LiveWell, a smartphone-based self-management intervention for bipolar disorder: Intervention participation and usability analysis

BACKGROUND

Understanding how individuals utilize and perceive digital mental health interventions may improve engagement and effectiveness. To support intervention improvement, participant feedback was obtained and app use patterns were examined for a randomized clinical trial evaluating a smartphone-based intervention for individuals with bipolar disorder.

METHODS

App use and coaching engagement were examined (n = 124). Feedback was obtained via exit questionnaires (week 16, n = 81) and exit interviews (week 48, n = 17).

RESULTS

On average, over 48 weeks, participants used the app for 4.4 h and engaged with the coach for 3.9 h. Participants spent the most time monitoring target behaviors and receiving adaptive feedback and the least time viewing self-assessments and skills. Participants reported that the daily check in helped increase awareness of target behaviors but expressed frustration with repetitiveness of monitoring and feedback content. Participants liked personalizing their wellness plan, but its use did not facilitate skills practice. App use declined over time which participants attributed to clinical stability, content mastery, and time commitment. Participants found the coaching supportive and motivating for app use.

LIMITATIONS

App engagement based on viewing time may overestimate engagement. The delay between intervention delivery and the exit interviews and low exit interview participation may introduce bias.

CONCLUSION

Utilization patterns and feedback suggest that digital mental health engagement and efficacy may benefit from adaptive personalization of targets monitored combined with adaptive monitoring and feedback to support skills practice and development. Increasing engagement with supports may also be beneficial.

Effects of a Smartphone-Based Self-management Intervention for Individuals With Bipolar Disorder on Relapse, Symptom Burden, and Quality of Life: A Randomized Clinical Trial

Importance

Bipolar disorder-specific psychotherapy combined with pharmacotherapy improves relapse risk, symptom burden, and quality of life, but psychotherapy is not easily accessible.

Objective

To determine if a smartphone-based self-management intervention (LiveWell) can assist individuals with bipolar disorder to maintain wellness.

Design, Setting, and Participants

An assessor-blind randomized clinical trial enrolled participants from March 20, 2017, to April 25, 2019, with 48-week follow-up ending on April 10, 2020. Participants were randomly assigned to usual care or usual care plus the smartphone intervention stratified by relapse risk based on initial clinical status (low risk: asymptomatic recovery; high risk: continued symptomatic, prodromal, recovering, symptomatic recovery). Participants with bipolar disorder I were recruited from clinics in the Chicago and Minneapolis-Saint Paul areas. Data were analyzed from June 19, 2020, to May 25, 2022.

Interventions

The smartphone-based self-management intervention consisted of an application (app), coach, and website. Over 16 weeks, participants had a coach visit followed by 6 phone calls, and they completed daily and weekly app check-ins. The app provided adaptive feedback and information for developing a personalized wellness plan, the coach provided support, and the website provided summary data and alerts.

Main Outcomes and Measures

The primary outcome was time to relapse. Secondary outcomes were percentage-time symptomatic, symptom severity, and quality of life.

Results

Of the 205 randomized participants (mean [SD] age, 42 [12] years; 125 female individuals [61%]; 5 Asian [2%], 21 Black [10%], 13 Hispanic or Latino [6%], 7 multiracial [3%], 170 White [83%], 2 unknown race [1%]), 81 (40%) were randomly assigned to usual care, and 124 (60%) were randomly assigned to usual care plus the smartphone intervention. This clinical trial did not detect a reduction in relapse risk for the smartphone intervention (hazard ratio [HR], 0.65; 95% CI, 0.39-1.09; log-rank P = .08). However, decreased relapse was observed for low-risk individuals (HR, 0.32; 95% CI, 0.12-0.88; log-rank P = .02) but not high-risk individuals (HR, 0.86; 95% CI, 0.47-1.57; log-rank P = .62). Reduced manic symptom severity was observed for low-risk individuals (mean [SE] difference, -1.4 [0.4]; P = .001) but not for high-risk individuals (mean [SE] difference, 0 [0.3]; P = .95). The smartphone-based self-management intervention decreased depressive symptom severity (mean [SE] difference, -0.80 [0.34]; P = .02) and improved relational quality of life (mean [SE] difference, 1.03 [0.45]; P = .02) but did not decrease percentage-time symptomatic (mean [SE] difference, -5.6 [4.3]; P = .20).

Conclusions and Relevance

This randomized clinical trial of a smartphone-based self-management intervention did not detect a significant improvement in the primary outcome of time to relapse. However, a significant decrease in relapse risk was observed for individuals in asymptomatic recovery. In addition, the intervention decreased depressive symptom severity and improved relational quality of life. These findings warrant further work to optimize the smartphone intervention and confirm that the intervention decreases relapse risk for individuals in asymptomatic recovery.

Trial Registration

ClinicalTrials.gov Identifier: NCT03088462.

A Smartphone-Based Self-management Intervention for Individuals With Bipolar Disorder (LiveWell): Empirical and Theoretical Framework, Intervention Design, and Study Protocol for a Randomized Controlled Trial

Background

Bipolar disorder is a severe mental illness with high morbidity and mortality rates. Even with pharmacological treatment, frequent recurrence of episodes, long episode durations, and persistent interepisode symptoms are common and disruptive. Combining psychotherapy with pharmacotherapy improves outcomes; however, many individuals with bipolar disorder do not receive psychotherapy. Mental health technologies can increase access to self-management strategies derived from empirically supported bipolar disorder psychotherapies while also enhancing treatment by delivering real-time assessments, personalized feedback, and provider alerts. In addition, mental health technologies provide a platform for self-report, app use, and behavioral data collection to advance understanding of the longitudinal course of bipolar disorder, which can then be used to support ongoing improvement of treatment.

Objective

A description of the theoretical and empirically supported framework, design, and protocol for a randomized controlled trial (RCT) of LiveWell, a smartphone-based self-management intervention for individuals with bipolar disorder, is provided to facilitate the ability to replicate, improve, implement, and disseminate effective interventions for bipolar disorder. The goal of the trial is to determine the effectiveness of LiveWell for reducing relapse risk and symptom burden as well as improving quality of life (QOL) while simultaneously clarifying behavioral targets involved in staying well and better characterizing the course of bipolar disorder and treatment response.

Methods

The study is a single-blind RCT (n=205; 2:3 ratio of usual care vs usual care plus LiveWell). The primary outcome is the time to relapse. Secondary outcomes are percentage time symptomatic, symptom severity, and QOL. Longitudinal changes in target behaviors proposed to mediate the primary and secondary outcomes will also be determined, and their relationships with the outcomes will be assessed. A database of clinical status, symptom severity, real-time self-report, behavioral sensor, app use, and personalized content will be created to better predict treatment response and relapse risk.

Results

Recruitment and screening began in March 2017 and ended in April 2019. Follow-up ended in April 2020. The results of this study are expected to be published in 2022.

Conclusions

This study will examine whether LiveWell reduces relapse risk and symptom burden and improves QOL for individuals with bipolar disorder by increasing access to empirically supported self-management strategies. The role of selected target behaviors (medication adherence, sleep duration, routine, and management of signs and symptoms) in these outcomes will also be examined. Simultaneously, a database will be created to initiate the development of algorithms to personalize and improve treatment for bipolar disorder. In addition, we hope that this description of the theoretical and empirically supported framework, intervention design, and study protocol for the RCT of LiveWell will facilitate the ability to replicate, improve, implement, and disseminate effective interventions for bipolar and other mental health disorders.

Trial Registration

ClinicalTrials.gov NCT03088462; https://www.clinicaltrials.gov/ct2/show/NCT03088462

International Registered Report Identifier (IRRID)

DERR1-10.2196/30710

A Smartphone-Based Self-management Intervention for Individuals With Bipolar Disorder (LiveWell): Protocol Development for an Expert System to Provide Adaptive User Feedback

BACKGROUND

Bipolar disorder is a severe mental illness that results in significant morbidity and mortality. While pharmacotherapy is the primary treatment, adjunctive psychotherapy can improve outcomes. However, access to therapy is limited. Smartphones and other technologies can increase access to therapeutic strategies that enhance self-management while simultaneously augmenting care by providing adaptive delivery of content to users as well as alerts to providers to facilitate clinical care communication. Unfortunately, while adaptive interventions are being developed and tested to improve care, information describing the components of adaptive interventions is often not published in sufficient detail to facilitate replication and improvement of these interventions.

OBJECTIVE

To contribute to and support the improvement and dissemination of technology-based mental health interventions, we provide a detailed description of the expert system for adaptively delivering content and facilitating clinical care communication for LiveWell, a smartphone-based self-management intervention for individuals with bipolar disorder.

METHODS

Information from empirically supported psychotherapies for bipolar disorder, health psychology behavior change theories, and chronic disease self-management models was combined with user-centered design data and psychiatrist feedback to guide the development of the expert system.

RESULTS

Decision points determining the timing of intervention option adaptation were selected to occur daily and weekly based on self-report data for medication adherence, sleep duration, routine, and wellness levels. These data were selected for use as the tailoring variables determining which intervention options to deliver when and to whom. Decision rules linking delivery of options and tailoring variable thresholds were developed based on existing literature regarding bipolar disorder clinical status and psychiatrist feedback. To address the need for treatment adaptation with varying clinical statuses, decision rules for a clinical status state machine were developed using self-reported wellness rating data. Clinical status from this state machine was incorporated into hierarchal decision tables that select content for delivery to users and alerts to providers. The majority of the adaptive content addresses sleep duration, medication adherence, managing signs and symptoms, building and utilizing support, and keeping a regular routine, as well as determinants underlying engagement in these target behaviors as follows: attitudes and perceptions, knowledge, support, evaluation, and planning. However, when problems with early warning signs, symptoms, and transitions to more acute clinical states are detected, the decision rules shift the adaptive content to focus on managing signs and symptoms, and engaging with psychiatric providers.

CONCLUSIONS

Adaptive mental health technologies have the potential to enhance the self-management of mental health disorders. The need for individuals with bipolar disorder to engage in the management of multiple target behaviors and to address changes in clinical status highlights the importance of detailed reporting of adaptive intervention components to allow replication and improvement of adaptive mental health technologies for complex mental health problems.

A Smartphone-Based Self-Management Intervention for Individuals with Bipolar Disorder (LiveWell): Qualitative Study on User Experiences of the Behavior Change Process

BACKGROUND

Bipolar disorder is a severe mental illness characterized by recurrent episodes of depressed, elevated, and mixed mood states. The addition of psychotherapy to pharmacological management can decrease symptoms, lower relapse rates, and improve quality of life; however, access to psychotherapy is limited. Mental health technologies such as smartphone apps are being studied as a means to increase access to and enhance the effectiveness of adjunctive psychotherapies for bipolar disorder. Individuals with bipolar disorder find this intervention format acceptable, but our understanding of how people utilize and integrate these tools into their behavior change and maintenance processes remains limited.

OBJECTIVE

The objective of this study was to explore how individuals with bipolar disorder perceive and utilize a smartphone intervention for health behavior change and maintenance.

METHODS

Individuals with bipolar disorder were recruited via flyers placed at university-affiliated and private outpatient mental health practices to participate in a pilot study of LiveWell, a smartphone-based self-management intervention. At the end of the study, all participants completed in-depth qualitative exit interviews. The behavior change framework developed to organize the intervention design was used to deductively code behavioral targets and determinants involved in target engagement. Inductive coding was used to identify themes not captured by this framework.

RESULTS

In terms of behavioral targets, participants emphasized the importance of managing mood episode-related signs and symptoms. They also discussed the importance of maintaining regular routines, sleep duration, and medication adherence. Participants emphasized that receiving support from a coach as well as seeking and receiving assistance from family, friends, and providers were important for managing behavioral targets and staying well. In terms of determinants, participants stressed the important role of monitoring for their behavior change and maintenance efforts. Monitoring facilitated self-awareness and reflection, which was considered valuable for staying well. Some participants also felt that the intervention facilitated learning information necessary for managing bipolar disorder but others felt that the information provided was too basic.

CONCLUSIONS

In addition to addressing acceptability, satisfaction, and engagement, a person-based design of mental health technologies can be used to understand how people experience the impact of these technologies on their behavior change and maintenance efforts. This understanding may then be used to guide ongoing intervention development. The participants' perceptions aligned with the intervention's primary behavioral targets and use of a monitoring tool as a core intervention feature. Participant feedback further indicates that developing additional content and tools to address building and engaging social support may be an important avenue for improving LiveWell. A comprehensive behavior change framework to understand participant perceptions of their behavior change and maintenance efforts may help facilitate ongoing intervention development.

A Smartphone-Based Self-management Intervention for Bipolar Disorder (LiveWell): User-Centered Development Approach

BACKGROUND

Bipolar disorder is a serious mental illness that results in significant morbidity and mortality. Pharmacotherapy is the primary treatment for bipolar disorder; however, adjunctive psychotherapy can help individuals use self-management strategies to improve outcomes. Yet access to this therapy is limited. Smartphones and other technologies have the potential to increase access to therapeutic strategies that enhance self-management while simultaneously providing real-time user feedback and provider alerts to augment care.

OBJECTIVE

This paper describes the user-centered development of LiveWell, a smartphone-based self-management intervention for bipolar disorder, to contribute to and support the ongoing improvement and dissemination of technology-based mental health interventions.

METHODS

Individuals with bipolar disorder first participated in a field trial of a simple smartphone app for self-monitoring of behavioral targets. To develop a complete technology-based intervention for bipolar disorder, this field trial was followed by design sessions, usability testing, and a pilot study of a smartphone-based self-management intervention for bipolar disorder. Throughout all phases of development, intervention revisions were made based on user feedback.

RESULTS

The core of the LiveWell intervention consists of a daily self-monitoring tool, the Daily Check-in. This self-monitoring tool underwent multiple revisions during the user-centered development process. Daily Check-in mood and thought rating scales were collapsed into a single wellness rating scale to accommodate user development of personalized scale anchors. These anchors are meant to assist users in identifying early warning signs and symptoms of impending episodes to take action based on personalized plans. When users identified personal anchors for the wellness scale, the anchors most commonly reflected behavioral signs and symptoms (40%), followed by cognitive (25%), mood (15%), physical (10%), and motivational (7%) signs and symptoms. Changes to the Daily Check-in were also made to help users distinguish between getting adequate sleep and keeping a regular routine. At the end of the pilot study, users reported that the Daily Check-in made them more aware of early warning signs and symptoms and how much they were sleeping. Users also reported that they liked personalizing their anchors and plans and felt this process was useful. Users experienced some difficulties with developing, tracking, and achieving target goals. Users also did not consistently follow up with app recommendations to contact providers when Daily Check-in data suggested they needed additional assistance. As a result, the human support roles for the technology were expanded beyond app use support to include support for self-management and clinical care communication. The development of these human support roles was aided by feedback on the technology's usability from the users and the coaches who provided the human support.

CONCLUSIONS

User input guided the development of intervention content, technology, and coaching support for LiveWell. Users valued the provision of monitoring tools and the ability to personalize plans for staying well, supporting the role of monitoring and personalization as important features of digital mental health technologies. Users also valued human support of the technology in the form of a coach, and user difficulties with aspects of self-management and care-provider communication led to an expansion of the coach's support roles. Obtaining feedback from both users and coaches played an important role in the development of both the LiveWell technology and human support. Attention to all stakeholders involved in the use of mental health technologies is essential for optimizing intervention development.

Development of Coaching Support for LiveWell: A Smartphone-Based Self-Management Intervention for Bipolar Disorder

Despite effective pharmacological treatment, bipolar disorder is a leading cause of disability due to recurrence of episodes, long episode durations, and persistence of interepisode symptoms. While adding psychotherapy to pharmacotherapy improves outcomes, the availability of adjunctive psychotherapy is limited. To extend the accessibility and functionality of psychotherapy for bipolar disorder, we developed LiveWell, a smartphone-based self-management intervention. Unfortunately, many mental health technology interventions suffer from high attrition rates, with users rapidly failing to maintain engagement with the intervention technology. Human support reduces this commonly observed engagement problem but does not consistently improve clinical and recovery outcomes. To facilitate ongoing efforts to develop human support for digital mental health technologies, this paper describes the design decisions, theoretical framework, content, mode, timing of delivery, and the training and supervision for coaching support of the LiveWell technology. This support includes clearly defined and structured roles that aim to encourage the use of the technology, self-management strategies, and communication with care providers. A clear division of labor is established between the coaching support roles and the intervention technology to allow lay personnel to serve as coaches and thereby maximize accessibility to the LiveWell intervention.

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.

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.

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.

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.

Deletion of Mecp2 in Sim1-expressing neurons reveals a critical role for MeCP2 in feeding behavior, aggression, and the response to stress

Rett Syndrome (RTT) is an autism spectrum disorder caused by mutations in the X-linked gene encoding methyl-CpG binding protein 2 (MeCP2). In order to map the neuroanatomic origins of the complex neuropsychiatric behaviors observed in patients with RTT and to uncover endogenous functions of MeCP2 in the hypothalamus, we removed Mecp2 from Sim1-expressing neurons in the hypothalamus using Cre-loxP technology. Loss of MeCP2 in Sim1-expressing neurons resulted in mice that recapitulated the abnormal physiological stress response that is seen upon MeCP2 dysfunction in the entire brain. Surprisingly, we also uncovered a role for MeCP2 in the regulation of social and feeding behaviors since the Mecp2 conditional knockout (CKO) mice were aggressive, hyperphagic, and obese. This study demonstrates that deleting Mecp2 in a defined brain region is an excellent approach to map the neuronal origins of complex behaviors and provides new insight about the function of MeCP2 in specific neurons.

Synergistic impairment of glucose homeostasis in ob/ob mice lacking functional serotonin 2C receptors

To investigate how serotonin and leptin interact in the regulation of energy balance and glucose homeostasis, we generated a genetic mouse model, the OB2C mouse, which lacks functional serotonin 2C receptors and the adipocyte hormone leptin. The OB2C mice exhibited a dramatic diabetes phenotype, evidenced by a synergistic increase in serum glucose levels and water intake. The severity of the animals' diabetes phenotype would not have been predicted from the phenotypic characterization of mice bearing mutations of either the leptin (OB mutant mice) or the serotonin 2C receptor gene (2C mutant mice). The synergistic impairment in glucose homeostasis developed at an age when OB2C mice did not differ in body weight from OB mice, suggesting that this impairment was not an indirect consequence of increased adiposity. We also demonstrated that the improvement in glucose tolerance in wild-type mice treated with the serotonin releaser and reuptake inhibitor fenfluramine was blunted in 2C mutant mice. These pharmacological and genetic findings provide evidence that the serotonin 2C receptor has direct effects on glucose homeostasis.

Brain-derived neurotrophic factor regulates energy balance downstream of melanocortin-4 receptor

The melanocortin-4 receptor (MC4R) is critically involved in regulating energy balance, and obesity has been observed in mice with mutations in the gene for brain-derived neurotrophic factor (BDNF). Here we report that BDNF is expressed at high levels in the ventromedial hypothalamus (VMH) where its expression is regulated by nutritional state and by MC4R signaling. In addition, similar to MC4R mutants, mouse mutants that expresses the BDNF receptor TrkB at a quarter of the normal amount showed hyperphagia and excessive weight gain on higher-fat diets. Furthermore, BDNF infusion into the brain suppressed the hyperphagia and excessive weight gain observed on higher-fat diets in mice with deficient MC4R signaling. These results show that MC4R signaling controls BDNF expression in the VMH and support the hypothesis that BDNF is an important effector through which MC4R signaling controls energy balance.

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.

Enhanced locomotor, reinforcing, and neurochemical effects of cocaine in serotonin 5-hydroxytryptamine 2C receptor mutant mice

Brain serotonin [5-hydroxytryptamine (5-HT)] systems substantially influence the effects of cocaine; however, the contributions of individual 5-HT receptor subtypes to the regulation of cocaine responses are unclear. A line of mutant mice devoid of 5-HT2C receptors was used to examine the contribution of this receptor subtype to the serotonergic modulation of cocaine responses. Mutants display enhanced exploration of a novel environment and increased sensitivity to the locomotor stimulant effects of cocaine. In an operant intravenous self-administration model under a progressive ratio schedule of reinforcement, mutants display elevated levels of lever pressing for cocaine injections, indicating that the drug is more reinforcing in these mice. Moreover, mutants exhibit enhanced cocaine-induced elevations of dopamine (DA) levels in the nucleus accumbens, a brain region implicated in the stimulant and rewarding properties of cocaine. In contrast, phenotypic differences in dorsal striatal DA levels were not produced by cocaine treatment. These findings strongly implicate 5-HT2C receptors in the serotonergic suppression of DA-mediated behavioral responses to cocaine and as a potential therapeutic target for cocaine abuse.

Estrogen receptor-alpha is required by the supporting somatic cells for spermatogenesis

The gene for estrogen receptor-alpha (ERalpha) was disrupted in embryonic stem cells by homologous recombination and these cells were used to generate mice with a targeted mutation in the ERalpha gene (alphaERKO mice). It was found that males homozygous for the mutation are infertile, indicating that estrogen signaling through this nuclear hormone receptor is required for male reproductive function. Although spermatogenesis appears normal in juvenile and young adult alphaERKO mice, the sperm produced are unable to fertilize eggs in vitro. To determine whether ERalpha is required by somatic or germ cells in the male reproductive tract, we transplanted germ cells from homozygous mutant (ERalpha(-/-)) males to the testes of wild-type (ERalpha(+/+)) males depleted of germ cells by busulfan treatment. The recipients ('surrogate fathers') sired offspring heterozygous for the mutation (ERalpha(+/-)) and carrying the coat-color marker of the infertile donor males. This indicated that ERalpha(-/-) germ cells are able to produce sperm competent to fertilize when they are supported by ERalpha(+/+) somatic cells. When ERalpha(+/-) offspring produced by germ cell transplantation were mated to produce ERalpha(-/-) males, these mice were found to have the same phenotype as originally reported for alphaERKO males. These studies showed that male germ cells do not require ERalpha for regulation of their own genes for development and function, and strongly imply that somatic cells of the male reproductive tract require ERalpha to support the production of sperm that are capable of fertilization.

Haploinsufficiency of protamine-1 or -2 causes infertility in mice

Protamines are the major DNA-binding proteins in the nucleus of sperm in most vertebrates and package the DNA in a volume less than 5% of a somatic cell nucleus. Many mammals have one protamine, but a few species, including humans and mice, have two. Here we use gene targeting to determine if the second protamine provides redundancy to an essential process, or if both protamines are necessary. We disrupted the coding sequence of one allele of either Prm1 or Prm2 in embryonic stem (ES) cells derived from 129-strain mice, and injected them into blastocysts from C57BL/6-strain mice. Male chimeras produced 129-genotype sperm with disrupted Prm1 or Prm2 alleles, but failed to sire offspring carrying the 129 genome. We also found that a decrease in the amount of either protamine disrupts nuclear formation, processing of protamine-2 and normal sperm function. Our studies show that both protamines are essential and that haploinsufficiency caused by a mutation in one allele of Prm1 or Prm2 prevents genetic transmission of both mutant and wild-type alleles.

Spermatogenic cells do not require estrogen receptor-alpha for development or function

Estrogen receptors alpha (ERalpha) and beta (ERbeta) are ligand-dependent transcription factors and members of the nuclear hormone receptor superfamily encoded by separate genes. Male mice homozygous for a mutation in the gene encoding ERalpha are infertile. To determine whether germ cells or somatic cells require ERalpha, germ cells were transplanted from donor males homozygous for the mutation (ERalpha-/-) to testes of wild-type (ERalpha+/+) recipient mice depleted of germ cells. The recipients served as "surrogate fathers" for the infertile ERalpha-/- males. When mated to wild-type females, the recipients sired offspring heterozygous for the mutation (ERalpha+/-) and carrying the coat-color marker of the ERalpha-/- donor mice. These studies show that male germ cells do not require ERalpha for development or to function in fertilization, and imply that male ERalpha-/- mice are infertile due to disruption of estrogen action within somatic cells of the male reproductive system.

Fertilization defects in sperm from mice lacking fertilin beta

Fertilin, a member of the ADAM family, is found on the plasma membrane of mammalian sperm. Sperm from mice lacking fertilin beta were shown to be deficient in sperm-egg membrane adhesion, sperm-egg fusion, migration from the uterus into the oviduct, and binding to the egg zona pellucida. Egg activation was unaffected. The results are consistent with a direct role of fertilin in sperm-egg plasma membrane interaction. Fertilin could also have a direct role in sperm-zona binding or oviduct migration; alternatively, the effects on these functions could result from the absence of fertilin activity during spermatogenesis.

Mouse spermatogenic cell-specific type 1 hexokinase (mHk1-s) transcripts are expressed by alternative splicing from the mHk1 gene and the HK1-S protein is localized mainly in the sperm tail

Unique type 1 hexokinase (HK1) mRNAs are present in mouse spermatogenic cells (mHk1-s). They encode a spermatogenic cell-specific sequence region (SSR) but not the porin-binding domain (PBD) necessary for HK1 binding to porin on the outer mitochondrial membrane. This study determined the origin of the multiple Hk1-s transcripts in mouse spermatogenic cells and verified that they are translated in mouse spermatogenic cells. It also showed that a single mHk1 gene encodes the mHk1 transcripts of somatic cells and the mHk1-sa and mHk1-sb transcripts of spermatogenic cells, that alternative exons are used during mHk1 gene expression in mouse spermatogenic cells, and that mHK1-S is translated in mouse spermatogenic cells and is localized mainly with the fibrous sheath in the tail region, not with the mitochondria in the midpiece of mouse sperm.

HSP70-2 is required for desynapsis of synaptonemal complexes during meiotic prophase in juvenile and adult mouse spermatocytes

Spermatogenic cells synthesize a unique 70-kDa heat shock protein (HSP70-2) during prophase of meiosis I, and targeted disruption of the Hsp70-2 gene has shown that this protein is required for spermatogenic cell differentiation in adult mice. HSP70-2 is associated with synaptonemal complexes formed between paired homologous chromosomes during meiotic prophase. The present study focuses on the nearly synchronous first wave of spermatogenesis in 12- to 28-day old juvenile mice to determine more precisely when HSP70-2 is required and what meiotic processes are affected by its absence. Spermatogenesis in homozygous mutant mice (Hsp70-2[−/−]) proceeded normally until day 15 when increasing numbers of pachytene spermatocytes became apoptotic and differentiation of cells beyond the pachytene stage began to falter. Synaptonemal complexes assembled in Hsp70-2(−/−) mice and spermatocytes developed through the final pachytene substage. However, synaptonemal complexes failed to desynapse and normal diplotene spermatocytes were not observed. Metaphase spermatocytes were not seen in tissue sections from testes of Hsp70-2(−/−) mice, and expression of mRNAs and antigens characteristic of late pachytene spermatocytes (e.g., cyclin A1) and development of spermatids did not occur. Thus, HSP70-2 is required for synaptonemal complex desynapsis, and its absence severely impairs the transition of spermatogenic cells through the late meiotic stages and results in apoptosis beginning with the first wave of germ cell development in juvenile mice.

Allosteric activation and tuning of ligand efficacy in cyclic-nucleotide-gated channels

Despite recent advances in the identification of ligand-binding and voltage-sensing regions of ion channels, the domains that couple such regions to channel opening have not been identified. Moreover, it is uncertain whether ligand binding or depolarization are obligatory steps that must precede channel opening (according to linear reaction schemes) or whether they act to stabilize the channel in an open state that can exist independently of ligand binding or depolarization (according to cyclic allosteric models). By comparing ligand-independent and ligand-dependent channel openings, we now show that retinal and olfactory cyclic-nucleotide-gated channels are activated by a cyclic allosteric mechanism. We further show that an amino-terminal domain, distinct from the pore and ligand-binding motifs, participates in the allosteric gating transition, accounting for differences in the free energy of gating of the two channels. The allosteric transition provides an important mechanism for tuning the physiological response of ligand-binding proteins, such as cyclic-nucleotide-gated channels, to different biological signals.

Targeted disruption of the estrogen receptor gene in male mice causes alteration of spermatogenesis and infertility

The reproductive system of male mice homozygous for a mutation in the estrogen receptor (ER) gene (ER knock-out; ERKO) appears normal at the anatomical level. However, these males are infertile, indicating an essential role for ER-mediated processes in the regulation of male reproduction. Adult ERKO male mice have significantly fewer epididymal sperm than heterozygous or wild-type males. Although spermatogenesis is occurring in some seminiferous tubules of 3- to 5-month-old ERKO males, other tubules either have a dilated lumen and a disorganized seminiferous epithelium with few spermatogenic cells or lack a lumen and contain mainly Sertoli cells. There are no obvious differences in seminiferous tubules at 10 days of age between wild-type and ERKO mice, but the lumen in ERKO males is dilated in all seminiferous tubules by 20 days. However, spermatogenesis progresses and similar numbers of sperm are present in the cauda epididymis of ERKO and wild-type males until 10 weeks of age. Disruption of spermatogenesis and degeneration of the seminiferous tubules become apparent after 10 weeks in the caudal pole of the testis and progresses in a wave to the cranial pole by 6 months. However, the seminal vesicles, coagulating glands, prostate, and epididymis do not appear to be altered morphologically in ERKO mice. Serum testosterone levels are somewhat elevated, but LH and FSH levels are not significantly different from those in wild-type males. Sperm from 8- to 16-week-old mice have reduced motility and are ineffective at fertilizing eggs in vitro. In addition, ERKO males housed overnight with hormone-primed wild-type females produce significantly fewer copulatory plugs than do heterozygous or wild-type males. These results suggest that estrogen action is required for fertility in male mice and that the mutation of the ER in ERKO males leads to reduced mating frequency, low sperm numbers, and defective sperm function.

Targeted gene disruption of Hsp70-2 results in failed meiosis, germ cell apoptosis, and male infertility

In addition to the five 70-kDa heat shock proteins (HSP70) common to germ cells and somatic tissues of mammals, spermatogenic cells synthesize HSP70-2 during meiosis. To determine if this unique stress protein has a critical role in meiosis, we used gene-targeting techniques to disrupt Hsp70-2 in mice. Male mice homozygous for the mutant allele (Hsp70-2 -/-) did not synthesize HSP70-2, lacked postmeiotic spermatids and mature sperm, and were infertile. However, neither meiosis nor fertility was affected in female Hsp70-2 -/- mice. We previously found that HSP70-2 is associated with synaptonemal complexes in the nucleus of meiotic spermatocytes from mice and hamsters. While synaptonemal complexes assembled in Hsp70-2 -/- spermatocytes, structural abnormalities became apparent in these cells by late prophase, and development rarely progressed to the meiotic divisions. Furthermore, analysis of nuclei and genomic DNA indicated that the failure of meiosis in Hsp70-2 -/- mice was coincident with a dramatic increase in spermatocyte apoptosis. These results suggest that HSP70-2 participates in synaptonemal complex function during meiosis in male germ cells and is linked to mechanisms that inhibit apoptosis.

Developmentally regulated expression of Hsp70-2 and a Hsp70-2/lacZ transgene during spermatogenesis

Germ cells synthesize large amounts of HSP70-2 protein during the meiotic phase of spermatogenesis. This developmentally regulated expression of HSP70-2 contrasts with the constitutive or inducible expression of other 70-kDa heat shock proteins (HSP70s). To better understand the genetic regulation of Hsp70-2, we used mRNA primer- extension, reverse transcriptase PCR (RT-PCR), and cDNA sequencing to determine that transcription began as far as 353 bp upstream of the start codon. We also identified a previously unrecognized 239-bp intron which is spliced out of the pre-mRNA transcript to leave a 114 nt 5'-untranslated region. Transgenic mice were then produced to delimit the upstream regulatory region required for developmental expression of Hsp70-2 during spermatogenesis. Results with multiple lines of transgenic mice containing promoter-reporter transgenes with varying lengths of Hsp7-2 sequence indicate that promoter sequences up to 640 bp upstream of the start codon and 287 bp upstream of the transcription start site are required for Hsp70-2/lacZ expression in spermatocytes. Histochemical detection of transgene beta- galactosidase activity was coincident with immunohistochemical detection of HSP70-2 protein, both in the first wave of spermatogenesis in juvenile mice and in ongoing spermatogenesis of adult mice. The distribution of Hsp7O-2 and Hsp7O-2/lacZ mRNAs was determined by Northern blot, in situ hybridization, and RT-PCR, and it was found that upregulation of expression of both Hsp7O-2 and Hsp7O-2/lacZ was specific to the meiotic phase of spermatogenesis.

Boar proacrosin expressed in spermatids of transgenic mice does not reach the acrosome and disrupts spermatogenesis

Transgenic mice that express boar proacrosin were produced to examine mechanisms for targeting hydrolytic enzymes to the acrosome. A 2.3 kb transgene was constructed by ligating the cDNA for boar preproacrosin with the mouse protamine 2 promoter region. Six founder mice that incorporated the transgene were identified by polymerase chain reaction and Southern blot analysis. Northern blots indicated that the two male founders (Ac.2 and Ac.5) and male progeny from three female founders (Ac.3, Ac.4, Ac.6) expressed the transgene mRNA in testis, but not in somatic tissues. In these transgenic animals boar proacrosin was detected by immunohistochemistry in condensing spermatids, but was not localized in the acrosome. This acrosomal targeting defect of the transgene product may result from its delayed expression during the later steps of haploid differentiation. Furthermore, both male founders and all Ac.4 and Ac.6 males were infertile, as determined by multiple matings for at least 2 months. Ac.3 males were either infertile or rarely transmitted the transgene to their offspring. The infertile males mated, produced copulatory plugs, and had seminal vesicle weights and testosterone levels within the normal range. However, they produced significantly fewer spermatozoa and had lower testis weights than controls. Although the mitotic and meiotic phases of spermatogenesis appeared normal by histological criteria, condensing spermatids were missing from most tubules, and multinucleated cells were present in the lumen of seminiferous tubules and in the epididymis. We hypothesize that boar proacrosin which fails to reach the acrosome is activated in these transgenic mice, and that its proteolytic activity disrupts spermatogenesis during spermatid formation.

Exposure of residues in the cyclic nucleotide-gated channel pore: P region structure and function in gating

In voltage-gated ion channels and in the homologous cyclic nucleotide-gated (CNG) channels, the loop between the S5 and S6 transmembrane segments (P region) is thought to form the lining of the pore. To investigate the structure and the role in gating of the P region of the bovine retinal CNG channel, we determined the accessibility of 11 cysteine-substituted P region residues to small, charged sulfhydryl reagents applied to the inside and outside of membrane patches in the open and closed states of the channel. The results suggest that the P region forms a loop that extends toward the central axis of the channel, analogous to the L3 loop of bacterial porin channels. Furthermore, the P region, in addition to forming the ion selectivity filter, functions as the channel gate, the structure of which changes when the channel opens.

Prostaglandin synthase 1 gene disruption in mice reduces arachidonic acid-induced inflammation and indomethacin-induced gastric ulceration

Cyclooxygenases 1 and 2 (COX-1 and COX-2) are key enzymes in prostaglandin biosynthesis and the target enzymes for the widely used nonsteroidal anti-inflammatory drugs. To study the physiological roles of the individual isoforms, we have disrupted the mouse Ptgs1 gene encoding COX-1. Homozygous Ptgs1 mutant mice survive well, have no gastric pathology, and show less indomethacin-induced gastric ulceration than wild-type mice, even though their gastric prostaglandin E2 levels are about 1% of wild type. The homozygous mutant mice have reduced platelet aggregation and a decreased inflammatory response to arachidonic acid, but not to tetradecanoyl phorbol acetate. Ptgs1 homozygous mutant females mated to homozygous mutant males produce few live offspring. COX-1-deficient mice provide a useful model to distinguish the physiological roles of COX-1 and COX-2.

Molecular mechanism of cyclic-nucleotide-gated channel activation

Studies on the activation of ligand- and voltage-gated ion channels have identified regions involved in both ligand binding and voltage sensing, but relatively little is known about how such domains are coupled to channel opening. Here we investigate the structural basis for the activation of cyclic-nucleotide-gated channels, which are directly opened by cytoplasmic cyclic nucleotides but are structurally homologous to voltage-gated channels. By constructing chimaeras between cyclic-nucleotide-gated channels cloned from bovine retinal photoreceptors and catfish olfactory neurons, we identify two distinct domains that are important for ligand binding and channel gating. A putative alpha-helix in the carboxy-terminal binding domain determines the selectivity of the channel for activation by cGMP relative to cAMP. A domain in the amino-terminal region determines the ease with which channels open and thus influences agonist efficacy. We propose that channel opening is coupled to an allosteric conformational change in the binding site which enhances agonist binding. Thus, cyclic nucleotides activate the channel by binding tightly to the open state and stabilizing it.

Aberrant reproductive phenotypes evident in transgenic mice expressing the wild-type mouse estrogen receptor

The estrogen receptor (ER) acts as a transcription factor to regulate multiple cellular functions involved in normal physiology, differentiation, and reproduction. To date, there is no known animal model for studying aberrant ER expression. Therefore, we created transgenic mice expressing the wild-type mouse ER under the control of the mouse metallothionein-I (MT) promoter to determine whether overexpression of the ER would disrupt normal reproductive processes. Five male and one female founder mice were produced, and all were fertile. The progeny from these mice were screened for MT-mER expression by the ribonuclease protection assay. Mice in all six lines were found to express the transgene in a variety of tissues, although generally at low levels. The highest level of expression was observed in the female reproductive tract of line E. Females in all six lines demonstrated aberrant reproductive phenotypes involving processes at parturition and, with some of the lines, a tendency toward reduced fertility. Gestational length was prolonged up to 4 days beyond the normal gestation of 19 days, providing evidence of delayed parturition. In addition, prolonged labor (up to 3 days in length to deliver all pups) and labors requiring cesarean sections for maternal survival demonstrated the occurrence of dystocia in the MT-mER females. As maternal age increased, the incidence of stillborn litters, delayed parturition, and dystocia approached 100% in the transgenic dams. Difficulties at parturition were not observed in nontransgenic control females. These phenotypes suggest that the mechanisms regulating parturition may be perturbed by improper expression of the ER. The MT-mER transgenic mice may provide a novel approach for studying the estrogen-regulated signals involved in parturition and fertility as well as a unique animal model for the human reproductive phenotypes of delayed parturition and dystocia.

Role of H5 domain in determining pore diameter and ion permeation through cyclic nucleotide-gated channels

Ion permeation through membrane channels is thought to be governed by a narrow region of the channel pore termed the selectivity filter, which has been proposed to discriminate among ions by both specific binding and molecular sieving, as determined by pore diameter. Recent evidence suggests that a conserved domain (known as H5, P or SS1-SS2) in voltage-gated potassium, sodium and calcium channels contributes to the lining of the pore. Here we investigate whether the H5 domain determines pore diameter and examine the role of pore diameter in controlling ion permeation. These studies rely on differences in single channel conductance, ion selectivity and apparent pore diameter between cyclic nucleotide-gated channels cloned from bovine retina and catfish olfactory neurons. Using chimaeric retinal-olfactory channels, we find that the H5 domain determines these differences in permeation properties, providing structural evidence that the cyclic nucleotide-gated channels are indeed members of the voltage-gated channel family. Moreover, these results show directly that the H5 domain helps form the selectivity filter and that molecular sieving is important in controlling ion permeation.

Molecular cloning and single-channel properties of the cyclic nucleotide-gated channel from catfish olfactory neurons

We have cloned a functional cDNA encoding the cyclic nucleotide-gated channel selectively expressed in catfish olfactory sensory neurons. The cyclic nucleotide-gated channels share sequence and structural features with the family of voltage-gated ion channels. This homology is most evident in transmembrane region S4, the putative voltage sensor domain, and the H5 domain, thought to form the channel pore. We have characterized the single-channel properties of the cloned catfish channel and compared these properties with the channel in native catfish olfactory sensory neurons. The channel is activated equally well by cAMP and cGMP, shows only a slight voltage dependence of gating, and exhibits a pH- and voltage-dependent subconductance state similar to that observed for the voltage-gated L-type calcium channel.

Teratogenicity of benzoic acid derivatives of retinoic acid in cultured mouse embryos

Isotretinoin (13-cis-RA) is a human teratogen and mouse embryos exposed to 13-cis-RA in vivo exhibit many of the same defects as humans. Early postimplantation mouse embryos exposed to 13-cis-RA in culture exhibit developmental alterations of the visceral arches, similar to those seen after in vivo exposure. Certain benzoic acid derivatives of retinoic acid have been shown to possess activity equal to or greater than retinoic acid in several in vitro systems. This study examines the teratogenic effects of some of these retinoids on mouse embryos in vitro. Day 8 CD-1 mouse embryos were cultured for 48 hours in the presence of these benzoic acid derivatives. With the exception of Ro-15-0778, all compounds produced visceral arch malformations similar to those seen in embryos exposed to 13-cis-RA, but at dramatically different effective concentrations. Extremely low concentrations of the retinoic acid-related compounds tested appear to have detrimental effects on embryonic development and these compounds may be poor candidates for therapeutic use.

Glucocorticoid teratogenesis in mouse whole embryo culture

Glucocorticoids, such as triamcinolone acetonide (TAC-A) and triamcinolone hexacetonide (TAC-HA), are potent inducers of cleft palate in vivo in various mouse strains when administered on day 11 of gestation, whereas they are poor or ineffective inducers of cleft lip when given on day 7. The purpose of the present study was to determine whether glucocorticoids are capable of interfering with early embryonic development in culture. CD-1 mouse embryos were cultured for 48 hours starting either on day 8 (plug day 0) with the embryo inside the yolk sac, or on day 10 with the embryo exteriorized from its functional yolk sac. At the end of the culture period, embryos were examined grossly for malformations and biochemically for altered DNA and protein levels. With the day 8 cultures, TAC-A produced a dose-dependent inhibition of growth along with malformations consisting of cardiac irregularities, abnormal rotation, and irregular neural tube closure. With the day 10 cultures, these malformations were not observed, presumably due to the advanced stage of development when the embryos were exposed to TAC-A; however, TAC-A did produce growth inhibition along with cleft lip. When TAC-HA was administered in vivo to pregnant donor females on day 7, in combination with TAC-A added on day 10 to the culture medium, there was a dramatic increase in the frequency of cleft lip along with other alterations in craniofacial appearance. Our results demonstrate that glucocorticoids are capable of directly affecting embryonic growth and development during the early stages of organogenesis.

Specific craniofacial defects induced by jervine in the cultured rat embryo

The Veratrum-derived steroidal alkaloid, jervine, induces cyclopia and limb malformations in sheep, and various other craniofacial malformations in several other mammalian and avian species. In the present study, the question whether jervine acts directly or indirectly on mammalian embryos to produce malformations and the nature of the target tissue or cells were examined using whole-embryo cultures of the CD rat. Embryos were explanted into culture at the presomite, early neurula stage and cultured in the presence or absence of jervine for 48 hours. Jervine (at 1-5 micrograms/ml) induced an oblong-head appearance and ventrally displaced optic vesicles, with little or no other effects observed on overall growth and development. The specific target tissue in the embryo was found to be the cranial neuroepithelium. This specificity of action is quite unusual since most teratogens examined in whole-embryo culture to date have various nonspecific effects on embryonic growth and differentiation.

Ethanol embryotoxicity: direct effects on mammalian embryos in vitro

Exposure to ethanol retards growth and differentiation in cultured rat embryos during organogenesis. The development of untreated embryos is indistinguishable from growth in utero. These data suggest that the hypoplastic features of children born to chronically alcoholic mothers are due, at least in part, to a direct action of ethanol, which causes reduced embryonic cellular proliferation early in gestation.