Thursday, April 28, 2011

Patent Ductus Arteriosis – An abnormal Condition that can Occur in Newborns

The fetus does not depend on its lungs to deliver oxygen to the growing organism in the uterus; it derives its oxygen and nutrition through the mother's placenta.  Before birth, a blood vessel called the ductus arteriosis (DA) allows blood to circumvent the nonfunctional fetal lungs by connecting the pulmonary artery (that transports blood to the lungs) with the aorta that sends blood throughout the body.  This is a temporary measure and, normally, this vessel closes a day or two following birth so that the lungs may begin normal function.  If this vessel does not close, there is abnormal blood circulation between the heart and lungs.  The resulting condition is called patent ductus arteriosis (PDA).  Infants with this condition exhibit certain characteristic symptoms including, fast breathing, poor eating habits, shortness of breath, poor growth and heart murmur.

PDA is often found in premature infants and those individuals born with neonatal respiratory distress syndrome as well as babies with congenital disorders such as Down's syndrome and mothers who contracted German measles during pregnancy.

Studying newborn mice, Doctor Katrin Echtler and his colleagues from Munich discovered that circulating platelets (specialized cells that play an essential  role in blood clotting) were involved in the normal closing of the DA, and that if platelet production was disrupted, the DA failed to close completely.   Their findings were reported in the Journal of Natural Medicine.  This could prove to be an important finding with possible direct application to infants susceptible to PDA. 

Friday, April 22, 2011

Chemical Intervention in the Brain’s Natural Response to Stress

The human brain has a complex and reliable response to stressful and life threatening situations.  This mechanism, however, can have untoward consequences for the organism if it is triggered too frequently.  In contemporary living, humans are constantly exposed to stressors that engage this system.  In order to fully understand this process, the nature of the brain's natural "alarm system" is more fully described below.

When faced with what the brain regards as a dangerous situation, a well orchestrated sequence of chemical events is set in motion that can lead ultimately to a "flight or fight" response.  The chain of events begins when the brain signals the hypothalamus, situated deep within the brain, to secrete corticotrophin-releasing hormone (CRH) that signals the nearby pituitary gland to subsequently release adrenocorticotropin hormone (ACTH) into the bloodstream.  ACTH binds to specific receptors on the adrenal glands, located near the kidneys.  This binding triggers a cascade of chemical events within the cells of the adrenal gland that ultimately produce cortisol that is released into the bloodstream.  Cortisol is a hormone that elicits a wide range of responses throughout the body that heightens the organism's ability to respond to challenging situations.  But the persistent release of this hormone can result in lasting damage.

In order to mitigate the potency of this mechanism, the body has countermeasures at its disposal.  One of these, Neuropeptide Y dampens the effects of CRH in various regions of the brain.  Another is dehydoepiandosterone (DHEA) that counteracts the role of the hormone cortisol.    It is believed that certain drugs and psychotherapy might be effective in stimulating the release of these natural agents.  This ability to cope with stress is referred to as resilience.  From the above description, it becomes quite evident that resilience is important in the maintenance of good health.

 in H


Sunday, April 10, 2011

Continued loss of Greenland and Antarctic Ice Sheets

Dr. Rignot and his colleagues from the University of California, Urvine have been measuring changes in the mass of the land-based ice sheets in Greenland and the Antarctic.  They have reported their findings in the scientific publication Nature Geoscience.

The current understanding of the process of climate warming in Greenland and the Antarctic suggests that snowfall may increase in the continents' interiors and, at the same time, accelerate melting on the coasts on account of the warmer air and ocean temperatures.  To further elucidate this mechanism, the team utilized highly sophisticated satellite radar observations between the years 1992 and 2006 covering 85% of Greenland's and Antarctica's coastlines to estimate the total mass movement of melt water into the ocean. 

Collecting this kind of information was once an extremely daunting task due to limitations in the ability to measure such intricate changes.  The technological advances over the past decades, however, have made it possible to measure trends on a monthly basis.  The results of such continuous observations demonstrate that the rate of the combined loss of the ice sheet has indeed increased and accelerated over the last eighteen years by a total of 36.3 Gigatons (Gt) per year.  A Gt is equivalent to 1 billion tons.   This rate is some three times faster than rate of ice melting in mountain glaciers and at the polar ice caps.  Should this rate of loss of land-bound ice continue unabated, it would prove to be the largest contributor to the ineluctable rise in the sea level by the end of this century.  This is not taking into account the distinct possibility that the rate of increase in atmospheric greenhouse gases as a result of human activity will increase over the coming decades.  According to Dr. Rignot, "Changes in glacier flow therefore have a significant, if not dominant impact on ice sheet mass balance."

This is a significant and troubling finding that adds yet another dimension to the disturbing prospects posed by the ever escalating concentration of greenhouse gases in the earth's environment.  Hopefully, the human community will use these kinds of data to implement policies that will ensure a tangible decrease in the actual use of fossil fuels to propel national economies.