A test of a model for planktivorous filter feeding by bream Abramis brama

Synopsis The planktivorous feeding of bream, Abramis brama on Daphnia hyalina and Bosmina coregoni was analyzed in a stepwise regression analysis with the average size (and standard deviation) of consumed organisms as dependent variable and the size of the fish, the average size (and standard deviation) of the organisms and their density in the environment as independent variables. Three basic predictions on filter feeding were formulated and tested. It was predicted that the (average) prey size should increase with fish size, but that the standard deviation should decline. Secondly the prey size should be strongly correlated with the prey size available and thirdly the prey density should have little effect on the size selection. These hypotheses could not be rejected for bream>10 cm feeding on B. coregoni and for bream>20 cm feeding on D. hyalina. The hypotheses were not valid for smaller bream as these acted as particulate or combined filter- and particulate feeders.     

武汉东湖磷含量的变动及其分布

本文总结了武汉东湖水体中磷含量（均以PO4计算）的周年逐月季节和年际变动及其分布上的差异（1973－1985年）。按面积加权法计算总磷的平均含量为0．244毫克／升（1983－1985年）,总溶解磷和溶解活性磷的平均含量分别为0．121毫克／升和0．051毫克／升（1981－1984年）,总磷和总溶解磷周年中出现两次高峰含量,即春季（3－5月）和夏末秋初（8－9月）。低含量出现在水温最低的冬季（12－2月）,周年中溶解活性磷高峰含量出现在冬末春初（1－3月）,低含量多数出现在春天夏初（5－7月）。东湖水体中磷含量平面分布有明显的差异,而垂直分布表层和底层差异小,各种形态磷的组成中颗粒磷所占比较最大（1983－1984年平均值）,平均占总磷63．4％,溶解非活性磷所占比较最小,平均占总磷12．0％。     

The effect of fire on nutrient losses and cycling in aQuercus coccifera garrigue (southern France)

The effects of burning on plant nutrient budgets and rates of carbonic gas and particulate matter emission during fires were evaluated in aQuercus coccifera (garrigue) shrubland. Nutrient levels were determined in field-collected pre-fire vegetation and combustion residues. The losses (increased elemental transfer) were calculated as the difference between the quantity of an element in the fuel (combustible standing vegetation plus litter) before burning and that present in the postfire residues (ash). Weight losses of elements are correlated with weight losses of burnt plant biomass. The relative order of nutrient losses was: N>C>Na>Ca>P>K>Mg. Estimated losses of N, C and P from combustible plant matter exceeded 98, 97 and 79% respectively. Copious N, C and P volatilization during burning was promoted by high concentrations of these elements in foliage and fine woody biomass of the aboveground vegetation and leaf litter of the garrigue. Elements were principally removed in the smoke. The quantities of gaseous emissions of CO₂, CO and particulate matter produced were estimated.     

Classical Conditioning-Induced Changes in Low-Molecular-Weight GTP-Binding Proteins in Rabbit Hippocampus

Classical conditioning of Hermissenda, involving paired light-rotation events, results in a 30-35% decrease in the levels of a 20-kDa G protein (cp20). To test whether a similar protein exists in vertebrates, rabbits were trained to associate a tone with periorbital electrical stimulation and G proteins were analyzed by photoaffinity labeling with [alpha-32P]GTP-azidoanilide. A 20-kDa G protein similar to cp20 decreased by 36% in the hippocampus of rabbits subjected to paired tone and electrical stimulation, but not in unpaired controls. Learning-specific decreases were also found in the amount of ras protein.     

Development and set-up of a portable device to monitor airway exhalation and deposition of particulate matter

The aim of this study was to assess and monitor airway exhalation and deposition of particulate matter (PM). After standardizing inspiratory/expiratory flow and volumes, a novel device was tested on a group of 20 volunteers and in a field study on workers exposed to cristobalite. Both male and female subjects showed a higher percentage of deposition in the 0.5?μm channel than in the 0.3?μm channel on a laser particle counter, but it was higher in the males because of their higher exhaled lung volumes. The device was tested on a wider range of particles (0.3–0.5–1.0–2.5?μm) in the cristobalite productive division. The device has low intrasubject variability and good reproducibility, with geometric mean of %CV?相似文献   

Particulate methane monooxygenase from Methylosinus trichosporium is a copper-containing enzyme

Particulate methane monooxygenase (pMMO) has been exfoliated and isolated from membranes of the Methylosinus trichosporium IMV 3011. It appears that the stability of pMMO in the exfoliation process is increased with increasing copper concentration in the growth medium, but extensive intracytoplasmic membrane formed under higher copper concentration may inhibit the exfoliation of active pMMO from membrane. The highest total activity of purified pMMO is obtained with an initial concentration of 6 microM Cu in the growth medium. The purified MMO contains only copper and does not utilize NADH as electron donor. Treatment of purified pMMO with EDTA resulted in little change in copper level, suggesting that the copper in the pMMO is tightly bound with pMMO.     

Stable carbon and nitrogen isotope signatures of decomposing tropical macrophytes

The Pantanal of Mato Grosso, Brazil, is a large, seasonal wetland, which exhibits high macrophyte productivity at the beginning of the rainy season, when the floodplain becomes flooded. During inundation, from December through May, there is rapid turnover of decomposing macrophyte litter, which is subsequently colonized and consumed by various organisms. In this paper, the variation in the carbon and nitrogen isotope signatures of decomposing macrophytes and detritus was determined to provide an isotopic baseline for the elucidation of higher trophic levels. Seven abundant macrophyte species, Cyperaceae sp., Pontederia lanceolata, Cabomba furcata, Salvinia auriculata, Eichhornia crassipes, Nymphaea amazonum and Paspalum repens, were exposed in mesocosm decomposition experiments lasting 21 or 100 days. Stable isotope ratios of carbon and nitrogen and the atomic C/N ratios were determined for decomposing plant material, particulate organic matter (POM), the microbial film, and aquatic invertebrate larvae. The ¹³C values for the macrophytes did not change during decomposition. However, the variability of ¹⁵N was high (range of ± 6 ) due to microbial activity. There was no consistent difference in the isotopic signatures of macrophytes and POM. C/N ratios decreased from 17 to 50 in macrophytes, to 7 to 12 in POM. The isotopic signatures and C/N ratios of the microbial film were the same as those of POM. We concluded that heterotrophic processes did not fractionate stable carbon isotopes but caused an increase in the variability of stable nitrogen ratios and a change in the C/N ratios in our experimental system. Therefore, it was not possible to distinguish fresh and senescent material or even POM when used as a food source. The ¹³C values of the aquatic larvae were closely coupled to those of the carbon source provided.     

Chloromethane stimulates growth of Methylomicrobium album BG8 on methanol

Studies were performed to determine if the growth of Methylomicrobium album BG8 on methanol could be enhanced through the provision of chloromethane. M. album BG8 was found to be able to oxidize chloromethane via the particulate methane monooxygenase with an apparent K(s) of 11+/-3 microM and V(max) of 15+/-0.6 nmol (min mg protein)(-1). When up to 2.6 mM chloromethane was provided with 5 mM methanol, methanotrophic growth was significantly enhanced in comparison to the absence of chloromethane, indicating that methanotrophs can utilize chloromethane to support growth, although it could not serve as a sole growth substrate. [(14)C]chloromethane was found to be oxidized to [(14)C]CO(2) as well as incorporated into biomass. These results indicate that reactions previously thought to be cometabolic may actually provide some benefit to methanotrophs and that these cells can use multiple compounds to enhance growth.     

Identification of intermediates of in vivo trichloroethylene oxidation by the membrane-associated methane monooxygenase

The rate and products of trichloroethylene (TCE) oxidation by Methylomicrobium album BG8 expressing membrane-associated methane monooxygenase (pMMO) were determined using 14C radiotracer techniques. [(14)C]TCE was degraded at a rate of 1.24 nmol (min mg protein)(-1) with the initial production of glyoxylate and then formate. Radiolabeled CO(2) was also found after incubating M. album BG8 for 5 h with [(14)C]TCE. Experiments with purified pMMO from Methylococcus capsulatus Bath showed that TCE could be mineralized to CO(2) by pMMO. Oxygen uptake studies verified that M. album BG8 could oxidize glyoxylate and that pMMO was responsible for the oxidation based on acetylene inactivation studies. Here we propose a pathway of TCE oxidation by pMMO-expressing cells in which TCE is first converted to TCE-epoxide. The epoxide then spontaneously undergoes HCl elimination to form glyoxylate which can be further oxidized by pMMO to formate and CO(2).     

北京市大气细颗粒污染物与老年呼吸系统疾病急诊就医关系的病例交叉研究

目的:探讨北京市大气细颗粒污染物对呼吸系统疾病急诊的影响。方法:收集2013年3月-2014年3月解放军305医院以及西三环的总参军训部北京第八干休所门诊部的临床病例急诊数据、北京市环境监测中心的大气细颗粒污染物和气象条件数据资料,应用病例交叉设计研究方法进行数据分析。结果:在控制气温、相对湿度的影响后,单向回顾性1:1配对病例交叉分析结果显示,滞后0天细颗粒物污染对慢性支气管炎、哮喘、慢性阻塞性肺病急诊影响的OR值最大,细颗粒物日平均浓度每升高10μg/m3,对应的OR值分别为1.032、1.033、1.035。结论:该研究区域内大气细颗粒物污染物浓度升高可以导致呼吸系统疾病相关的慢性支气管炎、哮喘、慢性阻塞性肺病疾病的急诊增加。