Search PubMed⌕ Search

Biomedical subjects

J Rivera

Publications and source records attributed to J Rivera.

At least 91 records · Page 5Linked to original sources
PubMed1999

Isoflavonoids do not inhibit in vivo lipid peroxidation in subjects with high-normal blood pressure.

The isoflavonoids genistein and daidzein have been shown to have antioxidant activity in vitro, but their effects on in vivo oxidation have not been assessed. The newly described F2-isoprostanes are believed to currently represent the best available marker of in vivo lipid peroxidation. Therefore we have assessed the effects of a 55 mg daily isoflavonoid supplement on urinary F2-isoprostane concentrations in subjects with high-normal blood pressure (BP). A total of 59 subjects completed an 8-week parallel design, randomized, double blind, and placebo-controlled study. F2-isoprostanes, isoflavonoids and creatinine were measured in 24-h urine samples taken at baseline and at the end of the intervention. There were significant increases in urinary excretion of genistein (5.22+/-0.75 mg/day, P < 0.0001) and daidzein (2.53+/-0.43 mg/day, P < 0.0001) in the group taking the isoflavonoid supplement. Creatinine excretion was significantly correlated with F2-isoprostanes at baseline (r = 0.45, P < 0.01). After adjustment for baseline values, there was no significant difference between groups in creatinine adjusted post-intervention F2-isoprostane concentrations (P = 0.74). In addition, changes in genistein and daidzein excretion were not significantly correlated with changes in F2-isoprostanes in the isoflavonoid treatment group. These results are not consistent with the suggestion that the two soy derived isoflavonoids have in vivo antioxidant activity at a level of intake achievable by dietary means and in subjects with high-normal BP.

Adult↗
PubMed1999

Dioxin like compounds from municipal waste incinerator emissions: assessment of the presence of polychlorinated naphthalenes.

Polychloronaphthalenes (PCN) were identified and quantified in emission samples collected from five different municipal waste incinerators (MWI). Polychlorodibenzo-p-dioxins (PCDD) and polychlorodibenzofurans (PCDF) were also determined to find a possible relationship between these classes of organochlorinated compounds. The analyses of PCDD/PCDF and PCN were carried out by high resolution gas chromatography coupled with high resolution mass spectrometry using a positive electron ionization source and operating in the selected ion monitoring analyzer mode (HRGC-HRMS/EI(+)-SIM). The total levels of PCN varied from 1.08 up to 21.36 ng/Nm3 (mono- to octachlorinated) and 0.33 to 5.72 ng/Nm3 (tetra- to octachlorinated), whereas the levels of PCDD/PCDF ranged between 1.14 and 276.26 ng/Nm3 (0.01 and 5 ng I-TEQ/Nm3), depending on the type of the MWI. These findings do not corroborate a PCN and PCDD/PCDF correlation.

Air Pollutants, Occupational↗
PubMed1999

2,3,7,8-Substituted PCDDs and PCDFs in sea lion (Otaria flavescens) skin biopsies from two South-western Atlantic populations.

Congener specific 2,3,7,8-chlorinated PCDDs and PCDFs were determined in skin biopsies taken from sea lions (Otaria flavescens) living in two areas of the South-western Atlantic on the coast of Argentina (Mar del Plata and Punta Bermeja). This is the first report on PCDDs and PCDFs in sea lion skin biopsies from the southern hemisphere. Differences were found in the congener pattern according to the sampling area. Animals living in the polluted area (Mar del Plata harbour) had detectable levels of all seventeen 2,3,7,8-substituted congeners. Sea lions living in a control environment (Punta Bermeja, Patagonia) only exhibited 5 detectable congeners out of all seventeen 2,3,7,8-substituted congeners. However, total levels were low in both colonies studied. These data are consistent with previous work which has indicated that dioxins occur at relatively low levels in marine mammals, possibly due to rapid catabolism or elimination.

Animals↗
PubMed1999

Polychlorinated naphthalenes in sediments from the Venice and Orbetello lagoons, Italy.

The purpose of this study was to evaluate the contamination caused by polychlorinated naphthalenes in two polluted Mediterranean lagoons. Surface sediment samples from Venice and Orbetello lagoons were analysed using HRGC-HRMS. The levels of the sum of mono- to octa-CN ranged from 0.03 to 1.51 ng/g. Differences in PCN levels were observed as a function of the sampling site, with levels at the industrial sites exceeding those at the control sites. Although the PCN patterns and profiles resembled one another in different sediment samples, they differed considerably when compared with those in the technical PCN formulation Halowax 1014.

Environmental Monitoring↗
PubMed1999

Comparative study of methodologies for the analysis of PCDDs and PDCFs in powdered full-fat milk. PCB, PCDD and PCDF levels in commercial samples from Spain.

Feasibility of two different extraction methods involving solid-liquid extraction and Soxhlet extraction, previously used for the determination of lipid contents and PCB levels on powdered full-fat milk, are now examined for simultaneous PCDD/F analysis. The results of this study are consistent with those found for PCBs. The solid-liquid procedure provides the most efficient extraction of both labelled spiked and endogenous PCDD/Fs with the lowest variability. The average recoveries were 101% (R.S.D. = 6.9%) for 13C12-2,3,7,8-TCDD and 95% (R.S.D. = 11%) for 13C12-1,2,3,4,7,8-HxCDD. The R.S.D.s for endogenous 2,3,7,8-PCDD/Fs were in the 9.3-25% range. In addition, this methodology simplified the subsequent clean-up step as it allowed a semi-selective extraction of the apolar lipids from the milk. The proposed method was applied to simultaneous PCB and PCDD/F analyses in different brands of powdered full-fat milks commercially available in Spain. In all cases, very similar PCB and PCDD/F levels were found. Differences among batches from the same manufacturer were even lower. The total i-TEQ average for PCDDs and PCDFs in the 22 powdered full-fat milk samples analysed was 1.87 pg/g fat basis. This value was similar to those found in cow's milk from other European countries.

Animals↗
PubMed1999

Levels of PCBs, PCDDs and PCDFs in commercial butter samples in Spain.

Feasibility of three different extraction methods for the simultaneous determination of polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in butter is discussed. The method based on liquid-liquid extraction with water of the non fatty solids from butter dissolved in hexane was found to be the most efficient for the determination of the lipid content and the levels of the investigated pollutants. This method was used to evaluate the background levels of PCBs, PCDDs and PCDFs in butters commercially available in Spain. Broad ranges of PCB, specifically, PCDD and PCDF concentrations were found in the different brands analysed. Levels, profiles and patterns of these pollutants in butter were compared with those previously reported for different Spanish dairy products. The toxic tetra-equivalents of 2,3,7,8-TCDD (1-TEQ) averages for PCDDs and PCDFs in the 21 butter samples analysed were 0.41 and 0.70 pg/g fat basis, respectively. These values were similar or lower than those cited in the literature for other countries.

Benzofurans↗
PubMed1999

Quality assessment of platelet concentrates supplemented with second-messenger effectors.

BACKGROUND: While reducing the potential for bacterial contamination, the storage of platelet concentrates (PCs) at refrigerated temperatures is not routine, because of the induction of the so-called platelet storage lesion. As the modulation of second-messenger levels might help to overcome this drawback, a quality assessment of PCs treated with a mixture of second-messengers effectors known as ThromboSol was performed. STUDY DESIGN AND METHODS: The PCs were supplemented with ThromboSol or phosphate-buffered saline, and stored in parallel at 22 degrees C with continuous agitation or at 4 degrees C. At 1, 5, and 9 days, an in vitro quality assessment of the PCs was performed, including measurement of cell number, metabolic and integrity markers, platelet surface expression of glycoproteins, platelet response to ristocetin and thrombin, and levels of cyclic adenosine 3', 5' monophosphate (cAMP) and thromboxane B2 (TxB2). RESULTS: Control PCs stored at 4 degrees C underwent aggregation and displayed a significant decrease in the platelet number (40% on Day 5). By contrast, the ThromboSol-treated PCs maintained 80 percent of their initial platelet concentration after 9 days of storage at 4 degrees C. Compared to PCs stored at 22 degrees C, refrigerated PCs exhibited minor changes in metabolic values throughout storage, but the addition of ThromboSol induced a rise in metabolic rate during storage at 22 degrees C. Platelet responsiveness to both ristocetin and thrombin was maximally preserved in the ThromboSol-treated PCs stored at 4 degrees C. These units also maintained high levels of cAMP and low concentrations of TxB2 during storage. CONCLUSION: The pharmacologic supplementation of PCs with ThromboSol significantly favors the maintenance of in vitro integrity and responsiveness of platelets during extended storage at refrigerated temperature. This protective effect seems to be a consequence of the ability of ThromboSol's components to sustain high levels of cAMP and to inhibit TxB2 production during the entire extended-storage period.

Blood Banks↗
PubMed1999

The number of platelet glycoprotein Ia molecules is associated with the genetically linked 807 C/T and HPA-5 polymorphisms.

BACKGROUND: The neutral 807 C/T (Phe224) polymorphism (807 C/T polymorphism) of the glycoprotein (GP)Ia gene has been recently associated with the number of GPIa molecules on the platelet surface. The association of the number of GPIa molecules with other GPIa polymorphisms, such as HPA-5 (Glu/Lys505) (HPA-5 polymorphism), involved in alloimmune thrombocytopenias is unknown. STUDY DESIGN AND METHODS: The association of the HPA-5 polymorphism with the number of GPIa molecules on the platelet surface in 159 white blood donors was investigated. The genetic linkage between the HPA-5 and the 807 C/T polymorphisms in 316 individuals was also determined. RESULTS: Both the 807 C/T and HPA-5 polymorphisms correlate with the number of GPIa molecules on the platelet surface. The 807 T and HPA-5b alleles are associated with increased numbers of GPIa molecules on the platelet surface. Moreover, the HPA-5b allele is genetically linked to 15.8 percent of the 807 C alleles. Therefore, the number of GPIa molecules on the platelet surface is dependent on both GPIa polymorphisms as follows: 807 T/T, HPA-5 a/a > 807 C/T, HPA-5 a/b > 807 C/T, HPA-5 a/a > 807 C/C, HPA-5 a/b > 807 C/C, HPA-5 a/a. CONCLUSION: Two GPIa polymorphisms (807 C/T and HPA-5) responsible for the variability in the numbers of GPIa/IIa molecules on the platelet surface in whites have been identified. Despite the genetic linkage between the two polymorphisms, their influence on the number of GPIa molecules on the platelet surface may occur through different mechanisms.

Adult↗
PubMed1999

VP1, the putative RNA-dependent RNA polymerase of infectious bursal disease virus, forms complexes with the capsid protein VP3, leading to efficient encapsidation into virus-like particles.

A cDNA corresponding to the coding region of VP1, the putative RNA-dependent RNA polymerase, of infectious bursal disease virus (IBDV) was cloned and inserted into the genome of a vaccinia virus inducible expression vector. The molecular mass and antigenic reactivity of VP1 expressed in mammalian cells are identical to those of its counterpart expressed in IBDV-infected cells. The results presented here demonstrate that VP1 is efficiently incorporated into IBDV virus-like particles (VLPs) produced in mammalian cells coexpressing the IBDV polyprotein and VP1. Incorporation of VP1 into VLPs requires neither the presence of IBDV RNAs nor that of the nonstructural polypeptide VP5. Immunofluorescence, confocal laser scanning microscopy, and immunoprecipitation analyses conclusively showed that VP1 forms complexes with the structural polypeptide VP3. Formation of VP1-VP3 complexes is likely to be a key step for the morphogenesis of IBDV particles.

Animals↗
PubMed1999

von Willebrand factor contained in a high purity FVIII concentrate (Fanhdi) binds to platelet glycoproteins and supports platelet adhesion to subendothelium under flow conditions.

BACKGROUND AND OBJECTIVE: There is evidence suggesting that von Willebrand factor (VWF) from high purity factor VIII concentrates could be of clinical use in the management of patients suffering from VWD. We analyzed structural and functional characteristics of VWF present in a high purity factor VIII concentrate VWFHPC (Fanhdi). The multimeric structure, the ability to bind to platelet GP Ib/IX or GP IIb/IIIa, and the capacity of VWFHPC to promote platelet adhesion on injured vessels were investigated and compared with that present in standard plasma cryoprecipitates [VWFCRYO]. DESIGN AND METHODS: Binding studies were carried out by incubating radiolabeled VWF and washed platelets, which were activated with either ristocetin (1 mg/mL; for GP Ib/IX), or thrombin (2.5 U/mL; for GP IIb/IIIa). Platelet adhesion was assessed in a perfusion system (shear rate = 800 s-1, 10 min) in which the source of VWF was added (at 0.4 or 0.8 U/mL VWF:Ag) to washed platelets and red cells suspended in a human albumin solution. The deposition of platelets onto the perfused subendothelial surface was morphometrically evaluated and expressed as percentage of surface coverage (%SC). RESULTS: The VWFHPC (152 Units VWF:RCof/mg protein; VWF:RCof/VWF:Ag = 0.97), lacked only a small proportion of high-molecular-weight multimers present in VWFCRYO. Binding affinities (Kd values, nM) of VWFHPC were similar to those of VWFCRYO (5.3 +/- 0.86 vs 5.2 +/- 0.95, for GP Ib/IX; and 11.6 +/- 2.7 vs 15.4 +/- 1.7 for GPIIb-IIIa). A slightly, though not significantly, higher binding capacity for these receptors (Bmax values, molecules/pit) was obtained for VWFHPC. The %SC in perfusions in the presence of albumin was < 10%. Addition of VWFHPC or VWFCRYO significantly increased the %SC, with values of 27.1 +/- 4.9 and 17.5 +/- 2.8%, respectively with 0.4 U/mL (p < 0.004 and p < 0.02 vs albumin); and 30.8 +/- 4.9% and 20.03 +/- 4.1%, respectively, at 0.8 U/mL (p < 0.001 and p < 0.02 vs albumin). INTERPRETATION AND CONCLUSIONS: Our data show that VWF present in the high purity FVIII concentrate Fanhdi retains the functional capacity to bind to GPs Ib/IX and IIb/IIIa and to promote platelet adhesion onto exposed subendothelium.

Albumins↗
PubMed1999

The prothrombin gene variant 20210A in venous and arterial thromboembolism.

Several hereditary disorders affecting coagulation factors have been identified as prothrombotic risk factors. Recently, the prothrombin 20210 A/G mutation has been identified as a second important polymorphism involved in venous thrombosis. This article reviews all published information about this new procoagulant mutation. Our group has been involved in a number of studies about the role and importance of polymorphisms in thromboembolic disease, including the analysis of the prothrombin 20210 A/G mutation. Moreover, an extensive Medline literature search was made to complete the review using the key words: prothrombin mutation, 20210, venous or arterial thrombosis. The combination of environmental and genetic risk factors determines the relative risk that any individual has of suffering a thrombotic episode. Some genetic mutations affecting coagulation factors have been described. Recently, Poort et al. described a new mutation in the 3'-untranslated region of the prothrombin gene. The prothrombin 20210 G/A mutation, associated with elevated levels of factor II in plasma, significantly increases the risk of developing venous thrombosis. In fact, this polymorphism is the second most important genetic risk factor for venous thrombosis in Caucasian populations. Moreover, and supporting the multifactorial feature of thromboembolic diseases, this mutation greatly increases the possibility of developing a thrombotic episode when combined with other environmental or genetic risk factors. The role of this procoagulant mutation in arterial vascular disease is, however, unclear.

Humans↗
PubMed1999

Clinical and analytical relevance of the combination of prothrombin 20210A/A and factor V Leiden: results from a large family.

We analysed the clinical and analytical features of 18 subjects from a Spanish family who bear several combinations of two prothrombotic mutations, factor V Leiden (FVL) and prothrombin 20210A. We identified three subjects homozygous for the 20210A prothrombin mutation which additionally were heterozygous for FVL. The combination of both mutations increases the risk of developing venous thrombotic episodes at the earlier age. However, even in association with FVL, the homozygous condition of the prothrombin 20210A mutation requires additional risk factors to induce a thrombotic event. Finally, the plasma level of factor II showed a significant relationship with the prothrombin genotype.

Adult↗
PubMed1999

Role of the 807 C/T polymorphism of the alpha2 gene in platelet GP Ia collagen receptor expression and function--effect in thromboembolic diseases.

The variability of the platelet GP Ia/IIa density has been associated with the 807 C/T polymorphism (Phe 224) of the GP Ia gene in American Caucasian population. We have investigated the genotype and allelic frequencies of this polymorphism in Spanish Caucasians. The T allele was found in 35% of the 284 blood donors analyzed. We confirmed in 159 healthy subjects a significant association between the 807 C/T polymorphism and the platelet GP Ia density. The T allele correlated with high number of GP Ia molecules on platelet surface. In addition, we observed a similar association of this polymorphism with the expression of this protein in other blood cell types. The platelet responsiveness to collagen was determined by "in vitro" analysis of the platelet activation and aggregation response. We found no significant differences in these functional platelet parameters according to the 807 C/T genotype. Finally, results from 3 case/control studies involving 302 consecutive patients (101 with coronary heart disease, 104 with cerebrovascular disease and 97 with deep venous thrombosis) determined that the 807 C/T polymorphism of the GP Ia gene does not represent a risk factor for arterial or venous thrombosis.

Aged↗
PubMed1999

Posttraumatic subgaleal hematoma: a case report and review of the literature.

INTRODUCTION: A subgaleal hematoma or subaponeurotic hemorrhage occurs infrequently and is usually seen in pediatric patients, especially in the neonatal period. It may be associated with coagulation disorders. CASE REPORT: We report on a previously healthy 19-month-old patient who presented with an extensive subgaleal hematoma and significant anemia secondary to a fall. DISCUSSION: A literature review was conducted, and the etiology, diagnosis, and treatment of the subgaleal hematoma are discussed. CONCLUSION: Conservative treatment, except in select severe cases, is recommended for this condition.

Accidental Falls↗
PubMed1999

Arthritis in patients with chronic hepatitis C virus infection.

OBJECTIVE: To describe the clinical picture of arthritis in patients with chronic infection by hepatitis C virus (HCV). METHODS: Two patient populations were studied. Patients with arthritis and evidence of serum elevation of alanine aminotransferase (ALT) at the consultation were checked for HCV infection. A second group of 303 consecutive patients with rheumatoid arthritis (RA) were also checked for the presence of HCV antibodies. All patients attended the outpatient rheumatology unit of a tertiary care teaching hospital. Chronic HCV infection was determined by the presence of viral RNA in serum. A group of 315 first-time blood donors served as controls. RESULTS: Twenty-eight patients with arthritis and chronic HCV infection were identified. Seven fulfilled criteria for RA, psoriatic arthritis was found in one patient, systemic lupus erythematosus in one, gout in 2, chondrocalcinosis in 2, osteoarthritis in 7, and tenosynovitis in one. In 7 patients with a clinical picture of intermittent arthritis, a definitive diagnosis could not be made. In these patients, mixed cryoglobulinemia was present in 6/7 (86%), whereas mixed cryoglobulinemia was found in 6/21 (28%) of the other patients. Among patients with RA, 23 (7.6%) had HCV antibodies, and active infection by HCV was found in 7 (2.3%) patients. The prevalence of HCV antibodies in a blood donor population was 0.95%, significantly different (p<0.001; 95% CI 0.03, 0.10) compared to patients with RA. The distribution of antibodies determined by recombinant immunoblot analysis was similar (p = NS) between RA patients and blood donors with HCV antibodies. CONCLUSION: There is not a single clinical picture of arthritis in patients with chronic HCV infection. There is a well defined picture of arthritis associated with the presence of mixed cryoglobulinemia that consists of an intermittent, mono or oligoarticular, nondestructive arthritis affecting large and medium size joints. Although a high prevalence of HCV antibodies is suspected in patients with RA, its occurrence may be coincidental and its interpretation is difficult to determine from the data in this study.

Adult↗
PubMed1998

[Markers of hemostatic activation in the coronary sinus versus peripheral circulation in coronary artery disease. Effects of percutaneous transluminal coronary angioplasty].

BACKGROUND: To evaluate haemostatic changes in coronary sinus (CS) and peripheral circulation (PC) in patients with cardiovascular disease (CAD) following PTCA. PATIENTS AND METHODS: We studied 12 patients scheduled for elective PTCA. Blood samples were obtained from CS and PC before angioplasty and after each balloon dilation. Expression of P selectin and several haemostatic parameters were determined. RESULTS: D-Dimers (DD) plasma levels were significantly increased in samples from CS. No significant differences were found in other haemostatic parameters. A significant decrease of thrombin-antithrombin III levels after PTCA was assessed. CONCLUSIONS: Intracoronary and peripheral hemostatic activation does not occur during and immediately following PTCA. No major differences in hemostatic parameters between CS and PC were observed in patients with CAD.

Adult↗