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Biomedical subjects

T K Kim

Publications and source records attributed to T K Kim.

At least 73 records · Page 4Linked to original sources
PubMed1999

Influence of instrument settings on flow signal and background noise in power Doppler US. An experimental study using a flow phantom with hyperechoic background.

OBJECTIVE: To determine the influence of various power Doppler instrument settings on intensities of flow signal and background noise in flow with a tissue-equivalent phantom. METHODS: Power Doppler images were obtained with changing wall filter level (low, medium, high, and maximum), pulse repetition frequency (PRF; 500, 700, 1000, 1500, 3000, and 6000 Hz), and Doppler gain (60%, 70%, 80%, 90%, and 100%) at different flow velocities (13.3, 26.5, and 49.8 cm/sec). To make a quantitative comparison of different settings, the authors measured the intensities of flow signal and background noise in obtained power Doppler images using the scanner and a computer program, calculated signal-to-noise difference (SND; intensity of flow signal--intensity of background noise), and evaluated the relation between SND and power Doppler settings. RESULTS: The intensities of flow signal and background noise were proportional to flow velocity and power Doppler gain but were inversely proportional to PRF and wall filter level. At constant wall filter level (medium), changes of PRF and Doppler gain to the same directions resulted in a high SND. At constant PRF (1000 Hz), changes of wall filter and Doppler gain to the same directions also resulted in a high SND. However, at constant Doppler gain (80%), a high SND was obtained with changing wall filter level and PRF to the opposite directions. CONCLUSIONS: Three Doppler instrument settings--wall filter level, pulse repetition frequency, and Doppler gain--have reciprocal influences on SND.

Blood Flow Velocity↗
PubMed1999

Cyclosporin A treatment alters characteristics of Ca2+-release channel in cardiac sarcoplasmic reticulum.

Chronic treatment with cyclosporin A (CsA) has been reported (H. S. Banijamali, M. H. ter Keurs, L. C. Paul, and H. E. ter Keurs. Cardiovasc. Res. 27: 1845-1854, 1993; I. Kingma, E. Harmsen, H. E. ter Keurs, H. Benediktsson, and L. C. Paul. Int. J. Cardiol. 31: 15-22, 1991) to induce reversible alterations of contractile properties in rat hearts. To define the molecular mechanisms underlying the physiological alterations, the Ca2+-release channel (CRC) and Ca2+-ATPase from sarcoplasmic reticulum in rats were examined. Ryanodine binding to whole homogenates of rat hearts shows time- and dose-dependent alterations in CRC properties by CsA. On 3 wk of treatment with 15 mg CsA. kg body wt-1. day-1, 1) maximal ryanodine binding (Bmax) decreased, 2) the dissociation constant of ryanodine (Kd) increased, 3) caffeine sensitivity of CRC increased, and 4) ruthenium red sensitivity of CRC decreased. On the other hand, Bmax and Kd of ryanodine binding in rat skeletal muscles were not changed. Ryanodine-sensitive oxalate-supported Ca2+ uptake in whole homogenates was lower in CsA-treated rat hearts than in control hearts, whereas total Ca2+ uptake in the presence of 500 M ryanodine was not changed. Functional experiments with rapamycin and Western blot analysis suggest that the CsA-induced alteration of ryanodine binding is due at least in part to an upregulation of calcineurin. The heart muscle-specific alterations of CRC could be responsible for the previously reported contractile changes of CsA-treated rat hearts.

Animals↗
PubMed1999

Hepatic changes in benign obstruction of the hepatic inferior vena cava: CT findings.

OBJECTIVE: The objective of this study was to describe CT findings of changes in the liver associated with benign obstruction of the hepatic inferior vena cava (IVC). MATERIALS AND METHODS: For a 10-year period, 35 patients with benign obstruction of the hepatic IVC underwent contrast-enhanced CT of the abdomen. These patients were included in this retrospective study. CT scans were analyzed for morphologic changes and abnormal enhancement of the liver, changes in intrahepatic vessels, and additional findings that might be related to obstruction of the IVC. RESULTS: Morphologic changes of the liver included hypertrophy of the caudate lobe (91%) and the left lobe (57%), atrophy of the right lobe (49%), and a nodular surface (74%). The most common pattern of attenuation change was areas of linear, irregular, or wedge-shaped hypoattenuation predominantly located in the peripheral portion of the liver (63%). Diffuse hypoattenuation was seen in six patients (19%) and was frequently found in areas in which hepatic veins filled with hypoattenuated thrombosis (67%). On CT, segmental IVC obstruction (80%) was seen as an obliterated segment of the hepatic IVC. However, membranous IVC obstruction (20%) was not seen on CT. The IVC below the level of obstruction was often revealed as rounded (89%) and occasionally contained thrombus (37%) or calcification (26%). CONCLUSION: CT shows a broad spectrum of morphologic and attenuation changes of the liver and of the hepatic vessels in benign obstruction of the hepatic IVC.

Adult↗
PubMed1999

Limitations of characterization of hepatic hemangiomas using a sonographic contrast agent (Levovist) and power Doppler ultrasonography.

Power Doppler ultrasonography using a sonographic contrast agent (Levovist) was evaluated in 20 patients with hepatic hemangiomas with a 2-4 MHz convex transducer according to a standardized examination protocol (pulse repetition frequency, 1000 Hz; medium wall filter; power Doppler gain, 50 to 85%). Enhancement patterns were assessed and were compared with those on dynamic magnetic resonance imaging (n = 11) or computed tomography (n = 9). The most common enhancement pattern was dotlike or linear enhancement located predominantly at the periphery of the tumor (15 cases, 75%). Diffuse homogeneous enhancement was seen in one case (5%). No definite contrast enhancement was evident in four cases (20%). The enhanced area on ultrasonograms was smaller than that on dynamic MR images or CT scans in 18 cases (90%). A transient centripetal fill-in pattern was identified in six cases (30%). Persistent enhancement until 300 s was not seen in any case. Therefore, specific diagnosis of hemangioma with power Doppler ultrasonography and contrast agent may not be possible.

Adult↗
PubMed1998

Efficient recruitment of TFIIB and CBP-RNA polymerase II holoenzyme by an interferon-beta enhanceosome in vitro.

The transcriptional activity of an in vitro assembled human interferon-beta gene enhanceosome is highly synergistic. This synergy requires five distinct transcriptional activator proteins (ATF2/c-JUN, interferon regulatory factor 1, and p50/p65 of NF-kappaB), the high mobility group protein HMG I(Y), and the correct alignment of protein-binding sites on the face of the DNA double helix. Here, we investigate the mechanisms of enhanceosome-dependent transcriptional synergy during preinitiation complex assembly in vitro. We show that the stereospecific assembly of the enhanceosome is critical for the efficient recruitment of TFIIB into a template-committed TFIID-TFIIA-USA (upstream stimulatory activity complex) and for the subsequent recruitment of the RNA polymerase II holoenzyme complex. In addition, we provide evidence that recruitment of the holoenzyme by the enhanceosome is due, at least in part, to interactions between the enhanceosome and the transcriptional coactivator CREB, cAMP responsive element binding protein (CBP). These studies reveal a unique role of enhanceosomes in the cooperative assembly of the transcription machinery on the human interferon-beta promoter.

Cyclic AMP Response Element-Binding Protein↗
PubMed1998

Resolution of salbutamol enantiomers in human urine by reversed-phase high performance liquid chromatography after derivatization with 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl isothiocyanate.

A stereospecific HPLC method has been developed for the resolution of the enantiomers of salbutamol in human urine. After solid-phase extraction and derivatization with 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl isothiocyanate, the diastereomeric derivatives were resolved (Rs = 1. 83) on 5 microns octadecylsilan column using 35% acetonitrile in 0.05 M ammonium acetate buffer (pH = 6) as a mobile phase with electrochemical detection. The diastereomeric derivatives were formed within 30 min. The detection limit of each enantiomer was 20 ng/ml (S/N = 3).

Acetates↗
PubMed1998

Experimentally induced pulmonary arterial occlusion with detachable balloon in pigs: thin-section CT findings.

RATIONALE AND OBJECTIVES: The authors evaluated changes of lung attenuation in pigs, with special attention to the mosaic pattern of low attenuation, at thin-section computed tomography (CT) after obstruction of the proximal pulmonary artery with a detachable balloon. MATERIALS AND METHODS: In seven pigs, nine sites of the descending pulmonary artery were obstructed with detachable balloons. This-section CT scans of the lungs were obtained immediately (n = 9) and at 1 week (n = 5), 2 weeks (n = 1), 3 weeks (n = 2), 4 weeks (n = 1), 6 weeks (n = 1), 8 weeks (n = 1), and 12 weeks (n = 1) after pulmonary artery obstruction. RESULTS: No statistically significant difference was found between the measured lung attenuation of the normal lung and that of the lung distal to the obstruction. Of the nine sites of pulmonary artery obstruction, five (56%) showed an irregular area of increased lung attenuation without lobular architecture. The diameter of the pulmonary artery after obstruction, compared with the diameter before obstruction, decreased by a range of 13%-57% (mean, 35%) and by 0-67% (mean, 44%) at levels 1 cm and 2 cm distal to the obstruction, respectively. CONCLUSION: This experimental study reveals that regional low-attenuation areas do not develop for up to 12 weeks after the obstruction of proximal pulmonary artery, despite a marked decrease in the diameter of the pulmonary artery distal to the obstruction.

Angiography↗
PubMed1998

Intratumoral vascularity of experimentally induced VX2 carcinoma: comparison of color Doppler sonography, power Doppler sonography, and microangiography.

RATIONALE AND OBJECTIVES: Tumor vascularity is useful for characterizing tumors and determining tumor management. The recent development of power Doppler sonography has enhanced the sensitivity of color Doppler imaging in the detection of blood flow because of low power noise and less angle dependence. The purpose of this study was to compare the capability of color and power Doppler sonography with that of microangiography for showing tumor vascularity of VX2 carcinoma. METHODS: Color and power Doppler sonography was performed on VX2 carcinomas in the rabbit thighs, and their findings were correlated with those of microangiography. For qualitative analysis, tumor vascularity was categorized into four items including distribution of tumor vessels, crowdedness of vessels, small vessels, (> or = 0.1 mm), and micro-vessels (< 0.1 mm). Tumor blood flow signals of color Doppler sonography and power Doppler sonography were graded as 3, 2, 1, and 0 and were compared with tumor vascularity on microangiography. For quantitative analysis, percentages of tumor vascular area per tumor area on each study were compared. RESULTS: The mean scores of tumor vascularity on power Doppler sonography were 2.87, 2.73, 2.93, and 2.73 in tumor vascular distribution, crowdedness of vessels, small vessels, and micro-vessels, respectively. Those on color Doppler sonography were 2.4, 2.2, 2.8, and 1.67, respectively. Power Doppler sonography was statistically superior to color Doppler sonography in displaying tumor vascular distribution (P < 0.05) and micro-vessels (P < 0.01). The means and medians of percentages of tumor vascular area per tumor area were 22.7% and 23.5% on microangiography, 17.9% and 21.4% on color Doppler sonography, and 36.4% and 34.7 % on power Doppler sonography, respectively. Percentages of tumor vascular area per tumor area on both color Doppler sonography (r = 0.70) and power Doppler sonography (r = 0.84) were well correlated with those on microangiography. CONCLUSIONS: Power Doppler sonography can demonstrate the tumor vascularity on microangiography relatively well, however, it tends to overestimate the blood flow signals. Color Doppler sonography may have some limitations in imaging tumor vascular distribution and micro-vessels and tends to underestimate tumor vascularity, but can display the blood flow direction. Therefore, power Doppler and color Doppler sonography could complement each other in demonstrating the tumor vascularity.

Angiography↗
PubMed1998

Atypical small hemangiomas of the liver: "bright dot" sign at two-phase spiral CT.

PURPOSE: To determine if a tiny enhancing dot is characteristic of small hemangiomas with low attenuation during the hepatic arterial phase (HAP) and portal venous phase (PVP) of two-phase spiral computed tomography (CT). MATERIALS AND METHODS: Among 249 consecutive patients with 377 hemangiomas who underwent two-phase spiral CT (performed 30 and 65 seconds after the start of injection), 34 hemangiomas in 20 patients were less than 2 cm in diameter, had low attenuation during the HAP and PVP, and showed characteristic findings on dynamic contrast material-enhanced magnetic resonance (MR) images. The CT scans were retrospectively reviewed for tiny enhancing dots and correlated with the MR images. RESULTS: Tiny enhancing dots were found in 26 of 34 hemangiomas (76%). The dots were seen during the HAP and PVP in 15 lesions (58%) and during the PVP alone in 11 lesions (42%). The lesions showed a tendency toward slow fill-in at MR imaging (only four lesions completely filled with contrast material within 5 minutes). The dots seen at CT corresponded to the initial enhancing area at MR imaging. CONCLUSION: Small hemangiomas with persistent low attenuation at two-phase spiral CT can be diagnosed with the "bright dot" sign.

Adult↗
PubMed1998

Nontumorous arterioportal shunt mimicking hypervascular tumor in cirrhotic liver: two-phase spiral CT findings.

PURPOSE: To determine the two-phase (hepatic arterial phase [HAP] and portal venous phase [PVP]) spiral computed tomographic (CT) findings of a nontumorous arterioportal shunt in the cirrhotic liver that can mimic a hypervascular tumor. MATERIALS AND METHODS: For 14 months, 803 patients with known or suspected hepatocellular carcinoma were referred for initial or repeated transcatheter arterial chemoembolization (TACE). Twenty-nine hyperattenuating lesions on HAP CT images obtained in 25 patients (23 men, two women; age range, 39-70 years) were regarded as nontumorous arterioportal shunts and were included in this study. The diagnosis of nontumorous arterioportal shunt was established by four radiologists who reviewed the two-phase spiral CT images and hepatic angiograms. RESULTS: The longest dimension of the lesion was 1.0-7.9 cm (mean dimension, 2.9 cm). The morphology at HAP CT was wedge-shaped in 25 (86%), geographic (ie, focal area with irregular outline) in two (7%), and nodular in two (7%) lesions. All lesions were homogeneous in attenuation. Hyperattenuating linear branching structures that represented early opacification of portal veins were demonstrated during the HAP in nine (31%) lesions. PVP CT images showed these lesions as isoattenuating (n = 20 [69%]) or slightly hyperattenuating (n = 9 [31%]). Iodized oil CT images showed faint or no accumulation of iodized oil in all lesions. CONCLUSION: In cirrhotic liver, nontumorous arterioportal shunts can be a cause of pseudolesions that mimic hypervascular tumors at two-phase spiral CT. Lesions that have the typical wedge-shaped and homogeneous appearance with or without internal linear branching structures during the HAP and that are isoattenuating or slightly hyperattenuating during the PVP can suggest this unusual condition.

Adult↗
PubMed1998

Hepatocellular carcinoma: power Doppler US with a contrast agent--preliminary results.

PURPOSE: To investigate the value of contrast material-enhanced power Doppler ultrasonography (US) in the demonstration and characterization of tumor vascularity in hepatocellular carcinoma (HCC). MATERIALS AND METHODS: Twenty patients with HCC were prospectively evaluated with power Doppler US before and after injection of the contrast agent SH U 508 A. The grade and pattern of tumor vascularity at power Doppler US were analyzed, along with the degree of tumor staining at angiography. RESULTS: Intra- and peritumoral flow signals were detected in 19 HCCs (95%) at unenhanced power Doppler US. After injection of contrast agent, flow signals increased in 19 lesions (95%). At contrast-enhanced power Doppler US, two tumors demonstrated grade 1 vascularity; four, grade 2; three, grade 3; and 11, grade 4. At angiography, two tumors demonstrated grade 1 staining; four, grade 2; eight, grade 3; and six, grade 4. The correlation between vascularity grades at contrast-enhanced power Doppler US and at angiography was statistically significant (P < .0001). Seventeen HCCs (85%) showed the intratumoral or basket pattern of vascularity at unenhanced power Doppler US; after injection of contrast material, 15 HCCs (75%) showed the mixed pattern. CONCLUSION: Contrast-enhanced power Doppler US is superior to unenhanced power Doppler US in the demonstration and characterization of tumor vascularity in HCC.

Adult↗
PubMed1998

Benign obstruction of the hepatic inferior vena cava complicated by hepatocellular carcinoma: combined interventional management.

OBJECTIVE: The risk of hepatocellular carcinoma is increased with benign obstruction of the hepatic inferior vena cava (IVC). The purpose of this study was to assess the usefulness of combined interventional treatment for benign obstruction of the hepatic IVC associated with hepatocellular carcinoma. MATERIALS AND METHODS: In a retrospective review of 51 patients with benign obstruction of the hepatic IVC, hepatocellular carcinoma was detected in 15 patients coincidentally or during the follow-up period. Obstruction of the IVC was treated with percutaneous transluminal balloon angioplasty in five patients and metallic stent placement in two patients. Immediate postprocedural and follow-up venacavography was performed to evaluate the effectiveness of this interventional management. Hepatocellular carcinomas were managed with transcatheter chemoembolization in all 15 patients using an emulsion of 3-12 ml of an iodized oil and 20-50 mg of doxorubicin hydrochloride. Gelfoam embolization was performed in three patients. Transcatheter chemoembolizations were repeated in seven patients. Initial response and long-term response to treatment were evaluated by monitoring the level of serum alpha-fetoprotein and by follow-up CT and angiography. RESULTS: During the follow-up period (1-8 years), the IVC was widely open except in one patient who developed moderate stenosis. Clinical symptoms of vena caval obstruction disappeared in all patients. After initial transcatheter chemoembolization, complete remission of the tumor occurred in six patients and partial remission occurred in seven patients. Five of the seven patients who underwent further chemoembolizations remained unchanged or in remission. CONCLUSION: Radiologic interventional treatment plays a significant role in managing both kinds of lesions in patients with benign obstruction of the hepatic IVC complicated by, hepatocellular carcinoma. A follow-up regimen should be designed to detect small hepatocellular carcinoma as early as possible after obstruction of the hepatic IVC is diagnosed.

Adult↗
PubMed1998

Intestinal mastocytosis and goblet cell hyperplasia in BALB/c and C3H mice infected with Neodiplostomum seoulense.

Mucosal mast cell (MMC) and goblet cell (GC) responses were observed in the small intestine of two strains of mice (BALB/c and C3H) infected with Neodiplostamum seoulense, and their roles in the host defense and worm expulsion were studied. From day 3 to 28 post-infection (PI) with 200 metacercariae, the worm recovery rate from BALB/c mice was consistently and remarkably higher than that from C3H mice. In the duodenum of both strains of mice, the main habitat of the flukes, mastocytosis was pronounced on day 7 PI but quickly diminished thereafter. Similar kinetics were observed in the jejunum and ileum, although the extent of mastocytosis was lesser in the ileum than other two areas. These MMC kinetics were not different between the two strains of mice. Moreover, the extent of mastocytosis was stronger in BALB/c mice than in C3H mice. GC hyperplasia was remarkable in the duodenum of BALB/c mice throughout the course of infection except day 14 PI, whereas it was recognizable only in the jejunum and ileum of C3H mice on day 7 PI. Mucin activation was evidently demonstrated in both strains of mice throughout the course of infection, but more marked in BALB/c than in C3H mice. The results strongly suggest that mastocytosis and GC hyperplasia are local immune responses against N. seoulense, however, they play a minor role in the host defense and worm expulsion.

Animals↗
PubMed1997

Trajectory of DNA in the RNA polymerase II transcription preinitiation complex.

By using site-specific protein-DNA photocrosslinking, we define the positions of TATA-binding protein, transcription factor IIB, transcription factor IIF, and subunits of RNA polymerase II (RNAPII) relative to promoter DNA within the human transcription preinitiation complex. The results indicate that the interface between the largest and second-largest subunits of RNAPII forms an extended, approximately 240 A channel that interacts with promoter DNA both upstream and downstream of the transcription start. By using electron microscopy, we show that RNAPII compacts promoter DNA by the equivalent of approximately 50 bp. Together with the published structure of RNAPII, the results indicate that RNAPII wraps DNA around its surface and suggest a specific model for the trajectory of the wrapped DNA.

Animals↗
PubMed1997

In vitro transcriptional activation of p21 promoter by p53.

The tumor suppressor p53 can control cell growth by inducing cell cycle arrest. This is effected, at least in part, by transcriptional activation of p21 gene, a cell cycle inhibitor. Here in vitro transcription assay for p21 has been established. The assay recapitulates activation of p21 promoter mediated by p53 in vitro. Thus this in vitro assay will allow to study how transcriptional regulation of p21 can be linked to cell cycle controls during development and neoplastic transformation processes.

Animals↗