Most clinical variables in animals follow biological rhythms which have a mathematical function defined by cosmic-climatic rhythms. Chronophysiology, chronopathology, chronopharmacology and chronotherapy have common elements but are frequently studied in isolation, thus making it difficult for a global understanding of clinical chronobiology as a unitary and well-defined discipline. The physiological effects of a drug depend not only on its molecular structure but also on the time-pattern of its administration. One of the main reasons for the importance of temporal patterns in drug activity is biological rhythm, and in particular that of the circadian period. These rhythms affect most physiological functions as well as drug metabolism, clearance, and dynamic processes that may alter drug availability and target cell responsiveness in relation to biological time. Chronotherapy studys the optimal level of drug effects and/or the minimizing of its toxicity by timing medications in relation to biological rhythms. This review focuses on medical chronobiology, which is much more technical since it only studies those aspects of clinical chronobiology having a health-care impact on daily practice.
In thoroughbred race horses, as in other species subjected to physical activity, there is a rise in the imbalance between free radical production and antioxidant agents which leads to oxidative stress. This stress may produce damage in several bio-molecules creating metabolic alterations affecting physical performance. The aim of this study was to find possible relationships between physical exercise and oxidative stress in trained horses. In order to achieve this we reported the results obtained while studying the effect of a physical exercise test on two groups of standardbreds. In particular, the study assessed levels of creatine kinase (CK) and aspartate amino transferase (AST) to evaluate possible muscle-cell membrane damage; reactive oxygen species (ROS), thiol antioxidant barrier (SHp) and antioxidant barrier (Oxy-adsorbent) to evaluate oxidative stress. Two groups of healthy standard bred (Ga and Gb) trained for 1600 and 2000 meter races were used for the study. Blood samples from all horses were collected at rest, immediately after racing, and 30 and 6 hours after racing. The ANOVA for repeated measures showed the highly significant effects of training on some of the studied parameters in both groups (Ga and Gb). Our results seem to indicate that in trained standard breeds acute exercise generates free radicals but they are unable to cause possible muscle-cell membrane damage. However, in order to know whether the inhibition of oxidative processes during exercise benefits physical performance, it would be necessary to simultaneously measure parameters relating to work capacity such as blood lactate, heart rate and oxygen consumption, both in basal conditions and at different times after a standardized race.
Depending on the intensity, duration and type of physical exercise, equine metabolism has to adapt to nervous, cardiovascular, endocrine and respiratory system requirements. In horses, exercise and training are known to have considerable effects on the mechanisms of hemostatic system involving platelet activity. The aim of the present study was to evaluate the effect of different training schedules on platelet aggregation in 15 Italian Saddle jumping horses. Animals were divided into three equal groups: Group A was subjected to a high intensity-training program; group B to a light training program, group C included sedentary horses. From each animal, blood samples were collected by jugular venipuncture at rest on the 1st, 3rd and 5th days, and afterwards, once a week, for a total of 5 weeks data recording, in order to assess the maximum degree of platelet aggregation and the initial velocity of aggregation (slope) platelet aggregation. Two-way analysis of variance (ANOVA) showed a significant effect of the different training schedules on studied parameters. The results revealed a different degree of platelet aggregation and a different initial velocity of platelet aggregation that changes during the different training schedules in horses that could represent a different protective endothelial mechanism. These findings could have an important role for a clearer knowledge of the physiological reference values of platelet aggregation and for a better interpretation of these variations during the training.
The aim of this study was to evaluate the effect of pre-partum versus post-partum periods on the biochemical profile in dairy cows. The effect of glucose tolerance test (GTT) on glucose (Gluon-farm) and β-Hydroxybutyrate (BHBon-farm) levels was also assessed. 42 Holstein cows from two different farms (farm A and farm B) were enrolled in the study. Body Condition Score (BCS) was determined for both groups. The GTT was carried out 7±5 days pre-partum and 7±5 days post-partum. In both periods blood samples were taken at T0 (pre-glucose administration), at T10 and T80 (10 and 80 minutes post-glucose administration). All samples were analysed for total protein, albumin, globulin,glucose, urea, aspartate aminotransferase (AST), alanine aminotransferase (ALT), calcium (Ca),phosphorus (P), sodium (Na), chloride (Cl), potassium (K), magnesium (Mg) and BHBon-farm. Twoway ANOVA was applied to determine significant effects of the transition period (pre-partum vs.post-partum) and farm (A vs. B) on the studied parameters as well as the effect of time before and after the GTT on Gluon-farm. The average values of BCS, glucose, urea, Ca, Cl and K are significantly lower in the post-partum when compared to the pre-partum period (P<0.05). The increase in AST concentrations during the post-partum period (P<0.05) is considered a suitable indicator of hepatic steatosis. The glucose tended to increase significantly at T10 (P<0.05) and returned to pre-infusion concentrations at T80. These results confirm that the transition period is an important metabolic challenge to high-yielding dairy cows. Therefore, this study provides useful information in order to prevent the outset of nutritional imbalance that typically occurs in high production dairy cows.
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