Biomedical subjects

A Delgado

Publications and source records attributed to A Delgado.

At least 19 recordsLinked to original sources

PubMed2006

Depolymerisation and rearrangement of actin filaments during exocytosis in rat peritoneal mast cells: involvement of ryanodine-sensitive calcium stores.

Cytoskeletal F-actin associated with synaptic vesicles and granules plays an important role during Ca(2+)-mediated exocytosis. In the present work, we have used amperometry and confocal fluorescence to study the role of internal Ca(2+) in the rearrangement of F-actin (visualised with phalloidin-Alexa 546) during exocytosis in rat mast cells. The F-actin-depolymerising drug, latrunculin A, and the ryanodine receptor agonists ryanodine and caffeine that, per se did not induce exocytosis, enhanced the exocytotic responses elicited by compound 48/80 (C48/80). They also induced cortical actin depolymerisation in the presence or absence of external Ca(2+). Degranulation induced by C48/80 was accompanied by the formation of a cytoplasmic F-actin network. Depletion of internal Ca(2+) with cyclopiazonic acid inhibited latrunculin potentiation of C48/80-stimulated exocytosis and completely blocked the formation of the cytoplasmic F-actin network. This indicates that the mobilisation of Ca(2+) from ryanodine-sensitive intracellular stores plays an important role in the depolymerisation of the cortical F-actin barrier and possibly in the formation of the internal F-actin network during exocytotic activation of peritoneal mast cells.

Actin Cytoskeleton↗

PubMed2006

Dynamic electrophoretic mobility of concentrated dispersions of spherical colloidal particles. On the consistent use of the cell model.

This paper outlines a complete and self-consistent cell model theory of the electrokinetics of dense spherical colloidal suspensions for general electrolyte composition, frequency of applied field, zeta potential, and particle size. The standard electrokinetic equations, first introduced for any given particle configuration, are made tractable to computation by averaging over particle configurations. The focus of this paper is on the systematic development of suitable boundary conditions at the outer cell boundary obtained from global constraints on the suspension. The approach is discussed in relation to previously published boundary conditions that have often been introduced in an ad hoc manner. Results of a robust numerical calculation of high-frequency colloidal transport properties, such as dynamic mobility, using the present model are presented and compared with some existing dense suspension models.

Journal Article↗

PubMed2006

Experimental and numerical study of heterogeneous pressure-temperature-induced lethal and sublethal injury of Lactococcus lactis in a medium scale high-pressure autoclave.

The present contribution is dedicated to experimental and theoretical assessment of microbiological process heterogeneities of the high-pressure (HP) inactivation of Lactococcus lactis ssp. cremoris MG 1363. The inactivation kinetics are determined in dependence of pressure, process time, temperature and absence or presence of co-solutes in the buffer system namely 4 M sodium chloride and 1.5 M sucrose. The kinetic analysis is carried out in a 0.1-L autoclave in order to minimise thermal and convective effects. Upon these data, a deterministic inactivation model is formulated with the logistic equation. Its independent variables represent the counts of viable cells (viable but injured) and of the stress-resistant cells (viable and not injured). This model is then coupled to a thermo-fluiddynamical simulation method, high-pressure computer fluid dynamics technique (HP-CFD), which yields spatiotemporal temperature and flow fields occurring during the HP application inside any considered autoclave. Besides the thermo-fluiddynamic quantities, the coupled model predicts also the spatiotemporal distribution of both viable (VC) and stress-resistant cell counts (SRC). In order to assess the process non-uniformity of the microbial inactivation in a 3.3-L autoclave experimentally, microbial samples are placed at two distinct locations and are exposed to various process conditions. It can be shown with both, experimental and theoretical models that thermal heterogeneities induce process non-uniformities of more than one decimal power in the counts of the viable cells at the end of the treatment.

Biotechnology↗

PubMed2006

Thermal stability of the thermoluminescence trap structure of bentonite.

This work reports about the thermal stability of the blue thermoluminescence (TL) of a well-characterised natural bentonite from Almeria (Spain). The main interest of this clay, mainly composed of montmorillonite, is because of its application in the field of high-level radioactive waste (HLW) repository in deep-lying rocks. As observed in other aluminosilicates, bentonite exhibits a very complex structure of the emission spectra based on a wide broad maximum peaked at approximately 265 degrees C that can be associated to physico-chemical processes such as dehydroxylation processes, consecutive breaking linking of bonds, formation of hydrolysed ions and redox reactions. The thermal stability tests performed at different temperatures confirm a continuum in the distribution of traps. Hence, the glow curve analysis methods commonly used for synthetic materials based on single discrete traps cannot be applied for this material and the kinetic parameters were fitted assuming an exponential distribution of trapped electrons.

Bentonite↗

PubMed2006

Evolution of the trapped charge distribution due to trap emptying processes in a natural aluminosilicate.

The evolution of the thermoluminescence glow curve of a natural Ca-Be rich aluminosilicate after annealing treatments at different temperatures has been studied in order to evaluate the changes in the trapped charge distribution. The glow curve consists of a single broad peak that continuously shifts toward higher temperatures when the sample is preheated up to increasing temperatures, thus indicating the presence of a continuous trap distribution. The glow curve fitting assuming different distribution functions shows how a gaussian distribution becomes a nearly exponential distribution owing to the thermal leakage of charge carriers from trapping centres.

Aluminum Silicates↗

PubMed2006

Combined high pressure and temperature induced lethal and sublethal injury of Lactococcus lactis--application of multivariate statistical analysis.

It was the aim of this work to determine the combined effects of pressure, temperature, and co-solutes on Lactococcus lactis, and to detect correlations between culture-dependent and culture-independent methods for assessment of cellular viability and sublethal injury. Therefore, the pressure induced inactivation of L. lactis MG 1363 was investigated in buffer and in buffer with 1.5 M sucrose or 4 M NaCl at a pressure range of 0.1 to 500 MPa and a temperature range of 5 to 50 degrees C. The inactivation was characterised by viable cell counts, stress resistant cell counts, membrane integrity, metabolic activity, and the activity of the multi-drug-resistance transport enzyme LmrP. L. lactis was most resistant to pressure application at 20-30 degrees C. Sucrose protected towards inactivation at any temperature, NaCl provided protection at high temperatures only. By using Principal Component Analysis, correlations were detected between viable cell counts and metabolic activity as well as stress resistant cell counts and LmrP activity. In conclusion, the pressure-inactivation of L. lactis is strongly temperature dependent, baroprotection by sucrose occurs at any temperature but the baroprotective effects of NaCl is temperature dependent. Further on, a combination of two experimental methods fully describe lethal and sublethal injury of pressure treated cells. These simplification of data acquisition and model development facilitates the establishment of pressure processes in food technology.

Bacterial Proteins↗

PubMed2005

Impact of a novel spray-chilling system on surface microflora, water activity and weight loss during beef carcass chilling.

Commercially slaughtered and dressed beef carcass sides (n=30) were followed through a standard commercial chill unit fitted with a new "Jasca" air humidification system adjusted to provide intermittent water spraying of carcass sides (spray cycle 2 min on, 1 min off) for 15 h. Immediately after dressing, and after 24h in the chill unit, the surface water activity, and the weight of each side was measured, and 5 cm2 samples were recovered from four locations, i.e. rump, flank, brisket and neck on the surface of each side. These samples, and similar samples from control sides (n=30) processed in a standard commercial chill unit, were subjected to microbiological examination by direct and resuscitation counts on plate count agar (PCA), MacConkey agar (MAC) and violet red bile glucose agar (VRBGA). No significant differences were observed between bacterial numbers on test and control samples on each of the above agars, at each sample point/occasion. Comparison of direct and resuscitation counts suggested the presence of substantial numbers of injured cells, at both stages (pre- and post-chill), on test and control sides. After 24 h in chill units, test sides exhibited an average weight loss of 1.36% (+/-0.36%), which is significantly less (P<0.001) than the average weight loss (1.55%+/-0.24%) from control sides. These results suggest that the Jasca spray-chilling system can limit carcass shrinkage (on average by 0.19%) without significantly increasing the surface populations of selected bacterial groups.

Abattoirs↗

PubMed2005

A fuzzy logic-based model for the multistage high-pressure inactivation of Lactococcus lactis ssp. cremoris MG 1363.

The high-pressure inactivation (200 to 600 MPa) of Lactococcus lactis ssp. cremoris MG 1363 suspended in milk buffer was investigated with both experimental and theoretical methods. The inactivation kinetics were characterised by the determination of the viable cell counts, cell counts of undamaged cells, LmrP activity, membrane integrity, and metabolic activity. Pressures between 200 and 600 MPa were applied, and pressure holding times were varied between 0 and 120 min. Experiments were carried out in milk buffer at pH values ranging between 4.0 and 6.5, and the effect of the addition of molar concentrations of NaCl and sucrose was furthermore determined. The inactivation curves of L. lactis, as characterised by viable cell counts, exhibited typical sigmoid asymmetric shapes. Generally, inactivation of the membrane transport system LmrP was the most sensitive indicator of pressure-induced sublethal injury. Furthermore, the metabolic activity was inactivated concomitant with or prior to the loss of viability. Membrane integrity was lost concomitant with or later than cell death. For example, treatments at 200 MPa for 60 min in milk buffer did not inactivate L. lactis, but fully inactivated LmrP activity and reduced the metabolic activity by 50%. The membrane integrity was unaffected. Thus, the assay systems chosen are suitable to dissect the multistep high-pressure inactivation of L. lactis ssp. cremoris MG 1363. A fuzzy logic model accounting for the specific knowledge on the multistep pressure inactivation and allowing the prediction of the quantities of sublethally damaged cells was formulated. Furthermore, the fuzzy model could be used to accurately predict pressure inactivation of L. lactis using conditions not taken into account in model generation. It consists of 160 rules accounting for several dependent and independent variables. The rules were generated automatically with fuzzy clustering methods and rule-oriented statistical analysis. The set is open for the integration of further knowledge-based rules. A very good overall agreement between measured and predicted values was obtained. Single, deviating results have been identified and can be explained to be measurement errors or model intrinsic deficiencies.

Animals↗

PubMed2005

Retrospective luminescence dosimetry: development of approaches to application in populated areas downwind of the Chernobyl NPP.

The cumulative absorbed dose in fired-clay bricks collected from ten buildings in the populated contaminated settlement (137Cs, 1,470 kBq m(-2)) of Stary Vishkov, located 175 km downwind of the Chernobyl Nuclear Power Plant (NPP) in the Bryansk administrative region of Russia, was determined using luminescence techniques by five laboratories. At each location, the cumulative dose, after subtraction of the natural background dose, was translated to absorbed dose in air using conversion factors derived from Monte Carlo simulations. The simulations employed source distributions inferred from contemporary soil contamination data and also took into account heterogeneity of fallout deposition. At four locations the cumulative dose at a reference location was calculated, enabling the luminescence determinations to be compared directly with values of cumulative absorbed dose in air obtained using deterministic models. A "local" conversion factor was also derived from the Monte Carlo simulations for locations where the disturbance of soil was significant. Values of the "local" cumulative dose in air calculated using this factor were compared with those predicted using the deterministic models at each sampled location, allowing location factors to be calculated. The methodology developed is generally applicable to populated areas contaminated by radioactive fallout in which brick buildings are found. The sensitivity of the luminescence techniques for bricks from this region of Russia was sufficient to evaluate cumulative absorbed dose in brick due to fallout of less than 20 mGy.

Air Pollutants, Radioactive↗

PubMed2005

Characterization of Staphylococcus aureus mutants expressing reduced susceptibility to common house-cleaners.

AIMS: To characterize mutants of Staphylococcus aureus expressing reduced susceptibility to house cleaners (HC), assess the impact of the alternative sigma factor SigB on HC susceptibility, and determine the MIC of clinical methicillin-resistant S. aureus (MRSA) to a HC. METHODS AND RESULTS: Susceptibility to HC, HC components, H2O2, vancomycin and oxacillin and physiological parameters were determined for HC-reduced susceptibility (HCRS) mutants, parent strain COL and COLsigB::kan. HCRS mutants selected with three HC expressed reduced susceptibility to multiple HC, HC components, H2O2 and vancomycin. Two unique HCRS mutants also lost the methicillin resistance determinant. In addition, all HCRS mutants exhibited better growth at two temperatures, and one HCRS mutant expressed reduced carotenoid production. COLsigB::kan demonstrated increased susceptibility to all HC and many HC components. sigB operon mutations were not detected in one HCRS mutant background. Of 76 clinical MRSA, 20 exhibited reduced susceptibility to a HC. CONCLUSIONS: HCRS mutants demonstrate altered susceptibility to multiple antimicrobials. While sigB is required for full HC resistance, one HCRS mechanism does not involve sigB operon mutations. Clinical MRSA expressing reduced susceptibility to a common HC were detected. SIGNIFICANCE AND IMPACT OF THE STUDY: This study suggests that HCRS mutants are not protected against, nor selected by, practical HC concentrations.

Disinfectants↗

PubMed2005

Comparison of the efficacy and safety of combinations of metopimazine or ondansetron with methylprednisolone in the prevention of delayed emesis in patients receiving chemotherapy.

BACKGROUND: Delayed emesis following chemotherapy in cancer patients remains an important challenge for treatment and contributes to poor quality of life and treatment compliance. OBJECTIVES: To compare the efficacy and tolerability of associations of metopimazine and ondansetron with methylprednisolone for the prevention of delayed chemotherapy-induced nausea and emesis. METHODS: A randomised, open-label, observational, cross-over design was used to compare two treatment strategies following two consecutive sessions of chemotherapy separated by at least 1 week. Patients were randomised to treatment with sublingual metopimazine (15 mg tid) or ondansetron lyophilisate (8 mg bid) for 5 days. All patients received oral methylprednisolone (48 mg). Patients reported episodes of nausea and emesis in a diary, and completed the Functional Living Index Emesis quality of life questionnaire. Adverse events were also evaluated. RESULTS: Ninety-nine patients were included in the study, 79.5% of whom were women, with a mean age of 52.7 years. Breast cancer was the most common individual cancer and most patients were receiving combinations of cytotoxic drugs. Treatment was successful at preventing delayed emesis in 73.6% of patients during treatment with the metopimazine-methylprednisolone association and 57.5% during the ondansetron-methylprednisolone association. Analysis of discordant pairs revealed a significant benefit in favour of the methopimazine-methylprednisolone association (p = 0.006). No significant difference was observed between treatments for the overall quality of life score. The incidence of gastrointestinal disorders, particularly constipation, was significantly higher during ondansetron-methylprednisolone treatment (p = 0.0112). CONCLUSION: Methopimazine is an effective and well-tolerated alternative to setrons for the treatment of delayed nausea and emesis in patients undergoing chemotherapy.

Adult↗

PubMed2004

Methadone implants for methadone maintenance treatment. In vitro and in vivo animal studies.

Methadone implant formulations elaborated with polylactide-co-glycolide (PLGA) and polylactic acid (PLA) for 1 week and 1 month release duration, respectively, were evaluated in vitro and in vivo. One-week implants prepared with methadone clorhydrate, methadone clorhydrate/methadone base blend or methadone base were tested in vitro. Results showed that the methadone release rate decreased as the methadone base increased. The best release profile was achieve when the methadone base implants, made by compression of a 50:50 PLGA (12 kDa) and methadone base mix, were coated with PLA (30 kDa). For 1-month implants, the methadone base load was increased to 65% and PLA of 30 kDa was used as a matrix component. In this case the implants were coated with the same polymer. Deconvolution methods could not be used for in vivo release estimation because an increase in methadone clearance was observed with methadone clorhydrate solution multiple-dose treatment. Therefore the amount of drug remaining within the implants was evaluated and the deconvolution was only used to establish the release profile range. The upper limit was estimated applying the absorption-disposition function obtained after multiple-dose administrations while the lower curve was estimated using the single-dose function. Methadone serum levels were maintained around 200 ng/ml during 1 week and approximately 5 weeks with the optimised implants. In vivo-in vitro correlations were always very good with slopes near 1.

Animals↗

PubMed2004

Gene expression in gastric biopsies from patients infected with Helicobacter pylori.

BACKGROUND: Helicobacter pylori infection has protean effects on gene expression in the host gastric mucosa, which have been investigated by gene chip analysis in vitro. In this study the effects of H. pylori infection on host gene expression in the gastric antral mucosa in patients were examined. METHODS: One gastric antral biopsy was obtained from a total of 18 untreated patients undergoing routine endoscopic evaluation of chronic abdominal complaints. Nine patients had histologic evidence of H. pylori infection and 9 age- and sex-matched patients had no histologic evidence of H. pylori infection. A microarray analysis was performed using a gene chip containing 35,000 human expressed sequence tags on RNA extracted from endoscopic, gastric antral biopsies, and average gene expression among infected and uninfected patients was compared. RESULTS: Underexpressed genes in infected patients' mucosa included gastric intrinsic factor and several metallothionein isoforms. Overexpressed genes in infected patients' mucosa comprised MHC Class II molecules, immunoglobulin and B-cell activation genes, as well as genes known to induce apoptosis. Changes in expression were confirmed for a subset of genes by SYBR green real-time PCR. CONCLUSIONS: Microarray analysis of antral biopsies from patients with and without H. pylori infection revealed differential expression of metal regulatory, immunity and inflammation-related genes.

Adult↗

PubMed2004

The effect of volatile fatty acids on the nitrification of a saline effluent.

Anaerobically produced volatile fatty acids (VFA) may affect the nitrification yield. The effect of the type of VFA (acetic, propionic and butyric acid) on nitrification of a saline (24 g NaCl l(-1)) medium was studied. Nitritation (40 mg N-NH4+ l(-1)) and nitratation (100 mg N-NO2- l(-1) were assessed in batch cultures fed with different VFA (32 mg TOC l(-1)). The effect of increasing VFA concentrations on nitrification was studied in batch reactors fed with an initial concentration of 40 mg N-NH4+ l(-1) and C/N ratios of 0, 2, 4, 8 and 16 as well as in a continuous mixed flow reactor operated at 30 degrees C and pH 7.5 and fed with 500 mg N-NH4+ l(-1) and 500, 1000, 2000, and 4000 mg TOC l(-1). Nitritation and nitratation rates were decreased by organic matter; inhibition increased with the VFA size. A non-competitive inhibition model fitted the experimental data on nitrification rate reduction at increasing acetic add concentrations; inhibition constants were 685 mg acetic acid l(-1) for ammonia oxidation and 74.3 mg acetic acid l(-1) for nitrite oxidation. The continuous reactor's nitrifying ability decreased from 82% to 40% at C/N ratios 1 and 4, respectively. Loss of nitrification, but a 50% ammonia removal was found at a C/N of 8. It was concluded that the nitrification rate reduction is proportional to the VFA molecular weight and that an increase in VFA concentration diminishes the nitrifying ability due to kinetic limitations.

Acetates↗

PubMed2004

A new area multidetector dosemeter for mixed n-gamma fields.

A new instrument to assess neutron ambient doses has been designed and constructed. In its design, spectrometric capabilities have been implemented that allow to take into account the energy spectrum of the neutron field in the evaluation of the operational magnitude, ambient dose equivalent, H*(10). This dosemeter is based on the moderation-absorption technique and can be employed over a wide range of energies from thermal to 20 MeV. It consists of a spherical shaped polyethylene moderator with a set of thermoluminescence dosemeters (TLDs) inserted in different positions of its interior to evaluate the external neutron energy spectrum. At this moment the system uses pairs 6LiF:Mg,Ti (TLD-600) and 7LiF:Mg,Ti (TLD-700) thermoluminescence dosemeters for a better gamma discrimination. The dosemeter response matrix was calculated using the MCNP4C Monte Carlo code (MC). The viability of the dosemeter for area dosemetry has been examined experimentally showing its capabilities over a wide range of energies.

Algorithms↗

PubMed2004

Comparison of retrospective luminescence dosimetry with computational modeling in two highly contaminated settlements downwind of the Chernobyl NPP.

The cumulative absorbed dose in bricks collected from six buildings in two heavily contaminated settlements (137Cs > 2,000 kBq m(-2)) located downwind of the Chernobyl Nuclear Power Plant was determined using luminescence techniques by six laboratories. The settlements, Vesnianoje in Ukraine and Zaborie in Russia, are located in, respectively, proximal and distal locations relative to the Chernobyl Nuclear Power Plant. The luminescence determinations of cumulative dose in brick, after subtraction of the natural background dose, were translated to absorbed dose in air at a Reference Location using conversion factors derived from Monte Carlo simulations of photon transport. The simulations employed source distributions inferred from contemporary soil contamination data and also took into account heterogeneity of fallout deposition. This translation enables the luminescence determinations to be compared directly with values of cumulative absorbed dose obtained by computational modeling and also other dose reconstruction methods. For each sampled location the cumulative dose was calculated using three deterministic models, two of which are based on the attenuation of dose-rate with migration of radionuclides in soil and the third on historic instrumental gamma dose-rate data. The results of the comparison of the two methods indicate overall agreement within margins of +/-25%. The methodology developed is generally applicable and adaptable to areas contaminated by much lower levels of radioactive fallout in which brick buildings are found.

Computer Simulation↗

PubMed2003

Ciprofloxacin implants for bone infection. In vitro-in vivo characterization.

To elucidate the antibiotic release mechanism from implants composed of calcium phosphates (hydroxyapatite [HAP] and tricalcium phosphate [TCP]), 30 kDa poly(DL-lactide) (PLA-30) and ciprofloxacin (CFX), nine formulations were prepared. In vitro results show that the release rate decreased as compression load and PLA/phosphates ratio increased. In contrast, a slower percent release rate was observed with higher drug loading. Swelling-erosion-disintegration of the implants was observed during the release assays, due to CFX swelling. Two CFX implant formulations were selected for implantation in the femur of rabbits, according to in vitro results. The implant drug loads tested were 10% and 40% of CFX. The in vivo results showed that the antibiotic concentrations achieved throughout the femur were higher for 4 weeks than the minimum inhibitory concentrations (MIC) against the most common of the pathogens that cause osteomyelitis. The CFX-10% implant was considered the best formulation as CFX was totally released within 6 weeks, and therapeutic bone levels were achieved, and the histological and radiographic analyses showed the osteoconductive properties of the materials. All these results showed that CFX release is limited by its solubility, and the erosion-disintegration and bone ingrowth into the implants enhanced the antibiotic release.

Animals↗

PubMed2003

The influence of transport phenomena during high-pressure processing of packed food on the uniformity of enzyme inactivation.

Here we deal with the influence of heat-transport effects on a high-pressure-induced enzyme inactivation in packed substances. Special attention is given to the influence of the geometrical scale and to the heat-transfer characteristics of the packaging material. The investigation is based on mathematical modeling and numerical simulation. The method accounts both for compression phase and holding phase. The model includes convective and conductive heat transfer, fluid motion as well as an enzyme transport equation with a first-order kinetic source term accounting for the inactivation. Three configurations with a total volume of 0.8 L, 6.3 L, and 50.3 L are considered. The pressure medium is water. The enzyme solution is B. subtilis alpha-amylase dissolved in a TRIS-HCl-buffer. The packaging material is polypropylene. The heat-transfer coefficient for conduction through the packaging material is varied to simulate both changes in the material properties as well as modifications of the packaging material thickness. It is found that the efficiency of the inactivation increases with increasing chamber volume as long as the kinetic inactivation constant is increasing with temperature. In the considered case the activity retention obtained in a 0.8 L volume is about 2.4 times larger than the one obtained for the same process carried out in a 50.3 L volume. Furthermore, it was found that the properties of the packaging material could induce a significant degree of nonuniformity (worst case = 69%). An appropriate choice of the material can lead to maximum inactivation and maximum process uniformity since advantage is taken from the slow heat exchange after the compression phase.

Bacillus subtilis↗