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        A Highly Accurate and Consistent Microfluidic Viscometer for Continuous Blood Viscosity Measurement

        Kang, Yang Jun,Yoon, Sang Youl,Lee, Kyeong‐,Hwan,Yang, Sung Blackwell Publishing Inc 2010 Artificial Organs Vol.34 No.11

        <P><B>Abstract</B></P><P>A high‐precision microfluidic viscometer with a microfluidic channel array composed of 100 indicating channels is demonstrated in this study. The relative viscosity of the sample fluid could be measured by simply counting the number of the indicating channels occupied by the sample and the reference fluids. Using lumped parameter modeling, an analytical solution of the relative viscosity is derived. In order to evaluate the performance of the developed microfluidic viscometer, the viscosity values obtained by the microfluidic viscometer are compared with the ones obtained by a conventional viscometer. In Newtonian fluid (sodium dodecyl sulfate [SDS] solution) tests, the normalized differences in the viscosities measured by two methods are less than 2.5%. In non‐Newtonian fluid (whole blood, 45% hematocrit) tests at various shear rates, the viscosities measured by two methods are evaluated by a regression analysis via power law (<IMG src='/wiley-blackwell_img/equation/AOR_1078_mu1.gif' alt ='inline image'/>). The <I>k</I> values for both the microfluidic viscometer and the conventional viscometer are 12.953 and 13.175, respectively; the <I>n</I> values are 0.797 and 0.807, respectively. The normalized differences in two parameters measured by two methods are less than 2%. Thus, it could be concluded that the microfluidic viscometer developed in this study is capable of measuring viscosity of both Newtonian fluid (SDS solution) and non‐Newtonian fluid (whole blood) with a relatively high accuracy in a continuous and near real‐time fashion. Furthermore, the viscometer could be potentially employed in cardiopulmonary bypass procedures by continuously monitoring viscosity changes due to blood damages and hemodilution.</P>

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        Treatment of Melasma in Asian Skin Using a Fractional 1,550-nm Laser: An Open Clinical Study

        LEE, HYOUN SEUNG,WON, CHONG HYUN,LEE, DONG HUN,AN, JEE SOO,CHANG, HANG WOOK,LEE, JONG HEE,KIM, KYU HAN,CHO, SOYUN,CHUNG, JIN HO Blackwell Publishing Inc 2009 Dermatologic surgery Vol.35 No.10

        <P>BACKGROUND</P><P>Melasma is a common hyperpigmentation disorder that can cause refractory cosmetic disfigurement, especially in Asians. Fractional photothermolysis (FP) has been reported to be effective for the treatment of melasma, despite small study populations and short follow-up periods.</P><P>OBJECTIVE</P><P>To evaluate the efficacy and safety of FP for the treatment of melasma in Asians.</P><P>PATIENTS AND METHODS</P><P>Twenty-five patients with melasma received four monthly FP sessions and were followed up to 24 weeks after treatment completion. Efficacy was evaluated using objective and subjective ratings, Melasma Area and Severity Index (MASI), melanin index tracking, and skin elasticity measurements.</P><P>RESULTS</P><P>Investigators observed clinical improvements in 60% and patients in 44% at 4 weeks after treatment, but the figures decreased to 52% and 35%, respectively, at 24 weeks after treatment. Mean MASI scores decreased significantly from 7.6 to 6.2. Mean melanin index decreased significantly after the first two sessions, but it relapsed slightly in subsequent follow-ups. The treatment did not alter skin elasticity. Hyperpigmentation was observed in three of 23 subjects (13%).</P><P>CONCLUSION</P><P>Treatment of melasma with FP led to some clinical improvements, but it was not as efficacious as previously reported at 6-month follow-up. We recommend judicious use of FP for the treatment of melasma in Asian skin because of its limited efficacy.</P>

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        Adipogenic Differentiation of Human Adipose Tissue–Derived Stem Cells Obtained from Cryopreserved Adipose Aspirates

        LEE, JUNG EUN,KIM, INOK,KIM, MIHYUNG Blackwell Publishing Inc 2010 Dermatologic surgery Vol.36 No.7

        <P>BACKGROUND</P><P>Although frozen adipose tissue is frequently used for soft tissue augmentation, the viability of frozen fat remains a controversy. The cryopreservation of adipose tissue is important for the future use of adipose-derived stem cells (ASCs) and adipocytes.</P><P>OBJECTIVE</P><P>To determine whether optimal cryopreservation techniques with regard to the addition of cryopreservative agents and preservation temperature is essential for the long-term storage of adipose tissue and whether ASCs from cryopreserved adipose aspirates are reliable for use in adipogenic differentiation.</P><P>MATERIALS AND METHODS</P><P>Adipose tissue was frozen directly or with cryoprotectant at −20°C or −80°C for 1 year. The viability of adipose aspirates and the differentiation of ASCs isolated from adipose tissue were evaluated.</P><P>RESULTS</P><P>The viability of adipose aspirates frozen with dimethyl sulfoxide at −80°C was approximately 87% after 2 months of storage. Moreover, ASCs from adipose tissue stored with cryoprotectant survived successfully for 1 year and differentiated into adipocytes, although ASCs were not detected in the directly frozen adipose tissue.</P><P>CONCLUSION</P><P>Adipose tissue cryopreserved with cryoprotectant and stored at optimal temperature might prove to be a reliable source of human ASCs and adipocytes.</P><P><I>The authors have indicated no significant interest with commercial supporters.</I></P>

      • Trends in the Health Status of Older Koreans

        Jang, Soong‐,Nang,Kim, Dong‐,Hyun Blackwell Publishing Inc 2010 Journal of the American Geriatrics Society Vol.58 No.3

        <P>Several recent studies have suggested that mortality, disability, and self‐rated health in older Americans have improved in last decade, but data from rapidly aging Asians remain sparse, and it is unclear that improvement extends to various health outcomes among older Korean populations. Trends in mortality, morbidity, disability, health behavior, and self‐rated health in older Koreans were assessed. Data were obtained from the National Death Statistics (1983–2006) and three representative and repeated cross‐sectional nationwide surveys: the National Elderly Activity Status and Welfare Needs Survey, the National Long‐term Care Needs Survey, and the Korean National Health and Nutrition Examination Survey. All‐cause mortality and disability decreased rapidly among older Koreans over the survey years, although some dimensions of health, including mortality from cancer, ischemic heart disease, and diabetes mellitus, have continued to deteriorate during this same period. Data on self‐rated health have also confirmed this trend toward diminished health status. These results are not consistent with the theory of compression of morbidity. Given the complexity and controversies characterizing health changes in the older population, continuing examination of the latest information about various aspects of mortality, disability, morbidity, and health behavior is necessary for the development of future improvements in healthy life expectancies in older Koreans.</P>

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        Optimizing the Circuit of a Pulsatile Extracorporeal Life Support System in Terms of Energy Equivalent Pressure and Surplus Hemodynamic Energy

        Lim, Choon Hak,Yang, Sung,Choi, Jae-Wook,Sun, Kyung Blackwell Publishing Inc 2009 Artificial Organs Vol.33 No.11

        <P>Abstract: </P><P>The nonpulsatile blood flow obtained using standard cardiopulmonary bypass (CPB) circuits is still generally considered an acceptable, nonphysiologic compromise with few disadvantages. However, numerous reports have concluded that pulsatile perfusion during CPB achieves better multiorgan response postoperatively. Furthermore, pulsatile flow during CPB has been consistently recommended in pediatric and high-risk patients. However, most (80%) of the total hemodynamic energy generated by a pulsatile pump is absorbed by the components of the extracorporeal circuit and only a small portion of the pulsatile energy is delivered to the patient. Therefore, we considered that optimizations of CPB unit and extracorporeal life support (ECLS) system circuit components were needed to deliver sufficient pulsatile flow. In addition, energy equivalent pressure, surplus hemodynamic energy, and total hemodynamic energy, calculated using pressure and flow waveforms, were used to evaluate the pulsatilities of pulsatile CPB and ECLS systems.</P>

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        Optimal Pressure Regulation of the Pneumatic Ventricular Assist Device With Bellows-Type Driver

        Lee, Jung Joo,Kim, Bum Soo,Choi, Jaesoon,Choi, Hyuk,Ahn, Chi Bum,Nam, Kyoung Won,Jeong, Gi Seok,Lim, Choon Hak,Son, Ho Sung,Sun, Kyung Blackwell Publishing Inc 2009 Artificial Organs Vol.33 No.8

        <P>Abstract</P><P>The bellows-type pneumatic ventricular assist device (VAD) generates pneumatic pressure with compression of bellows instead of using an air compressor. This VAD driver has a small volume that is suitable for portable devices. However, improper pneumatic pressure setup can not only cause a lack of adequate flow generation, but also cause durability problems. In this study, a pneumatic pressure regulation system for optimal operation of the bellows-type VAD has been developed. The optimal pneumatic pressure conditions according to various afterload conditions aiming for optimal flow rates were investigated, and an afterload estimation algorithm was developed. The developed regulation system, which consists of a pressure sensor and a two-way solenoid valve, estimates the current afterload and regulates the pneumatic pressure to the optimal point for the current afterload condition. Experiments were performed in a mock circulation system. The afterload estimation algorithm showed sufficient performance with the standard deviation of error, 8.8 mm Hg. The flow rate could be stably regulated with a developed system under various afterload conditions. The shortcoming of a bellows-type VAD could be handled with this simple pressure regulation system.</P>

      • SCISCIESCOPUS

        Potential of Fortified Fibrin/Hyaluronic Acid Composite Gel as a Cell Delivery Vehicle for Chondrocytes

        Park, Sang-Hyug,Cui, Ji Hao,Park, So Ra,Min, Byoung-Hyun Blackwell Publishing Inc 2009 Artificial Organs Vol.33 No.6

        <P>Abstract</P><P>Numerous treatment methods have been applied for use in cartilage repair, including abrasion, drilling, and microfracture. Although chondrocyte transplantation is the preferred treatment, it has some shortcomings, such as difficulty of application (large and posterior condylar regions), poor chondrocyte distribution, and potential cell leakage from the defect region. The cell delivery system of the tissue engineering technique can be used to overcome these shortcomings. We chose fibrin/hyaluronan (HA) composite gel as an effective cell delivery system to resolve these issues. Both components are derived from natural extracellular matrix. In the first trial, fortified fibrin/HA composite gels with rabbit chondrocytes were tested by implantation in nude mice. At 4 weeks, glycosaminoglycan contents in the fibrin/HA composite (0.186 ± 0.006 mg/mg) were significantly higher than those in the presence of fibrin alone (0.153 ± 0.017 mg/mg). As a next step, we applied the fibrin/HA composite gel to animal cartilage defects using full thickness cartilage defect rabbit models. The fibrin/HA composite gel with rabbit chondrocytes (allogenic) was implanted into the experimental group, and the control group was implanted with the fibrin/HA composite gel alone. Implanted chondrocytes with the fibrin/HA composite showed improved cartilage formation. In conclusion, the key to successful regeneration of cartilage is to provide the repair site with a sufficient supply of chondrogenic cells with a suitable delivery vehicle to ensure maximal differentiation and deposition of the proper extracellular matrix. This study suggests the feasibility of tissue-engineered cartilage formation using fibrin/HA composite gel.</P>

      • SCISCIESCOPUS

        Parametric Study of Blade Tip Clearance, Flow Rate, and Impeller Speed on Blood Damage in Rotary Blood Pump

        Kim, Nahn Ju,Diao, Chenguang,Ahn, Kyung Hyun,Lee, Seung Jong,Kameneva, Marina V.,Antaki, James F. Blackwell Publishing Inc 2009 Artificial Organs Vol.33 No.6

        <P>Abstract</P><P>Phenomenological studies on mechanical hemolysis in rotary blood pumps have provided empirical relationships that predict hemoglobin release as an exponential function of shear rate and time. However, these relations are not universally valid in all flow circumstances, particularly in small gap clearances. The experiments in this study were conducted at multiple operating points based on flow rate, impeller speed, and tip gap clearance. Fresh bovine red blood cells were resuspended in phosphate-buffered saline at about 30% hematocrit, and circulated for 30 min in a centrifugal blood pump with a variable tip gap, designed specifically for these studies. Blood damage indices were found to increase with increased impeller speed or decreased flow rate. The hemolysis index for 50-µm tip gap was found to be less than 200-µm gap, despite increased shear rate. This is explained by a cell screening effect that prevents cells from entering the smaller gap. It is suggested that these parameters should be reflected in the hemolysis model not only for the design, but for the practical use of rotary blood pumps, and that further investigation is needed to explore other possible factors contributing to hemolysis.</P>

      • SCISCIESCOPUS

        Comparison of Hemolytic Properties of Different Shapes of Occlusion of Blood Sac in Occlusive-type Pulsatile Blood Pump

        Choi, Hyuk,Min, Byoung Goo,Won, Yong Soon Blackwell Publishing Inc 2008 Artificial Organs Vol.32 No.2

        <P>Abstract: </P><P>The occlusive-type pulsatile extracorporeal blood pump (T-PLS, Seoul National University, Seoul, Korea) received the Communauté Européenne mark of the European Directives (2003) and Korea Food and Drug Administration approval (2004) for short-term application as an extracorporeal life support system. The pump system was recently upgraded in the ameliorated actuator head for reducing hemolysis, rather than in the existing actuator head. In this study, the hemolytic performance of the new pump system (assessed as the degree of occlusiveness of the blood sac) was compared with the existing one. A roller pump, the Stockert S3 (Stockert Instrumente GmbH, Munchen, Germany), was selected as a control device. Five tests were conducted for each pump, with each of these tests lasting for 6 h. A pump flow of 3 L/min with 50 beats per minute was included in the hemolytic test conditions. The lowest hemolytic results were obtained by the new pump system yielding a normalized index of hemolysis of less than 0.005 g/100 L, and this result was one-fourth that of the roller pump, Stockert S3.</P>

      • SCISCIESCOPUS

        Pulse Push/Pull Hemodialysis: In Vitro Study on New Dialysis Modality With Higher Convective Efficiency

        Lee, Kyungsoo,Lee, Sa Ram,Mun, Cho Hae,Min, Byoung Goo Blackwell Publishing Inc 2008 Artificial Organs Vol.32 No.5

        <P>Abstract: </P><P>Midsize molecule retention is related with renal-failure-associated mortality. Here, the authors describe a new dialysis modality, pulse push/pull hemodialysis (PPPHD), which increases convective clearance. Blood and dialysate are circulated by a pulsatile pump, but with pulsatile flow patterns that are 180° out of phase. This causes blood-to-dialysate pressure gradients that oscillate between positive and negative, and which cause consecutive periods of ultrafiltration and backfiltration. The devised PPPHD was compared with conventional high-flux hemodialysis (CHFHD) in terms of solute clearances, albumin loss, and total protein levels. Human plasma containing dissolved uremic marker molecules was used as a blood substitute, and clearances were investigated for blood urea nitrogen, creatinine, vitamin B12, and inulin. Observed clearances were found to be significantly higher for PPPHD by approximately 3–14% for low-molecular-weight solutes, by 47–48% for vitamin B12, and by 38–49% for inulin than for CHFHD. No albumin loss was observed in either of these two study groups. The authors conclude that PPPHD offers a simple straightforward means of enhancing uremic molecule removal by increasing total ultrafiltration volume without the need to infuse replacement fluid.</P>

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