Sequential interaction of the chaperones BiP and GRP94 with immunoglobulin chains in the endoplasmic reticulum

During their transit through the endoplasmic reticulum, newly synthesized light and heavy chains of immunoglobulins associate with two endoplasmic reticulum stress proteins. BiP/GRP78, a member of the HSP70 family, binds these polypeptides, presumably through promiscuously exposed hydrophobic sequences, soon after their translocation into the endoplasmic reticulum. GRP94, another endoplasmic reticulum stress protein homologous to HSP90, also associates with unassembled immunoglobulin chains, but its interaction is biochemically, kinetically and structurally distinct from BiP's. We report here that whereas BiP preferentially binds an early disulphide intermediate of light chain and dissociates within a few minutes, GRP94 exclusively binds fully oxidized molecules and dissociates with a half-time of 50 min. These results indicate that GRP94 is itself a chaperone which acts after BiP.

Muscular synergism--II. A minimum-fatigue criterion for load sharing between synergistic muscles

P6new physiological criterion for muscular load sharing is developed. The criterion is based on the assumption that the endurance time of muscular contractions is maximized, hence muscular fatigue is minimized. The optimization problem is cast in the form of a linearly constrained, non-linear MINIMAX optimization. The new method predicts that: (1) there is synergistic muscle action, (2) muscle force increases non-linearly with external force (load), (3) relatively more force is allocated to muscles that have a large maximum force (large muscles), (4) relatively more force is allocated to muscles with a high percentage of slow-twitch fibers (muscles that are fatigue-resistant), (5) the load sharing does not depend on the moment arm of the muscles (although the absolute force levels do depend on this variable). The predicted load sharing between two cat muscles during standing and walking is in good agreement with direct force measurement data from the literature.

Dutch Musculoskeletal Questionnaire: description and basic qualities

A questionnaire ('Dutch Musculoskeletal Questionnaire', DMQ) for the analysis of musculoskeletal workload and associated potential hazardous working conditions as well as musculoskeletal symptoms in worker populations is described and its qualities are explored using a database of 1575 workers in various occupations who completed the questionnaire. The 63 questions on musculoskeletal workload and associated potentially hazardous working conditions can be categorized into seven indices (force, dynamic and static load, repetitive load, climatic factors, vibration and ergonomic environmental factors). Together with four separate questions on standing, sitting, walking and uncomfortable postures, the indices constitute a brief overview of the main findings on musculoskeletal workload and associated potentially hazardous working conditions. Homogeneity of the indices is satisfactory. The divergent validity of the indices is fair when compared with an index of psychosocial working conditions and discomfort during exposure to physical loads. Worker groups with contrasting musculoskeletal loads can be differentiated on the basis of the indices and other factors. With respect to the concurrent validity, it appears that most indices and factors show significant associations with low back and/or neck-shoulder symptoms. This questionnaire can be used as a simple and quick inventory for occupational health services to identify worker groups in which a more thorough ergonomic analysis is indicated.

The relationship between leisure time, physical activities and musculoskeletal symptoms and disability in worker populations

OBJECTIVES

To assess the association between leisure time physical activity and musculoskeletal morbidity, as well as possible interactions with physical activity at work.

METHODS

A literature search was performed to collect all studies on musculoskeletal disorders in which physical activity was involved as a variable. Next, an analysis was made of questionnaire data on a group of 2,030 workers in various occupations, on self-reported physical activity in leisure time and at work, musculoskeletal symptoms (from low back, neck-shoulder and lower extremity) and sick leave due to these symptoms. A logistic regression analysis was carried out to estimate the association between musculoskeletal morbidity and four physical-activity indices (participation in sports and sedentary activities, active life style, sedentary life style), adjusted for age, gender, education and work load. Interaction of leisure activities with age and work load was tested too.

RESULTS

Available literature data (39 studies) showed inconsistent results. Most studies did not show any effects. Some studies indicated favourable effects of physical activity, both on low back and neck pain. Participation in some vigorous sports seemed associated with unfavourable effects. The empirical data showed no association between participation in sports and/or other physical activities in leisure time and musculoskeletal symptoms. Sedentary activity in leisure time was associated with higher prevalence rates of low back symptoms and sick leave due to low back symptoms.

CONCLUSIONS

Stimulation of leisure time physical activity may constitute one of the means of reducing musculoskeletal morbidity in the working population, in particular in sedentary workers.

Muscular synergism--I. On criteria for load sharing between synergistic muscles

The use of optimization techniques to predict individual muscle forces in redundant biomechanical systems implies the formulation of a criterion for load sharing between the muscles. In part I of this paper, the characteristics and performance of several linear and non-linear criteria reported in the literature have been compared for static-isometric knee flexion. The results show that linear criteria inherently predict discrete muscle action (orderly recruitment of muscles) whereas non-linear criteria can predict synergistic action. All criteria predict that relatively more force is allocated to muscles with large moment arms. When muscle stresses (or ratios of muscle force to maximum muscle force) are used as the decision variables in the objective function, then relatively more force is allocated to muscles with large maximum possible force as well. Future formulations of the optimization should consider the differences in fiber type composition among the muscles. Such an approach is presented in part II of the paper.

A single amino acid substitution in the variable region of the light chain specifically blocks immunoglobulin secretion

Although immunoglobulin light chains are usually secreted in association with heavy chains, free light chains can be secreted by lymphocytes. To identify the structural features of light chains that are essential for their secretion, we mutated a conserved sequence in the variable domain of a lambda I light chain. The effects of the mutations on secretion were assayed by transient expression in COS-1 cells. One mutant (AV60), which replaced Ala-60 with Val, was secreted as efficiently as wild-type lambda I by transfected COS-1 cells. This result was not surprising because secreted lambda II chains contain valine in this position. However, a second lambda I mutant (AV60FS62), which replaced Phe-62 with Ser as well as Ala-60 with Val, was not secreted. This mutant was arrested in the endoplasmic reticulum, as judged by immunofluorescence and by its association with a lumenal endoplasmic reticulum protein, immunoglobulin heavy chain binding protein (BiP). The defect in secretion was not due to gross misfolding of the lambda I chain, since cells cotransfected with AV60FS62 and an immunoglobulin heavy chain gene produced functional antigen-binding antibodies. These assembled IgM molecules were still not secreted. Hence, the replacement of Phe-62 with Ser specifically affects a determinant on the lambda I light chain that is necessary for the intracellular transport of this molecule.

A kinematic model of the human ankle

The spatial gross motion of the foot with respect to the shank is modelled as rotations about two fixed ankle axes: the upper ankle rotation axis (plantar flexion/dorsiflexion) and the subtalar rotation axis (inversion/eversion). The positions of the axes are determined by externally visible bony landmarks of the lower leg, and are measured for a living subject. The model input data are the plantar flexion/dorsiflexion and inversion/eversion rotation angles; the model output is a 4 X 4 transformation matrix which quantitatively describes the relative position of a foot coordinate system with respect to a shank coordinate system.

Both the environment and somatic mutations govern the aggregation pathway of pathogenic immunoglobulin light chain

Deposition of monoclonal immunoglobulin light chain (LC) aggregates in tissues is the hallmark of a class of fatal diseases with no effective treatment. In the most prevalent diseases two different types of LC aggregates are observed: fibrillar deposits in LC amyloidosis (AL) and granular aggregates in LC deposition disease (LCDD). The mechanisms by which a given LC forms either type of aggregate are not understood. Although some LCs are more aggregation-prone than others, this does not appear to be due to specific sequence determinants, but more likely from global properties that can be introduced by multiple somatic mutations. Moreover, a single LC isotype can sometimes form both fibrillar and granular aggregates within the same patient. To better understand how the different aggregation pathways arise, we developed a series of in vitro assays to analyze the formation of distinct aggregate types. The recombinant kappa IV LC (SMA) assembles into fibrils when agitated. We now show that SMA can also form granular aggregates upon exposure to copper, and that this aggregation can occur not only in vitro, but also in cells. A constellation of somatic mutations, consisting of His89/His94/Gln96, is sufficient to confer sensitivity to copper on wild-type kappa IV proteins. The formation of both types of aggregates is inhibited by synthetic peptides derived from the LC variable domain. However, the peptide that inhibits fibrillar aggregation is different from the peptide that inhibits copper-induced aggregation. Thus, distinct molecular surfaces of the LC underly each type of aggregate. We conclude that both the intrinsic properties of the sequence and extrinsic conditions govern the aggregation pathway of a LC.

A biomechanical model to quantify shoulder load at the work place

A simple two-dimensional biomechanical model of the shoulder has been developed to quantify shoulder muscle load, joint load and endurance time in work situations. The model is applicable to the analysis of working postures requiring elevated upper arm positions in the plane of the scapula, with the trunk upright, and the elbow flexed at 90°. The only input variable of the model, to be measured in the work situation, is the angle between the upper arm and the vertical line. In addition, the total body weight and the upper arm length should be known. For a given arm position, the model predicts the individual forces in the deltoid and supraspinatus muscles, and the reaction force at the glenohumeral joint. Furthermore, the model estimates the endurancetime of the given arm position, which is the period of time until the shoulder muscles become fatigued. The results show that maximum muscle forces occur at 80° of arm elevation, when the deltoid force is about 22% of its maximum force, and the supraspinatus 25%. The corresponding glenohumeral joint force is about 43% of total body weight. At 80° of arm elevation, the endurance time is about 5 minutes. If a working posture is maintained for more than 1 hour, the model suggests that the elevation angle between the upper arm and the trunk should be less than 15°, in order to prevent muscular fatigue in the shoulder muscles.

Ergonomic guidelines for the prevention of discomfort of static postures based on endurance data

This communication aims to show why guidelines to prevent discomfort of static postures can be based on endurance data, and to give insight in the aim and scope of a recent 'work-rest model for static postures' (WR model). The paper is a response to a recent paper of Mathiassen and Winkel (1992) who questioned the usefulness of discomfort and endurance data, and of the WR model for developing guidelines for static postures. It is concluded that discomfort can be considered as an independent evaluation variable for working postures, anchored in European legislation. Discomfort can be predicted from the 'remaining endurance capacity' (REC) because of a known relationship between the REC and discomfort as measured with the Borg rating scale. The WR model estimates at group level the mean REC of a static posture with or without an external force during and immediately after a work-rest schedule. The WR model is meant to assist practitioners in the assessment and optimization of static postures (and external forces) and work-rest schedules in order to avoid high levels of discomfort.

The murine VpreB1 and VpreB2 genes both encode a protein of the surrogate light chain and are co-expressed during B cell development

The surrogate light chain is composed of two polypeptides, VpreB and lambda 5. In the mouse there are two VpreB genes which are 99% identical within the coding regions. Extensive restriction enzyme mapping and sequencing of these two genes showed that only the coding region and immediate 5' and 3' flanking sequences exhibited such high homology. More distal sequences have diverged considerably. The region 5' of the respective gene directed transcription of a reporter gene in a pre-B cell line, indicating that it contained promoter, and perhaps enhancer function. The VpreB2 gene is functional, as it directed the production in COS cells of a 16-kDa protein that assembled with lambda 5 and was recognized by a VpreB-specific monoclonal antibody. Using transfected COS cells expressing either VpreB1 or VpreB2, a PCR assay was developed to examine the steady state level of transcripts from each gene. When this assay was applied to a number of cell lines representing early stages of B cell differentiation, co-expression of the two genes was observed in every case. VpreB1 and VpreB2 were co-expressed in the fetal liver of CB17 mice, where peak expression of each gene occurred at days 16-17 of gestation. Similarly, adult bone marrow from several strains of mice expressed both genes. In sorted bone marrow cells expression of both VpreB genes was detected in pro-B/pre-BI and large pre-BII cells, while the RNA steady state levels were at least 100-fold lower in small pre-BII and immature/mature B cells. Finally, single-cell reverse transcriptase-polymerase chain reaction on such sorted bone marrow cells detected VpreB1 and VpreB2 expression in at least 30% of all pro-B/pre-BI cells and large Ig heavy chain, surrogate light chain (pre-B receptor) expressing pre-BII cells. These results demonstrate that the control of expression of the two VpreB genes overlaps during development. They suggest that both VpreB1 and VpreB2 polypeptides can assemble with lambda 5 and mu to form pre-B cell receptor complexes.

International standards on working postures and movements ISO 11226 and EN 1005-4

Standards organizations have given considerable attention to the problem of work-related musculoskeletal disorders. The publication of international standards for evaluating working postures and movements, ISO 11,226 in 2000 and EN 1,005-4 in 2005, may be considered as a support for those involved in preventing and controlling these disorders. The first one is a tool for evaluation of existing work situations, whereas the latter one is a tool for evaluation during a design/engineering process. Key publications and considerations that led to the content of the standards are presented, followed by examples of application.

Partial block in B lymphocyte development at the transition into the pre-B cell receptor stage in Vpre-B1-deficient mice

The surrogate light chain (SL) is composed of two polypeptides, Vpre-B and lambda5. In large pre-BII cells the SL chain associates with Ig mu heavy chain (muH) to form the pre-B cell receptor (pre-BCR). In mice there are two Vpre-B genes which are 98% identical within the coding regions. The two genes are co-expressed at the RNA level and encode functional proteins that can assemble with lambda5. However, it is not known whether both gene products serve the same function in vivo. Here we have established mice that lack the Vpre-B1 gene (VpreB1(-/-)), but still express the Vpre-B2 gene, both as RNA and protein. In Vpre-B1(-/-) mice, the bone marrow cellularity and the percentage of B220+ cells is normal. However, among the B220+ cells, the percentage of pre-BI cells is increased, and the percentage of pre-BII and immature B cells is slightly decreased, suggesting that the lack of Vpre-B1 causes a partial block at the transition from pre-BI to pre-BII cells, i.e. into the pre-BCR stage. The number of cells that produce a functional pre-BCR is thus lower, but the cells that reach this stage are normal as they can be expanded by proliferation and then differentiate into more mature cells. The spleens of Vpre-B1 homozygous mutant mice show normal numbers of B and T lymphocytes. Moreover, the Ig loci are allelicly excluded and the homozygous mutant mice respond with normal levels of antigen-specific antibodies to T-dependent antigens. These results demonstrate that VpreB2 alone is capable of supporting B lymphocyte development in the bone marrow and can give rise to immuno-competent cells in the periphery.

The influence of climatic factors on non-specific back and neck-shoulder disease

An epidemiological study was carried out to explore the relationship between climatic factors and non-specific low-back and neck-shoulder symptoms in working populations. In a review of published literature, 27 studies were found which related climatic factors to musculoskeletal symptoms, but none of these studies specifically addressed the subject. It can be concluded that a relationship between climatic factors and musculoskeletal symptoms is considered at least plausible by both researchers, workers and patients, but that the epidemiological evidence appearing from literature is very weak. Questionnaire data which were collected on musculoskeletal symptoms, workload and perceptions of climatic conditions of 2030 workers in 24 different occupations were analysed multi-variately. About one-quarter of the workers related symptoms of the low back and neck-shoulders to climatic factors. They perceived climatic factors in most cases as aggravating factors for their symptoms. No seasonal influence on prevalence rates was reported. For low-back and neck-shoulder symptoms and for sick leave due to neck-shoulder symptoms, an association was found with climatic factors, and in particular with respect to draughts in relation to neck-shoulder symptoms. In addition, neck-shoulder symptoms were negatively related to frequent outdoor work. The findings suggest a relationship between climatic factors and musculoskeletal symptoms and call for further detailed investigations.

Simulation of tendon transfer surgery

A biomechanical model is used to simulate a tendon transfer operation. The model predicts the required forces in twelve ankle muscles during standing and walking, and also the endurance time of the (instantaneous) posture. In particular, the mechanical effect of anterior transfer of the posterior tibial tendon of a patient with muscle paralysis due to peroneal nerve injury is studied.

The results show that before surgery the patient can stand normally but cannot walk normally. Normal walking is mechanically not possible because the required muscle forces in early stance cannot be produced, although the necessary forces can be realized during the remainder of stance. After surgery, both normal standing and normal walking are mechanically possible. The cost is higher forces and shorter endurance times in the healthy muscles. The results agree with clinical findings.

Transcription stimulates recombination. I. Specialized transduction of Escherichia coli by lambda trp phages

Specialized transduction of Trp+ by lambda trp phages, whose trp genes were totally under the control of the PL promoter of lambda, was studied. In all cases the efficiency of transduction (EOT) was significantly reduced in homoimmune recipients. In Su- recipients the EOT by phages whose trp gene expression was N-dependent was reduced 2- to 3-fold by the lambda mutant Pam but 30- to 100-fold by an Nam mutant. With phages whose trp gene expression was N-independent, either Pam or Nam caused 2- to 3-fold reduction in the EOT. It was concluded that transcription of the trp genes of the specialized transducing phages had a direct, stimulatory effect on their recombination leading to transduction.

Transcription stimulates recombination. II. Generalized transduction of Escherichia coli by phages T1 and T4

Phage Mu was inserted in the trpE gene of one donor Escherichia coli strain and in the lac promoter of another. Strains with Mu prophage mutations which permitted transcription of genes whose transcription had been polarly blocked by the Mu insertion were isolated and called "bypass" strains. The transducing phages T1am, and T1am,ST, and, in one instance, T4GT7 were grown on both the bypass and the original strains. After growth on the bypass strains transducing phages were able to transduce Trp+ and Lac+, respectively, to a variety of Trp- and Lac- strains more efficiently than after growth on nonbypass strains. These results support the idea that crossovers required for generalized transduction occur more efficiently if the specific region is transcribed by both interacting parental molecules.

Enhancing the impact of ergonomics interventions

The aim of this paper was to provide recommendations for ergonomists involved in project design and evaluation. Twelve research and consultancy projects involving ergonomics interventions in a variety of settings in The Netherlands were analysed to identify factors important to success. Projects included participatory and non-participatory cases. Eight factors were identified for successful project design and for demonstrating project effectiveness.

Identification of high-risk groups among maintenance workers in a steel company with respect to musculoskeletal symptoms and workload

To determine priorities for ergonomic improvements in five maintenance departments of a steel company, a study was carried out to identify groups with a high prevalence of musculoskeletal problems or a high exposure to unfavourable musculoskeletal workload. All workers were asked to complete a standardized questionnaire on musculoskeletal symptoms and musculoskeletal workload. Response rate in the five departments varied between 60 and 80% (n = 436). Symptoms of low back and neck-shoulder (12-month prevalence rates of 53% and 36%, respectively) were most common, but not higher in comparison with a reference group of 396 non-sedentary workers. Self-reported exposure rates to physical and psychosocial loads as well as poor climatic conditions were comparable with the reference group; only exposure to vibration was higher. Significant differences were seen between the five departments as well as between task groups with the departments. Several task groups with relatively high symptom rates and high exposure levels could be identified. It is concluded that a questionnaire survey can constitute a valuable contribution to the selection of high-risk task groups that need ergonomic intervention.

The expression of membrane and secreted immunoglobulin during the in vitro differentiation of the murine B cell lymphoma CH12

The expression of membrane and secreted IgM was analyzed during mitogen-induced differentiation of the murine B cell lymphoma CH12. To characterize the Ig genes used by CH12, the nucleotide sequences of the variable gene segments (V mu and V kappa) were determined. The expressed V mu gene segment belongs to the VHII NPb-related family. The D (FL16.1a) and J (JH2) segments are the same as those used by the NP-specific hybridoma B1-8. The V kappa used by CH12 is almost identical to those used by the oxazolone-specific hybridomas NQ5.89.4 and NQ7.7.1. Treatment with lipopolysaccharide (LPS) induces up to 80% of CH12 cells to secrete IgM within 48 hr of culture. The steady state levels of secreted mu (mu s) and kappa mRNA increase four to fivefold over this period in cells stimulated with LPS compared with unstimulated cells. The kinetics are similar for both mRNA and parallel the increase in IgM secretion. EL-4 supernatants induce comparable changes in m mu s and kappa transcript levels. The simultaneous increase in m mu s and kappa transcripts suggests that coordinate control of RNA levels is used to increase the synthesis of secretory IgM during differentiation. The level of mRNA encoding the membrane form of mu (mu m) remains constant in stimulated cells and increases slightly in unstimulated cells. While the net rates of synthesis of membrane-bound mu-chains remain similar during LPS stimulation, the level of surface IgM on secreting cells is reduced three to fivefold. These observations suggest that the level of surface IgM expression during differentiation of CH12 is controlled largely by post-translational mechanisms. Our results demonstrate that the CH12 cell line regulates the expression of membrane and secreted IgM differently during its differentiation. The changes in IgM expression in CH12 parallel those occurring in normal B cells after mitogen or antigen challenge. Thus, the in vitro differentiation of CH12 is a good model for the analysis of late stages of B cell development.