Late gestation fetal hyperglucagonaemia impairs placental function and results in diminished fetal protein accretion and decreased fetal growth.

KEY POINTS: Fetal glucagon concentrations are elevated in the setting of placental insufficiency, hypoxia and elevated stress hormones. Chronically elevated glucagon concentrations in the adult result in profound decreases in amino acid concentrations and lean body mass. Experimental elevation of fetal glucagon concentrations in a late-gestation pregnant sheep results in lower fetal amino acid concentrations, lower protein accretion and lower fetal weight, in addition to decreased placental function. This study demonstrates a negative effect of glucagon on fetal protein accretion and growth, and also provides the first example of a fetal hormone that negatively regulates placental nutrient transport and blood flow. ABSTRACT: Fetal glucagon concentrations are elevated in the setting of placental insufficiency and fetal stress. Postnatal studies have demonstrated the importance of glucagon in amino acid metabolism, and limited fetal studies have suggested that glucagon inhibits umbilical uptake of certain amino acids. We hypothesized that chronic fetal hyperglucagonaemia would decrease amino acid transfer and increase amino acid oxidation by the fetus. Late gestation singleton fetal sheep received a direct intravenous infusion of glucagon (GCG; 5 or 50 ng/kg/min; n = 7 and 5, respectively) or a vehicle control (n = 10) for 8-10 days. Fetal and maternal nutrient concentrations, uterine and umbilical blood flows, fetal leucine flux, nutrient uptake rates, placental secretion of chorionic somatomammotropin (CSH), and targeted placental gene expression were measured. GCG fetuses had 13% lower fetal weight compared to controls (P = 0.0239) and >28% lower concentrations of 16 out of 21 amino acids (P < 0.02). Additionally, protein synthesis was 49% lower (P = 0.0005), and protein accretion was 92% lower in GCG fetuses (P = 0.0006). Uterine blood flow was 33% lower in ewes with GCG fetuses (P = 0.0154), while umbilical blood flow was similar. Fetal hyperglucagonaemia lowered uterine uptake of 10 amino acids by >48% (P < 0.05) and umbilical uptake of seven amino acids by >29% (P < 0.04). Placental secretion of CSH into maternal circulation was reduced by 80% compared to controls (P = 0.0080). This study demonstrates a negative effect of glucagon on fetal protein accretion and growth. It also demonstrates that glucagon, a hormone of fetal origin, negatively regulates maternal placental nutrient transport function, placental CSH production and uterine blood flow.

Novel degradable oligoethylenimine acrylate ester-based pseudodendrimers for in vitro and in vivo gene transfer.

A novel class of cationic hyperbranched polymers, containing branched oligoethylenimine (OEI 800 Da) as core, diacrylate esters as linkers and oligoamines as surface modification, was synthesized and evaluated regarding their structure-activity relationship as gene carriers. We show that pseudodendritic core characteristics as well as different surface modifications on the core influence DNA-binding ability, cytotoxicity and transfection efficiency. As most promising gene carrier, the pseudodendrimer HD O, that is, the OEI 800 Da core modified with hexane-1,6-diol diacrylate and surface-modified with OEI 800 Da, was identified. HD O exhibits efficient DNA-condensing ability to nanosized polyplexes (100-200 nm), low cytotoxicity, a degradation half-life of 3 days at 37 degrees C at physiological pH and in vitro reporter gene-expression levels similar to high molecular weight linear and branched polyethylenimines (PEIs) (LPEI and BPEI). In vivo studies in mice reveal that HD O/DNA polyplexes upon i.v. tail-vein injection have the potential for transfection of tumor tissue at levels comparable to that obtained with LPEI. Importantly, HD O was better tolerated than LPEI, while transgene expression was more tumor-specific and much lower in all other investigated organs, especially in the lung (15,000-fold lower compared with LPEI).

Determination of organic acids in seven wheat varieties by capillary gas chromatography.

Fresh wheat tops were extracted with acidic 90% ethanol, and the ethanol was evaporated and a portion of the aqueous residue loaded onto DEAE-Sephadex. Organic acids were eluted with pyridinium formate and then lyophilized and the dried residue was derivatized with 1% trimethylchlorosilane in bis(trimethylsilyl)trifluoroacetamide. The acids were then quantitatively determined using capillary gas chromatography and identified using capillary gas chromatography-mass spectrometry. The acidic ethanol extraction of fresh plant tissue was quantitative for all acids except citric while losses in the remaining procedures were controlled by using an internal standard. The ion exchange chromatography made the greatest contribution to experimental error, imposing a minimum loading requirement of 0.1 mumol of each acid for adequate precision. Organic acid profiles were determined for seven wheat cultivars (Triticum aestivum cv Carazinho, Teal, Lance, Warigal, Isis, Maringa, and BH1146) grown on gravel in solution culture for 30 days. Profiles were simple, consisting of only malic, aconitic, and citric acids, with levels of each acid for all varieties falling within the range 2-5 mumol/g fresh tissue. Storage of samples led to a large increase in sampling error and increased the amount of extractable citric acid.