Traumatic brain injury (TBI) is known to be accompanied by an increase in intracranial pressure (ICP) and in some cases, by spontaneous generation of cortical spreading depression (CSD) cycles. However, the role of CSD in the pathophysiology of cerebral contusion is still unknown. A multiparametric monitoring assembly was placed on the right hemisphere of the rat brain to evaluate ICP, DC potential, extracellular K(+), cerebral blood flow (CBF), and electrocorticogram in 27 rats during 5 h. Fluid percussion brain injury (FPBI) with the magnitude of the impact 2.9, 3.3, 4.1, and 5.0 atmospheres was induced to the left parietal cortex in animal groups A, B, C, and D, respectively. A slow increase in ICP was evident, and was pronounced in group C and especially in group D, where four of nine animals died during the monitoring. At the end of the 5 h experiment, the mean ICP levels were 6.75 +/- 2.87, 8.40 +/- 2.70, 12.75 +/- 4.03, 29.56 +/- 9.25, and the mean total number of CSD cycles was 2.00 +/- 1.41, 4.29 +/- 4.23, 11.71 +/- 13.29, and 20.11 +/- 19.26 in groups A, B, C, and D, respectively. The maximal level of intensity of CSD cycle generation after FPBI was obtained in group D, where almost constant activity was maintained until the end of the experiment. A significant coefficient of correlation between ICP level and total number of CSD cycles was found for all ICP measurements (r = 0.47-0.63, p < 0.05, n = 27), however more significant (p < 0.001) was the coefficient during the period of monitoring between 2 and 4 h after FPBI. Our results suggest that numerous repeating CSD cycles are typical phenomena in moderate and especially severe forms of FPBI. The rising number of CSD cycles under condition of an ICP level >/=20 mm Hg may demonstrate, with high probability, the unfavorable development of TBI, caused by growing secondary hypoxic insult.

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It is of great theoretical interest and applied importance to assess the structural change of the aquatic community or assemblage as a whole. Size spectrum, a tool allowing such assessment, most often describes the size distribution of organisms, irrespective of their taxonomy. The size-frequency distribution of taxonomic units in an assemblage is applied more and more often as another special case of size spectrum, and is called here traditional taxonomic size spectrum (TTSS). The Lake Kinneret (Israel) phytoplankton database was used to compare two periods of four years each, one typical and one of an extremely abnormal, perturbed community state. All eight annual TTSS curves had a similar pattern. Hierarchical cluster analysis was used to quantify the similarity between TTSS histograms. For the stable period (1982)(1983)(1984)(1985), the similarity measures (Pearson r) between TTSS of any pair of years were close to the 'ideal' value of 1, ranging from 0.927-0.985. For the extremely abnormal period (1996)(1997)(1998)(1999), they had a wider range (0.896-0.980), where the lowest estimates correspond to explicit distortions of the TTSS pattern. So the similarity comparison of TTSS histograms reveals persistent ecosystem characteristics, also giving information on strong perturbations.

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