In this small preliminary study, brain overgrowth in males with autism involved an abnormal excess number of neurons in the PFC.

Background Autism involves early brain overgrowth and dysfunction, which is most strongly evident in the prefrontal cortex. As assessed on pathological analysis, an excess of neurons in the prefrontal cortex among children with autism signals a disturbance in prenatal development and may be concomitant with abnormal cell type and laminar development. Methods To systematically examine neocortical architecture during the early years after the onset of autism, we used RNA in situ hybridization with a panel of layer- and cell-type– specific molecular markers to phenotype cortical microstructure. We assayed markers for neurons and glia, along with genes that have been implicated in the risk of autism, in prefrontal, temporal, and occipital neocortical tissue from postmortem samples obtained from children with autism and unaffected children between the ages of 2 and 15 years. Results We observed focal patches of abnormal laminar cytoarchitecture and cortical disorganization of neurons, but not glia, in prefrontal and temporal cortical tissue from 10 of 11 children with autism and from 1 of 11 unaffected children. We observed heterogeneity between cases with respect to cell types that were most abnormal in the patches and the layers that were most affected by the pathological features. No cortical layer was uniformly spared, with the clearest signs of abnormal expression in layers 4 and 5. Three-dimensional reconstruction of layer markers confirmed the focal geometry and size of patches. Conclusions In this small, explorative study, we found focal disruption of cortical laminar architecture in the cortexes of a majority of young children with autism. Our data support a probable dysregulation of layer formation and layer-specific neuronal differentiation at prenatal developmental stages. (Funded by the Simons Foundation and others.)

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Machado-Joseph disease (MJD) is an inherited neurodegenerative disorder caused by ataxin-3 with a polyglutamine expansion. It isproposed that a toxic cleavage fragment of mutant ataxin-3 alternatively spliced isoform mjd1a triggers neurodegeneration, although this fragment has not yet been detected in the brains of MJD patients or in animal models. We have now generated transgenic mice expressing human mutant (Q71) or normal (Q20) ataxin-3 mjd1a under the control of the mouse prion promoter. Q71 transgenic mice expressing mutant ataxin-3 mjd1a above a critical level developed a phenotype similar to MJD including progressive postural instability, gait and limb ataxia, weight loss, premature death, neuronal intranuclear inclusions, and decreased tyrosine hydroxylase-positive neurons in the substantia nigra (determined by unbiased stereology). Q20 transgenic mice had normal behavior and pathology. Brains from sick Q71 transgenic mice contained an abundant mutant ataxin-3 mjd1a putative-cleavage fragment (Fragment), which was scarce in normal Q71 transgenic mice. Reactivity of the Fragment with a panel of antibodies and comigration with truncations of mutant ataxin-3 revealed that it contained residues C terminal to amino acid 221 to include the polyglutamine expansion. A similar portion of mutant ataxin-3 mjd1a expressed in transfected neuroblastoma cells was toxic above a critical concentration. The Fragment was more abundant in two affected brain regions of MJD patients. Thus, we have developed a murine model for mutant ataxin-3 mjd1a toxicity and identified a putativecleavage fragment of the disease protein in the brains of these transgenic mice and MJD patients that is cytotoxic above a critical concentration.

We report that a low-calorie diet can lessen the severity of neurochemical deficits and motor dysfunction in a primate model of Parkinson's disease. Adult male rhesus monkeys were maintained for 6 months on a reduced-calorie diet [30% caloric restriction (CR)] or an ad libitum control diet after which they were subjected to treatment with a neurotoxin to produce a hemiparkinson condition. After neurotoxin treatment, CR monkeys exhibited significantly higher levels of locomotor activity compared with control monkeys as well as higher levels of dopamine (DA) and DA metabolites in the striatal region. Increased survival of DA neurons in the substantia nigra and improved manual dexterity were noted but did not reach statistical significance. Levels of glial cell linederived neurotrophic factor, which is known to promote the survival of DA neurons, were increased significantly in the caudate nucleus of CR monkeys, suggesting a role for glial cell line-derived neurotrophic factor in the anti-Parkinson's disease effect of the low-calorie diet.brain-derived neurotrophic factor ͉ cell death ͉ dopamine P arkinson's disease (PD) results from the dysfunction and degeneration of dopamine (DA) neurons in the substantia nigra (SN) and DA axon terminals, resulting in progressive motor dysfunction (1). The risk of PD increases with advancing age, suggesting that cellular and molecular changes that occur in the brain during normal aging may promote the degeneration of DA neurons. In this regard, increased oxidative stress and impaired energy metabolism and protein turnover occur in DA neurons during normal aging, and these changes are greatly exacerbated in PD (2, 3). Although a small number of cases of PD result from inherited genetic mutations in one of three genes, ␣-synuclein, Parkin, or DJ-1 (4), most cases are sporadic with an unknown environmental cause(s). Nevertheless, studies of genetic and neurotoxin-based animal models of PD point to the involvement of oxidative stress and impaired energy metabolism and protein turnover in the pathogenesis of PD (3-6). There is currently no established intervention to prevent, or decrease the risk of, PD.Most studies of humans have concluded that a decrease in the number of DA neurons in the SN occurs during normal aging, with PD being an acceleration of this process (7-9). However, some investigators have reported no age-related decline in the number of DA neurons (10). Studies in rhesus monkeys have been more consistent in reporting age-related decline in the number of tyrosine hydroxylase (TH)-positive SN neurons (11, 12). However, because some monkey studies have reported increased numbers of THpositive nigral neurons after treatment with neurotrophic factors, such as glial cell line-derived neurotrophic factor (GDNF), an age-related decline in expression of TH could be an alternative explanation to the results suggesting an age-related loss of nigral neurons (13).In a wide range of laboratory animals, caloric restriction (CR) has been shown to prolong lifespan, decrease the incid...

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Development, ageing, and a variety of neurological disorders are characterized by selective alterations in specific populations of nerve cells which are, in turn, associated with changes in the numbers of synapses in the target fields of these neurons. To begin to delineate the significance of changes in synapses in development, ageing, and disease, it is first essential to quantify the number of synapses in defined regions of the CNS. In the past, investigators have used EM methods to assess synapse numbers or density, but these approaches are costly, labour intensive, and technically difficult, particularly in autopsy material. To begin to define reliable strategies useful for studies of both animals and humans, we used three techniques to measure synaptophysin-immunoreactivity in rat brain. The levels of synaptophysin protein were determined by Western blots of five hippocampal subregions; the intensity of synaptophysin-immunoreactivity in dentate gyrus and stratum oriens was determined by optical densitometry of immunocytochemically stained sections; and the total number of synaptophysin-immunoreactivity presynaptic boutons in dentate gyrus and stratum oriens was assessed by unbiased stereology. Each approach has advantages and disadvantages. Western blotting is the least time-consuming of the three methods and allows simultaneous processing of multiple samples. In systematically sampled histological sections, both densitometry and stereology allow precise definition of the region of interest, and the stereological optical dissector method allows quantitation of the numbers of synaptophysin-immunoreactive boutons. Stereology was the only method that clearly demonstrated greater synaptophysin-immunoreactivity in the dentate gyrus as compared to stratum oriens. The use of systematic sampling and the dissector technique offer a high degree of anatomical resolution (lacking in Western blot methods) and has quantitative advantage over the greyscale-based density approach. Thus, at present, stereology is the most useful method for estimating synaptic numbers in defined regions of the brain.

Summary Lineal structures in biological tissue support a wide variety of physiological functions, including membrane stabilization, vascular perfusion, and cell‐to‐cell communication. In 1953, Smith and Guttman demonstrated a stereological method to estimate the total length density (Lv) of linear objects based on random intersections with a two‐dimensional sampling probe. Several methods have been developed to ensure the required isotropy of object–probe intersections, including isotropic‐uniform‐random (IUR) sections, vertical‐uniform‐random (VUR) slices, and isotropic virtual planes. The disadvantages of these methods are the requirements for inconvenient section orientations (IUR, VUR) or complex counting rules at multiple focal planes (isotropic virtual planes). To overcome these limitations we report a convenient and straightforward approach to estimate Lv and total length, L, for linear objects on tissue sections cut at any arbitrary orientation. The approach presented here uses spherical probes that are inherently isotropic, combined with unbiased fractionator sampling, to demonstrate total L estimation for thin nerve fibres in dorsal hippocampus of the mouse brain.