bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of graphite powder on the laser sintering behaviour of polycarbonate
Authors: Ho H.C.H. , Cheung W.L. , Gibson I.
Published: February 2003

A non‐contact infrared temperature sensor was used to monitor the temperature–time relation of a point on the powder bed during laser sintering. The results were translated into a temperature–distance relation of the monitored spot with respect to its distance from the laser beam. The effect of particle size of polycarbonate (PC) powder on the temperature–distance relation was studied. The maximum temperature attained at the monitored spot was found to increase with decreasing size of the PC particles. The phenomenon was probably caused by the higher packing density of the smaller particles, and more laser energy was absorbed near the powder bed surface. The temperature–distance relations of some common additives such as graphite, quartz, silica and talc were also studied, and graphite was found to give the highest temperature distribution. PC/graphite composite powders were blended and sintered under similar conditions. The surface temperature of the powder bed increased greatly with the addition of a small amount (up to 2 per cent) of graphite powder. The result was attributed to the higher absorptance of CO2 laser energy by the graphite powder.
Investigation of the processing dependence of SL solidification residual stresses
Authors: Karalekas D. , Rapti D.
Published: February 2003

This paper presents an experimental study undertaken to determine the polymerisation‐induced residual stresses generated in stereolithography (SL) built test specimens, by using the hole‐drilling strain gage method of stress relaxation. Experimentally measured strains, using special three‐element strain gage rosettes, were input into the blind‐hole analysis to calculate the induced residual stresses. The mechanical properties of resin specimens fabricated by the solidification process using an epoxy based photopolymer and post‐cured under ultraviolet (UV) and thermal exposure were determined and incorporated into the subsequent drill‐hole analysis. The effect of the pre‐selected fabrication parameters (hatching space and curing depth) and subsequent by the post‐curing procedure (UV, thermal curing) on the magnitude of the recorded strains is also presented.
Anisotropic material properties of fused deposition modeling ABS
Authors: Ahn Sung‐Hoon , Montero Michael , Odell Dan , Roundy Shad , Wright Paul K.
Published: February 2003

Rapid Prototyping (RP) technologies provide the ability to fabricate initial prototypes from various model materials. Stratasys Fused Deposition Modeling (FDM) is a typical RP process that can fabricate prototypes out of ABS plastic. To predict the mechanical behavior of FDM parts, it is critical to understand the material properties of the raw FDM process material, and the effect that FDM build parameters have on anisotropic material properties. This paper characterizes the properties of ABS parts fabricated by the FDM 1650. Using a Design of Experiment (DOE) approach, the process parameters of FDM, such as raster orientation, air gap, bead width, color, and model temperature were examined. Tensile strengths and compressive strengths of directionally fabricated specimens were measured and compared with injection molded FDM ABS P400 material. For the FDM parts made with a 0.003 inch overlap between roads, the typical tensile strength ranged between 65 and 72 percent of the strength of injection molded ABS P400. The compressive strength ranged from 80 to 90 percent of the injection molded FDM ABS. Several build rules for designing FDM parts were formulated based on experimental results.
A CASD/CASM method for prosthetic socket fabrication using the FDM technology
Authors: Tay Francis E.H. , Manna M.A. , Liu L.X.
Published: February 2003

As an application of the computer aided design and computer aided manufacturing (CAD/CAM) technology in prosthetics, computer aided socket design and computer aided socket manufacturing (CASD/CASM) is becoming an active field in the prosthetics research. In this paper, a CASD/CASM method for prosthetic socket fabrication is described in detail. This is different from other fabrication methods in its novel combination of the CAD/CAM technology with fused deposition modeling (FDM) technology. Prosthetic sockets for volunteer amputees have been designed and fabricated in a FDM machine. In order to test the fabrication result, a final product was used to perform a clinical trial and some results are reported. In addition, the deficiency of the long fabrication time is addressed and some feasible solutions are discussed.
Survey of Continuities of Curves and Surfaces
Authors: Veltkamp Remco C.
Published: February 2003

This survey presents an overview to various types of continuity of curves and surfaces, in particular parametric (Cn), visual or geometric (Cn, Gn), Frenet frame (Fn), and tangent surface continuity (Tn), and discusses the relation with curve and surface modeling, visibility of (dis) continuities, and graphics rendering algorithms. It is the purpose of this paper to provide an overview of types of continuity, and to put many terms and definitions on a common footing in order to give an understanding of the subject.

1991 Computing Reviews Classification:

I.3.5 [Computer Graphics] Computational geometry and object modeling.

I.3.7 [Computer Graphics] Three‐Dimensional Graphics and Realism.
User Interface Management Systems for Engineering Applications
Authors: Sastry Lakshmi
Published: February 2003

Essential features of a User Interface Management System (UIMS) from the perspective of engineering applications' user interface development are described. Three commercially available UIMS are validated against this set of essential features and the results of such a categorised evaluation are reported. The proliferation of user interface design tools necessitated an initialfiltering to select these tools on the basis of their availability on a wide range of platforms currently used by engineers, supplier support for the product and the prototyping tools the UIMS offer. Graphic Modelling System (GMS), TeleUSE and USEIT were selected for their potential utility to engineering applications.

An earlier version of this paper was presented at the 1991 European X User Group Annual Conference held at Queens' College, Cambridge, UK.

This comparative evaluation is compiled on behalf of the UK Science and Engineering Research Council, for the benefit of the UK academic engineering research community.
A Statistical Comparison of Two Hidden Surface Techniques: the Scan‐line and Z‐buffer Algorithms
Authors: Slater Mel , Drake Kieron , Davison Allan , Kordakis Emmanouell , Billyard Adam , Miranda Eliot
Published: February 2003

This paper compares two image space hidden surface removal algorithms for polygonal scenes. These are the z‐buffer and scan‐line algorithms. There is first an overview of each algorithm, followed by a simulation experiment, designed to compare the number of polygons per second which can be rendered by each algorithm. The simulation varies the number of polygons in the scene, and the size and distribution of polygons over the display. The results suggest that the z‐buffer is preferred for a large enough number of polygons, however, smaller polygons and uniform distribution of polygons favour the scan‐line approach. The analysis does not take into account the complexity of the shading rule, which is likely also to favour the scan‐line method.
PHIFI: A PHIGS Interactive System for the Visualization of Scalar and Vector Fields
Authors: Ascani Fabrizio , Moltedo Laura
Published: February 2003

This paper describes the characteristics of PHIFI, an interactive system for the visualization of scalar and vector fields. PHIFI has been developed at the IAC where applications of the system have also been investigated.
Integer de Casteljau Algorithm for Rasterizing NURBS Curves
Authors: Anantakrishnan Narayanan , Piegl Les A.
Published: February 2003

An integer version of the well‐known de Casteljau algorithm of NURBS curves is presented here. The algorithm is used to render NURBS curves of any degree on a raster device by turning on pixels that are closest to the curve. The approximation is independent of the parametrization, that is, it is independent of the weights used. The algorithm works entirely in the screen coordinate system and produces smooth rendering of curves without oversampling. Because of the integer arithmetic used, the algorithm is easily cast in hardware.
Ray Coherence Between a Sphere and a Convex Polyhedron
Authors: Horvath Tamas , Marton Gabor , Risztics Peter , Szirmay‐Kalos Laszlo
Published: February 2003

Using the two ray coherence theorems of Ohta and Maekawa the computation time of ray tracing algorithms for scenes of spheres and convex polyhedra can be reduced considerably. This paper presents further theorems which, together with the first two, may enable further reduction in computation time.
Comparison of NO titration and fiber optics catalytic probes for determination of neutral oxygen atom concentration in plasmas and postglows
Authors: Mozetič Miran , Ricard Andre , Babič Dušan , Poberaj Igor , Levaton Jacque , Monna Virginie , Cvelbar Uroš
Published: February 2003

A comparative study of two different absolute methods NO titration and fiber optics catalytic probe (FOCP) for determination of neutral oxygen atom density is presented. Both methods were simultaneously applied for measurements of O density in a postglow of an Ar/O2 plasma created by a surfatron microwave generator with the frequency of 2.45 GHz an adjustable output power between 30 and 160 W. It was found that the two methods gave similar results. The advantages of FOCP were found to be as follows: it is a nondestructive method, it enables real time measuring of the O density, it does not require any toxic gas, and it is much faster than NO titration. The advantage of NO titration was found to be the ability to measure O density in a large range of dissociation of oxygen molecules.
Transformation of a Simple Plastic into a Superhydrophobic Surface
Authors: Erbil H. Yıldırım , Demirel A. Levent , Avcı Yonca , Mert Olcay
Published: February 2003

Superhydrophobic surfaces are generally made by controlling the surface chemistry and surface roughness of various expensive materials, which are then applied by means of complex time-consuming processes. We describe a simple and inexpensive method for forming a superhydrophobic coating using polypropylene (a simple polymer) and a suitable selection of solvents and temperature to control the surface roughness. The resulting gel-like porous coating has a water contact angle of 160°. The method can be applied to a variety of surfaces as long as the solvent mixture does not dissolve the underlying material.
Genetic Control of Surface Curvature
Authors: Nath Utpal , Crawford Brian C. W. , Carpenter Rosemary , Coen Enrico
Published: February 2003

Although curvature of biological surfaces has been considered from mathematical and biophysical perspectives, its molecular and developmental basis is unclear. We have studied the
cin
mutant of
Antirrhinum
, which has crinkly rather than flat leaves. Leaves of
cin
display excess growth in marginal regions, resulting in a gradual introduction of negative curvature during development. This reflects a change in the shape and the progression of a cell-cycle arrest front moving from the leaf tip toward the base.
CIN
encodes a TCP protein and is expressed downstream of the arrest front. We propose that
CIN
promotes zero curvature (flatness) by making cells more sensitive to an arrest signal, particularly in marginal regions.
A New Species of Yunnanozoan with Implications for Deuterostome Evolution
Authors: Shu Degan , Morris Simon Conway , Zhang Z. F. , Liu J. N. , Han Jian , Chen Ling , Zhang X. L. , Yasui K. , Li Yong
Published: February 2003

Yunnanozoans are a distinctive clade of Lower Cambrian metazoans. Although widely accepted as deuterostomes, their exact placement within this superphylum is controversial. Here we describe a new species of
Haikouella
(
H. jianshanensis
) from the Chengjiang Lagerstätte (Yunnan, China) with exceptional preservation of a number of features. These include external gills, which suggest that the origin of the pharyngeal clefts was independent of the gills. The diagnostic branchial arches of chordates may, therefore, be composite structures. No evidence was found for the chordate-like structures that have been described in other yunnanozoans. We propose that yunnanozoans are stem-group deuterostomes, allied to the vetulicolians.
Requirement of the Adenovirus IVa2 Protein for Virus Assembly
Authors: Zhang Wei , Imperiale Michael J.
Published: February 2003

The adenovirus L1 52/55-kDa protein is required for viral DNA packaging and interacts with the viral IVa2 protein, which binds to the viral packaging sequence. Previous reports suggest that the IVa2 protein plays a role in viral DNA packaging and that this function of the IVa2 protein is serotype specific. To further examine the function of the IVa2 protein in viral DNA packaging, a mutant virus that does not express the IVa2 protein was constructed by introducing two stop codons at the beginning of the IVa2 open reading frame in a full-length bacterial clone of adenovirus type 5. The mutant virus,
pm
8002, was defective for growth in 293 cells, although it replicated its DNA and produced early and late viral proteins. Electron microscopic and gradient analyses revealed that the mutant virus did not assemble any viral particles in 293 cells. In 293-IVa2 cells, which express the IVa2 protein, infectious viruses were produced, although the titer of the mutant virus was lower than that of the wild-type virus, indicating that these cells may not fully complement the mutation. The mutant viral particles produced in 293-IVa2 cells were heterogeneous in size and shape, less stable, and did not traffic efficiently to the nucleus. Marker rescue experiments with a wild-type IVa2 DNA fragment confirmed that the only mutations present in
pm
8002 were in the IVa2 gene. The results indicate that the IVa2 protein is required for adenovirus assembly and suggest that virus particles may be assembled around the DNA rather than DNA being packaged into preformed capsids.
Potential Role for CD63 in CCR5-Mediated Human Immunodeficiency Virus Type 1 Infection of Macrophages
Authors: von Lindern Jana J. , Rojo Daniel , Grovit-Ferbas Kathie , Yeramian Christine , Deng Cheng , Herbein Georges , Ferguson Monique R. , Pappas Todd C. , Decker Julie M. , Singh Anjali , Collman Ronald G. , O'Brien William A.
Published: February 2003

Macrophages and CD4+lymphocytes are the principal target cells for human immunodeficiency virus type 1 (HIV-1) infection, but the molecular details of infection may differ between these cell types. During studies to identify cellular molecules that could be involved in macrophage infection, we observed inhibition of HIV-1 infection of macrophages by monoclonal antibody (MAb) to the tetraspan transmembrane glycoprotein CD63. Pretreatment of primary macrophages with anti-CD63 MAb, but not MAbs to other macrophage cell surface tetraspanins (CD9, CD81, and CD82), was shown to inhibit infection by several R5 and dualtropic strains, but not by X4 isolates. The block to productive infection was postfusion, as assessed by macrophage cell-cell fusion assays, but was prior to reverse transcription, as determined by quantitative PCR assay for new viral DNA formation. The inhibitory effects of anti-CD63 in primary macrophages could not be explained by changes in the levels of CD4, CCR5, or β-chemokines. Infections of peripheral blood lymphocytes and certain cell lines were unaffected by treatment with anti-CD63, suggesting that the role of CD63 in HIV-1 infection may be specific for macrophages.
Recruitment of Herpes Simplex Virus Type 1 Transcriptional Regulatory Protein ICP4 into Foci Juxtaposed to ND10 in Live, Infected Cells
Authors: Everett Roger D. , Sourvinos George , Orr Anne
Published: February 2003

At the early stages of herpes simplex virus type 1 (HSV-1) infection, parental viral genomes have a tendency to become juxtaposed to cellular nuclear structures known as PML (promyelocytic leukemia) nuclear bodies or ND10, while the immediate-early (IE) protein ICP0 precisely colocalizes with these structures. Previous indirect-immunofluorescence studies observed that the HSV-1 transcriptional regulator ICP4 has a mainly diffuse nuclear distribution early in infection and is later recruited into viral replication compartments. We have constructed HSV-1 variants expressing ICP4 and ICP0 linked to ECFP and EYFP, respectively, both singly and in combination. Coupled with an efficient method of expressing autofluorescent PML in ND10, we have studied the dynamics of ICP0, ICP4, and ND10 in live, infected cells. The greater sensitivity and lower background signals in live cells revealed that early in infection, ICP4 forms discrete foci, some of which are juxtaposed to ND10, while ICP0 was found to colocalize precisely with PML. As expected from these results, using a double-labeled virus, we observed that foci of ICP0 and ICP4 were also juxtaposed but not colocalized early in infection. Some of the ICP4 foci must have contained parental viral genomes, because they developed into replication compartments. We propose that a proportion of the ND10-associated ICP4 foci represent ICP4 molecules being recruited onto parental viral genomes, a process likely to be a critical step early in lytic infection. These results may be analogous to the localization of IE1 and IE2 during human cytomegalovirus infection, suggesting a principle common to the alpha- and betaherpesviruses.
The Epstein-Barr Virus SM Protein Induces STAT1 and Interferon-Stimulated Gene Expression
Authors: Ruvolo Vivian , Navarro Lorena , Sample Clare E. , David Michael , Sung Seung , Swaminathan Sankar
Published: February 2003

Viruses utilize numerous mechanisms to counteract the host's immune response. Interferon production is a major component of the host antiviral response. Many viruses, therefore, produce proteins or RNA molecules that inhibit interferon-induced signal transduction pathways and their associated antiviral effects. Surprisingly, some viruses directly induce expression of interferon-induced genes. SM, an early lytic Epstein-Barr virus (EBV) nuclear protein, was found to specifically increase the expression of several genes (interferon-stimulated genes) that are known to be strongly induced by alpha/beta interferons. SM does not directly stimulate alpha/beta interferon secretion but instead induces STAT1, an intermediate step in the interferon signaling pathway. SM is a posttranscriptional activator of gene expression and increases STAT1 mRNA accumulation, particularly that of the functionally distinct STAT1β splice variant. SM expression in B lymphocytes is associated with decreased cell proliferation but does not decrease cell viability or induce cell cycle arrest. These results indicate that EBV can specifically induce cellular genes that are normally physiological targets of interferon by inducing components of cytokine signaling pathways. Our findings therefore suggest that some aspects of the interferon response may be positively modulated by infecting viruses.
Neurovirulence in Mice of H5N1 Influenza Virus Genotypes Isolated from Hong Kong Poultry in 2001
Authors: Lipatov Aleksandr S. , Krauss Scott , Guan Yi , Peiris Malik , Rehg Jerold E. , Perez Daniel R. , Webster Robert G.
Published: February 2003

We studied the pathogenicity of five different genotypes (A to E) of highly pathogenic avian H5N1 viruses, which contained HA genes similar to those of the H5N1 virus A/goose/Guangdong/1/96 and five different combinations of “internal” genes, in a mouse model. Highly pathogenic, neurotropic variants of genotypes A, C, D, and E were isolated from the brain after a single intranasal passage in mice. Genotype B virus was isolated from lungs only. The mouse brain variants had amino acid changes in all gene products except PB1, NP, and NS1 proteins but no common sets of mutations. We conclude that the original H5N1/01 isolates of genotypes A, C, D, and E were heterogeneous and that highly pathogenic neurotropic variants can be rapidly selected in mice.
An Amino Acid in the Central Catalytic Domain of Three Retroviral Integrases That Affects Target Site Selection in Nonviral DNA
Authors: Harper Amy L. , Sudol Malgorzata , Katzman Michael
Published: February 2003

Integrase can insert retroviral DNA into almost any site in cellular DNA; however, target site preferences are noted in vitro and in vivo. We recently demonstrated that amino acid 119, in the α2 helix of the central domain of the human immunodeficiency virus type 1 integrase, affected the choice of nonviral target DNA sites. We have now extended these findings to the integrases of a nonprimate lentivirus and a more distantly related alpharetrovirus. We found that substitutions at the analogous positions in visna virus integrase and Rous sarcoma virus integrase changed the target site preferences in five assays that monitor insertion into nonviral DNA. Thus, the importance of this protein residue in the selection of nonviral target DNA sites is likely to be a general property of retroviral integrases. Moreover, this amino acid might be part of the cellular DNA binding site on integrase proteins.
Prevention of injury by early socialization of aggressive behavior
Authors: Tremblay R E
Published: February 2003

Frequent use of physical aggression by humans appears to reach its peak between 2 and 3 years of age. In the following years most children learn alternatives to physical aggression. Approximately 4% of children have high levels of physical aggression from early childhood to late adolescence. These children can be considered to show chronic physical aggression. They are at high risk of causing injuries to others and to themselves. They are also at high risk of many other co-morbid mental health conditions, school failure, substance abuse, depression, unemployment, spouse abuse, child abuse, and suicide. There is some evidence that, because of their risky style of behavior, they are also at high risk of many other medical conditions such as cardiovascular problems, cancer, and brain damage. Socialization of aggressive behavior during the preschool years should help prevent injuries throughout the life span.
Review of the quality of studies on the economic effects of smoke-free policies on the hospitality industry
Authors: Scollo M , Lal A , Hyland A , Glantz S
Published: February 2003

Objective:To compare the quality and funding source of studies concluding a negative economic impact of smoke-free policies in the hospitality industry to studies concluding no such negative impact.

Data sources:Researchers sought all studies produced before 31 August 2002. Articles published in scientific journals were located with Medline, Science Citation Index, Social Sciences Citation Index, Current Contents, PsychInfo, Econlit, and Healthstar. Unpublished studies were located from tobacco company websites and through internet searches.

Study selection:97 studies that made statements about economic impact were included. 93% of the studies located met the selection criteria as determined by consensus between multiple reviewers.

Data extraction:Findings and characteristics of studies (apart from funding source) were classified independently by two researchers. A third assessor blind to both the objective of the present study and to funding source also classified each study.

Data synthesis:In studies concluding a negative impact, the odds of using a subjective outcome measure was 4.0 times (95% confidence interval (CI) 1.4 to 9.6; p = 0.007) and the odds of not being peer reviewed was 20 times (95% CI 2.6 to 166.7; p = 0.004) that of studies concluding no such negative impact. All of the studies concluding a negative impact were supported by the tobacco industry. 94% of the tobacco industry supported studies concluded a negative economic impact compared to none of the non-industry supported studies.

Conclusion:All of the best designed studies report no impact or a positive impact of smoke-free restaurant and bar laws on sales or employment. Policymakers can act to protect workers and patrons from the toxins in secondhand smoke confident in rejecting industry claims that there will be an adverse economic impact.
AFLP-based assessment of genetic diversity among nine alfalfa germplasms using bulk DNA templates
Authors: Segovia-Lerma A , Cantrell R G , Conway J M , Ray I M
Published: February 2003

Improving commercial utilization of perennial Medicago collections requires developing approaches that can rapidly and accurately characterize genetic diversity among large numbers of populations. This study evaluated the potential of using amplified fragment length polymorphism (AFLP) DNA markers, in combination with DNA bulking over multiple genotypes, as a strategy for high-throughput characterization of genetic distances (D) among alfalfa (Medicago sativa L.) accessions. Bulked DNA templates from 30 genotypes within each of nine well-recognized germplasms (African, Chilean, Flemish, Indian, Ladak, Medicago sativa subsp. falcata, Medicago sativa subsp. varia, Peruvian, and Turkistan) were evaluated using 34 primer combinations. A total of 3754 fragments were identified, of which 1541 were polymorphic. The number of polymorphic fragments detected per primer combination ranged from 20 to 85. Pairwise D estimates among the nine germplasms ranged from 0.52 to 1.46 with M. sativa subsp. falcata being the most genetically dissimilar. Unweighted pair-group method arithmetic average (UPGMA) analysis of the marker data produced two main clusters, (i) M. sativa subsp. sativa and M. sativa subsp. varia, and (ii) M. sativa subsp. falcata. Cluster-analysis results and D estimates among the Chilean, Peruvian, Flemish, and M. sativa subsp. varia germplasms supported the hypothesis that Peruvian was more similar to original Spanish introductions into Central and South America than Chilean. Hierarchical arrangement of the nine germplasms was supported by their respective geographic, subspecific, and intersubspecific hybrid origins. Subsets of as few as seven highly informative primer pairs were identified that produced comparable D estimates and similar heirarchical arrangements compared with the complete dataset. The results indicate that use of primer-pair subsets for AFLP analysis of bulk DNA templates could serve as a high-throughput system for accurately characterizing genetic diversity among large numbers of alfalfa populations.Key words: Medicago sativa, DNA bulking, genetic distance.
Development, characterisation, inheritance, and cross-species utility of American lobster (Homarus americanus) microsatellite and mtDNA PCR-RFLP markers
Authors: Jones Matthew W , O'Reilly Patrick T , McPherson Arran A , McParland Tara L , Armstrong Dawn E , Cox Andrea J , Spence Koren R , Kenchington Ellen L , Taggart Chris T , Bentzen Paul
Published: February 2003

Effective management of exploited species demands contemporary knowledge of population structure and mating patterns. Genetic markers can prove useful in providing this knowledge. Despite its commercial importance, genetic markers for American lobster (Homarus americanus) are limited. We developed 12 tetra- and 1 trinucleotide microsatellite loci for American lobster that exhibit little stuttering after PCR amplification. Gene diversity of these loci ranged from 0.516 to 0.929. A four-locus multiplex permits rapid genotyping of progeny in parentage experiments with a paternity exclusion probability over the four loci of 97.8%. We examined the loci for conformity to Hardy-Weinberg expectations (HWE) and linkage using individuals from one location and found that four loci deviated from HWE. We also tested inheritance and pairwise linkage using 48 embryos from each of two females. With the exception of two loci that were derived from the same clone and separated by 72 bp, no evidence of linkage was found. We, for the first time, demonstrate the occurrence of multiple paternity in American lobster. We also observed an apparent occurrence of dispermic androgenesis, possibly the first documentation of such an event within a species. Ten of the loci amplified in European lobster (Homarus gammarus), although two were monomorphic and one deviated significantly from HWE. We quantified mitochondrial DNA (mtDNA) sequence variation through the use of PCR amplification of two DNA fragments, followed by digestion with restriction enzymes; eight haplotypes were detected. One of the two fragments amplified in European lobster. Both sets of markers should prove useful for population discrimination purposes, and the microsatellites, in particular the four-locus multiplex, should prove highly amenable to rapidly addressing questions about mating patterns.Key Words: low-stutter microsatellites, mtDNA PCRRFLP, multiple paternity, dispermic androgenesis, American lobster.
Multiple origins of cultivated radishes as evidenced by a comparison of the structural variations in mitochondrial DNA of Raphanus
Authors: Yamagishi Hiroshi , Terachi Toru
Published: February 2003

Configurations of mitochondrial coxI and orfB gene regions were analysed by polymerase chain reaction (PCR) in three wild and one cultivated species of Raphanus. A total of 207 individual plants from 60 accessions were used. PCR with five combinations of primers identified five different amplification patterns both in wild and cultivated radishes. While the mitochondrial DNA (mtDNA) type of Ogura male-sterile cytoplasm was distinguishable from the normal type, the mtDNAs of normal radishes were further classified into four types. The variations were common to wild and cultivated radishes, although contrasting features were found depending on the region of cultivation. These results provide evidence that cultivated radishes have multiple origins from various wild plants of Raphanus.Key words : Raphanus sativus, origin, PCR, mitochondrial coxI.
Enhancement of population densities of fluorescent pseudomonads in the rhizosphere of tomato plants by addition of acibenzolar-S-methyl
Authors: Fakhouri W D , Buchenauer H
Published: February 2003

Fluorescent pseudomonad isolates G309 and CW2, in combination with the resistance inducer acibenzolar-S-methyl (ASM), improved control of fungal and bacterial diseases on tomato plants. The interactions of the bacteria in the presence of ASM showed that in vitro growth of Pseudomonas fluorescens G309 and Pseudomonas sp. strain CW2 was not affected in King's B broth supplemented with 10 and 20 μM ASM. Also, the bacterial cells were not able to utilize ASM as a nutrient source. In vitro production of the two antimicrobial secondary metabolites phenazine-1-carboxylic acid and 2-OH-phenazine by the isolate CW2 was not affected within 3 days from incubation. In contrary, addition of ASM at a concentration of 20 μM to King's B liquid medium significantly increased production of salicylic acid by isolate G309. When roots of tomato plants were treated with G309 or CW2 cell suspensions containing 20 μM ASM, the number of bacterial cells recovered from the rhizosphere was significantly higher in the combined treatments than in the single applications 5, 10, and 15 days after inoculation. However, ASM at a higher concentration (50 μM) did not appreciably enhance the population sizes of either bacterial isolate in the rhizosphere. Enhanced bacterial cell densities in the rhizosphere of tomato plants were also determined following simultaneous treatments of tomato roots with 10 and 20 μM ASM in combination with the transformed isolate G309-384 (mini-Tn5gfp), which encodes the green fluorescent protein.Key words: acibenzolar-S-methyl, fluorescent pseudomonads, green fluorescent protein, tomato.
The improvement of lipase secretion and stability by addition of inert compounds intoAcinetobacter calcoaceticuscultures
Authors: Martinez Daniela A , Nudel B Clara
Published: February 2003

Acinetobacter calcoaceticus BD413 produces variable amounts of an exocellular lipase that becomes rapidly inactivated upon secretion. To achieve high yield and protect the enzyme, we assayed the addition of several inert compounds to cell-free supernatants, cell fractions, and whole cultures. Glass beads, poly(ethylene glycol) 600, Triton X-100, saccharose, gum arabic, and β-cyclodextrin were among the compounds tested. β-Cyclodextrin and gum arabic (and saccharose to a lesser extent) were effective enzyme stabilizers in cell-free supernatants, while gum arabic, glass beads, and Triton X-100 improved lipase secretion from cells, and, therefore, total lipase yield (3050%, according to the additive). In whole cultures, β-cyclodextrin was the most effective additive, particularly in combination with glass beads or gum arabic. Indeed, cultures containing β-cyclodextrin plus gum arabic were able to maintain 95% (±1.5%) of the initial lipase activity for more than 16 h, while control cultures with no additives maintained only 10% (±4%) of the enzyme activity after the same period. In conclusion, the addition of inert compounds in cultures may be considered a useful approach for achieving increased yield and lipase stabilization, amenable for downstream processing.Key words: Acinetobacter calcoaceticus, lipase, secretion, stabilization, inert additives.
Genetic profiling of noncultivated bacteria from the rhizospheres of sugar beet (Beta vulgaris) reveal field and annual variability but no effect of a transgenic herbicide resistance
Authors: Schmalenberger Achim , Tebbe Christoph C
Published: February 2003

In this field study, we compared the bacterial communities inhabiting the rhizosphere of a transgenic, herbicide-resistant sugar beet (Beta vulgaris) cultivar with those of its nonengineered counterpart, using a genetic profiling technique based on PCR amplifications of partial 16S rRNA gene sequences and single-strand conformation polymorphism (SSCP). As a control for the plasticity of the bacterial community, we also analyzed the influence of herbicides, the field heterogeneity, and the annual variation. DNA was isolated from bacterial cell consortia that were directly collected from root material. PCR was carried out with primers that hybridized to evolutionarily conserved regions flanking variable regions 4 and 5 of the 16S rRNA gene. SSCP patterns of these PCR products were composed of approximately 50 distinguishable bands, as detected by silver staining of the gels after electrophoresis. Patterns of the replicates and the different treatments were highly similar, but digital image and similarity analyses revealed differences that corresponded to the positions of the replicates in the field. In addition, communities collected from sugar beet in two successive growing seasons could be distinguished. In contrast, no effect of the transgenic herbicide resistance was detectable. Sequencing of 24 dominant products of the SSCP profiles indicated the presence of bacteria from different phylogenetic groups, with Proteobacteria and members of the CytophagaFlavobacteriumBacteroides group being most abundant.Key words: genetic profiles, rRNA genes, transgenic sugar beet, risk assessment, rhizosphere, PCRSSCP, microbial community analysis, glufosinate, phosphinothricin.
Lactobacillusgrowth and membrane composition in the presence of linoleic or conjugated linoleic acid
Authors: Jenkins Julie K , Courtney Polly D
Published: February 2003

Five Lactobacillus strains of intestinal and food origins were grown in MRS broth or milk containing various concentrations of linoleic acid or conjugated linoleic acid (CLA). The fatty acids had bacteriostatic, bacteriocidal, or no effect depending on bacterial strain, fatty acid concentration, fatty acid type, and growth medium. Both fatty acids displayed dose-dependent inhibition. All strains were inhibited to a greater extent by the fatty acids in broth than in milk. The CLA isomer mixture was less inhibitory than linoleic acid. Lactobacillus reuteri ATCC 55739, a strain capable of isomerizing linoleic acid to CLA, was the most inhibited strain by the presence of linoleic acid in broth or milk. In contrast, a member of the same species, L. reuteri ATCC 23272, was the least inhibited strain by linoleic acid and CLA. All strains increased membrane linoleic acid or CLA levels when grown with exogenous fatty acid. Lactobacillus reuteri ATCC 55739 had substantial CLA in the membrane when the growth medium was supplemented with linoleic acid. No association between level of fatty acid incorporation into the membrane and inhibition by that fatty acid was observed.Key words: Lactobacillus, conjugated linoleic acid, linoleic acid, cell membrane.
Phylogenetic analysis of bacterial populations in an anaerobic microbial consortium capable of degrading saturation concentrations of tetrachloroethylene
Authors: Dennis Philip C , Sleep Brent E , Fulthorpe Roberta R , Liss Steven N
Published: February 2003

An anaerobic microbial consortium able to biodegrade saturation levels of perchloroethylene (PCE) in a column containing a source zone of PCE was examined phylogenetically to determine microbial community structure and spatial variation in relation to the PCE source. The consortium was comprised of at least 34 members with 7 organisms sharing affiliations with known respiratory or cometabolic dechlorinators. Seven other organisms had their closest phylogenetic relative detected in other environments containing chlorinated compounds. Based on denaturing gradient gel electrophoresis, significant Bacteria were Dehalococcoides ethenogenes, Shewanella putrefaciens, and an Acetobacterium species. Spatial variations in community structure of the consortium relative to the PCE source zone were observed. A Pseudomonas species was predominant in a zone 30 cm from the PCE source. A Methanothrix species was predominant at points over 85 cm from the source zone. A Trichlorobacter species was detected where PCE concentrations were highest, up to 85 cm from the PCE source, whereas D. ethenogenes was ubiquitous to over 128 cm from the PCE source.Key words: tetrachloroethene, reductive dechlorination, bioremediation, phylogenetic analysis, microbial diversity.
Biophysical characteristics of a new mutation on the KCNQ1 potassium channel (L251P) causing long QT syndrome
Authors: Deschênes Dominic , Acharfi Said , Pouliot Valerie , Hegele Robert , Krahn Andrew , Daleau Pascal , Chahine Mohamed
Published: February 2003

The congenital long QT syndrome (LQTS) is a hereditary cardiac disease characterized by prolonged ventricular repolarization, syncope, and sudden death. Mutations causing LQTS have been identified in various genes that encode for ionic channels or their regulatory subunits. Several of these mutations have been reported on the KCNQ1 gene encoding for a potassium channel or its regulatory subunit (KCNE1). In this study, we report the biophysical characteristics of a new mutation (L251P) in the transmembrane segment 5 (S5) of the KCNQ1 potassium channel. Potassium currents were recorded from CHO cells transfected with either wild type or mutant KCNQ1 in the presence or in the absence of its regulatory subunit (KCNE1), using the whole-cell configuration of the patch clamp technique. Wild-type KCNQ1 current amplitudes are increased particularly by KCNE1 co-expression but no current is observed with the KCNQ1 (L251P) mutant either in the presence or in the absence of KCNE1. Coexpressing KCNE1 with equal amount of cDNAs encoding wild type and mutant KCNQ1 results in an 11-fold reduction in the amplitude of potassium currents. The kinetics of activation and inactivation and the activation curve are minimally affected by this mutation. Our results suggest that the dominant negative effect of the P251L mutation on KCNQ1 channel explains the prolonged repolarization in patients carrying this mutation.Key words: long QT syndrome, ventricular fibrillation, potassium channels, KCNQ1.
Mitogenic actions of neuropeptide Y in vascular smooth muscle cells: synergetic interactions with the β-adrenergic system
Authors: Pons Jennifer , Kitlinska Joanna , Ji Hong , Lee Edward W , Zukowska Zofia
Published: February 2003

Neuropeptide Y (NPY), a sympathetic cotransmitter and vasoconstrictor, also stimulates vascular smooth muscle cell (VSMC) growth, but which of its Y1Y5 receptors are involved remains unclear. In quiescent rat VSMCs, NPY receptor mRNAs were undetectable (reverse transcription  polymerase chain reaction), but Y1, Y2, and Y5 expression were upregulated or induced following NPY treatment. Concomitantly, NPY increased up to twofold [3H]thymidine incorporation and cell number bimodally, with a high-affinity peak at pM and low affinity peak at nM concentrations. The Y1 or Y5 (not Y2) antagonist alone did not change the high-affinity peak but decreased the low affinity peak by 50% and fully blocked NPY's response when combined. In VSMCs lacking NPY receptors and responsiveness, transient Y1 cDNA transfection restored their mitogenic response (blocked by the Y1 antagonist). In VSMCs with low or no NPY responsiveness, pre-exposure to β-adrenergic receptor agonist (isoproterenol), forskolin, or dibu tyryl cAMP augmented NPY's mitogenic effect, while upregulating Y1, Y2, and Y5 receptor expression (isoproterenol only). Thus, NPY is a potent vascular mitogen acting via Y1 and Y5 receptors. However, since their expression is low in nonproliferating cells, amplification of NPY's mitogenic responses requires upregulation of at least the Y1 receptor by NPY itself or β-adrenergic, cAMP-dependent activation.Key words: neuropeptide Y, NPY receptors, beta adrenergic receptor, cyclic AMP, vascular smooth muscle cells.
Cyclooxygenase-2 (COX-2) in acute myocardial infarction: cellular expression and use of selective COX-2 inhibitor
Authors: Saito Takayuki , Rodger Ian W , Shennib Hani , Hu Fu , Tayara Lara , Giaid Adel
Published: February 2003

Our previous work has shown strong expression of COX-2 in the myocardium of patients with end-stage ischemic heart failure. The purpose of this study was to determine the cellular expression of this enzyme in the setting of acute myocardial infarction (AMI) and determine the role of COX-2 in experimental animals using a selective COX-2 inhibitor. Experimental AMI was induced in rats by ligating the left coronary artery. Animals were either treated with a selective COX-2 inhibitor (5 mg·kg1·day1) or vehicle. Three days after ligation, cardiac function was assessed and infarct size was determined. Myocardial specimens were immunostained with antiserum to COX-2. Plasma concentration of prostanoids was measured by enzyme immunoassay. There was strong expression of COX-2 in the myocytes, endocardium, vascular endothelial cells, and macrophages in the infarcted zone of the myocardium. In contrast, little expression was seen in the myocardium of control rats. Animals treated with the COX-2 inhibitor showed a significant improvement in left ventricular (LV) end-diastolic pressure (P < 0.05) and LV systolic pressure (P < 0.01), and a reduction in infarct size (P < 0.05). Inhibition of COX-2 significantly decreased plasma concentration of thromboxane B2 (P < 0.05); however, it did not affect 6-keto-prostaglandin F1α. Induction of COX-2 during AMI appears to contribute to myocardial injury, and treatment with the specific inhibitor of the enzyme ameliorated the course of the disease.Key words: cyclooxygenase-2, inhibitor, acute myocardial infarction.
Selection of den, rendezvous, and resting sites by wolves in the Bialowieza Forest, Poland
Authors: Theuerkauf Jörn , Rouys Sophie , Jedrzejewski Wlodzimierz
Published: February 2003

We studied wolf (Canis lupus) selection of 19 den, 10 rendezvous, and 31 resting sites found between 1986 and 2000 in the Bialowieza Forest (Poland). Our objective was to determine whether wolves selected sites far from villages, forest edges, and roads, and whether these sites had dense ground cover for concealment. We also tested whether wolves selected a particular forest type for their den sites. Den and rendezvous sites were located at greater distances from villages, forest edges, and intensively used roads than random points. Locations of resting sites were not affected by these manmade structures. Wolves selected dry coniferous forests for den sites but also used other forest types. We concluded that the suitability of an area for pup raising depended mainly on the spatial distribution of forest, human settlements, and public roads, and to a lesser extent on habitat characteristics.
Relative abilities to correct rolling disturbances of three morphologically different fish
Authors: Eidietis L , Forrester T L , Webb P W
Published: February 2003

Responses of three fish species were measured following the addition of neutrally buoyant weight-float combinations that increased rolling instability. The three species were creek chub, Semotilus atromaculatus, largemouth bass, Micropterus salmoides, and bluegill, Lepomis macrochirus. Ability to correct posture was predicted to increase with fin size and body depth in the order creek chub < largemouth bass < bluegill. In a 90-s period, the least added torque causing fish to roll to 90° in response to disturbances, ΔT90, and the least added torque making fish unable to recover from rolling, ΔTcrit, were measured as limits of ability to correct postural disturbances. Contrary to expectations, creek chub required a 58% increase in body torque to reach ΔT90, significantly larger than the 11% increase for largemouth bass and 19% increase for bluegill. Similarly, ΔTcritwas a 78% increase in body torque for creek chub, 43% for largemouth bass, and 34% for bluegill. Increased rolling torques resulted in behaviors reducing and avoiding rolling, including tilting, which reduces metacentric height, inverted swimming, which stabilizes fish, and contacting surfaces, which generates static forces. The superior ability of creek chub to correct postural disturbances may be explained by a fin arrangement that facilitates interactions with the ground.
Sex determination in the sea otter (Enhydra lutris) from tissue and dental pulp using PCR amplification
Authors: Hattori Kaoru , Burdin Alexander M , Onuma Manabu , Suzuki Masatsugu , Ohtaishi Noriyuki
Published: February 2003

Historical specimens of sea otters (Enhydra lutris) provide valuable information about the pre-bottleneck population. However, the sex of these specimens is often not known. We attempted to determine the sex of sea otters by means of polymerase chain reaction (PCR) amplification of the amelogenin and the zinc finger (ZFX/ZFY) regions. The PCR fragments of amelogenin amplified were same size regardless of the sex. On the other hand, we were able to distinguish the sex accurately by means of the sea otter-specific restriction enzyme (NlaIII) to digest a polymorphic site in the ZFX/ZFY region. This method was applicable to dental pulp from skull specimens with the use of novel inner primers (KH1/KH2). We suggest that with some modification, the ZFX/ZFY system can be applied to other species and to a variety of archaeological specimens.
Female preferences and malemale interactions in zebrafish (Danio rerio)
Authors: Pyron M
Published: February 2003

Female preferences for male body size, male preferences for female body size, and malemale interactions were experimentally evaluated in zebrafish (Danio rerio) obtained from the pet trade. Female preferences were shown for larger males. Males did not show preferences for female body size. Zebrafish males have strong interactions when two males are placed together with a female. Body length of males and females was not different. These results indicate that the reproductive strategy of zebrafish is more elaborate than simply broadcast spawning: females are choosy and males compete for females. Mate preferences and malemale interactions of zebrafish are discussed and compared with expectations based on sexual selection theory.