• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1
  • 1
  • Tagged with
  • 3
  • 3
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Chemical contaminants in Chinese aquaculture imports, U.S. import security, and exposure assessment amongst vulnerable sub-populations

Nyambok, Edward Otieno January 1900 (has links)
Doctor of Philosophy / Food Science / Justin Kastner / Many Chinese aquaculture farmers use unapproved chemicals to treat their fish, many of which are diseased as a result of the country’s poor waste management and environmental practices. During 2006-2007, the United States (U.S.), the European Union, and Japan rejected large amounts of Chinese seafood imports due to the presence of unapproved chemicals or the presence of approved chemicals at concentrations that exceeded permitted levels. This dissertation examines the sources of environmental health and food safety problems in China; it also examines how effective the U.S. and Chinese governments’ regulations are in protecting consumers from hazards in Chinese aquaculture products. The study looks at specific chemical contaminants found in Chinese aquaculture imports, explores their potential toxicity or carcinogenicity, and examines the reasons for their prohibition from human food. The study exploits the available U.S. seafood consumption patterns (courtesy of the National Health and Nutrition Examination Survey—NHANES—database) and then uses probabilistic modeling (courtesy of CREMe Software Limited) to determine the extent to which specific sensitive U.S. consumer subpopulations were exposed to aquaculture chemical contaminants in the food supply in a contrived scenario using real consumption data (from NHANES) and actual contamination data (from the FDA). The study compares exposure between children and adult consumers, and also looks at exposure among women aged 18 years and older and the elderly aged 60 years and older. This study suggests a strong likelihood that NHANES children, as well as female consumers aged 18 years and older and elderly consumers aged 60 years and older, were (in the contrived scenario) all exposed to violative intake levels of chemical contaminants from Chinese aquaculture imports. Children forming the 99.5th and 99.9th percentiles of NHANES seafood consumers were exposed to higher levels of nitrofuran, gentian violet, and malachite green contaminants per kilogram of body weight than were their adult counterparts. Conversely, children were exposed to lower levels of fluoroquinolone contaminants per kilogram of body weight than were their adult counterparts. The 50th, 95th, and 99.9th percentiles of female consumers aged 18 and older and elderly consumers aged 60 years and older were exposed to violative daily intake levels of contaminants in Chinese aquaculture. The study concludes by examining what the U.S. and Chinese governments should do to address aquaculture safety.
2

Isolation et caractérisation des cellules stromales mésenchymateuses multipotentes du tissu adipeux: Étude des sous-populations et comparaison avec la moelle osseuse. / Isolation and characterization of multipotent mesenchymal stromal cells from adipose tissue: study of sub-populations and comparison with bone marrow.

Busser, Hélène 14 December 2015 (has links)
Multipotent mesenchymal stromal cells (MSC) were first discovered in bone marrow and can be isolated from “virtually all organs”. They could participate in tissue maintenance and self-renewing process. They are able to adhere to plastic surfaces and acquire a fibroblastic shape when isolated. They are characterized by a particular phenotype and are able to differentiate into several cell types if cultivated in a specific induction medium. These characteristics were defined on MSC in culture and do not represent how they may be in situ.MSC present particular properties. They can secrete growth factors and several cytokines that give them a trophic activity on one hand and the ability to modulate the immune system on the other hand. They are also able to differentiate. These different properties make them an attractive candidate for cell therapy.MSC are already the focus of several pre-clinical and clinical studies. Nevertheless, the results of these studies are difficult to interpret due to limited understanding of their basic biology. MSC are poorly defined in situ and are heterogeneous. Their heterogeneity is dictated by their tissue of origin and cell preparation. To date, there is no standard protocol for MSC isolation and culture. This leads to numerous questions regarding patient safety, and these questions require answers.The first part of the work deals with the methods used to optimize the extraction of MSC and purification from adipose tissue, one of the main sources of autologous MSC with bone marrow. Classical methods require an enzymatic digestion step. The enzyme used and the duration of adipose tissue digestion time can induce cellular alterations and modify cell functions. Moreover, the addition of a xenobiotic increases the risk of contamination and complicates the monitoring of good manufacturing practices (GMP). We propose a method that does not require this enzymatic digestion step while being easier, safer, faster, gentler and less expensive. Compared to the classical enzymatic method, our method yields an equivalent number of MSC from adipose tissue while preserving their properties.The second part of this work focuses on the characterization of the MSC subpopulations from adipose tissue and compares them to those from bone marrow, which are the historical gold standard. The study made it possible to deepen the knowledge of MSC surface markers in situ from these 2 sources. It also evaluated the various properties of the isolated subpopulations thanks to the cell surface markers CD271, SUSD2, MSCA-1, CD44 and CD34. We showed that MSC from bone marrow express MSCA-1, CD271 and SUSD2 markers in situ. We also found that a population clearly positive for the CD34 does exist in situ with different properties compared to those of the unselected populations or the negative counterpart. 2 populations that are negative and positive for CD44 also exist with similar properties.In contrast to bone marrow MSC, only one selection was able to effectively isolate MSC from adipose tissue by a positive selection based on the expression of CD34. We also isolated a CD271+ population but only from lipoaspirate samples and not from abdominoplasty samples. Collectively, our results suggest that MSCA-1 seems to be the best marker through which to isolate MSC from bone marrow and that CD34 is the only marker able to positively isolate cells from adipose tissue. Thus, we show that the MSC from the different sources share similar properties although they have specific characteristics. The choice of the source and of the marker with which to isolate a particular subpopulation is important depending on their intended clinical use. / Les cellules stromales mésenchymateuses multipotentes (CSM) ont été mises en évidence dans la moelle osseuse et peuvent être isolées de « virtuellement tous les organes ». Elles participeraient à la maintenance et au renouvellement des tissus. Une fois isolées, elles sont capables d’adhérer à des surfaces en plastique en prenant une forme fibroblastique. Elles sont caractérisées par un phénotype particulier et peuvent se différencier en divers types cellulaires lorsque cultivées dans un milieu d’induction spécifique. Ces caractéristiques ont été définies sur les CSM en culture et ne reflètent pas forcément ce qui se passe in situ.Les CSM présentent des propriétés particulières. Elles peuvent sécréter des facteurs de croissance ainsi que de nombreuses cytokines qui leur permettent d’une part d’avoir une activité trophique et d’autre part de moduler le système immunitaire. Elles sont aussi capables de se différencier. Ces différentes propriétés les rendent particulièrement attractives pour la thérapie cellulaire.Les CSM font déjà l’objet de nombreuses études pré-cliniques et cliniques dont les résultats sont difficilement interprétables car nous n’avons à l’heure actuelle qu’une compréhension limitée de leur biologie de base. Les CSM sont encore mal définies in situ et sont hétérogènes. Cette hétérogénéité provient de leur différence d’origine et de leur préparation cellulaire :il n’existe aucune standardisation des protocoles d’isolation et de culture. Cette hétérogénéité entraine de nombreuses questions relatives à la sécurité du patient qui doivent être élucidées.La première partie de ce travail cherche à optimiser les méthodes d’extraction et de purification des CSM du tissu adipeux humain, la principale source de CSM autologues avec la moelle osseuse. Les méthodes classiques requièrent une étape de digestion enzymatique dont l’enzyme utilisée et le temps de digestion du tissu adipeux peuvent induire des altérations cellulaires et modifier leurs fonctions. De plus, l’adjonction de xénobiotiques augmente le risque de contamination et complique le suivi des bonnes pratiques de fabrication (BPF). Nous proposons une méthode qui s’affranchit de cette étape de digestion enzymatique tout en étant plus facile, plus sûre, plus rapide, moins chère et moins traumatisante pour les cellules. Elle permet d’obtenir un nombre tout aussi important de CSM du tissu adipeux que la méthode enzymatique classique en préservant leurs propriétés.La deuxième partie de ce travail vise à caractériser les sous populations de CSM du tissu adipeux humain en les comparant à celles de la moelle osseuse, source de référence historique. Cette étude a permis d’approfondir la connaissance des marqueurs de surface des CSM de ces 2 sources in situ, tout en évaluant les différentes propriétés des sous-populations isolées grâce aux marqueurs de surface CD271, SUSD2, MSCA-1, CD44 et CD34. Nous avons montré que les CSM de la moelle osseuse expriment les marqueurs MSCA-1, CD271 et SUSD2 in situ et qu’il existait une sous-population clairement positive pour le CD34 avec des propriétés différentes de celles de la population non sélectionnée ou négative pour ce marqueur. Il existe aussi 2 sous-populations positive et négative pour le CD44 avec des propriétés similaires.Contrairement aux CSM de la moelle osseuse, une seule sélection a permis d’isoler efficacement les CSM du tissu adipeux par une sélection positive sur base de l’expression du CD34. Nous avons pu aussi isoler une population CD271+ mais seulement des prélèvements de lipoaspirations et non des abdominoplasties.Au vu de nos résultats, MSCA-1 semble le meilleur marqueur pour isoler les CSM de la moelle osseuse tandis que le CD34 est le seul marqueur capable d’isoler positivement celles du tissu adipeux. Ainsi, nous montrons que les CSM issues de différentes sources partagent des propriétés similaires avec cependant des caractéristiques propres. Le choix de la source et du marqueur pour isoler une sous-population sont donc importants en fonction de leur utilité clinique envisagée. / Doctorat en Sciences biomédicales et pharmaceutiques (Médecine) / info:eu-repo/semantics/nonPublished
3

Meta-Analysis to Determine Vulnerability of Rural Areas to Heat Mortality

Odame, Emmanuel, Li, Ying, Zheng, Shimin, Silver, Ken 11 April 2017 (has links)
Background: Numerous epidemiological studies have demonstrated a possible correlation between high temperature and mortality in different settings. Most of these studies have focused on urban settings in industrialized countries, concluding that urban populations are more vulnerable to heat effects than rural populations. This has mainly been attributed to the urban heat island (UHI) effect, a phenomenon which explains the elevated temperatures in urban areas. Others have contradicted this finding and concluded that rural residents are more vulnerable. For this study, we test the hypothesis that rural populations and sub-populations are also vulnerable to heat mortality. Method: A comprehensive literature search was conducted using PubMed, Web of Science and Google Scholar to identify peer-reviewed studies investigating heat mortality in rural settings. Using keywords and a set of rigorous inclusion and exclusion criteria, ten studies were selected. Meta-analysis was then performed using the Comprehensive MetaAnalysis V3.exe software. Results and discussion: The pooled relative risk (RR) was 1.191 (95% confidence interval: 1.130-1.251). Although rural populations may not be exposed to as high temperatures as urban populations, they remain vulnerable to heat effects. Conclusion: There is evidence of heat vulnerability in rural populations and subpopulations. Heat vulnerability is not only determined by heat exposure, but also by sensitivity and adaptive capacity. Rural populations and sub-populations may be vulnerable to heat mortality due to low adaptive capacity. Further studies are needed to assess risk factors that predispose rural populations and sub-populations to heat mortality in order to develop effective public health interventions.

Page generated in 0.0805 seconds