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1.
The incorporation of [1-14C] acetate into fatty acids by cultured epimastigotes ofTrypanosoma cruzi was studied. After 8, 24, and 48 hr incubation with labeled precursor, up to 2.8% of the initial radioactivity added to the
medium was found in theT. cruzi long chain fatty acids. Saturated (16∶0 and 18∶0), monounsaturated (18∶1ω9), and diunsaturated (18∶2ω6) fatty acids were
synthesized. Both the pattern of incorporation of labeled acetate into the fatty acids and the decarboxylation ratios found
suggest that de novo synthesis of fatty acids has taken place. 相似文献
2.
Ricardo J. Pollero 《Lipids》1983,18(1):12-17
Neutral lipid, phospholipids and fatty acids of the sea anemonePhymactis clematis from the south-west Atlantic were characterized and quantified in spring and autumn. Neutral lipids predominated over phospholipids
in both seasons. Triacylglycerol and diacylglycerol ethers were the major lipids. In spring, an increase of esterified sterols
was noted. The major fatty acids found were 22∶5ω3, 20∶5ω3 and 16∶0. The sea anemones were also incubated in vivo with either
[1-14C]linoleate or [1-14C] α-linolenate for 2 hr. Isotope incorporation into lipids and their transformations into higher fatty acids were examined.
Both precursors were incorporated into the lipids, mainly in triacylglycerols and mono-acylglycerols, while α-linolenate was
also incorporated into phospholipids. The radioactive linoleate was elongated to 20∶2, 22∶2 and 24∶2 fatty acids, but not
desaturated to 18∶3ω6. α-Linolenate was desaturated by Δ6 desaturase to 18∶4ω3. The specificity of Δ6-desaturase is discussed. 相似文献
3.
Fifteen-day-old rats divided into two groups were given [1-14C]acetate or [U-14C] glucose by intracranial injection and were sacrificed after 1 hr. Analysis of lipids from the two groups showed differences
in the incorporation of radioactivity in the polar lipids and cholesterol. Analysis of brain fatty acid showed that whereas
radioactivity from acetate was incorporated into saturated, monoand polyunsaturated fatty acids, the radioactivity from [U-14C] glucose was found only in 16∶0, 18∶0, and 18∶1. No radioactivity was found in polyunsaturated fatty acids even after concentration
of this fraction by AgNO3:SiO2 thin layer chromatographic method. This difference is discussed in hypothetical terms of nonhomogeneous acetyl CoA pool,
formation of acetyl CoA from glucose exclusively inside the mitochondria, and activation of injected acetate to acetyl CoA. 相似文献
4.
The incorporation of [1-14C]linoleic acid, and [1-14C]linoleic acid into cellular lipids of cultured human skin fibroblasts was studied. Cultured cells took up both labeled fatty
acids at nearly the same rate and incorporated them into a variety of lipid classes. At the end of 1 hr incubation with [1-14C]linoleic acid, radioactivity was found in the triacylglycerol (TG) and choline phosphoglyceride (CPG) pools preferentially.
Incorporation into the TG fraction decreased rapidly, while the uptake into CPG, serine phosphoglyceride (SPG), and ethanolamine
phosphoglyceride (EPG) fractions increased progressively with longer incubation times. Similar results were obtained with
[1-14C]linoleic acid as precursor. At the end of 24 hr, desaturation and chain elongation of 18∶3 n−3 was more extensive than conversion
of 18∶2 n−6 to higher polyenoic acids. During pulse-chase experiments with either fatty acid precursor, the incorporated radioactivity
was progressively lost from cellular lipids, particularly from the TG and CPG fractions, but continued to increase in the
SPG and EPG pools. The similar labeling pattern of cellular phospholipids with linoleic or linolenic acids, and data from
pulse-chase studies suggest that a direct transfer of fatty acids from CPG to EPG is a likely pathway in fibroblast cultures.
Incorporation into the EPG pool during the pulse-chase experiments paralleled extensive desaturation and elongation of linoleic
acid into 20∶4 n−6, and 22∶4 n−6; and of linolenic acid into 22∶5 n−3 and 22∶6 n−3. 相似文献
5.
Isolated bovine meibomian glands incorporated exogenous [1-14C] acetate into lipids. Thin layer chromatographic analysis of the lipids showed that wax esters and sterol esters contained
61% of the total label. Radio gas liquid chromatographic analysis of the acid and alcohol moieties of both ester fractions
showed the label was distributed equally between the two portions of the ester in both cases. Cholesterol and 5-α-cholest-7-en-3β-ol
were the major labeled sterols, and anteiso-C25, anteiso-C27 and anteiso-C23 were the most highly labeled alcohols. The major
labeled fatty acids in the wax esters were anteiso-C15,n-C16, anteiso-C17 andn-C18∶1, whereas anteiso-C25 and anteiso-C27 were the major labeled acids in the sterol esters. The diester region with 6%
of the total label contained labeled fatty acids and fatty alcohols each with anteiso-C25 as the major component and ω-hydroxy
acids in whichn-C32∶1 was the major labeled component. The trigly ceride fraction which contained 8% of the total lipids was composed of
labeled fatty acids similar to those found in both sterol and wax ester fractions. Chromatographic analyses of the labeled
lipids derived from exogenous labeled isoleucine showed that anteiso-branched products were preferentially labeled. The labeled
triglyceride fraction derived from [U-14C] isoleucine also contained esterified C15, C13, C11, C9, C7 and possibly shorter anteisobranched acids. 相似文献
6.
The de novo biosynthesis of fatty acids in the wild, calanoid copepodParacalanus parvus was studied. The incubation of labeled acetate proved the de novo biosynthesis of saturated and monounsaturated even fatty
acids from 14 to 20 carbons and the 22∶1 acid. Saturated and monounsaturated uneven fatty acids from 15 to 21 carbons were
also synthesized. The copepod could not synthesize linoleic and α-linolenic acids. By administration of [1-14C]palmitate, [1-14C] stearate and [1-14C]oleate, it was possible to elucidate the general pattern of the de novo biosynthesis of fatty acids in the wildP. parvus. 相似文献
7.
Uptake of fatty acids by the developing rat brain 总被引:1,自引:0,他引:1
Polyunsaturated fatty acids are avidly taken up by the developing rat brain. To explore the specificity of this process, [1-14C]labeled 16∶0, 18∶2n−6, 18∶3n−3, and 22∶6n−3 each were co-injected with [3H]18∶1n−9 into the jugular vein of two-wk-old functionally hepatectomized and shamoperated control rats. The radioactivities
present in the brain, liver and serum were assessed 30 min after injection. Uptake of labeled fatty acids into brain lipids
steadily increased with increasing degree of unsaturation, with more than twice as much uptake of 22∶6n−3 compared to 16∶0.
Phosphatidylcholine was the principal radioactive species in the brain except for animals injected with [1-14C]22∶6n−3, in which more of the label was incorporated into phosphatidylethanolamine. Determination of watersoluble oxidation
products in the brain and serum revealed that the greater uptake of the more unsatrated fatty acids did not result from differences
in rates of degradation. 相似文献
8.
The incorporation of [2-14C]acetate into the lipids of normal and peroxisome-deficient (Zellweger's syndrome) skin fibroblasts was examined. Most of
the label was incorporated into triacyglycerol fatty acids in normal as well as Zellweger's syndrome cells. Triacylglycerols
and cholesteryl esters in Zellweger's syndrome cells contained increased levels of labelled saturated and monounsaturated
very long-chain fatty acids (VLCFA, that is fatty acids with more than 22 carbon atoms), in particular hexacosanoic (26∶0)
and hexacosaenoic (26∶1) acids. As traces of labelled VLCFA with up to 32 carbon atoms were detected in triacylglycerols even
in control cells it is probable that these fatty acids are formed naturally during the elongation process. Our data suggest
that peroxisomes are involved in the chain shortening of the saturated and monounsaturated VLCFA. 相似文献
9.
Incorporation and metabolic conversion of erucic acid in various tissues of the rat in short term experiments 总被引:1,自引:1,他引:0
Rats were intravenously injected with a mixture of free (14-14C) erucic acid (22∶1) and (9–103H) oleic acid (18∶1). After 2, 4, 8, 16, and 30 min, radioactivity was examined in blood, liver, heart, kidneys, and spleen.
Free (14C) 22∶1 disappeared from the blood more rapidly than free (14C) 18∶1 between 0 and 8 min. Incorporation of label into triglycerides only appeared after 16 min and at 30 min they represented
4% of the injected radioactivity. In this fraction, 63% of14C radioactivity was present as 18∶1 and not as the original 22∶1, while almost all3H radioactivity was recovered as unchanged 18∶1. At all times studied, the majority of radioactivity was found in the liver,
primarily as triglycerides (60% of radioactivity in total lipids) and as phospholipids (20–30%).14C was present in nearly the same proportion as3H (13% of injected radioactivity after only 2 min, 11% at 30 min).14C radioactivity was contained in 18∶1 in higher proportion than 22∶1 (45% in triglycerides, 65% in phospholipids). Since labeled
triglycerides of blood, rich in (14C) 18∶1, mainly originate from the liver triglycerides, it appears that 18∶1 is the major form of utilization of 22∶1 in the
tissues after its conversion in liver. In the other organs tested, radioactivity was found 10–15 times lower than in liver.
In the heart,14C was 3 to 4 times higher than3H. More than 80% was recovered as 22∶1 in triglycerides. In spleen and kidneys, the14C:3H ratio was particularly high in free fatty acids and monoglycerides. In kidneys, 60% of14C was present as nervonic acid (24∶1) in monoglycerides and 40% in phospholipids, suggesting that the mononervonin formed
was used for phospholipid biosynthesis.
A preliminary report of this work was presented at the 10th International Congress of Nutrition, Kyoto, Japan, August 1975. 相似文献
10.
Suspension cell cultures of cocoa bean rapidly incorporated palmitic, stearic, oleic and linoleic acids into cellular lipids.
Thus, 75 and 20% of [1-14C] palmitic acid was incorporated into polar lipids and triglycerides, respectively, after 48 hr. When [1-14C] oleic and [1-14C] linoleic acid were added separately, polar lipids consistently contained most of the radioactive fatty acids. Ca. 60% of
the stearic acid accumulated as unesterified fatty acid in the cells. Palmitic and stearic acid were not desaturated, but
oleic acid and linoleic acid were further desaturated. The kinetics of conversion of oleic acid and linoleic acid suggested
a sequential desaturation pathway of 18∶1→18∶2→18∶3 in cocoa bean cell suspensions. 相似文献
11.
Which cell type is responsible for the high levels of very long chain polyunsaturated fatty acids in testis and whether this
fatty acid pattern is a result of a local synthesis are not presently known. In this study, fatty acid conversion from 20∶4n−6
to 22∶5n−6 and from 20∶5n−3 to 22∶6n−3 was investigated in isolated rat germ cells incubated with [1-14C]-labeled fatty acids. The germ cells elongated the fatty acids from 20- to 22-carbon atoms and from 22- to 24-carbon atoms
but had a low Δ6 desaturation activity. Thus, little [14C]22∶5n−6 and [14C]22∶6n−3 were synthesized. When Sertoli cells were incubated with [1-14C]20∶5n−3 for 24 h, an active fatty acid elongation and desaturation were observed. In vivo germ cells normally have a higher content of 22∶5n−6 or 22∶6n−3 than Sertoli cells. An eventual transport of essential fatty
acids from Sertoli cells to germ cells was thus studied. Different co-culture systems were used in which germ cells were on
one side of a filter and Sertoli cells on the opposite side. When isolated pachytene spermatocytes or round spermatids were
added to the opposite side of a semipermeable filter, approximately 1 nmol [14C]-22∶6n−3 crossed the filter. Little of this was esterified in the germ cells. Similarly, in using [1-14C]20∶4n−6 in identical experiments, very little [14C]22∶5n−6 was esterified in germ cells on the opposite side of the filter. Although the very active synthesis of 22∶5n−6 and
22∶6n−3 observed in Sertoli cells suggests a transport of these compounds to germ cells, this was not experimentally determined. 相似文献
12.
The biosynthesis of fatty acids in the diatomPhaeodactylum tricornutum was studied. The diatom was incubated with sodium [114C] acetate and the acids [1-14C] palmitic, [1-14C] stearic, [1-14C] linoleic and [1-14C] α-linolenic. The distribution of radioactivity in the products was determined by gas liquid radiochromatography. The diatom
synthesized “de novo” not only saturated and monounsaturated fatty acids, but also linoleic, α-linolenic and other fatty acids
including the highly polyunsaturated 20∶5ω3 and 22∶6ω3. When labeled acetate, stearic, α-linolenic or even linoleic acid were
incubated with the diatom, the polyunsaturated C20 fatty acids synthesized belonged predominantly to the ω 3 family. The existence of Δ9, Δ6, Δ5, Δ4, ω6 and possibly ω3 desaturases
inP. tricornutum is suggested.
Member of the Carrera del Investigador Científico of the Comisión de Investigaciones Científicas de la Provincia de Buenos
Aires.
Member of the Carrera del Investigador Cientifico of the Consejo Nacional de Investigaciones Cientificas y Técnicas. 相似文献
13.
A mixture ofcis-9-[1-14C] octadecenol and [1-14C] docosanol was injected into the brains of 19-day-old rats, and incorporation of radioactivity into brain lipids was determined
after 3, 12, and 24 hr. Both alcohols were metabolized by the brain but at different rates; each was oxidized to the corresponding
fatty acid, but oleic acid was more radily incorporated into polar lipids. Substantial amounts of radioactivity were incorporated
into 18∶1 alkyl and alk-1-enyl moieties of the ethanolamine phosphoglycerides and into 18∶1 alkyl moieties of the choline
phosphoglycerides. Even after the disappearance of the 18∶1 alcohol from the substrate mixture (12 hr), the 22∶0 alcohol was
not used to any measurable extent for alkyl and alk-1-enyl glycerol formation. 相似文献
14.
Liver nuclear incorporation of stearic (18∶0), linoleic (18∶2n−6), and arachidonic (20∶4n−6) acids was studied by incubation
in vitro of the [1-14C] fatty acids with nuclei, with or without the cytosol fraction at different times. The [1-14C] fatty acids were incorporated into the nuclei as free fatty acids in the following order: 18∶0>20∶4n−6≫18∶2n−6, and esterified
into nuclear lipids by an acyl-CoA pathway. All [1-14C] fatty acids were esterified mainly to phospholipids and triacylglycerols and in a minor proportion to diacylglycerols.
Only [1-14C] 18∶2n−6-CoA was incorporated into cholesterol esters. The incorporation was not modified by cytosol addition. The incorporation
of 20∶4n−6 into nuclear phosphatidylcholine (PC) pools was also studied by incubation of liver nuclei in vitro with [1-14C]20∶4n−6-CoA, and nuclear labeled PC molecular species were determined. From the 15 PC nuclear molecular species determined,
five were labeled with [1-14C]20∶4n−6-CoA: 18∶0–20∶4, 16∶0–20∶4, 18∶1–20∶4, 18∶2–20∶4, and 20∶4–20∶4. The highest specific radioactivity was found in
20∶4–20∶4 PC, which is a minor species. In conclusion, liver cell nuclei possess the necessary enzymes to incorporate exogenous
saturated and unsaturated fatty acids into lipids by an acyl-CoA pathway, showing specificity for each fatty acid. Liver cell
nuclei also utilize exogenous 20∶4n−6-CoA to synthesize the major molecular species of PC with 20∶4n−6 at the sn-2 position. However, the most actively synthesized is 20∶4–20∶4 PC, which is a quantitatively minor component. The labeling
pattern of 20∶4–20∶4 PC would indicate that this molecular species is synthesized mainly by the de novo pathway. 相似文献
15.
The effects of hypophysectomy and of testosterone administration on lipid composition and metabolism of rat testicular tissue
have been investigated. Increased concentrations of triacylglycerols and cholesterol were observed in testes of hypophysectomized
compared to control (non-hypophysectomized) rats on the eighth day posthypophysectomy. Administration of testosterone maintained
the concentrations of these lipids at about normal levels. The concentration of phospholipids was not affected by the hypophysectomy.
Incorporation of14C from 1-[14C] linoleate into testicular lipids was determined 24 hours after intratesticular injection. In hypophysectomized compared
to control rats there was more14C in C 16∶0, C 20∶2 and C 20∶3 and less14C in C 20∶4 and C 22∶4 of both phospholipids and triacylglycerols. After intratesticular injection of 1-[14C] eicosatrienoate there was more14C in C 16∶0 and C 20∶3 and less14C in C 20∶4 and C 22∶4 of both phospholipids and triacylglycerols of hypophysectomized compared to control rats. Intratesticular
injection of 1-[14C]-arachidonate resulted in less14C incorporation in C 22∶4 in testes of hypophysectomized than in those of control rats. Treatment with testosterone did not
affect the metabolism of any of the14C-substrates. These results indicate that the testicular desaturation of C 20∶3 to arachidonate, requiring a Δ5 desaturase,
is inhibited by hypophysectomy and that testosterone by itself may control the concentrations of some testicular lipid classes
but not the metabolism of the polyenoic acids. 相似文献
16.
The differential uptake and targeting of intravenously infused [1-14C]palmitic ([1-14C] 16∶0) and [1-14C]arachidonic ([1-14C]20∶4n−6) acids into heart lipid pools were determined in awake adult male rats. The fatty acid tracers were infused (170
μCi/kg) through the femoral vein at a constant rate of 0.4 mL/min over 5 min. At 10 min postinfusion, the rats were killed
using pentobarbital. The hearts were rapidly removed, washed free of exogenous blood, and frozen in dry ice. Arterial blood
was withdrawn over the course of the experiment to determine plasma radiotracer levels. Lipids were extracted from heart tissue
using a two-phase system, and total radioactivity was measured in the nonvolatile aqueous and organic fractions. Both fatty
acid tracers had similar plasma curves, but were differentially distributed into heart lipid compartments. The extent of [1-14C]20∶4n−6 esterification into heart phospholipids, primarily choline glycerophospholipids, was elevated 3.5-fold compared
to [1-14C]16∶0. The unilateral incorporation coefficient, k
*, which represents tissue radioactivity divided by the integrated plasma radioactivity for heart phospholipid, was sevenfold
greater for [1-14C]20∶4n−6 than for [1-14C]16∶0. In contrast, [1-14C]16∶0 was esterified mainly into heart neutral lipids, primarily triacylglycerols (TG), and was also found in the nonvolatile
aqueous compartment. Thus, in rat heart, [1-14C]20∶4n−6 was primarily targeted for esterification into phospholipids, while [1-14C]16∶0 was targeted for esterification into TG or metabolized into nonvolatile aqueous components. 相似文献
17.
The amount of docosahexaenoate (22∶6n−3)-containing phospholipid species decreases with aging in the rat retina. Most lipids,
but especially choline and serine glycerophospholipids, show a significant fall in 22∶6n−3, which is not compensated by increases
in other polyenoic fatty acids. The decrease not only affects 22∶6 but also various very long chain n−3 hexaenoic fatty acids
which, in phosphatidylcholine, have up to 36 carbon atoms, and which are probably synthesized by successive elongations of
22∶6n−3. The in vitro incorporation of [2-3H] glycerol into retinal lipids indicates that the de novo biosynthetic pathways are not impaired by aging. The incorporation
of [1-14C]docosahexaenoate is significantly stimulated into all lipids of aged retinas, but to the largest extent in those showing
the largest decreases in 22∶6, especially in choline glycerophospholipids. The results indicate that the decreased levels
of 22∶6 with aging are due not to an impaired activity of the enzymes involved in the synthesis and turnover of phospholipids
but to a decreased availability of this polyene in the retina. It is suggested that this may stem from a defect in some of
the enzymatic steps that lead to the synthesis of 22∶6n−3, probably that catalyzed by Δ4 desaturase, the effect on longer hexaenes being secondary to the decreased synthesis of 22∶6. 相似文献
18.
Two unusual lipid classes were detected by thin-layer chromatography in the neutral lipids derived from goat cauda-epididymal
sperm plasma membrane. The lipids were identified as wax esters and 1-O-alkyl-2,3-diacylglycerols based on chromatographic properties, identity of their hydrolysis products, and infrared/1H nuclear magnetic resonance spectral evidence. The membrane containedca. 3 and 5 μg/mg protein of wax esters and alkyldiacylglycerols, respectively. The relative proportions of wax esters and alkyldiacylglycerols
in the total neutral lipids were 1.5% and 2.4%, respectively. The lipids contained fatty acids with chain lengths of C14 to C22. The major fatty acids of the wax esters were 14∶0, 16∶0, 16∶1ω7, 18∶0 and 18∶1ω9. The fatty acids in alkyldiacylglycerol
were 16∶0, 18∶0, 22∶5ω3 and 22∶6ω3. Alkyldiacylglycerol was particularly rich in docosahexaenoic acid 22∶6ω3) representing
30% of the total fatty acids. The alcohols of wax ester were all saturated with C20–C29 carbon chains. The deacylated products derived from alkyldiacylglycerols were identified as hexadecyl, octadecyl and octadec-9′-enyl
glycerol ethers. 相似文献
19.
Two groups of rats were fed diets containing 20% by weight of either partially hydrogenated marine oil supplemented with sunflower
seed oil (PHMO) or palm oil (PO) for 8 wk. Using a liver perfusion system, the effect of dietary long chain monoenoic fatty
acids on the uptake and metabolism of [14-14C]erucic acid was studied. The perfusion times were 15 and 60 min, respectively. The two groups showed equal ability for erucic
acid uptake in the liver but differed in the channeling of the fatty acids into various metabolic pathways. A higher metabolic
turnover of 22∶1 in the PHMO livers relative to the PO livers was demonstrated by an increased recovery of total [14C]labeling in the triglyceride (TG) and phospholipid (PL) fractions, already evident after 15 min of perfusion. The chainshortening
capacity was highest in the PHMO group, reflected by a higher [14C]18∶1 incorporation in both TG and PL, and increasing from 15 to 60 min of perfusion. The amount of [14C]18∶1 found in PL and TG after 60 min of perfusion of livers from rats fed PO corresponded to that shown for the PHMO group
after 15 min. The PL demonstrated a discrimination against 22∶1 compared to TG, and, when available, 18∶1 was highly preferred
for PL-synthesis.
The total fatty acid distribution in the TG, as determined by gas liquid chromatography (GLC), reflected the composition of
the dietary fats. In the total liver PL, 22∶1 and 20∶1 were present in negligible amounts, although the PHMO diet contained
12–13% of both 22∶1 and 20∶1. In the free fatty acid fraction (FFA), the major part of the radioactivity (≈80%) was [14-14C]erucic acid, and only small amounts of [14C]18∶1(<2%) were presents, even after 60 min of perfusion. The shortened-chain 18∶1 was readily removed from the FFA pool
and preferentially used for lipid esterification. 相似文献
20.
Marine fish have an absolute dietary requirement for C20 and C22 highly unsaturated fatty acids. Previous studies using cultured cell lines indicated that underlying this requirement in
marine fish was either a deficiency in fatty acyl Δ5 desaturase or C18–20 elongase activity. Recent research in turbot cells found low C18–20 elongase but high Δ5 desaturase activity. In the present study, the fatty acid desaturase/elongase pathway was investigated
in a cell line (SAF-1) from another carnivorous marine fish, sea bream. The metabolic conversions of a range of radiolabeled
polyunsaturated fatty acids that comprised the direct substrates for Δ6 desaturase ([1-14C]18∶2n−6 and [1-14C]18∶3n−3), C18–20 elongase ([U-14C]18∶4n−3), Δ5 desaturase ([1-14C]20∶3n−6 and [1-14C]20∶5n−3), and C20–22 elongase ([1-14C]20∶4n−6 and [1-14C]20∶5n−3) were utilized. The results showed that fatty acyl Δ6 desaturase in SAF-1 cells was highly active and that C18–20 elongase and C20–22 elongase activities were substantial. A deficiency in the desaturation/elongation pathway was clearly identified at the level
of the fatty acyl Δ5 desaturase, which was very low, particularly with 20∶4n−3 as substrate. In comparison, the apparent activities
of Δ6 desaturase, C18–20 elongase, and C20–22 elongase were approximately 94-, 27-, and 16-fold greater than that for Δ5 desaturase toward their respective n−3 polyunsaturated
fatty acid substrates. The evidence obtained in the SAF-1 cell line is consistent with the dietary requirement for C20 and C22 highly unsaturated fatty acids in the marine fish the sea bream, being primarily due to a deficiency in fatty acid Δ5 desaturase
activity. 相似文献