Entity

Time filter

Source Type


Felgueiras H.P.,University of Paris 13 | Murthy N.S.,New Jersey Center for Biomaterials | Sommerfeld S.D.,New Jersey Center for Biomaterials | Bras M.M.,University of Porto | And 3 more authors.
ACS Applied Materials and Interfaces | Year: 2016

Proteins that get adsorbed onto the surfaces of biomaterials immediately upon their implantation mediate the interactions between the material and the environment. This process, in which proteins in a complex mixture compete for adsorption sites on the surface, is determined by the physicochemical interactions at the interface. Competitive adsorption of bovine serum albumin (BSA), fibronectin (Fn), and collagen type I (Col I), sequentially and from mixtures, was investigated so as to understand the performances of different surfaces used in biomedical applications. A quartz crystal microbalance with dissipation was used to monitor the adsorption of these proteins onto two materials used in functional bone replacement, a titanium alloy (Ti6Al4V) and Ti6Al4V physisorbed with poly(sodium styrenesulfonate) [poly(NaSS)], and three controls, gold, poly(desaminotyrosyltyrosine ethyl ester carbonate) [poly(DTEc)], and polystyrene (PS). In experiments with individual proteins, the adsorption was the highest with Fn and Col I and the least with BSA. Also, protein adsorption was the highest on poly(NaSS) and Ti6Al4V and the least on poly(DTEc). In sequential adsorption experiments, protein exchange was observed in BSA + Fn, Fn + Col I, and BSA + Col I sequences but not in Fn + BSA and Col I + BSA because of the lower affinity of BSA to surfaces relative to Fn and Col I. Protein adsorption was the highest with Col I + Fn on hydrophobic surfaces. In experiments with protein mixtures, with BSA & Fn, Fn appears to be preferentially adsorbed; with Fn & Col I, both proteins were adsorbed, probably as multilayers; and with Col I & BSA, the total amount of protein was the highest, greater than that in sequential and individual adsorption of the two proteins, probably because of the formation of BSA and Col I complexes. Protein conformational changes induced by the adsorbing surfaces, protein-protein interactions, and affinities of proteins appear to be the important factors that govern competitive adsorption. The findings reported here will be useful in understanding the host response to surfaces used for implants. © 2016 American Chemical Society. Source


Pinto P.,Servico de Ginecologia e Obstetricia | Pinto P.,University of Porto | Costa-Santos C.,University of Porto | Ayres-De-Campos D.,University of Porto | And 4 more authors.
Journal of Maternal-Fetal and Neonatal Medicine | Year: 2016

Objective: To assess combined maternal (MHR) and fetal heart rate (FHR) recordings during labor, in relation with maternal-fetal attachment and prediction of newborn acidemia.Study design: Fifty-nine simultaneous MHR and FHR recordings were acquired in the final minutes of labor. Computer analysis followed the FIGO guidelines with estimation of MHR and FHR baselines, accelerations, decelerations, short- (STV) and long-term variabilities. MHR and FHR characteristics, their differences and correlations were assessed in relation to labor progression and to newborn umbilical artery blood (UAB) pH lower than 7.15 and 7.20. To assess prediction of acidemia, areas under ROC curves (auROC) were calculated.Results: Progression of labor was associated with a significant increase in MHR accelerations and FHR decelerations both in the non-acidemic and acidemic fetuses (p < 0.01). At the same time there was an increase in MHR-FHR correlations and differences in accelerations and decelerations in acidemic fetuses. The auROC ranged between 0.50 for FHR accelerations and 0.77 for MHR baseline plus FHR STV.Conclusions: MHR and FHR respond differently during labor with signs of increased maternal-fetal attachment during labor progression in acidemic fetuses. Combined MHR-FHR analysis may help to improve prediction of newborn acidemia compared with FHR analysis alone. © 2015 Informa UK Ltd. Source


Almeida R.,University of Porto | Almeida R.,CIBER ISCIII | Almeida R.,Aragon Institute of Engineering Research | Goncalves H.,University of Porto | And 3 more authors.
Physiological Measurement | Year: 2014

Fetal heart rate monitoring is used for pregnancy surveillance in obstetric units all over the world but in spite of recent advances in analysis methods, there are still inherent technical limitations that bound its contribution to the improvement of perinatal indicators. In this work, a previously published wavelet transform based QRS detector, validated over standard electrocardiogram (ECG) databases, is adapted to fetal QRS detection over abdominal fetal ECG. Maternal ECG waves were first located using the original detector and afterwards a version with parameters adapted for fetal physiology was applied to detect fetal QRS, excluding signal singularities associated with maternal heartbeats. Single lead (SL) based marks were combined in a single annotator with post processing rules (SLR) from which fetal RR and fetal heart rate (FHR) measures can be computed. Data from PhysioNet with reference fetal QRS locations was considered for validation, with SLR outperforming SL including ICA based detections. The error in estimated FHR using SLR was lower than 20bpm for more than 80% of the processed files. The median error in 1min based FHR estimation was 0.13bpm, with a correlation between reference and estimated FHR of 0.48, which increased to 0.73 when considering only records for which estimated FHR> 110bpm. This allows us to conclude that the proposed methodology is able to provide a clinically useful estimation of the FHR. © 2014 Institute of Physics and Engineering in Medicine. Source


Costa A.M.,University of Minho | Costa A.M.,ICVS 3Bs PT Government Associate Laboratory | Pinto F.,University of Minho | Pinto F.,ICVS 3Bs PT Government Associate Laboratory | And 7 more authors.
Oncotarget | Year: 2015

Matrix metalloproteinases (MMPs) are proteolytic enzymes that degrade extracellular matrix (ECM), thus assisting invasion. Upregulation of MMPs, frequently reported in gliomas, is associated with aggressive behavior. WNK2 is a tumor suppressor gene expressed in normal brain, and silenced by promoter methylation in gliomas. Patients without WNK2 exhibited poor prognosis, and its downregulation was associated with increased glioma cell invasion. Here we showed that MMP2 expression and activity are increased in glioma cell lines that do not express WNK2. Also, WNK2 inhibited JNK, a process associated with decreasing levels of MMP2. Thus, WNK2 promoter methylation and silencing in gliomas is associated with increased JNK activation and MMP2 expression and activity, thus explaining in part tumor cell invasion potential. Source


Almeida R.,University of Porto | Almeida R.,Communications Technology Group GTC | Goncalves H.,University of Porto | Rocha A.P.,University of Porto | And 2 more authors.
Computing in Cardiology | Year: 2013

Fetal heart rate monitoring is widespread all over the world. However, despite recent advances in analysis methods, there are still inherent technical limitations. One of the main challenges is to extract accurate and useful information from the external fetal ECG, which may provide a better non-invasive characterization of the fetal cardiovascular system during the third trimester of pregnancy. In this work, maternal ECG waves were first located using a wavelet transform based system previously developed and validated. Then, a similar strategy with adapted parameters for fetal physiology was applied to detect fetal QRS, excluding signal singularities associated to maternal heartbeats. Single lead based annotations were combined in a single annotator from which RR and HRV fetal measures could be taken. Data provided from PhysioNet 2013 Challenge was considered. The average scores were: 521.43 / 401,50 for event 4 and 32.99 / 29,70 for event 5 on set B /A respectively. The median rate of true positives, false positives and false negatives, normalized by number of fetal beats, found in the (training) set A was, respectively 78%, 17% and 22%. Median FHR estimation error was 2.0 bpm. Correlation between reference and estimated median FHR was 0.65 for estimated FHR>120bpm. The proposed approach seems promising for assessing fetal cardiac rhythms from abdominal ECGs. © 2013 CCAL. Source

Discover hidden collaborations