Biomedical Engineering Reference
In-Depth Information
cells (Trigona et al.
2006
) . The nonenzymatic
antioxidants are tocopherols, ascorbic acid,
carotenoids, lipoic acid and GSH. Vitamin E
(a-tocopherol acetate) is the predominant anti-
oxidant found in biological membranes. The
tocopherols disrupt radical chain reactions that
lead to auto-oxidation of adjacent membrane-
associated fatty acids. For example, vitamin E
can act as a scavenger of both lipid radicals and
lipid peroxy radical by donating a hydrogen ion
with the formation of a tocopheroxyl radical. The
tocopheroxyl radical is then regenerated back to
its reduced form by vitamin C (Blokhina et al.
2003
). Ascorbic acid (vitamin C) is a water-solu-
ble antioxidant that plays a key role in maintain-
ing the redox state of cells. In addition to recycling
vitamin E, ascorbic acid can reduce several other
oxidised biomolecules and act as a direct scaven-
ger of free radicals (Blokhina et al.
2003
) . The
carotenoids are another important free radical
scavenger and are especially effective at quench-
ing singlet oxygen and can prevent the subse-
quent formation of secondary ROS. Lipoic acid
is a component of the pyruvate dehydrogenase
complex and plays a central role in energy metab-
olism. However, lipoic acid also can function as a
metal chelator and ROS scavenger. The reduced
form of lipoic acid, dihydrolipoic acid, can fur-
ther prevent accumulation of ROS by recycling
vitamins C and E (Blokhina et al.
2003
) .
has been previously exposed. However, if the
immune system is skewed towards Th2, then
viral and early pathogen (innate) immunity would
be suppressed, and the animals would be more
likely to have an allergic or autoimmune disease.
In India, animals are mainly reared on straw-
based diets which are low in major nutrients,
antioxidant vitamins and trace minerals. On these
diets, the cows are under stress especially during
periparturient period, this may lead to immuno-
suppression and can be afflicted with various dis-
eases. Considering these facts, supplementation
of antioxidants (combination of micronutrients,
i.e. copper/zinc and vitamin E) to the high pro-
ducers, especially during periparturient period
may prove to be beneficial. These antioxidants
may improve productivity of cows by reducing
the stress, thus protecting against the chances of
subclinical/clinical mastitis. A better understand-
ing of the complexity of these relationships in
farm animals will improve the animal health and
well-being.
References
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9
Conclusions
Many factors environmental or physiological can
influence the immune response of an animal to
stress. Stress can suppress or enhance or have a
balanced effect on the immune functions of an
animal. Many of the conflicting findings reported
may be partially explained by the types and dura-
tions of the stressors, age, genetics and social
status. Moreover, the aspect of the immune
system being assessed, the starting point of the
immune system and the balance between Th1
and Th2 may contribute to these discrepancies
between studies. If the immune system is in a
predominantly Th2 state, the animal may have
enhanced protection against pathogen to which it
