The objective of this study was to describe testosterone (T) response to GnRH challenge in antagonist-treated dogs over a 30-day period. Eight mongrel dogs were randomly assigned to either the GnRH antagonist acyline 330 μg/kg sc (ACY; n = 4) or a placebo group (PLA; n = 4). The dogs were serially challenged with the GnRH agonist, buserelin 0.2 μg/kg sc on days -1, 1, 3, 7, 10, 14, 21 and 30. On these days, blood samples for T determinations were collected before (-30 min) and 60, 120 and 180 min after the agonist injection. Basal (-30 min) and post-GnRH agonist stimulation T values were compared by anova for repeated measures. Before treatments (day -1), there were no differences in basal T serum concentrations between groups (p > 0.1). After treatments, basal T showed a significant interaction between treatment and day (p < 0.05). Furthermore, when both groups were analysed independently, basal T varied in the ACY (p < 0.01) but not in the PLA group (p > 0.1). On day -1, before treatments, the stimulation tests had only a time effect (p = 0.05) although on days 1 (p < 0.01), 3 (p < 0.01), 7 (p < 0.01), 10 (p < 0.01) and 14 (p < 0.05), the response to the agonist differed between groups, becoming similar on days 21 (p > 0.05) and 30 (p > 0.05). It was concluded that, in dogs, a single administration of the GnRH antagonist prevented canine gonadal axis to physiologically respond to agonistic challenge during 14 days.
Equine Arteritis Virus (EAV) has been shown to induce apoptosis in vitro but the induction of this mechanism has not been previously associated with any viral gene product. In this work, we found a citotoxicity effect of the EAV gP5 protein on baculovirus-insect cells and a low yield of protein recovery. Besides, different morphological features by electron transmission microscopy, DNA fragmentation in agarose gel, TUNEL analysis and caspase 3 activity were found. All these findings indicate that the EAV gP5 protein induces apoptosis in insect cells.
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