Polymeric Surface Modifications of Tantalum Stents

1996 ◽  
Vol 3 (3) ◽  
pp. 276-283 ◽  
Author(s):  
Arthur B. Fontaine ◽  
Kurt Koelling ◽  
Susan Dos Passos ◽  
Jody Cearlock ◽  
Randy Hoffman ◽  
...  
Keyword(s):  
Platelet Adhesion ◽  
Ex Vivo ◽  
Stent Group ◽  
Polymeric Surface ◽  
Stent Type ◽  
Significant Difference ◽  
Indium 111 ◽  
Time Periods ◽  
Scanning Em ◽  
Well Counter

Purpose: To compare two kinds of polymer-coated tantalum stents with bare tantalum stents (control) to determine if the coatings can improve thromboresistance. Methods: Twenty-seven Fontaine-Dake stents were balloon expanded in three 8-mm × 80-cm.polytetrafluoroethylene (PTFE) grafts; 9 stents were bare tantalum (T); 9 were coated with polyetherurethane (PL); and 9 were coated with parylene (PA). There were 9 stents placed in each graft as follows: 3 tantalum, 3 polyetherurethane, and 3 parylene. In swine whose platelets had been radiolabeled with indium 111, the ends of each stented graft were connected to 14F femoral and venous sheaths to create an ex vivo fistula. Each graft was exposed to blood for 30, 60, and 120 minutes. At the end of each test period, the stented grafts were disconnected from the sheaths, flushed with saline until clear, and then flushed with formalin. The stents were removed from the grafts, and a radionuclide well counter recorded radionuclide counts from each stent type at each period of blood contact. These values were converted to platelet density per 1000 mUm2. Stents were then photographed and scanned with electron microscopy (EM) for qualitative analysis. Possible significant differences in platelet adhesion with the three types of stents (both between stent groups and within stent groups) were examined using a two-tailed Student's f-test. Results: There were significantly fewer platelets adsorbed on PA versus T at all time periods (p < 0.005); on PL versus T at 60 and 120 minutes (p < 0.005); and on PA versus PL at 30 and 120 minutes (p < 0.0005). There was no significant difference in platelet density within each stent group (p = 0.1). Mean platelet density (number of platelets per 1000 mUm2 ± SD) was as follows: at 30 minutes: T = 1891 ± 965; PL = 373 ± 193; and PA = 27 ± 3; at 60 minutes: T = 6226 ± 1621; PL = 1573 ± 793; and PA = 1185 ± 710; at 120 minutes: T = 5307 ± 591; PL = 3164 ± 318; and PA = 180 ± 100. Gross inspection of the 120-minute groups demonstrated focal areas of thrombus on T, less on PL, and none on PA. Scanning EM demonstrated extensive platelet accumulation covering T at all time periods, less on PL, and even less on PA. Conclusions: Polymeric surface modification of tantalum stents with parylene and/or polyetherurethane can improve the acute thromboresistance of these devices; parylene appears to be the more thromboresistant of the two coatings.

Aerosol generation through pars plana vitrectomy

2020 ◽  
pp. bjophthalmol-2020-317214
Author(s):  
Hasan Naveed ◽  
Fong May Chew ◽  
Hanbin Lee ◽  
Edward Hughes ◽  
Mayank A Nanavaty
Keyword(s):  
Pars Plana Vitrectomy ◽  
Ex Vivo ◽  
Dynamic Changes ◽  
Aerosol Generation ◽  
Significant Difference ◽  
Optical Particle Counter ◽  
Pars Plana ◽  
23 Gauge ◽  
Set Up ◽  
Ex Vivo Study

PurposeTo assess whether pars plana vitrectomy (PPV) is an aerosol-generating procedure (AGP) in an ex vivo experimental model.MethodsIn this ex vivo study on 10 porcine eyes, optical particle counter was used to measure particles ≤10 μm using cumulative mode in the six in-built channels: 0.3 μm, 0.5 μm, 1 μm, 2.5 μm, 5 μm and 10 μm aerosols during PPV. Two parts of the study were as follows: (1) to assess the pre-experimental baseline aerosol count in the theatre environment where there are dynamic changes in temperature and humidity and (2) to measure aerosol generation with 23-gauge and 25-gauge set-up. For each porcine eye, five measurements were taken for each consecutive step in the experiment including pre-PPV, during PPV, fluid–air exchange (FAX) and venting using a flute with 23-gauge set-up and a chimney with 25-gauge set-up. Therefore, a total of 200 measurements were recorded.ResultsWith 23-gauge and 25-gauge PPV, there was no significant difference in aerosol generation in all six channels comparing pre-PPV versus PPV or pre-PPV versus FAX. Venting using flute with 23-gauge PPV showed significant reduction of aerosol ≤1 μm. Air venting using chimney with 25-gauge set-up showed no significant difference in aerosol of ≤1 μm. For cumulative aerosol counts of all particles measuring ≤5 μm, compared with pre-PPV, PPV or FAX, flute venting in 23-gauge set-up showed significant reduction unlike the same comparison for chimney venting in 25-gauge set-up.ConclusionPPV and its associate steps do not generate aerosols ≤10 μm with 23-gauge and 25-gauge set-ups.

The Influence of Force Direction on the Fracture Pattern and Fracture Resistance of Canine Teeth in Dogs

2017 ◽  
Vol 34 (1) ◽  
pp. 8-17 ◽  
Author(s):  
Stephanie Goldschmidt ◽  
Catherine Zimmerman ◽  
Caitlyn Collins ◽  
Scott Hetzel ◽  
Heidi-Lynn Ploeg ◽  
...  
Keyword(s):  
Fracture Resistance ◽  
Ex Vivo ◽  
Testing Machine ◽  
Fracture Pattern ◽  
Hard Tissue ◽  
Canine Tooth ◽  
Cross Sectional ◽  
Significant Difference ◽  
Force Direction ◽  
Testing Group

Biomechanical studies of the elongated canine tooth of animals are few, and thus our understanding of mechanical and physical properties of animal teeth is limited. The objective of the present study was to evaluate the influence of force direction on fracture resistance and fracture pattern of canine teeth in an ex vivo dog cadaver model. Forty-five extracted canine teeth from laboratory beagle dogs were standardized by hard tissue volume and randomly distributed among 3 force direction groups. The teeth were secured within a universal testing machine and a load was applied at different directions based on testing group. The maximum force to fracture and the fracture pattern classification were recorded for each tooth. After correcting for hard tissue cross-sectional area in a multivariate analysis, no significant difference in the amount of force required for fracture was apparent between the different force direction groups. However, the influence of force direction on fracture pattern was significant. The results of this study may allow the clinician to educate clients on possible causal force directions in clinically fractured teeth and, thus, help prevent any contributing behavior in the future.

scholarly journals Predicting chromosome damage in astronauts participating in international space station missions

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Alan Feiveson ◽  
Kerry George ◽  
Mark Shavers ◽  
Maria Moreno-Villanueva ◽  
Ye Zhang ◽  
...  
Keyword(s):  
International Space Station ◽  
Dose Response ◽  
Ex Vivo ◽  
Space Station ◽  
Space Radiation ◽  
Blood Samples ◽  
International Space ◽  
Significant Difference ◽  
Subject Specific

AbstractSpace radiation consists of energetic protons and other heavier ions. During the International Space Station program, chromosome aberrations in lymphocytes of astronauts have been analyzed to estimate received biological doses of space radiation. More specifically, pre-flight blood samples were exposed ex vivo to varying doses of gamma rays, while post-flight blood samples were collected shortly and several months after landing. Here, in a study of 43 crew-missions, we investigated whether individual radiosensitivity, as determined by the ex vivo dose–response of the pre-flight chromosome aberration rate (CAR), contributes to the prediction of the post-flight CAR incurred from the radiation exposure during missions. Random-effects Poisson regression was used to estimate subject-specific radiosensitivities from the preflight dose–response data, which were in turn used to predict post-flight CAR and subject-specific relative biological effectiveness (RBEs) between space radiation and gamma radiation. Covariates age, gender were also considered. Results indicate that there is predictive value in background CAR as well as radiosensitivity determined preflight for explaining individual differences in post-flight CAR over and above that which could be explained by BFO dose alone. The in vivo RBE for space radiation was estimated to be approximately 3 relative to the ex vivo dose response to gamma irradiation. In addition, pre-flight radiosensitivity tended to be higher for individuals having a higher background CAR, suggesting that individuals with greater radiosensitivity can be more sensitive to other environmental stressors encountered in daily life. We also noted that both background CAR and radiosensitivity tend to increase with age, although both are highly variable. Finally, we observed no significant difference between the observed CAR shortly after mission and at > 6 months post-mission.

scholarly journals Accuracy of the fluorescence-aided identification technique (FIT) for detecting tooth-colored restorations utilizing different fluorescence-inducing devices: an ex vivo comparative study

2021 ◽  
Author(s):  
W. Leontiev ◽  
E. Magni ◽  
C. Dettwiler ◽  
C. Meller ◽  
R. Weiger ◽  
...  
Keyword(s):  
Multivariate Analysis ◽  
Ex Vivo ◽  
Predictive Values ◽  
Composite Restorations ◽  
Significant Difference ◽  
Identification Technique ◽  
Illumination Method ◽  
Sensitivity Specificity ◽  
Entire Procedure ◽  
Higher Sensitivity

Abstract Objectives The aim of the present study was to compare the accuracy of the conventional illumination method (CONV) and the fluorescence-aided identification technique (FIT) for distinguishing between composite restorations and intact teeth using different fluorescence-inducing devices commonly used for FIT. Materials and methods Six groups of six dentists equipped with one of six different FIT systems each independently attempted to identify composite restorations and intact teeth on a full-mouth model with 22 composite restorations using CONV and, 1 h later, FIT. The entire procedure was repeated 1 week later. Sensitivity, specificity, and positive (PPV) and negative (NPV) predictive values, including 95% confidence intervals (CI), were calculated for CONV and FIT overall and for each device. The influence of examiner age, method, and device on each parameter was assessed by multivariate analysis of variance. Results The sensitivity (84%, CI 81–86%), specificity (94%, CI 93–96%), PPV (92%, CI 90–94%), and NPV (90%, CI 88–91%) of FIT was significantly higher than that of CONV (47%, CI 44–50%; 82%, CI 79–84%; 66%, CI 62–69%, and 69%, CI 68–71%, respectively; p<0.001). The differences between CONV and FIT were significant for all parameters and FIT systems except VistaCam, which achieved no significant difference in specificity. Examiners younger than 40 years attained significantly higher sensitivity and negative predictive values than older examiners. Conclusions FIT is more reliable for detecting composite restorations than the conventional illumination method. Clinical relevance FIT can be considered an additional or alternative tool for improving the detection of composite restorations.

scholarly journals Design of a force-measuring setup for colorectal compression anastomosis and first ex-vivo results

2021 ◽  
Author(s):  
Jana Steger ◽  
Isabella Patzke ◽  
Maximilian Berlet ◽  
Stefanie Ficht ◽  
Markus Eblenkamp ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Tissue Fixation ◽  
Force Transmission ◽  
Tissue Thickness ◽  
Colon Tissue ◽  
Device Development ◽  
Compression Anastomosis ◽  
Technical Requirements ◽  
Significant Difference

Abstract Purpose The introduction of novel endoscopic instruments is essential to reduce trauma in visceral surgery. However, endoscopic device development is hampered by challenges in respecting the dimensional restrictions, due to the narrow access route, and by achieving adequate force transmission. As the overall goal of our research is the development of a patient adaptable, endoscopic anastomosis manipulator, biomechanical and size-related characterization of gastrointestinal organs are needed to determine technical requirements and thresholds to define functional design and load-compatible dimensioning of devices. Methods We built an experimental setup to measure colon tissue compression piercing forces. We tested 54 parameter sets, including variations of three tissue fixation configurations, three piercing body configurations (four, eight, twelve spikes) and insertion trajectories of constant velocities (5 mms−1, 10 mms−1,15 mms−1) and constant accelerations (5 mms−2, 10 mms−2, 15 mms−2) each in 5 samples. Furthermore, anatomical parameters (lumen diameter, tissue thickness) were recorded. Results There was no statistically significant difference in insertion forces neither between the trajectory groups, nor for variation of tissue fixation configurations. However, we observed a statistically significant increase in insertion forces for increasing number of spikes. The maximum mean peak forces for four, eight and twelve spikes were 6.4 ± 1.5 N, 13.6 ± 1.4 N and 21.7 ± 5.8 N, respectively. The 5th percentile of specimen lumen diameters and pierced tissue thickness were 24.1 mm and 2.8 mm, and the 95th percentiles 40.1 mm and 4.8 mm, respectively. Conclusion The setup enabled reliable biomechanical characterization of colon material, on the base of which design specifications for an endoscopic anastomosis device were derived. The axial implant closure unit must enable axial force transmission of at least 28 N (22 ± 6 N). Implant and applicator diameters must cover a range between 24 and 40 mm, and the implant gap, compressing anastomosed tissue, between 2 and 5 mm.

scholarly journals Tissue stress from laparoscopic grasper use and bowel injury in humans: establishing intraoperative force boundaries

2021 ◽  
Vol 3 (1) ◽  
pp. e000084
Author(s):  
Amanda Farah Khan ◽  
Matthew Kenneth MacDonald ◽  
Catherine Streutker ◽  
Corwyn Rowsell ◽  
James Drake ◽  
...  
Keyword(s):  
Small Bowel ◽  
Tissue Injury ◽  
Ex Vivo ◽  
Gastrointestinal Surgery ◽  
Convenience Sample ◽  
Thickness Change ◽  
Novel Device ◽  
Significant Difference ◽  
Laparoscopic Grasper

ObjectivesWe aim to determine what threshold of compressive stress small bowel and colon tissues display evidence of significant tissue trauma during laparoscopic surgery.DesignThis study included 10 small bowel and 10 colon samples from patients undergoing routine gastrointestinal surgery. Each sample was compressed with pressures ranging from 100 kPa to 600 kPa. Two pathologists who were blinded to all study conditions, performed a histological analysis of the tissues. Experimentation: November 2018–February 2019. Analysis: March 2019–May 2020.SettingAn inner-city trauma and ambulatory hospital with a 40-bed inpatient general surgery unit with a diverse patient population.ParticipantsPatients were eligible if their surgery procured healthy tissue margins for experimentation (a convenience sample). 26 patient samples were procured; 6 samples were unusable. 10 colon and 10 small bowel samples were tested for a total of 120 experimental cases. No patients withdrew their consent.InterventionsA novel device was created to induce compressive “grasps” to simulate those of a laparoscopic grasper. Experimentation was performed ex-vivo, in-vitro. Grasp conditions of 0–600 kPa for a duration of 10 s were used.ResultsSmall bowel (10), M:F was 7:3, average age was 54.3 years. Colon (10), M:F was 1:1, average age was 65.2 years. All 20 patients experienced a significant difference (p<0.05) in serosal thickness post-compression at both 500 and 600 kPa for both tissue types. A logistic regression analysis with a sensitivity of 100% and a specificity of 84.6% on a test set of data predicts a safety threshold of 329–330 kPa.ConclusionsA threshold was discovered that corresponded to both significant serosal thickness change and a positive histological trauma score rating. This “force limit” could be used in novel sensorized laparoscopic tools to avoid intraoperative tissue injury.

scholarly journals A Tumbling Magnetic Microrobot System for Biomedical Applications

Micromachines ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 861
Author(s):  
Elizabeth E. Niedert ◽  
Chenghao Bi ◽  
Georges Adam ◽  
Elly Lambert ◽  
Luis Solorio ◽  
...  
Keyword(s):  
Ultrasound Imaging ◽  
Biomedical Applications ◽  
Imaging System ◽  
Ex Vivo ◽  
Negative Control ◽  
Circular Path ◽  
Rotational Axis ◽  
Significant Difference

A microrobot system comprising an untethered tumbling magnetic microrobot, a two-degree-of-freedom rotating permanent magnet, and an ultrasound imaging system has been developed for in vitro and in vivo biomedical applications. The microrobot tumbles end-over-end in a net forward motion due to applied magnetic torque from the rotating magnet. By turning the rotational axis of the magnet, two-dimensional directional control is possible and the microrobot was steered along various trajectories, including a circular path and P-shaped path. The microrobot is capable of moving over the unstructured terrain within a murine colon in in vitro, in situ, and in vivo conditions, as well as a porcine colon in ex vivo conditions. High-frequency ultrasound imaging allows for real-time determination of the microrobot’s position while it is optically occluded by animal tissue. When coated with a fluorescein payload, the microrobot was shown to release the majority of the payload over a 1-h time period in phosphate-buffered saline. Cytotoxicity tests demonstrated that the microrobot’s constituent materials, SU-8 and polydimethylsiloxane (PDMS), did not show a statistically significant difference in toxicity to murine fibroblasts from the negative control, even when the materials were doped with magnetic neodymium microparticles. The microrobot system’s capabilities make it promising for targeted drug delivery and other in vivo biomedical applications.

Abstract 2214: The Aptamer ARC1779 Is A Potent And Specific Inhibitor Of von Willebrand Factor (vWF) Mediated Ex Vivo Platelet Function In ST-elevation (STEMI) and non-ST elevation (NSTEMI) Acute Myocardial Infarction (AMI)

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Bernd Jilma ◽  
Florian B Mayr ◽  
Alexander O Spiel ◽  
Patricia G Merlino ◽  
Harold N Marsh ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Platelet Function ◽  
Platelet Adhesion ◽  
Ex Vivo ◽  
Specific Inhibitor ◽  
Citrate Anticoagulation ◽  
St Elevation ◽  
A1 Domain ◽  
The Impact ◽  
Novel Therapeutic

Background: ARC1779 is an aptamer which blocks the A1 domain binding of the vWF A1 domain to platelet GPIb receptors that is now in development for the treatment of AMI. vWF is increased in the elderly and in the setting of AMI, as reflected in higher vWF levels in circulation and in increased shear-dependent platelet function as measured by the platelet function analyzer (PFA-100) and cone and plate analyzer (IMPACT). Conventional therapy of AMI partially reduces platelet activation and aggregation, but does not address excessive vWF activity or platelet adhesion. Methods: We studied the ex vivo dose response curves for ARC1779 on PFA-100 and IMPACT platelet function tests, agonist-induced platelet aggregation, and vWF activity (free A1 domain sites) of patients with AMI on standard treatment including aspirin and clopidogrel (n=40), young (n=20) and elderly controls (n=20). Results: ARC1779 fully blocked collagen ADP induced platelet plug formation as measured by PFA-100 with an IC100 of ~ 1–2 mcg/mL with citrate anticoagulation, and 3–5 mcg/mL with hirudin anticoagulation. ARC1779 fully blocked shear-dependent platelet adhesion measured by the IMPACT analyzer with an IC100 of ~ 1 mcg/mL with citrate anticoagulation. In contrast to GPIIb/IIIa antagonists, ARC1779 did not inhibit platelet aggregation by ADP, collagen or arachidonic acid at concentrations (10mcg/mL) that fully inhibited vWF dependent platelet function. ARC1779 fully blocked vWF activity ex vivo with an IC90 of ~ 1 mcg/mL in young controls and 6 – 8 mcg/mL in STEMI and NSTEMI patients. Conclusions: ARC1779 potently and specifically inhibits vWF activity and vWF dependent platelet function, even in the setting of AMI where vWF activity is increased. ARC1779 represents a novel therapeutic principle (vWF antagonism) and a novel therapeutic class (aptamers). Potent and specific inhibition of VWF makes ARC1779 a promising development candidate for patients with AMI. Results

Abstract 56: Coagulation Factor XI Promotes Distal Platelet Activation and Single Platelet Consumption in the Bloodstream Under Shear Flow

2016 ◽  
Vol 36 (suppl_1) ◽  
Author(s):  
Jenya Zilberman-Rudenko ◽  
Chantal Wiesenekker ◽  
Asako Itakura ◽  
Owen J McCarty
Keyword(s):  
Shear Flow ◽  
Platelet Activation ◽  
Platelet Adhesion ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Coagulation Factor ◽  
Thrombin Inhibitor ◽  
Dependent Manner ◽  
Factor Xi ◽  
Primate Model

Objective: Coagulation factor XI (FXI) has been shown to contribute to thrombus formation on collagen or tissue factor (TF)-coated surfaces in vitro and in vivo by enhancing thrombin generation. Whether the role of the intrinsic pathway of coagulation is restricted to the local site of thrombus formation is unknown. This study was designed to determine whether FXI could promote both proximal and distal platelet activation and aggregate formation in the bloodstream. Approach and Results: Pharmacological blockade of FXI activation or thrombin activity in blood did not affect local platelet adhesion, yet reduced local platelet aggregation, thrombin localization and fibrin formation on immobilized collagen and TF under shear flow, ex vivo . Downstream of the thrombus formed on immobilized collagen or collagen and 10 pM TF, platelet CD62P expression and microaggregate formation and progressive platelet consumption were significantly reduced in the presence of FXI-function blocking antibodies or a thrombin inhibitor in a shear rate- and time-dependent manner. In a non-human primate model of thrombus formation, we found that inhibition of FXI reduced single platelet consumption in the bloodstream distal to a site of thrombus formation. Conclusions: This study demonstrates that the FXI-thrombin axis contributes to distal platelet activation and procoagulant microaggregate formation in the blood flow downstream of the site of thrombus formation. Our data highlights FXI as a novel therapeutic target for inhibiting distal platelet activation without affecting proximal platelet adhesion.

In vitro biomechanical comparison of load to failure testing of a canine unconstrained medial compartment elbow arthroplasty system and normal canine thoracic limbs

2013 ◽  
Vol 26 (05) ◽  
pp. 356-365 ◽  
Author(s):  
K. L. Wendelburg ◽  
S. Tepic ◽  
S. M. Stover ◽  
T. Garcia-Nolen ◽  
P. B. Stearns ◽  
...  
Keyword(s):  
Axial Load ◽  
Failure Modes ◽  
Ex Vivo ◽  
Medial Compartment ◽  
Elbow Arthroplasty ◽  
Total Arthroplasty ◽  
Significant Difference ◽  
Load To Failure ◽  
And Control

SummaryElbow dysplasia, primarily affecting the medial compartment, is the most common cause of lameness in the thoracic limb. Elbow arthroplasty is an option for end stage or severely affected patients. The purpose of this study was to compare ex vivo axial load to failure of an implanted novel elbow arthroplasty system to control limbs. The partial arthroplasty is a medial compartmental, unconstrained system, intended to allow conversion to total arthroplasty. We hypothesized that there would not be any significant difference between implanted and controlled limbs when loaded to failure. Six pairs of medium mixed breed canine cadaveric thoracic limbs were prepared for comparison of failure loading of control and implanted limbs. Axial compression was performed using a mechanical testing system. Failure loads were normalized to bodyweight. The mean normalized failure load (N/kg) for the implanted limbs and control limbs were 2.47 (range: 1.62-3.38) and 2.68 (range: 2.25-3.25), respectively. An implanted to control ratio of 0.93 ± 0.19 was calculated. The difference between paired control and implanted limbs in normalized failure loading was not significant (p = 0.38). There were not any differences noted in the yield load (p = 0.30), stiffness (p = 0.62), or energy (0.58). Failure modes were recorded. We concluded that the differences between implanted and control limbs in supra-physiologic axial load to failure were not significant.

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