Dementia in patients with AIDS is caused by a large, late invasion of HIV-infected macrophages into the brain, according to researchers at Temple University in Philadelphia. The finding debunks a longstanding “Trojan Horse” theory that early infection by macrophages remained latent until the latter stages of AIDS. “Late during AIDS, which is when most HIV patients develop dementia, there is a second—or late—invasion of infected macrophages which is not a ‘Trojan Horse’ but a ‘Trojan Herd,’” they said. “It’s not just a few cells but a huge number invading the brain.” Using antibody markers, the researchers reported a 15- to 20-fold increase in the number of total macrophages in the brain during HIV dementia, which “suggests that trafficking of the macrophages late in infection is really responsible for dementia in HIV patients.” The findings were reported in the June American Journal of Pathology.

Natural toxins found in the environment could contribute to the development of Parkinson’s disease, according to a study in rats published in the June 21 online edition of Annals of Neurology. The compounds—called proteasome inhibitors—are produced by bacteria and fungi; man-made proteasome inhibitors can also enter the environment. Researchers injected proteasome inhibitors into rats; after about two weeks, the animals began showing symptoms similar to Parkinson’s disease. The symptoms gradually worsened but were treatable with drugs used for patients with Parkinson’s disease. “These results suggest that we should determine how widespread these toxins are in the environment, how humans are exposed to them, and how such exposures correlate with the incidence of Parkinson’s disease,” the investigators said.

Researchers found that damage or surgery to the left hemisphere of the brain may make a right-handed person more susceptible to being immunocompromised. The results might help explain findings suggesting that people who had strokes on the left hemisphere of their brains were more susceptible to infections. The investigators examined immune response to brain surgery in 22 patients with epilepsy. Most patients who had left hemispheric surgery experienced significant decreases in immune function, they reported, while patients who had right-hemisphere surgery experienced an increase in immune productivity. The investigators noted that the finding may be valid only for right-handed persons; they did not have sufficient left-handed or ambidextrous participants to draw any conclusions, but they postulated that non–right-handed persons might experience the opposite reaction in their immune system/surgery side relationship. The findings were published in the May 24 online Annals of Neurology.

A new guideline developed by the American Academy of Neurology and the Child Neurology Society addressed the treatment of infantile spasms. Researchers reviewed all available scientific studies on the topic. They determined that adrenocorticotropic hormone “is probably effective for the short-term treatment of infantile spasms” though they were unable to recommend the optimum dosage and length of treatment. The investigators also reported that vigabatrin “is possibly effective” as another option for short-term treatment. They noted that there are “potentially serious” side effects to both those treatments; however, based on insufficient evidence, they were unable to recommend other treatments for infantile spasms. The guidelines were published in the May 25 Neurology.

German researchers have used diffusion-weighted imaging to show that brain lesions developed one to two days after an episode of transient global amnesia, according to a report in the June 22 Neurology. The investigators examined 31 patients within hours of the onset of amnesia and conducted follow-up MRI studies over the next 48 hours. “Lesions were rarely noted during the period of amnesia, but with follow-up MRI, they became visible by 48 hours,” the researchers said. All lesions were located in the hippocampus. The study confirms the involvement of hippocampal lesions in transient global amnesia and “may explain the incongruence of previous studies in this condition.”

Investigators from Harvard Medical School in Boston reported a “genetic signature” of aging in the human brain in the June 9 online Nature. The investigators examined postmortem brain tissue from 30 people (ages 26 to 106), looking at some 11,000 genes. They found that after age 40, about 400 genes showed significant changes in how hard they had been working while the person was alive. Slightly less than half those genes—including those for learning, memory, and communication between brain cells—were functioning at a lower level; the remainder—including genes for DNA repair, antioxidant defense, and stress and inflammatory response—were working harder. The authors said it is too early to determine what causes such changes, “but this gives us a starting point, because what we’ve shown is that there’s a genetic signature … of this aging process and now we can work to determine how that impacts brain function.”

A new vaccine successfully prevents the death of brain cells in a mouse model of Parkinson’s disease. The vaccine used copaxone, which was injected into the brains of mice with an experimental form of Parkinson’s disease. “The mice mounted an immune response to the brain protein that turned off inflammation,” the researchers reported. Mediating the inflammatory brain response by amplifying microglia and astrocytes reduces neuronal cell death and may prevent progression of neurodegenerative disease, they noted in the June 22 Proceedings of the National Academy of Sciences. The investigators called for clinical trials to determine if the observations seen in mice can be translated to humans.

Two reports in the June Radiology detailed the use of perfusion computed tomography to assist physicians in locating blockages in cerebral blood flow by showing how much blood is present in the brain and how quickly it is moving. It also measures cerebrovascular reserve. Physicians can zoom in on areas of interest, thus allowing comparisons, for example, between blood flow through a partially occluded carotid artery and a healthy carotid artery. The imaging technique was shown to give valuable information on patients undergoing a balloon-test occlusion in preparation for brain surgery, and in describing damaged tissue in cases of ischemic stroke. It may also have uses in subarachnoid hemorrhage and brain tumors, the investigators said.

Expressing high levels of the glycosylating protein LARGE in mice that lack the protein can prevent muscular dystrophy in these animals, according to researchers at the University of Iowa. The genetic transfer of the protein into deficient animals restored normal function to α-dystroglycan, which is disrupted in cases of congenital muscular dystrophy 1D. The LARGE protein also restored α-dystroglycan function without adversely affecting cells in cases of Fukuyama-type congenital muscular dystrophy, Walker-Warburg syndrome, and muscle-eye-brain disease, the investigators reported. The findings could lead to new treatments for this particular class of muscular dystrophies and other muscle diseases caused by glycosylation defects, they said. The studies were reported in the June 3 online edition of Cell and the June 6 advanced online Nature Medicine.

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