bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence of quorum sensing in the rumen ecosystem: detection of N-acyl homoserine lactone autoinducers in ruminal contents
Authors: Erickson D L , Nsereko V L , Morgavi D P , Selinger L B , Rode L M , Beauchemin K A
Published: June 2003

Acyl-homoserine lactone (AHL) based quorum-sensing systems are widespread among gram-negative bacteria, particularly in association with plants and animals. As yet, there have been no reports of AHL signaling in the anaerobic rumen environment, an ecosystem of great complexity in which cell-cell signaling is likely to occur. We detected multiple AHL autoinducers in the rumen contents of 6 out of 8 cattle fed a representative selection of diets. The signals were not associated with feed. Surprisingly, no pure cultures produced AHLs in vitro when grown under the laboratory conditions we tested. Our observations suggest that either (a) a factor specific to the rumen ecosystem is required for the rumen isolates we tested to produce AHLs or (b) a strain (or strains) that we were not able to culture but which grows to a high cell density in the rumen produces the AHLs we detected.Key words: quorum sensing, rumen, acyl-homoserine lactone, anaerobic environment, bacteria, cattle.
Impact of pulsed Nd:YAG laser on the marine biofilm-forming bacteria Pseudoalteromonas carrageenovora: significance of physiological status
Authors: Nandakumar Kanavillil , Shinozaki Tatsuya , Obika Hideki , Ooie Toshihiko , Utsumi Akihiro , Yano Tetsuo
Published: June 2003

The impact of pulsed Nd:YAG (neodymium-doped yttrium/aluminium garnet) laser irradiation on the marine biofilm-forming bacteria Pseudoalteromonas carrageenovora during two growth stages (log phase and stationary phase) and under two stresses (reduced temperature and nutrient limitation) was investigated. Bacteria were exposed to a laser fluence of 0.1 J·cm2 for 5, 10, and 15 min with a peak power of 20 MW·cm2, a pulse width of 5 ns, and an average power of 1 W·cm2 with a repetition rate of 10 Hz. The mortality of bacteria immediately after the irradiation as well as after a set period of time was determined. Mortality was higher among log-phase bacteria (72%) than bacteria in the stationary phase (51%) and those grown under nutrient limitation (51%). Bacteria grown at reduced temperature had a mortality of 49%. However, the differences in cell density of log-phase, stationary-phase, nutrient-limited, and low-temperature irradiated samples compared with controls after 5 h of incubation were 96, 93, 94, and 86%, respectively. The mortality values suggest that the same laser fluence has different degrees of effectiveness, depending on the physiological state of the bacteria.Key words: laser irradiation, biofilm-forming bacteria, physiological status, mortality.
Effect of amino acids on thaxtomin A biosynthesis by Streptomyces scabies
Authors: Lauzier Annie , Goyer Claudia , Ruest Luc , Brzezinski Ryszard , Crawford Don L , Beaulieu Carole
Published: June 2003

The regulatory effect of amino acids on the production of thaxtomin A, a phytotoxin produced by Streptomyces scabies, was investigated. Tryptophan had an important inhibitory effect on the toxin biosynthesis in all five strains of S. scabies tested. Two other aromatic amino acids (tyrosine and phenylalanine) also inhibited thaxtomin A biosynthesis, while aliphatic amino acids did not cause an important decline in thaxtomin A production. Methylation of tryptophan prevented or reduced the inhibitory effect on thaxtomin A biosynthesis. In spite of the inhibitory action of tryptophan and phenylalanine on thaxtomin A production, incorporation of these radiolabeled molecules into thaxtomin A confirmed that they are metabolic precursors for the biosynthesis of the phytotoxin.Key words: thaxtomin A, phytotoxin, Streptomyces scabies, common scab, nitroaromatic compounds, amino acids.
Campylobacter fetusadheres to and enters INT 407 cells
Authors: Graham Lori L
Published: June 2003

Campylobacter fetus is a Gram-negative bacterial pathogen of humans and ungulates and is normally transmitted via ingestion of contaminated food or water with infection resulting in mild to severe enteritis. However, despite clinical evidence that C. fetus infection often involves transient bacteremic states from which systemic infection may develop and the frequent isolation of C. fetus from extra-intestinal sites, this organism displays very poor invasiveness in in vitro models of infection. In this study, immunofluorescence microscopy and gentamicin protection assays were used to investigate the ability of six clinical isolates and one reference strain of C. fetus to adhere to and invade the human intestinal epithelial cell line, INT 407. During an initial 4-h infection period, all C. fetus strains were detected intracellularly using both techniques, though adherence and internalization levels were very low when determined from gentamicin protection assays. Microscopy results indicated that during a 4-h infection period, four of the five clinical strains tested were adherent to 41.387.3% of INT 407 cells observed and that 25.234.6% of INT 407 cells contained intracellular C. fetus. The C. fetus reference strain displayed the lowest levels of adherence and internalization. A modified infection assay revealed thatC. fetus adherence did not necessarily culminate in internalization. Despite the large percentage of INT 407 cells with adherent bacteria, the percentage of INT 407 cells with intracellular bacteria remained unchanged when incubation was extended from 4 h to 20 h. However, microscopy of INT 407 cells 24 h postinfection (p.i.) revealed that infected host cells contained clusters of densely packed C. fetus cells. Gentamicin protection assays revealed that intracellular C. fetus cells were not only viable 24 h p.i. but also that C. fetus had increased in number approximately three- to fourfold between 4 and 24 h p.i., indicative of intracellular replication. Investigation of the role of the host cell cytoskeleton revealed that pretreatment of host cells with cytochalasin D, colchicine, vinblastine, taxol, or dimethyl sulfoxide (DMSO) did not impact upon C. fetus adherence or internalization of INT 407 cells. Microscopy indicated neither rearrangement nor colocalization of either microtubules or microfilaments in INT 407 cells in response to C. fetus adherence or internalization. Together, these data indicate that clinical isolates of C. fetus are capable of adhering, entering, and surviving within the nonphagocytic epithelial cell line, INT 407.Key words: Campylobacter fetus, INT 407, immunofluorescence microscopy, S layer.
Characterization ofndvD, the third gene involved in the synthesis of cyclic β-(13),(16)-D-glucans inBradyrhizobium japonicum
Authors: Chen Rongji , Bhagwat Arvind A , Yaklich Robert , Keister Donald L
Published: June 2003

Previously, we identified two genes in Bradyrhizobium japonicum (ndvB, ndvC) that are required for cyclic β-(1[Formula: see text]3),(1[Formula: see text]6)-D-glucan synthesis and successful symbiotic interaction with soybean (Glycine max). In this study, we report a new open reading frame (ORF1) located in the intergenic region between ndvB and ndvC, which is essential for β-glucan synthesis and effective nodulation of G. max. This new gene is designated ndvD (nodule development). The ndvD translation product has a predicted molecular mass of 26.4 kDa with one transmembrane domain. Genetic experiments involving gene deletion, Tn5 insertion, and gene complementation revealed that the mutation of ndvD generated pleiotropic phenotypes, including hypoosmotic sensitivity, reduced motility, and defects in conjugative gene transfer, in addition to symbiotic ineffectiveness. Although deficient in in vivo β-glucan synthesis, membrane preparations from the ndvD mutant synthesized neutral β-glucans in vitro. Therefore, ndvD does not appear to be a structural gene for β-glucan synthesis. Our hypothesis for the mechanism of β-(1[Formula: see text]3),(1[Formula: see text]6)-D-glucan synthesis is presented. Key Words: β-glucans,Bradyrhizobium, soybean, nitrogen fixation.
Expression of a glycogen synthase protein kinase homolog from Colletotrichum gloeosporioides f.sp. malvae during infection of Malva pusilla
Authors: Goodwin Paul H , Chen Grace Y.-J
Published: June 2003

The potential role of a GSK3 protein kinase homolog, cggsk, was examined from Colletotrichum gloeosporioides f.sp. malvae, a fungal pathogen of Malva pusilla. A peak in cggsk expression relative to a constitutively expressed fungal actin gene occurred during host penetration and was followed by much lower expression levels during subsequent biotrophic and necrotrophic growth in host tissue. The peak level of cggsk expression observed during penetration was 21-fold greater than that during necrotrophic growth. Expression of cggsk showed small but reproducible changes during growth in culture; however, the levels were always similar to that during necrotrophic growth in the host. One possible role for cggsk could be to coordinate fungal development during host penetration.Key words: appressorium, biotrophy, GSK3, hemibiotrophy, necrotrophy.
Meron Pseudospin Solutions in Quantum Hall Systems
Authors: Ghosh Sankalpa , Rajaraman R.
Published: June 2003

In this paper we report calculations of some pseudospin textures for bilayer quantum hall systems with filling factor ν=1. The textures we study are isolated single meron solutions. Meron solutions have already been studied at great length by others by minimising the microscopic Hamiltonian between microscopic trial wavefunctions. Our approach is somewhat different. We calculate them by numerically solving the nonlinear integro-differential equations arising from extremisation of the effective action for pseudospin textures. Our results can be viewed as augmenting earlier results and providing a basis for comparison. Our differential equation approach also allow us to dilineate the impact of different physical effects like the pseudospin stiffness and the capacitance energy on the meron solution.
Ordering of Dipoles in Different Types of Microtubule Lattice
Authors: Trpišová B. , Brown J. A.
Published: June 2003

Microtubules (MTs) are the largest protein polymers in the cytoskeleton of eucaryotic cells in which they perform various functions. They are important in cell division, cell movement, they seem to be the devices through which are transferred signals in the nervous system. In this paper we continued to investigate the hypothesis that MTs can be viewed as assemblies of dipoles which are carried by the MT subunits, tubulin heterodimers. These assemblies were studied by means of the two-dimensional Ising model for both the A- and B-type arrangements of the tubulin subunits in a MT and the number of protofilaments 12, 13 and 14. We found that depending on these parameters and the magnitudes and orientations of the dipoles a MT may be at body temperature in an ordered phase or in a phase characterized by a random configuration of dipoles. The type of the ordered phase is determined by the above parameters as well, and it can be ferroelectric, antiferroelectric or ferrielectric. The dipolar ordering also depends on the presence of microtubule associated proteins, assuming that they can locally alter the dipolar interactions by binding to a MT, and external electric fields. The model presented here started by Tuszyński1–3 can be one of the first steps in the theoretical investigation of the electromagnetic features of MTs and their role in the MT behavior.
Integral Geometry in Statistical Physics
Authors: Mecke Klaus R.
Published: June 2003

The aim of this paper is to point out the importance of a morphological characterization of patterns in Statistical Physics. Integral geometry furnishes a suitable family of morphological descriptors, known as Minkowski functionals. They characterize not only the connectivity (topology) but also the content and shape (geometry) of spatial patterns. Integral geometry provides also powerful theorems and formulae, which makes the calculus convenient for many models of stochastic geometries, for instance, for the Boolean grain model. This model generates random structures in space by overlapping bodies or "grains" (balls, sticks) each with arbitrary location and orientation. We illustrate the integral geometric approach to stochastic geometries by applying morphological measures to such diverse topics as percolation, complex fluids, and the large-scale structure of the universe:

(A) Porous media may be generated by overlapping holes of arbitrary shape distributed uniformly in space. The percolation thresold of such porous media can be estimated accurately in terms of the morphology of the distributed pores.

(B) Under rather natural assumptions a general expression for the Hamiltonian of complex fluids can be derived that includes energy contributions related to the morphology of the spatial domains of homogeneous mesophases. We find that the Euler characteristic in the Hamiltonian stabilizes a highly connected bicontinuous structure resembling the middle-phase in oil-water microemulsions, for instance.

(C) Morphological measures are a novel method for the description of complex spatial structures aiming for relevant order parameters and structure information complement to correlation functions. Typical applications address Turing patterns in chemical reaction diffusion systems, homogeneous phases evolving during spinodal decomposition, and the distribution of galaxies and clusters of galaxies in the Universe as a prominent example of a point process in nature.
Dynamics of a Pair of Interacting Spins Coupled to an Environmental Sea
Authors: Dubé M. , Stamp P. C. E.
Published: June 2003

We solve for the dynamics of a pair of spins, coupled to each other and also to an environmental sea of oscillators. The environment mediates an indirect interaction between the spins, causing both mutual coherence effects and dissipation. This model describes a wide variety of physical systems, ranging from 2 coupled microscopic systems (e.g. magnetic impurities, chromophores, etc.), to 2 coupled macroscopic quantum systems.

We obtain analytic results for 3 regimes, viz., (i) The "locked" regime, where the 2 spins lock together; (ii) The "correlated relaxation" regime (mutually correlated incoherent relaxation); and (iii) The "mutual coherence" regime, with correlated damped oscillations.

These results cover most of the parameter space of the system.
A nonlinear two‐species oscillatory system: bifurcation and stability analysis
Authors: Bandyopadhyay Malay , Bhattacharya Rakhi , Chakrabarti C. G.
Published: June 2003

The present paper dealing with the nonlinear bifurcation analysis
of two‐species oscillatory system consists of three parts. The
first part deals with Hopf‐bifurcation and limit cycle analysis of
the homogeneous system. The second consists of travelling wave
train solution and its linear stability analysis of the system in
presence of diffusion. The last deals with an oscillatory
chemical system as an illustrative example.
Quasireducible operators
Authors: Kubrusly C. S.
Published: June 2003

We introduce the concept of quasireducible operators. Basic properties and illustrative examples are considered in some detail in order to situate the class of quasireducible operators in its due place. In particular, it is shown that every
quasinormal operator is quasireducible. The following result links this class with the invariant subspace problem: essentially normal quasireducible operators have a
nontrivial invariant subspace, which implies that quasireducible hyponormal operators have a nontrivial invariant subspace. The paper ends with some open questions on the characterization of the class of all quasireducible operators.
A note on integral modification of the Meyer‐König and Zeller operators
Authors: Gupta Vijay , Kumar Niraj
Published: June 2003

Guo (1988) introduced the integral modification of
Meyer‐Kö nig and Zeller operators and studied the rate of convergence for functions of bounded
variation. Gupta (1995) gave the sharp estimate for the operators . Zeng (1998) gave the exact bound and claimed to improve the results of Guo and Gupta, but there is a major mistake in the paper of Zeng. In the present
note, we give the correct estimate for the rate of convergence on bounded variation functions.
Simulated Digestion Status of Intact and Exoskeletally-Punctured Insects and Insect Larvae: A Spectroscopic Investigation
Authors: Prinz J.F. , Silwood C.J.L. , Claxson A.W.D. , Grootveld M.
Published: June 2003

In this study, we tested the hypothesis that puncturing the chitin exoskeleton of insect and insect larvae food sources aids the ingress of digestive fluids and increases the rate of digestion and energy uptake in insectivorous mammals. For this purpose 10 crickets (Acheta domesticus) and 10 mealworms (Tenebrio molitor larvae) were divided into two groups of 5; one group was punctured using a small blade to mimic the effect of a single bite, the remainder serving as controls. The insects were then individually immersed in 5 ml of a1 3 10–2 mol ? dm–3 solution of hydrochloric acid (pH 2.0) for a period of 2 h in order to mimic digestion in the stomach. The matrix was then centrifuged and the supernatant fluid subjected to spectrophotometric and high-resolution proton (1H) NMR analysis. Electronic absorption spectra of these supernatants revealed that puncturing the exoskeleton of mealworms and crickets gave rise to substantial elevations (up to 14-fold) in the concentrations of UV-absorbing biomolecules (p - 0.025 for both species). The 400-MHz 1H NMR profiles of supernatants derived from mealworm and cricket specimens with punctured exoskeletons contained a wide variety of prominent biomolecule resonances, whereas those from unpunctured (control) insects contained signals of a much lower intensity, ascribable only to selected biomolecules. We conclude that puncturing the cuticle of insects and insect larvae prior to swallowing confers significant nutritional advantages over swallowing prey whole.
A Cochlear Cell Line as an in vitro System for Drug Ototoxicity Screening
Authors: Kalinec Gilda M. , Webster Paul , Lim David J. , Kalinec Federico
Published: June 2003

Aminoglycoside antibiotics, loop diuretics, antineoplastic agents and other commonly used pharmacological drugs are ototoxic. Understanding of the cellular and molecular mechanisms underlying drug ototoxicity, however, has been hampered by the limited availability of inner ear tissues and drug side effects on laboratory animals. Immortalized cell lines derived from the auditory sensory organ, sensitive to ototoxic drugs and growing in environments that can be systematically manipulated, would facilitate the research directed at elucidating these mechanisms. Such immortalized cell lines could also be used to discover novel therapeutic agents for preventing drug-induced sensorineural hearing loss. Here, we report a conditionally immortalized organ of Corti-derived epithelial cell line, which shows evidence of activation of apoptosis when exposed to known ototoxic drugs. This cell line may be an excellent in vitro system to investigate the cellular and molecular mechanisms involved in ototoxicity and for screening of the potential ototoxicity or otoprotective properties of new pharmacological drugs.
Phylogenetic Assessment of the Mitochondrial DNA Displacement Loop Haplotype in Japanese Patients with Leber’s Hereditary Optic Neuropathy Harboring the Mitochondrial DNA G11778A Mutation
Authors: Isashiki Yasushi , Sonoda Shozo , Izumo Shuji , Sakamoto Taiji , Tachikui Hiroshi , Inoue Itsuro
Published: June 2003

To investigate the anthropological background and the association of mitochondrial DNA (mtDNA) haplotype with the disease phenotype, the nucleotide sequence in the hypervariable segment of the displacement loop (D-loop) region of mtDNA was determined in Japanese patients with Leber’s hereditary optic neuropathy (LHON) harboring the G11778A mutation. Genetic polymorphism of mtDNA was examined in 36 unrelated Japanese LHON patients who presented with bilateral optic nerve disease and had the mtDNA G11778A mutation. DNA was extracted from the peripheral blood after having obtained informed consent. The nucleotide sequence of the D-loop region (np 16,002–16,490) was directly determined. The intergenic deletion of the COII/tRNALys gene of mtDNA was also examined. From the data set of nucleotide alignments, the phylogeny of the mtDNA sequence and phenotypic diversity within the examined population were evaluated. One-base polymorphism was present at 37 different sites. The estimated value of nucleotide diversity was 0.69%. D-loop sequences were classified into 13 monophyletic clusters (CA to CM). There was not any definite ancestral haplotype of the D-loop sequence in the examined LHON population. Thus, the mutational event of G11778A appears to be independent of the evolutionary course in the D-loop haplotype. Patients with a CD plus CH cluster had a significantly older age at onset (p = 0.006), and had a family history being significantly lower as compared with patients with other clusters (p = 0.05). The mtDNA D-loop haplotype characterized by the presence of T16362C or C16290T, lacking G16129A and G16390A, may be a risk for older age at onset and other unusual clinical features in Japanese LHON patients with the G11778A mutation.
ECOLOGICAL HOLISM AND THEOLOGICAL DUALISM AS ROOTS OF ENVIRONMENTAL RACISM: MEDIEVAL LESSONS FOR MODERN RELIGIOUS SCHOLARS
Authors: Power Bratton Susan
Published: June 2003

The central hypothesis of this paper is that idealization of nature may fuel environmental racism when combined with dual interpretation of human religious or spiritual states. Medieval typological Biblical exegesis, originally based on historic rather than racial differentiation, encouraged presentation of Christianity as "natural" and Judaism as contra-natural. During the Gothic period, the stained glass of St. Denis Cathedral presented Judaism as occupying the material rather than the transcendent spheres of existence. In numerous stained glass windows, Jews appear as threats to nature by attacking Christ on a green cross, which symbolizes the renewal of all life, or the Lignum Vitae. As Christian architects and scientists increased their focus on the divine light of creation, prejudicial portrayals depicted Judaism as blind Synagogue, unable to fully appreciate nature. Pagan motifs, such as the Green Man, syncretized with Christian theological dualism, also serve to separate Judaism from living nature. These depictions purposefully conflict with Gothic aesthetic emphasis on proportion, clarity, and integrity and were intended to imply that religious minorities have no legitimate role in Christian European society. Modern religious scholarship must be cautious not to describe some religions as natural or nature religion, while neglecting others, particularly Judaism and Islam.
BIOTIC COMMUNITY—REAL OR UNREAL: A PHILOSOPHICAL DILEMMA
Authors: Landen Laura
Published: June 2003

As defined over time, biotic community has meant anything from superorganism to ecosystem. Some ecologists entirely reject any such holistic concept. This spectrum of positions—from holism to reductionism—reflects a divide among ecologists. Ordinarily, such battles pass with little notice beyond the confines of science. Ecology, however, has impact well outside its borders. In the popular arena the expression "biotic community" is widely, albeit sometimes uncritically, accepted. Even though both scientists and philosophers disagree about the validity of the concept, arguments for or against rely upon a common principle: novel properties signify a new reality. Conclusions divide based upon what may count as real. Must the new entity be a material object or is it merely conceptual? I review the evolution of meanings for biotic community and examine representative objections to either the reality or the utility of the concept. I argue that what is lacking in all discussions of biotic community is attention to the mode of existence of community, and conclude that biotic community is real, although its mode of existence is relational, not material.
TOWARD A VALUE-ORIENTED METAPHYSICS OF NATURE
Authors: Bracken Joseph
Published: June 2003

The English philosopher/theologian Colin Gunton argues that many of the problems besetting the contemporary Western world, including those dealing with the environment, are traceable to a mistaken understanding of the relationship between the One and the Many in practical life. A solution, however, is available in retrieval of the doctrine of the Trinity promoted by the early Greek Fathers, in particular the notion of perichoresis as the dynamic bond of unity among the divine persons. While agreeing with Gunton on this point, the author believes that perichoresis can only be applied to the world of creation in terms of a metaphysics of universal intersubjectivity such as he developed in a recent book. After laying out the basic contours of this new 'relational ontology', the author concludes by calling attention to the work of another process-oriented thinker, Douglas Sturm, with the latter's work on the 'politics of relationality' and an ethic of solidarity.
OVERPOPULATION: ECOLOGICAL AND BIBLICAL PRINCIPLES CONCERNING LIMITATION
Authors: Boorse Dorothy
Published: June 2003

There is an increasing consensus among ecologists that global ecosystems are under strain from unsustainable consumption habits and human overpopulation. However, there is no such consensus among many religious persons. Many Christians for example, are quite concerned about both overconsumption and overpopulation while others are uncomfortable with any discussion of either, or specifically with discussions about overpopulation. This discomfort may be due to concerns about undermining God's sovereignty or opposition to specific family planning policies. Two other reasons for this lack of consensus are misunderstandings of science and of Scripture. Central to the ecological understanding of the world is a belief in the concept of limitation. Some Christians, however, appear to believe that natural laws and limitations do not act on human populations. Furthermore, some Christians interpret the Bible as promoting high fertility. In contrast, I describe the ecological principles of allocation, optima, and limiting factors, which derive from the limitation of matter and energy. I propose to integrate these scientific principles with three scriptural principles: balance, wisdom, and corporate responsibility and to apply them to the current issue of overpopulation.
THE VIRTUOUS COOPERATOR: MODELING THE HUMAN IN AN ECOLOGICALLY ENDANGERED AGE
Authors: Schaefer Jame
Published: June 2003

A theological model of the human is needed to prompt responsible thinking about and acting within the physical world. Some basic components for modeling the human as a virtuous cooperator appear in the teachings of Thomas Aquinas. When appropriated cautiously and informed broadly by contemporary scientific findings, this model provides a promising way of thinking about humans in relation to other species and ecological systems, a framework for acting responsibly, and the motivation for making this behavior habitual.
A family of vortex wakes generated by a thrush nightingale in free flight in a wind tunnel over its entire natural range of flight speeds
Authors: Spedding G. R. , Rosén M. , Hedenström A.
Published: June 2003

In view of the complexity of the wing-beat kinematics and geometry, an important class of theoretical models for analysis and prediction of bird flight performance entirely, or almost entirely, ignores the action of the wing itself and considers only the resulting motions in the air behind the bird. These motions can also be complicated, but some success has previously been recorded in detecting and measuring relatively simple wake structures that can sometimes account for required quantities used to estimate aerodynamic power consumption. To date, all bird wakes, measured or presumed,seem to fall into one of two classes: the closed-loop, discrete vortex model at low flight speeds, and the constant-circulation, continuous vortex model at moderate to high speeds. Here, novel and accurate quantitative measurements of velocity fields in vertical planes aligned with the freestream are used to investigate the wake structure of a thrush nightingale over its entire range of natural flight speeds. At most flight speeds, the wake cannot be categorised as one of the two standard types, but has an intermediate structure, with approximations to the closed-loop and constant-circulation models at the extremes. A careful accounting for all vortical structures revealed with the high-resolution technique permits resolution of the previously unexplained wake momentum paradox. All the measured wake structures have sufficient momentum to provide weight support over the wingbeat. A simple model is formulated and explained that mimics the correct, measured balance of forces in the downstroke- and upstroke-generated wake over the entire range of flight speeds. Pending further work on different bird species, this might form the basis for a generalisable flight model.
Sweeping and striking: a kinematic study of the trunk during prey capture in three thamnophiine snakes
Authors: Alfaro Michael E.
Published: June 2003

The trunk plays an obvious and important role in the prey capture behavior of many species of snake, yet trunk function during predatory strikes is poorly understood. Axial kinematics of three thamnophiine snakes(Thamnophis couchii, Thamnophis elegans and Nerodia rhombifer) were studied to quantify differences between sideways-directed and forward-directed attacks and to investigate strike diversity at relatively low phylogenetic levels. Feeding strikes were filmed at 60 Hz, and 13 points along the head and body were digitized. These points were used to calculate body segment displacement, rotation and velocity during predatory strikes. Kinematic analysis revealed significant differences in the foraging modes of these aquatic-feeding species. T. couchii displayed a stereotypical pre-strike posture in which the entire body was arranged in a series of loops directed towards the prey. Forward displacement of body segments sometimes occurred over the entire body in T. couchii but was restricted to the anterior one-third of the trunk in T. elegans and N. rhombifer. T. couchii and N. rhombifer both struck rapidly compared with T. elegans, although N. rhombifer typically had a short strike distance. N. rhombifer struck significantly faster than T. elegans. Aquatic prey capture diversity appears to reflect ecological diversity in thamnophiine snakes.
Structural colouration of avian skin: convergent evolution of coherently scattering dermal collagen arrays
Authors: Prum Richard O. , Torres Rodolfo
Published: June 2003

Structural colours of avian skin have long been hypothesized to be produced by incoherent (Rayleigh/Tyndall) scattering. We investigated the colour,anatomy, nanostructure and biophysics of structurally coloured skin,ramphotheca and podotheca from 31 species of birds from 17 families in 10 orders from across Aves. Integumentary structural colours of birds include ultraviolet, dark blue, light blue, green and yellow hues. The discrete peaks in reflectance spectra do not conform to the inverse fourth power relationship predicted by Rayleigh scattering. The dermis of structurally coloured skin consists of a thick (100–500 μm) layer of collagen that is usually underlain by a layer of melanin granules. Transmission electron micrographs(TEMs) of this colour-producing dermal collagen layer revealed quasi-ordered arrays of parallel collagen fibres. Two-dimensional (2-D) Fourier analysis of TEMs of the collagen arrays revealed a ring of peak spatial frequencies in the spatial variation in refractive index that are the appropriate size to make the observed ultraviolet–yellow colours by coherent scattering alone. One species, Philepitta castanea (Eurylaimidae), has exceptionally ordered, hexagonal arrays of collagen fibres that produce a hexagonal pattern of spatial frequency peaks in the power spectra. Ultraviolet, blue, green and yellow structural colours of avian skin are produced by coherent scattering(i.e. constructive interference) by arrays of collagen fibres in the dermis. Some yellow and orange skin colours are produced with a combination of structural and pigmentary mechanisms. These combined colours can have reflectance spectra with discrete peaks that are more saturated than hues produced by carotenoid pigments alone. Bluish facial skin from two species of Neotropical antbirds (Thamnophilidae) are nanostructurally too small to produce visible light by coherent scattering, and the colour production mechanism in these species remains unknown. Based on the phylogenetic distribution of structurally coloured skin in Aves, this mechanism of colour production has evolved convergently more than 50 independent times within extant birds.
Food transport in theC. eleganspharynx
Authors: Avery Leon , Shtonda Boris B.
Published: June 2003

Pumping of the C. elegans pharynx transports food particles(bacteria) posteriorly. We examined muscle motions to determine how this posterior transport is effected. We find that the motions of the middle section of the pharynx, the anterior isthmus, are delayed relative to the anterior section, the corpus. Simulations in which particles are assumed to move at mean fluid velocity when not captured by the walls of the pharyngeal lumen show that delayed isthmus motions do indeed cause net particle transport; however, the amount is much less than in the real pharynx. We propose that the geometry of the pharyngeal lumen forces particles to the center, where they move faster than mean fluid velocity. When this acceleration is incorporated into the simulation, particles are transported efficiently. The transport mechanism we propose explains past observations that the timing of muscle relaxation is important for effective transport. Our model also makes a prediction, which we confirm, that smaller bacteria are better food sources for C. elegans than large ones.
Central circuitry in the jellyfishAglantha digitaleIV. Pathways coordinating feeding behaviour
Authors: Mackie G. O. , Marx R. M. , Meech R. W.
Published: June 2003

The hydromedusan jellyfish Aglantha digitale feeds on small planktonic organisms carried to the margin by tentacle flexions. During feeding, the manubrium bends across (`points') and seizes the prey with flared lips. In immobilized preparations, pointing to a source of electrical stimulation was accurate, 70% of the time, to within 15°. Cutting experiments showed that the conduction pathways concerned with pointing and lip flaring are located in eight radial strands consisting of a radial canal,a giant nerve axon and a bundle of small axons with FMRFamide-like immunoreactivity.

Application of food juices to sites on the margin and tentacles evoked trains of impulses in the axon bundles (F events; conduction velocity 15.5±3.7 cm s-1) and in the epithelium lining the radial canals (E events; conduction velocity 28.5±3.5 cm s-1). Impulses were conducted circularly in the outer nerve ring (F events) or in the ring canal (E events).

Unilateral flexions of the manubrium during pointing arise from preferential excitation of one or more of eight longitudinal `muscle bands' in the wall of the manubrium and peduncle. Lip flaring represents symmetrical contraction of all eight bands. Cutting experiments revealed that F events mediate pointing; E events mediate lip flaring. Thus the endodermal radial canals, which in other hydromedusae mediate protective `crumpling', provide the conduction pathway for manubrial lip flaring. Aglantha's alternative protective response – escape swimming – makes crumpling unnecessary, releasing the pathway for use in feeding.

Trains of E events, generated in the manubrium during ingestion, propagate to the margin and inhibit rhythmic (slow) swimming with a duration that depended on their number and frequency. Inhibition of swimming appeared to facilitate transfer of food from the margin to the mouth, but how it comes about is unclear.
Vibration-based damage identification in beam-like composite laminates by using artificial neural networks
Authors: Sahin M , Shenoi R A
Published: June 2003

This paper investigates the effectiveness of the combination of global (changes in natural frequencies) and local (curvature mode shapes) vibration-based analysis data as input for artificial neural networks (ANNs) for location and severity prediction of damage in fibre-reinforced plastic laminates. A finite element analysis tool has been used to obtain the dynamic characteristics of intact and damaged cantilever composite beams for the first three natural modes. Different damage scenarios have been introduced by reducing the local stiffness of the selected elements at different locations along the finite element model of the beam structure. After performing the sensitivity analyses aimed at finding the necessary parameters for the damage detection, different input-output sets have been introduced to various ANNs. In order to check the robustness of the input used in the analysis, random noise has been generated numerically and added to noise-free data during the training of the ANNs. Finally, trained feedforward back-propagation ANNs have been tested using new damage cases and checks have been made for severity and location prediction of the damage.
Mutagenicity, antioxidant potential, and antimutagenic activity against hydrogen peroxide of cashew (Anacardium occidentale) apple juice and cajuina
Authors: Melo Cavalcante Ana Amélia , Rubensam Gabriel , Picada Jaqueline N. , Gomes da Silva Evandro , Fonseca Moreira José Claúdio , Henriques João A.P.
Published: June 2003

Fresh and processed cashew (Anacardium occidentale) apple juice (CAJ) are among the most popular drinks in Brazil. Besides their nutritional benefits, these juices have antibacterial and antitumor potential. The chemical constituents of both the fresh juice and the processed juice (cajuina) were analyzed and characterized as complex mixtures containing high concentrations of vitamin C, various carotenoids, phenolic compounds, and metals. In the present study, these beverages exhibited direct and rat liver S9‐mediated mutagenicity in the Salmonella/microsome assay with strains TA97a, TA98, and TA100, which detect frameshifts and base pair substitution. No mutagenicity was observed with strain TA102, which detects oxidative and alkylating mutagens and active forms of oxygen. Both CAJ and cajuina showed antioxidant activity as determined by a total radical‐trapping potential assay. To test whether this antioxidant potential might result in antimutagenesis, we used a variation of the Salmonella/microsome assay that included pre‐, co‐, and posttreatment of hydrogen peroxide‐exposed Salmonella typhimurium strain TA102 with the juices. CAJ and cajuina protected strain TA102 against mutation by oxidative damage in co‐ and posttreatments. The antimutagenic effects during cotreatment with hydrogen peroxide may be due to scavenging free radicals and complexing extracellular mutagenic compounds. The protective effects in posttreatment may be due to stimulation of repair and/or reversion of DNA damage. The results indicate that CAJ and cajuina have mutagenic, radical‐trapping, antimutagenic, and comutagenic activity and that these properties can be related to the chemical constituents of the juices. Environ. Mol. Mutagen. 41:360–369, 2003. © 2003 Wiley‐Liss, Inc.
Positive correlation between the frequency of micronucleated cells and dysplasia in Papanicolaou smears
Authors: Guzmán Patricia , Sotelo‐Regil Rita C. , Mohar Alejandro , Gonsebatt María E.
Published: June 2003

Most cancers arise in epithelial tissues and these tissues are typically the targets of the carcinogens responsible for the tumors. Exfoliated epithelial cells have traditionally been used for cancer screening by cytopathologists and these cells also can be used for biomonitoring of genotoxic effects in humans. Cervical cancer results from the progression of preinvasive precursor lesions, called low‐grade squamous intraepithelial lesions (LGSILs), to high‐grade squamous intraepithelial lesions (HGSILs). The gradient from low to high‐grade lesions is characterized by increasing nuclear atypia and the failure of cellular differentiation in progressively more superficial levels of the epithelium. These phenotypic changes are hypothesized to be accompanied by increased genetic instability that can be documented using the micronucleus (MN) assay in exfoliated cervical cells. A retrospective study was performed to investigate the frequency of micronucleated cells in cervical smears from women at high risk for developing cervical cancer. Papanicolaou (Pap) smears from 275 women previously studied at a cancer clinic were coded and analyzed for the frequency of micronucleated cells. LGSIL, HGSIL, and invasive carcinoma smears had significantly higher frequencies than normal and ASCUS (abnormal squamous cells of undetermined origin) smears. HGSIL or severely dysplastic smears had the highest frequency of micronucleated cells (although not significantly higher than LGSIL smears), an observation that that could be useful in confirming these types of lesions. The results indicate that the MN frequency in exfoliated cervical cells may be an additional criterion for establishing cervical cancer risk. Environ. Mol. Mutagen. 41:339–343, 2003. © 2003 Wiley‐Liss, Inc.
Genotoxicity of surface water treated with different disinfectants using in situ plant tests
Authors: Monarca S. , Rizzoni M. , Gustavino B. , Zani C. , Alberti A. , Feretti D. , Zerbini I.
Published: June 2003

Disinfection of surface drinking water, in particular water chlorination, results in many by‐products with potential genotoxic and/or carcinogenic activity. In the present study, we evaluated the genotoxicity of surface water after treatment with different disinfectants by means of in situ plant genotoxicity assays (micronucleus and chromosomal aberration tests) which can detect both clastogenic and aneugenic effects. The study was carried out at a pilot plant using lake water after sedimentation and filtration. This water supplied four stainless steel basins: three basins were disinfected with sodium hypochlorite, chlorine dioxide, and peracetic acid and the fourth basin containing untreated lake water was used as a control. Plants were exposed in situ in the basins. The study was carried out using water collected in different seasons over a period of about 1 year in order to assess the treatments in different physical and chemical lake water conditions. The micronucleus test in root cells of Vicia faba (Vicia faba/MCN test) revealed genotoxicity in many samples of disinfected water. The micronucleus test in Tradescantia pollen cells and the chromosome aberration test in root cells of Allium cepa showed genotoxic effects only in some disinfected samples, but also revealed genotoxicity in raw water. The results of the study indicated that the Vicia faba/MCN test was the most sensitive plant assay for disinfected water and that peracetic acid disinfection produced similar or lower genotoxicity than sodium hypochlorite or chlorine dioxide treatment. Environ. Mol. Mutagen. 41:353–359, 2003. © 2003 Wiley‐Liss, Inc.
Cell‐cycle deregulation in BALB/c 3T3 cells transformed by 1,2‐dibromoethane and folpet pesticides
Authors: Santucci Maria Alessandra , Mercatali Laura , Brusa Gianluca , Pattacini Laura , Barbieri Enza , Perocco Paolo
Published: June 2003

The cell‐transforming potential of 1,2‐dibromoethane and folpet, two widely used agricultural pesticides that are potential sources of environmental pollution, has been previously ascribed to their promoting activity. In this study, we investigated whether BALB/c 3T3 transformation by these chemicals was associated with the deregulation of signals involved in cell‐cycle progression and in cell‐cycle checkpoint induction. We found that two BALB/c 3T3 cell clones transformed by in vitro medium‐term (8‐week) exposure to the carcinogens had a constitutive acceleration of cell transition from G1 to S phase and an abrogation of the radiation‐induced G1/S checkpoint. These events involved multiple signals; in particular, the inhibitors of cyclin/cyclin‐dependent kinase complexes p21 and p27 were significantly down‐modulated and the positive regulators of cell‐cycle progression cyclin D3 and E were up‐modulated. As anticipated for cells where the G1/S checkpoint was abrogated, the transformed cells exhibited a significant reinforcement of the radiation‐induced G2/M checkpoint, the only checkpoint remaining to protect genomic integrity. However, cyclin A1 and B1 coexpression and cyclin A1 overexpression were found despite the G2 arrest in irradiated cells and these signals likely attenuate the G2/M checkpoint. These alterations to normal cell cycling may promote the emergence of both numerical and structural chromosomal abnormalities and their tolerance. Such a condition could play a key role in neoplastic transformation and be crucial in tumor progression. Furthermore, cyclin A1 overexpression may play an autonomous role in the neoplastic transformation of BALB/c 3T3 cells, as it does in other cell types of mesenchymal origin. Environ. Mol. Mutagen. 41:315–321, 2003. © 2003 Wiley‐Liss, Inc.
Altered expression of zinc finger proteins, ADAMs, and integrin‐related proteins following treatment of cultured human cells with a low concentration of N‐methyl‐N′‐nitro‐N‐nitrosoguanidine
Authors: Jin Jinghua , Gao Zhihua , Guo Lei , Yang Jun , Yu Yingnian
Published: June 2003

Proteomic analysis is an important approach to characterize the proteome and study protein functions. It is also a powerful screening method for detecting unexpected alterations in protein expression that may be overlooked by conventional biochemical techniques. N‐Methyl‐N′‐nitro‐N‐nitrosoguanidine (MNNG) is an alkylating agent that can induce nontargeted mutagenesis in treated cells, although the mechanism remains unclear. Using an efficient proteomic method, we identified several cellular proteins that are responsive to low‐concentration MNNG treatment in human FL cells. After MNNG treatment, whole cellular proteins were separated using two‐dimensional gel electrophoresis and visualized by silver staining; the digitized images then were analyzed with 2D analysis software. More than 60 proteins showed significant changes in MNNG‐treated cells compared to control cells (DMSO treatment). Thirty‐one proteins only detected in MNNG‐treated or control cells were subjected to in‐gel digestion with trypsin and identified by matrix‐assisted laser desorption ionization‐time of flight (MALDI‐TOF) mass spectrometry using peptide mass fingerprinting. Eighteen of theses proteins have been identified, including several zinc finger proteins, two members of the ADAMs (a disintegrin and metalloprotease domain) family, and two integrins. Most of these proteins have unknown functions and their involvement in the cellular responses to alkylating agents have not been reported. Therefore, our findings may offer new insights into the mechanisms of low‐concentration MNNG‐induced nontargeted mutagenesis and these proteins may serve as new biomarkers for detecting exposure of human populations to environmental carcinogens. Environ. Mol. Mutagen. 41:344–352, 2003. © 2003 Wiley‐Liss, Inc.