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Biomedical subjects

G Ghiselli

Publications and source records attributed to G Ghiselli.

At least 37 records · Page 2Linked to original sources
PubMed1994

Imidazolylbenzopyrane derivatives: a new class of acyl-CoA: cholesterol acyltransferase (ACAT) inhibitors.

Inhibitors of the enzyme Acyl-CoA: Cholesterol Acyltransferase are regarded as potentially useful agents in the treatment of hypercholesterolemia and atherosclerosis. We report here a novel series of 2, 6-disubstituted-3-imidazolylbenzopyrane derivatives with significant in vitro ACAT inhibitory activity (IC50 range 0.05-0.5 microM). Compounds of this series such as 26 are examples of a new, structurally distinct class of potent ACAT inhibitors with high specificity for the aortic subtype of the enzyme. The structure-activity relationships of the 3-imidazolylbenzopyrane ACAT inhibitors were investigated by systematic manipulation of two regions of the parent compound 1 and the inhibitory activity resulted linked to the substituent in position 6 of the benzopyrane ring and modulated by the size of lipophilic substituents in position 2. Investigation of the mechanism of the inhibitory effect leads to the conclusion that these compounds act in a non-competitive fashion.

Animals↗
PubMed1993

A comparative study of low-density lipoprotein interaction with glycosaminoglycans.

The association between low-density lipoprotein (LDL) and a series of well characterized dermatan and chondroitin sulfates has been investigated by means of the fluorescence anisotropy technique with competition experiments using a fluorescein-labeled high LDL-affinity heparin fraction as a reference. Preparations of glycosaminoglycan (GAG) with sulfation degrees varying over a wide range, as obtained by fractionation or by chemical modification, were chosen for this study. The influence of chain length, which had been found sizeable in a former study of heparin affinity for LDL, was taken into account with an empirical correction of dissociation constants. After this correction, a linear relationship was found between the logarithm of dissociation constants and the number of sulfate groups per disaccharide unit, ns, both for dermatan and chondroitin sulfates, and for heparins. At comparable ns values, however, dermatan sulfates and heparins, which contain L-iduronic acid in their backbone, show higher LDL-affinity than chondroitin sulfates, which contain only D-glucuronic acid. Though confirming a non-specific, predominantly electrostatic interaction between GAGs and LDL, these results indicate modulation of LDL affinity by the polysaccharide backbone.

Binding Sites↗
PubMed1993

Percutaneous ultrasound-guided drainage of intra-abdominal abscesses.

A retrospective review of 200 patients with intra-abdominal abscesses treated by percutaneous ultrasound-guided drainage is reported. Abscesses were simple in 151 patients (75.5 per cent) and complex in 49 (24.5 per cent). In 12 patients the abscess communicated with the gastrointestinal tract. There were 17 critically ill patients for whom percutaneous drainage was the only therapeutic option possible. The success rate was 94.7 per cent (143 of 151 patients) for simple abscess and 69 per cent (34 of 49) for complex abscess. The overall success rate was 88.5 per cent. The mortality rate was 1.3 per cent (two patients) for simple and 16 per cent (eight patients) for complex abscess. The overall mortality rate was 5.0 per cent. Percutaneous ultrasound-guided drainage should be the initial drainage procedure in patients with a simple abdominal abscess. The presence of a complex abscess should not prevent an attempt at percutaneous catheter drainage, particularly in high-risk patients, although the risk of failure is greater in such cases.

Abdomen↗
PubMed1993

Decreased cholesterol biosynthesis in fibroblasts from patients with Parkinson disease.

The underlying cause of cellular degeneration in the substantia nigra of patients with Parkinson disease has not been clearly established. With the objective of investigating whether metabolic abnormalities would be detected in peripheral non-neuronal cells, we began assessing key metabolic parameters in skin fibroblasts of these patients. The present report focuses on the finding of a remarkably reduced cholesterol biosynthetic capability of fibroblasts from patients with Parkinson disease. 14C-Acetate incorporation into cholesterol of these fibroblasts was 27.8 +/- 9.4% that observed in normal fibroblasts, and the reduced cholesterol synthesis was confirmed by measuring the activity of the rate-limiting enzyme HMGCoA reductase which averaged 6.64 +/- 2.50 nmol/h/mg protein in the patient's fibroblasts compared to 14.70 +/- 0.69 nmol/h/mg protein in the control fibroblasts. Cholesterol esterifying activity, as cholesteryl oleate formed from 14C-oleate, of the fibroblasts from Parkinson patients, was reduced by an average 43%. Two hypotheses are put forward to link these findings with the current experimental evidences for both increased lipid peroxidation and defective mitochondrial respiratory chain complex I activity in a number of cell types from Parkinson patients. Considering that decreased cholesterol biosynthesis has been detected in all the Parkinson cell lines thus far investigated, it is suggested that this may be a hallmark of the disease.

Adult↗
PubMed1993

Interaction of oxidized HDLs with J774-A1 macrophages causes intracellular accumulation of unesterified cholesterol.

Uptake of modified lipoproteins by resident arterial monocytes/macrophages is believed to be a key event in the formation of foam cells and thus in the early phases of atherosclerosis. Low-density lipoproteins (LDLs) that undergo oxidative changes become suitable for uptake by macrophages through a specific scavenger receptor that leads to cholesteryl ester accumulation. Because the interaction of other oxidized lipoproteins with macrophages has been poorly investigated, we studied the effect of oxidatively modified high-density lipoproteins (HDLs) on the sterol metabolism of J774-A1 macrophages. Unlike native HDLs, oxidized HDLs caused a concentration-dependent accumulation of unesterified cholesterol and decreased [14C]oleate incorporation into steryl esters. Oxidized HDLs also decreased [14C]acetate incorporation into newly synthesized sterols. Cell surface binding of 125I-oxidized HDLs to the macrophages was saturable, with an apparent dissociation constant (Kd) of 0.96 nmol/mL. Both oxidized and acetylated LDLs but not native lipoproteins could compete for binding of 125I-oxidized HDL. The data support the conclusion that the effects elicited by oxidized HDLs on the sterol metabolism of macrophages are significantly different from those of native HDLs. The binding of oxidized HDLs to macrophages occurs at sites that are likely the same as those for modified LDLs. We speculate that, if occurring in vivo, HDL oxidation would generate modified lipoproteins capable of modulating the cholesterol homeostasis of macrophages.

Animals↗
PubMed1992

Heparin binding to human plasma low-density lipoproteins: dependence on heparin sulfation degree and chain length.

Binding between low-density lipoproteins (LDL) and fluorescein-labeled heparin was studied quantitatively with a modified form of a published procedure [Cardin, A. D., Randall, C. I., Hirose, N., & Jackson, R. L. (1987) Biochemistry 26, 5513-5518], using fluorescence anisotropy titrations. Assumption of binding site equivalence satisfactorily interpreted experimental data. Accordingly, the apparent total capacity, n, and the average dissociation constant, Kd, were estimated as n approximately 24 disaccharides per LDL particle and Kd approximately 4 microM in 0.05 M HEPES/0.1 M NaCl, pH 7.4, 22 degrees C. Competition experiments with unlabeled heparins were exploited for the quantitative study of Kd as a function of heparin chain length and sulfation degree (ns = sulfate groups per disaccharide). The former parameter was investigated with a series of bovine lung heparin fractions with Mw ranging from 1,800 to 21,000 and constant sulfation degree (ns = 2.8 +/- 0.1). A series of physically fractionated or chemically modified heparins having 1.2 less than ns less than 3.5 were used to explore the dependence on sulfation degree. LDL affinity was found to increase with increasing both ns and Mw: an empirical Mw-1.6 dependence represented very well the chain length data set; a linear dependence was observed for log Kd as a function of ns, after appropriate allowance was made for chain length differences among samples. This regularity confirmed that LDL-heparin binding is mainly driven by electrostatic forces.(ABSTRACT TRUNCATED AT 250 WORDS)

Apolipoprotein B-100↗
PubMed1992

Relationship of triglycerides and HDL cholesterol in hypertriglyceridemia.

Hypoalphalipoproteinemia (plasma HDL-cholesterol concentration at or below 35 mg/dl as reported in the National Cholesterol Education Program Guidelines) is a well known risk factor for premature coronary artery disease (CAD). In hypertriglyceridemic patients, hypoalphalipoproteinemia is commonly believed to be linked to the derangement of triglyceride metabolism. In this study the occurrence of primary hypoalphalipoproteinemia has been investigated in a cohort of hypertriglyceridemic patients whose plasma triglyceride concentration had been normalized either through diet or diet plus drug treatment. Following the initial visit, 115 hypertriglyceridemic patients received dietary advice and returned for the second visit four months later. Diet reduced plasma triglycerides in all the patients. HDL-cholesterol increased in 76 patients whereas in the others, it remained unchanged or even decreased. Plasma triglyceride concentration was normalized (less than 200 mg/dl) in 54 patients by diet alone, but among these 11 remained hypoalphalipoproteinemics. Patients in whom, despite dietary restrictions, triglycerides exceeded 200 mg/dl, were considered for pharmacological treatment with Bezafibrate (300 mg t.i.d.) for 4 months. Thirty-nine concluded the study. Treatment significantly decreased plasma triglyceride concentration in all the subjects. Normalization was achieved in 32 patients. Four of them, however, remained hypoalphalipoproteinemic. These results indicate that a subgroup of hypertriglyceridemic patients remained hypoalphalipoproteinemic even after normalization of triglyceride levels. In these patients hypertriglyceridemia and hypoalphalipoproteinemia may occur as expression of two distinct primary metabolic defects.

Adult↗
PubMed1992

Plasma lipoprotein(a) concentration in familial hypercholesterolemic patients without coronary artery disease.

Familial Hypercholesterolemia (FH) is a condition characterized by markedly elevated blood cholesterol, low-density lipoproteins (LDL), and apolipoprotein B-100 (apo B). The molecular basis of this monogenic disease is the defective functioning of the cellular receptor for LDL that recognizes apo B. Lipoprotein(a) [Lp(a)] is a circulating lipoprotein that is structurally related to LDL, as it also contains apo B. To assess the impact of the LDL receptor deficiency on the plasma Lp(a) concentration, we measured Lp(a) in 28 FH patients and in 31 unaffected relatives. Because elevation of Lp(a) concentration in plasma of patients with coronary artery disease (CAD) appears to occur independently from plasma cholesterol levels, to avoid potentially confounding problems, members of the families chosen had no history for the disease. Whereas apo B clearly showed a bimodality of distribution by being significantly higher in the FH patients (166 +/- 38 mg/dL) than in the unaffected relatives (92 +/- 18 mg/dL), Lp(a) concentration did not differ in the two groups of patients (30 +/- 24 mg/dL in the FH patients v 31 +/- 23 in the normolipidemic relatives). Similar results were obtained when only siblings were further considered. We conclude that although Lp(a) is closely related to LDL structurally, its level in plasma is not significantly affected by the LDL receptor activity.

Adolescent↗
PubMed1992

Oxidatively modified HDLs are potent inhibitors of cholesterol biosynthesis in human skin fibroblasts.

Several biological properties of lipoproteins are modified by oxidative reactions. Modified lipoproteins are rapidly degraded by macrophages, and this is likely to be a major pathway for the formation of foam cells in the early phases of atherosclerosis. The effect of modification on other aspects of cholesterol homeostasis has, however, received lesser attention. In this study, the influence of copper ion- as well as rat aortic smooth muscle cell-oxidation-modified high density lipoprotein (HDL) on cholesterol biosynthesis in human skin fibroblasts has been investigated. Modified lipoproteins eluted at higher ionic strength than did control HDL on a Mono-Q 5/5 anion-exchange column. However, only copper ion-modified HDLs displayed greater electrophoretic mobility than did control lipoproteins on agarose gel electrophoresis. Both control and modified HDLs decreased cholesterol esterification in fibroblasts. On the other hand, whereas control HDLs were virtually ineffective in modulating cholesterol biosynthesis, modified HDLs had a significant suppressing effect. This was observed in normal as well as low density lipoprotein (LDL) receptor-defective fibroblasts, which are unresponsive to the LDL-mediated downregulation of cholesterol synthesis. These results are consistent with the concept that oxidative modification of HDLs drastically alters their effect on cholesterol homeostasis in fibroblasts. The data furthermore suggest the existence of a lipoprotein pathway for cholesterol biosynthesis regulation that is independent of the LDL receptor-mediated pathway. Downregulation of cholesterol biosynthesis would be a new function for oxidatively modified lipoproteins.

Cells, Cultured↗
PubMed1992

[Ultrasonic diagnosis of gastroduodenal perforation].

Ultrasonography (US) is routinely used as a diagnostic approach in the surgical acute abdomen, even though its major limitation is the demonstration of the hollow viscus. In the present paper, the results obtained with US in 12 cases of gastric or duodenal perforations are reported. The diagnosis, of gastroduodenal perforation was correctly made in 58% of cases by means of US; in 91.7% of cases, at least one US finding correlable with gastroduodenal perforation was observed. Even though US exhibits poorer diagnostic sensitivity than conventional radiology, it can be considered a valuable diagnostic tool in the early diagnosis of gastroduodenal perforation especially when radiographic findings are negative.

Adult↗
PubMed1990

Identification of a detergent-solubilized plasma membrane protein from rat liver recognizing apolipoprotein A-IV.

Apolipoprotein A-IV (apo A-IV) is present in plasma associated to both HDL and as a complex with lipids that cannot be floated by ultracentrifugation at 1.21 g/ml density. Apo A-IV is likely an important molecular determinant in HDL binding to the liver. In this communication, data are presented supporting the view that a specific liver plasma membrane protein of Mr 95,000 is a constituent of the apo A-IV binding site. The protein was solubilized with CHAPS from purified rat liver plasma membranes and subjected to SDS-PAGE. Transblotted to nitrocellulose sheet could be identified as recognizing 125I-apo A-IV-DMPC by autoradiography. 125I-apo A-I-DMPC and radioiodinated rat apo E-poor HDL, also bound to the protein. Apo B-100 (as human LDL) and apo C-III did not bind. The protein identified is likely to be the same that has been previously identified by Graham and Oram [1987) J. Biol. Chem. 262, 7439-7442) as 'HDL receptor protein'.

Animals↗
PubMed1989

Metabolism of apolipoprotein A-IV in rat.

The metabolism of apolipoprotein A-IV (apo-IV) has been investigated in the rat. In this animal species, apoA-IV is a major protein constituent of plasma HDL and lymph chylomicron. The apolipoprotein is also present in the lipoprotein-deficient fraction (LDF) of plasma and lymph. In vivo studies with the radioiodinated protein showed the apoA-IV does not exchange freely between HDL and LDF and that LDF apoA-IV had a faster catabolism than HDL apoA-IV. ApoA-IV in chylomicrons is a direct precursor of apoA-IV in plasma HDL but not of that in LDF. On the other hand lymph LDF apoA-IV is an important precursor of plasma LDF apoA-IV. Transfer of apoA-IV from plasma to lymph is negligible, and since most of apoA-IV in lymph is present in LDF, we speculate that LDF apoA-IV is the major apoA-IV secretory product of the intestine. Studies aimed at identifying the site of catabolism of apoA-IV utilizing either radioiodinated or [14C]sucrose labelled apoA-IV, gave results consistent with the view that the liver plays a major role. When tested, human apoA-IV behaved in vivo in rat as the autologous protein. These findings, together with others previously published (Ghiselli, G. et al. (1987) J. Lipid Res. 27, 813-827), support the conclusion that the plasma metabolism of apoA-IV is remarkably similar in rat and human. We speculate that in mammals the rapid plasma catabolism of apoA-IV is mediated by an efficient uptake by the liver.

Animals↗
PubMed1989

Rapid modulation of rat adipocyte lipoprotein lipase: effect of calcium, A23187 ionophore, and thrombin.

The effect of calcium ions on the lipoprotein lipase (LPL) activity in rat adipocytes has been investigated. Incubation of the cells in the absence of extracellular calcium produced a rapid decline of LPL activity in the cells. The enzyme, however, could be immediately reactivated in less than 3 min by the addition of calcium. The degree of reactivation was proportional to the concentration of extracellular calcium. alpha 1 agonists phenylephrine and methoxamine affected LPL activity only slightly, as did vasopressin and angiotensin II. In contrast, calcium ionophore A23187 elicited a quick and transient enzyme activation which reached its peak 4 min after the addition of the drug. Thrombin (0.1 U/ml) produced the most rapid and intense response. The effect of thrombin was already evident 10 s after its addition, and the enzyme activity almost doubled above the basal level. Extracellular calcium was necessary to achieve thrombin activation. Contrary to previous thought, these data support the conclusion that LPL may undergo rapid activation, and that calcium ions are critically involved in this activation process. Thrombin rapidly raises LPL activity and may be one of its physiological activators in vivo.

Adipose Tissue↗
PubMed1986

Radioimmunoassay of rat apolipoprotein A-IV.

We have developed a specific and sensitive radioimmunoassay for rat apolipoprotein A-IV (apoA-IV). The protocol includes treatment of the samples for 1 h at 60 degrees C with 0.7% Tween 20. Under these conditions, linear logit-log plots have been obtained for apoA-IV in lymph and plasma lipoprotein fractions as well as for purified apoA-IV. The sensitivity of the assay is to 20 ng. Absolute mass values obtained with the assay were validated by comparison with values obtained with an independent method of colorimetric reading of apoA-IV separated by polyacrylamide gel electrophoresis from plasma high density lipoproteins. The concentration of apoA-IV in fasting plasma averaged 10.2 mg/dl and in the mesenteric duct lymph 15.8 and 12.6 mg/dl during the fasting and the fat absorption states, respectively.

Animals↗
PubMed1986

Binding of apoA-IV-phospholipid complexes to plasma membranes of rat liver.

Rat apoA-IV complexes with dimyristoyl phosphatidylcholine (apoA-IV-DMPC) have been prepared and their ability to bind to purified rat liver plasma membranes investigated. Binding equilibrium at 37 degrees C was reached in 30 minutes. Saturation binding experiments and subsequent analysis of the results with Scatchard plots gave results consistent with the presence of a single saturable binding site. DMPC or POPC unilamellar vesicles could not compete with apoA-IV-DMPC for binding; apoA-I-DMPC competed only partially. ApoE-poor HDL effectively competed with apoA-IV-DMPC. The fact that binding could be greatly reduced (greater than 70%) by preincubating the membrane with pronase (18 micrograms/ml), supports the conclusion that a membrane protein is involved in binding. Based on these results, we speculate that the rapid catabolism of apoA-IV in plasma may be mediated by a specific uptake mechanism in the liver. The implications of these results support the hypothesis that apoA-IV is involved in reverse cholesterol transport.

Animals↗
PubMed1986

Plasma catabolism of human apolipoprotein E isoproteins: lack of conversion of the doubly sialylated form to the asialo form in plasma.

Apolipoprotein E (apoE) circulates as a mixture of sialylated and asialylated forms. In this study the catabolic fate and the plasma turnover rate of the different apoE forms have been investigated in vivo in humans. Asialo apoE (E) and doubly sialylated apoE (Ess) were isolated by preparative isoelectrofocusing from the VLDL of subjects homozygous for the E3 allele. 131E3 and 125E3ss were injected simultaneously into three hypertriglyceridemic subjects, and plasma samples were collected up to the sixth day. VLDL were isolated by ultracentrifugation, and the apoE forms were separated by isoelectrofocusing. Gel bands corresponding to E3 and E3ss were cut out and counted for the associated radioactivity. Residence times in plasma for 131E3 and 125E3ss were 0.95 +/- 0.16 and 0.74 +/- 0.16 days, respectively. As determined from the gel count distribution up to 24 hours, no conversion of the injected sialylated form to the correspondent asialylated form was detected.

Aged↗
PubMed1986

Familial apolipoprotein E deficiency.

A unique kindred with premature cardiovascular disease, tubo-eruptive xanthomas, and type III hyperlipoproteinemia (HLP) associated with familial apolipoprotein (apo) E deficiency was examined. Homozygotes (n = 4) had marked increases in cholesterol-rich very low density lipoproteins (VLDL) and intermediate density lipoproteins (IDL), which could be effectively lowered with diet and medication (niacin, clofibrate). Homozygotes had only trace amounts of plasma apoE, and accumulations of apoB-48 and apoA-IV in VLDL, IDL, and low density lipoproteins. Radioiodinated VLDL apoB and apoE kinetic studies revealed that the homozygous proband had markedly retarded fractional catabolism of VLDL apoB-100, apoB-48 and plasma apoE, as well as an extremely low apoE synthesis rate as compared to normals. Obligate heterozygotes (n = 10) generally had normal plasma lipids and mean plasma apoE concentrations that were 42% of normal. The data indicate that homozygous familial apoE deficiency is a cause of type III HLP, is associated with markedly decreased apoE production, and that apoE is essential for the normal catabolism of triglyceride-rich lipoprotein constituents.

Adolescent↗