Neutral and niche theories give contrasting explanations for the maintenance of tropical tree species diversity. Both have some empirical support, but methods to disentangle their effects have not yet been developed. We applied a statistical measure of spatial structure to data from 14 large tropical forest plots to test a prediction of niche theory that is incompatible with neutral theory: that species in heterogeneous environments should separate out in space according to their niche preferences. We chose plots across a range of topographic heterogeneity, and tested whether pairwise spatial associations among species were more variable in more heterogeneous sites. We found strong support for this prediction, based on a strong positive relationship between variance in the spatial structure of species pairs and topographic heterogeneity across sites.

A group of novel 2-(2′-hydroxyphenyl)benzothiazole derivatives (1−4) with excited-state intramolecular proton transfer (ESIPT) character were synthesized. Their photophysical properties were studied by means of steady-state absorption and fluorescence spectra and time-resolved emission method as well as theoretical calculation in a variety of solvents. All of these compounds can yield single fluorescence at the green region in nonpolar solvents such as n-hexane, while dual fluorescence consisting of the blue and green bands was captured in strong polar solvents like acetonitrile. In addition, a third emission band between the former two bands was detected for these molecules simultaneously with the blue and green ones generating the wellstructured triple fluorescence in protic solvent like ethanol. Systematical comparison of the fluorescence of these compounds in a series of solvents demonstrated that nonpolar solvents would facilitate ESIPT process and the green emission from the keto format, while the strong polar solvents impede the ESIPT process and favor the blue normal emission from enol. Protic solvents facilitate deprotonation and make the phenolic anion coexist with keto and enol and consequently lead to triple fluorescence. On the premise of identical keto emission intensity, the normal emission intensity of these compound increases consecutively in the order of increasing electron-withdrawing ability of the substituents regardless of solvents. The results of quantum-chemical calculations are well in line with the experimental spectra.

It has been demonstrated that the number and differentiating potential of bone marrow mesenchymal stem cells (MSCs) decrease with age. Therefore, the search for alternative sources of MSCs is of significant value. In the present study, MSCs were isolated from umbilical cord blood (UCB) by combining gradient density centrifugation with plastic adherence. Cultured cells were treated with ascorbate acid-2-phosphate, dexamethasone, beta-glycerophosphate dexamethasone, insulin, 1-methyl-3-isobutylxamthine, indomethacin, beta-mercaptoethanol, butylated hydroxyanisole, FGF-4 and HGF. Differentiating characterization of UCB-derived MSCs were detected by cytochemistry, immunocytochemistry, radioimmunoassay, RT-PCR and urea assay. The results showed UCB-derived MSCs could differentiate into osteoblasts, adipocytes and neuron-like cells. When MSCs were cultured with FGF-4 and HGF, approximately 63.6% of cells became small, round and epithelioid on day 28 by morphology. Compared with the control, levels of AFP in the supernatant liquid increased significantly from day 12 and were higher on day 28 (P<0.01). Albumin increased significantly from day 16 (P<0.01). Urea was first detected on day 20 (P<0.01), and continued to increase on day 28 (P<0.01). Cells first expressed CK-18 on day 16 through immunocytochemistry analysis. RT-PCR analysis showed that differentiated cells could express a number of hepatocyte-specific genes in a time-dependent manner. Glycogen storage was first seen on day 24. Our results suggest that UCB-derived MSCs can differentiate not only into osteoblasts, adipocytes and neuron-like cells, but also into hepatocytes. Human UCB-derived MSCs are a new source of cell types for cell transplantation and therapy.

Melatonin exhibits antitumour activities in the treatment of many human cancers. In the present study, we aimed to improve the therapeutic potential of melatonin in gastric cancer. Our results confirmed that melatonin dose‐dependently suppressed the proliferation and necrosis, and increased G0/G1 phase arrest, apoptosis, autophagy and endoplasmic reticulum (ER) stress. The Ras‐Raf‐MAPK signalling pathway was activated in cells after melatonin treatment. RNA‐seq was performed and GSEA analysis further confirmed that many down‐regulated genes in melatonin‐treated cells were associated with proliferation. However, GSEA analysis also indicated that many pathways related to metastasis were increased after melatonin treatment. Subsequently, combinatorial treatment was conducted to further investigate the therapeutic outcomes of melatonin. A combination of melatonin and thapsigargin increased the apoptotic rate and G0/G1 cell cycle arrest when compared to treatment with melatonin alone. Melatonin in combination with thapsigargin triggered the increased expression of Bip, LC3‐II, phospho‐Erk1/2 and phospho‐p38 MAPK. In addition, STF‐083010, an IRE1a inhibitor, further exacerbated the decrease in survival rate induced by combinatorial treatment with melatonin and thapsigargin. Collectively, melatonin was effective in gastric cancer treatment by modifying ER stress.

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The synthesis and photophysics of two novel 2-(2'-hydroxyphenyl)benzothiazole (HBT) derivatives are presented. The electron-withdrawing trifluoromethyl (CF3) group in compound 1 facilitates the deprotonation of the phenolic hydroxy group. Well-resolved triple fluorescence from the enol, keto, and phenolic anion, which ranges from 350 to 600 nm, was detected for 1 in ethanol, which marks the first time triple fluorescence from an excited-state intramolecular proton transfer (ESIPT) molecule has been reported. Both triphenylamine and CF3 were introduced into derivative 2. Intramolecular charge transfer and the "red-edge effect" resulted in the bathochromic shift of dual fluorescence of 2. Triple fluorescence was also observed for 2 in ethanol. In mixed acetonitrile and ethanol, pure white-light emission with CIE coordinates of (0.33, 0.33) and a quantum yield of 0.25 was achieved for 2. This work provides a new avenue for the rational design of an ESIPT molecule to achieve white-light generation under mild conditions.

Phyllosphere harbors diverse microorganisms, which influence plant growth and health. In order to understand the extent to which environmental factors affect epiphytic microbial communities, we characterized microbial communities on leaves of three separate tree species present on the college campus, and also present within a forest park over two seasons. Quantitative PCR analysis showed the quantity of 16S rRNA genes was lower in May compared with October, while the abundances of functional genes (nifH and bacterial amoA genes) were extremely high in May. High-throughput sequencing revealed a large variation in the diversity and composition of bacterial and diazotrophic communities over the two seasons, and showed the abundance of functional genera, such as Nocardioides, Bacillus and Zoogloea were significantly elevated in May. In addition, xenobiotic biodegradation pathways of bacterial communities were clearly elevated in May. Network analysis showed the correlations between phyllospheric bacteria in May were more complex than that in October and showed greater negative correlations. These results were consistent in all tree species in this study. This study showed that phyllospheric bacteria varied greatly in different seasons, which implies that different growing seasons should be considered in the exploitation of the interactions between phyllospheric microorganisms and host plants.

HUCB-derived MSCs can differentiate into hepatocytes by induction of FGF-4 and HGF. HUCB-derived MSCs are a new source of cell types for cell transplantation therapy of hepatic diseases.