Population structure and dynamics of Gammarus fossarum (Amphipoda) upstream and downstream from effluents of sewage treatment plants.

Two streams in Germany (Körsch and Lockwitzbach), each with two sampling sites above and below a sewage treatment plant (STP) discharging effluent, were investigated. Sampling sites were characterized, and exposure monitoring for chemicals with known or assumed endocrine disrupting potential was carried out. Both the population structure and the population dynamics of Gammarus fossarum were examined. The physicochemical parameters measured at the sampling sites of the Lockwitzbach and Körsch streams were found not to reach levels having an acute toxic impact on the development of gammarids. The calculated estrogenic potential in the stream water was 22- to 35-fold higher at the downstream site of the Körsch compared with the other sampling sites, mainly because of the concentrations of 17alpha-ethinylestradiol on two sampling dates. At both streams, an influence of the respective STP effluent on the sex ratio of G. fossarum was not observed. Moreover, intersexuality was not induced by these effluents. Differences in the structure and dynamics of G. fossarum populations were more pronounced at the Körsch than at the Lockwitzbach. At the downstream sampling site at the Körsch, gammarids reached their highest abundances. Particularly at the downstream sampling site of the Körsch, the proportion of breeding female gammarids and the proportion of juvenile gammarids in the smallest body length class were decreased compared with upstream. Adult gammarids were larger from the Lockwitzbach downstream site, but they were smaller from the Körsch downstream site compared with the respective upstream site. At the Körsch, the earlier onset of the autumnal reproductive resting period could be caused by the influence of the STP effluent.

Endocrine effects in Gammarus fossarum (Amphipoda): influence of wastewater effluents, temporal variability, and spatial aspects on natural populations.

In a field study, individuals of autochthounous populations of the amphipod Gammarus fossarum were examined for their maturity status, oocyte development, and biochemical parameters associated with their reproductive cycle. Variability in these parameters was related to abiotic exposure parameters varying in accordance to wastewater discharges, stream identity, and time. Patterns of all investigated parameters showed predominantly seasonal rather than spatial influence for both exposure and biologic effects. Single selected-effect parameters, however--such as the maturity index, late vitellogenic oocyte size and atresia, and the hsp90 level--responded to a sewage treatment plant discharge showing an estrogenic potential and also correlated significantly with the concentration of potential xenoestrogens at the different locations.

Effects of terbutryn on aufwuchs and Lumbriculus variegatus in artificial indoor streams.

The effects of the herbicide terbutryn on a simple lotic food web were investigated during a 72-d exposure period in five artificial indoor streams in a greenhouse. The model compound terbutryn, an s-triazine and an inhibitor of photosynthesis, was applied once in each stream at nominal concentrations of 0.6, 6, 60, or 600 microg/L. Terbutryn concentrations in the water were analyzed by gas chromatography/mass spectrometry, and an overall time to 50% dissipation (DT50) of 28 d was calculated. The development of aufwuchs and the population growth and development of the oligochaete Lumbriculus variegatus were investigated. We determined that terbutryn was toxic to L. variegatus at 23.7 mg/L (96-h median lethal concentration [LC50]) and 16.5 mg/L (96-h median effective concentration [EC50]) in static acute toxicity tests. Terbutryn decreased aufwuchs production at 0.6 microg/L in the experimental streams. Population growth of L. variegatus was decreased by 50% at 6 microg/L. The effect of terbutryn on the aufwuchs was a direct effect of decreases in the periphyton. However, the effects on L. variegatus were an indirect effect of terbutryn as a consequence of decrease in the aufwuchs food source and occurred at three-orders-of-magnitude-lower concentrations of terbutryn than the acute toxicity effects. Our study demonstrates the utility of indoor lotic microcosm studies for evaluating both direct and indirect effects of contaminants on aquatic ecosystems.

Artificial indoor streams as a method to investigate the impact of chemicals on lotic communities.

The potential hazard of chemicals on aquatic communities are generally evaluated by standardised single-species bioassays. Safety assessment is based on results gained from organisms adapted to lentic systems and biological interactions in ecosystems are neglected. While lotic communities are often at first in contact with chemicals, it is astonishing that microcosms with lentic communities are mainly used as a bridge between laboratory bioassays and outdoor aquatic systems. Hence, we established five artificial indoor streams to simulate abiotic factors of small rivers. The closed-circuit system was filled with nutrients added to tap water. Washed pebbles were used as sediment. The dynamics of a simple biocoenoses consisting of aufwuchs, Lumbriculus variegatus Asellus aquaticus and Gammarus fossarum was investigated. The dynamic of aufwuchs and periphyton was determined as dry weight and chlorophyll-a, respectively and qualitatively by pigment pattern. The abundance of different developmental stages of L. variegatus was determined at the end of the experiment as well as the population dynamics of G. fossarum and A. aquaticus. Survival rates of gammarids and juveniles per female were investigated and data were used for modelling the population dynamics. The experiment was carried out to investigate the performance of the established artificial streams and the developed approaches to investigate effects of chemicals on a basic lotic community. The prime reason to establish this approach was to close a gap between complex artificial stream systems and laboratory single species tests to assess the impact of chemicals on the aquatic environment.

Isolation, purification, and characterization of newDaphnia-toxic compound from axenicMicrocystis flos-aquae strain PCC7806.

A new compound, that is toxic toDaphnia, called theDaphnia-toxic compound (DTC), was isolated and purified from water extracts ofMicrocystis PCC7806. An establishedDaphnia-bioassay was used as a detection system for the DTC in purified fractions. Temperature and pH stability were used to separate DTC from unstable compounds by changing the pH while the temperature was kept at 90°C. This was followed by ultracentrifugation at 100.000g. A molecular cutoff filtration technique was used to separate compounds with a molecular weight >100,000 Da and to reduce the volume of the fraction that was >500 Da. Evaporation in a vacuum led to a fraction that had a suitable volume for further characterization procedures. DTC was resistant to degradation by two bacteria that were isolated from a laboratory culture. DTC was not inactivated by incubation with protease K or pronase E. A strong anion-exchange resin at the stationary phase of the FPLC equipment was used to purify and concentrate the DTC. The molecular weight determined by gel filtration was between 1.0 and 3.1 kDa. A UV spectrum from this purified fraction exhibited absorption maxima at 220, 260, and 360 nm. The ecological and analytical relevance of the DTC is compared with microcystins.

[A clinico-histological study for the diagnosis and classification of spontaneous periodontal diseases in the dog]. / Klinisch-histologisch kontrollierte Studie zur Diagnostik und Klassifikation der spontanen Parodontalerkrankungen des Hundes.

Using standardized investigation methods periodontal parameters were proved for diagnostic application of spontaneous periodontal diseases in dogs. The diseases are classified in gingivitis simplex, g. granulomatosa, g. ulcerosa, g. hyperplastica, g. desquamativa, juvenile periodontitis, rapidly progressive p. and chronic p. This proposal can be used for further investigations in experimental dentistry and for therapeutic purposes in veterinary dentistry.

Magnetic resonance imaging of brain tumors: application of gadolinium-DTPA and comparison to computed tomography.

In general, CT examinations still seem to be necessary for preoperative classification of brain masses. With increasing experience it should become clear whether sensitivity and specifity of MRI in the diagnosis of brain tumors can be further improved. Although much more work will be necessary in order to establish the optimal dose, timing, and pulse sequences when using Gd-DTPA, this study demonstrates that contrast changes due to Gd-DTPA can have clinical value.

[Treatment of gonorrhea with spectinomycin and penicillin]. / Die Behandlung der Gonorrhoe mit Spectinomycin und Penicillin.

In an open clinical trial, spectinomycin and penicillin G were compared with regard to clinical efficacy, side effects, as well as bacteriological sensitivity in patients suffering from acute gonorrhea. The study was concerned with 176 female patients of a harbor medical practice who were frequently changing partners. 87 out of these patients were treated with spectinomycin, 89 of them with penicillin G. Smear specimens of all patients were tested microscopically; in addition, we performed bacteriological tests (as agar diffusion test, tube dilution test, beta-lactamase test). Both spectinomycin and penicillin showed a good clinical efficacy, except for one case of resistance against penicillin. Afterwards, this patient was successfully treated with spectinomycin. Apart from intermittent pain in the injection area, no side effects have been reported in either group of patients.