Growth characteristics of Heterosigma akashiwo virus and its possible use as a microbiological agent for red tide control.
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The growth characteristics of Heterosigma akashiwo virus clone 01 (HaV01) were examined by performing a one-step growth experiment. The virus had a latent period of 30 to 33 h and a burst size of 7.7 x 10(2) lysis-causing units in an infected cell. Transmission electron microscopy showed that the virus particles formed on the peripheries of viroplasms, as observed in a natural H. akashiwo cell. Inoculation of HaV01 into a mixed algal culture containing four phytoplankton species, H. akashiwo H93616, Chattonella antiqua (a member of the family Raphidophyceae), Heterocapsa triquetra (a member of the family Dinophyceae), and Ditylum brightwellii (a member of the family Bacillariophyceae), resulted in selective growth inhibition of H. akashiwo. Inoculation of HaV01 and H. akashiwo H93616 into a natural seawater sample produced similar results. However, a natural H. akashiwo red tide sample did not exhibit any conspicuous sensitivity to HaV01, presumably because of the great diversity of the host species with respect to virus infection. The growth characteristics of the lytic virus infecting the noxious harmful algal bloom-causing alga were considered, and the possibility of using this virus as a microbiological agent against H. akashiwo red tides is discussed. (+info)
Amphidinolide B, a powerful activator of actomyosin ATPase enhances skeletal muscle contraction.
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Amphidinolide B caused a concentration-dependent increase in the contractile force of skeletal muscle skinned fibers. The concentration-contractile response curve for external Ca2+ was shifted to the left in a parallel manner, suggesting an increase in Ca2+ sensitivity. Amphidinolide B stimulated the superprecipitation of natural actomyosin. The maximum response of natural actomyosin to Ca2+ in superprecipitation was enhanced by it. Amphidinolide B increased the ATPase activity of myofibrils and natural actomyosin. The ATPase activity of actomyosin reconstituted from actin and myosin was enhanced in a concentration-dependent manner in the presence or absence of troponin-tropomyosin complex. Ca2+-, K+-EDTA- or Mg2+-ATPase of myosin was not affected by amphidinolide B. These results suggest that amphidinolide B enhances an interaction of actin and myosin directly and increases Ca2+ sensitivity of the contractile apparatus mediated through troponin-tropomyosin system, resulting in an increase in the ATPase activity of actomyosin and thus enhances the contractile response of myofilament. (+info)
Freeze-fracture studies of the thecal membranes of Gonyaulax polyedra: circadian changes in the particles of one membrane face.
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Intramembrane faces were visualized in the marine dinoflagellate Gonyaulax polyedra by the freeze-fracture technique, in order to test a prediction of a membrane model for circadian oscillations--i.e;, that membrane particle distribution and size change with time in the circadian cycle. Cells from each of four cell suspensions in continuous light (500 1x, 20-21 degrees C) were frozen, without fixation or cryoprotection, at four circadian times in a cycle. This paper reports findings concerning the membranes associated with the theca, particularly the cytoplasmic membrane and the membrane of the large peripheral vesicle. While the number and size distribution of the particles of the PF face of the cytoplasmic membrane were constant with time, those of the EF face of the peripheral vesicle doubled in number at 18 h circadian time as compared with 06 h. Particles of the 120-A size class, in particular, were more numerous at 12 and 18 h circadian time than at 00 and 06 h. While the finding does not provide definitive confirmation of the membrane hypothesis for circadian rhythms, it is consistent with this model. It is suggested that the peripheral vesicle may be the site of bioluminescence in Gonyaulax. (+info)
An octaene fatty acid, 4,7,10,13,16,19,22,25-octacosaoctaenoic acid (28:8n-3), found in marine oils.
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We report structure determination of an octaene fatty acid, 4,7,10, 13,16,19,22,25-octacosaoctaenoic acid (28:8n-3). The molecular weight and double bond locations were determined using acetonitrile chemical ionization mass spectrometry (MS) and MS/MS and were confirmed by MS of hydrogenated and deuterogenated 28:8 and by argentation thin-layer chromatography. 28:8n-3 was 1.2 +/- 0.1%, in oil derived from the heterotrophic dinoflagellate Crypthecodinium cohnii and a commercial polyunsaturated fatty acid concentrate derived from fish oils (0.16 +/- 0.01%), both components of human dietary supplements. It was not found in whole bovine retina, cultured Y79 human retinoblastoma cells, or neonate baboon cerebral cortex. The long chain polyunsaturates present in the C. cohnii oil suggest a possible route for 28:8n-3 biosynthesis similar to that for biosynthesis of 22:6n-3. (+info)
Programmed cell death of the dinoflagellate Peridinium gatunense is mediated by CO(2) limitation and oxidative stress.
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The phytoplankton assemblage in Lake Kinneret is dominated in spring by a bloom of the dinoflagellate Peridinium gatunense, which terminates sharply in summer [1]. The pH in Peridinium patches rises during the bloom to values higher than pH9 [2] and results in CO(2) limitation. Here we show that depletion of dissolved CO(2) (CO(2(dis))) stimulated formation of reactive oxygen species (ROS) and induced cell death in both natural and cultured Peridinium populations. In contrast, addition of CO(2) prevented ROS formation. Catalase inhibited cell death in culture, implicating hydrogen peroxide (H(2)O(2)) as the active ROS. Cell death was also blocked by a cysteine protease inhibitor, E-64, a treatment which stimulated cyst formation. Intracellular ROS accumulation induced protoplast shrinkage and DNA fragmentation prior to cell death. We propose that CO(2) limitation resulted in the generation of ROS to a level that induced programmed cell death, which resembles apoptosis in animal and plant cells. Our results also indicate that cysteine protease(s) are involved in processes that determine whether a cell is destined to die or to form a cyst. (+info)
Cooccurrence of elevated urea levels and dinoflagellate blooms in temperate estuarine aquaculture ponds.
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In hybrid striped bass aquaculture ponds, dinoflagellate blooms were found on 10 of 14 occasions to co-occur with concentrations of urea in excess of 1.5 microM nitrogen. When urea levels were <1.5 microM nitrogen, on seven occasions, no evidence of dinoflagellate blooms was observed in these ponds. (+info)
Evidence for an inorganic carbon-concentrating mechanism in the symbiotic dinoflagellate Symbiodinium sp.
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The presence of a carbon-concentrating mechanism in the symbiotic dinoflagellate Symbiodinium sp. was investigated. Its existence was postulated to explain how these algae fix inorganic carbon (C(i)) efficiently despite the presence of a form II Rubisco. When the dinoflagellates were isolated from their host, the giant clam (Tridacna gigas), CO(2) uptake was found to support the majority of net photosynthesis (45%-80%) at pH 8.0; however, 2 d after isolation this decreased to 5% to 65%, with HCO(3)(-) uptake supporting 35% to 95% of net photosynthesis. Measurements of intracellular C(i) concentrations showed that levels inside the cell were between two and seven times what would be expected from passive diffusion of C(i) into the cell. Symbiodinium also exhibits a distinct light-activated intracellular carbonic anhydrase activity. This, coupled with elevated intracellular C(i) and the ability to utilize both CO(2) and HCO(3)(-) from the medium, suggests that Symbiodinium sp. does possess a carbon-concentrating mechanism. However, intracellular C(i) levels are not as large as might be expected of an alga utilizing a form II Rubisco with a poor affinity for CO(2). (+info)
Genetic analysis in the dinoflagellate (Crypthecodinium (Gyrodinium) cohnii: evidence for unusual meiosis.
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The atypical structure and behavior of dinoflagellate chromosomes suggests that the genetics of these organisms might show comparable peculiarities. We have begun genetic analysis of the neritic, marine heterotroph Crypthecodinium (Gyrodinium) cohnii by means of motility mutants that show complementation shortly after zygote formation, permitting identification of heterozygotes. Six mutations, conferring four microscopically distinguishable phenotypes, have been isolated and investigated. These "genes" were found to complement in double heterozygotes in all pairwise combinations, indicating that the lesions are recessive and non-allelic. Clones of all possible combinations of these factors have been established and each complements only those combinations expected on the assumption that there are six independent recessive mutant "genes." Tetrad analysis following isolation of over 200 complementing zygotes showed: (1) regular segregation with recovery of parental phenotypes and genotypes; (2) independent assortment, with one possible exception; (3) segregations that were always 1:1, that is, in all tetrads showing recombination, only the two reciprocal recombinant genotypes were found; there were no tetratypes. This behavior could result from centromere linkage or the absence of crossing over in an otherwise conventional meiosis, or it could result from an unusual one-division "meiosis." Some evidence is provided that favors the latter hypothesis. (+info)