Incorporation of n-3 polyunsaturated fatty acids into processed foods

The aim of dose reduction of chemotherapeutic agents following weight loss is to avoid excessive toxicity while maintaining an equivalent therapeutic effect. Several methods of calculating this dose reduction are currently in use, including dose reduction in proportion to the reduction in body surface area (BSA) or the amount of weight lost and no dose reduction unless significant toxicity occurs. Each of these methods results in the administration of a different dose and therefore different drug exposure, as measured by the area under the time versus concentration curve (AUC). We have used pharmacokinetic modeling software and normative data on the pharmacokinetics of high-dose methotrexate to determine the change in AUC resulting from dose reduction by each of the methods cited for patients with weight loss. Dose reduction in proportion to the reduction in weight results in the same AUC and therefore equivalent drug exposure as before weight loss. In contrast, the more common practice of dose reduction in proportion to the decrease in BSA (as determined by recalculating BSA) results in a higher AUC than before weight loss. This results in increased drug exposure and potentially increased toxicity, which may be avoided if dose reduction is carried out in proportion to the decrease in weight rather than in BSA. The same principles are applicable to other drugs, particularly those associated with dose-dependent toxicity.     

Determinants of the selection of phosphatidylcholine molecular species for secretion into bile in the rat

Several hypotheses have been proposed to explain why parent birds eat their nestlings' faecal sacs. Among them, the parental nutrition hypothesis suggests that faeces may provide alternative food to parent birds, while the economic disposal hypothesis proposes that eating faeces represents an economical alternative to carrying them away when birds are engaged in parental activities. In both cases the elimination of faeces could prevent contamination of the nest (nest sanitation). In the present study, we tested these hypotheses on the common swift, Apus apus. The behaviour of parents at the nest was videotaped and analysed in relation to sex, brood size and nestling age. The parents regularly swallowed faecal sacs during the first 3 weeks after the nestlings hatched, but only occasionally thereafter until they fledged. Both sexes ingested sacs at a similar rate in the first week after hatching, and ingestion rate was directly related to the number of feeding visits. Females ate significantly more sacs than males overall. The parents consumed faeces after actively searching into and around the nest cup, also during brooding spells. However, brooding decreased with increasing brood size and nestling age, while faeces consumption increased. Our results are consistent with the hypothesis that parent birds ingest their nestling faeces to recycle water and nutrients, making the 'best of a bad job' during periods of high energetic requirements. In addition, ingestion of faeces may be an alternative strategy to delay hunger and to facilitate the allocation of food to the offspring. As the nestlings grew, parents ate fewer faecal sacs. The increased begging behaviour of the young appeared to be an important factor in determining the decline of faeces consumption, as it hindered parents approaching the nest. Copyright 1998 The Association for the Study of Animal Behaviour.     

Distribution of plasma phosphatidylcholine molecular species in rabbits fed fish oil is modulated by dietary n-6 fatty acids

Natural occurrence of Fusarium mycotoxins (trichothecenes and fumonisins) and aflatoxin B1 (AFB1) were surveyed in 32 corn samples, harvested in 1993 and randomly sampled in 1994 in several districts of Hanoi, Vietnam. Corn samples were first milled into fine powder, extracted with methanol-water (3:1) and the crude extracts obtained from the same samples were used for the simultaneous analysis of the trichothecenes such as nivalenol (NIV), deoxynivalenol (DON), and T-2 toxin (T-2) by gas chromatography/mass spectrometry (GC/NS); fumonisins B1 (FB1), B2 (FB2), and B3 (FB3) by high-performance liquid chromatography (HPLC) with a flourescence detector; and AFB1 by and ELISA kit based on a monoclonal antibody. The data revealed that 14, 8, 4, 3, and 2 out of 15 corn kernel samples were positive for AFB1, FB1, FB2, FB3, and NIV with the average levels being 28, 1, 101, 276, 232, and 858 ppb, respectively, and neither DON nor T-2 were detected. As for the other 17 samples of corn powder, 13, 15, 12, 10, 4 and 2 were positive for AFB1, FB1, FB2, FB3, DON, and NIV with the average being 30, 780, 289, 176, 3, 170, and 1,365 ppb, respectively, and T-2 was not detected. Although their positive rates and levels fell in the ranges reported elsewhere, it was found for the first time that the Fusarium toxins (NIV, DON, and fumonisins) and an Aspergillus toxin (AFB1) were naturally co-contaminated in selected samples of corn produced in north Vietnam.     

Incorporation of radioactive amino acids into protein in isolated rat hepatocytes

The incorporation of radioactivity from a 14C-labelled amino acid mixture (algal protein hydrolysate) into protein in isolated rat hepatocytes has been studied. The incorporation rate declined with increasing cell concentration, an effect which could be explained partly by isotope consumption, partly (and largely) by isotope dilution due to the formation of non-labelled amino acids by the cells. At a high extracellular amino acid concentration, the rate of incorporation into protein became independent of cell concentration, because the isotope dilution effect was now quantitatively insignificant. The time course of protein labelling at various cells concentrations correlated better with the intracellular than with the extracellular amino acid specific activity, suggesting that amino acids for protein synthesis were taken from an intracellular pool. With increasing extracellular amino acid concentrations both the intracellular amino acid concentration, the intracellular radioactivity and the rate of incorporation into protein increased. Protein labelling exhibited a distinct time lag at high amino acid concentrations, presumably reflecting the time-dependent expansion of the intracellular amino acid pool. The gradual increase in the rate of protein labelling could be due either to an increased intracellular specific activity, or to a real stimulation of protein synthesis by amino acids, depending on whether the total intracellular amino acid pool or just the expandable compartment is the precursor pool for protein synthesis.     

Generation and remodeling of highly polyunsaturated molecular species of rat hepatocyte phospholipids

OBJECTIVE: We performed a clinical study in 99 children attending schools with moisture problems and compared the findings with those of 34 children from a reference school. The aim of the study was to evaluate the possible association between respiratory or allergic diseases in the pupils and moisture or mould problems in the school buildings. RESULTS: Asthma was diagnosed in nine (6.7%) children: eight of them came from the moisture-problem schools and all were over 10 y old. In addition, 17 non-asthmatic children had suffered from wheezing and 21 from long-term cough, both symptoms being suggestive of occult asthma. If moisture problems were observed both at home and in the school, the frequency of asthma was 21% and the combined frequency of asthma and wheezing was 43%. The presence of allergic rhinoconjuntivitis or atopic dermatitis had no association with moisture or mould problems. We performed skin-prick tests to 13 moulds in all the 133 children. A positive reaction (> 3 mm) was observed in only six (5%) of them. All six positive children reacted to at least one moisture-indicative mould, Fusarium roseum, Aspergillus fumigatus, Phoma herbarum or Rhodotorula rubra. None of these cases came from the reference school. There was a significant association between positive reactions to moisture-indicative moulds and asthma; four (44%) of the nine children with asthma had such reactions. In addition, all the 6 reactive children had either asthma or wheezing. CONCLUSIONS: We report preliminary evidence for an association between moisture or mould problems in the school building and the presence of manifest and occult asthma in the pupils. Our results show that skin-test positivity to moulds is rare in children. However, reactivity to moisture-indicative moulds seems to be associated with the occurrence of asthma or wheezing.     

Incorporation of polyunsaturated fatty acids into phospholipids of hemocytes from the tobacco hornworm, Manduca sexta

We examined the incorporation of four radioactive fatty acids, 18:1n-9, 18:2n-6, 20:4n-6 and 20:5n-3, into cellular lipids of hemocytes from tobacco hornworms, Manduca sexta. Most of the radioactivity associated with 18:1n-9 was recovered from triacylglycerols (TGs), and the radioactivity associated with 18:2n-6 was heavily incorporated into phospholipids (PLs) and TGs. Most of the radioactivity associated with the two eicosanoid-precursor polyunsaturated fatty acids (PUFAs), 20:4n-6 and 20:5n-3, was incorporated into PLs. The incorporated fatty acids were redistributed among the lipid classes during 2 h incubations. The two C20 PUFAs were moved from PLs to TGs. While 18:2n-6 underwent little change, 18:1n-9 was redistributed from TGs to PLs. Within PLs, each of the fatty acids were incorporated into phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylglycerol (PtG) and phosphatidylserine/inositol (PS/PI). The incorporation patterns changed over time, indicating that the incorporated fatty acids were redistributed among the four PL fractions. The radioactivity associated with 18:1n-9 was mostly recovered from the sn-1 position of PC (59%) and PE (83%). Most of the radioactivity associated with 18:2n-6 was found in the sn-2 position of PC (88%) and PE (67%). Over 90% of the radioactivity associated with 20:5n-3 was recovered from the sn-2 position of PC and PE. Incorporation of 20:4n-6 differed from 20:5n-3 because more radioactivity was recovered from the sn-2 position of PC (93%) than PE (69%). These findings are in line with the general background of lipid biochemistry, from which incorporation of 20:4n-6 into PE marks a notable departure: 31% of the radioactivity associated with this acid was recovered from the sn-1 position of PE. These findings indicate that hemocytes from the tobacco hornworm elaborate a fatty acid incorporation system, which exhibits specificity with respect to fatty acid structure and lipid class.     

Incorporation of exogenous precursors into neutral lipids and phospholipids in rat hepatocytes: effect of ethanol in vitro

We studied the incorporation of different radioactively labeled exogenous substrates into the lipids of rat hepatocytes previously incubated with ethanol. Glycerol, oleate, and serine were all incorporated into neutral lipids to a significantly greater degree in the presence of ethanol, the increase in radioactivity in the triacylglycerol fraction being quite substantial. A similar ethanol-induced increase was found in the incorporation of these substrates into the various phospholipids. This lipogenic activity did not occur when the metabolism of ethanol was blocked by 4-methylpyrazole, an inhibitor of hepatic ADH (alcohol:NAD+ oxidoreductase, EC 1.1.1.1) activity, thus demonstrating that one of the initial effects of ethanol on lipid biosynthesis was mediated by some products of its metabolism in the liver. The only alteration that persisted in the presence of 4-methylpyrazole was an inhibitory effect on the esterification of free cholesterol from oleate, suggesting that ethanol specifically inhibits hepatic ACAT (acyl CoA:cholesterol O-acyltransferase, EC 2.3.1.26) activity.     

Incorporation of photosensitive fatty acids into phospholipids of Escherichia coli and irradiation-dependent cross-linking of phospholipids to membrane proteins

In an approach to the study of phospholipid-protein interactions in biological membranes, the photoactivable fatty acids, omega-(m-azidophenoxy)-undecanoic acid (I) and omega-(m-diazirinophenoxy)-hexadecanoic acid (II), were incorporated biosynthetically into the phospholipids of the Escherichia coli fatty acid auxotroph, strain K1060-B5. The extent of incorporation of the two fatty acids was 43% and 21%, respectively, of the total fatty acid content of the phospholipids. Membrane vesicles prepared from cells grown on the fatty acid supplements and [32P]H3PO4 were irradiated at suitable wavelengths to generate the reactive nitrene or carbene intermediates. Subsequent analysis of solubilized membrane proteins by two-dimensional isoelectric focusing-polyacrylamide gel electrophoresis indicated cross-linking between radioactive phospholipids and an number of proteins. A corresponding experiment with cells grown on oleic acid showed only trace amounts of covalently cross-linked phospholipid-protein adducts. While the extent of cross-linking in vesicles from cells grown on I was only 3 times the background level observed for oleic acid-grown cells, cells grown on II showed 30 times this amount. The present results, together with the previously observed nonreactivity of the nitrene generated from I to undergo C-H insertion, show that the use of carbene precursors such as II is promising for chemical analysis of specific phospholipid-protein interactions in bacterial membranes under biologically meaningful conditions.     

The composition of individual molecular species of plasma phosphatidylcholine in human pregnancy

The role of medical informatics in telemedicine is dependent on using the power of the computerized database to not only feed patient specific information to the health care providers, but to use the epidemiological and statistical information in the data base to improve decision making and ultimately care. The computer is also a powerful tool to facilitate standardizing and monitoring of care and when applied in continuous quality improvement methodology it can enhance the improvement process well beyond what can be done by hand. The coupling of medical informatics with telemedicine allows sophisticated medical informatics systems to be applied in low population density and remote areas.     

Effect of fatty acids on lipid and apoprotein secretion and association in hepatocyte cultures

Increasing availability of free fatty acids (FFA) to liver results in enhanced rates of secretion of triglycerides in lipoproteins. However, as FFA uptake increases, triglyceride secretory rates reach a plateau and esterified fatty acids accumulate intracellularly, suggesting that something is limiting lipid transport out of the liver. One possibility could be the limited availability of apoproteins. To test this hypothesis, primary rat hepatocytes in culture were incubated with increasing amounts of FFA (0-2.1 mumol/dish) and the amounts of lipids and apoproteins inside the cells and in culture media were measured; the latter by specific radioimmunoassays. Media also were fractionated on Sepharose 2B and 6B columns and the elution profiles of apoproteins were obtained. With exposure to increasing amounts of free fatty acids, hepatocytes took up more fatty acids and intracellular levels of triglycerides rose (from 71 to 146 micrograms/mg cell protein). Concomitantly, media triglycerides nearly doubled (31 to 51 micrograms/mg). Incorporation of [3H]glyceride into cellular and media triglyceride also rose. However, levels of apoproteins A-I, B, C-III3, and E in cells and media were unchanged. The increasing amounts of triglycerides in media were present in larger particles, as demonstrated on gel permeation chromatography. The elution profiles of apoproteins B, C-III3, and E were altered in that a greater proportion of the apoproteins eluted with larger particles. Similar results were obtained when hepatocytes were preloaded with increasing amounts of FFA over 12 h and analyses of cells and media were carried out 8 and 22 h after removal of fatty acids from the media. During loading of cells, accumulation of cellular triglycerides was directly related to media FFA concentrations. During unloading, triglyceride secretory rates were related to cellular triglyceride levels. At higher triglyceride secretory rates larger particles were secreted and a greater proportion of apoproteins was associated with the larger particles, but total amounts of apoproteins in the system did not change. These data lead us to suggest that enhanced rates of apoprotein synthesis need not occur in the response to acute changes in hepatic lipid transport, rather, increased secretion of lipid is brought about by augmented intracellular lipid apoprotein association.     

Incorporation of amino acids into soluble and membrane protein fractions of dystrophic hamsters

The incorporation of labelled leucine was measured in protein fractions of muscle in intact control and dystrophic female hamsters and also in cell-free preparations obtained from these animals. The labelling of the soluble sarcoplasmic protein fraction, the microsomal protein fraction and the sarcolemma protein fraction was increased in the dystrophic hindleg muscle. The specific radioactivities of the sarcolemma protein fraction and other fractions were increased markedly relative to that of free leucine in the dystrophic muscle. In cell-free preparations where ribonuclease effects were avoided, the dystrophic muscle exhibited an increased synthesis of peptide bonds.     

Lipid binding to amyloid beta-peptide aggregates: preferential binding of cholesterol as compared with phosphatidylcholine and fatty acids

Amyloid beta-peptide (A beta) aggregates are one of the key neuropathological characteristics of Alzheimer's disease. A beta belongs to a group of proteins that aggregate and form beta-sheets, and some of these proteins bind cholesterol and other lipids. The purpose of the experiments reported here was to determine if cholesterol, fatty acids, and phosphatidylcholine (PC) would bind to A beta(1-40) and if such binding would be dependent on aggregation of A beta(1-40). Lipid binding was determined using fluorescent-labeled lipids. Incubation of A beta(1-40) for 0, 1, 3, 6, 21, and 24 h resulted in aggregation of the peptide with formation of dimers, trimers (1-24 h), and polymers (6-24 h) as determined by sodium dodecyl sulfate-gel electrophoresis. No change in the fluorescence of the lipids was observed when lipids were added to A beta(1-40) that had been incubated for 0, 1, or 3 h. However, the fluorescence intensities of cholesterol, saturated fatty acids, and PC were significantly increased (p < 0.0001) when added to A beta(1-40) that had been incubated for 6, 21, and 24 h in which A beta(1-40) polymers were detected. The binding affinity of cholesterol to A beta(1-40) polymers (K(D) of 3.24 +/- 0.315 x 10(-9) M) was markedly higher as compared with the other lipids (stearic acid, 9.42 +/- 0.41 x 10(-8) M; PC, 7.07 +/- 0.12 x 10(-7) M). The results of this study indicate that A beta(1-40) polymers bind lipids and have a higher affinity for cholesterol than PC or saturated fatty acids. Aggregated A beta(1-40) may affect lipid transport between cells or remove specific lipids from membranes, and such effects could contribute to neuronal dysfunction.     

Changes in dietary fatty acids alter phospholipid fatty acid composition in selected regions of rat brain

1. Eighty rats were randomized into four groups receiving one of the following diets: rat chow containing (1) 6% soybean oil, (2) 6% primrose oil, (3) 6% fish oil, (4) a combination of 4.5% primrose and 1.5% fish oil. 2. Following two months of each regimen, the rats were sacrificed by microwave irradiation and the brain's fatty acid composition was analysed with gas chromatography for each of the following regions: frontal cortex, striatum, occipital cortex, hippocampus, hypothalamus, cerebellum and pituitary. 3. Linoleic acid was decreased by both primrose and fish oil supplementations. The fish oil substitution resulted in a significant elevation of 20:3n-6, a decrease of 22:4n-6 and a non-significant decrease of 20:4n-6, probably reflecting inhibition of delta-5-desaturation. At the same time the fish oil diet significantly elevated 22:5n-3 while 22:5n-6 was decreased. 4. The primrose oil diet lowered the n-3/n-6 ratio in all regions except in the cerebellum. In contrast, the fish oil diet elevated the n-3/n-6 ratio in all regions. 5. The results demonstrate that changes in dietary fat composition can alter the fatty acid composition of the adult rat brain and that these effects are region specific. 6. This is of interest since metabolites of essential fatty acids may be involved in physiological and pathological processes in the brain and it has been hypothesized that dietary intake of fats may influence the outcome of psychiatric disorders such as schizophrenia.     

Effects of dicarboxylic acids on fatty acid-metabolizing enzymes in cultured rat hepatocytes

A clear chain-length dependent effect was observed for peroxisomal fatty acid beta-oxidation and carnitine acetyltransferase and also for mitochondrial carnitine palmitoyltransferase in primary cultures of rat hepatocytes. The extent of modulation of peroxisomal beta-oxidation was higher with even-carbon numbered dicarboxylic acids than with odd-carbon numbered ones, although such a tendency was not detected in the mitochondrial reactions. These results indicate difference in the effect of fatty acid-derived dicarboxylates on peroxisomal and mitochondrial functions.     

Acute effects of dietary fatty acids on the fatty acids of human milk

1. Effects on 5-HT function of sibutramine and its active metabolites, BTS 54 354 and BTS 54 505, were compared with fluoxetine, (+)-fenfluramine and (+)-amphetamine. 2. In vitro sibutramine weakly inhibited [3H]-5-HT uptake into brain synaptosomes. BTS 54 354, BTS 54 505 and fluoxetine were powerful [3H]-5-HT uptake inhibitors, whereas (+)-fenfluramine and (+)-amphetamine were very much weaker. Conversely, whilst sibutramine, its metabolites and fluoxetine did not release [3H]-5-HT from brain slices at < or = 10(-5)M, (+)-fenfluramine and (+)-amphetamine concentration-dependently increased [3H]-5-HT release. 3. Sibutramine and fluoxetine had no effect on 5-hydroxytryptophan (5-HTP) accumulation in either frontal cortex or hypothalamus at doses < 10 mg kg(-1). In contrast, (+)-amphetamine ( > or = 3 mg kg(-1)) reduced 5-HTP in hypothalamus, whilst (+)-fenfluramine (> or =1 mg kg(-1)) decreased 5-HTP in both regions. 4. Sibutramine (10 mg kg(-1) i.p.) and fluoxetine (10 mg kg(-1) i.p.) produced slow, prolonged increases of extracellular 5-HT in the anterior hypothalamus. In contrast, (+)-fenfluramine (3 mg kg(-1) i.p.) and (+)-amphetamine (4 mg kg(-1) i.p.) induced rapid, short-lasting increases in extracellular 5-HT. 5. Only (+)-fenfluramine (10 mg kg(-1)) altered 5-HT2A receptors in rat frontal cortex when given for 14 days, producing a 61% reduction in receptor number and a 18% decrease in radioligand affinity. 6. These results show that sibutramine powerfully enhances central 5-HT function via its secondary and primary amine metabolites; this effect, like that of fluoxetine, is almost certainly mediated through 5-HT uptake inhibition. By contrast, (+)-fenfluramine enhances 5-HT function predominantly by increasing 5-HT release. (+)-Amphetamine, though weaker than (+)-fenfluramine, also enhances 5-HT function by release.     

Essentiality of circulating fatty acids for glucose-stimulated insulin secretion in the fasted rat

We asked whether the well known starvation-induced impairment of glucose-stimulated insulin secretion (GSIS) seen in isolated rat pancreas preparations also applies in vivo. Accordingly, fed and 18-24-h-fasted rats were subjected to an intravenous glucose challenge followed by a hyperglycemic clamp protocol, during which the plasma-insulin concentration was measured. Surprisingly, the acute (5 min) insulin response was equally robust in the two groups. However, after infusion of the antilipolytic agent, nicotinic acid, to ensure low levels of plasma FFA before the glucose load, GSIS was essentially ablated in fasted rats, but unaffected in fed animals. Maintenance of a high plasma FFA concentration by coadministration of Intralipid plus heparin to nicotinic acid-treated rats (fed or fasted), or further elevation of the endogenous FFA level in nonnicotinic acid-treated fasted animals by infusion of etomoxir (to block hepatic fatty acid oxidation), resulted in supranormal GSIS. The in vivo findings were reproduced in studies with the perfused pancreas from fed and fasted rats in which GSIS was examined in the absence and presence of palmitate. The results establish that in the rat, the high circulating concentration of FFA that accompanies food deprivation is a sine qua non for efficient GSIS when a fast is terminated. They also serve to underscore the powerful interaction between glucose and fatty acids in normal beta cell function and raise the possibility that imbalances between the two fuels in vivo could have pathological consequences.     

Computer simulation of fatty acids

Fatty acids modified by sulfhydric collectors are investigated. Three-dimensional molecular models are constructed for these acids and the main computer parameters of the total steric energy are determined. Based on the computer design, new reagents are suggested and molecular models are constructed and the total steric energy is calculated for them.     

Incorporation of 5-substituted uracil derivatives into nucleic acids. Part IV. The synthesis of 5-ethynyluracil

5-Acetyluracil (I) has been treated with POCI3 to give 5-(1-chlorovinyl)-2,4-dichloropyrimidine (II). Treatment of II with KOEt gave a mixture of 2-ethoxy-5-ethynyl-4 (3H)-pyrimidinone (IIIA) and 4-ethoxy-5-ethynyl-2 (1H)-pyrimidinone (IIIB). IIIA and IIIB were isolated and characterised. The mixture of IIIA and IIIB upon treatment with HCI gave 5(1-chlorovinyl)uracil (IV). Reaction of IV with KOEt gave 5-ethynyluracil (V). 5-Ethynyluracil was more easily obtained by the treatment of II with KOH in aqueous dioxan.