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951.
Several theories predict a sex-biased investment either through unbalanced sex ratios in offspring or through differences in provisioning. According to them, one would expect an optimisation in indirect fitness, or else a compensation for increased mortality of one sex. In addition, biases in provisioning may also arise as a consequence of weight-dependent non-adaptive nutrient demands by offspring. This study examines milk provisioning and sex biases in offspring sex ratio together with maternal quality variables. Mothers of higher quality (weight and age) showed greater milk provisioning ability (in terms of production) resulting in greater calf weight gain. Mothers of sons produced greater yields of milk, milk protein, fat and lactose than mothers of daughters, and increased percentage of protein after controlling for higher male birth weight. In contrast, mothers of males did not differ from mothers of females in age or any body weight variables related to maternal quality. These results suggest that differences in milk production and composition for sons and daughters are rather a mechanism to optimise indirect fitness than a mechanism to compensate for increased mortality in male calves, or a consequence of greater weight-dependent nutrient demands by heavier male calves. Results also suggest that biases in milk provisioning may occur without biases in offspring sex ratio, and furthermore, in contrast to the prediction that biases should be relative to the mean investment of the population, that milk provisioning biases might not be relative.Communicated by F. Trillmich  相似文献   
952.
953.
Cytochrome P450-dependent microsomal monooxygenase (P450) activity was measured in control and atrazine-exposed third instar midge larvae, Chironomus tentans. Significantly elevated O-demethylase activity was observed in gut homogenates taken from midges exposed to atrazine concentrations from 1 to 10 ppm for 90 h. No significant induction was observed at atrazine concentrations below 1 ppm. A region of a cytochrome P450 family 4 gene was amplified and sequenced from C. tentans larvae. Alignments of inferred amino acid sequences with other insect CYP4 gene homologues indicate a high degree of similarity. Northern blot analysis employing the CYP4 gene fragment as a probe showed an over-expression in C. tentans exposed to atrazine. The results support the previously identified inducibility of cytochrome P450-dependent activity and provide insight into the potential consequences of atrazine exposure to aquatic organisms.  相似文献   
954.
The rainbow trout fish cell lines RTG-2 and RTL-W1 were used to determine the cytotoxic effects of the pesticides bifenthrin, cypermethrin, cyhalothrin, lambda-cyhalothrin, quinalphos and chlorpyrifos. Cytotoxicity was measured by EROD and beta-Gal enzymatic activities, the neutral red (NR) uptake assay, and the FRAME KB protein (KBP) assay. The beta-Gal activity was unaffected by the pesticide exposure. The EROD activity was induced by cyhalothrin and lambda-cyhalothrin (RTG-2 and RTL-W1) and by bifenthrin (RTL-W1). Dose dependent inhibition responses were observed for EROD activity in cells exposed to quinalphos (RTL-W1) and chlorpyrifos (RTG-2 and RTL-W1). RTL-W1 offered a better response for EROD induction. The EC50 values on EROD endpoint were more sensitive than NR and KBP. The acute fish toxicity of chlorpyrifos and quinalphos depends highly on the species; the species sensitivity distributions cover several orders of magnitude and the values obtained for EROS were within the lowest part of the reported ranges.  相似文献   
955.
This paper describes systematic work undertaken in the field of atmospheric emissions from Portuguese Kraft pulp mills. The study led to the determination of emission factors from stationary sources, which proved to be an important tool for assessing the need for investment in air pollution abatement equipment, specifically for malodorous gases.  相似文献   
956.
957.
Chemical fingerprinting approach to environmental assessment is illustrated in the evaluation of marine oil pollution in the coasts using two limpet species as bioindicator organisms, and based on profiles and concentrations of n-alkanes and aromatic hydrocarbons in their tissues. Accidental and chronic releases of hydrocarbons can contaminate the marine environment of the Canary Islands not only because of their geographical situation but also because of the very dense tanker traffic around. This situation affects coastal areas, fishing activities, tourism resort, etc. Concentrations of n-alkanes and aromatic hydrocarbons (polycyclic aromatic hydrocarbons and methyl-polycyclic aromatic hydrocarbons) in the soft tissues of the marine intertidal and subtidal limpets, Patella crenata and Patella ullysiponensis aspera, were evaluated. Limpet samples were collected at monthly intervals, at three locations on the southeast coast of Tenerife over a 3-year period (1991-93). Levels of hydrocarbons found in limpets are similar to concentrations found in unpolluted areas around the world. From application of principal component analysis, the interpretation of variable loading plots gives information on variable correlation and can be used to distinguish among potential sources of pollution and the ability of studied molluscs to be used as bioindicator organisms.  相似文献   
958.
This study was designed to evaluate the association between sugar cane plantation burning and hospital visits in Araraquara in the state of S?o Paulo, Brazil. From June 1 to August 31, 1995, the daily number of visits of patients who needed inhalation therapy in one of the main hospitals of the city was recorded and used as health impairment estimation. Sedimentation of particle mass (the amount of particles deposited on four containers filled with water) was measured daily. The association between the weight of the sediment and the number of visits was evaluated by means of Poisson regression models controlled for seasonality, temperature, day of the week, and rain. We found a significant and dose-dependent relationship between the number of visits and the amount of sediment. The relative risk of visit associated with an increase of 10 mg in the sediment weight was 1.09 (1-1.19), and the relative risk of an inhalation therapy was 1.20 (1.03-1.39) on the most polluted days (fourth quartile of sediment mass). These results indicate that sugar cane burning may cause deleterious health effects in the exposed population.  相似文献   
959.
Chloride imbalances in soil lysimeters   总被引:4,自引:0,他引:4  
The assumption that soil neither acts as a source or a sink of chloride is evaluated by incubating soil cores in lysimeters in a climate chamber under controlled conditions. Some of the lysimeters acted as a sink while others acted as a source of chloride. Considerable amounts of organic chlorine were lost by leaching. The loss by leaching of organic chlorine could only explain part of the discrepancy in the lysimeters where the soil acted as a sink and it could certainly not explain the cases where the soil acted as a source.The storage of organic chlorine was four times larger than the storage of chloride and comparably small changes in the organic chlorine storage will thus have a considerable influence on the chloride budget. However, the soil was too heterogeneous to determine whether a change in the storage had taken place or not. It is concluded that the observed chloride surplus and also, at least to some extent, the observed chloride deficit, most likely was caused by net-changes in the storage of organic chlorine in soil. An inverse correlation was found between the initial chloride content of the soil and the imbalance in the chloride budget.Dry deposition of chloride is generally assumed to equal the run-off minus the wet deposition. Extrapolation to the field situation suggests that the output of organic chlorine by soil leachate is at risk to cause an underestimation of the dry deposition by about 25%.  相似文献   
960.
On November 18, 1997, above-road particulate matter (PM) lidar (light detection and ranging) signals and heavy-duty (HD) and light-duty (LD) vehicle counts were simultaneously collected for 894 10-sec sampling periods at the Caldecott Tunnel in Orinda, CA, for the purpose of measuring the relative contributions of LD and HD vehicles to the PM lidar signal under real-world driving conditions. The relationship between the PM lidar signal and traffic activity (i.e., LD and HD traffic volumes) was examined using a time-series analysis technique, multilagged regression. The time-series model results indicate that the PM lidar signal in the current sampling period (PMt) depended on the level recorded in the previous three sampling periods (i.e., PMt-1, PMt-2, and PMt-3), the number of LD vehicles in the seventh past sampling period (LDt-7), and the number of HD vehicles measured 80 sec previous to the current sampling period (HDt-8). On a 10-sec period basis, the model results indicate that HD vehicles contributed, on average, 3 times more to above-road PM lidar signals than did LD vehicles. The observed lag in the relationship between vehicle types and the lidar signal 20 m above the road suggests that resuspended road dust, rather than tailpipe exhaust emissions, was the main source of the detected PM. Detection of road dust at such heights above the road suggests the need for investigating the processes governing the vertical transport and recycling of PM over the road as a function of vehicle dynamics under a range of meteorological conditions.  相似文献   
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