bluuebunny/crossref_metadata_2025 huggingface dataset:
Velocity pulse advances pressure pulse by close to 45° in the rat pial arterioles
Authors: Seki J. , Satomura Y. , Ooi Y.
Published: November 2024

In order to clarify the phase relationship between velocity pulse and pressure pulse propagating along microvessels, the red cell velocity and intravascular pressure were simultaneously measured in the rat pial arterioles of 41–53 μm in diameter with a high temporal resolution by a laser‐Doppler anemometer and a servo‐null micropressure system. It was found that the velocity pulse preceded the pressure pulse in all the measured arterioles by 18.7–35.6 ms. The corresponding phase difference was 43.6±6.9° (mean ± SD), which is not statistically different from 45°. The value is consistent with the phase difference predicted for the blood flow in microvessels with a small reflection coefficient at frequencies as low as the heart rate of the rats. The present results suggest that the upstream changes in blood flow are transmitted by the velocity pulse faster than by the pressure pulse in the microvasculature.
Low shear stress regulates monocyte adhesion to oxidized lipid‐induced endothelial cells via an IkappaBalpha dependent pathway
Authors: Zhu Chu‐hong , Ying Da‐jun , Mi Jian‐hong , Zhu Xing‐hong , Sun Jian‐sen , Cui Xiao‐ping
Published: November 2024

In regions of a vessel that experience low shear stress and reversing flow patterns, early features in the pathogenesis of atherosclerosis include the accumulation of oxidized LDL (OxLDL) and adhesion of monocytes to endothelial cells (EC). Here we investigated the hypothesis that low shear stress (2 dyn/cm2) and OxLDL are synergistic for enhanced expression of vascular cell adhesion molecule (VCAM‐1) and human aortic endothelial cell (HAEC)–monocyte adhesion. This study shows low shear stress can significantly reduce IkappaBalpha levels, activate NF‐kappaB, increase the expression of VCAM‐1 in HAEC and binding of monocytes. OxLDL itself cannot significantly increase the expression of VCAM‐1 in HAEC and binding of monocytes, but through activation of NF‐kappaB and degradation of IkappaBalpha induced by low shear stress it can significantly enhance VCAM‐1 expression and monocyte adhesion, over that in unmodified LDL or control. These results suggest that low shear stress can regulate monocyte adhesion to oxidized lipid‐induced endothelial cells via an IkappaBalpha‐dependent pathway, and that low shear stress together with OxLDL may likely play an important role in atherogenesis.
Shear linear behavior of brain tissue over a large frequency range
Authors: Nicolle S. , Lounis M. , Willinger R. , Palierne J.‐F.
Published: November 2024

The literature review about the shear linear properties of brain tissue reveals both a large discrepancy in the existing data and a crucial lack of information at high frequencies associated with traffic road and non‐penetrating ballistic impacts. The purpose of this study is to clarify and to complement the linear material characterisation of brain tissue. New data at small strains and high frequencies were obtained from oscillatory experiments. The tests were performed on thin porcine white matter samples (corona radiata) using an original custom‐designed oscillatory shear testing device. At 37°C, the results showed that the mean storage modulus (G′) and the mean loss modulus (G″) increased with the frequency (0.1 to 6310 Hz) from 2.1±0.9 kPa to 16.8±2.0 kPa and from 0.4±0.2 kPa to 18.7±2.3 kPa respectively. The reliability of these new dynamic data was checked over a partially common frequency range by conducting similar experiments using a standard rheometer (Bohlin C‐VOR 150). Data were also compared in the time field. From these experiments, the relaxation modulus (G(t)) was found to decrease from 24.4±2.1 kPa to 1.0±0.3 kPa between 10−5 s and 270 s.
Stimulation of regulatory volume decrease (RVD) by isolated bovine articular chondrocytes following F-actin disruption using latrunculin B
Authors: Kerrigan Mark J.P. , Hall Andrew C.
Published: November 2024

Articular chondrocytes are exposed to significant changes in extracellular osmolarity during normal joint activity, which can lead to changes in cell volume and metabolism of the extracellular matrix (ECM). Chondrocytes can respond to cell swelling/shrinking by volume regulatory pathways, but the signalling pathways are poorly understood although a role for the cytoskeleton is frequently implicated. Here, we have investigated the effects of disruption of the chondrocyte F-actin cytoskeleton on the recovery of cell volume by RVD. The cytoskeleton was perturbed using the relatively specific agent latrunculin B (5 μM; 30 min) and loss of F-actin integrity quantified using fluorescent phalloidin-labelling and confocal laser scanning microscopy (CLSM). Imaging of isolated chondrocytes labelled with Fura-2 to measure the fluorescence associated with cell volume changes, showed that the extent of hypo-osmotic swelling was unaffected by latrunculin B treatment. Two categories of the chondrocyte RVD response were observed: ‘fast’ RVD where at 3 min post-osmotic challenge there was a recovery in cell fluorescence of ≥80%, whereas other cells exhibited ‘slow’ RVD. Latrunculin B increased the proportion of chondrocytes demonstrating ‘fast’ RVD by ∼10 fold and reduced those cells showing ‘slow’ RVD. An inhibitor of chondrocyte RVD (REV 5901) had no significant effect on the integrity of the cytoskeleton showing that the RVD response could be inhibited independent of the state of the F-actin cytoskeleton. These results suggest that the intact cortical F-actin cytoskeleton has a restraining effect on the RVD response of isolated bovine articular chondrocytes.
Theoretical approach to blood ejection from the human left ventricle
Authors: Peng Yuhua , Wu Shigui , Geng Shizhao , Liepsch Dieter , Liao Donghua , Qiao Aike , Zeng Yanjun
Published: November 2024

An ejection dynamics mathematical model of human left ventricle (LV) based on physiological data of human heart is proposed in this study. The mathematical equations were expressed in terms of vorticity-stream function equations in a prolate spheroidal coordinate system. These equations combined with specified boundary conditions were numerically solved by using an alternating-direction-implicit (ADI) algorithm with second order accuracy. The unsteady aspects of the ejection process were subsequently introduced into the numerical simulation. The numerical results have shown that the present ellipsoidal model could be available to simulate the ejection process of the human LV. Such a model combined with cardiac muscle mechanics could be studied further to determine altered left ventricular function in cardiac diseases.
The distribution of rolling neutrophils in venular convergences
Authors: Lamkin-Kennard Kathleen A. , Chuang Johnson Y.-H. , Kim Michael B. , Sarelius Ingrid H. , King Michael R.
Published: November 2024

The aim of this study was to characterize the distribution of adherent leukocytes in branched venular convergences in vivo. Intravital microscopy was used to obtain video images of leukocyte adhesion in multiple branched sites in mouse cremaster muscle, during the mild inflammatory response induced by surgical preparation. The average number of cells/vessel length was obtained over several minutes for seven venular convergences with varying geometrical configurations. Results from this study demonstrate a strong tendency of leukocytes to adhere at junctional points between converging vessels. Different vessel configurations were studied and results were shown to be insensitive to precise vessel geometry. Thus, in post-capillary venules, leukocytes are most likely to adhere at points between converging vessels, regardless of the precise geometrical properties or configuration of the vessels. Hydrodynamic mechanisms due to flow behavior through convergences likely play a significant role in determining locations of cellular adhesion. Future work should concentrate on quantifying the relative contributions of hydrodynamic and biochemical mechanisms to aid in understanding disease processes and development of treatments or therapeutics.
Effect of enhanced red blood cell aggregation on blood flow resistance in an isolated-perfused guinea pig heart preparation
Authors: Yalcin Ozlem , Meiselman Herbert J. , Armstrong Jonathan K. , Baskurt Oguz K.
Published: November 2024

The role of red blood cell (RBC) aggregation as a determinant of in vivo blood flow is still unclear. This study was designed to investigate the influence of a well-controlled enhancement of RBC aggregation on blood flow resistance in an isolated-perfused heart preparation. Guinea pig hearts were perfused through a catheter inserted into the root of the aorta using a pressure servo-controlled pump system that maintained perfusion pressures of 30 to 100 mmHg. The hearts were beating at their intrinsic rates and pumping against the perfusion pressure. RBC aggregation was increased by Pluronic (F98) coating of RBC at a concentration 0.025 mg/ml, corresponding to about a 100% increment in RBC aggregation as measured by erythrocyte sedimentation rate. Isolated heart preparations were perfused with 0.40 l/l hematocrit unmodified guinea pig blood and with Pluronic-coated RBC suspensions in autologous plasma. At high perfusion pressures there were no significant differences between the flow resistance values for the two perfusates, with differences in flow resistance only becoming significant at lower perfusion pressures. These results can be interpreted to reflect the shear dependence of RBC aggregation: higher shear forces associated with higher perfusion pressures should have dispersed RBC aggregates resulting in blood flow resistances similar to control values. Experiments repeated in preparations in which the smooth muscle tone was inhibited by pre-treatment with papaverine indicated that significant effects of enhanced RBC aggregation could be detected at higher perfusion pressures, underlining the compensatory role of vasomotor control mechanisms.
Geometrical focusing of cells in a microfluidic device: An approach to separate blood plasma
Authors: Faivre Magalie , Abkarian Manouk , Bickraj Kimberly , Stone Howard A.
Published: November 2024

It is well known that when a suspension of cells flows in small vessels (arterioles or venules), there exists a cell-free layer of a few microns adjacent to the vascular walls. Using an in vitro model, we show experimentally that for a fixed flow rate a geometrical constriction in the flow can artificially enhance the cell-free layer. Also, we show that rapid variation of the geometry coupled to the deformability of the cells can dramatically modify their spatial distribution in the channel. The effects of the constriction geometry, flow rate, suspending fluid viscosity, cell concentration, and cell deformability are studied and the results are interpreted in terms of a model of the hydrodynamic drift of an ellipsoidal cell in a shear flow. We propose a microfluidic application of this focusing effect for separation of the red blood cells from the suspending plasma.
Oscillating viscometer – Evaluation of a new bedside test
Authors: Mark M. , Häusler K. , Dual J. , Reinhart W.H.
Published: November 2024

A viscometer for bedside blood measurements was developed, consisting of an oscillating resonator probe mounted directly into a disposable vacutainer tube for blood withdrawal. It was tested in vitro on blood samples with variable hematocrits (20–60%), increasing fibrinogen concentrations (0–20 g/l), increasing concentrations of an admixed radiographic contrast medium and erythrocyte suspensions in dextran 40 and dextran 70. Results were compared with those obtained with a conventional Couette viscometer. Oscillating viscometry yielded generally higher values than Couette viscometry, and had a good sensitivity for changes in hematocrit with a good correlation between the two methods (r=0.96, p<0.0001). Oscillating viscosity depended on the resonator frequency, it was higher at 3900 Hz than at 215 Hz, suggesting a viscoelastic behavior of blood. Erythrocyte aggregation, induced by increasing fibrinogen concentrations or dextran 70, affected oscillating viscometry. At a high frequency, i.e. a smaller penetration depth of the shear wave, oscillating viscosity tended to decrease, which suggests a depletion of the boundary layer from erythrocytes when they aggregate. At low frequency with a deeper shear wave penetration (about 50 μm), erythrocyte aggregation increased oscillating viscosity. Bedside tests in 17 patients with coronary heart disease and 10 controls confirmed the easy practicability of the test and showed lower oscillating viscosity in these patients despite higher fibrinogen concentrations presumably due to increased erythrocyte aggregation. We conclude that oscillating viscometry is an interesting bedside test, which is capable of providing new information on the biorheology of the erythrocyte-poor boundary layer near the vessel wall.
Mathematical description of stress relaxation of bovine femoral cortical bone
Authors: Iyo Toshiya , Sasaki Naoki , Maki Yasuyuki , Nakata Mitsuo
Published: November 2024

In 1993 we proposed an empirical formula for describing the relaxation modulus of cortical bone based on the results of stress relaxation experiments performed for 1×105 sec: [Formula: see text] where E0 is the initial value of the relaxation modulus, A is the portion of the first term, τ1 and τ2 are characteristic relaxation times, and β is a shape factor [Sasaki et al., J. Biomechanics 26 (1993), 1369]. Although the relaxation properties of bone under various external conditions were described well by the above equation, recent experimental results have indicated some limitations in its application. In order to construct an empirical formula for the relaxation modulus of cortical bone that has a high degree of completeness, stress relaxation experiments were performed for 6×105 seconds. The second term in the equation was determined as an apparently linear portion in a log E(t) vs t plot at t>1×104 sec. The same plot for experiments performed for 6×105 seconds revealed that the linear portion corresponding to the second term was in fact a curve with a large radius of curvature. On the basis of this fact, we proposed a second improved empirical equation [Formula: see text] to describe the stress relaxation of cortical bone. The early stage of the stress relaxation process, which could not be expressed by the first, is well described by the second equation.
Intracellular mechanics and mechanotransduction associated with chondrocyte deformation during pipette aspiration
Authors: Ohashi T. , Hagiwara M. , Bader D.L. , Knight M.M.
Published: November 2024

The present study utilised pipette aspiration and simultaneous confocal microscopy to test the hypothesis that chondrocyte deformation is associated with distortion of intracellular organelles and activation of calcium signalling. Aspiration pressure was applied to isolated articular chondrocytes in increments of 2 cm of water every 60 seconds up to a maximum of 10 cm of water. At each pressure increment, confocal microscopy was used to visualise the mitochondria and nucleus labelled with JC-1 and Syto-16, respectively. To investigate intracellular calcium signalling, separate cells were labelled with Fluo 4, rapidly aspirated to 5 cm of water and then imaged for 5 minutes at a tare pressure of 0.1 cm of water. Partial cell aspiration was associated with distortion of the mitochondrial network, elongation of the nucleus and movement towards the pipette mouth. Treatment with cytochalasin D or nocodazole produced an increase in cell aspiration indicating that both the actin microfilaments and microtubules provide mechanical integrity to the cell. When the data was normalised to account for the increased cell deformation, both actin microfilaments and microtubules were shown to be necessary for strain transfer to the intracellular organelles. Mitochondria and nucleus deformation may both be involved in chondrocyte mechanotransduction as well as cellular and intracellular mechanics. In addition, pipette aspiration induced intracellular calcium signalling which may also form part of a mechanotransduction pathway. Alternatively calcium mobilisation may serve to modify actin polymerisation, thereby changing cell mechanics and membrane rigidity in order to facilitate localised cell deformation. These findings have important implications for our understanding of cell mechanics and mechanotransduction as well as interpretation and modelling of pipette aspiration data.
Beneficial actions of hyaluronan (HA) on arthritic joints: Effects of molecular weight of HA on elasticity of cartilage matrix
Authors: Kato Yukio , Nakamura Shigeo , Nishimura Masahiro
Published: November 2024

Hyaluronan (HA) has viscoelastic, anti-inflammatory and protective actions in joint tissues, and is being widely used for treatment of OA and RA patients. However, the mechanisms underlying the pharmacological action of HA on OA and RA have not been fully understood. In this article, we review the molecular weight-dependent, anti-inflammatory actions of HA preparations – produced in Japan – in joint tissues, and show that the molecular weight of HA, but not its concentration, is crucial for maintenance of cartilage elasticity.
Post-traumatic osteoarthritis: The role of stress induced chondrocyte damage
Authors: Martin J.A. , Buckwalter J.A.
Published: November 2024

Post-traumatic osteoarthritis is the form of osteoarthritis (OA) that develops following joint injury. Although its end-stage is indistinguishable from idiopathic OA, many patients with post-traumatic OA are younger than those with idiopathic OA, and they have a well-defined precipitating insult. Clinical and experimental studies suggest that excessive acute impact energy or chronic mechanical overload cause the degeneration of the articular surface responsible for post-traumatic OA. Yet, the mechanisms by which excessive mechanical force causes OA remain unknown. For these reasons it has not been possible to develop effective methods of preventing or decreasing the risk of post-traumatic OA. We hypothesized that mechanical loading that exceeds the tolerance of the articular surface causes chondrocyte damage due to oxidative stress. Our in vitro tests of human articular cartilage samples showed that shear stress causes chondrocyte death and that anti-oxidants decrease the shear stress induced cell death. These observations suggest that specific patterns of loading are particularly damaging to articular surfaces and that improved treatments of joint injuries may include mechanical methods of minimizing shear stresses and biologic methods of minimizing oxidative damage.
Age-related quantitative MRI changes in healthy cartilage: Preliminary results
Authors: Goebel Jean Christophe , Watrin-Pinzano Astrid , Bettembourg-Brault Isabelle , Odille Freddy , Felblinger Jacques , Chary-Valckenaere Isabelle , Netter Patrick , Blum Alain , Gillet Pierre , Loeuille Damien
Published: November 2024

Objectives: As the early form of OA is characterized by elevated water content in the cartilage tissue, the purpose of this study was to verify in vivo if age-related changes in patellar cartilage in healthy volunteers can be detected using quantitative MRI with T2 mapping and volume measurement MRI methods. Design: Thirty healthy volunteers of various classes of age (18 to 65 years old) were enrolled in this study. MR images of the patellar cartilage were acquired at 1.5T. Patellar cartilage volume and T2 maps were determined. Results: Despite non-significance, there was a trend in reducing cartilage volume with ageing (r: −0.25). In contrast global T2 slightly increased with ageing (r: 0.46). BMI (r: 0.51) and bone volume (r: 0.69) are well correlated to cartilage volume. Conclusion. Age-related physiologic changes in the water content of patellar cartilage can be detected using MRI. The proposed T2-mapping method, coupled with other non-invasive MR cartilage imaging techniques, could aid in the early diagnosis of OA.
Effect of Peroxisome Proliferator Activated Receptor (PPAR)γ agonists on prostaglandins cascade in joint cells
Authors: Moulin David , Poleni Paul-Emile , Kirchmeyer Mélanie , Sebillaud Sylvie , Koufany Meriem , Netter Patrick , Terlain Bernard , Bianchi Arnaud , Jouzeau Jean-Yves
Published: November 2024

In response to inflammatory cytokines, chondrocytes and synovial fibroblasts produce high amounts of prostaglandins (PG) which self-perpetuate locally the inflammatory reaction. Prostaglandins act primarily through membrane receptors coupled to G proteins but also bind to nuclear Peroxisome Proliferator-Activated Receptors (PPARs). Amongst fatty acids, the cyclopentenone metabolite of PGD2, 15-deoxy- $\Delta\tsup{12,14}$ PGJ2 (15d-PGJ2), was shown to be a potent ligand of the PPARγ isotype prone to inhibit the production of inflammatory mediators. As the stimulated synthesis of PGE2 originates from the preferential coupling of inducible enzymes, cyclooxygenase-2 (COX-2) and membrane PGE synthase-1 (mPGES-1), we investigated the potency of 15d-PGJ2 to regulate prostaglandins synthesis in rat chondrocytes stimulated with interleukin-1β (IL-1β). We demonstrated that 15d-PGJ2, but not the high-affinity PPARγ ligand rosiglitazone, decreased almost completely PGE2 synthesis and mPGES-1 expression. The inhibitory potency of 15d-PGJ2 was unaffected by changes in PPARγ expression and resulted from inhibition of NF-κB nuclear binding and IκBα sparing, secondary to reduced phosphorylation of IKKβ. Consistently with 15d-PGJ2 being a putative endogenous regulator of the inflammatory reaction if synthesized in sufficient amounts, the present data confirm the variable PPARγ-dependency of its effects in joint cells while underlining possible species and cell types specificities.
IL-1β synthesis by chondrocyte analyzed by 3D microscopy and flow cytometry: Effect of Rhein
Authors: de Isla N.G. , Yang J.W. , Huselstein C. , Muller S. , Stoltz J.F.
Published: November 2024

Several factors are known to be involved in the destruction of the articular cartilage. Interleukin-1 (IL-1) plays an important role in the pathogenesis of osteoarthritis (OA) either directly or through the stimulation of catabolic factors. The action of IL-1 on articular cartilage is multifaceted and it most likely plays an important role in the mechanism of cartilage destruction. IL-1 suppresses the synthesis of the cartilage matrix components and promotes the degradation of cartilage matrix macromolecules. Diacerein is an anthraquinone molecule that has been shown to reduce the severity of OA, both in man and in animal models. The present study was designed to evaluate in vitro effects of diacerein on IL-1β expression in LPS or IL-1α stimulated chondrocytes. Intracellular IL-1β production was analysed in articular chondrocytes cultured in monolayer or in alginate 3D-biosystems in the presence of lipopolysaccharide (LPS) or IL-1α, with or without diacerein. The results show that LPS and IL-1α increase intracellular IL-1β and Diacerein inhibited LPS-induced and IL-1α induced IL-1β production by articular chondrocytes. Moreover, the effect of mechanical stimulation was analysed. An inhibitory effect of DAR at therapeutic concentrations on IL-1β production in articular chondrocytes is suggested.
Perspectives on chondrocyte mechanobiology and osteoarthritis
Authors: Buckwalter Joseph A. , Martin James A. , Brown Thomas D.
Published: November 2024

Osteoarthritis, the clinical syndrome of joint pain and dysfunction due to joint degeneration, is among the most frequent and symptomatic medical problems for middle aged and older people, and it is the most common cause of long term disability in most populations of people over 65. Currently there are no effective methods of preventing or curing osteoarthritis. Post-traumatic OA, the joint degeneration, pain and dysfunction that develop following joint injury, is the form of OA that is most directly related to elevated articular surface contact stress. However, mechanical stress that exceeds the tolerance of the articular surface can cause or accelerate the progression of joint degeneration in all individuals and in all synovial joints. In some patients, decreasing mechanical forces on degenerated joint surfaces stimulates formation of a new biologic articular surface. The advances in understanding of the effects of mechanical forces on chondrocytes and cartilage presented and discussed at the 4th Symposium on Mechanobiology: Cartilage and Chondrocyte will help in the efforts to develop new methods of preventing and treating osteoarthritis.
Enhanced platelet adhesion and aggregation by endothelial cell-derived unusually large multimers of von Willebrand factor
Authors: Kumar R. Anand , Moake Joel L. , Nolasco Leticia , Bergeron Angela L. , Sun Carol , Dong Jing-fei , McIntire Larry V.
Published: November 2024

Endothelial cells synthesize and secrete von Willebrand factor (VWF) multimers, including unusually large forms (ULVWF), which are usually cleaved into smaller multimers found in normal plasma (P-VWF). Thrombotic thrombocytopenic purpura (TTP) is a microangiopathic disorder characterized by systemic attachment of platelets to inadequately cleaved ULVWF multimers. We have compared ULVWF and P-VWF in their capacity to become immobilized onto surfaces in vitro and their ability to mediate platelet adhesion. We have also used functional assays to directly compare ULVWF forms with purified P-VWF in mediating platelet aggregation in solution. At comparable concentrations, ULVWF is more effectively adsorbed onto glass surfaces than P-VWF and supports increased platelet adhesion. ULVWF is also significantly more potent than P-VWF in mediating both shear-induced platelet aggregation and ristocetin-mediated platelet agglutination.
Hydrostatic pressure modulates mRNA expressions for matrix proteins in human meniscal cells
Authors: Suzuki Toru , Toyoda Takashi , Suzuki Hiroshi , Hisamori Noriyuki , Matsumoto Hideo , Toyama Yoshiaki
Published: November 2024

There have been few reports describing the effects of mechanical loading on the metabolism of meniscal cells. The aim of this study was to investigate the effects of hydrostatic pressure on meniscal cell metabolism. Human meniscal cells were cultured in alginate beads for 3 days. They were then subjected to 4 MPa hydrostatic pressure for 4 hours in either a static or cyclic (1 Hz) mode using a specially designed and constructed system. Immediately after the pressure application, the messenger RNA levels for aggrecan, type I collagen, matrix metalloproteinases (MMP) -1, -3, -9, -13 and tissue inhibitors of metalloproteinases (TIMP) -1 and -2 were measured. It was found that the application of static hydrostatic pressure caused a significant decrease in mRNA expression for MMP-1 and -13 (p<0.05). In contrast, the application of cyclic hydrostatic pressure was associated with a significant increase in type I collagen (p<0.01), TIMP-1 and -2 mRNA expression (p<0.01). These results would suggest that hydrostatic pressure in isolation can modulate mRNA expressions for matrix proteins in meniscal cells.
The mechanical behaviour of brain tissue: Large strain response and constitutive modelling
Authors: Hrapko M. , van Dommelen J.A.W. , Peters G.W.M. , Wismans J.S.H.M.
Published: November 2024

The non-linear mechanical behaviour of porcine brain tissue in large shear deformations is determined. An improved method for rotational shear experiments is used, producing an approximately homogeneous strain field and leading to an enhanced accuracy. Results from oscillatory shear experiments with a strain amplitude of 0.01 and frequencies ranging from 0.04 to 16 Hz are given. The immediate loss of structural integrity, due to large deformations, influencing the mechanical behaviour of brain tissue, at the time scale of loading, is investigated. No significant immediate mechanical damage is observed for these shear deformations up to strains of 0.45. Moreover, the material behaviour during complex loading histories (loading–unloading) is investigated. Stress relaxation experiments for strains up to 0.2 and constant strain rate experiments for shear rates from 0.01 to 1 s−1 and strains up to 0.15 are presented. A new differential viscoelastic model is used to describe the mechanical response of brain tissue. The model is formulated in terms of a large strain viscoelastic framework and considers non-linear viscous deformations in combination with non-linear elastic behaviour. This constitutive model is readily applicable in three-dimensional head models in order to predict the mechanical response of the intra-cranial contents due to an impact.
Developed pulsatile flow in a deployed coronary stent
Authors: Banerjee Rupak K. , Devarakonda Surendra B. , Rajamohan Divakar , Back Lloyd H.
Published: November 2024

The patho-physiologic process of restenosis and tissue growth may not be completely eliminated and is the primary concern of clinicians performing angioplasty and stent implantation procedures. Recent evidence suggests that the restenosis process is influenced by several factors: (1) geometry and size of vessel; (2) stent design; and (3) it's location that alter hemodynamic parameters, including local wall shear stress (WSS) distributions. The present three-dimensional (3D) analysis of pulsatile flow in a deployed coronary stent: (1) shows complex 3D variation of hemodynamic parameters; and (2) quantifies the changes in local WSS distributions for developed flow and compares with recently published WSS data for developing flow. Higher order of magnitude of WSS of 290 dyn/cm2 is observed on the surface of cross-link intersections at the entrance of the stent for developed flow, which is about half of that for developing flow. Low WSS of 0.8 dyn/cm2 and negative WSS of −8 dyn/cm2 are seen at the immediate upstream and downstream regions of strut intersections. Persistent recirculation is observed at the downstream region of each strut cross-link and the regions of low and negative WSS may lead to patho-physiologic conditions near the stented region. The key finding of this study is that the location of stent in the coronary artery determines the developing or developed nature of the flow, which in turn, results in varied level of WSS.
Hemodynamic simulation in a novel design for femoral bypass grafts
Authors: Qiao Aike , Matsuzawa Teruo
Published: November 2024

The effectiveness of femoral bypass grafts is correlated with the geometric configuration and hemodynamics of the bypass and the arteries. As an attempt to develop a new design for femoral bypass grafts, we present a novel geometric configuration for a symmetrically implanted 2-way bypass graft. In order to investigate how the symmetric 2-way bypass grafts affect the flow patterns through the anastomosis, physiologic blood flows in 1-way and 2-way models for a fully stenosed femoral bypass were simulated with the finite element method, and the hemodynamic factors in these models were studied. The temporal and spatial distributions of flow patterns and wall shear stresses in the vicinity of distal anastomosis during the cardiac cycle were analyzed. The results computed showed that the 2-way model has more preferable hemodynamics than the 1-way model in the distribution of flow patterns and wall shear stresses, and it may improve the flow conditions and decrease the probability of restenosis. However, the limitations of the 2-way bypass model may counteract the positive effects. More detailed hemodynamic studies are necessary to fully assess the viability of the 2-way bypass graft.
Remodelling of the zero-stress state and residual strains in apoE-deficient mouse aorta
Authors: Gregersen Hans , Zhao Jingbo , Lu Xiao , Zhou Ji , Falk Erling
Published: November 2024

Atherosclerosis is the most frequent cause of death and severe chronic disability in North America and Europe. The atherosclerosis-prone apolipoprotein E (apoE)-deficient mice contain the entire spectrum of lesions observed during atherogenesis. Significant remodelling of the artery occurs in atherosclerosis. The aim was to study the remodelling of the zero-stress state of the aorta in apoE-deficient mice up to 56 weeks of age. Normal wild-type mice served as control groups. The mice were euthanised at ages 10, 28 and 56 weeks and tissue rings where excised from several locations along the aorta. The rings where photographed in the no-load state (without any external forces applied), then cut radially to obtain the zero-stress state and photographed again. The cross-sectional wall area and wall thickness increased over time in apoE-deficient mice compared to controls (P<0.001). The residual strains at the inner and outer surface varied as function of aortic location both in controls and apoE-deficient mice (P<0.001). From age 28 to age 56 weeks a gradual increase in positive strain at the outer surface and negative strain at the inner surface was found in the apoE-deficient mice when compared to age-matched control mice (P<0.001). Furthermore, the inner residual strain in the plaque location was significantly smaller than in the non-plaque location in the rings with atherosclerotic plaques (P<0.001). The change over time of the opening angle was especially pronounced in the aortic arch. The opening angle increased to app. 200 degrees in the aortic arch in apoE-deficient mice at 56 weeks of age whereas it in age-matched controls was app. 125 degrees. Correspondingly, atherosclerotic plaques were prominent in the apoE-deficient mice, especially at week 56 in the ascending aorta and the aortic arch. In conclusion, a pronounced remodelling of the biomechanical properties in aorta was found in apoE-deficient mice. The stress gradient across the vessel wall in the plaque region is likely larger in vivo due to the smaller residual strain in the plaque area.
Rheological properties of synovial fluids
Authors: Fam H. , Bryant J.T. , Kontopoulou M.
Published: November 2024

Synovial fluid is the joint lubricant and shock absorber [Semin. Arthritis Rheum. 32 (2002), 10–37] as well as the source of nutrition for articular cartilage. The purpose of the present paper is to provide a comprehensive review of the rheological properties of synovial fluid as they relate to its chemical composition. Given its importance in the rheology of synovial fluid, an overview of the structure and rheology of HA (hyaluronic acid) is presented first. The rheology of synovial fluids is discussed in detail, with a focus on the possible diagnosis of joint pathology based on the observed differences in rheological parameters and trends. The deterioration of viscoelastic properties of synovial fluid in pathological states due to effects of HA concentration and molecular weight is further described. Recent findings pertaining to the composition and rheology of periprosthetic fluid, the fluid that bathes prosthetic joints in vivo are reported.
Peristaltic flow of a couple stress fluid in an asymmetric channel
Authors: Ali N. , Hayat T. , Sajid M.
Published: November 2024

This paper presents an analysis of the peristaltic flow of a couple stress fluid in an asymmetric channel. The asymmetric nature of the flow is introduced through the peristaltic waves of different amplitudes and phases on the channel walls. Mathematical modelling corresponding to a two-dimensional flow has been carried out. The flow analysis is presented under long wavelength and low Reynolds number approximations. Closed form solutions for the axial velocity, stream function and the axial pressure gradient are given. Numerical computations have been carried out for the pressure rise per wavelength, friction forces and trapping. It is noted that there is a decrease in the pressure when the couple stress fluid parameter increases. The variation of the couple stress fluid parameter with the size of the trapped bolus is also similar to that of pressure. Furthermore, the friction force on the lower channel wall is greater than that on the upper channel wall.
Optical analysis of red blood cell sediment formation
Authors: Mutrynowska J. , Grzegorzewski B.
Published: November 2024

The red blood cell (RBC) sediment formation was studied using an optical method. The intensity of light transmitted through the blood sample was measured as a function of time and distance from the bottom of the sample. Blood was obtained from healthy donors and measurements were performed at initial hematocrits ranging from 30 to 50%. Sedimentation curves and time dependence of the intensity averaged along the height of the RBC suspension were determined to give a cumulative description of the process. Detailed analysis of the transmitted light intensity revealed a moving interface between sedimenting RBC aggregates and the forming of a deposit of the cells. It was shown that although there is no discontinuity in the intensity an averaged interface can be found. A novel curve describing the sedimentation process called the deposit formation curve was found. Below this curve a formation of the RBC deposit occurs. Firstly, this curve represents the position of the interface between sedimenting RBC aggregates and a forming deposit, secondly this curve coincides with the last part of the sedimentation curve.
Viscoelastic properties of an exopolysaccharide: Aeromonas gum, produced by Aeromonas nichidenii 5797
Authors: Xu Xiaojuan , Chen Pan , Zhang Lina
Published: November 2024

The viscoelastic properties of Aeromonas (A) gum in water were investigated by using the Rheometric Scientific ARES controlled strain rheometer. An intrinsic viscosity of 8336 ml/g was obtained according to the Fuoss–Straus equation. The effect of salt concentration on intrinsic viscosity revealed that the A gum exists as semiflexible chain. Typical shear-thinning (pseudoplastic) behavior was observed at concentrations higher than 0.52%. The zero shear viscosity (η0) increased with increasing polysaccharide concentration (c) showing a gradient of approximately 1.0, 2.9 and 4.8 in different concentration domains. The critical concentrations c* and c**, at which the transitions from a dilute solution of independently moving chains to semidilute and then concentrated domains occurred, were determined roughly to be 1.2% and 3.5%. The results from dynamic experiments revealed that the A gum solution shows characteristics of polymer solutions without any evidence of gel-like character. All the results from steady and dynamic tests suggest that the A gum is a non-gelling polysaccharide. The temperature dependence of apparent viscosity was described by Arrhenius equation and the flow activation energy was estimated to be 45.2 kJ/mol, which is independent on polymer concentration.
IL-8 gene induction by low shear stress: Pharmacological evaluation of the role of signaling molecules
Authors: Cheng Min , Liu Xiaoheng , Li Yi , Tang Rong , Zhang Wensheng , Wu Jiang , Li Liang , Liu Xiaojing , Gang Yang , Chen Huaiqing
Published: November 2024

Shear stress can modulate endothelial cell function by regulating gene expression. We have previously demonstrated that low shear stress (4.2 dyn/cm2) induces the expression of interleukin-8 (IL-8) gene in endothelial cells. The present study was undertaken to further investigate both the effects of shear stress on IL-8 expression and the mechanisms controlling IL-8 mRNA up-regulation in human umbilical vein endothelial cells (HUVEC). We show that shear stress (from 2.23 to 19.29 dyn/cm2) induces the IL-8 expression at both the mRNA and protein levels by stimulating transcription. In order to determine the possible contribution of G protein, HUVEC were pretreated with an inhibitor of G-protein activation, GDPβS, which abrogated the low shear stress-induced IL-8 gene expression. Such gene expression was also partially inhibited by the tyrosine kinase inhibitor (tyrphostin-25) and in addition by EGTA, BATPA/AM (the intracellular Ca2+ chelator), Verapamil (a Ca2+ channel blocker), cAMP-dependent protein kinase inhibitor (KT5720) and phospholipase C inhibitor (neomycin). However, the cGMP-dependent protein kinase inhibitor, KT5823, had no effect on such expression. These findings therefore demonstrate the involvement of several signaling molecules, including tyrosine kinase, G protein, calcium, phospholipase C, and cAMP-dependent protein kinase, in the low shear stress-induced IL-8 gene expression.
Administrative Perspectives: A Qualitative Study of Correctional Administrator Impressions of a Train-the-Trainer Model for the Prison Rape Elimination Act
Authors: Smith Hayden P. , Ferdik Frank
Published: November 2024

To effectively eliminate sexual violence under the Prison Rape Elimination Act (PREA), it is crucial for correctional administrators to have a comprehensive understanding of this law. Train-the-Trainer models have gained popularity as an effective andragogy-based form of instruction for adult learners that can tackle complex subjects, including PREA. This study features interview data from 29 correctional administrators in a Southeastern state prison system who participated in a Train-the-Trainer seminar on this federal legislation. Thematic analysis of the data revealed key findings: (1) The model facilitated necessary cultural changes within institutions, fostering greater empathy toward sexual assault victims; and (2) Administrators expressed a need for more practical, rather than theoretical, knowledge on PREA. Policy implications are discussed.
A Qualitative Process Evaluation and Quality Improvement of a State Drug Overdose Reporting System Data Collection Approach
Authors: Lazar Mircea , Jayasundara Joshua , Korona-Bailey Jessica , Mukhopadhyay Sutapa
Published: November 2024

Tennessee registered the second-highest drug overdose mortality rate of any state in 2022; such deaths have grown by 90% from 2019 to 2022. Tennessee has participated in the State Unintentional Drug Overdose Reporting System (SUDORS) since 2018. An abstraction team synthesizes data for SUDORS from death certificates, autopsies, and other sources. The purpose of this study was to engage in a comprehensive qualitative evaluation of our SUDORS process to distill insights that could improve abstraction speed and quality while reducing abstractor burnout. We conducted 2 rounds of interviews and focus groups with all 7 members of the Tennessee abstraction team in late 2023 and early 2024. The researcher asked questions regarding the adequacy of the current project management approach and team communication level, abstractors’ stress levels, the need for further training, and whether additional data science-based tools could be deployed to increase the speed and accuracy of abstraction. The study yielded several actionable insights for improving abstraction capacity and lessening stress burdens. Accordingly, we made changes to our project management, team communication, and training approaches; worked to better integrate our extant data science tools; and took steps to improve mental well-being. As a result, the average time it takes for an abstractor to enter a case into the NVDRS platform dropped from 12.2 to 6.5 minutes, and all team members noted a decrease in stress levels. The changes made as a result of the findings of this study will help the State keep pace with a high case load and will support abstractors’ mental well-being.
Assessment of In-Office Tympanostomy Tube Insertion Tolerability in Children Under 2 Years
Authors: Cofer Shelagh A. , Badaoui Joseph N. , Rimell Frank , Nimmons Grace , Raisen Jay , Tombers Nicole , Truitt Theodore O.
Published: November 2024

Objective: In-office tympanostomy tube insertion (TTI) is becoming more available in the practice of pediatric otolaryngology. This study evaluated the tolerability of this procedure in young children. Method: Four methods were used to assess tolerability. (1) Standardized video recordings were collected from 30 patients under 24 months who underwent in-office TTI with a single-pass insertion device with topical anesthesia alone. The videos were then reviewed by 3 independent experts in pediatric care and rated at 5 procedural time points using a defined response scale developed with the U.S. Food and Drug Administration. (2) Separately, overall tolerability was subjectively assessed by the same experts. (3) Patient recovery was assessed by the participating otolaryngologist and support staff. (4) Patient caregivers were surveyed for their impressions of the procedure, including whether they would recommend it to other caregivers. Results: In a total of 90 reviews, 100% of children were successfully treated and were rated as having acceptably tolerated the in-office tympanostomy tube procedure. All patients returned to an acceptable baseline without inappropriate crying and were assessed as fully recovered immediately following the procedure or by the time the child was leaving clinic. For caregivers, 93% agreed or strongly agreed that they would recommend the use of in-office TTI to other caregivers. Conclusions: In-office TTI in young children was determined to be universally well tolerated in young children and is a procedure that patient caregivers would recommend to other caregivers for their children. These results should help reassure otolaryngology specialists and caregivers alike that in-office ear tube placement is a viable option for young children with middle ear disease.
Impact of iron-folic acid supplementation on maternal and neonatal outcomes: A systematic review & meta-analysis
Authors: Srivastava Manyata , Gulia Annu , Upadhyay Ashish Datt , Patel Kamalesh Kumar , Sankar Mari Jeeva , Sinha Anju , Kumar Pradeep
Published: November 2024

Background & Aims: Iron-folic acid (IFA) supplementation is widely recommended as both a preventive and therapeutic measure for pregnant women. Despite its widespread use, there is limited research exploring adherence to IFA supplementation during pregnancy and its impact on maternal and neonatal outcomes. This study aims to assess the effectiveness of IFA supplementation in improving pregnancy and neonatal outcomes. Methods: A comprehensive search on PubMed, Google Scholar, EMbase and Trip databases was conducted for relevant studies published up to May 31, 2024. Outcomes measured were preterm birth (PTB), low birth weight (LBW), neonatal mortality, perinatal mortality, small for gestational age (SGA) and stillbirth. Pooled risk ratios (RRs) with 95% confidence intervals (CIs), sensitivity analysis, publication bias, trial sequential analysis and quality assessment of the included studies were performed. Results: Eleven studies involving a total of 42,458 pregnant women who received IFA supplementation and 16,351 women who received folic acid (FA) alone or Control (no supplementation) were included. A significant reduction in overall neonatal mortality (RR = 0.73, 95% CI: 0.61–0.87) as well as in subgroup analyses (IFA vs. control and IFA vs. FA) was observed. However, a decrease in incidence of LBW was noted only in IFA vs. control group (RR = 0.79, 95% CI: 0.69–0.90). No significant association was found for overall LBW (RR = 0.48, 95% CI: 0.08–2.76), PTB (RR = 0.56, 95% CI: 0.09–3.50), perinatal mortality (RR = 0.85, 95% CI: 0.69–1.04), SGA (RR = 0.98, 95% CI: 0.86–1.12) and stillbirth (RR = 0.75, 95% CI: 0.48–1.16) when comparing to IFA vs. control and IFA vs. FA group. Conclusions: Our findings provide strong evidence supporting the effectiveness of IFA supplementation in reducing neonatal mortality and LBW among pregnant women, highlighting its importance in prenatal care.