Fronto-parietal alpha ERD and visuo-spatial attention in pregnant women.

Many pregnant women report impairments in their attentional capacities. However, comparative studies between pregnant and non-pregnant women using standardised attention paradigms are rare and inconsistent. During attention tasks alpha activity is known to suppress irrelevant sensory inputs and previous studies show that a large event-related desynchronisation (ERD) in the alpha range prior to target-onset predicts enhanced attentional processing. We quantified the relationship between performance (accuracy, response time) in a standardised visuo-spatial attention task and alpha ERD (∼6-12 Hz) as well as saliva estradiol level in fifteen pregnant women (M = 26.6, SD = 3.0 years) compared to fifteen non-pregnant, naturally cycling women (M = 23.1, SD = 4.3 years). Compared to non-pregnant women, alpha frequency was increased in pregnant women. Furthermore, pregnant women showed a greater magnitude of the alpha ERD prior to target-onset and a moderate increase in accuracy compared to non-pregnant women. In addition, accuracy correlated negatively with estradiol in pregnant women as well as with frontal alpha ERD in all women. These correlational findings indicate that pregnancy-related enhancement in alpha desynchronisation in a fronto-parietal network might modulate accuracy during a visuo-spatial attention task.

Benzo[a]pyrene and zinc solubilization by digestive fluids of benthic invertebrates--a cross-phyletic study.

Contaminant bioavailability via digestive exposure was examined for 18 species of marine benthic invertebrates, using incubation of digestive fluids with sediments that were spiked with either radiolabeled benzo-[a]-pyrene (BaP) or zinc. Interphyletic trends in contaminant solubilization were compared with measures of digestive biochemistry, including enzyme activities, surfactancy, pH, and fluid phase organic carbon, amino acids, and lipids. Contaminant solubilization ranged from values equal to that of a seawater control to as much as an order of magnitude higher but were lower than those obtained with commonly used chemical extractants. Digestive fluids from echinoderms and a cnidarian tended to be relatively weak, those from polychaetes and echiurans were relatively strong, and those from taxa such as sipunculans and mollusks were intermediate. These trends correlated strongly with concentrations or activities of digestive biochemicals but not with pH. These correlations are consistent with previous work on mechanisms of digestive solubilization of polycyclic aromatic hydrocarbons (PAH) and metals, though strong covariance among digestive parameters does not allow this approach to be used for identification of specific mechanism(s).

The Kinetics of Bacteriolysis in the Gut of the Deposit Feeder Arenicola marina.

A turbidimetric technique was used to measure the bacteriolytic activities of digestive fluids collected seasonally from the deposit-feeding polychaete Arenicola marina. Lysis of cultured sedimentary bacteria was monitored spectrophotometrically. The kinetics of the lytic reaction were characterized with respect to temperature, pH, reactant concentration, and time. Bacteriolysis generally followed saturation kinetics behavior and was apparently a first-order process with respect to the substrate (bacteria). Deviation from a simple Michaelis-Menten relationship, however, was observed at high substrate levels, at which inhibition of lysis was evident. The lytic rate decreased rapidly and sharply through time as the substrate was depleted. Lytic factors in the gut fluid acted as catalysts; rates increased with concentration of gut fluid, but no depletion in lytic capacity through time was observed. The lytic rate increased exponentially for all seasonal samples over the range of environmental temperatures (4 to 31(deg)C) but showed little relationship with pH under conditions likely to be experienced in situ. The lytic rate also varied among bacterial strains and with culture age.