Mechanobiology of conjunctival epithelial cells exposed to wall shear stresses.

The human conjunctival epithelial cells (HCEC) line the inner sides of the eyelids and the anterior part of the sclera. They include goblet cells that secret mucus into the tear film that protects the ocular surface. The conjunctival epithelium is subjected to mechano-physical stimuli due to eyelid movement during blinking, during wiping and rubbing the eyes, and when exposed to wind and air currents. We cultured primary HCEC under air-liquid interface (ALI) conditions in custom-designed wells that can be disassembled for installation of the in vitro model in a flow chamber. We exposed the HCEC after ALI culture of 8-10 days to steady and oscillatory airflows. The in vitro model of HCEC was exposed to steady wall shear stresses (sWSS) of 0.5 and 1.0 dyne/cm2 for lengths of 30 and 60 min and to oscillatory wall shear stresses (oWSS) of 0.5 and 0.77 dyne/cm2 amplitudes for a length of 10 min. Cytoskeletal alterations and MUC5AC mucin secretion in response to WSS were investigated using immunohistochemically fluorescent staining and enzyme-linked lectin assay (ELLA), respectively. The results revealed that both exposure times and sWSS values increased the polymerization of F-actin filaments while mucin secretion decreased. However, after a recovery of 24 h in the incubator we observed a decrease of F-actin fibers and mucin secretion only for exposure of 30 min. The length of exposure was more influential on cytoskeletal alterations than the level of sWSS. The very small effect of sWSS on mucin secretion is most likely related to the much smaller amount of goblet cell than in other mucus-secreting tissue. The results for both oWSS amplitudes revealed similar trends regarding F-actin and mucin secretion. Immediately post-exposure we observed an increase in polymerization of F-actin filaments while mucin secretion decreased. However, after 24-h recovery we observed that both F-actin and mucin secretion returned to the same values as for unexposed cultures. The results of this study suggest that WSS should be considered while exploring the physiological characteristics of HCEC.

The effect of clinically recommended Evolut sizes on anchorage forces after BASILICA.

Coronary artery obstruction (CAO), a fatal complication of transcatheter aortic valve replacement (TAVR), is commonly found after Valve-in-Valve implantation inside a degenerated bioprosthetic valve. Leaflet laceration (BASILICA technique) has been proposed to prevent CAO and to potentially reduce the risk of leaflet thrombosis. We have previously demonstrated that this technique can reduce the anchorage forces of the TAVR device, which may lead to future complications. In this short communication, we hypothesize that the anchorage force reduction can be minimized by implanting a TAVR with a larger diameter, if two sizes are clinically recommended. We evaluated this hypothesis by employing finite element models of the deployments of the Evolut 26 and 29 mm inside a 27 mm Mitroflow valve, with and without leaflet lacerations. The results show that a laceration substantially decreases the contact area between the Evolut stent and the Mitroflow valve. The larger Evolut has a larger contact area and stronger anchorage forces. Additionally, the anchorage forces are less sensitive to additional lacerations in the larger Evolut (29 case). The results suggest that a larger self-expending device can ensure stronger anchorage and can lower the risk of possible migration, when TAVR is performed in a lacerated bioprosthesis.

Tissue-engineered arterial intima model exposed to steady wall shear stresses.

The arterial intima is continuously under pulsatile wall shear stresses (WSS) imposed by the circulating blood. The knowledge of the contribution of smooth muscle cells (SMC) to the response of endothelial cell (EC) to WSS is still incomplete. We developed a co-culture model of EC on top of SMC that mimics the inner in vivo structure of the arterial intima of large arteries. The co-cultured model, as well as a monolayer model of EC, were developed in custom-designed wells that allowed for mechanobiology experiments. Both the monolayer and co-culture models were exposed to steady flow induced WSS of up to 24 dyne/cm2 and for lengths of 60 min. Quantification of WSS induced alterations in the cytoskeletal actin filaments (F-actin) and vascular endothelial cadherin (VE-cadherin) junctions were utilized from confocal images and flow cytometry. High confluency of both models was observed even after exposure to the high WSS. The quantitive analysis revealed larger post WSS amounts of EC F-actin polymerization in the monolayer, which may be explained by the relative help of the SMC to resist the external load of WSS. The VE-cadherin demonstrated morphological alterations in the monolayer model, but without significant changes in their content. The SMC in the co-culture maintained their contractile phenotype post high WSS which is more physiological, but not post low WSS. Generally, the results of this work demonstrate the active role of SMC in the intima performance to resist flow induced WSS.

Novel Design of Peripheral Infusion Catheter Improves the Kinetics of Intravenous Drug Release.

Short peripheral catheters are ubiquitous in today's healthcare environment, enabling effective and direct delivery of fluids and medications intravenously. A commonly associated complication of their use is thrombophlebitis-thrombus formation-involved inflammation of the vein wall. A novel design of a very short peripheral catheter showed promising results in a pig model in reducing the mechanical irritation to the vein wall. Here, the kinetics of drug release through the novel catheter was compared to a standard commercial catheter using experimental and computational models. In a good agreement, in vitro and in silico models reveal the superiority of the novel catheter design with faster washout time, favorable spatial distribution within the vein, and substantially lower wall shear stress. We submit therefore that the novel design has an improved drug removal profile compared to the conventional catheter and can potentially reduce chemical irritation to the vein wall and minimize the risk for thrombophlebitis. CLINICAL RELEVANCE: Short peripheral catheters are ubiquitous in today's healthcare environment, allowing effective and direct delivery of fluids and medications intravenously. It is well known, however, that prolonged exposure to an irritant drug may lead to its absorption in the endothelial layer lining the vein wall, promoting among other, thrombophlebitis that may lead to increased morbidity, delayed treatment, and prolonged hospitalization. There have been multiple calls to consider low infusion rates with various infusion protocols and to place the catheter tip as central as possible to promote faster drug clearance and reduce the potential vessel damage, but the requisite device had not been available, and the short peripheral catheter is still, and for decades, the standard of care. Towards this end, we recently introduced a novel very short peripheral catheter design, and here, we demonstrate using experimental and computational models its favorable spatial and temporal drug-releasing profiles compared with the standard catheter. The clinically potential relevance is underscore both by the more efficient perfusion of IV drugs and lower irritation to the vein wall at the site of injection. Graphical abstract.

Tissue engineered endometrial barrier exposed to peristaltic flow shear stresses.

Cyclic myometrial contractions of the non-pregnant uterus induce intra-uterine peristaltic flows, which have important roles in transport of sperm and embryos during early stages of reproduction. Hyperperistalsis in young females may lead to migration of endometrial cells and development of adenomyosis or endometriosis. We conducted an in vitro study of the biological response of a tissue engineered endometrial barrier exposed to peristaltic wall shear stresses (PWSSs). The endometrial barrier model was co-cultured of endometrial epithelial cells on top of myometrial smooth muscle cells (MSMCs) in custom-designed wells that can be disassembled for mechanobiology experiments. A new experimental setup was developed for exposing the uterine wall in vitro model to PWSSs that mimic the in vivo intra-uterine environment. Peristaltic flow was induced by moving a belt with bulges to deform the elastic cover of a fluid filled chamber that held the uterine wall model at the bottom. The in vitro biological model was exposed to peristaltic flows for 60 and 120 min and then stained for immunofluorescence studies of alternations in the cytoskeleton. Quantification of the F-actin mass in both layers revealed a significant increase with the length of exposure to PWSSs. Moreover, the inner layer of MSMCs that were not in direct contact with the fluid also responded with an increase in the F-actin mass. This new experimental approach can be expanded to in vitro studies of multiple structural changes and genetic expressions, while the tissue engineered uterine wall models are tested under conditions that mimic the in vivo physiological environment.

Numerical models of valve-in-valve implantation: effect of intentional leaflet laceration on the anchorage.

Transcatheter aortic valve implantation (TAVI) is currently recommended in practice guidelines for patients who are at intermediate to high surgical risk for surgical aortic valve replacement. Coronary artery obstruction is a fatal complication of TAVI that occurs in up to 3.5% of the implantations inside a failed surgical bioprosthetic valve (valve-in-valve, ViV). A new technique to address this problem is intentional laceration of the bioprosthetic leaflets, known as BASILICA. In this technique, the leaflets are lacerated to prevent coronary obstruction and may also help in preventing leaflet thrombosis. Our hypothesis is that this technique may harm the circumferential stress in the surgical valve and weaken the anchorage of the TAVI device. This study aims to compare the anchorage post-ViV implantations, with and without lacerations, using numerical modelling. Deployments of TAVI stents (Medtronic Evolut PRO; Edwards SAPIEN 3) inside an externally mounted surgical bioprosthetic valve (Sorin Mitroflow) were modelled by finite element analysis. The results show that each laceration reduces the contact area of the TAVI stent with its landing zone and that the anchorage contact force weakens. The BASILICA technique has lesser effect on the anchorage contact area and forces in the SAPIEN than in the Evolut cases, because the balloon inflation is less sensitive to the deployment region. TAVI stent migration was not found in any of the models. These results can help expanding the use of leaflet laceration by choosing a better matched TAVI devices for the BASILICA technique.

In vitro exposure of nasal epithelial cells to atmospheric dust.

Dust storms are common phenomena in many parts of the world, and significantly increase the level of atmospheric particulate matter (PM). The soil-derived dust is a mixture of organic and inorganic particles and even remnants of pesticides from agricultural areas nearby. The risk of human exposure to atmospheric dust is well documented, but very little is known on the impact of inhaled PM on the biological lining of the nasal cavity, which is the natural filter between the external environment and the respiratory tract. We developed a new system and methodology for in vitro exposure of cultured nasal epithelial cells (NEC) to atmospheric soil-dust pollutants under realistic and controlled laboratory simulations that mimic nasal breathing. We exposed cultured NEC to clean and dust-polluted airflows that mimic physiological conditions. The results revealed that the secretion of mucin and IL-8 from the NEC exposed to clean and dust-polluted airflows was less than the secretion at static conditions under clean air. The secretion of IL-8 from NEC exposed to dust-polluted air was larger than that of clean air, but not larger than in the static case. The experiments with dust air pollution that also contained agricultural pesticides did not reveal differences in the secretion of mucin and IL-8 as compared to the same pollution without pesticides.

Pressure drop and arterial compliance - Two arterial parameters in one measurement.

Coronary artery pressure-drop and distensibility (compliance) are two major, seemingly unrelated, parameters in the cardiovascular clinical setting, which are indicative of coronary arteries patency and atherosclerosis severity. While pressure drop is related to flow, and therefore serves as a functional indicator of a stenosis severity, the arterial distensibility is indicative of the arterial stiffness, and hence the arterial wall composition. In the present study, we hypothesized that local pressure drops are dependent on the arterial distensibility, and hence can provide information on both indices. The clinical significance is that a single measurement of pressure drop could potentially provide both functional and bio-mechanical metrics of lesions, and thus assist in real-time decision making prior to stenting. The goal of the current study was to set the basis for understanding this relationship, and define the accuracy and sensitivity required from the pressure measurement system. The investigation was performed using numerical fluid-structure interaction (FSI) simulations, validated experimentally using our high accuracy differential pressure measurement system. Simplified silicone mock coronary arteries with zero to intermediate size stenoses were used, and various combinations of arterial distensibility, diameter, and flow rate were simulated. Results of hyperemic flow cases were also compared to fractional flow reserve (FFR). The results indicate the potential clinical superiority of a high accuracy pressure drop-based parameter over FFR, by: (i) being more lesion-specific, (ii) the possibility to circumvent the FFR dependency on pharmacologically-induced hyperemia, and, (iii) by providing both functional and biomechanical lesion-specific information.

Ex Vivo Human Placental Perfusion Model for Analysis of Fetal Circulation in the Chorionic Plate.

OBJECTIVES: The purpose of this study was to develop an ex vivo placental perfusion model to assess changes in the umbilical artery systolic-to-diastolic (S/D) ratio due to progressive occlusion of the placental arterial system. METHODS: Ex vivo human placentas were connected to a computerized pulse duplicator mimicking pulsatile flow from the fetal heart. Doppler sonographic measurements were conducted on the umbilical and chorionic arteries of 25 mature placentas. Simulation of placental occlusion was performed by progressive ligature of the chorionic arteries, including one umbilical artery. The correlation between the umbilical artery S/D ratio and the severity of simulated placental occlusion was analyzed. RESULTS: The normal mean S/D ratio ± SD decreased gradually along the chorionic plate from 2.66 ± 0.47 at the cord insertion to 1.90 ± 0.59 in generation IV of the chorionic vessels. The Doppler index initially increased slowly with simulated placental occlusion. Only when all 4 generations were occluded was the umbilical artery S/D ratio elevated. Complete occlusion of one umbilical artery resulted in a 39% increase in the umbilical artery S/D ratio. CONCLUSIONS: This unique model combining Doppler sonography with perfusion of an ex vivo placenta can be used for a better understudying of pathologic placental blood flow circulation.

Evaluation of nasal airway patency by analysis of breathing sounds.

CONCLUSIONS: A simple non-invasive method, based on acoustic analysis of breathing signals, revealed a potential for objective evaluation of differences between the patency of nasal passageways. OBJECTIVES: To examine whether acoustic signals of nasal breathing contain information that can differentiate between obstructed and patent nasal passageways. METHOD: A technical study aimed to examine measurements of nasal airflow acoustic signals, taken, non-invasively, simultaneously from both external sides of the nostrils. The signals were acquired for several breathing cycles, with different respiratory efforts, before and after application of a nasal decongestant to the (narrower) side that yielded lower amplitudes. Data processing of the expiratory phase yielded the power spectrum density (PSD), which was used to compute the ratio of PSD areas between the signals from both sides of the nose. The study group was composed of 20 healthy volunteers. RESULTS: PSD changes were noted in accordance with the rise in expiratory efforts. The ratio of PSD areas between the two sides of the nasal cavity, calculated for maximal expiratory efforts, correlated well with the side that was treated with nasal decongestant in 18 out of the 20. Changes in the opposite direction were noted in two examinees.

High accuracy differential pressure measurements using fluid-filled catheters - A feasibility study in compliant tubes.

High accuracy differential pressure measurements are required in various biomedical and medical applications, such as in fluid-dynamic test systems, or in the cath-lab. Differential pressure measurements using fluid-filled catheters are relatively inexpensive, yet may be subjected to common mode pressure errors (CMP), which can significantly reduce the measurement accuracy. Recently, a novel correction method for high accuracy differential pressure measurements was presented, and was shown to effectively remove CMP distortions from measurements acquired in rigid tubes. The purpose of the present study was to test the feasibility of this correction method inside compliant tubes, which effectively simulate arteries. Two tubes with varying compliance were tested under dynamic flow and pressure conditions to cover the physiological range of radial distensibility in coronary arteries. A third, compliant model, with a 70% stenosis severity was additionally tested. Differential pressure measurements were acquired over a 3 cm tube length using a fluid-filled double-lumen catheter, and were corrected using the proposed CMP correction method. Validation of the corrected differential pressure signals was performed by comparison to differential pressure recordings taken via a direct connection to the compliant tubes, and by comparison to predicted differential pressure readings of matching fluid-structure interaction (FSI) computational simulations. The results show excellent agreement between the experimentally acquired and computationally determined differential pressure signals. This validates the application of the CMP correction method in compliant tubes of the physiological range for up to intermediate size stenosis severity of 70%.

Method for high accuracy differential pressure measurements using fluid-filled catheters.

The advantage of measuring differential pressure using fluid-filled catheters is that the system is relatively inexpensive, but the readings are not accurate and affected by the common mode pressure (CMP) distortion. High accuracy differential pressure measurements are required in various biomedical applications, such as in fluid-dynamic test rigs, or in the cath-lab, from cardiac valves efficacy to functional assessment of arterial stenoses. We have designed and built a unique system in which the pressure difference was measured along the fluid flow inside a rigid circular tube using a fluid-filled double-lumen catheter. The differential pressure measurements were taken across two side-holes near the catheter distal tip, spaced apart by 3 cm. The goal was to overcome the CMP error, which significantly distorted the output differential pressure signal and to formulate a restoration factor. A restoration formula was developed based on simultaneous gauge pressure measurements, and was tested in several different cases. Several representative cases are presented and show that the common mode artifact was reduced by factors of 12-27. The restored pressure gradient signal was validated using direct pressure drop measurements, and showed very good agreement.

General tube law for collapsible thin and thick-wall tubes.

Modeling the complex deformations of cylindrical tubes under external pressure is of interest in engineering and physiological applications. The highly non-linear post-buckling behavior of cross-section of the tube during collapse attracted researchers for years. Major efforts were concentrated on studying the behavior of thin-wall tubes. Unfortunately, the knowledge on post-buckling of thick-wall tubes is still incomplete, although many experimental and several theoretical studies have been performed. In this study we systematically studied the effect of the wall thickness on post-buckling behavior of the tube. For this purpose, we utilized a computational model for evaluation of the real geometry of the deformed cross-sectional area due to negative transmural (internal minus external) pressure. We also developed an experimental method to validate the computational results. Based on the computed cross-sections of tubes with different wall thicknesses, we developed a general tube law that accounts for thin or thick wall tubes and fits the numerical data of computed cross-sectional areas versus transmural pressures.

Wall shear stress effects on endothelial-endothelial and endothelial-smooth muscle cell interactions in tissue engineered models of the vascular wall.

Vascular functions are affected by wall shear stresses (WSS) applied on the endothelial cells (EC), as well as by the interactions of the EC with the adjacent smooth muscle cells (SMC). The present study was designed to investigate the effects of WSS on the endothelial interactions with its surroundings. For this purpose we developed and constructed two co-culture models of EC and SMC, and compared their response to that of a single monolayer of cultured EC. In one co-culture model the EC were cultured on the SMC, whereas in the other model the EC and SMC were cultured on the opposite sides of a membrane. We studied EC-matrix interactions through focal adhesion kinase morphology, EC-EC interactions through VE-Cadherin expression and morphology, and EC-SMC interactions through the expression of Cx43 and Cx37. In the absence of WSS the SMC presence reduced EC-EC connectivity but produced EC-SMC connections using both connexins. The exposure to WSS produced discontinuity in the EC-EC connections, with a weaker effect in the co-culture models. In the EC monolayer, WSS exposure (12 and 4 dyne/cm(2) for 30 min) increased the EC-EC interaction using both connexins. WSS exposure of 12 dyne/cm(2) did not affect the EC-SMC interactions, whereas WSS of 4 dyne/cm(2) elevated the amount of Cx43 and reduced the amount of Cx37, with a different magnitude between the models. The reduced endothelium connectivity suggests that the presence of SMC reduces the sealing properties of the endothelium, showing a more inflammatory phenotype while the distance between the two cell types reduced their interactions. These results demonstrate that EC-SMC interactions affect EC phenotype and change the EC response to WSS. Furthermore, the interactions formed between the EC and SMC demonstrate that the 1-side model can simulate better the arterioles, while the 2-side model provides better simulation of larger arteries.

Analysis of facial and inspiratory muscles performance during breastfeeding.

BACKGROUND: Breastfeeding is a dynamic process in which the infant recruits several muscle groups in his face, head and throat. OBJECTIVE: The objective of this study was to explore the relative role of the submental muscle group, the orbicularis oris and the sternocleidomastoid muscles to breastfeeding process and to the relatively high intra-oral vacuum measured during this process. METHODS: Electromyography (EMG) measurements were conducted on 11 infants (mean age 1.91 ± 1.0 days, mean weight 3364 ± 328 g) using surface electrodes. The EMG data were filtered with a low pass filter to yield the linear envelopes (IEMG). The maximal and mean value and the area under each linear envelope curve were examined. RESULTS: During active suckling significantly higher activity (P< 0.05) of the submental muscle group were measured compared with the orbicularis oris and sternocleidomastoid muscles (mean ± SE values of the maximal linear envelope were 24.4 ± 1 µV, 9.6 ± 0.6 µV and 14 ± 0.7 µV, respectively). CONCLUSION: These results confirmed that jaw movements have the primary role during breastfeeding, but also revealed that the inspiratory muscles have a substantial contribution to this process and probably have an important role in the generation of intra oral vacuum measured during breastfeeding.

Fluid-flow induced wall shear stress and epithelial ovarian cancer peritoneal spreading.

Epithelial ovarian cancer (EOC) is usually discovered after extensive metastasis have developed in the peritoneal cavity. The ovarian surface is exposed to peritoneal fluid pressures and shear forces due to the continuous peristaltic motions of the gastro-intestinal system, creating a mechanical micro-environment for the cells. An in vitro experimental model was developed to expose EOC cells to steady fluid flow induced wall shear stresses (WSS). The EOC cells were cultured from OVCAR-3 cell line on denuded amniotic membranes in special wells. Wall shear stresses of 0.5, 1.0 and 1.5 dyne/cm(2) were applied on the surface of the cells under conditions that mimic the physiological environment, followed by fluorescent stains of actin and ß-tubulin fibers. The cytoskeleton response to WSS included cell elongation, stress fibers formation and generation of microtubules. More cytoskeletal components were produced by the cells and arranged in a denser and more organized structure within the cytoplasm. This suggests that WSS may have a significant role in the mechanical regulation of EOC peritoneal spreading.

Evaluation of fatigue of respiratory and lower limb muscles during prolonged aerobic exercise.

The respiratory muscles may fatigue during prolonged exercises and thereby become a factor that limits extreme physical activity. The aim of the current study was to determine whether respiratory muscle fatigue imposes a limitation on extreme physical activity of well-trained young men. Electromyography (EMG) signals of respiratory (external intercostal and sternomastoid) and calf muscles (gastrocnemius) were measured (N = 8) during 1 hr of treadmill marching at a speed of 8 km/hr with and without a 15 kg backpack. The root mean square (RMS) and the mean power frequency of the EMG signals were evaluated for calculating fatigue indices. The EMG RMS revealed that the respiratory and calf muscles did not fatigue during the marching without a backpack load. The study did show, however, a significant rise in the EMG values when a backpack was carried with respect to the no-load condition (p < .05), which suggests that respiratory muscles should be trained in military recruits who are required to carry loaded backpacks while marching.

Static mechanical stretching accelerates lipid production in 3T3-L1 adipocytes by activating the MEK signaling pathway.

Understanding mechanotransduction in adipocytes is important for research of obesity and related diseases. We cultured 3T3-L1 preadipocytes on elastic substrata and applied static tensile strains of 12% to the substrata while inducing differentiation. Using an image processing method, we monitored lipid production for a period of 3-4 wk. The ratio of %-lipid area per field of view (FOV) in the stretched over nonstretched cultures was significantly greater than unity (P < 0.05), reaching ∼1.8 on average starting from experimental day ∼10. The superior coverage of the FOV by lipids in the stretched cultures was due to significantly greater sizes of lipid droplets (LDs) with respect to nonstretched cultures, starting from experimental day ∼10 (P < 0.05), and due to significantly more LDs per cell between days ∼10 and ∼17 (P < 0.05). The statically stretched cells also differentiated significantly faster than the nonstretched cells within the first ∼10 days (P < 0.05). Adding peroxisome proliferator-activated receptor-γ (PPARγ) antagonist did not change these trends, as the %-lipid area per FOV in the stretched cultures that received this treatment was still significantly greater than in the nonstretched cultures without the PPARγ antagonist (14.44 ± 1.96% vs. 10.21 ± 3%; P < 0.05). Hence, the accelerated adipogenesis in the stretched cultures was not mediated through PPARγ. Nonetheless, inhibiting the MEK/MAPK signaling pathway reduced the extent of adipogenesis in the stretched cultures (13.53 ± 5.63%), bringing it to the baseline level of the nonstretched cultures without the MEK inhibitor (10.21 ± 3.07%). Our results hence demonstrate that differentiation of adipocytes can be enhanced by sustained stretching, which activates the MEK signaling pathway.

Large, but not small sustained tensile strains stimulate adipogenesis in culture.

Understanding the mechanoresponsiveness of adipocytes and the characteristics of the mechanical stimuli that regulate adipogenesis is critically important in establishing knowledge in regard to the long-term effects of a sedentary lifestyle (or immobility in extreme medical conditions) as well as concerning obesity and related diseases. In this study we subjected 3T3-L1 preadipocytes cultured on elastic substrata to different levels of static equiaxial tensile strains within the physiological range, up to substrate tensile strain (STS) of 12%, while inducing differentiation in the cultures. Based on prior work which revealed that adipogenesis is accelerated in cultures subjected to STS of 12% by activating the mitogen-activated protein kinase kinase signaling pathway, we were specifically interested in identifying the STS levels which trigger this process. We hence monitored the production and accumulation of lipid droplets (LDs) using a non-destructive, image-processing-based method that we have previously developed, for a period of 4 weeks. The experimental data demonstrated accelerated adipogenesis in the cultures subjected to STS levels of 6%, 9%, and 12% with respect to cultures subjected to STS of 3% and (non-stretched) control cultures. This accelerated adipogenic response to the large sustained STS manifested in significantly larger numbers and greater sizes of LDs in the cultures that were stretched to large STS levels (p < 0.05), starting at approximately day 14 following induction of differentiation. Hence, indeed, there appears to be a certain tensile strain threshold, or domain-which is found within the physiological range-above which the responsiveness of adipocytes to sustained static stretching increases and is manifested in accelerated adipogenesis.

Climate chamber for environmentally controlled laboratory airflow experiments.

Climate chambers have been widely used in in vitro and in vivo studies which require controlled environmental temperature and humidity conditions. This article describes a new desktop climate chamber that was developed for application of respiratory airflows on cultured nasal epithelial cells (NEC) under controlled temperature and humidity conditions. Flow experiments were performed by connecting the climate chamber to an airflow generator via a flow chamber with cultured NEC. Experiments at two controlled climate conditions, 25 degrees C and 40% relative humidity (RH) and 37 degrees C and 80%RH, were conducted to study mucin secretion from the cultures inresponse to the flow. The new climate chamber is a relatively simple and inexpensive apparatus which can easily be connected to any flow system for climate controlled flow experiments. This chamber can be easily adjusted to various in vitro experiments, as well as to clinical studies with animals or human subjects which require controlled climate conditions.