Un dosage des somatomédines (IGF) plasmatiques de téléostéens a été mise au point, en utilisant u... more Un dosage des somatomédines (IGF) plasmatiques de téléostéens a été mise au point, en utilisant une protéine du sérum de truite qui lie spécifiquement les IGF humains (Niu and Le Bail 1993). Pour éliminer les risques d'interférence dues aux protéines de liaison (IGF-BP), l'activité IGF des différents échantillons a été extraite à l'aide de SP Sephadex C-25 en condition acide. La contamination en IGF-BP de ces extraits est estimée à 5% par dosage de la liaison et n'est pas détectable en western ligand blot. L'IGF-I humain a été utilisée comme standard et comme traceur. La sensibilité du dosage est de 0.15–0.40 ng/ml (ED90) et l'ED50 varie entre 1 et 3 ng/ml. L'IGF-II humain est reconnue partiellement mais aucune réaction croisée n'est observée avec de l'insuline de différentes espèces ni avec les autres hormones testées. Les courbes d'inhibition obtenues avec les sera de mammifères et de téléostéens sont parallèles à la courbe standard. Ces résultats montrent que le dosage par protéine de liaison est capable de quantifier une activité de type IGF dans le sérum des téléostéen, et que le site de liaison des IGF est resté bien conservé au cours de l'évolution des vertébrés. En utilisant ce dosage, nous avons mesuré l'activité IGF et les niveaux d'hormone de croissance (GH) dans des plasmas de jeunes truites arc-en-ciel abattues toutes les heures et demie durant 24h. Les profils nycthémér-aux des deux hormones, qui sont de type pulsatile, apparaissent similaires. Une corrélation significative est observée entre les niveaux de GH et les activités IGF circulant une heure et demie plus tard. Des observations analogues ont été faites chez des truites adultes cathétérisées. Cependant, les niveaux plasmatiques de GH sont très différents d'un animal à l'autre, alors que les variations de l'activité IGF sont moins prononcées. Dans une troisième expérience, des truites ont été réparties en trois groupes: un groupe contrôle, un groupe traité avec de la GH bovine et un groupe soumis à un jeûne prolongé. Chez les animaux à jeun, les niveaux de GH augmentent alors que les activités IGF diminuent. Chez les animaux injectés avec de la GH, les activités IGF sont significativement plus élevées que chez les animaux témoins. Ces résultats suggèrent que, comme chez les mammifères, la sécrétion des IGF plasmatiques est contrôlée par les niveaux circulants de GH et que les variations de la réceptivité tissulaire à la GH dépendent de l'état nutritionnel des animaux. Using rainbow trout plasma protein (IGF-BP) which specifically binds human insulin-like growth factor (IGF) (Niu and Le Bail 1993), we have developed an assay to measure plasma IGF-like levels in different teleost species. Before the assay and to prevent interference by IGF-BP, IGF-like was extracted from all samples, using SP Sephadex C-25 in acidic conditions. After this treatment, contamination of the IGF fraction by IGF-BP which was estimated by binding assay, was approximately 5%, and was not detectable by western ligand blot. Human IGF-I was used as standard and labelled hormone. Sensitivity of the assay was 0.15–0.40 ng/ml (ED90) and ED50 was 1–3 ng/ml. hIGF-II crossreaction was partial and no significant displacement was observed with Insulin from different species or with other hormones. Inhibition curves were obtained with plasma IGF fractions (but not with tissue extracts) from teleost and mammals and are parallel to the standard curve. These results suggest that the protein binding assay can quantify an IGF-like factor in the plasma of teleost and that the binding sites of IGF are well conserved during vertebrate evolution. Using this IGF binding assay, IGF-like was measured in parallel with growth hormone (GH) in plasma from young rainbow trout killed every 1.5h throughout one day. The daily profiles for both hormones, which appear pulsatile, are similar. A significant correlation was observed between GH levels and IGF-like levels with a 1.5h delay. Analogous observations were obtained in individual catheterized adult rainbow trout. Although plasma GH levels differ greatly between fish, less variability is found with IGF-like. In a third experiment, rainbow trout were starved or submitted to bovine GH treatment for four weeks. Starved fish, in which plasma GH levels increased, had plasma IGF-like level significantly lower than in fed fish. In bGH injected fish, plasma IGF-like level was significantly higher than in non-injected fish. These results suggest that, as in mammals, IGF-like secretion depends on plasma GH level and could be modulated by the nutritional status of fish.
The prevalent model for the generation of axial polarity in mouse embryos proposes that a radial ... more The prevalent model for the generation of axial polarity in mouse embryos proposes that a radial to a linear transition in the expression of primitive streak markers precedes the formation of the primitive streak on one side of the epiblast. This model contrasts with the models of mesoderm formation in other vertebrates as it suggests that the primitive streak is initially established in a radial pattern rather than a localized region of the epiblast. Here, we examine the proposed correlation between the expression of Brachyury and Wnt3, two genes reported as expressed radially in the proximal epiblast, with the movements of proximal anterior epiblast cells at stages leading to the formation of the primitive streak. Our results reveal that neither Brachyury nor Wnt3 forms a ring of expression in the proximal epiblast as previously thought. In embryos dissected between 5.5 and 6.5 dpc, Brachyury is first expressed in the distal extra-embryonic ectoderm and subsequently on one side of the epiblast. Wnt3 expression is evident first in the posterior visceral endoderm of 5.5 dpc embryos and later in the posterior epiblast. Lineage analysis shows that the movements of the proximal epiblast do not restrict Brachyury expression to the posterior epiblast. Our data suggest a model whereby the localized expression of these genes in the posterior epiblast, and hence the formation of the primitive streak, is the result of local cell -cell interactions in the future posterior portion of the egg cylinder rather than regionalization of a radial pattern of expression in proximal epiblast cells.
Several lines of evidence suggest that the extraembryonic endoderm of vertebrate embryos plays an... more Several lines of evidence suggest that the extraembryonic endoderm of vertebrate embryos plays an important role in the development of rostral neural structures. In mice, neural inductive signals are thought to reside in an area of visceral endoderm that expresses the Hex gene. Here, we have conducted a morphological and lineage analysis of visceral endoderm cells spanning pre-and postprimitive streak stages. Our results show that Hex-expressing cells have a tall, columnar epithelial morphology, which distinguishes them from other visceral endoderm cells. This region of visceral endoderm thickening (VET) is found overlying first the distal and then one side of the epiblast at stages between 5.5 and 5.75 days post coitum (d.p.c.). In addition, we show that the epiblast has an anteroposterior-compressed appearance that is aligned with the position of the VET. Intracellular labeling of VET/Hex-expressing cells reveals an anterior and anterolateral shift from their distal epiblast position. VET/Hex-expressing cells are first localized to the anterior side of the epiblast by 5.75 d.p.c. and form a crescent on the anterior half of the embryo at the onset of gastrulation. Subsequently, VET descendants are distributed along the embryonic/extraembryonic boundary by headfold stages at 7.5 d.p.c. The morphological characteristics and position of VET/Hex-expressing cells distinguishes the future anteroposterior axis of the embryo and provide landmarks to stage mouse embryos at preprimitive streak stages. Moreover, the morphological characteristics of pregastrulation mouse embryos together with the stereotyped shift in the position of visceral endoderm cells reveal similarities among amniote embryos that suggest an evolutionary conservation of the mechanisms that pattern the rostral neurectoderm at pregastrula stages.
The prevalent model for the generation of axial polarity in mouse embryos proposes that a radial ... more The prevalent model for the generation of axial polarity in mouse embryos proposes that a radial to a linear transition in the expression of primitive streak markers precedes the formation of the primitive streak on one side of the epiblast. This model contrasts with the models of mesoderm formation in other vertebrates as it suggests that the primitive streak is initially established in a radial pattern rather than a localized region of the epiblast. Here, we examine the proposed correlation between the expression of Brachyury and Wnt3, two genes reported as expressed radially in the proximal epiblast, with the movements of proximal anterior epiblast cells at stages leading to the formation of the primitive streak. Our results reveal that neither Brachyury nor Wnt3 forms a ring of expression in the proximal epiblast as previously thought. In embryos dissected between 5.5 and 6.5 dpc, Brachyury is first expressed in the distal extra-embryonic ectoderm and subsequently on one side of the epiblast. Wnt3 expression is evident first in the posterior visceral endoderm of 5.5 dpc embryos and later in the posterior epiblast. Lineage analysis shows that the movements of the proximal epiblast do not restrict Brachyury expression to the posterior epiblast. Our data suggest a model whereby the localized expression of these genes in the posterior epiblast, and hence the formation of the primitive streak, is the result of local cell -cell interactions in the future posterior portion of the egg cylinder rather than regionalization of a radial pattern of expression in proximal epiblast cells.
Several lines of evidence suggest that the extraembryonic endoderm of vertebrate embryos plays an... more Several lines of evidence suggest that the extraembryonic endoderm of vertebrate embryos plays an important role in the development of rostral neural structures. In mice, neural inductive signals are thought to reside in an area of visceral endoderm that expresses the Hex gene. Here, we have conducted a morphological and lineage analysis of visceral endoderm cells spanning pre-and postprimitive streak stages. Our results show that Hex-expressing cells have a tall, columnar epithelial morphology, which distinguishes them from other visceral endoderm cells. This region of visceral endoderm thickening (VET) is found overlying first the distal and then one side of the epiblast at stages between 5.5 and 5.75 days post coitum (d.p.c.). In addition, we show that the epiblast has an anteroposterior-compressed appearance that is aligned with the position of the VET. Intracellular labeling of VET/Hex-expressing cells reveals an anterior and anterolateral shift from their distal epiblast position. VET/Hex-expressing cells are first localized to the anterior side of the epiblast by 5.75 d.p.c. and form a crescent on the anterior half of the embryo at the onset of gastrulation. Subsequently, VET descendants are distributed along the embryonic/extraembryonic boundary by headfold stages at 7.5 d.p.c. The morphological characteristics and position of VET/Hex-expressing cells distinguishes the future anteroposterior axis of the embryo and provide landmarks to stage mouse embryos at preprimitive streak stages. Moreover, the morphological characteristics of pregastrulation mouse embryos together with the stereotyped shift in the position of visceral endoderm cells reveal similarities among amniote embryos that suggest an evolutionary conservation of the mechanisms that pattern the rostral neurectoderm at pregastrula stages.
As the deployment of expert systems has spread into more complex and sophisticated environments, ... more As the deployment of expert systems has spread into more complex and sophisticated environments, so inherent technological limitations have been observed. As a technique for overcoming this complexity barrier, researchers have started to build systems composed of multiple ...
As the deployment of expert systems has spread into more complex and sophisticated environments, ... more As the deployment of expert systems has spread into more complex and sophisticated environments, so inherent technological limitations have been observed. As a technique for overcoming this complexity barrier, researchers have started to build systems composed of multiple ...
CAPITULO I INTRODUCCIÓN 1. ANTECEDENTES En Bolivia hace varios años se ha iniciado la industria d... more CAPITULO I INTRODUCCIÓN 1. ANTECEDENTES En Bolivia hace varios años se ha iniciado la industria del reciclaje, hoy en día las empresas compran plásticos, vidrio, metal, papel, cartón, etc. En desuso para utilizar como materia prima en su producción. De acuerdo al diagnostico de la Gestión de Residuos en Bolivia elaborado por el Viceministerio de Agua Potable y Saneamiento Básico el 2011, se estima que en Bolivia, se generan 4.782 toneladas/día, equivalente a 1´745,280 toneladas/año de residuos solidos. La generación en el área urbana es de 87 porciento que equivale a 4.150 toneladas/día y 1´514.646 toneladas/año, mientras que la generación en el área rural es del 13 por ciento, equivale a 632 toneladas/día y 230.634 toneladas/año.
Un dosage des somatomédines (IGF) plasmatiques de téléostéens a été mise au point, en utilisant u... more Un dosage des somatomédines (IGF) plasmatiques de téléostéens a été mise au point, en utilisant une protéine du sérum de truite qui lie spécifiquement les IGF humains (Niu and Le Bail 1993). Pour éliminer les risques d'interférence dues aux protéines de liaison (IGF-BP), l'activité IGF des différents échantillons a été extraite à l'aide de SP Sephadex C-25 en condition acide. La contamination en IGF-BP de ces extraits est estimée à 5% par dosage de la liaison et n'est pas détectable en western ligand blot. L'IGF-I humain a été utilisée comme standard et comme traceur. La sensibilité du dosage est de 0.15–0.40 ng/ml (ED90) et l'ED50 varie entre 1 et 3 ng/ml. L'IGF-II humain est reconnue partiellement mais aucune réaction croisée n'est observée avec de l'insuline de différentes espèces ni avec les autres hormones testées. Les courbes d'inhibition obtenues avec les sera de mammifères et de téléostéens sont parallèles à la courbe standard. Ces résultats montrent que le dosage par protéine de liaison est capable de quantifier une activité de type IGF dans le sérum des téléostéen, et que le site de liaison des IGF est resté bien conservé au cours de l'évolution des vertébrés. En utilisant ce dosage, nous avons mesuré l'activité IGF et les niveaux d'hormone de croissance (GH) dans des plasmas de jeunes truites arc-en-ciel abattues toutes les heures et demie durant 24h. Les profils nycthémér-aux des deux hormones, qui sont de type pulsatile, apparaissent similaires. Une corrélation significative est observée entre les niveaux de GH et les activités IGF circulant une heure et demie plus tard. Des observations analogues ont été faites chez des truites adultes cathétérisées. Cependant, les niveaux plasmatiques de GH sont très différents d'un animal à l'autre, alors que les variations de l'activité IGF sont moins prononcées. Dans une troisième expérience, des truites ont été réparties en trois groupes: un groupe contrôle, un groupe traité avec de la GH bovine et un groupe soumis à un jeûne prolongé. Chez les animaux à jeun, les niveaux de GH augmentent alors que les activités IGF diminuent. Chez les animaux injectés avec de la GH, les activités IGF sont significativement plus élevées que chez les animaux témoins. Ces résultats suggèrent que, comme chez les mammifères, la sécrétion des IGF plasmatiques est contrôlée par les niveaux circulants de GH et que les variations de la réceptivité tissulaire à la GH dépendent de l'état nutritionnel des animaux. Using rainbow trout plasma protein (IGF-BP) which specifically binds human insulin-like growth factor (IGF) (Niu and Le Bail 1993), we have developed an assay to measure plasma IGF-like levels in different teleost species. Before the assay and to prevent interference by IGF-BP, IGF-like was extracted from all samples, using SP Sephadex C-25 in acidic conditions. After this treatment, contamination of the IGF fraction by IGF-BP which was estimated by binding assay, was approximately 5%, and was not detectable by western ligand blot. Human IGF-I was used as standard and labelled hormone. Sensitivity of the assay was 0.15–0.40 ng/ml (ED90) and ED50 was 1–3 ng/ml. hIGF-II crossreaction was partial and no significant displacement was observed with Insulin from different species or with other hormones. Inhibition curves were obtained with plasma IGF fractions (but not with tissue extracts) from teleost and mammals and are parallel to the standard curve. These results suggest that the protein binding assay can quantify an IGF-like factor in the plasma of teleost and that the binding sites of IGF are well conserved during vertebrate evolution. Using this IGF binding assay, IGF-like was measured in parallel with growth hormone (GH) in plasma from young rainbow trout killed every 1.5h throughout one day. The daily profiles for both hormones, which appear pulsatile, are similar. A significant correlation was observed between GH levels and IGF-like levels with a 1.5h delay. Analogous observations were obtained in individual catheterized adult rainbow trout. Although plasma GH levels differ greatly between fish, less variability is found with IGF-like. In a third experiment, rainbow trout were starved or submitted to bovine GH treatment for four weeks. Starved fish, in which plasma GH levels increased, had plasma IGF-like level significantly lower than in fed fish. In bGH injected fish, plasma IGF-like level was significantly higher than in non-injected fish. These results suggest that, as in mammals, IGF-like secretion depends on plasma GH level and could be modulated by the nutritional status of fish.
The prevalent model for the generation of axial polarity in mouse embryos proposes that a radial ... more The prevalent model for the generation of axial polarity in mouse embryos proposes that a radial to a linear transition in the expression of primitive streak markers precedes the formation of the primitive streak on one side of the epiblast. This model contrasts with the models of mesoderm formation in other vertebrates as it suggests that the primitive streak is initially established in a radial pattern rather than a localized region of the epiblast. Here, we examine the proposed correlation between the expression of Brachyury and Wnt3, two genes reported as expressed radially in the proximal epiblast, with the movements of proximal anterior epiblast cells at stages leading to the formation of the primitive streak. Our results reveal that neither Brachyury nor Wnt3 forms a ring of expression in the proximal epiblast as previously thought. In embryos dissected between 5.5 and 6.5 dpc, Brachyury is first expressed in the distal extra-embryonic ectoderm and subsequently on one side of the epiblast. Wnt3 expression is evident first in the posterior visceral endoderm of 5.5 dpc embryos and later in the posterior epiblast. Lineage analysis shows that the movements of the proximal epiblast do not restrict Brachyury expression to the posterior epiblast. Our data suggest a model whereby the localized expression of these genes in the posterior epiblast, and hence the formation of the primitive streak, is the result of local cell -cell interactions in the future posterior portion of the egg cylinder rather than regionalization of a radial pattern of expression in proximal epiblast cells.
Several lines of evidence suggest that the extraembryonic endoderm of vertebrate embryos plays an... more Several lines of evidence suggest that the extraembryonic endoderm of vertebrate embryos plays an important role in the development of rostral neural structures. In mice, neural inductive signals are thought to reside in an area of visceral endoderm that expresses the Hex gene. Here, we have conducted a morphological and lineage analysis of visceral endoderm cells spanning pre-and postprimitive streak stages. Our results show that Hex-expressing cells have a tall, columnar epithelial morphology, which distinguishes them from other visceral endoderm cells. This region of visceral endoderm thickening (VET) is found overlying first the distal and then one side of the epiblast at stages between 5.5 and 5.75 days post coitum (d.p.c.). In addition, we show that the epiblast has an anteroposterior-compressed appearance that is aligned with the position of the VET. Intracellular labeling of VET/Hex-expressing cells reveals an anterior and anterolateral shift from their distal epiblast position. VET/Hex-expressing cells are first localized to the anterior side of the epiblast by 5.75 d.p.c. and form a crescent on the anterior half of the embryo at the onset of gastrulation. Subsequently, VET descendants are distributed along the embryonic/extraembryonic boundary by headfold stages at 7.5 d.p.c. The morphological characteristics and position of VET/Hex-expressing cells distinguishes the future anteroposterior axis of the embryo and provide landmarks to stage mouse embryos at preprimitive streak stages. Moreover, the morphological characteristics of pregastrulation mouse embryos together with the stereotyped shift in the position of visceral endoderm cells reveal similarities among amniote embryos that suggest an evolutionary conservation of the mechanisms that pattern the rostral neurectoderm at pregastrula stages.
The prevalent model for the generation of axial polarity in mouse embryos proposes that a radial ... more The prevalent model for the generation of axial polarity in mouse embryos proposes that a radial to a linear transition in the expression of primitive streak markers precedes the formation of the primitive streak on one side of the epiblast. This model contrasts with the models of mesoderm formation in other vertebrates as it suggests that the primitive streak is initially established in a radial pattern rather than a localized region of the epiblast. Here, we examine the proposed correlation between the expression of Brachyury and Wnt3, two genes reported as expressed radially in the proximal epiblast, with the movements of proximal anterior epiblast cells at stages leading to the formation of the primitive streak. Our results reveal that neither Brachyury nor Wnt3 forms a ring of expression in the proximal epiblast as previously thought. In embryos dissected between 5.5 and 6.5 dpc, Brachyury is first expressed in the distal extra-embryonic ectoderm and subsequently on one side of the epiblast. Wnt3 expression is evident first in the posterior visceral endoderm of 5.5 dpc embryos and later in the posterior epiblast. Lineage analysis shows that the movements of the proximal epiblast do not restrict Brachyury expression to the posterior epiblast. Our data suggest a model whereby the localized expression of these genes in the posterior epiblast, and hence the formation of the primitive streak, is the result of local cell -cell interactions in the future posterior portion of the egg cylinder rather than regionalization of a radial pattern of expression in proximal epiblast cells.
Several lines of evidence suggest that the extraembryonic endoderm of vertebrate embryos plays an... more Several lines of evidence suggest that the extraembryonic endoderm of vertebrate embryos plays an important role in the development of rostral neural structures. In mice, neural inductive signals are thought to reside in an area of visceral endoderm that expresses the Hex gene. Here, we have conducted a morphological and lineage analysis of visceral endoderm cells spanning pre-and postprimitive streak stages. Our results show that Hex-expressing cells have a tall, columnar epithelial morphology, which distinguishes them from other visceral endoderm cells. This region of visceral endoderm thickening (VET) is found overlying first the distal and then one side of the epiblast at stages between 5.5 and 5.75 days post coitum (d.p.c.). In addition, we show that the epiblast has an anteroposterior-compressed appearance that is aligned with the position of the VET. Intracellular labeling of VET/Hex-expressing cells reveals an anterior and anterolateral shift from their distal epiblast position. VET/Hex-expressing cells are first localized to the anterior side of the epiblast by 5.75 d.p.c. and form a crescent on the anterior half of the embryo at the onset of gastrulation. Subsequently, VET descendants are distributed along the embryonic/extraembryonic boundary by headfold stages at 7.5 d.p.c. The morphological characteristics and position of VET/Hex-expressing cells distinguishes the future anteroposterior axis of the embryo and provide landmarks to stage mouse embryos at preprimitive streak stages. Moreover, the morphological characteristics of pregastrulation mouse embryos together with the stereotyped shift in the position of visceral endoderm cells reveal similarities among amniote embryos that suggest an evolutionary conservation of the mechanisms that pattern the rostral neurectoderm at pregastrula stages.
As the deployment of expert systems has spread into more complex and sophisticated environments, ... more As the deployment of expert systems has spread into more complex and sophisticated environments, so inherent technological limitations have been observed. As a technique for overcoming this complexity barrier, researchers have started to build systems composed of multiple ...
As the deployment of expert systems has spread into more complex and sophisticated environments, ... more As the deployment of expert systems has spread into more complex and sophisticated environments, so inherent technological limitations have been observed. As a technique for overcoming this complexity barrier, researchers have started to build systems composed of multiple ...
CAPITULO I INTRODUCCIÓN 1. ANTECEDENTES En Bolivia hace varios años se ha iniciado la industria d... more CAPITULO I INTRODUCCIÓN 1. ANTECEDENTES En Bolivia hace varios años se ha iniciado la industria del reciclaje, hoy en día las empresas compran plásticos, vidrio, metal, papel, cartón, etc. En desuso para utilizar como materia prima en su producción. De acuerdo al diagnostico de la Gestión de Residuos en Bolivia elaborado por el Viceministerio de Agua Potable y Saneamiento Básico el 2011, se estima que en Bolivia, se generan 4.782 toneladas/día, equivalente a 1´745,280 toneladas/año de residuos solidos. La generación en el área urbana es de 87 porciento que equivale a 4.150 toneladas/día y 1´514.646 toneladas/año, mientras que la generación en el área rural es del 13 por ciento, equivale a 632 toneladas/día y 230.634 toneladas/año.
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