MHC Class I Ligands of Rhesus Macaque Killer Cell Ig-like Receptors.

Definition of MHC class I ligands of rhesus macaque killer cell Ig-like receptors (KIRs) is fundamental to NK cell biology in this species as an animal model for infectious diseases, reproductive biology, and transplantation. To provide a more complete foundation for studying NK cell responses, rhesus macaque KIRs representing common allotypes of lineage II KIR genes were tested for interactions with MHC class I molecules representing diverse Macaca mulatta (Mamu)-A, -B, -E, -F, -I, and -AG alleles. KIR-MHC class I interactions were identified by coincubating reporter cell lines bearing chimeric KIR-CD3ζ receptors with target cells expressing individual MHC class I molecules and were corroborated by staining with KIR IgG-Fc fusion proteins. Ligands for 12 KIRs of previously unknown specificity were identified that fell into three general categories: interactions with multiple Mamu-Bw4 molecules, interactions with Mamu-A-related molecules, including allotypes of Mamu-AG and the hybrid Mamu-B*045:03 molecule, or interactions with Mamu-A1*012:01. Whereas most KIRs found to interact with Mamu-Bw4 are inhibitory, most of the KIRs that interact with Mamu-AG are activating. The KIRs that recognize Mamu-A1*012:01 belong to a phylogenetically distinct group of macaque KIRs with a 3-aa deletion in the D0 domain that is also present in human KIR3DL1/S1 and KIR3DL2. This study more than doubles the number of rhesus macaque KIRs with defined MHC class I ligands and identifies interactions with Mamu-AG, -B*045, and -A1*012. These findings support overlapping, but nonredundant, patterns of ligand recognition that reflect extensive functional diversification of these receptors.

Histological improvements following energy restriction and exercise: The role of insulin resistance in resolution of MASH.

BACKGROUND & AIMS: Metabolic-dysfunction associated steatohepatitis (MASH) is one of the most common liver diseases worldwide and is characterized by multi-tissue insulin resistance. The effects of a 10-month energy restriction and exercise intervention on liver histology, anthropometrics, plasma biochemistries, and insulin sensitivity were compared to standard of care (control) to understand mechanisms that support liver health improvements. METHODS: Following medical diagnosis of MASH, subjects were randomized to treatment (n=16) or control (n=8). Liver fat (MRS), 18-hour plasma biochemical measurements, and isotopically-labeled hyperinsulinemic-euglycemic clamps were completed pre- and post-intervention. Body composition and cardiorespiratory fitness (VO2peak) were also measured mid-intervention. Treatment subjects were counseled to reduce energy intake and completed supervised, high-intensity interval training (3x/week) for 10 months. Control subjects continued physician-directed care. RESULTS: Treatment induced significant (P<0.05) reductions in body weight, fat mass, and liver injury, while VO2peak (P<0.05) and fatty acid (NEFA) suppression (P=0.06) were improved. Both groups exhibited reductions in total energy intake, HbA1c, hepatic insulin resistance, and liver fat (P<0.05). Compared to control, treatment induced a two-fold increase in peripheral insulin sensitivity which was significantly related to higher VO2peak and resolution of liver disease, despite no group differences in peripheral insulin sensitivity. CONCLUSIONS: Exercise and energy-restriction elicited significant and clinically-meaningful treatment effects on liver health, potentially driven by a redistribution of excess nutrients to skeletal muscle, thereby reducing hepatic nutrient toxicity. Clinical guidelines should emphasize the addition of aerobic exercise in lifestyle treatments for the greatest histologic benefit in individuals with advanced MASH. CLINICAL TRIAL NUMBER: NCT03151798.

Detection of Blastomyces gilchristii via metagenomic sequencing in outbreak-associated soils.

Cases of blastomycosis, a serious fungal disease globally rare but endemic to North America, can appear both sporadically and in outbreaks. Tracing these outbreaks to their environment has traditionally used culturing and polymerase chain reaction. Here, we present our method for metagenomic detection of Blastomyces in a 2015 outbreak soil sample from central Wisconsin. By sequencing this sample to multiple depths, we simulated the minimum required depth to detect Blastomyces in this outbreak. Our methods and recommendations can be used to identify the sources of blastomycosis during outbreaks and to learn about the ecology of Blastomyces.

Structure and function of the global topsoil microbiome.

Soils harbour some of the most diverse microbiomes on Earth and are essential for both nutrient cycling and carbon storage. To understand soil functioning, it is necessary to model the global distribution patterns and functional gene repertoires of soil microorganisms, as well as the biotic and environmental associations between the diversity and structure of both bacterial and fungal soil communities1-4. Here we show, by leveraging metagenomics and metabarcoding of global topsoil samples (189 sites, 7,560 subsamples), that bacterial, but not fungal, genetic diversity is highest in temperate habitats and that microbial gene composition varies more strongly with environmental variables than with geographic distance. We demonstrate that fungi and bacteria show global niche differentiation that is associated with contrasting diversity responses to precipitation and soil pH. Furthermore, we provide evidence for strong bacterial-fungal antagonism, inferred from antibiotic-resistance genes, in topsoil and ocean habitats, indicating the substantial role of biotic interactions in shaping microbial communities. Our results suggest that both competition and environmental filtering affect the abundance, composition and encoded gene functions of bacterial and fungal communities, indicating that the relative contributions of these microorganisms to global nutrient cycling varies spatially.

Viral clearance capability of monoclonal antibody purification.

Viral clearance steps are routinely included in monoclonal antibody purification processes to safeguard product from potential virus contamination. These steps are often experimentally studied using product-specific feeds and parameters for each project to demonstrate viral clearance capability. However, published evidence suggests that viral clearance capability of many of these steps are not significantly impacted by variations in feed material or process parameter within commonly used ranges. The current investigation confirms robust retrovirus inactivation by low pH treatment and parvovirus removal by second-generation virus filters, independent to individual antibody molecules. Our results also reveal robust retrovirus removal by flowthrough anion exchange chromatography, inside the limits of protein load and host cell protein content. The cumulative viral clearance capability from these steps leads to an excess clearance safety factor of 10,000-fold for endogenous retrovirus-like particles. These results further justify the use of prior knowledge-based modular viral clearance estimation as opposed to repetitive experimentation.

Clinical Presentation of Blastomycosis is Associated With Infecting Species, Not Host Genotype.

Objective: To determine if host genetics may be a risk factor for severe blastomycosis.Design: A cohort of patients who had contracted blastomycosis underwent targeted SNP (single nucleotide polymorphism) genotyping. The genetics of these patients were compared to a set of age and gender-matched controls and between patients with severe versus mild to moderate blastomycosis.Setting: The Marshfield Clinic Health System in central and northern WisconsinParticipants: Patients with a diagnosis of blastomycosis prior to 2017 were contacted for enrollment in this study. A phone hotline was also set up to allow interested participants from outside the Marshfield Clinic Health System to request enrollment.Methods: SNP frequency was assessed for significant differences between the patient cohort and controls and between patients with severe versus mild to moderate blastomycosis. We also tested the effect of Blastomyces species identified in clinical isolates on disease symptoms and severity.Results: No significant differences were found in SNP frequency between cases and controls or between those with severe or mild to moderate blastomycosis. We did detect significant differences in symptom frequency and disease severity by Blastomyces species.Conclusions: Our study did not identify any genetic risk factors for blastomycosis. Instead, the species of Blastomyces causing the infection had a significant effect on disease severity.

Neurofilament light chain in spinal fluid and plasma in multiple system atrophy: a prospective, longitudinal biomarker study.

PURPOSE: There is a critical need for reliable diagnostic biomarkers as well as surrogate markers of disease progression in multiple system atrophy (MSA). Neurofilament light chain (NfL) has been reported to potentially meet those needs. We therefore sought to explore the value of NfL in plasma (NfL-p) in contrast to cerebrospinal fluid (NfL-c) as a diagnostic marker of MSA, and to assess NfL-p and NfL-c as markers of clinical disease progression. METHODS: Well-characterized patients with early MSA (n = 32), Parkinson's disease (PD; n = 21), and matched controls (CON; n = 15) were enrolled in a prospective, longitudinal study of synucleinopathies with serial annual evaluations. NfL was measured using a high-sensitivity immunoassay, and findings were assessed by disease category and relationship with clinical measures of disease progression. RESULTS: Measurements of NfL-c were highly reproducible across immunoassay platforms (Pearson, r = 0.99), while correlation between NfL-c and -p was only moderate (r = 0.66). NfL was significantly higher in MSA compared with CON and PD; the separation was essentially perfect for NfL-c, but there was overlap, particularly with PD, for NfL-p. While clinical measures of disease severity progressively increased over time, NfL-c and -p remained at stable elevated levels within subjects across serial measurements. Neither change in NfL nor baseline NfL were significantly associated with changes in clinical markers of disease severity. CONCLUSIONS: These findings confirm NfL-c as a faithful diagnostic marker of MSA, while NfL-p showed less robust diagnostic value. The significant NfL elevation in MSA was found to be remarkably stable over time and was not predictive of clinical disease progression.

Multi-institutional search for patient factors associated with adverse events following tracheotomy.

BACKGROUND: Tracheotomy is a common procedure for otolaryngologists. The risk of complications is difficult to predict. This study aims to identify measurable preoperative indicators associated with adverse events following tracheotomy. METHODS: The charts of adults undergoing tracheotomy for respiratory failure at one of four university-affiliated hospitals between 1/2012 and 8/2018 were reviewed. Complications were analyzed in the context of demographics, physiologic parameters, and comorbidities. RESULTS: Among 507 tracheotomies performed, the most common complications included infection, bleeding, and cardiac arrest. Mortality was 39 % in patients with pulmonary hypertension, 42 % in those with ejection fraction ≤ 40 and 32 % in those with abnormal right ventricular function, double the rates in patients without each of these findings. CONCLUSION: Many critically ill tracheotomy patients experience significant rates of adverse events. Risk factors for mortality include ejection fraction ≤ 40, pulmonary hypertension, and abnormal ventricular function. These should be considered for use in preoperative counseling.

Interprofessional Education to Address Substance Use among Adults with Persistent Pain: A Pre-Post Program Evaluation.

BACKGROUND: Substance use disorders (SUDs) are highly prevalent among adults with persistent pain. Yet, standard competencies for integrating pain and SUD content are lacking across health science student curricula. Additionally, pharmacotherapies to treat SUDs are underutilized. AIM: To address these gaps, a team of health science faculty created an interprofessional simulation activity using a standardized patient and evaluated learner outcomes related to assessment and treatment of comorbid persistent pain and substance use. METHODS: A total of 304 health science students representing nursing, medicine, pharmacy, and social work programs attended virtual learning sessions. Interprofessional student teams developed a team-based care plan for an adult with musculoskeletal pain who takes prescribed opioids while using alcohol. Pre- and post-activity surveys assessing knowledge and confidence were matched for 198 students. Descriptive statistics summarized survey data with inferential analysis of paired data. RESULTS: The largest significant improvements between pre- and post-activity knowledge were observed in items specific to pharmacotherapy options for alcohol and opioid use disorders. Similar gains were noted in students' confidence regarding pharmacotherapies. No significant differences were noted on pre-post-activity knowledge scores between the three main profession groups (medicine, nursing, and pharmacy). CONCLUSIONS: Students attending this interprofessional simulation demonstrated improved knowledge and confidence, particularly in pharmacotherapies for alcohol and opioid use disorders. Replication of such programs can be used to provide consistent content across health science disciplines to heighten awareness and receptivity to medications available to treat SUDs in people treated for persistent pain. The curriculum is freely available from the corresponding author.

Medical cannabis in schools: The experiences of caregivers.

Objectives: Implementing medical cannabis (MC) into a child's daily routine can be challenging and there is a lack of guidance for its therapeutic use in schools in Canada. Our objective was to learn about the experiences of caregivers of school-aged children who require MC. Methods: Qualitative description was used and caregivers were interviewed about MC in schools and in general. The transcripts were entered into Dedoose software for qualitative analysis and content analysis was performed. Sentences and statements were ascribed line by line into meaning units and labelled with codes, and organized according to categories and subcategories. Results: Twelve caregivers of school-aged children who take MC participated. The most common reasons for treatment were drug-resistant epilepsy (DRE), autism, or other developmental disorders. Approximately half of the participants' children (n = 6) took MC during the school day and most (5/6) perceived their experiences to be positive or neutral but reported a lack of knowledge about MC. While data saturation was not reached regarding MC in schools, rich dialogues were garnered about MC in general and three categories were identified: challenges (subcategories stigma, finding an authorizer, cost, dosing, and supply); parents as advocates (subcategories required knowledge, attitudes, skills, and sources of information); and caregiver relief for positive outcomes. Conclusions: Caregivers demonstrate remarkable tenacity despite the many challenges associated with MC use. Education and practice change are needed to ensure that children using MC can benefit from or continue to experience its positive outcomes within the school environment and beyond.

North America's Amish-Mennonites Adopt Abroad: The Ideologies and Institutional Conditions that Cracked the Homogeneity of an Ethnic Religion.

Under what social conditions would ethnic sectarians in developed countries engage in inter-country adoption, grafting ethnically-racially diverse children into their homogenous contexts? In this article, we present a case study of Amish-Mennonite adoption-oriented children's homes in underdeveloped countries. As the ethnic-sectarian, family-oriented, evangelical Amish-Mennonites meet little success proselytizing adults, adoption-oriented children's home allowed adoptive parents to demonstrate their commitment to mission while maintaining sectarian-style control over a child's socialization. Ultimately, the children's homes were short-lived, coming and going based on larger geo-political dynamics, signaling that this unusual international adoption project is internally motivated but enabled and constrained by larger institutional contexts. Though the actual percent of inter-country adoptees to Amish-Mennonite homes is small, this case demonstrates that the right combination of values and broader political dynamics create conditions facilitating migration of children from lesser developed countries into wealthy contexts, a process cracking - even if not fully opening - Amish-Mennonite ethnic/racial homogeneity.

Urine Antigen Testing is Equally Sensitive to B. dermatitidis and B. gilchristii Infections.

INTRODUCTION: Blastomycosis is endemic in Wisconsin with Blastomyces dermatitidis and B. gilchristii responsible for infections. Urine antigen testing is a non-invasive diagnostic method for blastomycosis with up to 93% test sensitivity. However, the test's sensitivity has not been evaluated with relationship to B. gilchristii infections. METHODS: We aimed to assess physician use of the urine antigen assay and its sensitivity to B. gilchristii and B. dermatitidis infections in a retrospective study. Culture confirmed clinical cases of blastomycosis from 2008-2016 were identified within Marshfield Clinic Health System (MCHS) and UW Hospital and Clinics (UWHC) medical records. Clinical data were abstracted from each medical record and included the following: patient demographics, presence of immune compromising and underlying medical conditions, treatment drugs, presence of isolated pulmonary or disseminated disease, death, urine antigen testing, timeframe of testing, and quantitative test values (EIA units or ng/mL). RESULTS: A total of 140 blastomycosis cases were included in this study, with MCHS contributing 114 cases to the study and UWHC contributing 26 cases. The majority of UWHC cases (n=22; 85%) were caused by B. dermatitidis and the majority of MCHS cases (n=73; 64%) were caused by B. gilchristii. UWHC physicians were significantly more likely to treat with multiple drugs during the course of infection and were more likely to prescribe amphotericin B and voriconazole. Urine antigen testing was more frequently used at UWHC (n=24; 92%) than MCHS (n=51; 45%; P < 0.00001). In this study, the urine antigen assay demonstrated 79% sensitivity. Sensitivity was significantly associated with the timeframe of testing (P < 0.05), with most true positive urine antigen tests (83%) being performed ≤ 7 days from diagnosis. In this study, the urine antigen assay was capable of detecting both B. dermatitidis and B. gilchristii at about equal sensitivity. Urine antigen concentration (ng/mL) trended higher in B. dermatitidis infections. CONCLUSION: This study found that the urine antigen assay is capable of detecting both species of Blastomyces at about the same sensitivity. We recommend continued use of the urine antigen assay for diagnosis of blastomycosis and recommend that the assay be used early in the diagnostic process to minimize the chance of false negative results.

mRNA processing in mutant zebrafish lines generated by chemical and CRISPR-mediated mutagenesis produces unexpected transcripts that escape nonsense-mediated decay.

As model organism-based research shifts from forward to reverse genetics approaches, largely due to the ease of genome editing technology, a low frequency of abnormal phenotypes is being observed in lines with mutations predicted to lead to deleterious effects on the encoded protein. In zebrafish, this low frequency is in part explained by compensation by genes of redundant or similar function, often resulting from the additional round of teleost-specific whole genome duplication within vertebrates. Here we offer additional explanations for the low frequency of mutant phenotypes. We analyzed mRNA processing in seven zebrafish lines with mutations expected to disrupt gene function, generated by CRISPR/Cas9 or ENU mutagenesis methods. Five of the seven lines showed evidence of altered mRNA processing: one through a skipped exon that did not lead to a frame shift, one through nonsense-associated splicing that did not lead to a frame shift, and three through the use of cryptic splice sites. These results highlight the need for a methodical analysis of the mRNA produced in mutant lines before making conclusions or embarking on studies that assume loss of function as a result of a given genomic change. Furthermore, recognition of the types of adaptations that can occur may inform the strategies of mutant generation.

Development of a national position statement on cancer patient navigation in Canada.

As the landscape of cancer care in Canada evolves, oncology nursing roles are developed to enhance the patient experience and address the changing needs of patients and families. Cancer Patient Navigation (CPN), an oncology nursing role focusing primarily on person-centred care coordination and system navigation, has become integral to providing high-quality cancer care in many Canadian jurisdictions. Since 2016, a national group of oncology nursing leaders have been engaged in convening and catalyzing our understanding of the role of patient navigation in the Canadian cancer context with the purpose of developing a national position statement on CPN. In this paper, we provide a historical analysis of the development of the forthcoming Canadian Association of Nurses in Oncology (CANO) position statement on CPN. We present an analysis of participant feedback from workshops at the 2016, 2017, and 2018 conferences, and meeting minutes from the National working group over this same time period. This paper serves as a concise historical summary of the evolution of CPN in Canada while providing a template for other groups looking to develop a consensus-based position statement.

Élaboration d'un énoncé de position national sur la navigation des patients atteints de cancer au Canada.

Au Canada, le paysage des soins du cancer évolue et les infirmières en oncologie sont appelées à jouer de nouveaux rôles afin d'améliorer l'expérience des patients et des familles et de répondre à leurs besoins toujours changeants. L'un de ces rôles, la navigation des patients atteints de cancer (NPC), vise principalement à coordonner les soins centrés sur la personne et à guider les patients dans le système de santé. Dans plusieurs provinces et territoires du Canada, la navigation est devenue essentielle pour offrir des soins de grande qualité aux patients cancéreux. Depuis 2016, des chefs de file des soins infirmiers oncologiques se réunissent au sein d'un groupe national pour synthétiser leur compréhension de la navigation des patients en contexte canadien afin d'élaborer un énoncé de position national sur la NPC. Dans le présent article, nous analyserons l'historique de l'élaboration de l'énoncé de position sur la NPC que publiera prochainement l'Association canadienne des infirmières en oncologie (ACIO/CANO). Nous analyserons également les commentaires des participants aux ateliers tenus dans le cadre des congrès de 2016, 2017 et 2018, de même que les comptes rendus des réunions du groupe de travail national qui ont eu lieu pendant cette même période. Le présent article se veut un sommaire historique concis de l'évolution de la NPC au Canada, ainsi qu'un modèle pour les autres groupes aspirant à rédiger un énoncé de position consensuel.

Introgression maintains the genetic integrity of the mating-type determining chromosome of the fungus Neurospora tetrasperma.

Genome evolution is driven by a complex interplay of factors, including selection, recombination, and introgression. The regions determining sexual identity are particularly dynamic parts of eukaryotic genomes that are prone to molecular degeneration associated with suppressed recombination. In the fungus Neurospora tetrasperma, it has been proposed that this molecular degeneration is counteracted by the introgression of nondegenerated DNA from closely related species. In this study, we used comparative and population genomic analyses of 92 genomes from eight phylogenetically and reproductively isolated lineages of N. tetrasperma, and its three closest relatives, to investigate the factors shaping the evolutionary history of the genomes.We found that suppressed recombination extends across at least 6 Mbp (∼ 63%) of the mating-type (mat) chromosome in N. tetrasperma and is associated with decreased genetic diversity, which is likely the result primarily of selection at linked sites. Furthermore, analyses of molecular evolution revealed an increased mutational load in this region, relative to recombining regions. However, comparative genomic and phylogenetic analyses indicate that the mat chromosomes are temporarily regenerated via introgression from sister species; six of eight lineages show introgression into one of their mat chromosomes, with multiple Neurospora species acting as donors. The introgressed tracts have been fixed within lineages, suggesting that they confer an adaptive advantage in natural populations, and our analyses support the presence of selective sweeps in at least one lineage. Thus, these data strongly support the previously hypothesized role of introgression as a mechanism for the maintenance of mating-type determining chromosomal regions.

Molecular detection of Blastomyces in an air sample from an outbreak associated residence.

Based on epidemiologic data during a blastomycosis outbreak, exposure within the home was suspected for two case patients that resided together. Soil and air samples were collected from the basement of their residence. Samples were tested for Blastomyces by culture and polymerase chain reaction (PCR) to compare with an available clinical isolate. An air sample from the basement of the residence was PCR positive for Blastomyces. Sequence data from the air sample and the outbreak clinical isolate were identified as different Blastomyces spp. Despite this, our findings suggest that the basement was suitable for the growth of Blastomyces and airborne organism was circulating.

Virus removal robustness of ion exchange chromatography.

Virus removal by ion exchange chromatography enhances the safety profile of therapeutic protein products. The robustness of virus removal depends on electrostatic binding between virus and oppositely charged chromatography media. However, model retrovirus Xenotropic Murine Leukemia Virus (XMuLV) binding remains robust even when virus and media are both positively charged. We investigated this counter-intuitive phenomenon using side-by-side comparison of virus-media binding behavior of XMuLV versus parvovirus, two viruses very different in size and structure but comparable in isoelectric point. When both viruses were negatively charged, XMuLV bound to positive anion exchange media with higher strength than parvovirus. When both viruses were positively charged, XMuLV remained tightly bound to positive media but parvovirus was dissociated. Likewise, XMuLV binding to media was much stronger than parvovirus under cation exchange conditions. These findings suggest that XMuLV binding could be enhanced by localized charge distribution not possessed by parvovirus, which is an important consideration for designing chromatography processes with robust virus removal capacity.

Latent tuberculosis may be missed by current screening practices: Analysis of interferon-gamma release assay results from a paediatric refugee clinic.

AIMS: (i) To determine the prevalence of latent tuberculosis infection (LTBI) and characteristics associated with LTBI in children attending a paediatric refugee clinic and (ii) to determine whether current New South Wales (NSW) Health screening practices could miss LTBI cases. METHODS: This was a retrospective analysis of tuberculosis (TB) screening data from refugee and asylum seeker children who attended a refugee clinic in a tertiary children's hospital during 2014 and 2015. We determined associations between LTBI and child characteristics at 5% significance levels. RESULTS: Of 358 children attending the clinic, 235 children (66%) received interferon-gamma release assay (IGRA) testing, of whom 28 (11.9%) had positive results. Of the 28 with positive IGRAs, 12 (42.9%) would have been missed using NSW Health screening guidelines: two because they were younger than 2 years old, one who was born in Australia and 10 because they were not born in high TB incidence countries. IGRA results were not significantly associated with any of the child characteristics examined, including age, gender, travel through transit countries, boat versus plane arrival into Australia, whether the child had been in a detention centre or TB incidence in the source country. CONCLUSIONS: We identified 12 children with LTBI who would have been missed using current NSW Health Department screening practices. These children are at risk of progression to active disease, particularly the two aged younger than 2 years old. We recommend universal screening.

Exploring occupational standing activities using accelerometer-based activity monitoring.

Prolonged standing at work is required by an estimated 60% of the employed population and is associated with a high prevalence of musculoskeletal disorders. 'Standing' is expected to encompass a range of activities of varying intensity. This study aimed to define a range of 'standing' work-based activities; and objectively explore differences between 'standing' occupations. The following movements were defined using a triaxial accelerometer (ActivPAL) through recordings of known movements (n = 11): static standing, weight-shifting, shuffling, walking and sitting. Movements over a working day were defined for chefs (n = 10), veterinary surgeons (n = 7) and office workers (n = 9). Despite veterinary surgeons and chefs spending a similar time in an upright posture, veterinary surgeons spent 62% of this time standing statically whereas chefs split their time between all the movements. Overall, this study provides the first attempt to define 'standing' activities, allowing the differentiation of activities between occupations spending similar periods of time upright. Practitioner Summary: This study identified a range of work-based 'standing' activities of varying intensity. Differences in activity were recorded between two occupations spending a similar time in an upright posture (veterinary surgeons and chefs). A broader definition of standing activities could be important when considering factors related to musculoskeletal disorders at work.