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Biomedical subjects

J K Han

Publications and source records attributed to J K Han.

At least 37 records · Page 2Linked to original sources
PubMed2001

Hepatic hemangiomas with arterioportal shunt: findings at two-phase CT.

PURPOSE: To determine the prevalence of arterioportal shunt associated with hepatic hemangiomas, describe the two-phase spiral computed tomographic (CT) findings, and correlate the presence of arterioportal shunt with the size and rapidity of enhancement of hemangiomas. MATERIALS AND METHODS: The study group consisted of 109 hepatic hemangiomas in 69 patients who underwent two-phase spiral CT during 1 year. CT scans were obtained during the hepatic arterial (30-second delay) and portal venous (65-second delay) phases after injection of 120 mL of contrast material (3 mL/sec). Arterioportal shunts were diagnosed when hepatic arterial phase CT scans showed a wedge-shaped or irregularly shaped homogeneous enhancement in the liver parenchyma adjacent to the tumor and when portal venous phase CT scans showed isoattenuation or slight hyperattenuation, compared with normal liver in that area, and when there was no demonstrable cause of these attenuation differences. The presence of arterioportal shunt in hemangioma was correlated with the size of the tumor and the rapidity of intratumoral enhancement. RESULTS: Arterioportal shunt was found in 28 (25.7%) of 109 hemangiomas. There was no statistically significant relationship between lesion size and presence of the arterioportal shunt (P =.653). Arterioportal shunt was more frequently found in hemangiomas with rapid enhancement (P <.01). CONCLUSION: Arterioportal shunts are not uncommonly seen in hepatic hemangiomas at two-phase spiral CT. Hemangiomas with arterioportal shunts tend to show rapid enhancement.

Arteriovenous Fistula↗
PubMed2001

Ultrasonographic evaluation of the gallbladder: comparison of fundamental, tissue harmonic, and pulse inversion harmonic imaging.

The purpose of our study was to compare pulse inversion harmonic imaging, tissue harmonic imaging, and fundamental imaging in the evaluation of normal and diseased gallbladder. Gallbladders in 170 patients were examined with fundamental imaging, tissue harmonic imaging, and pulse inversion harmonic imaging using a 2- to 5-MHz curved array transducer. Images were divided into normal and abnormal groups. The sharpness of the wall and degree of internal artifact were evaluated in normal groups, and lesion conspicuity and internal artifact were evaluated in abnormal groups. In images of both normal and abnormal gallbladder, significant differences were demonstrated among the 3 imaging methods (P < .001), and pulse inversion harmonic imaging provided the best image quality and the least artifact. Tissue harmonic imaging was the next best, providing better image quality and less artifact than fundamental imaging. In conclusion, pulse inversion harmonic imaging provided the best image quality and the least artifact among the 3 ultrasonographic methods in the evaluation of both normal and abnormal gallbladder.

Aged↗
PubMed2000

The IgA/IgM receptor expressed on a murine B cell lymphoma is poly-Ig receptor.

T560, a mouse B lymphoma that originated in gut-associated lymphoid tissue, expresses receptors that bind dimeric IgA and IgM in a mutually inhibitory manner but have little affinity for monomeric IgA. Evidence presented in this paper indicates that the receptor is poly-Ig receptor (pIgR) known in humans and domestic cattle to bind both IgA and IgM. The evidence includes the demonstration that binding of IgM is J chain dependent, and that pIg-precipitated receptor has an appropriate Mr of 116-120 kDa and can be detected on immunoblots with specific rabbit anti-mouse pIgR. Overlapping RT-PCR performed using template mRNA from T560 cells and oligonucleotide primer pairs designed from the published sequence of mouse liver pIgR indicate that T560 cells express mRNA virtually identical with that of the epithelial cell pIgR throughout its external, transmembrane, and intracytoplasmic coding regions. Studies using mutant IgAs suggest that the Calpha2 domain of dimeric IgA is not involved in high-affinity binding to the T560 pIgR. Inasmuch as this mouse B cell pIgR binds IgM better than IgA, it is similar to human pIgR and differs from rat, mouse, and rabbit epithelial cell pIgRs that bind IgA but not IgM. Possible explanations for this difference are discussed. All clones of T560 contain some cells that spontaneously secrete both IgG2a and IgA, but all of the IgA recoverable from the medium and from cell lysates is monomeric; it cannot be converted to secretory IgA by T560 cells.

Amino Acid Sequence↗
PubMed2000

Identification and developmental expression of par-6 gene in Xenopus laevis.

The par genes (partitioning defective) are required to establish polarity in the Caenorhabditis elegans embryo. We have identified the Xenopus homologue of C. elegans PAR-6 (XPAR-6). XPAR-6 is a protein of 377 amino acids with one PDZ domain which is involved in mediating protein-protein interactions. It shares 59% and 58% amino acid identity with the mouse and Drosophila PAR-6, respectively, and 54% overall identity with C. elegans PAR-6. Xpar-6 is expressed both maternally and zygotically. Xpar-6 is first detected in the animal half of the egg, and this pattern of expression persists into the cleavage and blastula stages. At the gastrula stage, the message is detected in animal pole area and in a broad domain of ventral region, but is excluded from dorsal region. With the onset of neurulation, the localized expression of Xpar-6 becomes more obvious, leading to it being enriched in the dorsolateral region along the lateral edges of neural plate and anterior presumptive head region surrounding the anterior border of neural plate. At late tailbud stage, Xpar-6 transcripts show localized expression throughout the head, labeling the branchial arches, eyes, otic vesicles and brain, while more posteriorly Xpar-6 labels the somites, pronephros, tail tip and proctodeum. Therefore, this analysis suggests that Xpar-6 has a regionalized pattern of expression during Xenopus early embryogenesis.

Amino Acid Sequence↗
PubMed2000

Modulation of lysophosphatidic acid-induced Cl- currents by protein kinases A and C in the Xenopus oocyte.

The roles of protein kinase C (PKC) and protein kinase A (PKA) in the regulation of lysophosphatidic acid (LPA)-induced Cl- currents in Xenopus oocytes were examined. PKC activation by phorbol 12-myristate 13-acetate (PMA) treatment completely blocked LPA-induced Cl- currents by inhibiting inositol 1,4,5-trisphosphate (IP3) elevation. This inhibitory effect of PMA on the LPA response was blocked by pretreatment of oocytes with staurosporine and 3-[N-(dimethylamino)propyl-3-indiolyll-4-[3-indolyl]maleimide (GF109203X), PKC inhibitors. In addition, treatment of oocytes with GF109203X enhanced the LPA response by increasing IP3 production. Elevation of the intracellular adenosine 3',5'-cyclic monophosphate (cAMP) concentration by treating oocytes with either forskolin (FK) plus isobutylmethylxanthine (IBMX) or 2'-O-dibutyryl-cAMP (dB-cAMP) reduced LPA-induced Cl- currents. The effect of activation of the cAMP pathway appears to be mediated by PKA, since treatment of oocytes with FK plus IBMX or dB-cAMP enhanced PKA activity. Furthermore, the inhibitory effect of dB-cAMP on the LPA response was blocked by treatment of oocytes with N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulframide-2 HCl (H-89), a selective inhibitor of PKA. Both FK plus IBMX and dB-cAMP treatment reduced IP3 generation in response to LPA stimulation. Inhibition of PKA activity with H-89 or Rp-cyclic 3',5'-hydrogen phosphorothioate adenosine triethylammonium had no effect on LPA-induced Cl- currents. Finally, inhibition of the LPA response by activation of PKA was independent of extracellular Ca2+. These results demonstrate that both PKC and PKA play active roles in modulating the LPA-induced signaling pathway.

Animals↗
PubMed2000

A novel gene family with a developmentally regulated expression in Xenopus laevis.

We have isolated a new maternal gene called 4G2. 4G2 cDNA encodes a predicted protein of 501 amino acids, and its apparent molecular mass of 61 kDa was determined by SDS-PAGE of 4G2 recombinant protein expressed in E. coli or in vitro translated in rabbit reticulocyte lysate. Amino acid analysis of 4G2 revealed the RGD and LDV motif with a potential cell attachment activity. The open reading frames (ORF) also contained a consensus bipartite nuclear localization signal (NLS). There were number of expressed tag sequences (ESTs) from Drosophila, zebrafish, chicken, mouse, and human origin that encode a high degree of identity to the predicted 4G2 protein, thereby suggesting that 4G2 may constitute a novel gene family whose function has not been elucidated. We also present evidence that 4G2 transcript is maternally synthesized in stage IV oocyte, localized to animal hemisphere of egg, and zygotically reactivated in mid-neurula stage.

Amino Acid Motifs↗
PubMed2000

Differential stereoselectivity of D- and L-myo-inositol 1,2,4, 5-tetrakisphosphate binding to the inositol 1,4,5-trisphosphate receptor and 3-kinase.

D- and L-myo-inositol 1,2,4,5-tetrakisphosphate (Ins(1,2,4,5)P(4)) were investigated for their ability to bind to the D-myo-inositol 1, 4,5-trisphosphate (Ins(1,4,5)P(3)) receptor in a bovine adrenal cortical membrane fraction, to mobilize intracellular Ca(2+) stores in Xenopus oocytes, and to bind to the rat brain Ins(1,4,5)P(3) 3-kinase overexpressed and purified in E. coli. In competitive binding experiments with the Ins(1,4,5)P(3) receptor, D-Ins(1,2,4, 5)P(4) effectively displaced [(3)H]Ins(1,4,5)P(3) in a concentration-dependent manner with a potency comparable to that of D-Ins(1,4,5)P(3), while L-Ins(1,2,4,5)P(4) was approximately 50-fold less effective than D-Ins(1,4,5)P(3) and D-Ins(1,2,4,5)P(4). The DL-Ins(1,2,4,5)P(4) racemate bound to the Ins(1,4,5)P(3) receptor with an apparent intermediate efficiency. Injection of D-Ins(1,2,4, 5)P(4) into oocytes evoked a chloride current dependent on intracellular Ca(2+) mobilization in which the agonists ranked in a similar order of potency as in the Ins(1,4,5)P(3) receptor binding. On the other hand, D-Ins(1,2,4,5)P(4) only inhibited the binding of [(3)H]Ins(1,4,5)P(3) to 3-kinase very weakly with a markedly reduced potency compared to D-Ins(1,4,5)P(3), indicating that D-Ins(1,2,4, 5)P(4) is not an effective competitor in the phosphorylation of [(3)H]-Ins(1,4,5)P(3) by 3-kinase. The results, therefore, clearly indicate that D-Ins(1,2,4,5)P(4) is as effective as D-Ins(1,4,5)P(3) in the binding to the receptor but not 3-kinase, and access of Ins(1, 2,4,5)P(4) over the Ins(1,4,5)P(3) receptor calls for stringent stereospecificity with D-Ins(1,2,4,5)P(4) being the active form in DL-Ins(1,2,4,5)P(4)-mediated Ca(2+) mobilization.

Animals↗
PubMed2000

Improved imaging of hepatic metastases with delayed pulse inversion harmonic imaging using a contrast agent SH U 508A: preliminary study.

To investigate the feasibility of delayed pulse-inversion harmonic imaging (PIHI) with the SH U 508A to improve imaging of hepatic metastases, we evaluated 20 patients with known hepatic metastases. Conventional ultrasound (US) was performed before administration, and PIHI was performed 5 min after a bolus injection of 4 G of microbubble contrast agent (300 mg/mL of SH U 508A). Intense, homogeneous enhancement in the liver parenchyma was seen in all patients on delayed PIHI. In 10 patients (50%), 1 or more focal liver lesions that were not seen on unenhanced imaging were detected on delayed PIHI. When comparing 55 lesions that were seen on both techniques, delayed PIHI was superior to unenhanced imaging in terms of lesion conspicuity and lesion-to-liver contrast (p < 0.001, respectively). Delayed PIHI with SH U 508A can improve conspicuity of hepatic metastases and reveal focal liver lesions that are not detected on unenhanced imaging.

Adult↗
PubMed2000

Comparison of harmonic and conventional power Doppler ultrasonography for assessment of slow flow in hyperechoic tissue: experimental study using a Doppler phantom.

RATIONALE AND OBJECTIVES: Despite the advantages of depicting slow flow in small vessels, conventional power Doppler ultrasound (US) has a basic limitation, specifically that artifactual power Doppler signals mimic blood flow, especially in hyperechoic tissue. The purpose of this study was to compare harmonic power Doppler US with power Doppler US using a Doppler phantom under various parameter settings, focusing on the assessment of slow flow in the hyperechoic tissue. METHODS: While controlling the flow velocity (5 and 10 cm/s), pulse repetition frequency (500, 700, and 1,000 Hz), wall filter (low and medium), and Doppler gain (90%, 96%, and 100%), the authors performed both harmonic Doppler US and power Doppler US by using a Doppler phantom/flow control system. We measured and compared the relative intensities of the Doppler signals (0-250 scale) in both the vessels and hyperechoic tissue-mimicking materials with the two different imaging modalities. RESULTS: Power Doppler US with any combination of the four parameters evaluated depicted strong flow signals (mean, 213) that were superior to harmonic Doppler US (mean, 61). Relatively strong artifactual signals within the hyperechoic tissue-mimicking materials were noted on all power Doppler US studies (mean, 106) but nearly none on harmonic Doppler US (mean, 3). The contrast-to-noise ratio of harmonic Doppler US was significantly greater than that of power Doppler US. CONCLUSIONS: Harmonic Doppler US is more useful in assessing slow flow in hyperechoic tissue than power Doppler US because it produces fewer artifactual Doppler signals originating from stationary hyperechoic tissues, which can be misjudged as true signals on power Doppler US.

Blood Flow Velocity↗
PubMed2000

Vascularity of hepatocellular carcinoma: assessment with contrast-enhanced second-harmonic versus conventional power Doppler US.

PURPOSE: To compare contrast material-enhanced harmonic power Doppler ultrasonography (US) with conventional power Doppler US in depicting the vascularity of hepatocellular carcinoma (HCC). MATERIALS AND METHODS: Twenty patients with nodular HCCs (2.6-13.2 cm in diameter; mean diameter, 4.8 cm) were prospectively examined with both conventional and harmonic power Doppler US. US was performed with a 2-4-MHz curved linear-array transducer according to a standard examination protocol (1,000-Hz pulse repetition frequency, medium wall filter, and power gain of 55%-84% for conventional power Doppler US; 700-Hz pulse repetition frequency, low wall filter, and power gain of 95%-98% for harmonic power Doppler US). Serial, dynamic scans were obtained before intravenous injection of the contrast agent (SH U 508A) and at 30, 60, 90, 120, 180, 240, and 300 seconds after injection with both techniques. RESULTS: The number of intratumoral power Doppler US signals was similar with both techniques at 30-90 seconds after contrast agent injection; however, after 90 seconds, conventional power Doppler US depicted significantly more signals than did harmonic power Doppler US. Harmonic power Doppler US was superior to conventional power Doppler US in terms of power Doppler artifacts such as "blooming" or motion-related artifacts. CONCLUSION: Although the effective enhancement duration is relatively short compared with that for conventional power Doppler US, contrast-enhanced harmonic power Doppler US can be effective in evaluating the vascularity of HCCs because of the advantage of fewer power Doppler artifacts.

Aged↗
PubMed2000

Hepatic tumors: contrast agent-enhancement patterns with pulse-inversion harmonic US.

PURPOSE: To evaluate contrast agent-enhancement patterns in hepatic hemangiomas, hepatic metastases, and hepatocellular carcinomas (HCCs) at pulse-inversion harmonic ultrasonography (US) with a microbubble contrast agent. MATERIALS AND METHODS: Twenty hepatic hemangiomas in 20 patients and 41 malignant hepatic tumors in 23 patients (33 metastases and eight HCCs) were evaluated with pulse-inversion harmonic US. US images were obtained before injection and every 10-15 seconds after injection of a 4-g bolus (300 mg/mL) of SH U 508A (a microbubble contrast agent) for 5 minutes. The contrast-enhancement patterns of 61 hepatic lesions were assessed. RESULTS: Of 20 hemangiomas, 19 revealed peripheral enhancement, which was globular in 14 (70%) and rimlike in five (25%), with centripetal fill-in; the remaining one (5%) showed homogeneous enhancement. In 33 metastases, the enhancement was rimlike in 16 (48%), homogeneous in seven (21%), and stippled in two (6%); in the remaining eight metastases (24%), no enhancement was seen. Of eight HCCs, four (50%) showed homogeneous enhancement and the remaining four (50%) showed heterogeneous enhancement. Centripetal fill-in of lesions with intratumoral enhancement was not seen in any malignancy. CONCLUSION: Pulse-inversion harmonic US with a microbubble contrast agent is potentially useful for the specific diagnosis of hemangiomas that demonstrate characteristic enhancement features.

Adult↗
PubMed2000

Gadolinium mesoporphyrin as an MR imaging contrast agent in the evaluation of tumors: an experimental model of VX2 carcinoma in rabbits.

OBJECTIVE: We determined the enhancement features of experimentally induced malignant tumors on MR imaging with the use of gadolinium mesoporphyrin, a recently developed MR contrast agent that may be necrosis-specific. MATERIALS AND METHODS: VX2 carcinoma was inoculated into 24 rabbit thighs. T1-weighted contrast-enhanced MR imaging with IV gadopentetate dimeglumine (2-min delay) and gadolinium mesoporphyrin (20-hr delay) was performed 3-4 days (n = 6), 6-7 days (n = 6), 10-11 days (n = 5), and 13-14 days (n = 7) after the implantation of VX2 carcinoma. All tumors were sectioned along the same plane of MR images, and a detailed MR imaging-histopathologic correlation was performed. RESULTS: Pathologically, areas enhanced with gadolinium mesoporphyrin included necrotic tissue, viable tumor, inflammatory granulation tissue, hemorrhage, and fibrosis. On gadopentetate dimeglumine-enhanced MR images, unenhanced areas of the tumor corresponded with intratumoral necrosis and hemorrhage. CONCLUSION: Gadolinium mesoporphyrin enhances tumor necrosis on delayed phase MR imaging; however, it is impossible to specifically depict necrosis with gadolinium mesoporphyrin because it also enhances other parts of lesions, including viable tumor.

Animals↗
PubMed2000

CT features of intraductal intrahepatic cholangiocarcinoma.

OBJECTIVE: The objective of this report was to describe the CT features of intraductal intrahepatic cholangiocarcinoma. CONCLUSION: Segmental or lobar dilatation of the intrahepatic bile ducts associated with or without intraductal polypoid mass, amorphous structures, or both with slight hyperattenuation are common CT findings of intraductal intrahepatic cholangiocarcinoma. The size of the intraductal mass determines the visibility on CT.

Adult↗
PubMed2000

A novel family of retrotransposons in Xenopus with a developmentally regulated expression.

SUMMARY: We have obtained a novel family of LTR-retrotransposons in Xenopus laevis, named Xretpos, from cDNA and genomic clones. Its long terminal repeats (LTRs) can be subdivided into U3, R, and U3 to U5 region, and are bounded by 6 bp inverted repeats. Xretpos contains primer binding site and polypurine tract, and multiple copies of Xretpos-related element are present in the genome. A long open reading frame (ORF) encodes the CCHC motif conserved in retroviral gag proteins and leucine zipper motif capable of forming the coiled-coil. However, no amino acid homology to usually conserved retroviral pol gene was revealed. We report that in vitro synthesized Xretpos complementary RNAs are translated to produce a predicted size of protein. We also show that zygotically activated Xretpos transcripts are restricted to ventro-posterior specific regions and induced by UV-irradiation and BMP-4 overexpression in cycloheximide-dependent way. genesis 26:198-207, 2000.

Amino Acid Sequence↗
PubMed2000

Spontaneous subcapsular and intrarenal hematoma demonstrated by various diagnostic modalities and monitored by ultrasonography until complete resolution.

A patient with acute right abdominal pain and nausea underwent various diagnostic imaging studies, including ultrasonography (US), computed tomography (CT), magnetic resonance imaging (MRI), technetium-99m DTPA renal study, and contrast arteriogram. The 99mTc renal study showed a linear photopenic area along the lateral cortical aspect of the right kidney and a focal cortical defect in the left kidney. These lesions corresponded to the findings of US, CT, MRI, and contrast angiography. Because of a suspected malignant mass, a CT-guided aspiration biopsy of the right kidney was performed that resulted in bloody fluid without malignant cells. The patient's condition was diagnosed as intrarenal and subcapsular renal hematoma. The patient was treated conservatively and followed up with CT and US studies. Sequential CT and US demonstrated gradual reduction of the size of the hematoma, and complete resolution was confirmed by US 1.5 years later. As long as underlying pathology can be ruled out, conservative management of spontaneous renal subcapsular hematoma is recommended.

Aged↗