冲击波负压对大鼠肺致伤效应的初步观察

观察了不同的冲击波负压峰值对大鼠肺的影响。各种条件下的冲击波负压值可由负压发生装置来模拟调节,这种装置可满足化爆、核爆和爆炸性减压下负压参数的一般要求,参数稳定,重复性好。冲击波负压峰值范围为-13～-90kPa,下降时间为1～90ms,持续时间为14～2 000ms。6组Wistar系大鼠,分别暴露在-47.2～-84.0kPa的冲击波负压环境中,伤后立即解剖动物,重点观察肺伤情。实验结果显示,在上述冲击波负压环境中,肺可出现从无伤至极重度伤;出血、充血以及肺表面压痕酷似肺冲击伤的病理表现。随着冲击波负压峰值的变化,各组肺伤情亦随着变化,冲击波负压峰值(△P)和减压倍数(P_i/P_a)分别与肺出血面积和动物死亡率相关显著或非常显著。本实验提示,一定条件下的冲击波负压具有明显的致伤作用,且伤情变化范围与超压所致肺伤情变化范围相同,超压和冲击波负压在一定条件下可通过伤情指标等效。     

Highly branched HK peptides are effective carriers of siRNA

BACKGROUND: Both viral and nonviral carriers have been used to carry small interfering RNA molecules (siRNA) to their cytosolic mRNA target. To date, few peptide carriers have been developed that have proved effective for siRNA delivery. Our previous branched carriers composed of histidine and lysine were useful for transfection of plasmids. In this study, we determined if these and more highly branched HK polymers were effective carriers of siRNA. METHODS: Several branched polymers were synthesized on a Ranin Voyager synthesizer. These polymers were then screened for their ability to transfer siRNA into SVR-bag4 cells, MDA-MB-435 cells, and C6 cells. After one polymer, H3K8b, was identified as an effective carrier of siRNA, additional polymers were synthesized to determine the essential domains for siRNA transport. The size/zeta-potential of HK : siRNA complexes were measured with the N4 submicron particle size analyzer and the Delsa 440 SX zeta-potential analyzer, respectively. Toxicity of the highly branched polymers in complex with siRNA was investigated by flow cytometry. RESULTS: In an endothelial cell line (SVR-bag4) that stably expressed beta-galactosidase (beta-gal), an siRNA in complex with the H3K8b polymer inhibited beta-gal expression by more than 80%. In contrast, the polymer H2K4b, which was an effective carrier of plasmids, was not an efficient carrier of siRNA. The size and surface charge did not distinguish effective from ineffective HK carriers of siRNA. By modifying H3K8b, we then determined what properties of H3K8b augmented siRNA delivery. The histidine-rich domain and the length of the terminal arms of H3K8 were important for siRNA delivery. The modestly more effective analog of H3K8b containing an integrin ligand, H3K8b(+RGD), was able to inhibit markedly intracellular beta-gal expression. Furthermore, we determined that H3K8b(+RGD) in complex with a luciferase-targeting siRNA inhibited luciferase expression in MDA-MB-435 cells. At its optimal concentration for inhibiting its target, H3K8b(+RGD) : siRNA complex had minimal toxicity. In contrast, carriers of siRNA such as Oligofectamine and Lipofectamine 2000 were significantly more toxic. CONCLUSIONS: Both the degree of complexity and the sequence specificity are important factors to be considered for developing the HK carrier of siRNA. In particular, we found that certain branched HK polymers (H3K8b, H3K8b(+RGD), and similar structural analogs) with eight terminal branches and a histidine-rich domain were effective carriers of siRNA.     

Simultaneous determination of pyrethroid and pyrethrin metabolites in human urine by gas chromatography-high resolution mass spectrometry

A new developed gas chromatographic-high resolution mass spectrometric method for the sensitive simultaneous determination of trans-chrysanthemumdicarboxylic acid, cis- and trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid, cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane carboxylic acid, 3-phenoxybenzoic acid and 4-fluoro-3-phenoxybenzoic acid in human urine is presented. These metabolites are biomarkers for an exposure to pyrethrum, allethrin, resmethrin, phenothrin, tetramethrin, cyfluthrin, cypermethrin, deltamethrin or permethrin. Therefore, with the help of this method for the first time a complete assessment of exposure to pyrethroid and pyrethrin insecticides is possible. After acid hydrolysis and extraction with tert-butyl-methyl-ether the residue is derivatized with 1,1,1,3,3,3-hexafluoroisopropanol and analyzed by GC/HRMS in electron impact mode (detection limits < 0.1 microg/l) as well as in negative chemical ionization mode (detection limit < 0.05 microg/l urine).     

Evidence for dissociation of chlorophyll b from the main light-harvesting complex in the oligomerization state isolated from marine alga, Bryopsis corticulans

We investigated the composition and organization of chlorophylls in monomers, trimers and oligomers (small aggregates) of the main light-harvesting complex (LHC II) isolated from marine alga, Bryopsis corticulans, using a combination of measurements with reversed-phase high performance liquid chromatography (RP-HPLC) and steady-state spectroscopy of absorption, circular dichroism (CD) and low temperature fluorescence. The composition and organization of the chlorophylls in monomeric and trimeric LHC II were essentially identical to those of LHC II from higher plants. For LHC II oligomers, a large decrease of chlorophyll (Chl) b absorption and of CD signals corresponding to Chl b was consistent with the quantitative analysis of Chl b by RP-HPLC, indicating that oligomerization of the LHC II proteins significantly influenced spectroscopic properties and led to the dissociation of Chl b molecules from LHC II. Our data strongly suggested that protein oligomerization constitutes a structural basis for the decrease of Chl b molecules in LHC II of B. corticulans. The LHC II of B. corticulans might play a photoprotective role with the reduction of the ability of light absorption via alteration of its own structural conformation.     

Cortactin phosphorylation as a switch for actin cytoskeletal network and cell dynamics control

Cortactin is an important molecular scaffold for actin assembly and organization. Novel mechanistic functions of cortactin have emerged with more interacting partners identified, revealing its multifaceted roles in regulating actin cytoskeletal networks that are necessary for endocytosis, cell migration and invasion, adhesion, synaptic organization and cell morphogenesis. These processes are mediated by its multi-domains binding to F-actin and Arp2/3 complex and various SH3 targets. Furthermore, its role in actin remodeling is subjected to regulation by tyrosine and serine/threonine kinases. Elucidating the mechanisms underlying cortactin phosphorylation and its functional consequences would provide new insights to various aspects of cell dynamics control.     

Inhibitory effects of anticancer peptide from Mercenaria on the BGC-823 cells and several enzymes

An anti-cancer peptide was purified from the Mercenaria (Meretrix meretrix Linnaeus) by the method of chromatography on Sephadex G-25 and FPLC, and its molecular weight was determined to be 3147 Da by the way of MALDI-TOF mass spectrum. The effects of this peptide on human gastric gland carcinoma cells (BGC-823) and their cytoskeletal morphology were investigated. The results showed that the peptide could inhibit the proliferation of BGC-823 cells and obviously destroy the skeletal structures of the cells. When the concentration of the peptide reached 4.0 microg/ml, the inhibition percentage of the cell growth was about 60%. The effects of this anticancer peptide on the activities of superoxide dismutase (SOD), alkaline phosphatase (ALP) and tyrosinase were studied. The results showed that the peptide activated ALP and SOD, but inhibit the tyrosinase activity. When the concentration of the peptide reached to 0.5 microg/ml, the relative activities of SOD, ALP and tyrosinase were determined to be 188.5%, 122.0% and 27.5%, respectively.     

Amyloid fibril formation by macrophage migration inhibitory factor

We demonstrate herein that human macrophage migration inhibitory factor (MIF), a pro-inflammatory cytokine expressed in the brain and not previously considered to be amyloidogenic, forms amyloid fibrils similar to those derived from the disease associated amyloidogenic proteins beta-amyloid and alpha-synuclein. Acid denaturing conditions were found to readily induce MIF to undergo amyloid fibril formation. MIF aggregates to form amyloid-like structures with a morphology that is highly dependent on pH. The mechanism of MIF amyloid formation was probed by electron microscopy, turbidity, Thioflavin T binding, circular dichroism spectroscopy, and analytical ultracentrifugation. The fibrillar structures formed by MIF bind Congo red and exhibit the characteristic green birefringence under polarized light. These results are consistent with the notion that amyloid fibril formation is not an exclusive property of a select group of amyloidogenic proteins, and contribute to a better understanding of the factors which govern protein conformational changes and amyloid fibril formation in vivo.     

Spatial structure and genetic diversity of three tropical tree species with different habitat preferences within a natural forest

Analyses of the spatial distribution pattern, spatial genetic structure and genetic diversity were carried out using a 33-ha plot in a hill dipterocarp forest for three dipterocarps with different habitat preferences, i.e. Shorea curtisii on the ridges, Shorea leprosula in the valleys and Shorea macroptera both on the ridges and in the valleys. The significant spatial aggregation in small-diameter trees of all the three species was explained by limited seed dispersal. At the large-diameter trees, only S. macroptera showed random distribution and this might further prove that S. macroptera is habitat generalist, whilst S. curtisii and S. leprosula are habitat specific. The levels of genetic diversity estimated based on five microsatellite loci were high and comparable in all the three studied species. As the three studied species reproduced mainly through outcrossing, the observed high levels of genetic diversity might support the fact that the plant mating system can be used as guideline to infer the levels of genetic diversity, regardless of whether the species is habitat specific or habitat generalist. The lack of spatial genetic structure but significant aggregation in the small-diameter trees of all the three species might indicate limited seed dispersal but extensive pollen flow. Hence, if seed dispersal is restricted but pollen flow is extensive, significant spatial aggregation but no spatial genetic structure will be observed at the small-diameter trees, regardless of whether the species is habitat specific or habitat generalist. The inferred extensive pollen flow might indicate that energetic pollinators are involved in the pollination of Shorea species in the hill dipterocarp forests.