Assessment of the use of gross lesions at post-mortem to detect outbreaks of classical swine fever

The performance of pathological findings as a diagnostic tool for the detection of classical swine fever (CSF) outbreaks during the 1997/1998 CSF-epidemic in The Netherlands was evaluated by constructing and analysing receiver operating characteristic (ROC) curves. This was done at the individual pig level and at the submission level (a group of pigs from the same herd submitted together for post-mortem investigation). At post-mortem examination, the tonsils, spleen, ileo-caecal valve and renal pelvis were sampled, sent to the reference laboratory, and tested by means of a CSF-specific fluorescent antibody test in combination with a confirmatory test. This resulted in an infection status at the individual pig level. The infection status and pathological findings of 1072 individual pigs from a total of 230 infected herds were included in this analysis. We also included submissions of pigs from herds that were sent to post-mortem examination because of a clinically CSF-suspect situation but afterwards were concluded to be from non-infected herds. Infection status and pathological findings of 1224 individual pigs from a total of 241 non-infected herds were included in the analysis. Pneumonia, pleuritis, chronic bronchitis, pulmonary oedema, chronic gastric ulceration, dry faecal contents in the colon, conjunctivitis, haemorrhages in the renal pelvis, renal haemorrhages, splenic enlargement, haemorrhages in the urinary bladder, haemorrhagic and enlarged lymph nodes were the most frequently recorded pathological findings during a post-mortem examination of pigs submitted in a CSF-suspect clinical situation. However, some of these pathological findings (e.g. pneumonia, pleuritis) were almost evenly distributed in infected and in non-infected pigs, resulting in a high sensitivity combined with a low specificity. The area under the ROC curve of pathological findings at the individual pig level and at the submission level was 0.720 and 0.782, respectively, which was significantly (P<0.0001) larger than the area under the random ROC curve. It was concluded that, although gross pathology is a legitimate test, its quantitative contribution to the detection of CSF is limited.     

Simulation of water use and production of potatoes as affected by soil compaction

Summary The SWACRO simulation model was used to calculate water balances and associated potatotuber productions in a loamy sand soil with different types of compaction. Results for a noncompacted soil were compared with those for soils with a strong ploughpan and those with compacted surface soil. Input data consisted of: (1) measured hydraulic conductivity and moisture retention data for major soil horizons, (2) measured rooting depths and water-table levels, (3) calculated potential transpiration according to the modified Penman equation and (4) measured precipitation. Root extraction of water was simulated by two approaches, comparing the Feddes and Hoogland et al. extraction terms. The former procedure yielded best results in this study. The SWACRO model yielded good predictions of the soil water regime and tuber productions for the three treatments in the dry year 1976. A sensitivity analysis indicated that variations of water-use efficiencies did not significantly affect thedifferences in crop productions observed. Formerly: Soil Survey Institute, P.O. Box 98, 6700 AA Wageningen, the Netherlands.     

In vitro effects of estradiol-17β on myoid and fibroblastic cell proliferation in the immature rainbow trout testis

This study sought to determine whether estradiol-17β (E₂) could induce proliferation of interstitial cells (fibroblasts and myoid cells) in the immature rainbow trout (Oncorhynchus mykiss) testis. To investigate this, a floating organ culture system was utilized. The results showed that a dose of 18.3n M E₂ added to the medium significantly increased interstitial cell proliferation. Pretreatment of the tissue with the estrogen receptor antagonist ICI 182,780 nullifies this proliferative effect. These results show that E₂ can enhance interstitial cell proliferation in the immature rainbow trout testis before spermatogenesis begins.     

Effects of Gonadotropins on In Vitro Maturation and of Electrical Stimulation on Parthenogenesis of Canine Oocytes

The objective of this study was to determine the effects of gonadotropins on in vitro maturation (IVM) and electrical stimulation on the parthenogenesis of canine oocytes. In experiment I, cumulus oocyte complexes were collected from ovaries at a random phase of the oestrus cycle and cultured on maturation medium treated with hCG or eCG for 48 or 72 h. There were no significant differences in the effects on the metaphase II (MII) rate between the hCG and eCG treatment groups over 48 h (5.4% vs 5.5%). The MII rate in the co-treatment group of hCG and eCG for 48 h was higher than in each hormone treated group (15.5%, p < 0.05). In experiment 2, the parthenogenetic effect on oocyte development, at various electrical field strengths (1.0, 1.5, 2.0 kV/cm DC) for 60 or 80 μs with a single DC pulse after IVM on the co-treatment of hCG and eCG, was examined. The rate of pronuclear formation (37.1%) in electrical activation at 1.5 kV/60 μs without cytochalasin B (CB) was higher than that of oocytes activated in the other groups (p < 0.05). However, we did not observe the cleavage stages. Also, CB did not influence parthenogenesis of canine oocytes. The results showed that the pronucleus formation rate, indicative of the parthenogenesis start point, could be increased by electrical stimulation. Therefore, these results can provide important data for the parthenogenesis of canine oocytes and suggest the probability of parthenogenesis in canines.