Modeling the photo-oxidation of dissolved organic matter by ultraviolet radiation in freshwater lakes: implications for mercury bioavailability

Uncertainties in projected ultraviolet (UV) radiation may lead to future increases in UV irradiation of freshwater lakes. Because dissolved organic carbon (DOC) is the main binding phase for mercury (Hg) in freshwater lakes, an increase in DOC photo-oxidation may affect Hg speciation and bioavailability. We quantified the effect of DOC concentration on the rate of abiotic DOC photo-oxidation for five lakes (DOC = 3.27–12.3 mg L−1) in Kejimkujik National Park, Canada. Samples were irradiated with UV-A or UV-B radiation over a 72-h period. UV-B radiation was found to be 2.36 times more efficient at photo-oxidizing DOC than UV-A, with energy-normalized rates of dissolved inorganic carbon (DIC) production ranging from 3.8 × 10−5 to 1.1 × 10−4 mg L−1 J−1 for UV-A, and from 6.0 × 10−5 to 3.1 × 10−4 mg L−1 J−1 for UV-B. Energy normalized rates of DIC production were positively correlated with DOC concentrations. Diffuse integrated attenuation coefficients were quantified in situ (UV-A Kd = 0.056–0.180 J cm−1; UV-B Kd = 0.015–0.165 J cm−1) and a quantitative depth-integrated model for yearly DIC photo-production in each lake was developed. The model predicts that, UV-A produces between 3.2 and 100 times more DIC (1521–2851 mg m−2 year−1) than UV-B radiation (29.17–746.7 mg m−2 year−1). Future increases in UV radiation may increase DIC production and increase Hg bioavailability in low DOC lakes to a greater extent than in high DOC lakes.

Monitoring guanine photo-oxidation by enantiomerically resolved Ru(II) dipyridophenazine complexes using inosine-substituted oligonucleotides

The intercalating [Ru(TAP)2(dppz)]2+ complex can photo-oxidise guanine in DNA, although in mixed-sequence DNA it can be difficult to understand the precise mechanism due to uncertainties in where and how the complex is bound. Replacement of guanine with the less oxidisable inosine (I) base can be used to understand the mechanism of electron transfer (ET). Here the ET has been compared for both L- and D-enantiomers of [Ru(TAP)2(dppz)]2+ in a set of sequences where guanines in the readily oxidisable GG step in {TCGGCGCCGA}2 have been replaced with I. The ET has been monitored using picosecond and nanosecond transient absorption and ps-time-resolved IR spectroscopy. In both cases inosine replacement leads to a diminished yield, but the trends are strikingly different for L- and D-complexes.

Induction of cold active acid phosphomonoesterase activity at low temperature in psychrotrophic ectomycorrhizal Hebeloma spp.

Hebeloma strains of arctic and temperature origin, grown at 22° or 6°, were assayed for wall-bound and extracellular acid phosphomonoesterase (pNPPase) across a temperature range 2-37°. Only when grown at 6° was a cold active extracellular pNPPase induced in all the arctic strains and most of the temperature strains tested. Such enzymes are suggested to be a adaptation to low soil temperatures, and are discussed in the context of ectomycorrhizal access to soil PO4− monoesters at low temperature.

Monitoring one-electron photo-oxidation of guanine in DNA crystals using ultrafast infrared spectroscopy

To understand the molecular origins of diseases caused by ultraviolet and visible light, and also to develop photodynamic therapy, it is important to resolve the mechanism of photoinduced DNA damage. Damage to DNA bound to a photosensitizer molecule frequently proceeds by one-electron photo-oxidation of guanine, but the precise dynamics of this process are sensitive to the location and the orientation of the photosensitizer, which are very difficult to define in solution. To overcome this, ultrafast time-resolved infrared (TRIR) spectroscopy was performed on photoexcited ruthenium polypyridyl–DNA crystals, the atomic structure of which was determined by X-ray crystallography. By combining the X-ray and TRIR data we are able to define both the geometry of the reaction site and the rates of individual steps in a reversible photoinduced electron-transfer process. This allows us to propose an individual guanine as the reaction site and, intriguingly, reveals that the dynamics in the crystal state are quite similar to those observed in the solvent medium.

Towards expressive rule induction on IP network event streams

In order to gain insights into events and issues that may cause errors and outages in parts of IP networks, intelligent methods that capture and express causal relationships online (in real-time) are needed. Whereas generalised rule induction has been explored for non-streaming data applications, its application and adaptation on streaming data is mostly undeveloped or based on periodic and ad-hoc training with batch algorithms. Some association rule mining approaches for streaming data do exist, however, they can only express binary causal relationships. This paper presents the ongoing work on Online Generalised Rule Induction (OGRI) in order to create expressive and adaptive rule sets real-time that can be applied to a broad range of applications, including network telemetry data streams.

Media damage following detergent sclerotherapy appears to be secondary to the induction of inflammation and apoptosis: an immunohistochemical study elucidating previous histological observations

Objective/Background: Traditionally, sclerotherapy has been thought to work by the cytotoxic effect of the sclerosant upon the endothelium alone. However, studies have shown that sclerotherapy is more successful in smaller veins than in larger veins. This could be explained by the penetration of the sclerosant, or its effect, into the media. This study aimed to investigate intimal and medial damage profiles after sclerosant treatment. Methods: Fresh human varicose veins were treated ex vivo with either 1% or 3% sodium tetradecyl sulphate (STS) for 1 or 10 minutes. The effect of the sclerosant on the vein wall was investigated by immunofluorescent labelling of transverse vein sections using markers for endothelium (CD31), smooth muscle (a-actin), apoptosis (p53) and inflammation (intercellular adhesion molecule-1 [ICAM-1]). Polidocanol (POL; 3%) treatment at 10 minutes was similarly investigated. Results: Endothelial cell death was concentration- and time-dependent for STS but incomplete for both sclerosants. Time, but not concentration, significantly affected cell death (p > .001). A 40% and 30% maximum reduction was observed for STS and POL, respectively. Destruction of 20e30% of smooth muscle cells was found up to 250 mm from the lumen after 3% STS treatment for 10 minutes. POL treatment for 10 minutes showed inferior destruction of medial cells. Following STS treatment and 24-hour tissue culture, p53 and ICAM-1 were upregulated to a depth of around 300 mm. This effect was not observed with POL. Conclusion: Inflammatory and apoptotic markers show the same distribution as medial cell death, implying that sclerotherapy with STS works by inducing apoptosis in the vein wall rather than having an effect restricted to the endothelium. Incomplete loss of endothelial cells and penetration of the sclerosant effect up to 250 mm into the media suggest that medial damage is crucial to the success of sclerotherapy and may explain why it is less effective in larger veins.

Callus induction and micropropagation improved by colchicine and phytoregulators in Kappaphycus alvarezii (Rhodophyta, Solieriaceae)

Tissue culture techniques were applied for micropropagation of the red alga Kappaphycus alvarezii in order to select the best strain and experimental system for in vitro culture. Five strains were tested: brown (BR), green (GR) and red (RD) tetrasporophytes, brown female gametophyte (BFG), and a strain originating from tetraspore germination (""Edison de Paula"", EP). The effects of three culture media were tested on callus formation, regeneration from explants and from callus in the three tetrasporophytic and EP strains: seawater enriched with half-strength of von Stosch`s (VS 50) and Guillard & Ryther`s (F/2 50) solutions, plus synthetic ASP 12-NTA medium, with or without gelling agent. Explants of the EP strain were treated with glycerol and the phytoregulators indole-3-acetic acid (IAA); 2,4-diclorophenoxyacetic acid (2,4-D); and benzylaminopurine (BA), alone or in combination. The effects of colchicine (0.01%) during 24, 48, 72 hours and 14 days were analyzed in the BFG and EP strains. The EP strain showed the highest percentage of explants forming callus and regeneration from explants in VS 50, indicating its high potential for micropropagation in comparison to the other strains. Regeneration from callus was very rare. Treatments with glycerol and IAA:BA (5:1 mg L(-1)) stimulated the regeneration from explants. Significant differences were observed in the percentages of regeneration of EP strain explants treated with colchicine for 14 days. Our results indicate that IAA and BA stimulated the regeneration process, and that colchicine produced explants with high potential for regeneration, being useful for improving the micropropagation of K. alvarezii.

Strong quenching of chlorophyll fluorescence in the desiccated state in three poikilohydric and homoiochlorophyllous moss species indicates photo-oxidative protection on highly light-exposed rocks of a tropical inselberg

The three poikilophydric and homoiochlorophyllous moss species Campylopus savannarum (C. Muell.) Mitt., Racocarpus fontinaloides (C. Muell.) Par. and Ptychomitrium vaginatum Besch. grow on sun-exposed rocks of a tropical inselberg in Brazil subject to regular drying and wetting cycles. Effective photo-oxidative protection in the light-adapted desiccated state in all three species is achieved by a reduction of ground chlorophyll fluorescence, F, to almost zero. Upon rewatering, the kinetics of the recovery of F in air dry cushions to higher values is very fast in the first 5min, but more than 80min are needed until an equilibrium is reached gradually. The kinetics were not different between the three species. The three moss species, have a distinct niche occupation and form a characteristic zonation around soil vegetation islands on the rock outcrops, where C. savannarum and R. fontinaloides form an inner and outer belt, respectively, around vegetation islands and P vaginatum occurs as small isolated cushions on bare rock. However, they were not distinguished by the reduction of F in the dry state and the rewetting recovery kinetics and only slightly different in their photosynthetic capacity. Stable isotope ratios (delta C-13, delta N-15) indicate that liquid films of water limiting diffusion of CO2 are important in determining carbon acquisition and suggest that limitation of CO2 fixation by water films must be more pronounced over time in P vaginatum than in the latter species. This is determined by both the micro site occupied and the form of the moss cushions. (c) 2007 Elsevier GmbH. All rights reserved.

Pharmacological properties of purinergic receptors and their effects on proliferation and induction of neuronal differentiation of P19 embryonal carcinoma cells

We have used P19 embryonal carcinoma cells as in vitro model for early neurogenesis to study ionotropic P2X and metabotropic P2Y receptor-induced Ca2+ transients and their participation in induction of proliferation and differentiation. In embryonic P19 cells, P2Y(1), P2Y(2) and P2X(4) receptors or P2X-heteromultimers with similar P2X4 pharmacology were responsible for ATP and ATP analogue-induced Ca2+ transients. In neuronal-differentiated cells, P2Y(2), P2Y(6), P2X(2) and possibly P2X(2)/P2X(6) heteromeric receptors were the major mediators of the elevations in intracellular free calcium concentration [Ca2+](i). We have collected evidence for the involvement of metabotropic purinergic receptors in proliferation induction of undifferentiated and neural progenitor cells by using a BrdU-incorporation assay. ATP-, UTP-, ADP-, 2-MeS-ATP- and ADP-beta S-induced proliferation in P19 cells was mediated by P2Y, and P2Y2 receptors as judged from pharmacological profiles of receptor responses. ATP-provoked acceleration of neuronal differentiation, determined by analysis of nestin and neuron-specific enolase gene and protein expression, also resulted from P2Y, and P2Y2 receptor activation. Proliferation- and differentiation-induction involved the activation of inositol-trisphosphate sensitive intracellular Ca2+ stores. (C) 2008 ISDN. Published by Elsevier Ltd. All rights reserved.

Induction of Lymphocyte Death by Short- and Long-Duration Triathlon Competitions

LEVADA-PIRES, A. C., M. F. CURY-BOAVENTURA, R. GORJAO, S. M. HIRABARA. E. F. PUGGINA, I. L. PELLEGRINOTTI, L. A. DOMINGUES FILHO, R. CURI, and T. C. PITHON-CURI. Induction of Lymphocyte Death by Short- and Long-Duration Triathlon Competitions. Med. Sci. Sporty Exerc., Vol. 4 1, No. 10, pp. 1896-1901, 2009. Purpose: The effect of triathlon competitions on death of lymphocytes from elite athletes was investigated. Material and Methods: Blood was collected from sedentary volunteers and triathletes at rest and after a short-duration triathlon (SDT) and after a long-duration triathlon (LDT-half Ironman) competitions. Results: The athletes had lowered lymphocyte proliferation capacity compared with sedentary volunteers either at rest or after the competitions. There was no difference in the parameters associated with lymphocyte death when sedentary volunteers were compared with triathletes at rest. Lymphocytes from triathletes after SDT competition showed an increase in DNA fragmentation, phosphatidylserine externalization, and mitochondrial transmembrane depolarization and did not alter membrane integrity when compared with cells from athletes at rest. In contrast, the LDT competition raised the proportion of lymphocytes with loss of membrane integrity when compared with cells from athletes at rest and did not change the apoptotic parameters. The LDT competition induced an increase of reactive oxygen species (ROS) production by lymphocytes compared with triathletes at rest. The SDT competition did not alter ROS production by lymphocytes when compared with cells from triathletes at rest. ROS production by lymphocytes after LDT competition was 60% higher than in SDT. Conclusions: Evidence is presented herein that an LDT competition caused lymphocyte death by necrosis, whereas an SDT induced lymphocyte apoptosis. The mechanism for lymphocyte death induced by the triathlon competitions may involve an increase in ROS production at different extents.

Short-term induction of thrombocytopenia delays periodontal healing in rats with periodontal disease: participation of endostatin and vascular endothelial growth factor

Background and Objective: Platelets contain factors, including VEGF and endostatin, that can modulate the healing process. We evaluated the effects of severe thrombocytopenia on periodontal healing in rats and determined the contribution of VEGF and endostatin to the healing process. Material and Methods: Rats were distributed into three test groups and two control groups. Cotton ligatures were placed at the gingival margin level of the lower first molar in the test groups. Sham-operated rats and rats in one of the periodontitis groups were killed 15 days later. Rats in the remaining two periodontitis groups had the ligatures removed in order to study the spontaneous recovery from the periodontal disease 15 days later, and these rats were treated with rabbit antiplatelet serum, in order to induce thrombocytopenia, or normal rabbit serum. An additional group without ligatures received antiplatet serum in the same period. Results: After ligature removal, rats treated with normal rabbit serum showed reduced myeloperoxidase activity, decreased alveolar bone loss and increased numbers of blood vessels. Thrombocytopenia caused a delay in alveolar bone regeneration, a decrease in the number of vessels and a modest decrease in myeloperoxidase activity. In the rats with periodontitis, serum endostatin concentrations were slightly decreased and serum VEGF remained unchanged compared with sham-operated animals. After ligature removal, a significant VEGF increase and endostatin decrease were observed in the rats treated with normal rabbit serum. Thrombocytopenia led to a dramatic fall in both VEGF and endostatin concentrations. Conclusion: Thrombocytopenia leads to a delay of periodontal healing in the situation of experimental periodontitis, which might be mediated in part by a decrease in the serum concentration of VEGF and endostatin derived from the platelets. However, other factors derived from the platelets may also have contributed to a delay of periodontal healing in the rats with thrombocytopenia.

Induction of neutralizing antibodies in mice immunized with an amino-terminal polypeptide of Streptococcus mutans P1 protein produced by a recombinant Bacillus subtilis strain

The oral pathogen Streptococcus mutans expresses a surface protein, P1, which interacts with the salivary pellicle on the tooth surface or with fluid-phase saliva, resulting in bacterial adhesion or aggregation, respectively. P1 is a target of protective immunity. Its N-terminal region has been associated with adhesion and aggregation functions and contains epitopes recognized by efficacious antibodies. In this study, we used Bacillus subtilis, a gram-positive expression host, to produce a recombinant N-terminal polypeptide of P1 (P1(39-512)) derived from the S. mutans strain UA159. Purified P1(39-512) reacted with an anti-full-length P1 antiserum as well as one raised against intact S. mutans cells, indicating preserved antigenicity. Immunization of mice with soluble and heat-denatured P1(39-512) induced antibodies that reacted specifically with native P1 on the surface of S. mutans cells. The anti-P1(39-512) antiserum was as effective at blocking saliva-mediated aggregation of S. mutans cells and better at blocking bacterial adhesion to saliva-coated plastic surfaces compared with the anti-full-length P1 antiserum. In addition, adsorption of the anti-P1 antiserum with P1(39-512) eliminated its ability to block the adhesion of S. mutans cells to abiotic surfaces. The present results indicate that P1(39-512), expressed and purified from a recombinant B. subtilis strain, maintains important immunological features of the native protein and represents an additional tool for the development of anticaries vaccines.

SpdR, a Response Regulator Required for Stationary-Phase Induction of Caulobacter crescentus cspD

The cold shock protein (CSP) family includes small polypeptides that are induced upon temperature downshift and stationary phase. The genome of the alphaproteobacterium Caulobacter crescentus encodes four CSPs, with two being induced by cold shock and two at the onset of stationary phase. In order to identify the environmental signals and cell factors that are involved in cspD expression at stationary phase, we have analyzed cspD transcription during growth under several nutrient conditions. The results showed that expression of cspD was affected by the medium composition and was inversely proportional to the growth rate. The maximum levels of expression were decreased in a spoT mutant, indicating that ppGpp may be involved in the signalization for carbon starvation induction of cspD. A Tn5 mutant library was screened for mutants with reduced cspD expression, and 10 clones that showed at least a 50% reduction in expression were identified. Among these, a strain with a transposon insertion into a response regulator of a two-component system showed no induction of cspD at stationary phase. This protein (SpdR) was able to acquire a phosphate group from its cognate histidine kinase, and gel mobility shift assay and DNase I footprinting experiments showed that it binds to an inverted repeat sequence of the cspD regulatory region. A mutated SpdR with a substitution of the conserved aspartyl residue that is the probable phosphorylation site is unable to bind to the cspD regulatory region and to complement the spdR mutant phenotype.

HOST-MEDIATED INDUCTION OF alpha-AMYLASES BY LARVAE OF THE MEXICAN BEAN WEEVIL Zabrotes subfasciatus (COLEOPTERA: CHRYSOMELIDAE: BRUCHINAE) IS IRREVERSIBLE AND OBSERVED FROM THE INITIATION OF THE FEEDING PERIOD

Larvae of Zabrotes subfasciatus secrete alpha-amylases that are insensitive to the alpha-amylase inhibitor found in seeds of Phaseolus vulgaris. By analyzing amylase activities during larval development on P. vulgaris, we detected activity of the constitutive amylase and the two inducible amylase isoforms at all stages. When larvae were transferred from the non alpha-amylase inhibitor containing seeds of Vigna unguiculata to P. vulgaris, the inducible alpha-amylases were expressed at the same level as in control larvae fed on P. vulgaris. Interestingly, when larvae were transferred from seeds of P. vulgaris to those of V. unguiculata, inducible alpha-amylases continued to be expressed at a level similar to that found in control larvae fed P. vulgaris continuously. When 10-day-old larvae were removed from seeds of V. unguiculata and transferred into capsules containing flour of P. vulgaris cotyledons, and thus maintained until completing 17 days ( age when the larvae stopped feeding), we could detect higher activity of the inducible alpha-amylases. However, when larvae of the same age were transferred from P. vulgaris into capsules containing flour of V. unguiculata, the inducible alpha-amylases remained up-regulated. These results suggest that the larvae of Z. subfasciatus have the ability to induce insensitive amylases early in their development. A short period of feeding on P. vulgaris cotyledon flour was sufficient to irreversibly induce the inducible alpha-amylase isoforms. Incubations of brush border membrane vesicles with the alpha-amylase inhibitor 1 from P. vulgaris suggest that the inhibitor is recognized by putative receptors found in the midgut microvillar membranes. (C) 2010 Wiley Periodicals, Inc.