Yury Kamenir

Effect of hyperbaric oxygenation on intracranial pressure elevation rate in rats during the early phase of severe traumatic brain injury

Intracranial pressure (ICP) was monitored to evaluate the therapeutic effect of hyperbaric oxygen (HBO(2)) treatment following traumatic brain injury (TBI). This subject is controversial. The aim of our study was to determine whether HBO(2) treatment has a therapeutic effect on ICP dynamics and survival following severe fluid percussion brain injury (FPBI) in rats. Changes in ICP level were analyzed every 30 min during an 8-h monitoring period following trauma and at the end of experiment (20 h). The control (A) and experimental (B) groups consisted of 7 and 4 rats, respectively. Group B was subjected to 1.5 atmospheres absolute (ATA) 100% oxygen for 60 min beginning 2 h after FPBI. No significant differences in ICP were noted between groups A and B before and after HBO(2) treatment until 3.5 h after trauma. At 4 h, for the first time, the difference became significant (P = 0.025; n = 11) and remained significant (P < 0.05) for all measurement points until end of monitoring, when mean ICP values reached 37.17 +/- 14.25 and 20.25 +/- 2.63 mm Hg in groups A and B, respectively. Linear approximation models showed different trends (b1 = 3.80 +/- 0.23; r(2) = 0.65, P < 0.001 and b1 = 1.56 +/- 0.25; r(2) = 0.77, P < 0.001) for groups A and B, respectively. Covariance analysis confirmed significant differences between slopes for groups A and B (F = 148.04, P < 0.001; df = 2,177), i.e., a significant difference in mean rate of ICP elevation. By the end of the experiment, 3 out of 7 rats from group A had died, but none from group B. We conclude that the application of HBO(2) during the early phase of severe FPBI significantly diminished ICP elevation rate and decreased mortality level.

The effect of aging on event-related potentials and behavioral responses: Comparison of tonal, phonologic and semantic targets

OBJECTIVE To investigate age-related changes in speech perception by measuring event-related potentials (ERPs) elicited by auditory stimuli varying in their linguistic characteristics from pure tones to words. METHODS ERPs were recorded from 64 subjects in three age groups (young, middle age and elderly) to auditory target stimuli, using an oddball paradigm. Three different tasks and stimuli were used: tonal, phonological and semantic. RESULTS N100 latency to tonal targets was significantly shorter than to both types of speech targets. P300 latency to tonal targets was significantly shorter than to phonological targets, which in turn was shorter than to semantic targets. P300 amplitude recorded to the speech targets was significantly larger over the left hemisphere than over the right hemisphere in the young subjects. However, the reverse pattern of asymmetry, favoring the right hemisphere was found in the elderly subjects. The pattern of the hemispheric distribution for the middle aged was somewhere in between the young and elderly. CONCLUSIONS The data indicate possible progressive changes in left-right asymmetry in language processing with aging. SIGNIFICANCE Findings may indicate an increased use of compensatory mechanisms for speech processing, or alternatively, an increased use of different generators as individuals age.

The long-term patterns of phytoplankton taxonomic size-structure and their sensitivity to perturbation: A Lake Kinneret case study

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 (1982–1985), 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 (1996–1999), 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.

Stable patterns in size structure of a phytoplankton species of Lake Kinneret

The aim of the study was a search for typical structure patterns of phytoplankton assemblages, based on the long-term dynamics analysis. As a test case we used the interannual phytoplankton variability of Lake Kinneret (Israel). The dominant phytoplankton species (Peridinium gatunense) structure was presented as the frequency-weighted taxonomic size spectrum (TSS) which describes the size distribution of the operational taxonomic unit (OTUj) occurrence frequencies. Using 24 years monitoring data, the TSS annual patterns of P. gatunense were compared. Typical persistent TSS patterns were evident even during years of pronounced deviations from the typical patterns of phytoplankton biomass dynamics and species composition. By correlation analysis, hierarchical cluster analysis and ANOVA the TSS variability was quantified and compared. While the TSS general shape was almost constant, its amplitude variations allowed us to distinguish between three levels of annual bloom intensity.

Phytoplankton dynamics in the Gulf of Aqaba (Eilat, Red Sea): a simulation study of mariculture effects.

The northern Gulf of Aqaba is an oligotrophic water body hosting valuable coral reefs. In the Gulf, phytoplankton dynamics are driven by an annual cycle of stratification and mixing. Superimposed on that fairly regular pattern was the establishment of a shallow-water fish-farm initiative that increased gradually until its activity was terminated in June 2008. Nutrient, water temperature, irradiation, phytoplankton data gathered in the area during the years 2007-2009, covering the peak of the fish-farm activity and its cessation, were analyzed by means of statistical analyses and ecological models of phytoplankton dynamics. Two datasets, one from an open water station and one next to the fish farms, were used. Results show that nutrient concentrations and, consequently, phytoplankton abundance and seasonal succession were radically altered by the pollution originating from the fish-farm in the sampling station closer to it, and also that the fish-farm might even have influenced the open water station.

Disturbance of Opportunistic Small-Celled Phytoplankton in Lake Kinneret

In spite of the chaotic dynamics of specific populations, similarity of annual species-abundance distributions was proven for phytoplankton assemblage during a “stable” period (1985–1994) of Lake Kinneret (Israel). This similarity declined during the “extreme” years (1995–1999) that followed, characterized by explicit changes in the phytoplankton annual-succession pattern. The rank-abundance distributions of species exhibit a pronounced difference between the taxonomically rich central region, producing the reliable assemblage backbone and highly variable tails of a few species. Therefore, the distribution pattern comparison enhances the importance of ubiquitous small disturbances valuable for diagnostics. Some phyla (in this case, Cyanophyta) were especially vulnerable to structural changes. A simple disturbance index was constructed, based on opportunistic small-celled species. The fine-structure disturbances, which can provide early-warning information, are discussed.

The vertical structure of the vegetative canopy of the brown algae Cystoseira (Black Sea)

In the coastal ecosystems of the Black Sea, macrophytobenthos and, in particular, the association of Cystoseira crinite, C. barbata, Cladostephus verticillatus, and Corallina mediterranea, with its thick vegetative canopy (VC), is the key contributor to primary production (PP). Though the vertical structure of the canopy, formed by the algal association, is of principal importance to the PP level, this subject has been long-neglected by researchers. The goal of our work was to compare vertical structures of the vegetative canopy of Cystoseira brown algae under diverse hydrodynamical conditions of the Crimean Peninsula coast. Samples were collected using the 50 cm×50 cm counting frame at eight stations positioned in shallow (55–60 cm deep) sites of Sevastopol Bay (Crimean Peninsula). Dry weight biomass of the VC was determined for all algae assemblage and for each algal species individually, per horizontal surface unit, at each height (Z). The study shows that: 1) the VC is characterized by unimodal vertical distribution of biomass, with maximum estimate in the lower part, where the biomass increases to 85% of the total biomass; 2) a series of single-peaked curves reliably describes the unimodal distribution of the biomass; thalli of different age groups are found along the canopy profile; and 3) algae found in epiphytic synusia prefer inhabiting the upper part of the VC. The role of environmental factors (seawater turbulence and solar radiation) is discussed in reference to the formation of the vertical structure, made up of the associations of the brown algae Cystoseira.

Consistent Patterns of Statistical Distributions in Natural Ecological Communities: Lake Phytoplankton

In spite of the very high time-space heterogeneity of lacustrine phytoplankton, a high level of orderliness of the phytoplankton taxonomic structure was found with the help of several approximation models. Stochastic dynamics of abundances and biomasses often emerges from mathematical models and experiments considering a small number of interacting species. Conversely, some predictable patterns and indices describing aquatic assemblages emerge from large-scale studies. Models with an extremely small number of parameters are discussed, applicable as good approximations for the annual and multi-annual taxonomic-unit distributions of lacustrine phytoplankton. Several statistical models (i.e., rank-abundance, rank-biomass, rank-frequency, and rank-size distributions) of the whole assemblage were built using 8-year monitoring data of Lake Kinneret phytoplankton. Due to the high coefficient of determination of linear regression, long-term geometric-series rank distribution models were selected as the best. Lognormal distributions produced by the scale-free food web lead to an explanatory model based on concepts of the living whirl (G. Cuvier), living matter (V. Vernadsky), and dissipative structures.