bluuebunny/crossref_metadata_2025 huggingface dataset:
Odd E. Hanssen and the Hanssen method for measurement of single-nephron glomerular filtration rate
Authors: Aukland Knut
Published: December 2017

In the middle of the twentieth century, the suspicion that deep and superficial nephrons might serve different functions created a demand for measurement of single-nephron glomerular filtration rate (SNGFR). Rather unexpectedly, the answer came from Odd E. Hanssen (1917–1964), a Norwegian physician working on his own in the Department of Pathological Anatomy, University of Oslo, with minimal support and no interaction with renal physiologists. In 1963, after nearly 10 years of work, he presented the ferrocyanide method, allowing simultaneous estimates ofSNGFR in a large number of nephrons in all layers of the kidney. This review first describes his early visions of the method and the elaborate and extremely time-consuming studies in mice to verify the technique. As a byproduct came valuable information on the relationship between nephron size and SNGFR, glomerular intermittency, and the emptying of the tubules on filtration stop. Hanssen died from a cerebral hemorrhage in 1964, and for several years the method seemed entirely forgotten. Fortunately, Andrew Baines took up the use of ferrocyanide in 1963–1964 while working on his thesis in Toronto, but his first publication came in 1969 from Saclay, France, in collaboration with Christian de Rouffignac. Modifications allowing determination of absolute SNGFR were worked out by de Rouffignac and by Jaime Coehlo in New York. Thereafter, the “Hanssen method” spread rapidly, and in the early 1980s about 50 reports had been published from 17 laboratories in 9 countries. The distribution of SNGFR in mammals, birds, and fish was described, as well as the response to water and salt loads, vasoactive substances, hormones, varying perfusion pressure, blood loss, etc. Finally, after mentioning two recent methods inspired by the Hanssen technique but using other filtration markers, the review concludes that most of our present knowledge on SNGFRdistribution and regulation has been obtained by the method developed by Hanssen 40 years ago.
Mechanism underlying diuretic effect ofl-NAME at a subpressor dose
Authors: Liang Mingyu , Berndt Theresa J. , Knox Franklyn G.
Published: December 2017

The diuretic effects of nitric oxide (NO) synthase inhibitors administered at subpressor dose in rats are controversial, and the tubular segments involved are not known. In the present study, we examined the effect of Nω-nitro-l-arginine methyl ester (l-NAME) at a subpressor dose on renal interstitial NO and cGMP activity and on renal tubular segmental reabsorption of fluid in the rat. Intravenous infusion of l-NAME at 1 μg · kg−1· min−1in Sprague-Dawley rats ( N = 8), which did not alter mean arterial pressure or glomerular filtration rate, significantly increased urine flow rate (Uv; from 78.2 ± 12.7 to 117.1 ± 14.9 μl/min, P < 0.05). Paradoxically, this effect of l-NAME was concomitant with significant increases in nitrite/nitrate (from 10.79 ± 1.20 to 16.50 ± 2.60 μM, P < 0.05) and cGMP (from 0.65 ± 0.09 to 0.98 ± 0.18 nM, P < 0.05) concentrations in renal cortical microdialysate as well as the nitrite/nitrate concentration in the medullary microdialysate. Micropuncture studies in the superficial nephron revealed that l-NAME significantly increased the flow rate (from 8.3 ± 0.9 to 12.2 ± 1.2 nl/min, P < 0.05) and fractional delivery of fluid to the distal tubule, but not those in the late proximal tubule. In conclusion, l-NAME, at the subpressor dose used in this study, increased renal nitrate/nitrite and cGMP and inhibited fluid reabsorption in tubular segments between the late proximal tubule and the distal tubule of superficial nephrons.
Interaction of cations, anions, and weak base quinine with rat renal cation transporter rOCT2 compared with rOCT1
Authors: Arndt Petra , Volk Christopher , Gorboulev Valentin , Budiman Thomas , Popp Christian , Ulzheimer-Teuber Isabel , Akhoundova Aida , Koppatz Stefan , Bamberg Ernst , Nagel Georg , Koepsell Hermann
Published: December 2017

The rat organic cation transporter (rOCT)-2 was characterized by electrical and tracer flux measurements compared with rOCT1. By applying choline gradients to voltage-clamped Xenopus oocytes expressing rOCT2, potential-dependent currents could be induced in both directions. Tracer flux measurements with seven organic cations revealed similar Michaelis-Menten constant values for both transporters, with the exception of guanidine. In parallel experiments with rOCT2 and rOCT1, inhibition of tetraethylammonium transport by 12 cations, 2 weak bases, corticosterone, and the anions para-amminohippurate, α-ketoglutarate, and probenecid was characterized. The IC50values of many inhibitors were similar for both transporters, whereas others were significantly different. Mepiperphenidol and O-methylisoprenaline showed an ∼70-fold lower and corticosterone a 38-fold higher affinity for rOCT2. With the use of these inhibitors together with previous information on cation transporters, experimental protocols are proposed to dissect out the individual contributions of rOCT2 and rOCT1 in intact proximal tubule preparations. Inhibition experiments at different pH levels strongly suggest that the weak base quinine passively permeates the plasma membrane at physiological pH and inhibits rOCT2 from the intracellular side.
Distinct characteristics of two human Nedd4 proteins with respect to epithelial Na+channel regulation
Authors: Kamynina Elena , Tauxe Caroline , Staub Olivier
Published: December 2017

The epithelial Na+channel (ENaC) is regulated via PY motif-WW domain interaction by the mouse (m) ubiquitin-protein ligase mNedd4-2 but not by its close relative mNedd4-1. Whereas mNedd4-1 is composed of one C2, three WW, and one HECT domain, mNedd4-2 comprises four WW domains and one HECT domain. Both proteins have human (h) homologs, hNedd4-1 and hNedd4-2; however, both of them include four WW domains. Therefore, we characterized hNedd4-1 and hNedd4-2 in Xenopus laevisoocytes with respect to ENaC binding and interaction. We found that hNedd4-2 binds to and abrogates ENaC activity, whereas hNedd4-1 does not coimmunoprecipitate with ENaC and has only modest effects on ENaC activity. Structure-function studies revealed that the C2 domain of hNedd4-1 prevents this protein from downregulating ENaC and that WW domains 3 and 4, involved in interaction with ENaC, do not by themselves provide specificity for ENaC recognition. Taken together, our data demonstrate that hNedd4-2 inhibits ENaC, implying that this protein is a modulator of salt homeostasis, whereas hNedd4-1 is not primarily involved in ENaC regulation.
Quantification of TGF-β1 mRNA along rat nephron in obstructive nephropathy
Authors: Fukuda Kyoichi , Yoshitomi Koji , Yanagida Taihei , Tokumoto Masanori , Hirakata Hideki
Published: December 2017

Unilateral ureteral obstruction (UUO) leads to interstitial fibrosis of the obstructed kidney, and transforming growth factor-β1 (TGF-β1) is thought to play an important role in this process. Although increased TGF-β1 mRNA expression in the obstructed kidney has been demonstrated, the source of the increased TGF-β1 remains to be elucidated. To determine the precise localization of TGF-β1 in the obstructed kidney, we examined TGF-β1 mRNA expression using in situ hybridization and competitive RT-PCR in rats with UUO. In situ hybridization demonstrated that TGF-β1 mRNA expression was preferentially increased in tubular epithelial cells and to a lesser degree in infiltrating macrophages in obstructed kidneys. Quantitative analysis using competitive RT-PCR in microdissected nephron segments revealed that levels of TGF-β1 mRNA in obstructed kidneys relative to control kidneys increased significantly in proximal tubules, thick ascending limbs of Henle, and distal convoluted tubules, whereas those in glomeruli and collecting ducts did not change significantly. Of the tubular segments, the proximal tubules appeared to predominantly contribute to increased TGF-β1 mRNA. Our findings suggest that renal tubules, particularly proximal tubules, are the main contributors to increased TGF-β1 mRNA expression in obstructed kidneys and to the subsequent interstitial fibrosis.
Hypokalemia induces renal injury and alterations in vasoactive mediators that favor salt sensitivity
Authors: Suga Shin-Ichi , Phillips M. Ian , Ray Patricio E. , Raleigh James A. , Vio Carlos P. , Kim Yoon-Goo , Mazzali Marilda , Gordon Katherine L. , Hughes Jeremy , Johnson Richard J.
Published: December 2017

We investigated the hypothesis that hypokalemia might induce renal injury via a mechanism that involves subtle renal injury and alterations in local vasoactive mediators that would favor sodium retention. To test this hypothesis, we conducted studies in rats with diet-induced K+deficiency. We also determined whether rats with hypokalemic nephropathy show salt sensitivity. Twelve weeks of hypokalemia resulted in a decrease in creatinine clearance, tubulointerstitial injury with macrophage infiltration, interstitial collagen type III deposition, and an increase in osteopontin expression (a tubular marker of injury). The renal injury was greatest in the outer medulla with radiation into the cortex, suggestive of an ischemic etiology. Consistent with this hypothesis, we found an increased uptake of a hypoxia marker, pimonidazole, in the cortex. The intrarenal injury was associated with increased cortical angiontensin-converting enzyme (ACE) expression and continued cortical angiotensin II generation despite systemic suppression of the renin-angiotensin system, an increase in renal endothelin-1, a decrease in renal kallikrein, and a decrease in urinary nitrite/nitrates and prostaglandin E2excretion. At 12 wk, hypokalemic rats were placed on a normal-K+diet with either high (4%)- or low (0.01%)-NaCl content. Despite correction of hypokalemia and normalization of renal function, previously hypokalemic rats showed an elevated blood pressure in response to a high-salt diet compared with normokalemic controls. Hypokalemia is associated with alterations in vasoactive mediators that favor intrarenal vasoconstriction and an ischemic pattern of renal injury. These alterations may predispose the animals to salt-sensitive hypertension that manifests despite normalization of the serum K+.
Increased renal Na-K-ATPase, NCC, and β-ENaC abundance in obese Zucker rats
Authors: Bickel Crystal A. , Verbalis Joseph G. , Knepper Mark A. , Ecelbarger Carolyn A.
Published: December 2017

Renal sodium retention, as a result of increased abundance of sodium transporters, may play a role in the development and/or maintenance of the increased blood pressure in obesity. To address this hypothesis, we evaluated the relative abundances of renal sodium transporters in lean and obese Zucker rats at 2 and 4 mo of age by semiquantitative immunoblotting. Mean systolic blood pressure was higher in obese rats relative to lean at 3 mo, P < 0.02. Furthermore, circulating insulin levels were 6- or 13-fold higher in obese rats compared with lean at 2 or 4 mo of age, respectively. The abundances of the α1-subunit of Na-K-ATPase, the thiazide-sensitive Na-Cl cotransporter (NCC or TSC), and the β-subunit of the epithelial sodium channel (ENaC) were all significantly increased in the obese rats' kidneys. There were no differences for the sodium hydrogen exchanger (NHE3), the bumetanide-sensitive Na-K-2Cl cotransporter (NKCC2 or BSC1), the type II sodium-phosphate cotransporter (NaPi-2), or the α-subunit of ENaC. These selective increases could possibly increase sodium retention by the kidney and therefore could play a role in obesity-related hypertension.
Rapamycin impairs recovery from acute renal failure: role of cell-cycle arrest and apoptosis of tubular cells
Authors: Lieberthal Wilfred , Fuhro Robert , Andry C. Christopher , Rennke Helmut , Abernathy Vivian E. , Koh Jason S. , Valeri Robert , Levine Jerrold S.
Published: December 2017

The immunosuppressive effect of rapamycin is mediated by inhibition of interleukin-2-stimulated T cell proliferation. We report for the first time that rapamycin also inhibits growth factor-induced proliferation of cultured mouse proximal tubular (MPT; IC50∼1 ng/ml) cells and promotes apoptosis of these cells by impairing the survival effects of the same growth factors. On the basis of these in vitro data, we tested the hypothesis that rapamycin would impair recovery of renal function after ischemic acute renal failure induced in vivo by renal artery occlusion (RAO). Rats given daily injections of rapamycin or vehicle were subjected to RAO or sham surgery. Rapamycin had no effect on the glomerular filtration rate (GFR) of sham-operated animals. In rats subjected to RAO, GFR fell to comparable levels 1 day later in vehicle- and rapamycin-treated rats (0.25 ± 0.08 and 0.12 ± 0.05 ml · min−1· 300 g−1, respectively) ( P = not significant). In vehicle-treated rats subjected to RAO, GFR increased to 0.61 ± 0.08 ml · min−1· 300 g−1on day 3 ( P < 0.02 vs. day 1) and then rose further to 0.99 ± 0.09 ml · min−1· 300 g−1on day 4 ( P < 0.02 vs. day 3). By contrast, GFR did not improve in rapamycin-treated rats subjected to RAO over the same time period. Rapamycin also increased apoptosis of tubular cells while markedly reducing their proliferative response after RAO. Furthermore, rapamycin inhibited activation of 70-kDa S6 protein kinase (p70S6k) in cultured MPT cells as well as in the renal tissue of rats subjected to RAO. We conclude that rapamycin severely impairs the recovery of renal function after ischemia-reperfusion injury. This effect appears to be due to the combined effects of increased tubular cell loss (via apoptosis) and profound inhibition of the regenerative response of tubular cells. These effects are likely mediated by inhibition of p70S6k.
Calpains mediate acute renal cell death: role of autolysis and translocation
Authors: Liu Xiuli , Rainey Juanita J. , Harriman Jay F. , Schnellmann Rick G.
Published: December 2017

The goals of this study were to determine 1) the expression of calpain isoforms in rabbit renal proximal tubules (RPT); 2) calpain autolysis and translocation, and calpastatin levels during RPT injury; and 3) the effect of a calpain inhibitor (PD-150606) on calpain levels, mitochondrial function, and ion transport during RPT injury. RT-PCR, immunoblot analysis, and FITC-casein zymography demonstrated the presence of only μ- and m-calpains in rabbit RPT. The mitochondrial inhibitor antimycin A decreased RPT μ- and m-calpain and calpastatin levels in conjunction with cell death and increased plasma membrane permeability. No increases in either μ- or m-calpain were observed in the membrane nor were increases observed in autolytic forms of either μ- or m-calpain in antimycin A-exposed RPT. PD-150606 blocked antimycin A-induced cell death, preserved calpain levels in antimycin A-exposed RPT, and promoted the recovery of mitochondrial function and active Na+transport in RPT after hypoxia and reoxygenation. The present study suggests that calpains mediate RPT injury without undergoing autolysis or translocation, and ultimately they leak from cells subsequent to RPT injury/death. Furthermore, PD-150606 allows functional recovery after injury.
LRP: a new adhesion molecule for endothelial and smooth muscle cells
Authors: Hu Chuan , Oliver Juan A. , Goldberg Michael R. , Al-Awqati Qais
Published: December 2017

We recently generated a monoclonal antibody that disrupted the association of endothelial cells with their target location during kidney development. Here, we purified the antigen of this monoclonal antibody to homogeneity using rat mesangial cell cytosol. Sequence revealed that it is a previously identified protein, termed the “laminin receptor precursor” (LRP). We found that this protein is expressed in most tissues, but immunocytochemistry revealed that it is present largely or entirely in blood vessels where it is located underneath endothelial cells and in between smooth muscle cells of the vascular wall. Vascular smooth muscle cells such as mesangial cells produce and secrete LRP into their extracellular matrix where it is present in several molecular weight forms. Endothelial cells produce very little if any of the protein, but they bind avidly to LRP-coated dishes. Anti-LRP antibodies prevent the binding of smooth muscle cells to uncoated plates, implying that cells that secrete it use it for attachment. In an assay for heterologous cell-to-cell interaction, antibodies to LRP inhibited the binding of smooth muscle cells to endothelial cells. Maturation and differentiation of blood vessels require interaction between endothelial and smooth muscle cells. LRP is a new component of the mesangial matrix, and we propose that it is an adhesion molecule that mediates an interaction between smooth muscle cells and endothelia.
CD2AP and p130Cas localize to different F-actin structures in podocytes
Authors: Welsch T. , Endlich N. , Kriz W. , Endlich K.
Published: December 2017

Mice lacking the 80-kDa CD2-associated protein (CD2AP) develop progressive renal failure that starts soon after birth with proteinuria and foot process effacement by unknown mechanisms. CD2AP has been identified and cloned independently by virtue of its interaction with the T cell protein CD2 and with the docking protein p130Cas. In the present study we examined the localization of CD2AP and p130Cas in the mouse glomerulus and in cultured podocytes. In glomeruli, CD2AP and p130Cas immunofluorescence were observed in podocytes, where they colocalized with F-actin in foot processes. In addition, p130Cas was strongly expressed in mesangial cells. Immunoelectron microscopy demonstrated that CD2AP was present in podocyte foot processes without a prevailing localization. In cultured podocytes, p130Cas was enriched at sites of focal adhesions, where it colocalized like vinculin with F-actin at stress fiber ends. In contrast, CD2AP colocalized with F-actin at the leading edge of lamellipodia and in small spots, which were unevenly distributed in the cytoplasm. The spot-shaped F-actin structures were also stained by antibodies against the actin nucleation Arp2/3 complex and cortactin, both contributing to dynamic actin assembly. Moreover, CD2AP spots in cultured podocytes were in close spatial association with actinin-4, but not actinin-1. Our results suggest that CD2AP and p130Cas, which both colocalize with F-actin in podocytes in situ, possess different functions. Whereas p130Cas is found in focal adhesions, CD2AP seems to be involved in the regulation of highly dynamic F-actin structures in podocyte foot processes.
Effects of all-transretinoic acid on renin-angiotensin system in rats with experimental nephritis
Authors: Dechow Claudius , Morath Christian , Peters Jörg , Lehrke Ingo , Waldherr Rüdiger , Haxsen Volker , Ritz Eberhard , Wagner Jürgen
Published: December 2017

We previously demonstrated that all- trans retinoic acid (RA) preserves glomerular structure and function in anti-Thy1.1 nephritis (Wagner J, Dechow C, Morath C, Lehrke I, Amann K, Floege J, and Ritz E. J Am Soc Nephrol 11: 1479–1489, 2000). Because the renin-angiotensin system (RAS) contributes to renal damage, we 1) studied retinoid-specific effects on its components and 2) compared the effects of all- trans-RA with those of the AT1-receptor blocker candesartan. Rats were pretreated for 3 days before injection of the OX-7 antibody and continued with treatment with either vehicle or daily injections of 10 mg/kg all- trans-RA only ( study 1) or 10 mg/kg body wt all- trans-RA, 1 mg/kg candesartan, or both ( study 2) for an additional 7 days. The blood pressure increase observed in anti-Thy1.1 nephritic rats was equally normalized by all- trans-RA and candesartan ( P < 0.05). In nephritic rats, mRNAs of angiotensinogen and angiotensin-converting enzyme (ACE) in the kidney were unchanged, but renin mRNA was lower ( P < 0.01). Renal and glomerular AT1-receptor gene and protein expression levels were higher in anti-Thy1.1 nephritic rats ( P < 0.05). In the renal cortex of nephritic rats, pretreatment with all- trans-RA significantly reduced mRNAs of all the examined RAS components, but in the glomeruli it increased ACE gene and protein expression ( P < 0.01). In nephritic rats, candesartan reduced the number of glomerular cells and mitoses ( P < 0.05) less efficiently than all- trans-RA ( P < 0.01). Both substances reduced cellular proliferation (proliferating cell nuclear antigen) significantly ( P < 0.05). No additive effects were noted when both compounds were combined. In conclusion, all- trans-RA influences the renal RAS in anti-Thy1.1 nephritis by decreasing ANG II synthesis and receptor expression. The beneficial effect of retinoids may be explained, at least in part, by reduction of RAS activity.
Immunolocalization of electrogenic sodium-bicarbonate cotransporters pNBC1 and kNBC1 in the rat eye
Authors: Bok Dean , Schibler Matthew J. , Pushkin Alexander , Sassani Pejvak , Abuladze Natalia , Naser Zarah , Kurtz Ira
Published: December 2017

The human NBC1 gene encodes two electrogenic sodium-bicarbonate cotransport proteins, pNBC1 and kNBC1, which are candidate proteins for mediating electrogenic sodium-bicarbonate cotransport in ocular cells. Mutations in the coding region of the human NBC1 gene in exons common to both pNBC1 and kNBC1 result in a syndrome with a severe ocular and renal phenotype (blindness, band keratopathy, glaucoma, cataracts, and proximal renal tubular acidosis). In the present study, we determined the pattern of electrogenic sodium-bicarbonate cotransporter protein expression in rat eye. For this purpose, pNBC1- and kNBC1-specific antibodies were generated and used to detect these NBC1 protein variants by immunoblotting and immunocytochemistry. pNBC1 is expressed in cornea, conjunctiva, lens, ciliary body, and retina, whereas the expression of kNBC1 is restricted to the conjunctiva. These results provide the first evidence for extrarenal kNBC1 protein expression. The data in this study will serve as a basis for understanding the molecular mechanisms responsible for abnormalities in ocular electrogenic sodium-bicarbonate cotransport in patients with mutations in the NBC1 gene.
Extracellular nucleotides regulate cellular functions of podocytes in culture
Authors: Fischer Karl-Georg , Saueressig Ulrich , Jacobshagen Claudius , Wichelmann Arndt , Pavenstädt Hermann
Published: December 2017

Extracellular nucleotides are assumed to be important regulators of glomerular functions. This study characterizes purinergic receptors in podocytes. The effects of purinergic agonists on electrophysiological properties and the intracellular free Ca2+concentration of differentiated podocytes were examined with the patch-clamp and fura 2 fluorescence techniques. mRNA expression of purinergic receptors was investigated by RT-PCR. Purinergic agonists depolarized podocytes. Purinergic agonists similarly increased intracellular free Ca2+concentration of podocytes. The rank order of potency of various nucleotides on membrane voltage and free cytosolic calcium concentration was UTP ≈ UDP > [adenosine 5′- O-(3-thiotriphosphate) (ATP-γ-S)] > ATP > 2-methylthioadenosine 5′-triphosphate (2-MeS-ATP) > 2′- and 3′- O-(4-benzoylbenzoyl)-adenosine 5′-triphosphate (BzATP) > ADP-β-S. α,β-Me-ATP was without effect. In the presence of UTP, BzATP did not cause an additional depolarization of podocytes. Incubation of cells with ATP or BzATP did not induce lactate dehydrogenase release. In RT-PCR studies, mRNAs of the P2Y1, P2Y2, P2Y6, and P2X7receptors were detected within glomeruli and podocytes. The data indicate that extracellular nucleotides modulate podocyte function mainly by an activation of both P2Y2and P2Y6receptors.
Heteromeric amino acid transporters: biochemistry, genetics, and physiology
Authors: Chillarón Josep , Roca Ramón , Valencia Alfonso , Zorzano Antonio , Palacín Manuel
Published: December 2017

The heteromeric amino acid transporters (HATs) are composed of two polypeptides: a heavy subunit (HSHAT) and a light subunit (LSHAT) linked by a disulfide bridge. HSHATs are N-glycosylated type II membrane glycoproteins, whereas LSHATs are nonglycosylated polytopic membrane proteins. The HSHATs have been known since 1992, and the LSHATs have been described in the last three years. HATs represent several of the classic mammalian amino acid transport systems (e.g., L isoforms, y+L isoforms, asc, x[Formula: see text], and b0,+). Members of the HAT family are the molecular bases of inherited primary aminoacidurias cystinuria and lysinuric protein intolerance. In addition to the role in amino acid transport, one HSHAT [the heavy subunit of the cell-surface antigen 4F2 (also named CD98)] is involved in other cell functions that might be related to integrin activation. This review covers the biochemistry, human genetics, and cell physiology of HATs, including the multifunctional character of CD98.
Modulation of membrane traffic by mechanical stimuli
Authors: Apodaca Gerard
Published: December 2017

All cells experience and respond to mechanical stimuli, such as changes in plasma membrane tension, shear stress, hydrostatic pressure, and compression. This review is an examination of the changes in membrane traffic that occur in response to mechanical forces. The plasma membrane has an associated tension that modulates both exocytosis and endocytosis. As membrane tension increases, exocytosis is stimulated, which acts to decrease membrane tension. In contrast, increased membrane tension slows endocytosis, whereas decreased tension stimulates internalization. In most cases, secretion is stimulated by external mechanical stimuli. However, in some cells mechanical forces block secretion. External stimuli also enhance membrane and fluid endocytosis in several cell types. Transduction of mechanical stimuli into changes in exocytosis/endocytosis may involve the cytoskeleton, stretch-activated channels, integrins, phospholipases, tyrosine kinases, and cAMP.
Comparison of two hydrodensitometric methods for estimating percent body fat
Authors: van der Ploeg Grant E. , Gunn Simon M. , Withers Robert T. , Modra Andrew C. , Crockett Alan J.
Published: December 2017

This study compared the two following hydrodensitometric methods for estimating percent body fat (%BF): 1) estimation of residual volume (RV) by helium dilution before and after measurement of immersed mass at RV, and 2) determination of immersed mass at a comfortable level of expiration (approximately functional residual capacity) with measurement of the associated gas volume by oxygen dilution. Twelve men [27.9 ± 7.5 (SD) yr; 79.32 ± 12.79 kg; 180.5 ± 9.9 cm] were tested for %BF via both methods on each of two separate visits within 3 days by using a counterbalanced design. The two helium dilution measurements yielded a technical error of measurement of 0.2% BF and an intraclass correlation coefficient of 0.999. Corresponding values for the oxygen dilution method were 0.4% BF and 0.999, respectively. There was no difference ( P = 0.80) between the helium dilution (16.9 ± 9.3% BF) and oxygen dilution (16.9 ± 9.4% BF) methods, and the individual differences ranged from −0.7 to 0.6% BF. The interclass correlation coefficient between the two methods was 0.999 with a SE of estimate of 0.4% BF. Whereas both methods were precise and reliable and yielded similar results, the oxygen dilution technique was more expedient and was preferred by the subjects because they were not required to exhale to RV.
Creatine reduces human muscle PCr and pH decrements and Piaccumulation during low-intensity exercise
Authors: Rico-Sanz Jesús
Published: December 2017

The purpose of this study was to examine with31P-magnetic resonance spectroscopy energy metabolism during repeated plantar flexion isometric exercise (Ex-1–Ex-4) at 32 ± 1 and 79 ± 4% of maximal voluntary contraction (MVC) before and during a creatine (Cr) feeding period of 5 g/day for 11 days. Eight trained male subjects participated in the study. ATP was unchanged with Cr supplementation at rest and during exercise at both intensities. Resting muscle phosphocreatine (PCr) increased ( P < 0.05) from 18.3 ± 0.9 (before) to 19.6 ± 1.0 mmol/kg wet wt after 9 days. At 79% MVC, PCr used, Piaccumulated, and pH at the end of Ex-1–Ex-4 were similar after 4 and 11 days of Cr supplementation. In contrast, PCr utilization and Piaccumulation were lower and pH was higher for exercise at 32% MVC with Cr supplementation, suggesting aerobic resynthesis of PCr was more rapid during exercise. These results suggest that elevating muscle Cr enhances oxidative phosphorylation during mild isometric exercise, where it is expected that oxygen delivery matches demands and predominantly slow-twitch motor units are recruited.
Passive energy absorption by human muscle-tendon unit is unaffected by increase in intramuscular temperature
Authors: Magnusson S. P. , Aagaard P. , Larsson B. , Kjaer M.
Published: December 2017

The present study measured hamstring intramuscular temperature and muscle-tendon unit viscoelastic properties in healthy young men before and after 10 and 30 min of running with ( day S) or without stretch ( day NS). On day NS, passive energy absorption and intramuscular temperature were measured before running (Preex), after 10 min of running at 70% of maximum O2uptake (Postex10), and after 30 min of running at 75% of maximum O2uptake (Postex30). On day S, the protocol was repeated with three stretches ( stretches 1–3) added after Postex10. Intramuscular temperature was elevated Postex10 ( P < 0.01) and further Postex30 ( P < 0.05). On day NS, the total energy absorbed Preex (14.3 ± 2.3 J), Postex10 (14.5 ± 3.2 J), and Postex30 (13.5 ± 2.4 J) was not different. On day S, the total energy absorbed in stretch 3 (10.8 ± 1.8 J) was lower than that Preex (14.5 ± 1.7 J, P < 0.01) and Postex10 (13.5 ± 1.9 J, P < 0.05) but not Postex30 (13.3 ± 1.8 J). The total energy absorbed Postex30 did not differ from Preex. In conclusion, warm-up and continuous running elevated intramuscular temperature but did not affect the passive energy absorption. Repeated passive stretching reduced the energy absorption immediately; however, the effect did not remain after 30 min of running. These data suggest that passive energy absorption of the human skeletal muscle is insensitive to physiological increases in intramuscular temperature.
Glucose ingestion and substrate utilization during exercise in boys with IDDM
Authors: Riddell M. C. , Bar-Or O. , Hollidge-Horvat M. , Schwarcz H. P. , Heigenhauser G. J. F.
Published: December 2017

This study was intended to compare exogenous [13C]glucose (Gluexo) oxidation in boys with insulin-dependent diabetes mellitus (IDDM) and healthy boys of similar age, weight, and maximal O2 uptake. In a control trial with water intake (CT) and in a 13C-enriched glucose trial (GT), subjects cycled for 60 min (58.8 ± 0.9% maximal O2 uptake) while the utilization of total glucose, total fat, and Gluexo was assessed. In CT, total glucose was 84.7 ± 9.2 vs. 91.3 ± 6.6 g/60 min (not significantly different) and total fat was 13.3 ± 2.2 vs. 11.1 ± 1.7 g/60 min (not significantly different) in IDDM vs. healthy boys, respectively. In GT, Gluexo was 10.4 ± 1.7 vs. 14.8 ± 1.1 g/60 min, corresponding to 9.0 ± 1.0 vs. 12.4 ± 0.5% of the total energy supply in IDDM and healthy boys, respectively ( P < 0.05). Endogenous glucose was spared in both groups by 12.6 ± 3.5% ( P < 0.05). Blood glucose and plasma insulin concentrations were two- to threefold higher in IDDM vs. healthy boys in both trials. In conclusion, Gluexo is impaired in exercising boys with IDDM, even when plasma insulin levels are elevated.
Vagal and mediator mechanisms underlying the tachypnea caused by pulmonary air embolism in dogs
Authors: Chen H. F. , Kou Y. R.
Published: December 2017

We investigated the vagal and mediator mechanisms underlying the tachypnea caused by pulmonary air embolism (PAE) in anesthetized and spontaneously breathing dogs. PAE was induced by infusion of air into the right atrium (0.2 ml ⋅ kg−1 ⋅ min−1for 10 min). The first PAE induction caused an increase in respiratory frequency accompanied by a decrease in tidal volume in each of the 30 animals studied. Subsequently, animals were evenly divided into five groups, and a second PAE induction was repeated after various experimental interventions. The tachypneic response to PAE was not significantly altered by pretreatment with a saline vehicle but was largely attenuated by either perivagal capsaicin treatment (a technique that selectively blocks the conduction of unmyelinated C fibers), pretreatment with ibuprofen (a cyclooxygenase inhibitor), or pretreatment with dimethylthiourea (a hydroxyl radical scavenger). Ultimately, the tachypneic response was nearly abolished by a bilateral cervical vagotomy. These results suggest that 1) lung vagal unmyelinated C-fiber afferents play a predominant role in evoking the reflex tachypneic response to PAE and 2) both cyclooxygenase products and hydroxyl radical are important in eliciting this vagally mediated response.
Adipose tissue lipolysis is increased during a repeated bout of aerobic exercise
Authors: Stich V. , de Glisezinski I. , Berlan M. , Bulow J. , Galitzky J. , Harant I. , Suljkovicova H. , Lafontan M. , Rivière D. , Crampes F.
Published: December 2017

The goal of the study was to examine whether lipid mobilization from adipose tissue undergoes changes during repeated bouts of prolonged aerobic exercise. Microdialysis of the subcutaneous adipose tissue was used for the assessment of lipolysis; glycerol concentration was measured in the dialysate leaving the adipose tissue. Seven male subjects performed two repeated bouts of 60-min exercise at 50% of their maximal aerobic power, separated by a 60-min recovery period. The exercise-induced increases in extracellular glycerol concentrations in adipose tissue and in plasma glycerol concentrations were significantly higher during the second exercise bout compared with the first ( P < 0.05). The responses of plasma nonesterified fatty acids and plasma epinephrine were higher during the second exercise bout, whereas the response of norepinephrine was unchanged and that of growth hormone lower. Plasma insulin levels were lower during the second exercise bout. The results suggest that adipose tissue lipolysis during aerobic exercise of moderate intensity is enhanced when an exercise bout is preceded by exercise of the same intensity and duration performed 1 h before. This response pattern is associated with an increase in the exercise-induced rise of epinephrine and with lower plasma insulin values during the repeated exercise bout.
Soft tissue body composition differences in monozygotic twins discordant for spinal cord injury
Authors: Spungen Ann M. , Wang Jack , Pierson Richard N. , Bauman William A.
Published: December 2017

To determine the effect of paralysis on body composition, eight pairs of male monozygotic twins, one twin in each pair with paraplegia, were studied by dual-energy X-ray absorptiometry. Significant loss of total body lean tissue mass was found in the paralyzed twins compared with their able-bodied co-twins: 47.5 ± 6.7 vs. 60.1 ± 7.8 (SD) kg ( P < 0.005). Regionally, arm lean tissue mass was not different between the twin pairs, whereas trunk and leg lean tissue masses were significantly lower in the paralyzed twins: −3.0 ± 3.3 kg ( P < 0.05) and −10.1 ± 4.0 kg ( P < 0.0005), respectively. Bone mineral content of the total body and legs was significantly related to lean tissue mass in the able-bodied twins ( R = 0.88 and 0.98, respectively) but not in the paralyzed twins. However, the intrapair difference scores for bone and lean tissue mass were significantly related ( R = 0.80 and 0.81, respectively). The paralyzed twins had significantly more total body fat mass and percent fat per unit body mass index than the able-bodied twins: 4.8 kg ( P < 0.05) and 7 ± 2% ( P< 0.01). In the paralyzed twins, total body lean tissue was significantly lost (mostly from the trunk and legs), independent of age, at a rate of 3.9 ± 0.2 kg per 5-yr period of paralysis ( R = 0.87, P < 0.005). Extreme disuse from paralysis appears to contribute to a parallel loss of bone with loss of lean tissue in the legs. The continuous lean tissue loss may represent a form of sarcopenia that is progressive and accelerated compared with that in ambulatory individuals.
Aging of skeletal muscle: a 12-yr longitudinal study
Authors: Frontera Walter R. , Hughes Virginia A. , Fielding Roger A. , Fiatarone Maria A. , Evans William J. , Roubenoff Ronenn
Published: December 2017

The present study examines age-related changes in skeletal muscle size and function after 12 yr. Twelve healthy sedentary men were studied in 1985–86 (T1) and nine (initial mean age 65.4 ± 4.2 yr) were reevaluated in 1997–98 (T2). Isokinetic muscle strength of the knee and elbow extensors and flexors showed losses ( P < 0.05) ranging from 20 to 30% at slow and fast angular velocities. Computerized tomography ( n = 7) showed reductions ( P < 0.05) in the cross-sectional area (CSA) of the thigh (12.5%), all thigh muscles (14.7%), quadriceps femoris muscle (16.1%), and flexor muscles (14.9%). Analysis of covariance showed that strength at T1 and changes in CSA were independent predictors of strength at T2. Muscle biopsies taken from vastus lateralis muscles ( n = 6) showed a reduction in percentage of type I fibers (T1 = 60% vs. T2 = 42%) with no change in mean area in either fiber type. The capillary-to-fiber ratio was significantly lower at T2 (1.39 vs. 1.08; P = 0.043). Our observations suggest that a quantitative loss in muscle CSA is a major contributor to the decrease in muscle strength seen with advancing age and, together with muscle strength at T1, accounts for 90% of the variability in strength at T2.
Different ontogeny of rate of force generation and shortening velocity in guinea pig trachealis
Authors: Chitano Pasquale , Wang Jizhong , Cox Carrie M. , Stephens Newman L. , Murphy Thomas M.
Published: December 2017

Juveniles of many species, including humans, display greater airway responsiveness than do adults. This may involve changes in airway smooth muscle function. In the present work we studied force production and shortening velocity in trachealis from 1-wk-old (1 wk), 3-wk-old (3 wk), and 3-mo-old (adult) guinea pigs. Strips were electrically stimulated (60 Hz, 18 V) at their optimal length ( l o) to obtain maximum active stress (Po) and rate of stress generation. Then, force-velocity curves were elicited at 2.5 s from the onset of the stimulus. By applying a recently developed modification of Hill's equation for airway smooth muscle, the maximum shortening velocity at zero load ( V o) and the value α ⋅ γ/β, an index of internal resistance to shortening (Rsi), were calculated (α, β, and γ are the constants of the equation). Poincreased little with maturation, whereas the rate of stress generation increased significantly (0.40 ± 0.03, 0.45 ± 0.03, 0.51 ± 0.03 P o/s for 1 wk, 3 wk, and adult animals). V o slightly increased early with maturation to decrease significantly later (1.79 ± 0.67, 2.45 ± 0.92, and 0.55 ± 0.09 l o/s for 1 wk, 3 wk, and adult animals), whereas the Rsi showed an opposite trend (14.98 ± 5.19, 8.99 ± 3.01, and 32.07 ± 5.54 mN ⋅ mm−2 ⋅ l o −1 ⋅ s for 1 wk, 3 wk, and adult animals). This early increase of force generation in combination with late increase of Rsi may explain the changes of V o with age. An elevated V o may contribute to the incidence of airway hyperresponsiveness in healthy juveniles.
Adaptive responses during anemia and its correction in lambs
Authors: Widness John A. , Lowe Lance S. , Bell Edward F. , Burmeister Leon F. , Mock Donald M. , Kistard James A. , Bard Harry
Published: December 2017

There is limited information available on which to base decisions regarding red blood cell (RBC) transfusion treatment in anemic newborn infants. Using a conscious newborn lamb model of progressive anemia, we sought to identify accessible metabolic and cardiovascular measures of hypoxia that might provide guidance in the management of anemic infants. We hypothesized that severe phlebotomy-induced isovolemic anemia and its reversal after RBC transfusion result in a defined pattern of adaptive responses. Anemia was produced over 2 days by serial phlebotomy (with plasma replacement) to Hb levels of 30–40 g/l. During the ensuing 2 days, Hb was restored to pretransfusion baseline levels by repeated RBC transfusion. Area-under-the-curve methodology was utilized for defining the Hb level at which individual study variables demonstrated significant change. Significant reciprocal changes ( P < 0.05) of equivalent magnitude were observed during the phlebotomy and transfusion phases for cardiac output, plasma erythropoietin (Epo) concentration, oxygen extraction ratio, oxygen delivery, venous oxygen saturation, and blood lactate concentration. No significant change was observed in resting oxygen consumption. Cardiac output and plasma Epo concentration increased at Hb levels <75 g/l, oxygen delivery and oxygen extraction ratio decreased at Hb levels <60 g/l, and venous oxygen saturation decreased and blood lactate concentration increased at Hb levels <55 g/l. We speculate that plasma Epo and blood lactate concentrations may be useful measures of clinically significant anemia in infants and may indicate when an infant might benefit from a RBC transfusion.
Airway distensibility in healthy and asthmatic subjects: effect of lung volume history
Authors: Johns David Peter , Wilson John , Harding Richard , Walters E. Haydn
Published: December 2017

Anatomic dead space (Vd) is known to increase with end-inspiratory lung volume (EILV), and the gradient of the relationship has been proposed as an index of airway distensibility (ΔVd). The aims of this study were to apply a rapid method for measuring ΔVd and to determine whether it was affected by lung volume history. Vd of 16 healthy and 16 mildly asthmatic subjects was measured at a number of known EILVs by using a tidal breathing, CO2-washout method. The effect of lung volume history was assessed by using three tidal breathing regimens: 1) three discrete EILVs (low/medium/high; LMH); 2) progressively decreasing EILVs from total lung capacity (TLC; TLC-RV); and 3) progressively increasing EILVs from residual volume (RV; RV-TLC). ΔVd was lower in the asthmatic group for the LMH (25.3 ± 2.24 vs. 21.2 ± 1.66 ml/l, means ± SE) and TLC-RV (24.3 ± 1.69 vs. 18.7 ± 1.16 ml/l) regimens. There was a trend for a lower ΔVd in the asthmatic group for the RV-TLC regimen (23.3 ± 2.19 vs. 18.8 ± 1.68 ml/l). There was no difference in ΔVd between groups. In conclusion, mild asthmatic subjects have stiffer airways than normal subjects, and this is not obviously affected by lung volume history.
HIF-1: mediator of physiological and pathophysiological responses to hypoxia
Authors: Semenza Gregg L.
Published: December 2017

All organisms can sense O2concentration and respond to hypoxia with adaptive changes in gene expression. The large body size of mammals necessitates the development of multiple complex physiological systems to ensure adequate O2delivery to all cells under normal conditions. The transcriptional regulator hypoxia-inducible factor 1 (HIF-1) is an essential mediator of O2homeostasis. HIF-1 is required for the establishment of key physiological systems during development and their subsequent utilization in fetal and postnatal life. HIF-1 also appears to play a key role in the pathophysiology of cancer, cardiovascular disease, and chronic lung disease, which represent the major causes of mortality among industrialized societies. Genetic or pharmacological modulation of HIF-1 activity in vivo may represent a novel therapeutic approach to these disorders.
Effect of different carbohydrate drinks on whole body carbohydrate storage after exhaustive exercise
Authors: Bowtell J. L. , Gelly K. , Jackman M. L. , Patel A. , Simeoni M. , Rennie M. J.
Published: December 2017

Seven untrained male subjects participated in a double-blind, crossover study conducted to determine the efficacy of different carbohydrate drinks in promoting carbohydrate storage in the whole body and skeletal muscle during recovery from exhaustive exercise. The postabsorptive subjects first completed an exercise protocol designed to deplete muscle fibers of glycogen, then consumed 330 ml of one of three carbohydrate drinks (18.5% glucose polymer, 18.5% sucrose, or 12% sucrose; wt/vol) and also received a primed constant infusion of [1-13C]glucose for 2 h. Nonoxidative glucose disposal (3.51 ± 0.28, 18.5% glucose polymer; 2.96 ± 0.32, 18.5% sucrose; 2.97 ± 0.16, 12% sucrose; all mmol ⋅ kg−1⋅ h−1) and storage of muscle glycogen (5.31 ± 1.11, 18.5% glucose polymer; 4.07 ± 1.05, 18.5% sucrose; 3.45 ± 0.85, 12% sucrose; all mmol ⋅ kg wet wt−1⋅ h−1; P < 0.05) were greater after consumption of the glucose polymer drink than after either sucrose drink. The results suggest that the consumption of a glucose polymer drink (containing 61 g carbohydrate) promotes a more rapid storage of carbohydrate in the whole body, skeletal muscle in particular, than an isoenergetic sucrose drink.
Fractal nature of regional ventilation distribution
Authors: Altemeier William A. , McKinney Steve , Glenny Robb W.
Published: December 2017

High-resolution measurements of pulmonary perfusion reveal substantial spatial heterogeneity that is fractally distributed. This observation led to the hypothesis that the vascular tree is the principal determinant of regional blood flow. Recent studies using aerosol deposition show similar ventilation heterogeneity that is closely correlated with perfusion. We hypothesize that ventilation has fractal characteristics similar to blood flow. We measured regional ventilation and perfusion with aerosolized and injected fluorescent microspheres in six anesthetized, mechanically ventilated pigs in both prone and supine postures. Adjacent regions were clustered into progressively larger groups. Coefficients of variation were calculated for each cluster size to determine fractal dimensions. At the smallest size lung piece, local ventilation and perfusion are highly correlated, with no significant difference between ventilation and perfusion heterogeneity. On average, the fractal dimension of ventilation is 1.16 in the prone posture and 1.09 in the supine posture. Ventilation has fractal properties similar to perfusion. Efficient gas exchange is preserved, despite ventilation and perfusion heterogeneity, through close correlation. One potential explanation is the similar geometry of bronchial and vascular structures.
Effect of carbohydrate ingestion on ammonia metabolism during exercise in humans
Authors: Snow Rodney J. , Carey Michael F. , Stathis Christos G. , Febbraio Mark A. , Hargreaves Mark
Published: December 2017

The present study was undertaken to examine the effect of carbohydrate ingestion on plasma and muscle ammonia (NH3denotes ammonia and ammonium) accumulation during prolonged exercise. Eleven trained men exercised for 2 h at 65% peak pulmonary oxygen consumption while ingesting either 250 ml of an 8% carbohydrate-electrolyte solution every 15 min (CHO) or an equal volume of a sweet placebo. Blood glucose and plasma insulin levels during exercise were higher in CHO, but plasma hypoxanthine was lower after 120 min (1.7 ± 0.3 vs. 2.6 ± 0.1 μmol/l; P < 0.05). Plasma NH3levels were similar at rest and after 30 min of exercise in both trials but were lower after 60, 90, and 120 min of exercise in CHO (62 ± 9 vs. 76 ± 9 μmol/l; P < 0.05). Muscle NH3levels were similar at rest and after 30 min of exercise but were lower after 120 min of exercise in CHO (1.51 ± 0.21 vs. 2.07 ± 0.23 mmol/kg dry muscle; P< 0.05; n = 5). These data are best explained by carbohydrate ingestion reducing muscle NH3production from amino acid degradation, although a small reduction in net AMP catabolism within the contracting muscle may also make a minor contribution to the lower tissue NH3levels.