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Transporte jejunal eletrogênico da glicose em ratos com deficiência de niacina.

Victoria, C. R.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 18-23
POR
Relevância na Pesquisa
46.06%
The active electrogenic absorption of glucose was studied in 12 niacin deficient rats using a method for measuring changes in transmural potential difference across jejunal mucosa. The glucose was infused in 6 different concentrations (2.5; 5.0; 10.0; 20.0; 50.0 and 100.0 mM/L) at a constant rate of 1.7 ml per minute. The apparent kinetic parameters (Km and Pdmax) of active electrogenic transport were obtained graphically from curves of glucose transfer potentials. The results were compared with that obtained in a control group. The curve of glucose transfer potential in niacin deficient group was significantly lower than that of the control group. The apparent Km of niacin deficient group was greater than in the control group (16.1 x 12.7 mM/L). Furthermore, the Pdmax of the deficient group was lower than that of the control group (12.5 x 19.4 mV). The results showed that in niacin deficiency occurs a decreasing of the active electrogenic glucose absorption. One of the possible interpretation of the differences in the kinetic characteristics of electrogenic glucose transport would be a depleted energy supplement for the active transport in the enterocyte of the niacin deficient rats.

Expression studies of GUP1 and GUP2, genes involved in glycerol active transport in Saccharomyces cerevisiae, using semi-quantitative RT-PCR

Oliveira, Rui Pedro Soares de; Lucas, Cândida
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em //2004 ENG
Relevância na Pesquisa
55.99%
Glycerol active uptake in Saccharomyces cerevisiae, characterised physiologically as a H+/symport, was previously described as repressed by glucose, induced by growth on non-fermentable carbon sources and unresponsive to growth under salt stress. GUP1 and GUP2 were identified and characterised as genes involved in glycerol active uptake. Using SQ-RT-PCR, GUP1 and GUP2 transcription was measured. Unlike active transport activity determined previously, this was shown to be constitutive and not affected by either glucose repression or growth under salt stress. Furthermore, transcription of GUP1 and GUP2 was still not affected in the gpd1gpd2 mutant strain grown under salt stress in the presence of small amounts of glycerol, in which case a very high Vmax of glycerol uptake has been reported. Intracellular compounds were determined. Glycerol, acetate and trehalose were found to be the major compounds accumulated. Surprisingly, gpd1gpd2 mutant was shown to produce significant amounts of glycerol. Yet, results do not evidence a correlation between the amount of each compound and glycerol transport activity in any of the strains.

Glycerol metabolism and transport activity regulation in Saccharomyces cerevisiae

Lages, Fernanda; Oliveira, Rui Pedro Soares de; Lucas, Cândida
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em //1999 ENG
Relevância na Pesquisa
46.06%
Apresentação e resumo efectuados no 17th Small Meeting on Yeast Transport and Energetics em Córdoba, Espanha de 9 a 12 de Setembro de 1999.; With the purpose of studying the correlation between glycerol metabolic pathway and glycerol active transport (1) in S. cerevisiae, an extensive study on glycerol transport was elaborated in all the available mutants from the genes of glycerol metabolic pathway having W303 as common genetic background: gut1∆, gut2∆, gpp1∆, gpp2∆, gpd∆1 and gpd2∆ and several double mutants. For this purpose we chose to diagnostic active transport determining uptake kinetic parameters (Km and Vmax) and maximum glycerol accumulation ratios, as well as the capacity of accumulated radiolabeled substrate to be extruded after accumulation in glucose- and ethanol-grown cells. All these mutant strains presented active uptake of the same order of magnitude of the wild type, except glycerol kinase deletion mutant, gut1∆. Ethanol-grown cells of gut1∆ presented active uptake with identical Km but lower Vmax (± 70%) than wild type strain. This indicated that, most probably, uptake Vmax determinations in all the other strains might present some contribution of glycerol kinase activity. This hypothesis was reinforced with measurements of glycerol kinase activity in cell free extracts obtained under the same physiological conditions. Furthermore...

Transporte ativo: perceção e comportamentos de segurança no percurso de casa-escola de jovens do 11º e 12º anos: relatório de estágio; Active transport: perception and safety behaviors in the course of homeschool commuting 11th and 12th grades: practicum report

Sampaio, Helena
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Trabalho de Conclusão de Curso
Publicado em //2014 POR
Relevância na Pesquisa
65.92%
Relatório de estágio de mestrado em Ensino de Educação Física nos Ensinos Básico e Secundário; O Relatório de Estágio está enquadrado no 2º ano do Mestrado em Ensino de Educação Física nos Ensinos Básico e Secundário da Universidade do Minho, referente ao ano letivo de 2013/2014. Com o presente documento pretendo analisar, refletir e descrever o meu percurso na Prática de Ensino Supervisionada, enquanto professora estagiária de Educação Física. Desta forma, comecei por fazer um enquadramento pessoal e institucional da minha prática pedagógica, centrando-me nos objetivos, contextos e limitações visando uma melhor compreensão de todo o trabalho desenvolvido no estágio. A organização e a gestão do processo do ensino-aprendizagem foram desenvolvidas em diferentes pontos, englobando a atividade profissional de um professor a vários níveis. Comecei por abordar a conceção, de seguida o planeamento, posteriormente a realização e por fim a avaliação do ensino. Nesta área, foram descritas as diferentes estratégias de intervenção, que garantiram os saberes dos alunos no ensino da educação física, conduzindo ao sucesso e eficácia pedagógica. Tracei a minha forma de agir e intervir, demonstrando um importante papel na aquisição...

Stimulation of Monovalent Cation Active Transport by Low Concentrations of Cardiac Glycosides: ROLE OF CATECHOLAMINES

Hougen, Thomas J.; Spicer, Nancy; Smith, Thomas W.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /11/1981 EN
Relevância na Pesquisa
46.14%
The stimulatory effect of low concentrations of ouabain on the Na-K pump in isolated guinea pig left atria was studied in vitro by assessing active transport of the K+ analog Rb+. Active transport of Rb+ was stimulated 20±8% (SEM, P < 0.05) above control values by 3 nM ouabain, but was inhibited by concentrations >10 nM. Preincubation with the β-adrenergic antagonist propranolol (1 μM) completely blocked stimulation of active transport of Rb+ by 3 nM ouabain. Norepinephrine, 10 nM, increased Rb+ active transport 29±10% (P < 0.02) above control values. The β-adrenergic agonist l-isoproterenol, 10 nM, increased active transport of Rb+ by 33±10% (P < 0.01) above control levels. This stimulatory effect was abolished if tissues were first exposed to propranolol. Tyramine (0.1 μM), a stimulator of endogenous catecholamine release, increased active transport of Rb+ 26±12% (P < 0.05) above control values. Rb+ active transport was not significantly changed when left atrial tissues were incubated with α-adrenergic agonists or antagonists. Ouabain stimulation of Rb+ active transport was prevented by in vivo depletion of myocardial endogenous catecholamines by either reserpine or 6-hydroxydopamine. These findings indicated that in myocardial tissue...

Flux Ratio and Driving Forces in a Model of Active Transport

Blumenthal, R.; Kedem, O.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /03/1969 EN
Relevância na Pesquisa
46.08%
In order to analyze the energetics of active transport, a hypothetical carrier model is considered in which the active transport process is reduced to a minimal number of elementary steps. The relation between the following three quantities is examined: The affinity of the reaction driving the active transport, the ratio of isotope fluxes between identical solutions (“short-circuit”), and the maximal chemical potential difference which the active transport system can maintain. The interdependence of isotopeinteraction and the degree of coupling between transport and chemical reaction is shown explicitly: when the transport and chemical reaction are completely coupled, there is marked isotope interaction. In general, the logarithm of the short-circuit flux ratio (multiplied by RT) and the maximal chemical potential are not equal. The two quantities are approximately equal, when coupling between metabolism and transport is very loose, or when the reaction step is much faster than the transfer of the adsorbed solute across the barrier. Without prior knowledge of the kinetic parameters of the carrier, the maximal potential and the dependence of the metabolic reaction on solute flow have to be measured in order to derive the affinity of the driving reaction. Measurement of the flux ratio in the same system will then yield independent information on the carrier mechanism.

Demonstration of a pump-mediated efflux in the epithelial potassium active transport system of insect midgut.

Blankemeyer, J T
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /08/1978 EN
Relevância na Pesquisa
46.07%
The larval midgut epithelium of lepidopteran insects (e.g., Hyalophora cecropia and Manduca sexta) actively transports potassium from hemolymph to lumen when mounted in a chamber. The potassium active transport is rheogenic and does not require the presence of other alkali ions. The transepithelial potential difference, short-circuit current, and electromotive force of active transport are rapidly diminished by anoxia. The efflux of potassium, opposite in direction to potassium active transport, dramatically increased in anoxia, whereas the effluxes of sodium, cesium, and chloride did not increase in anoxia. The increase in efflux was found to have an alkali selectivity similar to that of potassium active transport. It is concluded that the rise of efflux in anoxia is due to the change characteristics of the epithelial potassium active transport mechanism in anoxia.

Active Transport of D-Xylose in the Isolated Small Intestine of the Bullfrog

Lassen, Ulrik V.; Csáky, T. Z.
Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 01/05/1966 EN
Relevância na Pesquisa
46.09%
Fluxes of D-xylose-1-C14 (xylose) across the wall of the isolated intestine of the bullfrog were studied. When sodium was the principal cation in the mucosal bathing fluid, the transport rate of xylose from the mucosa to the serosa was about 5 times greater than the transport rate from the serosa to the mucosa, indicating an active intestinal transport for this sugar. With potassium as the principal cation on the mucosal side, the transport rate of xylose from the mucosal to the serosal compartment is reduced about 5 to 6 times without appreciable change in the serosal to mucosal transport. The asymmetry was also considerably reduced when ouabain was added to the mucosal and serosal compartments. The data confirm the in vitro and in vivo observations indicating active transport of xylose and are also in accord with the earlier findings that active transport of sugars in the intestine is dependent upon the presence of sodium ions in the mucosal compartment and is inhibited by cardioactive steroids. Since the chemical constitution of xylose does not meet the requirements which were hitherto considered necessary for active transport of sugars in the intestine, this structural requirement has to be revised.

Phenomenological Description of Active Transport of Salt and Water

Hoshiko, T.; Lindley, Barry D.
Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 01/01/1967 EN
Relevância na Pesquisa
46.13%
The phenomenological definition of active transport by Kedem and the methods of Kedem and Katchalsky have been used to obtain practical equations describing active transport in the single salt and bi-ionic systems. Procedures were devised to evaluate the required set of 10 coefficients for the single salt case and 15 for the bi-ionic. Three of these coefficients are unusual. They express the effects of active transport, i.e. of entrainment between metabolism and the conventional transport flows: active salt transport coefficient, a volume pump coefficient, and an electrogenicity coefficient. In the bi-ionic case a new passive coefficient, λ, was used to express the linkage between the fluxes of the two salts. However, if primary active transport involves only one ion, for example in the bi-ionic case, 12 coefficients suffice and certain relations can be predicted between the practical coefficients. Particular types of primary active transport could be identified by this means. The relation of active transport to membrane electrogenesis was also examined and the flux ratio equation was rederived in terms of the practical coefficients. Applications to specific parallel and series membrane systems have been analyzed.

The Effect of Osmotic Shock on Release of Bacterial Proteins and on Active Transport

Heppel, Leon A.
Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 01/07/1969 EN
Relevância na Pesquisa
56.03%
Osmotic shock is a procedure in which Gram-negative bacteria are treated as follows. First they are suspended in 0.5 M sucrose containing ethylenediaminetetraacetate. After removal of the sucrose by centrifugation, the pellet of cells is rapidly dispersed in cold, very dilute, MgCl2. This causes the selective release of a group of hydrolytic enzymes. In addition, there is selective release of certain binding proteins. So far, binding proteins for D-galactose, L-leucine, and inorganic sulfate have been discovered and purified. The binding proteins form a reversible complex with the substrate but catalyze no chemical change, and no enzymatic activities have been detected. Various lines of evidence suggest that the binding proteins may play a role in active transport: (a) osmotic shock causes a large drop in transport activity associated with the release of binding protein; (b) transport-negative mutants have been found which lack the corresponding binding protein; (c) the affinity constants for binding and transport are similar; and (d) repression of active transport of leucine was accompanied by loss of binding protein. The binding proteins and hydrolytic enzymes released by shock appear to be located in the cell envelope. Glucose 6-phosphate acts as an inducer for its own transport system when supplied exogenously...

Design of Active Transport Must Be Highly Intricate: A Possible Role of Myosin and Ena/VASP for G-Actin Transport in Filopodia

Zhuravlev, Pavel I.; Der, Bryan S.; Papoian, Garegin A.
Fonte: The Biophysical Society Publicador: The Biophysical Society
Tipo: Artigo de Revista Científica
Publicado em 21/04/2010 EN
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46.07%
Recent modeling of filopodia—the actin-based cell organelles employed for sensing and motility—reveals that one of the key limiting factors of filopodial length is diffusional transport of G-actin monomers to the polymerizing barbed ends. We have explored the possibility of active transport of G-actin by myosin motors, which would be an expected biological response to overcome the limitation of a diffusion-based process. We found that in a straightforward implementation of active transport the increase in length was unimpressive, ≤30%, due to sequestering of G-actin by freely diffusing motors. However, artificially removing motor sequestration reactions led to approximately threefold increases in filopodial length, with the transport being mainly limited by the motors failing to detach from the filaments near the tip, clogging the cooperative conveyer belt dynamics. Making motors sterically transparent led to a qualitative change of the dynamics to a different regime of steady growth without a stationary length. Having identified sequestration and clogging as ubiquitous constraints to motor-driven transport, we devised and tested a speculative means to sidestep these limitations in filopodia by employing cross-linking and putative scaffolding roles of Ena/VASP proteins. We conclude that a naïve design of molecular-motor-based active transport would almost always be inefficient—an intricately organized kinetic scheme...

What Moves Them? Active Transport among Inhabitants of Dutch Deprived Districts

Saris, Carla; Kremers, Stef; Van Assema, Patricia; Hoefnagels, Cees; Droomers, Mariël; De Vries, Nanne
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.12%
Background. Active modes of transport like walking and cycling have been shown to be valuable contributions to daily physical activity. The current study investigates associations between personal and neighbourhood environmental characteristics and active transport among inhabitants of Dutch deprived districts. Method. Questionnaires about health, neighbourhoods, and physical activity behaviour were completed by 742 adults. Data was analysed by means of multivariate linear regression analyses. Results. Being younger, female, and migrant and having a normal weight were associated with more walking for active transport. Being younger, male, and native Dutch and having a normal weight were associated with more cycling for active transport. Neighbourhood characteristics were generally not correlated with active transport. Stratified analyses, based on significant person-environment interactions, showed that migrants and women walked more when cars did not exceed maximum speed in nearby streets and that younger people walked more when speed of traffic in nearby streets was perceived as low. Among migrants, more cycling was associated with the perceived attractiveness of the neighbourhood surroundings. Discussion and Conclusion. Results indicated that among inhabitants of Dutch deprived districts...

Active transport of vesicles in neurons is modulated by mechanical tension

Ahmed, Wylie W.; Saif, Taher A.
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 27/03/2014 EN
Relevância na Pesquisa
46.11%
Effective intracellular transport of proteins and organelles is critical in cells, and is especially important for ensuring proper neuron functionality. In neurons, most proteins are synthesized in the cell body and must be transported through thin structures over long distances where normal diffusion is insufficient. Neurons transport subcellular cargo along axons and neurites through a stochastic interplay of active and passive transport. Mechanical tension is critical in maintaining proper function in neurons, but its role in transport is not well understood. To this end, we investigate the active and passive transport of vesicles in Aplysia neurons while changing neurite tension via applied strain, and quantify the resulting dynamics. We found that tension in neurons modulates active transport of vesicles by increasing the probability of active motion, effective diffusivity, and induces a retrograde bias. We show that mechanical tension modulates active transport processes in neurons and that external forces can couple to internal (subcellular) forces and change the overall transport dynamics.

A co-benefit analysis of alternative transportation in Adelaide, Australia: integrating perspectives from communities and stakeholders for sustainable change.

Xia, Ting
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2015
Relevância na Pesquisa
46.09%
Background The increasing number of motor vehicles in urban areas has a significant impact on the environment, as well as, on human health. Motor vehicle emissions contribute a considerable amount of energy-related greenhouse gases and cause non-negligible air pollution. In addition, over-dependence on cars has also encouraged a sedentary lifestyle and an obesity epidemic, which may lead to increased burden of diseases. These health and environmental costs of motor vehicle usage can be reduced by encouraging individuals to change their travel behaviours in order to increase their use of alternative transport. Such a strategy provides an opportunity for collaboration between people working in the transportation, environment and public health areas. However, limited studies currently exist to provide sufficient evidence for policy and interventions relating to this issue. Aims The aims of the research presented in this thesis are to improve our understanding of the co-benefit effects of alternative transport and to investigate perspectives from communities and stakeholders on sustainable travel behaviour change in Adelaide, South Australia. Methods A mixed-method study design was employed, with three interrelated studies conducted: two quantitative and one qualitative. The first study was focussed on a scenario-based modelling analysis. Separate models...

Transporte ativo: implementação e avaliação de um programa de intervenção sobre os hábitos de deslocação em bicicleta para a escola; Active transport: implementation and evaluation of an intervention program in the habits of bicycle commute to school

Lopes, Ricardo Abreu
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Trabalho de Conclusão de Curso
Publicado em //2014 POR
Relevância na Pesquisa
66.1%
Relatório de atividade profissional de mestrado em Ensino de Educação Física nos Ensinos Básico e Secundário; O presente relatório constitui uma reflexão crítica da atividade profissional e dedicou grande atenção à qualidade da ação docente. O tema da mobilidade sustentável e o potencial da bicicleta, enquanto modo ativo de deslocação regular, tem vindo a ganhar um crescente interesse. Este facto proporcionou uma oportunidade de investigação no âmbito do transporte ativo de bicicleta nos hábitos de mobilidade dos alunos para realizar o percurso de casa para a escola. Numa primeira fase o objetivo deste estudo foi descrever as opções de mobilidade dos alunos de uma escola pública do ensino secundário nas suas deslocações quotidianas para a escola e perceber a recetividade ao transporte ativo para cumprir este trajeto. Tratou-se de um estudo descritivo e a amostra foi constituída por 145 alunos do 10º ao 12º ano do ensino secundário de uma escola pública, com idades compreendidas entre os 15 e os 20 anos (média=16,4 anos; DP=1,16), sendo 79 do sexo masculino e 66 do sexo feminino. O instrumento utilizado foi adaptado de Pereira et al (2012) e aplicado no sentido de conhecer os modos de deslocação dos alunos para a escola...

L'association entre l'utilisation du transport actif et l'état de santé auto-rapporté chez des adultes montréalais

Boily, Geneviève
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
FR
Relevância na Pesquisa
56.07%
Introduction : Une majorité de Canadiens adopte un mode de vie sédentaire qui est un facteur de risque important pour différents problèmes de santé. Dernièrement, des interventions en santé publique ciblent le transport actif pour augmenter la pratique d’activité physique. Objectif : L’objectif de cette étude est de quantifier la direction et la taille de l’association entre l’état de santé rapporté par des adultes montréalais et leur utilisation de la marche et du vélo utilitaires. Méthode : L’échantillon comprend 4503 résidents de l’Île de Montréal, âgés de 18 ans et plus, ayant répondu à un sondage téléphonique sur la pratique de l’activité physique et du transport actif. Des analyses de régression logistique multiples ont été appliquées pour examiner l’association entre l’état de santé auto-rapporté et la pratique du vélo (N=4386) et entre l’état de santé auto-rapporté et la pratique de la marche utilitaire (N=4350). Résultats : Les gens ayant une santé perçue comme bonne et moyenne/mauvaise ont une probabilité plus faible de pratiquer la marche utilitaire (OR = 0,740; p < 0,05 et OR = 0,552; p < 0,01) que ceux rapportant une excellente santé, alors que cette association n’est pas significative pour la pratique du vélo utilitaire dans notre étude. Conclusion : Bien que les résultats obtenus ne soient pas tous statistiquement significatifs...

Transporte ativo para a escola e a sua relação com o IMC: um estudo em adolescentes de uma escola secundária de Guimarães: relatório de estágio; Active transportation to school and its relationship with BMI: a study of adolescents in a secondary school Guimarães: practicum report

Sousa, Hélder Cirilo Ribeiro de
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Trabalho de Conclusão de Curso
Publicado em //2014 POR
Relevância na Pesquisa
55.92%
Relatório de estágio de mestrado em Ensino de Educação Física nos Ensinos Básico e Secundário; O presente relatório está enquadrado no 2º ciclo de estudos para a obtenção do grau de mestre em Ensino de Educação Física nos Ensinos Básicos e Secundário, da Universidade do Minho, referente ao ano letivo de 2013/2014. Este relatório é um documento individual que visa descrever e refletir sobre a minha participação enquanto Professor de Educação Física e apresentar as soluções encontradas para os problemas que surgiram e demonstrar a minha evolução enquanto docente. Desta forma começo por fazer um enquadramento pessoal, exibindo as minhas expetativas, e um enquadramento institucional referindo o contexto onde este estágio foi realizado. No que concerne à Realização da Prática Profissional, são caracterizadas, ao longo do relatório três grandes áreas que comtemplam todo este processo, previstas no Documento Orientador de Estágio Profissional. Comecei por abordar a organização e gestão do ensino e da aprendizagem onde foram abordadas as conceções de estágio, passando pelos planeamentos, pela parte da realização e por último a avaliação do processo de ensino. De seguida é referida a participação na escola e relação com a comunidade demonstrando que a participação em eventos para toda a comunidade educativa dinamizam a escola e são fonte de aprendizagem. Relativamente à formação e investigação educacional em Educação Física elaborei um estudo sobre o transporte ativo nas rotinas de vida dos jovens e se este está relacionado com o Índice de Massa Corporal (IMC). A amostra é composta por 151 alunos do 11º e 12º anos de escolaridade. Verificou-se que a maior parte da amostra utiliza deslocamento passivo para a escola (77...

Political activity for physical activity: health advocacy for active transport

Richards, Rosalina; Murdoch, Linda; Reeder, Anthony I; Amun, Qa-t-a
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
Publicado em 29/05/2011 EN
Relevância na Pesquisa
46.12%
Effective health advocacy is a priority for efforts to increase population participation in physical activity. Local councils are an important audience for this advocacy. The aim of the current study was to describe features of advocacy for active transport via submissions to city council annual plans in New Zealand, and the impact of an information sheet to encourage the health sector to be involved in this process. Written submissions to city council's annual consultation process were requested for 16 city councils over the period of three years (2007/08, 2008/09, and 2009/10). Submissions were reviewed and categories of responses were created. An advocacy information sheet encouraging health sector participation and summarising some of the evidence-base related to physical activity, active transport and health was released just prior to the 2009/10 submission time. Over the period of the study, city councils received 47,392 submissions, 17% of which were related to active transport. Most submissions came from city residents, with a small proportion (2%) from the health sector. The largest category of submissions was in support of pedestrian and cycling infrastructure, design and maintenance of facilities and additional features to support use of these transport modes. Health arguments featured prominently in justifications for active transport initiatives...

Biochemical Studies on Active Transport

Pardee, Arthur B.
Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 01/07/1968 EN
Relevância na Pesquisa
56.02%
The active transport process, so important in cell function, has been studied in the past with intact cells. Models which have arisen from this work all depend on: first, a specific protein to recognize the substrate; second, translocation of the substrate across the cell membrane; third, release of substrate within the cell and restoration of the system to its initial state. These steps are adequate for facilitated transport, but in active transport an energy input is required to maintain a concentration gradient. Parts of transport systems have been isolated recently. A protein which specifically recognizes β-galactosides has been partially purified. In another case, a protein that appears to be the recognition part of the sulfate transport system of Salmonella typhimurium has been crystallized, and many of its properties have been described. The role of this protein in recognition and in translocation is discussed. Also proteins that phosphorylate a variety of sugars as they enter the cell's interior provide a mechanism for concentrating sugars as their phosphates, against a gradient.

Sites of dipeptide hydrolysis in relation to sites of histidine and glucose active transport in hamster intestine.

Wiseman, G
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /09/1983 EN
Relevância na Pesquisa
46.13%
The effects of dipeptides and amino acids on the active transport of L-histidine and D-glucose by sacs of everted small intestine of the hamster have been used to determine the sites of final hydrolysis of the dipeptides in relation to the sites of active transport of L-histidine and D-glucose. The results, plus earlier observations (Wiseman, 1977), show that (a) dipeptide active transport occurs at a superficial site, followed by progressively deeper sites for (b) final hydrolysis of glycyl-phenylalanine and phenylalanyl-glycine, then deeper (c) L-histidine active transport, then (d) final hydrolysis of alanyl-alanine, alanyl-leucine, glycyl-alanine, glycyl-proline, leucyl-alanine and leucyl-leucine, then (e) D-glucose active transport, then (f) final hydrolysis of alanyl-glycine, alanyl-valine, glycyl-glycine, prolyl-glycine, valyl-alanine and valyl-valine. The site of D-glucose active transport (2e) and all the sites superficial to it (2a-d) lie in the intestinal epithelial cell's brush-border. The location within the cell of site(s) 2f is not known; it may lie in the cytosol. All the dipeptides appeared to inhibit L-histidine active transport by the release of free amino acid and not by action of intact dipeptide, supporting the view that dipeptides and free amino acids do not share a common transport pathway in the epithelium of the small intestine.