Comment on “Fluid viscosity but not surface tension, determines the tamponade effect of intravitreal fluids in a novel in vitro eye model of retinal detachment” by A. Friehmann et al. (J. Mech. Behav. Biomed. Mater. 101 (2020) 103452)

2021 ◽  
Vol 113 ◽  
pp. 104128
Author(s):  
Yau Kei Chan ◽  
Liangyu Zhou ◽  
Ying Chen ◽  
David H. Steel
Keyword(s):  
Surface Tension ◽  
Retinal Detachment ◽  
Fluid Viscosity ◽  
Eye Model ◽  
Biomed Mater ◽  
Tamponade Effect

scholarly journals Increasing Silicone Oil Viscosity Increases Resistance to Volume Displacement in an in vitro Retinal Detachment Model

2018 ◽  
Vol 3 (3) ◽  
pp. 1-8 ◽  
Author(s):  
Alexander Rubowitz ◽  
Leena Asalee ◽  
Uri Zaretski
Keyword(s):  
Retinal Detachment ◽  
Silicone Oil ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Oil Viscosity ◽  
Volume Changes ◽  
Change Rate ◽  
Eye Model ◽  
Silicone Oils

Purpose: To determine whether higher-viscosity silicone oils offer greater resistance to volume displacement in an in vitro eye model of retinal detachment and could subsequently be expected to generate stronger retinal tamponades in cases of recurrent or complex retinal detachments. Methods: We used an eye model that included a membrane representing the retina. Silicone oils with different viscosities were injected, and oil displacement and resistance were measured. Results: Membrane movement and volume changes in an eye model were proportional to the viscosity of the oil: the lower the viscosity, the faster volume changes and displacement occurred. Conclusions: Our results show that the volume change rate has a linear relationship with oil viscosity. Our findings suggest that in this eye model, silicone oil tamponades the retina against the retinal pigment epithelium mainly through volume displacement and that silicone oil viscosity may play an important role in preventing retinal displacement and in providing tamponade.

Effects of surface tension and viscosity on airway reopening

1990 ◽  
Vol 69 (1) ◽  
pp. 74-85 ◽  
Author(s):  
D. P. Gaver ◽  
R. W. Samsel ◽  
J. Solway
Keyword(s):  
Surface Tension ◽  
Fluid Viscosity ◽  
Opening Pressure ◽  
Viscous Forces ◽  
Considerable Portion ◽  
Airway Opening ◽  
Wall Compliance ◽  
Large Opening ◽  
Surface Tension Forces ◽  
The Relationship

We studied airway opening in a benchtop model intended to mimic bronchial walls held in apposition by airway lining fluid. We measured the relationship between the airway opening velocity (U) and the applied airway opening pressure in thin-walled polyethylene tubes of different radii (R) using lining fluids of different surface tensions (gamma) and viscosities (mu). Axial wall tension (T) was applied to modify the apparent wall compliance characteristics, and the lining film thickness (H) was varied. Increasing mu or gamma or decreasing R or T led to an increase in the airway opening pressures. The effect of H depended on T: when T was small, opening pressures increased slightly as H was decreased; when T was large, opening pressure was independent of H. Using dimensional analysis, we found that the relative importance of viscous and surface tension forces depends on the capillary number (Ca = microU/gamma). When Ca is small, the opening pressure is approximately 8 gamma/R and acts as an apparent “yield pressure” that must be exceeded before airway opening can begin. When Ca is large (Ca greater than 0.5), viscous forces add appreciably to the overall opening pressures. Based on these results, predictions of airway opening times suggest that airway closure can persist through a considerable portion of inspiration when lining fluid viscosity or surface tension are elevated.

Release of Fluconazole from Contact Lenses Using a Novel In Vitro Eye Model

2016 ◽  
Vol 93 (4) ◽  
pp. 387-394 ◽  
Author(s):  
Chau-Minh Phan ◽  
Magdalena Bajgrowicz ◽  
Huayi Gao ◽  
Lakshman N. Subbaraman ◽  
Lyndon W. Jones
Keyword(s):  
Contact Lenses ◽  
Eye Model

scholarly journals Dynamic Colon Model (DCM): A Cine-MRI Informed Biorelevant In Vitro Model of the Human Proximal Large Intestine Characterized by Positron Imaging Techniques

Pharmaceutics ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 659
Author(s):  
Konstantinos Stamatopoulos ◽  
Sharad Karandikar ◽  
Mark Goldstein ◽  
Connor O’Farrell ◽  
Luca Marciani ◽  
...  
Keyword(s):  
Particle Motion ◽  
Wall Motion ◽  
Bulk Liquid ◽  
Cine Mri ◽  
Fluid Viscosity ◽  
Positron Emission ◽  
Volume Viscosity ◽  
Viscosity Fluid

This work used in vivo MRI images of human colon wall motion to inform a biorelevant Dynamic Colon Model (DCM) to understand the interplay of wall motion, volume, viscosity, fluid, and particle motion within the colon lumen. Hydrodynamics and particle motion within the DCM were characterized using Positron Emission Tomography (PET) and Positron Emission Particle Tracking (PEPT), respectively. In vitro PET images showed that fluid of higher viscosity follows the wall motion with poor mixing, whereas good mixing was observed for a low viscosity fluid. PEPT data showed particle displacements comparable to the in vivo data. Increasing fluid viscosity favors the net forward propulsion of the tracked particles. The use of a floating particle demonstrated shorter residence times and greater velocities on the liquid surface, suggesting a surface wave that was moving faster than the bulk liquid. The DCM can provide an understanding of flow motion and behavior of particles with different buoyancy, which in turn may improve the design of drug formulations, whereby fragments of the dosage form and/or drug particles are suspended in the proximal colon.

scholarly journals In vivo and in vitro reactivation impairment of a herpes simplex virus type 1 latency-associated transcript variant in a rabbit eye model.

1991 ◽  
Vol 65 (12) ◽  
pp. 6989-6993 ◽  
Author(s):  
M D Trousdale ◽  
I Steiner ◽  
J G Spivack ◽  
S L Deshmane ◽  
S M Brown ◽  
...  
Keyword(s):  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Virus Type ◽  
Herpes Simplex Virus Type ◽  
Eye Model ◽  
Rabbit Eye ◽  
Simplex Virus

Specific responses of axons and dendrites to cytoskeleton perturbations: an in vitro study

1993 ◽  
Vol 104 (2) ◽  
pp. 433-443 ◽  
Author(s):  
F. Lafont ◽  
M. Rouget ◽  
A. Rousselet ◽  
C. Valenza ◽  
A. Prochiantz
Keyword(s):  
Surface Tension ◽  
Actin Filaments ◽  
Cytochalasin B ◽  
In Vitro Study ◽  
Axonal Growth ◽  
Vitro Study ◽  
Tensile Forces ◽  
The Asymmetry

Several factors can influence the development of axons and dendrites in vitro. Some of these factors modify the adhesion of neurons to their substratum. We have previously shown that the threshold of neuron-substratum adhesion necessary for initiation and elongation of dendrites is higher than that required for axonal growth. To explain this difference we propose that, in order to antagonize actin-driven surface tension, axons primarily rely on the compression forces of microtubules whereas dendrites rely on adhesion. This model was tested by seeding the cells in conditions allowing the development either of axons or of axons and dendrites, then adding cytochalasin B or nocodazole 1 hour or 24 hours after plating. The addition of cytochalasin B, which depolymerizes actin filaments and thus reduces actin-tensile forces, increases the length of both axons and dendrites, indicating that both axons and dendrites have to antagonize surface tension in order to elongate. The addition of nocodazole, which acts primarily on microtubules, slightly reduces dendrite elongation and totally abolishes axonal growth. Similar results are obtained when the drugs are added 1 or 24 hours after plating, suggesting that the same mechanisms are at work both in initiation and in elongation. Finally, we find that in the presence of cytochalasin B axons adopt a curly morphology, a fact that could be explained by the importance of tensile forces in antagonizing the asymmetry created by polarized microtubules presenting a uniform minus/plus orientation.

Comparison of Four Surfactants: In Vitro Surface Properties and Responses of Preterm Lambs to Treatment at Birth

PEDIATRICS ◽  
1987 ◽  
Vol 79 (1) ◽  
pp. 38-46
Author(s):  
Machiko Ikegami ◽  
Yotaro Agata ◽  
Tarek Elkady ◽  
Mikko Hallman ◽  
David Berry ◽  
...  
Keyword(s):  
Surface Tension ◽  
Surface Properties ◽  
Surface Adsorption ◽  
Soluble Proteins ◽  
The Other ◽  
Clinical Responses ◽  
Spreading Rates ◽  
Surface Spreading

Natural sheep surfactant, rabbit surfactant, human surfactant, and surfactant TA were compared for in vitro surface properties and for responses of preterm lambs to treatment. Equivalent amounts of sheep, rabbit, and human surfactants were needed to lower the surface tension to less than 10 dynes/cm, whereas four times less surfactant TA similarly lowered the surface tension. Surface-spreading rates were similar for the surfactants. The surface adsorption of the batch of human surfactant tested was much slower than was adsorption of the other surfactants. Ventilation was significantly improved in all surfactant-treated lambs relative to the control lambs, indicating the general efficacy of the surfactant treatments. Overall, surfactant TA had the best in vitro characteristics, yet the preterm lambs treated at birth with surfactant TA had lower Po2 values and higher ventilatory requirements than did the sheep surfactant-treated lambs. The in vivo responses to rabbit surfactant were intermediate between the responses to sheep surfactant and to surfactant TA. Human surfactant resulted in the least effective clinical response. More of the phosphatidylcholine associated with human surfactant and surfactant TA was lost from the alveoli and lung tissue after four hours of ventilation than was lost from sheep or rabbit surfactant-treated lambs. More intravascular radiolabeled albumin leaked into the alveoli of the surfactant TA-treated lambs than sheep or rabbit surfactant-treated. lambs. The four surfactants also had different sensitivities to the effects on minimum surface tensions of the soluble proteins present in alveolar washes. The study demonstrates that the range of clinical responses was not predictable based on the in vitro surface properties that we measured. The surfactants behaved differently with respect to loss from the lungs and sensitivity to soluble proteins. Factors other than surface properties are important for the in vivo responses to surfactant treatments.

Alterations in the surface properties of lung surfactant in the torpid marsupial Sminthopsis crassicaudata

1998 ◽  
Vol 84 (1) ◽  
pp. 146-156 ◽  
Author(s):  
Olga V. Lopatko ◽  
Sandra Orgeig ◽  
Christopher B. Daniels ◽  
David Palmer
Keyword(s):  
Surface Tension ◽  
Surface Properties ◽  
Surface Activity ◽  
Pulmonary Surfactant ◽  
Lung Surfactant ◽  
Lung Compliance ◽  
Equilibrium Surface Tension ◽  
Sminthopsis Crassicaudata

Lopatko, Olga V., Sandra Orgeig, Christopher B. Daniels, and David Palmer. Alterations in the surface properties of lung surfactant in the torpid marsupial Sminthopsis crassicaudata. J. Appl. Physiol. 84(1): 146–156, 1998.—Torpor changes the composition of pulmonary surfactant (PS) in the dunnart Sminthopsis crassicaudata [C. Langman, S. Orgeig, and C. B. Daniels. Am. J. Physiol. 271 ( Regulatory Integrative Comp. Physiol. 40): R437–R445, 1996]. Here we investigated the surface activity of PS in vitro. Five micrograms of phospholipid per centimeter squared surface area of whole lavage (from mice or from warm-active, 4-, or 8-h torpid dunnarts) were applied dropwise onto the subphase of a Wilhelmy-Langmuir balance at 20°C and stabilized for 20 min. After 4 h of torpor, the adsorption rate increased, and equilibrium surface tension (STeq), minimal surface tension (STmin), and the %area compression required to achieve STmin decreased, compared with the warm-active group. After 8 h of torpor, STmin decreased [from 5.2 ± 0.3 to 4.1 ± 0.3 (SE) mN/m]; %area compression required to achieve STmindecreased (from 43.4 ± 1.0 to 27.4 ± 0.8); the rate of adsorption decreased; and STeqincreased (from 26.3 ± 0.5 to 38.6 ± 1.3 mN/m). ST-area isotherms of warm-active dunnarts and mice at 20°C had a shoulder on compression and a plateau on expansion. These disappeared on the isotherms of torpid dunnarts. Samples of whole lavage (from warm-active and 8-h torpor groups) containing 100 μg phospholipid/ml were studied by using a captive-bubble surfactometer at 37°C. After 8 h of torpor, STmin increased (from 6.4 ± 0.3 to 9.1 ± 0.3 mN/m) and %area compression decreased in the 2nd (from 88.6 ± 1.7 to 82.1 ± 2.0) and 3rd (from 89.1 ± 0.8 to 84.9 ± 1.8) compression-expansion cycles, compared with warm-active dunnarts. ST-area isotherms of warm-active dunnarts at 37°C did not have a shoulder on compression. This shoulder appeared on the isotherms of torpid dunnarts. In conclusion, there is a strong correlation between in vitro changes in surface activity and in vivo changes in lipid composition of PS during torpor, although static lung compliance remained unchanged (see Langman et al. cited above). Surfactant from torpid animals is more active at 20°C and less active at 37°C than that of warm-active animals, which may represent a respiratory adaptation to low body temperatures of torpid dunnarts.

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