Browsing by Author "Xavier, Cristina"
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- An aqueous extract of tuberaria lignosa inhibits cell growth, alters the cell cycle profile, and induces apoptosis of NCI-H460 tumor cellsPublication . Pereira, Joana M.; Lopes-Rodrigues, Vanessa; Xavier, Cristina; Lima, M. João; Lima, Raquel T.; Ferreira, Isabel C.F.R.; Vasconcelos, M. HelenaTuberaria lignosa (Sweet) Samp. is found in European regions, and has antioxidant properties due to its composition in ascorbic acid and phenolic compounds. Given its traditional use and antioxidant properties, the tumor cell growth inhibitory potential of aqueous extracts from T. lignosa (prepared by infusion and decoction) was investigated in three human tumor cell lines: MCF-7 (breast adenocarcinoma), NCI-H460 (non-small cell lung cancer), and HCT-15 (human colorectal adenocarcinoma). Both extracts inhibited the growth of these cell lines; the most potent one being the T. lignosa extract obtained by infusion in the NCI-H460 cells (GI50 of approximately 50 μg/mL). Further assays were carried out with this extract in NCI-H460 cells. At 100 μg/mL or 150 μg/mL it caused an increase in the percentage of cells in the G0/G1 phase and a decrease of cells in S phase of the cell cycle. Additionally, these concentrations caused an increase in the percentage of apoptotic cells. In agreement, a decrease in total poly (ADP-ribose) polymerase (PARP) and pro-caspase 3 levels was found. In conclusion, the T. lignosa extract obtained by infusion was more potent in NCI-H460 cells, altering the cell cycle progression and inducing apoptosis. This work highlights the importance of T. lignosa as a source of bioactive compounds with tumor cell growth inhibitory potential.
- Estudio de meta-analisis de las correlaciones entre las medidas de los tejidos obtenidas por ultrasonidos y sus homólogas de la canal de bovinosPublication . Xavier, Cristina; Gonzales-Barron, Ursula; Cadavez, VascoGlass (1976) empleó por primera vez el término meta-análisis para referirse al análisis estadístico de resultados de diferentes ensayos clínicos para evaluarlos conjuntamente. El meta-análisis es una metodología estadística de un conjunto de publicaciones, con el objetivo de agregar y de comparar los resultados obtenidos por diversos estudios sobre el mismo tema (Viechtbauer, 2010). Así, los estudios de meta-análisis permiten combinar los resultados de varios estudios y reconocer patrones en los resultados de trabajos independientes (Gonzales-Barron et al., 2012). Los estudios de meta-análisis pueden ser utilizados para estimar el efecto promedio y las diferencias de los efectos de varios estudios. Los trabajos que estudian las correlaciones de las medidas espesor de la grasa subcutánea (EGS) y del área del músculo Longissimus dorsi (AML), obtenidas por ultrasonido y las medidas homólogas efectuadas en la canal, presentan resultados muy variables y por veces contradictorios. De hecho, las correlaciones de cada uno de los trabajos son estimaciones y por tanto son portadores de imprecisiones. En este trabajo presentamos los resultados de un estudio de meta-análisis, de 9 estudios empíricos publicados en revistas internacionales, realizado con el objetivo de estimar el efecto promedio de las correlaciones de varios estudios.
- Estudio de meta-análisis del efecto de estimulación eléctrica en la fuerza de corte de la carne de vacunoPublication . Xavier, Cristina; Gonzales-Barron, Ursula; Muller, Alexandra; Cadavez, VascoThe objective of this work was to use meta-analysis to estimate the effect size of the electrical stimulation on beef tenderness through the study of the measurements of shear force. Eight independent studies were used based on comparison of shear force measurements on the Longissimus dorsi and Longissimus lumborum in cattle carcasses subject to electrical stimulation and unstimulated carcasses. For each study, the mean effect size and standard error was calculated in order to apply a random-effects meta-analysis model. The meta-analysis demonstrated that the electrical stimulation on beef carcasses decreases the values of shear-force of meat by an average of 1.34 kgf. Thus, this study confirmed the positive effect of the electrical stimulation on the beef meat tenderness. However, the effect size displayed high variation among studies which can be attributed to differences in their experimental conditions.
- An exposure assessment model of the prevalence of Salmonella spp. along the processing stages of Brazilian beefPublication . Gonzales-Barron, Ursula; Piza, Luciana; Xavier, Cristina; Costa, Ernane; Cadavez, VascoBeef cattle carrying Salmonella spp. represents a risk for contamination of meat and meat products. This study aimed to build an exposure assessment model elucidating the changes in Salmonella prevalence in Brazilian beef along the processing stages. To this effect, the results of a number of published studies reporting Salmonella incidences were assembled in order to model conversion factors based on beta distributions representing the effect of every production stage on the Salmonella incidence on beef carcasses. A random-effects meta-analysis modelled the hide-to-carcass transfer of Salmonella contamination. The Monte Carlo simulation estimated the Salmonella prevalence in beef cuts from processing plants to be â∼1/46.1% (95% CI: 1.4-17.7%), which was in reasonable agreement with a pool (n = 105) of surveys' data of Salmonella in Brazilian beef cuts (mean 4.9%; 95% CI: 1.8-11.5%) carried out in commercial establishments. The results not only underscored the significant increase in Salmonella prevalence that can occur during evisceration/splitting and boning but also reinforced that, when hygienic slaughter procedures are properly implemented, the load of Salmonella can be reduced at dehiding, rinsing and chilling. As the model was based on a systematic review and meta-analysis, it synthesised all available knowledge on the incidence of Salmonella in Brazilian beef.
- Melissa officinalis L. ethanolic extract inhibits the growth of a lung cancer cell line by interfering with the cell cycle and inducing apoptosisPublication . Magalhães, Daniela B.; Castro, Inês; Lopes-Rodrigues, Vanessa; Pereira, Joana M.; Barros, Lillian; Ferreira, Isabel C.F.R.; Xavier, Cristina; Vasconcelos, M. HelenaMelissa officinalis is a plant from the family Lamiaceae, native in Europe particularly in the Mediterranean region. Given our interest in identifying extracts and compounds capable of inhibiting tumor cell growth, and given the antioxidant content and the high consumption of Melissa officinalis in Portugal, this study aimed to test the tumor cell growth inhibitory activity of five different extracts of this plant (aqueous, methanolic, ethanolic, hydromethanolic and hydroethanolic) in three human tumor cell lines: MCF-7, AGS and NCI-H460. All extracts decreased cell growth in all cell lines in a concentration-dependent manner. The ethanolic extract was the most potent one, presenting a GI50 concentration of approximately 100.9 μg mL−1 in the NCI-H460 lung cancer cells. This extract was characterized by LC-DAD-ESI/MS regarding its phenolic composition, revealing rosmarinic acid as the most abundant compound. The GI75 concentration of this extract affected the cell cycle profile of these cells. In addition, both the GI50 and the GI75 concentrations of the extract induced cellular apoptosis. Moreover, treatment of NCI-H460 cells with this extract caused a decrease in pro-caspase 3 and an increase in p53 levels. This study emphasizes the relevance of the study of natural products as inhibitors of tumor cell growth.
- Meta-analysis of the incidence of foodborne pathogens in Portuguese meats and their productsPublication . Xavier, Cristina; Cadavez, Vasco; Paula, Vanessa B.; Estevinho, Leticia M.; Gonzales-Barron, UrsulaMeat and meat products are the main vehicles of foodborne diseases in humans caused by pathogens such as Salmonella spp., Campylobacter spp., Listeria monocytogenes, Yersinia enterocolitica, verotoxigenic Escherichia coli (VTEC) and Staphylococcus aureus. In order to prioritise research on those microbial hazards, a meta-analysis study was conducted to summarise available information on the presence of such pathogens in meats produced in Portugal. By using a logit-transformed proportion as effect size parameterisation, a number of multilevel random-effectmeta-analysismodelswere fitted to estimatemean occurrence rates of pathogens, and to compare them among meat categories (i.e., bovine meat, broiler meat, pork, minced beef and minced pork), and among meat product categories (i.e., intended to be eaten cooked, to be eaten raw and cured meats). The mean occurrence rate of Campylobacter in Portuguese broiler meat (40%; 95% CI: 22.0–61.4%) was about ten times higher than that of Salmonella (4.0%; 95% CI: 1.4–10.8%); although these levels were comparable to current EU ranges. Nevertheless, in the other meat categories, the meta-analysed incidences of Salmonella were slightly to moderately higher than EU averages. A semi-quantitative risk ranking of pathogens in Portuguese-produced pork pointed Salmonella spp. as critical (with a mean occurrence of 12.6%; 95% CI: 8.0–19.3%), and Y. enterocolitica as high (6.8%; 95% CI: 2.2–19.3%). In the case of the Portuguesemeat products, the non-compliance to EUmicrobiological criteria for L. monocytogenes (8.8%; 95% CI: 6.5–11.8%) and Salmonella spp. (9.7%; 95% CI: 7.0–13.4%) at sample units level, in the categories ‘intended to be eaten cooked’ and ‘to be eaten raw’, were considerably higher than EU levels for ready-to-eat products in comparable categories. S. aureuswas the pathogen of greatest concern given its high occurrence (22.6%; 95% CI: 15.4–31.8%) inmeat products. These results emphasised the necessity of Portuguese food safety agencies to take monitoring, and training actions for the maintenance of good hygiene practices during the production of the great variety of traditional meat products. This meta-analysis study also highlighted important gaps of knowledge, and may assist food safety authorities in the prioritisation of microbiological hazards, and the implementation of essential food safety assurance systems at primary production.
- Modelling beef meat quality traits during ageing by early post-mortem pH decay descriptorsPublication . Xavier, Cristina; Gonzales-Barron, Ursula; Muller, Alexandra; Cadavez, VascoPrevious work has demonstrated that beef carcasses can be promptly and accurately classified into optimal quality and cold-shortened in accordance to the concept of pH/temperature ‘ideal window’ by using carcass characteristics and early post-mortem pH/temperature decay descriptors. The objective of this study was to assess the combined effects of the aforementioned variables on the two main eating quality attributes of meat – namely, tenderness (measured as shear force) and juiciness (measured as cooking loss) – during chill ageing. The pH and temperature in longissimus thoracis muscle of 51 beef carcasses were recorded during 24 h post-mortem, and decay descriptors were then obtained by fitting exponential models. Measures of Warner-Bratzler shear force and cooking loss were obtained from cooked meat after 3, 8 and 13 days of cold ageing. The fitted mixed-effect models revealed that both meat tenderisation and cooking loss increased with ageing (P<0.01) although their rates slowed down in time (P<0.05). Beef carcasses with a higher pH (obtained at different endpoints: 1.5, 3.0, 4.5 or 6.0 h post-mortem) produced aged meat with increased tenderness (P=0.013) and increased water retention during cooking (P=0.016) than those of lower pH. Nonetheless, the slower the pH decay rate, as happens in a cold-shortened carcass, the lower the potential for tenderisation (P=0.038) and water retention (P=0.050) during ageing. Whereas sex affected shear force, with females producing meat of higher tenderness, aged meat of increased water retention was produced by heavier beef carcasses (P<0.001). The good fitting quality of the shear force (R2=0.847) and cooking loss (R2=0.882) models and their similarity among the different endpoints post-mortem indicated that both eating quality attributes can be approached by recording the pH decline of a beef carcass during the first 3.0 hours after slaughter.
- Modelling meat eating quality traits during ageing as affected by early post-mortem pH decayPublication . Cadavez, Vasco; Xavier, Cristina; Gonzales-Barron, UrsulaPrevious work has demonstrated that beef carcasses can be accurately classified into optimal quality and cold-shortened in accordance to the concept of pH/temperature ’ideal window’ by early post-mortem pH/temperature decay descriptors. The objective of this study was to assess the combined effects of such variables on the two main eating quality attributes of meat-tenderness (measured as shear force) and juiciness (measured as cooking loss)-during chill ageing. The pH and temperature of longissimus thoracis muscle of 51 beef carcasses were recorded during 24 h post-mortem, and decay descriptors were then obtained by fitting exponential models. Measures of Warner-Bratzler shear force and cooking loss were obtained from cooked meat after 3, 8 and 13 days of cold ageing. A fitted mixed-effect models revealed that both meat tenderisation and cooking loss increased with ageing (p<0.01) although their rates slowed down in time (p<0.05). Beef carcasses with a higher pH (obtained at different endpoints: 1.5, 3.0, 4.5 or 6.0 h post-mortem) produced aged meat with increased tenderness (p=0.013) and increased water retention during cooking (p=0.016) than those of lower pH. Nonetheless, the slower the pH decay rate, as happens in a cold-shortened carcass, the lower the potential for tenderisation (p=0.038) and water retention (p=0.050) during ageing. Whereas sex affected shear force, with females producing meat of higher tenderness, aged meat of increased water retention was produced by heavier beef carcasses (p<0.001). The good fitting quality of the shear force (R2=0.847) and cooking loss (R2=0.882) models indicated that both eating quality attributes can be approached by recording the pH decline of a beef carcass during the first 3.0 hours after slaughter.
- Modelling the temperature and pH decline early post-mortem of beef carcassesPublication . Xavier, Cristina; Gonzales-Barron, Ursula; Cadavez, Vasco; Muller, AlexandraThe objective of this work was to model the pH and temperature decline early post-mortem on beef carcasses and to study the effect of gender, genotype and weight class on the pH and temperature decline patterns. A total of 24 beef animals slaughtered in a local abattoir were sampled. pH and temperature were recorded using an OMEGA wireless receiver/host (UWTC-RECl). The decline of pH and temperature was modelled using one parameterisation of the exponential decay function, and its parameters were estimated using the software R. The fitted models were used to predict p H and temperature at 1.5 h, at 3.0 h and at 24 h; the time when p H reached 6.0, and the temperature at which p H reached 6.0. The rate parameters of the exponential decay function for pH (KpH) and temperature (KT) were found to be independent (r=0.35, P>0.05). The correlation between p H at 3 h and final p H (at 24 h) was very high (r=0.930, P<0.01). The KT was influenced by the time elapsed from slaughter until the first recording, and by the carcass weight. In opposition, those variables did not affect the KpH, The exponential decay function was able to model the early post-mortem decline of both p H and temperature, and the pII at 3 hours can be used as predictor of the final pH of beef meat.
- Robust regression models for predicting the lean meat proportion of lambs carcassesPublication . Xavier, Cristina; Cadavez, VascoThe aim of this study was to develop and evaluate robust regression models for predicting the carcass composition of lambs. One hundred and twenty lambs (34 females and 86 males) were slaughtered and their carcasses were cooled for 24 hours. The subcutaneous fat thickness (C12) was measured between the 12th and 13th rib, and the left side of carcasses was dissected and the proportions of lean meat (LMP) was calculated. A multiple regression model was fitted using robust regression (RR) methods, and the results were compared to ordinary least squares (OLS) estimates. For RR methods, the Bisquare and Welsch weighting functions were used, and model fitting quality was evaluated by the following statistics: the root mean square error (RMSE), the median absolute deviation (MAD), the mean absolute error (MAE), and the coefficient of determination (R2). The parameters obtained by RR presented lower standard error for C12 measurement (decreases by 12% when compared with OLS estimates). The RR methods or weighted least squares methods represents a good alternative to OLS approach for modelling the LMP of lambs carcass. In this study, the Bisquare weighting method presented the best results, however other weighting functions are available and should be tested and compared in the near future.