bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular dynamics studies of heterogeneous dynamics and dynamic crossover in supercooled atomic liquids
Authors: Andersen Hans C.
Published: May 2005

Supercooled liquids near the glass transition exhibit the phenomenon of heterogeneous relaxation; at any specific time, a nominally homogeneous equilibrium fluid undergoes dynamic fluctuations in its structure on a molecular distance scale with rates that are very different in different regions of the sample. Several theoretical and simulation studies have suggested a change in the nature of the dynamics of fluids as they are supercooled, leading to the concept of a dynamic crossover that is often associated with mode coupling theory. Here, we will review the use of molecular dynamics computer simulation methods to investigate heterogeneous dynamics and dynamic crossovers in models of atomic liquids.
Isolation and characterization of a retinal pigment epithelial cell fluorophore: An
all-trans
-retinal dimer conjugate
Authors: Fishkin Nathan E. , Sparrow Janet R. , Allikmets Rando , Nakanishi Koji
Published: May 2005

Several lines of investigation suggest that the nondegradable fluorophores that accumulate as lipofuscin in retinal pigment epithelium (RPE) cells contribute to the etiology of macular degeneration. Despite evidence that much of this fluorescent material may originate as inadvertent products of the retinoid cycle, the enzymatic pathway by which the 11-
cis
-retinal chromophore of rhodopsin is generated, the only fluorophores of the RPE to be characterized as yet have been A2E and its isomers. Here, we report the isolation and structural characterization of an additional RPE lipofuscin fluorophore that originates as a condensation product of two molecules of
all-trans
-retinal (ATR) dimer and forms a protonated Schiff base conjugate with phosphatidylethanolamine (PE), the latter conjugate (ATR dimer-PE) having UV-visible absorbance maxima at 285 and 506 nm. ATR dimer was found to form natively in bleached rod outer segments
in vitro
and when rod outer segments were incubated with ATR. HPLC analysis of eyecups that included RPE and isolated neural retina from
Abcr
-/- mice and RPE isolated from human donor eyes revealed the presence of a pigment with the same UV-visible absorbance and retention time as synthetic ATR dimer-PE conjugate. Evidence that ATR dimer undergoes a photooxidation process involving the addition of oxygens at double bonds as well as an aromatic demethylation also may indicate a role for this molecule, or its derivatives, in the photoreactivity of RPE lipofuscin.
Point mutation in AML1 disrupts subnuclear targeting, prevents myeloid differentiation, and effects a transformation-like phenotype
Authors: Vradii Diana , Zaidi Sayyed K. , Lian Jane B. , van Wijnen Andre J. , Stein Janet L. , Stein Gary S.
Published: May 2005

The multifunctional C terminus of the hematopoietic AML1 transcription factor interacts with coregulatory proteins, supports the convergence and integration of physiological signals, and contains the nuclear matrix targeting signal, the protein motif that is necessary and sufficient to target AML1 to subnuclear sites. The (8;21) chromosomal translocation, which replaces the C terminus of AML1 with the ETO protein, modifies subnuclear targeting of AML1 in acute myeloid leukemia (AML) and results in defective myelopoiesis. We therefore addressed the relevance of AML1 subnuclear targeting and associated functions that reside in the C terminus to myeloid differentiation. A single amino acid substitution that abrogates intranuclear localization was introduced in the AML1 subnuclear targeting signal. Expression of the mutant AML1 protein blocks differentiation of myeloid progenitors to granulocytes in the presence of endogenous AML1 protein, as also occurs in the (8;21) chromosomal translocation, where only one allele of theAML1gene is affected. The cells expressing the mutant AML1 protein continue to proliferate, maintain an immature blast-like morphology, and exhibit transformed properties that are hallmarks of leukemogenesis. These findings functionally link AML1 subnuclear targeting with competency for myeloid differentiation and expression of the transformed/leukemia phenotype.
Abundance, dispersion and parasitism of the stem borer Busseola fusca (Lepidoptera: Noctuidae) in maize in the humid forest zone of southern Cameroon
Authors: Chabi-Olaye A. , Nolte C. , Schulthess F. , Borgemeister C.
Published: May 2005

This study was conducted in the humid forest zone of Cameroon, in 2002 and 2003. The main objective was to investigate the effects of intercropping on infestation levels and parasitism of the noctuid maize stem borer Busseola fusca Fuller. Two trials were planted per year, one during the long and one during the short rainy season. Maize monocrops were compared with maize/legume or maize/cassava intercrops in two spatial arrangements: maize on alternate hills or in alternate rows. Spatial analyses showed that the stemborer egg batches were regularly dispersed in the maize monocrop and aggregated in the intercrops, as indicated by b, the index of dispersion of Taylor's power law. Depending on the crop association and planting pattern, intercrops reduced the percentage of plants with stem borer eggs by 47.4–58.4% and egg densities by 41.2–54.5% compared to monocropped maize. Consequently, larval densities were 44.4–61.5% lower in intercrops compared to monocrops. Intercropping maize with non-host plants did not affect larval parasitism. Up to two-fold higher levels of egg parasitism by scelionid Telenomus spp. were recorded in inter- compared to monocrops during the short rainy seasons of 2002 and 2003. No differences were found among the mixed cropping treatments and parasitism was lower during the long compared to the short rainy seasons. It was proposed that differences in levels of parasitism were due to density dependence effects rather than the effect of the presence of non-host plants in the system.
Ballooning dispersal using silk: world fauna, phylogenies, genetics and models
Authors: Bell J.R. , Bohan D.A. , Shaw E.M. , Weyman G.S.
Published: May 2005

Aerial dispersal using silk (‘ballooning’) has evolved in spiders (Araneae), spider mites (Acari) and in the larvae of moths (Lepidoptera). Since the 17th century, over 500 observations of ballooning behaviours have been published, yet there is an absence of any evolutionary synthesis of these data. In this paper the literature is reviewed, extensively documenting the known world fauna that balloon and the principal behaviours involved. This knowledge is then incorporated into the current evolutionary phylogenies to examine how ballooning might have arisen. Whilst it is possible that ballooning co-evolved with silk and emerged as early as the Devonian (410–355 mya), it is arguably more likely that ballooning evolved in parallel with deciduous trees, herbaceous annuals and grasses in the Cretaceous (135–65 mya). During this period, temporal (e.g. bud burst, chlorophyll thresholds) and spatial (e.g. herbivory, trampling) heterogeneities in habitat structuring predominated and intensified into the Cenozoic (65 mya to the present). It is hypothesized that from the ancestral launch mechanism known as ‘suspended ballooning’, widely used by individuals in plant canopies, ‘tip-toe’ and ‘rearing’ take-off behaviours were strongly selected for as habitats changed. It is contended that ballooning behaviour in all three orders can be described as a mixed Evolutionary Stable Strategy. This comprises individual bet-hedging due to habitat unpredictability, giving an underlying randomness to individual ballooning, with adjustments to the individual ballooning probability being conferred by more predictable habitat changes or colonization strategies. Finally, current methods used to study ballooning, including modelling and genetic research, are illustrated and an indication of future prospects given.
Inulin-type fructans and bone health: state of the art and perspectives in the management of osteoporosis
Authors: Coxam Véronique
Published: May 2005

If the primary role of diet is to provide sufficient nutrients to meet the metabolic requirements of an individual, there is an emerging rationale to support the hypothesis that, by modulating specific target functions in the body, it can help achieve optimal health. Regarding osteoporosis prevention, since Ca is most likely to be inadequate in terms of dietary intake, every strategy targeting an improvement in Ca absorption is very interesting. Actually, this process may be susceptible to manipulation by fermentable substrates. In this light, inulin-type fructans are very interesting, even if we need to gather more data targeting bone metabolism before health professionals can actively advocate their consumption to prevent senile osteoporosis. Besides targeting the prevention of postmenopausal osteoporosis, inulin-type fructans still remain a source for putative innovative dietary health intervention. Indeed, given in combination with isoflavones, they may have a potential for maintaining or improving the bone mass of human subjects, by modulating the bioavailability of phyto-oestrogens.
Prebiotics and resistance to gastrointestinal infections
Authors: Gibson G. R. , McCartney A. L. , Rastall R. A.
Published: May 2005

Acute gut disorder is a cause for significant medicinal and economic concern. Certain individual pathogens of the gut, often transmitted in food or water, have the ability to cause severe discomfort. There is a need to manage such conditions more effectively. The route of reducing the risk of intestinal infections through diet remains largely unexplored. Antibiotics are effective at inhibiting pathogens; however, these should not be prescribed in the absence of disease and therefore cannot be used prophylactically. Moreover, their indiscriminate use has reduced effectiveness. Evidence has accumulated to suggestthat some of the health-promoting bacteria in the gut (probiotics) can elicit a multiplicity of inhibitory effects against pathogens. Hence, an increase in their numbers should prove effective at repressing pathogen colonisation if/when infectious agents enter the gut. As such, fortification of indigenous bifidobacteria/lactobacilli by using prebiotics should improve protection. There are a number of potential mechanisms for lactic acid bacteria to reduce intestinal infections. Firstly, metabolic endproducts such as acids excreted by these micro-organisms may lower the gut pH to levels below those at which pathogens are able to effectively compete. Also, many lactobacilli and bifidobacteria species are able to excrete natural antibiotics, which can have a broad spectrum of activity. Other mechanisms include an improved immune stimulation, competition for nutrients and blocking of pathogen adhesion sites in the gut. Many intestinal pathogens like type 1 fimbriated Escherichia coli, salmonellae and campylobacters utilise oligosaccharide receptor sites in the gut. Once established, they can then cause gastroenteritis through invasive and/or toxin forming properties. One extrapolation of the prebiotic concept is to simulate such receptor sites in the gut lumen. Hence, the pathogen is ‘decoyed’ into not binding at the host mucosal interface. The combined effects of prebiotics upon the lactic acid flora and anti-adhesive strategies may lead towards new dietary interventions against food safety agents.
The concept of well-being: relevance to nutrition research
Authors: Smith Andrew P.
Published: May 2005

The aim of this paper is to discuss issues that fall within the general concept of well-being, with special emphasis on approaches that have been used in studies of nutrition and behaviour. Following this, two specific studies are described in detail, the first examining high-fibre breakfast cereals and the second investigating effects of inulin. Studies of nutrition and well-being can be categorised in a number of ways. One method involves examining acute effects of nutrition on mood and cognitive functioning. Another method has been to examine cross-sectional associations between dietary habits and questionnaire measures of reported health. Examples are given showing that regular consumption of a high-fibre diet is associated with better-reported physical and mental health. The problem with such correlational studies is that it is impossible to infer causality. Intervention studies are necessary to achieve this and some examples of this approach are given. In the first study reported here, we examined whether consumption of high-fibre breakfast cereal led to an increase in energy. Such an effect was observed and plausible biological mechanisms underlying such results are described. A similar methodology has recently been used to examine the effects of inulin. In this case the results showed no negative side-effects of taking inulin but there were no beneficial effects of inulin on measures of well-being (both subjective reports and objective measures). Possible reasons for these effects are discussed.
Modelling dishes and exploring culinary ‘precisions’: the two issues of molecular gastronomy
Authors: This Hervé
Published: May 2005

The scientific strategy of molecular gastronomy includes modelling ‘culinary definitions’ and experimental explorations of ‘culinary precisions’. A formalism that describes complex dispersed systems leads to a physical classification of classical sauces, as well as to the invention of an infinite number of new dishes
Application of prebiotics in infant foods
Authors: Veereman-Wauters Gigi
Published: May 2005

The rationale for supplementing an infant formula with prebiotics is to obtain a bifidogenic effect and the implied advantages of a ‘breast-fed-like’ flora. So far, the bifidogenic effect of oligofructose and inulin has been demonstrated in animals and in adults, of oligofructose in infants and toddlers and of a longchain inulin (10 %) and galactooligosaccharide (90 %) mixture in term and preterm infants. The addition of prebiotics to infant formula softens stools but other putative effects remain to be demonstrated. Studies published post marketing show that infants fed a long-chain inulin/galactooligosaccharide mixture (0·8 g/dl) in formula grow normally and have no side-effects. The addition of the same mixture at a concentration of 0·8 g/dl to infant formula was therefore recognized as safe by the European Commission in 2001 but follow-up studies were recommended. It is thought that a bifidogenic effect is beneficial for the infant host. The rising incidence in allergy during the first year of life may justify the attempts to modulate the infant's flora. Comfort issues should not be confused with morbidity and are likely to be multifactorial. The functional effects of prebiotics on infant health need further study in controlled intervention trials.
First records of dive durations for a hibernating sea turtle
Authors: Hochscheid Sandra , Bentivegna Flegra , Hays Graeme C
Published: May 2005

The first published record, from the early 1970s, of hibernation in sea turtles is based on the reports of the indigenous Indians and fishermen from Mexico, who hunted dormant green turtles (
Chelonia mydas
) in the Gulf of California. However, there were no successful attempts to investigate the biology of this particular behaviour further. Hence, data such as the exact duration and energetic requirements of dormant winter submergences are lacking. We used new satellite relay data loggers to obtain the first records of up to 7 h long dives of a loggerhead turtle (
Caretta caretta
) overwintering in Greek waters. These represent the longest dives ever reported for a diving marine vertebrate. There is strong evidence that the dives were aerobic, because the turtle surfaced only for short intervals and before the calculated oxygen stores were depleted. This evidence suggests that the common belief that sea turtles hibernate underwater, as some freshwater turtles do, is incorrect.
Relative contribution of abundant and rare species to species–energy relationships
Authors: Evans Karl L , Greenwood Jeremy J.D , Gaston Kevin J
Published: May 2005

A major goal of ecology is to understand spatial variation in species richness. The latter is markedly influenced by energy availability and appears to be influenced more by common species than rare ones; species–energy relationships should thus be stronger for common species. Species–energy relationships may arise because high-energy areas support more individuals, and these larger populations may buffer species from extinction. As extinction risk is a negative decelerating function of population size, this more-individuals hypothesis (MIH) predicts that rare species should respond more strongly to energy. We investigate these opposing predictions using British breeding bird data and find that, contrary to the MIH, common species contribute more to species–energy relationships than rare ones.
The evolution of a conjugative plasmid and its ability to increase bacterial fitness
Authors: Dionisio F , Conceição I.C , Marques A.C.R , Fernandes L , Gordo I
Published: May 2005

Conjugative plasmids are extra-chromosomal DNA elements that are capable of horizontal transmission and are found in many natural isolated bacteria. Although plasmids may carry beneficial genes to their bacterial host, they may also cause a fitness cost. In this work, we studied the evolution of the R1 plasmid and we found that, in spite of the R1 plasmid conferring an initial cost to its host, after 420 generations the cost disappeared in all five independent evolution experiments. In fact, in two of these five experiments evolved conjugative plasmids actually conferred a fitness advantage to their hosts. Furthermore, the relative fitness of the ancestral clone bearing one of the evolved plasmids is significantly higher than both the plasmid-free ancestral cells and the evolved cells carrying the evolved plasmid. Given that the R1 plasmid may spread among different species of enterobacteria, we wondered what the effect of the evolved plasmid would be insideSalmonella entericacells. We found that the evolved plasmid is also able to dramatically increase the relative fitness of these cells. Our results suggest that even if general usage of antibiotics is halted, conjugative plasmids that have been selected with antibiotics in previous years can still persist among bacterial populations or even invade new strains.
Selective foraging of fungi by collembolans in soil
Authors: Jørgensen Helene Bracht , Johansson Tomas , Canbäck Björn , Hedlund Katarina , Tunlid Anders
Published: May 2005

Soils contain highly diverse communities of microorganisms and invertebrates. The trophic interactions between these species are largely unknown. Collembolans form an abundant part of the invertebrate community in soils. A prevailing view is that soil collembolans are generalist feeders on fungi, lichens, fragmented litter and bacteria. However, in laboratory food choice experiments, it has been shown that collembolans preferentially select certain taxa of fungi. To examine this apparent contradiction, we developed a molecular technique based on the analysis of 18S ribosomal DNA (rDNA) sequences to explore the diversity of fungi in soils and in the guts of collembolans. We report that the diversity of fungi found in the natural soil was 33 times higher than that in the guts of the collembolan
Protaphorura armata
. The data support the view that collembolan species can be highly selective when foraging on fungi in soils.
Longer telomeres associated with higher survival in birds
Authors: Haussmann Mark F , Winkler David W , Vleck Carol M
Published: May 2005

Differences in individual quality and survival within species are a major focus in evolutionary ecology, but we know very little about the underlying physiological mechanisms that determine these differences. Telomere shortening associated with cellular senescence and ageing may be one such mechanism. To date, however, there is little evidence linking telomere length and survival. Here, we show that tree swallows (
Tachycineta bicolor
) with relatively short telomeres at the age of 1 year have lower survival than tree swallows of the same age with relatively long telomeres. The survival advantage in the long telomere group continues for at least three breeding seasons. It will be important to identify mechanisms that link telomere length with survival early in life.
The evolution of a batch-immigration death process subject to counts
Authors: Gillespie Colin S , Renshaw Eric
Published: May 2005

A bivariate batch immigration-death process is developed to study the degree to which the fundamental structure of a hidden stochastic process can be inferred purely from counts of escaping individuals. This question is of immense importance in fields such as quantum optics, where externally based radiation elucidates the nature of the underlying electromagnetic radiation process. Batches of
i
immigrants enter the population at rate
αq

i

, and each individual dies independently at rate
μ
. General expressions are developed for the population size cumulants and probabilities, together with those for the associated counting process. The strong link between these two structures is highlighted through two specific examples, involving
k
-batch immigration for
i
=
k
, and Schoenberg-batch immigration over
i
=2

m

(
m
=0, 1, 2, …), and shows that high quality inferences on the hidden population process can be inferred purely from externally counted observations.
Stability and eigenvalue bounds of the flow of a dipolar fluid between two parallel plates
Authors: Puri Pratap
Published: May 2005

In this article, we derive the Orr–Sommerfeld equation for the stability of parallel flows of a dipolar fluid. The classical results found by Squire, for viscous Newtonian fluids, are generalized to the case of dipolar fluids. A sufficient condition for stability is obtained for dipolar fluids and eigenvalue bounds for the Orr–Sommerfeld equation are found.
An improved trigonometrically fitted P-stable Obrechkoff method for periodic initial-value problems
Authors: Wang Zhongcheng , Zhao Deying , Dai Yongming , Wu Dongmei
Published: May 2005

In this paper we present an improved P-stable trigonometrically fitted Obrechkoff method with phase-lag (frequency distortion) infinity. Compared with the previous P-stable trigonometrically fitted Obrechkoff method developed by Simos, our new method is simpler in structure and more stable in computation. We have also improved the accuracy of the first-order derivative formula. From the numerical illustration presented, we can show that the new method is much more accurate than the previous methods.
Multisymplectic conservation laws for differential and differential-difference equations
Authors: Hydon P.E
Published: May 2005

Many well-known partial differential equations can be written as multisymplectic systems. Such systems have a structural conservation law from which scalar conservation laws can be derived. These conservation laws arise as differential consequences of a 1-form ‘quasi-conservation law’, which is related to Noether's theorem. This paper develops the above framework and uses it to introduce a multisymplectic structure for differential-difference equations. The shallow water equations and the Ablowitz–Ladik equations are used to illustrate the general theory. It is found that conservation of potential vorticity is a differential consequence of two conservation laws; this surprising result and its implications are discussed.
Secondary fluid flows driven electromagnetically in a two-dimensional extended duct
Authors: Chen Zhi-Min , Price W.G
Published: May 2005

This study focuses on two-dimensional fluid flows in a straight duct with free-slip boundary conditions applied on the channel walls
y
=0 and
y
=2
πN
with
N
>1. In this extended wall-bounded fluid motion problem, secondary fluid flow patterns resulting from steady-state and Hopf bifurcations are examined and shown to be dependent on the choice of longitudinal wave numbers. Some secondary steady-state flows appear at specific wave numbers, whereas at other wave numbers, both secondary steady-state and self-oscillation flows coexist. These results, derived through analytical arguments and truncation series approximation, are confirmed by simple numerical experiments supporting the findings observed from laboratory experiments.
Biosonar behaviour of free-ranging porpoises
Authors: Akamatsu Tomonari , Wang Ding , Wang Kexiong , Naito Yasuhiko
Published: May 2005

Detecting objects in their paths is a fundamental perceptional function of moving organisms. Potential risks and rewards, such as prey, predators, conspecifics or non-biological obstacles, must be detected so that an animal can modify its behaviour accordingly. However, to date few studies have considered how animals in the wild focus their attention. Dolphins and porpoises are known to actively use sonar or echolocation. A newly developed miniature data logger attached to a porpoise allows for individual recording of acoustical search efforts and inspection distance based on echolocation. In this study, we analysed the biosonar behaviour of eight free-ranging finless porpoises (Neophocaena phocaenoides) and demonstrated that these animals inspect the area ahead of them before swimming silently into it. The porpoises inspected distances up to 77 m, whereas their swimming distance without using sonar was less than 20 m. The inspection distance was long enough to ensure a wide safety margin before facing real risks or rewards. Once a potential prey item was detected, porpoises adjusted their inspection distance from the remote target throughout their approach.
[NiFe]-hydrogenases: spectroscopic and electrochemical definition of reactions and intermediates
Authors: Armstrong Fraser A , Albracht Simon P.J
Published: May 2005

Production and usage of di-hydrogen, H
2
, in micro-organisms is catalysed by highly active, ‘ancient’ metalloenzymes known as hydrogenases. Based on the number and identity of metal atoms in their active sites, hydrogenases fall into three main classes, [NiFe]-, [FeFe]- and [Fe]-. All contain the unusual ligand CO (and in most cases CN
−
as well) making them intriguing examples of ‘organometallic’ cofactors. These ligands render the active sites superbly ‘visible’ using infrared spectroscopy, which complements the use of electron paramagnetic resonance spectroscopy in studying mechanisms and identifying intermediates. Hydrogenases are becoming a focus of attention for research into future energy technologies, not only H
2
production but also H
2
oxidation in fuel cells. Hydrogenases immobilized on electrodes exhibit high electrocatalytic activity, providing not only an important new technique for their investigation, but also a basis for novel fuel cells either using the enzyme itself, or inspired synthetic catalysts. Favourable comparisons have been made with platinum electrocatalysts, an advantage of enzymes being their specificity for H
2
and tolerance of CO. A challenge for exploiting hydrogenases is their sensitivity to O
2
, but some organisms are known to produce enzymes that overcome this problem by subtle alterations of the active site and gas access channels.
Hydroxylation of C–H bonds at carboxylate-bridged diiron centres
Authors: Lippard Stephen J
Published: May 2005

Nature uses carboxylate-bridged diiron centres at the active sites of enzymes that catalyse the selective hydroxylation of hydrocarbons to alcohols. The resting diiron(III) state of the hydroxylase component of soluble methane monooxygenase enzyme is converted by two-electron transfer from an NADH-requiring reductase into the active diiron(II) form, which subsequently reacts with O
2
to generate a high-valent diiron(IV) oxo species (Q) that converts CH
4
into CH
3
OH. In this step, C–H bond activation is achieved through a transition state having a linear C⋯H⋯O unit involving a bound methyl radical. Kinetic studies of the reaction of Q with substrates CH
3
X, where X=H, D, CH
3
, NO
2
, CN or OH, reveal two classes of reactivity depending upon whether binding to the enzyme or C–H bond activation is rate-limiting. Access of substrates to the carboxylate-bridged diiron active site in the hydroxylase (MMOH) occurs through a series of hydrophobic pockets. In the hydroxylase component of the closely related enzyme toluene/
o
-xylene monooxygenase (ToMOH), substrates enter through a wide channel in the α-subunit of the protein that tracks a course identical to that found in the structurally homologous MMOH. Synthetic models for the carboxylate-bridged diiron centres in MMOH and ToMOH have been prepared that reproduce the stoichiometry and key geometric and physical properties of the reduced and oxidized forms of the proteins. Reactions of the diiron(II) model complexes with dioxygen similarly generate reactive intermediates, including high-valent species capable not only of hydroxylating pendant C–H bonds but also of oxidizing phosphine and sulphide groups.
Catalysis: principles, progress, prospects
Authors: Thomas John Meurig , Williams Robert J.P
Published: May 2005

In this introductory paper, we endeavour to bridge the gaps that currently exist between the three main subdivisions of catalysis: enzymatic, homogeneous and heterogeneous. Hitherto, there has been a tendency for each of these three divisions to grow separately using their own concepts, phrases and techniques. However, there is much that unites them, not least the notion of the catalytically active site and, in particular, its often unusual (constrained) state of electronic or atomic environmental disposition. We identify many points of similarity between, for example, the mode of action of, metalloenzymes on the one hand and the recent generation of transition metal ions embedded within nanoporous (usually siliceous) solids on the other. Useful unifying principles emerge from considerations of free-energy/reaction-coordinate plots.

We present a number of tabulations and comparisons designed to facilitate the understanding of the mode of operation of existing, and the performance of new, catalysts. In doing so, we have drawn on our own work as well as that of others, including contributions that are to be found in this volume, with the intention of covering the great variety of catalytic phenomena.
Intermediates in P450 catalysis
Authors: Poulos Thomas L
Published: May 2005

Cytochromes P450 catalyse the insertion of one O
2
-derived oxygen atom in unactivated C–H bonds, and as such, are potent oxidants. A significant amount is known about the P450 catalytic cycle owing partly to the single heme group at the active site that provides spectroscopic handles in tracking various intermediates. A sophisticated array of electron paramagnetic, electron double nuclear resonance, and more traditional absorption spectroscopies have been able to identify key intermediates, while crystallography has defined the structure of the substrate-free, -bound, and oxy-complexes. What has remained elusive is the Fe(IV)=O intermediate, thought to be the active hydroxylating agent. Here, theory and especially density functional calculations have provided valuable insights.
Asymptotic approach to combustion instability
Authors: Wu Xuesong
Published: May 2005

This paper presents an asymptotic approach to combustion instability in premixed flames under the assumptions of large activation energy and small Mach number. The entire flow consists of four distinct yet fully interactive sub-regions, which accommodate the chemical reaction, heat transport, hydrodynamics and acoustics, respectively. A reduced system was derived to describe the intricate coupling between the flame and acoustics that underlies the combustion instability. The asymptotically reduced system was employed to study the weakly nonlinear interaction between the Darrieus–Landau instability and the longitudinal acoustic mode of the combustion chamber. The general asymptotic formulation includes the influence of enthalpy fluctuation in the oncoming mixture. It is shown that one-dimensional enthalpy fluctuation, through its interaction with flame, produces sound waves, and may cause parametric instability of the flame. The mutual coupling between the sound wave and parametric instability is analysed at the instability thresholds.
How might cohesin hold sister chromatids together?
Authors: Nasmyth Kim
Published: May 2005

The sister chromatid cohesion essential for the bi-orientation of chromosomes on mitotic spindles depends on a multi-subunit complex called cohesin. This paper reviews the evidence that cohesin is directly responsible for holding sister DNAs together and considers how it might perform this function in the light of recent data on its structure.
Shugoshin protects cohesin complexes at centromeres
Authors: Watanabe Yoshinori , Kitajima Tomoya S
Published: May 2005

The different regulation of sister chromatid cohesion at centromeres and along chromosome arms is obvious during meiosis, because centromeric cohesion, but not arm cohesion, persists throughout anaphase of the first division. A protein required to protect centromeric cohesin Rec8 from separase cleavage has been identified and named shugoshin (or Sgo1) after
shugoshin
(‘guardian spirit’ in Japanese). It has become apparent that shugoshin shows marginal homology with
Drosophila
Mei-S332 and several uncharacterized proteins in other eukaryotic organisms. Because Mei-S332 is a protein previously shown to be required for centromeric cohesion in meiosis, it is now established that shugoshin represents a conserved protein family defined as a centromeric protector of Rec8 cohesin complexes in meiosis. The regional difference of sister chromatid cohesion is also observed during mitosis in vertebrates; the cohesion is much more robust at the centromere at metaphase, where it antagonizes the pulling force of spindle microtubules that attach the kinetochores from opposite poles. The human shugoshin homologue (hSgo1) is required to protect the centromeric localization of the mitotic cohesin, Scc1, until metaphase. Bub1 plays a crucial role in the localization of shugoshin to centromeres in both fission yeast and humans.
Towards understanding the molecular basis of bacterial DNA segregation
Authors: Leonard Thomas A , Møller-Jensen Jakob , Löwe Jan
Published: May 2005

Bacteria ensure the fidelity of genetic inheritance by the coordinated control of chromosome segregation and cell division. Here, we review the molecules and mechanisms that govern the correct subcellular positioning and rapid separation of newly replicated chromosomes and plasmids towards the cell poles and, significantly, the emergence of mitotic-like machineries capable of segregating plasmid DNA. We further describe surprising similarities between proteins involved in DNA partitioning (ParA/ParB) and control of cell division (MinD/MinE), suggesting a mechanism for intracellular positioning common to the two processes. Finally, we discuss the role that the bacterial cytoskeleton plays in DNA partitioning and the missing link between prokaryotes and eukaryotes that is bacterial mechano-chemical motor proteins.
Clinical Holistic Medicine: Chronic Pain in Internal Organs
Authors: Ventegodt Søren , Merrick Joav
Published: May 2005

Holistic medicine seems to be efficient in the treatment of chronic pain in internal organs, especially when the pain has no known cause. It is quite surprising that while chronic pain can be one of the toughest challenges in the biomedical clinic, it is often one of the simplest things to alleviate in the holistic clinic. These pains are regarded as being caused by repressed emotions and are explained as psychosomatic reactions. Using holistic medicine, the patients can often be cured of their suffering when they assume responsibility for the repressed feelings. The holistic process theory of healing states that the return to the natural (pain free) state of being is possible whenever the person obtains the resources needed for existential healing. This shift is explained by the related quality of life and life mission theories. The resources needed are “holding” or genuine care in the dimensions of awareness, respect, care, acknowledgment, and acceptance with support and processing in the dimensions of feeling, understanding, and letting go of negative attitudes and beliefs. The preconditions for the holistic healing to take place are “love” and trust. Obtaining the full trust of the patient, therefore, seems to be the biggest challenge of holistic medicine, especially when dealing with a patient in pain.
Impact of Hydrophobic Pollutants' Behavior on Occupational and Environmental Health
Authors: Kanu Ijeoma , Anyanwu Ebere
Published: May 2005

This paper reviews the influence of hydrophobic pollutant behavior on environmental hazards and risks. The definition and examples of hydrophobic pollutants are given as a guide to better understand the sources of release and the media of dispersion in the environment. The properties and behavior of hydrophobic pollutants are described and their influence on environmental hazard and risk is reviewed and evaluated. The overall outcome of the assessment and evaluation showed that all hydrophobic pollutants are hazardous and risky to all organisms, including man. Their risk effects are due to their inherent persistence, bioaccumulation potential, environmental mobility, and reactivity. Their hazardous effects on organisms occur at varying spatial and temporal degrees of emissions, toxicities, exposures, and concentrations.
Child Injury in Israel: Emergency Room Visits to a Children's Medical Center
Authors: Hemmo-Lotem Michal , Jinich-Aronowitz Claudia , Endy-Findling Liri , Molcho Michal , Klein Michal , Waisman Yehezkel , Danon Yehuda L. , Merrick Joav
Published: May 2005

The object of this study was to provide data for policy making and prevention program planning in Israel. The study examined all visits to the Department of Emergency Medicine at the Schneider Children's Medical Center in 1996 (41,279 visits in total). Approximately 22.6% of the emergency room patients were admitted following injury. Most (97%) were unintentional injury. Approximately 42% of the patients were less than 4 years old and about 20% were 2 years old. In all age groups, the rate of boys was double. Approximately 92% were Jews. Despite this low rate of non-Jewish patients, however, they constituted 20% of later hospitalizations. The main injuries recorded were bruises and wounds from blunt objects, falls, motor vehicle–related accidents, and sport injuries. The most commonly injured body parts were the head and upper and lower limbs. In 82%, medical treatment was reported and 7% were hospitalized. In examining injuries over the year, there were no significant differences between the different months, but there were clusters of injuries around various holidays—bicycle and skateboard accidents at Rosh Hashanah, Yom Kippur, and Succoth; pedestrian accidents around Lag BaOmer; burns on Purim, Hannukkah, and Passover; and accidental poisoning around Passover. The findings gave an indication of the nature of the injured population groups. These data could be useful for prevention strategy, both on the level of physical injury as well as on the level of the times of the year, when the risk was higher. The data collected very strongly raise the urgent need for establishing a national surveillance system, which would allow tracking injury-related data with respect to young people throughout the country.
p38 MAP kinase inhibition enables proliferation of adult mammalian cardiomyocytes
Authors: Engel Felix B. , Schebesta Michael , Duong Mychelle T. , Lu Gang , Ren Shuxun , Madwed Jeffery B. , Jiang Huiping , Wang Yibin , Keating Mark T.
Published: May 2005

Adult mammalian cardiomyocytes are considered terminally differentiated and incapable of proliferation. Consequently, acutely injured mammalian hearts do not regenerate, they scar. Here, we show that adult mammalian cardiomyocytes can divide. One important mechanism used by mammalian cardiomyocytes to control cell cycle is p38 MAP kinase activity. p38 regulates expression of genes required for mitosis in cardiomyocytes, including cyclin A and cyclin B. p38 activity is inversely correlated with cardiac growth during development, and its overexpression blocks fetal cardiomyocyte proliferation. Activation of p38 in vivo by MKK3bE reduces BrdU incorporation in fetal cardiomyocytes by 17.6%. In contrast, cardiac-specific p38α knockout mice show a 92.3% increase in neonatal cardiomyocyte mitoses. Furthermore, inhibition of p38 in adult cardiomyocytes promotes cytokinesis. Finally, mitosis in adult cardiomyocytes is associated with transient dedifferentiation of the contractile apparatus. Our findings establish p38 as a key negative regulator of cardiomyocyte proliferation and indicate that adult cardiomyocytes can divide.
Oral hepatitis B vaccine candidates produced and delivered in plant material
Authors: Streatfield Stephen J
Published: May 2005

Hepatitis B is a major global health problem; approximately two billion people are infected with the virus worldwide, despite the fact that safe and efficacious vaccines have been developed and used for nearly 20 years. Prohibitive costs for vaccine purchase and administration restrict uptake in many developing nations. Agencies such as the Global Alliance for Vaccination and Immunization are helping to make current vaccines more available, but reduced costs would greatly aid this effort. Oral delivery is an option to reduce the expense of administering hepatitis B vaccines. It may also improve compliance, and orally delivered vaccines may be more efficacious among poor responders to current vaccines. However, to induce protective efficacy, oral administration may require encapsulation of antigen and delivery of large doses. Plant‐based expression systems offer an oral delivery alternative with low production costs, and they also encapsulate the antigen. Some plant‐based systems also stabilize antigen and therefore reduce storage and distribution costs. The hepatitis B major surface antigen has been expressed in several plant systems. A variety of regulatory sequences and subcellular targets have been used to achieve expression suitable for early stage clinical trials. However, further increase in expression will be necessary for practical and efficacious products. Appropriate processing can yield palatable products with uniform antigen concentration. The antigen expressed in plant systems shows extensive disulphide cross‐linking and oligomerization and forms virus‐like particles. Oral delivery of the antigen in plant material can induce a serum antibody response, prime the immune system for a subsequent injection of antigen and give a boosted response to a prior injection. Small scale clinical trials in which the antigen has been delivered orally in edible plant material indicate safety and immunogenicity.
Detection of foreign RNA: Implications for RNAi
Authors: de Veer Michael J , Sledz Carol A , Williams Bryan RG
Published: May 2005

RNA interference (RNAi) is an exciting technology with applications in basic research, in elucidation and validation of drug targets, and as a direct therapeutic. In mammalian settings, it is based on the introduction or expression of small interfering RNA (siRNA) that guide the cleavage of a complementary target messenger RNA. While siRNA certainly directs specific silencing of genes in mammalian cells, longer RNA typically used to silence genes in other organisms potently activate mammalian cell defence mechanisms leading to a non‐specific halt in translation, to activation of transcription and often, to cell death. Recent research has revealed that siRNA in certain settings can also activate these RNA‐responsive pathways. With the recent advances in RNAi technology and its first forays into the in vivo setting now coming to light, it is pertinent to review the cellular response to ribonucleic acids typically used in RNAi methods.
Transgenic plants for the production of veterinary vaccines
Authors: Dus Santos María José , Wigdorovitz Andrés
Published: May 2005

The expression of antigens in transgenic plants has been increasingly used in the development of experimental vaccines, particularly oriented to the development of edible vaccines. Hence, this technology becomes highly suitable to express immunogenic proteins from pathogens. Foot and mouth disease virus, bovine rotavirus and bovine viral diarrhoea virus are considered to be the most important causative agents of economic loss of cattle production in Argentina, and they are thus optimal candidates for alternative means of immunization. Here, we present a review of our results corresponding to the expression of immunogenic proteins from these three viruses in alfalfa transgenic plants, and we discuss the possibility of using them for the development of plant‐based vaccines.
Is there a role for plant‐made vaccines in the prevention of HIV/AIDS?
Authors: Webster Diane E , Thomas Merlin C , Pickering Raelene , Whyte Andrew , Dry Ian B , Gorry Paul R , Wesselingh Steve L
Published: May 2005

Although educational programs have had some impact, immunization against HIV will be necessary to control the AIDS pandemic. To be effective, vaccination will need to be accessible and affordable, directed against multiple antigens, and delivered in multiple doses. Plant‐based vaccines that are heat‐stable and easy to produce and administer are suited to this type of strategy. Pilot studies by a number of groups have demonstrated that plant viral expression systems can produce HIV antigens in quantities that are appropriate for use in vaccines. In addition, these plant‐made HIV antigens have been shown to be immunogenic. However, given the need for potent cross‐clade humoral and T‐cell immunity for protection against HIV, and the uncertainty surrounding the efficacy of protein subunit vaccines, it is most likely that plant‐made HIV vaccines will find their niche as booster immunizations in prime‐boost vaccination schedules.