Care Ecosystem Collaborative Model and Health Care Costs in Medicare Beneficiaries With Dementia: A Secondary Analysis of a Randomized Clinical Trial

Importance

Collaborative dementia care programs are effective in addressing the needs of patients with dementia and their caregivers. However, attempts to consider effects on health care spending have been limited, leaving a critical gap in the conversation around value-based dementia care.

Objective

To determine the effect of participation in collaborative dementia care on total Medicare reimbursement costs compared with usual care.

Design, Setting, and Participants

This was a prespecified secondary analysis of the Care Ecosystem trial, a 12-month, single-blind, parallel-group randomized clinical trial conducted from March 2015 to March 2018 at 2 academic medical centers in California and Nebraska. Participants were patients with dementia who were living in the community, aged 45 years or older, and had a primary caregiver and Medicare fee-for-service coverage for the duration of the trial.

Intervention

Telehealth dementia care program that entailed assignment to an unlicensed dementia care guide who provided caregiver support, standardized education, and connection to licensed dementia care specialists.

Main Outcomes and Measures

Primary outcome was the sum of all Medicare claim payments during study enrollment, excluding Part D (drugs).

Results

Of the 780 patients in the Care Ecosystem trial, 460 (59.0%) were eligible for and included in this analysis. Patients had a median (IQR) age of 78 (72-84) years, and 256 (55.7%) identified as female. Participation in collaborative dementia care reduced the total cost of care by $3290 from 1 to 6 months postenrollment (95% CI, -$6149 to -$431; P = .02) and by $3027 from 7 to 12 months postenrollment (95% CI, -$5899 to -$154; P = .04), corresponding overall to a mean monthly cost reduction of $526 across 12 months. An evaluation of baseline predictors of greater cost reduction identified trends for recent emergency department visit (-$5944; 95% CI, -$10 336 to -$1553; interaction P = .07) and caregiver depression (-$6556; 95% CI, -$11 059 to -$2052; interaction P = .05).

Conclusions and Relevance

In this secondary analysis of a randomized clinical trial among Medicare beneficiaries with dementia, the Care Ecosystem model was associated with lower total cost of care compared with usual care. Collaborative dementia care programs are a cost-effective, high-value model for dementia care.

Trial Registration

ClinicalTrials.gov Identifier: NCT02213458.

Exploring behavioral phenotypes in a mouse model of fetal alcohol spectrum disorders

Fetal alcohol spectrum disorders are one of the leading causes of developmental abnormalities worldwide. Maternal consumption of alcohol during pregnancy leads to a diverse range of cognitive and neurobehavioral deficits. Although moderate-to-heavy levels of prenatal alcohol exposure (PAE) have been associated with adverse offspring outcomes, there is limited data on the consequences of chronic low-level PAE. Here, we use a model of maternal voluntary alcohol consumption throughout gestation in a mouse model to investigate the effects of PAE on behavioral phenotypes during late adolescence and early adulthood in male and female offspring. Body composition was measured by dual-energy X-ray absorptiometry. Baseline behaviors, including feeding, drinking, and movement, were examined by performing home cage monitoring studies. The impact of PAE on motor function, motor skill learning, hyperactivity, acoustic reactivity, and sensorimotor gating was investigated by performing a battery of behavioral tests. PAE was found to be associated with altered body composition. No differences in overall movement, food, or water consumption were observed between control and PAE mice. Although PAE offspring of both sexes exhibited deficits in motor skill learning, no differences were observed in basic motor skills such as grip strength and motor coordination. PAE females exhibited a hyperactive phenotype in a novel environment. PAE mice exhibited increased reactivity to acoustic stimuli, and PAE females showed disrupted short-term habituation. Sensorimotor gating was not altered in PAE mice. Collectively, our data show that chronic low-level exposure to alcohol in utero results in behavioral impairments.

"Out of the clear blue sky she tells me she loves me": Connection experiences between caregivers and people with dementia

BACKGROUND

Dementia can impede the relationship and connection between the person with dementia (PWD) and their caregiver. Yet, caregiving in dementia also offers opportunities for connection, which has implications for caregiver and PWD well-being. In this qualitative study, we describe and characterize ways caregivers felt connected to the person with dementia they care for.

METHODS

We conducted a telephone-based survey with caregivers of people with dementia. For this paper, we analyzed responses to an open-ended question focused on when caregivers feel most connected to the person they are caring for. Responses were analyzed and coded and themes were identified through an iterative process involving a multidisciplinary team of researchers and clinicians.

RESULTS

437 caregivers participated in this study. We identified two domains of connection: activity-based and emotion-based connections. Within activity-based connections, the following themes emerged: everyday activities; reminiscing; activities of caregiving; novel experiences; and time with family and friends. Within emotional connections, the following themes emerged: expressions of love, appreciation, and gratitude; physical affection; sharing an emotion or emotional experience; and times when the PWD seems like "themself" again.

CONCLUSIONS

Findings provide insights into ways caregivers experience a sense of connection with the person they care for. There is a call to shift away from focusing on reducing stress and toward optimizing positive experiences as a way to better support caregivers' health and well-being. Interventions that leverage these insights to foster caregiver - PWD connection could lead to better health and well-being for both members of the dyad. The amplification of a positive experience may be particularly important for caregivers who are struggling with limited support or respite. Clinicians may be interested in using a question about connection as a way to more fully understand a caregiver's current experience.

Effect of collaborative dementia care on potentially inappropriate medication use: Outcomes from the Care Ecosystem randomized clinical trial

INTRODUCTION

Potentially inappropriate medications (PIMs) cause adverse events and death. We evaluate the Care Ecosystem (CE) collaborative dementia care program on medication use among community-dwelling persons living with dementia (PLWD).

METHODS

Secondary analysis of a randomized clinical trial (RCT) comparing CE to usual care (UC) on changes in PIMs, over 12 months between March 2015 and May 2020. Secondary outcomes included change in number of medications, clinically relevant PIMs, and anti-dementia medications.

RESULTS

Of 804 PLWD, N = 490 had complete medication data. The CE resulted in significantly fewer PIMs compared to UC (-0.35; 95% CI, -0.49 to -0.20; P < 0.0001). Number needed to prevent an increase in 1 PIM was 3. Total medications, PIMs for dementia or cognitive impairment, CNS-active PIMs, anticholinergics, benzodiazepines, and opioids were also fewer. Anti-dementia medication regimens were modified more frequently.

CONCLUSION

The CE medication review intervention embedded in collaborative dementia care optimized medication use among PLWD.

HIGHLIGHTS

Compared to usual care (UC), the Care Ecosystem (CE) medication review intervention prevented increases in potentially inappropriate medications (PIMs). Use of anticholinergics, benzodiazepines, and opioids were significantly reduced, with a trend for antipsychotics. Anti-dementia medications were adjusted more frequently. The CE medication review intervention embedded in collaborative dementia care optimized medication use.

Loss of epigenetic information as a cause of mammalian aging

All living things experience an increase in entropy, manifested as a loss of genetic and epigenetic information. In yeast, epigenetic information is lost over time due to the relocalization of chromatin-modifying proteins to DNA breaks, causing cells to lose their identity, a hallmark of yeast aging. Using a system called "ICE" (inducible changes to the epigenome), we find that the act of faithful DNA repair advances aging at physiological, cognitive, and molecular levels, including erosion of the epigenetic landscape, cellular exdifferentiation, senescence, and advancement of the DNA methylation clock, which can be reversed by OSK-mediated rejuvenation. These data are consistent with the information theory of aging, which states that a loss of epigenetic information is a reversible cause of aging.

Complement Component C3 Loss leads to Locomotor Deficits and Altered Cerebellar Internal Granule Cell In Vitro Synaptic Protein Expression in C57BL/6 Mice

Complement component 3 (C3) expression is increased in the cerebellum of aging mice that demonstrate locomotor impairments and increased excitatory synapse density. However, C3 regulation of locomotion, as well as C3 roles in excitatory synapse function, remains poorly understood. Here, we demonstrate that constitutive loss of C3 function in mice evokes a locomotor phenotype characterized by decreased speed, increased active state locomotor probability, and gait ataxia. C3 loss does not alter metabolism or body mass composition. No evidence of significant muscle weakness or degenerative arthritis was found in C3 knockout mice to explain decreased gait speeds. In an enriched primary cerebellar granule cell culture model, loss of C3 protein results in increased excitatory synaptic density and increased response to KCl depolarization. Our analysis of excitatory synaptic density in the cerebellar internal granule cell and molecular layers did not demonstrate increased synaptic density in vivo, suggesting the presence of compensatory mechanisms regulating synaptic development. Functional deficits in C3 knockout mice are therefore more likely to result from altered synaptic function and/or connectivity than gross synaptic deficits. Our data demonstrate a novel role for complement proteins in cerebellar regulation of locomotor output and control.

The Role of Care Navigators Working with People with Dementia and Their Caregivers

BACKGROUND

Care navigation is an approach to personalized care management and care coordination that can help overcome barriers to care. Care navigation has not been extensively studied in dementia, where health care workforce innovations are needed as a result of increasing disease prevalence and resulting costs to the health care system.

OBJECTIVE

To identify facilitators and barriers to care navigation in dementia and to assess dementia caregiver satisfaction with care navigation.

METHODS

Methods include qualitative research (interviews, focus groups, observations) with "Care Team Navigators" (CTNs) who were part of a dementia care navigation program, the Care Ecosystem, and a quantitative survey with caregivers about their experiences with CTNs. Transcripts were analyzed to identify themes within the data.

RESULTS

CTNs identified the following facilitators to care navigation in dementia: working closely with caregivers; providing emotional support; tailoring education and resources; and coordinating with a clinical team around issues ranging from clinical questions to financial and legal decision-making. The barriers CTNS identified included burn-out, the progressive nature of the disease; coordinating with primary care providers; and identifying resources for dyads who are low-income, do not speak English, or live in rural areas. Caregivers across both sites highly rated CTNs, though satisfaction was higher among those in Nebraska and Iowa.

CONCLUSIONS

Innovative approaches to care delivery in dementia are crucial. Care navigation offers a feasible model to train unlicensed people to deliver care as a way to deliver larger-scale support for the growing population of adults living with dementia and their caregivers.

δ-Catenin engages the autophagy pathway to sculpt the developing dendritic arbor

The development of the dendritic arbor in pyramidal neurons is critical for neural circuit function. Here, we uncovered a pathway in which δ-catenin, a component of the cadherin-catenin cell adhesion complex, promotes coordination of growth among individual dendrites and engages the autophagy mechanism to sculpt the developing dendritic arbor. Using a rat primary neuron model, time-lapse imaging, immunohistochemistry, and confocal microscopy, we found that apical and basolateral dendrites are coordinately sculpted during development. Loss or knockdown of δ-catenin uncoupled this coordination, leading to retraction of the apical dendrite without altering basolateral dendrite dynamics. Autophagy is a key cellular pathway that allows degradation of cellular components. We observed that the impairment of the dendritic arbor resulting from δ-catenin knockdown could be reversed by knockdown of autophagy-related 7 (ATG7), a component of the autophagy machinery. We propose that δ-catenin regulates the dendritic arbor by coordinating the dynamics of individual dendrites and that the autophagy mechanism may be leveraged by δ-catenin and other effectors to sculpt the developing dendritic arbor. Our findings have implications for the management of neurological disorders, such as autism and intellectual disability, that are characterized by dendritic aberrations.

Long-term digital device-enabled monitoring of functional status: Implications for management of persons with Alzheimer's disease

INTRODUCTION

Informal caregiving is an essential element of health-care delivery. Little data describes how caregivers structure care recipients' lives and impact their functional status.

METHODS

We performed observational studies of community dwelling persons with dementia (PWD) to measure functional status by simultaneous assessment of physical activity (PA) and lifespace (LS). We present data from two caregiver/care-recipient dyads representing higher and average degrees of caregiver involvement.

RESULTS

We acquired >42,800 (subject 1); >41,300 (subject 2) PA data points and >154,500 (subject 1); >119,700 (subject 2) LS data points over 15 months of near continuous observation. PA and LS patterns provided insights into the caregiver's role in structuring the PWD's day-to-day function and change in function over time.

DISCUSSION

We show that device-enabled functional monitoring (FM) can successfully gather and display data at resolutions required for dementia care studies. Objective quantification of individual caregiver/care-recipient dyads provides opportunities to implement patient-centered care.

Using care navigation to address caregiver burden in dementia: A qualitative case study analysis

INTRODUCTION

Many caregivers of people with dementia experience burden and resulting health effects due to the intensive nature of caregiving. Phone- and web-based care navigation is an innovative model of care that may be useful in addressing caregiver burden in dementia.

METHODS

Qualitative methods (interviews, focus groups, and case study analysis) were used to identify care navigator approaches used to address caregiver burden in dementia as part of a dementia care navigation program.

RESULTS

Care navigators targeted caregiver burden by focusing on strategies to reduce caregiver guilt and frustration, manage patient-related behavior, address caregiver depression, and improve the relationship between the caregiver and person with dementia. The case studies presented demonstrate the ways that care navigators identified patient and caregiver needs and tailored their approaches to meet the specific social, cultural, economic, and geographic contexts of the dyads with which they worked.

DISCUSSION

Findings provide insights into strategies used to address caregiver burden through care navigation. Care navigators who speak the same language as the caregivers with whom they work and who have an in-depth understanding of the symptoms of different dementia syndromes may be particularly effective.

Effect of Collaborative Dementia Care via Telephone and Internet on Quality of Life, Caregiver Well-being, and Health Care Use: The Care Ecosystem Randomized Clinical Trial

IMPORTANCE

Few health systems have adopted effective dementia care management programs. The Care Ecosystem is a model for delivering care from centralized hubs across broad geographic areas to caregivers and persons with dementia (PWDs) independently of their health system affiliations.

OBJECTIVE

To determine whether the Care Ecosystem is effective in improving outcomes important to PWDs, their caregivers, and payers beyond those achieved with usual care.

DESIGN, SETTING, AND PARTICIPANTS

A single-blind, randomized clinical trial with a pragmatic design was conducted among PWDs and their caregivers. Each PWD-caregiver dyad was enrolled for 12 months between March 20, 2015, and February 28, 2017. Data were collected until March 5, 2018. Study interventions and assessments were administered over the telephone and internet by clinical and research teams in San Francisco, California, and Omaha, Nebraska. Of 2585 referred or volunteer PWD-caregiver dyads in California, Iowa, or Nebraska, 780 met eligibility criteria and were enrolled. A total of 512 PWD-caregiver dyads were randomized to receive care through the Care Ecosystem and 268 dyads to receive usual care. All eligible PWDs had a dementia diagnosis; were enrolled or eligible for enrollment in Medicare or Medicaid; and spoke English, Spanish, or Cantonese. Analyses were intention-to-treat.

INTERVENTION

Telephone-based collaborative dementia care was delivered by a trained care team navigator, who provided education, support and care coordination with a team of dementia specialists (advanced practice nurse, social worker, and pharmacist).

MAIN OUTCOMES AND MEASURES

Primary outcome measure: Quality of Life in Alzheimer's Disease based on caregiver's rating of 13 aspects of PWD's well-being (including physical health, energy level, mood, living situation, memory, relationships, and finances) on a 4-point scale (poor to excellent). Secondary outcomes: frequencies of PWDs' use of emergency department, hospitalization, and ambulance services; caregiver depression (score on 9-Item Patient Health Questionnaire; higher scores indicate more severe depression); and caregiver burden (score on 12-Item Zarit Burden Interview; higher scores indicate more severe caregiver burden).

RESULTS

The 780 PWDs (56.3% female; mean [SD] age, 78.1 [9.9] years) and 780 caregivers (70.9% female; mean [SD] age, 64.7 [12.0] years) lived in California (n = 452), Nebraska (n = 284), or Iowa (n = 44). Of 780 dyads, 655 were still active at 12 months, and 571 completed the 12-month survey. Compared with usual care, the Care Ecosystem improved PWD quality of life (B, 0.53; 95% CI, 0.25-1.30; P = .04), reduced emergency department visits (B, -0.14; 95% CI, -0.29 to -0.01; P = .04), and decreased caregiver depression (B, -1.14; 95% CI, -2.15 to -0.13; P = .03) and caregiver burden (B, -1.90; 95% CI, -3.89 to -0.08; P = .046).

CONCLUSIONS AND RELEVANCE

Effective care management for dementia can be delivered from centralized hubs to supplement usual care and mitigate the growing societal and economic burdens of dementia.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT02213458.

Association Between Caregiver Depression and Emergency Department Use Among Patients With Dementia

Importance

Current attempts to gauge the acute care needs of patients with dementia have not effectively addressed the role of caregivers, despite their extensive involvement in decisions about acute care management.

Objective

To determine whether caregiver depression is associated with increased use of the emergency department (ED) among patients with dementia.

Design, Setting, and Participants

This longitudinal cohort study used data from the Care Ecosystem study, a randomized clinical trial examining telephone-based supportive care for patients with dementia and their caregivers. Patients were 45 years or older with any type of dementia. A total of 780 caregiver-patient dyads were enrolled from March 20, 2015, until February 28, 2017, and 663 dyads contributed baseline and 6-month data and were included in the analysis.

Exposures

Caregiver depression (9-item Patient Health Questionnaire score of ≥10). Secondary analyses examined caregiver burden and self-efficacy.

Main Outcomes and Measures

The primary outcome was the number of ED visits in a 6-month period.

Results

Among the 663 caregivers (467 women and 196 men; mean [SD] age, 64.9 [11.8] years), 84 caregivers (12.7%) had depression at baseline. The mean incidence rate of ED visits was 0.9 per person-year. Rates of ED presentation were higher among dyads whose caregiver did vs did not have depression (1.5 vs 0.8 ED visits per person-year). In a Poisson regression model adjusting for patient age, sex, severity of dementia, number of comorbidities, and baseline ED use, as well as caregiver age and sex, caregiver depression continued to be associated with ED use, with a 73% increase in rates of ED use among dyads with caregivers with depression (adjusted incident rate ratio, 1.73; 95% CI, 1.30-2.30). Caregiver burden was associated with higher ED use in the unadjusted model, but this association did not reach statistical significance after adjustment (incident rate ratio, 1.19; 95% CI, 0.93-1.52). Caregiver self-efficacy was inversely proportional to the number of ED visits in the unadjusted and adjusted models (adjusted incident rate ratio, 0.96; 95% CI, 0.92-0.99).

Conclusions and Relevance

Among patients with dementia, caregiver depression appears to be significantly associated with increased ED use, revealing a key caregiver vulnerability, which, if addressed with patient- and caregiver-centered dementia care, could improve health outcomes and lower costs for this high-risk population.

Variations in Costs of a Collaborative Care Model for Dementia

OBJECTIVES

Care coordination programs can improve patient outcomes and decrease healthcare expenditures; however, implementation costs are poorly understood. We evaluate the direct costs of implementing a collaborative dementia care program.

DESIGN

We applied a micro-costing analysis to calculate operational costs per-participant-month between March 2015 and May 2017.

SETTING

The University of California, San Francisco (UCSF) and the University of Nebraska Medical Center (UNMC).

PARTICIPANTS

Participants diagnosed with dementia, enrolled in Medicare or Medicaid, 45 years of age or older, residents of California, Nebraska or Iowa, and having a caregiver. The sample was 272 (UCSF) and 192 (UNMC) participants.

INTERVENTION

A collaborative dementia care program provided by care team navigators (CTNs), advanced practice nurses, a social worker, and a pharmacist, focusing on caregiver support and education, medications, advance care planning, and behavior symptom management.

MEASUREMENTS

We measured costs (personnel, supplies, equipment, and training costs) during three program periods, Start-up, Early Operations, and Continuing Operations, and estimated the effects of caseload variation on costs.

RESULTS

Start-up and Early Operations costs were, respectively, $581 and $328 (California), and $501 and $219 (Nebraska) per-participant-month. Average costs decreased across phases to $241 (California) and $142 (Nebraska) per-participant-month during Continuing Operations. We estimated that costs would range between $75 (UNMC) and $92 (UCSF) per-participant-month with the highest projected caseloads (90).

CONCLUSION

We found that CTN caseload is an important driver of service cost. We provide strategies for maximizing caseload without sacrificing quality of care. We also discuss current barriers to broad implementation that can inform new reimbursement policies. J Am Geriatr Soc 67:2628-2633, 2019.

The costs of dementia subtypes to California Medicare fee-for-service, 2015

INTRODUCTION

Dementia is among the costliest of medical conditions, but it is not known how these costs vary by dementia subtype.

METHODS

The effect of dementia diagnosis subtype on direct health care costs and utilization was estimated using 2015 California Medicare fee-for-service data. Potential drivers of increased costs in Lewy body dementia (LBD), in comparison to Alzheimer's disease, were tested.

RESULTS

3,001,987 Medicare beneficiaries were identified, of which 8.2% had a dementia diagnosis. Unspecified dementia was the most common diagnostic category (59.6%), followed by Alzheimer's disease (23.2%). LBD was the costliest subtype to Medicare, on average, followed by vascular dementia. The higher costs in LBD were explained in part by falls, urinary incontinence or infection, depression, anxiety, dehydration, and delirium.

DISCUSSION

Dementia subtype is an important predictor of health care costs. Earlier identification and targeted treatment might mitigate the costs associated with co-occurring conditions in LBD.

The Care Ecosystem: Promoting self-efficacy among dementia family caregivers

OBJECTIVES

To illustrate specific psychosocial interventions aimed at improving self-efficacy among family caregivers enrolled in the Care Ecosystem, a model of navigated care designed to support persons with dementia and their primary caregivers. Enrolled family caregivers work with unlicensed care team navigators who are trained in dementia care and provide information, linkages to community resources, and emotional support by phone and email.

METHOD

We conducted focus groups and interviews with the care team navigators to identify the approaches they used to target caregiver self-efficacy. We assessed mean self-efficacy scores in a sample of 780 family caregivers and selected three exemplary cases in which the caregivers had low self-efficacy scores at baseline with significantly higher scores after six months of participation in the Care Ecosystem intervention.

RESULTS

Multiple psychosocial strategies were utilized by care team navigators working with patients with dementia and their family caregivers. Using thematic coding we identified three categories of Care Team Navigator intervention: emotional, informational, and instrumental support. These are consistent with a psychosocial approach to building self-efficacy.

DISCUSSION

Self-efficacy represents a family caregiver's knowledge and preparedness in managing the challenges of care. Psychosocial support shows benefit in improving caregiver self-efficacy that in turn, may positively influence caregiver health and well-being. The findings in this manuscript demonstrate how a model of navigated care can positively impact self-efficacy among dementia family caregivers.

Age-related changes in cerebellar and hypothalamic function accompany non-microglial immune gene expression, altered synapse organization, and excitatory amino acid neurotransmission deficits

We describe age-related molecular and neuronal changes that disrupt mobility or energy balance based on brain region and genetic background. Compared to young mice, aged C57BL/6 mice exhibit marked locomotor (but not energy balance) impairments. In contrast, aged BALB mice exhibit marked energy balance (but not locomotor) impairments. Age-related changes in cerebellar or hypothalamic gene expression accompany these phenotypes. Aging evokes upregulation of immune pattern recognition receptors and cell adhesion molecules. However, these changes do not localize to microglia, the major CNS immunocyte. Consistent with a neuronal role, there is a marked age-related increase in excitatory synapses over the cerebellum and hypothalamus. Functional imaging of these regions is consistent with age-related synaptic impairments. These studies suggest that aging reactivates a developmental program employed during embryogenesis where immune molecules guide synapse formation and pruning. Renewed activity in this program may disrupt excitatory neurotransmission, causing significant behavioral deficits.

Mobile Phone-Based Measures of Activity, Step Count, and Gait Speed: Results From a Study of Older Ambulatory Adults in a Naturalistic Setting

Background

Cellular mobile telephone technology shows much promise for delivering and evaluating healthcare interventions in cost-effective manners with minimal barriers to access. There is little data demonstrating that these devices can accurately measure clinically important aspects of individual functional status in naturalistic environments outside of the laboratory.

Objective

The objective of this study was to demonstrate that data derived from ubiquitous mobile phone technology, using algorithms developed and previously validated by our lab in a controlled setting, can be employed to continuously and noninvasively measure aspects of participant (subject) health status including step counts, gait speed, and activity level, in a naturalistic community setting. A second objective was to compare our mobile phone-based data against current standard survey-based gait instruments and clinical physical performance measures in order to determine whether they measured similar or independent constructs.

Methods

A total of 43 ambulatory, independently dwelling older adults were recruited from Nebraska Medicine, including 25 (58%, 25/43) healthy control individuals from our Engage Wellness Center and 18 (42%, 18/43) functionally impaired, cognitively intact individuals (who met at least 3 of 5 criteria for frailty) from our ambulatory Geriatrics Clinic. The following previously-validated surveys were obtained on study day 1: (1) Late Life Function and Disability Instrument (LLFDI); (2) Survey of Activities and Fear of Falling in the Elderly (SAFFE); (3) Patient Reported Outcomes Measurement Information System (PROMIS), short form version 1.0 Physical Function 10a (PROMIS-PF); and (4) PROMIS Global Health, short form version 1.1 (PROMIS-GH). In addition, clinical physical performance measurements of frailty (10 foot Get up and Go, 4 Meter walk, and Figure-of-8 Walk [F8W]) were also obtained. These metrics were compared to our mobile phone-based metrics collected from the participants in the community over a 24-hour period occurring within 1 week of the initial assessment.

Results

We identified statistically significant differences between functionally intact and frail participants in mobile phone-derived measures of percent activity (P=.002, t test), active versus inactive status (P=.02, t test), average step counts (P<.001, repeated measures analysis of variance [ANOVA]) and gait speed (P<.001, t test). In functionally intact individuals, the above mobile phone metrics assessed aspects of functional status independent (Bland-Altman and correlation analysis) of both survey- and/or performance battery-based functional measures. In contrast, in frail individuals, the above mobile phone metrics correlated with submeasures of both SAFFE and PROMIS-GH.

Conclusions

Continuous mobile phone-based measures of participant community activity and mobility strongly differentiate between persons with intact functional status and persons with a frailty phenotype. These measures assess dimensions of functional status independent of those measured using current validated questionnaires and physical performance assessments to identify functional compromise. Mobile phone-based gait measures may provide a more readily accessible and less-time consuming measure of gait, while further providing clinicians with longitudinal gait measures that are currently difficult to obtain.

Toll-Like Receptor 2 Is a Regulator of Circadian Active and Inactive State Consolidation in C57BL/6 Mice

Regulatory systems required to maintain behavioral arousal remain incompletely understood. We describe a previously unappreciated role that toll-like receptor 2 (Tlr2, a membrane bound pattern recognition receptor that recognizes specific bacterial, viral, and fungal peptides), contributes toward regulation of behavioral arousal. In 4–4.5 month old mice with constitutive loss of Tlr2 function (Tlr2^−/− mice), we note a marked consolidation in the circadian pattern of both active and inactive states. Specifically, Tlr2^−/− mice demonstrated significantly fewer but longer duration active states during the circadian dark cycle, and significantly fewer but longer duration inactive states during the circadian light cycle. Tlr2^−/− mice also consumed less food and water, and moved less during the circadian light cycle. Analysis of circadian rhythms further suggested that Tlr2^−/− mice demonstrated less day-to-day variability in feeding, drinking, and movement behaviors. Reevaluation of this same mouse cohort at age 8–8.5 months revealed a clear blunting of these differences. However, Tlr2^−/− mice were still noted to have fewer short-duration active states during the circadian dark cycle, and continued to demonstrate significantly less day-to-day variability in feeding, drinking, and movement behaviors. These results suggest that Tlr2 function may have a role in promoting transitions between active and inactive states. Prior studies have demonstrated that Tlr2 regulates sickness behaviors including hypophagia, hyperthermia, and decreased activity. Our work suggests that Tlr2 function also evokes behavioral fragmentation, another aspect of sickness behavior and a clinically significant problem of older adults.

Decreased home cage movement and oromotor impairments in adult Fmr1-KO mice

Fragile X syndrome (FXS) is a common inherited disorder that significantly impacts family and patient day-to-day living across the entire life span. The childhood and adolescent behavioral consequences of FXS are well appreciated. However, there are significantly fewer studies (except those examining psychiatric comorbidities) assessing behavioral phenotypes seen in adults with FXS. Mice engineered with a genetic lesion of fragile X mental retardation 1 (Fmr1) recapitulate important molecular and neuroanatomical characteristics of FXS, and provide a means to evaluate adult behavioral phenotypes associated with FXS. We give the first description of baseline behaviors including feeding, drinking, movement and their circadian rhythms; all observed over 16 consecutive days following extensive environmental habituation in adult Fmr1-KO mutant mice. We find no genotypic changes in mouse food ingestion, feeding patterns, metabolism or circadian patterns of movement, feeding and drinking. After habituation, Fmr1-KO mice show significantly less daily movement during their active phase (the dark cycle). However, Fmr1-KO mice have more bouts of activity during the light cycle compared with wild types. In addition, Fmr1-KO mice show significantly less daily water ingestion during the circadian dark cycle, and this reduction in water intake is accompanied by a decrease in the amount of water ingested per lick. The observed water ingestion and circadian phenotypes noted in Fmr1-KO mice recapitulate known clinical aspects previously described in FXS. The finding of decreased movement in Fmr1-KO mice is novel, and suggests a dissociation between baseline and novelty-evoked activity for Fmr1-KO mice.

Increased whole cerebellar serotonin in aged C57BL/6 mice

Mobility and locomotor impairments have high prevalence, morbidity, and significant mortality in older adult populations. Cerebellar functional changes have been implicated in the pathogenesis of these age-related mobility and gait deficits unrelated to stroke, Parkinson's disease, or degenerative joint disease. We thus examined total cerebellar glutamate, glutamine, GABA, glycine, dopamine, norepinephrine, tryptophan, serotonin, alanine, threonine, and asparagine content from male 2-3-month (young, n = 6) and 21-24-month-old (aged, n = 6) C₅₇BL/6 mice. Neurotransmitter and amino acid concentrations were determined by high-performance liquid chromatography followed with mass spectroscopy. We found a significant increase in cerebellar serotonin in aged versus young mice, but otherwise no significant phenotypic differences in measured neurotransmitter concentrations. Applying current thought about cerebellar aging and cerebellar serotonergic systems, we consider how this age-related increase in cerebellar serotonin may contribute to gait ataxia.

Development of an adaptive, personalized, and scalable dementia care program: Early findings from the Care Ecosystem

Katherine Possin and colleagues report on the implementation, development, and early findings of the Care Ecosystem, an adaptive, personalized, and scalable dementia care program.

Mice Lacking Serotonin 2C Receptors Have increased Affective Responses to Aversive Stimuli

Although central serotonergic systems are known to influence responses to noxious stimuli, mechanisms underlying serotonergic modulation of pain responses are unclear. We proposed that serotonin 2C receptors (5-HT2CRs), which are expressed within brain regions implicated in sensory and affective responses to pain, contribute to the serotonergic modulation of pain responses. In mice constitutively lacking 5-HT2CRs (2CKO mice) we found normal baseline sensory responses to noxious thermal, mechanical and chemical stimuli. In contrast, 2CKO mice exhibited a selective enhancement of affect-related ultrasonic afterdischarge vocalizations in response to footshock. Enhanced affect-related responses to noxious stimuli were also exhibited by 2CKO mice in a fear-sensitized startle assay. The extent to which a brief series of unconditioned footshocks produced enhancement of acoustic startle responses was markedly increased in 2CKO mice. As mesolimbic dopamine pathways influence affective responses to noxious stimuli, and these pathways are disinhibited in 2CKO mice, we examined the sensitivity of footshock-induced enhancement of startle to dopamine receptor blockade. Systemic administration of the dopamine D2/D3 receptor antagonist raclopride selectively reduced footshock-induced enhancement of startle without influencing baseline acoustic startle responses. We propose that 5-HT2CRs regulate affective behavioral responses to unconditioned aversive stimuli through mechanisms involving the disinhibition of ascending dopaminergic pathways.

Influence of age, irradiation and humanization on NSG mouse phenotypes

Humanized mice are frequently utilized in bench to bedside therapeutic tests to combat human infectious, cancerous and degenerative diseases. For the fields of hematology-oncology, regenerative medicine, and infectious diseases, the immune deficient mice have been used commonly in basic research efforts. Obstacles in true translational efforts abound, as the relationship between mouse and human cells in disease pathogenesis and therapeutic studies requires lengthy investigations. The interplay between human immunity and mouse biology proves ever more complicated when aging, irradiation, and human immune reconstitution are considered. All can affect a range of biochemical and behavioral functions. To such ends, we show age- and irradiation-dependent influences for the development of macrocytic hyper chromic anemia, myelodysplasia, blood protein reductions and body composition changes. Humanization contributes to hematologic abnormalities. Home cage behavior revealed day and dark cycle locomotion also influenced by human cell reconstitutions. Significant age-related day-to-day variability in movement, feeding and drinking behaviors were observed. We posit that this data serves to enable researchers to better design translational studies in this rapidly emerging field of mouse humanization.

Validation of Flow Cytometry and Magnetic Bead-Based Methods to Enrich CNS Single Cell Suspensions for Quiescent Microglia

Microglia are resident mononuclear phagocytes within the CNS parenchyma that intimately interact with neurons and astrocytes to remodel synapses and extracellular matrix. We briefly review studies elucidating the molecular pathways that underlie microglial surveillance, activation, chemotaxis, and phagocytosis; we additionally place these studies in a clinical context. We describe and validate an inexpensive and simple approach to obtain enriched single cell suspensions of quiescent parenchymal and perivascular microglia from the mouse cerebellum and hypothalamus. Following preparation of regional CNS single cell suspensions, we remove myelin debris, and then perform two serial enrichment steps for cells expressing surface CD11b. Myelin depletion and CD11b enrichment are both accomplished using antigen-specific magnetic beads in an automated cell separation system. Flow cytometry of the resultant suspensions shows a significant enrichment for CD11b(+)/CD45(+) cells (perivascular microglia) and CD11b(+)/CD45(-) cells (parenchymal microglia) compared to starting suspensions. Of note, cells from these enriched suspensions minimally express Aif1 (aka Iba1), suggesting that the enrichment process does not evoke significant microglial activation. However, these cells readily respond to a functional challenge (LPS) with significant changes in the expression of molecules specifically associated with microglia. We conclude that methods employing a combination of magnetic-bead based sorting and flow cytometry produce suspensions highly enriched for microglia that are appropriate for a variety of molecular and cellular assays.

Smart watch RSSI localization and refinement for behavioral classification using laser-SLAM for mapping and fingerprinting

As a first step toward building a smart home behavioral monitoring system capable of classifying a wide variety of human behavior, a wireless sensor network (WSN) system is presented for RSSI localization. The low-cost, non-intrusive system uses a smart watch worn by the user to broadcast data to the WSN, where the strength of the radio signal is evaluated at each WSN node to localize the user. A method is presented that uses simultaneous localization and mapping (SLAM) for system calibration, providing automated fingerprinting associating the radio signal strength patterns to the user's location within the living space. To improve the accuracy of localization, a novel refinement technique is introduced that takes into account typical movement patterns of people within their homes. Experimental results demonstrate that the system is capable of providing accurate localization results in a typical living space.

Measuring functional recovery in older patients discharged from intensive care units: is advanced technology an option?

The purpose of this descriptive study was to determine if older patients discharged from intensive care units (ICU) would be willing to use mobile phone and sensor technology (aka "mobile monitoring") to measure their functional recovery in the posthospitalization period. Semistructured interviews were conducted with 22 older ICU patients and/or their surrogates 24 to 48 hr prior to hospital discharge. While 11 respondents reported they would agree to participate in a future study involving mobile monitoring, an equal number reported they would not participate. Numerous contextual factors were found to affect older adults' willingness to participate including the belief the research would ultimately benefit themselves or other older adults, concerns about loss of privacy, perception that the research is feasible and valuable, and lack of skills using the technology. Future studies using the mobile monitoring technique with older survivors of a serious illness will require substantial recruitment and educational efforts.

Aging causes a slowing in ciliary beat frequency, mediated by PKCε

The elderly are at much higher risk for developing pneumonia than younger individuals. Pneumonia is a leading cause of death and is the third most common reason for hospitalization in the elderly. One reason that elderly people may be more susceptible to pneumonia is a breakdown in the lung's first line of defense, mucociliary clearance. Cilia beat in a coordinated manner to propel out invading microorganisms and particles. Ciliary beat frequency (CBF) is known to slow with aging, however, little is known about the mechanism(s) involved. We compared the CBF in BALB/c and C57BL/6 mice aged 2, 12, and 24 mo and found that CBF diminishes with age. Cilia in the mice at age 12 and 24 mo retained their ability to be stimulated by the β2 agonist procaterol. To help determine the mechanism of ciliary slowing, we measured protein kinase C alpha and epsilon (PKCα and PKCε) activity. There were no activity differences in PKCα between the mice aged 2, 12, or 24 mo. However, we demonstrated a significantly higher PKCε activity in the mice at 12 and 24 mo than the in the mice 2 mo of age. The increase in activity is likely due to a nearly threefold increase in PKCε protein in the lung during aging. To strengthen the connection between activation of PKCε and ciliary slowing, we treated tracheas of mice at 2 mo with the PKCε agonist 8-[2-(2-pentylcyclopropylmethyl)-cyclopropyl]-octanoic acid (DCP-LA). We noted a similar decrease in baseline CBF, and the cilia remained sensitive to stimulation with β2 agonists. The mechanisms for the slowing of baseline CBF have not been previously determined. In this mouse model of aging we were able to show that decreases in CBF are related to an increase in PKCε activity.

Pilot study of younger and older HIV-infected adults using traditional and novel functional assessments

OBJECTIVES

Emerging data suggest that HIV disease and its treatment affect the aging process. Accurate and reliable measures of functional status are needed to investigate this further.

DESIGN

A pilot study in groups of younger and older HIV-infected adults using objective measures of function.

METHODS

Evaluations included neuropsychological testing, grip strength, balance assessed by the Wii Balance Board, and actigraphy. Surveys were used for depression, fatigue, loneliness, self-reported activity level, and sexual function. Two-samplet test or Wilcoxon rank sum tests were used for continuous variables and exact chi-square tests were used for comparison between groups.

RESULTS

Twenty-one participants were 20 to 40 years old (younger; mean age, 31.5), and 20 were more than 50 years old (older; mean age, 56.5). There was no difference between groups for depression, fatigue, or loneliness. Overall, there was a trend to lower scores in the older age group for neuropsychologicalz score (P = .11) and for verbal learning (P = .09). Functioning in the memory domain was significantly lower in older subjects (P = .007). There was no difference in executive function, speed of processing, memory, motor skills, or total activity. Gender differences in sexual function were observed. Four older and 3 younger participants met the definition of frailty. Total activity by actigraphy did not correlate well with self-reported activity.

CONCLUSIONS

Objective tests were well accepted and feasible to perform, although not all are suitable for widespread clinical or research use. Objective measurements of activity did not correlate well with patient self-report, which has implications for future studies in this area.

A low-cost, reliable, high-throughput system for rodent behavioral phenotyping in a home cage environment

Inexpensive, high-throughput, low maintenance systems for precise temporal and spatial measurement of mouse home cage behavior (including movement, feeding, and drinking) are required to evaluate products from large scale pharmaceutical design and genetic lesion programs. These measurements are also required to interpret results from more focused behavioral assays. We describe the design and validation of a highly-scalable, reliable mouse home cage behavioral monitoring system modeled on a previously described, one-of-a-kind system. Mouse position was determined by solving static equilibrium equations describing the force and torques acting on the system strain gauges; feeding events were detected by a photobeam across the food hopper, and drinking events were detected by a capacitive lick sensor. Validation studies show excellent agreement between mouse position and drinking events measured by the system compared with video-based observation--a gold standard in neuroscience.

Assessing Smart Phones for Generating Life-space Indicators

Life-space is a promising method for estimating older adults' functional status. However, traditional life-space measures are costly and time consuming because they often rely on active subject participation. This study assesses the feasibility of using the global positioning system (GPS) function of smart phones to generate life-space indicators. We first evaluated the location accuracy of smart phone collected GPS points versus those acquired by a commercial GPS unit. We then assessed the specificity of the smart phone processed life-space information against the traditional diary method. Our results suggested comparable location accuracy between the smart phone and the standard GPS unit in most outdoor situations. In addition, the smart phone method revealed more comprehensive life-space information than the diary method, which leads to higher and more consistent life-space scores. We conclude that the smart phone method is more reliable than traditional methods for measuring life-space. Further improvements will be required to develop a robust application of this method that is suitable for health-related practices.

Treadmill gait speeds correlate with physical activity counts measured by cell phone accelerometers

A number of important health-related outcomes are directly related to a person's ability to maintain normal gait speed. We hypothesize that cellular telephones may be repurposed to measure this important behavior in a noninvasive, continuous, precise, and inexpensive manner. The purpose of this study was to determine if physical activity (PA) counts collected by cell phone accelerometers could measure treadmill gait speeds. We also assessed how cell phone placement influenced treadmill gait speed measures. Participants included 55 young, middle-aged, and older community-dwelling men and women. We placed cell phones as a pendant around the neck, and on the left and right wrist, hip, and ankle. Subjects then completed an individualized treadmill protocol, alternating 1 min rest periods with 5 min of walking at different speeds (0.3-11.3 km/h; 0.2-7 mi/h). No persons were asked to walk at speeds faster than what they would achieve during day-to-day life. PA counts were calculated from all sensor locations. We built linear mixed statistical models of PA counts predicted by treadmill speeds ranging from 0.8 to 6.4 km/h (0.5-4 mi/h) while accounting for subject age, weight, and gender. We solved linear regression equations for treadmill gait speed, expressed as a function of PA counts, age, weight, and gender. At all locations, cell phone PA counts were strongly associated with treadmill gait speed. Cell phones worn at the hip yielded the best predictive model. We conclude that in both men and women, cell phone derived activity counts strongly correlate with treadmill gait speed over a wide range of subject ages and weights.

COMT Val158Met genotype influences neurodegeneration within dopamine-innervated brain structures

OBJECTIVE

We sought to determine whether the Val(158)Met polymorphism in the catechol-O-methyltransferase (COMT) gene influences neurodegeneration within dopamine-innervated brain regions.

METHODS

A total of 252 subjects, including healthy controls and patients with Alzheimer disease, behavioral variant frontotemporal dementia, and semantic dementia, underwent COMT genotyping and structural MRI.

RESULTS

Whole-brain voxel-wise regression analyses revealed that COMT Val(158)Met Val allele dosage, known to produce a dose-dependent decrease in synaptic dopamine (DA) availability, correlated with decreased gray matter in the region of the ventral tegmental area (VTA), ventromedial prefrontal cortex, bilateral dorsal midinsula, left dorsolateral prefrontal cortex, and right ventral striatum. Unexpectedly, patients carrying a Met allele showed greater VTA volumes than age-matched controls. Gray matter intensities within COMT-related brain regions correlated with cognitive and behavioral deficits.

CONCLUSIONS

The results are consistent with the hypothesis that increased synaptic DA catabolism promotes neurodegeneration within DA-innervated brain regions.

Cellular telephones measure activity and lifespace in community-dwelling adults: proof of principle

OBJECTIVES

To describe a system that uses off-the-shelf sensor and telecommunication technologies to continuously measure individual lifespace and activity levels in a novel way.

DESIGN

Proof of concept involving three field trials of 30, 30, and 21 days.

SETTING

Omaha, Nebraska, metropolitan and surrounding rural region.

PARTICIPANTS

Three participants (48-year-old man, 33-year-old woman, and 27-year-old male), none with any functional limitations.

MEASUREMENTS

Cellular telephones were used to detect in-home position and in-community location and to measure physical activity. Within the home, cellular telephones and Bluetooth transmitters (beacons) were used to locate participants at room-level resolution. Outside the home, the same cellular telephones and global positioning system (GPS) technology were used to locate participants at a community-level resolution. Physical activity was simultaneously measured using the cellular telephone accelerometer.

RESULTS

This approach had face validity to measure activity and lifespace. More importantly, this system could measure the spatial and temporal organization of these metrics. For example, an individual's lifespace was automatically calculated across multiple time intervals. Behavioral time budgets showing how people allocate time to specific regions within the home were also automatically generated.

CONCLUSION

Mobile monitoring shows much promise as an easily deployed system to quantify activity and lifespace, important indicators of function, in community-dwelling adults.

Increased metabolic vulnerability in early-onset Alzheimer's disease is not related to amyloid burden

Patients with early age-of-onset Alzheimer's disease show more rapid progression, more generalized cognitive deficits and greater cortical atrophy and hypometabolism compared to late-onset patients at a similar disease stage. The biological mechanisms that underlie these differences are not well understood. The purpose of this study was to examine in vivo whether metabolic differences between early-onset and late-onset Alzheimer's disease are associated with differences in the distribution and burden of fibrillar amyloid-beta. Patients meeting criteria for probable Alzheimer's disease (National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's; Disease and Related Disorders Association criteria) were divided based on estimated age at first symptom (less than or greater than 65 years) into early-onset (n = 21, mean age-at-onset 55.2 +/- 5.9 years) and late-onset (n = 18, 72.0 +/- 4.7 years) groups matched for disease duration and severity. Patients underwent positron emission tomography with the amyloid-beta-ligand [(11)C]-labelled Pittsburgh compound-B and the glucose analogue [(18)F]-labelled fluorodeoxyglucose. A group of cognitively normal controls (n = 30, mean age 73.7 +/- 6.4) was studied for comparison. [(11)C]-labelled Pittsburgh compound-B images were analysed using Logan graphical analysis (cerebellar reference) and [(18)F]-labelled fluorodeoxyglucose images were normalized to mean activity in the pons. Group differences in tracer uptake were assessed on a voxel-wise basis using statistical parametric mapping, and by comparing mean values in regions of interest. To account for brain atrophy, analyses were repeated after applying partial volume correction to positron emission tomography data. Compared to normal controls, both early-onset and late-onset Alzheimer's disease patient groups showed increased [(11)C]-labelled Pittsburgh compound-B uptake throughout frontal, parietal and lateral temporal cortices and striatum on voxel-wise and region of interest comparisons (P < 0.05). However, there were no significant differences in regional or global [(11)C]-labelled Pittsburgh compound-B binding between early-onset and late-onset patients. In contrast, early-onset patients showed significantly lower glucose metabolism than late-onset patients in precuneus/posterior cingulate, lateral temporo-parietal and occipital corticies (voxel-wise and region of interest comparisons, P < 0.05). Similar results were found for [(11)C]-labelled Pittsburgh compound-B and [(18)F]-labelled fluorodeoxyglucose using atrophy-corrected data. Age-at-onset correlated positively with glucose metabolism in precuneus, lateral parietal and occipital regions of interest (controlling for age, education and Mini Mental State Exam, P < 0.05), while no correlations were found between age-at-onset and [(11)C]-labelled Pittsburgh compound-B binding. In summary, a comparable burden of fibrillar amyloid-beta was associated with greater posterior cortical hypometabolism in early-onset Alzheimer's disease. Our data are consistent with a model in which both early amyloid-beta accumulation and increased vulnerability to amyloid-beta pathology play critical roles in the pathogenesis of Alzheimer's disease in young patients.

Essential function of HIPK2 in TGFbeta-dependent survival of midbrain dopamine neurons

Transforming growth factor beta (TGFbeta) is a potent trophic factor for midbrain dopamine (DA) neurons, but its in vivo function and signaling mechanisms are not entirely understood. We show that the transcriptional cofactor homeodomain interacting protein kinase 2 (HIPK2) is required for the TGFbeta-mediated survival of mouse DA neurons. The targeted deletion of Hipk2 has no deleterious effect on the neurogenesis of DA neurons, but leads to a selective loss of these neurons that is due to increased apoptosis during programmed cell death. As a consequence, Hipk2(-/-) mutants show an array of psychomotor abnormalities. The function of HIPK2 depends on its interaction with receptor-regulated Smads to activate TGFbeta target genes. In support of this notion, DA neurons from Hipk2(-/-) mutants fail to survive in the presence of TGFbeta3 and Tgfbeta3(-/-) mutants show DA neuron abnormalities similar to those seen in Hipk2(-/-) mutants. These data underscore the importance of the TGFbeta-Smad-HIPK2 pathway in the survival of DA neurons and its potential as a therapeutic target for promoting DA neuron survival during neurodegeneration.

A null mutation of the serotonin 6 receptor alters acute responses to ethanol

The anatomical distribution and pharmacology of serotonin 6 receptors (5-HT6Rs) implicate them as contributors to the serotonergic regulation of complex behavior. To complement the limited range of pharmacological tools available to examine 5-HT6R function, we have generated a mouse line bearing a constitutive null mutation of the 5-HT6R gene. No perturbations of baseline behavior were noted in a wide array of assays pertinent to multiple neurobehavioral processes. However, 5-HT6R mutant mice demonstrated reduced responses to the ataxic and sedative effects of ethanol. No differences in ethanol metabolism were evident between wild-type and 5-HT6R mutant mice. These findings implicate 5-HT6Rs in the serotonergic modulation of responses to ethanol.

Hyperactivity and reduced energy cost of physical activity in serotonin 5-HT(2C) receptor mutant mice

We have observed late-onset obesity in mutant mice lacking the serotonin 5-HT(2C) receptor. Despite chronically elevated food intake, young adult mutants exhibit neither elevated adiposity nor altered glucose or fat homeostasis. However, obesity subsequently develops after 6 months of age without increases in their level of hyperphagia. In this study, we investigated determinants of energy expenditure in 5-HT(2C) receptor mutant mice. Young adult mutants displayed patterns of elevated activity levels that were enhanced by fasting and tightly associated with repeated visits to a food source. Surprisingly, subsequent obesity development occurred despite persisting locomotor hyperactivity and without age-related declines in resting metabolic rate. Rather, substantial reductions in the energy cost of locomotor activity (LA) were observed in 5-HT(2C) receptor mutant mice. Moreover, both mutant and wild-type mice displayed age-related declines in the energy cost of LA, indicating that this process may be regulated by both aging and serotonergic signaling. These results indicate that a mutation of the 5-HT(2C) receptor gene (htr2c) increases LA, which contributes to the maintenance of normal body composition in young adult mutants despite their hyperphagia. Moreover, age-dependent reductions in the energy cost of physical activity could contribute to the subsequent development of late-onset obesity in 5-HT(2C) receptor mutant mice.

Mouse models of serotonin receptor function: toward a genetic dissection of serotonin systems

Central serotonin (5-hydroxytryptamine, 5-HT) systems regulate a wide variety of complex behaviors, and are targeted by drugs used in the treatment of diverse neuropsychiatric disorders. The actions of 5-HT are mediated by a large and heterogeneous family of 5-HT receptor subtypes. Studies of the functional significance of individual subtypes have been complicated by the limited availability of selective receptor agonist and antagonist drugs. Molecular genetic techniques offer complementary approaches for studying the behavioral roles of individual 5-HT receptor subtypes through the generation of gene-targeted and transgenic lines of mice with altered expression of 5-HT receptor genes. This review will examine insights into the serotonergic regulation of behavior that have been produced by the study of these lines, as well as discuss important caveats to the interpretation of these studies.

Mechanical actions of heterogenic reflexes among ankle stabilizers and their interactions with plantarflexors of the cat hindlimb

1. The stretch-evoked reflex organization of muscles whose major action is to abduct [peroneus brevis (PB); peroneus longus (PL)] and adduct [tibialis posterior (TP); flexor digitorum longus (FDL); flexor hallucis longus (FHL)] the ankle, and their interactions with the hindlimb extensors gastrocnemius (G) and soleus (S), were studied in 27 unanesthetized decerebrate cats. Ramp-hold-release stretches of physiological amplitudes were applied to muscle tendons detached from their bony insertion, and muscle force output was measured in response to these perturbations. Flexion and crossed-extension reflexes were used to modulate baseline force. 2. PB and TP shared strong, length-dependent, short-latency inhibitory reflexes prominent when the muscles were either actively generating force or quiescent. The mechanical characteristics of this reflex suggest Ia reciprocal inhibition as the underlying mechanism. Just as reciprocal inhibition between S and tibialis anterior stiffens the ankle joint against sagittal perturbations, we propose that reciprocal inhibition between PB and TP stiffens the ankle joint against nonsagittal perturbations. 3. In all preparations (n = 7) and under all conditions examined, PB and PL shared well-demonstrated mutual excitation. The reflex responses were asymmetric (favoring excitation of PL), length dependent, and occurred simultaneously with the stretch reflex at a latency of 16-18 ms. Mutual monosynaptic projections previously described between these two muscles explain all of the above findings. Our data further demonstrate that, under certain conditions, the ensemble activity of this reflex interaction has a powerful effect on the mechanical behavior of the muscle. 4. The heterogenic reflex organization of the ankle adductors was as follows: FDL evoked a modest excitation on TP, whereas FHL evoked weak inhibition. Latency of the excitation from FDL onto TP (24 ms) was greater than expected if the reflex were mediated by heteronymous Ia afferents. In all preparations examined (n = 3), TP contributed no significant reflexes onto either FDL or FHL. 5. Mutual, asymmetric inhibition characterized interactions between PB and the plantarflexors S and G. Most remarkable was a novel, long-latency (72-74 ms) reflex inhibition evoked on both S and G by stretch of PB. When this inhibition occurred, it dramatically decreased the S (or G) stretch response. Longer PB lengths evoked greater inhibition of isometric S; regression analysis indicated that the model best predicting this inhibition contained muscle force and stiffness terms. No long-latency reflexes were noted from either G or S onto PB. The mechanism underlying long-latency inhibition is presently unknown; however, features of this interaction suggest interneurons receive either group II or group III afferent input. 6. G and TP shared short latency, mutually inhibitory, asymmetric reflexes favoring inhibition of TP. No long-latency interactions were noted, nor were there any mechanically significant interactions between S and TP. 7. Reflex interactions across the abduction/adduction axis thus favored inhibition of plantarflexion and adduction torques while emphasizing abduction torques: PB/S (or PB/G) interactions were mutual, asymmetric, and favored inhibition of G and S; TP/G interactions were mutual, asymmetric, and favored inhibition of TP; TP/PB interactions were approximately balanced. The overall mechanical outcome of these inhibitory interactions may partly underlie the global corrective strategy seen in intact cats subjected to linear perturbations. 8. No significant reflex interactions were demonstrated between PL and TP, G, or S, nor were any long-latency reflexes noted. Thus, whereas reflex interactions between the stereotypically activated PB and other stereotypically activated muscles (including TP, G, and S) were strong and well-demonstrated, interactions between the variably activated PL and these same muscles were far weaker.

Mechanical actions of heterogenic reflexes linking long toe flexors with ankle and knee extensors of the cat hindlimb

1. To study the means whereby ankle biomechanics are represented in the interneuronal circuitry of the spinal cord we examined stretch-evoked reflex interactions between the physiological extensors flexor hallucis longus (FHL) and flexor digitorum longus (FDL) as well as their interactions with gastrocnemius (G), soleus (S), and the quadriceps group (Q) in 34 unanesthetized decerebrate cats. To evoke stretch, DC motors provided ramp-hold-release length changes to tendons detached from their bony insertions. Semiconductor myographs measured resultant muscle force response. Reflexes were examined under both quiescent (no active force generation) and activated conditions; muscle activation was achieved through either crossed-extension or flexion reflexes. 2. FHL and FDL share mutual excitatory stretch-evoked interactions under most conditions examined. These interactions depended on muscle length, were asymmetric (with FHL contributing a larger magnitude of reflex excitation onto FDL), and occurred at a latency of 16 ms. Mutual Ia synergism previously described for these two muscles provides a basis for all of the above findings. Our data demonstrate that for this muscle pair, reflex connectivities revealed at the intracellular level can be extrapolated to cover the entire motoneuron pool; further, our data directly demonstrate the net mechanical result of ensemble synaptic events. 3. FHL was found to share strong, mutually inhibitory stretch-evoked interactions with G, S, and Q. Stepwise regression statistical analyses determined that these interactions depended on recipient muscle force and donor muscle force. These reflex interactions all occurred at a latency of 28 +/- 4 (SE) ms. Further, the heterogenic inhibition between FHL/G and FHL/S was attenuated by strychnine infusion (intravenous) but unaffected by either mecamylamine, picrotoxin, or baclofen infusion (intravenous, intrathecal). Disynaptic Ib inhibition previously described among hindlimb extensors provides a basis for the above findings; our data demonstrate that under certain conditions the ensemble activity of this system can cause a dramatic decline in whole muscle force output. 4. By contrast, FDL was found to share mutually inhibitory, stretch-evoked reflex interactions with G, S, and Q that were much weaker than those observed between FHL and these same muscles. The small magnitude of inhibition observed in these interactions made it difficult to assess reflex latency or to determine the factor(s) that best predicted the heterogenic inhibition. 5. This study provides further evidence of intrinsic differences in interneuronal organization between muscles whose activity occurs in a periodic manner during locomotion ("stereotypical") and a muscle whose locomotor activity is characterized by both periodic and nonperiodic components ("facultative").(ABSTRACT TRUNCATED AT 400 WORDS)

Reinnervated muscles fail to produce stretch reflexes

1. We studied the stretch-evoked reflex organization of hind limb muscles in two decerebrate cats 36 mo after unilateral section and immediate surgical repair of the common nerve supplying the lateral gastrocnemius (LG) and soleus (S) muscles. 2. The production of considerable reflex force by reinnervated muscles in response to electrical stimulation of uninjured nerves indicated substantial functional recovery of motor units. However, reduction in the responsiveness of reinnervated muscles to stretch of the untreated medial gastrocnemius (MG) muscle indicated some deficit in recovery of normal synaptic integration. 3. Stretch failed to elicit autogenic excitation of the reinnervated S and LG. This failure was observed whether the reinnervated muscles were quiescent or contracting in other reflexes. 4. The heterogenic reflex organization of reinnervated muscles was abnormal. Stretch of the reinnervated S failed to evoke heterogenic reflexes both in the untreated MG and in the reinnervated LG. Stretch of the reinnervated LG failed to produce excitation of MG. 5. These findings demonstrate deficiencies in proprioceptive feedback from reinnervated muscles and lead us to expect incomplete recovery of motor function after nerve section.

Control of torque direction by spinal pathways at the cat ankle joint

To study the biomechanics of the calcaneal tendon's complex insertion onto the calcaneus, we measured torque-time trajectories exerted by the triceps surae and tibialis anterior muscles in eight unanesthetized decerebrate cats using a multi-axis force-moment sensor placed at the ankle joint. The ankle was constrained to an angle of 110 degrees plantarflexion. Muscles were activated using crossed-extension (XER), flexion (FWR), and caudal cutaneous sural nerve (SNR) reflexes. Torque contributions of other muscles activated by these reflexes were eliminated by denervation or tenotomy. In two animals, miniature pressure transducers were implanted among tendon fibers from the lateral gastrocnemius (LG) muscle that insert straight into the calcaneus or among tendon fibers from the medial gastrocnemius (MG) that cross over and insert on the lateral aspect of calcaneus. Reflexively evoked torques had the following directions: FWR, dorsiflexion and adduction; SNR, plantarflexion and abduction; and XER, plantarflexion and modest abduction or adduction. The proportion of abduction torque to plantarflexion torque was always greater for SNR than XER; this difference was about 50% of the magnitude of abduction torque generated by tetanic stimulation of the peronei. During SNR, pressures were higher in regions of the calcaneal tendon originating from MG than regions originating from LG. Similarly, pressures within the MG portion of the calcaneal tendon were higher during SNR than during XER, although these two reflexes produced matched ankle plantarflexion forces. Selective tenotomies and electromyographic recordings further demonstrated that MG generated most of the torque in response to SNR, while soleus, LG, and MG all generated torques in response to XER.(ABSTRACT TRUNCATED AT 250 WORDS)