Assessing functional recovery following total knee replacement surgery using objective classification of level gait data and patient-reported outcome measures

BACKGROUND

Patient recovery can be quantified objectively, via gait analysis, or subjectively, using patient reported outcome measures. Association between these measures would explain the level of disability reported in patient reported outcome measures and could assist with therapeutic decisions.

METHODS

Total knee replacement outcome was assessed using objective classification and patient-reported outcome measures (Knee Outcome Survey and Oxford Knee Scores). A classifier was trained to distinguish between healthy and osteoarthritic characteristics using knee kinematics, ground reaction force and temporal gait data, combined with anthropometric data from 32 healthy and 32 osteoarthritis knees. For the osteoarthritic cohort, classification of 20 subjects quantified changes at up to 3 timepoints post-surgery.

FINDINGS

Osteoarthritic classification was reduced for 17 subjects when comparing pre- to post-operative assessments, however only 6 participants achieved non-pathological classification and only 4 of these were classified as non-pathological at 12 months. In 15 cases, the level of osteoarthritic classification did not decrease between every post-operative assessment. For an individual's recovery, classification outputs correlated (r > 0.5) with knee outcome survey for 75% of patients and oxford knee score for 78% of patients (based on 20 and 9 subjects respectively). Classifier outputs from all visits of the combined total knee replacement sample correlated moderately with knee outcome survey (r > 0.4) and strongly with oxford knee score (r > 0.6).

INTERPRETATION

Biomechanical deficits existed in most subjects despite improvements in Patient Reported Outcome Measures, with larger changes reported subjectively as compared to measured objectively. Objective Classification provides additional insight alongside Patient Reported Outcomes when reporting recovered outcomes.

Correlations between patient-perceived outcome and objectively-measured biomechanical change following Total Knee Replacement

BACKGROUND

Total Knee Replacement (TKR) surgery is being utilised in a younger, more active population with greater functional expectations. Understanding whether patient-perceived measures of function reflect objective biomechanical measures is critical in understanding whether functional limitations can be adequately captured within a clinical setting.

RESEARCH QUESTION

Do changes in objective gait biomechanics measures reflect patient-reported outcome measures at approximately 12 months following TKR surgery?

METHODS

Three-dimensional gait analysis was performed on 41 patients with OA who were scheduled for TKR surgery, 22 of which have returned for a (9-24 month) follow-up assessment. Principal Component Analysis was used to define features of variation between OA subjects and an additional 31 non-pathological control subjects. These were used to train the Cardiff Classifier, an objective classification technique, and subsequently quantify changes following TKR surgery. Patient-perceived changes were also assessed using the Oxford Knee Score (OKS), Knee Outcome Survey (KOS), and Pain Audit Collection System scores (PACS). Pearson and Spearman correlation coefficients were calculated to establish the relationship between changes in objectively-measured and perceived outcome.

RESULTS

Objective measures of biomechanical change were strongly correlated to changes in OKS(r=-0.695, p < 0.001) and KOS(r=-.810, p < 0.001) assessed outcomes. Pain (PACS) was only related to biomechanical function post-operatively (r=-.623, p = 0.003).

SIGNIFICANCE

In this biomechanics study, the relationship between changes in objective function and patient-reported measures pre to post TKR surgery is stronger than in studies which did not include biomechanics metrics. Quality of movement may hold more significance for a patient's perception of improvement than functional measures which consider only the time taken or distance travelled during functional activities.

Abnormal loading and functional deficits are present in both limbs before and after unilateral knee arthroplasty

Unilateral knee replacement is often followed by a contralateral replacement in time and the biomechanics of the other knee before and after knee replacement remains poorly understood. The aim of this paper is to distinguish the features of arthritic gait in the affected and unaffected legs relative to a normal population and to assess the objective recovery of gait function post-operatively, with the aim of defining patients at risk of poor post-operative function. Twenty patients with severe knee OA but no pain or deformity in any other lower limb joint were compared to twenty healthy subjects of the same age. Gait analysis was performed and quadriceps and hamstrings co-contraction was measured. Fifteen subjects returned 1year following knee arthroplasty. Moments and impulses were calculated, principal component analysis was used to analyse the waveforms and a classification technique (the Cardiff Classifier) was used to select the most discriminant data and define functional performance. Comparing pre-operative function to healthy function, classification accuracies for the affected and unaffected knees were 95% and 92.5% respectively. Post-operatively, the affected limb returned to the normal half of the classifier in 8 patients, and 7 of those patients returned to normal function in the unaffected limb. Recovery of normal gait could be correctly predicted 13 out of 15 times at the affected knee, and 12 out of 15 times at the unaffected knee based on pre-operative gait function. Focused rehabilitation prior to surgery may be beneficial to optimise outcomes and protect the other joints following knee arthroplasty.

The effect of osteoarthritis of the knee on the biomechanics of other joints in the lower limbs

The aim of this study was to examine the loading of the other joints of the lower limb in patients with unilateral osteoarthritis (OA) of the knee. We recruited 20 patients with no other symptoms or deformity in the lower limbs from a consecutive cohort of patients awaiting knee replacement. Gait analysis and electromyographic recordings were performed to determine moments at both knees and hips, and contraction patterns in the medial and lateral quadriceps and hamstrings bilaterally. The speed of gait was reduced in the group with OA compared with the controls, but there were only minor differences in stance times between the limbs. Patients with OA of the knee had significant increases in adduction moment impulse at both knees and the contralateral hip (adjusted p-values: affected knee: p < 0.01, unaffected knee p = 0.048, contralateral hip p = 0.03), and significantly increased muscular co-contraction bilaterally compared with controls (all comparisons for co-contraction, p < 0.01).

The other major weight-bearing joints are at risk from abnormal biomechanics in patients with unilateral OA of the knee.

Cite this article: Bone Joint J 2013;95-B:348–53.

A CaRBS analysis of hip replacement approaches and non-pathology

This study investigates the differences in hip biomechanics for subjects following a total hip arthroplasty (THA), through the lateral approach (LA) and posterior approach (PA), to those with no pathology (NP). The principal component analysis was performed on two kinematic and two kinetic waveforms (subject-based characteristics) from level gait to identify salient portions of the waveforms for comparison between the subject cohorts. These were classified to identify the differences between post-THA and non-pathological cohorts. The primary technique exposited in the THA analysis is classification and ranking belief simplex (CaRBS). Within the analysis, from the configuration of a CaRBS model, there is discussion on the model fit and contribution of the subject-based characteristics. Where appropriate, comparisons to the CaRBS model are made with the results from a logistic regression (LR) analysis. In terms of model fit, using CaRBS, 24 out of 27 LA/PA subjects (88.89%) and 13 out of 16 NP subjects (81.25%) were correctly classified as exhibiting either post-THA or NP hip functional characteristics during level gait, combining to 86.05% classification accuracy, compared with 81.40% classification accuracy when using LR.

Motion analysis of the glenohumeral joint during activities of daily living

The shoulder complex has a larger range of motion (ROM) than any other joint complex in the human body, leaving it prone to numerous injuries. Objective kinematic analysis could yield useful functional insights that may assist clinical practice. Non-invasive optoelectronic motion analysis techniques have been used to assess the shoulders of five healthy subjects performing ROM tasks and 10 functional tasks of daily living. The four most demanding tasks - touching the side and back of the head, brushing the opposite side of the head, lifting an object to shoulder height and lifting an object to head height, required 78%, 60%, 61% and 71%, respectively, of the glenohumeral elevation necessary for full abduction in the scapular plane for the 10 shoulders. This has implications for clinical practice where maximum arm elevation is commonly used to determine a patient's ability to return to work and other everyday activities.

Challenges Facing Quantification of Rat Locomotion along Beams of Varying Widths

Optoelectronic motion capture systems have been widely used to investigate temporal gait parameters in humans and animals in order to understand function and behavioural attributes of different pathologies, e.g. Parkinson's disease (PD). The aim of the present paper was to investigate the practicality of utilising this system to investigate the effects of a unilateral 6-hydroxydopamine (6-OHDA) lesion on rat locomotion while walking on beams of varying widths (graduated, narrow, and wide). Temporal gait parameters of ten male Lister Hooded rats (five controls and five hemiparkinsonian) were observed using passive markers placed in locations that were representative of their four limbs and their body axis. The results demonstrate that marker-based motion capture can provide an effective and simple approach to quantifying temporal gait parameters for rat models of PD. They also reveal how the width of the path affects the locomotion in both experimental cohorts. Such measurements can be compared with human motion analysis to explore correlations between the animal model and human behaviour, which is an important step for translational medicine.

Does the choice of stair gait cycle affect resulting knee joint kinematics and moments?

Stair gait is a useful activity for the assessment of knee function. The aim of this study was to determine whether knee joint kinematics and moments are affected by the choice of stair gait cycle (SGC) and the step used to measure ground reaction forces (GRFs). This was investigated through motion analysis of ten non-pathological subjects as they ascended and descended a four-step staircase. The SGCs compared for ascent were, first, step 1 (measuring GRFs) to step 3 and, second, step 2 (measuring GRFs) to step 4, and vice versa for stair descent. Knee joint kinematics were not significantly influenced by the choice of SGC. For ascent, significantly larger peak adduction moments were measured for SGCs beginning on step 1 (0.30 ± 0.08 N m/kg) than for SGCs beginning on step 2 (0.23 ± 0.09 N m/kg). For descent, the second flexion moment peak was found to be significantly larger for SGCs ending on step 2 (1.17 ± 0.25 N m/kg) than for SGCs ending on step 1 (0.97 ± 0.19 N m/kg), and the first adduction moment peak was found to be significantly larger for SGCs ending on step 2 (0.28 ± 0.15 N m/kg) than for SGCs ending on step 1 (0.21 ± 0.18 N m/kg). This study highlights important considerations when planning stair gait measurement protocols and comparing results from studies made by other laboratories.

Comparing different data collection and analysis techniques for quantifying healthy knee joint function during stair ascent and descent

There is currently no standard data collection or analysis method for the assessment of stair gait using motion analysis. This makes the comparison of results from different studies difficult. It is important to gain an appreciation of the discrepancies in kinematic and kinetic information generated by employing different computational approaches, as these differences may be critical in cases where methodologies were to change over a long-term study. This study explores the effect of using different methodologies for the assessment of non-pathological knee function of ten subjects during stair ascent and descent. Two methods of computing knee kinematics were compared: (a) using in-house software and a pointer method of anatomical calibration and (b) using commercial software, Visual3D (C-motion, Inc.) and skin-mounted markers. Significant differences were found between the two methods when calculating a frontal plane range of motion (p < 0.05). Three methods of computing knee moments were compared. Knee moments computed using the inverse dynamic analysis (IDA) approach of Visual3D (C-motion, Inc.) were significantly different (p < 0.05) to those calculated using in-house IDA software that ignores the foot and ankle and to those computed using a vector cross-product approach. This study highlights the implications of comparing data generated from different collection and analysis methods.

Dynamic tracking of the scapula using skin-mounted markers

The shoulder complex is prone to numerous pathologies and instabilities due to its large range of motion. The extent of injury is assessed through a series of observations and physical examinations. It is hypothesized that objective kinematic analysis of the shoulder could yield useful functional insights to aid clinical practice. Non-invasive motion analysis techniques to monitor shoulder function have been developed using passive markers; however, accurate measurement of scapula kinematics is problematic because of overlying tissue. The scapula locator is the accepted standard by which alternative non-invasive techniques of scapula tracking are validated. In this study, the viability of using skin-mounted markers to measure dynamic scapula movement is determined. Complete kinematic descriptions of ten healthy shoulders were obtained. Elevations of the glenohumeral joint were similar with both techniques, indicating that the skin marker method is suitable for gathering functional glenohumeral data. The main differences of note are seen at the scapulothoracic articulation where the skin marker method underestimated lateral rotation by more than 50 degrees at maximum elevation. However, the correlation between the two approaches is greater than 0.7, suggesting that it may be possible to derive linear regression models to predict dynamic scapulothoracic lateral rotation accurately using skin-mounted scapula markers.

Medical engineering at Cardiff University. Part 2: Postgraduate programmes of study

The Medical Engineering team within the School of Engineering, Cardiff University, delivers two postgraduate programmes of study. Established over 10 years ago, the part-time MSc programmes in Orthopaedic Engineering and Clinical Engineering offer the opportunity of further study while remaining within full-time employment. Both programmes deliver 120 taught credits over two academic years via a series of residential weekends, with successful completion enabling the student to undertake and then defend a 60-credit research dissertation. Fulfilling a specific role on the career pathway for both student cohorts, the strength of each programme is indicated by the consistent number of applicants.

Medical engineering at Cardiff University. Part 1: Undergraduate programmes of study

Cardiff University has offered a medical engineering undergraduate programme since 2001 and hence delivers one of the longest-running and most established medical engineering programmes within the UK. It currently offers BEng (Hons) and MEng (Hons) programmes that are both accredited by the Institution of Mechanical Engineers and include the option to undertake a year in industrial employment. The admissions policy ensures that the intake consists of a diverse range of students and is typically very successful in attracting female students. The programmes consist of six key academic threads which ensure that the content is both relevant and continuous, with all threads tailored to provide a patient-focused learning environment. Students initially learn core and fundamental principles in years 1 and 2, supported by a range of laboratories and practical experimentation. The latter years then encourage the students to corroborate and apply this knowledge, including involvement in a range of project-based learning exercises. The programme is delivered by a core of experienced academic medical engineers, with support from other engineering colleagues, as well as colleagues from the School of Biosciences, the School of Medicine, and the National Health Service. Thus, the programme delivers a wide range of modules which guarantee that graduating students have a thorough understanding of all possible career options. These two factors are significant in making it possible for students to follow their chosen career path upon graduation.

Objective functional assessment of total hip arthroplasty following two common surgical approaches: the posterior and direct lateral approaches

Despite the high number of total hip arthroplasty (THA) procedures performed each year, there is no common consensus on the best surgical approach. Gait is known to improve following THA although it does not return to what is typically quantified as normal, and surgical approach is believed to be a contributing factor. The current study evaluates postoperative hip function and provides an objective assessment following two common surgical approaches: the McFarland-Osborne direct lateral and the southern posterior. Faced with the common problem of providing an objective comparison from the wealth of data collected using motion analysis techniques, the current study investigates the application of an objective classification tool to provide information on the effectiveness of each surgery and to differentiate between the characteristics of hip function following the two approaches. Seven inputs for the classifier were determined through statistical analysis of the biomechanical data. The posterior approach group exhibited greater characteristics of non-pathological gait and displayed a greater range of functional ability as compared with the lateral approach cohort. The classification tool has proved to be successful in characterizing non-pathological and THA function but was insufficient in distinguishing between the two surgical cohorts.

An objective tool for assessing the outcome of total knee replacement surgery

The need for an objective tool to assess the outcome of total knee replacement (TKR) surgery is widely recognized. This study investigates the potential of an objective diagnostic tool for assessing the outcome of TKR surgery based on motion analysis techniques. The diagnostic tool has two main elements: collection of data using motion analysis, and the assessment of knee function using a classifier that is based around the Dempster-Shafer theory of evidence. The tool was used to analyse the knee function of nine TKR subjects preoperatively and at three stages post-operatively. Using important measurable characteristics of the knee, the tool was able to establish the level of benefit achieved by surgery and to enable a comparison of subjects. No subject recovered normal knee function following TKR surgery. This has important implications for knee implant designs.

Three-dimensional measurement of intervertebral kinematics in vitro using optical motion analysis

Measurement of the stiffness of spinal motion segments is widely used for evaluating the stability of spinal implant constructs. A three-dimensional motion analysis technique has been developed that allows accurate measurement of the relative movement of the vertebral bodies about a well-defined anatomical axis system. The position of marker clusters on each vertebra is tracked using digital infrared cameras (Qualisys AB, Gothenburg). Landmarks are identified using a marked pointer, and an anatomical coordinate system is defined for each vertebra. The transformation relating the upper and lower vertebrae is calculated, using the joint coordinate system approach of Grood and Suntay to find the rotations and translations in each anatomical plane. The stiffness of vertebrectomy constructs was investigated using a Synex vertebral body replacement and an anterior rod with one or two screws in each vertebral body, with or without damage to the posterior longitudinal ligament (PLL). A moment of 2 N m was applied about each anatomical axis, and the range of motion about each axis was calculated. The range of motion in flexion-extension and lateral bending was significantly greater with only one screw. When the PLL was cut, there was no significant increase in the range of motion.

How accurate is partial weightbearing?

The accuracy of partial weightbearing was assessed in six healthy volunteers and 23 patients who had sustained either a fracture of a lower limb or surgery. They were trained to weightbear partially using the conventional bathroom scale method and were assessed in a gait laboratory using force platforms. The amount of weight exerted on the involved limb during three-point crutch walking was determined. Four of six volunteers exerted a mean of 27% of body weight more than required. The remaining two volunteers exerted a mean of 8.5% of body weight less than required. Of the 23 patients, 21 exerted a mean of 35.3% of body weight more than that prescribed and two patients exerted a mean of 11.97% of body weight less than that prescribed. In both groups there was little relationship between the weightbearing prescribed and actual weightbearing. None of the patients or volunteers was able to reproduce the extent of partial weightbearing for which they were trained using the bathroom scale method, confirming that this technique of instructing patients in partial weightbearing is inaccurate.

A novel approach to forensic investigation: three-dimensional kinematic and kinetic motion analysis

Following a domestic incident, a five-year-old child was pronounced dead on arrival at hospital. The subsequent post-mortem examination found that the cause of death was peritonitis as a result of a rupture of the duodenum. During the police interview, the main suspect alleged that the injury occurred whilst playing a game which involved standing on the child's abdomen and chest. A reconstruction of the game was performed using 3-dimensional kinematic and kinetic motion analysis to investigate the feasibility of the statement as described by the defendant. Presented is a summary of the investigation together with a description of kinematic and kinetic methods employed.

Subjective assessment of blunt impacts

An important role of an eyewitness to an assault is to effectively quantify the degree of force used; yet evidence of this form is often subjective and relies on personal opinion. Twelve subjects were asked to strike a load cell with a wooden bat, using varying degrees of force. The strikes were recorded by video camera and 50 people observed the video and were asked to grade the strikes. On average 44% accurately assessed the severity of the strikes, whilst 26% over-estimated. Results suggest that the evidence of eyewitnesses should be treated with caution.

Dynamics of stab wounds: force required for penetration of various cadaveric human tissues

It is often said that once the skin has been penetrated no further force is required to produce penetration of underlying tissues. This experimental study has used technology which was not available to earlier investigators to examine this issue in detail. The results confirm the importance of skin penetration but indicate that the penetration of other tissues may also require significant force.

Stochastic game theory: for playing games, not just for doing theory

Recent theoretical advances have dramatically increased the relevance of game theory for predicting human behavior in interactive situations. By relaxing the classical assumptions of perfect rationality and perfect foresight, we obtain much improved explanations of initial decisions, dynamic patterns of learning and adjustment, and equilibrium steady-state distributions.

Atypical hyperplasia in the era of stereotactic core needle biopsy

BACKGROUND AND OBJECTIVES

To characterize both atypical hyperplasia (AH) and the malignancies typically present at open surgical biopsy in women diagnosed with AH by stereotactic core needle biopsy (SCNB).

METHODS

Patients with AH diagnosed by SCNB were advised to undergo surgical biopsy to rule out an associated malignancy. Mammography findings, pathology reports and follow-up data were analyzed.

RESULTS

AH was identified by SCNB in 38 of 893 (4.3%) patients. Carcinoma was identified in 12 of 33 (36.4%) patients who went on to surgical biopsy. Ductal carcinoma in situ (DCIS) was present in 11 of the 12 patients with malignancy. There were no characteristic mammographic findings which would identify patients with carcinoma.

CONCLUSIONS

When SCNB returns a diagnosis of AH there is a substantial risk of an associated malignancy in the breast. There appear to be no definitive criteria to distinguish which patients harbor a malignancy, and surgical biopsy should always serve as an adjunct diagnostic procedure.

Cloning of tobacco genes that elicit the hypersensitive response

We used a functional screening method to isolate genes whose products elicit the hypersensitive response (HR) pathway of defense against plant pathogens. A cDNA library derived from tobacco leaves undergoing the HR was cloned into a tobacco mosaic virus (TMV)-based expression vector. Infectious transcripts were generated and used to inoculate tobacco plants lacking the N resistance gene (genotype Xanthi nn). Approximately 1/1000 of the infectious transcripts produced local lesions, and may thus elicit the HR. The cDNA inserts from 50 lesion-forming clones were recovered by RT-PCR, and 12 unique clones were sequenced. Comparisons with protein databases revealed homologies to (a) ubiquitin, (b) tobacco tumor-related protein, similar to Kunitz-type trypsin inhibitors and (c) ribosomal protein S14. The remaining nine clones revealed no homology to known proteins and are thus considered novel. Five clones were able to induce the expression of PR2, a gene which is specifically activated in the tobacco HR. Northern and western blot analyses of leaves infected by the clone encoding ubiquitin strongly suggest that the infection produced a co-suppression response; the endogenous level of ubiquitin mRNA and protein in infected leaves are ca. 50% less than those found in healthy leaves. This observation supports a previous report on the involvement of the ubiquitin system in the tobacco HR [2], and validates and utility of the functional cloning method.

Internal mammary silicone lymphadenopathy mimicking recurrent breast cancer

This case describes a unique complication of silicone breast implantation that is previously undocumented. Internal mammary silicone lymphadenopathy mimicking breast cancer recurrence represents an important new clinical entity. The diagnosis and management of this clinical enigma are challenging. In our patient, videothoracoscopy proved to be minimally invasive and allowed complete resection of the entire chain of pathologic nodes. Explantation of the silicone prostheses and complete capsulectomy are indicated. Light microscopy alone can suggest the diagnosis of silicone lymphadenopathy. Infrared spectral analysis can be a helpful adjunct to allow an unequivocal diagnosis.

Expression of the green fluorescent protein-encoding gene from a tobacco mosaic virus-based vector

A cDNA fragment encompassing the Aequorea victoria green fluorescent protein-encoding gene (gfp) was introduced into a genomic cDNA clone of tobacco mosaic virus (TMV). Infectious RNA transcripts produced in vitro were used to inoculate tobacco (Nicotiana benthamiana) leaves. After 1-2 days, bright green fluorescent areas could be visualized upon illumination with a long-wave ultraviolet (UV) light source. The virus was capable of infecting and expressing gfp in plant tissues both locally (in the inoculated leaf) and systemically (throughout the entire plant). Continued observation of inoculated plants indicated that systemic infection resulted from a combination of two forms of virus movement: a slow, cell-to-cell spread with concomitant virus replication and gfp expression, and a rapid, vascular-mediated form of transport without gfp expression.

Mutational analysis of the movement protein of odontoglossum ringspot virus to identify a host-range determinant

Tobacco mosaic virus (TMV) which contains the movement protein (MP) of odontoglossum ringspot tobamovirus (ORSV) in place of the TMV MP systemically infects orchids but causes local infection in tobacco unless the carboxy-terminal 48 amino acids of the MP are deleted (C. A. Holt, C. A. Fenczik, S. J. Casper, and R. N. Beachy; Virology, in press, 1995). Frameshift mutations were created within the 3' ends of the MP gene that led to truncations of the ORSV MP by 11, 19, 28, 37, and 48 amino acids; each of the mutant MP genes was inserted into the cloned cDNA of TMV in place of the TMV MP and infectious transcripts were produced. Virus containing mutant MPs were used to infect vanilla orchids, a systemic host of ORSV, and tobacco plants. Removal of 11 amino acids from the ORSV MP prevented spread of the chimeric virus in orchids while restoring the ability to cause a systemic infection on tobacco. Further deletions of the MP affected the size of virus-induced necrotic local lesions on tobacco cv. Xanthi NN and the systemic spread and accumulation of virus in cv. Xanthi nn, a systemic host of TMV. However, each virus replicated to equivalent levels in protoplasts. A mechanism by which the ORSV MP limits the spread of the chimeric virus is proposed.

Effects of terminal deletion mutations on function of the movement protein of tobacco mosaic virus

A series of carboxy- and amino-terminal deletion mutations in the movement protein (MP) gene of tobacco mosaic virus (TMV) were ligated into a cloned TMV cDNA deleted for the endogenous MP gene. RNA transcripts were produced in vitro from clones carrying the various mutated MP genes. The effect of the deletion mutations on local and systemic movements of the infection was evaluated. Deletion of 9 or 33 amino acids from the carboxy terminus of the movement protein did not effect cell-to-cell movement as reflected by local lesion formation on Nicotiana tabacum cv. Xanthi NN plants. Deletion of 55 amino acids resulted in impaired MP that supported the formation of local lesions of 1 mm in diameter compared to lesions of 3-5 mm caused by the wild-type MP. Deletion of 74 amino acids (or more) from the carboxy terminus resulted in a protein that could not support virus movement. Modified viruses that contained repeated sequences in the 3' region of the MP gene lost the repeated sequences during replication and reverted to the wild type. This was evidenced by the size of the MP produced and by sequence analysis of reverse-transcribed PCR-amplified products, following infection by the modified virus. MP deleted for as few as 3 amino acids at the amino terminus could not support virus movement thus indicating that the amino-terminal domain is critical for MP activity.

The TMV movement protein: role of the C-terminal 73 amino acids in subcellular localization and function

The role of the C-terminal one-third of the tobacco mosaic virus (TMV) 30-kDa movement protein (MP) on its subcellular localization and on virus spread was investigated. We have constructed eight cDNAs encoding MPs with variable size deletions from the C-terminal end. Expression of the truncated proteins was verified in recombinant yeast using an antiserum directed to a synthetic peptide corresponding to 21 amino acids near the N-terminal end of the MP. In transgenic tobacco plants, MP from which more than 55 amino acids were deleted no longer accumulated in the cell wall fraction of a cellular extract, where the complete MP accumulates. Dye diffusion studies showed that both unmodified and modified MPs that accumulate in the cell wall fraction are able to alter plasmodesmatal size exclusion limits. Biological function of the modified MPs was tested in the transgenic plants with the TMV thermosensitive mutant Ls1 and a TMV genomic RNA transcript lacking a functional MP. There was a correlation between the cell wall localization of the modified MPs and its ability to potentiate virus spread. The results presented here demonstrate the dispensability of the C-terminal 55 amino acids of the MP in its subcellular localization in tobacco plants and its role in virus movement. Moreover, our results show that a stretch of 19 amino acids (195 to 213) is essential for localization of the MP to the cell wall fraction of plant cells.

In vivo complementation of infectious transcripts from mutant tobacco mosaic virus cDNAs in transgenic plants

A full-length cDNA clone of the U1 (common) strain of tobacco mosaic virus (TMV) was constructed, and highly infectious transcripts were produced in vitro using bacteriophage T7 RNA polymerase. Frameshift mutations designed to cause premature termination of translation were introduced into either the 30-kDa movement protein (MP) gene or the coat protein (CP) gene. The MP-frameshift mutant was unable to locally or systemically infect inoculated tobacco plants. However, inoculation of transgenic tobacco plants that expressed a wild-type TMV MP gene resulted in both local and systemic viral infection. The CP-frameshift mutant, although unable to move systemically in nontransformed tobacco, exhibited systemic movement in transgenic plants that expressed a wild-type TMV CP gene. Transgenic tobacco plants that expressed the appropriate wild-type TMV gene were thus able to complement, in trans, mutant viruses lacking a functional MP or CP gene.

Altered function of the tobacco mosaic virus movement protein in a hypersensitive host

The N gene in Nicotiana sp. confers hypersensitive resistance to all strains of tobacco mosaic virus (TMV) and limits the rate of virus spread in infected leaves. To examine the role of the movement protein (MP) of TMV in the hypersensitive reaction (HR), transgenic Nicotiana tabacum cv. Xanthi-nc (genotype NN) plants that express the MP gene were produced and the molecular size exclusion limit of plasmodesmata in leaf mesophyll cells was monitored. At the HR-permissive temperature (24 degrees) movement from cell to cell of fluorescein isothiocyanate-labeled dextran of molecular mass 3.9 kDa was detected while 9.4-kDa molecules failed to move. At the HR-nonpermissive temperature (33 degrees) the 9.4-kDa probe moved readily from cell to cell. In contrast, in transgenic Xanthi (genotype nn) which express the MP gene the 9.4-kDa probe moved from cell to cell at 24 and 33 degrees. These results suggest that the N gene may modify the ability of the MP to alter plasmodesmata molecular exclusion limits, although expression of the TMV-MP gene alone did not induce the HR. Furthermore, when MP(+) Xanthi-nc tobacco lines were inoculated with a TMV that lacked a MP gene the HR was induced, and the concentration of MP in the transgenic lines was correlated with the degree of the HR.

Transfer of the movement protein gene between two tobamoviruses: influence on local lesion development

The effects of transfer of the movement gene between the tobamoviruses tobacco mosaic virus (TMV) and tobacco mild green mosaic virus (TMGMV) were studied. The movement protein (MP) gene of TMGMV was cloned into an infectious cDNA of TMV to build the recombinant virus V23. V23, like TMV and TMGMV, caused systemic infection in Nicotiana tabacum Xanthi. In N. sylvestris V23 and TMV spread systemically although TMGMV produces necrotic local lesions on this host. V23 and TMV cause systemic infection on tomato plants while TMGMV does not infect tomato. In Xanthi nc plants, V23 produced necrotic local lesions similar in size to those produced by TMGMV. On the other hand in transgenic Xanthi nc tobacco plants that express a gene encoding the MP of TMV the necrotic lesions produced by V23 and TMGMV were similar in size to those produced by TMV. These results indicate that the size of necrotic lesions produced by TMGMV and TMV on Xanthi nc plants is influenced by the MP gene.

Molecular characterization and biological function of the movement protein of tobacco mosaic virus in transgenic plants

We previously demonstrated, in transgenic tobacco plants, that the role of the movement protein (MP) of tobacco mosaic virus is to facilitate the cell-to-cell spread of viral progeny during infection. An analysis of different tissues of these transgenic plants indicated that the MP accumulated in leaf, stem, and root tissue. The highest levels were detected in older leaves. The relative levels of MP in leaf tissue from transgenic plants were equivalent to, or higher than, the levels of MP in tobacco mosaic virus-infected leaf tissue. Results of subcellular fractionation of homogenates of transgenic leaf tissue showed that the MP was most abundant in the cell wall fraction of older leaves and that the protein remained at high levels in the cell wall fraction as the leaves continued to age. Significant levels of the MP were detected in a crude membrane/organelle fraction and a soluble fraction in younger leaves but decreased to low levels in older leaves. These results suggest that the MP accumulates and is stable in cell walls. We have previously shown that the MP modifies the molecular exclusion limit of plasmodesmata, which is consistent with the hypothesis that plant viruses move from cell to cell through altered plasmodesmata. We show here that the ability of the tobacco mosaic virus MP to modify the molecular exclusion limit of plasmodesmata in tobacco depends on the developmental stage of the leaf. The implications of these findings on understanding virus movement and how plasmodesmata function are discussed.

Falsification of clinical credentials by physicians applying for ambulatory-staff privileges

As part of a quality-assurance program, we reviewed the clinical credentials listed on applications from 773 physicians applying for clinical positions in the Humana MedFirst national ambulatory care program between March 1 and December 31, 1986. In 39 applications (5.0 percent), physicians presented false clinical credentials: 27 physicians (3.5 percent) gave false information about their residency, 10 (1.3 percent) falsely reported board certification, and 2 (0.3 percent) provided false information about both residency and board certification. There was no significant difference between the falsification rates among graduates of U.S. medical schools and those among graduates of foreign medical schools, or among those in the various medical specialties. Falsification was more common among physicians recruited locally than among those recruited nationally, and was significantly more common among applicants who graduated before 1970. Because of this sample included only applicants for ambulatory privileges within a single organization, the findings may be of uncertain generalizability to groups of physicians applying for other classes of privileges in other institutions. We conclude that in applying for some clinical privileges, physicians present inaccurate clinical credentials more frequently than might be expected.

Friend virus-specific cytotoxic T lymphocytes recognize both gag and env gene-encoded specificities

We have constructed a series of "synthetic" target cell lines for an analysis of the specificity of anti-Friend virus (FV) CTL. Our results show that murine H-2 genes and individual retroviral genes can be stable expressed in Fisher rat embryo (FRE) cells, and that their products have the potential to form target structures recognized by mouse CTL. Cells expressing H-2Db and either the env or gag genes of one component of FV, helper Friend murine leukemia virus (FMuLV), were lysed by anti-FV CTL and by CTL generated against FMuLV alone. Experiments with Db-transfected FRE clones infected only with the replication-defective spleen focus-forming virus (SFFV) component of FV indicate that the SFFV genome also provides specificities recognized by both anti-FV and anti-FMuLV CTL, thus demonstrating the existence of a crossreactive CTL population. An unexpected finding was that anti-FMuLV CTL, but not anti-FV CTL were also able to lyse FRE clones that expressed H-2Kb in either the presence or absence of FV. The use of heterologous cell lines for the construction of synthetic target cells thus offers a useful approach for the analysis of T cell specificity.

A new family of tandem repetitive early histone genes in the sea urchin Lytechinus pictus: evidence for concerted evolution within tandem arrays

We have isolated and characterized a third nonallelic tandemly arrayed histone cluster (LpE) from the sea urchin Lytechinus pictus. Although this tandem array is not intermingled with the other two early histone gene families also found in the L. pictus genome, the order and polarity of the five histone coding sequences in this family are the same as every other well characterized sea urchin early histone gene family. Heteroduplex analysis and restriction endonuclease mapping experiments indicate that the LpE family is more closely related to the B-C than the A-D family of early histone genes. Examination of several individual sperm DNA samples has revealed considerable polymorphism in each of the three tandem repeat families. Within an individual, however, each family is remarkably homogeneous. Thus, our results indicate that rapid fixation of variants acts to homogenize the members of a single tandem array at a considerably faster rate within a family than between families. However, at least some exchange of sequences between families is evident based on the conservation of many restriction endonuclease recognition sites and from analysis of a a cosmid clone in which the A-D and E tandem repeats are found adjacent to one another. These differences in the rate of fixation of variants within and between these families are likely to be responsible for the maintenance of diversity between the different families.

Lack of specificity for viral and H-2 antigens by anomalous T killer cells generated in murine leukocyte cultures

Mouse spleen cells, cultivated in vitro for 6 days in the presence or absence of syngeneic irradiated virus-induced tumor cells, lysed a variety of virus-induced tumor cells and normal cells in a long (19-hr) 51Cr-release cytotoxicity assay. Little or no specificity for viral or H-2 antigens was detected. This anomalous killing (AK) activity contrasted with H-2-restricted cytotoxic T lymphocyte (CTL) activity generated in secondary mixed leukocyte-tumor cell cultures and detected in a short (4- to 6-hr) 51Cr-release assay. Studies of competitive inhibition by unlabeled target cells in the long assay suggested that AK effectors were a broadly heterogeneous mixture of cells representing many clones, each recognizing a different antigenic determinant. AK effector cells shared properties with CTL: they could be generated from spleen cells of natural killer cell-deficient mice bearing the beige mutation but not from those of T cell-deficient nude mice; they expressed Thy-1 and Lyt-2 antigens; and they were nonphagocytic. AK activity could be generated from normal spleen cells of mice of all inbred strains examined, but the levels of activity generated varied in a strain-specific manner and were not significantly influenced by H-2 genotype.

Lack of specificity for viral and H-2 antigens by anomalous T killer cells generated in murine leukocyte cultures

Mouse spleen cells, cultivated in vitro for 6 days in the presence or absence of syngeneic irradiated virus-induced tumor cells, lysed a variety of virus-induced tumor cells and normal cells in a long (19-hr) 51Cr-release cytotoxicity assay. Little or no specificity for viral or H-2 antigens was detected. This anomalous killing (AK) activity contrasted with H-2-restricted cytotoxic T lymphocyte (CTL) activity generated in secondary mixed leukocyte-tumor cell cultures and detected in a short (4- to 6-hr) 51Cr-release assay. Studies of competitive inhibition by unlabeled target cells in the long assay suggested that AK effectors were a broadly heterogeneous mixture of cells representing many clones, each recognizing a different antigenic determinant. AK effector cells shared properties with CTL: they could be generated from spleen cells of natural killer cell-deficient mice bearing the beige mutation but not from those of T cell-deficient nude mice; they expressed Thy-1 and Lyt-2 antigens; and they were nonphagocytic. AK activity could be generated from normal spleen cells of mice of all inbred strains examined, but the levels of activity generated varied in a strain-specific manner and were not significantly influenced by H-2 genotype.

A re-examination of parturition scars on the human female pelvis

Pits, cavities and depressions located on the dorsal surface of the pubic symphysis of females have been attributed to the trauma of parturition. Earlier research based on human skeletal remains provides inadequate information on the individual's obstetrical history. The 68 female pubic bones that were studied had comprehensive medical records indicating whether or not each female had given birth. Fourteen and one-half percent of the females who had not given birth exhibited trace to small scarring of the pubic symphysis and 23.4% of the females who had not given birth exhibited medium to large scarring. It is suggested that bony changes previously used as an indicator of child bearing must be re-examined in light of the fact that "birth scarring" has been found in women known not to have had children.