Comparison of Asian clam field bioassays and benthic community surveys in quantifying effects of a coal-fired power plant effluent on Clinch River biota

Survival and growth of Asian clamsmay be more sensitive endpoints than benthicmacroinvertebrate community richness parametersat distinguishing biotic impairmentattributable to complex effluents fromcoal-burning utilities. We conducted (1) fieldbioassays with the Asian clam (Corbiculafluminea) during 2000–02 and (2) rapidbioassessments of benthic macroinvertebratecommunities during 2000–01 at sitesupstream/downstream of American ElectricPower's (AEP) Clinch River Plant (CRP) inRussell County, Virginia (U.S.A). Survival andgrowth of transplanted C. fluminea weresignificantly impaired within the CRP effluentplume (averages of 35% and 0.21 mm,respectively) relative to all other study siteswithin the Clinch River (averages of 89% and1.58 mm). Conversely, richness metrics forEphemeroptera,Ephemeroptera-Plecoptera-Trichoptera (EPT), andtotal taxa were not reduced downstream of theCRP. However, relative abundance metrics forEphemeroptera and EPT were minimally reduced atthe CRP-influenced site during 2000–01. Moreimportantly, our results suggest that richnessmetrics for benthic macroinvertebratecommunities may be inadequate for assessing theeffects of complex industrial effluents on C. fluminea. These findings have implicationsfor bioassessment techniques employed tomonitor streams inhabited by imperiledfreshwater mussels because (1) C. flumineaand Unionoidea are ecologicallysimilar and (2) recent findings suggest certaingenera of Unionidae may be more sensitive thanC. fluminea.     

Comparisons of P-Yield,Riparian Buffer Strips,and Land Cover inSix Agricultural Watersheds

Riparian buffer strips may protect streams from phosphorus (P) pollution. We compared 2 years of daily P-yield (μg m⁻² day⁻¹) from six southeast Wisconsin watersheds with contrasting riparian buffer attributes. Of the variables measured, mean daily P-yield was most closely correlated with the variability in riparian patch size. Variability in P-yield was most closely correlated with characteristics of the riparian buffer, such as percent wetland land cover, riparian continuity, and stream sinuosity. During the most extreme events, mean P-yield was negatively correlated with the percentage of wetland land cover in the upland watershed. Correlations suggest that riparian continuity may influence P-loading in these watersheds. Our results corroborate the importance of continuity and uniformity of riparian buffers as moderators of P flow from upland agricultural lands into streams. Received 1 June 2001; accepted 5 February 2002.     

Detecting and quantifying meat meal or meat and bone meal contamination in fishmeal by visible and near infrared reflectance spectra

The use of animal protein feeds such as meat meal or meat and bone meal (MMBM) play an important role in the feed manufacturing industry, but their safe and healthy use in animal feeds is of public concern in order to prevent the spread of bovine spongiform encephalopathy (BSE). The objective of the present work was to develop a technique using near infrared reflectance spectroscopy (NIRS) that would be suitable for detecting and quantifying contaminating levels of MMBM in fishmeal. To this end, a partial least squares (PLS) discriminant analysis and a modified partial least squares (MPLS) quantitative analysis, using visible and NIRS, were developed using a calibration set of 186 samples including 90 samples of pure fishmeal and 96 samples adulterated with MMBM at levels ranging from 10 to 320 g/kg. An external validation set, comprised of 39 pure samples and 54 adulterated samples, was used to validate the calibration model. A PLS discriminant analysis model developed with mathematic pretreatment 1,4,4,1, successfully detected fishmeal adulterated with MMBM. External validation indicated that all samples were discriminated correctly. A MPLS quantitative model, developed with mathematic pretreatment 1,4,4,1, also successfully predicted the MMBM in fishmeal with standard error of cross-validation (SECV) of 27.89 g/kg and ratio of the standard deviation of the validation set to the standard error of prediction (RPD) of 3.37. The calibration and validation results confirm that NIRS could provide the feed industry and inspection bodies with a rapid, non-destructive and non-invasive technique for the detection and quantification of MMBM in fishmeal.     

Effects of nitrogen source on the synthesis of the UV-screening compound, scytonemin, in the cyanobacterium Nostoc punctiforme PCC 73102

The effects of nitrogen source (N(2), NO(3)(-) and NH(4)(+)) on scytonemin synthesis were investigated in the heterocystous cyanobacterium Nostoc punctiforme PCC 73102. With the required UVA radiation included, Nostoc synthesized three to seven times more scytonemin while fixing nitrogen than when utilizing nitrate or ammonium. A similar increase in scytonemin synthesis occurred when nitrate or ammonium became depleted by growth and Nostoc switched to diazotrophic metabolism with the differentiation of heterocysts. In addition, UVA-exposed cultures grown in medium with both NO(3)(-) and NH(4)(+) synthesized some scytonemin but synthesis increased when NH(4)(+) was depleted and growth had become dependent on NO(3)(-) reduction. Although the mechanism is unclear, these results suggest that the greater the restriction in nitrogen accessibility, the greater the production of scytonemin. Perhaps the entire response may be an interaction between this restriction and a resultant sensitivity to UV radiation that acts as a cue for determining the level of scytonemin synthesis. Scytonemin is a stable UVR screening compound and appears to be synthesized by cyanobacteria as a long-term solution for reducing UVR exposure and damage, but mainly or solely, when metabolic activity is absent. It is likely that during metabolic resurgence, the presence of a dense scytonemin sheath would facilitate the recovery process without the need for active defenses against UV radiation.     

江河源区高山嵩草(Kobresia pygmaea)草甸植物和土壤碳、氮储量对覆被变化的响应

以青海省果洛州藏族自治州甘德县青珍乡高山嵩草Kobresia pygmaea草甸轻度退化草地和重度退化草地为研究对象,通过植物地上部分主要功能群(禾草类、杂类草、莎草类)、植物根系和土壤碳、氮浓度及储量动态研究,结果表明:高寒小嵩草草甸轻度退化草地地上部分主要功能群碳、氮浓度和C ∶ N比值明显高于重度退化草地的浓度.同一草地类型主要功能群比较,碳、氮浓度依次为杂类草>禾草类>莎草类;植物地上部分的碳、氮浓度明显高于地下根系的碳、氮浓度.重度退化草地植物根系碳、氮浓度高于轻度退化草地植物根系碳、氮浓度.重度退化草地土壤总有机碳浓度显著低于轻度退化草地土壤总有机碳浓度,随着土层的加深碳、氮浓度有减少的趋势.江河源区高山嵩草草甸的土壤有机碳、氮储量最大,植物根系碳、氮储量居中,植物地上部分碳、氮储量最小.重度退化草地总有机碳储量(13554.3 g/m2)较轻度退化草地储量(14669.2 g/m2)下降7.60%.其中,0～40cm土壤层碳储量下降4.10%,植物根系碳储量下降59.97%,植物地上部分碳储量下降15.39%;重度退化草地总氮储量(3780.6 g/m2)较轻度退化草地储量(3352.7 g/m2)高12.76%,其中,0～40cm土壤中总氮储量高13.07%,植物根系全氮储量下降55.09%,植物地上部分全氮下降16.00%.由于草地退化损失有机碳11149 kg/hm2,而全氮增加4278 kg/hm2.     

Effect of storage xyloglucans on peritoneal macrophages

Xyloglucans from seeds of Copaifera langsdorffii (XGC), Hymenaea courbaril (XGJ) and Mucuna sloanei (XGM) were obtained from milled and defatted cotyledons by aqueous extraction at 25 degrees C. The resulting fractions contained Glc, Xyl and Gal in molar ratios of 2.5: 1.5: 1.0 (XGC), 3.8: 2.6: 1.0 (XGJ) and 2.5: 1.6: 1.0 (XGM). HPSEC-MALLS/RI analysis showed that each polysaccharide fraction was homogeneous; M(w) values were 1.6 x 10(5), 2.0 x 10(5) and 1.5 x 10(5)g/mol, respectively. The effect of the xyloglucans on the production of O(2)*(-) and NO* and on the recruitment of macrophages to the mouse peritoneum was evaluated. All polysaccharides promoted an increase in the number of peritoneal macrophages in a dose-dependent manner. The largest increase, of 576% in comparison to the control group, was elicited by XGJ at 200 mg/kg. The effect of XGC, XGJ and XGM on O(2)*(-) production, in the presence or absence of phorbol 12-myristate 13-acetate (PMA), was not statistically significant. For NO(.) production, the lowest concentration of XGC (10 microg/ml) gave rise to an increase of 262% when compared to the control group; the effect was dose-dependent, reaching 307% at 50 microg/ml. On the other hand, XGJ at a concentration of 50 microg/ml enhanced NO* production by 92%. XGM did not affect NO* production significantly. The results indicate that xyloglucans from C. langsdorffii, H. courbaril and M. sloanei have immunomodulatory activity.     

大气中CO2、O3浓度升高对银杏成年叶片气孔数量特征的影响

利用开放式气室(OTC)持续观测了2个生长季(2005-2006年).在每年9月30日停止供气后,采样1次.观测高浓度CO2和O3处理的银杏(Ginkgo biloba)成年叶片气孔数量的变化规律.结果表明:在700 μmol·mol-1CO2处理条件下,叶片气孔的长度、宽度、周长和面积均明显高于对照(P<0.05);在80 μmol·mol-1O3处理条件下,气孔的长度、宽度、周长和面积却显著低于对照(P<0.01);成年叶片气孔在高浓度CO2影响下,气孔密度略有升高(P>0.05),而气孔指数显著减少(P<0.05);大气O3浓度升高对气孔密度影响不大(P>0.05),气孔指数显著减少(P<0.05);银杏成年叶片气孔的长度、宽度与气孔比密度存在一定的负相关关系,可用一元二次曲线方程较好地描述.     

The shared reward dilemma

One of the most direct human mechanisms of promoting cooperation is rewarding it. We study the effect of sharing a reward among cooperators in the most stringent form of social dilemma, namely the prisoner's dilemma (PD). Specifically, for a group of players that collect payoffs by playing a pairwise PD game with their partners, we consider an external entity that distributes a fixed reward equally among all cooperators. Thus, individuals confront a new dilemma: on the one hand, they may be inclined to choose the shared reward despite the possibility of being exploited by defectors; on the other hand, if too many players do that, cooperators will obtain a poor reward and defectors will outperform them. By appropriately tuning the amount to be shared a vast variety of scenarios arises, including the traditional ones in the study of cooperation as well as more complex situations where unexpected behavior can occur. We provide a complete classification of the equilibria of the n-player game as well as of its evolutionary dynamics.     

A multilevel approach to cancer growth modeling

Cancer growth models may be divided into macroscopic models, which describe the tumor as a single entity, and microscopic ones, which consider the tumor as a complex system whose behavior emerges from the local dynamics of its basic components, the neoplastic cells. Mesoscopic models (e.g. as based on the Local Interaction Simulation Approach [Delsanto, P.P., Mignogna, R., Scalerandi, M., Schechter, R., 1998. In: Delsanto, P.P. Saenz, A.W. (Eds.), New Perspectives on Problems in Classical and Quantum Physics, vol. 2. Gordon & Breach, New Delhi, p. 5174]), which explicitly consider the behavior of cell clusters and their interactions, may be used instead of the microscopic ones, in order to study the properties of cancer biology that strongly depend on the interactions of small groups of cells at intermediate spatial and temporal scales. All these approaches have been developed independently, which limits their usefulness, since they all include relevant features and information that should be cross-correlated for a deeper understanding of the mechanisms involved. In this contribution we consider multicellular tumor spheroids as biological reference systems and propose an intermediate model to bridge the gap between a macroscopic formulation of tumor growth and a mesoscopic one. Thus we are able to establish, as an important result of our formalism, a direct correspondence between parameters characterizing processes occurring at different scales. In particular, we analyze their dependence on an important limiting factor to tumor growth, i.e. the extra-cellular matrix pressure. Since the macro and meso-models stem from totally different roots (energy conservation and clinical observations vs. cell groups dynamics), their consistency may be used to validate both approaches. It may also be interesting to note that the proposed formalism fits well into a recently proposed conjecture of growth laws universality.     

Somatic embryogenesis from embryogenic cell suspension cultures of california poppy, Eschscholzia californica Cham

Summary A somatic embryogenesis protocol was developed for Eschscholzia californica Chan. (California poppy) using embryogenic cell suspensions and optimized media conditions. Rapidly-growing, finely-dispersed embryogenic cell suspension cultures were established from embryogenic callus and maintained in B5 liquid media supplemented with 0.5 mg 1⁻¹ (2.26 μM) 2,4-dichlorophenoxyacetic acid. Culture conditions were optimized by investigating the effect of basal media composition, gyratory shaker speed, various carbon sources, different cytokinins, and AgNO₃ on the efficiency of somatic embryogenesis. After 40 d in culture, the somatic embryos that formed were counted and their overall growth expressed as pecked cell volume. The selected media consisted of either Gamborg (B5) or Murashige and Skoog (MS) salts and vitamins supplemented with 40 g 1⁻¹ (117 mM) sucrose, 0.05 mg 1⁻¹ (0.22 μM) 6-benzylaminopurine, and 10 mg l⁻¹ (58.8 μM) AgNO₃. Somatic embryo production was substantially reduced at shaker speeds above 40 rpm. Glucose and snerose were the most effective carbon sources, whereas fructose, galactose, and maltose resulted in a reduced yield and growth of somatic embryos. The development of somatic embryos was promoted by AgNO₃ at concentrations below 10 mg l⁻¹ (58.8 μM). A semi-solid medium containing 1.5 g l⁻¹ Gel-rite produced the highest frequency of somatic embryo conversion, and promoted the efficient growth of plantlets. Using the reported protocol, over 500 viable somatic embryos were produced per 25 ml of embryogenic cell suspension culture.