Relative sensitivity of different soil biological properties to zinc

This study investigated the responses to Zn of selected enzymatic activities, potential nitrification and microbial activity in a soil contaminated with Zn at concentrations ranging from 74 to 3490 mg kg⁻¹. The main aims of the study were to evaluate different models for EC₅₀ estimation and to compare the relative sensitivity to Zn of the different biological properties studied. The EC₅₀ for each property was calculated using three different models, namely a logistic dose response model, and a full and a partial inhibition model based on Michaelis-Menten kinetics. Both total (aqua regia extractable) and labile (CaCl₂ extractable) Zn content were assessed and employed for application of the models. A response to increasing Zn concentrations was observed for most of the biological properties except for fluorescein diacetate hydrolysis activity (FDA) and acid phosphatase activity. Among the three models tested, the logistic model had the widest applicability and generally gave the best results in terms of EC₅₀ estimation and R² fit. Among the two kinetics models tested, the partial inhibition model was applicable only in a few cases, but in these cases results are generally better than for the full inhibition model. The utilization of either total or labile Zn data did not significantly affect the outcomes of the models. The sensitivity of the biological properties to Zn was ranked according to the models as follows: nitrate reductase > potential nitrification > β-galactosidase > dehydrogenase > phenol oxidase = urease = arylsulphatase. These ranking results were generally in accordance with evidence provided by other researchers, thus showing that the relative sensitivity of these properties, especially the most sensitive ones, is generally constant among different soil types. The relevance of this finding for soil ecological risk assessment is discussed.     

Scleroderma and the subcutaneous tissue

Our study revealed that as observed with both light and electron microscopy the most specific abnormality in sclerodermna skin is the replacement of the subcutaneous tissue by markedly abnormal connective tissue.     

Present and historical landscape structure shapes current species richness in Central European grasslands

Landscape Ecology - Current diversity and species composition of ecological communities can often not exclusively be explained by present land use and landscape structure. Historical land use may...     

Triacylglycerol analysis of potential margarine base stocks by high-performance liquid chromatography with atmospheric pressure chemical ionization mass spectrometry and flame ionization detection

Several margarine base stock candidates have previously been prepared for the purpose of finding better, more oxidatively stable food components: high-saturate vegetable oils, randomized vegetable oils, vegetable oil-hard stock blends, and interesterified vegetable oil-hard stock blends. Here are reported the triacylglycerol compositions of these products, determined using reverse-phase high-performance liquid chromatography (HPLC) coupled with a flame ionization detector or a quadrupole mass spectrometer with an atmospheric pressure chemical ionization source. Triacylglycerol percent composition results for samples of known composition (randomized and interesterified samples) exhibited less average error by HPLC coupled with a quadrupole mass spectrometer with an atmospheric pressure chemical ionization source, after application of response factors, than the results by HPLC coupled with a flame ionization detector. The fatty acid compositions calculated from the mass spectrometric data exhibited less average error than the fatty acid compositions resulting from the flame ionization detector data. The average error of the fatty acid compositions by the mass spectrometer was lowest for interesterified blend samples, next lowest for randomized samples, then followed by high-saturated fatty acid oils, normal oils, and blends. Analysis of the vegetable oil-hard stock blends by mass spectrometer required special treatment for calculation of response factors.     

The effects of three phthalate esters on the larval development of the grass shrimp Palaemonetes pugio (Holthuis)

The effects of three phthalic acid esters, dimethyl phthalate (DMP), di-n-butyl phthalate (DBP) and di-2-ethylhexyl phthalate (DEHP) on survival and development rate of larvae of the grass shrimp Palaemonetes pugio were investigated. Only 100 ppm DMP and 10 to 50 ppm DBP were acutely toxic to the larvae. DMP at a concentration of 100 ppm significantly increased the duration of larval development to the first postlarval stage. DEHP concentrations up to 1 ppm (the solubility limit of this ester) were without effect on either survival or development rate of the larvae. Phthalate esters were not detectable at or above the 2 ppm level in the tissues of larvae chronically exposed to phthalates for the duration of larval development, suggesting active metabolism of phthalates by this species.     

Modeling of hydrogenation kinetics from triglyceride compositional data

A mathematical model was developed to describe the reduction of soybean oil triglycerides during hydrogenation. The model was derived from reaction and transport mechanisms and formulated into a system of first-order irreversible rate expressions that included terms for temperature, hydrogen pressure, and catalyst concentration. The model parameters were estimated from experimental data, and the model was used to simulate the results of hydrogenation performed over the pressure range of 0.069-6.9 MPa. The model could be extended to include geometrical isomers formed during hydrogenation.     

Evolution of introduced Chinook salmon (Oncorhynchus tshawytscha) in Lake Huron: emergence of population genetic structure in less than 10 generations

Abstract – Population genetic structure was detected in Chinook salmon Oncorhynchus tshawytscha in their non‐native range of Lake Huron using microsatellite DNA. All Chinook salmon in this system descend from Green River, Washington cohorts, originally transplanted to Michigan hatcheries in the late 1960s. We tested for population genetic differentiation of age 0 fish collected from 13 rivers and two hatcheries in 2007. The amount of genetic differentiation among collection sites was low but statistically significant, with F_ST values ranging from 0.036 to 0.133 and R_ST values ranging from 0.008 to 0.157 for specific loci. Based on pairwise F_ST and R_ST values and Bayesian cluster analysis, the Maitland River population in the Main Basin of Lake Huron was genetically distinct from the remaining collection sites. Based on analysis of bycatch data from commercial gill net fisheries, Chinook salmon likely colonised the Main Basin by 1975 (10 generations ago) and the North Channel and southern Georgian Bay regions by 1980 (eight generations ago). Thus, population genetic structure has emerged in Lake Huron Chinook salmon in <10 generations.     

Effects of selenate addition on selenium accumulation and plant growth of two Prunus rootstock genotypes

A pot experiment was conducted with two Prunus genotypes (GF 677 and Mr.S.2/5, commercial rootstocks for peach), which are widely used in Italy and other European countries. Selenium (Se) was added as sodium selenate to 3‐month‐old micropropagated plants at a rate of 0 (control), 1.0, 2.5, and 5.0 mg Se (kg soil)^–1. Plant growth, gas exchange, and Se accumulation were studied. Selenium added at a rate of 2.5 and 5.0 mg Se kg^–1 appeared to be highly toxic for the two young peach rootstocks. Thirty‐three days after the treatment, the plants showed a high mortality rate. The fast growing rootstock, GF 677, appeared to be more sensitive to Se toxicity, the mortality rate reaching 52%. The higher the Se concentration in the soil, the higher it also was in the plant. In general, both genotypes were able to take up Se and to translocate high amounts from root to leaf. After selenate addition to the soil, both GF 677 and Mr.S.2/5 plants showed reduced plant growth with the highest Se treatments. Furthermore, Se induced a partial stomatal closure, as evidenced by the values of stomatal conductance, resulting in a reduction in net assimilation, and thus a decrease in dry‐matter production. Selenate applied at a low rate (1 mg Se kg^–1) stimulated plant growth in GF 677. One year after the Se treatment, a remobilization of Se from the storage organs to the young shoots was detected. This study demonstrates genotypic variation in Se uptake and accumulation in peach rootstocks.     

Olmec pottery production and export in ancient Mexico determined through elemental analysis

The first Mesoamerican civilization, the Gulf Coast Olmec, is associated with hierarchical society, monumental art, and an internally consistent ideology, expressed in a distinct style and salient iconography. Whether the Olmec style arose in just one area or emerged from interactions among scattered contemporaneous societies remains controversial. Using elemental analysis, we determined the regional clay sources of 725 archaeological ceramic samples from across Mesoamerica. Exported Olmec-style ceramics originated from the San Lorenzo region of the Gulf Coast, supporting Olmec priority in the creation and spread of the first unified style and iconographic system in Mesoamerica.     

Minimal residual disease in lymph nodes after achievement of complete remission predicts time to relapse in dogs with large B‐cell lymphoma

Most dogs with large B‐cell lymphoma (LBCL) that undergo chemotherapy and achieve clinical complete remission (CR) eventually relapse. However, time to relapse (TTR) is unpredictable. The aims of this prospective study were to assess the influence of post‐chemotherapy lymph node (LN) infiltration by large CD21+ cells using flow cytometry (FC) on TTR, and to establish a cut‐off value of prognostic significance. Dogs with newly‐diagnosed, completely staged LBCL in CR after treatment were enrolled. Minimal residual disease (MRD) analysis by FC was performed on LN aspirates. TTR was calculated between MRD and relapse. Thirty‐one dogs were enrolled: 4% had stage V disease, and diffuse large B‐cell lymphoma was the most common histotype (74%). Based on LN infiltration at MRD evaluation, three groups were created: (a) acellular samples, (b) ≤0.5% infiltration and (c) >0.5% infiltration. Overall median TTR was 154 days (range, 31‐1974): 22 (71%) dogs relapsed during the study period, whereas 9 (29%) dogs did not. The difference among the three groups was significant (P = 0.042 log‐rank test): median TTR was not reached for dogs with LN infiltration ≤0.5% (range, 195‐429 days), 164 days (range 63‐1974) for dogs with acellular LN samples, and 118 days (range, 31‐232) for dogs with LN infiltration >0.5%. These results demonstrate that MRD assessment by FC on LN aspirates in dogs with LBCL in clinical CR predicts TTR. LN infiltration by >0.5% large CD21+ cells after treatment is an unfavourable prognostic factor.