Sensitivity of Post-TAVR Hemodynamics to the Distal Aortic Arch Anatomy: A High-Fidelity CFD Study

PURPOSE

Patient-specific simulations of transcatheter aortic valve (TAV) using computational fluid dynamics (CFD) often rely on assumptions regarding proximal and distal anatomy due to the limited availability of high-resolution imaging away from the TAV site and the primary research focus being near the TAV. However, the influence of these anatomical assumptions on computational efficiency and resulting flow characteristics remains uncertain. This study aimed to investigate the impact of different distal aortic arch anatomies-some of them commonly used in literature-on flow and hemodynamics in the vicinity of the TAV using large eddy simulations (LES).

METHODS

Three aortic root anatomical configurations with four representative distal aortic arch types were considered in this study. The arch types included a 90-degree bend, an idealized distal aortic arch anatomy, a clipped version of the idealized distal aortic arch, and an anatomy extruded along the normal of segmented anatomical boundary. Hemodynamic parameters both instantaneous and time-averaged such as Wall Shear Stress (WSS), and Oscillatory Shear Index (OSI) were derived and compared from high-fidelity CFD data.

RESULTS

While there were minor differences in flow and hemodynamics across the configurations examined, they were generally not significant within our region of interest i.e., the aortic root. The choice of extension type had a modest impact on TAV hemodynamics, especially in the vicinity of the TAV with variations observed in local flow patterns and parameters near the TAV. However, these differences were not substantial enough to cause significant deviations in the overall flow and hemodynamic characteristics.

CONCLUSIONS

The results suggest that under the given configuration and boundary conditions, the type of outflow extension had a modest impact on hemodynamics proximal to the TAV. The findings contribute to a better understanding of flow dynamics in TAV configurations, providing insights for future studies in TAV-related experiments as well as numerical simulations. Additionally, they help mitigate the uncertainties associated with patient-specific geometries, offering increased flexibility in computational modeling.

Determinants of outflow rate through the ureteral access sheath during flexible ureteroscopy: an experimental in vivo study in an anesthetized porcine model

To evaluate the effect of different ureteroscope positions, saline pumping frequency, laser fiber diameter and ureteral access sheath (UAS) on outflow rate during flexible ureteroscopy (fURS). This study was performed in an anesthetized porcine model. The fURS setup included a manual pumping system, a 9.5 Fr single used-digital flexible ureteroscope and a ureteral access sheath (UAS). Outflow was collected and measured from the UAS during 1 min in all experimental settings. The evaluated variables were the position of the ureteroscope, the pumping frequency (2 s, 3 s or 5 s), the diameter of the used UAS (12/14 Fr or 14/16 Fr) and laser fiber (200 μm or a 272 μm). Ureteroscope position in the lower calyx was associated with significantly lower outflow rate (p < 0.05). The use of the 14/16 Fr UAS resulted in improved flow in the renal pelvis and upper calyx (p < 0.05) but not in the lower calyx. The use of a 200 μm laser fiber only improved flow in the upper calyx and when a 14/16 Fr UAS was being used. Pumping frequency did not show a significant correlation with outflow rate. The ureteroscope positioning and UAS size were important determinants of outflow rate through the UAS during fURS, while laser fiber diameter had a limited effect. In the lower calyx the outflow was minimal and was not improved by using a larger UAS.

Back table Preparation of the Right Lobe Live Donor Liver Allograft: A Crucial Part of the Adult Live Donor Liver Transplant Procedure

INTRODUCTION

We aimed to describe our procedure for vascular reconstruction and back table bench preparation for the right lobe live donor allograft. Live donor liver transplantation (LDLT) remains an important option for the expansion of the donor pool. The procedure has been widely used, and its success is dependent on a technically perfect operation with appropriate inflow and outflow of the allograft. Adequate preparation of the right lobe (RL) allograft prior to implantation remains a vital part of the procedure.

METHODS

Our technique of back table vascular reconstruction of the RL allograft has been performed using a hepatic vein patch venoplasty, inferior hepatic vein inclusion, portal vein reconstruction, and segment V and VIII reconstruction for all of our LDLTs.

RESULTS

Between March 2009 and January 2020, 321 consecutive adult LDLTs were performed and underwent back table reconstruction with the techniques described. During that time period, no patients had hepatic insufficiency. There was a single thrombosis of a superior mesenteric vein (SMV) to PV jump conduit.

CONCLUSIONS

Our technique of back table reconstruction of the LDLT right lobe graft remains a crucial part of the operative procedure. Our experience with RL grafts without middle hepatic vein (MHV) and our systematic approach for inflow and outflow reconstruction has yielded excellent results with no technical outflow issues and minimal inflow complications.

Spatio-temporal variations in water quality of a river-lake system during restoration treatments

To fill the knowledge gap about the functioning of the lake-river system subjected to restoration treatments, two tributaries, a shallow, restored lake and its outflow, were examined. The quality of water inflows, lake and outflow was compared before (BR), during sustainable (SR, deep water aeration, phosphorus inactivation and biomanipulation for 3 years) and limited lake restoration (LR, only aeration for 2 years). Physico-chemical parameters were analysed monthly at five stations. The nutrient concentrations at the inflows decreased over the years due to the improvement of water and sewage management in the catchment (in Mielcuch from 18.0 to 8.0 mgN L^-1 and 1.0 to 0.6 mgP L^-1). The decline at the outflow was the result of a better quality of water at the tributaries and SR in the lake. During LR, decrease of phosphorus concentration still occurred (0.11 mgP L^-1), but nitrogen concentration slightly increased (3.9 mgN L^-1). Although the outflowing waters still transported a high content of chlorophyll a and suspended solids during SR, their amount was lower (34.5 μg L^-1 and 17 mg L^-1, respectively) than that during BR and LR. During restoration, it is significant to monitor the water quality not only in the lake but also at the outflow. The slow deterioration of water quality at the outflow indicated that introducing changes in the applied restoration methods must be done carefully because the previously achieved effect may be lost. Hence, restoration of the upstream lake and good quality of its tributaries are of great importance for water bodies located downstream.

Cerebrospinal fluid may flow out from the brain through the frontal skull base and choroid plexus: a gold colloid and cadaverine injection study in mouse fetus

PURPOSE

It has been commonly accepted for a long time that the cerebrospinal fluid (CSF) drains into arachnoid granulations from the subarachnoid space to the dural venous sinus unidirectionally. However, recently, periventricular capillaries and lymphatic concepts have been introduced. The CSF moves along the perivascular space and drains into the capillary vessels or meningeal lymphatic tissues. CSF is involved in removing brain waste out of the brain. In this study, we investigated the outflow mechanism of substances in the CSF from the brain.

METHODS

We investigated the movement of CSF by injection of gold colloid conjugates (2, 40, and 200 nm) into the lateral ventricles of mouse fetuses and evaluated the deposition by silver stain with tissue transparency and electron microcopy. Cadaverine was also injected into the lateral ventricle to determine its movement tract.

RESULTS

The gold particle deposition was mainly observed in the frontal skull base. Electron microscopic study showed that the gold particle deposition was observed on the choroid plexus and ependyma in the lateral ventricle and also red blood cells in the heart and liver. Two-nanometer particles were exclusively observed in the liver. Cadaverine injection study demonstrated that cadaverine was observed at the extracranial frontal skull base, choroid plexus, ependymal surface, and perivascular area in the brain white matter.

CONCLUSION

The particles in the CSF were shown to move from the brain to the frontal skull base and also into the blood stream through the choroid plexus in the fetus. The outflow of particles in the CSF may be regulated by molecular size. This new information will contribute to the prevention of brain degeneration due to brain waste deposition.

Prosthetic versus native artery inflow for infrainguinal bypass

BACKGROUND

Infrainguinal bypass performed after previous prosthetic inflow reconstruction offers a choice of where to perform the proximal anastomosis. The hood of a previous inflow bypass might be technically easier to isolate during reoperative surgery. However, the more distal native artery might offer better patency to the outflow revascularization. The purpose of the present study was to compare the outcomes of infrainguinal bypass using the hood of a previous inflow bypass vs the native artery as the inflow source.

METHODS

A single vascular group's database was queried for all cases of infrainguinal bypass performed after previous prosthetic inflow bypass to a femoral artery from January 2006 to December 2016. The demographics, indications, operative details, and long-term results were recorded and analyzed. Two groups were compared stratified by the location of the proximal anastomosis for the distal bypass. In one group, the inflow source for the distal bypass was from the hood of a previous inflow graft (prosthetic). In the second group, the distal native arterial tree was used as the inflow source. A subset analysis of the patency of the distal bypass was also performed between the two groups for those in which the previous inflow reconstruction had become occluded. Patency was calculated using the Kaplan-Meier method.

RESULTS

A total of 197 patients had undergone infrainguinal bypass after previous inflow bypass from 2006 to 2016. Of the 197 procedures, 59 (30%) had used the hood of the previous bypass as the inflow source (prosthetic group) and 138 (70%) had used the native artery distal to the hood of the inflow bypass as the inflow source (native group). The indications were similar between the two groups. The two groups had a similar proportion of men and a similar incidence of hypertension, hyperlipidemia, coronary artery disease, tobacco use, and renal disease. The previous inflow procedures were also similar between the two groups. The native artery used for the inflow source in the native group was the profunda femoris in 80 (58%), common femoral artery in 51 (37%), and superficial femoral artery in 7 (5.1%). Patency was significantly greater for the native group at 1 year (91% vs 75%; P = .0221). Also, the patency after inflow bypass occlusion significantly favored the native group at 1 year (87% vs 40%; P = .0035).

CONCLUSIONS

Infrainguinal bypass performed after previous ipsilateral inflow bypass offers the option of using the hood of the bypass or a native artery as the inflow source. The present study demonstrated greater patency rates when using the distal native artery as the inflow source. The native artery option also offered continued patency when the inflow bypass occluded.

Dynamic left ventricular outflow tract gradient resulting from Takotsubo cardiomyopathy ameliorated by intra-aortic balloon pump counterpulsation: a case report

BACKGROUND

Takotsubo cardiomyopathy is a variant of acute coronary syndrome with characteristic acute left ventricular apical ballooning. Uncommonly, there can be associated left ventricular outflow tract (LVOT) obstruction causing cardiogenic shock refractory to inotropic support. The use of afterload-reducing mechanical support such as intra-aortic balloon pump (IABP) counterpulsation is not routinely employed in instances of this kind.

CASE SUMMARY

In our case report, we describe a 66-year-old female with acute Takotsubo cardiomyopathy and associated LVOT obstruction which failed to respond to high-dose dobutamine and whose clinical trajectory was worsened by fast atrial fibrillation with rapid ventricular response. Within 24 h of admission, the patient had an IABP placed which rapidly improved her haemodynamics. Two days later, IABP was removed and within 6 days of admission, apical ballooning and LVOT obstruction had fully recovered.

CONCLUSION

We recommend early use of mechanical support with IABP counterpulsation to expedite recovery in patients with acute Takotsubo cardiomyopathy with associated LVOT obstruction.

Assessment of the effects of human activity and natural condition on the outflow of Syr Darya River: A stepwise-cluster factorial analysis method

Water scarcity causes a series of eco-environmental problems, such as land salinization, biodiversity reduction and food crisis, which seriously restricts the sustainable development of the Aral Sea basin. In this study, a stepwise-cluster factorial analysis (SCFA) approach is proposed for assessing the effects of natural condition and human activity on the outflow of Syr Darya River (abbreviated as OSR) that has significant effects on the eco-environmental restoration of the Aral Sea. SCFA coupled stepwise cluster analysis and factorial analysis cannot only reflect the variability of outflow, but also identify the driving factors quantitatively. The results disclose that, in 1960-1991, the dominant factors (affecting the OSR) are upstream inflow (25.77%) > agricultural water use of Uzbekistan (7.21%) > industrial water use of Uzbekistan (4.53%) > agricultural water use of Kazakhstan (3.81%) > Precipitation (3.66%); interactions between upstream inflow and agricultural water use of Uzbekistan, Kazakhstan and Tajikistan and interactions between reservoir and evapotranspiration have the significant effects on the OSR. Results also indicate that, in 1992-2015, the dominant factors that affect the OSR are agricultural water use of Uzbekistan (23.31%) > agricultural water use of Kazakhstan (22.15%) > industrial water use of Uzbekistan (8.31%) > domestic water use of Kazakhstan (4.68%) > agricultural water use of Tajikistan (4.54%) > domestic water use of Uzbekistan (4.41%); the interactions between industrial water use and agricultural water use of Uzbekistan, Kazakhstan and Tajikistan and the interactions between reservoir and upstream inflow have the pivotal effects on OSR. In the future, when the agricultural water use of the basin decrease as 4% and the industry water use of Uzbekistan decrease as 2%, the OSR may recover to the middle level of 1970s. The results help identify the major factors affecting the outflow of Syr Darya River as well as seek an effective approach to restore the eco-environment of Aral Sea basin.

Spatio-temporal variability of near-surface air pollutants at four distinct geographical locations in Andhra Pradesh State of India

India is highly vulnerable to air pollution in the recent decade, especially urban areas with rapidly growing urbanisation and industrialisation. Here, we present spatio-temporal variability of air pollutants at four distinct locations in Andhra Pradesh State of India. The mean concentrations of air pollutants were generally higher at Visakhapatnam site than Amaravati, Rajahmundry, and Tirumala sites. The mean concentration of particulate matter of diameter less than 2.5 μm (PM_2.5) was higher at Visakhapatnam site (48.5 ± 27.3 μg/m³) by a factor of about 1.6 as compared to Tirumala site (29.5 ± 17 μg/m³). On the contrary, the mean concentrations of oxides of nitrogen (NO_x, 70.3 ± 28.1 μg/m³) and ammonia (NH₃, 20.5 ± 9.2 μg/m³) were higher at Tirumala by a factor of about 1.4 and 1.9, respectively, as compared to Visakhapatnam (49 ± 5 μg/m³ and 10.7 ± 5 μg/m³). This was mainly attributed to higher vehicular emissions at Tirumala site. PM_2.5, carbon monoxide (CO), NOx, and sulfur dioxide (SO₂) showed distinct seasonal variation, with higher concentrations in winter followed by post-monsoon, pre-monsoon and monsoon. The Concentration Weighted Trajectory analysis of PM_2.5 based on 5-days backward air mass trajectories showed that all sites experienced northeast air mass flow indicative of the outflow from Indo-Gangetic Plain, particularly in the post-monsoon and winter seasons. The Continuous Wavelet Transform analysis further showed that higher variations in PM_2.5 concentrations occurring at a regular interval from a week to 16 days at both Tirumala and Visakhapatnam sites, while weekly periods are dominant over Amaravati and Rajahmundry sites with 95% significance during post-monsoon and winter seasons. Overall, our results underline heterogeneity in air pollution emission sources and influx of pollutants from distant sources, which would be useful when formulating the policies and mitigation procedures for this region.

Outflow-Restricted Developmental Venous Anomaly Masquerading as a Tumefactive Lesion on Imaging

BACKGROUND

Developmental venous anomalies (DVA) are rarely symptomatic. We report an unusual case of outflow-restricted DVA presenting with seizures.

CASE DESCRIPTION

Expansile signal changes due to a hemorrhagic venous infarction in the draining territory of collector vein of DVA simulated a neoplasm. Follow-up imaging showed regression of mass effect and asymptomatic thrombosis of another distant vein. Investigation for prothrombotic conditions returned negative.

CONCLUSIONS

Atypical imaging findings in the draining territory of DVA ought to raise the possibility of outflow restriction.

Age-related changes in eye morphology and aqueous humor dynamics in DBA/2J mice using contrast-enhanced ocular MRI

PURPOSE

Here, we are testing the hypothesis that dynamic contrast enhanced MRI (DCE-MRI) is a useful approach for non-invasively evaluating age-related changes in aqueous humor outflow and its contribution to elevated intraocular pressure in the DBA/2J model of pigmentary glaucoma.

METHODS

A rodent-specific 7 T MRI was used to assess eye anatomy (anterior chamber (AC) and vitreous body (VB) morphology, eye size, lens size) and aqueous humor dynamics (via intravenous administration of Gd-DTPA and Gd-BOPTA contrast agents) in C57BL/6 and DBA/2J mice at 3 and 9 months of age.

RESULTS

Gd-MRI was used to demonstrate an anterior solute pathway into the mouse AC. Topical latanoprost treatment in C57BL/6J mice reduced Gd-BOPTA accumulation in the AC. Age-related increases in AC area, AC depth and eye size were observed in DBA/2J mice compared to C57BL/6J mice. The rate of Gd-DTPA accumulation and peak Gd-DTPA intensity was lowest in 9-month old DBA/2J mice compared to 3-month old DBA/2J mice and C57BL/6J mice at both ages. Leakage of Gd-DTPA posteriorly into the VB was also observed in 9-month old DBA/2J mice.

CONCLUSIONS

These studies support the idea that age-related changes in aqueous humor outflow contribute to elevated intraocular pressure (IOP) in the DBA/2J model of pigmentary glaucoma. Gd-MRI is a valuable tool for better understanding of mechanisms and dynamics of aqueous humor circulation in normal and glaucomatous mouse eyes or following topical administration of medicines to reduce IOP.

Segment 5 parenchymal sparing in extended left hepatectomy with respect to venous outflow-is it a feasible procedure?

BACKGROUND

Segment 5 (S5) sparing liver resection for cases that require an anatomic left trisectionectomy has not been reported yet. The authors intended to verify the outcome of S5-sparing extended left hepatectomy (ELH) in respect to venous outflow.

METHODS

All adult patients who underwent S5-sparing ELH between 2012 and 2017 in authors' institute have been enrolled in this study. S5-sparring ELH was defined as resection of S2, S3, S4, and S8 with or without S1. The surgery planning was based on the images from two-dimensional triphasic computed tomography and/or magnetic resonance imaging. A three-dimensional image reconstruction and liver volumetric study were performed retrospectively.

RESULTS

Out of 177 cases of major hepatic resection, only seven non-hilar cholangiocarcinoma patients underwent ELH during the study period. S5-sparing ELH was performed to five patients, in whom no tumor involvement in S5. The venous outflow of S5 has been maintained intraoperative, and S5 congestion has not been observed in all patients. Tailored management of the S5 venous outflow ensured an increase in functional remnant liver volume by 52.8% (range, 25.6 to 66.9%) by sparing of S5. A negative resection margin was achieved in all patients. One patient had postoperative bile leak requiring reoperation. No posthepatectomy liver failure (PHLF) has been observed.

CONCLUSION

S5-sparing ELH is technically feasible. Under the tailored management of S5 venous outflow, the functional future liver remnant can be increased. Further studies with larger sample size are needed to evaluate which circumstances the liver segment 5 could be preserved without venous reconstruction during the left extended hepatectomy.

Fluid outflow in the rat spinal cord: the role of perivascular and paravascular pathways

BACKGROUND

Cerebrospinal fluid (CSF) is thought to flow into the brain via perivascular spaces around arteries, where it mixes with interstitial fluid. The precise details concerning fluid outflow remain controversial. Although fluid dynamics have been studied in the brain, little is known about spinal cord fluid inflow and outflow. Understanding the normal fluid physiology of the spinal cord may give insight into the pathogenesis of spinal cord oedema and CSF disorders such as syringomyelia. We therefore aimed to determine the fluid outflow pathways in the rat spinal cord.

METHODS

A fluorescent tracer, Alexa-Fluor^®-647 Ovalbumin, was injected into the extracellular space of either the cervicothoracic lateral white matter or the grey matter in twenty-two Sprague-Dawley rats over 250 s. The rats were sacrificed at 20 or 60 min post injection. Spinal cord segments were sectioned and labelled with vascular antibodies for immunohistochemistry.

RESULTS

Fluorescent tracer was distributed over two to three spinal levels adjacent to the injection site. In grey matter injections, tracer spread radially into the white matter. In white matter injections, tracer was confined to and redistributed along the longitudinal axonal fibres. Tracer was conducted towards the pial and ependymal surfaces along vascular structures. There was accumulation of tracer around the adventitia of the intramedullary arteries, veins and capillaries, as well as the extramedullary vessels. A distinct layer of tracer was deposited in the internal basement membrane of the tunica media of arteries. In half the grey matter injections, tracer was detected in the central canal.

CONCLUSIONS

These results suggest that in the spinal cord interstitial fluid movement is modulated by tissue diffusivity of grey and white matter. The central canal, and the compartments around or within blood vessels appear to be dominant pathways for fluid drainage in these experiments. There may be regional variations in fluid outflow capacity due to vascular and other anatomical differences between the grey and white matter.

Future water availability in the largest freshwater Mediterranean lake is at great risk as evidenced from simulations with the SWAT model

Inter- and intra-annual water level fluctuations and changes in water flow regime are intrinsic characteristics of Mediterranean lakes. Additionally, considering climate change projections for the water-limited Mediterranean region, increased air temperatures and decreased precipitation are anticipated, leading to dramatic declines in lake water levels as well as severe water scarcity problems. The study site, Lake Beyşehir, the largest freshwater lake in the Mediterranean basin, is - like other Mediterranean lakes - threatened by climatic changes and over-abstraction of water for irrigated crop farming. Therefore, implementation of strict water level management policies is required. In this study, an integrated modeling approach was used to predict the future water levels of Lake Beyşehir in response to potential future changes in climate and land use. Water level estimation was performed by linking the catchment model Soil and Water Assessment Tool (SWAT) with a Support Vector Regression model (ε-SVR). The projected increase in temperature and decrease in precipitation based on the climate change models led to an enhanced potential evapotranspiration and reduced total runoff. On the other hand, the effects of various land use scenarios within the catchment appeared to be comparatively insignificant. According to the ε-SVR model results, changes in hydrological processes caused a water level reduction for all scenarios. Moreover, the MPI-ESM-MR General Circulation Model outputs produced the most dramatic results by predicting that Lake Beyşehir may dry out by the 2040s with the current outflow regime. The results indicate that shallow Mediterranean lakes may face a severe risk of drying out and losing their ecosystem values in the near future if the current intensity of water abstraction is not reduced. In addition, the results also demonstrate that outflow management and sustainable use of water sources are vital to sustain lake ecosystems in water-limited regions.

Blebs, Barriers, and Bagpipes: Why is It so Hard?

Doug Johnson was a clinician-scientist who made great contributions to the understanding of outflow from the eye. This lecture is in honour of Doug and explores the author's understanding of outflow in the surgical context.

HOW TO CITE THIS ARTICLE

Coote M. Blebs, Barriers, and Bagpipes: Why is It so Hard? J Curr Glaucoma Pract 2016; 10(3):79-84.

Effects of clamping procedures on central venous pressure during liver resection

BACKGROUND

Various clamping procedures are used to decrease bleeding during liver resections but their effect on central venous pressure (CVP) remains unclear. The aim of this study was to assess the variations of the CVP during two different clamping procedures.

METHODS

We retrospectively reviewed 29 patients (19 males, 10 females) who had Pringle maneuver (PM) and clamping of the inferior vena cava below the liver (IVCC) during major liver resections.

RESULTS

Mean decrease of the CVP after PM, IVCC, and PM+IVCC was 0.84 ± 1.37, 2.17 ± 2.13 and 3.17 ± 2.56 cmH20, respectively (P=0.02, P<0.0001 and P<0.0001, respectively). IVCC was more effective in inducing a decrease of the CVP than PM alone (P<0.05). The combination of both PM and IVCC induced the greatest decrease but not to a level of significance compared to IVCC alone (P=0.25).

CONCLUSION

IVCC remains the more efficient procedure to lower the CVP. However, although PM is commonly used to control vascular inflow within the liver its significant influence on the CVP could participate to the reduction of bleeding during liver resections.

Functional Anatomy of the Outflow Facilities

In order to understand the pathophysiology, select optimal therapeutic options for patients and provide clients with honest expectations for cases of canine glaucoma, clinicians should be familiar with a rational understanding of the functional anatomy of the ocular structures involved in this group of diseases. The topographical extension and the structural and humoral complexity of the regions involved with the production and the outflow of aqueous humor undergo numerous changes with aging and disease. Therefore, the anatomy relative to the fluid dynamics of aqueous has become a pivotal yet flexible concept to interpret the different phenotypes of glaucoma.

Reevaluation of Minamata Bay, 25 years after the dredging of mercury-polluted sediments

A detailed investigation of mercury concentrations in the bottom sediments of Minamata Bay was performed in May, 2012. A total of 691 sediment samples were obtained from 107 sampling points in the bay. The weighted average total mercury concentration and the total mass of mercury in the bottom sediments of Minamata Bay were estimated to be 2.3mg/kg dry weight basis and 3.4 tons, respectively. The average concentration of total mercury in the surface layer of the sediments was 3.0mg/kg dry weight basis, and the distribution pattern of total mercury concentrations in the surface layer was found to have changed little in comparison to results reported 25 years ago. In addition, based on the results of seawater monitoring in Minamata Bay from 2010 to 2012, the amounts of total mercury and methylmercury mobilized from sediments and dissolved in the water column were 0.7 and 0.1 kg/yr, respectively.

Walking through trabecular meshwork biology: Toward engineering design of outflow physiology

According to the World Health Organization, glaucoma remains the second leading cause of blindness in the world. Glaucoma belongs to a group of optic neuropathies that is characterized by chronic degeneration of the optic nerve along with its supporting glia and vasculature. Despite significant advances in the field, there is no available cure for glaucoma. The trabecular meshwork has been implicated as the primary site for regulation of intraocular pressure, the only known modifiable factor in glaucoma development. In this review, we describe the current models for glaucoma studies, primary culture, anterior eye segments, and animal studies and their limitations. These models, especially anterior eye segments and animal tissues, often require careful interpretation given the inter-species variation and are cumbersome and expensive. The lack of an available in vitro 3D model to study trabecular meshwork cells and detailed mechanisms of their regulation of intraocular pressure has limited progress in the field of glaucoma research. In this paper, we review the current status of knowledge of the trabecular meshwork and how the current advances in tissue engineering techniques might be applied in an effort to engineer a synthetic trabecular meshwork as a 3D in vitro model to further advance glaucoma research. In addition, we describe strategies for selection and design of biomaterials for scaffold fabrication as well as extracellular matrix components to mimic and support the trabecular architecture. We also discuss possible uses for a bioengineered trabecular meshwork for both developing a fundamental understanding of trabecular meshwork biology as well as high-throughput screening of glaucoma drugs.

Adult to adult living related liver transplantation: Where do we currently stand?

Adult to adult living donor liver transplantation (AALDLT) was first preformed in the United States in 1997. The procedure was rapidly integrated into clinical practice, but in 2002, possibly due to the first widely publicized donor death, the number of living liver donors plummeted. The number of donors has since reached a steady plateau far below its initial peak. In this review we evaluate the current climate of AALDLT. Specifically, we focus on several issues key to the success of AALDLT: determining the optimal indications for AALDLT, balancing graft size and donor safety, assuring adequate outflow, minimizing biliary complications, and maintaining ethical practices. We conclude by offering suggestions for the future of AALDLT in United States transplantation centers.