Question

1.Discuss at least two pieces of evidence supporting that there is a decline in immune function with aging.

2.Discuss at least two mechanisms in how caloric restriction aids in increasing life span.

3.The loss of vision due to clouding of the lens is?

Answer 1

Aging affects multiple organs but immune system is the most affected. Mature lymphoid cells persist for longer period of time and become susceptible to environmental changes. The decline in immune response makes old people susceptible infections such as influenza. Vaccination also does not produce antibodies with the pace as required for developing the immune response. Effects of aging are related to damage/change in functioning of T and B cells of immune system. The functional defects in T cells have been noted in elderly people. Changes in B cells reduce antibody production. The number of antigen responsive active T cells decreases. The composition and quality of the mature lymphocyte pool changes with increase in age. In young people, B and T cells after their production in the bone marrow and thymus migrate to secondary lymphoid tissues such as the spleen (lymphopoiesis). This generates immune response. In contrast in elderly people, primary lymphopoiesis is significantly diminished as the thymus is involuted. The reduction in lymphocyte development is related to changes in progenitor cells or the change in systemic environment.

Changes in levels of antioxidant capacity and oxidative damage lead to mitochondrial impairment. Increased oxidative stress damages to DNA, lipids and proteins. Impaired mitochondrial function causes shortage of ATP supply further affecting the biochemical pathways.

Calorie restriction (CR) has shown its beneficial effects on longevity, prevention of age-associated diseases, carcinogenesis. Studies suggest that CR increases bioavailability of NO, decreases ROS generation, activate ROS detoxification systems, exert anti-inflammatory effects, suppresses initiation/progression of vascular disease that accompanies aging. Calorie restriction reduces metabolic rate and oxidative damage. It decreases the incidence of cardiovascular diseases and alters neuroendocrine and sympathetic nervous system. Studies have shown that CR decreases production of reactive oxygen species (ROS) production thus minimizing oxidative damage. The reduction of oxidative stress extends the lifespan.
Clouding of eye lens is called cataract. Eyes lens is mainly made up of water and protein. The proteins are arranged in such a manner that lens stays clean, light is able to pass through and we can see. With aging, some of the proteins star clumping together forming a cloud over the area. The area grows larger with time making it harder to see. This can lead to blurd vision at initial stages followed by blindess in extreme cases (if not treated).