Maria do Carmo Pereira

Multiple linear regression and artificial neural networks based on principal components to predict ozone concentrations

Abstract The prediction of tropospheric ozone concentrations is very important due to the negative impacts of ozone on human health, climate and vegetation. The development of models to predict ozone concentrations is thus very useful because it can provide early warnings to the population and also reduce the number of measuring sites. The aim of this study was to predict next day hourly ozone concentrations through a new methodology based on feedforward artificial neural networks using principal components as inputs. The developed model was compared with multiple linear regression, feedforward artificial neural networks based on the original data and also with principal component regression. Results showed that the use of principal components as inputs improved both models prediction by reducing their complexity and eliminating data collinearity.

Influence of fluorinated and hydrogenated nanoparticles on the structure and fibrillogenesis of amyloid beta-peptide.

Peptide aggregation in amyloid fibrils is implicated in the pathogenesis of several diseases such as Alzheimers disease. There is a strong correlation between amyloid fibril formation and a decrease in conformational stability of the native state. Amyloid-beta peptide (Abeta), the aggregating peptide in Alzheimers disease, is natively unfolded. The deposits found in Alzheimers disease are composed of Abeta fibrillar aggregates rich in beta-sheet structure. The influence of fluorinated complexes on the secondary structure and fibrillogenesis of Abeta peptide was studied by circular dichroism (CD) spectroscopy and transmission electron microscopy (TEM). CD spectra show that complexes of polyampholyte and fluorinated dodecanoic acid induce alpha-helix structure in Abeta, but their hydrogenated analogous lead to beta-sheet formation and aggregation. The fluorinated nanoparticles with highly negative zeta potential and hydrophobic fluorinated core have the fundamental characteristics to prevent Abeta fibrillogenesis.

Epigallocatechin gallate-loaded polysaccharide nanoparticles for prostate cancer chemoprevention

AIMS Polysaccharide nanoparticles were studied as drug delivery vehicles for chemopreventive agents. MATERIALS & METHODS Green tea polyphenol epigallocatechin-3-gallate (EGCG) was incorporated into a carbohydrate matrix of gum arabic and maltodextrin with an encapsulation efficiency of approximately 85%. RESULTS Encapsulated EGCG retained its biological activity, reducing the cell viability and inducing apoptosis of Du145 prostate cancer cells. Clonogenic assay demonstrated that encapsulation of EGCG enhanced its inhibitory effect on cell proliferation (10-20%) at lower concentrations (1-2 µM), compared with free EGCG. CONCLUSION This study highlights the use of polysaccharide nanoparticles in chemoprevention as they can be used to deliver natural antioxidants capable of inhibiting steps of the tumorigenesis process.

Physiological changes induced by the quaternary ammonium compound benzyldimethyldodecylammonium chloride on Pseudomonas fluorescens

OBJECTIVES Antimicrobial resistance is a major public health concern, particularly in hospitals and other healthcare settings. For the rational design of disinfection strategies, it is of utmost importance to understand the mechanisms of action of antimicrobials. In this study, the mechanism of action of benzyldimethyldodecylammonium chloride (BDMDAC) was assessed against Pseudomonas fluorescens. METHODS The targets of antimicrobial action were studied using different bacterial physiological indices. The MIC, MBC, membrane permeabilization, intracellular potassium release, physico-chemical surface properties, surface charge, outer membrane protein (OMP) expression and morphological changes were assessed after BDMDAC exposure. RESULTS The MIC was found to be 20 mg/L and the MBC was 10 mg/L. BDMDAC led to a significant change in cell surface hydrophobicity and induced propidium iodide uptake. Such results suggest cytoplasmic membrane damage, corroborated by the release of intracellular potassium. The results obtained from the zeta potential measurement demonstrate a -31.2 mV value for untreated cells and -21.0 mV for cells at the MIC. Scanning electron microscopy revealed that cells treated with 20 mg/L were less bulky, and their membrane seemed to be rougher, wrinkled and deformed when compared with untreated cells. The overall bactericidal events occurred without detectable changes in OMP expression. CONCLUSIONS BDMDAC is an effective biocide against P. fluorescens. It binds by ionic and hydrophobic interactions to the cell membrane, causing changes in membrane properties and function, as manifested by phenomena such as cellular disruption and loss of membrane integrity with consequent leakage of essential intracellular constituents.

Selection and validation of parameters in multiple linear and principal component regressions

An improved design for a cage mill for disintegrating or reducing materials such as ore, grain, etc., consisting of a movable and a stationary portion for housing two cooperative rotatable cage assemblies mounted on coaxial shafts, and each having two rows of impact members alternating with those of the other cage assembly. The axial length of the impact members increases radially outwardly from the axis of the two shafts, and a disk for each cage assembly has a stepped portion for mounting the longer row of impact members and the ends of the members are protected by impact rings. The stepped portion provides an offset area for nesting the ring of a preceding row to protect the ring against abrasion. For each cage assembly a tapered split ring nut arrangement at the end of the shaft forces the cage against a hub rigidly secured to the shaft, and a locking means secures the nut to the shaft. The power means for rotating the cage assembly associated with the movable portion is mounted on the movable portion for movement therewith, and the sealing element between the movable and stationary portions of the housing is designed to always maintain a positive sealing condition yet allow for misalignment of the two portions.

Evaluation of nickel toxicity on liver, spleen, and kidney of mice after administration of high-dose metal ion

The toxic effects caused by nickel (Ni) per si were explored by performing in vivo studies on mice following subcutaneous administration of a metallic solution of nickel at 1, 2, 3, and 4 weeks to evaluate the side effects of this metal ion when released from stainless steel implants. Other groups were similarly injected with HBSS and used as controls. Accumulation of Ni ions on liver, spleen, and kidney was assessed by an electrochemical method, adsorptive stripping voltammetry (AdSV) using microelectrodes, and atomic absorption spectrometry (AAS). Alterations of those organs induced by Ni ions were studied, showing that several histological changes had been induced. Chemical analysis and histological features indicate that Ni is partially accumulated in the study organs.

Analysis of polycyclic aromatic hydrocarbons in atmospheric particulate samples by microwave-assisted extraction and liquid chromatography

A methodology based on microwave-assisted extraction (MAE) and LC with fluorescence detection (FLD) was investigated for the efficient determination of 15 polycyclic aromatic hydrocarbons (PAHs) regarded as priority pollutants by the US Environmental Protection Agency and dibenzo(a,l)pyrene in atmospheric particulate samples. PAHs were successfully extracted from real outdoor particulate matter (PM) samples with recoveries ranging from 81.4 +/- 8.8 to 112.0 +/- 1.1%, for all the compounds except for naphthalene (62.3 +/- 18.0%) and anthracene (67.3 +/- 5.7%), under the optimum MAE conditions (30.0 mL of ACN for 20 min at 110 degrees C). No clean-up steps were necessary prior to LC analysis. LOQs ranging from 0.0054 ng/m(3 )for benzo(a)anthracene to 0.089 ng/m(3) for naphthalene were reached. The validated MAE methodology was applied to the determination of PAHs from a set of real world PM samples collected in Oporto (north of Portugal). The sum of particulate-bound PAHs in outdoor PM ranged from 2.5 and 28 ng/m(3).

Influence of Traffic Emissions on the Carcinogenic Polycyclic Aromatic Hydrocarbons in Outdoor Breathable Particles

Abstract Because polycyclic aromatic hydrocarbons (PAHs) have been proven to be toxic, mutagenic, and/or carcinogenic, there is widespread interest in analyzing and evaluating exposure to PAHs in atmospheric environments influenced by different emission sources. Because traffic emissions are one of the biggest sources of fine particles, more information on carcinogenic PAHs associated with fine particles needs to be provided. Aiming to further understand the impact of traffic particulate matter (PM) on human health, this study evaluated the influence of traffic on PM10 (PM with aerodynamic diameter <10 µm) and PM2.5 (PM with aerodynamic diameter <2.5 µm), considering their concentrations and compositions in carcinogenic PAHs. Samples were collected at one site influenced by traffic emissions and at one reference site using low-volume samplers. Analysis of PAHs was performed by microwave-assisted extraction combined with liquid chromatography (MAE-LC); 17 PAHs, including 9 carcinogenic ones, were quantified. At the site influenced by traffic emissions, PM10 and PM2.5 concentrations were, respectively, 380 and 390% higher than at the background site. When influenced by traffic emissions, the total concentration of nine carcinogenic compounds (naphthalene, chrysene, benzo(a)anthracene, benzo(b) fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, dibenzo(a,h)anthracene, indeno(1,2,3-cd)pyrene, and dibenzo(a,l)pyrene) was increased by 2400 and 3000% in PM10 and PM2.5, respectively; these nine carcinogenic compounds represented 68 and 74% of total PAHs (ΣPAHs) for PM10 and PM2.5, respectively. All PAHs, including the carcinogenic compounds, were mainly present in fine particles. Considering the strong influence of these fine particles on human health, these conclusions are relevant for the development of strategies to protect public health.

Targeting nanoparticles across the blood-brain barrier with monoclonal antibodies

Development of therapeutics for brain disorders is one of the more difficult challenges to be overcome by the scientific community due to the inability of most molecules to cross the blood-brain barrier (BBB). Antibody-conjugated nanoparticles are drug carriers that can be used to target encapsulated drugs to the brain endothelial cells and have proven to be very promising. They significantly improve the accumulation of the drug in pathological sites and decrease the undesirable side effect of drugs in healthy tissues. We review the systems that have demonstrated promising results in crossing the BBB through receptor-mediated endocytic mechanisms for the treatment of neurodegenerative disorders such as Alzheimers and Parkinsons disease.

Lipid/particle assemblies based on maltodextrin-gum arabic core as bio-carriers.

A novel system to carry and protect epigallocatechin gallate (EGCG), an antioxidant from the green tea, is reported. The system consists of maltodextrin and gum arabic nanoparticles coated with egg-yolk l-alpha-phosphatidylcholine (Egg-PC)/stearylamine (SA) bilayers. In this study, the polysaccharide core was produced by homogenization followed by spray-drying. The lipid coating was performed by the lipid film hydration method. The polysaccharide core revealed negative zeta potential, which changed to opposite signs after lipid coating. The presence of lipid layers was evidenced by cryogenic-transmission (cryo-TEM) and scanning (cryo-SEM) electron microscopy studies. An increase in size was observed after lipid coating as determined by dynamic light scattering (DLS). Atomic force microscopy (AFM) demonstrated that the polysaccharide core provides high resistance to mechanical strength. The lipid/particle assemblies show high retention efficiency of EGCG at physiological pH, opening the possibility of their use for delivery and controlled release of tea catechins.