Chorotypes of seaweeds from the western Mediterranean Sea and the Adriatic Sea: An analysis based on the genera Audouinella (Rhodophyta), Cystoseira (Phaeophyceae) and Cladophora (Chlorophyta)

The aim of the present paper is to identify the possible existence of groups of species in the genera Audouinella (Rhodophyta), Cystoseira (Phaeophyceae) and Cladophora (Chloropyta) with significantly similar distribution patterns (chorotypes), in the western Mediterranean Sea and the Adriatic Sea. Of the 98 species studied, 59 were grouped into 11 chorotypes, whereas 39 species remained ungrouped. Thirty‐eight species were included in a generalist chorotype, whereas 6 chorotypes were monospecific. The relationships with the environmental factors that could explain the chorotypes are discussed.     

Removal of Prymnesium parvum (Haptophyceae) and its toxins using clay minerals

Laboratory experiments were conducted to examine the ability of several clay minerals from Sweden to remove the fish-killing microalga, Prymnesium parvum Carter, from suspension. In their commercial form (i.e. after incineration at 400 °C), seawater slurries (salinity = 26) of the three minerals tested were generally ineffective at removing P. parvum from culture within a range of 0.01 to 0.50 g/L, and after 2.5 h of flocculation and settling. Dry bentonite (SWE1) displayed the highest removal efficiency (RE) at 17.5%, with 0.50 g/L. Illite (SWE3) averaged only 7.5% RE between 0.10 to 0.50 g/L, while kaolinite (SWE2) kept the cells suspended instead of removing them. Brief mixing of the clay-cell suspension after SWE1 addition improved RE by a factor of 2.5 (i.e. 49% at 0.50 g/L), relative to no mixing. The addition of polyaluminum chloride (PAC, at 5 ppm) to 0.50 g/L SWE1 also improved RE to 50% relative to SWE1 alone, but only minor improvements in RE were seen with SWE2 and SWE2 combined with PAC. In further experiments, P. parvum grown in NP-replete conditions were removed in greater numbers than cells in N- or P-limited cultures, at 0.10–0.25 g/L of SWE1 and 5 ppm PAC. With 0.50 g/L, RE converged at 40% for all three culture conditions. The toxin concentration of NP-replete cultures decreased from 24.2 to 9.2 μg/mL (60% toxin RE) with 0.10–0.50 g/L SWE1 treatment and 5 ppm PAC. A strong correlation was found between cell and toxin RE (r²=0.995). For N-limited cultures, toxin RE ranged between 21 and 87% with the same clay/PAC concentrations, although the correlation between cell and toxin removal was more moderate (r²=0.746) than for NP-replete conditions. Interestingly, the toxin concentration within the clay-cell pellet increased dramatically after treatment, suggesting that clay addition may stimulate toxin production in N-stressed cells. For P-limited cultures, toxin concentration also decreased following clay/PAC treatment (i.e. 36% toxin RE), but toxin removal was poorly correlated to cell removal (r²=0.462). To determine whether incineration affected SWE1’s removal ability, a sample of its wet, unprocessed form was tested. The RE of wet bentonite (SWE4) was slightly better than that of SWE1 (31% versus 17%, respectively, at 0.50 g/L), but when 5 ppm PAC was added, RE increased from 10 to 64% with 0.05 g/L of SWE4, and increased further to 77% with 0.50 g/L. There were no significant differences in RE among NP-replete, N-limited and P-limited cultures using PAC-treated SWE4. Finally, RE varied with P. parvum concentration, reaching a maximum level at the lowest cell concentration (1×10³ cells/mL): 100% RE with 0.10 and 0.50 g/L SWE4 + 5 ppm PAC. RE dropped as cell concentration increased to 1×10⁴ and 5×10⁴ cells/mL, but rose again when concentration increased to 1×10⁵ cells/mL, the concentration used routinely for the removal experiments above. Based on these results, SWE4 with PAC was the most effective mineral sample against P. parvum. Overall, these studies demonstrated that clay flocculation can be effective at removing P. parvum and its toxins only under certain treatment conditions with respect to cell concentration, clay type and concentration, and physiological status.     

Richness, structure and functioning in metazoan parasite communities

Ecosystem functioning, characterized by components such as productivity and stability, has been extensively linked with diversity in recent years, mainly in plant ecology. The aim of our study was thus to quantify general relationships between diversity, community structure and ecosystem functions in metazoan parasite communities. We used data on parasite communities from 15 species of marine fish hosts from coastal Chile. The volumetric abundance (volume of all parasite species per individual host, in mm³) was used as a surrogate for productivity. Species diversity was measured using both species richness and evenness, while community structure was estimated using the co‐occurrence indices V‐ratio, C‐score and a new C‐score_s index standardized for the number of host replicates. After correcting for fish size, 47% of host species show no relationship, 13% show a hump shaped curve and 40% show positive monotonic relationships between productivity and parasite richness across all host individuals in a sample. We obtained a logarithmically decreasing relationship between evenness and productivity for all fish species, and propose a ‘dominance‐resistance’ hypothesis based on immunity to explain this pattern. The stability of the parasite community, measured as the coefficient of variation in productivity among individual hosts, was strongly and positively related to mean species richness across the 15 host species. The C‐score_s index, based on the number of checkerboard units in the host‐parasite presence/absence matrix, increases linearly with mean productivity across the 15 host species, suggesting that parasite communities tend to be more structured when they are more productive. This is the likely reason why linear relationships between richness and productivity were not observed consistently in all fish species. Parasite communities provide some clear patterns for the diversity–ecosystem functioning debate in ecology, although other factors, such as the history of community assembly, may also influence these patterns.     

Regulation of the mechanosensitive cation channels by ATP and cAMP in leech neurons

Single-channel recordings were used to study the modulation of stretch-activated channels (SACs) by intracellular adenosine nucleotides in identified leech neurons. These channels exhibited two activity modes, spike-like (SL) and multiconductance (MC), displaying different polymodal activation. In the absence of mechanical stimulation, internal perfusion of excised patches with ATP induced robust and reversible activation of the MC but not of the SL mode. The ATP effect on channel activity was dose-dependent within a range of 1 μM-1 mM and was induced at different values of intracellular pH and Ca²⁺. The non-hydrolyzable ATP analog AMP-PNP, ATP without Mg²⁺ or ADP also effectively enhanced MC activity. Adenosine mimicked the effect of its nucleotides. At negative membrane potentials, both ATP and adenosine activated the channel. Moreover, ATP but not adenosine induced a flickering block. Addition of cAMP during maximal ATP activation completely and reversibly inhibited the channel, with activation and deactivation times of minutes. However, cAMP alone only induced a weak and rapid channel activation, without inhibitory effects. The expression of these channels in the growth cones of leech neurons, their permeability to Ca²⁺ and their sensitivity to intracellular cAMP are consistent with a role in the Ca²⁺ oscillations associated with cell growth.     

Fishery of the Deep-water Rose Shrimp Parapenaeus longirostris (Lucas, 1846) (Crustacea: Decapoda) in the Northern Tyrrhenian Sea (Western Mediterranean)

The aim of this study is to provide information on the fishing pattern of Parapenaeus longirostris in the northern Tyrrhenian Sea (western Mediterranean), in order to improve the management of the resource in the area. Data were obtained from commercial fishery, covering the period 1991–2002. Catch rates revealed notable inter-annual fluctuation of the P. longirostris landing, probably due to the life cycle of the species. The highest yields (kg per hour of trawl) of the commercial fishery were obtained at depths ranging between 180 and 300 m, the lower ones at depths between 100 and 180 m, where small specimens are more abundant. Commercial catches were characterised by a very low presence of specimens smaller than 20 mm carapace length (CL), mainly due to the deeper localisation of the fishing grounds when compared to the recruitment areas of the species. The size at which 50% of the specimens were discarded by the fishermen was 15 mm CL, while the estimated size at first capture of the individuals caught by the commercial net was 12.4 mm CL.     

Synthesis and characterization of thiocyanato and chlorodioxo tungsten(VI) compounds: Comparative oxygen atom transfer capability with molybdenum analogs

Four new tungsten-oxo(VI) complexes have been synthesized, characterized spectroscopically and their molecular structure established by X-ray diffraction analysis. These bear identical environment as previously reported molybdenum-oxo(VI) complexes, which allowed direct comparison of their spectroscopic properties. Their capability as oxygen atom transfer agents was found to be significantly lower than their molybdenum analogs.     

Identification of a γ-hexachlorocyclohexane dehydrochlorinase (LinA) variant with improved expression and solubility properties

Under aerobic conditions, the enzyme γ-hexachlorocyclohexane dechlorinase (LinA) from Sphingomonas paucimobilis UT26 catalyses the elimination of chlorine atoms from the molecule of γ-hexachlorocyclohexane (γ-HCH) or lindane, a recalcitrant pesticide that is still widely used. In its native metabolic context, LinA starts the biodegradation process of lindane by transforming γ-HCH to 1,2,4 trichlorobenzene (TCB), a less persistent chemical. In an attempt to generate an improved version of this enzyme to be used in lindane bioremediation schemes, we have run an experimental evolution procedure on LinA, using Escherichia coli as the surrogate host. One round of random mutagenesis and subsequent screening for improved dechlorination in vivo sufficed to yield one mutant enzyme (LinAT10), bearing a single substitution C132R, that displayed a two-fold enhanced expression and three-fold enhanced solubility of the enzyme compared to the wild type protein. This resulted in a biological product with a six-fold increase in dechlorination ability when expressed in E. coli. The potential of this protein and its expression system for in situ bioremediation is discussed.     

GABAA Receptors of Cerebellar Granule Cells in Culture: Interaction with Benzodiazepines

GABA_A receptor mediated inhibition plays an important role in modulating the input/output dynamics of cerebellum. A characteristic of cerebellar GABA_A receptors is the presence in cerebellar granule cells of subunits such as α6 and δ which give insensitivity to classical benzodiazepines. In fact, cerebellar GABA_A receptors have generally been considered a poor model for testing drugs which potentially are active at the benzodiazepine site. In this overview we show how rat cerebellar granule cells in culture may be a useful model for studying new benzodiazepine site agonists. This is based on the pharmacological separation of diazepam-sensitive α1 β2/3 γ2 receptors from those which are diazepam-insensitive and contain the α6 subunit. This is achieved by utilizing furosemide/Zn²⁺ which block α6 containing and incomplete receptors.     

The 2-arachidonoylglycerol effect on myosin light chain phosphorylation in human platelets

In human platelets the endocannabinoid 2-arachidonoylglycerol (2-AG) stimulates some important pathways leading to thromboxane B₂ formation, calcium intracellular elevation, ATP secretion and actin polymerisation. The aim of the present study was to examine the 2-AG effect on myosin light chain (MLC) phosphorylation and to investigate the mechanisms involved. We demonstrated that 2-AG induced a rapid MLC phosphorylation, stimulating both the RhoA kinase (ROCK) and MLC kinase (MLCK) in a dose and time-dependent manner. In addition MLC phosphorylation was strengthened through the MLC phosphatase inhibition. MLC phosphatase inhibition was accomplished through the RhoA/ROCK and protein kinase C mediated phosphorylation of MLC phosphatase inhibiting subunits MYPT1 and CPI-17. The presence of CB1 receptor in human platelets and the involvement of CB1 receptor in MLC phosphorylation and MLC phosphatase inhibition was shown.