Older patients' preferences and views related to non-face-to-face diabetes chronic care management: a qualitative study from southeast Louisiana.

Background: Management of diabetes may be uniquely challenging for older individuals with multiple chronic conditions. Health systems and policymakers have attempted to reduce barriers to chronic care management (CCM) through incentives to provide non-face-to-face care. This qualitative study aimed to investigate and present views on non-face-to-face care management held by elderly patients with diabetes and other chronic conditions in order to contribute to improved programming for this population. Materials and methods: Semi-structured interviews were conducted with patients over the age of 64 who have been diagnosed with diabetes and at least one other chronic health condition. Interview recordings were transcribed and analyzed by experienced researchers using a thematic analytic approach, and an illustrative case study was developed. Results: Thirty individuals participated in this study. Participants were drawn from three health systems in south Louisiana, an area with high rates of morbidity and mortality related to chronic diseases. We identified themes related to lived experiences with diabetes and other medical conditions, perception of personal health status, perceived value of non-face-to-face programs, and support needs for future programming. Additionally, we present one case study describing in detail an individual patient's experience with non-face-to-face CCM. Conclusion: Health systems should consider intentionally recruiting participants who would benefit most from non-face-to-face care, including higher-need, less self-sufficient patients with resource constraints, while continuing to offer in-person services. Future research should examine whether tailoring non-face-to-face programming and support to address unique barriers can further enhance diabetes care at the population level.

DTI Detection of Longitudinal WM Abnormalities Due to Accumulated Head Impacts.

Longitudinal evaluation using diffusion-weighted imaging and collision event monitoring was performed on high school athletes who participate in American football. Observed changes in white matter health were suggestive of injury and found to be correlated with accumulation of head collision events during practices and games.

A mixture theory model of fluid and solute transport in the microvasculature of normal and malignant tissues. I. Theory.

In order to better understand the mechanisms governing transport of drugs, nanoparticle-based treatments, and therapeutic biomolecules, and the role of the various physiological parameters, a number of mathematical models have previously been proposed. The limitations of the existing transport models indicate the need for a comprehensive model that includes transport in the vessel lumen, the vessel wall, and the interstitial space and considers the effects of the solute concentration on fluid flow. In this study, a general model to describe the transient distribution of fluid and multiple solutes at the microvascular level was developed using mixture theory. The model captures the experimentally observed dependence of the hydraulic permeability coefficient of the capillary wall on the concentration of solutes present in the capillary wall and the surrounding tissue. Additionally, the model demonstrates that transport phenomena across the capillary wall and in the interstitium are related to the solute concentration as well as the hydrostatic pressure. The model is used in a companion paper to examine fluid and solute transport for the simplified case of an axisymmetric geometry with no solid deformation or interconversion of mass.

A mixture theory model of fluid and solute transport in the microvasculature of normal and malignant tissues. II: Factor sensitivity analysis, calibration, and validation.

The treatment of cancerous tumors is dependent upon the delivery of therapeutics through the blood by means of the microcirculation. Differences in the vasculature of normal and malignant tissues have been recognized, but it is not fully understood how these differences affect transport and the applicability of existing mathematical models has been questioned at the microscale due to the complex rheology of blood and fluid exchange with the tissue. In addition to determining an appropriate set of governing equations it is necessary to specify appropriate model parameters based on physiological data. To this end, a two stage sensitivity analysis is described which makes it possible to determine the set of parameters most important to the model's calibration. In the first stage, the fluid flow equations are examined and a sensitivity analysis is used to evaluate the importance of 11 different model parameters. Of these, only four substantially influence the intravascular axial flow providing a tractable set that could be calibrated using red blood cell velocity data from the literature. The second stage also utilizes a sensitivity analysis to evaluate the importance of 14 model parameters on extravascular flux. Of these, six exhibit high sensitivity and are integrated into the model calibration using a response surface methodology and experimental intra- and extravascular accumulation data from the literature (Dreher et al. in J Natl Cancer Inst 98(5):335-344, 2006). The model exhibits good agreement with the experimental results for both the mean extravascular concentration and the penetration depth as a function of time for inert dextran over a wide range of molecular weights.

Multiscale strain analysis of tissue equivalents using a custom-designed biaxial testing device.

Mechanical signals transferred between a cell and its extracellular matrix play an important role in regulating fundamental cell behavior. To further define the complex mechanical interactions between cells and matrix from a multiscale perspective, a biaxial testing device was designed and built. Finite element analysis was used to optimize the cruciform specimen geometry so that stresses within the central region were concentrated and homogenous while minimizing shear and grip effects. This system was used to apply an equibiaxial loading and unloading regimen to fibroblast-seeded tissue equivalents. Digital image correlation and spot tracking were used to calculate three-dimensional strains and associated strain transfer ratios at macro (construct), meso, matrix (collagen fibril), cell (mitochondria), and nuclear levels. At meso and matrix levels, strains in the 1- and 2-direction were statistically similar throughout the loading-unloading cycle. Interestingly, a significant amplification of cellular and nuclear strains was observed in the direction perpendicular to the cell axis. Findings indicate that strain transfer is dependent upon local anisotropies generated by the cell-matrix force balance. Such multiscale approaches to tissue mechanics will assist in advancement of modern biomechanical theories as well as development and optimization of preconditioning regimens for functional engineered tissue constructs.

Mapping nanomechanical properties of live cells using multi-harmonic atomic force microscopy.

The nanomechanical properties of living cells, such as their surface elastic response and adhesion, have important roles in cellular processes such as morphogenesis, mechano-transduction, focal adhesion, motility, metastasis and drug delivery. Techniques based on quasi-static atomic force microscopy techniques can map these properties, but they lack the spatial and temporal resolution that is needed to observe many of the relevant details. Here, we present a dynamic atomic force microscopy method to map quantitatively the nanomechanical properties of live cells with a throughput (measured in pixels/minute) that is ∼10-1,000 times higher than that achieved with quasi-static atomic force microscopy techniques. The local properties of a cell are derived from the 0th, 1st and 2nd harmonic components of the Fourier spectrum of the AFM cantilevers interacting with the cell surface. Local stiffness, stiffness gradient and the viscoelastic dissipation of live Escherichia coli bacteria, rat fibroblasts and human red blood cells were all mapped in buffer solutions. Our method is compatible with commercial atomic force microscopes and could be used to analyse mechanical changes in tumours, cells and biofilm formation with sub-10 nm detail.

Design of optimized diffusion-controlled transdermal drug delivery systems.

BACKGROUND: We describe a systematic approach to designing multilayer transdermal patches based on therapeutically relevant specifications of the drug. METHOD: Random search optimization techniques are used to optimize maximum drug release from the patch subject to the therapeutic specifications. Barrier layer thickness and relative concentrations of the drug in the drug-containing layers are used as key design parameters. RESULTS: A patch made of two drug-containing layers of equal thicknesses and relative drug concentrations of 20% and 80%, and a barrier layer with thickness of 14% compared to the total thickness of drug-containing layers was found to be the most optimum design. CONCLUSION: The proposed design is almost universally applicable and satisfies therapeutically relevant specifications while maximizing drug utilization.

Modeling the mechanical consequences of vibratory loading in the vertebral body: microscale effects.

Osteoporosis affects nearly 10 million individuals in the United States. Conventional treatments include anti-resorptive drug therapies, but recently, it has been demonstrated that delivering a low magnitude, dynamic stimulus via whole body vibration can have an osteogenic effect without the need for large magnitude strain stimulus. Vibration of the vertebral body induces a range of stimuli that may account for the anabolic response including low magnitude strains, interfacial shear stress due to marrow movement, and blood transport. In order to evaluate the relative importance of these stimuli, we integrated a microstructural model of vertebral cancellous bone with a mixture theory model of the vertebral body. The predicted shear stresses on the surfaces of the trabeculae during vibratory loading are in the range of values considered to be stimulatory and increase with increasing solid volume fraction. Peak volumetric blood flow rates also varied with strain amplitude and frequency, but exhibited little dependence on solid volume fraction. These results suggest that fluid shear stress governs the response of the vertebrae to whole body vibration and that the marrow viscosity is a critical parameter which modulates the shear stress.

A cellular solid model of the lamina cribrosa: mechanical dependence on morphology.

The biomechanics of the optic nerve head (ONH) may underlie many of the potential mechanisms that initiate the characteristic vision loss associated with primary open angle glaucoma. Therefore, it is important to characterize the physiological levels of stress and strain in the ONH and how they may change in relation to material properties, geometry, and microstructure of the tissue. An idealized, analytical microstructural model of the ONH load bearing tissues was developed based on an octagonal cellular solid that matched the porosity and pore area of morphological data from the lamina cribrosa (LC). A complex variable method for plane stress was applied to relate the geometrically dependent macroscale loads in the sclera to the microstructure of the LC, and the effect of different geometric parameters, including scleral canal eccentricity and laminar and scleral thickness, was examined. The transmission of macroscale load in the LC to the laminar microstructure resulted in stress amplifications between 2.8 and 24.5xIOP. The most important determinants of the LC strain were those properties pertaining to the sclera and included Young's modulus, thickness, and scleral canal eccentricity. Much larger strains were developed perpendicular to the major axis of an elliptical canal than in a circular canal. Average strain levels as high as 5% were obtained for an increase in IOP from 15 to 50 mm Hg.

In vitro characterization of a bone marrow stem cell-seeded collagen gel composite for soft tissue grafts: effects of fiber number and serum concentration.

Cell-seeded collagen hydrogels have been used in the engineering of many tissue types, from skin and vasculature to spinal cord. One of the primary limitations of collagen-based hydrogels for use in tissue-engineered grafts is that cells seeded within the gel cause it to contract as much as 70%. By forming a composite gel by adding short collagen fibers, Gentleman et al. (Tissue Eng. 10, 421, 2004) determined that the contraction due to fibroblasts was decreased and permeability was increased. Before these composite hydrogels can be used to design soft tissue replacements, however, the effect of fiber number and serum concentration should be addressed. Consequently, short collagen fibers were included in adult rat bone marrow stem cell-seeded hydrogels for composite support. The mass of fibers was varied from 1.6 to 31.3 mg per gel, and the effect of serum concentration in the growth medium was examined. It was determined that increasing fiber mass and decreasing serum concentration significantly decreased contraction, which plateaued after day 10. Cell number increased throughout the experiment, demonstrating the compatibility of bone marrow stem cells with the collagen composite gels. By using short collagen fibers to create a collagen composite gel, preservation of the original dimensions can be achieved without compromising cellular viability.

Short collagen fibers provide control of contraction and permeability in fibroblast-seeded collagen gels.

Tissue engineering may allow for the reconstruction of breast, facial, skin, and other soft tissue defects in the human body. Cell-seeded collagen gels are a logical choice for creating soft tissues because they are biodegradable, mimic the natural tissue, and provide a three-dimensional environment for the cells. The main drawback associated with this approach, however, is the subsequent contraction of the gel by the constituent cells, which severely reduces permeability, initiates apoptosis, and precludes control of the resulting shape and size of the construct. In this study, type I collagen gels were seeded with fibroblasts and cast either with or without the addition of short collagen fibers. Gel contraction was monitored and permeability was assessed after 7 and 14 days in culture. The addition of short collagen fibers both significantly limited contraction and increased permeability of fibroblast-seeded collagen gels. The addition of short collagen fibers had no detrimental effect on cell proliferation, and there were a high number of viable fibroblasts in gels with fibers and gels without fibers. Gels containing short collagen fibers demonstrated permeabilities that were 100 to 1000 times greater than controls and also closely maintained their casting dimensions (never less than 96% of original). By limiting contraction and maintaining permeability, the incorporation of short collagen fibers should enable the creation of larger constructs by allowing for greater nutrient diffusion, and permit the creation of more complicated shapes during gel casting.

A density-functional model for controlled release.

Polymer diffusion based on density-functional theory is applied to controlled release systems. These models explicitly treat the multiphase characteristics of biomolecule-polymer composites typical of drug delivery devices. Polymer diffusion was modeled using the modified Cahn-Hilliard equation with periodic boundary conditions in one dimension and near-zero concentration boundaries in the second dimension. The diffusional driving forces are differences in chemical potential based in part on the Flory-Huggins free energy of mixing in polymer systems rather than concentration gradients. Release rates from this model were compared to exponential models typically used in the drug delivery literature. Simulations based on this model showed that the diffusional exponent is 1/2; this exponent is consistent with Fickian models at early times. Particle growth, which also occurs in diffusing, dispersed systems, was observed. The particle growth exponent in these systems was 2/3, twice the value typical in bulk ripening systems. The increased growth rate was caused by the elimination of small particles due to diffusion out of the system, which removed the low particle size region of the distribution faster than ripening alone.

bFGF administration lowers the phosphate threshold for mineralization in bone marrow stromal cells.

Basic fibroblast growth factor (bFGF) is a potent mitogen and acts as an autocrine/paracrine factor for osteoblasts. Long-term administration of bFGF in vivo increases osteoblast number and stimulates matrix formation, but induces hypophosphatemia and impairs matrix mineralization. The goal of this study was to examine the interaction between bFGF and low levels of organic phosphate in an effort to better understand the possible long-term therapeutic effects of bFGF. These data show that in vitro administration of bFGF accelerates the calcification process and lowers the phosphate threshold needed for successful bone nodule formation. This correlates well with the observed upregulation of mRNA production for alkaline phosphatase and osteocalcin at day 7. These findings help elucidate the mechanisms of bFGF action on bone marrow stromal cell differentiation and mineralization and indicate that the delay in mineralization observed in vivo may not be caused by decreased phosphate availability alone.

Examination of continuum and micro-structural properties of human vertebral cancellous bone using combined cellular solid models.

Two- and three-dimensional structural models of the vertebral body have been used to estimate the mechanical importance of parameters that are difficult to quantify experimentally such as lattice disorder, trabecular thickness, trabecular spacing, connectivity, and fabric. Many of the models that investigate structure-function relationships of the vertebral body focus only on the trabecular architecture and neglect solid-fluid interactions. We developed a cellular solid model composed of two idealized unit cell geometries to investigate the continuum and micro-structural properties of human vertebral cancellous bone in a mathematically tractable model. Using existing histomorphological data we developed structure-function relationships for the mechanical properties of the solid phase, estimated the micro-structural strains, and predicted the fluid flow characteristics. We found that the micro-structural strains may be 1.7 to 2.2 times higher than the continuum level strains between the ages of 40 and 80. In addition, the predicted permeability agrees well with the experimental data.

Mechanical and chemical characteristics of mineral produced by basic fibroblast growth factor-treated bone marrow stromal cells in vitro.

It has been shown that various organ and cell cultures exhibit increased mineral formation with the addition of basic fibroblast growth factor (bFGF) and phosphate ions in the medium. However, to date there has been no attempt to relate the chemical composition of mineral formed in vitro to a measure of its mechanical properties. This information is important for understanding the in vivo mineralization process, the development of in vitro models, and the design of tissue-engineered bone substitutes. In this study we examined the reduced modulus; hardness; and mineral-to-matrix, crystallinity, carbonate-to-mineral, and calcium-to-phosphorus ratios of mineral formed by bFGF-treated rat-derived bone marrow stromal cells in vitro. The cells were treated with 1 or 3 mM beta-glycerophosphate for 3 and 4 weeks. Both mechanical parameters, reduced modulus and hardness, increased with increasing beta-glycerophosphate concentration. The only chemical measure of the mineral composition that exhibited the same dependency was the mineral-to-matrix ratio. The values of crystallinity and carbonate fraction were similar to those for intact cortical bone, but the calcium-to-phosphorus ratio was substantially lower than that of normal bone. These data indicate that the mineral formed by bFGF-treated bone cells is mechanically and chemically different from naturally formed lamellar bone tissue after 4 weeks in culture. These results can be used to improve in vitro models of mineral formation as well as enhance the design of tissue-engineered bone substitutes.

Osteoblasts respond to pulsatile fluid flow with short-term increases in PGE(2) but no change in mineralization.

Although there is no consensus as to the precise nature of the mechanostimulatory signals imparted to the bone cells during remodeling, it has been postulated that deformation-induced fluid flow plays a role in the mechanotransduction pathway. In vitro, osteoblasts respond to fluid shear stress with an increase in PGE(2) production; however, the long-term effects of fluid shear stress on cell proliferation and differentiation have not been examined. The goal of this study was to apply continuous pulsatile fluid shear stresses to osteoblasts and determine whether the initial production of PGE(2) is associated with long-term biochemical changes. The acute response of bone cells to a pulsatile fluid shear stress (0.6 +/- 0.5 Pa, 3.0 Hz) was characterized by a transient fourfold increase in PGE(2) production. After 7 days of static culture (0 dyn/cm(2)) or low (0.06 +/- 0.05 Pa, 0.3 Hz) or high (0.6 +/- 0.5 Pa, 3.0 Hz) levels of pulsatile fluid shear stress, the bone cells responded with an 83% average increase in cell number, but no statistical difference (P > 0.53) between the groups was observed. Alkaline phosphatase activity per cell decreased in the static cultures but not in the low- or high-flow groups. Mineralization was also unaffected by the different levels of applied shear stress. Our results indicate that short-term changes in PGE(2) levels caused by pulsatile fluid flow are not associated with long-term changes in proliferation or mineralization of bone cells.

The skeletal structure of insulin-like growth factor I-deficient mice.

The importance of insulin-like growth factor I (IGF-I) for growth is well established. However, the lack of IGF-I on the skeleton has not been examined thoroughly. Therefore, we analyzed the structural properties of bone from mice rendered IGF-I deficient by homologous recombination (knockout [k/o]) using histomorphometry, peripheral quantitative computerized tomography (pQCT), and microcomputerized tomography (muCT). The k/o mice were 24% the size of their wild-type littermates at the time of study (4 months). The k/o tibias were 28% and L1 vertebrae were 26% the size of wild-type bones. Bone formation rates (BFR) of k/o tibias were 27% that of the wild-type littermates. The k/o bones responded normally to growth hormone (GH; 1.7-fold increase) and supranormally to IGF-I (5.2-fold increase) with respect to BFR. Cortical thickness of the proximal tibia was reduced 17% in the k/o mouse. However, trabecular bone volume (bone volume/total volume [BV/TV]) was increased 23% (male mice) and 88% (female mice) in the k/o mice compared with wild-type controls as a result of increased connectivity, increased number, and decreased spacing of the trabeculae. These changes were either less or not found in L1. Thus, lack of IGF-I leads to the development of a bone structure, which, although smaller, appears more compact.

Dependence of intertrabecular permeability on flow direction and anatomic site.

The structure-function relationships for the permeability of trabecular bone may have relevance for tissue engineering, total joint replacements, and whole bone mechanics. To investigate such relationships, we used a constant flow rate permeameter to determine the intrinsic permeability of trabecular bone specimens, oriented longitudinally or transversely to the principal trabecular orientation, from the human vertebral body (n=20), human proximal femur (n=12), and bovine proximal tibia (n=24). Overall, the intertrabecular permeability ranged from 2.68 x 10(-11) to 2.00 x 10(-8) m2. Significant negative nonlinear relations between intertrabecular permeability and volume fraction were found for each group except the longitudinal bovine proximal tibial specimens (r2=0.34-0.80). The average permeability ratio, a measure of the anisotropy, was 2.05, 6.60, and 23.3 for the human vertebral body, bovine tibia, and human femur, respectively. The permeability depended strongly on flow direction relative to the principal trabecular orientation (p<0.0001) and anatomic site (p <0.0001). In addition to providing a comprehensive description of intertrabecular permeability as a function of anatomic site and flow direction, these data provide substantial insight into the underlying structure-function relationships.

Structure-function relationships for coralline hydroxyapatite bone substitute.

To improve the understanding of the functional requirements of trabecular bone substitutes, the structure-function relationships of coralline hydroxyapatite were determined and compared to those of trabecular bone from a variety of anatomic sites. Mechanical properties and permeability of cylindrical coralline hydroxyapatite specimens were measured and related to various morphological parameters that were obtained from analysis of high-resolution (20 microm) computer reconstructions of each specimen. Results indicated the average (+/-SD) Young's modulus (2900 +/- 1290 MPa, n = 20) and permeability (0.50 +/- 0.19 x 10(-9) m2, n = 21) of the coralline hydroxyapatite were within the range of values exhibited by high density trabecular bone; ultimate stress (5.87 +/- 1.92 MPa, n = 13), while in the range of mid-density trabecular bone, was low considering its high volume fraction (31.3 +/- 1.9%, n = 49); and ultimate strain (0.22 +/- 0.03%, n = 13) was much lower than that of trabecular bone from any anatomic site. The only correlation found between mechanical and morphological parameters was between Young's modulus and "fabric" (a scalar measure of architecture that combined the degree of microstructural anisotropy with orientation). These results provide insight into the in vivo performance of this implant, as well as the biomechanical requirements for successful trabecular bone substitutes in general.

Quantitative assessment of steady and pulsatile flow fields in a parallel plate flow chamber.

Steady and pulsatile flows were imaged and quantified in a parallel plate flow chamber that was designed to allow constant variation of the volumetric flow rate and to minimize pressure gradients across the width of the flow field. Results indicated that both the steady and pulsatile flow fields were uniform across the width of the flow chamber as shown by linear regression analysis. Further, the dynamic effects of the fluid pulse were transmitted almost instantaneously across the length of the flow field. These findings verify that parallel plate devices designed in this manner are suitable for delivering uniform steady and pulsatile shear stress to adherent cell populations in vitro.