Our Oxygen Exchange and Owl Adaptations

• Does breathing by humans contribute to increased carbon dioxide in the atmosphere? An average human body circulates about five quarts of blood carrying about 30 trillion red blood cells. These cells contain hemoglobin molecules that pick up oxygen in the lungs and carry it to all parts of the body. Hemoglobin releases oxygen in tissues where oxygen has been depleted, and exchanges it for carbon dioxide – a by-product of energy production. Red blood cells loaded with carbon dioxide return to the lung, and carbon dioxide is released to the atmosphere in exchange for another load of oxygen. It is reassuring to know that the amount of carbon dioxide our bodies release into the atmosphere is infinitesimal compared to that released by coal-fired power plants, vehicle engine exhaust, and forest fires. (; other sources)

• Owls are extraordinary birds adapted to silently hunt at night or in low light, relying as much on their hearing acuity as on their eyes. The front of an owl’s face, called the facial disk, is circular and slightly hollowed. It acts to “funnel” sound to the ears at the side of the head, where one is slightly higher than the other, allowing the owl to better triangulate sound. Owls’ wings are specially adapted too. They have a comb-like array along their trailing edges which helps muffle wing noise as they swoop down on unsuspecting prey, and the leading edges of their wings are serrated, which disrupts air flow to further minimize wing noise in flight. Seeing an owl in its natural habitat is an unexpected fringe benefit of hiking Door County trails. (;

• How do intestinal bacteria enhance our immune response? A team of German researchers infected two groups of mice with various viruses. One group had normal intestinal bacteria. Members of the second group had been treated with antibiotics and raised under sterile conditions, which eliminated intestinal bacteria. The immune response by bacteria-free mice was diminished, and the diseases caused by the viruses were much more severe. The researchers then showed that intestinal bacteria produced molecules that were picked up by cells in the lining of the intestine which, in turn, signaled certain immune cells to ramp up the immune response to inflammatory changes induced by the viruses. (Ganal et al, 2012, Immunity, May 20; Science Daily, Sept. 3, 2012)

• Urate is a powerful antioxidant that is a natural byproduct of eating meat and fish. It is formed when uric acid combines with a sodium, magnesium, or other kinds of ion. In excess, crystals of urate can cause kidney stones or form deposits in joints, resulting in gout, a painful arthritic condition. That’s the bad news.

Now for the good news. It is known that Parkinson’s Disease (PD) is caused by destruction of specific neurons that produce the neurotransmitter, dopamine. Scientists cultured dopamine-producing neurons in the laboratory and then exposed them to a toxic chemical that triggers PD-like symptoms by killing cells. Cell death was reduced by 50 percent.

The senior researcher in the project summed it up this way: “The results suggest there may be multiple ways that raising urate could help protect against neurodegeneration in diseases like Parkinson’s, and further support the development of treatments [in clinical trials] to elevate urate in the brain.” (Mind, Mood, & Memory, Mass. General Hospital, Aug., 2012; PLoS One, May, 2012)