bluuebunny/crossref_metadata_2025 huggingface dataset:
Lactosylceramide: a lipid second messenger in neuroinflammatory disease
Authors: Won Je‐Seong , Singh Avtar K. , Singh Inderjit
Published: November 2007

Inflammatory disease plays a critical role in the pathogenesis of many neurological disorders. Astrogliosis and induction of pro‐inflammatory mediators such as chemokines, cytokines and inducible nitric oxide synthase (iNOS) are the ‘hallmarks’ of inflammatory disease. Increased activity of lactosylceramide (LacCer) synthase and increased synthesis of LacCer during glial proliferation, and induction of pro‐inflammatory cytokines and iNOS suggests a role for LacCer in these cellular signaling pathways. Studies using complementary techniques of inhibitors and antisense reported that inhibition of LacCer synthesis inhibits glial proliferation, as well as the induction of pro‐inflammatory mediators (cytokines and iNOS). This inhibition was bypassed by exogenous LacCer, but not by other related lipids (e.g. glucosylceramide, galactocerebroside, GD1, GM1), indicating a role for LacCer in inflammatory signaling pathways. Furthermore, inhibition of glial proliferation and induction of inflammatory mediators by antisense to Ras GTPase, PI3Kinase and inhibitors of mitogen‐activated protein kinase indicate the participation of the phosphoinositide 3‐kinase (PI3Kinas)/Ras/mitogen‐activated protein kinase/nuclear factor‐κB (NF‐κB) signaling pathways in LacCer‐mediated inflammatory events thus exposing additional targets for therapeutics for inflammatory disease conditions.
The N‐glycan profile of mouse myelin, a specialized central nervous system membrane
Authors: Ishii Akihiro , Ikenaka Kazuhiro , Pfeiffer Steven E.
Published: November 2007

Understanding the rich complement of sugar chains found in cellular membranes is impeded by the complexity of cell types and membrane diversity. To overcome this, we have analyzed the N‐linked sugar chain composition of the glycoproteins of CNS myelin, an elaboration of the plasma membranes of oligodendrocytes (OLs) that result in a multilamellar wrapping of neuronal axons, facilitating nerve conduction with dramatic savings of space and energy. Due to an usually high lipid to protein ratio, myelin can be separated readily from other heavier membranes on sucrose gradients and further fractionated into subdomains related to myelin structure and function, including compact myelin and myelin‐associated axolemmal membrane (Menon et al. 2003). We analyzed these fractions for N‐linked sugar chains, using 2D HPLC following hydrazinolysis and pyridylamination. Our results indicate that compared with total brain homogenate, the amount of N‐glycans is 1.3‐fold higher in the myelin‐associated axolemmal membranes, but it is 0.5‐fold less in CM. M5 [Manα1–3((Manα1–3)(Manα1–6)Manα1–6)Manβ1–4GlcNAcβ1–4GlcNAc] is the most abundant sugar chain in total brain homogenate, compact myelin, and myelin‐associated axolemma, constituting ∼20% of sugar chains. Although the types of sugar chains are similar among the fractions, their expression levels vary significantly. In addition to high mannose type oligosaccharides, the core fucosylated, biantennary N‐glycans with bisecting N‐acetylglucosamine (GlcNAc) residue, A2G1(3)FB [Galβ1–4GlcNAcβ1–2Manα1–3(GlcNAcβ1–2Manα1–6)(GlcNAcβ1–4)Manβ1–4GlcNAcβ1–4(Fucα1–6)GlcNAc], A2G1(6)FB [GlcNAcβ1–2Manα1–3(Galβ1–4GlcNAcβ1–2Manα1–6)(GlcNAcβ1–4)Manβ1–4GlcNAcβ1–4 (Fucα1–6)GlcNAc] and BA‐1 [Manα1–3(GlcNAcβ1–2Manα1–6)(GlcNAcβ1–4)Manβ1–4GlcNAcβ1–4(Fucα1–6)GlcNAc], and A1(6)G0F [Manα1–3(GlcNAcβ1–2Manα1–6)Manβ1–4GlcNAcβ1–4(Fucα1–6) GlcNAc] are also present in relatively large proportions in compact myelin. We suggest that these differences may be related to myelin‐axolemmal function.
Isolation and characterization of 12 dinucleotide microsatellite loci in the anadromous fish Osmerus eperlanus (L.)
Authors: TAYLOR A. N. , TAYLOR M. I. , MCCARTHY I. D. , BEAUMONT A. R.
Published: November 2007

A subtractive hybridization method was used to isolate 12 dinucleotide microsatellite loci for the anadromous European smelt, Osmerus eperlanus (L.). Three to 17 (mean 8.08) alleles per locus were identified in the two populations screened, and observed heterozygosity ranged from 0.067 to 0.933. Loci in both populations showed significant deviations from Hardy–Weinberg expected frequencies. These 12 loci provide a good basis for investigation of O. eperlanus population structure.
Highly polymorphic microsatellite loci for the Gran Canarian skink (Chalcides sexlineatus) and their applicability in other Canarian Chalcides
Authors: SUÁREZ N. M. , BLOOR P. , BROWN R. P. , PESTANO J.
Published: November 2007

The scincid lizard Chalcides sexlineatus is endemic to the island of Gran Canaria, within which it shows a pronounced phylogeographical pattern. Understanding the maintenance of this pattern requires knowledge of nuclear DNA structuring. Eleven polymorphic tetranucleotide microsatellite loci were isolated from a library constructed from genomic DNA enriched for AAAG repeat sequence. The number of alleles per locus ranged from 12 to 19, and expected heterozygosities spanned from 0.738 to 0.933 (n = 30). The majority of these could be cross‐amplified in other endemic Canarian Chalcides. The loci will be used to investigate gene flow between the principal mitochondrial clades within C. sexlineatus.
On a log‐linear approach to detecting ecological interactions in monitored populations
Authors: FREEMAN STEPHEN N. , NEWSON STUART E.
Published: November 2007

We discuss a log‐linear model for series of regular bird counts taken at a number of survey sites. The model is parameterized in terms of annual growth rates rather than actual indices of abundance, as is more frequently done. This not only permits easy estimation of and inference about these rates, but also allows us to model the effects upon population growth of covariates, such as the local presence of a competitor or predator, which may themselves vary in space and over time. A recursive relationship permits the expected count at a site to be functionally dependent upon the expected count at the previous visit. We discuss the advantages of using this relationship, rather than replacing the latter with their observed counterparts, as has been used previously.
ON THE INFORMATIONAL EFFECT OF SHORT‐SALES CONSTRAINTS: EVIDENCE FROM THE TOKYO STOCK EXCHANGE
Authors: Isaka Naoto
Published: November 2007

Using a database of stock lending fees for Japanese centralized margin transactions, I show that short‐sales constraints reduce the adjustment speed of stock prices to negative information before the announcements of revised earnings forecasts disclosed by firms in the Tokyo Stock Exchange from July 1998 to December 2001. I find that the cumulative abnormal returns (CARs) of the stocks with high short‐sales costs are insensitive to negative information on pre‐announcement days, but the CARs of these stocks become significantly lower than the CARs of the stocks with low short‐sales costs when the announcements reveal negative information to the public.
FURTHER EVIDENCE ON INSIDER TRADING AND THE MERITS OF SECURITIES CLASS ACTIONS
Authors: Iqbal Zahid , Shetty Shekar , Wang Kun
Published: November 2007

To provide further evidence on the merits of securities class actions, we examine insider transactions immediately before and during the class period, using a larger and newer data set. We show that insiders reduce their stock sales by an abnormal amount immediately before the class period. Alternative measures of insider transactions and analysis of data before the enactment of the Private Securities Litigation Reform Act of 1995 provide consistent results. These new findings indicate that class actions, on average, have merit. Our data also reestablish a previous empirical result that there is no abnormal selling during the class period.
Mass spectrometric characterization of cholesterol esters and wax esters in epidermis of fetal, adult and keloidal human skin
Authors: Tachi Masahiro , Iwamori Masao
Published: November 2007

Abstract:  Mass spectrometry (MS) with chemical ionization was found to be a useful tool for characterizing epidermal cholesterol esters (CE) and wax esters (WE), and was applied to analyse them in the epidermis of fetal, adult and keloidal human skin. Increases in the concentrations of CE and WE had occurred by 20 weeks of gestation in association with increasing concentrations of ceramides and cholesterol sulphate. Although adult epidermis contained them in similar concentrations at 25–28 weeks of gestation (13–14% of the total less polar lipids), the molecular species were shown to differ between fetal and adult epidermis by MS. Cholesterol oleate comprised 45% of the total molecular species in adult CE, whereas saturated fatty acids with chain lengths of 15–19 were abundant in fetal CE. Also, unsaturated and shorter chain WE were abundant in adult epidermis in comparison with that in the fetal epidermis, the total chain lengths of fetal and adult WE being 34–42 with a mean chain length of 38.6, and 27–41 with a mean chain length of 34.0, respectively, and the unsaturated molecules in fetal and adult WE amounting to 29% and 45%, respectively. Also, CE and WE in the epidermis of keloidal skin were reduced to 67% and 20% of the levels in normal skin, respectively. Thus, epidermal CE and WE were shown to carry eligible structures for construction of the hydrophobic barrier at the skin and amniotic fluid interface as well as that at the skin and air interface.
Oxygen‐binding haem proteins
Authors: Wilson Michael T. , Reeder Brandon J.
Published: November 2007

Myoglobin and haemoglobin, the respiratory pigments of mammals and some molluscs, annelids and arthropods, belong to an ancient superfamily of haem‐associated globin proteins. Members of this family share common structural and spectral features. They also share some general functional characteristics, such as the ability to bind ligands, e.g. O2, CO and NO, at the iron atom and to undergo redox changes. These properties are used in vivo to perform a wide range of biochemical and physiological roles. While it is acknowledged that the major role of haemoglobin is to bind oxygen reversibly and deliver it to the tissues, this is not its only function, while the often‐stated role of myoglobin as an oxygen storage protein is possibly a misconception. Furthermore, haemoglobin and myoglobin express enzymic activities that are important to their function, e.g. NO dioxygenase activity or peroxidatic activity that may be partly responsible for pathophysiology following haemorrhage. Evidence for these functions is described, and the discussion extended to include proteins that have recently been discovered and that are expressed at low levels within the cell. These proteins are hexaco‐ordinate, unlike haemoglobin and myoglobin, and are widely distributed throughout the animal kingdom (e.g. neuroglobins and cytoglobins). They may have specialist roles in oxygen delivery to particular sites within the cell but may also perform roles associated with O2 sensing and signalling and in responses to stress, e.g. protection from reactive oxygen and nitrogen species. Haemoglobins are also widespread in plants and bacteria and may serve similar protective functions.
Intranasal Granulocyte-Macrophage Colony-Stimulating Factor Reduces theAspergillusBurden in an Immunosuppressed Murine Model of Pulmonary Aspergillosis
Authors: Quezada Gerardo , Koshkina Nadezhda V. , Zweidler-McKay Patrick , Zhou Zichao , Kontoyiannis Dimitrios P. , Kleinerman Eugenie S.
Published: November 2007

We demonstrated that intranasal granulocyte-macrophage colony-stimulating factor given to immunosuppressed mice infected with pulmonary aspergillosis resulted in a sixfold reduction in the lung fungal burden compared to the result for saline-treated mice (P= 0.045). These data suggest that lung-targeted immunotherapy may be complementary to antifungal agents and may improve patient responses.
Pharmacokinetics and Pharmacodynamics of Piperaquine in a Murine Malaria Model
Authors: Moore Brioni R. , Batty Kevin T. , Andrzejewski Christopher , Jago Jeffrey D. , Page-Sharp Madhu , Ilett Kenneth F.
Published: November 2007

Piperaquine (PQ) is an important partner in antimalarial treatment strategies. However, there is a paucity of detailed preclinical and pharmacokinetic data to link PQ serum concentrations and toxicity or efficacy. The aim of this study was to investigate the pharmacokinetics and pharmacodynamics of PQ in a murine malaria treatment model. The study comprised three arms. (i) PQ pharmacokinetic parameters were determined in healthy and malaria-infected mice (90 mg/kg PQ phosphate [PQP]). (ii) For determination of single-dose pharmacodynamics, Swiss mice were inoculated with
Plasmodium berghei
parasites and given PQP (10, 30, or 90 mg/kg intraperitoneally) at 2 to 5% starting parasitemia. After 60 days, the 90-mg/kg PQP group was reinoculated with
P. berghei
. (iii) Combination efficacy was investigated at doses of 10 mg/kg PQP and 30 mg/kg dihydroartemisinin (DHA). The median survival times were 4, 10, and 54 days for 0, 10, and 30 mg/kg PQP, respectively. All mice given 90 mg/kg PQP survived beyond 60 days, with a mean parasitemia of <1% before and after reinoculation. The nadir for DHA plus PQP was significantly lower (22-fold ± 12-fold) than the initial parasitemia for the individual drugs (DHA, 12-fold ± 5-fold; PQP, 13-fold ± 3-fold;
P
= 0.007 [analysis of variance]). The elimination half-lives of PQ in healthy and infected mice were 18 and 16 days, respectively, and the extrapolated residual PQ concentration at 60 days (<10 μg/liter) was ineffective at suppressing
P. berghei
infection. PQ has a potent antimalarial effect after single-dose treatment, and its efficacy was enhanced by combination with DHA.
Environmental Determinants of the Occurrence and Distribution of
Vibrio parahaemolyticus
in the Rias of Galicia, Spain
Authors: Martinez-Urtaza Jaime , Lozano-Leon Antonio , Varela-Pet Jose , Trinanes Joaquin , Pazos Yolanda , Garcia-Martin Oscar
Published: November 2007

Infections associated with
Vibrio parahaemolyticus
on the coast of Galicia (in northwestern Spain) were reported to be linked to large outbreaks of illness during 1999 and 2000. Little information is available about the ecological factors that influence the emergence of
V. parahaemolyticus
infections in this temperate region. We carried out a 3-year study to investigate the occurrence and distribution of
V. parahaemolyticus
at 26 sites located in the four main rias of Galicia in association with environmental and oceanographic variables.
V. parahaemolyticus
was detected in all the areas investigated and throughout the complete period of study with an overall incidence of 12.5%. Salinity was the primary factor governing the temporal and spatial distribution of
V. parahaemolyticus
, whereas seawater temperature had a secondary effect and only modulated the abundance in periods and areas of reduced salinities. Higher occurrence of
V. parahaemolyticus
was observed during periods of lower salinity in autumn, with a total of 61 positive samples (18%) and a mean density of 1,234 most probable number/100 g.
V. parahaemolyticus
was primarily detected in areas of reduced salinity close to freshwater discharge points, where it was found in up to 45% of the samples. Characterization of the isolates obtained from the study resulted in the first identification of two pathogenic
tdh
-positive strains of
V. parahaemolyticus
recovered from the marine environment in Galicia. These isolates showed serotypes identical to and DNA profiles indistinguishable from those of the clinical clone of
V. parahaemolyticus
dominant in infections in Spain in the last 10 years.
Microbial Interactions within a Cheese Microbial Community
Authors: Mounier Jérôme , Monnet Christophe , Vallaeys Tatiana , Arditi Roger , Sarthou Anne-Sophie , Hélias Arnaud , Irlinger Françoise
Published: November 2007

The interactions that occur during the ripening of smear cheeses are not well understood. Yeast-yeast interactions and yeast-bacterium interactions were investigated within a microbial community composed of three yeasts and six bacteria found in cheese. The growth dynamics of this community was precisely described during the ripening of a model cheese, and the Lotka-Volterra model was used to evaluate species interactions. Subsequently, the effects on ecosystem functioning of yeast omissions in the microbial community were evaluated. It was found both in the Lotka-Volterra model and in the omission study that negative interactions occurred between yeasts.
Yarrowia lipolytica
inhibited mycelial expansion of
Geotrichum candidum
, whereas
Y. lipolytica
and
G. candidum
inhibited
Debaryomyces hansenii
cell viability during the stationary phase. However, the mechanisms involved in these interactions remain unclear. It was also shown that yeast-bacterium interactions played a significant role in the establishment of this multispecies ecosystem on the cheese surface. Yeasts were key species in bacterial development, but their influences on the bacteria differed. It appeared that the growth of
Arthrobacter arilaitensis
or
Hafnia alvei
relied less on a specific yeast function because these species dominated the bacterial flora, regardless of which yeasts were present in the ecosystem. For other bacteria, such as
Leucobacter
sp. or
Brevibacterium aurantiacum
, growth relied on a specific yeast, i.e.,
G. candidum
. Furthermore,
B. aurantiacum
,
Corynebacterium casei
, and
Staphylococcus xylosus
showed reduced colonization capacities in comparison with the other bacteria in this model cheese. Bacterium-bacterium interactions could not be clearly identified.
Novel Candidate Virulence Factors in Rice Pathogen
Xanthomonas oryzae
pv. oryzicola as Revealed by Mutational Analysis
Authors: Wang Li , Makino Seiko , Subedee Ashim , Bogdanove Adam J.
Published: November 2007

Bacterial leaf streak, caused by
Xanthomonas oryzae
pv. oryzicola, is an important disease of rice. Transposon-mediated mutational analysis of the pathogen with a quantitative assay revealed candidate virulence factors including genes involved in the pathogenesis of other phytopathogenic bacteria, virulence factors of animal pathogens, and genes not previously associated with virulence.
Novel Mechanism for Conditional Aerobic Growth of the Anaerobic Bacterium
Treponema denticola
Authors: Lai Yanlai , Chu Lianrui
Published: November 2007

Treponema denticola
, a periodontal pathogen, has recently been shown to exhibit properties of a facultative anaerobic spirochete, in contrast to its previous recognition as an obligate anaerobic bacterium. In this study, the capacity and possible mechanism of
T. denticola
survival and growth under aerobic conditions were investigated. Factors detrimental to the growth of
T. denticola
ATCC 33405, such as oxygen concentration and hydrogen sulfide (H
2
S) levels as well as the enzyme activities of gamma-glutamyltransferase, cysteinylglycinase, and cystalysin associated with the cells were monitored. The results demonstrated that
T. denticola
grew only at deeper levels of broth (≥3 ml in a 10-ml tube), high inoculation ratios (≥20% of culture in medium), and short cultivation times (≤4 days for one passage) and in media containing
l
-cysteine or glutathione as the substrate for H
2
S production during aerobic growth. The determination of the factors showed that oxygen levels were always lower (0 to 0.6%) with significantly higher concentrations of H
2
S and higher activities of the three enzymes in all cultures grown aerobically. Further data revealed that H
2
S production from the
T. denticola
enzymes plus their substrates resulted in removal of dissolved O
2
in the growth cultures in a dose-dependent manner. These results demonstrated that
T. denticola
was able to generate microanaerobic environments in growth media for its survival and growth under aerobic conditions. Furthermore, the organism can be defined as a true obligate anaerobic spirochete. These findings suggest that spirochetes may play a significant role in maintaining the anaerobic environment at diseased sites in periodontitis.
Defining Targets for Complement Components C4b and C3b on the Pathogenic Neisseriae
Authors: Lewis Lisa A. , Ram Sanjay , Prasad Alpana , Gulati Sunita , Getzlaff Silke , Blom Anna M. , Vogel Ulrich , Rice Peter A.
Published: November 2007

Complement is a key arm of the innate immune defenses against the pathogenic neisseriae. We previously identified lipooligosaccharide onNeisseria meningitidisas an acceptor for complement C4b. Little is known about other neisserial targets for complement proteins C3 and C4, which covalently attach to bacterial surfaces and initiate opsonization and killing. In this study we demonstrate thatNeisseria gonorrhoeaeporin (Por) 1B selectively binds C4b via amide linkages and C3b via ester linkages. Using strains expressing hybrid Por1A/1B molecules, a region spanned by loops 4 and 5 of Por1B was identified as the preferred binding site for C4b. We also identified the opacity protein (Opa), a major adhesin of pathogenic neisseriae, as a target for C4b and C3b on bothN. meningitidisandN. gonorrhoeae. UsingN. gonorrhoeaevariants that predominantly expressed individual Opa proteins, we found that all Opa proteins tested (A, B, C, D, E, F, and I) bound C4b and C3b via amide and ester linkages, respectively. Amide linkages with Por1B and Opa were confirmed using serum containing only the C4A isoform, which exclusively forms amide linkages with targets. While monomers and heterodimers of C4Ab were detected on bacterial targets, C4Bb appeared to preferentially participate in heterodimer (C5 convertase) formation. Our data provide another explanation for the enhanced serum sensitivity of Por1B-bearing gonococci. The binding of C3b and C4b to Opa provides a rationale for the recovery of predominantly “transparent” (Opa-negative) neisserial isolates from persons with invasive disease, where the bacteria encounter high levels of complement.
Duplicate Copies oflic1Direct the Addition of Multiple Phosphocholine Residues in the Lipopolysaccharide ofHaemophilus influenzae
Authors: Fox Kate L. , Li Jianjun , Schweda Elke K. H. , Vitiazeva Varvara , Makepeace Katherine , Jennings Michael P. , Moxon E. Richard , Hood Derek W.
Published: November 2007

The genes of thelic1operon (lic1Atolic1D) are responsible for incorporation of phosphocholine (PCho) into the lipopolysaccharide (LPS) ofHaemophilus influenzae. PCho plays a multifaceted role in the commensal and pathogenic lifestyles of a range of mucosal pathogens, includingH. influenzae. Structural studies of the LPS of nontypeableH. influenzae(NTHI) have revealed that PCho can be linked to a hexose on any one of the oligosaccharide chain extensions from the conserved inner core triheptosyl backbone. In a collection of NTHI strains we found several strains in which there were two distinct but variantlic1DDNA sequences, genes predicted to encode the transferase responsible for directing the addition of PCho to LPS. The same isolates were also found to express concomitantly two PCho residues at distinct positions in their LPS. In one such NTHI isolate, isolate 1158, structural analysis of LPS fromlic1mutants confirmed that each of the two copies oflic1Ddirects the addition of PCho to a distinct location on the LPS. One position for PCho addition is a novel heptose, which is part of the oligosaccharide extension from the proximal heptose of the LPS inner core. Modification of the LPS by addition of two PCho residues resulted in increased binding of C-reactive protein and had consequential effects on the resistance of the organism to the killing effects of normal human serum compared to the effects of glycoforms containing one or no PCho. When bound, C-reactive protein leads to complement-mediated killing, indicating the potential biological significance of multiple PCho residues.
Global Transcriptome Analysis ofBorrelia burgdorferiduring Association with Human Neuroglial Cells
Authors: Livengood Jill A. , Schmit Virginia L. , Gilmore Robert D.
Published: November 2007

As adherence and entry of a pathogen into a host cell are key components to an infection, identifying the molecular mechanisms responsible for cellular association will provide a better understanding of a microbe's pathogenesis. We previously established an in vitro model forBorrelia burgdorferiinfection of human neuroglial cells. To expand on our earlier study, we performedB. burgdorferiwhole-genome expression analysis following a 20-hour infection of human neuroglial cells to identify borrelial genes that were differentially regulated during host-cell association compared with culturedBorreliain cell-free medium. This study identifies several regulated genes, the products of which may be important mediators of cellular pathogenesis.
Role of the BBA64 Locus of
Borrelia burgdorferi
in Early Stages of Infectivity in a Murine Model of Lyme Disease
Authors: Maruskova Mahulena , Esteve-Gassent M. Dolores , Sexton Valerie L. , Seshu J.
Published: November 2007

Borrelia burgdorferi
, the causative agent of Lyme disease, undergoes rapid adaptive gene expression in response to environmental signals encountered during different stages of its life cycle in the arthropod vector or the mammalian host. Among all the plasmid-encoded genes of
B. burgdorferi
, several linear plasmid 54 (lp54)-encoded open reading frames (ORFs) exhibit the greatest differential expression in response to mammalian host-specific temperature, pH, and other uncharacterized signals. These ORFs include members of the paralogous gene family 54 (pgf 54), such as BBA64, BBA65, and BBA66, present on lp54. In an attempt to correlate transcriptional up-regulation of these pgf 54 members to their role in infectivity, we inactivated BBA64 and characterized the phenotype of this mutant both in vitro and in vivo. There were no major differences in the protein profiles between the BBA64 mutant and the control strains, while immunoblot analysis indicated that inactivation of BBA64 resulted in increased levels of BBA65. Moreover, there was no significant difference in the ability of the BBA64 mutant to infect C3H/HeN mice compared to that of its parental or complemented control strains as determined by culturing of viable spirochetes from infected tissues. However, enumeration of spirochetes using quantitative real-time PCR revealed tissue-specific differences, suggesting a minimal role for BBA64 in the survival of
B. burgdorferi
in select tissues. Infectivity analysis of the BBA64 mutant suggests that
B. burgdorferi
may utilize multiple determinants to establish infection in mammalian hosts.
Enteropathogenic
Escherichia coli
O125:H6 Triggers Attaching and Effacing Lesions on Human Intestinal Biopsy Specimens Independently of Nck and TccP/TccP2
Authors: Bai Li , Schüller Stephanie , Whale Andrew , Mousnier Aurelie , Marches Olivier , Wang Lei , Ooka Tadasuke , Heuschkel Robert , Torrente Franco , Kaper James B. , Gomes Tânia A. T. , Xu Jianguo , Phillips Alan D. , Frankel Gad
Published: November 2007

Typical enteropathogenic
Escherichia coli
(EPEC) and enterohemorrhagic
E. coli
(EHEC) employ either Nck, TccP/TccP2, or Nck and TccP/TccP2 pathways to activate the neuronal Wiskott-Aldrich syndrome protein (N-WASP) and to trigger actin polymerization in cultured cells. This phenotype is used as a marker for the pathogenic potential of EPEC and EHEC strains. In this paper we report that EPEC O125:H6, which represents a large category of strains, lacks the ability to utilize either Nck or TccP/TccP2 and hence triggers actin polymerization in vitro only inefficiently. However, we show that infection of human intestinal biopsies with EPEC O125:H6 results in formation of typical attaching and effacing lesions. Expression of TccP in EPEC O125:H6, which harbors an EHEC O157-like Tir, resulted in efficient actin polymerization in vitro and enhanced colonization of human intestinal in vitro organ cultures with detectable N-WASP and electron-dense material at the site of bacterial adhesion. These results show the existence of a natural category of EPEC that colonizes the gut mucosa using Nck- and TccP-independent mechanisms. Importantly, the results highlight yet again the fact that conclusions made on the basis of in vitro cell culture models cannot be extrapolated wholesale to infection of mucosal surfaces and that the ability to induce actin polymerization on cultured cells should not be used as a definitive marker for EPEC and EHEC virulence.
Lipidation of an FlrC-Dependent Protein Is Required for Enhanced Intestinal Colonization by
Vibrio cholerae
Authors: Morris David C. , Peng Fen , Barker Jeffrey R. , Klose Karl E.
Published: November 2007

Vibrio cholerae
, the causative agent of cholera, has a sheathed, polar flagellum, and motility has been linked to virulence. An operon with two genes,
flgO
and
flgP
(VC2207 and VC2206), is positively regulated by FlrC, the activator of class III flagellar genes. Deletion of
flgP
results in a nonmotile phenotype, demonstrating the requirement of this gene for
V. cholerae
motility.
V. cholerae
Δ
flgP
cells synthesize fragile and defective flagella but transcribe flagellar genes similar to the wild-type strain. PhoA fusion analysis indicated that the putative lipoprotein FlgP is localized external to the cytoplasm, and fractionation demonstrated that it was localized to the outer membrane. Mutagenesis of the site of lipidation of FlgP (C18G) prevented [
3
H]palmitate incorporation and outer membrane localization. Interestingly, FlgP with the mutation C18G [FlgP(C18G)] could complement the Δ
flgP
mutant for motility, and the cells synthesized wild-type flagella. The Δ
flgP
mutant strain was defective for intestinal colonization (∼20-fold), but FlgP(C18G) was unable to complement this defect, demonstrating that lipidation of FlgP is essential for its role in intestinal colonization but not flagellar synthesis. FlgP thus represents a novel
V. cholerae
intestinal colonization factor that is regulated by the flagellar transcription hierarchy.
Extensive Proliferation of Transposable Elements in Heritable Bacterial Symbionts
Authors: Plague Gordon R. , Dunbar Helen E. , Tran Phat L. , Moran Nancy A.
Published: November 2007

We found that insertion sequence (IS) elements are unusually abundant in the relatively recently evolved bacterial endosymbionts of maize weevils. Because multicopy elements can facilitate genomic recombination and deletion, this IS expansion may represent an early stage in the genomic reduction that is common in most ancient endosymbionts.
Interactions of an EssentialBacillus subtilisGTPase, YsxC, with Ribosomes
Authors: Wicker-Planquart Catherine , Foucher Anne-Emmanuelle , Louwagie Mathilde , Britton Robert A. , Jault Jean-Michel
Published: November 2007

YsxC is a small GTPase ofBacillus subtiliswith essential but still unknown function, although recent works have suggested that it might be involved in ribosome biogenesis. Here, purified YsxC overexpressed inEscherichia coliwas found to be partly associated with high-molecular-weight material, most likely rRNA, and thus eluted from gel filtration as a large complex. In addition, purification of ribosomes from anE. colistrain overexpressing YsxC allowed the copurification of the YsxC protein. Purified YsxC was shown to bind preferentially to the 50S subunit ofB. subtilisribosomes; this interaction was modulated by nucleotides and was stronger in the presence of a nonhydrolyzable GTP analogue than with GTP. Far-Western blotting analysis performed with His6-YsxC and ribosomal proteins separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that YsxC interacted with at least four ribosomal proteins from the 50S subunit. Two of these putative protein partners were identified by mass spectrometry as L1 and L3, while the third reactive band in the one-dimensional gel contained L6 and L10. The fourth band that reacted with YsxC contained a mixture of three proteins, L7/L12, L23, and L27, suggesting that at least one of them binds to YsxC. Coimmobilization assays confirmed that L1, L6, and L7/L12 interact with YsxC. Together, these results suggest that YsxC plays a role in ribosome assembly.
Characterization of Integrative and Conjugative Element ICEKp1-Associated Genomic Heterogeneity in aKlebsiella pneumoniaeStrain Isolated from a Primary Liver Abscess
Authors: Lin Tzu-Lung , Lee Cha-Ze , Hsieh Pei-Fang , Tsai Shih-Feng , Wang Jin-Town
Published: November 2007

Genomic heterogeneity has been shown to be associated withKlebsiella pneumoniaestrains causing pyogenic liver abscesses (PLA) and metastatic infections. In order to explore the mechanism responsible for genomic heterogeneity inK. pneumoniae, we compared the complete genomic sequences of strains NTUH-K2044 and MGH78578. An ∼76-kbp DNA fragment located adjacent to an asparagine (asn) tRNA gene was present in NTUH-K2044 but not in MGH78578. This fragment could be divided into three regions with different functions, and structurally it resembled a functional integrative and conjugative element (ICE), ICEEc1, inEscherichia coli. The 5′ region of this fragment contained genes similar to a high-pathogenicity island (HPI) ofYersinia pestisandYersinia pseudotuberculosis. The middle region was similar to part of a large plasmid inK. pneumoniae, and the 3′ region contained genes responsible for DNA conjugative transfer. Therefore, this DNA fragment was designated ICEKp1. Precise excision and extrachromosomal circularization of ICEKp1were detected inK. pneumoniaewild-type strain NTUH-K2044. ICEKp1could integrate into theasntRNA loci of the chromosome of anotherK. pneumoniaeisolate. The prevalence of ICEKp1was higher in PLA strains (38 of 42 strains) than in non-tissue-invasive strains (5 of 32 strains). Therefore, ICEKp1may contribute to the transmission of the HPI and result inK. pneumoniaePLA infection-associated genomic heterogeneity.
One Pathway Can Incorporate either Adenine or Dimethylbenzimidazole as an α-Axial Ligand of B
12
Cofactors in
Salmonella enterica
Authors: Anderson Peter J. , Lango Jozsef , Carkeet Colleen , Britten Audrey , Kräutler Bernhard , Hammock Bruce D. , Roth John R.
Published: November 2007

Corrinoid (vitamin B
12
-like) cofactors contain various α-axial ligands, including 5,6-dimethylbenzimidazole (DMB) or adenine. The bacterium
Salmonella enterica
produces the corrin ring only under anaerobic conditions, but it can form “complete” corrinoids aerobically by importing an “incomplete” corrinoid, such as cobinamide (Cbi), and adding appropriate α- and β-axial ligands. Under aerobic conditions,
S. enterica
performs the corrinoid-dependent degradation of ethanolamine if given vitamin B
12
, but it can make B
12
from exogenous Cbi only if DMB is also provided. Mutants isolated for their ability to degrade ethanolamine without added DMB converted Cbi to pseudo-B
12
cofactors (having adenine as an α-axial ligand). The mutations cause an increase in the level of free adenine and install adenine (instead of DMB) as an α-ligand. When DMB is provided to these mutants, synthesis of pseudo-B
12
cofactors ceases and B
12
cofactors are produced, suggesting that DMB regulates production or incorporation of free adenine as an α-ligand. Wild-type cells make pseudo-B
12
cofactors during aerobic growth on propanediol plus Cbi and can use pseudo-vitamin B
12
for all of their corrinoid-dependent enzymes. Synthesis of coenzyme pseudo-B
12
cofactors requires the same enzymes (CobT, CobU, CobS, and CobC) that install DMB in the formation of coenzyme B
12
. Models are described for the mechanism and control of α-axial ligand installation.
The Leucine-Responsive Regulatory Protein, Lrp, Activates Transcription of thefimOperon inSalmonella entericaSerovar Typhimurium via thefimZRegulatory Gene
Authors: McFarland Kirsty A. , Lucchini Sacha , Hinton Jay C. D. , Dorman Charles J.
Published: November 2007

Thefimoperon ofSalmonella entericaserovar Typhimurium encodes type 1 fimbriae. The expression offimis controlled in response to environmental signals through a complex regulatory cascade involving the proteins FimW, FimY, and FimZ and a genetic locus,fimU, that encodes a rare arginine tRNA. We discovered that a knockout mutation inlrp, the gene that codes for the leucine-responsive regulatory protein (Lrp), inhibitedfimtranscription. The loss offimgene expression was accompanied by a corresponding loss of the mannose-sensitive hemagglutination that is a characteristic of type 1 fimbriae. Normal type 1 fimbrial expression was restored following the introduction into the knockout mutant of a plasmid carrying a functional copy of thelrpgene. Electrophoretic mobility shift analysis revealed no interactions between purified Lrp protein and the regulatory region of thefimA,fimU, orfimWgene. Instead, Lrp produced protein-DNA complexes with the regulatory region of thefimZgene, and the nature of these complexes was leucine sensitive. DNase I footprinting showed that Lrp binds within a region between −65 and −170 with respect to thefimZtranscription start site, consistent with the binding and wrapping of the DNA in this upstream region. Ectopic expression of thefimZgene from an inducible promoter caused Lrp-independent type 1 fimbriation in serovar Typhimurium. These data show that Lrp makes a positive contribution tofimgene expression through direct interaction with thefimZpromoter region, possibly by antagonizing the binding of the H-NS global repressor protein.
Effect of L-carnitine administration on the modulated rat brain protein concentration, acetylcholinesterase, Na+K+-ATPase and Mg2+-ATPase activities induced by forced swimming
Authors: Tsakiris T , Angelogianni P , Tesseromatis C , Tsakiris S , Schulpis K H
Published: November 2007

Background:

Forced exercise produces free radicals and L-carnitine (L-C) administration reduces oxidative stress.

Aim:

To investigate whether short (2 hours) or prolonged (3 hours) forced swimming could modulate total antioxidant status (TAS), protein concentration and activities of acetylcholinesterase (AChE), Na+K+-ATPase and Mg2+-ATPase in rat brain following intraperitonal administration of L-C (300 mg/kg).

Methods:

TAS, protein and enzyme activities were measured spectrophotometrically.

Results:

TAS, protein concentration and AChE activity were reduced, whereas Na+K+-ATPase and Mg2+-ATPase were significantly increased after either 2 or 3 hours of training. L-C administration resulted in a profound restoration of TAS and protein concentration whereas AChE and Na+K+-ATPase were increased before exercise, followed by AChE restoration and Na+K+-ATPase reduction after exercise. Mg2+-ATPase remained unchanged. An in vitro study using L-C incubation of brain homogenates previously treated with L-C resulted in complete restoration of the modulated enzymes, whereas the enzyme activities from untreated animals remained unaltered.

Conclusions:

Short or prolonged swimming in rats may result in a reduction of brain TAS, protein concentration and AChE activity, and an activation of Na+K+-ATPase and Mg2+-ATPase. L-C administration may prevent reduction in TAS and protein concentration, and a decrease in AChE and Na+K+-ATPase activity; the latter reached pre-exercise values after L-C incubation.
Development of a fibre size-specific job-exposure matrix for airborne asbestos fibres
Authors: Dement J M , Kuempel E D , Zumwalde R D , Smith R J , Stayner L T , Loomis D
Published: November 2007

Objective:

To develop a method for estimating fibre size-specific exposures to airborne asbestos dust for use in epidemiological investigations of exposure-response relations.

Methods:

Archived membrane filter samples collected at a Charleston, South Carolina asbestos textile plant during 1964–8 were analysed by transmission electron microscopy (TEM) to determine the bivariate diameter/length distribution of airborne fibres by plant operation. The protocol used for these analyses was based on the direct transfer method published by the International Standards Organization (ISO), modified to enhance fibre size determinations, especially for long fibres. Procedures to adjust standard phase contrast microscopy (PCM) fibre concentration measures using the TEM data in a job-exposure matrix (JEM) were developed in order to estimate fibre size-specific exposures.

Results:

A total of 84 airborne dust samples were used to measure diameter and length for over 18 000 fibres or fibre bundles. Consistent with previous studies, a small proportion of airborne fibres were longer than >5 μm in length, but the proportion varied considerably by plant operation (range 6.9% to 20.8%). The bivariate diameter/length distribution of airborne fibres was expressed as the proportion of fibres in 20 size-specific cells and this distribution demonstrated a relatively high degree of variability by plant operation. PCM adjustment factors also varied substantially across plant operations.

Conclusions:

These data provide new information concerning the airborne fibre characteristics for a previously studied textile facility. The TEM data demonstrate that the vast majority of airborne fibres inhaled by the workers were shorter than 5 μm in length, and thus not included in the PCM-based fibre counts. The TEM data were used to develop a new fibre size-specific JEM for use in an updated cohort mortality study to investigate the role of fibre dimension in the development of asbestos-related lung diseases.
Verticillium tolerance: resistance, susceptibility, or mutualism?
Authors: Robb Jane
Published: November 2007

Host tolerance to plant pathogens was first recognized over a century ago and tolerant interactions involving Verticillium spp. have been studied almost as long. Historically the phenomenon has been attributed to “intermediate resistance” or “resistance to symptom expression”; however, rapidly developing molecular approaches to studying interactions between plants and Verticillium are beginning to question these longheld views. Recent cell and molecular studies suggest that the classical interpretations of tolerance as intermediate resistance or resistance to symptom expression may be incorrect; rather, Verticillium spp. may resemble endophytes, tolerance really being a form of susceptibility leading to mutualism. This paper reviews the evolution of our perceptions of tolerance and the technical advances which contributed to it.
Distribution of arbuscular mycorrhizae in relation to microsites on primary successional substrates on Mount St. Helens
Authors: Titus Jonathan H. , Whitcomb Sean , Pitoniak Hillary Joy
Published: November 2007

Arbuscular mycorrhizae fungi (AMF) occur in most terrestrial ecosystems and are crucial to plant community structure and function. This study examined the distribution of AMF propagules, spores, and colonized plants across the Pumice Plain of Mount St. Helens 23 years after its eruption, documenting the changes since 1993. Propagules of AMF were detected by using the mycorrhizal inoculum potential assay in six microsite types across the Pumice Plain. Fifteen species of AMF were isolated from spore trap cultures, and spores were found in all of the microsites, although the distribution was aggregated. The vegetation of the Pumice Plain is currently composed primarily of facultatively mycotrophic species, which are predominantly associated with arbuscular mycorrhizae. Mycorrhizal colonization and propagule levels continue to increase as primary succession proceeds.
The interface between fungal hyphae and orchid protocorm cells
Authors: Peterson R. Larry , Uetake Yukari , Bonfante Paola , Faccio Antonella
Published: November 2007

Seeds of the orchids Platanthera hyperborea, Spiranthes lacera, and Spiranthes sinensis were germinated in vitro in the presence of compatible fungal species and the resulting colonized protocorms were studied by light microscopy, transmission electron microscopy, and colloidal-gold affinity techniques. Protocorm cells in early stages of colonization contained coils of fungal hyphae (pelotons) separated from host cell cytoplasm by the host plasma membrane and interfacial matrix material. Host cell walls were labelled by the colloidal gold – cellobiohydralase I (CBH-I) complex to detect cellulose and, particularly over the middle lamella, by antibodies that bind to pectins (JIM 5 and JIM 7). A polyclonal antibody that binds to β-1,3-glucans labelled the fungal cell wall heavily. None of the probes, however, labelled the interfacial matrix between the wall of active fungal hyphae and the surrounding plasma membrane. In contrast, the interfacial matrix material that ensheathed collapsing hyphae showed labelling after treatment with JIM 5, the polyclonal antibody, and the CBH-I complex. Labelling of host cell walls and fungal walls was similar to that described for early stages. Keywords: orchids, protocorms, mycorrhizas, affinity gold techniques, interfacial matrix.
Successive pot cultures reveal high species richness of arbuscular endomycorrhizal fungi in arid ecosystems
Authors: Stutz Jean C. , Morton Joseph B.
Published: November 2007

Three cycles of successive trap cultures were utilized to determine the taxonomic structure of arbuscular fungi associated with mesquite (Prosopis spp.) from three locations in the Sonoran desertscrub biotic community and one location in the Chihuahuan desertscrub biotic community. Unlike the low species richness found in previous studies of some arid habitats, seven to nine species were recovered from each sampling site. This number is comparable to that found in many other plant communities. Seventy-five percent of the species found after three culture cycles were not detected in the first trap cultures, suggesting that a high proportion of arbuscular fungi in arid habitats may be nonsporulating in the field. Low colonization levels may account for the absence of sporulation, but ecological factors such as moisture limitations also may be involved. Although a total of 10 different species was detected, generic richness was limited, with 9 of these species in Glomus and 1 in Entrophospora. As long as measurement of species richness is based on occurrence of sporulation, successive trap cultures provide a means of detecting nonsporulating mycorrhizal colonizers in arid and other habitats. Keywords: vesicular – arbuscular mycorrhizae, ecology, desert, Glomales.
Réaction géotropique des différents types de racines chez l'hévéa (Hevea brasiliensis)
Authors: Roux Yannick Le , Pagès Loïc
Published: November 2007

To describe the different types of geotropic reactions of hevea (Hevea brasiliensis), young seedlings were cultivated in root observation boxes and submitted to a double gravistimulation (90° rotation of the minirhizotrons in the vertical plane). It was demonstrated that the taproot is a strongly orthogeotropie organ since it resumed rapidly its prestimulation vertical position. Morphological and morphogenetic modifications were associated with the geotropic response: reduced speed of growth coupled with a reduction of the apical diameter as well as an alteration of ramification density in the curving zone and the following one. Early secondary roots showed a somewhat reduced orthogeotropism that was weaker as the growth direction before gravistimulation was more distant from the vertical. Secondary roots of the acropetal sequence were semiplagiotropic, that is only those roots oriented upward after the gravistimulation resumed, more or less, the original direction. Tertiary roots didn't respond to the gravistimulation and therefore were ageotropic. Complementary observations conducted in large laboratory rhizotrons showed that late forming secondary roots were plagiotropic in their younger stages, thereafter loosing most of their sensitivity to gravity. Quaternary roots were ageotropic. On the basis of these data, a geotropic gradient was defined within the hevea root system, where the strongly responding taproot and late secondary roots are opposed to the weakly or nonresponding tertiary and quaternary roots. Functional significations of these differential geotropic reactions in different hevea root types are discussed. Keywords: geotropism, gravistimulation, root system, growth, development, morphogenesis, root observation box, Hevea brasiliensis. [Journal translation]