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Biomedical subjects

G Ghiselli

Publications and source records attributed to G Ghiselli.

At least 55 records · Page 3Linked to original sources
PubMed1986

Plasma metabolism of apolipoprotein A-IV in humans.

As assessed by molecular sieve chromatography and quantitation by a specific radioimmunoassay, apoA-IV is associated in plasma with the triglyceride-rich lipoproteins, to a high density lipoprotein (HDL) subfraction of smaller size than HDL3, and to the plasma lipoprotein-free fraction (LFF). In this study, the turnover of apoA-IV associated to the triglyceride-rich lipoproteins, HDL and LFF was investigated in vivo in normal volunteers. Human apoA-IV isolated from the thoracic duct lymph chylomicrons was radioiodinated and incubated with plasma withdrawn from normal volunteers after a fatty meal. Radioiodinated apoA-IV-labeled triglyceride-rich lipoproteins, HDL, and LFF were then isolated by chromatography on an AcA 34 column. Shortly after the injection of the radioiodinated apoA-IV-labeled triglyceride-rich lipoproteins, most of the radioactivity could be recovered in the HDL and LFF column fractions. On the other hand, when radioiodinated apoA-IV-labeled HDL or LFF were injected, the radioactivity remained with the originally injected fractions at all times. The residence time in plasma of 125I-labeled apoA-IV, when injected in association with HDL or LFF, was 1.61 and 0.55 days, respectively. When 125I-labeled apoA-IV was injected as a free protein, the radioactivity distributed rapidly among the three plasma pools in proportion to their mass. The overall fractional catabolic rate of apoA-IV in plasma was measured in the three normal subjects and averaged 1.56 pools per day. The mean degradation rate of apoA-IV was 8.69 mg/kg X day. The results are consistent with the conclusions that: apoA-IV is present in human plasma in three distinct metabolic pools; apoA-IV associated with the triglyceride-rich lipoproteins is a precursor to the apoA-IV HDL and LFF pools; apoA-IV in LFF is not a free protein and its turnover rate is faster than that of apoA-IV in HDL; since no transfer of apoA-IV from the HDL or the LFF occurs, these pools may represent a terminal pathway for the catabolism of apoA-IV; and the catabolism of apoA-IV in HDL is dissociated from that of apoA-I although both apoproteins may reside on the same lipoprotein particles.

Apolipoprotein A-I↗
PubMed1985

Origin of apolipoprotein A-I polymorphism in plasma.

The origin and the functional significance of apo-A-I polymorphism in man has been investigated. Together with proapo-A-I (identified as A-I1 of the polymorphic series), four other isoforms are found in human plasma, namely A-I2, A-I3, A-I4, and A-I5. A-I3 is the "mature" product of proapo-A-I conversion in plasma. In this study we provide evidence that the other, more acidic, mature apo-A-I isoproteins are derived from A-I3 by a stepwise deamidation process. This conclusion is based on the following observations. 1) Incubation of A-I3 or A-I4, either free or associated with high density lipoprotein, produces a series of more acidic isoproteins corresponding to the sequence found in plasma. The conversion process fits in well with a first order reaction, and A-I3 to A-I4 conversion occurs virtually at the same rate as A-I4 to A-I5 conversion. 2) A-I3 and A-I4 have the same NH2- and C-terminal residues. 3) Formation of apo-A-I acidic isoproteins is accompanied by liberation of ammonia. In order to investigate whether deamidation of apo-A-I results in the production of forms which have different catabolism, a series of turnover studies was carried out in normal volunteers. A-I3 and A-I4 residence times in plasma were, respectively, 3.50 +/- 0.16 and 3.00 +/- 0.10 days (mean +/- S.E.; n = 3). Degradation rate of A-I3 was 8.81 +/- 0.69 mg/kg/day and that of A-I4 was 1.66 +/- 0.15 mg/kg/day (mean +/- S.E.; n = 3). Conversion of A-I3 to A-I4 and A-I4 to A-I5 occurred at the same rate in vivo as that observed in vitro. These results are consistent with the concept that A-I3 is the precursor to the other mature apo-A-I isoforms in plasma. A-I3 is the major isoform through which apo-A-I is eliminated from plasma.

Ammonia↗
PubMed1985

Proapolipoprotein A-I conversion kinetics in vivo in human and in rat.

We have determined the turnover rates for proapolipoprotein A-I (proapoA-I) and mature apolipoprotein A-I (apoA-I) in vivo in human and in rat. For the human study, high density lipoprotein (HDL)-associated 125I-labeled proapoA-I (A-I isoform 1) and 131I-labeled mature apoA-I (A-I isoforms 3, 4, and 5) were injected simultaneously into two normal volunteers. Blood samples were obtained serially and HDL proapoA-I and mature apoA-I were separated by isoelectrofocusing for the determination of the associated radioactivity. Residence times of proapoA-I and mature apoA-I were 0.13 and 3.9 days and production rates were 9.0 and 9.3 mg/kg per day, respectively. Analysis of the specific activity curves suggested a complete proapoA-I to mature apoA-I precursor-product relationship. Proprotein conversion was virtually completed in 24 hr. For the rat study, HDL- and lymph chylomicron- (flotation constant Sf greater than 400 S) associated 125I-labeled proapoA-I and 131I-mature apoA-I were injected into fasted rats. Residence times of proapoA-I and mature apoA-I injected in association with HDL were 0.13 and 0.28 day, respectively, and for injection associated with chylomicrons the residence times were 0.08 and 0.26 day. When associated with chylomicrons, proapoA-I was converted more efficiently to the mature form. As in the human study, the results demonstrated a complete proapoA-I to mature apoA-I precursor-product relationship. Our data are consistent with the concepts that (i) conversion to mature apoA-I is the major proapoA-I catabolic fate in plasma; (ii) mature apoA-I is conceivably derived solely from proapoA-I in plasma and proapoA-I is the major apoA-I form secreted in vivo; and (iii) a putative proapoA-I-chylomicron complex is the preferred substrate for the apoA-I propeptidase.

Adult↗
PubMed1985

Familial apolipoprotein A-I and C-III deficiency, variant II.

The biochemical, clinical, and genetic features were examined in the proband (homozygote) and heterozygotes (n = 17) affected with familial apolipoprotein A-I and C-III deficiency, variant II (previously described as apolipoprotein A-I absence). The proband was a 45-year-old white female with mild corneal opacification and significant three-vessel coronary artery disease (CAD), who died shortly after bypass surgery. Autopsy findings included significant atherosclerosis in the coronary and pulmonary arteries and the abdominal aorta as well as extracellular stromal lipid deposition in the cornea. No reticuloendothelial lipid deposits in the liver, bone marrow, or spleen were noted (unlike Tangier disease). Laboratory features included marked high density lipoprotein (HDL) deficiency and undetectable plasma apolipoproteins (apo) A-I and C-III. The percentage of plasma cholesterol in the unesterified form was normal at 30%. The activity and mass of lecithin:cholesterol acyltransferase (LCAT) were 42% and 36% of normal, respectively, and the cholesterol esterification rate was 43% of normal. Deficiencies of plasma vitamin E and essential fatty acid (linoleic, C18:2) were also noted. Evaluation of plasma lipoproteins and apolipoproteins in 37 kindred members revealed 17 heterozygotes with HDL cholesterol values below the 10th percentile of normal. Of these, all had apoA-I levels more than one standard deviation below the normal mean, and 37.5% had a similar decrease in apoC-III values. Mean (+/- SD) plasma HDL cholesterol, apoA-I, and apoC-III values (mg/dl) in heterozygotes were 54.0%, 62.4%, and 79.2% of normal, respectively. No evidence of CAD was observed in 10 heterozygotes 40 years of age or less; however, CAD was detected in 3 of 7 heterozygotes over 40 years of age, one of whom died at age 56 years of complications of myocardial infarction and stroke. The inheritance pattern in this kindred was autosomal codominant. ApoA-I isolated from a heterozygote had an isoelectric focusing pattern and amino acid composition similar to normal. Utilizing DNA isolated from two obligate heterozygotes, no abnormalities in the apoA-I or apoC-III genes were detected by Southern blot analysis utilizing specific probes following restriction enzyme digestion. The data indicate that familial apolipoprotein A-I and C-III deficiency, variant II, is similar to variant I (described by Norum et al. 1982. N. Engl. J. Med. 306: 1513-1519), but differs at the clinical level (lack of xanthomas), the biochemical level (lack of detectable apoA-I, lower apoA-II level), and at the gene level.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1985

Human apolipoprotein A-I isoprotein metabolism: proapoA-I conversion to mature apoA-I.

ProapoA-I (apoA-i+2 isoform) is the major apoA-I isoprotein secreted by the liver and intestine; however, it is a minor isoprotein in plasma and lymph where the major A-I apo-lipoprotein is mature apoA-I (apoA-I0, apoA-I-1, and apoA-I-2 isoforms). In the present report we provide evidence that apoA-I is rapidly and quantitatively converted to mature apoA-I, and the mature apoA-I isoforms are catabolized at equal rates. In these studies, human proapoA-I was isolated from thoracic duct chylomicrons collected during active fat absorption and mature apoA-I was isolated from plasma high density lipoproteins. The isolated lipoproteins were delipidated, fractionated by gel permeation chromatography, and the individual apoA-I isoforms were separated by preparative isoelectrofocusing. The metabolism of apoA-I isoproteins was studied in normal volunteers (N = 6) in a metabolic ward. In the first study proapoA-I and mature apoA-I (apoA-I0 isoform) were injected simultaneously into two normal subjects and the conversion of proapoA-I to mature apoA-I and the decay of radioactivity were followed in plasma and HDL over a 14-day period. ProapoA-I was rapidly and completely converted to mature apoA-I with a fractional rate of conversion of 4.0 pools/day. The average residence times of proapoA-I and mature apoA-I were 0.23 and 6.5 days, respectively. The mature apoA-I derived from proapoA-I had a residence time which was the same as the injected mature apoA-I.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Apolipoprotein E Bethesda. Isolation and partial characterization of a variant of human apolipoprotein E isolated from very low density lipoproteins.

A variant of apolipoprotein E, denoted E Bethesda, has been identified in the plasma of a 72-year-old woman with type III hyperlipoproteinemia. An offspring of the proband also has this variant and type III hyperlipoproteinemia. Apolipoprotein E Bethesda was isolated by preparative isoelectrofocusing followed by preparative SDS-polyacrylamide gel electrophoresis from the very low density lipoproteins of the proband's son. The purity and the identity of the preparation were analyzed by analytical SDS-polyacrylamide gel electrophoresis, two-dimensional gel electrophoresis and by immunochemical analysis. Apolipoprotein E Bethesda migrates in the E 1 position and its electrophoretic mobility is not affected by neuraminidase treatment. The protein is shifted to the E3 position after cysteamine treatment. The amino acid composition revealed the presence of two cysteine residues. These data support the concept that the apolipoprotein E Bethesda allele is derived from a mutation of the E2 or E2* allele.

Aged↗
PubMed1983

Identification of proapoa-I in rat lymph and plasma: metabolic conversion to "mature" apoA-I.

Rat apoA-I polymorphism has been analyzed in lymph and plasma. Two major proteins were present and their relative distribution was different in lymph and plasma lipoproteins. The basic protein (pI 5.60) was quantitatively most abundant among plasma lipoproteins and the acidic protein (pI 5.50) was predominant in lymph chylomicrons and lipoproteins. Microsequence amino acid analysis of the two proteins isolated by preparative isoelectrofocusing revealed that pI 5.50 apoA-I was proapoA-I with six additional amino acids (H2N-Ser-Glu-Phe-Trp-Gln-Gln) at the N-terminal end of "mature" apoA-I (pI 5.60 apoA-I). When radioiodinated proapoA-I was injected in rats, a conversion to "mature" apoA-I was observed and the process reached 92% completion in six hours. These data demonstrate the origin of apoA-I polymorphism in vivo.

Animals↗
PubMed1983

Apolipoprotein EBethesda: a new variant of apolipoprotein E associated with type III hyperlipoproteinemia.

Apolipoprotein E (apoE) is associated with plasma lipoproteins and is important in modulating the catabolism of remnants of triglyceride-rich lipoproteins. ApoE is a polymorphic protein, and homozygosity for the E2 allele is associated with type III hyperlipoproteinemia. A variant of apoE, apoEBethesda, was found that migrates in the E1 position on isoelectric focusing. Evaluation of the proband and her family showed that both individuals with apoEBethesda had type III hyperlipoproteinemia, and the analysis was consistent with the concept that apoEBethesda was coded by a new E allele and that this allele was expressed in a codominant fashion. The discovery of apoEBethesda and its association with type III hyperlipoproteinemia provides additional evidence for the genetic heterogeneity of the E allele and suggests that a number of different structural mutations of the E apolipoprotein may be associated with the type III phenotype.

Adult↗
PubMed1983

Apolipoprotein A-I isoforms in human lymph: effect of fat absorption.

The effect of fat feeding (100 g of cream) on the apoA-I isoproteins distribution has been analyzed by two-dimensional gel electrophoresis in the chylomicrons, VLDL, LDL, and HDL isolated from the thoracic duct lymph of patients undergoing lymph drainage for immunosuppression, Isoforms apoA-I3 and apoA-I4 are the most abundant apoA-I isoproteins in plasma lipoproteins as well as in lymph lipoproteins collected in the fasting state. Fat feeding, on the other hand, results in a marked change in the apoA-I isoform pattern in lymph chylomicrons and VLDL, with a significant increase in the relative concentration of the apoA-I1 isoform. As a result the total concentration of this isoprotein in the lymph increased. The data indicate that fat feeding is associated with major changes in the distribution of the apoA-I isoforms in the lymph (d less than 1.006 g/ml lipoproteins), which may be of significance in their plasma catabolism.

Apolipoprotein A-I↗
PubMed1982

Phenotype study of apolipoprotein E isoforms in hyperlipoproteinaemic patients.

It has been suggested that apolipoprotein E (apoE) is inherited at a single genetic locus with three common alleles designated E2, E3, and E4. The products of these three alleles are apoE2, apoE3, and apoE4. The apoE phenotypes of 74 normal subjects and 226 hyperlipoproteinaemic subjects were ascertained by gel isoelectrofocusing. Patients with type I, type IIa, type IIb, and type IV hyperlipoproteinaemia had an apoE phenotypic distribution which was similar to that of normal subjects, with 40.0 to 60.0% being homozygous for E3. In contrast, 75% of type III patients had an E2 phenotype and 25% were E2/3 heterozygotes. Among type V patients 31.4% had an E4 phenotype, and 42.9% were E4 heterozygotes. No type III patient and only 5.7% of type V patients had E3 phenotype. The results suggest that apoE2 and apoE4 are associated with two distinctly different dyslipoproteinaemias and that apoE has at least two different physiological functions.

Apolipoproteins↗
PubMed1982

Evidence that two synthetic pathways contribute to the apolipoprotein B pool of the low density lipoprotein fraction of rabbit plasma.

The plasma specific activity of apolipoprotein B was determined in normal rabbit injected with homologous radioiodinated very low and intermediate density lipoproteins (VLDL and IDL). The specific activity was followed in the same density range of the injected lipoproteins and in two low density lipoprotein subfractions (LDL1 and LDL2). VLDL B (d less than 1.006 g/ml) is cleared from plasma mainly in IDL (d = 1.006-1.019 g/ml), with minor radioactivity recovery in LDL1 (d = 1.019-1.040 g/ml) and LDL2 (d = 1.040-1.063 g/ml) fractions. The main catabolic product of IDL B is, on the other hand, LDL1 B. LDL2 B, which represent more than 20% of the whole LDL B plasma pool in this animal species, is not derived to a significant extent from either VLDL or IDL and, conceivably, is synthesized independently.

Animals↗
PubMed1982

Metformin reduces platelet hypersensitivity in hypercholesterolemic rabbits.

The effects of Metformin treatment on platelet responsiveness to aggregating agents was studied in cholesterol-fed rabbits. Three groups of animals were fed, for one month, either a normal (N), or a hypercholesterolemic (HC), or a hypercholesterolemic + 0.5% Metformin diet (HC + Met), Platelets from the HC rabbits required significantly lower collagen and arachidonic acid concentrations to aggregate, as compared to platelets from N rabbits. The platelet response from the HC + Met rabbits was not significantly different from that of normals. The cholesterol/phospholipid ratio in platelets was increased in both dietary groups (HC, HC + Met). The serum thromboxane B2 concentrations did not show any significant difference between the groups. Plasma exchange experiments failed to indicate a specific effect of the plasma environment on platelet behaviour. In view of the inactivity of metformin on the platelet cyclo-oxygenase pathway, the reported results suggest that metformin may act by an as yet unexplored mechanism.

Animals↗
PubMed1982

Increased prevalence of apolipoprotein E4 in type V hyperlipoproteinemia.

Type V hyperlipoproteinemia (HLP) is characterized clinically by hepatosplenomegaly, occasional eruptive xanthomas, and an increased incidence of pancreatitis. These patients have striking hypertriglyceridemia due to increased plasma chylomicron and very low density lipoprotein concentrations in the fasting state, without a deficiency of lipoprotein lipase or its activator protein, apolipoprotein (apo) C-II. ApoE, a protein constituent of triglyceride-rich lipoproteins, has been implicated in the receptor-mediated hepatic uptake of these particles. ApoE has three major alleles: E2, E3, and E4, and the products of these alleles are apoE2, apoE3, and apoE4, respectively. ApoE phenotypes were determined in 30 type V HLP patients as well as in 37 normal volunteers. Among the type V patients, 33.3% were noted to be homozygous, and 40.0% heterozygous for E4 (normal, 2.7 and 21.6%, respectively). These data suggest that apoE4 may play a role in the etiology of the hyperlipidemia in a significant number of type V HLP patients.

Apolipoprotein E4↗
PubMed1981

Type III hyperlipoproteinemia associated with apolipoprotein E deficiency.

Subjects with type III hyperlipoproteinemia develop premature atherosclerosis and have hyperlipidemia due to an increase in cholesterol-rich very low density lipoproteins (VLDL) of abnormal electrophoretic mobility. Apolipoprotein E is a major protein constituent of VLDL and appears to be important for the hepatic uptake of triglyceride-rich lipoproteins. A new kindred of patients with type III hyperlipoproteinemia is described in which no plasma apolipoprotein E could be detected, consistent with the concept that type III hyperlipoproteinemia may be due to an absence or striking deficiency of apolipoprotein E.

Apolipoproteins↗
PubMed1981

Effect of serum lipoproteins on the adenylate cyclase activity of rat liver plasma membranes.

Four rat lipoprotein classes [lymph chylomicrons, VLD (very-low-density), LD (low-density) and HD (high-density) lipoproteins] were tested for their ability to affect basal adenylate cyclase (EC 4.6.1.1) activity of rat liver plasma membranes. All the lipoproteins, with the exception of lymph chylomicrons, effectively increase the enzyme activity. VLD lipoproteins are the most active class (67% maximal increase), followed by HD lipoproteins (33%) and LD lipoproteins (23%). The effect of VLD lipoproteins is additive to that elicited by GTP or GTP plus glucagon (at least within a certain concentration range). VLD lipoproteins affect only the Vmax. of the enzyme, not the Km.

Adenylyl Cyclases↗