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  • 1
    Electronic Resource
    Electronic Resource
    Glucose transporter gene expression in rat conceptus during high glucose culture (1993)
    Springer
    Diabetologia 36 (1993), S. 696-706 
    Details
    ISSN: 1432-0428
    Keywords: Glucose transporter ; embryogenesis ; hyperglycaemia ; rat embryo culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We investigated the expression of glucose transporter genes and protein in embryo and yolk sac during organogenesis and the regulation of glucose transporters during culture in hyperglycaemic media. Erythrocyte-type glucose transporter (GLUT 1) and brain-type glucose transporter (GLUT 3) mRNA were expressed in embryo and yolk sac. The expression of GLUT-1 and GLUT-3 mRNA was abundant on day 9–11 and day 9–10 in the embryo, respectively, and day 9–14 and day 10–11 in the yolk sac, respectively. The levels of GLUT-1 protein in the embryo increased in parallel with the expression of GLUT-1 mRNA during the corresponding period. Immunohistochemical staining of GLUT-1 protein was found principally in the neuroepithelial cells surrounding the neural tube in the embryo on day 10 and appeared in the microvessels surrounding the neural tube after day 12. To test whether the expression of glucose transporter genes and protein was suppressed during hyperglycaemia, conceptuses were cultured in high glucose medium. The abundant expression of GLUT-1 protein was not decreased during culture in high glucose media for 24 h (day 9–10) and was only down-regulated by prolonged exposure to this media for 48 h (day 9–11). We have demonstrated the predominant expression of the high affinity glucose transporter (GLUT 1 and GLUT 3) genes and (GLUT 1) protein in embryo during the early period of organogenesis. The persistently abundant expression of glucose transporter during the critical period of neural tube formation (day 9–10) even in the presence of hyperglycaemia may explain one of the mechanisms of increased glucose flux into the neuroepithelium, which may lead to neural tube defects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00401139
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  • 2
    Electronic Resource
    Electronic Resource
    Glucose transporter gene expression in rat conceptus during early organogenesis and exposure to insulin-induced hypoglycemic serum (1993)
    Springer
    Acta diabetologica 30 (1993), S. 73-78 
    Details
    ISSN: 1432-5233
    Keywords: Embryogenesis ; Glucose transporter ; Growth retardation ; Hypoglycemia ; Neural tube defect ; Rat embryo culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We investigated the glucose transporter gene and protein expression during early organogenesis in the rat and in rat embryos cultured with hypoglycemic serum. Erythrocyte-type glucose transporter (GLUT-1) mRNA was expressed at a high level in embryos; peak levels were reached at days 10.5–11.5 and decreased as gestational age increased. In contrast, the insulin regulaable glucose transporter (GLUT-4) mRNA was not detected. The levels of GLUT-1 protein determined by Western blot analysis increased in parallel with expression of the glucose transporter (GLUT-1) gene and peak levels were observed on days 10.5 and 11.5, which correspond to the main periods of neural tube formation. Immunohistochemical staining of the embryo on day 10.5 showed that GLUT-1 protein was abundantly located in the tissue of neural tube. When embryos were cultured from day 9.5 to day 10.5 with insulin-induced hypoglycemic serum containing 2–3 mM glucose an increased frequency of anterior neural tube defects was observed in association with a significant reduction of the glycolytic flux. Increased levels of GLUT-1 mRNA and protein were not observed during the culture with hypoglycemic serum compared with the levels in embryos cultured in normal serum. Addition of insulin to normal serum (500 μU/ml) did not affect the GLUT-1 mRNA and protein levels. GLUT-1 mRNA and protein are strongly expressed in the embryo during early organogenesis, especially in the tissues of the neural tube, and the expression of the glucose transporter did not increase in response to prolonged glycopenia. This may account for the vulnerability of embryogenesis to hypoglycemia during these critical developmental periods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00578217
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  • 3
    Electronic Resource
    Electronic Resource
    Involvement of cytoplasmic pH in the production of ethylene, a potent inducer of sexual development inDictyostelium mucoroides (1991)
    Springer
    Protoplasma 160 (1991), S. 72-76 
    Details
    ISSN: 1615-6102
    Keywords: Dictyostelium mucoroides ; Cellular slime mold ; Cytoplasmic pH ; Ethylene ; Cyclic AMP ; Sexual development ; Macrocyst ; Sorocarp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Dictyostelium mucoroides-7 (Dm 7) and a mutant MF 1 derived from it exhibit two developmental pathways: sorocarp formation occurs during the asexual process, and macrocyst formation during the sexual cycle. The two developmental pathways are mainly regulated by two chemical substances: 3′,5′-cyclic adenosine monophosphate (cAMP) and ethylene. Recently, we have demonstrated that cytoplasmic pH (pHi) has a critical role for the choice of developmental pathways, higher pHi being favourable to macrocyst formation. Thereupon, attention was riveted to the relation of pHi to biosynthesis of cAMP and ethylene. Effect of pHi on the production and release of ethylene, a potent inducer of macrocyst formation, was examined, using the two facing culture method. The result showed that lowered pHi inhibits ethylene production, thus resulting in a failure of cells to form macrocysts. The accumulation of cAMP, an inhibitor of macrocyst formation, was found to vary depending on extracellular pH (pHo), but diethylstilbestrol (DES) that is a proton pump inhibitor and also an inhibitor of macrocyst formation had no significant effect on the accumulation. Taken together these results indicate that higher pHi may induce macrocyst formation through enhancement of ethylene production rather than inhibition of cAMP synthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01539958
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  • 4
    Electronic Resource
    Electronic Resource
    The ethylene action in the development of cellular slime molds: an analogy to higher plants (1992)
    Springer
    Protoplasma 167 (1992), S. 159-168 
    Details
    ISSN: 1615-6102
    Keywords: Dictyostelium mucoroides ; Ethylene ; Sexual development ; Macrocyst ; Sorocarp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The cellular slime moldDictyostelium mucoroides-7 (Dm 7) and its mutant (MF 1) exhibit sexual or asexual development depending upon culture conditions. During the sexual cycle macrocyst formation occurs, whereas sorocarps containing spores and stalk cells are asexually formed. As previously reported, the macrocyst formation is marked by the emergence of true zygotes, and is induced by a potent plant hormone, ethylene. The concentration of ethylene required for macrocyst induction was determined to establish the similarity of ethylene action between this organism and higher plants. Macrocysts are induced by low (1 μl/l) exogenous concentrations of ethylene. Higher concentrations (10–1,000 ul/l) also gave essentially the same inductive activity. Ethionine, an analogue of methionine, was found to inhibit zygote formation during sexual development through its interference with ethylene production by Dm 7 and MF 1 cells. In fact, the inhibitory effect of ethionine was mostly nullified by the application of ethylene, S-adenosyl-L-methionine, or 1-aminocyclopropane-1-carboxylic acid. Taken together these results suggest that both the effective concentration of ethylene and the pathway of ethylene biosynthesis inD. mucoroides may be similar to those in higher plants. Ethylene was also found to be produced in various species and strains of cellular slime molds, even during the asexual process. The possible functions of ethylene in the asexual development are discussed in relation to cell aggregation and differentiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01403379
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