Eunsoo Lee

ACT-PRESTO: Rapid and consistent tissue clearing and labeling method for 3-dimensional (3D) imaging.

Understanding the structural organization of organs and organisms at the cellular level is a fundamental challenge in biology. This task has been approached by reconstructing three-dimensional structure from images taken from serially sectioned tissues, which is not only labor-intensive and time-consuming but also error-prone. Recent advances in tissue clearing techniques allow visualization of cellular structures and neural networks inside of unsectioned whole tissues or the entire body. However, currently available protocols require long process times. Here, we present the rapid and highly reproducible ACT-PRESTO (active clarity technique-pressure related efficient and stable transfer of macromolecules into organs) method that clears tissues or the whole body within 1 day while preserving tissue architecture and protein-based signals derived from endogenous fluorescent proteins. Moreover, ACT-PRESTO is compatible with conventional immunolabeling methods and expedites antibody penetration into thick specimens by applying pressure. The speed and consistency of this method will allow high-content mapping and analysis of normal and pathological features in intact organs and bodies.

Effects of ECM protein micropatterns on the migration and differentiation of adult neural stem cells.

The migration and differentiation of adult neural stem cells (aNSCs) are believed to be strongly influenced by the spatial distribution of extracellular matrix (ECM) proteins in the stem cell niche. In vitro culture platform, which involves the specific spatial distribution of ECM protein, could offer novel tools for better understanding of aNSC behavior in the spatial pattern of ECM proteins. In this work, we applied soft-lithographic technique to design simple and reproducible laminin (LN)-polylysine cell culture substrates and investigated how aNSCs respond to the various spatial distribution of laminin, one of ECM proteins enriched in the aNSC niche. We found that aNSC preferred to migrate and attach to LN stripes, and aNSC-derived neurons and astrocytes showed significant difference in motility towards LN stripes. By changing the spacing of LN stripes, we were able to control the alignment of neurons and astrocytes. To the best of our knowledge, this is the first time to investigate the differential cellular responses of aNSCs on ECM protein (LN) and cell adhesive synthetic polymer (PDL) using surface micropatterns. Our findings would provide a deeper understanding in astrocyte-neuron interactions as well as ECM-stem cell interactions.

Impedance transformers for compact and robust coupled magnetic resonance systems

An innovative coupled magnetic resonance system (CMRS), introducing two lumped impedance transformers, is proposed. The source coil and load coil of conventional CMRS are replaced with two cored transformers so that the system can be quite compact in size and robust to ambient changes. The design of the system is simplified due to no magnetic flux leakage from the source coil and load coil. A class-E inverter at 500 kHz switching frequency was used for experiments. It is concluded in this paper that the CMRS, in general, is a special form of conventional inductive power transfer systems.

Commissioning of the PLS-II

After 14 years of successful operation, the Pohang Light Source (PLS) has completed PLS-II upgrade to meet the increasing demand from the growing user community. The PLS-II upgrade has increased the beam energy from 2.5 GeV to 3 GeV; the number of insertion devices has been increased by a factor of two (20 IDs); and the beam current has been increased to 400 mA from 200 mA. The beam emittance has been reduced to below 10 nm while retaining the existing PLS tunnel as well as the existing injection system. During the six months of commissioning in the latter half of 2011, we have successfully achieved 14 insertion device operations and top-up operations with 100 mA beam current and 5.8 nm beam emittance. In this paper, we report the experimental results obtained from the PLS-II commissioning.

See-Through Technology for Biological Tissue: 3-Dimensional Visualization of Macromolecules

Tissue clearing technology is currently one of the fastest growing fields in biomedical sciences. Tissue clearing techniques have become a powerful approach to understand further the structural information of intact biological tissues. Moreover, technological improvements in tissue clearing and optics allowed the visualization of neural network in the whole brain tissue with subcellular resolution. Here, we described an overview of various tissue-clearing techniques, with focus on the tissue-hydrogel mediated clearing methods, and discussed the main advantages and limitations of transparent tissue for clinical diagnosis.

LED Driver with TRIAC Dimming Control by Variable Switched Capacitance for Power Regulation

A TRIAC dimming LED driver that can control the brightness of LED arrays for a wide range of source voltage variations is proposed in this paper. Unlike conventional PWM LED drivers, the proposed LED driver adopts a TRIAC switch, which inherently guarantees zero current switching and has been proven to be quite reliable over its long lifetime. Unlike previous TRIAC type LED drivers, the proposed LED driver is composed of an LC input filter and a variable switched capacitance, which is modulated by the TRIAC turn-on timing. Thus, the LED power regulation and dimming control, which are done by a volume resistor in the same way as the conventional TRIAC dimmers, can be simultaneously performed by the TRIAC control circuit. Because the proposed LED driver has high efficiency and a long lifetime with a high power factor (PF) and low total harmonic distortion (THD) characteristics, it is quite adequate for industrial lighting applications such as streets, factories, parking garages, and emergency stairs. A simple step-down capacitive power supply circuit composed of passive components only is also proposed, which is quite useful for providing DC power from an AC source without a bulky and heavy transformer. A prototype 60 W LED driver was implemented by the proposed design procedure and verified by simulation and experimental results, where the efficiency, PF, and THD are 92%, 0.94, and 6.3%, respectively. The LED power variation is well mitigated to below ± 2% for 190 V < Vs < 250 V by using the proposed simple control circuit.

Protective role of superoxide dismutase in rat eustachian tubal mucosa against acute otitis media induced by upper respiratory tract infection

Superoxide dismutase has been known to play a role as an anti-oxidative system against oxidative injury during acute inflammation. To investigate the role of superoxide dismutase in eustachian tubal mucosa during acute otitis media (AOM), an animal model was made. Sprague-Dawley rats were inoculated with Streptococcus pneumoniae through the nasal cavity following development of virus-induced upper respiratory infection. The animals were divided into three groups according to their tympanic cavity conditions following bacterial inoculation; inoculated animals with no resultant AOM (no-AOM), animals with resultant AOM (AOM) and animals with resolving otitis media (recovery). The changes of superoxide dismutase in each tubal mucosa were compared with that of the normal control using immunohistochemistry and immunoblotting methods. On Western blot, there were little changes of optical density and surface area in no-AOM (213.5 +/- 22.4, 13.2 +/- 0.8 mm2) and recovery group (219.3 +/- 18.7, 14.8 +/- 0.7 mm2) compared to the normal control (223.5 +/- 26.2, 16.7 +/- 0.4 mm2). However, a marked decrease was found in the AOM model (167.6 +/- 19.3, 6.5 +/- 0.9 mm2). These findings suggest that superoxide dismutase may play a role in protecting tubal mucosa from free radical injury during AOM.

Cografting astrocytes improves cell therapeutic outcomes in a Parkinson’s disease model

Transplantation of neural progenitor cells (NPCs) is a potential therapy for treating neurodegenerative disorders, but this approach has faced many challenges and limited success, primarily because of inhospitable host brain environments that interfere with enriched neuron engraftment and function. Astrocytes play neurotrophic roles in the developing and adult brain, making them potential candidates for helping with modification of hostile brain environments. In this study, we examined whether astrocytic function could be utilized to overcome the current limitations of cell-based therapies in a murine model of Parkinson’s disease (PD) that is characterized by dopamine (DA) neuron degeneration in the midbrain. We show here that cografting astrocytes, especially those derived from the midbrain, remarkably enhanced NPC-based cell therapeutic outcomes along with robust DA neuron engraftment in PD rats for at least 6 months after transplantation. We further show that engineering of donor astrocytes with Nurr1 and Foxa2, transcription factors that were recently reported to polarize harmful immunogenic glia into the neuroprotective form, further promoted the neurotrophic actions of grafted astrocytes in the cell therapeutic approach. Collectively, these findings suggest that cografting astrocytes could be a potential strategy for successful cell therapeutic outcomes in neurodegenerative disorders.

Possibility of reciprocal infection of methicillin-resistant Staphylococcus aureus between medical personnel and patients undergoing middle ear surgery

The incidence of methicillin-resistant Staphylococcus aureus (MRSA) infection after middle ear surgery has recently increased in our hospital. In this study we tried to determine whether the strains of MRSA isolated from infected patients are identical to those obtained from medical personnel, to prove a reciprocal transmission between medical personnel and patients. Surveillance bacterial cultures of medical personnel were performed from the anterior nares and from the fingertip. Molecular epidemiological studies, ribotyping and pulsed-field gel electrophoresis (PFGE) were used to compare the 12 MRSA strains obtained from carriers among medical personnel with the 60 strains identified from patient’s otorrhea. Six different MRSA strains were identified from ribotyping, and three subtypes from PFGE. There was a particular subtype which was the most frequently identified strain found in both medical carriers and patients. Postoperative MRSA infection rates after the treatment of medical carriers and application of preventive procedures decreased from 11.9 to 5.7%. These findings suggest that the MRSA transmissions have occurred between medical personnel and patients.

Promotion of Cortical Neurogenesis from the Neural Stem Cells in the Adult Mouse Subcallosal Zone.

Neurogenesis occurs spontaneously in the subventricular zone (SVZ) of the lateral ventricle in adult rodent brain, but it has long been debated whether there is sufficient adult neurogenesis in human SVZ. Subcallosal zone (SCZ), a posterior continuum of SVZ closely associated with posterior regions of cortical white matter, has also been reported to contain adult neural stem cells (aNSCs) in both rodents and humans. However, little is known whether SCZ‐derived aNSC (SCZ‐aNSCs) can produce cortical neurons following brain injury. We found that SCZ‐aNSCs exhibited limited neuronal differentiation potential in culture and after transplantation in mice. Neuroblasts derived from SCZ initially migrated toward injured cortex regions following brain injury, but later exhibited apoptosis. Overexpression of anti‐apoptotic bcl‐xL in the SCZ by retroviral infection rescued neuroblasts from cell death in the injured cortex, but neuronal maturation was still limited, resulting in atrophy. In combination with Bcl‐xL, infusion of brain‐derived neurotropic factor rescued atrophy, and importantly, a subset of such SCZ‐aNSCs differentiated and attained morphological and physiological characteristics of mature, excitatory neurons. These results suggest that the combination of anti‐apoptotic and neurotrophic factors might enable the use of aNSCs derived from the SCZ in cortical neurogenesis for neural replacement therapy. Stem Cells 2016;34:888–901