bluuebunny/crossref_metadata_2025 huggingface dataset:
Leaf surface wax layers of Brassicaceae lack feeding stimulants for Phaedon cochleariae
Authors: Reifenrath Kerstin , Riederer Markus , Müller Caroline
Published: April 2005

Numerous reports have indicated that glucosinolates are important stimulants for specialist herbivores feeding on Brassicaceae, and that these metabolites might be present on the plant surface and thereby detectable by an alighting insect. We investigated the outermost layer of leaves of two species of Brassicaceae, Brassica napus L. var. ‘Martina’ and Nasturtium officinale R. Br., using two highly selective extraction methods. When the epicuticular wax layer was mechanically removed with gum arabic, no glucosinolates were detectable in the lower and upper leaf surfaces. Extracting the leaf surfaces with a threefold short rinse with chloroform/methanol/water (2 : 1 : 1 vol/vol/vol) led to varying results, depending on the light conditions under which plants had been kept in the period prior to extraction. In plants kept under light, glucosinolates were detectable in a first extraction in minor concentrations, with increasing amounts in a second and third extraction. In plants kept in darkness, glucosinolates were almost absent in the first extraction. We postulate that the polar glucosinolates are washed from the inner leaf tissue through open stomata to the outside during solvent extraction, but are not naturally present in the outermost wax layer. The response of the crucifer specialist Phaedon cochleariae (F.) (Coleoptera: Chrysomelidae) to leaf surfaces of the host plants B. napus and N. officinale and to a glucosinolate was tested. Adults preferred both the adaxial and abaxial leaf surfaces of host plants that had been treated with gum arabic in order to remove the epicuticular waxes over intact surfaces. Waxes may therefore prevent direct contact with the stimulants. Sinigrin (allyl glucosinolate) and/or surface extracts of N. officinale leaves applied on Pisum sativum leaf discs did not evoke feeding, but feeding did occur when total leaf extracts of B. napus or N. officinale were applied on this non‐host. We conclude that glucosinolates might only act as feeding stimulants for P. cochleariae in concert with compounds other than surface waxes.
Ecological speciation without host plant specialization; possible origins of a recently described crypticPapiliospecies
Authors: Scriber J. Mark , Ording Gabriel J.
Published: April 2005

North AmericanPapilio canadensisandP. glaucus(Lepidoptera: Papilionidae, thesePapilio = Pterourus) have previously been described as having allopatric distributions separated by a narrow hybrid zone running from Minnesota to southern New England, and southward in the Appalachian Mountains (possibly to northern Georgia). Recent patterns of hybridization and introgression suggest a more complex interaction between the two, possibly even resulting in the formation of a new species (Pterourus appalachiensisPavulaan & Wright, 2002). Recently, extensive northward interspecific introgression ofP. glaucus‐diagnostic traits has been observed in the hybrid zone. These include wing bands and other color patterns, the ability to feed on tulip tree leaves, andHk‐100allozymes; all are autosomally encoded. However, there has been little northward introgression of certain otherP. glaucustraits (such as facultative diapause and bivoltinism, andLdh‐100allozymes, both X‐linked; and the Y‐linked melanic mimicry gene in females). Interspecific recombination of the X‐chromosome has evidently occurred, as shown by discordant patterns of X‐linked markers. TheP. glaucusX‐linkedPgd‐100andPgd‐50alleles have introgressed 200–400 km north of the historical hybrid zone, yet theP. glaucusX‐linkedLdh‐100allele has not. The allele frequency shift for both genes is more closely related to the ‘thermal landscape’ (i.e., accumulated degree‐days above a developmental base threshold of 50 °F (=10 °C)) than to latitude. Delayed post‐diapause eclosion of cohorts within the hybrid zone, e.g., the New York/Vermont border area, has produced a natural ‘false‐second generation’ flight (a hybrid swarm of synchronous males and females, where 2300–2700 °F degree‐days have accumulated each year since 1998) that is reproductively isolated from flights of both parental species. Moreover, the newly describedP. appalachiensisexhibits a unique combination of traits. These include obligate diapause, a univoltine habit, and theLdh‐80orLdh‐40alleles (as forP. canadensis), thePgd‐100orPgd‐50alleles (as forP. glaucus), and a delayed ‘false‐second generation’ reproductive flight period (as observed in the hybrid zone). Since 2001, a rare allele or ‘hybrizyme’ (Ldh‐20) has appeared in this false second generation at high frequencies (40–50%). We hypothesize that strong selection against the facultative diapause (od‐)trait (and the linkedLdh‐100allele) in regions with 2800 °F degree‐days or less, and divergent selection in favor ofPgd‐100(or a closely linked trait) combined with allochronic reproductive isolation, has resulted in recombinational, parapatric, hybrid speciation. There is no evidence at present that host‐plant shifts or changes in sex pheromones have driven this process, in contrast to many other speciation events in the Lepidoptera.
The effect of fractionated Tagetes oil volatiles on aphid reproduction
Authors: Tomova Blagovesta S. , Waterhouse John S. , Doberski Julian
Published: April 2005

The biological activity of essential oil volatiles from Tagetes minuta L. (Mexican marigold) against three aphid species was investigated in a series of laboratory experiments. The aphid species (Homoptera: Aphididae) studied were: Acyrthosiphon pisum (Harris) (pea aphid), Myzus persicae (Sulzer) (peach‐potato aphid), and Aulacorthum solani (Kaltenbach) (glasshouse and potato aphid). Tagetes minuta oil volatiles significantly reduced aphid reproduction (up to 100% after 5 days of exposure). The effect depended on the quantity of essential oil used, and varied with the aphid species tested. Pea aphids were the most susceptible. Tagetes minuta oil was fractionated by vacuum distillation. Fractions and three pure compounds (limonene, (Z)‐ocimene, and β‐caryophyllene) were tested using the same experimental technique. The chemical composition of the volatiles was investigated by headspace–solid phase microextraction–gas chromatography mass spectrometry (HS‐SPME‐GCMS), and the main constituents of the oil were identified. Overall, applied in equal quantity, fractions predominantly containing sesquiterpenes and oxygenated monoterpenoids were more effective in restricting aphid population growth than fractions predominantly containing monoterpenes. When tested as a pure compound, the sesquiterpene β‐caryophyllene produced a greater effect than the monoterpenes limonene and ocimene. The study demonstrates that T. minuta oil volatiles have potential for aphid control.
Future directions in the study of induced plant responses to herbivory
Authors: Agrawal Anurag A.
Published: April 2005

This paper reviews current progress and makes recommendations for future studies of induced plant responses to herbivory in three research areas: the role of induction in structuring herbivore communities, costs associated with the expression of induced responses, and theory and data on the macro‐evolution of induced responses. It is argued that although mechanistic approaches will be important for progress, it is also critical to maintain a holistic approach, including a consideration of field environments, multi‐species interactions, and patterns over ecological and evolutionary time.
RATCHET BONDS: MAXIMUM REFUNDING EFFICIENCY AT MINIMUM TRANSACTION COST
Authors: Kalotay Andrew , Abreo Leslie
Published: April 2005

Callable bonds, which are widely used by corporate borrowers to manage interest rate risk, have several major drawbacks. Foremost is the transaction cost of refunding. In addition, poor execution—calling too early or too late—is common, causing a transfer of wealth from shareholders to bondholders.

The Ratchet bond captures the advantages of a callable bond—the ability to lower interest costs when rates decline—while eliminating its undesirable features. If rates fall after issuance, the coupon of a Ratchet bond automatically resets to the yield of a specified Treasury bond plus some fixed spread. The resulting “step‐down” cash flow pattern resembles that of a sequence of callable bonds that are refunded to the same original maturity date.

The Tennessee Valley Authority was the first to use this innovative structure. In June 1998, they sold $575 million 6.75%“PARRS” with a 30‐year maturity and annual rate resets beginning after five years. Moreover, as this article went to print, TVA announced its intent to sell another large Ratchet issue with features virtually identical to the PARRS described in this article.
THE MARKET'S PRICING OF DEBT IPOs
Authors: Datta Sudip , Iskandar‐Datta Mai , Patel Ajay
Published: April 2005

Based on the authors' recent study published in the Journal of Financial Economics, this article summarizes new evidence on the first‐day and aftermarket price performance of a firm's first public offer of bonds after its equity IPO. Unlike equity IPOs, such bond IPOs are not underpriced on average. However, bonds that are more equity‐like (junk bonds) are underpriced at the initial offer whereas high‐grade debt is actually overpriced. This finding supports the view that riskier debt issues have a larger equity component and, as a consequence, a higher degree of information asymmetry.

The authors' study also showed that less prestigious underwriters are associated with more underpriced offers, and that the issuer's stock market listing plays an important role in determining the first‐day price performance of bond IPOs. The degree of underpricing is lower for bonds issued by firms whose equity is listed on NYSE/AMEX than for bonds issued by firms listed on Nasdaq. Finally, the aftermarket performance for the full sample and various subsamples is consistent with bond market efficiency in the sense that, once prices adjust after the first day of trading, there are no clearly exploitable opportunities for excess returns.
CORPORATE CAPITAL COSTS: A PRACTITIONER'S GUIDE
Authors: Pettit Justin
Published: April 2005

Central to modern finance theory is an understanding of the cost of capital—the minimum required rate of return that is used by companies and investors for both valuation and ongoing performance measurement. This paper provides new insights into the market risk premium for U.S. equities, as well as better methods for measuring and quantifying a company's systematic risk. In so doing, it furnishes evidence that stock market investors now expect a 5% return premium over 30‐year government bonds—a decline from the 6–8% premiums suggested by the Ibbotson‐Sinquefeld data that extends from 1926 to the present. The author argues that, because of structural changes in the global economy and capital markets, only the most recent 40 or 50 years of data are relevant for estimating current risk premiums. Like the article that precedes it, this article also notes that the 30‐year Treasury bond has an increasing component of systematic risk, and the author provides a method of applying the CAPM that removes that risk component from the “risk‐free” rate and shifts it to the market risk premium.
PIV Measurements of Flow in a Centrifugal Blood Pump: Steady Flow
Authors: Day Steven W. , McDaniel James C.
Published: April 2005

Magnetically suspended left ventricular assist devices have only one moving part, the impeller. The impeller has absolutely no contact with any of the fixed parts, thus greatly reducing the regions of stagnant or high shear stress that surround a mechanical or fluid bearing. Measurements of the mean flow patterns as well as viscous and turbulent (Reynolds) stresses were made in a shaft-driven prototype of a magnetically suspended centrifugal blood pump at several constant flow rates (3–9L∕min) using particle image velocimetry (PIV). The chosen range of flow rates is representative of the range over which the pump may operate while implanted. Measurements on a three-dimensional measurement grid within several regions of the pump, including the inlet, blade passage, exit volute, and diffuser are reported. The measurements are used to identify regions of potential blood damage due to high shear stress and∕or stagnation of the blood, both of which have been associated with blood damage within artificial heart valves and diaphragm-type pumps. Levels of turbulence intensity and Reynolds stresses that are comparable to those in artificial heart valves are reported. At the design flow rate (6L∕min), the flow is generally well behaved (no recirculation or stagnant flow) and stress levels are below levels that would be expected to contribute to hemolysis or thrombosis. The flow at both high (9L∕min) and low (3L∕min) flow rates introduces anomalies into the flow, such as recirculation, stagnation, and high stress regions. Levels of viscous and Reynolds shear stresses everywhere within the pump are below reported threshold values for damage to red cells over the entire range of flow rates investigated; however, at both high and low flow rate conditions, the flow field may promote activation of the clotting cascade due to regions of elevated shear stress adjacent to separated or stagnant flow.
Functional Roles of the Leg Muscles When Pedaling in the Recumbent Versus the Upright Position
Authors: Hakansson Nils A. , Hull M. L.
Published: April 2005

An understanding of the coordination of the leg muscles in recumbent pedaling would be useful to the design of rehabilitative pedaling exercises. The objectives of this work were to (i) determine whether patterns of muscle activity while pedaling in the recumbent and upright positions are similar when the different orientation in the gravity field is considered, (ii) compare the functional roles of the leg muscles while pedaling in the recumbent position to the upright position to the upright position and (iii) determine whether leg muscle onset and offset timing for recumbent and upright pedaling respond similarly to changes in pedaling rate. To fulfill these objectives, surface electromyograms were recorded from 10 muscles of 15 subjects who pedaled in both the recumbent and upright positions at 75, 90, and 105rpm and at a constant workrate of 250W. Patterns of muscle activation were compared over the crank cycle. Functional roles of muscles in recumbent and upright pedaling were compared using the percent of integrated activation in crank cycle regions determined previously for upright pedaling. Muscle onset and offset timing were also compared. When the crank cycle was adjusted for orientation in the gravity field, the activation patterns for the two positions were similar. Functional roles of the muscles in the two positions were similar as well. In recumbent pedaling, the uniarticular hip and knee extensors functioned primarily to produce power during the extension region of the crank cycle, whereas the biarticular muscles crossing the hip and knee functioned to propel the leg through the transition regions of the crank cycle. The adaptations of the muscles to changes in pedaling rate were also similar for the two body positions with the uniarticular power producing muscles of the hip and knee advancing their activity to earlier in the crank cycle as the pedaling rate increased. This information on the functional roles of the leg muscles provides a basis by which to form functional groups, such as power-producing muscles and transition muscles, to aid in the development of rehabilitative pedaling exercises and recumbent pedaling simulations to further our understanding of task-dependent muscle coordination.
Mechanics of Curved Plasma Membrane Vesicles: Resting Shapes, Membrane Curvature, and In-Plane Shear Elasticity
Authors: Kosawada Tadashi , Inoue Kohji , Schmid-Schönbein Geert W.
Published: April 2005

Highly curved cell membrane structures, such as plasmalemmal vesicles (caveolae) and clathrin-coated pits, facilitate many cell functions, including the clustering of membrane receptors and transport of specific extracellular macromolecules by endothelial cells. These structures are subject to large mechanical deformations when the plasma membrane is stretched and subject to a change of its curvature. To enhance our understanding of plasmalemmal vesicles we need to improve the understanding of the mechanics in regions of high membrane curvatures. We examine here, theoretically, the shapes of plasmalemmal vesicles assuming that they consist of three membrane domains: an inner domain with high curvature, an outer domain with moderate curvature, and an outermost flat domain, all in the unstressed state. We assume the membrane properties are the same in these domains with membrane bending elasticity as well as in-plane shear elasticity. Special emphasis is placed on the effects of membrane curvature and in-plane shear elasticity on the mechanics of vesicle during unfolding by application of membrane tension. The vesicle shapes were computed by minimization of bending and in-plane shear strain energy. Mechanically stable vesicles were identified with characteristic membrane necks. Upon stretch of the membrane, the vesicle necks disappeared relatively abruptly leading to membrane shapes that consist of curved indentations. While the resting shape of vesicles is predominantly affected by the membrane spontaneous curvatures, the membrane shear elasticity (for a range of values recorded in the red cell membrane) makes a significant contribution as the vesicle is subject to stretch and unfolding. The membrane tension required to unfold the vesicle is sensitive with respect to its shape, especially as the vesicle becomes fully unfolded and approaches a relative flat shape.
Retreating Glacier Fronts on the Antarctic Peninsula over the Past Half-Century
Authors: Cook A. J. , Fox A. J. , Vaughan D. G. , Ferrigno J. G.
Published: April 2005

The continued retreat of ice shelves on the Antarctic Peninsula has been widely attributed to recent atmospheric warming, but there is little published work describing changes in glacier margin positions. We present trends in 244 marine glacier fronts on the peninsula and associated islands over the past 61 years. Of these glaciers, 87% have retreated and a clear boundary between mean advance and retreat has migrated progressively southward. The pattern is broadly compatible with retreat driven by atmospheric warming, but the rapidity of the migration suggests that this may not be the sole driver of glacier retreat in this region.
Modulation of Host Cytoskeleton Function by the Enteropathogenic
Escherichia coli
and
Citrobacter rodentium
Effector Protein EspG
Authors: Hardwidge Philip R. , Deng Wanyin , Vallance Bruce A. , Rodriguez-Escudero Isabel , Cid Victor J. , Molina Maria , Finlay B. Brett
Published: April 2005

EspG is a conserved protein encoded by the locus of enterocyte effacement (LEE) of attaching and effacing (A/E) pathogens, including enteropathogenic and enterohemorrhagic
Escherichia coli
and
Citrobacter rodentium
. EspG is delivered into infected host cells by a type III secretion system. The role of EspG in virulence has not yet been defined. Here we describe experiments that probe the virulence characteristics and biological activities of EspG in vitro and in vivo. A
C. rodentium espG
mutant displayed a significantly reduced ability to colonize C57BL/6 mice and to cause colonic hyperplasia. Epitope-tagged EspG was detected in the apical regions of infected colonic epithelial cells in infected mice, partially localizing with another LEE-encoded effector protein, Tir. EspG was found to interact with mammalian tubulin in both genetic screens and gel overlay assays. Binding to tubulin by EspG caused localized microtubule depolymerization, resulting in actin stress fiber formation through an undefined mechanism. Heterologous expression of EspG in yeast resulted in loss of cytoplasmic microtubule structure and function, preventing coordination between bud development and nuclear division. Yeast expressing EspG were also unable to control cortical actin polarity. We suggest that EspG contributes to the ability of A/E pathogens to establish infection through a modulation of the host cytoskeleton involving transient microtubule destruction and actin polymerization in a manner akin to the
Shigella flexneri
VirA protein.
Pertussis Toxin and Adenylate Cyclase Toxin Provide a One-Two Punch for Establishment of
Bordetella pertussis
Infection of the Respiratory Tract
Authors: Carbonetti Nicholas H. , Artamonova Galina V. , Andreasen Charlotte , Bushar Nicholas
Published: April 2005

Previously we found that pertussis toxin (PT), an exotoxin virulence factor produced by
Bordetella pertussis
, plays an important early role in colonization of the respiratory tract by this pathogen, using a mouse intranasal infection model. In this study, we examined the early role played by another exotoxin produced by this pathogen, adenylate cyclase toxin (ACT). By comparing a wild-type strain to a mutant strain (ΔCYA) with an in-frame deletion of the
cyaA
gene encoding ACT, we found that the lack of ACT confers a significant peak (day 7) colonization defect (1 to 2 log
10
). In mixed-infection experiments, the ΔCYA strain was significantly outcompeted by the wild-type strain, and intranasal administration of purified ACT did not increase colonization by ΔCYA. These data suggest that ACT benefits the bacterial cells that produce it and, unlike PT, does not act as a soluble factor benefiting the entire infecting bacterial population. Comparison of lower respiratory tract infections over the first 4 days after inoculation revealed that the colonization defect of the PT deletion strain was apparent earlier than that of ΔCYA, suggesting that PT plays an earlier role than ACT in the establishment of
B. pertussis
infection. Examination of cells in the bronchoalveolar lavage fluid of infected mice revealed that, unlike PT, ACT does not appear to inhibit neutrophil influx to the respiratory tract early after infection but may combat neutrophil activity once influx has occurred.
Synthesis and Characterization of Lipooligosaccharide-Based Conjugate Vaccines for Serotype B
Moraxella catarrhalis
Authors: Yu Shengqing , Gu Xin-Xing
Published: April 2005

Moraxella catarrhalis
is an important cause of otitis media in children and respiratory tract infections in the elderly. Lipooligosaccharide (LOS) is a major surface antigen of the bacterium that elicits bactericidal antibodies. Serological studies show that three major LOS types (A, B, and C) have been identified among clinical isolates. Our previous studies demonstrated that the type A LOS-based conjugates were immunogenic in animals. In this study, LOS from type B strain 26397 was detoxified and conjugated to tetanus toxoid (TT) or a cross-reactive mutant (CRM) of diphtheria toxin to form detoxified LOS (dLOS)-TT and dLOS-CRM, respectively, as vaccine candidates. The molar ratios of dLOS to TT and CRM in the conjugates were 43:1 and 19:1, respectively, while both weight ratios were around 0.9. The antigenicity of the conjugates was similar to that of the LOS, as determined by enzyme-linked immunosorbent assay using a rabbit antiserum to strain 26397. Subcutaneous immunization with each conjugate elicited a 180- to 230-fold rise of serum anti-LOS immunoglobulin G in mice and >2,000-fold rise in rabbits. In addition, both mouse and rabbit antisera showed elevated complement-mediated bactericidal activity against the homologous strain, and a representative rabbit antiserum showed bactericidal activity against nine of twelve clinical isolates studied. The bactericidal activity of the rabbit antiserum can be fully inhibited by the type B LOS but not the A or C LOS. These results indicate that the type B LOS-based conjugates can be used as vaccine components for further investigation.
Rapid Acquisition of Isolate-Specific Antibodies to Chondroitin Sulfate A-Adherent
Plasmodium falciparum
Isolates in Ghanaian Primigravidae
Authors: Cox Sharon E. , Staalsoe Trine , Arthur Paul , Bulmer Judith N. , Hviid Lars , Yeboah-Antwi Kojo , Kirkwood Betty R. , Riley Eleanor M.
Published: April 2005

Recent evidence suggests that pregnancy-associated malaria (PAM), associated with maternal anemia and low birth weight, results from preferential sequestration of parasitized red blood cells (pRBC) in the placenta via binding of variant surface antigens (VSA) expressed on the surface of pRBC to chondroitin sulfate A (CSA). The VSA mediating CSA binding (VSA
CSA
) and thus sequestration of pRBC in the placenta are antigenically distinct from those that mediate pRBC sequestration elsewhere in the body, and it has been suggested that VSA
CSA
are relatively conserved and may thus constitute an attractive target for vaccination against PAM. Using flow cytometry, levels of antibody to VSA and VSA
CSA
expressed on the surface of red blood cells infected with
Plasmodium falciparum
isolates were measured during pregnancy and lactation in Ghanaian primigravid women enrolled in a trial of maternal vitamin A supplementation. Antibody responses to VSA
CSA
were detected within the first trimester of pregnancy and increased with increasing duration of pregnancy, and they seemed to be isolate specific, indicating that different CSA-adherent parasite lines express antigenically distinct VSA and thus may not be as antigenically conserved as has been previously suggested. Levels of anti-VSA
CSA
were not significantly associated with placental malarial infection determined by histology, indicating that primary immune responses to VSA
CSA
may not be sufficient to eradicate placental parasitemia in primigravidae.
Laccase Expression in Murine Pulmonary
Cryptococcus neoformans
Infection
Authors: Garcia-Rivera Javier , Tucker Stephanie C. , Feldmesser Marta , Williamson Peter R. , Casadevall Arturo
Published: April 2005

Cryptococcus neoformans
laccase expression during murine infection was investigated in lung tissue by immunohistochemistry and immunogold electron microscopy. Laccase was detected in the fungal cell cytoplasm, cell wall, and capsule in vivo. The amount of laccase found in different sites varied as a function of the time of infection.
Surface Analyses and Immune Reactivities of Major Cell Wall-Associated Proteins of Group A Streptococcus
Authors: Cole Jason N. , Ramirez Ruben D. , Currie Bart J. , Cordwell Stuart J. , Djordjevic Steven P. , Walker Mark J.
Published: April 2005

A proteomic analysis was undertaken to identify cell wall-associated proteins of
Streptococcus pyogenes
. Seventy-four distinct cell wall-associated proteins were identified, 66 of which were novel. Thirty-three proteins were immunoreactive with pooled
S. pyogenes
-reactive human antisera. Biotinylation of the GAS cell surface identified 23 cell wall-associated proteins that are surface exposed.
Regulation of the Mitogen-Activated Protein Kinases byBrucellaspp. Expressing a Smooth and Rough Phenotype: Relationship to Pathogen Invasiveness
Authors: Jiménez de Bagüés María P. , Gross Antoine , Terraza Annie , Dornand Jacques
Published: April 2005

By comparing smooth wild-typeBrucellaspp. to their rough mutants, we show that the LPS O chain restricted the activation of the ERK1/2 and p38 mitogen-activated protein kinase (MAPK) pathways, thus preventing the synthesis of immune mediators that regulate host defense. We conclude that the MAPKs are a target for immune intervention by virulent smoothBrucella.
The Purinergic P2X7 Receptor Is Not Required for Control of Pulmonary
Mycobacterium tuberculosis
Infection
Authors: Myers Amy J. , Eilertson Brandon , Fulton Scott A. , Flynn JoAnne L. , Canaday David H.
Published: April 2005

The importance in vivo of P2X7 receptors in control of virulent
Mycobacterium tuberculosis
was examined in a low-dose aerosol infection mouse model. P2X7
−/−
mice controlled infection in lungs as well as wild-type mice, suggesting that the P2X7 receptor is not required for control of pulmonary
M. tuberculosis
infection.
Recent Advances in Chemistry and Applications of Substituted Poly(ethylene glycol)s
Authors: Sedlák Miloš
Published: April 2005

Poly(ethylene glycol)s are well defined and easily accessible macromolecules with suitable properties for applications in chemistry, biotechnologies and medicine. The terminal hydroxy groups of poly(ethylene glycol)s can easily be converted into reactive functional groups by a number of routine reactions of organic chemistry. The chemical reagents or catalysts anchored to poly(ethylene glycol) chains were used in a number of syntheses including the enantioselective ones. Poly(ethylene glycol)s serve as carriers in combinatorial syntheses in the liquid phase. Coupling of poly(ethylene glycol)s with other polymers was used to prepare series of block copolymers having numerous applications. From the point of view of medical applications it is significant that substituted poly(ethylene glycol)s are non-toxic and resistant to recognition by the immunity system. That is why they are often used as carriers of many low-molecular-weight as well as high-molecular-weight medical drugs (drug delivery systems). In the conjugates with drugs their biological activity increases and their toxicity decreases. A review with 41 references.
Novel Method for Preparation of Highly Substituted 6-Arylpurines by Reactions of 6-Alkynylpurines with Zirconacyclopentadienes
Authors: Turek Pavel , Kotora Martin , Hocek Michal , Votruba Ivan
Published: April 2005

Reactions of various zirconacyclopentadienes bearing alkyl and aryl groups with 6-alkynylpurines in the presence of NiBr2(PPh3)2 afforded the corresponding 6-arylpurines with highly hydrophobic aryl moieties in low to moderate yields. Some of the title purines showed interesting cytostatic activity.
P-Chiral 2-{1'-[Butyl(phenyl)phosphanyl]ferrocen-1-yl}-4-isopropyl-4,5-dihydrooxazoles: A Second Chirality Center in Catalytic System
Authors: Drahoňovský Dušan , Štěpnička Petr , Dvořák Dalimil
Published: April 2005

P-Chiral (S,RP)-2-{1'-[butyl(phenyl)phosphanyl]ferrocen-1-yl}-4-isopropyl-4,5-dihydrooxazole (6) and (S,SP)-2-{1'-[butyl(phenyl)phosphanyl]ferrocen-1-yl}-4-isopropyl-4,5-dihydrooxazole (7) were prepared by the procedure developed by Jugé, starting from enantiomerically pure (-)- or (+)-ephedrine and dichloro(phenyl)phosphine. Compounds 6 and 7 were examined for asymmetric induction in the Pd-catalyzed reaction of rac-1,3-diphenylallyl acetate with dimethyl malonate. The best results were obtained with 7 (98% ee), while 6 gave 82% ee.
Interaction of Polar Groups with a Bulky Hydrocarbon Residue: Polarizability and Steric Effects
Authors: Böhm Stanislav , Exner Otto
Published: April 2005

Energies of two series of branched hydrocarbon monosubstituted derivatives, 2-substituted 2-methylpropanes and 1-substituted bicyclo[2.2.2]octanes with 19 different substituents were calculated at the B3LYP/6-311+G(d,p) level and compared with the energies of straight-chain 1-substituted butanes. The comparison was carried out in terms of isodesmic homodesmotic reactions, in which the substituent is transferred from one hydrocarbon residue to another. The branched derivatives are mostly stabilized, in the extreme case by as much as 30 kJ mol-1 confirming that the additive rule used for estimating the enthalpies of formation is not valid for branched derivatives. The stabilization energies ∆E for the individual substituents X are not proportional to any known substituent parameters. In the qualitative respect, they are controlled by the first atom of the substituent - similarly as in the straight-chain isomers - but in the case of sterically demanding substituents they are perturbed by a destabilizing steric effect.
Geochemistry of metasedimentary rocks of the Proterozoic Xingxingxia complex: implications for provenance and tectonic setting of the eastern segment of the Central Tianshan Tectonic Zone, northwestern China
Authors: Li Qiugen , Liu Shuwen , Han Baofu , Zhang Jian , Chu Zhuyin
Published: April 2005

The eastern segment of the Central Tianshan Tectonic Zone in northwestern China includes the Proterozoic metasedimentary Xingxingxia complex. Because these rocks have been extensively deformed and metamorphosed to greenschist or amphibolite facies, a geochemical and Nd isotopic study was undertaken to constrain their provenance and tectonic setting, as well as to evaluate the effects of weathering and sedimentary processes on the source rock signature. Major- and trace-element data indicate that these samples are characterized by negative Eu anomalies, low chemical index of alteration values, and high index of compositional variability values. Chemical index of alteration values and the plot of molecular proportions Al2O3(CaO* + Na2O)K2O suggest low degrees of weathering of the source. They are compositionally immature and poorly sorted. Geochemical data and immobile elemental ratios, for example Al2O3/TiO2, Cr/Th, Eu/Eu* and (La/Yb)n, indicate that the clastic materials were derived predominantly from felsic sources. Sedimentary tectonic discrimination diagrams demonstrate that most of the samples of the Xingxingxia complex were deposited on an active continental margin or continental island-arc setting. Rare-earth element distributions, εNd(t) values (calculated at 1.20 Ga, varying from 3.00 to +6.1), TDM model ages (ranging from 1.30 to 2.30), and t  εNd(t) plot, indicate that sediments of the Proterozoic Xingxingxia complex were derived from varying degrees of mixing between Paleoproterozoic crust and juvenile materials with the former predominating. There is an increased flux of juvenile materials from Weiya in the east through Dikar to Kumishi. The secondary juvenile source may be 1.2 Ga arc-magma materials.
Physical fluxes, pelagic ecosystem structure, and larval fish survival in Hauraki Gulf, New Zealand
Authors: Zeldis John R , Oldman John , Ballara Sira L , Richards Laura A
Published: April 2005

The ecosystem supporting snapper (Pagrus auratus) larvae was studied during three springsummer (NovemberJanuary 19851988) spawning seasons in Hauraki Gulf, New Zealand. Upwelling-favourable winds caused more incursion of shelf water into the Gulf in 19851986 and 19861987 than in 19871988, but in the first two seasons, the winds were relatively weak. Stronger winds in 19871988 drove greater vertical diffusivity and correlated with greater mixed-layer primary biomass and productivity. Effects of vertical mixing appeared to dominate horizontal incursion of upwelled shelf water in supporting upper water column productivity. The more productive 19871988 season had greater abundances of nauplii, copepodites, adult copepods, cladocerans, chaetognaths, hydromedusae, decapod larvae, and numerous larval fish taxa (including snapper). There was much higher survival of snapper between the late-stage egg and post-first-feeding larval stages in 19871988, which correlated spatially and temporally with high larval prey densities. Neither higher egg production, fewer predators, nor less horizontal advection accounted for these strong larval snapper cohorts. We hypothesize that larval competence improved within the superior larval feeding environment, reducing predatory losses. The ecosystem response to wind mixing may partially explain the correlation of sea temperatures with recruitment, previously observed for the Hauraki Gulf snapper stock.
Is metabolic rate a reliable predictor of growth and survival of brown trout (Salmo trutta) in the wild?
Authors: Álvarez D , Nicieza A G
Published: April 2005

In salmonids, there seems to be a positive correlation between standard metabolic rate and growth rate under artificial rearing conditions. Several recent studies have suggested that phenotypic correlations between physiological or behavioural traits and developmental or life history responses might be common when assayed in low-complexity habitats but rare in those with a high degree of spatiotemporal complexity. This study provides the first test of the connection between metabolic and growth rates of juvenile brown trout (Salmo trutta) in natural streams. In two out of four streams, there was no relationship between metabolic rates and subsequent growth, whereas in the two others, growth and metabolic rates were negatively correlated. Furthermore, survival rates were either unaffected or negatively correlated with metabolic rates. These results reveal complex relationships between metabolic rate, growth, and environmental variability and suggest that (i) in the wild, negative selection on high metabolic rates may result from both juvenile mortality and reduced growth rates, (ii) the conclusions derived from laboratory experiments are not directly applicable to natural populations, and (iii) the correlations between metabolic rate and growth can prove useful after selection of the appropriate spatial and temporal scales.
Habitat-specific biomass, survival, and growth of rainbow trout (Oncorhynchus mykiss) during summer in a small coastal stream
Authors: Harvey Bret C , White Jason L , Nakamoto Rodney J
Published: April 2005

We observed significant habitat-scale variation in the density, survival, and growth of 811 passive integrated transponder tagged rainbow trout (Oncorhynchus mykiss) enclosed for 6368 days at natural density in 59 individual habitats (pools and riffles) in a small coastal California stream in summer 2001. The initial habitat-scale densities of trout were positively related to both depth and cover, although by the end of the experiment, the influence of cover on density was less apparent. Survival varied substantially, but with no clear relationship to any of the physical factors that we measured. Mean growth was density dependent, positively influenced by habitat depth, and also increased downstream within the 2-km study reach. The overall change in trout biomass over the experiment was also negatively related to fish density and positively influenced by habitat depth. Individual growth within habitats appeared to be unrelated to body size. The positive influences of water depth and distance downstream on trout growth in this experiment suggest that management actions that increase dry season discharge and limit aggradation will benefit salmonids in small streams.
Thermal histories, stress, and metabolic rates of chinook salmon (Oncorhynchus tshawytscha) in Lake Ontario: evidence from intra-otolith stable isotope analyses
Authors: Wurster C M , Patterson W P , Stewart D J , Bowlby J N , Stewart T J
Published: April 2005

We describe thermal histories for Lake Ontario chinook salmon (Oncorhynchus tshawytscha) as determined from otolith δ18O thermometry using computer-controlled micromilling techniques to recover otolith aragonite at subseasonal resolution. We find that during the summer months chinook salmon inhabited epilimnetic waters with temperatures of ~1920 °C as far back as the late 1980s. Chinook would approach but rarely exceed their reported upper incipient lethal limit of approximately 22 °C, which suggests that these fish were seeking water with temperatures as high as was tolerable while otolith growth occurred. These results contrast with expected midsummer temperatures for this cold-water salmonine. Bioenergetic simulations indicate significant stress imposed upon chinook salmon. We estimate consumption to be up to 20% more and gross conversion efficiency 18% less annually relative to nominal simulations where chinook salmon are modeled nearer their preferred temperature, reinforcing previous inferences that the chinook salmon population may be near the limits of sustainability. We also find a strong negative correlation between δ18O and δ13C values. Therefore, seasonal and ontogenetic variation in δ13C values of chinook salmon otoliths appear to be related to metabolic rate during pelagic residence and may provide an indirect method for evaluating field activity and other aspects of fish life history.
Biological control of collar rot disease with broad-spectrum antifungal bacteria associated with groundnut
Authors: Kishore G Krishna , Pande S , Podile A R
Published: April 2005

Bacteria associated with 6 habitats of groundnut were evaluated for their broad-spectrum antifungal activity and suppression of collar rot (Aspergillus niger) of groundnut. Three hundred and ninety-three strains were tested against 8 fungal pathogens of groundnut including 5 necrotrophic fungi, Aspergillus flavus, A. niger, Rhizoctonia bataticola, Rhizoctonia solani, and Sclerotium rolfsii, and 3 biotrophic fungi, Cercospora arachidicola, Phaeoisariopsis personata, and Puccinia arachidis. Pseudomonas sp. GRS 175, Pseudomonas aeruginosa GPS 21, GSE 18, GSE 19, and GSE 30, and their cell-free culture filtrates were highly antagonistic to all the test fungi. The cell-free culture filtrates of these bacteria were fungicidal and induced mycelial deformations including hyphal bulging and vacuolization in necrotrophic fungi. The cell-free culture filtrates at 10% (v/v) concentration significantly inhibited the spore germination of biotrophic fungi. In the greenhouse, P. aeruginosa GSE 18 emerged as an effective biocontrol agent of collar rot closely followed by P. aeruginosa GSE 19. The bacterium applied as a seed treatment reduced the pre-emergence rotting and postemergence wilting by >60%. Pseudomonas aeruginosa GSE 18 effectively colonized the groundnut rhizosphere, both in native and in A. niger infested potting mixtures. Ninety-day-old peat formulation of P. aeruginosa GSE 18 had biocontrol ability comparable with the midlog-phase cells. Pseudomonas aeruginosa GSE 18, tolerant to thiram, in combination with the fungicide had an improved collar rot control. The present study was a successful attempt in selection of broad-spectrum and fungicide tolerant biocontrol agents that can be a useful component of integrated management of collar rot.Key words: Arachis, biocontrol, crown rot, peanut.
Expression of thecry11Agene ofBacillus thuringiensisssp.israelensisinSaccharomyces cerevisiae
Authors: Quintana-Castro Rodolfo , Ramírez-Suero Montserrat , Moreno-Sanz Fernando , Ramírez-Lepe Mario
Published: April 2005

The complete cry11A region gene of Bacillus thuringiensis ssp. israelensis was fused in frame to the 3' end of the GST gene under the control of the Saccharomyces cerevisiae HXK1 promoter. The fusion protein GST-cry11A was expressed in S. cerevisiae strain AMW13C+. The fusion gene GST-cry11A was expressed when yeast cells were grown on galactose and a nonfermentable medium containing ethanol as carbon and energy source. When the cells were grown in glucose, mannose, fructose, or glycerol as carbon sources, the GST-cry11A gene was repressed. Thus, a regulated expression in accordance with the regulatory activity of the HXK1 gene promoter has been detected. The GST-cry11A fusion protein was detected in the transformed yeasts as a soluble protein. The fusion protein was purified by affinity chromatography using glutathione–Sepharose beads. Cell-free extracts from transformed yeasts grown in ethanol-containing culture media showed insecticidal activity against third-instar Aedes aegypti larvae. This insecticidal activity was increased about 4-fold when the purified fusion protein was assayed.Key words: cry11A, Bacillus thuringiensis, HXK1, Saccharomyces cerevisiae.
The morphology, behavior, and biomechanics of swimming in ascidian larvae
Authors: McHenry Matthew J
Published: April 2005

Ascidian larvae use a simple set of locomotor behaviors during dispersal and settlement. The swimming performance and the ability of an ascidian larva to orient within its environment depend on the biomechanics of its rudimentary locomotor morphology. The undulatory motion of the tail generates fluid forces that propel the body with a rate and direction determined by body mass and its spatial distribution. Differences in morphology and behavior among species influence these dynamics and create differences in swimming performance. Furthermore, the ability of a larva to orient within its environment depends on its ability to coordinate the motion of its body with respect to perceived sensory cues. Research on the swimming of ascidian larvae demonstrates the biomechanical basis of tactic orientation and interspecific differences in performance in a large and diverse group of animals.
Protochordate body plan and the evolutionary role of larvae: old controversies resolved?
Authors: Lacalli Thurston C
Published: April 2005

Motile larvae figure prominently in a number of past scenarios for chordate and vertebrate origins, notably in the writings of Garstang, Berrill, and Romer. All three focus on the motile larva of a primitively sessile tunicate ancestor as a vertebrate progenitor; Garstang went further in deriving chordates themselves by neoteny from a yet more ancient larva of the dipleurula type. Yet the molecular evidence currently available shows convincingly that the part of the tunicate larva that persists to the adult expresses only a subset of the genes required to specify a complete bilaterian body axis, and essentially the same appears to be true of dipleurula larvae. Specifically, both are essentially heads without trunks. Hence, both are highly derived and as such are probably poor models for any real ancestor. A more convincing case can be made for a sequence of ancestral forms that throughout their evolution were active, motile organisms expressing a full complement of axial patterning genes. This implies a basal, ancestral form resembling modern enteropneusts, although a pelagic organism at a hemichordate level of complexity is also possible. A reassessment is thus required of the role played by adult and larval tunicates, and of larvae more generally, in chordate evolution. Tunicates need to be interpreted with caution, since the extreme degree of modification in the adult may have been accompanied by reductions to the larva. Dipleurula larvae may retain some ancestral features (e.g., of apical, oral, and anal organization), but are otherwise probably too specialized to be central players in chordate evolution. Garstang nevertheless remains a key figure in the history of evolutionary thought for his innovative ideas on the relation between ontogeny and phylogeny, and the way in which major innovations in morphology and body plan arise.
The nervous system of amphioxus: structure, development, and evolutionary significance
Authors: Wicht Helmut , Lacalli Thurston C
Published: April 2005

Amphioxus neuroanatomy is important not just in its own right but also for the insights it provides regarding the evolutionary origin and basic organization of the vertebrate nervous system. This review summarizes the overall layout of the central nervous system (CNS), peripheral nerves, and nerve plexuses in amphioxus, and what is currently known of their histology and cell types, with special attention to new information on the anterior nerve cord. The intercalated region (IR) is of special functional and evolutionary interest. It extends caudally to the end of somite 4, traditionally considered the limit of the brain-like region of the amphioxus CNS, and is notable for the presence of a number of migrated cell groups. Unlike most other neurons in the cord, these migrated cells detach from the ventricular lumen and move into the adjacent neuropile, much as developing neurons do in vertebrates. The larval nervous system is also considered, as there is a wealth of new data on the organization and cell types of the anterior nerve cord in young larvae, based on detailed electron microscopical analyses and nerve tracing studies, and an emerging consensus regarding how this region relates to the vertebrate brain. Much less is known about the intervening period of the life history, i.e., the period between the young larva and the adult, but a great deal of neural development must occur during this time to generate a fully mature nervous system. It is especially interesting that the vertebrate counterparts of at least some postembryonic events of amphioxus neurogenesis occur, in vertebrates, in the embryo. The implication is that the whole of the postembryonic phase of neural development in amphioxus needs to be considered when making phylogenetic comparisons. Yet this is a period about which almost nothing is known. Considering this, plus the number of new molecular and immunocytochemical techniques now available to researchers, there is no shortage of worthwhile research topics using amphioxus, of whatever stage, as a subject.