32 research outputs found
Development of an SPME-GC-MS method for the specific quantification of dimethylamine and trimethylamine: use of a new ratio for the freshness monitoring of cod fillets
International audienceBACKGROUND: Fish is a highly perishable food, so it is important to be able to estimate its freshness to ensure optimum quality for consumers. The present study describes the development of an SPMEâGCâMS technique capable of quantifying both trimethylamine (TMA) and dimethylamine (DMA), components of what has been defined as partial volatile basic nitrogen (PVBâN). This method was used, together with other reference methods, to monitor the storage of cod fillets (Gadus morhua) conserved under melting ice.RESULTS: Careful optimisation enabled definition of the best parameters for extracting and separating targeted amines and an internal standard. The study of cod spoilage by sensory analysis and TVBâN assay led to the conclusion that the shelfâlife of cod fillet was between 6 and 7 days. Throughout the study, TMA and DMA were specifically quantified by SPMEâGCâMS; the first was found to be highly correlated with the values returned by steam distillation assays. Neither TMAâN nor DMAâN were able to successfully characterise the decrease in early freshness, unlike dimethylamine/trimethylamine ratio (DTR), whose evolution is closely related to the results of sensory analysis until the stage where fillets need to be rejected.CONCLUSION: DTR was proposed as a reliable indicator for the early decrease of freshness until fish rejection
BMC Cancer
BACKGROUND: In addition to tumor characteristics and lifestyle factors, cancer relapses are often related to the risk of death but have not been jointly studied. We investigate the prognostic factors of recurrent events and death after a diagnosis of breast cancer and predict individual deaths including a history of recurrences. METHODS: The E3N (Etude Epidemiologique aupres de Femmes de la Mutuelle Generale de l'Education Nationale) study is a prospective cohort study that was initiated in 1990 to investigate factors associated with the most common types of cancer. Overall survival and three types of recurrent events were considered: locoregional recurrence, metastasis, and second primary breast cancer. Recurrent events and death were analyzed using a joint frailty model. RESULTS: The analysis included 4926 women from the E3N cohort diagnosed with a first primary invasive breast cancer between June 1990 and June 2008; during the follow-up, 1334 cases had a recurrence (median time of follow-up is 7.2 years) and 469 women died. Cases with high grade, large tumor size, axillary nodal involvement, and negative estrogen and progesterone receptors had a higher risk of recurrence or death. Furthermore, smoking increased the risk of relapse. For cases with a medium risk profile in terms of tumor characteristics and lifestyle factors, the probability of dying between 5 and 10 years after diagnosis was 6, 20 and 36% for 0, 1 or 2 recurrences within the first 5 years after diagnosis, respectively. CONCLUSIONS: Our study showed the importance of considering baseline lifestyle characteristics and history of relapses to dynamically predict the risk of death in breast cancer cases. Medical experience coupled with an estimate of a patient's survival probability that considers all available information for this patient would enable physicians to make better informed decisions regarding their actions and thus improve clinical output
Quantification of fish partial volatile basic nitrogen by SPME-GC/MS
International audienceFreshness is a key parameter in the evaluation of the fish quality. As this matrix is highly perishable, objective tools for the freshness estimation are required. By the past, numerous methods including sensorial, chemical, microbiological and physical analysis were developed to follow evolution of odour, sight or texture throughout the spoiling process.Spoiling of fish is a complex process combining autolysis and exogenous degradations. One of the most famous examples is the degradation of trimethylamine-N-oxide (TMAO) in Gadidae by both TMAO reductases of specific spoiling organisms and TMAO demethylase, an endogenic enzyme. These reactions lead respectively to the production of trimethylamine (TMA) and dimethylamine (DMA). To date, TMA and DMA are routinely non-specifically measured among other volatile amines thanks to total volatile basic nitrogen (TVB-N) analysis; TMA can be nonetheless measured more specifically by TVB-N when formaldehyde is added. The concept of partial volatile base nitrogen (PVB-N) was implemented using SPME-GC/MS to quantify both TMA and DMA. Further, this technique allows specifically detecting and measuring TMA and DMA.Extraction (temperature, time, sample preparation) and separation (temperature, column phase, split type) parameters were optimized to obtain best chromatographic profiles. Both fresh and spoiled fish were analyzed by TVB-N and PVB-N techniques. First results show consistent conclusions. Moreover, comparison of TVB-N and PVB-N leads to the conclusion that the current TMA measurement, with addition of formaldehyde, is overestimating TMA content in the flesh of fish
Quantification de lâazote basique volatil partiel par SPME-GC-MS : Application au suivi de lâĂ©volution de la fraĂźcheur de filets de cabillaud (Gadus morhua)
National audienceLa fraĂźcheur est un paramĂštre clĂ© pour lâĂ©valuation de la qualitĂ© du poisson. Cette matrice Ă©tant extrĂȘmement pĂ©rissable, lâutilisation dâoutils objectifs est nĂ©cessaire. Par le passĂ© de nombreuses mĂ©thodes incluant les analyses sensorielles, chimiques, microbiologiques et physiques ont Ă©tĂ© dĂ©veloppĂ©es pour suivre lâĂ©volution de paramĂštres olfactifs visuels et tex-turaux tout au long du processus dâaltĂ©ration.LâaltĂ©ration du poisson est un processus complexe combinant des dĂ©gradations autolytiques et exogĂšnes. Un exemple connu concernant lâaltĂ©ration de la chair des GadidĂ©s est la dĂ©gra-dation de lâoxyde de trimĂ©thylamine (OTMA) selon deux voies cataboliques: la premiĂšre fait intervenir lâOTMA rĂ©ductase synthĂ©tisĂ©e par la flore spĂ©cifique dâaltĂ©ration et la seconde est le rĂ©sultat de lâactivitĂ© dâune enzyme endogĂšne du poisson lâOTMA dĂ©mĂ©thylase. Ces rĂ©ac-tions conduisent respectivement Ă la production de trimĂ©thylamine (TMA) et la dimĂ©thyla-mine (DMA).JusquâĂ prĂ©sent la TMA et la DMA sont mesurĂ©es en routine de façon non-spĂ©cifique avec dâautres amines volatiles grĂące lâanalyse des amines basiques volatiles totales (ABVT) ; la TMA pouvant nĂ©anmoins ĂȘtre analysĂ©e plus spĂ©cifiquement avec lâajout de formaldĂ©hyde lors du processus analytique de lâABVT. Le concept dâazote basique volatil partiel a Ă©tĂ© dĂ©ve-loppĂ© pour quantifier spĂ©cifiquement la DMA et la TMA Ă lâaide dâune SPME-GC-MS.La mĂ©thode dĂ©veloppĂ©e a fait lâobjet dâune phase dâoptimisation puis de sĂ©lection dâun Ă©talon interne avant de sâintĂ©resser Ă la plage de quantification. Suite Ă ce dĂ©veloppement un suivi dâaltĂ©ration a Ă©tĂ© rĂ©alisĂ© sur des filets de cabillaud stockĂ©s sous glace fondante. Aux diffĂ©-rents jours de conservation, trois filets ont Ă©tĂ© analysĂ©s Ă lâaide de diffĂ©rentes techniques : analyse sensorielle rĂ©alisĂ©e avec la mĂ©thode du Quality Index Method (QIM), analyses chi-miques par les mĂ©thodes dâABVT et ABVP. Les concentrations en TMA mesurĂ©es par la mĂ©thode dâABVT et celle dâABVP sont trĂšs bien corrĂ©lĂ©es (r=0,98). Au regard des rĂ©sultats de lâABVT et de ceux du QIM, il apparait que la limite dâacceptation/rejet des filets est situĂ©e au voisinage du 7Ăšme jour de conservation. La production de TMA en cours dâaltĂ©ration a pu ĂȘtre modĂ©lisĂ©e, nĂ©anmoins son utilisation seule nâapparait pas comme un bon indicateur du dĂ©clin de la fraĂźcheur lors des premiers jours dâaltĂ©ration. Afin de surmonter cette limite, lâutilisation dâun nouvel indicateur issu des rĂ©sultats de lâABVP, le ratio DMA sur TMA (DTR), a montrĂ© des rĂ©sultats encourageants avec une anti-corrĂ©lation significative (r = - 0,87 ; p-value < 0.001) lors de la phase prĂ©coce de dĂ©clin de la fraĂźcheur du poisson
Quantification of partial volatile basic nitrogen by SPME-GC-MS : Application to the monitoring of the evolution of cod fillets (Gadus morhua) freshness
International audienceLa fraĂźcheur est un paramĂštre clĂ© pour lâĂ©valuation de la qualitĂ© du poisson. Cette matrice Ă©tant extrĂȘmement pĂ©rissable, lâutilisation dâoutils objectifs est nĂ©cessaire. Par le passĂ© de nombreuses mĂ©thodes incluant les analyses sensorielles, chimiques, microbiologiques et physiques ont Ă©tĂ© dĂ©veloppĂ©es pour suivre lâĂ©volution de paramĂštres olfactifs visuels et texturaux tout au long du processus dâaltĂ©ration.LâaltĂ©ration du poisson est un processus complexe combinant des dĂ©gradations autolytiques et exogĂšnes. Un exemple connu concernant lâaltĂ©ration de la chair des GadidĂ©s est la dĂ©gradation de lâoxyde de trimĂ©thylamine (OTMA) selon deux voies cataboliques: la premiĂšre fait intervenir lâOTMA rĂ©ductase synthĂ©tisĂ©e par la flore spĂ©cifique dâaltĂ©ration et la seconde est le rĂ©sultat de lâactivitĂ© dâune enzyme endogĂšne du poisson lâOTMA dĂ©mĂ©thylase. Ces rĂ©actions conduisent respectivement Ă la production de trimĂ©thylamine (TMA) et la dimĂ©thylamine (DMA).JusquâĂ prĂ©sent la TMA et la DMA sont mesurĂ©es en routine de façon non-spĂ©cifique avec dâautres amines volatiles grĂące lâanalyse des amines basiques volatiles totales (ABVT) ; la TMA pouvant nĂ©anmoins ĂȘtre analysĂ©e plus spĂ©cifiquement avec lâajout de formaldĂ©hyde lors du processus analytique de lâABVT. Le concept dâazote basique volatil partiel a Ă©tĂ© dĂ©veloppĂ© pour quantifier spĂ©cifiquement la DMA et la TMA Ă lâaide dâune SPME-GC-MS.La mĂ©thode dĂ©veloppĂ©e a fait lâobjet dâune phase dâoptimisation puis de sĂ©lection dâun Ă©talon interne avant de sâintĂ©resser Ă la plage de quantification. Suite Ă ce dĂ©veloppement un suivi dâaltĂ©ration a Ă©tĂ© rĂ©alisĂ© sur des filets de cabillaud stockĂ©s sous glace fondante. Aux diffĂ©rents jours de conservation, trois filets ont Ă©tĂ© analysĂ©s Ă lâaide de diffĂ©rentes techniques : analyse sensorielle rĂ©alisĂ©e avec la mĂ©thode du Quality Index Method (QIM), analyses chimiques par les mĂ©thodes dâABVT et ABVP. Les concentrations en TMA mesurĂ©es par la mĂ©thode dâABVT et celle dâABVP sont trĂšs bien corrĂ©lĂ©es (r=0,98). Au regard des rĂ©sultats de lâABVT et de ceux du QIM, il apparait que la limite dâacceptation/rejet des filets est situĂ©e au voisinage du 7Ăšme jour de conservation. La production de TMA en cours dâaltĂ©ration a pu ĂȘtre modĂ©lisĂ©e, nĂ©anmoins son utilisation seule nâapparait pas comme un bon indicateur du dĂ©clin de la fraĂźcheur lors des premiers jours dâaltĂ©ration. Afin de surmonter cette limite, lâutilisation dâun nouvel indicateur issu des rĂ©sultats de lâABVP, le ratio DMA sur TMA (DTR), a montrĂ© des rĂ©sultats encourageants avec une anti-corrĂ©lation significative (r = - 0,87 ; p-value < 0.001) lors de la phase prĂ©coce de dĂ©clin de la fraĂźcheur du poisson
Use of degenerate primers to detect and quantify torA gene harbored by specific spoilage organisms of fish
International audienceFreshness is a key parameter of fish quality assessment. This matrix is highly perishable thus, objective tools for freshness estimation are required. Fish spoilage results from both autolytic activities and exogenous actions of specific spoilage organisms (SSO). The flesh of marine fish is characterized by the presence of Trimethylamine N-oxide (TMAO) involved in the osmoregulation process. TMAO can be used by bacteria from the genus Vibrio, Photobacterium, Shewanella as final electron acceptor and its reduction, thanks to TMAO reductase encoded by torA, leads to the production of TMA responsible of the specific fishy odor of spoiled fish.An in silico approach using biofinformatics tools combining R software, NRDB, NRPS primer (Laboratoire ProBioGEM) and AmplifX was set up to design and select primers. Forty torA sequences of Vibrio, nine of Shewanella and nine of Photobacterium were used to select a set of twelve primers. After a first in vitro screening of primers (absence of important primer dimers, ability to amplify a unique PCR product), a pair of primers amplifying a 400 bp fragment was selected to further analysis. The pair was tested on bacterial DNA of S.putrefaciens, P.phosphoreum, P.damselae, V.vulnificus, V.alginolyticus and two strains isolated from a spoiled whiting, identified as Burkholderia cepacia and member of S.putrefaciens group. Then, primer concentrations and annealing temperature were optimized for the selected pair with DNA from Photobacterium and Vibrio strains.Results on bacterial DNA are encouraging for Vibrio and Photobacterium species with a good efficiency (> 90%) and an acceptable range of quantification (”g.mL-1 to pg.mL-1). Selected primers showed a poor specificity on S.putrefaciens and whiting isolated strains but a 400 bp fragment is nevertheless observed. Secondly, total DNA extract from a few fresh and spoiled fish samples have been analyzed thanks to the selected pair of primers