Infected monocyte-derived macrophages (MDM) are thought by some investigators to play a central role in the neuropathogenesis of human immunodeficiency virus encephalitis (HIVE). It was recently proposed that these cells gain access to the central nervous system (CNS) through disruptions in blood-brain barrier (BBB) tight junctions, which occur in HIVE in association with accumulation of activated, HIV-1-infected, perivascular macrophages and serum protein extravasation (Am J Pathol 1999, 155: 1915-27). The present study tested this hypothesis in basal ganglia tissue from simian immunodeficiency virus (SIV)-infected macaques with encephalitis by examining vessels for immunohistochemical alterations in the tight junction-associated proteins, occludin and zonula occludens-1 (ZO-1). Compared to non-infected macaques and SIV-infected macaques without encephalitis, cerebral vessels from macaques with SIVE showed fragmentation and decreased immunoreactivity for both tight junction proteins. These alterations were associated with accumulation of perivascular macrophages and aberrant occludin and ZO-1 immunoreactivity within these cells. In addition, perivascular extravasation of fibrinogen, a plasma protein, and a change from a strong linear staining pattern to a more irregular pattern of glucose transporter isoform-1 (GLUT-1), a metabolic BBB marker, were observed in regions with vascular tight junction protein alterations. These findings demonstrate that tight junction disruption occurs in SIVE in association with perivascular macrophage accumulation. While it cannot be ascertained from these studies whether such changes precede macrophage infiltration, or are secondary to the chronic presence of macrophages around cerebral vessels, disruptions in BBB integrity could serve as portals for additional accumulation of perivascular macrophages in SIVE.
The WHO launched a multicentre study to explore the nature and prevalence of HIV-1-associated neurological, psychiatric, and neuropsychological abnormalities in persons living in different geographical and sociocultural contexts. The study is being conducted in Brazil, Germany, Kenya, Thailand, the United States of America, and Zaire. A comprehensive instrument for the collection of neuropsychiatric data (including a battery of neuropsychological tests suitable for cross-cultural use) has been developed, and the feasibility of the recruitment and assessment procedure designed for the main phase has now been demonstrated.
Cortex from rat, dog, and human brain was submitted to subcellular fractionation using an analytical approach consisting of a two-step procedure. First, fractions were obtained by differential centrifugation and were analyzed for their content of serotonin S2 and muscarinic receptors, serotonin uptake, and marker enzymes. Second, the cytoplasmic extracts were subfractionated by equilibration in sucrose density gradient. In human brain, serotonin and muscarinic receptors were found associated mostly with mitochondrial fractions which contain synaptosomes, whereas in rat brain they were concentrated mainly in the microsomal fractions. Density gradient centrifugation confirmed a more marked synaptosomal localization of receptors in human than in rat brain, the dog displaying an intermediate profile. In human brain, indeed, more receptor sites were found to be associated with the second peak characterized in electron microscopy by the largest number of nerve terminals. In addition, synaptosomes from human brain are denser than those from rat brain and some marker enzymes reveal different subcellular distribution in the three species. These data indicate that more receptors are of synaptosomal nature in human brain than in other species and this finding is compatible with a larger amount of synaptic contacts in human brain.
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