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G Schonfeld

Publications and source records attributed to G Schonfeld.

At least 19 recordsLinked to original sources
PubMed1992

Lengths of truncated forms of apolipoprotein B (apoB) determine their intestinal production.

Most truncations of apoB associated with hypobetalipoproteinemia (HBL) result from frame shift mutations of the apoB gene that give rise to premature stop codons and truncations of C-terminal sequences. The "natural" truncation, apoB-48, arises from a stop codon by cotranscriptional editing of intestinal apoB-100 mRNA. We hypothesized that mutant apoB mRNA would be normally edited and that only those apoB truncations shorter than apoB-48 would be expressed in enterocytes, because translation of mRNAs giving rise to longer truncations would be interrupted by the apoB-48 stop codon. Duodenal mucosal biopsies from HBL and normolipidemic subjects were incubated with [35S]methionine, apoB was immunoprecipitated and bands were visualized by autoradiography. Biopsies of three subjects heterozygous for apoB-54.8 or apoB-89 synthesized virtually only apoB-48. By contrast, the biopsy of a subject heterozygous for apoB-40 synthesized both apoB-48 and apoB-40. Thus, enterocytes in HBL edit the mutant mRNAs similarly to the apoB mRNA of normal enterocytes and the small intestine of heterozygotes with truncations longer than apoB-48 produce only apoB-48, as the apoB-48 stop codon terminates translation proximal to the mutant stop codon. By contrast, intestines of heterozygotes with truncations shorter than apoB-48 produce the truncated apoB because the mutant stop codon stops translation before the apoB-48 stop codon. In conclusion, only the liver secretes apoB truncations larger than apoB-48, whereas shorter truncations are secreted by both liver and intestine.

Apolipoproteins B↗
PubMed1992

Hormonal and nutritional stimuli modulate apolipoprotein B mRNA editing in mouse liver.

Human livers produce apoB-100, a major protein of VLDL, while intestines produce apoB-48, the major protein of chylomicrons. ApoB-48 is translated from apoB-100 mRNAs that are post-transcriptionally edited at codon 2153, converting CAA (glutamine) to TAA, a stop codon. In contrast to humans, mouse and rat livers contain the apoB-100 mRNA editing mechanism. Because hormones and nutrients affect the metabolism of apoB containing lipoproteins, we studied the effects of sex hormones and diets on apoB mRNA editing. Groups of male and female C3H/HeJ mice were castrated and treated with 17 beta-estradiol at 0.16 (E2L) or at 5 micrograms (E2H), or with testosterone propionate at 1 microgram/g body weight/day for 14 days. Plasma apoB levels and ratios of apoB-100/apoB-48 both increased 2-fold, but only in the E2H group. To determine if the increased apoB-100/apoB-48 ratios were associated with altered levels of apoB-100 and apoB-48 mRNA, both forms of apoB mRNA were quantified. We found that indeed ApoB-100 mRNA increased 1.8-fold (p < 0.025) compared to apoB-48 mRNA only in the E2H group. Next, we studied the individual effects of dietary fatty acids and dietary cholesterol on the relative abundance of apoB-100 and apoB-48 mRNA. Contrary to the estrogen effect, the high fat-combination diet increased apoB-48 mRNA relative to apoB-100 mRNA. Total plasma apoB as well as apoB-48 synthesis in liver also increased. Our studies demonstrate that estrogens and high fat diet both modulate apoB editing in mouse liver, but that estrogens and fat diet affected apoB mRNA editing in opposite directions.

Animals↗
PubMed1992

Dietary fatty acids and dietary cholesterol differ in their effect on the in vivo regulation of apolipoprotein A-I and A-II gene expression in inbred strains of mice.

Dietary cholesterol and dietary saturated fatty acids affected the plasma concentrations of various HDL components and the hepatic and intestinal expression of the apolipoprotein (apo) A-I gene and the hepatic expression of the A-II gene differently in three inbred strains of female mice. Thus, the HC diet (0.5% cholesterol, no added fatty acids) decreased HDL-cholesterol in C57BL and SWR strains but not in the C3H strain; plasma apo A-I and apo A-II concentrations decreased in all three strains. HDL-C/apo A-I and apo A-I/apo A-II mass ratios increased, suggesting that the HC diet altered both the concentrations and the compositions of HDL particles. In contrast, the HF diet (20% hydrogenated coconut oil, no added cholesterol) increased HDL cholesterol and apo A-I concentrations. The combination diet (HF/C, 20% coconut oil plus 0.5% cholesterol) increased HDL cholesterol and decreased triacylglycerols. Apo A-I concentrations were unaltered except for a significant increase in SWR mice. Apo A-II concentrations decreased in all strains. To examine molecular events that could lead to the changes in plasma apo A-I and apo A-II, we measured transcription rates in hepatic nuclei and steady state mRNA concentrations in liver and intestine and apo A-I synthetic rates in liver. Dietary cholesterol and fatty acids produced differing effects at transcriptional as well as post-transcriptional loci and the changes differed according to mouse strain. The most pronounced strain-related differences for both apo A-I and apo A-II occurred at post-transcriptional loci of apoprotein production. These could represent altered rates of translation in, or secretion from liver and/or intestine, or altered rates of clearance from plasma. In conclusion, the regulation of apo A-I and apo A-II gene expression by diet occurs at several steps of their production and perhaps also in catabolic pathways. This study identifies potential loci of regulation and forms the basis for future studies investigating specific genetic and molecular regulatory mechanisms.

Animals↗
PubMed1992

Double-blind comparison of bezafibrate versus placebo in male volunteers with hyperlipoproteinemia.

The efficacy and safety of bezafibrate were evaluated in 83 patients with type IIa, IIb, or IV hyperlipoproteinemia. Following a 12- to 14-week placebo period on a coronary-prudent diet (Period 1), patients were assigned randomly to receive either bezafibrate 600 mg/day or placebo, plus diet in a double-blind, 12-week treatment period (Period 2). The return of lipid and lipoprotein levels toward baseline was evaluated in a subsequent 8-week period on placebo plus diet (Period 3). In patients with type IIa hyperlipoproteinemia, bezafibrate significantly lowered total (14.6%, P less than 0.001) and LDL-cholesterol (16.4%, P less than 0.001) and total (29.9%, P less than 0.001) and VLDL-triglyceride (44.0%, P less than 0.001) and significantly increased HDL cholesterol (9.5%, P less than 0.001). In patients with type IIb, bezafibrate had a qualitatively similar effect to that seen in type IIa on each of these lipoproteins, but the sample size was too small for statistical evaluation. In patients with type IV, bezafibrate lowered total (48.3%, P less than 0.01) and VLDL-triglyceride (57.7%, P less than 0.001) and VLDL-cholesterol (56.8%, P less than 0.001) and increased HDL-cholesterol (16.6%, P less than 0.05). All values returned toward baseline during Period 3. Only two bezafibrate patients experienced adverse events that were considered definitely treatment related; one was dropped from the study because of elevations in SGOT and SGPT, 1.5- and 4-times the upper limit of normal, respectively. For other laboratory parameters, trends upward or downward were small and of doubtful clinical significance. Bezafibrate appears to be effective and safe for modifying lipid and lipoprotein levels in patients with types IIa, IIb and IV hyperlipoproteinemia.

Adolescent↗
PubMed1992

Short-term interruption of training affects both fasting and post-prandial lipoproteins.

Exercise training alters plasma lipoprotein profiles in a manner compatible with decreased coronary artery disease risk. The aim of this study was to ascertain whether interruption of training (detraining) was associated with potentially undesirable changes in the metabolism of post-prandial lipoproteins and plasma levels of Lp(a). Eight normolipidemic, male runners who ran 30-40 miles/week were studied in the trained state and after 14-22 days of detraining. Two of the subjects were studied in the reverse order to control for any confounding effects of exercise sequence. Detraining resulted in (1) a 12% (P = 0.002) reduction in the subjects' aerobic capacity, (2) a 7.7% (P = 0.007) reduction in fasting concentrations of high density lipoprotein cholesterol (HDL-C), (3) a 21% (P = 0.01) reduction in post-heparin lipoprotein lipase activity. Lp(a) concentrations did not change significantly (mean increase 15%, P = 0.076). Fasting plasma concentrations of total cholesterol (TC), triglycerides (TG) and low density lipoprotein-cholesterol (LDL-C) did not change in the detrained state. There was little fluctuation over 24 h in plasma concentrations of TC, LDL-C and HDL-C in either the trained or detrained states. TG concentrations fluctuated over the 24 h in accord with food intake, but there were no exercise-related changes. Exercise had a dramatic effect on chylomicron and chylomicron remnant metabolism as measured by retinyl palmitate measurements. The mean areas under the concentration vs. time curves (AUC) for chylomicron-retinyl esters increased by 41% (P = 0.013) and for chylomicron remnant-retinyl ester by 37% (P = 0.058) following detraining.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

A novel truncated apolipoprotein B (apo B55) in a patient with familial hypobetalipoproteinemia and atypical retinitis pigmentosa.

We have identified an apolipoprotein (apo) B mutation in a patient with an atypical form of retinitis pigmentosa (RP). In the family the eye disease is characterised by late age of onset and autosomal dominant inheritance. In addition to RP, the proband has low total cholesterol (4.5 mmol/l) and LDL-cholesterol (2.0 mmol/l) levels characteristic of the autosomal codominant apolipoprotein (apo) B deficiency disease hypobetalipoproteinemia (HBL). Using a monoclonal antibody directly against apo B and immunoblots of SDS polyacrylamide gel separated plasma, a normal apo B100 and a truncated apo B species with an estimated size of apo B54 was identified in the proband and his RP-affected sister. The location of the mutation in the apo B gene was identified using chemical cleavage of mismatch and this was confirmed by direct sequencing of an amplified fragment of DNA spanning the estimated site of the mutation. The mutation is a C----T transition at nucleotide 7692 which changes the CGA arginine2495 codon to a STOP codon resulting in the premature termination of apo B100. The truncated apo B protein is 2494 amino acids long with a predicted size of apo B55. Using allele specific oligonucleotides and oligonucleotide melting techniques, the proband, his sister and two other relatives out of a total of 20 family members, screened for the presence of the apo B55 mutation, were heterozygous for the mutation. The segregation of the apo B55 allele was confirmed in the family using the 3' variable number of tandem repeats of the apo B gene.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Apolipoprotein expression and cellular differentiation in Caco-2 intestinal cells.

Caco-2 cells, cultured for 18 days on porous filter supports and conventional plastic culture dishes, were used to study the effects of cellular differentiation on the expression of apolipoprotein (apo) genes. Media of filter-grown cells accumulated more apo B as apo B-48 and contained three times the amount of edited apo B mRNA compared with plastic-grown cells. The accumulation of apo A-I by media of plastic-grown cells was higher than accumulation by filter-grown cells, despite similar concentrations of apo A-I mRNA. The apo A-IV was detectable in the culture media earlier with filter-grown cells compared with plastic-grown cells, despite similar apo A-IV mRNA concentrations. Plastic-grown cells contained more apo E mRNA, and their media accumulated more apo E than filter-grown cells. With the exception of apo A-I, apo gene expression changed with Caco-2 cell differentiation to resemble more closely the patterns seen in adult enterocytes. There were no effects or minimal effects of added retinoic acid, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], or thyroid hormone on apo accumulation in media of filter-grown cultures of Caco-2 cells. However, 1,25(OH)2D3 and thyroid hormone increased apo B, apo A-IV, and apo A-I mRNA concentrations, retinoic acid increased apo B mRNA concentrations alone, and all three reduced apo E mRNA concentrations. Ratios of edited to unedited apo B mRNA were unaffected. In conclusion, culture substratum importantly influences Caco-2 cell differentiation. Soluble factors that influence cellular differentiation may affect apo gene expression over and above effects mediated by the culture substratum.(ABSTRACT TRUNCATED AT 250 WORDS)

Apolipoprotein A-I↗
PubMed1992

Lipoproteins containing the truncated apolipoprotein, Apo B-89, are cleared from human plasma more rapidly than Apo B-100-containing lipoproteins in vivo.

We have reported previously on two truncations of apolipoprotein B (apo B-40 and apo B-89) in a kindred with hypobetalipoproteinemia. Premature stop codons were found to be responsible for both apo B-40 and apo B-89, but the physiologic mechanisms accounting for the reduced plasma concentrations of these proteins have not been determined in vivo. This study investigates the metabolism of apo B-89 in two subjects heterozygous for apo B-89/apo B-100 and in one apo B-40/apo B-89 compound heterozygote. In both heterozygotes total apo B concentration is approximately 30% of normal and apo B-89 is present in lower concentrations in plasma than apo B-100. After the administration of [1-13C]leucine as a primed constant infusion over 8 h, 13C enrichments of plasma leucine as well as enrichments of VLDL-, IDL-, and LDL-apo B-89 leucine and VLDL-, IDL-, and LDL-apo B-100 leucine were measured over 110 h. Enrichment values were subsequently converted to tracer/tracee ratios and a multicompartmental model was used to estimate metabolic parameters. In both apo B-89/apo B-100 heterozygotes apo B-89 and apo B-100 were produced at similar rates. Respective transport rates of apo B-89 and apo B-100 for subject 1 were 2.13 +/- 0.18 and 2.56 +/- 0.13 mg.kg-1.d-1, and for subject 2, 6.59 +/- 0.18 and 8.23 +/- 0.39 mg.kg-1.d-1. However, fractional catabolic rates of VLDL, IDL, and LDL particles containing apo B-89 were 1.4-3 times higher than the rates for corresponding apo B-100-containing particles. Metabolic parameters of apo B-89 in the apo B-40/apo B-89 compound heterozygote compared favorably with those established for apo B-89 in apo B-89/apo B-100 heterozygotes. Thus, the enhanced catabolism of VLDL, IDL, and LDL particles containing the truncated apolipoprotein is responsible for the relatively low levels of apo B-89 seen in these subjects.

Adult↗
PubMed1992

Expression of low density lipoprotein receptor, apolipoprotein AI, AII and AIV in various rat organs utilizing an efficient and rapid method for RNA isolation.

Intact RNA from various rat organs was isolated by an efficient and rapid method. This method of RNA isolation is a modification of an earlier method that uses guanidinium isothiocynate followed by extraction in the presence of sarcosyl, acetate and phenol. The RNA obtained by the method reported here was comparable with the RNA prepared by the CsCl2 ultracentrifugation method and the commercially available kit based on published methods. The quality of RNA was found suitable for Northern blotting analysis, RNase protection assays and reverse transcriptase-polymerase chain reaction (RT-PCR). Since reverse transcriptase is active in the buffer used for Taq DNA polymerase, only one reaction needs to be set up. We also found that the use of aurintricarboxylic acid in the RNA preparation prevents the degradation of RNA during storage. Expression of low density lipoprotein (LDL) receptor, apolipoprotein (apo) AI, AII and AIV mRNAs were quantified in various rat organs. Our results indicated that rat LDL receptor mRNA is expressed in several organs whereas apoAI and AIV mRNAs were expressed mainly in the liver and intestine. However, apo AII mRNA is expressed mainly in the liver. Unlike mice and some species of monkeys, in the rat apoAI mRNA is expressed at 5-6 times higher levels in the intestine compared to liver. Apo AIV mRNA abundance was also found to be several fold higher in intestine compared to hepatic tissues. We present here, for the first time, data on the absolute amounts of LDL receptor, apoAI, AII and AIV mRNA in various rat organs which were quantified by a novel RNase protection/solution hybridization assay.

Animals↗
PubMed1992

Cholesteryl ester storage disease: complex molecular effects of chronic lovastatin therapy.

To better characterize the in vivo effects of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibition on human lipid metabolism, an adolescent male with cholesteryl ester storage disease (CESD) was treated chronically with lovastatin. Therapy was associated with decreased liver-spleen size, improved but not normal serum lipids, a 26% decrease in hepatic cholesteryl ester, a 12% decrease in unesterified hepatic cholesterol, and a fourfold increase in hepatic low density lipoprotein (LDL) receptor protein. Hepatic mRNA levels for the LDL receptor and apolipoprotein (apo) B standardized to levels of hepatic gamma actin mRNA were unchanged with therapy. Kinetic studies revealed no change in the LDL fractional catabolic rate and a decrease in the LDL production rate. Size exclusion chromatography showed striking reductions in plasma very low density lipoprotein (VLDL) cholesterol and intermediate density lipoprotein (LDL) cholesterol but not LDL cholesterol with therapy. Mean LDL particle size and the LDL particle size range were increased by treatment. However, there was no difference in the ability of pretreatment or treatment LDL to bind to the LDL receptor on cultured cells consistent with previous studies in animals, indicating that lovastatin may alter LDL particles to impair interaction with the LDL receptor in vivo but not in vitro. Lovastatin therapy in CESD appears to be clinically beneficial and has complex effects on lipid metabolism that may include a dominant inhibitory effect on hepatic lipoprotein production, posttranscriptionally mediated induction of the LDL receptor, and alterations of LDL particles that interfere with their clearance by the LDL receptor in vivo.

Actins↗
PubMed1992

ApoB-75, a truncation of apolipoprotein B associated with familial hypobetalipoproteinemia: genetic and kinetic studies.

We have identified a mutation of apolipoprotein B (apoB) in a kindred with hypobetalipoproteinemia. Four affected members had plasma concentrations of total cholesterol of 115 +/- 14, low density lipoprotein (LDL)-C of 48 +/- 11, and apoB of 28 +/- 9 (mg/dl mean +/- SD). The values correspond to approximately 30% the values for unaffected relatives. Triglyceride and high density lipoprotein (HDL)-C concentrations were 92 +/- 50 and 49 +/- 4, respectively, neither significantly different from unaffected relatives. Western blots of plasma apoB of affected subjects showed two major bands: apoB-100 and an apoB-75 (mol wt of approximately 418,000). DNA sequencing of the appropriate polymerase chain reaction (PCR)-amplified genomic DNA segment revealed a deletion of the cytidine at nucleotide position 10366, resulting in a premature stop codon at amino acid residue 3387. In apoB-75/apoB-100 heterozygotes, two LDL populations containing either apoB-75 or apoB-100 could be distinguished from each other by gel permeation chromatography and by immunoblotting of nondenaturing gels using monoclonal antibodies B1B3 (epitope between apoB amino acid residues 3506-3635) and C1.4 (epitope between residues 97-526). ApoB-75 LDL were smaller and more dense than apoB-100 LDL. To determine whether the low concentration of apoB-75 was due to its enhanced LDL-receptor-mediated removal, apoB-75 LDL were isolated from the proband's d 1.063-1.090 g/ml fraction (which contained most of the apoB-75 in his plasma) by chromatography on anti-apoB and anti-apoA-I immunoaffinity columns. The resulting pure apoB-75 LDL fraction interacted with the cells 1.5-fold more effectively than apoB-100 LDL (d 1.019-1.063 g/ml). To determine the physiologic mechanism responsible for the hypobetalipoproteinemia, in vivo kinetic studies were performed in two affected subjects, using endogenous labeling of apoB-75 and apoB-100 with [13C]leucine followed by multicompartmental kinetic analyses. Fractional catabolic rates of apoB-75 VLDL and LDL were 2- and 1.3-fold those of apoB-100 very low density lipoprotein (VLDL) and LDL, respectively. Production rates of apoB-75 were approximately 30% of those for apoB-100. This differs from the behavior of apoB-89, a previously described variant, whose FCRs were also increased approximately 1.5-fold relative to apoB-100, but whose production rates were nearly identical to those of apoB-100. Thus, in contrast to the apoB-89 mutation, the apoB-75 mutation imparts two physiologic defects to apoB-75 lipoproteins that account for the hypobetalipoproteinemia, diminished production and increased catabolism.

Adult↗
PubMed1991

In vivo regulation of apolipoprotein A-I gene expression by estradiol and testosterone occurs at the translational level in inbred strains of mice.

Testosterone and estrogen alter the hepatic synthesis of apoA-I in castrated inbred strains of mice, but apoA-I mRNA levels remain unaltered, suggesting post-transcriptional regulation of apoA-I production in liver. To test this hypothesis, females of the C3H/HeJ and C57BL/6J strains of mice were castrated and after 2 weeks were given testosterone propionate (Testo 1 microgram/g body weight/day,), 17 beta-estradiol (0.16 or 5 microgram/g/day, E2L, E2H, respectively) or vehicle (placebo) for 14 days (n = 5/group). Liver polysomes were isolated from pooled livers of each group and "run-off" assays were performed. Testo increased apoA-I gene translation to 124% and 171% of controls in C3H and C57BL strains, increased polysomal mRNA levels to 276% and 438% and increased apoA-I synthesis to 181% and 269% of respective controls. Decreases in polysomal "run-off", mRNA levels and apoA-I synthesis were produced by E2H. E2L produced non-parallel changes, i.e., it raised apoA-I synthesis and polysomal apoA-I mRNA, but did not affect rates of translation. The data suggest that sex hormones exert their effects on apoA-I gene expression at the translational level.

Animals↗
PubMed1991

In vivo regulation of low-density lipoprotein receptor and apolipoprotein B gene expressions by dietary fat and cholesterol in inbred strains of mice.

Two proteins that may be important in the hypercholesterolemia and atherosclerosis produced by dietary fat and/or cholesterol are apoB and the LDL-receptor. We evaluated the molecular and genetic regulation of these two proteins by two important components of atherogenic diets: dietary fatty acids and dietary cholesterol. The control diet (C) contained 5% corn oil; the high cholesterol (HC) diets, 5% corn oil plus 0.5% or 2% cholesterol; the high fat diet (HF) 1% corn oil and 20% hydrogenated coconut oil; the fat plus cholesterol diets (HF/C) were the same as HF diet plus either 0.5% or 2% cholesterol. Ten strains of inbred mice were fed the C and HF/C (2% cholesterol) diets. Three strains; C3H, C57BL and SWR, were studied in greater detail. In them the effects of dietary fat and cholesterol were assessed separately and together. These three strains were fed all six diets. Lipoprotein profiles of plasma and indexes of lipoprotein composition were obtained by gel filtration chromatography and in selected strains by gradient ultracentrifugation. Relative rates of transcription of LDL-receptor mRNA and apoB mRNA were measured in purified mouse liver nuclei and levels of LDL-receptor mRNA and apoB mRNA in liver and intestine were quantified by RNA excess solution hybridization assays. The HF/C diet produced rises in plasma total-, VLDL- and LDL-cholesterol and apoB concentrations in the ten strains. VLDL and LDL became cholesterol-enriched and the proportion of total cholesterol transported in VLDL and LDL rose at the expense of HDL. This general pattern of HF/C diet-induced changes was similar in all strains, but there were marked quantitative differences between strains with respect to lipid and lipoprotein concentrations, and compositions and the distribution of cholesterol on both the HC and HF/C diets. The strain-related differences were not due to differences in absorption of dietary cholesterol because, for any given diet, hepatic cholesterol levels increased to the same extent in all strains. Nor were the strain-related differences related to alleles of the apoB gene as determined by RFLP analyses. In the three strains, hepatic LDL-receptor mRNA transcription was suppressed by all diets. But, LDL-receptor mRNA levels in both intestine and liver were suppressed only by the HC and HF/C diets and not by the HF diet. Thus, dietary cholesterol decreased LDL-receptor mRNA levels by mechanisms operating at the transcriptional level, while dietary fatty acids, in addition to inhibiting transcription also appeared to enhance mRNA stability.(ABSTRACT TRUNCATED AT 400 WORDS)

Alleles↗
PubMed1991

Expression of LDL receptor, apolipoprotein B, apolipoprotein A-I and apolipoprotein A-IV mRNA in various mouse organs as determined by a novel RNA-excess solution hybridization assay.

We report expression of LDL receptor, apolipoprotein B (apoB), apolipoprotein A-I (apoA-I) and apolipoprotein A-IV (apoAIV) mRNA in various mouse organs. These mRNA were quantified by an RNA-excess solution hybridization assay. For preparing specific probes, we cloned cDNA fragments of rat LDL receptor, apoB and apoA-I and mouse apoA-IV into the polylinker region of pGEM3Zf(+) and used the recombinant vectors for preparing 32P-labeled cRNA probes as well as RNA standards using the T7 and SP6 promoters flanking the polylinker regions. Preparation of cRNA probes and RNA standards is faster and more convenient than preparing cDNA probes and ssDNA standards. Absolute levels of mRNA were quantified in the liver, intestine, kidney, heart, lung, spleen and adrenals of females of two mouse strains. C3H/HeJ and C57BL/6J. ApoB, apoA-I and apoA-IV genes in mice are expressed in the liver and intestine and LDL receptor gene is expressed mainly in liver, intestine and adrenals. ApoA-I mRNA levels were found to be 730 and 1039 molecules per cell in liver and intestine, respectively, in C3H mice and 762 and 952 molecules per cell in C57BL mice. ApoB mRNA levels were 66 and 170 molecules per cell in the liver and intestine of C3H and 83 and 243 molecules per cell in C57BL, respectively. ApoA-IV mRNA was found to be 3525 and 2964 molecules per cell in the liver and intestine of female C57BL mice, respectively. LDL receptor mRNA levels were 39, 32 and 14 molecules per cell in the liver, intestine and adrenals of C3H.

Animals↗
PubMed1991

The effects of probucol on the progression of atherosclerosis in mature Watanabe heritable hyperlipidaemic rabbits.

1. Probucol was administered to mature Watanabe heritable hyperlipidaemic (WHHL) rabbits (approximately 9 months old). Groups of WHHL rabbits were randomly selected and treated as follows: Group 1 killed at 9 months (n = 9); Group II placed on sham-treated diet at 9 months and followed for 6 months (n = 8); Group III placed on probucol at 9 months and followed for 6 months (n = 8). Probucol was administered by mixing 1% wt/wt drug with standard laboratory diet. 2. Plasma concentrations of probucol increased to 93 +/- 11 micrograms ml-1 in Group III during the initial 2 weeks and increased further to 149 +/- 24 micrograms ml-1 at the end of the treatment period. 3. Plasma concentrations of total cholesterol, unesterified cholesterol and phospholipids were significantly reduced overall by probucol, while triglycerides were not affected. 4. No statistically significant differences were observed in the presence of oxidized products in low density lipoproteins (LDL) isolated from plasma of controls compared to probucol-treated rabbits. However, LDL from probucol-treated animals was resistant to oxidation in the presence of Cu2+ (3 microM). 5. Group I had aortic atherosclerosis covering 70 +/- 5% of intimal area of thoracic aortae, that increased to 91 +/- 3% in Group II. This was associated with cholesterol contents of aortae increasing from 1.4 +/- 0.2 microgram mg-1 in Group I to 2.7 +/- 0.3 microgram mg-1 in Group II. Probucol administration did not produce a statistically significant reduction of atherosclerotic lesion area (78 +/- 7%). However, probucol treatment reduced cholesterol content to 1.9 + 0.3,ugmg-' (P < 0.01). Collagen content of aortae was not affected by probucol treatment. 6. Thus, while probucol did not promote regression, the drug did retard the continued deposition of cholesterol esters into atherosclerotic lesions of mature WHHL rabbits.

Animals↗
PubMed1991

Use of riboprobes for northern blotting analysis.

We compared cDNA and riboprobes for their use in Northern blotting analysis and found that higher hybridization signal can be obtained using riboprobes. Comparison of five nylon membranes for Northern blotting using riboprobe revealed that each nylon membrane differed in their performance. Background noise was minimal for all five membranes for two riboprobes. However, because of the higher thermal stability of RNA.RNA hybrids, the riboprobes could not be stripped out from the membrane even after five hours of treatment at 80 degrees C.

Animals↗
PubMed1991

Determination of kinetic parameters of apolipoprotein B metabolism using amino acids labeled with stable isotopes.

The use of amino acids labeled with stable isotopes represents a relatively new approach for determining kinetic parameters of apolipoprotein metabolism; thus, several aspects of experimental protocols need to be defined. The aims of the present study were to determine whether a) different amino acid tracers or b) different methods of tracer administration affected apolipoprotein (apo) B kinetic parameters obtained by multicompartmental modeling, and c) to compare very low density lipoprotein (VLDL)-apoB metabolic parameters determined by multicompartmental modeling with those estimated by linear regression or by monoexponential analysis. [1-13C]leucine and [15N]glycine were given either as bolus injections or as primed constant infusions. A bolus of one amino acid was administered simultaneously with a primed constant infusion (8 h) of the other amino acid into four healthy normolipidemic subjects (age 23.0 +/- 1.4 yr; BMI 20.9 +/- 0.9 kg.m-2). VLDL-, intermediate density lipoprotein (IDL)-, and low density lipoprotein (LDL)-apoB enrichments were followed over 110 h. For subsequent analysis these values were converted to tracer/tracee ratios. Using the multicompartmental model, the fractional catabolic rate (FCR) for VLDL-apoB was estimated to be 0.36 +/- 0.09 h-1 after the administration of the tracer as a primed constant infusion and 0.35 +/- 0.07 h-1 when the tracer was administered as a bolus. The values for VLDL-apoB production were 14.6 +/- 6.5 mg.kg-1.d-1 and 14.1 +/- 5.4 mg.kg-1.d-1, respectively. The corresponding values for LDL-apoB were 0.027 +/- 0.016 h-1 (0.026 +/- 0.018 h-1) for the FCR and 10.5 +/- 3.7 mg.kg-1.d-1 (10.4 +/- 3.8 mg.kg-1.d-1) for the production following administration of the tracer as a primed constant infusion and a bolus, respectively. Approximately 47% of VLDL-apoB ultimately reached the LDL fraction via the VLDL-IDL-LDL pathway. Thirty-five percent of LDL-apoB did not originate from this cascade pathway, but was shunted from a rapidly turning over VLDL compartment directly into the LDL fraction. While there was some variation between individuals, VLDL-apoB and LDL-apoB parameters derived from the bolus and the primed constant infusions showed no significant differences and were closely correlated. Metabolic parameters were also independent of the two amino acids tested. Although values for FCRs of VLDL-apoB obtained from linear regression (0.36 +/- 0.19 h-1) or monoexponential analysis (0.50 +/- 0.36 h-1) did not differ significantly from those obtained by the multicompartmental model, there was considerable variation and no significant correlation in a given individual.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗