Jisoo Park

Cell encapsulation via microtechnologies

The encapsulation of living cells in a variety of soft polymers or hydrogels is important, particularly, for the rehabilitation of functional tissues capable of repairing or replacing damaged organs. Cellular encapsulation segregates cells from the surrounding tissue to protect the implanted cell from the recipients immune system after transplantation. Diverse hydrogel membranes have been popularly used as encapsulating materials and permit the diffusion of gas, nutrients, wastes and therapeutic products smoothly. This review describes a variety of methods that have been developed to achieve cellular encapsulation using microscale platform. Microtechnologies have been adopted to precisely control the encapsulated cell number, size and shape of a cell-laden polymer structure. We provide a brief overview of recent microtechnology-based cell encapsulation methods, with a detailed description of the relevant processes. Finally, we discuss the current challenges and future directions likely to be taken by cell microencapsulation approaches toward tissue engineering and cell therapy applications.

Size-controllable networked neurospheres as a 3D neuronal tissue model for Alzheimer's disease studies.

Intensive in vitro studies on the neurotoxicity of amyloid beta have been conducted for decades; however, a three-dimensional neuronal tissue model for Alzheimers disease has not yet been achieved. In this study, we developed size-controllable networked neurospheres comprised of cerebral cortical neuronal cells that mimics the cytoarchitecture of the cortical region of the brain. The toxicity of amyloid beta on the neurosphere model was assessed quantitatively and qualitatively. Decreased cell viability after amyloid beta exposure was demonstrated using MTT and live/dead assays. Neurite degeneration after amyloid beta exposure was evident in both SEM and fluorescence images. Ultrastructural features of apoptotic neurons were analyzed and quantitative analysis of synapsin II concentration and an acetylcholine assay were also performed. The three-dimensional neurospheres, produced using a concave microwell array, are a potential in vitro model for Alzheimers disease studies.

The fate of photons absorbed by phytoplankton in the global ocean

Using solar energy suboptimally How efficient are phytoplankton at converting sunlight into the products of photosynthesis? The two other pathways that that absorbed energy can take are emission back to the environment by fluorescence or conversion to heat. Lin et al. measured phytoplankton fluorescence lifetimes in the laboratory and combined them with satellite measurements of variable chlorophyll fluorescence. Combined, they determined the quantum yields of photochemistry and fluorescence in four ocean basins. Approximately 60% of absorbed solar energy is converted to heat, a figure 50% higher than has been determined for conditions of optimal growth. Science, this issue p. 264 Phytoplankton convert more sunlight to heat than to fluorescence or photosynthesis. Solar radiation absorbed by marine phytoplankton can follow three possible paths. By simultaneously measuring the quantum yields of photochemistry and chlorophyll fluorescence in situ, we calculate that, on average, ~60% of absorbed photons are converted to heat, only 35% are directed toward photochemical water splitting, and the rest are reemitted as fluorescence. The spatial pattern of fluorescence yields and lifetimes strongly suggests that photochemical energy conversion is physiologically limited by nutrients. Comparison of in situ fluorescence lifetimes with satellite retrievals of solar-induced fluorescence yields suggests that the mean values of the latter are generally representative of the photophysiological state of phytoplankton; however, the signal-to-noise ratio is unacceptably low in extremely oligotrophic regions, which constitute 30% of the open ocean.

ABCG2 polymorphisms, 34G>A and 421C>A in a Korean population: analysis and a comprehensive comparison with other populations.

Background and objective:  ABCG2, also known as Breast Cancer Resistance Peptide (BCRP) or mitoxantrone‐resistant protein, is the second member of the G‐family of ABC transporters. The frequencies of ABCG2 34G>A and 421C>A polymorphisms in a Korean population were assessed using a newly developed multiplex pyrosequencing method, and compared with the corresponding frequencies seen in other ethnic groups.

Central Nervous System and its Disease Models on a Chip

Technologies for microfluidics and biological microelectromechanical systems have been rapidly progressing over the past decade, enabling the development of unique microplatforms for in vitro human central nervous system (CNS) and related disease models. Most fundamental techniques include manipulation of axons, synapses, and neuronal networks, and different culture conditions are possible, such as compartmental, co-culturing, and 3D. Various CNS disease models, such as Alzheimers disease (AD), Parkinsons disease (PD), multiple sclerosis (MS), epilepsy, N-methyl-D-aspartate receptor (NMDAR) encephalitis, migraine, diffuse axonal injury, and neuronal migration disorders, have been successfully established on microplatforms. In this review, we summarize fundamental technologies and current existing CNS disease models on microplatforms. We also discuss possible future directions, including application of these methods to pathological studies, drug screening, and personalized medicine, with 3D and personalized disease models that could generate more realistic CNS disease models.

Target-controlled propofol infusion for sedation in patients undergoing transrectal ultrasound-guided prostate biopsy.

The efficacy and safety of the routine use of target-controlled infusion of propofol for the sedation of patients undergoing transrectal ultrasound-guided prostate biopsy were assessed. The optimal level of sedation was also evaluated. A total of 250 patients were randomized into five groups according to sedation level determined by the Observers Assessment of Alertness/Sedation (OAA/S) scale. As the level of sedation was increased, the overall pain and discomfort score decreased and the satisfaction rate tended to increase, although hypoxia meant that intervention occurred more frequently at higher sedation levels. Target-controlled infusion of propofol provided safe and effective sedation during transrectal ultrasound-guided prostate biopsy, particularly if moderate sedation (OAA/S score of 3) was achieved. The effect-site concentration of propofol for this level of sedation was about 1.5 μg/ml.

Cardiac Arrest due to a Vagal Reflex Potentiated by Thoracic Epidural Analgesia

Reflex bradycardia and cardiac arrest may be the result of a vagal reflex, which can occur during a variety of surgical procedures. We report a patient who developed cardiac arrest as a result of a vagal reflex that was potentiated by thoracic epidural analgesia during general anaesthesia. A 53-year-old man was scheduled for subtotal gastrectomy because of an early gastric adenocarcinoma. After an epidural catheter had been inserted, general anaesthesia was induced. During surgery, an abdominal self-retaining retractor was set up but bradycardia and cardiac arrest developed. The patient returned to a normal sinus rhythm after successful resuscitation. We conclude that bradycardia as a result of a vagal reflex is mediated by potent abdominal wall traction and is potentiated by epidural analgesia. Early diagnosis and proper treatment can allow a full recovery, even in high-risk patients.

Spatial and temporal variation of net community production and its regulating factors in the Amundsen Sea, Antarctica

We observed ΔO2/Ar in the surface waters of the Amundsen Sea, Antarctica, during the austral summers in 2011 and 2012 to investigate the variability of net community production (NCP). Corresponding to the typical peak phytoplankton bloom period, the ΔO2/Ar of the Amundsen Sea Polynya (ASP) reached 30% in early January 2011 and had a strong positive correlation with the sea surface temperature (SST) and chlorophyll-a (Chl-a). In contrast, ΔO2/Ar decreased to −10% in the sea ice zone (SIZ), which was likely associated with either net O2 consumption in the unlit area or the entrainment of deep water containing low dissolved oxygen. Near the terminal stage of the phytoplankton bloom in late February 2012, we observed the same contrasting ΔO2/Ar features between the ASP and SIZ. However, the ΔO2/Ar in the ASP was not >10%, which corresponded with the overall reduction in Chl-a, solar radiation, and SST compared with the corresponding values in 2011. The average net community production in the ASP was 119 ± 79 mmol O2 m−2 d−1 in January 2011, and 23 ± 14 mmol O2 m−2 d−1 in February 2012. The strong correlations of NCP with SST and mixed layer depth (MLD) indicate that the ASP phytoplankton bloom is likely initiated by a combination of increased light availability and SST in early summer. Low SST and variable fluorescence to maximum florescence ratio (Fv/Fm) in February indicate that decreased solar radiation and Fe availability are likely responsible for the phytoplankton bloom demise.

Factors associated with radiologic progression of non‐cystic fibrosis bronchiectasis during long‐term follow‐up

Non‐cystic fibrosis (CF) bronchiectasis is a chronic airway inflammatory disease, exhibiting a diverse array of clinical courses. The purpose of this study was to determine the factors that predict radiologic progression of non‐CF bronchiectasis during a long‐term follow‐up.

Clinical impact of early bronchoscopy in mechanically ventilated patients with aspiration pneumonia: Early bronchoscopy in aspiration pneumonia

A handful of studies have reported that bronchoscopies influence the clinical outcome of mechanically ventilated patients with aspiration pneumonia. The purpose of the present study is to elucidate the therapeutic role of early bronchoscopy in patients with aspiration who are mechanically ventilated.