Using pulsed Doppler ultrasound, blood flow in the inferior vena cava (IVC) was studied in 47 normal fetuses from 24 to 40 weeks of gestation and 35 abnormal fetuses, with the exception of those with arrhythmias. The abnormal fetuses were divided into 4 groups according to diagnosis, i.e., 6 cases of heart disease with hydrops (group 1), 9 cases of heart disease without hydrops (group 2), 11 cases of hydrops without heart disease (group 3), and 9 cases of other fetal diseases (group 4). By measuring the velocity of IVC blood flow, we defined a new index, the change in parallel with reverse flow velocity, and called it the preload index (PLI). In normal fetuses, PLI values ranged from 0 to 0.37 and had no relation with gestational age. The PLI was significantly higher in groups 1–3 than in normal fetuses. In group 1, the PLI was also higher than in group 2. In group 3, the PLI values in 4 cases of chylothorax, 1 of chyloascites and 1 of cytomegalovirus infection were significantly lower than in the remaining 5 cases where the cause of hydrops was undetermined. The PLI was normal in 9 fetuses with other diseases and no hydrops. The PLI was increased in conditions in which excessive preload, tricuspid regurgitation, or some kind of structural heart disease were present.
Intrauterine injection of naked DNA expressing luciferase, green fluorescent protein (GFP), or beta-galactosidase (beta-gal) and fluorescein isothiocyanate-labeled oligodeoxynucleotide (FITC-ODN), in combination with microbubble-enhanced ultrasound (US), referred to as the "shotgun method" (SGM), produced high-level protein expression in fetal mice. With the SGM, luciferase expression increased approximately 10(3)-fold in comparison with expression after injection of naked DNA alone. Electron microscopic analysis demonstrated transient formation of pores on the skin surface after intraamniotic (i.a.) injection with the SGM. Widespread expression of GFP and beta-gal and delivery of FITC-ODN were observed in multiple fetal tissues adjacent to the injection points. PCR analysis indicated that germline transfection was only transient following intraperitoneal (i.p) injection, and there was no evidence of transfer of the reporter gene to the offspring. Thus, SGM might provide a useful means to clarify the molecular mechanisms of genetic diseases in utero, as well as a tool to develop gene therapies in utero.
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