Complex assessment of distinct cognitive impairments following ouabain injection into the rat dorsoloateral striatum.

A stroke in humans may induce focal injury to the brain tissue resulting in various disabilities. Although motor deficits are the most discernible, cognitive impairments seem to be crucial for patients mental well-being. The current lack of effective treatments encourages scientists and clinicians to develop novel approaches. Before applying them in clinic, testing for safety and effectiveness in non-human models is necessary. Such animal model should include significant cognitive impairments resulting from brain lesion. We used ouabain stereotactic injection into the right dorsolateral striatum of male Wistar rats, and enriched environment housing. To confirm the brain injury before cognitive testing, rats were given a beam-walking task to evaluate the level of sensorimotor deficits. To determine the cognitive impairment after focal brain damage, rats underwent a set of selected tasks over an observation period of 30 days. Brain injury induced by ouabain significantly impaired the acquisition of the T-maze habit learning task, where 'win-stay' strategy rules were applied. The injured rats also showed significant deficits in the performance of the T-maze switching task, which involved shifting from multiple clues previously relevant to the only one important clue. Focal brain injury also significantly changed 'what--where' memory, tested in the object exploration task, in which a novel object consecutively appeared in the same place while the location of a familiar item was continuously changed. In conclusion, we developed an animal model of distinct cognitive impairments after focal brain injury that provides a convenient method to test the effectiveness of restorative therapies.

[Monte-Carlo-Model for the aerosol bolus dispersion in the human lung--part 1: theoretical model description and application]. / Monte-Carlo-Modell der Aerosolbolusdispersion in der menschlichen Lunge--Teil 1: Theoretische Modellbeschreibung und Anwendung.

Aerosol bolus dispersion, which has excited enormous interest in lung medicine due to its possible use as an efficient toolfor the non-invasive clinical diagnosis of lung function, was simulated by a Monte Carlo model based on the concept of effective diffusivities and a stochastic lung geometry. The mathematical approach enabled the computation of essential characteristics of the exhaled bolus (half width, standard deviation, skewness, and mode shift) as well as the estimation of their dependence upon the volumetric lung depth (VLD) of the inhaled bolus. Results of the dispersion model generally show a very good correspondence with preliminary published experimental data. Half width and standard deviation of the exhaled bolus increase with VLD according to specific functions, whereas skewness and mode shift are subject to a decrease. While no correlation between bolus dispersion and flow rate could be worked out with the model, dispersion linearly increased with total lung capacity (TLC).

[Monte-Carlo-Model for the aerosol bolus dispersion in the human lung--part 2: model predictions for the diseased lung]. / Monte-Carlo-Modell der Aerosolbolusdispersion in der menschlichen Lunge--Teil 2: Modellvorhersagen für die kranke Lunge.

After a mathematical extension of the existing model for the theoretical description of the aerosol bolus dispersion, the behavior of particle pulses in diseased lung structures was simulated. The geometry usedJbr healthy lungs was modified in two aspects: First, a modelling of possible airway obstructions, which usually occur in patients with chronic bronchitis, chronic asthma or cystic fibrosis, was carried out and, second, a theoretical approximation of the emphysema, being observed in lungs of smokers, but also as an accompanying phenomenon in obstructive diseases, was established. According to the modified model, in lungs with airway obstructions the exhaled bolus exhibited a decreased dispersion with respect to healthy subjects, whereas in emphysematous lungs the respective half-width of the peak was increased. Standard deviation and skewness of the bolus were similarly influenced by the modified lung architecture. A combination of airway obstruction and emphysema caused an extensive compensation of individual dispersion effects, complicating a secure distinction from the healthy lung. According to the model, a special diagnostic value may be assigned to the bolus deposition, showing significant deviations from the normal case for all simulated diseases.