bluuebunny/crossref_metadata_2025 huggingface dataset:
TRACHELOMONAS HISPIDA VAR. CORONATA (EUGLENOPHYCEAE). III. ENVELOPE ELEMENTAL COMPOSITION AND MINERALIZATION1,2
Authors: West Larry K. , Walne Patricia L. , Bentley James
Published: August 2007

This report is the first direct demonstration of Mn deposition in envelopes (loricas) of Trachelomonas in culture. The envelopes of Trachelomonas hispida var. coronata Lemm. were analyzed for elemental composition by X‐ray fluorescence spectrometry (XRF), atomic absorption spectrophotometry (AA), and electron microscopic, energy‐dispersive X‐ray spectroscopy (EM‐EDS). The envelopes contained extensive deposits of manganese (20–60 wt. %) and lesser amounts of Si, Ca and either Ba or Ti, the last three together totalling less than 5% by weight. The average amount of Mn per envelope was estimated at 1.5 × 10−10 g. Traces of Na, K, P, S and Cl were also detectable. Biomineralization of envelopes was studied by comparison of envelope substructure and composition in lightly colored, golden and dark brown envelopes that were isolated by micromanipulation, processed individually or in groups, and analyzed by SEM, TEM, EM‐EDS, and scanning transmission EM‐EDS (STEM‐EDS). Dark envelopes were thicker (1–4 μm), more ornate and less porous than light envelopes, but the ultrastructure of the two was similar. In both types of envelopes, distribution and thickness of Mn‐containing fibrillar to needle‐like microcrystallites were similar. However, dark envelopes contained a greater density of granular deposits around the needle‐like microcrystallites than did light envelopes. Dark envelopes contained 2–40 times more Mn than did light envelopes, but since envelope mass is proportionately greater, Mn concentrations were similar. Our results suggest that the extent of mineralization depends upon the amount of mucilage secreted. Biomineralization studies with Trachelomonas offer the rare advantage that mineral deposition occurs extracellularly, and not within membrane‐bound compartments as in many other unicellular model systems.
STRUCTURE AND COMPOSITION OF PITHOPHORA OEDOGONIA (CHLOROPHYTA) CELL WALLS1
Authors: Pearlmutter Nina L. , Lembi Carole A.
Published: August 2007

Carbohydrates, amino acids and other cell wall components of Pithophora oedogonia (Montagne) Wittrock were identified by physical, biochemical, and cytochemical techniques as well as by light and electron microscopy. The major polysaccharides of P. oedogonia cell walls were cellulose and chitin. In addition to N‐acetylglucosamine and glucose, N‐acetylgalactosamine, galactose, arabinose, fucose, mannose, xylose, and galacturonic acid were the other sugars, amino sugars, and sugar derivatives detected. The carbohydrate content of the cell walls was estimated to be 65% non‐nitrogenous hexose and 6% chitin. Chitin was present in the crosswall disks and outer wall, whereas cellulose was confined to the inner wall. Protein and N‐ acetylgalactosamine were concentrated in the chitin‐rich wall fraction. The location of chitin in P. oedogonia cell walk is suggested as a basis for morphological differences between the two genera, Cladophora and Pithophora.
VERTICAL DISTRIBUTION OF SEAWEED SPORES IN A WATER COLUMN OFFSHORE OF NORTH CAROLINA1
Authors: Amsler Charles D. , Searles Richard B.
Published: August 2007

Differences in the vertical distribution of seaweed spores in a 20 m water column 30 km off the coast of North Carolina were documented. Spores were collected on plastic, and glass slides that were subsequently transferred to incubator cultures where germlings were grown and counted. Spores of green algae and bangiophycidean red algae were collected throughout the water column, whereas spores of brown algae and florideophycidean red algae occurred almost exclusively near the bottom. The occurrence of some kinds of spores in the upper water levels suggests relatively large dispersal shadows for those species. The taxa recovered in the upper levels were typically opportunistic organisms, many of them epiphytes. The collection of many Enteromorpha individuals in the upper and mid levels was of particular interest since locally this genus only occurs in abundance in shallow water habitats 35 km or more from the study site.
PHOTOSYNTHESIS OF THE RED ALGA GASTROCLONIUM COULTERI (RHODOPHYTA) IN RESPONSE TO CHANGES IN TEMPERATURE, LIGHT INTENSITY, AND DESICCATION1
Authors: Hodgson Lynn M.
Published: August 2007

Previously reported transplantation experiments in the field showed that Gastroclonium coulteri (Harvey) Kylin could survive above its normal intertidal range (0.0–0.5 m above MLLW), except during periods of daytime low tides in spring. Net photosynthetic rate measurements in the laboratory were performed to determine which physical factors might determine the upper boundary for this species in the intertidal zone.

Maximum net photosynthesis occurred between 15 and 20° C, but remained positive between 4 and 35° C. The air temperature extremes observed in the field were 2° C (only seen once) and 26° C. Net photosynthesis increased as expected with light intensity to the highest value obtainable in the laboratory, 1400 μEin m−2 s−1. Plants collected from the field under higher light intensity (up to 2000 μEin m−2 s−2) also showed high rates of photosynthesis. Neither the temperature nor light levels observed in the field were directly damaging to photosynthesis. Desiccation, however, resulted in a sharp decrease in both photosynthesis and respiration. G. coulteri fully recovered from successive daily treatments of about 35% desiccation, but not from successive treatments of 50% desiccation. One exposure to 70% desiccation allowed no recovery of photosynthetic capacity.
THE EFFECTS OF LIGHT AND NITROGEN ON GROWTH, PIGMENT CONTENT, AND BIOCHEMICAL COMPOSITION OF GRACILARIA FOLIIFERA V. ANGUSTISSIMA (GIGARTINALES, RHODOPHYTA)1
Authors: Lapointe Brian E.
Published: August 2007

The combined effects of light intensity and nitrogen (NO3−) on growth rate, pigment content, and biochemical composition of Gracilaria foliifera v. angustissima (Harvey) Taylor was investigated using outdoor continuous cultures.

Growth of Gracilaria increased linearly with increasing light to 0.43 doublings d−1 at high light levels (383 ly d−1 of in situ light), suggesting that light may often limit growth of this plant in nature. Chlorophyll a and phycoerythrin contents were inversely proportional to light level and growth rate. However, pigment content did not affect the growth capacity of Gracilaria. There was no increase in growth or pigment content with increasing additions of nitrogen. The low nitrogen treatment was unenriched seawater that had higher NO3− levels than most coastal waters (influent = 8.61 μM; residual = 0.94 μM). When growing near its maximum rate under high light intensities, Gracilaria had a significantly (P < 0.001) lower phycoerythrin: chlorophyll a ratio (phyco: Chl a) than did Gracilaria growing more slowly under lower light (Phyco:Chl a of 2.8 ± 0.2 vs. 3.8 ± 0.3). Faster growing plants also had C:N ratios above 10, indicating N‐ limitation. In addition to harvesting light the phycobiliproteins of Gracilaria may store nitrogen.

Growth rates of Gracilaria correlated negatively with ash (r =–0.85) and positively with the carbon: phycoerythrin ratio (r = 0.85), suggesting that these two indices can be used to estimate growth in the field.
SEDIMENTATION STUDIES OF RED ALGAL SPORES1
Authors: Okuda Takeo , Neushul Michael
Published: August 2007

More than 1000 spores from 11 species of red algae were collected; their differences in size and sinking rates were measured using a new micro‐video technique. A relationship between size and sinking rate was shown with larger spores generally sinking faster than smaller ones. Variability in spore size, or lack thereof, is a species characteristic. Cryptopleura violacea (J. G. Ag.) Kylin and Neoagardhiella baileyi (Kutz.) Wynne and Taylor were found to produce a wide range of spore sizes. Such variability in size may be related to differences in spore formation. Centrifugation was used to separate the contents of spores to show differences in them. The ecological implications of these observations are considered.
POLYSACCHARIDES FROM THE ENVELOPES OF HETEROCYSTS AND SPORES OF THE BLUE‐GREEN ALGAE ANABAENA VARIABILIS AND CYLINDROSPERMUM LICHENIFORME1
Authors: Cardemil Liliana , Wolk C. Peter
Published: August 2007

The polysaccharides from the envelopes of heterocysts of Cylindrospermum licheniforme Kütz., and of heterocysts and spores of Anabaena variabilis Kütz., like those from the differentiated cells of Anabaena cylindrica Lemm., have a 1,3‐linked backbone consisting of glucosyl and mannosyl residues in a molar ratio of approximately 3:1. As is the case with A. cylindrica the polysaccharides from A. variabilis and from the heterocysts of C. licheniforme have terminal xylosyl and galactosyl residues as side branches. In addition, the polysaccharide from C. licheniforme resembles that from A. cylindrica in having terminal mannosyl residues as side branches (absent from A. variabilis). The polysaccharides from A. variabilis resemble that from A. cylindrica in having glucose‐containing side branches (absent from the heterocyst polysaccharide from C. licheniforme), but in contrast to the polysaccharides from the other two species they also have terminal arabinosyl residues as side branches. All of the polysaccharides mentioned appear to be structurally related; we present tentative structures for those not previously investigated. In contrast, the envelope of spores of C. licheniforme contains only a largely 4‐linked galactan. The bulk of this envelope is not polysaccharide in nature, and contains aromatic groups.
COMPARATIVE KINETIC STUDIES OF PHOSPHATE‐LIMITED GROWTH AND PHOSPHATE UPTAKE IN PHYTOPLANKTON IN CONTINUOUS CULTURE1
Authors: Gotham Ivan J. , Rhee G‐Yull
Published: August 2007

A comparative kinetic study of phosphate‐limited growth and phosphate uptake was carried out in chemostat cultures of Anabaena flos‐aquae Lyng. Bréb., Ankistrodesmus falcatus (Corda) Ralfs, Asterionella formosa Hass., Fragilaria crotonensis Kitt., and Microcystis sp. Lemm. For each test organism the growth rate (μ) can be described as a function of total cell phosphorus (P), i.e. cell quota (q), or hot‐water‐extractable P (qsp).

Phosphate uptake rate in each species examined was a function of external P concentration (S) and intracellular P levels. The substrate parameter for uptake (Km) remained constant at all growth rates, but the apparent maximum uptake rate (Vm') increased with decreasing μ, or q, in all test organisms. At low growth rates Vm' was greater than the calculated steady‐state uptake rate (μq) by two to three orders of magnitude because Vm' is the uptake rate at S ≫ Km and μq is the rate at S ≪ Km. The difference between Vm' and μm decreased and virtually disappeared as μ approached the physiological maximum growth rate (μm), where q = qm and S ≫ Km.

An inverse relationship existed between Vm' and qsp which could be described by a function that mathematically resembles noncompetitive inhibition in enzyme kinetics. The inverse relation between Vm' and (q – q0) was described by a three‐parameter function. This empirical function provided a good description of this inverse relation over the range from Vm' at q approaching q0 up to and including calculated net, maximum uptake rates at q = qm.
AMPHIDINIUM CRYOPHILUM SP. NOV. (DINOPHYCEAE) A NEW FRESHWATER DINOFLAGELLATE. I. SPECIES DESCRIPTION USING LIGHT AND SCANNING ELECTRON MICROSCOPY1
Authors: Wedemayer Gary J. , Wilcox Lee W. , Graham Linda E.
Published: August 2007

Amphidinium cryophilum sp. nov. was found in the fall of 1979 in a small pond near Madison, Wisconsin. During the ensuing winter, it became the dominant phytoplankter. Cell numbers remained high despite a thick layer of ice and snow. After the ice melted in the spring the organism disappeared from plankton samples. A successful culture of A. cryophilum was established only when isolates were incubated at 5–7° C. It is compared with two morphologically similar species, A. amphidinioides (Geitler) Schiller and Gymnodinium inversum Nygaard. Amphidinium cryophilum is distinguished from the former by its pigmentation (golden‐yellow vs. blue‐green), the location of the cingulum, and its lack of an eyespot. It differs from the latter in cell shape, the route of the sulcus and position of the nucleus.
CYST FORMATION IN THE FRESHWATER DINOFLAGELLATE CERATIUM HIRUNDINELLA (DINOPHYCEAE)1
Authors: Chapman D. V. , Dodge J. D. , Heaney S. I.
Published: August 2007

Cyst formation in Ceratium hirundinella (O. F. Müll.) Bergh was studied by light and electron microscopy, using material from several lakes and reservoirs and also laboratory cultures. Cells preparing to encyst build up large quantities of starch and lipid and at the same time reduce their other cell components. The cyst is released from the theca as a naked cell bounded by a double membrane. The most commonly found cyst deposits a layer of electron‐dense granules containing silicon on the outer membrane and lays down a cellulose‐like material between the two membranes. Cysts without the electron‐dense granules are commonly formed in cultures but rarely found in lakes. These cysts appear less resistant to decay and do not show the reorganization of cell contents for dormancy. It is suggested that C. hirundinella has both a resting cyst, forming part of the life cycle, and a temporary cyst stage.
DEUCALION GEN. NOV. AND ANISOSCHIZUS GEN. NOV. (CERAMIACEAE, CERAMIALES), TWO NEW PROPAGULE‐FORMING RED ALGAE FROM SOUTHERN AUSTRALIA1
Authors: Huisman John M. , Kraft Gerald T.
Published: August 2007

Two new propagule‐farming red algae from southern Australia, Deucalion levringii (Lindauer) gen. et comb. nov. and Anisoschizus propaguli gen. et sp. nov., are described and defined largely on their development in laboratory culture. Deucalion is included in the tribe Compsothamnieae on the basis of its subapical procarp and alternate distichous branching. It differs from the other genera included in that tribe in that it produces 3‐celled propagules, polysporangia, a subapical cell of the fertile axis which bears 3 pericentral cells, and an apparently post‐fertilization involucre which develops from the hypogenous and sub‐hypogenous cells of the fertile axis. Its gametophyte morphology has been elucidated in culture, as only sporophytes are known from the field. Gametophytes do not appear to produce propagules. Anisoschizus is provisionally included in the tribe Spermothamnieae on the basis of its subdichotomous branching, possession of a prostrate system and the production of polysporangia. It differs from the other genera of the tribe in the production of 2‐celled propagules. Observations on the germination of the “monosporangia” of Mazoyerella arachnoidea and Monosporus spp. indicate that they are analagous to the propagules of Deucalion and Anisoschizus. The nature of these propagules and their role in recycling the parent plant are discussed and contrasted with true monosporangia. It is recommended that Monosporus be maintained as a form genus containing representatives from more than one tribe, as exemplified by plants from Lord Howe I. provisionally identified as M. indicus Boergesen which have both prostrate and erect, as opposed to only erect, axes.
THE NUCLEAR CELL CYCLE IN CHLAMYDOMONAS (CHLOROPHYCEAE)1
Authors: Coleman Annette W.
Published: August 2007

The timing of replication and division of the Chlamydomonas Ehrenberg nucleus in the vegetative cell cycle and at gametogenesis was examined, using fluorescence microspectrophotometry with two fluorochromes, mithramycin and 4′,6‐diamidino‐2‐phenylindole (DAPI). Under appropriate conditions, these bind specifically to DNA, and the fluorescence of the DNA fluorochrome complex is a quantitative measure of the DNA content. The alga is a haplont, which produces 2n daughter cells at the time of vegetative reproduction; cytokinesis and daughter cell release lag behind karyokinesis. No nucleus was found to contain more than the 2c quantity of DNA. Hence daughter cell production proceeds by doubling of the nuclear DNA followed by karyokinesis, in a repetitive sequence. As reported previously for C. reinhardtii Dangeard, the gametes of C. moewusii Gerloff contain the 1c amount of nuclear DNA. Several conflicting interpretations of the cell cycle sequence proposed in the literature were resolved.
THE MORPHOLOGY AND DEVELOPMENT OF SOME PROMINENTLY STALKED SOUTHERN AUSTRALIAN HALYMENIACEAE (CRYPTONEMIALES, RHODOPHYTA). I. CRYPTONEMIA KALLYMENIOIDES (HARVEY) KRAFT COMB. NOV. AND C. UNDULATA SONDER1
Authors: Scott Fiona J. , Wetherbee Richard , Kraft Gerald T.
Published: August 2007

Several southern Australian red algae of the family Halymeniaceae (Cryptonemiales) are differentiated into hard, massive stalks and considerably softer laminar blades or phyllodes. The taxonomy, morphology and pit‐connection ultrastructure of one such species, Cryptonemia kallymenioides (Harvey) Kraft comb. nov., are compared to C. undulata Sonder, which lacks massive stalks. In both species there is extensive periodic secondary cortication of the stalks, resulting in the formation of distinct “growth rings.” The blades of C. kallymenioides appear to be seasonal and its stalks perennial, while plants of C. undulata are apparently perennial but shorter lived than C. kallymenioides. As a result, stalks in the latter can reach 2–3 cm in diameter with up to 18 growth rings, compared to the 1–2 mm diameters and up to 6 rings within the stalks of C. undulata. Heavy secondary thickening of cortical cell walls occurs in both species and confers a “woody” texture to the stalks of C. kallymeniodes. Regardless of the large differences in average stalk diameters between the two species, the pit‐connection ultrastructure from cortex to medulla shows much the same sequence of morphological modification. Pit‐connections are standard red algal structures in the outer cortex, but become increasingly convoluted on the membrane‐bound surfaces abutting cytoplasm and develop wider apertures and less dense cores with increasing distance from the stalk surface. In occasional medullary cells of C. kallymenioides, the cytoplasm disintegrates, leaving cell walls and pit‐connections to play an apparently structural role which has not been reported in other red algae. It is suggested that the increase in aperture size and surface areas of pit‐connections is compatible with their playing a role in the intercellular transport of solutes towards the inner cell layers which may, in C. kallymenioides, lie many millimeters distant.
REPRODUCTIVE DEVELOPMENT OF THE PARASITIC RED ALGA GARDNERIELLA TUBERIFERA (SOLIERIACEAE, GIGARTINALES)1
Authors: Goff Lynda J. , Hommersand Max H.
Published: August 2007

Examination of the reproductive morphology of the adelphoparasitic red alga Gardneriella tuberifera Kylin reveals that this monotypic genus is correctly placed in the family Solieriaceae (Gigartinales), to which its host Agardhiella gaudichaudii (Montagne) Silva et Papenfuss also belongs. Gardneriella is multiaxial, nonprocarpic and has an inwardly directed, three‐celled carpogonial branch. The large, reniform uninucleate auxiliary cell is distinct prior to and after fertilization. It is diploidized by an unbranched, multicellular connecting filament which lacks pit connections. One or two connecting filaments arise from each fertilized carpogonium. From the diploidized auxiliary cell, the gonimoblast initial is cut off obliquely toward the interior of the thallus. The cells of the gonimoblast fuse with adjacent unpigmented vegetative cells of Gardneriella and pigmented cells of the host. These cells become incorporated into the developing cystocarp and, from those of Gardneriella, additional short chains of gonimoblast cells arise. The mature cystocarp is placentate, radiately lobed, and lacks a surrounding involucre. Carposporangia are borne in short chains and the unpigmented carpospores are released upon the dissolution of outer vegetative cells. No ostiole is present. Gardneriella appears to be most closely related to the placentate solieriacean genera Agardhiella, Sarcodiotheca, and Meristiella and therefore this genus should be placed in the tribe recently erected for these taxa, the Agardhielleae.
PHAGOTROPHY IN GYMNODINIUM FUNGIFORME (PYRRHOPHYTA): THE PEDUNCLE AS AN ORGANELLE OF INGESTION1
Authors: Spero Howard J.
Published: August 2007

The non‐photosynthetic phagotrophic dinoflagellate, Gymnodinium fungiforme Anissimova, ingests prey cytoplasm through a highly extensible structure called the peduncle. Although the peduncle is not observable when G. fungiforme is swimming, it protrudes 8–12 μm from the sulcal‐angular vicinity of the cell during feeding, and is approximately 3.3 μm wide when the cytoplasm of its prey is flowing through it. A circular‐oval ring of overlapping microtubules, the ‘microtubular basket’ may be seen in transmission electron microscope sections of G. fungiforme and it is inferred that this structure is a cross section of a retracted peduncle. The microtubular basket‐peduncle complex is discussed in relation to similar structures in other dinoflagellates and to the tentacle of the suctorian ciliates which have a homologous ingestion system.
CYTOMORPHOLOGICAL ASPECTS OF WOUND HEALING IN SELECTED SIPHONOCLADALES (CHLOROPHYCEAE)1
Authors: La Claire John W.
Published: August 2007

Wound healing in most of the Siphonocladales investigated differs markedly from healing processes known in other coenocytic green algae. No wound plug is evident during healing in Ernodesmis verticillata (Kützing) Børgesen, Boergesenia forbesii (Harvey) Feldmann, Cladophoropsis membranacea (C. Agardh) Børgesen, Siphonocladus tropicus (Crouan) J. Agardh, Struvea elegans Børgesen, Struvea sp. and Valonia spp. The wound response in these genera involves substantial protoplasmic motility which includes retraction of the cell contents from the wound site. The protoplasm then either closes around the central vacuole (e.g. Ernodesmis) or breaks up into numerous spherical protoplasts (e.g. Valonia ventricosa J. Agardh). An intermediate pattern of healing is present in Cladophoropsis where the protoplasm usually separates into a small number of portions that individually heal in a manner similar to Ernodesmis. In all cases, the protoplasts resulting from wounding are viable. Struvea anastomosans (Harvey) Piccone, Chamaedoris sp. and Boodlea sp. are unusual in producing a distinct wound plug during healing, thereby resembling the mode of healing reported in various codialean and dasycladalean genera. It is hypothesized, that wound‐induced protoplasmic motility in the Siphonocladales involves the same cellular mechanisms that segregate protoplasm during cell, division.
CARBONIC ANHYDRASE AND CARBON FIXATION IN COCCOLITHOPHORIDS1
Authors: Sikes C. Steven , Wheeler A. P.
Published: August 2007

Rates of carbon fixation in coccolithophorids in culture, unlike many other algae, are carbon limited at ambient levels of dissolved inorganic carbon (DIC). Apparently, plants often rely on activity of carbonic anhydrase (CA) to raise the level of CO2 in cells and achieve carbon saturation. However, CA activities in the coccolithophorids, Coccolithus (= Emiliania) huxleyi Lohmann and Hymenomonas (=Cricosphaera) carterae Braarud, were either not detectable or very low compared to activities in other systems, including other algae, higher plants, and representative animals. Furthermore, additions of CA to medium with 2 mM DIC at pH 8.1 resulted in nearly 30% enhancement of photosynthesis, but not coccolith formation. Although carbon fixation in coccolithophorids can be suppressed by the CA inhibitor acetazolamide, studies of CaCO3 nucleation revealed a non‐specific effect of the inhibitor. Using a 30 min assay based on pH decreases accompanying loss of dissolved. CO32‐, inhibition of crystal formation in the absence of CA at 1 mM acetazolamide was demonstrated for decalcified crab carapace, a tissue with which normal CaCo3 deposition in vitro has been shown. The results suggest only a minor role for CA in coccolithophorids.
ULTRASTRUCTURE OF THE FLAGELLAR APPARATUS OF PYROBOTRYS (CHLOROPHYCEAE)1
Authors: Hoops Harold J. , Floyd Gary L.
Published: August 2007

The flagellar apparatus of Pyrobotrys has a number of features that are typical of the Chlorophyceae, but others that are unusual for this class. The two flagella are inserted at the apex, but they extend to the side of the cell toward the outside of the colony, here designated as the ventral side. Four basal bodies are present, two of which extend into flagella. Four microtubular rootlets alternate between the functional and accessory basal bodies. In each cell, the two ventral rootlets are nearly parallel, but the dorsal rootlets are more widely divergent. The rootlets alternate between two and four microtubules each. A striated distal fiber connects the two functional basal bodies in the plane of the flagella. Two additional, apparently nonstriated, fibers connect the basal bodies proximal to the distal fiber. Another striated fiber is associated with each four‐membered rootlet near its insertion into the flagellar apparatus. A fine periodic component is associated with each two‐membered rootlet. A rhizoplast‐like structure extends into the cell from each of the functional basal bodies. The arrangement of these components does not reflect the 180° rotational symmetry that is usually present in the Chlorophyceae, but appears to be derived from a more symmetrical ancestor. It is suggested that the form of the flagellar apparatus is associated with the unusual colony structure of Pyrobotrys.
ULTRASTRUCTURE AND TAXONOMIC POSITION OF THE RARE VOLVOCALEAN ALGA, CHLORCORONA BOHEMICA1
Authors: Hoops Harold J. , Floyd Gary L.
Published: August 2007

Chlorcorona bohemica (Fott) Fott was previously of uncertain taxonomic affinities. The cell to cell connections, which are one of the chief features of the colony, are composed of wall extensions from adjacent cells. The outgrowths are connected by a fine fibrous component extending from wall to wall. The structure of the wall itself and the cell to cell connections, are similar to those of Pyrobotrys, although the connections in the latter are not as elongated. In addition, the flagellar apparatus of Chlorocorona is very similar to the flagellar apparatus of Pyrobotrys, and unlike that in other Chlorophyceae examined. These features suggest that Chlorcorona is closely related to Pyrobotrys and should be referred to the family Spondylomoraceae.
IMPROVED PROCEDURES FOR THE CLONING AND PURIFICATION OF MICROCYSTIS CULTURES (CYANOPHYTA)1
Authors: Parker Dorothy L.
Published: August 2007

A cloned axenic culture of Microcystis Kützing was obtained by combining two procedures: a) the disaggregation of multicellular Microcystis colonies by dilution into deionized water, and b) the selective growth of Microcystis in agar media containing Na2S, which inhibited or killed the associated contaminants. Microcystis growth was stimulated by 0.3–1 mM Na2SO3, but not by 0.1–33 mM Na2SO4. Although Microcystis cells survived temporary exposure to high Na2S concentrations, their growth was not stimulated by 1 × 10−5 to 1.0 M Na2S. Possible metabolic roles of reduced sulfur compounds are considered. Microcystis colonies disaggregated to unicells at ionic concentrations below 1 mM for univalent cations, 10–100 μM for the divalent cations, and 3–10 μM for Fe3+. Higher cation concentrations prompted cell aggregation. With > 100 mM Fe3+, the Microcystis capsule appeared rust‐colored. Neither nonionic solutes nor anions detectably influenced aggregation. These observations suggest cation interactions with the Microcystis capsule and are discussed with regard to: a) possible siderochrome activity, cation chelation or luxury uptake of cations, b) the questionability of using cell aggregation as a criterion for identifying Microcystis in samples of unknown ionic strength, c) the utility of low ionic strength media in releasing contaminating bacteria from the capsule and in obtaining algal unicells for cloning, and d) a model for cation interactions with the capsule.
PHOTOSYNTHETIC AND GROWTH RESPONSES TO SALINITY IN A MARINE ISOLATE OF NANNOCHLORIS BACILLARIS (CHLOROPHYCEAE)1
Authors: Brown Lewis M.
Published: August 2007

A marine unicellular alga, Nannochloris bacillaris Naumann, was studied with respect to growth, viability and photosynthesis during the steady‐state and also subsequent to changes in the concentration of artificial seawater medium. Cells grew exponentially over the range of 2% to 300% artificial seawater, but more rapidly at lower salinities. In contrast to growth, photosynthesis as measured by both oxygen evolution and bicarbonate photoassimilation was not obviously inhibited for cells adapted within the range of 7% to 200% artificial seawater. In 300% artificial seawater, photosynthesis, especially bicarbonate photoassimilation, was inhibited. Osmotic shocks caused by transferring cells from 200% to 7% artificial seawater had little if any effect on growth, viability or photosynthesis. However, equal shocks in the upward direction (from 7% to 200% artificial seawater) caused long lag phases in growth, totally inhibited photosynthesis and very often led to cell death. Intermediate upward shocks were less deleterious, but did result in lags in growth.
GROWTH RESPONSES OF THE DIATOM, CYCLOTELLA CRYPTICA (BACILLARIOPHYCEAE), TO GIBBERELLIC ACID1
Authors: Adair Olivia V. , Miller Margaret W.
Published: August 2007

The plant hormone, gibberellic acid (GA), stimulated growth of a marine diatom, Cyclotella cryptica Reimann, Lewin and Guillard. Four concentrations of GA (5 × 20 × 25 × and 35 × 10−6 g/mL) were added to axenic cultures of C. cryptica. Changes in cell densities, measured by cell counts and turbidimetric readings, confirmed that GA at 20 × 10−6 g/mL produced maximum stimulation. There was an increase in the total number of cells produced and a shorter lag phase of growth at this concentration. Coulter counter measurements of cell size, as well as ocular micrometer measurements, indicated there was no significant variation in cell volumes of GA grown cells over that of the controls.
The Effects of Information Overload on Software Project Risk Assessment*
Authors: Pennington Robin , Tuttle Brad
Published: August 2007

Managers are responsible for providing effective information technology governance of the software development process. Ineffective governance leads to serious resource misallocations and negative consequences concerning Sarbanes‐Oxley compliance. In order for managers to make informed decisions about software development projects, they often need more information than is available through normal information channels, that is, they need an in‐depth review of the at‐risk project. Such in‐depth reviews, however, are costly. Hence, accurate identification of at‐risk projects for in‐depth review is critical to management's ability to govern. This research considers how two factors, information load and time pressure, affect the quality of the project‐selection process. We examine quality by observing the decision strategies involved and then relating these strategies to subsequent decision making. An experiment was conducted with experienced information systems auditors using a combination of policy‐capturing and computerized process‐tracing techniques. The participants in our study cope with information overload by accelerating their decision‐making process and adopting noncompensatory decision processes. Contrary to prior research, our process‐tracing analysis suggests that participants rarely filter information, thus implying that decision makers are unable to process all the information. Coping by resorting to noncompensatory strategies did not decrease decision quality unless combined with accelerated information processing. Participants also increase their weight on the software project risk factors that they repeatedly access and that they view for longer periods of time. The theoretical contributions and practical implications regarding what actions managers can take to reduce the negative impact of information overload are discussed.
Semiparametric Approaches for Joint Modeling of Longitudinal and Survival Data with Time‐Varying Coefficients
Authors: Song Xiao , Wang C. Y.
Published: August 2007

SummaryWe study joint modeling of survival and longitudinal data. There are two regression models of interest. The primary model is for survival outcomes, which are assumed to follow a time‐varying coefficient proportional hazards model. The second model is for longitudinal data, which are assumed to follow a random effects model. Based on the trajectory of a subject's longitudinal data, some covariates in the survival model are functions of the unobserved random effects. Estimated random effects are generally different from the unobserved random effects and hence this leads to covariate measurement error. To deal with covariate measurement error, we propose a local corrected score estimator and a local conditional score estimator. Both approaches are semiparametric methods in the sense that there is no distributional assumption needed for the underlying true covariates. The estimators are shown to be consistent and asymptotically normal. However, simulation studies indicate that the conditional score estimator outperforms the corrected score estimator for finite samples, especially in the case of relatively large measurement error. The approaches are demonstrated by an application to data from an HIV clinical trial.
Modeling Individual Effects in the Cormack–Jolly–Seber Model: A State–Space Formulation
Authors: Royle J. Andrew
Published: August 2007

Summary In population and evolutionary biology, there exists considerable interest in individual heterogeneity in parameters of demographic models for open populations. However, flexible and practical solutions to the development of such models have proven to be elusive. In this article, I provide a state‐space formulation of open population capture–recapture models with individual effects. The state‐space formulation provides a generic and flexible framework for modeling and inference in models with individual effects, and it yields a practical means of estimation in these complex problems via contemporary methods of Markov chain Monte Carlo. A straightforward implementation can be achieved in the software package WinBUGS. I provide an analysis of a simple model with constant parameter detection and survival probability parameters. A second example is based on data from a 7‐year study of European dippers, in which a model with year and individual effects is fitted.
A Two‐Part Joint Model for the Analysis of Survival and Longitudinal Binary Data with Excess Zeros
Authors: Rizopoulos Dimitris , Verbeke Geert , Lesaffre Emmanuel , Vanrenterghem Yves
Published: August 2007

Summary Many longitudinal studies generate both the time to some event of interest and repeated measures data. This article is motivated by a study on patients with a renal allograft, in which interest lies in the association between longitudinal proteinuria (a dichotomous variable) measurements and the time to renal graft failure. An interesting feature of the sample at hand is that nearly half of the patients were never tested positive for proteinuria (≥1g/day) during follow‐up, which introduces a degenerate part in the random‐effects density for the longitudinal process. In this article we propose a two‐part shared parameter model framework that effectively takes this feature into account, and we investigate sensitivity to the various dependence structures used to describe the association between the longitudinal measurements of proteinuria and the time to renal graft failure.
Sexual Homicide: A Spatial Analysis of 25 Years of Deaths in Los Angeles
Authors: Van Patten Isaac T. , Delhauer Paul Q.
Published: August 2007

Abstract:Although it has been frequently studied over the last 100 years, empirical studies of sexual homicide are lacking. The majority of the existing studies have been descriptive in nature. In this study, we consider the spatial geometry of sexual homicide and the impact of time and distance on case solvability. An analysis of sexual homicides (n = 197) from 1980 to 2004 for Los Angeles County was conducted. Offender and victim journey to encounter site, journey to body disposal site, and journey‐after‐crime trips were examined. Descriptive and bivariate analyses were performed to examine victim, offender and case characteristics. Using logistic regression models both time factors and offense geometries were found to be significant predictors in case solvability. Simpler geometries are significantly more likely to be solved than cases with complex geometries and the longer a case remains unsolved the less likely it is that it will be closed. The results provide support for some of the findings from earlier descriptive studies and extend our understanding of the spatial geometry of sexual homicide.
Examination of Writings Concealed by Black Pressure Sensitive Adhesive Tape
Authors: Mahajan Meenakshi , Arya S.P.
Published: August 2007

Abstract: Examination of concealed writing is often a challenge for forensic document examiners. Although the published literature describes many techniques, these are often only successful when the writing has been concealed by pencil, pen, or by spreading inks of different tint or by smearing of the writing with colored fluids. When black pressure sensitive adhesive (PSA) tape is used, these procedures are ineffective. The present report describes the use of a straight chain hydrocarbon to remove the PSA tape and allow a comparison of the concealed writing with that of a suspect. The use of the solvent had no observable effect on either the writing or the substrate. The procedure is rapid and easy to use and is also effective with other colored PSA tapes.
Endogenous endophthalmitis: microorganisms, disposition and prognosis
Authors: Ness Thomas , Pelz Klaus , Hansen Lutz Lothar
Published: August 2007

Purpose:  Endogenous endophthalmitis is a severe and potentially blinding complication caused by haematogenous spreading of microorganisms. We evaluated the causative microorganisms, disposition to and prognosis of the disease.

Methods:  Thirty‐one eyes of 28 patients were treated between 1996 and 2006 as the result of an endogenous endophthalmitis.

Results:  The microorganisms responsible for infection could be identified in 94% of all eyes investigated. Candida isolates were obtained in 15, gram‐positive isolates in 11, gram‐negative in one and Aspergillus in two of the 29 eyes studied. The majority of patients suffered from severe general disease (immuno‐deficiency, severe surgical procedures, diabetes mellitus) and one third were intravenous drug abusers. Only one patient was otherwise healthy. The prognosis depended on the causative microorganisms. Whereas none of the eyes with Candida infection became blind, all except two of the eyes with gram‐positive bacteria, Nocardia or Aspergillus infection lost visual function or had to be enucleated.

Conclusion:  Compared to postoperative endophthalmitis, patients with endogenous endophthalmitis are more likely to have Candida isolates. Visual prognosis depends mainly on the underlying microorganisms, and is particularly poor in the case of infection with gram‐positive bacteria or Aspergillus.
Increased cyclooxygenase expression and thymine dimer formation after repeated exposures of humans to low doses of solar simulated radiation
Authors: Narbutt Joanna , Lesiak Aleksandra , Jochymski Cezary , Kozlowski Wojciech , Sysa‐Jedrzejowska Anna , Norval Mary
Published: August 2007

Abstract:  The impact of repeated doses of solar simulated radiation (SSR) has not been evaluated, particularly to determine if photoadaptation and photoprotection develop over time. In this study, erythema, pigmentation, cyclooxygenase (COX)‐1 and 2 expression and thymine dimer (dTT) formation were evaluated in the skin of irradiated subjects of phototype II or III. Groups of 7–10 volunteers were whole‐body irradiated with a low dose of SSR on each of 10 consecutive days followed by a single erythemal ultraviolet B (UVB) dose on a small body area, or irradiated only with the single erythemal UVB dose on a small body area, or irradiated with the low dose of SSR on each of 30 consecutive days, or were unirradiated. Erythema and pigmentation were measured 24 h after the final SSR or UVB, and skin biopsies collected for the assessment of COX+ cells and dTT+ nuclei. The repeated SSR exposures induced a small increase in pigmentation without erythema, and were slightly protective against the erythemal effects of the subsequent high UVB dose. The number of COX‐1+ and 2+ cells increased as a result of 10‐days SSR and rose still further after 30‐days SSR, indicating that photoadaptation had not developed. The SSR exposures did not result in any protection against the further increase in COX‐1 and 2 expression caused by the erythemal UVB dose. In contrast, for dTT formation, the repeated SSR exposures led to a limited degree of both photoadaptation and photoprotection.
Differential regulation of action potential firing in adult murine thalamocortical neurons by Kv3.2, Kv1, and SK potassium and N‐type calcium channels
Authors: Kasten Michael R. , Rudy Bernardo , Anderson Matthew P.
Published: August 2007

Sensory signals of widely differing dynamic range and intensity are transformed into a common firing rate code by thalamocortical neurons. While a great deal is known about the ionic currents, far less is known about the specific channel subtypes regulating thalamic firing rates. We hypothesized that different K+ and Ca2+ channel subtypes control different stimulus–response curve properties. To define the channels, we measured firing rate while pharmacologically or genetically modulating specific channel subtypes. Inhibiting Kv3.2 K+ channels strongly suppressed maximum firing rate by impairing membrane potential repolarization, while playing no role in the firing response to threshold stimuli. By contrast, inhibiting Kv1 channels with α‐dendrotoxin or maurotoxin strongly increased firing rates to threshold stimuli by reducing the membrane potential where action potentials fire (Vth). Inhibiting SK Ca2+‐activated K+ channels with apamin robustly increased gain (slope of the stimulus–response curve) and maximum firing rate, with minimum effects on threshold responses. Inhibiting N‐type Ca2+ channels with ω‐conotoxin GVIA or ω‐conotoxin MVIIC partially mimicked apamin, while inhibiting L‐type and P/Q‐type Ca2+ channels had small or no effects. EPSC‐like current injections closely mimicked the results from tonic currents. Our results show that Kv3.2, Kv1, SK potassium and N‐type calcium channels strongly regulate thalamic relay neuron sensory transmission and that each channel subtype controls a different stimulus–response curve property. Differential regulation of threshold, gain and maximum firing rate may help vary the stimulus–response properties across and within thalamic nuclei, normalize responses to diverse sensory inputs, and underlie sensory perception disorders.
Restriction of placental growth in sheep impairs insulin secretion but not sensitivity before birth
Authors: Owens Julie A. , Gatford Kathryn L. , De Blasio Miles J. , Edwards Lisa J. , McMillen I. Caroline , Fowden Abigail L.
Published: August 2007

Restricted growth before birth is associated with impaired insulin secretion but with initially enhanced insulin sensitivity in early postnatal life, which then progresses to insulin resistance and impaired glucose homeostasis by adulthood. This suggests that prenatal restraint impairs insulin secretion, but increases insulin sensitivity, before birth. Poor placental growth and function are major causes of restricted fetal growth in humans. We have therefore investigated the effects of restricted placental growth and function on plasma glucose, α‐amino nitrogen and insulin concentrations and glucose‐ and arginine‐stimulated insulin secretion in the fetal sheep at 120 and 140 days gestational age, and on insulin sensitivity, measured by hyperinsulinaemic euglycaemic clamp, at 130 days gestational age. Placental restriction decreased fetal blood pH and oxygen content, and weight in late gestation by ∼20%. Reduced fetal and placental weights and indices of poor placental function, in particular fetal hypoxia and hypoglycaemia, were associated with impaired glucose‐ and arginine‐stimulated insulin secretion, but not with changes in insulin sensitivity in the fetal sheep. We conclude that the impaired insulin secretion capacity reported in children and adults after intrauterine growth restriction, and in the neonatal and young adult sheep which is small at birth, is present in utero and persists. Whether this reflects the actions of the adverse intrauterine environment or changes to intrinsic capacity is unclear, but in utero interventions may be necessary to improve postnatal insulin secretion in the infant who is growth‐restricted before birth.
Localization of a Stable Neural Correlate of Associative Memory
Authors: Reijmers Leon G. , Perkins Brian L. , Matsuo Naoki , Mayford Mark
Published: August 2007

Do learning and retrieval of a memory activate the same neurons? Does the number of reactivated neurons correlate with memory strength? We developed a transgenic mouse that enables the long-lasting genetic tagging of c-
fos
–active neurons. We found neurons in the basolateral amygdala that are activated during Pavlovian fear conditioning and are reactivated during memory retrieval. The number of reactivated neurons correlated positively with the behavioral expression of the fear memory, indicating a stable neural correlate of associative memory. The ability to manipulate these neurons genetically should allow a more precise dissection of the molecular mechanisms of memory encoding within a distributed neuronal network.
Strand-Biased Spreading of Mutations During Somatic Hypermutation
Authors: Unniraman Shyam , Schatz David G.
Published: August 2007

Somatic hypermutation (SHM) is a major means by which diversity is achieved in antibody genes, and it is initiated by the deamination of cytosines to uracils in DNA by activation-induced deaminase (AID). However, the process that leads from these initiating deamination events to mutations at other residues remains poorly understood. We demonstrate that a single cytosine on the top (nontemplate) strand is sufficient to recruit AID and lead to mutations of upstream and downstream A/T residues. In contrast, the targeting of cytosines on the bottom strand by AID does not lead to substantial mutation of neighboring residues. This strand asymmetry is eliminated in mice deficient in mismatch repair, indicating that the error-prone mismatch repair machinery preferentially targets top-strand uracils in a way that promotes SHM during the antibody response.
Epoxide-Opening Cascades Promoted by Water
Authors: Vilotijevic Ivan , Jamison Timothy F.
Published: August 2007

Selectivity rules in organic chemistry have been inferred largely from nonaqueous environments. In contrast, enzymes operate in water, and the chemical effect of the medium change remains only partially understood. Structural characterization of the “ladder” polyether marine natural products raised a puzzle that persisted for 20 years: Although the stereochemistry of adjacent tetrahydropyran (THP) cycles would seem to arise from a biosynthetic cascade of epoxide-opening reactions, experience in organic solvents argued consistently that such a pathway would be kinetically disfavored. We report that neutral water acts as an optimal promoter for the requisite ring-opening selectivity, once a single templating THP is appended to a chain of epoxides. This strategy offers a high-yielding route to the naturally occurring ladder core and highlights the likely importance of aqueous-medium effects in underpinning certain noteworthy enzymatic selectivities.