The Experts below are selected from a list of 15423 Experts worldwide ranked by ideXlab platform
Johannes Von Lintig - One of the best experts on this subject based on the ideXlab platform.
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provitamin a conversion to retinal via the Beta Beta Carotene 15 15 oxygenase bcox is essential for pattern formation and differentiation during zebrafish embryogenesis
Development, 2003Co-Authors: Johanna M Lampert, Susanne Hessel, Jochen Holzschuh, Wolfgang Driever, Klaus Vogt, Johannes Von LintigAbstract:The egg yolk of vertebrates contains carotenoids, which account for its characteristic yellow color in some species. Such plant-derived compounds, e.g. Beta-Carotene, serve as the natural precursors (provitamins) of vitamin A, which is indispensable for chordate development. As egg yolk also contains stored vitamin A, carotenoids have so far been solely discussed as pigments for the coloration of the offspring. Based on our recent molecular identification of the enzyme catalyzing provitamin A conversion to vitamin A, we address a possible role of provitamin A during zebrafish (Danio rerio) development. We cloned the zebrafish gene encoding the vitamin A-forming enzyme, a Beta,Beta-Carotene-15,15'-oxygenase. Analysis of its mRNA expression revealed that it is under complex spatial and temporal control during development. Targeted gene knockdown using the morpholino antisense oligonucleotide technique indicated a vital role of the provitamin A-converting enzyme. Morpholino-injected embryos developed a morphological phenotype that included severe malformation of the eyes, the craniofacial skeleton and pectoral fins, as well as reduced pigmentation. Analyses of gene expression changes in the morphants revealed that distinct retinoic acid-dependent developmental processes are impaired, such as patterning of the hindbrain and differentiation of hindbrain neurons, differentiation of neural crest derivatives (including the craniofacial skeleton), and the establishment of the ventral retina. Our data provide strong evidence that, for several developmental processes, retinoic acid generation depends on local de novo formation of retinal from provitamin A via the Carotene oxygenase, revealing an unexpected, essential role for carotenoids in embryonic development.
Ana Lucia Dos - One of the best experts on this subject based on the ideXlab platform.
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The effect of alpha-tocopherol on the oxidative cleavage of Beta-Carotene.
Free radical biology & medicine, 2000Co-Authors: Kyung-jin Yeum, Robert M. Russell, Anjos Ferreiradonald Smith, Norman I. Krinsky, Ana Lucia DosAbstract:Two cleavage pathways of Beta-Carotene have been proposed, one by central cleavage and the other by random (excentric) cleavage. The central cleavage pathway involves the metabolism of Beta-Carotene at the central double bond (15, 15') to produce retinal by Beta-Carotene 15, 15'-dioxygenase (E.C.888990988). The random cleavage of Beta-Carotene produces Beta-apo-carotenoids, but the mechanism is not clear. To understand the various mechanisms of Beta-Carotene cleavage, Beta-Carotene was incubated with the intestinal postmitochondrial fractions of 10-week-old male rats for 1 h, and cleavage products of Beta-Carotene were analyzed using reverse-phase, high-performance liquid chromatography (HPLC). We also studied the effects of alpha-tocopherol and NAD(+)/NADH on Beta-Carotene cleavage. In addition to Beta-Carotene, we used retinal and Beta-apo-14'-carotenoic acid as substrates in these incubations. Beta-apo-14'-carotenoic acid is the two-carbon longer homologue of retinoic acid. In the presence of alpha-tocopherol, Beta-Carotene was converted exclusively to retinal, whereas in the absence of alpha-tocopherol, both retinal and Beta-apo-carotenoids were formed. Retinoic acid was produced from both retinal and Beta-apo-14'-carotenoic acid incubations only in the presence of NAD(+). Our data suggest that in the presence of an antioxidant such as alpha-tocopherol, Beta-Carotene is converted exclusively to retinal by central cleavage. In the absence of an antioxidant, Beta-Carotene is cleaved randomly by enzyme-related radicals to produce Beta-apo-carotenoids, and these Beta-apo-carotenoids can be oxidized further to retinoic acid via retinal.
Johanna M Lampert - One of the best experts on this subject based on the ideXlab platform.
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provitamin a conversion to retinal via the Beta Beta Carotene 15 15 oxygenase bcox is essential for pattern formation and differentiation during zebrafish embryogenesis
Development, 2003Co-Authors: Johanna M Lampert, Susanne Hessel, Jochen Holzschuh, Wolfgang Driever, Klaus Vogt, Johannes Von LintigAbstract:The egg yolk of vertebrates contains carotenoids, which account for its characteristic yellow color in some species. Such plant-derived compounds, e.g. Beta-Carotene, serve as the natural precursors (provitamins) of vitamin A, which is indispensable for chordate development. As egg yolk also contains stored vitamin A, carotenoids have so far been solely discussed as pigments for the coloration of the offspring. Based on our recent molecular identification of the enzyme catalyzing provitamin A conversion to vitamin A, we address a possible role of provitamin A during zebrafish (Danio rerio) development. We cloned the zebrafish gene encoding the vitamin A-forming enzyme, a Beta,Beta-Carotene-15,15'-oxygenase. Analysis of its mRNA expression revealed that it is under complex spatial and temporal control during development. Targeted gene knockdown using the morpholino antisense oligonucleotide technique indicated a vital role of the provitamin A-converting enzyme. Morpholino-injected embryos developed a morphological phenotype that included severe malformation of the eyes, the craniofacial skeleton and pectoral fins, as well as reduced pigmentation. Analyses of gene expression changes in the morphants revealed that distinct retinoic acid-dependent developmental processes are impaired, such as patterning of the hindbrain and differentiation of hindbrain neurons, differentiation of neural crest derivatives (including the craniofacial skeleton), and the establishment of the ventral retina. Our data provide strong evidence that, for several developmental processes, retinoic acid generation depends on local de novo formation of retinal from provitamin A via the Carotene oxygenase, revealing an unexpected, essential role for carotenoids in embryonic development.
Kyung-jin Yeum - One of the best experts on this subject based on the ideXlab platform.
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The effect of alpha-tocopherol on the oxidative cleavage of Beta-Carotene.
Free radical biology & medicine, 2000Co-Authors: Kyung-jin Yeum, Robert M. Russell, Anjos Ferreiradonald Smith, Norman I. Krinsky, Ana Lucia DosAbstract:Two cleavage pathways of Beta-Carotene have been proposed, one by central cleavage and the other by random (excentric) cleavage. The central cleavage pathway involves the metabolism of Beta-Carotene at the central double bond (15, 15') to produce retinal by Beta-Carotene 15, 15'-dioxygenase (E.C.888990988). The random cleavage of Beta-Carotene produces Beta-apo-carotenoids, but the mechanism is not clear. To understand the various mechanisms of Beta-Carotene cleavage, Beta-Carotene was incubated with the intestinal postmitochondrial fractions of 10-week-old male rats for 1 h, and cleavage products of Beta-Carotene were analyzed using reverse-phase, high-performance liquid chromatography (HPLC). We also studied the effects of alpha-tocopherol and NAD(+)/NADH on Beta-Carotene cleavage. In addition to Beta-Carotene, we used retinal and Beta-apo-14'-carotenoic acid as substrates in these incubations. Beta-apo-14'-carotenoic acid is the two-carbon longer homologue of retinoic acid. In the presence of alpha-tocopherol, Beta-Carotene was converted exclusively to retinal, whereas in the absence of alpha-tocopherol, both retinal and Beta-apo-carotenoids were formed. Retinoic acid was produced from both retinal and Beta-apo-14'-carotenoic acid incubations only in the presence of NAD(+). Our data suggest that in the presence of an antioxidant such as alpha-tocopherol, Beta-Carotene is converted exclusively to retinal by central cleavage. In the absence of an antioxidant, Beta-Carotene is cleaved randomly by enzyme-related radicals to produce Beta-apo-carotenoids, and these Beta-apo-carotenoids can be oxidized further to retinoic acid via retinal.
Susanne Hessel - One of the best experts on this subject based on the ideXlab platform.
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provitamin a conversion to retinal via the Beta Beta Carotene 15 15 oxygenase bcox is essential for pattern formation and differentiation during zebrafish embryogenesis
Development, 2003Co-Authors: Johanna M Lampert, Susanne Hessel, Jochen Holzschuh, Wolfgang Driever, Klaus Vogt, Johannes Von LintigAbstract:The egg yolk of vertebrates contains carotenoids, which account for its characteristic yellow color in some species. Such plant-derived compounds, e.g. Beta-Carotene, serve as the natural precursors (provitamins) of vitamin A, which is indispensable for chordate development. As egg yolk also contains stored vitamin A, carotenoids have so far been solely discussed as pigments for the coloration of the offspring. Based on our recent molecular identification of the enzyme catalyzing provitamin A conversion to vitamin A, we address a possible role of provitamin A during zebrafish (Danio rerio) development. We cloned the zebrafish gene encoding the vitamin A-forming enzyme, a Beta,Beta-Carotene-15,15'-oxygenase. Analysis of its mRNA expression revealed that it is under complex spatial and temporal control during development. Targeted gene knockdown using the morpholino antisense oligonucleotide technique indicated a vital role of the provitamin A-converting enzyme. Morpholino-injected embryos developed a morphological phenotype that included severe malformation of the eyes, the craniofacial skeleton and pectoral fins, as well as reduced pigmentation. Analyses of gene expression changes in the morphants revealed that distinct retinoic acid-dependent developmental processes are impaired, such as patterning of the hindbrain and differentiation of hindbrain neurons, differentiation of neural crest derivatives (including the craniofacial skeleton), and the establishment of the ventral retina. Our data provide strong evidence that, for several developmental processes, retinoic acid generation depends on local de novo formation of retinal from provitamin A via the Carotene oxygenase, revealing an unexpected, essential role for carotenoids in embryonic development.