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1,437 result(s) for "Kim, Hahn"
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Detecting hepatitis B virus in surgical smoke emitted during laparoscopic surgery
BackgroundHepatitis B virus (HBV) transmission is known to occur through direct contact with infected blood. There has been some suspicion that the virus can also be detected in aerosol form. However, this has never been directly shown. The purpose of this study was to sample and analyse surgical smoke from laparoscopic surgeries on patients with hepatitis B to determine whether HBV is present.MethodsA total of 11 patients who underwent laparoscopic or robotic abdominal surgeries between October 2014 and February 2015 at Korea University Anam Hospital were included in this study. A high efficiency collector was used to obtain surgical smoke in the form of hydrosol. The smoke was analysed by using nested PCR.ResultsRobotic or laparoscopic colorectal resections were performed in 5 cases, laparoscopic gastrectomies in 3 cases and laparoscopic hepatic wedge resections in another 3 cases. Preoperatively, all of the patients had positive hepatitis B surface antigen (HBsAg). 2 patients had detectable HBsAb, and 2 were positive for hepatitis B e antigen. 3 patients were taking antihepatitis B viral medications at the time of the study. The viral load measured in the patients’ blood was undetectable to 1.7×108 IU/mL. HBV was detected in surgical smoke in 10 of the 11 cases.ConclusionsHBV is detectable in surgical smoke. This study provides preliminary data in the investigation of airborne HBV infection.
SARS-CoV-2 requires cholesterol for viral entry and pathological syncytia formation
Many enveloped viruses induce multinucleated cells (syncytia), reflective of membrane fusion events caused by the same machinery that underlies viral entry. These syncytia are thought to facilitate replication and evasion of the host immune response. Here, we report that co-culture of human cells expressing the receptor ACE2 with cells expressing SARS-CoV-2 spike, results in synapse-like intercellular contacts that initiate cell-cell fusion, producing syncytia resembling those we identify in lungs of COVID-19 patients. To assess the mechanism of spike/ACE2-driven membrane fusion, we developed a microscopy-based, cell-cell fusion assay to screen ~6000 drugs and >30 spike variants. Together with quantitative cell biology approaches, the screen reveals an essential role for biophysical aspects of the membrane, particularly cholesterol-rich regions, in spike-mediated fusion, which extends to replication-competent SARS-CoV-2 isolates. Our findings potentially provide a molecular basis for positive outcomes reported in COVID-19 patients taking statins and suggest new strategies for therapeutics targeting the membrane of SARS-CoV-2 and other fusogenic viruses.
Optogenetic screening of MCT1 activity implicates a cluster of non-steroidal anti-inflammatory drugs (NSAIDs) as inhibitors of lactate transport
Lactate transport plays a crucial role in the metabolism, microenvironment, and survival of cancer cells. However, current drugs targeting either MCT1 or MCT4, which traditionally mediate lactate import or efflux respectively, show limited efficacy beyond in vitro models. This limitation partly arises from the existence of both isoforms in certain tumors, however existing high-affinity MCT1/4 inhibitors are years away from human testing. Therefore, we conducted an optogenetic drug screen in Saccharomyces cerevisiae on a subset of the FDA-approved drug library to identify existing scaffolds that could be repurposed as monocarboxylate transporter (MCT) inhibitors. Our findings show that several existing drug classes inhibit MCT1 activity, including non-steroidal estrogens, non-steroidal anti-inflammatory drugs (NSAIDs), and natural products (in total representing approximately 1% of the total library, 78 out of 6400), with a moderate affinity (IC 50 1.8–21 μM). Given the well-tolerated nature of NSAIDs, and their known anticancer properties associated with COX inhibition, we chose to further investigate their MCT1 inhibition profile. The majority of NSAIDs in our screen cluster into a single large structural grouping. Moreover, this group is predominantly comprised of FDA-approved NSAIDs, with seven exhibiting moderate MCT1 inhibition. Since these molecules form a distinct structural cluster with known NSAID MCT4 inhibitors, such as diclofenac, ketoprofen, and indomethacin, we hypothesize that these newly identified inhibitors may also inhibit both transporters. Consequently, NSAIDs as a class, and piroxicam specifically (IC 50 4.4 μM), demonstrate MCT1 inhibition at theoretically relevant human dosages, suggesting immediate potential for standalone MCT inhibition or combined anticancer therapy.
Role of Neuronal NADPH Oxidase 1 in the Peri-Infarct Regions after Stroke
The molecular mechanism underlying the selective vulnerability of neurons to oxidative damage caused by ischemia-reperfusion (I/R) injury remains unknown. We sought to determine the role of NADPH oxidase 1 (Nox1) in cerebral I/R-induced brain injury and survival of newborn cells in the ischemic injured region. Male Wistar rats were subjected to 90 min middle cerebral artery occlusion (MCAO) followed by reperfusion. After reperfusion, infarction size, level of superoxide and 8-hydroxy-2'-deoxyguanosine (8-oxo-2dG), and Nox1 immunoreactivity were determined. RNAi-mediated knockdown of Nox1 was used to investigate the role of Nox1 in I/R-induced oxidative damage, neuronal death, motor function recovery, and ischemic neurogenesis. After I/R, Nox1 expression and 8-oxo-2dG immunoreactivity was increased in cortical neurons of the peri-infarct regions. Both infarction size and neuronal death in I/R injury were significantly reduced by adeno-associated virus (AAV)-mediated transduction of Nox1 short hairpin RNA (shRNA). AAV-mediated Nox1 knockdown enhanced functional recovery after MCAO. The level of survival and differentiation of newborn cells in the peri-infarct regions were increased by Nox1 inhibition. Our data suggest that Nox-1 may be responsible for oxidative damage to DNA, subsequent cortical neuronal degeneration, functional recovery, and regulation of ischemic neurogenesis in the peri-infarct regions after stroke.
The effect of offline brand trust and perceived internet confidence on online shopping intention in the integrated multi-channel context
Purpose - The purpose of this research is to examine the influences of consumer trust and perceived internet confidence on consumer apparel shopping intention via the online retailer operated by a multi-channel retailer.Design methodology approach - A total of 261 students in a large US Midwestern University participated in the paper-based survey and provided usable responses. Structural equation modeling was used to test hypotheses.Findings - Consumer trust in an online retailer was a significant predictor of perceived internet confidence and search intention for product information via the online retailer. Search intention for product information via the online store and perceived internet confidence were significant and strong predictors of consumers' behavioral intention toward the online retailer.Research limitations implications - Limitations of the present study include sampling, which prevents the generalization of the results to all multi-channel shoppers.Practical implications - The findings of the study suggest that retailers offer an internet channel as part of a multi-channel retail strategy and provide consistent service throughout their various channels.Originality value - The paper finds that there are significant influences of consumer trust and perceived internet confidence on consumer apparel shopping intention via the online retailer operated by a multi-channel retailer.
Robotic versus Conventional Laparoscopic Surgery for Rectal Cancer: A Cost Analysis from A Single Institute in Korea
Background Since its introduction, robotic surgery has been applied actively in several fields of minimally invasive surgery, and its use in the field of colorectal surgery is also increasing. In the studies to date, feasibility and safety have been the main focus, but the economics involved are important to examine. We compared the economics of robotic surgery with those of laparoscopic surgery for rectal cancer. Material and methods We analyzed the clinical characteristics, total hospital charges, payments, operating room costs, and hospital profits for patients who underwent robotic and laparoscopic resection of rectal cancer at Korea University Anam Hospital between July 2007 and August 2010. Results From July 2007 and August 2010, 154 robot-assisted and 150 laparoscopic rectal surgeries were performed. The patient demographics were similar in the two groups with the exception of tumor location (6.7 vs 8.7 cm distal to the anal verge; p  = 0.043), preoperative chemoradiotherapy (22.7 vs 8 %; p  = 0.001), and operative time (285.2 vs 219.7 min; p  = 0.018). Postoperative course and complications were also similar in the two groups. The total hospital charges in U.S. dollars ($14,647 vs $9,978; p  = 0.001) and payments made by patients ($11,540 vs $3,956; p  < 0.001) were significantly higher in the robotic group. Hospital profit was significantly lower in the robotic group than in the laparoscopic group ($689 vs $1,671; p  < 0.001). Conclusions Robot-assisted surgery is more expensive than laparoscopic surgery for rectal cancer. Considering that robotic surgery can be applied more easily for low-lying cancers, the cost-effectiveness of robotic rectal cancer surgery should be assessed based on oncologic outcomes and functional results from future studies.
SHMT inhibition is effective and synergizes with methotrexate in T-cell acute lymphoblastic leukemia
Folate metabolism enables cell growth by providing one-carbon (1C) units for nucleotide biosynthesis. The 1C units are carried by tetrahydrofolate, whose production by the enzyme dihydrofolate reductase is targeted by the important anticancer drug methotrexate. 1C units come largely from serine catabolism by the enzyme serine hydroxymethyltransferase (SHMT), whose mitochondrial isoform is strongly upregulated in cancer. Here we report the SHMT inhibitor SHIN2 and demonstrate its in vivo target engagement with 13 C-serine tracing. As methotrexate is standard treatment for T-cell acute lymphoblastic leukemia (T-ALL), we explored the utility of SHIN2 in this disease. SHIN2 increases survival in NOTCH1-driven mouse primary T-ALL in vivo. Low dose methotrexate sensitizes Molt4 human T-ALL cells to SHIN2, and cells rendered methotrexate resistant in vitro show enhanced sensitivity to SHIN2. Finally, SHIN2 and methotrexate synergize in mouse primary T-ALL and in a human patient-derived xenograft in vivo, increasing survival. Thus, SHMT inhibition offers a complementary strategy in the treatment of T-ALL.
A small molecule G6PD inhibitor reveals immune dependence on pentose phosphate pathway
Glucose is catabolized by two fundamental pathways, glycolysis to make ATP and the oxidative pentose phosphate pathway to make reduced nicotinamide adenine dinucleotide phosphate (NADPH). The first step of the oxidative pentose phosphate pathway is catalyzed by the enzyme glucose-6-phosphate dehydrogenase (G6PD). Here we develop metabolite reporter and deuterium tracer assays to monitor cellular G6PD activity. Using these, we show that the most widely cited G6PD antagonist, dehydroepiandosterone, does not robustly inhibit G6PD in cells. We then identify a small molecule (G6PDi-1) that more effectively inhibits G6PD. Across a range of cultured cells, G6PDi-1 depletes NADPH most strongly in lymphocytes. In T cells but not macrophages, G6PDi-1 markedly decreases inflammatory cytokine production. In neutrophils, it suppresses respiratory burst. Thus, we provide a cell-active small molecule tool for oxidative pentose phosphate pathway inhibition, and use it to identify G6PD as a pharmacological target for modulating immune response. Identification of an improved glucose-6-phosphate dehydrogenase (G6PD) inhibitor G6PDi-1 blocks G6PD activity more robustly than the widely cited antagonist DHEA. G6PDi-1 treatment blocks T cell cytokine production and neutrophil oxidative burst.
Human SHMT inhibitors reveal defective glycine import as a targetable metabolic vulnerability of diffuse large B-cell lymphoma
The enzyme serine hydroxymethyltransferse (SHMT) converts serine into glycine and a tetrahydrofolate-bound one-carbon unit. Folate one-carbon units support purine and thymidine synthesis, and thus cell growth. Mammals have both cytosolic SHMT1 and mitochondrial SHMT2, with the mitochondrial isozyme strongly up-regulated in cancer. Here we show genetically that dual SHMT1/2 knockout blocks HCT-116 colon cancer tumor xenograft formation. Building from a pyrazolopyran scaffold that inhibits plant SHMT, we identify small-molecule dual inhibitors of human SHMT1/2 (biochemical IC50 ∼ 10 nM). Metabolomics and isotope tracer studies demonstrate effective cellular target engagement. A cancer cell-line screen revealed that B-cell lines are particularly sensitive to SHMT inhibition. The one-carbon donor formate generally rescues cells from SHMT inhibition, but paradoxically increases the inhibitor’s cytotoxicity in diffuse large B-cell lymphoma (DLBCL). We show that this effect is rooted in defective glycine uptake in DLBCL cell lines, rendering them uniquely dependent upon SHMT enzymatic activity to meet glycine demand. Thus, defective glycine import is a targetable metabolic deficiency of DLBCL.