bluuebunny/crossref_metadata_2025 huggingface dataset:
Acetic Acid Bacteria, Newly Emerging Symbionts of Insects
Authors: Crotti Elena , Rizzi Aurora , Chouaia Bessem , Ricci Irene , Favia Guido , Alma Alberto , Sacchi Luciano , Bourtzis Kostas , Mandrioli Mauro , Cherif Ameur , Bandi Claudio , Daffonchio Daniele
Published: September 2010

Recent research in microbe-insect symbiosis has shown that acetic acid bacteria (AAB) establish symbiotic relationships with several insects of the orders Diptera, Hymenoptera, Hemiptera, and Homoptera, all relying on sugar-based diets, such as nectars, fruit sugars, or phloem sap. To date, the fruit flies
Drosophila melanogaster
and
Bactrocera oleae
, mosquitoes of the genera
Anopheles
and
Aedes
, the honey bee
Apis mellifera
, the leafhopper
Scaphoideus titanus
, and the mealybug
Saccharicoccus sacchari
have been found to be associated with the bacterial genera
Acetobacter
,
Gluconacetobacter
,
Gluconobacter
,
Asaia
, and
Saccharibacter
and the novel genus
Commensalibacter
. AAB establish symbiotic associations with the insect midgut, a niche characterized by the availability of diet-derived carbohydrates and oxygen and by an acidic pH, selective factors that support AAB growth. AAB have been shown to actively colonize different insect tissues and organs, such as the epithelia of male and female reproductive organs, the Malpighian tubules, and the salivary glands. This complex topology of the symbiosis indicates that AAB possess the keys for passing through body barriers, allowing them to migrate to different organs of the host. Recently, AAB involvement in the regulation of innate immune system homeostasis of
Drosophila
has been shown, indicating a functional role in host survival. All of these lines of evidence indicate that AAB can play different roles in insect biology, not being restricted to the feeding habit of the host. The close association of AAB and their insect hosts has been confirmed by the demonstration of multiple modes of transmission between individuals and to their progeny that include vertical and horizontal transmission routes, comprising a venereal one. Taken together, the data indicate that AAB represent novel secondary symbionts of insects.
Maximizing Capture Efficiency and Specificity of Magnetic Separation for
Mycobacterium avium
subsp.
paratuberculosis
Cells
Authors: Foddai Antonio , Elliott Christopher T. , Grant Irene R.
Published: September 2010

In order to introduce specificity for
Mycobacterium avium
subsp.
paratuberculosis
prior to a phage amplification assay, various magnetic-separation approaches, involving either antibodies or peptides, were evaluated in terms of the efficiency of capture (expressed as a percentage) of
M. avium
subsp.
paratuberculosis
cells and the percentage of nonspecific binding by other
Mycobacterium
spp. A 50:50 mixture of MyOne Tosylactivated Dynabeads coated with the chemically synthesized
M. avium
subsp.
paratuberculosis
-specific peptides biotinylated aMp3 and biotinylated aMptD (i.e., peptide-mediated magnetic separation [PMS]) proved to be the best magnetic-separation approach for achieving 85 to 100% capture of
M. avium
subsp.
paratuberculosis
and minimal (<1%) nonspecific recovery of other
Mycobacterium
spp. (particularly if beads were blocked with 1% skim milk before use) from broth samples containing 10
3
to 10
4
CFU/ml. When PMS was coupled with a recently optimized phage amplification assay and used to detect
M. avium
subsp.
paratuberculosis
in 50-ml volumes of spiked milk, the mean 50% limit of detection (LOD
50
) was 14.4 PFU/50 ml of milk (equivalent to 0.3 PFU/ml). This PMS-phage assay represents a novel, rapid method for the detection and enumeration of viable
M. avium
subsp.
paratuberculosis
organisms in milk, and potentially other sample matrices, with results available within 48 h.
Engineering of
Corynebacterium glutamicum
with an NADPH-Generating Glycolytic Pathway for
l
-Lysine Production
Authors: Takeno Seiki , Murata Ryosuke , Kobayashi Ryosuke , Mitsuhashi Satoshi , Ikeda Masato
Published: September 2010

A sufficient supply of NADPH is a critical factor in
l
-lysine production by
Corynebacterium glutamicum
. Endogenous NAD-dependent glyceraldehyde 3-phosphate dehydrogenase (GAPDH) of
C. glutamicum
was replaced with nonphosphorylating NADP-dependent glyceraldehyde 3-phosphate dehydrogenase (GapN) of
Streptococcus mutans
, which catalyzes the reaction of glyceraldehyde 3-phosphate to 3-phosphoglycerate with the reduction of NADP
+
to NADPH, resulting in the reconstruction of the functional glycolytic pathway. Although the growth of the engineered strain on glucose was significantly retarded, a suppressor mutant with an increased ability to utilize sugars was spontaneously isolated from the engineered strain. The suppressor mutant was characterized by the properties of GapN as well as the nucleotide sequence of the gene, confirming that no change occurred in either the activity or the basic properties of GapN. The suppressor mutant was engineered into an
l
-lysine-producing strain by plasmid-mediated expression of the desensitized
lysC
gene, and the performance of the mutant as an
l
-lysine producer was evaluated. The amounts of
l
-lysine produced by the suppressor mutant were larger than those produced by the reference strain (which was created by replacement of the preexisting
gapN
gene in the suppressor mutant with the original
gapA
gene) by ∼70% on glucose, ∼120% on fructose, and ∼100% on sucrose, indicating that the increased
l
-lysine production was attributed to GapN. These results demonstrate effective
l
-lysine production by
C. glutamicum
with an additional source of NADPH during glycolysis.
In Vivo
and
Ex Vivo
Evaluations of Bacteriophages e11/2 and e4/1c for Use in the Control of
Escherichia coli
O157:H7
Authors: Rivas Lucia , Coffey Brid , McAuliffe Olivia , McDonnell Mary J. , Burgess Catherine M. , Coffey Aidan , Ross R. Paul , Duffy Geraldine
Published: September 2010

This study investigated the effect of bacteriophages (phages) e11/2 and e4/1c against
Escherichia
coli
O157:H7 in an
ex vivo
rumen model and in cattle
in vivo
. In the
ex vivo
rumen model, samples were inoculated with either 10
3
or 10
6
CFU/ml inoculum of
E. coli
O157:H7 and challenged separately with each bacteriophage. In the presence of phage e11/2, the numbers of
E. coli
O157:H7 bacteria were significantly (
P
< 0.05) reduced to below the limit of detection within 1 h. Phage e4/1c significantly (
P
< 0.05) reduced
E. coli
O157:H7 numbers within 2 h of incubation, but the number of surviving
E. coli
O157:H7 bacteria then remained unchanged over a further 22-h incubation period. The ability of a phage cocktail of e11/2 and e4/1c to reduce the fecal shedding of
E. coli
O157:H7 in experimentally inoculated cattle was then investigated in two cattle trials. Cattle (yearlings,
n
= 20 for trial one; adult fistulated cattle,
n
= 2 for trial two) were orally inoculated with 10
10
CFU of
E. coli
O157:H7. Animals (
n
= 10 for trial one;
n
= 1 for trial two) were dosed daily with a bacteriophage cocktail of 10
11
PFU for 3 days postinoculation.
E. coli
O157:H7 and phage numbers in fecal and/or rumen samples were determined over 7 days postinoculation.
E. coli
O157:H7 numbers rapidly declined in all animals within 24 to 48 h; however, there was no significant difference (
P
> 0.05) between the numbers of
E. coli
O157:H7 bacteria shed by the phage-treated or control animals. Phages were recovered from the rumen but not from the feces of the adult fistulated animal in trial two but were recovered from the feces of the yearling animals in trial one. While the results from the rumen model suggest that phages are effective in the rumen, further research is required to improve the antimicrobial effectiveness of phages for the elimination of
E. coli
O157:H7
in vivo
.
Nonlinear Biosynthetic Gene Cluster Dose Effect on Penicillin Production by
Penicillium chrysogenum
Authors: Nijland Jeroen G. , Ebbendorf Bjorg , Woszczynska Marta , Boer Rémon , Bovenberg Roel A. L. , Driessen Arnold J. M.
Published: September 2010

Industrial penicillin production levels by the filamentous fungus
Penicillium chrysogenum
increased dramatically by classical strain improvement. High-yielding strains contain multiple copies of the penicillin biosynthetic gene cluster that encodes three key enzymes of the β-lactam biosynthetic pathway. We have analyzed the gene cluster dose effect on penicillin production using the high-yielding
P. chrysogenum
strain DS17690 that was cured from its native clusters. The amount of penicillin V produced increased with the penicillin biosynthetic gene cluster number but was saturated at high copy numbers. Likewise, transcript levels of the biosynthetic genes
pcbAB
[δ-(
l
-α-aminoadipyl)-
l
-cysteinyl-
d
-valine synthetase],
pcbC
(isopenicillin N synthase), and
penDE
(acyltransferase) correlated with the cluster copy number. Remarkably, the protein level of acyltransferase, which localizes to peroxisomes, was saturated already at low cluster copy numbers. At higher copy numbers, intracellular levels of isopenicillin N increased, suggesting that the acyltransferase reaction presents a limiting step at a high gene dose. Since the number and appearance of the peroxisomes did not change significantly with the gene cluster copy number, we conclude that the acyltransferase activity is limiting for penicillin biosynthesis at high biosynthetic gene cluster copy numbers. These results suggest that at a high penicillin production level, productivity is limited by the peroxisomal acyltransferase import activity and/or the availability of coenzyme A (CoA)-activated side chains.
Catalytic Biomineralization of Fluorescent Calcite by the Thermophilic Bacterium
Geobacillus thermoglucosidasius
Authors: Yoshida Naoto , Higashimura Eiji , Saeki Yuichi
Published: September 2010

The thermophilic
Geobacillus
bacterium catalyzed the formation of 100-μm hexagonal crystals at 60°C in a hydrogel containing sodium acetate, calcium chloride, and magnesium sulfate. Under fluorescence microscopy, crystals fluoresced upon excitation at 365 ± 5, 480 ± 20, or 545 ± 15 nm. X-ray diffraction indicated that the crystals were magnesium-calcite in calcite-type calcium carbonate.
Development of an Environmental Functional Gene Microarray for Soil Microbial Communities
Authors: McGrath Ken C. , Mondav Rhiannon , Sintrajaya Regina , Slattery Bill , Schmidt Susanne , Schenk Peer M.
Published: September 2010

Functional attributes of microbial communities are difficult to study, and most current techniques rely on DNA- and rRNA-based profiling of taxa and genes, including microarrays containing sequences of known microorganisms. To quantify gene expression in environmental samples in a culture-independent manner, we constructed an environmental functional gene microarray (E-FGA) consisting of 13,056 mRNA-enriched anonymous microbial clones from diverse microbial communities to profile microbial gene transcripts. A new normalization method using internal spot standards was devised to overcome spotting and hybridization bias, enabling direct comparisons of microarrays. To evaluate potential applications of this metatranscriptomic approach for studying microbes in environmental samples, we tested the E-FGA by profiling the microbial activity of agricultural soils with a low or high flux of N
2
O. A total of 109 genes displayed expression that differed significantly between soils with low and high N
2
O emissions. We conclude that mRNA-based approaches such as the one presented here may complement existing techniques for assessing functional attributes of microbial communities.
The Antiretroviral Lectin Cyanovirin-N Targets Well-Known and Novel Targets on the Surface of Entamoeba histolytica Trophozoites
Authors: Carpentieri Andrea , Ratner Daniel M. , Ghosh Sudip K. , Banerjee Sulagna , Bushkin G. Guy , Cui Jike , Lubrano Michael , Steffen Martin , Costello Catherine E. , O'Keefe Barry , Robbins Phillips W. , Samuelson John
Published: September 2010

Entamoeba histolytica
, the protist that causes amebic dysentery and liver abscess, has a truncated Asn-linked glycan (
N
-glycan) precursor composed of seven sugars (Man
5
GlcNAc
2
). Here, we show that glycoproteins with unmodified
N
-glycans are aggregated and capped on the surface of
E. histolytica
trophozoites by the antiretroviral lectin cyanovirin-N and then replenished from large intracellular pools. Cyanovirin-N cocaps the Gal/GalNAc adherence lectin, as well as glycoproteins containing
O
-phosphodiester-linked glycans recognized by an anti-proteophosphoglycan monoclonal antibody. Cyanovirin-N inhibits phagocytosis by
E. histolytica
trophozoites of mucin-coated beads, a surrogate assay for amebic virulence. For technical reasons, we used the plant lectin concanavalin A rather than cyanovirin-N to enrich secreted and membrane proteins for mass spectrometric identification.
E. histolytica
glycoproteins with occupied
N
-glycan sites include Gal/GalNAc lectins, proteases, and 17 previously hypothetical proteins. The latter glycoproteins, as well as 50 previously hypothetical proteins enriched by concanavalin A, may be vaccine targets as they are abundant and unique. In summary, the antiretroviral lectin cyanovirin-N binds to well-known and novel targets on the surface of
E. histolytica
that are rapidly replenished from large intracellular pools.
Characterization of Glycoside Hydrolase Family 5 Proteins in Schizosaccharomyces pombe
Authors: Dueñas-Santero Encarnación , Martín-Cuadrado Ana Belén , Fontaine Thierry , Latgé Jean-Paul , del Rey Francisco , Vázquez de Aldana Carlos
Published: September 2010

In yeast, enzymes with β-glucanase activity are thought to be necessary in morphogenetic events that require controlled hydrolysis of the cell wall. Comparison of the sequence of the
Saccharomyces cerevisiae
exo-β(1,3)-glucanase Exg1 with the
Schizosaccharomyces pombe
genome allowed the identification of three genes that were named
exg1
+
(locus SPBC1105.05),
exg2
+
(SPAC12B10.11), and
exg3
+
(SPBC2D10.05). The three proteins have different localizations: Exg1 is secreted to the periplasmic space, Exg2 is a membrane protein, and Exg3 is a cytoplasmic protein. Characterization of the biochemical activity of the proteins indicated that Exg1 and Exg3 are active only against β(1,6)-glucans while no activity was detected for Exg2. Interestingly, Exg1 cleaves the glucans with an endohydrolytic mode of action.
exg1
+
showed periodic expression during the cell cycle, with a maximum coinciding with the septation process, and its expression was dependent on the transcription factor Sep1. The Exg1 protein localizes to the septum region in a pattern that was different from that of the endo-β(1,3)-glucanase Eng1. Overexpression of Exg2 resulted in an increase in cell wall material at the poles and in the septum, but the putative catalytic activity of the protein was not required for this effect.
Aspergillus fumigatus
flbB
Encodes Two Basic Leucine Zipper Domain (bZIP) Proteins Required for Proper Asexual Development and Gliotoxin Production
Authors: Xiao Peng , Shin Kwang-Soo , Wang Tianhong , Yu Jae-Hyuk
Published: September 2010

The opportunistic human pathogen
Aspergillus fumigatus
reproduces asexually by forming a massive number of mitospores called conidia. In this study, we characterize the upstream developmental regulator
A. fumigatus
flbB
(
AfuflbB
). Northern blotting and cDNA analyses reveal that
AfuflbB
produces two transcripts predicted to encode two basic leucine zipper domain (bZIP) polypeptides,
Afu
FlbBβ (420 amino acids [aa]) and
Afu
FlbBα (390 aa). The deletion of
AfuflbB
results in delayed/reduced sporulation, precocious cell death, the lack of conidiophore development in liquid submerged culture, altered expression of
AfubrlA
and
AfuabaA
, and blocked production of gliotoxin. While introduction of the wild-type (WT)
AfuflbB
allele fully complemented these defects, disruption of the ATG start codon for either one of the
Afu
FlbB polypeptides leads to a partial complementation, indicating the need of both polypeptides for WT levels of asexual development and gliotoxin biogenesis. Consistent with this,
Aspergillus nidulans
flbB

+

encoding one polypeptide (426 aa) partially complements the
AfuflbB
null mutation. The presence of 0.6 M KCl in liquid submerged culture suppresses the defects caused by the lack of one, but not both, of the
Afu
FlbB polypeptides, suggesting a genetic prerequisite for
Afu
FlbB in
A. fumigatus
development. Finally, Northern blot analyses reveal that both
AfuflbB
and
AfuflbE
are necessary for expression of
AfuflbD
, suggesting that FlbD functions downstream of FlbB/FlbE in aspergilli.
Predicting Plasmid Promiscuity Based on Genomic Signature
Authors: Suzuki Haruo , Yano Hirokazu , Brown Celeste J. , Top Eva M.
Published: September 2010

Despite the important contribution of self-transmissible plasmids to bacterial evolution, little is understood about the range of hosts in which these plasmids have evolved. Our goal was to infer this so-called evolutionary host range. The nucleotide composition, or genomic signature, of plasmids is often similar to that of the chromosome of their current host, suggesting that plasmids acquire their hosts’ signature over time. Therefore, we examined whether the evolutionary host range of plasmids could be inferred by comparing their trinucleotide composition to that of all completely sequenced bacterial chromosomes. The diversity of candidate hosts was determined using taxonomic classification and genetic distance. The method was first tested using plasmids from six incompatibility (Inc) groups whose host ranges are generally thought to be narrow (IncF, IncH, and IncI) or broad (IncN, IncP, and IncW) and then applied to other plasmid groups. The evolutionary host range was found to be broad for IncP plasmids, narrow for IncF and IncI plasmids, and intermediate for IncH and IncN plasmids, which corresponds with their known host range. The IncW plasmids as well as several plasmids from the IncA/C, IncP, IncQ, IncU, and PromA groups have signatures that were not similar to any of the chromosomal signatures, raising the hypothesis that these plasmids have not been ameliorated in any host due to their promiscuous nature. The inferred evolutionary host range of IncA/C, IncP-9, and IncL/M plasmids requires further investigation. In this era of high-throughput sequencing, this genomic signature method is a useful tool for predicting the host range of novel mobile elements.
Cadaverine Covalently Linked to Peptidoglycan Is Required for Interaction between the Peptidoglycan and the Periplasm-Exposed S-Layer-Homologous Domain of Major Outer Membrane Protein Mep45 in
Selenomonas ruminantium
Authors: Kojima Seiji , Ko Kyong-Cheol , Takatsuka Yumiko , Abe Naoki , Kaneko Jun , Itoh Yoshifumi , Kamio Yoshiyuki
Published: September 2010

The peptidoglycan of
Selenomonas ruminantium
is covalently bound to cadaverine (PG-cadaverine), which likely plays a significant role in maintaining the integrity of the cell surface structure. The outer membrane of this bacterium contains a 45-kDa major protein (Mep45) that is a putative peptidoglycan-associated protein. In this report, we determined the nucleotide sequence of the
mep45
gene and investigated the relationship between PG-cadaverine, Mep45, and the cell surface structure. Amino acid sequence analysis showed that Mep45 is comprised of an N-terminal S-layer-homologous (SLH) domain followed by α-helical coiled-coil region and a C-terminal β-strand-rich region. The N-terminal SLH domain was found to be protruding into the periplasmic space and was responsible for binding to peptidoglycan. It was determined that Mep45 binds to the peptidoglycan in a manner dependent on the presence of PG-cadaverine. Electron microscopy revealed that defective PG-cadaverine decreased the structural interactions between peptidoglycan and the outer membrane, consistent with the proposed role for PG-cadaverine. The C-terminal β-strand-rich region of Mep45 was predicted to be a membrane-bound unit of the 14-stranded β-barrel structure. Here we propose that PG-cadaverine possesses functional importance to facilitate the structural linkage between peptidoglycan and the outer membrane via specific interaction with the SLH domain of Mep45.
Crystallographic Insights into the Pore Structures and Mechanisms of the EutL and EutM Shell Proteins of the Ethanolamine-Utilizing Microcompartment ofEscherichia coli
Authors: Takenoya Mihoko , Nikolakakis Kiel , Sagermann Martin
Published: September 2010

The ethanolamine-utilizing bacterial microcompartment (Eut-BMC) ofEscherichia coliis a polyhedral organelle that harbors specific enzymes for the catabolic degradation of ethanolamine. The compartment is composed of a proteinaceous shell structure that maintains a highly specialized environment for the biochemical reactions inside. Recent structural investigations have revealed hexagonal assemblies of shell proteins that form a tightly packed two-dimensional lattice that is likely to function as a selectively permeable protein membrane, wherein small channels are thought to permit controlled exchange of specific solutes. Here, we show with two nonisomorphous crystal structures that EutM also forms a two-dimensional protein membrane. As its architecture is highly similar to the membrane structure of EutL, it is likely that the structure represents a physiologically relevant form. Thus far, of allEutproteins, only EutM and EutL have been shown to form such proteinaceous membranes. Despite their similar architectures, however, both proteins exhibit dramatically different pore structures. In contrast to EutL, the pore of EutM appears to be positively charged, indicating specificity for different solutes. Furthermore, we also show that the central pore structure of the EutL shell protein can be triggered to open specifically upon exposure to zinc ions, suggesting a specific gating mechanism.
A TRAP Transporter for Pyruvate and Other Monocarboxylate 2-Oxoacids in the Cyanobacterium
Anabaena
sp. Strain PCC 7120
Authors: Pernil Rafael , Herrero Antonia , Flores Enrique
Published: September 2010

In the cyanobacterium
Anabaena
sp. strain PCC 7120, open reading frames (ORFs)
alr3026
,
alr3027
, and
all3028
encode a tripartite ATP-independent periplasmic transporter (TRAP-T). Wild-type filaments showed significant uptake of [
14
C]pyruvate, which was impaired in the
alr3027
and
all3028
mutants and was inhibited by several monocarboxylate 2-oxoacids, identifying this TRAP-T system as a pyruvate/monocarboxylate 2-oxoacid transporter.
Increased C-reactive protein expression exacerbates left ventricular dysfunction and remodeling after myocardial infarction
Authors: Takahashi Toshiyuki , Anzai Toshihisa , Kaneko Hidehiro , Mano Yoshinori , Anzai Atsushi , Nagai Toshiyuki , Kohno Takashi , Maekawa Yuichiro , Yoshikawa Tsutomu , Fukuda Keiichi , Ogawa Satoshi
Published: September 2010

We previously reported serum C-reactive protein (CRP) elevation after acute myocardial infarction (MI) to be associated with adverse outcomes including cardiac rupture, left ventricular (LV) remodeling, and cardiac death. Experimental studies have indicated that CRP per se has various biological actions including proinflammatory and proapoptotic effects, suggesting a pathogenic role of CRP in the post-MI remodeling process. We tested the hypothesis that increased CRP expression would exacerbate adverse LV remodeling after MI via deleterious effects of CRP. Transgenic mice with human CRP expression (CRP-Tg) and their transgene-negative littermates (control) underwent left coronary artery ligation. There was no apparent difference in phenotypic features between CRP-Tg and control mice before MI. Although mortality and infarct size were similar in the two groups, CRP-Tg mice showed more LV dilation and worse LV function with more prominent cardiomyocyte hypertrophy and fibrosis in the noninfarcted regions after MI than controls. Histological evaluation conducted 1 wk post-MI revealed a higher rate of apoptosis and more macrophage infiltration in the border zones of infarcted hearts from CRP-Tg mice in relation to increased monocyte chemotactic protein (MCP)-1 expression and matrix metalloproteinase (MMP)-9 activity. Increased CRP expression exacerbates LV dysfunction and promotes adverse LV remodeling after MI in mice. The deleterious effect of CRP on post-MI LV remodeling may be associated with increased apoptotic rates, macrophage infiltration, MCP-1 expression, and MMP-9 activity in the border zone.
Individual differences in the heart rate response to activation of the muscle metaboreflex in humans
Authors: Watanabe Kazuhito , Ichinose Masashi , Fujii Naoto , Matsumoto Mayumi , Nishiyasu Takeshi
Published: September 2010

We tested the hypotheses that the heart rate (HR) response to muscle metaboreflex activation induced by postexercise muscle ischemia (PEMI) varies considerably among subjects and that individual differences in the HR response are associated with differences in cardiac autonomic tone and/or arterial baroreflex function during PEMI. Fifty-one healthy subjects (36 men and 15 women) performed a 1-min isometric handgrip exercise at 50% maximal voluntary contraction, which was followed by a 3.5-min period of imposed PEMI. We estimated cardiac autonomic tone using spectral analysis of beat-to-beat variation in the R-R interval (RRI). In addition, the sensitivity of the arterial baroreflex control of HR (BRS) was evaluated using transfer function analysis of systolic arterial pressure (SAP) and RRI. Although the mean RRI during the PEMI and subsequent recovery period did not differ from the resting value, the variance among the individual differences in RRI between the rest and PEMI periods was significantly greater than between the rest and recovery periods. The changes in RRI elicited by PEMI correlated significantly with changes in the spectral power of the RRI variability in the high-frequency range and the BRS. By contrast, no significant correlation was observed between changes in RRI and changes in mean arterial pressure or the power of the RRI variability in the low-frequency range. This suggests that, in humans, the HR response to PEMI-induced activation of muscle metaboreflex varies considerably from individual to individual and that these differences reflect changes in cardiac parasympathetic tone and spontaneous BRS during PEMI.
Baroreceptor and chemoreceptor contributions to the hypertensive response to bilateral carotid occlusion in conscious mice
Authors: Lataro R. M. , Castania J. A. , Chapleau M. W. , Salgado H. C. , Fazan R.
Published: September 2010

This study aimed to characterize the role played by baroreceptors and chemoreceptors in the hypertensive response to bilateral carotid occlusion (BCO) in conscious C57BL mice. On the day before the experiments the animals were implanted with pneumatic cuffs around their common carotid arteries and a femoral catheter for measurement of arterial pressure. Under the same surgical approach, groups of mice were submitted to aortic or carotid sinus denervation or sham surgery. BCO was performed for 30 or 60 s, promoting prompt and sustained increase in mean arterial pressure and fall in heart rate. Compared with intact mice, the hypertensive response to 30 s of BCO was enhanced in aortic-denervated mice (52 ± 4 vs. 41 ± 4 mmHg; P < 0.05) but attenuated in carotid sinus-denervated mice (15 ± 3 vs. 41 ± 4 mmHg; P < 0.05). Suppression of peripheral chemoreceptor activity by hyperoxia [arterial partial pressure of oxygen (PaO2) > 500 mmHg] attenuated the hypertensive response to BCO in intact mice (30 ± 6 vs. 51 ± 5 mmHg in normoxia; P < 0.05) and abolished the bradycardia. It did not affect the hypertensive response in carotid sinus-denervated mice (20 ± 4 vs. 18 ± 3 mmHg in normoxia; P < 0.05). The attenuation of the hypertensive response to BCO by carotid sinus denervation or hyperoxia indicates that the hypertensive response in conscious mice is mediated by both baro- and chemoreceptors. In addition, aortic denervation potentiates the hypertensive response elicited by BCO in conscious mice.
The nitric oxide donor molsidomine rescues cardiac function in rats with chronic kidney disease and cardiac dysfunction
Authors: Bongartz Lennart G. , Braam Branko , Verhaar Marianne C. , Cramer Maarten Jan M. , Goldschmeding Roel , Gaillard Carlo A. , Steendijk Paul , Doevendans Pieter A. , Joles Jaap A.
Published: September 2010

We recently developed a rat model of cardiorenal failure that is characterized by severe left ventricular systolic dysfunction (LVSD) and low nitric oxide (NO) production that persisted after temporary low-dose NO synthase inhibition. We hypothesized that LVSD was due to continued low NO availability and might be reversed by supplementing NO. Rats underwent a subtotal nephrectomy and were treated with low-dose NO synthase inhibition with Nω-nitro-l-arginine up to week 8. After 3 wk of washout, rats were treated orally with either the long-acting, tolerance-free NO donor molsidomine (Mols) or vehicle (Veh). Cardiac and renal function were measured on weeks 11, 13, and 15. On week 16, LV hemodynamics and pressure-volume relationships were measured invasively, and rats were killed to quantify histological damage. On week 15, blood pressure was mildly reduced and creatinine clearance was increased by Mols (both P < 0.05). Mols treatment improved ejection fraction (53 ± 3% vs. 37 ± 2% in Veh-treated rats, P < 0.001) and stroke volume (324 ± 33 vs. 255 ± 15 μl in Veh-treated rats, P < 0.05). Rats with Mols treatment had lower end-diastolic pressures (8.5 ± 1.1 mmHg) than Veh-treated rats (16.3 ± 3.5 mmHg, P < 0.05) and reduced time constants of relaxation (21.9 ± 1.8 vs. 30.9 ± 3.3 ms, respectively, P < 0.05). The LV end-systolic pressure-volume relationship was shifted to the left in Mols compared with Veh treatment. In summary, in a model of cardiorenal failure with low NO availability, supplementing NO significantly improves cardiac systolic and diastolic function without a major effect on afterload.
Cardioprotective PKG-independent NO signaling at reperfusion
Authors: Cohen Michael V. , Yang Xi-Ming , Liu Yanping , Solenkova Nataliya V. , Downey James M.
Published: September 2010

Cell models of ischemic preconditioning (IPC) indicate nitric oxide (NO) is involved in protection accruing during reoxygenation but disagree whether it acts through PKG. Using a more relevant intact heart model, we studied isolated rabbit hearts subjected to 30-min coronary artery occlusion/120-min reperfusion. We previously found protection from PKG activator 8-(4-chlorophenylthio)-guanosine 3′,5′-cyclic monophosphate (CPT-cGMP) at reperfusion was blocked by A2b adenosine receptor (A2bAR), ERK, or phosphatidylinositol 3-kinase (PI3-kinase) blockers. In this investigation A2bAR agonist BAY 60-6583 or CPT-cGMP at reperfusion reduced infarction comparably to IPC. Their protection was abrogated by Nω-nitro-l-arginine methyl ester (l-NAME), suggesting a PKG-independent NO synthase in IPC's mediator pathway downstream of PKG and A2bAR. NO donor S-nitroso- N-acetyl-d,l-penicillamine (SNAP) at reperfusion also protected. This protection was not blocked by PI3-kinase inhibitor wortmannin or ERK antagonist PD-98059, suggesting NO acted downstream of these kinases. Protection from SNAP was not affected by mitochondrial ATP-sensitive K+ channel closer 5-hydroxydecanoate, PKC antagonist chelerythrine, reactive oxygen species scavenger N-2-mercaptopropionylglycine, or soluble guanylyl cyclase antagonist 1 H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ). Absence of ODQ effect indicated NO was acting independently of PKG. BAY 58-2667, a soluble guanylyl cyclase activator, was protective, and l-NAME blocked its infarct-sparing effect, indicating a second signaling event dependent on NO generation but independent of PKG. SB216763, a blocker of glycogen synthase kinase-3β (GSK-3β), decreased infarct size, and its infarct-sparing effect was not affected by l-NAME, suggesting GSK-3β acted downstream or independently of NO. Hence, NO signaling occurs in IPC's mediator pathway downstream of Akt and ERK, and its protection is independent of PKG.
Time course of carotid artery growth and remodeling in response to altered pulsatility
Authors: Eberth John F. , Popovic Natasa , Gresham Vincent C. , Wilson Emily , Humphrey Jay D.
Published: September 2010

Elucidating early time courses of biomechanical responses by arteries to altered mechanical stimuli is paramount to understanding and eventually predicting long-term adaptations. In a previous study, we reported marked long-term (at 35–56 days) consequences of increased pulsatile hemodynamics on arterial structure and mechanics. Motivated by those findings, we focus herein on arterial responses over shorter periods (at 7, 10, and 14 days) following placement of a constrictive band on the aortic arch between the innominate and left carotid arteries of wild-type mice, which significantly increases pulsatility in the right carotid artery. We quantified hemodynamics in vivo using noninvasive ultrasound and measured wall properties and composition in vitro using biaxial mechanical testing and standard (immuno)histology. Compared with both baseline carotid arteries and left carotids after banding, right carotids after banding experienced a significant increase in both pulse pressure, which peaked at day 7, and a pulsatility index for velocity, which continued to rise over the 42-day study despite a transient increase in mean flow that peaked at day 7. Wall thickness and inner diameter also increased significantly in the right carotids, both peaking at day 14, with an associated marked early reduction in the in vivo axial stretch and a persistent decrease in smooth muscle contractility. Glycosaminoglycan content also increased within the wall, peaking at day 14, whereas increases in monocyte chemoattractant protein-1 activity and the collagen-to-elastin ratio continued to rise. These findings confirm that pulsatility is an important modulator of wall geometry, structure, and properties but reveal different early time courses for different microscopic and macroscopic metrics, presumably due to the separate degrees of influence of pressure and flow.
Treatment of Chronic Hepatitis C Virus Infection in Dialysis Patients: An Update
Authors: Weclawiak Hugo , Kamar Nassim , Ould-Mohamed Abdellatif , Cardeau-Desangles Isabelle , Izopet Jacques , Rostaing Lionel
Published: September 2010

Hepatitis C virus (HCV) infection is a blood-borne infection and its prevalence used to be elevated in hemodialysis (HD) patients. Its main mode of contamination relies on nosocomial transmission. HCV infection is frequently associated in HD patients with normal liver enzymes whereas liver histology can display some degree of HCV-related lesions. The assessment of HCV-related lesions, even in HD dialysis patients, can be done via noninvasive tests. After kidney transplantation, HCV-related lesions can worsen; however, in this setting antiviral treatment harbors the risk of acute rejection. Therefore, it is recommended to implement antiviral treatment while the patient is receiving dialysis therapy. In this setting, the rate of viral clearance is usually high. In case of sustained virological response, no relapse occurs after kidney transplantation, despite heavy immunosuppression.
Flow Cytometry and Polymerase Chain Reaction-Based Analyses of Minimal Residual Disease in Chronic Lymphocytic Leukemia
Authors: Uhrmacher Sabrina , Erdfelder Felix , Kreuzer Karl-Anton
Published: September 2010

New therapeutic strategies developed recently for chronic lymphocytic leukemia (CLL) have led to remarkable treatment response rates and complete hematological remissions. This means highly sensitive and specific techniques are increasingly needed to evaluate minimal residual disease (MRD) in CLL patients. Quantitative MRD levels can be used as prognostic markers, where total MRD eradication is associated with prolonged survival. Nowadays, PCR and flow cytometry techniques used to detect MRD in CLL patients can generate reliable and quantitative results with the highest sensitivity. MRD Flow is based on four-color flow cytometry using specific antibody combinations. For allele specific oligonucleotide real-time quantification (ASO RQ) PCR individual primers are designed to detect a specific immunoglobulin heavy chain (IgH) rearrangement in each patient clone. Five comprehensive studies investigated and compared the sensitivity and specificity of both methods. Groups of patients receiving different therapies were analyzed at different time points to generate quantitative MRD levels and MRD kinetics. All studies confirmed that both methods generate equivalent results with regard to sensitivity and MRD quantification, although each method has advantages and disadvantages in the daily routine of a standard hematological laboratory. Here, we review these investigations and compare their results in the light of modern therapies.
Computational Modeling of the Mechanism of Urease
Authors: Carlsson Håkan , Nordlander Ebbe
Published: September 2010

In order to elucidate aspects of the mechanism of the hydrolytic enzyme urease, theoretical calculations were undertaken on a model of the active site, using density functional theory. The bridging oxygen donor that has been found in the crystal structures was determined to be a hydroxide ion. The initial coordination of urea at the active site occurs most likely through the urea oxygen to the nickel ion with the lowest coordination number. This coordination can be made without much gain in energy. The calculations also showed that weak coordination of one of the urea amine nitrogen atoms to the second nickel atom is energetically feasible. Furthermore, a proposed mechanism including a tetrahedral intermediate generated by hydrolytic attack on the urea carbon by the bridging hydroxide was modeled, and the tetrahedral intermediate was found to be energetically unfavorable relative to terminal coordination of the substrate (urea).
Neimark‐Sacker Bifurcation in a Discrete‐Time Financial System
Authors: Xin Baogui , Chen Tong , Ma Junhai
Published: September 2010

A discrete‐time financial system is proposed by using forward Euler scheme. Based on
explicit Neimark‐Sacker bifurcation (also called Hopf bifurcation for map) criterion, normal
form method and center manifold theory, the system′s existence, stability and direction of
Neimark‐Sacker bifurcation are studied. Numerical simulations are employed to validate the
main results of this work. Some comparison of bifurcation between the discrete‐time financial
system and its continuous‐time system is given.
Comparative Analysis and EST Mining Reveals High Degree of Conservation among FiveBrassicaceaeSpecies
Authors: Bhati Jyotika , Sonah Humira , Jhang Tripta , Singh Nagender Kumar , Sharma Tilak Raj
Published: September 2010

Brassicaceaeis an important family of the plant kingdom which includes several plants of major economic importance. TheBrassica spp.andArabidopsisshare much-conserved colinearity between their genomes which can be exploited for the genomic research inBrassicaceaecrops. In this study, 131,286 ESTs of fiveBrassicaceaespecies were assembled into unigene contigs and compared withArabidopsisgene indices. Almost all the unigenes ofBrassicaceaespecies showed high similarities withArabidopsisgenes except those ofB. napus,where 90% of unigenes were found similar. A total of 9,699 SSRs were identified in the unigenes. PCR primers were designed based on this information and amplified across species for validation. Functional annotation of unigenes showed that the majority of the genes are present in metabolism and energy functional classes. It is expected that comparative genome analysis betweenArabidopsisand related crop species will expedite research in the more complexBrassicagenomes. This would be helpful for genomics as well as evolutionary studies, and DNA markers developed can be used for mapping, tagging, and cloning of important genes inBrassicaceae.
Nonlinear Modelling and Qualitative Analysis of a Real Chemostat with Pulse Feeding
Authors: Tian Yuan , Sun Kaibiao , Kasperski Andrzej , Chen Lansun
Published: September 2010

The control of substrate concentration in the bioreactor medium should be
due to the substrate inhibition phenomenon. Moreover, the oxygen demand
in a bioreactor should be lower than the dissolved oxygen content. The
biomass concentration is one of the most important factors which affect the
oxygen demand. In order to maintain the dissolved oxygen content in an
appropriate range, the biomass concentration should not exceed a critical
level. Based on the design ideas, a mathematical model of a chemostat with
Monod‐type kinetics and impulsive state feedback control for microorganisms
of any biomass yield is proposed in this paper. By the existence criteria
of periodic solution of a general planar impulsive autonomous system, the
conditions for the existence of period‐1 solution of the system are obtained.
The results simplify the choice of suitable operating conditions for continuous
culture systems. It also points out that the system is not chaotic according to
the analysis on the existence of period‐2 solution. The results and numerical
simulations show that the chemostat system with state impulsive control
tends to a stable state or a period solution.
The miR-17-92 Cluster of MicroRNAs Confers Tumorigenicity by Inhibiting Oncogene-Induced Senescence
Authors: Hong Lixin , Lai Maoyi , Chen Michelle , Xie Changchuan , Liao Rong , Kang Young Jun , Xiao Changchun , Hu Wen-Yuan , Han Jiahuai , Sun Peiqing
Published: September 2010

In mammalian cells, activation of oncogenes usually triggers innate tumor-suppressing defense mechanisms, including apoptosis and senescence, which are compromised by additional mutations before cancers are developed. The miR-17-92 gene cluster, a polycistron encoding six microRNAs (miRNA), is frequently overexpressed in human cancers and has been shown to promote several aspects of oncogenic transformation, including evasion of apoptosis. In the current study, we show a new role of miR-17-92 in inhibiting oncogenic ras-induced senescence. Further dissection of the miRNA components in this cluster reveals that the miR-17/20a seed family accounts for this antisenescence activity. miR-17 and miR-20a are both necessary and sufficient for conferring resistance to ras-induced senescence by directly targeting p21WAF1, a key effector of senescence. By contrast, these components are not essential for the ability of miR-17-92 to evade Myc-induced apoptosis. Moreover, disruption of senescence by miR-17-92 or its miR-17/20a components leads to enhanced oncogenic transformation by activated ras in primary human cells. Taken together with previous reports that miR-17-92 inhibits apoptosis by suppressing Pten via the miR-19 components, our results indicate that this miRNA cluster promotes tumorigenesis by antagonizing both tumor-suppressing mechanisms, apoptosis, and senescence, through the activities of different miRNA components encoded in this cluster. Cancer Res; 70(21); 8547–57. ©2010 AACR.
Transcriptional Activation by pRB and Its Coordination with SWI/SNF Recruitment
Authors: Flowers Stephen , Beck George R. , Moran Elizabeth
Published: September 2010

A central question in cancer biology is why most tumor susceptibility genes are linked with only limited types of cancer. Human germ-line mutation of the retinoblastoma susceptibility gene Rb1 is closely linked with just retinoblastoma and osteosarcoma, although the gene is universally expressed. Functional analysis of pRB and its close relatives, p107 and p130, has largely focused on their roles in repression of proliferation across all tissue types, but genetic evidence indicates an active requirement for pRB in osteoblast differentiation that correlates more directly with osteosarcoma susceptibility. Still, potential promoter targets of pRB and its role in normally differentiating osteoblasts remain insufficiently characterized. Here, an early marker of osteoblast differentiation, alkaline phosphatase, is identified as a direct promoter activation target of pRB. One role of pRB on this promoter is to displace the histone lysine demethylase KDM5A, thereby favoring trimethylation of H3K4, a promoter activation mark. A major new aspect of pRB-mediated transcriptional activation revealed in this promoter analysis is its role in recruitment of an activating SWI/SNF chromatin-remodeling complex. SWI/SNF is a critical coordinator of tissue-specific gene expression. In osteoblasts, SWI/SNF complexes containing the BRM ATPase repress osteoblast-specific genes to maintain the precursor state, whereas the alternative ATPase BRG1 distinguishes an activating SWI/SNF complex necessary for RNA polymerase-II recruitment. A switch from BRM to BRG1 on the alkaline phosphatase promoter marks the onset of differentiation and is accomplished in a precise two-step mechanism. Dissociation of BRM-containing SWI/SNF depends on p300, and association of BRG1-containing SWI/SNF depends on pRB. Cancer Res; 70(21); 8282–7. ©2010 AACR.
Determinants of Fecal Continence in Healthy, Continent Subjects: A Comprehensive Analysis by Anal Manometry, Rectal Barostat and a Stool Substitute Retention Test
Authors: Fox Mark , Thumshirn Miriam , Frühauf Heiko , Fried Michael , Schwizer Werner
Published: September 2010

Background/Aims: This study aimed to identify anal sphincter and rectal factors that determine anorectal filling sensations and continence during rectal filling in health. Methods: Measurements of anorectal physiology were collected from 42 continent healthy subjects participating in a prospective trial. Rectal function and capacity were assessed by barostat. Anal sphincter functions were assessed by manometry. A validated stool substitute retention test was performed in which a viscous suspension was infused into the rectum at 60 ml/min to 1,500 ml. Multivariate regression was applied to identify physiologic factors that determine anorectal sensation and continence during rectal filling. Results: The volume at which first awareness of rectal filling occurred associated with age (p < 0.03), rectal capacity (p < 0.06) and anal resting pressure (p < 0.003); urgency associated with rectal capacity (p < 0.0007), anal resting (p < 0.04) and squeeze pressure (p < 0.02); volume at first incontinence with rectal capacity (p < 0.0001) and squeeze pressure (p < 0.04) and the maximum volume retained were closely correlated with rectal capacity only (p < 0.0001). Conclusion: Anorectal filling sensations and continence in health require a rectal reservoir of adequate capacity and effective voluntary anal sphincter function. Complementary associations between continence, motor and sensory function indicate the presence of an adaptive mechanism that enables timely, appropriate responses to events that threaten fecal continence.