bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interaction of the Sigma‐1 Receptor with Endogenous Sphingolipids and Alkyl Amines
Authors: Ramachandran Subramaniam , Chu Uyen B. , Hajipour Abdol R. , Mavlyutov Timur , Jackson Meyer B. , Ruoho Arnold E. 
Published: June 2021

The sigma‐1 receptor (S1R) is a mammalian transmembrane protein implicated in anxiety, depression, schizophrenia, analgesia and drug dependence. The S1R displays promiscuous affinity for a range of pharmacological agents, however endogenous ligands are not known. Functions proposed for the S1R include ligand mediated chaperone activity, regulation of Ca2+ release, inhibition of K+ channels and antitumour effects.We have discovered that members of the class of endogenous sphingolipids (e.g. sphingosine, N, N’ dimethyl sphingosine) bind to the pure or membrane bound S1R with considerable affinity. While sphingosine binds to the S1R its phosphorylated counterpart sphingosine‐1 phosphate does not bind. Specific binding of sphingosine but not its phosphorylated analogue may indicate a mechanism for regulation of S1R function. Furthermore, the characteristics of sphingosine binding to the S1R appear to be different from a competitive interaction suggesting a possible allosteric role of these lipids at the receptor.In addition to sphingosine a series of aliphatic amines and their N‐substituted phenylpropyl derivatives were also found to interact with the S1R. These compounds modulated the voltage gated K+ channel, Kv1.4 expressed in HEK‐293 cells with EC50's for inhibition correlating strongly with their affinity at the S1R. These studies propose sphingosine as an endogenous modulator of the S1R and indicate a possible allosteric role for these lipids in S1R function and signal transduction.Supported by NIH R01MH065503
Macrophages mediate organophosphorus pesticide‐induced airway hyperreactivity in guinea pigs
Authors: Proskocil Becky J , Bruun Donald A , Jacoby David B , Lein Pamela J , Fryer Allison D 
Published: June 2021

Organophosphorus pesticide (OP) exposure is implicated in human asthma. At doses that do not inhibit acetycholinesterase, OPs such as parathion (Pth) block inhibitory neuronal M2 receptor function, which increases acetylcholine (ACh) release and potentiates vagally‐induced bronchoconstriction in guinea pigs. We tested whether macrophages mediate Pth‐induced airway hyperreactivity. Guinea pig alveolar macrophages were depleted with liposome‐encapsulated dichloromethylene‐diphosphonate (clodronate; prepared by Nico van Rooijen, Amsterdam) given intranasally 1 and 3 days prior to 1.0 mg/kg Pth sc. 24 hrs after Pth administration, animals were anesthetized and ventilated. In non‐Pth treated animals, bronchoconstriction induced by electrical stimulation of both vagus nerves was not affected by clodronate or PBS liposomes. Pth significantly potentiated bronchoconstriction in animals receiving PBS liposomes but did not potentiate bronchoconstriction in those pre‐treated with clodronate. ACh‐induced bronchoconstriction was not affected by any treatment, indicating that smooth muscle responsiveness was not changed. Macrophages mediate Pth‐induced airway hyperreactivity possibly by the release of interferon‐ã which decreases neuronal M2 RNA expression.Funding: NIH ES014521, ES014601, HL55543, HL54659, HL071795
Anatomical Differences in Response to Angiogenesis
Authors: Folkman Judah , Zaslavsky Alexander , Baek Kwan Hyuck , Chen Catherine , Ryeom Sandra 
Published: June 2021

Ten angiogenesis inhibitors are currently approved by the FDA in the U.S., to treat cancer and age‐related macular degeneration, and by regulatory agencies in >30 other countries.1 1,257,600 patients received prescriptions for these angiogenesis inhibitors during 2006.2 40 other antiangiogenic drugs are in late Phase III or Phase II clinical trials. Significant increases in survival have been reported for colorectal cancer, lung cancer and breast cancer. Of patients with progressive macular degeneration, 95% gain improved eyesight, and of those who are blind, 40% regain sight.3These clinical successes have increased the need to understand basic mechanisms of angiogenesis even beyond the level of detail that was necessary to discover angiogenesis inhibitors in the first place.One example is the differential result of angiogenic responses at different anatomic sites. In an animal model of human ovarian cancer, 5 of 5 tumor types in the lower abdominal cavity remain non‐angiogenic and do not grow beyond 1 mm.3 Tumors in the upper abdomen, are angiogenic and continue to expand to 140‐fold larger mass than lower abdominal tumors. The tumor cell proliferation rate is the same at both sites, but apoptosis is higher in non‐angiogenic tumors. In thrombospondin‐1 null mice all tumors in the lower abdomen become angiogenic and grow to an equivalent size as those in the upper abdomen. If both thrombospondin and endostatin are knocked out, the lower abdominal tumors are not only angiogenic, but are 3 times larger than the upper abdominal tumors.Conclusion: Potent endogenous angiogenesis inhibitors are differentially distributed in the stroma according to anatomical site.
Identification of a CFTR‐like Cl channel in A6 Distal Nephron Cells Under Hypotonic Conditions
Authors: Yu Ling , Helms My , Eaton Douglas C 
Published: June 2021

The osmolarity of fluid surrounding the renal collecting duct can change dramatically by several folds, and extreme changes in hypotonicity can cause tubular cells to immediately swell. Therefore, in order to prevent dramatic changes in cell volume, tubular epithelial cells can activate various transporters, such as K and Cl channels and secret KCl. Although swelling‐activated Cl channels have been intensively studied in various cell types, in most cases, the channel characteristics recorded in vivo are not comparable to studies performed with cloned Cl channels. In the present study, we were able to characterize a hypotonic‐activated Cl channel in A6 cells using single channel patch clamp analysis. We found that putative Cl channels can be activated by hypotonic bath solution (containing mainly KCl but not NaCl). These channels conduct both inward and outward current, and has single channel conductance of about 7–10 pS. After correcting for the liquid junction potential, the channel reversal potential does not significantly change by replacing pipette KCl with NMDG‐Cl. However, the channel activity is not seen when the pipette KCl is replaced by K‐Aspartic. Interestingly, the same channel is activated by cAMP, or PMA when the cells were bathed in isotonic solution. The conductance and kinetics of the channel that we describe above is similar to the CFTR Cl channel previously described by Ling et, al. JBC 272: 594–600, 1997.This work was supported by NIH grants HL071621‐01 and DK37963‐16 awarded to DCE.
Aquaporin 2 and Adducin Polymorphism Impact on Essential Hypertension
Authors: Procino Giuseppe , Romano Francesca , Mastrofrancesco Lisa , Tamma Grazia , Svelto Maria , Lanzani Chiara , Manunta Paolo , Bianchi Giuseppe , Valenti Giovanna 
Published: June 2021

Aim: In this study we tested the hypothesis that alteration in Aquaporin 2 (AQP2) expression/trafficking may contribute to the extracellular volume expansion observed in hypertension.Methods: To test this hypothesis we monitored the urinary AQP2 excretion in patients with essential hypertension carrying polymorphisms of the cytoskeletal protein adducin (ADD) known for increasing tubular sodium reabsorption. AQP2 urinary excretion was also measured in Milan Hypertensive Strain (MHS) rats carrying single nucleotide polymorphisms (SNPs) of ADD genes. AQP2 trafficking to the apical plasma membrane was also evaluated in MCD4 cells upon overexpression of human SNPs of ADD1 gene.Results: AQP2 excretion was significantly higher in hypertensive patients than in controls. In addition, after two hours of acute sodium load, AQP2 excretion was significantly higher in patients carrying ADD mutation. MHS rats showed a significant increase in total AQP2 protein and an increased expression at the apical plasma membrane compared to normotensive rats. In MCD4 cells, AQP2 trafficking to the apical plasma membrane was significantly increased upon co‐expression of mutated ADD.Conclusions: Taken together, these observations suggest that increase in AQP2 expression/trafficking possibly related to alteration of cytoskeleton structure, may contribute to the extracellular volume expansion observed in hypertension.
Arachidonic acid modulation of KV channel kinetics in retinal arteriolar myocytes
Authors: Kur Joanna , McGahon Mary K. , Scholfield C. Norman , McGeown J. Graham , Curtis Tim M. 
Published: June 2021

Recent studies have suggested that arachidonic acid (AA) may act as a vasoconstrictor in the brain and retina, but the mechanisms responsible are poorly understood. To address this issue, we examined the effects of AA on ionic currents in retinal vascular myocytes using the whole‐cell perforated patch‐clamp technique. AA (10μM) inhibited membrane currents between ‐20 and +40 mV (reduced from 19.72±4.34 to 1.64±1.88pA/pF at 0mV, n=7; P<0.005; Student's t‐test), although currents were enhanced at potentials positive to +60mV (increased from 87.14±22.02 to 203.53±29.68pA/pF at +100mV; n=7; P<0.005). As a first step in deciphering how AA modulates the membrane current, we isolated the A–type Kv current, which in these cells is carried mainly by Kv1.5+Kvβ1 containing channels (McGahon et al. 2007 Am J Physiol Heart Circ Physiol 292: H1001–8). AA modulated this current in two ways. It accelerated inactivation (control τ1=0.037±0.0033ms, τ2=0.37±0.064ms and AA τ1=0.016±0.0075ms, τ2=0.077±0.019ms; P<0.05 and P<0.001; n=8, step to +40mV), and shifted the voltage–dependence of inactivation to more negative potentials (V0.5control=−38.7±2.06mV and V0.5AA=−47.99±1.61mV; P<0.001, step to +60mV). This reduced the steady‐state “window” current at physiological membrane potentials. Effects of AA were observed within 30s of exposure and reached maximal effect at 7mins. We conclude that AA may act as a vasoconstrictor in the retinal vasculature by reducing steady–state Kv current leading to membrane potential depolarisation and an increased activation of voltage‐gated Ca2+ channels.Funded by Fight for Sight, UK, Wellcome Trust and JDRF.
Synthesis and breakdown of Very Low Density Lipoprotein Apo‐B100 measured with stable isotope methodology
Authors: Børsheim Elisabet , Tuvdendorj Demidmaa , Chinkes David L. , Volpi Elena , Zhang Xiao‐Jun , Aarsland Asle 
Published: June 2021

Increased concentration of Very Low Density Lipoprotein (VLDL) is an important and common risk factor for cardiovascular disease. VLDL concentration depends on the balance between synthesis and degradation, which can be influenced by many drugs and nutrients. The present study was designed to establish novel methods to simultaneously measure the fractional synthesis and breakdown rates of VLDL Apo‐B100. Six elderly (2 males, 4 females; 66.7 ± 2.4 (SE) years; 72.4 ± 6.8 kg) completed a study with constant infusion of two different tracers of leucine. 2H3‐leucine was infused for nine hours, whereas 1‐13C‐leucine was infused only for the first four hours. VLDL was isolated from plasma by ultracentrifugation, and Apo‐B100 was precipitated from this fraction by isopropanol. Basal Apo‐B100 fractional synthetic rate (FSR) was calculated from the linear part of the plasma enrichment slope of 2H3‐leucine vs. the plateau part of the slope. The fractional breakdown rate (FBR) of Apo‐B100 was obtained from the decay curve of the 1‐13C‐leucine, corrected for the incorporation of label. The basal FSR of Apo‐B100 was 18.33 ± 0.66 %/hr, whereas the FBR of Apo‐B100 was 16.31 ± 0.71 %/hr. These results are in agreement with previous reported measurements of Apo‐B100 secretion rates using isotope methodologies, and indicate that both fractional Apo‐B100 synthesis and breakdown can be reliably and simultaneously measured using stable isotopes.P30 AG024832 NIH/NIA, Shriners grant 8490, M01 RR 00073.
Threonine Requirement in Neonates Receiving Total Parenteral Nutrition (TPN)
Authors: Chapman Karen P. , Courtney‐Martin Glenda , Moore Aideen M. , Ball Ronald O. , Pencharz Paul B. 
Published: June 2021

Current neonatal threonine (THR) enteral requirement is 87 mg·kg‐1·d‐1. The THR requirement of the parenterally (TPN) fed human neonate has never been experimentally determined. Concentrations of THR in commercially available TPN solutions are derived from concentrations in cord blood, plasma amino acid profile during TPN feeding, or human milk, and are 30 to 80% higher than the enteral requirement. We showed in piglets that the neonatal TPN requirement for THR was 55% lower than the enteral requirement.Our objective was to determine the human neonatal TPN requirement for THR in post‐surgical neonates using the indicator amino acid oxidation technique with L[1–13C]phenylalanine. Neonates were randomized to receive one of twelve THR intakes ranging from 10 to 100 mg· kg‐1·d‐1. Preliminary data indicate a mean THR requirement between 30 and 40 mg·kg‐1·d‐1, only 30% of the THR concentration in the lowest THR containing TPN solution. We conclude that the THR requirement for TPN fed human neonates is significantly lower than the THR present in current TPN solutions and the recommended intake for orally fed infants. High THR intakes are a concern; THR is potentially neurotoxic and neonates are unable to oxidize excess
High salt intake enhances sympathetic modulation in the rat.
Authors: Farah Vera Azevedo , Fiorino Patricia , Roque Andre Prevides , Martins André Alves , Fonteles Manassés Claudino 
Published: June 2021

There is a significant association between salt intake and high blood pressure that could be related to alterations in autonomic modulation of cardiovascular system. The purpose of this study was to evaluate in rats the cardiovascular function induced by high salt intake. Male Wistar rats (n=5, each group) were divided in: 1) Control group (CG), without treatment and 2) Salt treatment (SG), salt added to the drinking water (1%) during 10 days. Arterial pressure (AP) was recorded and processed with a data acquisition system (2kHz sampling frequency). Systolic arterial pressure (SAP) and pulse interval (PI) time series were submitted to autoregressive spectral analysis to determine SAP and PI variability in time and frequency domains in order to evaluate autonomic influences on the circulation. AP was higher in SG (119 ± 2.2 mmHg) than in CG (104 ± 1.5 mmHg), whereas heart rate was not changed. There was an increase in SAP variance and its low frequency domain (9.3 ± 0.5 vs. 16.5 ± 1.5 mmHg2, variance and 6.3 ± 9.8 ± 0.5 mmHg2, LF, CG vs. SG). High salt intake also increased PI variability analyzed by either time (12 ± 0.8 vs. 27 ± 3.2 ms2, CG vs. SG) or frequency domains (9 ± 0.6 vs. 17 ± 1.5 ms2, CG vs. SG). The key findings of the present study were that high salt intake increased blood pressure that is associated with increased sympathetic modulation described herein.Financed by CNPq and MackPesquisa‐Brazil.
Consumption of a COX‐2 inhibitor stimulates muscle protein synthesis after resistance exercise in humans
Authors: Burd N A , Dickinson J M , LeMoine J K , Carroll C C , Haus J M , Hughes G , Sanders C , Trappe T A 
Published: June 2021

We have previously shown that non‐specific blockade of the cyclooxygenase (COX) enzymes in human skeletal muscle eliminates the normal increase in muscle protein synthesis following resistance exercise. We tested the hypothesis that this COX‐mediated increase in postexercise muscle protein synthesis is specifically regulated by the COX‐2 isoform. Sixteen males (23 ± 1 y, 177 ± 2 cm, 81.5 ± 3.4 kg) were randomly assigned to one of two groups that received three doses of either a specific COX‐2 inhibitor (celecoxib; 200 mg per dose, 600 mg total) or a placebo during the 24 h following a single bout of resistance exercise. Skeletal muscle fractional synthesis rate (FSR) was measured at rest and 24 hours postexercise. Mixed muscle FSR was increased following exercise to a greater extent (206%, p<0.05) in the COX‐2 group (0.052 ± 0.014 %/h) as compared with the placebo group (0.017 ± 0.007 %/h). These results suggest that specific inhibition of the COX‐2 isoform in human skeletal muscle causes a compensatory response in muscle protein synthesis. These data also highlight the involvement of the COX pathways in the regulation of muscle protein synthesis following resistance exercise.NIH R01 AG020532 (TT)
Inhibition of xanthine oxidase mediated reactive oxygen species during exercise attenuates mitochondrial biogenesis signalling in skeletal muscle
Authors: Wadley Glenn David , McConell Glenn 
Published: June 2021

INTRODUCTION:We tested the hypothesis that blocking the xanthine oxidase (XO)‐mediated increase in reactive oxygen species (ROS) with allopurinol during treadmill running in rats would inhibit phosphorylation of several key mitochondrial biogenesis signalling proteins.METHODS:Sprague Dawley rats rested (rest), exercised (Ex) or exercised following 30min pretreatment with 32 mg/kg of allopurinol by IP injection (Ex+allo). The exercise groups ran on a treadmill for 60 min (25m/min, 5% incline). Mitochondrial biogenesis signalling proteins were examined in the whole cell (phosphorylated p38 MAPK and AMPK) and nuclear fraction (phosphorylated CREB and ATF‐2) of the gastrocnemius via immunoblotting.RESULTS:Allopurinol treatment abolished the exercise‐induced phosphorylation of p38MAPK and ATF‐2 (P<0.05). There was a tendency (P=0.07) for exercise to increase phosphorylation of AMPK and allopurinol had no effect on this. CREB phosphorylation was not significantly different between groups.CONCLUSION:This data suggests that XO‐mediated increases in ROS during exercise are involved in some aspects of mitochondrial biogenesis signalling following exercise in skeletal muscle. Further studies are needed to examine if other aspects of the mitochondrial biogenesis pathway (eg PGC‐1 and NRF‐1) are also are also inhibited by allopurinol treatment during exercise.
The cysteine precursor L‐2‐oxothiazolidine‐4‐carboxylate does not delay diaphragm fatigue in vitro
Authors: Ferreira Leonardo F , Reid Michael B 
Published: June 2021

Metabolism of L‐2‐oxothiazolidine‐4‐carboxylate (OTC; Procysteine®) by 5‐oxoprolinase promotes intracellular cysteine and glutathione synthesis. The latter are important antioxidants in muscles. Therefore, we hypothesized that OTC would inhibit fatigue of diaphragm in vitro. Diaphragm strips from adult male ICR mice (n = 14) were incubated for 1 hr at 37 ºC with buffer (control, C) or OTC (10 mM) in an organ chamber. One min after completing a standardized force‐frequency protocol, muscles were stimulated (50 Hz, 500 ms train duration) every 2 s for 10 min. Force was measured at the onset and end of the fatigue trial. A fatigue index was calculated as the ratio of final‐to‐initial force. Data are presented as mean ± sem. Force developed at the onset of the fatigue protocol (C = 12.3 ± 2.3 N/cm2, OTC = 11.3 ± 1.5 N/cm2; p = 0.30) and the fatigue index (C = 0.43 ± 0.03, OTC = 0.51 ± 0.06; p = 0.45) were not different between control and OTC‐treated muscles. These results show that 10 mM OTC does not diminish diaphragm fatigue in vitro, and suggest that OTC may not be an effective treatment for muscle fatigue in vivo.Financial Support: AHA Postdoctoral Fellowship (0725334B) and NASA/NSBRI (MA00209)
Chemotherapeutic drug effects on spontaneous mobility and swimming endurance of mice
Authors: Pagala Murali K , Kharode Ishita , Dahan Nessy , Arama Leron 
Published: June 2021

Muscle weakness and enhanced fatigue are common complaints of cancer patients undergoing chemotherapy. In order to evaluate the underlying mechanisms, the present study assessed the acute effects of the chemotherapeutic drug, doxorubicin, on spontaneous motor activity and swimming performance of mice. Before and after i.p. injection of doxorubicin at 25 mg/kg into each mouse, the number of spontaneous movements was monitored for 24 hr using Columbus Instruments Opto‐varimax‐mini activity meter, and the integrated swimming activity (V.sec) was recorded for 40 min using a digital swimming monitor (Pagala, 1999).Doxorubicin, within the clinical dose range, significantly reduced the stereotypic, ambulatory, and thus the total number of spontaneous movements of the mice in a 24 hr period (Table 1). Doxorubicin also caused a significant reduction in the integrated swimming activity of the mice over a 40 min period (Table 1). These results indicate that chemotherapeutic agents may significantly decrease the motivation and endurance for physical activity.Supported by a special grant from Maimonides Med. Ctr.
Distribution of KATP channel among the different fiber types in skeletal muscle.
Authors: Banas Krystyna , Renaud Jean‐Marc 
Published: June 2021

The ATP‐sensitive K+ channel (KATP channel) is essential in preventing contractile dysfunctions during exercise and fatigue in skeletal muscle (Cifelli et al. 2007. J. Physiol. 582:843). The extent of the contractile dysfunctions varies in the order of FDB = EDL ≫ soleus. Our studies and others have shown that, in mouse, FDB is composed primarily of type IIA and IIX fibers, the EDL has primarily IIB and IIX while soleus is composed of I and IIA. The objective of this study was to test the hypothesis that the protein content for the KATP channel is in the order of I < IIA ≪ IIB = IIX. Fiber types were identified using specific antibodies for each of the four myosin isoforms while the KATP channel was quantify using an antibody against the Kir6.2 subunit, which forms the pore of the channel. The data showed large Kir6.2 protein content in type IIA fibers of FDB and soleus, while very low levels were found in these same fibers in EDL. Type IIB (EDL only) and type IIX fibers (EDL & FDB) contained large amount of Kir6.2, while type I (FDB and soleus) had the lowest content. It is concluded that the expression of the Kir6.2 subunit of the KATP channel not only vary among fiber types, but also for type IIA fibers among different muscles.Research supported by an operating grant from the Natural Sciences and Engineering Council of Canada (NSERC).
Dietary Cholesterol and Skeletal Muscle Hypertrophy with Resistance Training: A Randomized Placebo‐Controlled Trial
Authors: Riechman Steven E , Lee Chang Woock , Gasier Heath G , Chikani Gentle 
Published: June 2021

Background:We recently reported a strong positive association of dietary cholesterol and skeletal muscle responses to resistance training (Riechman, 2007). To confirm these findings we conducted a randomized placebo controlled trial in which we supplemented the diet with whole egg or egg white (control).Methods:3 groups of 50–69 year old generally healthy subjects (N=30) underwent 12 weeks of resistance exercise training (RET, 3x/week, 2–3 sets, 8–12 reps, 70% of max strength). Each group consumed 3.5 mg/kg lean/day (<200 mg/day, LC), 7.0 mg/kg lean/day (∼400 mg/day, MC), or 14.0 mg/kg lean/day (∼800 mg/day, HC) of cholesterol. Subjects were asked to complete 48 food records over the 12 wks to confirm dietary compliance. Body composition (DEXA) and maximal strength tests were conducted before and after the training.Results:Summary strength gain (chest press +leg press) was increased significantly (P<0.05) with increasing dietary cholesterol (HC=52±8%, MC=38±8%, LC=21±8%). The mean gain in lean mass was 1.7±1.0 kg (3.7%) where subjects also lost 0.5±1.7 kg of fat mass (1.6%). Changes in lean mass and fat mass between groups was not significantly different (P>0.05).Conclusion:Our results confirm our previous finding that high dietary cholesterol contributes to strength gain with resistance training; however, lean mass gains were inconsistent. Supported by US Poultry and Egg Association.