Biomedical subjects

Donghui Li

Publications and source records attributed to Donghui Li.

At least 37 records · Page 2Linked to original sources

PubMed2005

Determination of nucleic acids based on shifting the association equilibrium between tetracarboxy aluminum phthalocyanine and poly-lysine.

A new method based on near-infrared (near-IR) fluorescence recovery was presented for the determination of nucleic acids. This method employed a two-reagent system composed of anionic tetracarboxy aluminum phthalocyanine (AlC4Pc) and polycationic poly-lysine. The fluorescence of AlC4Pc, with the maximum excitation and emission wavelengths at 620 and 701 nm, respectively, was quenched by poly-lysine with a proper concentration, but recovered by adding nucleic acids. Under optimal conditions, the recovered fluorescence was in proportional to the concentration of nucleic acids. The linear ranges of the calibration curves were 5-200 ng mL(-1) for both calf thymus DNA (ctDNA) and fish sperm DNA (fsDNA) with the detection limit of 2.6 ng mL(-1) for ctDNA and 2.1 ng mL(-1) for fsDNA. The relative standard deviation (n = 6) was 1.9 and 1.3% for 50 ng mL(-1) ctDNA and fsDNA, respectively. The proposed method was applied to the determination of nucleic acids in synthetic samples with satisfactory results.

Animals↗

PubMed2005

5,10-Methylenetetrahydrofolate reductase polymorphisms and the risk of pancreatic cancer.

To test the hypothesis that 5,10-methylenetetrahydrofolate reductase (MTHFR) polymorphisms modify the risk of pancreatic cancer, we conducted a hospital-based, case-control study involving 347 patients with newly diagnosed pancreatic adenocarcinoma and 348 healthy controls, frequency matched by age, sex, and race. MTHFR polymorphisms were determined using the PCR-RFLP method. Association of these polymorphisms with the risk of pancreatic cancer was estimated by unconditional logistic regression analysis. We found that the C667T (but not the A1298C) polymorphism had a significant main effect on the risk of pancreatic cancer. The frequencies of the MTHFR 667CC, 667CT, and 667TT genotypes were 49.5%, 38.6%, and 11.9%, respectively, among cases compared with 48.5%, 45.0%, and 6.5%, respectively, among controls. Individuals with the 667TT genotype displayed a 2-fold increased risk for pancreatic cancer compared with those with the CC/CT genotypes [adjusted odds ratio (OR), 2.14; 95% confidence interval (95% CI), 1.14-4.01]. Multivariate analyses found that the effect of the 677TT genotype on the risk of pancreatic cancer was present among ever smokers (OR, 5.53; 95% CI, 2.0-15.3) and ever alcohol drinkers (OR, 3.16; 95% CI, 1.30-7.69) but not in never smokers (OR, 0.82; 95% CI, 0.33-2.06) and never drinkers (OR, 1.42; 95% CI, 0.56-3.62). Furthermore, a positive interaction between the MTHFR TT genotype and heavy smoking or heavy alcohol consumption was detected. The OR (95% CI) of pancreatic cancer was 6.83 (1.91-24.38) for heavy smokers among the TT carriers compared with never smokers with the CC/CT genotypes and 4.23 (0.88-20.3) for heavy drinkers with the TT genotype compared with nondrinkers with the CC/CT genotypes. These observations support a role for folate metabolism in pancreatic cancer, especially among smokers and heavy drinkers.

Adenocarcinoma↗

PubMed2005

Effect of dietary intake of phytoestrogens on estrogen receptor status in premenopausal women with breast cancer.

Although many dietary studies have focused on breast cancer risk, few have examined dietary influence on tumor characteristics such as estrogen receptor (ER) status. Because phytoestrogens may modulate hormone levels and ER expression, we analyzed ER status and phytoestrogen intake in a case-case study of 124 premenopausal breast cancer patients. We assessed intake with a food-frequency questionnaire and obtained ER status from medical records. Rather than focusing on risk, we evaluated whether low intakes were more strongly associated with ER-negative tumors than with ER-positive disease. In logistic regression adjusting for potential confounders, threefold greater risks of ER-negative tumors relative to ER-positive tumors were associated with low intake of the isoflavones genistein (odds ratio, OR=3.50; 95% confidence interval, CI=1.43-8.58) and daidzein (OR=3.10; 95% CI=1.31-7.30). Low intake of the flavonoid kaempferol (OR=0.36; 95% CI=0.16-0.83), the trace element boron (OR=0.33; 95% CI=0.13-0.83), and the phytosterol beta-sitosterol (OR=0.42; 95% CI=0.18-0.98) were associated with decreased risk of ER-negative tumors relative to ER-positive disease. Other phytoestrogens were not significantly associated with ER status. Thus, in premenopausal patients, some phytoestrogens may affect breast carcinogenesis by influencing ER status. Such findings suggest new directions for mechanistic research on dietary factors in breast carcinogenesis that may have relevance for prevention and clinical treatment.

Adult↗

PubMed2005

Serum amyloid A as a tumor marker in sera of nude mice with orthotopic human pancreatic cancer and in plasma of patients with pancreatic cancer.

We screened an orthotopic nude mouse model of human pancreatic cancer for candidate serum biomarkers and examined their presence in the plasma of pancreatic cancer patients. Nude mice were injected in the pancreas with L3.9pl human pancreatic cancer cells. One week later, the mice were randomized into 4 treatment groups: i) control, saline; ii) oral STI 571; iii) intraperitoneal gemcitabine; and iv) STI 571 and gemcitabine. After 1, 2, and 3 weeks of treatment, sera and tumors were collected from mice in each group as well as uninjected mice. All sera were analyzed by surface enhanced laser desorption ionization mass spectrometry using ProteinChip technology. Protein profiles were analyzed with the Biomarker Wizard software package. The concentration of candidate proteins was evaluated in mouse sera and plasma from 135 pancreatic cancer patients, 7 pancreatitis patients, and 113 healthy volunteers. The combination therapy inhibited tumor growth. A 11.7-kDa protein peak correlating with tumor weight was purified by gel filtration, separated by SDS-PAGE, and identified as mouse serum amyloid A (SAA) by amino acid sequencing and public database searches. The expression of SAA in mouse sera was confirmed by Western blotting and correlated with tumor weight. The level of SAA in plasma of pancreatic cancer patients correlated with clinical stage and was significantly higher than in normal volunteers (mean value: 180.1 microg/ml vs 27.9 microg/ml: P<0.01) or pancreatitis patients. For SAA used as a single tumor marker with a cut-off of 75 microg/ml, the sensitivity for pancreatic cancer was 96.5% and specificity was 31.9%. Our search for specific marker proteins to identify pancreatic cancer was unsuccessful. Although SAA is not specific for pancreatic cancer and not sensitive enough to detect stage I patients, it may be a candidate biomarker for detecting and monitoring the progressive growth of pancreatic cancer.

Animals↗

PubMed2004

Cytokines in pancreatic carcinoma: correlation with phenotypic characteristics and prognosis.

BACKGROUND: Cytokines have been implicated in diverse processes that are relevant to pancreatic carcinoma, including cachexia, asthenia, and tumor growth. The objective of this study was to examine the association between serum levels of proinflammatory and antiinflammatory or angiogenic cytokines and the outcomes of patients with pancreatic carcinoma. METHODS: Serum cytokine levels were measured by enzyme-linked immunosorbent assay from 51 patients with pancreatic carcinoma and from 48-62 healthy volunteers. Cytokine levels were compared with disease manifestations and overall survival. RESULTS: Circulating levels of vascular endothelial growth factor, tumor necrosis factor alpha, interleukin-1alpha (IL-1alpha), and IL-1beta were not elevated significantly in patients with pancreatic carcinoma, but levels of IL-6, IL-8, IL-10, and IL-1 receptor antagonist (IL-1RA) were elevated significantly (P <0.05). Cytokine levels were dichotomized based on an analysis of null Martingale residuals. Patients who had IL-6 levels > 5.2 pg/mL or IL-10 levels >9.8 pg/mL had significantly worse survival compared with patients who had lower IL-6 or IL-10 levels (P <0.05). IL-8 levels were not associated with survival differences. Patients who had IL-1RA levels <159 pg/mL had significantly worse survival compared with patients who had higher IL-1RA levels (P <0.05). Higher IL-6, IL-10, and IL-8 levels were associated with poor performance status and/or weight loss. In multivariate analysis, only T4 tumors and high IL-6 levels were selected as independent prognostic factors for poor survival. CONCLUSIONS: Circulating levels of several cytokines were high in patients with pancreatic carcinoma, and their association with weight loss and poor performance status suggested that they may be involved in these disease manifestations. Furthermore, serum cytokine levels, in particular IL-6, may be a useful prognostic marker.

Adult↗

PubMed2004

Protein expression profiles in pancreatic adenocarcinoma compared with normal pancreatic tissue and tissue affected by pancreatitis as detected by two-dimensional gel electrophoresis and mass spectrometry.

Pancreatic cancer is a rapidly fatal disease, and there is an urgent need for early detection markers and novel therapeutic targets. The current study has used a proteomic approach of two-dimensional (2D) gel electrophoresis and mass spectrometry (MS) to identify differentially expressed proteins in six cases of pancreatic adenocarcinoma, two normal adjacent tissues, seven cases of pancreatitis, and six normal pancreatic tissues. Protein extracts of individual sample and pooled samples of each type of tissues were separated on 2D gels using two different pH ranges. Differentially expressed protein spots were in-gel digested and identified by MS. Forty proteins were identified, of which five [i.e., alpha-amylase; copper zinc superoxide dismutase; protein disulfide isomerase, pancreatic; tropomyosin 2 (TM2); and galectin-1] had been associated previously with pancreatic disease in gene expression studies. The identified proteins include antioxidant enzymes, chaperones and/or chaperone-like proteins, calcium-binding proteins, proteases, signal transduction proteins, and extracellular matrix proteins. Among these proteins, annexin A4, cyclophilin A, cathepsin D, galectin-1, 14-3-3zeta, alpha-enolase, peroxiredoxin I, TM2, and S100A8 were specifically overexpressed in tumors compared with normal and pancreatitis tissues. Differential expression of some of the identified proteins was further confirmed by Western blot analyses and/or immunohistochemical analysis. These results show the value of a proteomic approach in identifying potential markers for early diagnosis and therapeutic manipulation. The newly identified proteins in pancreatic tumors may eventually serve as diagnostic markers or therapeutic targets.

Biomarkers, Tumor↗

PubMed2004

The PI 3-kinase/Akt signaling pathway is activated due to aberrant Pten expression and targets transcription factors NF-kappaB and c-Myc in pancreatic cancer cells.

The persistent activation of signaling cascades results in dramatic consequences that include loss of cellular growth control and neoplastic transformation. We show here that phosphoinositide 3-kinase (PI 3-kinase) and its mediator Akt were constitutively activated in pancreatic cancer and that this might be due to the aberrant expression of their natural antagonist MMAC/PTEN. Indeed, our results show that MMAC/PTEN expression was either lost or significantly reduced in five of eight cell lines and in twelve of seventeen tumor specimens examined. That the poor expression of MMAC/PTEN in pancreatic cancer cells could be due to promoter methylation was indicated by methylation-specific PCR analysis. Our studies also indicated that PI 3-kinase targeted two important transcription factors in pancreatic cancer cells. The ability of constitutively activated NF-kappaB to induce gene expression and the stabilization of c-MYC protein by decreased phosphorylation of Thr58 were both dependent on PI 3-kinase activity. When pancreatic cancer cells were treated with a peptide antagonist of NF-kappaB nuclear translocation, or stably transfected with a dominant-negative mutant of MYC, their proliferation was markedly inhibited. Taken together, these data indicate that the aberrant expression of MMAC/PTEN contributes to the activation of the PI 3-kinase/Akt pathway and its transcription factor mediators in pancreatic cancer.

Cell Line, Tumor↗

PubMed2004

Pancreatic cancer.

Pancreatic cancer remains a major unsolved health problem, with conventional cancer treatments having little impact on disease course. Almost all patients who have pancreatic cancer develop metastases and die. The main risk factors are smoking, age, and some genetic disorders, although the primary causes are poorly understood. Advances in molecular biology have, however, greatly improved understanding of the pathogenesis of pancreatic cancer. Many patients have mutations of the K-ras oncogene, and various tumour-suppressor genes are also inactivated. Growth factors also play an important part. However, disease prognosis is extremely poor. Around 15-20% of patients have resectable disease, but only around 20% of these survive to 5 years. For locally advanced, unresectable, and metastatic disease, treatment is palliative, although fluorouracil chemoradiation for locally advanced and gemcitabine chemotherapy for metastatic disease can provide palliative benefits. Despite pancreatic cancer's resistance to currently available treatments, new methods are being investigated. Preoperative chemoradiation is being advocated, with seemingly sound reasoning, and a wider role for gemcitabine is being explored. However, new therapeutic strategies based on the molecular biology of pancreatic cancer seem to hold the greatest promise.

Antineoplastic Agents↗

PubMed2004

Light-induced excitation energy redistribution in Spirulina platensis cells: "spillover" or "mobile PBSs"?

State transitions induced by light and redox were investigated by observing the 77 K fluorescence spectra for the intact cells of Spirulina platensis. To clarify if phycobilisomes (PBSs) take part in the state transition, the contributions of PBSs to light-induced state transition were studied in untreated cells and the cells treated by betaine which fixed PBSs firmly on the thylakoid membranes. It was observed that the betaine-treated cells did not show any light-induced state transition. This result definitely confirmed that the light-induced excitation energy regulation between the two photosystems is mainly dependent on a spatial movement of PBSs on the thylakoid membranes, which makes PBS cores partially decoupled from photosystem II (PSII) while PBS rods more strongly coupled with photosystem I (PSI) during the transition from state 1 to state 2. On the other hand, an energy exchange between the two photosystems was observed in both untreated and betaine-treated cells during redox-induced state transition. These observations suggested that two different mechanisms were involved in the light-induced state transition and the redox-induced one. The former involves only a physical movement of PBSs, while the latter involves not only the movement of PBS but also energy spillover from PSII to PSI. A model for light-induced state transition was proposed based on the current results as well as well known knowledge.

Betaine↗

PubMed2004

Diagnostic protein discovery using proteolytic peptide targeting and identification.

Plasma protein profiling with mass spectrometry is currently being evaluated as a diagnostic tool for cancer and other diseases. These experiments consist of three steps: plasma protein fractionation, analysis with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS), and comparisons of the MALDI profiles to develop diagnostic fingerprints using bioinformatic techniques. While preliminary results appear promising in small sample groups, the method is limited by the sensitivity of MALDI-MS for intact proteins, the limited mass range of MALDI-MS, and difficulties associated with isolating individual proteins for identification to validate the diagnostic fingerprint. Here we present an alternative and improved method directed toward diagnostic protein discovery, which incorporates proteolytic peptide profiling, bioinformatic targeting of ion signals, and MALDI tandem mass spectrometry (MS/MS) peptide sequencing, rather than fingerprinting. Pancreatic cancer patients, pancreatitis patients, and controls are used as the model system. Profiling peptides after enzymatic digestion improves sensitivity and extends the accessible protein molecular weight range when compared to intact protein profiling. The first step is to extract and fractionate the proteins from plasma. Each fraction is digested with trypsin and subsequently analyzed by MALDI-MS. Rather than using bioinformatic analysis as a pattern-matching technique, peptides are targeted based on the disease to control peak intensity ratios measured in the averages of all mass spectra in each group and t-tests of the intensity of each individual peak. The targeted peptide ion signals are subsequently identified using MALDI-MS/MS in quadrupole-TOF and tandem-TOF instruments. This study found not only the proteins targeted and identified by a previous protein profiling experiment, but also detected additional proteins. These initial results are consistent with the known biology of pancreatic cancer or pancreatitis, but are not specific to those diseases.

Adult↗

PubMed2004

Fluorescence quenching method for the determination of sodium dodecyl sulphate with near-infrared hydrophobic dye in the presence of Triton X-100.

A fluorophotometric method for the determination of anionic surfactant sodium dodecyl sulphate (SDS) was proposed. The method is based on the quenching effect of SDS on the fluorescence of near-infrared (NIR) hydrophobic dye, 2-[4'chloro-7'(3''hexadecyl-2''benzothiazolinylidene)-3',5'-(1''',3'''-propanediyl)-1',3',5'-heptatriene-1'-yl]-3-ethylbenzothiazolium iodide (dye I) in the presence of Triton X-100. The calibration graph is linear in the concentration range from 0 to 2 x 10(-6) mol L(-1) of SDS with a detection limit (LOD) of 8.3 x 10(-8) mol L(-1). The relative standard deviation for the determination of 7 x 10(-7) mol L(-1) SDS was 4.1%. Recoveries of 95.3-110.3% were found for the addition to 1.0 x 10(-6) mol L(-1) SDS in the analysis of environmental water samples. Preliminary research shows that the fluorescence quenching is due to the formation of dye aggregate facilitated by SDS.

Fluorescence↗

PubMed2004

High levels of oxidative DNA damage in lymphocyte DNA of premenopausal breast cancer patients from Egypt.

Egypt shows a parallel increase in premenopausal breast cancer and environmental pollution. The purpose of this study is to explore a possible relationship between oxidative DNA damage, urinary estrogen metabolites and breast cancer in Egyptian premenopausal women. We conducted a pilot study of Egyptian breast cancer involving 29 cases and 32 controls and analysed lymphocyte DNA levels of 7,8-dihydro-8-oxo-2'-deoxyguanine (8-oxo-dG), a measure of oxidative DNA damage using high performance liquid chromatography with electro-chemical detection (HPLC-ECD) method. We analysed levels of urinary estrogen metabolites, 2-hydroxyestrone (2-OHE) and 16alpha-hydroxyestrone (16alpha-OHE) by an enzyme immuno assay. We also collected residential, occupational, and reproductive histories of all study subjects. We detected, in all subjects, exceptionally high levels of 8-oxo-dG and thus oxidative DNA damage, the levels (mean 8-oxo-dG/10(5) dG+/-SD) were significantly (P<0.01) higher in breast cancer cases (139.4+/-78.4) than in controls (60.9+/-51.5). Urinary 2-OHE and 16alpha-OHE or their ratio was not significantly different between cases and controls. However, 8-oxo-dG levels were positively correlated (P<0.05) with 2-OHE and 16alpha-OHE from cases while controls showed a negative correlation (P<0.05). Urban residence (Odds Ratio [OR] 3.1; Confidence interval [CI], 1.1-9.3), infertility (OR [9.8]; CI [1.1-89.7]), age (OR [2.6]; CI [1.4-4.6]) and 8-oxo-dG (OR 5.8; CI 1.9-17.5) levels were found to be significant predictors of breast cancer. Our finding of exceptionally high levels of 8-oxo-dG, a common result of oxidative DNA damage, warrant future studies on a larger population of premenopausal women in Egypt with consideration of other susceptibility markers and dietary characteristics.

Adult↗

PubMed2004

Comparison of different classification algorithms for underwater target discrimination.

Classification of underwater targets from the acoustic backscattered signals is considered here. Several different classification algorithms are tested and benchmarked not only for their performance but also to gain insight to the properties of the feature space. Results on a wideband 80-kHz acoustic backscattered data set collected for six different objects are presented in terms of the receiver operating characteristic (ROC) and robustness of the classifiers wrt reverberation.

Acoustic Stimulation↗

PubMed2003

Molecular cloning and functional analysis of a novel type of Bowman-Birk inhibitor gene family in rice.

Bowman-Birk inhibitor (BBI) genes encode serine protease inhibitors that have repetitive cysteine-rich domains with reactive sites for the trypsin or chymotrypsin family. We have identified seven BBI genes from japonica rice (Oryza sativa subsp. japonica var Teqing). All of the genes identified were found in a single cluster on the southern end of the long arm of rice chromosome 1. Four of the seven BBI genes have two repetitive cysteine-rich domains, whereas one has a truncated domain with only one reactive site. We have also identified three novel BBI genes, each of which possesses three repetitive domains instead of two. In situ hybridization analyses indicated that the accumulation of rice BBI transcripts was differentially regulated in germinating embryos and also in the leaves, roots, and flower organs at later developmental stages. Different members of the rice BBI gene family displayed different expression patterns during rice seed germination, and wounding induced the expression of rice BBI transcripts. The three-domain BBIs had higher expression levels than the two-domain BBIs. It was also found that the mRNA of rice BBI genes was present in abundant amounts in scutellar epithelium and aleurone layer cells. RBBI3-1, one of the three-domain RBBI, exhibited in vitro trypsin-inhibiting activity but no chymotrypsin-inhibiting activity. Overexpression of RBBI2-3 in transgenic rice plants resulted in resistance to the fungal pathogen Pyricularia oryzae, indicating that proteinase inhibitors confer resistance against the fungal pathogen in vivo and that they might play a role in the defense system of the rice plant.

Amino Acid Sequence↗

PubMed2003

Probing connection of PBS with the photosystems in intact cells of Spirulina platensis by temperature-induced fluorescence fluctuation.

Temperature-dependent fluorescence for intact cells of cyanobacterium Spirulina platensis was detected to search for the connection of the phycobilisome (PBS) with Photosystem I (PSI) and Photosystem II (PSII). Some interesting results were obtained from the deconvoluted fluorescence components of C-phycocyanin (C-PC), allophycocyanin (APC), PSI and PSII as well as the fluorescence spectra of the intact cells at room temperature (RT=25 degrees C) and 0 degrees C. It was observed that, compared to those at RT, both of the fluorescence components for PSI and APC increased, whereas those for PSII and C-PC decreased at 0 degrees C with excitation at 580 nm, that is, the fluorescence for C-PC is not synchronous with that for APC, and the fluorescence fluctuation for PSI is not synchronous with that for PSII. On the other hand, the decrease in C-PC fluorescence is synchronous with the increase in PSI fluorescence, and the increase in APC fluorescence is synchronous with the decrease in PSII fluorescence. Therefore, it can be readily deduced that PBS should be coupled not only with PSII through the terminal acceptors in the APC core but also with PSI through C-PC in PBS rods at physiological condition, while at 0 degrees C, a migration of a PBS makes the APC partially detached from PSII but the C-PC more efficiently coupled with PSI. The results provide good evidences for "mobile PBS" model and "parallel connection" model but not for the "spillover" model.

Bacterial Proteins↗

PubMed2003

Reduced constitutive 8-oxoguanine-DNA glycosylase expression and impaired induction following oxidative DNA damage in the tuberin deficient Eker rat.

The Tsc-2 tumor suppressor gene encodes the protein tuberin, a multi-functional protein with sequence homology to the GTPase activating protein (GAP) for Rap1. Mutations in the Tsc-2 gene are associated with the development of renal tumors. The Eker rat (Tsc-2(EK/+)) bears a mutation in one allele of the Tsc-2 gene, which predisposes these animals to renal cancer. Treatment of wild-type (Tsc-2(+/+)) and mutant (Tsc-2(EK/+)) Eker rats with 2,3,5-tris-(glutathion-S-yl)hydroquinone (TGHQ; 7.5 micro mol/kg. i.v.), a potent redox active and nephrotoxic metabolite of hydroquinone increases the incidence of renal tumors only in animals carrying the mutant Tsc-2(EK/+) allele. We now show that the constitutive expression of 8-oxoguanine-DNA glycosylase (OGG1) in Tsc-2(EK/+) rats is three-fold lower than in wild-type Tsc-2(+/+) rats. Moreover, treatment of wild-type and mutant Eker rats with TGHQ greatly increases 8-oxo-deoxyguanosine (8-oxo-dG) levels within the outer stripe of the outer medulla. Tsc-2(EK/+) rats, with lower constitutive renal OGG1 expression, experience substantially higher levels of 8-oxo-dG than do wild type Tsc-2(+/+) rats. Interestingly, whereas OGG1 expression was rapidly (4 h) induced in Tsc-2(+/+) rats following exposure to TGHQ, it was significantly reduced in Tsc-2(EK/+) rats. The combination of the higher constitutive expression of OGG1 in Tsc-2(+/+) rats, and its rapid induction in response to TGHQ treatment, coupled to the initial decrease in OGG1 expression in Tsc-2(EK/+) rats, results in Tsc-2(EK/+) OGG1 protein levels just 5% of those seen in Tsc-2(+/+) rats 8 h after treatment. Coincidentally, 8-oxo-dG levels in Tsc-2(+/+) rats 8 h after treatment with TGHQ are just 5% of those that occur in Tsc-2(EK/+) rats. The results indicate that the Tsc-2 gene influences constitutive OGG1 expression and the ability of OGG1 to respond to an oxidative stress, consistent with the proposal that Tsc-2 is an acute-phase response gene. In keeping with this view, acute TGHQ-induced cytotoxicity was greater in Tsc-2(EK/+) rats than in Tsc-2(+/+) rats. The mechanism(s) coupling tuberin expression to the regulation of OGG1 are not known and are under investigation.

Animals↗

PubMed2003

Molecular evidence that the extracellular cutinase Pbc1 is required for pathogenicity of Pyrenopeziza brassicae on oilseed rape.

Recent evidence has suggested that cutinase is required for cuticular penetration and, therefore, is essential for pathogenicity of Pyrenopeziza brassicae, the causal organism of light leaf spot disease of oilseed rape and other brassicas. In order to acquire molecular evidence for the role of cutinase in pathogenesis, the single-copy P. brassicae cutinase gene Pbc1 was disrupted by a transformation-mediated approach. Southern hybridization analysis revealed that in one mutant, NH10-1224, the disruption was due to a tandem insertion of two copies of the disruption vector into the 5' coding region of Pbc1. In contrast to the wild type, no expression of Pbc1 was detected during in planta growth or in cutin-induced mycelium of NH10-1224 and no cutinase activity was detected in culture supernatants from NH10-1224 using p-nitrophenyl butyrate as substrate. Scanning electron microscopy of Brassica napus cotyledons infected with wild-type P. brassicae confirmed that entry into the host is by direct penetration of the cuticle. In contrast, the cutinase-deficient mutant NH10-1224 failed to penetrate the cuticular layer and was unable to develop disease symptoms. This evidence is consistent with the hypothesis that Pbc1 is required for P. brassicae to penetrate the plant cuticle. Demonstration that complementation of NH10-1224 with the Pbc1 wild-type gene restores both cutinase activity and pathogenicity will be required to definitively establish that cutinase is required for successful pathogenesis of brassicas by P. brassicae.

Brassica rapa↗

PubMed2003

Molecular epidemiology of pancreatic cancer.

Pancreatic cancer is the fourth leading cause of cancer-related death in the United States. Currently there is no early diagnostic test and no effective treatment options for this deadly disease. Prevention of pancreatic cancer is difficult because little is known about its etiology. The main modifiable risk factors for pancreatic cancer include cigarette smoking and dietary factors. Information from molecular epidemiological study of pancreatic cancer is very limited. DNA adducts derived from exposure to polycyclic aromatic hydrocarbon, aromatic amines, and heterocyclic amines have been detected in human pancreatic tissues. DNA damages derived from oxidative stress and lipid peroxidation are also present in the pancreas. No study has demonstrated a main effect of carcinogen-metabolizing genes and DNA repair genes on the risk of pancreatic cancer thus far. However, significant effects of these genes have been observed among individuals with known carcinogen exposure, such as smoking. A number of environmental and lifestyle factors, such as smoking, alcohol, coffee consumption, and exposure to organochlorine or hydrocarbon solvent, have been associated with the frequency and spectrum of K-ras mutation in pancreatic tumors. Dietary folate intake and serum levels of folate have been associated with the risk of pancreatic cancer among male smokers. These findings demonstrate the potential of the molecular epidemiology approach in understanding the etiology of pancreatic cancer. Further efforts should be made to understand the interactive relationship between genetic and environmental factors in the etiology of pancreatic cancer, which will in turn be important in identifying the high-risk population for the primary prevention of this deadly disease.

Carcinogens↗