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.     

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。     

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.     

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.     

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.     

Cortical barrel field ablation and unconditioned whisking kinematics

The effects of "barrel cortex" ablation upon the biometrics of "exploratory" whisking were examined in three head-fixed rats which had previously sustained unilateral ablation of the left cortical "barrel field" under electrophysiological control. Unconditioned movements of a pair of bilaterally homologous whiskers (C-1, Right, Left) were monitored, optoelectronically, with other whiskers present. Whisking movements on the intact and ablated side were analyzed with respect to kinematics (protraction amplitude and velocity) whisking frequency and phase relationships between whisking movement on the two sides of the face. Histological analysis confirmed complete removal of S-1 "barrel cortex". In normal animals whisking movements have a characteristic rhythm (6-9 Hz), and protractions on the two sides of the face tend to be both synchronous and of very similar amplitudes. In the lesioned animals, whisking frequency was unchanged and whisking movements remained bilaterally synchronous. However, there was a significant difference between the amplitude of Right and Left whisker movements which was evident many months postoperatively. Our results suggest that the deficits in vibrissa-mediated tactile discrimination reported after "barrel" field ablation may reflect an impairment in the animal's ability to modulate whisking parameters on the two sides of the face to meet the functional requirements of a discriminative whisking task. The effects upon whisking amplitude seen after unilateral barrel field ablation are consistent with a model in which the activity of a whisking Central Pattern Generator is modulated by descending inputs to achieve sensorimotor control of whisking movement parameters.     

Functional organization and plasticity in the adult rat barrel cortex: moving out-of-the-box

Recent advances in functional imaging and neuronal recording techniques demonstrate that the spatial spread and amplitude of whisker functional representation in the somatosensory cortex of the adult rodent is extensive, but subject to modulations. One of the strongest modulators is naturalistic whisker use. In the cortices of rodents that have been transferred from their home cage to live for an extensive period in a naturalistic habitat, there is suppression of evoked neuronal responses accompanied by contraction and sharpening of receptive fields, and contraction and weakening of whisker functional representations. These unexpected characteristics also describe modulations of whisker functional representations in the cortex of a freely exploring rodent during short whisker-based explorations. These and related findings suggest that cortical modulations and plasticity could follow a 'less is more' strategy and, therefore, highlight how different cortical strategies could be utilized for different behavioral demands.     

Beta barrel trans-membrane proteins: Enhanced prediction using a Bayesian approach

Membrane proteins, which constitute approximately 20% of most genomes, form two main classes: alpha helical and beta barrel transmembrane proteins. Using methods based on Bayesian Networks, a powerful approach for statistical inference, we have sought to address beta-barrel topology prediction. The beta-barrel topology predictor reports individual strand accuracies of 88.6%. The method outlined here represents a potentially important advance in the computational determination of membrane protein topology.     

Physical demands, injuries, and conditioning practices of stock car drivers

The purpose of this study was to assess the physical demands, injuries, and conditioning practices of stock car drivers. Forty stock car drivers from 27 states in the United States participated in the interviews for 43.9 ± 13.9 minutes. The interviews examined background information, the physical demands of racing, injuries associated with racing, and the athletic and fitness background and practices of the subjects. Numerical data were analyzed using Pearson's correlation coefficients. Responses to open-ended questions were analyzed using inductive content analysis. Results revealed significant correlation between track points standings and the length of the resistance training sessions (R = -0.71, p = 0.002) and subject self-assessment of their fitness (R = -0.53, p = 0.045). Results also revealed that "upper-body strength" was identified as the most important physical demand. Extreme fatigue was the most common feeling after a demanding race. Subjects reported that shoulder fatigue was the most common form of muscle soreness experienced after a race. Back and torso injuries were the most common injury, although head injuries most frequently required medical attention. The subjects' biggest fear was fire, followed closely by head and neck injury. The bench press and running were the most commonly performed resistance training and cardiovascular exercises, respectively. Subjects reported that their highest motivation for training was to improve their racing performance. Many subjects had athletic backgrounds with football identified as the sport they had most commonly participated in. This study provides additional detailed information. Results of this study can assist strength and conditioning professionals in the development of strength and conditioning programs for performance enhancement and injury prevention that are specific to the needs of this population of athletes.     

Larval distribution, abundance, and stock structure of British Columbia herring

Pacific herring Clupea pallasi spawn in shallow and intertidal areas. Larval distributions and abundance of three major and several minor stocks were examined to determine if larvae mix among different spawning locations. The surveys were short, intensive, and occurred mainly within the first 30 days of larval life. Each major stock had a discrete larval distribution with continuous larval distributions within stock boundaries. Some overlap of distributions occurred among smaller stocks. Most larvae were found in inshore waters but there were no obvious oceanographic factors, such as fronts or eddies, to explain all the distributions. Estuarine circulation in inlets could promote larval retention in some areas. The results support the present geographic definitions for local herring stocks. The results are generally consistent with the concept of discrete larval distribution, including retention areas, as the basis for herring Stock Structure.