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1.
Optimal conditions for analyzing HDL2 cholesterol in small amounts of rat plasma have been studied using different concentrations of dextran sulfate and MgCl2 to precipitate lipoproteins containing apolipoprotein B and/or apo E. When the MgCl2 level was 91 mM, the supernate cholesterol was rather constant at a level of about 50–60% of the total plasma cholesterol
concentration. Immunochemical determination of the apo A-I content indicated that no major losses of the HDL2 fraction took place under these conditions. The recovery of about 96% of HDL2 lipoproteins after the precipitation of rat plasma and the almost complete absence of lipoproteins belonging to the VLDL,
LDL and HDL1 fractions was demonstrated by agarose gel electrophoresis. Thus, the method should be suitable for screening the HDL2 cholesterol content in small volumes of rat plasma. 相似文献
2.
Human low density lipoproteins (LDL) were isolated and purified from individuals having widely differing serum lipid concentrations.
Very low density lipoproteins (VLDL) and high density lipoproteins (HDL) were also isolated and quantitated. HDL2 and HDL3 were separated by flotation velocity in the analytical ultracentrifuge and their relative weight percent determined. The
mean density of LDL from 41 individuals was determined by flotation velocity at two different solvent densities. The mean
density of LDL was directly proportional to the triglyceride (r=0.65) and VLDL (r=0.50) concentrations and inversely proportional
to the HDL (r=−0.55) and HDL2 (r=−0.74) concentrations (all significant at P<0.001). The mean molecular weight of LDL from 42 individuals was determined
by flotation equilibrium centrifugation. The mean molecular weight of LDL was directly proportional to the HDL (r=0.49) and
HDL2 (r=0.48) concentrations and inversely proportional to the serum triglyceride (r=−0.60) and VLDL (r=−0.48) concentrations
(all significant at P<0.005 except triglyceride—P<0.001). The molecular weight of LDL was inversely proportional to its density,
and thus inversely proportional to its protein/lipid ratio which was confirmed by composition measurements. The density and
molecular weight of LDL had no relationship to the concentration of LDL (r=0.04 and 0.03).
A preliminary report of this study was given at the American Society for Biological Chemists Meeting in St. Louis, June 1981. 相似文献
3.
Wolfgang Sattler Helga Reicher Pilar Ramos Ute Panzenboeck Marianne Hayn Hermann Esterbauer Ernst Malle Gerhard M. Kostner 《Lipids》1996,31(12):1303-1310
A simple, accurate, and fast procedure for quantitative analysis of fatty acids (FA) in simple lipid subclasses from different
biological specimens is presented. Lipid extracts of isolated plasma lipoproteins (very low, low, and high density lipoproteins;
VLDL, LDL, and HDL, respectively) and permanent J774 mouse macrophages were fractionated into lipid subclasses by thin-layer
chromatography (TLC) on silica gel 60 plates. Bands comigrating with authentic lipid standards were scraped off under argon
and subjected to direct,in situ transesterification with BF3/MeOH in the presence of the TLC adsorbent. Fatty acid methyl esters were subsequently quantitated by capillary gas chromatography.
A comparison of the FA content present in total lipid extracts and in lipid subclasses separated by TLC revealed recoveries
ranging from 93 (J774 cell extracts) to 99.7% (LDL). The method described is applicable for the measurement of FA in individual
lipid subclasses and was successfully applied to quantitatively analyze the FA composition of the phospholipid, triacylglycerol,
and cholesteryl ester fraction derived from VLDL, LDL, and HDL. In J774 lipid extracts, the FA composition of the phospholipid-,
monoacylglycerol-, diacylglycerol-, free fatty acid-, triacylglycerol-, and cholesteryl ester fraction was quantitated. In
addition we have analyzed the time-dependent loss of the major HDL polyunsaturated fatty acids (18:2, 20:4) in the phospholipid
and cholesteryl ester fraction during copper-dependent peroxidation of HDL. We have not encountered analytical problems concerning
low FA recoveries from CE-rich lipid extracts as indicated by almost quantitative recoveries of FA in LDL, HDL, and J774 extracts. 相似文献
4.
The content and structure of glycosphingolipids (GSL) in human plasma lipoproteins were studies. The quantitative distribution
of the neutral GSL(Glc-Cer, Gal-Glc-Cer, Gal-Gal-Glc-Cer, and GalNAc-Gal-Gal-Glc-Cer) and the principal ganglioside (AcNeu-Gal-Glc-Cer)
within the different lipoprotein classes was similar to that of whole plasma. The total amounts (μmol glucose/100 ml plasma)
of GSL in the plasma lipoproteins of three normal subjects were VLDL (very low density lipoproteins) (trace to 0.46), LDL
(low density lipoproteins) (1.08–1.48), HDL2 (high density lipoproteins2) (0.62–0.85), and HDL3 (high density lipoproteins3) (trace to 0.28). In subjects with Lp(a) lipoproteins, HDL2 rather than HDL3 contained most of the GSL in HDL. When the data were corrected for differences in the plasma concentrations of the lipoproteins,
the total amounts of GSL(nmol glucose/mg lipoprotein cholesterol) were VLDL(trace to 21.20), LDL(11.70–15.36), HDL2(8.50–9.10), and HDL3(3.12). No GSL were detected in lipoprotein deficient plasma. Mass spectrometry of the trimethylsilyl derivatives of the GSL
in LDL showed major fragment ions characteristic of their individual structural components. The elevated plasma levels of
the GSL(2–18 fold), in a homozygote for familial hypercholesterolemia, resided in LDL which contained an absolute increase
(per mg lipoprotein cholesterol) of GSL. Most, if not all, of the plasma GSL are associated with plasma lipoproteins and may
have an important role in their biological functions. 相似文献
5.
Oral administration of a single dose of tri- or hexadeuterium substituted 2R,4′R,8′R-α-tocopheryl acetate (d3- or d6-α-T-Ac) to humans was used to follow the absorption and transport of vitamin E in plasma lipoproteins. Three hr after oral
administration of d3-α-T-Ac (15 mg) to 2 subjects, plasma levels of d3-α-T were detectable; these increased up to 10 hr, reached a plateau at 24 hr, then decreased. Following administration of
d6-α-T-Ac (15–16 mg) to 2 subjects, the percentage of deuterated tocopherol relative to the total tocopherol in chylomicrons
increased more rapidly than the corresponding percentage in whole plasma. Chylomicrons and plasma lipoproteins were isolated
from 2 additional subjects following administration of d3-α-T-Ac (140 or 60 mg). The percentage of deuterated tocopherol relative to the total tocopherol increased most rapidly in
chylomicrons, then in very low density lipoproteins (VLDL), followed by essentially identical increases in low and high density
lipoproteins (LDL and HDL, respectively) and lastly, in the red blood cells. This pattern of appearance of deuterated tocopherol
is consistent with the concept that newly absorbed vitamin E is secreted by the intestine into chylomicrons; subsequently,
chylomicron remnants are taken up by the liver from which the vitamin E is secreted in VLDL. The metabolism of VLDL in the
circulation results in the simultaneous delivery of vitamin E into LDL and HDL. 相似文献
6.
While it is known that the transfer of cholesteryl ester (CE) from high density lipoprotein (HDL) to the apo B-containing
lipoproteins is increased in patients with diabetes, the extent to which the various lipoprotein fractions engage in neutral
lipid exchange and the magnitude to which triglyceride (TG) is translocated is not known. To examine in greater detail neutral
lipid net mass transfer in diabetes, the HDL subfractions and the apo B-containing lipoproteins were separated, and the net
mass transfer of CE and TG was compared to that of control subjects. In both groups, bidirectional transfer of CE from HDL3 to very low density lipoprotein (VLDL) + low density lipoprotein (LDL) and of TG from VLDL+LDL to HDL3, took place, but this process was significantly greater (P<.01) in insulin-dependent diabetes mellitus (IDDM). In contrast, CE and TG accumulated in HDL2 to a similar degree in normal and IDDM subjects. In recombination experiments with each of the apo B-containing lipoproteins,
IDDM VLDL had a greater capacity to facilitate the exchange of core lipids from both IDDM and control HDL3: on the other hand, LDL from IDDM and control subjects both donated TG and CE to HDL2 and affected little change in HDL3. These findings indicate that all the major plasma fractions normally participate in the trafficking of CE and TG among the
lipoproteins during neutral lipid transfer and show that the principal perturbation in cholesteryl ester transfer in IDDM
involves altered interaction between VLDL and the HDL3 subfraction. 相似文献
7.
The net transfer of labeled α-tocopherol from donor to acceptor lipoproteins at physiological concentrations was investigated.
Labeled lipoproteins were isolated i) followingin vitro addition of [3,4-3H]all rac-α-tocopherol to plasma, or ii) from plasma obtained 12–16 h after ingestion by normal subjects of an oral dose (100 mg each)
of 2R,4′R,8′R-α-[5,7-(C2H3)2]tocopheryl acetate and 2S,4′R′,R-α-[5-C2H3]tocopheryl acetate. A constant amount (on a protein basis) of labeled lipoprotein was incubated with an increasing amount
of unlabeled acceptor lipoprotein for 2 h at 37°C. No discrimination between stereoisomers of α-tocopherol was detected. Labeled
VLDL and labeled LDL (very low and low density lipoproteins, respectively) tended to retain their labeled tocopherol. Labeled
high density lipoproteins (HDL) readily transferred the labeled tocopherol to VLDL (>60% transferred), while the transfer
to LDL was dependent upon the ratio of labeled HDL/LDL with a lower net transfer at higher ratios. This dependency of the
distribution of tocopherol upon the ratio of HDL/LDL was also observedin vivo. The tocopherol/mg HDL protein was measured in 11 subjects with varying HDL levels. As the %HDL in the plasma increased from
14 to 50%, the tocopherol/HDL protein also increased (r2=0.37,P<0.05). 相似文献
8.
The fractionations of plasma lipoproteins by 2 methods were compared to evaluate the rapid separation (Airfuge®) method for lipoprotein distribution studies. When [125I] labeled very low density, low density, and high density lipoproteins (VLDL, LDL, HDL), were separately centrifuged in buffers at d=1.006, 1.06 or 1.2 g/ml by the conventional ultracentrifuge and the Airfuge®, separations of the fractions in the Airfuge® were incomplete at both 5 C and 24 C, especially at d=1.006. [3H] Benzo (a)pyrene, when added to plasma, associates with the plasma proteins and lipoproteins, especially LDL. Compared to the standard techniques, the Airfuge® method greatly overestimated its distribution into VLDL. The distribution of [3H] vitamin D3 into the VLDL plus LDL fraction was also overestimated by the Airfuge® procedure. It is concluded that caution should be observed in quantitative studies of lipoproteins in the Airfuge®. A careful comparison of the distribution into or fractionation of lipoproteins by the 2 methods should always precede any quantitative determinations involving the Airfuge®. 相似文献
9.
Native fish-eye disease plasma, which is deficient of both high density lipoproteins (HDL) and lecithin-cholesterol acyltransferase
activity (α-LCAT), processing the free cholesterol of these lipoproteins, has been supplemented with normal isolated HDL2 or HDL3 and incubated in vitro at 37 C. After incubation for 0,7.5 and 24 hr the very low density (VLDL) and low density (LDL) lipoproteins
as well as HDL were isolated, and their contents of triglycerides, phospholipids and free, esterified and total cholesterol
were quantified. The resulting net mass transfer of the different lipids revealed a functioning transfer of cholesteryl esters
and all other analyzed lipids between the lipoproteins, although no de novo esterification of the HDL cholesterol by LCAT
in this plasma occurred. In accordance with previous findings there was a functioning esterification process of the free cholesterol
of the combined VLDL and LDL of fish-eye disease plasma. The present results make it reasonable to conclude that the lack
of HDL cholesterol esterification in this disease is not a result of a deficiency of cholesteryl ester transfer or lipid transfer
activities. 相似文献
10.
Arne T. Høstmark Øystein Spydevold Einar Lystad Eva Kristensen Ida Goffeng Bay 《Lipids》1982,17(7):489-499
The effect of varying the dietary sunflower oil/sucrose (SO/SU) ratio on rat plasma lipid concentration and lipoprotein distribution
was studied. Four groups of 10 rats were fed for 4 weeks diets with varying SO/SU ratios. Lipoprotein components were then
estimated in whole plasma and after cumulative density ultracentrifugation. Whole plasma triacylglycerol (TG), total cholesterol
(TC) and free cholesterol (FC) decreased with increasing SO/SU ratio; the CE/FC ratio increased, because CE remained virtually
unaltered. Plasma TG-lowering was due to a decrease in VLDL and LDL-TG. Protein, CE and FC in d=1.063–1.100 g/ml (HDL2b) and d=1.100–1.125 g/ml (HDL2a) lipoproteins decreased upon increasing the SO/SU ratio. In contrast, in d=1.125–1.200 g/ml (HDL3) lipoproteins, there was a concomitant increase in these components. Although increasing the SO/SU ratio effected more protein
and CE transportation in HDL3 and less in HDL2, the total amount of these components in high density lipoproteins (d=1.063–1.200 g/ml) remained constant. Apo A-I and apo
C-III decreased in HDL2 but increased in HDL3 upon increasing the SO/SU ratio. Also, HDL2 apo E, and the apo C-II/apo C-III and small apo B/large apo B ratios in VLDL and LDL were lowered by increasing the SO/SU
ratio. The hepatic VLDL-TG output during isolated liver perfusion was lowest in rats fed the diet with the highest SO/SU ratio.
In perfusate, like in plasma, the VLDL and LDL apo C-II/apo C-III ratio, as well as the small apo B/large apo B ratio, decreased
upon increasing the dietary SO/SU ratio. The results indicate that there can be appreciable diet-dependent variations in plasma
HDL subgroup distribution in spite of unchanged total HDL levels. 相似文献
11.
High performance liquid chromatography with gel exclusion columns was used for quantitative measurement of plasma lipoproteins.
A combination of columns TKS 4000 PW and 3000 PW gave good separation of very low (VLDL), low (LDL) and high (HDL) density
lipoproteins. The area under each lipoprotein peak detected by absorbance at 280 nm was measured by digitizing and was expressed
as cm2. Purified lipoprotein standards isolated by ultracentrifugation were also chromatographed in increasing concentrations. The
area under the lipoprotein standard peak was linearly related to the amount of total protein over a wide range. The areas
of most of the measured plasma lipoproteins were within the linear range. The relationship between the area and the amount
of protein for each standard was used to quantitate the amount of protein and was expressed as mg/dl plasma. This technique
is simple and requires a small amount of plasma. The validated technique was applied to a large population of pedigreed baboons.
An average plasma lipoprotein profile of feral baboons on the chow diet was characterized by a high level of HDL (90.9±30.7
mg/dl) with a lesser amount of LDL (29.1±13.2 mg/dl). VLDL was present in much lower concentration (8.6±2.6 mg/dl). Feeding
a high cholesterol and high saturated fat (HCHF) diet raised both LDL (1.5-fold) and HDL levels (1.3-fold) without changing
VLDL levels. Progeny of sires with low response to dietary cholesterol increased their HDL protein when challenged with HCHF
diet without any change in their LDL or VLDL. Progeny of high-responding sires, however, had increases in both their HDL and
LDL levels when challenged with HCHF diet. The survey of lipoprotein profiles of the pedigreed baboon colony disclosed a number
of animals with interesting and unusual lipoprotein patterns. 相似文献
12.
Sandra H. Gianturco Christopher J. Packard James Shepherd Louis C. Smith Alberico L. Catapano Harley D. Sybers Antonio M. Gotto Jr. 《Lipids》1980,15(6):456-463
Our previous studies showed that hypertriglyceridemic very low density lipoproteins (HTG VLDL) are functionally abnormal.
HTG VLDL, but not normal VLDL, suppress HMG-CoA reductase in cultured normal human fibroblasts. To determine if the suppression
by HTG VLDL resulted from a subpopulation of smaller suppressive particles, more homogeneous subclasses of VLDL-VLDL1 (Sf 100–400), VLDL2 (Sf 60–100), and VLDL3 (Sf 20–60) were obtained from the d<1.006 (g°ml−1) fraction of normal and hypertriglyceridemic plasma by flotation through a discontinuous salt gradient and tested for suppression
in normal human fibroblasts. VLDL1 and VLDL2 from each of the 12 normolipemic subjects tested failed to suppress HMG-CoA reductase activity in normal fibroblasts. Eleven
out of 12 preparations of normal VLDL3 suppressed HMG-CoA reductase, but only one-third as effectively as LDL. By contrast, the VLDL1, VLDL2 and VLDL3 from 15 out of 17 hypertriglyceridemic patients (hyperlipoproteinemia Types IIb, III, IV and V) were highly effective in
suppression, with half-maximal suppression at 0.1–2.0 μg VLDL protein/ml. The VLDL abnormality is apparently associated with
hypertriglyceridemia and not hypercholesterolemia, since VLDL from a homozygous familial hypercholesterolemia patient with
a Type IIa pattern did not suppress whereas each of the VLDL subclasses from a Type IIb patient suppressed. Suppression by
HTG VLDL in normal cells is apparently a consequence of interaction of the protein portion of the VLDL with the specific LDL
cell surface receptor since HTG VLDL1 treated with 0.1 M 1,2-cyclohexanedione to block arginyl residues failed to suppress the enzyme. Moreover, hypertriglyceridemic
Sf 60–400 VLDL failed to suppress HMG-CoA reductase activity in LDL receptor-negative fibroblasts. There were no consistent
major compositional differences between comparable normal and hypertriglyceridemic VLDL subclasses which could account for
differences in suppression. All VLDL subclasses from Type III subjects were enriched in cholesteryl esters and depleted in
triglyceride, relative to the corresponding normal VLDL subclasses. However, Type IV and Type V VLDL subclasses were normal
in this repect. We conclude from these studies that small particle diameter is not required for suppression, since HTG VLDL1 and VLDL2 which contained few, if any, small particles were effective in suppression.
Presented as part of the symposium “Low Density and Very Low Density Lipoproteins” at the American Oil Chemists' Society meeting
on May 2, 1979, in San Francisco. 相似文献
13.
Se-Hwan Paek Joung-Hwan Cho Moon-Sik Kang Nam-Ki Min 《Korean Journal of Chemical Engineering》2001,18(2):263-269
A membrane immuno-chromatographic system that selectively separates plasma lipoproteins and generates a signal in proportion
to the concentration of cholesterol (HDL-C) within high-density lipoprotein (HDL) was investigated as a point-of-care device
for the prognosis of coronary heart disease. The system consists of three functional membrane strip pads connected in a sequence
for: (from the bottom) immuno-separation based on biotinstreptavidin reaction, catalytic conversion of cholesterol to hydrogen
peroxide, and production of a signal. For immunochromatography, a monoclonal antibody, specific to apolipoprotein B100 that
is present on the surfaces of low-density lipoproteins (LDL) and very low-density lipoproteins (VLDL), with a high binding
constant (5xl010 L/mol) was raised and chemically conjugated to streptavidin. The conjugate was first reacted with lipoprotein particles,
and this mixture was absorbed by the capillary action into the biotin pad of the system. After being transferred by medium,
immunocapture of LDL and VLDL particles onto the biotin pad took place, andin situ generation of a signal in proportion to HDL-C consecutively occurred. The capture was selective as well as effective (minimum
90% of LDL and VLDL in clinical concentration ranges), and the detection limit of HDL-C was far lower than 20 mg/dL. To construct
a userfriendly device, we are currently investigating the automation of such processes of reactions and separation by adapting
a liquid flow-controlling technology that programs the times for the immune reaction and separation. My group further pursues
an interdisciplinary study to develop a micro system employing semiconductor-based technologies that will eventually enable
the handling of sub-micro liter volume of body fluid as a specimen. 相似文献
14.
Heiner K. Berthold Jessica Mertens Julia Birnbaum Susanne Brämswig Thomas Sudhop P. Hugh R. Barrett Klaus von Bergmann Ioanna Gouni-Berthold 《Lipids》2010,45(6):491-500
Statins decrease apoB-100-containing lipoproteins by increasing their fractional catabolic rates through LDL receptor-mediated
uptake. Their influence on hepatic secretion of these lipoproteins is controversial. The objective of the study was to examine
the influence of simvastatin on the secretion of apoB-100-containing lipoproteins in fasting non-obese subjects. Turnover
of apoB-100-containing lipoproteins was investigated using stable isotope-labeled tracers. Multicompartmental modeling was
used to derive kinetic parameters. Eight male subjects (BMI 25 ± 3 kg/m2) with mild hypercholesterolemia (LDL cholesterol 135 ± 30 mg/dL) and normal triglycerides (111 ± 44 mg/dL) were examined
under no treatment (A), under chronic treatment with simvastatin 40 mg/day (B) and after an acute-on-chronic dosage of 80 mg
simvastatin under chronic simvastatin treatment (C). Lipoprotein concentrations changed as expected under 40 mg/day simvastatin.
Fractional catabolic rates increased in IDL and LDL but not in VLDL fractions versus control [VLDL +35% in B (n.s.) and +21%
in C (n.s.); IDL +169% in B (P = 0.08) and +187% in C (P = 0.032); LDL +87% in B (P = 0.025) and +133% in C (P = 0.025)]. Chronic (B) and acute-on-chronic simvastatin treatment (C) did not affect lipoprotein production rates [VLDL −8
and −13%, IDL +47 and +38%, and LDL +19 and +30% in B and C, respectively (all comparisons n.s.)]. The data indicate that
simvastatin does not influence the secretion of apoB-100-containing lipoproteins in non-obese subjects with near-normal LDL
cholesterol concentrations. 相似文献
15.
Hepatic synthesis of lipoproteins and apolipoproteins was investigated in male Wistar rats with severe nephrotic syndrome
induced by puromycin aminonucleoside by incubating liver slices with a mixture of14C-amino acids. Labeled lipoproteins were separated by preparative ultracentrifugation from the incubation medium after the
addition of carrier plasma. The incorporation of14C-amino acids into very low density lipoproteins (VLDL) (1.006 g/ml), low density lipoproteins (LDL) (1.006–1.063 g/ml) and
high density lipoproteins (HDL) (1.063–1.210 g/ml) was increased in nephrotic liver 6.1-, 5.7- and 5.0-fold, respectively.
The measurement of radioactivity associated to apolipoproteins isolated by SDS-PAGE documented an increased incorporation
into apolipoprotein E (apoE) of nephrotic VLDL (33.1% vs 20% of the total radioactivity incorporated into VLDL apoproteins)
and a markedly increased incorporation into apolipoprotein A-I (apoA-I) of nephrotic HDL (44.3% vs 16.3% of the total radioactivity
incorporated into HDL apoproteins). In nephrotic liver, the total incorporation of amino acids into apolipoproteins (apoVLDL+apoLDL+apoHDL)
was increased 12.6 times for apoA-I, 6.4 times for apoB, 5.0 times for apoE, 4.2 times for apoC+apoA-II and 2.5 times for
apoA-IV. We suggest that, in nephrotic liver: (a) the synthesis of VLDL, LDL and HDL is increased, and (b) the total synthesis
of apoA-I is selectively increased when compared to that of the other apolipoproteins.
Preliminary reports of this work were presented at the Annual Meeting of the European Society for the Study of the Liver (Düsseldorf,
September 13–15, 1979); at the 5th International Symposium on Atherosclerosis (Houston, November 6–9, 1979) and at the Annual
Meeting of the Italian Society for the Study of the Liver (Rome, December 14–15, 1979). 相似文献
16.
The incorporation of L-4,5-[3H]leucine into the ultracentrifugally separated apolipoproteins of very low, low, and high density lipoproteins (VLDL, LDL,
HDL) and into serum albumin was found three-to four-fold higher in nephrotic than in normal rats one hour after intravenous
injection. Incorporation of leucine into the circulating lipids was negligible. Increases of similar magnitude were obtained
in the incorporation of simultaneously injected 1,5[14C] citrate into the lipids of VLDL, LDL, and HDL of nephrotic rats. Of the citrate carbons incorporated into serum and liver
lipids, the proportion in cholesterol was higher in nephrotic rats when compared to normal rats. The incorporation of both
precursors into total proteins and lipids of the liver vs. the incorporation into the lipoproteins was relatively lower in
nephrotic than in control rats, indicating a preferential channeling into secretable products. The occurrence of enhanced
new lipid synthesis in nephrosis was corroborated by the finding of markedly enhanced synthesis of lipoprotein-borne fatty
acids and cholesterol from3H2O. These results point out that while leucine is not an efficient in vivo precursor of lipoprotein lipids in nephrosis, de
novo lipogenesis proceeds from other precursors. Similar trend of changes, though of smaller magnitude, was elicited in rats
after double plasmapheresis, 18 hr apart, when measured 3 hr after the second plasma withdrawal. This indicates that the loss
of circulating proteins either by direct removal or through kidney lesion stimulates the compensatory hepatic response involving
excessive lipoprotein synthesis. Time-course studies showed that peak incorporation of leucine and citrate into the protein
and lipid components of lipoproteins, respectively, as well as into serum albumin, occurred coincidentally 3 hr after the
second plasmapheresis, suggesting an interdependence of the enhanced protein and lipid synthesis. 相似文献
17.
Ultracentrifugation (UC) is the method most often employed for separation and quantification of lipoproteins. Because this
procedure requires expensive laboratory equipment, a large volume of fresh sample and an inordinate amount of time, it may
not be ideal for routine clinical/experimental use. The aim of the current study was to evaluate a method which combines selective
precipitation (HDL-P) and immunoseparation (LDL-I) for the rapid and reliable isolation of high density lipoproteins (HDL)
and low density lipoproteins (LDL) specifically for vitamin E and carotenoid determination within these fractions. Cholesterol
and triacylglycerol concentrations within the HDL and LDL were also determined to enable expression of vitamin E and carotenoid
concentrations per gram of lipid. Isolation of lipoproteins by UC was used as the reference method (HDL-UC/LDL-UC). There
were no significant differences between methods for α-and γ-tocopherol in LDL and HDL. Carotenoids measured in HDL and LDL
were comparable between the methods. The exception was higher lutein/zeaxanthin concentration in HDL-P and LDL-I compared
to HDL-UC and LDL-UC, respectively. Additionally, lycopene concentration was significantly lower in LDL-I compared to LDL-UC.
In comparing vitamin E and carotenoid values in lipoproteins separated from fresh and frozen plasma by the direct method,
there was no difference in α-tocopherol or the majority of carotenoids measured. In conclusion, a combination of selective
precipitation and immunoseparation of fresh or frozen plasma for subsequent α-and γ-tocopherol analyses provides an accurate
and reliable alternative to lipoprotein separation by UC. Additionally, carotenoid concentrations in HDL separated by selective
precipitation and analyses of α-and β-carotenes and β-cryptoxanthin in LDL separated by immunoseparation are also reliable,
while lycopene and lutein/zeaxanthin concentrations in LDL-I are not readily comparable to LDL-UC. 相似文献
18.
The demand for high density lipoprotein (HDL) quantitation has dramatically increased with the renewed awareness of the importance
of HDL as a negative risk factor for coronary heart disease. HDL is usually estimated by specific precipitation of the non-HDL
apoB-containing lipoproteins by polyanions and divalent cations followed by measurement of cholesterol in the supernatant.
A common procedure involves precipitation with sodium heparin at 1.3 mg/ml and MnCl2 at 0.046 M (final concentrations). This method is appropriate for serum but less than ideal for plasma because of incomplete
precipitation and sedimentation of the apoB-containing lipoproteins. A two-fold increase in Mn2+ to 0.096 M improves precipitation of the apoB-associated lipoproteins from plasma without excessive precipitation of HDL.
This modified heparin-Mn2+ procedure gives results nearly identical to the results with the ultracentrifugal reference method (cholesterol in the d>1.063
fraction corrected for losses and the presence of apoB-associated cholesterol). The dextran sulfate 500-Mg2+ and the sodium phosphotungstate-Mg2+ procedures give results consistently 2–4 mg/dl lower than does the reference method. In contrast, a heparin-Ca2+ method gives results 5–8 mg/dl higher than does the reference method. Immunochemical analysis of apoA-I in the precipitate
and apoB in the supernatant indicates that lower values for the phosphotungstate-Mg2+ procedure is due to partial precipitation of the A-I-containing lipoproteins, while higher values by the heparin-Ca2+ method are due to incomplete precipitation of the apoB-containing lipoproteins. Quantitation of the principal apoproteins
of HDL, A-I and A-II, represent an important additional index of HDL concentrations and composition. Quantitation of plasma
A-I and A-II concentrations by radial immunodiffusion indicates that women generally have higher HDL concentrations than men
(women, A-I, 135±25, A-II, 36±6; men, A-I, 120±20, A-II, 33±5; mean±S.D., in mg/dl). A-I and A-II do not increase with age
in men but show a slight increase with age in women. Estrogen increases HDL cholesterol and protein and may in part account
for the higher HDL in women. The lighter density HDL subclass has a higher A-I/A-II ratio than the denser HDL subclass, with
women generally having significantly more of the lighter HDL subclass. Density-gradient ultracentrifugation in CsCl2 gradients indicates that HDL contains subpopulations of differing hydrated density which vary in the A-I/A=II ratio. Immunoassay
of A-I and A-II when used in combination with HDL cholesterol analysis is a powerful tool for studies of HDL structure, epidemiology
and metabolism. 相似文献
19.
Fatty acid biosynthesis in Ehrlich cells in vitro was reduced when very low density lipoproteins (VLDL) isolated from the
ascites tumor plasma were added to the incubation medium. The degree of inhibition was dependent on the VLDL concentration.
At the VLDL concentrations usually present in the ascites plasma, there was a 30% decrease in biosynthesis as measured by3H2O incorporation into fatty acids. Analysis of the labeled fatty acids by gas liquid chromatography indicated that this decrease
was due to a reduction in fatty acid de novo biosynthesis and that chain elongation actually was increased when VLDL were
present. Although ascites plasma low- and high density lipoproteins also produced a concentration-dependent inhibition of
fatty acid biosynthesis, their effects were much smaller than those of the VLDL. Studies employing VLDL and radioactive free
fatty acids indicated that the cells took up and utilized fatty acids derived from these lipoproteins. When VLDL were present,
labeled free fatty acid incorporation into cell phospholipids, cholesteryl esters, and CO2 decreased, whereas its incorporation into the cell free fatty acid pool increased. By contrast, the cells incorporated only
very small amounts of fatty acid from either low- or high density lipoproteins. This suggests that the VLDL exert their inhibitory
effect on fatty acid synthesis by supplying exogenous fatty acids to the cells.
Presented in part at the AOCS Spring Meeting, Dallas, April 1975. 相似文献
20.
Human aortic smooth muscle cells (SMC) specifically bind and take up indiscriminately both the lipid and protein moietics
of homologous25I-very low density lipoproteins (VLDL) and125I-low density lipoproteins LDL). Sixty-five to 80% of absorbed lipids are incorporated into the cell lipids, preferentially
into the phospholipid fraction. Twenty to 35% of the lipid bound and the protein moiety are eliminated from the cells. Half
of the eliminated protein label is recovered as TCA soluble products. Five mM of p-chlorophenoxyisobutyrate (CPIB) raise the
level of intracellular radioactivity derived from the lipid moieties of VLDL and LDL by about 40% via a reduced elimination.
The processing of the protein moiety and lipoprotein binding to the cell surface are not affected by 5.0 mM of CPIB. CPIB
lowers the incorporation of14C-acetate,14C-pyruvate, and32phosphate radioactivity into fatty acids and phospholipids of aortic SMC. Five mM of CPIB reduce the overall palmitic acid
synthesis by shifting from de novo synthesis to the mechanism of chain elongation, although the further elongation to saturated
C18–C24 fatty acids is also depressed. The CPIB-enhanced retention of the lipid-derived lipoprotein radio-activity is interpreted
as a compensatory mechanism providing cellular fatty acids which are deficient as a result of the CPIB inhibited synthetic
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