阿尔茨海默病(Alzheimer’s Disease,AD)与动力相关蛋白1(dynamin-related protein 1,Drp1)

阿尔茨海默病(AD)已成为威胁老年人生活的一种常见病,对老年人的生活质量有着严重的影响,目前尚无有效地防治方法。最新研究发现在阿尔茨海默病的病理发生中,神经细胞伴有显著的线粒体代谢紊乱和动态变化的异常,其中动力相关蛋白1(Drp1)是参与线粒体动态变化的关键分子。深入研究阿尔茨海默病中线粒体动态变化的异常及Drp1等关键分子的作用机制,对于揭示AD的发生机制及寻找药物作用靶点具有重要意义。综述了Drp1在阿尔茨海默病中的调控机制。     

Surface EMG-force modelling for the biceps brachii and its experimental evaluation during isometric isotonic contractions

The aim of this study was to evaluate a surface electromyography (sEMG) signal and force model for the biceps brachii muscle during isotonic isometric contractions for an experimental set-up as well as for a simulation. The proposed model includes a new rate coding scheme and a new analytical formulation of the muscle force generation. The proposed rate coding scheme supposes varying minimum and peak firing frequencies according to motor unit (MU) type (I or II). Practically, the proposed analytical mechanogram allows us to tune the force contribution of each active MU according to its type and instantaneous firing rate. A subsequent sensitivity analysis using a Monte Carlo simulation allows deducing optimised input parameter ranges that guarantee a realistic behaviour of the proposed model according to two existing criteria and an additional one. In fact, this proposed new criterion evaluates the force generation efficiency according to neural intent. Experiments and simulations, at varying force levels and using the optimised parameter ranges, were performed to evaluate the proposed model. As a result, our study showed that the proposed sEMG–force modelling can emulate the biceps brachii behaviour during isotonic isometric contractions.     

Arabidopsis Villins Promote Actin Turnover at Pollen Tube Tips and Facilitate the Construction of Actin Collars

Apical actin filaments are crucial for pollen tube tip growth. However, the specific dynamic changes and regulatory mechanisms associated with actin filaments in the apical region remain largely unknown. Here, we have investigated the quantitative dynamic parameters that underlie actin filament growth and disappearance in the apical regions of pollen tubes and identified villin as the major player that drives rapid turnover of actin filaments in this region. Downregulation of Arabidopsis thaliana VILLIN2 (VLN2) and VLN5 led to accumulation of actin filaments at the pollen tube apex. Careful analysis of single filament dynamics showed that the severing frequency significantly decreased, and the lifetime significantly increased in vln2 vln5 pollen tubes. These results indicate that villin-mediated severing is critical for turnover and departure of actin filaments originating in the apical region. Consequently, the construction of actin collars was affected in vln2 vln5 pollen tubes. In addition to the decrease in severing frequency, actin filaments also became wavy and buckled in the apical cytoplasm of vln2 vln5 pollen tubes. These results suggest that villin confers rigidity upon actin filaments. Furthermore, an observed decrease in skewness of actin filaments in the subapical region of vln2 vln5 pollen tubes suggests that villin-mediated bundling activity may also play a role in the construction of actin collars. Thus, our data suggest that villins promote actin turnover at pollen tube tips and facilitate the construction of actin collars.     

Limited antioxidant effect after consumption of a single dose of tomato sauce by young males,despite a rise in plasma lycopene

This study investigated the effect of a single dose of tomato sauce on healthy male volunteers in a randomized crossover study. Healthy male subjects (n = 10) were enrolled. Placebo (rice and olive oil) or tomato (tomato sauce, rice and olive oil) meals were provided to the volunteers. Blood and urine samples were taken before consumption of meal (0 h) and 2, 4, 6, 24 and 48 h after meal. Consumption of tomato sauce increased plasma lycopene level by 5–22%, with a maximum level at 24 h (p<0.01) after the meal. Levels of plasma F₂-isoprostanes, hydroxyeicosatetraenoic acid products, allantoin and urinary 8-hydroxy-2′-deoxyguanosine did not change after either meal, but urinary F₂-isoprostanes (p<0.05) significantly decreased at 48 h compared to 0 h after the tomato sauce meal. This study showed that a single dose of tomato sauce meal had only a limited antioxidant effect in vivo.     

Pharmacokinetics Study of Amoxycillin and Clavulanic acid (8:1)-A New Combination in Healthy Chinese Adult Male Volunteers Using the LC–MS/MS Method

New oral granules of amoxicillin and clavulanic acid in 8:1 ratio have recently been developed and approved to conduct clinical trial in China. To date, there has been no report studying the pharmacokinetic characteristics of amoxicillin and clavulanic acid in man. Therefore, it is urgent to investigate the pharmacokinetic properties of amoxicillin and clavulanic acid in man. The aim of the study was to assess the pharmacokinetic properties of amoxicillin and clavulanic acid in 8:1 with different dosage in healthy volunteers and provide support for this drug to obtain marketing authorization in China. A liquid chromatography-tandem mass spectrometry method for determining the concentration of amoxicillin and clavulanic acid in human plasma was developed and applied to this open-label, single- and multiple-dose Pharmacokinetics study. Subjects were randomized to receive a single dose of 1, 2, and 4 pouches of the test granulation of amoxicillin and clavulanic acid in 8:1 ratio (amoxicillin is 250 mg and clavulanic acid is 31.25 mg per pouch). In the single-dose phase, blood samples were collected before dosing and at 0.25, 0.5, 0.75, 1, 1.5, 2, 2.5, 3, 5, 8, 12, and 24 h after drug administration. In the multiple-dose phase, samples were obtained before drug administration on days 1, 2, 3, and 4 to determine the C_min of amoxicillin and clavulanic acid. In the 4th day, samples were collected from 0.25 to 24 h after drug administration. Profiles of the concentration–time curves of amoxicillin and clavulanic acid were best fitted to two-compartment model. In this group of healthy Chinese subjects, the pharmacokinetics of amoxicillin fitted the linear dynamic feature at doses of 250,500 and 1,000 mg, and not obviously about clavulanic acid at doses of 31.25, 62.5, and 125 mg. The t _1/2 of single dose and multidoses were (1.45 ± 0.12) and (1.44 ± 0.26) h of amoxicillin and (1.24 ± 0.23) and (1.24 ± 0.17) of clavulanic acid, respectively; The AUC_0–24 of single dose and multidoses were (27937.85 ± 4265.59) and (24569.80 ± 3663.63) ng h mL^?1 of amoxicillin and (891.45 ± 194.30) and (679.61 ± 284.05) ng h mL^?1 of clavulanic acid, respectively; The C_max of single dose and multidoses were (8414.58 ± 1416.78) and (7929.17 ± 1291.54) ng mL^?1 of amoxicillin and (349.00 ± 89.54) and (289.00 ± 67.36) ng h mL^?1 of clavulanic acid, respectively. t _1/2, AUC_0–24, and C_max were similar after multiple-dose administration and after single-dose administration, suggesting that amoxicillin and clavulanic acid do not accumulate with multiple-dose administration of 500 and 62.5 mg, respectively.     

The Relationship Between Insulin Resistance and CpG Island Methylation of LMNA Gene in Polycystic Ovary Syndrome

We sought to investigate the relationship between the changes of CpG island methylation status of LMNA gene and insulin resistance in polycystic ovary syndrome (PCOS) patients. The genome-wide methylation microarray screening was done in three PCOS cases of insulin resistance and one case of a normal woman. The PCOS insulin resistance-related genes were identified as indicated by the results of gene chip screening. Then, 24 cases of insulin-resistant PCOS patients and 24 cases of normal individuals were studied to identify the effects of the candidate genes using genome-wide study of DNA from the peripheral blood analyzed by MassARRAY^®EpiTYPER? DNA methylation analysis technique. We found that the methylation status of CpG island in the promoter area of LMNA gene was changed. The 20 CG sites in CpG island of LMNA gene were examined using case control experiment among which 12 CpG sites differed significantly (P < 0.05) between two groups while the remaining eight CpG sites differed non-significantly. We, therefore, concluded that the changes in the hypermethylation status of CpG island of LMNA gene were related to the insulin resistance in PCOS patients, indicating that this gene may be involved in the regulation of PCOS-associated insulin resistance.     

Absolute Quantification of E1, Ubiquitin-Like Proteins and Nedd8–MLN4924 Adduct by Mass Spectrometry

Ubiquitin (Ub) and ubiquitin-like (Ubl) proteins regulate a variety of important cellular processes by forming covalent conjugates with target proteins or lipids. Ubl conjugation is catalyzed by a cascade of proteins including activating enzymes (E1), conjugating enzymes (E2), and in many cases ligation enzymes (E3). The discovery of MLN4924 (Brownell et al., Mol Cell 37: 102–111, 1), an investigational small molecule that is a mechanism-based inhibitor of NEDD8-activating enzyme (NAE), reveals a promising strategy of targeting E1/Ubl pathway for therapeutic purposes. In order to better understand, the biochemical dynamics of Ubl conjugation in cells and tissues, we have developed a mass spectrometry-based method to quantify E1 and Ubls using isotope-labeled proteins as internal standards. Furthermore, we have used the described method to quantify levels of the covalent Nedd8-inhibitor adduct formed in MLN4924 treated cells and tissues. The Nedd8–MLN4924 adduct is a tight-binding inhibitor of NAE, and its cellular concentration represents an indirect pharmacodynamic readout of NAE/Nedd8 pathway inhibition.     

Constitutive expression of cell wall invertase genes increases grain yield and starch content in maize

Grain size, number and starch content are important determinants of grain yield and quality. One of the most important biological processes that determine these components is the carbon partitioning during the early grain filling, which requires the function of cell wall invertase. Here, we showed the constitutive expression of cell wall invertase–encoding gene from Arabidopsis, rice (Oryza sativa) or maize (Zea mays), driven by the cauliflower mosaic virus (CaMV) 35S promoter, all increased cell wall invertase activities in different tissues and organs, including leaves and developing seeds, and substantially improved grain yield up to 145.3% in transgenic maize plants as compared to the wild‐type plants, an effect that was reproduced in our 2‐year field trials at different locations. The dramatically increased grain yield is due to the enlarged ears with both enhanced grain size and grain number. Constitutive expression of the invertase‐encoding gene also increased total starch content up to 20% in the transgenic kernels. Our results suggest that cell wall invertase gene can be genetically engineered to improve both grain yield and grain quality in crop plants.     

Inhibition of x‐box binding protein 1 reduces tunicamycin‐induced apoptosis in aged murine macrophages

Endoplasmic reticulum (ER) stress is induced by the accumulation of unfolded and misfolded proteins in the ER. Although apoptosis induced by ER stress has been implicated in several aging‐associated diseases, such as atherosclerosis, it is unclear how aging modifies ER stress response in macrophages. To decipher this relationship, we assessed apoptosis in macrophages isolated from young (1.5–2 months) and aged (16–18 months) mice and exposed the cells to the ER stress inducer tunicamycin. We found that aged macrophages exhibited more apoptosis than young macrophages, which was accompanied by reduced activation of phosphorylated inositol‐requiring enzyme‐1 (p‐IRE1α), one of the three key ER stress signal transducers. Reduced gene expression of x‐box binding protein 1 (XBP1), a downstream effector of IRE1α, enhanced p‐IRE1α levels and reduced apoptosis in aged, but not young macrophages treated with tunicamycin. These findings delineate a novel, age‐dependent interaction by which macrophages undergo apoptosis upon ER stress, and suggest an important protective role of IRE1α in aging‐associated ER stress‐induced apoptosis. This novel pathway may not only be important in our understanding of longevity, but may also have important implications for pathogenesis and potential treatment of aging‐associated diseases in general.