Effects of body size,diet, and transience on the demography of the arboreal boid snake Corallus grenadensis on Carriacou (Grenada Grenadines,West Indies)

Remarkably little is known about the demography of snakes in the family Boidae. This lack of information may be attributed, in part, to low population densities on the Neotropical mainland, rendering capture-recapture methods impractical for many species. Conversely, islands support fewer species but snake densities can be much higher. Corallus grenadensis is an arboreal boid endemic to the Grenada Bank and, relative to mainland boids, can be amazingly abundant. As young, its diet is comprised largely of native Anolis lizards, a ubiquitous and abundant food source; it then undergoes an ontogenetic shift in diet to a less abundant resource, rodents. From 2015 to 2019, we marked 254 C. grenadensis and used capture–recapture models to estimate abundance, capture probabilities, survival, and the proportion of transients. We hypothesized that the transient effect would increase with body size (snout–vent length [SVL]), prompted by their ontogenetic shift in diet. Capture probabilities increased with sampling effort and decreased with increasing SVL. Abundance ranged from 96 to 141 individuals and annual resident survival was 0.71, 95% confidence interval (CI) = 0.54–0.83. The proportion of transients increased with increasing SVL, with the estimate being distinguishable from zero starting at ~810 mm SVL, coinciding with the size at which their dietary shift from ectothermic to endothermic prey begins. Ontogenetic dietary shifts are widespread in snakes and occur in at least 11 of 17 species of West Indian boids. Thus, the prominence of transients in our study may be indicative of its demographic and ecological importance among other snake species.     

Adenomatous polyposis coli protein regulates the cellular response to DNA replication stress

The adenomatous polyposis coli (APC) tumor suppressor traffics between nucleus and cytoplasm to perform distinct functions. Here we identify a specific role for APC in the DNA replication stress response. The silencing of APC caused an accumulation of asynchronous cells in early S phase and delayed S phase progression in cells released from hydroxyurea-mediated replication arrest. Immunoprecipitation assays revealed a selective binding of APC to replication protein A 32kDa subunit (RPA32), and the APC-RPA32 complex increased at chromatin after hydroxyurea treatment. Interestingly, APC knock-down prevented accumulation at chromatin of the stress-induced S33- and S29-phosphorylated forms of RPA32, and reduced the expression of ATR-phosphorylated forms of S317-phospho-Chk1 and γ-H2AX. Using RPA32-inducible cells we showed that reconstitution of RPA32 diminished the S-phase delay caused by loss of APC. In contrast to full-length APC, the truncated APC mutant protein expressed in SW480 colon cancer cells was impaired in its binding and regulation of RPA32, and failed to regulate cell cycle after replication stress. We propose that APC associates with RPA at stalled DNA replication forks and promotes the ATR-dependent phosphorylation of RPA32, Chk1 and γ-H2AX in response to DNA replication stress, thereby influencing the rate of re-entry into the cell cycle.     

硫氧还蛋白抗体柱的制备

目的:探索硫氧还蛋白(Trx)抗体柱对Trx融合蛋白纯化的可行性。方法与结果:对含有Trx基因的质粒表达载体pTrxFus进行改造,在Trx读框之后加入6×His序列,并在大肠杆菌中表达C端带有6×His标签的Trx,经Ni2+柱亲和纯化后制备多克隆抗体;把经蛋白A纯化后的抗体偶联在溴化氰活化的琼脂糖凝胶上,制成Trx抗体柱;用此抗体柱纯化与Trx融合表达的豇豆胰蛋白酶抑制剂(CpTI),SDS-PAGE结果显示获得了纯度较高的Trx-CpTI。结论:用Trx抗体制成的免疫亲和层析柱可以有效纯化Trx融合蛋白。     

Are environmental factors important facilitators of pompom weed (<Emphasis Type="Italic">Campuloclinium macrocephalum</Emphasis>) invasion in South African rangelands?

The absence of natural enemies being keystone to the success of invasive alien plants (IAPs) can only be accepted once all the factors governing the invader and the ecosystems it invades have been established. Few studies have attempted this approach. This study reports on the relations between the invasive alien forb Campuloclinium macrocephalum (Less.) DC. (pompom weed), herbivory and the ecology of the rangelands invaded in South Africa. Eighty invaded rangelands in Gauteng Province were studied. Pompom weed herbivory was insignificant with the greatest damage being caused by native grasshoppers. Rainfall, topography and soil texture were the primary drivers of vegetation pattern. Pompom weed exhibited disturbance-mediated invasion strategies, favouring rangelands affected by non-sustainable commercial grazing practices, abandoned agricultural fields and drained wetlands. It invaded vegetation in poor condition with sward basal cover <19%. Weed density was exacerbated by high fire frequency. Vegetation susceptible to pompom weed was also invaded by other alien and native pasture weeds. The absence of natural enemies could give pompom weed a competitive advantage over native pioneer cohorts in disturbed rangelands, but is unlikely to increase fitness enabling its establishment in vegetation in good condition. Grazing strategies that promote the dominance of grass species adapted to frequent non-selective defoliation appear to restrict pompom weed better than degraded rangelands that are not utilised. Biotic resistance of rangelands to pompom weed invasion will be greatest in vegetation in good condition and under good management. The low abundance of pompom weed in rangelands in communal areas and fence-line contrasts in invaded and un-invaded road reserves warrants further investigation.     

Regulation of β-catenin nuclear dynamics by GSK-3β involves a LEF-1 positive feedback loop

Nuclear localization of β-catenin is integral to its role in Wnt signaling and cancer. Cellular stimulation by Wnt or lithium chloride (LiCl) inactivates glycogen synthase kinase-3β (GSK-3β), causing nuclear accumulation of β-catenin and transactivation of genes that transform cells. β-catenin is a shuttling protein; however, the mechanism by which GSK-3β regulates β-catenin nuclear dynamics is poorly understood. Here, fluorescence recovery after photobleaching assays were used to measure the β-catenin-green fluorescent protein dynamics in NIH 3T3 cells before and after GSK-3β inhibition. We show for the first time that LiCl and Wnt3a cause a specific increase in β-catenin nuclear retention in live cells and in fixed cells after detergent extraction. Moreover, LiCl reduced the rate of nuclear export but did not affect import, hence biasing β-catenin transport toward the nucleus. Interestingly, the S45A mutation, which blocks β-catenin phosphorylation by GSK-3β, did not alter nuclear retention or transport, implying that GSK-3β acts through an independent regulator. We compared five nuclear binding partners and identified LEF-1 as the key mediator of Wnt3a and LiCl-induced nuclear retention of β-catenin. Thus, Wnt stimulation triggered a LEF-1 positive feedback loop to enhance the nuclear chromatin-retained pool of β-catenin by 100-300%. These findings shed new light on regulation of β-catenin nuclear dynamics.     

Structure and function of BamE within the outer membrane and the β-barrel assembly machine

Insertion of folded proteins into the outer membrane of Gram-negative bacteria is mediated by the essential β-barrel assembly machine (Bam). Here, we report the native structure and mechanism of a core component of this complex, BamE, and show that it is exclusively monomeric in its native environment of the periplasm, but is able to adopt a distinct dimeric conformation in the cytoplasm. BamE is shown to bind specifically to phosphatidylglycerol, and comprehensive mutagenesis and interaction studies have mapped key determinants for complex binding, outer membrane integrity and cell viability, as well as revealing the role of BamE within the Bam complex.     

创伤患者急性肾功能损伤诊断与治疗

目的:探讨患者创伤后发生急性肾损伤的患者发病率、临床特点以及发病危险因素,以便有效预防和及早治疗。方法:回顾性分析我院重症监护室2004年1月至2010年12月收治的创伤患者相关临床资料,分析创伤后急性肾损伤的发病率以及发病危险因素。结果:共有106例患者纳入我们的研究,其中47例患者创伤后并发急性肾损伤。在发生急性肾损伤患者中,平均年龄为31±19岁,84.6%为男性;其中25例为脓毒血症引起,18例是因为低血压导致急性肾功能损伤。所有患者中,24例患者出现了少尿的症状,19例患者进行了透析治疗。腹部外伤[(OR)=3.66,P=0.027]和应用呋塞米[(OR=4.10,P=0.026)]是发生急性肾损伤的危险因素。结论:急性肾损伤时创伤后的严重并发症之一,死亡率高。只有找到创伤后发生急性肾损伤的危险因素,才能有效预防和及早治疗。     

中药夏枯草对人甲状腺癌细胞系SW579增殖周期及凋亡的影响

目的:探讨夏枯草对人甲状腺癌细胞系SW579细胞生长的抑制作用及其对细胞增殖周期和凋亡的影响。方法:采用甲基噻唑(MTT)比色法和生长曲线测定不同浓度夏枯草在不同作用时间内对在体外培养SW579细胞增殖的影响,同时应用流式细胞术检测细胞增殖周期及凋亡率的变化。结果:夏枯草可在G0/G1期阻滞人甲状腺癌细胞系SW579的增殖,使S期细胞比率降低;在一定范围内,夏枯草的浓度越高、作用时间越长,对肿瘤细胞生长的抑制作用越强,凋亡率也越高。结论:夏枯草能抑制人甲状腺癌细胞系SW579细胞生长,并诱导细胞凋亡而阻止细胞周期。     

Tuberous sclerosis-2 (TSC2) regulates the stability of death-associated protein kinase-1 (DAPK) through a lysosome-dependent degradation pathway

We previously identified a novel interaction between tuberous sclerosis-2 (TSC2) and death-associated protein kinase-1 (DAPK), the consequence being that DAPK catalyses the inactivating phosphorylation of TSC2 to stimulate mammalian target of rapamycin complex 1 (mTORC1) activity. We now report that TSC2 binding to DAPK promotes the degradation of DAPK. We show that DAPK protein levels, but not gene expression, inversely correlate with TSC2 expression. Furthermore, altering mTORC1 activity does not affect DAPK levels, excluding indirect effects of TSC2 on DAPK protein levels through changes in mTORC1 translational control. We provide evidence that the C-terminus regulates TSC2 stability and is required for TSC2 to reduce DAPK protein levels. Importantly, using a GTPase-activating protein-dead missense mutation of TSC2, we demonstrate that the effect of TSC2 on DAPK is independent of GTPase-activating protein activity. TSC2 binds to the death domain of DAPK and we show that this interaction is required for TSC2 to reduce DAPK protein levels and half-life. Finally, we show that DAPK is regulated by the lysosome pathway and that lysosome inhibition blocks TSC2-mediated degradation of DAPK. Our study therefore establishes important functions of TSC2 and the lysosomal-degradation pathway in the control of DAPK stability, which taken together with our previous findings, reveal a regulatory loop between DAPK and TSC2 whose balance can either promote: (a) TSC2 inactivation resulting in mTORC1 stimulation, or (b) DAPK degradation via TSC2 signalling under steady-state conditions. The fine balance between DAPK and TSC2 in this regulatory loop may have subtle but important effects on mTORC1 steady-state function.     

Magnetic Resonance Imaging Quantification of Pulmonary Perfusion using Calibrated Arterial Spin Labeling

This demonstrates a MR imaging method to measure the spatial distribution of pulmonary blood flow in healthy subjects during normoxia (inspired O₂, fraction (F_IO₂) = 0.21) hypoxia (F_IO₂ = 0.125), and hyperoxia (F_IO₂ = 1.00). In addition, the physiological responses of the subject are monitored in the MR scan environment. MR images were obtained on a 1.5 T GE MRI scanner during a breath hold from a sagittal slice in the right lung at functional residual capacity. An arterial spin labeling sequence (ASL-FAIRER) was used to measure the spatial distribution of pulmonary blood flow ^1,2 and a multi-echo fast gradient echo (mGRE) sequence ³ was used to quantify the regional proton (i.e. H₂O) density, allowing the quantification of density-normalized perfusion for each voxel (milliliters blood per minute per gram lung tissue). With a pneumatic switching valve and facemask equipped with a 2-way non-rebreathing valve, different oxygen concentrations were introduced to the subject in the MR scanner through the inspired gas tubing. A metabolic cart collected expiratory gas via expiratory tubing. Mixed expiratory O₂ and CO₂ concentrations, oxygen consumption, carbon dioxide production, respiratory exchange ratio, respiratory frequency and tidal volume were measured. Heart rate and oxygen saturation were monitored using pulse-oximetry. Data obtained from a normal subject showed that, as expected, heart rate was higher in hypoxia (60 bpm) than during normoxia (51) or hyperoxia (50) and the arterial oxygen saturation (SpO₂) was reduced during hypoxia to 86%. Mean ventilation was 8.31 L/min BTPS during hypoxia, 7.04 L/min during normoxia, and 6.64 L/min during hyperoxia. Tidal volume was 0.76 L during hypoxia, 0.69 L during normoxia, and 0.67 L during hyperoxia. Representative quantified ASL data showed that the mean density normalized perfusion was 8.86 ml/min/g during hypoxia, 8.26 ml/min/g during normoxia and 8.46 ml/min/g during hyperoxia, respectively. In this subject, the relative dispersion⁴, an index of global heterogeneity, was increased in hypoxia (1.07 during hypoxia, 0.85 during normoxia, and 0.87 during hyperoxia) while the fractal dimension (Ds), another index of heterogeneity reflecting vascular branching structure, was unchanged (1.24 during hypoxia, 1.26 during normoxia, and 1.26 during hyperoxia). Overview. This protocol will demonstrate the acquisition of data to measure the distribution of pulmonary perfusion noninvasively under conditions of normoxia, hypoxia, and hyperoxia using a magnetic resonance imaging technique known as arterial spin labeling (ASL). Rationale: Measurement of pulmonary blood flow and lung proton density using MR technique offers high spatial resolution images which can be quantified and the ability to perform repeated measurements under several different physiological conditions. In human studies, PET, SPECT, and CT are commonly used as the alternative techniques. However, these techniques involve exposure to ionizing radiation, and thus are not suitable for repeated measurements in human subjects.Download video file.^{(74M, mov)}