Ivan A. Shibley

Differential expression of glucose transporters during chick embryogenesis

Abstract. The patterns of Glut1 and Glut3 glucose transporter protein and mRNA expression were assessed during embryogenesis of chicken brain and skeletal muscle, Glut4 protein levels were also evaluated in skeletal muscle and heart, and Glut1 was examined in the developing heart and liver. Glut1 protein expression was detectable throughout brain ontogeny but was highest during early development. Glut1 mRNA levels in the brain remained very high throughout development. Glut3 protein was highest very early and very late and mRNA was highest during the last half of development. In embryonic skeletal muscle, the levels of Glut1and Glut3 proteins and mRNA were highest very early, and declined severely by mid-development. Glut1 protein and mRNA in the heart also peaked early and then decreased steadily. Although Glut1 mRNA levels were consistently high in the embryonic liver, Glut1 protein expression was not detected. These results suggest that (1) Glut1 is developmentally regulated in chick brain, skeletal muscle, and heart, (2) Glut1 mRNA is present in liver but does not appear to be translated, (3) Glut3 in brain increases developmentally but is virtually absent in muscle, and (4) Glut4 protein and mRNA appear to be absent from chick heart and skeletal muscle.

Signaling pathways regulating ornithine decarboxylase activity in the embryonic chicken.

The pathways regulating ornithine decarboxylase (ODC) activity in the chick embryo were studied to determine which kinase-signaling pathways regulate ODC activity levels during development. Insulin-dependent tyrosine kinase, protein kinase C and cAMP-dependent protein kinase were activated by the addition of insulin, tetradecanoylphorbol-12,13-acetate, and forskolin, respectively. All three drugs increased ODC activity and forskolin combined with insulin increased ODC activity above the increase caused by either drug alone. These results suggest that all three signaling pathways regulate ODC activity during development and that common intermediates exist among the pathways downstream of the kinases.

Alterations in the offsprings' response to an oral glucose challenge associated with acute maternal malnutrition during late pregnancy

Abstract An acutely malnourished pregnant rat model was used to test the effect of intrauterine growth retardation on the subsequent response of the offspring to a loading dose of glucose. Timed-pregnant Harlan-Sprague Dawley rats were given access to only tap water from day 17 through day 19 of their pregnancies (72 hours total). Control mothers had access to lab chow and water throughout their pregnancies. The litters were randomly culled to 4 males and 4 females, whenever possible, and the offspring were given oral glucose tolerance tests at 60, 180 and 360 days of age. At 60 and 180 days of age, malnourished offspring were glucose intolerant (e.g., at 60 days, control males 60 minute serum [glucose] = 9.3±0.1 mM, [malnourished] = 10.1±0.2; [control females] = 9.6±0.2 versus [malnourished] = 10.5±0.3; (overall P