Consistent formulation of the growth process at the kinematic and constitutive level for soft tissues composed of multiple constituents

Previous studies have investigated the possibilities of modelling the change in volume and change in density of biomaterials. This can be modelled at the constitutive or the kinematic level. This work introduces a consistent formulation at the kinematic and constitutive level for growth processes. Most biomaterials consist of many constituents and can be approximated as being incompressible. These two conditions (many constituents and incompressibility) suggest a straightforward implementation in the context of the finite element (FE) method which could now be validated more easily against histological measurements. Its key characteristic variable is the normalised partial mass change. Using the concept of homeostatic equilibrium, we suggest two complementary growth laws in which the evolution of the normalised partial mass change is governed by an ordinary differential equation in terms of either the Piola-Kirchhoff stress or the Green-Lagrange strain. We combine this approach with the classical incompatibility condition and illustrate its algorithmic implementation within a fully nonlinear FE approach. This approach is first illustrated for a simple uniaxial tension and extension test for pure volume change and pure density change and is validated against previous numerical results. Finally, a physiologically based example of a two-phase model is presented which is a combination of volume and density changes. It can be concluded that the effect of hyper-restoration may be due to the systemic effect of degradation and adaptation of given constituents.

The potential role of somatostatin analogues in the treatment of gastrointestinal (GI) cancers

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Background: Somatostatin receptors (sstr) are expressed in various normal and malignant tissues, including non-neuroendocrine GI solid tumors. Gastric cancer (GC) cells mainly express sstr2 and sstr5, colorectal cancer (CRC) cells predominantly express sstr1 followed by sstr5 and sstr2, and hepatocellular carcinoma (HCC) cells express mainly sstr5 as well as sstr1,2,3. Somatostatin analogues (SAs) may have direct and indirect antitumor activity. Octreotide and lanreotide primarily target sstr2, whereas the new agent pasireotide has high affinity for sstr1,2,3 and sstr5.

Methods: Published data evaluating the antitumor properties of SAs in GI tumors were reviewed.

Results: The table lists the results of clinical studies in which SAs were evaluated as antitumor therapies in GI cancers.

Conclusions: Although octreotide and lanreotide are efficacious in the treatment of symptoms of neuroendocrine tumors, these agents have demonstrated mixed results in the antitumor treatment of non-neuroendocrine GI tumors. Data suggesting potential favorable outcomes with SAs alone or in combination with other agents have been seen in solid tumors with predominant sstr2 expression such as GC. Novel SAs such as pasireotide may have improved antitumor effects in non-neuroendocrine solid tumors expressing multiple sstr compared with octreotide and lanreotide.

[Table: see text]

[Table: see text]

Erythropoiesis stimulating agents and anaemia of end-stage renal disease

Chronic kidney disease (CKD) is a widespread health problem in the world and anaemia of renal origin is a common problem. Anaemia associated with CKD covers significant risk for faster progression of chronic renal failure, decreased quality of life, and clinical manifestation of cardiovascular disease. The mainstay of anaemia treatment secondary to end-stage renal disease (ESRD) has become erythropoiesis stimulating agents (ESAs). More than 90 % of ESRD patients maintained on dialysis respond to traditional recombinant human erythropoietin (rHU EPO) or to EPO analogues, also called "biosimilars". Iron deficiency often co-exists in dialysis patients and must be evaluated and treated to reduce ESA requirements. Partial, but not complete correction of renal anaemia is associated with improved outcomes in patients with CKD. The use of ESAs does carry risks such as hypertension, pure red cell aplasia, or cancer, and these agents need to be used judiciously.

Bone morphogenetic protein (BMP)-7 expression is decreased in human hypertensive nephrosclerosis

Background

Bone Morphogenetic Protein (BMP)-7 is protective in different animal models of acute and chronic kidney disease. Its role in human kidneys, and in particular hypertensive nephrosclerosis, has thus far not been described.

Methods

BMP-7 mRNA was quantified using real-time PCR and localised by immunostaining in tissue samples from normal and nephrosclerotic human kidneys. The impact of angiotensin (AT)-II and the AT-II receptor antagonist telmisartan on BMP-7 mRNA levels and phosphorylated Smad 1/5/8 (pSmad 1/5/8) expression was quantified in proximal tubular cells (HK-2). Functional characteristics of BMP-7 were evaluated by testing its influence on TGF-β induced epithelial-to-mesenchymal transition (EMT), expression of TGF-β receptor type I (TGF-βRI) and phosphorylated Smad 2 (pSmad 2) as well as on TNF-α induced apoptosis of proximal tubular cells.

Results

BMP-7 was predominantly found in the epithelia of the distal tubule and the collecting duct and was less abundant in proximal tubular cells. In sclerotic kidneys, BMP-7 was significantly decreased as demonstrated by real-time PCR and immunostaining. AT-II stimulation in HK-2 cells led to a significant decrease of BMP-7 and pSmad 1/5/8, which was partially ameliorated upon co-incubation with telmisartan. Only high concentrations of BMP-7 (100 ng/ml) were able to reverse TNF-α-induced apoptosis and TGF-β-induced EMT in human proximal tubule cells possibly due to a decreased expression of TGF-βRI. In addition, BMP-7 was able to reverse TGF-β-induced phosphorylation of Smad 2.

Conclusions

The findings suggest a protective role for BMP-7 by counteracting the TGF-β and TNF-α-induced negative effects. The reduced expression of BMP-7 in patients with hypertensive nephrosclerosis may imply loss of protection and regenerative potential necessary to counter the disease.

Solid-state diffusion as an efficient doping method for silicon nanowires and nanowire field effect transistors

In this work we investigate doping by solid-state diffusion from a doped oxide layer, obtained by plasma-enhanced chemical vapor deposition (PECVD), as a means for selectively doping silicon nanowires (NWs). We demonstrate both n-type (phosphorous) and p-type (boron) doping up to concentrations of 10(20) cm(-3), and find that this doping mechanism is more efficient for NWs as opposed to planar substrates. We observe no diameter dependence in the range of 25 to 80 nm, which signifies that the NWs are uniformly doped. The drive-in temperature (800-950 °C) can be used to adjust the actual doping concentration in the range 2 × 10(18) to 10(20) cm(-3). Furthermore, we have fabricated NMOS and PMOS devices to show the versatility of this approach and the possibility of achieving segmented doping of NWs. The devices show high I(on)/I(off) ratios of around 10(7) and, especially for the PMOS, good saturation behavior and low hysteresis.

A finite element study of invariant-based orthotropic constitutive equations in the context of myocardial material parameter estimation

A previous study investigated a number of invariant-based orthotropic and transversely isotropic constitutive equations for their suitability to fit three-dimensional simple shear mechanics data of passive myocardial tissue. The study was based on the assumption of a homogeneous deformation. Here, we extend the previous study by performing an inverse finite element material parameter estimation. This ensures a more realistic deformation state and material parameter estimates. The constitutive relations were compared on the basis of (i) 'goodness of fit': how well they fit a set of six shear deformation tests and (ii) 'variability': how well determined the material parameters are over the range of experiments. These criteria were utilised to discuss the advantages and disadvantages of the constitutive relations. It was found that a specific form of the polyconvex type as well as the exponential Fung-type equations were most suitable for modelling the orthotropic behaviour of myocardium under simple shear.

Pharmacotherapy of end-stage renal disease

IMPORTANCE OF THE FIELD

The incidence and prevalence of end-stage renal disease (ESRD) requiring renal replacement therapy (RRT) continues to grow worldwide. ESRD causes significant morbidity and mortality and has enormous financial and personal costs.

AREAS COVERED IN THIS REVIEW

Major electronic databases (including the Cochrane Library, MEDLINE and EMBASE) were searched from 1989 to September 2009 to summarize current pharmacotherapy of ESRD-associated complications in adults receiving maintenance dialysis (hemodialysis or continuous ambulatory peritoneal dialysis). Current guidelines for the treatment of ESRD (e.g., NKF-K/DOQI, KDIGO, and the ERA-EDTA's European Renal Best Practice Guidelines) were included.

WHAT THE READER WILL GAIN

Commonly used pharmacological treatment strategies for chronic arterial hypertension, anemia, iron management, dyslipidemia, hyperglycemia, and for disturbances of bone and mineral metabolism, including hyperphosphatemia and secondary hyperparathyroidism in ESRD, are presented. In addition, the reader will learn that nonadherence to oral medication in ESRD can contribute significantly to excess morbidity and mortality of the dialysis population.

TAKE HOME MESSAGE

Improvements in pharmacotherapy of ESRD may be at least in part counteracted by continuously increasing age and comorbid disease of the dialysis population. Individualized and tailor-made pharmacological management of the ESRD patient remains a challenge for the future.

The putative role of human peritoneal adipocytes in the fight against bacteria: synthesis of the antimicrobial active peptide DEFA1-3

BACKGROUND

Spontaneous peritonitis is a rather rare event, even in peritoneal dialysis (PD). As defensins are natural antimicrobial peptides, we hypothesized that adipocytes as the major constituents of the omentum could play an important role in protecting against infection by generating defensin (DEFA1-3).

METHODS

We isolated adipocytes from the omentum majus and conducted qualitative and quantitative RT-PCR and immunohistochemical analyses.

RESULTS

For the first time described, we were able to detect DEFA1-3 mRNA in highly purified isolated omental adipocytes. The expression of DEFA1-3 in adipocytes was confirmed on the protein level by immunohistochemistry.

CONCLUSION

Our report of DEFA1-3 expression by human omental adipocytes adds to the role of adipocytes in the primary defense against bacterial infection. This may include PD, where the presence of the catheter as a foreign body and the nonphysiological dialysis solution may require constant defense measures to prevent peritonitis, a hypothesis that will require further testing.

Computer simulation of vertebral artery occlusion in endovascular procedures

OBJECTIVE

The aim of this work is to establish a computational pipeline for the simulation of blood flow in vasculatures and apply this pipeline to endovascular interventional scenarios, e.g. angioplasty in vertebral arteries.

METHODS

A patient-specific supra-aortal vasculature is digitized from a 3D CT angiography image. By coupling a reduced formulation of the governing Navier-Stokes equations with a wall constitutive equation we are able to solve the transient flow in elastic vessels. By further incorporating a bifurcation model the blood flow across vascular branches can be evaluated, thus flow in a large vasculature can be modeled. Vascular diseases are simulated by modifying the arterial tree configurations, e.g. the effective diameters, schematic connectivity, etc. Occlusion in an artery is simulated by removing that artery from the arterial tree.

RESULTS

It takes about 2 min per cardiac cycle to compute blood flow in an arterial tree consisting of 38 vessels and 18 bifurcations on a laptop PC. The simulation results show that blood supply in the posterior region is compensated from the contralateral vertebral artery and the anterior cerebral arteries if one of the vertebral arteries is occluded.

CONCLUSION

The computational pipeline is computationally efficient and can capture main flow patterns at any point in the arterial tree. With further improvement it can serve as a powerful tool for the haemodynamic analysis in patient-specific vascular structures.

Role of CX3C-chemokine CX3C-L/fractalkine expression in a model of slowly progressive renal failure

BACKGROUND

The chemokine/chemokine receptor pair CX(3)C-L/CX(3)C-R is suspected to play a role in renal fibrogenesis. The aim of this study was to investigate their function in an animal model of slowly progressive chronic renal failure.

METHODS

Functional data were analysed in folic acid nephropathy (FAN) at different time points (up to day 142 after induction). Immunostaining for CX(3)C-L, CD3, S100A4, collagen type I, fibronectin, alpha-smooth muscle actin, Tamm-horsfall protein, aquaporin 1 and 2 as well as quantitative real-time PCR (qRT-PCR) for CX(3)C-L, CX(3)C-R and fibroblast-specific protein 1 (FSP-1) were performed. Additionally, regulatory mechanisms and functional activity of CX(3)C-L in murine proximal and distal tubular epithelial cells as well as in fibroblasts were investigated.

RESULTS

CX(3)C-L/GAPDH ratio was upregulated in FAN 3.4-fold at day 7 further increasing up to 7.1-fold at day 106. The expression of mRNA CX(3)C-L correlated well with CX(3)C-R (R(2) = 0.96), the number of infiltrating CD3+ cells (R(2) = 0.60) and the degree of tubulointerstitial fibrosis (R(2) = 0.56) and moderately with FSP-1 (R(2) = 0.33). Interleukin-1beta, tumour necrosis factor-alpha, transforming growth factor-beta as well as the reactive oxygen species (ROS) H(2)O(2) were identified by qRT-PCR as inductors of CX(3)C-L/fractalkine (FKN) in tubular epithelial cells. Functionally, CX(3)C-L/FKN chemoattracts peripheral blood mononuclear cells, activates several aspects of fibrogenesis and induces the mitogen-activated protein kinases in renal fibroblasts.

CONCLUSIONS

In FAN, there is a good correlation between the expression of CX(3)C-L with markers of interstitial inflammation and fibrosis which may result from upregulation by pro-inflammatory and pro-fibrotic cytokines as well as by ROS in tubular epithelial cells. The FKN system may promote renal inflammation and renal fibrogenesis.

Association between tobacco control policies and smoking behaviour among adolescents in 29 European countries

AIMS

To investigate the associations between well-known, cost-effective tobacco control policies at country level and smoking prevalence among 15-year-old adolescents.

DESIGN

Multi-level modelling based on the 2005-06 Health Behaviour in School-aged Children Study, a cross-national study at individual level, and with country-level variables from the Tobacco Control Scale and published country-level databases.

SETTING

Twenty-nine European countries.

PARTICIPANTS

A total of 25 599 boys and 26 509 girls.

MAIN OUTCOME MEASURES

Self-reported regular smoking defined as at least weekly smoking, including daily smoking (dichotomous).

FINDINGS

Interaction effects between gender and smoking policies were identified, therefore boys and girls were analysed separately. Large cross-national differences in smoking prevalence were documented. Intraclass correlations (ICC) of 0.038 (boys) and 0.035 (girls) were found. In the final multi-level model for boys, besides the significance of the individual variables such as family affluence, country-level affluence and the legality of vending machines were related significantly to regular smoking [b(country affluence) = -0.010; b(partial restriction vending machines) = -0.366, P < 0.05]. Price policy was of borderline significance [b(price policy) = -0.026, P = 0.050]. All relationships were in the expected direction. The model fit is not as good for girls; only the legality of vending machines had a borderline significance in the final model [b(total ban vending machines) = -0.372, P = 0.06].

CONCLUSIONS

For boys, some of the currently recommended tobacco control policies may help to reduce smoking prevalence. However, the model is less suitable for girls, indicating gender differences in the potential efficacy of smoking policies. Future research should address this issue.

Adherence to prescribed oral medication in adult patients undergoing chronic hemodialysis: a critical review of the literature

Objective

Poor adherence to complex multimodal therapies is a widely recognized problem in the daily care of dialysis patients, contributing to excess morbidity and mortality of this population. While a few studies have been devoted to understanding patient nonadherence, their results were somewhat controversial. The goals of this review are to quantify nonadherence to certain oral medications, to raise awareness of factors that may cause problems in a patient's adherence to this treatment, and to describe strategies that may be used to improve adherence to prescribed pharmacotherapy.

Methods

A systematic literature review in the MEDLINE and PubMed database (1971-2008) was performed. Quantitative studies, which accurately indicated the total percentages of nonadherence to oral medication in adult patients receiving chronic hemodialysis, were identified.

Results

A total of 19 studies fulfilled the search criteria. Rates of nonadherence to the oral medication ranged from 3 - 80%. More than half of the included studies reported nonadherence rates of ≥ 50% (mean 67%). The use of phosphate binding therapy was the prevalent surveyed oral medication. Self reports, structured interviews, and predialysis serum phosphate levels were the most frequent assessment tools used to record adherence rates. Limitations of the reviewed studies included small patient cohorts, inconsistent definitions of adherence, and a lack of standardized methods for measuring nonadherence.

Conclusions

Nonadherence to oral medication in hemodialysis patients is still an underestimated, but life-threatening behaviour.

Myocardial material parameter estimation: a comparison of invariant based orthotropic constitutive equations

This study investigated a number of invariant based orthotropic and transversely isotropic constitutive equations for their suitability to fit three-dimensional simple shear mechanics data of passive myocardial tissue. A number of orthotropic laws based on Green strain components and one microstructurally based law have previously been investigated to fit experimental measurements of stress-strain behaviour. Here we extend this investigation to include several recently proposed functional forms, i.e. invariant based orthotropic and transversely isotropic constitutive relations. These laws were compared on the basis of (i) 'goodness of fit': how well they fit a set of six shear deformation tests, (ii) 'variability': how well determined the material parameters are over the range of experiments. These criteria were utilised to discuss the advantages and disadvantages of the constitutive laws. It was found that a specific form of the polyconvex type as well as the exponential Fung-type law from the previous study were most suitable for modelling the orthotropic behaviour of myocardium under simple shear.

Occurrence of HSV-1-induced pneumonitis in patients under standard immunosuppressive therapy for rheumatic, vasculitic, and connective tissue disease

BACKGROUND

Herpes simplex virus type-1 (HSV-1) has been described to cause respiratory tract infections in critically ill patients or in individuals that are immunocompromised. It is a continuing matter of debate under which circumstances HSV-1 is a relevant pathogen for pneumonitis. While its role during critical illness has been investigated by prospective interventional studies, comparatively little systematic data is available on the role of HSV-1 for pneumonitis in outpatients with autoimmune disease under a maintenance regimen of immunosuppression.

METHODS

We retrospectively reviewed the charts of approximately 1400 patients with rheumatoid arthritis, vasculitis, and systemic lupus erythematosus (SLE) that were followed at the outpatient clinic of a German University hospital during the years 2000-2007. Episodes of admission to a ward resulting in the diagnosis of pneumonia/pneumonitis were identified, and the type of pneumonia and clinical features retrospectively studied.

RESULTS

63 patients with rheumatoid arthritis, vasculitis, or SLE were admitted to a ward and diagnosed to have pneumonia/pneumonitis. Using bronchoscopy a total of 6 cases of pulmonary infection associated with HSV-1 in the lower respiratory tract were identified. Among those, 2 cases suggested a causative role of HSV-1 as the sole agent causing pneumonitis that proved clinically responsive to antiviral treatment. In the remaining 4 cases HSV-1 appeared as a bystander of bacterial infection. Maintenance therapy with leflunomide, which inhibits HSV-1 assembly in vitro, was associated with a milder course of pneumonitis in one patient. Detection of HSV-1 was associated with stronger immunosuppressive regimens and vasculitic disease.

CONCLUSION

The present study analyzed the frequency and hallmarks of cases of HSV-1 associated pneumonitis that occurred in a comparatively large cohort of patients with rheumatologic autoimmune diseases. In an area of controversy, this study provides further evidence that HSV-1 causes isolated pneumonitis in the immunocompromised. The study may provide an estimate on the frequency of relevant HSV-1 infection and bacterial agents in outpatients with autoimmune disease.