Biomedical subjects

C Y Cheung

Publications and source records attributed to C Y Cheung.

93 records · Page 6Linked to original sources

PubMedDate not supplied

Gene expression of atrial natriuretic factor in ovine fetal heart during development.

OBJECTIVE: The present study quantified the abundance of atrial natriuretic factor (ANF) messenger RNA (mRNA) and determined the developmental pattern of ANF gene expression in the four cardiac chambers of the ovine fetus during the last two-thirds of gestation. METHODS: Twenty-one fetuses from 13 time-dated pregnant ewes at gestational ages of 60-145 days were used for this study. Total RNA from fetal atria and ventricles was extracted and ANF mRNA was analyzed by Northern blotting. The ANF mRNA signal was quantified by light densitometry. The abundance of ANF mRNA in the cardiac chambers across gestational ages was analyzed by linear regression analysis and one-way analysis of variance. RESULTS: Atrial natriuretic factor mRNA was much more abundant in the atria than in the ventricles of all fetuses at each gestational age studied. Atrial ANF mRNA levels were lowest in the younger fetuses at 60 days and increased with advancing gestation. Ventricular ANF mRNA levels were highest in fetuses at 60 days and decreased to almost nondetectable levels near term. No difference in ANF mRNA abundance was noted between the right and left atria or the right and left ventricles at each gestational age. CONCLUSION: A developmental pattern of ANF gene expression is demonstrated in the ovine fetal heart during the last two-thirds of gestation. This pattern shows that atrial ANF mRNA abundance increases while ventricular abundance decreases as the fetus matures. Expression of the ANF gene in the fetal period may be regulated developmentally or induced by cardiovascular changes in utero.

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PubMedDate not supplied

Ontogeny of insulin-like growth factor-I and -II gene expression in ovine fetal heart.

OBJECTIVE: Insulin-like growth factors (IGF)-I and -II have been implicated in growth and differentiation during embryonic and fetal development. To examine the role of the IGFs in growth of the fetal heart, we determined the gene expression of IGF-I and IGF-II in the four cardiac chambers of the ovine fetus from 58 to 146 days' gestation (term = 147 days). METHODS: Total RNA was obtained from the cardiac chambers, analyzed by Northern blot, and hybridized to ovine specific cDNA probes for IGF-I and IGF-II. The resulting autoradiograms were subjected to light densitometry, and the intensity of the IGF signals was normalized to the respective 28S ribosomal RNA signals. RESULTS: In the atria and ventricles, IGF-I mRNA abundance was very low throughout the gestational period studied, whereas IGF-II mRNA levels were higher and readily detectable. In the atria, IGF-I mRNA was very low at 60 days' gestation and appeared to increase gradually toward term. Abundance of IGF-II mRNA was high at 60 days, increased further until 120 days, and decreased slightly toward term. In contrast, in the ventricles, IGF-I mRNA increased from 60 to 100 days and then declined moderately at term. Levels of IGF-II mRNA in the ventricles were high at 60 days and decreased progressively to low levels at term. No difference in IGF-I or IGF-II mRNA levels was noted between the right and left atria or right and left ventricles. CONCLUSION: These results suggest that developmental patterns for IGF-I and IGF-II gene expression exist in the ovine fetal heart, and the patterns differ between the atria and ventricles. Further, these gestational trends differ from those for atrial natriuretic factor (ANF) found in our previous studies, indicating that expression of the ANF gene in the fetal heart may not be associated with cardiac growth and differentiation.

Animals↗

PubMedDate not supplied

Vascular endothelial growth factor: possible role in fetal development and placental function.

Vascular endothelial growth factor (VEGF) is an endothelial cell mitogen with potent permeability properties. This growth factor exists in several isoforms; the most abundant form present in most tissues is VEGF165. The different isoforms exhibit differences in biologic function. During development, VEGF is expressed in multiple embryonic and fetal tissues, with the highest levels found in the lung, kidney, and heart. Vascular endothelial growth factor is also expressed in placental tissues and fetal membranes, and this expression increases with advancing gestation. In the fetal heart and placenta, VEGF expression is inducible by hypoxia. Two receptors, KDR and Flt-1, have been identified for VEGF. They are widely expressed in vascular endothelial cells and are also found in placental tissues where VEGF is localized. In humans, Flt-1 appears to be the predominant receptor, whereas in the cow and sheep, KDR is the major receptor expressed. The presence of VEGF and its receptors in placental tissues throughout gestation strongly suggests that VEGF plays an important role in the development and maintenance of placental vascular function during pregnancy. The localization of VEGF in fetal membranes and the fetal surface of the placenta raises the possibility that VEGF may be involved in the regulation of amniotic fluid volume and composition.

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