bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hypoxic regulation of cardiac Ca2+ channel: possible role of haem oxygenase
Authors: Rosa Angelo O. , Movafagh Shahrzad , Cleemann Lars , Morad Martin 
Published: July 2012

Key points
Lack of oxygen to the heart, hypoxia, triggers a cascade of events that within minutes leads to irreversible tissue damage.
One of the initial steps at the onset of hypoxia is suppression of the cellular calcium channels that control the strength of the heartbeat.
The role of oxygen in energy production is well known, but it is not known how lack of oxygen within seconds may suppress the calcium channels.
We tested the involvement of different regulatory pathways that are known to modulate the calcium channel in response to various stimuli, and succeeded to link it to a haem oxygenase protein that may act as the primary oxygen sensor.
Our findings provide a better understanding of the initial events that occur during episodes of acute hypoxia induced by coronary thrombosis and bring into focus a new set of therapeutic considerations.
Abstract  Acute and chronic hypoxias are common cardiac diseases that lead often to arrhythmia and impaired contractility. At the cellular level it is unclear whether the suppression of cardiac Ca2+ channels (CaV1.2) results directly from oxygen deprivation on the channel protein or is mediated by intermediary proteins affecting the channel. To address this question we measured the early effects of hypoxia (5–60 s, ) on Ca2+ current (ICa) and tested the involvement of protein kinase A (PKA) phosphorylation, Ca2+/calmodulin‐mediated signalling and the haem oxygenase (HO) pathway in the hypoxic regulation of CaV1.2 in rat and cat ventricular myocytes and HEK‐293 cells. Hypoxic suppression of ICa and Ca2+ transients was significant within 5 s and intensified in the following 50 s, and was reversible. Phosphorylation by cAMP or the phosphatase inhibitor okadaic acid desensitized ICa to hypoxia, while PKA inhibition by H‐89 restored the sensitivity of ICa to hypoxia. This phosphorylation effect was specific to Ca2+, but not Ba2+ or Na+, permeating through the channel. CaMKII inhibitory peptide and Bay K8644 reversed the phosphorylation‐induced desensitization to hypoxia. Mutation of CAM/CaMKII‐binding motifs of the α1c subunit of CaV1.2 fully desensitized the Ca2+ channel to hypoxia. Rapid application of HO inhibitors (zinc protoporphyrin (ZnPP) and tin protoporphyrin (SnPP)) suppressed the channel in a manner similar to acute hypoxia such that: (1) ICa and IBa were suppressed within 5 s of ZnPP application; (2) PKA activation and CaMKII inhibitors desensitized ICa, but not IBa, to ZnPP; and (3) hypoxia failed to further suppress ICa and IBa in ZnPP‐treated myocytes. We propose that the binding of HO to the CaM/CaMKII‐specific motifs on Ca2+ channel may mediate the rapid response of the channel to hypoxia.
Expression and properties of hyperpolarization‐activated current in rat dorsal root ganglion neurons with known sensory function
Authors: Gao L. L. , McMullan S. , Djouhri L. , Acosta C. , Harper A. A. , Lawson S. N. 
Published: July 2012

Key point
I
h is a hyperpolarisation‐activated current that influences neuronal excitability and is present in some sensory neurons.
The magnitude and properties of Ih in different groups of sensory neurons that respond to painful stimuli (nociceptors) or to non‐painful stimuli, such as low threshold mechanoreceptors (LTMs), were unknown.
We found that neurons with the greatest Ih were the nociceptors and LTMs with the fastest conducting fibres. The highest Ih of all was present in LTM neurons that sense muscle stretch and length (muscle spindle afferents).
The high levels of Ih could fundamentally influence excitability of fast conducting sensory neurons which detect muscle stretch/length, touch and pressure, and painful stimuli. Ih could thus influence sensations associated with all these.
The properties of Ih are similar to those of HCN1‐ and HCN2‐related Ih, suggesting that these channels underlie the current.
Abstract  The hyperpolarization‐activated current (Ih) has been implicated in nociception/pain, but its expression levels in nociceptors remained unknown. We recorded Ih magnitude and properties by voltage clamp from dorsal root ganglion (DRG) neurons in vivo, after classifying them as nociceptive or low‐threshold‐mechanoreceptors (LTMs) and as having C‐, Aδ‐ or Aα/β‐conduction velocities (CVs). For both nociceptors and LTMs, Ih amplitude and Ih density (at −100 mV) were significantly positively correlated with CV. Median Ih magnitudes and Ih density in neuronal subgroups were respectively: muscle spindle afferents (MSAs): −4.6 nA, −33 pA pF−1; cutaneous Aα/β LTMs: −2.2 nA, −20 pA pF−1; Aβ‐nociceptors: −2.6 nA, −21 pA pF−1; both Aδ‐LTMs and nociceptors: −1.3 nA, ∼−14 pA pF−1; C‐LTMs: −0.4 nA, −7.6 pA pF−1; and C‐nociceptors: −0.26 nA, −5 pA pF−1. Ih activation slow time constants (slow τ values) were strongly correlated with fast τ values; both were shortest in MSAs. Most neurons had τ values consistent with HCN1‐related Ih; others had τ values closer to HCN1+HCN2 channels, or HCN2 in the presence of cAMP. In contrast, median half‐activation voltages (V0.5) of −80 to −86 mV for neuronal subgroups suggest contributions of HCN2 to Ih. τ values were unrelated to CV but were inversely correlated with Ih and Ih density for all non‐MSA LTMs, and for Aδ‐nociceptors. From activation curves ∼2–7% of Ih would be activated at normal membrane potentials. The high Ih may be important for excitability of A‐nociceptors (responsible for sharp/pricking‐type pain) and Aα/β‐LTMs (tactile sensations and proprioception). Underlying HCN expression in these subgroups therefore needs to be determined. Altered Ih expression and/or properties (e.g. in chronic/pathological pain states) may influence both nociceptor and LTM excitability.
Antibacterial Properties of an Oligo-Acyl-Lysyl Hexamer Targeting Gram-Negative Species
Authors: Zaknoon Fadia , Goldberg Keren , Sarig Hadar , Epand Raquel F. , Epand Richard M. , Mor Amram 
Published: July 2012

ABSTRACT

Toward developing new tools for fighting resistance to antibiotics, we investigated the antibacterial properties of a new decanoyl-based oligo-acyl-lysyl (OAK) hexamer, aminododecanoyl-lysyl-[aminodecanoyl-lysyl]
5
(α
12
-5α
10
). The OAK exhibited preferential activity against Gram-negative bacteria (GNB), as determined using 36 strains, including diverse species, with an MIC
90
of 6.2 μM. The OAK's bactericidal mode of action was associated with rapid membrane depolarization and cell permeabilization, suggesting that the inner membrane was the primary target, whereas the observed binding affinity to lipoteichoic acid suggested that inefficacy against Gram-positive species resulted from a cell wall interaction preventing α
12
-5α
10
from reaching internal targets. Interestingly, perturbation of the inner membrane structure and function was preserved at sub-MIC values. This prompted us to assess the OAK's effect on the proton motive force-dependent efflux pump AcrAB-TolC, implicated in the low sensitivity of GNB to various antibiotics, including erythromycin. We found that under sub-MIC conditions, wild-type
Escherichia coli
was significantly more sensitive to erythromycin (the MIC dropped by >10-fold), unlike its
acr
-deletion mutant. Collectively, the data suggest a useful approach for treating GNB infections through overcoming antibiotic efflux.
Serotype and Clonal Evolution of Penicillin-Nonsusceptible Invasive Streptococcus pneumoniae in the 7-Valent Pneumococcal Conjugate Vaccine Era in Italy
Authors: Gherardi Giovanni , D'Ambrosio Fabio , Visaggio Daniela , Dicuonzo Giordano , Del Grosso Maria , Pantosti Annalisa 
Published: July 2012

ABSTRACT
The percentage of invasive penicillin-nonsusceptible pneumococci (PNSSP) isolated in Italy in the seven-valent pneumococcal conjugate vaccine (PCV7) era moderately increased in comparison to the pre-PCV7 era. Increase of nonvaccine serotypes was observed among PNSSP. The most frequent PNSSP clones were the same as those identified in the pre-PCV7 era, although they were present in different proportions. Clonal expansion, emergence of new clones, and acquisition of penicillin resistance by established clones contributed to the maintenance of penicillin resistance.
The Antibiotic Resistance Arrow of Time: Efflux Pump Induction Is a General First Step in the Evolution of Mycobacterial Drug Resistance
Authors: Schmalstieg Aurelia M. , Srivastava Shashikant , Belkaya Serkan , Deshpande Devyani , Meek Claudia , Leff Richard , van Oers Nicolai S. C. , Gumbo Tawanda 
Published: July 2012

ABSTRACT

We hypothesize that low-level efflux pump expression is the first step in the development of high-level drug resistance in mycobacteria. We performed 28-day azithromycin dose-effect and dose-scheduling studies in our hollow-fiber model of disseminated
Mycobacterium avium-M. intracellulare
complex. Both microbial kill and resistance emergence were most closely linked to the within-macrophage area under the concentration-time curve (AUC)/MIC ratio. Quantitative PCR revealed that subtherapeutic azithromycin exposures over 3 days led to a 56-fold increase in expression of MAV_3306, which encodes a putative ABC transporter, and MAV_1406, which encodes a putative major facilitator superfamily pump, in
M. avium
. By day 7, a subpopulation of
M. avium
with low-level resistance was encountered and exhibited the classic inverted U curve versus AUC/MIC ratios. The resistance was abolished by an efflux pump inhibitor. While the maximal microbial kill started to decrease after day 7, a population with high-level azithromycin resistance appeared at day 28. This resistance could not be reversed by efflux pump inhibitors. Orthologs of pumps encoded by MAV_3306 and MAV_1406 were identified in
Mycobacterium tuberculosis
,
Mycobacterium leprae
,
Mycobacterium marinum
,
Mycobacterium abscessus
, and
Mycobacterium ulcerans
. All had highly conserved protein secondary structures. We propose that induction of several efflux pumps is the first step in a general pathway to drug resistance that eventually leads to high-level chromosomal-mutation-related resistance in mycobacteria as ordered events in an “antibiotic resistance arrow of time.”
Novel Dehalogenase Mechanism for 2,3-Dichloro-1-Propanol Utilization in Pseudomonas putida Strain MC4
Authors: Arif Muhammad Irfan , Samin Ghufrana , van Leeuwen Jan G. E. , Oppentocht Jantien , Janssen Dick B. 
Published: June 2012

ABSTRACT

A
Pseudomonas putida
strain (MC4) that can utilize 2,3-dichloro-1-propanol (DCP) and several aliphatic haloacids and haloalcohols as sole carbon and energy source for growth was isolated from contaminated soil. Degradation of DCP was found to start with oxidation and concomitant dehalogenation catalyzed by a 72-kDa monomeric protein (DppA) that was isolated from cell lysate. The
dppA
gene was cloned from a cosmid library and appeared to encode a protein equipped with a signal peptide and that possessed high similarity to quinohemoprotein alcohol dehydrogenases (ADHs), particularly ADH IIB and ADH IIG from
Pseudomonas putida
HK. This novel dehalogenating dehydrogenase has a broad substrate range, encompassing a number of nonhalogenated alcohols and haloalcohols. With DCP, DppA exhibited a
k
cat
of 17 s
−1
.
1
H nuclear magnetic resonance experiments indicated that DCP oxidation by DppA in the presence of 2,6-dichlorophenolindophenol (DCPIP) and potassium ferricyanide [K
3
Fe(CN)
6
] yielded 2-chloroacrolein, which was oxidized to 2-chloroacrylic acid.
Distance-Decay Relationships Partially Determine Diversity Patterns of Phyllosphere Bacteria on Tamrix Trees across the Sonoran Desert
Authors: Finkel Omri M. , Burch Adrien Y. , Elad Tal , Huse Susan M. , Lindow Steven E. , Post Anton F. , Belkin Shimshon 
Published: June 2012

ABSTRACT

Dispersal limitation in phyllosphere communities was measured on the leaf surfaces of salt-excreting
Tamarix
trees, which offer unique, discrete habitats for microbial assemblages. We employed 16S rRNA gene pyrosequencing to measure bacterial community dissimilarity on leaves of spatially dispersed
Tamarix
specimens in sites with uniform climatic conditions across the Sonoran Desert in the Southwestern United States. Our analyses revealed diverse bacterial communities with four dominant phyla that exhibited differential effects of environmental and geographic variables. Geographical distance was the most important parameter that affected community composition, particularly that of betaproteobacteria, which displayed a statistically significant, distance-decay relationship.
Production of Aromatic Compounds by Metabolically Engineered Escherichia coli with an Expanded Shikimate Pathway
Authors: Koma Daisuke , Yamanaka Hayato , Moriyoshi Kunihiko , Ohmoto Takashi , Sakai Kiyofumi 
Published: June 2012

ABSTRACT

Escherichia coli
was metabolically engineered by expanding the shikimate pathway to generate strains capable of producing six kinds of aromatic compounds, phenyllactic acid, 4-hydroxyphenyllactic acid, phenylacetic acid, 4-hydroxyphenylacetic acid, 2-phenylethanol, and 2-(4-hydroxyphenyl)ethanol, which are used in several fields of industries including pharmaceutical, agrochemical, antibiotic, flavor industries, etc. To generate strains that produce phenyllactic acid and 4-hydroxyphenyllactic acid, the lactate dehydrogenase gene (
ldhA
) from
Cupriavidus necator
was introduced into the chromosomes of phenylalanine and tyrosine overproducers, respectively. Both the phenylpyruvate decarboxylase gene (
ipdC
) from
Azospirillum brasilense
and the phenylacetaldehyde dehydrogenase gene (
feaB
) from
E. coli
were introduced into the chromosomes of phenylalanine and tyrosine overproducers to generate phenylacetic acid and 4-hydroxyphenylacetic acid producers, respectively, whereas
ipdC
and the alcohol dehydrogenase gene (
adhC
) from
Lactobacillus brevis
were introduced to generate 2-phenylethanol and 2-(4-hydroxyphenyl)ethanol producers, respectively. Expression of the respective introduced genes was controlled by the T7 promoter. While generating the 2-phenylethanol and 2-(4-hydroxyphenyl)ethanol producers, we found that produced phenylacetaldehyde and 4-hydroxyphenylacetaldehyde were automatically reduced to 2-phenylethanol and 2-(4-hydroxyphenyl)ethanol by endogenous aldehyde reductases in
E. coli
encoded by the
yqhD
,
yjgB
, and
yahK
genes. Cointroduction and cooverexpression of each gene with
ipdC
in the phenylalanine and tyrosine overproducers enhanced the production of 2-phenylethanol and 2-(4-hydroxyphenyl)ethanol from glucose. Introduction of the
yahK
gene yielded the most efficient production of both aromatic alcohols. During the production of 2-phenylethanol, 2-(4-hydroxyphenyl)ethanol, phenylacetic acid, and 4-hydroxyphenylacetic acid, accumulation of some by-products were observed. Deletion of
feaB
,
pheA
, and/or
tyrA
genes from the chromosomes of the constructed strains resulted in increased desired aromatic compounds with decreased by-products. Finally, each of the six constructed strains was able to successfully produce a different aromatic compound as a major product. We show here that six aromatic compounds are able to be produced from renewable resources without supplementing with expensive precursors.
Host Preferences of Arbuscular Mycorrhizal Fungi Colonizing Annual Herbaceous Plant Species in Semiarid Mediterranean Prairies
Authors: Torrecillas E. , Alguacil M. M. , Roldán A. 
Published: June 2012

ABSTRACT

In this study, we have analyzed and compared the diversities of the arbuscular mycorrhizal fungi (AMF) colonizing the roots of five annual herbaceous species (
Hieracium vulgare
,
Stipa capensis
,
Anagallis arvensis
,
Carduus tenuiflorus
, and
Avena barbata
) and a perennial herbaceous species (
Brachypodium retusum
). Our goal was to determine the differences in the communities of the AMF among these six plant species belonging to different families, using
B. retusum
as a reference. The AMF small-subunit rRNA genes (SSU) were subjected to nested PCR, cloning, sequencing, and phylogenetic analysis. Thirty-six AMF phylotypes, belonging to
Glomus
group A,
Glomus
group B,
Diversispora
,
Paraglomus
, and
Ambispora
, were identified. Five sequence groups identified in this study clustered to known glomalean species or isolates: group
Glomus
G27 to
Glomus intraradices
, group
Glomus
G19 to
Glomus iranicum
, group
Glomus
G10 to
Glomus mosseae
, group
Glomus
G1 to
Glomus lamellosum/etunicatum/luteum
, and group
Ambispora
1 to
Ambispora fennica
. The six plant species studied hosted different AMF communities. A certain trend of AMF specificity was observed when grouping plant species by taxonomic families, highlighting the importance of protecting and even promoting the native annual vegetation in order to maintain the biodiversity and productivity of these extreme ecosystems.
Serratia marcescens Quinoprotein Glucose Dehydrogenase Activity Mediates Medium Acidification and Inhibition of Prodigiosin Production by Glucose
Authors: Fender James E. , Bender Cody M. , Stella Nicholas A. , Lahr Roni M. , Kalivoda Eric J. , Shanks Robert M. Q. 
Published: June 2012

ABSTRACT

Serratia marcescens
is a model organism for the study of secondary metabolites. The biologically active pigment prodigiosin (2-methyl-3-pentyl-6-methoxyprodiginine), like many other secondary metabolites, is inhibited by growth in glucose-rich medium. Whereas previous studies indicated that this inhibitory effect was pH dependent and did not require cyclic AMP (cAMP), there is no information on the genes involved in mediating this phenomenon. Here we used transposon mutagenesis to identify genes involved in the inhibition of prodigiosin by glucose. Multiple genetic loci involved in quinoprotein glucose dehydrogenase (GDH) activity were found to be required for glucose inhibition of prodigiosin production, including pyrroloquinoline quinone and ubiquinone biosynthetic genes. Upon assessing whether the enzymatic products of GDH activity were involved in the inhibitory effect, we observed that
d
-glucono-1,5-lactone and
d
-gluconic acid, but not
d
-gluconate, were able to inhibit prodigiosin production. These data support a model in which the oxidation of
d
-glucose by quinoprotein GDH initiates a reduction in pH that inhibits prodigiosin production through transcriptional control of the prodigiosin biosynthetic operon, providing new insight into the genetic pathways that control prodigiosin production. Strains generated in this report may be useful in large-scale production of secondary metabolites.
Enhanced Basophil Reactivities during Severe Malaria and Their Relationship with the Plasmodium falciparum Histamine-Releasing Factor Translationally Controlled Tumor Protein
Authors: Pelleau Stéphane , Diop Sylvie , Dia Badiane Méry , Vitte Joana , Beguin Pierre , Nato Farida , Diop Bernard M. , Bongrand Pierre , Parzy Daniel , Jambou Ronan 
Published: July 2012

ABSTRACT

Recent studies suggest shared pathogenic pathways during malaria and allergy. Indeed, IgE, histamine, and the parasite-derived
Plasmodium falciparum
histamine-releasing factor translationally controlled tumor protein (PfTCTP) can be found at high levels in serum from patients experiencing malaria, but their relationship with basophil activation remains unknown. We recruited
P. falciparum
-infected patients in Senegal with mild malaria (MM;
n
= 19) or severe malaria (SM;
n
= 9) symptoms and healthy controls (HC;
n
= 38). Levels of serum IgE, PfTCTP, and IgG antibodies against PfTCTP were determined by enzyme-linked immunosorbent assays (ELISA). Basophil reactivities to IgE-dependent and -independent stimulations were measured
ex vivo
using fresh blood by looking at the expression level of the basophil activation marker CD203c with flow cytometry. Unstimulated basophils from MM had significantly lower levels of CD203c expression compared to those from HC and SM. After normalization on this baseline level, basophils from SM showed an enhanced reactivity to calcimycin (A23187) and hemozoin. Although SM reached higher median levels of activation after anti-IgE stimulation, great interindividual differences did not allow the results to reach statistical significance. When primed with recombinant TCTP before anti-IgE, qualitative differences in terms of a better ability to control excessive activation could be described for SM. IgE levels were very high in malaria patients, but concentrations in MM and SM were similar and were not associated with basophil responses, which demonstrates that the presence of IgE alone cannot explain the various basophil reactivities. Indeed, PfTCTP could be detected in 32% of patients, with higher concentrations for SM. These PfTCTP-positive patients displayed significantly higher basophil reactivities to any stimulus. Moreover, the absence of anti-PfTCTP IgG was associated with higher responses in SM but not MM. Our results show an association between basophil reactivity and malaria severity and suggest a pathogenic role for plasmodial PfTCTP in the induction of this allergy-like mechanism.
Identification of Genes Important for Growth of Asymptomatic Bacteriuria Escherichia coli in Urine
Authors: Vejborg Rebecca M. , de Evgrafov Mari R. , Phan Minh Duy , Totsika Makrina , Schembri Mark A. , Hancock Viktoria 
Published: July 2012

ABSTRACT

Escherichia coli
is the most important etiological agent of urinary tract infections (UTIs). Unlike uropathogenic
E. coli
, which causes symptomatic infections, asymptomatic bacteriuria (ABU)
E. coli
strains typically lack essential virulence factors and colonize the bladder in the absence of symptoms. While ABU
E. coli
can persist in the bladder for long periods of time, little is known about the genetic determinants required for its growth and fitness in urine. To identify such genes, we have employed a transposon mutagenesis approach using the prototypic ABU
E. coli
strain 83972 and the clinical ABU
E. coli
strain VR89. Six genes involved in the biosynthesis of various amino acids and nucleobases were identified (
carB
,
argE
,
argC
,
purA
,
metE
, and
ilvC
), and site-specific mutants were subsequently constructed in
E. coli
83972 and
E. coli
VR89 for each of these genes. In all cases, these mutants exhibited reduced growth rates and final cell densities in human urine. The growth defects could be complemented in
trans
as well as by supplementation with the appropriate amino acid or nucleobase. When assessed
in vivo
in a mouse model,
E. coli
83972
carAB
and 83972
argC
showed a significantly reduced competitive advantage in the bladder and/or kidney during coinoculation experiments with the parent strain, whereas 83972
metE
and 83972
ilvC
did not. Taken together, our data have identified several biosynthesis pathways as new important fitness factors associated with the growth of ABU
E. coli
in human urine.