Ovid Technologies, Inc. Email Service ------------------------------ Search for: from 5 [1 and 2] keep 1-28 Citations: 1-28 Citation <1> Accession Number PREV200100054726 Author/Editor/Inventor Martin-Jezequel Veronique. Hildebrand Mark [a]. Brzezinski Mark A. Institution [a] Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA, 92093-0202: mhildebrand@ucsd.edu USA. Title Silicon metabolism in diatoms: Implications for growth. Source Journal of Phycology. [ print] 36(5). October, 2000. 821-840. Abstract Diatoms are the world's largest contributors to biosilicification and are one of the predominant contributors to global carbon fixation. Silicon is a major limiting nutrient for diatom growth and hence is a controlling factor in primary productivity. Because our understanding of the cellular metabolism of silicon is limited, we are not fully knowledgeable about intracellular factors that may affect diatom productivity in the oceans. The goal of this review is to present an overview of silicon metabolism in diatoms and to identify areas for future research. Numerous studies have characterized parameters of silicic acid uptake by diatoms, and molecular characterization of transport has begun with the isolation of genes encoding the transporter proteins. Multiple types of silicic acid transporter gene have been identified in a single diatom species, and multiple types appear to be present in all diatom species. The controlled expression and perhaps localization of the transport! ers in the cell may be factors in the overall regulation of silicic acid uptake. Transport can also be regulated by the rate of silica incorporation into the cell wall, suggesting that an intracellular sensing and control mechanism couples transport with incorporation. Sizable intracellular pools of soluble silicon have been identified in diatoms, at levels well above saturation for silica solubility, yet the mechanism for maintenance of supersaturated levels has not been determined. The mechanism of intracellular transport of silicon is also unknown, but this must be an important part of the silicification process because of the close coupling between silica incorporation and uptake. Although detailed ultrastructural analyses of silica deposition have been reported, we know little about the molecular details of this process. However, proteins occluded within silica that promote silicification in vitro have recently been characterized, and the application of molecular techniqu! es holds the promise of great advances in this area. Cellular energy for silicification and transport comes from aerobic respiration without any direct involvement of photosynthetic energy. As such, diatom silicon metabolism differs from that of other major limiting nutrients such as nitrogen and phosphorous, which are closely linked to photosynthetic metabolism. Cell wall silicification and silicic acid transport are tightly coupled to the cell cycle, which results in a dependency in the extent of silicification on growth rate. Silica dissolution is an important part of diatom cellular silicon metabolism, because dissolution must be prevented in the living cell, and because much of the raw material for mineralization in natural assemblages is supplied by dissolution of dead cells. Perhaps part of the reason for the ecological success of diatoms is due to their use of a silicified cell wall, which has been calculated to impart a substantial energy savings to organisms that hav! e them. However, the growth of diatoms and other siliceous organisms has depleted the oceans of silicon, such that silicon availability is now a major factor in the control of primary productivity. Much new progress in understanding silicon metabolism in diatoms is expected because of the application of molecular approaches and sophisticated analytical techniques. Such insight is likely to lead to a greater understanding of the role of silicon in controlling diatom growth, and hence primary productivity, and of the mechanisms involved in the formation of the intricate silicified structures of the diatom cell wall. Citation <2> Accession Number PREV200100027301 Author/Editor/Inventor Kroeger Nils [a]. Wetherbee Richard. Institution [a] Biochemie I, Universitaet Regensburg, 93053, Regensburg: nils.kroeger@vkl.uni-regensburg.de Germany. Title Pleuralins are involved in theca differentiation in the diatom Cylindrotheca fusiformis. Source Protist. [ print] 151(3). October, 2000. 263-273. Abstract Diatom cells are encased within a silica-based cell wall (frustule) that serves as armour-like protection for the enclosed protoplast. Maintaining the integrity of the frustule requires a precise coupling between the biogenesis of new frustule components and the cell cycle. Thus far, the molecular mechanisms by which this coupling is achieved are unknown. This study demonstrates that pleuralins (formerly HEPs), a previously characterized family of diatom cell wall proteins, are involved in cell cycle-dependent frustule development. The frustule is made up of two, overlapping half-shells termed the epitheca and hypotheca. Both thecae are morphologically identical, yet immunolocalisation with anti-pleuralin antibodies demonstrates that their protein composition is clearly different. During interphase, pleuralins are associated only with the epitheca, where they are confined to the inner surface of the terminal elements (pleural bands) in the region of overlap with the hypothec! a. At cell division, pleuralins also become associated with the newly formed pleural bands of the hypotheca. Remarkably, this process is concomitant with the functional conversion of the parental hypotheca into the epitheca of one of the progeny cells. These results indicate that developmentally controlled association of pleuralins with the frustule is involved in hypotheca-epitheca differentiation, which is a crucial process to ensure proper frustule development. Citation <3> Accession Number PREV200000478509 Author/Editor/Inventor Hildebrand Mark [a]. Dahlin Katherine. Institution [a] Marine Biology, Research Division, Scripps Institution of Oceanography, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA, 92093-0202 USA. Title Nitrate transporter genes from the diatom Cylindrotheca fusiformis (Bacillariophyceae): mRNA levels controlled by nitrogen source and by the cell cycle. Source Journal of Phycology. [ print] 36(4). August, 2000. 702-713. Abstract The molecular characterization of components involved in nitrate uptake and assimilation in phytoplankton is likely to provide new insights into these processes, their regulation, and their effect on primary production. We report the cloning and initial characterization of the first nitrate transporter genes in a marine organism, from the diatom Cylindrotheca fusiformis Reimann et Lewin. A clone isolated from a silicon-responsive cDNA library was shown by sequence comparison to encode a homolog of high-affinity nitrate transporters. The C. fusiformis nitrate transporter cDNA was named NAT (NitrAte Transporter). The NAT cDNA was used to isolate a genomic clone that contained two additional nitrate transporter genes, NAT1 and NAT2, arranged in tandem. The cDNA and two genomic sequences were highly conserved, and only 18 of 1446 nucleotides in the coding region differed. At least four copies of NAT genes were present in C. fusiformis and as shown by hybridization, multiple copi! es were present in other diatom species. The transcript abundance of NAT genes in cultures with different nitrogen sources was monitored by RNase protection assays. NAT mRNA levels were high in the presence of nitrate, at nearly the same level during nitrogen starvation, and also high in urea-containing cultures. Lower mRNA levels occurred in nitrite-grown cultures. NAT transcript levels were highly repressed with NH4Cl or NH4NO3 as the nitrogen source, although very low amounts were detected. These results suggested that monitoring NAT mRNA levels could serve as a marker for (1) nitrate uptake in nitrate medium, (2) nitrogen starvation, and (3) ammonium use by virtue of absence of expression. NAT mRNA levels were not directly regulated by light or dark, but were apparently related to cellular growth and protein synthesis. Using light/dark synchronized cultures to monitor cell cycle responses, NAT mRNA levels were high in early G1 phase, decreased through the remainder of G1, ! then increased during DNA synthesis in S phase and into G2, and finally decreased after M phase. In silicon-starvation synchronized cultures, levels were high at the G1/S phase boundary, high throughout S and G2, and finally decreased after M phase. It was clear that NAT expression, and by inference nitrate uptake, did not occur at continuous levels throughout the cell cycle. The results of the RNase protection experiments suggested that transcriptional regulation is a major contributing factor in the control of diatom nitrate uptake. The cloning of the C. fusiformis nitrate transporter genes provides a new tool for investigating diatom nitrogen uptake and metabolism. In addition, the regulation of NAT expression by nitrogen source is likely to be useful in developing techniques to specifically control the expression of genes fused to NAT regulatory sequences in transgenic diatoms. Citation <4> Accession Number PREV200000311052 Author/Editor/Inventor Furuya Ken. Matsumoto Kazuhiko. Institution [a] Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, University of Tokyo, Yayoi, Bunkyo, Tokyo, 113-8657 Japan. Title Cell cycle and growth rate of a natural diatom population in a mesocosm. Source Mer (Tokyo). [ print] 37(3). Nov., 1999. 111-119. Abstract Diel variations in nuclear DNA concentrations were examined in a mesocosm to study the cell cycle and growth phase of a natural population of a pennate diatom Nitzschia rectilongae. Microfluorometry was applied to quantify DAPI-stained DNA molecules. Durations and abundance of cell cycle phases were estimated based on the DNA histograms. S phased cells were consistently present in a considerable amount, and both S and G2+M phase cells comprised a mojor portion of the pupulation both during the day and night. In contrast, G1phase cells were less abundant. These observations indicate that cells were directed towards replication shortly after mitosis and that cell division was initiated rather frequently. S and G2+M phases showed a rhythmic temporal fluctuation. Phase duration of S and G2+M phases and growth rates were estimated by two different approaches, an application of the model developed for dinoflagellates and the cell cohort analysis. Discrepancy in the results obtaine! d by these two approaches may be ascribed to the characteristic lack of a clear synchrony of cell division in diatoms. Citation <5> Accession Number PREV200000031576 Author/Editor/Inventor Shipe Rebecca F [a]. Brzezinski Mark A. Institution [a] Department of Ecology, Evolution and Marine Biology, Marine Science Institute, University of California, Santa Barbara, CA, 93106 USA. Title A study of Si deposition synchrony in Rhizosolenia (Bacillariophyceae) mats using a novel 32Si autoradiographic method. Source Journal of Phycology. 35(5). Oct., 1999. 995-1004. Abstract A 32Si autoradiographic technique using a liquid photographic emulsion was developed for the study of diatom silica deposition in culture or in natural water samples. The method was used in the Central North Pacific to study silica deposition by diatoms of the genus Rhizosolenia. The species examined form centimeter-sized aggregates commonly referred to as mats. The Rhizosolenia mats examined were composed of a matrix of R. fallax Sundstrom chains, embedded with chains of larger cells, either R. debyana H. Peragallo or R. acuminata H. Peragallo. The autoradiographs revealed distinct rings of labeled intercalary bands and/or labeled valves. A greater proportion of the frustule of the larger species was labeled during the incubations with 32Si, implying higher rates of silicification by R. debyana and R. accuminata compared to R. fallax. A quantitative consideration of these differences in species-specific Si production combined with abundance and surface area estimatesfor eac! h species indicates that cells of the larger species carry out the majority of silica production in Rhizosolenia mats. The large cell size (pervalvar axis 240 to 3000 mum) and elongate frustule morphology of Rhizosolenia cells enabled us to localize the deposition of silica along the pervalvar axis. Positions of labeled bands along this axis indicate progress through the Si deposition cycle, and the results suggest that cell division is phased, with either a bimodal or unimodal age distribution of cells within the cell cycle for all species in a mat. Species-specific doubling times from 25 to 60 h were implied by the mean fractions of frustule that were labeled. 32Si autoradiography revealed unique species-specific differences in diel patterns of cell division and silica deposition and has potential for studies of Si deposition by other diatom species and assemblages. Citation <6> Accession Number PREV199900264844 Author/Editor/Inventor Ng Christine K F. Lam Connie M C. Yeung Patrick K K. Wong J T Y [a]. Institution [a] Biology Department, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong China. Title Flow cytometric analysis of nocodazole-induced cell-cycle arrest in the pennate diatom Phaeodactylum tricornutum Bohlin. Source Journal of Applied Phycology. 10(6). 1998. 569-572. Abstract The microtubule inhibitor, nocodazole (2.5 mg L-1), can arrest the cell cycle of the pennate diatom Phaeodactylum tricornutum Bohlin at G2 + M phase. Flow cytometric analysis of cells treated with nocodazole suggest that the proportion of cells at G2 + M phase can accumulate to over 95%. Even after a 48-h treatment with nocodazole (2.5 mg L-1), the cells can still exit mitosis, suggesting that the cell-cycle arrest is reversible. Citation <7> Accession Number PREV199900240266 Author/Editor/Inventor Carbonnelle D. Pondaven P [a]. Morancais M. Masse G. Bosch S. Jacquot C. Briand G. Robert J M. Roussakis C. Institution [a] Laboratoire de Pharmacologie Marine, Faculte de Pharmacie, ISOMer (Institut des Substances et Organismes de la Mer), 44035, Nantes cedex 01, Brittany France. Title Antitumor and antiproliferative effects of an aqueous extract from the marine diatom Haslea ostrearia (Simonsen) against solid tumors: Lung carcinoma (NSCLC-N6), kidney carcinoma (E39) and melanoma (M96) cell lines. Source Anticancer Research. 19(1A). Jan.-Feb., 1999. 621-624. Abstract An aqueous extract of the marine diatom Haslea ostrearia (Simonsen) was studied for its antiproliferative properties against human solid tumors: lung carcinoma (NSCLC-N6), kidney carcinoma (E39) and melanoma (M96). These types of carcinoma are particularly chemoresistant. The extract has a potent cytostatic effect in vitro on the three cell lines and blocks the NSCLC-N6 line in the G1/S phase of the cell cycle. Moreover, the extract strongly inhibits tumor growth of NSCLC-N6 bearing nude mice. These preliminary results indicate that the aqueous extract of Haslea ostrearia exhibits inhibitory effects both in vitro and in vivo against solid carcinoma lines, suggesting the presence of a new potent antitumor agent in the aqueous algal homogenate. Citation <8> Accession Number PREV199800054280 Author/Editor/Inventor Buma A G J [a]. Engelen A H. Gieskes W W C. Institution [a] Dep. Marine Biology, Univ. Groningen, P.O. Box 14, 9750 AA Haren Netherlands. Title Wavelength-dependent induction of thymine dimers and growth rate reduction in the marine diatom Cyclotella sp. exposed to ultraviolet radiation. Source Marine Ecology-Progress Series. 153(1-3). July 10, 1997. 91-97. Abstract Cultures of the marine diatom Cyclotella sp. were subjected to various polychromatic exposures of UVB radiation (280-320 nm), UVA radiation (320-400 nm) and photosynthetically active radiation, PAR (400-700 nm). Changes in growth rate and residual thymine dimer content (a measure for DNA damage) were measured during prolonged exposure (6 to 7 d) to these conditions. Also, changes in mean cell size were studied as an indication of UV radiation induced cell cycle arrest in Cyclotella sp. Growth rate reduction was strongly related with residual thymine dimer content in treatments including wavelengths below 302 nm. Additionally, significant increases in mean cell size were found in these cultures. This suggests that UVB-induced residual DNA damage is followed by cell cycle arrest and growth rate reduction in Cyclotella sp. We discuss how these results can be interpreted in relation to changes in the solar spectrum as a result of stratospheric ozone reduction. Citation <9> Accession Number PREV199799712664 Author/Editor/Inventor Buma A G J [a]. Zemmelink H J. Sjollema K. Gieskes W W C. Institution [a] Dep. Marine Biol., Biol. Cent., Univ. Groningen, PO Box 14, 9750 AA Haren Netherlands. Title UVB radiation modifies protein and photosynthetic pigment content, volume and ultrastructure of marine diatoms. Source Marine Ecology-Progress Series. 142(1-3). 1996. 47-54. Abstract Three marine diatom species (Cyclotella sp., Nitzschia closterium and Thalassiosira nordenskioldii) were exposed to a range of daily doses of ultraviolet B radiation (UVBR: 280-320 nm). The lowest UVBR treatments ( lt 2000 J m-2 d-1, DNA weighted biologically effective dose, normalised at 300 nm: daily BED-DNA300nm) resulted in decreased division rates, volume enlargement and elevated cellular protein and pigment content levels. The highest UVBR treatments (between 2000 and 3800 J m-2 d-1 daily BED-DNA300nm) resulted in complete growth inhibition, accompanied by only minor changes in protein, pigments and cell volume. Recovery of cell division after UVBR exposure was decreasingly successful with increasing UVBR (lose rates. Ultrastructural examination of exposed Cyclotella cells indicated that high UVBR levels induced plasmolysis and disorientation of cell organelles. Lower levels ( lt 2000 J m-2 d-1 daily BED-DNA300nm) seemed to cause an increase in volume and the amount of! chloroplasts. The results support the notion conceived earlier that UVBR causes DNA damage, an arrest in the S or G2 phase of the cell cycle, and consequently growth without cell division. Citation <10> Accession Number PREV199799694184 Author/Editor/Inventor Berge J P. Bourgougnon N. Carbonnelle D. Le Bert V. Tomasoni C. Durand P. Roussakis C [a]. Institution [a] Inst. Substances Organismes de la Mer, Lab. Pharmacol. Marine, Fac. Pharm., B.P. 1024, 44035 Nantes cedex 01 France. Title Antiproliferative effects of an organic extract from the marine diatom Skeletonema costatum (Grev.) Cleve. against a non-small-cell bronchopulmonary carcinoma line (NSCLC-N6). Source Anticancer Research. 17(3C). 1997. 2115-2120. Abstract An organic extract of the marine diatom Skeletonema costatum was studied in vitro for its effect on asynchronous cells of a human non-small-cell bronchoplumanory carcinoma line (NSCLC-N6). Cell growth appeared to be inhibited in the G-1 phase of the cell cycle, and kinetic studies in pretreated cells showed that this growth arrest was irreversible. These events are related to a terminal maturation induction. Citation <11> Accession Number PREV199799296370 Author/Editor/Inventor Buma Anita G J [a]. Van Hannen Erik J. Veldhuis Marcel J W. Gieskes Winfried W C [a]. Institution [a] Dep. Marine Biol., Univ. Groningen, P.O. Box 14, 9750 AA Haren Netherlands. Title UV-B induces DNA damage and DNA synthesis delay in the marine diatom Cyclotella sp. Source Scientia Marina. 60(SUPPL. 1). 1996. 101-106. Abstract The effect of UV-B on the occurrence of DNA damage and consequences for the cell cycle were studied in the marine diatom Cyclotella sp. DNA damage was quantified by immunofluorescent detection of thymine dimers in nuclear DNA of single cells using flow cytometry. A total UV-B dose (biologically effective dose BE-DNA300nm) of 1.05 kJ m-2 caused detectable damage in about 20% of the exposed population. In the period after the UV-B treatment, when the culture was exposed to PAR (450 mu-mol m-2s-1) only, thymine dimers were removed; after 8 hours none of these photoproducts remained. Cellular DNA content measurements and quantification of the fraction of recently divided cells revealed that the DNA synthesis rate as well as the rate of cell division were reduced during and shortly after UV-B exposure. Apparently, UV-B irradiation extends the cell cycle of Cyclotella sp. in the S (DNA synthesis) phase until the dimers are removed. Citation <12> Accession Number PREV199698819587 Author/Editor/Inventor Mayer Christine. Schmid Anna-Maria M [a]. Institution [a] Univ.-Salzburg, Plantphysiology, Hellbrunnerstr. 34, A-5020 Salzburg Austria. Title Morphology, cell-cycle, and growth-rates of Odontella regia. Source Diatom Research. 10(2). 1995. 299-320. Abstract The morphology and cell-cycle of the bipolar centric, marine diatom Odontella regia C. A. Agardh were studied, after establishing optimal growth conditions. The siliceous part of the cell wall is composed of loculate areolae with perforated sidewalls, which are internally attached to a system of parallel ribs arising from an elongated annulus. Two rimoportulae (RPs) are diagonally situated outside this primary band-i.e., the annulus. Their speedier and more massive silicification during morphogenesis causes a sigmoid distortion of the valve. Thickening of the wall occurs from outside to inside. There are 2 open girdle bands in the mature thecae. The nucleus is suspended in the cell centre, with cytoplasmic strands attached mainly to the with the events in Biddulphiopsis titiana (Franz & Schmid 1994). Also, the reorientation, complete reduction and then new outgrowth of cytoplasmic strands is similar, but no diaphragm is formed. Post cytokinetic shaping of the cleavage furrow! provides the mould for the gross morphology of the valve. Results are compared with those of B. titiana (Franz & Schmid 1994). Citation <13> Accession Number PREV199598544456 Author/Editor/Inventor Davidovich N A. Institution Karadag Branch, Inst. Biol. South. Seas, Ukr. Acad. Sci., Feodosiya, Ukraine. Title Size of initial cells of the diatom alga Nitzschia lanceolata formed under different lighting conditions. [Russian] Source Tsitologiia. 37(3). 1995. 257-265. Abstract The ability of Nitzschia lanceolata to realize all the stages of dioecious sexual reproduction in the absence of light has been shown elsewhere. Results of investigation of the length of auxospores, formed in dark or light, are presented, in addition to those of a preceding light-dark regimen on the readiness to auxosporulation and on the length of auxospores. It is determined that the length of auxospores is in average by 5-10% more in the presence of light, than in darkness. The readiness of parental cells to sexual reproduction decreased under continuous lighting. The availability of dark period was favorable for the alga sexualization. The sexual partners of N. lanceolata are able to enter the sexual process even without storing materials sufficient for a complete auxospore development. The results obtained are discussed in terms of a relationship between the auxospore formation and the vegetative cell cycle. Citation <14> Accession Number PREV199598522104 Author/Editor/Inventor Abraham R T. Acquarone M. Andersen A. Asensi A. Belle R. Berger F. Bergounioux C. Brunn G. Buquet-Fagot C. Fagot D. Glab N. Goudeau H. Goudeau M. Guerrier P. Houghton P. Hendriks H. Kloareg B. Lippai M. Marie D. Maro B. Meijer L [a]. Mester J. Mulner-Lorillon O. Poulet S A. Schierenberg E. Schutte B. Vaulot D. Verlhac M H. Institution [a] CNRS, Stn. Biol., BP 74, 29680 Roscoff France. Title Cellular effects of olomoucine, an inhibitor of cyclin-dependent kinases. Source Biology of the Cell (Paris). 83(2-3). 1995. 105-120. Abstract Olomoucine (2-(2-hydroxyethylamino)-6-benzylamino-9-methylpurine) has been recently described as a competitive inhibitor (ATP-binding site) of the cell cycle regulating p34-cdc2/cyclin B, p33-cdk2/cyclin A and p33-cdk2/cyclin E kinases, the brain p33-cdk5/p35 kinase and the ERK1/MAP-kinase. The unusual specificity of this compound towards cell cycle regulating enzymes suggests that it could inhibit certain steps of the cell cycle. The cellular effects of olomoucine were investigated in a large variety of plant and animal models. This compound inhibits the G1/S transition of unicellular algae (dinoflagellate and diatom). It blocks Fucus zygote cleavage and development of Laminaria gametophytes. Stimulated Petunia mesophyll protoplasts are arrested in G1 by olomoucine. By arresting cleavage it blocks the development of Calanus copepod larvae. It reversibly inhibits the early cleavages of Caenorhabditis elegans embryos and those of ascidian embryos. Olomoucine inhibits the sero! tonin-induced prophase/metaphase transition of clam oocytes; furthermore, it triggers the release of these oocytes from their meiotic metaphase I arrest, and induces nuclei reformation. Olomoucine slows down the prophase/metaphase transition in cleaving sea urchin embryos, but does not affect the duration of the metaphase/anaphase and anaphase/telophase transitions. It also inhibits the prophase/metaphase transition of starfish oocytes triggered by various agonists. Xenopus oocyte maturation, the in vivo and in vitro phosphorylation of elongation factor EF-1 are inhibited by olomoucine. Mouse oocyte maturation is delayed by this compound, whereas parthenogenetic release from metaphase II arrest is facilitated. Growth of a variety of human cell lines (rhabdomyosarcoma cell lines Rh1, Rh18, Rh28 and Rh30; MCF-7, KB-3-1 and their adriamycin-resistant counterparts; National Cancer Institute 60 human tumor cell lines comprising nine tumor types) is inhibited by olomoucine. Cell cyc! le parameter analysis of the non-small cell lung cancer cell line MR65 shows that olomoucine affects GI and S phase transits. Olomoucine inhibits DNA synthesis in interleukin-2-stimulated T lymphocytes (CTLL-2 cells) and triggers a GI arrest similar to interleukin-2 deprivation. Both cdc2 and cdk2 kinases (immunoprecipitated from nocodazole- and hydroxyurea-treated CTLL-2 cells, respectively) are inhibited by olomoucine. Both yeast and Drosophila embryos were insensitive to olomoucine. Taken together the results of this Noah's Ark approach show that olomoucine arrests cells both at the G1/S and the G2/M boundaries, consistent with the hypothesis of a prevalent effect on the cdk2 and cdc2 kinases, respectively. Citation <15> Accession Number PREV199598355348 Author/Editor/Inventor Crawford Richard M. Hinz Friedel. Institution Alfred-Wegener Inst. Polar Marine Res., Columbusstrasse, Postfach 120161, D-27515 Bremerhaven, Germany. Title The spines of the centric diatom Corethron criophilum: Light microscopy of vegetative cell division. Source European Journal of Phycology. 30(2). 1995. 95-105. Abstract As part of a study of the biology of the marine planktonic centric diatom Corethron criophilum, cells have been followed through the vegetative cell cycle from immediately before cytokinesis until separation of the two daughter cells. After cytoplasmic cleavage, which lasts 30 min, each of the daughter cells becomes shorter and leaves space for the spines to develop on each of the new hypovalves. The relationship of the two cingula of each cell remains static for approximately 12 h while the new valves are developed. Expansion of both of the daughter cells in the pervalvar axis then withdraws the girdles from one another thus revealing the mature spines of the new hypovalves which now spring out to assume their final positions. The function of the cingulum in protecting and releasing the spines in this diatom is discussed. Citation <16> Accession Number PREV199598193594 Author/Editor/Inventor Franz Susanne M. Schmid Anna-Maria M [a]. Institution [a] Univ. Salzburg, Plantphysiol., Hellbrunnerstr. 34, A-5020 Salzburg Austria. Title Cell-cycle and phenotypes of Biddulphiopsis titiana in culture. Source Diatom Research. 9(2). 1994. 265-288. Abstract The cell cycle and intraclonal variation were studied in the bipolar centric diatom Biddulphiopsis titiana (Grunow) v. Stosch & Simonsen. Three differently sized subclones, small (S), large (L), and extra large (XL), and a tripolar strain were all derived from a single cell and cultivated under identical conditions. No difference in ultrastructure was apparent, except for the additional pole in the tripolar cells, coupled to a reduction in the number of rimoportulae per pole. Cell size parameters were compared using SDS-cleaned cell walls of 5 different cell-cycle stages. In the living cell, except during cell division, plastids perform karyostrophic movement (i.e. to the nucleus) during the dark phase or whenever exposed to strong incident light. Plasmolysis can clearly be distinguished from a contraction of the protoplast in response to physiological or mechanical shock. The reactions differ in degree and speed. Preprophase is correlated with cell elongation and the format! ion of the second girdle band of the hypotheca. A hitherto undescribed diaphragm in the plane of the prospective division forms prior to prophasic nuclear migration, and coincides with the plane of cytokinesis. The pattern of cleavage is intermediate between that in circular, centric diatoms and that in pennate diatoms. In concert with mitosis and cleavage, a reorientation, complete reduction and then new outgrowth of cytoplasmic strands occurs. The cortical sites of anchorage of the strands are found chiefly at the rimoportulae (LPs), which are situated at the poles. Post cytokinetic shaping of the cleavage surface provides the mould for the gross morphology of the valves. Citation <17> Accession Number PREV199598075024 Author/Editor/Inventor Schmid Anna-Maria M. Institution Inst. Pflanzenphysiologie, Univ. Salzburg, Hellbrunnerstrasse 34, A-5020 Salzburg, Austria. Title Aspects of morphogenesis and function of diatom cell walls with implications for taxonomy. Source Protoplasma. 181(1-4). 1994. 43-60. Abstract Aspects of morphogenesis and morphology of diatom cell walls are reviewed to highlight functional correlations between wall structures and three-dimensional cytoplasmic activities during the cell cycle. Morphogenesis of the siliceous valve within the silica deposition vesicle is discussed in the fight of the dependency on a precisely orchestrated moulding machinery, involving the cytoskeleton, mitochondria, endoplasmic reticulum, spacer vesicles produced by the Golgi apparatus, and the plasmalemma, in combination with adhesion of the cells to parts of the parental wall and localized "plasmolyses". Sensitivity of morphogenetic events to fluctuations of external factors has implications for taxonomy. Citation <18> Accession Number PREV199598055426 Author/Editor/Inventor Doehler Guenter [a]. Biermann Thomas. Institution [a] Botanisches Inst. Univ., Siesmayerstr. 70, D-60054 Frankfurt am Main Germany. Title Impact of UV-B radiation on the lipid and fatty acid composition of synchronized Ditylum brightwellii (West) Grunow. Source Zeitschrift Fuer Naturforschung Section C Biosciences. 49(9-10). 1994. 607-614. Abstract The marine diatom Ditylum brightwellii (West) Grunow isolated from the Baltic Sea could be synchronized by a light/dark rhythm of 6.5: 17.5 h (,white light intensity 8 W m-2) at 18 degree C and 0.035 vol.% CO-2. Content of protein. DNA and RNA increased linearly up to the end of the cell cycle. Pigments (chlorophyll a, chlorophyll a, chlorophyll c-1+c-2, carotenoids) and galactolipids were synthesized in the light period only. A lag phase of 2 h was observed in the biosynthesis of sulphoquinovosyl diacylglycerol and phosphatidylglycerol. Formation of phosphatidylglycerol and phosphatidylcholine continued in the dark period (30% and 28%, respectively). The pattern of major fatty acids (C-14:0, C-16:1. C-18:1 and C-20:5) varied during the cell cycle of Ditylum. Biosynthesis of acyl lipids was reduced in dependence on the UV-B dose. The most sensitive lipid was digalactosyl diacylglycerol (total inhibition at 585 J m-2), whereas phosphatidylcholine was less affected (20% reduct! ion). UV-B radiation during the dark period had no effect on the lipid and pigment content. Strongest inhibitory effect of UV-B on cell division, synthesis of protein, pigments. sulphoquinovosyl diacylglycerol and phosphatidylglycerol was found after UV-B radiation at the beginning of the cell cycle (0.-2, h). An exposure time at the end of the light period (4.-6. h) led to a marked damage on the synthesis of monogalactosyl diacylglycerol and phosphatidylglycerol. These findings indicate a stage-dependent response of Ditylum to UV-B irradiance. The impact of UV-B resulted in an increase of unsaturated long chained fatty acids (C-18, C-20) and in a diminution of short chained fatty acids (C-14,C-16). Content of ATP was not affected by UV-B radiation under the used conditions. The inhibitory effect of UV-B on synthesis of DNA, RNA, protein and acyl lipids was mainly reversible. Results were discussed with reference to UV-B damage on the enzymes involved in the biosynthesis of ac! yl lipids and by a reduction of available metabolites. Citation <19> Accession Number PREV199497400591 Author/Editor/Inventor Lin Senjie [a]. Chang Jeng. Carpenter Edward J. Institution [a] Marine Sci. Res. Cent., State Univ. New York, Stony Brook, NY 11794 USA. Title Detection of proliferating cell nuclear antigen analog in four species of marine phytoplankton. Source Journal of Phycology. 30(3). 1994. 449-456. Abstract Proliferating cell nuclear antigen (PCNA) is an auxiliary protein for polymerase-delta and therefore is essential for cellular DNA synthesis. The synthesis and abundance of PCNA in the cell are cell-cycle-dependent, both increasing markedly during the S phase. Such a protein could be a useful cell cycle marker, which is required for estimating algal species-specific growth rates via the cell cycle approach. By using commercially available monoclonal anti rat-PCNA antibody and an enhanced chemiluminescence technique, PCNA-like proteins were detected in four species of marine phytoplankton. The strong single band detected on western blots of Isochrysis galbana Parke, Thalassiosira weissflogii Cleve, and Dunaliella tertiolecta Butcher had an apparent molecular weight of 33-36 kDa. This molecular weight is within the range as observed for PCNA in a wide phylogenetic array of organisms (33-36 kDa). In the diatom Sketetonema costatum (Grev.) Cleve, the PCNA antibody detected a maj! or band of about 19 kDa as well as a minor band of 38 kDa. The detected proteins were specifically recognized by the monoclonal anti-rat-PCNA antibody. The PCNA-like proteins in I. galbana, T. weissflogii, and D. tertiolecta were more abundant in the exponential growth stage and then decreased became undetectable in the late stationary stage. Our results show that the detected antigens appear to be algal analogs of PCNA. Citation <20> Accession Number PREV199395079055 Author/Editor/Inventor Davidovich N A. Institution A.O. Kovalevskii Inst. Biol. South Seas, Acad. Sci. Ukr., Sudak, Ukraine. Title The division rates of cells of the diatom alga Haslea subagnita during various periods of its life cycle. [Russian] Source Fiziologiya Rastenii (Moscow). 39(3). 1992. 599-605. Abstract The duration of cell division was calculated in the cells of Haslea subagnita (Pr.-Lavr.) Makar. et Kar. (Bacillariophyta), from the time necessary for the formation of valvules in daughter cells. An equation was suggested, according to which the duration of division was related to the change of proliferative pool and to the rate of cell proliferation for a certain period of time. The conditions of alga cultivation have favored the synchronization of cell cycle. The variation of the proliferative pool during period of illumination can be described by the Gauss curve. The duration of cell division depends upon the cell size and therefore on the life cycle. The division time decreased almost by half during the cell cycle of the alga because the cell sizes in clonal cultures varied from maximum values typical of marine algae to small sizes characteristic of auxospore formation. However the average daily rate of asexual reproduction remained constant. Citation <21> Accession Number 094060501 Authors Thomas D N. Baumann M E M. Gleitz M. Institution ALFRED WEGENER INSTITUTE POLAR MARINE RESEARCH, AM HANDELSHAFEN 12, 2850 BREMERHAVEN, GER. Title EFFICIENCY OF CARBON ASSIMILATION AND PHOTOACCLIMATION IN A SMALL UNICELLULAR CHAETOCEROS-SPP FROM THE WEDDELL SEA ANTARCTICA INFLUENCE OF TEMPERATURE AND IRRADIANCE. Source Journal of Experimental Marine Biology & Ecology 157 (2). 1992. 195-209. Abstract It is well established that Antarctic phytoplankton and sea-ice algae are able to thrive at low temperatures and it has been proposed that a reduction in respiration may be important in enabling them to do this. This possibility was studied in an Antarctic clone of a small unicellular Chaetoceros species isolated from the Weddell Sea (Antarctica), using comparative measurements of C assimilation during long- and short-term incubation series over a range of temperatures (-1.5 to 4.degree. C) at two irradiances (5 and 55 .mu.mol m-2 s-1). Even though doubling times varied considerably, the total amount of C assimilated per cell per generation time was similar at each of the temperature and light conditions. However, over one cell cycle, significant respiratory C losses were determined by divergence in C assimilation patterns between cumulative and long-term incubations at both light intensities at 0 and 4.degree. C. At -1.5.degree. C, insignificant C losses were recorded.! No significant extracellular release of dissolved organic material (DOC) was observed. It is hypothesized that an increase in C assimilation and growth rates at higher temperatures in this diatom is achieved at the expense of a decrease in efficiency of C metabolism. This study provides further evidence that respiration rates during light periods are of importance in C mass balance determinations of algae. The photoacclimation potential of this species was also investigated over the same temperature range. Differences in photosynthetic parameters and Chl a concentrations between "low" and "high"-light-acclimated cells revealed a high photoacclimation capacity irrespective of incubation temperature. Citation <22> Accession Number 094037913 Authors Chang J. Carpenter E J. Institution MARINE SCI. RES. CENT., STATE UNIV. N.Y., STONY BROOK, N.Y. 11794. Title SPECIES-SPECIFIC PHYTOPLANKTON GROWTH RATES VIA DIEL DNA SYNTHESIS CYCLES V. APPLICATION TO NATURAL POPULATIONS IN LONG ISLAND SOUND. Source Marine Ecology-Progress Series 78 (2). 1991. 115-122. Abstract A field experiment was conducted in Long Island Sound New York, USA, in July 1987 to test the ability of the cell cycle analysis method to estimate species-specific phytoplankton growth rates. The growth rates of 3 species - the diatom Leptocylindrus danicus and the dinoflagellates Prorocentrum triestinum and Dinophysis acuminata - were measured, and diffusion (cage) cultures were used in a parallel experiment to obtain independent estimates of growth rate. Growth rates estimated by the cell cycle method were 0.07 to 0.25 d-1 for L. danicus 0.43 and 0.44 d-1 for P. triestinum, and 0.54 and 0.67 d-1 for D. acuminata. The variation was higher for L. danicus because the degree of synchrony in this species was low. Growth rates measured by the diffusion culture methods were about 0.1 d-1 different from the corresponding rates from cell cycle analysis. The attempt to use the frequency of double nucleated cells as a means to check the accuracy of growth rate estimates was not s! uccessful. The estimated growth rates fit the observed pattern of phytoplankton succession. Citation <23> Accession Number 043113107 Authors Berdalet E. Latasa M. Estrada M. Institution INST. CIENCIES DEL MAR, CSIC, PG. NACIONAL S/N, 08039 BARCELONA, SPAIN. Title VARIATIONS IN BIOCHEMICAL PARAMETERS OF HETEROCAPSA-SP AND OLISTHODISCUS-LUTEUS GROWN IN 12 12 LIGHT DARK CYCLES I. CELL CYCLE AND NUCLEIC ACID COMPOSITION. Source FIFTH GAP (GROUP FOR AQUATIC PRIMARY PRODUCTIVITY) INTERNATIONAL WORKSHOP ON THE DAILY GROWTH CYCLE OF PHOTOTROPHIC MICROORGANISMS, BREUKELEN, NETHERLANDS, APRIL 20-28, 1990. Hydrobiologia 238 1992. 139-148. Citation <24> Accession Number 093062484 Authors Beech P L. Heimann K. Melkonian M. Institution BOTANISCHES INSTITUT, LEHRSTUHL 1, UNIVERSITAET ZU KOELN, GYRHOFSTRASSE 15, D-W-5000 KOELN 41, GER. Title DEVELOPMENT OF THE FLAGELLAR APPARATUS DURING THE CELL CYCLE IN UNICELLULAR ALGAE. Source Protoplasma 164 (1-3). 1991. 23-37. Abstract Recent evidence has shown that algal cells acquire different flagella and a heterogeneous basal apparatus through the prolonged development of these structures over more than one cell cycle. A system for numbering algal flagella and basal bodies, which is based on developmental studies, is discussed along with the various means by which the flagellar/basal body developmental cycle can be determined. We review the information now available on development of the separate components of the flagellar apparatus-this comes particularly from the Chlorophyta and the Chromophyta- and attempt to elucidate any information which may help in phylogenetic comparisons. New data is provided on developmental changes in the cartwheel part of the basal body and basal body-associated connecting fibrils in green algae. Citation <25> Accession Number 092110114 Authors Brzezinski M A. Olson R J. Chisholm S W. Institution DEP. BIOLOGICAL SCI., UNIV. CALIFORNIA, SANTA BARBARA, CALIFORNIA 93106, USA. Title SILICON AVAILABILITY AND CELL-CYCLE PROGRESSION IN MARINE DIATOMS. Source Marine Ecology-Progress Series 67 (1). 1990. 83-96. Abstract The role of silicon availability on cell-cycle progression in marine diatoms was examined using flow cytometric methods. Silicon deprivation halted the progresson of cells through the cell cycle with cells arresting in G1, G2 and M in 6 or 7 species examined (5 centric and 1 pennate species). The exception, Phaeodactylum tricornutum, did not require silicon for growth and did not have a silicon-dependent segment within its cell cycle. This species was also the only one lacking a light-dependent arrest point late in its cells cycle suggesting that the arrest of diatom cells in G2 and M in the dark is related to silicon metabolism. Chaetoceros spp. were unique in that they had 2 silicon-dependent segments in G1: one at the G1/S boundary apparently associated with a silicon requirement for DNA synthesis and a second earlier in G1 associated with the deposition of siliceous setae. Silicon limitation of Thalassiosira weissflogii led to an increase in the duration of G2 with ! a duration of G1, S and M remaining as observed under nutrient-replete conditions. In severely limited cells, G2 comprised 82% of the cell cycle and lasted for over 2 d. More complicated responses were observed for Cylindrotheca fusiformis and Chaetoceros simplex. Modest silicon limitation of C. fusiformis led to increases in the duration of GS and possibly M. More severe silicon stress did not lengthen M further, but both G2 and G1 increased in duration. For C. simplex, modest silicon limitation led to the expansion of G1 alone, while more severe limitation lengthened G1, G2, and M. Changes in cell cycle durations in this species appeared related to a decline in the silicon content of siliceous setae deposited during G1. These results corroborate past observations that silicon metabolism in linked to specific segments of the cell cycle, but indicate that these regions can lengthen dramatically in response to silicon limitation. Citation <26> Accession Number 091002051 Authors Li C W. Lee M. Volcani B E. Institution INST. LIFE SCI., NATL. TSING HUA UNIVERSITY, HSINCHU, TAIWAN. Title VASE-SHAPED MITOCHONDRIA OF THE CENTRIC DIATOM STEPHANOPYXIS-TURRIS. Source Diatom Research 5 (1). 1990. 51-54. Abstract Two morphological forms of mitochondria, vase-shaped and discoid, are described in a centric diatom, Stephanopyxis turris (Greville) Ralfs, and their three-dimensional structure reconstructed from serial sections. The vase-shaped mitochondria, previously unreported in unicellular organisms, constitute the majority, no matter what the stage of the cell cycle. A comparison is made between the vase-shaped mitochondria and the cup-shaped mitochondria that are found in a few multicellular organisms. Citation <27> Accession Number 090107821 Authors Inokuchi M. Maruyama K. Institution INST. APPLIED MICROBIOL., UNIV. TOKYO, TOKYO 113, JAPAN. Title INFRASPECIFIC DIFFERENCES IN CYCLOTELLA-COMTA POPULATIONS IN THE FUJI FIVE LAKES AND LAKE ASHINO-KO IN JAPAN. Source Japanese Journal of Phycology 38 (2). 1990. 105-118. Abstract The valve diameter (D), marginal width (M) and striae (S) and cell densities of Cyclotella comat populations together with the nutrient profile of the water were examined by using samples collected from coastal surface water at thirty-five stations in the Fuji Five Lakes and Lake Ashino-ko in 1987. The natural populations of C. comta were found to show a statistically significant annual change in the valve diameter and markings on the valve surface. In a population, M decreases, but S increases and M/D does not change or increases, when D decreases, while the correlation coefficients of D-M, D-S and D-M/D decreases in the order. D, M and M/D get smaller and S larger from spring from spring to autumn, while keeping at the above feature. The cell type defined by two variables such as D-M, D-S or D-M/D seems to be present in each lake. The dependency of cell type on cell density and environmental factors was observed. Citation <28> Accession Number 089112403 Authors Beech P L. Wetherbee R. Institution BOTANY SCH., UNIV. MELBOURNE, PARKVILLE, 3052 VICTORIA, AUST. Title THE FLAGELLAR APPARATUS OF MALLOMONAS-SPLENDENS SYNUROPHYCEAE AT INTERPHASE AND ITS DEVELOPMENT DURING THE CELL CYCLE. Source Journal of Phycology 26 (1). 1990. 95-111. Abstract The interphase configuration of th flagellar apparatus of Mallomonas splendens (G.S. West) Playfair displays several features that are novel in the Synurophyceae. One of the two basal bodies usually has no flagellum, and two fibrous bands connect the basal bodies. Surrounding the basal bodies is a distinctive, fibrous capsule which is continuous with a thick, fibrous band that constitutes the anterior portion of the rhizoplast. The remainder of the rhizoblasts spreads over the nuclear apex as numerous, prominently striated straps. A single, three-membered, microtubular root (R1) forms a loop at the cell anterior and then descends from the loop to abutt on the rhizoplast near the nuclear apex. The descending portion of R1 displays at least two orientations with respect to the basal bodies. Two new basal bodies appear before mitosis and bear the rudiments of new R1s. At preprophase these new roots are 2-3 .mu.m long, and new rhizoplasts, which organize (nucleate?) micr! otubules of the incipient mitotic spindle, arise from the proximal end of the new basal bodies. The latter produce new flagella as the parental flagellum shortens. Simultaneous to these developments is the disassembly of the parental rhizoplast and the descending portion of the parental R1. At metaphase the two pairs of basal bodies have separated so that each pairs consists of a parental and a daughter basal body. The parental R1 loop is absent and the new R1s form semi-loops around each pair of basal bodies. The rhizoplasts extend down either side of the nuclear material as the spindle becomes fully formed. The new loops are completed at mid-cytokinesis. At the end of cytokinesis the roots elongate towards the nuclear apex, and each rhizoplast takes on the interphase appearance. Mitosis in M. spendens is compared to that in the Chrysophyceae.