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Biomedical subjects

B A Nassar

Publications and source records attributed to B A Nassar.

At least 19 recordsLinked to original sources
PubMed2001

Relationship of the Glu298Asp polymorphism of the endothelial nitric oxide synthase gene and early-onset coronary artery disease.

BACKGROUND: The Glu298Asp polymorphism of endothelial nitric oxide synthase (eNOS) gene has been associated with coronary artery disease (CAD) in some but not all studies. To determine the impact of the mutant Asp298 eNOS allele on the development of premature CAD, we examined the prevalence of this mutation in patients with early-onset CAD compared with those manifesting CAD later in life. If this mutation confers an increased risk of premature CAD, we hypothesized that the frequency of the homozygous mutation (Asp298Asp298) would be greater among the younger patient group. METHODS: A total of 299 patients with a history of myocardial infarction (MI) or angina pectoris plus angiographically documented CAD were studied. Patients were divided into 2 groups: group 1 (149 patients) included patients with CAD before the age of 50 years and group 2 (150 patients) included patients with a first presentation of CAD at >65 years old. Prevalence of eNOS Glu298 and Asp298 alleles was assessed by molecular analysis and compared for the 2 groups. RESULTS: There was no significant difference in the frequency of the mutant Asp298 allele between the 2 groups (G1: 42% vs G2: 42.7%, P =.79). The frequencies of the Glu298Glu298, Glu298Asp298, and Asp298Asp298 genotypes were similar in both groups (34.9%, 46.3%, and 18.8% for G1 and 29.3%, 56%, and 14.7% for G2, respectively, P =.29). CONCLUSIONS: Our study does not support the conclusion that the eNOS Asp298 allele contributes to the development of premature CAD.

Age Factors↗
PubMed2000

Effect of folic acid and antioxidant vitamins on endothelial dysfunction in patients with coronary artery disease.

OBJECTIVES: The purpose of this study was to determine whether lowering homocysteine levels with folic acid, with or without antioxidants, will improve endothelial dysfunction in patients with coronary artery disease (CAD). BACKGROUND: Elevated plasma homocysteine levels are a risk factor for atherosclerosis. Homocysteine may promote atherogenesis through endothelial dysfunction and oxidative stress. METHODS: In a double-blind, placebo-controlled, randomized trial, we used vascular ultrasound to assess the effect of folic acid alone or with antioxidants on brachial artery endothelium-dependent flow-mediated dilation (FMD). Seventy-five patients with CAD (screening homocysteine level > or =9 micromol/liter) were randomized equally to one of three groups: placebo, folic acid alone or folic acid plus antioxidant vitamins C and E. Patients were treated for four months. Plasma folate, homocysteine, FMD and nitroglycerin-mediated dilation were measured before and after four months of treatment. RESULTS: Plasma folate, homocysteine and FMD were unchanged in the placebo group. Compared with placebo, folic acid alone increased plasma folate by 475% (p < 0.001), reduced plasma homocysteine by 11% (p = 0.23) and significantly improved FMD from 3.2 +/- 3.6% to 5.2 +/- 3.9% (p = 0.04). The improvement in FMD correlated with the reduction in homocysteine (r = 0.5, p = 0.01). Folic acid plus antioxidants increased plasma folate by 438% (p < 0.001), reduced plasma homocysteine by 9% (p = 0.56) and insignificantly improved FMD from 2.6 +/- 2.4% to 4.0 +/- 3.7% (p = 0.45), as compared with placebo. Nitroglycerin-mediated dilation did not change significantly in any group. CONCLUSIONS: Folic acid supplementation significantly improved endothelial dysfunction in patients with coronary atherosclerosis. Further clinical trials are required to determine whether folic acid supplementation may reduce cardiovascular events.

Aged↗
PubMed2000

Oral glucose loading acutely attenuates endothelium-dependent vasodilation in healthy adults without diabetes: an effect prevented by vitamins C and E.

OBJECTIVES: The goal of this study was to determine whether postprandial hyperglycemia, induced by oral glucose loading, attenuates endothelial function in healthy subjects without diabetes and whether coadministration of vitamins C and E could prevent these postprandial changes. BACKGROUND: Epidemiologic evidence suggests that postprandial hyperglycemia, below diabetic levels, is a risk factor for cardiovascular disease. Postprandial hyperglycemia may promote atherosclerosis through endothelial dysfunction and oxidative stress. METHODS: We evaluated the acute effects of oral glucose loading (75 g), alone and with vitamins C (2 g) and E (800 IU), on endothelium-dependent flow-mediated dilation (FMD) of the brachial artery, in a randomized, double-blind, placebo-controlled, crossover study of 10 healthy volunteers. Changes in the levels of markers of oxidative stress (plasma malondialdehyde and erythrocyte glutathione, glutathione peroxidase and superoxide dismutase) were also assessed. RESULTS: Increases in plasma glucose and insulin after glucose loading were unaffected by vitamin coadministration. With glucose loading alone, FMD fell from 6.5+/-2.2 at baseline to 5.4+/-1.7, 3.7+/-2.1*, 4.1+/-3.5* and 5.7+/-1.9% at 1, 2, 3 and 4 h (*p < 0.05 vs. 0 h). In contrast, FMD did not change significantly after glucose plus vitamins (6.4+/-1.3, 7.6+/-1.8, 7.9+/-2.7, 6.9+/-2.3, 6.9+/-1.9% at 0, 1, 2, 3 and 4 h). By two-way repeated measures analysis of variance we found a significant interaction between vitamin treatment and time (p = 0.0003), indicating that vitamins prevented the glucose-induced attenuation of FMD. Oxidative stress markers did not significantly change with glucose loading alone or with vitamins. CONCLUSIONS: Oral glucose loading causes an acute, transient decrease of FMD in healthy subjects without diabetes, which is prevented by vitamins C and E.

Adult↗
PubMed1999

Relation of genetic polymorphisms of apolipoprotein E, angiotensin converting enzyme, apolipoprotein B-100, and glycoprotein IIIa and early-onset coronary heart disease.

OBJECTIVE: Apolipoprotein E (APOE) E4, apolipoprotein B-100 (APOB) Q3611 allele, the angiotensin converting enzyme (ACE) deletion (D) allele and glycoprotein IIIa (GP3A) P33 mutant allele are reported to predispose to early-onset coronary heart disease (CHD). These associations were not all confirmed in more recent studies. To determine the impact of these alleles on CHD, we examined the prevalence of these mutations in patients presenting with early-onset CHD and compared them to those manifesting CHD later in life. The delayed-onset was considered a sign of longevity and would serve as a comparative group to assess prevalence of the biochemical and genetic risk factors. METHODS: 300 patients with a history of myocardial infarction or angina pectoris and angiographically documented CHD were studied. Patients were divided into two groups: group 1 (G1 = 150 patients) presenting with these findings under the age of 50 years; while group 2 (G2 = 150 patients) were patients presenting for the first time over the age of 65 years. Prevalence of the alleles of APOE, APOB, ACE and GP3A was assessed by molecular analysis. An association of any of these genotypes with early onset CHD could lead to a higher prevalence in the younger age group. RESULTS AND CONCLUSIONS: None of the suspected alleles namely APOB Q3611 [G1: 10.7% vs. G2: 9.0%, p = 0.57], ACE D (G1: 52.0% vs. G2: 49.7%, p = 0.57), or the GP3A P33 (G1: 17.3% vs. G2: 15.7%; p = 0.58) showed any significant difference between the two groups. Subjects with APOE E4 were more frequent in the younger age group (G1: 18.3% vs. G2: 13.7%; p = 0.047), while APOE E2 was more frequent in G2 (G2: 10.0% vs. G1: 2.7%; p = 0.0002). Multivariate analysis showed an odds ratio of APOE E2 allele in G1 of 0.27 with a confidence interval of 0.10-0.73.

Adult↗
PubMed1998

A novel mutation in Exon 4 of the low density lipoprotein receptor gene resulting in heterozygous familial hypercholesterolemia associated with decreased ligand binding.

Familial hypercholesterolemia (FH) is an autosomal dominant disorder caused by mutations in the low density lipoprotein (LDL) receptor gene. Currently, diagnosis of heterozygous FH relies on clinical phenotype; however, the use of clinical criteria for the diagnosis of heterozygous FH does not always permit unequivocable diagnosis of the disease. Molecular diagnosis of FH is clinically valuable especially in regions where founder mutations exist or where polygenic hypercholesterolemia is prevalent. In this paper we report the identification of a novel mutation, a cytosine to guanine substitution, at codon 152 in exon 4 of the LDL receptor gene in a Nova Scotian family clinically diagnosed with heterozygous FH. The mutation creates a recognition sequence for the restriction endonuclease BsrI, and can be readily detected by BsrI restriction analysis of a 160 bp amplicon spanning the mutation. This analysis was used to show that the mutation segregated with the disease in this family and is the probable cause of FH in this kindred.

Adult↗
PubMed1998

Relation of HFE gene mutations, high iron stores and early onset coronary artery disease.

OBJECTIVE: To determine the impact of mutations in the HFE gene (human leukocyte antigen H) on predisposition to coronary artery disease (CAD) in patients not diagnosed with hereditary hemochromatosis. BACKGROUND: Elevated iron stores can predispose to acute myocardial infarction. Two mutations (C282Y and H63D) in the novel major histocompatibility complex (MHC) class 1 gene HFE were found in most patients with hereditary hemochromatosis causing high iron stores. The effect of these mutations on predisposition to CAD has not been investigated previously. METHODS: Three hundred patients with a history of myocardial infarction or angina pectoris and angiographically documented CAD were studied. Patients were divided into two groups: group 1 (150 patients), manifesting early onset CAD and presenting with these findings under age 50 years; and group 2 (150 patients), presenting for the first time over age 65 years. Prevalence of the C282Y and H63D mutations was assessed by molecular analysis, and plasma ferritin was measured immunochemically. RESULTS: There was no difference in the prevalence of homozygous, heterozygous or compound heterozygous (C282Y/H63D) states between the groups. Males in group 1 had higher plasma ferritin than those in group 2 (234 +/- 174 micrograms/L versus 136 +/- 103 micrograms/L, P < 0.0001), but this was not significantly different in females (75 +/- 54 micrograms/L versus 92 +/- 73 micrograms/L, P = 0.26). Ferritin remained higher in group 1 than in group 2 males after exclusion of mutation carriers (195 +/- 121 micrograms/L versus 109 +/- 76 micrograms/L, respectively, P < 0.0001), but did not change in females. CONCLUSIONS: Higher iron stores were found in males with early onset CAD. This association was not related to the C282Y or H63D mutation in HFE. It is suggested that association of the MHC locus with delayed onset CAD is probably unrelated to HFE in these patients, and that HFE mutations are not a major risk factor in the development of high iron stores in early onset CAD.

Coronary Disease↗
PubMed1997

Detection of a R173W mutation in the porphobilinogen deaminase gene in the Nova Scotian "foreign Protestant" population with acute intermittent porphyria: a founder effect.

OBJECTIVES: Acute intermittent porphyria (AIP) is caused by mutations in the porphobilinogen deaminase (PBGD) gene that disrupt the function of the enzyme. Many mutations that lead to decreased PBGD activity have been described. An Arg to Trp substitution at codon 173 (CGG-->TGG in exon 10) and designated R173W, which leads to a CRIM-negative phenotype, has been reported in Swedish, Finnish, Scottish, and South African kindreds, and in a Nova Scotian proband with fatal AIP. In this work, we investigated the presence of this mutation in a Nova Scotian patient population presenting with AIP. DESIGN AND METHODS: Single-strand conformation polymorphism analysis and DNA sequencing by TA cloning and Sanger's dideoxy chain termination method, were used to confirm the maternal transmission of this mutation to the proband. The mutation also eliminates an Ncil (also Mspl) endonuclease restriction site, which allows for detection of the mutant allele by polymerase chain reaction amplification and restriction enzyme digestion. RESULTS: The family of the Nova Scotian proband and four other AIP kindreds showed the presence of the same mutation. These five families are descendants of German, Swiss, and French immigrants historically known as the "Foreign Protestants," who were recruited to Nova Scotia in the 1750s. CONCLUSION: In all these families, descent from one couple that settled in Nova Scotia in 1751 has been identified by genealogy research, consistent with a founder effect within this population. This is the first identified mutation in PBGD causing AIP that has been linked to a founder effect in descendants of an immigrant population to North America, and which could be traced to such a distant background, similar to the South African variegate porphyria mutation.

Adult↗
PubMed1995

Heteroduplex analysis detects frameshift and point mutations in patients with acute intermittent porphyria.

We used heteroduplex analysis to screen for mutations in the porphobilinogen deaminase gene in 21 patients with acute intermittent porphyria (AIP). Unique banding patterns were investigated by direct sequencing of polymerase chain reaction products and, when indicated, sequencing of cloned DNA containing the exon of interest. Two frameshift mutations were found, a 2-bp deletion in exon 5 and a 1-bp insertion in exon 7. Both mutations generate a premature stop codon. Two point mutations, in exons 10 and 14, were also observed. The C-->T mutation in exon 10 codes for an Arg173 to Trp substitution, while a G-->A mutation in exon 14 changes Trp283 into a premature stop codon. This study extends the spectrum of mutations that cause AIP and demonstrates the utility of heteroduplex analysis as a screening technique.

Base Sequence↗
PubMed1995

Effects of acutely raising intracranial pressure on cardiac sympathetic efferent neuron function.

OBJECTIVE: To determine whether acutely raising intracranial pressure modifies the function of cardiac efferent autonomic neurons. METHODS: The effects of suddenly raising intracranial pressure above systemic vascular pressure on heart rate, left atrial and left ventricular chamber pressures, as well as right and left ventricular intramyocardial pressures, were studied following removal of the adrenal glands from the circulation. Cardiac effects induced by systemic administration of nicotine, tyramine or isoproterenol were investigated before and after raising intracranial pressure: (1) in 9 dogs with neurally intact hearts in which cardiac release of catecholamines and intrinsic cardiac neuronal activity were studied; (2) in another 8 dogs in which intrathoracic autonomic neurons were disconnected from central neurons; (3) in another 8 dogs after decentralizing intrathoracic sympathetic but not parasympathetic neurons; (4) in 2 animals after decentralizing intrathoracic parasympathetic, not sympathetic neurons. RESULTS: Increasing intracranial pressure in neurally intact preparations induced ventricular augmentation followed by depression such that after 12 min of cerebral ischemia left ventricular systolic pressure was 62 +/- 5 mmHg. Isoproterenol and tyramine augmented right ventricular inotropism similarly before and after raising intracranial pressure, their effects on left ventricular systolic pressures being reduced secondary to the systemic vascular hypotension. Although nicotine excited intrinsic cardiac neurons similarly before and after raising intracranial pressure, it failed to enhance cardiac liberation of noradrenaline after compared to before raising intracranial pressure. Nicotine-induced ventricular augmentation was obtunded after brain death despite the fact that ventricular myocytes underwent no detectable histological changes. In contrast, nicotine induced similar cardiac augmentation before and after raising intracranial pressure when intrathoracic autonomic neurons or when intrathoracic sympathetic, not parasympathetic neurons, were decentralized. CONCLUSION: Cardiac sympathetic efferent neuronal function is obtained by acutely raising intracranial pressure.

Adrenalectomy↗
PubMed1994

Detection of familial defective apolipoprotein B-100 among patients clinically diagnosed with heterozygous familial hypercholesterolemia in maritime Canada.

Familial defective apolipoprotein B-100 (FDB) is a genetic disorder resulting from a mutation in the apolipoprotein B-100 (apo B-100) gene, most frequently at position 3500, in which arginine is substituted for glutamine in the mature protein. This mutation drastically decreases the affinity of the mutant apo B-100 particle for the low-density lipoprotein (LDL) receptor, and hence decreases the clearance of cholesterol from the circulation. Familial hypercholesterolemia (FH), also a disorder of lipid metabolism, results from mutations in the gene for the LDL receptor. Both FDB and heterozygous FH occur at approximately the same frequency (1 in 500) among Caucasians and both produce clinical symptoms and signs that can be indistinguishable. Polymerase chain reaction (PCR) amplification and subsequent restriction analysis have been used to detect the substitution at codon 3500 in the apo B-100 gene using mutagenic PCR primers. At least one proband from 10 unrelated families with a history of hypercholesterolemia was screened by mutagenic PCR for FDB. Only one of 10 patients demonstrated the mutation for FDB. The mutant apo B-100 allele was shown to segregate with other clinically affected family members. These results demonstrate that molecular analysis is essential to distinguish between FDB and heterozygous FH in hypercholesterolemic families.

Adult↗
PubMed1992

The effect of chemical hepatocarcinogenesis on liver phospholipid composition in rats fed N-6 and N-3 fatty acid-supplemented diets.

The effect of dietary fats on essential fatty acid metabolism in rats subjected to chemically induced hepatocarcinogenesis was studied. Sixty male rats were fed a diet supplemented with one of the following three oil compositions: 10% hydrogenated coconut oil (HCO); 5% hydrogenated coconut oil and 5% gamma-linolenic acid (18:3n-6)-rich evening primrose oil (EPO); or 5% hydrogenated coconut oil and 5% marine oil (FO). Half of the animals in each dietary regimen were subjected to hepatocarcinogenesis induction using diethylnitrosamine and 2-acetylaminofluorene (2-AAF) followed by partial hepatectomy, whereas the other half underwent hepatectomy without receiving diethylnitrosamine and 2-acetylaminofluorene. Liver phospholipid composition was analyzed. In comparison to the HCO group, the EPO group showed raised levels of arachidonic acid (20:4n-6) and suppressed n-3 fatty acids. The FO group, on the other hand, showed suppressed levels of n-6 and increased n-3 fatty acids. Hepatocarcinogenesis suppressed the level of 20:4n-6 and this effect was greater in the FO rats. The levels of dihomo-gamma-linolenic acid (20:3n-6) were increased by the hepatocarcinogenic treatment, and this effect was further accentuated in the EPO rats. These results suggest that hepatocarcinogenesis may suppress the activity of delta-5-desaturase, which may be one of the reasons why tumor cell membranes have low levels of long chain fatty acids, especially 20:4n-6 cells, and have an impaired capacity to undergo lipid peroxidation.

Animals↗
PubMed1990

Release of essential fatty acids from the rat mesenteric vascular bed perfused in vitro: modulation by zinc.

The rat mesenteric vascular bed releases prostaglandins when perfused in vitro. The present study evaluated the effect of perfusion of the rat mesenteric vascular bed in vitro with a buffer containing 0, 3, 6, or 9 nM of added zinc on the release of essential fatty acids over a 150-min period. Long chain fatty acids in the mesenteric lipids and in total lipid of the perfusion effluent were assayed by gas liquid chromatography. The presence of 6 nM zinc in the perfusing buffer almost completely prevented the change in 16-22 carbon long chain fatty acids in the mesenteric phospholipids and decreased the release of free fatty acids in comparison to that occurring in the absence of additional zinc. The results suggest that physiological amounts of zinc in the perfusion medium reduce the release of essential fatty acid from rat mesenteric lipids.

Animals↗
PubMed1989

The prostaglandin outflow from perfused mesenteric vasculature of rats fed different fats.

The effects of dietary n-6 polyunsaturated fatty acids and replacement with saturated fat or fish oil on the prostaglandin outflow from perfused mesenteric vasculature in rats were studied. Seventy-two weanling male rats were fed ad libitum a semi-synthetic diet supplemented with 10% by weight of oil, composed wholly of n-6 fatty acid-rich evening primrose oil, or replaced partly or completely (25, 50, 75 or 100%) by n-6 fatty acid-deficient fish oil or hydrogenated coconut oil for 8 weeks. The outflows of 6-keto-PGF1 alpha, thromboxane B2, and prostaglandin E from the perfused mesenteric vasculature were measured at 60 min-time point after starting the perfusion. In general, the release of prostanoids from the mesenteric vasculature was significantly reduced in rats fed a diet in which evening primrose oil was partly or completely replaced by either hydrogenated coconut or fish oil. This was probably due to the insufficient conversion of linoleic acid to arachidonic acid. The extent of reduction was greater in fish oil-fed than in hydrogenated coconut oil-fed rats, while the levels of arachidonic acid in aortic phospholipids were similar between these two groups. This result implies that the greater reduction of prostaglandin synthesis in rats fed fish oil was due to the inhibitory effect of eicosapentaenoic and docosahexaenoic acids in fish oil on the conversion of arachidonate to eicosanoids.

6-Ketoprostaglandin F1 alpha↗
PubMed1988

The influence of phenelzine and tranylcypromine on the release of prostaglandins from the rat mesenteric vascular bed.

We investigated the effects of phenelzine and tranylcypromine on the release of prostacyclin, thromboxane A2, prostaglandin E2, and prostaglandin E1 from the isolated perfused rat mesenteric vascular bed. Perfusion of the preparation with phenelzine in concentrations of 15, 45, and 135 microM for 150 min led to attenuated release of all four prostaglandins measured. Inhibition generally occurred with the lowest dose used and was most prominent with the highest concentration. Tranylcypromine also decreased prostaglandin formation. However, low doses were not effective in the suppression of prostacyclin release. Both drugs had an inhibitory effect on production of prostaglandin E1, which is a metabolite of dihomo-gamma-linolenic acid, the precursor of arachidonic acid, but this was only shown to be significant with phenelzine. In this work we demonstrate that phenelzine and tranylcypromine have an inhibitory effect on the production of 2-series prostaglandins derived from arachidonic acid, and possibly a similar effect on prostaglandins of the 1-series derived from dihomo-gamma-linolenic acid.

Alprostadil↗
PubMed1987

Effect of different ratios of dietary N-6 and N-3 fatty acids on fatty acid composition, prostaglandin formation and platelet aggregation in the rat.

Five groups of male Sprague-Dawley rats (150 g) were fed a fat-free diet supplemented with 10% by weight of evening primrose oil (Efamol, rich in linoleic acid and gamma-linolenic acid) and/or marine oil (Polepa, rich in eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3) combined in several ratios (Efamol/Polepa; 10.0%/0%; 7.5%/2.5%; 5.0%/5.0%; 2.5%/7.5%; 0%/10.0%). The n-6 fatty acid levels in aortic, platelet and plasma phospholipids decreased in proportion as Efamol was replaced with Polepa. The exception in phospholipids was dihomo-gamma-linolenic acid (20:3n-6), which increased when marine oil was provided in the diet with Efamol. The ratio of 20:3n-6 to arachidonic acid (20:4n-6) was positively correlated with 20:5n-3, docosapentaenoic acid (22:5n-3) or 22:6n-3 in aortic, platelet and plasma phospholipids under these dietary conditions. In contrast, 20:3n-6 in plasma cholesterol esters, triglycerides and free fatty acids did not show any increase in the presence of Polepa. Aortic prostaglandin (PG) production (6-keto-PGF1 alpha, PGE2 and PGE1) was reduced as Efamol was progressively replaced with Polepa. Aortic PG production was positively correlated with 20:4n-6 content in aortic phospholipids. Thrombin-induced thromboxane B2 production in whole blood was related to 20:4n-6 content in platelet phospholipids. However, ADP-induced platelet aggregation was significantly decreased only in the 7.5% Efamol/2.5% Polepa group as compared to the other 4 groups. These results suggest that combined treatment with Efamol and Polepa increases the ratio of 20:3n-6 to 20:4n-6 in tissue and plasma phospholipids. An appropriate ratio of these oils favorably affects aortic PG production and platelet ADP aggregation.

Adenosine Diphosphate↗