Phenotypic heterogeneity in sporadic Creutzfeldt-Jakob disease (sCJD) is well documented, but there is not yet a systematic classification of the disease variants. In a previous study, we showed that the polymorphic codon 129 of the prion protein gene (PRNP), and two types of protease-resistant prion protein (PrP(Sc)) with distinct physicochemical properties, are major determinants of these variants. To define the full spectrum of variants, we have examined a series of 300 sCJD patients. Clinical features, PRNP genotype, and PrP(Sc) properties were determined in all subjects. In 187, we also studied neuropathological features and immunohistochemical pattern of PrP(Sc) deposition. Seventy percent of subjects showed the classic CJD phenotype, PrP(Sc) type 1, and at least one methionine allele at codon 129; 25% of cases displayed the ataxic and kuru-plaque variants, associated to PrP(Sc) type 2, and valine homozygosity or heterozygosity at codon 129, respectively. Two additional variants, which included a thalamic form of CJD and a phenotype characterized by prominent dementia and cortical pathology, were linked to PrP(Sc) type 2 and methionine homozygosity. Finally, a rare phenotype characterized by progressive dementia was linked to PrP(Sc) type 1 and valine homozygosity. The present data demonstrate the existence of six phenotypic variants of sCJD. The physicochemical properties of PrP(Sc) in conjunction with the PRNP codon 129 genotype largely determine this phenotypic variability, and allow a molecular classification of the disease variants.

Phenotypic heterogeneity in sporadic Creutzfeldt‐Jakob disease (sCJD) is well documented, but there is not yet a systematic classification of the disease variants. In a previous study, we showed that the polymorphic codon 129 of the prion protein gene (PRNP), and two types of protease‐resistant prion protein (PrPSc) with distinct physicochemical properties, are major determinants of these variants. To define the full spectrum of variants, we have examined a series of 300 sCJD patients. Clinical features, PRNP genotype, and PrPSc properties were determined in all subjects. In 187, we also studied neuropathological features and immunohistochemical pattern of PrPSc deposition. Seventy percent of subjects showed the classic CJD phenotype, PrPSc type 1, and at least one methionine allele at codon 129; 25% of cases displayed the ataxic and kuru‐plaque variants, associated to PrPSc type 2, and valine homozygosity or heterozygosity at codon 129, respectively. Two additional variants, which included a thalamic form of CJD and a phenotype characterized by prominent dementia and cortical pathology, were linked to PrPSc type 2 and methionine homozygosity. Finally, a rare phenotype characterized by progressive dementia was linked to PrPSc type 1 and valine homozygosity. The present data demonstrate the existence of six phenotypic variants of sCJD. The physicochemical properties of PrPSc in conjunction with the PRNP codon 129 genotype largely determine this phenotypic variability, and allow a molecular classification of the disease variants. Ann Neurol 1999;46:224–233

The role of microglia in the removal of amyloid deposits after systemically administered anti-A␤ antibodies remains unclear. In the current study, we injected Tg2576 APP transgenic mice weekly with an anti-A␤ antibody for 1, 2, or 3 months such that all mice were 22 months at the end of the study. In mice immunized for 3 months, we found an improvement in alternation performance in the Y maze. Histologically, we were able to detect mouse IgG bound to congophilic amyloid deposits in those mice treated with the anti-A␤ antibody but not in those treated with a control antibody. We found that Fc␥ receptor expression on microglia was increased after 1 month of treatment, whereas CD45 was increased after 2 months of treatment. Associated with these microglial changes was a reduction in both diffuse and compact amyloid deposits after 2 months of treatment. Interestingly, the microglia markers were reduced to control levels after 3 months of treatment, whereas amyloid levels remained reduced. Serum A␤ levels and anti-A␤ antibody levels were elevated to similar levels at all three survival times in mice given anti-A␤ injections rather than control antibody injections. These data show that the antibody is able to enter the brain and bind to the amyloid deposits, likely opsonizing the A␤ and resulting in Fc␥ receptor-mediated phagocytosis. Together with our earlier work, our data argue that all proposed mechanisms of anti-A␤ antibody-mediated amyloid removal can be simultaneously active.

3-4-(2-Fluoro-alpha-methyl-[1,1'-biphenyl]-4-acetyloxy)-3-methoxyphenyl]-2-propenoic acid 4-nitrooxy butyl ester (NCX-2216), a nitric oxide (NO)-releasing derivative of the cyclooxygenase-1-preferring nonsteroidal anti-inflammatory drug (NSAID) flurbiprofen, dramatically reduced both beta-amyloid (Abeta) loads and Congo red staining in doubly transgenic (Tg) amyloid precursor protein plus presenilin-1 mice when administered at 375 ppm in diet between 7 and 12 months of age. This reduction was associated with a dramatic increase in the number of microglia expressing major histocompatibility complex-II antigen, a marker for microglial activation. In contrast, ibuprofen at 375 ppm in diet caused modest reductions in Abeta load but not Congo red staining, suggesting that the effects of this nonselective NSAID were restricted primarily to nonfibrillar deposits. We detected no effects of the cyclooxygenase-2-selective NSAID celecoxib at 175 ppm on amyloid deposition. In short-term studies of 12-month-old Tg mice, we found that the microglia-activating properties of NCX-2216 (7.5 mg small middle dot kg(-1) small middle dot d(-1), s.c.) were present after 2 weeks of treatment. Microglia were not activated by NCX-2216 in non-Tg mice lacking Abeta deposits, nor were microglia activated in Tg animals by flurbiprofen (5 mg small middle dot kg(-1) small middle dot d(-1)) alone. These data are consistent with the argument that activated microglia can clear Abeta deposits. We conclude that the NO-generating component of NCX-2216 confers biological actions that go beyond those of typical NSAIDs. In conclusion, NCX-2216 is more efficacious than ibuprofen or celecoxib in clearing Abeta deposits from the brains of Tg mice, implying potential benefit in the treatment of Alzheimer's dementia.

We present 8 examples of a neoplasm with features of both astrocytoma and ependymoma that may represent a distinct clinicopathologic entity. The cerebral hemispheric tumors occurred in patients that were 3, 4, 12, 14, 15, 26, 30, and 37 years of age. All presented with seizures that, with the exception of 2, began in childhood. Magnetic resonance imaging studies showed ill-defined, T2-hyperintense, generally noncontrast-enhancing lesions that, although centered on the cortex or amygdala, extended into the underlying white matter for a short distance. Histologically, the variably infiltrative tumors were distinctively angiocentric with well-developed perivascular pseudorosettes in some cases. Longitudinal and/or circumferential orientations of perivascular cells were common also. The cells were uniform in their cytologic features from case to case and were bipolar in all but one case. A glial nature was inferred from immunoreactivity for GFAP, and ependymal differentiation was suggested by positivity for EMA in three cases and ultrastructural features in one. Overall, the tumors were biologically indolent except for one that recurred and ultimately proved fatal.

In this review, we emphasize neuropathologic and neurobehavioral aspects of central pontine and extrapontine myelinolysis (CPM/EPM), also known as the osmotic demyelination syndrome. The literature is reviewed from the time of the initial report in 1959 and from key developments that have occurred more recently. Particular consideration is given to pathogenic mechanisms as revealed by recent animal studies. The role of white matter pathology in neurobehavioral dysfunction is also considered. The "then" and "now" of CPM and EPM tell 2 different stories. Yet, in many respects, this expansion of information over the past nearly 50 years simply represents a continuum, as well as recognition, of the vast gaps that still persist in our understanding of this disorder.

We have previously shown erythropoietin (Epo) and its receptor (Epo-R) to be present in the fetal human central nervous system (CNS), and Epo to be present in the spinal fluid of normal preterm and term infants. To investigate the cellular specificities and developmental patterns of expression of these polypeptides in the human brain-areas that have not been well researched-we designed the following study. Human brains ranging in maturity from 5 weeks post-conception to adult were preserved at the time of elective abortion, surgical removal (tubal pregnancy, or removal for temporal lobe epilepsy), or autopsy. Immunohistochemistry was used to localize Epo and Epo-R reactivity in brains of different stages of development. Astrocytes, neurons, and microglia were identified in sequential tissue sections by specific antibodies. At 5 to 6 weeks post-conception, both Epo and Epo-R localized to cells in the periventricular germinal zone. At 10 weeks post-conception, Epo immunoreactivity was present throughout the cortical wall, with the most intense immunoreactivity present in the ventricular and subventricular zones. Epo-R, in contrast, was localized primarily to the subventricular zone, with little staining evident in the ventricular zone. In late fetal brains, Epo-R reactivity was most prominent in astrocytic cells, although modest reactivity was observed in certain neuron populations. In contrast, Epo staining localized primarily to neurons in fetal brains, although a subpopulation of astrocytes was also immunoreactive. In postnatal brains, both astrocyte and neuron populations were immunoreactive with antibodies to Epo-R and Epo. From these results it is clear that Epo and its receptor are present in the developing human brain as early as 5 weeks post-conception, and each protein shows a specific distribution that changes with development. We speculate that Epo is important in neurodevelopment, and that it also plays a role in brain homeostasis later in life, functioning in an autocrine or paracrine manner.

The presence of activated microglia in postmortem Alzheimer disease specimens is used to support the argument that inflammation contributes to Alzheimer pathogenesis. Transgenic mice overexpressing the amyloid precursor protein (APP) gene form amyloid plaques that are accompanied by local activation of microglia/macrophages in a manner similar to the human disease. Many markers of microglial activation and inflammation increase in an age-dependent manner in these mice. However, manipulation of these inflammatory reactions can lead to unexpected outcomes with several instances of reduced pathology when microglia/macrophages are activated further. In particular, anti-Abeta immunotherapy in amyloid-depositing transgenic mice causes a complex series of changes in microglial markers, negating the implicit belief that such activation is monotonic and represented equally well by any of several "activation" markers. A survey of the peripheral macrophage literature identifies at least 2 distinct activation states of macrophages with different consequences for the surrounding tissue. These different activation states can often be distinguished by the markers that are expressed. Several markers are identified from studies outside the brain that neuroscientists might consider evaluating when attempting to more definitively describe the activation state of the monocyte-derived cells in the brain.