Biorheology - Volume 57, issue 1

Authors: Borin, Daniele | Peña, Brisa | Taylor, Matthew R.G. | Mestroni, Luisa | Lapasin, Romano | Sbaizero, Orfeo

Article Type: Research Article

Abstract: BACKGROUND: Laminopathies are genetic diseases caused by mutations in the nuclear lamina. OBJECTIVE: Given the clinical impact of laminopathies, understanding mechanical properties of cells bearing lamin mutations will lead to advancement in the treatment of heart failure. METHODS: Atomic force microscopy (AFM) was used to analyze the viscoelastic behavior of neonatal rat ventricular myocyte cells expressing three human lamin A/C gene (LMNA) mutations. RESULTS: Cell storage modulus was characterized, by two plateaus, one in the low frequency range, a second one at higher frequencies. The loss modulus instead showed a “bell” shape with a relaxation toward fluid properties …at lower frequencies. Mutations shifted the relaxation to higher frequencies, rendering the networks more solid-like. This increase of stiffness with mutations (solid like behavior) was at frequencies around 1 Hz, close to the human heart rate. CONCLUSIONS: These features resulted from a combination of the properties of cytoskeleton filaments and their temporary cross-linker. Our results substantiate that cross-linked filaments contribute, for the most part, to the mechanical strength of the cytoskeleton of the cell studied and the relaxation time is determined by the dissociation dynamics of the cross-linking proteins. The severity of biomechanical defects due to these LMNA mutations correlated with the severity of the clinical phenotype. Show more

Keywords: Viscoelasticity, lamin A/C, AFM, cardiomyocytes, storage modulus, loss modulus

DOI: 10.3233/BIR-190229

Citation: Biorheology, vol. 57, no. 1, pp. 1-14, 2020

Authors: Juliar, Benjamin A. | Strieder-Barboza, Clarissa | Karmakar, Monita | Flesher, Carmen G. | Baker, Nicki A. | Varban, Oliver A. | Lumeng, Carey N. | Putnam, Andrew J. | O’Rourke, Robert W.

Article Type: Research Article

Abstract: BACKGROUND: Obesity-induced chronic inflammation and fibrosis in adipose tissue contributes to the progression of type 2 diabetes mellitus (DM). While fibrosis is known to induce mechanical stiffening of numerous tissue types, it is unknown whether DM is associated with alterations in adipose tissue mechanical properties. OBJECTIVE: The purpose of this study was to investigate whether DM is associated with differences in bulk viscoelastic properties of adipose tissue from diabetic (DM) and non-diabetic (NDM) obese subjects. METHODS: Bulk shear rheology was performed on visceral (VAT) and subcutaneous (SAT) adipose tissue, collected from obese subjects undergoing elective bariatric …surgery. Rheology was also performed on the remaining extracellular matrix (ECM) from decellularized VAT (VAT ECM). Linear mixed models were used to assess whether correlations existed between adipose tissue mechanical properties and DM status, sex, age, and body mass index (BMI). RESULTS: DM was not associated with significant differences in adipose tissue viscoelastic properties for any of the tissue types investigated. Tissue type dependent differences were however detected, with VAT having significantly lower shear storage and loss moduli than SAT and VAT ECM independent of DM status. CONCLUSION: Although DM is typically associated with adipose tissue fibrosis, it is not associated with differences in macroscopic adipose tissue mechanical properties. Show more

Keywords: Rheology, diabetes mellitus, subcutaneous adipose tissue, visceral adipose tissue, decellularized adipose tissue

DOI: 10.3233/BIR-190234

Citation: Biorheology, vol. 57, no. 1, pp. 15-26, 2020

Authors: Minh, Nguyen Ngoc | Obara, Hiromichi

Article Type: Research Article

Abstract: BACKGROUND: The gallbladder filling and emptying cycle controls bile flow into the duodenum. Disruption of this emptying and refilling cycle leads to bile stasis and subsequent gallstone formation. The bile flow rate is inversely proportional to its viscosity. Moreover, bile is a complex material with varying density in different people because of its diverse components. These density changes alter the viscosity. Prediction of shear viscosity from density measurements may thus contribute to medical assessment and treatment of the patient. OBJECTIVE: To investigate the relationship between the shear viscosity and density of bile. METHODS: Natural and filtered …bile samples were prepared for density, viscosity and pressure drop measurements. The density and shear viscosity were measured by a density meter and viscometer, respectively, and a relationship was established between them. Measurements of the pressure drop in a glass tube were used to estimate the apparent viscosity and compared with shear viscosity obtained with the viscometer. RESULTS: The natural bile with higher density showed a greater shear viscosity than the filtered bile, especially at low shear rates. Bile viscosity was proportional to density. In addition, the pressure drop of the natural samples was greater than that of the filtered sample. The viscosity measured by the viscometer deviated from the results obtained using Poiseuille’s law and the tube pressure drop measurements. The density difference between the natural and filtered bile samples was smaller than 1%. However, the viscosities of the natural and filtered bile samples varied by up to >30%. CONCLUSIONS: Porcine bile viscosity is proportional to density. Based on the bile density, one can easily evaluate the shear viscosity using a linear relationship. The density considerably influences the bile viscosity, with small density increases greatly increasing the shear viscosity. Show more

Keywords: Mucus, gallstones, pressure drop, suspension components

DOI: 10.3233/BIR-190238

Citation: Biorheology, vol. 57, no. 1, pp. 27-36, 2020

Authors: Çırakoğlu, Ömer Faruk | Aslan, Ahmet Oguz | Yilmaz, Ahmet Seyda | Kul, Selim | Dursun, İhsan

Article Type: Research Article

Abstract: BACKGROUND: Despite improvements in treatment of ST-segment myocardial infarction (STEMI), thrombus formation in the left ventricle is still a concerning complication that may lead to systemic thromboembolism and stroke. OBJECTIVES: To evaluate the predictive value of estimated whole blood viscosity (WBV) for left ventricular thrombus development in patients surviving an acute anterior myocardial infarction (AAMI). MATERIALS \& METHODS: Seven hundred eighty AAMI patients who were treated percutaneously were enrolled consecutively. Serial echocardiographic examinations were performed within 24h of admission, before hospital discharge, and at 1, 3, 6 and 12 months following hospital discharge. WBV was calculated …according to de Simones formula. RESULTS: One hundred patients (12.8%) developed thrombus formation within one year following AAMI. Patients with left ventricular thrombus (LVT) had significantly higher WBV values. Supramedian values of WBV at both low (0.5 sec−1 ) and high (208 sec−1 ) shear rates were found to be an independent predictor of LVT development. CONCLUSION: As an easily accessible parameter, WBV might be a useful predictor of LVT formation within one year following acute anterior myocardial infarction. Show more

Keywords: Blood viscosity, shear stress, left ventricular thrombus, myocardial infarction

DOI: 10.3233/BIR-200240

Citation: Biorheology, vol. 57, no. 1, pp. 37-51, 2020