Strain Fields on Cell Stressing Devices Employing Clamped Circular Elastic Diaphragms as Substrates

1992 ◽  
Vol 114 (3) ◽  
pp. 377-384 ◽  
Author(s):  
J. L. Williams ◽  
J. H. Chen ◽  
D. M. Belloli
Keyword(s):  
Nonlinear Equations ◽  
Excellent Agreement ◽  
Surface Strain ◽  
Optical Measurements ◽  
Strain Fields ◽  
Symmetrical Deformation ◽  
Plate Equations ◽  
Center Deflection ◽  
Clamped Edge

Solutions are presented for the surface strain fields on inflated elastomeric circular diaphragms used for in vitro cell stressing experiments. It is shown, by using the method developed by Way (1934) to solve the nonlinear von Karman plate equations, that the surface strains due to bending are not negligible and that large negative radial strains arise near the clamped edge for center deflection-to-thickness ratios (w/h)< 10. The method of Hart-Smith and Crisp (1967) was used for w/h>10 to solve the nonlinear equations for symmetrical deformation of axially symmetrical rubber-like membranes. In the membrane solutions the circumferential strains drop parabolically to zero at the clamped edge of the diaphragm, while the radial strains increase slightly with the radius. The solutions for w/h>10 are compared to optical measurements of in-plane displacements used to calculate the circumferential strains on the diaphragm, yielding excellent agreement with the theory.

Optical measurements of intracellular oxygen concentration of rat heart in vitro

1978 ◽  
Vol 191 (1) ◽  
pp. 8-22 ◽  
Author(s):  
Mamoru Tamura ◽  
Nozomu Oshino ◽  
Britton Chance ◽  
Ian A. Silver
Keyword(s):  
Oxygen Concentration ◽  
Rat Heart ◽  
Optical Measurements

scholarly journals Reassessing the Role of Intra-Arterial Drug Delivery for Glioblastoma Multiforme Treatment

2015 ◽  
Vol 2015 ◽  
pp. 1-15 ◽  
Author(s):  
Jason A. Ellis ◽  
Matei Banu ◽  
Shaolie S. Hossain ◽  
Rajinder Singh-Moon ◽  
Sean D. Lavine ◽  
...  
Keyword(s):  
Drug Delivery ◽  
Targeted Delivery ◽  
Optical Measurements ◽  
Pharmacological Agents ◽  
Cellular Targets ◽  
Therapeutic Landscape ◽  
Rational Drug

Effective treatment for glioblastoma (GBM) will likely require targeted delivery of several specific pharmacological agents simultaneously. Intra-arterial (IA) delivery is one technique for targeting the tumor site with multiple agents. Although IA chemotherapy for glioblastoma (GBM) has been attempted since the 1950s, the predicted benefits remain unproven in clinical practice. This review focuses on innovative approaches to IA drug delivery in treating GBM. Guided by novel in vitro and in vivo optical measurements, newer pharmacokinetic models promise to better define the complex relationship between background cerebral blood flow and drug injection parameters. Advanced optical technologies and tracers, unique nanoparticles designs, new cellular targets, and rational drug formulations are continuously modifying the therapeutic landscape for GBM. Personalized treatment approaches are emerging; however, such tailored approaches will largely depend on effective drug delivery techniques and on the ability to simultaneously deliver multidrug regimens. These new paradigms for tumor-selective drug delivery herald dramatic improvements in the effectiveness of IA chemotherapy for GBM. Therefore, within this context of so-called “precision medicine,” the role of IA delivery for GBM is thoroughly reassessed.

Effect of the In Vitro Boundary Conditions on the Surface Strain Experienced by the Vertebral Body in the Elastic Regime

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Valentina Danesi ◽  
Paolo Erani ◽  
Nicola Brandolini ◽  
Mateusz M. Juszczyk ◽  
Luca Cristofolini
Keyword(s):  
Boundary Conditions ◽  
Axial Loading ◽  
Surface Strain ◽  
Strain Gauges ◽  
Nondestructive Tests ◽  
Elastic Regime ◽  
Vertebral Strength ◽  
Strain Magnitude ◽  
Principal Strains

The vertebral strength and strain can be assessed in vitro by both using isolated vertebrae and sets of three adjacent vertebrae (the central one is loaded through the disks). Our goal was to elucidate if testing single-vertebra-specimens in the elastic regime provides different surface strains to three-vertebrae-segments. Twelve three-vertebrae sets were extracted from thoracolumbar human spines. To measure the principal strains, the central vertebra of each segment was prepared with eight strain-gauges. The sets were tested mechanically, allowing comparison of the surface strains between the two boundary conditions: first when the same vertebra was loaded through the disks (three-vertebrae-segment) and then with the endplates embedded in cement (single-vertebra). They were all subjected to four nondestructive tests (compression, traction, torsion clockwise, and counterclockwise). The magnitude of principal strains differed significantly between the two boundary conditions. For axial loading, the largest principal strains (along vertebral axis) were significantly higher when the same vertebra was tested isolated compared to the three-vertebrae-segment. Conversely, circumferential strains decreased significantly in the single vertebrae compared to the three-vertebrae-segment, with some variations exceeding 100% of the strain magnitude, including changes from tension to compression. For torsion, the differences between boundary conditions were smaller. This study shows that, in the elastic regime, when the vertebra is loaded through a cement pot, the surface strains differ from when it is loaded through the disks. Therefore, when single vertebrae are tested, surface strain should be taken with caution.

Biomechanics of a Novel Minimally Invasive Lumbar Interspinous Spacer: Effects on Kinematics, Facet Loads, and Foramen Height

2010 ◽  
Vol 66 (suppl_1) ◽  
pp. ons-126-ons-133 ◽  
Author(s):  
Bruno C.R. Lazaro ◽  
Leonardo B.C. Brasiliense ◽  
Anna G.U. Sawa ◽  
Phillip M. Reyes ◽  
Nicholas Theodore ◽  
...  
Keyword(s):  
Range Of Motion ◽  
Axial Rotation ◽  
Surface Strain ◽  
Interspinous Spacer ◽  
Instantaneous Axis Of Rotation ◽  
Flexion Extension ◽  
Before And After ◽  
Biomechanical Effect ◽  
Foraminal Height

Abstract Objective: To study the alteration to normal biomechanics after insertion of a lumbar interspinous spacer (ISS) in vitro by nondestructive cadaveric flexibility testing. Methods: Seven human cadaveric specimens were studied before and after ISS placement at L1–L2. Angular range of motion, lax zone, stiff zone, sagittal instantaneous axis of rotation (IAR), foraminal height, and facet loads were compared between conditions. Flexion, extension, lateral bending, and axial rotation were induced using pure moments (7.5 Nm maximum) while recording motion optoelectronically. The IAR was measured during loading with a 400 N compressive follower. Foraminal height changes were calculated using rigid body methods. Facet loads were assessed from surface strain and neural network analysis. Results: After ISS insertion, range of motion and stiff zone during extension were significantly reduced (P &lt; .01). Foraminal height was significantly reduced from flexion to extension in both normal and ISS-implanted conditions; there was significantly less reduction in foraminal height during extension with the ISS in place. The ISS reduced the mean facet load by 30% during flexion (P &lt; .02) and 69% during extension (P &lt; .015). The IAR after ISS implantation was less than 1 mm from the normal position (P &gt; .18). Conclusion: The primary biomechanical effect of the ISS was reduced extension with associated reduced facet loads and smaller decrease in foraminal height. The ISS had little effect on sagittal IAR or on motion or facet loads in other directions.

Strain Localisation during a Tensile Test of Metallic Plates: Experimental and Numerical Results

2009 ◽  
Vol 417-418 ◽  
pp. 569-572
Author(s):  
D.A. Cendón ◽  
Jose M. Atienza ◽  
Manuel Elices Calafat
Keyword(s):  
Tensile Test ◽  
Strain Curve ◽  
Maximum Load ◽  
Surface Strain ◽  
Displacement Curve ◽  
Strain Localisation ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Strain Fields ◽  
Developed Surface

The stress-strain curve of a material is usually obtained from the load-displacement curve measured in a tensile test, assuming no strain localisation up to maximum load. However, strain localisation and fracture phenomena are far from being completely understood. Failure and strain localisation on plane tensile specimens has been studied in this work. A deeply instrumented experimental benchmark on steel specimens has been developed. Surface strain fields have been recorded throughout the tests, using an optical extensometer. This allowed characterisation of the strain localisation and failure processes. Tests have been numerically modelled for a more detailed analysis. Preliminary results show a substantial influence of geometrical specimen defects on the strain localisation phenomena that may be critical on the stress-strain curves obtained and in the failure mechanisms.

scholarly journals Optical Characterization of Sodium Fluorescein In Vitro and Ex Vivo

2021 ◽  
Vol 11 ◽  
Author(s):  
Ran Xu ◽  
Wanda Teich ◽  
Florian Frenzel ◽  
Katrin Hoffmann ◽  
Josefine Radke ◽  
...  
Keyword(s):  
Optical Properties ◽  
Laser Scanning ◽  
Tumor Tissue ◽  
Ex Vivo ◽  
Bathochromic Shift ◽  
Emission Spectra ◽  
Optical Measurements ◽  
Confocal Laser ◽  
Sodium Fluorescein

ObjectiveThe utilization of fluorescein-guided biopsies and resection has been recently discussed as a suitable strategy to improve and expedite operative techniques for the resection of central nervous system (CNS) tumors. However, little is known about the optical properties of sodium fluorescein (NaFl) in human tumor tissue and their potential impact on ex vivo analyses involving fluorescence-based methods.MethodsTumor tissue was obtained from a study cohort of an observational study on the utilization of fluorescein-guided biopsy and resection (n=5). The optical properties of fluorescein-stained tissue were compared to the optical features of the dye in vitro and in control samples consisting of tumor tissue of high-grade glioma patients (n=3) without intravenous (i.v.) application of NaFl. The dye-exposed tumor tissues were used for optical measurements to confirm the detectability of NaFl emission ex vivo. The tissue samples were fixed in 4%PFA, immersed in 30% sucrose, embedded in Tissue-Tek OCT compound, and cut to 10 μm cryosections. Spatially resolved emission spectra from tumor samples were recorded on representative slides with a Confocal Laser Scanning Microscope FV1000 (Olympus GmbH, Hamburg, Germany) upon excitation with λexc = 488 nm.ResultsOptical measurements of fluorescein in 0.9% sodium chloride (NaCl) under in vitro conditions showed an absorption maximum of λmax abs = 479 nm as detected with spectrophotometer Specord 200 and an emission peak at λmax em = 538 nm recorded with the emCCD detection system of a custom-made microscope-based single particle setup using a 500 nm long-pass filter. Further measurements revealed pH- and concentration-dependent emission spectra of NaFl. Under ex vivo conditions, confocal laser scanning microscopy of fluorescein tumor samples revealed a slight bathochromic shift and a broadening of the emission band.ConclusionTumor uptake of NaFl leads to changes in the optical properties – a bathochromic shift and broadening of the emission band – possibly caused by the dye’s high pH sensitivity and concentration-dependent reabsorption acting as an inner filter of the dye’s emission, particularly in the short wavelength region of the emission spectrum where absorption and fluorescence overlap. Understanding the ex vivo optical properties of fluorescein is crucial for testing and validating its further applicability as an optical probe for intravital microscopy, immunofluorescence localization studies, and flow cytometry analysis.

scholarly journals THE UPTAKE OF RADIOCOLLOIDS BY MACROPHAGES IN VITRO

1956 ◽  
Vol 39 (5) ◽  
pp. 625-649 ◽  
Author(s):  
Robert E. Gosselin
Keyword(s):  
Cell Surface ◽  
Colloidal Gold ◽  
Particle Diameter ◽  
Extracellular Fluid ◽  
Metabolic Energy ◽  
Optical Measurements ◽  
Affinity Constant ◽  
Cell Agglutination ◽  
Surface Saturation

Macrophages isolated from the rabbit peritoneal cavity extract radioactive colloidal gold from solutions in vitro. This reaction (ultraphagocytosis) involves two phases: the reversible adsorption of gold on the cell surface and the subsequent irreversible removal of surface-bound colloid into the cell. The latter process (called ingestion) appears to proceed at a rate which is proportional at any moment to the amount of gold attached to the cell surface; the latter in turn can be related to the concentration in extracellular fluid by a simple adsorption isotherm. In terms of rate, therefore, ingestion is related to the extracellular gold concentration in the same way that many enzyme reactions are related to the substrate concentration. Although enzyme kinetics are useful in describing rates of ultraphagocytosis, there is no evidence that enzymes participate in either adsorption or ingestion or that metabolic energy is required of the macrophage. Exudative leucocytes of the heterophilic series show little or no interaction with these finely dispersed gold sols (mean particle diameter 6 to 9 millimicrons). 37°C. three parameters are sufficient to characterize the reaction between gold and a suspension of macrophages, namely an affinity constant (1/Ks), an adsorption maximum (L), and a rate constant of ingestion (k3). Although numerical values differed markedly among cells of different exudates, all three parameters were estimated in three instances. In these suspensions between 2 and 20 per cent of the surface-bound gold was ingested each minute (37°C., pH 7.4). Under conditions of surface saturation, it was estimated that tens of thousands of gold particles were attached to the surface of an average macrophage; this amount of colloid, however, occupied less than 1 per cent of the geometric area of the cell surface. Although surface saturation imposed an upper limit on the rate of ingestion, no practical limit was noted in the capacity of macrophages to continue the reaction. Optical measurements imply that within the cell agglutination of colloidal gold began promptly after its ingestion. These data are compared with published kinetic studies on the phagocytosis of microscopic particulates and on the parasitism of bacteria by virus.

scholarly journals Anisotropic and hyperelastic identification of in vitro human arteries from full-field optical measurements

2010 ◽  
Vol 43 (15) ◽  
pp. 2978-2985 ◽  
Author(s):  
Stéphane Avril ◽  
Pierre Badel ◽  
Ambroise Duprey
Keyword(s):  
Optical Measurements ◽  
Full Field ◽  
Human Arteries

Variations in Rupture Site and Surface Strains at Failure in the Maturing Rabbit Medial Collateral Ligament

1995 ◽  
Vol 117 (4) ◽  
pp. 455-461 ◽  
Author(s):  
T. C. Lam ◽  
N. G. Shrive ◽  
C. B. Frank
Keyword(s):  
Medial Collateral Ligament ◽  
Surface Strain ◽  
Collateral Ligament ◽  
Anterior Portion ◽  
Femoral Insertion ◽  
Tibial Insertion ◽  
Medial Side ◽  
Optical Strain Measurement ◽  
Optical Strain

The relationship between the pattern of surface strain and the site of failure in maturing rabbit ligaments was studied in vitro. Bone-medial collateral ligament (MCL)-bone complexes of 24 female New Zealand White rabbits at 3, 6, 9 and 12 months of age (n = 6 rabbits, 12 MCLs per group) were tested in tension to failure. A video dimension analysis (VDA) system was used to map the surface strain at failure across the width and along the length of the medial side of each MCL during testing. Results showed that the highest strains were consistently located at the femoral insertion decreasing towards the midsubstance, with the highest strain occurring in the anterior portion of the MCL immediately adjacent to the femoral insertion. Strains of the complex at failure increased with rabbit maturation. The strain distribution however, did not change dramatically, even though the locations of MCL failure changed from exclusively tibial avulsion in the three month old rabbits to predominantly midsubstance failures in the 12 month old rabbits. In the six month old rabbits, there was a particular dissociation with all MCLs failing near the tibial insertion while femoral strains were apparently the highest. These results suggest two possibilities beyond that of some unknown artifacts of optical strain measurement. First, since failure sites rarely correlated with areas of maximum surface strain in this study, it seems possible that higher strains could exist deeper in the tissue, particularly at the bone-ligament interface of the tibial insertion in immature animals and somewhere within the midsubstance of the MCL in the adult. Secondly, it is possible that the ligament material may be heterogeneous.

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