Oxidative Stress During Pregnancy In The Sheep

During physiological pregnancy, all tissues and, mostly, placenta and foetus require high amounts of oxygen. Reactive oxygen species (ROS), generated both by mother and foetus, are implicated in foetal growth because they promote replication, differentiation and maturation of cells and organs. Nevertheless, ROS excess, if not properly counterbalanced, may lead to an alteration in cell constituents, with harmful effects both on mother and foetus.ROS exert a biphasic effect because adequate ROS concentration is essential for embryo development, implant, foetal defence against uterine infections, steroidogenesis, pregnancy maintainance and partum. On the other hand, an uncontrolled ROS generation, beyond physiological antioxidant defences, may lead to embryo resorption, placental degeneration with subsequent alteration in maternal‐foetal exchanges, delay in foetal growth, pregnancy interruption, stillbirths. This review investigates the mechanisms underlying ROS generation and effects, throughout physiological and pathological pregnancy in sheep, with a look to antioxidants and their importance in such a critical phase of the reproductive cycle of the sheep.     

Calcium-permeable AMPA receptor dynamics mediate fear memory erasure

Traumatic fear memories can be inhibited by behavioral therapy for humans, or by extinction training in rodent models, but are prone to recur. Under some conditions, however, these treatments generate a permanent effect on behavior, which suggests that emotional memory erasure has occurred. The neural basis for such disparate outcomes is unknown. We found that a central component of extinction-induced erasure is the synaptic removal of calcium-permeable α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate receptors (AMPARs) in the lateral amygdala. A transient up-regulation of this form of plasticity, which involves phosphorylation of the glutamate receptor 1 subunit of the AMPA receptor, defines a temporal window in which fear memory can be degraded by behavioral experience. These results reveal a molecular mechanism for fear erasure and the relative instability of recent memory.     

Hydrogen radicals, nitrogen radicals, and the production of O3 in the upper troposphere

The concentrations of the hydrogen radicals OH and HO2 in the middle and upper troposphere were measured simultaneously with those of NO, O3, CO, H2O, CH4, non-methane hydrocarbons, and with the ultraviolet and visible radiation field. The data allow a direct examination of the processes that produce O3 in this region of the atmosphere. Comparison of the measured concentrations of OH and HO2 with calculations based on their production from water vapor, ozone, and methane demonstrate that these sources are insufficient to explain the observed radical concentrations in the upper troposphere. The photolysis of carbonyl and peroxide compounds transported to this region from the lower troposphere may provide the source of HOx required to sustain the measured abundances of these radical species. The mechanism by which NO affects the production of O3 is also illustrated by the measurements. In the upper tropospheric air masses sampled, the production rate for ozone (determined from the measured concentrations of HO2 and NO) is calculated to be about 1 part per billion by volume each day. This production rate is faster than previously thought and implies that anthropogenic activities that add NO to the upper troposphere, such as biomass burning and aviation, will lead to production of more O3 than expected.     

Comparison of tiletamine-zolazepam-ketamine and tiletamine-zolazepam-ketamine-xylazine anaesthesia in sheep

Summary The anaesthetic effects of intravenous tiletamine-zolazepam 6.6 mg/kg-ketamine 6.6 mg/kg (TK) and tiletamine-zolazepam 6.6 mg/kg-ketamine 6.6 mg/kg-xylazine 0.11 mg/kg (TKX) were evaluated in six wethers. Heart rate, respiration rate, arterial blood pressure, and the electrocardiogram were monitored during anaesthesia. Analgesia was tested by electrical stimulation in the left flank. Atropine (0.03 mg/kg) was given intramuscularly before induction, but after recording of baseline heart rate and respiratory rate. The duration of analgesia was 28.7 ± 6.9 min with TK and 82.8 ± 26.6 min with TKX. Heart rate increased significantly within 5 min after TK or TKX administration. Respiratory rate remained unchanged after TK administration, but increased significantly from 5 to 45 min after TKX administration. Arterial blood pressure decreased significantly at 15 min with TK and 30 min with TKX. Sheep remained recumbent for 201 min with TK and 166 min with TKX. All recovered uneventfully. We conclude that either TK or TKX may be used for anaesthetising sheep.     

Adonis microcarpa (pheasant''s eye) toxicity in pigs fed field pea screenings

Seed of Adonis microcarpa (pheasant's eye) fed at 5.6 g/kg of the diet induced virtually total feed refusal within 3 d in growing and finishing pigs. It also caused vomiting, rapid and shallow breathing and death in a minority. These effects were probably caused by cardiac glycosides whose structure and effects closely resemble those of digoxin. Feed intake and growth recovered within 2 weeks of removal of the seed.