bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of injury and insulin on lipid synthesis from glucose by the rat thoracic aorta.
Authors: Capron L , Jarnet J
Published: June 2011

Chronic hyperinsulinemia is suspected of enhancing the development of arterial diseases. However, direct metabolic effects of insulin on the inner arterial wall are poorly documented. To assess the possible influence of variations in smooth muscle phenotype, we measured lipogenesis from glucose by rat thoracic aortas that had been injured with a balloon catheter. Aortas were exposed to insulin during either a 1-hour incubation or a 9-minute perfusion. Injury transiently stimulated lipogenesis by the intima-media (by 111% and 225% on the second day after injury in two separate experiments). However, insulin added either to the incubation medium or to the perfusion medium, even at a very high concentration (10(5) microunits/ml), did not modify lipogenesis by the intima-media as long as 14 days after injury. In contrast, two days after injury, the adventitia responded to insulin in a dose-dependent manner. We conclude that: 1) Injury transiently stimulates lipogenesis from glucose by the intima-media. 2) The change in smooth muscle cell phenotype, from contractile to synthetic, does not influence the metabolic sensitivity of the intima-media to insulin. 3) Our results do not substantiate the view that insulin contributes to the development of cardiovascular diseases through a direct lipogenic effect on arterial smooth muscle cells.
Endothelial cells reestablish functional integrity after reversible permeabilization.
Authors: Fennell D F , Whatley R E , McIntyre T M , Prescott S M , Zimmerman G A
Published: June 2011

Permeabilization is an important tool in cell biology that allows manipulation of intracellular mechanisms by introduction of probes and regulatory molecules into the cell cytoplasm. We found that incubation of endothelial cells (ECs) with glass beads resulted in nonspecific permeabilization of human and bovine ECs without removal of the cells from monolayer culture. This poration of the plasma membrane allowed the introduction of macromolecules (dextrans less than or equal to 152 kd and immunoglobulins) as well as small, charged molecules (Lucifer Yellow). We found that nonspecific permeabilization of the EC was transient and defined the conditions under which integrity of the plasma membrane was reestablished. This process was dependent on time, temperature, and the presence of extracellular calcium. We also demonstrated that permeabilized ECs regain functional characteristics. This was defined by a number of criteria, including the ability to rapidly reestablish confluent monolayer morphology, to extrude Lucifer Yellow, to adhere and spread after passage, and to synthesize biologically active molecules after stimulation with a receptor-mediated agonist. Thus, transiently porated ECs loaded with appropriate probes can be used in studies of regulatory mechanisms while remaining in monolayer culture, a condition in which many phenotypic features are similar to in situ endothelium. Furthermore, the porated EC may be a useful model for defining the mechanisms that influence the repair of endothelial plasma membrane injury.
Nitric oxide and prostacyclin. Divergence of inhibitory effects on monocyte chemotaxis and adhesion to endothelium in vitro.
Authors: Bath P M , Hassall D G , Gladwin A M , Palmer R M , Martin J F
Published: June 2011

Monocyte-endothelial interactions are of fundamental importance in determining the movement of monocytes from the blood stream into the vessel wall. This study reports that two endothelium-derived factors, nitric oxide and prostacyclin, alter in vitro monocyte behavior. Nitric oxide (greater than 10(-5) M) inhibited monocyte adhesion to porcine aortic endothelial cell monolayers, whereas prostacyclin (10(-9) to 10(-5) M) had no effect. Both nitric oxide and prostacyclin inhibited monocyte chemotaxis stimulated by N-formyl-methionyl-leucyl-phenylalanine and induced dose-dependent increases in intracellular cyclic guanosine monophosphate and cyclic adenosine monophosphate concentrations, respectively. The cell surface expression of the CD11b/CD18 adhesion receptor, a glycoprotein complex known to mediate monocyte intracellular adhesion, was not altered by either nitric oxide or by prostacyclin. Thus, endothelium-derived nitric oxide and prostacyclin may have a physiological role in modulating monocyte-vascular wall interactions. Alterations in this system may contribute to the increased monocyte emigration from the blood stream into the vessel wall observed in atherogenesis.
Oxidation of beta-very low density lipoprotein by endothelial cells enhances its metabolism by smooth muscle cells in culture.
Authors: Horrigan S , Campbell J H , Campbell G R
Published: June 2011

We have previously shown that beta-very low density lipoprotein (beta-VLDL) incubated with bovine aortic endothelial cells (ECs) is bound and internalized more readily by cultured rabbit aortic smooth muscle cells (SMCs) than is beta-VLDL incubated in the absence of ECs, resulting in enhanced accumulation of cholesterol. To investigate the mechanism by which this occurs, beta-VLDL from hypercholesterolemic rabbit serum was incubated with cultured bovine aortic ECs. This resulted in the formation of thiobarbituric acid (TBA)-reactive material indicating extensive lipid peroxidation. The formation of TBA-reactive material, the increased metabolism of beta-VLDL by rabbit aortic SMCs, and the increased accumulation of cholesterol were prevented by superoxide dismutase, EDTA, several antioxidants, and, to a lesser extent, by 5,8,11,14-eicosatetraynoic acid, but not by acetylsalicylic acid, suggesting that potential oxidizing agents were the superoxide anion, metal ions, and lipoxygenase derivatives, but not cyclooxygenase derivatives. The percentage composition of phospholipid, protein, triglyceride, and free and esterified cholesterol of EC-modified beta-VLDL did not differ significantly from the unmodified lipoprotein. Displacement studies showed that only part of the interaction of both EC-beta-VLDL and unmodified beta-VLDL occurred through the B/E receptor and that the EC-beta-VLDL displaced 125I-beta-VLDL to a greater extent than did unmodified beta-VLDL. This indicated that the EC-beta-VLDL interacted more strongly with receptors on SMCs.
Genetic and environmental factors affecting the incidence of coronary artery disease in heterozygous familial hypercholesterolemia.
Authors: Hill J S , Hayden M R , Frohlich J , Pritchard P H
Published: June 2011

This study explores the influence of selected genetic and environmental factors on the clinical expression of heterozygous familial hypercholesterolemia (FH). A detailed examination of the physical and biochemical features of FH was performed in a large cohort of 208 females and 156 males. Females with FH had higher levels of total, low density lipoprotein (LDL), and high density lipoprotein (HDL) cholesterol when compared with males, although the concentration of HDL cholesterol was significantly lower for both sexes when compared with normals. The reported incidence of coronary artery disease (CAD) was 31% for men and 13% for women, which was lower when compared with figures from previous studies. The average age of onset of coronary symptoms was delayed in females, with a mean age of 55 years compared with 48 years for males (p less than 0.05). A greater risk of developing CAD in men was associated with lower levels of HDL cholesterol and a history of smoking. In women, however, CAD was associated with elevated triglycerides and the presence of hypertension. The frequencies of the epsilon 2, epsilon 3, and epsilon 4 alleles of apolipoprotein E in 125 unrelated FH subjects did not differ significantly from the normal population. In addition, there was no apparent relation between apo E4 and the concentration of any of the parameters in the plasma lipid profile; however, the presence of the E2 isoform was associated with significantly elevated triglycerides in both sexes. This study has allowed us to identify those factors, which, in addition to total cholesterol levels, are associated with the development of premature coronary atherosclerosis in heterozygous FH.
Enhanced susceptibility to in vitro oxidation of the dense low density lipoprotein subfraction in healthy subjects.
Authors: de Graaf J , Hak-Lemmers H L , Hectors M P , Demacker P N , Hendriks J C , Stalenhoef A F
Published: June 2011

Oxidative modification of low density lipoprotein (LDL) has been implicated as a factor in the generation of macrophage-derived foam cells, the hallmark of atherosclerotic plaques. Because LDL consists of discrete subfractions with different physicochemical characteristics, the question arises as to whether these LDL subfractions differ in their susceptibility to oxidative modification. To answer this question, three LDL subfractions, LDL1, LDL2, and LDL3, were isolated from the plasmas of 11 healthy volunteers by density gradient ultracentrifugation. The LDL subfractions were oxidatively modified by incubation with copper ions. Differences in the subfractions' susceptibilities to lipid peroxidation were studied by measuring the formation of the 234-nm-absorbing oxidation products every 3 minutes on an ultraviolet spectrophotometer. A significant inverse linear relation was found between LDL subfractions and lag time (regression coefficient = -8.50, p less than 0.001), indicating that both the dense LDL3 and the light LDL2 were less well protected against oxidative modification than the very light LDL1. The LDL subfractions showed a positive linear relation with the rate of oxidation (regression coefficient = 0.46, p less than 0.001) and the amount of conjugated dienes formed in the LDL subfractions after 4 hours of oxidation (regression coefficient = 9.24, p less than 0.001). Thus, both LDL3 and LDL2 were more extensively modified in time than LDL1, which may be explained by the significantly higher concentration of polyunsaturated fatty acids in LDL3 (micromoles per gram LDL cholesterol) compared with LDL1 (Tukey's test, p less than 0.05). These results indicate that the more dense LDL subfractions, that is, LDL2 and LDL3, are more susceptible to oxidative modification and therefore may contribute more to foam cell formation than the less dense LDL subfraction LDL1.
Plasma fibrinogen and ischemic heart disease risk factors.
Authors: Møller L , Kristensen T S
Published: June 2011

The association between risk factors for ischemic heart disease and plasma fibrinogen level was analyzed in a cross-sectional population study. All 51-year-old men living in a certain area within the county of Copenhagen were invited; 439 of 542 (81%) participated in the study. Data were collected via questionnaire and at health examinations. The following independent variables were analyzed: social variables, which included social class, marital status, and job strain; psychological and psychosomatic variables, which included abdominal pain, personal and economic problems, self-assessed state of health, and degree of loneliness; behavioral variables, which included smoking, drug consumption, physical activity, use of sugar, and alcohol consumption; and physiological variables, which included high density lipoprotein (HDL) and low density lipoprotein (LDL) cholesterol, physical fitness, fasting glucose level, waist-to-hip ratio, and systolic blood pressure. In the multivariate analyses, the following variables showed an independent positive association with plasma fibrinogen level: one social variable (low social class); two psychological variables (abdominal pain index and personal/economic problems); two behavioral variables (smoking and physical inactivity during leisure time); and three physiological variables (low HDL cholesterol, low physical fitness, and high LDL cholesterol). The strongest independent associations with plasma fibrinogen level were found for smoking, social class, LDL cholesterol, and HDL cholesterol. These analyses suggest that smoking is a major risk factor for an elevated plasma fibrinogen level, but that other factors such as social class, cholesterol level, physical inactivity/physical fitness, and psychological problems also influence plasma fibrinogen level.
Effects of the apolipoprotein E polymorphism on levels of lipids, lipoproteins, and apolipoproteins among Mexican-Americans in Starr County, Texas.
Authors: Hanis C L , Hewett-Emmett D , Douglas T C , Bertin T K , Schull W J
Published: June 2011

Genetic variability has been implicated as a significant contributor to the variation in levels of lipids, lipoproteins, and apolipoproteins (apos) through a variety of direct and indirect investigations. Among the direct investigations, apo E has been shown to be polymorphic and to explain a small but statistically significant proportion of the variability in cholesterol. The apo E polymorphism was typed in 964 randomly selected Mexican-Americans from Starr County, Tex., and its effects determined on levels of cholesterol, triglycerides, total high density lipoprotein (HDL) cholesterol, subfractions (HDL2 and HDL3), alpha- and beta-lipoprotein cholesterol, low density lipoprotein (LDL) cholesterol, and apos A-I, A-II, B, C-II, C-III, and E. Effects are reported for the entire sample and in each of three groups, namely, premenopausal females, postmenopausal women, and males. In the entire sample, significant effects were observed on cholesterol, beta-lipoprotein cholesterol, LDL, apo B, and apo E. There is evidence for significant physiological interaction of the apo E polymorphism effect in females by menopausal status. This is most evident for apo E levels, in which 5.9% of the variability in the entire sample is explained by the apo E polymorphism. In premenopausal females, however, the polymorphism accounts for 27.5% of the variability. In postmenopausal women and males, there is no significant effect. It is shown that the apo E polymorphism can be treated as a two-locus, two-allele system. Doing so identifies substitutions in amino acid position 158 as the mediators of most of the observed effects of this polymorphism.
Synthesis of prostaglandins and thromboxane B2 by cholesterol-fed rabbits.
Authors: Wang T , Falardeau P , Powell W S
Published: June 2011

Alterations in the synthesis of thromboxane A2 (TxA2) and prostacyclin have been implicated in the development of atherosclerosis. We measured the amounts of the degradation products of these substances, TxB2 and 6-oxo-prostaglandin F1 alpha (6-oxo-PGF1 alpha), respectively, as well as PGE2, that were synthesized by slices and the luminal surfaces of aortas from rabbits fed either a control diet or a diet supplemented with cholesterol and peanut oil. For these studies, we developed conditions that were designed to minimize the autoinactivation of cyclooxygenase during removal and preparation of the tissue. Pretreatment of aortas with a medium containing ibuprofen and EDTA resulted in an approximately twofold increase in 6-oxo-PGF1 alpha production upon subsequent incubation. Despite the increased lipid peroxidation associated with atherosclerotic lesions, we observed no changes in either aortic 6-oxo-PGF1 alpha production or in the levels of its major urinary metabolite, 2,3-dinor-6-oxo-PGF1 alpha, after as long as 15 weeks of dietary supplementation with cholesterol and peanut oil. Similarly, synthesis of PGE2 by aortic slices and the aortic lumen was the same in cholesterol-fed and control rabbits. In contrast to aortic 6-oxo-PGF1 alpha and PGE2 synthesis, there was a dramatic 10-fold increase in TxB2 released from slices of thoracic aorta after 15 weeks on the atherogenic diet. This was much greater than the approximately twofold increase in the synthesis of TxB2 by the luminal surface of the thoracic aorta, suggesting that the primary site of TxB2 synthesis in the aorta is in the inner part of the blood vessel.(ABSTRACT TRUNCATED AT 250 WORDS)
Variation in the low density lipoprotein receptor gene is associated with differences in plasma low density lipoprotein cholesterol levels in young and old normal individuals from Italy.
Authors: Humphries S , Coviello D A , Masturzo P , Balestreri R , Orecchini G , Bertolini S
Published: June 2011

We have used four restriction fragment length polymorphisms (RFLPs) of the human low density lipoprotein receptor (LDL-R) gene, detected by the restriction enzymes Ava II, Pvu II, and ApaLI (5' and 3'), to study the effect of variation at this gene locus in determining plasma cholesterol and LDL cholesterol levels. Two hundred eighty-nine normolipidemic individuals were studied from the Liguria region of Italy. The Pvu II RFLP was significantly associated with differences in plasma total and LDL cholesterol levels, explaining 9.6% of the sample variance in LDL cholesterol levels. The other RFLPs, which are in strong linkage disequilibrium with the Pvu II RFLP, were associated with smaller effects on LDL cholesterol. The Pvu II allele, distinguished by the presence of the variable cutting site (P2 allele), was associated with lower levels of total and LDL cholesterol, and the frequency of the P2 allele was significantly reduced in individuals with LDL cholesterol levels higher than the 75th percentile. The frequency of the P2 allele was significantly higher in the group of individuals over 65 years old, and in this group the P2 allele was also associated with a similar reduction in LDL cholesterol levels. Because of linkage disequilibrium, only four RFLP haplotypes were common in this sample. Of these, only the haplotype P2A2VI (relative frequency, 0.269) was associated with a reduction in LDL cholesterol (average excess, -11.5 mg/dl).(ABSTRACT TRUNCATED AT 250 WORDS)
A common genetic polymorphism associated with lower coagulation factor VII levels in healthy individuals.
Authors: Green F , Kelleher C , Wilkes H , Temple A , Meade T , Humphries S
Published: June 2011

We have identified a genetic polymorphism of factor VII that is strongly associated with plasma factor VII coagulant activity (factor VIIc) in healthy individuals from the United Kingdom. This polymorphism was detected after Msp I digestion of polymerase chain reaction-amplified genomic DNA. In a sample of 284 men, the frequency of the M2 allele (loss of cutting site) is 0.1, and individuals with the M1M2 genotype have factor VIIc levels 22% below the sample mean (p less than 0.0001). Msp I genotype was found to be the strongest predictor of factor VIIc, accounting for 20.2% of the variance, with cholesterol accounting for an additional 3.5%. The base change that gives rise to the Msp I polymorphism is a G-to-A substitution in the codon for amino acid 353, leading to replacement of arginine (Arg) with glutamine (Gln) in the protein product of the M2 allele (designated Gln 353). Three individuals homozygous for the M2 allele have both low factor VIIc and low factor VII protein concentrations. The conformation of the Gln 353 molecule may be different from that of the Arg 353 protein, affecting its intracellular processing, secretion, turnover in plasma, or activity. In view of its association with lower factor VIIc levels, possession of the M2 allele may confer protection against thrombosis and myocardial infarction.
Specificity of the low density lipoprotein-glycosaminoglycan interaction.
Authors: Sambandam T , Baker J R , Christner J E , Ekborg S L
Published: June 2011

There is ample documentation of the binding of chondroitin sulfate/dermatan sulfate proteoglycans to low density lipoprotein (LDL) both in vivo and in vitro. The interaction of these two species may be an early and important step in atherogenesis. Therefore, there is interest in defining the features of both molecules that are critical for their interaction. We employed a recently described competitive microassay that measures initial binding of proteoglycan to immobilized LDL. We confirmed the work of others that it is the apolipoprotein B component and, at least in part, a heparin-binding domain of LDL that are responsible for binding chondroitin sulfate/dermatan sulfate proteoglycans. The principal thrust of our study was concerned with the effects of a glycosaminoglycan's degree of sulfation on the binding to LDL. Initial experiments comparing dermatan sulfate and chondroitin sulfate proteoglycans indicated that the former was more efficient at binding LDL than the latter and that oversulfation, rather than chain length or iduronate content, was the preeminent feature involved. Additional binding studies with dermatan sulfate, chemically sulfated chondroitin-4-sulfate, and naturally occurring oversulfated chondroitin sulfates indicated that the degree of sulfation, not the position of sulfation, determined affinity for LDL. These results suggest that studies should be undertaken to determine whether oversulfated segments of glycosaminoglycans are especially involved in associations with LDL, leading to lipid accumulation, in the artery wall.
Low density lipoprotein kinetics in a family having defective low density lipoprotein receptors in which hypercholesterolemia is suppressed.
Authors: Vega G L , Hobbs H H , Grundy S M
Published: June 2011

Heterozygous familial hypercholesterolemia (FH) usually presents with severe elevations of low density lipoprotein (LDL) cholesterol. Recently, a family with FH was described in which several members heterozygous for a mutation in the LDL receptor gene had normal LDL cholesterol levels. Kinetic studies of LDL apolipoprotein B (apo B) were conducted to determine the metabolic differences between the normolipidemic and hypercholesterolemic FH heterozygotes in the family. Studies were performed in 14 family members including the proband (who has homozygous FH), four FH heterozygotes with high LDL levels, four FH subjects with normolipidemia, and five healthy relatives without FH. The proband had a very low fractional catabolic rate (FCR) for LDL (0.15 pool/day). All the FH and non-FH subjects studied, excluding the FH homozygote, had higher than expected FCRs for LDL. The average FCRs for LDL of hypercholesterolemic and normocholesterolemic subjects were not significantly different (0.39 +/- 0.06 versus 0.37 +/- 0.02 pool/day), and these values were 70-80% of those in unaffected relatives. Compared with hypercholesterolemic FH heterozygotes, normolipidemic heterozygotes had much lower input rates for LDL (17.1 +/- author query macros2.6 versus 8.7 +/- 0.9 pools/day, respectively). These low input rates, together with the higher than usual FCRs for LDL, are responsible for the normal concentrations of LDL cholesterol in some of the FH heterozygotes. The low input of LDL could be due to either a decreased secretion of apo B-containing lipoproteins or an enhanced clearance of LDL precursor lipoproteins.
Age and dietary polyunsaturated fat alter high density lipoprotein subfraction cholesterol concentrations in a pediatric population of African green monkeys.
Authors: Wolfe M S , Parks J S , Morgan T M , Rudel L L
Published: June 2011

African green monkeys were raised from birth to 60 months of age on diets containing cholesterol (0.8 mg/kcal) and enriched in polyunsaturated (polyunsaturated to saturated fat ratio [P:S] = 2.5) or saturated (P:S = 0.3) fat. Lipoproteins were isolated from plasma of a group of animals (N = 123) and were separated by gel filtration chromatography at 9, 14, 26, 38, and 50 months of age, which covered a period through adolescence into young adulthood. Total plasma cholesterol (TPC) concentrations were 16% lower (p = 0.01) in the polyunsaturated fat-fed group, and high density lipoprotein (HDL) cholesterol concentrations averaged 20% lower (p = 0.008) in this group between 14 and 50 months of age, while plasma apolipoprotein A-I (apo A-I) averaged 7% lower (p = 0.06) over this age interval in the animals. The HDL cholesterol to apo A-I ratio was found to be significantly lower (p = 0.006) in the animals fed the polyunsaturated fat diet. This suggested that the HDL subfraction distribution might differ between groups. In a subset of animals (n = 105, 64 male and 41 female), HDL was subfractionated by density gradient ultracentrifugation into six subfractions, HDL-I to HDL-VI, from lowest to highest density. The saturated fat-fed animals had significantly higher cholesterol concentrations in HDL-I and significantly lower cholesterol concentrations in HDL-III, HDL-IV, and HDL-V. These effects held across all ages studied; therefore, these diet effects were not age dependent. In both diet groups, the HDL subfraction pattern changed with age such that the HDL-I and HDL-II cholesterol concentrations decreased, and those of HDL-IV, HDL-V, and HDL-VI increased as the animals matured. The decrease in HDL-I with age appeared to result primarily from a decrease in HDL-I in males, while the HDL-I cholesterol concentration in females did not change with age. We conclude that diet, age, and gender all affect HDL subfraction distribution and therefore can potentially modify the relative atherogenicity of the plasma HDL populations. It remains for future studies to demonstrate the effectiveness of each subfraction in promoting or preventing the cholesterol deposition of atherosclerosis.
Homocysteine thiolactone disposal by human arterial endothelial cells and serum in vitro.
Authors: Dudman N P , Hicks C , Lynch J F , Wilcken D E , Wang J
Published: June 2011

Previous work with cultured mammalian cells and perfused laboratory animals suggested to us that hydrolysis of homocysteine thiolactone was catalyzed in these systems. We confirmed this finding by measuring the sulfhydryl-releasing activity of cultured endothelial cells from human umbilical arteries in homocysteine thiolactone solution, pH 7.4, 37 degrees C. The reaction was vigorous and stereospecific and showed saturation kinetics (Km values for L- and D,L-homocysteine thiolactone were 3.9 and 8.2 mmol/l, respectively, and Vmax values were 10.75 and 10.1 mumol/min/10(9) cells, respectively). L-Homocysteine thiolactone was quantitatively converted to homocysteine, as measured by amino acid analysis. Human serum also accelerated the elimination of homocysteine thiolactone, although in this process, the majority of the newly formed sulfhydryl-containing product was precipitable by sulfosalicylic acid, indicating likely homocysteinylation of serum proteins. However, approximately 38% of the sulfhydryl-containing product was not precipitated, and because thiolactone elimination stereospecifically favored the L-enantiomer, a possible subsidiary role for serum-catalyzed hydrolysis of the thiolactone was suggested. No homocysteine thiolactone could be found in serum samples from six patients with acute myocardial infarction, three patients with cystathionine beta-synthase deficiency, and six normal subjects. Thus, humans have active vascular systems for elimination of homocysteine thiolactone, a process that could be responsible for an absence of the compound in serum.
Fabric organization of the subendothelium of the human brain artery by polarized-light microscopy.
Authors: Finlay H M , Dixon J G , Canham P B
Published: June 2011

The thickened subendothelium of brain arteries that is characteristic of atherosclerosis was assessed for the directional organization of the two main birefringent components, smooth muscle cells and collagen. Thirty-three arteries from 16 autopsy cases were pressure fixed at 30, 60, 110, and 200 mm Hg, sectioned at a thickness of 7 microns , and stained with silver impregnation to enhance tissue birefringence. The intended focus of the study was on muscle organization, but it also included the collagen among the cells because of the coalignment of the two tissues and their similar staining properties for polarized-light microscopy. The birefringent medial fabric at all pressures was circumferentially oriented, with a mean deviation of the 33 sections of 1.4 degrees from circumferential with an average circular standard deviation of 3.5 degrees, thereby showing remarkable coherence. In contrast, the subendothelium showed great variability both in thickness and in organization. Many arteries had no measurable subendothelium, and others had as much as 100%, with some atherosclerotic lesions as much as 300% of the medial width. Measurements from the subendothelium revealed a helical arrangement of tissue, often divided into separate regions, with a balance of left- and right-handed helical components and generally with lower pitch angles in the layers adjacent to the lumen. The average circular standard deviation within individual subendothelial layers was 14.5 degrees.
Clinical signs of familial hypercholesterolemia in patients with familial defective apolipoprotein B-100 and normal low density lipoprotein receptor function.
Authors: Myant N B , Gallagher J J , Knight B L , McCarthy S N , Frostegård J , Nilsson J , Hamsten A , Talmud P , Humphries S E
Published: June 2011

In a previous study (Tybjaerg-Hansen et al, Atherosclerosis 1990;80:235-242), we identified nine patients heterozygous for the apolipoprotein B (apo B) arginine-to-glutamine (Arg3,500----Gln) mutation (familial defective apolipoprotein B-100 [FDB]). Six of these had been diagnosed clinically as familial hypercholesterolemic (FH) heterozygotes. We have since examined low density lipoprotein (LDL) receptor function in the FDB index patients and in three of their families. Skin fibroblasts from seven of seven unrelated FDB patients from whom cell lines were established exhibited normal high-affinity binding and degradation of normal LDL in vitro. In the three families, a raised plasma LDL concentration did not segregate with a haplotype of two polymorphic restriction sites at the LDL receptor locus. We conclude that the clinical and biochemical signs of classical FH can occur in the presence of the FDB mutation and a normal LDL receptor gene. In a four-generation family with 11 proven or presumed FDB heterozygotes, expression of the mutation ranged from normal plasma LDL concentrations and no clinical signs in two individuals, to hypercholesterolemia and death from myocardial infarction at age 31. Variable expression of the FDB mutation could not be explained conclusively by variation in diet, body mass index, smoking habit, apo E genotype, or plasma Lp(a) concentration.
Thrombin-induced platelet aggregates have a dynamic structure. Time-dependent redistribution of glycoprotein IIb-IIIa complexes and secreted adhesive proteins.
Authors: Heilmann E , Hourdillé P , Pruvost A , Paponneau A , Nurden A T
Published: June 2011

The role of glycoprotein (GP) IIb-IIIa complexes and of adhesive proteins in mediating platelet aggregation is now well defined. However, less is known of the changes that occur once aggregation has begun. We report immunogold staining of thin sections of platelets or platelet aggregates, embedded in Lowicryl K4M, after the use of polyclonal antibodies to GP IIb or GP IIIa, fibrinogen (Fg), von Willebrand factor (vWF), and thrombospondin (TSP). Bound immunoglobulin G (IgG) was located by species-specific anti-IgG coupled to 5-nm gold particles and by electron microscopy. Initial experiments with platelet-rich plasma confirmed the feasibility of visualizing adhesive proteins between platelets in aggregates. Experiments then continued, using stirred suspensions of washed platelets incubated with alpha-thrombin. After 20 seconds, platelets were in contact without detectable release, although giant secretory vesicles containing adhesive proteins were seen. Internal pools of GP IIb-IIIa were progressively externalized within the aggregate. Secreted Fg was readily detected between platelets at 40 seconds. After 3 minutes, when most of the secretion had occurred, Fg had a patchwork-like distribution within the aggregate. After 6 minutes, zones with closely interspaced surface membranes, usually representing pseudopods, were dominant and Fg free. Results for vWF and TSP were similar to those for Fg. Nonetheless, GP IIb-IIIa complexes continued to be located between adjacent surface membranes throughout the aggregate. Thrombin-induced platelet aggregates were isolated, and sodium dodecyl sulfate-soluble extracts were obtained. Western blot experiments showed that, although fibrinopeptide A had been cleaved, degradation of adhesive proteins by platelet proteases had not occurred. These results emphasize that a platelet aggregate is a dynamic structure and suggest that not all surface-contact interactions are mediated by Fg or the other adhesive proteins tested in this study.
Nutrient intake comparisons between Framingham and rural and Urban Puriscal, Costa Rica. Associations with lipoproteins, apolipoproteins, and low density lipoprotein particle size.
Authors: Campos H , Willett W C , Peterson R M , Siles X , Bailey S M , Wilson P W , Posner B M , Ordovas J M , Schaefer E J
Published: June 2011

To assess cross-cultural relations between dietary intake and plasma lipoproteins, we randomly selected 222 men and 243 women from the urban and rural areas of Puriscal, Costa Rica; related their dietary composition (assessed by a food-frequency questionnaire), fitness level, and body fat to plasma lipids, apolipoproteins, and low density lipoprotein (LDL) particle size; and compared these data with those from a subsample of 280 adults from the Framingham Offspring Study. Total cholesterol and LDL cholesterol levels were significantly (p less than 0.0001) higher in Framingham (207 and 137 mg/dl, respectively) than in Puriscal (184 and 114 mg/dl, respectively) residents. Elevated triglyceride and apolipoprotein (apo) B levels (25% and 16% higher), low HDL cholesterol and apo A-I levels (12% and 29% lower), and smaller LDL particles (17%) were more frequent in Puriscal than in Framingham residents. Urban Puriscal residents had a significantly lower fitness level; increased body fat, total cholesterol, and triglyceride levels; decreased HDL cholesterol in men; and higher apo B levels in women compared with rural Puriscal residents. Body fat, animal fat, and saturated fat intakes were significantly correlated with total cholesterol, LDL cholesterol, and apo B levels in both men and women in Puriscal. Intakes of protein and animal fat were higher among urban (10.7% and 14.1%, respectively) compared with rural (8.9% and 9.9%, respectively) Puriscal residents and in Framingham (16.0% and 20.8%, respectively) compared with Puriscal residents. No significant differences were found in dietary cholesterol. Saturated fat (largely from palm oil in Puriscal) intakes were significantly different among the three groups: rural Puriscal, 10.7% of calories; urban Puriscal, 11.6%; and Framingham residents, 12.9%. These data indicate that the more atherogenic plasma lipid profile among urban compared with Puriscal residents was largely explained by increased adiposity, decreased fitness level, and higher saturated fatty acid intake. Puriscal residents consumed less animal fat and more carbohydrate than did Framingham residents, and these differences were associated with a 21% lower LDL cholesterol level, a 12% lower HDL cholesterol level, a 29% lower apo A-I level, a 25% higher triglyceride level, a 16% higher apo B level, and a 17% smaller LDL particle size. Some of these cross-cultural differences may be due to differences in ethnic background and physical activity as well.
A role for platelets and thrombin in the juvenile stroke of two siblings with defective thrombin-adsorbing capacity of fibrin(ogen).
Authors: Di Minno G , Martinez J , Cirillo F , Cerbone A M , Silver M J , Colucci M , Margaglione M , Tauro R , Semeraro N , Quattrone A
Published: June 2011

Binding of iodine-125-labeled thrombin to fibrin clots from two siblings with juvenile stroke was 30% of normal, and abnormally high amounts of the radioligand (not adsorbed by fibrin) were found in the supernatant. In concordance with this finding, supernatants from the patients' fibrin clots caused abnormal enhancement of platelet aggregation, ATP secretion, and binding of 125I-fibrinogen to platelets exposed to subthreshold concentrations of ADP or epinephrine. Hirudin suppressed the enhancing effect of the patients' supernatants, and substitution of gamma-thrombin for alpha-thrombin led to normalization of platelet responses. Under some experimental conditions, degradation of the patients' fibrinogen by plasmin was impaired. However, the euglobulin lysis time, the rate of fibrin degradation by plasmin, and the lysis of the patients' plasma clots by human melanoma tissue-type plasminogen activator were normal. Patients' plasmas, as well as purified fibrinogen, showed a prolonged thrombin time (partially corrected by 10 mM CaCl2) and an impaired release of fibrinopeptide A in response to thrombin. However, the release in response to reptilase was normal, and the reptilase, ancrod, and thrombin coagulase times were within control (normal) values. In addition, the patients' fibrinogen showed normal polymerization of preformed fibrin monomers, normal sialic acid content, and normal binding to ADP or epinephrine-stimulated platelets. Our studies support the concept that thrombin and platelets play an important role in the occurrence of stroke in these patients and suggest a direction to be followed to identify the mechanism(s) contributing to thrombosis in subjects with abnormal fibrinopeptide release.
Comparison between morning and evening doses of simvastatin in hyperlipidemic subjects. A double-blind comparative study.
Authors: Saito Y , Yoshida S , Nakaya N , Hata Y , Goto Y
Published: June 2011

Previous studies have shown that simvastatin, a hydroxymethyl glutaryl coenzyme A reductase inhibitor, reduces plasma cholesterol levels when administered once a day. In the present study, the efficacy and tolerability of a morning and an evening dose were compared. The dosages employed were 2.5 and 5 mg for 12 weeks. This investigation was a double-blind, placebo-controlled study involving 172 hyperlipidemic subjects whose plasma cholesterol levels were higher than 220 mg/dl. During the study period, mean changes in plasma cholesterol level (from baseline) were -11% with the 2.5-mg q.a.m. regimen, -15% with the 2.5-mg q.p.m. regimen, -14% with the 5-mg q.a.m. regimen, and -21% with the 5-mg q.p.m. regimen. Each of these changes was statistically significant when compared with that in the placebo group (p less than 0.001). In addition, the reduction in cholesterol level was significantly greater with the evening regimen than with the morning regimen for both the 2.5-mg (p less than 0.05) and the 5-mg (p less than 0.05) dosages. The changes in triglyceride and high density lipoprotein cholesterol levels in each group were not significantly different from those in the placebo group. There were no differences in the incidence of clinical adverse reactions among the various treatment groups. In conclusion, when simvastatin was administered orally once per day in the evening, it reduced cholesterol levels to a significantly greater degree than when it was given in the morning.
Dissociation between postprandial lipemia and high density lipoprotein cholesterol concentrations in endurance-trained men.
Authors: Cohen J C , Stray-Gundersen J , Grundy S M
Published: June 2011

Previous studies have indicated an inverse relation between circulating high density lipoprotein (HDL) concentrations and the rate of chylomicron clearance. Because chronic exercise has been shown to augment chylomicron clearance, we measured HDL cholesterol concentrations and plasma triglyceride and retinyl palmitate responses to high- (140 g) and low- (50 g) fat meals in endurance-trained men. Plasma HDL cholesterol concentrations in these men ranged from 36 to 105 mg/dl. Intraindividual variation in the cholesterol concentration of the HDLs occurred primarily in HDL2. The magnitude of postprandial lipemia induced by both the high- and the low-fat meals was uniformly low compared with values reported previously for sedentary men and was not correlated with HDL cholesterol concentrations. Postprandial retinyl palmitate concentrations, which reflect chylomicron remnant metabolism, also showed no correlation with HDL cholesterol concentrations. These data indicate that the degree of postprandial lipemia is not the primary determinant of HDL cholesterol concentrations in endurance-trained men. Accordingly, the wide range of HDL cholesterol concentrations measured in these men must be attributable to other factors.
Expression of lipoprotein lipase mRNA in rat heart is localized mainly to mesenchymal cells as studied by in situ hybridization.
Authors: Stein O , Stein Y , Schwartz S P , Reshef A , Chajek-Shaul T , Ben-Naim M , Friedman G , Leitersdorf E
Published: June 2011

The expression of lipoprotein lipase mRNA (LPL mRNA) was studied in rat hearts by use of a sulfur-35-labeled antisense mRNA probe. Rats were studied under three conditions: fed, fasted, and injected with cholera toxin (an irreversible agonist of adenylate cyclase) and then fasted. The highest LPL activity was found in the hearts of cholera toxin-injected, fasted rats. After injection of cholera toxin, LPL mRNA levels were 3.5-fold higher than those from fed rats. Using in situ hybridization, we studied the site of expression of LPL mRNA under the same three experimental conditions. In sections of hearts from cholera toxin-injected, fasted rats, concentrations of autoradiographic grains, representing the site of LPL mRNA, were seen over interstitial elements, which comprise capillary and perivascular cells. A more diffuse and sparse reaction was seen over cardiac myocytes and was not always distinguishable from background. A similar but much less definitive localization was seen in sections of hearts from fasted rats. The present results indicate that in the rat heart, the main site of LPL synthesis and processing, especially after stimulation with an irreversible agonist of adenylate cyclase, is localized to interstitial elements rather than to adult cardiac myocytes.
Effects of transforming growth factor-beta 1 on human arterial smooth muscle cells in vitro.
Authors: Björkerud S
Published: June 2011

Control of the thickness of the arterial wall is critical, as excessive overgrowth of constituent smooth muscle cells (SMCs) may interfere with blood flow. Effects on SMCs in vitro of several growth factors that are present in blood and/or that are produced endogenously in the arterial wall under certain conditions suggest that influences of endocrine, paracrine, and autocrine nature from stimulating and inhibiting factors may control the smooth muscle tissue mass in the artery. This possibility was explored further by investigating the degree of myodifferentiation in terms of the presence of differentiation-specific filamentous alpha-smooth muscle actin and growth, as measured by the synthesis of DNA and cell number, of SMCs as influenced by their exposure to the mitogens, platelet-derived growth factor and epidermal growth factor, and the bifunctional growth factor, transforming growth factor-beta 1 (TGF-beta 1). Exposure to TGF-beta 1 markedly enhanced differentiation-specific filamentous alpha-smooth muscle actin. This effect did not require arrest of growth, which speaks against a direct causal relation between loss of myodifferentiation (modulation) and multiplication. When quiescent cultures were exposed to TGF-beta 1, alpha-smooth muscle actin was further increased, indicating a more specific differentiation-promoting effect by TGF-beta 1 than mere inhibition of growth. Exposure to TGF-beta 1 also increased spreading, which occurred in parallel with increased filamentous alpha-smooth muscle actin and appearance of stress fibers. Exposure to platelet-derived growth factor under serum-free conditions and to epidermal growth factor in cultures exposed to serum markedly decreased the number of alpha-actin-positive SMCs, indicating a dedifferentiating effect by these mitogens. Exposure of SMCs to TGF-beta 1 under serum-free conditions had pronounced effects on growth, with a concentration-dependent inhibition of platelet-derived growth factor-induced DNA synthesis and cell multiplication. The basal synthesis of DNA in the absence of added growth factors was also greatly inhibited. With serum-free cultures, some loss of cells occurred even with very low concentrations of TGF-beta 1 (5 pg/ml), against which platelet-derived growth factor or a dense cultural state had a protective effect. Enhancement of cell multiplication was not detected for cultivated human SMCs exposed to TGF-beta 1, irrespective of culture density, in contrast to that reported for dense cultures of rat SMCs. TGF-beta 1 is present in and may be released from platelets in situations that promote platelet adherence such as endothelial injury; TGF-beta 1 may also be released from activated macrophages and T lymphocytes either during an immune reaction or inflammation or from the endothelium.(ABSTRACT TRUNCATED AT 400 WORDS)
Leukocytosis in rabbits with diet-induced atherosclerosis.
Authors: Feldman D L , Mogelesky T C , Liptak B F , Gerrity R G
Published: June 2011

In cholesterol-fed rabbits the extent of monocyte involvement in atherogenesis may be influenced by the level of circulating leukocytes during hypercholesterolemia. We characterized the leukocytosis in rabbits fed either a 0.25% or a 0.1% cholesterol-enriched diet (0.25% or 0.1% rabbits, respectively). Circulating leukocytes were elevated by 1 week of feeding, and the elevation was sustained for at least 30 weeks. Differential counts were unchanged. Immature leukocytes were not seen, indicating that the leukocytosis was not due to premature release of bone marrow cells. Animals were free of bacterial or parasitic disease; selected rabbits with leukocytosis had normal body temperatures. Spleen weights averaged at least 100% higher in 0.25% rabbits but did not show histological evidence for hematopoiesis that could account for the leukocytosis. At approximately 22 weeks there was a second rise in leukocytosis in bilirubinemic 0.25% rabbits, suggesting that in the late stages of hypercholesterolemia, leukocytosis is related to liver failure. Cholesterol-fed rabbits also showed thrombocytosis. Existing leukocytosis and hypercholesterolemia were reversed to pretreatment levels by switching the rabbits to chow diets. In bone marrow from 0.25% rabbits, the mean number of cells per gram was greater (p less than 0.05) than that from normocholesterolemic rabbits. In 0.25% rabbits, the fraction of blood mononuclear cells showing phagocytosis of immunoglobulin G-coated red blood cells did not differ from that of controls, suggesting an unchanged population of these cells with regard to Fc and phagocytic function during hypercholesterolemia. These data suggest an effect (direct or indirect) of hypercholesterolemia on the production of leukocytes in the bone marrow and/or on the circulation kinetics of leukocytes in the blood.