bluuebunny/crossref_metadata_2025 huggingface dataset:
Binding Properties and Adhesion-Mediating Regions of the Major Sheath Protein ofTreponema denticolaATCC 35405
Authors: Edwards Andrew M. , Jenkinson Howard F. , Woodward Martin J. , Dymock David
Published: April 2005

There is growing evidence that a number of oralTreponemaspecies, in particularTreponema denticola, are associated with the progression of human periodontal disease. The major sheath (or surface) protein (Msp) ofT. denticolais implicated in adhesion of bacteria to host cells and tissue proteins and is likely to be an important virulence factor. However, the binding regions of the Msp are not known. We have purified fromEscherichia colirecombinant Msp (rMsp) polypeptides corresponding to the following: full-length Msp (rMsp) minus 13 N-terminal amino acid (aa) residues, an amino-terminal fragment (rN-Msp, 189 aa residues), a 57-aa residue segment from the central region (rV-Msp), and a C-terminal fragment (rC-Msp, 272 aa residues). rMsp (530 aa residues) bound to immobilized fibronectin, keratin, laminin, collagen type I, fibrinogen, hyaluronic acid, and heparin. The N- and V-region polypeptides, but not rC-Msp, also bound to these substrates. Binding of rMsp to fibronectin was targeted to the N-terminal heparin I/fibrin I domain. Antibodies to the N-region or V-region polypeptides, but not antibodies to the rC-Msp fragment, blocked adhesion ofT. denticolaATCC 35405 cells to a range of host protein molecules. These results suggest that the N-terminal half of Msp carries epitopes that are surface exposed and that are involved in mediating adhesion. Binding of rMsp onto the cell surface of low-level fibronectin-bindingTreponemaisolates conferred a 10-fold increase in fibronectin binding. This confirms that Msp functions autonomously as an adhesin and raises the possibility that phenotypic complementation of virulence functions might occur within mixed populations ofTreponemaspecies.
Serologic Responses to ACYW135 Polysaccharide Meningococcal Vaccine in Saudi Children under 5 Years of Age
Authors: Al-Mazrou Y. , Khalil M. , Borrow R. , Balmer P. , Bramwell J. , Lal G. , Andrews N. , Al-Jeffri M.
Published: April 2005

An immunization campaign with meningococcal ACYW135 polysaccharide vaccine was conducted in 2003 by the Saudi Arabian Ministry of Health and included a study to evaluate the immune responses in children under 5 years of age in the Al Qassim region of Saudi Arabia. Children who were ≥24 months old were given one dose of tetravalent polysaccharide vaccine, while younger children were given two doses with an interval of 2 to 3 months. Blood samples were collected prevaccination and 1 month after the second dose for children younger than 24 months old and 1 month after the single dose for older children. Serogroup-specific antibody responses were determined by serum bactericidal antibody (SBA) assays and a tetraplex immunoglobulin G (IgG) bead assay. Significant increases in the proportions of individuals who were ≥24 months old with SBA titers of ≥8 were observed pre- to postvaccination for all serogroups. Age-dependent increases in the percentage of individuals with SBA titers of ≥8 1 month postvaccination were observed for each serogroup. Age-dependent increases in postvaccination IgG levels were observed for serogroup A (menA), serogroup W135 (menW), and serogroup Y (menY) but not for serogroup C (menC). Two doses of tetravalent polysaccharide vaccine in individuals who were ≤18 months old were poorly immunogenic for menC, menW, and menY. However, for menA, 42% of the children who were 18 months old were putatively protected with SBA titers of ≥8. A high percentage of subjects who were ≥2 years of age were putatively protected for menA; a similar level was observed for menY for children who were 4 years of age but not for younger children. However, for menC and menW poor levels of putative protection were still evident at 4 years of age.
Pseudomonas aeruginosa
SoxR Does Not Conform to the Archetypal Paradigm for SoxR-Dependent Regulation of the Bacterial Oxidative Stress Adaptive Response
Authors: Palma Marco , Zurita Juan , Ferreras Julian A. , Worgall Stefan , Larone Davise H. , Shi Lei , Campagne Fabien , Quadri Luis E. N.
Published: April 2005

SoxR is a transcriptional regulator that controls an oxidative stress response in
Escherichia coli
. The regulator is primarily activated by superoxide anion-dependent oxidation. Activated SoxR turns on transcription of a single gene,
soxS
, which encodes a transcriptional regulator that activates a regulon that includes dozens of oxidative stress response genes. SoxR homologues have been identified in many bacterial species, including the opportunistic pathogen
Pseudomonas aeruginosa
. However, the expected SoxR partner, SoxS, has not been found in
P. aeruginosa
. Thus, the primary gene target(s) of
P. aeruginosa
SoxR is unknown and the involvement of this regulator in the oxidative stress response of the bacterium remains unclear. We utilized transcriptome profiling to identify the
P. aeruginosa
SoxR regulon and constructed and characterized an unmarked
P. aeruginosa
Δ
soxR
mutant. We provide evidence indicating that
P. aeruginosa
SoxR activates a six-gene regulon in response to O
2
·−
-induced stress. The regulon includes three transcriptional units: (i) the recently identified
mexGHI
-
ompD
four-gene operon, which encodes a multidrug efflux pump system involved in quorum-sensing signal homeostasis; (ii) gene PA3718, encoding a probable efflux pump; and (iii) gene PA2274, encoding a probable monooxygenase. We also demonstrate that
P. aeruginosa
SoxR is not a key regulatory player in the oxidative stress response. Finally, we show that
P. aeruginosa
SoxR is required for virulence in a mouse model of intrapulmonary infection. These results demonstrate that the
E. coli
-based SoxRS paradigm does not hold in
P. aeruginosa
and foster new hypotheses for the possible physiological role of
P. aeruginosa
SoxR.
Induction of Nod1 and Nod2 Intracellular Pattern Recognition Receptors in Murine Osteoblasts following Bacterial Challenge
Authors: Marriott Ian , Rati Dana M. , McCall Samuel H. , Tranguch Susanne L.
Published: April 2005

Osteoblasts produce an array of immune molecules following bacterial challenge that could recruit leukocytes to sites of infection and promote inflammation during bone diseases, such as osteomyelitis. Recent studies from our laboratory have shed light on the mechanisms by which this cell type can perceive and respond to bacteria by demonstrating the functional expression of members of the Toll-like family of cell surface pattern recognition receptors by osteoblasts. However, we have shown that bacterial components fail to elicit immune responses comparable with those seen following challenge with the intracellular pathogens salmonellae and
Staphylococcus aureus
. In the present study, we show that UV-killed bacteria and invasion-defective bacterial strains elicit significantly less inflammatory cytokine production than their viable wild-type counterparts. Importantly, we demonstrate that murine osteoblasts express the novel intracellular pattern recognition receptors Nod1 and Nod2. Levels of mRNA encoding Nod molecules and protein expression are significantly and differentially increased from low basal levels following exposure to these disparate bacterial pathogens. In addition, we have shown that osteoblasts express Rip2 kinase, a critical downstream effector molecule for Nod signaling. Furthermore, to begin to establish the functional nature of Nod expression, we show that a specific ligand for Nod proteins can significantly augment immune molecule production by osteoblasts exposed to either UV-inactivated bacteria or bacterial lipopolysaccharide. As such, the presence of Nod proteins in osteoblasts could represent an important mechanism by which this cell type responds to intracellular bacterial pathogens of bone.
Infection of the Reproductive Tract and Eggs with
Salmonella enterica
Serovar Pullorum in the Chicken Is Associated with Suppression of Cellular Immunity at Sexual Maturity
Authors: Wigley Paul , Hulme Scott. D. , Powers Claire , Beal Richard K. , Berchieri Angelo , Smith Adrian , Barrow Paul
Published: April 2005

Salmonella enterica
serovar Pullorum causes persistent infections in laying hens. Splenic macrophages are the main site of persistence. At sexual maturity, numbers of bacteria increase and spread to the reproductive tract, which may result in vertical transmission to eggs or chicks. In this study we demonstrate that both male and female chickens may develop a carrier state following infection but that the increases in bacterial numbers and spread to the reproductive tract are phenomena restricted to hens, indicating that such changes are likely to be related to the onset of egg laying. The immunological responses during the carrier state and through the onset of laying in hens were determined. These indicate that chickens produce both humoral and T-cell responses to infection, but at the onset of laying both the T-cell response to
Salmonella
and nonspecific responses to mitogenic stimulation fall sharply in both infected and noninfected birds. The fall in T-cell responsiveness coincided with the increase in numbers of
Salmonella
serovar Pullorum and its spread to the reproductive tract. Three weeks after the onset of egg laying, T-cell responsiveness began to increase and bacterial numbers declined. Specific antibody levels changed little at the onset of laying but increased following the rise in bacterial numbers in a manner reminiscent of a secondary antibody response to rechallenge. These findings indicate that a nonspecific suppression of cellular responses occurs at the onset of laying and plays a major role the ability of
Salmonella
serovar Pullorum to infect the reproductive tract, leading to transmission to eggs. The loss of T-cell activity at the point of laying also has implications for
Salmonella enterica
serovar Enteritidis infection and transmission to eggs, along with its control by vaccination offering a “window of opportunity” in which infection may occur.
Synthetic Toll-Like Receptor 4 Agonists Stimulate Innate Resistance to Infectious Challenge
Authors: Cluff Christopher W. , Baldridge Jory R. , Stöver Axel G. , Evans Jay T. , Johnson David A. , Lacy Michael J. , Clawson Valerie G. , Yorgensen Vonnie M. , Johnson Craig L. , Livesay Mark T. , Hershberg Robert M. , Persing David H.
Published: April 2005

A compound family of synthetic lipid A mimetics (termed the aminoalkyl glucosaminide phosphates [AGPs]) was evaluated in murine infectious disease models of protection against challenge withListeria monocytogenesand influenza virus. For theListeriamodel, intravenous administration of AGPs was followed by intravenous bacterial challenge 24 h later. Spleens were harvested 2 days postchallenge for the enumeration of CFU. For the influenza virus model, mice were challenged with virus via the intranasal/intrapulmonary route 48 h after intranasal/intrapulmonary administration of AGPs. The severity of disease was assessed daily for 3 weeks following challenge. Several types of AGPs provided strong protection against influenza virus orListeriachallenge in wild-type mice, but they were inactive in the C3H/HeJ mouse, demonstrating the dependence of the AGPs on toll-like receptor 4 (TLR4) signaling for the protective effect. Structure-activity relationship studies showed that the activation of innate immune effectors by AGPs depends primarily on the lengths of the secondary acyl chains within the three acyl-oxy-acyl residues and also on the nature of the functional group attached to the aglycon component. We conclude that the administration of synthetic TLR4 agonists provides rapid pharmacologic induction of innate resistance to infectious challenge by two different pathogen classes, that this effect is mediated via TLR4, and that structural differences between AGPs can have dramatic effects on agonist activity in vivo.
A Monoclonal Antibody That Conveys In Vitro Killing and Partial Protection in Experimental Syphilis Binds a Phosphorylcholine Surface Epitope ofTreponema pallidum
Authors: Blanco David R. , Champion Cheryl I. , Dooley Alek , Cox David L. , Whitelegge Julian P. , Faull Kym , Lovett Michael A.
Published: April 2005

Immunization with purifiedTreponema pallidumouter membrane vesicles (OMV) has previously resulted in high-titer complement-dependent serum bactericidal activity. In this study, OMV immunization resulted in the isolation of a monoclonal antibody, M131, with complement-dependent killing activity. Passive immunization of rabbits with M131 administered intravenously conferred significant immunity demonstrated by the failure of syphilitic lesions to appear at 29% of intradermal challenge sites (7/24) and a mean delay of approximately 8 days to lesion appearance at the remaining sites (17/24). M131 not only bound to OMV and to the surfaces of intact motileT. pallidumcells but also bound to organisms whose outer membranes were removed, indicating both surface and subsurface locations for the killing target. This target was determined to be aT. pallidumlipid. Lipid extracted fromT. pallidumand made into liposomes bound M131. Reverse-phase high-pressure liquid chromatography separation and fraction collection mass spectrometry (LC-MS+) ofT. pallidumlipid showed that the target of M131 was phosphorylcholine. M131 binding required both liposome formation and a critical concentration of phospholipid containing phosphorylcholine, suggesting that the epitope has both a conformational and a compositional requirement. M131 did not react with red blood cells, which have phosphorylcholine-containing lipids in their exterior membrane leaflets, or with Venereal Disease Research Laboratory antigen that also contains phosphorylcholine, further indicating the specificity of M131. This is the first physical demonstration of an antigen on theT. pallidumsurface and indication that such a surface antigen can be a target of immunity.
Maturation of theLegionella pneumophila-Containing Phagosome into a Phagolysosome within Gamma Interferon-Activated Macrophages
Authors: Santic Marina , Molmeret Maëlle , Abu Kwaik Yousef
Published: April 2005

Legionella pneumophilais an intracellular pathogen that modulates the biogenesis of its phagosome to evade endocytic vesicle traffic. TheLegionella-containing phagosome (LCP) does not acquire any endocytic markers and is remodeled by the endoplasmic reticulum during early stages. Here we show that intracellular replication ofL. pneumophilais inhibited in gamma interferon (IFN-γ)-activated, bone marrow-derived mouse macrophages and IFN-γ-activated, human monocyte-derived macrophages in a dose-dependent manner. This inhibition of intracellular replication is associated with the maturation of the LCP into a phagolysosome, as documented by the acquisition of LAMP-2, cathepsin D, and lysosomal tracer Texas Red ovalbumin, and with the failure of the LCP to be remodeled by the rough endoplasmic reticulum. We conclude that IFN-γ-activated macrophages override the ability ofL. pneumophilato evade endocytic fusion and that the LCP is processed through the “default” endosomal-lysosomal degradation pathway.
The Concentration of Apolipoprotein A-I Decreases during Experimentally Induced Acute-Phase Processes in Pigs
Authors: Carpintero R. , Piñeiro M. , Andrés M. , Iturralde M. , Alava M. A. , Heegaard P. M. H. , Jobert J. L. , Madec F. , Lampreave F.
Published: April 2005

In this work, apolipoprotein A-I (ApoA-I) was purified from pig sera. The responses of this protein after sterile inflammation and in animals infected withActinobacillus pleuropneumoniaeorStreptococcus suiswere investigated. Decreases in the concentrations of ApoA-I, two to five times lower than the initial values, were observed at 2 to 4 days. It is concluded that ApoA-I is a negative acute-phase protein in pigs.
Voltammetric Determination of Fluoren-9-ol and 2-Acetamidofluorene Using Carbon Paste Electrodes
Authors: German Natalija , Armalis Saulius , Zima Jiří , Barek Jiří
Published: April 2005

Square wave voltammetry and differential pulse voltammetry have been used for the determination of 2-acetamidofluorene and fluoren-9-ol using carbon paste electrodes, following the study of the influence of the carbon paste composition on the voltammetric signals of the analytes. The methods are based on the oxidation of the above compounds and they include adsorptive accumulation of the analyte on the surface of the working electrode. The limit of detection was 1 μmol l-1for fluoren-9-ol in a medium of 0.1 M H2SO4, and 40 nmol l-1for 2-acetamidofluorene in Britton-Robinson buffer (pH 7).
Poly(ethylene glycol)-Based Polymer Carrier of Doxorubicin Degradable by Both Enzymatic and Chemical Hydrolyses
Authors: Pechar Michal , Braunová Alena , Ulbrich Karel
Published: April 2005

The synthesis and characterization of a water-soluble biodegradable multiblock polyurethane based on poly(ethylene glycol) blocks interconnected by a pentapeptide derivative N,N'-bis(aspartylprolyl)lysine is described. The pentapeptide linkages are susceptible both to chemical hydrolysis in neutral and mild acid medium (pH 5) and to enzymatic degradation by lysosomal enzyme cathepsin B. Anti-cancer drug doxorubicin was attached to a hydrazide derivative of the polymer via a hydrolytically labile hydrazone bond. Both the pH-triggered hydrolytic release of the drug and the degradation of the polymer carrier by enzymatic and chemical hydrolysis were studied using liquid chromatography.
Model averaging to estimate rebuilding targets for overfished stocks
Authors: Brodziak Jon , Legault Christopher M
Published: April 2005

Reducing overfishing and recovering overfished fish stocks is a challenging and important global problem. Rebuilding targets are essential ingredients for guiding overfished stocks to recovery. Having robust estimates of rebuilding targets is likely a necessary condition for effective long-term management of fishery resources. In this paper, we show how Bayesian model averaging can be applied to estimate rebuilding targets under alternative hypotheses about stockrecruitment dynamics. Using alternative hypotheses about stockrecruitment dynamics and environmental variation is important because using only a single hypothesis can lead to substantially different reference points and policy implications. The alternative hypotheses are augmented with prior information collected from meta-analyses of stockrecruitment data to construct a set of age-structured production models. We illustrate our approach using three overfished New England groundfish stocks. We fit alternative model likelihoods to observed data using Bayesian inference techniques. The Schwarz goodness-of-fit criterion was used to calculate model probabilities. Bayesian model averaging was used to estimate rebuilding targets that were robust to model selection uncertainty. Model-averaged estimates suggested that rebuilding targets for overfished stocks can be reasonably well determined if adequate prior information on stock productivity is available. Nonetheless, results had wide confidence intervals that reflected the underlying uncertainty in rebuilding targets.
The "Crustacean Seas"  an evolutionary perspective on the PontoCaspian peracarids
Authors: Cristescu Melania EA , Hebert Paul DN
Published: April 2005

A spectacular adaptive radiation of crustaceans has occurred in the Black, Caspian, and Aral seas. This study tests several evolutionary scenarios based on the extent of genetic differentiation and the phylogenetic relationships among endemic mysids and gammarid amphipods from the Black and Caspian seas. Molecular phylogenies for these taxa were based on two mitochondrial genes: cytochrome c oxidase subunit I and the large ribosomal RNA subunit (16S), and one nuclear gene, the large ribosomal RNA subunit (28S). The results support the monophyly of the PontoCaspian gammarids (genera Dikerogammarus, Echinogammarus, Obesogammarus, and Pontogammarus), suggesting their origin from one colonization event. By contrast, several colonization events preceded the radiation of the PontoCaspian mysids (genera Limnomysis and Paramysis). Levels of intraspecific divergence were variable, with mysids showing either no geographic structure or deep genetic splits reflecting a long history of reproductive isolation between populations in marine settings and those in fresh waters. These findings suggest that the diversity of the PontoCaspian crustaceans has been underestimated and that species regarded as euryhaline are often composed of distinct evolutionary groups whose taxonomic status should be reevaluated.
Escaping the tyranny of the grid: a more realistic way of defining fishing opportunities
Authors: Branch Trevor A , Hilborn Ray , Bogazzi Eugenia
Published: April 2005

A large part of fishing behavior is choosing where to fish. Trawl skippers usually choose between known fishing opportunities, which are observed as groups of trawls that are conducted in the same portion of a fishing ground, or go exploratory fishing. We outline a simple clustering method based on Euclidean distances between trawls that offers a more realistic way of defining fishing opportunities than grid cells or statistical areas. The resulting cluster tree of trawls is divided into individual groups of trawls (fishing opportunities) using a recommended cut point. Our method correctly classified simulated trawls into fishing opportunities. Fishing opportunities were obtained for vessels in the British Columbia groundfish trawl fishery; each vessel usually fished at a wide variety (mean 26, standard deviation 16, range 269) of fishing opportunities. Within each fishing opportunity, trawls generally caught similar species. In the Argentina scallop fishery, our method was able to divide exploratory from regular fishing trawls, with obvious applications for catch-per-unit-effort calculations. Our method could also be used to detect positional errors in data from these fisheries. Fishing opportunities could provide indications of how fishermen might react to marine protected areas and to the imposition of quotas on multispecies fisheries.
Likelihood-based confidence intervals of relative fitness for a common experimental design
Authors: Kalinowski Steven T , Taper Mark L
Published: April 2005

Statistical inferences concerning the relative fitness of different types of individuals in a population have not been well developed. We present a method for calculating confidence intervals for maximum likelihood estimates of relative fitness obtained from an experimental design that is common in the fisheries literature. Analysis and simulation show that these confidence limits are reliable. We also show that the bias of the estimates is low for realistic sample sizes.
Novel antibacterial proteins from entomocidal crystals of Bacillus thuringiensis ssp. israelensis
Authors: Revina Lyudmila P , Kostina Lyubov I , Dronina Maria A , Zalunin Igor A , Chestukhina Galina G , Yudina Tatyana G , Konukhova Anna V , Izumrudova Anna V
Published: April 2005

Proteins with molecular masses of 36 and 34 kDa (Bti36 and Bti34) were isolated from entomocidal crystals formed by Bacillus thuringiensis ssp. israelensis cells. The samples of Bti36 contained the admixture of a protein with a molecular mass of 33 kDa (Bti33), apparently a product of proteolysis of Bti36. These 3 proteins are significantly different in N-terminal sequences from known δ-endotoxins of B. thuringiensis and show antibacterial activity toward Micrococcus luteus. The combination of Bti36 and Bti33 also suppresses the growth of some other microorganisms including Streptomyces chrysomallus. The effects of the mixture of Bti36 and Bti33 on the M. luteus cell surface and on the surface of S. chrysomallus cells and exospores are similar, but they are different from the effect of endotoxin Cry11A on micrococcal cells.Key words: Bacillus thuringiensis, δ-endotoxins, antibacterial activity, Micrococcus luteus, Streptomyces chrysomallus.
Genetic differentiation of charcoal rot pathogen,Macrophomina phaseolina, into specific groups using URP-PCR
Authors: Jana T K , Singh N K , Koundal K R , Sharma T R
Published: April 2005

Forty isolates of Macrophomina phaseolina, a pathogen causing charcoal dry root rot of soybean, cotton, and chickpea, were genetically characterized with universal rice primers (URP; primers derived from DNA repeat sequences in the rice genome) using polymerase chain reaction (URP-PCR). Out of 12 URPs used in this study, 5 primers were effective in producing polymorphic fingerprint patterns from the DNA of M. phaseolina isolates. Three primers (URP-2F, URP-6R, and URP-30F) were quite informative and produced high levels of polymorphism among the isolates of M. phaseolina. Analysis of the entire fingerprint profiles using unweighted pair-group method with arithmetic averages (UPGMA) clearly differentiated M. phaseolina isolates obtained from soybean, cotton, and chickpea hosts into specific groups. In this study, we found for the first time transferability and use of PCR primers derived from plant genomes to generate host-specific fingerprint profiles of M. phaseolina, a broad host range plant pathogenic fungus. These results demonstrate that URPs are sensitive and technically simple to use for assaying genetic variability in M. phaseolina populations.Key words: Macrophomina phaseolina, molecular variability, soybean, cotton, chickpea.
Purification and characterization of an intracellular aspartyl acid proteinase (pumAi) fromUstilago maydis
Authors: Mercado-Flores Yuridia , Trejo-Aguilar Adriana , Ramírez-Zavala Bernardo , Villa-Tanaca Lourdes , Hernández-Rodríguez César
Published: April 2005

The intracellular proteinase pumAi in Ustilago maydis has been associated with yeast-mycelium dimorphic transition. The proteinase was purified from a cell-free extract by ammonium sulfate fractionation and chromatographic steps including hydrophobic interactions on a Phenyl Superose column, ion exchange on a Mono Q column, and gel filtration on Superose 12 columns. The enzyme has a mass of 35.3–36.6 kDa, a pH and temperature optimum of 4.0 and 40 °C, respectively, and a pI of 5.5. The enzyme degraded hemoglobin, gelatin, albumin, and casein, but not collagen, and the enzymatic activity was strongly inhibited by pepstatin A, an aspartyl proteinase-specific inhibitor. The biochemical characteristics of pumAi are similar to other fungal intracellular aspartyl proteinases, however, this is the first biochemical characterization of a basidiomycete proteinase probably associated with dimorphic yeast-mycelium transition.Key words: aspartyl proteinase, yeast-mycelium transition, Ustilago maydis.
Amphioxus molecular biology: insights into vertebrate evolution and developmental mechanisms
Authors: Shimeld Sebastian M , Holland Nicholas D
Published: April 2005

The cephalochordate amphioxus is the best available proxy for the last common invertebrate ancestor of the vertebrates. During the last decade, the developmental genetics of amphioxus have been extensively examined for insights into the evolutionary origin and early evolution of the vertebrates. Comparisons between expression domains of homologous genes in amphioxus and vertebrates have strengthened proposed homologies between specific body parts. Molecular genetic studies have also highlighted parallels in the developmental mechanisms of amphioxus and vertebrates. In both groups, a similar nested pattern of Hox gene expression is involved in rostrocaudal patterning of the neural tube, and homologous genes also appear to be involved in dorsoventral neural patterning. Studies of amphioxus molecular biology have also hinted that the protochordate ancestor of the vertebrates included cell populations that modified their developmental genetic pathways during early vertebrate evolution to yield definitive neural crest and neurogenic placodes. We also discuss how the application of expressed sequence tag and gene-mapping approaches to amphioxus have combined with developmental studies to advance our understanding of chordate genome evolution. We conclude by considering the potential offered by the sequencing of the amphioxus genome, which was completed in late 2004.
Rejection patterns in botryllid ascidian immunity: the first tier of allorecognition
Authors: Rinkevich Baruch
Published: April 2005

Botryllid ascidians, a small but geographically widely distributed group of compound tunicates, are being used as a model system for the study of allorecognition. Botryllid ascidians possess a unique type of immunity. Pairs of colonies that meet through their extending ampullae either fuse to form a chimera or develop cytotoxic lesions at contact zones (rejection). This first tier of allorecognition is succeeded (in cases of fusion) by two additional tiers, not reviewed here (the colony resorption phenomenon and the phenomenon of somatic and germ cell parasitism). Fusion and rejection are controlled by a single highly polymorphic gene locus termed the fusibility/histocompatibility (Fu/HC) locus. One shared allele on the Fu/HC locus is enough for fusion. Rejecting colonies do not share any Fu/HC alleles. To date, 14 botryllid ascidians have been studied for their fusibility patterns; of these, the cosmopolitan species Botryllus schlosseri (Pallas, 1766) has emerged as the most studied taxon. This review summarizes studies revealing the various types of noncompatible responses that are expressed following the application of the "colony allorecognition assay" and the "cut surface assay". These include divergent alloresponses related to different populations of the same botryllid species, distinctive allorecognition sites, polymorphism and a repertoire of Fu/HC alleles, a state of low responsiveness as opposed to the expected immunological memory, the retreat growth phenomenon, and the irreversible nature of the rejection process. A detailed description of the accumulated knowledge on the effector cells (morula cells and macrophages), the humoral and cellular molecules (at the biochemical and molecular levels), and the prophenoloxidase system is given. Links between allogeneic responses and the evolutionary ecology of botryllid ascidians are revealed. Since tunicates occupy a key phylogenetic position in the origin of the vertebrates, the study of colony allorecognition in this group may shed light on self/nonself recognition elements in other multicellular organisms, including vertebrates.
Molecular phylogeny of the protochordates: chordate evolution
Authors: Zeng Liyun , Swalla Billie J
Published: April 2005

The deuterostomes are a monophyletic group of multicellular animals that include the Chordata, a phylum that exhibits a unique body plan within the metazoans. Deuterostomes classically contained three phyla, Echinodermata, Hemichordata, and Chordata. Protochordata describes two invertebrate chordate subphyla, the Tunicata (Urochordata) and the Cephalochordata. Tunicate species are key to understanding chordate origins, as they have tadpole larvae with a chordate body plan. However, molecular phylogenies show only weak support for the Tunicata as the sister-group to the rest of the chordates, suggesting that they are highly divergent from the Cephalochordata and Vertebrata. We believe that members of the Tunicata exhibit a unique adult body plan and should be considered a separate phylum rather than a subphylum of Chordata. The molecular phylogeny of the deuterostomes is reviewed and discussed in the context of likely morphological evolutionary scenarios and the possibility is raised that the ancestor of the Tunicata was colonial. In this scenario, the colonial tadpole larva would more resemble an ancestral chordate than the solitary tadpole larva. In contrast, the true chordates (vertebrates and cephalochordates) would have evolved from filter-feeding benthic worms with cartilaginous gill slits, similar to extant enteropneust hemichordates.
SCALING EFFECTS IN THE PENNA AGEING MODEL
Authors: ŁASZKIEWICZ A. , CEBRAT S. , STAUFFER D.
Published: April 2005

We have analyzed the possibility of scaling the sexual Penna ageing model. Assuming that the number of genes expressed before the reproduction age grows linearly with the genome size and that the mutation rate per genome and generation is constant, we have found that the fraction of defective genes expressed before the minimum reproduction age drops with the genome size, while the number of defective genes eliminated by the genetic death grows with genome size. Thus, the evolutionary costs decrease with increasing genome size. After rescaling the time scale according to the mutational clock, age distributions of populations do not depend on the genome size. Nevertheless, enlarging the genome increases the reproduction potential of populations.
IMPROVING VEHICLE FLOW WITH TRAFFIC LIGHTS
Authors: POLI J. , MONTEIRO L. H. A.
Published: April 2005

A probabilistic cellular automata is used for investigating how a traffic light placed on a street intersection influences vehicle velocities. Numerical simulations reveal that above a critical density of cars, the traffic light improves the flow in both directions.
MAPS AND CARTOGRAMS OF THE 2004 US PRESIDENTIAL ELECTION RESULTS
Authors: GASTNER M. T. , SHALIZI C. R. , NEWMAN M. E. J.
Published: April 2005

Conventional maps of election results can give a misleading picture of the popular support that candidates have because population is highly non-uniform and equal areas on a map may not correspond to equal numbers of voters. Taking the example of the 2004 United States presidential election, we show how this problem can be corrected using a cartogram — a map in which the sizes of regions such as states are rescaled according to population or some other variable of interest.
Constitutive secretion of serum albumin requires reversible protein tyrosine phosphorylation events in trans-Golgi
Authors: Webb Rachel J. , Judah Jacob D. , Lo Lee-Chiang , Thomas Geraint M. H.
Published: April 2005

Serum albumin secretion from rat hepatocytes proceeds via the constitutive pathway. Although much is known about the role of protein tyrosine phosphorylation in regulated secretion, nothing is known about its function in the constitutive process. Here we show that albumin secretion is inhibited by the tyrosine kinase inhibitor genistein but relatively insensitive to subtype-selective inhibitors or treatments. Secretion is also blocked in a physiologically identical manner by the tyrosine phosphatase inhibitors pervanadate and bisperoxo(1,10-phenanthroline)-oxovanadate. Inhibition of either the kinase(s) or phosphatase(s) leads to the accumulation of albumin between the trans-Golgi and the plasma membrane, whereas the immediate precursor proalbumin builds up in a proximal compartment. The trans-Golgi marker TGN38 is rapidly dispersed under conditions that inhibit tyrosine phosphatase action, whereas the distribution of the cis-Golgi marker GM130 is insensitive to genistein or pervanadate. By using a specifically reactive biotinylation probe, we detected protein tyrosine phosphatases in highly purified rat liver Golgi membranes. These membranes also contain both endogenous tyrosine kinases and their substrates, indicating that enzymes and substrates for reversible tyrosine phosphorylation are normal membrane-resident components of this trafficking compartment. In the absence of perturbation of actin filaments and microtubules, we conclude that reversible protein tyrosine phosphorylation in the trans-Golgi network is essential for albumin secretion and propose that the constitutive secretion of albumin is in fact a regulated process.
K+ channel KVLQT1 located in the basolateral membrane of distal colonic epithelium is not essential for activating Cl− secretion
Authors: Liao Tianjiang , Wang Ling , Halm Susan Troutman , Lu Luo , Fyffe Robert E. W. , Halm Dan R.
Published: April 2005

The cellular mechanism for Cl− and K+ secretion in the colonic epithelium requires K+ channels in the basolateral and apical membranes. Colonic mucosa from guinea pig and rat were fixed, sectioned, and then probed with antibodies to the K+ channel proteins KVLQT1 ( Kcnq1) and minK-related peptide 2 (MiRP2, Kcne3). Immunofluorescence labeling for Kcnq1 was most prominent in the lateral membrane of crypt cells in rat colon. The guinea pig distal colon had distinct lateral membrane immunoreactivity for Kcnq1 in crypt and surface cells. In addition, Kcne3, an auxiliary subunit for Kcnq1, was detected in the lateral membrane of crypt and surface cells in guinea pig distal colon. Transepithelial short-circuit current ( Isc) and transepithelial conductance ( Gt) were measured for colonic mucosa during secretory activation by epinephrine (EPI), prostaglandin E2 (PGE2), and carbachol (CCh). HMR1556 (10 μM), an inhibitor of Kcnq1 channels (Gerlach U, Brendel J, Lang HJ, Paulus EF, Weidmann K, Brüggemann A, Busch A, Suessbrich H, Bleich M, and Greger R. J Med Chem 44: 3831–3837, 2001), partially (∼50%) inhibited Cl− secretory Isc and Gt activated by PGE2 and CCh in rat colon with an IC50 of 55 nM, but in guinea pig distal colon Cl− secretory Isc and Gt were unaltered. EPI-activated K+-secretory Isc and Gt also were essentially unaltered by HMR1556 in both rat and guinea pig colon. Although immunofluorescence labeling with a Kcnq1 antibody supported the basolateral membrane presence in colonic epithelium of the guinea pig as well as the rat, the Kcnq1 K+ channel is not an essential component for producing Cl− secretion. Other K+ channels present in the basolateral membrane presumably must also contribute directly to the K+ conductance necessary for K+ exit during activation of Cl− secretion in the colonic mucosa.
Evidence that the COOH terminus of human presenilin 1 is located in extracytoplasmic space
Authors: Oh Young S. , Turner R. James
Published: April 2005

The polytopic membrane protein presenilin 1 (PS1) is a component of the γ-secretase complex that is responsible for the intramembranous cleavage of several type I transmembrane proteins, including the β-amyloid precursor protein (APP). Mutations of PS1, apparently leading to aberrant processing of APP, have been genetically linked to early-onset familial Alzheimer’s disease. PS1 contains 10 hydrophobic regions (HRs) sufficiently long to be α-helical membrane spanning segments. Most topology models for PS1 place its COOH terminal ∼40 amino acids, which include HR 10, in the cytosolic space. However, several recent observations suggest that HR 10 may be integrated into the membrane and involved in the interaction between PS1 and APP. We have applied three independent methodologies to investigate the location of HR 10 and the extreme COOH terminus of PS1. The results from these methods indicate that HR 10 spans the membrane and that the COOH terminal amino acids of PS1 lie in the extracytoplasmic space.
Spinal reflexes and coactivation of ankle muscles during a submaximal fatiguing contraction
Authors: Lévénez Morgan , Kotzamanidis Christos , Carpentier Alain , Duchateau Jacques
Published: April 2005

This study examined the involvement of spinal mechanisms in the control of coactivation during a sustained contraction of the ankle dorsiflexors at 50% of maximal voluntary contraction. Changes in the surface electromyogram (EMG) of the tibialis anterior and of two antagonist muscles, the soleus and lateral gastrocnemius, were investigated during and after the fatigue task. Concurrently, the compound action potential (M-wave) and the Hoffmann reflex of the soleus and lateral gastrocnemius were recorded. The results showed that the torque of the ankle dorsiflexors and the average EMG of the tibialis anterior during maximal voluntary contraction declined by 40.9 ± 17.7% (mean ± SD; P < 0.01) and 37.0 ± 19.9% ( P < 0.01), respectively, at task failure. During the submaximal fatiguing contraction, the average EMG of both the agonist and antagonist muscles increased, leading to a nearly constant ratio at the end of the contraction when normalized to postfatigue values. In contrast to the monotonic increase in average EMG of the antagonist muscles, the excitability of their spinal reflex pathways exhibited a biphasic modulation. The amplitude of the Hoffman reflexes in the soleus and lateral gastrocnemius increased to 147.5 ± 52.9% ( P < 0.05) and 166.7 ± 74.9% ( P < 0.01), respectively, during the first 20% of the contraction and then subsequently declined to 66.3 ± 44.8 and 74.4 ± 44.2% of their initial values. In conclusion, the results show that antagonist coactivation did not contribute to task failure. The different changes in voluntary EMG activity and spinal reflex excitability in the antagonist muscles during the fatiguing contraction support the concept that the level of coactivation is controlled by supraspinal rather than spinal mechanisms. The findings indicate, however, that antagonist coactivation cannot simply be mediated by a central descending “common drive” to the motor neuron pools of the agonist-antagonist muscle pairs. Rather, they suggest a more subtle regulation of the drive, possibly through presynaptic mechanisms, to the motoneurons that innervate the antagonist muscles.
Delay-Period Activity in Visual, Visuomovement, and Movement Neurons in the Frontal Eye Field
Authors: Lawrence Bonnie M. , White Robert L. , Snyder Lawrence H.
Published: April 2005

In the present study, we examined the role of frontal eye field neurons in the maintenance of spatial information in a delayed-saccade paradigm. We found that visual, visuomovement, and movement neurons conveyed roughly equal amounts of spatial information during the delay period. Although there was significant delay-period activity in individual movement neurons, there was no significant delay-period activity in the averaged population of movement neurons. These contradictory results were reconciled by the finding that the population of movement neurons with memory activity consisted of two subclasses of neurons, the combination of which resulted in the cancellation of delay-period activity in the population of movement neurons. One subclass consisted of neurons with significantly greater delay activity in the preferred than in the null direction (“canonical”), whereas the other subclass consisted of neurons with significantly greater delay activity in the null direction than in the preferred direction (“paradoxical”). Preferred direction was defined by the saccade direction that evoked the greatest movement-related activity. Interestingly, the peak saccade-related activity of canonical neurons occurred before the onset of the saccade, whereas the peak saccade-related activity of paradoxical neurons occurred after the onset of the saccade. This suggests that the former, but not the latter, are directly involved in triggering saccades. We speculate that paradoxical neurons provide a mechanism by which spatial information can be maintained in a saccade-generating circuit without prematurely triggering a saccade.
Involvement of Kv1 Potassium Channels in Spreading Acidification and Depression in the Cerebellar Cortex
Authors: Chen Gang , Gao Wangcai , Reinert Kenneth C. , Popa Laurentiu S. , Hendrix Claudia M. , Ross M. Elizabeth , Ebner Timothy J.
Published: April 2005

Spreading acidification and depression (SAD) is a form of propagated activity in the cerebellar cortex characterized by acidification and a transient depression in excitability. This study investigated the role of Kv1 potassium channels in SAD using neutral red, flavoprotein autofluorescence, and voltage-sensitive dye optical imaging in the mouse cerebellar cortex, in vivo. The probability of evoking SAD was greatly increased by blocking Kv1.1 as well as Kv1.2 potassium channels by their specific blockers dendrotoxin K (DTX-K) and tityustoxin (TsTX), respectively. DTX-K not only greatly lowered the threshold for evoking SAD but also resulted in multiple cycles of spread and spontaneous SAD. The occurrence of spontaneous SAD originating from spontaneous parallel fiber-like beams of activity suggests that blocking Kv1 channels increased parallel fiber excitability. This was confirmed by the generation of parallel fiber-like beams with the microinjection of glutamate into the upper molecular layer in the presence of DTX-K. The dramatic effects of DTX-K suggest a possible connection between SAD and episodic ataxia type 1 (EA1), a Kv1.1 potassium channelopathy. The threshold for evoking SAD was significantly lowered in the Kv1.1 heterozygous knockout mouse compared with wild-type littermates. Carbamazepine and acetazolamide, both effective in the treatment of EA1, significantly decreased the likelihood of evoking SAD. Blocking GABAergic neurotransmission did not alter the effectiveness of DTX-K. The cyclin D2 null mouse, which lacks cerebellar stellate cells, also exhibited SAD. Therefore blocking Kv1 potassium channels establishes the conditions needed to generate SAD. Furthermore, the results are consistent with the hypothesis that SAD may underlie the transient attacks of ataxia characterizing EA1.
Growth Factors Mobilize Multiple Pools ofKCaChannels in Developing Parasympathetic Neurons: Role of ADP-Ribosylation Factors and Related Proteins
Authors: Chae Kwon-Seok , Oh Kwang-Seok , Dryer Stuart E.
Published: April 2005

In developing ciliary ganglion (CG) neurons, movement of functional large-conductance (BK type) Ca2+-activated K+( KCa) channels to the cell surface is stimulated by the endogenous growth factors TGFβ1 and β-neuregulin-1 (NRG1). Here we show that a brief NRG1 treatment (0.5–1.5 h) mobilizes KCachannels in a post-Golgi compartment, but longer treatments (>3.5 h) mobilize KCachannels located in the endoplasmic reticulum or Golgi apparatus. Specifically, the effects of 3.5 h NRG1 treatment were completely blocked by treatments that disrupt Golgi apparatus function. These include inhibition of microtubules, or inhibition of the ADP-ribosylation factor-1 (ARF1) system by brefeldin A, by over-expression of dominant-negative ARF1, or over-expression of an ARF1 GTPase-activating protein that blocks ARF1 cycling between GTP- and GDP-bound states. These treatments had no effect on stimulation of KCaevoked by 1.5 h treatment with NRG1, indicating that short-term responses to NRG1 do not require an intact Golgi apparatus. By contrast, both the acute and sustained effects of NRG1 were inhibited by treatments that block trafficking processes that occur close to the plasma membrane. Thus mobilization of KCawas blocked by treatments than inhibit ADP-ribosylation factor-6 (ARF6) signaling, including overexpression of dominant-negative ARF6, dominant-negative ARNO, or dominant-negative phospholipase D1. TGFβ1, the effects of which on KCaare much slower in onset, is unable to selectively mobilize channels in the post-Golgi pool, and its effects on KCaare completely blocked by inhibition of microtubules, Golgi function and also by plasma membrane ARF6 and phospholipase D1 signaling.