bluuebunny/crossref_metadata_2025 huggingface dataset:
Tubular sodium handling and tubuloglomerular feedback in experimental diabetes mellitus
Authors: Pollock C. A. , Lawrence J. R. , Field M. J.
Published: December 2017

Tubular Na handling and tubuloglomerular feedback (TGF) activity were assessed using micropuncture techniques during the hyperfiltration phase of streptozotocin-induced diabetes mellitus in Sprague-Dawley rats. Three animal groups were studied, designated as having severe diabetes [blood sugar level (BSL) 18-25 mmol/l], moderate diabetes (BSL 13-18 mmol/l) and control (BSL less than 10 mmol/l). Single-nephron glomerular filtration rate (SNGFR) measured at both late proximal (LP) and early distal (ED) sites was elevated in severe diabetes compared with both other groups. TGF activity, determined as the difference between LP and ED measurements of SNGFR, was significantly increased in severe diabetes (46.4 +/- 6.6 vs. 30.1 +/- 6.5 vs. 14.8 +/- 1.9 nl/min). Tubular Na transport was higher in severe diabetes compared with control, as demonstrated by a decrease in fractional delivery of Na to the LP (42.9 +/- 3.0 vs. 52.9 +/- 1.9%), as well as to the ED site (4.5 +/- 0.4 vs. 12.3 +/- 0.9%). Administration of phlorizin to severely diabetic animals resulted in a BSL comparable to that observed in moderate diabetes, and whole animal GFR, as well as SNGFR, TGF activity, and tubular Na handling were also similar to those found in moderate diabetes. Studies performed during mannitol infusion demonstrated that osmotic diuresis alone was not associated with the changes in TGF and tubular Na handling observed in the diabetic state. These data suggest that the hyperfiltration occurring in early diabetes is associated with enhanced proximal and loop resorption of Na independent of Na-glucose cotransport and osmotic diuresis. Activation of TGF serves to limit the rise in GFR, which results from factors as yet unrecognized in the diabetic state.
Responses to renin inhibition in conscious primates
Authors: Humke U. , Levens N. , Wood J. , Hofbauer K.
Published: December 2017

A method for the measurement of renal clearances was adapted in a novel manner to the conscious marmoset. Twenty-four hours before an experiment, animals underwent surgery for placement of both femoral arterial and venous catheters. A catheter was also implanted into the urinary bladder through the abdominal wall. The urinary catheter consisted of two tubes. One tube was connected to a pump, which removed the urine, while the other tube remained open to prevent the formation of a vacuum inside the bladder. Using this technique, we kept renal clearances stable for at least 3 h. All catheters were removed the day after the clearance experiment, and the bladder was reconstructed using microsurgical techniques. The bladder operation did not appear to produce lasting anatomical or functional changes, since the animals were able to void spontaneously and, after 3 mo, the bladder had regained its normal size and shape. Reimplantation of both the vessel and bladder catheters at this time allowed for an additional study of renal clearances within the same animals. Administration of the renin inhibitor CGP 29287 (1 mg/kg) to furosemide-pretreated conscious marmosets lowered blood pressure and increased renal blood flow. Glomerular filtration rate remained unchanged by CGP 29287, leading to a fall in the effective filtration fraction. Urinary volume and urinary sodium excretion also were unchanged by the renin inhibitor. We describe a novel method for the study of renal clearances in a small conscious primate and suggest that the renin-angiotensin system plays an important role in the control of renal function in the sodium-depleted marmoset.
Central effects of atrial natriuretic factor on renal salt excretion
Authors: Rohmeiss P. , Demmert G. , Unger T.
Published: December 2017

Atrial natriuretic factor (ANF) has been localized in periventricular brain areas involved in cardiovascular and fluid control. We investigated the effect of intracerebroventricular (icv) ANF (alpha-rat atriopeptin III) on renal sodium excretion in unilaterally nephrectomized, conscious unrestrained rats fitted with a chronic ureteral catheter. Isotonic NaCl (1 ml/h) was infused intravenously. ANF injected at doses (icv) of 1 ng (n = 6), 100 ng (n = 7), and 1 microgram (n = 7) reduced urinary sodium excretion (all values mumol/45 min, means +/- SE) from 111.6 +/- 24.4 to 83 +/- 20 (P less than 0.05), from 96.9 +/- 25.2 to 55 +/- 14 (P less than 0.01), and from 90.8 +/- 14.2 to 51 +/- 9 (P less than 0.01), respectively, whereas urinary flow rate did not change. The antinatriuretic effect was immediate in onset and lasted for greater than or equal to 60 min. Blood pressure remained unaltered. ANF (100 ng icv) increased efferent sympathetic renal nerve activity (+36%; n = 6, P less than 0.05), plasma renin activity (4.6 +/- 0.6 to 7.5 +/- 0.5 pmol angiotensin I.ml-1.h-1; n = 9, P less than 0.01), plasma angiotensin II (68.7 +/- 2.5 to 84.7 +/- 3.4 fmol/ml; n = 8, P less than 0.01), and aldosterone (22.3 +/- 3.6 to 37.2 +/- 4.0 ng/ml; n = 9, P less than 0.02). Renal denervation reduced the antinatriuretic effect of ANF by 37%. We conclude that brain ANF has antinatriuretic actions, which may be partly explained by activation of renal nerves.
Aldosterone metabolism in combined isolated perfused rat liver and kidney
Authors: Egfjord Martin , Daugaard Henrik , Olgaard Klaus
Published: December 2017

Pages 536–548: Martin Egfjord, Henrik Daugaard, and Klaus Olgaard. “Aldosterone metabolism in combined isolated perfused rat liver and kidney.” Page 545, Table 2: braces in columns 1, 2, and 6 were inadvertently omitted in the final printing.

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Synthesis and action of nitric oxide in rat glomerular mesangial cells
Authors: Shultz P. J. , Tayeh M. A. , Marletta M. A. , Raij L.
Published: December 2017

Macrophages and certain tumor cell lines can be induced to synthesize nitric oxide (NO) from L-arginine after stimulation with lipopolysaccharide (LPS) or cytokines. In the present study, we have found that culture medium collected after 24 h from unstimulated rat mesangial cells (MC) contains 6.3 +/- 1.2 microM of NO3-/NO2- (the degradation products of NO). These levels were significantly increased when MC were incubated with LPS (10 micrograms/ml) for 24 h (23.9 +/- 4.1, P less than 0.05). The specific inhibitor of NO synthesis, NG-monomethyl-L-arginine (L-NMMA) completely inhibited LPS-stimulated production of NO3-/NO2-, confirming that the NO3-/NO2- was derived from NO within the MC. Recent studies suggest that endothelium-derived relaxing factor (EDRF) produced by vascular endothelium is also NO, and we have previously shown that both EDRF and NO stimulate increases in MC guanosine 3',5'-cyclic monophosphate (cGMP). Thus we sought to determine whether NO synthesized by the MC could affect cGMP levels within the same cells. After 24-h incubation with LPS (10 micrograms/ml), intracellular cGMP level within the MC was 706.3 +/- 197 (SE) compared with 40.5 +/- 7 fmol/micrograms protein in control MC incubated in media alone (P less than 0.01). The changes in cGMP in response to LPS were inhibited by greater than 90% by L-NMMA. Similar to LPS, incubation of MC with the cytokine gamma-interferon also increased NO3-/NO2- in the culture media and increased cGMP levels within MC. The induction of NO synthesis within MC and the concomitant stimulation of MC cGMP may be important in the modulation of the effects of endotoxemia, as well as inflammation, within the glomerulus.
Regulation of Na(+)-H+ exchange by ATP depletion and calmodulin antagonism in renal epithelial cells
Authors: Burns K. D. , Homma T. , Harris R. C.
Published: December 2017

The present studies examined effects of ATP depletion and calmodulin antagonism on stimulation of Na(+)-H+ exchange by cytosolic acidification in renal epithelial cells (LLC-PK1). ATP depletion significantly inhibited both amiloride-sensitive 22Na+ uptake (P less than 0.001; n = 12) and Na(+)-dependent intracellular pH (pHi) recovery in 2',7'-bis (carboxyethyl)-5(6)-carboxyfluorescein acetoxymethylester (BCECF/AM)-loaded cells. Calmodulin antagonists, N-(6-aminohexyl)-5-chloro-1-naphthalene-sulfonamide (W-7) and calmidazolium, both caused a concentration-dependent inhibition of Na(+)-H+ exchange activity. The W-7-induced inhibition of Na(+)-H+ exchange occurred in cells incubated for 24 h with phorbol 12-myristate 13-acetate, indicating that the effect of W-7 was not mediated by protein kinase C inhibition. Both W-7 and ATP depletion shifted the pHi dependence of the antiporter, and ATP depletion also reduced the maximal activity. In LLC-PK1/CL4 cells grown on permeable filters, W-7 inhibited the cytosolic acidification-stimulated basolateral exchanger by 54 +/- 5% (P less than 0.005; n = 7) and, in contrast, stimulated the apical exchanger by 28 +/- 13% (P less than 0.05; n = 6). ATP depletion significantly inhibited apical Na(+)-H+ exchange. These results suggest that an ATP-Ca(2+)-calmodulin-dependent process is involved in regulation of Na(+)-H+ exchange in LLC-PK1 cells. A Ca(2+)-calmodulin-dependent process activated the amiloride-sensitive basolateral Na(+)-H+ exchanger and inhibited the amiloride-resistant apical antiporter. Phosphorylation of these two Na(+)-H+ exchangers or regulatory proteins by a Ca(2+)-calmodulin-dependent protein kinase may mediate this differential regulation.
Apical maxi K channels in intercalated cells of CCT
Authors: Pacha J. , Frindt G. , Sackin H. , Palmer L. G.
Published: December 2017

High-conductance (maxi) K channels in the apical membrane of rat and rabbit cortical collecting tubules (CCT) were studied using the patch-clamp technique. Principal cells (PC) and intercalated cells (IC) were distinguished with Hoffman modulation optics in split-open tubules. IC were further identified by staining tubules with the fluorescent mitochondrial dye, rhodamine 123. Maxi-K channels were distinguished by their high conductance (greater than 80 pS) and voltage-dependent kinetics. In CCT of rats on a low-Na diet, maxi K channels were observed in 11% of the cell-attached patches on PC and 79% of patches on IC. In rats on a normal diet, the channels were seen in 23 and 79% of patches on PC and IC, respectively. In the rabbit CCT, maxi K channels were observed in 12% (4 of 32) of the patches on PC and 82% (122 of 148) of the patches on IC. The greater abundance of channels in IC was confirmed in rat CCT using the whole-cell clamp technique. Current through the maxi K channels (IK) was measured as the tetraethylammonium (TEA)-sensitive (2.5 mM) outward current in cells equilibrated with 115 mM K and 10(-5) M Ca2+ in the pipette solution. When the cell was clamped to an internal potential of +40 mV, the average IK per cell was -4 +/- 5 pA in PC and 290 +/- 90 pA in IC. Lowering cytoplasmic Ca2+ from 10(-5) M to 10(-7) M reduced IK to 32 +/- 21 pA. Neither single Na channels nor amiloride-sensitive whole-cell currents were seen in IC. Finally, maxi K channels could be activated by pipette suction (10-40 cm H2O) in either cell-attached or inside-out patches on IC from rabbit CCT. This mechanosensitivity was observed even after chelation of free Ca2+ with ethylene glycol-bis (beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) in the pipette or the bath solutions, implying that stretch activation of these channels was not mediated by increased Ca2+ entry into the cell. The IC maxi K channel may play a role in cell volume regulation or in K secretion during elevation of luminal hydrostatic pressure.
Detection of interactions between myogenic and TGF mechanisms using nonlinear analysis
Authors: Chon K. H. , Chen Y. M. , Marmarelis V. Z. , Marsh D. J. , Holstein-Rathlou N. H.
Published: December 2017

Previous studies using linear techniques have provided valuable insights into the dynamic characteristics of whole kidney autoregulation and have led to the general conclusion that the myogenic mechanism and tubuloglomerular feedback (TGF) are highly nonlinear control mechanisms. To explore further the dynamic nature of these nonlinear autoregulatory mechanisms, we introduce the technique of nonlinear modeling using Volterra-Wiener kernels. In the past several years, use of Volterra-Wiener kernels for nonlinear approximation has been most notably applied to neurophysiology. Recent advances in algorithms for computation of the kernels have made this technique more attractive for the study of the dynamics of nonlinear physiological systems, such as the system mediating renal autoregulation. In this study, the general theory and requirements for using this technique are discussed. The feasibility of using the technique on whole kidney pressure and flow data is examined, and a basis for using the Volterra-Wiener kernels to detect interactions between physiological control mechanisms is established. As a result of this method, we have identified the presence of interactions between the oscillating components of the myogenic and the TGF mechanisms at the level of the whole kidney blood flow in normotensive rats. An interaction between these oscillatory components had previously been demonstrated only at the single-nephron level.
Rabbit renal epithelial angiotensin II receptors
Authors: Dulin N. O. , Ernsberger P. , Suciu D. J. , Douglas J. G.
Published: December 2017

The characteristics of angiotensin II (ANG II) receptors were compared in basolateral (BLM) and brush-border membranes (BBM) of rabbit kidney cortex. BLM showed high-affinity binding of 125I-labeled [Sar1]ANG II [dissociation constant (Kd) = 0.31 +/- 0.04 nM and maximum binding capacity (Bmax) = 136 +/- 17 fmol/mg protein]. Losartan inhibited 125I-[Sar1]ANG II in a heterogeneous manner, with 73 +/- 4% of the sites showing high affinity [inhibition constant (Ki) = 2.63 +/- 0.82 nM] and 27 +/- 4% of sites having low affinity (Ki = 125 +/- 18 nM). Masking studies confirmed the presence of two different binding sites. The sites with high affinity for losartan resemble the AT1A receptor, previously described and cloned. The sites with low affinity resemble the pharmacological AT1B subtype, previously identified as the minority subtype in mesangial cells. In BBM, two sites could be distinguished on the basis of 125I-[Sar1,Ile8]ANG II affinity, with Kd values of 1.43 +/- 0.26 and 782 +/- 90 nM for ANG II. The low-affinity site, however, comprised the main population of binding sites. ANG II binding to BBM was not sensitive to losartan. PD-123319 and CGP-42112A competed for binding with a one-half inhibitory concentration (IC50) of approximately 100 and 19.0 +/- 1.0 microM, respectively. 125I-labeled AT2-selective antagonist PD-122979 bound specifically and with high magnitude to both BLM and BBM. A very high rate of ANG II degradation was observed, despite the presence of protease inhibitors, suggesting the possibility of the presence of receptors for ANG II fragments in BLM and BBM.(ABSTRACT TRUNCATED AT 250 WORDS)
Bradykinin-induced in vitro contraction of rat mesangial cells via a B2 receptor type
Authors: Bascands J. L. , Pecher C. , Bompart G. , Rakotoarivony J. , Tack J. L. , Girolami J. P.
Published: December 2017

The effect of bradykinin (BK) on the contraction of rat mesangial cells (MC) was compared with that of various vasoactive agents. BK induced a dose-dependent contraction [one-half maximal effective dose (ED50) = 50 nM] inhibited by the B2 antagonist, HOE-140 (ED50 = 10 nM). BK-induced MC contraction was independent of extracellular calcium and was reduced by inhibition of protein kinase C (PKC). Neomycin completely prevented the increase in intracellular calcium and the formation of inositol 1,4,5-trisphosphate induced by BK but only reduced cell contraction. Inhibition of prostaglandin (PG) formation and administration of the endoperoxide antagonist SQ-27427 also partly decreased the effect of BK. Interestingly, only the addition of both neomycin and mepacrine resulted in a complete inhibition of cell contraction. These results suggest that BK, via a B2-kinin receptor, induces contraction of MC through two distinct mechanisms, one associated to the phospholipase C pathway and subsequent activation of PKC and the second one dependent on PG formation. These in vitro effects may be relevant in explaining the effects of BK and converting enzyme inhibitors on glomerular hemodynamics.
Anatomic pairing of afferent arterioles and renin cell distribution in rat kidneys
Authors: Casellas D. , Dupont M. , Bouriquet N. , Moore L. C. , Artuso A. , Mimran A.
Published: December 2017

Close afferent arteriolar (AA) connectivity is a prerequisite for hemodynamic interaction between superficial rat nephrons. Studies were conducted in rat, mouse, rabbit, and human renal vasculatures obtained by an HCl maceration-microdissection technique to document the extent of AA connectivity. In rat kidneys, we assessed the possibility for a slow component of internephron coupling, as reflected by arteriolar renin cell distribution after specific immunostaining for renin. In the four species examined, 51% (human) to 60% (mouse) of total AA populations were organized as vascular units consisting of mostly two AA sharing a common origin and a connecting arterial segment. In rat AA pairs, branch lengths were significantly correlated, suggesting coordinated arteriolar growth. The sum of AA branch lengths averaged 278 +/- 6 microns. Rat arteriolar renin status, ranging from no renin cells to renin-recruited midafferent arterioles, distributed in a significantly nonrandom fashion within AA pairs, and 52% of the pairs had equal renin status. Hence, AA pairing is a consistent anatomic characteristic of mammalian kidneys and may constitute an optimal vascular design for hemodynamic as well as endocrine interactions.
Lipoxygenase product formation and cell adhesion during neutrophil-glomerular endothelial cell interaction
Authors: Brady H. R. , Lamas S. , Papayianni A. , Takata S. , Matsubara M. , Marsden P. A.
Published: December 2017

Leukotriene (LT) and lipoxin (LX) levels were monitored in ionophore-stimulated coincubations of polymorphonuclear neutrophils (PMN) and microvascular kidney glomerular endothelial cells (GEN) to determine the profile of lipoxygenase (LO) products generated during cell-cell interactions and the relative contributions of transcellular pathways to LO product biosynthesis in this setting. LTB4 and LTC4 were the major products formed, as determined by reverse-phase high-performance liquid chromatography and radioimmunoassay. LTB4 and LTC4 levels were increased by 23 and 185%, respectively, in coincubations of PMN and GEN, compared with incubations of PMN alone. In contrast, LXA4 and LXB4 levels were not changed in the presence of GEN. These data suggested that GEN utilize PMN-derived LTA4 to generate LT. In keeping with this hypothesis, LT biosynthesis was enhanced if PMN were primed with human granulocyte-macrophage colony-stimulating factor (GM-CSF), a cytokine that augments LTA4 biosynthesis by activated PMN. The influence of LT on PMN adhesion to GEN was also assessed, since adhesion appears to be a pivotal event in recruitment of PMN in acute glomerulonephritis. Under basal conditions, LTB4 provoked low levels of adhesion via a PMN-directed CD11/CD18-dependent mechanism. The level of adhesion was markedly enhanced by prior priming of PMN with GM-CSF or activation of GEN with tumor necrosis factor-alpha (TNF). LTB4 was as potent in this regard as the complement component C5a, platelet-activating factor (PAF), and interleukin-8 (IL-8), other mediators that contribute to the entrapment of PMN in inflamed glomeruli. LTC4 also provoked PMN-GEN adhesion via a CD11/CD18-dependent mechanism, but, in contrast to LTB4, via actions with GEN. This action of LTC4 appeared to be mediated, at least in part, by induction of PAF synthesis by GEN. Interestingly, LT-induced PMN-GEN adhesion was markedly attenuated following remodeling of PMN phospholipids with 15(S)-hydroxyeicosatetraenoic acid, a product of 15-LO, which has been implicated as an anti-inflammatory eicosanoid in some experimental and human inflammatory diseases. Taken together, these results provide further evidence that 1) transcellular biosynthetic pathways may amplify the profiles of inflammatory mediators and thereby contribute to leukocyte recruitment in acute glomerulonephritis and 2) that products of the 5-LO and 15-LO pathways may exert opposing actions on PMN trafficking during glomerular inflammation in vivo.
Ca(2+)-dependent protein kinases modulate proline transport across the renal brush-border membrane
Authors: Zelikovic I. , Przekwas J.
Published: December 2017

The cellular mechanisms controlling reabsorption of amino acids in the renal proximal tubule are unknown. Ca(2+)-dependent protein kinases modulate the activity of several ion channels and carriers in the kidney. The role of these enzymes in regulating tubular amino acid transport has not been established. We investigated the effect of Ca(2+)- and phospholipid-dependent protein kinase C (PKC) and Ca2+/calmodulin-dependent protein kinase II (CaMK II) on Na(+)- and Cl(-)-dependent proline transport across the rat renal brush-border membrane (BBM). Bioassays utilizing selective peptide substrates for Ca(2+)-dependent protein kinases demonstrated the presence of PKC and CaMK II in the BBM. Renal brush-border membrane vesicles (BBMV) were phosphorylated using the "hyposmotic shock" technique. Endogenous (membrane-bound) CaMK II and PKC, as well as exogenous, highly purified PKC inhibited NaCl-linked proline uptake by phosphorylated, lysed/resealed BBMV compared with control vesicles. The inhibitory effect of Ca2+ on proline transport, without the presence of other kinase activators, was mediated by activation of endogenous CaMK II. The CaMK II- and PKC-induced inhibition of proline uptake was reversed by the specific kinase inhibitor peptides CaMK II-(281-302) and PKC-(19-31), respectively. These data suggest that Ca(2+)-dependent protein kinase-mediated phosphorylation inhibits NaCl-dependent proline transport across the tubular luminal membrane.
ADH-evoked [Cl-]i-dependent transient in whole cell current of distal nephron cell line A6
Authors: Nakahari T. , Marunaka Y.
Published: December 2017

The effect of antidiuretic hormone (ADH) on a distal nephron cell line (A6) was studied using the whole cell patch-clamp technique. A6 cells were cultured on a permeable support filter for 10-14 days in media containing 10% fetal bovine serum without supplemental aldosterone. In the unstimulated condition A6 cells had very small conductances of Na+,K+, and Cl-. Arginine vasotocin (AVT, 140 mU/ml, 280 nM) evoked a "transient" increase in whole cell currents as did dibutyryl-adenosine 3',5'-cyclic monophosphate (5 mM). These transients consisted of two components; one was the nonselective cation conductance, and the other was the Cl- conductance. Activation of these conductances was dependent on intracellular Cl- concentration ([Cl-]i). At low [Cl-]i (< or = 50 mM) both conductances were activated, whereas when [Cl-]i was 80 mM, only the Cl- conductance was activated. At high [Cl-]i (125 mM), both conductances were inhibited. It seems likely that the [Cl-]i maintained at a low level (< or = 50 mM) is an important requirement for A6 cells to respond to AVT.
Diaphragm capillarity and oxidative capacity during postnatal development
Authors: Sieck G. C. , Cheung T. S. , Blanco C. E.
Published: December 2017

In the cat diaphragm, fiber capillarity, cross-sectional area, and succinate dehydrogenase (SDH) activity were measured across the first 6 wk of postnatal development. Fibers were classified as type I, IIa, IIb, or IIc on the basis of staining for myofibrillar adenosinetriphosphatase (ATPase). Capillaries were identified in sections stained for ATPase at pH 4.2. Fiber cross-sectional areas and SDH activities were quantified using an image-processing system. During postnatal development, the proportions of type I fibers increased while type II fibers decreased. At birth, all type II fibers were IIc. From the 1st to the 2nd postnatal wk, the proportion of type IIc fibers decreased while the numbers of IIa and IIb increased. Thereafter the proportion of type IIb fibers continued to increase while the number of IIa steadily declined. At birth, capillarity, cross-sectional areas, and SDH activities of type I and II fibers were low compared with other postnatal age groups. Fiber cross-sectional areas increased progressively with age. The number of capillaries surrounding type I and II fibers increased markedly by the 2nd wk and then continued to increase at a slower rate. The number of capillaries per fiber area reached a peak by the 2nd wk and then declined as fiber cross-sectional area increased. Postnatal changes in capillarity depended on fiber type, being greatest in IIb. SDH activities of type I and II fibers were initially low during the first 2 postnatal wk and then peaked by the 3rd wk. After the 6th wk, fiber SDH activities decreased to adult values. Among the type II fibers, IIb showed the greatest change in SDH activity during early postnatal development.
Shunt effect of gas compression inside pneumotachographs during forced oscillations
Authors: Louis B. , Harf A. , Lorino H. , Isabey D.
Published: December 2017

Determination of the frequency response of pneumotachographs is needed whenever they are used to measure high-frequency flows, such as in the forced oscillation method. When screen and capillary pneumotachographs are calibrated using an adiabatic compression in a closed box as a reference impedance, they can be adequately described by a series of inertial-resistive elements. However, this type of reference impedance strongly differs from the actual respiratory impedance (ZL). We studied the frequency response of pneumotachographs up to 250 Hz in reference to the impedance of a compressible gas oscillating in a long tube, taken as a more generalizable model of actual ZL. We found that, with this device, the series resistance-inertance models fail to describe the frequency response of the pneumotachograph. However, when compressible effects in the pneumotachograph are taken into account by adding to the resistive models a compliance (Cpn) corresponding to the compression in half of the inner volume of the pneumotachograph, the agreement with experiments becomes satisfactory. Gas compression-related phenomena were demonstrated to be negligible only when the parameter omega Cpn magnitude of ZL is much smaller than 1 (omega pulsation). Results obtained in normal humans have shown that such a correction is required above 100 Hz. Similar correction at lower frequency might also be necessary in cases of large respiratory impedance (e.g., babies, subjects with pathological lungs, and intubated subjects).
Effect of mild-to-moderate airflow limitation on exercise capacity
Authors: Babb T. G. , Viggiano R. , Hurley B. , Staats B. , Rodarte J. R.
Published: December 2017

To determine the effect of mild-to-moderate airflow limitation on exercise tolerance and end-expiratory lung volume (EELV), we studied 9 control subjects with normal pulmonary function [forced expired volume in 1 s (FEV1) 105% pred; % of forced vital capacity expired in 1 s (FEV1/FVC%) 81] and 12 patients with mild-to-moderate airflow limitation (FEV1 72% pred; FEV1/FVC % 58) during progressive cycle ergometry. Maximal exercise capacity was reduced in patients [69% of pred maximal O2 uptake (VO2max)] compared with controls (104% pred VO2max, P less than 0.01); however, maximal expired minute ventilation-to-maximum voluntary ventilation ratio and maximal heart rate were not significantly different between controls and patients. Overall, there was a close relationship between VO2max and FEV1 (r2 = 0.62). Resting EELV was similar between controls and patients [53% of total lung capacity (TLC)], but at maximal exercise the controls decreased EELV to 45% of TLC (P less than 0.01), whereas the patients increased EELV to 58% of TLC (P less than 0.05). Overall, EELV was significantly correlated to both VO2max (r = -0.71, P less than 0.001) and FEV1 (r = -0.68, P less than 0.001). This relationship suggests a ventilatory influence on exercise capacity; however, the increased EELV and associated pleural pressures could influence cardiovascular function during exercise. We suggest that the increase in EELV should be considered a response reflective of the effect of airflow limitation on the ventilatory response to exercise.
Sweat ammonia excretion during submaximal cycling exercise
Authors: Czarnowski D. , Gorski J.
Published: December 2017

This study was undertaken to investigate whether part of the ammonia formed during muscular exercise was excreted with the sweat. Male medical students volunteered for the experiment. They exercised 30 min on a bicycle ergometer at 80 and 40% of the predetermined maximal O2 uptake (VO2max). Exercise at 80% VO2max was performed twice, at room temperature (20 degrees C) and in a cold room (0 degrees C), whereas exercise at 40% was performed only at room temperature (20 degrees C). Blood was collected from the antecubital vein immediately before and after exercise. Sweat was collected from the hypogastric region by use of gauze pads. It was shown that the plasma ammonia level was elevated after exercise at 80% VO2max and remained stable after exercise at 40% VO2max. The volume of sweat produced during exercise at 80% VO2max at 20 degrees C was 428 +/- 138 ml and at 0 degrees C 245 +/- 86 ml and during exercise at 40% VO2max was 183 +/- 69 ml. The ammonia concentration in the sweat after exercise at 80% VO2max at 20 degrees C was 7,140 mumol/l and at 0 degrees C 11,816 mumol/l. After exercise at 40% VO2max, it was 2,076 mumol/l. The total ammonia lost through the sweat during exercise at 80% VO2max was similar at both temperatures, despite the difference in the sweat volume (at 20 degrees C, 3,360 +/- 2,080 mumol; at 0 degrees C, 3,310 +/- 1,250 mumol). During exercise at 40% VO2max, it was 350 +/- 230 mumol. These results show that part of ammonia formed during exercise is lost with sweat. The amount lost increases with increased work rate and the plasma ammonia concentration.
Chemical activation of thin-fiber phrenic afferents. 2. Cardiovascular responses
Authors: Hussain S. N. , Chatillon A. , Comtois A. , Roussos C. , Magder S.
Published: December 2017

To assess the effects of groups III and IV (thin-fiber) phrenic afferents on arterial pressure, heart rate, and distribution of cardiac output, we injected capsaicin into phrenic arteries of in situ isolated and innervated left diaphragms of dogs anesthetized with chloralose, vagotomized, and mechanically ventilated. Blood flow in the ascending aorta, common carotid, renal, superior mesenteric, and femoral arteries was measured by electromagnetic and Doppler flow probes. Injection of 1 mg capsaicin into the left phrenic artery produced congruent to 15% increase in mean arterial pressure and congruent to 7% increase in heart rate with no change in aortic flow. Phrenic arterial flow decreased by 64%, renal arterial flow by 16%, and superior mesenteric arterial flow by 10%, whereas carotid flow increased by 13% and flow to the right gastrocnemius muscle did not change. Mean arterial pressure, heart rate, and blood flow distribution (with the exception of the decline in phrenic blood flow) returned to baseline within 60 s of the injection. Injection of 1.5 mg capsaicin into the right isolated and innervated gastrocnemius produced congruent to 35% increase in mean arterial pressure, 17% rise in heart rate, and no change in aortic blood flow. Phrenic and carotid arterial flow rose by 240 and 41%, respectively, whereas renal and superior mesenteric flow declined by 50 and 20%, respectively. In conclusion, thin-fiber phrenic afferents have an excitatory effect on arterial pressure and heart rate. They redistribute blood flow away from the renal and intestinal vascular beds and toward the carotid vascular bed. On the other hand, the cardiovascular reflex from thin-fiber phrenic afferents seems less potent than that from limb muscle afferents.
Separation of late bronchial responses from airway hyperresponsiveness in allergic sheep
Authors: Soler M. , Sielczak M. , Abraham W. M.
Published: December 2017

Allergic sheep with antigen-induced early and late responses were used to determine whether airway hyperresponsiveness (AHR) to carbachol is present during the late response and whether blocking the late response with the leukotriene D4 (LTD4) antagonist MK-571 also blocks this AHR. To do this, we first showed that MK-571 blocked the antigen-induced late response, and then, in a separate study, we determined the effect of MK-571 treatment on airway responsiveness 6 h after antigen challenge (at the start of the late response). MK-571 (5 mg, by metered dose inhaler) given 30 min before and 4 h after Ascaris suum challenge had no effect on the acute response to antigen but blocked (P less than 0.05) the late response compared with placebo (n = 7). In the second study (n = 6), the antigen-induced acute increases in mean specific lung resistance (sRL) were also similar in the placebo (249%) and drug trials (247%). By 6 h postchallenge, however, mean sRL in the placebo trial began to increase (54%, P less than 0.05), whereas in the drug trial mean sRL was baseline. Nevertheless, AHR was apparent in both trials as indicated by a mean twofold leftward shift in the dose-response curves to inhaled carbachol (P less than 0.05 vs. prechallenge). Bronchoalveolar lavage at 6 h showed that MK-571 did not prevent the inflammatory cell influx into the lung. These observations suggest that although LTD4 may be a mediator of the late response in sheep, it is not a primary mediator affecting cholinergic AHR during this period.
A simple Hill element-nonlinear spring model of muscle contraction biomechanics
Authors: Schultz A. B. , Faulkner J. A. , Kadhiresan V. A.
Published: December 2017

The purpose of this study was to develop a model to predict the mechanical response of muscles during isometric tetanic, afterloaded isotonic and isovelocity shortening contractions. Two versions of the model were developed. Both incorporated a contractile element that obeyed a Hill force-velocity relationship and a series elastic element. In a quadratic spring version, the series elastic element force was represented as proportional to the square of the stretch; in a cubic spring version, it was represented as proportional to the cube of the stretch. Both versions provided closed-form equations for response predictions that involved four independent parameters. Once the four parameters were chosen, each of these responses could be predicted. Model validity was established by comparing predicted and observed responses in slow and fast hindlimb muscles of rodents. Significant model-predicted responses seldom differed by more than 15% from experimental values. The model can provide insights into how changes in individual properties affect the overall mechanical behavior of muscles in a variety of circumstances and reduce the need for collection of experimental data.
Aerosolized surfactant treatment of preterm lambs
Authors: Lewis J. F. , Ikegami M. , Jobe A. H. , Tabor B.
Published: December 2017

To evaluate the potential for aerosolized surfactant treatments of surfactant deficiency, twin lamb fetuses were delivered at 130-132 days gestational age and received nebulized natural surfactant (Neb NS), nebulized Survanta (Neb Surv), tracheally instilled natural surfactant (Inst NS), or nebulized saline (Neb Saline). Neb NS and Neb Surv groups had significant increases in ventilatory efficiency index and dynamic compliance values (P less than 0.05). Both groups also had pressure-volume curves that were comparable to the Inst NS group. The Neb Saline control group had deterioration of the ventilation efficiency index and dynamic compliance values over time as well as pressure-volume curves that demonstrated smaller lung volumes compared with all three surfactant-treated groups (P less than 0.01). Delivery of aerosolized surfactant to the lung was only approximately 2 mg lipid/kg for the nebulized groups, a dose one-twentieth of that previously noted to be effective in instillation protocols. Distribution histograms of the aerosolized surfactant-treated groups differed from the instilled animals as there was more deposition in the right upper lobes and tracheae in the nebulized groups compared with the instilled group (P less than 0.05). Pulmonary blood flow was not altered by aerosolized surfactant treatment. Administration of aerosolized surfactant to preterm lambs improved lung function at a very low surfactant dose.
Autonomic regulation of subsidiary atrial pacemakers during exercise
Authors: Ardell J. L. , Randall W. C. , Pomeroy G. , Lawton M. , Kim T.
Published: December 2017

Cardiac responses to graded treadmill exercise were compared in conscious dogs before and after excision of the sinoatrial node (SAN) and adjacent tissue along the sulcus terminalis. The chronotropic and dromotropic responses to dynamic exercise were compared with and without selective muscarinic (atropine) and/or beta-adrenergic (timolol) blockade. With the SAN intact, cardiac acceleration was prompt during onset of exercise and in proportion to work intensity. Immediately after SAN excision (1-7 days), pacemaker activity exhibited marked instability in rate and pacemaker location, with rapid shifts between atrial and junctional foci. Soon thereafter (1-2 wk), subsidiary atrial pacemakers (SAPs) assumed the primary pacemaker function. Although the SAP foci demonstrated stable heart rates and atrioventricular (AV) intervals at rest and during exercise, heart rates at rest and during steady-state exercise were reduced 34% from corresponding levels in the SAN-intact state, both with and without selective autonomic blockade. For control of dromotropic function, animals with SAP foci showed pronounced shortening in AV interval in conjunction with exercise that was further exacerbated by pretreatment with atropine. Eight weeks after excision of the primary SAN pacemakers, direct electrophysiological mapping localized the SAP foci to either the inferior right atrium along the sulcus terminalis or the dorsal cranial right atrium (in or near Bachmann's bundle). Animals with SAPs localized to the inferior right atrium had a more marked suppression in heart rate with a corresponding greater decrease in AV interval during exercise than dogs with SAP foci identified within the dorsal cranial right atrium.
Abnormal high-energy phosphate metabolism in human muscle phosphofructokinase deficiency
Authors: Bertocci L. A. , Haller R. G. , Lewis S. F. , Fleckenstein J. L. , Nunnally R. L.
Published: December 2017

We studied the pattern of high-energy phosphate metabolism in five patients with phosphofructokinase deficiency (PFKD) and five healthy subjects (HS) during graded rhythmic handgrip performed for 5 min at 17, 33, 50, and 100% of maximal voluntary contraction (MVC). The range of MVC was similar in both groups. Force production was recorded, and intracellular concentrations of phosphorus compounds and pH were measured in the flexor digitorum profundus of the active forearm. At exercise intensities greater than or equal to 50% MVC, changes in concentrations of high-energy phosphate metabolites were abnormal in PFKD. During maximal effort, [ADP], calculated from the creatine kinase reaction, was 64.3 +/- 13.5 (SE) mumol/kg in PFKD vs. 25.7 +/- 4.0 in HS (P less than 0.05). Ammonia (NH3), a product of AMP deamination and an index of muscle [AMP], increased approximately twofold more in venous effluent during maximal forearm exercise in PFKD than in HS (P less than 0.05). Phosphocreatine concentration was 9.4 +/- 1.3 (SE) mmol/kg in HS and 13.0 +/- 1.7 in PFKD (P less than 0.05). Inorganic phosphate concentration was 15.8 +/- 1.4 mmol/kg in HS and 7.4 +/- 0.5 in PFKD (P less than 0.05). During strenuous exercise, PFKD patients exhibit an impairment in the rephosphorylation of ADP related to a subnormal oxidative capacity, an absence of glycolysis, and an attenuated breakdown of phosphocreatine.
Tone-dependent responses to endothelin in the isolated perfused fetal sheep pulmonary circulation in situ
Authors: Cassin S. , Kristova V. , Davis T. , Kadowitz P. , Gause G.
Published: December 2017

Pulmonary vascular responses to endothelin (ET-1), a peptide derived from endothelial cells in culture, were investigated in the ovine fetus delivered by cesarean section from chloralose-anesthetized ewes with intact umbilical circulation. Circulation to the lower left lobe of the fetal lung was isolated in situ and perfused at constant flow with blood withdrawn from the inferior vena cava. Injection of graded doses of ET-1 into the left pulmonary artery decreased pulmonary arterial perfusion pressure in a dose-related manner. At doses of 100, 300, and 1,000 ng, pulmonary vascular resistance per kilogram body weight (PVR/kg) was decreased 30, 40, and 42%, respectively. However, when fetuses were ventilated with 100% oxygen, 100- and 300-ng doses of ET-1 decreased PVR/kg by 5 and 9%, respectively. In contrast, injection of 1,000 ng of ET-1 resulted in a reversal of the response, and PVR/kg was increased by 70%. Ventilation of the right lung alone resulted in a similar reversal of the vasodilator response to 1,000 ng of ET-1, and a 138% increase in PVR/kg was recorded. These studies demonstrate for the first time that ET-1 has vasodilator activity in the normally high-tone ovine fetal pulmonary circulation. In addition, these results show that ET-1 has vasoconstrictor activity in the newly ventilated low-tone pulmonary vasculature. The present data indicate the pulmonary vascular responses to ET-1 are tone dependent in the ovine fetal pulmonary circulation.
Inspiratory resistive load detection in conscious dogs
Authors: Davenport P. W. , Dalziel D. J. , Webb B. , Bellah J. R. , Vierck C. J.
Published: December 2017

The physiological mechanisms mediating the detection of mechanical loads are unknown. This is, in part, due to the lack of an animal model of load detection that could be used to investigate specific sensory systems. We used American Foxhounds with tracheal stomata to behaviorally condition the detection of inspiratory occlusion and graded resistive loads. The resistive loads were presented with a loading manifold connected to the inspiratory port of a non-rebreathing valve. The dogs signaled detection of the load by lifting their front paw off a lever. Inspiratory occlusion was used as the initial training stimulus, and the dogs could reliably respond within the first or second inspiratory effort to 100% of the occlusion presentations after 13 trials. Graded resistances that spanned the 50% detection threshold were then presented. The detection threshold resistances (delta R50) were 0.96 and 1.70 cmH2O.l-1.s. Ratios of delta R50 to background resistance were 0.15 and 0.30. The near-threshold resistive loads did not significantly change expired PCO2 or breathing patterns. These results demonstrate that dogs can be conditioned to reliably and specifically signal the detection of graded inspiratory mechanical loads. Inspiration through the tracheal stoma excludes afferents in the upper extrathoracic trachea, larynx, pharynx, nasal passages, and mouth from mediating load detection in these dogs. It is unknown which remaining afferents (vagal or respiratory muscle) are responsible for load detection.
Attenuation of IL-2-induced multisystem organ edema by phalloidin and antamanide
Authors: Welbourn R. , Goldman G. , Kobzik L. , Valeri C. R. , Hechtman H. B. , Shepro D.
Published: December 2017

Interleukin 2 (IL-2) is a potent cytokine with diverse effects, including the ability to stimulate lymphocyte differentiation into cells capable of lysing tumor. Its therapeutic efficacy is limited because of side effects such as breakdown of the microvascular barrier and edema. Control of the microvascular barrier is in part regulated by endothelial cell cytoskeletal contractile proteins. This study tests whether the cyclopeptides that maintain actin filament organization and distribution and reduce macromolecular flux across the endothelial cell junction in vitro would similarly maintain barrier tightness and prevent early edema produced by IL-2 in vivo. Anesthetized rats were treated at 30-min periods with intravenous saline (0.5 ml, n = 41), phalloidin (20 micrograms in 0.5 ml, n = 21), or antamanide, (20 micrograms in 0.5 ml, n = 21), starting 30 min before the 1-h infusion of 10(6) U of recombinant human IL-2 or saline. Six hours after the start of IL-2, there was edema in the saline/IL-2 group, as measured by increased wet-to-dry ratios (W/D) in the lungs, heart, and kidney. With saline/IL-2, bronchoalveolar lavage (BAL) fluid contained an elevated protein concentration and higher plasma thromboxane levels compared with controls. The number of neutrophils sequestered in the lungs was more than twice that of saline controls. Phalloidin significantly attenuated edema in lung and reduced BAL protein leak. Antamanide treatment was as effective in limiting lung and heart edema, but, in contrast to phalloidin, antamanide prevented kidney edema and did not lead to an alteration in the liver W/D. Antamanide also prevented BAL fluid protein leak.(ABSTRACT TRUNCATED AT 250 WORDS)
Dietary carbohydrate, muscle glycogen, and power output during rowing training
Authors: Simonsen J. C. , Sherman W. M. , Lamb D. R. , Dernbach A. R. , Doyle J. A. , Strauss R.
Published: December 2017

The belief that high-carbohydrate diets enhance training capacity (mean power output) has been extrapolated from studies that have varied dietary carbohydrate over a few days and measured muscle glycogen but did not assess power output during training. We hypothesized that a high-carbohydrate (HI) diet (10 g.kg body mass-1.day-1) would promote greater muscle glycogen content and greater mean power output during training than a moderate-carbohydrate (MOD) diet (5 g.kg body mass-1.day-1) over 4 wk of intense twice-daily rowing training. Dietary protein intake was 2 g.kg body mass-1.day-1, and fat intake was adjusted to maintain body mass. Twelve male and 10 female collegiate rowers were randomly assigned to the treatment groups. Training was 40 min at 70% peak O2 consumption (VO2) (A.M.) and either three 2,500-m time trials to assess power output or interval training at 70-90% peak VO2 (P.M.). Mean daily training was 65 min at 70% peak VO2 and 38 min at greater than or equal to 90% peak VO2. Mean muscle glycogen content increased 65% in the HI group (P less than 0.05) but remained constant at 119 mmol/kg in the MOD group over the 4 wk. Mean power output in time trials increased 10.7 and 1.6% after 4 wk in the HI and MOD groups, respectively (P less than 0.05). We conclude that a diet with 10 g carbohydrate.kg body mass-1.day-1 promotes greater muscle glycogen content and greater power output during training than a diet containing 5 g carbohydrate.kg body mass-1.day-1 over 4 wk of intense twice-daily rowing training.(ABSTRACT TRUNCATED AT 250 WORDS)
Initial recruitment of neutrophils to alveolar structures in acute lung injury
Authors: Kindt G. C. , Gadek J. E. , Weiland J. E.
Published: December 2017

The adult respiratory distress syndrome and bacterial pneumonia are both characterized by an influx of neutrophils into the lung. The neutrophil has been implicated as having a “pathological” role in adult respiratory distress syndrome, in contrast to its role in bacterial pneumonia. We hypothesized that processes resulting in neutrophil recruitment to the lung are distinct, depending on whether the inflammatory stimulus arises in the intravascular or the alveolar compartment of the lung. Anesthetized sheep with lung lymph fistulas were utilized to access the three compartments of the lung relevant to studies of transpulmonary neutrophil migration. Serum, lung lymph, and bronchoalveolar lavage fluid were studied for neutrophil influx and chemotactic activity before and after administration of endotoxin by either an intravascular or inhaled alveolar route. Both groups developed significant neutrophil influx into the lymph and bronchoalveolar lavage fluid by 3 h postendotoxin. Those animals receiving intravascular endotoxin developed chemotactic gradients opposing neutrophil migration into the lung in contrast to animals receiving alveolar endotoxin, suggesting that neutrophil influx into the lung occurs by random migration.