The acceptance and attitudes towards using assistive technology for people with stroke in Jordan: caregivers' perspectives

The aim of this study is to evaluate the acceptance and attitudes toward assistive technology (AT) for people with stroke from their caregivers' perspectives in Jordan. Also, this study further validates the Unified Theory of Acceptance and Use of Technology (UTAUT) questionnaire. This is a cross-sectional study that includes a three-sections survey: the first section contains demographic data, the second section includes the Unified Theory of Acceptance and Use of Technology (UTAUT) questionnaire, and the third section consists of two optional open-ended questions. Among 123 caregivers of people with stroke over 18 years of age who participated in this study, 23% were male. The findings indicate a moderate to high acceptance of using AT for stroke survivors, confirm the validity and reliability of the UTAUT questionnaire, and clarify novel issues regarding AT based on the caregivers' perspectives.

Beyond dyadic communication: Network of communication in inflammatory arthritis teams

OBJECTIVE

To explore how communication is perceived and care is negotiated amongst IA healthcare teams by drawing on the perspectives of each team member.

METHOD

This analysis drew on data from an ongoing three-year study exploring team-based IA care. We interviewed 11 participants including two men with IA and their family care providers and healthcare providers. We used a three-staged analytic process and integrated broad tenets of social network theory to understand the relational dimensions of team members experiences.

RESULT

Analysis revealed three themes regarding communication and care: (1) seeking/sharing information, (2) striving to coordinate unified care, and (3) providing patients a voice.

DISCUSSION

This study emphasizes the importance of understanding team dynamics beyond the dyad of patient and care provider. Negotiating power and decision-making in IA care is a dynamic process involving shifting levels of responsibility amongst a care team. Communication-based strategies that extend dyadic interactions may enhance teamwork and health outcomes in chronic conditions.

What does receiving autism diagnosis in adulthood look like? Stakeholders' experiences and inputs

INTRODUCTION

The age of diagnosis is crucial for optimal health outcomes; however, some individuals with Autism Spectrum Disorder (ASD) may not be diagnosed until adulthood. Limited information is available about the lived experience of receiving a diagnosis during adulthood. Thus, we aimed to investigate stakeholders' experiences about the ASD diagnosis during adulthood.

METHOD

We interviewed 18 individuals including 13 adults with ASD who had received a late diagnosis during adulthood and 5 parents of individuals with ASD from various Canadian provinces.

RESULTS

Using a thematic analysis, three main themes emerged: (a) noticing differences and similarities, (b) hindering elements to diagnosis, and (c) emotional response to diagnostic odyssey.

CONCLUSION

This study adds to the literature about experiences of receiving ASD diagnosis in adulthood. Given the impact of diagnosis on individuals, it is important to minimize the barriers to ensure individuals who require ASD-related supports can access them in a timely and effective manner. This study highlights the importance of receiving an ASD diagnosis and facilitates positive health outcomes. The findings from the current study can be used to guide adult diagnostic processes and practices to help make ASD diagnosis more accessible.

Resilience and Coping Strategies in Adults with Autism Spectrum Disorder

Individuals with Autism spectrum disorder (ASD) are prone to stress and anxiety affecting their mental health. Although developing coping and resilience are key to cope with stressors of life, limited research exists. We aimed to explore stakeholders' experiences related to the coping and resilience of adults with ASD. We interviewed 22 participants, including 13 adults with ASD, five parents, and four service provides of adults with ASD from various Canadian provinces. Using thematic analysis, three themes emerged including: (a) societal expectations and conformity, (b) adjusting daily routines, and (c) learning overtime. This study highlights the importance of coping and informs the development of services to help enhance resilience among adults with ASD.

Effectiveness of physical rehabilitation in improving physical functioning and quality of life for long-term-care residents with dementia: a systematic review protocol

OBJECTIVE

The objective of this review is to evaluate the effectiveness of physical rehabilitation versus non-rehabilitation control in improving physical functioning and quality of life in long-term care residents with dementia.

INTRODUCTION

Many long-term-care residents live with dementia and have impaired physical function and poor quality of life. Physical rehabilitation can improve physical function and quality of life for people living with dementia, yet many long-term-care residents with dementia do not receive this intervention, and health care providers are unsure of which rehabilitation interventions are effective. Studies synthesizing effective rehabilitation programs are needed to guide practice in the long-term-care sector where many residents live with dementia. Previous studies have focused broadly on long-term care, specific professions, interventions or outcomes, or people with dementia in the community. Our review will focus on long-term-care residents living with dementia and a broader definition of physical rehabilitation.

INCLUSION CRITERIA

This review will include studies that evaluate physical rehabilitation in comparison with non-rehabilitation controls among long-term-care residents with any severity of dementia. We will include studies that measure the effect on performance-based physical functioning and self- or proxy-reported quality of life.

METHODS

Searches will be conducted in APA PsycINFO (EBSCO), CINAHL (EBSCO), MEDLINE (Ovid), Embase, Scopus, and the Cochrane CENTRAL database with no date or language limitations. Two independent reviewers will conduct a critical appraisal of eligible studies, assess methodological quality, and extract the data. Where possible, studies will be pooled in a statistical meta-analysis.

SYSTEMATIC REVIEW REGISTRATION NUMBER

PROSPERO CRD42022308444.

A personalized biomedical risk assessment infographic for people who smoke with COPD: a qualitative study

Background

Chronic obstructive pulmonary disease (COPD) causes 3 million deaths each year, yet 38% of COPD patients continue to smoke. Despite proof of effectiveness and universal guideline recommendations, smoking cessation interventions are underused in practice. We sought to develop an infographic featuring personalized biomedical risk assessment through future lung function decline prediction (with vs without ongoing smoking) to both prompt and enhance clinician delivery of smoking cessation advice and pharmacotherapy, and augment patient motivation to quit.

Methods

We recruited patients with COPD and pulmonologists from a quaternary care center in Toronto, Canada. Infographic prototype content and design was based on best evidence. After face validation, the prototype was optimized through rapid-cycle design. Each cycle consisted of: (1) infographic testing in a moderated focus group and a clinician interview (recorded/transcribed) (with questionnaire completion); (2) review of transcripts for emergent/critical findings; and (3) infographic modifications to address findings (until no new critical findings emerged). We performed iterative transcript analysis after each cycle and a summative qualitative transcript analysis with quantitative (descriptive) questionnaire analysis.

Results

Stopping criteria were met after 4 cycles, involving 20 patients (58% male) and 4 pulmonologists (50% male). The following qualitative themes emerged: Tool content (infographic content preferences); Tool Design (infographic design preferences); Advantages of Infographic Messaging (benefits of an infographic over other approaches); Impact of Tool on Determinants of Smoking Cessation Advice Delivery (impact on barriers and enablers to delivery of smoking cessation advice in practice); and Barriers and Enablers to Quitting (impact on barriers and enablers to quitting). Patient Likert scale ratings of infographic content and format/usability were highly positive, with improvements in scores for 20/21 questions through the design process. Providers scored the infographic at 77.8% (“superior”) on the Suitability Assessment of Materials questionnaire.

Conclusions

We developed a user preference-based personalized biomedical risk assessment infographic to drive smoking cessation in patients with COPD. Our findings suggest that this tool could impact behavioural determinants of provider smoking-cessation advice delivery, while increasing patient quit motivation. Impacts of the tool on provider care, patient motivation to quit, and smoking cessation success should now be evaluated in real-world settings.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13722-021-00283-1.

Utilization of health services among adults with autism spectrum disorders: Stakeholders' experiences

BACKGROUND

Autism spectrum disorder (ASD) is a lifelong disorder, beginning in early childhood, which often accompanies with several healthcare challenges. There is a need for consistent and continued healthcare services throughout the life of an individual with ASD. The majority of previous studies have examined healthcare services in children with ASD and there is limited evidence about healthcare needs of adults with ASD.

OBJECTIVE

The aim of this project was to capture the experiences of stakeholders including adults with ASD in receiving healthcare services.

METHOD

We interviewed 22 stakeholders, including adults with ASD (n = 13), parents of adults with ASD (n = 5), and service providers (n = 4). Open-ended questions were used to explore their experiences with the healthcare system. We analysed the data thematically to develop the overarching themes.

RESULTS

Three themes emerged from interviews including a) availability and accessibility of healthcare services, b) provision of quality healthcare and service delivery, and c) striving for better health outcomes.

CONCLUSION

This study found that many adults with ASD can experience a continued lack of access to services and the care they receive is often of limited quality. The unmet healthcare needs lead stakeholders to feel stress, frustration, exhaustion, and possible burnout. The detrimental cost of limited services not only impacts adults with ASD but also their caregivers.

Independent living in adults with autism spectrum disorder: Stakeholders' perspectives and experiences

Independent living is a basic human right that enables individuals with disabilities to determine where they live, who they live with and what kind of support that they receive. Limited research exists regarding the challenges that adults with autism spectrum disorder (ASD) may face when attempting to live independently. Given the importance of independent living for adults with ASD, this study aimed to examine the perspectives of stakeholders about independent living among adults with ASD.

METHODS

We recruited a total of 19 stakeholders including adults with ASD and parents of adults with ASD from Canadian provinces. In-depth, semi-structured interviews were conducted to identify factors affecting independent living among adults with ASD. Interviews were transcribed and analyzed using thematic analysis to identify overarching themes.

RESULTS

Three themes emerged in our findings, including: a) Psychophysical stability and daily living; b) Financial management and planning; and c) Integrated community living and independence.

CONCLUSION

The findings from this study suggest that adults with ASD face several challenges related to independent living. Factors related to psychophysical stability and daily living, financial management, and integrated community living and housing were all found to influence the ability of adults with ASD to live independently. By exploring stakeholders' perspectives of independent living for adults with ASD, this study provides some insight that can help inform the development of programs and services to facilitate independent living for adults with ASD.

Healthcare Services During the Transitions to Adulthood Among Individuals with ASD Aged 15-25 Years Old: Stakeholders' Perspectives

Although previous research has shown that the transition to adulthood may be challenging, there exists a lack of research regarding perspectives of stakeholders on the transition of individuals with Autism Spectrum Disorder (ASD). This study aimed to investigate stakeholders' experiences regarding healthcare services for youth with ASD during their transition. We involved 20 stakeholders, including 17 parents of youth with ASD as well as 3 services providers. The study yielded three major themes including: (a) accessibility and quality of care; (b) tensions and conflicts; and (c) navigation and integrated care. The findings can be used to direct change within the healthcare services towards better practices for youth with ASD and increasing the likelihood of positive health outcomes.

Investigating joint attention in a guided interaction between a child with ASD and therapists: A pilot eye-tracking study

Introduction

Deficits in joint attention are commonly seen in children with autism spectrum disorder. Research examining joint attention in autism spectrum disorder commonly uses two broad strategies to cue and measure joint attention: behavioral observation and eye tracking. These strategies trade off prioritizing ecological validity vs. gaze measurement accuracy, with a focus on one sacrificing the other. The purpose of this case study was to develop a method to accurately measure gaze position while maintaining an ecologically valid dyadic interaction.

Methods

A child with autism spectrum disorder completed two developmentally appropriate tabletop activities. Each activity was guided by a different occupational therapist who purposefully used a different interaction style with the child. Mobile eye trackers worn by both the child and the therapist recorded the dyadic interactions. Data collection included audio and video recording of interactive behaviors, eye movements and visual fixations in regions of shared interest.

Results

Differences were detected in gaze use and interactive joint attention behaviors between the therapists working with the child and within the child’s respective dyadic interactions.

Conclusions

The proof of concept method maintained both ecological validity and measurement accuracy of therapist–child joint attention. This method has promise to be scaled for larger studies.

The impact of person–environment–occupation transactions on joint attention in children with autism spectrum disorder: A scoping review

Introduction

Individuals with autism spectrum disorder demonstrate difficulty with joint attention, affecting social and occupational performance. Studies of joint attention in children with autism spectrum disorder employ a variety of instrumentation, environments and occupations. From the occupational therapy perspective, current literature lacks a rigorous analysis of the transactions of person, environment and occupation embedded within the procedures of these studies. The goal of this scoping review was to investigate how these components transact to affect occupational performance.

Method

Using the Person–Environment–Occupation model as an evaluative lens, a scoping review was completed to summarize person, environment and occupation transactions in studies examining joint attention in children aged 6–12 years with autism spectrum disorder.

Results

Six studies were included. Findings indicated that simplified social environments and demonstrations of joint attention promoted higher joint attention performance in children with autism spectrum disorder, at the cost of ecological validity. Maintaining ecological validity in complex social environments resulted in lower joint attention performance.

Conclusion

The Person–Environment–Occupation model can be used to develop an occupational therapy perspective on literature from outside the discipline. There is a relationship between the person, environment, occupation transactions and joint attention in children with autism spectrum disorder.

Effects of Exergaming on Balance of Healthy Older Adults: A Systematic Review and Meta-analysis of Randomized Controlled Trials

Balance is critical for older adults to perform daily activities. However, age-related declines in balance increase the risk of falls and severe injuries, such as bone fractures and head injuries. Exergames have been widely applied to improve health-related outcomes in older adults. This meta-analysis aims to quantify the effects of exergaming interventions on balance performance in healthy older adults. A literature search was performed using PubMed, ScienceDirect, SPORTDiscus, COCHRANE, EBSCO, and EMBASE. A total of 16 experimental studies met inclusion criteria for a full-text review. Data synthesis examined balance functions, including static, dynamic, proactive, and perceived balance abilities when performing daily activities. Intervention protocols of the reviewed studies included an average of two to three 40-minute exergaming sessions per week for 8 weeks. A random effects model identified significant effects in favor of the exergaming group, with moderate effect size in dynamic balance (Hedges' g = 0.36, 95% CI = 0.26-1.30, P < 0.001), and perceived balance (Hedges' g = 0.31, 95% CI = 0.04-0.58, P = 0.02); and considerable effect size in Chair Stand Test (Hedges' g = 0.78, 95% CI = 0.26-1.30, P = 0.003), and balance test batteries (Hedges' g = 0.72, 95% CI = 0.42-1.02, P < 0.001). No significant effect was found in the static balance (Hedges' g = 0.22, 95% CI = -0.31 to 0.76, P = 0.42), or proactive balance (Hedges' g = 0.54, 95% CI = -0.12 to 1.20, P = 0.11). Meta-analysis identified exergaming-associated benefits in older adults' balance function and confidence. This finding supports the feasibility of exergaming as a supplementary approach to improve balance for healthy older adults. Health professionals may optimize treatment effect by integrating exergaming sessions into a traditional balance exercise program.

Design Elements During Development of Videogame Programs for Children with Autism Spectrum Disorder: Stakeholders' Viewpoints

Introduction: Research has demonstrated that videogame programs can be an effective intervention targeting social challenges among children with autism spectrum disorder (ASD). Despite the rapid growth in developing videogame programs, incorporation of stakeholders' views has been limited. Objective: This project aimed to identify the design elements that should be considered during development of videogame programs for children with ASD, from the perspectives of stakeholders. Materials and Methods: We involved 26 stakeholders, including parents of children with ASD, youth with ASD, and clinicians working with individuals with ASD in focus groups and interviews. Results: Thematic analysis yielded three themes: (1) addressing heterogeneity and diverse needs; (2) mirroring real world; and (3) teaching strategies. Conclusion: Incorporating these elements during development of videogame programs can help enhance the outcomes for children with ASD. By including stakeholders' voices, it is assumed that the developed videogame programs may serve as user-friendly and engaging tools to potentially complement traditional interventions when overcoming social difficulties in individuals with ASD.

Social Stories for Children with Autism Spectrum Disorder: Validating the Content of a Virtual Reality Program

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that affects socio-emotional skills and perspective-taking abilities. Although social stories in a form of virtual reality program can help children with ASD, developing them and identifying appropriate responses might be subjective and thus challenging. Using Delphi method, and guided by general case training, we involved 63 parents and clinicians of individuals with ASD, in two rounds of online iteration to refine the stories. Scenarios that reached a 75% agreement level were accepted. This project is the first study to develop and validate a library of 75 short socio-emotional stories that illustrate various types and intensities of emotion in three social contexts of home, school, and community as the content of a virtual reality program.

Biological motion perception is affected by age and cognitive style in children aged 8-15

The current paper aims to address the question of how biological motion perception in different social contexts is influenced by age or also affected by cognitive styles. We examined developmental changes of biological motion perception among 141 school children aged 8-15 using point-light displays in monadic and dyadic social contexts. Furthermore, the cognitive styles of participants were investigated using empathizing-systemizing questionnaires. Results showed that the age and empathizing ability strongly predicted improvement in action perception in both contexts. However the systemizing ability was an independent predictor of performance only in monadic contexts. Furthermore, accuracy of action perception increased significantly from 46.4% (SD = 16.1) in monadic to 62.5% (SD = 11.5) in dyadic social contexts. This study can help to identify the roles of social context in biological motion perception and shows that children with different cognitive styles may present different biological motion perception.

Effect of internal versus external focus of attention on implicit motor learning in children with developmental coordination disorder

Children with developmental coordination disorder (DCD) struggle to learn new motor skills. It is unknown whether children with DCD learn motor skills more effectively with an external focus of attention (focusing on impact of movement on the environment) or an internal focus of attention (focusing on one's body movements) during implicit (unconscious) and explicit (conscious) motor learning.

PURPOSE

This paper aims to determine the trends of implicit motor learning in children with DCD, and how focus of attention influences motor learning in children with DCD in comparison with typically developing children.

METHODS

25 children, aged 8-12, with (n=12) and without (n=13) DCD were randomly assigned to receive instructions that focused attention externally or internally while completing a computer tracking task during acquisition, retention, and transfer phases. The motor task involved tracking both repeated and random patterns, with the repeated pattern indicative of implicit learning.

RESULTS

Children with DCD scored lower on the motor task in all three phases of the study, demonstrating poorer implicit learning. Furthermore, graphical data showed that for the children with DCD, there was no apparent difference between internal and external focus of attention during retention and transfer, while there was an advantage to the external focus of attention group for typically developing children.

CONCLUSION

Children with DCD demonstrate less accuracy than typically developing children in learning a motor task. Also, the effect of focus of attention on motor performance is different in children with DCD versus their typically developing counterparts during the three phases of motor learning.

IMPLICATIONS

Results may inform clinicians how to facilitate motor learning in children with DCD by incorporating explicit learning with either internal or external focus of attention within interventions.

Postural control impairments in individuals with autism spectrum disorder: a critical review of current literature

CONTEXT

Motor impairments in individuals with autism spectrum disorder (ASD) have been frequently reported. In this review, we narrow our focus on postural control impairments to summarize current literature for patterns, underlying mechanisms, and determinants of posture in this population.

EVIDENCE ACQUISITION

A literature search was conducted through Medline, ISI web of Knowledge, Scopus and Google Scholar to include studies between 1992 and February 2013.

RESULTS

Individuals with ASD have problems in maintaining postural control in infancy that well persists into later years. However, the patterns and underlying mechanisms are still unclear.

CONCLUSIONS

Examining postural control as an endophenotype or early diagnostic marker of autism is a conceptual premise which should be considered in future investigations. At the end of the review, methodological recommendations on the assessment of postural control have also been provided.

Effects of visual search vs. auditory tasks on postural control in children with autism spectrum disorder

Recent research in motor control shows the interactive role of cognitive factors in postural control. However, there is little understanding in how children with autism spectrum disorder (ASD) develop their postural behaviors. This study compares the interference of visual or auditory tasks on postural control in children with ASD. We examined 19 children with ASD (10-15 years old) and also 28 age-matched typically developing (TD) children. They were asked to perform two tasks during postural control: (1) a visual searching task (2) an auditory digit span task. Postural performances were measured with a force platform. Results showed that children with ASD indicated higher postural sway scores in visual task vs. auditory task; as root mean square (p=0.04), mean velocity (p=0.01) and sway area (p=0.02) but TD children scores remained unchanged. Children with ASD also showed significantly higher sway scores than TD children in all parameters. We conclude that in addition to primary differences in patterns of postural control of children with ASD compared to TD children, visual and auditory tasks may differently influence the postural control in this population.

Cognitive flexibility impairments in children with autism spectrum disorders: links to age, gender and child outcomes

There are still many questions about the cognitive flexibility in autism spectrum disorder (ASD) that remain unanswered. The goal of current study was to evaluate cognitive flexibility patterns and their demographic, clinical and behavioral correlates in large sample of children with ASD. A total of 123 children (94 boys and 29 girls) with ASD aged 7-14 years were assessed on the Wisconsin card sorting test (WCST). Findings showed that gender but not age was associated with the cognitive flexibility performance in ASD. Individuals who had more parent-reported language deficits, lower level of intelligence and education, and showed lower daily sleep time or more engagement in solitary instead of social daily activities were more likely to demonstrate perseveration. Findings provide tentative evidence of a link between cognitive flexibility deficits and sociodemographic or clinical child outcomes in ASD.

Cross-cultural adaptation, reliability, and validity of the autism treatment evaluation checklist in persian

OBJECTIVE

The objectives of the current study were to translate and adapt Autism Treatment Evaluation Checklist (ATEC) into Persian language and to investigate its reliability and validity in an Iranian autistic sample.

METHODS

A total sample of 134 children with autism spectrum disorders aged 6-15 years were assigned to the study. The process of cross-cultural adaptation was performed according to international methodological steps as following: translation, back-translation, revision by an expert committee and pretest. A sample of 20 primary caregivers of autistic children were pretested. The content validity of the ATEC was reviewed by the expert committee all through the stages. The construct quality of the questionnaire was evaluated by comparison of the adapted version of the instrument with similar tests assessed similar factors. Moreover, the reliability of the questionnaire was evaluated through stability and homogeneity assessments.

FINDINGS

The results showed good content validity and internal consistency (Cronbach's alpha: 0.86-0.93). In relation to construct validity, there was significant correlation between ATEC subscales and raw data obtained from Autism Diagnostic Interview-Revised (ADI-R) (r=0.38-0.79). The Intraclass Correlation Coefficient for the test-retest reliability was excellent for all the subscales and also for total scores (ICC: 0.79 - 0.93).

CONCLUSION

Cross-cultural adaptation of ATEC was successful. The psychometric properties were verified and indicated that the adapted questionnaire is valid and reliable to use in Iranian culture.

General purpose, field-portable cell-based biosensor platform

There are several groups of researchers developing cell-based biosensors for chemical and biological warfare agents based on electrophysiologic monitoring of cells. In order to transition such sensors from the laboratory to the field, a general-purpose hardware and software platform is required. This paper describes the design, implementation, and field-testing of such a system, consisting of cell-transport and data acquisition instruments. The cell-transport module is a self-contained, battery-powered instrument that allows various types of cell-based modules to be maintained at a preset temperature and ambient CO(2) level while in transit or in the field. The data acquisition module provides 32 channels of action potential amplification, filtering, and real-time data streaming to a laptop computer. At present, detailed analysis of the data acquired is carried out off-line, but sufficient computing power is available in the data acquisition module to enable the most useful algorithms to eventually be run real-time in the field. Both modules have sufficient internal power to permit realistic field-testing, such as the example presented in this paper.

Single-molecule spectroscopy of the beta(2) adrenergic receptor: observation of conformational substates in a membrane protein

Single-molecule studies of the conformations of the intact beta(2) adrenergic receptor were performed in solution. Photon bursts from the fluorescently tagged adrenergic receptor in a micelle were recorded. A photon-burst algorithm and a Poisson time filter were implemented to characterize single molecules diffusing across the probe volume of a confocal microscope. The effects of molecular diffusion and photon number fluctuations were deconvoluted by assuming that Poisson distributions characterize the molecular occupation and photon numbers. Photon-burst size histograms were constructed, from which the source intensity distributions were extracted. Different conformations of the beta(2) adrenergic receptor cause quenching of the bound fluorophore to different extents and hence produce different photon-burst sizes. An analysis of the photon-burst histograms shows that there are at least two distinct substates for the native adrenergic membrane receptor. This behavior is in contrast to one peak observed for the dye molecule, rhodamine 6G. We test the reliability and robustness of the substate number determination by investigating the application of different binning criteria. Conformational changes associated with agonist binding result in a marked change in the distribution of photon-burst sizes. These studies provide insight into the conformational heterogeneity of G protein-coupled receptors in the presence and absence of a bound agonist.

Functionally different agonists induce distinct conformations in the G protein coupling domain of the beta 2 adrenergic receptor

G protein-coupled receptors represent the largest class of drug discovery targets. Drugs that activate G protein-coupled receptors are classified as either agonists or partial agonists. To study the mechanism whereby these different classes of activating ligands modulate receptor function, we directly monitored ligand-induced conformational changes in the G protein-coupling domain of the beta(2) adrenergic receptor. Fluorescence lifetime analysis of a reporter fluorophore covalently attached to this domain revealed that, in the absence of ligands, this domain oscillates around a single detectable conformation. Binding to an antagonist does not change this conformation but does reduce the flexibility of the domain. However, when the beta(2) adrenergic receptor is bound to a full agonist, the G protein coupling domain exists in two distinct conformations. Moreover, the conformations induced by a full agonist can be distinguished from those induced by partial agonists. These results provide new insight into the structural consequence of antagonist binding and the basis of agonism and partial agonism.

Agonist-induced conformational changes in the G-protein-coupling domain of the beta 2 adrenergic receptor

The majority of extracellular physiologic signaling molecules act by stimulating GTP-binding protein (G-protein)-coupled receptors (GPCRs). To monitor directly the formation of the active state of a prototypical GPCR, we devised a method to site specifically attach fluorescein to an endogenous cysteine (Cys-265) at the cytoplasmic end of transmembrane 6 (TM6) of the beta(2) adrenergic receptor (beta(2)AR), adjacent to the G-protein-coupling domain. We demonstrate that this tag reports agonist-induced conformational changes in the receptor, with agonists causing a decline in the fluorescence intensity of fluorescein-beta(2)AR that is proportional to the biological efficacy of the agonist. We also find that agonists alter the interaction between the fluorescein at Cys-265 and fluorescence-quenching reagents localized to different molecular environments of the receptor. These observations are consistent with a rotation and/or tilting of TM6 on agonist activation. Our studies, when compared with studies of activation in rhodopsin, indicate a general mechanism for GPCR activation; however, a notable difference is the relatively slow kinetics of the conformational changes in the beta(2)AR, which may reflect the different energetics of activation by diffusible ligands.

The effect of pH on beta(2) adrenoceptor function. Evidence for protonation-dependent activation

The transition of rhodopsin from the inactive to the active state is associated with proton uptake at Glu(134) (1), and recent mutagenesis studies suggest that protonation of the homologous amino acid in the alpha(1B) adrenergic receptor (Asp(142)) may be involved in its mechanism of activation (2). To further explore the role of protonation in G protein-coupled receptor activation, we examined the effects of pH on the rate of ligand-induced conformational change and on receptor-mediated G protein activation for the beta(2) adrenergic receptor (beta(2)AR). The rate of agonist-induced change in the fluorescence of NBD-labeled, purified beta(2)AR was 2-fold greater at pH 6.5 than at pH 8, even though agonist affinity was lower at pH 6.5. This biophysical analysis was corroborated by functional studies; basal (agonist-independent) activation of Galpha(s) by the beta(2)AR was greater at pH 6.5 compared with pH 8.0. Taken together, these results provide evidence that protonation increases basal activity by destabilizing the inactive state of the receptor. In addition, we found that the pH sensitivity of beta(2)AR activation is not abrogated by mutation of Asp(130), which is homologous to the highly conserved acidic amino acids that link protonation to activation of rhodopsin (Glu(134)) and the alpha(1B) adrenergic receptor (Asp(142)).

Mutation of a highly conserved aspartic acid in the beta2 adrenergic receptor: constitutive activation, structural instability, and conformational rearrangement of transmembrane segment 6

Movements of transmembrane segments (TMs) 3 and 6 play a key role in activation of G protein-coupled receptors. However, the underlying molecular processes that govern these movements, and accordingly control receptor activation, remain unclear. To elucidate the importance of the conserved aspartic acid (Asp-130) in the Asp-Arg-Tyr motif of the beta2 adrenergic receptor (beta2AR), we mutated this residue to asparagine (D130N) to mimic its protonated state, and to alanine (D130A) to fully remove the functionality of the side chain. Both mutants displayed evidence of constitutive receptor activation. In COS-7 cells expressing either D130N or D130A, basal levels of cAMP accumulation were clearly elevated compared with cells expressing the wild-type beta2AR. Incubation of COS-7 cell membranes or purified receptor at 37 degrees C revealed also a marked structural instability of both mutant receptors, suggesting that stabilizing intramolecular constraints had been disrupted. Moreover, we obtained evidence for a conformational rearrangement by mutation of Asp-130. In D130N, a cysteine in TM 6, Cys-285, which is not accessible in the wild-type beta2AR, became accessible to methanethiosulfonate ethylammonium, a charged, sulfhydryl-reactive reagent. This is consistent with a counterclockwise rotation or tilting of TM 6 and provides for the first time structural evidence linking charge-neutralizing mutations of the aspartic acid in the DRY motif to the overall conformational state of the receptor. We propose that protonation of the aspartic acid leads to release of constraining intramolecular interactions, resulting in movements of TM 6 and, thus, conversion of the receptor to the active state.

Characterization of ligand-induced conformational states in the beta 2 adrenergic receptor

Drugs acting at G protein coupled receptors can be classified in biological assays as either agonists, partial agonists, neutral antagonists, or as inverse agonists. Very little is known about the actual molecular events and structural changes that occur in the receptor following ligand binding and during transmission of a signal across the membrane. Therefore, the structural basis for the biological classification of drug action remains unknown. To date, the conformational state of G protein coupled receptors has been inferred from the activity of the effector enzyme modulated by the G protein. We have used two different approaches to monitor conformational changes in beta 2 adrenergic receptor. Fluorescence spectroscopy can be used to directly monitor structural changes in purified beta 2 adrenergic receptor in real-time. The emission from many fluorescent molecules is strongly dependent on the polarity of the environment in which they are located. Thus, fluorescent probes covalently bound to proteins can be used as sensitive indicators of conformational changes and protein-protein interactions. In addition, we examined functional differences between agonists and partial agonists using fusion proteins between wild-type beta 2 receptor or a constitutively active beta 2 receptor mutant and Gs alpha. These receptor-G protein fusion proteins guarantee highly efficient coupling with a defined stoichiometry. The results of these experiments will be discussed in the context of current models of G protein coupled receptor activation.

Examination of ligand-induced conformational changes in the beta2 adrenergic receptor

The environmentally sensitive and cysteine reactive fluorescent probe, IANBD, was used to monitor ligand-induced structural changes in the beta2 adrenergic receptor (beta2AR) by fluorescent spectroscopy. We found that agonists caused a dose-dependent and reversible decrease in fluorescence from the purified IANBD-labeled beta2AR. This suggested that agonists promote a conformational change in the receptor that leads to an increase in the polarity of the environment around one or more IANBD labeled cysteines. The wildtype receptor contains eight free cysteines and mutagenesis and peptide mapping experiments have indicated that several of these sites are accessible for chemical derivatization. Thus, to identify the cysteine(s) involved in the agonist-induced change in fluorescence and thereby map agonist-induced conformational changes in the beta2AR, we generated a series of mutant receptors having limited numbers of cysteines available for fluorescent labeling. Fluorescence spectroscopy analysis of the purified and site-selectively IANBD-labeled mutants showed that IANBD labeled 125Cys and 285Cys are responsible for the observed changes in fluorescence consistent with movements of TM III and VI in response to agonist binding.

Agonists induce conformational changes in transmembrane domains III and VI of the beta2 adrenoceptor

Agonist binding to G protein-coupled receptors is believed to promote a conformational change that leads to the formation of the active receptor state. However, the character of this conformational change which provides the important link between agonist binding and G protein coupling is not known. Here we report evidence that agonist binding to the beta2 adrenoceptor induces a conformational change around 125Cys in transmembrane domain (TM) III and around 285Cys in TM VI. A series of mutant beta2 adrenoceptors with a limited number of cysteines available for chemical derivatization were purified, site-selectively labeled with the conformationally sensitive, cysteine-reactive fluorophore IANBD and analyzed by fluorescence spectroscopy. Like the wild-type receptor, mutant receptors containing 125Cys and/or 285Cys showed an agonist-induced decrease in fluorescence, while no agonist-induced response was observed in a receptor where these two cysteines were mutated. These data suggest that IANBD bound to 125Cys and 285Cys are exposed to a more polar environment upon agonist binding, and indicate that movements of transmembrane segments III and VI are involved in activation of G protein-coupled receptors.

A DNA minor groove-binding ligand both potentiates and arrests transcription by RNA polymerase II. Elongation factor SII enables readthrough at arrest sites

RNA polymerase II encounters various obstacles to transcript elongation both in vivo and in vitro. These include DNA sequence elements and protein bound to the major groove of DNA. Elongation factor SII binds to RNA polymerase II and enables the enzyme to bypass these impediments. SII also activates nascent RNA cleavage by the arrested transcription elongation complex, an activity intimately involved in the readthrough process. Here we identify another type of reversible blockage to RNA polymerase II transcription, the antitumor antibiotic distamycin, which binds in the minor groove of A + T-rich DNA. SII facilitates readthrough of arrest sites resulting from DNA-binding of the drug. In response to SII, these complexes cleave their nascent RNA chains. These findings confirm that SII is a general elongation factor that potentiates transcription through a variety of impediments. They also strengthen the idea that SII stimulates transcription by activating nascent RNA cleavage. In some cases, distamycin can potentiate transcription through a naturally occurring pause site. We also show that the template undergoes a conformational change in the presence of distamycin. This suggests that distamycin can transform DNA from an elongation-non-permissive configuration into an elongation-permissive form and we take this as independent evidence confirming that DNA structure influences transcription elongation by RNA polymerase II.

Transcription elongation by RNA polymerase II: mechanism of SII activation

RNA chain elongation by RNA polymerase is a dynamic process. Techniques that allow the isolation of active elongation complexes have enabled investigators to describe individual steps in the polymerization of RNA chains. This article will describe recent studies of elongation by RNA polymerase II (pol II). At least four types of blockage to chain elongation can be overcome by elongation factor SII: (a) naturally occurring "arrest" sequences, (b) DNA-bound protein, (c) drugs bound in the DNA minor groove, and (d) chain-terminating substrates incorporated into the RNA chain. SII binds to RNA polymerase II and stimulates a ribonuclease activity that shortens nascent transcripts from their 3' ends. This RNA cleavage is required for chain elongation from some template positions. As a result, the pol II elongation complex can repeatedly shorten and reextend the nascent RNA chain in a process we refer to as cleavage-resynthesis. Hence, assembly of large RNAs does not necessarily proceed in a direct manner. The ability to shorten and reextend nascent RNAs means that a transcription impediment through which only half the enzyme molecules can proceed per encounter, can be overcome by 99% of the molecules after six iterations of cleavage-resynthesis. Surprisingly, the boundaries of the elongation complex do not move upstream after RNA cleavage. The physico-chemical alterations in the elongation complex that accompany RNA cleavage and permit renewed chain elongation are not yet understood.

The RNA polymerase II elongation complex. Factor-dependent transcription elongation involves nascent RNA cleavage

Regulation of transcription elongation is an important mechanism in controlling eukaryotic gene expression. SII is an RNA polymerase II-binding protein that stimulates transcription elongation and also activates nascent transcript cleavage by RNA polymerase II in elongation complexes in vitro (Reines, D. (1992) J. Biol. Chem. 267, 3795-3800). Here we show that SII-dependent in vitro transcription through an arrest site in a human gene is preceded by nascent transcript cleavage. RNA cleavage appeared to be an obligatory step in the SII activation process. Recombinant SII activated cleavage while a truncated derivative lacking polymerase binding activity did not. Cleavage was not restricted to an elongation complex arrested at this particular site, showing that nascent RNA hydrolysis is a general property of RNA polymerase II elongation complexes. These data support a model whereby SII stimulates elongation via a ribonuclease activity of the elongation complex.