Silent Mad Cow

Feb. 28, 2014

By Medical Discovery News

Ten years after bovine spongiform encephalopathy (BSE), commonly called mad cow disease, was diagnosed in cattle in Britain, the British government admitted that it could be transferred to humans in a new form called variant Creutzfeldt Jakob disease (vCJD).

Cases of BSE spread to cattle in other countries, and more people in different countries were being diagnosed with vCJD. By 2004, the U.S. had passed various laws to eliminate BSE-infected cattle from the market. However, to this day, there are still sporadic reports of cows diagnosed with BSE both in the U.S. and abroad.

BSE and vCJD are neurological diseases that arise from prion plaques that form in the brain. Prions are simply misfolded proteins. This can be caused by a genetic mutation, spontaneous misfolding, or consuming infected beef. These misfolded proteins can convert healthy or normal proteins into misfolded ones. Once they appear, abnormal prion proteins aggregate, or clump together. Investigators think these protein aggregates may lead to loss of brain cells and other brain damage. Areas of the brain’s grey matter are slowly displaced and the brain develops holes or a spongy appearance, hence the name spongiform. There is no treatment or cure and eventually the damage is severe enough to lead to death. 

Initially cattle acquired the prion proteins in feed supplements made from infected sheep brains and spinal cord tissues. Once regulators understood the source, they passed laws banning the process of feeding dead animals to livestock. Unlike meat contaminated with bacteria, cooking does not destroy prion proteins. In an effort to eliminate prions from the food supply, the U.S. Department of Agriculture has imposed a rule that the brains and spinal cords of cattle must be removed prior to processing into edible meat. 

There have been 175 people in Great Britain diagnosed with vCJD and an additional 49 people in 11 other countries. A large study indicates that 1 in 20,000 people in Britain (30,000 total) carry the misfolded prion proteins and are at risk of developing vCJD. These new results suggest that many people in Britain may be carrying the prions but are symptomless, at least for now. This could also mean that these cases are silent carriers, who will not develop clinical vCJD. It remains a mystery that only time and additional studies will solve. 

Since there is no blood test for vCJD, carriers could unwittingly pass on this disease to others when they give blood. Earlier research suggested that the incubation period for vCJD was about eight years, but now scientists think that there are at least three types of the misfolded prion proteins, with different incubation periods and different types of prion disease.

Blood tests need to be developed to protect against the inadvertent transmission of vCJD. Better farm and food practices and laws will also help eliminate other sources of prion disease. Scientists in a number of countries are exploring potential treatments for these disorders.

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An Early Start to Alzheimer’s

April 12, 2013

By Medical Discovery News

More and more data suggest that treatment for Alzheimer’s disease may be more effective if started early, even before symptoms appear. In addition, recent clinical trials of treatments for mild to moderate Alzheimer’s have failed, suggesting that waiting to treat the disease until these stages may be too late, and once the degenerative process has started it cannot be stopped. But since Alzheimer’s has no identifiable markers in its early stages, how would doctors know when and whom to treat?

 

Alzheimer’s is a form of dementia that causes an irreversible loss in brain function and gradually gets worse over time, affecting memory, thinking, and behavior. Buildup of insoluble proteins in the brain causes amyloid plaques or neurofibrillary tangles, two hallmarks of the disease along with a loss in connections between electrically active nerve cells called neurons. There is no definite diagnosis, other than autopsy.

A recent study of an extended family of 5,000 people from Colombia who inherited a form of Alzheimer’s revealed that the disease begins much earlier, and the deterioration of the brain occurs in more ways than previously thought. Affected family members had mild problems thinking and remembering at an average age of 45 and dementia at 53. However, researchers also noticed changes in affected family members at younger ages, before the first signs of plaques in the brain.

The study compared twenty 18- to 26-year-old family members who carried a mutation called presenilin1 E280A and were very likely to develop early onset Alzheimer’s with 24 non-carriers. Both groups underwent a variety of tests including MRIs, memory tests, cognitive tests, blood tests, and cerebral spinal fluid sampling. The groups did not differ significantly in their dementia ratings or psychological scores. However, carriers had fewer neurons in several regions of the brain that are affected by Alzheimer’s. Carriers also had higher levels of the amyloid protein that causes plaques in their cerebral spinal fluid. 

Previous studies of Alzheimer’s patients showed they have lower levels of amyloid than normal, which had been attributed to amyloid accumulating in the brain. Based on this information, scientists thought Alzheimer’s was explained by the progressive buildup of amyloid in plaques that causes brain cells to die, leading to symptoms of Alzheimer’s. This new study suggests that there are early changes in the brain even before amyloid plaques. 

This challenges what we know about when and how Alzheimer’s develops. Inherited, early onset Alzheimer’s may be caused by the body producing too much amyloid, while late onset Alzheimer’s may be the result of the body’s inability to clear amyloid from the brain. Researchers are now focusing on family members ages seven to 17 to determine if they can detect any brain differences even earlier.

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