bluuebunny/crossref_metadata_2025 huggingface dataset:
Maintenance and recovery stages of postischemic acute renal failure in humans
Authors: Ramaswamy Deepa , Corrigan Geraldine , Polhemus Catherine , Boothroyd Derek , Scandling John , Sommer F. Graham , Alfrey Edward , Higgins John , Deen William M. , Olshen Richard , Myers Bryan D.
Published: March 2015

Postischemic injury in 38 recipients of 7-day-old cadaveric renal allografts was classified into sustained ( n = 15) or recovering ( n = 23) acute renal failure (ARF) according to the prevailing inulin clearance. Recipients of long-standing allografts that functioned optimally ( n = 16) and living transplant donors undergoing nephrectomy ( n = 10) served as functional and structural controls, respectively. A combination of physiological and morphometric techniques were used to evaluate glomerular filtration rate and its determinants 1–3 h after reperfusion and again on day 7 to elucidate the mechanism for persistent hypofiltration in ARF that is sustained. Glomerular filtration rate in the sustained ARF group on day 7 was depressed by 90% (mean ± SD); the corresponding fall in renal plasma flow was proportionately less. Neither plasma oncotic pressure nor the single-nephron ultrafiltration coefficient differed between the sustained ARF and the control group, however. A model of glomerular ultrafiltration and a sensitivity analysis were used to compute the prevailing transcapillary hydraulic pressure gradient (ΔP), the only remaining determinant of ΔP. This revealed that ΔP varied between 27 and 28 mmHg in sustained ARF and 32–38 mmHg in recovering ARF on day 7 vs. 47–54 mmHg in controls. Sustained ARF was associated with persistent tubular dilatation. We conclude that depression of ΔP, perhaps due partially to elevated tubule pressure, is the predominant cause of hypofiltration in the maintenance stage of ARF that is sustained for 7 days.
Rho inhibits cAMP-induced translocation of aquaporin-2 into the apical membrane of renal cells
Authors: Tamma Grazia , Klussmann Enno , Maric Kenan , Aktories Klaus , Svelto Maria , Rosenthal Walter , Valenti Giovanna
Published: March 2015

First published August 8, 2001; 10.1152/ajprenal.00091.2001.—We have recently demonstrated that actin depolymerization is a prerequisite for cAMP-dependent translocation of the water channel aquaporin-2 (AQP2) into the apical membrane in AQP2-transfected renal CD8 cells (29). The Rho family of small GTPases, including Cdc42, Rac, and Rho, regulates the actin cytoskeleton. In AQP2-transfected CD8 cells, inhibition of Rho GTPases with Clostridium difficile toxin B or with C. limosum C3 fusion toxin, as well as incubation with the Rho kinase inhibitor, Y-27632, caused actin depolymerization and translocation of AQP2 in the absence of the cAMP-elevating agent forskolin. Both forskolin and C3 fusion toxin-induced AQP2 translocation were associated with a similar increase in the osmotic water permeability coefficient. Expression of constitutively active RhoA induced formation of stress fibers and abolished AQP2 translocation in response to forskolin. Cytochalasin D induced both depolymerization of F-actin and AQP2 translocation, suggesting that depolymerization of F-actin is sufficient to induce AQP2 translocation. Together, these data indicate that Rho inhibits cAMP-dependent translocation of AQP2 into the apical membrane of renal principal cells by controlling the organization of the actin cytoskeleton.
Murine and human type I Na-phosphate cotransporter genes: structure and promoter activity
Authors: Soumounou Youssouf , Gauthier Claude , Tenenhouse Harriet S.
Published: March 2015

First published August 15, 2001; 10.1152/ajprenal.00092.2001.—Na-phosphate (Pi) cotransporters in the apical membrane of renal proximal tubular cells play a major role in the maintenance of Pihomeostasis. Although two such cotransporters, Npt1 and Npt2, have been identified, little is known about the function and regulation of Npt1. We cloned and characterized the murine ( Npt1) and human ( NPT1) genes, isolated the 5′-flanking region of Npt1, and analyzed its promoter activity. Npt1 is ∼29 kb with 12 exons, whereas NPT1 is ∼49 kb with one additional exon. The Npt1 promoter has a TATA-like box but no CAAT box, and the transcription start site was identified by primer extension and 5′-rapid amplification of cDNA ends. Transfection of opossum kidney cells with Npt1 promoter-reporter gene constructs demonstrated significant activity in a 570-bp fragment that was completely inhibited by cotransfection with the transcription factor, hepatocyte nuclear factor (HNF)-3β. Deletion of 200 bp from the 3′-end of the 570-bp fragment abrogated its promoter activity. In addition, promoter activity of a 4.5-kb fragment, but not the 570-bp fragment, was stimulated fourfold by cotransfection with HNF-1α. Other well-characterized cis-acting elements were identified in the Npt1 promoter. We suggest that Npt1 expression is transcriptionally regulated and provide a basis for the investigation of Npt1 function by targeted mutagenesis.
Novel Schering and ouabain-insensitive potassium-dependent proton secretion in the mouse cortical collecting duct
Authors: Petrovic Snezana , Spicer Zachary , Greeley Tracey , Shull Gary E , Soleimani Manoocher
Published: March 2015

The intercalated (IC) cells of the cortical collecting duct (CCD) are important to acid-base homeostasis by secreting acid and reabsorbing bicarbonate. Acid secretion is mediated predominantly by apical membrane Schering (SCH-28080)-sensitive H+-K+- ATPase (HKA) and bafilomycin-sensitive H+-ATPase. The SCH-28080-sensitive HKA is believed to be the gastric HKA (HKAg). Here we examined apical membrane potassium-dependent proton secretion in IC cells of wild-type HKAg (+/+) and HKAg knockout (−/−) mice to determine relative contribution of HKAg to luminal proton secretion. The results demonstrated that HKAg (−/−) and wild-type mice had comparable rates of potassium-dependent proton secretion, with HKAg (−/−) mice having 100% of K+-dependent H+secretion vs. wild-type mice. Potassium-dependent proton secretion was resistant to ouabain and SCH-28080 in HKAg knockout mice but was sensitive to SCH-28080 in wild-type animals. Northern hybridizations did not demonstrate any upregulation of colonic HKA in HKAg knockout mice. These data indicate the presence of a previously unrecognized K+-dependent SCH-28080 and ouabain-insensitive proton secretory mechanism in the cortical collecting tubule that may play an important role in acid-base homeostasis.
Aquaporin-2: COOH terminus is necessary but not sufficient for routing to the apical membrane
Authors: Deen Peter M. T. , Van Balkom Bas W. M. , Savelkoul Paul J. M. , Kamsteeg Erik-Jan , Van Raak Marcel , Jennings Michael L. , Muth Theodoor R. , Rajendran Vanathy , Caplan Michael J.
Published: March 2015

Renal regulation of mammalian water homeostasis is mediated by the aquaporin-1 (AQP1) water channel, which is expressed in the apical and basolateral membranes of proximal tubules and descending limbs of Henle, and aquaporin-2 (AQP2), which is redistributed from intracellular vesicles to the apical membrane (AM) of collecting duct cells with vasopressin. In transfected Madin-Darby canine kidney cells, AQP1 and AQP2 are regulated similarly, which indicates that routing elements reside in their primary sequences. We studied the role of the AQP2 COOH terminus in apical routing and AQP2 shuttling. An AQP1 chimera (AQP1 with an AQP2 tail: AQP1/2-N220) was located only in the AM independent of forskolin treatment. Forskolin increased the apical expression of AQP1 and AQP1/2-N220 less than twofold; that of AQP2 increased more than fourfold with concomitant changes in osmotic water permeabilities. The dimeric AQP2 tail coupled to placental alkaline phosphatase (AQP2-Plap) was retained in intracellular vesicles different from those of homotetrameric wild-type AQP2; the same protein without the AQP2 tail (TMR-Plap) was only expressed in the AM. The study shows that the AQP2 COOH tail is necessary but not sufficient for routing to the AM and suggests that other parts of AQP2 are needed for AQP2 accumulation in intracellular vesicles.
Renal principal cell-specific expression of green fluorescent protein in transgenic mice
Authors: Zharkikh Ludmilla , Zhu Xiaohong , Stricklett Peter K. , Kohan Donald E. , Chipman Greg , Breton Sylvie , Brown Dennis , Nelson Raoul D.
Published: March 2015

The purpose of this study is to develop transgenic mice with principal cell-specific expression of green fluorescent protein (GFP). After the cloning and sequencing of the mouse aquaporin-2 (AQP2) gene, 9.5 kb of the promoter were used to drive expression of GFP in transgenic mice. In transgenic mice, GFP was selectively expressed in principal cells of the renal collecting duct and not in intercalated cells. Expression was increased by dehydration of mice. AQP2 and GFP expression was maintained in primary cultures of renal medulla that were stimulated with cAMP or vasopressin analogs. GFP-expressing cells were then isolated by fluorescence-activated cell sorting. RT-PCR analysis showed expression of AQP2, AQP3, AQP4, vasopressin type 2 receptor, and cAMP response element binding protein but not H+-ATPase B1 subunit or anion exchanger 1. After expansion of these cells in culture, RT-PCR analysis showed continued expression of the same genes. This pattern of gene expression is that of principal cells rather than intercalated cells. This transgenic mouse model can be used in future studies of gene expression during the development, differentiation, and maturation of renal principal cells.
Upregulation of H+-peptide cotransporter PEPT2 in rat remnant kidney
Authors: Takahashi Kazushige , Masuda Satohiro , Nakamura Nobuhiko , Saito Hideyuki , Futami Takahiro , Doi Toshio , Inui Ken-Ichi
Published: March 2015

First published August 21, 2001; 10.1152/ajprenal.0346.2001.—The progression of renal damage resulting from reduced nephron mass has been extensively studied in the 5/6 nephrectomized rat. However, reabsorption of small peptides andd-glucose across the renal proximal tubule in this model remains poorly understood. In this study, we examined the alterations of H+-peptide cotransporters (PEPT1 and PEPT2) and Na+-d-glucose cotransporters (SGLT1 and SGLT2) in chronic renal failure. Two weeks after surgery, H+-dependent [14C]glycylsarcosine uptake by the renal brush-border membrane vesicles isolated from 5/6 nephrectomized rats was significantly increased compared with that from sham-operated controls. Kinetic analysis revealed that the maximum velocity value for [14C]glycylsarcosine uptake by the high-affinity-type of peptide transporter was increased threefold by 5/6 nephrectomy, without significant changes in the apparent Michaelis-Menten constant value. Competitive PCR analyses indicated that the expression of PEPT2 mRNA was markedly increased in the remnant kidney, but PEPT1, SGLT1, and SGLT2 mRNA levels showed no significant changes. These findings indicated that the high-affinity-type H+-peptide cotransport activity is upregulated by 5/6 nephrectomy, accompanied by the increased expression of PEPT2. The upregulation of PEPT2 expression would result in an increase in reabsorption of small peptides and peptide-like drugs across the brush-border membranes in chronic renal failure.
IGF-I, IgA, and IgG responses to bovine colostrum supplementation during training
Authors: Mero Antti , Kähkönen Jonne , Nykänen Tarja , Parviainen Tapani , Jokinen Ilmari , Takala Timo , Nikula Tuomo , Rasi Simo , Leppäluoto Juhani
Published: March 2015

This study examined the effect of bovine colostrum (Dynamic colostrum) supplementation on blood and saliva variables ( study 1) and the absorption of orally administered human recombinant insulin-like growth factor (IGF)-I (rhIGF-I) labeled with 123I (123I-rhIGF-I) ( study 2). In study 1, adult male and female athletes were randomly assigned in a double-blind fashion to either an experimental (Dynamic; n = 19) or a control (Placebo; n = 11) group. The former consumed daily 20 g of Dynamic supplement, and the latter 20 g of maltodextrin during a 2-wk training period. After bovine colostrum supplementation, significant increases were noticed in serum IGF-I ( P < 0.01) and saliva IgA ( P < 0.01) in Dynamic compared with Placebo. In study 2, gel electrophoresis was carried out in 12 adult subjects with serum samples taken 60 min after ingestion of123I-rhIGF-I and showed peaks at 0.6 and at 40–90 kDa, with the former inducing 96% and the latter 4% of the total radioactivity. It was concluded that a long-term supplementation of bovine colostrum (Dynamic) increases serum IGF-I and saliva IgA concentration in athletes during training. Absorption data show that ingested 123I-rhIGF-I is fragmented in circulation and that no radioactive IGF-I is eluted at the positions of free, or the IGF, binding proteins, giving no support to the absorption of IGF-I from bovine colostrum.
Pulmonary responses to tracheal or esophageal acidification in guinea pigs with airway inflammation
Authors: Lopes Fernanda D. T. Q. S. , Alvarenga Glauco S. , Quiles Raquel , Dorna Mayra B. , Vieira Joaquim E. , Dolhnikoff Marisa , Martins Milton A.
Published: March 2015

The association between asthma and gastroesophageal reflux has been attributed to microaspiration of gastric contents and/or vagally mediated reflex bronchoconstriction. In previous experimental studies concerning the pulmonary effects of tracheal or esophageal acid infusion, only animals without airway inflammation have been studied. We assessed the effects of esophageal and tracheal administration of hydrochloric acid (HCl) on normal guinea pigs (GP) and GP with airway inflammation induced by repeated ovalbumin exposures. These GP were anesthetized (pentobarbital sodium) and received 1) 20 μl of either 0.2 N HCl or saline into the trachea, or 2) 1 ml of either 1 N HCl or saline into the esophagus. Intratracheal HCl resulted in a significant increase in both respiratory system elastance and resistance ( P < 0.001). There were no significant changes in respiratory mechanics when HCl was infused into the esophagus. In conclusion, we observed that infusion of large volumes of HCl into the esophagus did not change pulmonary mechanics significantly, even in guinea pigs with chronic allergen-induced airway inflammation. In contrast, intratracheal administration of small amounts of acid had substantial effects in normal GP and GP with airway inflammation.
Reduced respiratory-related evoked activity in subjects with obstructive sleep apnea syndrome
Authors: Akay Metin , Leiter J. C. , Daubenspeck J. Andrew
Published: March 2015

Midlatency respiratory-related evoked potentials were measured during wakefulness by using a 60-electrode array placed over the cortical region of the scalp. We studied the responses evoked by 200-ms pressure pulses at −5 and −10 cmH2O applied at inspiratory onset and during control tests (no pressure applied) in 14 subjects with obstructive sleep apnea syndrome (OSAS) and 18 normal subjects. Wavelet decomposition was used to smooth and dissect the respiratory-related evoked potentials in frequency and time in 8 frequency bands. After denoising, selected wavelet scales were used to reconstruct the respiratory-related evoked potentials, which were quantified by using global field power estimates. The time course of the global field power activity in OSAS subjects compared with normal subjects was significantly depressed in the period 55–70 ms poststimulus onset, a time when afferent traffic from upper airway receptors arrives in normal subjects. The reduced evoked response in subjects with OSAS suggests that these subjects receive less afferent input from upper airway mechanoreceptors. This may reflect reduced sensitivity of mechanoreceptors or reduced mechanoreceptor stimulation due to decreased upper airway compliance during wakefulness in OSAS.
Interactive effects of mental and physical stress on cardiovascular control
Authors: Wasmund Wendy L. , Westerholm Erin C. , Watenpaugh Donald E. , Wasmund Stephen L. , Smith Michael L.
Published: March 2015

Physiological responses to mental tasks and physical exercise were studied independently and combined. We hypothesized that combined mental and physical stresses produce a synergistic interaction. We studied cardiovascular responses to 5 min of static handgrip, mental arithmetic, and the combined stimuli in random order in 12 healthy subjects. Muscle sympathetic nerve activity (SNA) and mean arterial blood pressure (MAP) responses to handgrip and the combined stimuli exceeded responses to mental arithmetic, yet no significant difference existed between responses to handgrip and the combined stimuli. Peak changes in SNA (in %) were greatest during handgrip (188 ± 41), followed by the combined stimuli (166 ± 31) and mental arithmetic (51 ± 9). Peak changes in MAP (in mmHg) were also greatest during handgrip (26 ± 4), followed by the combined stimuli (23 ± 3) and then mental arithmetic (8 ± 2). Peak changes in heart rate (in beats/min) followed the same trend: handgrip (15 ± 2), combined (13 ± 2), and mental arithmetic (10 ± 2). Mental stimulation did not synergistically interact with or add to the responses elicited by handgrip exercise; in fact, a trend existed for math during handgrip to reduce responses relative to handgrip alone.
Ventilatory phenotypes among four strains of adult rats
Authors: Hodges Matthew R. , Forster Hubert V. , Papanek Paula E. , Dwinell Melinda R. , Hogan Genevieve E.
Published: March 2015

Our purpose in this study was to identify different ventilatory phenotypes among four different strains of rats. We examined 114 rats from three in-house, inbred strains and one outbred strain: Brown Norway (BN; n = 26), Dahl salt-sensitive ( n = 24), Fawn-hooded Hypertensive (FHH: n = 27), and outbred Sprague-Dawley rats (SD; n = 37). We measured eupneic (room air) breathing and the ventilatory responses to hypoxia (12% O2-88% N2), hypercapnia (7% CO2), and two levels of submaximal exercise. Primary strain differences were between BN and the other strains. BN rats had a relatively attenuated ventilatory response to CO2( P < 0.001), an accentuated ventilatory response to exercise ( P < 0.05), and an accentuated ventilatory roll-off during hypoxia ( P < 0.05). Ventilation during hypoxia was lower than other strains, but hyperventilation during hypoxia was equal to the other strains ( P > 0.05), indicating that the metabolic rate during hypoxia decreased more in BN rats than in other strains. Another strain difference was in the frequency and timing components of augmented breaths, where FHH rats frequently differed from the other strains, and the BN rats had the longest expiratory time of the augmented breaths (probably secondary to the blunted CO2sensitivity). These strain differences not only provide insight into physiological mechanisms but also indicate traits (such as CO2sensitivity) that are genetically regulated. Finally, the data establish a foundation for physiological genomic studies aimed at elucidating the genetics of these ventilatory control mechanisms.
Phonospirometry for noninvasive measurement of ventilation: methodology and preliminary results
Authors: Que Cheng-Li , Kolmaga Christof , Durand Louis-Gilles , Kelly Suzanne M. , Macklem Peter T.
Published: March 2015

We measured tracheal flow from tracheal sounds to estimate tidal volume, minute ventilation (V˙i), respiratory frequency, mean inspiratory flow (Vt/Ti), and duty cycle (Ti/Ttot). In 11 normal subjects, 3 patients with unstable airway obstruction, and 3 stable asthmatic patients, we measured tracheal sounds and flow twice: first to derive flow-sound relationships and second to obtain flow-volume relationships from the sound signal. The flow-volume relationship was compared with pneumotach-derived volume. When subjects were seated, facing forward and with neck rotation, flexion, and standing, flow-volume relationship was within 15% of pneumotach-derived volume. Error increased with neck extension and while supine. We then measured ventilation without mouthpiece or nose clip from tracheal sounds during quiet breathing for up to 30 min. Normal results ± SD revealed tidal volume = 0.37 ± 0.065 liter, respiratory frequency = 19.3 ± 3.5 breaths/min, V˙i = 6.9 ± 1.2 l/min, Vt/Ti = 0.31 ± 0.06 l/s, and Ti/Ttot = 0.37 ± 0.04. Unstable airway obstruction had large V˙i due to increased Vt/Ti. With the exception of Ti/Ttot, variations in ventilatory parameters were closer to log normal than normal distributions and tended to be greater in patients. We conclude that phonospirometry measures ventilation reasonably accurately without mouthpiece, nose clip, or rigid postural constraints.
Acetylcholine released from cholinergic nerves contributes to cutaneous vasodilation during heat stress
Authors: Shibasaki Manabu , Wilson Thad E. , Cui Jian , Crandall Craig G.
Published: March 2015

Nitric oxide (NO) contributes to active cutaneous vasodilation during a heat stress in humans. Given that acetylcholine is released from cholinergic nerves during whole body heating, coupled with evidence that acetylcholine causes vasodilation via NO mechanisms, it is possible that release of acetylcholine in the dermal space contributes to cutaneous vasodilation during a heat stress. To test this hypothesis, in seven subjects skin blood flow (SkBF) and sweat rate were simultaneously monitored over three microdialysis membranes placed in the dermal space of dorsal forearm skin. One membrane was perfused with the acetylcholinesterase inhibitor neostigmine (10 μM), the second membrane was perfused with the NO synthase inhibitor N G-nitro-l-arginine methyl ester (l-NAME; 10 mM) dissolved in the aforementioned neostigmine solution (l-NAMENeo), and the third membrane was perfused with Ringer solution as a control site. Each subject was exposed to ∼20 min of whole body heating via a water-perfused suit, which increased mean body temperature from 36.4 ± 0.1 to 37.5 ± 0.1°C ( P < 0.05). After the heat stress, SkBF at each site was normalized to its maximum value, identified by administration of 28 mM sodium nitroprusside. Mean body temperature threshold for cutaneous vasodilation was significantly lower at the neostigmine-treated site relative to the other sites (neostigmine: 36.6 ± 0.1°C, l-NAMENeo: 37.1 ± 0.1°C, control: 36.9 ± 0.1°C), whereas no significant threshold difference was observed between thel-NAMENeo-treated and control sites. At the end of the heat stress, SkBF was not different between the neostigmine-treated and control sites, whereas SkBF at thel-NAMENeo-treated site was significantly lower than the other sites. These results suggest that acetylcholine released from cholinergic nerves is capable of modulating cutaneous vasodilation via NO synthase mechanisms early in the heat stress but not after substantial cutaneous vasodilation.
Prior exercise increases basal and insulin-induced p38 mitogen-activated protein kinase phosphorylation in human skeletal muscle
Authors: Thong Farah S. L. , Derave Wim , Ursø Birgitte , Kiens Bente , Richter Erik A.
Published: March 2015

We have examined the effects of insulin on p38 mitogen-activated protein kinase (MAPK) phosphorylation in human skeletal muscle and the effects of prior exercise hereon. Seven men performed 1-h one-legged knee extensor exercise 3 h before the initiation of a 100-min euglycemic-hyperinsulinemic (600 pmol/l) clamp. Glucose uptake across the legs was measured with the leg balance technique, and muscle biopsies were obtained from the rested and exercised vastus lateralis before and during insulin infusion. Net glucose uptake during the clamp was ∼50% higher ( P< 0.05) in the exercised leg than in the rested leg. Insulin induced a modest sustained 1.2- and 1.3-fold increase ( P < 0.05) in p38 MAPK phosphorylation in the rested and exercised legs, respectively. However, p38 phosphorylation was ∼50% higher ( P < 0.05) in the exercised compared with the rested leg before and during insulin infusion. We conclude that a physiological concentration of insulin causes modest but sustained activation of the p38 MAPK pathway in human skeletal muscle. Furthermore, the stimulatory effect of exercise on p38 phosphorylation is persistent for at least 3 h after exercise and remains evident during subsequent insulin stimulation. Because p38 MAPK has been suggested to play a necessary role in activation of GLUT-4 at the cell surface, the present data may suggest a putative role of p38 MAPK in the increased insulin sensitivity of skeletal muscle after exercise.
A reevaluation of the validity of unrestrained plethysmography in mice
Authors: Lundblad Lennart K. A. , Irvin Charles G. , Adler Andy , Bates Jason H. T.
Published: March 2015

Presently, unrestrained plethysmography is widely used to assess bronchial responsiveness in mice. An empirical quantity known as enhanced pause is derived from the plethysmographic box pressure [Pb( t), where t is time] and assumed to be an index of bronchoconstriction. We show that Pb( t) is determined largely by gas conditioning when normal mice breathe spontaneously inside a closed chamber in which the air is at ambient conditions. When the air in the chamber is heated and humidified to body conditions, the changes in Pb( t) are reduced by about two-thirds. The remaining changes are thus due to gas compression and expansion within the lung and are amplified when the animals breathe through increased resistances. We show that the time integral of Pb( t) over inspiration is accurately predicted by a term containing airway resistance, functional residual capacity, and tidal volume. We conclude that unrestrained plethysmography can be used to accurately characterize changes in airway resistance only if functional residual capacity and tidal volume are measured independently and the chamber gas is preconditioned to body temperature and humidity.
Invited Review: Clearance of lung liquid during the perinatal period
Authors: Barker Pierre M. , Olver Richard E.
Published: March 2015

At birth, the distal lung epithelium undergoes a profound phenotypic switch from secretion to absorption in the course of adaptation to air breathing. In this review, we describe the developmental regulation of key membrane transport proteins and the way in which epinephrine, oxygen, glucocorticoids, and thyroid hormones interact to bring about this crucial change in function. Evidence from molecular, transgenic, cell culture, and whole lung studies is presented, and the clinical consequences of the failure of the physiological mechanisms that underlie perinatal lung liquid absorption are discussed.
Experimental determination of net protein charge and AtotandKaof nonvolatile buffers in human plasma
Authors: Staempfli Henry R. , Constable Peter D.
Published: March 2015

The mechanism for an acid-base disturbance can be determined by using the strong ion approach, which requires species-specific values for the total concentration of plasma nonvolatile buffers (Atot) and the effective dissociation constant for plasma weak acids ( Ka). The aim of this study was to experimentally determine Atotand Kavalues for human plasma by using in vitro CO2tonometry. Plasma Pco2was systematically varied from 25 to 145 Torr at 37°C, thereby altering plasma pH over the physiological range of 6.90–7.55, and plasma pH, Pco2, and concentrations of quantitatively important strong ions (Na+, K+, Ca2+, Mg2+, Cl-, lactate) and buffer ions (total protein, albumin, phosphate) were measured. Strong ion difference was estimated, and nonlinear regression was used to calculate Atotand Kafrom the measured pH and Pco2and estimated strong ion difference; the Atotand Kavalues were then validated by using a published data set (Figge J, Rossing TH, and Fencl V, J Lab Clin Med 117: 453–467, 1991). The values (mean ± SD) were as follows: Atot= 17.2 ± 3.5 mmol/l (equivalent to 0.224 mmol/g of protein or 0.378 mmol/g of albumin); Ka= 0.80 ± 0.60 × 10-7; negative log of Ka= 7.10. Mean estimates were obtained for strong ion difference (37 meq/l) and net protein charge (13+.0 meq/l). The experimentally determined values for Atot, Ka, and net protein charge should facilitate the diagnosis and treatment of acid-base disturbances in critically ill humans.
Role of skin blood flow and sweating rate in exercise thermoregulation after bed rest
Authors: Lee Stuart M. C. , Williams W. Jon , Schneider Suzanne M.
Published: March 2015

Two potential mechanisms, reduced skin blood flow (SBF) and sweating rate (SR), may be responsible for elevated intestinal temperature (Tin) during exercise after bed rest and spaceflight. Seven men underwent 13 days of 6° head-down bed rest. Pre- and post-bed rest, subjects completed supine submaximal cycle ergometry (20 min at 40% and 20 min at 65% of pre-bed rest supine peak exercise capacity) in a thermoneutral room. After bed rest, Tin was elevated at rest (+0.31 ± 0.12°C) and at the end of exercise (+0.33 ± 0.07°C). Percent increase in SBF during exercise was less after bed rest (211 ± 53 vs. 96 ± 31%; P ≤ 0.05), SBF/Tin threshold was greater (37.09 ± 0.16 vs. 37.33 ± 0.13°C; P ≤ 0.05), and slope of SBF/Tin tended to be reduced (536 ± 184 vs. 201 ± 46%/°C; P = 0.08). SR/Tin threshold was delayed (37.06 ± 0.11 vs. 37.34 ± 0.06°C; P ≤ 0.05), but the slope of SR/Tin(3.45 ± 1.22 vs. 2.58 ± 0.71 mg · min−1 · cm−2 · °C−1) and total sweat loss (0.42 ± 0.06 vs. 0.44 ± 0.08 kg) were not changed. The higher resting and exercise Tin and delayed onset of SBF and SR suggest a centrally mediated elevation in the thermoregulatory set point during bed rest exposure.
Substance P released from intrinsic airway neurons contributes to ozone-enhanced airway hyperresponsiveness in ferret trachea
Authors: Wu Zhong-Xin , Satterfield Brian E. , Dey Richard D.
Published: March 2015

Exposure to ozone (O3) induces airway hyperresponsiveness mediated partly through the release of substance P (SP) from nerve terminals in the airway wall. Although substantial evidence suggests that SP is released by sensory nerves, SP is also present in neurons of airway ganglia. The purpose of this study was to investigate the role of intrinsic airway neurons in O3-enhanced airway responsiveness in ferret trachea. To remove the effects of sensory innervation, segments of ferret trachea were maintained in culture conditions for 24 h before in vitro exposure to 2 parts/million of O3 or air for 1 h. Sensory nerve depletion was confirmed by showing that capsaicin did not affect tracheal smooth muscle responsiveness to cholinergic agonist or contractility responses to electrical field stimulation (EFS). Contractions of isolated tracheal smooth muscle to EFS were significantly increased after in vitro O3 exposure, but the constrictor response to cholinergic agonist was not altered. Pretreatment with CP-99994, an antagonist of the neurokinin 1 receptor, attenuated the increased contraction to EFS after O3 exposure but had no effect in the air exposure group. The number of SP-positive neurons in longitudinal trunk ganglia, the extent of SP innervation to superficial muscular plexus nerve cell bodies, and SP nerve fiber density in tracheal smooth muscle all increased significantly after O3 exposure. The results show that release of SP from intrinsic airway neurons contributes to O3-enhanced tracheal smooth muscle responsiveness by facilitating acetylcholine release from cholinergic nerve terminals.
Volume-dependent variations of regional lung sound, amplitude, and phase
Authors: Kiyokawa Hiroshi , Pasterkamp Hans
Published: March 2015

Acoustic imaging of the respiratory system demonstrates regional changes of lung sounds that correspond to pulmonary ventilation. We investigated volume-dependent variations of lung sound phase and amplitude between two closely spaced sensors in five adults. Lung sounds were recorded at the posterior right upper, right lower, and left lower lobes during targeted breathing (1.2 ± 0.2 l/s; volume = 20–50 and 50–80% of vital capacity) and passive sound transmission (≤0.2 l/s; volumes as above). Average sound amplitudes were obtained after band-pass filtering to 75–150, 150–300, and 300–600 Hz. Cross correlation established the phase relation of sound between sensors. Volume-dependent variations in phase (≤1.5 ms) and amplitude (≤11 dB) were observed at the lower lobes in the 150- to 300-Hz band. During inspiration, increasing delay and amplitude of sound at the caudal relative to the cranial sensor were also observed during passive transmission in several subjects. This previously unrecognized behavior of lung sounds over short distances might reflect spatial variations of airways and diaphragms during breathing.
Selected Contribution: Evidence that the decrease in liver glycogen is associated with the exercise-induced increase in IGFBP-1
Authors: Lavoie Jean-Marc , Fillion Yovan , Couturier Karine , Corriveau Pierre
Published: March 2015

The purpose of the present study was to test the hypothesis that the exercise-induced increase in insulin-like growth factor binding protein (IGFBP)-1 is not always linked to a decrease in blood glucose level and to examine whether the decreasing levels of liver glycogen during exercise may be associated with the increase in IGFBP-1. Three groups of rats were submitted to a 70-min treadmill exercise. One group of rats was fed normally, and the two other groups had their food intake restricted by 50% (50% fast) the night before the experiment. One of these two 50% fasted groups of rats was infused (intravenously) with glucose throughout exercise to maintain euglycemia. Exercise in noninfused 50% fasted rats, compared with the normally fed rats, resulted in significantly lower blood glucose ( minute 70) and insulin levels, significantly lower liver glycogen content, no change in IGF-I, and significantly higher increases in free fatty acid, glycerol, β-hydroxybutyrate, and IGFBP-1. Maintenance of euglycemia during exercise in glucose-infused 50% fasted rats reduced to a large extent the decrease in insulin levels but only slightly attenuated the lipid response and the IGFBP-1 response seen in noninfused 50% fasted rats. Comparisons of all individual liver glycogen and IGFBP-1 values revealed that liver glycogen values were highly ( P < 0.001) predictive of the IGFBP-1 response during exercise ( R = 0.564). The present results indicate that the IGFBP-1 response during exercise is not always linked to a decrease in plasma glucose and suggest that the increase in IGFBP-1 during exercise may be related to the decrease in liver glycogen content.
Invited Review: Exercise training-induced changes in insulin signaling in skeletal muscle
Authors: Zierath Juleen R.
Published: March 2015

This review will provide insight on the current understanding of the intracellular signaling mechanisms by which exercise training increases glucose metabolism and gene expression in skeletal muscle. Participation in regular exercise programs can have important clinical implications, leading to improved health in insulin-resistant persons. Evidence is emerging that insulin signal transduction at the level of insulin receptor substrates 1 and 2, as well as phosphatidylinositol 3-kinase, is enhanced in skeletal muscle after exercise training. This is clinically relevant because insulin signaling is impaired in skeletal muscle from insulin-resistant Type 2 diabetic and obese humans. The molecular mechanism for enhanced insulin-stimulated glucose uptake after exercise training may be partly related to increased expression and activity of key proteins known to regulate glucose metabolism in skeletal muscle. Exercise also leads to an insulin-independent increase in glucose transport, mediated in part by AMP-activated protein kinase. Changes in protein expression may be related to increased signal transduction through the mitogen-activated protein kinase signaling cascades, a pathway known to regulate transcriptional activity. Understanding the molecular mechanism for the activation of insulin signal transduction pathways after exercise training may provide novel entry points for new strategies to enhance glucose metabolism and for improved health in the general population.
Genotypic differences in ethanol sensitivity in two tests of motor incoordination
Authors: Crabbe John C. , Metten Pamela , Yu Chia-Hua , Schlumbohm Jason P. , Cameron Andy J. , Wahlsten Douglas
Published: March 2015

Motor incoordination is frequently used as a behavioral index of intoxication by drugs that depress the central nervous system. Two tasks that have been used to assay incoordination in mice, the balance beam and the grid test, were evaluated to optimize aspects of apparatus and testing procedures for studying genetic differences. Mice of eight inbred strains were given one of several doses of ethanol or saline and tested for intoxication. Strains differed in sensitivity to ethanol in both tests, indicating a significant influence of genotype on ethanol sensitivity. For the balance beam, the width of the beam affected the strain sensitivity pattern, and only the widest beam worked well at all doses. For the grid test, both ethanol dose and the time after drug injection affected strains differentially. Although the behavioral sign of intoxication recorded for both tests was a foot-slip error, the correlations of strain means for ethanol sensitivity across the two tasks were generally not significant. This suggests that the genes influencing ethanol sensitivity in the two tasks are mostly different. These results make clear that a single set of task parameters is insufficient to characterize genetic influences on behavior. Several other issues affect the interpretation of data using these tests.
Locally and systemically active glucocorticosteroids modify intestinal absorption of sugars in rats
Authors: Thiesen A. , Wild G. E. , Keelan M. , Clandinin M. T. , Thomson A. B. R.
Published: March 2015

Glucocorticosteroids enhance digestive and absorptive functions of the intestine of weaning and adult rats. This study was undertaken to assess the influence of treatment of weaning male rats with budesonide (Bud), prednisone (Pred), or control vehicle on the in vitro jejunal and ileal uptake of glucose and fructose. Bud and Pred had no effect on the uptake ofd-glucose by sodium glucose transporter-1. In contrast, the uptake of d-fructose by GLUT-5 was similarly increased with Bud and with Pred. The increases in the uptake of fructose were not due to variations in the weight of the intestinal mucosa, food intake, or in GLUT-5 protein or mRNA expression. There were no steroid-associated changes in mRNA expression of c- myc, c- jun, c- fos, proglucagon, or selected cytokines. However, the abundance of ileal ornithine decarboxylase mRNA was increased with Pred. Giving postweaning rats 4 wk of Bud or Pred in doses equivalent to those used in clinical practice increases fructose but not glucose uptake. This enhanced uptake of fructose was likely regulated by posttranslational processes.
Murine model of gastrointestinal ischemia associated with complement-dependent injury
Authors: Zhao Hui , Montalto Michael C. , Pfeiffer Kristine J. , Hao Liming , Stahl Gregory L.
Published: March 2015

Gastrointestinal ischemia-reperfusion (I/R) injury is often associated with remote tissue injury. Complement activation plays an important role in local and remote tissue injury associated with gastrointestinal I/R. We developed a new murine model of gastrointestinal I/R that has complement-dependent local and remote tissue injury. Twenty, but not thirty, minutes of gastrointestinal ischemia followed by 3 h of reperfusion induced a significant loss of intestinal lactate dehydrogenase that was significantly prevented by a murine anti-murine C5 monoclonal antibody. Anti-C5 also significantly decreased neutrophil infiltration into the gut and lung. Gastrointestinal I/R significantly increased pulmonary intercellular adhesion molecule-1 mRNA and protein expression that was significantly inhibited by anti-C5. Pulmonary macrophage inflammatory protein-2 mRNA was significantly induced by gastrointestinal I/R and inhibited by anti-C5 treatment. These data demonstrate that brief periods of murine gastrointestinal I/R activate complement, leading to tissue injury and neutrophil accumulation. Anti-C5 treatment attenuates tissue injury, neutrophil recruitment, and leukocyte adherence molecule and chemokine expression in the mouse. This model will be well suited to investigate the role of complement-mediated tissue injury and gene expression after gastrointestinal I/R.
Aging and the time and frequency structure of force output variability
Authors: Vaillancourt David E. , Newell Karl M.
Published: March 2015

The present study examined the time and frequency structure of force output in adult humans to determine whether the changes in complexity with age are dependent on external task demands. Healthy young (20–24 yr), old (60–69 yr), and older-old (75–90 yr) humans produced isometric force contractions to constant and sine wave targets that also varied in force level. First, force variability on each force task increased with advancing age. Second, both time and frequency analysis showed that the structure of the force output in the old and older-old adults was less complex in the constant-force level task and more complex in the sine wave force task. Third, the alterations in force output with aging were primarily due to low-frequency bands <4 Hz. These results support the postulation that the observed increase or decrease in physiological complexity with aging is influenced by the relatively fast time scale of external task demands (Vaillancourt DE and Newell KM. Neurobiol Aging 23: 1–11, 2002).
Exercise endurance 1, 3, and 6 h after caffeine ingestion in caffeine users and nonusers
Authors: Bell Douglas G. , McLellan Tom M.
Published: March 2015

The purpose of the present study was to examine the duration of caffeine's ergogenic effect and whether it differs between users and nonusers of the drug. Twenty-one subjects (13 caffeine users and 8 nonusers) completed six randomized exercise rides to exhaustion at 80% of maximal oxygen consumption after ingesting either a placebo or 5 mg/kg of caffeine. Exercise to exhaustion was completed once per week at either 1, 3, or 6 h after placebo or drug ingestion. Exercise time to exhaustion differed between users and nonusers with the ergogenic effect being greater and lasting longer in nonusers. For the nonusers, exercise times 1, 3, and 6 h after caffeine ingestion were 32.7 ± 8.4, 32.1 ± 8.6, and 31.7 ± 12.0 min, respectively, and these values were each significantly greater than the corresponding placebo values of 24.2 ± 6.4, 25.8 ± 9.0, and 23.2 ± 7.1 min. For caffeine users, exercise times 1, 3, and 6 h after caffeine ingestion were 27.4 ± 7.2, 28.1 ± 7.8, and 24.5 ± 7.6 min, respectively. Only exercise times 1 and 3 h after drug ingestion were significantly greater than the respective placebo trials of 23.3 ± 6.5, 23.2 ± 7.1, and 23.5 ± 5.7 min. In conclusion, both the duration and magnitude of the ergogenic effect that followed a 5 mg/kg dose of caffeine were greater in the nonusers compared with the users.
Pco 2 in the large intestine of mice, rats, guinea pigs, and dogs and effects of the dietary substrate
Authors: Rasmussen Henrik , Mirtaheri Peyman , Dirven Hubert , Johnsen Helge , Kvarstein Gunnvald , Tønnessen Tor Inge , Midtvedt Tore
Published: March 2015

Pco 2 in the lumen and serosa of cecum and colon was measured in rats, guinea pigs, and dogs to examine the relationship between serosal Pco 2 and the incidence of intestinal necrotic lesions after administration of gas-carrier contrast agents in rodents. The effects of the dietary substrate were tested in a group of mice maintained on a diet based on glucose as the only carbohydrate source. The anesthetic used was a fentanyl-fluanison-midazolam mixture (rodents) and pentobarbital (dogs). Pco 2 was measured in vivo and postmortem, and the kinetics of the postmortem serosal Pco 2 [transmural CO2 flux ( J CO2 )] was calculated. Pco 2 in the cecal serosa and lumen, respectively, was 64 ± 4 and 392 ± 18 Torr in rats, 67 ± 3 and 276 ± 17 Torr in guinea pigs, and 73 ± 6 and 137 ± 7 Torr in mice on glucose-based diet. In the colon serosa and lumen of dogs, Pco 2 was 30 ± 6 and 523 ± 67 Torr, respectively. Serosal Pco 2increased rapidly after death in rats and slower in guinea pigs and mice, and the slowest change was observed in dogs. Compared with dogs, serosal Pco 2 and J CO2 of rats and guinea pigs were significantly higher. Serosal Pco 2 of guinea pigs was similar to that of rats, whereas the J CO2 of guinea pigs was significantly lower. These data suggest a causal relationship between the ability of the cecal and colonic wall to act as a barrier to CO2 diffusion and the presence of characteristic gas-carrier contrast agent-induced intestinal lesions in mice and rats and their absence in guinea pigs, dogs, and other species.
Intramuscular triacylglycerol utilization in human skeletal muscle during exercise: is there a controversy?
Authors: Watt Matthew J. , Heigenhauser George J. F. , Spriet Lawrence L.
Published: March 2015

Intramuscular triacylglyerols (IMTGs) represent a potentially important energy source for contracting human skeletal muscle. Although the majority of evidence from isotope tracer and1H-magnetic resonance spectroscopy (MRS) studies demonstrate IMTG utilization during exercise, controversy regarding the importance of IMTG as a metabolic substrate persists. The controversy stems from studies that measure IMTG in skeletal muscle biopsy samples and report no significant net IMTG degradation during prolonged moderate-intensity (55–70% maximal O2consumption) exercise lasting 90–120 min. Although postexercise decrements in IMTG levels are often reported from direct muscle measurements, the marked between-biopsy variability (∼23%) that has been reported with this technique in untrained subjects is larger than the expected decrease in IMTG content, effectively precluding significant findings. In contrast, recent data obtained in endurance-trained subjects demonstrated reduced variability between duplicate biopsies (∼12%), and significant changes in IMTG were detected after 120 min of moderate-intensity exercise. Therefore, it is our contention that the muscle biopsy, isotope tracer, and1H-MRS techniques report significant and energetically important oxidation of free fatty acids derived from IMTGs during prolonged moderate exercise.
Detection of inspiratory resistive loads in double-lung transplant recipients
Authors: Zhao Weiying , Martin A. Daniel , Davenport Paul W.
Published: March 2015

The afferent pathways mediating respiratory load perception are still largely unknown. To assess the role of lung vagal afferents in respiratory sensation, detection of inspiratory resistive loads was compared between 10 double-lung transplant (DLT) recipients with normal lung function and 12 healthy control (Nor) subjects. Despite a similar unloaded and loaded breathing pattern, the DLT group had a significantly higher detection threshold (2.91 ± 0.5 vs. 1.55 ± 0.3 cmH2O · l−1 · s) and Weber fraction (0.50 ± 0.1 vs. 0.30 ± 0.1) compared with the Nor group. These results suggest that inspiratory resistive load detection occurs in the absence of vagal afferent feedback from the lung but that lung vagal afferents contribute to inspiratory resistive load detection response in humans. Lung vagal afferents are not essential to the regulation of resting breathing and load compensation responses.