Value of ecosystem hydropower service and its impact on the payment for ecosystem services

Hydropower is an important service provided by ecosystems. We surveyed all the hydropower plants in the Zagunao River Basin, Southwest China. Then, we assessed the hydropower service by using the InVEST (The Integrated Value and Tradeoff of Ecosystem Service Tools) model. Finally, we discussed the impact on ecological compensation. The results showed that: 1) hydropower service value of ecosystems in the Zagunao River Basin is 216.29 Euro/hm(2) on the average, of which the high-value area with more than 475.65 Euro/hm(2) is about 750.37 km(2), accounting for 16.12% of the whole watershed, but it provides 53.47% of the whole watershed service value; 2) ecosystem is an ecological reservoir with a great regulation capacity. Dams cannot completely replace the reservoir water conservation function of ecosystems, and has high economic and environmental costs that must be paid as well. Compensation for water conservation services should become an important basis for ecological compensation of hydropower development. 3) In the current PES cases, the standard of compensation is generally low. Cascade development makes the value of upstream ecosystem services become more prominent, reflecting the differential rent value, and the value of ecosystem services should be based on the distribution of differentiated ecological compensation.

An elevated plasma level of visfatin increases the risk of myocardial infarction

Visfatin, an adipocytokine involved in metabolic and immune disorders, plays an important role in the etiology of cardiovascular disease. Recent evidence has shown that an elevated plasma level of visfatin may increase the risk of myocardial infarction (MI), but individual published studies have shown inconclusive results. This study aimed to obtain a more precise estimate of the association between the plasma visfatin level and MI risk through a detailed meta-analysis of studies published in peer-reviewed journals. A literature search of articles published before May 1, 2013 was performed on the PubMed, Embase, Web of Science, and China BioMedicine databases. Crude standardized mean differences (SMDs) with 95% confidence intervals (CI) were calculated. Eleven case-control studies comprising 362 MI patients and 322 healthy controls were included. The meta-analysis revealed that an elevated plasma level of visfatin was associated with an increased risk of MI (SMD = 3.82, 95%CI = 2.67-4.98, P < 0.001). Further stratification based on the source of the controls showed that an elevated plasma level of visfatin was significantly associated with increased risk of MI in both hospital-based and population-based studies (SMD = 4.12, 95%CI = 2.23-6.01, P < 0.001 and SMD = 3.65, 95%CI = 2.67- 4.98, P < 0.001, respectively). No publication bias was evident in this meta-analysis. In conclusion, the current meta-analysis indicates that an elevated plasma level of visfatin increases the risk of MI. Therefore, plasma visfatin may be a promising biomarker for the diagnosis of MI.

Abstract P2-06-02: Pparg deacetylation by SIRT1 determines breast tumor lipid synthesis and growth

Peroxisome proliferator-activated receptorg (Pparγ) is a member of the nuclear receptor (NR) superfamily, which regulates diverse biological functions including lipogenesis and differentiation, anti-inflammation, insulin sensitivity, cellular proliferation, and autophagy. Independent lines of evidence support a role for Pparγ as either a collaborative oncogene or as a tumor suppressor. Heterozygous mutations of Pparγ have been detected in 4/55 patients with colon cancer and a chromosomal translocation between PAX8 and Pparγ in follicular thyroid cancer appeared to serve as a dominant inhibitor of endogenous Pparγ expression. Pparγ agonists reduced tumorigenesis in several in vivo models. In contrast, several studies suggest Pparγ may enhance tumor growth. Pparγ ligands increased polyp numbers in the Apc mouse model of familial adenomatosis. Pparγ and its ligands inhibit breast tumor growth; however, constitutively active Pparγ collaborated in mammary oncogenesis with polyoma middle T antigen or oncogenic ErbB2.

Pparγ activation involves post-translational modifications including phosphorylation and sumoylation upon growth factor or ligand stimulus. Mutation of the Pparγ1 sumoylation site at K77 and K365 demonstrated that K77 may either reduce Pparγ-dependent gene induction and enhance repression or reduce repression, depending upon the synthetic reporter gene used. Lysine residues of nuclear receptors also serve as substrates for acetylation and Pparγ binds co-activators and co-repressors with intrinsic or associated histone acetylase or deacetylase activity including NCoR, SMRT, SIRT1, and p300. Initially characterized for the ERα, AR and, subsequently, the orphan nuclear receptor steroidogenic factor 1 (SF-1), acetylation occurs at a conserved lysine motif shared amongst evolutionarily related nuclear receptors. Several nuclear receptors and co-integrators involved in lipid metabolism are regulated by acetylation including p300, PGC1α, FXR, LXR and RAR. Both TSA- and NAD-sensitive HDACs (e.g. SIRT1) regulate Pparγ function and SIRT1 inhibits Pparγ-dependent adipocyte differentiation. Whether Pparγ is acetylated in cancer cells and how Pparγ exerts it's crucial, though controversial, function in tumorigenesis have not been established.

Pparγ induces gene transcription through binding specific NR half-sites and through non-canonical binding sequences (such as CREB/AP-1 sites). Transcriptional repression involves Pparγ sumoylation at lysine 77 (K77). Herein, Pparγ was shown to be acetylated at nine distinct lysine residues. SIRT1 bound and deacetylated Pparγ at K154/155. ChIP-Seq analysis for genome-wide DNA binding demonstrated the acetylation site was required for binding NR half-sites, but was not required for non-canonical site binding. Breast tumor growth, de novo lipid synthesis, induction of autophagy and evasion of apoptosis was promoted by K154/155 and inhibited by K77 in vivo. Pparγ acetylation induced a gene signature that was increased in breast cancer, associated with a reduction in SIRT1 abundance and poor outcome. The Pparγ acetylation site determines binding to autophagy and apoptosis signaling to regulate breast tumor lipid metabolism and growth.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-06-02.

Evidence for Borna disease virus infection in neuropsychiatric patients in three western China provinces

Borna disease virus (BDV) is a non-cytolytic, neurotropic RNA virus that can infect a wide variety of vertebrate species from birds and primates to humans. Several studies have been carried out to investigate whether BDV is associated with neuropsychiatric diseases. However, this association is still inconclusive. Two panels of subjects consisting of 1,679 various neuropsychiatric patients and healthy people from three western China provinces were enrolled in this study. BDV p24 or p40 RNA in peripheral blood mononuclear cells (PBMCs) were detected in the first panel of 1,481 subjects using reverse transcription quantitative polymerase chain reaction (RT-qPCR) and cerebrospinal fluid (CSF) samples from the BDV RNA-positive individuals were subjected to BDV p24 antibodies testing by enzyme-linked immunosorbent assay (ELISA). BDV p24 or p40 RNA in PBMCs and p24 antibodies in plasma were detected in the second panel of 198 subjects by RT-qPCR and Western blot. A higher prevalence for BDV RNA was demonstrated in patients with viral encephalitis (6.70%), Guillain-Barré syndrome (6.70%), schizophrenia (9.90%) and chronic fatigue syndrome (CFS) (12.70%) compared to healthy controls in the first panel. CSF p24 antibodies were demonstrated in three viral encephalitis patients, two schizophrenia patients and two major depressive disorder (MDD) patients. The prevalences of p24 antibodies in plasma from patients with viral encephalitis (13.24%), multiple sclerosis (25.00%) and Parkinson's disease (22.73%) were significantly higher than healthy controls. This study demonstrates that BDV infection also exists in humans from three western China provinces, and suggests the involvement of the contribution of BDV in the aetiology of Chinese patients with some neuropsychiatric disorders, including viral encephalitis, schizophrenia, CFS, multiple sclerosis and Parkinson's disease.

Overexpression of nuclear distribution protein (hNUDC) causes pro-apoptosis and differentiation in Dami megakaryocytes

OBJECTIVES

Overexpression of hNUDC, a member of the nuclear distribution protein family, reduces cell population growth in prostate cancer cell lines, concurrent with induced morphological change and enhanced polyploidization. These phenomena are also closely associated with terminal phases of megakaryocyte maturation.

MATERIALS AND METHODS

In Dami cells, MTT and trypan blue assays were used to investigate cell viability and proliferation effects of hNUDC, and flow cytometry was used to analyse cell cycle and DNA content. Real-time RT-PCR was employed to detect mRNA expression. Activations of caspase-3, ERK, Akt and Stat-5 were determined by immunoblotting. May-Grünwald-Giemsa staining was performed to reveal cell morphology.

RESULTS AND CONCLUSION

Functional studies using adenovirus-mediated hNUDC overexpression led to inhibition of megakaryocyte proliferation via cell cycle arrest in G2/M transition phase. This process could have been be mediated by upregulation of p21 and downregulation of its downstream targets, including cyclin B1, cyclin B2 and c-myc. Enhanced apoptosis in turn ensued, characterized by increased caspase-3 activation, upregulation of pro-apoptotic Bax and downregulation of anti-apoptotic Bcl-2. Furthermore, hNUDC overexpression elevated the level of megakaryocyte maturation, associated with increased polyploidy, cell morphological changes and increased expression of cell surface differentiation markers, including CD10, CD44, CD41 and CD61. Our results further suggest that the ERK signalling pathway was involved in hNUDC overexpression-induced apoptosis. Taken together, this study provides experimental evidence for overexpression of hNUDC in Dami cells and suggests that activation of apoptotic machinery may be involved in megakaryocytic differentiation.

Compact engineering of path-entangled sources from a monolithic quadratic nonlinear photonic crystal

An integrated realization of photonic entangled states becomes an inevitable tendency toward integrated quantum optics. Here we report the compact engineering of steerable photonic path-entangled states from a monolithic quadratic nonlinear photonic crystal. The crystal acts as a coherent beam splitter to distribute photons into designed spatial modes, producing the heralded single-photon and appealing beamlike two-photon path entanglement. We characterize the path entanglement by implementing quantum spatial beating experiments. Such a multifunctional entangled source can be further extended to the high-dimensional fashion and multiphoton level, which paves a desirable way to engineering miniaturized quantum light sources.

Association between Helicobacter pylori infection and the risk of colorectal neoplasia: a systematic review and meta-analysis

AIM

The existing evidence on the relationship between Helicobacter pylori infection and the risk of colorectal neoplasia is inconsistent. We conducted a systematic review with a meta-analysis to explore this relationship and to determine whether the relationship varies according to the study characteristics.

METHOD

We searched the PubMed database and the reference lists of pertinent articles published up to July 2012. Summary odds ratios (ORs) with their 95% confidence intervals (CIs) were estimated using a random-effects model.

RESULTS

Twenty-seven studies including 3792 cases of colorectal adenoma (CRA) and 3488 cases of colorectal cancer (CRC) were identified. Overall, H. pylori infection was associated with an increased risk of CRA (OR = 1.66, 95% CI 1.39-1.97, I(2)  = 54.3%) and CRC (OR = 1.39, 95% CI 1.18-1.64, I(2)  = 35.8%), although there was significant heterogeneity among the studies. Subgroup analysis revealed that the positive correlation did not differ by sex, geographic variation or subsite of neoplasia, but might vary by the method of detection of H. pylori. The study was underpowered to determine the risk of colorectal neoplasia associated with cytotoxin-associated gene A-positive H. pylori.

CONCLUSION

This meta-analysis demonstrates a positive association between H. pylori infection and the risk of colorectal neoplasia.

Racial differences in determinants of live donor kidney transplantation in the United States

Few studies have compared determinants of live donor kidney transplantation (LDKT) across all major US racial-ethnic groups. We compared determinants of racial-ethnic differences in LDKT among 208 736 patients who initiated treatment for end-stage kidney disease during 2005-2008. We performed proportional hazards and bootstrap analyses to estimate differences in LDKT attributable to sociodemographic and clinical factors. Mean LDKT rates were lowest among blacks (1.19 per 100 person-years [95% CI: 1.12-1.26]), American Indians/Alaska Natives-AI/ANs (1.40 [1.06-1.84]) and Pacific Islanders (1.10 [0.78-1.84]), intermediate among Hispanics (2.53 [2.39-2.67]) and Asians (3.89 [3.51-4.32]), and highest among whites (6.46 [6.31-6.61]). Compared with whites, the largest proportion of the disparity among blacks (20%) and AI/ANs (29%) was attributed to measures of predialysis care, while the largest proportion among Hispanics (14%) was attributed to health insurance coverage. Contextual poverty accounted for 16%, 4%, 18%, and 6% of the disparity among blacks, Hispanics, AI/ANs and Pacific Islanders but none of the disparity among Asians. In the United States, significant disparities in rates of LDKT persist, but determinants of these disparities vary by race-ethnicity. Efforts to expand preESKD insurance coverage, to improve access to high-quality predialysis care and to overcome socioeconomic barriers are important targets for addressing disparities in LDKT.

Heralded generation of multipartite entanglement for one photon by using a single two-dimensional nonlinear photonic crystal

We propose a compact scheme for the heralded generation of single-photon multipartite entanglement by using a single two-dimensional nonlinear photonic crystal. Studies have shown that by appropriate structure design, the single-photon entanglement shared among three spatially distinct optical modes can be generated through three concurrent spontaneous parametric down-conversion processes by using the other photon in an identical spatial mode as a trigger. Furthermore, we analyze the entanglement of such heralded single-photon tripartite W-type state theoretically. This method can be expanded for the heralded single-photon N-partite entanglement generation. This compact and stable quantum light source may act as a key ingredient in quantum information science.

Wnt/β-catenin signalling pathway mediates high glucose induced cell injury through activation of TRPC6 in podocytes

OBJECTIVES

Diabetic nephropathy is a major complication of diabetes and a frequent cause of end-stage renal disease and recent studies suggest that podocyte damage may play a role in the pathogenesis of this. At early onset of diabetic nephropathy there is podocyte drop-out, which is thought to provoke glomerular albuminuria and subsequent glomerular injury; however, the underlying molecular mechanisms of this remain poorly understood. Here we report that we tested the hypothesis that early diabetic podocyte injury is caused, at least in part, by up-regulation of transient receptor potential cation channel 6 (TRPC6), which is regulated by the canonical Wnt signalling pathway, in mouse podocytes.

MATERIALS AND METHODS

Mechanism of injury initiation in mouse podocytes, by high concentration of D-glucose (HG, 30 mM), was investigated by MTT, flow cytometry, real-time quantitative PCR, and western blot analysis.

RESULTS

HG induced apoptosis and reduced viability of differentiated podocytes. It caused time-dependent up-regulation of TRPC6 and activation of the canonical Wnt signalling pathway, in mouse podocytes. In these cells, blockade of the Wnt signalling pathway by dickkopf related protein 1 (Dkk1) resulted in effective reduction of TRPC6 up-regulation and amelioration of podocyte apoptosis. Furthermore, reduction of cell viability induced by HG was attenuated by treatment with Dkk1.

CONCLUSION

These findings indicate that the Wnt/β-catenin signalling pathway may potentially be active in pathogenesis of TRPC6-mediated diabetic podocyte injury.

Primary genome scan for complex body shape-related traits in the common carp Cyprinus carpio

To identify quantitative trait loci (QTL) that affect body shape in common carp Cyprinus carpio, a linkage map, 2159·23 cM long, was constructed with a total of 307 markers covering 51 linkage groups (LG). The map included 167 new single nucleotide polymorphism (SNP) markers derived from expressed sequence tags (EST) together with 140 microsatellite markers reported earlier. A primary genome scan was conducted for QTL for standard length (L(S)), head length (L(H)), body height (H(B)), body width (W(B)) and tail length (L(TAIL)) in an F1 line containing 92 offspring. A total of 15 suggestive QTL on six LGs were found to associate with L(S), L(H), H(B), W(B) and L(TAIL) which explained 10·7-17·4% of the variance. Five significant QTL were detected for body-shape related traits and located for LGs (lg1, 12 and 20). These QTL included: one associated with L(S) (21·1% variance explained), three for H(B) (almost 20% variance explained) and one for W(B) (20·7% variance explained).

Generation of polarization-entangled photon pairs via concurrent spontaneous parametric downconversions in a single χ(2) nonlinear photonic crystal

We propose a scheme for generating polarization-entangled photon pairs using a χ((2)) nonlinear photonic crystal, which is designed for enabling two concurrent quasi-phase-matched spontaneous parametric downconversion processes. Beamlike photon pairs produced from each process are collinear but noncollinear with the pump. Moreover, the source we design works in a postselection-free way and applies to both degenerate and nondegenerate cases. Combining possible waveguide technologies, our scheme may provide an integrated polarization entanglement source.

Far-infrared polarimetry diagnostic for measurement of internal magnetic field dynamics and fluctuations in the C-MOD Tokamak (invited)

A laser-based (2.55 THz) mulitchord polarimeter is now operational on Alcator C-Mod and is used to make measurements of the internal magnetic field structure as well as plasma fluctuations. The polarimeter is designed to measure the Faraday effect for high-field (up to 8.3 T) and high-density (up to 5 × 10(20) m(-3)) ITER relevant plasma conditions. Initial 3 chord tests are consistent with magnetic equilibrium reconstructions and indicate no measurable contamination from the toroidal magnetic field due to the Cotton-Mouton effect or misalignment. Time response of <1 μs enables the measurement of fast equilibrium temporal dynamics as well as high-frequency fluctuations.

Differences in numbers of termicins expressed in two termite species affected by fungal contamination of their environments

Termicin is a defensin-like antimicrobial peptide of termites that has strong antifungal activity. Fifty-six different termicin mRNAs encoding 46 different peptides were amplified and identified from Odontotermes formosanus (Termitidae), a species that inhabits environments with a large variety of microbial fauna. In contrast, only 38 different termicin mRNAs encoding 21 different peptides were amplified and identified from Reticulitermes chinensis (Rhinotermitidae). All mRNAs were amplified by reverse transcript PCR, with primers designed from reported termicin mRNA sequences. All of these genes showed high intraspecific sequence identity and were found to be highly homologous with other reported termicin genes. These two termite species live in different environments; the latter encounters relatively fewer pathogens in its habitat. We conclude that differences in microenvironmental pressure can affect the number of termicin genes expressed in termite species.

Altered Aggrecan Synthesis and Collagen Expression Profiles in Chondrocytes from Patients with Kashin—Beck Disease and Osteoarthritis

OBJECTIVES: To investigate cell morphology, aggrecan expression, and type I, II, III and X collagen expression in chondrocytes from adults with Kashin—Beck disease or osteoarthritis (OA). METHODS: Samples of knee articular cartilage were taken during surgery; cartilage samples obtained from fresh cadavers without arthritic disease were used as controls. Samples were digested with collagenase; isolated chondrocytes were cultured in monolayers. Aggrecan was detected by toluidine blue staining; collagen and aggrecan protein levels were evaluated by immuno cytochemistry and immunofluorescence staining. RESULTS: Samples were obtained from six participants per group. Aggrecan and type II collagen levels in chondrocytes from patients were significantly lower than those from controls, but levels of type I, III and X collagen were enhanced in patients compared with controls. Production of type III and X collagen was higher in chondrocytes from patients with Kashin—Beck disease than in those from OA patients. CONCLUSIONS: Biochemical and morphological mechanisms underlying Kashin—Beck disease and OA include enhanced dedifferentiation and hypertrophy of chondrocytes, increased type I, III and X collagen levels, and suppressed type II collagen and aggrecan production compared with control samples.

Genetic analysis of NR4A2 gene in a large population of Han Chinese patients with Parkinson's disease

BACKGROUND

NR4A2 gene is a transcription factor crucial for differentiation and survival of midbrain dopamine (DA) neurons, and several variants have been eported to be associated with Parkinson's disease (PD) in the Caucasian population.

METHODS

To determine whether there is any association of NR4A2 mutation or variation with PD in the Han Chinese population, we performed a genetic analysis of all the exons and exon-intron boundaries in 689 PD patients and 672 controls from mainland China using direct sequencing analysis.

RESULTS

We identified four novel variants and two previously reported variants. Two novel variants (exon 2 c.-20 C>G and exon 3 c.711 C>A) were only found in PD. The others (exon 2 c.-35 A>G; exon 8 c.1615 G>A; intron 4 IVS4-16 G>T; and intron 6 IVS6 + 18 insG) were found in both PD and controls at different frequencies.

CONCLUSIONS

Collectively, our results suggest that NR4A2 may be a susceptibility gene for PD in the Chinese population.

Molecular cloning and single nucleotide polymorphism analysis of IGF2a genes in the common carp (Cyprinus carpio)

We studied whether two IGF2 transcripts in common carp are similar to those found in zebrafish. The full-length IGF2a cDNA contains a 5'-terminal untranslated region (UTR) of 105 bp, a 3'-terminal UTR of 1358 bp and an open reading frame of 612 bp, which encodes a 206-amino acid protein. A 6614-bp full-length IGF2a DNA molecule, including the 5'-flanking region, was isolated. Genomic DNA structure analysis revealed that the IGF2a gene contains four exons and three introns. Bioinformatics analysis indicated that the proteins encoded by IGF2a genes in common carp have one signal peptide and one apparent transmembrane region. Bootstrapping was performed 1000 times to obtain support values for each branch. The common carp IGF2a were clustered in one group, while the outgroup (common carp IGF1) clustered in another group. We identified two new single nucleotide polymorphisms in intron 2 of the gene. One polymorphism, A/N, can be found only in the Huanghe carp. The other polymorphism, C/N, can be found in both male Huanghe carp × female Heilongjiang carp and male Huanghe carp × female Jian carp. The second polymorphism, C/N, is primarily transferred from the male and may be related to heterosis.

Hong-Ou-Mandel interference mediated by the magnetic plasmon waves in a three-dimensional optical metamaterial

We studied the quantum properties of magnetic plasmon waves in a three-dimensional coupled metamaterial. A Hong-Ou-Mandel dip of two-photon interference with a visibility of 86 ± 6.0% was explicitly observed, when the sample was inserted into one of the two arms of the interferometer. This meant that the quantum interference property survived in such a magnetic plasmon wave-mediated transmission process, thus testifying the magnetic plasmon waves owned a quantum nature. A full quantum model was utilized to describe our experimental results. The results showed that the metamaterials could not only steer the classical light but also the non-classical light and they might have potential application in the future quantum information.

Decreased NURR1 and PITX3 gene expression in Chinese patients with Parkinson's disease

BACKGROUND AND PURPOSE

The preferential degeneration of midbrain dopaminergic (mDA) neurons in the substantia nigra pars compacta is the pathological hallmark in Parkinson's disease (PD). The transcription factors NURR1 and PITX3 have been shown to play a crucial role in the maturation and survival of mDA neurons, and both of them were potential susceptibility genes for PD.

METHODS

  To determine whether NURR1 and PITX3 gene expression are altered in Chinese patients with PD, we measured their gene expression in human peripheral blood lymphocytes (PBL) in 255 patients with PD and 211 age- and gender-matched healthy controls by quantitative real-time PCR technique.

RESULTS

 We found that both NURR1 and PITX3 gene expression in PBL were significantly decreased in patients with PD as compared with controls (P < 0.0001). Lower levels of NURR1 and PITX3 gene expression were significantly associated with the increased risk for PD in male and older subjects, respectively.

CONCLUSIONS

  Our results provide useful information that the NURR1 and PITX3 gene expression is decreased in the PBL of Chinese patients with PD, indicating their possible systemic involvement in PD.

Involvement of Kv1.3 and p38 MAPK signaling in HIV-1 glycoprotein 120-induced microglia neurotoxicity

Inflammatory responses mediated by activated microglia play a pivotal role in the pathogenesis of human immunodeficiency virus type 1 (HIV-1)-associated neurocognitive disorders. Studies on identification of specific targets to control microglia activation and resultant neurotoxic activity are imperative. Increasing evidence indicate that voltage-gated K⁺ (K_v) channels are involved in the regulation of microglia functionality. In this study, we investigated K_v1.3 channels in the regulation of neurotoxic activity mediated by HIV-1 glycoprotein 120 (gp120)-stimulated rat microglia. Our results showed treatment of microglia with gp120 increased the expression levels of K_v1.3 mRNA and protein. In parallel, whole-cell patch-clamp studies revealed that gp120 enhanced microglia K_v1.3 current, which was blocked by margatoxin, a K_v1.3 blocker. The association of gp120 enhancement of K_v1.3 current with microglia neurotoxicity was demonstrated by experimental results that blocking microglia K_v1.3 attenuated gp120-associated microglia production of neurotoxins and neurotoxicity. Knockdown of K_v1.3 gene by transfection of microglia with K_v1.3-siRNA abrogated gp120-associated microglia neurotoxic activity. Further investigation unraveled an involvement of p38 MAPK in gp120 enhancement of microglia K_v1.3 expression and resultant neurotoxic activity. These results suggest not only a role K_v1.3 may have in gp120-associated microglia neurotoxic activity, but also a potential target for the development of therapeutic strategies.

Modulation of ascorbic acid-induced DNA cleavage by polyamide: cleavage manner, kinetics and mechanism

Manipulation of DNA presents a great interest in biotechnology and therapeutics. The molecules that damage DNA selectively offer new prospects for controlled manipulation of DNA. The conjugations of DNA-code reading molecules such as polyamides to reagents that induce DNA damages provide an approach to reach this goal. In this work, a new compound which contained polyamide and ascorbic acid conjugated by flexible linker (polyamide-Vc), was successfully synthesized, characterized, and evaluated as DNA cleavage agent, compared with that by using ascorbic acid molecule. The kinetics data showed that polyamide-Vc successfully promoted the cleavage of plasmid DNA, with k(max) of 0.314 h(-1) and K(d) of 0.105 mM. The evaluation of DNA linearization elicited that the activity of cleaving double-strand in the supercoiled pUC18 plasmid DNA by polyamide-Vc was enhanced remarkably, achieving n1/n2 ratio of 13.9 at 1.2 mM for 1 h. The introduction of polyamide to Vc could also partially weaken the inhibition of hydrogen radical to double-strand cleavage process because of its good binding activity to DNA. We anticipate that this work could provide a method for improving the efficiency of double-strand cleavage, especially to oxidative cleavage agents.

Physiological and molecular characterization of genetic competence in Streptococcus sanguinis

Streptococcus sanguinis is a major component of the oral flora and an important cause of infective endocarditis. Although S. sanguinis is naturally competent, genome sequencing has suggested significant differences in the S. sanguinis competence system relative to those of other streptococci. An S. sanguinis mutant possessing an in-frame deletion in the comC gene, which encodes competence-stimulating peptide (CSP), was created. Addition of synthetic CSP induced competence in this strain. Gene expression in this strain was monitored by microarray analysis at multiple time-points from 2.5 to 30 min after CSP addition, and verified by quantitative reverse transcription-polymerase chain reaction. Over 200 genes were identified whose expression was altered at least two-fold in at least one time point, with the majority upregulated. The 'late' response was typical of that seen in previous studies. However, comparison of the 'early' response in S. sanguinis with that of other oral streptococci revealed unexpected differences with regard to the number of genes induced, the nature of those genes, and their putative upstream regulatory sequences. Streptococcus sanguinis possesses a comparatively limited early response, which may define a minimal streptococcal competence regulatory circuit.