bluuebunny/crossref_metadata_2025 huggingface dataset:
Cessation ofTrichinella spiralisTransmission Among Scavenging Mammals After the Removal of Infected Pigs From a Poorly Managed Farm: Implications for Trichinae Transmission in the US
Authors: Hill D. E. , Pierce V. , Darwin Murrell K. , Ratliffe N. , Rupp B. , Fournet V. M. , Zarlenga D. S. , Rosenthal B. M. , Ray Gamble H. , Kelly K. , Dulin M.
Published: December 2009

Pigs infected with the zoonotic parasiteTrichinella spiraliswere detected on a farm in Maryland during an animal welfare investigation. Sera and/or tissues were collected from 49 pigs and three pig carcasses (7 weeks of age to adult, mixed sex). The tissues were tested for the presence ofT. spiralismuscle larvae (ML) by tissue digestion, and the sera were tested for the presence of anti‐Trichinellaantibodies by ELISA. Seventeen of 50 (34%) pigs were infected withT. spiralisbased on tissue digestion. Of these 17 pigs, sera were collected from 16; nine were serologically positive, three sera had OD values that were very close to the positive cut‐off (0.30), but were still negative, and four were negative (suggesting that they had become infected within a few weeks of testing). All pigs that tested negative by tissue digestion for ML were also ELISA negative. The farm was subsequently depopulated of pigs. Six months later, testing of trapped scavenging mammals in the farm environment demonstrated that 41% were infected withT. spiralis. After 12 months, 10% of trapped animals wereT. spiralispositive, and after 18 months,T. spiraliscould not be detected in the scavenging mammal population surrounding the farm. Results of the study suggest thatT. spiralis, typically transmitted in the peridomestic rat–pig–human cycle in the US, was not maintained in scavenging mammals in the absence of infected pigs.
A Retrospective Survey of Human Hydatidosis Based on Hospital Records During The Period 1990–2003 in Ngorongoro, Tanzania
Authors: Ernest E. , Nonga H. E. , Kynsieri N. , Cleaveland S.
Published: December 2009

A 13‐year (1990–2003) retrospective study was carried out to investigate the occurrence of cystic echinococcosis (CE) in patients at Wasso hospital in Ngorongoro district, Tanzania. Hospitalization records were reviewed and confirmed cases of CE were classified according to ward of residence, age, sex, cyst location and type. A total of 171 hydatidosis patients were diagnosed and operated giving an average of 13 cases per year, equivalent to approximately 10 cases per 100 000 people per year. Cystic echinococcosis affected more females (59.1%) than males (40.9%). A significantly higher number of CE cases were recorded in individuals <30 years of age (22.8–30.4%) than in those >30 years of age (2.3–9.4%) (P < 0.05). High proportion of CE (81.5%) occurred in the liver than in other sites, and more females had higher hepatic cysts (47.4%) than males (31.0%). Solitary cysts and single organ involvement were noted in 81.5% cases and multiple cysts in 18.5% cases. Higher multiple organ infections (14.1%) and cyst recurrences (5.3%) were also recorded in females. Orgosorok ward had the highest number (18.7%) of CE cases, while Nainokanoka had the lowest (1.2%). It was concluded that CE infection occurs frequently in humans in Ngorongoro district and female and youths are those most affected. These findings merit for more extensive epidemiological investigations of CE in human to better determine the prevalence, economic impact and risk factors for the disease in this district and other areas of Tanzania.
Electrical and mechanical properties of carbon nanotube-polyimide composites
Authors: Thuau D. , Koutsos V. , Cheung R.
Published: December 2009

The use of carbon nanotubes (CNTs) as a conductive and high strength filler into polymer hosts has attracted great attention recently. However, in order to increase the conductivity of the polymer and to reinforce mechanically the polymer structure at low weight fraction of CNTs, the integration of the CNTs into the polymer matrix has to be effective. In this study, CNT-polyimide (CNT-Pi) composite has been fabricated by solution mixing. The electrical and mechanical properties of the composite have been investigated as a function of CNT’s loading fraction as well as temperature. It has been found that the electrical and mechanical properties of the CNT-Pi can be improved by integrating the CNTs into the polymer. In particular, the presence of an ac electric field is believed to induce dielectrophoresis (DEP), hence the possible CNT’s alignment inside the polyimide matrix during curing. The DEP effect can play an important role in enhancing the properties of the polymer matrix by reducing the percolation threshold. An ac electric field of 800kV∕cm at a frequency of 1kHz has been found to be the optimal conditions for integrating the CNTs into the polymer.
Perturbed frequency-selective surfaces fabricated on large thin polymer membranes for multiband infrared applications
Authors: Sanz-Fernández Juan-José , Goussetis George , Cheung Rebecca
Published: December 2009

The design, fabrication, and characterization of single-screen perturbed frequency-selective surfaces (FSS) at infrared frequencies for single and multiband applications are reported. Single-band FSS based on parallel strips have been perturbed by decreasing the length of every second strip within the array in order to achieve dual band-stop responses. The same principle has been extended to design FSS exhibiting tri- and quadreflection bands. In addition, strip FSSs have been perturbed by replacing every second strip for a metallic ring, resulting in dual-band filters with different polarization responses of the bands. These designs have been fabricated on large thin polyimide membranes using sacrificial silicon wafers. An oxide interlayer between the sacrificial silicon wafer and the polyimide membrane is employed to stop the silicon etching and is wet etched subsequently by a solution of ammonium fluoride and acetic acid that does not attack either the polyimide membrane or the aluminium FSS elements. Fourier transform infrared spectroscopy measurements are presented to validate the predicted responses of the fabricated prototypes.
Nanostructuring of epitaxial graphene layers on SiC by means of field-induced atomic force microscopy modification
Authors: Rius G. , Camara N. , Godignon P. , Pérez-Murano F. , Mestres N.
Published: December 2009

Micrometer-size graphene ribbons are generated by epitaxial growth on SiC substrates and contacted by electron beam lithography. The isolated graphene islands are patterned at nanometer scale by atomic force microscopy (AFM) under the application of an external polarization to the graphene layers. Contrary to previous reports, the patterning can be made at positive and negative polarizations and using significantly lower absolute voltages. The technique is used to tune the electrical resistance of the graphene ribbons. Combination of graphitization of SiC and AFM nanopatterning is, in consequence, a powerful approach for the fabrication of prototyped graphene-based nanoelectronic devices.
Advanced silicon processing for active planar photonic devices
Authors: Shearn Michael , Diest Kenneth , Sun Xiankai , Zadok Avi , Atwater Harry , Yariv Amnon , Scherer Axel
Published: December 2009

Using high quality, anisotropically etched Si waveguides bonded to InGaAsP, the authors demonstrate a hybrid laser, whose optical profile overlaps both Si and III-V regions. Continuous wave laser operation was obtained up to 45°C, with single facet power as high as 12.7mW at 15°C. Planar Si optical resonators with Q=4.8×106 are also demonstrated. By using a SF6∕C4F8 reactive ion etch, followed by H2SO4∕HF surface treatment and oxygen plasma oxide, the optical losses due to the waveguide and the bonding interface are minimized. Changes of optical confinement in the silicon are observed due to waveguide width variation.
Iterative phase recovery using wavelet domain constraints
Authors: Baghaei Leili , Rad Ali , Dai Bing , Pianetta Piero , Pease R. Fabian W. , Miao Jianwei
Published: December 2009

Phase retrieval is a central problem in coherent x-ray diffraction microscopy. Various methods have been proposed to solve the problem with the most successful being iterative methods with a finite spatial support constraint. In this work, a new constraint is formulated in the wavelet domain using low-resolution a priori information. Experimental results indicate that the constraint is sufficient to reconstruct an object from Fourier modulus measurements.
Mask observation results using a coherent extreme ultraviolet scattering microscope at NewSUBARU
Authors: Harada Tetsuo , Kishimoto Junki , Watanabe Takeo , Kinoshita Hiroo , Lee Dong Gun
Published: December 2009

A coherent scattering microscope for extreme ultraviolet (EUV) light has been developed for the actinic inspection of EUV lithography masks. It was installed at the NewSUBARU synchrotron facility. It provides aberration-free, diffraction-limited imaging and a high numerical aperture. Coherent EUV light scattered (diffracted) from a mask is recorded using an EUV charged coupled device camera with a numerical aperture of 0.15. An image of the sample is reconstructed using a hybrid input-output algorithm, which retrieves the phase from the intensity data. Masks containing periodic line-and-space and hole patterns with a half-pitch ranging from 100to400nm were fabricated in the laboratory and imaged. The reconstructed images correlate well with images obtained with a scanning electron microscope (SEM). The actinic critical dimension of the linewidth of TaN absorber patterns on a mask was measured and was consistently found to be 25nm larger than that obtained from the SEM data.
Effects of visible light illumination on the conductance of Al∕AlOx single-electron transistors
Authors: George Hubert C. , Orlov Alexei O. , Joyce Robin A. , Tang Yong , Snider Gregory L.
Published: December 2009

This report presents a study of the effects of light illumination, from near infrared to blue, on the characteristics of Al∕AlOx single-electron transistors (SETs) at low temperatures (0.3–4.2K). Several effects on the SET conductance are observed when the devices are subjected to light illumination, including changes in the Coulomb blockade oscillation period and amplitude. To determine the origin of the observed effects, SETs with different device geometries were fabricated on semiconducting and insulating substrates. The results show that illumination of semiconducting (Si) substrates leads to the excitation of mobile carriers at the insulator-semiconductor interface that strongly influence the SETs, while the use of wide bandgap insulating substrates (quartz) enables SET operation that is immune to visible light illumination from incident powers of 3μW∕mm2 (flux of about 10photons∕nm2s for whole visible light spectrum).
Diameter-dependent guided resonance of dielectric hole-array membrane
Authors: Ou Neil , Shyu J. H. , Lee H. M. , Wu J. C.
Published: December 2009

Silicon nitride photonic crystal slabs having various submicron lattice constants and hole diameters have been investigated, in which optical transmission measurements were utilized in the characterization of the guided resonance. Samples were fabricated by using standard electron beam lithography in combination with KOH wet etching and reactive ion etching dry etching through a silicon substrate and silicon nitride membrane, respectively. The transmittance data reveal the asymmetrical shape of absorption dips associated with Fano resonance, and the positions of the resonance were found to be in accordance with the lattice constant. In addition, multiabsorption dips were evolved from the main absorption dip and became discernable when increasing the hole diameter. The plane wave expansion method was used to identify the mode splitting in the band structure that is caused by a finite size hole diameter, giving rise to the multiabsorption dips. Furthermore, the finite element method was used to calculate the transmission spectra. The simulated representations were in positive agreement with the experimental results.
Development of an Allele-Specific PCR for Detection of the K65R Resistance Mutation in Patients Infected with Subtype C Human Immunodeficiency Virus Type 1
Authors: Toni Thomas A. , Brenner Bluma G. , Asahchop Eugene L. , Ntemgwa Michel , Moisi Daniella , Wainberg Mark A.
Published: December 2009

The selection of drug-resistant variants of human immunodeficiency virus type 1 (HIV-1) is an impediment to the efficiency of antiretroviral (ARV) therapy. We have developed an allele-specific real-time PCR assay to explore the presence of K65R minority species among treated HIV-1 subtype B and C infections. Thirty HIV-1 subtype C- and 26 subtype B-infected patients lacking K65R as determined by conventional sequencing methods were studied, and viral minority species were found in four HIV-1 subtype C samples.
Antiviral Efficacy of the Novel Compound BIT225 against HIV-1 Release from Human Macrophages
Authors: Khoury Gabriela , Ewart Gary , Luscombe Carolyn , Miller Michelle , Wilkinson John
Published: December 2009

Building on previous findings that amiloride analogues inhibit HIV-1 replication in monocyte-derived macrophages (MDM), Biotron Limited has generated a library of over 300 small-molecule compounds with significant improvements in anti-HIV-1 activity. Our lead compound, BIT225, blocks Vpu ion channel activity and also shows anti-HIV-1 activity, with a 50% effective concentration of 2.25 ± 0.23 μM (mean ± the standard error) and minimal
in vitro
toxicity (50% toxic concentration, 284 μM) in infected MDM, resulting in a selectivity index of 126. In this study, we define the antiretroviral efficacy of BIT225 activity in macrophages, which are important drug targets because cells of the monocyte lineage are key reservoirs of HIV-1, disseminating virus to the peripheral tissues as they differentiate into macrophages. In assays with acutely and chronically HIV-1
Ba-L
-infected MDM, BIT225 resulted in significant reductions in viral integration and virus release as measured by real-time PCR and a reverse transcriptase (RT) activity assay at various stages of monocyte-to-macrophage differentiation. Further, the TZM-bl assay showed that the
de novo
virus produced at low levels in the presence of BIT225 was less infectious than virus produced in the absence of the compound. No antiviral activity was observed in MDM chronically infected with HIV-2, which lacks Vpu, confirming our initial targeting of and screening against this viral protein. The activity of BIT225 is post-virus integration, with no direct effects on the HIV-1 enzymes RT and protease. The findings of this study suggest that BIT225 is a late-phase inhibitor of the viral life cycle, targeting Vpu, and is a drug capable of significantly inhibiting HIV-1 release from both acute and chronically infected macrophages.
Treponema denticolaSuppresses Expression of Human β-Defensin-3 in Gingival Epithelial Cells through Inhibition of the Toll-Like Receptor 2 Axis
Authors: Shin Ji Eun , Kim Young Sook , Oh Ju-Eun , Min Byung-Moo , Choi Youngnim
Published: December 2009

We reported previously thatTreponema denticola, one of the periodontal pathogens, suppresses the expression of human β-defensins (HBDs) in human gingival epithelial cells. To identify the mechanisms involved in this suppression, immortalized and normal human gingival epithelial cells were infected with live or heat-killedT. denticolafor 24 h, and then the expression of HBDs was examined by real-time RT-PCR. LiveT. denticolasuppressed the expression of HBD-3 substantially and also suppressed the expression of HBD-1 and HBD-2. However, heat-killed bacteria did not produce a suppressive effect but instead slightly upregulated the levels of HBD-2 and HBD-3. In contrast to liveT. denticola, which reduced the activation of mitogen-activated protein kinase (MAPK) and NF-κB within an hour of infection, heat-killed bacteria did not show any inhibitory effect on the MAPK and NF-κB signaling pathways. Knockdown of Toll-like receptor 2 (TLR2) via RNA interference abolished the suppressive effect ofT. denticolaon the expression of HBD-3. Heat-killedT. denticolabut not live bacteria could activate TLR2 in CHO/CD14/TLR2 reporter cells, suggesting thatT. denticolacontains a heat-labile inhibitor(s) of TLR2 in addition to ligands recognized by TLR2. Indeed, liveT. denticolawas able to inhibit TLR2 activation by Pam3CSK. In conclusion,T. denticolasuppressed the expression of HBD-3 by inhibiting the TLR2 axis in gingival epithelial cells. These results may provide new insight into the pathogenesis of periodontitis caused byT. denticola.
Genetic Control of the Innate Immune Response toBorrelia hermsiiInfluences the Course of Relapsing Fever in Inbred Strains of Mice
Authors: Benoit Vivian M. , Petrich Annett , Alugupalli Kishore R. , Marty-Roix Robin , Moter Annette , Leong John M. , Boyartchuk Victor L.
Published: December 2009

Host susceptibility to infection is controlled in large measure by the genetic makeup of the host. Spirochetes of the genusBorreliainclude nearly 40 species of vector-borne spirochetes that are capable of infecting a wide range of mammalian hosts, causing Lyme disease and relapsing fever. Relapsing fever is associated with high-level bacteremia, as well as hematologic manifestations, such as thrombocytopenia (i.e., low platelet numbers) and anemia. To facilitate studies of genetic control of susceptibility toBorrelia hermsiiinfection, we performed a systematic analysis of the course of infection using immunocompetent and immunocompromised inbred strains of mice. Our analysis revealed that sensitivity toB. hermsiiinfections is genetically controlled. In addition, whereas the role of adaptive immunity to relapsing fever-causing spirochetes is well documented, we found that innate immunity contributes significantly to the reduction of bacterial burden. Similar to human infection, the progression of the disease in mice was associated with thrombocytopenia and anemia. Histological and fluorescencein situhybridization (FISH) analysis of infected tissues indicated that red blood cells (RBCs) were removed by tissue-resident macrophages, a process that could lead to anemia. Spirochetes in the spleen and liver were often visualized associated with RBCs, lending support to the hypothesis that direct interaction ofB. hermsiispirochetes with RBCs leads to clearance of bacteria from the bloodstream by tissue phagocytes.
Proliferated, bisporangiate, and other atypical cones occurring on young, plantation-grown Larix laricina
Authors: Tosh Kathleen J. , Powell G. R.
Published: December 2009

Atypical cones were found in 1983 and 1984 on many trees in three young plantations of Larix laricina (Du Roi) K. Koch. On-shoot and within-crown locations of cones of each type were noted as the cones were collected, at the stage of anthesis or receptivity, for analysis by dissection or sectioning. Development of other cones of each type was monitored. Proliferated seed cones had more bracts than typical seed cones and were commonly located where more vigorous vegetative development (neoformation) was likely. Most bisporangiate cones had proximal microsporophylls and distal bracts; a few also had microsporophylls at their apices. The bisporangiate cones were subdivided according to proportions of different appendages. Those with more female appendages tended to occur on short-shoot axes more distally located along the parent long shoot and thus where more vigorous development was likely. Bisporangiate cones with mainly female appendages developed to seed-cone maturity. Those with mainly male appendages died soon after anthesis. Pollen cones usually have no basal foliage leaves, but some pollen cones with such leaves occurred. The leaves died with the cone tissues after anthesis. Occurrence, composition, and development of these atypical cones were discussed in relation to their position, shoot vigour, and preformation.
Effect of Glomus intraradices on infection by Fusarium oxysporum f.sp. radicis-lycopersici in tomatoes over a 12-week period
Authors: Caron M. , Fortin J. A. , Richard C.
Published: December 2009

The interaction between Glomus intraradices Schenck & Smith, a vesicular–arbuscular mycorrhizal fungus, and Fusarium oxysporum Schlecht f.sp. radicis-lycopersici Jarvis & Shoemaker and its effect on tomato plants were investigated over a 12-week period. The root colonization by Glomus was not affected by the presence of Fusarium. The number of Fusarium propagules was consistently lower when the plants were inoculated with Glomus. The presence of Glomus decreased root necrosis caused by Fusarium in weeks 5, 11, and 12, but no significant effect was observed for the other 9 weeks. The results obtained at any observation time for the endomycorrhizal colonization and the Fusarium population, but not for the percent of root necrosis evaluation, were consistent throughout the 12-week experiment. It is concluded that the parameters used to study the interaction between a vesicular–arbuscular mycorrhizal fungus, a fungal root pathogen, and a host plant must be measured at different times after inoculation with the pathogen to make sure that observations are representative of the interaction under study.
Sirotrema: a new genus in the Tremellaceae
Authors: Bandoni R. J.
Published: December 2009

Sirotrema, a new genus in the Tremellaceae, is described for S. translucens (Gordon) Bandoni, comb, nov., S. parvula, Bandoni, sp. nov., and S. pusilla Bandoni, sp. nov. The species, parasitizing hypodermataceous fungi, share basidiocarp characteristics with taxa in Sirobasidium and Tremella. Their haploid states are yeasts.
A discussion of microstructural changes in wood during decomposition by white rot basidiomycetes
Authors: Otjen Lewis , Blanchette Robert A.
Published: December 2009

The classical concepts of wood decay are reviewed. All white rot fungi do not cause the same type of cell wall decomposition. At least two micromorphologically distinct types of cell wall attack have been found. Many factors can affect the type of macroscopic and microscopic decay patterns caused by white rot basidiomycetes. Host cell type and nutrients, as well as genetic and physiologic differences among these fungi, may influence the resulting decay.
Abondance relative et diversité des Endogonacées dans un sol de verger du Québec
Authors: Dalpé Y. , Granger R. L. , Furlan V.
Published: December 2009

Studies of soil samples from an apple orchard in Frelighsburg revealed the presence of seven species of Endogonaceae, six of which generated vesicular and arbuscular mycorrhizae on Tagetes erecta L. While Glomus constrictum Trappe, Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe, and Sclerocystis rubiformis Gerd. & Trappe made up more than 90% of the organisms observed, Gigaspora calospora (Nicol. & Gerd.) Gerd. & Trappe, Glomus aggregatum Schenck & Smith, and Glomus etunicatum were seen in approximately half of the samples. An enumeration of the Endogonaceae observed is followed herein by a discussion dealing with the frequency and the relative abundance of these species in the soil and with the practical interest which arises from this type of survey.
Effect of vesicular–arbuscular mycorrhizal fungi and phosphorus on the survival and growth of flowering dogwood (Cornus florida)
Authors: Sylvia David M.
Published: December 2009

Mycorrhizal development and growth of flowering dogwood (Cornus florida L.) seedlings were investigated in a field nursery and glasshouse. Seedlings and associated soil were collected from April to November from a fumigated nursery bed that contained areas of both stunted and rapidly growing plants. The rate of mycorrhizal colonization and associated spore formation were greater on the rapidly growing seedlings. In a glasshouse test, dogwood seedlings were inoculated with chlamydospores of Glomus etunicatum, G. intraradices, or a control solution which contained microorganisms associated with the mycorrhizal fungi, and were fertilized weekly with Hoagland's solutions which had 0, 47, or 93 mg P∙L−1. After 12 weeks, seedlings inoculated with G. etunicatum had greater survival, shoot dry mass, and root fresh mass than seedlings inoculated with G. intraradices or the control. However, G. etunicatum did not affect the concentration or total uptake of P into shoots. This fungus can apparently enhance the survival and growth of dogwood seedlings without improving P nutrition.
The ecology of Ramalina menziesii. III. In situ diurnal field measurements at two sites on a coast–inland gradient
Authors: Matthes-Sears U. , Nash III T. H. , Larson D. W.
Published: December 2009

Diurnal courses of gross CO2 uptake and thallus water content of the lichen Ramalina menziesii Tayl. were measured together with the environmental variables temperature, irradiance, and atmospheric humidity at a coastal and an inland site in central California. Twenty-three days, distributed over all seasons and a variety of weather conditions, were recorded at the inland site; 14 were recorded at the coastal site. Conditions in both habitats were similar in that the most frequent reason for photosynthetic inactivity in R. menziesii was insufficient thallus hydration. Irradiance was another factor controlling photosynthetic rates; temperature, on the other hand, had little influence. At the inland site, CO2 fixation was concentrated in the rainy winter season and very little CO2 fixation took place during the hot summers. In contrast, fog and high atmospheric humidity that frequently occur during summers at the coast provided sufficient moisture for frequent photosynthetic activity, thus resulting in intermittent activity throughout the year. While extremely high gross photosynthetic rates of up to 15 mg CO2 g−1 thallus dry weight were measured at the inland site, rates at the coast were always much lower.
Differential distribution of specific indole alkaloids in leaves of Catharanthus roseus
Authors: Mersey Brent G. , Cutler Adrian J.
Published: December 2009

In leaves of the periwinkle plant (Catharanthus roseus (L.) G. Don) idioblasts are randomly distributed in the mesophyll. They are distinguishable from ordinary palisade and spongy parenchyma cells as large, refractile, and autofluorescent cells. Density gradient centrifugation of protoplasts derived from leaves resulted in fractions enriched in idioblast protoplasts. Analysis of indole alkaloid composition by high pressure liquid chromatography has shown that idioblasts are enriched in vindoline and catharanthine relative to other mesophyll cells. The significance of these observations for attempts to produce specific indole alkaloids in cell cultures is discussed.
Les teneurs ioniques des plants d'Isoetes setacea au cours de la réactivation par réhydratation
Authors: Michaux-Ferrière N.
Published: December 2009

Ionic amounts of S, P, K+, Ca2+, and Mg2+ have been determined by chemical measures in different parts of Isoetes setacea (shoot apical meristem, cortical zone, and central stele) for plants in normal growth, in drought resistance, and during rehydration. Study of modifications in the ionic amounts during experimental rehydration showed that the significant increase of K+, Ca2+, and Mg2+ by the 24th h of experimentation was one of the earliest signals observed for the cells of the apical meristem (which are at that time blocked in G1 presynthesis phase) as well as for the differentiated cells. By the 7th day of rehydration, just before their entrance into the synthesis phase, meristematic cells have recovered ionic rates equivalent to those measured for active plants. The same thing happens in the nonmeristematic tissues. This increase of ionic amounts in the whole plant can be explained by a differential entrance of ions with water. This new balance of the ionic amounts according to the pattern found in the active plants can be considered as a prerequisite event for the recovery of an active metabolism for a meristematic or differentiated cell in water stress.
Degradation of Spartina lignocellulose by individual and mixed cultures of salt-marsh fungi
Authors: Torzilli A. P. , Andrykovitch G.
Published: December 2009

Spartina alterniflora tissue, either in the absence or presence of a nitrogen supplement, was inoculated with a single-species or a mixed-species inoculum of salt-marsh fungi. After 42 days of incubation at 25 °C, lignocellulose decomposition was determined by measuring the amount of residual total lignocellulose, cellulose, hemicellulose, and lignin. A two-way analysis of variance of these results indicated an interaction between fungal treatments and nitrogen treatments. Pairwise comparisons of mean residual weights showed that all individual and mixed fungal inocula resulted in significant degradation of the total lingo-cellulosic, cellulosic, and hemicellulosic fractions of Spartina tissue with levels of decomposition ranging from approximately 16 to 40%, depending on the fungal – nitrogen treatment and the cell wall fraction examined. Lignin degradation was not detected for any of the treatments. Cultures with a mixture of fungi showed less decomposition than was observed for the most efficient decomposer when it occurred alone.
Interactions among plant hormones, carbon dioxide, and light in the relief of thermoinhibition of lettuce seed germination: studies in a flow-through gaseous system
Authors: Saini H. S. , Bassi P. K. , Consolacion E. D. , Spencer M. S.
Published: December 2009

The effects of gibberellin A3 (GA3), kinetin, C2H4, CO2, and (or) red light (5-min single exposure) on the germination of lettuce (Lactuca sativa L. cv. Grand Rapids) seeds at 32 °C were studied in a continuous-flow system. This system permitted strict control of the gaseous environment, which has not been possible in previous experimental set-ups. Except for a minor effect of light (10% enhancement), none of the treatments applied singly had any effect on the germination of these thermo-inhibited seeds. The action of any one hormone (GA3, kinetin, C2H4) required the presence of at least one more hormone or CO2 or light. Complete alleviation of thermoinhibition required a minimum of three factors in the following combinations: GA3 with two of kinetin, C2H4, or CO2, and kinetin either with GA3 + light or C2H4 + light. Given in combination with light, kinetin, GA3 + C2H4, GA3 + CO2, or C2H4 + CO2 induced above 75% germination. Approximately half maximal germination was obtained with GA3 + kinetin, GA3 + CO2, and C2H4 + light. Other treatment combinations showed either no or only a weak interaction. Results showed that the action of hormones, particularly that of GA3, was markedly influenced by CO2. Carbon dioxide was also able to substitute for a number of other treatments that interacted with GA3. In addition, the effects of several interactive treatments were further accentuated by CO2.
Relationships in Taeniatherum (Poaceae)
Authors: Frederiksen Signe , Bothmer Roland Von
Published: December 2009

Hybridization and cytogenetic studies of Taeniatherum caput-medusae (L.) Nevski were carried out on three diploid subspecies (2n = 14) including ssp. caput-medusae, ssp. crinitum (Schreb.) Melderis, and ssp. asperum (Simk.) Melderis. Most combinations showed high sterility. A high degree of bivalent pairing was observed in meiosis, indicating that all taxa have the same basic genome and that the differences between them are genetic rather than segregational. The occurrence of local population adaptation is assumed.
Desiccation tolerance in mosses. I. Development of a method for measuring cell damage
Authors: Streusand V. J. , Ikuma H.
Published: December 2009

Preliminary studies indicated that samples of moss varied widely in cell damage both before and after desiccation and rehydration. In the present study, various parameters associated with cell damage in mosses were investigated. Determination of the percent cell damage in a particular sample of moss requires that (i) a large number of cells be counted throughout a given leaf and (ii) a large number of leaves and shoots be utilized. The use of large sample size is necessitated by large variance within leaves and among leaves and shoots of the same clump. In the present study a standardized method was developed which involves counting at least 10 cells in six areas of each leaf, six leaves on each shoot, and 10 shoots per treatment. Although the variance within samples is still high, this method was found to be effective for indexing desiccation damage, providing a near perfect correlation with shoot survival (r = 0.98).
Growth and physiological responses of aspen and jack pine to intermittent SO2 fumigation episodes
Authors: L'Hirondelle S. J. , Addison P. A. , Huebert D. B.
Published: December 2009

Five-week-old aspen seedlings and 8-week-old jack pine seedlings were exposed to a 3-h SO2 fumigation episode (peak = 0.78 μL L−1; mean = 0.30 μL L−1) 0, 2, or 5 times per week. Intermittent fumigation of both species for up to 8 weeks had no consistent, significant effect on aboveground biomass or on net assimilation rate and leaf resistance. A significant decrease (as much as 47%) in biomass of fumigated jack pine seedlings was found after 6 weeks of SO2 exposure, but after 7 weeks the decrease was not significant. In contrast, a significant increase in biomass of fumigated aspen seedlings was found, but only at 6 weeks, and apparently related to increased leaf retention. Fumigation caused transient decreases in net assimilation rate of both species. The maximum decrease in net assimilation rate measured just after an SO2 episode was 13% for aspen and 35% for jack pine, with a mean decrease for both of 12%. During SO2 fumigation, aspen net assimilation rate decreased as much as 38% and leaf resistance increased up to 47%. Both aspen and pine seedlings recovered from these transient SO2 effects, and there was no evidence for increased sensitivity to fumigation with time. After exposure to a single SO2 episode in the laboratory, field-collected branches of mature aspen showed a 30% decrease in net assimilation rate and a 50% increase in leaf resistance, from initial values similar to those of the greenhouse seedlings.
Light and electron microscopy of the interaction between the sunflower rust fungus (Puccinia helianthi) and leaves of the nonhost plant, French bean (Phaseolus vulgaris)
Authors: Wood Lesley A. , Heath Michèle C.
Published: December 2009

Growth of the sunflower rust fungus (Puccinia helianthi Schw.) was compared by light microscopy in sunflower leaves, in untreated French bean leaves, in bean leaves given a preinoculation heat treatment, and on collodion membranes. Results suggested that fungal growth was slightly reduced and the formation of haustorial mother cells was inhibited in untreated bean leaves. Haustorial mother cells, when present, did not form haustoria and adjacent mesophyll cell walls usually were highly refractive. Preinoculation heat treatment reduced the incidence of refractive cell walls and increased that of haustorial mother cells and haustoria. Ultrastructurally, infection hyphae in unheated bean leaves appeared unusually vacuolate and often contained wall appositions where they touched the plant cells. Silicalike deposits were present in and on mesophyll cell walls at most infection sites. In heated plants, necrotic haustoria with small bodies were seen at the few sites that lacked silicalike deposits. At other sites, the fungus appeared to have stopped growing during the formation of the penetration peg or the haustorial neck, and such necks were encrusted with silicalike material. At most sites, penetration pegs were occluded resulting in the unusual situation in which the haustorial mother cell remained seemingly alive in spite of the necrosis of the haustorium.
Nitrogen fixation in relation to Hudsonia tomentosa: a pioneer species in sand dunes, northeastern Alberta
Authors: Nelson S. D. , Buss L. C. , Mayo J. M.
Published: December 2009

Blue-green algae, including species of Oscillatoria, Lyngbya, Microcystis, and Nostocaceae were isolated from green sand associated with Hudsonia tomentosa. Green sands were consistently found in the buried phyllosphere and rhizosphere of Hudsonia and on the surface to varying depths under Hudsonia plants. Organisms in these sands fixed nitrogen at maximum rates of 1 nmol C2H4∙g soil−1∙h−1. Seasonal variation in rates was largely explained by optima of 30% soil water content and 28 to 33 °C soil temperature. Green sands were not associated with any other vascular plant at the study sites. The results suggest a preference of free-living blue-green algae for Hudsonia which may relate to the ability of this dwarf shrub to colonize nutrient-poor sand sites, such as blowouts and sand dunes in the Pinus banksiana – lichen woodlands of northeastern Alberta.
Anatomy and vasculature of the floral nectaries of Brassica napus (Brassicaceae)
Authors: Davis A. R. , Peterson R. L. , Shuel R. W.
Published: December 2009

The floral nectaries of Brassica napus L. (Argentine or Swede rape) consist of two pairs of glands which are supplied by phloem only. The lateral pair has an extensive phloem supply and produces most of the flowers' nectar, whereas the median pair is supplied by limited phloem and produces relatively little nectar. Because both lateral and median nectaries contain cells exhibiting similar structural features, the disparity in phloem supply between them could account for the observed difference in nectar production. Ultrastructural evidence suggests an energy-requiring, eccrine mechanism of nectar secretion in Brassica napus. Both apoplastic and symplastic routes for nectar movement and escape appear feasible. Stomata on the nectary surfaces may serve as exits.
Cytochemical studies on Puccinia graminis f. sp. tritici in a compatible wheat host. II. Haustorium mother cell walls at the host cell penetration site, haustorial walls, and the extrahaustorial matrix
Authors: Chong J. , Harder D. E. , Rohringer R.
Published: December 2009

Various cytochemical tests on the wheat stem rust fungus were used to determine differences in components of the walls of the haustorium mother cell at the host cell penetration site and the haustorial neck and body and to describe some of the chemical properties of the extrahaustorial matrix. There were two transition zones with respect to wall composition. The first was at the host cell penetration site; chitin, present in haustorium mother cell walls, was not detected in haustorial neck walls. The second transition zone was at the neck ring; compared with walls of the proximal neck region, those distal to the neck ring contained more protein and lost much of their periodate – thiocarbohydrazide – silver proteinate reactive material and all concanavalin A binding material after treatment with protease. The two wall layers of the distal part of the haustorial neck were continuous with those of the haustorium; the wall layers of young haustorial bodies shared their staining properties and lectin affinities with those of the distal part of the haustorial necks, reflecting their common origin. As the haustoria matured, their body walls bound wheat germ lectin, but the neck walls did not. Tests indicated that polysaccharide and glycoprotein were present in the extrahaustorial matrix.
Pollen tube growth in tristylous Pontederia cordata (Pontederiaceae)
Authors: Anderson J. M. , Barrett S. C. H.
Published: December 2009

Pollen tube growth rates in legitimate cross- and self-pollinations were compared by controlled hand pollination in two varieties of Pontederia cordata L. (Pontederiaceae). In each pollen–stigma combination pollen germinated readily on stigmas and pollen tubes penetrated stigmatic tissue. Pollen tube length in styles was positively correlated with pollen size. In most pollinations legitimate pollen tubes grew more rapidly in styles than self pollen tubes. This difference was statistically significant in most comparisons. Inhibition of incompatible pollen tubes was either in the style or ovary. It is suggested that the mechanisms of incompatibility may differ among the floral morphs and depend on the particular pollen size involved in pollinations. The observed differences in pollen tube growth of legitimate cross- and self-pollinations in P. cordata suggest that the species is primarily outbreeding.
Anatomy of first-order roots in the Cyclanthaceae (Monocotyledoneae). I. Epidermis, cortex, and pericycle
Authors: Wilder George J.
Published: December 2009

Epidermal cells are persistent or nonpersistent. In most species the common walls between epidermal and exodermal cells are relatively thick and hydrophobic. Sclerenchyma tissue is generally present in the endodermis, but exodermal sclerenchyma occurs in relatively few species. Between the endodermis and exodermis cortical sclerenchyma may comprise a circumcortical ring, intervening sclerenchyma tissue, or a circumstelar ring. The cortex also contains parenchyma cells and sometimes extracellular mucilage canals, tubular cells, and crystal sacs (crystal idioblasts) other than tubular cells. Periderm is sometimes present. Intermediates between various cell types may occur, creating problems in cell classification.
Vegetation colonizing the bed of a recently drained thermokarst lake (Illisarvik), Northwest Territories
Authors: Ovenden Lynn
Published: December 2009

Illisarvik is the site of a thermokarst lake that was artificially drained in August 1978. The lake bed is now dry in most areas and wind erosion is extensive. The surface material is either sandy peat or organic lake mud, except along the eastern margin, where it is sandy. Substrate type appears to have had little influence on distributional patterns of the colonizing vegetation. More important factors are probably erosion, surface wetness, and proximity of the lake-bed margin. Common on the lake bed are Puccinellia borealis and Arctagrostis latifolia. Other widespread species include Senecio congestus, Carex aquatilis, Descurainia sophioides, Matricaria ambigua, Artemisia tilesii, Arctophila fulva, and Stellaria longipes. Senecio and Arctophila form dense stands around the two small residual ponds. Eroded surfaces have a very scant cover of Descurainia seedlings and Puccinellia tussocks. Many elements of Illisarvik's flora are common to other recently disturbed sites near the Arctic coast of northwestern North America.
Factors affecting 13C/12C ratios of inland halophytes. II. Ecophysiological interpretations of patterns in the field
Authors: Guy Robert D. , Reid David M. , Krouse H. Roy
Published: December 2009

By measuring δ13C values, 9 of 42 species inhabiting saline sites in Alberta were found to be C4 plants. None of these, however, are dominant species in wet saline situations. A salinity gradient was studied along a transect to provide improved field data on δ13C variations among C3 halophytes. Soils were dominated by sulphates of sodium and, less so, magnesium. Soil water potential [Formula: see text] was highest at a depth of about 10 cm and, on a daily basis, changed little. The δ13C values of Puccinellia nuttalliana (Schultes) Hitch, were well correlated with [Formula: see text]. The same appeared true for Salicornia europaea L. ssp. rubra (Nels.) Brietung. In a scattergram representing five major species, a close correlation was also evident for Hordeum jubatum L. The relationship could not be extended to Triglochin maritima L. and Sonchus arvensis L., but values for these two species were not separable from those of P. nuttalliana and H. jubatum. Salicornia europaea ssp. rubra, however, differed by having δ13C values that were markedly more negative. Although partly associated with cover by other species, this tendency may reflect a lower water-use efficiency as afforded by a greater reliance on the uptake of readily available salt for osmotic adjustment.
Effects of density and soil nitrogen levels on growth of Galinsoga quadriradiata and G. parviflora in pure and mixed stands
Authors: Rai J. P. N. , Tripathi R. S.
Published: December 2009

The responses of two sympatric annual weeds, Galinsoga quadriradiata Ruiz & Pavon (G. ciliata (Raf.) Blake) and G. parviflora Cav., which occur abundantly in croplands and early secondary successional communities of hill regions in northeast India, were studied in relation to population density, soil nitrogen, and nature of the stand (pure versus mixed stands). Both weeds exhibited density-dependent mortality which increased at a higher nitrogen level. In the case of G. quadriradiata more individuals survived in a mixture than in monoculture, whereas G. parviflora showed the reverse trend. Growth of both weeds was better at a higher soil nitrogen level. Increased mortality and suppression of growth caused by an increase in density was also minimized in G. quadriradiata at the higher level of soil nitrogen. With an increase in population density, per-plant biomass and capitula production in both weeds showed an increase in positive skewness which, however, decreased at an increased nitrogen level. Galinsoga quadriradiata was less sensitive to density than G. parviflora regardless of soil nitrogen. At lower densities, both weeds grew better in a mixture than in pure stands, but at higher densities G. quadriradiata suppressed the growth of G. parviflora. Although the crude reproductive effort of the two weeds was independent of soil nitrogen, G. quadriradiata, in contrast to G. parviflora, exhibited a greater crude reproductive effort when grown either at higher densities or in a mixture.
Biotrophic associations between lodgepole pine seedlings and postfire ascomycetes (Pezizales) in monoxenic culture
Authors: Egger Keith N. , Paden J. W.
Published: December 2009

Twenty-two species of postfire ascomycetes belonging to the order Pezizales were screened for biotrophic interactions with roots of lodgepole pine (Pinus contorta Dougl.). Biotrophic associations ranged from pathogenicity to mycorrhizal symbiosis, but most species tested did not show any affinity for roots. Pyropyxis rubra (Peck) Egger and Rhizina undulata Fr. were aggressive pathogens that infected the vascular cylinder and killed the seedlings. Tricharina praecox (Karst.) Dennis var. intermedia Egger, Yang & Korf also had some ability to infect the vascular cylinder, but usually did not kill the seedlings. Geopyxis carbonaria (A. & S.) Sacc. and Trichophaea hemisphaerioides (Mont.) Graddon invaded the cortex, forming complex intracellular structures, but did not penetrate the vascular cylinder. They may form mutualistic associations under certain conditions. The only confirmed mutualistic species was Sphaerosporella brunnea (A. & S.) Svrcek & Kubicka, which formed ectendomycorrhizae. Anthracobia maurilabra (Cooke) Boud. and A. tristis (Bomm., Rouss. & Sacc.) Boud. appear to be primarily root-surface inhabitants with limited capacity to infect cortical tissues through breaks in the epidermis. Gyromitra infula (Schaef.) Quél. penetrated the epidermis but was unable to overcome host defences against pathogenic infection.
Topodeme differentiation in Ontario taxa of Crataegus (Rosaceae: Maloideae): leaf morphometric evidence
Authors: Dickinson T. A.
Published: December 2009

Variation in the two-dimensional shape of short-shoot subterminal leaves was examined quantitatively in samples of nine topodemes of Crataegus section Crus-galli Loud. (representing C. crus-galli L. s.str., C. fontanesiana (Spach) Steud., C. ?disperma Ashe, and C. ?grandis Ashe) plus three of section Punctatae Loud. (C. punctata Jacq.). Shape was described by 23 linear measurements comprising a network of box trusses. These measurements were summarized by means of sheared principal components analysis, so as to obtain two axes maximizing different size-independent contrasts in shape among the 12 samples. Topodemes of section Crus-galli were more differentiated from one another and, on the whole, less variable than those of C. punctata. These results resemble those obtained earlier with these taxa, with flower and fruit data. A probable explanation for these results is the contrasting reproductive behavior found in C. section Crus-galli (agamospermy, self-compatibility) and C. punctata (apomixis absent, self-incompatible). Such an explanation also illuminates the possible origin of much of the taxonomic complexity of the genus Crataegus in North America.