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Biomedical subjects

J Rivera

Publications and source records attributed to J Rivera.

At least 55 records · Page 3Linked to original sources
PubMed2001

Survival study of rheumatoid arthritis patients in Madrid (Spain). A 9-year prospective follow-up.

OBJECTIVE: To determine the risk and causes of death in rheumatoid arthritis (RA) patients in Madrid. METHODS: A longitudinal survival analysis was made. 182 RA patients of the rheumatology clinic of a tertiary care hospital were studied. 42 (23%) males and 140 (77%) females. All were followed-up for a 9-year period or to the date of death. Kaplan-Meier survival curves for both male and female cohorts were performed. The logrank test was used to compare both distributions and to determine the statistical significance. RESULTS: The mortality rate for the RA patient cohort was 15.4 deaths/1000 person-years (10.2/1000 for the female and 34.2/1000 for the male cohorts). The mortality rate ratio was 3.3. The logrank test showed a statistical difference (p=0.0023). The standardized mortality ratio was 1.85 for RA patients. The causes of death were: cardiovascular diseases 5 (21%), infections 5 (21%). amyloidosis 4 (17%), malignant diseases 2 (8%). CONCLUSIONS: Mortality is nearly two times higher in our population of RA patients. Male patients have a much lower survival probability than females. Cardiovascular diseases, infections and amyloidosis were the most common causes of death.

Adolescent↗
PubMed2001

Full breast-feeding for at least four months has differential effects on growth before and after six months of age among children in a Mexican community.

This study examines the relationship between breast-feeding and growth from 0 to 6 and 6 to 20 mo among 185 children in a Mexican community. Infants from a previous 6-mo longitudinal study were followed up for additional anthropometric measurements at a mean age of 19.9 mo. Size at 6 mo and at follow-up were modeled as outcomes of whether infants were fully breast-fed (exclusively or predominantly breast-fed) for at least 4 mo, controlling for size at birth and 6 mo, respectively, and potential confounders. From birth to 6 mo, fully breast-fed infants had ponderal index increments of 0.07 units larger (P = 0.04) than comparison infants. There were no differences in weight. For length, an interaction between full breast-feeding and socioeconomic status (SES) was found, with fully breast-fed infants of low SES growing more than comparison infants, whereas the opposite was seen at upper SES levels. From 6 to 20 mo, fully breast-fed infants had weight and length increments of 0.53 cm (P < 0.001) and 0.72 kg (P = 0.01) smaller than those of comparison infants. For ponderal index, an interaction between mother's education and breast-feeding revealed an inverted U-shaped response across levels of education. Additionally, logistic regressions of monthly breast-feeding on lagged measurements revealed that relatively heavier infants had higher odds of being fully breast-fed at 2 and 3 mo. Our findings indicate that the benefits of full breast-feeding on growth may be most pronounced early in life. Further research of unmeasured confounders may explain the association of full breast-feeding with slower growth beyond 6 mo.

Body Weight↗
PubMed2001

Vav1 regulates phospholipase cgamma activation and calcium responses in mast cells.

The hematopoietic cell-specific protein Vav1 is a substrate of tyrosine kinases activated following engagement of many receptors, including FcepsilonRI. Vav1-deficient mice contain normal numbers of mast cells but respond more weakly than their normal counterparts to a passive systemic anaphylaxis challenge. Vav1-deficient bone marrow-derived mast cells also exhibited reduced degranulation and cytokine production, although tyrosine phosphorylation of FcepsilonRI, Syk, and LAT (linker for activation of T cells) was normal. In contrast, tyrosine phosphorylation of phospholipase Cgamma1 (PLCgamma1) and PLCgamma2 and calcium mobilization were markedly inhibited. Reconstitution of deficient mast cells with Vav1 restored normal tyrosine phosphorylation of PLCgamma1 and PLCgamma2 and calcium responses. Thus, Vav1 is essential to FcepsilonRI-mediated activation of PLCgamma and calcium mobilization in mast cells. In addition to its known role as an activator of Rac1 GTPases, these findings demonstrate a novel function for Vav1 as a regulator of PLCgamma-activated calcium signals.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Structure-function analysis of Lyn kinase association with lipid rafts and initiation of early signaling events after Fcepsilon receptor I aggregation.

The first step in immunoreceptor signaling is represented by ligand-dependent receptor aggregation, followed by receptor phosphorylation mediated by tyrosine kinases of the Src family. Recently, sphingolipid- and cholesterol-rich plasma membrane microdomains, called lipid rafts, have been identified and proposed to function as platforms where signal transduction molecules may interact with the aggregated immunoreceptors. Here we show that aggregation of the receptors with high affinity for immunoglobulin E (FcepsilonRI) in mast cells is accompanied by a co-redistribution of the Src family kinase Lyn. The co-redistribution requires Lyn dual fatty acylation, Src homology 2 (SH2) and/or SH3 domains, and Lyn kinase activity, in cis or in trans. Palmitoylation site-mutated Lyn, which is anchored to the plasma membrane but exhibits reduced sublocalization into lipid rafts, initiates the tyrosine phosphorylation of FcepsilonRI subunits, Syk protein tyrosine kinase, and the linker for activation of T cells, along with an increase in the concentration of intracellular Ca(2+). However, Lyn mutated in both the palmitoylation and myristoylation sites does not anchor to the plasma membrane and is incapable of initiating FcepsilonRI phosphorylation and early signaling events. These data, together with our finding that a constitutively tyrosine-phosphorylated FcepsilonRI does not exhibit an increased association with lipid rafts, suggest that FcepsilonRI phosphorylation and early activation events can be initiated outside of lipid rafts.

Animals↗
PubMed2001

Study of plasma factors associated with neutrophil activation and lipid peroxidation in preeclampsia.

Neutrophil activation occurs in women with preeclampsia and is resolved after delivery. The present study examined whether circulating factors in plasma of women with preeclampsia caused neutrophil activation and lipid peroxidation. Twenty-one women with proteinuric preeclampsia were matched for age and gestational age with 19 normal pregnant women. Plasma was collected from all subjects before delivery and at 6 weeks postpartum and incubated with autologous white-cell buffy coat collected at the postpartum visit. Neutrophil activation was assessed by level of CD11b and CD18 expression after incubation with autologous antepartum or postpartum plasma. Lipid peroxidation was assessed by measurement of F(2)-isoprostanes in plasma, plasma-white cell incubates, and urine. Neutrophil CD11b and CD18 expression was not differentially altered by incubation with plasma from either women with preeclampsia or normal pregnant women and was similar between groups when incubation was performed with plasma collected after delivery. In preeclampsia, plasma F(2)-isoprostanes were significantly increased before and after delivery compared with controls. Plasma F(2)-isoprostanes were increased 2-fold after incubation of plasma with buffy coat, but preeclamptic women had higher levels compared with those of controls when either pregnant or postpartum plasma was used. In pregnant preeclamptics, plasma F(2)-isoprostanes were positively correlated with lymphocyte count. Six weeks after delivery, plasma F(2)-isoprostanes in the preeclamptic women were significantly positively associated with lymphocyte count and cholesterol and negatively associated with albumin. In conclusion, the present study does not suggest that a stable circulating factor causes neutrophil activation in preeclampsia. However, lipid peroxidation is elevated before and after delivery in women with preeclampsia, which suggests that these women may have an underlying predisposition to increased oxidative stress that may be driven by or contribute to a persistent low-grade inflammatory response.

Adult↗
PubMed2001

Binding of recombinant apolipoprotein(a) to human platelets and effect on platelet aggregation.

The interaction of lipoprotein(a) [Lp(a)] with platelets is not well defined, particularly with regards to the individual contribution of the protein components of Lp(a), the apo B-100 and the apolipoprotein apo(a). This study investigated the binding of different recombinant apo(a) [r-apo(a)] isoforms, to human platelets and its effect on platelet aggregation. Scatchard analysis of saturation binding experiments demonstrated that human platelets display a single class of high affinity r-apo(a) binding sites (71 +/- 46 molec./platelet, Kd = 5.6 +/- 2.0 nmol/L). Platelet activation with strong agonists (thrombin, arachidonic acid) increased 2- to 10-fold the r-apo(a) binding, without affecting the affinity. Competition assays showed that the binding sites are highly specific for r-apo(a) and Lp(a). At high concentration t-PA could also bind to the r-apo(a) binding sites. By contrast, neither fibrinogen nor plasminogen inhibited to the r-apo(a) binding. The lysine analogue EACA inhibits the binding of r-apo(a) to platelets, thus suggesting the involvement of lysine residues in that interaction. Moreover, the r-apo(a) binding to platelets is unlikely mediated by GPIIb/IIIa-attached fibrin since it is not affected by platelet treatment with either LJ-CP8, a monoclonal antibody that specifically blocks fibrinogen binding to GPIIb/IIIa, nor GPRP, an inhibitor of fibrin polymerisation. Finally, we show that the distinct recombinant apo(a) proteins, as well as native Lp(a), promote an aggregation response of platelets to otherwise subaggregant doses of arachidonic acid. This proaggregant effect of r-apo(a) is dependent on its binding to platelets since it requires a minimum incubation time, and it is prevented by EACA at concentration inhibiting the r-apo(a)-platelet interaction. These results suggest that the prothrombotic action of Lp(a) may be in part mediated by modulating the platelet function through the interaction of its apo(a) subunit with a specific receptor at the platelet surface.

Adenosine Diphosphate↗
PubMed2001

Protein kinase C theta is expressed in mast cells and is functionally involved in Fcepsilon receptor I signaling.

We investigated possible expression and function in mast cells of protein kinase C (PKC) theta, a member of the PKC family with demonstrated function in a limited range of cell types. We found that PKC theta is expressed in bone marrow-derived mast cells and in the RBL-2H3 mast cell line. PKC theta underwent translocation to the membrane in response to Fcepsilon receptor I (FcepsilonR I) activation. Receptor activation induced phosphorylation of PKC theta. The tyrosine phosphorylation of PKC theta is delayed relative to PKC delta and coincides temporally with PKC theta association with c-src family members Lyn and SRC: Studies of RBL-2H3 cells transduced with PKC theta constructs indicated a role for PKC theta in receptor-induced activation of extracellular regulated kinases, interleukin-3 gene transcription, and degranulation in response to antigen stimulation. These studies extend the known functions of PKCtheta to another important immune cell type and indicate the concurrent participation of multiple PKCs in the FcepsilonR I-mediated response of mast cells.

Animals↗
PubMed2001

Effect of cold-storage in the accumulation of bioreactive substances in platelet concentrates treated with second messenger effects.

BACKGROUND AND OBJECTIVES: The mandatory 5-day of shelf-life platelet concentrates (PCs) creates outdating and inventory control problems in blood banking. Moreover, storage of PCs at 22-24 degrees C has been associated with a time-dependent accumulation of pyrogenic cytokines, potentially harmful for recipients. Previous studies have shown that supplementation of PCs with ThromboSol, a mixture of second-messengers effectors, might allow storage of functionally active platelets at refrigerated temperature to be extended. This study further investigates this storage approach by comparing the accumulation of bioactive compounds in standard and refrigerated PCs. DESIGN AND METHODS: The PCs were supplemented with ThromboSol or a control solution and stored in parallel at 24 degrees C with continuous agitation or undisturbed at 4 degrees C. Samples were removed on days 1, 5, 9 of storage, and assayed for their content of interleukin (IL)-6, IL-8, tumour necrosis factor (TNF)-alpha, transforming growth factor (TGF)-beta1, and anaphylatoxins C3a and C4a. RESULTS: Throughout storage, refrigerated PCs, both ThromboSol-treated and untreated units, displayed a slightly lower level of IL-6 and significantly lower concentration of IL-8 than conventionally stored PCs. ThromboSol slightly reduced the level of these cytokines in PCs. Throughout storage at 22 degrees C, an accumulation of anaphylatoxins C3a and C4a was seen both in both control and ThromboSol-treated PCs. This accumulation was significantly reduced in control PCs stored at 4 degrees C, but not in refrigerated PCs supplemented with ThromboSol. Cold-storage, with or without ThromboSol, had a minor effect on the accumulation of TGF-beta1 in PCs. INTERPRETATION AND CONCLUSIONS: Our data confirm that release of bioactive compounds during in vitro storage of PCs is a temperature-sensitive process. The ThromboSol-refrigeration system could be a useful alternative for extending storage of PCs, without increasing the accumulation of cytokines (IL-6, IL-8), known to be involved in febrile reactions in recipients. Nevertheless, this storage system has no benefit on the level of other bioactive compounds (TGF-beta1, anaphylatoxins C3a and C4a) in PCs.

Blood Platelets↗
PubMed2001

Diterpenes and other constituents from Croton draco (Euphorbiaceae).

Croton draco (Euphorbiaceae) from Guadalupe, San José, Costa Rica was collected in July 1992 and phytochemically studied (leaves, seeds, wood, bark, sap and flowers separately). Commonly known compounds such as 1-hydroxyjunenol, p-hydroxybenzaldehyde, p-methoxybenzoic acid, 3,4,5-trimethoxycinnamyl alcohol, the coumarin scopoletin, the nor-terpenoids 9-dehydrovomifoliol and 2,3-dihydrovomifoliol were obtained. Taspine, two aporphinic alkaloids, the diterpenes 9(11)-dehydrokaurenic acid, hardwikiic acid, the corresponding new 12-oxo derivative as well as five clerodanes and a phorbol ester were also isolated. Three clerodanes were not previously described and their NMR spectroscopical data and MS fragmentation patterns are reported.

Diterpenes↗
PubMed2001

Role of one day epidural adhesiolysis in management of chronic low back pain: a randomized clinical trial.

Epidural fibrosis is seen as a common phenomenon among postlumbar laminectomy syndrome patients, contributing to approximately 60% of symptom recurrence. Percutaneous epidural lysis of adhesions has been described as a modality to effectively manage chronic low back pain secondary to epidural fibrosis. Forty-five patients were randomly assigned, with fifteen patients in the control group, or Group I, who were treated with conservative modalities of treatments, including medication, physical therapy, and an exercise program; and, thirty patients in Group II, who were treated with percutaneous epidural adhesiolysis and hypertonic saline neurolysis. The patients were evaluated over a period of 1 1/2 years to 3 years. Results showed that cumulative relief, defined as relief greater than 50% with one to three injections, in the treatment group was 97% at 3 months, 93% at 6 months, and 47% at 1 year. The study also showed that overall health status improved significantly in the treatment group in all parameters with average pain, physical health, mental health, functional status, psychological status and narcotic intake. Analysis also showed that this is a cost-effective treatment, with cost for 1-year improvement of quality of life at $2693. In conclusion, epidural adhesiolysis with hypertonic saline neurolysis performed on a 1-day basis is an effective modality of treatment in managing chronic low back pain in patients who failed to respond to fluoroscopically directed epidural steroid injections and also were demonstrated not to have facet joint mediated pain.

Journal Article↗
PubMed2001

Interventional techniques in the management of chronic pain: Part 2.0.

The practice guidelines for interventional techniques in the management of chronic pain are systematically developed statements to assist physician and patient decisions about appropriate health care related to chronic pain. These guidelines are professionally derived recommendations for practices in the diagnosis and treatment of chronic or persistent pain. They were developed utilizing a combination of evidence and consensus based techniques, to increase patient access to treatment, improve outcomes and appropriateness of care, and optimize cost-effectiveness. The guidelines include a discussion of their purpose, rationale, and importance, including the patient population served, the methodology and the pathophysiologic basis for intervention. Various interventional techniques will be discussed addressing the rationale for their use in chronic pain with analysis of the outcomes data and cost effectiveness. These guidelines do not constitute inflexible treatment recommendations. It is expected that a provider will establish a plan of care on a case-by-case basis, taking into account an individual patient's medical condition, personal needs, and preferences, and the physician's experience. Based on an individual patient's needs, treatment different from that outlined here could be warranted.

Journal Article↗
PubMed2000

Evaluation of a new automated cleanup system for the analysis of polychlorinated dibenzo-p-dioxins and dibenzofurans in environmental samples.

An automated cleanup system (Power-Prep, Fluid Management Systems, Inc.) was evaluated for the analysis of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/PCDF) in environmental samples. The study was firstly carried out against standard mixtures containing labeled and unlabeled PCDD/PCDF and a certified reference material (fly ash CRM 490). Next, a comparison between a conventional cleanup procedure and the new automated system for PCDD/PCDF analysis in environmental samples such as flue gas emissions, fly ashes, sludges, ambient air and soils was also made. The suitability of the system was finally assessed from the participation in an interlaboratory exercise. Owing to its capability to successfully perform the sample cleanup the Power-Prep apparatus is an alternative to the conventional methods.

Automation↗
PubMed2000

Evaluating the environmental impact of an old municipal waste incinerator: PCDD/F levels in soil and vegetation samples.

In order to determine the temporal variation in the levels of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in the vicinity of an old municipal solid waste incinerator (MSWI) (S. Adrià del Besòs, Barcelona, Spain), 24 soil and vegetation samples were collected at the same sampling points in which samples had been taken 1 year before. Each sample was analyzed for PCDDs and PCDFs by high-resolution gas chromatography/high-resolution mass spectrometry. While in the previous study PCDD/F concentrations in soil ranged from 1.22 to 34. 28 ng I-TEQ/kg (median and mean values: 9.06 and 12.24 ng I-TEQ/kg), in the present study, PCDD/F levels ranged from 1.33 to 54.23 ng I-TEQ/kg (median and mean values: 11.85 and 14.41 ng I-TEQ/kg). On the other hand, in the previous study, PCDD/F levels in vegetation ranged from 0.33 to 1.98 ng I-TEQ/kg (median and mean values: 0.58 and 0.70 ng I-TEQ/kg), whereas in the present study, PCDD/F levels ranged from 0.32 to 2.52 ng I-TEQ/kg (median and mean values: 0.82 and 0.97 ng I-TEQ/kg). During the last 12 months, PCDD/F levels increased in 16 of the 24 soil samples and in 17 of the 24 vegetation samples analyzed. However, no significant differences in the median I-TEQ concentrations of both studies were found either in soil or vegetation samples.

Benzofurans↗
PubMed2000

The Src homology 2 domain of Vav is required for its compartmentation to the plasma membrane and activation of c-Jun NH(2)-terminal kinase 1.

Vav is a hematopoietic cell-specific guanine nucleotide exchange factor (GEF) whose activation is mediated by receptor engagement. The relationship of Vav localization to its function is presently unclear. We found that Vav redistributes to the plasma membrane in response to Fcin receptor I (FcinRI) engagement. The redistribution of Vav was mediated by its Src homology 2 (SH2) domain and required Syk activity. The FcinRI and Vav were found to colocalize and were recruited to glycosphingolipid-enriched microdomains (GEMs). The scaffold protein, linker for activation of T cells (LAT), and Rac1 (a target of Vav activity) were constitutively present in GEMs. Expression of an SH2 domain-containing COOH-terminal fragment of Vav inhibited Vav phosphorylation and movement to the GEMs but had no effect on the tyrosine phosphorylation of the adaptor protein, SLP-76 (SH2 domain-containing leukocyte protein of 76 kD), and LAT. However, assembly of the multiprotein complex containing these proteins was inhibited. In addition, FcinRI-dependent activation of c-Jun NH(2)-terminal kinase 1 (JNK1) was also inhibited. Thus, Vav localization to the plasma membrane is mediated by its SH2 domain and may serve to regulate downstream effectors like JNK1.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Platelet GP Ib/IX/V complex: physiological role.

Platelets play an essential role in primary hemostasis and in thrombotic events, particularly in arterial vessels, as rheological conditions originate closer interactions between platelets and endothelium than lower shear rates. In response to vascular injury, platelets adhere to the subendothelial matrix by membrane receptors potentiating the generation of thrombin, become activated, and a series of biochemical processes induce platelet aggregation and liberation of intracellular metabolic products to the extracelular medium. Among platelet receptors, glycoprotein (GP) Ib/IX/V complex is peculiar, as it binds adhesive proteins, mainly von Willebrand factor (vWF), and thrombin, the main platelet agonist. Platelet adhesion and subsequent aggregation under conditions of high shear flow, essentially relies upon this receptor's capacity of binding to the subendothelial matrix, initiating signal transduction. Two proteins associated to GP Ib/IX/V, actin-binding protein (ABP) 280 and 14-3-3zeta, are potential mediators of signal transduction by the complex, but their specific contribution in this process is not yet fully understood. Additionally, two proteins implicated in signal transduction by immune stimuli, FcgammaRIIA and FcR gamma-chain, associate with GPIb/IX/V complex, and increasing data indicate a potential role in GPIbalpha mediated signal transduction.

14-3-3 Proteins↗
PubMed2000

Transabdominal surgical approach in the management of renal tumors involving the retrohepatic inferior vena cava.

Multiple reports over the last decade have documented the clear superiority of surgery over other alternative treatments in the management of renal cell carcinoma with extension into the inferior vena cava (IVC). Controversy persists, however, regarding the management of tumor thrombus that extends retrohepatically, but not entering the right atrium. In this report, we retrospectively review our experience with the use of a feasible transabdominal technique without any form of bypass or anticoagulation for safe removal of renal tumor involving the retrohepatic IVC. From 1988 to 1998, 132 patients with renal cell carcinoma underwent radical nephrectomies at the urology service of our hospital. Five patients (3.8%) had retrohepatic venous extension through the renal vein into the IVC. Our transabdominal approach was accomplished by complete mobilization of the liver, control of the hepatocaval connection, total vascular exclusion of the IVC without heparin administration, removal of the tumor thrombus, and primary closure of the longitudinal vena cavotomy. From our results, we found the transabdominal approach with total vascular exclusion of the IVC to be satisfactory, with no early deaths, acceptable morbidity, and a remarkable limitation of blood loss and transfusion requirements.

Adult↗
PubMed2000

Extraction of polychlorinated dibenzo-p-dioxins and dibenzofurans from solid samples using the Randall technique.

This study deals with a new sample extraction technique which minimizes pollution in analytical laboratories whilst reducing sample preparation time and cost. The device uses the Randall technique for solid sample extraction, performed by immersion of the sample in boiling solvent. The fast solubilization operated by the hot solvent leads to a sharp reduction in extraction time. This method was tested for the extraction of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) from different solid matrices using toluene as extractant, and compared with the conventional Soxhlet. The reduction in the extraction times (from 48 to 2 h) with an efficiency similar to or higher than that afforded by the conventional Soxhlet technique indicates the suitability of this method.

Benzofurans↗