fatty acid distributions were analyzed by gas chromatography. BOR feeding resulted in increases in the proportion of n-6 fatty acids (18:3n6, 20:3n6, 20:4n6) in platelets and aorta. Animals fed the LSO diet had increased levels of n-3 fatty acids (18:3n3, 20:5n3, 22:6n3). The SES-based diet resulted in an increase in 18:1n9 in both aorta and platelets. Following ethanol exposure alone, the most marked change in the fatty acid profile was a decrease in 20:4n6 in the platelet. This effect was not observed in rats supplemented with BOR. No significant changes were observed in the aortic fatty acid content at this level of ethanol exposure. The results suggested that, in the rat, a diet enriched with BOR effectively prevented ethanol-induced alterations in platelet fatty acid composition.

Lipoxygenation in rat brain?

It has been previously claimed that rodent brain possesses lipoxygenase activity, based upon the structure of products which were formed from arachidonic acid and the inhibition of this activity by "lipoxygenase inhibitors." Our studies confirm that various positional isomers of hydroxyeicosatetraenoic acids (HETE) are formed (e.g., 15-, 12-, 11-, 9-, 8- and 5-HETE) by brain homogenate and that their production is inhibited by certain lipoxygenase inhibitors, such as nordihydroguaiaretic acid (NDGA) but not by cyclooxygenase or cytochrome P-450 inhibitors. However, stereochemical analysis indicated racemic distributions of these products suggesting that they were not formed by a lipoxygenase enzyme but rather by a peroxidative process. It should also be noted that the presence of 12(S)-lipoxygenase activity could be demonstrated by stereochemical analysis only when the brain was not perfused properly, indicating this activity was due to blood cell contamination. It is known that many lipoxygenase inhibitors are also capable of inhibiting peroxidative reactions apparently due to their free radical scavenging properties. For these reasons, it is essential that the stereochemical purity of purported lipoxygenase products be determined and that previous claims of lipoxygenase activity in mammalian brain be reexamined.

Aminophospholipid molecular species asymmetry in the human erythrocyte plasma membrane

The transbilayer distribution of the molecular species of aminophospholipids in human red blood cell plasma membrane has been investigated using a covalent labelling technique. Separation and quantitative analysis of the molecular species of phosphatidylethanolamine (PE) and phosphatidylserine (PS) was performed using high-performance liquid chromatography with UV detection of the trinitrophenyl derivatives obtained after reaction with trinitrobenzenesulfonic acid (TNBS). When the molecular species distribution obtained with intact cells was compared to that of the whole membrane, a molecular species asymmetry was evident. This phenomenon was most clearly evident when the reaction was performed at low temperatures (0 degrees C) and was obscured by the excessive labelling or probe permeation associated with higher temperatures or longer incubation times. The monoene species were enriched in the outer leaflet, they comprised about 30% of the PE species in this leaflet. The polyunsaturates were preferentially localized in the inner leaflet and this was true of the arachidonyl species in particular as they represented up to 35% of this pool. The w-3 polyunsaturated fatty acids displayed a preferential localization in the plasmalogen subclass in comparison to the diacyl fraction, i.e., they comprised about 58 of the former and 42% of the latter subclass of cellular PE w-3 species. Data concerning the separation, identification and quantification of PS molecular species in human erythrocytes is also presented. The internal localization of the polyunsaturated species as well as the compartmentalization of the w-3 and w-6 pools will have metabolic, structural and physical implications for membrane function.

Separation of lipid classes by solid phase extraction

A rapid and reliable method for the separation of lipid classes is described using aminopropyl disposable columns. This method is a modification to an existing procedure that allows the separation of both neutral and acidic phospholipid fractions and a high recovery of the latter. Acidic phospholipids were eluted with a mixture of hexane-2-propanol-ethanol-0.1 M ammonium acetate-formic acid 420:350:100:50:0.5 containing 5% phosphoric acid after neutral phospholipids had been eluted with methanol. It was verified that extremely high recoveries of cholesterol (CH), triglycerides (TG), free fatty acids (FFA), phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatidylserine (PS), phosphatidic acid (PA), sphingomyelin (SM), and cerebrosides were obtained with this method. In addition, there appeared to be no preferential losses or degradation of any particular molecular species as the fatty acid distribution of bovine brain PS and the molecular species profile of plant PI were unaltered by the procedure. Depending on the tissue, this method may yield fractions containing pure lipid classes and/or simple mixtures of lipid classes of similar polarity. These fractions may then be more easily separated by thin-layer chromatography or high performance liquid chromatography for a complete lipid class analysis.

Stereochemical analysis of hydroxylated docosahexaenoates produced by human platelets and rat brain homogenate

The stereochemical configuration of hydroxylated products of docosahexaenoic acid (22:6w3) formed by human platelets and rat brain homogenate were characterized for the first time. Chiral phase HPLC was employed along with autooxidized 22:6w3 as reference material. The 14- and 11-hydroxy 22:6w3 (HDHE) products produced by human platelets were in the S configuration. Rat brain homogenate produced all of the ten possible positional isomers when incubated with 22:6w3. Their retention behavior on the reversed and chiral phase HPLC columns and GC/MS/EI analysis indicated that they were 20-, 17-, 16-, 14-, 13-, 11-, 10-, 8-, 7- and 4-HDHE. However, stereochemical analysis revealed that each positional isomer was a racemic mixture, suggesting that these were not formed by lipoxygenation but mainly by peroxidation process.

Formation of 15-lipoxygenase product from docosahexaenoic acid (22:6w3) by human platelets

The metabolism of docosahexaenoic acid (22:6w3) by 15-lipoxygenase activity of washed human platelets was investigated. Platelets produced 17-hydroxydocosahexaenoic acid (HDHE) when incubated with 22:6w3. Similarly, 15-hydroxyeicosatetraenoic acid (HETE) and 13- and 9-hydroxyoctadecadienoic acids (HODD) were produced when incubated with 20:4w6 and 18:2w6, respectively. However, these products were observed only as minor components in the platelet incubation mixture. Control studies with carefully purified platelets and mononuclear cells indicated that these products were formed by the platelets. Chiral phase HPLC analysis indicated that these compounds were mainly in the S configuration with the exception of the 9-HODD, thus, confirming that a lipoxygenase is responsible for their production. The 9-HODD produced by platelets was a racemic mixture.

Docosahexaenoic acid (22:6n3)-induced relaxation of the rat aorta

Dietary consumption of fish and fish oil supplements, containing eicosapentaenoic acid and docosahexaenoic acid, has been associated with favorable alterations in the cardiovascular system, such as, a reduction in blood pressure. Therefore, the effects of docosahexaenoic acid (22:6n3) on isometric tension of rat aortic smooth muscle were investigated. A concentration-dependent (1-127 microM) relaxation (6-30%) was induced by 22:6n3 in non-precontracted vessels. Docosaehexaenoic acid, concentration dependently (1-44 microM) reversed contractions of rat aortic rings induced by phenylephrine (7-43%) and by U44069 (8-52%). These results indicate that the relaxant effects produced by 22:6n3 in the rat aorta are concentration-dependent and not specific to the contractile agonist.

The effects of chemical sterilisation on the dimensional stability of some elastomeric impression materials

The dimensional stability of a range of dental elastomeric impression materials has been assessed, to study the effect of storage in sterilising solutions. Experiments were carried out on polysulphides, a poly(ether urethane) and several condensation and addition silicones. The last materials had the greatest dimensional stability over a range of storage conditions, which included aqueous glutaraldehyde and hypochlorite solutions.

Analysis of aminophospholipid molecular species by high performance liquid chromatography

A new method is described for the separation of individual molecular species of the aminophospholipids, phosphatidylethanolamine and phosphatidylserine. Trinitrobenzene-sulfonic acid was used to derivatize both aminophospholipids and the derivatives were purified by thin-layer chromatography. A reversed-phase high performance liquid chromatography technique was developed to separate and quantify individual molecular species based upon ultraviolet detection of the attached chromophore. The retention times of the molecular species on the C18 reversed-phase column were longer with increasing carbon chain length and decreasing degree of unsaturation of fatty acyl chain. The overall procedure allowed a quantitative recovery of the aminophospholipid species. The lower limit of detection was about 10 pmol and a linear response was observed in the range of 0.1-10 nmol of phospholipid. Using this method, we were able to separate and quantify trinitrophenyl-phosphatidylethanolamine molecular species of both subclasses (diacyl and alkenyl) from human red blood cells and rat brains. Separation of species was confirmed by gas-liquid chromatographic analysis of the fatty acid content of each peak and by thermospray liquid chromatography-mass spectrometry. This new method provides a convenient and sensitive technique for studies of aminophospholipid molecular species composition. Furthermore, it appears to be a useful tool for the analysis of asymmetric distribution of these species in biological membranes.

Formation of PGI3 in the rat during dietary fish oil supplementation

Conflicting results exist in the literature on the conversion of eicosapentaenoic acid (EPA) to trienoic prostaglandins and its influence on the formation of dienoic prostaglandins from arachidonic acid (AA). Tissues from animals fed fish oils produce little, if any, trienoic prostaglandins and reduced amounts of dienoic ones. Excretion of the major urinary metabolite of PGI2 is not reduced in humans taking fish oil, however, and substantial amounts of one derived from PGI3 have been found, by GC/MS. We have addressed this possible species difference by examining the urine of rats fed fish oil for 2.3 dinor-6-keto-PGF1 alpha and its delta 17 analog, formed from PGI2 and PGI3, respectively, and compared them with rats fed corn oil. Fatty acid differences in erythrocyte and aortic lipids were also determined. Rats fed fish oil do make PGI3 from eicosapentaenoic acid in vivo and do not suppress their production of PGI2, despite having more EPA than AA in aortic lipids.

Prostaglandins in cerebrospinal fluid of healthy human volunteers, abstinent alcoholics and rhesus monkeys

A sensitive and selective assay for measuring prostaglandins in cerebrospinal fluid has been developed, based on the selected-ion-monitoring, electron-capture negative ionization GC/MS detection for the MO-PFB-TMS derivatives of prostaglandins E2, E1, F2 alpha, F1 alpha, and 6-keto-F1 alpha. Improvements over previously published assay procedures have been made, and the new assay has been applied to measurement of prostaglandin concentrations in lumbar CSF of healthy human volunteers, abstinent alcoholic patients, in cisternal CSF of Rhesus monkeys, and continuously sampled lumbar CSF of awake Rhesus monkeys. Results indicated that the concentrations of PGE2, PGE1, PGF1 alpha, and 6-keto-PGF1 alpha were below 15 pg/mL CSF in lumbar CSF of healthy humans and abstinent alcoholics, and in cisternal CSF of Rhesus monkeys. In contrast, continuously sampled lumbar CSF of awake Rhesus monkeys contained more than 200 pg/mL of PGE2, PGF2 alpha, and 6-keto-PGF1 alpha, probably present as a result of local production.

Synthesis of paf-acether from exogenous precursors by the prokaryote Escherichia coli

Paf-acether (paf) is a potent mediator of inflammatory diseases and septic shock. Using normal-phase HPLC, a paf-like activity was found in culture supernatants from E. coli. Prokaryotic paf exhibited the same biological and physico-chemical properties as eukaryotic cells and synthetic paf. Further, reverse-phase HPLC indicates that paf generated by bacteria is predominantly of the hexadecyl and octadecyl species. When cultures were supplemented with lyso-paf, a dramatic increase in paf production was observed. The purity and molecular structure of bacterial paf were further characterized by mass spectral analysis. These results could be of importance considering the pathogenetic role of enterobacteria. Further, it appears that the competence to form and release paf is an early phylogenetic development.

Preparation and the structural determination of hydroperoxy derivatives of docosahexaenoic acid and other polyunsaturates by thermospray LC/MS

A new method to determine the structure of lipoxygenase reaction products is presented. Thermospray mass spectra of hydroperoxy derivatives of polyunsaturates contain both molecular ion species and fragments reflecting the position of oxygenation. Data are presented for hydroperoxy-docosahexaenoic, eicosapentaenoic, arachidonic and linoleic acids in this regard. Ten positional isomers of hydroperoxy docosahexaenoic acid were prepared by autooxidation and their structures were determined by thermospray LC/MS and confirmed by electron impact GC/MS after suitable derivatives were made. This technique was particularly useful in determining the structure of unknown metabolites by direct monitoring of the reaction mixture without derivatization. In this paper, the value of this approach is demonstrated using a soybean lipoxygenase reaction mixture as a simple example.

Essential fatty acid deficiency and neutrophil function: studies of lipid-free total parenteral nutrition in monkeys

Linoleic acid (18:2 omega 6), the obligate precursor of arachidonic acid (20:4 omega 6), is an essential nutrient for humans and other mammals. Because arachidonic acid release and metabolism are components of neutrophil activation by certain stimuli, we questioned whether neutrophils depleted of arachidonate as a result of essential fatty acid deficiency might be functionally impaired. We examined this possibility by producing essential fatty acid deficiency in monkeys with lipid-free total parenteral nutrition (TPN). Rhesus and African green monkeys were given calorically equal TPN for up to 23 days with and without a vegetable fat emulsion rich in linoleic acid. Fatty acids were analyzed in total lipid extracts of serum and isolated blood neutrophils by gas-liquid chromatography. Although fatty acids in the serum and neutrophils of monkeys given TPN with lipid did not change, linoleic acid levels decreased by at least 60% in serum and 50% in neutrophils from animals given TPN with no lipid. Moreover, arachidonate levels in neutrophil lipids decreased by at least 50% within 12 days of lipid-free TPN, and the abnormal fatty acid 20:3 omega 9 (characteristic of essential fatty acid deficiency) appeared and steadily increased with time. These biochemical signs of omega 6 fatty acid deficiency were associated with impaired neutrophil function in vitro. Both migration responses and superoxide generation stimulated by N-formyl-methionyl-leucyl-phenylalanine were significantly decreased by 12 days of lipid-free TPN, as was the capacity of activated cells to synthesize leukotriene B4. In contrast, functional responses of fatty acid-deficient neutrophils to leukotriene B4 and phorbol myristate acetate, which have little or no effect on arachidonate release or metabolism, were not significantly altered. These findings indicate that endogenous supplies of arachidonic acid and other essential omega 6 fatty acids influence the functional responsiveness of neutrophils. These studies also indicate that altered neutrophil function is a feature of essential fatty acid deficiency and that it may contribute to the increased risk of infection and decreased inflammatory responses observed in this condition.