bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isoflurane Alters the Amount of Dopamine Transporter Expressed on the Plasma Membrane in Humans
Authors: Votaw John R. , Byas-Smith Michael G. , Voll Ronald , Halkar Raghu , Goodman Mark M. 
Published: October 2004

Background
Isoflurane increases extracellular dopamine concentration and causes trafficking of the dopamine transporter (DAT) in transfected cells. Also, the binding potentials of highly specific positron-emitting DAT ligands are altered by isoflurane in rhesus monkeys. The purpose of this study was to determine the dose-response curve for isoflurane altering the binding potential of one of these ligands ([F-18]FECNT) in humans.

Methods
Twenty human volunteers underwent positron emission tomography using [F-18]FECNT. All subjects were scanned while awake and then again after assignment to one of four groups (n = 5 each): awake-control, propofol-control, or light or deep isoflurane anesthesia as defined by Bispectral Index monitoring. Bispectral Index values in the light anesthesia group were 40 +/- 7 (end-tidal isoflurane, 1.02 +/- 0.08) versus 27 +/- 10 (end-tidal isoflurane, 1.6 +/- 0.3) in the deep anesthesia group. The within-subject percent change in putamen binding potential between the awake and second scans was determined for each subject, averaged within groups, and compared across groups.

Results
The [F-18]FECNT binding potential exhibited a biphasic shape as a function of anesthetic dose. The binding potential for the second scan in the awake-control and propofol-control groups was significantly less than the initial scan; for the light anesthesia group, the binding potential was significantly increased during anesthesia, and no change was detected between the two scans in the deeper anesthesia group.

Conclusion
Isoflurane causes a dose-dependent change in the [F-18]FECNT binding potential for DAT consistent with isoflurane causing trafficking of the DAT between the plasma membrane and the cell interior. Concentrations of isoflurane below minimum alveolar concentration causes DAT to be trafficked to the plasma membrane from the cell interior, but no net trafficking occurs at higher concentrations. The data are most easily explained if isoflurane alters the amount of functionally expressed DAT through an indirect pathway. This phenomena should be more fully explored to help make the next generation of anesthetics more mechanistically specific and to reduce undesired side effects.
THE PAS/ACCUMULATION BODIES IN PROROCENTRUM LIMA AND PROROCENTRUM MACULOSUM (DINOPHYCEAE) ARE DINOFLAGELLATE LYSOSOMES1
Authors: Zhou Juan , Fritz Lawrence 
Published: October 2004

ABSTRACTNumerous spherical bodies containing electron‐dense material, fibrous material, and membranous material are present in the cytoplasm of two dinoflagellate species, Prorocentrum lima (Ehr.) Dodge and Prorocentrum maculosum Faust. Similar bodies have been observed in other dinoflagellates and have been termed accumulation bodies or PAS bodies. In both Prorocentrum species, these bodies autofluoresce under blue light excitation and increase in size with cell culture age. They possess acid phosphatase activity, react positively with the periodic acid/Schiff reagent, and stain with acridine orange. All these properties are characteristic of eukaryotic lysosomes; thus, we propose that dinoflagellate accumulation bodies and PAS bodies are identical organelles and are, in fact, dinoflagellate lysosomes.
SILICON DEPOSITION DURING THE CELL CYCLE OF THALASSIOSIRA WEISSFLOGII (BACILLARIOPHYCEAE) DETERMINED USING DUAL RHODAMINE 123 AND PROPIDIUM IODIDE STAINING1
Authors: Brzezinski Mark A. , Conley Daniel J. 
Published: October 2004

ABSTRACTThe relatively non‐toxic dye, rhodamine 123 (R123), was incorporated into the frustule of Thalassiosira weissflogii Grun. clone ACTIN in direct proportion to biogenic silica (BSi). R123 was used together with the DNA stain propidium iodide to track and quantify Si deposition during the cell cycle of T. weissflogii using flow cytometry. Silicon deposition was not continuous through the cell cycle. Deposition of the valves occurred during M phase. The hypocingulum was largely deposited during G1 with some suggestion of minor girdle band deposition during G2. Silicon deposition did not occur during S phase. Assuming that a complete frustule consists of an epivalve, epicingulum, hypocingulum, and hypovalve, then 40% of cellular BSi was contained within the cingulum of T. weissflogii with 60% present in the valves. These percentages correspond to 0.38 pmol Si in the two cingula and 0.57 pmol Si in the valves. Temporal differences in the timing of silicic acid uptake and deposition during the cell cycle of T. weissflogii suggested that deposition of both the new valves and the cingulum is supported by an internal pool of dissolved Si acquired during G2.
TRACKING DISPERSAL ROUTES: PHYLOGEOGRAPHY OF THE ARCTIC‐ANTARCTIC DISJUNCT SEAWEED ACROSIPHONIA ARCTA (CHLOROPHYTA)1
Authors: van Oppen Madeleine J. H. , Diekmann Onno E. , Wiencke Christian , Stam Wytze T. , Olsen Jeanine L. 
Published: October 2004

ABSTRACTPhylogenetic relationships in the Arctic‐Antarctic disjunct seaweed species Acrosiphonia arcta (Dillwyn) J. G. Agardh (Acrosiphoniales, Chlorophyta) were examined using restriction fragment‐length polymorphism analysis of the fast‐evolving nuclear ribosomal intergenic spacer (IGS) region and random amplified polymorphic DNA (RAPD) markers. Twenty‐two isolates collected from 10 different locations in both hemispheres were compared. Five IGS length classes were identified among the 10 locations. Throughout the North Atlantic, IGS regions were found to be extremely homogeneous whereas RAPD patterns revealed subdivided populations that suggest founder effects. Acrosiphonia arcta populations found in the Arctic and North Atlantic oceans are hypothesized to be of Pacific origin. Extensive differences found between Arctic Greenland populations and those in the North Atlantic suggest that colonization of Arctic Greenland occurred as an independent event. Recolonization of the Antarctic peninsula from Southern Chile is favored, whereas the directionality of transequatorial passage along the western coast of the Americas could be in either direction.
MOLECULAR DELINEATION OF SPECIES AND SYNGENS IN VOLVOCACEAN GREEN ALGAE (CHLOROPHYTA)1
Authors: Coleman Annette W. , Suarez Arturo , Goff Lynda J. 
Published: October 2004

ABSTRACTTwo species of the colonial green flagellate family Volvocaceae are worldwide in distribution yet exhibit contrasting species structure. Geographically disparate isolatesof Gonium pectoraleMueller can interbreed while isolates ofPandorina morumBory behave quite differently. More than 20 sexually isolated subpopulations occur within this species; these have been termed “syngens” (sensu Sonneborn). Because prezygotic barriers to mating cause intersyngen pairings to fail, breeding analyses cannot be used to estimate genetic relatedness among the syngens of P.morum.DNA comparisons provide an alternative method of assessing genetic relatedness. We compared the nucleotide sequence of the internal transcribed spacer (ITS) region of the nuclear ribosomal repeat among clones of P.morumand ofG. pectorale.Members of syngens ofP. morumwith distribution restricted to one small geographical area show great similarity. Likewise, members of any syngen of worldwide distribution show near uniformity, even those from different continents. However, the ITS sequence of each syngen differs from that of other syngens. In contrast,G. pectorale, which has an ITS region that is remarkably uniform throughout the world, appears to consist of a single syngen within North America and Europe by mating tests. The molecular data are in complete conformity with previous syngen assignment. Because the latter is based on mating affinity, with two complementary mating types per syngen, the evolution of new mating type pairs appears to be the basis of microevolution in these algae. We infer that eitherP. morumis a more ancient species thanG. pectoraleor thatP. morumhas a less stable genome. In either case, the biogeographic distribution of certain syngens may reflect climatological changes of the past.
CIRCADIAN GROWTH RHYTHM IN JUVENILE SPOROPHYTES OF LAMINARIALES (PHAEOPHYTA)1
Authors: Lüning Klaus 
Published: October 2004

ABSTRACTA circadian rhythm in growth was detected by computer‐aided image analysis in 3–4‐cm‐long, juvenile sporophytes of the kelp species Pterygophora California Rupr. and in seven Laminaria spp. In P. californica, the free‐running rhythm occurred in continuous white fluorescent light, had a period of 26 h at 10°or 15°C, and persisted for at least 2 weeks in white or blue light. The rhythm became insignificant in continuous green or red light after 3 cycles. Synchronization by white light‐dark regimes, e.g. by 16 h light per day, resulted in an entrained period of 24 h and in a shift of the circadian growth minimum into the middle of the light phase. A morning growth peak represented the decreasing portion of the circadian growth curve, and an evening peak the increasing portion. The circadian growth peak was not visible during the dark phase, because growth rate decreased immediately after the onset of darkness. At night, some growth still occurred at 16 or 12 h light per day, whereas growth stopped completely at 8 h light per day, as in continuous darkness. During 11 days of darkness, the thallus area became reduced by 3.5%, but growth rate recovered in subsequent light–dark cycles, and the circadian growth rhythm reappeared in subsequent continuous light.
A CYANOPHYTE CAPABLE OF FIXING NITROGEN UNDER HIGH LEVELS OF OXYGEN1
Authors: Prosperi Carlos H. 
Published: October 2004

ABSTRACT Nostoc cordubensis Prosperi (Cyanophyta, Nostocaceae) is characterized by its mucilaginous colonies. Much of this mucilage is produced by heterocysts. By controlling growth conditions, heterocysts with and without mucilage were obtained. Mucilaginous heterocysts retained nitrogen‐fixing capability at high oxygen concentrations, whereas heterocysts lacking mucilage were unable to fix nitrogen at oxygen concentrations higher than 20%. Comparison of results obtained using tetrazolium salts as indicators of highly reduced zones showed similar results.
PHOTOSYNTHETIC ACTIVITY OF TWO DEVELOPMENTAL STAGES OF A NOSTOC STRAIN (CYANOBACTERIA) ISOLATED FROM GEOSIPHON PYRIFORME (MYCOTA)1
Authors: Bilger Wolfgang , Büdel Burkhard , Mollenhauer Resi , Mollenhauer Dieter 
Published: October 2004

ABSTRACTSessile colonies and motile hormogonia, the two main developmental stages in the life cycle of a Nostoc strain isolated from the endocytobiosis with Geosiphon pyriforme (Kützing) F. v. Wettstein, were investigated for their photosynthetic competence. Large‐scale fractionation of the two stages is presented. Photosynthetic parameters were assessed by measurement of chlorophyll fluorescence and oxygen evolution. Hormogonia were as photosynthetically competent as the colonial stage. In addition, hormogonia showed an enhanced capability for nonradiative dissipation of absorbed light energy, a feature that might be important for their function as propagula. Data for the quantum yield of photosystem II of the isolated Nostoc strain were compared to the values determined in situ in G. pyriforme and indicated the possibility of a higher photosynthetic capacity of the endosymbiotic as compared to the isolated cyanobacterium.
FUNCTIONAL ASPECTS OF SECONDARY CAROTENOIDS IN HAEMATOCOCCUS LACUSTRIS (VOLVOCALES). III. ACTION AS A “SUNSHADE”1
Authors: Hagen Christoph , Braune Wolfram , Björn Lars Olof 
Published: October 2004

ABSTRACTWe investigated the protection from photoinhibition by different developmental stages of Haematococcus lacustris [Girod] Rostafinski using chlorophyll fluorescence measurements of single cells and suspensions. An overall correlation between higher cellular content of secondary carotenoids and the capacity to withstand excessive irradiation was observed in flagellated cells and aplanospores of H. lacustris. Low‐light‐reversible spreading of extra‐chloroplastic secondary carotenoids occurred in the periphery of the cell during strong irradiation. This process resulted in increased shading of the cup‐shaped chloroplast as demonstrated by a decrease in chlorophyll fluorescence. Extrachloroplastic accumulation of secondary carotenoids in H. lacustris can be interpreted as a specific adaptation to habitats that exhibit strong insolation.
FREEZING STRESS AND OSMOTIC DEHYDRATION IN FUCUS DISTICHUS (PHAEOPHYTA): EVIDENCE FOR PHYSIOLOGICAL SIMILARITY1
Authors: Pearson Gareth A. , Davison Ian R. 
Published: October 2004

ABSTRACTThe effects of osmotic dehydration and freezing on photosynthesis were studied in the brown alga Fucus distichus L. The data indicated that F. distichus exhibits similar physiological responses to both osmotic dehydration and freezing stress and that these responses resemble those in the literature for the effect of desiccation in air. Both stresses inhibited light‐limited (Psubsat) and light‐saturated (Pmax) photosynthesis measured immediately after plants were reimmersed in seawater. The degree of initial inhibition and subsequent recovery of photosynthesis were proportional to the severity of the dehydration or freezing treatment. Psubsat and Pmax recovered completely from osmotic dehydration for 3 h in 200% and 3 hr at – 10°C, but recovery was only partial following 3 h in 300%o or 3 h at – 15°C. In most cases, recovery was complete within 2 h following dehydration, with little further recovery occurring between 2 and 24 h posttreatment. No time‐dependent recovery occurred following severe freezing. Observations using the vital stain fluorescein diacetate suggested that the lack of complete recovery might be due to severe damage or death of a proportion of cells in the thallus. There were no clear effects of either osmotic dehydration or freezing on dark respiration (Rd), although Rd was stimulated in all emersed treatments (frozen plants and 5° C controls) immediately following reimmersion. Measurement of chlorophyll fluorescence induction kinetics indicated that both osmotic dehydration and freezing reduced the ratio of variable to maximum florescence (Fv/Fm), indicating a decrease in the quantum efficiency of photosystem I. Based on these data, we suggest that there are common cellular and physiological components involved in the response of fucoid algae to a range of water stresses. This hypothesis was supported by experiments that showed that osmoacclimation in hyperosmotic seawater (51%o)for 2 weeks increased the ability of F. distichus to recover from freezing at – 15° C. During acclimation, mannitol content increased under hyperosmotic conditions and decreased under hypoosmotic conditions. Changes in plasma membrane integrity, determined by fresh weight: dry weight ratio, and amino acid release following freezing indicated an increasing gradient of freezing tolerance from low to high salinity. However, none of these physiological changes fully explained the marked increase in the freezing tolerance of photosynthesis observed in plants acclimated under hyperosmotic conditions.
STORAGE OF PHOSPHORUS IN NITROGEN‐FIXING ANABAENA FLOS‐AQUAE (CYANOPHYCEAE)1
Authors: Thompson Patsy‐Ann , Oh Hee‐Mock , Rhee G‐Yull 
Published: October 2004

ABSTRACTP accumulation and metabolic pathway in N2‐fixing Anabaena flos‐aquae (Lyngb.) Bréb were investigated in P‐sufficient (20 μMP) and P‐limited (2 μMP) turbidostats in combined N‐free medium. The cyanobacterium grew at its maximum rate (μmax, 1.13 d−1) at the high P concentration and at 65% of μmax under P limitation, with total cell P concentrations (QP) at steady states of 12.0 and 5.2 fmol·cell−1, respectively. At steady state, polyphosphates (PPi) accounted for only 3% of QP (0.4 fmol·cell−1) in P‐rich cells. Its concentration in P‐limited cells was 5.8% (0.3 fmol·cell−1). On the other hand, sugar P was very high at 22% of QP in P‐rich cells and was undetectable in P‐limited cells. Pulse chase experiments with 32P showed that P‐rich cells initially incorporated the labeled P into the acid‐soluble PPi fraction within the first few minutes and to a lesser extent into nucleotide P. Radioactivity in the PPi then declined rapidly with concomitant increases in sugar P and nucleotide P fractions. In contrast, in P‐limited cells, no radiolabel was detected in acid‐soluble PPi, and 32P was initially incorporated into nucleotide P, sugar P, and ortho P fractions. The latter two fractions then subsequently declined. Therefore, under N2‐fixing conditions the cyanobacteria appeared to store P as sugar P and also utilize P through different pathways under P‐rich and ‐limited conditions. When nitrate was supplied as the N source under P‐sufficient conditions, PPi accounted for about 15% of steady‐state QP, but no sugar P was detected. Therefore, the same organism stored P in different cell P fractions depending on its N sources.
THE EFFECT OF HYDROXYUREA AND FLUORODEOXYURIDINE ON CELL CYCLE EVENTS IN THE CHLOROCOCCAL ALGA SCENEDESMUS QUADRICAUDA (CHLOROPHYTA)1
Authors: Zachleder Vilém 
Published: October 2004

ABSTRACTThe effect of hydroxyurea and 5‐fluorodeoxyuridine (FdUrd) on the course of growth (RNA and protein synthesis) and reproductive (DNA replication and nuclear and cellular division) processes was studied in synchronous cultures of the chlorococcal alga Scenedesmus quadricauda (Turp.) Bréb. The presence of hydroxyurea (5 mg·L−1)from the beginning of the cell cycle prevented growth and further development of the cells because of complete inhibition of RNA synthesis. In cells treated later in the cell cycle at the time when the cells were committed to division, hydroxyurea present in light affected the cells in the same way as a dark treatment without hydroxyurea; i. e. RNA synthesis was immediately inhibited followed after a short time period by cessation of protein synthesis. Reproductive processes including DNA replication to which the commitment was attained, however, were initiated and completed. DNA synthesis continued until the constant minimal ratio of RNA to DNA was reached.FdUrd (25 mg·L−1) added before initiation of DNA replication in control cultures prevented DNA synthesis in treated cells. Addition of FdUrd at any time during the cell cycle prevented or immediately stopped DNA replication. However, by adding excess thymidine (100 mg·L−1), FdUrd inhibition of DNA replication could be prevented. FdUrd did not affect synthesis of RNA, protein, or starch for at least one cell cycle. After removal of FdUrd, DNA synthesis was reinitiated with about a 2‐h delay. The later in the cell cycle FdUrd was removed, the longer it took for DNA synthesis to resume. At exposures to FdUrd longer than two or three control cell cycles, cells in the population were gradually damaged and did not recover at all.
ULTRASTRUCTURE OF PRYMNESIUM NEMAMETHECUM SP. NOV. (PRYMNESIOPHYCEAE)1
Authors: Pienaar Richard N. , Birkhead Monica 
Published: October 2004

ABSTRACTBased on material collected from Cape Town, a new sand‐dwelling, marine species of Prymnesium is described. Using light and electron microscopy, Prymnesium nemamethecum sp. nov. has been found to resemble other species of the genus in size, organelle arrangement, and swimming behavior. It differs from other described species in that it has three types of scales, one of which is confined to the region of appendage insertion and forms a sheath of simple plate scales over the haptonema. In addition, the scales constituting the proximal body scale layer(s) are unusual because they are not simple plate scales but are specifically ornamented.
TIP CELL GROWTH AND THE FREQUENCY AND DISTRIBUTION OF CELLULOSE MICROFIBRIL‐SYNTHESIZING COMPLEXES IN THE PLASMA MEMBRANE OF APICAL SHOOT CELLS OF THE RED ALGA PORPHYRA YEZOENSIS1
Authors: Tsekos Ioannes , Reiss Hans‐Dieter 
Published: October 2004

ABSTRACTThe supramolecular organization of the plasma membrane of apical cells in shoot filaments of the marine red alga Porphyra yezoensis Ueda (conchocelis stage) was studied in replicas of rapidly frozen and fractured cells. The protoplasmic fracture (PF) face of the plasma membrane exhibited both randomly distributed single particles (with a mean diameter of 9.2 ± 0.2 nm) and distinct linear cellulose microfibril‐synthesizing terminal complexes (TCs) consisting of two or three rows of linearly arranged particles (average diameter of TC particles 9.4 plusmn; 0.3 nm). The density of the single particles of the PF face of the plasma membrane was 3000 μm−2, whereas that of the exoplasmic fracture face was 325 μm−2. TCs were observed only on the PF face. The highest density of TCs was at the apex of the cell (mean density 23.0 plusmn; 7.4 TCs μm−2 within 5 μm from the tip) and decreased rapidly from the apex to the more basal regions of the cell, dropping to near zero at 20 μm. The number of particle subunits of TCs per μm2 of the plasma membrane also decreased from the tip to the basal regions following the same gradient as that of the TC density. The length of TCs increased gradually from the tip (mean length 46.0 plusmn; 1.4 nm in the area at 0–5 μm from the tip) to the cell base (mean length 60.0 plusmn; 7.0 μm in the area at 15–20 μm). In the very tip region (0–4 μm from the apex), randomly distributed TCs but no microfibril imprints were observed, while in the region 4–9 μm from the tip microfibril imprints and TCs, both randomly distributed, occurred. Many TCs involved in the synthesis of cellulose microfibrils were associated with the ends of microfibril imprints. Our results indicate that TCs are involved in the biosynthesis, assembly, and orientation of cellulose microfibrils and that the frequency and distribution of TCs reflect tip growth (polar growth) in the apical shoot cell of Porphyra yezoensis. Polar distribution of linear TCs as “cellulose synthase” complexes within the plasma membrane of a tip cell was recorded for the first time in plants.
TEMPORAL VARIATIONS IN THE TAXONOMIC COMPOSITION OF FLAGELLATED NANOPLANKTON IN A TEMPERATE FJORD1
Authors: Smith Patricia J. , Hobson Louis A. 
Published: October 2004

ABSTRACTWe studied the taxonomic composition of flagellated nanoplankton in a temperate Canadian fjord, Saanich Inlet, for 1 year using electron microscopy. Most of the species that we identified were from the algal classes Prasinophyceae, Prymnesiophyceae, and Chrysophyceae and the protistan order Choanoflagellida. During summer months, we observed a diverse group of prymnesiophyte, prasinophyte, and chrysophyte species. In fall and winter, the number of species of prasinophyte and prymnesiophyte species in our samples decreased. At times, numerous chrysophyte species were present, and many of these were heterotrophic and typical of freshwater environments, presumably having been carried into the inlet by freshwater runoff. We suggest that during the winter months of 1991 a food web composed of dissolved and particulate organic debris, bacteria, algal cells, and choanoflagellates was an important feature of the plankton.We identified 71 species from 41 genera, and most of these have been reported for either other parts of the world ocean or freshwater environments, indicating that they have widespread distributions. Some species differed in cell and scale morphologies from those documented in the literature, and these distinctions are described. Thirty‐two of these species were recorded for the first time from the coastal waters of the northeastern Pacific Ocean.