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Biomedical subjects

L Cheng

Publications and source records attributed to L Cheng.

At least 253 records · Page 14Linked to original sources
PubMed1998

Reduced DNA repair capacity in head and neck cancer patients.

Head and neck cancers (HNCs) are malignancies that can be induced by tobacco use, although host-specific factors such as the DNA repair capacity (DRC) may modulate individual susceptibility to tobacco carcinogenesis. To test the hypothesis that genetically determined DRC modulates HNC susceptibility, we measured the DRC in the peripheral blood lymphocytes of 55 patients with newly diagnosed, previously untreated HNC and 61 healthy controls by the host-cell reactivation assay using a reporter gene damaged by benzo(a)pyrene diol epoxide, an ultimate tobacco-related carcinogen. The mean DRC was significantly lower in cases (8.6%) than it was in controls (12.4%; P < 0.001). The DRC was an independent risk factor for HNC (P < 0.01); those in the middle and lowest tertiles of DRC had increased odds ratios [2.17 (95% confidence interval, 0.74-6.39) and 4.27 (confidence interval, 1.45-12.5), respectively] for HNC. These findings suggest that individuals with reduced DRC may be at increased risk of developing HNC.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1998

Disposition and metabolism of 14C-rifapentine in healthy volunteers.

Rifapentine is a long-acting cyclopentyl-derivative of rifampin. This study was designed to investigate the mass balance and biotransformation of 14C-rifapentine in humans. Four healthy male volunteers received a single 600-mg oral dose of 14C-rifapentine in a hydroalcoholic solution. Whole blood, urine, and fecal samples were collected before and at frequent intervals after drug administration. Amount of radioactivity recovered in urine and feces was assessed for up to 18 days postdose. Metabolite characterization in urine and feces was conducted using high-performance liquid chromatography with radiometric detection and liquid chromatography/mass spectroscopy. The total recovery of radioactive dose was 86.8%, with the majority of the radioactive dose recovered in feces (70.2%). Urine was a minor pathway for excretion (16.6% of the dose recovered). More than 90% of the excreted radioactivity was profiled as 14C chromatographic peaks and 50% was structurally characterized. These characterized compounds found in feces and urine were rifapentine, 25-desacetyl-rifapentine, 3-formyl-rifapentine, and 3-formyl-25-desacetyl-rifapentine. The 25-desacetyl metabolite, formed by esterase enzymes found in blood, liver, and other tissues, was the most abundant compound in feces and urine, contributing 22% to the profiled radioactivity in feces and 54% in urine. The 3-formyl derivatives of rifapentine and 25-desacetyl-rifapentine, formed by nonenzymatic hydrolysis, were also prominent in feces and, to a lesser extent, in urine. In contrast to the feces and urine, rifapentine and 25-desacetyl-rifapentine accounted for essentially all of the plasma radioactivity (99% of the 14C area under the concentration-time curve), indicating that 25-desacetyl-rifapentine is the primary metabolite in plasma. It appears, therefore, that the nonenzymatic hydrolysis of rifapentine to 3-formyl byproducts occurs primarily in the gut and the acidic environment of the urine.

Administration, Oral↗
PubMed1998

Cytomegalovirus iritis.

We describe a case of focal cytomegalovirus iritis in a patient with acquired immunodeficiency syndrome (AIDS) who had CMV retinitis. The autopsy showed histologic evidence of focal iritis in the left eye. This iritis was characterized by infiltration of acute inflammatory cells mixed with cytomegalic cells, which was confirmed by CMV-specific immunohistochemical staining. The case suggested that cytomegalovirus could be a direct causative agent of infectious iritis in AIDS patients.

AIDS-Related Opportunistic Infections↗
PubMed1997

Relationship between the size and margin status of ductal carcinoma in situ of the breast and residual disease.

BACKGROUND: For women with ductal carcinoma in situ (DCIS) of the breast who have been treated with breastconserving surgery, the usefulness of size and surgical margin status (i.e., presence or absence of disease at the point of excision) as prognostic factors for predicting residual disease has not been well established. This study was conducted to determine more clearly the relationship between size and margin status of mammary DCIS to residual disease. METHODS: The pathology records of 232 consecutive patients with mammary DCIS who had been initially treated with lumpectomy at the University Hospitals of Cleveland were retrospectively reviewed. The size of the DCIS and the surgical margins of lumpectomy were analyzed. Residual disease was defined as the persistence of DCIS in the re-excision and/or mastectomy specimens. RESULTS: Residual disease was found in 15 of 101 patients with DCIS of less than 1.0 cm in longest dimension, in 27 of 96 patients with DCIS of 1.0-2.4 cm in size, and in 24 of 35 patients with DCIS of greater than or equal to 2.5 cm in size (P<.001). Residual disease was found in 30 of 77 patients with DCIS and positive margins, in 11 of 59 patients with DCIS and close margins (< or =1mm), and in 10 of 73 patients with DCIS and negative margins (>1 mm) (P =.001). In multivariate analysis, the occurrence of residual disease was associated with large tumor size (i.e., > or =2.5 cm) (odds ratio [OR] = 7.7; 95% confidence interval [CI] = 3.13-20.00; two-sided P = .0001) and with positive margin status (OR = 2.2; 95% CI = 1.02-4.55; two-sided P = .04). CONCLUSIONS: The size and margin status of DCIS each were found to be independent predictors of residual disease.

Adult↗
PubMed1997

The results of intraoperative consultations in 181 ductal carcinomas in situ of the breast.

BACKGROUND: The utility of frozen section (FS) examination in the intraoperative management of breast lesions is well established. The accuracy of FS in the diagnosis of borderline noninvasive or preinvasive breast lesions is uncertain. METHODS: The authors retrospectively reviewed the results of intraoperative consultations/frozen section examinations of 181 ductal carcinomas in situ (DCIS) of the breast. Various clinical and pathologic factors were analyzed and correlated with FS diagnosis. RESULTS: FS examination was performed on 153 cases (85%) and only macroscopic examination on 28 cases (15%). FS diagnoses were as follows: DCIS in 76 cases (50%), atypical ductal hyperplasia/suspicious for DCIS in 8 cases (5%), benign in 55 cases (36%), deferred in 13 cases (8%), and invasive carcinoma in 1 case. FS accuracy, false-negative rate, and false-positive rate were 55%, 36%, and 0.6%, respectively. Sampling error was the main reason for the low detection rate, and technical inadequacy was a major factor contributing to interpretive problems. In multivariate regression analysis, FS accuracy was significantly associated with the clinical presentation of a palpable mass (odds ratio [OR] = 4.16, 95% confidence interval [CI]: 2.04-8.45), the macroscopic finding of a mass (OR = 3.03, 95% CI: 1.45-6.67), and necrosis (OR = 3.13, 95% CI: 1.4-6.67). CONCLUSIONS: The authors concluded that the accuracy of FS diagnosis of DCIS was low, mainly due to sampling error. In general, FS examination should not be performed when no lesion/mass is identified by macroscopic examination.

Adolescent↗
PubMed1997

Reduced expression of mismatch repair genes measured by multiplex reverse transcription-polymerase chain reaction in human gliomas.

Microsatellite instability (MIN) is frequently observed in hereditary nonpolyposis colon cancer and in other sporadic cancers including gliomas. Abnormalities in at least one of five mismatch repair (MMR) genes are implicated in the development of cancers in hereditary nonpolyposis colon cancer and the associated MIN. Using a newly developed multiplex reverse transcription-PCR assay, we evaluated the expression of the five known human MMR genes (hMSH2, hMLH1, hPMS1, hPMS2, and GTBP) in human gliomas by measuring simultaneously the relative levels of the transcripts. The beta-actin gene was used as an internal control for RNA degradation and DNA contamination and as a reference for quantifying the levels of their transcripts. Of the 33 gliomas examined, 42% (14) had low expression of hMSH2 (at least 4-5-fold lower than normal mean), 21% (7) had low expression of hMLH1, and 18% (6) had low expression of hPMS1 compared with the expression in the lymphocytes from 13 normal individuals. Furthermore, six of the 33 (18%) tumor samples had decreased expression of more than one MMR gene. Two of these six patients with multiple gene abnormalities had second primary cancers, and an additional patient had multifocal gliomas. Further molecular analysis of available DNA samples indicated that one of five of those tumors with aberrant expression of MMR genes had MIN, as compared with none of five tumors with normal expression. These data suggest that reduced expression of MMR genes is frequent in human gliomas and that aberrant expression of more than one MMR gene may be associated with increased risk of second primary malignancies in glioma patients.

Adaptor Proteins, Signal Transducing↗
PubMed1997

The involvement of tissue-type plasminogen activator in parietal endoderm outgrowth.

When F9 stem cells are treated in suspension with retinoic acid, they differentiate into embryoid bodies (EBs) consisting of an inner core of undifferentiated stem cells surrounded by an outer layer of visceral endoderm (VE). When these EBs are plated onto a fibronectin (FN)-coated substrate, VE-derived parietal endoderm (PE) cells migrate onto the substrate. It has been suggested that increased levels of tPA associated with the emerging PE cells may help mediate PE outgrowth. We now show that goat anti-human tPA, an anticatalytic antibody that crossreacts with mouse tPA, and a panel of serine protease inhibitors partially inhibit PE outgrowth. Extracellular matrix (ECM) degradation analysis demonstrates that PE cell-mediated degradation of [3H]proline-labeled ECM is time- and cell concentration-dependent. A serine protease inhibitor reduced the extent of degradation, suggesting that tPA might play a role in PE outgrowth by cleaving the ECM. In support of this contention, we demonstrate that incubation of purified FN with conditioned medium plus plasminogen results in FN proteolysis. The degradation of FN is blocked by either serine protease inhibitors or goat anti-human tPA. Our data suggest that enhanced production of tPA during PE outgrowth may facilitate the migratory behavior of PE cells by mediating the degradation of ECM components such as FN.

Animals↗
PubMed1997

Mechanism of anti-beta-adrenoceptor antibody mediated myocardial damage in dilated cardiomyopathy.

Antibodies against beta(1)-adrenoceptor can be detected in serum of patients with dilated cardiomyopathy (DCM), which have beta-agonist-like activity, and induce a positive chronotropic effect on cardiac myocytes by its persistence at full strength. Effects of the antibodies against beta-adrenoceptor from sera of patients with DCM on myocardial cytotoxicity and cytoplasmic free Ca(2+)-concentration ([Ca2+]i) were observed in the cultured single layer SD rat ventricular cells by using the cytotoxicity assay and fluorescent Ca(2+)-indicator fura-2/AM. The positive sera of the anti-beta-adrenoceptor antibodies from patients with DCM markedly enhanced myocardial [Ca2+]i. Betaloc, a beta(1)-receptor blocker, might inhibit the increase of the antibody-mediated myocardial [Ca2+]i, and the sera from healthy donors had no effect on myocardial [Ca2+]i. Our results suggest that the anti-beta-adrenoceptor antibody might increase myocardial [Ca2+]i and result in myocardial damage. The antibodies might activate receptor-gating Ca(2+)-channel, thereby causing myocardial [Ca2+]i rise and calcium overload. Early use of betaloc is recommended in the treatment of dilated cardiomyopathy.

Adult↗
PubMed1997

A GFP reporter system to assess gene transfer and expression in human hematopoietic progenitor cells.

Hematopoietic stem cells are widely recognized as attractive targets for gene therapy but current protocols to transduce these cells using recombinant retroviral vectors are inefficient. To evaluate optimization of retroviral transduction of hematopoietic stem cells and stability of gene expression in their progeny, the green fluorescent protein (GFP) was explored as a reporter. We first improved sensitivity of detection > 100-fold over that achieved previously by using a novel retroviral vector (termed MGIN) expressing a high level of an enhanced GFP gene. Primitive human hematopoietic cells bearing the CD34 surface antigen and lacking lineage differentiation markers (CD34+ Lin-) were transduced with the MGIN vector using a clinically applicable supernatant procedure. Under the conditions employed, > 75% of the target cells retained the CD34+ Lin- primitive phenotype after 4-5 days in culture, of those > or = 25% expressed a high level of GFP detectable by both flow cytometric analysis and fluorescence microscopy. When transduced cells were cultured in clonogenic progenitor assays, GFP fluorescence was readily detected in situ, indicating that GFP expression was stable and not detrimental to the differentiative potential of the transduced CD34+ Lin- cells. We conclude that GFP is effective as a vital marker to quantity retrovirus-mediated gene transfer into human hematopoietic and perhaps other types of stem/progenitor cells, and monitor gene expression during their subsequent cell lineage determinations.

Antigens, CD34↗
PubMed1997

Follicular basal cell hyperplasia overlying dermatofibroma.

Follicular basal cell hyperplasia (FBCH) overlying dermatofibroma represents aborted or impeded pilar differentiation. Historically, this hyperplasia has been misinterpreted as basal cell carcinoma. In a large series of dermatofibroma (258 cases), those that contained primitive or malformed follicular structures over the lesion (59 cases) were compared with those without such elements (199 cases). Statistical analysis of various clinicopathologic features showed that FBCH was significantly associated with younger age, trunk location, hypercellular dermatofibroma, loss of a Grenz zone, clear cell hyperplasia, and seborrheic keratosis-like change. There was an inverse correlation between epidermal atrophy, lichen simplex chronicus-like change, and lower extremity location with FBCH. Histologic features favoring a diagnosis of FBCH over basal cell carcinoma are the focal nature and superficial location of the lesion, lack of cytologic atypia and mitoses, recognizable components of hair follicle differentiation, focal condensation of mesenchymal cells around basal cell proliferation, and the association of epidermal hyperplasia. Our findings suggest that FBCH, clear cell hyperplasia, and seborrheic keratosis-like change all represent an expression of follicular differentiation overlying dermatofibroma.

Adult↗
PubMed1997

Demonstration of cytoplasmic tyrosinase mRNA in tissue-cultured cells by reverse transcription (RT) in situ polymerase chain reaction (PCR) and RT PCR in situ hybridization.

To evaluate the specificity and applicability to the study of human tumor cells of the reverse transcription (RT) in situ PCR and RT polymerase chain reaction (PCR) in situ hybridization techniques, we examined five melanoma cell lines and five nonmelanoma lines for tyrosinase mRNA using primers specific for tyrosinase. Each procedural step was optimized and minutely controlled, and results from the in situ techniques and solution-phase RT-PCR were compared. All melanoma lines showed a specific pattern of perinuclear cytoplasmic reaction not seen in nonmelanoma lines. There was exact agreement between the results from the RT in situ PCR and RT-PCR in situ hybridization techniques and those from solution-phase RT-PCR. Ribonuclease digestion abolished cytoplasmic staining, as did omission of the reverse transcriptase step. Nuclear staining was seen in melanoma and nonmelanoma lines, apparently as a result of DNA synthesis from repair-replication and mispriming or nonspecific amplification. Neither high concentrations of deoxyribonuclease nor long incubation periods abolished this effect completely. Demonstration of cytoplasmic mRNA by RT in situ PCR and RT-PCR in situ hybridization specifically identifies cells of melanocytic lineage.

Colonic Neoplasms↗
PubMed1997

Direct correlation between DNA repair capacity and metastatic potential of K-1735 murine melanoma cells.

The purpose of this study was to determine whether the ability of K-1735 murine melanoma cells to repair DNA damage correlates with their metastatic potential. Three nonmetastatic clones, four metastatic clones, and three somatic-cell hybrids between metastatic and nonmetastatic clones were exposed to incident ultraviolet (UV) light (254 nm). Cell survival was determined by the microculture tetrazolium assay, which measures cell metabolic activity. DNA repair capacity was determined with a host-cell reactivation assay, which measures the activities of chloramphenicol acetyltransferase encoded by the reporter gene in both UV-damaged and undamaged plasmid (control) pCMV cat 40 h after transfection. No discernible differences in transfection efficiencies were found between K-1735 clones with low and high metastatic potential or between cells transfected with UV-damaged and control plasmids. DNA repair capacity directly correlated with cell survival (p < 0.05) and with metastatic potential in the K-1735 clones and somatic cell hybrids (p < 0.05). These data suggest that the intrinsic resistance of melanoma metastases to systemic chemotherapy may be due, in part, to the cells' enhanced DNA repair capacity.

Animals↗
PubMed1997

Nucleoside Oxidase, a Hydrogen Peroxide-Forming Oxidase, from Flavobacterium meningosepticum.

A novel enzyme which catalyzes the oxidation of nucleosides to nucleoside-5(prm1)-carboxylic acids, forming hydrogen peroxide, was purified to homogeneity from Flavobacterium meningosepticum T-2799. The enzyme has a molecular weight of about 500,000, and four nonidentical subunits (molecular weights of 81,000, 69,000, 33,000, and 16,000) were detected on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. On the basis of visible absorption spectra of the purified enzyme, the enzyme is concluded to be a hemoprotein. It also contains covalently bound flavin adenine dinucleotide. The various nucleosides, such as adenosine (K(infm) = 48 (mu)M), inosine (K(infm) = 66 (mu)M), guanosine (K(infm) = 21 (mu)M), thymidine (K(infm) = 50 (mu)M), uridine (K(infm) = 80 (mu)M), and cytidine (K(infm) = 50 (mu)M), were oxidized by the enzyme, but nucleotides, bases, and ribose were not.

Journal Article↗
PubMed1997

Redistribution of intracellular Ca2+ stores after beta-adrenergic stimulation of rat tail artery SMC.

beta-Adrenergic agonists induce the relaxation of vascular smooth muscle by a mechanism that activates the extrusion of Na+ and Ca2+ from the cell. A primary source of contractile Ca2+ resides in the sarcoplasmic reticulum (SR), which releases Ca2+ in response to vasoactive agents through inositol trisphosphate-mediated channels. To determine if smooth muscle relaxation induced by beta 2-adrenergic agonists involves the redistribution of intracellular Ca2+, we studied the effects of isoproterenol (Iso) on freshly isolated, single rat tail artery smooth muscle cells loaded with fura 2, using digital ratiometric fluorescence imaging. Stimulation with 1 microM phenylephrine (PE) or norepinephrine produced phasic and tonic increases in cytoplasmic intracellular Ca2+ concentration ([Ca2+]i) associated associated with cell shortening. Exposure to caffeine and to Ca2(+)-free solutions eliminated the phasic and tonic components, respectively, from the Ca2+ signal. Intermittent superfusion with PE or caffeine was used to evaluate SR Ca2+ stores after stimulation by Iso. Exposure to 1 microM Iso induced a time-dependent decrease in PE-activated peak and tonic [Ca2+]i without any change in resting [Ca2+]i. Intermittent stimulation with 10 mM caffeine revealed a similar decline in peak [Ca2+]i, indicating Iso-dependent depletion of SR Ca2+ stores. The Ca2+ that remained in the SR after prolonged exposure to Iso (30% of the pre-Iso level by 80 min at 22 degrees C) failed to elicit a contractile response. The cells, perfused with a Na(+)- and Ca2(+)-free medium to block Na+/ Ca2+ exchange, prevented depletion of the SR Ca2+ stores by Iso. We propose that Iso inhibits agonist-mediated Ca2+ influx through sarcolemmal Ca2+ channels and activates Ca2+ redistribution from storage sites in the SR to the extracellular compartment by a mechanism that involves Na+/Ca2+ exchange. These combined effects of Iso facilitate smooth muscle relaxation (and reduce vascular tonus) by reducing the increase in cytoplasmic Ca2+ evoked by vasoconstrictors.

Adrenergic beta-Agonists↗
PubMed1997

Expression of five selected human mismatch repair genes simultaneously detected in normal and cancer cell lines by a nonradioactive multiplex reverse transcription-polymerase chain reaction.

Abnormalities in at least 1 of 5 mismatch repair (MMR) genes (hMSH2, hMLH1, hPMS1, hPMS2 and GTBP/hMSH6) are found in hereditary nonpolyposis colon cancer and sporadic colon cancers. We used a single-reaction multiplex reverse transcription (RT)-polymerase chain reaction (PCR), with the beta-actin gene as an internal control, to simultaneously evaluate expression of these 5 known human MMR genes in normal and tumor cell lines with known or uncharacterized mutations in MMR genes. The relative quantitation of the transcripts is demonstrated by controlling the number of PCR cycles and titrating cDNA with a dose-curve. The 13 normal cell lines tested were derived from normal lymphocytes, skin, thymus, breast, lung, colon, liver and kidney. The 26 cancer cell lines were derived from melanoma and cancers of the brain, breast, lung, colon, pancreas and prostate. All 5 MMR genes were ubiquitously expressed in all normal cell lines tested, suggesting their housekeeping roles. Aberrant MMR gene expression was only observed in the colon cancer cell lines. Two previously uncharacterized colon cancer cell lines did not express hMLH1. These data suggest that this nonradioactive multiplex RT-PCR assay for MMR gene expression may be useful for fast screening for genetic alterations that may affect gene expression and so may aid molecular analysis of MMR-related colon cancer.

Adaptor Proteins, Signal Transducing↗
PubMed1997

Activation of mitogen-activated protein kinases (ERK/JNK) and AP-1 transcription factor in rat carotid arteries after balloon injury.

Smooth muscle cell proliferation is a key event in neointimal formation after balloon angioplasty. The molecular signals that mediate this process have yet to be identified. Mitogen-activated protein (MAP) kinases are thought to play a pivotal role in transmitting transmembrane signals required for cell proliferation in vitro. The present studies were designed to investigate whether the signal transduction pathways of MAP kinases were involved in the development of restenosis in the injured arteries. Rat carotid arteries were isolated at various time points after balloon injury, and activities of MAP kinases, including extracellular signal-regulated kinases (ERK), and stress activated protein kinases (SAPK)/c-Jun N-terminal protein kinases (JNK), were determined in protein extracts of the vasculature using protein kinase assay and Western blot analysis. After balloon angioplasty, ERK2 and JNK1 activities in the vessel wall increased rapidly, reached a high level in 5 minutes and maintained for 1 hour. A sustained increase in ERK2 kinase activity was observed over the next 7 days in the arterial wall and 14 days in neointima after injury. In contrast, opposite and uninjured arteries did not show significant changes in these kinase activities. Concomitantly, Western blot analysis confirmed that the ERK2 kinase in the injured vessels was indeed activated or phosphorylated, showing a slowly migrating species of a 42-kDa protein containing phosphorylated tyrosine. Kinase activation is followed by an increase in c-fos and c-jun gene expression and enhanced activator protein 1 (AP-1) DNA-binding activity. Thus, balloon injury rapidly activates the MAP kinases in rat carotid arteries. These kinase activations may be crucial in mediating smooth muscle cell proliferation in response to vascular angioplasty.

Angioplasty, Balloon↗
PubMed1997

Molecular cloning of TA16, a transcriptional repressor that may mediate glucocorticoid-induced growth arrest of leiomyosarcoma cells.

The DDT1 MF2 smooth muscle tumor cell line was derived from an estrogen/androgen-induced leiomyosarcoma that arose in the ductus deferens of a Syrian hamster. The growth of this cell line is arrested at the G0/G1 phase of the cell cycle after treatment with glucocorticoids. To identify the putative gene(s) that are potentially involved in this hormone-induced cell growth arrest, we have used a differential screening technique to clone those genes whose expression is induced or up-regulated by glucocorticoids. A number of glucocorticoid response genes were thereby isolated from the leiomyosarcoma cells. One of these clones, termed TA16, was found to be markedly up-regulated by glucocorticoids in DDT1 MF2 cells, but only marginally changed in GR1 cells, a glucocorticoid-resistant variant that was selected from the wild type DDT1 MF2 cell. Isolation and sequencing of its intact cDNA indicated that the TA16 encodes a protein 485 amino acids long, and its sequence is closely homologous to a novel transcriptional repressor that presumably represses the transcription activity of some zinc finger transcriptional factors through a direct interaction. Transfection assays demonstrated that introduction of an antisense TA16 cDNA expression vector, controlled by an MMTV promoter, into the DDT1 MF2 cell significantly relieved the glucocorticoid-induced cell growth arrest. This finding suggests that TA16 might participate in the mediation of glucocorticoid-induced cell cycle arrest in leiomyosarcoma cells.

Amino Acid Sequence↗