bluuebunny/crossref_metadata_2025 huggingface dataset:
Localization in Microresonator Arrays: Influence of Natural Frequency Tuning
Authors: Dick Andrew J. , Balachandran Balakumar , Mote C. Daniel
Published: December 2009

Intrinsic localized modes are localization events caused by intrinsic nonlinearities within an array of perfectly periodic coupled oscillators. Recent developments in microscale fabrication techniques have allowed for the studies of this phenomenon in micro-electromechanical systems. Studies have also identified a relationship between the spatial profiles of intrinsic localized modes and forced nonlinear vibration modes, as well as a potential sensitivity to fundamental frequency relationships of one-to-one and three-to-one between adjacent oscillators. For the system considered, the one-to-one frequency relationship is determined to provide nonideal conditions for studying intrinsic localized modes. The influence of the three-to-one frequency relationship on the behavior of the intrinsic localized modes is studied with analytical methods and numerical simulations by tuning the fundamental frequencies of the oscillators. While the perfect tuning condition is not determined to produce a unique phenomenon, the number and energy concentration of the localization events are found to increase with the increased frequency ratio, which results in a decrease in the effective coupling stiffness within the array.
Nonlinear Free Vibration of a Symmetrically Conservative Two-Mass System With Cubic Nonlinearity
Authors: Pirbodaghi T. , Hoseini S.
Published: December 2009

In this study, the nonlinear free vibration of conservative two degrees of freedom systems is analyzed using the homotopy analysis method (HAM). The mathematical model of such systems is described by two second-order coupled differential equations with cubic nonlinearities. First, novel approximate analytical solutions for displacements and frequencies are established using HAM. Then, the homotopy Padé technique is applied to accelerate the convergence rate of the solutions. Comparison between the obtained results and those available in the literature shows that the first-order approximation of homotopy Padé technique leads to accurate solutions with a maximum relative error less than 0.068 percent for all the considered cases.
Comparison of Three-Dimensional Flexible Beam Elements for Dynamic Analysis: Classical Finite Element Formulation and Absolute Nodal Coordinate Formulation
Authors: Schwab A. L. , Meijaard J. P.
Published: December 2009

Three formulations for a flexible spatial beam element for dynamic analysis are compared: a Timoshenko beam with large displacements and rotations, a fully parametrized element according to the absolute nodal coordinate formulation (ANCF), and an ANCF element based on an elastic line approach. In the last formulation, the shear locking of the antisymmetric bending mode is avoided by the application of either the two-field Hellinger–Reissner or the three-field Hu–Washizu variational principle. The comparison is made by means of linear static deflection and eigenfrequency analyses on stylized problems. It is shown that the ANCF fully parametrized element yields too large torsional and flexural rigidities, and shear locking effectively suppresses the antisymmetric bending mode. The presented ANCF formulation with the elastic line approach resolves most of these problems.
Electrothermal actuation of silicon carbide ring resonators
Authors: Mastropaolo Enrico , Cheung Rebecca , Henry Anne , Janzén Erik
Published: December 2009

Silicon carbide (SiC) ring resonators have been designed, simulated, and fabricated in order to achieve higher resonant frequency compared to beam resonators. The resonant frequency as a function of the ring radius and central hole radius, as well as the influence of the electrode design on the actuation efficiency have been investigated. Aluminum (Al) electrodes have been fabricated on top of the structures in order to study the electrothermal actuation of the structures. The bimorph Al/SiC ring resonators have been constructed by etching the SiC in inductively coupled plasma. The release of the Si sacrificial layer has been performed with a XeF2 chemical etching. The radial release and area release have been characterized as a function of the central hole dimension at chamber pressure of 1 and 2 Torr, whereby the release rates have been found to increase as the hole dimensions and the etching pressure increases. In addition, the release process has shown to be governed by aperture effects. The rings fabricated with different dimensions have been actuated mechanically and electrothermally, and the resonant frequency detected optically. The resonant frequency has been shown to increase as the ring radius decreases and the hole radius increases, both theoretically and experimentally.
Recombination between
ccrC
Genes in a Type V (5C2&5) Staphylococcal Cassette Chromosome
mec
(SCC
mec
) of
Staphylococcus aureus
ST398 Leads to Conversion from Methicillin Resistance to Methicillin Susceptibility
In Vivo
Authors: Chlebowicz Monika A. , Nganou Kristelle , Kozytska Svitlana , Arends Jan P. , Engelmann Susanne , Grundmann Hajo , Ohlsen Knut , van Dijl Jan Maarten , Buist Girbe
Published: December 2009

Various types of the staphylococcal cassette chromosome
mec
(SCC
mec
) are known to confer methicillin resistance on the human pathogen
Staphylococcus aureus
. Such cassettes are not always stably maintained. The present studies were aimed at identifying the mechanism underlying the
in vivo
conversion of methicillin-resistant
S. aureus
(MRSA) to methicillin-susceptible
S. aureus
(MSSA) derivatives as encountered in two patients suffering from pneumonia and an umbilicus infection, respectively. All MRSA and MSSA isolates identified belong to multilocus sequence type (MLST) 398, have
spa
type t034, and are Panton-Valentine leukocidin positive. Sequencing of 27,616 nucleotides from the chromosomal SCC
mec
insertion site in
orfX
to the
hsdR
gene for a restriction enzyme revealed a type V (5C2&5) SCC
mec
. Sequence comparisons show that parts of the cassette are highly similar to sequences within SCC
mec
elements from coagulase-negative staphylococci, indicating a possible common origin. The cassette investigated contains
ccrC
-carrying units on either side of its class C2b
mec
gene complex.
In vivo
loss of the
mec
gene complex was caused by recombination between the recombinase genes
ccrC1
allele 8 and
ccrC1
allele 10.
In vitro
, the SCC
mec
was very stable, and low-frequency MRSA-to-MSSA conversion was only observed when MRSA isolates were cultivated at 41°C for prolonged periods of time. In this case also, loss of the
mec
complex was due to
ccrC
gene recombination. Interestingly, the MRSA and MSSA isolates studied displayed no detectable differences in competitive growth and virulence, suggesting that the presence of the intact type V (5C2&5) SCC
mec
has no negative bearing on staphylococcal fitness under the conditions used.
Ineffectiveness of Tigecycline against Persistent
Borrelia burgdorferi
Authors: Barthold Stephen W. , Hodzic Emir , Imai Denise M. , Feng Sunlian , Yang Xiaohua , Luft Benjamin J.
Published: December 2009

The effectiveness of a new first-in-class antibiotic, tigecycline (glycylcycline), was evaluated during the early dissemination (1 week), early immune (3 weeks), or late persistent (4 months) phases of
Borrelia burgdorferi
infection in C3H mice. Mice were treated with high or low doses of tigecycline, saline (negative-effect controls), or a previously published regimen of ceftriaxone (positive-effect controls). Infection status was assessed at 3 months after treatment by culture, quantitative
ospA
real-time PCR, and subcutaneous transplantation of joint and heart tissue into SCID mice. Tissues from all saline-treated mice were culture and
ospA
PCR positive, tissues from all antibiotic-treated mice were culture negative, and some of the tissues from most of the mice treated with antibiotics were
ospA
PCR positive, although the DNA marker load was markedly decreased compared to that in saline-treated mice. Antibiotic treatment during the early stage of infection appeared to be more effective than treatment that began during later stages of infection. The viability of noncultivable spirochetes in antibiotic-treated mice (demonstrable by PCR) was confirmed by transplantation of tissue allografts from treated mice into SCID mice, with dissemination of spirochetal DNA to multiple recipient tissues, and by xenodiagnosis, including acquisition by ticks, transmission by ticks to SCID mice, and survival through molting into nymphs and then into adults. Furthermore, PCR-positive heart base tissue from antibiotic-treated mice revealed RNA transcription of several
B. burgdorferi
genes. These results extended previous studies with ceftriaxone, indicating that antibiotic treatment is unable to clear persisting spirochetes, which remain viable and infectious, but are nondividing or slowly dividing.
Influence of Alpha-1 Glycoprotein Acid Concentrations and Variants on Atazanavir Pharmacokinetics in HIV-Infected Patients Included in the ANRS 107 Trial
Authors: Barrail-Tran A. , Mentré F. , Cosson C. , Piketty C. , Chazallon C. , Gérard L. , Girard P. M. , Taburet A. M.
Published: December 2009

Atazanavir is an HIV-1 protease inhibitor with high protein binding in human plasma. The objectives were first to determine thein vitrobinding characteristics of atazanavir and second to evaluate whether plasma protein binding to albumin and alpha-1 glycoprotein acid (AAG) influences the pharmacokinetics of atazanavir in HIV-infected patients. For thein vitrostudy, atazanavir protein binding characteristics were determined in AAG- and albumin-containing purified solutions. Atazanavir was found to bind AAG on a high-affinity saturable site (association constant, 4.61 × 105liters/mol) and albumin on a low-affinity nonsaturable site. For thein vivostudy, blood samples from 51 patients included in trial ANRS 107—Puzzle 2 were drawn prior to drug intake at week 6. For 10 patients included in the pharmacokinetic substudy, five additional blood samples were collected during one dosing interval at week 6. Atazanavir concentrations were assayed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Albumin concentrations, AAG concentrations, and phenotypes were also measured in these patients. Concentrations of atazanavir were modeled using a population approach. A one-compartment model with first-order absorption and elimination best described atazanavir pharmacokinetics. Atazanavir pharmacokinetic parameters and their interindividual variabilities were as follows: absorption rate constant (ka), 0.73 h−1(139.3%); apparent clearance (CL/F), 13.3 liters/h (26.7%); and apparent volume of distribution (V/F), 79.7 liters (27.0%). Atazanavir CL/Fdecreased significantly when alanine aminotransferase and/or AAG levels increased (P< 0.01). The ORM1*S phenotype also significantly increased atazanavirV/F(P< 0.05). Thesein vivoresults indicate that atazanavir pharmacokinetics is moderately influenced by its protein binding, especially to AAG, without expected clinical consequences.
International Spread and Persistence of TEM-24 Is Caused by the Confluence of Highly Penetrating
Enterobacteriaceae
Clones and an IncA/C
2
Plasmid Containing Tn
1696
::Tn
1
and IS
5075
-Tn
21
Authors: Novais Ângela , Baquero Fernando , Machado Elisabete , Cantón Rafael , Peixe Luísa , Coque Teresa M.
Published: December 2009

TEM-24 remains one of the most widespread TEM-type extended-spectrum β-lactamases (ESBLs) among
Enterobacteriaceae
. To analyze the reasons influencing its spread and persistence, a multilevel population genetics study was carried out on 28 representative TEM-24 producers from Belgium, France, Portugal, and Spain (13
Enterobacter aerogenes
isolates, 6
Escherichia coli
isolates, 6
Klebsiella pneumoniae
isolates, 2
Proteus mirabilis
isolates, and 1
Klebsiella oxytoca
isolate, from 1998 to 2004). Clonal relatedness (XbaI pulsed-field gel electrophoresis [PFGE] and
E. coli
phylogroups) and antibiotic susceptibility were determined by standard procedures. Plasmid analysis included determination of the incompatibility group (by PCR, hybridization, and/or sequencing) and comparison of restriction fragment length polymorphism (RFLP) patterns. Characterization of genetic elements conferring antibiotic resistance included integrons (classes 1, 2, and 3) and transposons (Tn
3
, Tn
21
, and Tn
402
). Similar PFGE patterns were identified among
E. aerogenes
,
K. pneumoniae
, and
P. mirabilis
isolates, while
E. coli
strains were diverse (phylogenetic groups A, B2, and D). Highly related 180-kb IncA/C
2
plasmids conferring resistance to kanamycin, tobramycin, chloramphenicol, trimethoprim, and sulfonamides were identified. Each plasmid contained defective In0-Tn
402
(
dfrA1
-
aadA1
,
aacA4
, or
aacA4
-
aacC1
-
orfE
-
aadA2
-
cmlA1
) and In4-Tn
402
(
aacA4
or
dfrA1
-
aadA1
) variants. These integrons were located within Tn
21
, Tn
1696
, or hybrids of these transposons, with IS
5075
interrupting their IR
tnp
and IR
mer
. In all cases,
bla
TEM-24
was part of an IS
5075
-ΔTn
1
transposon within
tnp

1696

, mimicking other genetic elements containing
bla
TEM-2
and
bla
TEM-3
variants. The international dissemination of TEM-24 is fuelled by an IncA/C
2
plasmid acquired by different enterobacterial clones which seem to evolve by gaining diverse genetic elements. This work highlights the risks of a confluence between highly penetrating clones and highly promiscuous plasmids in the spread of antibiotic resistance, and it contributes to the elucidation of the origin and evolution of TEM-2 ESBL derivatives.
Miltefosine Efficiently Eliminates
Leishmania major
Amastigotes from Infected Murine Dendritic Cells without Altering Their Immune Functions
Authors: Griewank Klaus , Gazeau Caroline , Eichhorn Andreas , von Stebut Esther
Published: December 2009

As a treatment for leishmaniasis, miltefosine exerts direct toxic effects on the parasites. Miltefosine also modulates immune cells such as macrophages, leading to parasite elimination via oxidative radicals. Dendritic cells (DC) are critical for initiation of protective immunity against
Leishmania
through induction of Th1 immunity via interleukin 12 (IL-12). Here, we investigated the effects of miltefosine on DC in
Leishmania major
infections. When cocultured with miltefosine for 4 days, the majority of
in vitro
-infected DC were free of parasites. Miltefosine treatment did not influence DC maturation (upregulation of major histocompatibility complex II [MHC II] or costimulatory molecules, e.g., CD40, CD54, and CD86) or significantly alter cytokine release (IL-12, tumor necrosis factor alpha [TNF-α], or IL-10). Further, miltefosine DC treatment did not alter antigen presentation, since unrestricted antigen-specific proliferation of CD4
+
and CD8
+
T cells was observed upon stimulation with miltefosine-treated, infected DC. In addition, miltefosine application
in vivo
did not lead to maturation/emigration of skin DC. DC NO
−
production, a mechanism used by phagocytes to rid themselves of intracellular parasites, was also unaltered upon miltefosine treatment. Our data confirm prior studies indicating that in contrast to, e.g., pentavalent antimonials, miltefosine functions independently of the immune system, mostly through direct toxicity against the
Leishmania
parasite.
High Concentration of Raltegravir in Semen of HIV-Infected Men: Results from a Substudy of the EASIER-ANRS 138 Trial
Authors: Barau Caroline , Delaugerre Constance , Braun Joséphine , de Castro Nathalie , Furlan Valérie , Charreau Isabelle , Gérard Laurence , Lascoux-Combe Caroline , Molina Jean-Michel , Taburet Anne-Marie
Published: December 2009

Raltegravir concentrations and human immunodeficiency virus type 1 (HIV-1) RNA levels in semen samples from 10 treatment-experienced HIV-1-infected patients were measured after 24 weeks of raltegravir-based highly active antiretroviral therapy (HAART). Semen and plasma HIV-1 RNA levels were below 100 copies/ml and 50 copies/ml, respectively, in all samples. The median raltegravir concentrations in semen samples (
n
= 10) and in plasma samples (
n
= 9) drawn simultaneously were 345 (range, 83 to 707) ng/ml and 206 (range, 106 to 986) ng/ml, respectively. The median semen-to-plasma ratio of raltegravir concentration was 1.42 (range, 0.52 to 6.66), indicating good although variable levels of drug penetration of raltegravir in the seminal compartment.
Structure and cytochemistry of the walls of urediospores, germ tubes, and appressoria of Puccinia graminis tritici
Authors: Harder D. E. , Chong J. , Rohringer R. , Kim W. K.
Published: December 2009

Several cytochemical methods demonstrated that urediospore walls of Puccinia graminis f. sp. tritici were probably composed of five layers, including the pellicle as the outermost layer. Two previously undescribed layers were located around the inner periphery of the spore walls. Staining for periodate-sensitive glycosubstances occurred uniformly and heavily throughout the wall except that the pellicle was unstained, and the innermost layer (3c) was more lightly stained by periodic acid – thiocarbohydrazide – silver proteinate. There was little wheat germ lectin or concanavalin A binding to the urediospore wall except in the hilar region, where wheat germ lectin bound heavily, and in the germ pore region, where binding of concanavalin A occurred. The walls of about one-half of the urediospores that were examined contained silicon deposits. Germ tube walls were composed of two layers: a broad outer layer and a narrower inner layer. The inner layer stained more heavily for periodate-sensitive glycosubstances than did the outer layer. Germ tube walls bound wheat germ lectin, but not concanavalin A. Appressorial walls were also composed of two layers, but the inner layer was much broader than that of germ tube walls, and the outer layer stained more heavily for periodate-sensitive glycosubstances. There was strong wheat germ lectin binding to the appressorial walls, but concanavalin A binding was sparse. Both germ tubes and appressoria were coated with a mucilagenouslike substance.
Structure and dynamics of jack pine stands near Elk Lake, Ontario: a multivariate approach
Authors: Kenkel N. C.
Published: December 2009

Multivariate techniques were utilized to examine even-aged jack pine stands on upland sandy sites at the southern edge of the boreal forest near Elk Lake, Ontario. Cluster analysis of 180 stands led to the recognition of 10 vegetation types, each showing a unique combination of floristics, physiognomy, and environmental components. Classification of common species led to the recognition of five ecological groupings, which show varying degrees of association with the vegetation types. Nonmetric multidimensional scaling of the stands suggested a vegetational continuum in response to overall moisture availability. A corresponding ordination of common species indicated the development of interspecific associations related to soil moisture conditions. It is suggested that the vegetational composition of upland jack pine forests is determined by both probabilistic and deterministic effects, and this is discussed in the context of vegetation structure and dynamics.
The phytogeography of Ceratophyllum demersum and C. echinatum (Ceratophyllaceae) in glaciated North America
Authors: Les Donald H.
Published: December 2009

The present-day distributions of Ceratophyllum demersum and C. echinatum are useful in interpreting the Quaternary distributional history of aquatic plants. East–west North American disjunct distributions of submersed hydrophytes are probably due to incomplete interglacial migrations. Widespread species such as C. demersum have successfully bridged gaps formed when populations migrated into isolated southern réfugia to escape glaciation. Species with narrower ranges, such as C. echinatum, are still in the process of doing so. Northern disjunct distributions of C. demersum indicate that the species also survived glaciation in northwest refugia. It is apparent that many submersed aquatic plants have endured the migrational pressures imposed during glacial periods. Their ability to do so is attributable to four factors: (i) long species durations, (ii) formerly continuous distributional ranges, (iii) high vagility, and (iv) adaptation to cold, oligotrophic conditions. Extant hydrophyte communities in glaciated North America may resemble those in existence during former interglacial periods.
Volume and osmotic potential changes in relation to inhibition of photosynthesis by water stress in intact leaves
Authors: Bunce James A.
Published: December 2009

It has been reported that for osmotically stressed leaf slices of a wide range of species, carbon dioxide saturated photosynthesis is uniformly inhibited by stress when water status is expressed as relative volume. Comparable data for intact leaves of a range of species are lacking. It is also unknown whether the same pattern of response applies to carbon dioxide limited photosynthesis. For these reasons responses of photosynthesis to carbon dioxide partial pressure were determined at 21% oxygen at high irradiance in intact leaves of five species as water deficits developed slowly in intact plants. Relative water content (volume) and total and osmotic water potentials were measured at each level of water stress. Three species adjusted osmotically such that volume remained unchanged over a range of water potentials. Regardless of whether volume was maintained, carbon dioxide saturated photosynthesis decreased as water potentials decreased. In contrast to the data for osmotically stressed leaf slices, relative volume, relative osmotic potential, and total water potential did not indicate a uniform level of inhibition of either carbon dioxide saturated or carbon dioxide limited photosynthesis across species. In some species the carbon dioxide compensation point increased with stress. The initial slope of photosynthesis versus substomatal carbon dioxide partial pressure was relatively less inhibited by stress than was the saturated rate. This difference was greater in some species than in others.
Four zoospore subtypes in the Rhizophlyctis–Karlingia complex (Chytridiomycetes)
Authors: Barr Donald J. S. , Désaulniers Nichole L.
Published: December 2009

Four subtypes of zoospores are described, with the use of the transmission electron microscope, for chytridiomycetous fungi that can be classified with light microscopy in the Rhizophlyctis–Karlingia complex. Subtype A has ribosomes dispersed throughout the cytoplasm; a long fibrillar rhizoplast; mitochondria and microbody closely associated with the rhizoplast; and numerous lipid globules that have occasional association with microbody. Subtype B has ribosomes concentrated into the center of the zoospore, and these are partially surrounded by endoplasmic reticulum; a short fibrillar rhizoplast; microbody associated with a basal lip of the nucleus; mitochondria that surround the rhizoplast; and numerous lipid globules that have occasional association with microbody. Subtype C has ribosomes concentrated (as in subtype B); several mitochondria interwound with microbody in the basal area between the kinetosome and nucleus; and numerous lipid globules that have occasional association with microbody. Subtype D has ribosomes concentrated (as in subtypes B and C); a long heel-like segment of the nucleus that extends to a point adjacent to the kinetosome; a close association between the nuclear heel, microbody, and mitochondria; and a large lipid globule which has close association with microbody and is partially surrounded by endoplasmic reticulum. None of the subtypes contain cytoplasmic microtubules. The taxonomic significance of the cytology is discussed. It is concluded that these subtypes of zoospores are more closely related to the Spizellomycetales than the Chytridiales.
A new procedure for determining the heterogeneity of agar polymers in the cell walls of Gracilaria spp. (Gracilariaceae, Rhodophyta)
Authors: Lahaye Marc , Rochas Cyrille , Yaphe Wilfred
Published: December 2009

The heterogeneity of agar polymers in the cell walls of Gracilaria tenuistipitata, G. eucheumoides, and G. blodgettii was demonstrated by sequential extraction of the algae in water at 22 °C; in boiling 80, 60, 40, and 20% ethanol–water solutions; and in water at 100 and 121 °C. Agar polymers in each extract were analyzed by 1H and 13C nuclear magnetic resonance spectroscopy. The agar polymers extracted from the three algae with water at 22 °C had a high concentration of repeat units substituted by alkali-labile sulfate. Methylated agar polymers were extracted with boiling 80 and 60% ethanol from G. tenuistipitata and G. eucheumoides, the former having a high content of 6-O-methyl-D-galactose and a low concentration of 2-O-methyl-3,6-anhydro-L-galactose and the latter consisting mainly of 2-O-methyl-3,6-anhydro-L-galactose. Sulfated agar polymers (alkali-stable sulfate) were extracted from G. tenuistipitata and G. blodgettii with boiling 20% ethanol and water (100 and 121 °C). Floridean starch was detected by 13C nuclear magnetic resonance in the extracts from G. tenuistipitata and G. eucheumoides.
Effects of atmospheric fluorides on foliage, and cone and seed production in balsam fir, black spruce, and larch
Authors: Sidhu S. S. , Staniforth R. J.
Published: December 2009

Fluoride accumulations and damage symptoms to foliage, cones, and seeds of balsam fir (Abies balsamea (L.) Mill.), black spruce (Picea mariana (Mill.) B.S.P.), and larch (Larix laricina (Du Roi) K. Koch) were monitored at six sites downwind from a phosphorus plant that emitted fluorides during 1982. Atmospheric fluoridation rates ranged from 347.4 μg F∙dm−2∙week−1 (11.38 μg F∙m−3) at 1.4 km from the fluoride source to 2.5 μg F∙dm−2∙week−1 (0.08 μg F∙m−3) at 18.7 km. Various degrees of foliar damage (chlorosis, necrosis, needle damage, and defoliation) occurred where fluoride accumulations in the foliage exceeded 20 ppm. This occurred at sites where the fluoridation rates were in excess of 26.0 μg F∙dm−2∙ week−1, and at distances less than 10.3 km downwind from the fluoride source. Reductions in seed size, percent germination, numbers of seeds per cone, number of cones per tree, number of fertile trees, and size reduction, distortion, or mortality of the cones occurred under the same fluoridation rates. Seed output on the windward sides of trees was significantly less than that on the leeward sides. At the most polluted site, seed production in balsam fir, black spruce, and larch, respectively, was reduced to 3.6, 2.6, and 0.0% of that at a control site. All three species in the study are considered to be susceptible to fluoride damage, with respect to both vegetative and reproductive symptoms. Reproductive failure and past mortality of fluoride-damaged conifers have resulted in their replacement by more tolerant hardwood species (e.g., birch (Betula papyrifera Marsh.), alder (Alnus crispa (Ait.) Pursh)) as the dominant forest species in the vicinity of the phosphorus plant.
Les bruyères in vitro. VI. Croissance de Calluna vulgaris sur milieu strictement nitrique ou ammoniacal et cinétique du pH en fonction du développement des plantes
Authors: Congard Benoit , Beaujard François , Viemont Jean-Daniel
Published: December 2009

Calluna vulgaris L. Hull was cultured in vitro on a medium containing either nitrate or ammonium salts. Apical shoots, used as cuttings, regenerated twigs and roots after 15 to 25 days. The uptake of mineral nitrogen by roots had an influence on the pH of the medium. There was either an increase of pH when the N source was NO3 or a decrease in pH of the medium with ammonium. Acidification began with the formation of the first new roots; an increase in pH occurred later with the formation of second order roots. The results were difficult to express, owing to rooting heterogeneity. This problem was overcome by changing the origin of the abscissa, the new origin starting with the date of rooting. This procedure allowed the study of pH changes in relation to different stages of plant growth. With the aid of a standard curve, the study of the leakage of H+ and OH− showed great homogeneity in plant behaviour.
Évolution de différentes formes d'azote chez des rameaux de Pirus malus cv. Calville Blanc sains ou infestés par Eriosoma lanigerum
Authors: Jeanneau Yves
Published: December 2009

The concentrations of total nitrogen, of soluble and insoluble nitrogen, and of amino acids and free amides are always higher in tumors caused by Eriosoma lanigerum Haussm. on Pirus malus L. cv. Calville Blanc than in the controls. The highest concentrations are found in branches on the first days after their infestation by the aphid. Some of these compounds, such as asparagine and arginine, are notably present in the tumors and seem to be specific features of the tumoral state.
Influence of tree age and growth rate on the radial resin duct system in loblolly pine (Pinus taeda)
Authors: DeAngelis J. D. , Nebeker T. E. , Hodges J. D.
Published: December 2009

Formation of radial resin ducts and their associated secretory cells in loblolly pine (Pinus taeda L.) is influenced by the age and growth rate of the annual ring in which the ducts are formed. The spatial pattern of radial ducts on the tangential plane is nonrandom, exhibiting a regular or dispersed pattern. A significantly higher density of radial ducts was found in the inner, first-formed growth rings at all heights within the tree. Radial duct formation was found to be positively correlated with radial growth rate, when growth rate is expressed as increment of cross-sectional area growth. These findings may partially explain why older, slower growing trees tend to be more susceptible to attack by the southern pine beetle, Dendroctonus frontalis Zimmermann, and associated microorganisms, since the resin-producing system is a primary defense against these agents.
A comparative light and electron microscopic study of microspore and tapetal development in male fertile and cytoplasmic male sterile oilseed rape (Brassica napus)
Authors: Grant I. , Beversdorf W. D. , Peterson R. L.
Published: December 2009

The cytological development of male cells and the tapetum of male fertile and combined cytoplasmic triazine-resistant cyto-plasmic-genetic male sterile (ctr) lines of B. napus L. was studied using light, scanning electron, and transmission electron microscopy. Development of the cytoplasmic-genetic male sterile anther was similar to the normal anther up to and including meiotic prophase I. After this stage, degeneration of the microspore mother cells occurs within the callose walls, and tetrads of microspores are not formed. These degenerating microspore mother cells appear to develop numerous endoplasmic reticulum derived vesiculated structures, which may be involved in lysis of organelles. Degeneration occurs simultaneously with a proliferation of the tapetum, which eventually fills the anther locule. It is not clear whether the abortion of the microspore mother cells during meiosis stimulates proliferation of the tapetum or whether the proliferating tapetum actually interferes with microspore development thereby causing degeneration. Dilated endoplasmic reticulum cisternae containing crystalline-like deposits, and plastids with osmiophilic bodies, are frequent in cells of the proliferated tapetum of cytoplasmic-genetic male sterile anthers.
Morphology and possible mycobiont (Suillus pictus) of a tuberculate ectomycorrhiza on Pinus strobus
Authors: Randall B. L. , Grand L. F.
Published: December 2009

Suillus pictus was consistently associated with tuberculate ectomycorrhizae (tubercles) on Pinus strobus in North Carolina. Histological, cultural, and chemical reaction studies were used to examine this association. Tubercles were examined by light and scanning electron microscopy. Clamp connections, a reduced to absent tannin layer, and appressed mantle hyphae were observed. Naturally occurring rhizomorphs of Suillus pictus and tubercles have a similar morphology consisting of an outer pseudoparenchymatous sheath, large vessel-like cells, and a prosenchymatous layer between the sheath and the vessel-like cells. Similar macroscopic chemical color reactions to 10% FeSO4, 15% KOH, concentrated NH4OH, concentrated H2SO4, and Melzer's reagents were observed on rhizomorphs of S. pictus and tubercles, surface of tubercles, and stipes of S. pictus. Chemical color reactions and growth characteristics of S. pictus and the tubercle mycobiont were similar on different agar media.
Life-history studies–a new approach to the taxonomy of ligulate species of Desmarestia (Phaeophyceae) from the Pacific coast of Canada
Authors: Peters Akira F. , Müller Dieter G.
Published: December 2009

Life histories of two ligulate forms of Desmarestia with different phylloid width from one site on the Canadian Pacific coast were studied in culture. Meiospores from a form with narrow phylloids germinated into monoecious gametophytes. Meiospores from a form with broad phylloids developed into dioecious gametophytes, showing sexual dimorphism characteristic for dioecious species of Desmarestia. The two growth forms also differed in culture conditions required for gametogenesis. We conclude that at least two different species of ligulate Desmarestia occur on the Pacific coast of North America.
Cytological and histochemical characteristics of the axenic root surface of Alnus glutinosa
Authors: Prin Yves , Rougier Mireille
Published: December 2009

The aim of the present study was to investigate the Alnus root surface using seedlings grown axenically. This study has focused on root zones where infection by the symbiotic actinomycete Frankia takes place. The zones examined extend from the root cap to the emerging root hair zone. The root cap ensheaths the Alnus root apex and extends over the root surface as a layer of highly flattened cells closely appressed to the root epidermal cell wall. These cells contain phenolic compounds as demonstrated by various histochemical tests. They are externally bordered by a thin cell wall coated by a thin mucilage layer. The root cap is ruptured when underlying epidermal cells elongate, and cell remnants are still found in the emerging root hair zone. Young emerging root hairs are bordered externally by a cell wall covered by a thin mucilage layer which reacts positively to the tests used for the detection of polysaccharides, glycoproteins, and anionic sites. The characteristics of the Alnus root surface and the biological function of mucilage and phenols present at the root surface are discussed in relation to the infection process.
A checklist of benthic marine algae of the tropical and subtropical western Atlantic
Authors: Wynne Michael J.
Published: December 2009

A checklist of 1058 species of benthic marine algae has been compiled for the tropical and subtropical western Atlantic, covering the region from North Carolina (U.S.A.) through southern Brazil. This list comprises 655 species of Rhodophyceae, 150 of Phaeophyceae, and 253 of Chlorophyceae. Literature references subsequent to 1960 are included in the bibliography, and notes in regard to some of the species are given, where appropriate.
Megagametophyte development in Hordeum vulgare. 2. Later stages of wall development and morphological aspects of megagametophyte cell differentiation
Authors: Cass D. D. , Peteya D. J. , Robertson B. L.
Published: December 2009

The micropylar quartet of nuclei in the barley megagametophyte is first partitioned by a vertical wall between the synergid nuclei and by an initially horizontal wall between the micropylar polar and egg nuclei. The latter wall continues to grow in an expanding horizontal plane forming much of the upper wall of all three egg apparatus cells and eventually fusing with the megagametophyte wall peripherally. A branch of the egg – polar nucleus wall grows in a micropylar direction and becomes attached to the megagametophyte wall. After partitioning, the egg apparatus is composed of three flat cells having a ceiling wall and two upright supporting walls, which are fused centrally. The micropylar polar nucleus lies just chalazal to the ceiling wall. Expansion of the egg apparatus results in rounding of all three cells followed by lengthening and thinning of their walls in contact with the central cell. Probable membrane contacts may facilitate sperm transmission after pollination. Partitioning of the chalazal quartet of nuclei exhibits many similarities to that of the egg apparatus but with a different cellular arrangement. Transfer cell wall ingrowths appear in cells at both poles of the megagametophyte. Such ingrowths appear in the two synergid cells, representing the filiform apparatus. They also develop in two of the original three antipodal cells where these cells are in contact with the megagametophyte wall. Either the micropylar or chalazal polar nucleus migrates to a position close to the other polar nucleus. Partial fusion of polar nuclei occurs later.
Root–fungus interactions observed on initial stages of mantle formation and Hartig net establishment in mycorrhizas of Amanita muscaria on Picea abies in pure culture
Authors: Kottke I. , Oberwinkler F.
Published: December 2009

Initial stages of mantle formation and Hartig net establishment of Amanita muscaria (L. ex Fr.) Hooker on roots of Picea abies (L.) Karst. in pure culture were observed. Decomposition of root cap cells seems to be a common feature and facilitates contact to living cortical cells. Both processes seem to stimulate mantle formation, since hyphae become enlarged and form a pseudoparenchymatic structure. Remnants of root cap cell walls remain as a boundary structure in the differentiated mantle. Wall ingrowths were observed on cortical cells in contact with the hyphal sheath and intercellular penetrating hyphae, which may be interpreted as transfer cell structures. A stimulating effect of nutrient supply on mantle formation in early stages of mycorrhizal development is supported by these observations.
Desiccation tolerance in mosses. II. Differences in the responses of Hedwigia ciliata and Mnium cuspidatum to desiccation and rehydration
Authors: Streusand V. J. , Weber J. A. , Ikuma H.
Published: December 2009

The responses of two mosses, Hedwigia ciliata and Mnium cuspidatum, to desiccation and rehydration were studied. Cell and shoot survival were about 30% lower in Mnium than in Hedwigia after the same desiccation and rehydration treatment. Time courses of water loss showed that both species lost water at the same rate and to the same extent, indicating that Hedwigia is desiccation tolerant rather than dehydration resistant. Chlorophyll content decreases in both species after desiccation and rehydration, but in Hedwigia net photosynthesis after desiccation and rehydration was at a rate similar to that in undesiccated plants whereas in Mnium photosynthetic rates were lower after desiccation and rehydration. This decreased photosynthetic rate suggests that chloroplast damage during desiccation and dry storage contributes to Mnium's lessened ability to survive after desiccation and rehydration.
High-resolution studies of growth oscillations during stem elongation
Authors: Kristie D. N. , Jolliffe P. A.
Published: December 2009

A linear-displacement transducer system coupled to a signal differentiator was used to obtain continuous high-resolution measurements of stem elongation rate in etiolated Sinapis alba L., Raphanus sativus L., Cucumis sativus L., Helianthus annuus L., and Avena sativa L. seedlings. The sensitivity of the measuring system was sufficient to resolve changes in length of ± 0.2 μm and changes in growth rate of ±3 μm h−1. Under constant conditions of darkness, 25 ± 0.1 °C, 100% relative humidity, and buffered root pH, the elongation rate of etiolated seedlings was not constant but oscillated in most of the seedlings studied. Large amplitude, long (> 45 min) period oscillations were common in all species except S. alba. Visual observations using a green safelight indicated that such oscillations were artifacts generated by nutational bending. Sustained, short (< 45 min) period oscillations were common in all species except H. annuus. In dicots, short period oscillations were not caused by bobbing of the hypocotyl hook but originated lower in the hypocotyl axis. Temperature shifts changed the frequency of short period oscillation with a Q10 > 2. The results suggest that the short period oscillations are not due to local environmental fluctuations but are spontaneously produced by a seedling undergoing synchronized variations in the rate of cell elongation.
Cysteine proteinase of Phascolomyces articulosus: purification and properties
Authors: Balasubramanian R. , Manocha M. S.
Published: December 2009

A proteinase from the mycelial extracts of Phascolomyces articulosus has been purified by salting out with ammonium sulphate, gel filtration, hydroxyapatite adsorption, and affinity chromatography. The proteinase rapidly hydrolysed haemoglobin but failed to hydrolyse any of the synthetic peptides tested. The enzyme is a glycoprotein with an apparent molecular weight of 12 800. The carbohydrate content was estimated to be 65%. It has a temperature optimum of 20 °C, pH optimum of 3.0, and has a Km value of 6.6 mg∙mL−1 for denatured haemoglobin. Iodoacetic acid, iodoacetamide, benzamidine, as well as all the heavy metals tested inhibited the enzyme activity. The enzyme activity was not enhanced by reducing agents such as cysteine, ethylenediaminetetra acetic acid, and dithiothreitol, the latter, however, reversed inhibition by phenylmethylsulfonyl fluoride. The inhibitor studies suggest that the enzyme belongs to the group of cysteine proteinases.
Effects of fertilization on three tundra plant communities of a polar desert oasis
Authors: Henry G. H. R. , Freedman B. , Svoboda J.
Published: December 2009

Three plant communities studied at a high arctic oasis on Ellesmere Island responded to nutrient addition. Response to nitrogen was greatest in the driest community and weaker in the more mesic and wet-mesic communities. Nutrient addition resulted in (i) increased inflorescence densities of dicotyledonous and certain graminoid species; (ii) increased tiller densities of wet sedge species; and (iii) increased net production of graminoids and forbs at high rates of application, and in some dwarf shrubs at lower rates. These results parallel those of studies at lower latitudes in the Arctic, and support the hypothesis that arctic ecosystems are typically oligotrophic.
The nodal roots of Zea: their development in relation to structural features of the stem
Authors: Hoppe D. C. , McCully M. E. , Wenzel C. L.
Published: December 2009

The framework of the root system of a mature, field-grown corn plant of variety Seneca Chief consists of about 70 axile roots. One of these is the primary root. The others develop on the stem, a single tier at each of the seven basal nodes. Just over half of these roots grow out at or above ground level from nodes 6 and 7 late in the development of the plant, with those of node 7 entering the soil just before flowering. The mean diameter of the root produced at successively higher nodes increases, as does also the mean number of large metaxylem elements seen in a cross section, so that about 75% of the large xylem conduits between the root system and the stem are in the roots of the two uppermost tiers. Nodal root primordia develop initially in situ from an extensive region of dedifferentiated stem cortex. A sleeve-like extension of the stem encloses the base of each root formed at aerial nodes. At each node the complexity of vascular interconnections results in all of the framework roots being indirectly linked to each other and to the vascular traces from all of the leaves.
Growth phenology of Pleurophycus gardneri (Phaeophyceae, Laminariales), a deciduous kelp of the northeast Pacific
Authors: Germann Iddamaria
Published: December 2009

Growth phenology of the monotypic northeast Pacific kelp Pleurophycus gardneri was assessed between 1982 and 1984. The study gives evidence that Pleurophycus is a deciduous perennial. Pleurophycus shows complete and synchronous defoliation during a short period of time in late fall and commences new blade growth after about 2 weeks of quiescence. Pleurophycus sheds the lamina along an abscission zone at the transition between stipe and blade. The abscission zone is macroscopically evident through a change in color and a slight indentation in senescent plants. After separation, outer cortical cells constitute a protective layer which increases in thickness as new blade outgrowth progresses. Temperature of 14 to 15 °C is assumed to be a triggering factor for the induction of blade senescence. Warm water intrusion, associated with E1 Ninõ, induced premature blade senescence and blade abscission in 1983. Growth of the new blade is completely inhibited in darkness. The induction of new outgrowth is not mediated through a photoperiodic effect and showed no day-length saturation.
Influence de la teneur en gaz carbonique sur la morphogenèse de la vigne en culture in vitro
Authors: Fournioux Jean-Claude , Bessis Roger
Published: December 2009

Two different types of morphogenesis are induced in vitro in the grapevine by changing the system of sealing the culture tubes (with or without Parafilm). The differences appear mainly in the degree of miniaturiation: the plants the most miniaturized, those with Parafilm, have all the characteristics of an immature juvenile state. The others, without Parafilm, show an intermediate morphology between the adult and the juvenile forms. It follows then that the importance of juvenile characters is linked to the degree of miniaturization. One of the effects of Parafilm is in the modification of the amount of CO2 in the atmosphere of the tubes: in excess during the dark phase and in severe shortage during the light phase. We have found then, that among all the environmental factors which could influence the morphogenesis of the grapevine in vitro, CO2 appears to play a relatively important role.
Effect of three ectomycorrhizal fungi on growth and phosphorus uptake of Pinus silvestris seedlings at increasing phosphorus levels
Authors: Tyminska A. , Tacon F. Le , Chadoeuf J.
Published: December 2009

The objective of this study was to determine the different effects of three ectomycorrhizal fungi (Laccaria laccata, Hebeloma crustuliniforme, and Thelephora terrestris) on the growth and mineral nutrition of Pinus silvestris at different levels of soluble phosphorus. Even a low intensity of infection by Laccaria laccata stimulated Pinus silvestris growth greatly. The ability of this ectomycorrhizal fungus to increase Pinus silvestris growth seemed to be more related to its capacity to produce growth substances than to its capacity to stimulate phosphorus uptake. The poor efficiency of Hebeloma crustuliniforme compared with Laccaria laccata at any level of phosphorus could result from differences in diversion of carbohydrates from the host to fungal structures.
Observations on North American Gomphoneis. III. Gomphoneis septa comb.nov.
Authors: Kociolek J. P. , Stoermer E. F. , Bahls L. L.
Published: December 2009

The valvar ultrastructure of the diatom Gomphonema septum Mogh. was investigated with scanning electron microscopy and is discussed with regard to the taxonomic position of this species. Ultrastructural features include striae composed of double rows of puncta, presence of a narrow axial plate which is responsible for the image of longitudinal lines, and apical pore fields composed of pores dissimilar in appearance from the puncta. These and other ultrastructural characteristics point to a close relationship between G. septum and members of the genus Gomphoneis. A transfer of Gomphonema septum to Gomphoneis is proposed. Information supplemental to previous observations on the size range and variability of this species is presented.