Benthic marine and blue-green algal species as a source of choline.
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Animal Feed↗
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Inhibitory activity on lipid peroxidation of extracts from marine brown alga.
Several extracts from marine brown alga Sargassum micracanthum (Kuetzing) Endlicher were screened for their inhibitory activity on lipid peroxidation. In an in vitro study, methanol extract (Sm-M), chloroform/ methanol (3:1) extract and ethyl acetate fraction of Sm-M inhibited lipid peroxidation in rat liver homogenates. The IC(50) values were 0.70, 0.70 and 0.37 micro g/mL, respectively. These inhibitions were stronger than vitamin C and E. These extracts showed reductive activity on DPPH, the IC(50) values were 34, 37 and 11 micro g/mL, respectively. In an in vivo study, Sm-M had the effect on CCl4 induced liver injury in rats and Sm-M (120-1200 mg/kg, p.o.) lowered dose-dependently the level of lipid peroxidation in liver.
Animals↗
Biological activity of Spatoglossum asperum: a brown alga.
Chloroform and methanol fractions of an ethanol extract of Spatoglossum asperum showed antifungal activity against the highly destructive plant pathogen, Macrophomina phaseolina while the n-hexane fraction showed activity against Rhizoctonia solani and Fusarium solani. n-Hexane and methanol fractions also showed nematicidal activity against the plant parasitic nematode, Meloidogyne javanica. Column chromatography of the ethanol extract of seaweed yielded oily fractions named SA-I to SA-VI. GC-MS data of these oily fractions showed the presence of various fatty acid esters. Some of these oily fractions exhibited strong antifungal and nematicidal activities. Oily fractions of S. asperum also showed hypolipidaemic activity in normal, triton-induced and high fat diet-induced hyperlipidaemic rats without producing any ill effect on cardiac and liver enzymes.
Animals↗
Inhibitory activity on HIV-1 reverse transcriptase and integrase of a carmalol derivative from a brown Alga, Ishige okamurae.
The bioassay-directed isolation of a marine brown alga, Ishige okamurae, afforded a carmalol derivative, diphlorethohydroxycarmalol. This compound exhibited inhibitory effects on HIV-1 reverse transcriptase and integrase with IC(50) values of 9.1 microM and 25.2 microM, respectively. However, diphlorethohydroxycarmalol did not show an inhibitory activity against HIV-1 protease. Moreover, diphlorethohydroxycarmalol nonaacetate obtained by acetylation and fucosterol failed to show any inhibitory activity against these viral enzymes.
Anti-HIV Agents↗
Analysis of lipids in crude extracts by 13C nuclear magnetic resonance.
Phospho- and glycolipids with mono- or polyunsaturated fatty acid chains, free and acylated steroids, carotenes and carotenoids, chlorophylls, and related pheophytins were detected in crude extracts by NMR spectroscopy without any need for prior separation. A broad range of molecules belonging to different lipid classes could be identified in one-dimensional 13C NMR spectra obtained by applying a polarization transfer pulse sequence (DEPT 135 degrees). Directly detected or 1H-detected two-dimensional heterocorrelated NMR experiments were performed to facilitate the assignment of peaks arising from carotenoids, unsaturated fatty acid chains, and chlorophylls. 13C NMR data of crude lipid extracts from the macroalagae Ulva rigida and Fucus virsoides are shown to yield an informative overview of their lipid content. NMR is thus proposed as a simple, nonselective, and nondestructive technique for the first screening of the main lipid classes in complex lipid mixtures.
Carbon Isotopes↗
The extrinsic proteins of photosystem II in photosynthetic organisms: distribution, properties and evolutionary implications.
Photosystem II from higher plant chloroplasts contains extrinsic proteins of molecular weights 33, 23 and 16 kDa. Cyanobacteria, which are thought to be closely related to the evolutionary progenitor of chloroplasts, have a protein homologous to the largest of these, but lack homologues of the smaller ones. Here we report immunological evidence for the occurrence of the 33 kDa extrinsic protein in red and chromophyte algae and its absence from anoxygenic photosynthetic bacteria. The 23 kDa protein was absent from all three groups. The red algal protein was found to be hydrophilic and rather more loosely associated with the thylakoid membrane than its higher plant equivalent. These findings support an origin for all plastids among the oxygenic prokaryotes, in contrast to the phylogeny inferred from ribulose bisphosphate carboxylase-oxygenase sequence data.
Biological Evolution↗
Retinal identification in Pelvetia fastigiata.
Unidirectional blue light directs the rhizoid-thallus axis in the apolar zygote of the brown alga Pelvetia fastigiata. This effect is mediated by an increase in the intracellular concentration of cGMP. Here, we show the extraction, purification and identification of 1 microgram of all-trans retinal from 1.2 x 10(6) Pelvetia zygotes. The number of retinal molecules per cell was about 4 x 10(9). Since retinal, wherever present, is exclusively associated with an opsin to form a light sensitive complex (rhodopsin-like proteins), and since the physiological response originated by this protein produces a variation of cGMP concentration, this new finding suggests that a rhodopsin-like protein could be the photoreceptor in this brown alga.
Chromatography, High Pressure Liquid↗
Intracellular pH and its regulation in Pelvetia zygotes.
We have investigated the role of intracellular pH (pHi) in early plant development using ion-selective microelectrodes to record from eggs and embryos of the brown alga Pelvetia. Temporal changes in pHi were investigated by recording from zygotes at all stages of the first cell cycle. pHi was 7.57 +/- 0.09 in recently fertilized eggs, but decreased by approximately 0.2 units a few hours postfertilization. Proton motive force (pmf) was also monitored and found to be less than -50 mV throughout the first cell cycle. Because of the low pmf values, we suggest that secondary active transport is probably not coupled to H+, and instead we propose that solute transport is driven by the Na+ electrochemical potential. Zygotes strictly regulated pHi over a wide range of extracellular pH (pHo); pHi varied by less than 0.2 units over pHo values from 6.2 to 9.2. Inhibitor studies were conducted to investigate the mechanism of regulation. Agents known to inhibit the H(+)-ATPase (antimycin A, KCN, carbonylcyanide m-chlorophenylhydrazone, N,N'-dicyclohexylcarbodiimide, and erythrosin B) caused marked cytoplasmic acidification. Addition of amiloride, an inhibitor of Na+/H+ antiport, also resulted in acidification, as did removal of NaCl from the medium. By contrast, increasing extracellular NaCl concentration caused transient alkalinization of the cytoplasm. Taken together, these results indicate that proton pumping by an H(+)-ATPase and Na+/H+ antiporter contribute to pH regulation.
Amiloride↗
Pronuclear positioning and migration during fertilization in Pelvetia.
The position and migration of egg and sperm pronuclei were studied in the brown alga Pelvetia. The egg pronucleus was located near the center of the cell before and after fertilization and, unlike pronuclei in animal eggs, did not migrate. Inhibitor studies indicated that anchoring of the egg pronucleus in the cell center was dependent on microtubules and microfilaments. An extensive array of microtubules, many of which extended into the actin-rich egg cortex, was associated with the egg pronucleus. Migration of the sperm pronucleus was investigated quantitatively in both living and fixed zygotes. Migration occurred linearly at rates from 0.11 to 0.29 microns/min and was oriented directly toward the egg pronucleus in the cell center. Sperm penetration was inhibited by cytochalasin D, which disrupts F-actin function, whereas sperm pronuclear migration was sensitive to the microtubule-depolymerizing drug, nocodazole. Microtubules associated with the migrating sperm pronucleus formed a sperm trail that terminated at the egg cortex. As these were the only microtubules associated with the sperm at early stages of migration, we conclude that they provide the force for migration.
Cell Nucleus↗
Cell wall and rhizoid polarity in Pelvetia embryos.
The developmental potentials of the rhizoid and thallus cells of two-celled Pelvetia embryos were investigated. Ablation of either the thallus or the rhizoid cell was accomplished by puncture with a micropipette. Thallus cells continued to divide repeatedly after rhizoid ablation, and in no case did the thallus initiate new rhizoid growth. In the reciprocal experiment, rhizoid cells elongated and divided in the normal transverse orientation after ablation of the thallus cell. The rhizoid did not appear to initiate a new thallus. Similar results were obtained when laser irradiation was applied to arrest division in one of the two cells. Thus, neither thallus nor rhizoid cell compensated for ablation or arrest of its sibling cell. The role of the cell wall-plasma membrane connections in organizing polar growth in the rhizoid cell was investigated by separating the wall from the protoplast. This was accomplished in two ways, by plasmolysis and by enzymatic wall digestion. Wall digestion yielded rhizoid cell protoplasts capable of wall regeneration and division, but the polar growth habit was irreversibly lost. Loss of polar growth correlated with loss of polarity in the microtubule cytoskeleton as visualized by indirect immunofluorescence using confocal microscopy. Transient plasmolysis of rhizoid cells resulted in abandonment of the preexisting apex and the initiation of a new rhizoid tip after rehydration. We suggest that interaction between the cell wall and the plasma membrane is involved in organizing polar growth.
Cell Division↗
Spatial redistribution of poly(A)+ RNA during polarization of the Fucus zygote is dependent upon microfilaments.
Asymmetrical distribution of mRNA has been associated with polarization and cell fate determination during early development of animal embryos. In this report we determine the distribution pattern of poly(A)+ RNA during early embryogenesis of the brown alga Fucus. Poly(A)+ RNA is symmetrically distributed in the egg and early zygote. Shortly after the polar axis is established, poly(A)+ RNA becomes segregated to the thallus pole of the zygote. Following cytokinesis, most of poly(A)+ RNA is partitioned into the thallus cell. We show that the spatial redistribution of poly(A)+ RNA requires intact microfilaments and the fixation of the polar axis, but is not dependent upon polarized growth of the rhizoid, intact microtubules, or orientation of the division plane.
Cell Division↗
The coupling of cyclic GMP and photopolarization of Pelvetia zygotes.
Unidirectional blue light directs the rhizoid-thallus axis in the apolar zygotes of Fucus and Pelvetia. Here, it is shown that blue light (but not red light) increased cyclic GMP levels of Pelvetia zygotes by about a factor of 2. When the increase in cyclic GMP was blocked by a guanylyl cyclase inhibitor, photopolarization was also blocked. Bathing the cells in a permeant cyclic GMP analog, which should tend to collapse intracellular cyclic GMP gradients, reduced the degree of photopolarization. Growing the cells in the dark in a gradient of the analog caused the rhizoids to tend to form on the low concentration side. It appears that the stimulation of the blue light photoreceptors on the side nearer the light activates guanylyl cyclase and results in a transcytoplasmic cyclic GMP gradient that is necessary for polarization.
1-Methyl-3-isobutylxanthine↗
Alignment of centrosomal and growth axes is a late event during polarization of Pelvetia compressa zygotes.
Zygotes and embryos of the fucoid brown alga Pelvetia compressa undergo a series of asymmetric cleavages. We are interested in the developmental role of these cleavages and the mechanism controlling their alignment. To assess the importance of division plane alignment, the orientation of the first asymmetric division was altered and the effects on subsequent embryo elongation rates were analyzed. Although this division is normally oriented transversely (90 degrees) to the growth axis, deviations up to 45 degrees had no significant effects on embryo elongation. However, division planes that were parallel with the growth axis (0-45 degrees) had drastic effects. Embryo elongation was severely inhibited and the wall often bifurcated and avoided the rhizoid tip. The orientation of the division plane is determined by the position of the centrosomes. We therefore investigated centrosomal position and function during the first cell cycle within the three-dimensional context of the cell. We found that, after karyogamy, microtubule organization changed from a radially symmetric circumnuclear array into a bipolar centrosomal array. The reorganization coincided with the migration of the centrosomes around the nucleus. The centrosomes separated slowly and asynchronously until they reached opposite sides of the nuclear envelope. At this time the centrosomal axis, defined by the position of the two centrosomes, was oriented randomly with respect to the cortical growth axis. The centrosomal axis then rotated into alignment parallel with the growth axis late in the first cell cycle. These results indicate that the growth axis and the centrosomal axis develop independently of each other and that the centrosomal axis does not align with the growth axis until just prior to mitosis.
Cell Cycle↗
Inhibition of the establishment of zygotic polarity by protein tyrosine kinase inhibitors leads to an alteration of embryo pattern in Fucus.
Fucoid algae, including the genus Fucus and Pelvetia, are recognized as model systems to study early embryogenesis in plants. In particular the zygotes of these fucoid algae are highly suitable experimental systems for investigating the establishment of polarity and its requirement for later embryogenesis. However, the transduction pathways involved in the initiation of polarization are still poorly understood, and the link between the early polarization processes and embryo long-term patterning has never been experimentally demonstrated. We, therefore, have investigated the putative role of protein phosphorylation in the regulation of early embryogenesis, using a combined pharmacological and biochemical approach. Among the various protein kinase inhibitors tested, a subset of well-known PTK inhibitors, including genistein, prevented germination but had no effect on growth of germinated zygotes and embryos. Inhibition of germination appeared to be a direct consequence of prevention of polarization since genistein and other PTK inhibitors specifically inhibited axis formation in a light-independent manner. Genistein inhibited cellular events associated with polarization such as polarized secretion of cell wall sulfated compounds. Anchorage of F-actin at the rhizoid pole was also inhibited and F-actin redistributed in response to a new light vector. Zygotes inhibited in the polarization process over the period of axis formation recovered from the treatment and displayed differentiated cellular structures after a few days. However, they exhibited a deeply disorganized pattern, suggesting that the early polarization process is essential for normal patterning of the embryo. Western blot analysis of protein phosphorylation showed that the patterns of protein phosphorylation changed during development and were disturbed by treatments with genistein. This drug also inhibited in vitro autophosphorylation. The nature of the genistein-sensitive kinases required for polarization and long-term patterning is discussed in light of these data.
Actins↗
Cortical actin filaments form rapidly during photopolarization and are required for the development of calcium gradients in Pelvetia compressa zygotes.
Previous research has shown that cortical gradients of cytosolic Ca(2+) are formed during the photopolarization of Pelvetia compressa zygotes, with elevated Ca(2+) on the shaded hemisphere that will become the site of rhizoid germination. We report here that the marine sponge toxin, latrunculin B, which blocks photopolarization at nanomolar concentrations, inhibited the formation of the light-driven Ca(2+) gradients. Using low concentrations of microinjected fluorescent phalloidin as a tracer for actin filaments, we found that exposure to light induced a striking increase in actin filaments in the cells as indicated by an increase in fluorescence. The increase was quantified in the cortex, where it was most apparent, and the fluorescence there was found to increase by about a factor of 3. This increase in cortical phalloidin fluorescence was inhibited by latrunculin B at the same concentration required to inhibit Ca(2+) gradient formation and photopolarization. The distribution of the increasing phalloidin fluorescence was uniform with respect to the developing rhizoid-thallus axis during the formation of the axis, and no intense patches of fluorescence were observed. After germination, fluorescence suggestive of an apical ring of actin filaments was seen near the rhizoid tip. Finally, inhibitor studies indicated that myosin may be involved in the photopolarization process.
Calcium↗
The ecotoxicity of chlorate to aquatic organisms: a critical review.
In order to assess the risk posed by chlorate in aquatic ecosystems, data on the effects of chlorate on aquatic organisms (microorganisms, algae, invertebrates, and fish) and mesocosm studies have been collated and critically reviewed. The geometric mean E(L)C50 values for both freshwater and marine species were (as ClO3-): microorganisms, 38,583 mg.liter-1; microalgae, 563 mg.liter-1; invertebrates, 2442 mg.liter-1; fish, 3815 mg.liter-1. Marine macro red algae were insensitive to chlorate, whereas marine macro brown algae (e.g., Fucus sp.) appeared to be exceptionally sensitive to chlorate, adverse long-term effects having been reported at concentrations as low as 0.015 mg ClO3-.liter-1. Evidence for the mechanism by which chlorate is thought to be particularly toxic to these species is also reviewed. It is concluded that, based on the species reported, chlorate is nontoxic (acute toxicity > 100 mg.liter-1) to most of the freshwater and marine species examined. However, chlorate is highly toxic (acute toxicity < 0.1 mg.liter-1) to certain macro brown algal species. For macro brown algae, the NOEC after 6 months was reported to be approximately 0.005 mg ClO3-.liter-1. It is also concluded that an improved understanding of the actual mode of action of chlorate in sensitive species is desirable. Together with further information on the environmental fate of chlorate, this will improve the risk assessment for chlorate in the aquatic environment.
Animals↗
Toxicity of chlorate and chlorite to selected species of algae, bacteria, and fungi.
The present study confirms that chlorate is toxic only to brown algae and not to species of other ecologically relevant taxa. The brown alga Ectocarpus variabilis exhibited a LOEC of 0.005 mM (0.4 mg ClO3-/liter) and an LC50 of 0.012 mM, when cultured with nitrate as a sole source of nitrogen. The toxicity to species other than brown algae as measured in growth inhibition tests ranged from 0.75 mM (96-h NOEC) for Selenastrum capricornutum to > or = 7.48 mM (48-h NOEC) for the fungus Trichoderma hamatum. The nitrogen source, nitrate or ammonium, did not significantly influence the toxicity to the nonsensitive species. The tests on brown algae found that as compared with ammonium, the toxicity to nitrate-grown cultures is higher by a factor of about 10. This confirms the hypothesis that nitrate reductase is involved in the toxic effects of chlorate on brown algae. Chlorite, tested as a potential toxic metabolite of chlorate, demonstrated high toxicity to many of the taxa tested and only low toxicity to E. variabilis. It may be concluded that brown algae are exceptionally sensitive to chlorate. It may also be concluded that various nitrogen sources could not induce toxicity in nonsensitive species. From these experiments no conclusions could be drawn as to the potential role of chlorite in chlorate toxicity. Furthermore it may be concluded that E. variabilis is a suitable laboratory test species for further investigations into the mechanism of chlorate toxicity to brown algae.
Bacteria↗
Kinetic study of metal biosorption to a brown alga, Kjellmaniella crassiforia.
A kinetic study of cadmium and lead biosorption to a brown alga, Kjellmaniella crassiforia, was carried out. The shrinking core model derived by M. Gopala Rao and A. K. Gupta (Chem. Eng. J.24, 181, (1982)) was modified and adapted for description of the rate process of cadmium and lead biosorption to the alga. The biosorption rate process was well described and average apparent diffusion coefficient of about 9 x 10(-6) cm(2) s(-1) was found for both cadmium and lead ions. The value was 20 to 50 times higher than the apparent diffusion coefficients of cadmium and lead ions in strong-acid resins like Dowex 50W-X8.
Adsorption↗