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Biomedical subjects

R Méndez

Publications and source records attributed to R Méndez.

At least 19 recordsLinked to original sources
PubMed2006

Patterns of constitutive and IFN-gamma inducible expression of HLA class II molecules in human melanoma cell lines.

Major histocompatibility complex (MHC) class II proteins (HLA-DR, HLA-DP and HLA-DQ) play a fundamental role in the regulation of the immune response. The level of expression of human leukocyte antigen (HLA) class II antigens is regulated by interferon-gamma (IFN-gamma) and depends on the status of class II trans-activator protein (CIITA), a co-activator of the MHC class II gene promoter. In this study, we measured levels of constitutive and IFN-gamma-induced expression of MHC class II molecules, analysed the expression of CIITA and investigated the association between MHC class II transactivator polymorphism and expression of different MHC class II molecules in a large panel of melanoma cell lines obtained from the European Searchable Tumour Cell Line Database. Many cell lines showed no constitutive expression of HLA-DP, HLA-DQ and HLA-DR and no IFN-gamma-induced increase in HLA class II surface expression. However, in some cases, IFN-gamma treatment led to enhanced surface expression of HLA-DP and HLA-DR. HLA-DQ was less frequently expressed under basal conditions and was less frequently induced by IFN-gamma. In these melanoma cell lines, constitutive surface expression of HLA-DR and HLA-DP was higher than that of HLA-DQ. In addition, high constitutive level of cell surface expression of HLA-DR was correlated with lower inducibility of this expression by IFN-gamma. Finally, substitution A-->G in the 5' flanking region of CIITA promoter type III was associated with higher expression of constitutive HLA-DR (p<0.005). This study yielded a panel of melanoma cell lines with different patterns of constitutive and IFN-gamma-induced expression of HLA class II that can be used in future studies of the mechanisms of regulation of HLA class II expression.

Alleles↗
PubMed2006

Start-up of the Anammox process in a membrane bioreactor.

The start-up of an Anammox process was studied in a membrane sequencing batch reactor (MSBR) in which a submerged hollow fibre membrane module was used to retain the biomass. The reactor was seed with Anammox biomass and fed using the Van de Graaf medium. During a first operating stage, salt precipitation was observed and interfered with microbial activity and caused a decrease of the nitrogen removal rate of the reactor from 100 to only 10 mgl(-1) per day. Salt precipitation was avoided by diminishing adequately the Ca and P concentrations of the Van de Graaf medium during the last operating stage. This action increased quickly the activity of the system, and nitrogen removal rate reached up to 710 mgl(-1) per day with almost full nitrite removal. Sporadic flotation of the sludge was observed in the MSBR. The use of the membrane avoided biomass wash-out from the system. Moreover, a surprising fact was that Anammox biomass did not grow in flocs in the MSBR, but in granules. This fact showed that this kind of microorganisms have a trend to grow in aggregates. Results indicated that the use of the MSBR could be a suitable system for nitrogen removal by using the Anammox reaction.

Ammonia↗
PubMed2006

Effects of mechanical stress on Anammox granules in a sequencing batch reactor (SBR).

The effect of shear stress on Anammox process was studied in a sequencing batch reactor (SBR). The reactor was operated during 218 days under different stirring speeds (60-250 rpm) in order to expose the system to different shear conditions and to study the stability of the Anammox granules referred to their biological activity and size. The nitrogen loading rate (NLR) fed to the SBR was kept around 0.3g N(L day)(-1). The nitrite (limiting substrate) removal percentage was 98% during most of the operational period. The specific Anammox activity of the biomass was practically constant and around 0.4 g N(g VSSday)(-1) and the average feret diameter of the formed granules was 0.64 mm. Obtained results indicated that stirring speeds up to 180 rpm have no negative effect on the performance of the Anammox process, whereas Anammox activity decreased to 40% when a rotating speed of 250 rpm was tested and the average diameter decreased in 45%, the concentration of solids in the effluent increased to 0.2g TSSL(-1) and nitrite was accumulated in the reactor up to 60 mg NL(-1).

Anaerobiosis↗
PubMed2006

Anammox process for nitrogen removal from anaerobically digested fish canning effluents.

The Anammox process was used to treat the effluent generated in an anaerobic digester which treated the wastewater from a fish cannery once previously processed in a Sharon reactor. The effluents generated from the anaerobic digestion are characterised by their high ammonium content (700-1000 g NH4+ -Nm(-3)), organic carbon content (1000-1300 g TOCm(-3)) and salinity up to 8,000-10,000 g NaCl m(-3). In the Sharon reactor, approximately 50% of the NH4+ -N was oxidised to NO2- -N via partial nitrification. The effluent of the Sharon step was fed to the Anammox reactor which treated an averaged nitrogen loading rate of 500 g N m(-3) x d(-1). The system reached an averaged nitrogen removal efficiency of 68%, mainly limited due to the nonstoichiometric relation, for the Anammox process, between the ammonium and nitrite added in the feeding. The Anammox reactor bacterial population distribution, followed by FISH analysis and batch activity assays, did not change significantly despite the continuous entrance to the system of aerobic ammonium oxidisers coming from the Sharon reactor. Most of the bacteria corresponded to the Anammox population and the rest with slight variable shares to the ammonia oxidisers. The Anammox reactor showed an unexpected robustness despite the continuous variations in the influent composition regarding ammonium and nitrite concentrations. Only in the period when NO2- -N concentration was higher than the NH4+ -N concentration did the process destabilise and it took 14 days until the nitrogen removal percentage decreased to 34% with concentrations in the effluent of 340g NH4+ -N m(-3) and 440 g NO2- -N m(-3), respectively. Based on these results, it seems that the Sharon-Anammox system can be applied for the treatment of industrial wastewaters with high nitrogen load and salt concentration with an appropriate control of the NO2- -N/NH4+ -N ratio.

Anaerobiosis↗
PubMed2006

[Platelet-rich plasma (platelet gel) in secondary alveoloplasty in cleft patients].

INTRODUCTION: The use of Platelet-rich plasma (platelet gel--PRP--) was introduced in the oral and maxilofacial surgery 10 years ago. Its good results are due to the quickly generation of new bone and the acceleration of the period of surgical scar formation. Its employment in the alveolar reconstruction of the cleft patient is not still consistent and the works published in the literature are infrequent. The objective of this preliminary study is presenting our experience with the use of PRP in the reconstruction of the alveolar congenital defects of cleft patients. PATIENTS AND METHODS: Between July 2002 and January 2004 were operated 14 patients with congenital alveolar cleft carrying out an standard secondary alveoloplasty. In 12 cases was employed cancellous bone of iliac crest and in two cases the donor area was tibial. The laboratory of Hematology of our Hospital prepared the plasma gel rich in platelets by means of a double centrifuge of autologous serum of the patient. After adding calcium a rich gel in platelets in approximate quantities of 1-2 ml was obtained. In this preliminary report we have studied the aspect of the surgical injury the 3er postoperative day, and the first and second weeks after intervention. These results were compared carried out previously with the Standard alveoloplasty without use of the PRP. Likewise we evaluated the bony density by means of intraoral Rx at 3 and 6 months postoperative. RESULTS: The injury of the alveoloplasty healed more quickly in the patients in which plasma enriched gel was employed. The patients referred less pain and edema in the first days of the postoperative period. The alveolar bony regeneration was faster to the 3 months, though the result was similar in the intraoral Rx to the 6 months. The necessary quantities of cancellous bone were smaller in all cases in which the plasma enriched gel was used (30% less). CONCLUSIONS: The use of Platelet-rich plasma (PRP) is a valid protocol for the reconstruction in patients with congenital alveolar clefts. Its low price and morbidity do it recommendable for its employment in cleft patients.

Alveolar Process↗
PubMed2005

Study of the neutron field in the vicinity of an unshielded PET cyclotron.

The neutron field in the proximity of an unshielded PET cyclotron was investigated during 18F radioisotope production with an 18 MeV proton beam. Thermoluminescent detector (TLD) models TLD600 and TLD700 as well as Bonner moderating spheres were irradiated at different positions inside the vault room where the cyclotron is located to determine the thermal neutron flux, neutron spectrum and dose equivalent. Furthermore, from a combination of measurements and Monte Carlo simulations the neutron source intensity at the target was estimated. The resulting intensity is in good agreement with the IAEA recommendations. Neutron doses derived from the measured spectra were found to vary between 7 and 320 mSv per 1 microA h of proton-integrated current. Finally, gamma doses were determined from TLD700 readings and amounted to around 10% of the neutron doses.

Cyclotrons↗
PubMed2004

Stability of the ANAMMOX process in a gas-lift reactor and a SBR.

In the last years, the ANAerobic AMMonium OXidation (ANAMMOX) process has been put forward as a promising alternative to treat ammonium rich wastewaters. An ANAMMOX gas-lift reactor and a sequential batch reactor (SBR) were operated during around 200 days in this study, reaching nitrogen loading rates (NLRs) of 2.0 and 0.75 g l(-1) per day, respectively. The efficiency in the nitrite (limiting substrate) removal was 99%. The ammonium and nitrite influent concentrations were increased stepwise until biomass in the reactors started to float. These flotation events coincided with periods when the NLR exceeded the maximum specific ANAMMOX activity (MSAA) of the sludge. The MSAA, determined in batch experiments, was 0.9 and 0.44 g g(-1) per day for biomasses from the gas-lift reactor and the SBR, respectively. Flotation of the biomass occurred most likely due to a granule density decrease caused by dinitrogen gas accumulation inside the granules and an apparent breakage of the granules. Further research is needed to understand this phenomenon and to optimise the corresponding strategies to counteract the flotation.

Bacteria, Anaerobic↗
PubMed2004

Life cycle assessment as a tool for the environmental improvement of the tannery industry in developing countries.

A representative leather tannery industry in a Latin American developing country has been studied from an environmental point of view, including both technical and economic analysis. Life Cycle Analysis (LCA) methodology has been used for the quantification and evaluation of the impacts of the chromium tanning process as a basis to propose further improvement actions. Four main subsystems were considered: beamhouse, tanyard, retanning, and wood furnace. Damages to human health, ecosystem quality, and resources are mainly produced by the tanyard subsystem. The control and reduction of chromium and ammonia emissions are the critical points to be considered to improve the environmental performance of the process. Technologies available for improved management of chromium tanning were profoundly studied, and improvement actions related to optimized operational conditions and a high exhaustion chrome-tanning process were selected. These actions related to the implementation of internal procedures affected the economy of the process with savings ranging from US dollars 8.63 to US dollars 22.5 for the processing of 1 ton of wet salt hides, meanwhile the global environmental impact was reduced to 44-50%. Moreover, the treatment of wastewaters was considered in two scenarios. Primary treatment presented the largest reduction of the environmental impact of the tanning process, while no significant improvement for the evaluated impact categories was achieved when combining primary and secondary treatments.

Animals↗
PubMed2004

Relevance of assessing quadriceps endurance in patients with COPD.

The aims of this study were to investigate whether the impairment in endurance of limb muscles is a general finding in chronic obstructive pulmonary disease (COPD) patients, affecting even those with mild-to-moderate disease or relatively normal physical activity. In addition, this study aimed to determine the physiopathology of exhaustion in local endurance tests and whether the reduction in quadriceps endurance can be predicted from muscle strength measurements. A total of 75 volunteers were assigned to one of two groups according to pulmonary function tests: COPD patients or healthy age-matched controls. Functional assessment included both quadriceps strength (maximum voluntary contraction (QMVC)), and quadriceps endurance (contractions against a load equivalent to 10% QMVC until task failure or for up to a limiting time of 30 min (QTlim)). COPD patients showed a decrease of approximately 43%, in QMVC and approximately 77% in QTlim compared with controls. Task failure occurred only in COPD patients and was due to muscle fatigue, since limiting symptoms were associated with a decrease in the median frequency of quadriceps electromyographical signal and a reversible decrease in QMVC. The impairment in skeletal muscle endurance was present even in patients with mild-to-moderate airflow obstruction and individuals with relatively normal physical activity, and was irrespective of lung function variables, anthropometrical data or quadriceps strength. Peripheral muscle endurance was impaired in chronic obstructive pulmonary disease patients, even in those with relatively normal physical activity and mild-to-moderate airflow obstruction. This impairment associated with an early onset of muscle fatigue and could not be predicted from the severity of the disease or the reduction in quadriceps strength.

Age Distribution↗
PubMed2004

[New Modern Magpi: meatal advancement and glanuloplasty clinical course].

INTRODUCTION: Meatal advancement and glanuloplasty (MAGPI) described by Duckett, has been the most accepted technique for distal hypospadias repair along the last 20 years. Only 50% of the distal variants are amenable to the Magpi; last years several modifications has been reported in order to reach better cosmetic results and to make it available for the most of the distal hypospadias. We report the first 20 cases with some modifications of Magpi. MATERIALS AND METHODS: The basic steps of the technique are: we remove a triangular segment of glanular tissue distal to the meatus. Dissection of the dorsal and lateral urethral sides is made, accomplishing the urethral advancement without any tension. Strips of glandular epithelium are excised on each side, and glans tissue is sutured above the ventral urethral wall. RESULTS: There were 11 coronal, and 9 glanular hypospadias (3 with megameatus). 8 cases showed a slight incurvation that disappeared after releasing any cutaneous chordee. The posoperative follow-up was 35 weeks (R=7-48 weeks). Cosmetic and functional results were excellent, showing a natural circumcized penis. There wasn't any complications as meatal retraction, stenosis or incurvation. There was only a transitional hematoma and a minimal fistula that closed expontanely. CONCLUSIONS: New Modern Magpi adds minimal variations to the original technique, avoiding the cosmetic limitations derived from borderline indications. New Modern Magpi is amenable to near all of glanular hypospadias and most of coronal hypospadias.

Child, Preschool↗
PubMed2003

Coupled BAS and anoxic USB system to remove urea and formaldehyde from wastewater.

Wastewater containing formaldehyde and urea was treated using a coupled system consisting of a biofilm airlift suspension (BAS) reactor and an anoxic upflow sludge blanket (USB) reactor. The anoxic USB reactor was used to carry out denitrification and urea hydrolysis, while the BAS reactor was used to carry out nitrification. In a first step, individual experiments were carried out to investigate the effects of both compounds on the nitrifying and denitrifying biomass. The BAS reactor was fed with a synthetic medium containing 500 mg N-NH4(+)l(-1) and 100mg N-urea l(-1), that were added continuously to this medium. Neither urea hydrolysis nor inhibition of nitrification was observed. Nitrification efficiency decreased when formaldehyde was fed during shocks at concentrations of 40, 80 and 120 mg C-formaldehyde l(-1). The anoxic USB reactor was fed with a synthetic medium containing nitrate, formaldehyde and urea. Concentrations of formaldehyde in the reactor of 100-120 mg C-formaldehyde l(-1) caused a decrease in the denitrification and urea hydrolysis rates. In a second step, the coupled system was operated at recycling ratios (R) of 3 and 9. Fed C/N ratios of 0.58, 1.0 and 1.5 g C-formaldehyde g(-1) N-NH4(+) were used for every recycling ratio. The maximum nitrogen removal percentages were achieved at a C/N ratio of 1.0 g C-formaldehyde g(-1) N-NH4(+) for both recycling ratios. A fed C/N ratio of 1.5 g C-formaldehyde g(-1) N-NH4(+) caused a decrease in the efficiency of the system with respect to nitrogen removal, due to the presence of formaldehyde in the BAS reactor, which decreased the nitrification. Formaldehyde was completely removed in the BAS reactor and a heterotrophic layer formed around the nitrifying biofilm.

Biofilms↗
PubMed2003

[Involvement of betamimetics in increased survival during fetal surgery in sheep].

INTRODUCTION: Fetal surgery is a therapeutic reality. Available only in a few centres worldwide. Experimental animal models are needed to continue research in this field. The target problem being the control of preterm labour. OBJECTIVES: To find a tocolytic drug regimen in order to reduce fetal loss. MATERIAL AND METHODS: Pregnant sheep were divided randomly in two groups. At a gestation age of seventy days sheep were operated in order to create a myelomeningocel model in the fetus. Follow-up with weekly amniocentesis guided by ultrasound scan. Group A (n = 6) were treated pre and post-op with indomethacine and with magnesium sulphate during surgery and in the following 24 hours. Group B (n = 8) were treated with diclofenac pre-op, and post-op with ritodrine until the end of pregnancy. RESULTS: Group A we find a survival rate 50% (n = 3) being 87% (n = 7) in group B. Fetal weight being higher in group A. We find an increase heart rate and a weight loss in both the fetus and mother in group B. Urea and creatinine amniotic fluid levels were increase in group B. CONCLUSIONS: The use of ritodrine as a tocolytic agent reduces fetal loss significantly. Ritodrine increases fetal and mother cardiac output causing weight loss.

Adrenergic beta-Agonists↗
PubMed2003

[Success of endoscopic management in vesicoureteral reflux, conditioned by ureteral dilatation].

INTRODUCTION: Endoscopic management has become an important alternative in the treatment of vesicoureteral reflux in children. Since 1995 we indicate it in our Hospital in children with grade II VUR (vesicoureteral reflux) after 1 year of medical management, in all children with grade III VUR and in children with grade IV VUR without reflux nephropathy. According to International Classification of reflux (IRSC), grade IV VUR differ to grade III mainly by the blunting of the calyces and the obliteration of sharp angle of the fornices. There may be seen in the high grades of reflux, important differences in the ureteral dilatation. AIM: The aim of this work is to study the influence of ureteral dilatation in the success of endoscopic management VUR. MATERIAL AND METHODS: A number of 245 refluxing renal units (URR) were treated endoscopically in our Hospital from 1995. We review the first 3.5 years (58 patients with 90 RRU). In a double blind study with the voiding cystourethrographies we graduated the ureteral dilatation in slight-normal, moderate and severe. The success rate after the first injection was compared between the 3 grades of ureteral dilatation. RESULTS: 3 patients had grade I VUR, 10 grade II, 54 grade III and 23 grade IV. After double blind study 39 patients had slight-normal ureteral dilatation, 39 moderate and 12 severe. There were statistical differences between the 3 grades of ureteral dilatation when we consider: all the patients, considering only grade III and IV reflux and studying only the patients with grade III reflux. However there wasn't statistical differences between grade III and IV VUR of the International Classification. CONCLUSIONS: The results show that ureteral dilatation is an important prognostical factor of the success rate in the endoscopic management of vesicoureteral reflux in children.

Child↗
PubMed2003

Anaerobic treatment of natural tannin extracts in UASB reactors.

Tannin extracts are substances commonly used in leather production processes. Since most of the steps of tannery manufacturing processes are carried out in aqueous environments, the presence of these compounds in the wastewaters is important. The aim of this work is to study the feasibility of the anaerobic degradation of three natural tannin extracts in three Upflow Anaerobic Sludge Blanket (UASB) reactors, which were fed with increasing concentrations of two condensed (quebracho and wattle) and one hydrolysable tannin extract (chestnut). Concentrations of applied extracts were 100, 200, 400, 800 and 1,000 mg/l, and 5 g/l of glucose was used as cosubstrate. Reactors were operated during 210 days and their performance was evaluated from the values of total and soluble COD, total and intermediate alkalinity, volatile fatty acids, pH and UV absorption at 280 nm. COD removal efficiencies higher than 85% were achieved in all cases. However, tannin extract removal efficiencies (based on UV-280 nm absorption measurements) were significantly lower, around 20% for condensed extracts and 60% for the hydrolysable one, when the reactors operated with the highest tannin extract concentration. The operation of the reactors was stable, commonly with alkalinity ratios below 0.30. Mass balances carried out indicate that most of the COD removal efficiencies are due to the removal of the readily biodegradable organic matter (glucose), whereas the tannin extracts are hardly anaerobically biodegradable, especially condensed extracts (wattle and quebracho).

Animals↗
PubMed2003

A membrane assisted hybrid bioreactor for the post treatment of an anaerobic effluent from a fish canning factory.

An innovative membrane assisted hybrid bioreactor was used to treat a mixture of two streams produced in a fish canning factory: a highly loaded stream that had previously been treated in an anaerobic contact reactor, and a second stream with a relatively low COD and N concentration. Experiments were carried out during two experimental stages: an aerobic stage, which is focused in the study on the aerobic oxidation of ammonia and COD and a nitrification-denitrification stage in which the study was mainly focused on the removal of nitrogen. Results of the aerobic period pointed out that it was feasible to achieve ammonia and COD removals of around 99% at OLR of 6.5 kg COD/m3 x d and NLR of 1.8 kg N-NH4+/m3 x d. Specific nitrifying activities of up to 0.78 g N-NH4+/g protein x d and 0.25 g N-NH4+/g VSS x d, were recorded for the attached and suspended biomass, respectively. Around 50-60% of the nitrifying capacity of the reactor was a result of the nitrifying capacity of the biofilm. During the nitrification-denitrification stage 76% of nitrogen removal was attained at an NLR of 0.8 kg N-NH4+/m3 x d. The biofilm nitrifying activity was not affected by the operating conditions of the system, as a result of the preferential consumption of COD by suspended biomass in the reactor. Thus, the combination of a hybrid system, with both suspended and attached biomass, and an ultrafiltration membrane module might be an alternative for treating wastewaters in compact biological systems. The intrinsic characteristics of the system made it feasible to operate at high OLR without problems related with the settling properties of the sludge or the drop in the nitrogen conversion. There were no solids in the effluent as a result of the use of the membrane filtration module.

Bacteria, Anaerobic↗