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Biomedical subjects

D Tormene

Publications and source records attributed to D Tormene.

At least 19 recordsLinked to original sources
PubMed2005

Megakaryocytes endocytose and subsequently modify human factor V in vivo to form the entire pool of a unique platelet-derived cofactor.

Factor Va (FVa), derived from plasma or released from stimulated platelets, is the essential cofactor in thrombin production catalyzed by the prothrombinase complex. Plasma-derived factor V (FV) is synthesized in the liver. The source(s) of the platelet-derived cofactor remains in question. We identified a patient homozygous for the FV(Leiden) mutation, who received a liver transplant from a homozygous wild-type FV donor. Eighteen days post-transplant, phenotypic analysis of the patient's platelet-derived FV indicated that the platelets were acquiring wild-type FV, consistent with the temporal differentiation of megakaryocytes and subsequent platelet production. Nine months post-transplant, the platelet-derived FV pool consisted entirely of wild-type FV. Consequently, megakaryocyte endocytosis of plasma-derived FV must account for the entire platelet-derived pool, because blood-borne platelets cannot bind or endocytose FV. Subsequent to this endocytic process, the patient's platelet-derived FV was cleaved to a partially active cofactor, and rendered resistant to phosphorylation catalyzed by a platelet-associated kinase, and hence less susceptible to activated protein C-catalyzed inactivation. These data provide the first in vivo demonstration of an endocytosed plasma protein undergoing intracellular modifications that alter its function. This process results in the sequestration of active FVa within the platelet compartment, poised for immediate action subsequent to release from platelets at a site of injury.

Adult↗
PubMed2005

The incidence of venous thromboembolism in carriers of antithrombin, protein C or protein S deficiency associated with the HR2 haplotype of factor V: a family cohort study.

In order to assess whether the HR2 haplotype of the factor V gene (HR2) increases the risk of venous thromboembolism (VTE) in carriers of antithrombin (AT), protein C (PC) or S (PS) defects, we performed this determination in 336 subjects, who were family members of 66 symptomatic patients with clotting inhibitors defects. We first assessed the presence of previous VTE, and then followed prospectively subjects without prior VTE. VTE episodes had occurred in 26 individuals: 18 in 139 carriers of clotting inhibitors defects alone (annual incidence, 0.55%), four in 33 carriers of clotting inhibitors defects combined with HR2 (0.52%) and four in 151 non-carriers (0.1%), resulting in a relative risk (RR) for VTE of 4.9 (95% CI: 1.7-14.4) and 4.62 (95% CI: 1.2-18.4), respectively. After an overall follow-up of 2557 patient-years, VTE episodes developed in 12 subjects: nine in 121 carriers of clotting inhibitors defects alone (annual incidence, 0.92%), three in 29 carriers of clotting inhibitors defects combined with HR2 (1.0%) and none in 147 non-carriers. In family members of patients with AT, PC or PS defects the coinheritance of HR2 haplotype does not seem to increase the thromboembolic risk.

Adult↗
PubMed2005

High vs. low doses of low-molecular-weight heparin for the treatment of superficial vein thrombosis of the legs: a double-blind, randomized trial.

In contrast with extensive information on the management of deep vein thrombosis of the lower extremities, little is known on the most appropriate treatment of the superficial vein thrombosis (SVT). In a multicenter, prospective, controlled, double-blind, double-dummy clinical trial, 164 consecutive patients with acute SVT of the great saphenous vein were randomized to receive the s.c. administration of either fixed prophylactic doses (2850 a-Xa IU) or body-weight adjusted therapeutic doses of nadroparin once daily for 1 month. The main study outcome was to compare the rate of asymptomatic and symptomatic extension of SVT and/or venous thromboembolic (VTE) complications during a 3-month follow-up period. Of the 81 patients randomized to the prophylactic doses, seven [8.6%; 95% confidence interval (CI), 3.5-17.0] developed SVT progression or VTE complications as compared with six of the 83 (7.2%; 95% CI, 2.8-15.1) allocated to the treatment group (absolute difference, 1.4; 96% CI, -6.9 to 9.7; P = 0.74). No patient in either group developed major bleeding. Our findings suggest that therapeutic doses of low-molecular-weight heparin, administered for 1 month in patients with SVT of the greater saphenous vein do not improve results obtained by prophylactic doses, administered for the same period, over a 3-month follow-up period.

Aged↗
PubMed2005

Expression of the normal factor V allele modulates the APC resistance phenotype in heterozygous carriers of the factor V Leiden mutation.

BACKGROUND: Functional defects of the protein C pathway, detectable in plasma as activated protein C (APC) resistance, are a prevalent risk factor for venous thrombosis. The factor V (FV) Leiden mutation causes APC resistance by interfering with the APC-mediated inactivation of both FVa and FVIIIa. Co-inheritance of FV Leiden and quantitative FV deficiency on different alleles, a rare condition known as pseudo-homozygous APC resistance, is associated with pronounced APC resistance and 50% reduced FV levels, because of non-expression of the non-Leiden FV allele. OBJECTIVES: The role of normal FV in modulating the APC resistance phenotype in carriers of FV Leiden was investigated in patients with pseudo-homozygous APC resistance and in model systems. PATIENTS/METHODS: Four functional plasma assays probing both components of APC resistance (susceptibility of FVa to APC and cofactor activity of FV in FVIIIa inactivation) were employed to compare seven clinically and genetically characterized FV Leiden pseudo-homozygotes to 30 relatives with different FV genotypes (including 12 FV Leiden heterozygotes and seven carriers of FV deficiency) and to 32 unrelated FV Leiden homozygotes. RESULTS AND CONCLUSIONS: All assays consistently indicated that FV Leiden pseudo-homozygotes are significantly more APC-resistant than heterozygotes and indistinguishable from homozygotes. Thrombin generation measurements in FV-deficient plasma reconstituted with purified normal FV and FV Leiden confirmed these observations and showed that the expression of the normal FV allele is an important modulator of APC resistance in FV Leiden heterozygotes. These findings provide an explanation for the higher thrombotic risk of FV Leiden pseudo-homozygotes when compared with heterozygotes.

Activated Protein C Resistance↗
PubMed2004

Long term use of oral contraceptives without thrombosis in patients with FV Leiden polymorphism: a study of 37 patients (2 homozygous and 35 heterozygous).

It is commonly accepted that women on oral contraceptive therapy have about a four fold increased incidence of venous thrombosis in comparison to non users. Women with FV Leiden polymorphism have an even higher incidence. The purpose of the paper is to show that women with FV Leiden polymorphism may sometimes remain asymptomatic in spite of long-term use of oral contraceptives. We have studied and followed 37 women with this polymorphism (35 heterozygotes and 2 homozygotes) who remained asymptomatic even after a long use, occasionally up to 10-12 years of oral contraception. Furthermore, these women remained asymptomatic in spite of the fact that the majority of them took preparations containing third generation progestins (gestodene or desogestrel). These progestins are considered to be more thrombogenic as compared to older ones. Finally, several of these women became pregnant before, during interruptions or after the contraceptive therapy and remained also asymptomatic but for one patient with varicose veins who developed superficial phlebitis during one pregnancy. These data indicate that FV Leiden polymorphism, as far as oral contraceptive therapy is concerned, is not a very strong prothrombotic condition and probably does not represent an absolute contraindication to its use. Unfortunately so far there is no sure way to distinguish the women with this polymorphism who will develop venous thrombosis from those who will remain asymptomatic during oral contraceptive therapy.

Adult↗
PubMed2002

Seasonal variation in the incidence of deep vein thrombosis in patients with deficiency of protein C or protein S.

An attempt was made to identify circaseptanal or seasonal variation of deep vein thrombosis (DVT) in a population with protein C or protein S deficit. Forty-four patients with DVT and protein C or protein S deficit were studied for 1 year. A significant circannual rhythm was found for the total population that peaked during winter. There was also a significant falling circaseptanal rhythm on Fridays. These observations may optimize an adequate and precise anticoagulant therapy in patients with protein C or protein S deficits.

Adult↗
PubMed2001

Long-term use of oral contraceptive therapy in women with the prothrombin 20210 G-A polymorphism without thrombotic complications: a study of 13 women (12 heterozygotes and 1 homozygote).

Thirteen female patients with the prothrombin 20210 G-A abnormality (twelve heterozygotes and one homozygote) were selected out of 551 patients admitted to our Department of Medicine or to our Outpatient Hemostasis Units between January 1999 and October 2000. The selection was based on the fact that all patients had taken or were still taking oral contraceptives (OC) for a period of 3 years or longer than 3 years. None of these patents as gathered from history, physical examination, private physician records and our records has shown any DVT during or immediately after OC intake. Physical and compression ultrasonography examinations at the time of study were all negative. The average length of oral contraceptives therapy (OCT) was 10 years (range 3-23). The average age of patients at the time of oral contraception was 30 years. The 13 women had also 17 pregnancies without any venous thrombosis. The observations casts several doubt about the prothrombotic effect of this polymorphism. Since DVT has been shown to occur occasionally even in normal women, it is likely that the same may occur in women with this polymorphism regardless of the existence or not of any pathogenetic relationship between the two phenomena. Occasional reports suggesting a link between this polymorphism and oral contraception-related venous thrombosis should be carefully evaluated in order to avoid premature and incorrect conclusions.

Adult↗
PubMed2001

Factor V Leiden and prothrombin gene mutation in inflammatory bowel disease in a Mediterranean area.

BACKGROUND: Thromboembolism has been reported to be associated with inflammatory bowel disease. AIM: To evaluate the association of factor V Leiden and prothrombin gene mutation with inflammatory bowel disease in a population of patients with thromboembolic events and inflammatory bowel disease and in a control population of patients with inflammatory bowel disease without thromboembolic events. PATIENTS AND METHODS: A series of 18 patients with inflammatory bowel disease and a history of arterial or venous thrombosis and 45 patients with inflammatory bowel disease without thromboembolic events were evaluated for the presence of factor V Leiden and prothrombin gene mutation. Frequency of gene mutation was compared with its occurrence in 100 healthy controls. RESULTS: One patient with inflammatory bowel disease without thromboembolic events was heterozygous for factor V Leiden mutation. whereas no patient with a thromboembolic event had factor V Leiden mutation. No patients (either cases or controls) had prothrombin gene mutation. In the healthy population the frequency of factor V Leiden and prothrombin mutation was 5% and 2%, respectively. CONCLUSIONS: Data emerging from the present study do not support any role of factor V Leiden and prothrombin gene mutation as the cause of thromboembolism in inflammatory bowel disease.

Colitis, Ulcerative↗
PubMed2001

Diagnosis of recurrent deep vein thrombosis.

Long-term follow-up studies demonstrated that venous thromboembolism is a chronic disease, as the rate of recurrent deep vein thrombosis (DVT) continuously increases after the primitive thrombotic episode. Objective testing is mandatory to confirm or refute the presence of recurrent DVT, as only 30% of patients with suspected recurrence have a new documented thrombotic episode. There is no consensus on the preferred diagnostic procedure; furthermore, both invasive and noninvasive methods are limited in this context. Venography, the established gold standard, is invasive, costly, inconvenient and requires high technical skills. Among noninvasive techniques, serial impedance plethysmography, alone or in combination with leg scanning and venography, and serial compression ultrasound (CUS), were adequately investigated. At present, the recommended approach is represented by a quantitative CUS method that possesses an excellent reproducibility and accuracy. The safety of withholding anticoagulants from patients with a normal quantitative CUS work-up has been recently demonstrated in a prospective management study.

Anticoagulants↗
PubMed2001

Homozygous patients with the 20210 G to A prothrombin polymorphism remain often asymptomatic in spite of the presence of associated risk factors.

Patients who are homozygous for the G to A nontranslated prothrombin polymorphism only occasionally have venous thrombosis. An evaluation of all published papers on the subjects has disclosed that nine patients of the 35 so far reported remained asymptomatic in spite of the presence of associated congenital or acquired thrombotic risk factors. We saw an additional patient recently, bringing the total to 10 of 36 patients. Some of these patients remained asymptomatic in spite of multiple or repetitive risk factors (e.g., five pregnancies in the case of one patient). Twelve patients who were homozygous and who had this polymorphism developed symptoms only in the presence of the same risk factors. This may suggest that this abnormality played a small role, if any, in both groups of patients. The finding that several patients with this abnormality remained asymptomatic in spite of associated risk factors casts serious doubts about the prothrombotic significance of this polymorphism. Until this problem is clarified, the clinician must abstain from attributing a prothrombotic effect to this polymorphism.

Adolescent↗
PubMed2001

ProC global: a new automated screening assay for the evaluation of total function of the protein C system.

Protein C (PC) pathway represents a major physiologic inhibitory mechanism regulating the coagulation cascade. A new automated functional screening assay (ProC Global) for the evaluation of the PC-system was tested to define its ability to identify patients with known inherited defects such as factor V (FV) Leiden mutation and PC and protein S (PS) deficiency. A total of 249 patients who were symptomatic or asymptomatic for previous venous thromboembolism (VTE) were evaluated, 50 of whom had FV Leiden mutation, 36 had PC deficiency, and 34 had PS deficiency. One hundred healthy subjects were also tested, as well as 40 blood donors of both sexes in whom coagulation abnormalities were not found. Results of ProC Global test were expressed as normalized ratio (NR) and values below an established cut-off level were consistent with a positive test. ProC Global was positive in all 50 patients with the FV Leiden mutation (mean NR = 0.59; range, 0.37 to 0.69). ProC Global correctly identified 32 of 36 (89%) PC defects (mean NR = 0.63; range, 0.34 to 1.21) and 25 of 34 (73.5%) PS defects (mean NR = 0.76; range, 0.5 to 1.23). Overall, 92.5% of hereditary defects of the PC system considered in this study were identified by ProC Global test. ProC Global exhibited NR above cut-off level in all 40 blood donors without coagulation defects. ProC Global is a new automated screening test with some diagnostic potential in identifying patients with defects of the PC system. However, ProC Global in its current form cannot substitute the assay of each single component of this inhibitory system in the daily screening for thrombophilia.

Adolescent↗
PubMed2001

Abnormal propeptide processing resulting in the presence of two abnormal species of protein C in plasma: characterization of the dysfunctional protein C Padua3 (protein C(R-1L/propeptide)).

A heterozygous G-->T transversion at position 1388 of the protein C (PC) gene which predicted the substitution of Arg(-1) to a Leu (PC(R-1L)) was identified in a thrombophilic patient. The PC(R-1L) was purified from the patient's plasma by immunoaffinity chromatography using Ca++-independent and Ca++-dependent monoclonal antibodies. NH2-terminal sequencing of the light chain of PC(R-1L) revealed two amino acid sequences: one was identical to the complete propeptide sequence of PC, while the other matched the normal PC light chain sequence elongated by one amino acid (Leucine at position 1). Activated PC(R-1L/propeptide) exhibited normal amidolytic and impaired anticoagulant activity. Thus, the substitution of a Leu for an Arg at position -1 of PC shifts the propeptidase cleavage site by one amino acid. In addition, in PC(R-1L/propeptide) the propeptide cleavage at Lys(-2) is less efficient since approximately 60% of PC variant molecules present in patient's plasma retained the entire propeptide. Our findings suggest that depending on the specific amino acid substitution at position-1, PC can be secreted in plasma containing the entire propeptide attached to the light chain. Impaired interaction of elongated APC molecules with a membrane-surface and/or factor Va which is the physiological substrate for APC, is manifested in vivo by thrombophilia.

Amino Acid Sequence↗