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At least 19 recordsLinked to original sources
PubMed1981

Displacement of the human apoprotein A-I by the human apoprotein A-II from complexes of (apoprotein A-I)-phosphatidylcholine-cholesterol.

Reassembly experiments, involving isolated human apoproteins A-I and A-II and (dimyristoylglycerophosphocholine)-cholesterol vesicles were performed with apoprotein mixtures at apoprotein A-I/A-II molar ratios varying between 0 and 3. The apoproteins were incubated at 24 degrees C. 28 degrees C and 32 degrees C with either pure dimyristoyl-glycerophosphocholine vesicles or with dimyristoylglycerophosphocholine cholesterol vesicles containing 2, 5, 10, 15 mol/100 mol cholesterol. The kinetics of association were followed by measuring the increase of the fluorescence polarization ratio after labeling the lipids with diphenyl hexatriene. The complexes were separated from the free protein by gradient ultracentrifugation. Total protein was assayed and the apoproteins A-I and A-II were quantified separately by immunonephelometry. The content of apoprotein A-I was also monitored by measuring the intrinsic tryptophan fluorescence. The results suggest that apoprotein A-II has a greater affinity than apoprotein A-I for the phospholipid-cholesterol vesicles and that apoprotein A-II is able to quantitatively displace apoprotein A-I from the lipid-protein complexes. The content of apoprotein A-II in the complexes increases proportionally to the concentration of apoprotein A-II in the incubation mixture until saturation is reached. At saturation the dimyristoylglycerophosphocholine/apoprotein A-II ratio in the complex is dependent upon the cholesterol content of the original vesicles and increases from 60 to 275 mol/mol between 0 and 15 mol/100 mol cholesterol. From these experiments one can calculate that 1 mol human apoprotein A-I is displaced by 2 mol human apoprotein A-II.

Apolipoprotein A-I↗
PubMed1988

Comparison of commercial kits for apoprotein A-I and apoprotein B with standardized apoprotein A-I and B radioimmunoassays performed at the Northwest Lipid Research Center.

There has recently been a proliferation of commercial kits available for apoproteins A-I and B. Since reference procedures for apoproteins have not yet been established we have elected to compare apoprotein kit methods with highly standardized apoprotein B and A-I radioimmunoassays developed at the Northwest Lipid Research Center. Commercial radial immunodiffusion kits for apoproteins A-I and B were obtained from three separate companies, Calbiochem, Daiichi Pure Chemicals, and Tago, and a commercial radioimmunoassay kit for apoprotein A-I was obtained from Ventrex Laboratories. Considerable differences were observed between the commercial kit methods and the Northwest Lipid Research radioimmunoassay methods. Some of the differences between methods were related to the assigned value of the reference materials. Other differences between methods were clearly method-dependent.

Apolipoprotein A-I↗
PubMed1985

Molecular weights of apoprotein B obtained from human low-density lipoprotein (apoprotein B-PI) and from rat very low density lipoprotein (apoprotein B-PIII).

Human low-density lipoproteins (LDL) were isolated from single donors by differential centrifugation between densities of 1.020 and 1.050 g/mL. The LDL were reduced and alkylated in 7 M guanidine hydrochloride, and the lipid was removed by multiple extractions in the cold with a mixture of diethyl ether and ethanol. Sedimentation studies on the resultant human apoprotein B (apoprotein B-PI) at low concentrations in 6.00 M guanidine hydrochloride showed a single sharp boundary with a sedimentation coefficient of 2.15 +/- 0.04 S at 25 degrees C, uncorrected for viscosity or density. Diffusion experiments performed in the same solvent at low speeds in the analytical ultracentrifuge gave a D25 = 0.694 +/- 0.043 Fick. Combining these values with an apparent specific volume of 0.703 mL/g yielded a molecular weight of 387 000, indistinguishable from that obtained by sedimentation equilibrium analysis in 7 M guanidine hydrochloride. Similar values were also obtained by calibrated sedimentation analysis, by Sepharose 2B chromatography in guanidine hydrochloride, and by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Rat very low density lipoproteins (VLDL), isolated from sera of Triton WR1339 treated animals, were used as the source of rat apoprotein B-PIII. The delipidated VLDL were solubilized in sodium dodecyl sulfate, and apoprotein B-PIII was isolated by Sepharose 4B chromatography. With appropriate corrections for density and viscosity, the behavior of rat apoprotein B-PIII was identical, upon analytical ultracentrifugation, in 6 and 7.7 M guanidine hydrochloride, corresponding to sedimentation and diffusion coefficients of 1.47 S and 0.92 Fick, respectively, in 6 M guanidine hydrochloride. These data may be combined to yield a molecular weight of 210 000. Similar values were obtained by calibrated sedimentation analysis, by Sepharose 2B chromatography in guanidine hydrochloride, and by polyacrylamide gel electrophoresis in sodium dodecyl sulfate.

Animals↗
PubMed1989

Comparison of two commercial nephelometric methods for apoprotein A-I and apoprotein B with standardized apoprotein A-I and B radioimmunoassays.

Normotriglyceridemic and hypertriglyceridemic samples were analyzed for apoproteins A-I and B using the Beckman Array System and the Behring Nephelometer, and the nephelometric values were compared to values obtained by highly standardized radioimmunoassays developed at the Northwest Lipid Research Center. Although the means of the apoA-I values obtained by each method were similar, comparison of sample values by least-squares regression analysis revealed large differences (Sy = 20 mg/dl for Beckman, Sy = 18 mg/dl for Behring) (Sy = standard error of the estimate) regardless of whether the comparison included hypertriglyceridemic samples. For normotriglyceridemic samples, there was good agreement between apoB values obtained by the Behring Nephelometer and those obtained by RIA (r = 0.91, m = 1.03, Sy = 12 mg/dl). However, significantly higher apoB values were obtained on hypertriglyceridemic samples by the Behring Nephelometer. ApoB values for normotriglyceridemic samples obtained by the Beckman System and RIA showed fairly good correlation (r = 0.86, m = 0.71, Sy = 14 mg/dl). However, the nephelometric values for normotriglyceridemic samples averaged 29% lower than those obtained by RIA. This difference could largely be accounted for by the low apoprotein B value assigned to the Beckman calibrator. Significantly lower apoprotein B values were obtained on hypertriglyceridemic samples by the Beckman Nephelometer even after correction for calibration differences. Apoprotein values obtained by nephelometric methods may be inaccurate, particularly if the samples are hypertriglyceridemic.

Apolipoprotein A-I↗
PubMed1986

Parallel expression of the MB19 genetic polymorphism in apoprotein B-100 and apoprotein B-48. Evidence that both apoproteins are products of the same gene.

Immunochemical studies have demonstrated that apoprotein B-100 and apoprotein B-48 share some antigenic determinants, but whether they are products of the same gene has remained uncertain. Utilizing a specific mouse monoclonal antibody, MB19, we recently characterized a common form of genetic polymorphism that was expressed in apo-B-100 (Young, S. G., Bertics, S. J., Curtiss, L. K., Casal, D. C., and Witztum, J.L. (1985) Proc. Natl. Acad. Sci. U.S.A., in press). Antibody MB19 binds different allotypes of apo-B-100 (MB19(1) and MB19(2] with high and low affinities, respectively. Compared to a rabbit antiserum against human low density lipoprotein, which detects 100% of apo-B mass in all individuals, antibody MB19 detects 100% of apo-B with allotype MB19(1) but less than 10% of apo-B with allotype MB19(2). Western blots demonstrate that MB19 binds to both apo-B-100 and apo-B-48. To determine if apo-B-48 and apo-B-100 from the same individual express the same polymorphism, chylomicrons and very low density lipoproteins were isolated from 23 subjects in whom the allotypes of apo-B-100 were known. Delipidated apoproteins were separated electrophoretically and then transferred to nitrocellulose membranes. Nitrocellulose membranes were incubated with 125I-MB19 (to detect the polymorphism) and 131I-antiserum to human apo-B (to quantitate total apo-B transferred to nitrocellulose membranes). Apo-B-100 and apo-B-48 bands were removed and the ratio of 125/131 counts in each band was calculated. In all 23 subjects studied, the same MB19 polymorphism was present in both apo-B-100 and apo-B-48. This observation provides strong evidence that both apoproteins are products of the same gene.

Adult↗
PubMed1983

Metabolism of apoprotein B in cynomolgus monkey: evidence for independent production of low-density lipoprotein apoprotein B.

The catabolism of very-low-density lipoprotein apoprotein B and its conversion to low-density lipoprotein was studied in five chow-fed cynomolgus monkeys following injection of radioiodinated homologous very-low-density lipoproteins. The mean (+/- SD) fractional catabolic rate of very-low-density lipoprotein apoprotein B was 0.97 +/- 0.20 h-1 and the mean (+/- SD) production rate was 0.76 +/- 0.20 mg X kg-1 X h-1. The percent of conversion of very-low-density lipoprotein apoprotein B to low-density lipoprotein ranged from 33 to 59%. In separate studies of low-density lipoprotein apoprotein B turnover performed using homologous radiolabeled low-density lipoprotein in five additional animals, the mean (+/- SD) fractional catabolic rate for low-density lipoprotein apoprotein B was 0.050 +/- 0.017 h-1 and the mean (+/- SD) apoprotein B production rate was 0.70 +/- 0.18 mg X kg-1 X h-1. Comparison of the total low-density lipoprotein apoprotein B production with that derived from very-low-density lipoprotein apoprotein B suggested that a large fraction of plasma low-density lipoprotein apoprotein B was derived from a source exclusive of circulating very-low-density lipoprotein apoprotein B. This was confirmed in two animals by simultaneous injection of radiolabeled very-low-density and low-density lipoproteins. Thus, a significant proportion of cynomolgus monkey low-density lipoproteins are produced either by direct hepatic secretion or by rapid conversion of lower-density lipoproteins before they appear in the peripheral circulation.

Animals↗
PubMed1980

A-Imilano apoprotein. Isolation and characterization of a cysteine-containing variant of the A-I apoprotein from human high density lipoproteins.

A recently discovered familial lipoprotein disorder is characterized by reduced plasma levels of high density lipoproteins (HDL) and elevated triglyceride levels. The clinical aspects of this disorder are presented in an accompanying article (Franceschini et al. 1980. J. Clin. Invest. 66: 892-900). The apoprotein content of the HDL isolated from these patients differed markedly from that of normal HDL in that three apoprotein bands not previously described in man were present as major protein components. As determined by sodium dodecyl sulfate (SDS) gel electrophoresis, the relative molecular weights (Mr) of these new apoprotein bands were 55,000, 35,000, and 28,000. Although the Mr 28,000 apoprotein coelectrophoresed with authentic A-I on SDS polyacrylamide gels and showed immunochemical identity with the A-I apoprotein when tested with monospecific apo-A-I antiserum, it contained two amino acid residues, cysteine and isoleucine, which were not present in the amino acid sequence of normal human apo-A-I. This variant form of the A-I apoprotein was designated the A-IMilano apoprotein and denoted A-Icys. By virtue of the presence of cysteine (2 mol/mol A-Icys), the A-Icys apoprotein was capable of forming intermolecular disulfide bonds, and dimer formation of A-Icys produced the Mr 55,000 apoprotein. The Mr 35,000 apoprotein was composed of two different subunits, A-Icys and A-II. By analogy to the apo(E--A-II) complex, which also occurs in human HDL, this mixed disulfide complex was designated as the apo(A-Icys--A-II) complex. The A-IMilano (A-Icys) is the first example of a variation in the primary sequence of a protein of plasma lipoproteins.

Adolescent↗
PubMed1976

Incorporation of 75Se-selenomethionine into human apoproteins. III. Kinetic behavior of isotopically labeled plasma apoprotein in man.

The metabolism of lipoprotein-apoprotein was examined in four subjects with normal lipid metabolism and in one subject with type II hyperlipemia by means of isotopic tracer methodology. Studies were performed after intravenous injection of a radioactive amino acid precursor for apoprotein synthesis (75Se-selenomethionine), in both the basal state and following the acute injection of intravenous heparin. Computer technics were used to evaluate a series of multicompartmental models, and a general model is proposed that yields optimum fitting of experimental data for serum free amino acid precursor, very-low-density lipoprotein-apoprotein (VLD-apoprotein), and low-density lipoprotein-apoprotein (LDL-apoprotein) in man. The analysis demonstrates that approximately half of the transport of 75Se-apoVLDL from the plasma VLDL pool is converted to 75Se-apoLDL. The acute injection of heparin in two normal subjects results in a two-and-a-half-fold increase in this rate of conversion of 75Se-apoVLDL to 75Se-apoLDL. 75Se-apoLDL is metabolized by rapid transport into a recycling extravascular pool and by irreversible catabolism. The fractional rate of recycling is large relative to the fractional rate of catabolism of apoLDL (3.7:1.0), suggesting extravascular recycling as a potential site of regulation of the plasma concentration of apoLDL. In a patient with type II hyperlipemia, the extravascular recycling pathway is reduced and is not corrected with D-thyroxine therapy. However, this therapy did reduce conversion of apoVLDL to apoLDL in this type II patient. The kinetic data support the validity of the compartmental model in simulating both normal and pathologic apoprotein metabolism and that perturbation of physiology seen with heparin injection and D-thyroxine therapy. These data support a quantitative role of apoVLDL as a precursor of apoLDL and identify an important recycling pathway of apoLDL metabolism in addition to that of catabolism.

Adult↗
PubMed1987

The development of monospecific antibodies against human thromboplastin apoprotein (apoprotein III) and their application in the immunocytochemical detection of the antigen in blood cells.

Human thromboplastin apoprotein (apoprotein III) purified by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) was purified a further 2-4 fold by PAGE in the presence of digitonin. Subsequent line immunoelectrophoresis of the protein revealed several lines, only one of which contained inhibitory antibodies. New inhibitory antibodies which were raised by using this particular line to immunize rabbits produced only a single line in immunoelectrophoresis of apoprotein III, with precipitated inhibitory antibodies being present only in the line. When these antibodies were used in electroblot immunobinding studies of crude thromboplastin after SDS-PAGE staining was found mainly in a single band of MW about 50,000, but also to some extent in immunologically related higher MW material. Prior deglycosylation of the thromboplastin using trinitrobenzenesulfonic acid resulted in a shift of the bulk of the main band representing an apparent MW reduction of 16%, and a corresponding shift in the position of protein with the capacity to bind inhibitory antibodies. Besides being a good criterion of specificity of the antibodies this also suggests that non-carbohydrate parts of apoprotein III may be involved in the interaction with Factor VII. Immunoperoxidase staining of unstimulated or endotoxin stimulated blood cells using the antibodies revealed the presence of significant amounts of apoprotein III only in stimulated monocytes, apparently available on the surface of the cells since it was detectable also by preembedding staining of fixed cells in suspension. The result is strong evidence that apoprotein III is synthesized de novo in monocytes upon endotoxin stimulation.

Antibodies↗
PubMed1990

Chlorophyll regulates accumulation of the plastid-encoded chlorophyll apoproteins CP43 and D1 by increasing apoprotein stability.

Chlorophyll apoprotein accumulation in higher plant chloroplasts is controlled by light-dependent chlorophyll formation. Dark-grown plants lack chlorophyll and chlorophyll apoproteins. However, the plastid genes encoding the chlorophyll apoproteins are transcribed; chlorophyll apoprotein mRNA accumulates and associates with polysomes in plastids of dark-grown plants. Pulse-labeling assays revealed a population of short-lived proteins in plastids of dark-grown plants. One of these transiently labeled proteins was CP43, a chlorophyll apoprotein associated with photosystem II. Pulse-chase assays showed that newly synthesized CP43 was rapidly degraded in plastids of dark-grown plants, which lack chlorophyll. In contrast, CP43 synthesized in plastids from illuminated plants was stable. The synthesis of D1, a chlorophyll apoprotein of the photosystem II reaction center, was also analyzed in plastids of dark-grown and illuminated plants. Radiolabel accumulation into full-length D1 was only detected in plastids of illuminated plants. However, D1 translation intermediates of 15-25 kDa were detected in both plastid populations. Pulse-chase assays showed that the 15- to 25-kDa D1 translation products were precursors of mature D1 in plastids of illuminated plants. In contrast, in plastids of dark-grown plants, the 15- to 25-kDa translation intermediates were converted into a 23-kDa polypeptide previously suggested to be a proteolytic product of D1. These results indicate that chlorophyll produced in illuminated plants stabilizes D1 nascent polypeptides, which allows accumulation of mature D1.

Apoproteins↗
PubMed1979

Apoproteins of avian very low density lipoprotein: demonstration of a single high molecular weight apoprotein.

The high molecular weight apoproteins of very low density lipoprotein (VLDL) were compared after preparation of VLDL from plasma and sera of diethylstilbestrol-treated roosters. When prepared from plasma with adequate control of endogenous proteolytic activity, VLDL contained a single high molecular weight apoprotein (apo-VLDL-B) as judged by electrophoresis in polyacrylamide gels containing sodium dodecyl sulfate. Serum VLDL contained multiple apoprotein species, the largest of which corresponded to apo-VLDL-B. Immunological analyses showed that the multiple apoproteins of serum VLDL were quantitatively and qualitatively indistinguishable from plasma apo-VLDL-B. These data indicate that apo-VLDL-B can be cleaved during VLDL isolation to produce an apparent heterogeneity of high molecular weight apoproteins. The molecular weight of plasma apo-VLDL-B was estimated to be 350 000. This protein was stable to reduction and S-carboxymethylation and showed no association with apo-VLDL-II [Chan, L., Jackson, R.L., O'Malley, B. W., & Means, A.R. (1976) J. Clin. Invest. 58, 368] through disulfide linkage. Apo-VLDL-B and apo-VLDL-II represented 54% and 46%, respectively, of the total VLDL protein recovered following gel filtration chromatography in sodium dodecyl sulfate. Protein recovery in the chromatographic analyses (92%) was sufficient to conclude that apo-VLDL-B and apo-VLDL-II are the major and possibly the only apoproteins of chicken VLDL. The molar ratio of the apo-VLDL-II monomer to apo-VLDL-B was estimated to be 32.

Animals↗
PubMed1981

Studies on the apoproteins of rat lymph chylomicrons: characterization and metabolism of a new chylomicron-associated apoprotein.

The apoprotein composition of rat lymph chylomicrons and very low density lipoprotein (VLDL) was investigated following isolation and purification by preparative gel electrophoresis. The medium molecular weight apoproteins in the 27,000-60,000 range were characterized by electrophoretic mobility, immunochemical identification, amino acid composition, and molecular weight determination. In addition to three previously identified apoproteins, A-I, E, and A-IV, present in both rat serum high density lipoproteins (HDL) and lymph chylomicrons, a fourth peptide of molecular weight 59,000 was always a consistent major component of lymph VLDL washed free of serum protein contaminants by repeated ultracentrifugation. The protein formed complexes with phosphatidylcholine vesicles, was amphipathic in nature, and, when injected into rats, became associated with serum HDL and lymph chylomicrons. It was removed from chylomicrons after gel filtration through agarose columns but not after repeated ultracentrifugation; it differed slightly in amino acid composition and did not show immunochemical identity against antisera to any other apoprotein. The results of in vivo studies suggest that the protein preferentially associates with lymph chylomicrons and thus may play some important role in the metabolism of exogenous triglyceride transport. Since A-I, A-II, and A-IV apoproteins are also integral components of lymph chylomicrons, we suggest that the protein be designated A-V apoprotein. The distribution of A-I, E, A-IV, and A-V in serum HDL and lymph VLDL was approximately 54, 10, 12, and 0%, and 22, 3, 19, and 22%, prospectively.

Amino Acids↗
PubMed1984

Interaction of thromboplastin apoprotein of different tissues with concanavalin A--evidence for heterogeneous glycosylation of the human apoprotein.

Thromboplastin apoproteins of different tissues were solubilized with Triton X-100. Induction of plasma coagulation by these extracts was dependent on the presence of factor VII. Binding of the apoprotein-Triton complex to Concanavalin A-Sepharose 4B was studied. The apoprotein activity extracted from rabbit brain and bovine brain was almost completely bound to Concanavalin A-Sepharose. Under the same conditions, only partial binding was observed with human lung, human brain and human placenta apoproteins. These results suggest that human apoprotein is heterogeneous with respect to its carbohydrate moiety.

Animals↗
PubMed1983

Apoprotein A and apoprotein B in patients with chronic renal failure undergoing hemodialysis and in renal graft recipients.

Serum concentrations of high density lipoproteins (HDL)-cholesterol, apoprotein A and apoprotein B has been studied in 13 patients with chronic renal failure treated with hemodialysis and in 12 patients with functioning renal graft. 5 patients on hemodialysis and 6 with a renal graft had hypertriglyceridemia. In the hemodialyzed patients, the increase in triglycerides was associated to a decreased concentration of serum apoprotein B. HDL-cholesterol was substantially reduced in the hemodialyzed patients without this being associated with a drop in serum apoprotein A concentration, thus suggesting that there are changes in the qualitative composition of the HDL. In renal graft recipients, the HDL-cholesterol and the apoprotein A concentration were increased. It is suggested that the risk of developing accelerated atheromatosis in patients carrying a renal graft cannot be related to changes in HDL. In patients undergoing hemodialysis, the development of atheromatosis would be related to decreased concentration and also qualitative changes in the HDL together with the increase in the VLDL and LDL.

Adult↗
PubMed1983

In vivo metabolism of human apoprotein A-I-phospholipid complexes. Comparison with human high density lipoprotein-apoprotein A-I metabolism.

The metabolism of apolipoprotein A-I was investigated in healthy young adults. The apoprotein was injected intravenously in one of the four following forms: radiolabelled high density lipoproteins, HDL incubated with labelled apo A-I, labelled A-I-dipalmitoyl- or dimyristoylphosphatidylcholine complexes or free apoprotein A-I. The radioactivity-time curves of high density lipoproteins were followed for 15 days. The kinetic studies demonstrate similar fractional catabolic rates, half-lifes and rates of synthesis. Fractional catabolic rate calculated from plasma data was in reasonable agreement with the value derived from the urine/plasma activity ratio. When free apo A-I was injected, the unusual form of the U/P ratio curve is interpreted as the result of different fates of the injected molecules. This study indicates that the half-life of apo A-I seems not to be affected by the form in which the apoprotein is injected and that kinetics of apo A-I-phospholipid complexes may be used as a valid index of apoprotein A-I/HDL metabolism.

Apolipoprotein A-I↗
PubMed1989

Cloning of apoprotein AI gene and observation on DNA polymorphism of apoprotein AI/CIII gene-loci in genomic library from a liver of Chinese.

For the research on the structure and function of the HDL apoproteins, we have successfully constructed a complete genomic library, in self-prepared EMBL3 lambda vector and the packaging extracts of lysogenic strains BHB2688, BHB2690, from a Chinese fetal liver, which will be widely used in the research on the structure and function of apoproteins. In this study, a DNA sequence polymorphism, revealed by digestion of human DNA with the restriction endonuclease Sst1 and hybridization with an apoprotein AI cDNA probe, has been shown to be located at apoAI/CIII gene-loci. Three gene related fragments (5.7 Kb, 4.0 Kb and 3.0 Kb) were detected. The 5.7 Kb fragment is common and the polymorphism is demonstrated by the presence of either a 4.0 Kb fragment (S1 allele) or the 3.0 Kb fragment (S2 allele). Individuals were genotyped S1S1 or S1S2. Our result showed that the frequency of genotype S1S2 was higher in hypertriglyceridemic subjects than that in normolipidemic subjects.

Apolipoprotein A-I↗
PubMed1984

Age-related changes of serum apoprotein SASSAM, apoprotein A-I and low-density lipoprotein levels in senescence accelerated mouse (SAM).

Age-related changes of serum concentration of apo SASSAM, an apoprotein of high density lipoprotein (HDL) which cross-reacts with antiserum against murine senile amyloid fibril protein (ASSAM) were estimated in senescence accelerated mouse (SAM-P) and in senescence resistant series (SAM-R), as a control, using a single radial immunodiffusion technique. Serum concentrations of apo A-I, a major apoprotein of HDL, and low density lipoprotein (LDL) were also measured. In SAM-P (SAM-P/1 and SAM-P/2) with a high incidence of senile systemic amyloidosis, we observed age-associated decreases in serum apo SASSAM levels. The concentrations of apo SASSAM at 16 months of age were below 40% of the concentration at 2 months of age, regardless of the sex. In contrast with SAM-P, we observed no age-associated decrease of serum apo SASSAM levels in SAM-R (SAM-R/1 and SAM-R/2) with a low incidence of amyloidosis. Serum apo SASSAM concentration was higher in SAM-R/1 than in any other strain of mice observed. Serum apo A-I concentration was highly and significantly correlated with the serum concentration of apo SASSAM and decreased with advancing age in SAM-P but not in SAM-R. Age-related changes of LDL were not observed in any strain, but the concentration was lower in the females. In old SAM-P (16 months' old), the concentration of apo SASSAM decreased to one-third of that in the young SAM-P (4 months' old) and the serum concentrations of albumin and total protein did not decrease, compared with those in the young mice. All these findings taken together suggest that abnormality of metabolism in apo SASSAM, putative precursor of ASSAM, might occur in SAM-P.

Aging↗
PubMed1990

Concentrations of apoprotein CII, CIII, and E in total serum and in the apoprotein B-containing lipoproteins, determined by a new enzyme-linked immunosorbent assay.

We describe a new enzyme-linked immunosorbent assay (ELISA) that permits direct determination of apoprotein (apo) CII, CIII, and E in total serum as well as in apo B-containing lipoprotein particles. To validate this ELISA technique, we studied several aspects of the assay: its specificity, the influence of the conditions of conservation of plasma and of lipoprotein fractions, the effect of delipidation, and its reproducibility. We measured the concentrations of apo CII, CIII, and E in total serum and in apo B-containing lipoproteins from a pool of normal sera and in sera from 75 healthy subjects. After sequential ultracentrifugation, the content of apo CII, CIII, and E in the major lipoprotein fractions was also determined. Total serum or plasma could be stored at -20 or -50 degrees C for at least six weeks and the isolated lipoprotein fractions for as long as four weeks, which suggests a protective effect of total serum on lipoprotein particle structure. Advantages of this ELISA include (a) its specificity, sensitivity, and reliability; (b) better discrimination than determination of total serum apoprotein; (c) easier application and greater rapidity; and (d) the possibility of application to population screening.

Apolipoproteins B↗