Gestation-specific reference intervals for right and left ventricular ejection force from 12 to 40 weeks of gestation

Aim:? Ejection force of the fetal cardiac ventricles has previously been described from 18 weeks of gestation. We aimed to establish gestation-specific reference intervals for ventricular ejection force (VEF) from 12 to 40 weeks of pregnancy.Material and Methods:? In a cross-sectional observational study of singleton pregnancies, examinations were performed in 236 women evenly distributed across each week of pregnancy from 12 to 40 weeks. Each mother was scanned once. For the aortic and pulmonary valves, the time to peak velocity (TPV) and the average (TAV) and peak flow velocity in systole (PSV) was measured. For each we averaged values from three consecutive complexes. The outlet valve diameters were measured and the VEF on both the right and left sides were calculated using the formula VEF = (1.055 × valve area × time to peak velocity × TAV) × (PSV/TPV) where 1.055 represents the density of blood. Measurements were repeated in 40 women to assess intraobserver reproducibility and in 19 women for interobserver variability.Results:? We present reference intervals for right and left VEF. We demonstrated that the ventricular force on both right and left sides increases with advancing gestational age.Conclusion:? Fetal cardiac physiology can be studied and Doppler indices reliably measured as early as the late first trimester of pregnancy. Ventricular ejection force and its relationship with fetal growth could be explored in future studies and this may eventually provide better understanding of changes which may predispose to adult cardiac disease.<br/

Effects of nitrogen form on growth, CO2 assimilation, chlorophyll fluorescence, and photosynthetic electron allocation in cucumber and rice plants*

Cucumber and rice plants with varying ammonium (NH4 +) sensitivities were used to examine the effects of different nitrogen (N) sources on gas exchange, chlorophyll (Chl) fluorescence quenching, and photosynthetic electron allocation. Compared to nitrate (NO3 −)-grown plants, cucumber plants grown under NH4 +-nutrition showed decreased plant growth, net photosynthetic rate, stomatal conductance, intercellular carbon dioxide (CO2) level, transpiration rate, maximum photochemical efficiency of photosystem II, and O2-independent alternative electron flux, and increased O2-dependent alternative electron flux. However, the N source had little effect on gas exchange, Chl a fluorescence parameters, and photosynthetic electron allocation in rice plants, except that NH4 +-grown plants had a higher O2-independent alternative electron flux than NO3 −-grown plants. NO3 − reduction activity was rarely detected in leaves of NH4 +-grown cucumber plants, but was high in NH4 +-grown rice plants. These results demonstrate that significant amounts of photosynthetic electron transport were coupled to NO3 − assimilation, an effect more significant in NO3 −-grown plants than in NH4 +-grown plants. Meanwhile, NH4 +-tolerant plants exhibited a higher demand for the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) for NO3 − reduction, regardless of the N form supplied, while NH4 +-sensitive plants had a high water-water cycle activity when NH4 + was supplied as the sole N source