Zooplankton composition and distribution off the coast of Galicia, Spain

During June and September 1984, zooplankton samples were collectedwith other hydrographic and biological data along the Galiciancoast (NW of Spain). In June copepods contributed {small tilde}60%to the total zooplankton community, with larvaceans, siphonophoresand cladocerans also abundant. In September >90% of the zooplanktonsampled were copepods. The dominant species of copepods in bothJune and September were Acartia clausi, Paracalanus parvus andTemora longicornis. The meroplankton was dominated by echinoderms,bryozoans, barnacle larvae and bivalve larvae. In June the averagezooplankton biomass was 31.08 mg C m^–3; the Septemberaverage was 41.69 mg C m^–3. The relationship between theslopes of the regression equations (biomass versus abundance)suggests that the zooplankton assemblage in June was composedby larger animals than in September. The major concentrationof zooplankton was between 0 and 50 m, with both June and Septemberdaytime surface samples having 6–7 times the amount oforganisms than the lower water column (50–100 m). Therewere no distinct differences in total zooplankton abundancesat the inshore and offshore stations; however, the inshore stationsoften had a higher percentage of meroplankton than the offshorestations. In June zooplankton abundance at the northern transectsand the western transects was similar. In September there weregreater concentrations of zooplankton in the western Galicianshelf as compared with the northern shelf. These differencesin the horizontal distribution of the zooplankton were relatedto upwelling events.     

Choline derivatives and sodium fluoride protect acetylcholinesterase against irreversible inhibition and aging by DFP and paraoxon

A light addressable potentiometric sensor was used to measure acetylcholinesterase (AChE) activity in order to evaluate the protective effects of quaternary compounds and NaF against enzyme phosphorylation and aging by two organophosphates. The use of the immobilized AChE made possible the quick removal of reagents (i.e., organophosphate, 2-pralidoxime, and protectant), thereby permitting accurate determination of AChE activity before and after phosphorylation and aging. Paraoxon was 15-fold more potent in inhibiting AChE than DFP, while the percent aging following phosphorylation by diiso-propylfluorophosphate (DFP) was much higher. Sodium fluoride (NaF), the most effective protectant against phosphorylation and aging, and the quaternary ammonium compounds reduced significantly AChE inhibition by DFP and paraoxon, to similar degrees. Even though the percent AChE activity that was lost to aging was reduced by these agents, aging as a percent of phosphorylated AChE was not reduced. Thus, their major effect was in reducing the percent AChE phosphorylation, which consequently resulted in reduction of total aged AChE. The finding that quaternary ammonium compounds protect against phosphorylation is consonant with the proposed presence of the active site of AChE in an aromatic gorge.     

Pharmacological specificity of a nicotinic acetylcholine receptor optical sensor

The pharmacological specificity of a nicotinic acetylcholine receptor (nAChR) optical biosensor was investigated using three fluorescein isothiocyanate (FITC)-tagged neurotoxic peptides that vary in the reversibility of their receptor inhibition: alpha-bungarotoxin (alpha-BGT), alpha-Naja toxin (alpha-NT), and alpha-conotoxin (GI) (alpha-CNTX). Kinetic analysis of the time course of binding of FITC-neurotoxins to the nAChR-coated fiber gave association rate constants (k+1) of 8.4 x 10(6) M-1 min-1 for FITC-alpha-BGT, 6.0 x 10(6) M-1 min-1 for FITC-alpha-NT and 1.4 x 10(6) M-1 min-1 for FITC-alpha-CNTX. The dissociation rate constants (k-1) for the three neurotoxins were 7.9 x 10(-3) min-1. 4.8 x 10(-2) min-1 and 8.0 x 10(-1) min-1 for FITC-alpha-BGT. FITC-alpha-NT and FITC-alpha-CNTX, respectively. The equilibrium dissociation constant (Kd) values for the three toxins. calculated from these rare constants, were similar to published values obtained from tissue responses or ligand binding assays. The optical signal generated by FITC-alpha-NT binding to the nAChR-coated fiber was effectively quenched by agonists and antagonists of the nAChR but not by most of the tested agonists and antagonists of muscarinic cholinergic, adrenergic, glutamatergic, serotonergic, dopaminergic or GABAergic receptors. Interestingly, 5-hydroxy-tryptamine, haloperidol and (+)cis-methyldioxolane gave significant inhibition of FITC-alpha-NT binding to the immobilized receptor. Equilibrium constants of inhibition (Ki) for d-tubocurarine (d-TC) and carbamylcholine (carb) were determined from competition studies using FITC-alpha-CNTX. FITC-alpha-NT or FITC-alpha-BGT as probes for receptor occupancy. When the more reversible probe FITC-alpha-CNTX was used, the Ki value for d-TC was an order of magnitude lower than those determined using the less reversible probes. Ki values for carb however, were independent of the FITC-toxin probe used.     

Prolongation of canine pancreas allograft survival with cyclosporin A: preliminary report.

Studies were conducted on dogs to test the efficacy of cyclosporin A (CyA) in prolonging normoglycaemia and graft survival after whole-organ pancreas allograft transplantation. Five dogs subjected to pancreatectomy alone served as controls. Withholding immunosuppression after transplantation (five animals) resulted in the same median duration of survival as occurred in the controls (13 days). Azathioprine and steroids (seven animals) produced median durations of normoglycaemia and survival of 9 and 23 days respectively. Animals given CyA 18 mg/kg/day (five) and 25 mg/kg/day (10), however, showed median durations of normoglycaemia of 18 and 55 days (p less than 0.05 and p less than 0.02) respectively and median survival times of 36 and 85 days (NS and p less than 0.02). If CyA proved effective in controlling rejection of pancreas allografts in man it would offer unstable diabetics in renal failure a more hopeful outlook than conventional immunosuppression.     

Climate drives differences in the germination niche of a globally distributed invasive grass

外来入侵物种在入侵地经常面临很强的选择压力,这常常导致种内变异。在生活史事件发生的时间上,种群分化对气候梯度的响应被认为是促进许多入侵物种扩张的重要机制。对于产生种子的植物来说,种子萌发的时间决定了萌芽所经历的第一个环境条件,这对入侵植物的成功定植、种群建立和传播具有重要意义——尽管对于萌发在植物入侵成功中所起的作用仍然知之甚少。在本研究中,我们评估了入侵植物石茅(Sorghum halepense)在北美分布的10个种群的种子萌发在温度和降水梯度上的动态变化,以及这种变化是否与本地气候有关。种子被放置于一个较宽的温度范围(11-48˚C)以及两个水分梯度处理中。我们发现,石茅的种子可以在很宽的温度范围下萌发,但在不同的种群中,种子萌发的比例随温度和水分的不同而有较大的变化。有证据表明,当石茅的生长范围从温暖的气候扩展到寒冷的气候时,种子萌发温度的生态位也同时发生了向低温的转变。我们的研究结果表明,石茅种子的萌发已经适应了当地的气候,使其在整个生长范围内的萌发最大化,这可能是其入侵新环境的一个重要贡献因素。     

Evolution and maintenance of microbe‐mediated protection under occasional pathogen infection

Every host is colonized by a variety of microbes, some of which can protect their hosts from pathogen infection. However, pathogen presence naturally varies over time in nature, such as in the case of seasonal epidemics. We experimentally coevolved populations of Caenorhabditis elegans worm hosts with bacteria possessing protective traits (Enterococcus faecalis), in treatments varying the infection frequency with pathogenic Staphylococcus aureus every host generation, alternating host generations, every fifth host generation, or never. We additionally investigated the effect of initial pathogen presence at the formation of the defensive symbiosis. Our results show that enhanced microbe‐mediated protection evolved during host‐protective microbe coevolution when faced with rare infections by a pathogen. Initial pathogen presence had no effect on the evolutionary outcome of microbe‐mediated protection. We also found that protection was only effective at preventing mortality during the time of pathogen infection. Overall, our results suggest that resident microbes can be a form of transgenerational immunity against rare pathogen infection.