The effects of interleukin-10 depletion in vivo on the immune response to Porphyromonas gingivalis in a murine model

Background: The immune response to Porphyromonas gingivalis in the mouse abscess model is known to be dependent upon CD4 T-cell activation and the regulatory role of cytokines. The role of interleukin-10 (IL-10) in this mouse model was examined in vivo. Methods: One-week-old, female BALB/c mice were divided into 4 groups. Groups 1 and 2 were given intraperitoneal (ip) injections of phosphate buffered saline (PBS) weekly for 5 weeks. Group 3 was given an ip injection of rat immunoglobulin. Group 4 was injected with rat anti-IL-10 antibodies. At week 6, group 1 was sham-immunized with PBS, and groups 2, 3, and 4 were injected with P gingivalis lipopolysaccharide (Pg-LPS) weekly for 2 weeks. One week after the final immunization, delayed-type hypersensitivity (DTH) was assessed by footpad swelling to Pg-LPS. The level of serum antibodies to Pg-LPS and IFN-gamma (IFN-gamma) was determined by enzyme-linked immunosorbent assay. Dorsal abscess formation induced by the injection of viable P gingivalis was examined daily for 30 days. Results: The footpad swelling of the anti-IL-10-treated group (group 4) was significantly higher than that of groups 1 to 3. Similarly, the serum IFN-gamma level in group 4 was much higher than that of the other experimental groups. There was no significant difference in serum IgG antibodies to Pg-LPS in any of the experimental groups. However, the level of IgM antibodies in group 4 mice was significantly lower than that in groups 2 and 3. In addition, serum IgG1 was suppressed in group 4 mice, while IgG2a antibodies were raised. However, there was no difference observed between the levels of IgG2b and IgG3 antibodies in any group of mice. The lesions in sham-immunized mice (group 1) persisted for 30 days, and those in group 2 and 3 were undetected by day 18 and 20, respectively. In sharp contrast, lesions in group 4 had healed completely by day 13. Conclusions: This study has shown that IL-10 depletion in vivo in P gingivalis LPS-induced immune response in mice led to an elevated DTH response, an increase in serum IFN-gamma levels, and raised levels of IgG and IgG2a antibodies. Treatment with anti-IL-10 antibodies resulted in suppressed IgG I and IgM responses and a more rapid healing of abscesses than in non-IL-10-depleted mice. These results suggest that IL-10 depletion in Pg-LPS-induced immune response in mice may lead to a Th1-like immune response and provide strong protection against a subsequent challenge with live P gingivalis in an abscess model.

Effects of concentrated viral communities on photosynthesis and community composition of co-occurring benthic microalgae and phytoplankton

Marine viruses have been shown to affect phytoplankton productivity; however, there are no reports on the effect of viruses on benthic microalgae (microphytobenthos). Hence, this study investigated the effects of elevated concentrations of virus-like particles on the photosynthetic physiology and community composition of benthic microalgae and phytoplankton. Virus populations were collected near the sediment surface and concentrated by tangential flow ultrafiltration, and the concentrate was added to benthic and water column samples that were obtained along a eutrophication gradient in the Brisbane River/Moreton Bay estuary, Australia. Photosynthetic and community responses of benthic microalgae, phytoplankton and bacteria were monitored over 7 d in aquaria and in situ. Benthic microalgal communities responded to viral enrichment in both eutrophic and oligotrophic sediments. In eutrophic sediments, Euglenophytes (Euglena sp.) and bacteria decreased in abundance by 20 to 60 and 26 to 66%, respectively, from seawater controls. In oligotrophic sediments, bacteria decreased in abundance by 30 to 42% from seawater controls but the dinoflagellate Gymnodinium sp. increased in abundance by 270 to 3600% from seawater controls, The increased abundance of Gymnodinium sp. may be related to increased availability of dissolved organic matter released from lysed bacteria. Increased (140 to 190% from seawater controls) initial chlorophyll a fluorescence measured with a pulse-amplitude modulated fluorometer was observed in eutrophic benthic microalgal incubations following virus enrichment, consistent with photosystem II damage. Virus enrichment in oligotrophic water significantly stimulated carbon fixation rates, perhaps due to increased nutrient availability by bacterial lysis. The interpretation of data from virus amendment experiments is difficult due to potential interaction with unidentified bioactive compounds within seawater concentrates. However, these results show that viruses are capable of influencing microbial dynamics in sediments.

ENCORE: The effect of nutrient enrichment on coral reefs. Synthesis of results and conclusions

Coral reef degradation resulting from nutrient enrichment of coastal waters is of increasing global concern. Although effects of nutrients on coral reef organisms have been demonstrated in the laboratory, there is little direct evidence of nutrient effects on coral reef biota in situ. The ENCORE experiment investigated responses of coral reef organisms and processes to controlled additions of dissolved inorganic nitrogen (N) and/or phosphorus (P) on an offshore reef(One Tree Island) at the southern end of the Great Barrier Reef, Australia. A multi-disciplinary team assessed a variety of factors focusing on nutrient dynamics and biotic responses. A controlled and replicated experiment was conducted over two years using twelve small patch reefs ponded at low tide by a coral rim. Treatments included three control reefs (no nutrient addition) and three + N reefs (NH4Cl added), three + P reefs (KH2PO4 added), and three + N + P reefs. Nutrients were added as pulses at each low tide (ca twice per day) by remotely operated units. There were two phases of nutrient additions. During the initial, low-loading phase of the experiment nutrient pulses (mean dose = 11.5 muM NH4+; 2.3 muM PO4-3) rapidly declined, reaching near-background levels (mean = 0.9 muM NH4+; 0.5 muM PO4-3) within 2-3 h. A variety of biotic processes, assessed over a year during this initial nutrient loading phase, were not significantly affected, with the exception of coral reproduction, which was affected in all nutrient treatments. In Acropora longicyathus and A. aspera, fewer successfully developed embryos were formed, and in A. longicyathus fertilization rates and lipid levels decreased. In the second, high-loading, phase of ENCORE an increased nutrient dosage (mean dose = 36.2 muM NH4+; 5.1 muM PO4-3 declining to means of 11.3 muM NH4+ and 2.4 muM PO4-3 at the end of low tide) was used for a further year, and a variety of significant biotic responses occurred. Encrusting algae incorporated virtually none of the added nutrients. Organisms containing endosymbiotic zooxanthellae (corals and giant clams) assimilated dissolved nutrients rapidly and were responsive to added nutrients. Coral mortality, not detected during the initial low-loading phase, became evident with increased nutrient dosage, particularly in Pocillopora damicornis. Nitrogen additions stunted coral growth, and phosphorus additions had a variable effect. Coral calcification rate and linear extension increased in the presence of added phosphorus but skeletal density was reduced, making corals more susceptible to breakage. Settlement of all coral larvae was reduced in nitrogen treatments, yet settlement of larvae from brooded species was enhanced in phosphorus treatments. Recruitment of stomatopods, benthic crustaceans living in coral rubble, was reduced in nitrogen and nitrogen plus phosphorus treatments. Grazing rates and reproductive effort of various fish species were not affected by the nutrient treatments. Microbial nitrogen transformations in sediments,were responsive to nutrient loading with nitrogen fixation significantly increased in phosphorus treatments and denitrification increased in all treatments to which nitrogen had been added. Rates of bioerosion and grazing showed no significant effects of added nutrients, ENCORE has shown that reef organisms and processes investigated ill situ were impacted by elevated nutrients. Impacts mere dependent on dose level, whether nitrogen and/or phosphorus mere elevated and were often species-specific. The impacts were generally sub-lethal and subtle and the treated reefs at the end of the experiment mere visually similar to control reefs. Rapid nutrient uptake indicates that nutrient concentrations alone are not adequate to assess nutrient condition of reefs. Sensitive and quantifiable biological indicators need to be developed for coral reef ecosystems. The potential bioindicators identified in ENCORE should be tested in future research on coral reef/nutrient interactions. Synergistic and cumulative effects of elevated nutrients and other environmental parameters, comparative studies of intact vs. disturbed reefs, offshore vs, inshore reefs, or the ability of a nutrient-stressed reef to respond to natural disturbances require elucidation. An expanded understanding of coral reef responses to anthropogenic impacts is necessary, particularly regarding the subtle, sub-lethal effects detected in the ENCORE studies. (C) 2001 Published by Elsevier Science Ltd.

Effects of phosphonate and salicylic acid treatments on anthracnose disease development and ripening of 'Kensington Pride' mango fruit

This study investigated treatment of mango (Mangifera indica L.) fruit with 2 host defence-promoting compounds for suppression of anthracnose disease (Colletotrichum gloeosporioides). Cultivar 'Kensington Pride' fruit were treated at concentrations of up to 1000 mg/L with either potassium phosphonate or salicylic acid. Applications were by various combinations of pre- and postharvest dips and vacuum infiltration. Postharvest treatments at up to 2000 mg/L salicylic acid were evaluated in a second fruiting season. Fruit were either uninoculated or inoculated with the fungal pathogen. Colour, firmness and disease-severity were assessed during shelf life at 23 degreesC. There were no significant (P>0.05) effects of potassium phosphonate or salicylic acid on anthracnose disease severity in the first season. Moreover, phosphonate or salicylic acid treatment did not significantly affect fruit colour or firmness changes. There were significant (P

Traffic and residue cover effects on infiltration

Wheel traffic can lead to compaction and degradation of soil physical properties. This study, as part of a study of controlled traffic farming, assessed the impact of compaction from wheel traffic on soil that had not been trafficked for 5 years. A tractor of 40 kN rear axle weight was used to apply traffic at varying wheelslip on a clay soil with varying residue cover to simulate effects of traffic typical of grain production operations in the northern Australian grain belt. A rainfall simulator was used to determine infiltration characteristics. Wheel traffic significantly reduced time to ponding, steady infiltration rate, and total infiltration compared with non-wheeled soil, with or without residue cover. Non-wheeled soil had 4-5 times greater steady infiltration rate than wheeled soil, irrespective of residue cover. Wheelslip greater than 10% further reduced steady infiltration rate and total infiltration compared with that measured for self-propulsion wheeling (3% wheelslip) under residue-protected conditions. Where there was no compaction from wheel traffic, residue cover had a greater effect on infiltration capacity, with steady infiltration rate increasing proportionally with residue cover (R-2 = 0.98). Residue cover, however, had much less effect on infiltration when wheeling was imposed. These results demonstrated that the infiltration rate for the non-wheeled soil under a controlled traffic zero-till system was similar to that of virgin soil. However, when the soil was wheeled by a medium tractor wheel, infiltration rate was reduced to that of long-term cropped soil. These results suggest that wheel traffic, rather than tillage and cropping, might be the major factor governing infiltration. The exclusion of wheel traffic under a controlled traffic farming system, combined with conservation tillage, provides a way to enhance the sustainability of cropping this soil for improved infiltration, increased plant-available water, and reduced runoff-driven soil erosion.

Tillage and traffic effects on runoff

Traffic and tillage effects on runoff and crop performance on a heavy clay soil were investigated over a period of 4 years. Tillage treatments and the cropping program were representative of broadacre grain production practice in northern Australia, and a split-plot design used to isolate traffic effects. Treatments subject to zero, minimum, and stubble mulch tillage each comprised pairs of 90-m 2 plots, from which runoff was recorded. A 3-m-wide controlled traffic system allowed one of each pair to be maintained as a non-wheeled plot, while the total surface area of the other received a single annual wheeling treatment from a working 100-kW tractor. Rainfall/runoff hydrographs demonstrate that wheeling produced a large and consistent increase in runoff, whereas tillage produced a smaller increase. Treatment effects were greater on dry soil, but were still maintained in large and intense rainfall events on wet soil. Mean annual runoff from wheeled plots was 63 mm (44%) greater than that from controlled traffic plots, whereas runoff from stubble mulch tillage plots was 38 mm (24%) greater than that from zero tillage plots. Traffic and tillage effects appeared to be cumulative, so the mean annual runoff from wheeled stubble mulch tilled plots, representing conventional cropping practice, was more than 100 mm greater than that from controlled traffic zero tilled plots, representing best practice. This increased infiltration was reflected in an increased yield of 16% compared with wheeled stubble mulch. Minimum tilled plots demonstrated a characteristic midway between that of zero and stubble mulch tillage. The results confirm that unnecessary energy dissipation in the soil during the traction process that normally accompanies tillage has a major negative effect on infiltration and crop productivity. Controlled traffic farming systems appear to be the only practicable solution to this problem.

Effects of gall damage by the introduced biocontrol agent Epiblema strenuana (Lep., Tortricidae) on the weed Parthenium hysterophorus (Asteraceae)

Effects of gall damage by the introduced moth Epiblema stremiana on different growth stages of the weed Parathenium hysterophorus was evaluated in a field cage using potted plants with no competition and in naturally regenerated populations with intraspecific competition. Gall damage at early stages of plant growth reduced the plant height, main stem height, flower production, lear production, and shoot and root biomass. All galled, potted plants with no competition produced flowers irrespective of the growth stage at which the plants were affected by galling, but lesser than in ungalled plants. Gall induction during early growth stages in field plants experiencing competition prevented 30% of the plants reaching flowering. However, 6% of the field plants escaped from gall damage, as their main stems were less vigorous to sustain the development of galls. Flower production per unit total plant biomass was lower in galled plants than in ungalled plants, and the reduction was more intense when gall damage was initiated at early stages of plant growth. In potted plants with no competition, the number of galls increased with the plant vigour, as the gall insects preferred more vigorous plants. But in field plants there were no relationship between gall abundance and plant vigour, as intraspecific competition enhanced the negative effects of galling by reducing the vigour of the weed.

Effects of moist chilling and solid matrix priming on germination of loblolly pine (Pinus taeda L.) seeds

Loblolly pine ( Pinus taeda L.) seeds from sources with a mild climate under maritime influence (North Carolina) required shorter moist chilling to achieve maximum germination vigor than seeds from sources with a harsher continental climate (Oklahoma). Solid matrix priming (SMP) for 6 d achieved as much as 60 d of moist chilling to improve rapidity, synchrony and completeness of germination for three of the four families studied. SMP after moist chilling increased the rapidity, synchrony and completeness of germination. The benefit of SMP was greatest for non-stratified seeds and the benefit decreased with length of moist chilling. In general, delaying planting for one week after SMP had minor effects on germination when seeds were kept in the SMP matrix at 4 degreesC. Delayed planting after SMP can increase germination rapidity and synchrony of seeds that have received long moist chilling and reduce the benefit of SMP in non-moist-chilled seeds.

Differential activities of decapeptide agonists of human C5a: the conformational effects of backbone N-methylation

Analogues of the potent, conformationally biased, decapeptide agonist of human C5a anaphylatoxin, C5a(65-74)Y65,F67,P69,P71,D-Ala73 (YSFKPMPLaR, peptide 54), were synthesized with methyl groups occupying specific C5a,, amide nitrogen atoms along the peptide backbone. This N-methylation induced crucial extended backbone conformations in a manner similar to the two Pro residues, but without eliminating the contributions made by the side-chain of the residue for which Pro was substituted. The presence of backbone N-methyl groups on peptide 54 analogues had pronounced detrimental effects on the ability to bind and activate C5aRs expressed on human PMNs, but not on the ability to contract smooth muscle of human umbilical artery. Several N-methylated analogues of peptide 54 (peptides 56, 67, 124, 125, and 137) were significantly more selective for smooth muscle contraction, which is mediated by tissue resident macrophages, than for enzyme release from PMNs. Indeed, peptide 67, YSFKDMP(MeL)aR was almost 3000-fold more selective for smooth muscle contraction than for PMN enzyme release. Consistent with these differential activities was the observation that peptide 67 expressed a significantly greater binding affinity to C5aRs expressed on rat macrophages than on rat PMNs. This differential activity was also observed in vivo in the rat where peptide 67 induced a hypotensive response similar to peptide 54 and rhuC5a, but without accompanying neutropenia. (C) 2001 Elsevier Science B.V. All rights reserved.

The effects of silica fillers on the gelation and vitrification of highly filled epoxy-amine thermosets

Highly filled thermosets are used in applications such as integrated circuit (IC) packaging. However, a detailed understanding of the effects of the fillers on the macroscopic cure properties is limited by the complex cure of such systems. This work systematically quantifies the effects of filler content on the kinetics, gelation and vitrification of a model silica-filled epoxy/amine system in order to begin to understand the role of the filler in IC packaging cure. At high cure temperatures (100 degreesC and above) there appears to be no effect of fillers on cure kinetics and gelation and vitrification times. However, a decrease in the gelation and vitrification times and increase the reaction rate is seen with increasing filler content at low cure temperatures (60-90 degreesC). An explanation for these results is given in terms of catalysation of the epoxy amine reaction by hydrogen donor species present on the silica surface and interfacial effects.

Evaluation of synergistic interactions between the Colorado potato beetle (Coleoptera : Chrysomelidae) pathogen Beauveria bassiana and the insecticides, imidacloprid, and cyromazine

Laboratory studies investigated the interaction between the fungal entomopathogen Beauveria bassiana (Balsamo) Vuillemin and sublethal doses of the insecticides imidacloprid and cyromazine when applied to larvae of the Colorado potato beetle, Leptinotarsa decemlinenta (Say). When second instars were fed potato leaf discs treated with sublethal doses of imidacloprid and a range of doses of B. bassiana, a synergistic action was demonstrated. Similar results were observed when larvae were sprayed directly with B. bassiana conidia and immediately fed leaf discs treated with imidacloprid. No synergistic interaction was detected when larvae were fed leaf discs treated with sublethal doses of imidacloprid 24 h after application of R. bassiana conidia to larvae. However, a synergistic interaction was detected when larvae were fed leaf discs treated with imidacloprid and sprayed with B, bassiana conidia 24 h later. Although sublethal doses of both imidacloprid and the triazine insect growth regulator (IGR) cyromazine prolonged the duration of the second instar, only imidacloprid interacted with B. bassiana to produce a synergistic response in larval mortality. In leaf consumption studies, the highest dose of B, bassiana tested promoted feeding in inoculated second instars. Feeding was inhibited when larvae were fed foliage treated with sublethal doses of imidacloprid and significantly reduced when fed foliage treated with a sublethal dose of cyromazine. Starvation of larvae for 24 h immediately after B. bassiana treatment produced a similar result to the combined treatment of B. bassiana and imidacloprid and increased the level of mycosis when compared with B. bassiana controls. Imidacloprid treatment affected neither the rate of germination of B. bassiana conidia on the insect cuticle nor the rate at which conidia were removed from the integument after application. The statistical analysis used to detect synergism and the possible role of starvation-induced stress factors underlying the observed synergistic interactions are discussed.