Biomedical subjects

J Rivera

Publications and source records attributed to J Rivera.

At least 37 records · Page 2Linked to original sources

PubMed2003

An episode of dioxin contamination in feedingstuff: the choline chloride case.

In 2000, as part of a survey programme, the German authorities detected high levels of dioxins in a choline chloride (CC) premix used as animal food component. The contaminated additive consisted of different products of mineral and vegetable origin acting as a carrier. The CC was manufactured in Belgium. The final product was produced in and distributed from a plant in Spain. The German authorities informed all European Community members of the incident. The Spanish Ministry of Agriculture, Fisheries and Food and the Regional Authorities immediately conducted a survey in collaboration with the Spanish Council for Scientific Research (CSIC) to determine and isolate the source of the contamination. Analysis of a large number of samples of pure CC, pine sawdust, almond shell and other substances currently used in the preparation of the premix confirmed the presence of a significant amount of polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans in mixtures in which pine sawdust was present. An analysis of the congener profiles revealed similarities with those found in technical pentachlorophenol (PCP) formulations. The conclusion was that PCP-contaminated sawdust as carrier for CC was source of dioxin contamination in feedingstuff.

Animal Feed↗

PubMed2003

Study on PCBs, PCDD/Fs, organochlorine pesticides, heavy metals and arsenic content in freshwater fish species from the River Turia (Spain).

In this study samples of common trout, European eel and barbel have been analysed for the levels of heavy metals such as lead (Pb), cadmium (Cd), zinc (Zn), copper (Cu), and the metalloid arsenic (As). Polychlorinated biphenyls (PCBs), including three non-ortho substituted PCBs, 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and DDT and its two main metabolites were also analysed in some selected samples, in order to evaluate the extent of contamination of the River Turia basin. All samples presented detectable levels of the elements analysed, presenting zinc the highest concentrations. European eel was the species found to highly accumulate these contaminants. Regarding organochlorinated compounds, seven samples exhibited detectable levels of the most toxic PCDD/Fs congener, the 2,3,7,8-TCDD. Non-ortho PCBs were not detected or not quantified in almost all samples and the sum of the individual PCB congeners determined were low compared to other aquatic ecosystems with similar fish species.

Animals↗

PubMed2002

Toxic potency of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and polychlorinated biphenyls in food samples from Catalonia (Spain).

A surveillance program on polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs) in 29 foodstuff samples produced all over the four provinces in Catalonia (Spain) is presented. The study included the analyses of milk, egg, meat (beef, chicken, and pork), mussel, and olive oil samples. A previously developed method for the simultaneous analysis of the 2,3,7,8-substituted PCDDs/PCDFs and the dioxin-like PCBs, as well as the indicator PCBs, was employed. Total toxicity equivalent (TEQ) values were calculated using the toxicity equivalent factors (TEFs) proposed by the World Health Organization (WHO) for dioxin-like PCBs, PCDDs, and PCDFs. The TEQ(PCDD/F) levels were below the limits proposed in the draft of the EC regulation for food commercialization in the European countries. These limits are the following: 2 pg WHO-TEQ/g fat for pork, 3 pg WHO-TEQ/g fat for milk and chicken, 5 pg WHO-TEQ/g fat for egg and beef, and 3 pg WHO-TEQ/g whole product for fish. The contributions of PCDDs/Fs and dioxin-like PCBs in the total toxicity of the samples were calculated for each matrix. The results showed that the TEQ(PCB) contribution varied from 27% in olive oil samples to 81% in mussel samples. These findings suggest that the regulation of TEQ contents in food should include not only the TEQ(PCDD/F), but also the TEQ(PCB).

Adipose Tissue↗

PubMed2002

Degradation of polyethoxylated nonylphenols in a sewage treatment plant. Quantitative analysis by isotopic dilution-HRGC/MS.

Polyethoxylated alkylphenols (APnEO, where n is the number of ethylene oxide molecules), are non-ionic surfactants widely used for domestic and industrial purposes. Most of APnEO are polyethoxylated nonylphenols (NPnEO). NPnEO are widespread environmental pollutants with relatively low toxicity for mammals and higher toxicity for aquatic organisms. In addition, they have been described as endocrine disrupters in recent publications. One of the main problems related to these surfactants is their uncomplete degradation, even in the most effective sewage treatment plants. Usually, the final products, more toxic and resistant to biological degradation than NPnEO, are nonylphenol (NP), monoethoxylated nonylphenol (NP1EO), diethoxylated nonylphenol (NP2EO), nonylphenoxy acetic acid (NP1EC), and nonylphenoxyethoxy acetic acid (NP2EC). In this paper, the degradation of NPnEO was studied in the different processes of a sewage treatment plant. For this purpose, NP, NP1EO and NP2EO were analysed in composite samples collected at different points along the plant (influent, pre-treatment effluent, primary effluent, plant effluent). Analyses were carried out by isotopic dilution-HRGC/MS, using available labelled nonylphenols (13C6-NP, 13C6-NP1EO, 13C6-NP2EO) as internal standards. Extraction of NPnEO from aqueous samples, previous to analysis, was performed by the Likens-Nickerson method (simultaneous steam distillation/solvent extraction, SDE).

Biodegradation, Environmental↗

PubMed2002

Determination of PCDDs and PCDFs in different animal feed ingredients.

As result of a study to control feedstuff, analyses were carried out to evaluate the contamination caused by PCDDs and PCDFs in different animal feed ingredients. Thirty two samples were selected, including ingredients of animal and mineral origin. For samples of mineral origin, some additives widely employed as binder and anticaking agents, such as bentonite, damoline, kaolin, magnesite, sepiolite and zeolite were selected. And, for ingredients of animal origin, samples of hemoglobin, animal fat, fish oil, fish meal and meat and bone meal were analyzed. The levels ranged from 0.52 to 9.08 pg WHO-TEQ/g fat for samples of animal origin, and from 0.05 to 460.59 pg WHO-TEQ/g for samples of mineral origin. The higher concentrations were observed for the kaolin samples that presented high levels of dioxin contamination.

Animal Feed↗

PubMed2002

PCDD/F levels in the neighbourhood of a municipal solid waste incinerator after introduction of technical improvements in the facility.

In 1998 and 1999, the concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were determined in soil and herbage samples collected in the vicinity of an old municipal solid waste incinerator (MSWI) (S. Adrià del Besòs, Barcelona, Spain). Just after the 1999 collection, an adaptation to the EU legislation on pollutant emissions from the stack was carried out in this facility. The purpose of the present study was to determine the current concentrations of PCDD/Fs in soil and herbage samples collected in the neighbourhood of the MSWI and to compare these concentrations with those obtained in the 1998 and 1999 surveys. During the period 1998-1999, an increase of 31% (P>.05) was found in the median PCDD/F levels in soils, while a reduction of 40% (P>.05) was observed in the period 1999-2000. Similarly, in the period 1998-1999 an increase of 41% (P>.05) was found in the levels of PCDD/Fs in vegetation, while a 30% decrease (P<.05) was seen in the period 1999-2000. Although after introduction of the technical improvements in the MSWI a notable reduction in the levels of PCDD/Fs in soil and vegetation has been noted, the median decreases have not been as great as it could be expected according to the very pronounced reductions in PCDD/F emissions from the stack. It indicates that other emission sources of PCDD/Fs also have a notable impact on the area under direct influence of the MSWI.

Benzofurans↗

PubMed2002

Platelet aggregation through prothrombinase activation induced by non-aggregant doses of platelet agonists.

Activation of the prothrombinase complex, which catalyzes the formation of thrombin from prothrombin, is crucial for the (patho)physiological processes of hemostasis and thrombosis. We here report that washed platelets supplemented with prothrombin can be irreversibly aggregated with otherwise non-aggregant doses of adenosine diphosphate (10 micromol/l), thrombin (0.06 U/ml), or collagen (1 microg/ml). Prothrombinase-catalyzed prothrombin to thrombin conversion most probably supports this aggregation response, since inhibitors of thrombin (hirudin or heparin) and an inhibitor of activated factor X (DX-9065a) impair the response. A certain degree of agonist-induced platelet activation seems to be required for this prothrombin-supported aggregation response, since prothrombin alone does not induce aggregation, and blockade of glycoprotein Ia/IIa with a specific antibody inhibits the platelet aggregation response to collagen and prothrombin. These results may suggest that activation of the prothrombinase complex could be a common step of the platelet response to distinct agonists, which may be achieved at low levels of platelet stimulation.

Adenosine Diphosphate↗

PubMed2001

Toxic potency assessment of non- and mono-ortho PCBs, PCDDs, PCDFs, and PAHs in northwest Mediterranean sediments (Catalonia, Spain).

Forty-five marine sediments from the Catalonian coast were analyzed for non-ortho and mono-ortho chlorine substituted PCB congeners, PCDDs and PCDFs, and 16 PAHs. Concentrations of total PCBs ranged from 1.1 to 311 ng/g dry weight (d.w.), and the levels of the sum of the 16 PAHs analyzed ranged between 13.4 ng/g d.w. and 16.7 microg/g d.w. The PCB and PAH contamination was greater near the sites of urban and industrial impact. Total toxicity equivalent (TEQ) values were calculated using the toxicity equivalent factors (TEFs) proposed by WHO for dioxin-like PCBs, PCDDs, and PCDFs. These levels ranged between 0.03 and 24.8 pg WHO-TEQ/g d.w. for PCBs and from 0.4 to 39.2 pg WHO-TEQ/g d.w. for PCDDs/PCDFs. Therefore, the suggested sediment quality guideline was sometimes exceeded. Moreover, TEA values were calculated for PAH concentrations, applying different TEFs proposed by the literature. The results obtained were between 0.3 pg TEQ/g d.w. and 18.4 ng TEQ/g d.w. and showed that the TEQ(PCDD/F) and TEQ(PCB) values were several times lower than the TEQ(PAH) values in the marine sediment samples investigated.

Benzofurans↗

PubMed2001

IgE receptor type I-dependent regulation of a Rab3D-associated kinase: a possible link in the calcium-dependent assembly of SNARE complexes.

Following activation through high affinity IgE receptors (FcepsilonRI), mast cells release, within a few minutes, their granule content of inflammatory and allergic mediators. FcepsilonRI-induced degranulation is a SNARE (soluble N-ethylmaleimide attachment protein receptors)-dependent fusion process. It is regulated by Rab3D, a subfamily member of Rab GTPases. Evidence exists showing that Rab3 action is calcium-regulated although the molecular mechanisms remain unclear. To obtain an understanding of Rab3D function we have searched for Rab3D-associated effectors that respond to allergic triggering through FcepsilonRI. Using the RBL-2H3 mast cell line we detected a Ser/Thr kinase activity, termed here Rak3D (from Rab3D-associated kinase), because it was specifically co-immunoprecipitated with anti-Rab3D antibody. Rak3D activity, as measured by its auto- or transphosphorylation, was maximal in resting cells and decreased upon stimulation. The down-regulation of the observed activity was blocked with EGTA, but not with other degranulation inhibitors, suggesting that its activity functions downstream of calcium influx. We found that Rak3D phosphorylates the NH(2)-terminal regulatory domain of the t-SNARE syntaxin 4, but not syntaxin 2 or 3. The phosphorylation of syntaxin 4 decreased its binding to its partner SNAP23. Thus, we propose a novel phosphorylation-dependent mechanism by which Rab3D controls SNARE assembly in a calcium-dependent manner.

Animals↗

PubMed2001

Suitability of several carbon sorbents for the fractionation of various sub-groups of toxic polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans.

Feasibility of several sorbents, Amoco PX-21, Carbosphere, Carbopack B and C and 2-(1-pyrenyl) ethyldimethylsilylated silica gel (PYE), for the fractionation of polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins and furans was investigated. Selection was based on their suitability for quantitative isolation of the target compounds with special attention for the most toxic mono- and non-ortho-CBs to prevent coelution with other congeners during the final determination by gas chromatography. Cost-effectiveness in terms of solvent and time consumption as well as feasibility for routine analysis and automation were considered additional merits of the methods compared. Final evaluation of the procedures providing the best results was done by comparison of the results obtained from the analysis of real-life samples. The results showed that, among the sorbents tested, Carbopack B and PYE were the most suitable for routine analysis. In particular, these sorbents allowed a more reliable determination of the toxic congeners and, consequently, of the toxic equivalents of 2,3,7,8-tetrachlorodibenzo-p-dioxin content in environmental samples.

Benzofurans↗

PubMed2001

Protection of rabbits against rabbit hemorrhagic disease virus by immunization with the VP60 protein expressed in plants with a potyvirus-based vector.

A new plum pox potyvirus (PPV)-based vector has been constructed for the expression of full-length individual foreign proteins. The foreign sequences are cloned between the NIb replicase and capsid protein (CP) cistrons. The heterologous protein is split from the rest of the potyviral polyprotein by cleavage at the site that originally separated the NIb and CP proteins and at an additional NIa protease recognition site engineered at its amino-terminal end. This vector (PPV-NK) has been used to clone different genes, engendering stable chimeras with practical applications. We have constructed a chimera expressing high levels of jellyfish green fluorescent protein, which can be very useful for the study of PPV molecular biology. The VP60 structural protein of rabbit hemorrhagic disease virus (RHDV) was also successfully expressed by making use of the PPV-NK vector. Inoculation of extracts from VP60-expressing plants induced a remarkable immune response against RHDV in rabbits, its natural host. Moreover, these animals were protected against a lethal challenge with RHDV.

Amino Acid Sequence↗

PubMed2001

Evaluation of an automated clean-up system for the isotope-dilution high-resolution mass spectrometric analysis of PCB, PCDD, and PCDF in food.

An automated clean-up system was evaluated for the simultaneous analysis of polychiorinated dibenzo-p-dioxins (PCDD), dibenzofurans (PCDF), and biphenyls (PCB) in different foods. In addition to the seventeen 2,3,7,8-substituted PCDDIPCDF and four non-ortho PCB, by use of the clean-up system studied, it was possible to collect the eight mono-ortho and two di-ortho PCB and the seven indicator PCB in two separate fractions during the same clean-up run. The study was first performed using standard mixtures containing PCDD, PCDF and PCB, and a certified reference material. The recoveries of the 13C-labeled compounds ranged from 51 to 90%, indicating that the PCDD, PCDF, and PCB clean-up worked satisfactorily. Next, the automated system for PCDD, PCDF, and PCB analysis was evaluated for foods such as milk, egg, meat (beef, chicken, and pork), mussel, and olive oil. The recoveries of the 13C-labeled compounds ranged from 40 to 120% for PCB and from 57 to 113% for PCDD/ PCDF, meeting the requirements of well accepted methods. Thus, the automated clean-up system studied is a suitable alternative to conventional clean-up methods.

Automation↗

PubMed2001

Evaluation of dioxin contamination in sewage sludge discharges on coastal sediments from Catalonia, Spain.

The fate of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) in sewage sludges after discharge into the sea was investigated. Sediment samples were analysed at a sewage sludge disposal site as well as in the surrounding areas. Moreover, eight sediment samples from two rivers in Catalonia and three sediment samples from Catalonian Coast were analysed to determine the background levels of contamination. Total international toxicity equivalent (I-TEQ) values for these sediments ranged from 0.42 to 8.01 pg g, with a mean value of 4.15 pg/g and a median value of 3.69 pg/g. However, the I-TEQ values of sludge-treated areas were higher: 57.04 pg/g at the dumping site, and within a range of 13.42-47.76 pg/g near this site. Thus, European sediment quality objectives were exceeded. The higher concentrations coincided with changes in the ratio between PCDD and PCDF levels, suggesting the influence of the sewage sludge on coastal sediments.

Benzofurans↗

PubMed2001

PCDD/F concentrations in soil and vegetation in the vicinity of a municipal waste incinerator after a pronounced decrease in the emissions of PCDD/Fs from the facility.

Emission of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) by municipal solid waste incinerators (MSWI) is an issue of great concern. In 1997, an adaptation to the EU legislation on pollutant emissions from the stack was carried out in an MSWI from Tarragona (Catalonia, Spain). As a result, PCDD/F emissions were significantly reduced. The aim of this study was to determine the current levels of PCDD/Fs in soil and vegetation samples collected near the facility and to compare these levels with those obtained in previous surveys (1996 and 1997). In the period 1997-1999, PCDD/F concentrations in vegetation samples were significantly decreased (60%). By contrast, the levels of PCDD/Fs in soil samples increased slightly (14%, P > 0.05) during the same period. An exhaustive analysis of the present data indicates that other emission sources of PCDD/Fs have also a notable environmental impact on the area under direct influence of the MSWI.

Air Pollution↗

PubMed2001

Levels of polychlorinated dibenzo-p-dioxins and dibenzofurans in soil samples from Spain.

Soil analyses were carried out to evaluate the contamination caused by PCDDs and PCDFs in different soil samples. Monitoring was undertaken at different locations throughout Spain, from 1993 to 1999. A total of 230 samples were analysed. The levels ranged from 0.10 pg I-TEQ/g to 1.08 ng I-TEQ/g. Differences in dioxin levels were observed as a function of the sampling site, with levels at the industrial sites exceeding those at the control sites.

Benzofurans↗

PubMed2001

Polymorphisms of P-selectin glycoprotein ligand-1 are associated with neutrophil-platelet adhesion and with ischaemic cerebrovascular disease.

P-selectin glycoprotein ligand (PSGL-1) shares common features with platelet glycoprotein Ibalpha. A recently described polymorphism in this receptor that results in a variable number of tandem repeats (VNTR) sequence present either 16, 15 or 14 times (alleles A, B or C) could, similar to GPIbalpha, be functionally relevant. The allelic frequency of this polymorphism was investigated in 469 individuals from the south of Spain, and was similar to that previously described in other Caucasian populations: 85% A, 14% B and 1% C alleles. We identified two new polymorphisms genetically linked to the C isoform, resulting in the Ser273Phe and Met274Val changes. To assess the functional consequence of the polymorphisms in the receptor, we performed flow cytometric analysis of P-selectin dependent neutrophil-platelet interaction. Neutrophils carrying the shortest C allele and the amino acid variations in residues 273 and 274 exhibited a significantly lower capacity to bind activated platelets than A/B and A/A samples (mean fluorescence intensity of CD42b+ neutrophils 262 versus 303 and 319 respectively, P < 0.05). The distribution of the VNTR was analysed in three case-control studies including 104 cerebrovascular (CVD), 101 coronary heart disease (CHD) and 150 deep venous thrombosis (DVT) patients. The results showed that smaller (B and C) alleles seem to be associated with a lower risk of developing CVD (P = 0.008) but not to be related to CHD or DVT. In conclusion, polymorphisms of the PSGL-1 receptor may influence the neutrophil-platelet binding, and represent a risk factor for CVD.

Adolescent↗

PubMed2001

Identification and characterization of the Cryptococcus neoformans phosphomannose isomerase-encoding gene, MAN1, and its impact on pathogenicity.

The polysaccharide capsule surrounding Cryptococcus neoformans comprises manose, xylose and glucuronic acid, of which mannose is the major constituent. The GDP-mannose biosynthesis pathway is highly conserved in fungi and consists of three key enzymes: phosphomannose isomerase (PMI), phosphomannomutase (PMM) and GDP-mannose pyrophosphorylase (GMP). The MAN1 gene, encoding for the PMI enzyme, was isolated and sequenced from C. neoformans, and a disruption of the MAN1 gene was generated. One MAN1 disruption mutant, man1, which showed poor capsule formation, reduced polysaccharide secretion and morphological abnormalities, was chosen for virulence studies. In both the rabbit and the mouse models of invasive cryptococcosis, man1 was shown to be severely impaired in its virulence, with complete elimination of the yeast from the host. A reconstituted strain of man1 was constructed using gene replacement at the native locus. The wild-type and reconstituted strains were significantly more virulent than the knock-out mutant in both animal models. Our findings reveal that PMI activity is essential for the survival of C. neoformans in the host. The fact that the man1 mutant was not pathogenic suggests that blocking mannose synthesis could be fungicidal in the mammalian host and thus an excellent target for antifungal drug development.

Amino Acid Sequence↗

PubMed2001

Role of facet joints in chronic low back pain in the elderly: a controlled comparative prevalence study.

Evaluation of the age related prevalence of persistent low back pain has been estimated to be consistently higher in the elderly compared to the younger population. Facet joints have been shown to be the cause of chronic low back pain in 15% to 45% of the patients in controlled studies. Prevalence of facet joint mediated pain has not been studied in the elderly. The study population consisted of 100 patients. Group I consisted of 50 patients that were 64 years of age or younger. Group II consisted of 50 patients 65 years of age or older. The patients were randomly allocated into 1 of the 2 groups. Facet joints were investigated with diagnostic blocks initially using lidocaine 1% followed by bupivacaine 0.25%, usually 2 weeks apart. The prevalence of facet joint mediated pain was determined to be 30% in the adults and 52% in the elderly, which was significantly higher with a false positive rate of 26% in adults and 33% in the elderly. In conclusion, the results of this study show that facet joint mediated pain is a significant problem in all patients suffering with chronic low back pain with the prevalence of 52% in the elderly and 30% in adults.

Journal Article↗