Oxidative stress in heroin administered mice and natural antioxidants protection

The oxidative stress of heroin administered mice via intraperitoneal injection, and the therapeutic effects of exogenous antioxidants on the restrain of the oxidative damage of biomolecules and withdrawal syndrome were studied. After administered with heroin, mice showed decrease of total antioxidant capacity in blood, increase of reactive oxygen species production in white blood cells, and increase of oxidative damages of protein and lipid in brain and liver, but not in heart. On the other hand, exogenous antioxidants could restrain the oxidative stress, even alleviate withdrawal syndrome.     

DNA microarray data imputation and significance analysis of differential expression

MOTIVATION: Significance analysis of differential expression in DNA microarray data is an important task. Much of the current research is focused on developing improved tests and software tools. The task is difficult not only owing to the high dimensionality of the data (number of genes), but also because of the often non-negligible presence of missing values. There is thus a great need to reliably impute these missing values prior to the statistical analyses. Many imputation methods have been developed for DNA microarray data, but their impact on statistical analyses has not been well studied. In this work we examine how missing values and their imputation affect significance analysis of differential expression. RESULTS: We develop a new imputation method (LinCmb) that is superior to the widely used methods in terms of normalized root mean squared error. Its estimates are the convex combinations of the estimates of existing methods. We find that LinCmb adapts to the structure of the data: If the data are heterogeneous or if there are few missing values, LinCmb puts more weight on local imputation methods; if the data are homogeneous or if there are many missing values, LinCmb puts more weight on global imputation methods. Thus, LinCmb is a useful tool to understand the merits of different imputation methods. We also demonstrate that missing values affect significance analysis. Two datasets, different amounts of missing values, different imputation methods, the standard t-test and the regularized t-test and ANOVA are employed in the simulations. We conclude that good imputation alleviates the impact of missing values and should be an integral part of microarray data analysis. The most competitive methods are LinCmb, GMC and BPCA. Popular imputation schemes such as SVD, row mean, and KNN all exhibit high variance and poor performance. The regularized t-test is less affected by missing values than the standard t-test. AVAILABILITY: Matlab code is available on request from the authors.     

Regulation of CO on heterocyst differentiation and nitrate uptake in the cyanobacterium Anabaena sp. PCC 7120

AIMS: The aim of the present investigation was to study the effects of different inorganic carbon and nitrogen sources on nitrate uptake and heterocyst differentiation in the culture of cyanobacterium Anabaena sp. PCC 7120. METHODS AND RESULTS: Anabaena was cultivated in media BG11 containing combined nitrogen and supplementary NaHCO3 or CO2. Cell growth, heterocyst differentiation, nitrate reductase (NR, EC 1.7.7.2), glucose-6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49) and NO uptake were analysed. The cells cultivated in BG11(0) medium with aeration were taken as reference. Experimental results showed that the differentiation frequency of heterocysts when the cells were cultivated with elevated CO2 was higher than that of the cells grown with air or bicarbonate. Heterocysts appeared unexpectedly when CO2 was introduced into the medium containing nitrate. However, no heterocysts emerged when CO2 was added to medium containing NH or urea, or when NaHCO3 was supplied to the medium with nitrate. Both nitrate uptake rate and nitrate reduction enzyme activity were depressed by the supplement of CO2 to the culture. The activity of G6PDH was enhanced with the increase in heterocyst differentiation frequency. CONCLUSION: CO2 might compete with NO for energy and electrons in the uptake process and CO2 appears favoured. This led to a high intracellular C/N ratio and a relative N limitation. So the process of heterocyst differentiation was activated to supplement nitrogen uptake. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provided an attractive possibility to form more heterocysts by rapid growth of Anabaena cells cultivated in the medium containing nitrate in order to increase nitrogen fixation and hydrogen production.     

Synthesis and structure-activity relationships of 1,2,4-triazoles as a novel class of potent tubulin polymerization inhibitors

A novel triazole-containing chemical series was shown to inhibit tubulin polymerization and cause cell cycle arrest in A431 cancer cells with EC(50) values in the single digit nanomolar range. Binding experiments demonstrated that representative active compounds of this class compete with colchicine for its binding site on tubulin. The syntheses and structure-activity relationship studies for the triazole derivatives are described herein.     

Loss of viability during freeze–thaw of intact and adherent human embryonic stem cells with conventional slow-cooling protocols is predominantly due to␣apoptosis rather than cellular necrosis

Summary A major challenge in the widespread application of human embryonic stem (hES) cells in clinical therapy and basic scientific research is the development of efficient cryopreservation protocols. Conventional slow-cooling protocols utilizing standard cryoprotectant concentrations i.e. 10% (v/v) DMSO, yield extremely low survival rates of <5% as reported by previous studies. This study characterized cell death within frozen–thawed hES colonies that were cryopreserved under standard conditions. Surprisingly, our results showed that immediately after post-thaw washing, the overwhelming majority of hES cells were viable (≈98%), as assessed by the trypan blue exclusion test. However, when the freshly-thawed hES colonies were incubated within a 37 °C incubator, there was observed to be a gradual reduction in cell viability over time. The kinetics of cell death was drastically slowed-down by keeping the freshly-thawed hES colonies at 4 °C, with >90% of cells remaining viable after 90 min of incubation at 4 °C. This effect was reversible upon re-exposing the cells to physiological temperature. The vast majority of low temperature-exposed hES colonies gradually underwent cell death upon incubation for a further 90 min at 37 °C. Terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end-labeling (TUNEL) assay confirmed apoptosis-induced nuclear DNA fragmentation in frozen–thawed hES cells after incubation at 37 °C for 90 min. Expression of active caspase-3 enzyme, which is another prominent marker of apoptosis, was confirmed by immunocytochemical staining, while transmission electron microscopy showed typical ultrastructural features of apoptosis such as chromatin condensation and margination to the nuclear membrane. Hence, our results demonstrated that apoptosis instead of cellular necrosis, is the major mechanism of the loss of viability of cryopreserved hES cells during freeze–thawing with conventional slow-cooling protocols.     

Culture of neural stem cells in calcium alginate beads

Neural stem cells (NSCs) with the capacity of extensive self-renewal and multilineage differentiation have attracted more and more attention in research as NSCs will play an important role in the nerve disease treatment and nerve injury repair. The shortage of NSCs, both their sources and their numbers, however, is the biggest challenge for their clinic application, and hence, in vitro culture and expansion of NSCs is vitally important to realize their potentials. In this work, mouse-derived NSCs were cultured in three-dimensional calcium alginate beads (Ca-Alg-Bs). Gelling conditions, cell density, and cell harvest were determined by the exploration of formation and dissociation parameters for Ca-Alg-Bs. Additionally, the recovered and the subsequent induced cells were identified by immunofluorescence staining of Nestin, beta-tubulin, and GFAP. The results show that the 2-mm diameter Ca-Alg-Bs, prepared with 1.5% sodium alginate solution and 3.5% CaCl2 solution and with gelling for 10 min, is suitable for the NSCs culture. The seeding density of 0.8 x 10(5) cells x mL-1 for the encapsulation of NSCs resulted in the most expansion, and the NSCs almost doubled during the experiment. The average cell recovery rate is over 88.5%, with the Ca-Alg-Bs dissolving in 55 mM sodium citrate solution for 10 min. The recovered cells cultured in the Ca-Alg-Bs still expressed Nestin and had the capacity of multilineage differentiation into neurons and glial cells and, thus, remained to be NSCs. These results demonstrate that NSC expansion within Ca-Alg-Bs is feasible and provides further possibilities for NSC expansion in bioreactors of the scale of clinical relevance.     

Soil Carbon Changes Following Afforestation with Olga Bay Larch （Larix olgensis Henry） in Northeastern China

After converting cropland to forest, carbon Is sequestered in the aggradlng blomass of the new forests, but the question remains, to what extent will the former arable soil contribute as a sink for CO2？ Quantifying changes In soil carbon Is an Important consideration In the large-scale conversion of cropland to forest. Extensive field studies were undertaken to Identify a number of suitable sites for comparison of soil properties under pasture and forest. The present paper describes results from a study of the effects of first rotation larch on soil carbon In seven stands In an afforestation chronosequence compared with adjacent Korean pine, pasture, and cropland. An adjacent 250-year-old natural forest was Included to give Information on the possible long-term changes In soil carbon In northeast China In 2004. Soil carbon Initially decreased during the first 12 yr before a gradual recovery and accumulation of soil carbon occurred. The Initial （0-12 yr） decrease In soil carbon was an average 1.2% per year among case studies, whereas the Increase In soil carbon （12-33 yr） was 1.90% per year. Together with the carbon sequestration of forest floors, this led to total soil carbon stores of approximately 101.83 Mg/hm^2 over the 33-year chronosequence. Within the relatively short time span, carbon sequestration occurred mainly In tree blomees, whereas soil carbon stores were clearly higher In the 250-year-old plantation （184 Mg/hm^2）. The ongoing redistribution of mineral soil carbon In the young stands and the higher soil carbon contents In the 250-year-old afforested stand suggest that nutrient-rich afforestation soils may become greater sinks for carbon （C） In the long term.