bluuebunny/crossref_metadata_2025 huggingface dataset:
Vibrations and Stability of an Axially Moving Rectangular Composite Plate
Authors: Yang Xiao-Dong , Chen Li-Qun , Zu Jean W.
Published: June 2010

The vibrations and stability are investigated for an axially moving rectangular antisymmetric cross-ply composite plate supported on simple supports. The partial differential equations governing the in-plane and out-of-plane displacements are derived by the balance of linear momentum. The natural frequencies for the in-plane and out-of-plane vibrations are calculated by both the Galerkin method and differential quadrature method. It can be found that natural frequencies of the in-plane vibrations are much higher than those in the out-of-plane case, which makes considering out-of-plane vibrations only is reasonable. The instability caused by divergence and flutter is discussed by studying the complex natural frequencies for constant axial moving velocity. For the axially accelerating composite plate, the principal parametric and combination resonances are investigated by the method of multiple scales. The instability regions are discussed in the excitation frequency and excitation amplitude plane. Finally, the axial velocity at which the instability region reaches minimum is detected.
Nodal Signaling Recruits the Histone Demethylase Jmjd3 to Counteract Polycomb-Mediated Repression at Target Genes
Authors: Dahle Øyvind , Kumar Amit , Kuehn Michael R.
Published: June 2010

Developmental signaling integrates with epigenetic processes to control the expression of Nodal target genes.
Preventing Spasms After Spinal Cord Injury
Authors: Gough Nancy R.
Published: June 2010

Following spinal cord injury, motoneurons switch to a constitutively active serotonin receptor, which contributes to muscle spasticity.
Herpes Virus MiRNA Modulation
Authors: Riddihough Guy
Published: June 2010

A viral noncoding RNA regulates the level of a complementary host cell’s microRNA.
Infrared Snake Eyes: TRPA1 and the Thermal Sensitivity of the Snake Pit Organ
Authors: Panzano Vincent C. , Kang Kyeongjin , Garrity Paul A.
Published: June 2010

Many vertebrates and invertebrates rely on the ion channel TRPA1 to detect both warmth and chemicals.
NagZ Inactivation Prevents and Reverts β-Lactam Resistance, Driven by AmpD and PBP 4 Mutations, in
Pseudomonas aeruginosa
Authors: Zamorano Laura , Reeve Thomas M. , Deng Lehua , Juan Carlos , Moyá Bartolomé , Cabot Gabriel , Vocadlo David J. , Mark Brian L. , Oliver Antonio
Published: June 2010

AmpC hyperproduction is the most frequent mechanism of resistance to penicillins and cephalosporins in
Pseudomonas aeruginosa
and is driven by
ampD
mutations or the recently described inactivation of
dacB
, which encodes the nonessential penicillin-binding protein (PBP) PBP 4. Recent work showed that
nagZ
inactivation attenuates β-lactam resistance in
ampD
mutants. Here we explored whether the same could be true for the
dacB
mutants with
dacB
mutations alone or in combination with
ampD
mutations. The inactivation of
nagZ
restored the wild-type β-lactam MICs and
ampC
expression of PAO1
dacB
and
ampD
mutants and dramatically reduced the MICs (for example, the MIC for ceftazidime dropped from 96 to 4 μg/ml) and the level of
ampC
expression (from ca. 1,000-fold to ca. 50-fold higher than that for PAO1) in the
dacB
-
ampD
double mutant. On the other hand,
nagZ
inactivation had little effect on the inducibility of AmpC. The NagZ inhibitor
O
-(2-acetamido-2-deoxy-
d
-glucopyranosylidene)amino-
N
-phenylcarbamate attenuated the β-lactam resistance of the AmpC-hyperproducing strains, showing a greater effect on the
dacB
mutant (reducing the ceftazidime MICs from 24 to 6 μg/ml) than the
ampD
mutant (reducing the MICs from 8 to 4 μg/ml). Additionally,
nagZ
inactivation in the
dacB
mutant blocked the overexpression of
creD
(
blrD
), which is a marker of the activation of the CreBC (BlrAB) regulator involved in the resistance phenotype. Finally, through population analysis, we show that the inactivation of
nagZ
dramatically reduces the capacity of
P. aeruginosa
to develop ceftazidime resistance, since spontaneous mutants were not obtained at concentrations ≥8 μg/ml (the susceptibility breakpoint) for the
nagZ
mutant but were obtained with wild-type PAO1. Therefore, NagZ is envisaged to be a candidate target for preventing and reverting β-lactam resistance in
P. aeruginosa
.
Mycobacterium tuberculosis
Dihydrofolate Reductase Is Not a Target Relevant to the Antitubercular Activity of Isoniazid
Authors: Wang Feng , Jain Paras , Gulten Gulcin , Liu Zhen , Feng Yicheng , Ganesula Krishna , Motiwala Alifiya S. , Ioerger Thomas R. , Alland David , Vilchèze Catherine , Jacobs William R. , Sacchettini James C.
Published: June 2010

Mycobacterium tuberculosis
enoyl-acyl-ACP reductase (InhA) has been demonstrated to be the primary target of isoniazid (INH). Recently, it was postulated that
M. tuberculosis
dihydrofolate reductase (DHFR) is also a target of INH, based on the findings that a 4R-INH-NADP adduct synthesized from INH by a nonenzymatic approach showed strong inhibition of DHFR
in vitro
, and overexpression of
M. tuberculosis dfrA
in
M. smegmatis
conferred a 2-fold increase of resistance to INH. In the present study, a plasmid expressing
M. tuberculosis dfrA
was transformed into
M. smegmatis
and
M. tuberculosis
strains, respectively. The transformant strains were tested for their resistance to INH. Compared to the wild-type strains, overexpression of
dfrA
in
M. smegmatis
and
M. tuberculosis
did not confer any resistance to INH based on the MIC values. Similar negative results were obtained with 14 other overexpressed proteins that have been proposed to bind some form of INH-NAD(P) adduct. An
Escherichia coli
cell-based system was designed that allowed coexpression of both
M. tuberculosis katG
and
dfrA
genes in the presence of INH. The DHFR protein isolated from the experimental sample was not found bound with any INH-NADP adduct by enzyme inhibition assay and mass spectroscopic analysis. We also used whole-genome sequencing to determine whether polymorphisms in
dfrA
could be detected in six INH-resistant clinical isolates known to lack mutations in
inhA
and
katG
, but no such mutations were found. The
dfrA
overexpression experiments, together with the biochemical and sequencing studies, conclusively demonstrate that DHFR is not a target relevant to the antitubercular activity of INH.
Defining the Role of Mutations inPlasmodium vivaxDihydrofolate Reductase-Thymidylate Synthase Gene Using an EpisomalPlasmodium falciparumTransfection System
Authors: Auliff Alyson M. , Adams John H. , O'Neil Michael T. , Cheng Qin
Published: June 2010

Plasmodium vivaxresistance to antifolates is prevalent throughout Australasia and is caused by point mutations within the parasite dihydrofolate reductase (DHFR)-thymidylate synthase. Several unique mutations have been reported inP. vivaxDHFR, and their roles in resistance to classic and novel antifolates are not entirely clear due, in part, to the inability to cultureP. vivax in vitro. In this study, we use a homologous system to episomally express both wild-type and various mutantP. vivax dhfr(pvdhfr) alleles in an antifolate-sensitive line ofP. falciparumand to assess their influences on the susceptibility of the recipientP. falciparumline to commonly used and new antifolate drugs. Although the wild-typepvdhfr-transfectedP. falciparumline was as susceptible to antifolate drugs as theP. falciparumparent line, the single (117N), double (57L/117T and 58R/117T), and quadruple (57L/58R/61M/117T) mutantpvdhfralleles conferred a marked reduction in their susceptibilities to antifolates. The resistance index increased with the number of mutations in these alleles, indicating that these mutations contribute to antifolate resistance directly. In contrast, the triple mutant allele (58R/61M/117T) significantly reversed the resistance to all antifolates, indicating that 61M may be a compensatory mutation. These findings help elucidate the mechanism of antifolate resistance and the effect of existing mutations in the parasite population on the current and new generation of antifolate drugs. It also demonstrates that the episomal transfection system has the potential to provide a rapid screening system for drug development and for studying drug resistance mechanisms inP. vivax.
In Vitro
Effect of Sulfamethoxazole-Trimethoprim against
Histoplasma capsulatum
var.
capsulatum
Authors: Nogueira Brilhante Raimunda Sâmia , Bezerra Fechine Maria Auxiliadora , de Aguiar Cordeiro Rossana , Gadelha Rocha Marcos Fábio , Ribeiro Joyce Fonteles , Jalles Monteiro André , de Lima Rita Amanda Chaves , Lima Mesquita Jacó Ricarte , de Camargo Zoilo Pires , Costa Sidrim José Júlio
Published: June 2010

This study evaluated the
in vitro
effect of sulfamethoxazole-trimethoprim against
Histoplasma capsulatum
var.
capsulatum
isolated from HIV-positive patients. The drugs were tested by microdilution testing in accordance with the CLSI guidelines. All of the strains were inhibited by sulfamethoxazole-trimethoprim, with MIC ranges of 0.039 (sulfamethoxazole)/0.0078 (trimethoprim) mg/ml to 0.625/0.125 mg/ml for mycelial forms and 0.0025/0.0005 to 0.02/0.004 mg/ml for yeast-like forms. However,
in vivo
studies are necessary to evaluate the significance of these results.
Hydroxymethylnitrofurazone Is Active in a Murine Model of Chagas' Disease
Authors: Davies Carolina , Cardozo Rubén Marino , Negrette Olga Sánchez , Mora María Celia , Chung Man Chin , Basombrío Miguel Ángel
Published: June 2010

The addition of a hydroxymethyl group to the antimicrobial drug nitrofurazone generated hydroxymethylnitrofurazone (NFOH), which had reduced toxicity when its activity against
Trypanosoma cruzi
was tested in a murine model of Chagas' disease. Four groups of 12 Swiss female mice each received 150 mg of body weight/kg/day of NFOH, 150 mg/kg/day of nitrofurazone (parental compound), 60 mg/kg/day of benznidazole (BZL), or the solvent as a placebo. Treatments were administered orally once a day 6 days a week until the completion of 60 doses. NFOH was as effective as BZL in keeping direct parasitemia at undetectable levels, and PCR results were negative. No histopathological lesions were seen 180 days after completion of the treatments, a time when the levels of anti-
T. cruzi
antibodies were very low in mice treated with either NFOH or BZL. Nitrofurazone was highly toxic, which led to an overall rate of mortality of 75% and necessitated interruption of the treatment. In contrast, the group treated with its hydroxymethyl derivative, NFOH, displayed the lowest mortality (16%), followed by the BZL (33%) and placebo (66%) groups. The findings of histopathological studies were consistent with these results, with the placebo group showing the most severe parasite infiltrates in skeletal muscle and heart tissue and the NFOH group showing the lowest. The present evidence suggests that NFOH is a promising anti-
T. cruzi
agent.
Neutralization of Malaria GlycosylphosphatidylinositolIn Vitroby Serum IgG from Malaria-Exposed Individuals
Authors: de Souza J. Brian , Runglall Manohursingh , Corran Patrick H. , Okell Lucy C. , Kumar Sanjeev , Gowda D. Channe , Couper Kevin N. , Riley Eleanor M.
Published: June 2010

Parasite-derived glycosylphosphatidylinositol (GPI) is believed to be a major inducer of the pathways leading to pathology and morbidity duringPlasmodium falciparuminfection and has been termed a malaria “toxin.” The generation of neutralizing anti-GPI (“antitoxic”) antibodies has therefore been hypothesized to be an important step in the acquisition of antidisease immunity to malaria; however, to date the GPI-neutralizing capacity of antibodies induced during naturalPlasmodium falciparuminfection has not been evaluated. Here we describe the development of anin vitromacrophage-based assay to assess the neutralizing capacity of malarial GPI-specific IgG. We demonstrate that IgG fromPlasmodium falciparum-exposed individuals can significantly inhibit the GPI-induced activation of macrophagesin vitro, as shown by reduced levels of tumor necrosis factor production and attenuation of CD40 expression. The GPI-neutralizing capacity of individual IgG samples was directly correlated with the anti-GPI antibody titer. IgG from malaria-exposed individuals also neutralized the macrophage-activating effects ofP. falciparumschizont extract (PfSE), but there was only a poor correlation between PfSE-neutralizing activity and the anti-GPI antibody titer, suggesting that PfSE contains other macrophage-activating moieties, in addition to GPI. In conclusion, we have established anin vitroassay to test the toxin-neutralizing activities of antimalarial antibodies and have shown that anti-GPI antibodies from malaria-immune individuals are able to neutralize GPI-induced macrophage activation; however, the clinical relevance of anti-GPI antibodies remains to be proven, given that malarial schizonts contain other proinflammatory moieties, in addition to GPI.
Natural Selection in the Chicken Host Identifies 3-Deoxy-
d
-
manno
- Octulosonic Acid Kinase Residues Essential for Phosphorylation of
Pasteurella multocida
Lipopolysaccharide
Authors: Harper Marina , Cox Andrew D. , St. Michael Frank , Ford Mark , Wilkie Ian W. , Adler Ben , Boyce John D.
Published: June 2010

Pasteurella multocida
is the causative agent of a number of diseases in animals, including fowl cholera.
P. multocida
strains simultaneously express two lipopolysaccharide (LPS) glycoforms (glycoforms A and B) that differ only in their inner core structure. Glycoform A contains a single 3-deoxy-
d
-
manno
-octulosonic acid (Kdo) residue that is phosphorylated by the Kdo kinase, KdkA, whereas glycoform B contains two unphosphorylated Kdo residues. We have previously shown that
P. multocida
mutants lacking the heptosyltransferase, HptA, produce full-length glycoform B LPS and a large amount of truncated glycoform A LPS, as they cannot add heptose to the glycoform A inner core. These
hptA
mutants were attenuated in chickens because the truncated LPS made them vulnerable to host defense mechanisms, including antimicrobial peptides. However, here we show that birds inoculated with high doses of the
hptA
mutant developed fowl cholera and the
P. multocida
isolates recovered from diseased birds no longer expressed truncated LPS. Sequencing analysis revealed that the
in vivo
-derived isolates had mutations in
kdkA
, thereby suppressing the production of glycoform A LPS. Interestingly, a number of the spontaneous KdkA mutant strains produced KdkA with a single amino acid substitution (A112V, R123P, H168Y, or D193N). LPS structural analysis showed that complementation of a
P. multocida kdkA
mutant with wild-type
kdkA
restored expression of glycoform A to wild-type levels, whereas complementation with any of the mutated
kdkA
genes did not. We conclude that in
P. multocida
KdkA, the amino acids A112, R123, H168, and D193 are critical for Kdo kinase function and therefore for glycoform A LPS assembly.
Protocol for a mixed-methods study on leader-based interventions in construction contractors' safety commitments
Authors: Pedersen Betina Holbæk , Dyreborg Johnny , Kines Pete , Mikkelsen Kim Lyngby , Hannerz Harald , Andersen Dorte Raaby , Spangenberg Søren
Published: June 2010

Background

Owing to high injury rates, safety interventions are needed in the construction industry. Evidence-based interventions tailored to this industry are, however, scarce. Leader-based safety interventions have proven more effective than worker-based interventions in other industries.

Objective

To test a leader-based safety intervention for construction sites. The intervention consists of encouraging safety coordinators to provide feedback on work safety to the client and line management. The intention is to increase communication and interactions regarding safety within the line management and between the client and the senior management. It is hypothesised that this, in turn, will lead to increased communication and interaction about safety between management and coworkers as well as an increased on-site safety level.

Setting

A group-randomised double-blinded case study of six Danish construction sites (three intervention sites and three control sites). The recruitment of the construction sites is performed continuously from January 2010 to June 2010. The investigation of each site lasts 20 continuous weeks.

Methods

Confirmatory statistical analysis is used to test if the safety level increased, and if the probability of safety communications between management and coworkers increases as a consequence of the intervention. The data collection will be blinded. Qualitative methods are used to evaluate if communication and interactions about safety at all managerial levels, including the client, increase.

Outcome measures

(1) The proportion of safety-related communications out of all studied communications between management and coworkers. (2) The safety level index of the construction sites.
Effectiveness of pads and enclosures as safety interventions on consumer trampolines
Authors: Alexander Keith , Eager David , Scarrott Carl , Sushinsky George
Published: June 2010

Background

Trampolines continue to be a major source of childhood injury.

Objective

To examine available data on trampoline injuries in order to determine the effectiveness of padding and enclosures.

Design

Trampoline injuries from the NEISS database from 2002 to 2007 were reclassified into five cause-categories, to examine evidence for injury trends.

Setting

The ASTM trampoline standard recommendations for safety padding were upgraded in 1999 and enclosures were introduced in 1997. This is the first study to examine the impact of these changes.

Patients

The sampling frame comprises patients with NEISS product code ‘consumer trampolines’ (1233). A systematic sample of 360 patients each year is taken.

Interventions

The prominent interventions recommended by the ASTM are netting enclosures to prevent falling off and safety padding to cover frames and springs.

Main outcome measures

Proportion of injuries within each cause-category and trend estimates.

Results

There was no evidence for a decline within the injury cause-categories that should be prevented by these interventions from 2002 to 2007.

Conclusions

If these interventions were effective the associated injury causes would be in decline. Instead they remain close to half of all trampoline injuries with no significant change over the period of the study. Follow-up studies are proposed to determine the reasons. Given the number of injuries involved it is recommended that steps be taken to ensure these safety interventions or their equivalents are in place, work properly and remain effective for the life of consumer trampolines.
Ultrastructural localization in host tissues of a toxic glycopeptide produced by Ophiostoma ulmi, using monoclonal antibodies
Authors: Benhamou Nicole , Lafontaine J. G. , Joly J. R. , Ouellette G. B.
Published: June 2010

Monoclonal antibodies against a phytotoxic glycopeptide from Ophiostoma ulmi (Buism.) Nannf., the Dutch elm disease pathogen, were used in a postembedding protein A – gold labeling technique to localize this toxin in experimentally infected tissues of young elm seedlings. Significant labeling was observed over pit membranes, over the innermost wall layer (protective layer) of paratracheal parenchyma cells, and over the intercellular spaces and, adjacently, the middle lamella. Host secondary walls, cytoplasm, and various organelles, except regions of amyloplastids, were free of labeling. From day 1 to day 4 after inoculation an intensification of the labeling reaction was noted that corresponded to an increase in the disease symptoms. This specific and sensitive technique has thus proved to be highly suitable for the in situ identification of antigenic macromolecules in diseased elm tissues. The classification of the toxic glycopeptide among the group of vivotoxins is discussed.
Sphagnum production in forested bogs of northern Minnesota
Authors: Grigal D. F.
Published: June 2010

Annual production of Sphagnum on three perched and three raised forested bogs was determined and compared. Perched bogs occupy small depressions in glacial moraines and raised bogs occur on broad, flat plains. Data from both cranked rods and threads were used with regression techniques to determine rates of growth on hummocks and hollows of bog microrelief. Hummocks and hollows were operationally defined by the characteristic moss species that dominated each position. Over a 3-year sampling period, average rate of moss growth in perched bogs was 3.9 (± 4%) on hummocks and 13.1 cm year−1 (± 13%) in hollows. In raised bogs, the growth was 3.6 (± 4%) and 9.1 cm year−1 (± 14%), respectively. About half the lineal growth occurred early in the growing season, and slightly more of the remaining growth occurred in midseason compared with late season. Conversion to ovendry mass per unit surface area of bog indicates production of 320 on hummocks and 520 in hollows on perched bogs; 300 on hummocks and 370 g m−2 year−1 in hollows on raised bogs. Because of the hummock–hollow microrelief, total surface area occupied by moss is about 35% greater than the vertically projected area of the bog. Final estimates of Sphagnum production per unit vertically projected bog area, taking this information into account, were 380 (± 19%) on perched bogs and 320 g m−1 year−1 (± 19%) on raised bogs.
Régression holocène du couvert coniférien à la limite des forêts (Québec nordique)
Authors: Gagnon Réjean , Payette Serge
Published: June 2010

The occurrence of tamarack (Larix laricina (Du Roi) K. Koch) and black spruce (Picea mariana (Mill.) B.S.P.) macrofossils or subfossils on the tundroid patches at the forest limit indicates that those patches were colonized by trees in the past. The aim of this study is to reconstruct the fluctuations of the coniferous formations by macrofossil analysis. More than 465 macrofossils and 30 charcoals were collected, 31 and 23 of which, respectively, were 14C dated. The results of charcoal analysis indicated that fires were more frequent in the southern part of the forest limits than in the northern part. During the last millenium three periods of fire (modern, 400, and 900 years) were noted in the southern part, two periods (modern and 600 years) at the forest limit, and none north of the forest limit. The majority of collected macrofossils are from the modern period; their death is related to the action of fire. The mosaic landscape of the forest tundra is related to a deterioration of the climatic conditions coupled with the history of fires.
Stem vascular anatomy and leaf area in seedlings of six black walnut (Juglans nigra) families
Authors: Parker William C. , Pallardy Stephen G.
Published: June 2010

The vascular anatomy and the balance between leaf area and biomass and vascular water supply capacity of 2-year-old, half-sib black walnut (Juglans nigra L.) seedlings representing six families were investigated. Vessel radius, vessel density, stem transverse area occupied by vessel lumina, and volume flow rate of stems predicted by the Poiseuille flow equation differed among families. Variation among families in predicted flow was related to differences in vessel radius, vessel density, and transverse xylem area. Variation in the capacity of the vascular system to supply water to leaves was suggested by differences in leaf area:conductive area and leaf area:stem flow ratios. For all seedlings, leaf area and dry weight were positively correlated with vessel radius, stem conductive area, total xylem area, and predicted flow rate and were negatively correlated with vessel density. Vessel radius and density were inversely related, with increased conductive area resulting from smaller numbers of larger vessels per unit stem area. These data suggest that in black walnut, stem conductive capacity is more effectively increased through development of greater amounts of xylem and larger vessels than by increased density of comparatively narrow vessels. This pattern suggests that the risk of cavitation may not have been a significant selective force in genetic differentiation in the families studied.
Light-influenced extracellular accumulation of b (pathogenesis-related) proteins in Nicotiana green tissue induced by various chemicals or prolonged floating on water
Authors: Asselin Alain , Grenier Jean , Côté François
Published: June 2010

The extracellular accumulation of b (pathogenesis-related) proteins in Nicotiana tabacum cv. Xanthi-nc and cv. Samsun and in Nicotiana sylvestris was studied by floating leaf disks on solutions (50 μM – 5 mM) of putative inducers at pH 4 to 8 for 72 h. Intercellular fluid b proteins were detected only in green tissue, and optimal conditions required specific light regimes. Amino acids, organic acids, sugars, nucleotides, amines, vitamins, hormones, metals, and several other chemicals were compared with acetylsalicylate at 0.3 mM for the presence of b proteins in intercellular fluid extracts analyzed by native polyacrylamide gel electrophoresis. Several protein and non-protein amino acids and some of their derivatives were inducers in addition to thiamine, thiamine derivatives, and a few other chemicals at concentrations ranging from 200 μM to 5 mM. Various ways of introducing inducers into tissue (floating, injection, infiltration, root uptake) allowed b protein accumulation. Stimulation of b protein accumulation was observed when osmotica (sucrose at 200 mM) were added to inducers. Chelating agents, spermidine, lysine, and hydroquinone could inhibit b protein accumulation induced by L-serine, thiamine, L-α-aminoisobutyrate, and silver nitrate. Results with inducing chemicals and with prolonged floating of tissue on water, which was also conducive to b protein accumulation, support the hypothesis that b protein accumulation is a green tissue generalized response to various forms of prolonged stress.
Nodulation speed of Frankia sp. on Alnus glutinosa, Alnus crispa, and Myrica gale
Authors: Nesme Xavier , Normand Philippe , Tremblay Francine M. , Lalonde Maurice
Published: June 2010

The question of compatibility between actinorhizal host plants and Frankia sp. was addressed using nodulation speed on Alnus spp. seedlings and Myrica gale seedlings. It was found that the speed of nodulation, defined as the mean time taken for the formation of the first prenodule, was a stable phenotype of both the Frankia strains and the host plants and that a distinction between slow-, medium-, and fast-nodulating Frankia strains could be made. The speed of nodulation of a given Frankia strain did not appear to be positively correlated to the original host plant from which isolation was first performed. It was, however, positively correlated with the Frankia strain and with the host plant species used for inoculation. Some optimal host plant – endophyte combinations were thus defined. Pure spore inocula of Frankia and in vitro propagated Alnus glutinosa plantlets were used to confirm that both the host plant and the microbial partners genetically influenced the nodulation process.
Orchidaceous rhizoctonias in pot cultures of vesicular–arbuscular mycorrhizal fungi
Authors: Williams P. G.
Published: June 2010

The paper reports that previously undescribed, sterile, septate fungi (Rhizoctonia) with affinity to and attributes of orchid mycorrhizal fungi, commonly occur in pot cultures of vesicular–arbuscular (V–A) mycorrhizal fungi. Seventeen pot cultures of V–A endophytes from several sources were studied. The endophytes included unidentified organisms as well as species of Glomus, Acaulospora, and Gigaspora. A Rhizoctonia was present in every pot culture. In different cases, Rhizoctonia isolates were obtained from sporelike cells in intramatrical vesicles, extramatrical hyphae, and chlamydospores or roots of pot culture plants. In pure culture, the rhizoctonias formed pale or yellow–brown, submerged colonies composed of narrow, irregularly septate hyphae. Monilioid hyphae and terminal or intercalary, spherical chlamydospores about 12 μm in diameter developed in older mycelia. Fruiting experiments by J. H. Warcup indicated that the teleomorph of three Rhizoctonia isolates is related to Sebacina vermifera Oberwinkler, a mycorrhizal endophyte of certain Australian terrestrial orchids. Positive tests for symbiotic germination of orchid seed with one isolate are described. Pasture legumes and ryegrass plants were inoculated with mycelia of Rhizoctonia strains in the presence or absence of V–A mycorrhizal fungi. Inoculation affected plant growth only when V–A mycorrhizal fungi were present: in steamed soil containing residual inoculum of a V–A endophyte, the growth response following infection by the V–A endophyte occurred in inoculated plants several weeks earlier than in uninoculated plants; in different natural soils, inoculation increased, decreased, or had no effect on growth, depending on the strain of Rhizoctonia used.
Effect of an exogenous supply of urea on the content and secretion of soluble carbohydrates of Evernia prunastri
Authors: Vicente C. , Blanco María José
Published: June 2010

Thallus samples of Evernia prunastri, rehydrated in the light, accumulate both mannitol and arabitol as products of the conversion of photosynthates which have been translocated from the photobiont to the mycobiont. The concentration of accumulated polyols, measured as milligrams mannitol per gram dry thallus, is about 600 times higher than that of glucose. By supplying urea to the thallus, a urease is induced to produce carbon dioxide and ammonia from urea. However, the increase in CO2 availability does not lead to an increase in the concentration of photosynthates, since the ratio of mannitol to glucose decreases to a third of its initial value. This decrease does not result from the loss of polyols to the incubation media but from an inhibition of the conversion of glucose to polyols.
Phytochrome enhances nitrate reductase activity in the lichen Evernia prunastri
Authors: Avalos A. , Vicente C.
Published: June 2010

The lichen Evernia prunastri shortly after collection shows low nitrate reductase activity. The enzyme is induced by nitrate in the dark and this effect is enhanced by red light, the action of which is reversed by far-red light. Nitrate reductase is located in both symbionts, but mycobiont cells are responsible for the increase of enzyme activity in whole thalli floated on nitrate in the dark. When this increase is achieved in the light, it can be related to the Pfr content of the photobiont cells, whereas changes in the activity of the fungal enzyme are negligible.
A monograph of Valsa on hardwoods in North America
Authors: Spielman Linda J.
Published: June 2010

The species of Valsa and Cytospora found on hardwoods in North America are reevaluated, based on morphological studies of type specimens, herbarium specimens, and fresh collections. Three sections are accepted in Valsa: sections Valsa, Monostichae Nits., and Cypri Urban, distinguished by the number, size, and arrangement of perithecia, the distribution of ostioles in the disc, and the size of ascospores. Four sections are accepted in Cytospora: sections Cytospora, Torsellia (Fr.) Gvrit., Cytophoma (Hoehn.) Gvrit., and Cytosporopsis (Hoehn.) Gvrit., based on the number and shape of the locules. Correlations between the teleomorphic and anamorphic sections Valsa–Cytospora, Monostichae–Torsellia, and Cypri–Cytophoma are reaffirmed. Six species of Valsa on North American hardwoods are accepted, and two new subspecies are proposed: V. ambiens subsp. ambiens and V. ambiens subsp. leucostomoides (Peck) Spielman. Six species of Cytospora are accepted.
Electron microscopy on a nematode-trapping fungus, Acaulopage pectospora
Authors: Saikawa Masatoshi , Morikawa Chiharu
Published: June 2010

Trapping organs of Acaulopage pectospora Drechsler, a nematode-destroying fungus, were examined by electron microscopy at various stages of infection. The trapping organs arise from sparsely developed nonseptate hyphae as short, lateral branches, each with a slightly inflated terminal knob. Nematodes arc captured by adhesive secreted from the knob. Electron microscopy revealed the following ultrastructural aspects: (i) the trap's cytoplasm is occupied by large electron-dense vesicles (0.5–0.9 μm) before secretion of the adhesive; (ii) the secreted adhesive derived from the large vesicles has a high electron density and contains a number of bubbles; (iii) the cell wall of the traps becomes doubled after the secretion of adhesive and an aliquot of the adhesive remains in the intervening space between the outer and inner cell wall; (iv) the outer wall of the terminal knob exhibits a rimose appearance. Ultrastructural evidence indicates that Acaulopage pectospora is very similar to Zoophagus insidians Sommerstorff.
How tree branches are attached to trunks
Authors: Shigo Alex L.
Published: June 2010

The vascular cambium and the growth ring it produces are continuous from trunk to branch, but the cells formed by the cambium in the upper junction of branch and trunk are oriented at approximately right angles to the normal orientation in the trunk and branch. Branch tissues begin to develop before trunk tissues early in the growing season. Maturation of branch tissues proceeds basipetally. The branch xylem is oriented downward at the branch base and encircles it to form a collar. The collar tissues meet on the trunk below the branch. The branch collar is enveloped later in the growing season by a collar of trunk xylem. Xylem in the trunk collar meet above and below the branch. Conduction into and out of the branch follows the pathway of the branch collar. The branch is structurally attached to the trunk by a series of trunk collars that envelop the branch collars every growing season. When the trunk collar was injured or removed by branch pruning, the trunk xylem above and below the cut was rapidly and extensively infected and decay developed. When pruning cuts did not injure or remove the trunk collar, no infections developed in the trunk xylem. Dye movement and the patterns of spread of bacterial and fungal pathogens also suggested that there was no local direct conduction between trunk xylem above a branch and within a branch.
The development, structure, and histochemistry of sclerotia of ectomycorrhizal fungi. II. Paxillus involutus
Authors: Grenville D. J. , Peterson R. L. , Piché Y.
Published: June 2010

Sclerotia of Paxillus involutus (Batsch) Fr. were produced in association with Pinus strobus L. and Pinus resinosa Ait. in plastic growth pouches and on agar-solidified nutrient medium. They were fixed and embedded for light microscopy and scanning and transmission electron microscopy. Sclerotia consisted of an outer pigmented rind, a thin cortical layer, and a large central medulla of isodiametric cells. Large deposits of glycogen, as well as smaller deposits of protein and lipid, were present in medullary and cortical cells. Structural characteristics indicate that these sclerotia are persistent propagules which may function to reinfect tree roots following environmental stresses. Since they can be produced in pure culture, it may be possible to inoculate seedlings directly with sclerotia.
Leaf development and morphology in ash: influence of gamma radiation
Authors: Dugle Janet R. , Hawkins Janice L.
Published: June 2010

Under the stress of long-term exposure to gamma radiation at dose rates ranging from 1.83 to 62.48 mGy/h, planted saplings of black ash (Fraxinus nigra Marsh.) responded in a variety of ways. These were compared with naturally growing black ash trees and saplings and with green ash (F. pennsylvanica Marsh.). With increasing dose, development time shortened, the number of leaflets decreased, and phyllotaxy changed from opposite to helical. The LD50 (lethal dose to 50% of exposed plants) (acute, seed germination) was 98 for F. nigra and 174 Gy for F. pennsylvanica. In black ash, the long-term LR50 (lethal dose rate to 50% of exposed plants, in milligrays per hour) has leveled off at approximately 14 mGy/h, while the accumulative LD50 (total accumulated lethal dose to 50% of exposed plants, in grays) continued to increase with additional irradiation, and after 11 years of irradiation was over 900 Gy. Plantation black ash is surviving, and even thriving, at a dose rate of 15.6 mGy/h, which may be a stable survival dose rate. Leaves in the two species are similar, with more leaflets per leaf on later developed nodes. Leaf size increased with total accumulated dose. Green ash is surviving at the highest dose rate at which it has been found (5.93 mGy/h). The frequency of morphological changes, most of which are teratological (e.g., apparent fused leaves, alternate or missing leaflets, chlorophyll mottling and sectoring, abnormal venation, irregular leaves), increased with radiation dose. In locations with severe winters, stresses during the winter dormant period are very important to survival. It is proposed that some of the features that enable ash to survive in a "harsh" environment may help it to tolerate the stress of gamma irradiation better than other species.
The taxonomy of Synura (Chrysophyceae) in Ontario with special reference to taste and odour in water supplies
Authors: Nicholls K. H. , Gerrath J. F.
Published: June 2010

Electron microscopy of silica scales was used in the identification of 13 taxa of the colonial chrysophyte Synura found in Ontario lakes and ponds, one of which has not been reported previously from North America (Synura spinosa f. longispina Petersen & Hansen). Two other taxa found in Ontario (Synura splendida Korshikov and Synura petersenii f. praefracta Asmund) have previously been reported only once from North America. One new combination is proposed (Synura leptorrhabda (Asmund) Nicholls) which provides for more consistent taxonomy of species in the Synura echinulata group (S. echinulata Korshikov, Synura mammillosa Takahashi, Synura multidentata (Balonov & Kuzmin) Péterfi & Momeu, and S. leptorrhabda). The systematics of other problematic taxa, including the related genus Chrysodidymus, are discussed. Samples containing Synura spp., previously implicated in 11 recent cases of "fishy" taste and odour in Ontario lakes, were reexamined by electron microscopy and found to be dominated by S. petersenii Korshikov. All affected sites were lakes of the Precambrian Shield (pH 5.7 – 7.5; alkalinity < 1 – 45 mg CaCO3/L). No evidence of obnoxious tastes or odours from other Synura species has been found.
A new species of Dwayaangam parasitic on eggs of rotifers and nematodes
Authors: Barron G. L.
Published: June 2010

Dwayaangam heterospora is described as a new Hyphomycete attacking the eggs of rotifers and nematodes. The fungus attaches to the eggshell by an appressorium-like swelling. After penetration a postinfection bulb is produced from which haustorium-like assimilative hyphae develop and consume the contents of the egg. The fungus produces several morphologically different types of conidia from inconspicuous conidiogenous cells. The conidia are solitary, hyaline and septate and are either scolecospores or staurospores. Key words: egg parasite, rotifers, Dwayaangam, Triposporina, aquatic hyphomycetes.
Electron microscopic observations of the envelopes of isolated algal packets of Azolla
Authors: Uheda Eiji , Kitoh Shunji
Published: June 2010

The envelopes of isolated algal packets from cyanobiont-containing and cyanobiont-free Azolla were examined with the electron microscope. Both types of envelope were 10–20 nm thick and composed of three layers. The three-layer structure was also observed when algal packets were treated with cellulase, pectinase, lipase, protease, sodium hydroxide, nitric acid, or sodium dodecylsulfate. Thus, the envelopes do not appear to be membrane-like in nature and the presence and ultrastructure of the envelopes are not affected by cyanobiont filaments. Key words: algal packet, cyanobiont-free Azolla, Azolla, electron microscopic studies, envelope.
Gender dependent and independent morphological dimorphism in sexual and apomictic Antennaria monocephala sensu lato
Authors: Chmielewski J. G. , Chinnappa C. C.
Published: June 2010

Taxa included in the Antennaria monocephala DC. polyploid complex were previously circumscribed at the specific, subspecific, or varietal levels without concensus. The purpose of this phenetic study was to construct a taxonomy that not only reflects the presumed evolutionary history of the complex but also presents a taxonomy that is both functional and informative, regardless of an individual's gender or more importantly, the reproductive mode of the population. The rank of subspecies (A. monocephala ssp. monocephala and A. monocephala ssp. angustata (Green) Hultén) was accepted as the most appropriate level of gender independent circumscription that satisfied the purpose of the phenetic study. These subspecies differ with respect to tomentum, chromosome number, reproductive biology, and (in part) provenance. The former taxon, A. monocephala ssp. monocephala, is a sexual diploid (2n = 28); the latter taxon, A. monocephala ssp. augustata, is an apomictic polyploid, with chromosome numbers ranging from tetraploid (2n = 56) to octoploid (2n = 112). In A. monocephala ssp. monocephala the adaxial surface of the basal and cauline leaves is glabrous-strigose, as is the stem. In A. monocephala ssp. angustata the adaxial surface of both basal and cauline leaves is floccose-tomentose, as is the surface of the stem. Key words: Antennaria monocephala polyploid complex, multivariate analyses.
Litter mass-loss rates and decomposition patterns in some needle and leaf litter types. Long-term decomposition in a Scots pine forest. VII
Authors: Berg Björn , Ekbohm Gunnar
Published: June 2010

The decomposition dynamics of four types of needle litter and three types of leaf litter were followed for 4 years. Mass losses and certain chemical changes were studied. Most of the nutrient-rich litters appeared to decompose relatively quickly during the first 12–18 months. After 3–4 years, however, their accumulated mass losses were lower compared with litter types that intially had lower rates. Thus the more nutrient-rich litters had considerably lower mass-loss rates in the later stages. This pattern was even more pronouced for extract-free lignocellulose: its mass-loss rate was negatively related to the lignin concentration, which increased progressively as litter decomposition proceeded. During late stages in litter with a high nitrogen content, there was also a clear negative relation between nitrogen concentration and lignin mass-loss rate, as well as between nitrogen concentration and litter mass-loss rate. By extrapolation of measured mass-loss values, maximum values for accumulated litter–mass loss were estimated. A nonlinear statistical model predicted that the proportion of mass lost through decomposition should be 50% for grey alder leaves, 54% for green leaves of white birch, and 57% for brown leaves of white birch. For Scots pine the predicted maximums for accumulated mass loss were 68% for green needles and 89% for brown needles, whereas corresponding values for lodgepole pine needles were 81% (green) and 100% (brown). Lodgepole pine is an introduced species in this system. Key words: litter, decomposition, lignin, nitrogen, maxium mass loss.
Postglacial vegetation history of oak savanna in southern Ontario
Authors: Szeicz J. M. , MacDonald G. M.
Published: June 2010

Sizable areas of oak savanna were present in southern Ontario when the region was first settled by Europeans. The objective of this study was to reconstruct the vegetation history of oak savanna at a site in Ontario and to test the hypothesis that the savanna was created by Indian burning. The fossil pollen, plant macrofossil, and fossil charcoal records of the sediments of a small lake were used to reconstruct postglacial vegetation development in an area formerly occupied by oak savanna. The fossil record from the site extends from approximately 11 800 BP to the present. The initial vegetation around the lake was an open Picea woodland similar to that reported from other late glacial sites in southern Ontario. Pinus banksiana forest dominated the vegetation of the site between about 10 000 and 9000 BP. Pinus strobus replaced Pinus banksiana and remained the dominant tree species in the area until approximately 6000 BP. The persistence of Pinus strobus as the dominant tree species until 6000 BP is unique in southern Ontario. Between 6000 and 4000 BP the Pinus strobus forest was replaced by oak savanna. Oak savanna occupied the area until land clearance by Europeans at approximately A.D. 1850. The early date at which oak savanna developed makes it unlikely that Indian burning was the cause of savanna formation. Determining the cause of the late persistence of Pinus strobus-dominated vegetation and its replacement by oak savanna is difficult. It is possible that the late persistence of Pinus strobus in the study area is related to dry climatic conditions during the mid-Holocene (~8000 to 6000 BP). The establishment of oak savanna may have been caused by the transition to moister climatic conditions in the later half of the Holocene. The particularly dry and well-drained substrates associated with oak savanna may have restricted occupation of these regions by more mesic tree species and maintained herb and graminoid dominated openings by promoting natural fires. Key words: Palaeoecology, fossil pollen, Holocene, oak savanna, southern Ontario.
Disturbance effects on aquatic vegetation in regulated and unregulated lakes in northern Minnesota
Authors: Wilcox Douglas A. , Meeker James E.
Published: June 2010

The effects of water-level regulation on aquatic macrophyte communities were investigated by comparing two regulated lakes in northern Minnesota with a nearby unregulated lake. Natural annual fluctuations of about 1.8 m were replaced with fluctuations of 1.1 m and 2.7 m in the regulated lakes, and the timing of water-level changes was also altered. Quadrats were sampled along transects that followed depth contours representing different plant habitats in the unregulated lake. Ordinations showed that the macrophyte communities at all sampled depths of the regulated lakes differed from those in the unregulated lake. The unregulated lake supported structurally diverse plant communities at all depths. In the lake with reduced fluctuations, only four taxa were present along transects that were never dewatered; all were erect aquatics that extended through the entire water column. In the lake with increased fluctuations, rosette and mat-forming species dominated transects where drawdown occurred in early winter and disturbance resulted from ice formation in the sediments. The natural hydrologic regime at the unregulated lake resulted in intermediate disturbance and high diversity. There was either too little or too much disturbance from water-level fluctuations in the regulated lakes, both resulting in reduced structural diversity. Key words: reservoirs, lake-level regulation, winter drawdown, aquatic vegetation, growth form, disturbance.
The systemic nature of the sunflower disease caused by Diaporthe helianthi
Authors: Muntanola-Cvetković M. , Vukojević Jelena , Mihaljčević M.
Published: June 2010

The systemic nature of the disease of sunflower plants caused by Diaporthe helianthi, the leaf–petiole–stem route of the host invasion by the fungus, and the plant tissues that were successively affected were demonstrated through histological studies. After penetration into the host, the infection hyphae invade the intercellular spaces and terminal veinlets of the lamina and spread toward larger branches of the conducting system, the midrib, and the petiole. Xylem elements are invaded but are affected less by the fungus attack than the phloem and the parenchyma tissues, which disintegrate completely. Hyphae spread through the leaf axil to the tissues of the stem cortex, where pycnidia of the Phomopsis anamorph are initiated from internal masses of mycelium. Key words: systemic plant diseases, sunflower diseases, Diaporthe helianthi, Phomopsis helianthi.