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At least 127 records · Page 7Linked to original sources

Brown tides and mariculture in Saldanha Bay, South Africa.

In 1997, the brown tide organism, Aureococcus anophageffens, was detected for the first time in Saldanha Bay, South Africa. Its presence was limited to an isolated, tidal dam that was similarly impacted during the late summer of the following two years but not in 2000. Bloom concentrations are typically of the order of 10(-9) cells l-1. This is one of the few reported occurrences of these nuisance blooms outside the north-eastern United States. A small oyster grow-out facility based in the dam has been severely affected by the reduced growth of oysters during these blooms. Reduced flushing of this culture site is a possible explanation for bloom initiation and persistence. However, Aureococcus blooms can be considerably more extensive as was evident during 1998 when the whole of the bay system, including Langebaan Lagoon, was affected for 6-8 weeks during late summer.

Animals↗

Sterol composition of Aureoumbra lagunensis, the Texas brown tide alga.

Aureoumbra lagunensis, the alga responsible for the "Texas brown tide", contains (E)-24-propylidenecholesterol (35.7% of total sterols) as its dominant sterol, in common with other members of the Pelagophyceae. Other major sterols are stigmasterol (22.2%), sitosterol (19.2%), cholesterol (14.1%), and (24R)-24-propylcholesterol (5.2%). Trace amounts of 24-methylenecholesterol, crinosterol, clerosterol, campesterol, dihydrobrassicasterol, and 24-isopropylcholesterol were also detected.

Chromatography, High Pressure Liquid↗

Photosensitizing hemolytic toxin in Heterocapsa circularisquama, a newly identified harmful red tide dinoflagellate.

Red tides of Heterocapsa circularisquama (H. circularisquama), recently identified as a novel species of dinoflagellate, have frequently caused mass mortality of several species of bivalves in Japan, while no harmful effects of this flagellate on fish have been reported so far. We found that the cell-free ethanol extract prepared from H. circularisquama caused hemolysis of rabbit erythrocytes and demonstrated cytotoxic effects in HeLa cells and on the microzooplankton rotifer (B. plicatilis) in a dose- and time-dependent manner. Interestingly, the hemolytic activity and cytotoxic effects of the extract were completely dependent on the presence of light. When the experiments were conducted in the dark, no hemolysis was observed even at very high concentration of the extract. These results suggest that H. circularisquama has photosensitizing hemolytic toxin which can be easily extracted into ethanol. This may be the first report documenting the occurrence of photosensitizing hemolytic toxin in marine phytoplankton species.

Animals↗

Tide-associated biological rhythms of some White Sea littoral invertebrates.

We report the results from two years of laboratory observations of the tide-associated rhythms of activity of White Sea intertidal invertebrates, Mya arenaria (Bivalvia) and Gammarus finmarchicus (Amphipoda). The tidal associated activity of these invertebrates could not be estimate as a clear circatidal clock. Gammarus activity could be phase shifted by a 0.5 h exposure to turbulent water twice a day for 2-3 days. Mya's rhythm could be changed by a single drainage of aquariums lasting about 15 min. This kind of timing system may be a relatively primitive evolution feature.

Activity Cycles↗

Mechanism of superoxide anion generation in the toxic red tide phytoplankton Chattonella marina: possible involvement of NAD(P)H oxidase.

Red tide phytoplankton Chattonella marina is known to produce reactive oxygen species (ROS), such as superoxide anion (O(2)(-)), hydrogen peroxide (H(2)O(2)) and hydroxyl radical (&z.rad;OH), under normal physiological conditions. Although several lines of evidence suggest that ROS are involved in the mortality of fish exposed to C. marina, the mechanism of ROS generation in C. marina remains to be clarified. In this study, we found that the cell-free supernatant prepared from C. marina cells showed NAD(P)H-dependent O(2)(-) generation, and this response was inhibited by diphenyleneiodonium, an inhibitor of mammalian NADPH oxidase. When the cell-free supernatant of C. marina was analyzed by immunoblotting using antibody raised against the human neutrophil cytochrome b558 large subunit (gp91phox), a main band of approximately 110 kDa was detected. The cell surface localization of the epitope recognized with this antibody was also demonstrated in C. marina by indirect immunofluorescence. Furthermore, Southern blot analysis performed on genomic DNA of C. marina with a probe covering the C-terminal region of gp91phox suggested the presence of a single-copy gene coding for gp91phox homologous protein in C. marina. These results provide evidence for the involvement of an enzymatic system analogous to the neutrophil NADPH oxidase as a source of O(2)(-) production in C. marina.

Amino Acid Sequence↗

Olfactory ensheathing cells: ripples of an incoming tide?

Until now, brain and spinal cord injuries that sever nerve fibres have resulted in a degree of incurable functional loss. An incoming tide of research is now beginning to challenge this as yet unbreached sea wall. One of the most promising approaches involves a recently discovered type of cell, the olfactory ensheathing cell, which can be obtained from the adult nasal lining. In animal models transplantation of cultured olfactory ensheathing cells into an injured spinal cord induces regeneration, remyelination of severed spinal nerve fibres, and functional recovery. Although several clinical centres worldwide have shown an interest in applying this approach to patients with spinal cord injury, there is no agreement on cell technology, and claims of beneficial results lack independent confirmation. Important aspects still need to be worked out at the laboratory level. Overall, the outlook is optimistic, but there is still some way to go.

Animals↗

Possible factors responsible for the toxicity of Cochlodinium polykrikoides, a red tide phytoplankton.

Cochlodinium polykrikoides, a harmful red tide dinoflagellate, is highly toxic to fish, but the toxic mechanism is still unknown. Recent study has suggested that C. polykrikoides generates reactive oxygen species (ROS) such as superoxide anion (O(2)(-)) and hydrogen peroxide (H(2)O(2)), and the ROS-mediated ichthyotoxicity has been proposed. In this study, we found that the levels of O(2)(-) and H(2)O(2) detected in C. polykrikoides were trace levels as compared with those of Chattonella marina which is well-known to produce ROS. Furthermore, no significant increase in O(2)(-) generation by C. polykrikoides was observed in the presence of lectins such as concanavalin A (Con A) and wheat germ agglutinin (WGA) or fish mucus prepared from skin and gill of yellowtail, whereas C. marina generated increased level of O(2)(-) responding to these stimuli. Interestingly, the cell-free aqueous extract prepared from C. polykrikoides showed toxic effect on the HeLa cells, but the extract of C. marina had no significant effect. Furthermore, gradual accumulation of polysaccharides in the medium was observed during the growth of C. polykrikoides, and the medium gradually became viscous, but no such changes were observed in the medium of C. marina. These results suggest that multiple factors may be responsible for the toxic mechanism of C. polykrikoides.

Animals↗

Cost-utility analysis of assistive technologies in the European Commission's TIDE Program. Technology Initiative for Disabled and Elderly People.

Socioeconomic evaluation is an issue dealt with in the European Commission's research program TIDE. The principles of cost-utility analysis have been examined for usability in the assessment of rehabilitative technologies. A case study, the choice of a type of wheelchair, is described to demonstrate how estimates of utility can be derived and how cost-utility ratios can be used to guide decision making.

Aged↗

On-line high-performance liquid chromatography-electrospray ionization mass spectrometry for the determination of brevetoxins in "red tide" algae.

On-line high-performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESMS) has been successfully applied to the separation and identification of brevetoxins associated with "red tide" algae. Brevetoxins are toxic polyethers produced by the marine dinoflagellate Gymnodinium breve. They are responsible for fish kills, and they pose certain health risks to humans. The LC-MS method employs reversed-phase microbore HPLC on a C18 column with a mobile phase consisting of 85:15 methanol/water, a flow rate of 8 microL/min, and a postcolumn split ratio of 3:1 (UV absorbance detector/mass spectrometer). A brevetoxin culture sample was found to contain at least six components, including two well-separated peaks corresponding to the brevetoxins PbTx-2 and PbTx-1, as well as several unknown compounds, including one with a molecular mass of 899 Da (possibly an isomer of PbTx-9). The brevetoxin molecules exhibited a high tendency to bind to alkali cations in positive ion ESMS. For standard PbTx-9, PbTx-2, and PbTx-1 brevetoxins analyzed on our LC-MS system, the detection limits (employing mass spectrometer scans of 100 m/z units) were determined to be less than 600 fmol, 1 pmol, and 50 fmol, respectively (S/N = 3); the total analysis time was about 35 min.

Animals↗

Electrospray ionization tandem mass spectrometry for structural elucidation of protonated brevetoxins in red tide algae.

Brevetoxins, the toxic components of "red tide" algae, all share one of two robust polycyclic ether backbone structures, but they are distinguished by differing side-chain substituents. Electrospray ionization mass spectrometry analyses of brevetoxins have shown that the polyether structure invariably has a very high affinity for sodium cations that results in the production of abundant (M + Na)+ ions even when sodium cations are only present as impurities. Because the ionic charge tends to remain localized on the sodium atom and because at least two bonds must be broken in order to produce polycyclic backbone fragmentation, it is extremely difficult to obtain abundant product ions (other than Na+) from (M + Na)+ brevetoxin precursor ions in low-energy collision-induced dissociation (CID) MS/MS experiments. This report establishes that acid additives (oxalic acid, trifluoroacetic acid, and particularly hydrochloric acid) in aqueous methanol solutions can promote high yields of protonated brevetoxin molecules (MH+ ions) for Btx-1, -2, and -9 brevetoxins. Most importantly, unlike their (M + Na)+ counterparts, MH+ precursor ions offer readily detectable product ions in CID MS/MS experiments, even under low-energy collisions. This direct structural characterization approach has provided decomposition information from brevetoxins that was previously inaccessible, including the identification of diagnostic product ions for "type A" brevetoxins (m/z 611) and "type B" brevetoxins (m/z 779, 473, 179) and characteristic ions for Btx-1 (m/z 221, 139), Btx-2 (m/z 153), and Btx-9 (m/z 157, 85). Precursor ion scans and constant neutral loss scans are proposed to enable screening of individual type A or type B brevetoxins present in naturally occurring mixtures.

Animals↗

"@-Tides": the 1,2-dihydro-3(6H)-pyridinone unit as a beta-strand mimic.

The cyclic amino acid surrogate 1 was designed to mimic the extended conformation of a peptide unit and to provide hydrogen bond donor and acceptor functions conducive to beta-sheet formation. A convenient synthesis of this unit and solution and solid-phase methods for its incorporation into an oligomer alternating with peptide units have been devised. The resulting "@-tides", as these oligomers have been designated, show a high propensity for self-association in comparison to oligopeptides; insights into the structure and dynamical properties of their antiparallel dimers have been obtained by NMR.

Kinetics↗

@-Tide-stabilized beta-hairpins.

As minimalist versions of beta-structure, two-stranded beta-hairpins are commonly employed as platforms for assessing the interactions that stabilize beta-sheets in proteins. We have found that the presence of a 1,6-dihydro-3(2H)-pyridinone moiety (the "@-unit") as an amino acid replacement at the i - 1 or i + 4 positions relative to a beta-turn strongly stabilizes the hairpin conformation. Hybrids of this type bridge the gap between natural beta-hairpins and unnatural beta-sheets because the @-unit only replaces one residue in a peptide while stabilizing the hairpin conformation to a greater extent than a normal amino acid. In this report, we describe the synthesis of a variety of @-tide-templated hairpins and the NMR and CD characterization of their conformations in both polar and nonpolar solvents.

Hydrogen Bonding↗

Growth and photosynthesis limitation of marine red tide alga Skeletonema costatum by low concentrations of Zn2+.

The specific growth rate, cell final yields and extracellar carbonic anhydrase activity of the red tide alga Skeletonema costatum increased with increasing concentrations of Zn2+ from 0 to 12 pM, but decreased when Zn2+ was over 24 pM. However, cells grown under high concentrations of Zn2+ had higher activities of intracellular carbonic anhydrase than those grown under low concentrations of Zn2+. Chlorophyll a-specific light-saturated photosynthetic rate (P(Chla)), dark respiration rate (R(chla)) and apparent photosynthetic efficiency (alpha(chla)) significantly increased with increasing concentrations of Zn2+ from 0 to 3 pM, but decreased when increasing concentrations of Zn2+ from 3 to 66 pM. Photorespiration is the lowest when cells cultured in 3 pM Zn2+. The results suggest physiological activity of Skeletonema costatum is very sensitive to the prevailing concentration of Zn2+.

Carbonic Anhydrases↗

Lunar nodal tide and distance to the Moon during the Precambrian.

The pace of tidal evolution for the past approximately 450 Myr implies an Earth/Moon collision some 1,500-2,000 Myr BP, an event for which there is no corroborating evidence. Here we present the first direct determination of the lunar distance in the Precambrian. We interpret a 23.3 +/- 0.3-yr periodicity preserved in a 2,500 Myr BP Australian banded iron formation (BIF) as reflecting the climatic influence of the lunar nodal tide, which has been detected with its modern 18.6-yr periodicity in some modern climate records. The lunar distance at 2,500 Myr BP would then have been about 52 Earth radii. The implied history of Precambrian tidal friction is in accord with both the more recent palaeontological evidence and the long-term stability of the lunar orbit. The length of the Milankovitch cycles that modulate the ice ages today also evolve with the Earth-Moon system. Their detection in the Precambrian sedimentary record would then permit an independent determination of the lunar distance.

Climate↗

Brevetoxicosis: red tides and marine mammal mortalities.

Potent marine neurotoxins known as brevetoxins are produced by the 'red tide' dinoflagellate Karenia brevis. They kill large numbers of fish and cause illness in humans who ingest toxic filter-feeding shellfish or inhale toxic aerosols. The toxins are also suspected of having been involved in events in which many manatees and dolphins died, but this has usually not been verified owing to limited confirmation of toxin exposure, unexplained intoxication mechanisms and complicating pathologies. Here we show that fish and seagrass can accumulate high concentrations of brevetoxins and that these have acted as toxin vectors during recent deaths of dolphins and manatees, respectively. Our results challenge claims that the deleterious effects of a brevetoxin on fish (ichthyotoxicity) preclude its accumulation in live fish, and they reveal a new vector mechanism for brevetoxin spread through food webs that poses a threat to upper trophic levels.

Animals↗

Lipid and fatty acid contents in red tides from tropical fish ponds of the coastal water of South China Sea.

Microplanktonic red tide blooms (dominated by dinoflagellates) were observed in brackish water fish ponds of Terengganu between March 1992 to January 1993. The first short-lived bloom (2-3 days) occurred in October 1992 while the second long-lived bloom (6-7 days) occurred in January 1993. The dominant dinoflagellate species comprised of Peridinium quinquecorne (> 90% total cell count) with considerable proportion of Protoperidinium excentricum. Ciliophora consisting of Tintinopsis sp. and Favella sp. were also present during the bloom period. The total ash, chlorophyll, phaeopigment, lipid and fatty acid content of the microplankton were studied. Considerable amounts (6-11% of the total fatty acid) of the polyunsaturated fatty acid 18:3w3 (linolenic acid) were present in the microplankton. However, high amounts of 20:5w3 (eicosapentanoic acid) and 22:6w3 (docosahexaenoic acid) were present with variable but usually high amounts of 22:4w6 and 22:5w6 acids. The latter microplankton bloom contained higher amounts of 20:5w3 and 22:6w3 acids than the earlier bloom. Lipid content were three to five times higher than chlorophyll a. There was an increase with successive day after bloom outbreak in the relative proportion of total C18, C20, and C22 fatty acid components. The algae microplankton contained the w3-polyunsaturated fatty acids (PUFAs) probably needed for the growth and survival rate of grazing pond animals.

Animals↗

Implications of dinoflagellate life cycles on initiation of Gymnodinium breve red tides.

Florida Gymnodinium breve red tides are initiated in off-shore (approx. 18 to 74 km) coastal waters primarily in late summer-fall months. Past culture studies by W. B. Wilson suggested that this species could have a sexual cycle, inferring the possibility of an alternation of cytological and/or morphological generations. This possibility is further supported by numerous recent advances in dinoflagellate life cycle work which are reviewed in detail. If G. breve has a benthic resting stage (hypnozygote), as is suggested, then seed populations or seed "beds" can possibly be pinpointed and mapped.

Animals↗

Chimeric plastid proteome in the Florida "red tide" dinoflagellate Karenia brevis.

Current understanding of the plastid proteome comes almost exclusively from studies of plants and red algae. The proteome in these taxa has a relatively simple origin via integration of proteins from a single cyanobacterial primary endosymbiont and the host. However, the most successful algae in marine environments are the chlorophyll c-containing chromalveolates such as diatoms and dinoflagellates that contain a plastid of red algal origin derived via secondary or tertiary endosymbiosis. Virtually nothing is known about the plastid proteome in these taxa. We analyzed expressed sequence tag data from the toxic "Florida red tide" dinoflagellate Karenia brevis that has undergone a tertiary plastid endosymbiosis. Comparative analyses identified 30 nuclear-encoded plastid-targeted proteins in this chromalveolate that originated via endosymbiotic or horizontal gene transfer (HGT) from multiple different sources. We identify a fundamental divide between plant/red algal and chromalveolate plastid proteomes that reflects a history of mixotrophy in the latter group resulting in a highly chimeric proteome. Loss of phagocytosis in the "red" and "green" clades effectively froze their proteomes, whereas chromalveolate lineages retain the ability to engulf prey allowing them to continually recruit new, potentially adaptive genes through subsequent endosymbioses and HGT. One of these genes is an electron transfer protein (plastocyanin) of green algal origin in K. brevis that likely allows this species to thrive under conditions of iron depletion.

Algal Proteins↗