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PubMed1979

The incorporation and distribution of 3H oleic acid in the isolated perfused guinea-pig heart: a biochemical and EM autoradiographic study.

The incorporation of 3H oleic acid into tissue lipids of guinea pig heart was studied after 15, 30, 60 or 120 sec perfusion using EM autoradiography with 'hypothetical grain' analysis and lipid analysis by thin-layer chromatography. Radioactivity in triacylglycerol and phospholipid increased and in free fatty acid decreased with time. This corresponded to an increase in radioactivity associated with lipid droplets in the autoradiographs. High levels of radioactivity were found associated with the mitochondria after only 15 sec. The movement of fatty acids is interpreted in terms of transport mechanisms, concentration gradients and bound and unbound molecules.

Animals↗
PubMed1981

Desaturation of Fatty acids associated with monogalactosyl diacylglycerol: the effects of san 6706 and san 9785.

The effects of two substituted pyridazinone herbicides, San 6706 and San 9785, on photosynthesis, dark respiration, and fatty acid metabolism were studied in mature leaf tissue of Vicia faba.Both San 6706 and San 9785 inhibited photosynthesis within 2 hours after initial exposure of leaf tissue to the chemicals although San 9785 was more effective in inhibiting photosynthesis than San 6706. Neither San 6706 nor San 9785 had any marked effect on dark respiration.Kinetic studies using (14)CO(2) indicated that synthesis of 18:3 esterified to monogalactosyl diacylglycerol (MGDG) was not completely inhibited by San 9785 up to 48 hours after feeding. Radioactivity was observed to accumulate in MGDG (digalactosyl diacylglycerol [DGDG] and sulpholipid [SL]) 18:2 at the expense of 18:3 but the specific radioactivity of MGDG 18:3 continued to increase throughout the experiment indicating only partial inhibition of MGDG 18:3 synthesis. No significant differences were observed in the metabolism of other fatty acids. The metabolism of fatty acids from leaf tissue was not affected by treatment with San 6706.The data indicate that there are at least two sites for 18:2 desaturation to form 18:3, one associated with MGDG in the chloroplast, which is inhibited by San 9785, and one or more sites not inhibited by San 9785. The fatty acid specific radioactivity data support the hypothesis that there is vectorial transfer of fatty acids from phosphatidyl choline to MGDG to produce the large quantities of MGDG 18:3 found in higher plant tissue.

Journal Article↗
PubMed1994

In vivo metabolism of [1-14C]linolenic acid (18:3(n-3)) and [1-14C]eicosapentaenoic acid (20:5(n-3)) in a marine fish: time-course of the desaturation/elongation pathway.

The metabolism (via the desaturation/elongation pathways) of [1-14C]18:3(n-3) and [1-14C]20:5(n-3) in a marine fish, gilthead sea bream (Sparus aurata L.), were investigated over 8 days to determine the time-courses for the production of delta 6 and delta 5-desaturase products and 22:6(n-3). Fish were starved for 1 week prior to, and during, the period of the experiment. The recovery of radioactivity from [1-14C]20:5(n-3) in tissue lipids exceeded that of [1-14C]18:3(n-3) at all time points. The recoveries of both fatty acids decreased by 85-89% between days 2 and 8, indicating that substantial loss of radioactivity due to beta-oxidation occurred. Incorporation of 18:3(n-3) and 20:5(n-3) was predominantly into triacylglycerol but during the time-course of the experiment there were decreased percentages of radioactivity from both labelled fatty acids recovered in triacylglycerol with concomitant increased percentages recovered in phospholipids indicating preferential oxidation of fatty acids in triacylglycerol and/or redistribution of incorporated fatty acids. Recovery of radioactivity in 22:6(n-3) was 10-fold greater with [1-14C]20:5(n-3) than with [1-14C]18:3(n-3). However, there were few consistently significant trends in the levels of components of the desaturation/elongation pathways during the time-course of the experiment. In particular, the relative recovery of radioactivity in 22:6(n-3) did not increase during the experiment with either substrate. Substantial amounts of radioactivity were found in 24:5(n-3) and 24:6(n-3), particularly after injection with [1-14C]20:5(n-3), indicating that the conversion of 20:5(n-3) to 22:6(n-3) in sea bream may occur by a pathway utilizing delta 6-desaturase activity rather than by a delta 4-desaturation.

Animals↗
PubMed1993

Influence of fatty acid backdiffusion on compartmental analysis of external detection curves obtained with 123-iodohexadecenoic acid in isolated rat heart.

In isolated rat hearts, we investigated a possible backdiffusion of fatty acids and tried to determine whether it impaired our compartmental analysis of myocardial time-radioactivity curves obtained with an iodinated fatty acid, 16-iodo-9-hexadecenoic acid (IHA). Backdiffusion was not observed directly in the coronary effluents but was estimated by analysis of the external detection curves. Furthermore, when backdiffusion was not taken into account in the mathematical analysis, we obtained similar data on IHA intramyocardial metabolism.

Albumins↗
PubMed1983

Influence of temperature, environmental salinity and fasting on the patterns of fatty acids synthesized by gills and liver of the european eel (Anguilla anguilla).

A rise in temperature on the average from 8 to 28 degrees C resulted in an enhanced relative incorporation of [1-14C]acetate into saturated fatty acids in liver tissue. The same effect was seen in gill tissue, but only after incubation in vitro and when the precursor was injected into the eel. When [1-14C]acetate was added to the water in the incubation tank such a "homeoviscous adaption" was not observed in gill tissue. A rise in temperature resulted in less relative incorporation of radioactivity into saturated gill fatty acids. We attribute this difference to a specific labelling of salt transport cells in the gills, due to the labelled precursor itself taking part in biological ion transport when it is added to the water. It would appear that palmitoleic acid plays a special role in the function of the salt transport cell. When [1-14C]acetate was added to the water in the incubation tank there was a significantly enhanced percentage incorporation into saturated gill fatty acids in fresh water relative to sea water. Fasting led to less relative incorporation of [1-14C]acetate into saturated liver fatty acids in vitro.

Acetates↗
PubMed1992

Generation of arachidonic acid and diacylglycerol second messengers from polyphosphoinositides in ischemic fetal brain.

Intracerebral administration of [3H]arachidonic acid ([3H]ArA) into 19-20-day-old rat embryos, resulted in a rapid incorporation of label into brain lipids. One hour after injection, 55.6 +/- 8.2, 18.0 +/- 3.4, and 13.7 +/- 1.3% of the total radioactivity was associated with phosphatidylcholine, phosphatidylinositol, and phosphatidylethanolamine, respectively. Approximately 10% of radioactivity was found acylated in neutral lipids of which free ArA comprised only 1.5 +/- 0.2% of the total radioactivity. Complete restriction of the maternal-fetal circulation for < or = 40 min did not affect the rate of [3H]ArA incorporation (t1/2 = 2 min) into fetal brain lipids, suggesting an effective acylation mechanism that proceeds irrespective of the impaired blood flow. After a short restriction period (5 min), the radioactivity in diacylglycerol was elevated by 50%. After a longer restriction period (20 min), the radioactivity in the free fatty acid and diacylglycerol fractions increased to values of 130 and 87%, respectively. Polyphosphoinositides prelabeled with either [3H]ArA or 32P were rapidly degraded after 5 min of ischemia. After 20 min, the decrease in phosphatidylinositol-4-phosphate and phosphatidylinositol-4,5-bisphosphate radioactivity was 47 and 70%, respectively. Double labeling of phospholipids with [14C]palmitic acid and [3H]ArA indicated a preferential loss of [3H]ArA within the polyphosphoinositide species after 20 min, but not after 5 min of ischemia. The specific activity of [14C]palmitate remained unchanged. The current data suggest phospholipase C-mediated diacylglycerol formation at the beginning of the insult followed by a phospholipase A2-mediated ArA liberation at a later time, both enzymes presumably acting preferentially on polyphosphoinositide species.

Animals↗
PubMed1990

Effect of albumin on oleic acid lymphatic absorption in rats.

1. The aim of this study was to investigate how fatty acid absorption was affected when exogenous fatty acids were complexed with albumin in absence of bile. Experiments were carried out in vivo, in order to study overall absorption processes. 2. An equimolar mixture of 14C oleic acid, palmitic acid and monopalmitin was infused intraduodenally in bile- and pancreatic juice-diverted rats. 3. Lipids were emulsified with either sodium taurocholate or fatty acids complexed with albumin. 4. Lymphatic lipid output was compared during the 6 hr following infusion of 90 mumol of the radioactive lipid mixture. 5. Lymphatic radioactive lipid recovery was significantly decreased by albumin. 6. Only 17% of the infused radioactivity was recovered in lymph when fatty acids were complexed with albumin against 37% when lipids were emulsified with sodium taurocholate. 7. Unrecovered lymph radioactivity was found at the distal part of intestine. Moreover, albumin significantly decreased lymph flow. 8. We conclude that undigested albumin acted at the luminal level of lipid absorption processes and specifically decreased fatty acid uptake.

Absorption↗
PubMed1976

The influence of vitamin E deficiency and combined deficiency in vitamin E and polyunsaturated fatty acids on the biosynthesis and degradation of rat central nervous system myelin.

The ability to incorporate intracranially injected 14C-labelled leucine into central nervous system (CNS) myelin was studied in developing rats fed a control diet, a diet deficient in vitamin E and a diet deficient both in vitamin E and polyunsaturated fatty acids. The turnover of radioactivity incorporated into myelin and the distribution of radioactivity between the individual proteins of rat CNS myelin at various stages of the deficiency state was studied. Impaired myelin formation was found in cases of both types of deficiency. The level of incorporated radioactivity was raised by both types of deficiency throughout the experimental period. The mean half life of myelin radioactivity was found higher in combined deficient animals as compared to control and vitamin-E-deficient rats. The distribution of radioactivity between myelinproteins, separated by polyacrylamide gel electrophoresis, appeared identical in the three experimental groups.

Age Factors↗
PubMed1983

Evidence that the multifunctional polypeptides of vertebrate and fungal fatty acid synthases have arisen by independent gene fusion events.

The enoyl reductase (NADPH binding site) of rabbit mammary fatty acid synthase has been radioactively labelled using pyridoxal phosphate and sodium [3H]borohydride. Using this method we have been able to add this site to the four sites whose location has already been mapped within the multifunctional polypeptide chain of the protein. The results show that the enoyl reductase lies between the 3-oxoacylsynthase and the acyl carrier. This confirms that the active sites occur in a different order on the single multifunctional polypeptide of vertebrate fatty acid synthase and the two multifunctional polypeptides of fungal fatty acid synthase, and suggests that these two systems have arisen by independent gene fusion events.

Animals↗
PubMed1992

Distribution of radioactivity of 14C-amino acids added to the medium in cells and metabolites in cultures of rumen fungi.

A mixture of L-(U-14C) amino acids was added to cultures of 11 strains of rumen anaerobic fungi belonging to Neocallimastix frontalis, Neocallimastix joyonii, Sphaeromonas communis and Piromonas communis. Fungi were grown in a complex medium with glucose for 4 days. The radioactivity was found in cellular protein (27.7-65.3% of the total radioactivity recovered), lactate (16.9-41.8%), volatile fatty acids (7.4-25.7%) and ethanol (4.6-10.5%). A small amount of radioactivity was recovered in lipids (0.2-1.8%) and CO2 (0.3-1.0%). The results suggest that the assimilation of amino acids by growing fungal cells was quantitatively comparable with their dissimilation to metabolites.

Amino Acids↗
PubMed1978

Fatty acid synthesis by isolated chromoplasts from the daffodil. [14C]Acetate incorporation and distribution of labelled acids.

Isolated daffodil (Narcissus pseudonarcissus) chromoplasts showed high rates of [14C]acetate incorporation into lipids. The fatty acids synthesized were predominantly palmitic acid (93%). The radioactivity incorporated was shared mainly between long-chain acyl-CoA (25%), free fatty acids (24%), phosphatidic acid (17%), diacylglycerol (15%), and phosphatidycholine (11%). Galactolipids were not labelled. ATP, NaHCO3, and also the structural integrity of the organelles were essential. Omission of exogenous CoA led to a decreased incorporation (49%); under these conditions the label was distributed mainly between free fatty acids (66%) and diacylglycerol (19%). Addition of lysophosphatidylcholine increased the labelling of phosphatidylcholine, whereas addition of glycerol 1-phosphate increased the labelling of phosphatidic acid and diacylglycerol. Acyl-CoA synthetase and acyl thioesterase (acyl-Coa) activities could be demonstrated. The results are discussed in terms of chromoplasts as non-photosynthetic organelles exhibiting high lipid-synthesizing capabilities.

Acetates↗
PubMed1971

La localisation microsomale de la synthese des acides gras dans le foie de la souris vivante.

Mice were given glucose-U-(14)C and the radioactivity of triglyceride and phospholipid glycerol and fatty acids was measured 30 sec, 3 or 30 min after the i.v. administration in liver microsomes and supernatant. After the acetate administration the radioactivity of palmitic and stearic acids and that of their carboxyl carbons was also measured. The repartition of the radioactivity was discussed in relation with the localization of fatty acid synthesis. In agreement with our previous results it was suggested that the endoplasmic reticulum is the main site of this synthesis.

Journal Article↗
PubMed1975

Uptake and metabolism of alpha-monopalmitin by rat lung in vitro.

CO2 production from and uptake of alpha-glyceryl mono (palmitate-1-14C) were studied in an in vitro system using minced rat lung. Monoglyceride radioactivity was readily incorporated into lung tissue lipids. In a time course of 5-120 min, ca. 2.9-21.9% of the initial medium 14C-radioactivity was recovered in tissue lipids, including free fatty acid and monoglyceride, per one g of tissue. From 93 to 72% of the initial radioactivity remained in the medium during the same incubation periods. The ratio of tissue neutral lipid to phospholipid radioactivity decreased from 2:1 at 5 min to ca. 1:2.1 at 120 min. Most of the phospholipid-14C was in phosphatidyl choline, and this accounted for 80% of phospholipid-14C. Analysis of the tissue lipid radioactivity pattern revealed that during early periods of incubation (5-15 min) there was a rapid accumulation of 14C in monoglycerides and free fatty acids, which decreased with increasing incubation time concomitant with increase in radioactivity of tissue phospholipids and triglycerides. During the same time course, 6.5-85.3% of medium-14C was in free fatty acid, indicating the presence of an active alpha-monopalmitin-hydrolyzing system. After 2 hr of incubation, only 1.8% of the initial medium-14C had been oxidized to CO2. Under the same experimental conditions, 14C-alpha-monopalmitin and palmitate-1-14C were almost equally utilized and the patterns of lipid incorporated from both substrates were similar. It is suggested that rat lungs can utilize alpha-monopalmitin in a similar manner as palmitate after the former is hydrolyzed.

Animals↗
PubMed1976

Simple assay for the condensation component enzyme (beta-ketoacyl synthetase) of fatty acid synthetase.

A simple assay is described for estimating the activity of the condensation component enzyme (beta-ketoacyl synthetase) of the yeast fatty acids synthetase complex. The radioactivity liberated as 14CO2 from [1,3-14C]malonyl-CoA was trapped in phenethylamine and measured by liquid scintillation spectroscopy. Three enzyme-catalysed steps are involved: acetyl-CoA transacylase, malonyl-CoA transacylase and beta-ketoacyl synthetase; however, beta-ketoacyl synthetase is rate-limiting. beta-Ketoacyl synthetase activity was made independent of subsequent enzyme activities of the complex by excluding NADPH from the assay, thus blocking beta-ketoacyl reductase and preventing fatty acid synthesis. By this assay beta-ketoacyl synthetase activity was about 0.28 of the activity of the complex for fatty acid synthesis, compared with approximately 0.001 for published assays. Several pyridine nucleotides and derivatives were tested after it was discovered that NADH stimulated beta-ketoacyl synthetase activity to a greater extent than could be accounted for by its reactivity in providing a pathway from acetoacetyl-enzyme to fatty acid synthesis. Presumably, the release of acetoacetate from the central sulphydryl of the complex is the rate-limiting step in the assay procedure.

Acetyl Coenzyme A↗
PubMed1977

Stability of lactic Acid bacteria to freezing as related to their Fatty Acid composition.

The viability of Streptococcus lactis and Lactobacillus sp. A-12 after freezing at -17 degrees C for 48 h was better preserved when the cells were grown in medium supplemented with oleic acid or Tween 80 (polyoxyethylene sorbitan monooleate). A pronounced change in the cellular fatty acid composition was noted when the bacteria were grown in the presence of Tween 80. In S. lactis the ratio of unsaturated to saturated fatty acids increased from 1.18 to 2.55 and in Lactobacillus sp. A-12 it increased from 0.85 to 1.67 when Tween 80 was added to the growth medium. The antibiotic cerulenin markedly inhibited the growth of lactic acid bacteria in tomato juice (TJ) medium but had almost no effect on the growth of the bacteria in TJ medium containing Tween 80 (or oleic acid). The antibiotic inhibited markedly the incorporation of [1-C]acetate but had no inhibitory effect on the incorporation of exogenous [1-C]oleate (or [1-C]palmitate) into the lipid fractions of lactic acid bacteria. Thus, the fatty acid composition of lactic acid bacteria, inhibited by the antibiotic cerulenin, can be modulated by exogenously added oleic acid (or Tween 80) without the concurrent endogenous fatty acid synthesis from acetate. The data obtained suggest that cerulenin inhibits neither cyclopropane fatty acid synthesis nor elongation of fatty acid acyl intermediates. The radioactivity of cells grown in the presence of [1-C]oleate and cerulenin was associated mainly with cyclopropane Delta19:0, 20:0 + 20:1, and 21:0 acids. As a consequence, cerulenin caused a decrease in the ratio of unsaturated to saturated fatty acids in lactic acid bacteria as compared with cells grown in TJ medium plus Tween 80 but without cerulenin. Cerulenin caused a decrease in the viability of S. lactis and Lactobacillus sp. A-12 after freezing at -17 degrees C for 48 h only when Tween 80 was present in the growth medium. We conclude that the sensitivity of lactic acid bacteria to damage from freezing can be correlated with specific alterations in the cellular fatty acids.

Journal Article↗
PubMed1990

Lipid synthesis in vitro by rabbit Meibomian gland tissue and its inhibition by tetracycline.

Rabbit Meibomian gland tissue was incubated with radioactive acetate, propionate, valine, leucine or isoleucine. The time-course of incorporation of radioactivity into total lipids from acetate and isoleucine was studied in Hanks' or Krebs medium. Incorporation of acetate or isoleucine into lipid classes was followed by TLC, and of acetate label into individual fatty acids and alcohols by GLC with radioactivity detection. Radioactivity was highest in the minor acid components C16:1 and C18:1. Levels in branched fatty acids fell with chain length, reflecting the time-course of successive chain elongations. Use of amino acids or propionate as precursors suggested that molecules containing a specific branched structure were preferentially incorporated; this indicates a binding preference at the level of the fatty acid synthase which might explain the very high proportion of anteiso-branched structures in the rabbit secretion. Incorporation of label into total lipids was significantly reduced by tetracycline in the medium, with 50% reduction at about 1.5 mg/ml for acetate and 0.7 mg/ml for isoleucine.

Amino Acids↗
PubMed1992

Administration modalities and intestinal lymph absorption of arachidonic acid in rats.

We investigated the effects of the proportion of arachidonic acid on lymph lipoprotein synthesis in rats, when infused in the presence of lipids with varying degrees of saturation. A single dose of 90 mumol of lipid was administered intraduodenally and intestinal lymph was collected. Emulsion lipid constituents were 90 mumol of [14C]arachidonic acid alone, or either 30 mumol of [14C]arachidonic acid or 5 mumol of [14C]arachidonic acid and 25 mumol of linoleic acid, with 30 mumol of a free fatty acid and 30 mumol of a monoglyceride (the more saturated: oleic acid + monopalmitin; the more unsaturated: linoleic acid + monoolein). Radioactive lymph recovery of [14C]arachidonic acid infused alone reached 32.6 +/- 1.3% of the radioactivity administered and the presence of another fatty acid and a monoglyceride increased it from 38.7 +/- 2.6 to 51.9 +/- 1.1%. For 30 mumol of arachidonic acid, integration into lymph phospholipids was higher when arachidonic acid was infused with oleic acid and monopalmitin than with linoleic acid and monoolein (7.3 +/- 2.7 and 2.8 +/- 0.2% at the absorption peaks, respectively), and it was 4.8 +/- 0.5% when arachidonic acid was infused alone. For 5 mumol of arachidonic acid, the degree of unsaturation of the added lipid did not modify phospholipid incorporation, which was maintained at 6.9 to 7.2%. The proportion and size of chylomicrons increased with the degree of lipid emulsion unsaturation. Percentages of [14C]phospholipids and of chylomicrons were highly correlated. The proportion of arachidonic acid and degree of lipid emulsion unsaturation affected lymphatic arachidonic acid absorption modalities.

Animals↗