Binding of pyrimidin-2-one ribonucleoside by cytidine deaminase as the transition-state analogue 3,4-dihydrouridine and the contribution of the 4-hydroxyl group to its binding affinity

Cytidine deaminase, purified to homogeneity from constitutive mutants of Escherichia coli, was found to bind the competitive inhibitors pyrimidin-2-one ribonucleoside (apparent Ki = 3.6 x 10(-7) M) and 5-fluoropyrimidin-2-one ribonucleoside (apparent Ki = 3.5 x 10(-8) M). Enzyme binding resulted in a change of the lambda max of pyrimidin-2-one ribonucleoside from 303 nm for the free species to 239 nm for the bound species. The value for the bound species was identical with that of an oxygen adduct formed by combination of hydroxide ion with 1,3-dimethyl-2-oxopyrimidinium (239 nm), but lower than that of a sulfur adduct formed by combination of the thiolate anion of N-acetylcysteamine with 1,3-dimethyl-2-oxopyrimidinium (259 nm). The results suggest that pyrimidin-2-one ribonucleoside is bound by cytidine deaminase as an oxygen adduct, probably the covalent hydrate 3,4-dihydrouridine, rather than intact or as an adduct involving a thiol group of the enzyme. In dilute solution at 25 degrees C, the equilibrium constant for formation of a single diastereomer of 3,4-dihydrouridine from pyrimidin-2-one ribonucleoside was estimated as approximately 4.7 x 10(-6), from equilibria of dissociation of water, protonation of 1-methylpyrimidin-2-one, and combination of the 1,3-dimethylpyrimidinium cation with the hydroxide ion.(ABSTRACT TRUNCATED AT 250 WORDS)

Asparagine synthetase is an independent predictor of surgical survival and a potential therapeutic target in hepatocellular carcinoma

Background:

Asparagine synthetase (ASNS) is associated with drug resistance in leukaemia, and the function of this enzyme in the context of hepatocellular carcinoma (HCC) is not clear. In this study, the relationship between ASNS expression and clinical outcomes after surgical resection was investigated, and the therapeutic value of ASNS was also evaluated.

Methods:

The expression of ASNS was evaluated in HCC samples by real-time PCR and immunohistochemistry assays. The correlation between ASNS expression and clinicopathological features was investigated. Potential clinicopathological prognostic factors were examined by univariate and multivariate survival analysis. Asparagine synthetase was overexpressed and knocked down in HCC cell lines to assess the influence of the enzyme on cell proliferation, migration and tumourigenicity. L-asparaginase was used to treat HCC cells with high or low levels of ASNS in vitro and in vivo to examine the therapeutic efficacy.

Results:

The expression of ASNS was higher in HCC tumour tissues and was closely correlated with the serum AFP level, tumour size, microscopic vascular invasion, tumour encapsulation, TNM stage and BCLC stage. Patients with low ASNS expression levels had a poor prognosis with respect to overall survival (OS). The multivariate survival analysis indicated that ASNS is an independent prognostic factor for OS. Furthermore, functional studies demonstrated that ASNS significantly inhibits the proliferation, migration and tumourigenicity of HCC cells. The knockdown of ASNS markedly increased sensitivity to L-asparaginase, indicating that cells with different ASNS protein levels have different sensitivities to L-asparaginase.

Conclusion:

The expression of ASNS is an independent factor affecting the survival of HCC patients, and low ASNS expression in HCC was correlated with worse surgical outcomes. The ASNS may be a promising therapeutic target for the treatment of HCC.

Immunomodulatory and anti-inflammatory properties of artesunate in experimental colitis

BACKGROUND

Inflammatory bowel disease is a chronic and idiopathic gastrointestinal inflammation mediated by disregulated immune responses. Artemisinin (a chemical from a traditional Chinese herbal medicine Artemisia annua L.) and its derivatives have been proven to exhibit anti-inflammatory and immunomodulatory effects in the treatment of systemic lupus erythematosus and rheumatoid arthritis with low side-effects. This study is aimed to evaluate the potential therapeutic value of artesunate for inflammatory bowel disease.

METHODS

Murine colitis was induced by either oral administration of dextran sulfate sodium salt (DSS) or intrarectal delivery of 2,4,6- trinitrobenzene sulfonic acid (TNBS) or oxazolone. Mice were treated with artesunate (150mg/kg/day). Peritoneal macrophages were stimulated with lipopolysaccharide (LPS) in the presence or absence of artesunate. Changes in cytokines or proteins of interests were analyzed by enzyme-linked immunosorbent assay (ELISA) or SDS-PAGE/Western blot.

RESULTS

Artesunate significantly ameliorated DSS colitis and TNBS colitis (but not oxazolone colitis), including reduced weight loss and disease activity, as well as macroscopic and microscopic colonic injury. The expression of NF-κBp65 and p-IκB-α were reduced in artesunate treated TNBS colitis compared with untreated. The levels of IFN-γ, IL-17, and TNF-α were significantly decreased in artesunate treated TNBS colitis or DSS colitis. Furthermore, in vitro artesunate treatment significantly inhibited TNF-α production by LPS-activated macrophages.

CONCLUSIONS

Artesunate suppresses TNF-α expression in vitro and in vivo as well as T-helper (Th)1/Th17 responses in TNBS colitis model. Our data suggest a novel clinical application of artesunate as a potential therapy for Crohn's disease.

Homozygous DNAH1 frameshift mutation causes multiple morphological anomalies of the sperm flagella in Chinese

This study aimed to investigate the genetic pathogeny of multiple morphological anomalies of the flagella (MMAF), which is a genetically heterogeneous disorder leading to male infertility. Nine patients with severe asthenozoospermia caused by MMAF were recruited. Whole genome sequencing and Sanger sequencing were performed, and we found that four of the nine patients were affected by the same homozygous frameshift mutation c.11726_11727delCT (p.[Pro3909ArgfsTer33]) in exon 73 of dynein axonemal heavy chain 1 ( DNAH1 ) gene. The parents and the sibling of proband 1 were all identified as heterozygous carriers. This mutation was distinct from previously reported DNAH1 mutations associated with MMAF and only affected the East Asian group. Furthermore, the variant DNAH1 protein could not be detected in spermatozoa by Western blot or immunofluorescence staining although DNAH1 mRNA was expressed in the spermatozoa. Scanning electron microscopy and transmission electron microscopy analysis showed the anomalies in sperm flagella morphology and ultrastructure in patients carrying this genetic variant. In conclusion, our results add to knowledge of the genetic pathogeny of MMAF and further confirmed the effectiveness of genetic screening in the diagnosis of MMAF.

Lactational response to soybean meal, heated soybean meal, and extruded soybeans with ruminally protected methionine

Seventy-three high producing Holstein cows were arranged in a 3 X 2 factorial to evaluate three protein supplements (soybean meal, heat-treated soybean meal, and extruded blend of soybeans and soybean meal) without or with 15 g/head/d of ruminally protected DL-methionine during wk 4 through 16 postpartum. Total mixed diets contained (DM basis) 30% corn silage, 15% alfalfa hay, and 55% of the respective concentrate mix. Milk production was higher when cows were fed either heated soybean product instead of soybean meal. Methionine supplementation increased production when fed with soybean meal (32.2 and 33.8 kg/d) but not when fed with heat-treated soybean meal (34.5 and 33.0 kg/d) or extruded soybeans (36.2 and 34.4 kg/d). Milk fat percentages were lower with extruded soybeans (3.01, 2.93, and 2.66) and were similar without (2.83) or with (2.90) supplemental methionine. Milk protein percentages were highest when fed soybean meal, lowest with extruded soybeans (3.02, 2.92, and 2.87), and higher with supplemental methionine (2.91 and 2.96). Dry matter intake was higher when fed supplemental methionine (20.0 and 21.3 kg/d). Production of milk in early lactation high producing dairy cows was increased by supplementing a soybean meal diet with ruminally protected methionine or by replacing the soybean meal with heat-treated soybean meal, soybeans, or a mixture of the two.

Role of hippocampal p11 in the sustained antidepressant effect of ketamine in the chronic unpredictable mild stress model

Although ketamine shows a rapid and sustained antidepressant effect, the precise mechanisms underlying its effect are unknown. Recent studies indicate a key role of p11 (also known as S100A10) in depression-like behavior in rodents. The present study aimed to investigate the role of p11 in the antidepressant-like action of ketamine in chronic unpredictable mild stress (CUMS) rat model. The open-field test, forced swimming test and sucrose preference test were performed after administration of ketamine (10 mg kg(-1)) or a combination of ketamine and ANA-12 (a tropomyosin-related kinase B (TrkB) antagonist; 0.5 mg kg(-1)). The lentivirus vector for p11 was constructed to knock down the hippocampal expression of p11. In the CUMS rats, ketamine showed a rapid (0.5 h) and sustained (72 h) antidepressant effect, and its effect was significantly blocked by co-administration of ANA-12. Furthermore, ketamine significantly increased the reduced expression of brain-derived neurotrophic factor (BDNF) in the hippocampus of CUMS rats, whereas ketamine did not affect the expression of p11 in CUMS rats 0.5 h after administration. In addition, ketamine significantly increased the reduced ratio of p-TrkB/TrkB in the hippocampus by CUMS rats, and its effect was also blocked by ANA-12. Moreover, the reduced expression of BDNF and p11 in the hippocampus of CUMS rats was significantly recovered to control levels 72 h after ketamine administration. Interestingly, knockdown of hippocampal p11 caused increased immobility time and decreased sucrose preference, which were not improved by ketamine administration. These results suggest that p11 in the hippocampus may have a key role in the sustained antidepressant effect of ketamine in the CUMS model of depression.

Molecular cloning and characterization of DdCAD-1, a Ca2+-dependent cell-cell adhesion molecule, in Dictyostelium discoideum

Dictyostelium discoideum expresses EDTA-sensitive cell-cell adhesion sites soon after the initiation of development, and a Ca2+-binding protein of Mr 24,000 (designated DdCAD-1) has been implicated in this type of adhesiveness. We have previously purified DdCAD-1 to homogeneity and characterized its cell binding activity (Brar, S. K., and Siu, C.-H. (1993) J. Biol. Chem. 268, 24902-24909). In this report, we describe the cloning of DdCAD-1 cDNAs. DNA sequencing revealed a single open reading frame coding for a polypeptide containing 213 amino acids. The identity of the cDNA was confirmed by amino acid sequences of two cyanogen bromide peptides. The deduced amino acid sequence of DdCAD-1 exhibits a relatively high degree of sequence similarity with members of the cadherin family and protein S of Myxococcus xanthus. Unlike the other cadherins, the carboxyl-terminal region of DdCAD-1 contains a Ca2+-binding motif. Although analyses of the sequence suggest that the polypeptide lacks a signal peptide sequence and a transmembrane domain, immunofluorescence microscopy demonstrates the association of DdCAD-1 with the ecto-surface of the plasma membrane. To investigate the structure/function relationships of DdCAD-1, glutathione S-transferase fusion proteins containing different DdCAD-1 fragments were expressed and assayed for their 45Ca2+ and cell binding activities. These studies revealed that the cell binding activity is dependent on the amino-terminal segment and not the carboxyl-terminal Ca2+-binding domain and showed additional Ca2+-binding site(s) within the amino-terminal segment.

Synthesis of an anti-methicillin-resistant Staphylococcus aureus (MRSA) carbapenem via stannatrane-mediated Stille coupling

[formula: see text] A short synthesis of carbapenem 1 is described. They key step involves the cross-coupling of an enol triflate with an amino-substituted sp3 carbon. This cross-couping, which allows the introduction of the complete side chain in one step, utilizes a stannatrane as the heteroalkyl transfer reagent.

Forensic source differentiation of petrogenic, pyrogenic, and biogenic hydrocarbons in Canadian oil sands environmental samples

To facilitate monitoring efforts, a forensic chemical fingerprinting methodology has been applied to characterize and differentiate pyrogenic (combustion derived) and biogenic (organism derived) hydrocarbons from petrogenic (petroleum derived) hydrocarbons in environmental samples from the Canadian oil sands region. Between 2009 and 2012, hundreds of oil sands environmental samples including water (snowmelt water, river water, and tailings pond water) and sediments (from river beds and tailings ponds) have been analyzed. These samples were taken from sites where assessments of wild fish health, invertebrate communities, toxicology and detailed chemistry are being conducted as part of the Canada-Alberta Joint Oil Sands Monitoring Plan (JOSMP). This study describes the distribution patterns and potential sources of PAHs from these integrated JOSMP study sites, and findings will be linked to responses in laboratory bioassays and in wild organisms collected from these same sites. It was determined that hydrocarbons in Athabasca River sediments and waters were most likely from four sources: (1) petrogenic heavy oil sands bitumen; (2) biogenic compounds; (3) petrogenic hydrocarbons of other lighter fuel oils; and (4) pyrogenic PAHs. PAHs and biomarkers detected in snowmelt water samples collected near mining operations imply that these materials are derived from oil sands particulates (from open pit mines, stacks and coke piles).

Detection of phylogenetically diverse human immunodeficiency virus type 1 groups M and O from plasma by using highly sensitive and specific generic primers

The high degree of genetic diversity within human immunodeficiency virus type 1 (HIV-1), which includes two major groups, M (major) and O (outlier), and various env subtypes within group M (subtypes A to J), has made designing assays that will detect all known HIV-1 strains difficult. We have developed a generic primer set based on the conserved immunodominant region of transmembrane protein gp41 that can reliably amplify as few as 10 copies/PCR of viral DNA from near-full-length clones representing group M subtypes A to H (subtypes I and J were not available). The assay is highly sensitive in detecting plasma viral RNA from HIV-1 strains of diverse geographic origins representing different subtypes of HIV-1 group M as well as HIV-1 group O. Of the 253 group M plasma specimens (subtypes A, 68 specimens; B, 71; C, 19; D, 27; E, 23; F, 33; and G, 12), 250 (98.8%) were amplified by using the gp41 M/O primer set. More importantly, all 32 (100%) group O plasma samples were also amplified with these primers. In vitro spiking experiments further revealed that the assay could reliably detect as few as 25 copies/ml of viral RNA and gave positive signals in HIV-1-seropositive specimens with plasma copy numbers below the limits of detection by all commercially available viral load assays. In addition, analysis of five seroconversion panels indicated that the assay is highly sensitive for early detection of plasma viremia during the "window period." Thus, the highly sensitive assay will be useful for early detection of HIV-1 in clinical specimens from all known HIV-1 infections, regardless of their genotypes and geographic origins.

Alkaline biodegradable implants for osteoporotic bone defects--importance of microenvironment pH

Change of microenvironment pH by biodegradable implants may ameliorate unbalanced osteoporotic bone remodeling. The present work demonstrated that a weak alkaline condition stimulated osteoblasts differentiation while suppressed osteoclast generation. In vivo, implants with an alkaline microenvironment pH (monitored by a pH microelectrode) exhibited a promising healing effect for the repair of osteoporotic bone defects.

INTRODUCTION

Under osteoporotic conditions, the response of the bone microenvironment to an endosseous implant is significantly impaired, and this substantially increases the risk of fracture, non-union and aseptic implant loosening. Acid-base equilibrium is an important factor influencing bone cell behaviour. The present purpose was to study the effect of a series of alkaline biodegradable implant materials on regeneration of osteoporotic bone defect, monitoring the microenvironment pH (μe-pH) over time.

METHODS

The proliferation and differentiation potential of osteoporotic rat bone marrow stromal cells and RAW 264.7 cells were examined under various pH conditions. Ovariectomized rat bone defects were filled with specific biodegradable materials, and μe-pH was measured by pH microelectrode. New osteoid and tartrate-resistant acid phosphatase-positive osteoclast-like cells were examined by Goldner's trichrome and TRAP staining, respectively. The intermediate layer between implants and new bone were studied using energy-dispersive X-ray spectroscopy (EDX) linear scanning.

RESULTS

In vitro, weak alkaline conditions stimulated osteoporotic rat bone marrow stromal cells (oBMSC) differentiation, while inhibiting the formation of osteoclasts. In vivo, μe-pH differs from that of the homogeneous peripheral blood and exhibits variations over time particular to each material. Higher initial μe-pH was associated with more new bone formation, late response of TRAP-positive osteoclast-like cells and the development of an intermediate 'apatitic' layer in vivo. EDX suggested that residual material may influence μe-pH even 9 weeks post-surgery.

CONCLUSION

The pH microelectrode is suitable for in vivo μe-pH detection. Alkaline biodegradable materials generate an in vivo microenvironmental pH which is higher than the normal physiological value and show promising healing effects in the context of osteoporotic bone defects.

Mechanism of Cdc42-induced actin polymerization in neutrophil extracts

Cdc42, activated with GTPgammaS, induces actin polymerization in supernatants of lysed neutrophils. This polymerization, like that induced by agonists, requires elongation at filament barbed ends. To determine if creation of free barbed ends was sufficient to induce actin polymerization, free barbed ends in the form of spectrin-actin seeds or sheared F-actin filaments were added to cell supernatants. Neither induced polymerization. Furthermore, the presence of spectrin-actin seeds did not increase the rate of Cdc42-induced polymerization, suggesting that the presence of Cdc42 did not facilitate polymerization from spectrin-actin seeds such as might have been the case if Cdc42 inhibited capping or released G-actin from a sequestered pool. Electron microscopy revealed that Cdc42-induced filaments elongated rapidly, achieving a mean length greater than 1 micron in 15 s. The mean length of filaments formed from spectrin-actin seeds was <0.4 micron. Had spectrin-actin seeds elongated at comparable rates before they were capped, they would have induced longer filaments. There was little change in mean length of Cdc42-induced filaments between 15 s and 5 min, suggesting that the increase in F-actin over this time was due to an increase in filament number. These data suggest that Cdc42 induction of actin polymerization requires both creation of free barbed ends and facilitated elongation at these ends.

Cytochrome P450 CYP6DA2 regulated by cap 'n'collar isoform C (CncC) is associated with gossypol tolerance in Aphis gossypii Glover

Cotton plants accumulate phytotoxins, such as gossypol and related sesquiterpene aldehydes, to resist insect herbivores. The survival of insects exposed to toxic secondary metabolites depends on the detoxification metabolism mediated by limited groups of cytochrome P450. Gossypol has an antibiotic effect on Aphis gossypii, and as the concentrations of gossypol were increased in the present study, the mortality of cotton aphids increased from 4 to 28%. The fecundity of the cotton aphids exposed to gossypol was also significantly reduced compared with the control. The transcriptional levels of CYP6DA2 in cotton aphids were significantly induced when exposed to gossypol, and knockdown of the CYP6DA2 transcripts by RNA interference (RNAi) significantly increased the toxicity of gossypol to cotton aphids. To further understand the gossypol regulatory cascade, the 5'-flanking promoter sequences of CYP6DA2 were isolated with a genome walker, and the promoter was very active and was inducible by gossypol. Co-transfection of the cap 'n' collar isoform C (CncC) and CYP6DA2 promoters dramatically increased the expression of CYP6DA2, and suppression of the CncC transcripts by RNAi significantly decreased the expression levels of CYP6DA2, and significantly increased the toxicity of gossypol to cotton aphids. Thus, the transcriptional regulation of CYP6DA2 involved the transcriptional factor CncC.

The G to C polymorphism at -174 of the interleukin-6 gene is rare in a Southern Chinese population

Interleukin-6 is thought to be involved in the pathogenesis of coal workers' pneumoconiosis. Recently, a functional G to C polymorphism at position -174 of the promoter of the IL-6 gene has been described. We examined the -174 polymorphisms in 259 retired Chinese men from Guangxi province (all retired coal miners). Only one GC heterozygous and no CC homozygous variants were found. Our results suggest that the frequency of the C allele in this Chinese population is lower than in Caucasian and east Indian populations.

Hydroxyl-mediated ethanol selectivity of CO2 hydrogenation

Oxide-supported Rh nanoparticles have been widely used for CO2 hydrogenation, especially for ethanol synthesis. However, this reaction operates under high pressure, up to 8 MPa, and suffers from low CO2 conversion and alcohol selectivity. This paper describes the crucial role of hydroxyl groups bound on Rh-based catalysts supported on TiO2 nanorods (NRs). The RhFeLi/TiO2 NR catalyst shows superior reactivity (≈15% conversion) and ethanol selectivity (32%) for CO2 hydrogenation. The promoting effect can be attributed to the synergism of high Rh dispersion and high-density hydroxyl groups on TiO2 NRs. Hydroxyls are proven to stabilize formate species and protonate methanol, which is easily dissociated into *CH x , and then CO obtained from the reverse water-gas shift reaction (RWGS) is inserted into *CH x to form CH3CO*, followed by CH3CO* hydrogenation to ethanol.

Characterization of immortalized mesenchymal stem cells derived from foetal porcine pancreas

Islet replacement therapy is limited by shortage of donor islet cells. Usage of islet cells derived from porcine pancreatic stem cells (PSCs) is currently viewed as the most promising alternative for human islet transplantation. However, PSCs are rare and have a finite proliferative lifespan. In this study, we isolated and established an immortalized mesenchymal stem cell (MSC) line derived from foetal porcine pancreas, by transfecting human telomerase reverse transcriptase (hTERT) and called these immortalized pancreatic mesenchymal stem cells (iPMSCs). The iPMSCs have been cultured for more than 80 passages and have capacity to differentiate into neurons, cardiomyocytes, germ cells and islet-like cells, analysed by morphology, RT-PCR, western blotting, immunofluorescence, immunocytochemistry and transplantation assay. Islets derived from iPMSCs reversed hyperglycaemia in streptozotocin-induced diabetic mice and secreted insulin and C-peptide in vitro. These results demonstrated that iPMSCs might provide unlimited resources for islet replacement therapy and models for functional cell differentiation.

Breast tumor aromatase: functional role and transcriptional regulation

Aromatase has been shown to be expressed at a higher level in human breast cancer tissue than in normal breast tissue, by means of enzyme activity measurement, immunocytochemistry, and RT-PCR analysis. Cell culture including MCF-7 breast cancer cells, animal experiments using aromatase-transfected breast cancer cells, and transgenic mouse studies have demonstrated that estrogen production in situ plays a more important role than circulating estrogens in breast tumor promotion. In addition, tumor aromatase is believed to be able to stimulate breast cancer growth through both autocrine and paracrine pathways, as demonstrated by a three-dimensional cell culture study. RT-PCR and gene transcriptional studies have revealed that the aromatase promoter is switched from a glucocorticoid-stimulated promoter, I.4, in normal tissue to cAMP-stimulated promoters, I.3 and II, in cancerous tissue. Recently, we identified and characterized a cAMP-responsive element (CREaro) upstream from promoter I.3 by DNA deletion and mutational analyses. Our results from promoter functional analysis also demonstrated an interaction between the CREaro and the silencer element (S1) that was identified previously in our laboratory. In the presence of cAMP, the positive regulatory CREaro can overcome the action of the silencer on the function of promoter I.3. On the basis of results generated from our own and other laboratories, we propose that, in normal breast adipose stromal cells and fibroblasts, aromatase expression is driven by promoter I.4 (glucocorticoid dependent), and that the action of promoters I.3 and II is suppressed by the silencer negative regulatory element. However, in cancer cells and surrounding adipose stromal cells, the cAMP level increases, and aromatase promoters are switched to cAMP-dependent promoters - I.3 and II. Furthermore, we applied the yeast one-hybrid screening method to search for proteins interacting with the silencer element, S1. The major protein identified was ERRalpha-1; however, SF-1, which is present in the ovary, is not detected in breast cancer tissue. Using a reporter plasmid with the aromatase genomic fragment containing promoter I.3 and S1, in breast cancer SK-BR-3 cells, ERRalpha-1 was found to have a positive regulatory function. It is believed that the silencer element in the human aromatase gene may function differently in different tissues, as a result of distinct expression patterns of transcription factors.

Steady flow and wall compression in stenotic arteries: a three-dimensional thick-wall model with fluid-wall interactions

Severe stenosis may cause critical flow and wall mechanical conditions related to artery fatigue, artery compression, and plaque rupture, which leads directly to heart attack and stroke. The exact mechanism involved is not well understood. In this paper a nonlinear three-dimensional thick-wall model with fluid-wall interactions is introduced to simulate blood flow in carotid arteries with stenosis and to quantify physiological conditions under which wall compression or even collapse may occur. The mechanical properties of the tube wall were selected to match a thick-wall stenosis model made of PVA hydrogel. The experimentally measured nonlinear stress-strain relationship is implemented in the computational model using an incremental linear elasticity approach. The Navier-Stokes equations are used for the fluid model. An incremental boundary iteration method is used to handle the fluid-wall interactions. Our results indicate that severe stenosis causes considerable compressive stress in the tube wall and critical flow conditions such as negative pressure, high shear stress, and flow separation which may be related to artery compression, plaque cap rupture, platelet activation, and thrombus formation. The stress distribution has a very localized pattern and both maximum tensile stress (five times higher than normal average stress) and maximum compressive stress occur inside the stenotic section. Wall deformation, flow rates, and true severities of the stenosis under different pressure conditions are calculated and compared with experimental measurements and reasonable agreement is found.

Predictive models for carcinogenicity and mutagenicity: frameworks, state-of-the-art, and perspectives

Mutagenicity and carcinogenicity are endpoints of major environmental and regulatory concern. These endpoints are also important targets for development of alternative methods for screening and prediction due to the large number of chemicals of potential concern and the tremendous cost (in time, money, animals) of rodent carcinogenicity bioassays. Both mutagenicity and carcinogenicity involve complex, cellular processes that are only partially understood. Advances in technologies and generation of new data will permit a much deeper understanding. In silico methods for predicting mutagenicity and rodent carcinogenicity based on chemical structural features, along with current mutagenicity and carcinogenicity data sets, have performed well for local prediction (i.e., within specific chemical classes), but are less successful for global prediction (i.e., for a broad range of chemicals). The predictivity of in silico methods can be improved by improving the quality of the data base and endpoints used for modelling. In particular, in vitro assays for clastogenicity need to be improved to reduce false positives (relative to rodent carcinogenicity) and to detect compounds that do not interact directly with DNA or have epigenetic activities. New assays emerging to complement or replace some of the standard assays include Vitotox, GreenScreenGC, and RadarScreen. The needs of industry and regulators to assess thousands of compounds necessitate the development of high-throughput assays combined with innovative data-mining and in silico methods. Various initiatives in this regard have begun, including CAESAR, OSIRIS, CHEMOMENTUM, CHEMPREDICT, OpenTox, EPAA, and ToxCast. In silico methods can be used for priority setting, mechanistic studies, and to estimate potency. Ultimately, such efforts should lead to improvements in application of in silico methods for predicting carcinogenicity to assist industry and regulators and to enhance protection of public health.

Cloning and characterization of full-length human ribosomal protein L15 cDNA which was overexpressed in esophageal cancer

The aim of this investigation was trying to identify the genes differentially expressed in esophageal cancer. By combining suppression subtractive hybridization (SSH) with reverse Northern high density blots, a gene named EC45 was obtained, which dramatically overexpressed in 70% esophageal cancer (18/26). EC45 was mapped to 3p12-3p11.2 by radiation hybrid mapping (RH mapping). The putative full length EC45 cDNA (1987 bp) was identified by cDNA libraries screening of esophageal cancer. EC45 encoded 204 amino acids, and it shared a 100% similarity with ribosomal protein L15 (635 bp, mRNA) in ORF, but no similarity in 5' UTR or 3' UTR. Northern blot panel of multiple adult human normal tissues showed EC45 distributed in almost normal tissues tested. All these data suggested that EC45, encoding ribosomal protein L15 and overexpressing in esophageal cancer might play a possible role in carcinogenesis of esophagus.

Structure/function relationship of the cAMP response element in tyrosine hydroxylase gene transcription

Expression of tyrosine hydroxylase (TH) is limited to catecholamine-producing neurons and neuroendocrine cells in a cell type-specific manner and is inducible by the cAMP-regulated signaling pathway. Previous results indicated that the cAMP response element (CRE) residing at -45 to -38 base pairs upstream of the transcription initiation site is essential for both basal and cAMP-inducible promoter activity of the 2.4-kilobase or shorter upstream sequence of the TH gene (Kim, K. S., Lee, M. K., Carroll, J. , and Joh, T. H. (1993) J. Biol. Chem. 268, 15689-15695; Lazaroff, M. , Patankar, S., Yoon, S. O., and Chikaraishi, D. M. (1995) J. Biol. Chem. 270, 21579-21589). Here, we further report that the CRE is critical for the promoter activity of the 5.6- or 9.0-kilobase upstream sequences of the rat TH gene, which had been shown to direct the cell-specific TH expression in vivo. To define the structure/function relationship of the CRE in transcriptional activation of the TH gene, we performed saturated mutational analyses of 12 nucleotides encompassing the CRE. Mutation of any nucleotide within the octamer motif results in a significant decrease of both basal and cAMP-inducible transcriptional activity of the TH reporter gene construct. Among the four nucleotides adjacent to the CRE (two 5' and two 3'), only the G residue at the immediate 3' position is important for full transcriptional activity. DNase I footprint analysis indicates a positive correlation between in vivo promoter activity and in vitro interaction between the CRE motif and its cognate protein factor(s). Reconstruction experiments using a TH promoter in which the native CRE was rendered inactive show that the CRE can transactivate transcription in either orientation through a window of approximately 200 base pairs upstream of the transcription initiation site, suggesting that CRE supports transcriptional activation of the TH gene in a distance-dependent manner. Finally, when the distance between the CRE and TATA box was changed by inserting an additional 5 or 10 bases, it was observed that both insertional mutations increased activity by approximately 3-fold. The cAMP inducibility was as intact as the wild type construct. Together, these results are consistent with a model in which transcriptional activation of the TH gene by the CRE requires that it be located within a certain proximity of the CAP site but does not depend on a stringent stereospecific alignment in relationship to the TATA element.

Tyrosine kinase inhibition in diffuse large B-cell lymphoma: molecular basis for antitumor activity and drug resistance of dasatinib

Diffuse large B-cell lymphoma (DLBCL) is the most common type of non-Hodgkin lymphoma. Although some patients can be cured by current therapies, novel agents are needed to further improve outcomes. We hypothesized that Src tyrosine kinase inhibition by dasatinib may have antilymphoma effects. Here, we demonstrate that dasatinib inhibits cell growth through G(1)-S blockage in five of seven DLBCL cell lines at clinically achievable concentrations. Compared to resting B cells, DLBCL has increased tyrosine phosphorylation activities. As expected, dasatinib inhibits phosphorylation of several Src family kinase members. However, this inhibition occurs in all cell lines regardless of their proliferative response to the drug. In contrast, the activity of two downstream signaling molecules, Syk and phospholipase Cgamma2 (PLCgamma2), are well correlated with cell line sensitivity to dasatinib, suggesting that these molecules are crucial in mediating the proliferation of activated lymphoma cells. Furthermore, dasatinib inhibits B-cell receptor signaling in primary lymphoma cells. Together, our findings not only show dasatinib as a potentially useful therapy for DLBCL but also provide insights into the pathogenesis of the lymphoma. The results further suggest the possibility of using Syk and PLCgamma2 as biomarkers to predict dasatinib therapeutic response in prospective clinical trials.