The Val103Ile Polymorphism of Melanocortin‐4 Receptor Regulates Energy Expenditure and Weight Gain

Objective: The melanocortin‐4 receptor (MC4R) regulates energy intake. On the basis of animal studies, it may also regulate energy expenditure. Research Methods and Procedures: The effect of the Val103Ile polymorphism of the MC4R gene on energy metabolism was studied in 229 middle‐aged nondiabetic subjects (Group 1, age 51.2 ± 9.8 years, BMI 26.8 ± 4.5 kg/m²) and on weight gain in 1013 elderly subjects (Group 2, age 69.9 ± 2.9 years, BMI 27.4 ± 4.1 kg/m²) during a 3.5‐year follow‐up study. In Group 1, insulin sensitivity, energy expenditure, and substrate oxidation were measured with the hyperinsulinemic euglycemic clamp combined with indirect calorimetry. Results: In Group 1, the Val103Ile genotype was associated with high rates of energy expenditure (63.42 ± 13.40 in eight subjects with the Val103Ile genotype vs. 59.86 ± 7.33 J/kg per minute in 221 subjects with the Val103Val genotype, p = 0.007), high rates of glucose oxidation (8.90 ± 6.15 vs. 6.07 ± 4.38 μmol/kg per minute, p = 0.020), and low levels of free fatty acids (0.45 ± 0.18 vs. 0.56 ± 0.23 mM, p = 0.029) in the fasting state, and with high rates of glucose oxidation during the clamp (18.88 ± 4.63 vs. 17.60 ± 3.24 μmol/kg per minute, p = 0.031). In Group 2, the 103Ile allele was associated with an increase in weight gain during the follow‐up (0.78 ± 3.98 vs. ?0.82 ± 3.98 kg, p = 0.038). Discussion: The Val103Ile polymorphism of the MC4R gene is associated with energy expenditure in humans. Furthermore, it may associate with glucose oxidation, free fatty acid levels, and weight gain.     

虎纹捕鸟蛛毒素虎纹毒素-III对美洲蜚蠊神经细胞电压门控离子通道的影响

HWTX-III是从中国虎纹捕鸟蛛Ornithoctonus huwena粗毒中分离纯化到的一种昆虫神经多肽。通过应用全细胞膜片钳技术研究了HWTX-III对美洲蜚蠊Periplaneta americana神经细胞电压门控离子通道的影响。发现HWTX-III特异性地抑制美洲蜚蠊背侧不成对中间(dorsal unpaired median, DUM）神经细胞的电压门控钠通道(IC50≈1.106 μmol/L),而对电压门控钾通道没有明显的影响。HWTX-III通过一种新型的不同于其他蜘蛛毒素的机制抑制昆虫电压门控钠通道,它不影响通道的激活与失活动力学,也不明显地漂移稳态失活曲线。HWTX-III对昆虫神经细胞电压门控钠通道的特异性与新型作用机制为研究电压门控钠通道分子结构的多样性以及开发新的安全的杀虫剂提供有用的工具。     

Assessing Invader Roles Within Changing Ecosystems: Historical and Experimental Perspectives on an Exotic Mussel in an Urbanized Lagoon

It is often difficult to accurately assess the long-term effects of invaders because of a lack of data and the changing nature of ecosystems. However, available historical information can be used to make comparisons with current conditions and generate hypotheses that can be tested experimentally. This approach was used to examine changes in the bivalve community of Mission Bay, San Diego, California, USA. A 20-year dataset on subtidal bivalves shows a marked increase in abundance of the exotic mussel Musculista senhousia, and concomitant declines in species richness and the abundance of the native Solen rostriformis. Currently, Musculista also dominates the tidal creeks of a remnant salt marsh and an adjacent restored marsh, and is 100 times more abundant than any native bivalve species. A comparison of the bivalves now present in the remnant marsh creek to the community present 35 years ago demonstrates that while Musculista increased in abundance, the native Chione fluctifraga disappeared from the creek. In the same time frame, two other natives, Macoma nasuta and C. undatella, appeared in the system. Experiments demonstrate that the growth and survivorship of the surface-dwelling, suspension-feeding Chione spp. significantly decrease in the presence of Musculista, whereas the deeper-dwelling, deposit-feeding Macoma nasuta shows no such inhibition. Viewing these results in the broader context of physical change within the wetland explains some patterns of observed change and suggests effects due at least in part to Musculista, but also demonstrates the complexities associated with assessing long-term patterns in systems affected by multiple factors. This revised version was published online in July 2006 with corrections to the Cover Date.     

苦皮藤素Ⅳ和Ⅴ混合物对棉铃虫幼虫神经细胞钠通道的影响

杀虫植物苦皮藤Celastrus angulatus的主要活性成分苦皮藤素Ⅳ和Ⅴ处理后昆虫的中毒症状分别表现为麻醉和兴奋,但苦皮藤素Ⅳ对苦皮藤素Ⅴ的毒杀效果具有增效作用,苦皮藤素Ⅴ对苦皮藤素Ⅳ的麻醉作用基本没有影响。应用全细胞膜片钳技术,就苦皮藤素Ⅳ和Ⅴ不同比例（3∶1,1∶1,1∶3）混合物对棉铃虫Helicoverpa armigera幼虫离体培养神经细胞钠离子通道的影响进行了比较。结果表明：苦皮藤素Ⅳ和苦皮藤素Ⅴ的不同比例混合物对钠通道（TTX-S）电流作用与二者所占比例有关,苦皮藤素Ⅳ比例大,表现出苦皮藤素Ⅳ对通道的阻滞效应,钠电流被抑制; 苦皮藤素Ⅴ比例大,则表现出对通道的激活,钠电流增大。另外,两者不同比例混合物对钠通道（TTX-S）电流的激活电压无明显影响,但对峰值电压影响显著,可使其向正电位方向移动10～20 mV。这些结果说明苦皮藤素Ⅳ和Ⅴ可能作用于一个相同的钠通道结合位点或别构偶联位点,二者对钠通道的作用是一种拮抗作用。     

SUMO modification of PCNA is controlled by DNA

Post-translational modification by the ubiquitin-like protein SUMO is often regulated by cellular signals that restrict the modification to appropriate situations. Nevertheless, many SUMO-specific ligases do not exhibit much target specificity, and--compared with the diversity of sumoylation substrates--their number is limited. This raises the question of how SUMO conjugation is controlled in vivo. We report here an unexpected mechanism by which sumoylation of the replication clamp protein, PCNA, from budding yeast is effectively coupled to S phase. We find that loading of PCNA onto DNA is a prerequisite for sumoylation in vivo and greatly stimulates modification in vitro. To our surprise, however, DNA binding by the ligase Siz1, responsible for PCNA sumoylation, is not strictly required. Instead, the stimulatory effect of DNA on conjugation is mainly attributable to DNA binding of PCNA itself. These findings imply a change in the properties of PCNA upon loading that enhances its capacity to be sumoylated.     

Functional stabilization of Kv1.5 protein by Hsp70 in mammalian cell lines

The aim of this study was to elucidate the mechanisms for regulations of cardiac Kv1.5 channel expression. We particularly focused on the role of heat shock proteins (Hsps). We tested the effects of Hsps on the stability of Kv1.5 channels using biochemical and electrophysiological techniques: co-expression of Kv1.5 and Hsp family proteins in mammalian cell lines, followed by Western blotting, immunoprecipitation, pulse-chase analysis, immunofluorescence and whole-cell patch clamp. Hsp70 and heat shock factor 1 increased the expression of Kv1.5 protein in HeLa and COS7 cells, whereas either Hsp40, 27 or 90 did not. Hsp70 prolonged the half-life of Kv1.5 protein. Hsp70 was co-immunoprecipitated and co-localized with Kv1.5-FLAG. Hsp70 significantly increased the immunoreactivity of Kv1.5 in the endoplasmic reticulum, Golgi apparatus and on the cell membrane. Hsp70 enhanced Kv1.5 current of transfected cells, which was abolished by pretreatment with brefeldin A or colchicine. Thus, Hsp70, but not other Hsps, stabilizes functional Kv1.5 protein.     

The unit event of sliding of the chemo-mechanical enzyme composed of myosin and actin with regulatory proteins

Various myosin-actin systems do not always show the same sliding behaviors. To make the situation clear, discussions are concentrated on the unit event of sliding of the chemo-mechanical enzyme composed of a single myosin head and a single actin filament with regulatory proteins. The popular idea of the one-to-one correspondence between the chemical state and the physical state or between the chemical reaction step and the physical conformational change is reexamined. It is likely that the sites and the modes of interaction between myosin head and actin filament during the ATP hydrolysis are more multiple and variable, and the input-output coupling in the chemo-mechanical enzyme is loose.     

Utilization of fluorescence tracer in hyperinsulinemic-euglycemic clamp test in mice

The hyperinsulinemic–euglycemic clamp test is considered to be a gold standard for the evaluation of insulin sensitivity. Here, a new version of the clamp test that used the fluorescence tracer 2-NBDG was tested. C57BL/6J mice were induced insulin resistant (IR) with a high-calorie diet. Rosiglitazone was administrated to IR mice and diabetic db/db mice. Insulin resistance was estimated with the oral glucose tolerance test (OGTT), the insulin tolerance test (ITT), the serum insulin level and the homeostasis model assessment of insulin resistance (HOMA-IR), and then confirmed by the hyperinsulinemic–euglycemic clamp test with 2-NBDG. The 2-NBDG content was measured by the fluorescence intensity. The characteristics of insulin resistance were shown remarkably with the increased values of serum insulin and HOMA-IR in IR mice, and with the results from OGTT and ITT in both IR and db/db mice. In the hyperinsulinemic–euglycemic clamp test, the glucose infusion rate and amount of 2-NBDG taken up into the liver, adipose, and skeletal muscle were decreased significantly in IR mice and db/db mice, respectively. The clearing rates of 2-NBDG from the circulation were much slower in both mouse models. All markers were reversed significantly by rosiglitazone treatment. The results indicate that with the fluorescence tracer 2-NBDG, the hyperinsulinemic–euglycemic clamp test can be used to estimate insulin sensitivity in vivo.     

含有食饵自庇护的食饵-捕食模型的模糊滑模控制

针对一类令布食饵自虞护的食饵-捕食系统,当环境变化时,系统参数的扰动处于动态状态,利用其扰动边界的特性,通过设计模糊滑模控制器将失控系统引至平稳轨道,并使系统全局稳定,从理论上实现了失控系统的有效控制,为防治食饵种群灭绝,引起食物链断裂,导致生态平衡破坏提供了一定的理论依据．最后的仿真结果表明了此方法在理论上的有效性．