Baseline neuropsychiatric symptoms and psychotropic medication use midway through data collection of the Longitudinal Early-Onset Alzheimer's Disease Study (LEADS) cohort

INTRODUCTION

We examined neuropsychiatric symptoms (NPS) and psychotropic medication use in a large sample of individuals with early-onset Alzheimer's disease (EOAD; onset 40-64 years) at the midway point of data collection for the Longitudinal Early-onset Alzheimer's Disease Study (LEADS).

METHODS

Baseline NPS (Neuropsychiatric Inventory - Questionnaire; Geriatric Depression Scale) and psychotropic medication use from 282 participants enrolled in LEADS were compared across diagnostic groups - amyloid-positive EOAD (n = 212) and amyloid negative early-onset non-Alzheimer's disease (EOnonAD; n = 70).

RESULTS

Affective behaviors were the most common NPS in EOAD at similar frequencies to EOnonAD. Tension and impulse control behaviors were more common in EOnonAD. A minority of participants were using psychotropic medications, and use was higher in EOnonAD.

DISCUSSION

Overall NPS burden and psychotropic medication use were higher in EOnonAD than EOAD participants. Future research will investigate moderators and etiological drivers of NPS, and NPS differences in EOAD versus late-onset AD.

Sex and APOE ε4 carrier effects on atrophy, amyloid PET, and tau PET burden in early-onset Alzheimer's disease

INTRODUCTION

We used sex and apolipoprotein E ε4 (APOE ε4) carrier status as predictors of pathologic burden in early-onset Alzheimer's disease (EOAD).

METHODS

We included baseline data from 77 cognitively normal (CN), 230 EOAD, and 70 EO non-Alzheimer's disease (EOnonAD) participants from the Longitudinal Early-Onset Alzheimer's Disease Study (LEADS). We stratified each diagnostic group by males and females, then further subdivided each sex by APOE ε4 carrier status and compared imaging biomarkers in each stratification. Voxel-wise multiple linear regressions yielded statistical brain maps of gray matter density, amyloid, and tau PET burden.

RESULTS

EOAD females had greater amyloid and tau PET burdens than males. EOAD female APOE ε4 non-carriers had greater amyloid PET burdens and greater gray matter atrophy than female ε4 carriers. EOnonAD female ε4 non-carriers also had greater gray matter atrophy than female ε4 carriers.

DISCUSSION

The effects of sex and APOE ε4 must be considered when studying these populations.

HIGHLIGHTS

Novel analysis examining the effects of biological sex and apolipoprotein E ε4 (APOE ε4) carrier status on neuroimaging biomarkers among early-onset Alzheimer's disease (EOAD), early-onset non-AD (EOnonAD), and cognitively normal (CN) participants. Female sex is associated with greater pathology burden in the EOAD cohort compared to male sex. The effect of APOE ε4 carrier status on pathology burden was the most impactful in females across all cohorts.

White matter hyperintensities are higher among early-onset Alzheimer's disease participants than their cognitively normal and early-onset nonAD peers: Longitudinal Early-onset Alzheimer's Disease Study (LEADS)

INTRODUCTION

We compared white matter hyperintensities (WMHs) in early-onset Alzheimer's disease (EOAD) with cognitively normal (CN) and early-onset amyloid-negative cognitively impaired (EOnonAD) groups in the Longitudinal Early-Onset Alzheimer's Disease Study.

METHODS

We investigated the role of increased WMH in cognition and amyloid and tau burden. We compared WMH burden of 205 EOAD, 68 EOnonAD, and 89 CN participants in lobar regions using t-tests and analyses of covariance. Linear regression analyses were used to investigate the association between WMH and cognitive impairment and that between amyloid and tau burden.

RESULTS

EOAD showed greater WMHs compared with CN and EOnonAD participants across all regions with no significant differences between CN and EOnonAD groups. Greater WMHs were associated with worse cognition. Tau burden was positively associated with WMH burden in the EOAD group.

DISCUSSION

EOAD consistently showed higher WMH volumes. Overall, greater WMHs were associated with worse cognition and higher tau burden in EOAD.

HIGHLIGHTS

This study represents a comprehensive characterization of WMHs in sporadic EOAD. WMH volumes are associated with tau burden from positron emission tomography (PET) in EOAD, suggesting WMHs are correlated with increasing burden of AD. Greater WMH volumes are associated with worse performance on global cognitive tests. EOAD participants have higher WMH volumes compared with CN and early-onset amyloid-negative cognitively impaired (EOnonAD) groups across all brain regions.

Cerebrospinal fluid biomarkers in the Longitudinal Early-onset Alzheimer's Disease Study

INTRODUCTION

One goal of the Longitudinal Early Onset Alzheimer's Disease Study (LEADS) is to define the fluid biomarker characteristics of early-onset Alzheimer's disease (EOAD).

METHODS

Cerebrospinal fluid (CSF) concentrations of Aβ1-40, Aβ1-42, total tau (tTau), pTau181, VILIP-1, SNAP-25, neurogranin (Ng), neurofilament light chain (NfL), and YKL-40 were measured by immunoassay in 165 LEADS participants. The associations of biomarker concentrations with diagnostic group and standard cognitive tests were evaluated.

RESULTS

Biomarkers were correlated with one another. Levels of CSF Aβ42/40, pTau181, tTau, SNAP-25, and Ng in EOAD differed significantly from cognitively normal and early-onset non-AD dementia; NfL, YKL-40, and VILIP-1 did not. Across groups, all biomarkers except SNAP-25 were correlated with cognition. Within the EOAD group, Aβ42/40, NfL, Ng, and SNAP-25 were correlated with at least one cognitive measure.

DISCUSSION

This study provides a comprehensive analysis of CSF biomarkers in sporadic EOAD that can inform EOAD clinical trial design.

Influence of amyloid and diagnostic syndrome on non-traditional memory scores in early-onset Alzheimer's disease

INTRODUCTION

The Rey Auditory Verbal Learning Test (RAVLT) is a useful neuropsychological test for describing episodic memory impairment in dementia. However, there is limited research on its utility in early-onset Alzheimer's disease (EOAD). We assess the influence of amyloid and diagnostic syndrome on several memory scores in EOAD.

METHODS

We transcribed RAVLT recordings from 303 subjects in the Longitudinal Early-Onset Alzheimer's Disease Study. Subjects were grouped by amyloid status and syndrome. Primacy, recency, J-curve, duration, stopping time, and speed score were calculated and entered into linear mixed effects models as dependent variables.

RESULTS

Compared with amyloid negative subjects, positive subjects exhibited effects on raw score, primacy, recency, and stopping time. Inter-syndromic differences were noted with raw score, primacy, recency, J-curve, and stopping time.

DISCUSSION

RAVLT measures are sensitive to the effects of amyloid and syndrome in EOAD. Future work is needed to quantify the predictive value of these scores.

HIGHLIGHTS

RAVLT patterns characterize various presentations of EOAD and EOnonAD Amyloid impacts raw score, primacy, recency, and stopping time Timing-based scores add value over traditional count-based scores.

An explainable machine learning model of cognitive decline derived from speech

INTRODUCTION

Traditional Alzheimer's disease (AD) and mild cognitive impairment (MCI) screening lacks the sensitivity and timeliness required to detect subtle indicators of cognitive decline. Multimodal artificial intelligence technologies using only speech data promise improved detection of neurodegenerative disorders.

METHODS

Speech collected over the telephone from 91 older participants who were cognitively healthy (n = 29) or had diagnoses of AD (n = 30) or amnestic MCI (aMCI; n = 32) was analyzed with multimodal natural language and speech processing methods. An explainable ensemble decision tree classifier for the multiclass prediction of cognitive decline was created.

RESULTS

This approach was 75% accurate overall-an improvement over traditional speech-based screening tools and a unimodal language-based model. We include a dashboard for the examination of the results, allowing for novel ways of interpreting such data.

DISCUSSION

This work provides a foundation for a meaningful change in medicine as clinical translation, scalability, and user friendliness were core to the methodologies.

Highlights

Remote assessments and artificial intelligence (AI) models allow greater access to cognitive decline screening.Speech impairments differ significantly between mild AD, amnestic mild cognitive impairment (aMCI), and healthy controls.AI predictions of cognitive decline are more accurate than experts and standard tools.The AI model was 75% accurate in classifying mild AD, aMCI, and healthy controls.

A blood biomarker test for brain amyloid impacts the clinical evaluation of cognitive impairment

OBJECTIVE

The objective of this study was to examine clinicians' patient selection and result interpretation of a clinically validated mass spectrometry test measuring amyloid beta and ApoE blood biomarkers combined with patient age (PrecivityAD® blood test) in symptomatic patients evaluated for Alzheimer's disease (AD) or other causes of cognitive decline.

METHODS

The Quality Improvement and Clinical Utility PrecivityAD Clinician Survey (QUIP I, ClinicalTrials.gov Identifier: NCT05477056) was a prospective, single-arm cohort study among 366 patients evaluated by neurologists and other cognitive specialists. Participants underwent blood biomarker testing and received an amyloid probability score (APS), indicating the likelihood of a positive result on an amyloid positron emission tomography (PET) scan. The primary study outcomes were appropriateness of patient selection as well as result interpretation associated with PrecivityAD blood testing.

RESULTS

A 95% (347/366) concordance rate was noted between clinicians' patient selection and the test's intended use criteria. In the final analysis including these 347 patients (median age 75 years, 56% women), prespecified test result categories incorporated 133 (38%) low APS, 162 (47%) high APS, and 52 (15%) intermediate APS patients. Clinicians' pretest and posttest AD diagnosis probability changed from 58% to 23% in low APS patients and 71% to 89% in high APS patients (p < 0.0001). Anti-AD drug therapy decreased by 46% in low APS patients (p < 0.0001) and increased by 57% in high APS patients (p < 0.0001).

INTERPRETATION

These findings demonstrate the clinical utility of the PrecivityAD blood test in clinical care and may have added relevance as new AD therapies are introduced.

Articulatory Gain Predicts Motor Cortex and Subthalamic Nucleus Activity During Speech

Speaking precisely is important for effective verbal communication, and articulatory gain is one component of speech motor control that contributes to achieving this goal. Given that the basal ganglia have been proposed to regulate the speed and size of limb movement, that is, movement gain, we explored the basal ganglia contribution to articulatory gain, through local field potentials (LFP) recorded simultaneously from the subthalamic nucleus (STN), precentral gyrus, and postcentral gyrus. During STN deep brain stimulation implantation for Parkinson's disease, participants read aloud consonant-vowel-consonant syllables. Articulatory gain was indirectly assessed using the F2 Ratio, an acoustic measurement of the second formant frequency of/i/vowels divided by/u/vowels. Mixed effects models demonstrated that the F2 Ratio correlated with alpha and theta activity in the precentral gyrus and STN. No correlations were observed for the postcentral gyrus. Functional connectivity analysis revealed that higher phase locking values for beta activity between the STN and precentral gyrus were correlated with lower F2 Ratios, suggesting that higher beta synchrony impairs articulatory precision. Effects were not related to disease severity. These data suggest that articulatory gain is encoded within the basal ganglia-cortical loop.

Nilotinib Effects on Safety, Tolerability, and Biomarkers in Alzheimer's Disease

OBJECTIVE

Preclinical evidence with nilotinib, a US Food and Drug Administration (FDA)-approved drug for leukemia, indicates improvement in Alzheimer's disease phenotypes. We investigated whether nilotinib is safe, and detectable in cerebrospinal fluid, and alters biomarkers and clinical decline in Alzheimer's disease.

METHODS

This single-center, phase 2, randomized, double-blind, placebo-controlled study investigated the safety, tolerability, and pharmacokinetics of nilotinib, and measured biomarkers in participants with mild to moderate dementia due to Alzheimer's disease. The diagnosis was supported by cerebrospinal fluid or amyloid positron emission tomography biomarkers. Nilotinib 150 mg versus matching placebo was taken orally once daily for 26 weeks followed by nilotinib 300 mg versus placebo for another 26 weeks.

RESULTS

Of the 37 individuals enrolled, 27 were women and the mean (SD) age was 70.7 (6.48) years. Nilotinib was well-tolerated, although more adverse events, particularly mood swings, were noted with the 300 mg dose. In the nilotinib group, central nervous system (CNS) amyloid burden was significantly reduced in the frontal lobe compared to the placebo group. Cerebrospinal fluid Aβ40 was reduced at 6 months and Aβ42 was reduced at 12 months in the nilotinib group compared to the placebo. Hippocampal volume loss was attenuated (-27%) at 12 months and phospho-tau-181 was reduced at 6 months and 12 months in the nilotinib group.

INTERPRETATION

Nilotinib is safe and achieves pharmacologically relevant cerebrospinal fluid concentrations. Biomarkers of disease were altered in response to nilotinib treatment. These data support a larger, longer, multicenter study to determine the safety and efficacy of nilotinib in Alzheimer's disease. ANN NEUROL 2020 ANN NEUROL 2020;88:183-194.

Nilotinib and bosutinib modulate pre-plaque alterations of blood immune markers and neuro-inflammation in Alzheimer's disease models

Alzheimer's disease (AD) brains exhibit plaques and tangles in association with inflammation. The non-receptor tyrosine kinase Abl is linked to neuro-inflammation in AD. Abl inhibition by nilotinib or bosutinib facilitates amyloid clearance and may decrease inflammation. Transgenic mice that express Dutch, Iowa and Swedish APP mutations (TgAPP) and display progressive Aβ plaque deposition were treated with tyrosine kinase inhibitors (TKIs) to determine pre-plaque effects on systemic and CNS inflammation using milliplex® ELISA. Plaque Aβ was detected at 4months in TgAPP and pre-plaque intracellular Aβ accumulation (2.5months) was associated with changes of cytokines and chemokines prior to detection of glial changes. Plaque formation correlated with increased levels of pro-inflammatory cytokines (TNF-α, IL-6, IL-1α, IL-1β) and markers of immunosuppressive and adaptive immunity, including, IL-4, IL-10, IL-2, IL-3, Vascular Endothelial Growth Factor (VEGF) and IFN-γ. An inverse relationship of chemokines was observed as CCL2 and CCL5 were lower than WT mice at 2months and significantly increased after plaque appearance, while soluble CX3CL1 decreased. A change in glial profile was only robustly detected at 6months in Tg-APP mice and TKIs reduced astrocyte and dendritic cell number with no effects on microglia, suggesting alteration of brain immunity. Nilotinib decreased blood and brain cytokines and chemokines and increased CX3CL1. Bosutinib increased brain and blood IL-10 and CX3CL1, suggesting a protective role for soluble CX3CL1. Taken together these data suggest that TKIs regulate systemic and CNS immunity and may be useful treatments in early AD through dual effects on amyloid clearance and immune modulation.

Beta amyloid-independent role of amyloid precursor protein in generation and maintenance of dendritic spines

Synapse loss induced by amyloid beta (Abeta) is thought to be a primary contributor to cognitive decline in Alzheimer's disease. Abeta is generated by proteolysis of amyloid precursor protein (APP), a synaptic receptor whose physiological function remains unclear. In the present study, we investigated the role of APP in dendritic spine formation, which is known to be important for learning and memory. We found that overexpression of APP increased spine number, whereas knockdown of APP reduced spine density in cultured hippocampal neurons. This spine-promoting effect of APP required both the extracellular and intracellular domains of APP, and was accompanied by specific upregulation of the GluR2, but not the GluR1, subunit of AMPA receptors. In an in vivo experiment, we found that cortical layers II/III and hippocampal CA1 pyramidal neurons in 1 year-old APP-deficient mice had fewer and shorter dendritic spines than wild-type littermates. In contrast, transgenic mice overexpressing mutant APP exhibited increased spine density compared to control animals, though only at a young age prior to overaccumulation of soluble amyloid. Additionally, increased glutamate synthesis was observed in young APP transgenic brains, whereas glutamate levels were decreased and GABA levels were increased in APP-deficient mice. These results demonstrate that APP is important for promoting spine formation and is required for proper spine development.

Physiological identification of the human pedunculopontine nucleus

BACKGROUND

The pedunculopontine nucleus (PPN) is a brainstem structure with widespread connections to the basal ganglia. Despite the recent introduction of PPN deep brain stimulation (DBS) for the treatment of gait disorders, little is known about its physiology in humans.

METHODS

Single unit discharge characteristics of neurons in the PPN region were analysed in four patients and PPN local field potentials (LFP) in one patient, recorded during the course of DBS implantation. Two patients had Parkinson disease, and two had non-sinemet responsive parkinsonism. Cell locations were plotted in the coordinate system of a human brainstem atlas.

RESULTS

Fifty-six units in the PPN region were studied, of which 32 mapped to within PPN boundaries. The mean (SD) discharge rate of neurons in the PPN was 23.2 (15.6) Hz. Spontaneous neuronal firing rate and burst discharge rate were significantly different between neurons in the region dorsal to PPN and those in the PPN. Responses to passive movement of contralateral and ipsilateral limbs were found. Theta and beta band oscillations were present in the PPN LFP.

CONCLUSION

PPN discharge characteristics may prove useful in the electrophysiological identification of PPN during DBS implantation surgery.

Amyloid-beta-induced ion flux in artificial lipid bilayers and neuronal cells: resolving a controversy

Understanding the pathogenicity of amyloid-beta (Abeta) peptides constitutes a major goal in research on Alzheimer's disease (AD). One hypothesis entails that Abeta peptides induce uncontrolled, neurotoxic ion flux through cellular membranes. The exact biophysical mechanism of this ion flux is, however, a subject of an ongoing controversy which has attenuated progress toward understanding the importance of Abeta-induced ion flux in AD. The work presented here addresses two prevalent controversies regarding the nature of transmembrane ion flux induced by Alphabeta peptides. First, the results clarify that Alphabeta can induce stepwise ion flux across planar lipid bilayers as opposed to a gradual increase in transmembrane current; they show that the previously reported gradual thinning of membranes with concomitant increase in transmembrane current arises from residues of the solvent hexafluoroisopropanol, which is commonly used for the preparation of amyloid samples. Second, the results provide additional evidence suggesting that Abeta peptides can induce ion channel-like ion flux in cellular membranes that is independent from the postulated ability of Alphabeta to modulate intrinsic cellular ion channels or transporter proteins.

Testing basal ganglia motor functions through reversible inactivations in the posterior internal globus pallidus

To test current hypotheses on the contribution of the basal ganglia (BG) to motor control, we examined the effects of muscimol-induced inactivations in the skeletomotor region of the internal globus pallidus (sGPi) on visually directed reaching. Injections were made in two monkeys trained to perform four out-and-back reaching movements in quick succession toward four randomly selected target locations. Following sGPi inactivations the following occurred. 1) Peak velocity and acceleration were decreased in nearly all sessions, whereas movement duration lengthened inconsistently. 2) Reaction times were unaffected on average, although minor changes were observed in several individual sessions. 3) Outward reaches showed a substantial hypometria that correlated closely with bradykinesia, but directional accuracy was unaffected. 4) Endpoint accuracy was preserved for the slow visually guided return movements. 5) No impairments were found in the rapid chaining of out-and-back movements, in the selection or initiation of four independent reaches in quick succession or in the quick on-line correction of initially misdirected reaches. 6) Inactivation-induced reductions in the magnitude of movement-related muscle activity (EMG) correlated with the severity of slowing and hypometria. There was no evidence for inactivation-induced alterations in the relative timing of EMG bursts, excessive cocontraction, or impaired suppression of antagonist EMG. Therefore disconnecting the BG motor pathway consistently produced bradykinesia and hypometria, but seldom affected movement initiation time, feedback-mediated guidance, the capacity to produce iterative reaches, or the ability to abruptly reverse movement direction. These results are discussed with reference to the idea that the BG motor loop may regulate energetic expenditures during movement (i.e., movement "vigor").

Normalizing motor-related brain activity: subthalamic nucleus stimulation in Parkinson disease

OBJECTIVE

To test whether therapeutic unilateral deep brain stimulation (DBS) of the subthalamic nucleus (STN) in patients with Parkinson disease (PD) leads to normalization in the pattern of brain activation during movement execution and control of movement extent.

METHODS

Six patients with PD were imaged off medication by PET during performance of a visually guided tracking task with the DBS voltage programmed for therapeutic (effective) or subtherapeutic (ineffective) stimulation. Data from patients with PD during ineffective stimulation were compared with a group of 13 age-matched control subjects to identify sites with abnormal patterns of activation. Conjunction analysis was used to identify those areas in patients with PD where activity normalized when they were treated with effective stimulation.

RESULTS

For movement execution, effective DBS caused an increase of activation in the supplementary motor area (SMA), superior parietal cortex, and cerebellum toward a more normal pattern. At rest, effective stimulation reduced overactivity of SMA. Therapeutic stimulation also induced reductions of movement related "overactivity" compared with healthy subjects in prefrontal, temporal lobe, and basal ganglia circuits, consistent with the notion that many areas are recruited to compensate for ineffective motor initiation. Normalization of activity related to the control of movement extent was associated with reductions of activity in primary motor cortex, SMA, and basal ganglia.

CONCLUSIONS

Effective subthalamic nucleus stimulation leads to task-specific modifications with appropriate recruitment of motor areas as well as widespread, nonspecific reductions of compensatory or competing cortical activity.

The basal ganglia network mediates the planning of movement amplitude

This study addresses the hypothesis that the basal ganglia (BG) are involved specifically in the planning of movement amplitude (or covariates). Although often advanced, based on observations that Parkinson's disease (PD) patients exhibit hypokinesia in the absence of significant directional errors, this hypothesis has been challenged by a recent alternative, that parkinsonian hypometria could be caused by dysfunction of on-line feedback loops. To re-evaluate this issue, we conducted two successive experiments. In the first experiment we assumed that if BG are involved in extent planning then PD patients (who exhibit a major dysfunction within the BG network) should exhibit a preserved ability to use a direction precue with respect to normals, but an impaired ability to use an amplitude precue. Results were compatible with this prediction. Because this evidence did not prove conclusively that the BG is involved in amplitude planning (functional deficits are not restricted to the BG network in PD), a second experiment was conducted using positron emission tomography (PET). We hypothesized that if the BG is important for planning movement amplitude, a task requiring increased amplitude planning should produce increased activation in the BG network. In agreement with this prediction, we observed enhanced activation of BG structures under a precue condition that emphasized extent planning in comparison with conditions that emphasized direction planning or no planning. Considered together, our results are consistent with the idea that BG is directly involved in the planning of movement amplitude or of factors that covary with that parameter.

On-line motor control in patients with Parkinson's disease

Recent models based, in part on a study of Huntington's disease, suggest that the basal ganglia are involved in on-line movement guidance. Two experiments were conducted to investigate this idea. First, we studied advanced Parkinson's disease patients performing a reaching task known to depend on on-line guidance. The task was to 'look and point' in the dark at visual targets displayed in the peripheral visual field. In some trials, the target location was slightly modified during saccadic gaze displacement (when vision is suppressed). In both patient and control groups, the target jump induced a gradual modification of the movement which diverged smoothly from its original path to reach the new target location. No deficit was found in the patients, except for an increased latency to respond to the target jump (Parkinson's disease: 243 ms; controls: 166 ms). A computational simulation indicated that this response slowing was likely to be a by-product of bradykinesia. The unexpected inconsistency between this result and previous reports was investigated in a second experiment. We hypothesized that the relevant factor was the characteristics of the corrections to be performed. To test this prediction, we investigated a task requiring corrections of the same type as investigated in Huntington's disease, namely large, consciously detected errors induced by large target jumps at hand movement onset. In contrast with the smooth adjustments observed in the first experiment, the subjects responded to the target jump by generating a discrete corrective sub-movement. While this iterative response was relatively rapid in the control subjects (220 ms), Parkinson's disease patients exhibited either dramatically late (>730 ms) or totally absent on-line corrections. When on-line corrections were absent, the initial motor response was completed before a second corrective response was initiated (the latency of the corrective response was the same as the latency of the initial response). Considered together, these results suggest that basal ganglia dependent circuits are not critical for feedback loops involving a smooth modulation of the ongoing command. These circuits may rather contribute to the generation of discrete corrective sub-movements. This deficit is in line with the general impairment of sequential and simultaneous actions in patients with basal ganglia disorders.

X11alpha modulates secretory and endocytic trafficking and metabolism of amyloid precursor protein: mutational analysis of the YENPTY sequence

The neuronal adaptor X11alpha interacts with the conserved -GYENPTY- sequence in the C-terminus of amyloid precursor protein (APP) or its Swedish mutation (APPswe) to inhibit Abeta40 and Abeta42 secretion. We hypothesized that the -YENP- motif essential for APP endocytosis is also essential for X11alpha-mediated effects on APP trafficking and metabolism, and that X11alpha modulates APP metabolism in both secretory and endocytic pathways. X11alpha failed to interact with the endocytic-defective APPswe mutants Y738A, N740A, or P741A, and thus did not modulate their trafficking or metabolism. However, endocytic-competent APPswe Y743A had unique trafficking and metabolism including a prolonged half-life and increased secretion of catabolites compared with APPswe. In contrast to endocytic-defective mutants, X11alpha interacted with APPswe Y743A as well as with APPswe. Thus, similar to APPswe, coexpression of X11alpha with APPswe Y743A retarded its maturation, prolonged its half-life, and inhibited APPs, Abeta40, and Abeta42 secretion. Collectively, these data suggest that by direct interaction with the APPswe -YENP- motif in the cytoplasmic tail, X11alpha modulated its trafficking and processing in both secretory and endocytic compartments, and may reduce secretion of Abeta generated in either pathway.

Basal ganglia network mediates the control of movement amplitude

In the present study we address the hypothesis that the basal ganglia are specifically involved in the planning of movement amplitude (or related covariates). This prediction has often been put forward based on the observation that Parkinson's disease (PD) patients exhibit hypokinesia. A close examination of the literature shows, however, that this commonly reported clinical symptom is not consistently echoed by experimental observations. When required to point to visual targets in the absence of vision of the moving limb, PD subjects exhibit various patterns of inaccuracy, including hypometria, hypermetria, systematic direction bias, or direction-dependent errors. They have even been shown to be as accurate as healthy, age-matched subjects. The main aim of the current study is to address the origin of these inconsistencies. To this end, we required nine patients presenting with advanced PD and 15 age-matched control subjects to perform planar reaching movements to visual targets. Eight targets were presented in equally spaced directions around a circle centered on the hand's starting location. Based on a previously validated parsing procedure, end-point errors were segmented into localization and planning errors. Localization errors refer to the existence of systematic biases in the estimation of the initial hand location. These biases can potentially transform a simple pattern of pure amplitude errors into a complex pattern involving both amplitude and direction errors. Results indicated that localization errors were different in the PD patients and the control subjects. This is not surprising knowing both that proprioception is altered in PD patients and that the ability to locate the hand at rest relies mainly on the proprioceptive sense, even when vision is available. Unlike normal subjects, localization errors in PD were idiosyncratic, lacking a consistent pattern across subjects. When the confounding effect of initial hand localization errors was canceled, we found that end-point errors were only due to the implementation of an underscaled movement gain (15%), without direction bias. Interestingly, the level of undershoot was found to increase with the severity of the disease (inferred from the Unified Parkinson's Disease Rating Scale, UPDRS, motor score). We also observed that movement variability was amplified (32%), but only along the main movement axis (extent variability). Direction variability was not significantly different in the patient population and the control group. When considered together, these results support the idea that the basal ganglia are specifically involved in the control of movement amplitude (or of some covariates). We propose that this structure participates in extent planning by modulating cortical activity and/or the tuning of the spinal interneuronal circuits.

Spontaneous intracranial hypotension causing reversible frontotemporal dementia

Spontaneous intracranial hypotension (SIH) causes postural headache and neurologic symptoms owing to traction and brain compression. A 66-year-old man with chronic headache and progressive personality and behavioral changes typical of frontotemporal dementia was examined. He had MRI findings of SIH with low CSF pressure. His headache, dementia, and imaging abnormalities abated after treatment with prednisone. SIH can cause reversible frontotemporal dementia, and should be considered when dementia and behavioral changes are accompanied by headache.

The protease inhibitor, MG132, blocks maturation of the amyloid precursor protein Swedish mutant preventing cleavage by beta-Secretase

Amyloid (Abeta) peptides found aggregated into plaques in Alzheimer's disease are derived from the sequential cleavage of the amyloid precursor protein (APP) first by beta- and then by gamma-secretases. Peptide aldehydes, which inhibit cysteine proteases and proteasomes, reportedly block Abeta peptide secretion by interfering with gamma-secretase cleavage. Using a novel, specific, and sensitive enzyme-linked immunosorbent assay for the beta-secretase-cleaved fragment of the Swedish mutant of APP (APPSw), we determined that the peptide aldehyde, MG132, prevented beta-secretase cleavage. This block in beta-secretase cleavage was not observed with clasto-lactacystin beta-lactone and thus, cannot be attributed to proteasomal inhibition. MG132 inhibition of beta-secretase cleavage was compared with the serine protease inhibitor, 4-(2-aminoethyl)benzenesulfonyl fluoride hydrochloride (AEBSF). AEBSF inhibition of beta-secretase cleavage was immediate and did not affect alpha-secretase cleavage. With MG132, inhibition was delayed and it decreased secretion of alpha-cleaved APPSw as well. Furthermore, MG132 treatment impaired maturation of full-length APPSw. Both inhibited intracellular formation of the beta-cleaved product. These results suggest that peptide aldehydes such as MG132 have multiple effects on the maturation and processing of APP. We conclude that the MG132-induced decrease in beta-secretase cleavage of APPSw is due to a block in maturation. This is sufficient to explain the previously reported peptide aldehyde-induced decrease in Abeta peptide secretion.

Modulation of amyloid precursor protein metabolism by X11alpha /Mint-1. A deletion analysis of protein-protein interaction domains

Modulation of amyloid precursor protein (APP) metabolism plays a pivotal role in the pathogenesis of Alzheimer's disease. The phosphotyrosine-binding/protein interaction (PTB/PI) domain of X11alpha, a neuronal cytosolic adaptor protein, binds to the YENPTY sequence in the cytoplasmic carboxyl terminus of APP. This interaction prolongs the half-life of APP and inhibits Abeta40 and Abeta42 secretion. X11alpha/Mint-1 has multiple protein-protein interaction domains, a Munc-18 interaction domain (MID), a Cask/Lin-2 interaction domain (CID), a PTB/PI domain, and two PDZ domains. These X11alpha protein interaction domains may modulate its effect on APP processing. To test this hypothesis, we performed a deletion analysis of X11alpha effects on metabolism of APP(695) Swedish (K595N/M596L) (APP(sw)) by transient cotransfection of HEK 293 cells with: 1) X11alpha (X11alpha-wt, N-MID-CID-PTB-PDZ-PDZ-C), 2) amino-terminal deletion (X11alpha-DeltaN, PTB-PDZ-PDZ), 3) carboxyl-terminal deletion (X11alpha-DeltaPDZ, MID-CID-PTB), or 4) deletion of both termini (PTB domain only, PTB). The carboxyl terminus of X11alpha was required for stabilization of APP(sw) in cells. In contrast, the amino terminus of X11alpha was required to stimulate APPs secretion. X11alpha, X11alpha-DeltaN, and X11alpha-PTB, but not X11alpha-DeltaPDZ, were effective inhibitors of Abeta40 and Abeta42 secretion. These results suggest that additional protein interaction domains of X11alpha modulate various aspects of APP metabolism.

The pathology of REM sleep behavior disorder with comorbid Lewy body dementia

A patient with REM sleep behavior disorder who subsequently developed probable Lewy body dementia is now reported to have a definite pathologic diagnosis of Lewy body dementia. Examination of brain revealed Lewy bodies as well as marked neuronal loss in brainstem monoaminergic nuclei-particularly locus coeruleus and substantia nigra-that inhibit cholinergic neurons in the pedunculopontine nucleus mediating atonia during REM sleep.

Corticostriatal activity in primary motor cortex of the macaque

Although input from corticostriatal neurons (CSNs) plays a critical role in basal ganglia functions, little is known about CSN activity during behavior. We compared the properties of antidromically identified CSNs with those of antidromically identified neurons that project via the cerebral peduncle to distant targets. Both types of neurons were recorded in primary motor cortex (M1) of two monkeys as they performed a step-tracking task in which static loads opposed or assisted simple and precued movements of the elbow or wrist. Multiple lines of evidence suggested that CSNs and corticopeduncular neurons (CPNs) belong to distinct populations. No cells were activated from both striatum and peduncle. Compared with CPNs, CSNs had slow conduction velocities and low spontaneous rates, and the activity of most was unmodulated by sensory testing or within the tasks used. CSN activity resembled that described for M1-recipient striatal neurons: perimovement firing was small in magnitude, strongly directional, and rarely showed muscle-like load effects. Contrary to a previous report, perimovement activity in most CSNs began before movement onset. CSN activity was more selective than that of CPNs: CSN sensory responses and perimovement activities were often directionally specific, CSNs were often activated exclusively by sensory stimulation, active movement, or movement preparation, and a substantial fraction of CSNs (19%) was unresponsive to any task or manipulation. Thus, CSNs transmit signals distinct from those sent to spinal cord/brainstem. The highly selective activity of CSNs suggests that a discrete (i.e., sparse) code is used to signal cortical activation states to striatum.

What Persian Gulf War syndrome?

Recent reports of physical and neuropsychological syndromes putatively associated with service in the Persian Gulf War and ostensibly providing evidence for Gulf War Syndrome (GWS) are critically reviewed. Major methodological weaknesses are identified in the studies and it is contended that there is no solid evidence for GWS at this time. Suggestions are given for future investigations of symptoms associated with service during the Gulf War which may accurately lead to a tangible identification of a war-related illness entity.

Role of the posterior parietal cortex in updating reaching movements to a visual target

The exact role of posterior parietal cortex (PPC) in visually directed reaching is unknown. We propose that, by building an internal representation of instantaneous hand location, PPC computes a dynamic motor error used by motor centers to correct the ongoing trajectory. With unseen right hands, five subjects pointed to visual targets that either remained stationary or moved during saccadic eye movements. Transcranial magnetic stimulation (TMS) was applied over the left PPC during target presentation. Stimulation disrupted path corrections that normally occur in response to target jumps, but had no effect on those directed at stationary targets. Furthermore, left-hand movement corrections were not blocked, ruling out visual or oculomotor effects of stimulation.

Differentiated human NT2-N neurons possess a high intracellular content of myo-inositol

myo-Inositol plays a key role in signal transduction and osmotic regulation events in the CNS. Despite the known high concentrations of inositol in the human CNS, relatively little is known about its distribution within the different cell types. In this report, inositol homeostasis was studied in NT2-N cells, a unique cell culture model of human CNS neurons. Differentiation of precursor NT2 teratocarcinoma cells into NT2-N neurons by means of retinoic acid treatment resulted in an increase in inositol concentration from 24 to 195 nmol/mg of protein. After measurement of intracellular water spaces, inositol concentrations of 1.6 and 17.4 mM were calculated for NT2 and NT2-N cells, respectively. The high concentrations of inositol in NT2-N neurons could be explained by (1) an increased uptake of inositol (3.7 vs. 1.6 nmol/mg of protein/h, for NT2-N and NT2 cells, respectively) and (2) a decreased efflux of inositol (1.7%/h for NT2-N neurons vs. 9.0%/h for NT2 cells). Activity of inositol synthase, which mediates de novo synthesis of inositol, was not detected in either cell type. The observation that CNS neurons maintain a high intracellular concentration of inositol may be relevant to the regulation of both phosphoinositide signaling and osmotic stress events in the CNS.

Molecular analysis of the X11-mLin-2/CASK complex in brain

A heterotrimeric complex containing Lin-10/X11alpha, Lin-2/CASK, and Lin-7 is evolutionarily conserved from worms to mammals. In Caenorhabditis elegans, it localizes Let-23, a receptor tyrosine kinase, to the basolateral side of vulval epithelium, a step crucial for proper vulva development. In mammals, the complex may also participate in receptor targeting in neurons. Accordingly, phosphotyrosine binding (PTB) and postsynaptic density-95/Discs large/Zona Occludens-1 domains found in X11alpha and mLin-2/CASK bind to cell-surface proteins, including amyloid precursor protein, neurexins, and syndecans. In this paper, we have further analyzed the X11alpha-mLin-2/CASK association that is mediated by a novel protein-protein interaction. We show that the mLin-2/CASK calmodulin kinase II (CKII) domain directly binds to a 63 amino acids peptide located between the Munc-18-1 binding site and the PTB domain in X11alpha. Ca2+/calmodulin association with mLin-2/CASK does not modify the X11alpha-mLin-2 interaction. A region containing the mLin-2/CASK guanylate kinase domain also interacts with X11alpha but with a lower affinity than the CKII domain. Immunostaining of X11alpha in the brain shows that the protein is expressed in areas shown previously to be positive for mLin-2/CASK staining. Together, our data demonstrate that the X11alpha-mLin-2 complex contacts many partners, creating a macrocomplex suitable for receptor targeting at the neuronal plasma membrane.

Identification of an evolutionarily conserved heterotrimeric protein complex involved in protein targeting

In Caenorhabditis elegans, lin-2, lin-7, and lin-10 genetically interact to control the trafficking of the Let-23 growth factor receptor to the basolateral surface of body epithelia. The human homologue of the lin-10 gene has recently been identified as a member of the X11 gene family. The X11 proteins contain one phosphotyrosine binding (PTB) and two PSD-95.Dlg.ZO-1 (PDZ) domains as well as an extended amino terminus. We have previously shown that the PTB domain of X11alpha (also known as Mint1) can bind to the amyloid precursor protein (APP) in a phosphotyrosine-independent fashion and can markedly inhibit the processing of APP to the amyloid beta (Abeta) peptide. Here, we report that X11alpha directly binds to the mammalian homologue of Lin-2 (mLin-2), also known as CASK. This binding is mediated by direct interaction between the Calmodulin Kinase II (CKII)-like domain of mLin-2 and the amino terminus of X11alpha. Furthermore, we can detect direct interactions between mLin-2 and mammalian Lin-7 (mLin-7). In mouse brain, we have identified a heterotrimeric complex that contains mLin-2, mLin-7, and X11alpha and that is likely important for the localization of proteins in polarized cells. This complex may play an important role in the trafficking and processing of APP in neurons.

The chaperone BiP/GRP78 binds to amyloid precursor protein and decreases Abeta40 and Abeta42 secretion

Recent studies of cellular amyloid precursor protein (APP) metabolism demonstrate a beta-/gamma-secretase pathway resident to the endoplasmic reticulum (ER)/Golgi resulting in intracellular generation of soluble APP (APPsbeta) and Abeta42 peptide. Thus, these intracellular compartments may be key sites of amyloidogenic APP metabolism and Alzheimer's disease pathogenesis. We hypothesized that the ER chaperone immunoglobulin binding protein (BiP/GRP78) binds to and facilitates correct folding of nascent APP. Metabolic labeling and immunoprecipitation of transiently transfected human embryonic kidney 293 cells demonstrated co-precipitation of APP with GRP78, revealing their transient interaction in the ER. Maturation of cellular APP was impaired by this interaction. Furthermore, the levels of APPs, Abeta40, and Abeta42 recovered in conditioned medium were lower compared with cells transfected with APP alone. Co-expression with APP of GRP78 T37G, an ATPase mutant, almost completely blocked cellular APP maturation as well as recovery of APPs, Abeta40, and Abeta42 in conditioned medium. The inhibitory effects of GRP78 and GRP78 T37G on Abeta40 and Abeta42 secretion were magnified by co-expression with the Swedish mutation of APP (K670N/M671L). Collectively, these data suggest a transient and direct interaction of GRP78 with APP in the ER that modulates intracellular APP maturation and processing and may facilitate its correct folding.

Motor subcircuits mediating the control of movement velocity: a PET study

The influence of changes in the mean velocity of movement on regional cerebral blood flow (rCBF) was studied using positron emission tomography (PET) in nine healthy right-handed adults while they performed a smooth pursuit visuomanual tracking task. Images of relative rCBF were obtained while subjects moved a hand-held joystick to track the movement of a target at three different rates of a sinusoidal displacement (0.1, 0.4, and 0.7 Hz). Significant changes in rCBF between task conditions were detected using analysis of variance and weighted linear contrasts. The kinematics of arm and eye movements indicated that subjects performed tasks in a similar manner, particularly during the faster two tracking conditions. Significant increases in rCBF during arm movement (relative to an eye tracking only control condition) were detected in a widespread network of areas known for their involvement in motor control. The activated areas included primary sensorimotor (M1S1), dorsal and mesial premotor, and dorsal parietal cortices in the left hemisphere and to a lesser extent the sensorimotor and superior parietal cortices in the right hemisphere. Subcortically, activations were found in the left putamen, globus pallidus (GP), and thalamus, in the right basal ganglia, and in the right anterior cerebellum. Within the cerebral volume activated with movement, three areas had changes in rCBF that correlated positively with the rate of movement: left M1S1, left GP, and right anterior cerebellum. No movement-related sites had rCBF that correlated negatively with the rate of movement. Regressions of mean percent change (MPC) in rCBF onto mean hand velocity yielded two nonoverlapping subpopulations of movement-related loci, the three sites with significant rate effects and regression slopes steeper than 0.17 MPC.cm-1.s-1 and all other sites with nonsignificant rate effects and regression slopes below 0.1 MPC.cm-1. s-1. Moreover, the effects of movement per se and of movement velocity varied in magnitude independently. These results confirm previous reports that movement-related activations of M1S1 and cerebellum are sensitive to movement frequency or some covarying parameter of movement. The activation of GP with increasing movement velocity, not described in previous functional-imaging studies, supports the hypothesis that the basal ganglia motor circuit may be involved preferentially in controlling or monitoring the scale and/or dynamics of arm movements. The remaining areas that were activated equally for all movement rates may be involved in controlling higher level aspects of motor control that are independent of movement dynamics.

X11 interaction with beta-amyloid precursor protein modulates its cellular stabilization and reduces amyloid beta-protein secretion

The protein interaction domain of the neuronal protein X11 binds to the YENPTY motif within the cytoplasmic domain of beta-amyloid precursor protein (betaAPP). Amyloid-beta protein (Abeta), the major constituent of the amyloid deposited in brain of Alzheimer's disease patients, is generated by proteolytic processing of betaAPP, which occurs in part following betaAPP internalization. Because the YENPTY motif has a role in the internalization of betaAPP, the effect of X11 binding on betaAPP processing was studied in mouse neuroblastoma N2a, human embryonic kidney 293, monkey kidney COS-1, and human glial U251 cell lines transfected with wild type or mutated betaAPP cDNAs. Secretion of soluble betaAPP via alpha-secretase activity increased significantly in cells transfected with betaAPP variants containing mutations that impair interaction with X11 when compared with cells transfected with wild type cDNA. Cotransfection of betaAPP and X11 caused retention of cellular betaAPP, decreased secretion of sbetaAPPalpha, and decreased Abeta secretion. Thus, betaAPP interaction with the protein interaction domain of X11 stabilizes cellular betaAPP and thereby participates in the regulation of betaAPP processing pathways.

GABAA receptor pharmacology and subtype mRNA expression in human neuronal NT2-N cells

Human NT2 teratocarcinoma cells differentiate into neuron-like NT2-N cells when treated with retinoic acid. GABA evoked concentration-dependent whole-cell currents in NT2-N cells with an EC50 of 21.8 microM and a Hill slope of 1.2. GABAA receptor (GABAR) currents reversed at ECl- and did not display voltage-dependent rectification. GABAR single channels opened in bursts to a 23 pS main conductance level and a 19 pS subconductance level, with infrequent openings to a 27 pS conductance level. Kinetic properties of the main conductance level were similar to other native and recombinant GABAR channels. Diazepam and zolpidem enhanced GABAR currents with moderate affinity, whereas methyl-6, 7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate inhibited GABAR currents. Loreclezole enhanced GABAR currents with high affinity, but furosemide antagonized GABAR currents with low affinity. The neurosteroids alphaxalone and pregnenolone sulfate appropriately modulated GABAR currents. Zinc blocked GABAR currents with low affinity, but lanthanum did not significantly alter NT2-N GABAR currents. Reverse transcription PCR (RT-PCR) performed on RNA from NT2-N cells clearly detected transcripts encoding human alpha2, alpha3, alpha5, beta3, gamma3, and pi subtypes. The combined pharmacological and RT-PCR results are most consistent with a single or predominant GABAR isoform composed of an alpha2 and/or alpha3 subtype combined with the beta3 and gamma3 subtypes. The data do not rule out receptors containing combinations of alpha2 and/or alpha3 subtypes with the alpha5 subtype or receptors with both beta1 and beta3 subtypes. The presence or absence or the pi subunit in functionally expressed receptors could not be determined.

The X11alpha protein slows cellular amyloid precursor protein processing and reduces Abeta40 and Abeta42 secretion

Constitutive amyloid precursor protein (APP) metabolism results in the generation of soluble APP (APPs) and Abeta peptides, including Abeta40 and Abeta42-the major component of amyloid plaques in Alzheimer's disease brain. The phosphotyrosine binding (PTB) domain of X11 binds to a peptide containing a YENPTY motif found in the carboxyl terminus of APP. We have cloned the full-length X11 gene now referred to as X11alpha. Coexpression of X11alpha with APP results in comparatively greater levels of cellular APP and less APPs, Abeta40, and Abeta42 recovered in conditioned medium of transiently transfected HEK 293 cells. These effects are impaired by a single missense mutation of either APP (Y682G within the YENPTY motif) or X11alpha (F608V within the PTB domain), which diminishes their interaction, thus demonstrating specificity. The inhibitory effect of X11alpha on Abeta40 and Abeta42 secretion is amplified by coexpression with the Swedish mutation of APP (K595N/M596L), which promotes its amyloidogenic processing. Pulse-chase analysis demonstrates that X11alpha prolongs the half-life of APP from approximately 2 h to approximately 4 h. The effects of X11alpha on cellular APP and APPs recovery were confirmed in a 293 cell line stably transfected with APP. The specific binding of the PTB domain of X11alpha to the YENPTY motif-containing peptide of APP appears to slow cellular APP processing and thus reduces recovery of its soluble fragments APPs, Abeta40, and Abeta42 in conditioned medium of transfected HEK 293 cells. X11alpha may be involved in APP trafficking and metabolism in neurons and thus may be implicated in amyloidogenesis in normal aging and Alzheimer's disease brain.

Probable diffuse Lewy body disease presenting as REM sleep behavior disorder

Rapid eye movement sleep behavior disorder may herald several neurodegenerative disorders associated with parkinsonism, including Parkinson's disease. A 72-year-old man with a 17-year history of rapid eye movement sleep behavior disorder confirmed by polysomnography developed a progressive dementia that met operational clinical criteria for diffuse Lewy body disease. The differential diagnosis of progressive neurodegenerative disorders heralding as rapid eye movement sleep behavior disorder should now include diffuse Lewy body disease.

Pallidal discharge related to the kinematics of reaching movements in two dimensions

Movement-related discharge of neurons in the internal and external segments of the globus pallidus (GPi and GPe, respectively) of two monkeys was studied during reaching movements in a two-dimensional work-space. Discharge was studied during movements to targets in eight directions and at three distances from the starting position under three behavioral conditions that manipulated target visibility and movement triggering. A total of 73 neurons (57 in GPe and 18 in GPi) with changes in discharge in concert with arm movements were included in a quantitative analysis. Of these, 83% also changed their discharge during manipulation of the contralateral arm outside of the task. Although 73% of changes in discharge began before the initiation of movement, they seldom preceded the initial activity of the antagonist muscles. Decreases in discharge were more common than reported previously, constituting 40% of the changes in discharge detected. In GPi neurons, decreases also tended to begin earlier than increases. Changes in discharge in GPe neurons were of larger magnitude than those in GPi, and increases in discharge were larger than decreases. Onsets of changes in discharge were temporally linked to movement onset in 69% of neurons. Time locking of neural onset to trigger presentation and movement termination was found in only 30 and 1% of neurons, respectively. Direction of movement influenced the magnitude of changes in discharge in 78% of cells. Directional modulations were broadly tuned and preferred directions were uniformly distributed across the range of directions. When directional modulations were large, preferred directions were consistent for different amplitudes of movement and for different behavioral conditions. Amplitude of movement influenced the magnitude of changes in discharge in 78% of cells, and in 80% of cases that relation had a significant linear component. Amplitude effects were not more common or stronger for movements in directions close to a cell's preferred direction. Linear relations to movement amplitude were more common and accounted for more of the trial-to-trial variance in discharge rate than relations to either average velocity or movement duration. The relation to movement amplitude was consistent for two behavioral conditions when the change in discharge was scaled strongly with movement amplitude. Movement-related changes in discharge of neurons in the skeletomotor portions of both pallidal segments reflect the kinematics of movement. This information, encoded in combination with sensory and contextual information, may play an on-line role in the selective facilitation and suppression of different frontal thalamocortical circuits.

Vaccinia virus serves as an efficient vector for expressing heterologous proteins in human NTera 2 neurons

The human teratocarcinoma cell line NTera 2 (NT2) can be induced to differentiate into post-mitotic neurons possessing well-defined axonal and dendritic morphology. Highly enriched neurons (NT2-N cells) can be prepared in large numbers, thus combining many of the advantages of both primary and continuous cell culture systems. Unfortunately, it has proven difficult to express foreign genes in NT2-N cells. We examined whether vaccinia virus (VV) can express heterologous proteins in NT2-N cells and characterized the response of NT2-N cells to VV infection. NT2-N cells were infected with VV vectors expressing the envelope glycoprotein (gp160) from the human immunodeficiency type 1 virus (HIV 1). These vectors were chosen because VV-directed synthesis and post-translational processing of gp160 have been well characterized in many cell types. Approximately 85% of the neurons expressed gp160 which underwent native post-translational cleavage. The rate of gp160 synthesis was maximal at 5-48 hours postinfection, but was detectable for as long as 4 days. Surprisingly, NT2-N cells showed no VV-induced alterations in morphology, downregulation of host protein synthesis, or cytotoxicity, as measured by lactate dehydrogenase release. These results indicate that VV can serve as an efficient vector for introducing foreign genes in NT2-N cells without the cytotoxic effects often associated with VV infection. These properties, in conjunction with the advantages provided by NT2-N cells, provide new options for analyzing the cellular and molecular functions of human neurons.

Treatment of advanced Parkinson's disease by posterior GPi pallidotomy: 1-year results of a pilot study

The effects of posterior internal pallidal ablation (GPi pallidotomy) on parkinsonian signs and symptoms were studied in 15 patients with medically intractable Parkinson's disease (PD). The sensorimotor territory of the internal portion of the globus pallidus and the adjacent optic tract and internal capsule were identified with microelectrode recording and stimulation. Radiofrequency lesions were then created in the identified sensorimotor territory. Pallidotomy significantly improved all cardinal parkinsonian motor signs (tremor, rigidity, akinesia/bradykinesia, and gait dysfunction) and reduced drug-induced motor fluctuations and dyskinesias. The improvements occurred predominately contralateral to the lesion, but were also present ipsilaterally. Early postoperative (3-month), mean total United Parkinson's Disease Rating Scale scores improved by 30.1% from preoperative values. Mean combined "on/off" Schwab and England Scale scores, a measure of functional independence, increased from 48.8% to 73.0% postoperatively. The mean total United Parkinson's Disease Rating Scale and Schwab and England scores did not show a statistically significant decline over the 1-year postoperative period. Surgery resulted in little morbidity, including a lack of significant deficits on neuropsychological and psychiatric testing. Physical and social functioning and vitality measures on the Medical Outcome Scale also showed significant improvement over the postoperative period. The findings of this pilot study demonstrate that ablation of the sensorimotor portion of the internal pallidum is a highly effective treatment for advanced PD, with benefits sustained at 1 year.

Amyloids beta40 and beta42 are generated intracellularly in cultured human neurons and their secretion increases with maturation

Previous studies have demonstrated the presence of amyloid beta (Abeta) in neurons (NT2N) derived from a human embryonal carcinoma cell line (NT2) by steady state metabolic radiolabeling and immunoprecipitation. We show here that Abeta is present intracellularly since trypsin digestion of intact NT2N cells at 4 degrees C did not eliminate the Abeta recovered in cell lysates. To determine whether both Abeta40 and Abeta42 are produced intracellularly, quantitative sandwich enzyme-linked immunosorbent assay (ELISA) was performed using COOH-terminal end-specific anti-Abeta monoclonal antibodies. Sandwich ELISA detected intracellular Abeta40 and A++beta42 in NT2N cell lysates at a ratio of 3:1, whereas secreted Abeta40 and Abeta42 were recovered in medium conditioned by NT2N cells at a ratio of approximately 20:1. Metabolic steady state and pulse-chase labeling studies demonstrated a 2-h delay in the detection of cell-associated Abeta40/Abeta42 in the medium, suggesting that Abeta is generated at a slow rate intracellularly prior to its secretion. Finally, as NT2N cells mature over time in culture, the secretion of Abeta40 and Abeta42 increases more than 5-fold over 7 weeks. This increase in the secretion of Abeta40/Abeta42 in NT2N cells as a function of time may recapitulate a similar phenomenon in the aging brain.

Clinical, neuroimaging, and pathologic features of progressive nonfluent aphasia

We report the clinical, neuroimaging, and neuropathologic features of progressive nonfluent aphasia (PNFA), a rare neurodegenerative syndrome most notable for its distinct language disturbance. Longitudinal observations of 3 patients revealed progressively telegraphic speech and writing, followed by gradual deterioration of sentence comprehension, and finally, preterminal mutism and dementia. Magnetic resonance imaging revealed cortical atrophy most pronounced in anterior regions of the left hemisphere. Functional neuroimaging demonstrated reduced cerebral activity most prominently in left frontal and temporal regions. At necropsy, microscopic pathology of brain was most consistent with the diagnosis of "dementia lacking distinctive histology" (DLDH). A review of published primary progressive aphasia cases with adequate clinical and histopathological descriptions reveals that the most common pathology underlying PNFA is DLDH. PNFA is one example of a family of clinical syndromes with similar underlying histopathology that affects different regions of the frontal lobe.

Directional variation of spatial and temporal characteristics of limb movements made by monkeys in a two-dimensional work space

1. The directional variation of kinematic and electromyographic (EMG) characteristics of two-joint arm movements made to targets in a two-dimensional work space was studied in monkeys trained to make targeted arm movements under different behavioral conditions. 2. In each animal, kinematic measures of movement (movement amplitude, movement time, peak velocity, and trajectory curvature) and endpoint spatial position within the target zone varied as a function of the direction of the target from the starting position. Movements made toward the body into the ipsilateral hemispace generally had the smallest amplitude, lowest peak velocity, and longest movement time. 3. Although the directional variation in peak velocity could partially be accounted for by predicted anisotropies in the inertial load imposed by the arm, deviations from these predictions suggest that movement amplitude is controlled more rigorously by the CNS. Adjustments in movement time may be used to compensate for inertial anisotropies. 4. The spatial characteristics of movements (amplitude, trajectory curvature, or endpoint error) were influenced little by the visibility of the target during movement, the advanced knowledge of target location, or the presence or absence of an external trigger cue. However, temporal characteristics (movement time, peak velocity, and for some animals, reaction time) varied more as sensory cues were changed. 5. The time of initial EMG activity in muscles acting around the shoulder varied systematically as a function of target direction. A cosine model accounted for a large fraction of the variability in initial onset time, as determined in a trial-by-trial analysis. The amplitude of the EMG activity was more narrowly tuned, however. Muscles acting at the elbow showed less activity and more variable directional tuning. 6. We conclude that directional variations in the kinematic characteristics of movement, and thus, the dynamic force requirements of the task, must be taken into consideration as contributors to the apparent directional coding described for neuronal populations in different portions of the CNS.

Postoperative total hip prosthetic femoral head dislocations. Incidence, etiologic factors, and management

Twenty-five dislocations occurred after 561 total hip arthroplasties performed by the author from 1971 to 1992. Acetabular shell and liner loosening must be differentiated from true dislocations. The dislocation rate of 5.49% in female patients was higher than the 2.8% rate in male patients. The 4.76% rate after 84 total hip revisions was slightly higher than the 3.98% rate after 477 primary replacements. No dislocations occurred using the anterolateral approach for 53 patients. Dislocation rates varied using different prosthetic systems for 508 patients who had the posterolateral approach used. Femoral prostheses with larger neck diameters were more prone to dislocation. These differences were not statistically significant with the sample sizes used, according to the chi square test for equality of proportions. Fluoroscopy aided reduction of one multiplanar recurrent case. Single hip spica abduction casts with and without knee hinges used for three to four months, along with abduction isometric exercises, led to stability in six recurrent cases.

The incidence of deep-vein thrombosis after upper tibial osteotomy. A venographic study

We performed postoperative venography on 84 consecutive patients who had undergone upper tibial osteotomy for medial compartment osteoarthritis of the knee. Deep-vein thrombosis was demonstrated in 41%. Only 15% of the cases were diagnosed clinically, all in the calf veins. Cases of proximal thromboses (3) and mixed-vein thromboses (12) were only revealed by venography.

Human neurons derived from a teratocarcinoma cell line express solely the 695-amino acid amyloid precursor protein and produce intracellular beta-amyloid or A4 peptides

The beta-amyloid or beta/A4 peptides that accumulate as filamentous aggregates in the extracellular space of Alzheimer disease (AD) brains are derived from one or more alternatively spliced amyloid precursor proteins (APPs). The more abundant APPs in the central nervous system are the 695-(APP695), 751- (APP751), and 770- (APP770) amino acid isoforms, and each could be the source of beta/A4 peptide that accumulates in the AD brain. It is plausible that altered metabolism of these APPs by central nervous system neurons could lead to the release and deposition of beta/A4 peptide in brain parenchyma. Thus, we examined the expression and processing of the three major brain APPs in nearly pure human neurons (NT2N cells) derived from a teratocarcinoma cell line (NTera2/c1.D1 or NT2 cells) after retinoic acid treatment. NT2N neurons expressed almost exclusively APP695, whereas NT2 cells expressed predominantly APP751/770. Furthermore, the processing of the APPs in NT2N cells was distinct from NT2 and nonneuronal cells. Most significantly, the NT2N neurons but not the NT2 cells constitutively generated intracellular beta/A4 peptide and released it into the culture medium. This work demonstrates the intracellular production of beta/A4 peptide and suggests that cultured NT2N cells may provide a unique model system for understanding the contribution of neurons and APP695 to amyloidogenesis in the AD brain.

Use of historical assessment for evaluation of process-based model projections of future environmental change: Lake acidification in the Adirondack mountains, New York, USA

Because of the considerable uncertainties associated with modeling complex ecosystem processes, it is essential that every effort be made to test model performance prior to relying on model projections for assessment of future surface water chemical response to environmental perturbation. Unfortunately, long-term chemical data with which to validate model performance are seldom available. The authors present here an evaluation of historical acidification of lake waters in the northeastern United States, and compare historical changes in a set of lakes to hindcasts from the same watershed model (MAGIC) used to estimate future changes in response to acidic deposition. The historical analyses and comparisons with MAGIC model hindcasts and forecasts of acid-base response demonstrate that the acidic and low-ANC lakes in this region are responsive to strong acid inputs. However, the model estimates suggest lakewater chemistry is more responsive to atmospheric inputs of sulfur than do the estimates based on paleolimnological historical analyses. A 'weight-of-evidence approach' that incorporates all available sources of information regarding acid-base response provides a more reasonable estimate of future change than an approach based on model projections alone. The results of these analyses have important implications for predicting future surface water chemical change in response to acidic deposition, establishing critical loads of atmospheric pollutants, and other environmental assessment activities where natural variation often exceeds the trends under investigation (high noise-to-signal ratio). Under these conditions, it is particularly important to evaluate future model projections in light of historical trends data.

Sensitivity to change for low-ANC eastern US lakes and streams and brook trout populations under alternative sulfate deposition scenarios

A weight-of-evidence approach was used by the US National Acid Precipitation Assessment Program (NAPAP) to assess the sensitivity of chemistry and biology of lakes and streams to hypothesized changes in sulfate deposition over the next 50 years. The analyses focused on projected effects in response to differences in the magnitude and the timing of changes in sulfate deposition in the north-eastern United States, the Mid-Appalachian Highlands, and the Southern Blue Ridge Province. A number of tools was used to provide the weight of evidence that is required to have confidence in an assessment that has many uncertainties because of the complexity of the systems for which the projections of future conditions were made and because of limited historical data. The MAGIC model provided the projections of chemical changes in response to alternative deposition scenarios. Projected chemical conditions were input into biological models that evaluate effects on fish populations. The sensitivity of water chemistry and brook trout resources to the hypothesized changes in deposition was found to be greatest in the Adirondacks and Mid-Atlantic Highlands. Under the hypothesized sulfur deposition reduction scenarios, chemical conditions suitable for fish were projected to improve 20-30 years sooner than with the scenario that assumed no new legislated controls. Other lines of evidence, e.g. other models, field observations, and paleolimnological findings, were used to evaluate uncertainty in the projections. Model parameter/calibration uncertainty for the chemical models and population sampling uncertainty were explicitly quantified. Model structural uncertainties were bracketed using model comparisons, recent measured changes, and paleolimnological reconstructions of historical changes in lake chemistry.