Muscle tissue may be damaged during an intense physical activity due to metabolic or mechanical factors. The serum level of the enzymes and skeletal muscle protein is an indicator for assessing the functional status of muscle tissue and a wide range of physiological and pathological conditions.Material and Method: Six Arabian horse aged between 3 and 6 years old were selected. The race was conducted in the 1250 meters and 1400 meters in climate temperate during autumn. Blood samples were collected by heparinized syringes from the jugular vein at time intervals including 1 h before the race, immediately after the race, 1 and 24 h after the end of race. Results and Discussion: Creatine phosphokinase (CK), aspartate aminotransferase (AST), LDH, BUN, Creatinin, myoglobin and troponin were measured in plasma samples. For evaluation of antioxidant defense, Catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPX) activities, protein carbonyl and total antioxidant defense (TAC) levels were measured. Total amount of serum lipid peroxidation was indicated by the level of malondealdehyde (MDA). The lowest levels of CK, LDH and AST in both races were seen in 1250 and 1400 meters, 1 hour before the race. At the end of the race, a significant increase in plasma CK, LDH and AST levels was observed, which was continued up to 1 hour after the race. Plasma myoglobin showed a significant increase in both races and reached to its maximum at 1 hour after the race. The troponin increased significantly in both races 24 hours after the race. The results showed that CAT activity and Plasma TAC in the horse increased immediately after the race (P≤0.01) and then gradually decreased. The highest glutathione peroxidase activity in red blood cells was recorded 1 h before the start of the race (0.41 ± 3.84 U/ml). SOD showed an incremental pattern and the lowest activity was recorded 1 h before the race. MDA level increased gradually and the maximum value was recorded (P<0.01) 24 h after the race. Plasma protein carbonyl levels increased significantly (P < 0.05) 1 h after the race, and then decreased. Generally, this study showed that the Arabian horse was able to withstand the oxidative stress resulting from the race at the intervals of 1200 and 1400 meters and is suggested that the use of antioxidant supplements could improve their efficiency during the race. Based on the findings of this study, the above indicators can be used to evaluate the muscle's post-race condition.

Sudden Death Syndrome (SDS) is one of the most important disorders and causes of economic losses in the broiler industry. This syndrome is one of the metabolic diseases associated with the cardiovascular system in broiler chicks. Several management and nutritional factors have been implicated in the occurrence of this syndrome, however, its etiology has not been completely identified. Hypoxia as the main pathophysiologic cause of heart disorders have been mentioned in SDS cases and sudden cardiac deaths of humans, however, so far, metabolic and molecular changes related to hypoxia in the heart muscle of SDS chicks have not been investigated. The aim of the present study was to investigate the metabolic and molecular changes of the hypoxia-dependent molecules in the heart muscle and serum levels of broiler chicks consumed by sudden death syndrome. For this purpose during the second to fifth weeks of the two breeding periods, tissue samples (left and right ventricles of the heart) were divided into 36 control and patient groups (SDS), plus 10 serum samples at about 20 minutes after death from both groups collected. The concentrations of glucose, triglyceride (TG) and unstrifieted fatty acids (NEFA) were measured in serum samples taken from each group. The levels of lactate and the activity of lactate dehydrogenase (LDH) and creatine phosphokinase (CPK) enzymes were measured in serum and tissue samples of the studied groups using commercial kits. Also, molecular variations in the expression of HIF1α, MCT4, GLUT-1 and PDHK4 genes in the heart muscle were performed using polymerase chain reaction in real time PCR. The results showed increased serum and tissue concentrations of lactate and activity of LDH and CPK enzymes in the patient group in comparison with the control group during the whole period of breeding. In addition, a significant reduction of serum levels of NEFA and no changes in blood glucose and TG concentrations was observed in the SDS group as compared to the control group. The level of expression of HIF1α, MCT4 and GLUT-1 genes in the SDS group was higher than the control group during the whole period of breeding. The expression of PDHK4 gene in the patient group was reduced in comparison to the control group throughout the breeding period. Overall, The findings of present study suggest that, metabolic and molecular changes in the heart muscle of SDS chicks confirmed the activation of the pathway in response to hypoxia in the heart muscle. Since a stable source of oxygen is essential for survival and cardiac function, hypoxia may be an important factor in the pathogenesis of SDS in broiler chickens.

 Toxoplasmosis caused by the protozoan parasite Toxoplasma gondii, is a zoonotic parasitic disease. Since, increased free radicals and oxidative stress are reported in many parasitic diseases, the purpose of the present study was to evaluate the oxidative stress in acute and chronic experimental toxoplasmosis. Thirty female Wistar rats were infected with RH strain of Toxoplasma tachyzoites and twenty five other female rats were considered as the control group that received RPMI media. To reactivate chronic toxoplasmosis, Control and infected rats of 45 day post infection received intraperitoneal injection of dexamethasone. Blood and tissue samples from liver, heart and brain on 0, 3, 5, 8, 45 and 55 days post infection were collected. PCR assay was used to confirm acute and chronic phase of infection. As biochemical markers of oxidative stress, endogenous concentrations of GSH, GPX and SOD activity, total antioxidant capacity, MDA level and protein carbonyl content were determined in blood and mentioned tissues of control and infected rats. Based on the results, the amounts of blood glutathione on day 3 and 45 and plasma total antioxidant capacity on day 3 and 8 post infection were significantly decreased in infected rats when compared to control group. There was also a significant rise in blood SOD activity on the eighth day post infection in comparison to uninfected rats. On day 3, 5 and 8 post infection the level of hepatic glutathione were significantly decreased in infected rats when compared to control. There was a significant rise in hepatic glutathione peroxidase activity and malondialdehyde level on the third day post infection in comparison to uninfected rats. Significant elevation of Superoxide dismutase activity and malondialdehyde level on 5 day post infection and protein carbonyls and total antioxidant capacity on 8 day post infection in infected livers were obtained. Significant changes in cardiac homogenate was observed in glutathione level, total antioxidant capacity and protein carbonyls content on days 3, 5 and 45, respectively. Measured parameters were constant throughout all stages of experiment in brain of infected rats (p>0.05). Significant change in some parameters was observed in immunosuppressed rats but due to secondary infections changes cannot be certainly attributable to toxoplasmosis.
Indeed increased production of reactive oxygen species and oxidant/antioxidant imbalance accompanies with Toxoplasma infection in experimentally infected rats. It should be mentioned that the process of the changes was different in various tissues. Therefore, oxidative stress can probably play a role in parasitic stage interconversion and shifting the toxoplasmosis into the chronic phase