bluuebunny/crossref_metadata_2025 huggingface dataset:
Family History: An Essential Tool for Cardiovascular Genetic Medicine
Authors: Morales Ana , Cowan Jason , Dagua Jimena , Hershberger Ray E.
Published: May 2008

We are pleased to provide a new section devoted to topics in cardiovascular genetic medicine. An emerging field, cardiovascular genetic medicine is devoted to the identification and understanding of cardiac conditions resulting from genetic mechanisms and to the development and validation of treatment algorithms and guidelines. Cardiovascular genetic medicine is rapidly enlarging, and we anticipate a broad range of comprehensive reviews. We will first focus on the most tractable diagnoses to apply the principles of cardiovascular genetic medicine: the cardiomyopathies such as dilated, hypertrophic, arrhythmogenic right ventricular dysplasia/cardiomyopathy and the channelopathies such as long QT syndrome and related disorders. These conditions follow classical or Mendelian genetics, otherwise known as the single gene disorders. As greater numbers of disease genes and their specific mutations are identified, and as large clinical cohorts of affected probands and their at‐risk family members become available for study, clinical recommendations, and then guidelines, will follow. Progress is also evident for those conditions considered to be complex or multigenic diseases, such as coronary disease and hypertension, which affect large segments of the population. Risk alleles are now being identified that may rapidly lead to genetic testing to assess risk for these conditions. Cardiovascular genetic medicine must also be responsive to public concerns regarding confidentiality, and it must also demonstrate clinical integrity and utility for genetic testing. Our first topic features the role of family history in cardiovascular genetic medicine. Assisted by my clinical and research group—genetic counselors and nursing personnel devoted to the field—we have provided a glossary with explanations of genetic terminology, as illustrated in this first article, and will continue to do so for the series. We will prepare additional topics and others will be solicited from experts in the field. I also invite any potential contributors to propose and submit topics that are both of interest to you and relevant to the field. Please also give us your feedback, especially to improve the clarity, diversity, and timeliness of the genetic concepts presented. So, away we go.—Ray E. Hershberger, MD, Section Editor
An Experimental Investigation of Spur Gear Efficiency
Authors: Petry-Johnson T. T. , Kahraman A. , Anderson N. E. , Chase D. R.
Published: May 2008

In this study, a test methodology was developed for the measurement of spur gear efficiency under high-speed and variable torque conditions. A power-circulating test machine was designed to operate at speeds to 10,000rpm and transmitted power levels to 700kW. A precision torque measurement system was implemented, and its accuracy and repeatability in measuring torque loss in the power loop was demonstrated. Tests were conducted on gears with two values of modules and two surface roughness levels, operating in a dry sump jet-lubrication environment with three different gear lubricants. These tests were used to quantify the influence of these parameters on both load-dependent (mechanical), load-independent (spin), and total power loss. Trends in mechanical gear mesh efficiency and total gearbox efficiency were discussed in terms of rotational speed and transmitted torque. Finally, recommendations were made for the design of spur gear pairs, surface roughness, and lubricant selection for improved efficiency.
Rational Motion Interpolation Under Kinematic Constraints of Spherical 6R Closed Chains
Authors: Purwar Anurag , Jin Zhe , Ge Q. J.
Published: May 2008

The work reported in this paper brings together the kinematics of spherical closed chains and the recently developed free-form rational motions to study the problem of synthesizing rational interpolating motions under the kinematic constraints of spherical 6R closed chains. The results presented in this paper are an extension of our previous work on the synthesis of piecewise rational spherical motions for spherical open chains. The kinematic constraints under consideration are workspace related constraints that limit the position of the links of spherical closed chains in the Cartesian space. Quaternions are used to represent spherical displacements. The problem of synthesizing smooth piecewise rational motions is converted into that of designing smooth piecewise rational curves in the space of quaternions. The kinematic constraints are transformed into geometric constraints for the design of quaternion curves. An iterative algorithm for constrained motion interpolation is presented. It detects the violation of the kinematic constraints by searching for those extreme points of the quaternion curve that do not satisfy the constraints. Such extreme points are modified so that the constraints are satisfied, and the resulting new points are added to the ordered set of the initial positions to be interpolated. An example is presented to show how this algorithm produces smooth spherical rational spline motions that satisfy the kinematic constraints of a spherical 6R closed chain. The algorithm can also be used for the synthesis of rational interpolating motions that approximate the kinematic constraints of spherical 5R and 4R closed chains within a user-defined tolerance.
A Family of Kinematically Redundant Planar Parallel Manipulators
Authors: Ebrahimi Iman , Carretero Juan A. , Boudreau Roger
Published: May 2008

Parallel manipulators feature relatively high payload and accuracy capabilities compared to their serial counterparts. However, they suffer from small workspace and low maneuverability. Kinematic redundancy for parallel manipulators can improve both of these characteristics. This paper presents a family of new kinematically redundant planar parallel manipulators with six actuated-joint degrees of freedom based on a 3-PṞRR architecture obtained by adding an active prismatic joint at the base of each limb of the 3-ṞRR manipulator. First, the inverse displacement of the manipulators is explained, then their reachable and dexterous workspaces are obtained. Comparing the proposed redundant manipulators to the original 3-ṞRR nonredundant manipulator, both reachable and dexterous workspaces are substantially larger. Next, the Jacobian matrices of the manipulators are derived, and different types of singularities are analyzed and demonstrated. It is shown that the vast majority of singularities can be avoided by using kinematic redundancy.
Risk-Based Resource Allocation for Collaborative System Design in a Distributed Environment
Authors: Qiu Yuming , Ge Ping , Yim Solomon C.
Published: May 2008

Risk analysis is important in system design because of its essential role in evaluating functional reliability and mitigating system failures. In this work, we aim at expanding existing risk modeling methods to collaborative system designs: specifically, to facilitate resource allocation among distributed stakeholders. Because of different perspectives and limited local information, inconsistent and/or incoherent risk assessments (such as different probability and confusing consequence evaluations) may occur among stakeholders, who are responsible for same or different risk components of a system. The discrepancies can become potential barriers in achieving consensus or acceptable disagreement for distributed resource allocation. Built upon our previous work, a risk-based distributed resource allocation methodology (R-DRAM) is developed to help a system manager allocate limited resources among collaborating stakeholders based on a cost-benefit measure of risk. Besides probability and consequence, two additional risk aspects, tolerance and hierarchy, are considered for system risk modeling in a collaborative/distributed environment. Given a total amount of resources to be allocated, the four risk aspects are combined to form the cost-benefit measure in a multiobjective optimization framework for achieving a desired risk reduction of a targeted system. An example is used to demonstrate the implementation process of the methodology. The preliminary investigation shows promise of the R-DRAM as a systematic and quantifiable approach in facilitating distributed resource allocation for collaborative system design.
A Geometric Design Model for the Circolimaçon Positive Displacement Machine
Authors: Sultan Ibrahim A.
Published: May 2008

A circolimaçon positive displacement machine is driven by a limaçon mechanism, but the profiles of its rotor and housing are circular arcs. As such, its design models are different from those of the limaçon-to-limaçon machines, whose profiles are cut to the limaçon equations. For the benefit of the reader, the paper starts with a brief background on the general geometric aspects of the limaçon fluid processing technology. However, the focus is then turned to the circolimaçon machine, where its design parameters are introduced and geometric models are proposed to assist with the design process. Also, a computational inverse design model has been employed to work out a set of congruent geometric parameters to meet certain design requirements. Case studies are presented at the end of the paper to give the reader a numerical perspective on the design process of this class of positive displacement machines.
Synthesis of Rectilinear Motion Generating Spatial Mechanism With Application to Automotive Suspension
Authors: Zhao Jing-Shan , Chu Fulei , Feng Zhi-Jing
Published: May 2008

This paper proposes a synthesis method for rectilinear motion generating spatial mechanism with application to automotive suspension. First, it presents a generic process to synthesize the kinematic chains of a mechanism with the prescribed mobility, and then it deduces the construction criteria of feasible kinematic chains for such a mechanism. The most outstanding advantages of the rectilinear motion generating spatial mechanism used as the independent automotive suspension are that the orientation and position parameters such as kingpin, caster, camber, axis distance, and wheel track are always maintained constant during jounce and rebound. These ideal characteristics are guaranteed by the particular rigid guidance mechanism whose end effector only has one translation along an exact straight line.
Geometric Modeling and Optimization of Multimaterial Compliant Mechanisms Using Multilayer Wide Curves
Authors: Zhou Hong , Ting Kwun-Lon
Published: May 2008

Multimaterial compliant mechanisms enhance the performance of regular single-material compliant mechanisms by adding a new design option, material type variation. This paper introduces a geometric modeling method for multimaterial compliant mechanisms by using multilayer wide curves. Based on the introduced modeling method, a geometric optimization approach for multimaterial compliant mechanisms is proposed. A multilayer wide curve is a curve with variable cross sections and multiple materials. In this paper, every connection in the multimaterial compliant mechanism is represented by a multilayer wide curve, and the whole mechanism is modeled as a set of connected multilayer wide curves. The geometric modeling and the optimization of a multimaterial compliant mechanism are considered as the generation and the optimal selection of the control parameters of the corresponding multilayer wide curves. The deformation and performance of multimaterial compliant mechanisms are evaluated by the isoparametric degenerate-continuum nonlinear finite element procedure. The problem-dependent objectives are optimized, and the practical constraints are imposed during the optimization process. The effectiveness of the proposed geometric modeling and optimization procedures is verified by the demonstrated examples.
Establishment of a Cell-Based Assay for Screening of Compounds Inhibiting Very Early Events in the Cytomegalovirus Replication Cycle and Characterization of a Compound Identified Using the Assay
Authors: Fukui Yoshiko , Shindoh Keiko , Yamamoto Yumiko , Koyano Shin , Kosugi Isao , Yamaguchi Toyofumi , Kurane Ichiro , Inoue Naoki
Published: May 2008

To simplify the detection of infectious human cytomegalovirus (HCMV), we generated a cell line that produced luciferase in a dose-dependent manner upon HCMV infection. Using this cell line, we identified anti-HCMV compounds from a diverse library of 9,600 compounds. One of them, 1-(3,5-dichloro-4-pyridyl)piperidine-4-carboxamide (DPPC), was effective against HCMV (Towne strain) infection of human lung fibroblast cells at a 50% effective concentration of 2.5 μM. DPPC also inhibited the growth of clinical HCMV isolates and guinea pig and mouse cytomegaloviruses. Experiments using various time frames for treatment of the cells with DPPC demonstrated that DPPC was effective during the first 24 h after HCMV infection. DPPC treatment decreased not only viral DNA replication but also IE1 and IE2 expression at mRNA and protein levels in the HCMV-infected cells. However, DPPC did not inhibit the attachment of HCMV particles to the cell surface. DPPC is a unique compound that targets the very early phase of cytomegalovirus infection, probably by disrupting a pathway that is important after viral entry but before immediate-early gene expression.
Reduced Tissue Parasitic Load and Infectivity to Sand Flies in Dogs Naturally Infected byLeishmania(Leishmania)chagasifollowing Treatment with a Liposome Formulation of Meglumine Antimoniate
Authors: Ribeiro Raul R. , Moura Eliane P. , Pimentel Vitor M. , Sampaio Weverton M. , Silva Sydnei M. , Schettini Dante A. , Alves Cintia F. , Melo Ferdinan A. , Tafuri Wagner L. , Demicheli Cynthia , Melo Maria N. , Frézard Frédéric , Michalick Marilene S. M.
Published: May 2008

The toxicity and antileishmanial effectiveness of a novel liposome formulation of meglumine antimoniate in mongrel dogs with visceral leishmaniasis (VL) obtained from a region where VL is endemic in Brazil have been investigated. Groups of 12 animals received by the intravenous route four doses (with 4-day intervals) of either liposomal meglumine antimoniate (group I [GI], 6.5 mg Sb/kg of body weight/dose), empty liposomes (GII), or isotonic saline (GIII). Evaluation of markers of hematopoietic, hepatic, and renal functions before and just after treatment showed no significant change. On the other hand, transitory adverse reactions, including prostration, defecation, tachypnea, and sialorrhea, were observed during the first 15 min after injections in GI and GII. Parasitological evaluation of sternal bone marrow 4 days after the last dose showed a significant reduction of parasite burden in GI, compared to the other groups. Immunocytochemical evaluations of the skin, bone marrow, cervical lymph nodes, livers, and spleens of dogs for parasites, 150 days after treatment, indicated significant parasite suppression (higher than 95.7%) in the lymph nodes, livers, and spleens of GI, compared to control groups. Feeding ofLutzomyia longipalpisphlebotomines on dogs from GI, 150 days after treatment, resulted in a significant reduction of sand fly infection efficiency, compared to feeding on animals from GII and GIII. This is the first report of both long-term parasite suppression and reduction of infectivity to sand flies in naturally infected dogs following treatment with a liposome-encapsulated drug. Importantly, this was achieved using a 20-fold-lower cumulative dose of Sb than is used for conventional antimonial treatment.
Identification of a Novel Multidrug Efflux Pump of
Mycobacterium tuberculosis
Authors: Danilchanka Olga , Mailaender Claudia , Niederweis Michael
Published: May 2008

The impermeability of the outer membrane in combination with drug efflux are major determinants of the natural drug resistance of mycobacteria. β-Lactams are the most widely used antibiotics for treatment of bacterial infections. However, it is unknown how β-lactams enter
Mycobacterium tuberculosis
and whether efflux pumps exist that can export these drugs out of the cell. To identify the molecular mechanisms of
M. tuberculosis
resistance to β-lactams, a library of 7,500 transposon mutants was generated in the model organism
Mycobacterium bovis
BCG. Thirty-three unique insertion sites were determined that conferred medium or high-level (≥2,000 μg/ml) resistance to ampicillin. Three mutants in sulfolipid synthesis or transport were highly resistant to ampicillin, indicating an indirect effect of the lipid composition on the outer membrane permeability of
M. bovis
BCG to ampicillin. Mutants with insertions in genes encoding surface molecules such as PPE proteins or lipoarabinomannan were also completely resistant to ampicillin, thus suggesting a lack of transport across the outer membrane. Insertion of the transposon in front of
bcg0231
increased transcription of the gene and concomitantly the resistance of
M. bovis
BCG to ampicillin, streptomycin, and chloramphenicol by 32- to 64-fold. Resistance to vancomycin and tetracycline was increased four- to eightfold. Bcg0231 and Rv0194 are almost identical ATP-binding cassette transporters. Expression of
rv0194
significantly reduced accumulation of ethidium bromide and conferred multidrug resistance to
Mycobacterium smegmatis
. Both effects were abrogated in the presence of the efflux pump inhibitor reserpine. These results demonstrate that Rv0194 is a novel multidrug efflux pump of
M. tuberculosis
.
In Vivo Pharmacodynamic Profiling of Doripenem againstPseudomonas aeruginosaby Simulating Human Exposures
Authors: Kim Aryun , Banevicius Mary Anne , Nicolau David P.
Published: May 2008

Doripenem is a new broad-spectrum carbapenem with activity against a range of gram-negative pathogens, including nonfermenting bacteria such asPseudomonas aeruginosa. The objective of this study was to evaluate simulated human exposures to doripenem using a neutropenic murine thigh infection model against 24 clinicalP. aeruginosaisolates with a wide range of MICs. Dosing regimens in mice were designed to approximate the free time above MIC (fT>MIC) observed with 500 mg doripenem every 8 h given as either a 1-h or 4-h intravenous infusion in humans. Maximal antibacterial killing was associated with doripenem exposures of ≥40%fT>MIC; bacteriostatic effects were noted at ≈20%fT>MIC. The simulated 1-h infusion provided bactericidal effects for isolates with MICs of ≤2 μg/ml, while variable killing was noted for isolates with MICs of 4 to 8 μg/ml and regrowth for isolates with an MIC of 16 μg/ml. The 4-h infusion regimen displayed similar killing for isolates with MICs of ≤2 μg/ml and enhanced activity for two of the four isolates with an MIC of 4 μg/ml. Given that the 4-h regimen yields negligiblefT>MIC for MICs of ≥8 μg/ml, regrowth was generally observed. Simulated doses of 500 mg doripenem every 8 h infused over 1 h demonstrated antibacterial killing forP. aeruginosaisolates with MICs of 0.125 to 8 μg/ml. Exposures of ≥40%fT>MIC resulted in the most pronounced bactericidal effects, while killing was variable for 20 to 30%fT>MIC. Infusing doses over 4 h enhanced efficacy against selected pseudomonal isolates with an MIC of 4 μg/ml.
Impact of the RNA Chaperone Hfq on the Fitness and Virulence Potential of Uropathogenic
Escherichia coli
Authors: Kulesus Richard R. , Diaz-Perez Karen , Slechta E. Susan , Eto Danelle S. , Mulvey Matthew A.
Published: May 2008

Hfq is a bacterial RNA chaperone involved in the posttranscriptional regulation of many stress-inducible genes via small noncoding RNAs. Here, we show that Hfq is critical for the uropathogenic
Escherichia coli
(UPEC) isolate UTI89 to effectively colonize the bladder and kidneys in a murine urinary tract infection model system. The disruption of
hfq
did not affect bacterial adherence to or invasion of host cells but did limit the development of intracellular microcolonies by UTI89 within the terminally differentiated epithelial cells that line the lumen of the bladder. In vitro, the
hfq
mutant was significantly impaired in its abilities to handle the antibacterial cationic peptide polymyxin B and reactive nitrogen and oxygen radicals and to grow in acidic medium (pH 5.0). Relative to the wild-type strain, the
hfq
mutant also had a substantially reduced migration rate on motility agar and was less prone to form biofilms. Hfq activities are known to impact the regulation of both the stationary-phase sigma factor RpoS (σ
S
) and the envelope stress response sigma factor RpoE (σ
E
). Although we saw similarities among
hfq
,
rpoS
, and
rpoE
deletion mutants in our assays, the
rpoE
and
hfq
mutants were phenotypically the most alike. Cumulatively, our data indicate that Hfq likely affects UPEC virulence-related phenotypes primarily by modulating membrane homeostasis and envelope stress response pathways.
Expression of CD1d and Ligand-Induced Cytokine Production Are Tissue Specific in Mucosal Epithelia of the Human Lower Reproductive Tract
Authors: Kawana Kei , Matsumoto Junko , Miura Shiho , Shen Li , Kawana Yukiko , Nagamatsu Takeshi , Yasugi Toshiharu , Fujii Tomoyuki , Yang Huixia , Quayle Alison J. , Taketani Yuji , Schust Danny J.
Published: May 2008

Mucosal epithelia of the human lower reproductive tract (vagina, cervix, and penile urethra) are exposed to sexually transmitted microbes, includingChlamydia trachomatis. The in vivo susceptibility of each tissue type to infection withC. trachomatisis quite distinct. CD1d is expressed on the surface of antigen-presenting cells, including mucosal epithelial cells, and interacts specifically with invariant NKT cells. Invariant NKT cells play a role in both innate and adaptive immune responses to microbes. Here we assessed CD1d expression in normal reproductive tissues by using immunohistochemistry. Immortalized epithelial cell lines from the human lower reproductive tract (vagina, endocervix, and penile urethra) were examined for CD1d expression and for ligand-induced cytokine production induced by CD1d cross-linking. CD1d expression in normal tissue was strong in the vagina but weak in the endocervix and penile urethra. Gamma interferon exposure induced CD1d transcription in all of the cell types studied, with the strongest induction in vaginal cells. Flow cytometry revealed cell surface expression of CD1d in vaginal and penile urethral epithelial cells but not in endocervical cells. Ligation of surface-expressed CD1d by monoclonal antibody cross-linking promoted interleukin-12 (IL-12) and IL-15, but not IL-10, production in vaginal and penile urethral cells. No induction was demonstrated in endocervical cells. CD1d-mediated cytokine production in penile urethral cells was abrogated byC. trachomatisinfection. Basal deficiency in CD1d-mediated immune responsiveness may result in susceptibility to sexually transmitted agents. Decreased CD1d-mediated signaling may helpC. trachomatisevade detection by innate immune cells.
Assessment of fungal diversity: macromycetes, the problems
Authors: Watling Roy
Published: May 2008

The various difficulties in recording macromycetes and assessing their diversity are given and explored based on both temperate and tropical information. The importance of the tropical situation is emphasized but five steps are suggested by which some headway can be made. The ability of switching hosts by ectomycorrhizal fungi is emphasized. Key words: climate, fruiting, host switching, recording, succession, systematics.
Regulation of chitin synthesis during growth of fungal hyphae: the possible participation of membrane stress
Authors: Gooday Graham W. , Schofield David A.
Published: May 2008

Apical hyphal extension involves very localized apical deposition of newly synthesized wall skeletal material, notably chitin. A branch forms where a new localized site of chitin deposition occurs in the lateral wall. Key enzymes involved are the chitin synthases. Their activity must be under tight regulation to achieve the orderly deposition of chitin. There is evidence that inactive chitin synthase is distributed throughout the hyphal plasma membrane and activated at the apex and at an incipient branch site. At these sites, the wall is plastic. We have investigated the hypothesis that physical stressing of the membrane, a consequence of the cell's turgor pressure acting at these weaker points, may locally activate the chitin synthase. Results show that cells that have been subjected to hypoosmotic stress have raised native chitin synthase activities. It is suggested that stressing the membrane may cause a conformational change in chitin synthase molecules in the membrane or changes in the interactions between chitin synthase and associated polypeptides, leading to activation. This process may act along with other regulatory mechanisms discussed here, such as post-translational modification and availability of allosteric effectors, to restrict the enzymic activity to sites where chitin synthesis is required. Key words: chitin synthase, zymogen, turgor pressure, membrane stress, Candida albicans, hyphal growth.
Control of filamentous growth by mating and cyclic-AMP inUstilago
Authors: Kronstad James , Bakkeren Guus , Gold Scott , Yee Arthur , Laity Carole , Duncan Gillian , Barrett Katherine , Giasson Luc , Campbell Roderick , Athwal George
Published: May 2008

Mating between compatible haploid cells of the corn smut fungus, Ustilago maydis, results in a switch from budding to filamentous growth. We are analyzing the multiallelic b incompatibility locus that governs maintenance of the infectious, filamentous dikaryon. Specificity regions have been identified in the N-terminal portions of the bE and bW genes at the b locus. In addition, we have found that heterozygosity at the b locus attenuates fusion. This result suggests that b gene products may exert a negative influence on some processes, in addition to their generally recognized role in maintaining filamentous growth. The b genes have also been characterized in Ustilago hordei. This species has a bipolar mating system in which the b genes are linked to genes required for pheromone production and response to form one large mating-type region (MAT locus) with two allelic specificities. In a separate study, we have discovered that defects in adenylate cyclase result in constitutive filamentous growth and greatly reduce the virulence of U. maydis on corn seedlings. Mutations have been identified that suppress the adenylate cyclase defect and restore budding growth. Sequence analysis revealed that one of the suppressor mutations is in the gene encoding the regulatory subunit of cAMP-dependent protein kinase (PKA). Mutants altered in PKA activity have the interesting phenotype of multiple budding and frequent mislocalization of the bud site. Key words: smut, dimorphism, b locus, sex.
The population genetics ofSeptoria tritici(teleomorphMycosphaerella graminicola)
Authors: McDonald B. A. , Pettway R. E. , Chen R. S. , Boeger J. M. , Martinez J. P.
Published: May 2008

The DNA-based markers of molecular genetics were combined with the analytical tools of population genetics to learn about the population biology of the wheat pathogen Mycosphaerella graminicola. DNA-based genetic markers, including restriction fragment length polymorphisms in nuclear and mitochondrial DNA, DNA fingerprints, and electrophoretic karyotypes were used in combination to show that the amount and distribution of genetic variation within and among field populations of M. graminicola is similar around the world. Measures of gametic disequilibrium suggested that the sexual stage of reproduction has a more significant impact on the genetic structure of M. graminicola populations than asexual reproduction. A field experiment conducted over a 3-year period showed that populations had a high degree of genetic stability over time. The potential effects of selection were quantified in a cultivar mixture experiment with four wheat cultivars that varied in resistance to M. graminicola. In combination, these experiments demonstrated the utility of selectively neutral genetic markers to elucidate the population genetics of fungi. Key words: genetic diversity, wheat, gene flow, RFLPs, DNA fingerprinting.
Using genetic markers to investigate natural selection in fungal populations
Authors: Ennos R. A. , McConnell K. C.
Published: May 2008

Naturally occurring genetic markers can be exploited in a number of ways to measure natural selection in fungal populations. The potentials and pitfalls of these approaches are outlined. A review of existing experiments that have used genetic markers to estimate selection coefficients (s) in experimental and natural fungal populations indicates that differences in fitness between clones, populations, and subspecies may be substantial (mean s = 0.322), and that significant changes in the intensity and direction of selection may occur when environmental conditions alter. A reciprocal transplant experiment is described in which the relative selective values of three genetically marked populations of the canker pathogen Crumenulopsis sororia were compared under natural conditions. Large differences in selective value were found both among populations and within sites, but there was no evidence that genetic differentiation among populations was adaptive. The potential application of genetic markers for experimentally investigating mechanisms of speciation, adaptive genetic differentiation, and response to environmental change in fungi is discussed. Key words: genetic marker, natural selection, selection coefficient, Crumenulopsis sororia.
Interactions of proteins with other wall components: a pivotal step in fungal cell wall construction
Authors: Sentandreu R. , Sentandreu M. , Elorza M. V. , Iranzo M. , Mormeneo S.
Published: May 2008

Following synthesis of its individual components, the cell wall of Candida albicans is assembled extracellularly in two steps. First, a viscoelastic composite is formed by noncovalent interactions between mannoproteins and other wall components. Second, the initial network is consolidated by formation of covalent cross-linkages among the wall polymers. In both processes, specific proteins may regulate the final yeast or mycelial morphology. These proteins might carry out part of what could be called a morphogenetic code. Experimental results have shown that some mannoproteins form supramolecular complexes. They are secreted independently, but released together from cell walls by hydrolases. In C. albicans cell walls a transglutaminase activity has been detected that could be responsible for the formation of covalent bonds between structural proteins. Key words: fungal cell wall, construction, morphogenesis, protein interactions, noncovalent linkages, covalent linkages.
Cell biology of early events in the plant resistance response to infection by pathogenic fungi
Authors: Kobayashi I. , Murdoch L. J. , Hardham A. R. , Kunoh H.
Published: May 2008

In addition to passive (or constitutive) defence mechanisms, plants have evolved a range of active (or inducible) responses that occur rapidly on infection with an incompatible (avirulent) pathogen and that are thought to play a major role in the expression of resistance. These defence reactions are only induced if the plant possesses the ability to recognize and respond to the pathogen. Signal reception by the host must initiate a cascade of events that lead to the expression of resistance. Some resistance responses, such as callose deposition, do not require the expression of new genes. Many responses, for example the synthesis and secretion of toxic compounds or molecules that enhance the strength of physical barriers, result from changes in the pattern of gene transcription. Other defence phenomena include hypersensitive cell collapse, intercellular signalling, and the induction of defence gene transcripts in surrounding cells. Changes in cell biochemistry and physiology are accompanied by characteristic structural modifications in the infected cells, such as the redeployment of selected organelles and dramatic modifications of the host cell wall. Recent evidence indicates that microtubules and microfilaments of the plant cytoskeleton facilitate the rapid localization of these and other plant defence responses to the region of infection. Key words: plant resistance, plant cytoskeleton, microtubules, microfilaments, fungal pathogens, polarity of defence response.
Peritoxins and their effects on sorghum
Authors: Dunkle Larry D. , Macko Vlado
Published: May 2008

Peritoxins are low molecular weight, chlorinated peptides produced only by pathogenic strains of the sorghum root rot fungus, Periconia circinata. Genetic data relating sensitivity of sorghum (Sorghum bicolor (L.) Moench) to these toxins and susceptibility to the pathogen are consistent with the hypothesis that both traits are controlled by a single semidominant gene (Pc). At low concentrations (5–500 nM), the toxin selectively reproduces disease symptoms, inhibits growth of primary roots, stops mitosis, induces electrolyte leakage, and enhances the synthesis of a group of 16-kDa proteins and the corresponding mRNAs. Enhanced expression of these 16-kDa proteins and disease symptoms are also induced in a nongenotype-specific manner by treatment with mercury, suggesting that the two events are causally related. However, the upregulation of 16-kDa protein expression induced by a fungal elicitor is independent of visible disease symptoms and is, therefore, not a direct cause of damage. Results of experiments with treatments that protect seedlings against the effects of toxin (e.g., proteinase, heat shock, inhibitors of protein or RNA synthesis, inhibitors of protein kinase C activity, and biotinylation of membrane proteins) suggest that disease symptoms result from an interaction of peritoxin with a proteinaceous receptor on or near the cell surface and interference with the normal function of a signal transduction pathway. Key words: peritoxin, sorghum, Periconia circinata, host-selective toxin, milo disease, Periconia root rot.
Alternaria toxins and their effects on host plants
Authors: Otani Hiroshi , Kohmoto Keisuke , Kodama Motoichiro
Published: May 2008

There are now nine or more Alternaria pathogens that produce host-specific toxins, and the structures of most of the toxins have been elucidated. Alternaria host-specific toxins are classified in three groups in terms of the primary site action. ACT-, AF-, and AK-toxins have in common an epoxy-decatrienoic acid structure and exert their primary effect on the plasma membrane of susceptible cells. A rapid increase in electrolyte loss from tissues and invaginations in the plasma membranes are common effects of these toxins. The second group is represented by ACR(L)-toxin, which induces changes in mitochondria, including swelling, vesiculation of cristae, decrease in the electron density of the matrix, increase in the rate of NADH oxidation, and inhibition of malate oxidation. The third group consists of AM-toxin, which appears to exert an early effect on both chloroplasts and plasma membranes. AM-toxin induces vesiculation of grana lamellae, inhibition of CO2 fixation, invagination of plasma membranes, and electrolyte loss. The roles of host-specific toxins in pathogenesis are discussed. Key words: Alternaria, host-specific toxin, plasma membrane, mitochondrion, chloroplast.
Molecular interactions ofBipolaris maydisT-toxin and maize
Authors: Levings III Charles S. , Rhoads David M. , Siedow James N.
Published: May 2008

The toxins (T-toxins) produced by the fungal pathogens Bipolaris maydis race T (BmT) and Phyllosticta maydis (Pm) target the mitochondrial receptor, URF13, in maize (Zea mays L.) plants containing the Texas male-sterile cytoplasm (cms-T). URF13, a 13-kDa protein, is the product of the maize mitochondrial gene T-urf13, which is found only in the mitochondrial genome of cms-T maize and is thought to be responsible for cytoplasmically inherited male sterility and disease susceptibility. Pm-toxin binds specifically to URF13 in a cooperative manner, and Pm- and BmT-toxins compete for the same, or overlapping, binding sites. The binding of T-toxin to URF13 causes rapid permcabilization of the inner mitochondrial membrane, which results in leakage of NAD+and other ions from the matrix. A pore consisting of at least six transmembrane α-helices is required for NAD+leakage. Cross-linking experiments showed that URF13 oligomers are present in the mitochondrial membrane. A model of the secondary structure of URF13 proposes that each monomer contains three transmembrane α-helices. Studies combining site-directed mutagenesis and chemical cross-linking of URF13 expressed by Escherichia coli cells indicate that the oligomers are composed of a central core of helices II that line the center of the URF13 pores. Key words: maize cytoplasmic male sterility, URF13, mitochondrial pores, T-toxin receptor, Bipolaris maydis race T, Phyllosticta maydis, Helminthosporium maydis.
Cellular and molecular approaches in the characterization of symbiotic events in functional arbuscular mycorrhizal associations
Authors: Gianinazzi-Pearson Vivienne , Gollotte Armelle , Tisserant Benoit , Franken Philipp , Dumas-Gaudot Eliane , Lemoine Marie-Claude , Tuinen Diederik van , Gianinazzi Silvio , Lherminier Jeanine
Published: May 2008

Arbuscular mycorrhizas represent the most widespread, and probably most ancient, type of plant–fungus association in which the large majority of terrestrial plants must have evolved with compatibility systems towards the fungal symbionts. Cellular interactions leading to reciprocal morphofunctional integration between symbionts during mycorrhiza establishment are complex. Some plant genes and cellular events may be shared with nodulation processes, but there is evidence of molecular modifications specific to arbuscular mycorrhiza formation. Plant defence responses, which are normally weakly activated during the symbiotic state, are strongly elicited by arbuscular mycorrhizal fungi in genetically altered, resistant hosts suggesting control over defence gene expression during establishment of a successful symbiosis. Modifications are also induced in the fungal symbionts during colonization of host tissues, with changes in wall metabolism and protein expression. Nothing is known of the genetic make-up of arbuscular mycorrhizal fungi which are recalcitrant to pure culture. Recent cloning of DNA from these fungi opens the possibility of identifying functional genes in order to study their regulation and role in symbiosis establishment. Key words: arbuscular mycorrhiza, reciprocal symbiosis, molecular mechanisms, plant determinants, fungal molecules.
Ericoid mycorrhizal fungi: cellular and molecular bases of their interactions with the host plant
Authors: Perotto Silvia , Peretto Renato , Faccio Antonella , Schubert Andrea , Bonfante Paola , Varma Ajit
Published: May 2008

A number of soil-borne fungi are able to form typical ericoid mycorrhizae with plants belonging to Ericales. Together with Hymenoscyphus ericae, the first isolate from roots of ericaceous plants, other fungal species belonging to the genus Oidiodendron and many sterile mycelia have been recognized as mycorrhizal by several authors. A high genetic diversity was even found when a population of ericoid mycorrhizal fungi isolated from a single plant of Calluna vulgaris was analysed with morphological and molecular techniques. Ericoid fungi have a relevant saprotrophic potential, as they can degrade several organic polymers present in the soil matrices. Different cell wall degrading enzymes, which are part of this arsenal and are produced in vitro by several ericoid fungi, have been investigated biochemically. Immunocytochemical studies on the production of pectin degrading enzymes during the infection process of host and non-host plants suggest that regulation mechanisms for the production of cell wall degrading enzymes in vivo may be a crucial step for the establishment of successful mycorrhiza with host plants. Key words: ericoid mycorrhizae, cell wall degrading enzymes, polygalacturonase, DNA-RAPD techniques.
Experimental studies with foliose macrolichens: fungal responses to spatial disturbance at the organismic level and to spatial problems at the cellular level during drought stress events
Authors: Honegger Rosmarie
Published: May 2008

Improved culture methods and the application of cryotechniques in light and electron microscopy have allowed new insights at the organismic and cellular levels in mycobiont–photobiont relations of selected lichen species. Growth, regenerative capacity, and the ability to cope with spatial disturbances were tested in the foliose macrolichens Xanthoria parietina and Parmelia sulcata. These mycobionts can sense and partly correct an inverted position and thus insure adequate illumination for the photobiont cell population. In both taxa, the apical/marginal pseudomeristem and adjacent elongation zone bend backwards. Parmelia sulcata continues this bending process and grows arch-like until its margin reaches the substratum. Xanthoria parietina stops bending and growing but regenerates new primordial stages along the marginal rim and cut edges. These primordia develop into new lobes with a normal upside up topography. Its remarkable regenerative capacity permits X. parietina to develop a new rosette from an assembly of minute thallus fragments that had been fixed to a ceramic substratum. Cryotechniques applied at the light and electron microscopy levels allow us to visualize drought stress induced structural alterations at the cellular level in lichen bionts. Neither partner of the symbiosis plasmolyses under extreme drought stress. The globose to ovoid green algal or cyanobacterial photobiont cells and their walls shrivel dramatically but the fungal cell wall cannot be deformed to such a high degree during stress events. Ascomycetous lichen mycobionts of three different orders formed a large, intracellular gas bubble of unknown ontogeny and content when their turgor pressure dropped to very low values. This cytoplasmic "air bag" allows the protoplast to shrink and, at the same time, to keep the cell membrane in contact with the wall. In the desiccated state many lichens tolerate extreme stress conditions. Thallus fragments of dry X. parietina grew normally after having been cryofixed in subcooled liquid nitrogen, sputter coated, and examined in a low temperature scanning electron microscope. Fully hydrated samples did not survive this treatment. Key words: culturing experiments, regenerative capacity, drought stress, LTSEM, freeze substitution, intracellular gas bubble.
Experimental cultivation of lichens and lichen symbionts
Authors: Stocker-Wörgötter Elfie
Published: May 2008

Culture experiments with lichens and lichen symbionts are helpful for giving answers to many open questions in different fields of modern lichenology. Cultures are especially required for investigations where the analysis of naturally grown thalli is inconclusive and more standardized research material is needed. In the first part a short review of the artificial resynthesis of the cyanobacterial Peltigera praetextata along with new results obtained by the culture of isidia are presented. Another series of experiments report a successful resynthesis of the photosymbiodeme Peltigera leucophlebia. Details of the thallus morphogenesis and the formation of cephalodia in culture are shown. The related Peltigera aphthosa was cultured from small thallus fragments. In this case, the alpine P. aphthosa forms solely the cephalodiate thallus. A cyanobacterial morphotype as known from other culture experiments and the related P. britannica is missing in culture. Further culture experiments are conducted with alpine species of the genus Cladonia (e.g., Cl. fimbriata, Cl. furcata). Results show a quick redifferentiation and regeneration of squamules and podetia both by soredia and fragments. The high capacity of thallus regeneration as shown for Cl. furcata seems to be absent in representatives of the Cladina group (e.g., Cl. portentosa, Cl. rangiferina). Key words: lichen culture, resynthesis, tissue culture, Peltigeraceae, cyanobacterial lichens, photosymbiodemes, Peltigera leucophlebia, Peltigera aphthosa, Cladoniaceae, Cl. fimbriata, Cl. furcata.
Mixia osmundae: transfer from the Ascomycota to the Basidiomycota based on evidence from molecules and morphology
Authors: Nishida Hiromi , Ando Katsuhiko , Ando Yasuo , Hirata Aiko , Sugiyama Junta
Published: May 2008

To determine phylogenetic placement of Mixia osmundae (T. Nishida) Kramer (Mixiaceae, Protomycetales), we sequenced the nuclear small subunit ribosomal RNA (18S rRNA) gene from M. osmundae IFO-32408 and compared it with that from 4 archiascomycetes (Ascomycota) and 24 basidiomycetes. Our molecular phylogeny indicates that M. osmundae and the basidiomycetes Rhodosporidium toruloides, Leucosporidium scottii, Sporobolomyces roseus, Sporidiobolus johnsonii, Cronartium ribicola, Peridermium harknessii, and Erythrobasidium hasegawianum group together in 100% of bootstrap replicates. The M. osmundae spores on the host fern Osmunda japonica have been regarded as ascospores (i.e., endogenously produced within an ascus), but our light microscopic, SEM, and TEM observations for fresh materials of M. osmundae on O. japonica in Japan clearly demonstrated that these are produced exogenously, blastically, and simultaneously from the sporogenous cell. Evidence from both molecular and morphological characters suggests that M. osmundae is not a member of the ascomycetes and is not related to either the Taphrinales or Protomycetales. Obviously Mixia osmundae is a member of the basidiomycetes and placed within the simple septate basidiomycete lineage. Key words: fungal evolution, basidiomycete phylogeny, Mixia osmundae, Taphrinales, Protomycetales, 18S rRNA.
Molecular systematics of the Hypocreales: a teleomorph gene phylogeny and the status of their anamorphs
Authors: Rehner Stephen A. , Samuels Gary J.
Published: May 2008

Phylogenetic relationships among 40 species in the Hypocreales and Clavicipitales were inferred from sequence data obtained from the nuclear large-subunit ribosomal DNA. Cladistic analysis of these data support the monophyly of the Hypocreales, with the Clavicipitales derived from within the Hypocreales. Four groupings were resolved and are informally designated as the Hypocrea, Claviceps, Bionectria, and Nectria groups. Phylogenetic placement of teleomorphs including Melanospora and cleistothecial taxa, such as Heleococcum, Mycoarachis, and Roumegueriella, demonstrate the facility of molecular phylogenies to accommodate taxa with highly modified morphologies. Similarly, the hypocrealean origins of the anamorph species Verticillium lecanii and Acremonium chrysogenum illustrate the potential of the molecular phylogenetic approach to accommodate anamorph isolates within the context of a teleomorph phylogeny. Together these results suggest that a comprehensive classification of the Hypocreales, inclusive of teleomorph and anamorph states, is attainable through a molecular phylogenetic approach. Key words: Ascomycotina, Clavicipitaceae, Hypocreales, phylogeny, pyrenomycete, rDNA.
Molecular relationships among hyphal ascomycetous yeasts and yeastlike taxa
Authors: Kurtzman C. P. , Robnett C. J.
Published: May 2008

The circumscription of mycelial genera among the ascomycetous yeasts has been controversial because of widely different interpretations of the taxonomic significance of their phenotypic characters. Relationships among species assigned to mycelial genera were determined from extent of divergence in a ca. 600-nucleotide region near the 5′ end of the large subunit (26S) ribosomal DNA gene. Phylogenetic analyses showed that Stephanoascus is distinct from Zygoascus and that Blastobotrys, Sympodiomyces, and Arxula represent anamorphs of the Stephanoascus clade. The analyses demonstrated the following teleomorphic taxa to be congeneric: Ambrosiozyma/Hormoascus, Saccharomycopsis/Guilliermondella/Botryoascus/Arthroascus, Dipodascus/Galactomyces, and Eremothecium/Ashbya/Nematospora/Holleya. Species assigned to Dipodascus comprise two separate clades. New taxonomic combinations are proposed that reflect the phylogenetic relationships determined. Key words: mycelial yeasts, ribosomal rRNA/rDNA, molecular systematics.