Computational biodynamics of human knee joint in gait: from muscle forces to cartilage stresses

Using a validated finite element model of the intact knee joint we aim to compute muscle forces and joint response in the stance phase of gait. The model is driven by reported in vivo kinematics-kinetics data and ground reaction forces in asymptomatic subjects. Cartilage layers and menisci are simulated as depth-dependent tissues with collagen fibril networks. A simplified model with less refined mesh and isotropic depth-independent cartilage is also considered to investigate the effect of model accuracy on results. Muscle forces and joint detailed response are computed following an iterative procedure yielding results that satisfy kinematics/kinetics constraints while accounting at deformed configurations for muscle forces and passive properties. Predictions confirm that muscle forces and joint response alter substantially during the stance phase and that a simplified joint model may accurately be used to estimate muscle forces but not necessarily contact forces/areas, tissue stresses/strains, and ligament forces. Predictions are in general agreement with results of earlier studies. Performing the analyses at 6 periods from beginning to the end (0%, 5%, 25%, 50%, 75% and 100%), hamstrings forces peaked at 5%, quadriceps forces at 25% whereas gastrocnemius forces at 75%. ACL Force reached its maximum of 343 N at 25% and decreased thereafter. Contact forces reached maximum at 5%, 25% and 75% periods with the medial compartment carrying a major portion of load and experiencing larger relative movements and cartilage strains. Much smaller contact stresses were computed at the patellofemoral joint. This novel iterative kinematics-driven model is promising for the joint analysis in altered conditions.     

Protein kinase-mediated regulation of calcineurin through the phosphorylation of modulatory calcineurin-interacting protein 1

Calcineurin is a serine/threonine protein phosphatase that plays a critical role in many physiologic processes such as T-cell activation, skeletal myocyte differentiation, and cardiac hypertrophy. We previously showed that active MEKK3 is capable of stimulating calcineurin/nuclear factor of activated T-cells (NFAT) signaling in cardiac myocytes through phosphorylation of modulatory calcineurin-interacting protein 1 (MCIP1). However, the protein kinases that function downstream of MEKK3 to mediate MCIP1 phosphorylation and the mechanism of MCIP1-mediated calcineurin regulation have not been defined. Here, we show that MEK5 and big MAP kinase 1 (BMK1) function downstream of MEKK3 in a signaling cascade that induces calcineurin activity through phosphorylation of MCIP1. Genetic studies showed that BMK1-deficient mouse lung fibroblasts failed to mediate MCIP1 phosphorylation and activate calcineurin/NFAT in response to angiotensin II, a potent NFAT activator. Conversely, restoring BMK1 to the deficient cells restored angiotensin II-mediated calcineurin/NFAT activation. Thus, using BMK1-deficient mouse lung fibroblast cells, we provided the genetic evidence that BMK1 is required for angiotensin II-mediated calcineurin/NFAT activation through MICP1 phosphorylation. Finally, we discovered that phosphorylated MCIP1 dissociates from calcineurin and binds with 14-3-3, thereby relieving its inhibitory effect on calcineurin activity. In summary, our findings reveal a previously unrecognized essential regulatory role of mitogen-activated protein kinase signaling in calcineurin activation through the reversible phosphorylation of a calcineurin-interacting protein, MCIP1.     

Mechanical and In Vitro Biological Performance of Graphene Nanoplatelets Reinforced Calcium Silicate Composite

Calcium silicate (CaSiO₃, CS) ceramic composites reinforced with graphene nanoplatelets (GNP) were prepared using hot isostatic pressing (HIP) at 1150°C. Quantitative microstructural analysis suggests that GNP play a role in grain size and is responsible for the improved densification. Raman spectroscopy and scanning electron microscopy showed that GNP survived the harsh processing conditions of the selected HIP processing parameters. The uniform distribution of 1 wt.% GNP in the CS matrix, high densification and fine CS grain size help to improve the fracture toughness by ∼130%, hardness by ∼30% and brittleness index by ∼40% as compared to the CS matrix without GNP. The toughening mechanisms, such as crack bridging, pull-out, branching and deflection induced by GNP are observed and discussed. The GNP/CS composites exhibit good apatite-forming ability in the simulated body fluid (SBF). Our results indicate that the addition of GNP decreased pH value in SBF. Effect of addition of GNP on early adhesion and proliferation of human osteoblast cells (hFOB) was measured in vitro. The GNP/CS composites showed good biocompatibility and promoted cell viability and cell proliferation. The results indicated that the cell viability and proliferation are affected by time and concentration of GNP in the CS matrix.     

Calreticulin regulates insulin receptor expression and its downstream PI3 Kinase/Akt signalling pathway

Defects in insulin signalling and glucose metabolism are associated with the development of diabetes. Insulin signalling is initiated by the binding of insulin to its receptor and triggering cascades of events including activation of PI3kinase/Akt signalling pathway. Calreticulin (CRT) is a calcium binding chaperone molecule located in the endoplasmic reticulum. Targeted deletion of CRT in mice is embryonic lethal as a result of developmental and metabolic abnormalities. Rescued CRT null mice develop severe hypoglycemia the reason for which is not known. In addition, ventricular cardiomyocytes isolated from CRT null (crt-/-) mice have increased glycogen deposits. Therefore, the aim of this study was to investigate the changes in the glucose uptake and insulin signalling pathway (mainly PI3 kinase/Akt) in the absence of CRT. Here we show a significant increase in the glucose uptake by the crt-/- cells. This increase was accompanied by a significant increase in both insulin receptor beta expression, Insulin receptor substrate-1 phosphorylation, GLUT-1 expression and in insulin stimulated Akt phosphorylation and kinase activity in the crt-/- cells. Intriguingly, the increased expression of insulin receptor beta in the crt-/- was due to decreased levels of p53 protein. The current study is the first evidence for the up-regulation of insulin receptor density and activity in the absence of CRT function.     

Mast cells and inflammation

Mast cells are well known for their role in allergic and anaphylactic reactions, as well as their involvement in acquired and innate immunity. Increasing evidence now implicates mast cells in inflammatory diseases where they are activated by non-allergic triggers, such as neuropeptides and cytokines, often exerting synergistic effects as in the case of IL-33 and neurotensin. Mast cells can also release pro-inflammatory mediators selectively without degranulation. In particular, IL-1 induces selective release of IL-6, while corticotropin-releasing hormone secreted under stress induces the release of vascular endothelial growth factor. Many inflammatory diseases involve mast cells in cross-talk with T cells, such as atopic dermatitis, psoriasis and multiple sclerosis, which all worsen by stress. How mast cell differential responses are regulated is still unresolved. Preliminary evidence suggests that mitochondrial function and dynamics control mast cell degranulation, but not selective release. Recent findings also indicate that mast cells have immunomodulatory properties. Understanding selective release of mediators could explain how mast cells participate in numerous diverse biologic processes, and how they exert both immunostimulatory and immunosuppressive actions. Unraveling selective mast cell secretion could also help develop unique mast cell inhibitors with novel therapeutic applications. This article is part of a Special Issue entitled: Mast cells in inflammation.     

A trs20 Mutation That Mimics an SEDT‐Causing Mutation Blocks Selective and Non‐Selective Autophagy: A Model for TRAPP III Organization

TRAPP is a multisubunit complex that functions in membrane traffic. Mutations in the mammalian TRAPP protein C2 are linked to the skeletal disorder spondyloepiphyseal dysplasia tarda (SEDT) that is thought to arise from an inability to secrete procollagen from the endoplasmic reticulum. Here, we show that C2 binds to the SNARE protein Syntaxin 5 and this interaction is weakened by an SEDT‐causing missense mutation (D47Y). Interestingly, the equivalent mutation (D46Y) in the yeast C2 homolog Trs20p does not block anterograde traffic but did affect endocytosis. The trs20D46Y mutation interfered with the interaction between Trs20p and Trs85p (TRAPP III‐specific subunit), Trs120p and Trs130p (TRAPP II‐specific subunits). Size exclusion chromatography suggested that this yeast mutation destabilized the TRAPP III complex that is involved in autophagy. We further show that this mutation blocks both the selective cytosol‐to‐vacuole (cvt) pathway as well as non‐selective autophagy. We demonstrate that the apparent molecular size of the TRAPP III complex is dependent upon membranes, and that the presence of TRAPP III is dependent upon Atg9p. Finally, we demonstrate that lipidated Bet3p is enriched in TRAPP III and that lipidation increases the efficiency of autophagy. Our study suggests that Trs20p acts as an adaptor for Trs85p and Trs120p and reveals complexities in TRAPP III assembly and function. The implications of C2D47Y in SEDT are discussed .     

Social life cycle assessment for material selection: a case study of building materials

Purpose

Sustainability of a material-based product mainly depends on the materials used for the product itself or during its lifetime. A material selection decision should not only capture the functional performance required but should also consider the economical, social, and environmental impacts originated during the product life cycle. There is a need to assess social impacts of materials along the full life cycle, not only to be able to address the “social dimension” in sustainable material selection but also for potentially improving the circumstances of affected stakeholders. This paper presents the method and a case study of social life cycle assessment (S-LCA) specialized for comparative studies. Although the authors’ focus is on material selection, the proposed methodology can be used for comparative assessment of products in general.

Methods

The method is based on UNEP/SETAC “guidelines for social life-cycle assessment of products” and includes four main phases: goal and scope definition, life cycle inventory analysis, life cycle impact assessment, and life cycle interpretation. However, some special features are presented to adjust the framework for materials comparison purpose. In life cycle inventory analysis phase, a hot spot assessment is carried out using material flow analysis and stakeholder and experts’ interviews. Based on the results of that, a pairwise comparison method is proposed for life cycle impact assessment applying analytic hierarchy process. A case study was conducted to perform a comparative assessment of the social and socio-economic impacts in life cycle of concrete and steel as building materials in Iran. For hot spot analysis, generic and national level data were gathered, and for impact assessment phase, site-specific data were used.

Result and discussion

The unique feature of the proposed method compared with other works in S-LCA is its specialty to materials and products comparison. This leads to some differences in methodological issues of S-LCA that are explained in the paper in detail. The case study results assert that “steel/iron” in the north of Iran generally has the better social performance than “concrete/cement.” However, steel is associated with many negative social effects in some subcategories, e.g., freedom of association, fair salary, and occupational health in extraction phase. Against, social profile of concrete and cement industry is damaged mainly due to the negative impact of cement production on safe and healthy living condition. The case study presented in this article shows that the evaluation of social impacts is possible, even if the assessment is always affected by subjective value systems.

Conclusions

Application of the UNEP/SETAC guidelines in comparative studies can be encouraged based on the results of this paper. It enables a hotspot assessment of the social and socio-economic impacts in life cycle of alternative materials. This research showed that the development of a specialized S-LCA approach for materials and products comparison is well underway although many challenges still persist. Particularly characterization method in life cycle impact assessment phase is challenging. The findings of this case study pointed out that social impacts are primarily connected to the conduct of companies and less with processes and materials in general. These findings confirm the results of Dreyer et al. (Int J Life Cycle Assess 11(2):88–97, 2006). The proposed approach aims not only to identify the best socially sustainable alternative but also to reveal product/process improvement potentials to facilitate companies to act socially compatible. It will be interesting to apply the UNEP/SETAC approach of S-LCA to other materials and products; materials with a more complex life cycle will be a special challenge. As with any new method, getting experience on data collection and evaluation, building a data base, integrating the method in software tools, and finding ways for effective communication of results are important steps until integrating S-LCA in routine decision support.     

Renal impairment and analgesia: From effectiveness to adverse effects

Kidney pain is one of the clinically significant features of renal dysfunction. Mild to severe pain is seen in the lower back area. Painkillers are mostly recommended in these cases to relieve the symptom. Yet, several analgesics are associated with side effects that can worsen the state of the disease. This review is based on the studies conducted in these aspects analgesics used to treat kidney pain and their effectiveness, renal consequences of postoperative analgesia, and pharmacogenetics of these palliatives are briefly summarized in this paper.     

Arachidonic acid mobilization and phosphoinositide turnover by the terminal complement complex, C5b-9, in rat oligodendrocyte x C6 glioma cell hybrids

Previously, we have shown that rat oligodendrocytes release phospholipid and generate arachidonic acid (AA) and leukotriene B4 in response to sublytic C5b-9 formation. In the present study, we investigated the biochemical pathways by which C5b-9 generates AA from clone ROC-1, a fusion product of rat oligodendrocytes and C6 glioma. Cells were incubated for 24 h in the presence of [3H]AA or [3H]myoinositol. They were then sensitized with antibody against hybrid cell stroma and treated for 1 h with C9-depleted human serum (C9D-HS) or C9D-HS reconstituted with C9. Alternatively, cells were treated with C8,C9D-HS or C8,C9D-HS reconstituted with C8 or C8 plus C9 for 1 h. Qualitative and quantitative analysis of the released [3H]AA and [3H]myoinositol radiolabeled products were performed by thin layer chromatography/autoradiography and anion exchange chromatography, respectively. The major [3H]AA radiolabeled products after C5b-9 stimulation comigrated with intact phospholipid and AA standards, and the major [3H]myoinositol radiolabeled product was inositol-1-phosphate. Treatment of cells with phospholipase A2 inhibitors, mepacrine and bromophenacyl bromide, abolished AA release by C5b-9. In the absence of extracellular Ca2+, C5b-9 also failed to induce the release of AA. Interestingly, 1-(5-isoquinolinsulfonyl)-2-methylpiperazine (H-7), a potent inhibitor of protein kinases, inhibited AA release by C5b-9, whereas AA release stimulated by the calcium ionophore A23187 was not blocked by H-7. The results suggest that AA generation by C5b-9 from the ROC-1 clone involves activation of Ca2+-dependent phospholipase A2 which is regulated by protein kinase-dependent mechanisms.