PubMed · 15030554
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Joan Rest. 2004. A historical perspective.. https://doi.org/10.1111/j.1365-3164.2004.00399.x
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Under the EU Directive 2004/28/EC, an environmental risk assessment of new veterinary medicinal products is required. Given the nature of risk assessment for new applications, there is a need to model exposure concentrations. Critical evaluations are essential to ensure that the use of models by regulators does not result in the propagation of misleading information. The empirical validations of soil exposure models, previously discussed in this journal, indicate that it is impossible to analyse the contribution of every model parameter to the variability in the predictions. In particular, the prediction of the slurry concentration is challenged by uncertainties concerning dilution, mixing and dissipation of residues. Surface water and groundwater models generated highly deviating results compared to the field results, questioning the usefulness of the available screening models. Animal husbandry, slurry handling and environmental conditions throughout Europe are considered in order to define realistic worst case scenarios, to be used in conjunction with distribution models for the environmental risk assessment of veterinary medicinal products at registration. Given the variability in manure management practice throughout Europe, a deterministic approach for the manure-to-soil model was selected. Both worst case and best case scenario were developed. Several modelling assumptions applied in the surface water exposure model for fish nursery effluent were validated against newly available data. Since the available data give no proof that a settling tank contributes to the removal of pesticides from waste water, it is recommended for risk assessment purposes to consider the contribution of the settling tank to removal of pesticides and medicines to be negligible. Surface water dilution factors may be considered to be rather small, a factor of 2, for low flow situations.
Infections with Eimeria parasites can lead to severe diarrhoea with considerable clinical and economic consequences in first-year grazing stock. To identify and characterise the cause of diarrhoea observed during previous years, 164 animals on 14 dairy farms in northwestern Germany were included in this study. The calves were physically and parasitologically examined prior to turnout and until 21 days post turnout (d.p.t.). Mean animal weights decreased from 194.9 kg at the start to 189.3 kg bodyweight at the end of the study. In all herds, oocyst counts were very low prior to turnout and increased after the calves had been kept on pasture for at least 7 days. On Day 9 post turnout, 90% and at the end of the study (21 d.p.t.) 70% of all animals showed Eimeria-positive faecal samples. During the course of the study, 79 (48.2%) animals passed faecal samples with more than 100,000 oocysts per gram. The predominant species identified was Eimeria alabamensis, which accounted for more than 83% of the oocysts counted. These parasitological findings matched the clinical observations. Diarrhoea was found in 130 (79.3%) of the study animals. At 5d.p.t. and thus prior to the rise of faecal oocyst counts, a significant increase in diarrhoea was recorded. Calves showing diarrhoea excreted statistically significantly more often over 100,000 E. alabamensis oocysts per gram faeces (0.28; p = 0.0002) than calves without diarrhoea. Diarrhoea was also found during significantly more study days in animals with high oocyst counts (0.39; p = 0.0001). These data indicate that in endemic areas first-year grazing calves must be considered at risk to develop clinical coccidiosis due to E. alabamensis infection during the first 2-3 weeks post turnout.
A protocol for successful induction of androgenetic cloning of the Buenos Aires tetra (BT), Hemigrammus caudovittatus, with contrasting gray and golden strains is described. At the intensity of 4.2 W/m(2), UV irradiation for 2.75 min totally inactivated the maternal genome in eggs of gray BT. Following activation by sperm of golden BT, the 25-min-old embryos were shocked at 41 degrees C for 2 min to restore diploidy. Interestingly, the hatching success of the haploid fry was always higher than that of the diploid fry, indicating that the enhanced homozygosity (Y(2)Y(2)) is more deleterious than haploidy. Maternal genomic inactivation was confirmed by (i) expression of green fluorescent protein (GFP) gene in the 6-16 hr old live haploid and aneuploid embryos, (ii) golden body color in the diploid fry and adult and (iii) progeny testing. Survival of androgenotes was 10% at hatching and 6% at sexual maturity. Reproductive performance of F(0) and F(1) males (Y(2)Y(2)) was superior to that of normal ones (X(1)Y(2)), but that of the F(0) and F(1) females (X(2)X(2)) was inferior to the control (X(1)X(2)). Of 21 crosses involving homozygous androgenetic (Y(2)Y(2)) males and heterozygous (X(1)X(2)) females, 7 of them (33%) produced 3-9% unexpected female progenies. But only a single cross (14%) generated 3-4% unexpected female progenies, when 7 pairs of homozygous androgenetic (Y(2)Y(2)) males and (X(2)X(2)) females were crossed. Hence, the paternal autosomes, inherited by the homozygous androgenetic female (X(2)X(2)), produced female progenies in significantly less number of crosses, also at lower frequencies than the crosses with heterozygous females (X(1)X(2)), which carried an equal number of paternal and maternal autosomes. However, progenies resulting from the cross between gray female (X(1)X(2)) and golden male (Y(2)Y(2)), after undergoing androgenesis, were males, with paternal chromosomes alone, indicating that the presence of Y(2)Y(2) appears to override the modifying effect of autosomes, but the paternal or maternal autosomes seemed to override the single Y(2) present with X(1) or X(2), and induced the production of unexpected female progenies. Using Double sex Mab3 related transcription factor (DMRT 1)-specific primers, PCR analyses of the genomic DNA of the normal (X(1)Y(2)) and androgenetic males (X(1)Y(2)) produced two amplicons of 237 and 300 bp length. However, they were not detectable in the female (X(1)X(2)) genomic DNA, which amplified only one amplicon of 100 bp. Genomic DNA extracted from the 18 unexpected female progenies expressed the (X(1)Y(2)) genotype-specific banding pattern with two amplicons of 237 and 300 bp length and thereby confirmed that they were genotypic males. A partial sequencing of the male-specific sequence indicated that DMRT 1-specific primer was bound to the fragment of the genomic DNA of the male tetra, although the male-specific sequence of DMRT 1 was not completely detectable.