Biomedical subjects

Jae Hyuk Lee

Publications and source records attributed to Jae Hyuk Lee.

7 recordsLinked to original sources

PubMed2006

Analyzing solution-phase time-resolved x-ray diffraction data by isolated-solute models.

Extracting transient structural information of a solute from time-resolved x-ray diffraction (TRXD) data is not trivial because the signal from a solution contains not only the solute-only term as in the gas phase, but also solvent-related terms. To obtain structural insights, the diffraction signal in q space is often Fourier sine transformed (FT) into r space, and molecular dynamics (MD) simulation-aided signal decomposition into the solute, cage, and solvent terms has so far been indispensable for a clear-cut assignment of structural features. Here we present a convenient method of comparative structural analysis without involving MD simulations by incorporating only isolated-species models for the solute. FT is applied to both the experimental data and candidate isolated-solute models, and comparison of the correlation factors between the experimental FT and the model FTs can distinguish the best candidate among isolated-solute models for the reaction intermediates. The low q region whose influence by solvent-related terms is relatively high can be further excluded, and this mode of truncated Fourier transform (TFT) improves the correlation factors and facilitates the comparison. TFT analysis has been applied to TRXD data on the photodissociation of C(2)H(4)I(2) in two different solvents (methanol and cyclohexane), HgI(2) in methanol, and I(3) (-) in methanol excited at 267 nm. The results are consistent with previous conclusions for C(2)H(4)I(2) in methanol and HgI(2) in methanol, and the new TRXD data reveal that the C(2)H(4)I transient radical has a bridged structure in cyclohexane and I(3) (-) in methanol decomposes into I+I(2) (-) upon irradiation at 267 nm. This TFT method should greatly simplify the analysis because it bypasses MD simulations.

Journal Article↗

PubMed2006

Spatiotemporal reaction kinetics of an ultrafast photoreaction pathway visualized by time-resolved liquid x-ray diffraction.

We have studied the reaction dynamics for HgI(2) in methanol by using time-resolved x-ray diffraction (TRXD). Although numerous time-resolved spectroscopic studies have provided ample information about the early dynamics of HgI(2), a comprehensive reaction mechanism in the solution phase spanning from picoseconds up to microseconds has been lacking. Here we show that TRXD can provide this information directly and quantitatively. Picosecond optical pulses triggered the dissociation of HgI(2), and 100-ps-long x-ray pulses from a synchrotron probed the evolving structures over a wide temporal range. To theoretically explain the diffracted intensities, the structural signal from the solute, the local structure around the solute, and the hydrodynamics of bulk solvents were considered in the analysis. The results in this work demonstrate that the determination of transient states in solution is strongly correlated with solvent energetics, and TRXD can be used as an ultrafast calorimeter. It also is shown that a manifold of structural channels can be resolved at the same time if the measurements are accurate enough and that global analysis is applied. The rate coefficients for the reactions were obtained by fitting our model against the experimental data in one global fit including all q-values and time delays. The comparison between all putative reaction channels confirms that two-body dissociation is the dominant dissociation pathway. After this primary bond breakage, two parallel channels proceed. Transient HgI associates nongeminately with an iodine atom to form HgI(2), and I(2) is formed by nongeminate association of two iodine atoms.

Journal Article↗

PubMed2006

Expression of PTEN in the progression of cervical neoplasia and its relation to tumor behavior and angiogenesis in invasive squamous cell carcinoma.

BACKGROUND AND OBJECTIVES: Loss of PTEN expression has been associated with tumor progression and adverse patient outcome. The purpose of this study was to evaluate PTEN expression in the successive steps of progression in cervical neoplasia and to determine its correlation with tumor angiogenesis and clinicopathologic features in squamous cell carcinoma of the uterine cervix. METHODS: Immunohistochemical staining with anti-PTEN antibody was performed in a total of 160 patients with 12 normal cervical epithelium, 63 cervical intraepithelial neoplasia (33 CIN I, 30 CIN III), and 85 cervical squamous cell carcinomas. Microvessels were immunohistochemically labeled with an antibody for CD34. Computerized image analysis was used to evaluate microvessel density (MVD). RESULTS: Reduced PTEN expression progressively increased along the continuum from normal epithelium to squamous cell carcinoma (P < 0.01). There was no significant correlation between PTEN expression and MVD. On univariate analysis, stage and reduced PTEN expression were significant prognostic factors for both disease-free and overall survival. However, stage was the only independent prognostic factor by multivariate analysis. CONCLUSIONS: Our results suggest that tumor progression in the cervical epithelium is accompanied by loss of PTEN protein expression. Reduced PTEN expression is not associated with tumor angiogenesis of squamous cell carcinoma of the uterine cervix.

Adult↗

PubMed2004

The course of patients with lacunar infarcts and a parent arterial lesion: similarities to large artery vs small artery disease.

BACKGROUND: The significance of occlusive lesions of the parent artery in patients with lacunar syndrome (LS) and small deep infarcts (SDIs) on diffusion-weighted imaging remains unclear. OBJECTIVE: To compare the recurrence of stroke in patients with LS and SDIs between those with vs without a parent arterial lesion. DESIGN: Analysis of data from a prospective acute stroke registry. SETTING: University hospital. PATIENTS: Using clinical syndrome, diffusion-weighted imaging, and vascular studies, we divided 173 patients into 3 groups: (1) parent arterial disease occluding deep perforators (PAD), LS with SDIs, and a parent arterial lesion (n = 32); (2) small artery disease (SAD) (n = 70); and (3) large artery disease (LAD) (n = 71). MAIN OUTCOME MEASURES: Recurrent strokes and the prognosis were registered for 1 year, and the outcome of the PAD group was compared with that of the SAD and LAD groups. RESULTS: During follow-up, there were 9 deaths (6 vascular) and 18 recurrent strokes. The recurrence rate in the PAD group (16%) was significantly higher than that in the SAD group (1%) (P =.01) but similar to that in the LAD group (17%) (P =.87). The presence of the parent arterial lesion was the only independent predictor of stroke recurrence in patients with LS and SDIs (odds ratio, 13.8; 95% confidence interval, 1.5-123.9; P =.02). CONCLUSIONS: Although LS on examination, SDIs on diffusion-weighted imaging, and a stable hospital course suggest lacunar stroke of benign course, our results indicate that the PAD group represents an intracranial type of LAD.

Adult↗

PubMed2004

Expression of cyclooxygenase-2 in adenocarcinomas of the uterine cervix and its relation to angiogenesis and tumor growth.

OBJECTIVE: The purpose of this study was to evaluate cyclooxygenase (COX)-2 expression in adenocarcinomas of the uterine cervix and its correlation with clinicopathologic features, angiogenesis, and tumor growth. METHODS: Thirty-nine cases of FIGO clinical stage I and II adenocarcinoma of the uterine cervix were examined by immunohistochemical studies with anti-COX-2. Microvessels were immunohistochemically labeled with an antibody to CD34. Computerized image analysis was used to evaluate microvessel density (MVD). The apoptotic cells were visualized by terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling (TUNEL) and proliferative cells were visualized by staining with Ki-67 antibody. RESULTS: Twenty-eight tumors (71.8%) were classified as COX-2 positive. COX-2 expression correlated with FIGO stage (P < 0.01). Tumors expressing COX-2 had a significantly higher MVD and Ki-67 index than those that did not express COX-2 (P < 0.05). However, COX-2 expression did not correlate with the apoptotic index. In univariate long-rank analysis, COX-2 expression, MVD, and FIGO stage were associated with shortened survival. However, FIGO stage and MVD were the only independent prognostic factors by multivariate analysis. CONCLUSIONS: Our results suggest that COX-2 expression in cervical adenocarcinomas may contribute to tumor progression by increasing angiogenesis and cell proliferation.

Adenocarcinoma↗

PubMed2004

Clinicopathological characteristics of signet ring cell carcinoma of the stomach.

BACKGROUND: Signet ring cell (SRC) carcinoma of the stomach is characterized by its poor prognosis and potential to infiltrate the wall of stomach, although survival studies comparing carcinomas with and without SRC features have yielded inconsistent results. This study compared the clinicopathological features and prognosis of patients with SRC carcinoma with those with non-signet ring cell carcinoma of the stomach (NSRC). METHODS: We reviewed the records of 2358 patients diagnosed with gastric carcinoma who were treated surgically between January 1980 and December 1999 at the Department of Surgery, Chonnam National University Hospital. There were 204 patients (8.7%) with SRC carcinoma as compared to 2154 with NSRC. RESULTS: Significant differences were noted in the mean patient age, mean tumour size, depth of invasion, prevalence of hepatic and regional lymph node metastases, tumour stage, and curability between the patients with SRC histology and NSRC. There were no statistically significant differences in patient gender, location, or peritoneal dissemination between patients with SRC carcinoma and NSRC. SRC carcinoma of the stomach had a higher prevalence of early gastric carcinoma (46.1%) than NSRC (21.7%). The overall 5-year survival of all the patients with SRC carcinoma was 60.2% as compared with 48.9% for the patients with NSRC (P < 0.01). Using Cox proportional hazards model, lymph node metastasis and curability were significant factors affecting the outcome. Signet ring cell histology itself was not an independent prognostic factor. CONCLUSIONS: Patients with SRC histology do not have a worse prognosis than patients with other types of gastric carcinoma.

Adult↗

PubMed2003

Comparison of epigenetic and genetic alterations in mucinous cystic neoplasm and serous microcystic adenoma of pancreas.

Mucinous cystic neoplasms and serous microcystic adenomas account for the majority of cystic tumors of pancreas. Mucinous cystic neoplasms and serous microcystic adenomas have different frequencies of progression to malignancy. The genetic and epigenetic alterations of these tumors have not been studied in detail. In this study, we compared methylation status of p16, p14, VHL, and ppENK genes by methylation-specific PCR (MSP), and genetic alterations including K-ras and beta-catenin gene mutations, chromosome 3p loss, and microsatellite instability in 15 mucinous cystic neoplasms (10 benign and 5 borderline) and 16 serous microcystic adenomas. There were no significant differences between mucinous cystic neoplasms and serous microcystic adenomas in methylation of p16 (14%, 2/14 and 12%, 2/16), p14 (15%, 2/13 and 37%, 6/16), VHL (0/14 and 7%, 1/14), and ppENK (0/14 and 0/13), respectively. K-ras mutation was present only in mucinous cystic neoplasms but not in serous microcystic adenomas (33%, 5/15 versus 0/16; P =.004). In addition, LOH at 3p25, the chromosomal location of VHL gene, was present in 57% (8/14) of serous microcystic adenomas compared with in 17% (2/12) of mucinous cystic neoplasms (P =.03). No beta-catenin mutation, microsatellite instability, or mutation of transforming growth factor beta type II receptor was present in either type of tumors. In conclusion, K-ras mutations and allelic loss of VHL locus at 3p25, but not methylation, distinguished mucinous cystic neoplasms and serous microcystic adenomas. The differences in genetic alterations but not epigenetic alterations may explain the pathogenesis and progression to malignancy of these cystic tumors of pancreas.

Adenoma↗