蚯蚓细胞色素P450酶系对土壤中芘或苯并[a]芘的响应

以赤子爱胜蚓(Eisenia fetida)为受试生物,通过人工污染草甸棕壤微宇宙试验方法,研究了暴露于不同环境浓度芘或苯并[a]芘(添加量分别为0.12、0.24、0.48、0.96 mg·kg~(-1))污染的土壤中14 d后,蚯蚓体内细胞色素P450(CYPs)酶系,如CYPs总量、CYP1A1及CYP2C9活性的变化.结果显示,芘或苯并[a]芘暴露导致蚯蚓CYPs总量、CYP1A1及CYP2C9活性的变化不同.其中,CYPs总量与CYP1A1活性对芘的响应趋势相似:试验3 d后,0.96 mg·kg~(-1)芘导致二者都显著高于对照水平;14 d后,都显著低于对照水平;CYP1A1活性对芘的响应更为敏感.CYPs总量与CYP2C9活性对苯并[a]芘的响应趋势相似:暴露初期,苯并[a]芘最高暴露剂量(0.96 mg·kg~(-1))导致二者都显著低于对照水平;试验结束后,苯并[a]芘最低暴露剂量(0.12 mg·kg~(-1))导致二者都显著高于对照水平,最高剂量暴露导致二者都显著低于对照水平,CYP2C9活性对苯并[a]芘的响应更为敏感.因此,推断CYPs亚酶对污染物的响应具有选择性且亚酶的响应敏感度高于CYPs总量.将CYPs总量与CYP1A1活性结合,或与CYP2C9活性结合分别诊断土壤芘污染或并[a]芘污染,较为准确有效.     

Testing hypotheses on shape and distribution of ecological response curves

Niche theory with hypotheses on shape and distribution of ecological response curves is used in the studies of resource sharing of competing plant species. Predictions based on theory should be applicable when, e.g., effects of competing species on the ecological tolerances are assessed or species’ diversity along a resource gradient is evaluated. We studied the ecological response curves of competing plant species along a resource gradient in boreal forests. The study was based on nation-wide soil and vegetation data collected from 455 sample plots on boreal forests in Finland. Species response curves along a soil fertility gradient (in terms of C/N ratio) were estimated using generalized additive models. Distribution of species optima and the relationship of niche width and skewness to the location of the optimum were analyzed with new bootstrap tests. The developed tests can account for the effects of truncation observed in the response curves of several species and for the uneven distribution of observations on the gradient.The estimated response curves of the major field layer species of boreal forests were not evenly distributed along soil C/N gradient. The density of optima peaked with relatively high nitrogen availability. Species with optima at low nitrogen availability had relatively broad realized niches. Niche width was negatively correlated with the density of optima. Species optima were packed and niches were narrow at high resource levels. This result suggests that a greater number of more specialized species can occur and interspecific competition decreases niche widths at high resource levels. Species were packed in the gradient where the C/N ratio was lower than 25, i.e., in conditions where nitrification can take place. This indicates that the majority of the vascular plants of boreal forests are favoured by the availability of NO₃⁻. Those few species thriving at high C/N ratios have broader realized niches.     

Bioavailability and toxicological potential of sunflower-bound residues of 14C-chlorpyrifos insecticide in rats

Sunflower plants were treated with ¹⁴C-chlorpyrifos under conditions simulating local agricultural practice. Residues present in the oil, methanol extract and cake of the treated sunflower seeds were 7.2, 2.8, and 12 ppm, respectively. When rats fed on sunflower cake containing bound residues for three days, the animals eliminated 46 % of the radioactivity in urine, 25 % in feces and 10 % in the expired air. A further bioavailable amount of 8 % was found in selected organs indicating that the bound residues were highly bioavailable. Chromatographic analysis of urine extract revealed the presence of the parent compound, its oxon, desethyl chlorpyrifos and desethyl chlorpyrifos oxon as free metabolites in addition to a conjugated metabolite. It was liberated by acid hydrolysis and identified as 3,5,6-trichloro-2-hydroxypyridine. Bound residues were found to have biological effects such as inhibition of rat plasma ChE, elevations of liver parameters (ALT, AST, and ALP), decrease in total protein and albumin content suggesting a hepatotoxic potential. A significant increase in the values of creatinine, urea, cholesterol, triglycerides and significant decrease in Catalase and Glutathion-S-Transfrase were observed in treated rats.     

Use of Congeneric Assessment to Reveal the Linked Genetic Histories of Two Threatened Fishes in the Murray‐Darling Basin,Australia

Abstract: The intensely regulated Murray‐Darling Basin in southeastern Australia is the nation's most extensive and economically important river system, and it contains fragmented populations of numerous fish species. Among these is the Murray hardyhead (Craterocephalus fluviatilis), a species listed as endangered (International Union for Conservation of Nature Red List) in the mid‐1990s prior to its acute decline with the progression of a severe drought that began in 1997. We compared the genetic structure of Murray hardyhead with 4 congeneric species (Darling hardyhead[C. amniculus], Finke hardyhead[C. centralis], Lake Eyre hardyhead[C. eyresii], and unspecked hardyhead[C. stercusmuscarum]), selected on the basis of their taxonomic or biological similarity to Murray hardyhead, in order to affirm species boundaries and test for instances of introgressive hybridization, which may influence species ecology and conservation prospects. We used allozyme (52 loci) and mtDNA markers (1999 bp of ATPase and cytochrome b) to provide a comparative genetic assessment of 139 Murray hardyhead, which represented all extant and some recently extirpated populations, and 71 congeneric specimens from 12 populations. We confirmed that Murray hardyhead and Darling hardyhead are taxonomically distinct and identified a number of potential conservation units, defined with genetic criteria, in both species. We also found allozyme and mtDNA evidence of historic genetic exchange between these 2 allopatric species, apparently involving one population of each species at the geographic edge of the species’ ranges, not in the most proximate populations sampled. Our results provide information on species boundaries and offer insight into the likely causes of high genetic diversity in certain populations, results which are already being used to guide national recovery planning and local action. Given the prevalence of incorrect taxonomies and introgression in many organismal groups, we believe these data point to the need to commence genetic investigations of any threatened species from an initially broad taxonomic focus.     

Interannual Changes in the C:N:P Ratios of Seston and Zooplankton of a High Mountain Lake in Sierra Nevada,Spain

We investigated the carbon, nitrogen and phosphorus content inthe seston and the zooplankton of a high-mountain lake duringthree years of contrasting physical and chemical conditions.Carbon in seston was ten times higher in 1995 than in 1996 and1997. Phosphorus content in seston was variable for the studyperiod, increasing gradually towards late summer in 1995, butpeaking abruptly in 1996 and 1997, reflecting atmosphericdepositions. Seston C:P were high and did not fit any definitepattern in 1995, and were particularly low after the thaw, increasing towards mid-summer in 1996 and 1997. As the seasonprogressed, major decreases in these ratios occurred coincidingwith important atmospheric inputs in the lake area. ZooplanktonN:P and C:P were negatively associated to the appearance ofrotifers and copepod nauplii in 1995, but positively correlatedto the ontogenetic development of the most abundant species,Mixodiaptomus laciniatus, in 1996. Seasonal variations inzooplankton N:P and C:P ratios showed limited interannual, butlarge intraannual variability. The comparison between the bulkcarbon in seston and zooplankton demands for this elementindicated that zooplankton were above food-quantity thresholdsfor maximum growth in 1995, 1996 and mid-season of 1997,therefore suffering only from food-quantity constraints afterthe thaw (nauplii dominance) and towards late season (adultdominance) in the latter year. The high C:P ratios in sestonrelative to zooplankton in 1995 imply that the zooplankton mayhave faced severe food-quality constraints (in terms ofphosphorus) during this year. Differences between bulkzooplankton and seston elemental nutrients are also discussed inrelation to the competitive abilities of species, andparticularly of Daphnia.     

Comprehensive temperature monitoring in an in-vessel forced-aeration static-bed composting process

Comprehensive temperature monitoring was done in an in-vessel forced-aeration static-bed composting process using sewage sludge. The three layers that divided the compost pile horizontally showed different temperature distributions. The temperature of the top layer appeared not to be influenced by the ambient temperature. The temperature of the center area of the top layer was taken to be the representative temperature for evaluating composting start-up performance. The temperature of the bottom layer was strongly influenced by the ambient temperature, and the temperature of the center area of the bottom layer was taken to be the representative temperature for pathogen control as it was the minimum temperature in the reactor. Composting start-up performance was influenced by several factors when the ambient temperature was either below or above 20°C. When the ambient temperature was below 20°C, the time taken to reach 65°C (T ₆₅) was influenced by the temperature of inflowing air, but when the temperature was higher than 20°C, it was influenced by the ratio of sewage sludge to seed compost (F/S). T ₆₅ was least when F/S was 1–2. Received: January 9, 2001 / Accepted: October 10, 2001     

The effect of age,gender and marital status on residential satisfaction

ABSTRACT

Residential satisfaction is a vital component of individual quality of life which has been explored by researchers from different perspectives. This study takes the stance to investigate residential satisfaction from sociodemographic standpoints. The purpose is to contribute to further research on residential satisfaction by exploring specifically the impact of age, gender and marital status on overall residential satisfaction and in more detail with components of residential satisfaction of residents living in apartment buildings in Dhaka, Bangladesh. Quantitative analyses of a survey of 204 residents living 59 apartment buildings in Dhaka was conducted to examine whether there is any relation between residential satisfaction with age, gender and marital status of the apartment dwellers. This study also examined if these sociodemographic characteristics had a moderator effect on some of the key components of residential satisfaction. Primary findings indicate that there exists a significant relationship between residential satisfaction with age, gender, and marital status. Further analysis revealed that the “Married” group was more satisfied than the “Single/Never married” group, senior people tend to be more satisfied than are younger respondents and females were more satisfied than males concerning overall residential satisfaction. This study concludes that potential sociodemographic differences among households in apartment developments in Dhaka should be considered for effective residential satisfaction and to create a socially sustainable living environment.     

Response of Organic and Inorganic Carbon and Nitrogen to Long-Term Grazing of the Shortgrass Steppe

We investigated the influence of long-term (56 years) grazing on organic and inorganic carbon (C) and nitrogen (N) contents of the plant–soil system (to 90 cm depth) in shortgrass steppe of northeastern Colorado. Grazing treatments included continuous season-long (May–October) grazing by yearling heifers at heavy (60–75% utilization) and light (20–35% utilization) stocking rates, and nongrazed exclosures. The heavy stocking rate resulted in a plant community that was dominated (75% of biomass production) by the C₄ grass blue grama (Bouteloua gracilis), whereas excluding livestock grazing increased the production of C₃ grasses and prickly pear cactus (Opuntia polycantha). Soil organic C (SOC) and organic N were not significantly different between the light grazing and nongrazed treatments, whereas the heavy grazing treatment was 7.5 Mg ha^–1 higher in SOC than the nongrazed treatment. Lower ratios of net mineralized N to total organic N in both grazed compared to nongrazed treatments suggest that long-term grazing decreased the readily mineralizable fraction of soil organic matter. Heavy grazing affected soil inorganic C (SIC) more than the SOC. The heavy grazing treatment was 23.8 Mg ha^–1 higher in total soil C (0–90 cm) than the nongrazed treatment, with 68% (16.3 Mg ha^–1) attributable to higher SIC, and 32% (7.5 Mg ha^–1) to higher SOC. These results emphasize the importance in semiarid and arid ecosystems of including inorganic C in assessments of the mass and distribution of plant–soil C and in evaluations of the impacts of grazing management on C sequestration.