Compressive Stimuli Research Articles

Ultrasound Elastography: Review of Techniques and Clinical Applications.

Elastography-based imaging techniques have received substantial attention in recent years for non-invasive assessment of tissue mechanical properties. These techniques take advantage of changed soft tissue elasticity in various pathologies to yield qualitative and quantitative information that can be used for diagnostic purposes. Measurements are acquired in specialized imaging modes that can detect tissue stiffness in response to an applied mechanical force (compression or shear wave). Ultrasound-based methods are of particular interest due to its many inherent advantages, such as wide availability including at the bedside and relatively low cost. Several ultrasound elastography techniques using different excitation methods have been developed. In general, these can be classified into strain imaging methods that use internal or external compression stimuli, and shear wave imaging that use ultrasound-generated traveling shear wave stimuli. While ultrasound elastography has shown promising results for non-invasive assessment of liver fibrosis, new applications in breast, thyroid, prostate, kidney and lymph node imaging are emerging.Here, we review the basic principles, foundation physics, and limitations of ultrasound elastography and summarize its current clinical use and ongoing developments in various clinical applications.

Ultrafast mechano-responsive photonic hydrogel towards multicolor displays via the pressure sensation

In this work, the magnetic assembly combined with fast photopolymerization is applied for the preparation of mechano-responsive photonic hydrogel. The as-prepared hydrogel exhibits switchable color with ultrafast speed (Δλ/t=~1.2nm/ms) across a broad wavelength range (Δλ=~250nm), which is attributed to fast changing of the interparticle distance d of one dimensional (1 D) Fe3O4 nanoparticle chains fixed inside the hydrogel matrix in response to compressive force stimulus. The pressure chromatic sensitivity is high (Δλ/σ=20–40nmkPa−1) in touch region. With the aid of 3D printing technique, we innovatively demonstrate simultaneous multicolor displays on the hydrogel.

The Mechanics of Breast Pumping: Compression Stimuli Increased Milk Ejection.

The use of breast pumps with a compression component has shown their higher efficacy compared with vacuum pumps. However, the direct role of the compression stimulus is not sufficiently proven in the removal of milk from the main milk ducts of the breast. The aim of this study was to determine the contribution pulsating compression component of the breast pump has on total volume milk ejection by vacuum and compression stimuli. Twenty-four lactating women of 21-30 years of age, who volunteered to be included in this study, were examined. Experimental breast pump with vacuum and compressive components were used to express breast milk. It was found that volume milk ejection together with vacuum and compression stimuli was 10-46% more than expressing only with vacuum stimuli. Average values were 40.5% ± 5% for expression only with vacuum stimuli and 59.5% ± 5% for expression with vacuum and compression stimuli. Compression stimuli increased the efficacy of the breast pump, which is not only due to the effective formation milk ejection reflex but also directly to an additional squeezing of milk from the breast.

Functional role of mechanosensitive ion channel Piezo1 in human periodontal ligament cells.

To evaluate the function of Piezo1, an evolutionarily conserved mechanically activated channel, in periodontal ligament (PDL) tissue homeostasis under compressive loading. Primary human PDL cells (hPDLCs) were isolated, cultured, and then subjected to 2.0 g/cm(2) static compressive loading for 0.5, 3, 6, and 12 hours, respectively. The expressions of Piezo1 and osteoclastogenesis marker gene were assessed by semiquantitative reverse transcription-polymerase chain reaction. In addition, Piezo1 inhibitor, GsMTx4, was used to block the function of Piezo1, and tumor necrosis factor-α was also used as a positive control. After 12 hours of compressive loading the PDLCs were co-cultured with murine monocytic cell line RAW264.7. Immunofluorescence, western blot, enzyme-linked immunosorbent assay, and tartrate-resistant acid phosphatase staining were also used to test the potency of PDLCs to induce osteoclastogenesis and the activation of nuclear factor (NF)-κB. Piezo1, cyclooxygenase-2, receptor activator of NF-κB ligand, and prostaglandin E2 were significantly upregulated under static compressive stimuli. GsMTx4 repressed osteoclastogenesis in the mechanical stress-pretreated PDLCs-RAW264.7 co-culture system. Furthermore, NF-κB signaling pathway was involved in the mechanical stress-induced osteoclastogenesis. Piezo1 exerts a transduction role in mechanical stress-induced osteoclastogenesis in hPDLCs.

Modulation of Chondrocyte Phenotype by Bioreactor Assisted Static Compression in a 3D Polymeric Scaffold with Potential Implications to Functional Cartilage Tissue Engineering

Functional cartilage tissue engineering aims at augmenting the regeneration process of chondrocyte seeded three dimensional scaffolds by application of external biomechanical stimuli. The effect of static compressive stimuli in modulating the phenotype of chondrocytes cultured in porous scaffolds using a bioreactor is being investigated in the present study. Chondrocytes were seeded in porous Poly (vinyl) alcohol-Poly capro lactone scaffold and was subjected to static unconfined compressive strain of 10% for 1h everyday for a period of 7days using a bioreactor. After culture period, chondrogenic phenotype of seeded cells was assessed by live dead assay, biochemical histological and real time PCR analysis. Bioreactor seems to be a promising tool in delivering the desired biomechanical stimuli to the cell seeded constructs. However, application of biomechanical stimuli in the form of static compression doesn’t seem beneficial as it modulates chondrogenic phenotype by reverting to a fibroblastic morphology with the secretion of collagen type 1 extra cellular matrix molecules

Effect of input compression and input frequency response on music perception in cochlear implant users

Objective: A study was conducted to determine whether modifications to input compression and input frequency response characteristics can improve music-listening satisfaction in cochlear implant users. Design: Experiment 1 compared three pre-processed versions of music and speech stimuli in a laboratory setting: original, compressed, and flattened frequency response. Music excerpts comprised three music genres (classical, country, and jazz), and a running speech excerpt was compared. Experiment 2 implemented a flattened input frequency response in the speech processor program. In a take-home trial, participants compared unaltered and flattened frequency responses. Study sample: Ten and twelve adult Nucleus Freedom cochlear implant users participated in Experiments 1 and 2, respectively. Results: Experiment 1 revealed a significant preference for music stimuli with a flattened frequency response compared to both original and compressed stimuli, whereas there was a significant preference for the original (rising) frequency response for speech stimuli. Experiment 2 revealed no significant mean preference for the flattened frequency response, with 9 of 11 subjects preferring the rising frequency response. Conclusions: Input compression did not alter music enjoyment. Comparison of the two experiments indicated that individual frequency response preferences may depend on the genre or familiarity, and particularly whether the music contained lyrics.

Perceptual versus cognitive speed in a time-compressed speech task

Time-compression retains the information-bearing spectral change present uncompressed speech, although at a rate that may outstrip cognitive processing speed. To compare the relative importance of perceptual and cognitive processing speed, we compared the understanding of (1) time-compressed stimuli expanded in time via gaps with (2) uncompressed stimuli where spectral change information was removed. We hypothesized that, despite the initial compression, the compressed and expanded stimuli would be more intelligible as it would retain relatively more information-bearing spectral change. Participants were somewhat older listeners (mid-1950s to mid-1960s) with normal hearing or mild hearing loss. Stimuli were spoken seven-digit strings time-compressed via pitch synchronous overlap and add (PSOLA) at three uniform compression ratios (2:1, 3:1, and 5:1). In gap insertion conditions, the total duration of the compressed stimuli was restored via introduction of periodic gaps. This produced signal-to-gap ratios ...

The contribution pulsating pressure component of the breast pump mechanism on process milk expression from mammary gland lactating women

The aim of this study was to determine the contribution pulsating compression component of the breast pump in total volume milk ejection by vacuum and compression stimuli. It was found that volume milk ejection together with vacuum and compression stimuli was on 10-46% more than expressing only vacuum stimuli. Average values 40,5 ± 5%, for expression only vacuum stimuli and 59,5 ± 5% for expression vacuum with compression stimuli. It was conclude that compression stimuli increase the efficacy of the breast pump is not only due to the effective formation milk ejection reflex, but also directly by an additional squeezing the milk from the breast.

2F12 周期的な圧縮・電界複合刺激が軟骨組織再生に及ぼす影響(OS15-1:骨・軟骨再生のための組織工学的アプローチ(1))

2F12 周期的な圧縮・電界複合刺激が軟骨組織再生に及ぼす影響(OS15-1:骨・軟骨再生のための組織工学的アプローチ(1))

Autophagy is activated in compression-induced cell degeneration and is mediated by reactive oxygen species in nucleus pulposus cells exposed to compression

To determine whether autophagy contributes to the pathogenesis of degenerative disc disease (DDD) or retards the intervertebral disc (IVD) degeneration, and investigate the possible relationship between compression-induced autophagy and intracellular reactive oxygen species (ROS) in nucleus pulposus (NP) cells invitro. The autophagosome and autophagy-related markers were used to explore the role of autophagy in rat NP cells under compressive stress, which were measured directly by electronic microscopy, monodansylcadaverine (MDC) staining, immunofluorescence, western blot, and indirectly by analyzing the impact of pharmacological inhibitors of autophagy such as 3-methyladenine (3-MA) and chloroquine (CQ). And the relationship between autophagy and apoptosis was investigated by Annexin-V/propidium iodide (PI)-fluorescein staining. In addition, ROS were measured to determine whether these factors are responsible for the development of compression-induced autophagy. Our results indicated that rat NP cells activated autophagy in response to the same strong apoptotic stimuli that triggered apoptosis by compression. Autophagy and apoptosis were interconnected and coordinated in rat NP cells exposed to compression stimuli. Compression-induced autophagy was closely related to intracellular ROS production. Enhanced degradation of damaged components of NP cells by autophagy may be a crucial survival response against mechanical overload, and extensive autophagy may trigger autophagic cell death. Regulating autophagy and reducing the generation of intracellular ROS may retard IVD degeneration.

Characterization of the oculocardiac reflex during compression of the globe in Beagle dogs and rabbits

This investigation characterizes the occurrence of oculocardiac reflex (OCR) in conscious rabbits and dogs by observing the effect of an ocular compression stimulus on heart rate (HR). Thirty-four clinically healthy adult rabbits and 15 clinically healthy adult Beagle dogs were studied. An electrocardiogram was used to record the heart rhythm and HR continuously. Digital pressure was exerted over the eyelid on right eye, left eye and both eyes together for 1 min, with one-minute intervals between each compression. Variations in HR were observed in each minute by counting complexes on the electrocardiographs. There were no differences in HR between stages without ocular compressions both in dogs and in rabbits. HR reduction caused by ocular compression was statistically significant in rabbits only when both eyes were compressed in contrast with all stages without compression. In dogs, a statistically significant reduction in HR was seen during compression of just the right eye or the left eye compared with the baseline HR, and when both the right and left eyes were compressed together compared with baseline or after compression of the right eye. In dogs, compression of individual eyes produced a change similar to that seen during compression of both eyes. This study shows that OCR can occur during experimental ocular compression in conscious rabbits and Beagle dogs and characterizes the reduction in HR. Knowledge of this physiological response is important for veterinary anesthetists and ophthalmologists during ophthalmic surgery or eye manipulations.

Randomized Trial Comparing the Effectiveness of 2 Electric Breast Pumps in the NICU

Mothers with preterm infants may need to express milk for considerable periods. Research to improve breast pump design has focused on compression stimuli, frequencies, and vacuums. This study aimed to compare the effectiveness of 2 electric pumps: Medela Symphony (pump S) and a novel pump (Philips AVENT Twin electronic pump; pump A). Both offer flexibility of rate and suction; pump A also incorporates petal compression cushions. Primary outcomes were (1) milk weight expressed during 10-day study period and (2) weight of milk expressed in a 15-minute test. Seventy-one mothers with preterm infants < 34 weeks were randomized. Mothers completed 10-day diaries including weight of milk expressed. Milk weight expressed during a single 15-minute test period and data on pumping mode, skin-to-skin contact, breastfeeding at infant discharge, and mothers' opinions of the pump were recorded. There was no significant difference in milk expressed during the first 10 days between groups. Pump S mothers expressed significantly more milk during a fixed 15-minute period. Mothers using pump A awarded higher scores for certain characteristics of the pump, notably location of control button and ease of use. Similar proportions of infants received breast milk at discharge, but pump A mothers were more likely to be directly breastfeeding (odds ratio, 4.27 [95% confidence interval, 1.29, 14.1]). The breast pumps showed similar effectiveness in terms of milk expression and maternal opinions. The finding that breast pump design may influence breastfeeding at infant discharge merits further investigation.

음성압축 방식의 변화가 한국어 단음절 숫자 인지기능에 미치는 영향의 비교 연구

다양한 음성 압축방식이 여러 분야에서 광범위하게 사용되고 있으며 그 심리음향적 인지결과는 대상 언어의 특성과 압축 방식에 따라서 다를 수가 있다. 한국어에서도 이러한 인지 결과를 비교하는 정량적인 자료가 관련된 임상이나 응용 분야에서 필요하지만 구체적인 내용이 확인되어 있지 않다. 본 연구에서는 통제된 언어적 특성을 갖는 0에서 9까지 한국어 단음절 숫자 들이 무작위로 조합되는 다섯 쌍 조합(quintet set)을 대상으로 하여 자주 사용되는 세가지 대표적인 음성 압축방식의 특성을 비교 분석하였다. 비교 기준으로는 기존의 연구에서 분석 정리된 시간과 주파수 정보가 모두 일정하게 변화되는 PNT (Preserving No Trait) 압축에서 얻은 자료를 비교 근거로 선정하였다. 이를 기준으로 하여 동일한 조건의 정상인 그룹에서 심리음향적 피치(pitch) 정보가 주로 보전되는 PPT (Preserving Pitch Trait), 시간 정보가 주로 보전되는 PTT (Preserving Time Trait) 압축방식의 인지 결과를 기록하고 분석하였다(N=20). 본 연구 결과에서 얻어진 자료를 보면, 정보의 압축비율이 높을 수록 심리음향학적으로 중요한 주파수 정보(피치)를 보전하는 것이 인지도 측면에서 가장 유리한 것으로 나타났다(PPT>PTT>PNT). 또한, 세가지 압축방법에서 50% 인지율을 보이는 압축률의 역치도 PPT가 20%, PTT가 42%, PNT가 44% 순으로 나타났다. 따라서 인지도 측면에서만 살펴보면 본 조건에서는 PPT 압축 방식이 가장 우수한 것으로 추정되었다. 이러한 숫자 자극을 이용한 평가 방법은 향후 새로운 압축 방식의 효율성과 인지도 측면을 비교 가능하게 하며, 이를 이용하면, 청각정보처리기능을 진단하거나 압축 관련 특수 보청기 적합 재활에서 정량적인 지표를 제공하는 도구로도 사용될 수 있을 것으로 판단된다. The performances of speech compression schemes appeared to be dependent on the response profiles to compressed stimuli and the features of individual languages to some extent. Although these response profiles were critical in comparing various compression outcomes, the related data were limited in number for Korean monosyllabic words. From the previous study, data from PNT (Preserving No Trait) compression was selected as a base set for comparison. In this study, the outcomes from PPT (Preserving Pitch Trait) and PTT (Preserving Time Trait) were analyzed under the same condition. Then, the properties of these three widely used representative compression schemes were quantitatively compared in normal hearing adults (N=20) for controlled Korean quintet digit sets (0 through 9). Results showed that PPT compression scheme exhibited the best perceptual performances for the Korean quintet digit sets in the final outcomes (PPT>PTT>PNT). The compression ratios of 50% performances were estimated as about 20%, 42%, and 44% for PPT, PTT, and PNT, respectively. The data indicated the influences of the salient psychoacoustic features of the three representative compressions on perceiving Korean monosyllabic digit words. This controlled procedure with monosyllabic quintet sets can evaluate efficiency and effectiveness of other compression schemes and may also contribute to diagnosing auditory processing disorders and fitting special hearing aids with compression issues.

Compression-induced hyperaemia in the rabbit masseter muscle: a model to investigate vascular mechano-sensitivity of skeletal muscle

Recent evidence suggests that the mechano-sensitivity of the vascular network may underlie rapid dilatory events in skeletal muscles. Previous investigations have been mostly based either on in vitro or on whole-limb studies, neither preparation allowing one to assess the musculo-vascular specificity under physiological conditions. The aim of this work is to characterize the mechano-sensitivity of an exclusively-muscular vascular bed in vivo. In five anesthetized rabbits, muscle blood flow was continuously monitored in the masseteric artery, bilaterally (n = 10). Hyperaemic responses were evoked by compressive stimuli of different extent (50, 100 and 200 mm Hg) and duration (0.5, 1, 2 and 5 s) exerted by a servo-controlled motor on the masseter muscle. Peak amplitude of the hyperaemic response ranged from 340 ± 30% of baseline (at 50 mm Hg) to 459 ± 57% (at 200 mm Hg) (P < 0.05), did not depend on stimulus duration and exhibited very good reliability (ICC = 0.98) when reassessed at 30 min intervals. The time course of the response depended neither on applied pressure nor on the duration of the stimulus. In conclusion, for its high sensitivity and reliability this technique is adequate to characterize mechano-vascular reactivity and may prove useful in the investigation of the underlying mechanisms, with implications in the control of vascular tone and blood pressure in health and disease.

Effect of Cyclic Compressive Stimuli on Mechanical Anisotropy of Chondrocyte-Seeded Agarose Gel Culture

Effect of Cyclic Compressive Stimuli on Mechanical Anisotropy of Chondrocyte-Seeded Agarose Gel Culture

Investigation of VHI Affected by the Density of Mechanoreceptive units for Virtual Sensation

Abstract The velvet hand illusion (VHI) is an innovative tactile illusion that enables a human to perceive a velvety sensation by gently rubbing the hands on both sides of wire mesh string through a frame. In order to enhance tactile displays presentation ability, VHI’s mechanism is applied through a series of psychophysical experiments. In this paper, we have investigated the effects of several physical parameters on intensity variation of VHI in subjects’ fingers and fingertips, such as wire distance D and a dimensionless ratio of wire stroke r to wire distance r/D in passive touch based on psychophysical experiment. We obtain D = 45 mm and r/D ≈ 1 as optimum values for VHI intensity for wire distance and the ratio, respectively. Furthermore, as the result of comparison between the present result and the previous result for palm, we conclude that a combination of mechanoreceptive afferent units, SAI, SAII and FAI, are involved in VHI. VHI mechanism is induced when movement of wires is accepted through FAI under constant compressive stimulus for SAI and no shearing force for SAII. This result indicates that VHI can be generated by normal pin matrix type tactile displays because no stimulation of SAII is required.

Observation and Evaluation of Real-time Cellular Responses Using a Cell Compression Stimulus Microdevice

Observation and Evaluation of Real-time Cellular Responses Using a Cell Compression Stimulus Microdevice

Force sensor in simulated skin and neural model mimic tactile SAI afferent spiking response to ramp and hold stimuli

BackgroundThe next generation of prosthetic limbs will restore sensory feedback to the nervous system by mimicking how skin mechanoreceptors, innervated by afferents, produce trains of action potentials in response to compressive stimuli. Prior work has addressed building sensors within skin substitutes for robotics, modeling skin mechanics and neural dynamics of mechanotransduction, and predicting response timing of action potentials for vibration. The effort here is unique because it accounts for skin elasticity by measuring force within simulated skin, utilizes few free model parameters for parsimony, and separates parameter fitting and model validation. Additionally, the ramp-and-hold, sustained stimuli used in this work capture the essential features of the everyday task of contacting and holding an object.MethodsThis systems integration effort computationally replicates the neural firing behavior for a slowly adapting type I (SAI) afferent in its temporally varying response to both intensity and rate of indentation force by combining a physical force sensor, housed in a skin-like substrate, with a mathematical model of neuronal spiking, the leaky integrate-and-fire. Comparison experiments were then conducted using ramp-and-hold stimuli on both the spiking-sensor model and mouse SAI afferents. The model parameters were iteratively fit against recorded SAI interspike intervals (ISI) before validating the model to assess its performance.ResultsModel-predicted spike firing compares favorably with that observed for single SAI afferents. As indentation magnitude increases (1.2, 1.3, to 1.4 mm), mean ISI decreases from 98.81 ± 24.73, 54.52 ± 6.94, to 41.11 ± 6.11 ms. Moreover, as rate of ramp-up increases, ISI during ramp-up decreases from 21.85 ± 5.33, 19.98 ± 3.10, to 15.42 ± 2.41 ms. Considering first spikes, the predicted latencies exhibited a decreasing trend as stimulus rate increased, as is observed in afferent recordings. Finally, the SAI afferent’s characteristic response of producing irregular ISIs is shown to be controllable via manipulating the output filtering from the sensor or adding stochastic noise.ConclusionsThis integrated engineering approach extends prior works focused upon neural dynamics and vibration. Future efforts will perfect measures of performance, such as first spike latency and irregular ISIs, and link the generation of characteristic features within trains of action potentials with current pulse waveforms that stimulate single action potentials at the peripheral afferent.

Development of a micro cell compression stimulator for evaluating real-time cellular responses

This paper presents a micro cell compression stimulator for evaluating real-time cellular responses to compression stimuli. The device was produced by a micro three-dimensional structure fabrication process using multiple exposures to the photoresist. The device consists of a pressure inlet port, cell inlet ports, a gasket, microchannels, cell culture chambers, and a diaphragm on the culture chamber for applying compressive pressure to cells. Compression stimuli applied to the cells can be controlled by regulating the expansion of the diaphragm via a pressure control. The device permits the observation of cellular responses to compressive pressure in real time because it is made of transparent materials and stimulates the cells without deforming the cell culture surface, when observed by optical microscopy. We demonstrated the validity of the fabrication process, evaluated the performance of the fabricated device, and compared the experimental results with the FEM structural analysis results. We found through operational testing that the diaphragm was deformed quickly by applying negative/positive pressure and that the diaphragm displacement became larger with increasing applied pressure. These results indicate that this device can be used to control the intensity and the cell stimulus profile by regulating the applied pressure. In all cases, the cellular deformation during compression stimulus was successfully observed in real time using an optical microscope. The device is expected to facilitate the control of stem cell differentiation and the clarification of cellular mechanoreceptor mechanisms and signal transduction pathways.

Anisotropic hydrogel based on bilayers: color, strength, toughness, and fatigue resistance

In this highlight, we introduce a novel anisotropic hydrogel with a perfect 1D photonic crystal structure based on the uniaxial alignment of lamellar bilayers. The gel was synthesized in a one-pot polymerization from a precursor solution containing a polymerizable surfactant (dodecyl glyceryl itaconate: DGI), acrylamide, and a cross-linker. By applying shear flow to the precursor solution, lamellar bilayers of self-assembled DGI were aligned in one direction parallel to the substrate surface. The polymerized lamellar bilayers were stacked periodically and entrapped in the polyacrylamide matrix to give a hydrogel with a 1D photonic crystal structure. This hydrogel, containing 94–95 wt% water and 1.0–1.5 wt% bilayer molecules, shows perfect one-dimensional swelling, strong anisotropy in the elastic modulus, and magnificent structural color by multilayer interference according to Bragg's law of diffraction. Owing to the softness and large deformability, the color of the gel can be reversibly tuned by both compressive and tensile mechanical stimuli over the entire wavelength range of visible color. The single-domain lamellar bilayer not only diffracts light but also serves as a reversible sacrificial bond that dissociates upon deformation, exhibiting large hysteresis as an energy dissipation mechanism, which gives the gel high tensile strength and fatigue resistance. Both the molecular dissociation and lipid-like mobile nature of DGI molecules in the bilayers dramatically enhance the resistance against crack propagation by the formation of extraordinary blunting, which gives the gel an extraordinarily high toughness.