Preplay of future place cell sequences by hippocampal cellular assemblies

During spatial exploration, hippocampal neurons show a sequential firing pattern in which individual neurons fire specifically at particular locations along the animal's trajectory (place cells). According to the dominant model of hippocampal cell assembly activity, place cell firing order is established for the first time during exploration, to encode the spatial experience, and is subsequently replayed during rest or slow-wave sleep for consolidation of the encoded experience. Here we report that temporal sequences of firing of place cells expressed during a novel spatial experience occurred on a significant number of occasions during the resting or sleeping period preceding the experience. This phenomenon, which is called preplay, occurred in disjunction with sequences of replay of a familiar experience. These results suggest that internal neuronal dynamics during resting or sleep organize hippocampal cellular assemblies into temporal sequences that contribute to the encoding of a related novel experience occurring in the future.     

阻塞性睡眠呼吸暂停患者的上气道狭窄与头姿变化

探讨阻塞性睡眠呼吸暂停（Ｏｂｓｔｒｕｃｔｉｖｅｓｌｅｅｐａｐｎｅａ，ＯＳＡ）患者上气道狭窄的程度、头姿改变情况，以及这些形态学指标与病理生理学参数之间的关系。研究对象为８６例男性ＯＳＡ患者及３７名健康男性。经整夜多导睡眠仪检查诊断或排除ＯＳＡ；采用数字化技术摄取受试者头颅侧位片，并用ＮＩＨＩｍａｇｅ软件测定上气道口径、面积及头姿指标共１５项。ＯＳＡ患者各水平上气道前后径均显著小于对照组；经年龄及身高体重指数校正后，上述结果不变。重症ＯＳＡ患者呈显著头颅前倾。头姿变化指标与呼吸暂停指数及多个水平的气道前后径呈显著相关。亚洲人种ＯＳＡ患者存在明显及广泛的上气道狭窄；随ＯＳＡ程度加重及上气道阻塞程度加重，患者可能出现代偿性头姿改变     

犬c-yes原癌基因

利用Ｓｏｕｔｈｅｎ ｂｌｏｔ和ＤＮＡ碱基序列分析技术，对正常犬ｃ－ｙｅｓ原癌基因的颁布规律及ｃ－ｙｅｓ ｃＤＮＡ的结构进行了分析。结果表明。犬体细胞染色质中ｃ－ｙｅｓ基因均一分布，ｃ－ｙｅｓ ｃＤＮＡ开放阅读框架有５３９个氨基酸组成，分子量为６０，３６８Ｄａ，与人和鸡ｐ６１＾ｃ－ｙｅｓ同源性分别为９５．９％和９０．４％。该产物具有ｓｒｃ（ＳＨ）３，ＳＨ２同源区和酷氨酸激酶序列，该序列与人和鸡的同源     

A SNP in the ABCC11 gene is the determinant of human earwax type

Human earwax consists of wet and dry types. Dry earwax is frequent in East Asians, whereas wet earwax is common in other populations. Here we show that a SNP, 538G --> A (rs17822931), in the ABCC11 gene is responsible for determination of earwax type. The AA genotype corresponds to dry earwax, and GA and GG to wet type. A 27-bp deletion in ABCC11 exon 29 was also found in a few individuals of Asian ancestry. A functional assay demonstrated that cells with allele A show a lower excretory activity for cGMP than those with allele G. The allele A frequency shows a north-south and east-west downward geographical gradient; worldwide, it is highest in Chinese and Koreans, and a common dry-type haplotype is retained among various ethnic populations. These suggest that the allele A arose in northeast Asia and thereafter spread through the world. The 538G --> A SNP is the first example of DNA polymorphism determining a visible genetic trait.     

Structural basis for the spectral difference in luciferase bioluminescence

Fireflies communicate with each other by emitting yellow-green to yellow-orange brilliant light. The bioluminescence reaction, which uses luciferin, Mg-ATP and molecular oxygen to yield an electronically excited oxyluciferin species, is carried out by the enzyme luciferase. Visible light is emitted during relaxation of excited oxyluciferin to its ground state. The high quantum yield of the luciferin/luciferase reaction and the change in bioluminescence colour caused by subtle structural differences in luciferase have attracted much research interest. In fact, a single amino acid substitution in luciferase changes the emission colour from yellow-green to red. Although the crystal structure of luciferase from the North American firefly (Photinus pyralis) has been described, the detailed mechanism for the bioluminescence colour change is still unclear. Here we report the crystal structures of wild-type and red mutant (S286N) luciferases from the Japanese Genji-botaru (Luciola cruciata) in complex with a high-energy intermediate analogue, 5'-O-[N-(dehydroluciferyl)-sulfamoyl]adenosine (DLSA). Comparing these structures to those of the wild-type luciferase complexed with AMP plus oxyluciferin (products) reveals a significant conformational change in the wild-type enzyme but not in the red mutant. This conformational change involves movement of the hydrophobic side chain of Ile 288 towards the benzothiazole ring of DLSA. Our results indicate that the degree of molecular rigidity of the excited state of oxyluciferin, which is controlled by a transient movement of Ile 288, determines the colour of bioluminescence during the emission reaction.     

Highly controlled acetylene accommodation in a metal-organic microporous material

Metal-organic microporous materials (MOMs) have attracted wide scientific attention owing to their unusual structure and properties, as well as commercial interest due to their potential applications in storage, separation and heterogeneous catalysis. One of the advantages of MOMs compared to other microporous materials, such as activated carbons, is their ability to exhibit a variety of pore surface properties such as hydrophilicity and chirality, as a result of the controlled incorporation of organic functional groups into the pore walls. This capability means that the pore surfaces of MOMs could be designed to adsorb specific molecules; but few design strategies for the adsorption of small molecules have been established so far. Here we report high levels of selective sorption of acetylene molecules as compared to a very similar molecule, carbon dioxide, onto the functionalized surface of a MOM. The acetylene molecules are held at a periodic distance from one another by hydrogen bonding between two non-coordinated oxygen atoms in the nanoscale pore wall of the MOM and the two hydrogen atoms of the acetylene molecule. This permits the stable storage of acetylene at a density 200 times the safe compression limit of free acetylene at room temperature.