Evaluating the efficacy of the punch-out technique in systemic-to-pulmonary shunts: A computational fluid dynamics approach.

BACKGROUND: Systemic-to-pulmonary shunt is a palliative procedure used to decrease pulmonary blood flow in congenital heart diseases. Shunt stenosis or occlusion has been reported to be associated with mortality; therefore, the management of thrombotic complications remains a challenge for most congenital cardiovascular surgeons. Despite its importance, the optimal method for shunt anastomosis remains unclear. OBJECTIVE: The study investigates the clinical benefits of the punch-out technique over conventional methods in the anastomosis process of Systemic-to-pulmonary shunt, focusing on its potential to reduce shunt-related complications. METHODS: Anastomotic models were created by two different surgeons employing both traditional slit and innovative punch-out techniques. Computational tomography was performed to construct three-dimensional models for computational fluid dynamics (CFD) analysis. We assessed the flow pattern, helicity, magnitude of wall shear stress, and its gradient. RESULTS: The anastomotic flow area was larger in the model using the punch-out technique than in the slit model. In CFD simulation, we found that using the punch-out technique decreases the likelihood of establishing a high wall shear stress distribution around the anastomosis line in the model. CONCLUSION: The punch-out technique emerges as a promising method in SPS anastomosis, offering a reproducible and less skill-dependent alternative that potentially diminishes the risk of shunt occlusion, thereby enhancing patient outcomes.

Correction: 2-cyanopyridine derivatives enable N-terminal cysteine bioconjugation and peptide bond cleavage of glutathione under aqueous and mild conditions.

[This corrects the article DOI: 10.1039/D4RA00437J.].

2-cyanopyridine derivatives enable N-terminal cysteine bioconjugation and peptide bond cleavage of glutathione under aqueous and mild conditions.

Inspired by the chemical reactivity of apalutamide, we have developed an efficient method for N-terminal cysteine bioconjugation with 2-cyanopyridine derivatives. Systematic investigations of various 2-cyanopyridines revealed that 2-cyanopyridines with electron-withdrawing groups react efficiently with cysteine under aqueous and mild conditions. Moreover, the highly reactive 2-cyanopyridines enable the peptide bond cleavage of glutathione. The utility of our method is demonstrated by its application to the cysteine-selective chemical modification of bioactive peptides.

Development and initial performance of a miniature axial flow blood pump using magnetic fluid shaft seal.

In this study, we developed a new catheter-mounted micro-axial flow blood pump (MFBP) using a new miniature magnetic fluid shaft seal (MFSS). The prototype of the catheter-mounted MFBP had a maximum diameter of 8 mm and a length of 50 mm. The new MFSS composed a neodymium magnet ring, an iron ring, and a magnetic fluid particularly designed for the MFSS. The new MFSS had outer and inner diameters of 4.0 mm and 2.6 mm, respectively, and a length of 3.0 mm. The sealing pressure of the MFSS was calculated to be 432 mmHg using FEM (Finite Element Method) result; therefore, the MFSS had sufficient sealing pressure for the catheter-mounted MFBP. The friction loss of the MFSS included the friction owing to the viscosity of the magnetic fluid and the magnetic force between the iron ring and ring magnet. The total friction loss of the MFSS was 0.08-0.09 W in the pump operational speed range from 22,000 to 35,000 rpm. From the in vitro experimental results, the catheter-mounted MFBP using the MFSS had a pump output of 3 L/min. against a differential pressure of 60 mmHg, and the pump characteristics of the MFBP were almost the same as those of Impella 5.0.

In vitro performance of trans-valve left ventricular assist device installed at aortic valve position.

In this study, we developed a trans-valve left ventricular assist device (LVAD) that unites a rear-impeller axial-flow blood pump (AFBP) and a polymer membrane valve placed at the aortic valve position. The diameter and length of the rear impeller AFBP was 12 and 63 mm, respectively. The polymer membrane valve was similar to the jelly-fish valve consisting of a valve leaflet made of silicone rubber (thickness 0.5 mm), valve ring (diameter: 25 mm), and valve spokes. The trans-valve LVAD was examined in a mock circulation. An implantable pulsatile flow (PF) VAD was connected to an atrial reservoir to simulate the left ventricle (LV), and the Hall valve was worn in the inflow port, and the trans-valve LVAD was placed in the outflow port as an outflow valve. When the motor rotational speed increased to 26 400 rpm, the mean aortic flow increased from 4.2 to 5.3 L/min, mean aortic pressure increased from 83.4 to 100 mm Hg, and mean motor current of the implantable PF VAD decreased from 1.18 to 0.94 A (unloading effect on LV -21%). The energy equivalent pressure increased from 85.2 to 102 mm Hg, and surplus hemodynamic energy (SHE) decreased by -15.4% from the baseline. In conclusion, the trans-valve LVAD has an advantage of preserving pulsatility without any complicated mechanism and is a novel and promising LV support device.

Development of rear-impeller axial flow blood pump for realization of axial flow blood pump installed at aortic valve position.

In this study, rear-impeller axial flow blood pumps (RIAFBP) were developed to realize a trans-valve axial ventricular assist device (VAD) which consists of the latter blood pump and a polymer monomembrane aortic valve, such as the jellyfish valve. The motor of the RIAFBP is installed in the left ventricle, and its impeller is placed at the aortic valve position. In the prototype RIAFBP, the rotation of the motor is sustained by polyethylene bushings. The RIAFBP has a length of 50 mm and diameter of 19.6 mm. The miniature RIAFBP has the same construction as that of the prototype; however, it employs a ceramic bearing and fin bearing to improve endurance and to reduce blood stagnation. The miniature RIAFBP has a length of 63 mm and diameter of 12 mm. Both RIAFBPs were examined by an in vitro experiment using a 33% glycerin solution. The prototype RIAFBP achieved a maximum pump outflow of 8.5 L/min against a pump head of 100 mm Hg at a rotational speed of 12 000 rpm. The miniature RIAFBP achieved 7 L/min against a pump head of 70 mm Hg at a rotational speed of 21 600 rpm. In conclusion, the miniature RIAFBP has enough pump performance to realize the trans-valve axial VAD.

Ocular Surface and Tear Film Characteristics in a Sclerodermatous Chronic Graft-Versus-Host Disease Mouse Model.

PURPOSE: To report the characteristics of the ocular surface in a previously established sclerodermatous chronic graft-versus-host disease (cGVHD) mouse model. METHODS: The ocular surface features and tear film parameters of the mouse model were assessed by histopathology, immunohistochemistry, electron microscopy, quantitative polymerase chain reaction, and flow cytometry. RESULTS: The mice exhibited loss of body weight and decreased tear secretion (P < 0.001), mimicking the clinical features of patients with cGVHD. Ocular examination demonstrated significant corneal epithelial staining, conjunctival (P < 0.001), and eyelid (P = 0.015) fibrosis compared with the control mice. The density of both goblet cells (P = 0.043) and microvilli was lower (P < 0.001), and the microvilli were shorter (P = 0.007) in the conjunctiva of cGVHD mice than those of the controls. The immunohistochemical studies demonstrated greater expression of CD45, CD4, and CD8 cells in the conjunctiva and eyelid tissues compared with the controls (P < 0.05 for all). In addition, reduced Forkhead box P3 (Foxp3)+ cells were found in both the peripheral blood (P < 0.001) and conjunctiva (P = 0.042) of cGVHD mice compared with the controls. CONCLUSIONS: The constellation of these findings suggests that the sclerodermatous cGVHD mouse model well recapitulates ocular manifestations of cGVHD in humans. This model can be used to study the mechanisms involved in the pathogenesis and treatment of chronic ocular graft-versus-host disease.

Measurement of hemodynamic changes with the axial flow blood pump installed in descending aorta.

We have developed various axial flow blood pumps to realize the concept of the Valvo pump, and we have studied hemodynamic changes under cardiac assistance using an axial flow blood pump in series with the natural heart. In this study, we measured hemodynamic changes of not only systemic circulation but also cerebral circulation and coronary circulation under cardiac support using our latest axial flow blood pump placed in the descending aorta in an acute animal experiment. The axial flow blood pump was installed at the thoracic descending aorta through a left thoracotomy of a goat (43.8 kg, female). When the pump was on, the aortic pressure and aortic flow downstream of the pump increased with preservation of pulsatilities. The pressure drop upstream of the pump caused reduction of afterload pressure, and it may lead to reduction of left ventricular wall stress. However, cerebral blood flow and coronary blood flow were decreased when the pump was on. The axial flow blood pump enables more effective blood perfusion into systemic circulation, but it has the potential risk of blood perfusion disturbance into cerebral circulation and coronary circulation. The results indicate that the position before the coronary ostia might be suitable for implantation of the axial flow blood pump in series with the natural heart to avoid blood perfusion disturbances.

Application of low-vacuum scanning electron microscopy in cytopathology: To what extent can adenocarcinoma be morphologically distinguished from squamous cell carcinoma in lung cancer?

BACKGROUND: Anticancer drugs for targeted molecular therapies have been applied to the treatment of lung cancer. Since the effects of medicine for adenocarcinoma (ADC) or squamous cell carcinoma (SQCC) differ, the ability to discriminate these lesions is important. In the present study, we examined whether ADC and SQCC could be distinguished using low-vacuum scanning electron microscopy (LVSEM) to examine cytopathological specimens. METHODS: Thirty-seven cases of bronchoscopic samples were retrospectively examined using LVSEM on the surface structures of the cancer cells. RESULTS: Among the Pap-stained slides, 81.1% of the cases could be distinguished: 96.2% of the ADC cases were distinguishable, and 45.5% of the SQCC cases were distinguishable. Among the significant findings for ADC using LVSEM, a spherical shape (73.1%), long filaments (65.4%), dense filaments (80.8%), and depression (57.7%) were seen. Among the significant findings for SQCC as observed using LVSEM, however, a flat shape (81.8%), sparse filaments (72.7%), and non-filament (81.8%) were seen. The overall accuracy of diagnosis using LVSEM was 83.8%: 80.8% for ADC and 90.9% for SQCC. The accuracy of a combination of Papstained slides and LVSEM was 97.3%. CONCLUSIONS: The LVSEM method is useful as an ancillary examination for cytopathology after the classification of Pap-stained slides.

In Vivo FRET Imaging of Tumor Endothelial Cells Highlights a Role of Low PKA Activity in Vascular Hyperpermeability.

Vascular hyperpermeability is a pathological hallmark of cancer. Previous in vitro studies have elucidated roles of various signaling molecules in vascular hyperpermeability; however, the activities of such signaling molecules have not been examined in live tumor tissues for technical reasons. Here, by in vivo two-photon excitation microscopy with transgenic mice expressing biosensors based on Förster resonance energy transfer, we examined the activity of protein kinase A (PKA), which maintains endothelial barrier function. The level of PKA activity was significantly lower in the intratumoral endothelial cells than the subcutaneous endothelial cells. PKA activation with a cAMP analogue alleviated the tumor vascular hyperpermeability, suggesting that the low PKA activity in the endothelial cells may be responsible for the tumor-tissue hyperpermeability. Because the vascular endothelial growth factor (VEGF) receptor is a canonical inducer of vascular hyperpermeability and a molecular target of anticancer drugs, we examined the causality between VEGF receptor activity and the PKA activity. Motesanib, a kinase inhibitor for VEGF receptor, activated tumor endothelial PKA and reduced the vascular permeability in the tumor. Conversely, subcutaneous injection of VEGF decreased endothelial PKA activity and induced hyperpermeability of subcutaneous blood vessels. Notably, in cultured human umbilical vascular endothelial cells, VEGF activated PKA rather than decreasing its activity, highlighting the remarkable difference between its actions in vitro and in vivo These data suggested that the VEGF receptor signaling pathway increases vascular permeability, at least in part, by reducing endothelial PKA activity in the live tumor tissue. Cancer Res; 76(18); 5266-76. ©2016 AACR.

Application of low vacuum scanning electron microscopy for Papanicolaou-stained slides for cytopathology examinations.

Papanicolaou (Pap)-stained slides are usually observed using a transmitted light microscope for cytopathology. However, progress in pathological examinations has created a need for new diagnostic tools, because cytopathological preparations do not allow additional examinations without a loss of specimen, unlike histopathology. Low-vacuum scanning electron microscopy (LVSEM) can reveal the surface topography at an ultrastructual resolution without metal coating. The aim of this study was to determine the conditions required for observing Pap-stained slides of oral smears using LVSEM without any loss of specimen and to reexamine the same slides again using light microscopy, while preserving the cytopathological information.

Initial Acute Animal Experiment Using a New Miniature Axial Flow Pump in Series With the Natural Heart.

We have advocated an axial flow blood pump called "valvo pump" that is implanted at the aortic valve position, and we have developed axial flow blood pumps to realize the concept of the valvo pump. The latest model of the axial flow blood pump mainly consists of a stator, a directly driven impeller, and a hydrodynamic bearing. The axial flow blood pump has a diameter of 33 mm and length of 74 mm, and the length of anatomical occupation is 33 mm. The axial flow blood pump is anastomosed to the aorta with polytetrafluoroethylene (PTFE) cuffs worn on the inflow and outflow ports. Dp-Q curves of the axial flow blood pump are flatter than those of ordinary axial flow pumps, and pump outflow of 5 L/min was obtained against a pressure difference of 50 mm Hg at a rotational speed of 9000 rpm in vitro. The axial flow blood pump was installed in a goat by anastomosing with the thoracic descending aorta using PTFE cuffs, and it was rotated at a rotational speed of 8000 rpm. Unlike in case of the ventricular assistance in parallel with the natural heart, pulsatilities of aortic pressure and aortic flow were preserved even when the pump was on, and mean aortic flow was increased by 1.5 L/min with increase in mean aortic pressure of 30 mm Hg. In conclusion, circulatory assistance in series with the natural heart using the axial flow blood pump was able to improve hemodynamic pulsatility, and it would contribute to improvement of end-organ circulation. .

Development of anti-HER2 fragment antibody conjugated to iron oxide nanoparticles for in vivo HER2-targeted photoacoustic tumor imaging.

Photoacoustic (PA) imaging is a promising imaging modality that provides biomedical information with high sensitivity and resolution. Iron oxide nanoparticles (IONPs) have been regarded as remarkable PA contrast agents because of their low toxicity and biodegradable properties. However, IONP delivery is restricted by its modest leakage and retention in tumors. In this study, we designed IONPs (20nm, 50nm, and 100nm) conjugated with anti-HER2 moieties [whole IgG, single-chain fragment variable (scFv), and peptide] for HER2-targeted PA tumor imaging. The binding affinity, cellular uptake, and in vivo biodistribution were examined. We propose 20-nm anti-HER2 scFv-conjugated IONPs (SNP20) as a novel PA contrast agent. SNP20 demonstrated high affinity and specific binding to HER2-expressing cells; it selectively visualized HER2-positive tumors in PA imaging studies. These data indicate that SNP20 is a potential PA contrast agent for imaging of HER2-expressing tumors. FROM THE CLINICAL EDITOR: Iron oxide nanoparticles have been demonstrated to be good contrast agents for tumor imaging. They may also be useful in photoacoustic (PA) imaging, which can provide high sensitivity data and image resolution. The authors here coupled iron oxide nanoparticles with anti-HER2 antibody fragment and showed significant retention of these nanoparticles in tumors. This combination may provide another option for enhanced imaging of tumors.

Near-infrared dye-conjugated amphiphilic hyaluronic acid derivatives as a dual contrast agent for in vivo optical and photoacoustic tumor imaging.

Amphiphilic hyaluronic acid (HA) derivatives bearing hydrophobic indocyanine green dye derivatives and hydrophilic poly(ethylene glycol) were synthesized through the use of condensation and copper-catalyzed click cyclization reactions. The amphiphilic HA derivatives dissolved in water and formed self-assemblies in which the near-infrared dyes were tightly packed and arranged to form dimers or H-aggregates. By irradiating an aqueous solution of HA derivatives with near-infrared light, photoacoustic signals were detected along with fluorescence emission. Self-assemblies consisting of HA derivatives could smoothly accumulate in tumor tissues by passive tumor targeting. By utilizing HA derivatives as a contrast agent, tumor sites were clearly visualized by optical imaging as well as by photoacoustic tomography.

Passive magnetic bearing in the 3rd generation miniature axial flow pump-the valvo pump 2.

The new miniature axial flow pump (valvo pump 2) that is installed at the base of the ascending aorta consists of a six-phase stator, an impeller in which four neodymium magnets are incorporated, and passive magnetic bearings that suspend the impeller for axial levitation. The impeller is sustained by hydrodynamic force between the blade tip of the impeller and the inner housing of the stator. The passive magnetic bearing consists of a ring neodymium magnet and a columnar neodymium magnet. The ring neodymium magnet is set in the stationary side and the columnar neodymium magnet is incorporated in the impeller shaft. Both neodymium magnets are coaxially mounted, and the anterior and posterior passive magnetic bearings suspend the impeller by repulsion force against the hydrodynamic force that acts to move the impeller in the inflow port direction. The passive magnetic bearing was evaluated by a tensile test, and the levitation force of 8.5 N and stiffness of 2.45 N/mm was obtained. Performance of the axial flow pump was evaluated by an in vitro experiment. The passive magnetic bearing showed sufficient levitation capacity to suspend the impeller in an axial direction. In conclusion, the passive magnetic bearing is promising to be one of levitation technology for the third-generation axial flow blood pump.

A magnetic fluid seal for rotary blood pumps: image and computational analyses of behaviors of magnetic fluids.

A magnetic fluid (MF) seal has excellent durability. The performance of an MF seal, however, has been reported to decrease in liquids (several days). We have developed an MF seal that has a shield mechanism. The seal was perfect for 275 days in water. To investigate the effect of a shield, behaviors of MFs in a seal in water were studied both experimentally and computationally. (a) Two kinds of MF seals, one with a shield and one without a shield, were installed in a centrifugal pump. Behaviors of MFs in the seals in water were observed with a video camera and high-speed microscope. In the seal without a shield, the surface of the water in the seal waved and the turbulent flow affected behaviors of the MFs. In contrast, MFs rotated stably in the seal with a shield in water even at high rotational speeds. (b) Computational fluid dynamics analysis revealed that a stationary secondary flow pattern in the seal and small velocity difference between magnetic fluid and water at the interface. These MF behaviors prolonged the life of an MF seal in water.

A magnetic fluid seal for rotary blood pumps: Behaviors of magnetic fluids in a magnetic fluid seal.

A magnetic fluid (MF) seal has excellent durability. The performance of an MF seal, however, has been reported to decrease in liquids (several days). We have developed an MF seal that has a shield mechanism. The seal was perfect for 275 days in water. To investigate the effect of a shield, behaviors of MFs in a seal in water were studied both experimentally and computationally. (a) Two kinds of MF seals, one with a shield and one without a shield, were installed in a centrifugal pump. Behaviors of MFs in the seals in water were observed with a video camera and high-speed microscope. In the seal without a shield, the surface of the water in the seal waved and the turbulent flow affected behaviors of the MFs. In contrast, MFs rotated stably in the seal with a shield in water even at high rotational speeds. (b) Computational fluid dynamics analysis revealed that a stationary secondary flow pattern in the seal and small velocity difference between magnetic fluid and water at the interface. These MF behaviors prolonged the life of an MF seal in water.

Analysis of flow within a left ventricle model fully assisted with continuous flow through the aortic valve.

Blood compatibility of a ventricular assist device (VAD) depends on the dynamics of blood flow. The focus in most previous studies was on blood flow in the VAD. However, the tip shape and position of the VAD inflow cannula influence the dynamics of intraventricular blood flow and thus thrombus formation in the ventricle. In this study, blood flow in the left ventricle (LV) under support with a catheter-type continuous flow blood pump was investigated. The flow field was analyzed both numerically and experimentally to investigate the effects of catheter tip shape and its insertion depth on intraventricular flow patterns. A computational model of the LV cavity with a simplified shape was constructed using computer-aided design software. Models of catheters with three different tip shapes were constructed and each was integrated to the LV model. In addition, three variations of insertion depth were prepared for all models. The fully supported intraventricular flow field was calculated by computational fluid dynamics (CFD). A transparent LV model made of silicone was also fabricated to analyze the intraventricular flow field by the particle image velocimetry technique. A mock circulation loop was constructed and water containing tracer particles was circulated in the loop. The motion of particles in the LV model was recorded with a digital high-speed video camera and analyzed to reveal the flow field. The results of numerical and experimental analyses indicated the formation of two large vortices in the bisector plane of the mitral and aortic valve planes. The shape and positioning of the catheter tip affected the flow distribution in the LV, and some of these combinations elongated the upper vortex toward the ventricular apex. Assessment based on average wall shear stress on the LV wall indicated that the flow distribution improved the washout effect. The flow patterns obtained from flow visualization coincided with those calculated by CFD analysis. Through these comparisons, the numerical analysis was validated. In conclusion, results of these numerical and experimental analyses of flow field in the LV cavity provide useful information when designing catheter-type VADs.

A hydrodynamically suspended, magnetically sealed mechanically noncontact axial flow blood pump: design of a hydrodynamic bearing.

To overcome the drive shaft seal and bearing problem in rotary blood pumps, a hydrodynamic bearing, a magnetic fluid seal, and a brushless direct current (DC) motor were employed in an axial flow pump. This enabled contact-free rotation of the impeller without material wear. The axial flow pump consisted of a brushless DC motor, an impeller, and a guide vane. The motor rotor was directly connected to the impeller by a motor shaft. A hydrodynamic bearing was installed on the motor shaft. The motor and the hydrodynamic bearing were housed in a cylindrical casing and were waterproofed by a magnetic fluid seal, a mechanically noncontact seal. Impeller shaft displacement was measured using a laser sensor. Axial and radial displacements of the shaft were only a few micrometers for motor speed up to 8500 rpm. The shaft did not make contact with the bearing housing. A flow of 5 L/min was obtained at 8000 rpm at a pressure difference of 100 mm Hg. In conclusion, the axial flow blood pump consisting of a hydrodynamic bearing, a magnetic fluid seal, and a brushless DC motor provided contact-free rotation of the impeller without material wear.