bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation studies on the GAM oscillation and damping in helical configurations
Authors: Satake S. , Sugama H. , Watanabe T.-H.
Published: August 2007

Collisionless damping of the geodesic acoustic mode (GAM) in helical magnetic configuration is investigated by a drift-kinetic simulation. We utilize the neoclassical transport code ‘FORTEC-3D’, which solves the drift-kinetic equation based on the δfmethod, to study how the magnetic configuration affects the collisionless damping of GAMs. In a recent analytical study, in which a simplified expression for helical magnetic field was used, it was found that the helical ripples strengthen the damping rate of the GAM oscillation. In this paper, the change in the damping rate is investigated in detail for realistic magnetic field configurations of the Large Helical Device. It is found that the GAM damping is faster and the frequency is lower as the magnetic axis is shifted inwards. This result suggests the possibility of controlling both the neoclassical transport level and the GAM oscillation, or the zonal flow, in helical plasmas. The collisional effect on GAM damping is also investigated, however, it is found that the GAM oscillation in helical plasmas is insensitive to the collisional effect because the enhancement of collisionless damping by the magnetic field ripples is very strong.
ErbB4 Isoforms Selectively Regulate Growth Factor–induced Madin-Darby Canine Kidney Cell Tubulogenesis
Authors: Zeng Fenghua , Zhang Ming-Zhi , Singh Amar B. , Zent Roy , Harris Raymond C.
Published: August 2007

ErbB4, a member of the epidermal growth factor (EGF) receptor family that can be activated by heregulin β1 and heparin binding (HB)-EGF, is expressed as alternatively spliced isoforms characterized by variant extracellular juxtamembrane (JM) and intracellular cytoplasmic (CYT) domains. ErbB4 plays a critical role in cardiac and neural development. We demonstrated that ErbB4 is expressed in the ureteric buds and developing tubules of embryonic rat kidney and in collecting ducts in adult. The predominant isoforms expressed in kidney are JM-a and CYT-2. In ErbB4-transfected MDCK II cells, basal cell proliferation and hepatocyte growth factor (HGF)-induced tubule formation were decreased by all four isoforms. Only JM-a/CYT-2 cells formed tubules upon HB-EGF stimulation. ErbB4 was activated by both HRG-β1 and HB-EGF stimulation; however, compared with HRG-β1, HB-EGF induced phosphorylation of the 80-kDa cytoplasmic cleavage fragment of the JM-a/CYT-2 isoform. HB-EGF also induced early activation of ERK1/2 in JM-a/CYT-2 cells and promoted nuclear translocation of the JM-a/CYT-2 cytoplasmic tail. In summary, our data indicate that JM-a/CYT-2, the ErbB4 isoform that is proteinase cleavable but does not contain a PI3K-binding domain in its cytoplasmic tail, mediates important functions in renal epithelial cells in response to HB-EGF.
Old World Arenavirus Infection Interferes with the Expression of Functional α-Dystroglycan in the Host Cell
Authors: Rojek Jillian M. , Campbell Kevin P. , Oldstone Michael B.A. , Kunz Stefan
Published: August 2007

α-Dystroglycan (α-DG) is an important cellular receptor for extracellular matrix (ECM) proteins as well as the Old World arenaviruses lymphocytic choriomeningitis virus (LCMV) and the human pathogenic Lassa fever virus (LFV). Specific O-glycosylation of α-DG is critical for its function as receptor for ECM proteins and arenaviruses. Here, we investigated the impact of arenavirus infection on α-DG expression. Infection with an immunosuppressive LCMV isolate caused a marked reduction in expression of functional α-DG without affecting biosynthesis of DG core protein or global cell surface glycoprotein expression. The effect was caused by the viral glycoprotein (GP), and it critically depended on α-DG binding affinity and GP maturation. An equivalent effect was observed with LFVGP. Viral GP was found to associate with a complex between DG and the glycosyltransferase LARGE in the Golgi. Overexpression of LARGE restored functional α-DG expression in infected cells. We provide evidence that virus-induced down-modulation of functional α-DG perturbs DG-mediated assembly of laminin at the cell surface, affecting normal cell–matrix interactions.
Rab27b Is Expressed in a Wide Range of Exocytic Cells and Involved in the Delivery of Secretory Granules Near the Plasma Membrane
Authors: Gomi Hiroshi , Mori Kenichi , Itohara Shigeyoshi , Izumi Tetsuro
Published: August 2007

Rab proteins regulate multiple, complex processes of membrane traffic. Among these proteins, Rab27a has been shown to function specifically in regulated exocytic pathways. However, the roles of Rab27b, another Rab27 subfamily member, have not been well characterized. We disrupted the Rab27b gene in mice. The targeting vector was designed to insert LacZ downstream of the initiation codon of the Rab27b gene so that the authentic promoter should drive this reporter gene. A comprehensive analysis of Rab27b expression using this mouse strain indicated that it is widely expressed not only in canonical secretory cells, but also in neurons and cells involved in surface protection and mechanical extension. To evaluate the function in pituitary endocrine cells where the isoform Rab27a is coexpressed, we generated Rab27a/Rab27b double knockout mice by crossing Rab27b knockout mice with Rab27a-mutated ashen mice. The polarized distribution of secretory granules close to the plasma membrane was markedly impaired in the pituitary of double knockout mice, indicating that the Rab27 subfamily is involved in the delivery of granules near the exocytic site. In conjunction with a phenotype having a pituitary devoid of the Rab27 effector granuphilin, we discuss the relationship between the residence and the releasable pool of granules.
MeTaDoR: a comprehensive resource for membrane targeting domains and their host proteins
Authors: Bhardwaj Nitin , Stahelin Robert V. , Zhao Guijun , Cho Wonhwa , Lu Hui
Published: August 2007

Motivation: Protein-lipid interactions play a central role in cellular signaling and membrane trafficking and at the core of these interactions are domains specialized in lipid binding and membrane targeting. Considering the importance of these domains, we have created MeTaDoR, a comprehensive resource dedicated to membrane targeting domains (MTDs).

Result: MeTaDoR begins with a brief introduction about all the important MTDs including their subcellular localization and structural features. Sequences of all known MTDs are then provided in two formats: standard Prosite format and a parsed tab-delimited format that provides a manually curated classification into binding or non-binding. Structures of all MTDs and host proteins known so far are provided with links to PDB and Pfam databases. Membrane-binding orientation of these proteins, whether experimentally determined or proposed, is also provided with links to the appropriate literature. To facilitate molecular dynamics studies of these proteins, the force-field parameters for many non-standard lipids that commonly interact with these proteins are also provided. Finally, an online server for predicting membrane-binding proteins and a search function with various search fields are included. The resource is publicly available and will be updated on a regular basis.

Availability:  http://proteomics.bioengr.uic.edu/metador

Contact:  huilu@uic.edu
Metal reduction kinetics inShewanella
Authors: Lall Raman , Mitchell Julie
Published: August 2007

Motivation: Metal reduction kinetics have been studied in cultures of dissimilatory metal reducing bacteria which include the Shewanella oneidensis strain MR-1. Estimation of system parameters from time-series data faces obstructions in the implementation depending on the choice of the mathematical model that captures the observed dynamics. The modeling of metal reduction is often based on Michaelis–Menten equations. These models are often developed using initial in vitro reaction rates and seldom match with in vivo reduction profiles.

Results: For metal reduction studies, we propose a model that is based on the power law representation that is effectively applied to the kinetics of metal reduction. The method yields reasonable parameter estimates and is illustrated with the analysis of time-series data that describes the dynamics of metal reduction in S.oneidensis strain MR-1. In addition, mixed metal studies involving the reduction of Uranyl (U(VI)) to the relatively insoluble tetravalent form (U(IV)) by S.alga strain (BR-Y) were studied in the presence of environmentally relevant iron hydrous oxides. For mixed metals, parameter estimation and curve fitting are accomplished with a generalized least squares formulation that handles systems of ordinary differential equations and is implemented in Matlab. It consists of an optimization algorithm (Levenberg–Marquardt, LSQCURVEFIT) and a numerical ODE solver. Simulation with the estimated parameters indicates that the model captures the experimental data quite well. The model uses the estimated parameters to predict the reduction rates of metals and mixed metals at varying concentrations.

Contact:  rl8q@cms.mail.virginia.edu

Supplementary information: Supplementary data are available at Bioinformatics online.
Tools for visually exploring biological networks
Authors: Suderman Matthew , Hallett Michael
Published: August 2007

Many tools exist for visually exploring biological networks including well-known examples such as Cytoscape, VisANT, Pathway Studio and Patika. These systems play a key role in the development of integrative biology, systems biology and integrative bioinformatics. The trend in the development of these tools is to go beyond ‘static’ representations of cellular state, towards a more dynamic model of cellular processes through the incorporation of gene expression data, subcellular localization information and time-dependent behavior. We provide a comprehensive review of the relative advantages and disadvantages of existing systems with two goals in mind: to aid researchers in efficiently identifying the appropriate existing tools for data visualization; to describe the necessary and realistic goals for the next generation of visualization tools. In view of the first goal, we provide in the Supplementary Material a systematic comparison of more than 35 existing tools in terms of over 25 different features.

Contact:  msuder@mcb.mcgill.ca

Supplementary information: Supplementary data are available at Bioinformatics online.
A comparison of background correction methods for two-colour microarrays
Authors: Ritchie Matthew E. , Silver Jeremy , Oshlack Alicia , Holmes Melissa , Diyagama Dileepa , Holloway Andrew , Smyth Gordon K.
Published: August 2007

Motivation: Microarray data must be background corrected to remove the effects of non-specific binding or spatial heterogeneity across the array, but this practice typically causes other problems such as negative corrected intensities and high variability of low intensity log-ratios. Different estimators of background, and various model-based processing methods, are compared in this study in search of the best option for differential expression analyses of small microarray experiments.

Results: Using data where some independent truth in gene expression is known, eight different background correction alternatives are compared, in terms of precision and bias of the resulting gene expression measures, and in terms of their ability to detect differentially expressed genes as judged by two popular algorithms, SAM and limma eBayes. A new background processing method (normexp) is introduced which is based on a convolution model. The model-based correction methods are shown to be markedly superior to the usual practice of subtracting local background estimates. Methods which stabilize the variances of the log-ratios along the intensity range perform the best. The normexp+offset method is found to give the lowest false discovery rate overall, followed by morph and vsn. Like vsn, normexp is applicable to most types of two-colour microarray data.

Availability: The background correction methods compared in this article are available in the R package limma (Smyth, 2005) from http://www.bioconductor.org.

Contact:  smyth@wehi.edu.au

Supplementary information: Supplementary data are available from http://bioinf.wehi.edu.au/resources/webReferences.html.
An improved algorithm for clustering gene expression data
Authors: Bandyopadhyay Sanghamitra , Mukhopadhyay Anirban , Maulik Ujjwal
Published: August 2007

Motivation: Recent advancements in microarray technology allows simultaneous monitoring of the expression levels of a large number of genes over different time points. Clustering is an important tool for analyzing such microarray data, typical properties of which are its inherent uncertainty, noise and imprecision. In this article, a two-stage clustering algorithm, which employs a recently proposed variable string length genetic scheme and a multiobjective genetic clustering algorithm, is proposed. It is based on the novel concept of points having significant membership to multiple classes. An iterated version of the well-known Fuzzy C-Means is also utilized for clustering.

Results: The significant superiority of the proposed two-stage clustering algorithm as compared to the average linkage method, Self Organizing Map (SOM) and a recently developed weighted Chinese restaurant-based clustering method (CRC), widely used methods for clustering gene expression data, is established on a variety of artificial and publicly available real life data sets. The biological relevance of the clustering solutions are also analyzed.

Contact:  anirbanbuba@yahoo.com

Supplementary information: The processed and normalized data sets, supplementary figures, tables and other related materials are available at http://d.1asphost.com/anirbanmukhopadhyay/simmts.html
Silver eel mortality during downstream migration in the River Meuse, from a population perspective
Authors: Winter Hendrik V. , Jansen Henrice M. , Breukelaar André W.
Published: August 2007

Winter, H. V., Jansen, H. M., and Breukelaar, A. W. 2007. Silver eel mortality during downstream migration in the River Meuse, from a population perspective. – ICES Journal of Marine Science, 64: 1444–1449. The European eel (Anguilla anguilla) population has decreased sharply over the past few decades owing to a combination of many factors. To determine the impact of hydropower and fisheries during the downstream migration of silver eel in the River Meuse, telemetry experiments were performed during the years 2002–2006, using 18 detection stations (NedapTrail-System®) in the river and two at the entrance to the hydropower turbines. Recaptures in fisheries were used to assess fisheries mortality. In all, 300 silver eels were surgically implanted with Nedap-transponders. For each stretch between subsequent stations, mortality rates were assessed and related to the different factors. However, to determine the overall effect on the escapement of silver eels from the River Meuse, insight into the distribution of silver eels in the entire catchment of the River Meuse is required. At two locations, mark-recapture experiments in 2002 revealed that the estimated number of migrating silver eels increased strongly in a downstream direction, suggesting that a large proportion of silver eels start their migration from the downstream stretches and tributaries of the River Meuse. Approaches and monitoring requirements that can be used to determine the impact on silver eel populations in a river basin are discussed.
Knots in the Skyrme–Faddeev model
Authors: Sutcliffe Paul
Published: August 2007

The Skyrme–Faddeev model is a modified sigma model in three-dimensional space, which has string-like topological solitons classified by the integer-valued Hopf charge. Numerical simulations are performed to compute soliton solutions for Hopf charges up to 16, with initial conditions provided by families of rational maps from the three-sphere into the complex projective line. A large number of new solutions are presented, including a variety of torus knots for a range of Hopf charges. Often these knots are only local energy minima, with the global minimum being a linked solution, but for some values of the Hopf charge they are good candidates for the global minimum energy solution. The computed energies are in agreement with Ward's conjectured energy bound.
Songbirds use pulse tone register in two voices to generate low-frequency sound
Authors: Jensen Kenneth K , Cooper Brenton G , Larsen Ole N , Goller Franz
Published: August 2007

The principal physical mechanism of sound generation is similar in songbirds and humans, despite large differences in their vocal organs. Whereas vocal fold dynamics in the human larynx are well characterized, the vibratory behaviour of the sound-generating labia in the songbird vocal organ, the syrinx, is unknown. We present the first high-speed video records of the intact syrinx during induced phonation. The syrinx of anaesthetized crows shows a vibration pattern of the labia similar to that of the human vocal fry register. Acoustic pulses result from short opening of the labia, and pulse generation alternates between the left and right sound sources. Spontaneously calling crows can also generate similar pulse characteristics with only one sound generator. Airflow recordings in zebra finches and starlings show that pulse tone sounds can be generated unilaterally, synchronously or by alternating between the two sides. Vocal fry-like dynamics therefore represent a common production mechanism for low-frequency sounds in songbirds. These results also illustrate that complex vibration patterns can emerge from the mechanical properties of the coupled sound generators in the syrinx. The use of vocal fry-like dynamics in the songbird syrinx extends the similarity to this unusual vocal register with mammalian sound production mechanisms.
Evolution of a single niche specialist in variable environments
Authors: Jasmin Jean-Nicolas , Kassen Rees
Published: August 2007

The pattern (space versus time) and scale (relative to the lifetime of individuals) of environmental variation is thought to play a central role in governing the evolution of the ecological niche and the maintenance of genetic variance in fitness. To evaluate this idea, we serially propagated an initially genetically uniform population of the bacteriumPseudomonas fluorescensfor a few hundred generations in environments that differed in both the pattern and scale at which two highly contrasted carbon substrates were experienced. We found that, contrary to expectations, populations often evolved into a single niche specialist adapted to the less-productive substrate in variable environments and that the genetic variance in fitness across different components of the environment was not generally higher in variable environments when compared with constant environments. We provide evidence to suggest that our results reflect a novel constraint on niche evolution imposed by the supply of beneficial mutations available to selection in variable environments.
Implications of a large global root biomass for carbon sink estimates and for soil carbon dynamics
Authors: Robinson David
Published: August 2007

Recent evidence suggests that significantly more plant carbon (C) is stored belowground than existing estimates indicate. This study explores the implications for biome C pool sizes and global C fluxes. It predicts a root C pool of at least 268 Pg, 68% larger than previously thought. Although still a low-precision estimate (owing to the uncertainties of biome-scale measurements), a global root C pool this large implies stronger land C sinks, particularly in tropical and temperate forests, shrubland and savanna. The land sink predicted from revised C inventories is 2.7 Pg yr
−1
. This is 0.1 Pg yr
−1
larger than current estimates, within the uncertainties associated with global C fluxes, but conflicting with a smaller sink (2.4 Pg yr
−1
) estimated from C balance. Sink estimates derived from C inventories and C balance match, however, if global soil C is assumed to be declining by 0.4–0.7% yr
−1
, rates that agree with long-term regional rates of soil C loss. Either possibility, a stronger land C sink or widespread soil C loss, argues that these features of the global C cycle should be reassessed to improve the accuracy and precision of C flux and pool estimates at both global and biome scales.
INSULIN AS A VASCULAR HORMONE: IMPLICATIONS FOR THE PATHOPHYSIOLOGY OF CARDIOVASCULAR DISEASE
Authors: Cleland Stephen J , Petrie John R , Ueda Shinichiro , Elliott Henry L , Connell John MC
Published: August 2007

1. Metabolic disorders, such as obesity and non‐insulin‐dependent diabetes mellitus, and cardiovascular disorders, such as essential hypertension, congestive cardiac failure and atherosclerosis, have two features in common, namely relative resistance to insulin‐mediated glucose uptake and vascular endothelial dysfunction.

2. Significant increases in limb blood flow occur in response to systemic hyperinsulinaemia, although there is marked variation in the results due to a number of confounding factors, including activation of the sympathetic nervous system. Local hyperinsulinaemia has a less marked vasodilator action despite similar plasma concentrations, but this can be augmented by co‐infusing D‐glucose.

3. Insulin may stimulate endothelial nitric oxide production or may act directly on vascular smooth muscle via stimulation of the Na+–H+ exchanger and Na+/K+‐ATPase, leading to hyperpolarization of the cell membrane and consequent closure of voltage‐gated Ca2+ channels.

4. There is evidence both for and against the existence of a functional relationship between insulin‐mediated glucose uptake (insulin sensitivity) and insulin‐mediated vasodilation (which can be regarded as a surrogate measure for endothelial function).

5. If substrate delivery is the rate‐limiting step for insulin‐mediated glucose uptake (in other words, if skeletal muscle blood flow is a determinant of glucose uptake), then endothelial dysfunction, resulting in a relative inability of mediators, including insulin, to stimulate muscle blood flow, may be the underlying mechanism accounting for the association of atherosclerosis and other cardiovascular disorders with insulin resistance.

6. Glucose uptake may determine peripheral blood flow via stimulation of ATP‐dependent ion pumps with consequent vasorelaxation.

7. A ‘third factor’ may cause both insulin resistance and endothelial dysfunction in cardiovascular disease. Candidates include skeletal muscle fibre type and capillary density, distribution of adiposity and endogenous corticosteroid production.

8. A complex interaction between endothelial dysfunction, abnormal skeletal muscle blood flow and reduced insulin‐ mediated glucose uptake may be central to the link between insulin resistance, blood pressure, impaired glucose tolerance and the risk of cardiovascular disease. An understanding of the primary mechanisms resulting in these phenotypes may reveal new therapeutic targets in metabolic and cardiovascular disease.
ALLOSTERIC INTERACTIONS AT MUSCARINIC CHOLINOCEPTORS
Authors: Christopoulos Arthur , Lanzafame Alfred , Mitchelson Fred
Published: August 2007

1. An allosteric interaction occurs when the binding of a ligand to its site on a receptor is able to modify the binding of another ligand to a topographically distinct site on the same receptor and vice versa. The muscarinic cholinoceptors represent the best‐studied examples of allosteric phenomena among the G‐protein‐coupled receptor superfamily.

2. The simplest model describing allosteric interactions at muscarinic cholinoceptors is the ternary complex model, which allows for a three‐way interaction between the receptor, a classical (orthosteric) ligand and an allosteric modulator. The interaction may be quantified using the dissociation constant of each ligand for its respective binding site on the free receptor and the ‘co‐operativity factor’α. This latter term is the ratio of affinities of a ligand for the occupied versus the unoccupied receptor and is a measure of the magnitude of the co‐ operativity between two concomitantly bound ligands.

3. Identification of allosteric phenomena requires the utilization of both radioligand binding and functional approaches. Manifestations of allosterism include: (i) a limited ability to influence radioligand binding as the concentration of the latter is increased; (ii) alterations in the dissociation rate of orthosteric ligands; (iii) curvilinear Schild regressions; and (iv) non‐ additivity of agonist/orthosteric antagonist/allosteric modulator combination concentration ratios.

4. Allosteric modulators of muscarinic cholinoceptors represent a diverse range of compounds. Some of the most studied agents include gallamine, alcuronium and thebis‐ammonium compounds, C7/3′‐phth and W84. Alcuronium has proven a most useful pharmacological tool, as it has been shown to display both positive and negative co‐operativity, depending on the receptor subtype and orthosteric ligand involved in the interaction.

5. Evidence has accumulated pointing to the existence of a common allosteric binding site on the muscarinic cholinoceptors, located close to the orthosteric site, but at a more extracellular level. However, the possibility of more than one accessory binding site on various receptor subtypes cannot be excluded.

6. Allosteric modulators offer a number of potential therapeutic advantages, including a ceiling level to their effects and the possibility of ‘absolute selectivity’ of action, based on the degree of co‐operativity rather than the affinity of the modulator for any one receptor subtype.
SODIUM BALANCE AND JEJUNAL ION AND WATER ABSORPTION IN DAHL SALT‐SENSITIVE AND SALT‐RESISTANT RATS
Authors: Pácha Jirˇí
Published: August 2007

1. Apparent Na+ absorption and jejunal water, Na+, Cl− and K+ absorption in vivo was evaluated in young (prepubertal) and adult Dahl salt‐sensitive (DS) and Dahl salt‐resistant (DR) rats kept on a low‐salt (low‐salt rat chow + distilled water) or a high‐salt diet (HS1 diet: NaCl‐enriched rat chow + distilled water; HS2 diet: standard rat chow + 1% saline as drinking fluid). These two high‐salt diets were chosen because the HS1 regimen has been shown to increase blood pressure (BP) in DS rats and the HS2 regimen decreases jejunal water and ion absorption in normotensive Wistar rats.

2. The HS1 or HS2 diet increased BP in young and adult DS rats but had no effect on the BP of young and adult DR rats.

3. Irrespective of dietary Na+ intake, no significant difference of apparent Na+ absorption (dietary Na+ intake minus faecal Na+ output) was observed between DS and DR rats both in prepuberty and in adulthood. Young DS rats kept on a low‐salt diet had increased faecal Na+ output in comparison with young DR rats. This difference disappeared with increasing dietary Na+ intake.

4. There were no interstrain differences on the effect of a high‐salt diet on jejunal Na+ and K+ absorption in young and adult DS and DR rats. However, high‐salt diets stimulated jejunal water and Cl− absorption in young DS rats, but not in adult DS rats and young and adult DR rats. Interstrain differences of water and Cl− absorption were observed only in adulthood. Adult DR rats kept on an HS2 diet absorbed more water and Cl− than their DS counterparts.

5. Our results do not indicate any abnormalities of apparent Na+ absorption and jejunal water and electrolyte transport in DS and DR rats. We conclude that there is no relationship between intestinal Na+ absorption and sensitivity or resistance to induction of experimental salt hypertension.
THE EFFECT OF DAYLENGTH AND LIGHT INTENSITY ON THE GROWTH RATE OF THE MARINE DIATOM DETONULA CONFERVACEA (CLEVE) GRAN1
Authors: Holt Marjorie G. , Smayda Theodore J.
Published: August 2007

The influence of 40 combinations of temperature (2, 7 C), light intensity (50, 200, 600, 1200, 1800 ft‐c), and photoperiod (24, 15:9, 12:12, and 8:16 LD) at 30% salinity on the rate of cell division of the Narragansett Bay clone of Detonula confervacea (Det‐1) was examined following appropriate preconditioning. At 2 C Detonula is a long day species (24 L) and prefers low light intensities (200–600 ft‐c); poorest growth occurred at 12:12 and 8:16 LD, and the compensation intensity was about 10 ft‐c. Increasing temperature to 7 C increased the mean growth rate, reduced the optimal daylength (15:9 LD), even though Detonula remained a long day species and increased the optimal light intensity (600–800 ft‐c). The compensation intensity varied with daylength and ranged from about 10–50 ft‐c. Photoperiods of 12:12 and 8:16 LD were least favorable for growth at both temperatures; light limitation and inhibition were observed at 50 and 1800 ft‐c. respectively; inhibition was less pronounced at 7 C. There is some indication that the conditions of growth that the stock cultures were exposed to prior to preconditioning for use in the experiments may have sometimes influenced response.

Detonula produced resting spores without nutrient depletion at 2 and 7 C at all light intensities when the photoperiod was lengthened. Auxospore formation was also observed.

Although short daylengths (9:15 LD) limit Detonula's growth during the early stages of the winter bloom, it competes successfully against Skeletonema costatum initially. This results from its higher rates of growth and of photosynthesis at the prevailing temperature and light conditions and a lower compensation intensity than reported for Skeletonema. The main causes of Detonula's growth inception and termination in Narragansett Bay differ.
ULTRASTRUCTURE OF THE FILAMENTOUS HABIT IN THE DIATOM NAVICULA CONFERVACEA (KÜTZ.) GRUN.1
Authors: Busch David E.
Published: August 2007

Frustules of the filamentous diatom Navicula confervacea (Kütz.) Grun. are united by the overlapping of marginal teeth located alongside the junction of valve face and mantle. Scanning and transmission electron microscopy show this connecting mechanism to differ from the previously reported inter‐digitating spines or teeth in the genera Melosira, Stephanodisus, and Fragilaria.
MICROAUTORADIOGRAPHIC STUDIES OF THE MARINE PHYCOBIONTS RHIZOSOLENIA AND RICHELIA1
Authors: Weare N. M. , Azam F. , Mague T. H. , Holm‐Hansen O.
Published: August 2007

Microautoradiography was used to study photosynthetic and heterotrophic activities in cells of the diatom Rhizosolenia styliformis var. longispina containing the nitrogen‐fixing, endophytic, blue‐green alga Richelia intracellularis. In field studies with 14C‐labeled bicarbonate, the blue‐green alga appeared to be actively photosynthesizing but the diatom did not. Neither Richelia nor Rhizosolenia assimilated, 3H‐labeled acetate, glucose, or an amino acid mixture. The diatom lacked cytoplasmic streaming and appeared, to be in a senescent condition. Implications of these observations for the nature of this algal association are discussed.
CELL DIVISION INCHLAMYDOMONAS MOEWUSII1
Authors: Triemer Richard E. , Brown R. Malcolm
Published: August 2007

Cell division inChlamydomonas moewusiiis described. The cells become immobile with flagellar abscission prior to mitosis. The basal bodies migrate toward the nucleus and become intimately associated with the nuclear membrane which is devoid, of ribosomes where adjacent to the basal bodies. The basal bodies replicate at preprophase. The nucleolus fragments at this stage. By prophase the basal body pairs have migrated, to the nuclear poles. Spindle fibers become prominent in the nucleus. The nuclear membrane does not fragment. The nucleus assumes a crescent‐form by metaphase. Polar fenestrae are absent. Kinetochores appear at anaphase. An interzonal spindle elongates as the chromosomes move to the nuclear poles. Daughter nuclei become abscised by an ingrowth of nuclear membrane, leaving behind a separated, degenerating interzonal spindle. Ribosomes reappear on the outer nuclear membrane at late telophase. Nucleoli reform early in cytokinesis. The cleavage furrow, associated microtubules, and endoplasmic reticulum comprise the phycoplast. Cytokinesis proceeds rapidly after the completion of telophase. The basal body‐nucleus relationship becomes reorganized into the typical interphase condition late in cytokinesis. Specific and predictable organelle rearrangements during mitosis have been described. Cell division inC. moewusiiis compared with other algae, especiallyC. reinhardi.
A NUTRITIONAL ANALYSIS OF A SUBLITTORAL DIATOM ASSEMBLAGE EPIPHYTIC ONENTEROMORPHAFROM A LONG ISLAND SALT MARSH1,2
Authors: Lee John J. , McEnery Marie E. , Kennedy Eileen M. , Rubin Howard
Published: August 2007

The diatom population structure of a salt marsh epiphytic community growing onEnteromorpha intestinaliswas studied at one station throughout the summer. A total of 218 species or varieties were recognized. Six species— Fragilaria construens, Cocconeis scutellum, Cocconeis placentula, Achnanthes hauckianavarieties,Achnanthes pinnata, andAmphora coffeaeformis(var.acutiuscula)–dominated theEnteromorphaepiphytic community during the summer months and comprised ∼ 40% of the total populations.Melosira nummuloides, Opephora martyi, Synedra fasiculatavar.tabulata, S. affinis, Navicula platyventris, andN. pavillardiwere also very common species (13% of the total population). The distribution of many species in the community was seasonal. A series of differential media have been developed which are effective as tools for the isolation and nutritional characterization of the algae and bacteria from the community. Many diatom species can be recognized by their colony type or growth pattern on solidified media. A key and illustrated plates aid in identification. Changes in population structure of the community were reflected by changes in the nutritional patterns as judged by differences in the growth of diatoms and bacteria on the differential media tested. The nutritional requirements, selectivity, and rank order of media for individual species is given.

Almost half of the colony types (32–33) grew on either unenriched seawater from the collection site or basal synthetic seawater. Erdschreiber was a poorer medium for the isolation of algae than seawater alone. Few algal colonies grew on either marine nutrient agar or trypticase soy agar. Nitrite inhibited algal growth. Media enriched with thiamine, biotin, or nitrate, phosphate, and B12were stimulatory. Soil extract or an acetone extract ofEnteromorphatripled growth; a complex vitamin mixture, or glycerol, or mannitol, or an autoclaved extract ofEnteromorphadoubled colony numbers. The greatest numbers of diatom types (43) and total colonies (655) were recovered on media enriched with acetone extract ofEnteromorpha, suggesting a possible nutritional relationship betweenEnteromorphaand its epiphytes.

The representativeness of the isolations from the natural community as a function of time was also considered. Concentrations of selected dissolved potential growth‐stimulating nutrients were measured within and external toEnteromorphacommunities. We conclude that the algal assemblage growing epiphytically onEnteromorpha intestinalishas a diverse auxotrophic profile which contributes to the productivity and stability within this important component of the epiphytic community and that much of the organic substrates used by individual species originate within and are recycled among the community members.
ENHANCEMENT OF PHYTOPLANKTON GROWTH BY MARINE BACTERIA12
Authors: Ukeles Ravenna , Bishop Jean
Published: August 2007

Investigations were conducted into the effect of 3 marine bacteria,Vibrio anguillarum #19264,V. anguillarum #19109, andEscherichia coli, on the growth of 10 phytoplakters. A disc method on agar plates was used to evaluate growth responses. Growth enhancement of all algae in the presence ofV. anguillarum #19264 occurred on an enriched agar medium; the other bacteria yielded variable responses. Evidence available is consistent with the hypothesis that growth enhancement of algae is related to the release of stimulating substances through bacterial hydrolysis of the agar.
A MORPHOLOGICAL AND TAXONOMIC CONSIDERATION OF TABELLARIA (BACILLARIOPHYCEAE) FROM THE NORTHCENTRAL UNITED STATES1,2
Authors: Koppen John D.
Published: August 2007

The taxonomy, distribution, and ecology of the diatom genus Tabellaria Ehr. from a portion of the northcentral United States were studied from collections made from August 1968 to October 1971. Using the transmission electron microscope with carbon replicas of the frustule surfaces, taxonomically significant characters were identified and related to those visible with the light microscope, four morphologically distinguishable taxa were recognized. The frustular morphology of T. fenestrata (Lyngbye) kütz. em. Knudson var. fenestrata was confirmed by both light and electron microscopy. T. flocculosa (Roth) Kütz. var. flocculosa is composed of 3 morphologically distinguishable strains. One of which is sufficiently different from the nominate variety to be described as T. flocculosa var. linearis var. nov. Also, a planktonic ecotype of one of the strains was identified.
RELATIONSHIP BETWEEN PHOTOSYNTHESIS AND CELL SIZE OF MARINE DIATOMS12
Authors: Taguchi Satoru
Published: August 2007

Three photosynthetic parameters of 7 species of marine diatoms were studied using Na214CO3 at 5–8 C using log phase axenic cultures. The cell volumes of the different species varied from 70 μm3 to 40 × 105μm3. The present experiment is consistent with the interpretation that the initial slope α (mg C · [mg chl a]−1· h−1· w−1· m2) of photosynthesis vs. light curves is controlled by self‐shading of chlorophyll a in the cell. Pm, the rate of photosynthesis at light saturation (mg C · [mg cell, C]−1· h−1) and R, the intercept at zero light intensity (mg C · [mg cell C]−1· H−1) are both dependent on the ratio of surface area to volume of cell.
BACTERIAL ENDOSYMBIONTS INVOLVOX CARTERI(CHLOROP HYCEAE)1
Authors: Lee Wen‐Shen Betty , Kochert Gary
Published: August 2007

The morphology of the bacterial endosymbiont ofVolvox carteriStein (Clone KA‐1) was studied with the electron microscope. Endosymbionts were found in the cytoplasm of somatic cells, gonidia and sperm, but never in nuclei, chloroplasts or mitochondria. DNA preparations contained, an extra DNA species assumed to be endosymbiont DNA. Attempts to isolate the endosymbionts or to “cure” the alga with antibiotics were unsuccessful. All progeny from crosses of infected and noninfected strains contained the endosymbiont.
SEXUAL REPRODUCTION OFPERIDINIUM WILLEI(DINOPHYCEAE)1
Authors: Lois Pfiester A., O.P.
Published: August 2007

Sexual reproduction was induced in the dinoflagellatePeridinium willeiHuitfeld‐Kass when exponentially growing cells were inoculated into nitrogen deficient medium. Small, naked vegetative cells produced by division of thecate cells acted as gametes. The zygote remained motile 13–14 days, during which time it enlarged and the theca formed became warty. Fourteen to 15 days following plasmogamy the zygote was nonmotile with the protoplast contracted. A large red oil droplet appeared and the wall thickened, becoming chitinized. Hypnozygotes with 4 nuclei were observed 7–8 wk following formation. Meiosis was inferred. The hypnozygote germinated, within 8 wk producing one post‐zygotic cell retaining the red oil droplet. This cell divided within 24 h into 2 daughter cells each with a prominent red oil droplet. These daughter cells divided after 2 to 3 days into ordinary vegetative cells. Attempts to induce sexual reproduction by inoculation of cells into media deficient in a number of basic elements were unsuccessful.
EFFECTS OF LIGHT INTENSITY ON DIVISION RATE, STIMULABLE BIOLUMINESCENCE AND CELL SIZE OF THE OCEANIC DINOFLAGELLATESDISSODINIUM LUNULA, PYROCYSTIS FUSIFORMISANDP. NOCTILUCA12
Authors: Swift Elijah , Meunier Valerie
Published: August 2007

Preadapted cultures were grown in a 12:12 LD cycle at a series of light intensities under cool‐white, fluorescent lamps.Pyrocystis fusiformisMurray maintained high division rates at low light intensities at the expense of cell size. In contrast,Dissodinium lunula(Schuett) Taylor had relatively lower division rates at low light intensities with little concomitant decrease in size. The response ofP. noctilucaMurray was intermediate between these two species. For all three, cell numbers did not increase above an intensity of 5–10 μEin·m−2·sec−1and division rate was saturated atca.30, 60, and 60μEin·m−2·sec−1forP. fusiformis, P. noctiluca, andD. lunula, respectively. The capacity for stimulable bioluminescence was saturated at light intensities of 0.15 μEin·m−2·day in short‐term (2‐day) experiments. In cultures ofP. fusiformisandP. noctiluca, maintained for at least one month at lower intensities than needed to saturate division rate, a decrease in the capacity for stimulable bioluminescence was accompanied by a reduction in cell size. Our results suggest that cell size and bioluminescent capacity may prove to be a potentially useful indication of the history of exposure of natural populations ofPyrocystisspp. to ambient intensities.
THECAL ULTRASTRUCTURE OF THE TOXIC MARINE DINOFLAGELLATE GONYAULAX CATENELLA1
Authors: Postek Michael T. , Cox Elenor R.
Published: August 2007

The toxic marine dinoflagellate Gonyaulax catenella Whedon & Kofoid was studied with scanning and transmission electron microscopy to describe the thecal morphology and to accurately define the taxonomic characters of the species. The closing platelet which lies in a U‐shaped apical pore was revealed to be disassociable from a partly obscured apical platelet. Two previously unreported sulcal plates were charaterized and described. The entire complement of thecal plates numbered 33.
CHARACTERIZATION OF PIGMENT MUTANTS IN A BLUEGREEN ALGA, ANACYSTIS NIDULANS1
Authors: Stevens C. L. R. , Myers Jack
Published: August 2007

Characteristics of 2 types of pigment mutants of the bluegreen alga, Anacystis nidulans, are described. “Yellow‐green” mutants (YG) which have normal chlorophyll but only half the phycocyanin of the parent are similar to the parent in number of reaction centers/cell, number of chlorophylls/reaction center, maximum turnover rate of the reaction centers, quantum yields at 620 and 686 nm and specific growth rate; they have a reduced action at 620 nm. “Blue” mutants (BL) with somewhat higher phycocyanin but only one‐third the chlorophyll of the parent are dissimilar to the parent. BL's have fewer reaction centers/cell, a smaller number of chlorophylls/reaction center, a higher maximum turnover rate of reaction centers, and a lower specific growth rate. BL's show ca. half the quantum yield of the parent at 620 nm and at 686 nm show a “red rise” rather than a “red drop.” The consequences attending low chlorphyll in the BL's are more drastic than those attending the low phycocyanin of the YG's.
INHIBITION OF CHLORELLA (CHLOROPHYCEAE) GROWTH BY FATTY ACIDS, USING THE PAPER DISC METHOD1,2
Authors: McGrattan Carol J. , Sullivan James D. , Ikawa Miyoshi
Published: August 2007

Using the paper disc‐agar plate method, a number of fatty and related acids have been tested for tested activity for inhibiting the growth of Chlorella pyrenoidosa Chick. Of the saturated acids, a peak in growth inhibiting activity wax observed in the C7–C12 range, where inhibition wax observed when solutions down to 0.02 M were applied to the discs. Most of the unsaturated acids tested showed greater inhibition than did the corresponding saturated acids. Acrylic acid showed detectable inhibition at 0.001 M concentration.
CONTINUOUS CULTURE OF MARINE DIATOMS UNDER SILICATE LIMITATION. II. EFFECT OF LIGHT INTENSITY ON GROWTH AND NUTRIENT UPTAKE OFSKELETONEMA COSTATUM1,2
Authors: Davis Curtiss O.
Published: August 2007

Two replicate experiments were conducted to investigate the effect of light intensity on the growth and nutrient uptake ofSkeletonema costatum(Grev.) Cleve in silicate‐limited continuous culture. Each experiment began with 4 identical chemostat cultures ofS. costatumgrowing at the normal laboratory light (0.14 ly · min−1, continuous illumination) under strong silicate limitation. Screens were placed over 3 cultures reducing them to light intensities of 0.042, 0.021 and 0.0018 ly · min−1.

Based on growth rules, nutrient uptake rates, cell morphology and chemical composition, the cultures receiving 0.021, and 0.0018 ly · min−1appeared to he light‐limited, whereas the culture receiving 0.14 ly.
A COMPARISON OF THE ATTACHED ALGAL COMMUNITIES OF A NATURAL AND AN ARTIFICIAL SUBSTRATE1
Authors: Brown Helen Davis
Published: August 2007

A study of communities of attached algae in Lake Mize Florida, wax made during July 1969, July‐August 1970 and April 1971. The substrates exposed during the study included glass slides mid the terrestrial form of the amphibious sedge, Eleocharis baldwinii (Torr.) Chapman. Counts were used to determine the relative abundance and densities of the species present on the 2 substrates under different environmental conditions. Such analyses indicated that at any given lime and place, a number of factors influenced the composition of the periphyton. Generally, lightly adhering, resupinate species attained higher densities on glass slides than filamentous and loosely associated metaphytonic species. The epiphytic flora of E. baldwinii contained a large number of both strong attachers and the metaphyton. The vertical range of many attached species was also greater on E. baldwinii than on glass slides.
EXTRACELLULAR LYSIS OF THE BLUEGREEN ALGA PHORMIDIUM LURIDUM BY BDELLOVIBRIO BACTERIOVORUS1
Authors: Burnham Jeffrey C. , Stetak Thomas , Locher Gregory
Published: August 2007

When either cells of the bacterium, Bdellovibrio bacteriovorus (Stolp & Starr), strain 15143, or a heat‐resistant lytic factor derived from these cells is added to viable cultures of Phormidium luridum var. olivacea Boresch all the algal cells underwent gradual lysis. This effect was obtained with a mean initial bdellovibrio:algal cell ratio of 7.5:1. When P. luridum was mixed with the bdellovibrio cultures the algal chlorophyll content showed an 8‐fold decrease. Concomitantly, this interspecies interaction caused, a 75% inhibition of algal photosynthesis after‐4 h. Heat, treatment of the B. bacteriovorus culture supernatant fluid increased its ability to inhibit photosynthesis approximately 14%. Light, microscopy showed pale granules and intracellular spaces to form in the P. luridum within 16 h after adding the bdellovibrio lytic factor. Subsequent morphological changes included the development of large intracellular spaces, intercellular spaces, spheroplast formation and finally Complete lysis of the algal cells.
AN UNUSUAL METHOD FOR CULTURE OF UNICELLULAR MARINE ALGAE1
Authors: Ukeles Ravenna , Bishop Jean
Published: August 2007

A method for the axenic culture of marine microscopic algae that utilizes various types of paper as solid substrates for growth is described. Investigations into the growth of 39 algal, strains on various paper substrates were conducted. Applications of the method to bioassay are discussed.
SEASONAL, SUCCESSION OF ALGAE IN RIVERS. I. EXAMPLES FROM THE AVON, A LARGE SLOW‐FLOWING RIVER1
Authors: Moore James W.
Published: August 2007

The epipelic, epilithic and epiphytic algae in a large slow‐flowing river (the Avon) situated in southern England usually exhibited a pronounced bloom during early spring probably in response, to increasing daylength. Although floods caused a reduction in the standing crop of most communities both through scouring action and possibly long‐term alteration of microhabitat, they also seemed essential for the renovation of sediment and, rock substrates after periods of rapid algal growth. Because of the attachment characteristics of the predominant epiphytic species, the community attached to Cladophora remained relatively unaffected by flooding. Water velocity may have been important in determining the species composition of some communities, particularly the epiphytic associations. Nutrients probably seldom limited development, but during part of the summer competition with planktonic diatoms for silicon appeared to limit attached algae. During the summer, large scale detachment (which greatly reduced algal density) apparently correlates with a high photosynthetic rate. Algal, numbers in the plankton occasionally decreased in response to a loss of buoyancy of the predominant species.