Second heart field and the development of the outflow tract in human embryonic heart.

The second heart field (SHF) is indicated to contribute to the embryonic heart development. However, less knowledge is available about SHF development of human embryo due to the difficulty of collecting embryos. In this study, serial sections of human embryos from Carnegie stage 10 (CS10) to CS16 were stained with antibodies against Islet-1 (Isl-1), Nkx2.5, GATA4, myosin heavy chain (MHC) and α-smooth muscle actin (α-SMA) to observe spatiotemporal distribution of SHF and its contribution to the development of the arterial pole of cardiac tube. Our findings suggest that during CS10 to CS12, SHF of the human embryo is composed of the bilateral pharyngeal mesenchyme, the central mesenchyme of the branchial arch and splanchnic mesoderm of the pericardial cavity dorsal wall. With development, SHF translocates and consists of ventral pharyngeal mesenchyme and dorsal wall of the pericardial cavity. Hence, the SHF of human embryo shows a dynamic spatiotemporal distribution pattern. The formation of the Isl-1 positive condense cell prongs provides an explanation for the saddle structure formation at the distal pole of the outflow tract. In human embryo, the Isl-1 positive cells of SHF may contribute to the formation of myocardial outflow tract (OFT) and the septum during different development stages.

Diosmetin prevents TGF-ß1-induced epithelial-mesenchymal transition via ROS/MAPK signaling pathways.

AIMS: Epithelial-mesenchymal transition (EMT) plays a critical role in airway repair and remodeling in many respiratory diseases such as asthma and pulmonary fibrosis. The flavone aglycone, diosmetin, possesses anti-remodeling activity in a murine model of chronic asthma, but little is known about its effects on EMT. Herein, we investigated whether diosmetin inhibits transforming growth factor-ß1 (TGF-ß1)-induced EMT with underlying mechanisms in human bronchial epithelial (HBE) cells. MAIN METHODS: HBE cells were incubated with TGF-ß1 (10ng/ml), either alone or in combination with diosmetin for indicated times. We measured reactive oxygen species (ROS) levels using FACScan and immunofluorescent assays. We assessed protein expression of NADPH oxidase 4 (NOX4), superoxide dismutase (SOD), catalase, Akt, Erk, p38, and phosphorylation levels of Akt, Erk and p38 by Western blot analysis. KEY FINDINGS: TGF-ß1 promoted EMT and ROS generation in HBE cells. Diosmetin significantly suppressed TGF-ß1-induced increases in cell migration and altered N-cadherin, E-cadherin, and α-smooth muscle actin expression. In addition, diosmetin prevented TGF-ß1-induced intracellular ROS generation, down-regulated NOX4, and up-regulated SOD and catalase expression. Furthermore, diosmetin remarkably inhibited TGF-ß1-induced phosphorylation of phosphoinositide 3-kinase (PI3K)/Akt and mitogen activated protein kinase (MAPK) pathways in HBE cells. SIGNIFICANCE: Our results demonstrate for the first time that diosmetin alleviates TGF-ß1-induced EMT by inhibiting ROS generation and inactivating PI3K/Akt and MAPK pathways. Our findings revealed a new role for diosmetin in reducing airway remodeling and fibrogenesis.

[Responses of CO2 fluxes to light intensity and temperature in rice paddy field].

CO2 fluxes in rice paddy ecosystem in subtropical hilly region were measured continuously using eddy covariance technique. The objectives were to investigate the responses of CO2 fluxes to light intensity and temperature in the paddy ecosystem. Results showed a rectangular hyperbolic light-response function could be used to describe the relationship of CO2 flux and photosynthetic photon flux density (PPFD). The absolute values of CO2 fluxes increased with the increment of PPFD. When PPFD was higher than 1000 micromol/(m2 x s), the maximum was observed. CO2 fluxes responded differently to light between early and late rice. Values of quantum yield of late rice (0.0465-0.0999 micromol/micromol) were general higher than that of early rice (0.0176-0.0541 micromol/micromol). Moreover, the quantum yield and the maximum rate of photosynthesis assimilation in the blooming stage were higher than that in tillering and ripening stages. In nighttime, respiration from soil and plants (ecosystem respiration, Reco) changed exponentially with the increase of soil temperature at the depth of 5 cm (T5), 10 cm (T10), and 20 cm (T20), respectively. Whereas, T5 was more feasible than others to be considered as the temperature parameter for Reco calculation. During early rice growing season, Reco was more sensitive to temperature change than that during late rice growing season.

[Seasonal characteristics of CO2 fluxes from the paddy ecosystem in subtropical region].

CO2 fluxes from paddy ecosystem in subtropical hilly region were measured continuously using eddy covariance technique. Based on data rejecting, correcting and filling, the daily and annual CO2 fluxes were calculated from the instantaneous values, respectively. The objectives were to investigate the variation of CO2 fluxes on seasonal temporal scale, analyze the relationship between CO2 fluxes and environmental factors, and to quantify the annual net ecosystem exchange (NEE) from the paddy ecosystem. Results show the values of GPP, R(eco) and NEE are higher from Jun. to Sep. and lower in the other months. The NEE from May to Sep. accounted for above 80% of the annual value and is crucial to the whole annual value. Photosynthetically active radiation (PAR) and mean daily air temperature (T(a)) were two main influential factors for controlling the seasonal trend of GPP and NEE and could be described by binary linear functions, respectively. The annual NEE in paddy ecosystem was 2 475.6 g/(m2 x a). This is showed that paddy ecosystem was a carbon sink for the atmosphere in subtropical region.