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  • 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.
121

Targeting RNA Structures with Multivalent Branched Peptide Libraries

Bryson, David Irby 03 May 2012 (has links)
RNA is essential for the transfer of genetic information, as the central dogma of biology dictates. The role of RNA, however, is not limited to serving as an information shuttle between DNA and fully functional protein. Indeed, RNA has experienced a surge of interest in the field of chemical biology for its other critical roles in biology including those in control of transcription, translation, splicing, genetic replication, and catalysis. RNA has proven to be a difficult and complex target for the design of small molecular ligands because of its structural heterogeneity and conformational flexibility. Yet, the highly folded tertiary structures of these oligomers present unique scaffolds which designed ligands should be able to selectively target. To that end, two branched peptide libraries ranging in size from 4,096–46,656 unique sequences were screened for their ability to bind HIV-1 related RNA structures, the transactivation response element (TAR) and the Rev response element (RRE). In addition to discovering a mid-nanomolar branched peptide ligand for TAR, the first branched boronic acid peptide library designed to target RNA was screened for binding to RRE. Each of these efforts resulted in the identification of selective binders to their respective RNA targets, and the unnatural branching of these compounds was demonstrated to provide a multivalent binding interaction with the RNA. Furthermore, these compounds were shown to be cell permeable and displayed little to no cytotoxicity in HeLa and A2780 cells. / Ph. D.
122

<b>Production and Glucose Metabolism Responses Related to Late Gestational Muscle Reserves and Supplementation of Branched-Chain Volatile Fatty Acids in Transition Dairy Cattle</b>

Kyrstin Michele Gouveia (19180165) 19 July 2024 (has links)
<p dir="ltr">The periparturient period involves coordinated physiological adaptations as the dairy cow transitions from a non-lactating to lactating state. The ability of dairy cattle to adapt to the onset of lactation is impacted both by physiological and nutritional factors, and a poor transition can result in reduced productivity and welfare for the animal. Additionally, disease and disorder development are heightened in the transition period, with increased risk for involuntary culling occurring in early lactation. This study aimed to evaluate if the amount of late gestational muscle reserves and prepartum supplementation of branched-chain volatile fatty acids (BCVFA) impacts health and production parameters in multiparous, periparturient dairy cattle. Forty-eight multiparous Holstein dairy cattle were assigned to either a high or low muscle group (HM or LM, respectively) based on their <i>longissimus dorsi</i><i> </i>muscle depth 42 days before expected (BEC). After assignment to group, cattle were then randomly assigned to a control (CON; 80 g/d soyhull pellets as-fed basis) or BCVFA (40 g/d isobutyrate product, 20 g/d isovalerate product, 20 g/d 2-methybutyrate product, fed as calcium salt products on an as-fed basis) treatment, which was top-dressed in the prepartum period only. After parturition, treatment was no longer provided and cattle were fed a common lactating diet. Blood samples, ultrasound images, and feed intake were collected and recorded from 42 BEC through 28 days in milk (DIM), milk yield and composition data was collected from parturition until 28 DIM.</p><p dir="ltr">HM cattle began mobilizing muscle reserves prior to parturition, while LM cattle began to accrete muscle reserves prior to parturition. This difference in prepartum muscle utilization did not impact other body measurements (i.e. body weight or body condition score) between the groups of cows but did result in increased blood glucose concentrations prepartum for HM cows compared with LM. This increase in glucose concentrations is likely due to the increased supply of gluconeogenic precursors as a result of the degradation of muscle tissue. The difference in glucose concentration was not observed postpartum, neither was there a difference in tissue mobilization between the groups postpartum. HM cattle had greater DMI both pre- and postpartum, and produced greater yields of milk, milk fat, milk protein, and milk lactose postpartum compared to the LM group. Despite the increased milk yield, there was no difference in feed efficiency between the groups, as the HM cows consumed more feed. Prepartum supplementation of BCVFA did not impact body measurement changes throughout the entire transition period, but did increase pre- and postpartum DMI, likely due to increased fiber digestibility. The BCVFA treatment increased blood glucose concentrations both pre- and postpartum and reduced milk urea nitrogen concentrations postpartum, likely due to improved nitrogen efficiency. Results show that prepartum supplementation of BCVFA has an improved ruminal carryover effect into early lactation.</p><p dir="ltr">At 14 days BEC and 7 DIM, an intravenous glucose tolerance test (IVGTT) was performed on a sub-set of cows, to evaluate if insulin response could be a mechanism impacting the efficiency and production differences observed between muscle groups and BCVFA supplementation. BCVFA supplementation increased glucose area under the curve in the prepartum period only. No other differences were observed between muscle group or treatment in either the pre- or postpartum period. Because there were no major differences between the cows in response to an IVGTT, we cannot conclude that glucose metabolism is a mechanism to explain differences in production responses observed. IVGTT cannot measure peripheral tissue insulin sensitivity, which is a limitation of this assessment, so our conclusions cannot assess if muscle reserves or BCVFA treatment impact peripheral tissue insulin sensitivity response. These results highlight that the amount of muscle plays a key role in the production responses observed in early lactation and that providing a BCVFA supplement could increase DMI during a period of negative nutrient balance and improve rumen efficiency.</p>
123

Temperature-dependent structure and dynamics of highly-branched poly(N -isopropylacrylamide) in aqueous solution

Al-Baradi, A.M., Rimmer, Stephen, Carter, Steven, de Silva, J.P., King, S.M., Maccarini, M., Farago, B., Noirez, L., Geoghegan, M. 28 May 2019 (has links)
Yes / Small-angle neutron scattering (SANS) and neutron spin-echo (NSE) have been used to investigate the temperature-dependent solution behaviour of highly-branched poly(N-isopropylacrylamide) (HB-PNIPAM). SANS experiments have shown that water is a good solvent for both HB-PNIPAM and a linear PNIPAM control at low temperatures where the small angle scattering is described by a single correlation length model. Increasing the temperature leads to a gradual collapse of HB-PNIPAM until above the lower critical solution temperature (LCST), at which point aggregation occurs, forming disperse spherical particles of up to 60 nm in diameter, independent of the degree of branching. However, SANS from linear PNIPAM above the LCST is described by a model that combines particulate structure and a contribution from solvated chains. NSE was used to study the internal and translational solution dynamics of HB-PNIPAM chains below the LCST. Internal HB-PNIPAM dynamics is described well by the Rouse model for non-entangled chains.
124

Generation and Use of Functional Hydrogels That Can Rapidly Sample Infected Surfaces

Swift, Thomas, Pinnock, A., Shivshetty, N., Pownall, David, MacNeil, S., Douglas, I., Garg, P., Rimmer, Stephen 09 August 2022 (has links)
Yes / This paper outlined our method for developing polymer-linked contact lens type materials for rapid detection and differentiation of Gram-positive, Gram-negative bacteria and fungi in infected corneas. It can be applied to both model synthetic or ex-vivo corneal models and has been successfully trialed in an initial efficacy tested animal study. First a hydrogel substrate for the swab material is selected, we have demonstrated selective swabs using a glycerol monomethacrylate hydrogel. Alternatively any commercial material with carboxylic acid functional groups is suitable but risks nonspecific adhesion. This is then functionalised via use of N-hydroxysuccinimide reaction with amine groups on the specified highly branched polymer ligand (either individually gram negative, gram positive or fungal binding polymers or a combination of all three can be employed for desired sensing application). The hydrogel is then cut into swabs suitable for sampling, used, and then the presence of gram positive, game negative and fungi are disclosed by the sequential addition of dyes (fluorescent vancomycin, fluorescein isothiocyanate and calcofluor white). In summary this method presents: Method to produce glycerol monomethacrylate hydrogels to minimize nonspecific binding Methods of attaching pathogen binding highly branched polymers to produce selective hydrogel swabs Method for disclosing bound pathogens to this swab using sequential dye addition
125

Role of Thioredoxin-Interacting Protein (TXNIP) in Regulating Redox Balance and Mitochondrial Function in Skeletal Muscle

DeBalsi, Karen Lynn January 2013 (has links)
<p>The Muoio lab studies the interplay between lipid whole body energy balance,</p><p>mitochondrial function and insulin action in skeletal muscle. Data from our lab suggests that lipid-induced insulin resistance in skeletal muscle may stem from excessive incomplete oxidation of fatty acids, which occurs when high rates of &beta;-­oxidation exceed TCA cycle flux (Koves et al., 2005; Koves et al., 2008). Most notably, we have shown that mice with a genetically engineered decrease in mitochondrial uptake and oxidation of fatty acids are protected against diet-­induced insulin resistance (Koves et al., 2008). This</p><p>suggests that an excessive and/or inappropriate metabolic burden on muscle</p><p>mitochondria provokes insulin resistance. Our working model predicts that: 1) high rates of incomplete &beta;-oxidation reflect a state of &rdquo;mitochondrial stress,&rdquo; and 2) that energy-overloaded mitochondria generate a yet unidentified signal that mediates insulin</p><p>resistance. One possibility is that this putative mitochondrial-derived signal stems from redox imbalance and disruptions in redox sensitive signaling cascades. Therefore, we are interested in identifying molecules that link redox balance, mitochondrial function and insulin action in skeletal muscle. The work described herein identifies thioredoxin-interacting protein (TXNIP) as an attractive candidate that regulates both glucose homeostasis and mitochondrial fuel selection.</p><p>TXNIP is a redox sensitive, &alpha;-arrestin protein that has been implicated as a negative regulator of glucose control. Mounting evidence suggested that TXNIP might play a key role in regulating mitochondrial function; however, the molecular nature of this relationship was poorly defined. Previous studies in TXNIP knockout mice reported that deficiency of this protein compromises oxidative metabolism, increases glycolytic activity and promotes production of reactive oxygen species (ROS), while also affording protection against insulin resistance. Therefore, we hypothesized that TXNIP might serve as a nutrient sensor that couples cellular redox status to the adjustments in mitochondrial function. We tested this hypothesis by exploiting loss of function models to evaluate the effects of TXNIP deficiency on mitochondrial metabolism and respiratory function.</p><p>In chapter 3, we comprehensively evaluated oxidative metabolism, substrate</p><p>selection, respiratory kinetics and redox balance in mice with total body and skeletal muscle-­specific TXNIP deficiency. Targeted metabolomics, comprehensive bioenergetics analysis, whole-body respirometry and conventional biochemistry showed that TXNIP deficiency results in reduced exercise tolerance with marked impairments in skeletal muscle oxidative metabolism. The deficits in substrate oxidation were not secondary to decreased mitochondrial mass or increased H<sub>2</sub>O<sub>2</sub> emitting potential from the electron transport chain. Instead, the activities of several mitochondrial dehydrogenases involved in branched-chain amino acid and ketone catabolism, the tricarboxylic acid (TCA) cycle and fatty acid &beta;-oxidation were significantly diminished in TXNIP null muscles. These deficits in mitochondrial enzyme activities were accompanied by decreased protein abundance without changes in mRNA expression. Taken together, these results suggest that in skeletal muscle TXNIP plays an essential role in maintaining protein synthesis and/or stability of a subset of mitochondrial dehydrogenase enzymes that permit muscle use of alternate fuels under conditions of glucose deprivation.</p><p>Based on these conclusions, we questioned whether additional regulatory</p><p>mechanisms could contribute to the reduced oxidative metabolism in the absence ofTXNIP. Several metabolic enzymes of the TCA cycle have been shown to be redox-sensitive protein targets regulated by the thioredoxin (TRX1/TRX2) and glutathione (GSH) redox-mediated circuits. TXNIP has been shown to respond to oxidative stress by shuttling to the mitochondria where it binds to TRX2 and/or other proteins, thus affecting downstream signaling pathways, such as the apoptotic cascade. Therefore, we speculated whether there was a role for redox imbalance in mediating the mitochondrial phenotype of the TXNIP knockout (TKO) mice. In chapter 4, we present preliminary evidence that increased glucose uptake promotes non-mitochondrial ROS production, causing a shift in redox balance, decreased GSH/GSSG, and S-glutathionylation of &alpha;-­ketoglutarate dehydrogenase (&alpha-KGD). This post-translational modification protects the protein from permanent oxidative damage, but at the cost of reversible loss of activity and subsequent disruption of TCA cycle flux that contributes, in part, to the diminished oxidative metabolism observed in the TXNIP deficient mice.</p><p>In aggregate, this work sheds new light onto the physiological role of TXNIP in</p><p>skeletal muscle as it pertains to substrate metabolism and fuel switching in response to nutrient availability. This work has important implications for metabolic diseases such as obesity and type 2 diabetes, which are characterized by marked disruptions in fuel selection.</p> / Dissertation
126

Elucidating the metabolic pathways responsible for higher alcohol production in Saccharomyces cerevisiae

Styger, Gustav 03 1900 (has links)
Thesis (PhD (Wine Biotechnology))--University of Stellenbosch, 2011. / Includes bibliography. / ENGLISH ABSTRACT: Alcoholic fermentation, and especially wine fermentation, is one of the most ancient microbiological processes utilized by man. Yeast of the species Saccharomyces cerevisiae are usually responsible for most of the fermentative activity, and many data sets clearly demonstrate the important impact of this species on the quality and character of the final product. However, many aspects of the genetic and metabolic processes that take place during alcoholic fermentation remain poorly understood, including the metabolic processes that impact on aroma and flavour of the fermentation product. To contribute to our understanding of these processes, this study took two approaches: In a first part, the initial aim had been to compare two techniques of transcriptome analysis, DNA oligo-microarrays and Serial Analysis of Gene Expression (SAGE), for their suitability to assess wine fermentation gene expression changes, and in particular to assess their potential to, in combination, provide combined quantitative and qualitative data for mRNA levels. The SAGE methodology however failed to produce conclusive data, and only the results of the microarray data are shown in this dissertation. These results provide a comprehensive overview of the transcriptomic changes during model wine fermentation, and serve as a reference database for the following experiments and for future studies using different fermentation conditions or genetically modified yeast. In a second part of the study, a screen to identify genes that impact on the formation of various important volatile aroma compounds including esters, fatty acids and higher alcohols is presented. Indeed, while the metabolic network that leads to the formation of these compounds is reasonably well mapped, surprisingly little is known about specific enzymes involved in specific reactions, the genetic regulation of the network and the physiological roles of individual pathways within the network. Various factors that directly or indirectly affect and regulate the network have been proposed in the past, but little conclusive evidence has been provided. To gain a better understanding of the regulations and physiological role of this network, we took a functional genomics approach by screening a subset of the EUROSCARF strain deletion library, and in particular genes encoding decarboxylases, dehydrogenases and reductases. Thus, ten genes whose deletion impacted most significantly on the aroma production network and higher alcohol formation were selected. Over-expression and single and multiple deletions of the selected genes were used to genetically assess their contribution to aroma production and to the Ehrlich pathway. The results demonstrate the sensitivity of the pathway to cellular redox homeostasis, strongly suggest direct roles for Thi3p, Aad6p and Hom2p, and highlight the important role of Bat2p in controlling the flux through the pathway. / AFRIKAANSE OPSOMMING: Alkoholiese fermentasie, en veral die maak van wyn, is een van die vroegste mikrobiologiese prosesse wat deur die mensdom ingespan is. Die gisspesie Saccharomyces cerevisiae is gewoonlik grotendeels verantwoordelik vir die fermentasie and verskeie vorige studies het gedemonstreer dat hierdie spesie ‘n baie belangrike rol speel in die uiteindelike kwaliteit en karakter van die voltooide produk. Nieteenstaande die feit is daar steeds baie aspekte van beide die genetiese en metaboliese prosesse wat plaasvind tydens alkoholiese fermentatsie wat nog swak verstaan word, insluitende metaboliese padweë wat ‘n impak het op die smaak en aroma van die fermentasie produk. Om ons kennis van die veld uit te brei het die studie twee aanslae geneem: In die eerste geval is gepoog om twee tegnieke van transkriptoom analiese, nl. DNA oligomikro- arrays en Serial Analysis of Gene Expression (SAGE) te bestudeer vir hul vermoë om geen ekspressie veranderinge tydens wynfermentasie te ondersoek en meer spesifiek om hul potensiaal om ‘n kombinasie van kwantitatiewe sowel as kwalitatiewe data met betreking to mRNA vlakke te produseer. Die SAGE metode kon egter geen betroubare resultate produseer nie en dus word slegs die resultate van die mikro-array eksperimente in die tesis bespreek. Die resultaat is ‘n geheeloorsig oor die geenekspressie veranderinge wat so ‘n wyngis tydens alkoholiese fermentasie ondergaan en dien as ‘n verwysingsraamwerk vir toekomstige studies met geneties gemodifiseerde gis of selfs verskillende fermentasieparameters. Die tweede deel van die studie het gefokus op die identifikasie van gene wat ‘n impak het op die vorming van belangrike, vlugtige aroma komponente, o. a. Esters vetsure en hoër alkohole d.m.v. ‘n siftingseksperiment. Alhoewel daar redelik baie inligting is oor die onderligende metaboliese netwerke wat lei tot die vorming van die verbindings, is daar min kennis van die genetiese regulasie van die netwerk en die fisiologiese rol van individuele padweë wat die netwerk vorm. Verskeie faktore – wat of die netwerk direk of indirek affekteer – is al voorgestel, meer met min konkrete bewyse. Dus het ons gepoog om meer lig op die onderwerp te laat m.b.v. ‘n funksionele genoom aanslag deur ‘n siftingseksperiment te doen op ‘n subgroep (spesifiek gene wat kodeer vir dekarboksilase, dehidrogenase en reduktase ensieme) van die EUROSCARF delesiebiblioteek. Dus is tien gene geïdentifiseer – die delesie waarvan ‘n merkbare effek het op die aroma produksie netwerk en spesifiek die van hoër alkohole. Ooruitdrukkings en enkel en meervoudige delesie rasse van die tien gene is gemaak om d.mv. genetiese analiese, hulle rol in aroma produksie en die Ehrlich padweh uit te pluis. Die resultate toon dat hierdie padweg sensitief is teenoor die sellulêre redoks balans en dui op direkte rolle vir Thi3p, Aad6p en Hom2p, asook dat Bat2p ‘n baie belangrike rol speel in die werking van die padweg.
127

Degradace alifatických polyesterů - Vliv velikosti tělesa a jeho tvaru / Aliphatic polyesters degradation - Influence of the body size and habitus

Injinnash, Anudari January 2015 (has links)
In the theoretical part of this thesis are described the synthesis, properties and mechanism of biodegradation of aliphatic polymers - polylactic acid, polyglycolic acid and their copolymer PLGA. There are also discussed the possibilities of modifying the properties, such as block copolymer PEG-PLGA synthesis. Summary informations concerning the production and use of biodegradable polymers are also shortly described. The aim of the experimental part was to observe the effect of PLGA polymer matrix size and ionic strength of the aqueous medium on the polymer swelling and erosion. Samples with weight 150 mg and 1000 mg were placed into 37 řC citrate buffer with pH 6. Each of the used mediums had various concentration c [0; 0,125; 0,25; 0,5; 1]. Measurement was carried out in period of 28 days. Values of degree of swelling and of erosion were measured. The pulsion behavior of swelling in both sample sizes was confirmed. However, the sample size has a strong impact on the rate and extent of swelling. It was demonstrated that larger samples disintegrate faster which is explained by a higher rate of autocatalysis within the polymer matrix. The results demonstrated also the effect of ionic strength on erosion when isotonic solution suppressed erosion rate.
128

Perfil genotípico de pacientes chilenos com Doença da Urina do Xarope de Bordo / Chilean patients genotypic profile with Maple Syrup Urine Disease

Campanholi, Diana Ruffato Resende 17 April 2019 (has links)
Introdução: A Doença da Urina do Xarope de Bordo é uma doença hereditária do metabolismo dos aminoácidos de cadeia ramificada, de caráter autossômico recessivo. O diagnóstico precoce é fundamental na prevenção da deterioração neurológica, que se dá pela ausência da implementação do tratamento nutricional adequado. Objetivo: Realizar triagem das mutações em todos os éxons dos três genes envolvidos na Doença da Urina do Xarope de Bordo (BCKDHA, BCKDHB e DBT) através do sequenciamento gênico direto e correlacionar com a heterogeneidade fenotípica. Métodos: Estudo clínico transversal com pacientes chilenos diagnosticados com Doença da Urina do Xarope de Bordo. A genotipagem foi realizada com produtos purificados de reação em cadeia da polimerase (PCR) de DNA.Foi realizada análise in silico das substituições de nucleotídeos através dos softwares MutPred® v1.2, Polyphen-2® - Polymorphism Phenotyping v2 e SIFT®. As características clínicas dos pacientes foram fornecidas pela equipe de nutrição do Instituto de Nutrição e Tecnologia da Universidade de Chile (INTA). Foi realizado um teste exato de Fisher no grupo de pacientes portadores da mutação mais prevalente na amostragem, a I214K com a intenção de avaliar o grau de correlação entre algumas variáveis clínicas e genéticas para verificar a possibilidade de se estabelecer uma relação fenótipo/genótipo. Resultados: Dos 18 pacientes 88% apresentaram mutação no gene BCKDHB, 1 pacientes 5% apresentou mutação no gene BCKDHA e 1 (5%) paciente apresentou mutação no gene DBT. Foram encontradas um total de 8 mutações na amostra e 4 novas mutações (50%). Não se pode afirmar que há correlação de nenhuma das variáveis clínicas com os genótipos encontrados nessa amostragem. Conclusão: Este estudo reportou 4 novas mutações em pacientes portadores de DXB na população chilena, o que pode ajudar em futuros diagnósticos genéticos da doença. Se a DXB fosse diagnosticada de forma mais rápida, na triagem neonatal, talvez fosse possível estabelecer uma relação genótipo-fenótipo de forma mais eficiente / Introduction: Maple Syrup Urine Disease (MSUD) is an autossomal recessive hereditary disease of the branched-chain amino acid metabolism. Early diagnosis is essential in preventing neurological deterioration, which occurs due to inadequate nutritional implametation treatment. Purpose: Screen mutations in all exons from the three genes involved in MSUD (BCKDHA, BCKDHB and DBT) through direct gene sequencing and correlation with phenotypic heterogeneity. Methods: A cross-sectional study with Chilean patients diagnosed with Maple Syrup Urine Disease. Genotyping was performed using purified polymerase chain reaction (PCR) DNA. Nucleotide substitutions In Silico analysis was performed using MutPred® v1.2, Polyphen-2® - Polymorphism Phenotyping v2 and SIFT® softwares. Patients clinical characteristics were provided by the nutrition team from Chile University, Nutriton and Technology Institute (INTA). Results: Of the 18 patients, 88% presented mutation in BCKDHB gene, 1 patient had mutation in BCKDHA gene and 1 patient (5%) presented a mutation in DBT gene. A total of 8 mutations in the sample and 4 new mutations (50%) were found. It can not be affirmed that there is correlation between clinical variables and genotypes in this sample. Conclusion: This study reported 4 new mutations in patients with MSUD in Chilean population, which may help in future genetic diagnosis. If MSUD was diagnosed more rapidly in neonatal screening, it might be possible to establish a genotype-phenotype relationship more efficiently
129

Reconstruction des températures continentales en Europe de l'Ouest à partir de l'étude des tétraéthers ramifiés dans les sédiments du lac de Saint-Front (Massif Central, France) / Continental temperature reconstruction in Western Europe from branched tetraether analysis in the sediments of lake St-Front (Massif Central, France)

Martin, Céline 21 September 2018 (has links)
Cette thèse a pour but de reconstituer le climat des 100 000 dernières années en Europe de l’ouest. L’étude du climat du passé permet de mieux comprendre la variabilité naturelle du climat sur laquelle se surimpose aujourd’hui le réchauffement climatique d’origine anthropique. Ce sont des molécules fossiles bactériennes dont la structure varie en fonction des conditions environnementales qui ont permis dans cette étude de reconstituer le paléoclimat à partir des sédiments du lac St Front dans le Massif Central. Les indices dérivés de ces molécules révèlent la variabilité climatique à long terme mais également les évènements rapides de changement climatique ainsi qu’une forte action anthropique en surimposition des changements climatiques régionaux sur les 5000 dernières années. Ce travail montre l’importance de la compréhension de l’outil utilisé et du fonctionnement du système naturel dans lequel il est étudié, préalables indispensables à l’obtention d’une séquence climatique crédible / This thesis aims to reconstruct the climate of the last 100,000 years in western Europe. The study of past climate allows to better understand the natural variability of climate on which human-induced global warming is superimposed today. Bacterial fossil molecules whose structure varies according to the environmental conditions were used in this study to reconstruct the paleoclimate from the sediments of lake St Front in the Massif Central. The indices derived from these molecules reveal the long-term climatic variability but also the rapid events of climate change as well as a strong anthropogenic action in superimposition of the regional climatic changes over the last 5000 years. This work shows the importance of understanding the tool used and the functioning of the natural system in which it is studied, essential prerequisites for obtaining a credible climate reconstruction
130

Suplementação com aminoácios de cadeia ramificada atenua em proles os efeitos mediados pela dieta materna restrita em proteína / Branched-chain amino acids supplementation attenuates in offspring the effects mediated by maternal protein-restrict diet.

Teodoro, Gabriela Fullin Resende 12 August 2010 (has links)
Estudos em animais mostram que a desnutrição proteica intrauterina pode acarretar redistribuição do fluxo sanguíneo intraútero, podendo promover modificações permanentes na estrutura e funcionalidade de alguns órgãos, o que ocasiona modificações no metabolismo. Além disso, a desnutrição intrauterina pode afetar a secreção de hormônios que atuam no crescimento fetal, podendo conduzir à restrição do crescimento intrauterino. Esse fenômeno pode parcialmente ser explicado pela hipótese da programação fetal, na qual é sugerido que ocorra uma adaptação metabólica e fisiológica do feto a uma condição intrauterina adversa, que pode induzir o desenvolvimento de doenças crônicas não transmissíveis na vida adulta. Neste contexto, pesquisas com suplementação de aminoácidos de cadeia ramificada (BCAA) têm verificado a capacidade desses nutrientes promoverem a síntese proteica mesmo em condições catabólicas, por meio da ativação de uma via bioquímica intracelular intercedida pela proteína quinase Alvo da Rapamicina em Mamíferos (mTOR), a qual está envolvida no estímulo à etapa de tradução proteica. Assim, o presente trabalho avaliou o efeito da suplementação de BCAA em proles submetidas à desnutrição proteica materna. Para tanto, ratas Wistar foram acasaladas com ratos adultos de mesma raça. Uma vez constatada a gravidez, as matrizes foram distribuídas em grupos de acordo com a dieta que seria fornecida no decorrer da gestação: CON (20% proteína); VAL/ISO (5% proteína + 2% VAL + 2% ISO); AAE (5% proteína + 4% AAE); e BCAA (5% proteína + 4% BCAA). O protocolo de restrição proteica materna adotado causou redução no crescimento corporal e na massa de órgãos das proles. Embora a suplementação com VAL/ISO e AAE não tenha recuperado os efeitos mediados pela deficiência de proteína, foi constatado que a suplementação com BCAA reverteu parte do déficit observado no crescimento das proles, uma vez que foi eficaz em minimizar ou mesmo em restaurar plenamente diversos parâmetros como peso de órgãos, massa de gordura da carcaça e parâmetros indicativos do estado nutricional proteico, como as concentrações de proteína e RNA hepáticas e musculares. Estes efeitos podem parcialmente ser explicados pelo estímulo induzido pela suplementação com BCAA, na via de sinalização da mTOR, considerando que foi verificado no fígado das proles de matrizes que receberam esta suplementação, aumento na fosforilação desta proteína (P < 0,05), a qual é responsável por desencadear uma cascata de eventos biomoleculares que culminam, em última instância, no acréscimo da síntese proteica. Diante disto, torna-se relevante a realização de pesquisas que avaliem em longo prazo, os efeitos da suplementação com BCAA em proles submetidas à dieta materna restrita em proteína. / Animal studies show that intrauterine malnutrition may cause redistribution of blood flow in uterus, which may promote permanent changes in structure and function of some organs, which causes changes in metabolism. Furthermore, intrauterine malnutrition can affect the secretion of hormones that act on fetal growth and may lead to intrauterine growth restriction. This phenomenon can partly be explained by the hypothesis of fetal programming, which is suggested that occur a metabolic and physiological adaptation of the fetus to an adverse intrauterine condition, which can induce the development of chronic diseases in later life. In this context, researches with supplementation of branched chain amino acids (BCAA), especially leucine, have verified the ability of these nutrients to promote protein synthesis in catabolic conditions, through the activation of an intracellular biochemical pathway interceded by protein kinase Mammalian Target of Rapamycin (mTOR), which is involved in the stimulating of protein translation stage. Thus, this study evaluated the effect of BCAA supplementation in offspring subjected to maternal protein-restrict diet. To this, Wistar rats were mated with adult rats of the same race. Once was confirmed the pregnancy, the pregnants were distributed into groups according to the diet that would be provided during pregnancy: CON (20% protein); VAL/ISO (5% protein + 2% + 2% VAL/ISO), AAE (5% protein + 4% EAA) and BCAA (5% protein + 4% BCAA). The protocol adopted maternal protein restriction caused a reduction in body growth and weight of the offspring\'s organs. Although supplementation with VAL/ISO and AAE has not recovered the effects mediated by protein deficiency, it was found that supplementation with BCAA has reversed part of the deficit observed in the growth of the offspring, since it was effective in minimizing or even fully restoring various parameters such as organ weight, carcass fat mass and parameters indicative of nutritional protein, such as the concentrations of protein and RNA in liver and muscle. These effects may be partially explained by the stimulation induced by BCAA supplementation on the mTOR signaling pathway, considering that was verified in the liver of the offspring from dams that received this supplementation augment on the phosphorylation of this protein (P < 0,05), which is responsible for triggering a cascade of molecular events that culminate, ultimately, in increased protein synthesis. Given this, it becomes relevant to conducting research to assess long-term effects of supplementation with BCAA in offspring subjected to maternal protein-restricted diet.

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