Biodegradability of natural dissolved organic matter collected from a UK moorland stream.

The fate of dissolved organic matter (DOM) exported from headwaters is a large uncertainty in global carbon models and catchment biogeochemical process understanding. We examined the biodegradability of stream DOM collected during different flow conditions (n = 12) from a heather-dominated moorland headwater in NE Scotland. Freeze-dried DOM isolates were characterised, re-dissolved to 10 mg C L(-1), inoculated with indigenous stream sediment microbes and incubated, with and without added nutrients, to assess decomposition rates at different times up to 41 days. Biodegradable DOM ranged from 5.0 to 19% of the total transported DOM, representing 8.54 kg C ha(-1) yr(-1) (11.1% of the total DOC flux, calculated as 77.2 ± 39.0 kg C ha(-1) yr(-1)). No simple patterns with flow rate were apparent but accumulated antecedent rainfall, specific UV absorbance of DOM and (15)N content were significant predictors of the proportion of organic matter decomposed. In headwater streams draining organic-rich catchments, in-stream DOM decomposition processes act as a secondary control on the spatial variability of carbon species, and are important for establishing accuracy of aquatic carbon fluxes and cycling budgets. Moreover, biologically-mediated DOM decomposition represents a net 'climate forcing effect' via the soil-stream-atmosphere pathway, drives downstream ecosystem metabolism and should be incorporated in carbon predictive modelling and ecosystem process studies.

The biogeochemical reactivity of suspended particulate matter at nested sites in the Dee basin, NE Scotland.

Variation in the organic matter content associated with suspended particulate matter (SPM) is an often overlooked component of carbon cycling within freshwater riverine systems. The potential biogeochemical reactivity of particulate organic carbon (POC) that affect its interactions and fate, i.e. respired and lost to the atmosphere along river continua or ultimately exported to estuarine and oceanic pools was assessed. Eleven contrasting sites draining nested catchments (5-1837 km(2)) in the River Dee basin, NE Scotland were sampled during summer 2008 to evaluate spatio-temporal variations in quantity and quality (biogeochemical reactivity) of SPM during relatively low flow conditions. Mean SPM concentrations increased from 0.21 to 1.22 mg L(-1) between the uppermost and lowest mainstem sites. Individually, POC concentrations ranged from 0.08 to 0.55 mg L(-1) and accounted for ca. 3-15% of total aqueous organic carbon transported. The POC content was partitioned into autotrophic (2.78-73.0 mg C g(-1) SPM) and detrital (119-388 mg C g(-1) SPM) biomass carbon content. The particulate respired CO(2)-C as a % of the total carbon associated with SPM, measured by MicroResp™ over 18 h, varied in recalcitrance from 0.49% at peat-dominated sites to 3.20% at the lowermost mainstem site. Significant (p<0.05) relationships were observed between SPM biogeochemical reactivity measures (% respired CO(2)-C; chlorophyll α; bioavailable-phosphorus) and arable and improved grassland area, associated with increasing biological productivity downstream. Compositional characteristics and in-stream processing of SPM appear to be related to contributory land use pressures, that influence SPM characteristics and biogeochemistry (C:N:P stoichiometry) of its surrounding aqueous environment. As moorland influences declined, nutrient inputs from arable and improved grasslands increasingly affected the biogeochemical content and reactivity of both dissolved and particulate matter. This increases the potential for recycling of the organic matter that is either transported from upstream or entering further along the riverine continuum.

Application of luminescent biosensors for monitoring the degradation and toxicity of BTEX compounds in soils.

AIMS: To assess the changes in acute toxicity and biodegradation of benzene, toluene, ethylbenzene and xylene (collectively referred to as BTEX) compounds in soil over time and compare the performances of biological and chemical techniques. METHODS AND RESULTS: Biological methods (lux-based bacterial biosensors, basal respiration and dehydrogenase activity) were related to changes in the concentration of the target compounds. There was an initial increase in toxicity determined by the constitutively expressed biosensor, followed by a continual reduction as degradation proceeded. The biosensor with the BTEX-specific promoter was most induced when BTEX concentrations were highest. The treatment with nutrient amendment had a significant increase in microbial activity, while the sterile control produced the lowest level of degradation. SIGNIFICANCE AND IMPACT OF THE STUDY: Luminescent biosensors were able to monitor changes in contaminant toxicity and bioavailability in aqueous extracts from BTEX-impacted soils as degradation proceeded. The integration of biological tests with chemical analysis enables a fuller understanding of the biodegradation processes occurring at their relative rates. CONCLUSIONS: The biological methods were successfully used in assessing the performance of different treatments for enhancing natural attenuation of BTEX from contaminated soils. While, chemical analysis showed biodegradation of parent BTEX compounds in biologically active soils, the biosensor assays reported on changes in bioavailability and potentially toxic intermediate fractions as they estimated the integrative effect of contaminants.

Comparative evaluation of a bioluminescent bacterial assay in terrestrial ecotoxicity testing.

Despite the widespread and successful use of luminescence-based bioassays in water testing, their applications to soils and sediments is less proven. In part this is because such bioassays have mainly been carried out in an aqueous-based medium and, as such, favour contaminants that are readily water-soluble. In this study, aqueous solutions and soils contaminated with heavy metals (HM), polar organic contaminants and hydrophobic organic contaminants (HOCs) were tested using a range of luminescence-based bioassays (Vibrio fischeri, Escherichia coli HB101 pUCD607 and Pseudomonas fluorescens 10586r pUCD607). For the first two chemical groups, the assays were highly reproducible when optimised extraction procedures were employed but for HOCs the bioassay response was poor. Quantitative structure-activity relationships (QSARs) obtained from aqueous solutions had a linear response although correlation for the chemicals tested using bacterial bioassays was significantly less sensitive than that of sublethal tests for Tetrahymena pyriformis. Bacterial and Dendrobaena veneta bioassay responses to extracts from HM amended soils showed that a clear relationship between trophic levels could be obtained. There is no doubt that the wide range of bioluminescent-based bioassays offers complementary applications to traditional testing techniques but there is a significant need to justify and optimise the extraction protocol prior to application.

Degradation and toxicity of phenyltin compounds in soil.

Although the fate of organotins has been widely studied in the marine environment, fewer studies have considered their impact in terrestrial systems. The degradation and toxicity of triphenyltin in autoclaved, autoclaved-reinoculated and non-sterilised soil was studied in a 231 day incubation experiment following a single application. Degradation and toxicity of phenyltin compounds in soil was monitored using both chemical and microbial (lux-based bacterial biosensors) methods. Degradation was significantly slower in the sterile soil when compared to non-sterilised soils. In the non-sterilised treatment, the half-life of triphenyltin was 27 and 33 days at amendments of 10 and 20 mg Sn kg(-1), respectively. As initial triphenyltin degradation occurred, there was a commensurate increase in toxicity, reflecting the fact that metabolites produced may be both more bioavailable and toxic to the target receptor. Over time, the toxicity reduced as degradation proceeded. The toxicity impact on non-target receptors for these compounds may be significant.

Linking biosensor responses to Cd, Cu and Zn partitioning in soils.

Soils bind heavy metals according to fundamental physico-chemical parameters. Bioassays, using bacterial biosensors, were performed in pore waters extracted from 19 contrasting soils individually amended with Cd, Cu and Zn concentrations related to the EU Sewage Sludge Directive. The biosensors were responsive to pore waters extracted from Zn amended soils but less so to those of Cu and showed no toxicity to pore water Cd at these environmentally relevant amended concentrations. Across the range of soils, the solid-solution heavy metal partitioning coefficient (K(d)) decreased (p<0.01) with increasing amendments of Cu and Zn; Cu exhibited the highest K(d) values. Gompertz functions of Cu and Zn, K(d) values against luminescence explained the relationship between heavy metals and biosensors. Consequently, biosensors provide a link between biologically defined hazard assessments of metals and standard soil-metal physico-chemical parameters for determining critical metal loadings in soils.

Is in-stream processing an important control on spatial changes in carbon fluxes in headwater catchments?

Data on small-scale spatial variations in instantaneous fluxes and concentrations of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC) and free carbon dioxide (CO2) are presented for a small acidic headwater stream in NE Scotland. Chloride is used as a conservative element to estimate additional, diffuse inputs of water into the main stem of the stream, other than those from tributaries. Downstream changes in instantaneous carbon fluxes were calculated and then used to estimate losses and gains of carbon within the stream system. Dissolved organic carbon concentrations in the stream ranged from 1.19-6.06 mg l(-1) at its source to a maximum of 10.0-25.3 mg l(-1) as the stream passed through deep peats; DOC concentrations then declined in the lower part of the catchment. DIC concentrations were initially low, increased to 1.5-3.0 mg l(-1) and then decreased to 0.1-1.65 mg l(-1) at the lowest site. Free CO2 concentrations increased from 0.35 mg l(-1) at the stream source to 3.30 mg l(-1) as the stream passed through the peat dominated area. Continually high inputs of CO2-rich water (> 6.0 mg l(-1)) from tributaries maintained these high concentrations in the main stem, until approximately 1.74 km downstream, when there was a rapid decline in concentration. Significant changes in DOC, DIC and CO2 fluxes occur over a distance of 2.7 km downstream from the stream source to the catchment outlet. Between 5.64-41.5 mg C s(-1) as DOC and 2.52-16.2 mg C s(-1) as DIC are removed from the water column. Between 6.81 and 19.0 mg C s(-1) as CO2 is lost along the stream length as progressive equilibration with the atmosphere occurs. We estimate that 11.6-17.6% of the total DOC flux is removed from streamwater by in-stream processes. Dissolved inorganic carbon (HCO3- and free CO2) losses are in excess of nine times its measured flux at the outlet of the catchment. These results suggest that in-stream processing of DOC and DIC and outgassing of CO2 are important controls on the spatial variability of carbon fluxes within headwater streams in upland catchments dominated by organic-rich soils.

A randomized study comparing laparoscopic versus open repair of perforated peptic ulcer using suture or sutureless technique.

OBJECTIVE: This study compares laparoscopic versus open repair and suture versus sutureless repair of perforated duodenal and juxtapyloric ulcers. BACKGROUND DATA: The place of laparoscopic repair of perforated peptic ulcer followed by peritoneal toilet of the peritoneal cavity has been established. Whether repair of the perforated peptic ulcer by the laparoscopic approach is better than conventional open repair and whether sutured repair is better than sutureless repair are both undetermined. METHODS: One hundred three patients were randomly allocated to laparoscopic suture repair, laparoscopic sutureless repair, open suture repair, and open sutureless repair. RESULTS: Laparoscopic repair of perforated peptic ulcer (groups 1 and 2) took significantly longer than open repair (groups 3 and 4; 94.3 +/ 40.3 vs. 53.7 +/ 42.6 minutes: Student's test, p < 0.001), but the amount of analgesic required after laparoscopic repair was significantly less than in open surgery (median 1 dose vs. 3 doses) (Mann-Whitney U test, p = 0.03). There was no significant difference in the four groups of patients in terms of duration of nasogastric aspiration, duration of intravenous drip, total hospital stay, time to resume normal diet, visual analogue scale score for pain in the first 24 hours after surgery, morbidity, reoperation, and mortality rates. CONCLUSIONS: Laparoscopic repair of perforated peptic ulcer is a viable option. Sutureless repair is as safe as suture repair and it takes less time to perform.

Muscarinic autoinhibition of acetylcholine release in mouse atria is not transduced through cyclic AMP or protein kinase C.

1. The present study investigated the second messenger pathways that may mediate muscarinic receptor autoinhibition of acetylcholine release in mouse atria. The stimulation-induced (S-I) outflow of radioactivity from mouse isolated atria incubated with [3H]-choline was Ca(2+)-dependent and tetrodotoxin-sensitive and was used as an index of neuronal acetylcholine release. 2. The cell permeable analogue of cyclic AMP, 8-bromocyclic AMP (1 x 10(-3)M) enhanced the S-I outflow of radioactivity (33%), lower concentrations having no effect. Similarly, the adenylate cyclase activator forskolin (1 x 10(-5)M) had a small facilitatory effect on acetylcholine release. On the other hand the phosphodiesterase inhibitor 3-isobutylmethylxanthine (1 x 10(-4)M) had no effect on the S-I outflow of radioactivity. Together these results suggest that the adenylate cyclase/cyclic AMP system does not have an appreciable role in the modulation of acetylcholine release. 3. The protein kinase C activator phorbol dibutyrate (0.1-3 x 10(-6)M) enhanced the S-I acetylcholine release (maximally by 45%). The effects of phorbol dibutyrate were attenuated by the protein kinase inhibitor staurosporine (1 x 10(-7)M), which by itself had no effect on the S-I outflow of radioactivity. This latter result suggests that there is no tonic activation of protein kinase C during acetylcholine release. 4. Atropine (1 x 10(-7)M) markedly enhanced (232%) the S-I outflow of radioactivity, presumably by preventing feedback inhibition on acetylcholine release through prejunctional muscarinic receptors. This effect is unlikely to involve adenylate cyclase or protein kinase C since it was far greater than the effects of activation of either system with forskolin and phorbol dibutyrate, respectively. Furthermore, the facilitatory effect of atropine was not attenuated by staurosporine, which although a protein kinase C inhibitor, is also an effective inhibitor of cyclic AMP dependent protein kinase (protein kinase A).

A new humidifier.

A new heated water-bath humidifier operates on a new basic principle which overcomes the practical disadvantages of existing systems. A heated hose is used to control a temperature drop along the whole length of the delivery line instead of raising the temperature of the gases in the delivery line as in previous systems. Therefore the tank does not have to fully saturate the gases and a simple, totally cleanable design is possible. A temperature sensor at the delivery point controls the hose heater, constituting a rapid response, low thermal inertia system and delivery temperature is displayed on the unit. Compensation for varying gas flows and ambient temperature changes is inherent and the unit is suitable for neonatal/paediatric and adult use without special adjustment. The tank has a separate reservoir chamber which feeds an evaporation chamber via a cleanable float valve, conferring many advantages including clearly visible water levels, easy filling without breaking the circuit and constant compression volume. Full fail-safe alarm systems are incorporated.

Attack rate of tuberculosis in a 5-year period among close family contacts of tuberculous patients under domiciliary treatment with isoniazid plus PAS or isoniazid alone.

This report from the Tuberculosis Chemotherapy Centre, Madras, considers the risk, over a 5-year period, to close family contacts of sputum-positive patients treated at home for 1 year with a standard regimen of isoniazid plus PAS or one of 3 regimens of isoniazid alone. The attack rate of tuberculosis in the contacts did not appear to be influenced by the treatment received by the patients in the first year or by the duration in the 5-year period for which the patients had (1) positive sputum smears, (2) positive cultures, or (3) isoniazid-resistant cultures. Further, over half the cases of tuberculosis developed in the first year, many of these being in the first 3 months. These findings confirm the conclusions reached from an earlier study, namely, that the major risk to the contacts is from exposure to the infectious patient before diagnosis, and that the risks from the other possible sources of infection (the patient during treatment and the urban environment of Madras) are, in comparison, small.

A controlled study of the influence of segregation of tuberculous patients for one year on the attack rate of tuberculosis in a 5-year period in close family contacts in South India.

This report is the last of a series of nine publications from the Tuberculosis Chemotherapy Centre, Madras, concerning various aspects of an investigation of the role of ambulatory chemotherapy for pulmonary tuberculosis. It presents the attack rates of tuberculosis over a 5-year period of follow-up of close family contacts of patients, all of whom were treated for one year with isoniazid plus PAS, half (selected at random) in sanatorium and half at home. The incidence of active tuberculosis and of tuberculous infections was no greater in the contacts of patients treated at home than in the contacts of patients treated in sanatorium, either in the first year or over the subsequent four years. The major risk to the contacts resulted from exposure to the patient before diagnosis. These findings reaffirm that close family contacts of patients treated at home were at no additional risk of developing tuberculosis, provided the patients received effective chemotherapy. Finally, this study has shown that it is possible in South India to obtain extremely good co-operation from a group of families over a period of several years.

A 5-year study of patients with pulmonary tuberculosis in a concurrent comparison of home and sanatorium treatment for one year with isoniazid plus PAS.

This report from the Tuberculosis Chemotherapy Centre, Madras, summarizes the progress over a 5-year period of 193 patients with newly diagnosed, sputum-positive pulmonary tuberculosis who were admitted to a concurrent comparison of home and sanatorium treatment for one year with isoniazid plus PAS. Previous reports have shown that, despite the traditional advantages of sanatorium treatment-rest, adequate diet, nursing and supervised drug-administration-the home patients responded nearly as well as the sanatorium patients in the first year; further, the relapse rates over a 2-year period of follow-up were similar. The findings in the present report are based on a 4-year period of follow-up and extend these conclusions, the relapse rates over the period being 7% for the home patients and 10% for the sanatorium patients.Patients who failed to respond to treatment in the first year and those who had a bacteriological relapse in the second or subsequent years were usually re-treated with reserve regimens, first with streptomycin plus pyrazinamide and, if this was ineffective, with cycloserine plus ethionamide. Considering the findings over the entire 5-year period, five home patients and three sanatorium patients died from non-tuberculous causes. Of the remainder, 5% of the home patients and 6% of the sanatorium patients died of tuberculosis, 4% in each series had bacteriologically active disease at five years and 90% and 89%, respectively, had bacteriologically quiescent disease at that time. These findings are very encouraging, particularly for developing countries such as India, where tuberculosis is a major problem and sanatorium beds are very few.