Segmental and Regional Differences in Neuronal Expression of the Leech Hox Genes Lox1 and Lox2 During Embryogenesis

Using double immunofluorescence experiments, we described the expression of the leech Hox genes, Lox1 and Lox2 by central neurons that stained for either serotonin or the leech-specific neuronal marker, Laz1-1. The goal is to determine whether the segmental boundaries of Lox1 and Lox2 expression in identified neurons coincide with segmental and regional differences in the differentiation of these cells. A number of neurons described here have been previously identified. The anteromedial serotonergic neurons are restricted to rostral ganglion 1 (R1) to midbody ganglion 3 (M3), but only express Lox1 in M2 and M3. The posteromedial serotonergic neurons which are situated in all segments as bilateral pairs early in development, but later become unpaired starting at M3, expressed Lox1 only in M2 and M3, and Lox2 in M8 to M21, in all paired and unpaired stages. The Retzius neurons, which stain for serotonin, express Lox2 in M7 to M21 where they exhibit different morphologies from their segmental homologs of the sex ganglia in M5 and M6. The Laz1-1 immunoreactive (Laz1-1⁺) heart accessory-like neurons express Lox1 in M4 and Lox2 in M7 to M17, but not in their segmental homologs of the heart accessory (HA) neurons located exclusively in M5 and M6. Also, Laz1-1⁺ neurons, which we named Lz3 expressed Lox1 in M4 to M8 where they are unpaired, but express Lox2 in M9 to M16 where they are bilaterally paired. Other Laz1-1 cells show more restricted and isolated Lox1 and Lox2 expression patterns. These results suggest a role of Lox1 and/or Lox2 in defining the anteroposterior boundaries of segmentally iterated neurons.     

Salmon stock and recruitment, and stock enhancement

The precise nature of the stock and recruitment relationship in natural populations is of vital importance to any attempt at stock enhancement by removing or by-passing a limiting factor, or at management by manipulation of spawning stock. In this paper the evidence for and against a dome-shaped stock and recruitment curve is reviewed, and consideration given to several factors which complicate the conventional, simplistic interpretation of density-dependent mortality. These include environmentally mediated changes in 'carrying capacity', distribution of spawning, and the need to consider whole river systems. The implications of these factors for fisheries management and stock enhancement are discussed.     

TAILOR: Transgene Activation and Inactivation Using Lox and Rox in Zebrafish

The ability to achieve precisely tailored activation and inactivation of gene expression represents a critical utility for vertebrate model organisms. In this regard, Cre and other site-specific DNA recombinases have come to play a central role in achieving temporally regulated and cell type-specific genetic manipulation. In zebrafish, both Cre and Flp recombinases have been applied for inducible activation, inactivation and inversion of inserted genomic elements. Here we describe the addition of Dre, a heterospecific Cre-related site-specific recombinase, to the zebrafish genomic toolbox. Combining Dre-based recombination in zebrafish with established Cre/lox technology, we have established an effective strategy for transgene activation and inactivation using lox and rox (TAILOR). Using stable transgenic lines expressing tamoxifen-inducible CreER^T2 and RU486-inducible DrePR fusions, we demonstrate that Cre and Dre retain non-overlapping specificities for their respective lox and rox target sites in larval zebrafish, and that their combinatorial and sequential activation can achieve precisely timed transgene activation and inactivation. In addition to TAILOR, the successful application of Dre/rox technology in zebrafish will facilitate a variety of additional downstream genetic applications, including sequential lineage labeling, complex genomic rearrangements and the precise temporal and spatial control of gene expression through the intersection of partially overlapping promoter activities.     

大豆脂肪氧化酶-3基因(Lox3)启动子的克隆及其瞬时表达分析

利用PCR技术从大豆基因组DNA中分离脂肪氧化酶-3基因启动子片段Lox3p。PLACE在线启动子预测工具分析表明:序列中含有多种典型的种子及胚特异性表达元件。将克隆得到的Lox3p片段替换pCAMBIA1301中的CaMV35S启动子,构建表达载体pCAM-Lox3p。通过农杆菌介导法在大豆种子中进行瞬时表达,GUS组织化学染色及荧光测定都显示出Lox3p驱动GUS基因表达的强度高于CaMV35S启动子。结果表明,该Lox3p启动子片段具备一定的胚特异表达特性,为探明大豆脂肪氧化酶-3基因启动子胚特异表达调控序列及其调控机制的研究奠定基础。     

Radiolaria: Sinking population,standing stock,and production rate

A method is presented for estimating sinking population, rate of production, and residence time in the living zone for Radiolaria. This method employs vertical flux measurements from PARFLUX sediment traps and laboratory sinking speed measurements of the radiolarian skeletons.The estimated population sinking through the oceanic water column is approximately equal to the standing stock at several hundred meters depth reported from direct measurements by other workers. The rate of production of total Radiolaria was estimated to be approximately 80 shells m^?3 day^?1 in the western equatorial Atlantic (E) and central Pacific (P₁) stations and 230 shells m^?3 day^?1 in the Panama Basin (PB). The production of Nassellaria is greater than that of the other suborders. The average residence time for Radiolaria in the living zone (0–200 m) was estimated to be between 16 and 42 days.     

大豆脂肪氧化同工酶(Lox1)单克隆抗体的制备

利用薄层等电聚焦电泳检测缺失大豆脂氧酶近等基因系-Su系列,将标记不同缺失类型种子经脱脂、干燥、浸提、离心后制成样品,通过非变性聚丙烯酰胺凝胶电泳分离和电泳洗脱仪回收获得蛋白。间接ELISA测定Lox1免疫血清效价为1∶1600,免疫BALB/C小鼠的脾细胞和达到对数生长期的SP2/0骨髓瘤细胞融合培养,筛选杂交瘤细胞的阳性克隆,应用有限稀释法和交叉分析,获得3株能稳定传代且分泌Lox1单克隆抗体的、与其他Lox类型没有交叉反应的杂交瘤细胞,各株单抗的效价均在1∶64以上。大豆脂肪氧化同工酶Lox1单克隆抗体用于检测脂氧酶的缺失类型,可为辅助育种提供投资少、见效快的鉴定方法,可为研制大豆脂肪氧化同工酶检测试剂盒提供实验基础。     

Lox6, a leech Dfd ortholog, is expressed in the central nervous system and in peripheral sensory structures

 Sequence analysis of a newly isolated Hirudo medicinalis cDNA containing an Antennapedia (Antp)-class homeobox suggests that the corresponding gene, Lox6, is an ortholog of the Drosophila Deformed (Dfd) gene. In situ hybridization of whole-mounted preparations shows that the major sites of Lox6 expression during embryogenesis are the central nervous system (CNS) and the peripheral sensory system. Lox6 mRNA can be detected in a subset of neurons in each ganglion from the subesophageal ganglion (RG2) to the most posterior ganglion, with the highest level of expression seen in RG3. Peripherally, Lox6 is expressed principally in the primordia of the sensillae and in the eyes. This pattern of expression of Lox6 suggests that one of its functions may be to contribute to the diversification of neuronal phenotypes. Received: 16 August 1997/Accepted: 20 December 1997     

Betaine-homocysteine methyltransferase: zinc in a distorted barrel

Betaine-homocysteine methyl transferase (BHMT) catalyzes the synthesis of methionine from betaine and homocysteine (Hcy), utilizing a zinc ion to activate Hcy. BHMT is a key liver enzyme that is important for homocysteine homeostasis. X-ray structures of human BHMT in its oxidized (Zn-free) and reduced (Zn-replete) forms, the latter in complex with the bisubstrate analog, S(delta-carboxybutyl)-L-homocysteine, were determined at resolutions of 2.15 A and 2.05 A. BHMT is a (beta/alpha)(8) barrel that is distorted to construct the substrate and metal binding sites. The zinc binding sequences G-V/L-N-C and G-G-C-C are at the C termini of strands beta6 and beta8. Oxidation to the Cys217-Cys299 disulfide and expulsion of Zn are accompanied by local rearrangements. The structures identify Hcy binding fingerprints and provide a prototype for the homocysteine S-methyltransferase family.     

Taking stock of our models: the function and future of stock centres

Stock centres for our animal models are as important as other scientific resources, such as the primary literature or genome databases. But they need forward planning, international cooperation and secure funding to keep pace with the explosion in functional genomics that relies so heavily on them.     

中国草地生态系统固碳现状、速率和潜力研究

正中国草地面积约4亿hm~2,占国土总面积的41.7%。作为中国面积最大的陆地生态系统类型,草地不仅每年为畜牧业生产提供了3–4亿t优质饲草,而且在防风固沙、水土保持、水源涵养、生物多样性保育和生态系统碳固持等方面具有极其重要的生态功能(白永飞等,2014;沈海花等,2016)。草地是个巨大的碳库,全球草地总碳储量约为308 Pg,其中约92%储存在土壤中(Schuman et al.,2002)。中国草     

Clusters in alpha/beta barrel proteins: implications for protein structure, function, and folding: a graph theoretical approach

The alpha/beta barrel fold is adopted by most enzymes performing a variety of catalytic reactions, but with very low sequence similarity. In order to understand the stabilizing interactions important in maintaining the alpha/beta barrel fold, we have identified residue clusters in a dataset of 36 alpha/beta barrel proteins that have less than 10% sequence identity within themselves. A graph theoretical algorithm is used to identify backbone clusters. This approach uses the global information of the nonbonded interaction in the alpha/beta barrel fold for the clustering procedure. The nonbonded interactions are represented mathematically in the form of an adjacency matrix. On diagonalizing the adjacency matrix, clusters and cluster centers are obtained from the highest eigenvalue and its corresponding vector components. Residue clusters are identified in the strand regions forming the beta barrel and are topologically conserved in all 36 proteins studied. The residues forming the cluster in each of the alpha/beta protein are also conserved among the sequences belonging to the same family. The cluster centers are found to occur in the middle of the strands or in the C-terminal of the strands. In most cases, the residues forming the clusters are part of the active site or are located close to the active site. The folding nucleus of the alpha/beta fold is predicted based on hydrophobicity index evaluation of residues and identification of cluster centers. The predicted nucleation sites are found to occur mostly in the middle of the strands. Proteins 2001;43:103-112.     

Regional and segmental differences in the embryonic expression of a putative leech Hox gene,Lox2, by central neurons immunoreactive to FMRFamide-like neuropeptides

We performed immunofluorescence experiments using a rat polyclonal antibody on formaldehyde-fixed whole-mount embryos to characterize the expression of a putative leech Hox gene, Lox2, during embryonic development. The main goal was to determine whether the differentiation of subsets of FMRFamide-like immunoreactive (FLI) neurons coincide with the expression domain of Lox2. The earliest expression of Lox2 was detected in relatively large, prominent nuclei in the posterior region at embryonic day 4, a very early stage. Lox2 expression was also detected in subsets of central neurons (neurons located in the CNS) located in midbody ganglia 6 (M6)–M21. In addition, Lox2 was expressed by a number of segment-specific and segmentally repeated central FLI neurons. Lox2-positive FLI neurons of interest included some of those previously identified: the rostral most ventral (RMV) neurons, the circular ventral (CV) neurons, and cell 261. The paired RMVs, which are located in all midbody ganglia, expressed Lox2 only in M7–M19. The CV neurons, specialized motor neurons that innervate the circular ventral muscles of the body wall, expressed Lox2 in M7–M19. The putative cell 261 expressed Lox2 in M7–M12, where Lox1 is also expressed. FMRFamide staining in putative segmental homologs of cell 261 was not detected in other segmental ganglia. Our results suggest a role for Lox2 in very early embryonic development (before the formation of the CNS), and in the differentiation of segmentally repeated and region-specific FLI neurons.     

Seasonal,lunar, and diel patterns in spawning by the giant barrel sponge,Xestospongia muta

Coral Reefs - Temporal patterns in giant barrel sponge (Xestospongia muta) spawning were compiled from 32 observations spanning 17 years and three Caribbean locations (Florida, Belize, and...     

Water relations and photosynthesis of a barrel cactus,Ferocactus acanthodes,in the Colorado desert

Summary The structural characteristics, water relations, and photosynthesis of Ferocactus acanthodes (Lemaire) Britton and Rose, a barrel cactus exhibiting Crassulacean acid metabolism (CAM), were examined in its native habitat in the western Colorado desert. Water storage in its succulent stem permitted nighttime stomatal opening ot continue for about 40 days after the soil water potential became less than that of the stem, a period whe the plant would be unable to extract water from the soil. After 7 months of drought and consequent unreplenished water loss from a plant, diurnal stomatal activity was not observed and the stem osmotic pressure was 6.4 bars, more than double the value measured during wet periods with nighttime stomatal opening. F. acanthodes had a shallow root system (mean depth of 8 cm) which responded within 24 h to rainfall.When the nocturnal stem surface temperature was raised from 8.0° C to 35.0° C, the stomatal resistance increased 4-fold, indicating that cool nighttime temperatures are advantageous for gas exchange by F. acanthodes. Moreover, the optimal temperature for CO₂ uptake in the dark was only 12.6° C. CO₂ uptake at night became maximal for 3.0 mEinsteins cm^-2 of photosynthetically active radiation incident during the preceding day, and the minimum number of incident quanta absorbed per CO₂ fixed was 68. The transpiration ratio (mass of water transpired/mass of CO₂ fixed) had the relatively low value of 70 for an entire year, consistent with values obtained for other CAM plants. The total amount of water annually diverted to the floral structures was about 6% of the stem wet weight. The annual growth increment estimated from the net CO₂ assimilation corresponded to about 10% of the stem mass for barrel cacti 34 cm tall, in agreement with measured dimension changes, and indicated that such plants were about 26 years old.