Protective effect of inactivated bovine herpesvirus-1 in calves experimentally infected with bovine herpesvirus-1 and Pasteurella haemolytica.
The protective effect of an inactivated whole-virion bovine herpesvirus-1 (BHV-1) immunising inoculum, without adjuvant, against viral-bacterial respiratory disease was studied in three experimental treatment groups of five calves each. One group was boosted 14 days after the first vaccination and at this time the second group received their initial inoculation. Seven days later, calves were challenged with BHV-1 in aerosol and four days after this challenge all calves were exposed to Pasteurella haemolytica A1 in aerosol. Among the three groups, differences in rectal temperature responses four days after viral challenge (P less than 0.01) did not relate to protection. However the main response variable, viral-bacterial pneumonia, was reduced in boosted calves (P less than 0.05).
Clearance and shedding of infectious bovine rhinotracheitis virus from the nasal mucosa of immune and nonimmune calves.
Infectious bovine rhinotracheitis virus was rapidly cleared from the nasal mucosa of calves after intranasal aerosol exposure. Nonimmune calves (experiment 1) cleared 10(9) plaque-forming units (PFU) of virus from the nasal mucosa in less than 4 hours and 10(6) PFU of virus in 1 hour. An eclipse phase followed the clearance of viral inoculum. Replicating virus was first detected at 9 hours. Viral titers increased stepwise until maximum was attained on postinoculation day 4. Virus persisted in the nasal mucus until day 12. Clinical signs of disease corresponded with the shedding of virus. In contrast to nonimmune calves, immune calves (experiment 2; same calves as in experiment 1, but 30 days after initial exposure) cleared 10(9) PFU of virus in 1 hour and 10(6) PFU of virus in less than 5 minutes. An abortive reinfection occurred after exposure of immune calves with 10(9) PFU of virus. Virus was first detected in these calves at 14 hours after exposure and was not detected beyond 24 hours after inoculation. Immune calves given 10(6) PFU of virus did not shed virus after clearance of inoculum. Clinical signs of infection were not observed in immune calves after viral challenge exposure. The date indicated that there was no detectable residual virus beyond 3 hours after the exposure.
Inhibition of Root Growth and Polyamine Metabolism in Sunflower (Helianthus annuus) Seedlings Under Cadmium and Copper Stress
Although sunflower is usually regarded as a highly tolerant crop, impairment of root growth at initial stages of plant development may result in poor crop establishment and higher susceptibility to pathogen attack. In order to evaluate if Cd2+ and Cu2+ may impact on sunflower germination and initial root development, a pot experiment under controlled conditions was carried out. Possible involvement of polyamine metabolism in sunflower response to these stressors was also investigated. Although Cd2+ and Cu2+ treatments affect neither seed germination nor radicle emergence, sunflower seedlings grown in the presence of these heavy metals showed significant inhibition of root growth, being this inhibition greater for Cd2+. Both metals caused significant increases in proline contents at the highest concentrations tested (0.5 and 1 mM), and these increments were more pronounced for Cd2+ treatments, especially between days 3 and 10. Metals also increased putrescine (Put) contents at all concentrations assayed from the seventh day onward, causing no variations on this polyamine time-course pattern. Spermine and spermidine contents, however, were increased only by 1 mM Cd2+. Arginine decarboxylase seems to have been the enzyme responsible for Put increases under both metal treatments. This work demonstrates that initial root growth of sunflower seedlings may be significantly impaired in Cd2+ or Cu2+ contaminated soils. It also shows that polyamines are key biological compounds, which are probably involved in signaling pathways triggered under stress environmental conditions.