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Biomedical subjects

A Rivas

Publications and source records attributed to A Rivas.

At least 19 recordsLinked to original sources
PubMed2007

Oestrogenicity of paper and cardboard extracts used as food containers.

Bisphenol-A (BPA), dibutyl phthalate (DBP), and di-2-ethylhexyl phthalate (DEHP), which are common chemical residues in food-packaging materials, were investigated in paper and cardboard containers used for take-away food. The oestrogenicity of aqueous extracts was tested in E-Screen bioassay and analysis carried out by high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC/MS). Oestrogenicity was demonstrated in 90% of extracts (geometric mean [GM] = 11.97 pM oestradiol equivalents g(-1)). DEHP, DBP, and BPA (GM = 341.74, 37.59, and 2.38 ng g(-1) of material) were present in 77.50, 67.50, and 47.50% of samples, respectively. In bivariate analyses, no significant association was found between the levels of these chemicals and oestrogenicity in cardboard/paper extracts. A close-to-significant association was found between oestrogenicity and DBP (beta = 1.25; p = 0.06) in paper extracts, which reached statistical significance in multivariate analysis (beta = 1.61; p = 0.03). Paper and cardboard used in food packaging may contribute to the inadvertent exposure of consumers to endocrine-disrupting chemicals.

Benzhydryl Compounds↗
PubMed2005

Clozapine prevents apoptosis and enhances receptor-dependent respiratory burst in human neutrophils.

The present study was undertaken to determine if the antipsychotic drug clozapine (CLZ) in the concentration range 2-50 microM can rescue polymorphonuclear cells (PMNs) from undergoing apoptosis. Our results indicate that 20 microM CLZ can rescue PMNs both from UVB-accelerated (28.0% vs. 45.9% for control without CLZ; P < 0.05) and from spontaneous (35.8% vs. 57.6%; P < 0.05) apoptosis whereas 50 microM CLZ could rescue PMNs from spontaneous (34.3% vs. 57.6%; P < 0.05) apoptosis only. Furthermore, since apoptosis has been reported to involve the impairment of PMN function, we evaluated the effects of CLZ on respiratory burst in UVB-irradiated and in unirradiated PMNs. When 20 or 50 microM CLZ-pretreated PMNs were aged in a culture during 4 h, the luminol-dependent chemiluminescence (CL) response was 3-fold (P < 0.01) and 2.5-fold (P < 0.05) increased, respectively, by subsequent exposure to serum opsonized zymosan (OZ). When 50 microM-pretreated PMNs were either UVB-irradiated or unirradiated, the CL response was 2.6-fold (P < 0.05) and 3.3-fold (P < 0.05) increased, respectively, after subsequent exposure to formyl-methionyl-leucyl-phenylalanine (fMLP). In contrast, the degree of enhancement was negligible upon subsequent exposure to ionomycin or phorbol myristate acetate (PMA). When incubation times were extended up to 22 h, the CL response induced by OZ in 20 microM CLZ-treated PMNs had a 4.9-fold increase (P < 0.001). This priming effect could be reverted when 20 microM CLZ-treated PMNs (aged 4 h in culture) were coincubated for 5 min with the protein tyrosine kinase inhibitor genistein as well as with the phosphatidylinositol 3-kinase (PI3-K) inhibitor wortmannin. These findings suggest that CLZ primes respiratory burst and prevents PMN apoptosis as a consequence of tyrosine phosphorylation- and PI3-K activation-dependent signal transduction pathways.

Androstadienes↗
PubMed2005

[Study of vascular access (VA) by color Doppler ultrasonography (CDU). Comparison between delta-H and CDU methods in measuring VA blood flow rate].

INTRODUCTION: The color Doppler ultrasonography (CDU) is a noninvasive vascular access (VA) monitoring technique that provides both structural and hemodynamic information from VA. On the other hand, the delta-H (AH) method is another noninvasive technique that measures the VA blood flow rate during hemodialysis (HD). OBJECTIVE: 1) To analyze some anatomic and functional parameters of VA by CDU. 2) To compare AH and CDU methods in measuring VA blood flow rate. PATIENTS AND METHODS: We explored the VA (radial arteriovenous fistula AVF 60.6%, brachial AVF 24.2%, femoral graft 15.2%; mean VA duration 33.5 +/- 31.5 months) of 33 stable ESRD (mean age 61.7 +/- 13.3 yr, sex M: 48.5%; F: 51.5%; mean time on hemodialysis HD 39.3 +/- 33.3 months; 9.1% diabetes) patients (pts) by CDU over 3 months period. All CDU examinations were performed off HD by the same radiologist using a 5-10 MHz linear transducer. The arterial and venous blood flow rates were calculated by CDU using the equation: flow (ml/min) = time average velocity (mean of three cardiac cycles) (m/s) x cross-sectional area (mm2) x 60. No VA explored had any sign of dysfunction prior to CDU evaluation. All pts with significant VA stenosis by CDU (> or = 50% reduction in the luminal diameter) were referred for angiography (AG). All functional parameters were measured in duplicate and the values were averaged. In addition, QA was also calculated in the same week by the deltaH method during HD using the Crit Line III Monitor. RESULTS: Feeding artery (FA) results. Mean FA diameter (FAd): 0.7 +/- 0.2 cm. Mean peak systolic velocity: 161.8 +/- 44.5 m/s. Mean FA blood flow rate (FA flow) (n = 27): 2,030.8 +/-987.1 ml/min. We found a positive correlation between mean FA flow and mean FAd (R2 = 0.39, p < 0.001). Arterialized vein (AV) results. Mean AV diameter (AVd): 0.7 +/- 0.2 cm. Mean AV blood flow rate (AVflow): 1,783.8 +/- 1,009.7 ml/min (range, 398-5,843 ml/min). Mean coefficient of variation for duplicate AV flow measurements: 9.2%. We found a positive correlation between mean AV flow and: mean FAd (R2 = 0.22, p = 0.005), mean FAflow (R2 = 0. 19, p = 0.022) and mean AVd (R2 = 0.14, p = 0.034). Three pts (9.1%) showed significant VA stenosis by CDU and in, all cases, the location and degree of stenoses were confirmed by AG. The mean AVflow was lower in VA with significant stenosis (511.0 +/- 179.1 ml/min) compared to VA without stenosis (1,911.1 +/- 968.7 ml/min) (p = 0.006). The calculated values of VA blood flow rate obtained by the CDU technique (AV flow) were highly correlated with those determined by the AH method (QA) when considering all comparison values (n = 33, ICC = 0.74, p < 0.0001), for AV flow < 2,000 ml/min (n = 23, ICC = 0.82, p < 0.0001) and for AV flow < 1,500 ml/min (n = 14, ICC = 0.73, p = 0.001). No significant difference was found when QA (1,593.8 +/- 645.7 ml/min, range 559-2,778 ml/min) and AV flow were compared (p = 0.082). CONCLUSIONS: 1) The CDU technique is a valuable and reproducible method for AV flow measurement and for early diagnosis of significant VA stenosis. 2) The AV flow is related to FA parameters. 3) Both methods, CDU and AH, correlated highly with each other when were applied on VA blood flow rate measurement.

Adult↗
PubMed2004

[The contribution of impression cytology towards the diagnosis of cicatricial ocular pemphigoid in its primary stages].

PURPOSE: To study the conjunctival epithelium by means of impression cytology in the cicatricial ocular pemphigoid (COP) in search of a possible relation between the degree of squamous metaplasia and clinical severity of the disease, in order to facilitate the earliest possible diagnosis. METHODS: Impression cytology specimens were collected from 20 patients with varying degrees of active COP. A clinical ophthalmologic examination was performed by biomicroscopy, impression cytology, conjunctival biopsy, study of direct (IFd) and of indirect immunofluorescence (IFi). RESULTS: Patients with COP grade I had a normal distribution of non-secretory epithelial cells with a decrease in goblet cell density of around 85% compared to control and mucin content was decrease. Patients with grade II showed a slight degree of squamous metaplasia. Goblet cell density decreased by around 95% and mucin content was scarce. Patients with clinical grade III had a moderate degree of squamous metaplasia in non-secretory cells whilst goblet cell density decreased by around 99%; mucin content was almost zero. Patients with clinical grade IV showed a moderate to severe degree of squamous metaplasia in non-secretory cells; there was a total absence of goblet cells. CONCLUSIONS: Conjunctival impression cytology in COP showed a significant decrease in goblet cells from the early stages of disease without significant alterations in non-secretory epithelial cells. In patients with negative IFd impression cytology could enable the identification of a possible COP.

Aged↗
PubMed2003

[Bone scintigraphy and somatostatin receptor scintigraphy in pediatric patients with bone involvement in Langerhans cell histiocytosis].

Langerhans cell histiocytosis (LCH) is a granulomatous disease which can involve multiples sites of the body. Diagnostic imaging is of utmost importance in the management of these patients. Up to now radiographic skeletal survey and bone scintigraphy (BS) have been used to assess bone involvement (both with low specificity). Magnetic resonance imaging (MRI) and CT have been used to assess visceral involvement but with the limitation that they cannot give information about the functional status. Recently somatostatin receptor scintigraphy (SSRS) has been proposed to detect active lesions and to monitor response to treatment. The aim of this study is to assess bone and somatostatin receptor scintigraphy in the detection of bone involvement in LCH in children. Twenty scintigraphies (12 SSRS and 8 BS) were performed in seven patients (3 girls and 4 boys) aged at diagnosis: 18 month-12 years (mean age 6 years). The findings obtained in the scintigraphies were compared with clinical evolution and other imaging techniques. Bone scintigraphy detected all the LCH bone lesions, and discovered one unknown lesion. SSRS scintigraphy visualised the active lesions in 3 patients (clinical and other imaging techniques were also positive). SSRS was negative in one patient classified as disease free and another in clinical remission. SSRS detected 2 new unknown bone lesions, but could not detect LCH bone lesions confirmed in other imaging techniques in 2 patients. Somatostatin receptor and Bone scintigraphy can be used to detect active LCH bone lesions in children and can help to monitor response to treatment. Further studies with more patients are needed to confirm the diagnostic usefulness of these techniques.

Biomarkers↗
PubMed2003

[Impression cytology study of dry eyes in patients with congenital aniridia].

PURPOSE: To evaluate the long-term results of ocular surface reconstruction by means of medical treatment, limbal transplantation or amniotic membrane transplantation in patients with congenital aniridia. MATERIAL AND METHODS: Thirty-six eyes from 18 consecutive patients with aniridia were studied by clinical tests (Schirmer test, break-up time and vital rose bengal staining) and impression cytology. Thirteen patients were treated with lubricant drops for ocular dryness. Two eyes from 2 patients also received limbal transplantation, and other 4 eyes underwent amniotic membrane transplantation. RESULTS: Corneal and conjunctival epithelium improved in all patients treated with lubricant drops. Ocular surface epithelium condition was worse in those patients not receiving artificial tears. After 12 months of limbal transplantation, clinical and morphological results showed a significant corneal recovery of at least two grades of squamous metaplasia in comparison with the previous situation. We also carried out amniotic membrane transplantation in patients with aniridia. The improvement was initially observed after 2 months and by the sixth month there was a significant improvement in clinical signs and symptoms, with normal corneal cells next to altered ones. CONCLUSIONS: All the aniridic patients showed dry eye. Treatment with lubricant drops is necessary to decrease the squamous metaplasia process. Limbal transplantation and amniotic membrane implantation are needed for effective corneal surface reconstruction in patients with aniridia, which is followed by a significant improvement of the dry eye.

Adolescent↗
PubMed2002

Physical and mechanical properties evaluation of Acropora palmata coralline species for bone substitution applications.

The search for ideal materials for bone substitution has been a challenge for many decades. Numerous natural and synthetic materials have been studied. For this application, exoskeletons of coral have been considered a good alternative given its tendency to resorption, biocompatibility and similarity to the mineral bone phase. Very few studies of these materials consider a detailed analysis of the structure-property relationship. The purpose of this work was to carry out the microstructural characterization of a coralline species named Acropora palmata and the determination of the mechanical and physico-chemical properties. Measurements of hardness, compressive strength, bulk density and apparent porosity were performed. From these results it was determined that this marine coral species could be an alternative xenograft due to its mechanical properties and osteoconductive nature.

Journal Article↗
PubMed2001

Altered peptide ligand vaccination with Flt3 ligand expanded dendritic cells for tumor immunotherapy.

Most tumor-associated antigens represent self-proteins and as a result are poorly immunogenic due to immune tolerance. Here we show that tolerance to carcinoembryonic antigen (CEA), which is overexpressed by the majority of lethal malignancies, can be reversed by immunization with a CEA-derived peptide. This peptide was altered to make it a more potent T cell antigen and loaded onto dendritic cells (DCs) for delivery as a cellular vaccine. Although DCs are rare in the blood, we found that treatment of advanced cancer patients with Flt3 ligand, a hematopoietic growth factor, expanded DCs 20-fold in vivo. Immunization with these antigen-loaded DCs induced CD8 cytotoxic T lymphocytes that recognized tumor cells expressing endogenous CEA. Staining with peptide-MHC tetramers demonstrated the expansion of CD8 T cells that recognize both the native and altered epitopes and possess an effector cytotoxic T lymphocyte phenotype (CD45RA(+)CD27(-)CCR7(-)). After vaccination, two of 12 patients experienced dramatic tumor regression, one patient had a mixed response, and two had stable disease. Clinical response correlated with the expansion of CD8 tetramer(+) T cells, confirming the role of CD8 T cells in this treatment strategy.

Adjuvants, Immunologic↗
PubMed2001

Human exposure to endocrine disrupters: standardisation of a marker of estrogenic exposure in adipose tissue.

In many epidemiological studies based on the direct measurement of exposure to organochlorines, the chemicals of concern are determined directly from adipose tissue samples. Although the measurement of all possible organochlorines, their metabolites, isomers and congeners may be desirable, it is expensive and time-consuming and many chemicals with hormonal activity may not yet have been identified. Testing systems are therefore required to screen for estrogenicity and to identify appropriate biomarkers of human exposure. To address this issue, we developed and standardised a method to assess the total estrogenic xenobiotic burden in human adipose tissue. The method extracts and separates the more lipophilic xenoestrogens from ovarian estrogens, with a subsequent bioassay determination of the cumulative effect of the xenoestrogens. It was applied to 400 women, using 200 mg of adipose tissue: 65% of samples showed measurable estrogenicity in the fraction where most non-polar xenoestrogens eluted, and 76% of fractions where ovarian estrogens eluted were positive for estrogenicity. Residues of 16 organochlorine pesticides were determined. No correlation was found between pesticide content and estrogenicity of the samples. The high percentage of positive samples suggests that the method is sensitive enough to be used as a biomarker of human exposure to estrogenic xenobiotics and can be applied in epidemiological studies.

Biomarkers↗
PubMed2001

Application of mathematical tools to improve the design and operation of activated sludge plants. Case study: the new WWTP of Galindo-Bilbao. Part I: Optimum design.

This paper presents a mathematical formulation for the optimum design of a new activated sludge WWTP. The WWTP optimum design problem has been formulated as a Mathematical Programming problem, which is solved through a nonlinear optimisation method. The plant model has been based on the ASM1. The minimum volume of the biological reactors and the minimum total cost (including construction and exploitation costs) have been considered as optimisation criteria. Some practical results are also included, using as a case study the design of the second stage of the Galindo-Bilbao WWTP.

Algorithms↗
PubMed2001

Application of mathematical tools to improve the design and operation of activated sludge plants. Case study: the new WWTP of Galindo-Bilbao. Part II: Operational strategies and automatic controllers.

This paper presents a new sensitivity analysis methodology for Activated Sludge WWTPs. It is based on both (a) the calculation of the range of "manipulated input variables" that satisfy the restrictions imposed on the "output variables" and (b) on the computation of isolines of the output variables inside the feasible operating space. This analysis allows a more precise description of the operating constraints, facilitates the understanding of the steady-state behaviour of the process and detects possible areas where the process is very sensitive to small disturbances. The feasible operating space for two Activated Sludge WWTP processes for CN removal (RDN, DRDN), using SRT and DO level as "input variables" as well as effluent quality and exploitation costs as the main "output variables" is studied. The proposed methodology facilitates the selection of the appropriate operational strategy and the design of automatic controllers. Some examples of the application of this methodology for the design of automatic controllers in a real WWTP are briefly presented.

Ammonia↗
PubMed2001

New simulators for the optimum management and operation of wastewater treatment plant.

This paper presents the basic description and the first full-scale implementation of a new kind of simulator specially designed to facilitate and improve the management and operation of modern wastewater treatment plants (WWTP). This new kind of simulator for plant operation is specifically adapted to every WWTP and the software is developed considering the common needs of the operators in plant exploitation. The internal structure of the plant operation simulator is based on a complete connection between the real data and the mathematical model of the plant. The software is then able to perform the processing, storage and management of the plant data and to predict the evolution of the process reading the required inputs from its stored files. The results obtained with the first application recommend the implementation of this new kind of simulators for plant operation in other treatment plants. However, it is important to note that the application of this technology implies a systematic and rigorous methodology in the acquisition and processing of the most significant plant data.

Data Collection↗
PubMed2000

Are myeloma patients with renal failure candidates for autologous stem cell transplantation?

INTRODUCTION: Renal function is one of the most important prognostic factors in multiple myeloma (MM). Patients with renal failure are generally excluded from high dose therapy even though they display a poor prognosis with conventional chemotherapy schemes. The aim of this study was to analyze the outcome of MM patients with renal insufficiency undergoing autologous stem cell transplantation (ASCT), including the evaluation of the quality of PB stem cell collections, kinetics of engraftment, transplant-related mortality, response to high dose chemotherapy and survival. MATERIALS AND METHODS: From a total of 566 valuable patients included in the MM Spanish ASCT registry, three groups of patients were defined: group BA, patients with abnormal renal function at diagnosis but normal at transplant (73 cases); group BB, patients with abnormal function both at diagnosis and at transplant (14 cases); and group AA (control group, 479 cases), patients who constantly had normal renal function. RESULTS AND CONCLUSION: Patients from groups BA and BB presented with a significantly higher number of adverse prognostic factors, reflecting that we were dealing with high tumor MM cases, as compared with patients from group AA. The number of mononuclear cells, CD34+ cells and CFU-GM cells collected in patients with non-reversible renal insufficiency was similar to those harvested in MM patients with normal renal function. Moreover, neutrophil and platelet engraftments were identical in patients with and without renal failure (days +11 and +12, respectively). By contrast, transplant-related mortality (TRM) was significantly higher in group BB patients (29%) than in groups BA (4.1%) and AA (3.3%). In multivariate analysis only three variables showed independent influence on TRM: poor performance status (ECOG 3), hemoglobin <9.5 g/dl and serum creatinine > or =5 mg/dl. The response to high dose therapy was independent of renal function. Interestingly, 43% of patients from group BB showed an improvement in renal function (creatinine < 2 mg/dl) after transplant. The three-year overall survival from transplantation was 56, 49 and 61% for the BB, BA and AA groups, respectively, with a statistically significant difference favoring group AA (P<0.01). PFS did not differ significantly between the three groups of patients. In multivariate analysis the only unfavorable independent prognostic factors for overall survival were poor performance status either at diagnosis or at transplant, high beta(2)-microglobulin levels, and no response to transplant. According to these results, ASCT is an attractive alternative for MM patients with renal insufficiency, and it should not constitute a criterion for exclusion from transplant unless patients display poor performance status and very high creatinine levels (>5 mg/dl).

Adult↗
PubMed2000

Determination of bisphenol A and related aromatic compounds released from bis-GMA-based composites and sealants by high performance liquid chromatography.

Most of the composites and sealants used in dentistry are based on bisphenol A diglycidylether methacrylate (Bis-GMA). Reports revealed that in situ polymerization is not complete and that free monomers can be detected by different analytic methods. Concerns about the estrogenicity of bisphenol A (BPA) and other aromatic components leached from commercial products have been expressed. We studied biphenolic components eluted from seven composites and one sealant before and after in vitro polymerization using HPLC and gas chromatography/mass spectrometry and we investigated how pH modifications affect the leaching of these components. We found BPA (maximal amount 1.8 microg/mg dental material), its dimethacrylate derivative (Bis-DMA, 1.15 microg/mg), bisphenol A diglycidylether (6. 1 microg/mg), Bis-GMA (2.0 microg/mg), and ethoxylate and propoxylate of bisphenol A in media in which samples of different commercial products were maintained under controlled pH and temperature conditions. Our results confirm the leaching of estrogenic monomers into the environment by Bis-GMA-based composites and sealants in concentrations at which biologic effects have been demonstrated in in vivo experimental models. The main issue with implications for patient care and dentist responsibility is to further determine the clinical relevance of this estrogenic exposure.

Benzhydryl Compounds↗