The Experts below are selected from a list of 9 Experts worldwide ranked by ideXlab platform
C A R Boyd - One of the best experts on this subject based on the ideXlab platform.
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characterisation of l tryptophan transporters in human placenta a comparison of Brush Border and basal membrane Vesicles
The Journal of Physiology, 2001Co-Authors: Yoshiki Kudo, C A R BoydAbstract:The mechanisms responsible for L-tryptophan transport at both the maternal- and fetal-facing surfaces of the term placenta have been determined in isolated membrane Vesicles as part of a study on placental indoleamine 2,3-dioxygenase, the L-tryptophan-catabolising enzyme recently shown to regulate feto-maternal immunology. Brush Border Vesicle uptake of L-tryptophan is substantially into an osmotically active space. It is sodium independent and N-ethylmaleimide sensitive. Uptake of L-tryptophan, which is markedly stereospecific, has a Km of 26.3 microM and Vmax of 1.72 pmol (mg protein)(-1) s(-1) and is completely abolished by the L-system-specific substrate 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH). These findings are in keeping with L-tryptophan transport being exclusively via system L (induced by the heterodimeric heavy chain of CD98 and system L-amino acid transporter-1 (LAT-1)). 1-Methyl-tryptophan (which is a known competitive inhibitor of indoleamine 2,3-dioxygenase) is a competitive inhibitor of L-tryptophan flux through this transport system (Ki = 113 microM). Basal membrane transport of L-tryptophan is more complex. Uptake is slower than at the Brush Border and although, as in the Brush Border, uptake is sodium independent, it is less sensitive to N-ethylmaleimide. There is clear evidence that two systems contribute to basal membrane transport since BCH is (in sodium-free media) only a partial inhibitor whereas L-histidine and L-cysteine are fully effective. The simplest explanation of these and other findings is that the basal membrane possesses two systems, one of which is similar to that induced by the heavy chain of CD98 and system L-amino acid transporter-2 (LAT-2). The other appears to be system y+L since in the presence of BCH inhibition by L-leucine but not by L-lysine is sodium dependent. These findings suggest the existence of non-identical carrier-mediated transport systems for L-tryptophan in Brush Border and basal membranes. This asymmetry may explain net transplacental transfer of this amino acid.
Yoshiki Kudo - One of the best experts on this subject based on the ideXlab platform.
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characterisation of l tryptophan transporters in human placenta a comparison of Brush Border and basal membrane Vesicles
The Journal of Physiology, 2001Co-Authors: Yoshiki Kudo, C A R BoydAbstract:The mechanisms responsible for L-tryptophan transport at both the maternal- and fetal-facing surfaces of the term placenta have been determined in isolated membrane Vesicles as part of a study on placental indoleamine 2,3-dioxygenase, the L-tryptophan-catabolising enzyme recently shown to regulate feto-maternal immunology. Brush Border Vesicle uptake of L-tryptophan is substantially into an osmotically active space. It is sodium independent and N-ethylmaleimide sensitive. Uptake of L-tryptophan, which is markedly stereospecific, has a Km of 26.3 microM and Vmax of 1.72 pmol (mg protein)(-1) s(-1) and is completely abolished by the L-system-specific substrate 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH). These findings are in keeping with L-tryptophan transport being exclusively via system L (induced by the heterodimeric heavy chain of CD98 and system L-amino acid transporter-1 (LAT-1)). 1-Methyl-tryptophan (which is a known competitive inhibitor of indoleamine 2,3-dioxygenase) is a competitive inhibitor of L-tryptophan flux through this transport system (Ki = 113 microM). Basal membrane transport of L-tryptophan is more complex. Uptake is slower than at the Brush Border and although, as in the Brush Border, uptake is sodium independent, it is less sensitive to N-ethylmaleimide. There is clear evidence that two systems contribute to basal membrane transport since BCH is (in sodium-free media) only a partial inhibitor whereas L-histidine and L-cysteine are fully effective. The simplest explanation of these and other findings is that the basal membrane possesses two systems, one of which is similar to that induced by the heavy chain of CD98 and system L-amino acid transporter-2 (LAT-2). The other appears to be system y+L since in the presence of BCH inhibition by L-leucine but not by L-lysine is sodium dependent. These findings suggest the existence of non-identical carrier-mediated transport systems for L-tryptophan in Brush Border and basal membranes. This asymmetry may explain net transplacental transfer of this amino acid.
Mcgarrity T - One of the best experts on this subject based on the ideXlab platform.
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The epidermal growth factor receptor (EGF-R) is present on the basolateral, but not the apical, surface of enterocytes in the human gastrointestinal tract.
1996Co-Authors: Playford R J, Hanby A M, Gschmeissner S, Peiffer L P, Wright N A, Mcgarrity TAbstract:BACKGROUND: While it is clear that luminal epidermal growth factor (EGF) stimulates repair of the damaged bowel, its significance in maintaining normal gut growth remains uncertain. If EGF is important in maintaining normal gut growth, the EGF receptor (EGF-R) should be present on the apical (luminal) surface in addition to the basolateral surface. AIMS/SUBJECTS/METHODS: This study examined the distribution of the EGF-R in the epithelium throughout the human gastro-intestinal tract using immunohistochemistry, electron microscopy, and western blotting of Brush Border preparations. RESULTS: Immunostaining of the oesophagus showed circumferential EGF-R positivity in the cells of the basal portions of the stratified squamous epithelium but surface cells were EGF-R negative. In the normal stomach, small intestine, and colon, immunostaining localised the receptor to the basolateral surface with the apical membranes being consistently negative. EGF-R positivity within the small intestine appeared to be almost entirely restricted to the proliferative (crypt) region. Western blotting demonstrated a 170 kDa protein in whole tissue homogenates but not in the Brush Border Vesicle preparations. CONCLUSIONS: As the EGF-R is located only on the basolateral surfaces in the normal adult gastrointestinal tract, the major role of luminal EGF is probably to stimulate repair rather than to maintain normal gut growth
Sebastião, Isis [unesp] - One of the best experts on this subject based on the ideXlab platform.
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Toxicidade e interação de proteínas Cry1 de Bacillus thuringiensis em Helicoverpa armigera (Hübner) (Lepidóptera: Noctuidae)
Universidade Estadual Paulista (UNESP), 2015Co-Authors: Sebastião, Isis [unesp]Abstract:Studies attempting interaction of Bacillus thuringiensis Cry proteins in order to find combinations for developing Bt plants are fundamental in controlling lepidopteran pests. H. armigera causes severe damage to agricultural crops and their introduction in Brazil has led the search for efficient control and B. thuringiensis may be a good control agent. The aim of this research was to evaluate the toxicity of Cry1Aa, Cry1Ab, Cry1Ac and Cry1Ca proteins from B. thuringiensis to H. armigera, as well as interaction of these proteins with the receptors present in insect midgut. Toxicity was estimated from the lethal concentration LC50 of the tested proteins and protein interactions with the receptors were found in a binding analysis between activated and biotinylated protein with the midgut Brush Border Vesicle membrane (BBMV) of H. armigera, and heterologous competitive binding assays. Among the tested proteins, Cry1Ac protein was the most toxic, followed by the Cry1Ab and Cry1Aa proteins. The Cry1Ca protein showed no toxicity. The Cry1Aa, Cry1Ab and Cry1Ac proteins showed specific binding to the midgut membrane receptors of H. armigera caterpillars. Heterologous competitive binding assays revealed that Cry1Aa, Cry1Ab, Cry1Ac compete for a common receptor in the midgut larvaeEstudos que visam a interação das proteínas Cry de Bacillus thuringiensis, a fim de encontrar combinações adequadas para o desenvolvimento de plantas Bt são ferramentais fundamentais no controle de lepidópteros-praga. A lagarta H. armigera causa danos severos nas culturas agrícolas e sua introdução no Brasil levou a busca de formas de controle eficientes e nesse contexto B. thuringiensis pode ser um bom agente de controle. Diante do exposto o presente trabalho objetivou avaliar a toxicidade das proteínas Cry1Aa, Cry1Ab, Cry1Ac e Cry1Ca de B. thuringiensis à H. armigera, assim como interação dessas proteínas aos receptores do mesêntero do inseto. A toxicidade foi estimada com bioensaios de dose resposta com as proteínas testadas e a interação das proteínas com os receptores foram verificadas em análise de união entre a proteína ativada e marcada com a vesícula da borda em escova da membrana apical das células do intestino (Brush Border mambrane Vesicle- BBMV) do mesêntero larval de H. armigera, e ensaios de competição heteróloga. Dentre as proteínas testadas, a Cry1Ac destacou-se como a mais efetiva, seguida das proteínas Cry1Ab e Cry1Aa. A proteína Cry1Ca não apresentou toxicidade. As proteínas Cry1Aa, Cry1Ab e Cry1Ac se ligaram aos receptores da membrana do intestino médio das lagartas de H. armigera de forma especifica. Os ensaios de competição heteróloga revelaram que as proteínas Cry1Aa, Cry1Ac e Cry1Ab competem entre si pelo mesmo recepto
Playford R J - One of the best experts on this subject based on the ideXlab platform.
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The epidermal growth factor receptor (EGF-R) is present on the basolateral, but not the apical, surface of enterocytes in the human gastrointestinal tract.
1996Co-Authors: Playford R J, Hanby A M, Gschmeissner S, Peiffer L P, Wright N A, Mcgarrity TAbstract:BACKGROUND: While it is clear that luminal epidermal growth factor (EGF) stimulates repair of the damaged bowel, its significance in maintaining normal gut growth remains uncertain. If EGF is important in maintaining normal gut growth, the EGF receptor (EGF-R) should be present on the apical (luminal) surface in addition to the basolateral surface. AIMS/SUBJECTS/METHODS: This study examined the distribution of the EGF-R in the epithelium throughout the human gastro-intestinal tract using immunohistochemistry, electron microscopy, and western blotting of Brush Border preparations. RESULTS: Immunostaining of the oesophagus showed circumferential EGF-R positivity in the cells of the basal portions of the stratified squamous epithelium but surface cells were EGF-R negative. In the normal stomach, small intestine, and colon, immunostaining localised the receptor to the basolateral surface with the apical membranes being consistently negative. EGF-R positivity within the small intestine appeared to be almost entirely restricted to the proliferative (crypt) region. Western blotting demonstrated a 170 kDa protein in whole tissue homogenates but not in the Brush Border Vesicle preparations. CONCLUSIONS: As the EGF-R is located only on the basolateral surfaces in the normal adult gastrointestinal tract, the major role of luminal EGF is probably to stimulate repair rather than to maintain normal gut growth
