Biomedical subjects

M Pueyo

Publications and source records attributed to M Pueyo.

11 recordsLinked to original sources

PubMed2001

Certification of the extractable contents of Cd, Cr, Cu, Ni, Pb and Zn in a freshwater sediment following a collaboratively tested and optimised three-step sequential extraction procedure.

Sequential extraction procedures have been used during the last decades to study and determine trace element mobility in aquatic sediments. However, the results obtained are operationally defined and, therefore, the significance of the analytical results is related to the extraction scheme used. So, there is a need for suitable reference materials for this type of study to enable the validation of the methodologies and to control the quality of the measurements. This paper describes the preparation of a sediment reference material, BCR-701, the homogeneity and stability studies and the analytical work performed for the certification of the extractable contents of some trace elements, following a collaboratively tested and optimised sequential (three-step) extraction procedure. The paper contains all the results and gives the methods used to certify the extractable contents (mass fractions expressed as mg kg-1 on a dry matter basis) of Cd, Cr, Cu, Ni, Pb and Zn in all steps. Moreover, indicative values are given for the aqua regia extractable contents of the six elements in the sediment and the residue obtained after sequential extraction.

Chemistry Techniques, Analytical↗

PubMed2001

A new organic-rich soil reference material certified for its EDTA- and acetic acid- extractable contents of Cd, Cr, Cu, Ni, Pb and Zn, following collaboratively tested and harmonised procedures.

There is an increasing requirement for assessment of the bioavailable metal fraction and the mobility of trace elements in soils upon disposal. One of the approaches is the use of leaching procedures, but the results obtained are operationally defined; therefore, their significance is highly dependent on the extraction protocol performed. So, for this type of study, there is a need for reference materials that allow the quality of measurements to be controlled. This paper describes the steps involved in the certification of an organic-rich soil reference material, BCR-700, for the EDTA- and acetic acid-extractable contents of some trace elements, following collaboratively tested and harmonised extraction procedures. Details are given for the preparation of the soil, homogeneity and stability testing, analytical procedures and the statistical selection of data to be included in the certification.

Acetic Acid↗

PubMed2001

[Ciliary ablation with diode laser. Long-term study].

PURPOSE: The effects of contact transscleral cyclophotocoagulation with diode laser for refractory glaucoma have been analyzed. METHODS: A diode laser system was used to treat twenty one eyes with refractory glaucoma. The mean follow-up was 22.24+/-9.89 months. All the eyes were treated with 15 laser spots placed over 270 degrees, 1 mm posterior to the limbus, using 3.0 J (1.0 W X 3.0 sg). RESULTS: The mean preoperative intraocular pressure was 40.95+/-11.76 mmHg and the mean intraocular pressure at the end of the follow-up was 24.28+/-7.80 mmHg (p<0.5). An intraocular pressure below 21 mmHg was obtained in 10 out the 13 eyes (76.92%). Six of the 8 painful eyes had pain relief (75.00%). The principal complications included a decreased visual acuity in 5 eyes and chronic uveitis in 2 patients. CONCLUSIONS: These results suggest that semiconductor diode transscleral cyclophotocoagulation can be used successfully to reduce intraocular pressure in the treatment of refractory glaucoma.

Adult↗

PubMed1999

Endothelium-derived nitric oxide and vascular physiology and pathology.

In 1980, Furchgott and Zawadzki demonstrated that the relaxation of vascular smooth muscle cells in response to acetylcholine is dependent on the anatomical integrity of the endothelium. Endothelium-derived relaxing factor was identified 7 years later as the free radical gas nitric oxide (NO). In endothelium, the amino acid L-arginine is converted to L-citrulline and NO by one of the three NO synthases, the endothelial isoform (eNOS). Shear stress and cell proliferation appear to be, quantitatively, the two major regulatory factors of eNOS gene expression. However, eNOS seems to be mainly regulated by modulation of its activity. Stimulation of specific receptors to various agonists (e.g., bradykinin, serotonin, adenosine, ADP/ATP, histamine, thrombin) increases eNOS enzymatic activity at least in part through an increase in intracellular free Ca2+. However, the mechanical stimulus shear stress appears again to be the major stimulus of eNOS activity, although the precise mechanisms activating the enzyme remain to be elucidated. Phosphorylation and subcellular translocation (from plasmalemmal caveolae to the cytoskeleton or cytosol) are probably involved in these regulations. Although eNOS plays a major vasodilatory role in the control of vasomotion, it has not so far been demonstrated that a defect in endothelial NO production could be responsible for high blood pressure in humans. In contrast, a defect in endothelium-dependent vasodilation is known to be promoted by several risk factors (e.g., smoking, diabetes, hypercholesterolemia) and is also the consequence of atheroma (fatty streak infiltration of the neointima). Several mechanisms probably contribute to this decrease in NO bioavailability. Finally, a defect in NO generation contributes to the pathophysiology of pulmonary hypertension. Elucidation of the mechanisms of eNOS enzyme activity and NO bioavailability will contribute to our understanding the physiology of vasomotion and the pathophysiology of endothelial dysfunction, and could provide insights for new therapies, particularly in hypertension and atherosclerosis.

Animals↗

PubMed1998

[Effects of angiotensin ii on vascular remodeling].

Classically the AT1 receptors to angiotensin II are considered to be present on the smooth muscle cell membrane in the arterial wall, in which they diffusely regulate peripheral resistances. They are also present on numerous other cell types, including fibroblasts and myofibroblasts, monocytes and macrophages, endothelial cells, where they participate to the phenotypic modulation of the cell, involved in their activation leading to tissular remodeling. The intra-cellular pathway involving the phospholipase C activation and the mobilization of intra-cellular calcium is predominantly involved in the functional vasomotor response to angiotensin II. In contrast the intra-cellular signaling pathway leading to production of oxygen free radicals and activation of the NF-kappa-B system is probably mainly involved in the phenotypic modulation of target cells and their consequences on the vascular tissue remodeling.

Angiotensin II↗

PubMed1992

Relationship between the functional regions of the RecA protein and ATP hydrolysis in UV-irradiated Escherichia coli cells.

The time course of the intracellular ATP concentration in several UV-irradiated RecA protease constitutive (Cptc) mutants of E. coli has been studied. All Cptc mutants harboring a mutation in region 3 of the RecA protein (including amino acid residues 298-301) increased ATP after UV damage but without any subsequent decrease. Nevertheless, these mutants induced the SOS response after UV irradiation. Likewise, truncated RecA proteins lacking region 3 are also unable to carry out massive ATP hydrolysis in UV-irradiated cells. On the other hand, mutants in region 1 (including amino acids 25-39) or 2 (amino acids 157-184) of the RecA protein showed an increase in ATP concentration during the first 20 min following UV irradiation, which dropped afterwards to the basal level. All these data indicate that region 3 of the RecA protein must be involved in the ATP hydrolysis process. Furthermore, a relationship between the quantity of the UV-mediated ATP produced and the strength of the different RecA Cptc mutants has also been found. Accordingly, both lexA71::Tn5 and null lexA mutants of E. coli only show a cellular ATP increase after UV irradiation when containing a multicopy plasmid carrying either a wild-type lexA or a lexA (Ind-) gene.

Adenosine Triphosphate↗

PubMedDate not supplied

Semiconductor diode laser transscleral cyclophotocoagulation versus filtering surgery with Mitomycin-C.

Both filtering surgery with Mitomycin-C and diode laser cyclophotocoagulation have proved to be effective alternatives in cases of glaucoma with poor surgical prognosis. The right eyes of 40 pigmented rabbits were randomly divided into 2 groups: Mitomycin-C group underwent filtering surgery with application of 0.4 mg/ml of Mitomycin-C whereas the diode laser (DL) group received 15 applications of 1.8 J (1800 mW. 1000 ms) distributed in 270 degrees. Mean IOP showed statistical differences in two periods between days 3-13 and 45-60-Mann-Whitney U test -with a higher IOP lowering in the DL group. The comparison of IOP survival curves (Log-Rank test) was not significant p = 0.070809. Ocular hypertension, hyphema and inflammatory signs were higher in the DL group, both in short and long term, but in terms of statistical significance only ocular hypertension showed differences p = 0.00011717-Fisher exact test. Microscopic examination revealed patent sclerostomies in 60% of the MMC group eyes with different grades of fibroblastic proliferation. In the DL group we observed necrosis of the scleral stroma and of the pigmented and unpigmented ciliary epithelium, with signs of thermal coagulation of the ciliary stroma and of the stromal vasculature. We must point out that the treatment with laser has proved to be more effective although both treatments showed very acceptable IOP lowering until 2 months after the surgery.

Administration, Topical↗

PubMedDate not supplied

Assessment of diurnal tensional curve in early glaucoma damage.

We know very little about the relationship between the diurnal intraocular pressure variations and the progression of visual field loss. A prospective study of 149 eyes of 149 patients suffering from intraocular hypertension has been carried out through a minimum period of five years. At least 4 years before the appearance of field defects, we detected significant oscillations of IOP in the 64% of the cases prone to develop visual field loss. Likewise, we have found a statistically significant relationship between the presence of defects in the RNFL (retinal nerve fiber layer) and the existence of significant oscillations of IOP.

Circadian Rhythm↗

PubMedDate not supplied

Diode laser photocoagulation in retinopathy of prematurity.

We used diode laser photocoagulation to treat 22 eyes of 12 patients with retinopathy of prematurity. Three infants were followed for at least six months and nine for at least one year. We treated 14 eyes with threshold disease and 8 eyes with prethreshold disease. The treatment was administered within 72 hours of diagnosis and topical anesthesia and sedation were used. No evidence of lesions of the anterior segment of preretinal or vitreous hemorrhages was found after the treatment. External inflammatory signs were neglibible. Systemic complications occurred only in three treatment sessions. Eight of the 14 eyes with threshold disease (57%) and all eight eyes with prethreshold disease had favorable outcomes. In total 73% with ROP had favorable outcomes. Treatment with the diode laser is easily performed, effective essentially in cases of prethreshold disease but in threshold disease too, with minimal ocular or systemic complications.

Anesthesia, Local↗

PubMedDate not supplied

Long-term effects of postoperative subconjunctival injections of mitomycin-C in the rabbit eye.

AIM: Single or multiple subconjunctival injections of mitomycin-C (MMC) may offer one way of establishing the total dosage of MMC more accurately. The method also allows re-applications later postoperatively. In this experimental, randomized prospective study we compared the effects of a single intraoperative application of MMC at the filtering site and a single postoperative subconjunctival injection of the drug. METHODS: The left eyes of 32 pigmented rabbits were divided into two groups. In the first group we applied MMC intraoperatively (IO) with a 4 x 1 mm surgical sponge soaked in a MMC solution (0.5 mg/ml). In the second group we injected 0.4 ml of the same solution subconjunctivally (SC) immediately after (conjunctival) suture. Post-operative evaluation was carried out every day during the first week, then every three days until day 58. Survival analyses were done for intraocular pressure (IOP) and bleb failure. Log-rank tests were used to compare survival differences between the groups. RESULTS: The IO group showed longer survival parameters than the SC group (p < 0.05), both in the control of IOP and as regards blebs. The histological persistence of fistulas was similar. The IO group, however, had a higher incidence of undesirable side effects. CONCLUSIONS: Our findings suggest IO application of MMC is more effective in reducing fibroblast ingrowth. However, subconjunctival application offers certain advantages such as the possibility of repeating the treatment postoperatively and, therefore, using a smaller initial dose.

Animals↗

PubMedDate not supplied

Prediction of trace element mobility in contaminated soils by sequential extraction.

The modified three-step sequential extraction procedure proposed by the Community Bureau of Reference (or Bureau Communautaire de Reference, BCR) was used to predict trace element mobility in soils affected by an accidental spill comprising arsenopyrite- and heavy metal-enriched sludge particles and acid waste waters. The procedure was used to obtain the distribution of both the major (Al, Ca, Fe, Mg, and Mn) and trace elements (As, Bi, Cd, Cu, Pb, Tl, and Zn) in 13 soils of contrasting properties with various levels of contamination and in the sludge itself. The distributions of the major elements enabled us to confirm the main soil fractions solubilized in each of the three steps, and, in turn, to detect the presence of pyritic sludge particles by the high Fe extractability obtained in the third step. Cadmium was identified as being the most mobile of the elements, having the highest extractability in the first step, followed by Zn and Cu, Lead, Tl, Bi, and As were shown to be poorly mobile or nonmobile. In the case of some of the trace elements, the residual fractions decreased at higher levels of contamination, which was attributed to the anthropogenic contributions to the polluted samples. Comparison with soil-plant transfer factors, calculated in plants growing in the affected area, indicated that a relative sequence of trace element mobility was well predicted from data of the first step.

Accidents↗