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Biomedical subjects

T G Lee

Publications and source records attributed to T G Lee.

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

Ki-67 expression as a prognostic marker in patients with hepatocellular carcinoma.

Ki-67 expression in tumours has been shown to be associated with prognosis in patients with hepatocellular carcinoma (HCC). In this study, primary HCC samples were obtained from 67 patients undergoing surgical resection. None of these patients had been subjected previously to any other form of therapy, such as arterial embolization or chemotherapy. Histologically normal liver tissues from liver resection for metastatic colon cancer were taken as controls (n = 8). Monoclonal antibody against Ki-67 was used for immunostaining and flow cytometry was used to measure tumour DNA ploidy. The mean Ki-67 labelling index (percentage of Ki-67-positive cells) of the HCC (26 +/- 22%; range 0.1-89%) was significantly higher than that of the normal controls (39 +/- 0.8%, P < 0.05). The mean Ki-67 labelling index (19 +/- 15%; n = 28) of the tumours with diploid DNA pattern was significantly lower than those with aneuploid DNA pattern (32 +/- 25%, n = 39; P = 0.01). Hepatocellular carcinoma patients (n = 47) with Ki-67 index > 10% had a significantly lower disease-free and overall survival than those (n = 20) with Ki-67 index < or = 10% (P = 0.0009 and P = 0.02, respectively). Multivariate analysis showed that Ki-67 expression and tumour node metastasis stage were two independent prognostic factors for disease-free and overall survival rates. Our results suggest that the expression of Ki-67 is an independent prognostic indicator for patients with HCC after resection and could be of assistance in the decision-making of adjuvant therapy.

Aged↗
PubMed1997

Phorbol myristate acetate-dependent association of protein kinase C alpha with phospholipase D1 in intact cells.

A phospholipase D1 (PLD1) was purified from rat brain by the use of antibody-coupled protein A Sepharose. We found that protein kinase C alp (PKCalpha) stimulated PLD1 activity in the presence of phorbol myristate acetate (PMA). PMA-dependent association of PKCalpha with PLD1 was verified in NIH-3T3 fibroblast cells, and COS7 cells transiently expressing PLD1 as well as in vitro suggesting that the activation of PLD1 resulted from direct association of PKCalpha with PLD1.

3T3 Cells↗
PubMed1997

Immunological identification of cholesterol ester hydrolase in the steroidogenic tissues, adrenal glands and testis.

Monoclonal antibodies were generated against the purified pancreatic cholesterol ester hydrolase (CEH, EC 3.1.1.13) to examine the expression of CEH in various bovine tissues. The presence of CEH isozyme antigenically indistinguishable from pancreatic enzyme in the steroidogenic tissues, adrenal glands and testis has been first demonstrated here using the immunoprecipitation method. These results suggest that CEH isozyme, similar to pancreatic CEH, might be involved in the cholesterol metabolism in the steroidogenic tissue.

Adrenal Glands↗
PubMed1997

Effect of a novel saponin adjuvant derived from Quillaja saponaria on the immune response to recombinant hepatitis B surface antigen.

Adjuvant activity of saponins extracted from the South American tree Quillaja saponaria has been demonstrated with many antigens. Recently, four saponin fractions (designated as QS-7, QS-17, QS-18, and QS-21) with adjuvant activity were purified by reverse phase chromatography. In particular, efficacy of the less toxic QS-21 fraction has been demonstrated with several recombinant viral antigens including HIV gp120. Here, we report a novel saponin fraction (designated as QS-L1) derived from Quillaja saponaria. Unlike previously identified saponins, QS-L1 had a different chemical structure and showed adjuvant activity only when administered in the presence of alum-precipitated antigen. Interestingly, the QS-L1 greatly increased not only a humoral immune response but also cellular immune response to recombinant hepatitis B virus surface antigen (HBsAg). Furthermore, QS-L1 showed lower toxicity in vivo and in vitro than the previously identified saponin fraction, QS-21. Finally, we examined the chemical structure of the QS-L1 using mass spectroscopic analysis, carbohydrate composition analysis and NMR spectroscopic analysis. Thus, our results indicated that this novel QS-L1 saponin fraction had several desirable properties required for an effective adjuvant.

Adjuvants, Immunologic↗
PubMed1997

Development and evaluation of a chicken breakfast sausage manufactured with mechanically deboned chicken meat.

Leghorn spent hen mechanically deboned chicken meat (MDCM) was utilized in the preparation of a value-added chicken sausage. The sausage was manufactured by combining MDCM with hand-deboned skinless chicken thigh meat, fat replacer ingredients (blend of modified food starch and oat flour), and either 1) no ingredient with antioxidant properties, 2) Colorlife powdered rosemary concentrate, 3) Herbalox Type O oleoresin rosemary extract or 4) Tenox 6 antioxidant. The 454-g sausage chubs were stored at 4 +/- 1 C (refrigerated) and -20 +/- 1 C (frozen) for 10 d and 6 mo, respectively. A shelf life evaluation (based on daily examination of product, panelists responses, and psychrotrophic organism counts) of 8 d and 6 mo was attained for the sausage stored at 4 +/- 1 and -20 +/- 1 C, respectively. Flavor intensity, texture, and color were maintained for all treatments, and no significant (P > 0.05) off-flavors were detected through 8 d and 6 mo storage. Colorlife and Herbalox rosemary ingredients, and Tenox 6 antioxidant had no adverse effects on sensory characteristics of the chicken sausage. Psychrotrophic organisms increased with increased storage time for the refrigerated sausage, and remained static for the frozen sausage.

Animals↗
PubMed1997

cDNA cloning of the 210-kDa paraneoplastic pemphigus antigen reveals that envoplakin is a component of the antigen complex.

Although the 210 and 190-kDa proteins are the most frequently detected antigens reacting with sera of patients with paraneoplastic pemphigus (PNP) in immunoblot analysis, there is still uncertainty as to the nature of these PNP antigens. To isolate and characterize a cDNA clone encoding the 210-kDa PNP antigen, we screened a human keratinocyte lambda gt 11 cDNA expression library by the immunoperoxidase method with serum IgG from a PNP patient. The IgG used for the immunoscreening of a keratinocyte cDNA expression library recognized 210- and 190-kDa antigens by immunoblotting. A single clone, called here the PNP clone, producing a fusion protein that reacted strongly with the patient's IgG, was further characterized. Only the PNP patient's IgG, but not IgG from a normal control, pemphigus foliaceus, or pemphigus vulgaris patients, bound the plaques of this positive clone. Furthermore, PNP IgG affinity purified on plaques of this clone, but not unrelated clones, bound to keratinocyte cell surfaces by immunofluorescence and reacted with the 210-kDa PNP antigen by immunoblotting. EcoRI digestion of the clone's cDNA insert demonstrated a 1.4-kbp fragment. This cDNA insert was placed into a M13 mp 18 vector and sequenced. Sequence analysis revealed that the cDNA insert of the PNP clone encodes a part of the central rod domain and the COOH-terminal C domain of envoplakin, a newly defined precursor of the cornified envelope that is homologous to desmoplakin. This result demonstrates that the 210-kDa PNP antigen is envoplakin and PNP is an autoimmune disease that produces autoantibodies against intermediate filament-associated proteins in desmosomes and hemidesmosomes, desmoplakin, bullous pemphigoid antigen 1 (BPAG 1), and envoplakin.

Autoantibodies↗
PubMed1996

Generation of a novel poliovirus with a requirement of hepatitis C virus protease NS3 activity.

Hepatitis C virus (HCV) is the major etiologic agent of non-A, non-B hepatitis. One of the difficulties in developing anti-HCV drugs is the lack of an efficient HCV cultivation system. We have generated an artificial surrogate virus suitable for testing the antiviral effects of drugs affecting HCV protease NS3, an enzyme believed to be essential for HCV proliferation. The surrogate virus genome is composed of most of the poliovirus genome and HCV protease NS3 and an NS3-specific cleavage site. The activity of HCV protease NS3 is required for proliferation of this chimeric virus. The antiviral efficacy of HCV protease inhibitors can, therefore, be evaluated by examining the effects of the drugs on the surrogate virus proliferation.

Amino Acid Sequence↗
PubMed1996

Inhibition of phospholipase D by a protein factor from bovine brain cytosol. Partial purification and characterization of the inhibition mechanism.

A specific protein inhibitor of partially purified bovine brain phospholipase D (PLD) was identified from bovine brain cytosol. The PLD inhibitor has been enriched through several chromatographic steps and characterized with respect to size and mechanism of inhibition. The inhibitor showed an apparent molecular mass of 30 kDa by Superose 12 gel exclusion chromatography and inhibited PLD activity with an IC50 of 7 nM. The inhibitor had neither proteolytic activity nor phospholipid-hydrolyzing activity. Because phosphatidylinositol 4,5-bisphosphate (PIP2), which is included in substrate vesicles, is an essential cofactor for PLD, we examined whether the inhibition might be mediated by sequestration of PIP2. PIP2 hydrolysis by phospholipase C (PLC)-beta1 was not affected by the inhibitor and the inhibitor did not bind to substrate vesicles containing PIP2. In contrast, a PH domain derived from PLC-delta1, which could bind to PIP2, showed a nearly identical inhibition of both PLC-beta1 and PLD activities. Thus, the PLD inhibition by the inhibitor is due to the specific interaction with not PIP2 but PLD. The suppression of PLD activity by the inhibitor was largely eliminated by the addition of ADP-ribosylation factor (ARF) and GTPgammaS. We propose that the inhibitor plays a negative role in regulation of PLD activity by PIP2 and ARF.

Animals↗
PubMed1995

Cerebral venous thrombosis associated with maxillary and ethmoid sinusitis--a case report.

We herein report a young patient with cerebral venous thrombosis (CVT) with clinical and neuroradiological findings of the left maxillary and anterior ethmoid sinusitis. Serial brain MRIs showed cerebral venous infarct and thrombosis in the superior sagittal sinus (SSS). MR angiography demonstrated nonvisualization of SSS and bilateral transverse sinus. According to our knowledge, CVT associated with maxillary and ethmoid sinusitis has been reported very rarely. High index of suspicion and neuroimaging studies, especially brain MRI, and conventional or MR angiography are very important for the early diagnosis of CVT.

Adult↗
PubMed1994

The 58-kilodalton inhibitor of the interferon-induced double-stranded RNA-activated protein kinase is a tetratricopeptide repeat protein with oncogenic properties.

The interferon-induced RNA-dependent protein kinase (PKR) is considered to play an important role in the cellular defense against viral infection and, in addition, has been suggested to be a tumor suppressor gene because of its growth-suppressive properties. Activation of PKR by double-stranded RNAs leads to the phosphorylation of the alpha subunit of eukaryotic initiation factor 2 (eIF-2 alpha) and a resultant block to protein synthesis initiation. To avoid the consequences of kinase activation, many viruses have developed strategies to down-regulate PKR. Recently, we reported on the purification and characterization of a cellular inhibitor of PKR (referred to as p58), which is activated during influenza virus infection. Subsequent cloning and sequencing has revealed that p58 is a member of the tetratricopeptide repeat (TPR) family of proteins. To further examine the physiological role of this PKR inhibitor, we stably transfected NIH 3T3 cells with a eukaryotic expression plasmid containing p58 cDNA under control of the cytomegalovirus early promoter. By taking advantage of a recently characterized p58 species-specific monoclonal antibody, we isolated cell lines that overexpressed p58. These cells exhibited a transformed phenotype, growing at faster rates and higher saturation densities and exhibiting anchorage-independent growth. Most importantly, inoculation of nude mice with p58-overexpressing cells gave rise to the production of tumors. Finally, murine PKR activity and endogenous levels of eIF-2 alpha phosphorylation were reduced in the p58-expressing cell lines compared with control cells. These data, taken together, suggest that p58 functions as an oncogene and that one mechanism by which the protein induces malignant transformation is through the down-regulation of PKR and subsequent deregulation of protein synthesis.

3T3 Cells↗
PubMed1994

Two forms of phospholipase C-beta 1 generated by alternative splicing.

Phospholipase C-beta 1 (PLC-beta 1) exists as two immunologically indistinguishable polypeptides of 150 and 140 kDa and is encoded in rat brain by two distinct transcripts of 5.4 and 7.2 kilobases (kb). cDNA corresponding to the entire 5.4-kb transcript as reported previously reveals an open reading frame that is capable of coding a 1216-amino acid polypeptide (Suh, P. G., Ryu, S. H., Moon, K. H., Suh, H. W., and Rhee, S. G. (1988) Cell 54, 161-169). We have now isolated cDNAs corresponding to the entire 7.2-kb transcript from a rat brain cDNA library. The 7.2-kb transcript differs from the previously reported 5.4-kb transcript by possessing both an additional 118 nucleotides located near the end of the coding sequence and a 1738-nucleotide extension of the 3'-flanking region. The presence of the 118-nucleotide insert in the cumulative 7.2-kb sequence gives rise to an open reading frame that is capable of coding a 1173-amino acid polypeptide (PLC-beta 1b), the carboxyl-terminal sequence of which differs from that of the 1216-amino acid polypeptide (PLC-beta 1a) derived from the 5.4-kb transcript. Antibodies were raised against synthetic peptides corresponding to the carboxyl-terminal portions of PLC-beta 1a and PLC-beta 1b. Immunoblot analysis with these isozyme-specific antibodies revealed that both PLC-beta 1a and PLC-beta 1b are expressed in rat brain and C6Bu-1 glioma cells and that PLC-beta 1a and PLC-beta 1b correspond to the previously identified 150- and 140-kDa PLC-beta 1 enzymes, respectively. Analysis of PLC-beta 1 genomic DNA indicates that PLC-beta 1a and PLC-beta 1b are derived from a single gene by alternative RNA splicing.

Alternative Splicing↗
PubMed1994

The 58,000-dalton cellular inhibitor of the interferon-induced double-stranded RNA-activated protein kinase (PKR) is a member of the tetratricopeptide repeat family of proteins.

PKR is a serine/threonine protein kinase induced by interferon treatment and activated by double-stranded RNAs. As a result of activation, PKR becomes autophosphorylated and catalyzes phosphorylation of the alpha subunit of protein synthesis eukaryotic initiation factor 2 (eIF-2). While studying the regulation of PKR in virus-infected cells, we found that a cellular 58-kDa protein (P58) was recruited by influenza virus to downregulate PKR and thus avoid the kinase's deleterious effects on viral protein synthesis and replication. We now report on the cloning, sequencing, expression, and structural analysis of the P58 PKR inhibitor, a 504-amino-acid hydrophilic protein. P58, expressed as a histidine fusion protein in Escherichia coli, blocked both the autophosphorylation of PKR and phosphorylation of the alpha subunit of eIF-2. Western blot (immunoblot) analysis showed that P58 is present not only in bovine cells but also in human, monkey, and mouse cells, suggesting the protein is highly conserved. Computer analysis revealed that P58 contains regions of homology to the DnaJ family of proteins and a much lesser degree of similarity to the PKR natural substrate, eIF-2 alpha. Finally, P58 contains nine tandemly arranged 34-amino-acid repeats, demonstrating that the PKR inhibitor is a member of the tetratricopeptide repeat family of proteins, the only member identified thus far with a known biochemical function.

Amino Acid Sequence↗
PubMed1994

Initial and follow-up brain MRI findings and correlation with the clinical course in Wilson's disease.

We performed pretreatment brain MRIs in 25 patients with neurologically symptomatic Wilson's disease (WD) and clinical and MRI follow-up in 16 of them. All 25 pretreatment MRIs revealed abnormalities, with abnormal high-signal intensity (HSI) in bilateral thalami being the most common (92%). HSI lesions in the brainstem (84%) and the basal ganglia (72%) were also common. Brain atrophy was present in 88% of the 25 patients. In the follow-up period of 5 to 24 months, during which the patients were treated with D-penicillamine, both HSI lesions and neurologic symptoms improved in 88% of the 16 patients, but the brain atrophy did not change.

Adolescent↗