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Biomedical subjects

M H Chung

Publications and source records attributed to M H Chung.

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

Serum 8-hydroxy-guanine levels are increased in diabetic patients.

OBJECTIVE: The production of reactive oxygen species is increased in diabetic patients, especially in those will poor glycemic control. We have investigated oxidative damage in type 2 diabetic patients using serum 8-hydroxyguanine (8-OHG) as a biomarker. RESEARCH DESIGN AND METHODS: We studied 41 type 2 diabetic patients and compared them with 3 nondiabetic control subjects. Serum 8-OHG concentration was assayed using high-pressure liquid chromatography. RESULTS: The type 2 diabetic patients had significantly higher concentrations of 8-OHG in their serum than the control subjects (5.03 +/- 0.69 vs. 0.96 +/- 0.15 pmol/ml P < 0.01). There was no association between the levels of 8-OHG and HbA1c. We also could not and any correlation between serum 8-OHG levels and age, duration of diabetes, serum lipids, or creatinine or albumin exeretion rate. Creatinine clearance showed marginal correlation with serum 8-OHG levels (P = 0.06). Among the diabetic patients, those with proliferative retinopathy had significantly higher 8-OHG levels than those with nonproliferative retinopathy or without retinopathy. Likewise, the serum 8-OHG levels in patients who had advanced nephropathy (azotemia) were higher than in patients with normoalbuminuria, microalbuminuria, or overt proteinuria. CONCLUSIONS: Our findings show that measuring serum 8-OHG is a novel convenient method for evaluating oxidative DNA damage. Diabetic patients, especially those with advanced microvascular complications, had significantly higher serum 8-OHG levels; this suggests that such changes may contribute to the development of microvascular complications of diabetes.

Albuminuria↗
PubMed2001

Systemic irinotecan or regional floxuridine chemotherapy prolongs survival after hepatic cryosurgery in patients with metastatic colon cancer refractory to 5-fluorouracil.

Most colorectal cancers metastatic to the liver are resistant to chemotherapy and are not amenable to surgical resection. This study evaluated our 6-year experience (July 1992-July 1998) in treating patients with unresectable hepatic colorectal metastases refractory to systemic 5-fluorouracil (5-FU). One hundred fifty-three patients underwent cryosurgical ablation (CSA) of 5-FU-resistant hepatic metastases. The patients then received either hepatic arterial floxuridine (FUDR), systemic CPT-11, or no postoperative adjuvant chemotherapy. Number, size, and location of hepatic metastases, carcinoembryonic antigen (CEA) levels, and type of postoperative treatment were analyzed. One to 15 lesions were frozen (median number, 3; median size, 6 cm), for a total of 73 synchronous and 80 metachronous lesions. Overall median survival was 28.4 months from the date of diagnosis of liver metastases and 16.1 months from the time of CSA. After cryosurgery alone, median survival was 13 months, which was significantly shorter than the post-CSA survival of 23.6 months with adjuvant CPT-11 and 21.2 months with hepatic FUDR (P = 0.007). Predictors of survival included preoperative CEA, postoperative reduction in CEA, and adjuvant chemotherapy (P < 0.05). Neither size, number of lesions, nor tumor location impacted survival. At a median follow-up of 13 months, 67% of patients have recurred (35% hepatic, 16% extrahepatic, and 49% both). Twenty percent of the recurrences were in the lobe of the CSA site. The 25 patients who underwent a second CSA had a median survival of 28.4 months from CSA and 40 months from the date of diagnosis of liver metastases. These data indicate that CSA offers an effective alternative for unresectable patients resistant to 5-FU. Systemic CPT-11 or regional FUDR may further prolong survival after CSA.

Antimetabolites, Antineoplastic↗
PubMed2000

Identification of Escherichia coli 8-oxoguanine endonuclease.

7,8-Dihydro-8-oxoguanine (oh8Gua) endonuclease is a DNA repair enzyme in Escherichia coli to remove oh8Gua, a promutagenic DNA adduct. Due to the unique mode of enzyme action and substrate specificity, this DNA repair enzyme has been suggested to be identical to 2,6-diamino-4-hydroxyformamidopyrimidine (Fapy)-DNA glycosylase (Fpg). However, oh8Gua endonuclease had not been definitely identified because it had not been homogeneously purified. In this study, we attempted to purify and identify the enzyme. Through several purification procedures, we obtained two proteins (32 kD and 29 kD). The larger protein co-migrated with Fpg in 12% SDS-PAGE gel. Sequences of N-terminal amino acids of these two proteins were identical to that of Fpg; the smaller one is a degraded product of oh8Gua endonuclease during purification steps. These results indicate that oh8Gua endonuclease is identical to Fpg, implying that oh8Gua in oxidatively damaged DNA rather than Fapy is more physiologically relevant substrate for Fpg.

Chromatography, Affinity↗
PubMed2000

Leukemic cell line, KG-1 has a functional loss of hOGG1 enzyme due to a point mutation and 8-hydroxydeoxyguanosine can kill KG-1.

We tested the cytotoxic action of 8-hydroxyguanine (8ohG) by observing the viability of several leukemic cell lines (KG-1, U937, Jurkat and K 562) in the presence of 8-hydroxydeoxyguanosine (8ohdG), a nucleoside of 8ohG. It was found that 8ohdG showed cytotoxic action only to KG-1 and that only KG-1 showed a homozygous arginine 209 to glutamine mutation in the hOGG1 gene with an almost negligible hOGG1 enzyme activity. Possibly, the selective cytotoxicity in 8ohdG to KG-1 may be due to its low capacity to cope with an increase in the 8ohG level in DNA resulting from the incorporation of 8ohdG present in the culture media. The mutational impairment of hOGG1 in KG-1 is the first report in leukemic cell lines. Using KG-1 with impaired hOGG1, we demonstrated cytotoxicity of 8ohdG probably due to its incorporation into cellular DNA. This new property of KG-1 may allow it to serve as an useful tool for studies of OGG1, oxidative DNA damage and the cytotoxic action of 8ohG. Oncogene (2000) 19, 4476 - 4479.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2000

A sds22 homolog that is associated with the testis-specific serine/threonine protein phosphatase 1gamma2 in rat testis.

Two cDNAs sequences (1320 bp and 1180 bp) of the 55-kDa subunit associated with a testis-specific serine/threonine protein phosphatase 1gamma2 (PP1gamma2) were cloned. They were the same up to 1180 bp, suggesting that they may be generated by alternative splicing. Sequence studies showed that the 1320 bp-cDNA is a homolog of the human sds22alpha(1) (thus, named rat sds22alpha(1)). The 1180 bp-cDNA is a new splice-variant since its sequence at the 3' end has not been identified in human sds22 genes (named rat sds22alpha(3)). The 1320 bp-cDNA is ubiquitously expressed in various tissues including the immature testis. However, the expression of 1180 bp-cDNA was only observed in the testis after puberty. This expression pattern matches very well with that of PP1gamma2, suggesting that 1180 bp-cDNA may encode the 55-kDa subunit to associate with PP1gamma2 in rat testis and is involved in spermatogenesis by controlling PP1gamma2 activity.

Aging↗
PubMed2000

Reactive oxygen species-specific mechanisms of drug resistance in paraquat-resistant acute myelogenous leukemia sublines.

Reactive oxygen species (ROS)-specific mechanisms of drug resistance were explored in paraquat (PQ)-resistant acute myelogenous leukemia cell (OCI/AML-2) sublines. For this, PQ-resistant AML sublines, AML-2/PQ100 and AML-2/PQ400, were selected in the presence of PQ concentrations of 100 microg/ml and 400 microg/ml, respectively. They showed a moderate level of cross resistance to cisplatin and doxorubicin. They were also slightly more resistant than the parental cell (AML-2/WT) to etoposide, camptothecin and daunorubicin. The resistance of PQ-resistant AML-2 sublines to cisplatin seemed to be due to increased amounts of metallothionein, which was not only supported by reversal of resistance to cisplatin by propargylglycin (an inhibitor of metallothionein synthesis) but also confirmed by Western blot analysis and reverse transcription-PCR assay. In addition, both AML-PQ100 and /PQ400 sublines showed increased activities of Cu-, Zn-containing superoxide dismutase (Cu,Zn-SOD) and Mn-containing superoxide dismutase (Mn-SOD), whereas AML-2/PQ400, but not AML-2/PQ100, showed increased glutathione S-transferase activity as compared to that of AML-2/WT. However, there was no difference in other ROS-related cellular antioxidants between AML-2/WT and its PQ-resistant sublines. Taken together, these results strongly suggest that increases in levels of metallothionein, glutathione S-transferase, Cu,Zn-SOD and Mn-SOD play important roles in protective mechanisms against toxicity of PQ or ROS in AML cells.

Alkynes↗
PubMed2000

MR imaging of solitary pulmonary lesion: emphasis on tuberculomas and comparison with tumors.

The aim of this study was to determine whether solitary pulmonary tuberculoma and malignant tumor can be differentiated on the basis of magnetic resonance (MR) signal intensity. Twenty-eight patients with solitary pulmonary lesions were prospectively studied with MR imaging: T1-weighted, enhanced T1-weighted, proton density-weighted, and T2-weighted spin echo images were obtained. The confirmation methods used were computed tomography (CT)-guided biopsy in seven patients with lung cancer and four patients with tuberculosis; surgery in ten patients with lung cancer and five patients with tuberculosis; and laboratory data in two patients with tuberculosis. Morphologic features and MR signal intensity were examined in detail. As the test for detection of tuberculoma, signal difference on T2-weighted images was carefully analyzed. The signal intensity ratio of the nodule to thoracic muscle signal intensity was measured. The signal intensities obtained from the lung cancers and tuberculomas were variable on pre-and post-enhanced T1-weighted images and proton density-weighted images. Masses were hypointense in 2 of 17 patients with lung cancer and in 9 of 11 patients with tuberculoma on T2-weighted images (sensitivity 82%, specificity 89%, accuracy 87%). The mean signal intensity ratios of the tuberculomas to muscle were significantly lower than those of malignant tumors on T1-weighted, enhanced T1-weighted, proton density-weighted, and T2-weighted images (P < 0.0001). After gadolinium-DTPA enhancement, 2 malignant tumors and 7 tuberculomas showed a marginal rim enhancement pattern, whereas 15 malignant tumors and 2 tuberculomas revealed a diffuse enhancement. The results of MR imaging were consistent with those of CT in 84% of the patients. MR imaging is a helpful adjunctive method in terms of differentiating a tuberculoma from a malignant tumor.

Diagnosis, Differential↗
PubMed2000

Paragonimus westermani: a cytosolic glutathione S-transferase of a sigma-class in adult stage.

We purified cytosolic glutathione S-transferase (GST) of adult Paragonimus westermani monitoring its activity with 1-chloro-2,4-dinitrobenzene (CDNB). The enzyme was purified 18.4-fold to electrophoretic homogeneity with 21% recovery rate through a three-step procedure. The purified enzyme (Pw28GST) has a subunit molecular weight of 28 kDa with an isoelectric point at 4.6. Monoclonal antibody (anti-Pw28GST) against Pw28GST did not cross-react with GSTs from other helminths. cDNA library was constructed in lambdaZAP II bacteriophage and screened with anti-Pw28GST. The corresponding gene containing a single open reading frame of 804 bp encoded 211 amino acids. The predicted amino acid sequence exhibited a higher homology with catalytic domain near N-terminus of class sigma GSTs (58%) than with schistosome 28-kDa GSTs (45-41%) or with class sigma GSTs themselves (33-31%). The sequence contained both Tyr-6 and Tyr-10 that are highly conserved in mammalian and helminth GSTs. The apparent K(m) value of a recombinant enzyme was 0.78 mM. Both native and recombinant enzymes showed the highest activity against CDNB, relatively weak activity against ethacrynic acid and reactive carbonyls, and no activity against epoxy-3-(p-nitrophenoxy)-propane. The activities were inhibited by bromosulfophthalein, cibacron blue, and albendazole, but not by praziquantel. These findings indicate that adult P. westermani has a class sigma GST.

Amino Acid Sequence↗
PubMed2000

Increased 8-hydroxyguanine formation and endonuclease activity for its repair in ischemic-reperfused hearts of rats.

A type of oxidative DNA damage, 8-hydroxyguanine (8-OH-Gua) formation, and the activity for its subsequent repair, 8-OH-Gua endonuclease activity, were examined in an ischemia-reperfusion model of isolated rat hearts. The level of 8-OH-Gua in myocardial DNA was measured by a high performance liquid chromatography (HPLC) equipped with an electrochemical detector, and the 8-OH-Gua endonuclease activity was analysed by the endonuclease nicking assay using a synthetic double-stranded oligonucleotide containing an 8-OH-Gua residue as a substrate. The Langendorff-perfused rat hearts were subjected to 30 or 60 min of global ischemia, followed by reperfusion with an oxygenated or a nitrogenated Krebs-Henseleit solution. The 8-OH-Gua content in the DNA of the ischemic hearts reperfused with an oxygenated solution was three to four times higher than that of the control hearts. The levels of 8-OH-Gua did not increase either in the ischemic hearts reperfused with a nitrogenated solution or in the ischemic-reperfused hearts treated with SOD, mannitol or allopurinol. When the myocardial extract was incubated with the 8-OH-Gua-containing oligonucleotide substrate, a specific cleavage at the site of an 8-OH-Gua residue was detected. The endonuclease activity responsible for this cleavage increased two-fold in the ischemic-reperfused hearts, compared to the control. This study demonstrates that the formation of 8-OH-Gua in DNA as well as the level of its repair process, 8-OH-Gua endonuclease activity, increase in the ischemic-reperfused rat hearts in response to oxidative stress due to higher levels of oxygen free radicals.

Animals↗
PubMed2000

Floral spray transformation can efficiently generate Arabidopsis transgenic plants.

In this study, floral spray and floral dip were used to replace the vacuum step in the Agrobacterium-mediated transformation of a superoxide dismutase (SOD) gene into Arabidopsis. The transgene was constructed by using a CaMV 35S promoter to drive a rice cytosolic CuZnSOD coding sequence in Arabidopsis. The transgene construct was developed in binary vectors and mobilized into Agrobacterium. When Arabidopsis plants started to initiate flower buds, the primary inflorescence shoots were removed and then transformed by floral spray or floral dip. More than 300 transgenic plants were generated to assess the feasibility of floral spray used in the in planta transformation. The result indicates that the floral spray method of Agrobacterium can achieve rates of in planta transformation comparable to the vacuum-infiltration and floral dip methods. The floral spray method opens up the possibility of in planta transformation of plant species which are too large for dipping or vacuum infiltration.

Arabidopsis↗
PubMed2000

Effects of retinoic acid, triiodothyronine and hydrocortisone on mucin and lysozyme expression in cultured human middle ear epithelial cells.

Mucous hypersecretion is a major complication of otitis media and can prolong the disease course and increase morbidity. Mucin, a major component of mucus, is a macromolecular complex of glycoprotein and makes mucus viscous. Lysozyme is a secretory element of the middle ear mucosa. which has a non-specific and innate antibacterial function. We attempted to identify factors that regulate these secretory products and their morphological phenotype using cultured human middle ear epithelial cells. Cellular differentiation was induced by creating an air liquid interface on culture day 9 in serum-free conditioned media. Omission of retinoic acid (RA) caused decrease in the secretion of mucin and lysozyme, and in the cellular expression of MUC 2, MUC 5AC and MUC 5B mRNA. In contrast, removal of triiodothyronine (T3) caused an increase in the secretion of mucin and the level of MUC5AC mRNA. When hydrocortisone (HC) was removed from the media, the secretion of mucin was decreased with out an apparent change of message level. The expression of MUC 1 mRNA was not changed by the respective deficiency of RA. T3 or HC. The effect of T3 or HC on lysozyme was not significant. This study shows that RA, T3 and HC influence the morphological phenotype and the secretory function of mucin and lysozyme in cultured human middle ear epithelial cells. This culture system can serve as an in vitro model for study of the regulation of various cellular secretions in human middle ear epithelium.

Anti-Inflammatory Agents↗
PubMed2000

Cyclin D1 expression in high-grade endometrial carcinomas--association with histologic subtype.

Endometrial endometrioid adenocarcinoma (EC) and serous carcinoma (ESC) are associated with different epidemiologic risk factors, precursor lesions, morphology, and survival outcomes. They also possess distinct molecular profiles. We investigated the expression of cyclin D1, a member of the G1 cyclin family that regulates the G1/S transition in the cell cycle, and estrogen and progesterone receptors (ERs and PRs, respectively) in a group of ECs and ESCs matched for histological grade. We also sought to correlate the expression of cyclin D1 with ER and PR because cyclin D1 has been reported to stimulate transcription of ER- and PR-regulated genes (1,2). We hypothesize that cyclin D1 expression covaries with histologic subtype and is related to the expression of ER and PR. Twenty ESCs and 21 ECs were examined histologically and evaluated immunohistochemically for cyclin D1, ER, and PR using commercially available monoclonal antibodies in archival, formalin-fixed, and paraffin-embedded tissue. Three ESCs (15%) and 10 ECs (48%) expressed cyclin D1 (p = 0.02). Twelve ESCs (60%) and 16 ECs (76%) expressed ER, which is not significantly different. ER-positive ECs were significantly more likely to express cyclin D1 compared with ER-positive ESCs (p = 0.03), but a relationship between cyclin D1 and ER expression in EC was not found. We also did not find a significant relationship between cyclin D1 and PR expression. Therefore, cyclin D1 expression in poorly differentiated endometrial carcinomas is associated with endometrioid histology. This is consistent with pathobiologic divergence in poorly differentiated endometrial carcinomas.

Adenocarcinoma↗
PubMed2000

Multiple pulmonary nodules in AIDS: usefulness of CT in distinguishing among potential causes.

PURPOSE: To determine whether the computed tomographic (CT) appearances of multiple pulmonary nodules in patients with acquired immunodeficiency syndrome (AIDS) can help differentiate the potential infectious and neoplastic causes. MATERIALS AND METHODS: The thoracic CT scans obtained in 60 patients with AIDS and multiple pulmonary nodules were reviewed retrospectively by two thoracic radiologists who were blinded to clinical and pathologic data. The scans were evaluated for nodule size, distribution, and morphologic characteristics. CT findings were correlated with final diagnoses. RESULTS: Thirty-six (84%) of 43 patients with opportunistic infection had a predominance of nodules smaller than 1 cm in diameter, whereas 14 (82%) of 17 patients with a neoplasm had a predominance of nodules larger than 1 cm (P <.001). Of the 43 patients with opportunistic infection, 28 (65%) had a centrilobular distribution of nodules; only one (6%) of 17 patients with a neoplasm had this distribution (P <.001). Seven (88%) of eight patients with a peribronchovascular distribution had Kaposi sarcoma (P <.001). CONCLUSION: In patients with AIDS who have multiple pulmonary nodules at CT, nodule size and distribution are useful in the differentiation of potential causes. Nodules smaller than 1 cm, especially those with a centrilobular distribution, are typically infectious. Nodules larger than 1 cm are often neoplastic. A peribronchovascular distribution is suggestive of Kaposi sarcoma.

AIDS-Related Opportunistic Infections↗
PubMed2000

Inhibitory mechanism of aloe single component (alprogen) on mediator release in guinea pig lung mast cells activated with specific antigen-antibody reactions.

We previously reported that the glycoprotein extracted from aloe strongly inhibited the mediator releases caused by the activation of guinea pig lung mast cells. Therefore, this study aimed to purify a single component that has an antiallergic effect from crude aloe extract and then to assess the effects of aloe single component (alprogen) on the mechanism of mediator releases caused by the mast cell activation. We purified aloe extracts by using various columns. We also purified mast cells from guinea pig lung tissues by using enzyme digestion, rough and discontinuous density Percoll gradient. Mast cells were sensitized with IgG(1) (anti-ovalbumin) and challenged with ovalbumin. Histamine was assayed by using a fluorometric analyzer and leukotrienes by radioimmunoassay. [Ca(2+)](i) level was analyzed by using a confocal laser scanning microscope. Protein kinase activity was determined by the protein phosphorylated with [gamma-(32)P]ATP. The phospholipase D activity was assessed by the labeled phosphatidylalcohol. The amount of mass 1,2-diacylglycerol (DAG) was measured by the [(3)H]DAG produced when prelabeled with [(3)H]myristic acid. Phospholipase A(2) activity was determined by measuring the lyso-phosphatidylcholine released from the labeled phospholipids. Alprogen significantly decreased histamine and leukotriene releases and blocked completely Ca(2+) influx during mast cell activation. The protein kinase C and phospholipase D activities were decreased by alprogen in dose-dependent manner. Alprogen inhibited mass DAG formation and the phospholipase A(2) activity during mast cell activation. The data suggest that alprogen purified from aloe inhibits multiple signals as well as blocking Ca(2+) influx caused by mast cells activated with specific antigen-antibody reactions and that then the inhibition of histamine and leukotriene release follows.

Aloe↗
PubMed1999

Immunohistochemical detection of oxidative DNA damage induced by ischemia-reperfusion insults in gerbil hippocampus in vivo.

There is much evidence to suggest that ischemic injury occurs during the reperfusion phase of ischemia-reperfusion insults, and that the injury may be due to reactive-oxygen-species (ROS)-mediated oxidative events, including lipid peroxidation and DNA damage. However, oxidative DNA damage has until now not been examined in situ. In the present study, we report for the first time observation of cell type- and region-specific oxidative DNA damages in 5 min transient ischemic model by immunohistochemical methods, using monoclonal antibody against 8-hydroxy-2'-deoxyguanosine (8-OHdG), an oxidative DNA product. The cell types containing 8-OHdG immunoreactivity were neurons, glia and endothelial cells in the hippocampus. The 8-OHdG immunoreactivity was present in the nucleus but not the cytoplasm of these cells. The level of 8-OHdG in CA1 increased significantly (P<0.05) at the end of 30 min after ischemia, but there was no increase within CA2 and CA3 areas. The 8-OHdG levels in the hippocampus increased significantly (about fourfold) after 3 h of reperfusion and remained significantly (P<0.01) elevated for at least 12 h. At 4 days after ischemia, 8-OHdG levels in the CA2 and CA3 areas decreased to levels of the sham without neuronal loss, while disappearance of 8-OHdG immunoreactivity in the CA1 coincided with neuronal death in this area. These findings strongly suggest that ischemia-induced DNA damage evolves temporally and spatially, and that oxidative DNA damage may be involved in delayed neuronal death in the CA1 region.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1999

Role of the 78-kDa glucose-regulated protein as an activity modulator of protein phosphatase1gamma2.

We have previously found the 78-kDa glucose-regulated protein (Grp78) to be a subunit of protein phosphatase1(PP1)gamma2. To determine the role of Grp78 in PP1gamma2 holoenzyme, we compared the two forms of this enzyme, PP1gamma2 holoenzyme containing Grp78 and Grp78-dissociated PP1gamma2 in rat testes in terms of their kinetic constants and sensitivities to inhibitors of this enzyme. The enzymatic activity of the Grp78-dissociated enzyme was much lower at whole range of concentrations of a substrate (phosphorylase a) than that of the holoenzyme; the Km value was about ten-fold higher in Grp78-dissociated enzyme than in holoenzyme, while the Vmax was similar. IC50s of the Grp78-dissociated enzyme for three inhibitors (microcystin-LR, inhibitor-2, and okadaic acid) were more than ten-fold higher than those of the holoenzyme. These results indicate that the Grp78 subunit modulates the activity of PP1gamma2 through its actions to control the binding of substrates or inhibitors to PP1gamma2.

Animals↗
PubMed1999

Aloesin and arbutin inhibit tyrosinase activity in a synergistic manner via a different action mechanism.

In this study, we present evidence that cotreatment of aloesin and arbutin inhibits tyrosinase activity in a synergistic manner by acting through a different action mechanism. Aloesin or arbutin similarly inhibited enzyme activity of human- and mushroom-tyrosinases with an IC50 value of 0.1 or 0.04 mM, respectively. Lineweaver-Burk plots of the enzyme kinetics data showed that aloesin inhibited tyrosinase activity noncompetitively with a Ki value of 5.3 mM, whereas arbutin did it competitively (Maeda, 1996). We then examined whether cotreatment of these agents inhibits the tyrosinase activity in a synergistic manner. The results showed that 0.01 mM aloesin in the presence of 0.03 mM arbutin inhibited activity of mushroom by 80% of the control value and the reverse was also true. The inhibitory effects were calculated to be synergistic according to the Bürgi method. Taken together, we suggest that aloesin along with arbutin inhibits in synergy melanin production by combined mechanisms of noncompetitive and competitive inhibitions of tyrosinase activity.

Agaricales↗