bluuebunny/crossref_metadata_2025_split huggingface dataset:
Why Is Carbonic Anhydrase Essential to
Escherichia coli
?
Authors: Merlin Christophe , Masters Millicent , McAteer Sean , Coulson Andrew 
Published: October 2003

ABSTRACT

The
can
(previously
yadF
) gene of
Escherichia coli
encodes a β-class carbonic anhydrase (CA), an enzyme which interconverts CO
2
and bicarbonate.Various essential metabolic processes require either CO
2
or bicarbonate and, although carbon dioxide and bicarbonate spontaneously equilibrate in solution, the low concentration of CO
2
in air and its rapid diffusion from the cell mean that insufficient bicarbonate is spontaneously made in vivo to meet metabolic and biosynthetic needs. We calculate that demand for bicarbonate is 10
3
- to 10
4
-fold greater than would be provided by uncatalyzed intracellular hydration and that enzymatic conversion of CO
2
to bicarbonate is therefore necessary for growth. We find that
can
expression is ordinarily required for growth in air. It is dispensable if the atmospheric partial pressure of CO
2
is high or during anaerobic growth in a closed vessel at low pH, where copious CO
2
is generated endogenously. CynT, the single
E. coli
Can paralog, can, when induced with azide, replace Can; also, the γ-CA from
Methanosarcina thermophila
can at least partially replace it. Expression studies showed that
can
transcription does not appear to respond to carbon dioxide concentration or to be autoregulated. However,
can
expression is influenced by growth rate and the growth cycle; it is expressed best in slow-growing cultures and at higher culture densities. Expression can vary over a 10-fold range during the growth cycle and is also elevated during starvation or heat stress.
Isolation and Characterization of Mutants of the
Bacillus subtilis
Oligopeptide Permease with Altered Specificity of Oligopeptide Transport
Authors: Solomon Jonathan , Su Laura , Shyn Stanley , Grossman Alan D. 
Published: October 2003

ABSTRACT

Bacterial oligopeptide permeases are members of the large family of ATP binding cassette transporters and typically import peptides of 3 to 5 amino acids, apparently independently of sequence. Oligopeptide permeases are needed for bacteria to utilize peptides as nutrient sources and are sometimes involved in signal transduction pathways. The
Bacillus subtilis
oligopeptide permease stimulates competence development and the initiation of sporulation, at least in part, by importing specific signaling peptides. We isolated rare, partly functional mutations in
B. subtilis opp
. The mutants were resistant to a toxic tripeptide but still retained the ability to sporulate and/or become competent. The mutations, mostly in the oligopeptide binding protein located on the cell surface, affected residues whose alteration appears to change the specificity of oligopeptide transport.
The Gene
yjcG
, Cotranscribed with the Gene
acs
, Encodes an Acetate Permease in
Escherichia coli
Authors: Gimenez Rosa , Nuñez María Felisa , Badia Josefa , Aguilar Juan , Baldoma Laura 
Published: October 2003

ABSTRACT

We isolated an
Escherichia coli
mutant strain that suppresses the glycolate-negative phenotype of a strain deficient in both GlcA and LldP transporters of this compound. This suppressing phenotype was assigned to
yjcG
, a gene whose function was previously unknown, which was found to encode a membrane protein able to transport glycolate. On the basis of sequence similarity, the
yjcG
gene product was classified as a member of the sodium:solute symporter family. Northern experiments revealed that
yjcG
is cotranscribed with its neighbor,
acs
, encoding acetyl coenzyme A synthetase, which is involved in the scavenging acetate. The fortuitous presence of an IS
2
element in
acs
, which impaired
yjcG
expression by polarity in our parental strain, allowed us to conclude that the alternative glycolate carrier became active after precise excision of IS
2
in the suppressed strain. The finding that
yjcG
encodes a putative membrane carrier for glycolate and the cotranscription of
yjcG
with
acs
suggested that the primary function of the
yjcG
gene product (proposed gene name,
actP
) could be acetate transport and allowed us to define an operon involved in acetate metabolism. The time course of [1,2-
14
C]acetate uptake and the results of a concentration kinetics analysis performed with cells expressing ActP or cells deficient in ActP supported the the hypothesis that this carrier is an acetate transporter and suggested that there may be another transport system for this monocarboxylate.
Nucleotide Sequence of the Integration Site of the Temperate Bacteriophage 6220, Which Carries the Shiga Toxin Gene
stx
1ox3
Authors: Koch Claudia , Hertwig Stefan , Appel Bernd 
Published: October 2003

ABSTRACT

The integration site,
attR
, of the Shiga toxin-encoding phage 6220 (
stx
1ox3
) has been determined. The phage integrates into the chromosome of its
Escherichia coli
host strain, CB6220, within a gene that is homologous to gene Z2577 and encodes an oxidoreductase. This new integration site was found in different Stx1ox3-producing enterohemorrhagic
E. coli
strains, which were analyzed by PCR.
Development of Parallel Codes for the Study of Nonlinear Beam Dynamics
Authors: Giovannozzi M. , Mcintosh E. 
Published: October 2003

We consider the nonlinear transverse motion in a circular particle accelerator. A key parameter for accelerator performance is the so-called dynamic aperture. This quantity is defined as the volume in phase space of the stable initial conditions. The accurate numerical computation of such a volume is very CPU-time consuming. In this paper we present some original parallel algorithms to speed up the evaluation of the dynamic aperture. A detailed analysis of different algorithms implemented is carried out. Furthermore, we studied the dependence of the CPU-time on the phase space parameters as well as the load balancing of the proposed techniques.
Bifurcations of Links of Periodic Orbits in Non-Singular Systems with Two Rotational Symmetries on S3
Authors: Campos B. , Martínez Alfaro J. , Vindel P. 
Published: October 2003

A topological characterization of all possible links composed of the periodic orbits of a Non Singular Morse-Smale flow on S3 has been made by M. Wada. The presence of symmetry forces the appearance of given types of links. In this paper we introduce a geometrical tool to represent these type of links when a symmetry around two axes is considered on NMS systems: mosaics. On the other hand, we use mosaics to study what kind of bifurcation can occur in this type of system maintaining the symmetry.
Modifying Queries on Complex Objects in Database Federations
Authors: Vermeer Mark. W. W. , Apers Peter M. G. 
Published: October 2003

We discuss the modification of queries against an integrated view in a federation of object-oriented databases. We present a generalization of existing algorithms for simple global query modification that works for arbitrarily defined integration classes. We then extend this algorithm to deal with object-oriented features that have been neglected in literature, viz. queries involving path expressions and nested queries. We show how properties of the OO-style of modeling relationships through object references can be exploited to reduce the number of subqueries necessary to evaluate such queries.
A Dynamic Causal Modeling Study on Category Effects: Bottom–Up or Top–Down Mediation?
Authors: Mechelli Andrea , Price Cathy J. , Noppeney Uta , Friston Karl J. 
Published: October 2003

Abstract
In this study, we combined functional magnetic resonance imaging (fMRI) and dynamic causal modeling (DCM) to investigate whether object category effects in the occipital and temporal cortex are mediated by inputs from early visual cortex or parietal regions. Resolving this issue may provide anatomical constraints on theories of category specificity— which make different assumptions about the underlying neurophysiology. The data were acquired by Ishai, Ungerleider, Martin, Schouten, and Haxby (1999, 2000) and provided by the National fMRI Data Center (http://www.fmridc.org). The original authors used a conventional analysis to estimate differential effects in the occipital and temporal cortex in response to pictures of chairs, faces, and houses. We extended this approach by estimating neuronal interactions that mediate category effects using DCM. DCM uses a Bayesian framework to estimate and make inferences about the influence that one region exerts over another and how this is affected by experimental changes. DCM differs from previous approaches to brain connectivity, such as multivariate autoregressive models and structural equation modeling, as it assumes that the observed hemodynamic responses are driven by experimental changes rather than endogenous noise. DCM therefore brings the analysis of brain connectivity much closer to the analysis of regionally specific effects usually applied to functional imaging data. We used DCM to estimate the influence that V3 and the superior/inferior parietal cortex exerted over category-responsive regions and how this was affected by the presentation of houses, faces, and chairs. We found that category effects in occipital and temporal cortex were mediated by inputs from early visual cortex. In contrast, the connectivity from the superior/inferior parietal area to the category-responsive areas was unaffected by the presentation of chairs, faces, or houses. These findings indicate that category effects in the occipital and temporal cortex can be mediated by bottom–up mechanisms—a finding that needs to be embraced by models of category specificity.
Goal-Directed Hand Movements Are Not Affected by the Biased Space Representation in Spatial Neglect
Authors: Himmelbach Marc , Karnath Hans-Otto 
Published: October 2003

Abstract
Patients with spatial neglect exhibit a severe shift of spontaneous explorative movements to the right side, indicating a bias of long-living representations of space. Whether or not goal-directed movements likewise are affected by this rightward bias has been controversially discussed throughout the last decade. Unfortunately, substantial differences regarding patient selection and data analysis prevented a direct comparison of these results. We thus studied pointing movements in a new sample of subjects covering all different patient groups previously investigated on this issue. We analyzed all the different measures of hand path curvature used so far and, in addition, suggest a new measure that avoids the disadvantages of the previously used parameters. Despite their severe bias for exploratory movements, we did not find systematic, direction-specific deviations of goal-directed hand movements that were specific for the patients with spatial neglect. The results strongly suggest that the disturbance of long-living spatial representations underlying the bias of exploratory behavior in patients with neglect does not influence the performance of goal-directed movements. The data support the view of a dual mode of space representation in the posterior parietal and the superior temporal cortex.
Comparison of Early Cortical Networks in Efficient and Inefficient Visual Search: An Event-Related Potential Study
Authors: Leonards Ute , Palix Julie , Michel Christoph , Ibanez Vicente 
Published: October 2003

Abstract
Functional magnetic resonance imaging studies have indicated that efficient feature search (FS) and inefficient conjunction search (CS) activate partially distinct frontoparietal cortical networks. However, it remains a matter of debate whether the differences in these networks reflect differences in the early processing during FS and CS. In addition, the relationship between the differences in the networks and spatial shifts of attention also remains unknown. We examined these issues by applying a spatio-temporal analysis method to high-resolution visual event-related potentials (ERPs) and investigated how spatio-temporal activation patterns differ for FS and CS tasks. Within the first 450 msec after stimulus onset, scalp potential distributions (ERP maps) revealed 7 different electric field configurations for each search task. Configuration changes occurred simultaneously in the two tasks, suggesting that contributing processes were not significantly delayed in one task compared to the other. Despite this high spatial and temporal correlation, two ERP maps (120–190 and 250–300 msec) differed between the FS and CS. Lateralized distributions were observed only in the ERP map at 250–300 msec for the FS. This distribution corresponds to that previously described as the N2pc component (a negativity in the time range of the N2 complex over posterior electrodes of the hemisphere contralateral to the target hemifield), which has been associated with the focusing of attention onto potential target items in the search display. Thus, our results indicate that the cortical networks involved in feature and conjunction searching partially differ as early as 120 msec after stimulus onset and that the differences between the networks employed during the early stages of FS and CS are not necessarily caused by spatial attention shifts.
DE-CENTRING RELIGIOUS SINGULARITY: THE GLOBALIZATION OF CHRISTIANITY AS A CASE IN POINT
Authors: Beyer Peter 
Published: October 2003

AbstractRecent scholarship in religious studies has again questioned the validity of the idea of religions and of certain religions in particular, such as Hinduism. The debate raises the question of how any religion, including Christianity, can be thought of or lived as a singular identity in today's world. While this is a very broad question with a very long history, this presentation translates the matter into one of the relation between globalization, localization, and religion. It argues that in the more recent phases of historical globalization, the issue of unity, identity, and singularity in religion has fundamentally changed from one which depends on a hierarchical and core/periphery distribution of defining power to one in which singularity is the observed or recognized outcome of multiple localizations of a contested and global model. Thus the singularity of a religion is not just the product of uneven power relations between those who get to define and those who do not, but rather the internally and externally observed synthesis of plural glocalizations. This abstract thesis is illustrated on hand of an examination of developments in global Christianity especially in the 19th and 20th centuries.
THE EVOLUTION OF RELIGIONS
Authors: Wunn Ina 
Published: October 2003

AbstractThe article contributes to a theoretical framework for a theory that describes and explains the distribution and development of the various religions from a genetical and historical point of view. While religious evolution until now has been understood as a process of progress, the theory outlined in this paper focuses on the biological Theory of Evolution in order to direct the attention to the main characteristics of natural evolutionary processes. By drawing parallels between biological and religious evolution the evolution of religions is described as the adaptive modification of religions throughout history. After discussing the question of a natural systematic unit in the world of religions, the different means of evolutionary processes are investigated. As a result, a theory is presented that understands the development of religions in a way which explains their recent phenotype as well as their modifications during history.
"SCIENCE" VS. "RELIGION" IN CLASSICAL AYURVEDA
Authors: Engler Steven 
Published: October 2003

AbstractThis paper evaluates claims that classical Ayurveda was scientific, in a modern western sense, and that the many religious and magical elements found in the texts were all either stale Vedic remnants or later brahminic impositions. It argues (1) that Ayurveda did not manifest standard criteria of "science" (e.g., materialism, empirical observation, experimentation, falsification, quantification, or a developed conception of proof) and (2) that Vedic aspects of the classical texts are too central to be considered inauthentic or marginal. These points suggest that attempting to apply the modern western categories of "science" and "religion" to ancient South Asian medical texts at best obscures more important issues and, at worst, imports inappropriate orientalist assumptions. Having set aside the distraction of "science" vs. "religion" in classical Ayurveda, the paper finds support for claims that brahminic elements were later additions to the texts. It concludes by arguing that this is best explained not in terms of a conceptual tension between religion and science but in terms of social and economic tensions between physicians and brahmins.
Identifying effects of toe clipping on anuran return rates: the importance of statistical power
Authors: McCarthy Michael , Parris Kirsten 
Published: October 2003

AbstractToe clipping is a common method of marking anurans for population studies. We re-analysed data from four published studies investigating the relationship between return rate and number of toes clipped for three anuran species: Bufo fowleri, Crinia signifera and Hyla labialis. Although these studies claimed contradictory results, a re-analysis of the data with proper attention to statistical power demonstrated a statistically significant decline of 6-18% in the probability of return for each toe removed after the first, in three of the four studies examined. The probability that the fourth study would detect a statistically significant effect of toe clipping was low unless the size of the effect was overwhelming. These results provide consistent evidence that toe clipping decreases the return rate of marked anurans, and demonstrates the importance of considering statistical power during data analysis. Use of toe clipping for mark-recapture studies may produce estimates of population parameters that are biased by the same magnitude as the return rates, unless researchers control for the effect of this marking method.
Male reproductive cycle of the water frog Rana epeirotica in northwestern Greece
Authors: Kyriakopoulou-Sklavounou  , Tsiora  
Published: October 2003

AbstractThe reproductive cycle of male Rana epeirotica was studied with emphasis on spermatogenetic activity and changes in the weights of testis, fat body and liver. The spermatogenesis of Rana epeirotica is of the potentially continuous type. Significant seasonal variations were observed in testis, fat body and liver weight. The seasonal variation of testis weight showed a good agreement with the spermatogenetic cycle. The reduction of fat body weight during the pre-hibernating period was attributed to mobilizing of lipids to other body parts or to transformation into other metabolites. The significant decrease of liver weight in the dormant period indicates that this frog consumes mainly glycogen during wintering. The greatest decrease of fat body and liver weight in May results from the intensive activities related to reproduction and maintenance.
Scanning electron microscopic studies on spermatozoa of anurans from India and Sri Lanka
Authors: Joshy Hareesh , Kuramoto Mitsuru 
Published: October 2003

AbstractThe shape and size of spermatozoa of 11 frog species from India and Sri Lanka were examined by scanning electron microscopy. The spermatozoa of the genera Limnonectes and Euphlyctis were of the generalized type with a thick sperm head and a thin tail, whereas Indirana semipalmata had peculiar spermatozoa with a densely coiled sperm head and a thick tail. Rhacophorus microtympanum is likely to belong to the genus Philautus from sperm morphology. The spermatozoa of Microhyla ornata and Ramanella obscura were very similar, with a cone-shaped sperm head and a thin tail.
Reproductive behaviour of the Chinhai Salamander (Echinotriton chinhaiensis) (Caudata: Salamandridae)
Authors: Sparreboom Max , Fei Liang , Xie Feng 
Published: October 2003

AbstractThe Chinhai Salamander, Echinotriton chinhaiensis, mates on land. The male of a courting pair marks a trail by a mucous excretion from his cloaca. The pair follows an ellipsoid track during which manoeuvre a spermatophore is deposited. Partners align their bodies such that the female is led over the spermatophore. Clasping was not observed. The female traces the spermatophore with her cloaca through shifting movements with the pelvic region. A male may deposit several spermatophores on one evening. The courtship is compared to that in the genus Tylototriton.
Annual cycle of the speckle pattern on the carapace of immature hawksbill turtles (Eretmochelys imbricata) in Cuba
Authors: Kobayashi Mari 
Published: October 2003

AbstractThe black speckles in the carapace surface pattern of the hawksbill turtle go through two periods of development: one is the formation period and the other is a period of less formation, and these periods occur once a year. The results of this study show that these cycles have nothing to do with genetics or the growth of the shell. These cycles are highly correlated with the changes in the water surface temperature in the sea near Cuba. The black-speckle formation period falls before and after March, which is the dry season (a low-temperature period), while the amber color area tends to take shape during the wet season (high-temperature) in Cuba.
Responses to prey and plant chemicals by three iguanian lizards: relationship to plants in the diet
Authors: Espinoza Robert , Habegger Jason , Cooper William 
Published: October 2003

AbstractWe examined responses of three iguanian lizards, the phrynosomatid Sceloporus poinsettii and the tropidurids Tropidurus hispidus and Phymaturus punae, to prey chemicals and plant chemicals. When chemical stimuli were presented on cotton swabs or on ceramic tiles, neither S. poinsettii nor T. hispidus discriminated among prey, plant, and control stimuli. In contrast, an individual of P. punae discriminated both prey and plant chemicals from control stimuli in swab tests, typically biting swabs bearing prey or plant cues. These findings are consistent with the hypothesis that plant chemical discrimination evolves in herbivorous iguanians such as P. punae. Sceloporus poinsettii, which appears to be entirely insectivorous at some times, but eats substantial quantities of flowers at others, did not discriminate among the stimuli. Because all previously tested herbivores and omnivores responded strongly to prey and plant chemicals, the absence of such discriminations by S. poinsettii raises questions about the degree and regularity of herbivory that may be required for plant chemical discrimination to evolve. The results extend the absence of prey chemical discrimination in ambush foragers to T. hispidus.
Movements, distribution pattern and density in a population of Salamandra atra aurorae (Caudata: Salamandridae)
Authors: Bonato Lucio , Fracasso Giancarlo 
Published: October 2003

AbstractSpatial behaviour of Salamandra atra aurorae Trevisan, 1982, was investigated by a capture-recapture program during a whole season of activity. Salamanders changed their behaviour with growth: while juveniles usually dispersed on the ground, adults showed a strong fidelity to a limited area, a few square metres wide, also from year to year. Each individual frequently changed its diurnal refuge over the course of the whole activity season, choosing among a large variety of potential shelters. The distribution pattern of the home ranges was slightly aggregated, irrespective of age and sex. Under the assumptions of a closed population and an equal catchability among individuals, a density of 475 (±184; 95% confidence interval) salamanders per hectare was estimated in a mature and quite open wood, whereas a density of 97 (±23; 95% confidence interval) salamanders per hectare was estimated in a thicker wood.