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Biomedical subjects

Y Choi

Publications and source records attributed to Y Choi.

At least 289 records · Page 16Linked to original sources
PubMed1994

Use of positron emission tomography with fluorodeoxyglucose in patients with extracranial head and neck cancers.

BACKGROUND: The purpose of this study was to evaluate the utility of positron emission tomography- (PET) 2-[18F]-fluoro-2-deoxy-D-glucose (FDG) imaging in extracranial head and neck cancers. METHODS: Sixty patients with biopsy-proven cancers were studied using PET-FDG. Thirty-four patients were studied before therapy (staging), of which 15 patients received primary radiotherapy and serial PET-FDG imaging (monitoring). Seven patients with advanced disease had laser excision (monitoring), and 19 patients were evaluated for recurrent disease (recurrence). RESULTS: Four patients had unknown primary lesions. PET-FDG imaging located the primary tumor in two of four patients, and magnetic resonance imaging (MRI) in none of four. In the remaining patients (staging), PET-FDG imaging detected the primary tumor in 29 of 30 patients, and MRI in 23 of 30. In the staging group, PET-FDG imaging identified the presence or absence of lymph node involvement in 32 of 34 patients, and MRI in 31 of 34. PET-FDG imaging was helpful in evaluating tumor response to radiation therapy or laser excision. Ten patients evaluated for recurrent disease had biopsy-confirmed recurrences, and 7 had no recurrence. PET-FDG imaging results were positive for primary tumor recurrence in 9 of 10 patients, and MRI results were positive in 6 of 10. MRI results were negative for lymph node disease in one of these patients with recurrent primary tumor where PET-FDG imaging and biopsy demonstrated nodal involvement. PET-FDG results were negative for recurrent disease in seven of seven patients, and MRI results were negative for recurrent disease in in four of seven. CONCLUSION: In this series, the authors found that PET-FDG is a useful diagnostic modality for evaluating the patient with an unknown primary, monitoring response to therapy, and in detecting recurrent tumors.

Adult↗
PubMed1994

Rapid differentiation between Hantaan and Seoul viruses by polymerase chain reaction and restriction enzyme analysis.

The majority of causative strains of hemorrhagic fever with renal syndrome (HFRS) are known as Hantaan and Seoul viruses in Korea. The clinical manifestations may be indistinguishable between both viruses, although the clinical course of Hantaan virus infection is more severe than that of the Seoul virus. Therefore, the differentiation of Hantaan or Seoul virus may be important for predicting the prognosis. The primers were selected from the published sequences of the S segments of Hantaan virus strain 76-118 and Seoul virus strain SR-11, which made it possible to obtain the same size of 403 bp amplified product by reverse transcriptase polymerase chain reaction (RT-PCR) and nested PCR from both viral strains. The differentiation of the amplified products was carried out by restriction enzyme digestion. With HindIII, the 403 bp amplified product from Hantaan virus strain 76-118 was cleaved into two segments of 175 bp and 228 bp. By contrast, the 403 bp product from Seoul virus strain SR-11 was not cut by HindIII. With HinfI, the 403 bp amplified product from Hantaan virus strain 76-118 was divided into two bands of 280 bp and 60 bp on the electrophoresis. In the case of the digestion of 403 bp PCR product from Seoul virus strain SR-11 with HinfI, more than four bands (155 bp, 115 bp, 60 bp, and 32/29 bp) were observed on the 2% agarose gel electrophoresis. This rapid technique may be useful for the differential diagnosis of Asian HFRS in Korea.

Animals↗
PubMed1994

Haemorrhagic fever with renal syndrome in Korean children. Korean Society of Pediatric Nephrology.

Haemorrhagic fever with renal syndrome (HFRS) is an acute disease caused by Hantavirus and clinically characterised by abrupt onset of fever, various haemorrhagic manifestations and transient renal and hepatic dysfunction. We retrospectively reviewed 63 cases of HFRS in children from 13 different hospitals in Korea who presented over a 15-year period. The age of the patients ranged from 7 to 15 years, with a male to female ratio of 8 to 1. Fifty-four (86%) patients were 10 years or older. On admission, 24 (38%) were in the febrile phase and 35 (56%) were in the oliguric phase. Fever (100%) abdominal pain (91%), headache (76%) and vomiting (73%) were the most common symptoms. Backache, subconjunctival haemorrhage and hypertension were also noted in about one-third of patients. Hypotension was documented in only 7 (11%) patients. Leucocytosis (> 10,000/mm3) and thrombocytopenia (< 150,000/mm3) were noted in more than two-thirds of patients. Elevated blood urea nitrogen and serum creatinine was observed in 94% by the 7th (median) day of illness. Elevated aspartate aminotransferase and/or alanine aminotransferase were found in more than two-thirds of patients. Renal biopsy was performed in 12 patients and revealed various stages of acute tubular necrosis with occasional interstitial cell infiltration and oedema. Only 2 showed evidence of interstitial haemorrhage. Eleven patients required 1-3 days of dialysis and the remaining patients required only conservative management. Three (5%) patients died of shock, respiratory failure and pulmonary haemorrhage. All other patients recovered without sequelae. Although childhood cases were much less common than adults, clinical and laboratory findings were in general similar between children and adults.

Adolescent↗
PubMed1994

Hemolytic uremic syndrome: MR findings of CNS complications.

MR findings of a patient with hemolytic uremic syndrome involving the CNS are described. Abnormal high signal intensity on T2-weighted images combined with swelling in the lentiform nucleus, posterior limb of internal capsule, external capsule bilaterally, and left extreme capsule was shown on initial MR; a small low signal intensity in the left putamen on T1- and T2-weighted images and generalized atrophy in the area of high signal intensity on previous T2-weighted images was shown on follow-up MR. These findings indicate infarct with focal hemorrhage, which is one of the histopathological features of CNS complication in hemolytic uremic syndrome.

Brain Diseases↗
PubMed1994

Diagnostic value of C-reactive protein in acute appendicitis.

Serum C-reactive protein was measured in 56 patients hospitalized with a suspected diagnosis of acute appendicitis. Based on these determinations, four groups of patients were defined: Group A = 26 patients with acute appendicitis who had a C-reactive protein level higher than 2.5 mg/dl. Group B = 4 patients with a C-reactive protein level lower than 2.5 mg/dl who, after surgery based on a presumed diagnosis of acute appendicitis, were found to have a normal appendix. Group C = 22 patients with nonspecific abdominal pain, 18 (72 percent) of whom had an elevated C-reactive protein level, although in only 4 (7.1 percent) were these levels higher than 2.5 percent mg/dl. Group D = 4 patients who had diseases other than acute appendicitis. It is concluded that an increase in C-reactive protein levels to more than 2.5 mg/dl is not a definite indicator of acute appendicitis. However, if the C-reactive protein level in blood drawn 12 hours after the onset of symptoms is less than 2.5 mg/dl, acute appendicitis can be excluded.

Acute Disease↗
PubMed1994

Effect of exercise supplementation during adenosine infusion on hyperemic blood flow and flow reserve.

Physical stress might modulate myocardial blood flow in near-maximally dilated coronary arteries by increasing coronary perfusion pressure, myocardial contractility, and heart rate. The net effect of these changes on hyperemic blood flows has not yet been defined in humans. To quantify the effect of physical exercise on pharmacologically induced hyperemia, myocardial blood flow was measured in 11 healthy volunteers. Measurements were performed with positron emission tomographic imaging with nitrogen-13 ammonia at rest, during intravenous (i.v.) adenosine administration (140 micrograms.kg-1.min-1 over 6 minutes), and during i.v. adenosine administration plus supine bicycle exercise with a maximal workload of 125 W. Myocardial blood flow was quantified by using a previously validated graphic analysis. Heart rate, systolic blood pressure, rate-pressure product, and mean aortic blood pressures were significantly higher during combined physical and pharmacologic stress than during pharmacologic stress alone. However, myocardial blood flow decreased from 2.6 +/- 0.4 to 2.2 +/- 0.4 ml.min-1.gm-1 with the addition of physical stress (p < 0.05). This decline was associated with a significant increase in coronary vascular resistance (35 +/- 6 vs 52 +/- 13 mm Hg.ml-1.gm.min; p < 0.05). Accordingly, myocardial flow reserve declined, from 5.0 +/- 0.9 to 4.3 +/- 1.0, with exercise supplementation (p < 0.05). Exercise in addition to pharmacologic stress increases coronary vascular resistance and thus significantly decreases hyperemic myocardial blood flow and flow reserve. This decrease results most likely from an increase in extravascular restrictive forces caused by higher ventricular pressures and contractility during physical stress.

Adenosine↗
PubMed1994

Evaluation of the effect of glucose ingestion and kinetic model configurations of FDG in the normal liver.

UNLABELLED: The liver plays an important role in glucose homeostasis. PET studies with 2-[F-18]fluoro-2-deoxy-D-glucose (FDG) of the liver (e.g., in neoplasms) require an understanding of the effects of dietary conditions on hepatic FDG uptake. METHODS: Twenty studies were performed on 10 normal volunteers (ages 24 +/- 4) after fasting 4 to 19 hr and again after oral consumption of 100 g of dextrose to investigate tracer kinetic model configurations of FDG in the normal liver and to evaluate the impact of oral glucose on liver in normal subjects. Dynamic PET images were acquired for about 1 hr using a Siemens/CTI 931 tomograph. RESULTS: A three-compartment model with an input function delay time parameter was the statistically preferred model configuration. The model estimated transport rate constant from plasma to liver, K1, increased significantly (p < 0.05) from 0.864 +/- 0.136 ml/min/g in fasting studies to 1.058 +/- 0.269 ml/min/g in postglucose studies. Glucose loading also significantly increased (p < 0.01) the rate constant for FDG phosphorylation, k3, from 0.005 +/- 0.003 min-1 in fasting studies to 0.013 +/- 0.007 min-1 in postglucose administration and, consequently, significantly increased both the phosphorylation fraction (k3/(k2 + k3)) and the influx constant (K1k3/(k2 + k3)). No significant differences in the liver-to-plasma transport rate constant, k2, dephosphorylation constant, k4, or distribution volume of FDG (K1/(k2 + k3)) were observed. CONCLUSION: Dynamic FDG-PET studies can be used to evaluate kinetics of liver glucose metabolism. The results indicate that dietary conditions have a significant effect on hepatic FDG kinetics. Because of the higher net FDG uptake by normal liver after glucose loading, fasting conditions are preferred for FDG liver tumor studies to increase the tumor-to-background contrast.

Administration, Oral↗
PubMed1993

Positron emission tomography with fluorodeoxyglucose to evaluate tumor response and control after radiation therapy.

PURPOSE: Following radiation therapy, evaluation of viable tumor can often be difficult with anatomic imaging criteria (tumor size alone). In this study, the utility of biochemical imaging with the glucose analog 2-[F-18]fluoro-2-deoxy-D-glucose and positron emission tomography was investigated in patients treated with radiation therapy. METHODS AND MATERIALS: Between 1990 and 1992, 19 patients were studied, including 15 patients with head and neck cancer, (4 oropharynx, 4 sinus, 3 larynx, 2 hypopharynx, 2 oral cavity [one patient], 1 nasopharynx), and 4 patients with breast cancer. Post-radiation positron emission tomography with 2-[F-18]fluoro-2-deoxy-D-glucose studies were done in all patients, with 9 head and neck patients receiving pre-radiation positron emission tomography with 2-[F-18]fluoro-2-deoxy-D-glucose scans as well. Results were correlated with other imaging techniques and pathology. RESULTS: Positron emission tomography with 2-[F-18]fluoro-2-deoxy-D-glucose detected head and neck primary tumors and lymph node metastases in all nine pre-radiation scans, while magnetic resonance imaging failed to detect two primary tumors. Serial positron emission tomography with 2-[F-18]fluoro-2-deoxy-D-glucose showed a significant decrease in tumor activity after radiation therapy, compared to pre-radiation levels, (p < 0.05), except for two patients with increased uptake at the primary site. Biopsies of these two patients showed persistent/recurrent disease after radiation therapy, which was not detected by magnetic resonance imaging. Six additional head and neck patients, with suspicious examination and inconclusive magnetic resonance imaging, were imaged with positron emission tomography after radiation therapy only. Five patients had increased positron emission tomography activity, with corresponding biopsies positive in four patients, and negative in one patient with clinically worsening symptoms. The remaining sixth patient had minimal and stable positron emission tomography uptake, and is improving clinically. Four patients had mammogram findings suspicious for recurrence after conservation treatment for breast cancer. Positron emission tomography with 2-[F-18]fluoro-2-deoxy-D-glucose showed no focal activity in the breast in two patients, and increased activity in the area suspicious for recurrence in the other two patients. Biopsies correlated with positron emission tomography results. CONCLUSION: Changes and presence of positron emission tomography with 2-[F-18]fluoro-2-deoxy-D-glucose activity correlated with pathologic findings in head and neck and breast cancer patients in this series. In patients with elevated or rising positron emission tomography activity after radiation therapy, persistent or recurrent disease was found in 89% of patients, (8/9). Magnetic resonance imaging did not detect the head and neck recurrences, and mammography was suspicious in patients with both benign and malignant breast changes after radiation therapy. In addition, our data indicate that in head and neck patients with pre-radiation positron emission tomography scans, a significant decrease in activity should occur after radiation therapy, if local control is to be expected.

Adult↗
PubMed1993

Direct evidence for the role of COOH terminus of mouse mammary tumor virus superantigen in determining T cell receptor V beta specificity.

It has recently been shown that open reading frames in the 3' long terminal repeats of mouse mammary tumor viruses encode superantigens. These viral superantigens (vSAGs) stimulate most T cells expressing appropriate V beta s almost regardless of the rest of the variable components of the T cell receptors (TCR) expressed by those cells. vSAGs produce a type II integral membrane protein with a nonessential short cytoplasmic domain and a large glycosylated extracellular COOH-terminal domain, which is predicted to interact with major histocompatibility complex class II molecules and the TCR. The transmembrane region of vSAG also has an internal positively charged lysine residue of unknown significance. A set of chimeric and mutant vSAG genes has been used in transfection experiments to show that only the extreme COOH-terminal portion of vSAGs determine their TCR V beta specificities, and to show that the lysine residue in the transmembrane domain is not essential for the function of vSAG.

Amino Acid Sequence↗
PubMed1993

Ex vivo clonotype primer-directed gene amplification to identify malignant T cell repertoires.

A novel strategy that utilizes input genomic DNA and overcomes limitations encountered with traditional RNA reverse transcription-polymerase chain reaction (PCR) amplification methodology is described to screen for T cell receptor (TCR) repertoires. The methodology has been developed to identify individual T cell clonotypes with regard to their unique receptor beta chain variable/diversity/joining (VDJ) region gene rearrangement. The technique avoids preselection for a given antigen specificity and is therefore independent of artificial bias introduced by in vitro cell population expansion. This technique was used to detect and identify genetically of malignant clones from heterogeneous mononuclear cell populations from an array of hemato-oncological disorders, including mycosis fungoides/Sézary Syndrome, adult T cell leukemia, and large granular lymphoproliferative disease. An initial primary PCR, directed by a TCR-J beta generic primer and a complement of family-specific TCR-V beta primers, defines predominant T cell receptor variable gene usage. Use of a TCR-J beta generic primer supplants the use of a constant region primer anchor and thus eliminates the need to target mRNA. The process of variable gene screening also expedites gene sequencing. By sequencing through the VDJ juxtaposed region, i.e., the third complementarity determinant region, clonotype-specific primers are developed and used in a secondary clonotype primer-directed PCR (CPD-PCR) to detect, with extreme sensitivity and specificity, unique T cell clonal repertoires. Analysis of the products of the CPD-PCR permits the detection of a single malignant cell among one million polyclonal cells and supercedes the constraints of prior studies that provide a limited evaluation of family variable gene repertoire usage. This strategy may be applied in the detection of minimal residual disease, in surveillance after induction of disease-free states, and in analyzing the effectiveness of purging autologous bone marrow of malignant clones.

Base Sequence↗
PubMed1993

An animal model for in vivo evaluation of tumor glycolytic rates with positron emission tomography.

We developed a method for evaluating tumor glycolytic rates in vivo with nude mice injected with 2-[F-18]fluoro-2-deoxy-D-glucose (FDG) and a dedicated animal positron emission tomography (PET) scanner. Animals were injected with NR-6 mouse fibroblast tumor cell lines. When tumors achieved a large enough size to be macroscopically visible, quantitative measurements of FDG uptake in vivo were obtained, using both standard nonlinear regression with the FDG tracer kinetic model to generate estimates of model parameters, including KNLR, the rate constant for net phosphorylation of FDG. Additionally, we determined the values of KPAT, the rate constant for net phosphorylation of FDG measured with a non-iterative graphical method. Estimates of K were highly correlated (r = 0.95) with both methods, and parametric images of KPAT demonstrate both the tumor location and size, but are also scaled in units of phosphorylation of FDG. The method is suitable for serial studies of tumor glucose metabolism during and after therapeutic interventions, such as chemotherapeutic trials.

Animals↗
PubMed1993

Factors affecting myocardial 2-[F-18]fluoro-2-deoxy-D-glucose uptake in positron emission tomography studies of normal humans.

The goal of this study was to identify the anatomic and physiologic factors affecting left ventricular myocardial 2-[F-18]fluoro-2-deoxy-D-glucose (FDG) uptake and myocardial glucose utilization rates (MRGlc) in normal humans. Eighteen healthy male volunteers were studied in the fasting state (4-19 h) and 16 after oral glucose loading (100 g dextrose) with positron emission tomography (PET) and FDG. Substrate and hormone concentrations were measured in each study. The kinetics of myocardial FDG uptake were evaluated using both a three-compartment model and Patlak graphical analysis. Systolic blood pressures and rate pressure products were similar in the fasting and postglucose states. MRGlc averaged 0.24 +/- 0.17 mumol/min/g in fasting subjects and rose to 0.69 +/- 0.11 mumol/min/g after glucose loading. Phosphorylation rate constant, k3, and MRGlc were linearly related (P < 0.001). Increases in MRGlc following glucose loading were correlated with plasma glucose, insulin and free fatty acid concentrations, ratios of insulin to glucagon levels, and influx rate constants of FDG. Glucose loading improved the diagnostic image quality due to more rapid clearance of tracer from blood and higher myocardial FDG uptake. When MRGlc, glucose and insulin concentrations, and insulin to glucagon ratios exceeded 0.2 mumol/min/g, 100 mg/dl, 19 microU/ml, and 0.2 microU/pg, respectively, myocardial uptake of FDG was always adequate for diagnostic use. FDG image quality and MRGlc were similar after relatively short (6 +/- 2 h) and overnight (16 +/- 2 h) fasting. Significant (P < 0.05) regional heterogeneity of myocardial FDG uptake and MRGlc was observed in both the fasting and the postglucose studies. MRGlc and FDG uptake values in the posterolateral wall were higher than those in the anterior wall and septum. Thus, both 6-h and overnight fasts resulted in similarly low myocardial glucose utilization rates. While MRGlc and myocardial FDG uptake depended on plasma glucose, free fatty acid, and insulin concentrations, the results also suggest an additional dependency on plasma glucagon levels. Regional heterogeneities in myocardial FDG uptake and MRGlc are evident and independent of the subjects' dietary state. These regional heterogeneities need to be considered in studies of patients with cardiac disease.

Adult↗