Biofilm structure and function and possible implications for riverine DOC dynamics

Biofilms are major sites of carbon cycling in streams and rivers. Here we elucidate the relationship between biofilm structure and function and river DOC dynamics. Metabolism (extracellular enzymatic activity) and structure (algae, bacteria, C/N content) of light-grown (in an open channel) and dark-grown (in a dark pipe) biofilms were studied over a year, and variations in dissolved organic carbon (DOC) and biodegradable DOC (BDOC) were also recorded. A laboratory experiment on 14C-glucose uptake and DOC dynamics was also performed by incubating natural biofilms in microcosms. On the basis of our field (annual DOC budget) and laboratory results, we conclude that light-grown biofilm is, on annual average, a net DOC consumer. This biofilm showed a high monthly variability in DOC uptake/release rates, but, on average, the annual uptake rate was greater than that of the dark-grown biofilm. The higher algal biomass and greater structure of the light-grown biofilm may enhance the development of the bacterial community (bacterial biomass and activity) and microbial heterotrophic activity. In addition, the light-grown biofilm may promote abiotic adsorption because of the development of a polysaccharide matrix. In contrast, the dark-grown biofilm is highly dependent on the amount and quality of organic matter that enters the system and is more efficient in the uptake of labile molecules (higher 14C-glucose uptake rate per mgC). The positive relationships between the extracellular enzymatic activity of biofilm and DOC and BDOC content in flowing water indicate that biofilm metabolism contributes to DOC dynamics in fluvial systems. Our results show that short-term fluvial DOC dynamics is mainly due to the use and recycling of the more labile molecules. At the river ecosystem level, the potential surface area for biofilm formation and the quantity and quality of available organic carbon might determine the effects of biofilm function on DOC dynamics.

Geosmin occurrence in riverine cyanobacterial mats: is it causing a significant health hazard?

Toxicity endpoints (nonspecific cytotoxicity, hepatotoxicity, neurotoxicity, immunotoxicity, and mutagenicity) were studied in cyanobacterial mats obtained from a shallow river. Some of the cyanobacterial mats tested were known to be non-geosmin producers, while others were geosmin-producers. No microcystin-like compounds were detected by HPLC in any of the biofilm samples. The mutagenicity and neurotoxicity of biofilm metabolites was negligible, and generally weak adverse effects of biofilm extracts detected in a battery of in-vitro assays indicated relatively low human health risks associated with biofilm toxicity. While the toxicity responses detected in the studied biofilms were weak, effects were not related to production of geosmin. It was therefore concluded that the production of this metabolite cannot be taken as an indication per se of the existence of a health hazard.

Nuisance odours produced by benthic cyanobacteria in a Mediterranean river

Geosmin dynamics in the Llobregat waters were related to the waxing and waning of benthic cyanobacterial mats developing in the river. Geosmin concentration in the water during 2002 reached a maximum of 204 ng L(-1), and coincided with an abundance of cyanobacteria in the river. Cyanobacterial mats were favoured by the high nutrient content of the waters. The cyanobacterial mats experienced a process of growth in thickness (attached forms), until they became unattached and drifted downstream (free-floating forms), accumulating in shallow areas of the river. Geosmin in the biofilm ranged from 0.55 +/- 0.97 ng geosmin per mg DW(-1) in the attached biofilms and 5.25 +/- 4.96 ng geosmin per mg DW(-1) in the free-floating biofilms. While the attached mats could be responsible for the local occurrence of geosmin at a given site, the free-floating mats became a relevant agent for the dispersion of the metabolite downstream. This impression was reinforced by the extremely high correlation between the geosmin content in the free-floating biofilm and in the water (r = 0.917, p = 0.00001). In order to reduce the geosmin concentration and accumulation of the cyanobacterial mats in shallow river waters, the nutrient content should be controlled and the natural flow conditions restored, to prevent the growth and accumulation of the geosmin-producing cyanobacterial mats.

Contrasting effects of organic and inorganic toxicants on freshwater periphyton

This study analyses the factors influencing the response of periphyton communities to toxicants in order to test the validity of the short-term physiological method. The effects of two model compounds, atrazine and zinc, on the photosynthesis of periphyton from different lotic systems were analyzed using short-term toxicity tests. Periphyton communities from seven sites belonging to a relatively small area were used to explore the ecological parameters affecting toxicity in flowing waters. Furthermore, time course studies of zinc toxicity on intact and suspended periphyton were carried out in order to evaluate the significance of periphyton structure (thickness) on toxicity. Atrazine toxicity varied slightly (0.42-2.42 microM) in tests with photosynthesis as an endpoint. Only environmental light was detected to lead to systematic changes in sensitivity of field collected communities. In contrast, the range of EC(10) values for zinc was very broad (7->1000 microM), and mainly related to algal biomass, while also water chemistry (alkalinity) was important. The results of time-course experiments indicated that the penetration of zinc into thick biofilms was limited. The model compounds tested in the present study may exemplify two different situations. In the case of atrazine, the effect on periphyton is easy to predict from the physiological tests used here. On the other hand, zinc toxicity assessed using photosynthesis of periphyton is much affected by many biological and chemical variables. It is concluded that toxicity tests of metals and other organic and inorganic compounds should be based on longer times of exposure.

The effect of copper exposure on a simple aquatic food chain

The effect of copper (44 microg l(-1)) on a simple food chain was studied using indoor experimental channels to identify the changes in periphyton community (metabolism, chlorophyll a content, abundance, composition and lipid and protein content) and in herbivore (Stagnicola vulnerata) growth rate and reproduction. The algal community was sensitive to copper at the beginning but differences between treatments were not significant during the experiment. However, copper affected growth rate, reproduction and embryo hatching on snails. These results indicate that the effects on snails are more sensitive endpoints in assessing sublethal copper toxicity than effects on periphyton.

Variability in zinc tolerance, measured as incorporation of radio-labeled carbon dioxide and thymidine, in periphyton communities sampled from 15 European river stretches

Fifteen European rivers and streams belonging to watersheds in Sweden, the Netherlands, and Spain respectively, were sampled by allowing periphyton to colonize submerged glass substrata. Their zinc tolerances were quantified in short-term laboratory tests, where inhibition of photosynthesis in microalgae and thymidine incorporation in bacterial DNA was measured, and expressed as EC50 values. The variability in zinc tolerances was high reaching 1.5-2.5 orders of magnitude, ranging from 25-8145 microM for photosynthesis and 15-467 microM for thymidine assays. Based on the observed variability, uncertainty factors were estimated for the extrapolation of zinc toxicity data from river to river, both regionally and interregionally. Under the assumption to protect 95% of the observed communities the regional uncertainty factors were 1.7-4.3 and the interregional 2.4-8.6. The sampling sites were characterized in terms of biotope physiography, water chemistry, periphyton biomass, trace element content, and species composition. Multivariate analysis of the data using PLS (Projection to Latent Structure), was used to generate hypotheses about the relation between periphyton zinc tolerance and the 123 so-called predictor variables. Zinc contamination, phosphate, nitrogen nutrients, pH, calcium, bicarbonate, dissolved organic carbon, and various diatom species are important predictors for zinc tolerance in the entire data set representing all 15 river stretches. Regional models suggested that very different factors determined the zinc tolerance in the Swedish and Dutch periphyton. The results are interpreted in terms of Pollution-Induced Community Tolerance (PICT) and the bioavailability of zinc.

Leaf litter dynamics and nitrous oxide emission in a Mediterranean riparian forest: implications for soil nitrogen dynamics

Mediterranean riparian zones can experience severe drought periods that lead to low soil moisture content, which dramatically affects their performance as nitrate removal systems. In the Mediterranean riparian zone of this study, we determined that N2O emission was practically nil. To understand the role of forest floor processes in nitrogen retention of a Mediterranean riparian area, we studied leaf litter dynamics of two tree species, London planetree [Platanus x acerifolia (Aiton) Willd.] and alder [Alnus glutinosa (L.) Gaertn.], for two years, along with soil nitrogen mineralization rates. Annual leaf litter fall equaled 562.6 +/- 10.1 (standard error) g dry wt. m(-2), 68% of which was planetree and 32% of which was alder. The temporal distribution of litterfall showed a two-peak annual cycle, one occurring in midsummer, the other in autumn. Planetree provided the major input of organic nitrogen to the forest floor, and the amount of planetree leaves remaining on the forest floor was equivalent to approximately four years of stock. Leaf litter decomposition was three times higher for alder (decay coefficient [k] = 1.13 yr(-1)) than for planetree (k = 0.365 yr(-1)). Mineralization rates showed a seasonal pattern, with the maximum rate in summer (1.92 mg N kg(-1) d(-1)). Although the forest floor was an important sink for nitrogen due to planetree leaf accumulation, 7.5% of this leaf litter was scoured to the streambed by wind. This loss was irrelevant for alder leaves. Due to the litter quality, the forest floor of this Mediterranean riparian forest acts as a nitrogen sink.

Responses of biofilms to combined nutrient and metal exposure

Numerous studies have reported marked sensitivities of diatom species to phosphate and organic pollution but have ignored interactions with other common contaminants. The aim of the present study was to investigate the single and joint effects of increased phosphate and metal (cadmium, zinc) concentrations on benthic diatom communities. Microalgal biofilms from a relatively unpolluted stream were exposed in the laboratory to Zn, Cd, and P, separately and in combination, in concentrations found at a polluted stream in the same catchment. The Zn concentration reduced algal growth in biofilms more than the Cd concentration. Phosphate compensated for the single effect of each metal but not for their combined effects. Diatom community changes were evaluated using water quality indices based on the empirical sensitivities of taxa to nutrients (TDI) and organic pollution (%PTV). Phosphate exposure resulted in an increase of the eutrophy rank and presumed pollution-tolerant taxa. In contrast, exposure to Zn, Zn+Cd, and Zn+Cd+P caused a marked reduction of the TDI and %PTV community values. The successional trends in the laboratory matched the observed differences in microphyte communities in the reference and polluted river stations. However, the autoecology of the species present also revealed that the resulting composition of diatom communities cannot be attributed solely to the direct toxic effects of metal and nutrients and their interaction. Observed changes in the relative abundance of species are also determined by their growth form and microdistribution in biofilms.

Effects of atrazine on periphyton under grazing pressure

An experiment was carried out using indoor experimental channels to assess the long-term effect (18 days) of herbivores (Physella acuta, Gastropoda) on periphyton communities exposed to low levels of atrazine (14 microg l(-1)). We hypothesized that herbivorism modifies the response of periphyton to atrazine. Carbon incorporation, chlorophyll-a content, biovolume and algal taxonomic composition in the channels that contained atrazine were not significantly different from the control channels (not receiving atrazine). In channels with grazers and atrazine, there was a significant reduction of carbon incorporation and algal density. In this treatment, physiognomic forms and algal composition were significantly different from the others. The biomass of grazers (measured as change in dry mass) was not significantly affected by the addition of atrazine. Grazers maintained low levels of periphyton biomass, enhancing algal cell exposition to toxicant and inhibiting any adaptation of the algae to the toxic exposure. The increase in atrazine toxicity with grazing not only affected the metabolism, but also the structure of the algal community, which suggests that effects were not transient but permanent.

Algal biomass in a disturbed Atlantic river: water quality relationships and environmental implications

Benthic algal biomass was determined at 38 sites along the Oria, a river with intense human activity on its watershed. Water temperature, total suspended solids and nutrient concentration affected algal biomass in different ways. Lower values of algal biomass [(chlorophyll-a concentration and ash-free dry weight (AFDW)] were found in the headwaters and forested tributaries, but also at sites receiving high deposition of solids (due to the outflow from paper mills and quarries). Higher values of algal biomass (both chlorophyll-a and AFDW) were common both in the main stretch of the river and in some tributaries receiving urban sewage outflows. Averages and ranges of temperature and dissolved oxygen concentration were compared for two continuously monitored stations. One of them (forested, nutrient-poor) had low algal biomass, while the second (open, nutrient-rich) showed high chlorophyll-a concentration. Accumulation of algal biomass had environmental implications both in water quality and in the fish diversity of the Oria. Diel variations of dissolved oxygen were much higher (and reached hypoxia) at the site with higher biomass accumulation. The abundance of a fish community (dominated by cyprinids) more tolerant to hypoxia at that site can partly be attributed to the influence of algal biomass accumulation.

[Oncologic treatment of oto-neuro-ophthalmological metastases and their complications]

INTRODUCTION

Cerebral metastases and the sequelae of their treatment are the major cause of neurological symptoms in patients with cancer.

OBJECTIVE

In this article we review the oto-neuro-ophthalmological complications of the treatment of metastases with radiotherapy and/or chemotherapy.

DEVELOPMENT

When speaking of the iatrogenic diseases caused by radiotherapy treatment of metastases, it is important to emphasize that the major complications of this form of treatment are seen in the long term, in general, months or years later. When dealing with incurable diseases, such as most metastatic cancers, the benefit/risk balance of each therapeutic option has to be taken into account. Thus we have a population of patients with symptoms secondary to metastatic involvement, and with an overall life expectancy which may be measured in months. The oto-neuro-ophthalmological toxicity of the chemotherapy may present as an infrequent and unexpected complication or as a usual, expected secondary effect of the drug used. A large variety of drugs are used for the systemic control of cancer (cystostatic drugs, hormones and modifiers of the biological response) which, in one way or another, may cause neurological signs.

CONCLUSION

The increasingly frequent use of high dose chemotherapy and of the combined use of chemotherapy and radiotherapy mean that these types of toxicity have become common clinical syndromes in current oncological practices.

Influence of algal biomass on extracellular enzyme activity in river biofilms

Relationships between biofilm structural components (algal and bacterial biomass) and the activities of some extracellular enzymes that contribute to the ability to degrade organic matter) were explored for six Atlantic and three Mediterranean streams and rivers. The biofilms in these fluvial systems accounted for a wide range of bacterial and algal biomass and colonized the most common benthic habitats. Ratio of bacteria/algae biomass was lower in Atlantic than in Mediterranean streams, but enzymatic activities (β-glucosidase, β-xylosidase, phosphatase) were in general greater in the Mediterranean stream biofilms. Climatic characteristics (especially temperature) may explain the differences in enzymatic activities between biofilms of similar structure but different flow regime. The ratio β-xylosidase: β-glucosidase was similar (around 0.5) for all streams and substrata considered, showing that there is a general higher utilization of cellobiosic than xylobiosic molecules in fluvial systems. In general, highly heterotrophic biofilms showed lower extracellular enzymatic activities than more autotrophic biofilms. Maximum enzymatic activity is achieved when the algal biomass is two- to threefold higher than the bacterial biomass. The relevance of algal biomass on the heterotrophic ability of biofilms may be related to the physical proximity between the two, but also to the high proportion of polymeric carbohydrates included in algal exudates and lysis products, whose use is enzyme-mediated.

Translocation of microbenthic algal assemblages used for In situ analysis of metal pollution in rivers

Effects of metal pollution from a zinc factory on microbenthic algal communities were assessed in three neighboring streams on the Dutch-Belgian border. Diatom species composition was experimentally related to water quality by transferring racks with colonized glass discs from a polluted stream to a reference stream and vice versa. The succession of species and the changes in biomass and metal accumulation were measured during experiments in spring, autumn, and winter. Metal concentrations and dry weight in translocated biofilms tended to conform with those in local biofilms within an incubation time of 14 to 18 days. Bray-Curtis similarity values from the different communities indicated that diatom communities responded more completely to the metal-polluted conditions than to the reference water quality. Cymbella minuta, Diatoma vulgare var. ehrenbergii, Navicula sp., and Melosira varians had a lower percentage in assemblages placed in the metal-polluted streams. In contrast, Pinnularia sp. and Neidium ampliatum decreased in assemblages from the polluted streams that were transferred to the reference stream. Achnanthes minutissima and Navicula seminulum (N. atomus) proliferated on any translocation, possibly reflecting an opportunistic strategy and a high tolerance for Zn and Cd. The behavior of the species in relation to metal pollution generally accorded with observations in the literature. However, it seems that metal tolerance is not the only selective factor, and other ecological variables may also influence the composition of microphytobenthic communities.http://link.springer-ny. com/link/service/journals/00244/bibs/37n1p19.html

Impact of radiotherapy on local control and survival in uterine sarcomas: a retrospective study from the Grup Oncologic Català-Occità

PURPOSE

In order to provide more information for the clinician and to analyze the impact of radiation therapy on the loco-regional disease-free interval (LRFI), disease-free interval (DFI) and specific overall survival (OS), a multicentric retrospective study of uterine sarcomas has been undertaken using cases reported to the Grup Oncològic Català-Occità (GOCO).

PATIENTS AND METHODS

One hundred three patients were selected for this study with a median follow-up period of 49 months. Patients were restaged using the FIGO classification for endometrial adenocarcinoma. Radiotherapy was administered postoperatively to the entire pelvis in 52% of cases (54/103) and was combined with brachytherapy in 24 patients. Mean given dose was 48 Gy, with a 95% confidence interval of 45 to 50 Gy. Variables have been tested for homogeneity between hospitals. Univariate and multivariate analyses have also been carried out.

RESULTS

Mean age of the selected patients was 59 years (range 35-84). Stages were distributed as follows: 66 patients (64%) in Stage I; 16 in Stage II (15.5%); 12 in Stage III (11.5%); 9 patients in Stage IVa (9%). Pathological distribution was 41.5% leiomyosarcoma, 39% mixed Mullerian tumours, 16.5% stromal sarcomas, and 2.9% of a miscellaneous group. Overall survival for the entire group was 63.7% and 56% at 2 and 5 years, respectively. Probability of LRFI reached 59.8% at 2 years and 57.4 at 5 years. The DFI at 2 and 5 years were 52.9 % and 48.7%, respectively. The LRFI probability was 41% and 36% at 2 and 5 years, respectively, without radiotherapy and reached 76% at 2 and 5 years among those patients treated with radiotherapy. There was also an increase in DFI probability because of the effect of radiotherapy, from 35% to 68.5% and from 33% to 53% at 2 and 5 years, respectively. The overall survival probability for patients treated with radiotherapy was 76% and 73% at 2 and 5 years, respectively and 51% at 2 years and 37% at 5 years without radiotherapy. Multivariate analysis demonstrated that radiotherapy improved LRFI, DFI, and overall survival.

CONCLUSION

We conclude that postoperative radiotherapy in our series of patients diagnosed with uterine sarcoma has an impact on loco-regional and disease-free progression intervals and survival.

[Evaluation of an automatic system (MB/BacT) for the isolation of Mycobacterium spp]

BACKGROUND

The study purpose was to evaluate the MB/BacT automated system against Löwenstein-Jensen solid media for the isolation of Mycobacterium species.

METHODS

1,511 specimens were processed from 15/10/96 to 28/4/97. For digestion and decontamination NALC-NaOH was used. Auramine smear was performed and both culture media were inoculated after digestion-decontamination. Inoculation on MB/BacT bottles was performed according to the manufacturer's instructions, apart from a modification in MAS antibiotic supplement with the addition of vancomycin at 1 microgram/ml as final concentraction. Both media were incubated for 40 days at 37 degrees C.

RESULTS

In total 101 (6.6%) mycobacteria species were isolated. 78 M. tuberculosis, 14 M. avium, 6 M. gordonae, 2 M. chelonae and 1 M. fortuitum. 98 (6.4%) Mycobacterium spp. were isolated in MB/BacT and 79 (5.2%) were isolated in Löwenstein-Jensen. 22 (1.4%) out of 101 grew only in MB/BacT and 3 (0.2%) out of 101 grew only in Löwenstein-Jensen. Sensitivity in MB/BacT was 97% compared to 78% in Löwenstein-Jensen, this difference was estatically significant (p < 0.001). Contamination rate was 1.8% in MB/BacT and 13.3% in Löwentein-Jensen. The average time to detection of Mycobacterium spp. was 15.9 days in MB/BacT and 22.4 in Löwenstein-Jensen.

CONCLUSIONS

We believe that MB/BacT is a good system for rapid and reliable detection of Mycobacterium spp.