Effects of chlorpyrifos in freshwater model ecosystems: the influence of experimental conditions on ecotoxicological thresholds

Three experiments were conducted to determine the impact of the insecticide chlorpyrifos (single applications of 0.01 to 10 microg AI litre(-1)) in plankton-dominated nutrient-rich microcosms. The microcosms (water volume approximately 14 litres) were established in the laboratory under temperature, light regimes and nutrient levels that simulated cool 'temperate' and warm 'Mediterranean' environmental conditions. The fate of chlorpyrifos in the water column was monitored and the effects on zooplankton, phytoplankton and community metabolism were followed for 4 or 5 weeks. The mean half-life (t1/2) of chlorpyrifos in the water of the test systems was 45 h under 'temperate' conditions and about 30 h under 'Mediterranean' environmental conditions. Microcrustaceans (cladocerans and copepod nauplii) were amongst the most sensitive organisms. All three experiments yielded community NOEC (no observed effect concentrations) of 0.1 microg AI litre(-1), similar to those derived from more complex outdoor studies. Above this threshold level, responses and effect chains, and time spans for recovery, differed between the experiments. For example, algal blooms as an indirect effect from the impact of exposure on grazing organisms were only observed under the 'Mediterranean' experimental conditions. The relatively simple indoor test system seems to be sufficient to provide estimates of safe threshold levels for the acute insecticidal effects of low-persistence compounds such as chlorpyrifos. The robustness of the community NOEC indicates that this threshold level is likely to be representative for many freshwater systems.     

Chromosome segregation errors as a cause of DNA damage and structural chromosome aberrations

Various types of chromosomal aberrations, including numerical (aneuploidy) and structural (e.g., translocations, deletions), are commonly found in human tumors and are linked to tumorigenesis. Aneuploidy is a direct consequence of chromosome segregation errors in mitosis, whereas structural aberrations are caused by improperly repaired DNA breaks. Here, we demonstrate that chromosome segregation errors can also result in structural chromosome aberrations. Chromosomes that missegregate are frequently damaged during cytokinesis, triggering a DNA double-strand break response in the respective daughter cells involving ATM, Chk2, and p53. We show that these double-strand breaks can lead to unbalanced translocations in the daughter cells. Our data show that segregation errors can cause translocations and provide insights into the role of whole-chromosome instability in tumorigenesis.     

Temporal-spatial epidemiology of foot-and-mouth disease outbreaks in Mongolia, 2000 – 2002

Prior to 2000, foot-and-mouth disease (FMD) had not been observed in Mongolia since 1973; however, between April 2000 and July 2002, Mongolia reported 44 FMD outbreaks that affected cattle, sheep, goats, and camels. The objectives of this study were to describe the distributions of the 44 reported FMD outbreaks in Mongolia and to assess their spatial clustering and directions of movement. Official reports were collected to obtain the number and species of animals both affected and at risk, and the date and geographical coordinates of each outbreak. Significant global and local spatial clusters of reported FMD outbreaks were identified. Disease spread during the second epidemic moved 76° northeast and the spread of the disease during the third epidemic moved 110° northwest. FMD outbreaks were clustered intensely close to other FMD-positive counties. These findings can be used in the future to help plan prevention and control measures in high risk areas.     

Hepatic encephalomyelopathy in a calf with congenital portosystemic shunt (CPSS)

A 4-month-old female Holstein Friesian calf was referred to the Veterinary Teaching Hospital, University of Berne, Switzerland for evaluation of ataxia, weakness, apathy and stunted growth. Clinical examination revealed generalized ataxia, propioceptive deficits, decreased menace response and sensibility. Postmortem examination did not reveal macroscopic changes of major organs. Histologically, the brain and the spinal cord lesions were characterized by polymicrocavitation, preferentially affecting the white matter fibers at the junction of grey and white matter and by the presence of Alzheimer type II cells. The liver revealed lesions consistent with a congenital portosystemic shunt, characterized by increased numbers of arteriolar profiles and hypoplasia to absence of portal veins. The pathological investigations along with the animal history and clinical signs indicated a hepatic encephalomyelopathy due to a congenital portosystemic shunt.