大鼠皮层听-视多感觉神经元和听-视信息整合

应用常规电生理技术,研究SD大鼠皮层听-视多感觉神经元的分布和听-视信息整合.共记录到130个听-视双模态神经元,其中65个A-V型神经元,28个v-A型神经元和37个a-V型神经元.这些双模态神经元主要分布于听区的背侧,听皮层和视皮层的交界处,具有明显的区域性,呈条带状分布,v-A型神经元较多地位于近听皮层一侧,a-V型神经元则主要位于近视皮层一侧,A-V型神经元位于两者之间.在条带中,双模态神经元分布不均一,有片状分布趋势.双模态神经元的听-视信息整合效应分为增强型、抑制型和调制型.整合效应与声-光组合刺激的时间间隔有关,其中75%的神经元获得最大整合效应的时间间隔在30～50ms之间.研究结果提示,大鼠皮层存在听-视多感觉神经元分布区,这些神经元遵循存在于其他动物相关脑区多感觉信息整合规律,参与听-视感觉信息整合.     

Effects of Spirogyra arcta on biomass and structure of submerged macrophyte communities

The presence of algae can greatly reduce the amount of light that reaches submerged macrophytes, but few experimental studies have been conducted to examine the effects of algae on biomass and structure of submerged macrophyte communities. We constructed communities with four submerged macrophytes (Hydrilla verticillata, Egeria densa, Ceratophyllum demersum, and Chara vulgaris) in three environments in which 0 (control), 50 and 100% of the water surface was covered by Spirogyra arcta. Compared to the control treatment, the 100% spirogyra treatment decreased biomass of the submerged macrophyte communities and of all the four macrophytes except C. demersum. Compared to the control and 50% treatments, the 100% treatment significantly increased relative abundance of C. demersum and decreased that of E. densa. Therefore, the presence of S. arcta can greatly affect the productivity and alter the structure of submerged macrophyte communities. To restore submerged macrophyte communities in conditions with abundant algae, assembling communities consisting of C. demersum or similar species may be a good practice.     

Dominance of a clonal green sulfur bacterial population in a stratified lake

For many years, the chemocline of the meromictic Lake Cadagno, Switzerland, was dominated by purple sulfur bacteria. However, following a major community shift in recent years, green sulfur bacteria (GSB) have come to dominate. We investigated this community by performing microbial diversity surveys using FISH cell counting and population multilocus sequence typing [clone library sequence analysis of the small subunit (SSU) rRNA locus and two loci involved in photosynthesis in GSB: fmoA and csmCA ]. All bacterial populations clearly stratified according to water column chemistry. The GSB population peaked in the chemocline ( c . 8 × 10⁶ GSB cells mL⁻¹) and constituted about 50% of all cells in the anoxic zones of the water column. At least 99.5% of these GSB cells had SSU rRNA, fmoA , and csmCA sequences essentially identical to that of the previously isolated and genome-sequenced GSB Chlorobium clathratiforme strain BU-1 (DSM 5477). This ribotype was not detected in Lake Cadagno before the bloom of GSB. These observations suggest that the C. clathratiforme population that has stabilized in Lake Cadagno is clonal. We speculate that such a clonal bloom could be caused by environmental disturbance, mutational adaptation, or invasion.     

Demographic genetics of the American beech, Fagus grandifolia. II. Genet substructure of populations for the Blue Ridge, Piedmont and the Great Smoky Mountains

Populations of American beech in Virginia and the Great Smoky Mountain National Park in Tennessee and North Carolina were investigated for demographic genetic substructurings. Two Virginia populations, one on the Blue Ridge (WG1) and the other on the Piedmont (WG2) occur over an elevational gradient of several hundreds meters. One of the Great Smoky Mountain populations (GS1) was in a 'beech gap' and the other (GS2) in a 'cove forest' along a creek. The populations in the Great Smoky Mountain National Park were only separated by a few hundred meters in elevation, but both on the same physiographic province. The populations had two growth forms. Trees produced extensive root suckers at WG1, GS1 and GS2, but WG2 had no root suckers and all individuals had obviously been established from seeds. A total of 1335 shoots were mapped at the four sites, their size measured [diameter at breast height (DBH) or diameter at ground height (DGH)], and genotypes were determined for each locus using allozyme analysis. F_IS among five different size-classes revealed an excess of homozygotes in WG1, GS1 and GS2, and an excess of heterozygotes in WG2. The offshoot formation from root suckers obviously contributed to the abundance of intermediate size-classes in WG1, GS1 and GS2. Exceedingly localized patchiness of different multilocus genotypes reveals genetic clustering of shoots that have obviously originated from root suckers in WG1, GS1 and GS2. The Piedmont population (WG2), on the other hand, showed loose localization of genetically related trees at a scale of 35–40 m in area, suggesting broader ranges of pollen and seed dispersal. The data are discussed in the light of the differences in growth form and mode of reproduction, and also in relation to the post-glacial migration and the current geographic distribution of the species.     

猪瘟DNA疫苗在猪体及环境的生物安全性研究

DNA疫苗生物安全性是其走向临床所须解决的关键问题之一。以猪瘟DNA疫苗为研究对象 ,探讨了其两个方面的生物安全性问题。一方面 ,将两种不同的猪瘟DNA疫苗质粒免疫猪后 ,利用PCR技术分析了其与猪细胞基因组整合的可能性 ,结果在灵敏度为 30拷贝的检测条件下 ,未发现猪瘟DNA疫苗整合到细胞基因组 ;另一方面 ,以PCR技术检测了免疫现场环境样品 ,以分析猪瘟DNA疫苗上的E2基因、CMV启动子基因和抗性基因是否在环境细菌中发生转移和扩散。结果未发现DNA疫苗转化环境细菌的直接证据。因此认为DNA疫苗对猪体和环境是安全的。     

Genetic diversity of Typha latifolia (Typhaceae) and the impact of pollutants examined with tandem-repetitive DNA probes

Genetic diversity at variable-number-tandem-repeat (VNTR) loci was examined in the common cattail, Typha latifolia (Typhaceae), using three synthetic DNA probes composed of tandemly repeated “core” sequences (GACA, GATA, and GCAC). The principal objectives of this investigation were to determine whether: (1) the previously reported almost complete lack of polymorphism at allozyme loci in this species was indicative of a reduced amount of genetic diversity at VNTR loci as well; (2) VNTR markers were informative about possible clonal propagation; and (3) significant differences in genetic structure of sampling sites were associated with differences in environmental levels of pollutants at those sites. Previously, widespread sampling across the eastern United States, surveying across ten allozyme loci, has detected only two genotypes, involving a difference at a single locus, among 104 populations. In this study, the amount of genetic diversity detected at VNTR loci: (1) among ramets (N = 40; 40 genotypes detected) collected at ∼8-km intervals along a 320-km transect; (2) among ramets (N = 220; 117 genotypes detected) from five study sites separated by 50–3000 m; and (3) even among ramets within each study site [N = 44 per site; from 13 to 34 genotypes detected per site (270 m²)] exceeds that previously found in those more geographically widespread allozyme surveys. Among the 260 ramets analyzed here, the mean number of bands scored per individual was 48.61 (SD = 2.80). Mean genetic similarity among ramets collected along the 320-km transect was 0.91, which was within the range of mean genetic similarity within the five study sites (range: 0.89–0.95). Among the five study sites, 61% of the samples analyzed appeared to be clonal ramets, with up to 12 clones detected for 44 ramets sampled within a site. Clones grew intermingled and ranged up to 39 m in extent. Permutation tests of genetic similarity revealed significant genetic differentiation between each of the five study sites. Consistent with the previous allozyme studies, T. latifolia was characterized by extremely low genetic variation relative to levels of polymorphism detected at VNTR loci in other plant species. Estimated heterozygosity among ramets along the 320-km transect ranged from 0.11 to 0.13, while that within the five study sites ranged from 0.05 to 0.12. Estimates of F_st (0.32–0.41) also indicated considerable genetic subdivision among these stands. Significantly higher genetic diversity was detected at the two study sites that chemistry and toxicity data indicate to be the most severely impacted by pollutants. Although this correlation does not establish cause and effect, the results of this study indicate that the analysis of genetic diversity at VNTR loci may be a useful tool for monitoring anthropogenic-induced changes in the genetic structure of natural populations of plants.     

Post-natal heart adaptation in a knock-in mouse model of calsequestrin 2-linked recessive catecholaminergic polymorphic ventricular tachycardia

Cardiac calsequestrin (CASQ2) contributes to intracellular Ca²⁺ homeostasis by virtue of its low-affinity/high-capacity Ca²⁺ binding properties, maintains sarcoplasmic reticulum (SR) architecture and regulates excitation–contraction coupling, especially or exclusively upon β-adrenergic stimulation. Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited arrhythmogenic disease associated with cardiac arrest in children or young adults. Recessive CPVT variants are due to mutations in the CASQ2 gene. Molecular and ultra-structural properties were studied in hearts of CASQ2^R33Q/R33Q and of CASQ2^−/− mice from post-natal day 2 to week 8. The drastic reduction of CASQ2-R33Q is an early developmental event and is accompanied by down-regulation of triadin and junctin, and morphological changes of jSR and of SR-transverse-tubule junctions. Although endoplasmic reticulum stress is activated, no signs of either apoptosis or autophagy are detected. The other model of recessive CPVT, the CASQ2^−/− mouse, does not display the same adaptive pattern. Expression of CASQ2-R33Q influences molecular and ultra-structural heart development; post-natal, adaptive changes appear capable of ensuring until adulthood a new pathophysiological equilibrium.     

稻瘟病菌致病突变体的REMI诱变与鉴定

以水稻“爱知旭”(Aichi—aShahi)为寄主,将带选择标记的质粒pCSN43和pBF101为外源DNA,利用限制酶诱导整合(REMI)这种新方法转化稻瘟病菌原生质体,从筛选到的数百个转化体中分离出3个与致病能力密切相关的突变体R2H65、R2H69和R281565。其中,R2H65和R2H69只产生畸形分生孢子,分生孢子的发育和附着胞的形成以及黑色素的合成均受到极大影响,致病性测试证明完全丧失致病能力;R281565的许多表型与野生型的相似,但致病能力却大大降低。     

Biochemical and structural studies of yeast Vps4 oligomerization

The ESCRT (endosomal sorting complexes required for transport) pathway functions in vesicle formation at the multivesicular body, the budding of enveloped RNA viruses such as HIV-1, and the final abscission stage of cytokinesis. As the only known enzyme in the ESCRT pathway, the AAA ATPase (ATPase associated with diverse cellular activities) Vps4 provides the energy required for multiple rounds of vesicle formation. Like other Vps4 proteins, yeast Vps4 cycles through two states: a catalytically inactive disassembled state that we show here is a dimer and a catalytically active higher-order assembly that we have modeled as a dodecamer composed of two stacked hexameric rings. We also report crystal structures of yeast Vps4 proteins in the apo- and ATPγS [adenosine 5′-O-(3-thiotriphosphate)]-bound states. In both cases, Vps4 subunits assembled into continuous helices with 6-fold screw axes that are analogous to helices seen previously in other Vps4 crystal forms. The helices are stabilized by extensive interactions between the large and small AAA ATPase domains of adjacent Vps4 subunits, suggesting that these contact surfaces may be used to build both the catalytically active dodecamer and catalytically inactive dimer. Consistent with this model, we have identified interface mutants that specifically inhibit Vps4 dimerization, dodecamerization, or both. Thus, the Vps4 dimer and dodecamer likely form distinct but overlapping interfaces. Finally, our structural studies have allowed us to model the conformation of a conserved loop (pore loop 2) that is predicted to form an arginine-rich pore at the center of one of the Vps4 hexameric rings. Our mutational analyses demonstrate that pore loop 2 residues Arg241 and Arg251 are required for efficient HIV-1 budding, thereby supporting a role for this “arginine collar” in Vps4 function.