bluuebunny/crossref_metadata_2025 huggingface dataset:
Poly(d,l-Lactide-Coglycolide) Particles Containing Gentamicin: Pharmacokinetics and Pharmacodynamics inBrucella melitensis- Infected Mice
Authors: Lecaroz M. C. , Blanco-Prieto M. J. , Campanero M. A. , Salman H. , Gamazo C.
Published: January 2007

Drug delivery systems containing gentamicin were studied as a treatment against experimental brucellosis in mice. Micro- and nanoparticles prepared by using poly(d,l-lactide-coglycolide) (PLGA) 502H and microparticles made of PLGA 75:25H were successfully delivered to the liver and the spleen, the target organs forBrucella melitensis. Both polymers have the same molecular weight but have different lactic acid/glycolic acid ratios. Microparticles of PLGA 502H and 75:25H released their contents in a sustained manner, in contrast to PLGA 502H nanoparticles, which were degraded almost completely during the first week postadministration. The values of the pharmacokinetic parameters after administration of a single intravenous dose of 1.5 mg/kg of body weight of loaded gentamicin revealed higher areas under the curve (AUCs) for the liver and the spleen and increased mean retention times (MRTs) compared to those for the free drug, indicating the successful uptake by phagocytic cells in both organs and the controlled release of the antibiotic. Both gentamicin-loaded PLGA 502H and 75:25H microparticles presented similar pharmacokinetic parameter values for the liver, but those made of PLGA 75:25 H were more effective in targeting the antibiotic to the spleen (higher AUCs and MRTs). The administration of three doses of 1.5 mg/kg significantly reduced the load associated with the splenicB. melitensisinfection. Thus, the formulation made with the 75:25H polymer was more effective than that made with 502H microspheres (1.45-log and 0.45-log reductions, respectively, at 3 weeks posttreatment). Therefore, both, pharmacokinetic and pharmacodynamic parameters showed the suitability of 75:25H microspheres to reduce the infection of experimentally infected mice withB. melitensis.
Sequencing and Analysis of the Biosynthetic Gene Cluster of the Lipopeptide Antibiotic Friulimicin in
Actinoplanes friuliensis
Authors: Müller C. , Nolden S. , Gebhardt P. , Heinzelmann E. , Lange C. , Puk O. , Welzel K. , Wohlleben W. , Schwartz D.
Published: January 2007

Actinoplanes friuliensis
produces the lipopeptide antibiotic friulimicin, which is a cyclic peptide with one exocyclic amino acid linked to a branched-chain fatty acid acyl residue. The structural relationship to daptomycin and the excellent antibacterial performance of friulimicin make the antibiotic an attractive drug candidate. The complete friulimicin biosynthetic gene cluster of 24 open reading frames from
A. friuliensis
was sequenced and analyzed. In addition to genes for regulation, self-resistance, and transport, the cluster contains genes encoding peptide synthetases, proteins involved in the synthesis and linkage of the fatty acid component of the antibiotic, and proteins involved in the synthesis of the nonproteinogenic amino acids pipecolinic acid, methylaspartic acid, and 2,3-diaminobutyric acid. By using heterologous gene expression in
Escherichia coli
, we provide biochemical evidence for the stereoselective synthesis of
l
-pipecolinic acid by the deduced protein of the lysine cyclodeaminase gene
pip
. Furthermore, we show the involvement of the
dabA
and
dabB
genes in the biosynthesis of 2,3-diaminobutyric acid by gene inactivation and subsequent feeding experiments.
In Vitro Studies with DQ-113 and Comparison Fluoroquinolones To Determine Propensities To Select Resistance in Gram-Positive Cocci
Authors: Hong Seong Geun , Moland Ellen Smith , Wickman Paul A. , Black Jennifer A. , Hossain Ashfaque , Hanson Nancy D. , Thomson Kenneth S.
Published: January 2007

DQ-113 was compared in vitro to sitafloxacin, moxifloxacin, levofloxacin, and ciprofloxacin for potential to select mutational resistance in multiresistant staphylococci, pneumococci, and enterococci. Its ability to select less-susceptible mutants varied according to species, being lowest with staphylococci, intermediate with pneumococci, and greatest with enterococci.
Heterologous Production of Albicidin: a Promising Approach to Overproducing and Characterizing This Potent Inhibitor of DNA Gyrase
Authors: Vivien Eric , Pitorre Delphine , Cociancich Stéphane , Pieretti Isabelle , Gabriel Dean W. , Rott Philippe C. , Royer Monique
Published: January 2007

The phytotoxin and polyketide antibiotic albicidin produced by
Xanthomonas albilineans
is a highly potent DNA gyrase inhibitor. Low yields of albicidin production have slowed studies of its chemical structure. Heterologous expression of albicidin biosynthetic genes in
X. axonopodis
pv. vesicatoria resulted in a sixfold increase in albicidin production, offering promising strategies for engineering overproduction.
Histidine Decarboxylases and Their Role in Accumulation of Histamine in Tuna and Dried Saury
Authors: Kanki Masashi , Yoda Tomoko , Tsukamoto Teizo , Baba Eiichiroh
Published: January 2007

Histamine-producing bacteria (HPB) such as
Photobacterium phosphoreum
and
Raoultella planticola
possess histidine decarboxylase (HDC), which converts histidine into histamine. Histamine fish poisoning (HFP) is attributable to the ingestion of fish containing high levels of histamine produced by HPB. Because freezing greatly decreases the histamine-producing ability of HPB, especially of
P. phosphoreum
, it has been speculated that HFP is caused by HDC itself from HPB cells autolyzing during frozen storage, even when HPB survive frozen storage. Here we constructed recombinant HDCs of
P. phosphoreum
,
Photobacterium damselae
,
R. planticola
, and
Morganella morganii
and investigated the ability of HDCs to produce sufficient histamine to cause HFP. To elucidate the character of these HDCs, we examined the specific activity of each recombinant HDC at various temperatures, pH levels, and NaCl concentrations. Further, we also investigated the stability of each HDC under different conditions (in reaction buffer, tuna, and dried saury) at various temperatures.
P. damselae
HDC readily produced sufficient histamine to cause HFP in fish samples. We consider that if HDC is implicated as an independent cause of HFP in frozen-thawed fish, the most likely causative agent is HDC of
P. damselae
.
Adaptation of a Luciferase Gene Reporter and
lac
Expression System to
Borrelia burgdorferi
Authors: Blevins Jon S. , Revel Andrew T. , Smith Alexandra H. , Bachlani Gulnaz N. , Norgard Michael V.
Published: January 2007

The development of new genetic systems for studying the complex regulatory events that occur within
Borrelia burgdorferi
is an important goal of contemporary Lyme disease research. Although recent advancements have been made in the genetic manipulation of
B. burgdorferi
, there still remains a paucity of basic molecular systems for assessing differential gene expression in this pathogen. Herein, we describe the adaptation of two powerful genetic tools for use in
B. burgdorferi
. The first is a
Photinus pyralis
firefly luciferase gene reporter that was codon optimized to enhance translation in
B. burgdorferi
. Using this modified reporter, we demonstrated an increase in luciferase expression when
B. burgdorferi
transformed with a shuttle vector encoding the outer surface protein C (OspC) promoter fused to the luciferase reporter was cultivated in the presence of fresh rabbit blood. The second is a
lac
operator/repressor system that was optimized to achieve the tightest degree of regulation. Using the aforementioned luciferase reporter, we assessed the kinetics and maximal level of isopropyl-β-
d
-thiogalactopyranoside (IPTG)-dependent gene expression. This
lac
-inducible expression system also was used to express the gene carried on lp25 required for
b
orrelial
p
ersistence in
t
icks (
bptA
). These advancements should be generally applicable for assessing further the regulation of other genes potentially involved in virulence expression by
B. burgdorferi
.
Screening Marine Fungi for Inhibitors of the C
4
Plant Enzyme Pyruvate Phosphate Dikinase: Unguinol as a Potential Novel Herbicide Candidate
Authors: Motti Cherie A. , Bourne David G. , Burnell James N. , Doyle Jason R. , Haines Dianne S. , Liptrot Catherine H. , Llewellyn Lyndon E. , Ludke Shilo , Muirhead Andrew , Tapiolas Dianne M.
Published: January 2007

A total of 2,245 extracts, derived from 449 marine fungi cultivated in five types of media, were screened against the C
4
plant enzyme pyruvate phosphate dikinase (PPDK), a potential herbicide target. Extracts from several fungal isolates selectively inhibited PPDK. Bioassay-guided fractionation of one isolate led to the isolation of the known compound unguinol, which inhibited PPDK with a 50% inhibitory concentration of 42.3 ± 0.8 μM. Further kinetic analysis revealed that unguinol was a mixed noncompetitive inhibitor of PPDK with respect to the substrates pyruvate and ATP and an uncompetitive inhibitor of PPDK with respect to phosphate. Unguinol had deleterious effects on a model C
4
plant but no effect on a model C
3
plant. These results indicate that unguinol inhibits PPDK via a novel mechanism of action which also translates to an herbicidal effect on whole plants.
De Novo Sphingolipid Synthesis Is Essential for Viability, but Not for Transport of Glycosylphosphatidylinositol-Anchored Proteins, in African Trypanosomes
Authors: Sutterwala Shaheen S. , Creswell Caleb H. , Sanyal Sumana , Menon Anant K. , Bangs James D.
Published: January 2007

De novo sphingolipid synthesis is required for the exit of glycosylphosphatidylinositol (GPI)-anchored membrane proteins from the endoplasmic reticulum in yeast. Using a pharmacological approach, we test the generality of this phenomenon by analyzing the transport of GPI-anchored cargo in widely divergent eukaryotic systems represented by African trypanosomes and HeLa cells. Myriocin, which blocks the first step of sphingolipid synthesis (serine + palmitate → 3-ketodihydrosphingosine), inhibited the growth of cultured bloodstream parasites, and growth was rescued with exogenous 3-ketodihydrosphingosine. Myriocin also blocked metabolic incorporation of [
3
H]serine into base-resistant sphingolipids. Biochemical analyses indicate that the radiolabeled lipids are not sphingomyelin or inositol phosphorylceramide, suggesting that bloodstream trypanosomes synthesize novel sphingolipids. Inhibition of de novo sphingolipid synthesis with myriocin had no adverse effect on either general secretory trafficking or GPI-dependent trafficking in trypanosomes, and similar results were obtained with HeLa cells. A mild effect on endocytosis was seen for bloodstream trypanosomes after prolonged incubation with myriocin. These results indicate that de novo synthesis of sphingolipids is not a general requirement for secretory trafficking in eukaryotic cells. However, in contrast to the closely related kinetoplastid
Leishmania major
, de novo sphingolipid synthesis is essential for the viability of bloodstream-stage African trypanosomes.
Molecular Cloning of Apicoplast-Targeted
Plasmodium falciparum
DNA Gyrase Genes: Unique Intrinsic ATPase Activity and ATP-Independent Dimerization of PfGyrB Subunit
Authors: Dar Mohd Ashraf , Sharma Atul , Mondal Neelima , Dhar Suman Kumar
Published: January 2007

DNA gyrase, a typical type II topoisomerase that can introduce negative supercoils in DNA, is essential for replication and transcription in prokaryotes. The apicomplexan parasite
Plasmodium falciparum
contains the genes for both gyrase A and gyrase B in its genome. Due to the large sizes of both proteins and the unusual codon usage of the highly AT-rich
P. falciparum gyrA
(Pf
gyrA
) and Pf
gyrB
genes, it has so far been impossible to characterize these proteins, which could be excellent drug targets. Here, we report the cloning, expression, and functional characterization of full-length PfGyrB and functional domains of PfGyrA. Unlike
Escherichia coli
GyrB, PfGyrB shows strong intrinsic ATPase activity and follows a linear pattern of ATP hydrolysis characteristic of dimer formation in the absence of ATP analogues. These unique features have not been reported for any known gyrase so far. The Pf
gyrB
gene complemented the
E. coli
gyrase temperature-sensitive strain, and, together with the N-terminal domain of PfGyrA, it showed typical DNA cleavage activity. Furthermore, PfGyrA contains a unique leucine heptad repeat that might be responsible for dimerization. These results confirm the presence of DNA gyrase in eukaryotes and confer great potential for drug development and organelle DNA replication in the deadliest human malarial parasite,
P. falciparum
.
A UspA2H-Negative Variant of
Moraxella catarrhalis
Strain O46E Has a Deletion in a Homopolymeric Nucleotide Repeat Common to
uspA2H
Genes
Authors: Wang Wei , Pearson Melanie M. , Attia Ahmed S. , Blick Robert J. , Hansen Eric J.
Published: January 2007

Moraxella catarrhalis
strains can express either a UspA2 protein or a UspA2H protein. The latter protein is encoded by a gene that possesses a homopolymeric nucleotide tract containing eight adenine (A) residues [i.e., a poly(A) tract] which is located near the 5′ end. A spontaneous UspA2H-negative variant of
M. catarrhalis
strain O46E, designated O46E.U2V, was found to have a
uspA2H
poly(A) tract that contained seven A residues. Northern blot analysis of total RNA from the O46E parent strain revealed a readily detectable
uspA2H
mRNA transcript, whereas little or no
uspA2H
transcript was detectable in total RNA from the UspA2H-negative variant O46E.U2V. The 5′ end of the
uspA2H
genes from both the O46E parent strain and the O46E.U2V variant were ligated to a promoterless
lacZ
gene to prepare translational fusions for use as reporter constructs. The level of β-galactosidase activity expressed by the fusion construct containing eight A residues in its poly(A) tract was 200-fold greater than that obtained with the construct that had seven A residues. Site-directed mutagenesis of the 5′ end of the
uspA2H
gene confirmed that translation was initiated at a GTG codon located 21 nucleotides (nt) upstream of the poly(A) tract. Primer extension analysis determined that the transcriptional start site of the
uspA2H
gene was located 291 nt upstream from the GTG translational start codon. This poly(A) tract was also found to be present in the
uspA2H
genes of other
M. catarrhalis
strains.
Surfactant Protein A2 (SP-A2) Variants Expressed in CHO Cells Stimulate Phagocytosis of
Pseudomonas aeruginosa
More than Do SP-A1 Variants
Authors: Mikerov Anatoly N. , Wang Guirong , Umstead Todd M. , Zacharatos Mario , Thomas Neal J. , Phelps David S. , Floros Joanna
Published: January 2007

Surfactant protein A (SP-A) enhances phagocytosis of
Pseudomonas aeruginosa
. Two functional genes,
SP-A1
and
SP-A2
, encode human SP-A. As we showed before, baculovirus-mediated insect cell-expressed SP-A2 enhances the association of
P. aeruginosa
with rat alveolar macrophages (rAMs) more than does SP-A1. However, true phagocytosis (internalization) was not shown, and insect cell derived proteins lack or are defective in certain mammalian posttranslational modifications that may be important for SP-A1 and SP-A2 activity and specificity. Here we used SP-A1 (6A
2
, 6A
4
) and SP-A2 (1A
0
, 1A
1
) allele variants expressed by CHO (Chinese hamster ovary) mammalian cells to study their effect on association and/or internalization of
P. aeruginosa
by rAMs and/or human AMs (hAMs) and to study if phagocytosis can be modulated differentially and/or more effectively by CHO cell-expressed SP-A variants than by insect-cell expressed SP-A variants. For cell association and internalization assessments, light microscopy and fluorescence-activated cell sorter analyses were used, respectively. We found the following for the first time. (i) SP-A2 variants enhanced phagocytosis (cell association and/or internalization) of
P. aeruginosa
more than SP-A1 variants did, and the cell association correlated with internalization. (ii) Differences in the activities of SP-A variants were observed in the following order: 1A
1
>1A
0
>6A
2
>6A
4
. (iii) rAMs, although more active than hAMs, are an appropriate model, as SP-A2 variants exhibited activity higher than that seen for SP-A1 variants with either rAMs or hAMs. (iv) CHO cell-expressed SP-A was considerably more active than insect cell-expressed variants. We conclude that SP-A2 variants stimulate phagocytosis of
P. aeruginosa
more effectively than SP-A1 variants and that posttranslational modifications positively influence the phagocytic activity of SP-A.
Phagocytosis ofBorrelia burgdorferiandTreponema pallidumPotentiates Innate Immune Activation and Induces Gamma Interferon Production
Authors: Moore Meagan W. , Cruz Adriana R. , LaVake Carson J. , Marzo Amanda L. , Eggers Christian H. , Salazar Juan C. , Radolf Justin D.
Published: January 2007

We examined the interactions of live and lysed spirochetes with innate immune cells. THP-1 monocytoid cells were activated to comparable extents by liveBorrelia burgdorferiand byB. burgdorferiandTreponema pallidumlysates but were poorly activated by liveT. pallidum. Because THP-1 cells poorly internalized live spirochetes, we turned to an ex vivo peripheral blood mononuclear cell system that would more closely reflect spirochete-mononuclear phagocyte interactions that occur during actual infection. In this system,B. burgdorferiinduced significantly greater monocyte activation and inflammatory cytokine production than did borrelial lysates orT. pallidum, and onlyB. burgdorferielicited gamma interferon (IFN-γ) from NK cells.B. burgdorferiwas phagocytosed avidly by monocytes, whileT. pallidumwas not, suggesting that the enhanced response to liveB. burgdorferiwas due to phagocytosis of the organism. When cytochalasin D was used to block phagocytosis of liveB. burgdorferi, cytokine production decreased to levels comparable to those induced byB. burgdorferilysates, while the IFN-γ response was abrogated altogether. In the presence of human syphilitic serum,T. pallidumwas efficiently internalized and initiated responses resembling those observed with liveB. burgdorferi, including the production of IFN-γ by NK cells. Depletion of monocytes revealed that they were the primary source of inflammatory cytokines, while dendritic cells (DCs) directed IFN-γ production from innate lymphocytes. Thus, phagocytosis of live spirochetes initiates cell activation programs in monocytes and DCs that differ qualitatively and quantitatively from those induced at the cell surface by lipoprotein-enriched lysates. The greater stimulatory capacity ofB. burgdorferiversusT. pallidumappears to be explained by the successful recognition and phagocytosis ofB. burgdorferiby host cells and the ability ofT. pallidumto avoid detection and uptake by virtue of its denuded outer membrane rather than by differences in surface lipoprotein expression.
Role of Unsaturated Fatty Acid Biosynthesis in Virulence of
Streptococcus mutans
Authors: Fozo Elizabeth M. , Scott-Anne Kathy , Koo Hyun , Quivey Robert G.
Published: January 2007

An insertionally inactivated
fabM
strain of
Streptococcus mutans
does not produce unsaturated membrane fatty acids and is acid sensitive (E. M. Fozo and R. G. Quivey, Jr., J. Bacteriol. 186:4152-4158, 2004). In this study, the strain was shown to be poorly transmissible from host to host. Animals directly infected with the
fabM
strain exhibited fewer and less severe carious lesions than those observed in the wild-type strain.
FNR Is a Global Regulator of Virulence and Anaerobic Metabolism inSalmonella entericaSerovar Typhimurium (ATCC 14028s)
Authors: Fink Ryan C. , Evans Matthew R. , Porwollik Steffen , Vazquez-Torres Andres , Jones-Carson Jessica , Troxell Bryan , Libby Stephen J. , McClelland Michael , Hassan Hosni M.
Published: January 2007

Salmonella entericaserovar Typhimurium must successfully transition the broad fluctuations in oxygen concentrations encountered in the host. InEscherichia coli, FNR is one of the main regulatory proteins involved in O2sensing. To assess the role of FNR in serovar Typhimurium, we constructed an isogenicfnrmutant in the virulent wild-type strain (ATCC 14028s) and compared their transcriptional profiles and pathogenicities in mice. Here, we report that, under anaerobic conditions, 311 genes (6.80% of the genome) are regulated directly or indirectly by FNR; of these, 87 genes (28%) are poorly characterized. Regulation by FNR in serovar Typhimurium is similar to, but distinct from, that inE. coli.Thus, genes/operons involved in aerobic metabolism, NO· detoxification, flagellar biosynthesis, motility, chemotaxis, and anaerobic carbon utilization are regulated by FNR in a fashion similar to that inE. coli. However, genes/operons existing inE. colibut regulated by FNR only in serovar Typhimurium include those coding for ethanolamine utilization, a universal stress protein, a ferritin-like protein, and a phosphotransacetylase. Interestingly,Salmonella-specific genes/operons regulated by FNR include numerous virulence genes withinSalmonellapathogenicity island 1 (SPI-1), newly identified flagellar genes (mcpAC,cheV), and the virulence operon (srfABC). Furthermore, the role of FNR as a positive regulator of motility, flagellar biosynthesis, and pathogenesis was confirmed by showing that the mutant is nonmotile, lacks flagella, is attenuated in mice, and does not survive inside macrophages. The inability of the mutant to survive inside macrophages is likely due to its sensitivity to the reactive oxygen species generated by NADPH phagocyte oxidase.
Ligand-Controlled Proteolysis of theEscherichia coliTranscriptional Regulator ZntR
Authors: Pruteanu Mihaela , Neher Saskia B. , Baker Tania A.
Published: January 2007

Proteases play a crucial role in remodeling the bacterial proteome in response to changes in cellular environment.Escherichia coliZntR, a zinc-responsive transcriptional regulator, was identified by proteomic experiments as a likely ClpXP substrate, suggesting that protein turnover may play a role in regulation of zinc homeostasis. When intracellular zinc levels are high, ZntR activates expression of ZntA, an ATPase essential for zinc export. We find that ZntR is degraded in vivo in a manner dependent on both the ClpXP and Lon proteases. However, ZntR degradation decreases in the presence of high zinc concentrations, the level of ZntR rises, and transcription of thezntAexporter is increased. Mutagenesis experiments reveal that zinc binding does not appear to be solely responsible for the zinc-induced protection from proteolysis. Therefore, we tested whether DNA binding was important in the zinc-induced stabilization of ZntR by mutagenesis of the DNA binding helices. Replacement of a conserved arginine (R19A) in the DNA binding domain both enhances ZntR degradation and abolishes zinc-induced transcriptional activation ofzntA. Biochemical and physical analysis of ZntRR19Ademonstrates that it is structurally similar to, and binds zinc as well as does, the wild-type protein but is severely defective in binding DNA. Thus, we conclude that two different ligands—zinc and DNA—function together to increase ZntR stability and that ligand-controlled proteolysis of ZntR plays an important role in fine-tuning zinc homeostasis in bacteria.
Enhancement of the Synthesis of RpoN, Cra, and H-NS by Polyamines at the Level of Translation in
Escherichia coli
Cultured with Glucose and Glutamate
Authors: Terui Yusuke , Higashi Kyohei , Taniguchi Shiho , Shigemasa Ai , Nishimura Kazuhiro , Yamamoto Kaneyoshi , Kashiwagi Keiko , Ishihama Akira , Igarashi Kazuei
Published: January 2007

Proteins whose synthesis is enhanced by polyamines at the level of translation were identified in a polyamine-requiring mutant cultured in the presence of 0.1% glucose and 0.02% glutamate instead of 0.4% glucose as an energy source. Under these conditions, enhancement of cell growth by polyamines was almost the same as that in the presence of 0.4% glucose. It was found that synthesis of RpoN, Cra, and H-NS was enhanced by polyamines at the level of translation at the early logarithmic phase of growth (
A
540
of 0.15). The effects of polyamines on synthesis of RpoN, H-NS, and Cra were due to the existence of unusual Shine-Dalgarno sequences (RpoN and H-NS) and an inefficient GUG initiation codon (Cra) in their mRNAs. Thus,
rpoN
,
cra
, and
hns
genes were identified as new members of the polyamine modulon. Because most of the polyamine modulon genes thus far identified encode transcription factors (RpoS [σ
38
], Cya, FecI [σ
18
], Fis, RpoN [σ
54
], Cra, and H-NS), DNA microarray analysis of mRNA expressed in cells was performed. At the early logarithmic phase of growth, a total of 97 species of mRNAs that were up-regulated by polyamines more than twofold were under the control of seven polyamine modulon genes mentioned above.
The Sugar Phosphotransferase System of
Vibrio fischeri
Inhibits both Motility and Bioluminescence
Authors: Visick Karen L. , O'Shea Therese M. , Klein Adam H. , Geszvain Kati , Wolfe Alan J.
Published: January 2007

Magnesium-dependent induction of
Vibrio fischeri
flagellar (Mif) biogenesis depends upon two diguanylate cyclases, suggesting an inhibitory role for cyclic di-GMP. Here, we report that cells defective for the sugar phosphotransferase system (PTS) exhibited a magnesium-independent phenotype similar to that of mutants of the Mif pathway. Unlike Mif mutants, PTS mutants also were hyperbioluminescent.
The Orphan Response Regulator HP1021 of
Helicobacter pylori
Regulates Transcription of a Gene Cluster Presumably Involved in Acetone Metabolism
Authors: Pflock Michael , Bathon Melanie , Schär Jennifer , Müller Stefanie , Mollenkopf Hans , Meyer Thomas F. , Beier Dagmar
Published: January 2007

Helicobacter pylori
is a gastric pathogen for which no nonhuman reservoir is known. In accordance with the tight adaptation to its unique habitat, the human stomach,
H. pylori
is endowed with a very restricted repertoire of regulatory proteins. Nevertheless, the three complete two-component systems of
H. pylori
were shown to be involved in the regulation of important virulence traits like motility and acid resistance and in the control of metal homeostasis. HP1021 is an orphan response regulator with an atypical receiver domain whose inactivation has a considerable impact on the growth of
H. pylori
. Here we report the identification of HP1021-regulated genes by whole-genome transcriptional profiling. We show that the transcription of the essential housekeeping genes
nifS
and
nifU
, which are required for the assembly of Fe-S clusters, is activated by HP1021. Furthermore, we demonstrate that the expression of a gene cluster comprising open reading frames hp0690 to hp0693 and hp0695 to hp0697 which is probably involved in acetone metabolism is strongly upregulated by HP1021. Evidence is provided for a direct regulation of the hp0695-to-hp0697 operon by the binding of HP1021 to its promoter region.
Immunologically Active Autoantigens: The Role of Toll-Like Receptors in the Development of Chronic Inflammatory Disease
Authors: Marshak-Rothstein Ann , Rifkin Ian R.
Published: January 2007

Pattern recognition receptors (PRRs), expressed on cells of both the innate and adaptive immune systems, serve as sentinels, waiting to alert the host to the first signs of microbial infection and to activate the initial line of immune defense. Research has increasingly demonstrated that many of the same PRRs also recognize self-epitopes that either are released from dying or damaged cells or are present at the surface of apoptotic cells or apoptotic bodies. In this context, PRRs play a critical role in tissue repair and the clearance of cellular debris. However, failure to appropriately regulate self-responses triggered by certain PRRs can have serious pathological consequences. The Toll-like receptor (TLR) gene family represents a case in point. TLR7, 8, and 9 were originally identified as receptors specific for bacterial and viral RNA and DNA, but more recent in vitro and in vivo studies have now linked these receptors to the detection of host RNA, DNA, and RNA- or DNA-associated proteins. In this context, they likely play a key role in the development of systemic autoimmune diseases.
Zoned Out: Functional Mapping of Stromal Signaling Microenvironments in the Thymus
Authors: Petrie Howard T. , Zúñiga-Pflücker Juan Carlos
Published: January 2007

All hematopoietic cells, including T lymphocytes, originate from stem cells that reside in the bone marrow. Most hematopoietic lineages also mature in the bone marrow, but in this respect, T lymphocytes differ. Under normal circumstances, most T lymphocytes are produced in the thymus from marrow-derived progenitors that circulate in the blood. Cells that home to the thymus from the marrow possess the potential to generate multiple T and non-T lineages. However, there is little evidence to suggest that, once inside the thymus, they give rise to anything other than T cells. Thus, signals unique to the thymic microenvironment compel multipotent progenitors to commit to the T lineage, at the expense of other potential lineages. Summarizing what is known about the signals the thymus delivers to uncommitted progenitors, or to immature T-committed progenitors, to produce functional T cells is the focus of this review.
The Immunobiology of SARS
Authors: Chen Jun , Subbarao Kanta
Published: January 2007

Severe acute respiratory syndrome (SARS) presented as an atypical pneumonia that progressed to acute respiratory distress syndrome in ∼20% of cases and was associated with a mortality of about 10%. The etiological agent was a novel coronavirus (CoV). Angiotensin-converting enzyme 2 is the functional receptor for SARS-CoV; DC-SIGN and CD209L (L-SIGN) can enhance viral entry. Although the virus infects the lungs, gastrointestinal tract, liver, and kidneys, the disease is limited to the lungs, where diffuse alveolar damage is accompanied by a disproportionately sparse inflammatory infiltrate. Pro-inflammatory cytokines and chemokines, particularly IP-10, IL-8, and MCP-1, are elevated in the lungs and peripheral blood, but there is an unusual lack of an antiviral interferon (IFN) response. The virus is susceptible to exogenous type I IFN but suppresses the induction of IFN. Innate immunity is important for viral clearance in the mouse model. Virus-specific neutralizing antibodies that develop during convalescence prevent reinfection in animal models.
Macromolecular transport in heart valves. II. Theoretical models
Authors: Zeng Zhongqing , Yin Yongyi , Jan Kung-Ming , Rumschitzki David S.
Published: January 2007

This paper proposes a new, two-dimensional convection-diffusion model for macromolecular transport in heart valves based on horseradish peroxidase (HRP) experiments on rats presented in the first of the papers in this series (Part I; Zeng Z, Yin Y, Huang AL, Jan KM, Rumschitzki DS. Am J Physiol Heart Circ Physiol 292: H2664–H2670, 2007). Experiments require two valvular intimae, one underneath each endothelium. Tompkins et al. (Tompkins RG, Schnitzer JJ, Yarmush ML. Circ Res 64: 1213–1223, 1989) found large variations in shape and magnitude in transvalvular125I-labeled low-density lipoprotein (LDL) profiles from identical experiments on four squirrel monkeys. Their one-dimensional, uniform-medium diffusion-only model fit three parameters independently for each profile; data variability resulted in large parameter spreads. Our theory aims to explain their data with one parameter set. It uses measured parameters and some aortic values but fits the endothelial mass transfer coefficient ( ka= kv= 1.63 × 10−8cm/s, where subscripts a and v indicate aortic aspect and ventricular aspect, respectively) and middle layer permeability ( K[Formula: see text]= 2.28 × 10−16cm2) and LDL diffusion coefficient [ D2(LDL) = 5.93 × 10−9cm2/s], using one of Tompkins et al.'s profiles, and fixes them throughout. It accurately predicts Part I's rapid localized HRP leakage spot growth rate in rat leaflets that results from the intima's much sparser structure, dictating its far larger transport parameters [ K[Formula: see text]= 1.10 × 10−12cm2, D1(LDL/HRP) = 1.02/4.09 × 10−7cm2/s] than the middle layer. This contrasts with large arteries with similarly large HRP spots, since the valve has no internal elastic lamina. The model quantitatively explains all of Tompkins et al.'s monkey profiles with these same parameters. Different numbers and locations of isolated macromolecular leaks on both aspects and different section-leak(s) distances yield all profiles.
Role of interleukin-6 in cardiac inflammation and dysfunction after burn complicated by sepsis
Authors: Zhang Hongchao , Wang Huan-You , Bassel-Duby Rhonda , Maass David L. , Johnston William E. , Horton Jureta W. , Tao Weike
Published: January 2007

To examine the role of myocardial interleukin-6 (IL-6) in myocardial inflammation and dysfunction after burn complicated by sepsis, we performed 40% total body surface area contact burn followed by late (7 days) Streptococcus pneumoniae pneumonia sepsis in wild-type (WT) mice, IL-6 knockout (IL-6 KO) mice, and transgenic mice overexpressing IL-6 in the myocardium (TG). Twenty-four hours after sepsis was induced, isolated cardiomyocytes were harvested and cultured in vitro, and supernatant concentrations of IL-6 and tumor necrosis factor (TNF)-α were measured. Cardiomyocyte intracellular calcium ([Ca2+]i) and sodium ([Na+]i) concentrations were also determined. Separate mice in each group underwent in vivo global hemodynamic and cardiac function assessment by cannulation of the carotid artery and insertion of a left ventricular pressure volume conductance catheter. Hearts from these mice were collected for histopathological assessment of inflammatory response, fibrosis, and apoptosis. In the WT group, there was an increase in cardiomyocyte TNF-α, [Ca2+]i, and [Na+]iafter burn plus sepsis, along with cardiac contractile dysfunction, inflammation, and apoptosis. These changes were attenuated in the IL-6 KO group but accentuated in the TG group. We conclude myocardial IL-6 mediates cardiac inflammation and contractile dysfunction after burn plus sepsis.
Atropine pretreatment enhances airway hyperreactivity in antigen-challenged guinea pigs through an eosinophil-dependent mechanism
Authors: Verbout Norah G. , Lorton Jesse K. , Jacoby David B. , Fryer Allison D.
Published: January 2007

Airway hyperreactivity in antigen-challenged animals is mediated by eosinophil major basic protein (MBP) that blocks inhibitory M2muscarinic receptors on parasympathetic nerves, increasing acetylcholine release onto M3muscarinic receptors on airway smooth muscle. Acutely, anticholinergics block hyperreactivity in antigen-challenged animals and reverse asthma exacerbations in the human, but are less effective in chronic asthma. We tested whether atropine, given before antigen challenge, affected hyperreactivity, M2receptor function, eosinophil accumulation, and activation. Sensitized guinea pigs received atropine (1 mg/kg ip) 1 h before challenge and 6 h later. Twenty-four hours after challenge, animals were anesthetized, vagotomized, paralyzed, and ventilated. Airway reactivity to electrical stimulation of the vagi and to intravenous acetylcholine was not altered by atropine pretreatment in nonsensitized animals, indicating that atropine was no longer blocking postjunctional muscarinic receptors. Antigen challenge induced airway hyperreactivity to vagal stimulation that was significantly potentiated by atropine pretreatment. Bronchoconstriction induced by acetylcholine was not changed by antigen challenge or by atropine pretreatment. M2receptor function was lost in challenged animals but protected by atropine pretreatment. Eosinophils in bronchoalveolar lavage and within airway tissues were significantly increased by challenge but significantly reduced by atropine pretreatment. However, extracellular MBP in challenged airways was significantly increased by atropine pretreatment, which may account for reduced eosinophils. Depleting eosinophils with antibody to IL-5 before challenge prevented hyperreactivity and significantly reduced MBP in airways of atropine-pretreated animals. Thus atropine pretreatment potentiated airway hyperreactivity by increasing eosinophil activation and degranulation. These data suggest that anticholinergics enhance eosinophil interactions with airway nerves.
Wigglism: A Philosophoid Entity Turns Ten
Authors: Fisher Ebon
Published: January 2007

The author describes The Wigglism Manifesto, a work authored amidst the fury of early exchange on the World Wide Web. The term Wigglism refers to a quality shared by biological and artificial life forms alike. The manifesto has taken an open-source approach to its cultivation, allowing numerous voices to nurture the entity into being. This collective approach to truth cultivation embodied by the manifesto was inspired, in part, by the author's experiences with community-based media rituals in the North Brooklyn community before it gentrified in the mid-1990s. The project has affirmed its initiator's sense that cultivating a living system can be a vital alternative to traditional creative practices more aligned with manufacturing and commerce.
Cover Picture: Nanoscale Deposition of Single‐Molecule Magnets onto SiO2 Patterns (Adv. Mater. 2/2007)
Authors: Martínez R. V. , García F. , García R. , Coronado E. , Forment‐Aliaga A. , Romero F. M. , Tatay S.
Published: January 2007

The cover shows a schematic of scanning probe nanolithography based on the spatial confinement of an oxidation reaction within a water meniscus, and its application for fabricating ordered arrays of cationic Mn12 single‐molecule magnets. Romero, Coronado, Garcìa, and co‐workers report on p. 291 that electrostatic interactions between the molecules and trapped charges within the nanodots drive the positioning of the molecules at the nanoscale.
Prediction of volumetric productivity of an outdoor photobioreactor
Authors: Bosma Rouke , van Zessen Erik , Reith Johannes H. , Tramper Johannes , Wijffels René H.
Published: January 2007

Volumetric productivity of Monodus subterraneus cultivated in an outdoor pilot‐plant bubble column was predicted with a mathematical model. Two border cases to model the photobioreactor were chosen. Firstly, a model with no light integration in which it is assumed that microalgae can adapt immediately to local light conditions. Secondly, full light integration implicating that microalga can convert all absorbed light with a photosynthetic yield based on average light intensity. Because temperature and light conditions in our photobioreactor changed during the day, photosynthetic yields at any combination of temperature and light intensity were needed. These were determined in repeated‐batch lab‐scale experiments with an experimental design. The model was evaluated in an outdoor bubble column at different natural light conditions and different temperatures. Volumetric productivities in the bubble column were predicted and compared with experimental volumetric productivities. The light integration model over‐estimated productivity, while the model in which we assumed no light integration under‐estimated productivity. Light integration occurred partly (47%) during the period investigated. The average observed biomass yield on light was 0.60 g·mol−1. The model of partly light integration predicted an average biomass yield on light of 0.57 g·mol−1 and predicted that productivity could have been increased by 19% if culture temperature would have been maintained at 24°C. Biotechnol. Bioeng. 2007; 97: 1108–1120. © 2007 Wiley Periodicals, Inc.
Influence of Substrate Surface Polarity on Epitaxial Layer Growth of CuInSe2 on GaAs
Authors: Schumann B. , Neumann H. , Nowak E. , Kühn G.
Published: January 2007

CuInSe2 thin films with thicknesses of about 0.1 μm were deposited onto (III) B‐oriented GaAs substrates by flash evaporation. At substrate temperatures Tsub = 695–820 K the films have the chalcopprite structure with some admixture of the cubic sphalerite phase. At Tsub > 820 K only the sphalerite phase was found All the films are partly polycrystalline. From the electrical properties it follows that the films are characterized by nearly complete compensation at Tsub = 695–820 K. At Tsub = 870 K the films are p‐type conducting and show two acceptor states with ionization energies of about 8 meV and 105 meV.
Experimental Determination and Thermodynamic Calcultions of the Relationship between Vapour Phase Composition and Mixed Crystal Composition in the Ga‐HCI‐PH3‐AsH3‐(NH3)‐H2 System
Authors: Jacobs K. , Peuschel G.‐P. , Peuschel R. , Probst R. , Butter E. , Bugge F.
Published: January 2007

The relationship between the composition of GaAs1–xPx layers and the composition of the vapour phase has been investigated experimentally and theoretically. Using KIRWAN'Sequilibrium constants excellent agreement between calculated and experimental data is obtained over the whole composition range. Different models and parameters for the calculation of the soild solution activity coefficients result in only small differences for the calculated alloy composition so that no decision can be made from the experiments for one model to be preferred. Increasing addition of NH3 to the vapour phase up to concentrations exceeding those of the crystal forming gases by an order of magnitude has no influence on the alloy composition, although the nitrogen concentration in the layers increases as deduced from the shift of the wavelength of the maximum photoluminescence intensity.
On the Preparation of ZnO Single Crystals
Authors: Fischer K. , Sinn E.
Published: January 2007

ZnO single crystals were prepared by means of two methods:i slow cooling of ZnO/PbF2 (PbO) high temperature solution, (ii) flux reaction technique, hydrolysis of ZnF2 in PbF2 as a solvent. At cooling rate ≥ 0.9 K/h the known plates, hexagonal prisms, and hollow crystals were obtained. At the cooling rate 0.6 K/h compact crystals have grown. This habit was also formed with the flux reaction technique. An estimation of the deposition rates of both methods has shown approximative agreement between the cooling runs with 0.6 K/h and the flux reaction technique under the chosen conditions. The deposition rate appears to be a relevant parameter for forming compact ZnO crystals in these systems.
An Improved Method for Purification of β‐Copperphthalocyanine
Authors: Mizuguchi Jin
Published: January 2007

A sublimation apparatus in which a high temperature slightly lower than the sublimation point of copperphthalocyanine remains constant over a long condensation region has been developed. A sufficiently pure material for electrophotographic measurements can be obtained only when this high temperature is maintained nearly constant over the long condensation region along the sublimation tube. After the thired sublimation, the value of copper contents in the sample is 11.03 · 0.02%, according to the chelatometric titrations, while the theoreitcal value of stoichimetric composition is 11.03%. Emission spectrochemical analysis shows that only traces of Si and Mg are found in the sample after the sixth sublimation. Single crystal srown in the sublimation tube are characterized and the growth mechanism is discussed.
Microstructures of Tin Iodide Single Crystals Grown in Silica Gels
Authors: Desai C. C. , Rai J. L.
Published: January 2007

Single crystals of tin iodide (SnI2) have been grown in silica gels. A detailed microtopographical study of {100} faces have been described. Horizontal striations are predominant on these faces for most of the crystals, while few of them show vertical striations. The horizontal striations are associated with the two‐dimensional nucleation theory whereas the vertical striations relate to the growth fronts. Growth layers modified by the presence of misaligned microcystals have been illustrated. The natural etch pits on {100} faces of the crystal are attributed to the dissolution of crystals in the acid set gel. In the light of these observations, the mechanism of the development and growth of these faces have been assessed and the implications are discussed.
Diamond Synthesis in Cool Plasma
Authors: Mania R. , Stobierski L. , Pampuch R.
Published: January 2007

The conditions of low pressure autoepitaxy of diamond are analysed and theoretical concepts concerning the plasmochemical method of diamond synthesis put forward. The experimental method used is described. The obtained results have demonstrated the utility of the plasmochemical method for obtainment of diamond and confirmed the validity of the presented theoretical concepts.
Kinetics of Scale Growth from Quiescent Solutions of Soluble Substances
Authors: Veverka F. , Söhnel O.
Published: January 2007

The kinetics of scale growth on a cooling surface from quiescent aqueous solutions of oxalic acid, Na2HPO4 × 12 H2O, KNO3, Na2SO4 × 10 H2O, and Na3PO4 × 12 H2O saturated at 65, 32, 48.2, 31, and 39.2 °C, resp., was studied. The incurstations formed during 2 min of growth consist of loosely packed dendrites or needle‐like crystals (the former 3 substances), or of tightly packed crystals forming a scale with a “smooth surface” (the latter 2 salts). The kinetic order of growth, g, assessed on the basis of experimental data was smaller than unity in all the studied cases; the g values of smooth incrustations were higher than those of the dendritic ones. It follows from the considerations concerning the possible mechanism of scale growth that the growth is controlled by a mononuculear mechanism. The experimental values of g compare reasonably well with the expected theoretical values.
Temperature and Intensity Behaviour of the pAl0.7Ga0.3As‐pGaAs‐nGaAs Concentrator Solar Cell
Authors: Díaz P. , Hernandez L. , Romero R.
Published: January 2007

A semiempirical approch for calculation of pAl0.7Ga0.3As‐pGaAs‐nGaAs concentrator solar cell behaviour in a very wide range of operating temperatures (77 K – 490 K) is developed. Experimental values of cell collection efficiency, short circuit current and open circuit voltage are given, while cell fill factor and overall conversion efficiency are calculated. Optimum cell operating conditions are found both for AM 1 and AM 0 radiation.
Diffusion Phenomena during the heteroepitaxy of Ternary Compounds of the Type (AxB1–x)1–ΔC1+Δ
Authors: Schäfer P. , Bremser W.
Published: January 2007

In heteroepitaxy of ternary compound systems of the type (AxB1–x)1–ΔC1+Δ has to be taken into account the occurrence of complex diffusion phenomena independent on the epitaxial method applied which cannot be considered within a quasi‐binary system AC–BC. Based on the statements of thermodynamics of irreversible processes a model for the calculation of diffusion profiles, regarding the influence of the compound crystal composition x on the deviation from stoichiometry Δ, is presented. Concentration profiles calculated in accordance to this model show typical maxima and minima. – Tellurium distribution profiles determined on heterostructures of the type (Pb1–xSnx)1–ΔTe1+Δ /PbTe got by electron‐probe microanalysis may be explained qualitatively within the presented model. With the EBIC‐method additional p‐n junctions at the position of the extrema in the tellurium distribution were found.
Isothermal Ageing in the T Range from 0°C to 180°C of a Technical Al‐2.0 at.% Zn‐1.3 at.% Mg Alloy after Direct Quench
Authors: Gerlach R. , Löffler H.
Published: January 2007

The variations of the structure and the mechanical properties had been investigated by means of TEM investigations and determination of the microhardness number in the Ta range between 0 °C and 180 °C. The main results are the following: – At the starting period of the isothermal ageing an incubation time, tinc, occurs. tinc plotted versus Ta yields two intersecting C curves at about 100 °C. – At Ta = 70 °C the only decomposition product are G.P. zones. – At 70 °C <Ta <100 °C the G.P. zones formed in the first period of decomposition can be transformed into η‐phase or spherical hexagonal (S.H.) zones. – Above about 110 °C the precipitates present in the matrix are quasi‐homogeneously formed at nucleation sites delivered by clusters of impurity atoms.