Mechanobiological Modulation of Cytoskeleton and Calcium Influx in Osteoblastic Cells by Short-Term Focused Acoustic Radiation Force

Mechanotransduction has demonstrated potential for regulating tissue adaptation in vivo and cellular activities in vitro. It is well documented that ultrasound can produce a wide variety of biological effects in biological systems. For example, pulsed ultrasound can be used to noninvasively accelerate the rate of bone fracture healing. Although a wide range of studies has been performed, mechanism for this therapeutic effect on bone healing is currently unknown. To elucidate the mechanism of cellular response to mechanical stimuli induced by pulsed ultrasound radiation, we developed a method to apply focused acoustic radiation force (ARF) (duration, one minute) on osteoblastic MC3T3-E1 cells and observed cellular responses to ARF using a spinning disk confocal microscope. This study demonstrates that the focused ARF induced F-actin cytoskeletal rearrangement in MC3T3-E1 cells. In addition, these cells showed an increase in intracellular calcium concentration following the application of focused ARF. Furthermore, passive bending movement was noted in primary cilium that were treated with focused ARF. Cell viability was not affected. Application of pulsed ultrasound radiation generated only a minimal temperature rise of 0.1°C, and induced a streaming resulting fluid shear stress of 0.186 dyne/cm2, suggesting that hyperthermia and acoustic streaming might not be the main causes of the observed cell responses. In conclusion, these data provide more insight in the interactions between acoustic mechanical stress and osteoblastic cells. This experimental system could serve as basis for further exploration of the mechanosensing mechanism of osteoblasts triggered by ultrasound

The effect of membrane diffusion potential change on anionic drugs Indomethacin and Barbitone induced human red blood cell shape change and on cellular uptake of drugs.

The effect of membrane potential change on anionic drugs Indomethacin and barbitone induced human erythrocyte shape change and red cell uptake of drug has been studied using microscopy and spectrophotometry techniques respectively. The membrane potential was changed by reducing the extracellular chloride concentration while maintaining the ionic strength and the osmolarity of the cell suspending solutions constant. At indomethacin and barbitone concentractions necessary to cause marked cell crenation membrane diffusion potential change from - 7.1 mV to 16 . 4niV, led to the reversal of the shape changing properly of the drugs to cup formers. The cellular uptake of drug increased with increasing membrane potential. The membrane potential dependent shape change was also reversible on revering the membrane potential. The results suggest that cellular uptake of drug and drug induced cell shape change was strongly dependent on changes in the extracellular chloride concentration which alter the potential across the erythrocyte membrane. These findings may be of medical significance such as in the design of drugs, for example, for sickle cell diseases, malarial diseases, since knowledge of the concentration and location of the molecules with respect to the membrane surface is required

Membrane potential change effects on cationic and neutral drug - induced erythrocyte shape change and cellular uptake of drugs.

The effect of membrane potential change of the human erythrocytes on cationic drugs tetracaine and chlorpromazine and neutral drug benzyl alcohol induced cell shape change and red cell uptake of drug has been quantitated using light microscopy and spectrophotometry respectively. At the drug concentration necessary to cause cell membrane cell shape change membrane potential change from -7.1 mV to 1 6.4mV let to the reversal of the cup-forming property of chlorpromazine and tetracaine to that of a crenetor at both 20°C and 37°C. The effect of altering the membrane potential from -7. lmV to 16.4mV also led to the decrease of cellular uptake of drug with increasing membrane diffusion potential. The membrane potential dependent drug induced cell shape change with also reversible on reversing the membrane potential. The results therefore suggest that the cellular uptake of drug and drug induced cell shape change in human erythrocytes was dependent on change in extracellular chloride concentratio

Modelling condensation and the initiation of chondrogenesis in chick wing bud mesenchymal cells levitated in an ultrasound trap

Chick wing bud mesenchymal cell micromass culture allows the study of a variety of developmental mechanisms, ranging from cell adhesion to pattern formation. However, many cells remain in contact with an artificial substratum, which can influence cytoskeletal organisation and differentiation. An ultrasound standing wave trap facilitates the rapid formation of 2-D monolayer cell aggregates with a defined zero time-point, independent from contact with a surface. Aggregates formed rapidly (within 2 min) and intercellular membrane spreading occurred at points of contact. This was associated with an increase in peripheral F-actin within 10 min of cell-cell contact and aggregates had obtained physical integrity by 30 min. The chondrogenic transcription factor Sox9 could be detected in cells in the ultrasound trap within 3 h (ultrasound exposure alone was not responsible for this effect). This approach facilitates the study of the initial cell-cell interactions that occur during condensation formation and demonstrates that a combination of cell shape and cytoskeletal organisation is required for the initiation and maintenance of a differentiated phenotype, which is lost when these phenomena are influenced by contact with an artificial substrate

Acoustic Particle Manipulation to Enhance the Sensing of Cells within Microfluidic Chambers

The sensing of cells within micro-fluidic components can be greatly enhanced by maximizing the concentration of particles around the sensor element. To encourage bacterial cells to move to a surface, acoustic radiation forces are employed, which rely on the compressibility and density of the particulate matter. This provides an alternative to electric or magnetic field-assisted particle manipulation, and can operate over greater length scales. This paper describes the simulation of a device used to demonstrate the principle and reveals how the geometric design of the system influences the acoustic field and is paramount to the particle manipulation process. Predictions of particle concentrations upon a surface compare excellently with experimental result

THE EFFECTS OF EXTENSIONAL STRESS ON RED BLOOD CELL HEMOLYSIS

[[abstract]]Arti¯cial prostheses create non-physiologic °ow conditions with stress forces that may induce blood cell damage, particularly hemolysis. Earlier computational °uid dynamics (CFD) prediction models based on a quanti¯ed power model showed signi¯cant discrepancies with actual hemolysis experiments. These models used the premise that shear stresses act as the primary force behind hemolysis. However, additional studies have suggested that extensional stresses play a more substantial role than previously thought and should be taken into account in hemolysis models. We compared extensional and shear stress °ow ¯elds within the contraction of a short capillary with sharp versus tapered entrances. The °ow ¯eld was calculated with CFD to determine stress values, and hemolysis experiments with porcine red blood cells were performed to correlate the e®ects of extensional and shear stress on hemolysis. Our results support extensional stress as the primary mechanical force involved in hemolysis, with a threshold value of 1000 Pa under exposure time less than 0.060 ms.[[notice]]補正完