Showing posts with label changes. Show all posts
Showing posts with label changes. Show all posts

Tuesday, August 30, 2011

Vascular changes linked to dementia, experts say

ScienceDaily (July 22, 2011) — The same artery-clogging process (atherosclerosis) that causes heart disease can also result in age-related vascular cognitive impairments (VCI), according to a new American Heart Association/American Stroke Association scientific statement published online in Stroke: Journal of the American Heart Association.See Also:Health & MedicineHeart DiseaseStroke PreventionCholesterolMind & BrainDementiaStrokeIntelligenceReferenceMulti-infarct dementiaDementia with Lewy bodiesDementiaStroke

Cognitive impairment, also known as dementia, includes difficulty with thinking, reasoning and memory, and can be caused by vascular disease, Alzheimer's disease, a combination of both and other causes.

Atherosclerosis is a build- up of plaque in the arteries associated with elevated blood pressure, cholesterol, smoking and other risk factors. When it restricts or blocks blood flow to the brain, it is called cerebrovascular disease, which can result in vascular cognitive impairment.

Alzheimer's disease is a progressive brain disorder that damages and destroys brain cells. "We have learned that cerebrovascular disease and Alzheimer's disease may work together to cause cognitive impairment and the mixed disorder may be the most common type of dementia in older persons," said Philip B. Gorelick, M.D., M.P.H., co-chair of the writing group for the statement and director of the Center for Stroke Research at the University of Illinois College of Medicine at Chicago.

The prevalence of dementia increases with advancing age and affects about 30 percent of people over 80 years of age, costing more than $40,000 per patient annually in the United States, according to the statement authors. . .

Treating risk factors for heart disease and stroke with lifestyle changes and medical management may prevent or slow the development of dementia in some people, Gorelick said. Physical activity, healthy diet, healthy body weight, tobacco avoidance as well as blood pressure and cholesterol management could significantly help many people maintain their mental abilities as they age.

"Generally speaking, what is good for the heart is good for the brain," Gorelick said. "Although it is not definitely proven yet, treatment or prevention of major risk factors for stroke and heart disease may prove to also preserve cognitive function with age."

Understanding common causes of late-life cognitive impairment and dementia has advanced and many of the traditional risk factors for stroke also are risk markers for Alzheimer's disease and vascular cognitive impairment. For example:

• Reducing high blood pressure is recommended to reduce the risk of vascular cognitive impairment. High blood pressure in mid-life may be an important risk factor for cognitive decline later in life. • Controlling high cholesterol and abnormal blood sugar may also help reduce the risk of vascular cognitive impairment, although more study is needed to confirm the role of these interventions. • Smoking cessation could lessen the risk of vascular cognitive impairment. • Increasing physical exercise, consuming a moderate level of alcohol (i.e., up to 2 drinks for men and 1 drink for non-pregnant women) for those who currently consume alcohol; and maintaining a healthy weight may also lessen the risk of VCI, but more study is needed to confirm usefulness. • Taking B vitamins or anti-oxidant supplements, however, does not prevent vascular cognitive impairment, heart disease or stroke.

Identifying people at risk for cognitive impairment is a promising strategy for preventing or postponing dementia and for public health cost savings, the writers said. "We encourage clinicians to use screening tools to detect cognitive impairment in their older patients and continue to treat vascular risks according to nationally- or regionally-accepted guidelines." Vascular cognitive impairment is most obvious after a stroke, but there could be cognitive repercussions from small strokes, microbleeds or areas of diminished blood flow in the brain that cause no obvious neurological symptoms, according to the statement.

In many cases, the risk factors for vascular cognitive impairment are the same as for stroke, including high blood pressure, high cholesterol, abnormalities in heart rhythm and diabetes. The American Academy of Neurology and the Alzheimer's Association have endorsed the statement.

Other members of the writing group include: Angelo Scuteri, co-chair, M.D., Ph.D.; David Bennett, M.D.; Sandra E. Black, M.D.; Charles DeCarli, M.D.; Helena C. Chui, M.D.; Steven M. Greenberg, M.D., Ph.D.; Randall T. Higashida, M.D.; Costantino Iadecola, M.D.; Lenore J. Launer, M.D.; Stephane Laurent, M.D.; Oscar L. Lopez, M.D.; David Nyenhuis, Ph.D.; Ronald C. Petersen, M.D., Ph.D.; Julie A. Schneider, M.D.; Christophe Tzourio, M.D., Ph.D.; Donna K. Arnett, Ph.D.; Ruth Lindquist, Ph.D., R.N.; Peter M. Nilsson, M.D., Ph.D.; Gustavo C. Roman, M.D.; Frank W. Sellke, M.D.; and Sudha Seshadri, M.D. Author disclosures are on the manuscript.

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Sunday, August 28, 2011

Chromosome number changes in yeast

ScienceDaily (July 21, 2011) — Researchers from Trinity College Dublin have uncovered the evolutionary mechanisms that have caused increases or decreases in the numbers of chromosomes in a group of yeast species during the last 100-150 million years. The study, to be published on July 21st in the open-access journal PLoS Genetics, offers an unprecedented view of chromosome complement (chromosome number) changes in a large group of related species.See Also:Plants & AnimalsGeneticsMolecular BiologyEpigenetics ResearchEvolutionary BiologyCell BiologyNew SpeciesReferenceChromosomal crossoverSomatic cellVector (biology)Sex linkage

A few specific cases of chromosome number changes have been studied in plants and animals, for example the fusion of two great ape chromosomes that gave rise to chromosome 2 in humans, giving humans a chromosome count of 23 pairs compared to 24 pairs in great apes. The family of yeasts studied in this new research spans a similar evolutionary distance to that of vertebrates. The availability of completely sequenced genomes facilitated the reconstruction of ancestral genome structures at different evolutionary time points. Tracing the positions of essential parts of chromosomes (centromeres and telomeres) through time allowed for the identification of specific genome rearrangement events that resulted in chromosome complement changes.

The addition of large numbers of genes is not often tolerated by cells, and neither are deletions of large numbers of genes. This restricts the types of possible changes in chromosome complement to rearrangements of genes on chromosomes that maintain the same number of genes.

The researchers show that, in yeasts, chromosome complement has decreased in all except one notable event, a whole genome duplication -- an event that doubled the complement of an ancestor of several of the species from 8 chromosomes to 16. The decreases in chromosome number were mostly by the fusion of whole chromosomes, similar to the one that gave rise to chromosome 2 in humans. One exception to this mechanism was the breakage of a chromosome and the subsequent fusion of the two broken edges to two different chromosome ends.

Although some aspects of the research are specific to yeast, many of the mechanisms of chromosome number change in yeast are similar to those found in other organisms and therefore shed light on how chromosome complements evolve.

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