bluuebunny/crossref_metadata_2025 huggingface dataset:
Propofol and Sevoflurane Depress Spinal Neurons In Vitro via Different Molecular Targets
Authors: Grasshoff Christian , Antkowiak Bernd
Published: October 2004

Background

The capacity of general anesthetics to produce immobility is primarily spinally mediated. Recently, compelling evidence has been provided that the spinal actions of propofol involve gamma-aminobutyric acid type A (GABAA) receptors, whereas the contribution of glycine receptors remains uncertain. The relevant molecular targets of the commonly used volatile anesthetic sevoflurane in the spinal cord are largely unknown, but indirect evidence suggests a mechanism of action distinct from propofol.

Methods

The effects of sevoflurane and propofol on spontaneous action potential firing were investigated by extracellular voltage recordings from ventral horn interneurons in cultured spinal cord tissue slices obtained from embryonic rats (embryonic days 14-15).

Results

Propofol and sevoflurane reduced spontaneous action potential firing of neurons. Concentrations causing half-maximal effects (0.11 microm propofol, 0.11 mm sevoflurane) were lower than the median effective concentration immobility (1-1.5 microm propofol, 0.35 mm sevoflurane). At higher concentrations, complete inhibition of action potential activity was observed with sevoflurane but not with propofol. Effects of sevoflurane were mediated predominantly by glycine receptors (45%) and GABAA receptors (38%), whereas propofol acted almost exclusively via GABAA receptors (96%).

Conclusions

The authors' results suggest that glycine and GABAA receptors are the most important molecular targets mediating depressant effects of sevoflurane in the spinal cord. They provide evidence that sevoflurane causes immobility by a mechanism distinct from the actions of the intravenous anesthetic propofol. The finding that propofol acts exclusively via GABAA receptors can explain its limited capacity to depress spinal neurons in the authors' study.
Phase mixing of Alfvén pulses and wavetrains propagating in coronal holes
Authors: Hood A. W. , Brooks S. J. , Wright A. N.
Published: October 2004

The propagation of Alfvén pulses into an inhomogeneous model of a solar coronal hole is investigated. The algebraic damping of single and bi–polar pulses remains for the leading and trailing pulses as the number of pulses is increased but the decay of the internal pulses returns to the exponential damping of an infinite wavetrain when three pulses or more are present. Thus, wavetrains with most of their energy residing in internal oscillations will be dominated by efficient exponential damping. In contrast, short wavetrains with most of their energy in the leading and trailing pulses will suffer less efficient algebraic damping. The implications of both the damping of these disturbances to the heating of coronal holes and the nonlinear wave pressure to the acceleration of the solar wind are discussed.
Molecular dynamics simulation of the interaction between the complex iron–sulfur flavoprotein glutamate synthase and its substrates
Authors: Coiro Vincenza M. , Di Nola Alfredo , Vanoni Maria A. , Aschi Massimiliano , Coda Alessandro , Curti Bruno , Roccatano Danilo
Published: October 2004

Glutamate synthase (GltS) is a complex iron–sulfur flavoprotein that catalyzes the reductive transfer of L‐glutamine amide group to the C2 carbon of 2‐oxoglutarate yielding two molecules of L‐glutamate. Molecular dynamics calculations in explicit solvent were carried out to gain insight into the conformational flexibility of GltS and into the role played by the enzyme substrates in regulating the catalytic cycle. We have modelled the free (unliganded) form of Azospirillum brasilense GltS α subunit and the structure of the reduced enzyme in complex with the L‐glutamine and 2‐oxoglutarate substrates starting from the crystallographically determined coordinates of the GltS α subunit in complex with L‐methionine sulphone and 2‐oxoglutarate. The present 4‐ns molecular dynamics calculations reveal that the GltS glutaminase site may exist in a catalytically inactive conformation unable to bind glutamine, and in a catalytically competent conformation, which is stabilized by the glutamine substrate. Substrates binding also induce (1) closure of the loop formed by residues 263–271 with partial shielding of the glutaminase site from solvent, and (2) widening of the ammonia tunnel entrance at the glutaminase end to allow for ammonia diffusion toward the synthase site. The Q‐loop of glutamate synthase, which acts as an active site lid in other amidotransferases, seems to maintain an open conformation. Finally, binding of L‐methionine sulfone, a glutamine analog that mimics the tetrahedral transient species occurring during its hydrolysis, causes a coordinated rigid‐body motion of segments of the glutaminase domain that results in the inactive conformation observed in the crystal structure of GltS α subunit.
THE EFFECT OF LABELING INTENSITY, ESTIMATED BY REAL‐TIME CONFOCAL LASER SCANNING MICROSCOPY, ON FLOW CYTOMETRIC APPEARANCE AND IDENTIFICATION OF IMMUNOCHEMICALLY LABELED MARINE DINOFLAGELLATES1
Authors: Vrieling Engel G. , Draaijer Arie , van Zeijl Wilhelmus J. M. , Peperzak Louis , Gieskes Winfried W. C. , Veenhuis Marten
Published: October 2004

Two different fluorescein isothiocyanate (FITC) conjugates were used to analyze the effect of labeling intensity on the flow cytometric appearance of marine dinoflagellates labeled with antibodies that specifically recognized the outer cell wall. Location of the labeling was revealed by epifluorescence and real‐time confocal laser scanning microscopy using an anti‐rabbit IgG/FITC‐conjugated secondary antiserum. Flow cytometric measurements showed that cells ofProrocentrumspecies labeled this way could not always be distinguished from unlabeled cells. The labeling intensity increased several times when a biotinylated anti‐rabbit IgG secondary antiserum was used in combination with a streptavidin/FITC conjugate. Flow cytometry indicated that the labeling intensity had increased 50%, which resulted in an improved separation of clusters of labeled and unlabeled cells.
BIOCHEMICAL AND CYTOLOGICAL EVIDENCE FOR THE STIMULATION OFCLATHRIN‐COATED PIT (VESICLE) FORMATION BY EXOGENOUS FOLIC ACID IN DUNALIELLA SALINA (CHLOROPHYTA)1
Authors: Zhang Xiao Qing , Dubacq Jean‐Paul , Alfsen Annette
Published: October 2004

The effects of two kinds of molecules, Pb2+ and folic acid, on the formation of clathrin‐coated pits and vesicles were studied in the unicellular green alga, Dunaliella salina Teod. Measurable amounts of algal clathrin were obtained in the postmicrosomal fraction from cells treated with folic acid. In contrast, algal clathrin heavy chains were below the detection limit in the postmicrosomal fraction from control and lead nitrate‐treated cells. Consistent with the biochemical evidence, electron microscopy showed more clathrin‐coated pits and vesicles in folic acid‐treated cells compared to control cells or cells treated with lead nitrate alone. Observations of folic acid/lead nitrate‐treated cells confirmed the endocytosis of Pb2+ through clathrin‐coated pits and vesicles. As additional evidence for clathrin in the folic acid‐stimulated cells of Dunaliella salina, clathrin was isolated and, for the first time in algae, the calcium‐dependent reconstitution of clathrin cages was successfully obtained in vitro.
A STERILIZATION PROTOCOL FOR THE DICTYOTALES (PHAEOPHYCEAE)1
Authors: Aguirre‐Lipperheide Mercedes , Evans Leonard V.
Published: October 2004

Following a study on the effect of several physical (brushing and ultrasound) and chemical (antiseptic and antibiotic) treatments on the brown seaweedStypopodium zonale(Lamoroux) Papenfuss (Dictyotales, Phaeophyceae), bactericidal treatments that were not phytotoxic to the alga were selected. The sterilization protocol consisted of 1) surface brushing of the explants, 2) incubation in the antiseptic betadine (0.50%) for 5 min, and 3) incubation in an antibiotic mixture (650 mg · L−1kanamycin, neomycin, and penicillin G) for 48 h. The response of the material to the treatments was assessed by means of an oxygen electrode, and a bacterial test was performed to test bactericidal efficiency. The protocol rendered photosynthetically active axenic explants ofS. zonaleand other members of the order (e.g.Zonaria tournefortii(Lam.) Montagne).
BENTHIC DIATOMS FROM THE NORTH CAROLINA CONTINENTAL SHELF: INNER AND MID SHELF1
Authors: Cahoon Lawrence B. , Laws Richard A.
Published: October 2004

Sediment samples collected by SCUBA divers at two times and three sites on inner and middle continental shelf of North Carolina a well‐developed benthic diatom flora. The most abundant species included the pennate forms Cocconeis disculoides, Diploneis papula, Naticula pullus, Delphineis surrirella, Amphora sublaevis, and A. tenerrima. Biomass of this distinct benthic microflora ranged from 16 to 97 mg chl a + m−2 and is comparable to sediment chlorophyll a values reported in previous studies.
ULTRASTRUCTURE AND 18S RRNA GENE SEQUENCE FOR PELAGOMONAS CALCEOLATA GEN. ET SP. NOV. AND THE DESCRIPTION OF A NEW ALGAL CLASS, THE PELAGOPHYCEAE CLASSIS NOV.1
Authors: Andersen Robert A. , Saunders Gary W. , Paskind Michael P. , Sexton Julianne P.
Published: October 2004

Pelagomonas calceolata gen. et sp. nov., an ultra‐planktonic marine alga, is described using electron microscopy and the cytoplasmic small subunit (18S) ribosomal RNA (rRNA) gene sequence. Cells are uniflagellate, about 1.5 × 3 μm in size. The flagellium has two rows of bipartite hairs, the paraxonemal rod has a dentate appearance, and a two‐gyred transitional helix is present between two transitional plates. Microtubular roots, striated roots, and a second basal body are absent. A thin organic theca surrounds most of the cell. There is a single chloroplast with a girdle lamella and a single, dense mitochondrion with tubular cristae. A single Golgi body with swelled cisternae lies beneath the flagellum, and each cell has an ejectile organelle that putatwely releases a cylindrical structure. A vacuole, or cluster of vacuoles, contains the putative carbohydrate storage product. The 18S rRNA gene was sequenced completely in both directions, excluding three primer regions. When compared to the same gene sequence from other organisms, Pelagomonas calceolata gen. et sp. nov. occupies an unresolved position among other chromophyte algae and is distinct from members of any of these classes. Based on morphological, ultrastructural, and molecular data, we describe this alga as a new species, and we place this highly unusual new species in a new genus, family, order, and class.
DISTRIBUTION AND SYSTEMATICS OFBATRACHOSPERMUM(BATRACHOSPERMALES, RHODOPHYTA) IN NORTH AMERICA. 3. SECTIONSETACEA1
Authors: Sheath Robert G. , Vis Morgan L. , Cole Kathleen M.
Published: October 2004

Six populations ofBatirachospermumsectionSetaceafrom North America were compared to eight type specimens using multivariate morphometrics and image analysis. From this analysis, four species in this section were distinguished worldwide:B. atrum(Hudson) Hartley [syn.B. gallaeiSirodot]; B. orrthostichumSkuja,B. sertularina(Bory) Bory]; B. diatychesEntwisle; B. androinvolucrumsp. nov.; andB. puiggarianumGrunow in Wittrock et Nordstedt (syn.B. angolenseWelwitsch ex West et West,B. nigrescensWelwitsch ex West et West).Two of these species were found in North America: B. atrumin California and Texas andB. androinvolucrumin British Columbia, Washington State, and Alabama. The new species,B. androinvolucrum, is distinguished by having spermatangia restricted to one‐celled involucral bracts of the carpogonial branch.
IMMUNOLOCALIZATION OF CENTER IN THE FLAGELLAR APPARATUS OF MALE GAMETES OF ECTOCARPUS SILICULOSUS (PHAEOPHYCEAE) AND OTHER BROWN ALGAL MOTILE CELLS1
Authors: Katsaros Christos I. , Maier Ingo , Melkonian Michael
Published: October 2004

Centrin or a centrin homologue was localized using immunofluorescence in the flagellar basal body region in zoids of five brown algal species: Ectocarpus siliculosus (Dillw.) Lyngb., Scytosiphon lomentaria (Lyngb.) Link, Laminaria digitata (Huds.) Lamour., Sphacelaria rigidula (Kütz.) Prud'homme van Reine, and Fucus serratus L. The antigen is restricted to short rods extending along the basal body(ies) and towards the nucleus, which always remains firmly linked to the flagellar apparatus in isolated cytoskeletons. To identify these antigenic sites, pre‐ and postembedding immunogold electron microscopy was applied to male gametes of E. siliculosus. At least three different structures associated with the basal bodies were antigenic: a fibrous structure connecting the proximal end of the posterior basal body to the nucleus (nucleus‐basal body connector), a striated band that links the two basal bodies to each other and is located in the angel formed by them, and amorphous material interconnecting the basal bodies in their most proximal regions. In addiction, specific labeling occurs along the external surface and within the lumen of both basal bodies and in the flagellar transitional region. The possible function of these centrin‐containing structures is discussed.
OBSERVATIONS ON LICHENIZED AND FREE‐LIVING PHYSOLINUM (CHLOROPHYTA, TRENTEPOHLIACEAE)1
Authors: Davis Joseph S. , Rands David G.
Published: October 2004

Lichenized Physolinum Printz and free‐living Physolinum from a dimly lit cave were studied from fresh collections and cultures, preserved specimens fixed in situ, and cultures that had persisted for 5 years in an environmental chamber. The branched filamentous association consists of a phycobiont and a characteristic ascomycetous mycobiont of one layer that completely ensheathes the algal partner. Epiphytic blue‐green algae commonly occur attached to the mycobiont. The phycobiont, Physolinum monilia (De Wildem.) Printz, produces thick‐walled, green spiny cells, some of which enlarge and contact the sheathing mycobiont cells; the phycobiont and mycobiont may then develop into new lichenized filaments. The hyaline mycobiont cells extend haustoria bound by the fungus wall deeply into the phycobiont chloroplasts. The epiphytes, Synechocystis‐like colonies, are firmly attached to the outer walls of the mycobiont and are associated with several‐celled extensions of the fungus beyond the apical phycobiont cells. Free‐living Physolinum monilia filaments are branched and moniliform; the search‐containing uninucleate cells are spherical to pyriform and have walls of cellulose. Each cell has a single massive chloroplast with plastoglobuli among tightly packed thylakoids. Except for their larger cells, P. monilia filaments appear to be identical to the phycobiont of lichenized Physolinum.
ULTRASTRUCTURE OF THE BASAL APPARATUS AND PUTATIVE VESTIGIAL FEEDING APPARATUSES IN A QUADRIFLAGELLATE EUGLENOID (EUGLENOPHYTA)1
Authors: Triemer Richard E. , Lewandowski Carole L.
Published: October 2004

The flagellar apparatus and presumptive vestigial feeding apparatuses of a cold‐water, photosynthetic, quadriflagellate euglenoid is described. The organism possesses two similar sets of flagella each consisting of one short and one long flagellum. Each pair of flagella is associated with three microtubular roots for a total of six roots in the basal apparatus. At the level of the ventral basal bodies, each intermediate root is nine‐membered, while the ventral roots are composed of eight to nine microtubules. Only one of the ventral roots lines the single microtubule reinforced pocket. A four‐membered dorsal root attaches to each dorsal basal body, and at the level of the reservoir each gives rise to a dorsal band. An additional bundle of microtubules, not arising from the microtubular roots of the basal apparatus, begins posterior to the basal apparatus as a small group of a few microtubules and extends anteriorly on the right ventral side of the reservoir ending at the canal. At the level of the stigma, the microtubules are organized into a multi‐layered bundle that continues to increase in size and eventually splits to form two bundles at the level of the canal. We postulate that these bundles may represent the remnants of a rod‐and‐vane‐type feeding apparatus like that found in many phagotrophic euglenoids.
PROTEINACEOUS AND IMMUNOCHEMICAL DISTINCTIONS BETWEEN THE OVAL AND FUSIFORM MORPHOTYPES OF PHAEODACTYLUM TRICORNUTUM (BACILLARIOPHYCEAE)1
Authors: Gutenbrunner Sabine A. , Thalhamer Joseph , Schmid Anna‐Maria M.
Published: October 2004

Two morphotypes, fusiform and oval, were isolated from a single clone of the diatom Phaeodactylum tricornutum Bohlin and maintained as subclones by culturing in liquid and solid substrates, respectively. Salinity of the medium, from brackish to marine, had no effect on expression of the phenotypes. The oval cell is generated endogenously within a “transformed”fusiform cell upon transfer from liquid medium to agar plates. With the light microscope, normal and “transformed”fusiform cells, prior to giving rise to oval cells, can be discriminated by means of their staining response to toluidine blue.

Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis of protein extracts from lysed cells revealed slight differences in polypeptide composition between fusiform and oval types. A phenotype‐restoration experiment from oval to fusiform demonstrated that the oval type readily reestablished not only fusiform morphology but also the protein pattern characteristic for the fusiform type. Immunochemical analyses (western blots) using antisera raised against whole and lysed cells of both morphotypes revealed antigenic alterations of the oval morphotype. Several antigenic determinants restricted mainly to the surface of oval cells were detected. Results indicate that environmentally induced phenotypes of Phaeodactylum may be not only the consequence of specific gene expression but also the result of significant, general post‐translational modifications.
MEIOSIS, BLADE DEVELOPMENT, AND SEX DETERMINATION INPORPHYRA PURPUREA(RHODOPHYTA)1
Authors: Mitman Grant G. , van der Meer John P.
Published: October 2004

The discovery in the early 1980s that meiosis occurs during germination of conchospores ofPorphyra yezoensisUeda suggested that the sexually divided fronds ofPorphyra purpurea(Roth) C. Agardh might similarly originate from meiotic segregation of a pair of sex‐determining alleles during early sporeling development. After establishing conditions suitable for propagatingP. purpureain culture, observations on developing sporelings demonstrated that meiosis takes place during the first two divisions of the germinating conchospores. In the first division, the spore is split into an upper and lower cell. In the second, an anticlinal division in the upper cell yields two daughter cells situated one beside the other, and a periclinal division in the bottom cell gives two cells arranged one above the other. Thus, during normal development, the first four cells of the sporeling constitute a meiotic tetrad whose cells are arranged in a characteristic fashion. Stable color mutants ofP. purpureawere isolated, genetically characterized, and used as genetic markers to follow the fate of individual cells of the tetrad during subsequent frond development. Nearly the entire blade of the mature thallus is derived from the two upper cells of the tetrad, with the two lower cells mostly giving rise to the rhizoidal holdfast region. Cell lineage boundaries laid down by the segregation of color alleles at meiosis corresponded perfectly with those later defined by sexual differentiation on the same fronds, strongly supporting the hypothesis that sex determination inP. purpureais controlled by alleles at a segregating chromosomal locus.
PHYSIOLOGICAL ECOTYPES IN THE MARINE ALGA BOSTRYCHIA RADICANS (CERAMIALES, RHODOPHYTA) FROM THE EAST COAST OF THE U.S.A1
Authors: Karsten Ulf , West John A. , Zuccarello Giuseppe , Kirst Gunter O.
Published: October 2004

The comparative ecophysiology of nine culture isolates of the eulittoral red alga Bostrychia radicans (Montagne) Montague collected at sites from seven states along the east coast of the U.S.A. was investigated. The growth response in relation to different salinity and light conditions as well as photosynthesis‐irradiance curves were studied. In addition, the effect of salt treatment on the content of the isomeric polyols d‐sorbitol and d‐dulcitol was also studied. All isolates grew between salinities of 5.3 and 70 ppt but with quite different optima and maxima. The isolates were all adapted to low light levels, i.e. growth was already recorded at 2.5 μmol photons·m−2·s−1, and growth rates peaked between 40 and 60 μmol photons·m−2·s‐1. These low‐light requirements were also reflected by the photosynthesis‐irradiance curves: all plants had low light compensation points (2.5–9.7 μmol photons ·m−2·−1) and low photon fluence rates for initial saturation of photosynthesis (38.1–84.7 μmol photons·m−2·s−1, indicating that these isolates are “shade‐adapted.” Isolates from Florida and Georgia synthesized and accumulated both the osmolytes d‐sorbitol and d‐dulcitol in increasing salinities, whereas only d‐sorbitol was present in plants from North Carolina north to Connecticut. d‐sorbitol was always strongly involved in osmotic acclimation. In various isolates from the same location in South Carolina, both polyol patterns were found, i.e. d‐sorbitol plus d‐dulcitol and d‐sorbitol only. All data indicate that B. radicans exhibits a broad salinity tolerance and a low‐light preference, which explain the successful colonization of this alga on various intertidal and shaded substrates. The data also clearly indicate intraspecific differences among the nine isolates, which is interpreted as development of different physiological ecotypes.
ORGANIC CARBON RELEASE BYDUNALIELLA SALINA(CHLOROPHYTA) UNDER DIFFERENT GROWTH CONDITIONS OF CO2, NITROGEN, AND SALINITY1
Authors: Giordano Mario , Davis Joseph S. , Bowes George
Published: October 2004

Two strains ofDunaliella salina(Dunal) Teod., UTEX 1644 and UTEX 200, were cultured under different growth regimes, including 10 mM NO3−or NH4+, 1.5 or 3.0 M NaCl, and low (0.035%) or high (5%) CO2in air. The release of14C‐labeled dissolved organic carbon (DOC), expressed as a rate and as a percentage of photosynthetic14CO2assimilation, was subsequently determined. The percentage of DOC released was inversely related to cell density in the assay medium, but photosynthesis on a per‐cell basis was not. Release of DOC was low, in the range of 1–5% of photosynthesis, but during acclimation to growth on NH4+, it rose to 11%. The presence of NH4+rather than NO3−in the growth medium increased therateof release by both strains, but thepercentagerelease was stimulated only in UTEX 200 cells, because their photosynthetic rate was depressed by NH4+. For UTEX 1644, high, as compared to low, CO2‐grown cells, had somewhat higher rates and percentages of DOC release, but release from UTEX 200 cells was unaffected by the growth‐CO2. The rate of DOC release by high CO2‐grown cells was not enhanced at a low concentration of dissolved inorganic carbon, indicating that the released material did not originate from the photorespiratory pathway. The effects of NaCl on DOC release varied with strain and growth conditions. For UTEX 200, the cells in NO3−, but not NH4+, exhibited a doubling or more in percentage of release with a doubling in NaCl concentration, irrespective of growth‐CO2. With UTEX 1644 the low CO2‐grown cells showed the greatest enhancement in 3.0 M NaCl. Organic matter accumulated on the external surface of the cell membrane and constituted a well‐defined cell‐coat, which was more dense in NH4+than in NO3−‐grown cells. Microtubules, which may play a role in maintaining cell shape, were observed just below the plasma membrane.

From a practical viewpoint, the presence of organic material in the hypersaline ponds of salt‐works is detrimental to salt production. WhenD. salinacells become abundant in such ponds, the attendant, continuous release of DOC may make a significant contribution to the problem.
LIGHT AND ELECTRON MICROSCOPIC CHARACTERIZATION OF TWO TYPES OF PYRENOIDS INGONIUM(GONIACEAE, CHLOROPHYTA)1
Authors: Nozaki Hisayoshi , Kuroiwa Haruko , Kuroiwa Tsuneyoshi
Published: October 2004

The single, basal pyrenoids ofGonium quadratumPringsheim ex Nozaki andG. pectoraleMüller (Goniaceae, Chlorophyta) differed in appearance when vegetative colonies were cultured photoheterotrophically in medium containing sodium acetate. Chloroplasts ofG. quadratumhad distinct pyrenoids when grown in medium without major carbon compounds. However, the pyrenoids degenerated and were markedly reduced in size when such cells were inoculated into a medium containing 400 mg·L−1of sodium acetate. No pyrenoids were visible under the light microscope; however, with electron microscopy small pyrenoids and electron‐dense bodies were visible within the degenerating chloroplasts, which had only single layers of thylakoid lamellae at the periphery. The chloroplasts subsequently developed distinct pyrenoids and several layers of thylakoid lamellae as the culture aged. In contrast, vegetative cells ofG. pectoralealways showed distinct pyrenoids when cells were inoculated into medium containing sodium acetate, sodium pyruvic acid, sodium lactate, and/or yeast extract. Therefore, we propose two terms, “unstable pyrenoids” and “stable pyrenoids,” for pyrenoids ofG. quadratumandG. pectorale, respectively. Chloroplasts of the colonial green flagellates should thus be examined under various culture conditions in order to determine whether their pyrenoids are unstable or stable when pyrenoids are used as taxonomic indicators. Immunogold electron microscopy showed that the ratios of gold particle density of ribulose‐1,5‐biphosphate carboxylase/oxygenase (RuBisCO) between pyrenoid matrix and chloroplast stroma inG. quadratumgrown in medium with or without sodium acetate were lower than those ofG. pectorale.Heavy labeling by anti‐RuBisCO was observed in both the electron‐dense bodies and pyrenoid matrix ofG. quadratum.This is the first electron microscopic demonstration of degeneration and development of both pyrenoids and thylakoid lamellae in the chloroplast as a function of culture condition in green algae.
SYSTEMATIC SIGNIFICANCE OF THE ABSENCE OF PIT‐PLUG CAP MEMBRANES IN THE BATRACHOSPERMALES (RHODOPHYTA)1
Authors: Pueschel Curt M.
Published: October 2004

Four species of the Batrachospermales were examined by transmission electron microscopy to determine whether or not cap membranes, a typical structural component of pit plugs in several orders of red algae, were present. Routine specimen preservation methods used in past studies led to contradictory reports, soBatrachospermum keratophytumBory,B. sirodotiiSkuja ex Reis,Sirodotia suecicaKylin, andS. tenuissima(Collins) Skuja ex Flint were prepared by secondary fixation in potassium permanganate or a combination of potassium ferrocyanide‐osmium tetroxide to enhance membrane contrast. These fixation procedures produced clear, well‐contrasted images in which cap membranes were absent. The absence of cap membranes inS. suecicaandS. tenuissimaand the presence of cap membranes in two members of the Nemaliales was confirmed by freeze‐substitution methods. Absence of cap membranes in representatives of the Batrachospermales further distinguishes the Batrachospermales from the Nemaliales, the order in which they long resided, and demonstrates the value of this character in elucidating ordinal alliances among the Rhodophyta.
PHYLOGENETIC RELATIONSHIPS WITHIN THE COLONIAL VOLVOCALES (CHLOROPHYTA) INFERRED FROM CLADISTIC ANALYSIS BASED ON MORPHOLOGICAL DATA1
Authors: Nozaki Hisayoshi , Itoh Motomi
Published: October 2004

A cladistic analysis was used to deduce the phylogenetic relationships within the colonial Volvocales. Forty‐one pairs of characters related to gross morphology and ultrastructure of vegetative colonies as well as asexual and sexual reproduction were analyzed based on parsimony, using the PAUP 3.0 computer program, for 25 species belonging to nine volvocacean and goniacean genera of the colonial Volvocales.Chlamydomonas reinhardtiiDangeard was the outgroup. The strict consensus tree indicated the presence of two monophyletic groups, one composed of all the volvocacean species analyzed in this study and the other containing the goniacean species except for the four‐celled speciesGonium sociale(Dujardin) Warming. In addition, these two groups constitute a large monophyletic group, to whichG. socialeis a sister group. A new combinationTetrabaena socialis(Dujardin) Nozaki et Itoh and a new family Tetrabaenaceae Nozaki et Itoh are thus proposed forG. sociale.In addition, the analysis suggests that the volvocacean generaEudorinaandPleodorinaare paraphyletic groups, respectively, and that the monotypic genusYamagishiellahas no autapomorphic characters and represents primitive features of the anisogamous and oogamous genera of the Volvocaceae. Phylogenetic relationships within the Volvocaceae and the Goniaceae, as well as the various modes of sexual reproduction exhibited by these organisms, are discussed on the basis of the analysis.
IMMUNOLOCALIZATION OF CENTRIN IN OXYRRHIS MARINA (DINOPHYCEAE)1
Authors: Höhfeld Ingo , Beech Peter L. , Melkonian Michael
Published: October 2004

A new polyclonal antibody was raised against centrin isolated from the flagellate green alga Spermatozopsis similis (Chlorophyta; anti‐SSC). It stains by immunofluorescence and immunoelectron microscopy well‐known reference systems for centrin like the nucleus–basal body connectors in Chlamydomonas reinhardtii (Chlorophyta) and the system II fibers (rhizoplasts) of Scherffelia dubia (Chlorophyta). In addition, it recognizes in immunoblots a single 20‐kDa protein in isolated cytoskeletons of Spermatozopsis similis and Tetraselmis striata (Chlorophyta) as well as purified centrin isolated from Tetraselmis striata. Using this antibody, centrin was localized in whole cells and isolated cytoskeletons of Oxyrrhis marina Dujardin (Dinophyceae) by immunofluorescence and immunogold electron microscopy. In the flagellar apparatus of O. marina, five different structures were antigenic. Four short fibers (connectives 1–4) link the basal bodies to the four major fibrous flagellar roots, which do not cross‐react with anti‐centrin. The most prominent of the labeled structures (connective 5), a crescent‐shaped fiber, extends from the flagellar canal of the transverse flagellum along the base of the tentacle to the flagellar canal of the longitudinal flagellum, interconnecting the distal parts of the microtubular roots/bands in the basal apparatus. For most of its length, it underlies and is connected to a transversely oriented subamphiesmal microtubular band. In immunoblot analyses, anti‐SSC recognizes only a single 20‐kDa protein in cytoskeletons of O. marina. Functional and phylogenetic aspects of centrin‐containing structures in dinoflagellates are discussed.
ASSESSING THE RELATIONSHIPS OF SOME COCCOID GREEN LICHEN ALGAE AND THE MICROTHAMNIALES (CHLOROPHYTA) WITH 18S RIBOSOMAL RNA GENE SEQUENCE COMPARISONS1
Authors: Friedl Thomas , Zeltner Cornelia
Published: October 2004

Eight complete nuclear‐encoded small‐subunit ribosomal RNA (18S rRNA) gene sequences were determined for four genera of the Microthamniales (Pleurastrophyceae) and forGloeotilopsis planctonicaIyengar & Philipose (Ulvophyceae, Ulotrichales) to investigate evolutionary relationships within the Microthamniales and the taxonomic position of this order within the green algae. Phylogenies inferred from these data revealed specific relationships at the level of genera and species that disagree with those inferred from vegetative cell morphology but agree with those inferred from motile cell characters. The rRNA phylogenies provide even better resolution than that gained from morphology alone. The coccoid lichen algaTrebouxiaspp. is specifically related to other coccoid lichen and soil algae (i.e.Myrmecia biatorellaeBoye‐Petersen andFriedmannia israelensisChantanachat & Bold), forming the “Lichen Algae Group,” an evolutionarily distinct lineage within the Microthamniales.Trebouxiais a paraphyletic andPleurastruma polyphyletic genus in rRNA phylogenies. In contrast to previous hypotheses based on morphology,Pleurastrum terrestreFritsch & John is not closely related toTrebouxiabut occupies an isolated position within the Microthamniales. The filamentous algaMicrothamnion kuetzingianumis not ancestral to coccoid members of the Microthamniales but is closely related with the coccoidFusochloris perforata(Lee & Bold) Floyd, Watanabe & Deason. The Microthamniales are inferred to be an array of independent lineages that radiate nearly simultaneously and may also include some autosporic coccoid taxa previously classified in the Chlorophyceae. Monophyly of the Microthamniales could not be demonstrated unequivocally. In contrast to a hypothesis based on ultrastructure, the Microthamniales are evolutionarily distinct from the Ulotrichales. The latter are ancestral to the radiation of the Microthamniales and the Chlorophyceae in the rRNA phylogenies.
VARIABILITY OF NITRATE UPTAKE CAPACITY IN MACROCYSTIS PYRIFERA (LAMINARIALES, PHAEOPHYTA) WITH NITRATE AND LIGHT AVAILABILITY1
Authors: Kopczak Charles D.
Published: October 2004

The nitrate uptake capacity of mature blade tissue of the giant kelp, Macrocystis pyrifera (L.) C. Ag., was examined as a function of the availability of light and nitrate. Time course measurements indicated that nitrate uptake rate, as measured by the incorporation of 15N, was significantly increased by N starvation. The response was linear over the first hour of exposure regardless of the N status of the tissue indicating that surge uptake was not responsible for the increase. The Michaelis‐Menten parameters Vmax and Ks, however, were not significantly changed by either growth nitrate concentration or growth irradiance as a result of high variability among blades. Similarly, the initial slope (α) of the nitrate uptake kinetics curves was unaffected. Concentration of photosynthetic pigments increased in response to increased nitrate availability but not to increased growth irradiance. Time course and pigment data demonstrated that mature blade tissue responds to increased N availability by decreasing its capacity to take up nitrate and by increasing its investment in photosynthetic pigments, perhaps for N storage or enhanced light‐harvesting capabilities and the increase in reducing power available for N assimilation. This study provides evidence for a dynamic regulatory system that responds to changes in nitrate availability in an integrated manner.
THE UPTAKE OF IODATE BY MARINE PHYTOPLANKTON1
Authors: Moisan Tiffany A. , Dunstan William M. , Udomkit Ajcharaporn , Wong George T. F.
Published: October 2004

Several studies have suggested that phytoplankton play a role in the iodine cycle. Using a short‐term incubation technique for determining the uptake of iodate by phytoplankton, cultures of Thalassiosira oceanica Hasle, Skeletonema costatum (Greville) Cleve, Emiliania huxleyi (Lohmann) Hay and Mohler, and Dunaliella tertiolecta Butcher were found to be capable of assimilating iodate at rates ranging from 0.003 to 0.24 nmol IO3−·μg chlorophyll a−1·h−1. The kinetics for the uptake of iodate can be modeled, and the similarity between the model and experimental results suggests that there is a steady state between iodate uptake and release of dissolved iodine from the cells, presumably in the form of iodide. Two experiments were conducted in the Sand Shoal Inlet of the Cobb Bay estuary (37°15′N, 75°50′W). The uptake of iodate was 0.26 and 0.08 nmol IO3−·μg chlorophyll a−1·h−1 during high and low tide, respectively. Using field estimates based on measured levels of iodate in the estuary, we estimate that phytoplankton can take up as much as 3% of the ambient pool of iodate on a daily basis and the entire pool in about 1 month. Thus, phytoplankton can be a significant component of the global iodine cycle by mediating changes in the speciation of iodine in the marine environment.
SHORT‐TERM RESPONSE OF THE DIADINOXANTHIN CYCLE AND FLUORESCENCE YIELD TO HIGH IRRADIANCE IN CHAETOCEROS MUELLERI (BACILLARIOPHYCEAE)1
Authors: Olaizola Miguel , Yamamoto Harry Y.
Published: October 2004

The relationship between the diadinoxanthin cycle and changes in fluorescence yield in the diatom Chaetoceros muelleri Lemm. (clone CH10, Amorient Aquafarm, Inc., Hawaii) was investigated. High‐light‐induced changes in fluorescence yield and xanthophyll de‐epoxidation occurred very rapidly (first order rate constant 1.60 min−1). The observed light‐induced changes in diatoxanthin and diadinoxanthin concentration were consistent with a two‐pool scheme for diadinoxanthin, one of which does not undergo de‐epoxidation. Changes in xanthophyll concentration correlated with changes in in vivo absorbance indicating that diadinoxanthin cycle activity in vivo can be monitored spectrophotometrically. However, changes in cell absorbance were small relative to total optical absorption cross section. Increases in the concentration of diatoxanthin were linearly correlated with increases in the rate constant for thermal de‐excitation in the antenna of photosystem II (PSII). Antenna quenching produced or mediated by diatoxanthin may, thus, protect the PSII reaction center in diatoms. Changes in the maximum fluorescence yield suggested that changes in the reaction center also contributed to nonphotochemical quenching of fluorescence. Thus, reaction center quenching affected the relationship between antenna quenching and changes in photochemical efficiency producing the effect of a decrease in fluorescence yield without a decrease in photochemical efficiency.
PHOTOSYNTHETIC PROPERTIES OF PROTOPLASTS, AS COMPARED WITH THALLI, OF ULVA FASCIATA (CHLOROPHYTA)1
Authors: Beer Sven , Björk Mats
Published: October 2004

Protoplasts were prepared from Ulva fasciata Delile, and their photosynthetic performance was measured and compared with that of thalli discs. These protoplasts maintained maximal rates of photosynthesis as high as those of thalli (up to 300 μmol O2·mg chlorophyll−1·h−1) for several hours after preparation and were therefore considered suitable for kinetic studies of inorganic carbon utilization. The photosynthetic K1/2(inorganic carbon) at pH 6.1 was 3.8 μM and increased to 67, 158, and 1410 μM at the pH values 7.0, 7.9, and 8.9, respectively. Compared with these protoplasts, thalli had a much lower affinity for CO2 but approximately the same affinity for HCO3−. Comparisons between rates of photosynthesis and the spontaneous dehydration of HCO3− (at 50 μM inorganic carbon) revealed that photosynthesis of both protoplasts (which lacked apparent activity of extracellular/surface‐bound carbonic anhydrase) and thalli (which were only 25% inhibited by the external carbonic anhydrase inhibitor acetazolamide) could not be supported by CO2 formation in the medium at the higher pH values, indicating HCO3− uptake. Since both protoplasts and thalli were sensitive to 4,4′‐diisothiocyanostilbene‐2,2′‐disulfonate, we suggest that HCO3− transport was facilitated by the membrane‐located anion exchange protein recently reported to function in certain Ulva thalli. These findings suggest that the presence of a cell wall may constitute a diffusion barrier for CO2, but not for HCO3−, utilization under natural seawater conditions.
THE EVOLUTION OF PARASITISM IN RED ALGAE: CELLULAR INTERACTIONS OF ADELPHOPARASITES AND THEIR HOSTS1
Authors: Goff Lynda J. , Zuccarello Giuseppe
Published: October 2004

In the initial stages of cell–cell interactions (spore germination and host penetration), the adelphoparasites Gardneriella tuberifera Kyl. and Gracilariophila oryzoides Setch. & Wilson form infection rhizoids that fuse directly with underlying host epidermal or cortical cells. In so doing, parasite nuclei and other organelles enter the cytoplasm of the host. The resulting heterokaryon may fuse with adjacent host cells either directly, via secondary pit connections, or by the dissolution or dislodgment of pit plugs from existing pit connections. The cell fusion events result in a heterokaryotic syncytium in which parasite nuclei replicate. In Gardneriella, formation of the syncytium induces surrounding host tissues to divide to form a photosynthetic callus. The internalized syncytium forms conjunctor and rhizoidal cells that fuse with host callus, eventually transforming the host callus into cells containing parasite nuclei. Gracilariophila does not induce surrounding host tissue to divide. Rather, division of the initial heterokaryotic tissue gives rise to the colorless mantle that protrudes from the host and forms reproductive structures. The heterokaryotic tissue also fuses with underlying host cells, thereby spreading parasite nuclei throughout adjacent host cells. In both these adelphoparasites, transformation of host cells by parasite nuclear invasion results in plastid dedifferentiation, an increase in mitochondria, autolysis of organelles, and accumulation of large amounts of floridean starch. The development and physiology of these parasites is similar to normal post‐fertilization processes in the hosts that give rise to carposporophytes and suggests that these adelphoparasites may have originated from perturbations of developmental pathways involved in their host's post‐fertilization development.
A MOLECULAR ANALYSIS OF ANALIPUS AND RALFSIA (PHAEOPHYCEAE) SUGGESTS THE ORDER ECTOCARPALES IS POLYPHYLETIC1
Authors: Tan Ian H. , Druehl Louis D.
Published: October 2004

We report partial 18S ribosomal DNA sequences of Analipus japonicus (Harvey) Wynne and Ralfsia fungiformis (Grunnerus) Setchell et Gardner. These sequences were compared with the corresponding sequences of 13 brown algae representing six phaeophycean orders: Dictyotales, Ectocarpales, Fucales, Laminariales, Sphacelariales, and Syringodermatales. These 15 brown algae included 10 ectocarpoids representing nine ectocarpacean (sensu Gabrielson et al. 1989) families: Chordariaceae, Dictyosiphonaceae, Ectocarpaceae, Elachistaceae, Heterochordariaceae, Leathesiaceae, Punctariaceae, Ralfsiaceae, and Scytosiphonaceae. We addressed the controversial taxonomic placement of A. japonicus and R. fungiformis in the Ectocarpales by analysis of DNA sequences. Neighbor‐joining and maximum parsimony‐inferred phylogenies provided evidence that A. japonicus and R. fungiformis are not closely associated with the other representatives of the Ectocarpales. Bootstrap analyses suggest polyphyly of the order Ectocarpales (sensu Gabrielson et al.). However, our analysis failed to resolve the phylogenetic relationship between A. japonicus and R. fungiformis. Our results suggest that the ectocarpoids are just as distantly related to A. japonicus and R. fungiformis as they are to members of the advanced orders Desmarestiales, Dictyotales, Fucales, Laminariales, Sphacelariales, and Syringodermatales.
18S rDNA AND EVOLUTION IN THE DASYCLADALES (CHLOROPHYTA): MODERN LIVING FOSSILS1
Authors: Olsen Jeanine L. , Stam Wytze T. , Berger Sigrid , Menzel Diedrik
Published: October 2004

Phylogenetic relationships were inferred from parsimony and distance analyses of nuclear small‐subunit ribosomal DNA sequences taken from 14 species representing 8 of the 11 extant genera in the Dasycladales. Of 1733 aligned positions, 412 (23.8%) were variable and 251 (61%) of those were phylogenetically informative within the Dasycladales. Secondary structure was analyzed and taken into account during all phases of data analysis. Robustness of the trees was assessed using bootstrap analysis and g1statistics of tree‐length decay. Strongly supported branches were robust to all methods of analysis regardless of weighting schemes used. The secondary structure of the 18S within the Dasycladales agrees with that of other green algae with the exception of a shared deletion in stemloop E10‐1 (ca. 13 nucleotides long), which provides additional support for the uniqueness of this monophyletic group. A molecular clock was calibrated from the dasyclad fossil record and suggests a radiation of the Acetabulariaceae at 120 ± 30 million years (Ma) ago and the Dasycladaceae 215 ± 40 Ma ago. The split of the two lineages from a shared ancestor is estimated at 265 ± 50 Ma ago. Within the Dasycladaceae,NeomerisandCymopoliaare sister taxa, as areBatophoraandChlorocladus. Bornetellagroups with theNeomerisandCymopoliaclade in 78% of the bootstrap replicates. Relationships among the Acetabulariaceae show thatAcetabulariaandPolyphysado not form monophyletic groups as presently circumscribed. No evidence indicates thatAciculariais the oldest genus.Halicoryne, Chalmasia, andDasycladuswere not included in the analysis. Molecular data provide afresh background perspective from which to discuss the evolution of one of the most ancient lineages of green plants.
IDENTIFICATION OF GROUP‐ AND STRAIN‐SPECIFIC GENETIC MARKERS FOR GLOBALLY DISTRIBUTED ALEXANDRIUM (DINOPHYCEAE). I. RFLP ANALYSIS OF SSU rRNA GENES1
Authors: Scholin Christopher A. , Anderson Donald M.
Published: October 2004

Two distinct small‐subunit ribosomal RNA genes (SSU rDNAs), termed the “A gene” and “B gene,” were recently found in the toxic dinoflagellate Alexandrium fundyense Balech. A restriction fragment length polymorphism (RFLP) assay was developed to rapidly detect the A and B genetic markers. SSU rDNA from 58 cultures with species designations of A. tamarense (Lebour) Balech, A. catenella (Whedon et Kofoid) Balech, A. fundyense, A. affine (Fukuyo et Inoue)Balech, A. minutum Halim, A. lusitanicum Balech, and A. andersoni Balech were screened. These cultures represent toxic and non‐toxic isolates from North America, western Europe, Thailand, Japan, Australia, and the ballast water of several cargo ships. The RFLP assay revealed five distinct groups. Three subdivided the A. tamarense/catenella/fundyense“species complex” into clusters defined by geographic origin, not by morphospecies designations. The fourth group consisted of A. affine, whereas the fifth group was represented by A. minutum, A. lusitanicum, and A. andersoni.

The B gene was only found in A. tamarense, A. catenella, and A. fundyense, but not in all isolates. However, all North American isolates of this closely related group harbored this gene, and it also was found in some A. tamarense from scattered locations in Japan and in the ballast water of one ship that operated exclusively between Japan and Australia. Isolates without the B gene appeared to have only a single class of SSU rDNA. The B sequence was not essential for toxin production, but thus far those organisms harboring it were toxic. The A. tamarense/catenella/fundyense complex is composed of genetically distinct populations, within which may exist two or all three of the mophotypically defined species. The B gene is a promising taxonomic and biogeographic marker and may be useful for tracking the regional and/or global dispersal of particular populations.
NOTE. NEW EUENDOLITHIC CYANOBACTERIA FROM THE BAHAMA BANK AND THE ARABIAN GULF: HYELLA RACEMUS SP. NOV.1
Authors: Al‐Thukair Assad A. , Golubic Stjepko , Rosen Geoffroy
Published: October 2004

A new species of endolithic cyanobacteria, Hyella racemus sp. nov. (order Pleurocapsales), penetrates ooid grains in actively shoaling sands in shallow (0.5–5 m) waters of the Bahama carbonate platform and the Arabian Gulf. Hyella racemus is characterized by prolific branching, resulting in dense grape‐like cell clusters that penetrate the carbonate substrate. The clusters radiate inward and form deep, isodiametric pits. Resin casts of these pits are framboid (raspberry‐like) in shape. The borehole morphology conforms with the shape of the endolith body and can be identified in resin‐cast preparations. Cell division is by cleavage with regular alternation of division planes. The sheath is tight, layered, and colorless or yellow‐brown when under strong illumination. The new species is one of the most common endoliths in ooids of the Bahamas and the Arabian Gulf It differs from other members of this endolithic genus by its branching pattern and less prominent apical cells.