Normal Physiological Pressure Research Articles

Recent Advancements of Bioinks for 3D Bioprinting of Human Tissues and Organs.

3D bioprinting is recognized as a promising biomanufacturing technology that enables the reproducible and high-throughput production of tissues and organs through the deposition of different bioinks. Especially, bioinks based on loaded cells allow for immediate cellularity upon printing, providing opportunities for enhanced cell differentiation for organ manufacturing and regeneration. Thus, extensive applications have been found in the field of tissue engineering. The performance of the bioinks determines the functionality of the entire printed construct throughout the bioprinting process. It is generally expected that bioinks should support the encapsulated cells to achieve their respective cellular functions and withstand normal physiological pressure exerted on the printed constructs. The bioinks should also exhibit a suitable printability for precise deposition of the constructs. These characteristics are essential for the functional development of tissues and organs in bioprinting and are often achieved through the combination of different biomaterials. In this review, we have discussed the cutting-edge outstanding performance of different bioinks for printing various human tissues and organs in recent years. We have also examined the current status of 3D bioprinting and discussed its future prospects in relieving or curing human health problems.

Walking on water: subchondral vascular physiology explains how joints work and why they become osteoarthritic.

This review of bone perfusion introduces a new field of joint physiology, important in understanding osteoarthritis. Intraosseous pressure (IOP) reflects conditions at the needle tip rather than being a constant for the whole bone. Measurements of IOP in vitro and in vivo, with and without proximal vascular occlusion confirm that cancellous bone is perfused at normal physiological pressures. Alternate proximal vascular occlusion may be used to give a perfusion range or bandwidth at the needle tip more useful than a single IOP measure. Bone fat is essentially liquid at body temperature. Subchondral tissues are relatively delicate but are micro-flexible. They tolerate huge pressures with loading. Collectively, the subchondral tissues transmit load mainly by hydraulic pressure to the trabeculae and cortical shaft. Normal MRI scans demonstrate subchondral vascular marks which are lost in early osteoarthritis. Histological studies confirm the presence of those marks and possible subcortical choke valves which support hydraulic pressure load transmission. Osteoarthritis appears to be at least partly a vasculo-mechanical disease. Understanding subchondral vascular physiology will be key to better MRI classification and prevention, control, prognosis and treatment of osteoarthritis and other bone diseases.

Colorectal and bladder prokinetic activity of [Lys5, MeLeu9, Nle10]-NKA(4-10) after intranasal or sublingual delivery in dogs.

The feasibility of eliciting defecation and urination after intranasal (IN) or sublingual (SL) delivery of a small peptide NK2 receptor agonist, [Lys5, MeLeu9, Nle10]-NKA(4-10), was examined using prototype formulations in dogs. In anesthetized animals, administration of 100 or 300 µg/kg IN or 2.0-6.7 mg/kg SL increased colorectal peak pressure and area under the curve. Peak bladder pressure was also increased at the same doses, and this was accompanied by highly efficient voiding at normal physiological bladder pressure. The onset of these effects was rapid (≤2.5 min), and the primary contractions lasted ∼25 min, returning to baseline in <60 min. Slight hypotension lasting a few minutes and causing<10% change from baseline was detected after higher doses and was statistically significant after only 100 µg/kg IN. In conscious dogs, there was a dose-related increase in voiding responses and reduction in the latency to urinate and defecate after 300 and 1000 µg/kg IN; emesis was also observed at these doses. SL administration of 6.7 mg/kg induced urination within 10 min, but not defecation or emesis. These findings support the feasibility of developing a convenient dosage form of small peptide NK2 receptor agonists as on-demand defecation or urination therapies.

Tricuspid annulus cinching force under pulmonary hypertensive right ventricle conditions: An ex vivo study

This study investigates the force required to reduce or “cinch” the tricuspid annulus under elevated right ventricular pressures, commonly seen in patients with pulmonary hypertension. Tricuspid regurgitation affects 1.6 million Americans. Approximately 43% of patients who undergo tricuspid valve repair to correct tricuspid regurgitation will develop residual pulmonary hypertension, putting them at risk for developing increased right ventricle pressures. Previous studies have quantified the forces required to cinch the tricuspid annulus by only pressurizing the right ventricle, leaving out forces from the pressurized left ventricle and septal wall unaccounted for. This study pressurized both left and right ventricles of 10 porcine hearts to their normal physiological pressures of 110 mmHg and 30 mmHg respectively, then increased right ventricular pressures to mimic moderate and severe pulmonary hypertension. A suture was anchored around the free wall of the tricuspid annulus with the free end attached to a force transducer. The force transducer was mounted on a slider system which pulled the suture at regular intervals. The cinching force on the tricuspid annulus was quantified with each annular reduction by simulating peak systole condition in both ventricles. The data was compared with only the right ventricle pressurized as previous studies did. There were significant differences in required cinching forces with each increase in right ventricular pressure and between trials that pressurized both ventricles versus only the right ventricle, suggesting adoption of this physiologically improved protocol. We also found with increased cinching of the tricuspid annulus, notable changes occur in the mitral annulus.

ARTERIAL STIFFNESS IN HYPERTENSIVE CRISIS DEPENDING ON PATIENT DIPPING PROFILE

Abstract Objective: Arterial stiffness and its value, approximated from pulse wave velocity, correlate with cardiovascular risk. Therapeutic restoration of normal physiologic blood pressure reduction by 10–20% during night-time sleep is the most significant independent predictor of decreased cardiovascular risk. The aim of this study was to present the difference in pulse wave velocity value between gender and their dipping profile. Design and method: We divided 205 patients (54% female) in four groups by their dipping profile and gender. Additionally, because pulse wave velocity depends on age, we created five main age groups (&lt;50, 51–60, 61–70, 71–80 and over 80 years). We checked their dipping profile with 24-hour ambulatory blood pressure monitoring. Pulse wave velocity was checked by Agedio oscillometer. Also, serum creatinine and glomerular filtration rate was calculated by CKD-EPI formula in all patients. Results: An average glomerular filtrate rate in dipper patients was significantly higher than non-dippers (81.32 vs 72.82 ml/min/1.73m2; p &lt; 0.05). The number of non-dippers was higher than dippers (103 vs. 39 patients, p &lt; 0.01). Women were significantly older than men (69.02 vs. 62.01 years, p &lt; 0.01). Comparing pulse wave velocity by age groups and dipping profile in men the results were: 1 – 8.20 vs 8.31m/s; 2 – 8.78 vs. 9.30m/s; 3 – 10.01m/s vs. 10.35m/s, p = NS; 4 – 11.70 vs. 13.27m/s, p &lt; 0.01. In women we found statistically higher values of pulse wave velocity compared to men of the same age groups (11.71 vs. 10.44m/s, p &lt; 0.05). By age groups and their dipping profile the results were: 1 – 9.01 vs. 9.04m/s; 2 – 9.66 vs 9.97m/s, p = NS; 3 – 10.35 vs. 11.34m/s, p &lt; 0.05; 4 – 11.85 vs. 12.91m/s, p &lt; 0.01). Conclusions: Non-dipping profile could be a potential risk factor for hypertensive crisis development. Pulse wave velocity values increased more rapidly in non-dippers compared to dippers and turned out to be higher in women compared to men of the same age. Treating and discovering non-dipper patients could decrease the level of the cardiovascular risk and potentially prevent the incidence of the hypertensive crisis events. Kidney function restoration also showed its importance in cardiovascular prevention.

Design and evaluation of a novel anti-reflux biliary stent with cone spiral valve.

Endoscopic placement of biliary stent is a well-established palliative treatment for biliary obstruction. However, duodenobiliary reflux after stent placement has been a common problem which may lead to dreadful complications. This paper designed a novel anti-reflux biliary stent with a cone spiral valve. Fluid-Structure Interaction (FSI) simulations were established to evaluate the efficiency of the anti-reflux stent comparing with a clinically applied standard stent. According to the stress distribution of the valve, the fatigue performance in the stress concentration area was analyzed. The results show that when the antegrade flow through the valve, the cone spiral valve could stretch and open to realize adequate drainage under the normal physiological pressure of biliary tract; When the duodenal reflux through the valve, the valve would be compressed and close with a result of nearly zero at the outlet flow rate. Furthermore, the anti-reflux stent achieved improved radial mechanical performance with 2.7 times higher radial stiffness than standard stent. Finite element analysis (FEA) also indicates that compared with the standard stent, the addition of the anti-reflux valve had little negative effect on flexibility of the stent. Fatigue analysis results showed that the valve was reliable. This research provides the new stent with a cone spiral valve and proves that it is technically feasible and effective for preventing the duodenobiliary reflux while ensuring the antegrade bile flow without compromising the other biomechanical performances.

Response of hypogastric afferent fibers to bladder distention or irritation in cats

The goal of this study in anesthetized cats was to identify silent hypogastric nerve (HGN) afferent fibers that do not respond to bladder distention but become responsive after chemical irritation of the bladder. The HGN was split into multiple filaments small enough for recording action potentials from single or multiple afferent fibers. The bladder was distended by infusion of either saline or 0.5% acetic acid (AA) through a urethral catheter while recording intravesical pressure. A total of 90 HGN filaments from 17 cats responded to bladder distention with saline or AA. Three types of HGN afferents were identified. The first type was non-nociceptive mechano-sensitive that responded to bladder distention at normal physiological pressures (10–40 cmH2O). The second type was nociceptive mechano-sensitive that only responded to high-pressure (50–80 cmH2O) bladder distention with saline but responded to low-pressure bladder distention after sensitization with AA. The third type was chemo-sensitive nociceptive that was silent even during high-pressure bladder distention but after sensitization with AA did respond to low-pressure bladder distention. These results indicate that HGN afferents as well as pelvic nerve afferents may play a role in bladder nociception. The HGN afferent fibers that are silent during bladder distention at normal physiological pressures but become responsive after chemical irritation are important for understanding the possible pathophysiological mechanism underlying bladder allodynia in painful bladder syndrome.

Nucleus of Circulating Tumor Cell Determines Its Translocation Through Biomimetic Microconstrictions and Its Physical Enrichment by Microfiltration.

The mechanism of cells passing through microconstrictions, such as capillaries and endothelial junctions, influences metastasis of circulating tumor cells (CTCs) in vivo, as well as size-based enrichment of CTCs in vitro. However, very few studies observe such translocation of microconstrictions in real time, and thus the inherent biophysical mechanism is poorly understood. In this study, a multiplexed microfluidic device is fabricated for real-time tracking of cell translocation under physiological pressure and recording deformation of the whole cell and nucleus, respectively. It is found that the deformability and size of the nucleus instead of the whole cell dominate cellular translocation through microconstrictions under a normal physiological pressure range. More specifically, cells with a large and stiff nucleus are prone to be blocked by relatively small constrictions. The same phenomenon is also observed in the size-based enrichment of CTCs from peripheral blood of metastatic cancer patients. These findings are different from a popular viewpoint that the size and deformability of a whole cell mainly determine cell translation through microconstrictions, and thus may elucidate interactions between CTCs and capillaries from a new perspective and guide the rational design of size-based microfilters for rare cell enrichment.

POTENTIAL BENEFITS FOR USING ePTFE AS A MATERIAL FOR PROSTHETIC HEART VALVES

Background The current study highlights potential benefits of using ePTFE, a polymeric material, as the main component suitable for fabrication of prosthetic heart valves. Novel polymeric materials seem to be promising for replacing biological elements commonly used in medical products for cardiovascular surgery. High biocompatibility and mechanical properties prolong their lifespan during direct blood contact. Nevertheless, it is necessary to conduct a series of specific tests to determine their properties and benefits of their application. Despite well-known biological properties of ePTFE, there are few studies assessing it as a material for heart valve leaflets. Aim To evaluate the mechanical properties of the commercially available sample of ePTFE and to conduct a numerical experiment assessing its potential for the application. Methods The polymer properties (Gore &amp; Associates Inc., USA) were evaluated under uniaxial tension in two mutually perpendicular directions to determine the degree of anisotropy of the material. A xenopericardial patch (ZAO “NeoCor”, Russia), routinely used for the fabrication of bioprosthetic leaflets, was taken as the control sample. The spatial model of the investigated material was carried out in CAD SolidWorks 2016 (Dassault Systemes, USA). Numerical modeling of the samples was performed with the finite element method using the orthotropic material model in the Abaqus/CAE (Dassault Systemes, USA). Results There are significant difference found in the mechanical properties of the studied materials: the tension at stretching of ePTFE in the longitudinal and transverse directions differed from xenopericardium by 1.9 and 7.5 times, respectively (p&lt;0.05). The elongation before rupture of ePTFE in direction I and direction II was greater than that of xenopericardium (2.39 vs. 1.9 times, respectively). Numerical modeling demonstrated insignificant qualitative differences in the valve opening while applying pressure equal to normal physiological pressure&gt;&lt; 0.05). The elongation before rupture of ePTFE in direction I and direction II was greater than that of xenopericardium (2.39 vs. 1.9 times, respectively). Numerical modeling demonstrated insignificant qualitative differences in the valve opening while applying pressure equal to normal physiological pressure and low pressure. In addition, the zones of high stress in commissural racks, which are critical zones for fatigue resistance, have been identified, albeit require additional in vitro research. Conclusion Mechanical properties of ePTFE suggests it to be a promising polymeric material suitable for fabrication of flexible leaflets of the heart valve prosthesis. It has similar leaflet functioning, compared with the xenopericardium sample, routinely used in manufacturing. ePTFE is more resistant to rupture, which confirms its greater fatigue strength. However, it requires further study by advanced methods.

Fluoroscopy-Assisted Transnasal Onyx Occlusion of the Eustachian Tube for Lateral Skull Base Cerebrospinal Fluid Leak Repair

Objectives To describe transnasal Eustachian tube (ET) occlusion with a liquid embolic solution for lateral skull base cerebrospinal fluid (CSF) leaks. Design A lateral skull base CSF fistula model was developed by the authors using fresh cadaveric heads. Using a transtympanic needle, regulated pressurized pigmented saline was continuously instilled into the middle ear space and visualized endoscopically in the nasopharynx. An angioembolization catheter was then placed through the cartilaginous ET orifice just medial to the bony ET. Under endoscopic and fluoroscopic guidance, a column of liquid embolic agent was deployed into the bony ET segment up to the middle ear space. Setting Tertiary care academic center. Participants Cadaveric specimens. Main Outcome Measures Cessation of CSF flow after occlusion at supraphysiologic pressures. Results In two cadavers, a CSF fistula model was developed and endoscopic visualization of irrigant flow into the nasopharynx was confirmed. Fluoroscopy provided adequate anatomic views of the ET and middle ear, in addition to dynamic views of embolization. Cessation of flow after occlusion was successfully achieved with pressures up to 25 mm Hg, which exceeds normal physiological intracranial pressure. Conclusion Eustachian tube occlusion with a liquid embolic solution is feasible in a novel cadaveric CSF leak model. In the future, this relatively short, straightforward procedure may become an outpatient alternative to manage intermittent or low-flow CSF fistulae following lateral skull base surgery.

A Comparison of Ex Vivo Leak Pressures for Four Enterotomy Closures in a Canine Model.

Initial and maximum intraluminal leak pressures of four enterotomy closures were compared. Closure patterns included a modified Gambee, simple interrupted, simple continuous, and skin staple closure. Forty-eight 3-cm enterotomy constructs were created from jejunal segments harvested from 12 dogs. Twelve each were randomly assigned to the four closure methods. Time of closure, as well as initial and maximum leak pressures, were measured and compared. The modified Gambee closure was the slowest closure to perform, with skin staple closure being the fastest. All suture patterns tested had higher mean initial leak pressures than reported physiologic intestinal pressures during peristalsis, although the skin staple closures resulted in leakage below normal physiologic pressure in several samples. The modified Gambee closure was able to sustain a significantly higher initial leak pressure than skin staple closures. The modified Gambee suture pattern had the greatest maximum leak pressure of all enterotomy closure patterns tested. Use of the modified Gambee suture pattern should be considered in enterotomy closure, although in vivo studies are required to determine if these differences are clinically significant.

Further experimental evidence of the compressibility of arteries

Further experimental evidence on the compressibility of arteries under normal physiological pressure range is provided using the experimental apparatus introduced in Yosibash et al., JMBBM 39(2014):339–354. We enlarged the experimental database by including almost twice the number of experiments, we considered a different artery – the porcine common carotid that allowed longer and larger diameters.In the physiological pressure range of 50–200mmHg, a relative volume change of 5% was obtained, lower compared to the sapheneous and femoral arteries (2–6%). Most of the arteries had a relative volume change of 1.5%.The relative volume change is found to be almost linearly proportional to the pressure, and inversely proportional to the dimensions of the experimented arteries (especially the artery length). The smaller the artery tested, the larger the relative volume change (such a phenomenon was also realized in Yosibash et al., JMBBM 39(2014):339–354.).We realized in recent past publications a flaw in the experimental protocol that results in an overestimation of the relative volume change (thus underestimating the bulk modulus). It is due to the consideration of experimental observations close to the zero pressure. Nontheless, in view of the experimental evidence, the pre-assumption of incompressibility in many phenomenological constitutive models of artery walls should be re-evaluated.

Mechanisms underlying the volume regulation of interstitial fluid by capillaries: a simulation study

BackgroundControl of the extracellular fluid volume is one of the most indispensable issues for homeostasis of the internal milieu. However, complex interdependence of the pressures involved in determination of fluid exchange makes it difficult to predict a steady-state tissue volume under various physiological conditions without mathematical approaches. MethodsHere, we developed a capillary model based on the Starling's principle, which allowed us to clarify the mechanisms of the interstitial-fluid volume regulation. Three well known safety factors against edema: (1) low tissue compliance in negative pressure ranges; (2) lymphatic flow driven by the tissue pressure; and (3) protein washout by the lymph, were incorporated into the model in sequence. ResultsAn increase in blood pressure at the venous end of the capillary induced an interstitial-fluid volume increase, which, in turn, reduced negative tissue pressure to prevent edema. The lymphatic flow alleviated the edema by both carrying fluid away from the tissue and decreasing the colloidal osmotic pressure. From the model incorporating all three factors, we found that the interstitial-fluid volume changed quickly after the blood pressure change, and that the protein movement towards a certain equilibrium point followed the volume change. ConclusionMathematical analyses revealed that the system of the capillary is stable near the equilibrium point at steady state and normal physiological capillary pressure. The time course of the tissue-volume change was determined by two kinetic mechanisms: rapid fluid exchange and slow protein fluxes.

Age‐related Changes in Endothelial Ca2+ Signaling Revealed by Imaging from Inside Arteries at Normal Physiological Pressures

Aging is the summation of many, mostly invisible, but deleterious changes associated with altered structure and function of the cardiovascular system. Age‐induced impairment of endothelial function contributes to and reinforces the changes that occur in vascular disease. Normally, the endothelium transduces multiple chemical and mechanical signals into changes in cytoplasmic calcium (Ca2+) concentration that control vascular function. Thus, understanding age‐related functional changes in the endothelium requires an appreciation of Ca2+ control. We developed a wide‐field, gradient‐index (GRIN) fluorescence imaging system to visualize the endothelium from within the lumen of intact, pressurized arteries. The GRIN system enables rapid imaging of a 500 μm diameter area of the curved endothelial surface (~200 endothelial cells; ECs) with subcellular resolution. We also developed a semi‐automated data extraction procedure to quantify signal dynamics in the individual ECs loaded with fluorescent Ca2+ indicators. In the carotid artery of young rats (3 months), acetylcholine (ACh) evoked endothelial Ca2+ signals that were suppressed as intraluminal pressure increased. In aged rats (18 months) the pressure‐dependent suppression of ACh‐evoked Ca2+ signaling and the frequency of ACh‐evoked intracellular Ca2+ oscillations were reduced, whilst the temporal propagation of Ca2+ signals increased. Significantly, dose response measurements revealed that aging increased EC sensitivity to ACh, yet had no effect on the magnitude of the Ca2+ response in each cell. We propose that such alterations in EC Ca2+ signaling may manifest as a loss of functionality, and explain endothelial dysfunction in aging.

Resistant hypertension and chronotherapy.

Resistant hypertension is defined as blood pressure that remains above 140/90 mmHg in spite of the continuous use of three antihypertensive agents in optimal dose, including diuretic, and lifestyle changes. According to data from United States of America and Europe, the prevalence ranges from 10 up to 30% in patients with hypertension. Numerous biological and lifestyle factors can contribute to the development of resistant hypertension: medications, volume overload, obesity, diabetes mellitus, older age, renal parenchymal and renovascular disease, primary aldosteronism, obstructive sleep apnea, pheochormocytoma, Cushing’s syndrome, thyroid diseases, aortic coarctation. For diagnosing patient’s history is important, assessing compliance, regular blood pressure measurement, physical examination, biochemical evaluation and noninvasive imaging. The evaluation including 24h ambulatory monitoring of blood pressure (ABPM) in the identification of “non-dipper” hypertension. Non-dipper has particular importance and the prevalence of abnormally high sleep blood pressure is very often in chronic kidney patients. Therapeutic restoration of normal physiologic blood pressure reduction during night-time sleep (circadial variation) is the most significant independent predictor of decreased risk and the basis for the chronotherapy. The resistant hypertension treatment is achieved with nonpharmacological and pharmacological approach, treating secondary hypertension causes and invasive procedures.

Prehospital Emergency Care: Evaluation of the Junctional Emergency Tourniquet Tool With a Perfused Cadaver Model

Junctional bleeding from the groin is a leading cause of potentially preventable death on the battlefield. To address this problem, a novel device called the Junctional Emergency Treatment Tool (JETT™) was developed. The JETT was designed to stabilize pelvic ring fractures while controlling lower extremity bleeding sustained during high-energy traumatic events on the battlefield and in the civilian environment. Our purpose was to assess the effectiveness of the JETT in the control of simulated life threatening hemorrhage from proximal injuries in the groin of a perfused cadaver.The JETT was compared with the standard issue combat tourniquet and a Food and Drug Administration (FDA)-cleared junctional hemorrhage control clamp (CRoC™) in a perfused human cadaver model. The JETT?s ability to stop pulsatile flow at the common femoral artery was assessed through proximal aorta and distal measurements of arterial flow rates and pressures.In three cadavers, when the JETT or the CRoC was applied in the groin, there was an immediate cessation of fluid flow from the common femoral artery while the inlet flow aortic pulsatile pressure was maintained. However, the time to bilateral application of the JETT was faster (10 seconds vs. 68 seconds) than bilateral sequential application of two CRoC devices.The JETT is a single device capable of effectively and quickly controlling bilateral lower extremity junctional hemorrhage at normal physiological blood pressures.

How securely is the testicular artery occluded in the spermatic cord by using a ligature?

There are no studies on the ideal ligature technique for the spermatic cord. To compare the maximal resistance pressure in the testicular artery and the maximal tensile forces to produce failure of 2 different ligature techniques used for ligation of the equine spermatic cord. The capabilities of 2 types of ligatures, single knot loop and double knot loop, were assessed using a pressure-resistance test in testicular arteries and with an in vitro mechanical evaluation of the tensile strength by single cycle-to-failure testing. In the pressure-resistance test, the mean ± s.d. peak force at failure of the single knot loop was 354.4 ± 91.7 mmHg and for the double knot loop 303.2 ± 62.0 mmHg. There was no significant difference between the maximal load to failure of the single knot loop and double knot loop technique. The pressure needed for rupture was significantly higher (P = 0.001) than for leakage. The maximal tensile force at failure of the single knot loop was significantly higher than the double knot loop (P = 0.028). There was no significant difference in load elongation properties to failure between the single knot loop and double knot loop. Although no significant differences were obtained in the pressure-resistance test, the single knot loop sustained significantly greater load to failure than the double knot loop in single cycle-to-failure testing. Based on these findings, it would appear that the performance of the single knot loop should be superior to the double knot loop. Both ligature techniques are able to withstand the normal physiological intravascular pressure. The single knot loop has the greater breaking strength of the 2 ligatures tested and is less time consuming to perform and may therefore have advantages during equine castration.

The Role of Actin Filament Dynamics in the Myogenic Response of Cerebral Resistance Arteries

The myogenic response has a critical role in regulation of blood flow to the brain. Increased intraluminal pressure elicits vasoconstriction, whereas decreased intraluminal pressure induces vasodilatation, thereby maintaining flow constant over the normal physiologic blood pressure range. Improved understanding of the molecular mechanisms underlying the myogenic response is crucial to identify deficiencies with pathologic consequences, such as cerebral vasospasm, hypertension, and stroke, and to identify potential therapeutic targets. Three mechanisms have been suggested to be involved in the myogenic response: (1) membrane depolarization, which induces Ca(2+) entry, activation of myosin light chain kinase, phosphorylation of the myosin regulatory light chains (LC(20)), increased actomyosin MgATPase activity, cross-bridge cycling, and vasoconstriction; (2) activation of the RhoA/Rho-associated kinase (ROCK) pathway, leading to inhibition of myosin light chain phosphatase by phosphorylation of MYPT1, the myosin targeting regulatory subunit of the phosphatase, and increased LC(20) phosphorylation; and (3) activation of the ROCK and protein kinase C pathways, leading to actin polymerization and the formation of enhanced connections between the actin cytoskeleton, plasma membrane, and extracellular matrix to augment force transmission. This review describes these three mechanisms, emphasizing recent developments regarding the importance of dynamic actin polymerization in the myogenic response of the cerebral vasculature.

A bilayer prototype woven vascular prosthesis with improved radial compliance

To minimize radial compliance mismatch between native arteries and vascular prostheses over the entire blood pressure range, a biomimetic woven prosthesis sample with a bilayer wall has been developed. Poly(trimethylene terephthalate) (PTT) filaments were used as the circumferential yarns in the inner layer to increase the radial compliance of the inner wall, and poly(ethylene terephthalate) (PET) filaments formed the outer layer to provide a strong and more rigid external prosthesis wall. The two layers were joined together axially along the sample's length by a stitched weave. By means of a special weave design, the cross‐section of the tubular sample included a circumferentially crimped outer layer woven around the inner layer. This bilayer wall structure allowed only the inner layer of the sample to deform radially under small loads equivalent to low normal physiological (diastolic) blood pressures. As the load increased, the inner layer stretched until it came into contact with the outer layer. At higher (systolic) pressures, further loading caused both layers of the wall to deform together. As a result, the prosthesis showed high pressure‐induced compliance when the load was within the normal diastolic pressure range and lower compliance at higher systolic pressures.

Evaluating the Risk of Eye Injuries: Intraocular Pressure During High Speed Projectile Impacts

Purpose: To evaluate the risk of eye injuries by determining intraocular pressure during high speed projectile impacts.Methods: A pneumatic cannon was used to impact eyes with a variety of projectiles at multiple velocities. Intraocular pressure was measured with a small pressure sensor inserted through the optic nerve. A total of 36 tests were performed on 12 porcine eyes with a range of velocities between 6.2 m/s and 66.5 m/s. Projectiles selected for the test series included a 6.35 mm diameter metal ball, a 9.25 mm diameter aluminum rod, and an 11.16 mm diameter aluminum rod. Experiments were designed with velocities in the range of projectile consumer products such as toy guns.Results: A range of intraocular pressures ranged between 2017 mmHg to 26426 mmHg (39 psi–511 psi). Four of the 36 impacts resulted in globe rupture.Conclusions: Intraocular pressures dramatically above normal physiological pressure were observed for high speed projectile impacts. These pressure data provide critical insight to chronic ocular injuries and long-term complications such as glaucoma and cataracts.