Biomedical subjects

K S Choi

Publications and source records attributed to K S Choi.

At least 73 records · Page 4Linked to original sources

PubMed1996

Interaction of the human T-cell lymphotropic virus type 1 tax transactivator with transcription factor IIA.

The Tax protein of human T-cell lymphotropic virus type 1 (HTLV-1) is a 40-kDa transcriptional activator which is critical for HTLV-1 gene regulation and virus-induced cellular transformation. Tax is localized to the DNA through its interaction with the site-specific activators cyclic AMP-responsive element-binding protein, NF-kappaB, and serum response factor. It has been suggested that the recruitment of Tax to the DNA positions Tax for interaction with the basal transcriptional machinery. On the basis of several independent assays, we now report a physical and functional interaction between Tax and the transcription factor, TFIIA. First, Tax was found to interact with the 35-kDa (alpha) subunit of TFIIA in the yeast two-hybrid interaction system. Importantly, two previously characterized mutants with point mutations in Tax, M32 (Y196A, K197S) and M41 (H287A, P288S), which were shown to be defective in Tax-activated transcription were unable to interact with TFIIA in this assay. Second, a glutathione-S-transferase (GST) affinity-binding assay showed that the interaction of holo-TFIIA with GST-Tax was 20-fold higher than that observed with either the GST-Tax M32 activation mutant or the GST control. Third, a coimmunoprecipitation assay showed that in HTLV-1-infected human T lymphocytes, Tax and TFIIA were associated. Finally, TFIIA facilitates Tax transactivation in vitro and in vivo. In vitro transcription studies showed reduced levels of Tax-activated transcription in cell extracts depleted of TFIIA. In addition, transfection of human T lymphocytes with TFIIA expression vectors enhanced Tax-activated transcription of an HTLV-1 long terminal repeat-chloramphenicol acetyltransferase reporter construct. Our study suggests that the interaction of Tax with the transcription factor TFIIA may play a role in Tax-mediated transcriptional activation.

Amino Acid Sequence↗

PubMed1996

Central neurocytoma: proliferative potential and biological behavior.

The authors analyzed 13 central neurocytomas diagnosed at Seoul National University Hospital between January 1982 and December 1993 to clarify the proliferative potential and biological behavior of these tumors. The tumor was confined to the lateral and third ventricles in 12 cases and in one case extended from the posterior thalamus to the body and trigone area of the lateral ventricle. In all 13 cases, typical clinical and radiological findings were observed, and histological diagnosis was performed via craniotomy. The diagnosis was made using light microscopic examination, immunohistochemical staining for neuronal markers, and electron microscopic findings of neuronal differentiation. One patient died due to tumor progression with recurrence 26 months after subtotal removal plus radiation therapy. Another patient had a recurrence 18 months after total tumor removal. The remaining 11 patients are free of recurrent tumor after a follow-up period that ranged from 14 to 109 months (median 50 months). To predict the proliferative potential, immunoreactivity to proliferating cell nuclear antigen (PCNA), silver colloid staining for nucleolar organizing regions (AgNORs), and DNA flow cytometry were performed in 10 of the 13 cases. The proportion of PCNA-positive cells was less than 1% in all cases and the AgNORs score ranged from 1.11 to 2.0 (mean 1.67). The DNA flow cytometry revealed diploidy in all cases and the calculated proliferation index ranged from 5.1% to 9.6% (mean 7.8%). The one case of tumor recurrence, in which the authors performed the study of proliferative potential, and another case that demonstrated mild nuclear pleomorphism also showed low percentages of PCNA-positive cells, low AgNORs scores, and diploidy in DNA flow cytometry. It is suggested that most central neurocytomas follow a benign clinical course with low proliferative potential assessed by PCNA, AgNORs, and DNA flow cytometry; however, recurrence is possible within a relatively short time period.

Adolescent↗

PubMed1996

Cerebral sparganosis: clinical manifestations, treatment, and outcome.

Cerebral sparganosis is a rare parasitic disease caused by infestation by the plerocercoid larva of Spirometra mansoni. The authors retrospectively analyzed 17 cases of cerebral sparganosis treated at Seoul National University Hospital between 1986 and 1994. The patients' ages at diagnosis ranged from 6 to 57 years (median 32 years) and the male/female ratio was 13:4. Diagnosis was based on radiological findings, serological test results, operative findings, and histopathological examinations. Characteristic magnetic resonance (MR) findings consisted of widespread white matter degeneration and cortical atrophy, mixed-signal lesion (low in the central and high in the peripheral regions on T2-weighted images) with irregular dense enhancement of central foci and changes in the location and shape of the enhancing lesion in follow-up studies. Ten patients underwent surgical removal of the parasitic lesion, six received medical treatment alone (five with praziquantel and one with antiepileptic drugs), and one underwent insertion of a ventriculoperitoneal shunt and a course of praziquantel. Follow-up periods ranged from 13 to 111 months (mean 49 months). Seven patients who underwent complete removal of the lesion, live worm, or degenerative worm with surrounding granuloma showed a favorable course. Patients who received medical treatment alone or incomplete removal exhibited progression in their neurological deficits and their seizures could not be controlled. Medication with praziquantel seemed to have no killing effect on live worms. The authors conclude that MR imaging is the most valuable modality for the early detection of cerebral sparganosis and that complete surgical removal of granuloma together with worms, whether they are alive or degenerative, is the treatment of choice.

Adolescent↗

PubMed1996

Peritoneal catheter-related complications: a comparison between hemodialysis and intermittent peritoneal dialysis in the break-in period.

We prospectively monitored the clinical outcome of 89 curled, double-cuff peritoneal catheters (PC) implanted by surgeons over one year. Thirty-six cases (40%) were supported with hemodialysis (HD) (group A) and 53 cases (60%) were supported with weekly intermittent peritoneal dialysis (IPD) (small exchange volume with a cycler) (group B) for four weeks before commencing continuous ambulatory peritoneal dialysis (CAPD). PC-related complications between the two groups were compared. Ten cases failed to complete the six-month observation period (8 died, 1 received kidney transplant, and 1 defaulted follow-up),Total experience accumulated was 494 patient-months (195 patient-months in group A, 299 patient-months in group B). The incidence of pericatheter leakage (group A vs group B) was significantly higher in group B (0% vs 13%, p < 0.05). There were no significant differences in the incidence of other PC-related complications, removal of PC, and mortality rate in the two groups. The incidence of pericatheter leakage was significantly higher in diabetic patients (71% vs 22%, p < 0.05), and group B patients with leakage had a higher incidence of external cuff erosion 57% vs 7%, p < 0.005) and delay in CAPD training (71% vs 7%, p < 0.005). We conclude that both HD and IPD are equally safe renal replacement therapies in the break-in period, while patients supported with IPD had a higher incidence of pericatheter leakage, which was associated with other catheter-related morbidities including external cuff erosion and delay in CAPD training.

Adult↗

PubMed1995

The retinoblastoma gene product negatively regulates transcriptional activation mediated by the human cytomegalovirus IE2 protein.

The IE2 gene product of human cytomegalovirus (HCMV) is one of a few viral regulatory proteins expressed immediately upon infection of the host cell. It is a potent transcriptional activator of many viral and cellular promoters. We found that the retinoblastoma susceptibility gene product (Rb) dramatically suppressed this IE2 transactivation of various promoters. However, unlike another tumor suppressor protein, p53, Rb did not have any significant effect on basal levels of transcription, suggesting that Rb specifically interacts with IE2 rather than other cellular factors involved in the general transcription machinery. We found by protein-affinity chromatography that Rb in nuclear extracts or produced by in vitro translation directly bound to IE2. Our results suggest that Rb may regulate the life cycle of HCMV, which is endemic in the human population. Furthermore, these data may provide new insights into the slow rate of HCMV DNA replication in cells and the possible involvement of HCMV in tumorigenesis.

Cell Line↗

PubMed1995

99mTc-HMPAO labeled leukocyte SPECT in intracranial lesions.

BACKGROUND: Scintigraphy with 111In (indium-111)-oxine or 99mTechnetium-hexamethylpropyleneamine oxime (99mTc-HMPAO) labeled leukocytes has been used to differentiate brain abscess from brain tumor. However, there are false positive or false negative results from planar scintigraphic images. So a more specific and sensitive scintigraphic technique needs to be developed. METHODS: Planar and single photon emission computed tomography (SPECT) images were obtained and reviewed in 14 patients with intracerebral ring-enhancing lesions on computed tomography (CT) or magnetic resonance imaging (MRI). In all patients, diagnosis was confirmed by histopathologic examination. The effect of steroids or antibiotics on scintigraphic finding was examined. RESULTS: Abscess was confirmed in six patients, tumor in six, tuberculoma and cysticercosis in one each, respectively. In all the patients with abscess, SPECT showed increased focal activity irrespective of steroid or antibiotic therapy. Increased radioactivity, which could not be detected on planar images, could be identified in two patients with abscess. In three of the six patients with tumor, radiolabeled leukocytes did not accumulate in the tumor. In the other three patients with tumor, SPECT showed focally increased activity that was less intense than the activity shown in the patients with abscess. CONCLUSIONS: 99mTc-HMPAO labeled leukocyte SPECT is useful for the differential diagnosis of intracerebral ring-enhancing lesions, and the use of steroids or antibiotics does not influence the sensitivity of SPECT. Diagnostic sensitivity of scintigraphy with labeled leukocytes could be improved by SPECT in addition to planar image.

Adult↗

PubMed1995

Loss of heterozygosity on chromosome 10, 13q(Rb), 17p, and p53 gene mutations in human brain gliomas.

Using the methods of restriction fragment length polymorphism (RFLP) and single strand conformation polymorphism (SSCP) analyses, we have examined 33 cases of human gliomas with various malignant grades to detect the deletions of putative tumor suppressor gene loci, chromosome 10, 13q(retinoblastoma gene, Rb), 17p, and p53 mutation. We observed loss of heterozygosity (LOH) at loci on chromosome 10 (36%), 13q(Rb) (54%), and 17p(50%) in malignant gliomas. There, however was no allelic loss on chromosome 10 and 17p in low-grade gliomas. Rb gene deletions were seen in low-grade gliomas, including oligodendroglioma and ependymoma. This finding suggests that Rb inactivation may be an early genetic event in the development and progression of gliomas. We correlated the results of LOH on chromosome 17p and p53 mutation. Among the 8 cases which showed LOH on chromosome 17p, only three cases (38%) revealed p53 mutations. Low incidence of p53 mutations in cases with chromosome 17p deletions suggests that some other tumor suppressor genes may be located on chromosome 17p.

Astrocytoma↗

PubMed1994

Bacterial expression, purification of full length and carboxyl terminal fragment of Alzheimer amyloid precursor protein and their proteolytic processing by thrombin.

Human amyloid protein precursor(APP770) and its carboxyl terminal portion (CT105) including beta/A4 domain were highly expressed using strong expression systems in E. coli. These recombinant APP peptides were purified with a combination of urea solubilization and ion-exchange chromatography and used for proteolytic processing by thrombin. Three thrombin cleavage sites were predicted by the decrease of APP770 and the appearance of M(r) 56, 27 and 18 kDa fragments containing beta/A4 domain on SDS-PAGE gel and on the immunoblot. A similar but limited proteolysis of platelet APPs exposed to thrombin resulted in the stimulated production of 60 and 27 KDa carboxyl terminal peptides containing the intact beta/A4. This thrombin mediated proteolysis was completely blocked by hirudin, the specific thrombin inhibitor. These results suggest that thrombin may play a role in altered processing of APP to generate potentially amyloidogenic intermediates in vivo leading to amyloid deposition.

Amino Acid Sequence↗

PubMed1994

Diastematomyelia--clinical manifestation and treatment outcome.

Diastematomyelia is a rare congenital anomaly characterized by a division of the spinal cord or the filum terminale into two parts. In Korea, only one case has been reported. The authors have operated on 5 cases of diastematomyelia with septum since July, 1978. The ages ranged from 1 to 44 years (median; 11 years). There were 2 boys, 2 girls and an adult man. The disease manifested by cutaneous abnormalities and neurological or orthopedic deficits. Pain was a chief complaint in the adult patient. The symptoms had progressed in 3 cases. The diagnosis was made correctly by CT myelography or MRI in 4 cases. The median septum was located at the lumbar area in 4 cases and at the lumbosacral region in 1 case. Associated abnormalities included low lying conus (5 cases), lipoma (2 cases), thickened filum terminale (1 case), hemilipomyelomeningocele (1 case) and syrinx (1 case). The median septum was removed. The dural sleeve adjoining the septum was resected and the dural sac was reconstructed. The role of MRI in the diagnosis and planning of surgery and the high frequency of associated low lying conus were emphasized. Though the surgical treatment relieved pain, it did not reverse the neurological deficits or orthopedic deformities significantly, which suggests the beneficial effects of early surgical intervention in the cases with progressive symptoms.

Adolescent↗

PubMed1994

Peritoneal equilibration test in Chinese patients.

Since the introduction of the peritoneal equilibration test (PET) by Twardowski in 1987, it became a widely accepted test that provided useful prognostic information on continuous ambulatory peritoneal dialysis (CAPD). It had been shown to be a readily reproducible test if the standard procedure was followed. Although there was wide interpersonal difference in the test results, the mean and range (and standard deviation, SD) were remarkably similar as suggested by Davies et al. in 1993 (3). We had performed PET on our CAPD patients for a few years, and all along we used the reference range established by Twardowski to classify our patients into High, High average, Low average, and Low transporters because no reference range had ever been established in Chinese. The aim of this study was to define the normal mean and range of the PET results in Chinese CAPD patients. We analyzed 100 PET results from 100 Chinese CAPD patients. The mean +/- (SD) of the ratio of dialysate/plasma of creatinine and glucose at four-hour dwell times were 0.71 (0.15) and 0.37 (0.12), respectively. There was a significant difference in the dialysate/plasma ratio of creatinine (p < 0.01) while that of glucose was similar when compared with those found by Twardowski. There was no difference in the solute transfer in diabetic and nondiabetic patients. We concluded that the creatinine clearance of the peritoneal membrane in Chinese CAPD patients was higher than the previously reported result in North American patients.

Adult↗

PubMed1993

Intracranial mesenchymal chondrosarcoma: a case report and literature review.

Intracranial mesenchymal chondrosarcoma is a rare entity. The case of a 13-year-old girl with mesenchymal chondrosarcoma which seemed to arise from the dura mater is presented here together with a review of the literature. In the present case, the tumor involved the superior sagittal sinus. It recurred 21 months after gross total removal of the mass and coagulation of the involved wall of the superior sagittal sinus. Reoperation was performed followed by radiation therapy.

Adolescent↗

PubMed1993

MRI of intracranial subependymoma: report of a case.

Subependymoma is a rare, benign intraventricular tumour and a case of septum pellucidum origin examined with CT and MR is reported. Well demarcated non-enhancing mass with multiple small intratumoral cysts is demonstrated on CT and MR images. The differential diagnosis from ependymoma has some therapeutic implications but may not be possible by CT or MRI.

Cerebral Ventricle Neoplasms↗

PubMed1993

Cerebral aspergillosis in immunologically competent patients.

Aspergillosis of the central nervous system is a rare disease, especially if the patient's immune system is not compromised. The authors report three cases of cerebral aspergillosis in the immunocompetent state: a rhinocerebral form in a diabetic patient, a direct extension from chronic Aspergillus otitis media, and a postoperative Aspergillus brain abscess after brain tumor surgery. In spite of the poor prognosis of cerebral aspergillosis, two of the patients survived. The pathogenesis, predisposing factors, radiologic findings including magnetic resonance image, and the outcome are presented. The pertinent literature of cerebral aspergillosis is also reviewed.

Adult↗

PubMed1993

Histopathological changes of the cat brain in experimental sparganosis.

Histopathological changes of the brain were observed in 22 mongrel cats each of which was subjected to intracranial inoculation of 3 or 5 plerocercoids of Spirometra erinacei. The brains were examined at 2 weeks, 1, 3, and 6 months post-inoculation (PI). Grossly, the brain lesion consisted of a mass of worm capsule and/or hemorrhagic tract. Microscopically hypertrophied astrocytes, lymphocytes, plasma cells, RBCs, polymorphonuclear leukocytes, and hemosiderin laden macrophages were found around the worms or tracts in all groups. The number of reactive astrocytes increased mainly in the white matter. In the lesions 3 months PI, the sectioned worms were encircled with fibrous tissue along with numerous RBCs, inflammatory cells, and necrotic debris. Collagenous fibers were also demonstrated. Outside the inflammation, a wide edematous zone developed and numerous neuroglial fibers were also found. The location of the worms or the tracts was random in the brain lobes, but the worm seemed to migrate mainly along the white matter.

Animals↗

PubMed1992

Effects of site-directed mutations on processing and activities of penicillin G acylase from Escherichia coli ATCC 11105.

Penicillin G acylase from Escherichia coli ATCC 11105 is synthesized from its precursor polypeptide into a catalytically active heterodimer via a complex posttranslational processing pathway. Substitutions in the pair of aminoacyl residues at the cleavage site for processing the small and large subunits were made. Their processing phenotypes and penicillin G acylase activities were analyzed. By the introduction of a prolyl residue at either position, the processing of the small subunit was blocked without a change in enzymatic activity. Four other substitutions had no effect. At the site for processing the large subunit, four substitutions out of the seven examined blocked processing. In general, penicillin G acylase activity seemed to be proportional to the efficiency of the large-subunit-processing step. Ser-290 is an amino acid critical for processing and also for the enzymatic activity of penicillin G acylase. In the mutant pAATC, in which Ser-290 is mutated to Cys, the precursor is processed, but there is no detectable enzymatic activity. This suggests that there is a difference in the structural requirements for the processing pathway and for enzymatic activity. Recombination analysis of several mutants demonstrated that the small subunit can be processed only when the large subunit is processed first. Some site-directed mutants from which signal peptides were removed showed partial processing phenotypes and reduced enzymatic activities. Their expression showed that the prerequisite for penicillin G acylase activity is the efficient processing of the large subunit and that the maturation of the small subunit does not affect the enzymatic activity.

DNA Mutational Analysis↗

PubMed1992

Intraventricular neurocytoma: clinicopathological analysis of seven cases.

A retrospective analysis of seven patients with intraventricular neurocytoma is presented. Patient age at diagnosis ranged from 15 to 38 years (mean 24.6 years) and the male:female ratio was 6:1. Raised intracranial pressure due to hydrocephalus was the main cause of the clinical manifestations. An isodense mass with multiple intratumoral cysts and homogeneous contrast enhancement was the characteristic computerized tomography finding. The lesions commonly involved the lateral ventricle with or without extension to the third ventricle. Cerebral angiography showed homogeneous vascular staining in five patients. Magnetic resonance images revealed a mass isointense with the cerebral cortex on both T1- and T2-weighted images. Gadolinium-diethylenetriaminepenta-acetic acid-enhanced images showed homogeneous enhancement. Total removal of the tumor was possible in four patients. Pathologically, six cases were initially diagnosed as oligodendroglioma and the remaining case as ependymoma. However, immunohistochemical studies demonstrated strong positivity for neuron-specific enolase in all seven cases and for synaptophysin in five cases. On electron microscopy, three cases showed well-defined neurosecretory granules and 10-nm microtubules in their cytoplasm and cytoplasmic processes. One patient developed a recurrent tumor 18 months after surgery. The remaining six patients are free of recurrent tumors at 2 to 62 months after surgery. It is suggested that neurocytoma must be included in the differential diagnosis of intraventricular lesions, and that electron microscopic and immunohistochemical studies should be undertaken.

Adolescent↗

PubMed1992

Compartmental analysis of RBC circulation through the rabbit kidney.

This experiment involved 12 rabbits of both sexes, weighing 2.1 kg. After anesthesia, the kidneys were exposed, isolated and cannulated in the renal artery, ureter and sometimes in the vein as well. The kidney were perfused through the renal artery with Krebs-Henseleit solution, which were then filtered to be free of particles, gased with 95% O2-5% CO2, and kept at 37 degrees C. We measured RBCs concentrations by means of Coulter Counter in the venous outflow collected, and plotted them against the volume perfused. Using 2 different flow rates, 9 ml/min (group I) and 19 ml/min (group II), we found that the RBCs decreased in a multiexponential decay fashion and a biophysical model for each flow rate was constructed. These models indicated that there were more cell stores (2.20 x 10(10)) in the fast compartment of group II than in group I (1.72 x 10(10)). This difference is not statistically significant, but certainly coincides with urine flow collected from ureter cannula during perfusion. Our present data clearly suggest that in order to clear 99% blood cells out of 10-12 gm rabbit kidneys, at least 3-6 ml of cell free perfusate is required while clearing the whole blood cells out of human kidneys (200-240 gm) may need 600 ml or more. Thus, we recommend that at least 600 ml of perfusate should be used to clear most of the blood cells in the renal vasculature before renal transplantation is performed.

Animals↗

PubMed1991

[Factors predicting development of decubitus ulcers among patients admitted for neurological problems].

In this prospective study, factors contributing to the development of decubitus ulcers were examined. Factors were identified by a literature review and a conceptual framework was developed. Regular observations were made during the subjects' hospitalization to determine the incidence of decubitus ulcers, and to assess other decubitus ulcer risk factors. Seventeen out of 146 admitted for neurological problems patients developed decubitus ulcers during the three month study period. There were no significant differences in the level of serum albumin, hemoglobin or age between those who developed decubitus ulcers and those who did not. There also was no difference in incidence between patient who were paralyzed and those not paralyzed. Mean hospitalization days until decubitus ulcer development was 6.5 days. According to the results of discriminant analysis, four factors--1) friction and shear, 2) sensory perceptual impairment, 3) low diastolic pressure, and 4) multiple use of sedative medications--predicted 84.93% of decubitus ulcer incidence.

Humans↗