Hebert and Carruthers (1992) showed that the human erythrocyte glucose transporter is an allosteric complex of four GLUT1 proteins whose structure and substrate binding properties are stabilized by reductant-sensitive noncovalent subunit interactions. The GLUT1 tetramer dissociates into dimers upon exposure to reductant but subunits are not associated via disulfide bridges. Each subunit of SDS-denatured tetrameric GLUT1 exposes only two thiols while reduced denatured GLUT1 exposes all six sulfhydryl groups. They hypothesized that glucose transporter oligomeric structure and cooperative catalytic function resulted from noncovalent subunit interactions promoted or stabilized by intramolecular disulfide bridges. These interactions give rise to an antiparallel arrangement of substrate binding sites within the transporter complex. In the present studies, we tested aspects of this model. Specifically, we wanted 1) to understand why the native, noncovalent, homotetrameric GLUT1 complex is sensitive to reductant, 2) to determine whether the tetramer is more catalytically efficient than the dimer in situ, and 3) to test the hypothesis that it is the antiparallel arrangement of substrate binding sites between subunits that provides the transporter with its catalytic advantage. We used biochemical and molecular biological approaches to isolate specific determinants of transporter oligomeric structure and/or transport function in purified isolated transporter preparations, in intact red cells and in CHO cells. We have also examined the hypothesis that net sugar transport in the human erythrocyte is rate limited by reduced cytosolic diffusion of sugars and/or by reversible sugar association with intracellular macromolecules. Our findings support the hypothesis that each subunit of the parental glucose transporter contains a single intramolecular disulfide bridge located between cysteine residues 347 and 421. This disulfide seems to be necessary for GLUT1 tetramerization. Our findings suggest that GLUT1 N-terminal residues 1 through 199 provide contact surfaces for subunit dimerization but are insufficient for subunit tetramerization. Our studies also show that in situ disulfide disruption by cell impermeant reductants results in the loss of cooperative subunit interactions and a 3 to 15-fold reduction in the transport efficiency of the transporter. We further find that in situ GLUT1 is susceptible to exofacial proteolysis. Exofacial trypsin cleavage eliminates cooperativity between subunits but does not affect transporter oligomeric structure or transport activity. Thus catalytic efficiency does not derive directly from cooperative interactions between substrate binding sites on adjacent subunits. We have confirmed that 30MG transport in human erythrocytes is a diffusion limited process. We find that steady-state sugar uptake in red cells and K562 cells measures two processes - sugar translocation and intracellular sugar binding. We propose a model for native GLUT1 structure and function.

The structure-function relationship explains how the human erythrocyte glucose transport protein (GLUT1) catalyzes sugar transport across the plasma membrane. This work investigates the glucose transport mechanism, the structural arrangement and dynamics of GLUT1 membrane-spanning α-helices, the molecular basis for glucose transport regulation by ATP, and how cysteine accessibility contributes to GLUT1 structure. A rapid kinetics approach was applied to examine the conformational changes GLUT1 undergoes during the transport cycle. To transition from a global to molecular focus, a novel mass spectrometry technique was developed to resolve GLUT1 sequence that is associated either with membrane embedded GLUT1 subdomains or with water exposed domains. By studying accessibility changes of specific amino acids to covalent modification by a Sulfo-NHS-LC-Biotin probe, specific protein regions associated with glucose transport modulation by ATP were identified. Finally, mass spectrometry was applied to examine cysteine residue accessibility under native and reducing conditions. This thesis presents data supporting the isolation of an intermediate, occluded GLUT1 conformational state that temporally bridges import and export configurations during glucose translocation. Our results confirm that amphipathic α-helices line the translocation pathway and promote interactions with the aqueous environment and substrate. In addition, we show that GLUT1 is conformationally dynamic, undergoes reorganization in the cytoplasmic region in response to ATP modulation, and that GLUT1 contains differentially exposed cysteine residues that affect its folding.

The experiment was conducted at Experimental Station of Flowering and Cruzamento of the Serra do Ouro -PMGCA RIDESA ,in the municipality of Murici - AL (09 ° 14 '22, 86 "N, 35 º 50' 11.05" W, 480 m height). The cultivar RB867515 was underwent to four different treatments, T0 - only conventional fertilization (28, 44, 28, 6, 6 and 3 grams of N, P, K, Zn, Cu and Mn, respectively), T1 - conventional fertilization + 2 kg of gypsum (1 kg at the bottom of the pit and 1 kg in coverage), T2 - conventional fertilization + 0.058 mol-1 of calcium sulphate in the leaf e T3 - conventional fertilization + 0.058 mol-1 of potassium silicate in the leaf. Each experimental plot consisted of a clump. Before and after flowering (at 183 and 239 days after planting respectively) were evaluated morphological parameters such as counting the number of stems per plot, height, stalk diameter and number of internodes per stem. The data were underwent avarage comparison by Tukey. The biochemical analysis of the apical meristem of plants of the variety RB867515 show that application of foliar calcium resulted in its accumulation produces a negative correlation between the calcium and potassium in the plant, which may have caused the delay and the decrease in flowering plants this treatment. The application of silicon on the leaves have little or no influence on the composition of minerals, sugars in the apical meristem and on the process of flowering. / Fundação de Amparo a Pesquisa do Estado de Alagoas / O presente trabalho teve por finalidade avaliar o efeito da aplicação de cálcio e silício no florescimento da variedade de cana-de-açúcar RB867515. Para tanto, o experimento foi instalado na área experimental da Estação de Florescimento e Cruzamento Serra do Ouro - PMGCA - RIDESA, município de Murici AL (09º 14 22, 86 S, 35º 50 11,05 W, 480 m de altitude). A cultivar RB867515 foi submetida a quatro diferentes tratamentos, sendo T0 adubação convencional (28, 44, 28, 6, 6 e 3 gramas de N, P, K, Zn, Cu e Mn, respectivamente), T1 adubação convencional + 2 kg de gesso (1 kg no fundo da cova e 1 kg em cobertura), T2 adubação convencional + 0,058 mol-1 de sulfato de cálcio via foliar, T3 adubação convencional + 0,058 mol-1 de silicato de potássio via foliar. O delineamento experimental utilizado foi o de blocos casualizados com dez repetições. A parcela experimental foi composta por uma touceira. Antes e depois do florescimento (aos 183 e 239 dias após o plantio respectivamente), foram avaliados parâmetros morfológicos como: contagem do número de colmos por parcela, altura, diâmetro de colmos e número médio de entrenós por colmo. Os dados obtidos foram submetidos a análise de variância e teste de médias por Tukey. As análises bioquímicas do meristema apical das plantas da variedade RB867515 mostram que a aplicação de cálcio via foliar resultou no seu acúmulo produzindo uma correlação negativa entre os teores de cálcio e potássio na planta, o que pode ter causado o retardo e a diminuição do florescimento nas plantas deste tratamento. A aplicação de silício via foliar tem pouca ou nenhuma influência sobre a composição de minerais, açúcares no meristema apical e sobre o processo de florescimento.

Introdução: A ingestão de carboidrato (CHO) durante o exercício de resistência aeróbica de longa duração tem se mostrado capaz de otimizar o desempenho dos atletas. Alguns estudos recentes têm reportado também um efeito ergogênico quando a proteína (PTN) é adicionada a uma bebida carboidratada. Além disso, a coingestão tem sido relacionada com a atenuação do dano muscular, tido como fator limitante da recuperação muscular. No entanto, pouco se investigou sobre a influência dessas suplementações, comparadas a uma bebida placebo (PLA), no duatlo de distância olímpica. Objetivo: Comparar o efeito de três diferentes estratégias nutricionais de suplementação (CHO vs. CHO+PTN vs. PLA), durante um teste simulado de duatlo (TSD) olímpico, no desempenho e recuperação muscular de duatletas amadores. Métodos: Em um ensaio clínico, cruzado, randomizado e duplo-cego, treze atletas amadores do sexo masculino, com idade média de 29,7 ± 7,7 anos, participaram de três TSD consumindo: bebida carboidratada (CHO, 75 g); bebida isocalórica combinando carboidrato e proteína, na proporção 4:1 (CHO+PTN, 60,5 g CHO e 14,5 g PTN); e bebida placebo (PLA). Aos atletas informou-se apenas que o estudo visava investigar a influência de três diferentes tipos de suplementação. Após jejum de 8 h, sujeitos recebiam um café da manhã padrão, com 1,5 g/kg CHO e 45 min depois iniciavam o protocolo. As intensidades da primeira corrida (10 km) e da sessão de ciclismo (40 km) foram controladas, utilizando dados previamente coletados em testes preliminares, e a corrida final, de 5 km, foi tratada como um contrarrelógio (t5km). Coletas de sangue foram realizadas antes, imediatamente após e 24h após cada teste simulado, e analisou-se concentrações de glicose e creatina quinase (CK). Pico de torque (PT) isométrico foi mensurado no início do estudo e 24h após cada teste. Resultados: Os atletas completaram as distâncias totais do duatlo olímpico em ~1h 51min. Não houve diferença significativa no t5km entre as condições CHO (1270,3 ± 130,5 s) vs. CHO+PTN (1267,2 ± 138,9 s) vs. PLA (1275,4 ± 120 s); p = 0,87; TE ≤ 0,1. Os resultados de PT não demonstraram alterações significativas entre as condições basal (302,2 ± 52,8 N.m) vs. pós-24h CHO (300,1 ± 41,4 N.m) vs. pós-24h CHO+PTN (292,2 ± 49,4 N.m) vs. pós-24h PLA (282,1 ± 43,1 N.m); p = 0,24; TE ≤ 0,4. Embora, os resultados de CK tenham mostrado aumento significativo para todas as condições na comparação pré vs. pós-24h: CHO (300%; p < 0,01; TE = 0,93); CHO+PTN (82%; p < 0,01; TE = 0,73) e PLA (190%; p = 0,01; TE = 1,04), não foram encontradas diferenças entre as condições nos diferentes momentos - pré, imediatamente após e pós-24h (p = 0,32; TE = 0,3 – 1,04). Conclusão: Em uma prova simulada de duatlo olímpico, com refeição pré-teste contendo 1,5g/kg de carboidrato, as suplementações de CHO e de CHO+PTN não oferecem benefícios extras quando comparadas a uma bebida placebo no que diz respeito ao desempenho e recuperação muscular dos atletas. / Introduction: Carbohydrate (CHO) intake during long-term endurance exercise has been shown to optimize performance in athletes. Some recent studies have also reported an ergogenic effect when protein (PRO) is added to a carbohydrate drink. Furthermore, the coingestion has been related to the attenuation of muscle damage, seen as a limiting factor in muscle recovery. However, little has been investigated about the influence of such supplementation, compared to a placebo drink (PLA), in an Olympic-distance (OD) duathlon. Purpose: This study aimed to compare the effects of three different nutritional supplementation strategies (CHO vs. CHO+PRO vs. PLA) during a simulated OD duathlon, on performance and indices of muscle recovery of amateurs duathletes. Methods: In a crossover, randomized, double-blind clinical trial, thirteen male amateur athletes, mean age 29.7 ± 7.7 years, participated in three simulated OD duathlons consuming either a carbohydrate drink (CHO, 75 g); an isocaloric drink combining carbohydrate and protein in a 4:1 ratio (CHO+PRO, 60.5 g CHO and 14.5 g PRO); or a placebo (PLA) drink. The athletes were informed that the study aimed to investigate the influence of three different types of supplementation. After an 8 hours fast, subjects received a standard breakfast, with 1.5 g / kg CHO and 45 min later the protocol began. The intensities of the first running (10 km) and cycling session (40 km) were controlled using previously collected data, and the final running, 5 km, was treated as a time-trial (t5km). Blood samples were taken before, immediately after and 24 hours after each simulated duathlon and glucose and creatine kinase (CK) levels were analyzed. Isometric peak torque (PT) was measured at baseline and 24 hours after each test. Results: The athletes completed the OD duathlons in ~ 1h 51min. There was no significant difference in t5km between CHO (1270.3 ± 130.5 sec) vs. CHO+PRO (1267.2 ± 138.9 sec) vs. PLA (1275.4 ± 120 sec); p = 0.87; ES ≤ 0.1. The results of PT showed no significant changes between baseline conditions (302.2 ± 52.8 Nm) vs. 24h post-CHO (300.1 ± 41.4 Nm) vs. 24h post-CHO+PRO (292.2 ± 49.4 Nm) vs. 24h post-PLA (282.1 ± 43.1 Nm); p = 0.24; ES ≤ 0.4. Although CK results showed significant increase for all conditions when comparing pre vs. post 24h CHO (300%; p <0.01; ES = 0.93); CHO+PRO (82%; p <0.01; ES = 0.73) and PLA (190%, p = 0.01; ES = 1.04), no differences were found between the conditions in the different moments - pre, immediately after and after 24 hours (p = 0.32; ES = 0.3 – 1.04). Conclusion: In a simulated Olympic-distance duathlon, with pre-meal test containing 1.5g / kg of carbohydrate, the ingestion of CHO and CHO+PRO does not provide additional benefits when compared to a placebo drink regarding athletes’ performance and muscle recovery.

Orientador: Prof. Dr. Anderson Orzari Ribeiro / Tese (doutorado) - Universidade Federal do ABC. Programa de Pós-Graduação em Ciência e Tecnologia/Química, 2017. / Uma estatistica do IARC (Agencia Internacional de Pesquisa sobre o Cancer) preve que 19,5 milhoes de pessoas serao afetadas pela doenca no ano 2025. Diferentes tipos de cancer podem ser tratados por cirurgia, radioterapia, quimioterapia ou transplante de celulas. O composto 1,5-bis-(4-hidroxi-3-metoxifenil)-1,4-pentadien-3-ona (HB1) foi estudado pelo nosso grupo de pesquisa e exibiu destacada atividade antitumoral nos testes in vitro contra varias celulas tumorais humanas e mostrou uma taxa de toxicidade muito baixa. Outro composto importante obtido foi o composto 3-((Z)-3-cloro-3-(4-iodofenil) alilideno)pentano-2,4-diona (C21), que mostrou atraves de testes in vitro tambem uma elevada atividade antitumoral contra a celula tumoral B16F10 (IC50 = 0,73 ¿Êg/mL, na concentracao de 1 ¿Êg/mL apos 24 horas de tratamento) e baixa toxicidade contra celulas normais. Uma estrategia para aumentar a atividade antitumoral e a combinacao de hidratos de carbono com substancias biologicamente ativas. Um exemplo do efeito de associado a hidrato de carbono sao as interacoes especificas entre carboidratos e lectinas na parede celular, que contribuem para muitos processos de reconhecimento intercelular. O primeiro objetivo desta proposta foi a sintese de analogos de curcumina ligados a porcoes C-Glicosidicas. Iniciou-se com a C-Ramnosilacao utilizando a reacao de tricloroacetimidatos de tetra-O-benzil-rhamnosilo com fenois ricos em eletrons na presenca de triflato de trimetilsililo (TMSOTf) para obter ligacoes C-glicosidicas. Atraves da analise por RMN foi possivel observar a formacao do composto O- Glicosilado (15), o que e tambem muito interessante. A fim de obter os compostos (24) e (25) e subsequentemente obter novos compostos C-Glicosilados (28, 30, 35, 43 e 46) foram feitas varias reacoes sinteticas a partir da D-Galactose. O primeiro passo foi a acetilacao de todos os grupos hidroxilo livres e, em seguida, o grupo hidroxilo protegido com acetilo anomerico foi substituido por grupo bromo por tratamento com brometo de hidrogenio para obter o composto (17). Atraves da glicosilacao de Helferich, converteu-se o glicosido bromado (17) no galactopiranosido (18) um alilglicosido, que atraves das condicoes Zemplen proporcionou a obtencao do composto (19), que foi subsequentemente protegido pela reacao de benzilacao dando o composto (20). A desalquilacao anomerica foi realizada utilizando catalisada com cloreto de paladio (II), formando o produto (21), que foi convertido na lactona (22) pela oxidacao com o reagente de Dess-Martin. Com a reacao de Grignard, obteve-se o hemiacetal (23) e finalmente com trietilsilano e BF3.OEt2, obteve-se o composto (24) por reducao com rendimento significativo. A desprotecao total para grupos benzilas foi realizada por tricloreto de boro e o composto (25) foi sintetizado em uma hora com alto rendimento. / A statistic of IARC (International Agency for Research on Cancer) predicts that 19.5 million people will be affected by the disease in the year 2025th. Different types of cancer are treated by surgery, radiotherapy, chemotherapy or stem cell transplantation. The compound 1,5-bis(4-hydroxy-3-methoxyphenyl)-1,4-pentadien-3-one (HB1) has been studied by our working group and exhibited high antitumoral activities regarding in vitro screening against several human tumor cell lines and showed very low toxicity rate. Another important compound obtained, was the compound 3-((Z)-3-chloro-3-(4-iodophenyl)allylidene)pentane-2,4-dione (C21), which has shown through in vitro tests also high antitumor activity against tumoral cell B16F10 (IC50 = 0.73 he specific interactions between carbohydrates and lectins on the cell wall, which contribute to many intercellular recognition processes. The first target of this proposal was the synthesis of curcumin analogues linked to C-Glycosidic moieties. It was started with the C-rhamnosylation using the reaction of tetra-O-benzyl-rhamnosyl trichloroacetimidates with electron-rich phenols in the presence of trimethylsilyl triflate (TMSOTf) to get C-glycosidic linkages. Unfortunately the C-Glycosylated compound was not obtained. Through NMR analysis it was possible to observe the formation of the O-Glycosylated compound (15), which seems to be also very interesting. In order to obtain the compound (24) and (25) and subsequently obtaining new C-Glycosylated compounds (28, 30, 35, 43 and 42) were made several synthetic reactions starting from D-Galactose. The first step was the acetylation of all free hydroxyl groups presents and then, the anomeric acetyl-protected hydroxy group was replaced by bromo group via hydrogen bromide treatment to obtain the compound (17). Through glycosylation Helferich the brominated glycoside (17) was converted into the galactopyranoside (18) an allyl-glycoside, which through Zemplen conditions afforded the compound (19), which was subsequently protected by benzylation reaction giving the compound (20). The anomeric dealkylation was performed using palladium (II) chloride-catalyzed, forming the product (21), which was converted into the lactone (22) by Dess-Martin periodinane oxidation. With the Grignard reaction, the hemiacetal (23) was obtained and finally with triethylsilane and BF3.OEt2, the compound (24) was obtained through reduction with significant yield. The total deprotection for benzyls groups was performed by boron trichloride and then de compound (25) was synthesized in one hour with high yield.

O controle glicêmico intensificado pode prevenir e/ou retardar o aparecimento das complicações crônicas do diabetes melito (DM). O carboidrato da dieta é o principal determinante da glicemia pós-prandial, sendo o índice glicêmico (IG) e a carga glicêmica (CG) úteis para prever a resposta glicêmica aos alimentos. O objetivo deste manuscrito foi revisar criticamente o papel das dietas de baixo IG na prevenção e controle metabólico do DM tipo 2 (DMT2). O risco para desenvolvimento de DMT2 com dietas de alto IG variou de 1,21 a 1,59. A redução de 12 a 32 unidades no IG da dieta diminuiu em 0,39 a 0,50 pontos percentuais a HbA1c. Os efeitos dessas dietas no perfil lipídico e peso corporal no DMT2 permanecem controversos. Em conclusão, as evidências atuais indicam que a incorporação do IG no planejamento dietético de pacientes com DMT2 contribui para a melhora do controle glicêmico. / The tight glycemic control can prevent and/or delay the development of chronic complications of diabetes mellitus (DM). Dietary carbohydrates are the main determinant of postprandial blood glucose and glycemic index (GI) and glycemic load are used to predict blood glucose response to foods. The aim of this paper was to critically review the role of low GI diets in type 2 DM (T2DM) prevention and metabolic control. The risk for development of T2DM with high GI diets ranged from 1.21 to 1.59.The reduction from 12- 32 units in the GI of diets decreased 0.39-0.50% in HbA1c values. However, the effects of these diets on lipid profile and body weight in patients with T2DM remain controversial. In conclusion, the current evidence indicates that the inclusion of GI in the dietary planning for patients with T2DM contributes to the improvement of glycemic control.

Made available in DSpace on 2014-06-11T19:33:37Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-06-15Bitstream added on 2014-06-13T20:45:31Z : No. of bitstreams: 1 martins_mr_dr_jabo.pdf: 769408 bytes, checksum: 09516289dc86d18336022a2e115970e7 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O presente trabalho teve como objetivo geral determinar como as plantas influenciam a estabilidade de agregados, a composição de carboidratos, o acúmulo de C orgânico do solo (COS) e de C microbiano em um Latossolo Vermelho. Na primeira parte do estudo, verificou-se que as sequências de culturas com milho (Zea mays L.) no verão e as milheto (Pennisetum glaucum (L.) Leeke) e sorgo granífero (Sorghum bicolor (L.) Moench) no inverno proporcionaram maior diâmetro médio ponderado (DMP) de agregados estáveis do solo. Assim como observado para o DMP, as sequências de culturas envolvendo milho no verão proporcionaram os maiores teores de xilose do solo. A menor proporção de carboidratos de origem microbiana em relação aos de origem vegetal foram observados com o cultivo mais frequente de espécies de monocotiledôneas. Na segunda parte do estudo, notou-se que os maiores valores de C presente como matéria orgânica particulada (C-MOP) do solo foram encontrados sob cultivo de guandu, o qual proporcionou valores 54%, 46% e 48% maiores em relação ao cultivo de milho, girassol e nabo forrageiro, respectivamente. As variações nos teores de C-MOP explicaram o efeito das culturas nos teores de COS. Notou-se um acúmulo conjunto de C-MOP e de resíduos fúngicos e bacterianos no solo. Na terceira parte do estudo, verificou-se que os materiais de monocotiledôneas adicionados ao solo apresentaram as maiores taxas de mineralização do compartimento de C não lábil (k), os maiores teores de pentose do solo e o maior DMP de agregados do solo em comparação à testemunha e às dicotiledôneas, em período posterior de decomposição. Isso sugere que k e teores de pentoses do solo controlam a estabilidade de agregados do Latossolo em período tardio de incubação. O efeito da decomposição dos materiais vegetais na agregação do solo ocorreu independente da variação da quantidade do teor de COS / The general aim of this study was to determine how the plants influence the aggregate stability, carbohydrate composition and accumulation of soil organic C and microbial C of an Oxisol. In the first part of this study, it was found that summer crop sequences involving corn (Zea mays L.) and the winter crops millet (Pennisetum glaucum (L.) Leeke) and grain sorghum (Sorghum bicolor (L.) Moench) provided the highest mean weight diameter (MWD) of soil aggregate. The crop sequences involving corn in summer also provided the highest soil xylose contents. The lowest proportions of carbohydrates of microbial origin in relation to those of plant origin were found in soil under most frequent cultivation of plant species from monocots. In second part of this study, it was found that soil organic C content with pigeon pea was 20% higher compared to corn and 18% higher compared to sunflower. Likewise, the highest values of C associated to soil particulate organic matter (C-POM) was found with pigeon pea cultivation, which provided 54%, 46% and 48% higher contents than corn, sunflower and oilseed radish, respectively. The variation in C-POM explained the crop effects on soil organic C content. The results of the present study showed a co-accumulation of C-POM and microbial residues in soil. In the third part of this study, it was found that monocots plant materials presented the highest mineralization rates of non-labile pool of C (k), soil pentose content, plant pentose input and soil aggregate MWD. The results of the present study suggest that non-labile C pool, especially related to pentoses, controls the soil aggregation of an Oxisol in long-term. This effect appears to be independent of the variation in soil organic C content

Made available in DSpace on 2014-06-11T19:33:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2005-07-26Bitstream added on 2014-06-13T19:44:34Z : No. of bitstreams: 1 silva_cj_dr_jabo.pdf: 317118 bytes, checksum: f4634086de9339bbdcfc22de27d467da (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Com o objetivo de avaliar diferentes estresses sobre o acúmulo e partição de massa seca, abortamento, desenvolvimento, produção de grãos e concentração de metabólitos glicídicos e nitrogenados em plantas de milho, conduziuse um experimento em casa de vegetação. Os tratamentos foram: testemunha; plantas com desfolhamento de 66%; omissão do nitrogênio; déficit hídrico (20 - 30% da capacidade de retenção); sombreamento de 70%. Os estresses foram impostos dos dois aos quarenta dias após a polinização (DAP) e as avaliações realizadas em cinco coletas aos 0, 10, 20, 30 e 40 DAP. A omissão de N na fase reprodutiva não afetou a massa seca das plantas e não promoveu alterações nos grãos das plantas de milho, em função da grande remobilização deste elemento acumulado nas folhas e colmos durante o período vegetativo. O desfolhamento reduziu o acúmulo de massa seca no colmo e na espiga, causou abortamento de grãos, não afetou a massa dos grãos remanescentes, resultando em menor número e produção de grãos por planta. O sombreamento intensificou a translocação de fotossintatos do colmo e folhas para os grãos, causou redução no acúmulo de massa seca na planta, abortamento de grãos, menor peso dos grãos remanescentes, menor acúmulo de amido e menor produção de grãos por planta. O déficit hídrico reduziu a área foliar, a fotossíntese, o período de enchimento dos grãos, o acúmulo de MS na planta e a translocação de fotoassimilados para os grãos, resultando em abortamento de grãos do ápice da espiga, acúmulo de açúcares redutores e aminoácidos livres nas folhas e colmos e menor massa de grãos e produção por planta. A redução na produção foi maior no estresse por déficit hídrico, sombreamento de 70%, desfolhamento de 66% e deficiência de N, sendo o número de grãos por espiga e peso médio dos grãos os componentes da produção mais afetados. / To evaluate the effect of different stress on the accumulation and distribution of dry matter, abortion, development and production of grains and concentration of glycidic and nitrogen metabolites in maize plant, it was conducted an experiment on greenhouse conditions. The following treatments were used: control; defoliation (plants 66% defoliated); nitrogen omission; water deficit (20 - 30% of the retention capacity); shading (70%). The stress factors were imposed from two to forty days after pollination (DAP) and the analyses at 0, 10, 20, 30 and 40 DAP. The nitrogen omission at the reproductive stage did not affect plant dry mass or grains because of the high rate of remobilization of the N accumulated in leaves and stems during the vegetative stage. Defoliation reduced the dry matter accumulation in the stem and ears, increased kernel abortion, no caused any effect on photoassimilate translocation or weight from remaining grains. Also, resulted in a decrease on the total-N level, amino acids, grain reducing sugars and starch, fewer grains and lower production per plant. Shading intensified photoassimilate translocation indicating that in shaded plants the photosynthesis limitation is supplied by the high remobilization rate of reducing sugars, sucrose and starch from the stem and leaves to the grain. However, this stress causes reduction of dry matter accumulation, kernel abortion, and lower weight of remaining grains, starch accumulation and production of grains per plant. The water deficit reduced leaf area, photosynthesis, grain filling period, dry matter accumulation and photoassimilate translocation from vegetative organs to kernels, resulting in kernel abortion at the ear top, accumulation of reducing sugars and free amino acids in leaves and stems and lower weight of 1,000 grains and production per plant... (Complete abstract, click electronic address below)

Made available in DSpace on 2014-06-11T19:33:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-08-23Bitstream added on 2014-06-13T19:44:36Z : No. of bitstreams: 1 silva_ar_dr_jabo.pdf: 434685 bytes, checksum: 7a18945b647512a2133168a7a96479ee (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O objetivo deste trabalho foi avaliar respostas do capim-tifton 85 a doses de nitrogênio (N) associadas a doses e fontes de boro (B). Em casa de vegetação, conduziu-se um experimento fatorial 3 ´ 3 ´ 3 {três doses de N (0, 100 e 200 mg kg–1), três doses de B (0, 1,3 e 2,6 mg kg–1) e três fontes de B [colemanita fundida ao termofosfato (CF), colemanita em mistura com termofosfato (CM) e ácido bórico (H3BO3)]} em delineamento inteiramente ao acaso. As plantas cresceram em vasos preenchidos com amostra de um Latossolo Vermelho distrófico. Elas foram avaliadas em três ciclos de crescimento. O N foi aplicado no início de cada ciclo e o B apenas antes do plantio. A aplicação de N aumentou a massa seca da parte aérea e o número de perfilhos do capim nos três ciclos. A aplicação de B, isolada ou associada à de N, não teve influência nesses atributos, embora o solo tivesse baixo teor de B disponível. O suprimento de N aumentou também os teores de carboidratos de reserva na raiz da planta nos dois ciclos em que foram avaliados (primeiro e terceiro). O suprimento de B aumentou o teor desses carboidratos na base do caule no primeiro ciclo. Os fornecimentos de N e B aumentaram seus respectivos teores na parte aérea do capim no três ciclos, exceto no caso do teor de B no terceiro ciclo. Todas as fontes de B aumentaram o teor de B disponível no solo, mas a CM e o H3BO3 aumentaram mais do que a CF. O efeito mais evidente da aplicação conjunta de N e B ocorreu no acúmulo de B na parte aérea da planta, aumentando mais com a combinação das duas aplicações. O teor inicial de B no solo (0,15 mg dm–3) foi suficiente para atender as necessidades do capim-tifton 85 nos três ciclos de crescimento. / The objective of this work was to evaluate responses of Tifton 85 bermudagrass to nitrogen (N) rates associated with boron (B) rates and sources. In greenhouse, it was carried out a factorial experiment 3 ´ 3 ´ 3 {three N rates (0, 100 and 200 mg kg–1), three B rates (0, 1.3 and 2.6 mg kg–1) and three B sources [colemanite fused to termophosphate (CF), colemanite in mixture with termophosphate (CM) and boric acid (H3BO3)]} in complete randomized design. The plants grew in pots filled with sample of a Typic Haplustox. They were evaluated during three growth cycles. The N was applied at the beginning of each cycle and the B just before the planting. The N application increased both top dry mass and tiller number of the grass in the three cycles. The B application, isolated or associated with N application, did not have influence on these attributes, though the soil had low available B content. The N supply increased reserve carbohydrates contents in plant root in the two cycles in which they were evaluated (first and third). The B supply increased the content of these carbohydrates in the stem base in the first cycle. The N and B furnishings increased their respective contents in top grass in the three cycles, except in the case of the B content in the third cycle. All the sources increased the available B content in soil, but CM and H3BO3 increased more than CF. The most evident effect of the N and B applications together occurred in the B accumulation in top plant, increasing more with the combination of the two applications. The initial B content in soil (0.15 mg dm–3) was enough to attend necessities of Tifton 85 bermudagrass in the three growth cycles.

The mechanism of mechanotransduction in chondrocyte matrix metabolism is not well understood, in part because of the density of cartilage and in part because of limitations in in vitroculture systems. Using alginate covalently modified to include the integrin adhesion ligand R-G-D (arginine-glycine-aspartate) represents a unique approach to studying mechanotransduction in that it allows for exploration of the role of integrin adhesion in mediating changes to chondrocyte behavior. The hypothesis of this research was that chondrocytes will form a cytoskeletal adhesion to RGD-alginate mediated integrins, that this attachment will enable chondrocyte sensation of mechanical signals, and this signaling will alter chondrocyte matrix metabolism. The first aim of this research was to characterize chondrocyte attachment to RGD-alginate, and assess the role of substrate mechanics on chondrocyte attachment kinetics and morphology. Secondly, the effect of chondrocyte attachment to RGD-alginate in 3D culture on matrix biosynthesis was assessed, as were changes in substrate mechanics. Finally, this research aimed to determine the metabolic response of chondrocytes to changes in intrinsic and extrinsic mechanics. It was found that the RGD ligand functionalized the alginate scaffold, enabling chondrocytes to sense the mechanical environment. Attachment kinetics, morphology, and proteoglycan metabolism were found to adapt to hydrogel matrix stiffness when an integrin adhesion was present. Externally applied compression was transmitted through this integrin attachment, causing changes in proteoglycan synthesis. Components of media serum were found to modulate the effects of integrin mechanotransduction. These results were obtained by analyzing a novel approach with established techniques, such as the DMB dye assay for sulfated GAG content. The conclusions conform to diverse data from cartilage explant loading and monolayer culture studies, yet were accomplished using one versatile system in a straightforward manner. The potential of this system extends further, into identification of intracellular signaling pathways and extracellular modulation of matrix components. Seeded RGD-alginate is well suited for studying consequences of integrin attachment.