Link among apolipoprotein E E4, gait, and cognition in neurodegenerative diseases: ONDRI study

INTRODUCTION

Apolipoprotein E E4 allele (APOE E4) and slow gait are independently associated with cognitive impairment and dementia. However, it is unknown whether their coexistence is associated with poorer cognitive performance and its underlying mechanism in neurodegenerative diseases.

METHODS

Gait speed, APOE E4, cognition, and neuroimaging were assessed in 480 older adults with neurodegeneration. Participants were grouped by APOE E4 presence and slow gait. Mediation analyses were conducted to determine if brain structures could explain the link between these factors and cognitive performance.

RESULTS

APOE E4 carriers with slow gait had the lowest global cognitive performance and smaller gray matter volumes compared to non-APOE E4 carriers with normal gait. Coexistence of APOE E4 and slow gait best predicted global and domain-specific poorer cognitive performances, mediated by smaller gray matter volume.

DISCUSSION

Gait slowness in APOE E4 carriers with neurodegenerative diseases may indicate extensive gray matter changes associated with poor cognition.

HIGHLIGHTS

APOE E4 and slow gait are risk factors for cognitive decline in neurodegenerative diseases. Slow gait and smaller gray matter volumes are associated, independently of APOE E4. Worse cognition in APOE E4 carriers with slow gait is explained by smaller GM volume. Gait slowness in APOE E4 carriers indicates poorer cognition-related brain changes.

Association of plasma biomarkers with cognition, cognitive decline, and daily function across and within neurodegenerative diseases: Results from the Ontario Neurodegenerative Disease Research Initiative

INTRODUCTION

We investigated whether novel plasma biomarkers are associated with cognition, cognitive decline, and functional independence in activities of daily living across and within neurodegenerative diseases.

METHODS

Glial fibrillary acidic protein (GFAP), neurofilament light chain (NfL), phosphorylated tau (p-tau)181 and amyloid beta (Aβ)42/40 were measured using ultra-sensitive Simoa immunoassays in 44 healthy controls and 480 participants diagnosed with Alzheimer's disease/mild cognitive impairment (AD/MCI), Parkinson's disease (PD), frontotemporal dementia (FTD) spectrum disorders, or cerebrovascular disease (CVD).

RESULTS

GFAP, NfL, and/or p-tau181 were elevated among all diseases compared to controls, and were broadly associated with worse baseline cognitive performance, greater cognitive decline, and/or lower functional independence. While GFAP, NfL, and p-tau181 were highly predictive across diseases, p-tau181 was more specific to the AD/MCI cohort. Sparse associations were found in the FTD and CVD cohorts and for Aβ42/40 .

DISCUSSION

GFAP, NfL, and p-tau181 are valuable predictors of cognition and function across common neurodegenerative diseases, and may be useful in specialized clinics and clinical trials.

White matter hyperintensity burden predicts cognitive but not motor decline in Parkinson's disease: results from the Ontario Neurodegenerative Diseases Research Initiative

BACKGROUND AND PURPOSE

The pathophysiology of Parkinson's disease (PD) negatively affects brain network connectivity, and in the presence of brain white matter hyperintensities (WMHs) cognitive and motor impairments seem to be aggravated. However, the role of WMHs in predicting accelerating symptom worsening remains controversial. The objective was to investigate whether location and segmental brain WMH burden at baseline predict cognitive and motor declines in PD after 2 years.

METHODS

Ninety-eight older adults followed longitudinally from Ontario Neurodegenerative Diseases Research Initiative with PD of 3-8 years in duration were included. Percentages of WMH volumes at baseline were calculated by location (deep and periventricular) and by brain region (frontal, temporal, parietal, occipital lobes and basal ganglia + thalamus). Cognitive and motor changes were assessed from baseline to 2-year follow-up. Specifically, global cognition, attention, executive function, memory, visuospatial abilities and language were assessed as were motor symptoms evaluated using the Movement Disorder Society Unified Parkinson's Disease Rating Scale Part III, spatial-temporal gait variables, Freezing of Gait Questionnaire and Activities Specific Balance Confidence Scale.

RESULTS

Regression analysis adjusted for potential confounders showed that total and periventricular WMHs at baseline predicted decline in global cognition (p < 0.05). Also, total WMH burden predicted the decline of executive function (p < 0.05). Occipital WMH volumes also predicted decline in global cognition, visuomotor attention and visuospatial memory declines (p < 0.05). WMH volumes at baseline did not predict motor decline.

CONCLUSION

White matter hyperintensity burden at baseline predicted cognitive but not motor decline in early to mid-stage PD. The motor decline observed after 2 years in these older adults with PD is probably related to the primary neurodegenerative process than comorbid white matter pathology.

Cognitive correlates of antisaccade behaviour across multiple neurodegenerative diseases

Oculomotor tasks generate a potential wealth of behavioural biomarkers for neurodegenerative diseases. Overlap between oculomotor and disease-impaired circuitry reveals the location and severity of disease processes via saccade parameters measured from eye movement tasks such as prosaccade and antisaccade. Existing studies typically examine few saccade parameters in single diseases, using multiple separate neuropsychological test scores to relate oculomotor behaviour to cognition; however, this approach produces inconsistent, ungeneralizable results and fails to consider the cognitive heterogeneity of these diseases. Comprehensive cognitive assessment and direct inter-disease comparison are crucial to accurately reveal potential saccade biomarkers.

We remediate these issues by characterizing twelve behavioural parameters, selected to robustly describe saccade behaviour, derived from an interleaved pro- and antisaccade task in a large cross-sectional dataset comprising five disease cohorts (Alzheimer’s disease/mild cognitive impairment, amyotrophic lateral sclerosis, frontotemporal dementia, Parkinson’s disease, cerebrovascular disease; n=391, age 40-87) and healthy controls (n=149, age 42-87). These participants additionally completed an extensive neuropsychological test battery. We further subdivided each cohort by diagnostic subgroup (for Alzheimer’s disease/mild cognitive impairment and frontotemporal dementia) or degree of cognitive impairment based on neuropsychological testing (all other cohorts). We sought to understand links between oculomotor parameters, their relationships to robust cognitive measures, and their alterations in disease. We performed a factor analysis evaluating interrelationships among the twelve oculomotor parameters and examined correlations of the four resultant factors to five neuropsychology-based cognitive domain scores. We then compared behaviour between the abovementioned disease subgroups and controls at the individual parameter level.

We theorized that each underlying factor measured the integrity of a distinct task-relevant brain process. Notably, factor 3 (voluntary saccade generation) and factor 1 (task disengagements) significantly correlated with attention/working memory and executive function scores. Factor 3 also correlated with memory and visuospatial function scores. Factor 2 (preemptive global inhibition) correlated only with attention/working memory scores, and factor 4 (saccade metrics) correlated with no cognitive domain scores. Impairment on several mostly antisaccade-related individual parameters scaled with cognitive impairment across disease cohorts, while few subgroups differed from controls on prosaccade parameters.

The interleaved pro- and antisaccade task detects cognitive impairment, and subsets of parameters likely index disparate underlying processes related to different cognitive domains. This suggests that the task represents a sensitive paradigm that can simultaneously evaluate a variety of clinically relevant cognitive constructs in neurodegenerative and cerebrovascular diseases and could be developed into a screening tool applicable to multiple diagnoses.

Neuropsychiatric Symptom Burden across Neurodegenerative Disorders and its Association with Function

OBJECTIVE

Neuropsychiatric symptoms (NPS) are prevalent in neurodegenerative disorders, however, their frequency and impact on function across different disorders is not well understood. We compared the frequency and severity of NPS across Alzheimer's disease (AD) (either with mild cognitive impairment or dementia), Cerebrovascular disease (CVD), Parkinson's disease (PD), frontotemporal dementia (FTD), and amyotrophic lateral sclerosis (ALS), and explored the association between NPS burden and function.

METHODS

We obtained data from Ontario Neurodegenerative Disease Research Initiative (ONDRI) that included following cohorts: AD (N = 111), CVD (N = 148), PD (N = 136), FTD (N = 50) and ALS (N = 36). We compared the frequency and severity of individual NPS (assessed by the neuropsychiatric inventory questionnaire) across cohorts using generalized estimating equations and analysis of variance. Second, we assessed the relationship of NPS burden with instrumental (iADLs) and basic (ADLs) activities of living across cohorts using multivariate linear regression while adjusting for relevant demographic and clinical covariates.

RESULTS

Frequency of NPS varied across cohorts (χ²₍₄₎ = 34.4, p < .001), with post-hoc tests showing that FTD had the greatest frequency as compared to all other cohorts. The FTD cohort also had the greatest severity of NPS (H₍₄₎ = 34.5, p < .001). Further, there were differences among cohorts in terms of the association between NPS burden and ADLs (F_(4,461) = 3.1, p = 0.02). Post-hoc comparisons suggested that this finding was driven by the FTD group, however, the differences did not remain significant following Bonferroni correction. There were no differences among cohorts in terms of the association between NPS burden and IADLs.

CONCLUSIONS

NPS frequency and severity are markedly greater in FTD as compared to other neurodegenerative diseases. Further, NPS burden appears to be associated differently with function across neurodegenerative disorders, highlighting the need for individualized clinical interventions.

Characteristics of the Ontario Neurodegenerative Disease Research Initiative cohort

INTRODUCTION

Understanding synergies between neurodegenerative and cerebrovascular pathologies that modify dementia presentation represents an important knowledge gap.

METHODS

This multi-site, longitudinal, observational cohort study recruited participants across prevalent neurodegenerative diseases and cerebrovascular disease and assessed participants comprehensively across modalities. We describe univariate and multivariate baseline features of the cohort and summarize recruitment, data collection, and curation processes.

RESULTS

We enrolled 520 participants across five neurodegenerative and cerebrovascular diseases. Median age was 69 years, median Montreal Cognitive Assessment score was 25, median independence in activities of daily living was 100% for basic and 93% for instrumental activities. Spousal study partners predominated; participants were often male, White, and more educated. Milder disease stages predominated, yet cohorts reflect clinical presentation.

DISCUSSION

Data will be shared with the global scientific community. Within-disease and disease-agnostic approaches are expected to identify markers of severity, progression, and therapy targets. Sampling characteristics also provide guidance for future study design.

Caregiving concerns and clinical characteristics across neurodegenerative and cerebrovascular disorders in the Ontario neurodegenerative disease research initiative

OBJECTIVES

Caregiving burdens are a substantial concern in the clinical care of persons with neurodegenerative disorders. In the Ontario Neurodegenerative Disease Research Initiative, we used the Zarit's Burden Interview (ZBI) to examine: (1) the types of burdens captured by the ZBI in a cross-disorder sample of neurodegenerative conditions (2) whether there are categorical or disorder-specific effects on caregiving burdens, and (3) which demographic, clinical, and cognitive measures are related to burden(s) in neurodegenerative disorders?

METHODS/DESIGN

N = 504 participants and their study partners (e.g., family, friends) across: Alzheimer's disease/mild cognitive impairment (AD/MCI; n = 120), Parkinson's disease (PD; n = 136), amyotrophic lateral sclerosis (ALS; n = 38), frontotemporal dementia (FTD; n = 53), and cerebrovascular disease (CVD; n = 157). Study partners provided information about themselves, and information about the clinical participants (e.g., activities of daily living (ADL)). We used Correspondence Analysis to identify types of caregiving concerns in the ZBI. We then identified relationships between those concerns and demographic and clinical measures, and a cognitive battery.

RESULTS

We found three components in the ZBI. The first was "overall burden" and was (1) strongly related to increased neuropsychiatric symptoms (NPI severity r = 0.586, NPI distress r = 0.587) and decreased independence in ADL (instrumental ADLs r = -0.566, basic ADLs r = -0.43), (2) moderately related to cognition (MoCA r = -0.268), and (3) showed little-to-no differences between disorders. The second and third components together showed four types of caregiving concerns: current care of the person with the neurodegenerative disease, future care of the person with the neurodegenerative disease, personal concerns of study partners, and social concerns of study partners.

CONCLUSIONS

Our results suggest that the experience of caregiving in neurodegenerative and cerebrovascular diseases is individualized and is not defined by diagnostic categories. Our findings highlight the importance of targeting ADL and neuropsychiatric symptoms with caregiver-personalized solutions.

Feasibility of a continuous, multi-sensor remote health monitoring approach in persons living with neurodegenerative disease

BACKGROUND

Remote health monitoring with wearable sensor technology may positively impact patient self-management and clinical care. In individuals with complex health conditions, multi-sensor wear may yield meaningful information about health-related behaviors. Despite available technology, feasibility of device-wearing in daily life has received little attention in persons with physical or cognitive limitations. This mixed methods study assessed the feasibility of continuous, multi-sensor wear in persons with cerebrovascular (CVD) or neurodegenerative disease (NDD).

METHODS

Thirty-nine participants with CVD, Alzheimer's disease/amnestic mild cognitive impairment, frontotemporal dementia, Parkinson's disease, or amyotrophic lateral sclerosis (median age 68 (45-83) years, 36% female) wore five devices (bilateral ankles and wrists, chest) continuously for a 7-day period. Adherence to device wearing was quantified by examining volume and pattern of device removal (non-wear). A thematic analysis of semi-structured de-brief interviews with participants and study partners was used to examine user acceptance.

RESULTS

Adherence to multi-sensor wear, defined as a minimum of three devices worn concurrently, was high (median 98.2% of the study period). Non-wear rates were low across all sensor locations (median 17-22 min/day), with significant differences between some locations (p = 0.006). Multi-sensor non-wear was higher for daytime versus nighttime wear (p < 0.001) and there was a small but significant increase in non-wear over the collection period (p = 0.04). Feedback from de-brief interviews suggested that multi-sensor wear was generally well accepted by both participants and study partners.

CONCLUSION

A continuous, multi-sensor remote health monitoring approach is feasible in a cohort of persons with CVD or NDD.

Bilingualism in Parkinson's disease: Relationship to cognition and quality of life

Some studies have found that bilingualism promotes cognitive reserve.

OBJECTIVE

We aimed to determine whether bilingualism, defined as regularly (i.e. daily) using at least two languages at least since early adulthood, is associated with cognitive advantages in Parkinson's disease (PD) or whether the possible benefits of bilingualism are lost in the context of PD, possibly affecting quality of life (QoL) and independence.

METHOD

Participants with idiopathic PD (n = 140, mean age = 67.9 [SD = 6.4], 78% men) completed standard neuropsychological tasks evaluating attention/working memory, language, executive function, memory, and visuospatial ability, as well as measures of wellbeing and functional independence.

RESULTS

Bilinguals with PD (n = 21) performed worse than monolinguals with PD (n = 92) on attention/working memory and language measures. The between-group differences in attention/working memory were restricted to verbally-based measures. When measured along a continuum, a higher degree of bilingualism was correlated with lower scores on measures of attention/working memory and language. There were no group differences in self- or informant-reported cognitive decline, PD health-related QoL, or functional independence.

CONCLUSIONS

Bilingualism in PD was not associated with better cognitive performance. Lower scores on language-based measures may reflect a distributed fund of linguistic information across more than one language, lower language proficiency in English, and/or other cultural artifacts. Furthermore, using normative data specific to the dominant language spoken or conducting neuropsychological testing in participants' self-reported most proficient language may enhance additional studies addressing this topic. Future research may also examine the roles of bilingualism over time and across other neurodegenerative diseases with and without EF impairment to illuminate further the impact of bilingualism on cognition and QoL, and shape culturally and linguistically diverse research and clinical care.

Parkinson's Disease, NOTCH3 Genetic Variants, and White Matter Hyperintensities

BACKGROUND

White matter hyperintensities (WMH) on magnetic resonance imaging may influence clinical presentation in patients with Parkinson's disease (PD), although their significance and pathophysiological origins remain unresolved. Studies examining WMH have identified pathogenic variants in NOTCH3 as an underlying cause of inherited forms of cerebral small vessel disease.

METHODS

We examined NOTCH3 variants, WMH volumes, and clinical correlates in 139 PD patients in the Ontario Neurodegenerative Disease Research Initiative cohort.

RESULTS

We identified 13 PD patients (~9%) with rare (<1% of general population), nonsynonymous NOTCH3 variants. Bayesian linear modeling demonstrated a doubling of WMH between variant negative and positive patients (3.1 vs. 6.9 mL), with large effect sizes for periventricular WMH (d = 0.8) and lacunes (d = 1.2). Negative correlations were observed between WMH and global cognition (r = -0.2).

CONCLUSION

The NOTCH3 rare variants in PD may significantly contribute to increased WMH burden, which in turn may negatively influence cognition. © 2020 International Parkinson and Movement Disorder Society.

The Quality Assurance and Quality Control Protocol for Neuropsychological Data Collection and Curation in the Ontario Neurodegenerative Disease Research Initiative (ONDRI) Study

As large research initiatives designed to generate big data on clinical cohorts become more common, there is an increasing need to establish standard quality assurance (QA; preventing errors) and quality control (QC; identifying and correcting errors) procedures for critical outcome measures. The present article describes the QA and QC approach developed and implemented for the neuropsychology data collected as part of the Ontario Neurodegenerative Disease Research Initiative study. We report on the efficacy of our approach and provide data quality metrics. Our findings demonstrate that even with a comprehensive QA protocol, the proportion of data errors still can be high. Additionally, we show that several widely used neuropsychological measures are particularly susceptible to error. These findings highlight the need for large research programs to put into place active, comprehensive, and separate QA and QC procedures before, during, and after protocol deployment. Detailed recommendations and considerations for future studies are provided.

The utility of multivariate outlier detection techniques for data quality evaluation in large studies: an application within the ONDRI project

BACKGROUND

Large and complex studies are now routine, and quality assurance and quality control (QC) procedures ensure reliable results and conclusions. Standard procedures may comprise manual verification and double entry, but these labour-intensive methods often leave errors undetected. Outlier detection uses a data-driven approach to identify patterns exhibited by the majority of the data and highlights data points that deviate from these patterns. Univariate methods consider each variable independently, so observations that appear odd only when two or more variables are considered simultaneously remain undetected. We propose a data quality evaluation process that emphasizes the use of multivariate outlier detection for identifying errors, and show that univariate approaches alone are insufficient. Further, we establish an iterative process that uses multiple multivariate approaches, communication between teams, and visualization for other large-scale projects to follow.

METHODS

We illustrate this process with preliminary neuropsychology and gait data for the vascular cognitive impairment cohort from the Ontario Neurodegenerative Disease Research Initiative, a multi-cohort observational study that aims to characterize biomarkers within and between five neurodegenerative diseases. Each dataset was evaluated four times: with and without covariate adjustment using two validated multivariate methods - Minimum Covariance Determinant (MCD) and Candès' Robust Principal Component Analysis (RPCA) - and results were assessed in relation to two univariate methods. Outlying participants identified by multiple multivariate analyses were compiled and communicated to the data teams for verification.

RESULTS

Of 161 and 148 participants in the neuropsychology and gait data, 44 and 43 were flagged by one or both multivariate methods and errors were identified for 8 and 5 participants, respectively. MCD identified all participants with errors, while RPCA identified 6/8 and 3/5 for the neuropsychology and gait data, respectively. Both outperformed univariate approaches. Adjusting for covariates had a minor effect on the participants identified as outliers, though did affect error detection.

CONCLUSIONS

Manual QC procedures are insufficient for large studies as many errors remain undetected. In these data, the MCD outperforms the RPCA for identifying errors, and both are more successful than univariate approaches. Therefore, data-driven multivariate outlier techniques are essential tools for QC as data become more complex.

Motor Phenotype in Neurodegenerative Disorders: Gait and Balance Platform Study Design Protocol for the Ontario Neurodegenerative Research Initiative (ONDRI)

Background:

The association of cognitive and motor impairments in Alzheimer’s disease and other neurodegenerative diseases is thought to be related to damage in the common brain networks shared by cognitive and cortical motor control processes. These common brain networks play a pivotal role in selecting movements and postural synergies that meet an individual’s needs. Pathology in this “highest level” of motor control produces abnormalities of gait and posture referred to as highest-level gait disorders. Impairments in cognition and mobility, including falls, are present in almost all neurodegenerative diseases, suggesting common mechanisms that still need to be unraveled.

Objective:

To identify motor-cognitive profiles across neurodegenerative diseases in a large cohort of patients.

Methods:

Cohort study that includes up to 500 participants, followed every year for three years, across five neurodegenerative disease groups: Alzheimer’s disease/mild cognitive impairment, frontotemporal degeneration, vascular cognitive impairment, amyotrophic lateral sclerosis, and Parkinson’s disease. Gait and balance will be assessed using accelerometers and electronic walkways, evaluated at different levels of cognitive and sensory complexity, using the dual-task paradigm.

Results:

Comparison of cognitive and motor performances across neurodegenerative groups will allow the identification of motor-cognitive phenotypes through the standardized evaluation of gait and balance characteristics.

Conclusions:

As part of the Ontario Neurodegenerative Research Initiative (ONDRI), the gait and balance platform aims to identify motor-cognitive profiles across neurodegenerative diseases. Gait assessment, particularly while dual-tasking, will help dissect the cognitive and motor contribution in mobility and cognitive decline, progression to dementia syndromes, and future adverse outcomes including falls and mortality.

The Feasibility and Potential Impact of Brain Training Games on Cognitive and Emotional Functioning in Middle-Aged Adults

Objectives:To investigate whether a commercially available brain training program is feasible to use with a middle-aged population and has a potential impact on cognition and emotional well-being (proof of concept).

Method: Fourteen participants (ages 46–55) completed two 6-week training conditions using a crossover (counterbalanced) design: (1) experimental brain training condition and (2) active control “find answers to trivia questions online” condition. A comprehensive neurocognitive battery and a self-report measure of depression and anxiety were administered at baseline (first time point, before training) and after completing each training condition (second time point at 6 weeks, and third time point at 12 weeks). Cognitive composite scores were calculated for participants at each time point.

Results: Study completion and protocol adherence demonstrated good feasibility of this brain training protocol in healthy middle-aged adults. Exploratory analyses suggested that brain training was associated with neurocognitive improvements related to executive attention, as well as improvements in mood.

Conclusion: Overall, our findings suggest that brain training programs are feasible in middle-aged cohorts. We propose that brain training games may be linked to improvements in executive attention and affect by promoting cognitive self-efficacy in middle-aged adults.

Novel verbal fluency scores and structural brain imaging for prediction of cognitive outcome in mild cognitive impairment

INTRODUCTION

The objective of this study was to assess the utility of novel verbal fluency scores for predicting conversion from mild cognitive impairment (MCI) to clinical Alzheimer's disease (AD).

METHOD

Verbal fluency lists (animals, vegetables, F, A, and S) from 107 MCI patients and 51 cognitively normal controls were transcribed into electronic text files and automatically scored with traditional raw scores and five types of novel scores computed using methods from machine learning and natural language processing. Additional scores were derived from structural MRI scans: region of interest measures of hippocampal and ventricular volumes and gray matter scores derived from performing ICA on measures of cortical thickness. Over 4 years of follow-up, 24 MCI patients converted to AD. Using conversion as the outcome variable, ensemble classifiers were constructed by training classifiers on the individual groups of scores and then entering predictions from the primary classifiers into regularized logistic regression models. Receiver operating characteristic curves were plotted, and the area under the curve (AUC) was measured for classifiers trained with five groups of available variables.

RESULTS

Classifiers trained with novel scores outperformed those trained with raw scores (AUC 0.872 vs 0.735; P < .05 by DeLong test). Addition of structural brain measurements did not improve performance based on novel scores alone.

CONCLUSION

The brevity and cost profile of verbal fluency tasks recommends their use for clinical decision making. The word lists generated are a rich source of information for predicting outcomes in MCI. Further work is needed to assess the utility of verbal fluency for early AD.

Visual selective attention in amnestic mild cognitive impairment

OBJECTIVES

Subtle deficits in visual selective attention have been found in amnestic mild cognitive impairment (aMCI). However, few studies have explored performance on visual search paradigms or the Simon task, which are known to be sensitive to disease severity in Alzheimer's patients. Furthermore, there is limited research investigating how deficiencies can be ameliorated with exogenous support (auditory cues).

METHOD

Sixteen individuals with aMCI and 14 control participants completed 3 experimental tasks that varied in demand and cue availability: visual search-alerting, visual search-orienting, and Simon task.

RESULTS

Visual selective attention was influenced by aMCI, auditory cues, and task characteristics. Visual search abilities were relatively consistent across groups. The aMCI participants were impaired on the Simon task when working memory was required, but conflict resolution was similar to controls. Spatially informative orienting cues improved response times, whereas spatially neutral alerting cues did not influence performance. Finally, spatially informative auditory cues benefited the aMCI group more than controls in the visual search task, specifically at the largest array size where orienting demands were greatest.

DISCUSSION

These findings suggest that individuals with aMCI have working memory deficits and subtle deficiencies in orienting attention and rely on exogenous information to guide attention.

Maple syrup urine disease (MSUD): a case with long-term follow-up after liver transplantation

Maple syrup urine disease (MSUD) is a rare hereditary metabolic condition where the body is unable to breakdown amino acids causing toxic buildup. Acute and long-term management of MSUD involves a restricted diet and regular monitoring of amino acid levels; however, more recently liver transplants have been shown to be successful in treating this condition. Even with successful management of MSUD there is evidence from pediatric cases that shows a distinct pattern of neurocognitive deficits associated with this condition, including impaired nonverbal skills and psychomotor functioning with relatively intact verbal abilities. In the present paper, we report an adult case of MSUD with associated neurocognitive deficits and functional limitations following liver transplantation. Neuroimaging revealed no structural abnormalities, while the results from the neuropsychological evaluation showed impairment in visual-spatial processing, attention, executive functioning, and psychomotor abilities, with relative strengths in verbal skills. The patient also showed reduced adaptive functioning and mild anxiety. This case demonstrates neurocognitive deficiencies within the context of normal magnetic resonance imaging. The possible underlying mechanism of this neuropsychological profile is discussed in relation to other neurodevelopmental models.

Shifting efficacy, distribution of attention and controlled processing in two subtypes of mild cognitive impairment: response time performance and intraindividual variability on a visual search task

A visual search task was used to investigate how visual attention and intraindividual variability changes with mild cognitive impairment (MCI). Specifically, we examined the contribution of shifting efficacy, distribution of attention, and controlled processing to declines in visual attention in two groups with MCI (single-domain amnestic and multi-domain amnestic), and measured changes in intraindividual variability. Our results demonstrate that visual search performance is attenuated in multi-domain amnestic MCI, but not single-domain amnestic MCI. In addition, we found that the multi-domain amnestic MCI group was more variable than the older controls and single-domain amnestic MCI participants. These between-group differences in search efficacy and intraindividual variability increased as a function of task complexity. We attribute these decrements in performance to changes in the control of attention and shifting efficacy, but not the distribution of attention.

Expression of EpCAM is up-regulated during regeneration of renal epithelia

The human epithelial cell adhesion molecule (hEpCAM) is involved in epithelial morphogenesis and repair of epithelial tissues. We hypothesized that changes in hEpCAM expression in vivo correlate with regeneration of renal epithelia after ischaemia/reperfusion injury (IRi). Unilateral IRi was performed on kidneys of hEpCAM transgenic mice. Changes in hEpCAM expression were investigated by quantitative RT-PCR in renal cortex and medulla dissected by laser dissection microscopy and expression patterns of hEpCAM in regenerating kidneys were assessed by immunohistochemistry. The mechanism of hEpCAM promoter activation was investigated in vitro, by real-time bioluminescent imaging in HK-2 cells and in primary tubular epithelial cells (PTECs) subjected to hypoxia and reoxygenation. In vivo, the transcription of the human epcam gene significantly increased in the renal cortex during tubular re-epithelialization (p < 0.01). Moreover, the number of tubuli that expressed hEpCAM protein more than doubled in the renal cortex during regeneration. De novo expression of hEpCAM was detected in the S1 segments of proximal tubuli. Under hypoxic conditions in vitro, activity of the hEpCAM promoter was up-regulated two-fold in the HK-2 proximal epithelial cell line. Moreover, both in primary proximal epithelial cells and in HK-2 cells, hEpCAM protein expression was increased after hypoxia and reoxygenation. The significant up-regulation of hEpCAM during post-ischaemic renal regeneration in vivo and during in vitro hypoxia indicates that hEpCAM expression is associated with renal regeneration.

Charge-transfer excitons in DNA

There have been a number of theoretical treatments of excitons in DNA, most neglecting both the intrachain and interchain wavefunction overlaps of the electron and hole, treating them as Frenkel excitons. Recently, the importance of the intrachain and interchain coupling has been highlighted. Experiments have shown that in (dA)n oligomers and in duplex (dA)n.(dT)n, to be abbreviated (A/T), where A is adenine and T is thymine, the exciton wavefunction is delocalized over several bases. In duplexes it is possible to have charge-transfer (CT) excitons. Theoretical calculations have suggested that CT excitons in DNA may have lower energy than single chain excitons. In all the calculations of excitons in DNA, the polarization of the surrounding water has been neglected. Calculations have shown, however, that polarization of the water by an excess electron or a hole in DNA lowers its energy by approximately 1/2 eV, causing it to become a polaron. It is therefore to be expected that polarization charge induced in the surrounding water has a significant effect on the properties of the exciton. In what follows, we present calculations of some properties CT excitons would have in an A/T duplex taking into account the wavefunction overlaps, the effect of the surrounding water, which results in the electron and hole becoming polarons, and the ions in the water. As expected, the CT exciton has lowest energy when the electron and hole polarons are directly opposite each other. By appropriate choice of the dielectric constant, we can obtain a CT exciton delocalized over the number of sites found in photoinduced absorption experiments. The absorption threshold that we then calculate for CT exciton creation in A/T is in reasonable agreement with the lowest singlet absorption deduced from available data.

Cancer immunotherapy: insights from transgenic animal models

A wide range of strategies in cancer immunotherapy has been developed in the last decade, some of which are currently being used in clinical settings. The development of these immunotherapeutical strategies has been facilitated by the generation of relevant transgenic animal models. Since the different strategies in experimental immunotherapy of cancer each aim to activate different immune system components, a variety of transgenic animals have been generated either expressing tumor associated, HLA, oncogenic or immune effector cell molecule proteins. This review aims to discuss the existing transgenic mouse models generated to study and develop cancer immunotherapy strategies and the variable results obtained. The potential of the various transgenic animal models regarding the development of anti-cancer immunotherapeutical strategies is evaluated.

The epithelial glycoprotein 2 (EGP-2) promoter-driven epithelial-specific expression of EGP-2 in transgenic mice: a new model to study carcinoma-directed immunotherapy

The human pancarcinoma-associated epithelial glycoprotein-2 (EGP-2), a M(r) 38,000 transmembrane antigen also known as 17-1A or Ep-CAM, is commonly used for targeted immunotherapy of carcinomas because it is strongly expressed by most carcinomas. EGP-2 is, however, also expressed in most normal epithelia. To evaluate anti-EGP-2-directed treatment-associated effects on tumors and on EGP-2-positive normal tissue, we generated EGP-2-expressing transgenic mice. A 55-kb DNA fragment consisting of the 14-kb genomic coding sequence of the human EGP-2 gene with approximately 10-kb-upstream and approximately 31-kb-downstream sequences was isolated and used to direct EGP-2 expression in an epithelium-specific manner. In the EGP-2 transgenic mice, EGP-2 appeared to be specifically expressed in all of those epithelial tissues that also express EGP-2 in humans, whereas all of the other tissues were negative. The specific in vivo localization of the i.v. administered anti-EGP-2 monoclonal antibody MOC31 was studied in EGP-2-positive and -negative tumors induced s.c. in this EGP-2 transgenic mouse model. Immunohistochemical analysis showed specific localization of MOC31 in the EGP-2-positive tumors but not in the EGP-2-negative tumors. No anti-EGP-2 monoclonal antibody localization was observed in any of the EGP-2-positive normal mouse tissues, which indicated a limited in vivo accessibility. In conclusion, an EGP-2 transgenic mouse model has been generated that expresses the EGP-2 antigen as in humans and, therefore, can serve as a model to evaluate the efficacy and safety of a variety of anti-EGP-2-based immunotherapeutic modalities in both tumors and normal tissue.

The ubiquitin-activating enzyme E1-like protein in lung cancer cell lines

The UBE1L gene isolated from the chromosome 3p21 region has an extremely reduced level of mRNA in lung cancer. Sequence analysis showed a 45% homology to the human ubiquitin-activating enzyme E1 at the amino acid level. To further characterize the protein product, we generated UBE1L protein-specific antibodies. Immunoblot analysis revealed a full-length gene product of approximately 112 kDa. Assessment of the level and distribution pattern of the UBE1L protein in normal and tumor tissue using the generated antibodies showed that the UBE1L protein was present in normal lung cells and non-lung cancer cell lines, but was undetectable in all 14 human lung cancer cell lines analyzed. This difference in expression of the UBE1L protein between normal lung tissue and lung tumor-derived cell lines suggests a possible involvement of an E1-like protein in the origin and/or progression of lung tumors.

Muscle glutamine production in diabetic ketoacidotic rats

The mechanism of activation of glutamine production by the hindlimb during diabetic ketoacidosis (DKA) was investigated in rats. Muscle glutamine production was estimated to account for over 90% of the total glutamine produced by the hindlimb. DKA produced significant increases in the concentrations of NH4+ and IMP in hindlimb muscles, suggesting that AMP deaminase is activated by DKA. NH4Cl- and HCl-induced acidosis did not produce these changes, indicating either that acidosis itself is not the stimulus for increased AMP deaminase activity or that the more severe degree of acidosis accompanying DKA is necessary for activation. Muscle glutamine concentrations were depressed in DKA. Experiments with isolated epitrochlearis muscle showed that the transport and permeability properties of the muscle cells (as judged by uptake and release of alpha-aminoisobutyrate and glutamine) were not altered by DKA. However, glutamine uptake by muscle cells was significantly inhibited by L-leucine, the concentration of which, along with other branched-chain amino acids, is markedly elevated in DKA.

Ketone body effects on glutamine metabolism in isolated kidneys and mitochondria

beta-Hydroxybutyrate (but not acetoacetate) caused marked inhibition of ammonia production and glutamine extraction in isolated perfused kidneys from normal rats. Glutamine synthesis was not affected by beta-hydroxybutyrate (BHB). Measurement of metabolite levels in freeze-clamped kidneys showed that BHB increased glutamine concentration, decreased ammonia concentration, and reduced the mitochondrial NAD+/NADH ratio (calculated) in perfused kidneys. BHB inhibited flux through the glutamate dehydrogenase pathway, probably as a result of reduction in the NAD+/NADH ratio, in isolated renal mitochondria. In isolated perfused kidneys from acidotic rats, ammonia production and mitochondrial NAD+/NADH were both elevated and BHB did not inhibit renal ammoniagenesis. Although ammonia production in the acidotic kidneys was not directly related to the mitochondrial NAD+/NADH ratio, the elevation of this ratio may have permitted a normal rate of oxidation of glutamine end products--which is essential for maintaining the elevated ammoniagenesis--to take place in the presence of BHB.