The hypoxanthine level in cord blood--a potential indicator of foetal hypoxia

Hypoxia is one of the commonest causes of perinatal morbidity and mortality. The worst affected are tissues with high oxygen consumption, in particular nervous tissue (Trojan 1978). Criteria enabling prompt and reliable evaluation of the length and intensity of hypoxia are therefore being sought (Saugstad 1975a,b, Tuchschmidt et al .1981, O'Connor et al. 1981a,b). In recent years, conflicting information has appeared in the literature on the possibilities of utilizing the hypoxanthine and xanthine level in body fluids as an indicator of oxygen deficiency (Saugstad 1975a, Tuchschmidt et al. 1981). We therefore tested this criterion in newborn infants at risk from intrauterine hypoxia.     

Psychophysical principles of discrete event-driven vibrotactile feedback for prostheses

Abstract

Purpose/aim of the study: We aimed to establish psychophysical principles for non-invasive vibrotactile feedback signalling discrete transition events (e.g., extension to flexion) during use of prostheses, especially for the upper limbs.

Materials and methods: Two vibrotactile actuators were used on both upper arms of 10 able-bodied human participants. Absolute thresholds, psychometric functions, and magnitude estimates were measured to equalize the sensation magnitudes for the tested vibrotactile frequencies and skin sites. Then, same-different and pattern recognition tasks were run to evaluate, respectfully, the discrimination and closed-set identification of stimuli with varying parameters (2 frequencies, 2 magnitudes, 2 sites). Finally, parameters of the left/right stimuli were mapped to hypothetical prosthesis events representing object/force and movement type. The stimuli were applied sequentially in accordance with the discrete event-driven feedback paradigm.

Results: Reliable psychophysical models could be established for individual participants as verified by repetitive threshold measurements and relative adjustment of stimulus levels based on sensation magnitudes. Discrimination accuracy was higher for magnitude versus frequency comparisons; and magnitude discrimination accuracy was correlated with magnitude estimate differences. Pattern recognition recall/precision rates decreased from ～0.7 to ～0.5 for sequential delivery of two stimulus patterns to one arm versus to two arms. Using the patterns as two and three consecutive prosthesis events yielded statistically similar performance rates not correlated with magnitude estimate differences.

Conclusions: By careful calibration of stimuli based on psychophysical principles, discrete event-driven vibrotactile feedback can be used to signal manipulated object and movement information with moderate identification rates as shown by confusion matrices.     

Contamination and environmental risk assessment of heavy metals in marine sediments from Tahaddart estuary (NW of Morocco)

Abstract

The distribution, contamination status, and ecological risks of heavy metals in Tahaddart estuary were investigated. 24 surface sediment samples and two cores were collected and analyzed for major (Al and Fe), heavy metals (As, Cd, Cr, Cu, Ni, Pb, and Zn), and grain size composition. The heavy metals assessment was carried out using different environmental indices. The results indicated that the spatial distribution patterns of Al, Fe, and Zn were mainly determined by the distribution of the finer grained fraction (<63?μm) in the sediment. In contrast, As, Cd, Cr, Cu, Ni, and Pb concentrations were controlled by anthropogenic activities (vehicular traffic from Highway Bridge and thermal power plant). The distribution of heavy metals in sediment cores showed an upward enrichment in heavy metals with high concentration found in the uppermost may related to the increasing in human activities. The pollution indexes confirmed that the Tahaddart estuary sediment was considerably to high contaminated by heavy metals near to different anthropogenic inputs. Similarly, the potential ecological risk index and the biological risk index present 21% probability of toxicity posing potential risk to the aquatic organisms. These results provide basic information that can be used to protect and improve the quality of this ecosystem.     

N-acetylcysteine counteracts oxidative stress and protects alveolar epithelial cells from lung contusion-induced apoptosis in rats with blunt chest trauma

The aim of this study was to investigate the protective effects of N-acetylcysteine (NAC) on peroxidative and apoptotic changes in the contused lungs of rats following blunt chest trauma. The rats were randomly divided into three groups: control, contusion, and contusion + NAC. All the rats, apart from those in the control group, performed moderate lung contusion. A daily intramuscular NAC injection (150 mg/kg) was given immediately following the blunt chest trauma and was continued for two additional days following cessation of the trauma. Samples of lung tissue were taken in order to evaluate the tissue malondialdehyde (MDA) level, histopathology, and epithelial cell apoptosis using terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay and active caspase-3 immunostaining. In addition, we immunohistochemically evaluated the expression of surfactant protein D (SP-D) in the lung tissue. The blunt chest trauma-induced lung contusion resulted in severe histopathological injury, as well as an increase in the MDA level and in the number of cells identified on TUNEL assay together with active caspase-3 positive epithelial cells, but a decrease in the number of SP-D positive alveolar type 2 (AT-2) cells. NAC treatment effectively attenuated histopathologic, peroxidative, and apoptotic changes, as well as reducing alterations in SP-D expression in the lung tissue. These findings indicate that the beneficial effects of NAC administrated following blunt chest trauma is related to the regulation of oxidative stress and apoptosis.     

Behavioural response of plant-associated Eurycercus lamellatus (Ö.F. Müller) to different food sources and fish cues

The habitat preference and activity pattern of a large-bodied plant-associated chydorid, Eurycercus lamellatus, were experimentally tested under laboratory conditions using different food sources and fish cues. In the absence of epiphyton, we found significantly higher densities of E. lamellatus on plants when concentrations of phytoplankton were high, while no differences were found for real plants hosting epiphytes. In the absence of predator cues, E. lamellatus preferred plants. Exposure of E. lamellatus to chemical cues released by 0⁺ roach (Rutilis rutilis) previously fed on E. lamellatus or Ceriodaphnia spp. induced a habitat shift from plants to the bottom of the experimental chambers or to the sediment. However, the activity level of the test animals significantly varied between treatments. Test animals were found to be more agitated (as measured by intensity of crawling and jumping activities) in the presence of cues from E. lamellatus-fed roach then when exposed to Ceriodaphnia spp-fed roach. Most likely, the presence of cues from the conspecific E. lamellatus induced the agitated behaviour of E. lamellatus, which may be an attempt to bury within the sediment to avoid predation. Time series experiments in the presence and absence of sediment showed an almost immediate response of E. lamellatus to the addition of fish cues. The animals, however, returned to the plants during the next 7–24 h, most likely reflecting a rapid degradation of the chemical cues. The results suggest a significant influence of chemical cues on the behaviour of plant-associated microcrustaceans in the littoral zones of lakes. This revised version was published online in August 2006 with corrections to the Cover Date.