Towards a dynamic clamp for neurochemical modalities

The classic dynamic clamp technique uses a real-time electrical interface between living cells and neural simulations in order to investigate hypotheses about neural function and structure. One of the acknowledged drawbacks of that technique is the limited control of the cells' chemical microenvironment. In this manuscript, we use a novel combination of nanosensor and microfluidic technology and microfluidic and neural simulations to add sensing and control of chemical concentrations to the dynamic clamp technique. Specifically, we use a microfluidic lab-on-a-chip to generate distinct chemical concentration gradients (ions or neuromodulators), to register the concentrations with embedded nanosensors and use the processed signals as an input to simulations of a neural cell. The ultimate goal of this project is to close the loop and provide sensor signals to the microfluidic lab-on-a-chip to mimic the interaction of the simulated cell with other cells in its chemical environment.

Controlling porosity in lignin-derived nanoporous carbon for supercapacitor applications

Low-cost renewable lignin has been used as a precursor to produce porous carbons. However, to date, it has not been easy to obtain high surface area porous carbon without activation processes or templating agents. Here, we demonstrate that low molecular weight lignin yields highly porous carbon with more graphitization through direct carbonization without additional activation processes or templating agents. We found that molecular weight and oxygen consumption during carbonization are critical factors to obtain high surface area, graphitized porous carbons. This highly porous carbon from low-cost renewable lignin sources is a good candidate for supercapacitor electrode materials.

Controlling porosity in lignin-derived nanoporous carbon for supercapacitor applications

Low-cost renewable lignin has been used as a precursor to produce porous carbons. However, to date, it has not been easy to obtain high surface area porous carbon without activation processes or templating agents. Here, we demonstrate that low molecular weight lignin yields highly porous carbon with more graphitization through direct carbonization without additional activation processes or templating agents. We found that molecular weight and oxygen consumption during carbonization are critical factors to obtain high surface area, graphitized porous carbons. This highly porous carbon from low-cost renewable lignin sources is a good candidate for supercapacitor electrode materials.

Age and mortality after injury: is the association linear?

INTRODUCTION

Multiple studies have demonstrated a linear association between advancing age and mortality after injury. An inflection point, or an age at which outcomes begin to differ, has not been previously described. We hypothesized that the relationship between age and mortality after injury is non-linear and an inflection point exists.

METHODS

We performed a retrospective cohort analysis at our urban level I center from 2007 through 2009. All patients aged 65 years and older with the admission diagnosis of injury were included. Non-parametric logistic regression was used to identify the functional form between mortality and age. Multivariate logistic regression was utilized to explore the association between age and mortality. Age 65 years was used as the reference. Significance was defined as p < 0.05.

RESULTS

A total of 1,107 patients were included in the analysis. One-third required intensive care unit (ICU) admission and 48 % had traumatic brain injury. 229 patients (20.6 %) were 84 years of age or older. The overall mortality was 7.2 %. Our model indicates that mortality is a quadratic function of age. After controlling for confounders, age is associated with mortality with a regression coefficient of 1.08 for the linear term (p = 0.02) and a regression coefficient of -0.006 for the quadratic term (p = 0.03). The model identified 84.4 years of age as the inflection point at which mortality rates begin to decline.

CONCLUSIONS

The risk of death after injury varies linearly with age until 84 years. After 84 years of age, the mortality rates decline. These findings may reflect the varying severity of comorbidities and differences in baseline functional status in elderly trauma patients. Specifically, a proportion of our injured patient population less than 84 years old may be more frail, contributing to increased mortality after trauma, whereas a larger proportion of our injured patients over 84 years old, by virtue of reaching this advanced age, may, in fact, be less frail, contributing to less risk of death.

Visceral abdominal obesity measured by CT scan is associated with an increased risk of Barrett's oesophagus: a case-control study

OBJECTIVE

Abdominal obesity has been associated with increased risk of Barrett's oesophagus (BE) but the underlying mechanism is unclear. We examined the association between visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) and the risk of BE.

DESIGN

A case-control study among eligible patients scheduled for elective oesophagastroduodenoscopy (EGD) and in a sample of patients eligible for screening colonoscopy recruited at the primary care clinic. All cases with definitive BE and a random sample of controls without BE were invited to undergo standardised mid-abdomen non-contrast computerised axial tomography images, which were analysed by semiautomated image segmentation software. The effect of VAT and SAT surface areas and their ratio (VAT to SAT) on BE were analysed in logistic regression models.

RESULTS

A total of 173 BE cases, 343 colonoscopy controls and 172 endoscopy controls underwent study EGD and CT scan. Participants with BE were more than twice as likely to be in the highest tertile of VAT to SAT ratio (OR: 2.42 (1.51 to 3.88) and adjusted OR 1.47 (0.88 to 2.45)) than colonoscopy controls, especially for those long (≥3 cm) segment BE (3.42 (1.67 to 7.01) and adjusted OR 1.93 (0.92 to 4.09)) and for white men (adjusted OR 2.12 (1.15 to 3.90)). Adjustment for gastroesophageal reflux disease (GERD) symptoms and proton pump inhibitors (PPI) use attenuated this association, but there was a significant increase in BE risk even in the absence of GERD or PPI use.

CONCLUSIONS

Large amount of visceral abdominal fat relative to subcutaneous fat is associated with a significant increase in the risk of BE. GERD may mediate some but not all of this association.

Pediatric kidney transplantation in the developing world: challenges and solutions

The prevalence of pediatric RRT and transplantation are low in developing countries, 6-12 and <1 to 5 per million child population (pmcp), respectively. This is due to low GDP/capita of <$10 000, government expenditure on health of <2.6-9% of GDP and paucity of facilities. The reported incidence of pediatric CKD and ESRD is <1.0-8 and 3.4-35 pmcp, respectively. RRT and transplantation are offered mostly in private centers in cities where HD costs $20-100/session and transplants $10 000-20 000. High costs and long distance to centers results in treatment refusal in up to 35% of the cases. In this backdrop 75-85% of children with ESRD are disfranchised from RRT and transplantation. Our center initiated an integrated dialysis-transplant program funded by a community-government partnership where RRT and transplantation was provided "free of cost" with life long follow-up and medication. Access to free RRT at doorsteps and transplantation lead to societal acceptance of transplantation as the therapy of choice for ESRD. This enabled us to perform 475 pediatric transplants in 25 years with 1- and 5-year graft survival of 96% and 81%, respectively. Our model shows that pediatric transplantation is possible in developing countries when freely available and accessible to all who need it in the public sector.

The association between serological and dietary vitamin D levels and hepatitis C-related liver disease risk differs in African American and white males

BACKGROUND

Vitamin D may affect the severity of HCV-related liver disease.

AIM

To examine the association between serum vitamin D levels and advanced liver disease in a multiethnic US cohort of HCV patients, and account for dietary and supplemental intake.

METHODS

We measured serum 25-hydroxyvitamin D levels and used FibroSURE-ActiTest to assess hepatic pathology in a cohort of HCV-infected male veterans. We estimated and adjusted for daily intake of vitamin D from diet using a Dietary History Questionnaire, and dispensed prescriptions prior to study enrolment. We used race-stratified logistic regression analyses to evaluate the relationship between serum vitamin D levels and risk of advanced fibrosis (F3/F4-F4) and advanced inflammation (A2/A3-A3).

RESULTS

A total of 163 African American (AA) and 126 White non-Hispanics were studied. Overall, ~44% of AAs and 15% of Whites were vitamin D deficient (<12 ng/mL) or insufficient (12-19 ng/mL); 4% of AAs and 9% of White patients had an elevated level (>50 ng/mL). Among AAs, patients with elevated serum vitamin D levels had significantly higher odds of advanced fibrosis (OR = 12.91, P = 0.03) than those with normal levels. In contrast, AAs with insufficient or deficient levels had > two-fold excess risk of advanced inflammation (P = 0.06). Among White males there was no association between vitamin D levels and advanced fibrosis (F3/F4-F4) or inflammation (A2/A3-A3) risk.

CONCLUSIONS

We observed potential differences in the association between vitamin D levels and degree of HCV-related hepatic fibrosis between White and African American males. Additional research is necessary to confirm that high serum vitamin D levels may be associated with advanced fibrosis risk in African American males, and to evaluate whether racial differences exist in HCV-infected females.

Abstract 4129: Efficient cancer cell separation using size and deformability based filtration

Break-free cancer cells in the blood stream are statistically larger (mainly &gt;15 microns) than the majority of normal cells (5-11 microns). Therefore, filters with engineered pores, for example, 8 μm circular pores, could be used to isolate rare cancer cells from billions of hematologic cells in the blood sample. Size exclusion based filtration, however, is not immune to methodological constraint. Loss of cells smaller than the size cutoff and failure of separating cancer cells from normal cells of similar sizes have been the problems. Incorporating a second separation parameter by controlling cell deformability during the enrichment process could minimize the cell loss and increase the purity of the product. Recent advances using column-wall or crescent-post microfluidic chips have demonstrated the potential of utilizing cell size and deformability based separation techniques for rare cell enrichment. In this paper, we propose an innovative filter that aims to provide similar enrichment effect at quicker time (∼minutes/mL blood) and lower manufacturing cost. The key to realize efficient filtration process is the pattern design of highly dense pores. The effect of pore size on cell separation was first studied using rectangular shaped Polydimethylsiloxane (PDMS) microchannels, which were microfabricated by the technique of soft lithography. In the experiments, intact breast cancer cells (MDA-MB-231 and MDA-MB-453) or human leukocytes were guided through the PDMS channels of different sizes. The flow rates and pressure drop were monitored. The deformation of the cells was visualized using a high-speed camera. The optimal pore size was selected to be the microchannel size that most leukocytes passed through, but not for the majority of the cancer cells, at high flow rate and low pressure-drop. As a second step, the effect of pore shape on cell separation was studied. We used the method of focused ion beam (FIB) to micromill pores into a thin polymer membrane, which have the size equal to or smaller than the optimal size obtained and a variety of shapes. FIB is an electron/ ion dual beam system, in which high-speed ion flow carries high momentum to engrave micro-sized pattern into substrate materials with high precision. The micromilled membrane was then integrated into a microfluidic flow chamber for cell separation. Pressure drop and cell deformation were recorded during the translocation of cells on the membrane. We conclude that both pore size and shape affect the size cutoff of cells to be separated. Under the pressure conditions that preserve the cell integrity and viability, cancer cells can be separated from normal cells at high flow rate, purity (&gt;70%) and recovery (&gt;80%). Our results could provide a detailed guidance for developing an efficient cell filter that can be used for rapid enrichment of rare cancer cells in blood for cancer detection and characterization.

Citation Format: Yuhao Xu, Ali Hashmi, Wael A. Harb, Bin Hong, Jie Xu. Efficient cancer cell separation using size and deformability based filtration. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4129. doi:10.1158/1538-7445.AM2013-4129

Using whole-exome sequencing to identify inherited causes of autism

Despite significant heritability of autism spectrum disorders (ASDs), their extreme genetic heterogeneity has proven challenging for gene discovery. Studies of primarily simplex families have implicated de novo copy number changes and point mutations, but are not optimally designed to identify inherited risk alleles. We apply whole-exome sequencing (WES) to ASD families enriched for inherited causes due to consanguinity and find familial ASD associated with biallelic mutations in disease genes (AMT, PEX7, SYNE1, VPS13B, PAH, and POMGNT1). At least some of these genes show biallelic mutations in nonconsanguineous families as well. These mutations are often only partially disabling or present atypically, with patients lacking diagnostic features of the Mendelian disorders with which these genes are classically associated. Our study shows the utility of WES for identifying specific genetic conditions not clinically suspected and the importance of partial loss of gene function in ASDs.

Leidenfrost levitation: beyond droplets

Friction is a major inhibitor in almost every mechanical system. Enlightened by the Leidenfrost effect – a droplet can be levitated by its own vapor layer on a sufficiently hot surface – we demonstrate for the first time that a small cart can also be levitated by Leidenfrost vapor. The levitated cart can carry certain amount of load and move frictionlessly over the hot surface. The maximum load that the cart can carry is experimentally tested over a range of surface temperatures. We show that the levitated cart can be propelled not only by gravitational force over a slanted flat surface, but also self-propelled over a ratchet shaped horizontal surface. In the end, we experimentally tested water consumption rate for sustaining the levitated cart, and compared the results to theoretical calculations. If perfected, this frictionless Leidenfrost cart could be used in numerous engineering applications where relative motion exists between surfaces.

Oscillating bubbles: a versatile tool for lab on a chip applications

With the fast development of acoustic and multiphase microfluidics in recent years, oscillating bubbles have drawn more-and-more attention due to their great potential in various Lab on a Chip (LOC) applications. Many innovative bubble-based devices have been explored in the past decade. In this article, we first briefly summarize current understanding of the physics of oscillating bubbles, and then critically summarize recent advancements, including some of our original work, on the applications of oscillating bubbles in microfluidic devices. We intend to highlight the advantages of using oscillating bubbles along with the challenges that accompany them. We believe that these emerging studies on microfluidic oscillating bubbles will be revolutionary to the development of next-generation LOC technologies.

Freezing of a liquid marble

In this study, we present for the first time the observations of a freezing liquid marble. In the experiment, liquid marbles are gently placed on the cold side of a thermo-electric cooler (TEC), and the morphological changes are recorded and characterized thereafter. These liquid marbles are noticed to undergo a shape transition from a spherical to a flying-saucer-shaped morphology. The freezing dynamics of liquid marbles is observed to be very different from that of a freezing water droplet on a superhydrophobic surface. For example, the pointy tip appearing on a frozen water drop could not be observed for a frozen liquid marble. In the end, we highlight a possible explanation of the observed morphology.

A renal transplantation model for developing countries

The estimated incidence of end-stage renal disease (ESRD) in Pakistan is 100 per million population. Paucity and high costs of renal replacement therapy allows only 10% to get dialysis and 4-5% transplants. Our center, a government organization, started a dialysis and transplant program in 1980s where all services were provided free of charge to all patients. It was based on the concept of community government partnership funded by both partners. The guiding principles were equity, transparency, accountability and development of all facilities under one roof. This partnership has sustained itself for 30 years with an annual budget of $25 million in 2009. Daily 600 patients are dialyzed and weekly 10-12 receive transplants. One- and 5-year graft survival of 3000 transplants is 92% and 85%, respectively. The institute became a focus of transplantation in Pakistan and played a vital role in the campaign against transplant tourism and in promulgation of transplant law of 2007, and also helped to increase altruistic transplants in the country. This model emphasizes that in developing countries specialized centers in government sector are necessary for transplantation to progress and community support can make it available to the common man.

Need for a new trial to evaluate postoperative radiotherapy in renal cell carcinoma: a meta-analysis of randomized controlled trials

BACKGROUND

A meta-analysis was conducted to assess the impact of postoperative radiotherapy (PORT) in renal cell carcinoma (RCC) on overall survival (OS), disease-free survival (DFS) and locoregional failure (LRF).

MATERIALS AND METHODS

The Medline, CANCERLIT, Cochrane library database and search engines were searched to identify randomized controlled studies comparing radical nephrectomy alone with radical nephrectomy followed by PORT for localized RCC. Further, radiotherapy techniques and associated side-effects were evaluated.

RESULTS

Seven controlled trials with a total patient population of 735 were identified. Pooled results from these trials showed a significant reduction of LRF in patients treated with PORT (P < or = 0.0001). However, there was no difference in OS (P = 0.29) and DFS (P = 0.14). The majority of patients was treated with larger field sizes with parallel-opposed anteroposterior fields. PORT was generally well tolerated; in total, six PORT-related deaths were seen. The resultant funnel plot was broader (Egger test P = 0.14) due to low number of patients.

CONCLUSIONS

PORT significantly reduces LRF but has no effect on OS and DFS. However, due to poor patient accrual and older radiotherapy techniques in previous studies, there is a need for a new trial to evaluate PORT using conformal and intensity-modulated radiotherapy techniques.

Adrenal myelolipoma: a report of three cases and review of literature

Adrenal myelolipoma is a rare and benign tumour composed of mature adipose tissue and haematopoietic elements that resemble bone marrow. It is mostly discovered incidentally on imaging of abdomen done for non adrenal related reasons or at autopsy. Usually asymptomatic, but has been reported to present with symptoms such as flank pain resulting from tumour bulk, necrosis or spontaneous retroperitoneal haemorrhage. Symptomatic tumours, growing tumours or tumours larger than 10 cm should be excised surgically. We report cases of 3 male patients presenting with flank pain and upper pole renal masses. All three were treated surgically with adrenalectomy. Myelolipoma was confirmed in all three on histology.