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<p class="MsoNormal" style="margin: 0cm 0cm 0pt"><font size="3"><font face="Times New Roman"><span style="mso-tab-count: 1"> </span>Dementia due to HIV is the leading cause of cognitive decline in people under 40 years of age, says Stuart Lipton, a biologist at the Burnham Institute for Medical Research in <st1:place w:st="on"><st1:city w:st="on">La Jolla</st1:city>, <st1:state w:st="on">California</st1:state></st1:place>, who led the study in Cell Stem Cell1. Researchers aren’t sure what causes the condition, which afflicts 10-30% of people with HIV and causes symptoms including forgetfulness and leg weakness. If untreated with antiretroviral drugs, sufferers can turn comatose.</font></font></p>
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<p class="MsoNormal" style="margin: 0cm 0cm 0pt"><font size="3"><font face="Times New Roman"><span style="mso-tab-count: 1"> </span>A study showing how HIV could prevent the brain from making new neurons offers an explanation for why some AIDS patients get dementia — and suggests a possible treatment. </font></font></p>
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<p class="MsoNormal" style="margin: 0cm 0cm 0pt"><font face="Times New Roman" size="3">Biologists have two theories to explain AIDS-related dementia.</font></p>
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<p class="MsoNormal" style="margin: 0cm 0cm 0pt 39pt; text-indent: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 39.0pt"><span style="font-family: Symbol; mso-fareast-font-family: Symbol; mso-bidi-font-family: Symbol"><span style="mso-list: Ignore"><font size="3">·</font><span style="font-weight: normal; font-size: 7pt; line-height: normal; font-style: normal; font-variant: normal" new="" times=""> </span></span></span><font face="Times New Roman" size="3">It could be that when HIV infects a type of white blood cell called a macrophage, the cell pumps out inflammatory chemicals to battle the infection that also, unfortunately, wipe out neurons.</font></p>
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<p class="MsoNormal" style="margin: 0cm 0cm 0pt 39pt; text-indent: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 39.0pt"><span style="font-family: Symbol; mso-fareast-font-family: Symbol; mso-bidi-font-family: Symbol"><span style="mso-list: Ignore"><font size="3">·</font><span style="font-weight: normal; font-size: 7pt; line-height: normal; font-style: normal; font-variant: normal" new="" times=""> </span></span></span><font face="Times New Roman" size="3">HIV could inflict its damage more directly. One previous study showed that a protein in the virus’s shell — called gp120 — can stop brain stem cells from dividing. </font></p>
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<p class="MsoNormal" style="margin: 0cm 0cm 0pt"><font size="3"><font face="Times New Roman"><span style="mso-tab-count: 1"> </span>To investigate, Lipton and postdoc Shu-ichi Okamoto studied a strain of mice genetically engineered to make the virus’s gp120 protein. Under the microscope, the mouse brains look just like those of humans with AIDS-related dementia, says Lipton.</font></font></p>
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<p class="MsoNormal" style="margin: 0cm 0cm 0pt"><font size="3"><font face="Times New Roman"><span style="mso-tab-count: 1"> </span>When the team studied the mice more closely, they found many of their neural stem cells were stuck in the cellular equivalent of ‘neutral’, unable to divide and make new cells.</font></font></p>
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<p class="MsoNormal" style="margin: 0cm 0cm 0pt"><font size="3"><font face="Times New Roman"><span style="mso-tab-count: 1"> </span>Neural stem cells in the transgenic mice also contained more of a protein called p38 than normal mice.Drugs that block p38 are already in clinical trials for autoimmune diseases such as rheumatoid arthritis, and Lipton’s team is currently testing one such drug in mice as a possible treatment for AIDS-related dementia.</font></font></p>
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