Modelling cancer cell budding in-vitro as a self-organised, non-equilibrium growth process.

Tissue self-organization into defined and well-controlled three-dimensional structures is essential during development for the generation of organs. A similar, but highly deranged process might also occur during the aberrant growth of cancers, which frequently display a loss of the orderly structures of the tissue of origin, but retain a multicellular organization in the form of spheroids, strands, and buds. The latter structures are often seen when tumors masses switch to an invasive behavior into surrounding tissues. However, the general physical principles governing the self-organized architectures of tumor cell populations remain by and large unclear. In this work, we perform in-vitro experiments to characterize the growth properties of glioblastoma budding emerging from monolayers. We further propose a theoretical model and its finite element implementation to characterize such a topological transition, that is modelled as a self-organised, non-equilibrium phenomenon driven by the trade-off of mechanical forces and physical interactions exerted at cell-cell and cell-substrate adhesions. Notably, the unstable disorder states of uncontrolled cellular proliferation macroscopically emerge as complex spatio-temporal patterns that evolve statistically correlated by a universal law.

Studies on the purification and characterization of human factor 8.

Factor VIII (antihemophilic globulin) has been prepared from Hyland method IV AHG and cryoprecipitate using limited chymotryptic digestion followed by Sepharose gel filtration. The activity of factor VIII is unaffected by the digestion procedure, while fibrinogen in converted to large noncoagulable fragments. The purified factor VIII has been found to be a macromolecular glycoprotein with a major subunit of 240,000, as shown by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. Carbohydrate analysis of factor VIII gave values of 1% sialic acid, 2.8% hexosamine, and 1-2% hexose (mannose, galactose, and fucose). The lipid content was found to be less than 5% of the protein content, and included no detectable phospholipid. The amino acid content is also reported. Immunoelectrophoretic analysis using rabbit antibody to purified factor VIII produced a single precipitin line. The chymotrypsin digestion step facilitates the preparation of factor VIII by reducing the viscosity of fibrinogen in the crude starting material, thereby increasing fivefold the quantity of material which can be processed at one time. It also improves markedly the resolution between factor VIII and fibrinogen on gel filtration.

Molecular analysis of insertion/deletion mutations in protein 4.1 in elliptocytosis. II. Determination of molecular genetic origins of rearrangements.

Protein 4.1 is an approximately 80-kD structural protein in the membrane skeleton which underlies and supports the erythrocyte plasma membrane. The preceding companion paper presents a biochemical study of two abnormal protein 4.1 species from individuals with the red blood cell disorder, hereditary elliptocytosis. These variants, "protein 4.1(68/65)" and "protein 4.1(95)," have altered molecular weights due to internal deletions and duplications apparently localized around the spectrin-actin binding domain. Here we use polymerase chain reaction (PCR) techniques to clone and sequence the corresponding mutant reticulocyte mRNAs, and correlate the deletion/duplication end points with exon boundaries of the gene. Protein 4.1(68/65) mRNA lacks sequences encoding the functionally important spectrin-actin binding domain due to a 240 nucleotide (nt) deletion spanning the codons for Lys407-Gly486. Protein 4.1(95) mRNA encodes a protein with two spectrin-actin binding domains by virtue of a 369 nt duplication of codons for Lys407-Gln529. These deletions and duplications correspond to gene rearrangements involving three exons encoding 21, 59, and 43 amino acids, respectively. The duplicated 21 amino acid exon in the 4.1(95) gene retains its proper tissue-specific expression pattern, being spliced into reticulocyte 4.1 mRNA and out of lymphocyte 4.1 mRNA.

Mutant forms of spectrin alpha-subunits in hereditary elliptocytosis.

Two variant spectrins have been described in hereditary elliptocytosis (HE) and pyropoikilocytosis (HPP). Both are characterized by increased susceptibility of the alpha I (N-terminal) 80-kD domain to mild tryptic digestion, yielding peptides of 46-50 or 65-68 kD (T50a and T68 in our terminology). In this report we add a third unstable spectrin alpha I domain found in three kindreds with HE; alpha IT80 in this type of spectrin is cleaved by mild tryptic digestion to a 50-kD peptide (T50b) distinguished from T50a by its more basic isoelectric point. All three spectrins show impaired self-association to form oligomers. Intermediate tryptic peptides of the three unstable alpha I domains from HE spectrins were characterized by monoclonal immunoblotting and I125 limit peptide mapping and affinity purified using polyclonal anti-alpha IT80. Partial amino acid sequences of alpha I domain peptides were obtained from two unrelated patients for each of the three variant spectrins. T50a results from cleavage at arginine 250 or lysine 252 of alpha IT80; a proline replaced the normal leucine or serine at residues 254 and 255, respectively. T50b and a 19-kD peptide result from cleavage at arginine 462 or arginine 464; a proline replaced the normal residue 465 (in T19b) in one of the two patients studied. T68 results from cleavage at arginine 131. In both 68-kD peptides examined, a leucine is inserted at residue 150. The relationship of the sequence changes to the new tryptic cleavages, to the current model of alpha I domain structure, and to defective spectrin self-association is discussed.

Common structural polymorphisms in human erythrocyte spectrin.

Restricted tryptic digestion of erythrocyte spectrin at 4 degrees C followed by two-dimensional (isoelectric-focusing/sodium dodecyl sulfate) polyacrylamide electrophoresis yields highly reproducible maps of approximately 50 peptides with molecular weights between 80,000 and 12,000. Based on molecular weight and isoelectric point (pI), each unique alpha- and beta-subunit domain can be identified and compared with spectrin peptides from other individuals. The alpha-subunit of spectrin from 60 Caucasian donors contains a 46,000-mol-wt tryptic domain, called alpha II-T46, Type 1; more extensive tryptic digestion of this domain generates peptides with molecular weights of 35,000, 30,000, 25,000, and 16,000. Spectrin from 29 of 37 black donors representing 14 kindreds shows variation in the molecular weight and/or pI of peptides from the alpha II domain. In the most common form, Type 2, alpha II tryptic peptides are increased in molecular weight by 4,000, and the pI becomes more basic. Other alpha II variants are characterized by either the 4,000 increase in molecular weight (Type 3) or by the basic shift in pI (Type 4). When limit peptide maps of intermediate-sized tryptic and CNBr peptides from the alpha II-domain Types 1 and 2 are compared, a consistent alteration in the chromatographic mobility of one limit peptide is observed. Polymorphism in the alpha II subunit of spectrin did not itself produce anemia, nor did it appear to alter the expression of an underlying hereditary spherocytosis or elliptocytosis. In six family studies, the alpha II 46,000-mol-wt variations observed were consistent with Mendelian inheritance.

Molecular analysis of insertion/deletion mutations in protein 4.1 in elliptocytosis. I. Biochemical identification of rearrangements in the spectrin/actin binding domain and functional characterizations.

Protein 4.1 (80 kD) interacts with spectrin and short actin filaments to form the erythrocyte membrane skeleton. Mutations of spectrin and protein 4.1 are associated with elliptocytosis or spherocytosis and anemia of varying severity. We analyzed two mutant protein 4.1 molecules associated with elliptocytosis: a high molecular weight 4.1 (95 kD) associated with mild elliptocytosis without anemia, and a low molecular weight 4.1 (two species at 68 and 65 kD) associated with moderate elliptocytosis and anemia. 4.1(95) was found to contain a approximately 15-kD insertion adjacent to the spectrin/actin binding domain comprised, at least in part, of repeated sequence. 4.1(68/65) was found to lack the entire spectrin-actin binding domain. The mechanical stability of erythrocyte membranes containing 4.1(95) was identical to that of normal membranes, consistent with the presence of an intact spectrin-actin binding domain in protein 4.1. In contrast, membranes containing 4.1(68/65) have markedly reduced mechanical stability as a result of deleting the spectrin-actin binding domain. The mechanical stability of these membranes was improved following reconstitution with normal 4.1. These studies have thus enabled us to establish the importance of the spectrin-actin binding domain in regulating the mechanical stability of the erythrocyte membrane.

Mutation of a highly conserved residue of betaI spectrin associated with fatal and near-fatal neonatal hemolytic anemia.

We studied an infant with severe nonimmune hemolytic anemia and hydrops fetalis at birth. His neonatal course was marked by ongoing hemolysis of undetermined etiology requiring repeated erythrocyte transfusions. He has remained transfusion-dependent for more than 2 yr. A previous sibling born with hemolytic anemia and hydrops fetalis died on the second day of life. Peripheral blood smears from the parents revealed rare elliptocytes. Examination of their erythrocyte membranes revealed abnormal mechanical stability as well as structural and functional abnormalities in spectrin. Genetic studies revealed that the proband and his deceased sister were homozygous for a mutation of betaIsigma1 spectrin, L2025R, in a region of spectrin that is critical for normal function. The importance of leucine in this position of the proposed triple helical model of spectrin repeats is highlighted by its evolutionary conservation in all beta spectrins from Drosophila to humans. Molecular modeling demonstrated the disruption of hydrophobic interactions in the interior of the triple helix critical for spectrin function caused by the replacement of the hydrophobic, uncharged leucine by a hydrophilic, positively charged arginine. This mutation must also be expressed in the betaIsigma2 spectrin found in muscle, yet pathologic and immunohistochemical examination of skeletal muscle from the deceased sibling was unremarkable.

Recurrent fatal hydrops fetalis associated with a nucleotide substitution in the erythrocyte beta-spectrin gene.

We studied a kindred in which four third-trimester fetal losses occurred, associated with severe Coombs-negative hemolytic anemia and hydrops fetalis. Postmortem examination of two infants revealed extensive extramedullary erythropoiesis. Studies of erythrocytes and erythrocyte membranes from the parents revealed abnormal erythrocyte membrane mechanical stability as well as structural and functional abnormalities in spectrin, the principal structural protein of the erythrocyte membrane. Genetic studies identified a point mutation of the beta-spectrin gene, S2019P, in a region of beta spectrin that is critical for normal spectrin function. Both parents and two living children were heterozygous for this mutation; three infants dying of hydrops fetalis were homozygous for this mutation. In an in vitro assay using recombinant peptides, the mutant beta-spectrin peptide demonstrated a significant abnormality in its ability to interact with alpha spectrin. This is the first description of a molecular defect of the erythrocyte membrane associated with hydrops fetalis.

Sequence and exon-intron organization of the DNA encoding the alpha I domain of human spectrin. Application to the study of mutations causing hereditary elliptocytosis.

We have determined the exon-intron organization and the nucleotide sequence of the exons and their flanking intronic DNA in cloned genomic DNA that encodes the first 526 amino acids of the alpha I domain of the human red cell spectrin polypeptide chain. From the gene sequence we designed oligonucleotide primers to use in the polymerase chain reaction technique to amplify the appropriate exons in DNA from individuals with three variants of hereditary elliptocytosis characterized by the presence of abnormal alpha I spectrin peptides, 46-50 and 65-68 kD in size, in partial tryptic digests of spectrin. The alpha I/68-kD abnormality resulted from a duplication of leucine codon 148 in exon 4: TTG-CTG to TTG-TTG-CTG. The alpha I/50a defect was associated in different individuals with two separate single base changes in exon 6: CTG to CCG (leucine to proline) encoding residue 254, and TCC to CCC (serine to proline) encoding residue 255. In another individual with the alpha I/50a polypeptide defect, the nucleotide sequence encoding amino acid residues 221 through 264 was normal. The alpha I/50b abnormality resulted from a single base change of CAG (glutamine) to CCG (proline) encoding residue 465 in exon 11 in two unrelated individuals. In a third individual with alpha I/50b-kD hereditary elliptocytosis, the entire exon encoding residues 445 through 490 was normal. The relationship of the alpha I domain polypeptide structure to these mutations and the organization of the gene is discussed.

Reconstruction of fingertip defects with the neurovascular tranquilli-leali flap.

For many years, bipedicled palmar advancement flaps were used rarely in fingers because they sacrificed the dorsal branches of the digital arteries, risking dorsal skin necrosis. In 1995, a short bipedicled neurovascular VY advancement flap raised distally to the PIP flexion crease, which spared the dorsal blood supply, was described by Elliot et al. (1995). This paper includes an anatomical study on 28 fresh cadaver fingers to evaluate the advancement potential of this flap. It also reviews 22 fingertip reconstructions in 22 patients using this flap. The mean advancement of the flap in the cadaver study was 14 (range 10-16) mm. This procedure gave good clinical results in respect of healing, sensibility, bone cover and appearance. Complications occurred in four fingers (18%), viz. two infections, one neuroma and one stiff proximal interphalangeal joint. Our study suggests that this flap can be used to treat fingertip defects of a size of approximately half of the pulp of the distal phalangeal segment of the finger.

Natriuretic peptides levels are related to HDL-cholesterol with no influence on endothelium dependent vasodilatation.

BACKGROUND: The natriuretic peptides, Brain Natriuretic Peptide (BNP), C-type Natriuretic Peptide (CNP), are mediators of cardiovascular homeostasis. The impairment of arterial ability to vasodilate, also known as endothelial dysfunction, represents the first stage of atherosclerotic damage and may be assessed as brachial flow mediated vasodilation (FMV) in human. Generally an altered brachial FMV is documented in association to several cardiovascular risk factors as hypercholesterolemia. Aim of the study was to evaluate the behaviour of BNP and CNP in hyperlipemia and the potential relationship to FMV. PATIENTS AND METHODS: Forty-four hyperlipemic patients (LDL-cholesterol > 130 mg/dl and/or triglycerides > 150, age 35-60 y) of both genders and 20 normolipemic patients, matched for age and sex were investigated. RESULTS: Patients had lower values of brachial FMV in comparison to controls (3.9 +/- 3.5 vs 7.5 +/- 0.5%, p < 0.005), no differences were observed in BNP (4.6 +/- 4.6 vs 5.9 +/- 3.4 ng/mL, p = n.s) and CNP (4.1 +/- 5.8 vs 5.7 +/- 3.3 ng/mL, p = n.s). Univariate analysis showed a positive correlation between BNP and HDL-cholesterol values (r = 0.36, p = 0.001). In the multivariate analysis, LDL-cholesterol (beta = -0.57), HDL-cholesterol (beta = 0.26) and brachial artery diameter (beta = -0.33) were predictors of brachial FMV. The only predictive variable for CNP was HDL-cholesterol (beta = 0.37). CONCLUSIONS: The present study suggested that natriuretic peptides, BNP and CNP, are not altered in patients affected by hypercholesterolemia. Nevertheless, the levels of HDL-cholesterol are strictly related to the values of CNP. This observation, in humans, adds another mechanism to the vascular control exerted by HDL.

Isolation of human platelet glycoproteins.

Human platelet glycoproteins were isolated from whole platelets by two methods. The first method, that of affinity chromatography on wheat germ agglutinin, is based on the known affinity of lectins for cell surface glycoproteins. When solubilized whole platelets are used as starting material for this procedure, elution with N-acetylglucosamine yields primarily a glycoprotein of Mr approximately 150 000 as estimated by sodium dodecyl sulfate-acrylamide gel electrophoresis. The second method is based on the ability of the chaotropic salt lithium diiodosalicylate to extract glycoprotein from particulate cell fractions in water-soluble form. This method yields three major glycopeptides with apparent molecular weights after sulfhydryl reduction of 145 000, 125 000, and 95 000 as estimated on 5.6% sodium dodecyl sulfate-acrylamide gels. Carboxymethylation of these preparations in the presence of sulfhydryl-reducing agent further resolves a glycoprotein of Mr approximately 165 000. Treatment of whole platelets by periodate oxidation and sodium[3H]-borohydride reduction labels the three major glycoproteins extracted by lithium diiodosalicylate and the glycoprotein of Mr approximately 150 000 isolated on wheat germ agglutinin confirming their surface orientation. However, glycoprotein with Mr approximately 165 000 resolved by carboxymethylation of the lithium diiodosalicylate extracted glycoprotein mixture was not labelled by this method, suggesting that it represents the granule protein with similar electrophoretic characteristics described by others. Phosphorylation of intact platelets with 32Pi also results in labelling of glycoproteins isolated by both methods, suggesting that these molecules traverse the bilipid layer of the platelet membrane, bearing reactive groups on both outer and cytoplasmic surfaces.

[Subclinical atherosclerosis in young patients with rheumatoid arthritis and low disease activity]. / Aterosclerosi subclinica in giovani pazienti con artrite reumatoide e bassa attività di malattia.

BACKGROUND: There is an increasing body of evidence suggesting that subjects with rheumatoid arthritis (RA) are characterized by acceleration of atherosclerotic process of arterial wall. However, all investigations performed so far to evaluate subclinical atherosclerosis in RA included subjects without selection for age and degree of disease activity that may represent confounding factors in such an evaluation. OBJECTIVES: To verify signs of accelerated subclinical atherosclerosis in young subject suffering from RA but with low disease activity. METHODS: Thirty-two patients with RA and 28 age- and sex-matched control subjects with non-inflammatory rheumatic diseases were enrolled. Inclusion criteria were age less than 60 and low disease activity with score < or =3.2 according to DAS28, while subjects with traditional risk factors for and/or overt cardiovascular disease were ruled out from the study. Both patients and controls underwent evaluation of carotid and femoral artery intima-media thickness by ultrasounds. RESULTS: Patients had higher intima-media thickness than controls of all the sites evaluated at carotid artery level, whereas there were no differences at the comparison of the superficial and common femoral artery wall. At the univariate analysis, a positive correlation between LDL cholesterol levels and intima-media thickness at the carotid bifurcation was found. CONCLUSIONS: Young patients with RA and low disease activity have acceleration of atherosclerosis development as shown by increased intima-media thickness of carotid artery with respect to subjects without inflammatory rheumatic disease. It is conceivable that the organic damage of arterial wall could be the result of persistent endothelial dysfunction induced by chronic inflammation and immune dysregulation which characterize RA.

Spectrin: structure, function, and abnormalities.

A number of proteins that make up the membrane skeleton have been identified, and we have a rough but tantalizing picture of the ways in which they interact to maintain its integrity. An approximate molecular model of spectrin has been proposed, and many new analytic procedures have been developed to search for biochemical variants that may be related to membrane defects. Even at this rudimentary stage of molecular description we have been able to identify structural changes in spectrin that are correlated with pathophysiologic states. The prospects for some genuine insights into the pathogenesis of some congenital hemolytic anemias seem good.

Impaired flow-mediated vasoactivity during post-prandial phase in young healthy men.

Impaired flow-mediated vasodilation in large arteries is an expression of endothelial dysfunction and an established marker of early atherosclerosis. Post-prandial lipemia can induce an impairment of the endothelial function. The aim of our study was to evaluate the effects of post-prandial phase on flow-mediated vasodilation in a group of ten young (23 +/- 2 years) healthy men without cardiovascular risk factors, who underwent an oral fat-loading test. Flow-mediated vasodilation of the brachial artery and serum lipid profile were assessed under fasting conditions and 2, 4, 6 and 8 h after a high-fat meal. Triglycerides increased from 0.6 +/- 0.2 fasting to 1.1 +/- 0.5 and 1.3 +/-0.6 mmol/l at the 2nd and 4th hour (both P < 0.01), and decreased thereafter. Flow-mediated vasodilation fell significantly from 14.5 +/- 6.6% fasting to 3.5 +/- 1.5% and 4.0 +/- 2.2% at the 2nd and 4th hour (both P < 0.01), and returned to the basal values at the 6th and 8th hour. A strong inverse correlation was observed between the area under the incremental curve of post-prandial triglycerides (i.e. after subtraction of baseline triglycerides) and the area under the decremental curve of post-prandial flow-mediated vasodilation (r = -0.70, P = 0.025). No association was found between post-prandial vasodilation changes and fasting triglycerides, other lipid parameters or insulin. We conclude that a transient post-prandial impairment in brachial artery flow-mediated vasodilation is evident in young healthy men after a high-fat meal, and is closely associated with triglyceride levels. These data provide support for a role of post-prandial phase in vascular regulation in young healthy subjects.

Optimizing assessment of carotid and femoral intima-media thickness in essential hypertension.

Large artery intima-media thickness (IMT) is considered an integrated marker for the total individual burden of arteriosclerosis, and a graded index for cardiovascular risk. However, several different aggregate indexes of IMT on B-mode ultrasound have been used by various investigators, and the optimal number of IMT readings is currently unsettled. In 128 newly diagnosed, never treated, uncomplicated hypertensive subjects aged <55 years (43 +/- 9 years, blood pressure [BP] 152/99 mm Hg), we measured left ventricular mass (M-mode echocardiography, average of five or more measurements) and IMT of common carotid and common femoral arteries. For each segment, 12 IMT measurements were performed, and the average of 1 and 3 readings (right far wall), 6 readings (right side), and 12 readings (right and left side, far and near wall, 3 sampling points) was analyzed. The relation of IMT with left ventricular mass increased progressively with increasing number of readings, from 0.35 (1 reading) to 0.51 (12 readings) for common carotid artery, and from 0.31 to 0.56 for common femoral artery (both P <.001). For each 0.2-mm increase in common femoral IMT, the age-adjusted relative risk of having left ventricular hypertrophy was 1.31 for 1 reading, and increased up to 3.59 for the average of 12 readings. In summary, the association of IMT with left ventricular mass depends strongly on the number of IMT readings. The average of several readings in each segment, including right and left side and far and near wall, carries the closest association to left ventricular mass, and should be preferred for clinical purposes in hypertensive subjects.

Postprandial lipemia and associated metabolic disturbances in healthy and hyperlipemic postmenopausal women.

The increased risk for coronary artery disease observed in postmenopausal women is partly explained by a more atherogenic fasting lipoprotein profile. Moreover, natural menopause has been associated with an altered postprandial lipid profile. To better characterize the interaction between fasting and postprandial lipid profile after menopause, we examined postprandial changes in several lipid parameters in three age-matched groups of postmenopausal women (16 affected by mixed hyperlipemia, 17 by common hypercholesterolemia, and 17 normolipemic), who underwent a standardized oral fat-loading test. The magnitude of postprandial lipemia, expressed as 8-hour triglyceride incremental area under the curve, was greater in women with mixed hyperlipemia (1,326 +/- 372 mg x dL(-1) x h(-1)) than in normal (484 +/- 384 mg x dL(-1) x h(-1)) and hypercholesterolemic (473 +/- 223 mg x dL(-1) x h(-1); both P <.0001) women, and the differences held after adjustment for body mass index and fasting insulin. Women with mixed hyperlipemia showed a significant postprandial decrease in high-density lipoprotein 2 (HDL(2)) cholesterol, lipoprotein (a), and low-density lipoprotein (LDL) particle size. Both hypercholesterolemic and normolipemic women showed a significant postprandial decrease in HDL cholesterol and lipoprotein (a) levels but not in LDL size. In a multiple linear regression analysis, fasting triglyceride levels, insulin level, and waist-hip ratio were all independent predictors of the magnitude of postprandial lipemia. In conclusion, postmenopausal women with mixed hyperlipemia show a greater postprandial triglyceride increase and a more pronounced reduction in HDL cholesterol level and LDL size than hypercholesterolemic and normolipemic subjects. The presence of the features of insulin resistance syndrome could contribute to the deterioration of postprandial lipemic response in these subjects.

Uterine embolization in a patient with postabortal hemorrhage.

A case of postabortal hemorrhage in a patient with von Willebrand's disease was controlled by arteriographic embolization of the uterine branch of the internal iliac artery. Selective internal iliac artery embolization has been effectively used to control postpartum hemorrhage and hemorrhage resulting from pelvic malignancy. A discussion is presented for expanding the use of selective embolization for controlling uterine hemorrhage to patients suffering from postabortal bleeding as a means of controlling hemorrhage without sacrificing fertility.

Association between endothelial dysfunction and major cardiovascular events in peripheral arterial disease.

BACKGROUND: Patients with peripheral arterial disease (PAD) are characterized by a high mortality for cardiovascular events. An impairment of endothelial function, expressed as brachial-artery flow-mediated vasodilation (FMV), has been described in PAD patients. Aim of this study was to investigate the association between FMV and cardiovascular events in patients with PAD. PATIENTS AND METHODS: Thirty-eight patients with intermittent claudication (71% men, mean age 71 years) were divided into two groups according to the presence or absence of previous major cardiovascular events (myocardial infarction or stroke). RESULTS: Brachial FMV was significantly lower in patients with a history of myocardial infarction or stroke (n = 16) than in patients without cardiovascular events (3.2 +/- 3.6% vs. 5.7 +/- 3.6%; p = 0.042). In the group with cardiovascular events there was a significantly higher proportion of subjects in the lower FMV tertile (56% vs. 18%), and a lower proportion of subjects in the upper tertile (25% vs. 41%; chi 2 test, p = 0.047). CONCLUSION: We conclude that FMV of the brachial artery is significantly reduced in PAD patients with a history of stroke and myocardial infarction. These cross-sectional results suggest a potential role of FMV as a marker of major cardiovascular events.