Biomedical subjects

Sang Chul Lee

Publications and source records attributed to Sang Chul Lee.

At least 19 recordsLinked to original sources

PubMed2006

Alteration of the substrate specificity of Thermus caldophilus ADP-glucose pyrophosphorylase by random mutagenesis through error-prone polymerase chain reaction.

Expanding the scope of stereoselectivity is of current interest in enzyme catalysis. In this study, using error-prone polymerase chain reaction (PCR), a thermostable adenosine diphosphate (ADP)-glucose pyrophosphorylase (AGPase) from Thermus caldophilus GK-24 has been altered to improve its catalytic activity toward enatiomeric substrates including [glucose-1-phosphate (G-1-P) + uridine triphosphate (UTP)] and [N-acetylglucosamine-1-phosphate (GlcNAc) + UTP] to produce uridine diphosphate (UDP)-glucose and UDP-N-acetylglucosamine, respectively. To elucidate the amino acids responsible for catalytic activity, screening for UDP-glucose pyrophosphorylase (UGPase) and UDP-N-acetylglucosamine pyrophosphorylase (UNGPase) activities was carried out. Among 656 colonies, two colonies showed UGPase activities and three colonies for UNGPase activities. DNA sequence analyses and enzyme assays showed that two mutant clones (H145G) specifically have an UGPase activity, indicating that the changed glycine residue from histidine has the base specificity for UTP. Also, three double mutants (H145G/A325V) showed a UNGPase, and A325 was associated with sugar binding, conferring the specificity for the sugar substrates and V325 of the mutant appears to be indirectly involved in the binding of the N-acetylamine group of N-acetylglucosmine-1-phosphate.

Amino Acid Sequence↗

PubMed2006

The survival rate and prognostic factors in 26 perforated colorectal cancer patients.

PURPOSE: The treatment for perforated colorectal cancer is not easy and the prognosis for this disease is not so predictable. There are some controversies about performing radical operations because colorectal cancer perforation was considered as an advanced stage disease due to the possibility of tumor cell dissemination through the perforation site. METHODS: We selected and enrolled 26 patients with perforated colorectal cancers among the 1,227 patients who underwent operation for colorectal cancer. These cases were retrospectively analyzed by using their medical records and clinicopathological data. RESULTS: Twenty-eight cases (2.3%) with perforated colorectal cancers were studied and the overall operative mortality rate was 11%. The overall 5-year survival rate was 57.8% when excluding the operative mortality. The overall 5-year cancer-free survival rate was 52.8%. There were significant differences in the survival rate and the cancer-free survival rate between the stages (p=0.008 and p<0.001, respectively). A univariate analysis of the prognostic factors revealed that the number of the metastatic lymph nodes (p=0.018) and the perforation proximal to the cancer (p=0.005) were significantly correlated to worse survival, and the higher number of the metastatic lymph nodes was correlated to a poorer cancer-free survival rate (p<0.001). CONCLUSION: For the perforated colorectal cancers, the stage, the perforation proximal to the cancer, and the number of the metastatic lymph nodes were correlated, with the survival and the cancer-free survival as factors of a poor prognosis. The surgical approach selected for perforated colorectal cancer should be in line with the principles of an appropriate cancer operation because the clinical pathway of perforated colorectal cancer is similar to that of uncomplicated colorectal cancer.

Adult↗

PubMed2006

Quantitative relationship of dioxin-responsive gene expression to dioxin response element in Hep3B and HepG2 human hepatocarcinoma cell lines.

Dioxin response element (DRE) is a cis-acting DNA sequence mediating the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced gene expression. The present study was undertaken to elucidate TCDD-responsive gene expression profiles and their relationships to the number of DREs in liver cancer cells. Hep3B and HepG2 human hepatocarcinoma cells were exposed to 50-nM TCDD for 0, 1, 2 and 4h in culture, after which gene expression profiles were analyzed by the microarray hybridization using a chip containing 24,000 cDNAs prepared from the human liver. The TCDD-responsive expression levels in each gene were calculated by dividing the densitometric values of the hybridization signal for h1, h2 and h4 by that of h0, followed by transformation of the resulting data into a log scale with the base of 2. Up- and down-regulated gene expressions were defined as >0.585 and <-0.585 by the log scale (>1.5 and <1/1.5 arithmetically), respectively, exhibited at any time after h0. Hep3B and HepG2 cells had 27 and 58 TCDD-responsive, up-regulated genes, respectively, of which 78% (21/27) and 62% (36/58) had one or more DREs. Of these 85, 80 genes were up-regulated exclusively in one of the two lines, with CYP1A1 and PPP1R15A being so regulated in both lines. Expression levels of the up-regulated genes at h1, h2 and h4 were correlated with each other (P<0.01) and the mean of these regressed to the number of DRE(s) in both lines (P<0.01). However, expression of a total of 93 TCDD-responsive, down-regulated genes, of which 46% contained DRE(s), had no relation to the number of DRE(s). In conclusion, results suggest that DREs may cooperatively mediate the expression of TCDD-responsive genes in liver cancer cells.

Antigens, Differentiation↗

PubMed2006

Congenital nephrogenic diabetes insipidus presented with bilateral hydronephrosis: genetic analysis of V2R gene mutations.

Most cases of hydronephrosis are caused by urinary tract obstruction. However, excessive polyuric syndrome rarely gives rise to non-obstructive hydronephrosis, megaureter, and a distended bladder. The authors report here on two cases of congenital nephrogenic diabetes insipidus (NDI) with severe bilateral hydronephrosis and megaureter. It is Interesting that the patients were symptomless except for their polyuria, and they both presented with bilateral hydronephrosis. Fluid deprivation testing revealed the presence of AVP resistant NDI. Gene analysis for these patients showed the AVP receptor 2 (V2R) missense mutations (Q225X and S126F), which have previously been reported on in other studies. We made the diagnosis of NDI by using a physiologic test, and we confirmed it by mutation analysis of the V2R gene.

Adult↗

PubMed2006

Significance of macroscopic tumor necrosis as a prognostic indicator for renal cell carcinoma.

PURPOSE: We investigated the prognostic significance of macroscopic tumor necrosis in renal cell carcinoma. MATERIALS AND METHODS: We retrospectively analyzed the records of 485 patients who underwent surgical treatment for organ confined or metastatic renal cell carcinoma. The presence or absence of tumor necrosis was evaluated based on macroscopic description of the tumor, and tumors were considered necrotic only if they exhibited more than 10% macroscopic necrosis. RESULTS: Macroscopic tumor necrosis was identified in 27% of total patients. Patients with macroscopic necrotic renal cell carcinoma were more likely to have larger tumor, metastatic disease, higher local stage and higher tumor grade (all p < 0.001). Pathological features of microvascular invasion (p = 0.026) and sarcomatoid differentiation (p = 0.002) along with several laboratory findings were also observed to be associated with macroscopic tumor necrosis. Among the total subjects those without macroscopic tumor necrosis had significantly higher progression-free (p < 0.0001) and disease specific survival (p < 0.0001). When survival analysis was limited to nonmetastatic tumors only, the same logic applied, which was not the case for the patients with metastatic disease (p > 0.05). Among the different histological subtypes of renal cell carcinoma, macroscopic tumor necrosis was observed to have a significant impact only for the clear cell subtype. In patients with nonmetastatic RCC multivariate analysis revealed that macroscopic tumor necrosis (p = 0.004) was an independent prognostic predictor of disease specific survival along with pathological T stage, tumor grade and tumor size. CONCLUSIONS: Our results suggest that macroscopic tumor necrosis may be a reliable prognostic indicator for nonmetastatic clear cell renal cell carcinoma which should routinely be examined for during pathological analysis.

Adult↗

PubMed2005

Trabecular thickness measurement in cancellous bones: postmortem rat studies with the zoom-in micro-tomography technique.

Using the cross-sectional images taken with the zoom-in micro-tomography technique, we measured trabecular thicknesses of femur bones in postmortem rats. Since the zoom-in micro-tomography technique is capable of high resolution imaging of a small local region inside a large subject, we were able to measure the trabecular thickness without extracting bone samples from the rats. For the zoom-in micro-tomography, we used a micro-tomography system consisting of a micro-focus x-ray source, a 1248 x 1248 flat-panel x-ray detector and a precision scan mechanism. To compensate for the limited spatial resolution in the zoom-in micro-tomography images, we used the fuzzy distance transform for the calculation of the trabecular thickness. To validate the trabecular thickness measurement with the zoom-in micro-tomography images, we compared the measurement results with those obtained from the conventional micro-tomography images of the extracted bone samples. The difference between the two types of measurement results was less than 2.5%.

Animals↗

PubMed2005

Injectable polysaccharide microcapsules for prolonged release of minocycline for the treatment of periodontitis.

Injectable polysaccharide microcapsules holding minocycline were fabricated from alginate and chitosan for the treatment of periodontitis. The microcapsules were examined for the release and degradation of minocycline, as well as antimicrobial activity. The microcapsules were biodegradable and released minocycline between 10 and 1000 microg ml(-1), which was higher than the usual therapeutic concentration (1-5 microg ml(-1)), for up to 7 days. These microcapsules showed a statistically significant suppression of pathogenic bacteria, such as Prevotella intermedia causing periodontitis. The microcapsules are thus potentially useful for drug delivery for the treatment of periodontitis.

Absorbable Implants↗

PubMed2004

Redox regulation of OxyR requires specific disulfide bond formation involving a rapid kinetic reaction path.

The Escherichia coli OxyR transcription factor is activated by cellular hydrogen peroxide through the oxidation of reactive cysteines. Although there is substantial evidence for specific disulfide bond formation in the oxidative activation of OxyR, the presence of the disulfide bond has remained controversial. By mass spectrometry analyses and in vivo labeling assays we found that oxidation of OxyR in the formation of a specific disulfide bond between Cys199 and Cys208 in the wild-type protein. In addition, using time-resolved kinetic analyses, we determined that OxyR activation occurs at a rate of 9.7 s(-1). The disulfide bond-mediated conformation switch results in a metastable form that is locally strained by approximately 3 kcal mol(-1). On the basis of these observations we conclude that OxyR activation requires specific disulfide bond formation and that the rapid kinetic reaction path and conformation strain, respectively, drive the oxidation and reduction of OxyR.

DNA-Binding Proteins↗

PubMed2004

Structural basis of cellular redox regulation by human TRP14.

Thioredoxin-related protein 14 (TRP14) is involved in regulating tumor necrosis factor-alpha-induced signaling pathways in a different manner from human thioredoxin 1 (Trx1). Here, we report the crystal structure of human TRP14 determined at 1.8-A resolutions. The structure reveals a typical thioredoxin fold with characteristic structural features that account for the substrate specificity of the protein. The surface of TRP14 in the vicinity of the active site includes an extended loop and an additional alpha-helix, and the distribution of charged residues in the surface is different from Trx1. The distinctive dipeptide between the redox-active cysteines contributes to stabilizing the thiolate anion of the active site cysteine 43, increasing reactivity of the cysteine toward substrates. These structural differences in the active site suggest that TRP14 has evolved to regulate cellular redox signaling by recognizing a distinctive group of substrates that would complement the group of proteins regulated by Trx1.

Amino Acid Sequence↗

PubMed2004

X-ray micro-tomography system for small-animal imaging with zoom-in imaging capability.

Since a micro-tomography system capable of microm-resolution imaging cannot be used for whole-body imaging of a small laboratory animal without sacrificing its spatial resolution, it is desirable for a micro-tomography system to have local imaging capability. In this paper, we introduce an x-ray micro-tomography system capable of high-resolution imaging of a local region inside a small animal. By combining two kinds of projection data, one from a full field-of-view (FOV) scan of the whole body and the other from a limited FOV scan of the region of interest (ROI), we have obtained zoomed-in images of the ROI without any contrast anomalies commonly appearing in conventional local tomography. For experimental verification of the zoom-in imaging capability, we have integrated a micro-tomography system using a microfocus x-ray source, a 1248 x 1248 flat-panel x-ray detector, and a precision scan mechanism. The mismatches between the two projection data caused by misalignments of the scan mechanism have been estimated with a calibration phantom, and the mismatch effects have been compensated in the image reconstruction procedure. Zoom-in imaging results of bony tissues with a spatial resolution of 10 lp mm(-1) suggest that zoom-in micro-tomography can be greatly used for high-resolution imaging of a local region in small-animal studies.

Algorithms↗

PubMed2004

Identification of B-cell translocation gene 1 as a biomarker for monitoring the remission of acute myeloid leukemia.

Acute myeloid leukemia (AML) is a biologically heterogeneous disease of the hematopoietic system characterized by a clonal accumulation of immature blast cells in bone marrow. We used a proteomic approach based on two-dimensional electrophoresis and mass spectrometry to search for biomarkers related to the complete remission (CR) state of AML patients. We detected one AML-related protein, which was identified as the B-cell translocation gene 1 (BTG1) protein that belongs to anti-proliferative protein family. In the CR state of AML-M2 and M3 patients (by French-American-British subtype classification), the BTG1 protein was upregulated in bone marrow mononuclear cells. It was also expressed robustly in normal bone marrow mononuclear cells. In addition, the BTG1 levels in AML-M2 patients in a non-remission state after therapy did not increase as they did before therapy. Overexpression of BTG1 mRNA was also observed in the CR state of all-trans-retinoic acid (ATRA)-treated AML-M3 patients and ATRA-treated HL-60 cells. Taken together, these results suggest that BTG1 may play a role in the differentiation process of myeloid cells and can therefore be used as a potential treatment-related biomarker for monitoring the remission status of AML-M2 and M3 patients.

Biomarkers↗

PubMed2004

Identification of caspase-3 degradome by two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization-time of flight analysis.

The activation of caspases is a critical event for the execution phase of programmed cell death. Caspases are highly specific in their ability to activate or inhibit many crucial proteins in the cell via site-specific cleavage. To date, more than 60 proteins have been shown to be substrates of one or more caspases in mammalian cells, and the list is still growing. In this study, to identify human caspase-3 substrates, we digested lysates obtained from a caspase-3-deficient MCF-7 cell line with purified caspase-3 and analyzed eliminated or decreased spots by 2-DE. Proteins degraded by caspase-3, termed as caspase-3 degradome, are involved in a variety of cellular functions, such as stress-responsive proteins, signaling molecules, structural proteins, and unclassified proteins. Interestingly, the cellular level of vinculin, a caspase-3 substrate, was dramatically reduced during the apoptotic process, where the expression level of caspase-3 was increased. This degradomic approach could provide a powerful tool in finding physiological substrates of many proteolytic enzymes whose functions remain to be determined.

Apoptosis↗

PubMed2004

Identification of the degradome of Isp-1, a major intracellular serine protease of Bacillus subtilis, by two-dimensional gel electrophoresis and matrix- assisted laser desorption/ionization-time of flight analysis.

Intracellular serine protease-1 (Isp-1) is a major intracellular serine protease of Bacillus subtilis, whose functions still remain largely unknown. Furthermore, physiological substrates are yet to be determined. To identify Isp-1 substrates, we digested extract obtained from an Isp-1 deficient Bacillus mutant with purified Isp-1 and examined eliminated or decreased spots by two-dimensional gel and matrix-assisted laser desorption/ionization-time of flight analyses. Proteins degraded by Isp-1, termed the Isp-1 degradome, are involved in a variety of cellular functions such as DNA packing, genetic competence, and protein secretion. From the degradome we selected ClpC and EF-Tu as putative Isp-1 substrates and studied their in vitro degradation. ClpC and EF-Tu contain putative cleavage sites for Isp-1. N-terminal sequencing of in vitro proteolytic fragments of ClpC and EF-Tu revealed that these sites are indeed recognized and cleaved by Isp-1. Moreover, the cellular levels of ClpC and EF-Tu were dramatically reduced at the late stationary phase, where the expression level of Isp-1 was greatly increased. These results suggest that the regulated proteolysis of ClpC by Isp-1 plays an important role in the stationary phase adaptive response. This degradomic approach could provide a powerful tool for finding physiological substrates of many proteolytic enzymes whose functions remain to be determined.

Bacillus subtilis↗

PubMed2004

Proteome analysis of red deer antlers.

Deer antlers are the only mammalian organs capable of repeated regeneration. Although antlers are known to develop from pedicles, which arise from antlerogenic cells of cranial periosteum, their developmental process is not fully elucidated. For example, while endocrine and environmental factors influence the antler development, it is still unclear which signaling pathways are involved in the transduction of such stimuli. To study the developmental process of antlers and identify proteins functioning in their growth, we have established proteome maps of red deer (Cervus elaphus) antlers. With two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization mass spectrometry, we analyzed more than 800 protein spots and identified approximately 130 individual proteins derived from the growing tip of antlers. The overall profile of the antler proteome was dissimilar to those of other types of tissue. Also comparison of proteomes derived from proximal bony tissue and the growing tip of antlers revealed substantial differences. Moreover several cell growth or signaling-related proteins are expressed exclusively in the growing tip, suggesting that these proteins function in the growth and differentiation of antlers. Currently, using the antler proteome maps, we are actively searching for the regulatory factor(s) that may control the antler development.

Animals↗

PubMed2003

A flat-panel detector based micro-CT system: performance evaluation for small-animal imaging.

A dedicated small-animal x-ray micro computed tomography (micro-CT) system has been developed to screen laboratory small animals such as mice and rats. The micro-CT system consists of an indirect-detection flat-panel x-ray detector with a field-of-view of 120 x 120 mm2, a microfocus x-ray source, a rotational subject holder and a parallel data processing system. The flat-panel detector is based on a matrix-addressed photodiode array fabricated by a CMOS (complementary metal-oxide semiconductor) process coupled to a CsI:T1 (thallium-doped caesium iodide) scintillator as an x-ray-to-light converter. Principal imaging performances of the micro-CT system have been evaluated in terms of image uniformity, voxel noise and spatial resolution. It has been found that the image non-uniformity mainly comes from the structural non-uniform sensitivity pattern of the flat-panel detector and the voxel noise is about 48 CT numbers at the voxel size of 100 x 100 x 200 microm3 and the air kerma of 286 mGy. When the magnification ratio is 2, the spatial resolution of the micro-CT system is about 14 1p/mm (line pairs per millimetre) that is almost determined by the flat-panel detector showing about 7 1p/mm resolving power. Through low-contrast phantom imaging studies, the minimum resolvable contrast has been found to be less than 36 CT numbers at the air kerma of 95 mGy. Some laboratory rat imaging results are presented.

Animals↗

PubMed2003

Myocardial thallium defects in apical hypertrophic cardiomyopathy are associated with a benign prognosis. Thallium defects in apical hypertrophy.

BACKGROUND: We investigated whether myocardial thallium-201 defects in patients with apical hypertrophic cardiomyopathy are associated with an unfavorable clinical outcome, and additionally compared the presence of defects to echocardiography and angiography findings. METHODS: Dipyridamole thallium-201 single photon emission tomography was performed in 26 apical hypertrophic cardiomyopathy patients, aged 41-78 (22 men, 6 women). Patients with or without perfusion defects were compared for echocardiographic measurements of wall thickness, chamber dimensions, and fractional shortening. Twelve patients underwent coronary angiography. The occurrence of cardiac events was evaluated during clinical follow-up for a mean period of 4.3 +/- 1.9 years (range: 1.0-7.0 year). RESULTS: Thirteen patients (50%) showed perfusion defects, which were predominantly reversible (fixed in 1) and mostly apical (9 of 13). Patients with and without defects did not differ in symptoms, EKG findings, echocardiographic morphology or fractional shortening (41 +/- 4 vs. 41 +/- 7%). Coronary angiography was normal in all patients in whom it was performed (nine with and three without defects). During follow-up, there were no deaths or myocardial infarction. Of the defect positive group, one case developed paroxysmal supraventricular tachycardia, and another had a cerebrovascular accident. Of the defect negative group, one case developed sick sinus syndrome, while another had a hospital admission for anginal pain. CONCLUSIONS: While reversible thallium defects in the absence of coronary artery disease occur frequently in patients with apical hypertrophic cardiomyopathy, the prognosis remains benign despite the presence of ischemia and there is no evidence for an association with adverse patient outcome.

Adult↗

PubMed2003

Analysis of spinal cord proteome in the rats with mechanical allodynia after the spinal nerve injury.

Proteome analysis was carried out to identify the proteins associated with neuropathic pain after peripheral nerve injury. Five proteins displayed different expression levels among three groups of rats. Among these proteins, creatine kinase B expression level was lower in the pain-positive rats compared to the sham or pain-negative rats. Therefore, a lower creatine kinase B expression level may be important in the development and maintenance of neuropathic pain.

Animals↗

PubMed2003

Initial dose cascade of TTS fentanyl with proper adjuvant medications in cancer pain.

According to the three step-ladder analgesics in patients with cancer pain, adjuvant drugs are required for pain relief according to the pain character and also to reduce side effects of opioids. Pain clinicians sometimes want to decide to jump directly from naive and mild opioid to transdermal therapeutic system (TTS) fentanyl with less side effects. We investigated the safety, efficacy, and satisfaction of the patients of TTS fentanyl converting from opioid-naive and mild-opioid with adjuvant drug medications in related to dose cascade of TTS fentanyl. Both opioid-naive (n=3) and opioid-using (n=34) patients started with TTS fentanyl in the lowest available delivery rate (25 microg/hr) with rescue medication. A numeric rating scale (NRS, from 0=no pain to 10=worst pain imaginable), satisfaction of the patients with the transdermal therapy and side effects were recorded everyday during 29 days. Average reductions of NRS scores were 1.79 and 2.77, and the mean doses were 35.14 and 44.12 microg/hr on the 15th and 29th day, respectively. Reported level of satisfaction with the transdermal patch and generalized pain management were 'completely satisfied' and 'satisfied'. Frequent side effects were nausea, vomiting, and constipation. In conclusion, initial application of TTS fentanyl with proper adjuvant medications is effective, safe, and well tolerated.

Administration, Cutaneous↗