| 1. |
- Semb, Gunvor, et al.
(författare)
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A Scandcleft randomised trials of primary surgery for unilateral cleft lip and palate: 1. Planning and management.
- 2017
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Ingår i: Journal of Plastic Surgery and Hand Surgery. - : Taylor & Francis. - 2000-656X .- 2000-6764. ; 51:1, s. 2-13
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND AND AIMS: Longstanding uncertainty surrounds the selection of surgical protocols for the closure of unilateral cleft lip and palate, and randomised trials have only rarely been performed. This paper is an introduction to three randomised trials of primary surgery for children born with complete unilateral cleft lip and palate (UCLP). It presents the protocol developed for the trials in CONSORT format, and describes the management structure that was developed to achieve the long-term engagement and commitment required to complete the project.METHOD: Ten established national or regional cleft centres participated. Lip and soft palate closure at 3-4 months, and hard palate closure at 12 months served as a common method in each trial. Trial 1 compared this with hard palate closure at 36 months. Trial 2 compared it with lip closure at 3-4 months and hard and soft palate closure at 12 months. Trial 3 compared it with lip and hard palate closure at 3-4 months and soft palate closure at 12 months. The primary outcomes were speech and dentofacial development, with a series of perioperative and longer-term secondary outcomes.RESULTS: Recruitment of 448 infants took place over a 9-year period, with 99.8% subsequent retention at 5 years.CONCLUSION: The series of reports that follow this introductory paper include comparisons at age 5 of surgical outcomes, speech outcomes, measures of dentofacial development and appearance, and parental satisfaction. The outcomes recorded and the numbers analysed for each outcome and time point are described in the series.TRIAL REGISTRATION: ISRCTN29932826.
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| 2. |
- Havstam, Christina, 1963, et al.
(författare)
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Evaluation of VPI-assessment with videofluoroscopy and nasoendoscopy.
- 2005
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Ingår i: British journal of plastic surgery. - : Elsevier BV. - 0007-1226. ; 58:7, s. 922-31
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to investigate how different amounts of visual assessment information influence the recommended treatment for velopharyngeal insufficiency (VPI). Is a patient presented with videofluoroscopy (VF) in lateral projection recommended the same treatment as when frontal projection, nasoendoscopy, or both, are added? Retrospective material with video recorded assessment of VPI was blinded and copied in random order. Each patient was then presented in four separate combinations: VF in lateral projection; VF in lateral and frontal projection; VF in lateral projection and nasoendoscopy; and VF in lateral and frontal projection and nasoendoscopy (all of the available assessment material). The cleft palate team of Göteborg, Sweden, mutually rated velopharyngeal function and recommended action based on the presented material. SUBJECTS: Nineteen consecutive patients (median age 7:5 years, range 4:4-19:7) investigated with VF in lateral and frontal projection and nasoendoscopy during 1997-99 at the cleft palate centre in Göteborg, Sweden. Post operative assessments were excluded. Percent agreement and Kappa calculations were used to compare the different combinations of parts of information to all of the available information. RESULTS: Thirteen of the 19 patients (68%) were recommended the same action regardless of the amount of presented information. Percent agreement (Kappa) between parts and all of the available information: VF in lateral projection 84% (0.75), VF in lateral and frontal projection 79% (0.74), and VF in lateral projection and nasoendoscopy 84% (0.72). CONCLUSIONS: VF in lateral projection is recommended to be the first step in visualising velopharyngeal function, and nasoendoscopy the next when further investigation is required.
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| 3. |
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| 4. |
- Palle, Nanna, et al.
(författare)
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The effectiveness of phonological intervention in preschool children: a single-subject design study.
- 2014
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Ingår i: Logopedics, phoniatrics, vocology. - : Informa UK Limited. - 1651-2022 .- 1401-5439. ; 39:1, s. 19-29
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Tidskriftsartikel (refereegranskat)abstract
- The purpose was to investigate an intervention model for treating preschool children with phonological processes. Six children, three girls and three boys, between 4y 1m and 5y 7m, with similar developmental phonological disorder (PD) received an individually adjusted intervention including articulatory, phonological, and meta-phonological approaches. A single-subject multiple-baseline design with /f/ and /s/ as target phonemes and velar plosives and /r/ as control phonemes was used. An improved production of the treated phonemes was found in five of the children, while one girl established /f/ but not /s/. The control phonemes remained unchanged for all children. Six to 18 therapy sessions were needed to reach the intervention goal. The study highlights the importance of considering heterogeneity in children with PD.
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| 5. |
- Persson, Agneta, 1963, et al.
(författare)
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Cell density-dependent swimming patterns of Alexandrium fundyense early stationary phase cells
- 2013
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Ingår i: Aquatic Microbial Ecology. - : Inter-Research Science Center. - 0948-3055 .- 1616-1564. ; 68:3, s. 251-258
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Tidskriftsartikel (refereegranskat)abstract
- Different life-history stages of Alexandrium fundyense have different swimming behaviors and show different responses to water movement. Early stationary phase cells assemble in bioconvection patterns along the water surface and as stripes in the water, while cells in exponential growth do not. We studied the swimming behavior of early stationary phase A. fundyense cells, both on the individual level and on the population level. Cells assembled in spots in shallow Petri dishes, and were studied using an inverted microscope. We analyzed 53 videos of cells at different distances from the center of accumulated spots of cells with the program CellTrak for swimming behavior of individual cells. The closer the cells were to the center of spots, the faster they swam (>600 µm s-1 in the center of spots compared to ca. 300 µm s-1 outside) and the more often they changed direction (>1400 degrees s-1 in the center compared to <400 degrees s-1 outside). On a population level, the behavior of spots of assembled cells was studied using time-lapse photography. The spots entrained more and more cells as they grew and fused with each other; the closer the spots came to each other, the faster they moved until they fused. We suggest that chemical attraction between gametes causes the observed behavior.
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| 6. |
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| 7. |
- Persson, Agneta, 1963, et al.
(författare)
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Differences in pigmentation between life cycle stages in Scrippsiella lachrymosa (dinophyceae)
- 2016
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646. ; 52:1, s. 64-74
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Tidskriftsartikel (refereegranskat)abstract
- Various life cycle stages of cyst-producing dinoflagellates often appear differently colored under the microscope; gametes appear paler while zygotes are darker in comparison to vegetative cells. To compare physiological and photochemical competency, the pigment composition of discrete life cycle stages was determined for the common resting cyst-producing dinoflagellate Scrippsiella lachrymosa. Vegetative cells had the highest cellular pigment content ( 25.2 +/- 0.5 pg cell-1), whereas gamete pigment content was 22% lower. The pigment content of zygotes was 82% lower than vegetative cells, even though they appeared darker under the microscope. Zygotes of S. lachrymosa contained significantly higher cellular concentrations of beta- carotene ( 0.65 +/- 0.15 pg cell -1) than all other life stages. Photoprotective pigments and the de- epoxidation ratio of xanthophylls- cycle pigments in S. lachrymosa were significantly elevated in zygotes and cysts compared to other stages. This suggests a role for accessory pigments in combating intracellular oxidative stress during sexual reproduction or encystment. Resting cysts contained some pigments even though chloroplasts were not visible, suggesting that the brightly colored accumulation body contained photosynthetic pigments. The differences in pigmentation between life stages have implications for interpretation of pigment data from field samples when sampled during dinoflagellate blooms.
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| 8. |
- Persson, Agneta, 1963, et al.
(författare)
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Differences in Specific Mass Density Between Dinoflagellate Life Stages and Relevance to Accumulation by Hydrodynamic Processes
- 2021
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 57:5, s. 1492-1503
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Tidskriftsartikel (refereegranskat)abstract
- One previously unstudied aspect of differences between sexual and asexual life stages in large-scale transport and accumulation is density (mass per unit volume) of cells in each life stage. The specific density was determined for Scrippsiella lachrymosa cells in medium with and without nitrogen (N) enrichment through density-gradient centrifugation. Growth medium without N addition is often called "encystment medium" when used for the purpose of resting cyst formation in cyst-forming dinoflagellates; mating gametes are usually seen after 2-3 days. Significant differences in specific density were found after 2 days in encystment medium simultaneously with the observation of typical gamete swimming behavior and mating. The specific density of cells in encystment medium was 1.06 g center dot cm(-3); whereas, the specific density of cells in growth medium was 1.11 g center dot cm(-3). Cells in encystment medium were found to have significantly increased lipid content, reduced chlorophyll content, and reduced internal complexity. The findings may explain differential transport of less dense and chemotactically aggregating gametes into surface blooms in contrast to denser vegetative cells that perform daily vertical migration and do not aggregate. Passive accumulation of non-migrating gametes into layers in stagnant water also can be explained, as well as sinking of zygotes when the storage of highly dense starch increases. Resting cysts had a density of over 1.14 g center dot cm(-3) and would sink to become part of the silt fraction of the sediment. We suggest that differences in behavior and buoyancy between sexual and asexual life stages cause differences in cell accumulation, and therefore large-scale, environmental transport could be directly dependent upon life-cycle transitions.
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| 9. |
- Persson, Agneta, 1963, et al.
(författare)
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Differences in swimming pattern between life cycle stages of the toxic dinoflagellate Alexandrium fundyense
- 2013
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Ingår i: Harmful Algae. - : Elsevier BV. - 1568-9883. ; 21-22, s. 36-43
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Tidskriftsartikel (refereegranskat)abstract
- Different life stages of Alexandrium fundyense have different swimming behavior; gametes often are said to "swarm" or "dance" before mating. This behavior was studied, and quantitative measures of these motility patterns in two-dimensions were generated using motion-analysis software applied to video records of individual-cell movements. Behavior, swimming patterns, and growth were studied in two strains of A. fundyense and compared in encystment medium and growth medium. Vegetative cells swam straight, rotating around the apical axis until they hit something and then swam straight in a different direction. Gamete swimming behavior was slower and characterized by frequent direction changes and circular motion. Gametes contacted other cells frequently (>5 cell contacts min(-1) cell(-1)). Zygotes swam slowly when newly formed and later became nearly immobile; these cells continued to contact other cells and also surfaces. The results are in accordance with field observations of long swimming distances for vegetative cells, accumulation in thin layers of gametes, and sinking of developing resting cysts attached to marine snow for zygotes. (C) 2012 Elsevier B.V. All rights reserved.
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| 10. |
- Persson, Agneta, 1963, et al.
(författare)
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Dinoflagellate Cysts in Recent Sediments from the West Coast of Sweden
- 2000
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Ingår i: Botanica Marina. - 0006-8055. ; 43:1, s. 69-79
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Tidskriftsartikel (refereegranskat)abstract
- This is the first study of dinoflagellate cysts in recent coastal sediments from the Swedish west coast. Sediments from 19 sites were investigated. Fifty-four types of cysts were encountered, of these 40 were identified to species level, representing 13 genera. The most common species were those of Lingulodinium polyedrum, Protoceratium reticulatum, Scrippsiella trochoidea, Pentapharsodinium dalei and Gonyaulax cf. spinifera. Cysts of the potentially toxic species Alexandrium minutum and Alexandrium tamarense were widely distributed as well as Gymnodinium nolleri, the non-toxic G. catenatum-like microreticulate cyst found in Northern Europe. Nine of the species found in this survey have not previously been reported from Sweden: Diplopelta parva, D. symmetrica, Diplopsalopsis latipeltata, Diplopsalis lebourae, Protoperidinium americanum, P. avellana, P. divaricatum, P. nudum and P. stellatum.
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| 11. |
- Persson, Agneta, 1963, et al.
(författare)
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Dinoflagellate gamete formation and environmental cues: Observations, theory, and synthesis
- 2008
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Ingår i: Harmful Algae. - : Elsevier BV. - 1568-9883. ; 7:6, s. 798-801
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Tidskriftsartikel (refereegranskat)abstract
- For some species of cyst-producing dinoflagellates, the sexual life cycle is well studied in laboratory cultures. Dinoflagellate blooms in stratified waters, vertical migration of vegetative cells, and the accumulation of populations within thin layers are well-documented phenomena in nature. We propose a conceptual model that places these phenomena in a functional, ecological context: vegetative cells of a dinoflagellate population display vertical migration, but at the end of the bloom, environmental or internal cues shift the cell cycle to gamete formation. Then the vertical migrations cease, and cells accumulate in a layer at the pycnocline where gametes fuse to form zygotes, which then sink to the sediment as resting cysts. We support this conceptual model with experimental and environmental evidence. (C) 2008 Elsevier B.V. All rights reserved.
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| 12. |
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| 13. |
- Persson, Agneta, 1963, et al.
(författare)
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Grazing on toxic Alexandrium fundyense resting cysts and vegetative cells by the eastern oyster (Crassostrea virginica)
- 2006
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Ingår i: Harmful Algae. - : Elsevier BV. - 1568-9883. ; 5:6, s. 678-684
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Tidskriftsartikel (refereegranskat)abstract
- In laboratory experiments, oysters (Crassostrea virginica) were fed Alexandrium fundyense (strain CB501) vegetative cells or resting cysts (from strains CB501 and GMT25) produced from laboratory cultures. The toxicity per cyst was 1.7 pg STXequiv/cyst and for vegetative cells 3.9 pg STXequiv/cell. The toxic, resting cysts and vegetative cells were removed from suspension in the experimental containers within about 4 h. Oysters fed toxic vegetative cells digested 72% of cells ingested, and 28% survived gut passage by forming temporary cysts. Toxin levels of oysters fed vegetative cells averaged 27 μg STXequiv/100 g meat. Resting cysts added to the experimental containers adhered to the walls so that only 40% of the cysts added were available to the oysters during the experiment. Of the cysts that were ingested, approximately 59% were digested, and oysters accumulated toxins (an average of 1.2 μg STXequiv/100 g meat), showing that consumption of resting cysts can cause toxicity in oysters. Direct consumption of resting cysts, thus, may explain shellfish toxicity in areas without known blooms, but with toxic resting cysts in the sediment. These results suggest a possible role of toxic cysts in mediating time-lags between surface blooms and appearance of toxicity in benthic grazers, and the possible role of benthic grazers in controlling seed populations, except in anoxic areas, which can serve as cyst “refuges” from grazing mortality.
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| 14. |
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| 15. |
- Persson, Agneta, 1963
(författare)
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Possible predation of cysts - a gap in the knowledge of dinoflagellate ecology?
- 2000
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Ingår i: Journal of Plankton Research. ; 22:4, s. 803-809
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Tidskriftsartikel (refereegranskat)abstract
- A theoretical model of dinoflagellate ecology is presented. The model incorporates currently neglected aspects of potential importance in the field of plankton research, such as losses to the cyst seed bank due to predation or microbial degradation.
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| 16. |
- Persson, Agneta, 1963
(författare)
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Proliferation of cryptic protists and germination of resting stages from untreated sediment samples with emphasis on dinoflagellates
- 2002
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Ingår i: Ophelia. - 0078-5326. ; 55:3, s. 151-166
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Tidskriftsartikel (refereegranskat)abstract
- Incubation of untreated sediment samples from the northern part of the Swedish west coast resulted in a conspicuous proliferation of various protists. Samples from ten coastal sites were incubated in filtered seawater and the resulting vegetative stages were recorded for a period of two weeks. At least 47 different dinoflagellate taxa were encountered as vegetative stages, more than 46 different ciliate taxa and at least 64 living diatom taxa were present. There were also cyanobacteria, haptophytes, cryptophytes, euglenophytes, prasinophytes, chlorophytes and amoebae. As total 263 taxa were identified from less than 100 cm(3) sediment, suggesting that most microorganisms are ubiquitous, present almost everywhere within their geographic region, but often rare or cryptic. All dinoflagellates present in the area that are known to be cyst-producing were found, corresponding to 25% of the known dinoflagellates at the Swedish west coast. Approximately 26% of the planktonic and 22% of the pennate diatoms recorded at the Swedish west coast were present in the samples.
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| 17. |
- Persson, Agneta, 1963, et al.
(författare)
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Sexual life stages and temperature dependent morphological changes allow cryptic occurrence of the Florida red tide dinoflagellate Karenia brevis
- 2013
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Ingår i: Harmful Algae. - 1568-9883. ; 30, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Karenia brevis, the Florida red tide dinoflagellate, has been studied extensively, but very little attention has been paid to its sexual life cycle. We found that the life cycle of K. brevis is heterothallic, most probably not resting cyst-producing, but with life stages of different morphology. The isogamous gametes were slightly smaller than vegetative cells and not as broad and flat. The late zygote was yellow-brown in appearance with a thicker wall and more rounded shape lacking carina. Pellicle cysts of these zygotes closely resembled the few earlier descriptions of "possible cysts" of the species. In addition, temperature-dependent, morphological changes and pellicle-cyst formation were observed. Cells placed in the cold (15 degrees C) formed spherical, thin-walled pellicle cysts that germinated into cells that were round in cross-section and longer than wide - so morphologically different from vegetative cells that they would not be correctly identified if encountered in field samples. Cells grown at 25 degrees C were wider and flatter than cells grown at 20 degrees C. Cells warmed from cold conditions became flat and wide within hours, returning to the typical shape. Also the morphological differences between sexual life stages were large enough to allow misidentification and cryptic occurrence of K. brevis. The cell shape of K. brevis was not fixed, but could vary from very wide and flat to elongate with rounded cross-section in the same culture of clonal cells and in the same cells within a short time (hours). In addition to the culture studies, sediment samples from a Karenia "hot spot" area were concentrated, and the dinoflagellate cyst fraction was investigated for resting cysts. Cysts were not found, and Karenia cells did not germinate from slurry cultures of the concentrated cyst fraction. (C) 2013 Elsevier B.V. All rights reserved.
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| 18. |
- Persson, Agneta, 1963, et al.
(författare)
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The Eastern mudsnail, Ilyanassa obsoleta, actively forages for, consumes, and digests cysts of the dinoflagellate, Scrippsiella lachrymosa
- 2008
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Ingår i: Malacologia. - 0076-2997. ; 50:1-2, s. 341-345
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Tidskriftsartikel (refereegranskat)abstract
- The Eastern mudsnail, Ilyanassa obsoleta, was attracted to, consumed, and digested resting cysts of the dinoflagellate Scrippsiella lachrymosa when cysts were presented in grazing experiments. Twenty snails were observed individually for one hour in petri dishes divided into four parts wherein cysts were present in one quadrant, sediment particles of the same size range were in another quadrant, and two quadrants were free of particles. Actively foraging snails were nearly twice as likely to be found in quadrants containing S. lachrymosa cysts as in the other quadrants until cysts were consumed. Microscope observations of fecal pellets from snails feeding on cysts revealed digestive destruction of the cysts. These findings indicate that deposit-feeding grazers can actively seek dinoflagellate cysts as a food item, thereby influencing distribution of cysts and subsequent germination of dinoflagellate vegetative cells.
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| 19. |
- Persson, Agneta, 1963
(författare)
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The use of sediment slurry culture to search for organisms producing resting stages
- 2001
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Ingår i: Hallegraeff, G.M., Blackburn, S.I., Bolch, C.J. & Lewis, R.J. (eds.), Harmful Algal Blooms 2000. – IOC, Paris. Conference proceedings: IXth International Conference on Harmful Algal Blooms, 7-11 February, 2000, Hobart, Tasmania, Australia. ; , s. 191-194
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Tidskriftsartikel (refereegranskat)abstract
- Sediment slurries were used successfully in experiments aiming to survey the northern Swedish west coast for dinoflagellate cysts as well as in a pilot study to investigate the presence of phytoplankton resting stages in ballast water and sediment. Untreated aliquots of sediment or concentrated (by filtration) ballast water were cultured using filtered seawater to allow germination of resting stages. The resulting mixed cultures were studied for a period of two weeks and documented directly from the flasks using an inverted microscope. This simple and unselective germination of resting stages proved a very useful complement to a "traditional" dinoflagellate cyst survey or a survey for resting stages in ballast sediment or water. Many organisms appeared in the cultures that were not found as resting stages, probably due to their resting stages being few, small and inconspicous or of unknown appearance. Cultures of sediments from the Swedish west coast contained copepods, rotifers, ciliates (at least 46 types), dinoflagellates (at least 47 species), diatoms (at least 128 species), cyanobacteria, haptophytes, cryptophytes, euglenophytes, prasionophytes, clorophytes and amoebae. Cultures of ballast water and sediment contained mainly cosmopolitan diatom species.
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| 20. |
- Persson, Agneta, 1963, et al.
(författare)
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Toxin content differs between life stages of Alexandrium fundyense (Dinophyceae)
- 2012
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Ingår i: Harmful Algae. - : Elsevier BV. - 1568-9883. ; 19:-, s. 101-107
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Tidskriftsartikel (refereegranskat)abstract
- Different life stages of two mating-compatible clones of the paralytic shellfish toxin (PST)-producing dinoflagellate Alexandrium fundyense Balech were separated using a combination of techniques; culturing and sampling methods were used to separate vegetative cells and gametes, and sorting flow cytometry was used to separate zygotes. PST profiles were significantly different between life stages; the two gonyautoxins GTX1 and 2 were present in vegetative and senescent cells, but disappeared from gametes and zygotes. Toxin-profile changes were shown to occur very quickly in both strains when pellicle cyst formation was induced by shaking (four minutes) followed by rinsing on a screen. These pellicle cysts produced from exponentially-growing, vegetative cells lost GTX1 and 2 completely. Rapid toxin epimerization of GTX1 to GTX4 and GTX2 to GTX3 is one possible explanation, although the biological advantage of this remains unclear. Another possible explanation is that during the mating phase of a bloom or when cells are disturbed, GTX1 and GTX2 are released into the surrounding water. It may be advantageous for a dinoflagellate bloom to be surrounded by free toxins in the water. (c) 2012 Elsevier B.V. All rights reserved.
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| 21. |
- Smith, B. C., et al.
(författare)
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A particle separator used to concentrate Dinoflagellate cysts from sediment
- 2009
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Ingår i: Limnology and Oceanography: Methods. ; 7, s. 521-526
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Tidskriftsartikel (refereegranskat)abstract
- A device has been developed to separate and collect large numbers of dinoflagellate cysts from sediment samples of several liters volume. The apparatus consists of a 152.5 x 44.5 x 38-cm fiberglass tank with a 20-µm screen inserted diagonally across the long dimension, creating an inclined plane as the bottom of a settling tank. A peristaltic pump delivers resuspended bottom material to the top of the deep end of the tank. The particles settle according to mass and friction as the water moves to a drain near the top center of the shallow end of the screen. The desired particles can be vacuumed from specific areas of the screen and further refined with a final sieving step. More than 16 L marine mud were processed in this apparatus at one time. In a reference sediment sample collected from beneath New Haven Harbor (Connecticut, USA), cyst recovery was 25% for living cysts. The sediment in the uppermost part of the sorter had approximately 376 times more cysts/mL than the sediment originally added. The cyst fraction (particles 20-100 µm) contained ten times more cysts in the uppermost part of the sorter than at the middle or lower ends. Cysts within the cyst-rich zone of the separator settled differently depending upon species, size, and morphology.
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| 22. |
- Smith, B. C., et al.
(författare)
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Dinoflagellate cell density limits explored using Scrippsiella lachrymosa cultured in flow-through cages
- 2023
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Ingår i: Journal of Applied Phycology. - : Springer Science and Business Media LLC. - 0921-8971 .- 1573-5176. ; 35, s. 613-623
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Tidskriftsartikel (refereegranskat)abstract
- Dinoflagellates constitute one of the most important groups of primary producers and micro-zooplankton on earth, common in both marine and freshwater environments. Despite their prominent position among phytoplankton, they are difficult to grow into dense cultures in the laboratory. This discrepancy between field and laboratory indicates serious limitations caused by the laboratory culturing conditions. A difficult to study but important factor is the constraints of enclosure in a limited volume of water. We conducted an experiment wherein the dinoflagellate Scrippsiella lachrymosa was grown in "flow cells" - 100 cm(3) cylindrical cages constructed from plankton net, inserted in larger volumes of growth medium, allowing an exchange of medium without dilution of the culture. Cell numbers far exceeding the normal for culturing of this species and dinoflagellates in general were attained, even though the experiment was terminated before cultures reached stationary phase. A cell number ten times higher than under regular batch culturing was achieved (up to 340,000 cells mL(-1)). Pattern formation was distinct in cultures when cells were plentiful and water movements caused cell accumulation, not dispersion. High cell density concurrent with access to new growth medium promoted induction of the sexual cell cycle. The results indicate serious limitations to growth set by enclosure in a limited water volume in laboratory experiments; thus, maximum growth rates of dinoflagellates in favourable field conditions may be vastly underestimated. Cell accumulation behavior of dinoflagellates during the sexual life cycle may together with physical transport by larger forces in nature explain sudden bloom occurrences.
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| 23. |
- Smith, B. C., et al.
(författare)
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Dinoflagellate cyst production in one-liter containers
- 2004
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Ingår i: Journal of Applied Phycology. - 0921-8971 .- 1573-5176. ; 16:5, s. 401-405
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Tidskriftsartikel (refereegranskat)abstract
- Methods for the production of dinoflagellate cysts in two types of 1 L containers have been developed. Using these methods, dinoflagellate cysts can be produced in amounts large enough for shellfish grazing experiments or whenever large amounts of cysts are needed. The species used were Scrippsiella lachrymosa (B-10) and toxic Alexandrium fundyense (CB501 and GTM25). Cultures of S. lachrymosa yielded 628 ± 74 cysts mL–1 and A. fundyense cultures yielded 350 ± 98 cysts mL–1. Findings suggest that aspects of the boundary layer between the media and the wall of the container are important for gamete mating; especially, the slope of the container wall appears to be relevant, which offers some explanation of previous observations that the shape of the container is important in the formation of dinoflagellate resting cysts. These observations may support the theory that physical interfaces in nature facilitate dinoflagellate encystment.
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| 24. |
- Smith, B. C., et al.
(författare)
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Synchronization of encystment of Scrippsiella lachrymosa (Dinophyta)
- 2005
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Ingår i: Journal of Applied Phycology. - 0921-8971 .- 1573-5176. ; 17:4, s. 317-321
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Tidskriftsartikel (refereegranskat)abstract
- The encystment of Scrippsiella lachrymosa cells (strain B-10), which can be induced reliably in encystment medium, was inhibited by stirring the culture. 100 mL cultures in glass beakers were stirred at 1 rotation s−1. Stirring inhibited vegetative cells from congregating (swarming) at the walls of the culture container. When stirring was stopped, a rapid induction of sexual reproduction was seen. As soon as stirring stopped (within 2 min), cells were observed swarming near the edges of the glass beaker. Four days after cessation of stirring, large percentages of the cells were mating and, after 7 days, most were zygotes. Cultures were observed after 31, 38, and, 45 days of stirring. When cultures were stirred for 45 days, cysts developed in the stirred treatments, but these cysts were attached to flocculent material that had also formed in the medium. The use of this laboratory method is advantageous for the study of the mating through cyst stages of the dinoflagellate life history. This method may also demonstrate the need for a ‘surface’ as a place for the dinoflagellate to congregate in order to successfully encyst and may help explain environmental observations of encystment at pycnoclines.
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| 25. |
- Smith, B.C., et al.
(författare)
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Toxin profile change in vegetative cells and pellicle cysts of Alexandrium fundyense after gut passage in the eastern oyster Crassostrea virginica
- 2011
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Ingår i: Aquatic biology. - : Inter-Research Science Center. - 1864-7790 .- 1864-7782. ; 13:2, s. 193-201
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Tidskriftsartikel (refereegranskat)abstract
- Abstract: Vegetative cells and pellicle cysts of the toxic dinoflagellate Alexandrium fundyense Balech were fed to the eastern oyster Crassostrea virginica Gmelin under controlled conditions. Para lytic shellfish toxins (PSTs) were measured in vegetative cells and pellicle cysts prior to feeding and directly after passage through the oyster alimentary canal and defecation as intact cells. Oysters fed with vegetative cells and those fed with pellicle cysts accumulated toxins. One experimental treatment tested for direct uptake of toxins from the water (oysters and A. fundyense cells were separated by a screen); PSTs were not accumulated from the water by the oysters. There were no significant changes in total, per-cell toxicity after passage through the oyster alimentary canal, suggesting limited transfer of toxins from intact cells to the oysters. However, there were statistically significant changes in the toxin composition of cells following gut passage. Vegetative cells and pellicle cysts from feces had increased amounts of saxitoxin (STX) and decreased amounts of gonyautoxin 4 (GTX4) per cell, compared to amounts prior to gut passage. Following gut passage, pellicle cysts showed better survival in the feces than vegetative cells, which is consistent with the view of pellicle-cyst formation as a successful survival strategy against adverse conditions.
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| 26. |
- Wängberg, Sten-Åke, 1955, et al.
(författare)
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Effects of UV-B radiation on synthesis of mucosporine-like amino acids and growth in Heterocapsa triquetra
- 1997
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Ingår i: Journal of Photochemistry and Photobiology B: Biology. ; 37:1-2, s. 141-146
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Tidskriftsartikel (refereegranskat)abstract
- Unialgal cultures of the dinoflagellate Heterocapsa triquetra (Ehrenberg) Stein were exposed to artificial UV-B radiation and the growth and synthesis of mycosporine-like amino acids (MAAs) were compared with cultures shielded from UV-B radiation by sharp cut-off films. The UV-B radiation did not affect the growth (the increase in total cell volume of the culture) but resulted in an increase in the size of the individual cells and synthesis of MAAs. The synthesis of MAAs during UV-B radiation was synchronised with the cell cycle, being maximal during periods of increases in cell size without division. The absorbance spectra of the MAAs during UV-B radiation changed, showing higher absorption in the UV-B range as compared to the controls.
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