Another reason for senile dementia
The brain pays the price for barren yearsAlla Solodova, Infox.ru
Senile human problems are not alien to chimpanzees. But the brain of aging monkeys shrinks, degrades and accumulates dangerous proteins not as fast as human. Biologists are sure that a person pays with senile dementia for the years lived after the loss of reproductive abilities.
Humanized diseasesHomo sapiens differs from other primates with a large brain and longevity.
The combination of these characteristics "humanizes" some neuropathologies. For example, only people die from Alzheimer's disease.
"Even 'healthy' aging is associated with brain changes, degradation of some parts of the nervous system," write the authors of a new study comparing the age–related changes in the brains of monkeys and humans. – In the cerebral cortex, the area responsible for learning and storing information, beta–amyloid accumulates with age, the density of dendritic processes and the number of synapses decreases, NMDA receptors and the myelin sheath degrade. These changes correlate with disorders of mental (cognitive) activity. Microstructural and molecular changes are characteristic not only for humans, but also for other primates."
Referring to the results of previous work, researchers from US universities led by Chet C. Sherwood from George Washington University write that the volume of the aging human brain is decreasing. Some areas of the brain shrink more than others: "The frontal lobe and hippocampus are especially vulnerable to age–related atrophy - areas involved in solving complex abstract tasks, forming emotions and transitioning short-term memory into long-term memory."
StudyHowever, the team of Chet Sherwood draws attention to the fact that in macaques, like in humans, the brain volume also decreases with age, although less noticeably.
Amyloid plaques also appear in aging gorillas, chimpanzees and orangutans. And neurofibrillary tangles characteristic of the human brain were also found in a 41-year-old female chimpanzee.
"Despite the generality of aging, genetic changes occurring in the cerebral cortex during aging do not unite humans with great apes and other mammals. A person is more vulnerable to diseases such as Alzheimer's disease and Parkinson's disease," the researchers continue.
Chet Sherwood's group suggested that human senile problems are related to life expectancy. Scientists have studied the age-related shrinkage of the brain in chimpanzees and humans. Using magnetic resonance imaging (MRI), biologists assessed changes in the entire brain, but paid special attention to the frontal lobe and hippocampus – the areas in which neurons work most actively. The scientists also assessed the dynamics of the volume of white and gray matter (the body of neurons and the myelin sheath).
Primates are getting oldThe subjects were ninety-nine chimpanzees (animals aged from 10 to 51 years) and eighty-seven volunteers of different ages (22-88 years).
"There were no noticeable changes in the structure of the brain in chimpanzees, which cannot be said about humans," the scientists write, summing up the results of the study. In male brains, age-related changes in the volume of brain structures were smaller compared to female ones. Nevertheless, the human brain steadily decreased in size with age, and the ratio of white matter and gray also changed. But the brains of 10– and 45-year-old animals were almost the same. Moreover, in chimpanzees, signs of brain aging appeared only after the animals reached their maximum age.
Biologists conducted an additional study of the brain of deceased chimpanzees, after which they came to the conclusion that a person pays with dementia for living too long. "In the wild, 30-year-old chimpanzees begin to lose teeth, weaken. Nevertheless, fertility persists until the end of life – up to fifty years. In humans, somatic aging occurs more slowly, but a woman loses her reproductive functions at about fifty years of age. That is, at the moment when the female chimpanzees are already dying. It turns out that the reproductive potential of chimpanzees and humans is the same," the authors of the study write at the end of the article published in PNAS (on the right is an illustration from the article by Sherwood et al., Aging of the cerebral cortex differs between humans and chimpanzees – VM).
Scientists believe that a person pays with age-related dementia for the years that he lives after the loss of reproductive abilities. The brain is the most vulnerable part only because it is an "energy glutton".
"Cell aging and many pathologies are associated with impaired functions of mitochondria – organelles that provide cells with energy. The cerebral cortex shows tremendous metabolic activity," the scientists continue, explaining why mitochondria in neurons "break down" more often and earlier than in other cells.
However, other mechanisms are also involved in the processes of brain degradation. And trying to keep the brain young by saving energy on thinking is not worth it. It has been proven that the thinking brain itself creates a cure for senile dementia.
Portal "Eternal youth" http://vechnayamolodost.ru26.07.2011