Evaluation of apoptosis markers in different cell lines infected with equine arteritis virus.

Equine arteritis virus (EAV) induces apoptosis in infected cells. Cell death caused by EAV has been studied mainly using three cell lines, BHK-21, RK-13 and Vero cells. The mechanism of apoptosis varies among cell lines and results cannot be correlated owing to differences in EAV strains used. We evaluated different markers for apoptosis in BHK-21, RK-13 and Vero cell lines using the Bucyrus EAV reference strain. Acridine orange/ethidium bromide staining revealed morphological changes in infected cells, while flow cytometry indicated the extent of apoptosis. We also observed DNA fragmentation, but the DNA ladder was detected at different times post-infection depending on the cell line, i.e., 48, 72 and 96 h post-infection in RK-13, Vero and BHK-21 cells, respectively. Measurement of viral titers obtained with each cell line indicated that apoptosis causes interference with viral replication and therefore decreased viral titers. As an unequivocal marker of apoptosis, we measured the expression of caspase-3 and caspases-8 and -9 as extrinsic and intrinsic markers of apoptosis pathways, respectively. Caspase-8 in BHK-21 cells was the only protease that was not detected at any of the times assayed. We found that Bucyrus EAV strain exhibited a distinctive apoptosis pathway depending on the cell line.

A single administration of the GnRH antagonist acyline inhibits basal and GnRH-stimulated serum testosterone concentrations in male dogs.

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.

Domestic queens under natural temperate photoperiod do not manifest seasonal anestrus.

Domestic cat seasonality between the tropics and the arctic zones is scarcely described and results are inconsistent. The aim of this study was to describe domestic feline seasonal patterns under a natural temperate photoperiod. A total of 372 estrous cycles were studied in 34 post pubertal cats during 900 days. The queens were housed in a cat colony (31°25' South Latitude, 64°11' West Longitude), acclimated under natural photoperiod and daily observed for reproductive behavior. Vaginal cytology was conducted three times a week. For each cat the number of estrous cycles and days in estrus per month for each year were recorded. The months of the year were grouped in four periods of 3 months each according to day length and photoperiod. Comparisons of estrous days among periods were performed by ANOVA for repeated measures. All the cats had estrous cycles throughout the year without intervals of anestrus. Mean number of estrous days differed among the periods (P<0.01), those of long day length and ascending photoperiod being greater (12.5±0.6) to those of descending photoperiod either with long (8.9±0.7) or short (9.3±0.7) days. When the two periods with ascending day lengths were merged and compared to the two periods with descending day lengths merged, the number of estrous days were greater when day length ascended (P<0.01). Nearly 60% of the estrous cycles occurred during the periods of ascending day length. It is concluded, that domestic cats under natural temperate photoperiod have estrous cycles throughout the year showing peak activity the months with increasing photoperiod.