Cellulose microfibril angle variation in Picea crassifolia tree rings improves climate signals on the Tibetan plateau

Microfibril angle (MFA) is an important factor in determining the mechanical properties of individual cells and wood as a whole. While some studies have described the variation of MFA within trees, little work has been done on the extent to which MFA is influenced by climate, despite it being known to respond to climatic events. Year-to-year variation in MFA and ring width was measured at high resolution by SilviScan-3^? on 30 dated Picea crassifolia trees growing in the northeastern Tibetan plateau. The climate signals registered in MFA and ring width were analyzed using dendroclimatological methods. The response function of MFA accounted for 67% of total variance, of which 60% was explained by climate elements. The response function of ring width explained 57% total variance, 37% of which was explained by climate variables. MFA significantly responded to July–August temperatures, and to precipitation in March, May and September. Over the period 1987–2009 temperatures generally increase and appeared to have a greater influence on MFA. A decrease in the strength of the relationship between MFA and ring width over the period 1987–2009 was also observed. MFA offers the potential to build robust climate proxies. The strong climate sensitivity of MFA to increasing temperature or the observed changes in the MFA–ring width relationship may contribute to resolving the “divergence problem” in temperature reconstructions. As far as we are aware, this study is the first to show a strong climate response in MFA and suggests that it might be a useful climate proxy.     

Effect of two selenium sources on hepatocarcinogenesis and several angiogenic cytokines in diethylnitrosamine-induced hepatocarcinoma rats

This experiment was designed to compare the effect of two selenium sources at the dosage of therapeutic level on hepatocarcinogenesis and angiogenic cytokines in DEN-induced hepatocarcinoma rats to further approach their possible anticancer's mechanism. One hundred and seventy-eight Sprague-Dawley (SD) rats (average weight being 100–120 g) were randomly divided into 5 groups (I–V). Animals in group I, group II and group III served as the negative control, sodium selenite control (SS) and positive controls respectively, and received 0.1, 3.0, and 0.1 mg/kg selenium from sodium selenite supplemented diets during the whole experimental time. Rats in group IV and group V were fed with selenium from selenium-enriched malt (SEM) and sodium selenite (SS) supplemented diets (3 mg/kg respectively). To balance the nutritional content among each group, normal malt which was not treated with selenium was added into the diets of the challenge groups. The nutrition contents, except the selenium of the diet in each group, were similar and in accordance with NRC standards. Rats in groups III–V were treated by aqueous diethylnitrosamine solution (100 mg/L) at the dosage of 10 mg/kg body weight every day for 16 weeks to induce hepatocarcinoma, and drank sterilized water for an additional two weeks. Rats in group I and group II drank sterilized water throughout the experiment. At 4th, 8th, 12th, 16th week, five rats in each group were then sacrificed by cervical decapitation. At the termination of the study, at 18th week, the surplus rats were sacrificed by cervical decapitation. Feed was withheld from the rats for 12 h before sampling. The number of hepatoma nodules in liver and mortality of rats were calculated. The values of the following items, including α-fetoprotein (AFP), gamma-glutamyltranspeptidase (GGT), tumor necrosis factor-α (TNF-α), insulin-like growth factors-II (IGF-II), nitric oxide (NO) and total nitric oxide synthase (T-NOS) in plasma were determined. At the same time, the positive numbers of vascular endothelial growth factor (VEGF) and protein kinase C-α (PKCα) staining cells in tumor tissue were analyzed by immunohistochemistry using the Envision two step methods with a kit. The results indicated that SEM could significantly decrease the mortality of rats and the number of hepatoma nodules, values of GGT and AFP, and the levels of IGF-II, NO and NOS and lessen the positive numbers of VEGF and PKCα staining cells in tumor tissue. Moreover, SEM could increase the levels of TNF-α in the initiated time of hepatocarcinogenesis, whereas, decrease the levels of TNF-α in the progressive time of hepatocarcinogenesis. SS could only significantly inhibit the positive numbers of PKCα staining cells in tumor tissue, decrease the levels of GGT, AFP and TNF-α at minority sampling times, and increase the levels of NO. In conclusion, SEM could reduce the mortality. It might be related to deaden significantly the lesion of liver, delay the cause of hepatocarcinogenesis, and inhibit the progress of angiogenesis to increase the livability of DEN-induced hepatocarcinoma rats. SS at the same therapeutic dosage had less effect on the hepatocarcinogenesis by inhibiting angiogenesis and relative cytokines to some extent.     

Topoisomerase I‐Mediated Antiproliferative Activity of 10‐Substituted and 12‐Substituted Homocamptothecins

Homocamptothecin (hCPT) is an E‐ring modified camptothecin (CPT) analogue, which showed pronounced inhibitory activity of topoisomerase I. In search of novel hCPT‐type anticancer agents, two series of hCPT derivatives were synthesized and evaluated in vitro against three human tumor cell lines. The results indicated that the 10‐substituted hCPT derivatives had a considerably higher cytotoxic activity than the 12‐substituted ones. Among the 10‐substituted compounds, 8a, 8b, 9b , and 9i showed an equivalent or even more potent activity than the positive control drug topotecan against the lung cancer cell line A‐549. Moreover, the hCPT analogues 8a and 8b exhibited a higher topoisomerase I inhibitory activity than CPT at a concentration of 100 μM .     

CARAGANA FABR. PROMOTES REVEGETATION AND SOIL REHABILITATION IN SALINE-ALKALI WASTELAND

To determine how plantations of Caragana microphylla shrubs affect saline-alkali soil amelioration and revegetation, we investigated the vegetation and sampled soils from saline-alkali wasteland (SAW), perennial Caragana forestland (PCF), Caragana forest after fire disturbance (CFF). Results showed that with the development of Caragana Fabr., highly dominant species of Poaceae family, including Elymus dahuricus, Thermopsis lanceolata, Stipa tianschanica, died out in PCF. Moreover, Papilionaceae family, including Lespedeza indica, Oxytropis psammocharis, and Astragalus scaberrimus, was established both in PCF and CFF. Phytoremediation of saline-alkali wasteland (SAW) was achieved by plantation, resulting in the reduced soil pH, sodium adsorption ratio, exchangeable sodium percentage, salinity, and Na⁺ concentration around Caragana shrubs. Greater amounts of soil organic, total nitrogen, ammonium nitrogen, available phosphorus, and available potassium were observed in PCF topsoil than in SAW topsoil. The concentration of mineralized N in PCF soil was significantly lower than that in SAW soil at all sampled depths, indicating that Caragana shrubs were just using N and therefore less measured in soils. Fire disturbance resulted in decreased soil pH and salinity, but increased organic content, total nitrogen, and ammonium nitrogen. The improved soil parameters and self-recovery of shrubs indicated that Caragana shrubs were well established after burning event.     

Aluminum Tolerance in Moso Bamboo (<Emphasis Type="Italic">Phyllostachys pubescens</Emphasis>)

Moso bamboo (Phyllostachys pubescens) is widely distributed in the acid soil region of Southern China, where great potential of aluminum (Al) toxicity exists. To evaluate the Al tolerance of Moso bamboo, seed germination and root elongation were compared with two rice cultivars, and physical and physiological damages were examined under various levels of Al stress. Results showed that Moso bamboo seed germination was inhibited when Al concentration increased to 500 μM, and the median lethal concentration was 2,000 μM. Comparatively, the rice seed germination was not inhibited even at a concentration of 2,000 μM Al. Aluminum accumulated mainly in the cell wall of root apices, and entered into protoplasts as treating time prolonged and/or Al concentration increased, which resulted in apoptosis. The bamboo root epidermis degraded significantly in the presence of 2,000 μM Al. In conclusion, Moso bamboo is moderately weak in Al tolerance.