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T C Lee

Publications and source records attributed to T C Lee.

At least 163 records · Page 9Linked to original sources
PubMed1993

Intraoperative high-dose rate interstitial irradiation of hepatic metastases from colorectal carcinoma. Results of a phase I-II trial.

BACKGROUND: Resection of liver metastases from colorectal carcinoma can be curative. Unresectable but liver-confined metastases might be ablated by high-dose radiation with a similar curative result. METHODS: At Georgetown University Hospital, 22 patients with unresectable hepatic metastases from colorectal carcinoma underwent 24 interstitial irradiation procedures at laparotomy in a Phase I-II study. A single dose was administered with a high-dose rate iridium-192 afterloader. Dose to the tumor periphery was 20 Gy, 25 Gy, and 30 Gy in 13, 9, and 2 procedures, respectively. RESULTS: No acute or chronic radiation toxicity has occurred at a median follow-up of 11 months. Median actuarial local control at irradiated sites was 8 months, with 26% actuarial local control at 26 months by computed tomography (CT) or magnetic resonance imaging (MRI) scanning. In the two patients undergoing two procedures each, a second biopsy of previously irradiated areas demonstrated tumor eradication. CONCLUSIONS: This innovative, radical approach to unresectable colorectal hepatic metastases proved safe. Additional study is needed to determine whether interstitial irradiation is as effective as surgical resection, or whether it alters the natural history of the disease or longevity.

Adult↗
PubMed1993

Protection of a rat tracheal epithelial cell line from paraquat toxicity by inhibition of glucose-6-phosphate dehydrogenase.

Transformed rat tracheal epithelial cells (U2) were found to be 3.6-fold more sensitive than lung fibroblasts (RLF) to paraquat. Although the toxic effects of paraquat are associated with the generation of very active superoxides, U2 cells contained higher levels of superoxide dismutase and catalase than RLF cells. On the other hand, the specific activities of both NADPH-cytochrome c reductase and glucose-6-phosphate dehydrogenase (G6DP) were 3- to 4-fold higher in U2 cells than in RLF cells. Treatment with dehydroepiandrosterone (DHEA) and epiandrosterone (EPI), G6PD inhibitors, significantly decreased the intracellular NADPH and protected U2 cells from paraquat toxicity. Since DHEA and EPI treatment did not affect the uptake of paraquat, our results suggest that paraquat sensitivity may depend on the redox cycling-associated activities of paraquat.

Androsterone↗
PubMed1993

Evidence for biosynthesis of plasmenylcholine from plasmenylethanolamine in HL-60 cells.

Both [3H]plasmenylethanolamine and [3H]plasmenylcholine were produced from substrates of [3H]alk-1-enylglycerol and [3H]alk-1-enyllysoglycerophosphoethanolamine by intact HL-60 cells. Molecular species analysis of the [3H]plasmenylcholine and [3H]plasmenylethanolamine formed indicated the major portion of plasmenylcholine originates from plasmenylethanolamine by a series of reactions catalyzed by phospholipase A2, lysophospholipase D, acyltransferase, phosphohydrolase, and cholinephosphotransferase. However, a significant but much smaller portion of the plasmenylcholine appeared to be synthesized from plasmenylethanolamine via a direct base-exchange or a coupled phospholipase C/cholinephosphotransferase reaction.

Diacylglycerol Cholinephosphotransferase↗
PubMed1993

Primary structure of three distinct isoabrins determined by cDNA sequencing. Conservation and significance.

A family of toxic proteins, the isoabrins, which possess N-glycosylase activity toward eukaryotic 28 S r-RNA, may have potential use in cancer chemotherapy. By polymerase chain reaction techniques, cDNA clones of three isoabrins, carrying A and B-chain sequences, were isolated and their nucleotide sequences were determined. The isoabrins consist of an A-chain comprised of 250 of 251 amino acids, followed by a 10 amino acid linker and a B-chain of 267 amino acids. There is substantial conservation in the B-chain of the three isoabrins, with less than six amino acid substitutions, whereas as many as 46 amino acid substitutions occur in the A-chains. Based on the relationships between the biological activities and the putative amino acid sequences of the isoabrins, three isoabrins, abrin-a, -b and -d, could be identified and the potential epitope of immunological response of these isoabrins could be assigned.

Abrin↗
PubMed1993

Induction of chromatid breaks and tetraploidy in Chinese hamster ovary cells by treatment with sodium arsenite during the G2 phase.

Treatment of Chinese hamster ovary (CHO) cells with sodium arsenite during the G2 phase induced poorly condensed chromosomes and chromatid breaks. The induction of chromatid breaks was confirmed by the appearance of micronucleated cells after arsenite-treated G2 cells were allowed to re-enter interphase. When the duration of the G2 phase was artificially divided into 4 periods, more chromatid breaks were induced by treatment with arsenite during the very early G2 phase (or G2/S boundary). In addition to the induction of chromatid breaks, arsenite treatment also remarkably retarded the re-entry of mitotic cells into interphase. By replating and incubating arsenite-treated G2 cells in drug-free medium, we subsequently observed the appearance of a population of cells whose DNA content was between 4C and 8C, and metaphase cells with near-tetraploid chromosome numbers in the next mitotic division.

Animals↗
PubMed1993

Increased biliary transferrin excretion following parenteral aluminium administration to rats.

Aluminium accumulates in the livers of patients receiving either parenteral nutrition or haemodialysis. When given parenterally to rats, aluminium causes cholestasis. However, the mechanism of hepatic aluminium uptake and the fate of aluminum in the liver are poorly understood. We examined the effect of parenteral aluminium administration on biliary excretion of transferrin, the major circulating aluminum-binding protein. Male Wistar rats were given parenterally aluminum 5 mg/kg/day for 1-14 days. Bile was collected for 3 hr at the end of the study period. Biliary total protein concentration and IgA/total protein were unaffected by up to 14 days of parenteral aluminium administration. However, biliary transferrin excretion increased with duration of aluminum administration up to five-fold by day 14. Biliary transferrin concentration and transferrin/total protein was higher in aluminum treated rats than controls after 7 and 14 days of study. Hepatic aluminum concentration reached a maximum after 4 days of parenteral aluminum administration, at which time serum bile acid and alanine amino transferase values were not different from controls. Since biliary transferrin is normally derived from the serum, it is likely that aluminum promotes hepatocellular uptake of transferrin and that aluminum enters the hepatocyte bound to transferrin. We postulate that transferrin may direct aluminum to intracellular sites where its toxic effects would be minimized.

Alanine Transaminase↗
PubMed1993

Growth of 28 Legionella species on selective culture media: a comparative study.

We compared the growth of 28 Legionella spp. on four manufacturers' buffered charcoal-yeast extract (BCYE) agar media and selective BCYE media that contained polymyxin B, anisomycin, and vancomycin or cefamandole. With BCYE as a "gold standard," growth for Legionella pneumophila was significantly better than for the nonpneumophila species on all media tested. L. pneumophila and 24 other Legionella spp. grew on vancomycin-containing media, while L. santicrucis, L. rubrilucens, and L. erythra grew poorly. In contrast, 11 of 28 species (notably L. micdadei and L. bozemanii) did not grow on cefamandole-containing media and 8 of 28 species only grew marginally. We demonstrated that selective BCYE media that contain vancomycin or cefamandole may not support the growth of all Legionella spp. One commercial manufacturer's media were consistently suboptimal. Laboratories should not rely on a manufacturer's quality control testing in lieu of their own.

Culture Media↗
PubMed1993

Mechanisms of stimulation of interleukin-1 beta and tumor necrosis factor-alpha by Mycobacterium tuberculosis components.

The granulomatous immune response in tuberculosis is characterized by delayed hypersensitivity and is mediated by various cytokines released by the stimulated mononuclear phagocytes, including tumor necrosis factor-alpha (TNF alpha) and IL-1 beta. We have demonstrated that Mycobacterium tuberculosis cell wall component lipoarabinomannan (LAM), mycobacterial heat shock protein-65 kD, and M. tuberculosis culture filtrate, devoid of LPS as assessed by the Amebocyte Lysate assay, stimulate the production of TNF alpha and IL-1 beta proteins and mRNA from mononuclear phagocytes (THP-1 cells). The effect of LAM on the release of these cytokines was specific, as only LAM stimulation was inhibited by anti-LAM monoclonal antibody. Interestingly, we found that LAM and Gram-negative bacterial cell wall-associated endotoxin LPS may share a similar mechanism in their stimulatory action as demonstrated by inhibition of TNF alpha and IL-1 beta release by monoclonal antibodies to CD14. Anti-CD14 monoclonal antibody MY4 inhibited both TNF alpha and IL-1 beta release with LAM and LPS but no effect was observed with other mycobacterial proteins. An isotype antibody control did not inhibit release of cytokines under the same experimental conditions. M. tuberculosis and its components upregulated IL-1 beta and TNF alpha mRNAs in THP-1 cells. Nuclear run-on assay for IL-1 beta demonstrated that LAM increased the transcription rate. The induction of IL-1 beta was regulated at the transcriptional level, in which these stimuli acted through cis-acting element(s) on the 5' flanking region of the IL-1 beta genomic DNA. M. tuberculosis cell wall component LAM acts similarly to LPS in activating mononuclear phagocyte cytokine TNF alpha and IL-1 beta release through CD14 and synthesis at the transcriptional level; both cytokines are key participants in the host immune response to tuberculosis.

Antibodies, Monoclonal↗
PubMed1993

Expression of P-glycoprotein and glutathione-S-transferase in recurrent lymphomas: the possible role of Epstein-Barr virus, immunophenotypes, and other predisposing factors.

PURPOSE: We previously have reported the poor prognoses of recurrent peripheral T-cell lymphoma (PTCL) and Epstein-Barr virus (EBV)-associated PTCL (J Clin Oncol 7:725-731, 1989; Blood 77:799-808, 1991). To study the role that drug resistance plays in this scenario, we conducted a retrospective study of 23 adult patients. PATIENTS AND METHODS: All patients had recurrent lymphoma tissue available for immunophenotyping and screening for the existence of EBV DNA in tumor cells by Southern blot analysis and in situ hybridization. Expression of a multidrug resistance P-glycoprotein ([P-gp]mdr-1) and a glutathione redox cycle-related glutathione-S-transferase pi (GST-pi) was determined by an immunohistochemistry method. RESULTS: Expression of mdr-1 or GST-pi was found in 11 (48%) and 12 (52%) cases, respectively. Most (11 of 12) of the GST-pi expression occurred simultaneously with mdr-1. Prechemotherapy tumor tissues were available in 11 cases; only two (18.2%) of these cases expressed mdr-1. Four (36%) of 11 cases that expressed mdr-1 (mdr-1(+)) and nine (90%) of 10 cases that did not express mdr-1 (mdr-1(-)) responded to second-line chemotherapy (P < .05). The survival-after-recurrence (SAR) curves significantly favored mdr-1(-) recurrent lymphoma (P < .05). The mdr-1 expression was further correlated with the immunophenotype and EBV association. All six cases of EBV-associated lymphoma (PTCL, five cases; Hodgkin's disease, one case) had significant simultaneous expression of mdr-1 and GST-pi in their recurrent tumor tissues. CONCLUSION: (1) mdr-1 expression is a significant prognostic factor in recurrent lymphomas; (2) high expression of mdr-1 is observed in recurrent EBV-associated PTCL; and (3) GST-pi usually expresses simultaneously with mdr-1 in recurrent lymphomas. The role of EBV in the development of mdr-1 and the biologic significance of the simultaneous expression of mdr-1 and GST-pi in recurrent lymphomas are well worth further exploration.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1993

Pedicle fixation: an adjuvant for the treatment of thoracolumbar metastases.

For a long time, radiotherapy was considered as the best treatment for spinal metastases. However, radiotherapy alone could not resolve the problem of pathological fracture which is an important complication of spinal metastases. In this paper, we introduce pedicle fixation system as an adjuvant to radiotherapy to treat eight patients with thoracolumbar metastases. The result was encouraging that all the patients achieved spinal stabilisation and all but one had immediate postoperative relief of back pain. The operation time was short and none of the patients required a blood transfusion. Tissue diagnosis was possible through this approach.

Adult↗
PubMed1993

Changing seroepidemiology of hepatitis A virus infection between two regions in Taiwan differing in socioeconomic status.

In Taiwan, hepatitis A virus (HAV) infection is hyperendemic, and prior to the late 1970s more than 85% of the population was infected by 15 years of age. In this study, the prevalence of HAV infection in two regions of Taiwan with differing standards of living is evaluated. Serum antibody to HAV (anti-HAV) was determined by enzyme immunoassay. A total of 4,218 subjects under the age of 16 years were enrolled. The first group of 1,581 subjects were residents of the prosperous western plain region where the socioeconomic status and living environment have improved greatly in the past 20 years; the second group of 2,637 subjects were aborigines inhabiting the eastern and central mountain regions where improvement in the standard of living lags far behind the western region. All serum samples were collected in 1991 except for 1,100 samples collected in 1989 from elementary and junior middle school students in Tainan city. The prevalence of HAV infection was 11.9% for the western region and 81.0% for the eastern and central regions. In the eastern and central regions, 80% of the subjects had been infected with HAV before the age of six years, in contrast to 0% in the western region. By the age of 13 years, only 6% of the subjects were infected in the western region; however 97% had been infected in the eastern and central regions. Among children under the age of 10 years, only 10.6% (10/94) of the IgM-anti-HAV positive cases had clinical symptoms. These findings indicate that HAV infection has a close relationship with socioeconomic status and environmental sanitation.

Adolescent↗
PubMed1992

Glutathione S-transferase pi in an arsenic-resistant Chinese hamster ovary cell line.

A glutathione S-transferase (GST) was purified from an arsenic-resistant Chinese hamster ovary cell line, SA7. The SA7 GST was shown to catalyse the conjugation of glutathione and ethacrynic acid, a specific substrate for Pi class GST. Its N-terminal amino-acid sequence has 80% identical residues to that of rat GST P and human GST pi. Thus, the GST purified from SA7 cells belongs to the Pi family. Treatment with Cibacron Blue or ethacrynic acid, which are GST inhibitors, significantly decreased the resistance of SA7 cells to sodium arsenite. On the other hand, pretreatment of SA7N cells, a partial revertant of SA7 cells, with sublethal doses of sodium arsenite, cadmium acetate or zinc sulphate resulted in re-elevation of GST activities and the cells regained the arsenic resistance. The regained arsenic resistance was well correlated with the levels of GST pi which were induced dose-dependently by zinc sulphate. Heat-shock treatment (45 degrees C for 10 min) did not increase GST pi expression or arsenic resistance of SA7N cells. The results indicate that GST pi is possibly involved in the mechanism of arsenic detoxification.

Amino Acid Sequence↗
PubMed1992

Displacement of BrdUrd-induced YY1 by serum response factor activates skeletal alpha-actin transcription in embryonic myoblasts.

Muscle-restricted transcription of the skeletal alpha-actin gene is controlled in part by a positive regulator, serum response factor (SRF), and a negative regulator, F-ACT1, which bind competitively to the most proximal serum response element (SRE1). We show here that F-ACT1 is identical to a transcription factor recently cloned and described as YY1, NF-E1, delta, or UCRBP. We found that although the DNA-binding activity of SRF accumulates during myogenesis, that of YY1 diminishes simultaneously. Myoblasts rendered incapable of differentiation by BrdUrd treatment exhibited the highest level of YY1 and the lowest level of SRF activities. Transfected SRF could directly transactivate the skeletal alpha-actin promoter by overcoming the inhibitory effect of BrdUrd-induced YY1. The transactivation depends on intact SRE DNA elements and requires the DNA-binding/dimerization domain of SRF as well as its C-terminal half rich in serines and threonines. Since the functions of YY1 and SRF appear to be developmentally regulated, the convergence of their binding sites upon the SRE constitutes an integrated mechanism whereby temporal and spatial muscle gene expression may be accomplished.

Actins↗
PubMed1992

A novel CoA-independent transacetylase produces the ethanolamine plasmalogen and acyl analogs of platelet-activating factor (PAF) with PAF as the acetate donor in HL-60 cells.

In this study, we demonstrate the presence of a unique membrane-associated transacetylase that transfers the acetate group from platelet-activating factor (PAF) to lysoplasmalogen (in the presence of EDTA and sodium acetate) with the formation of 1-alk-1-enyl-2-acetyl-sn-glycero-3-phosphoethanolamine (alk-1-enylacetyl-GPE). The identity of alk-1-enylacetyl-GPE was confirmed by acid hydrolysis, phospholipases A2 or C treatment and derivatization by fluorodinitrobenzene. The transacetylase has no requirement for Ca2+, Mg2+, or CoA and a broad pH optimum (7.0-8.0) with Km values of 12.0 microM for PAF and 106.4 microM for lysoplasmalogens. The enzyme activity from the isolated membrane fraction is not changed when whole cells are supplemented with 20:4, induced to differentiate into granulocytes, or treated with ionophore A23187. Radyllyso-sn-glycero-3-phosphocholine (GPC), radyllyso-GPE, acyllyso-sn-glycero-3-phosphoserine (GPS), acyllyso-sn-glycero-3-phosphoinositol (GPI), alkyllyso-sn-glycero-3-phosphate (GP), acyllyso-GP, or cis-9-octadecen-1-ol can also serve as acetate acceptors, whereas alkylglycerol, acylglycerol, or cholesterol are inactive. Differences in substrate acceptor specificity, sensitivity toward phenylmethylsulfonyl fluoride, and response to temperature suggest that the CoA-independent transacetylase and the CoA-independent transacylase that transfers long-chain acyl moieties are two separate enzymes. With intact differentiated HL-60 cells, [3H]acetate from [3H]PAF can be incorporated into alk-1-enylacetyl-GPE in the presence of ionophore A23187, but not in its absence. Moreover, phospholipase A2 inhibitors (p-bromophenacyl bromide and mepacrine) block the transacetylation process in whole cell system. These results indicate the production of alk-1-enyllyso-GPE is a rate-limiting factor for the subsequent transacetylation step during cell activation. We conclude that the transacetylase may participate in the biosynthesis of ethanolamine plasmalogen and acyl analogs of PAF, in vivo, fine-tuning of PAF biological responses, and cross-talk between de novo and remodeling pathways of PAF biosynthesis.

Acetates↗
PubMed1992

Posttreatment with sodium arsenite alters the mutational spectrum induced by ultraviolet light irradiation in Chinese hamster ovary cells.

Arsenic, a potent carcinogen, fails to induce gene mutations in mammalian cells. However, posttreatment of ultraviolet light (UV) irradiated cells with sodium arsenite synergistically enhances the mutation frequency on the hypoxanthine (guanine) phosphoribosyltransferase locus. To investigate the molecular mechanism of the comutagenic effects of sodium arsenite, we characterized the alterations of nucleotide sequences in 30 UV-induced and 39 sodium arsenite enhanced hprt mutants from Chinese hamster ovary K1 cells by direct sequencing of mRNA-PCR amplified cDNA. The majority of sequence alterations derived from UV irradiation (80%) and from sodium arsenite posttreatment (70%) were single base substitutions. UV irradiation induced all types of base substitutions. Among them, 57% were transversions. The frequency of transversions increased to 70% in sodium arsenite enhanced mutants. While base substitutions observed in UV-induced mutants were evenly distributed along with the whole coding region, exons 3 and 8 were most frequently mutated in sodium arsenite enhanced mutants. Sodium arsenite posttreatment did not alter the strand bias for mutation induction, i.e., 73% and 78%, of the mutations were located on the non-transcribed strand in UV-induced and sodium arsenite enhanced mutants, respectively. In contrast to UV-induced mutations, bases at the 5' position of TT and the 3' position of CT sequences were the most frequent mutation sites observed in sodium arsenite enhanced mutants. We hypothesize that sodium arsenite may interfere with the process of mutation fixation of TT and CT dimers during DNA replication.

Animals↗