bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of muscle metaboreceptor stimulation on middle cerebral artery blood velocity in humans
Authors: Braz Igor D. , Scott Clare , Simpson Lydia L. , Springham Emma L. , Tan Beverly W. L. , Balanos George M. , Fisher James P. 
Published: September 2014

New Findings
What is the central question of this study?
Is the ability of metabolically sensitive skeletal muscle afferents (muscle metaboreceptors) to increase cerebral perfusion masked by a hyperventilation‐mediated reduction in the arterial (indexed using end‐tidal hence cerebral vasoconstriction, during post exercise muscle ischaemia?
What is the main finding and its importance?
We found that cerebral perfusion is elevated during post exercise muscle ischaemia when is clamped at baseline, but when is permitted to fluctuate no such elevation occurs. These findings indicate that muscle metaboreceptors increase cerebral perfusion when the confounding effects of changes in are obviated.
Regional anaesthesia to attenuate skeletal muscle afferent feedback abolishes the exercise‐induced increase in middle cerebral artery mean blood velocity (MCA Vmean). However, such exercise‐related increases in cerebral perfusion are not preserved during post exercise muscle ischaemia (PEMI) where the activation of metabolically sensitive muscle afferents is isolated. We tested the hypothesis that a hyperventilation‐mediated decrease in the arterial partial pressure of CO2, hence cerebral vasoconstriction, masks the influence of muscle metaboreceptor stimulation on MCA Vmean during PEMI. Ten healthy men (20 ± 1 years old) performed two trials of fatiguing isometric hand‐grip exercise followed by PEMI, in control conditions and with end‐tidal CO2 ( clamped at ∼1 mmHg above the resting partial pressure. In the control trial, decreased from rest during hand‐grip exercise and PEMI, while MCA Vmean was unchanged from rest. By design, remained unchanged from rest throughout the clamp trial, while MCA Vmean increased during hand‐grip (+10.6 ±1.8 cm s−1) and PEMI (+9.2 ± 1.6 cm s−1; P < 0.05 versus rest and control trial). Increases in minute ventilation and mean arterial pressure during hand‐grip and PEMI were not different in the control and clamp trials (P > 0.05). These findings indicate that metabolically sensitive skeletal muscle afferents play an important role in the regional increase in cerebral perfusion observed in exercise, but that influence can be masked by a decrease in when they are activated in isolation during PEMI.
Can Bayliss and Starling gut hormones cure a worldwide pandemic?
Authors: Scott R. V. , Tan T. M. , Bloom S. R. 
Published: September 2014

AbstractBayliss and Starling first coined the term ‘hormone’ with reference to secretin, a substance they found that was produced by the gut, but released into the blood stream to act at a distance. The intestine is now known as the largest endocrine organ in the body, and it produces numerous hormones with a wide range of functions. These include controlling appetite and energy homeostasis. Obesity is one of the greatest health threats facing the world today. At present, the only successful treatment is surgery. Bariatric procedures such as the Roux‐en‐Y bypass work by elevating gut hormones that induce satiety. Significant research has gone into producing versions of these hormones that can be delivered therapeutically to treat obesity. This review looks at the role of gut hormones in obesity, and the development of gut hormone‐derived obesity treatments.
A mathematical model of salt‐sensitive hypertension: the neurogenic hypothesis
Authors: Averina Viktoria A. , Othmer Hans G. , Fink Gregory D. , Osborn John W. 
Published: September 2014

AbstractSalt sensitivity of arterial pressure (salt‐sensitive hypertension) is a serious global health issue. The causes of salt‐sensitive hypertension are extremely complex and mathematical models can elucidate potential mechanisms that are experimentally inaccessible. Until recently, the only mathematical model for long‐term control of arterial pressure was the model of Guyton and Coleman; referred to as the G‐C model. The core of this model is the assumption that sodium excretion is driven by renal perfusion pressure, the so‐called ‘renal function curve’. Thus, the G‐C model dictates that all forms of hypertension are due to a primary shift of the renal function curve to a higher operating pressure. However, several recent experimental studies in a model of hypertension produced by the combination of a high salt intake and administration of angiotensin II, the AngII–salt model, are inconsistent with the G‐C model. We developed a new mathematical model that does not limit the cause of salt‐sensitive hypertension solely to primary renal dysfunction. The model is the first known mathematical counterexample to the assumption that all salt‐sensitive forms of hypertension require a primary shift of renal function: we show that in at least one salt‐sensitive form of hypertension the requirement is not necessary. We will refer to this computational model as the ‘neurogenic model’. In this Symposium Review we discuss how, despite fundamental differences between the G‐C model and the neurogenic model regarding mechanisms regulating sodium excretion and vascular resistance, they generate similar haemodynamic profiles of AngII–salt hypertension. In addition, the steady‐state relationships between arterial pressure and sodium excretion, a correlation that is often erroneously presented as the ‘renal function curve’, are also similar in both models. Our findings suggest that salt‐sensitive hypertension is not due solely to renal dysfunction, as predicted by the G‐C model, but may also result from neurogenic dysfunction.
Healthy humans with a narrow upper airway maintain patency during quiet breathing by dilating the airway during inspiration
Authors: Cheng Shaokoon , Brown Elizabeth C. , Hatt Alice , Butler Jane E. , Gandevia Simon C. , Bilston Lynne E. 
Published: September 2014

Key points
During quiet breathing, the muscles of the upper airway of healthy humans contract to dilate the airway during inspiration.
We used dynamic tagged magnetic resonance imaging to show that the amount of active upper airway dilatation during inspiration increases as airway cross‐sectional area decreases.
Older and more overweight subjects have smaller airways, and this is linked to increased active airway dilatation.
These data show that healthy subjects with narrow airways can overcome anatomical risk factors for airway collapse by actively dilating their airways during inspiration.
In contrast, obstructive sleep apnoea patients with similarly narrow airways show either little or no dilatory motion during inspiration or abnormal bi‐directional movement. This regulation of airway behaviour fails in these patients.AbstractA patent upper airway is essential for survival. Increased age, obesity and some upper airway anatomical features are associated with failure to maintain upper airway patency during sleep, leading to obstructive sleep apnoea. However, many healthy subjects with these risk factors do not develop this condition. The aim of this study was to determine how anatomical factors and active dilator muscle contraction contribute to upper airway patency in healthy volunteers across a broad range of age and body mass index (BMI). A ‘tagged’ magnetic resonance imaging technique quantified respiratory‐related motion of the anterior and lateral walls of the upper airway during quiet breathing in the supine position. Fifty‐two subjects aged 22−68 years with BMI from 17.5 to 40.1 kg m−2 were studied. Higher BMI was associated with smaller airway cross‐sectional area at the level of soft palate (P < 0.05). The genioglossus moved anteriorly to dilate the upper airway during inspiration. This movement increased with increasing BMI, increasing age, a smaller airway area, and steeper tongue‐base angle (all P < 0.05). Motion of the lateral upper airway at the soft‐palate level was variable and less strongly linked to anatomical features of the upper airway. Multiple regression indicated that anterior genioglossus motion decreased with increasing airway area (P = 0.03) and with increasing tongue‐base angle (P = 0.02). These data suggest that healthy humans, including those whose anatomy places them at increased risk of airway closure, can maintain upper airway patency by dynamically dilating the airway during inspiration.
Suprachiasmatic nucleus function and circadian entrainment are modulated by G protein‐coupled inwardly rectifying (GIRK) channels
Authors: Hablitz L. M. , Molzof H. E. , Paul J. R. , Johnson R. L. , Gamble K. L. 
Published: September 2014

Key points
Many time‐of‐day cues are mediated by G protein‐coupled signals within the clock centre (the suprachiasmatic nucleus, SCN) of the mammalian brain.
The role of G protein‐coupled inwardly rectifying potassium (GIRK) channels in SCN function and entrainment has yet to be determined.
GIRK channels are necessary for proper day‐time SCN neuronal resting membrane potential, neuropeptide Y signalling, and re‐entrainment to phase advances of the light–dark (LD) cycle.
GIRK channel activation is sufficient to mimic non‐photic phase shifts of the molecular clock.
GIRK channels act as an essential part of the non‐photic entrainment system, and could play a critical role in diseases such as epilepsy or addiction that have strong circadian comorbidities.
AbstractG protein signalling within the central circadian oscillator, the suprachiasmatic nucleus (SCN), is essential for conveying time‐of‐day information. We sought to determine whether G protein‐coupled inwardly rectifying potassium channels (GIRKs) modulate SCN physiology and circadian behaviour. We show that GIRK current and GIRK2 protein expression are greater during the day. Pharmacological inhibition of GIRKs and genetic loss of GIRK2 depolarized the day‐time resting membrane potential of SCN neurons compared to controls. Behaviourally, GIRK2 knockout (KO) mice failed to shorten free running period in response to wheel access in constant darkness and entrained more rapidly to a 6 h advance of a 12 h:12 h light–dark (LD) cycle than wild‐type (WT) littermate controls. We next examined whether these effects were due to disrupted signalling of neuropeptide Y (NPY), which is known to mediate non‐photic phase shifts, attenuate photic phase shifts and activate GIRKs. Indeed, GIRK2 KO SCN slices had significantly fewer silent cells in response to NPY, likely contributing to the absence of NPY‐induced phase advances of PER2::LUC rhythms in organotypic SCN cultures from GIRK2 KO mice. Finally, GIRK channel activation is sufficient to cause a non‐photic‐like phase advance of PER2::LUC rhythms on a Per2Luc+/− background. These results suggest that rhythmic regulation of GIRK2 protein and channel function in the SCN contributes to day‐time resting membrane potential, providing a mechanism for the fine tuning responses to non‐photic and photic stimuli. Further investigation could provide insight into disorders with circadian disruption comorbidities such as epilepsy and addiction, in which GIRK channels have been implicated.
Breast tissue decomposition with spectral distortion correction: A postmortem study
Authors: Ding Huanjun , Zhao Bo , Baturin Pavlo , Behroozi Farnaz , Molloi Sabee 
Published: September 2014

Purpose:To investigate the feasibility of an accurate measurement of water, lipid, and protein composition of breast tissue using a photon‐counting spectral computed tomography (CT) with spectral distortion corrections.Methods:Thirty‐eight postmortem breasts were imaged with a cadmium‐zinc‐telluride‐based photon‐counting spectral CT system at 100 kV. The energy‐resolving capability of the photon‐counting detector was used to separate photons into low and high energy bins with a splitting energy of 42 keV. The estimated mean glandular dose for each breast ranged from 1.8 to 2.2 mGy. Two spectral distortion correction techniques were implemented, respectively, on the raw images to correct the nonlinear detector response due to pulse pileup and charge‐sharing artifacts. Dual energy decomposition was then used to characterize each breast in terms of water, lipid, and protein content. In the meantime, the breasts were chemically decomposed into their respective water, lipid, and protein components to provide a gold standard for comparison with dual energy decomposition results.Results:The accuracy of the tissue compositional measurement with spectral CT was determined by comparing to the reference standard from chemical analysis. The averaged root‐mean‐square error in percentage composition was reduced from 15.5% to 2.8% after spectral distortion corrections.Conclusions:The results indicate that spectral CT can be used to quantify the water, lipid, and protein content in breast tissue. The accuracy of the compositional analysis depends on the applied spectral distortion correction technique.
Investigation of sagittal image acquisition for 4D‐MRI with body area as respiratory surrogate
Authors: Liu Yilin , Yin Fang‐Fang , Chang Zheng , Czito Brian G. , Palta Manisha , Bashir Mustafa R. , Qin Yujiao , Cai Jing 
Published: September 2014

Purpose:The authors have recently developed a novel 4D‐MRI technique for imaging organ respiratory motion employing cine acquisition in the axial plane and using body area (BA) as a respiratory surrogate. A potential disadvantage associated with axial image acquisition is the space‐dependent phase shift in the superior–inferior (SI) direction, i.e., different axial slice positions reach the respiratory peak at different respiratory phases. Since respiratory motion occurs mostly in the SI and anterior–posterior (AP) directions, sagittal image acquisition, which embeds motion information in these two directions, is expected to be more robust and less affected by phase‐shift than axial image acquisition. This study aims to develop and evaluate a 4D‐MRI technique using sagittal image acquisition.Methods:The authors evaluated axial BA and sagittal BA using both 4D‐CT images (11 cancer patients) and cine MR images (6 healthy volunteers and 1 cancer patient) by comparing their corresponding space‐dependent phase‐shift in the SI direction and in the lateral direction , respectively. To evaluate sagittal BA 4D‐MRI method, a motion phantom study and a digital phantom study were performed. Additionally, six patients who had cancer(s) in the liver were prospectively enrolled in this study. For each patient, multislice sagittal MR images were acquired for 4D‐MRI reconstruction. 4D retrospective sorting was performed based on respiratory phases. Single‐slice cine MRI was also acquired in the axial, coronal, and sagittal planes across the tumor center from which tumor motion trajectories in the SI, AP, and medial–lateral (ML) directions were extracted and used as references from comparison. All MR images were acquired in a 1.5 T scanner using a steady‐state precession sequence (frame rate ∼ 3 frames/s).Results:4D‐CT scans showed that was significantly greater than (p‐value: 0.012); the median phase‐shift was 16.9% and 7.7%, respectively. Body surface motion measurement from axial and sagittal MR cines also showed was significantly greater than . The median and was 11.0% and 9.2% (p‐value = 0.008), respectively. Tumor motion trajectories from 4D‐MRI matched with those from single‐slice cine MRI: the mean (±SD) absolute differences in tumor motion amplitude between the two were 1.5 ± 1.6 mm, 2.1 ± 1.9 mm, and 1.1 ± 1.0 mm in the SI, ML, and AP directions from this patient study.Conclusions:Space‐dependent phase shift is less problematic for sagittal acquisition than for axial acquisition. 4D‐MRI using sagittal acquisition was successfully carried out in patients with hepatic tumors.
Free-Living and Particle-Associated Bacterioplankton in Large Rivers of the Mississippi River Basin Demonstrate Biogeographic Patterns
Authors: Jackson Colin R. , Millar Justin J. , Payne Jason T. , Ochs Clifford A. 
Published: September 2014

ABSTRACT

The different drainage basins of large rivers such as the Mississippi River represent interesting systems in which to study patterns in freshwater microbial biogeography. Spatial variability in bacterioplankton communities in six major rivers (the Upper Mississippi, Missouri, Illinois, Ohio, Tennessee, and Arkansas) of the Mississippi River Basin was characterized using Ion Torrent 16S rRNA amplicon sequencing. When all systems were combined, particle-associated (>3 μm) bacterial assemblages were found to be different from free-living bacterioplankton in terms of overall community structure, partly because of differences in the proportional abundance of sequences affiliated with major bacterial lineages (
Alphaproteobacteria
,
Cyanobacteria
, and
Planctomycetes
). Both particle-associated and free-living communities ordinated by river system, a pattern that was apparent even after rare sequences or those affiliated with
Cyanobacteria
were removed from the analyses. Ordination of samples by river system correlated with environmental characteristics of each river, such as nutrient status and turbidity. Communities in the Upper Mississippi and the Missouri and in the Ohio and the Tennessee, pairs of rivers that join each other, contained similar taxa in terms of presence-absence data but differed in the proportional abundance of major lineages. The most common sequence types detected in particle-associated communities were picocyanobacteria in the
Synechococcus
/
Prochlorococcus
/
Cyanobium
(Syn/Pro) clade, while free-living communities also contained a high proportion of LD12 (SAR11/
Pelagibacter
)-like
Alphaproteobacteria
. This research shows that while different tributaries of large river systems such as the Mississippi River harbor distinct bacterioplankton communities, there is also microhabitat variation such as that between free-living and particle-associated assemblages.
Major Role of NAD-Dependent Lactate Dehydrogenases in the Production of
l
-Lactic Acid with High Optical Purity by the Thermophile Bacillus coagulans
Authors: Wang Limin , Cai Yumeng , Zhu Lingfeng , Guo Honglian , Yu Bo 
Published: September 2014

ABSTRACT

Bacillus coagulans
2-6 is an excellent producer of optically pure
l
-lactic acid. However, little is known about the mechanism of synthesis of the highly optically pure
l
-lactic acid produced by this strain. Three enzymes responsible for lactic acid production—NAD-dependent
l
-lactate dehydrogenase (
l
-nLDH; encoded by
ldhL
), NAD-dependent
d
-lactate dehydrogenase (
d
-nLDH; encoded by
ldhD
), and glycolate oxidase (GOX)—were systematically investigated in order to study the relationship between these enzymes and the optical purity of lactic acid.
Lactobacillus delbrueckii
subsp.
bulgaricus
DSM 20081 (a
d
-lactic acid producer) and
Lactobacillus plantarum
subsp.
plantarum
DSM 20174 (a
dl
-lactic acid producer) were also examined in this study as comparative strains, in addition to
B. coagulans
. The specific activities of key enzymes for lactic acid production in the three strains were characterized
in vivo
and
in vitro
, and the levels of transcription of the
ldhL
,
ldhD
, and GOX genes during fermentation were also analyzed. The catalytic activities of
l
-nLDH and
d
-nLDH were different in
l
-,
d
-, and
dl
-lactic acid producers. Only
l
-nLDH activity was detected in
B. coagulans
2-6 under native conditions, and the level of transcription of
ldhL
in
B. coagulans
2-6 was much higher than that of
ldhD
or the GOX gene at all growth phases. However, for the two
Lactobacillus
strains used in this study,
ldhD
transcription levels were higher than those of
ldhL
. The high catalytic efficiency of
l
-nLDH toward pyruvate and the high transcription ratios of
ldhL
to
ldhD
and
ldhL
to the GOX gene provide the key explanations for the high optical purity of
l
-lactic acid produced by
B. coagulans
2-6.
Calcium-Enhanced Twitching Motility in Xylella fastidiosa Is Linked to a Single PilY1 Homolog
Authors: Cruz Luisa F. , Parker Jennifer K. , Cobine Paul A. , De La Fuente Leonardo 
Published: September 2014

ABSTRACT

The plant-pathogenic bacterium
Xylella fastidiosa
is restricted to the xylem vessel environment, where mineral nutrients are transported through the plant host; therefore, changes in the concentrations of these elements likely impact the growth and virulence of this bacterium. Twitching motility, dependent on type IV pili (TFP), is required for movement against the transpiration stream that results in basipetal colonization. We previously demonstrated that calcium (Ca) increases the motility of
X. fastidiosa
, although the mechanism was unknown. PilY1 is a TFP structural protein recently shown to bind Ca and to regulate twitching and adhesion in bacterial pathogens of humans. Sequence analysis identified three
pilY1
homologs in
X. fastidiosa
(PD0023, PD0502, and PD1611), one of which (PD1611) contains a Ca-binding motif. Separate deletions of PD0023 and PD1611 resulted in mutants that still showed twitching motility and were not impaired in attachment or biofilm formation. However, the response of increased twitching at higher Ca concentrations was lost in the
pilY1
-1611 mutant. Ca does not modulate the expression of any of the
X. fastidiosa
PilY1 homologs, although it increases the expression of the retraction ATPase
pilT
during active movement. The evidence presented here suggests functional differences between the PilY1 homologs, which may provide
X. fastidiosa
with an adaptive advantage in environments with high Ca concentrations, such as xylem sap.
A Highly Stable
d
-Amino Acid Oxidase of the Thermophilic Bacterium Rubrobacter xylanophilus
Authors: Takahashi Shouji , Furukawara Makoto , Omae Keishi , Tadokoro Namiho , Saito Yayoi , Abe Katsumasa , Kera Yoshio 
Published: September 2014

ABSTRACT

d
-Amino acid oxidase (DAO) is a biotechnologically attractive enzyme that can be used in a variety of applications, but its utility is limited by its relatively poor stability. A search of a bacterial genome database revealed a gene encoding a protein homologous to DAO in the thermophilic bacterium
Rubrobacter xylanophilus
(RxDAO). The recombinant protein expressed in
Escherichia coli
was a monomeric protein containing noncovalently bound flavin adenine dinucleotide as a cofactor. This protein exhibited oxidase activity against neutral and basic
d
-amino acids and was significantly inhibited by a DAO inhibitor, benzoate, but not by any of the tested
d
-aspartate oxidase (DDO) inhibitors, thus indicating that the protein is DAO. RxDAO exhibited higher activities and affinities toward branched-chain
d
-amino acids, with the highest specific activity toward
d
-valine and catalytic efficiency (
k
cat
/

K
m

) toward
d
-leucine. Substrate inhibition was observed in the case of
d
-tyrosine. The enzyme had an optimum pH range and temperature of pH 7.5 to 10 and 65°C, respectively, and was stable between pH 5.0 and pH 8.0, with a
T
50
(the temperature at which 50% of the initial enzymatic activity is lost) of 64°C. No loss of enzyme activity was observed after a 1-week incubation period at 30°C. This enzyme was markedly inactivated by phenylmethylsulfonyl fluoride but not by thiol-modifying reagents and diethyl pyrocarbonate, which are known to inhibit certain DAOs. These results demonstrated that RxDAO is a highly stable DAO and suggested that this enzyme may be valuable for practical applications, such as the determination and quantification of branched-chain
d
-amino acids, and as a scaffold to generate a novel DAO via protein engineering.