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Biomedical subjects

J S Yu

Publications and source records attributed to J S Yu.

At least 73 records · Page 4Linked to original sources
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↗
PubMed1996

Treatment with genetically engineered fibroblasts producing NGF or BDNF can accelerate recovery from traumatic spinal cord injury in the adult rat.

We tested the hypothesis that NGF or BDNF can protect damaged neural structures following spinal cord injury. Spinal contusions were produced in adult rats by a weight drop method. Thereafter, unmodified Rat 1 fibroblasts or fibroblasts engineered to secrete NGF or BDNF were injected into the injury site. Weekly assessments of recovery were made for 6 weeks using a locomotor rating scale. All rats were immediately paraplegic, then began to recover. At 1 week after injury, the ratings of locomotor performance in rats implanted with NGF- or BDNF-secreting fibroblasts were significantly increased over those of rats implanted with unmodified fibroblasts. This trend toward enhanced recovery persisted during the duration of the experiment, although the difference became smaller. Histological examination after 6 weeks showed a larger cross-sectional area of spinal cord at the maximal injury site in the animals treated with NGF or BDNF. These results demonstrate a significant biological effect of treatment with neurotrophins in traumatic spinal cord injury.

Animals↗
PubMed1996

Overexpression of protein kinase FA/GSK-3 alpha (a proline-directed protein kinase) correlates with human hepatoma dedifferentiation/progression.

Computer analysis of protein phosphorylation sites sequence revealed that transcriptional factors and viral oncoproteins are prime targets for regulation of proline-directed protein phosphorylation, suggesting an association of the proline-directed protein kinase (PDPK) family with neoplastic transformation and tumorigenesis. In this report, an immunoprecipitate activity assay of protein kinase FA/glycogen synthase kinase-3 alpha (kinase F(A)/GSK-3 alpha) (a member of PDPK family) has been optimized for human hepatoma and used to demonstrate for the first time significantly increased (P < 0.01) activity in poorly differentiated SK-Hep-1 hepatoma (24.2 +/- 2.8 units/mg) and moderately differentiated Mahlavu hepatoma (14.5 +/- 2.2 units/mg) when compared to well differentiated Hep 3B hepatoma (8.0 +/- 2.4 units/mg). Immunoblotting analysis revealed that increased activity of kinase FA/GSK-3 alpha is due to overexpression of the protein. Elevated kinase FA/GSK-3 alpha expression in human hepatoma biopsies relative to normal liver tissue was found to be even more profound. This kinase appeared to be fivefold overexpressed in well differentiated hepatoma and 13-fold overexpressed in poorly differentiated hepatoma when compared to normal liver tissue. Taken together, the results provide initial evidence that overexpression of kinase FA/GSK-3 alpha is involved in human hepatoma dedifferentiation/progression. Since kinase FA/GSK-3 alpha is a PDPK, the results further support a potential role of this kinase in human liver tumorigenesis, especially in its dedifferentiation/progression.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1996

Electrophoresis of DNA in novel thermoreversible matrices.

We demonstrate the feasibility of temperature-sensitive polymers as novel matrices for capillary and slab electrophoresis of DNA. These matrices combine the case-of-use of agarose with resolution properties of polyacrylamide. Two classes of matrices are used: (i) aqueous suspensions of gel microspheres and (ii) solutions containing uncross-linked temperature-sensitive polymers. When heated, the viscosity of these solutions drops dramatically because of the phase transition behavior of these polymers, and therefore these formulations are easy to pour or load. Results are presented for separation of double-stranded DNA fragments (< 2000 bp) in capillary, tube, and slab electrophoresis. Preliminary results are also presented for separation of single-stranded sequencing fragments by capillary electrophoresis. In the tube format, good resolution was obtained for phi X174/HaeIII fragments. In the slab format, excellent resolution of double-stranded DNA was obtained, including simultaneous separation of a 10 bp ladder up to 150 base pairs. In the capillary format, pBR322/MspI fragments were completely resolved, and single-base resolution of sequencing fragments was obtained up to 150 bases. We believe that temperature-sensitive polymers represent a new and promising class of electrophoretic media.

DNA↗
PubMed1996

Activation of the ATP.Mg-dependent type 1 protein phosphatase by the Fe2+/ascorbate system.

The ATP.Mg-dependent type 1 protein phosphatase is inactive as isolated but can be activated in several different ways. In this report, we show that the phosphatase can also be activated by the Fe2+/ascorbate system. Activation of the phosphatase requires both Fe2+ ion and ascorbate and the level of activation is dependent on the concentrations of Fe2+ ion and ascorbate. In the presence of 20 mM ascorbate, the Fe2+ ion concentrations required for half-maximal and maximal activation are about 0.3 and 3 mM, respectively. Several common divalent metal ions, including CO2+, Ni2+, Cu2+, Mg2+, and Ca2+ ions, cannot cooperate with ascorbate to activate the phosphatase, and SH-containing reducing agents such as 2-mercaptoethanol and dithiothreitol cannot cooperate with Fe2+ ion to activate the phosphatase, indicating that activation of the phosphatase by the Fe2+/ascorbate system is a specific process. Moreover, H2O2, a strong oxidizer, could significantly diminish the phosphatase activation by the Fe2+/ascorbate system, suggesting that reduction mechanism other than SH-SS interchange is a prerequisite for the Fe2+/ascorbate-mediated phosphatase activation. Taken together, the present study provides initial evidence for a new mode of type 1 protein phosphatase activation mechanism.

Animals↗
PubMed1996

Posterolateral aspect of the knee: improved MR imaging with a coronal oblique technique.

PURPOSE: To determine if angling the coronal plane in magnetic resonance (MR) imaging of the knee increases the conspicuity of the posterolateral structures. MATERIALS AND METHODS: A coronal oblique MR imaging sequence performed parallel to the popliteal tendon proximally was added to our routine study in patient knee examinations. One hundred patients (age range, 12-72 years) underwent MR imaging. RESULTS: Coronal oblique images depicted the arcuate ligament in 46%, the fabellofibular ligament in 48%, and the fibular origin of the popliteal muscle in 53% of the patients, whereas standard coronal images depicted these in 10%, 34%, and 8% of the patients, respectively. Sagittal oblique images did not adequately depict these structures. CONCLUSION: Depiction of the structures in the posterolateral aspect of the knee was optimal on coronal oblique images. We advocate obtaining coronal oblique T2-weighted images in patients with either posterolateral knee pain or suspected injury to the posterolateral ligamentous structures.

Adolescent↗
PubMed1996

The calcaneus: applications of magnetic resonance imaging.

The calcaneus is the largest bone in the foot and is an important primary weightbearing structure. Pathologic processes that affect this bone may manifest in a variety of clinical presentations, including pain, abnormal motion, instability, or fracture. The purpose of this article is to present a pictorial essay of the wide spectrum of pathologic entities that may affect the calcaneus, emphasizing applications of magnetic resonance imaging and characteristic magnetic resonance features of these processes.

Calcaneus↗
PubMed1996

Magnetic resonance imaging (MRI) of the knee: a pattern approach for evaluating bone marrow edema.

The applications of magnetic resonance imaging (MRI) have become numerous for the assessment of disorders involving the knee. Once a technique used nearly exclusively in the evaluation of internal derangement of this joint, it now plays an important role in the diagnosis of processes that affect the bone marrow, including those that occur as a result of trauma, infection, tumor, and rheumatologic disorders. Signal alterations in the bone marrow frequently are present in association with these pathological processes. When the signal is of low intensity on T1-weighted images and becomes heterogeneously increased in intensity on T2-weighted images, it indicates the presence of edema in the bone marrow. Two types of marrow edema are presented in this review: posttraumatic and reactive. In many situations, the area of altered signal intensity is radiographically occult. The distribution of marrow edema often reflects the mechanism of injury in trauma and may correlate with additional injuries to the surrounding soft tissues. Reactive marrow edema occurs either in response to an inflammatory focus in the bone and/or joint or a neoplastic process in or adjacent to the bone.

Adolescent↗
PubMed1995

The hyperthermophilic bacterium Thermotoga neapolitana possesses two isozymes of the 3-phosphoglycerate kinase/triosephosphate isomerase fusion protein.

The phosphoglycerate kinase (pgk), triosephosphate isomerase (tpi), and enolase (eno) genes from Thermotoga neapolitana have been cloned and expressed in Escherichia coli. In high copy number, the pgk gene complemented an E. coli pgk- strain. In T. neapolitana, the pgk and tpi genes appear to be fused and eno is near those genes. Like T. maritima, T. neapolitaná produces phosphoglycerate kinase as both an individual enzyme and a fusion protein with triosephosphate isomerase, and triosephosphate isomerase activity is not found without associated phosphoglycerate kinase activity. Unlike T. maritima, which forms only a 70-kDa fusion protein, T. neapolitana expresses both 73-kDa and 81-kDa isozymes of this fusion protein. These isozymes are present in both T. neapolitana cells and in E. coli cells expressing T. neapolitana genes.

Cloning, Molecular↗
PubMed1995

Phosphorylation/activation of phosphorylase b kinase by cAMP/Ca2(+)-independent, autophosphorylation-dependent protein kinase.

Phosphorylase b kinase from rabbit skeletal muscle can be phosphorylated and activated by a cyclic nucleotide- and Ca2(+)-independent protein kinase previously identified as an autophosphorylation-dependent multifunctional protein kinase (auto-kinase) from brain and liver (Yang et al., J. Biol. Chem. 262, 7034-7040 (1987) and Yang et al. J. Biol. Chem. 262, 9421-9427 (1987)). This independent kinase phosphorylates both alpha and beta subunits of phosphorylase b kinase and results in a approximately 5-fold activation of the kinase when 0.55 and 0.5 mol of phosphate are incorporated into the alpha and beta subunits, respectively. Activation of phosphorylase b kinase catalyzed by auto-kinase is about 70% of that observed with cAMP-dependent protein kinase. Analysis of phosphopeptide maps of alpha and beta subunits further reveals that both kinases phosphorylate almost the same sites on both alpha and beta subunits, suggesting that activation of phosphorylase b kinase by the two kinases may be through a common molecular action mechanism. Taken together with the previous result that auto-kinase can inactivate glycogen synthase, the present study provides initial evidence that a coordinate control mechanism for simultaneous regulation of glycogenolysis and glycogenesis can be modulated by autophosphorylation-dependent protein kinase in a cAMP- and Ca2(+)-independent pathway, representing a new mode of control mechanism for the regulation of glycogen metabolism in cells.

Animals↗
PubMed1995

Overexpression of cellular activity and protein level of protein kinase FA/GSK-3 alpha correlates with human thyroid tumor cell dedifferentiation.

Computer analysis of protein phosphorylation sites sequence revealed that transcriptional factors and viral oncoproteins are prime targets for regulation of proline-directed protein phosphorylation, suggesting an association of the proline-directed protein kinase (PDPK) family with neoplastic transformation and tumorigenesis. In this report, an immunoprecipitate activity assay of protein kinase FA/glycogen synthase kinase-3 alpha (kinase FA/GSK-3 alpha) (a member of the PDPK family) has been optimized for human thyroid tissue and used to demonstrate for the first time significantly increased (P < 0.001) activity in thyroid carcinoma (24.2 +/- 2.8 units/mg of protein) (n = 7), thyroid adenoma (14.5 +/- 2.2 units/mg of protein) (n = 6), and thyroid hyperplasia (8.0 +/- 2.4 units/mg of protein) (n = 5) when compared to five normal controls (4.1 +/- 1.8 units/mg of protein). Immunoblotting analysis further revealed that increased activity of kinase FA/GSK-3 alpha in thyroid tumor cells is due to overexpression of the protein synthesis of the enzyme. Taken together, the results provide initial evidence that overexpression of protein level and cellular activity of kinase FA/GSK-3 alpha is involved in human thyroid tumor cell dedifferentiation, supporting an association of PDPK with neoplastic transformation and tumorigenesis. Since kinase FA/GSK-3 alpha may function as a possible regulator of transcription factors/protooncogenes, kinase FA/GSK-3 alpha may therefore play an important role in thyroid cell carcinogenesis, especially in its differentiation.

Adenoma↗
PubMed1995

Dysfunction of protein kinase FA/GSK-3 alpha in lymphocytes of patients with schizophrenic disorder.

As compared to normal people, the lymphocytes of patients with schizophrenia were found to have an impairment of ATP.Mg-dependent protein phosphatase activation. More importantly, the impaired protein phosphatase activation in the lymphocytes of schizophrenic patients could be consistently and completely restored to normal by exogenous pure protein kinase FA/glycogen synthase kinase-3 alpha (kinase FA/GSK-3 alpha) (the activating factor of ATP.Mg-dependent protein phosphatase), indicating that the molecular mechanism for the impaired protein phosphatase activation in schizophrenic patients may be due to a functional loss of kinase FA/GSK-3 alpha. Immunoblotting and kinase activity analysis in an anti-kinase FA/GSK-3 alpha immunoprecipitate further demonstrate that both cellular activities and protein levels of kinase FA/GSK-3 alpha in the lymphocytes of schizophrenic patients were greatly impared as compared to normal controls. Statistical analysis revealed that the lymphocytes isolated from 37 normal people contain kinase FA/GSK-3 alpha activity in the high levels of 14.8 +/- 2.4 units/mg of cell protein, whereas the lymphocytes of 48 patients with schizophrenic disorder contain kinase FA/GSK-3 alpha activity in the low levels of 2.8 +/- 1.6 units/mg, indicating that the different levels of kinase FA/GSK-3 alpha activity between schizophrenic patients and normal people are statistically significant. Taken together, the results provide initial evidence that patients with schizophrenic disorder may have a common impairment in the protein levels and cellular activities of kinase FA/GSK-3 alpha, a multisubstrate protein kinase and a multisubstrate protein phosphatase activator in their lymphocytes.

Amino Acid Sequence↗