大熊猫的生境选择特征

基于王朗国家级自然保护区1997—2009年的连续监测数据,利用分布频率法和Bai-ley法,从地形因子、森林群落结构和主食竹3个方面研究了大熊猫的生境选择特征.结果表明:王朗国家级自然保护区的大熊猫对生境具有明显的选择性.在地形上,多选择海拔在2500～3000 m的山体脊部、上部和中部的均匀坡和凸坡,坡向西南,坡度在6°～30°,与水源距离>300 m的环境;森林群落结构上,多选择起源为次生林、针阔混交林,微生境为竹林的生境,乔木平均高度在20～29 m,灌木盖度在0～24%;主食竹多选择平均高度在2～5 m,竹丛盖度>50%,混生,生长状况良好的缺苞箭竹.     

Biosynthesis of bile acids in a variety of marine bacterial taxa

Several marine bacterial strains, which were isolated from seawater off the island Dokdo, Korea, were screened to find new bioactive compounds such as antibiotics. Among them, Donghaeana dokdonensis strain DSW-6 was found to produce antibacterial agents, and the agents were then purified and analyzed by LC-MS/MS and 1D- and 2D-NMR spectrometries. The bioactive compounds were successfully identified as cholic acid and glycine-conjugated glycocholic acid, the 7alpha-dehydroxylated derivatives (deoxycholic acid and glycodeoxycholic acid) of which were also detected in relatively small amounts. Other masine isolates, taxonomically different from DSW-6, were also able to produce the compounds in a quite different production ratio from DSW-6. As far as we are aware of, these bile acids are produced by specific members of the genus Streptomyces and Myroides, and thought to be general secondary metabolites produced by a variety of bacterial taxa that are widely distributed in the sea.     

Egr-1, a new downstream molecule of Epstein-Barr virus latent membrane protein 1

To investigate the effect of Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) on human cancer cells, we sought to identify and analyze potential target genes that were differentially expressed in the presence and absence of LMP1. Our cDNA microarray analysis revealed that expression of early growth response gene-1 (Egr-1) was increased by LMP1 expression in MCF7 and Jurkat cells. An NFkappaB inhibitor (SN50) antagonized LMP1-induced enhancement of Egr-1 expression, indicating that LMP1 induced Egr-1 via NFkappaB. Furthermore, three lines of evidence indicated that Egr-1 was required for LMP1-induced cancer cell survival. First, Egr-1 expression enhanced the survival of doxorubicin-treated MCF7 cells. Second, inhibition of Egr-1 expression by siRNA (siEgr-1) effectively suppressed LMP-1-induced survival of MCF7 cells. Third, Egr-1 knockdown decreased LMP1-induced expression of Bfl-1. Similar relationships among EBV infection, Egr-1 and drug resistance were also observed in tissues of peripheral T-cell lymphoma-unspecified (PTCL-u) patients.     

Hydrotropic polymeric micelles for enhanced paclitaxel solubility: in vitro and in vivo characterization

The purpose of this investigation was to characterize the in vitro stability and in vivo disposition of paclitaxel in rats after solubilization of paclitaxel into hydrotropic polymeric micelles. The amphiphilic block copolymers consisted of a micellar shell-forming poly(ethylene glycol) (PEG) block and a core-forming poly(2-(4-vinylbenzyloxy)-N,N-diethylnicotinamide) (P(VBODENA)) block. N,N-Diethylnicotinamide (DENA) in the micellar inner core resulted in effective paclitaxel solubilization and stabilization. Solubilization of paclitaxel using polymeric micelles of poly(ethylene glycol)-b-P(D,L-lactide) (PEG-b-PLA) served as a control for the stability study. Up to 37.4 wt % paclitaxel could be loaded in PEG-b-P(VBODENA) micelles, whereas the maximum loading amount for PEG-b-PLA micelles was 27.6 wt %. Thermal analysis showed that paclitaxel in the polymeric micelles existed in the molecularly dispersed amorphous state even at loadings over 30 wt %. Paclitaxel-loaded hydrotropic polymeric micelles retained their stability in water for weeks, whereas paclitaxel-loaded PEG-b-PLA micelles precipitated in a few days. Hydrotropic polymer micelles were more effective than PEG-PLA micelle formulations in inhibiting the proliferation of human cancer cells. Paclitaxel in hydrotropic polymer micelles was administered orally (3.8 mg/kg), intravenously (2.5 mg/kg), or via the portal vein (2.5 mg/kg) to rats. The oral bioavailability was 12.4% of the intravenous administration. Our data suggest that polymeric micelles with a hydrotropic structure are superior as a carrier of paclitaxel due to a high solubilizing capacity combined with long-term stability, which has not been accomplished by other existing polymeric micelle systems.     

8-Hydroxydeoxyguanosine induces senescence-like changes in KG-1, human acute myelocytic leukemia cell line

8-Hydroxydeoxyguanosine (oh⁸dG) treatment induced senescence-like changes in KG-1 cells, a human acute myelocytic leukemia cell line. The oh⁸dG-treated cells stained positive for senescence associated β-galactosidase (SA-β-galactosidase) and had enlarged cell shape, both of which are senescence indexes. The oh⁸dG-treated cells were also cell growth inhibited and arrested at G₁ in the cell cycle. The accumulation of cdk (cyclin dependent kinase) inhibitors, such as p16, p21, and p27, also implies that cellular senescence was induced in oh⁸dG-treated cells. However, these changes were not accompanied by cell differentiation or telomerase activity. Taken together, we conclude that oh⁸dG treatment of KG-1 cells induces cellular senescence.     

Comparative proteomic analysis of virulent Korean Mycobacterium tuberculosis K-strain with other mycobacteria strain following infection of U-937 macrophage

In Korea, the Mycobacterium tuberculosis K-strain is the most prevalent clinical isolates and belongs to the Beijing family. In this study, we conducted comparative porteomics of expressed proteins of clinical isolates of the K-strain with H37Rv, H37Ra as well as the vaccine strain of Mycobacterium bovis BCG following phagocytosis by the human monocytic cell line U-937. Proteins were analyzed by 2-D PAGE and MALDITOF-MS. Two proteins, Mb1363 (probable glycogen phosphorylase GlgP) and MT2656 (Haloalkane dehalogenase LinB) were most abundant after phagocytosis of M. tuberculosis K-strain. This approach provides a method to determine specific proteins that may have critical roles in tuberculosis pathogenesis.     

Synaptic connections of cone bipolar cells that express the neurokinin 1 receptor in the rabbit retina

We have investigated and further characterized, in the rabbit retina, the synaptic connectivity of the ON-type cone bipolar cells that are immunoreactive for an antibody against the neurokinin-1 receptor (NK1R). NK1R-immunoreactive bipolar cell axons terminate in stratum 4 of the inner plexiform layer. The axons of NK1R-positive bipolar cells receive synaptic inputs from amacrine cells through conventional synapses and from putative AII amacrine cells via gap junctions. The major outputs from NK1R-positive bipolar cells make contacts with amacrine cell processes. The most frequent postsynaptic dyads comprise two amacrine cell processes. Double-labeling experiments with antibodies against NK1R and either calretinin or glycine have demonstrated that NK1R-immunoreactive bipolar cells form gap junctions with AII amacrine cells. Thus, NK1R-positive cone bipolar cells, together with calbindin-positive cone bipolar cells, may play an important role in transferring rod signals to the ON-type ganglion cells of the cone pathway in the rabbit retina.I.-B. Kim and M.R. Park contributed equally to this work.This work was supported by the Ministry of Science and Technology of Korea (grant no. M1-0108-00-0059; Neurobiology Support Grant).     

Cell cycle regulation of astrocytes by extracellular nucleotides and fibroblast growth factor-2

Extracellular ATP enhances the mitogenic activity of fibroblast growth factor-2 (FGF2) in astrocytes, but the molecular mechanism underlying this synergistic interaction is not known. To determine whether the potentiating effect of extracellular ATP involves cell cycle control mechanisms, we have measured the expression of cyclins that are induced in different phases of the cell cycle in primary cultures of rat cortical astrocytes. We found that ATP potentiated the ability of FGF2 to stimulate expression of cyclin D1, a regulator of cell cycle entry, as well as cyclin A, a regulator of DNA replication. Because FGF2 and P2 purinergic receptors are coupled to extracellular signal regulated protein kinase (ERK), a key member of a signaling cascade that regulates proliferation, we also investigated the role of ERK in regulating cyclin expression induced by FGF2 and ATP. We found that the potentiating effect of ATP on cyclin expression was significantly reduced by U0126, an inhibitor of MEK, the upstream activator of ERK. P2 receptor agonist studies revealed that UTP enhanced FGF2-induced cyclin expression and mitogenesis whereas 2-methylthioADP was ineffective. By contrast, 2′,3′-O-(4-benzoyl)-benzoyl-ATP markedly inhibited FGF2-induced mitogenesis. Consistent with opposing effects of P2Y and P2X receptors on mitogenesis, UTP stimulated a transient activation of ERK whereas BzATP stimulated a more sustained ERK signal. These findings suggest that signaling by P2Y receptors, most likely of the purine/pyrimidine subtype, enhance the ability of FGF2 to stimulate entry into a new cell cycle, as well as DNA replication, by an ERK-dependent mechanism, whereas signaling by P2X receptors, possibly the P2X7 subtype, inhibits FGF2-induced mitogenesis in astrocytes. Interactions between P2Y, P2X and polypeptide growth factor signaling pathways may have important implications for CNS development as well as injury and repair.     

4-1BB costimulation enhances HSV-1-specific CD8+ T cell responses by the induction of CD11c+CD8+ T cells

Since 4-1BB plays a predominant role in CD8+ T cell responses, we investigated the effects of 4-1BB triggering on the primary and memory CD8+ T responses to HSV-1 infection. 4-1BB was detected on 10-15% of CD4+ and CD8+ T cells following the infection. 4-1BB-positive T cells were in the proliferative mode and showed the enhanced expression of anti-apoptotic proteins. Agonistic anti-4-1BB treatment exerted preferential expansion of CD8+ T cells and gB/H-2Kb-positive CD8+ T cells, and enhanced cytotoxicity against HSV-1 that was mainly mediated by CD11c+CD8+ T cells. CD11c+CD8+ T cells were re-expanded following re-challenge with HSV-1 at post-infection day 50, indicating that CD11c+CD8+ phenotype was maintained in memory CD8+ T cell pool. Our studies demonstrated that 4-1BB stimulation enhanced both primary and memory anti-HSV-1 CD8+ T cell responses, which was mediated by a massive expansion of antigen-specific CD11c+CD8+ T cells.     

Chilling tolerance of cucumber (Cucumis sativus) seedling radicles is affected by radicle length, seedling vigor, and induced osmotic- and heat-shock proteins

Cucumber seedling radicles decrease in chilling tolerance as they increase in length or decrease in vigor. The protein content of the apical 5 mm of the radicle decreased with decreases in chilling tolerance ( R ² = 0.92). This general reduction in protein content was reflected in a decrease of six dehydrin-like proteins with apparent molecular weights of 13.0, 15.0, 16.8, 23.0, 26.8, and 33.5 kDa. The disappearance of naturally occurring dehydrin-like proteins in cucumber seedling radicles as they elongate or lose vigor was correlated with a loss of chilling tolerance. Exposure to an osmotic (0.6 M mannitol) or heat (2 min at 45°C) stress enhanced chilling tolerance. The osmotic-shock treatment induced both chilling tolerance and the appearance or strengthening of dehydrin-like proteins previously present in radicles. The heat-shock treatment also induced high levels of chilling tolerance and protein(s) that reacted with a 23 and 70 kDa antibody. However, these heat-shock protein (HSPs) did not cross react with the probe for dehydrin-like proteins. When organized into high, medium, and low chilling tolerance groups, radicle that were chilling tolerant contained either the 13.0 and 16.8 kDa dehydrin-like proteins, or the 15.0 and 23.0 kDa dehydrin-like proteins, or the 23 or 70 kDa HSP.