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Biomedical subjects

J S Yu

Publications and source records attributed to J S Yu.

At least 37 records · Page 2Linked to original sources
PubMed1998

MR imaging during arterial portography for assessment of hepatocellular carcinoma: comparison with CT during arterial portography.

OBJECTIVE: The purpose of this study was to document the usefulness of MR imaging during arterial portography (MRAP) versus CT during arterial portography (CTAP) in the diagnosis and assessment of hepatocellular carcinoma. SUBJECTS AND METHODS: In addition to static T1- and T2-weighted MR imaging, MRAP was performed immediately after hepatic angiography through contrast material injection into intraarterially placed catheters (superior mesenteric or splenic artery) in 21 patients with nodular hepatocellular carcinoma. CTAP was performed afterward for each patient. The sensitivity and specificity of MRAP for lesion detection and the differential diagnosis of hepatocellular carcinoma were compared with the sensitivity and specificity of CTAP. RESULTS: MRAP revealed more perfusion defects (n = 56) than did CTAP (n = 46). The sensitivity for detection of hepatocellular carcinoma was higher for MRAP (94%) than for CTAP (83%); however, the difference was not statistically significant (p > .05). More hepatocellular nodules with unknown malignant potential were revealed on MRAP (n = 7) than on CTAP (n = 2). For the differential diagnosis of perfusion defects commonly revealed by both techniques, more benign lesions and pseudolesions (n = 14) were shown on MRAP through the combined interpretation with static images than on unenhanced and contrast-enhanced CTAP (n = 11). CONCLUSION: Because of its high sensitivity and its ability to enable radiologists to differentiate benign from malignant conditions, MRAP may have merit compared with CTAP in the assessment of hepatocellular carcinoma.

Adult↗
PubMed1998

Hepatic cavernous hemangioma: sonographic patterns and speed of contrast enhancement on multiphase dynamic MR imaging.

OBJECTIVE: Our purpose was to investigate a correlation between the speed of contrast enhancement in patients with hepatic cavernous hemangioma revealed by dynamic MR imaging and the internal echo pattern revealed by sonography. MATERIALS AND METHODS: Forty-five patients underwent multiphase IV contrast-enhanced dynamic MR imaging that revealed 71 hepatic cavernous hemangiomas less than 4 cm in diameter; the MR findings were compared with the sonographic findings in these patients. On MR imaging, the hemangiomas were classified as rapid-, intermediate-, and slow-enhancing. We classified sonographic features as hypoechoic, iso- or mixed-echoic, and hyperechoic according to the relative echogenicity seen between lesions and the surrounding hepatic parenchyma. Sonographic patterns and MR imaging findings of individual lesions were then compared. RESULTS: Rapid-enhancing hemangiomas revealed on dynamic MR imaging tended to be hypoechoic on sonography (18/24, 75%; p = .0143), and lesions that were slow-enhancing on MR imaging tended to be hyperechoic (26/29, 90%; p < .0001). Hypoechoic lesions on sonography tended to be rapid-enhancing on dynamic MR imaging (18/18, 100%). Likewise, hyperechoic lesions on sonography tended to be slow-enhancing on MR imaging (26/33, 79%; p = .0009). CONCLUSION: In most patients with hepatic cavernous hemangiomas, we found that the speed of contrast enhancement on multiphase dynamic MR imaging enabled us to predict the echo pattern in sonography and vice versa.

Contrast Media↗
PubMed1998

Diabetic foot and neuroarthropathy: magnetic resonance imaging evaluation.

Neuropathic osteoarthropathy occurs commonly in patients with long-standing diabetes mellitus and is one of the leading causes of debilitating complications of the foot. In this article, the pathologic and radiologic features of neuropathic joint disease are reviewed, with an emphasis on MRI.

Diabetic Foot↗
PubMed1997

Selective interaction of protein kinase FA/glycogen synthase kinase-3alpha with membrane phospholipids.

Previously we reported that the activity of protein kinase FA/glycogen synthase kinase-3alpha (kinase FA/GSK-3alpha) can be detected in several brain membrane fractions. In this report, we examined whether kinase FA/GSK-3alpha can directly interact with membrane phospholipids by using anti-kinase FA/GSK-3alpha antibody as a more specific studying tool. It was found that kinase FA/GSK-3alpha can associate with NaOH-extracted brain membranes and selectively interact with several kinds of reconstituted phospholipid vesicles including phosphatidic acid (PA), phosphatidyl ethanolamine (PE), phosphatidyl inositol (PI), and phosphatidyl serine (PS) vesicles. Increasing ionic strength in the reaction could disrupt the interaction between kinase FA/GSK-3alpha and PA, PI, or PE vesicles but had no effect on the interaction between kinase FA/GSK-3alpha and PS vesicles, indicating that both ionic and non-ionic interactions are involved in this process, respectively. Moreover, both kinase activity and protease sensitivity of kinase FA/GSK-3alpha can be affected profoundly by these phospholipid vesicles and different forms of the kinase can be produced when it binds to distinct types of phospholipid vesicles. Taken together, the results demonstrate a direct interaction of kinase FA/GSK-3alpha with membrane phospholipids and suggest that membrane phospholipids may be directly involved in regulating kinase FA/GSK-3alpha activity.

Animals↗
PubMed1997

Gene therapy for metastatic brain tumors by vaccination with granulocyte-macrophage colony-stimulating factor-transduced tumor cells.

We have developed an ex vivo gene therapy paradigm for the treatment of brain tumors using granulocyte-macrophage colony-stimulating factor (GM-CSF). Murine B16 melanoma cells were infected with MFG recombinant retrovirus containing the mouse GM-CSF cDNA. Subcutaneous vaccination of syngeneic mice with irradiated GM-CSF-secreting B16 melanoma cells was capable of completely protecting animals against subsequent intracranial B16 tumor inoculation, with up to 5 x 10(3) cells. Histologic evaluation revealed the presence of neutrophils, eosinophils, and lymphocytes, including CD4+, CD8+, and CD45R+ cells, in the intracerebral inoculation site, peaking 4 days after intracranial inoculation. In contrast, nonvaccinated animals or animals vaccinated with irradiated, nontransduced B16 cells succumbed to intracranial tumor within 3 weeks after inoculation. Treatment of established intracranial B16 melanoma tumors with subcutaneous injection of irradiated GM-CSF-secreting B16 cells significantly delayed death, as compared to injection of irradiated nontransduced B16 cells or no treatment. In addition, treatment of established intracerebral GL261 gliomas by vaccination with irradiated GM-CSF-secreting B16 cells mixed with irradiated, transduced, or nontransduced GL261 cells also extended survival. These B16/GL261 co-vaccinations also improved outcome and, in some cases, induced immunological memory that protected survivors from subsequent intracranial challenge with GL261 tumor cells. These findings indicate that peripheral vaccination with irradiated tumor cells in the presence of GM-CSF-producing cells can initiate a potent antitumor immune response against intracranial neoplasms.

Animals↗
PubMed1997

Reversible tyrosine phosphorylation/dephosphorylation of proline-directed protein kinase FA/glycogen synthase kinase-3alpha in A431 cells.

Modulation of protein kinase FA/glycogen synthase kinase-3alpha (kinase FA/GSK-3alpha) by reversible tyrosine phosphorylation/dephosphorylation was investigated. In addition to genistein, other protein tyrosine kinase (PTK) inhibitors, such as tyrphostin A47 and B42, also could induce tyrosine dephosphorylation and inactivation of kinase FA/GSK-3alpha in A431 cells, and this process was found to be reversible. Pretreatment of the cells with 100 microM orthovanadate, a protein tyrosine phosphatase (PTP) inhibitor, could diminish significantly the effects of PTK inhibitors on both enzyme activity and phosphotyrosine content of the kinase, suggesting that the PTK inhibitors induced tyrosine dephosphorylation/inactivation of this kinase is mediated by orthovanadate-sensitive PTP(s) in A431 cells. Moreover, the phosphotyrosine moiety of kinase FA/GSK-3alpha was found to be highly turned over in resting cells. Interestingly, we found that the less active, tyrosine-dephosphorylated form of kinase FA/GSK-3alpha immunoprecipitated from genistein-treated cells was able to reactivate partially with concomitant rephosphorylation of tyrosine residue in vitro. Taken together, these findings demonstrate that tyrosine phosphorylation and concomitant activation of kinase FA/GSK-3alpha can be carried out both in vitro and in vivo and an in vivo phosphatase activity may function in antagonism to PTK activation of kinase FA/GSK-3alpha.

Animals↗
PubMed1997

Gorham syndrome of the thorax and cervical spine: CT and MRI findings.

Gorham syndrome is a rare disorder that is characterized by local osseous invasion and surrounding soft tissues by an angiomatous mass, eventually causing lysis of the affected bone. To date, only four cases have reported the MR imaging appearance of this disease and the findings have been variable. We present a case involving the cervical and thoracic spine and part of the osseous hemithorax with attention to the MR findings.

Angiomatosis↗
PubMed1997

Plasmid pRQ7 from the hyperthermophilic bacterium Thermotoga species strain RQ7 replicates by the rolling-circle mechanism.

The hyperthermophilic bacterium Thermotoga species strain RQ7 harbors an 846-bp plasmid, pRQ7, with a single open reading frame. Previously published analyses of the DNA sequence of pRQ7 suggested that it may replicate by a rolling-circle (RC) replication mechanism, and this report provides experimental evidence supporting this hypothesis. Single-stranded pRQ7 DNA accumulates in strain RQ7, as evidenced by the facts that this DNA bound to nitrocellulose membranes under nondenaturing conditions, was sensitive to S1 nuclease digestion, and hybridized to only one of two homologous DNA probes specific for each strand of the plasmid. The DNA encoding the open reading frame was cloned and expressed in Escherichia coli and gave a protein with a molecular mass of 26 kDa, similar to that deduced by sequence analysis. This protein bound to a fragment of pRQ7 that contains a putative double-stranded replication region in a magnesium-dependent reaction and made this fragment sensitive to S1 nuclease activity. It did not cause this same S1 nuclease sensitivity in the remainder of pRQ7. This activity on pRQ7 DNA suggests that this protein plays a role in plasmid replication.

Amino Acid Sequence↗
PubMed1997

Meniscal flounce MR imaging.

PURPOSE: To determine the prevalence of a meniscal flounce, the magnetic resonance (MR) imaging characteristics, and whether the flounce is associated with a meniscal tear. MATERIALS AND METHODS: Knee MR images obtained in 3,159 examinations over 2 years were prospectively evaluated. Ten adult patients (six with true flounces, four with flouncelike folds associated with meniscal tears) with an S-shaped fold in the free edge of a meniscus on sagittal images were included. Five underwent arthroscopic surgery. RESULTS: The prevalence of a flounce was 0.2% (six of 3,159 examinations). Five occurred in the medial meniscus (MM) and one occurred in the lateral meniscus (LM). All appeared truncated in the coronal plane. Four meniscal tears also demonstrated flouncelike folds. Three were confirmed with surgery and one was confirmed with clinical findings. Of the 3,159 MR examinations, 1,151 demonstrated an MM tear, 832 an LM tear, 542 MM degeneration, and 270 LM degeneration. CONCLUSION: A meniscal flounce is a fold that occurs in the absence of a tear, and presence of it does not increase the prevalence of a tear. Because tears may result in a flouncelike fold, a flounce should be considered a normal variant only in the absence of other indications of a meniscal tear.

Adolescent↗
PubMed1997

Small arterial-portal venous shunts: a cause of pseudolesions at hepatic imaging.

PURPOSE: To compare hepatic angiographic findings of small arterial-portal venous shunts with those of other imaging modalities, and to determine whether these shunts are related to hepatocellular carcinoma. MATERIALS AND METHODS: At hepatic angiography in 223 patients, small arterial-portal venous shunts not directly related to hepatocellular carcinoma and focal areas of parenchymal contrast material enhancement more than 1 cm in diameter were found in 28 patients. These 28 patients were prospectively evaluated with computed tomography (CT) during arterial portography (CTAP) (n = 12), CT after iodized oil administration (n = 23), intraoperative ultrasonography (n = 5), or follow-up hepatic angiography (n = 13). Magnetic resonance (MR) images (n = 10) and dynamic CT scans (n = 4) in these patients were retrospectively reviewed. RESULTS: Arterial-portal venous shunts noted at angiography manifested as perfusion defects at CTAP in 10 patients and as an area of arterial contrast enhancement at dynamic CT in three patients. No lesion was seen at MR imaging, and no persistent iodized oil uptake was seen at CT. There was no evidence of hepatocellular carcinoma tumor growth around the shunts at follow-up angiography, and no tumor was present at surgery. CONCLUSION: Understanding of the hemodynamic changes caused by these small shunts can aid in the interpretation of vascular imaging findings.

Angiography↗
PubMed1997

MR imaging of tophaceous gout.

OBJECTIVE: MR imaging is not routinely used for evaluation of tophaceous gout. However, gout may present clinically in an atypical, unusual, or confusing manner. A gouty tophus occasionally mimics an infectious or neoplastic process, and MR imaging may be obtained under these circumstances. The purpose of this study was to determine the MR imaging characteristics of intraosseous and soft-tissue tophi. MATERIALS AND METHODS: We identified 13 MR imaging examinations performed during a 27-month period on nine patients with gouty arthritis. All were men 42-70 years old. T1-, proton density-, and T2-weighted spin-echo MR images were obtained for all the examinations. Nine examinations included contrast-enhanced MR images. The findings were then evaluated, as were the corresponding radiographs. RESULTS: Five patients presented with articular involvement, three patients with an isolated soft-tissue mass, and one patient with persistent soft-tissue swelling. The duration of symptoms ranged from 3 months to more than 20 years. Nearly all the tophi were of intermediate signal intensity on T1-weighted images. On T2-weighted images, three sites revealed an overall increase in the signal intensity of the tophi, whereas 10 studies showed a heterogeneous decrease in signal intensity. All but one tophus showed homogeneous enhancement. Erosion of adjacent bone, synovial pannus, joint effusion, soft-tissue edema, and bone marrow edema were common associated findings. CONCLUSION: The MR appearance of tophi in patients with tophaceous gout is constant on T1- but quite variable on T2-weighted images. This variability in signal intensity could be related to calcium within a tophus. Tophaceous gout should be considered in the differential diagnosis when a mass reveals heterogeneously low to intermediate signal intensity, particularly if the adjacent bone shows typical erosive changes or if other joints are involved. When faced with this situation, radiologists may find it helpful to obtain a further clinical history and recommend evaluating the patient's serum urate level.

Adult↗
PubMed1997

A case of bleeding from the Dieulafoy lesion of the jejunum.

Dieulafoy lesion is an uncommon cause of gastrointestinal bleeding, reported to be only 2% of acute or chronic upper gastrointestinal bleeding episodes. Bleeding occurs from a small mucosal erosion involving an unusually large submucosal artery in an otherwise normal mucosa. It is associated with massive, life threatening hemorrhage and is difficult to diagnosis. In most cases the lesion is encountered in the proximal stomach, antrum, duodenum, colon and rectum. In particular, extragastric Dieulafoy lesion is an extremely rare source of intestinal bleeding. In Korea, no case of bleeding from a Dieulafoy lesion of the small intestine has been previously reported. We experienced one case of bleeding from a jejunal Dieulafoy lesion, which was confirmed by the pathologic examination of the resected specimen, and report here.

Adult↗
PubMed1996

Retroviral delivery and tetracycline-dependent expression of IL-1beta-converting enzyme (ICE) in a rat glioma model provides controlled induction of apoptotic death in tumor cells.

Interleukin 1beta-converting enzyme (ICE) is a member of a growing family of cysteine proteases shown to be a crucial component in the activation of a genetic program that leads to autonomous cell death in mammalian cells. In this study, a murine ICE-lacZ fusion gene was introduced into a novel retroviral vector designed to achieve regulated ectopic expression of a foreign gene in mammalian cells. By delivering the ICE-lacZ gene within a retroviral vector and under the control of a tetracycline-regulated promoter, we were able to utilize the intrinsic cell death program of ICE as a means for tumoricidal therapy in a rat brain tumor model. Both in culture and in vivo suppression of ICE-lacZ expression was extremely tight in the presence of tetracycline, as determined by the lack of X-galactosidase-positive tumor cells and by cell viability. When tetracycline was withdrawn, ICE-lacZ gene expression was rapidly turned on and apoptosis-mediated cell death occurred in essentially all tumor cells.

Animals↗