A necrotic cell death model in a protist

While necrotic cell death is attracting considerable interest, its molecular bases are still poorly understood. Investigations in simple biological models, taken for instance outside the animal kingdom, may benefit from less interference from other cell death mechanisms and from better experimental accessibility, while providing phylogenetic information. Can necrotic cell death occur outside the animal kingdom? In the protist Dictyostelium, developmental stimuli induced in an autophagy mutant a stereotyped sequence of events characteristic of necrotic cell death. This sequence included swift mitochondrial uncoupling with mitochondrial 2',7'-dichlorofluorescein diacetate fluorescence, ATP depletion and increased oxygen consumption. This was followed by perinuclear clustering of dilated mitochondria. Rapid plasma membrane rupture then occurred, which was evidenced by time-lapse videos and quantified by FACS. Of additional interest, developmental stimuli and classical mitochondrial uncouplers triggered a similar sequence of events, and exogenous glucose delayed plasma membrane rupture in a nonglycolytic manner. The occurrence of necrotic cell death in the protist Dictyostelium (1) provides a very favorable model for further study of this type of cell death, and (2) strongly suggests that the mechanism underlying necrotic cell death was present in an ancestor common to the Amoebozoa protists and to animals and has been conserved in evolution.     

三种啮齿类动物非酒精性脂肪肝形成及机制探讨

目的 分析物种差异对NAFLD模型复制的影响,探讨不同鼠种NAFLD形成及其机制.方法 长爪沙鼠、SD大鼠、ICR小鼠各20只,按种属随机分为对照组及模型组,对照组给予普通饲料,模型组给予高脂饲料.16周后,观察肝脏HE及Mallory三色染色病理变化,计算肝指数,检测血清血脂(CHO、TG、LDL-c、HDL-c)、肝功能(GOP、GPT)及肝组织中抗氧化酶(SOD、GSH-PX、CAT)活性及羟脯氨酸(Hyp)、丙二醛(MDA)、游离脂肪酸(FFA)水平.结果 与对照组比较,各模型组:沙鼠Hyp、CHO、TG、LDL-c、HDL-c、肝指数、GOP、GPT、MDA、FFA均升高,SOD、GSH-PX、CAT活性降低(P＜0.05,P＜0.01),肝脏出现纤维化;大鼠CHO、肝指数、GOP、GPT、FFA、SOD活性升高,MDA含量、GSH-PX、CAT活性降低(P ＜0.05,P＜0.01),有局灶性脂肪肝炎;小鼠CHO、LDL-c、HDL-c、肝指数、CAT活性升高,MDA含量降低(P ＜0.05,P＜0.01),肝脏病理正常.结论 三种动物在脂质代谢、肝功能、氧化应激等方面有显著的差异,并形成了不同的NAFLD模型:沙鼠形成伴高TG、CHO血症的肝纤维化模型、大鼠形成伴高CHO血症的局灶性脂肪肝炎模型、小鼠形成高胆固醇血症模型但肝脏未发生明显的病理改变.     

长春新碱诱导建立人结肠癌多药耐受性小鼠模型及MDR1和MRP1基因表达

目的建立人结肠癌多药耐受性动物模型并初步探索其耐药机制。方法结合体内外诱导方法建立人结肠癌多药耐受性动物模型,利用VCR和CTX的肿瘤抑制实验评价其MDR特性;利用real-time PCR和West-ern blotting等方法分析其P-gp/MDR1和MRP1基因和蛋白的表达。结果肿瘤抑制实验结果显示,MDR和敏感型结肠癌模型的肿瘤生长速度差异不显著,MDR结肠癌动物模型对于VCR和CTX的耐药性均有较大程度的提高;表达分析结果显示,人结肠癌MDR动物模型的P-gp/MDR1表达水平有较大提高,而MRP1表达没有显著变化。结论人结肠癌多药耐受性动物模型具有较好的多药耐受性,其多药耐受性表型主要是由于P-gp/MDR1过量表达所导致。     

TGFβ-induced GRK2 expression attenuates AngII-regulated vascular smooth muscle cell proliferation and migration

Through diametric actions, the transforming growth factor β (TGFβ) and Angiotensin II (AngII) play important roles in regulating various biological responses such as cell proliferation and migration. Signaling initiated by TGFβ and AngII occurs through two structurally and functionally distinct receptor super families, the serine/threonine kinase and G protein-coupled receptors (GPCRs). Previously, we identified the G protein-coupled receptor kinase-2 (GRK2), a key regulatory factor in the desensitization of GPCRs, as a direct downstream target of the TGFβ signaling cascade. GRK2 acts through a negative feed-back loop mechanism to terminate TGFβ-induced smad signaling. To investigate the impact of TGFβ-induced GRK2 expression on GPCR signaling, we examined its effect on AngII signaling in vascular smooth muscle cells (VSMCs). In this study, we show that activation of the TGFβ signaling cascade in VSMCs results in increased GRK2 expression levels, which consequently inhibits AngII-induced ERK phosphorylation and antagonizes AngII-induced VSMC proliferation and migration. Moreover, the inhibitory effect of TGFβ on AngII signaling occurs at the Mek-Erk interface and is abrogated when an anti-sense oligonucleotide directed against GRK2 is used. Thus, we conclude that TGFβ signaling antagonizes AngII-induced VSMC proliferation and migration through the inhibition of ERK phosphorylation and that GRK2 is a key factor mediating the cross-talk between these two receptor super families.     

Zinc supplementation does not alter plasma homocysteine,vitamin B12 and red blood cell folate concentrations in French elderly subjects

Background/aimsIn ageing, low folates and vitamin B12 status are frequent and can explain the increase of plasma homocysteine level. Zinc is involved in the folates and vitamin B12 metabolism with opposite actions. The aim of this study was to investigate the effects of zinc supplementation on homocysteine and vitamin B12 plasma levels as well as red blood cell folate level in French ageing subjects participating in the ZENITH study.MethodsApparently healthy middle-aged (55–70 years) and free-living older (70–85 years) subjects were enrolled. They were randomly allocated to three groups: 0, 15 or 30 mg Zn per day for 6 months as zinc gluconate in addition to their usual dietary intake.ResultsAt baseline, plasma homocysteine levels (15.2±3.5 μmol/L) in older people were higher than in the middle-aged subjects (12.7±2.7 μmol/L) and was negatively correlated with vitamin B12 values (p=0.0036, r=?0.215) and with RBC folate levels (p<0.0001, r=?0.30). These results are in agreement with previous data. However, we found no correlation between the biomarkers of zinc status and homocysteine, vitamin B12 or folate levels at baseline. Moreover, 6-month zinc supplementation did not modify homocysteine, vitamin B12 and RBC folate values in either of the groups.ConclusionsZinc supplementation at moderate doses do not lead to deleterious effect on folate or vitamin B12 status in ageing healthy free-living people, but does not have any beneficial effects on homocysteine metabolism either.     

Reporting of Quantitative Protein Electrophoresis in Australia and New Zealand: a Call for Standardisation

Background

The lack of guidelines on reporting standards for protein electrophoresis may have led to significant differences in reports from different laboratories.

Objective

To determine the extent of variation in reporting of protein electrophoresis results in Australia and New Zealand.

Method

Questionnaires were distributed to laboratories throughout Australia and New Zealand asking about protein electrophoresis practices and reporting.

Results

Extensive variation was found in the following reporting practices: (a) units for urine Bence Jones protein (BJP); (b) reporting absence of a paraprotein rather than a normal pattern; (c) numerical reporting of all protein fractions or only the paraprotein; (d) warning of possible inaccuracy in the serum immunoglobulin result of the paraprotein type; (e) co-migration of a paraprotein with a normal serum protein; (f) use of a confirmatory test when a known paraprotein is no longer detectable.

Conclusions

A working party should be established to make recommendations on the reporting of protein electrophoresis. Implementation of such recommendations should reduce both report variation between laboratories and the risk of misinterpretation of reports.     

Effects of an exotic invasive macrophyte (tropical signalgrass) on native plant community composition,species richness and functional diversity

1. The issue of freshwater species being threatened by invasion has become central in conservation biology because inland waters exhibit the highest species richness per unit area, but apparently have the highest extinctions rates on the planet. 2. In this article, we evaluated the effects of an exotic, invasive aquatic grass (Urochloa subquadripara– tropical signalgrass) on the diversity and assemblage composition of native macrophytes in four Neotropical water bodies (two reservoirs and two lakes). Species cover was assessed in quadrats, and plant biomass was measured in further quadrats, located in sites where tropical signalgrass dominated (D quadrats) and sites where it was not dominant or entirely absent (ND quadrats). The effects of tropical signalgrass on macrophyte species richness, Shannon diversity and number of macrophyte life forms (a surrogate of functional richness) were assessed through regressions, and composition was assessed with a DCA. The effects of tropical signalgrass biomass on the likelihood of occurrence of specific macrophyte life forms were assessed through logistic regression. 3. Tropical signalgrass had a negative effect on macrophyte richness and Shannon and functional diversity, and also influenced assemblage composition. Emergent, rooted with floating stems and rooted submersed species were negatively affected by tropical signalgrass, while the occurrence of free‐floating species was positively affected. 4. Our results suggest that competition with emergent species and reduction of underwater radiation, which reduces the number of submersed species, counteract facilitation of free‐floating species, contributing to a decrease in plant diversity. In addition, homogenisation of plant assemblages shows that tropical signalgrass reduces the beta diversity in the macrophyte community. 5. Although our results were obtained at fine spatial scales, they are cause for concern because macrophytes are an important part of freshwater diversity.     

Alzheimer's β-amyloid peptide blocks vascular endothelial growth factor mediated signaling via direct interaction with VEGFR-2

Beta-amyloid peptides (Aβ) are the major constituents of senile plaques and cerebrovascular deposits in the brains of Alzheimer's disease patients. We have shown previously that soluble forms of Aβ are anti-angiogenic both in vitro and in vivo . However, the mechanism of the anti-angiogenic activity of Aβ peptides is unclear. In this study, we examined the effects of Aβ1–42 on vascular endothelial growth factor receptor 2 (VEGFR-2) signaling, which plays a key role in angiogenesis. Aβ inhibited VEGF-induced migration of endothelial cells, as well as VEGF-induced permeability of an in vitro model of the blood brain barrier. Consistently, exogenous VEGF dose-dependently antagonized the anti-angiogenic activity of Aβ in a capillary network assay. Aβ1–42 also blocked VEGF-induced tyrosine phosphorylation of VEGFR-2 in two types of primary endothelial cells, suggesting an antagonistic action of Aβ toward VEGFR-2 signaling in cells. Moreover, Aβ was able to directly interact with the extracellular domain of VEGFR-2 and to compete with the binding of VEGF to its receptor in a cell-free assay. Co-immunoprecipitation experiments confirmed that Aβ can bind VEGFR-2 both in vitro and in vivo . Altogether, our data suggest that Aβ acts as an antagonist of VEGFR-2 and provide a mechanism explaining the anti-angiogenic activity of Aβ peptides.