Introduction: La consommation de poissons gras semble diminuer le risque de déclin cognitif lors du vieillissement. Cet effet serait potentiellement attribuable à deux acides gras oméga-3 concentrés dans le poisson: l'acide docosahexaénoïque (DHA) et l'acide eicosapentaénoïque (EPA). Cependant, ce lien n'est pas valide chez les personnes porteuses du génotype de l'apolipoprotéine E epsilon 4 (ApoE4), le facteur de risque génétique le plus important pour la maladie d'Alzheimer. Ces données suggèrent un débalancement dans le métabolisme du DHA chez les porteurs de l'ApoE4. Objectif: Évaluer si le polymorphisme de l'ApoE4 débalance le métabolisme d'un traceur DHA marqué au carbone 13 ([indice supérieur 13] C-DHA). Méthodologie: Quarante participants de plus de 50 ans ont été recrutés. De ce nombre, 14 sont des hommes et 26 sont des femmes. Ils ont consommé une dose unique de 50 mg de [indice supérieur 13] C-DHA afin de suivre son métabolisme sur une période de 28 j. L'incorporation plasmatique ainsi que la p-oxydation du [indice supérieur 13] C-DHA ont été suivis à l'aide d'échantillons de plasma et d'haleine prélevés avant la prise du [indice supérieur 13] C-DHA et 1 h, 2 h, 4 h, 6 h, 8 h, 24 h, 7 j, 14 j, 21 j et 28 j post-consommation. Résultats: 6 participants étaient porteurs de l'ApoE4 et 34 étaient non-porteurs. L'incorporation plasmatique du [indice supérieur 13] C-DHA était 3,7 fois moins grande chez les porteurs de l'ApoE4 2 h post-consommation (p = 0,04) et 1,9 fois moins grande 4 h post-consommation (p = 0,04) comparativement aux non-porteurs de l'ApoE4. La beta-oxydation du [indice supérieur 13] C-DHA était 1,8 fois plus grande chez les porteurs de l'ApoE4 7 j post-consommation (p = 0,05), 2,4 fois plus grande 21 j post-consommation (p = 0,02) et 2,3 fois plus grande 28 j post-consommation comparativement aux non- porteurs. Discussion/conclusion: Ces résultats suggèrent que les porteurs de l'ApoE4 montrent un débalancement dans leur métabolisme du [indice supérieur 13] C-DHA. Ceci pourrait modifier l'apport recommandé en DHA chez les porteurs de l'ApoE4 afin que ceux-ci soient protégés contre le déclin cognitif par la consommation d'acides gras oméga-3.

This dissertation serves as a comprehensive, natural-abundance analysis of the present-day spatial and temporal dynamics and trophic linkages of nitrogen from within the Florida Keys National Marine Sanctuary (FKNMS). This work was accomplished by documenting the delta 15 N of particulate organic matter (POM), several genera of aquatic vegetation and herbivorous fish, as well as dissolved water column nitrogen. Seasonal and spatial variations in delta 15 N were assessed, trophic level variations among reef constituents were quantified, and relative contributions of both natural and anthropogenic nitrogen into the reef tract were determined. The measured mean delta 15 N of POM (3.64 per mil), aquatic vegetation (Dictyota = 2.39 per mil; Thalassia = 1.91 per mil; Rhizophora mangle = 1.46 per mil; Halimeda = 1.62 per mil; sponges = 4.13 per mil; turf algae = 2.67 per mil), herbivorous fish (4.92 to 8.47 per mil), as well as the delta 15 N and delta 18 O of nitrate (4.40 and 20.36 per mil, respectively) suggest that the primary nutrient sources directly impacting the reef are from natural sources, principally nitrogen fixation, and not anthropogenic wastes. Clear trophic linkages, without evidence of disturbances from anthropogenic wastes, are apparent in this study; herbivorous fishes show distinct 3 to 4 per mil enrichments over their food source. The presence of anthropogenic wastes was detected in the delta 15 N and delta 18 O of nitrate from Key Largo canal waters (10.09 per mil), however, sewage derived nutrients did not exist in any measurable or detectable amount outside the canals. Additionally, an assessment of the total yearly nitrogen contributions to the FKNMS was conducted, demonstrating that nitrogen fixation was the largest contributor of nitrogen to the ecosystem, delivering approximately 43 percent of all nitrogen. Anthropogenic wastes, however, contributed only about 8 percent to the total nitrogen budget, far less than biotic (non-human) wastes (13 percent), upwelling (10 percent), and gyre waters from the Gulf of Mexico (9 percent). For the first time, a long term, spatially diverse investigation has presented a more complete depiction of delta 15 N composition of various reef components found in the FKNMS, critical and imperative for accurately assessing nutrient pressures on coral reefs. As such, the data presented in this study do not support the theory that continuous anthropogenic nutrient loading from nearshore populations is the sole cause of reef decline in the FKNMS.

Small quantities of amorphous content can have a profound influence on the properties of a material, however their instability means that quantifying amorphous content over time is important for proving the stability of a drug. Quantifying amorphous content in α-lactose monohydrate by solid state 13C CP MAS NMR, has been carried out by use of proton saturation recovery relaxation and differentiating between spectra by partial least squares (PLS), however these techniques have not proved sensitive on their own, this work investigates their sensitivity in combination. Crystalline α-lactose monohydrate and a rapidly quenched melt were combined to create a set of calibration mixes, whose spectra were recorded using proton saturation recovery relaxations ranging from 2 to 60 seconds. This technique showed a limit of detection of 0.17% (LOD = intercept + 3xSy/x), with a relaxation delay of 15 s and was able to recognise amorphous materials generated by spray and freeze drying. The atmospheric effects on the proton saturation recovery relaxation times of different amorphous lactose preparations were investigated. This found that an oxygen atmosphere reduced the relaxation times, of amorphous lactose that was prepared from a rapidly quenched melt. The loss of moisture from spray dried and freeze dried samples to less than 1% removed the significance of this effect. Lactose is an important excipient in pharmaceuticals and a key ingredient of confectionary, very little research has been carried out in to the quantification of the isomers of different preparations of amorphous lactose. This work quantifies the isomer content by Gas Chromatography with Flame Ionisation Detection (GC-FID) using a DB-17 15m 0.53mm 1.00 μm column and derivatisation with N- (trimethylsilyl)imidazole.

No / Traditional methods of dietary reconstruction do not allow the investigation of dietary variability within the lifetimes of individual hominins. However, laser ablation stable isotope analysis reveals that the ¿13C values of Paranthropus robustus individuals often changed seasonally and interannually. These data suggest that Paranthropus was not a dietary specialist and that by about 1.8 million years ago, savanna-based foods such as grasses or sedges or animals eating these foods made up an important but highly variable part of its diet.

O estudo de um testemunho coletado às margens de uma lagoa situada em meio a vegetação de Mata Atlântica no Parque Estadual Turístico do Alto Ribeira, sul do estado de São Paulo, permitiu a reconstituição da história da vegetação local ao longo dos últimos 2500 anos. Para isso, foram realizadas análises elementares, isotópicas e palinológicas. Também a partir de material retirado deste testemunho procedeu-se a comparação entre dois protocolos de tratamento químico para análises palinológicas do Quaternário. Os protocolos utilizados seguiram as metodologias propostas por Faegri e Iversen, 1989 (Protocolo 2) e por Colinvaux et al., 1999 (Protocolo 1). Foi desenvolvido um método de comparação que envolveu a quantidade de palinomorfos e a quantidade de matéria orgânica amorfa encontrados em 450 pontos escolhidos aleatoriamente em lâminas de ambos os protocolos e também foram levados em consideração o tempo, a praticidade de aplicação em rotina laboratorial, os custos e as quantidades e tipos de resíduos para cada protocolo. Cinco amostras de sedimento foram utilizadas para comparação e o Protocolo 1 apresentou em média 10% menos matéria orgânica amorfa e quase três vezes mais palinomorfos que o Protocolo 2. Os resultados das análises isotópicas e da palinologia mostraram que a vegetação da área em estudo teve uma fisionomia florestal pelo menos desde os últimos 2550 anos. Os valores de \'delta\'13C, em torno de - 29%o, indicaram a presença de plantas C3 em todo o período estudado e registraram um enriquecimento isotópico (-24,9%o) entre aproximadamente 1650 e 1480 anos AP. A análise palinológica apontou para a ocorrência de um clima mais frio que o atual entre 2550 anos AP e 2000 anos AP, com aumento na freqüência de Araucaria e diminuição de Arecaceae. Também foi detectada a ocorrência de um período de clima mais quente e mais úmido entre aproximadamente 1000 anos AP e 680 anos AP, com desaparecimento de Araucaria e aumento de Arecaceae, Weinmannia e de pteridófitas. A maior umidade deste período também é apontada pelos valores de C/N que indicam aumento de influência terrestre no sedimento e pelo aumento de Botryococcus. Em todas as camadas foram encontradas partículas carbonizadas, indicando períodos de ocorrência de paleoincêndios e de abertura florestal provavelmente associados à presença humana na região / One sediment core collected at the margins of a lake surrounded by Atlantic rainforest vegetation at Parque Estadual do Alto Ribeira (PETAR), southern São Paulo state (Brazil), was analyzed, in order to reconstruct the history of the local vegetation over the last 2500 years. Elemental (Total Organic Carbon TOC and Total Organic Nitrogen), isotopic (C and N), pollen analysis and radiocarbon dating were integrated on this work. Also was made a comparison of two protocols for Quaternary pollen chemical treatment. The tested protocols were proposed by Faegri and Iversen, 1989 (Protocol 2) and by Colinvaux et al., 1999 (Protocol 1). The comparison methods developed in this study checked the protocols performance on the quantity of palinomorphs and of organic matter found in 450 random areas of microscope slides of each protocol. The time consuming, laboratory routine, costs and residue production by the protocols were considered for comparison. Five samples were used for comparison and the Protocol 1 showed an average of 10% less organic matter and more palinomorphs than Protocol 2. According to the isotopic and pollen results, the study area vegetation maintained as a forest for the last 2500 years BP. \'delta\'13C values of -29%o indicated the presence of C3 plants during all the sediment study and a isotopic enrichment (- 24,9%o) was observed between 1650 and 1480 yrs BP. Pollen analysis suggested the occurrence of colder climatic conditions between 2550 and 2000 yrs BP and a warmer and humid period was suggested between 1000 and 680 yrs BP. Charcoal particles were found since 2550 yrs BP indicating paleofire probably associated to the human activities

O estudo de um testemunho coletado às margens de uma lagoa situada em meio a vegetação de Mata Atlântica no Parque Estadual Turístico do Alto Ribeira, sul do estado de São Paulo, permitiu a reconstituição da história da vegetação local ao longo dos últimos 2500 anos. Para isso, foram realizadas análises elementares, isotópicas e palinológicas. Também a partir de material retirado deste testemunho procedeu-se a comparação entre dois protocolos de tratamento químico para análises palinológicas do Quaternário. Os protocolos utilizados seguiram as metodologias propostas por Faegri e Iversen, 1989 (Protocolo 2) e por Colinvaux et al., 1999 (Protocolo 1). Foi desenvolvido um método de comparação que envolveu a quantidade de palinomorfos e a quantidade de matéria orgânica amorfa encontrados em 450 pontos escolhidos aleatoriamente em lâminas de ambos os protocolos e também foram levados em consideração o tempo, a praticidade de aplicação em rotina laboratorial, os custos e as quantidades e tipos de resíduos para cada protocolo. Cinco amostras de sedimento foram utilizadas para comparação e o Protocolo 1 apresentou em média 10% menos matéria orgânica amorfa e quase três vezes mais palinomorfos que o Protocolo 2. Os resultados das análises isotópicas e da palinologia mostraram que a vegetação da área em estudo teve uma fisionomia florestal pelo menos desde os últimos 2550 anos. Os valores de \'delta\'13C, em torno de - 29%o, indicaram a presença de plantas C3 em todo o período estudado e registraram um enriquecimento isotópico (-24,9%o) entre aproximadamente 1650 e 1480 anos AP. A análise palinológica apontou para a ocorrência de um clima mais frio que o atual entre 2550 anos AP e 2000 anos AP, com aumento na freqüência de Araucaria e diminuição de Arecaceae. Também foi detectada a ocorrência de um período de clima mais quente e mais úmido entre aproximadamente 1000 anos AP e 680 anos AP, com desaparecimento de Araucaria e aumento de Arecaceae, Weinmannia e de pteridófitas. A maior umidade deste período também é apontada pelos valores de C/N que indicam aumento de influência terrestre no sedimento e pelo aumento de Botryococcus. Em todas as camadas foram encontradas partículas carbonizadas, indicando períodos de ocorrência de paleoincêndios e de abertura florestal provavelmente associados à presença humana na região / One sediment core collected at the margins of a lake surrounded by Atlantic rainforest vegetation at Parque Estadual do Alto Ribeira (PETAR), southern São Paulo state (Brazil), was analyzed, in order to reconstruct the history of the local vegetation over the last 2500 years. Elemental (Total Organic Carbon TOC and Total Organic Nitrogen), isotopic (C and N), pollen analysis and radiocarbon dating were integrated on this work. Also was made a comparison of two protocols for Quaternary pollen chemical treatment. The tested protocols were proposed by Faegri and Iversen, 1989 (Protocol 2) and by Colinvaux et al., 1999 (Protocol 1). The comparison methods developed in this study checked the protocols performance on the quantity of palinomorphs and of organic matter found in 450 random areas of microscope slides of each protocol. The time consuming, laboratory routine, costs and residue production by the protocols were considered for comparison. Five samples were used for comparison and the Protocol 1 showed an average of 10% less organic matter and more palinomorphs than Protocol 2. According to the isotopic and pollen results, the study area vegetation maintained as a forest for the last 2500 years BP. \'delta\'13C values of -29%o indicated the presence of C3 plants during all the sediment study and a isotopic enrichment (- 24,9%o) was observed between 1650 and 1480 yrs BP. Pollen analysis suggested the occurrence of colder climatic conditions between 2550 and 2000 yrs BP and a warmer and humid period was suggested between 1000 and 680 yrs BP. Charcoal particles were found since 2550 yrs BP indicating paleofire probably associated to the human activities

Juniper trees (Juniperus osteosperma, J. monosperma, J. deppeana and J. scopulorum) grow under widely varying climatic and edaphic conditions throughout the American southwest. This study is chiefly concerned with a test of the climatic response in the partitioning of the stable isotopes of carbon in such trees. The relationships developed here, for example, might be used to extract paleoclimatic information from ancient juniper samples preserved in cave middens. In order to test for a climatic response in the leaf cellulose δ¹³C values, leaves from a total of 29 trees were sampled in the immediate vicinity of 9 meteorological stations across the state of Arizona. Care was taken to insure that 22 of the trees experienced only the temperature and precipitation values reflected by their site meteorological stations. As a cross-check, 7 trees exposed to temperature and/or precipitation levels clearly deviant from their site averages were also sampled. In general, each tree was sampled at four places, approximately 2 m above the ground. All leaf samples were reduced to cellulose (holocellulose) before combustion and analysis for their δ¹³C value. The δ¹³C value for each site was derived from an average of 2 to 4 trees per site, the value of each tree being the average of its individual samples. The one sigma 13C variation found between trees at any given site is ±0.38‰; within a single tree, ±0.36‰; and for repeat combustions, ±0.20‰. The δ¹³C values of the juniper sites were regressed against the temperature and precipitation of the individual months and running averages of months across the year using polynomial, multiple regression analysis. Temperature and precipitation were entered as separate variables in a general multiple regression model and also as a combined, single variable (T /P) in a more specific approach. The pattern formed by the multiple correlation coefficients, when plotted by months across the year, closely follows the seasonal variations in photosynthetic activity. Cellulose δ¹³C values have minimum correlation with temperature and precipitation (considered jointly) during summer months and maximum correlation during spring months. For an individual month, the temperature and precipitation (jointly) of April correlated at the highest level with a multiple adj. R = 0.994 and an F = 166; for a maximum seasonal response, March-May reached a multiple adj. R = 0.985, F = 66. The results using the combined, single variable (T /P) were nearly equivalent for the same months: April's adj. R = 0.957, F = 45; March-May's adj. R = 0.985 with an F = 132. The ability of T and P as independent predictors is considerably less than their ability in combination; e.g., 13C g(T) for March-May has an adj. R = 0.80 and 6 13C = h(P) has an adj. R = -0.67 compared to their in- concert adj. R value of 0.985. The results of this study, therefore, strongly support a high degree of climatic sensitivity in the partitioning of the stable isotopes of carbon in juniper leaf cellulose: the correlation coefficients and their F statistics are sufficiently high to consider temperature and precipitation (acting jointly) as accurate predictors of cellulose δ¹³C values in the system studied.

Over the past century, woody plants and shrubs have increased in abundance at the expense of grasslands in many semiarid regions. The availability and concentrations of nutrients influence the relative success of plants, but the effects of fire frequency on soil nutrients is unknown for semiarid grasslands. On the gunnery ranges of Fort Huachuca in southeastern Arizona, study sites were established to examine the effects of fire frequency on soil biogeochemistry, plant biochemistry, and δ¹³C values in soil organic matter (SOM). The sites were on homogeneous granitic alluvium where wildfire frequency history is known from 1973 to present and no cattle grazing has occurred in recent decades. Subplots represent fire frequencies of no burns, 3 fires per decade, and 5 fires per decade. The "no burn" plot has abundant C₃ Prosopis veleruina (mesquite) trees, whereas the burned plots are open C₄-dominated grasslands with scattered mesquite trees. Prosopis trees have altered SOM pools by the concentration of plant nutrients and the addition of isotopically light shrub litter. Frequent fires have altered the basic geochemistry and nutrient availabilities of the soil, and the changes appear to be significant enough to affect plant growth. Soil pH increases with burning frequency, and TOC, total nitrogen, and plant -available phosphorus show significant increases on the infrequently burned plot. Burning is advantageous for preservation or restoration of grasslands, as total living grass biomass is greater on the two burned plots. Root biomass is significantly lower on the "frequently burned" plot. Concentrations of the key nutrients nitrogen and phosphorus are reduced in plants on the burned sites compared to plants on the unburned site. Fires help re-distribute nutrients but evidence of nutrient concentrations and δ¹³C values are retained in SOM for many decades. Estimates of bulk carbon turnover rates range from 112 to 504 years. Evidence for modern C₃ shrub expansion is found in the shift of SOM δ¹³C values from values characteristic of C₄ grasses to C₃ shrubs in surface soil layers. δ¹³C(SOM) values indicate that the Holocene and Late Pleistocene were dominated by C₄ grasslands, and the pre-Late Pleistocene vegetation was a C₄-grass savanna with abundant C₃ plants.

No description available.