bluuebunny/crossref_metadata_2025 huggingface dataset:
Survival of the Enveloped Virus Phi6 in Droplets as a Function of Relative Humidity, Absolute Humidity, and Temperature
Authors: Prussin Aaron J. , Schwake David Otto , Lin Kaisen , Gallagher Daniel L. , Buttling Lauren , Marr Linsey C.
Published: April 2018

Infectious diseases caused by enveloped viruses, such as influenza, severe acute respiratory syndrome (SARS), and Middle East respiratory syndrome (MERS), cause thousands of deaths and billions of dollars of economic losses per year. Studies have found a relationship among temperature, humidity, and influenza virus incidence, transmission, or survival; however, there are contradictory claims about whether absolute humidity (AH) or relative humidity (RH) is most important in mediating virus infectivity. Using the enveloped bacteriophage Phi6, which has been suggested as a surrogate for influenza viruses and coronaviruses, we designed a study to discern whether AH, RH, or temperature is a better predictor of virus survival in droplets. Our results show that Phi6 survived best at high (>85%) and low (<60%) RHs, with a significant decrease in infectivity at mid-range RHs (∼60 to 85%). At an AH of less than 22 g · m
−3
, the loss in infectivity was less than 2 orders of magnitude; however, when the AH was greater than 22 g · m
−3
, the loss in infectivity was typically greater than 6 orders of magnitude. At a fixed RH of 75%, infectivity was very sensitive to temperature, decreasing two orders of magnitude between 19°C and 25°C. We used random forest modeling to identify the best environmental predictors for modulating virus infectivity. The model explained 83% of variation in Phi6 infectivity and suggested that RH is the most important factor in controlling virus infectivity in droplets. This research provides novel information about the complex interplay between temperature, humidity, and the survival of viruses in droplets.

IMPORTANCE
Enveloped viruses are responsible for a number of infectious diseases resulting in thousands of deaths and billions of dollars of economic losses per year in the United States. There has been a lively debate in the literature over whether absolute humidity (AH) or relative humidity (RH) modulates virus infectivity. We designed a controlled study and used advanced statistical modeling techniques specifically to address this question. By providing an improved understanding of the relationship between environmental conditions and virus infectivity, our work will ultimately lead to improved strategies for predicting and controlling disease transmission.
Salt-Induced Stress Stimulates a Lipoteichoic Acid-Specific Three-Component Glycosylation System in Staphylococcus aureus
Authors: Kho Kelvin , Meredith Timothy C.
Published: April 2018

Lipoteichoic acid (LTA) in
Staphylococcus aureus
is a poly-glycerophosphate polymer anchored to the outer surface of the cell membrane. LTA has numerous roles in cell envelope physiology, including regulating cell autolysis, coordinating cell division, and adapting to environmental growth conditions. LTA is often further modified with substituents, including
d
-alanine and glycosyl groups, to alter cellular function. While the genetic determinants of
d
-alanylation have been largely defined, the route of LTA glycosylation and its role in cell envelope physiology have remained unknown, in part due to the low levels of basal LTA glycosylation in
S. aureus
. We demonstrate here that
S. aureus
utilizes a membrane-associated three-component glycosylation system composed of an undecaprenol (Und)
N
-acetylglucosamine (GlcNAc) charging enzyme (CsbB; SAOUHSC_00713), a putative flippase to transport loaded substrate to the outside surface of the cell (GtcA; SAOUHSC_02722), and finally an LTA-specific glycosyltransferase that adds α-GlcNAc moieties to LTA (YfhO; SAOUHSC_01213). We demonstrate that this system is specific for LTA with no cross recognition of the structurally similar polyribitol phosphate containing wall teichoic acids. We show that while wild-type
S. aureus
LTA has only a trace of GlcNAcylated LTA under normal growth conditions, amounts are raised upon either overexpressing CsbB, reducing endogenous
d
-alanylation activity, expressing the cell envelope stress responsive alternative sigma factor SigB, or by exposure to environmental stress-inducing culture conditions, including growth media containing high levels of sodium chloride.

IMPORTANCE
The role of glycosylation in the structure and function of
Staphylococcus aureus
lipoteichoic acid (LTA) is largely unknown. By defining key components of the LTA three-component glycosylation pathway and uncovering stress-induced regulation by the alternative sigma factor SigB, the role of
N
-acetylglucosamine tailoring during adaptation to environmental stresses can now be elucidated. As the
dlt
and glycosylation pathways compete for the same sites on LTA and induction of glycosylation results in decreased
d
-alanylation, the interplay between the two modification systems holds implications for resistance to antibiotics and antimicrobial peptides.
Convergence of PASTA Kinase and Two-Component Signaling in Response to Cell Wall Stress in Enterococcus faecalis
Authors: Kellogg Stephanie L. , Kristich Christopher J.
Published: April 2018

Two common signal transduction mechanisms used by bacteria to sense and respond to changing environments are two-component systems (TCSs) and eukaryote-like Ser/Thr kinases and phosphatases (eSTK/Ps).
Enterococcus faecalis
is a Gram-positive bacterium and a serious opportunistic pathogen that relies on both a TCS and an eSTK/P pathway for intrinsic resistance to cell wall-targeting antibiotics. The TCS consists of a histidine kinase (CroS) and a response regulator (CroR) that become activated upon exposure of cells to cell wall-targeting antibiotics, leading to a modulation of gene expression. The eSTK/P pathway consists of a transmembrane kinase (IreK) and its cognate phosphatase (IreP), which act antagonistically to mediate antibiotic resistance through an unknown mechanism. Because both CroS/R and IreK/P contribute to enterococcal resistance toward cell wall-targeting antibiotics, we hypothesized that these signaling systems are intertwined. To test this hypothesis, we analyzed CroR phosphorylation and CroS/R-dependent gene expression to probe the influence of IreK and IreP on CroS/R signaling. In addition, we analyzed the phosphorylation state of CroS, which revealed the IreK-dependent phosphorylation of a Thr residue important for CroS function. Our results are consistent with a model in which IreK positively influences CroR-dependent gene expression through the phosphorylation of CroS to promote antimicrobial resistance in
E. faecalis
.

IMPORTANCE
Two-component signaling systems (TCSs) and eukaryote-like Ser/Thr kinases (eSTKs) are used by bacteria to sense and adapt to changing environments. Understanding how these pathways are regulated to promote bacterial survival is critical for a more complete understanding of bacterial stress responses and physiology. The opportunistic pathogen
Enterococcus faecalis
relies on both a TCS (CroS/R) and an eSTK (IreK) for intrinsic resistance to cell wall-targeting antibiotics. We probed the relationship between CroS/R and IreK, revealing the convergence of IreK and the sensor kinase CroS to enhance signaling through CroS/R and increase antimicrobial resistance in
E. faecalis
. This newly described example of eSTK/TCS convergence adds to our understanding of the signaling networks mediating antimicrobial resistance in
E. faecalis
.
Association of ω with the C-Terminal Region of the β′ Subunit Is Essential for Assembly of RNA Polymerase in Mycobacterium tuberculosis
Authors: Mao Chunyou , Zhu Yan , Lu Pei , Feng Lipeng , Chen Shiyun , Hu Yangbo
Published: April 2018

The ω subunit is the smallest subunit of bacterial RNA polymerase (RNAP). Although homologs of ω are essential in both eukaryotes and archaea, this subunit has been known to be dispensable for RNAP in
Escherichia coli
and in other bacteria. In this study, we characterized an indispensable role of the ω subunit in
Mycobacterium tuberculosis
. Unlike the well-studied
E. coli
RNAP, the
M. tuberculosis
RNAP core enzyme cannot be functionally assembled in the absence of the ω subunit. Importantly, substitution of
M. tuberculosis
ω with ω subunits from
E. coli
or
Thermus thermophilus
cannot restore the assembly of
M. tuberculosis
RNAP. Furthermore, by replacing different regions in
M. tuberculosis
ω with the corresponding regions from
E. coli
ω, we found a nonconserved loop region in
M. tuberculosis
ω essential for its function in RNAP assembly. From RNAP structures, we noticed that the location of the C-terminal region of the β′ subunit (β′CTD) in
M. tuberculosis
RNAP but not in
E. coli
or
T. thermophilus
RNAP is close to the ω loop region. Deletion of this β′CTD in
M. tuberculosis
RNAP destabilized the binding of
M. tuberculosis
ω on RNAP and compromised
M. tuberculosis
core assembly, suggesting that these two regions may function together to play a role in ω-dependent RNAP assembly in
M. tuberculosis
. Sequence alignment of the ω loop and the β′CTD regions suggests that the essential role of ω is probably restricted to mycobacteria. Together, our study characterized an essential role of
M. tuberculosis
ω and highlighted the importance of the ω loop region in
M. tuberculosis
RNAP assembly.

IMPORTANCE
DNA-dependent RNA polymerase (RNAP), which consists of a multisubunit core enzyme (α
2
ββ′ω) and a dissociable σ subunit, is the only enzyme in charge of transcription in bacteria. As the smallest subunit, the roles of ω remain the least well studied. In
Escherichia coli
and some other bacteria, the ω subunit is known to be nonessential for RNAP. In this study, we revealed an essential role of the ω subunit for RNAP assembly in the human pathogen
Mycobacterium tuberculosis
, and a mycobacterium-specific ω loop that plays a role in this function was also characterized. Our study provides fresh insights for further characterizing the roles of bacterial ω subunit.
Developing and Evaluating Inhibitors against the RNase H Active Site of HIV-1 Reverse Transcriptase
Authors: Boyer Paul L. , Smith Steven J. , Zhao Xue Zhi , Das Kalyan , Gruber Kevin , Arnold Eddy , Burke Terrence R. , Hughes Stephen H.
Published: April 2018

We tested three compounds for their ability to inhibit the RNase H (RH) and polymerase activities of HIV-1 reverse transcriptase (RT). A high-resolution crystal structure (2.2 Å) of one of the compounds showed that it chelates the two magnesium ions at the RH active site; this prevents the RH active site from interacting with, and cleaving, the RNA strand of an RNA-DNA heteroduplex. The compounds were tested using a variety of substrates: all three compounds inhibited the polymerase-independent RH activity of HIV-1 RT. Time-of-addition experiments showed that the compounds were more potent if they were bound to RT before the nucleic acid substrate was added. The compounds significantly inhibited the site-specific cleavage required to generate the polypurine tract (PPT) RNA primer that initiates the second strand of viral DNA synthesis. The compounds also reduced the polymerase activity of RT; this ability was a result of the compounds binding to the RH active site. These compounds appear to be relatively specific; they do not inhibit either
Escherichia coli
RNase HI or human RNase H2. The compounds inhibit the replication of an HIV-1-based vector in a one-round assay, and their potencies were only modestly decreased by mutations that confer resistance to integrase strand transfer inhibitors (INSTIs), nucleoside analogs, or nonnucleoside RT inhibitors (NNRTIs), suggesting that their ability to block HIV replication is related to their ability to block RH cleavage. These compounds appear to be useful leads that can be used to develop more potent and specific compounds.

IMPORTANCE
Despite advances in HIV-1 treatment, drug resistance is still a problem. Of the four enzymatic activities found in HIV-1 proteins (protease, RT polymerase, RT RNase H, and integrase), only RNase H has no approved therapeutics directed against it. This new target could be used to design and develop new classes of inhibitors that would suppress the replication of the drug-resistant variants that have been selected by the current therapeutics.
Antimicrobial Resistance in
Campylobacter
spp
Authors: Shen Zhangqi , Wang Yang , Zhang Qijing , Shen Jianzhong
Published: April 2018

Campylobacter
is a major foodborne pathogen and has become increasingly resistant to clinically important antimicrobials. To cope with the selection pressure from antimicrobial use in both veterinary and human medicine,
Campylobacter
has developed multiple mechanisms for antibiotic resistance, including modification or mutation of antimicrobial targets, modification or inactivation of antibiotics, and reduced drug accumulation by drug efflux pumps. Some of these mechanisms confer resistance to a specific class of antimicrobials, while others give rise to multidrug resistance. Notably, new antibiotic resistance mechanisms continuously emerge in
Campylobacter
, and some examples include the recently discovered multidrug resistance genomic islands harboring multiple genes involved in the resistance to aminoglycosides and macrolides, a novel Cfr(C) conferring resistance to phenicols and other drugs, and a potent multidrug efflux pump CmeABC variant (RE-CmeABC) that shows a significantly enhanced function in multidrug resistance and is associated with exceedingly high-level resistance to fluoroquinolones. These newly emerged resistance mechanisms are horizontally transferable and greatly facilitate the adaptation of
Campylobacter
in the food-producing environments where antibiotics are frequently used. In this article, we will discuss how
Campylobacter
resists the action of various classes of antimicrobials, with an emphasis on newly discovered mechanisms.
Long-Term Electroacupuncture Stimulation Prevents Osteoporosis in Ovariectomised Osteopaenic Rats through Multiple Signalling Pathways
Authors: Zheng Xuefeng , Nie Yan , Sun Chengtao , Wu Guangwen , Cai Qiaoyan , Huang Shu , Lin Yanping
Published: April 2018

Background

The pathogenic mechanisms of postmenopausal osteoporosis (PMOP) development are complex and are related to multiple cellular signalling transduction pathways. The aim of this study was to compare the effects of electroacupuncture (EA) at GV4/GV6 versus BL20/BL23 on the bones in ovariectomised (OVX) rats to explore the pathways that mediate the effects of EA on bone.

Methods

Forty female Sprague-Dawley rats were allocated to one of four groups (n=10 rats each) that received sham surgery (Sham group), OVX surgery only (OVX group), OVX surgery plus EA at GV4/GV6 (GV group) and OVX surgery plus EA at BL20/BL23 (BL group). Bone turnover markers osteocalcin (OC) and tartrate-resistant acid phosphatase 5b (TRACP 5b) were measured in serum, and bone mineral density (BMD) of the lumbar vertebrae and histomorphology of the femur were evaluated. Moreover, the expression of osteoprotegerin (OPG) and receptor activator of nuclear factor-κB ligand (RANKL) was detected by ELISA. The expression of lipoprotein receptor-related protein (LRP) 5, β-catenin, runt-related transcription factor (Runx) 2 involving Wnt/β-catenin signalling and p38, c-Jun N-terminal kinase (JNK) and extracellular regulated protein kinases 1/2 involving mitogen-activated protein kinase signalling were determined by Western blotting.

Results

The two EA-treated groups demonstrated increased levels of OC and the BMD of lumbar vertebrae, decreased levels of TRACP 5b and improved bone microstructure in the femur, compared with the untreated OVX group (P<0.05). Histomorphology analysis showed that EA treatment significantly increased the values of the trabeculae (µm), trabecular area (%) and trabecular bone number (per mm) and reduced trabecular separation (mm), compared with the OVX group. In addition, the ratio of OPG to RANKL and LRP5, β-catenin and Runx2 expression were significantly upregulated, while the expression of phosphorylated (p)-p38 and p-JNK were downregulated in EA-treated groups compared with the OVX group.

Conclusion

EA attenuates PMOP and it appears that the mechanism involves the regulation of multiple targets and pathways.
Predicting opioid use disorder in patients with chronic pain who present to the emergency department
Authors: Gardner Robert Andrew , Brewer Kori L , Langston Dennis B
Published: April 2018

Background

Emergency department (ED) patients with chronic pain challenge providers to make quick and accurate assessments without an in-depth pain management consultation. Emergency physicians need reliable means to determine which patients may receive opioid therapy without exacerbating opioid use disorder (OUD).

Methods

Eighty-nine ED patients with a chief complaint of chronic pain were enrolled. Researchers administered questionnaires and reviewed medical and state prescription monitoring database information. Participants were classified as either OUD or non-OUD. Statistical analysis included a bivariate analysis comparing differences between groups and multivariate logistic regression evaluating ORs.

Results

The 45 participants categorised as OUD had a higher proportion of documented or reported psychiatric diagnoses (p=0.049), preference of opioid treatment (p=0.005), current oxycodone prescription (p=0.043), borrowed pain medicine (p=0.004) and non-authorised dose increase (p<0.001). The state prescription monitoring database revealed the OUD group to have an increased number of opioid prescriptions (p=0.005) and pills (p=0.010). Participants who borrowed pain medicine and engaged in non-authorised dose increase were 5.2 (p=0.025, 95% CI 1.24 to 21.9) and 6.1 times (p=0.001, 95% CI 1.55 to 24.1) more likely to have OUD, respectively.

Limitations

Major limitations of our study include a small sample size, self-reported measures and convenience sample which may introduce selection bias.

Conclusion

Patients with chronic pain with OUD have distinguishable characteristics. Emergency physicians should consider such evidence-based variables prior to opioid therapy to ameliorate the opioid crisis and limit implicit bias.
Opioid analgesia on the battlefield: a retrospective review of data from Operation HERRICK
Authors: Lewis Pip , Wright C , Hooper C
Published: April 2018

Background

Acute pain secondary to trauma is commonly encountered on the battlefield. The use of morphine to manage pain during combat has been well established since the 19th century. Despite this, there is relatively little research on analgesia use in this environment. This study aims to review the use and complications of morphine and other opioids during Operation HERRICK.

Methods

A database search of the Joint Theatre Trauma Registry was completed looking for all incidences of morphine, fentanyl or naloxone use from February 2007 to September 2014. Microsoft Excel was used to analyse the results.

Results

Opioid analgesia was administered to 5801 casualties. Morphine was administered 6742 times to 3808 patients. Fentanyl was administered 9672 times to 4318 patients. Naloxone was used 18 times on 14 patients, giving a complication rate of 0.24%. Opioid doses prior to naloxone administration range from 0 to 72 mg of morphine and from 0 to 100 mcg of fentanyl. Four casualties (two local civilians and two coalition forces) received naloxone despite no recorded opioids being administered. Opium abuse was prevalent among the local population in Afghanistan, and this could explain the rationale behind two local national casualties receiving naloxone without any documented opioids being given.

Conclusion

The use of opioids in a battlefield environment is extremely safe. Complication rates are similar to previously published data which is reassuring. The efficacy of different opioids was not covered by this study, and further analysis is required, particularly following the introduction of oral transmucosal fentanyl citrate and the availability of novel non-opioid analgesics.
An Efficient High-Throughput Generic QAM Transmitter with Scalable Spiral FIR Filter
Authors: Figuli Shalina Percy Delicia , Becker Jürgen
Published: April 2018

The need for efficient Finite Impulse Response (FIR) filters in high-speed applications such as telecommunications targets Field Programmable Gate Arrays (FPGAs) as an effective and flexible platform for digital implementation. Although FIR filter offers many advantages, its convolution nature poises a challenge in parallelization due to data dependency and computational complexity. To resolve this, we propose a novel FPGA-based reconfigurable filter architecture, which processes several data samples in parallel and breaks down data interdependency in a spiral fashion. Experimental results show a throughput of 7.2[Formula: see text]GSPS with an operating frequency of only 450[Formula: see text]MHz for a filter length of 11 with 16 parallel inputs. With parallelization of 4, it is 4.44 times faster than the state-of-the-art solution for a filter length of 16 and a promising 1.04[Formula: see text]GSPS throughput is achieved for a higher order of length 61. Incorporated into a generic Quadrature Amplitude Modulation (QAM) transmitter fitted with Forward Error Correction technique, a maximum throughput of 23[Formula: see text]Gb/s is achieved by the system for processing 16 input samples in parallel. In comparison to the state-of-the-art mixed domain approach, a threefold performance gain, while utilizing comparatively less Look-up Tables (LUTs), registers and DSP48 slices with an average gain factor of 43.3[Formula: see text], 4.7[Formula: see text] and 3.9[Formula: see text], respectively, is accomplished.
Shape Descriptors for Porous Media Analysis Using Computed Tomography Images
Authors: Ngom Ndeye Fatou , Ndiaye Cheikh H. T. C. , Niang Oumar , Sidibe Samba
Published: April 2018

In this study, we propose a new framework for 3D porous media shape characterization using quantitative data driven shape descriptors. The main conceptual innovations are the introduction of shape descriptors based on geometrical parameters of the shape and empirical mode decomposition (EMD) of the shape skeleton. The EMD yields a decomposition with intrinsic mode functions based on local properties of the skeleton. Efficient methods for computing the defined descriptors from a network of balls representation of the pore space are provided. A multivariate analysis is carried out to describe the relationships between the shape descriptors and justify their use in the context of shape analysis. The proposed descriptors are also used to group together objects by their similarity and perform optimal approximation of the porous media by primitives set. Properties on the approximation are given and discussed. The proposed framework is illustrated with computed tomography images of real soil sample. The results have demonstrated the performance of our methodology for shape characterization, optimal shape decomposition and comparison.
Image Appearance-Based Facial Expression Recognition
Authors: Wu Zhaoqi , Xiamixiding Reziwanguli , Sajjanhar Atul , Chen Juan , Wen Quan
Published: April 2018

We investigate facial expression recognition (FER) based on image appearance. FER is performed using state-of-the-art classification approaches. Different approaches to preprocess face images are investigated. First, region-of-interest (ROI) images are obtained by extracting the facial ROI from raw images. FER of ROI images is used as the benchmark and compared with the FER of difference images. Difference images are obtained by computing the difference between the ROI images of neutral and peak facial expressions. FER is also evaluated for images which are obtained by applying the Local binary pattern (LBP) operator to ROI images. Further, we investigate different contrast enhancement operators to preprocess images, namely, histogram equalization (HE) approach and a brightness preserving approach for histogram equalization. The classification experiments are performed for a convolutional neural network (CNN) and a pre-trained deep learning model. All experiments are performed on three public face databases, namely, Cohn–Kanade (CK[Formula: see text]), JAFFE and FACES.
Pharmacological regulation of outflow resistance distal to Schlemm’s canal
Authors: McDonnell Fiona , Dismuke W. Michael , Overby Darryl R. , Stamer W. Daniel
Published: April 2018

The trabecular meshwork (TM) and Schlemm’s canal generate the majority of outflow resistance; however, the distal regions of the conventional outflow pathway account for 25–50% of total resistance. Sections of distal vessels are surrounded by α-smooth muscle actin-containing cells, indicating that they may be vasoregulated. This study examined the effect of a potent vasodilator, nitric oxide (NO), and its physiological antagonist, endothelin-1 (ET-1), on the regulation of outflow resistance in the distal regions of the conventional outflow pathway. Using a physiological model of the conventional outflow pathway, human and porcine anterior segments were perfused in organ culture under constant flow conditions, while intrachamber pressure was continually monitored. For porcine anterior segments, a stable baseline outflow facility with TM intact was first achieved before anterior segments were removed and a trabeculotomy was performed. For human anterior segments, a trabeculotomy was immediately performed. In human anterior segments, 100 nM ET-1 significantly decreased distal outflow facility from 0.49 ± 0.26 to 0.31 ±  0.18 (mean ± SD) µl·min−1·mmHg, P < 0.01. Perfusion with 100 µM diethylenetriamine-NO in the presence of 1 nM ET-1 immediately reversed ET-1 effects, significantly increasing distal outflow facility to 0.54 ± 0.35 µl·min−1·mmHg, P = 0.01. Similar results were obtained in porcine anterior segment experiments. Therefore, data show a dynamic range of resistance generation by distal vessels in both the human and the porcine conventional outflow pathways. Interestingly, maximal contraction of vessels in the distal outflow tract of trabeculotomized eyes generated resistance very near physiological levels for both species having an intact TM.
Lipidated connexin mimetic peptides potently inhibit gap junction-mediated Ca2+-wave propagation
Authors: Cotter Maura L. , Boitano Scott , Vagner Josef , Burt Janis M.
Published: April 2018

Connexin (Cx) mimetic peptides (e.g., Gap27: SRPTEKTIFII; Peptide5: VDCFLSRPTEKT) reversibly inhibit hemichannel (HCh) and gap junction channel (GJCh) function in a concentration- and time-dependent manner (HCh: ~5 µM, <1 h; GJCh: ~100 µM, > 1 h). We hypothesized that addition of a hexadecyl tail to SRPTEKT (SRPTEKT- Hdc) would improve its ability to concentrate in the plasma membrane and consequently increase its inhibitory efficacy. We show that SRPTEKT- Hdc inhibited intercellular Ca2+-wave propagation in Cx43-expressing MDCK and rabbit tracheal epithelial cells in a time (61–75 min)- and concentration (IC50: 66 pM)-dependent manner, a concentration efficacy five orders of magnitude lower than observed for the nonlipidated Gap27. HCh-mediated dye uptake was inhibited by SRPTEKT- Hdc with similar efficacy. Following peptide washout, HCh-mediated dye uptake was restored to control levels, whereas Ca2+-wave propagation was only partially restored. Scrambled and reverse sequence lipidated peptides had no detectable inhibitory effect on Ca2+-wave propagation or dye uptake. Cx43 expression was unchanged by SRPTEKT- Hdc incubation; however, Triton-insoluble Cx43 was reduced by SRPTEKT- Hdc exposure and reversed following washout. In summary, our results show that SRPTEKT- Hdc blocked HCh function and intercellular Ca2+ signaling at concentrations that minimally affected dye coupling. Selective inhibition of intercellular Ca2+ signaling, likely indicative of channel conformation-specific SRPTEKT- Hdc binding, could contribute significantly to the protective effects of these mimetic peptides in settings of injury. Our data also demonstrate that lipidation represents a paradigm for development of highly potent, efficacious, and selective mimetic peptide inhibitors of hemichannel and gap junction channel-mediated signaling.
Gonadotropin-releasing hormone agonist in premenopausal women does not alter hypothalamic-pituitary-adrenal axis response to corticotropin-releasing hormone
Authors: Gavin Kathleen M. , Shea Karen L. , Gibbons Ellie , Wolfe Pamela , Schwartz Robert S. , Wierman Margaret E. , Kohrt Wendy M.
Published: April 2018

Sex hormones appear to play a role in the regulation of hypothalamic-pituitary-adrenal (HPA) axis activity. The objective was to isolate the effects of estradiol (E2) on central activation of the HPA axis. We hypothesized that the HPA axis response to corticotropin-releasing hormone (CRH) under dexamethasone (Dex) suppression would be exaggerated in response to chronic ovarian hormone suppression and that physiologic E2 add-back would mitigate this response. Thirty premenopausal women underwent 20 wk of gonadotropin-releasing hormone agonist therapy (GnRHAG) and transdermal E2 (0.075 mg per day, GnRHAG + E2, n = 15) or placebo (PL) patch (GnRHAG + PL, n = 15). Women in the GnRHAG + PL and GnRHAG + E2 groups were of similar age (38 (SD 5) yr vs. 36 (SD 7) yr) and body mass index (27 (SD 6) kg/m2 vs. 27 (SD 6) kg/m2). Serum E2 changed differently between the groups ( P = 0.01); it decreased in response to GnRHAG + PL (77.9 ± 17.4 to 23.2 ± 2.6 pg/ml; P = 0.008) and did not change in response to GnRHAG + E2 (70.6 ± 12.4 to 105 ± 30.4 pg/ml; P = 0.36). The incremental area under the curve (AUCINC) responses to CRH were different between the groups for total cortisol ( P = 0.03) and cortisone ( P = 0.04) but not serum adrenocorticotropic hormone (ACTH) ( P = 0.28). When examining within-group changes, GnRHAG + PL did not alter the HPA axis response to Dex/CRH, but GnRHAG + E2 decreased the AUCINC for ACTH (AUCINC, 1,623 ± 257 to 1,211 ± 236 pg/ml·min, P = 0.004), cortisone (1,795 ± 367 to 1,090 ± 281 ng/ml·min, P = 0.009), and total cortisol (7,008 ± 1,387 to 3,893 ± 1,090 ng/ml·min, P = 0.02). Suppression of ovarian hormones by GnRHAG therapy for 20 wk did not exaggerate the HPA axis response to CRH, but physiologic E2 add-back reduced HPA axis activity compared with preintervention levels.
Role of the saturated fatty acid palmitate in the interconnected hypothalamic control of energy homeostasis and biological rhythms
Authors: Tse Erika K. , Salehi Ashkan , Clemenzi Matthew N. , Belsham Denise D.
Published: April 2018

The brain, specifically the hypothalamus, controls whole body energy and glucose homeostasis through neurons that synthesize specific neuropeptides, whereas hypothalamic dysfunction is linked directly to insulin resistance, obesity, and type 2 diabetes mellitus. Nutrient excess, through overconsumption of a Western or high-fat diet, exposes the hypothalamus to high levels of free fatty acids, which induces neuroinflammation, endoplasmic reticulum stress, and dysregulation of neuropeptide synthesis. Furthermore, exposure to a high-fat diet also disrupts normal circadian rhythms, and conversely, clock gene knockout models have symptoms of metabolic disorders. While whole brain/animal studies have provided phenotypic end points and important clues to the genes involved, there are still major gaps in our understanding of the intracellular pathways and neuron-specific components that ultimately control circadian rhythms and energy homeostasis. Because of its complexity and heterogeneous nature, containing a diverse mix cell types, it is difficult to dissect the critical hypothalamic components involved in these processes. Of significance, we have the capacity to study these individual components using an extensive collection of both embryonic- and adult-derived, immortalized hypothalamic neuronal cell lines from rodents. These defined neuronal cell lines have been used to examine the impact of nutrient excess, such as palmitate, on circadian rhythms and neuroendocrine signaling pathways, as well as changes in vital neuropeptides, leading to the development of neuronal inflammation; the role of proinflammatory molecules in this process; and ultimately, restoration of normal signaling, clock gene expression, and neuropeptide synthesis in disrupted states by beneficial anti-inflammatory compounds in defined hypothalamic neurons.
Insulin-like growth factor-binding protein-4 inhibits epithelial growth and proliferation in the rodent intestine
Authors: Austin Kaori , Tsang Derek , Chalmers Jennifer A. , Maalouf Michael F. , Brubaker Patricia L.
Published: April 2018

Insulin-like growth factor-binding protein-4 (IGFBP-4) is a binding protein that modulates the action of insulin-like growth factor-1 (IGF-1), a growth factor whose presence is required for the intestinotrophic effects of glucagon-like peptide-2 (GLP-2). GLP-2 is a gut hormone that uses both IGF-1 and epidermal growth factor (EGF) as intermediary factors to promote intestinal growth. Therefore, to elucidate the mechanism through which IGFBP-4 regulates IGF-1 activity in the intestine, proliferation assays were conducted using rat intestinal epithelial cells (IEC-6). IGF-1 and EGF synergistically enhanced proliferation, an effect that was dose-dependently decreased by IGFBP-4 ( P < 0.05–0.001) in an IGF-1 receptor (R)- and MEK1/2- but not a phosphatidylinositol 3-kinase-dependent manner ( P > 0.05 for IGFBP-4 effects with IGF-1R and MEK1/2 inhibitors). Intestinal organoids derived from IGFBP-4 knockout mice demonstrated significantly greater Ki-67 expression and an enhanced surface area increase in response to IGF-1 treatment, compared with organoids from control mice ( P < 0.05–0.01). GLP-2 is also known to increase the mucosal expression of IGFBP-4 mRNA. To investigate whether this occurs through the actions of its intermediaries, IGF-1 and EGF, inducible intestinal epithelial-IGF-1R knockout and control mice were treated for 10 days with and without the pan-ErbB inhibitor, CI-1033. However, no differences in mucosal IGFBP-4 mRNA expression were found for any of the treatment groups ( P > 0.05). Consistently, IEC-6 cells treated with IGF-1 and/or EGF displayed no alteration in IGFBP-4 mRNA or in cellular and secreted IGFBP-4 protein ( P > 0.05). Overall, this study establishes that endogenous IGFBP-4 plays an important role in inhibiting IGF-1-induced intestinal epithelial proliferation and that mucosal IGFBP-4 expression is independent of IGF-1 and EGF.

NEW & NOTEWORTHY This study demonstrates, for the first time, the inhibitory role of locally expressed insulin-like growth factor-binding protein-4 (IGFBP-4) on the intestinal proliferative actions of IGF-1 and supports the notion of the synergistic roles of IGF-1 and EGF in promoting intestinal epithelial growth. In turn, intestinal IGFBP-4 expression was not found to be regulated by IGF-1 and/or EGF.
Elastin, arterial mechanics, and cardiovascular disease
Authors: Cocciolone Austin J. , Hawes Jie Z. , Staiculescu Marius C. , Johnson Elizabeth O. , Murshed Monzur , Wagenseil Jessica E.
Published: April 2018

Large, elastic arteries are composed of cells and a specialized extracellular matrix that provides reversible elasticity and strength. Elastin is the matrix protein responsible for this reversible elasticity that reduces the workload on the heart and dampens pulsatile flow in distal arteries. Here, we summarize the elastin protein biochemistry, self-association behavior, cross-linking process, and multistep elastic fiber assembly that provide large arteries with their unique mechanical properties. We present measures of passive arterial mechanics that depend on elastic fiber amounts and integrity such as the Windkessel effect, structural and material stiffness, and energy storage. We discuss supravalvular aortic stenosis and autosomal dominant cutis laxa-1, which are genetic disorders caused by mutations in the elastin gene. We present mouse models of supravalvular aortic stenosis, autosomal dominant cutis laxa-1, and graded elastin amounts that have been invaluable for understanding the role of elastin in arterial mechanics and cardiovascular disease. We summarize acquired diseases associated with elastic fiber defects, including hypertension and arterial stiffness, diabetes, obesity, atherosclerosis, calcification, and aneurysms and dissections. We mention animal models that have helped delineate the role of elastic fiber defects in these acquired diseases. We briefly summarize challenges and recent advances in generating functional elastic fibers in tissue-engineered arteries. We conclude with suggestions for future research and opportunities for therapeutic intervention in genetic and acquired elastinopathies.
Small-conductance Ca2+-activated K+channel activation deteriorates hypoxic ventricular arrhythmias via CaMKII in cardiac hypertrophy
Authors: Tenma Taro , Mitsuyama Hirofumi , Watanabe Masaya , Kakutani Naoya , Otsuka Yutaro , Mizukami Kazuya , Kamada Rui , Takahashi Masayuki , Takada Shingo , Sabe Hisataka , Tsutsui Hiroyuki , Yokoshiki Hisashi
Published: April 2018

The molecular and electrophysiological mechanisms of acute ischemic ventricular arrhythmias in hypertrophied hearts are not well known. We hypothesized that small-conductance Ca2+-activated K+(SK) channels are activated during hypoxia via the Ca2+/calmodulin-dependent protein kinase II (CaMKII)-dependent pathway. We used normotensive Wistar-Kyoto (WKY) rats and spontaneous hypertensive rats (SHRs) as a model of cardiac hypertrophy. The inhibitory effects of SK channels and ATP-sensitive K+channels on electrophysiological changes and genesis of arrhythmias during simulated global hypoxia (GH) were evaluated. Hypoxia-induced abbreviation of action potential duration (APD) occurred earlier in ventricles from SHRs versus. WKY rats. Apamin, a SK channel blocker, prevented this abbreviation in SHRs in both the early and delayed phase of GH, whereas in WKY rats only the delayed phase was prevented. In contrast, SHRs were less sensitive to glibenclamide, a ATP-sensitive K+channel blocker, which inhibited the APD abbreviation in both phases of GH in WKY rats. SK channel blockers (apamin and UCL-1684) reduced the incidence of hypoxia-induced sustained ventricular arrhythmias in SHRs but not in WKY rats. Among three SK channel isoforms, SK2 channels were directly coimmunoprecipitated with CaMKII phosphorylated at Thr286(p-CaMKII). We conclude that activation of SK channels leads to the APD abbreviation and sustained ventricular arrhythmias during simulated hypoxia, especially in hypertrophied hearts. This mechanism may result from p-CaMKII-bound SK2 channels and reveal new molecular targets to prevent lethal ventricular arrhythmias during acute hypoxia in cardiac hypertrophy.

NEW & NOTEWORTHY We now show a new pathophysiological role of small-conductance Ca2+-activated K+channels, which shorten the action potential duration and induce ventricular arrhythmias during hypoxia. We also demonstrate that small-conductance Ca2+-activated K+channels interact with phosphorylated Ca2+/calmodulin-dependent protein kinase II at Thr286in hypertrophied hearts.
Tricellular tight junction-associated angulins in the gill epithelium of rainbow trout
Authors: Kolosov Dennis , Kelly Scott P.
Published: April 2018

Molecular physiology of the tricellular tight junction (tTJ)-associated proteins lipolysis-stimulated lipoprotein receptor ( lsr, = angulin-1) and an immunoglobulin-like domain-containing receptor ( ildr2, ≈angulin-3) was examined in model trout gill epithelia. Transcripts encoding lsr and ildr2 are broadly expressed in trout organs. A reduction in lsr and ildr2 mRNA abundance was observed during and after confluence in flask-cultured gill cells. In contrast, as high-resistance and low-permeability characteristics developed in a model gill epithelium cultured on permeable polyethylene terephthalate membrane inserts, lsr and ildr2 transcript abundance increased. However, as epithelia entered the developmental plateau phase, lsr abundance returned to initial values, while ildr2 transcript abundance remained elevated. When mitochondrion-rich cells were introduced to model preparations, lsr mRNA abundance was unaltered and ildr2 mRNA abundance significantly increased. Transcript abundance of ildr2 was not altered in association with corticosteroid-induced tightening of the gill epithelium, while lsr mRNA abundance decreased. Transcriptional knockdown of the tTJ protein tricelluin (Tric) reduced Tric abundance, increased gill epithelium permeability, and increased lsr without significantly altering ildr2 transcript abundance. Data suggest that angulins contribute to fish gill epithelium barrier properties but that Lsr and Ildr2 seem likely to play different roles. This is because ildr2 typically exhibited increased abundance in association with decreased model permeability, while lsr abundance changed in a manner that suggested a role in Tric recruitment to the tTJ.
Adipose transcriptome analysis provides novel insights into molecular regulation of prolonged fasting in northern elephant seal pups
Authors: Martinez Bridget , Khudyakov Jane , Rutherford Kim , Crocker Daniel E. , Gemmell Neil , Ortiz Rudy M.
Published: April 2018

The physiological and cellular adaptations to extreme fasting in northern elephant seals ( Mirounga angustirostris, NES) are remarkable and may help to elucidate endocrine mechanisms that regulate lipid metabolism and energy homeostasis in mammals. Recent studies have highlighted the importance of thyroid hormones in the maintenance of a lipid-based metabolism during prolonged fasting in weaned NES pups. To identify additional molecular regulators of fasting, we used a transcriptomics approach to examine changes in global gene expression profiles before and after 6–8 wk of fasting in weaned NES pups. We produced a de novo assembly and identified 98 unique protein-coding genes that were differentially expressed between early and late fasting. Most of the downregulated genes were associated with lipid, carbohydrate, and protein metabolism. A number of downregulated genes were also associated with maintenance of the extracellular matrix, consistent with tissue remodeling during weight loss and the multifunctional nature of blubber tissue, which plays both metabolic and structural roles in marine mammals. Using this data set, we predict potential mechanisms by which NES pups sustain metabolism and regulate adipose stores throughout the fast, and provide a valuable resource for additional studies of extreme metabolic adaptations in mammals.
Hollow Mesoporous Silica@Zeolitic Imidazolate Framework Capsules and Their Applications for Gentamicin Delivery
Authors: Xu Xiaoxiang , Chen Heyin , Wu Xia , Chen Sen , Qi Jing , He Zuhong , Zou Shengyu , Xie Le , Xu Kai , Yuan Haitao , Sun Yu , Zheng Haoquan , Kong Weijia
Published: April 2018

We have synthesized hollow mesoporous silica (HMS) at a zeolitic imidazolate framework (ZIF) capsule that can be used as a drug delivery system for gentamicin (GM). The GM is first loaded into HMS. Then, the outer surface of the GM/HMS is coated with uniformed ZIF nanoparticles (denoted as GM/HMS@ZIF). The GM/HMS@ZIF has been successfully prepared and acts as a capsule for GM. The GM/HMS@ZIF shows a good biocompatibility and a good cellular uptake in House Ear Institute-Organ of Corti 1 (HEI-OC1) cells. The GM is released slowly within 10 h under acidic conditions, which is used to simulate the pH of the endosome and lysosome compartments. The in vivo assay shows that the signal from fluorescein isothiocyanate (FITC) can be observed after 15 days, when the mice were injected with FITC/HMS@ZIF. This opens new opportunities to construct a delivery system for GM via one controlled low dose and sustained release for the therapy of Ménière’s disease.
Dynamic Characteristics of Blade with Viscoelastic Damping Block Based on Complex Eigenvalue Method
Authors: Wang Jiao , Zhang Yue-hao , Yu Tao , Han Qing-kai
Published: April 2018

A novel method for vibration suppression is proposed, adding a viscoelastic damping block to the root of the blade. The dynamical equation for a rotational viscoelastic damping block‐blade (VE‐blade) in a centrifugal force field and aerodynamic force field is established to calculate the dynamical natural frequency and responses of the VE‐blade. Complex modulus model is applied to represent the constitutive law of viscoelastic material and shear force acting on the VE‐blade formulates the effect of viscoelastic damping at the root interfaces. The dynamical equation of the system is established and the Galerkin method is used to discretize the partial differential equations to a 3‐DOF system so as to compute the dynamic natural frequencies and responses of the VE‐blade. Then the differential equations of motion with 3‐DOF are numerically solved by using complex eigenvalue method. A cantilever VE‐blade is simplified according to testing the first three natural frequencies of the real blade to obtain geometric parameters of cantilever beam. The effects of various parameters including thickness, storage modulus, loss factor of viscoelastic damping block, and rotating speed on natural frequency and modal damping ratio of VE‐blade are discussed in detail.
Comparison Evaluations of VRF and RTU Systems Performance on Flexible Research Platform
Authors: Lee Je-hyeon , Im Piljae , Munk Jeffrey D. , Malhotra Mini , Kim Min-seok , Song Young-hak
Published: April 2018

The energy performance of a variable refrigerant flow (VRF) system was evaluated using an occupancy‐emulated research building in the southeastern region of the United States. Full‐ and part‐load performance of the VRF system in heating and cooling seasons was compared with a conventional rooftop unit (RTU) variable‐air‐volume system with electric resistance heating. During both the heating and cooling seasons, full‐ and part‐load conditions (i.e., 100%, 75%, and 50% thermal loads) were maintained alternately for 2 to 3 days each, and the energy use, thermal conditions, and coefficient of performance (COP) for the RTU and VRF system were measured. During the cooling season, the VRF system had an average COP of 4.2, 3.9, and 3.7 compared with 3.1, 3.0, and 2.5 for the RTU system under 100%, 75%, and 50% load conditions and resulted in estimated energy savings of 30%, 37%, and 47%, respectively. During the heating season, the VRF system had an average COP ranging from 1.2 to 2.0, substantially higher than the COPs of the RTU system, and resulted in estimated energy savings of 51%, 47%, and 27% under the three load conditions, respectively.