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1.
This study compared the effect of environmental temperature on sebum composition in 2 breeds of cattle, British (SH) and Brahman
(GB), which differ in their abilities to tolerate heat. By long-term exposure of both breeds to environmental temperatures
of 24 C and 32 C and the more heat-tolerant GB breed to 38 C, it was possible to make breed comparison at (a) different body
temperatures, i.e, when all animals were exposed to the same environmental temperature, and (b), at the same body temperature,
i.e., when the 2 breeds were exposed to different ambient temperatures. The composition of sebum excreted to saturation level
on the skin surface was determined. At the same body temperatures, the amounts of fatty acids in each lipid class were higher
in GB than in SH animals except during hyperthermia when the amounts of triglyceride fatty acids were similar in both breeds.
The total amounts of individual fatty acids except 14∶1, 16∶1, 20∶0 and 14∶OH were higher in both breeds at 32 C than at 24
C. The GB cattle excreted more essential fatty acids (EFA) than the SH cattle at 24 C and at 32 C. There was a significant
genotype by environment interaction in the amounts of EFA partitioned between triglycerides and wax esters; in GB cattle,
the amount of EFA excreted in triglycerides decreased whereas the amount excreted in wax esters increased with rising body
temperature. 相似文献
2.
Sheila M. Innis Roger Dyer Louis Wadsworth Paul Quinlan Deborah Diersen-Schade 《Lipids》1993,28(7):645-650
Platelet lipid composition is important to normal platelet morphology and function, and is influenced by dietary fatty acids
and cholesterol. The fatty acid composition and cholesterol content of infant formulas differs from those of human milk, but
the possible effects on platelet lipids in young infants is not known. This was studied in piglets fed from birth to 18 d
of age with one of eight formulas differing in saturated fatty acid chain length, or content of 18∶1, 20∶5n−3 plus 22∶6n−3,
or cholesterol. A reference group of piglets fed sow milk was also studied. Sow milk has a fatty acid composition and cholesterol
content similar to that of human milk. Piglets fed formulas high in 18∶1 (34.9–40.8% wt fatty acids) and low in 16.0 (≤6.5%
wt fatty acids) had lower platelet counts and greater platelet size than piglets fed sow milk (40.4% 18∶1, 30.7% 16∶0). Piglets
fed formulas high in 16∶0 (27–29.6%) and 18∶1 (40–40.6%), or low in both 16∶0 (5.9–6.1%) and 18∶1 (10.8–11.2%), had similar
platelet counts and size to piglets fed sow milk. Platelet phospholipid % 20∶4n−6 was lower in all the groups of piglets fed
formula than in the group fed sow milk. Addition of fish oil with 20∶5n−3 plus 22∶6n−3 to the formula further decreased platelet
phospholipid 20∶4n−6. Addition of cholesterol to the formula increased the platelet phospholipid % 20∶4n−6 and platelet volume. 相似文献
3.
An analysis of the phospholipid, cholesterol, and phospholipid fatty acyl composition of isolated plasma membranes of 3T3
and SV3T3 mouse embryo cells has been performed. The results show that the plasma membrane of SV3T3 cells contain relatively
less phosphatidylethanolamine and sphingomyelin and more cholesterol than 3T3 plasma membranes. The fatty acyl composition
of individual phospholipid classes as determined by gas liquid chromatography also showed differences between 3T3 and SV3T3
plasma membranes. The plasma membranes of SV40 transformed 3T3 cells contain: (a) a higher percentage of 18∶1 and less 20∶3
and 20∶4 in phosphatidylethanolamine; (b) a higher percentage of 18∶1 in phosphatidylserine; and (c) a higher percentage of
18∶2 and 20∶4 in phosphatidylinositol. 相似文献
4.
The lipid composition of the pineal organ from the rainbow trout (Oncorhynchus mykiss) was determined to establish whether the involvement of this organ in the control of circadian rhythms is reflected by specific
adaptations of lipid composition. Lipid comprised 4.9% of the tissue wet weight and triacylglycerols were the major lipid
class present (47% of total lipid). Phosphatidylcholine (PC) was the principal polar lipid, and smaller proportions of other
phospholipids and cholesterol were also present. Plasmalogens contributed 11% of the ethanolamine glycerophospholipids (EGP).
No cerebrosides were detected. The fatty acid composition of triacylglycerols was generally similar to that of total lipids
in which saturated, monounsaturated and polyunsaturated fatty acids (PUFA) were present in almost equal proportions. Each
of the polar lipid classes had a specific fatty acid composition. With the exception of phosphatidylinositol (PI), in which
20∶4n−6 comprised 27.4% of the total fatty acids, 22∶6n−3 was the principal PUFA in all lipid classes. The proportion of 20∶5n−3
never exceeded 6.0% of the fatty acids in any lipid class. The predominant molecular species of PC were 16∶0/22∶6n−3 and 16∶0/18∶1,
which accounted for 33.2 and 28.5%, respectively, of the total molecular species of this phospholipid. Phosphatidylethanolamine
(PE) contained the highest level of di-22∶6n−3 (13.0%) of any phospholipid. There was also 4.9% of this molecular species
in phosphatidylserine (PS) and 4.1% in PC. In PE, the species 16∶0/22∶6, 18∶1/22∶6 and 18∶0/22∶6 totalled 45.1%, while in
PS 18∶0/22∶6 accounted for 43.9% of the total molecular species. The most abundant molecular species of PI was 18∶0/20∶4n−6
(37.8%). The lipid composition of the pineal organ of trout, and particularly the molecular species composition of PI, is
more similar to the composition of the retina than that of the brain.
Molecular species are abbreviated as follows: e.g., 16∶0/22∶6 PC is 1-palmitoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine. 相似文献
5.
Changes in dietary lipid intake are known to alter the fatty acid composition of cardiac muscle of various animals. Because
changes in cardiac muscle membrane structure and function may be involved in the pathogenesis of arrythmia and ischemia, we
have examined the effects of dietary lipid supplements on the phospholipid distribution and fatty acid composition of rat
atria and ventricle following 20 weeks feeding of diets supplemented with either 12% sunflower-seed oil or sheep fat.
Neither lipid supplement produced significant changes in the proportions of cholesterol, total phospholipids or phosphatidylcholine,
phosphatidylethanolamine or diphosphatidylglycerol,—the phospholipid classes that together account for more than 90% of the
total phospholipids of rat cardiac muscle. Significant changes were found in the profiles of the unsaturated fatty acids of
all 3 phospholipid components of both atria and ventricle. Although similar, the changes between these tissues were not identical.
However, in general, feeding a linoleic acid-rich sunflower seed oil supplement resulted in an increase in the ω-6 family
of fatty acids, whereas feeding the relatively linoleic acid-poor sheep fat supplement decreased the level of ω-6 fatty acids
but increased the levels of the ω-3 family, resulting in major shifts in the proportions of these families of acids. In particular,
the ratio of arachidonic acid: docosahexaenoic acid (20∶4, ω-6/22∶6, ω-3), which is higher in all phospholipids of atria than
ventricle, is increased by feeding linoleic acid, primarily by increasing the level of arachidonic acid in the muscle membranes.
As dosahexaenoic acid does not occur in the diet, the increase in this acid which occurs after feeding animal fat, presumably
arises from increased conversion of the small amounts of linolenic acid in all diets when the amount of linoleic acid present
is reduced. 相似文献
6.
Human endothelial cells in culture were examined in different growth conditions. The human endothelial cell line, EA.hy 926
cell line, was used and cells were studied either in exponential growth phase, at confluence, or growth-arrested by serum
deprivation. Phospholipids were separated and analyzed by high-performance thin-layer chromatography, and their fatty acids
were quantified by gas-liquid chromatography. No significant differences in the phospholipid distributions were found between
exponentially growing and confluent endothelial cells in which phosphatidylcholine (PC) represented the major phospholipid.
In comparison, serum-deprived cells exhibited higher proportions of sphingomyelin and lower content of PC. We also found that
among the total lipids, cholesterol level for dividing endothelial cells was lower than for cells growth-arrested either by
serum deprivation or by contact inhibition at confluence. The global fatty acid distribution was not affected by the growth
conditions. Thus, oleate (18∶1n−9 and 18∶1n-7), palmitate (C16∶0), and stearate (C18∶0) were the main components of endothelial cell membranes. However, the fatty acid distributions obtained from each phospholipid
species differed with the growth status. Altogether, the data indicated that subtle modulations of endothelial cell metabolism
appear upon cell growth. The resulting membrane-dependent cellular functions such as cholesterol transport and receptor activities
can be expected to be relevant for lipid trafficking within the vessel wall in vitro and in vivo. 相似文献
7.
Normal phase high performance liquid chromatography methods are described for the separation of neutral lipid, fatty acid
and five phospholipid classes using spectrophotometric detection at 206 nm. Separations were accomplished in less than 10
min for each lipid class. A mobile phase consisting of hexane/methyltertiarybutylether/acetic acid (100∶5∶0.02) proved effective
in separating cholesteryl ester and triglyceride with recoveries of 100% for radiolabeled cholesteryl oleate and 98% for radiolabeled
triolein. Free fatty acid and cholesterol were separated by two different mobile phases. The first, hexane/methyltertiarybutylether/acetic
acid (70∶30∶0.02) effectively separated free fatty acids and cholesterol, but did not separate cholesterol from 1,2-diglyceride.
A mobile phase consisting of hexane/isopropanol/acetic acid (100∶2∶0.02) effectively separated free fatty acid, cholesterol,
1,2-diglyceride and 1,3-diglyceride. Recoveries of oleic acid and cholesterol were 100% and 97%, respectively. Five phospholipid
classes were separated using methylteriarybutylether/methanol/aqueous ammonium acetate (pH 8.6) (5∶8∶2) as the mobile phase.
The recoveries of phosphatidylinositol, phosphatidylethanolamine, phosphatidylcholine, sphingomyelin and lysophosphatidylcholine
were each greater than 96%. 相似文献
8.
Fatty acids ofSterculia foetida were added to the medium used to maintain the Morris hepatoma 7288C in culture. The effect of this supplement on the lipid
composition was examined. Overall, monoene levels were decreased with 18∶1 levels reduced by 40%. Saturated fatty acid levels
were increased, with stearate (18∶0) levels 220% of control values. No effect occurred on the level of polyunsaturates (18∶2,
20∶4, 22∶5, 22∶6). These changes in fatty acid makeup were observed in both neutral and phospholipid fractions, and all lipid
classes were affected. Triglycerides were most affected with a 66% decrease in 18∶1. There appeared to be little specificity
of effect in the phospholipids with 18∶1 levels decreased 40–60% in all classes. All classes were therefore dependent on an
endogenous supply of 18∶1. Examination of the distribution of geometrical isomers of 18∶1 reveals that in all lipid classes,
except diphosphatidylglycerol (DPG), the ratio of Δ11 to Δ9 isomer decreased toward the isomeric distribution displayed by
total medium lipids. In DPG, although 18∶1 levels were lowered, the isomeric distribution increased. DPG, synthesized and
found in the mitochondria, may use a separate pool of 18∶1 during synthesis. Cyclopropene fatty acids (sterculic and malvalic)
were incorporated into both neutral and phospholipid fractions with preferential incorporation into triglycerides. Cyclopropene
fatty acids were not selectively incorporated into any phospholipid species. Sphingomyelin did not incorporate cyclopropene
fatty acids, indicating that a different class of acyltransferase is used in the formation of this phospholipid class. 相似文献
9.
The effect of a long-term adaptation of rainbow trout to 8 and 18°C combined with a corn oil-or a fish oil-supplemented diet
on the characteristics of the spermatozoan plasma membrane was investigated. The experiment lasted up to 22 mon during which
spermatozoa were collected from the mature males. Spermatozoan plasma membranes were isolated by nitrogen cavitation, and
the cholesterol content, phospholipid composition and fatty acid pattern were investigated. Membrane viscosity was assessed
on whole cells by electron spin resonance using spin-labeled phospholipids. Neither diet nor rearing temperature influenced
the cholesterol content of the plasma membrane nor the phospholipid class distribution. The rearing temperature of the broodstock
only slightly affected the phospholipid fatty acids. A minor decrease in 18∶0 and increase in monounsaturated fatty acids
was observed for the cold-adapted fish. These modifications were not sufficient to affect membrane fluidity, and we conclude
that trout spermatozoa do not display any homeoviscous adaptations in these conditions. On the contrary, the dietary fatty
acid intake greatly modified the fatty acid profile of plasma membrane phospholipids. The fish oil-fed trout displayed a much
higher n−3/n−6 fatty acid ratio than did the corn oil-fed ones, but the 22∶6n−3 levels remained unchanged. Modifications in
plasma membrane composition by the diet were obtained although neither of the two diets was deficient in essential fatty acids.
The enrichment in n−3 fatty acids, however, did not affect plasma membrane fluidity which was unchanged by the diets. 相似文献
10.
Lido Calorini Anna Fallani Donatella Tombaccini Emanuela Barletta Gabriele Mugnai Maria F. Di Renzo Paolo M. Comoglio Salvatore Ruggieri 《Lipids》1989,24(8):685-690
To determine whether a metastatic phenotype may be corelated with a characteristic lipid pattern, we compared the lipid composition
of low metastasizing Balb/c 3T3 cells transformed by the B77 strain of Rous sarcoma virus (B77-3T3 cells) with that of a subclone
isolated by growth in 0.6% agar, the B77-AA6 cells, which exhibit a high capacity for spontaneous metastasis. B77-3T3 cells
revealed characteristics in their lipid composition common to other systems of transformed cells, i.e., an accumulation of
ether-linked lipids, a reduction of the more complex gangliosides, an increase of oleic acid (18∶1) and a decrease of arachidonic
(20∶4) and C22 polyunsaturated fatty acids in phospholipids. High metastatic B77-AA6 cells showed: a) an even more marked
decrease of complex gangliosides; b) a more pronounced increase of 18∶1 and decrease of 20∶4 and 22 polyunsaturated fatty
acids in certain phospholipid classes; and c) a higher percentage of alkyl-acyl subfractions in both phosphatidylcholine and
phosphatidylethanolamine than B77-3T3 cells.
Comparing the data for other systems of metastatic cells with those of lipid studies of spontaneously metastasizing B77-AA6
cell system leads us to conclude that the metastatic phenotype is characterized by a change in ether-linked lipids, rather
than in fatty acids. 相似文献
11.
A study of the fatty acid composition of red cell phosphatidylcholine and phosphatidylethanolamine and serum cholesterol was
undertaken in 185 Canadian Inuit (age 2 months-82 years). Samples from 24 Canadian men and women (21–50 years) living in Vancouver
were also analyzed as a reference for the Inuit in this age range. Dietary survey of the Inuit community (325 Inuit) demonstrated
a diet based on traditional foods in which the principal source of n−3 fatty acid was marine mammal flesh (mean intake: 164
g/person/day) rather than fish (mean intake: 13 g/person/day). Compared to the Vancouver samples, the Inuit phosphatidylethanolamine
had higher 20∶5n−3 and 22∶6n−3 and lower 20∶4n−6, but similar 18∶2n−6 levels. The level of 20∶5n−3 was higher and 20∶4n−6
was lower in the Inuit than in the Vancouver red cell phosphatidylcholine. Despite these differences in percentage content
of C20 and C22 n−6 and n−3 fatty acids, the mean chain length and unsaturation index of the Inuit and Vancouver red cell phosphatidylcholine
and phosphatidylethanolamine were very similar. Serum cholesterol concentration showed no sex difference within the Inuit,
and no difference from Vancouver men and women of similar age. The analyses suggest that the fatty acid composition of the
Inuit red cell phospholipids are primarily a reflection of their diet-fat composition. 相似文献
12.
Reticulocytosis was induced in rats by injecting phenylhydrazine, a potent oxidizing agent. Red cell morphology was analyzed
by scanning electron microscopy. The majority of red cells from rats given injections of phenylhydrazine were types 2 and
3 echinocytes. Stomatocytes were also observed, but pitted lobular reticulocytes were not detected. Echinocytes have not previously
been observed in reticulocyte populations. In the reticulocytes, the relative levels of 16∶1 and 18∶1 were significantly greater
than in erythrocytes. These differences in monoenoic acids may be due to the presence of endoplasmic reticulum, the site of
desaturase activity in reticulocytes. Of all the fatty acids, the polyunsaturates are the most susceptible to attack during
peroxidation. However, the polyunsaturated fatty acid composition of reticulocytes was similar both to that of erythrocytes
and to reported values of young erythrocytes isolated by density. Therefore, it is unlikely that lipid peroxidation caused
the formation of echinocytes.
Presented at the 72nd Annual AOCS Meeting, New Orleans, May 1981. 相似文献
13.
Two experiments were conducted to investigate the relationship between Δ9 desaturase (stearoyl-coenzyme A desaturase) activity and fatty acid composition in subcutaneous adipose tissue from cattle
of different backgrounds. In Experiment 1, subcutaneous adipose tissue samples were taken from carcasses of pasture-fed cattle
and feedlot cattle fed for 100, 200, or 300 d. Adipose tissue from pasture-fed cattle had significantly lower total saturated
fatty acids and higher total unsaturated fatty acids than feedlot cattle. Desaturase activity correspondingly was 60–85% higher
in pasture-fed cattle than in feedlot cattle. There was no difference in the fatty acid composition or desaturase activity
among samples from the 100-, 200-, and 300-d feedlot cattle. In Experiment 2, adipose tissue samples were collected from carcasses
of feedlot cattle fed for 180 d with either a standard feedlot ration (control group), or a ration containing rumen-protected
cottonseed oil (CSO) for the last 70–80 d. Adipose tissue from the CSO-fed cattle was more saturated than that from the control
group, having significantly more 18∶0 and less 16∶1 and 18∶1. Correspondingly, adipose tissue from the CSO group had significantly
lower desaturase activity. The elevated 18∶2 in adipose tissue from the CSO group confirmed that unsaturated fatty acids (including
cyclopropenoid fatty acids) were protected from biohydrogenation. Further studies are needed to determine whether the repression
of desaturase activity results from direct inhibition by cyclopropenoic acids or by higher dietary contents of 18∶2. 相似文献
14.
The lipid composition of plasma membranes isolated from differentialted and undifferentiated L6 myoblasts has been compared. In general, the plasma membranes of differentiated L6 myoblasts have a higher cholesterol to phospholipid molar ratio than plasma membranes of undifferentiated cells. Differentiated
L6 myoblasts have increased relative amounts of phosphatidylethanolamine and phosphatidylcholine in their plasma membrane and
a decreased relative amount of sphingomyelin when compared with the plasma membranes of undifferentiated myoblasts. In addition,
preliminary results show that differentiated L6 myoblasts plasma membrane phospholipid shows differences in the fatty acyl composition, specifically there appears to be
relatively more 17∶0 and 24∶1 and less 16∶1 and 18∶1 than in plasma membrane phospholipids of undifferentiated L6 myoblasts. These observations indicate that significant changes in plasma membrane lipid composition occur during myoblast
differentiation. The role that changes in lipid composition play in control of cellular differentiation, however, remains
to be elucidated. 相似文献
15.
The effect of essential fatty acid (EFA) deficiency on the lipid composition of basolateral plasma membranes (BPM) from intestinal
mucosal cells was investigated in weaning pigs fed control or EFA-deficient diets for 12 weeks. The phospholipid and cholesterol
contents relative to protein were similar in both groups, showing a cholesterol/phospholipid molar ratio of 0.6. The distribution
of phospholipid classes was also unaffected by the diet. In contrast, fatty acid profiles of the two phospholipid main classes,
phosphatidylcholine and phosphatidylethanolamine were altered by EFA deficiency. Linoleic acid (18∶2n−6) was largely reduced,
whereas arachidonic acid (20∶4n−6) only slightly decreased in EFA-deficient pigs. The unsaturation index was essentially maintained
by high levels of oleic acid (18∶1n−9) and by conversion of oleic acid to 5,8,11-eicosatrienoic acid (20∶3n−9). Finally, during
the period of EFA deficiency, the lipid composition of BPM of the intestinal mucosal cells was little affected, suggesting
a preferential uptake of 20∶4n−6 and (or) precursor mobilized from other tissues. However, an effect of dietary treatment
on the function of membrane-associated proteins cannot be ruled out. 相似文献
16.
To examine whether dietary fat alters membrane lipid composition and peroxidation of polyunsaturated fatty acids in “non-proliferative”
and “proliferative” cells in the large intestine, Sprague-Dawley rats were fed diets providing a polyunsaturated-to-saturated
fatty acid ratio of 1.2 or 0.3 at a high or low level of fat intake for a 25-day period. Cell populations were isolated and
the effect of dietary fat on membrane polyunsaturated fatty acid content and peroxide levels was determined. Neither fat level
nor fatty acid composition of diet influenced total cholesterol, total phospholipids, and percentage of phospholipid classes
in membrane phospholipids. Feeding the high fat and/or high polyunsaturated-to-saturated fatty acid ratio diet increased polyunsaturated
fatty acid content of mucosal cell phospholipids. Increase in polyunsaturated fatty acid content was paralleled by a decrease
in the monounsaturated fatty acid content of mucosal cell phospholipids. Membrane content of total saturated fatty acids was
not significantly affected by diet. Variation in phospholipid fatty acid composition between “non-proliferative” and ”proliferative”
cells was observed. Lipid peroxide levels in mucosal cell lipid fractions were altered by dietary fat treatment. Animals fed
high fat diets, compared to groups fed low fat diets, exhibited higher membrane peroxide levels when results are expressed
as nmol/mg protein. Higher peroxide levels were observed in mucosal cells for rats fed high polyunsaturated-to-saturated fatty
acid ratio diets when results were expressed per nmol of phospholipid. It is concluded that changes in fat level and fatty
acid composition of the diet alters the mucosal cell membrane lipid composition in the rat large intestine and influences
susceptibility of mucosal cell lipid to peroxidation. Further research is required to delineate which dietary factors—fat
level, polyunsaturated-to-saturated fatty acid ratio, or both—have a primary influence on the degree of lipid peroxidation. 相似文献
17.
AVibrio species of bacterium known to contain the polyunsaturated fatty acid 20∶5n−3 was grown in both freshwater and seawater media
at 5 and 20°C and examined for adaptive changes in lipid composition. Phosphatidylethanolamine (PE) and phosphatidylglycerol
(PG), together with a smaller proportion of nonesterified fatty acids (NEFA), comprised almost all the lipid under all growth
conditions examined. Temperature had a more pronounced effect than the salinity of the medium on lipid composition. The proportion
of PE in total lipid was always higher at 5 than at 20°C. Conversely, the proportion of NEFA was lower at 5 than 20°C whereas
that of PG was not altered. The levels of saturated fatty acids in total lipid, PE and PG were all decreased by growth at
5°C. No differences were observed with respect to growth temperature in the levels ofcis 16∶1n−7, the principal monoenoic fatty acid in both PE and PG.Trans 16∶1n−7 was found to comprise 12.8–15.2% of fatty acids in PE and PG of bacteria grown at 5°C but only 4.4–8.5% of phospholipid
fatty acids in bacteria cultured at 20°C. Regardless of medium composition, a reduction in growth temperature from 20 to 5°C
also caused the proportions of 20∶5n−3 to increase from around 0.8 to 4.4% in PE and from around 4 to 20% in PG. The simultaneous
occurrence oftrans 16∶1n−7 and 20∶5n−3 is unique to thisVibrio species of bacterium. The increased proportions of both these fatty acids with decreasing temperature suggest that they have
a role in retailoring biomembrane phospholipids during temperature acclimation of the bacterium. 相似文献
18.
The emperor penguin (Aptenodytes forsteri) is an Antarctic seabird feeding mainly on fish and therefore has a high dietary intake of n-3 polyunsaturated fatty acids.
The yolk is accumulated in the developing oocyte while the females are fasting, and a large proportion of the fatty acid components
of the yolk lipids are derived by mobilization from the female's adipose tissue. The fatty acid composition of the total lipid
of the yolk was characterized by high levels of n-3 polyunsaturated fatty acids. However, it differed in several respects
from that of the maternal adipose tissue. For example, the proportions of 14∶0, 16∶1n−7, 20∶1n−9, 22∶1n−9, 20∶5n−3, and 22∶6n−3
were significantly greater in adipose tissue than in yolk. Thus adipose tissue lipids contained 7.6±0.3% and 8.0±0.3% (wt%
of total fatty acids; mean ±SE; n=5) of 20∶5n−3 and 22∶6n−3, respectively, whereas the yolk total lipid contained 1.6±0.1 and 5.5±0.3% of these respective
fatty acids. The proportions of 16∶0, 18∶0, 18∶1n−9, 18∶2n−6, and 20∶4n−6 were significantly lower in the adipose tissue than
in the yolk lipids. The proportions of triacylglycerol, phospholipid, free cholesterol, and cholesteryl ester in the yolk
lipid were, respectively, 67.0±0.2, 25.4±0.3, 5.3±0.2, and 1.8±0.2% (wt% of total yolk lipid). The proportions of 20∶4n−6,
20∶5n−3, 22∶5n−3, and 22∶6n−3 were, respectively, 5.7±0.3, 2.8±0.2, 1.4±0.1, and 11.7±0.5% in phospholipid and 0.4±0.0, 1.2±0.1,
0.8±0.1 and 3.6±0.3% in triacylglycerol. About 95% of the total vitamin E in the yolks was in the form of α-tocopherol with
γ-tocopherol forming the remainder. Two species of carotenoids, one identified as lutein, were present. 相似文献
19.
The aim of this study was to investigate the effect of the oxysterol 5α-cholestane-3β, 5, 6β-triol (triol) on the metabolism
of linoleic acid (18∶2n−6) to arachidonic acid (20∶4n−6) and on the cell membrane fatty acid composition. Porcine kidney cells
were incubated in medium with or without 10 μg/mL of triol for 24 h, then incubated for 1, 6, or 12 h in a medium which contained
50 μM of either [14C]linoleic acid or unlabeled linoleic acid. The cellular uptake of [14C] linoleic acid was significantly higher in the triol-treated cells than in control cells. After 1- and 6-h incubations despite
the increase of [14C]linoleic acid pool size in the triol-treated cells, neither total n−6 polyunsaturated fatty acids (PUFA) metabolites nor
arachidonic acid were increased in the triol-treated cells as compared to the control cells, but trienoic acids accumulated
to a greater extent in the triol-treated cells. Therefore, the ratios of n−6 PUFA metabolites vs. pool size of linoleic acid
and of tetraenoic acids vs. dienoic acids were significantly decreased in triol-treated cells as compared to the control cells.
The cellular fatty acid composition also showed that linoleic acid percentage was significantly increased while arachidonic
acid percentage was significantly decreased in the triol-treated cells, and that the accumulation of trienoic acids (18∶3n−6+20∶3n−6)
observed from the [14C]linoleic acid experiment was due solely to increased 20∶3n−6 content. This latter finding indicates that a decrease of elongase
activity by triol is unlikely. Our results also showed that the triol-treated cells had a lower level of free cholesterol
but higher levels of phospholipid and triol in their membranes, suggesting that triol displaced free cholesterol from the
cell membrane. 相似文献
20.
Lipid peroxidation in unilamellar liposomes of known cholesterol-phospholipid composition was monitored under conditions of
autoxidation or as induced by a superoxide radical generating system, γ-irradiation or cumene hydroperoxide. Formation of
cholesterol oxidation products was indexed to the level of lipid peroxidation. The major cholesterol oxidation products identified
were 7-keto-cholesterol, isomeric cholesterol 5,6-epoxides, isomeric 7-hydroperoxides and isomeric 3,7-cholestane diols. Other
commonly encountered products included 3,5-cholestadiene-7-one and cholestane-3β,5α,6β-triol. Superoxide-dependent peroxidation
required iron and produced a gradual increase in 7-keto-cholesterol and cholesterol epoxides. Cholesterol oxidation was greatest
in liposomes containing high proportions of unsaturated phospholipid to cholesterol (4∶1 molar ratio), intermediate with low
phospholipid to cholesterol ratios (2∶1) and least in liposomes prepared with dipalmitoylphosphatidylcholine and cholesterol.
This relationship held regardless of the oxidizing conditions used. Cumene hydroperoxide-dependent lipid peroxidation and/or
more prolonge oxidations with other oxidizing systems yielded a variety of products where cholesterol-5β,6β-epoxide, 7-ketocholesterol
and the 7-hydroperoxides were most consistently elevated. Oxyradical initiation of lipid peroxidation produced a pattern of
cholesterol oxidation products distinguishable from the pattern derived by cumene hydroperoxide-dependent peroxidation. Our
findings indicate that cholesterol autoxidation in biological membranes is modeled by the peroxide-induced oxidation of liposomes
bearing unsaturated fatty acids and suggest that a number of cholesterol oxidation products are derived from peroxide-dependent
propagation reactions occurring in biomembranes. 相似文献