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.

Effect of the Passy-Muir Valve on aspiration in patients with tracheostomy.

OBJECTIVE: To assess potential benefit of a Passy-Muir Speaking Valve (PMV) in decreasing aspiration in patients with a tracheostomy. BACKGROUND: Many patients with tracheostomy exhibit clinically significant aspiration. It has been previously noted that aspiration can often be reduced or eliminated by plugging or removing the tracheostomy tube. Some patients, however, do not tolerate removal or plugging of their tracheostomy tube, which then leads to persistent aspiration. We postulated that a one-way speaking valve may restore more normal subglottic and glottic air flow and reduce aspiration. METHODS: Alert patients with a tracheostomy and clinical evidence of aspiration were eligible for study. Eleven patients with tracheostomy and known aspiration were studied with a modified barium swallow. Radiographic examination was used to evaluate the presence and amount of aspiration while patients swallowed both with and without a PMV in place on their tracheostomy tube. RESULTS: Aspiration was reduced (or eliminated) during swallowing in all 11 patients when they wore a PMV, when compared to swallowing with an open (unvalved) tube. This improvement was achieved with liquids, semisolids, and pureed consistencies. CONCLUSION: This study demonstrates that a Passy-Muir speaking valve facilitated swallow and reduced aspiration in patients with a tracheostomy and known aspiration.

A comparison of lexical-semantic impairments in left hemisphere stroke and Alzheimer's disease.

Patients with aphasia due to left hemisphere stroke and patients with Alzheimer's disease, who were matched for severity of naming impairment, were compared on tests of lexical-semantic processing. The results suggest that the lexical-semantic impairments in both groups are due to a combination of impaired access to, and loss of, lexical-semantic information, but that impaired access is more prominent in stroke patients, whereas Alzheimer's disease patients suffer a greater loss of information. The results are discussed in terms of a brain model of the storage and processing of lexical-semantic information, and with respect to implications for treatment strategies.

Contrast media-induced side effects on excitation and conduction of electrical activity in the heart on intracardiac application. Investigations in anaesthetized dogs.

In several series of experiments with intracardiac application in anaesthetized dogs, the following contrast media were tested for their adverse effects on excitation and conduction of electrical activity in the heart. Diatrizoate, lysine-diatrizoate, lysine-sodium-diatrizoate, ioxaglate, iopamidol, iodamide, ioxitalamate, ioglicinate and metrizamide. Blood pressure and, using the His' bundle-ECG technique, the parameters P0-P1 (heart rate), A1-H1 period (conduction time in the AV-node), and H1-V1 period (conduction time in the TAWARA branches) were measured. A statistical correlation exists between osmolarity and blood pressure (higher osmolarity causes a greater decrease in blood pressure), as well as between osmolality and decrease in heart rate (higher osmolarity causes a greater decrease in heart rate). The delay in conduction time in the AV-node correlates only with viscosity and sodium content (increased viscosity with increased sodium content delays the time of conduction). A tendency towards delay in conduction in the TAWARA branches could not be correlated to any one of the physico-chemical parameters studied.