Evaluating Osteoarthritis Management Programs: outcome domain recommendations from the OARSI Joint Effort Initiative.

OBJECTIVE: To develop sets of core and optional recommended domains for describing and evaluating Osteoarthritis Management Programs (OAMPs), with a focus on hip and knee Osteoarthritis (OA). DESIGN: We conducted a 3-round modified Delphi survey involving an international group of researchers, health professionals, health administrators and people with OA. In Round 1, participants ranked the importance of 75 outcome and descriptive domains in five categories: patient impacts, implementation outcomes, and characteristics of the OAMP and its participants and clinicians. Domains ranked as "important" or "essential" by ≥80% of participants were retained, and participants could suggest additional domains. In Round 2, participants rated their level of agreement that each domain was essential for evaluating OAMPs: 0 = strongly disagree to 10 = strongly agree. A domain was retained if ≥80% rated it ≥6. In Round 3, participants rated remaining domains using same scale as in Round 2; a domain was recommended as "core" if ≥80% of participants rated it ≥9 and as "optional" if ≥80% rated it ≥7. RESULTS: A total of 178 individuals from 26 countries participated; 85 completed all survey rounds. Only one domain, "ability to participate in daily activities", met criteria for a core domain; 25 domains met criteria for an optional recommendation: 8 Patient Impacts, 5 Implementation Outcomes, 5 Participant Characteristics, 3 OAMP Characteristics and 4 Clinician Characteristics. CONCLUSION: The ability of patients with OA to participate in daily activities should be evaluated in all OAMPs. Teams evaluating OAMPs should consider including domains from the optional recommended set, with representation from all five categories and based on stakeholder priorities in their local context.

Measures of cardiovascular function suggest autonomic nervous system dysregulation after surgical induction of joint injury in the male Lewis rat.

OBJECTIVES: Functional changes in the autonomic nervous system may help explain variability in the progression of knee osteoarthritis (OA). Thus, the objective of this study was to evaluate autonomic nervous system shifts, measured via heart rate response variables, in rat knee joint injury and OA models. METHODS: Cardiovascular characteristics were measured at baseline and bi-weekly for 8 weeks after skin incision, medial collateral ligament transection (MCLT), or MCLT+medial meniscus transection (MCLT+MMT). Heart rate was also assessed during a mild stressor (elevated maze). At endpoint, cardiovascular responses to mechanical knee stimuli were evaluated, as well as responses to 1-phenylbiguanide, a 5HT3A receptor agonist with reported ability to stimulate vagal responses. RESULTS: During low activity, a slower heart rate occurred in MCLT (299 ± 10 bpm) and MCLT+MMT (310 ± 10 bpm) animals compared to controls (325 ± 10 bpm). Furthermore, patellar ligament mechanical stimuli produced an immediate decrease in heart rate and blood pressure in all groups. Finally, a larger drop in heart rate was observed in MCLT (252 ± 40 bpm) and MCLT+MMT (263 ± 49 bpm) following administration of 1-phenylbiguanide compared to skin incision (168 ± 45 bpm). CONCLUSIONS: Acute mechanical stimulation of the patellar ligament produced drops in heart rate, suggesting a possible joint-brain connection that modulates autonomic responses. With both joint injury, cardiac vagal activation was altered in response to pharmacological stimulation, with chronic longitudinal heart rate reduction. These data provide some preliminary evidence of potential functional shifts in autonomic nervous system function in models of joint injury and OA.

Epidemiology of osteoarthritis.

OBJECTIVE: To summarize the current state of the evidence regarding osteoarthritis (OA) prevalence, incidence and risk factors at the person-level and joint-level. DESIGN: This was a narrative review that took a comprehensive approach regarding inclusion of potential risk factors. The review complements prior reviews of OA epidemiology, with a focus on new research and emerging topics since 2017, as well as seminal studies. RESULTS: Studies continue to illustrate the high prevalence of OA worldwide, with a greater burden among older individuals, women, some racial and ethnic groups, and individuals with lower socioeconomic status. Modifiable risk factors for OA with the strongest evidence are obesity and joint injury. Topics of high interest or emerging evidence for a potential association with OA risk or progression include specific vitamins and diets, high blood pressure, genetic factors, metformin use, bone mineral density, abnormal joint shape and malalignment, and lower muscle strength/quality. Studies also continue to highlight the heterogenous nature of OA, with strong interest in understanding and defining OA phenotypes. CONCLUSIONS: OA is an increasingly prevalent condition with worldwide impacts on many health outcomes. The strong evidence for obesity and joint injury as OA risk factors calls for heightened efforts to mitigate these risks at clinical and public health levels. There is also a need for continued research regarding how potential person- and joint-level risk factors may interact to influence the development and progression of OA.

Spatially-resolved nanometer-scale measurement of cartilage extracellular matrix mobility.

OBJECTIVE: Tissues have complex structures, comprised of solid and fluid phases. Improved understanding of interactions between joint fluid and extracellular matrix (ECM) is required in models of cartilage mechanics. X-ray photon correlation spectroscopy (XPCS) directly measures nanometer-scale dynamics and can provide insight into biofluid-biosolid interactions in cartilage. This study applies XPCS to evaluate dynamic interactions between intact cartilage and biofluids. DESIGN: Cartilage biopsies were collected from bovine femoral condyles. During XPCS measurements, cartilage samples were exposed to different fluids: deionized water, PBS, synovial fluid, or sonicated synovial fluid. ECM-biofluid interactions were also assessed at different length scales and different depths from the cartilage surface. RESULTS: Using XPCS, cartilage ECM mobility was detected at length scales from 50 to 207 nm. As length scale decreased, time scale for autocorrelation decay decreased, suggesting smaller ECM components are more mobile. ECM dynamics were slowed by dehydrating the sample, demonstrating XPCS assesses matrix mobility in hydrated environments. At all length scales, the matrix was more mobile in deionized water and slowest in synovial fluid. Using the 207 nm length scale assessment, ECM dynamics in synovial fluid were fastest at the cartilage surface and progressively slowed as depth into the sample increased, demonstrating XPCS can assess spatial distribution of ECM dynamics. Finally, ECM mobility increased for degraded synovial fluid. CONCLUSIONS: This study demonstrates the potential of XPCS to provide unique insights into nanometer-scale cartilage ECM mobility in a spatially resolved manner and illustrates the importance of biosolid-biofluid interactions in dictating ECM dynamics.

Development of a core capability framework for qualified health professionals to optimise care for people with osteoarthritis: an OARSI initiative.

OBJECTIVE: Develop a generic trans-disciplinary, skills-based capability framework for health professionals providing care for people with OA. DESIGN: e-Delphi survey. An international inter-professional Delphi Panel (researchers; clinicians; consumer representatives) considered a draft framework (adapted from elsewhere) of 131 specific capabilities mapped to 14 broader capability areas across four domains (A: person-centred approaches; B: assessment, investigation and diagnosis; C: management, interventions and prevention; D: service and professional development). Over three rounds, the Panel rated their agreement (Likert or numerical rating scales) on whether each specific capability in Domains B and C was essential (core) for all health professionals when providing care for all people with OA. Those achieving consensus (≥80% of Panel) rating of ≥ seven out of ten (Round 3) were retained. Generic domains (A and D) were included in the final framework and amended based on Panel comments. RESULTS: 173 people from 31 countries, spanning 18 disciplines and including 26 consumer representatives, participated. The final framework comprised 70 specific capabilities across 13 broad areas i) communication; ii) person-centred care; iii) history-taking; iv) physical assessment; v) investigations and diagnosis; vi) interventions and care planning; vii) prevention and lifestyle interventions; viii) self-management and behaviour change; ix) rehabilitative interventions; x) pharmacotherapy; xi) surgical interventions; xii) referrals and collaborative working; and xiii) evidence-based practice and service development). CONCLUSION: Experts agree that health professionals require an array of skills in person-centred approaches; assessment, investigation and diagnosis; management, interventions and prevention; and service and professional development to provide optimal care for people with OA.

A graphic user interface for the evaluation of knee osteoarthritis (GEKO): an open-source tool for histological grading.

OBJECTIVE: In osteoarthritis (OA) models, histology is commonly used to evaluate the severity of joint damage. Unfortunately, semi-quantitative histological grading systems include some level of subjectivity, and quantitative grading systems can be tedious to implement. The objective of this work is to introduce an open source, graphic user interface (GUI) for quantitative grading of knee OA. METHODS: Inspired by the 2010 OARSI histopathology recommendations for the rat, our laboratory has developed a GUI for the evaluation of knee OA, nicknamed GEKO. In this work, descriptions of the quantitative measures acquired by GEKO are presented and measured in 42 histological images from a rat knee OA model. Using these images, across-session and within-session reproducibility for individual graders is evaluated, and inter-grader reliability across different levels of OA severity is also assessed. RESULTS: GEKO allowed histological images to be quantitatively scored in less than 1 min per image. In addition, intra-class coefficients (ICCs) were largely above 0.8 for across-session reproducibility, within-session reproducibility, and inter-grader reliability. These data indicate GEKO aided in the reproducibility and repeatability of quantitative OA grading across graders and grading sessions. CONCLUSIONS: Our data demonstrate GEKO is a reliable and efficient method to calculate quantitative histological measures of knee OA in a rat model. GEKO reduced quantitative grading times relative to manual grading systems and allowed grader reproducibility and repeatability to be easily assessed within a grading session and across time. Moreover, GEKO is being provided as a free, open-source tool for the OA research community.

Physical therapy vs internet-based exercise training for patients with knee osteoarthritis: results of a randomized controlled trial.

OBJECTIVE: To compare the effectiveness of physical therapy (PT, evidence-based approach) and internet-based exercise training (IBET), each vs a wait list (WL) control, among individuals with knee osteoarthritis (OA). DESIGN: Randomized controlled trial of 350 participants with symptomatic knee OA, allocated to standard PT, IBET and WL control in a 2:2:1 ratio, respectively. The PT group received up to eight individual visits within 4 months. The IBET program provided tailored exercises, video demonstrations, and guidance on progression. The primary outcome was the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC, range 0 [no problems]-96 [extreme problems]), assessed at baseline, 4 months (primary time point) and 12 months. General linear mixed effects modeling compared changes in WOMAC among study groups, with superiority hypotheses testing differences between each intervention group and WL and non-inferiority hypotheses comparing IBET with PT. RESULTS: At 4-months, improvements in WOMAC score did not differ significantly for either the IBET or PT group compared with WL (IBET: -2.70, 95% Confidence Interval (CI) = -6.24, 0.85, P = 0.14; PT: -3.36, 95% (CI) = -6.84, 0.12, P = 0.06). Similarly, at 12-months mean differences compared to WL were not statistically significant for either group (IBET: -2.63, 95% CI = -6.37, 1.11, P = 0.17; PT: -1.59, 95% CI = -5.26, 2.08, P = 0.39). IBET was non-inferior to PT at both time points. CONCLUSIONS: Improvements in WOMAC score following IBET and PT did not differ significantly from the WL group. Additional research is needed to examine strategies for maximizing benefits of exercise-based interventions for patients with knee OA. TRIAL REGISTRATION: NCT02312713.

Unique spatiotemporal and dynamic gait compensations in the rat monoiodoacetate injection and medial meniscus transection models of knee osteoarthritis.

OBJECTIVE: In rodent osteoarthritis (OA) models, behavioral changes are often subtle and require highly sensitive methods to detect these changes. Gait analysis is one assay that may provide sensitive, quantitative measurement of these behavioral changes. To increase detection sensitivity of gait assessments relative to spatiotemporal gait collection alone, we combined our spatiotemporal and dynamic gait collection systems. Using this combined system, gait was assessed in the rat medial meniscus transection (MMT) model and monoiodoacetate (MIA) injection model of knee OA. DESIGN: 36 male Lewis rats were separated into MMT (n = 8), medial collateral ligament transection (MCLT) (n = 8), skin incision (n = 4), MIA injection (n = 8), and saline injection (n = 8) groups. After initiation of OA, gait data were collected weekly in each group out to 4 weeks. RESULTS: The MMT and MIA injection models produced unique pathologic gait profiles, with MMT animals developing a shuffling gait and MIA injection animals exhibiting antalgic gait. Spatiotemporal changes were also observed in the MMT model at week 1 (P < 0.01), but were not observed in the MIA injection model until week 3 (P < 0.01). Dynamic gait changes were observed in both models as early as 1 week post-surgery (P < 0.01). CONCLUSION: Combined analysis of spatiotemporal and dynamic gait data increased detection sensitivity for gait modification in two rat OA models. Analyzing the combined gait data provided a robust characterization of the pathologic gait produced by each model. Furthermore, this characterization revealed different patterns of gait compensations in two common rat models of knee OA.

Comparing intra-articular CTXII levels assessed via magnetic capture or lavage in a rat knee osteoarthritis model.

OBJECTIVE: Parallel measures of osteoarthritis (OA) across species can help evaluate OA models relative to humans. Toward this need, our group recently developed a magnetic nanoparticle-based technology, termed magnetic capture, to analyze biomarkers within a rat knee. The objectives of this study were to directly compare magnetic capture to lavage, and assess c-telopeptide of collagen type II (CTXII) in the rat medial meniscus transection (MMT) model of knee OA. DESIGN: MMT surgery was performed in 30 male Lewis rats (3 months, 250 g). Using lavage or magnetic capture, CTXII was assessed in the OA-affected and contralateral knee at 1 week (n = 6 per group) or 4 weeks (n = 8 per group) after surgery. RESULTS: While lavage detected elevated CTXII concentrations in the OA-affected knee at 1 week (P = 0.002), magnetic capture detected elevated CTXII levels in the OA-affected knee at 4 weeks (P = 0.016). While magnetic capture did not detect significant elevation of CTXII at week 1, five of six rats evaluated with magnetic capture had higher CTXII levels in the OA-affected joint relative to the contralateral limb. Moreover, with magnetic capture, CTXII levels increased from 1 week to 4 weeks, corresponding to histological damage. CTXII concentrations evaluated via lavage were relatively constant across time. CONCLUSIONS: Magnetic capture and lavage evaluate CTXII in different ways: Magnetic capture measures total CTXII in the joint, while lavage measures concentration. Our data indicate magnetic capture may be advantageous at later time points, where CTXII can be diluted by effusions.

Effects of cocoa-enriched diet on orofacial pain in a murine model.

OBJECTIVES: To investigate and discuss the effects of cocoa on orofacial pain. SETTING AND SAMPLE POPULATION: The Department of Orthodontics at the University of Florida (UF). Male and female hairless rats (N=20/group) were tested. MATERIALS AND METHODS: Rats were tested using the Orofacial Pain Assessment Device (OPAD) before and after changing their food from the standard chow to a cocoa-enriched or control-equivalent diet. RESULTS: Male rats fed the cocoa diet had a significantly higher operant pain index when tested at 37°C as compared to control diet-fed animals. Female rats on the cocoa diet had a significantly higher pain index when tested at 18°C and 44°C, as compared to animals fed the control diet. Capsaicin-induced pain was inhibited, with cocoa-diet male rats having a significantly higher pain index than control-diet male rats and cocoa-diet female rats at both 37°C and 44°C. Cocoa-diet female rats had a significantly higher pain index at 44°C than control-diet females. Mechanical sensitivity was affected following capsaicin cream, with a significantly decreased tolerated bottle distance in both cocoa- and control-diet animals, but there was no difference between cocoa- and control-diet groups. CONCLUSION: Using the OPAD operant system, we demonstrated that a diet rich in cocoa was effective in inhibiting neurogenic inflammatory pain in rats. This has implications for the use of novel alternative therapies such as diet modification for pain control.

Gait analysis methods for rodent models of arthritic disorders: reviews and recommendations.

Gait analysis is a useful tool to understand behavioral changes in preclinical arthritis models. While observational scoring and spatiotemporal gait parameters are the most widely performed gait analyses in rodents, commercially available systems can now provide quantitative assessments of spatiotemporal patterns. However, inconsistencies remain between testing platforms, and laboratories often select different gait pattern descriptors to report in the literature. Rodent gait can also be described through kinetic and kinematic analyses, but systems to analyze rodent kinetics and kinematics are typically custom made and often require sensitive, custom equipment. While the use of rodent gait analysis rapidly expands, it is important to remember that, while rodent gait analysis is a relatively modern behavioral assay, the study of quadrupedal gait is not new. Nearly all gait parameters are correlated, and a collection of gait parameters is needed to understand a compensatory gait pattern used by the animal. As such, a change in a single gait parameter is unlikely to tell the full biomechanical story; and to effectively use gait analysis, one must consider how multiple different parameters contribute to an altered gait pattern. The goal of this article is to review rodent gait analysis techniques and provide recommendations on how to use these technologies in rodent arthritis models, including discussions on the strengths and limitations of observational scoring, spatiotemporal, kinetic, and kinematic measures. Recognizing rodent gait analysis is an evolving tool, we also provide technical recommendations we hope will improve the utility of these analyses in the future.

Clinical algorithms to aid osteoarthritis guideline dissemination.

BACKGROUND: Numerous scientific organisations have developed evidence-based recommendations aiming to optimise the management of osteoarthritis (OA). Uptake, however, has been suboptimal. The purpose of this exercise was to harmonize the recent recommendations and develop a user-friendly treatment algorithm to facilitate translation of evidence into practice. METHODS: We updated a previous systematic review on clinical practice guidelines (CPGs) for OA management. The guidelines were assessed using the Appraisal of Guidelines for Research and Evaluation for quality and the standards for developing trustworthy CPGs as established by the National Academy of Medicine (NAM). Four case scenarios and algorithms were developed by consensus of a multidisciplinary panel. RESULTS: Sixteen guidelines were included in the systematic review. Most recommendations were directed toward physicians and allied health professionals, and most had multi-disciplinary input. Analysis for trustworthiness suggests that many guidelines still present a lack of transparency. A treatment algorithm was developed for each case scenario advised by recommendations from guidelines and based on panel consensus. CONCLUSION: Strategies to facilitate the implementation of guidelines in clinical practice are necessary. The algorithms proposed are examples of how to apply recommendations in the clinical context, helping the clinician to visualise the patient flow and timing of different treatment modalities.

OARSI Clinical Trials Recommendations: Design and conduct of implementation trials of interventions for osteoarthritis.

Rigorous implementation research is important for testing strategies to improve the delivery of effective osteoarthritis (OA) interventions. The objective of this manuscript is to describe principles of implementation research, including conceptual frameworks, study designs and methodology, with specific recommendations for randomized clinical trials of OA treatment and management. This manuscript includes a comprehensive review of prior research and recommendations for implementation trials. The review of literature included identification of seminal articles on implementation research methods, as well as examples of previous exemplar studies using these methods. In addition to a comprehensive summary of this literature, this manuscript provides key recommendations for OA implementation trials. This review concluded that to date there have been relatively few implementation trials of OA interventions, but this is an emerging area of research. Future OA clinical trials should routinely consider incorporation of implementation aims to enhance translation of findings.

Racial differences in osteoarthritis pain and function: potential explanatory factors.

OBJECTIVE: This study examined factors underlying racial differences in pain and function among patients with hip and/or knee osteoarthritis (OA). METHODS: Participants were n=491 African Americans and Caucasians enrolled in a clinical trial of telephone-based OA self-management. Arthritis Impact Measurement Scales-2 (AIMS2) pain and function subscales were obtained at baseline. Potential explanatory variables included arthritis self-efficacy, AIMS2 affect subscale, problem- and emotion-focused pain coping, demographic characteristics, body mass index, self-reported health, joint(s) with OA, symptom duration, pain medication use, current exercise, and AIMS2 pain subscale (in models of function). Variables associated with both race and pain or function, and which reduced the association of race with pain or function by >or=10%, were included in final multivariable models. RESULTS: In simple linear regression models, African Americans had worse scores than Caucasians on AIMS2 pain (B=0.65, P=0.001) and function (B=0.59, P<0.001) subscales. In multivariable models race was no longer associated with pain (B=0.03, P=0.874) or function (B=0.07, P=0.509), indicating these associations were accounted for by other covariates. Variables associated with worse AIMS2 pain and function were: worse AIMS2 affect scores, greater emotion-focused coping, lower arthritis self-efficacy, and fair or poor self-reported health. AIMS2 pain scores were also significantly associated with AIMS2 function. CONCLUSION: Factors explaining racial differences in pain and function were largely psychological, including arthritis self-efficacy, affect, and use of emotion-focused coping. Self-management and psychological interventions can influence these factors, and greater dissemination among African Americans may be a key step toward reducing racial disparities in pain and function.

Symptoms of the knee and hip in individuals with and without limb length inequality.

OBJECTIVE: This cross-sectional study examined the association of limb length inequality (LLI) with chronic joint symptoms at the hip and knee in a large, community-based sample, adjusting for the presence of radiographic osteoarthritis (OA) and other confounders. METHODS: The total study group comprised 3012 participants with complete knee symptoms data, 3007 participants with complete hip symptoms data, and 206 with LLI>or=2 cm. Presence of chronic knee symptoms was defined as report of pain, aching, or stiffness (symptoms) of the knee on most days. Presence of chronic hip symptoms was defined as hip pain, aching, or stiffness on most days or groin pain. Multiple logistic regression models were used to examine the relationship of LLI with knee and hip symptoms, while adjusting for demographic and clinical factors, radiographic knee or hip OA and history of knee or hip problems (joint injury, fracture, surgery, or congenital anomalies). RESULTS: Participants with LLI were more likely than those without LLI to have knee symptoms (56.8% vs 43.0%, P<0.001), and hip symptoms (49.5% vs 40.0%, P=0.09). In adjusted models, knee symptoms were significantly associated with presence of LLI (adjusted odds ratio [aOR]=1.41, 95% confidence interval, [95% CI] 1.02-1.97), but the relationship between hip symptoms and LLI (aOR=1.20, 95% CI 0.87-1.67) was not statistically significant. CONCLUSION: LLI was moderately associated with chronic knee symptoms and less strongly associated with hip symptoms. LLI may be a new modifiable risk factor for therapy of people with knee or hip symptoms.

Racial differences in self-reported pain and function among individuals with radiographic hip and knee osteoarthritis: the Johnston County Osteoarthritis Project.

OBJECTIVE: This study compared pain and function among African Americans and Caucasian with radiographic hip and/or knee osteoarthritis (OA), controlling for radiographic severity and other patient characteristics. METHODS: Participants were 1368 individuals (32% African American) from the Johnston County Osteoarthritis Project with only knee OA, only hip OA, and both knee and hip OA. Linear regression models examined racial differences in Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) total scores and pain and function subscales, adjusting for radiographic severity, age, gender, education, body mass index (BMI), depressive symptoms, and WOMAC pain (last variable in models of function). RESULTS: Among those with only knee OA, African Americans had significantly worse mean WOMAC total scores than Caucasian (32.8 vs 24.3, P<0.001), and worse pain and function scores (P<0.001). Racial differences in WOMAC total, pain, and function scores persisted when controlling for radiographic severity and demographic factors but were not significant when also controlling for BMI and depressive symptoms. In models of WOMAC function, pain was the most strongly associated variable and substantially reduced the association of race with function. There were no racial differences in WOMAC scores among those with only hip OA or with both knee and hip OA. CONCLUSION: Among participants with knee OA, racial differences in pain and function may be explained by BMI and depressive symptoms, and racial differences in function may also be largely influenced by pain. Improving management of weight and depressive symptoms may be key steps toward reducing racial disparities in knee OA symptoms.

Daily pain variations among patients with hand, hip, and knee osteoarthritis.

OBJECTIVE: This study examined within-day osteoarthritis (OA)-related pain patterns and associated patient characteristics. METHODS: Participants with physician diagnoses and self-reported symptoms of hand (N=40), hip (N=32), and knee (N=85) OA recorded pain using a handheld computer on one weekday and one weekend day, with ratings beginning immediately after waking, then approximately every 2h following. Pain was rated on a sliding visual analog scale with hidden coding of 1-100. Multivariable linear mixed models examined associations of patient demographic characteristics, enrollment site (Durham VA Medical Center vs Duke University Medical Center), joint site, body mass index, and pain medication use with within-day pain range (maximum minus minimum pain rating) and area under the curve (AUC) of pain ratings, which incorporates the magnitude of all pain measurements. RESULTS: Pain patterns differed substantially across individuals. The sample means of the average, maximum, and minimum weekday pain scores were 35.3, 54.4, and 17.9, respectively. The mean pain range was 36.4, and the mean pain AUC was 564.3 (possible range: 16-1600). Pain scores were similar on weekends. In multivariable mixed models, both knee and hip OA were associated with a greater within-day pain range than hand OA. Only VA enrollment site was associated with a significantly greater pain AUC. CONCLUSION: There is substantial within-day range in OA-related pain. Both pain range and overall within-day magnitude vary according to patient characteristics. Patients' records of within-day pain patterns could be used in clinical encounters to tailor recommendations for the timing of medication use and behavioral strategies.

Biogenesis of thylakoid membranes is controlled by light intensity in the conditional chlorophyll b-deficient CD3 mutant of wheat.

Biogenesis of thylakoid membranes in the conditional chlorophyll b-deficient CD3 mutant of wheat is dramatically altered by relatively small differences in the light intensity under which seedlings are grown. When the CD3 mutant is grown at 400 microE/m2 S (high light, about one-fifth full sunlight) plants are deficient in chlorophyll b (chlorophyll a/b ratio greater than 6.0) and lack or contain greatly reduced amounts of the chlorophyll a/b-binding complexes CPII/CPII (mobile or peripheral LHCII), CP29, CP24 and LHCI, as shown by mildly denaturing 'green gel' electrophoresis, by fully denaturing SDS-PAGE, and by Western blot analysis. High light CD3 chloroplasts display an unusual morphology characterized by large, sheet-like stromal thylakoids formed into parallel unstacked arrays and a limited number of small grana stacks displaced toward the edges of the arrays. Changes in the supramolecular organization of CD3 thylakoids, seen with freeze-fracture electron microscopy, include a reduction in the size of EFs particles, which correspond to photosystem II centers with variable amounts of attached LHCII, and a redistribution of EF particles from the stacked to the unstacked regions. When CD3 seedlings are grown at 150 microE/m2 S (low light) there is a substantial reversal of all of these effects. Thus, chlorophyll b and the chlorophyll a/b-binding proteins accumulate to near wild-type levels (chlorophyll a/b ratio = 3.5-4.5) and thylakoid morphology is more nearly wild type in appearance. Growth of the CD3 mutant in the presence of chloramphenicol stimulates the accumulation of chlorophyll b and its binding proteins (Duysen, M. E., T. P. Freeman, N. D. Williams, and L. L. Huckle. 1985. Plant Physiol. 78:531-536). We show that this partial rescue of the CD3 high light phenotype is accompanied by large changes in thylakoid structure. The CD3 mutant, which defines a new class of chlorophyll b-deficient phenotype, is discussed in the more general context of chlorophyll b deficiency.