Browsing by Author "Azqueta, Amaya"
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- DNA damage in circulating leukocytes measured with the comet assay may predict the risk of deathPublication . Bonassi, Stefano; Ceppi, Marcello; Møller, Peter; Azqueta, Amaya; Milić, Mirta; Neri, Monica; Brunborg, Gunnar; Godschalk, Roger; Koppen, Gudrun; Langie, Sabine A.S.; Teixeira, João Paulo; Bruzzone, Marco; Da Silva, Juliana; Benedetti, Danieli; Cavallo, Delia; Ursini, Cinzia Lucia; Giovannelli, Lisa; Moretti, Silvia; Riso, Patrizia; Del Bo’, Cristian; Russo, Patrizia; Dobrzyńska, Malgorzata; Goroshinskaya, Irina A.; Surikova, Ekaterina I.; Staruchova, Marta; Barančokova, Magdalena; Volkovova, Katarina; Kažimirova, Alena; Smolkova, Bozena; Laffon, Blanca; Valdiglesias, Vanessa; Pastor, Susana; Marcos, Ricard; Hernández, Alba; Gajski, Goran; Spremo-Potparević, Biljana; Živković, Lada; Boutet-Robinet, Elisa; Perdry, Hervé; Lebailly, Pierre; Perez, Carlos L.; Basaran, Nursen; Nemeth, Zsuzsanna; Safar, Anna; Dusinska, Maria; Collins, Andrew; Anderson, Diana; Andrade, Vanessa; Pereira, Cristiana Costa; Costa, Solange; Gutzkow, Kristine B.; Ladeira, Carina; Moretti, Massimo; Costa, Carla; Orlow, Irene; Rojas, Emilio; Pourrut, Bertrand; Kruszewski, Marcin; Knasmueller, Siegfried; Shaposhnikov, Sergey; Žegura, Bojana; Stopper, HelgaThe comet assay or single cell gel electrophoresis, is the most common method used to measure strand breaks and a variety of other DNA lesions in human populations. To estimate the risk of overall mortality, mortality by cause, and cancer incidence associated to DNA damage, a cohort of 2,403 healthy individuals (25,978 person-years) screened in 16 laboratories using the comet assay between 1996 and 2016 was followed-up. Kaplan-Meier analysis indicated a worse overall survival in the medium and high tertile of DNA damage (p < 0.001). The effect of DNA damage on survival was modelled according to Cox proportional hazard regression model. The adjusted hazard ratio (HR) was 1.42 (1.06-1.90) for overall mortality, and 1.94 (1.04-3.59) for diseases of the circulatory system in subjects with the highest tertile of DNA damage. The findings of this study provide epidemiological evidence encouraging the implementation of the comet assay in preventive strategies for non-communicable diseases.
- DNA strand break levels in cryopreserved mononuclear blood cell lines measured by the alkaline comet assay: results from the hCOMET ring trialPublication . Møller, Peter; Azqueta, Amaya; Rodriguez-Garraus, Adriana; Bakuradze, Tamara; Richling, Elke; Bankoglu, Ezgi Eyluel; Stopper, Helga; Claudino Bastos, Victoria; Langie, Sabine A.S.; Jensen, Annie; Ristori, Sara; Scavone, Francesca; Giovannelli, Lisa; Wojewódzka, Maria; Kruszewski, Marcin; Valdiglesias, Vanessa; Laffon, Blanca; Costa, Carla; Costa, Solange; Paulo Teixeira, João; Marino, Mirko; Del Bo, Cristian; Riso, Patrizia; Zheng, Congying; Shaposhnikov, Sergey; Collins, AndrewThe comet assay is widely used in biomonitoring studies for the analysis of DNA damage in leukocytes and peripheral blood mononuclear cells. Rather than processing blood samples directly, it can be desirable to cryopreserve whole blood or isolated cells for later analysis by the comet assay. However, this creates concern about artificial accumulation of DNA damage during cryopreservation. In this study, 10 laboratories used standardized cryopreservation and thawing procedures of monocytic (THP-1) or lymphocytic (TK6) cells. Samples were cryopreserved in small aliquots in 50% foetal bovine serum, 40% cell culture medium, and 10% dimethyl sulphoxide. Subsequently, cryopreserved samples were analysed by the standard comet assay on three occasions over a 3-year period. Levels of DNA strand breaks in THP-1 cells were increased (four laboratories), unaltered (four laboratories), or decreased (two laboratories) by long-term storage. Pooled analysis indicates only a modest positive association between storage time and levels of DNA strand breaks in THP-1 cells (0.37% Tail DNA per year, 95% confidence interval: -0.05, 0.78). In contrast, DNA strand break levels were not increased by cryopreservation in TK6 cells. There was inter-laboratory variation in levels of DNA strand breaks in THP-1 cells (SD = 3.7% Tail DNA) and TK6 reference sample cells (SD = 9.4% Tail DNA), whereas the intra-laboratory residual variation was substantially smaller (i.e. SD = 0.4%-2.2% Tail DNA in laboratories with the smallest and largest variation). In conclusion, the study shows that accumulation of DNA strand breaks in cryopreserved mononuclear blood cell lines is not a matter of concern.
- Hazard characterization of the mycotoxins enniatins and beauvericin to identify data gaps and improve risk assessment for human healthPublication . Behr, Anne-Cathrin; Fæste, Christiane Kruse; Azqueta, Amaya; Tavares, Ana M.; Spyropoulou, Anastasia; Solhaug, Anita; Olsen, Ann-Karin; Vettorazzi, Ariane; Mertens, Birgit; Zegura, Bojana; Streel, Camille; Ndiaye, Dieynaba; Spilioti, Eliana; Dubreil, Estelle; Buratti, Franca Maria; Crudo, Francesco; Eriksen, Gunnar Sundstøl; Snapkow, Igor; Teixeira, João Paulo; Rasinger, Josef D.; Sanders, Julie; Machera, Kyriaki; Ivanova, Lada; Gaté, Laurent; Le Hegarat, Ludovic; Novak, Matjaz; Smith, Nicola M.; Tait, Sabrina; Fraga, Sónia; Hager, Sonja; Marko, Doris; Braeuning, Albert; Louro, Henriqueta; Silva, Maria João; Dirven, Hubert; Dietrich, JessicaEnniatins (ENNs) and beauvericin (BEA) are cyclic hexadepsipeptide fungal metabolites which have demonstrated antibiotic, antimycotic, and insecticidal activities. The substantial toxic potentials of these mycotoxins are associated with their ionophoric molecular properties and relatively high lipophilicities. ENNs occur extensively in grain and grain-derived products and are considered a food safety issue by the European Food Safety Authority (EFSA). The tolerable daily intake and maximum levels for ENNs in humans and animals remain unestablished due to key toxicological and toxicokinetic data gaps, preventing full risk assessment. Aiming to find critical data gaps impeding hazard characterization and risk evaluation, this review presents a comprehensive summary of the existing information from in vitro and in vivo studies on toxicokinetic characteristics and cytotoxic, genotoxic, immunotoxic, endocrine, reproductive and developmental effects of the most prevalent ENN analogues (ENN A, A1, B, B1) and BEA. The missing information identified showed that additional studies on ENNs and BEA have to be performed before sufficient data for an in-depth hazard characterisation of these mycotoxins become available.
- Inter-laboratory variation in DNA damage using a standard comet assay protocolPublication . Forchhammer, Lykke; Ersson, Clara; Loft, Steffen; Moller, Lennart; Godschalk, Roger W. L.; van Schooten, Frederik J; Jones, George D. D.; Higgins, Jennifer A.; Cooke, Marcus; Mistry, Vilas; Karbaschi, Mahsa; Collins, Andrew R.; Azqueta, Amaya; Phillips, David H.; Sozeri, Osman; Routledge, Michael N.; Nelson-Smith, Kirsty; Riso, Patrizia; Porrini, Marisa; Matullo, Giuseppe; Allione, Alessandra; Stepnik, Maciej; Komorowska, Magdalena; Teixeira, João Paulo; Costa, Solange; Corcuera, Laura-Ana; Lopez de Cerain, Adela; Laffon, Blanca; Valdiglesias, Vanessa; Moller, PeterThere are substantial inter-laboratory variations in the levels of DNA damage measured by the comet assay. The aim of this study was to investigate whether adherence to a standard comet assay protocol would reduce inter-laboratory variation in reported values of DNA damage. Fourteen laboratories determined the baseline level of DNA strand breaks (SBs)/alkaline labile sites and formamidopyrimidine DNA glycosylase (FPG)-sensitive sites in coded samples of mononuclear blood cells (MNBCs) from healthy volunteers. There were technical problems in seven laboratories in adopting the standard protocol, which were not related to the level of experience. Therefore, the inter-laboratory variation in DNA damage was only analysed using the results from laboratories that had obtained complete data with the standard comet assay protocol. This analysis showed that the differences between reported levels of DNA SBs/alkaline labile sites in MNBCs were not reduced by applying the standard assay protocol as compared with the laboratory's own protocol. There was large inter-laboratory variation in FPG-sensitive sites by the laboratory-specific protocol and the variation was reduced when the samples were analysed by the standard protocol. The SBs and FPG-sensitive sites were measured in the same experiment, indicating that the large spread in the latter lesions was the main reason for the reduced inter-laboratory variation. However, it remains worrying that half of the participating laboratories obtained poor results using the standard procedure. This study indicates that future comet assay validation trials should take steps to evaluate the implementation of standard procedures in participating laboratories.
- Inter-laboratory variation in measurement of DNA damage by the alkaline comet assay in the hCOMET ring trialPublication . Møller, Peter; Azqueta, Amaya; Collia, Miguel; Bakuradze, Tamara; Richling, Elke; Bankoglu, Ezgi Eyluel; Stopper, Helga; Bastos, Victoria Claudino; Langie, Sabine A.S.; Jensen, Annie; Ristori, Sara; Scavone, Francesca; Giovannelli, Lisa; Wojewódzka, Maria; Kruszewski, Marcin; Valdiglesias, Vanessa; Laffon, Blanca; Costa, Carla; Costa, Solange; Teixeira, João Paulo; Marino, Mirko; Del Bo, Cristian; Riso, Patrizia; Zheng, Congying; Shaposhnikov, Sergey; Collins, AndrewThe comet assay is a simple and versatile method for measurement of DNA damage in eukaryotic cells. More specifically, the assay detects DNA migration from agarose gel-embedded nucleoids, which depends on assay conditions and the level of DNA damage. Certain steps in the comet assay procedure have substantial impact on the magnitude of DNA migration (e.g. electric potential and time of electrophoresis). Inter-laboratory variation in DNA migration levels occurs because there is no agreement on optimal assay conditions or suitable assay controls. The purpose of the hCOMET ring trial was to test potassium bromate (KBrO3) as a positive control for the formamidopyrimidine DNA glycosylase (Fpg)-modified comet assay. To this end, participating laboratories used semi-standardized protocols for cell culture (i.e. cell culture, KBrO3 exposure, and cryopreservation of cells) and comet assay procedures, whereas the data acquisition was not standardized (i.e. staining of comets and image analysis). Segregation of the total variation into partial standard deviation (SD) in % Tail DNA units indicates the importance of cell culture procedures (SD = 10.9), comet assay procedures (SD = 12.3), staining (SD = 7.9) and image analysis (SD = 0.5) on the overall inter-laboratory variation of DNA migration (SD = 18.2). Future studies should assess sources of variation in each of these steps. On the positive side, the hCOMET ring trial demonstrates that KBrO3 is a robust positive control for the Fpg-modified comet assay. In conclusion, the hCOMET ring trial has demonstrated a high reproducibility of detecting genotoxic effects by the comet assay, but inter-laboratory variation of DNA migration levels is a concern.
- Long-term cryopreservation of potassium bromate positive assay controls for measurement of oxidatively damaged DNA by the Fpg-modified comet assay: results from the hCOMET ring trialPublication . Møller, Peter; Azqueta, Amaya; Rodriguez-Garraus, Adriana; Bakuradze, Tamara; Richling, Elke; Bankoglu, Ezgi Eyluel; Stopper, Helga; Claudino Bastos, Victoria; Langie, Sabine A.S.; Jensen, Annie; Ristori, Sara; Scavone, Francesca; Giovannelli, Lisa; Wojewódzka, Maria; Kruszewski, Marcin; Valdiglesias, Vanessa; Laffon, Blanca; Costa, Carla; Costa, Solange; Paulo Teixeira, João; Marino, Mirko; Del Bo’, Cristian; Riso, Patrizia; Zheng, Congying; Shaposhnikov, Sergey; Collins, AndrewThe formamidopyrimidine DNA glycosylase (Fpg)-modified comet assay is widely used for the measurement of oxidatively generated damage to DNA. However, there has not been a recommended long-term positive control for this version of the comet assay. We have investigated potassium bromate as a positive control for the Fpg-modified comet assay because it generates many Fpg-sensitive sites with a little concurrent generation of DNA strand breaks. Eight laboratories used the same procedure for the treatment of monocytic THP-1 cells with potassium bromate (0, 0.5, 1.5, and 4.5 mM) and subsequent cryopreservation in a freezing medium consisting of 50% foetal bovine serum, 40% RPMI-1640 medium, and 10% dimethyl sulphoxide. The samples were analysed by the Fpg-modified comet assay three times over a 3-year period. All laboratories obtained a positive concentration-response relationship in cryopreserved samples (linear regression coefficients ranging from 0.79 to 0.99). However, there was a wide difference in the levels of Fpg-sensitive sites between the laboratory with the lowest (4.2% Tail DNA) and highest (74% Tail DNA) values in THP-1 cells after exposure to 4.5 mM KBrO3. In an attempt to assess sources of inter-laboratory variation in Fpg-sensitive sites, comet images from one experiment in each laboratory were forwarded to a central laboratory for visual scoring. There was high consistency between measurements of %Tail DNA values in each laboratory and the visual score of the same comets done in the central laboratory (r = 0.98, P < 0.001, linear regression). In conclusion, the results show that potassium bromate is a suitable positive comet assay control.
- Measuring DNA modifications with the comet assay: a compendium of protocolsPublication . Collins, Andrew; Møller, Peter; Gajski, Goran; Vodenková, Soňa; Abdulwahed, Abdulhadi; Anderson, Diana; Bankoglu, Ezgi Eyluel; Bonassi, Stefano; Boutet-Robinet, Elisa; Brunborg, Gunnar; Chao, Christy; Cooke, Marcus S.; Costa, Carla; Costa, Solange; Dhawan, Alok; de Lapuente, Joaquin; Bo’, Cristian Del; Dubus, Julien; Dusinska, Maria; Duthie, Susan J.; Yamani, Naouale El; Engelward, Bevin; Gaivão, Isabel; Giovannelli, Lisa; Godschalk, Roger; Guilherme, Sofia; Gutzkow, Kristine B.; Habas, Khaled; Hernández, Alba; Herrero, Oscar; Isidori, Marina; Jha, Awadhesh N.; Knasmüller, Siegfried; Kooter, Ingeborg M.; Koppen, Gudrun; Kruszewski, Marcin; Ladeira, Carina; Laffon, Blanca; Larramendy, Marcelo; Hégarat, Ludovic Le; Lewies, Angélique; Lewinska, Anna; Liwszyc, Guillermo E.; de Cerain, Adela López; Manjanatha, Mugimane; Marcos, Ricard; Milić, Mirta; de Andrade, Vanessa Moraes; Moretti, Massimo; Muruzabal, Damian; Novak, Matjaž; Oliveira, Rui; Olsen, Ann-Karin; Owiti, Norah; Pacheco, Mário; Pandey, Alok K.; Pfuhler, Stefan; Pourrut, Bertrand; Reisinger, Kerstin; Rojas, Emilio; Rundén-Pran, Elise; Sanz-Serrano, Julen; Shaposhnikov, Sergey; Sipinen, Ville; Smeets, Karen; Stopper, Helga; Teixeira, João Paulo; Valdiglesias, Vanessa; Valverde, Mahara; van Acker, Frederique; van Schooten, Frederik-Jan; Vasquez, Marie; Wentzel, Johannes F.; Wnuk, Maciej; Wouters, Annelies; Žegura, Bojana; Zikmund, Tomas; Langie, Sabine A.S.; Azqueta, AmayaThe comet assay is a versatile method to detect nuclear DNA damage in individual eukaryotic cells, from yeast to human. The types of damage detected encompass DNA strand breaks and alkali-labile sites (e.g., apurinic/apyrimidinic sites), alkylated and oxidized nucleobases, DNA-DNA crosslinks, UV-induced cyclobutane pyrimidine dimers and some chemically induced DNA adducts. Depending on the specimen type, there are important modifications to the comet assay protocol to avoid the formation of additional DNA damage during the processing of samples and to ensure sufficient sensitivity to detect differences in damage levels between sample groups. Various applications of the comet assay have been validated by research groups in academia, industry and regulatory agencies, and its strengths are highlighted by the adoption of the comet assay as an in vivo test for genotoxicity in animal organs by the Organisation for Economic Co-operation and Development. The present document includes a series of consensus protocols that describe the application of the comet assay to a wide variety of cell types, species and types of DNA damage, thereby demonstrating its versatility.
- Minimum Information for Reporting on the Comet Assay (MIRCA): recommendations for describing comet assay procedures and resultsPublication . Møller, Peter; Azqueta, Amaya; Boutet-Robinet, Elisa; Koppen, Gudrun; Bonassi, Stefano; Milić, Mirta; Gajski, Goran; Costa, Solange; Teixeira, João Paulo; Costa Pereira, Cristiana; Dusinska, Maria; Godschalk, Roger; Brunborg, Gunnar; Gutzkow, Kristine B.; Giovannelli, Lisa; Cooke, Marcus S.; Richling, Elke; Laffon, Blanca; Valdiglesias, Vanessa; Basaran, Nursen; Del Bo’, Cristian; Zegura, Bojana; Novak, Matjaz; Stopper, Helga; Vodicka, Pavel; Vodenkova, Sona; de Andrade, Vanessa Moraes; Sramkova, Monika; Gabelova, Alena; Collins, Andrew; Langie, Sabine A.S.The comet assay is a widely used test for the detection of DNA damage and repair activity. However, there are interlaboratory differences in reported levels of baseline and induced damage in the same experimental systems. These differences may be attributed to protocol differences, although it is difficult to identify the relevant conditions because detailed comet assay procedures are not always published. Here, we present a Consensus Statement for the Minimum Information for Reporting Comet Assay (MIRCA) providing recommendations for describing comet assay conditions and results. These recommendations differentiate between 'desirable' and 'essential' information: 'essential' information refers to the precise details that are necessary to assess the quality of the experimental work, whereas 'desirable' information relates to technical issues that might be encountered when repeating the experiments. Adherence to MIRCA recommendations should ensure that comet assay results can be easily interpreted and independently verified by other researchers.
- Potassium bromate as positive assay control for the Fpg-modified comet assayPublication . Møller, Peter; Muruzabal, Damian; Bakuradze, Tamara; Richling, Elke; Bankoglu, Ezgi Eyluel; Stopper, Helga; Langie, Sabine A.S.; Azqueta, Amaya; Jensen, Annie; Scavone, Francesca; Giovannelli, Lisa; Wojewódzka, Maria; Kruszewski, Marcin; Valdiglesias, Vanessa; Laffon, Blanca; Costa, Carla; Costa, Solange; Teixeira, João Paulo; Marino, Mirko; Del Bo’, Cristian; Riso, Patrizia; Shaposhnikov, Sergey; Collins, AndrewThe comet assay is a popular assay in biomonitoring studies. DNA strand breaks (or unspecific DNA lesions) are measured using the standard comet assay. Oxidative stress-generated DNA lesions can be measured by employing DNA repair enzymes to recognise oxidatively damaged DNA. Unfortunately, there has been a tendency to fail to report results from assay controls (or maybe even not to employ assay controls). We believe this might have been due to uncertainty as to what really constitutes a positive control. It should go without saying that a biomonitoring study cannot have a positive control group as it is unethical to expose healthy humans to DNA damaging (and thus potentially carcinogenic) agents. However, it is possible to include assay controls in the analysis (here meant as a cryopreserved sample of cells i.e. included in each experiment as a reference sample). In the present report we tested potassium bromate (KBrO3) as a positive comet assay control for the formamidopyrimidine DNA glycosylase (Fpg)-modified comet assay. Ten laboratories used the same procedure for treatment of monocytic THP-1 cells with KBrO3 (0.5, 1.5 and 4.5 mM for 1 h at 37°C) and subsequent cryopreservation. Results from one laboratory were excluded in the statistical analysis because of technical issues in the Fpg-modified comet assay. All other laboratories found a concentration-response relationship in cryopreserved samples (regression coefficients from 0.80 to 0.98), although with different slopes ranging from 1.25 to 11.9 Fpg-sensitive sites (%DNA in tail) per 1 mM KBrO3. Our results demonstrate that KBrO3 is a suitable positive comet assay control.
- The hCOMET project: International database comparison of results with the comet assay in human biomonitoring. Baseline frequency of DNA damage and effect of main confoundersPublication . Milić, Mirta; Ceppi, Marcello; Bruzzone, Marco; Azqueta, Amaya; Brunborg, Gunnar; Godschalk, Roger; Koppen, Gudrun; Langie, Sabine; Møller, Peter; Teixeira, João Paulo; Alija, Avdulla; Anderson, Diana; Andrade, Vanessa; Andreoli, Cristina; Asllani, Fisnik; Bangkoglu, Ezgi Eyluel; Barančoková, Magdalena; Basaran, Nursen; Boutet-Robinet, Elisa; Buschini, Annamaria; Cavallo, Delia; Costa Pereira, Cristiana; Costa, Carla; Costa, Solange; Da Silva, Juliana; Del Boˊ, Cristian; Dimitrijević Srećković, Vesna; Djelić, Ninoslav; Dobrzyńska, Malgorzata; Duračková, Zdenka; Dvořáková, Monika; Gajski, Goran; Galati, Serena; García Lima, Omar; Giovannelli, Lisa; Goroshinskaya, Irina A.; Grindel, Annemarie; Gutzkow, Kristine B.; Hernández, Alba; Hernández, Carlos; Holven, Kirsten B.; Ibero-Baraibar, Idoia; Ottestad, Inger; Kadioglu, Ela; Kažimirová, Alena; Kuznetsova, Elena; Ladeira, Carina; Laffon, Blanca; Lamonaca, Palma; Lebailly, Pierre; Louro, Henriqueta; Mandina Cardoso, Tania; Marcon, Francesca; Marcos, Ricard; Moretti, Massimo; Moretti, Silvia; Najafzadeh, Mojgan; Nemeth, Zsuzsanna; Neri, Monica; Novotna, Bozena; Orlow, Irene; Paduchova, Zuzana; Pastor, Susana; Perdry, Hervé; Spremo-Potparević, Biljana; Ramadhani, Dwi; Riso, Patrizia; Rohr, Paula; Rojas, Emilio; Rossner, Pavel; Safar, Anna; Sardas, Semra; Silva, Maria João; Sirota, Nikolay; Smolkova, Bozena; Staruchova, Marta; Stetina, Rudolf; Stopper, Helga; Surikova, Ekaterina I.; Ulven, Stine M.; Ursini, Cinzia Lucia; Valdiglesias, Vanessa; Valverde, Mahara; Vodicka, Pavel; Volkovova, Katarina; Wagner, Karl-Heinz; Živković, Lada; Dušinská, Maria; Collins, Andrew R.; Bonassi, StefanoThe alkaline comet assay, or single cell gel electrophoresis, is one of the most popular methods for assessing DNA damage in human population. One of the open issues concerning this assay is the identification of those factors that can explain the large inter-individual and inter-laboratory variation. International collaborative initiatives such as the hCOMET project - a COST Action launched in 2016 - represent a valuable tool to meet this challenge. The aims of hCOMET were to establish reference values for the level of DNA damage in humans, to investigate the effect of host factors, lifestyle and exposure to genotoxic agents, and to compare different sources of assay variability. A database of 19,320 subjects was generated, pooling data from 105 studies run by 44 laboratories in 26 countries between 1999 and 2019. A mixed random effect log-linear model, in parallel with a classic meta-analysis, was applied to take into account the extensive heterogeneity of data, due to descriptor, specimen and protocol variability. As a result of this analysis interquartile intervals of DNA strand breaks (which includes alkali-labile sites) were reported for tail intensity, tail length, and tail moment (comet assay descriptors). A small variation by age was reported in some datasets, suggesting higher DNA damage in oldest age-classes, while no effect could be shown for sex or smoking habit, although the lack of data on heavy smokers has still to be considered. Finally, highly significant differences in DNA damage were found for most exposures investigated in specific studies. In conclusion, these data, which confirm that DNA damage measured by the comet assay is an excellent biomarker of exposure in several conditions, may contribute to improving the quality of study design and to the standardization of results of the comet assay in human populations.