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.

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.

Event related potentials (ERPs) and behavioral responses: comparison of tonal stimuli to speech stimuli in phonological and semantic tasks.

Event related potentials (ERPs) were recorded from 20 young subjects to auditory target stimuli while they were performing three different tasks, using an oddball paradigm: 1. Tones: Subjects were instructed to respond to a 1 kHz tone, and ignore a 2 kHz tone; 2. Phonological: Subjects were instructed to respond only to pseudowords that had a specific ending ('f"); 3. Semantic: Subjects were instructed to respond to words that belonged to a specific category (animals). EEGs were recorded from 19 electrode sites. Peak amplitude of the early component (N100) did not differ significantly across the three tasks, although N100 peak latency differed significantly across tasks. In contrast, the later endogenous component (P300) was stimulus- and task-dependent. P300 latency differed significantly across stimuli and tasks: 336 ms to target tones; 682 ms to the phonological targets; and 727 ms to target words in the semantic task. P300 amplitude was significantly larger to tones than to speech stimuli. P300 peak amplitude recorded from electrode sites over the left hemisphere to the tonal target stimuli did not differ significantly from that recorded over the right hemisphere. In contrast, P300 amplitude recorded to both the phonological and semantic targets was significantly larger over the left hemisphere than over the right hemisphere at the parietal electrodes. The present results can contribute to our understanding of how humans process linguistic stimuli. These findings emphasize the importance of using similar experimental protocols when conducting broad comparisons of ERPs to a variety of stimuli and tasks.

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.