bluuebunny/crossref_metadata_2025 huggingface dataset:
Aortic caliber changes during development of hypertension in freely moving rats
Authors: Michelini L. C. , Krieger E. M.
Published: December 2017

The availability of a chronically implanted electrolytic strain gauge has permitted us to monitor, for the first time in freely moving rats, sequential changes of both resting caliber and mechanical properties of the aorta during onset and maintenance of sustained hypertension. Normotensive rats were subjected to subdiaphragmatic aortic constriction under ether anesthesia. There was an immediate and sustained rise of pressure (on average a 50% increase over base-line mean arterial pressure of 101 +/- 4 mmHg), whereas mean aortic caliber (6.552 +/- 0.142 mm) dilated gradually with no significant change at 6 h and had a significant dilation of 3.4 and 6.8% after 24 and 48 h, respectively. On the 2nd day of hypertension, dilation of the aorta was accompanied by a marked increase in both mean distensibility and dynamic distensibility of the aortic wall (7-fold and 1.5-fold increase over basal values of 0.128 +/- 0.015 and 0.056 +/- 0.005 X 10(-6) dyn/cm2, respectively). No further dilation was observed for up to 5 days, but the dynamic distensibility of the aorta returned to normal values on the 3rd day of hypertension. Maximal dilation at 48 h was produced by the increase of both pulsation and diastolic caliber of the aorta with the displacement of diastolic caliber (94.8%) being the major determinant of aortic dilation. Thus the time required for the aorta to achieve the new resting diastolic position during the development of sustained hypertension (48 h) coincides with the time course of complete resetting of aortic baroreceptors as we demonstrated before in the same preparation. These two findings taken together suggest that alterations in the geometry of the aortic wall play an important role in the resetting process.
Determination of effects of internal countershock by direct cardiac recordings during normal rhythm
Authors: Colavita P. G. , Wolf P. , Smith W. M. , Bartram F. R. , Hardage M. , Ideker R. E.
Published: December 2017

Recording cardiac electrical activity after a countershock has been limited by amplifier saturation. Modifications to our computer-assisted mapping system allowed us to record electrical activity from 56 epicardial electrodes within 5 ms of the end of a countershock. Modifications included the use of solid-state switches to disconnect the filter section of the amplifiers during the shock and changing the low-frequency response of the amplifiers from 0.1 to 10 Hz to filter out large, low-frequency potentials after the shock. Six-millisecond truncated exponential shocks were delivered between the superior vena cava and right ventricular apex through a quadripolar catheter during normal rhythm in seven dogs. As shocks of increasing voltage were delivered during the T-Q interval, progressively more of the epicardium was directly depolarized. A shock of 109 +/- 17 (SD) V directly depolarized the entire epicardium. Shocks of constant voltage were then delivered with increasing prematurity during diastole. As the ventricles became more refractory with increasing shock prematurity, the amount of epicardium depolarized became progressively less. Thus computer-assisted mapping techniques are capable of measuring the area depolarized by a shock during normal rhythm and may be useful during arrhythmias to improve our understanding of defibrillation and cardioversion.
Heterogeneous response of subsarcolemmal heart mitochondria to calcium
Authors: Palmer J. W. , Tandler B. , Hoppel C. L.
Published: December 2017

he Ca2+ -uptake capacity of two distinct populations of rat heart mitochondria was characterized by monitoring Ca2+ movements directly (using both 45Ca and dual-wavelength spectroscopy) and indirectly (monitoring effects of Ca2+ on respiration, enzyme release, and morphology). Interfibrillar mitochondria accumulated up to 930 nmol/mg protein, whereas the capacity of the subsarcolemmal mitochondria for Ca2+ uptake was limited to 620 nmol/mg protein. In both mitochondrial populations, uptake of the maximal amount of Ca2+ was accompanied by increased proton permeability and subsequent release of the accumulated Ca2+. Even when calcium was taken up and apparently retained by the subsarcolemmal mitochondria, resting respiratory rates increased. Morphological examination of these mitochondria revealed that, although the majority of mitochondria were in the aggregated, energized conformation, a considerable number were disrupted. These damaged mitochondria were probably responsible for the increased resting respiratory rates. No net release of calcium was observed, however, since the intact mitochondria could take up any calcium released by the damaged mitochondria. Morphological disruption of this subset of subsarcolemmal mitochondria was accompanied by release of not only cytochrome c but also of mitochondrial marker enzymes into the extramitochondrial milieu. In contrast, the interfibrillar mitochondria were relatively unaffected in terms of morphology and marker enzyme release, even when their capacity to retain calcium was exceeded.
O2 gradients from sarcolemma to cell interior in red muscle at maximal VO2
Authors: Gayeski T. E. , Honig C. R.
Published: December 2017

The intracellular distribution of O2 in cross sections of dog gracilis muscles was determined by myoglobin (Mb) cryospectrophotometry. The volume sampled by the photometer was approximately 30 micron3 and contained 1-2 mitochondria. Measurements could be made to within 3 micron of capillaries without interference from hemoglobin. Mb saturation was uniform at all loci examined when respiration was blocked with cyanide. During twitch contraction at maximum O2 consumption, saturations within a cell cross section varied by up to 20%. The corresponding difference in partial pressure of O2 (PO2) was 1.5 Torr. Circumferential O2 gradients parallel to and 5 micron from the sarcolemma were greatest near capillaries. They did not exceed 0.1 Torr/micron and were dissipated within 25 micron of the sarcolemma. Gradients perpendicular to the sarcolemma were less than 0.02 Torr/micron. Saturation was not significantly correlated with cell diameter. Minimum PO2 was seldom located at the center of the cell cross section. Differences in saturation between contiguous cells often exceeded 10%. The distribution of O2 within cells appeared to reflect both an intercellular O2 flux and and an O2 flux from adjacent capillaries. Data agree qualitatively and quantitatively with mathematical models that take account of the particulate nature of blood and facilitated diffusion by Mb.
Dynamics of pure parasystole
Authors: Glass L. , Goldberger A. L. , Belair J.
Published: December 2017

A mathematical model is proposed for ventricular parasystole. In this model, there are two separate rhythms, a sinus rhythm and a ventricular ectopic rhythm. An ectopic beat will occur if the ectopic depolarization falls during a time interval when the ventricles are not refractory. Following an ectopic beat there is a compensatory pause. Analysis of this model, utilizing numerical simulation and techniques in number theory, demonstrates several new rules for parasystole. Specifically, for any set of fixed values for the sinus and ectopic frequencies and the ventricular refractory time, there are at most three different values for the number of sinus beats between ectopic beats. One and only one of these values is odd, and the sum of the two smaller values is one less than the larger value. The variation in the allowed values of the number of sinus beats between ectopic beats, as a function of the parameters of the model, is classified. Clinical cases found in the literature display certain aspects of the predictions of the theoretical model. Theoretical analysis of this kind provides new approaches to assessing the mechanism of complex ventricular arrhythmias.
Filling and arterial pressures as determinants of left ventricular stroke volume in fetal lambs
Authors: Thornburg K. L. , Morton M. J.
Published: December 2017

Left ventricular (LV) function was investigated in 16 fetal lambs (125-140 days gestation), each instrumented with an electromagnetic flow sensor on the ascending aorta and vascular catheters. Control arterial blood values were pH 7.38 +/- 0.02 (SD), PCO2 46.3 +/- 3.2 Torr, PO2 19.4 +/- 1.3 Torr, and hematocrit 34.8 +/- 4.3%. Control values for LV output (228 +/- 108 ml X min-1 X kg-1) and arterial pressure (AP, 47.4 +/- 6.5 Torr) were unchanged by administration of atropine and propranolol. LV function curves relating stroke volume (SV) to mean left atrial pressure (LAP) were generated by rapid withdrawal and reinfusion of fetal blood with or without concomitant infusion of nitroprusside (NP) or phenylephrine hydrochloride (PE) to lower or raise mean arterial pressure (AP). The control LV function curve was composed of a steep ascending limb of 0.39 +/- 0.34 ml X kg-1 X Torr-1 and a plateau of 0.04 +/- 0.04 ml X kg-1 X Torr-1. The breakpoint joining the limbs of the control curve was LAP 3.1 +/- 1.2 Torr and LVSV 1.3 +/- 0.5 ml/kg, and these values were not different from control LAP and SV. Function curve slopes were not affected by PE or NP treatment. Multiple linear regression of SV, LAP, and AP showed a small but significant coefficient for AP [-0.002 +/- 0.001 (SE) ml X kg-1 X Torr-1] and LAP [+0.053 +/- 0.004 (SE) ml X kg-1 X Torr-1] at LAP greater than breakpoint.(ABSTRACT TRUNCATED AT 250 WORDS)
Generalization of the Fahraeus principle for microvessel networks
Authors: Pries A. R. , Ley K. , Gaehtgens P.
Published: December 2017

Microvessel hematocrits and diameters were determined in each vessel segment between bifurcations of three complete microvascular networks in rat mesentery. Classification of the segments as arteriolar, venular, or arteriovenular (av) was based on flow direction at branch points. Photographic and videomicroscopic mapping was used to obtain quantitative information on the architecture and topology of the networks. This topological information allowed the analysis of hematocrit distribution within a series of consecutive-flow cross sections, each of which carried the total flow through the network. The observed reduction of mean hematocrit in the more peripheral cross sections is explained by the presence of a “vessel” and a “network” Fahraeus effect. The vessel Fahraeus effect results from velocity difference between red cells and blood within the individual vessel segments due to the existing velocity and cell concentration profiles. The network Fahraeus effect is based on the velocity difference of red cells and blood caused by velocity and hematocrit heterogeneity between the vessels constituting any of the complete-flow cross sections. The network Fahraeus effect is found to account for approximately 20% of the total hematocrit reduction and increases toward the most distal cross sections.
Vascular reactivity of contralateral kidney in awake Goldblatt hypertensive dog
Authors: Zimmerman Ben G.
Published: December 2017

Pages H1043–H1049: Ben G. Zimmerman. “Vascular reactivity of contralateral kidney in awake Goldblatt hypertensive dog.” Page H1044: methods, fourth sentence should read “In a second operative procedure, an electromagnetic blood flow probe (4–6 mm Zepeda Instruments, Seattle, WA) was installed around and a small catheter (PE-10 tubing) inserted into the left renal artery, as previously described (34).” Page H1045: Table 2 should appear as follows:

(See PDF)
Effects of cord compression on fetal blood flow distribution and O2 delivery
Authors: Itskovitz J. , LaGamma E. F. , Rudolph A. M.
Published: December 2017

We used the radionuclide microsphere technique in nine fetal lambs to examine the effect of partial cord compression on distribution of cardiac output and O2 delivery to fetal organs and venous flow patterns. With a 50% reduction in umbilical blood flow the fraction of fetal cardiac output distributed to the brain, heart, carcass, kidneys, and gastrointestinal tract increased. Pulmonary blood flow fell. O2 delivery to the brain and myocardium was maintained but was reduced to peripheral, renal, and gastrointestinal circulations. Hepatic blood flow decreased and O2 delivery fell by 75%. The proportion of umbilical venous blood passing through the ductus venosus increased from 43.9 to 71.8%. The preferential distribution of ductus venosus blood flow through the foramen ovale was enhanced (29.4 vs. 47.2%) and the proportion of O2 delivery to upper body organs derived from the ductus venosus increased (33.2 vs. 49.4%). Abdominal inferior vena caval blood flow increased, and it was also preferentially distributed through the foramen ovale (21.9 vs. 44.2%) and constituted the major fraction of the arterial blood supply to the upper body organs (16.5 vs. 36.4%). Thus cord compression modified the distribution of cardiac output and the patterns of venous returns in the fetus. This pattern of circulatory response differs from that observed with other causes of reduced O2 delivery.
Differentiation of sarcoplasmic reticulum during cardiac myogenesis
Authors: Pegg W. , Michalak M.
Published: December 2017

The composition and function of fetal and mature sheep cardiac sarcoplasmic reticulum membranes were investigated. Phospholamban, a major phosphoprotein in the mature sarcoplasmic reticulum membranes, was present in early stages of cardiac myogenesis. This fetal form of phospholamban was phosphorylated by cAMP-dependent protein kinase but not in the presence of Ca2+ and calmodulin. Ca2+ uptake and Ca2+-dependent ATPase activity were low in fetal sarcoplasmic reticulum compared with the adult controls, although the apparent affinities for Ca2+ were similar. Sarcoplasmic reticulum vesicles isolated at all developmental stages had very low levels of plasma membrane (as determined by Na+-K+-ATPase and Na+-Ca2+ exchanger activities) and mitochondrial contamination. Sarcoplasmic reticulum Ca2+ uptake and Ca2+-dependent ATPase activities were not affected by micromolar concentrations of vanadate, and the accumulated Ca2+ could not be released by the addition of NaCl. The amount of both the 110- and 55-kDa protein bands, identified with specific antibodies as Ca2+-ATPase and calsequestrin, respectively, was low in early stages of cardiac myogenesis. Age-related differences in the Ca2+ transport properties of cardiac sarcoplasmic reticulum and in the amount of the Ca2+-ATPase and calsequestrin may explain alterations in the regulation of intracellular Ca2+ concentrations in the fetal heart. This may contribute to the developmental changes in myocardial function.
Flow-induced detachment of adherent platelets from fibrinogen-coated surface
Authors: Jen C. J. , Li H. M. , Wang J. S. , Chen H. I. , Usami S.
Published: December 2017

A study of the shear forces under which adherent platelets of different morphologies can be detached from surfaces was carried out using a newly designed tapered flow chamber, which covered the entire shear range of physiological circulation. Platelets that naturally settled on a fibrinogen-coated surface were exposed to shear flow and were subsequently processed for scanning electron microscopic observation. We found that 1) the density of platelets remaining after flow exposure decreased with local shear stress, 2) adherent platelets of different morphologies withstood different levels of shear stress: most round cells and 40% of the cells that had a few short pseudopods were detached at < 10 dyn/cm2, whereas most spread cells could withstand 50 dyn/cm2, 3) pulsatile flow was more effective in removing adherent platelets than equivalent steady flow, 4) cytochalasin D and colchicine retarded platelet shape change and made them more easily detached by shear forces, and 5) metabolic energy-depleted platelets spread readily and formed shear-resistant clumps. Our observations indicated that adherent platelets of different morphologies on a fibrinogen-coated surface could withstand different levels of flow shear stress.
Calcium entry activated by store depletion in coronary endothelium is promoted by tyrosine phosphorylation
Authors: Sharma N. R. , Davis M. J.
Published: December 2017

Application of substance P (SP), a potent endothelium-dependent vasodilator, to porcine coronary artery endothelial cells (PCAECs) results in release of Ca2+ from intracellular stores followed by extracellular Ca2+ influx. We tested the hypothesis that intracellular store depletion results in tyrosine phosphorylation, which promotes Ca2+ influx. PCAECs labeled with antiphosphotyrosine antibody conjugated to fluorescein isothiocyanate showed a 3.3- to 3.4-fold increase in fluorescence in response to SP or 2,5-di-tert-butylhydroquinone (BHQ), an agent that depletes intracellular stores by inhibiting the endoplasmic reticulum Ca(2+)-adenosinetriphosphatase. In both cases, the tyrosine kinase inhibitor, genistein, reduced the fluorescence intensity to near-basal levels. Pretreatment of PCAECs with the tyrosine kinase inhibitors, genistein or tyrphostin, induced a significant reduction in the plateau phase of SP-induced Ca2+ elevation with no effect on the release of Ca2+ from stores. Neither daidzein, a structurally similar but inactive analogue of genistein, nor H-7, a serine-threonine kinase inhibitor, affected SP-induced Ca2+ influx. Voltage-clamp recordings using the perforated patch technique with simultaneous Ca2+ measurements showed that intracellular Ca2+ elevation and inward current activated by SP and BHQ were reduced by 60-70% in response to genistein. These data indicate that the link between store depletion and Ca2+ influx in endothelial cells requires tyrosine phosphorylation.
Gender does not influence sympathetic neural reactivity to stress in healthy humans
Authors: Jones P. P. , Spraul M. , Matt K. S. , Seals D. R. , Skinner J. S. , Ravussin E.
Published: December 2017

Previous data support the idea of heightened sympathetically mediated cardiovascular reactivity in males. However, definitive conclusions cannot be made because of inconsistent reports, possibly stemming from imprecise measurement of sympathetic activity and/or failure to equate the stress stimuli between genders. The present study tested the hypothesis that males exhibit heightened sympathetic reactivity that is associated with heightened cardiovascular and plasma catecholamine responses. In 37 healthy adults (20 males, 17 females: age = 20-42 yr), direct recordings of skeletal muscle sympathetic nerve activity (MSNA), plasma catecholamines, heart rate, blood pressure, and perceived stress were measured before and during three laboratory stressors (isometric handgrip, cold pressor, and mental arithmetic). MSNA, catecholamine, and cardiovascular reactivity (defined as change from rest) were not consistently different between genders. For the isometric handgrip, when expressed as absolute unit changes, males had larger MSNA responses (P < 0.01), which were partially explained by greater contraction force; they did not differ in terms of percent change from baseline or in perceived stress. The responses to the cold pressor and mental arithmetic tasks were similar between genders. These findings indicate that stress-evoked vasoconstrictor neural excitation and the associated increases in blood pressure are not consistently influenced by gender.
Maleate-induced bicarbonaturia in the dog: a carbonic anhydrase-independene effect
Authors: Gougoux A , Lemieux G , Lavoie N
Published: December 2017

Studies were performed to characterize the renal effects of maleate in anesthetized dogs. Following the intravenous administration of maleate or maleic acid (50 mg/kg), mean fractional bicarbonate excretion (CHCO3/GFR) rose to as high as 26%. Na, K, and phosphate excretion also increased markedly, whereas C1 excretion remained low. An initial transient fall in urinary pH from 6.53 to 6.13 contrasted sharply with the rapid alkalinization of the urine induced by acetazolamide administration. During saline expansion CHCO3/GFR rose from 4 to 37% after maleate administration, whereas Cl excretion did not change significantly. During continuous carbonic anhydrase inhibition with acetazolamide, maleate administration resulted in a further rise in CHCO3/GFR from 22 to 35%. Whereas CPO4/GFR increased only from 1 to 3% during acetazolamide administration, this ratio reached 75% following the addition of maleate. Fumarate, the transisomer of maleate, and malonate, a well-known inhibitor of Krebs cycle, failed to affect bicarbonate excretion. This study demonstrates that maleate inhibits the fraction of bicarbonate reabsorption uncatalyzed by carbonic anhydrase. Impaired anionic reabsorption of bicarbonate or accelerated passive backflux of this ion into proximal tubular lumen are the two mechanisms that best explain the bicarbonaturia induced by maleate.
Mechanism of maleic acid-induced glucosuria in dog kidney
Authors: Silverman M , Huang L
Published: December 2017

The multiple indicator-dilution technique in vivo and isolated brush-border membranes in vitro have been used to explore the mechanism of maleic acid-induced glucosuria in dog kidney. The interaction of D-glucose with the antiluminal membrane from the peritubular fluid surface is unaltered. It is demonstrated that alpha-methyl-D-glucoside (alpha MG) enters and exits from the proximal tubular cell only across the brush-border membrane. Then using alphaMG as a reference indicator, it is shown that maleic acid does not cause complete inhibition of D-glucose interaction with the antiluminal membrane from the cytoplasmic surface. The binding of [3H]phlorizin both in vivo and in vitro is not affected by prior administration of maleic acid, indicating that D-glucose interaction with the outside surface of the brush border is also not affected by maleic acid. The data are therefore consistent with the concept that maleic acid-induced glucosuria is due either to i) partial inhibition of D-glucose movement from cytoplasm across the antiluminal membrane into the blood, ii) stimulated movement back across the brush-border membrane into urine, or iii) a combination of the two effects.
Glutamine synthetase and glutamyltransferase in the kidney of man, dog, and rat
Authors: Lemieux G , Baverel G , Vinay P , Wadoux P
Published: December 2017

Glutamine synthetase (GS) is known to exist in the kidney of the rat, guinea pig, rabbit, and sheep but not in that of the dog, pig, cat, or pigeon. No data is available in man. Assay of histologically normal renal tissue obtained in human subjects during surgery for abdominal vascular disease failed to demonstrate significant GS activity. In addition, L-glutamine gamma-glutamyltransferase (GT) activity was also very low. The same results were observed in the dog, in which both GS and GT activities did not exceed 15% of those found in the kidney of the normal rat. In the latter animal both GS and GT activities are higher in the outer medulla (312 and 1,165 mumol/h per g wet wt, respectively) than in the cortex (230 and 844, respectively). During metabolic acidosis, GT activity did not change but GS activity decreased in the outer medulla by 40%. When renal cortex slices from normal rats were incubated in the presence of ammonia, glutamate, and octanoate (as a source of ATP), net synthesis of glutamine was readily demonstrated in contrast to slices from normal DOGS. The present studies demonstrate that the kidney of man, like that of the dog, is devoid of significant glutamine synthetase and glutamine gamma-glutamyltransferase activities. In the rat, we have confirmed the functional significance of GS activity in the kidney. We have also shown that renal GT activity is ammoniagenic in vitro in this animal, but the contribution of this system to total ammonia production in vivo remains to be demonstrated.
The laboratory rat as a model for hyperthermic syndromes in humans
Authors: Hubbard RW , Matthew WT , Linduska JD , Curtis FC , Bowers WD , Leav I , Mager M
Published: December 2017

To assess the lethal effects of work-induced hyperthermia on exercising animals, untrained rats were run to exhaustion at 5 and 20-26 degrees C or restrained at 41.5 degrees C. An exercise-induced core temperature of 40.4 degrees C represented a base line above which mortalities occurred. With increasing core temperature at exhaustion (between 40.4 and 43 degrees C), mortality increased within 24 h. A dose-respones curve with an LD50 equivalent to a core temperature of 41.5 +/- 0.1 degrees C was calculated. Although differences in body weight loss, core temperature at exhaustion, and cooling rate will clearly distinguish between survivors and fatalities, the severity of heat injury as inferred from survival times is best measured by the time versus intensity of hyperthermia in degree-minutes.
Cycle-length-dependent properties of AV nodal activation in rabbit hearts
Authors: Billette J , Janse MJ , van Capelle FJ , Anderson RH , Touboul P , Durrer D
Published: December 2017

Cycle-length-dependent changes in AV nodal cell activation were studied in isolated preparations from rabbit hearts. Transmembrane action potentials were recorded from the node while it was propagating impulses initiated in the atrium with an accelerating train of stimuli. This train consisting of five successive stimuli separated by progressively shorter intervals was uniformly repeated at every 10th basic beat, each time reproducing a sequence of five different increasing AV nodal delays. The AN and NH cells were found to contribute only slightly to the cycle-length-dependent AV nodal delay which developed mainly in the small N zone, located centrally in the AV node. With the increasing delay, the action potentials from this N zone typically dissociated into two components synchronous with late AN and early NH activity, respectively. The amplitude of the first component decreased, wheareas that of the second increased progressively in N cells activated progressively later. No cells were activated at an intermediate time between the two components. This dissociation was not accompanied by changes in the activation pattern of the AV node. The different nodal cells classified according to their response to the accelerating train delineated functional zones corresponding to different anatomic structures. The possible mechanisms which would explain the cycle-length-dependent AV nodal delay are discussed.
Effects of psychosocial stimuli on plasma renin activity in rats
Authors: Clamage DM , Sanford CS , Vander AJ , Mouw DR
Published: December 2017

The effects of two types of psychosocial stimuli on plasma renin activity (PRA) were studied in unanesthetized rats, blood being collected by decapitation. Thirty minutes of exposure to a novel environment ("open field") produced statistically significant increases of PRA in rats maintained on either a standard (1% NaCl) or sodium-free diet. No change in plasma renin substrate occurred. Prior treatment with propranolol (approximately 2 mg/kg) reduced the renin response by approximately 50% but did not completely abolish it. Plasma renin activity was also increased significantly by exposure of caged rats to the presence of a hungry cat for 30 min. We conclude that psychosocial stimuli can produce significant increases in renin secretion and that this response is mediated, at least in part, by the sympathetic nervous system.
Effect of methionine sulfoximine on glutathione and amino acid levels in the nephron
Authors: Brehe JE , Chan AW , Alvey TR , Burch HB
Published: December 2017

The effect of L-methionine-DL-sulfoximine (MSO) on renal glutathione concentration and aspartic acid transport has been studied by analyses of parts of individual freeze-dried glomeruli, early and late proximal convoluted, early and late proximal straight, and distal straight and convoluted tubules, and patches from thinlimb and papilla areas. Glutathione normally varies threefold along the kidney nephron, being highest in the convoluted and early straight proximal tubule, lowest in the distal straight tubule. Large loads of aspartate cause 20% diminution of glutathione in outer cortex, due entirely to changes in proximal tubule segments. MSO alone lowers glutathione 90% in all parts of the proximal tubule, with no change elsewhere. MSO does not affect the large increase in aspartate in proximal tubules caused by saturating aspartate loads, suggesting that glutathione is not directly involved in transport of this amino acid. Aspartate loads cause a large increase in renal glutamine, which is especially marked in the proximal straight tubule. MSO effectively blocks this increase and depresses tissue glutamine below normal levels.
Glucose transport in isolated perfused proximal tubules of snake kidney
Authors: Barfuss DW , Dantzler WH
Published: December 2017

Glucose transport was studied in isolated, perfused snake (Thamnophis spp.) renal tubules. When 14C-labeled and unlabeled glucose concentrations for bath and perfusate were identical, net transepithelial glucose transport occurred from lumen to bath. Maximum rates of transport were 1.24 X 10-12 and 2.17 X 10-12 mol min-1 mm-1 in proximal-proximal and distal-proximal segments, respecitvely. Glucose concentration in cells of perfused tubules of both segments was less than that of bath and lumen when tubules spontaneously stopped transporting glucose. Transepithelial glucose permeability ath leads to lumen) was about 0.25 X 10-5 cm sec-1 for both segments. Peritubular membrane permeability (bath leads to cell) was about 0.50 X 10-5 cm sec-1 for both segments. Luminal membrane permeabilities (cell leads to lumen) were 0.29 X 10-5 and 0.65 X 10-5 cm sec-1 for proximal-proximal and distal-proximal segments, respectively. Luminal membrane permeability in opposite direction (lumen leads to cell) was about 10.0 X 10-5 cm sec-1 for both segments. These results indicate that, during maximum glucose absorption, glucose enters cells down concentration gradient across luminal membrane by a mediated process and is transported out of the cells against concentration gradient at peritubular membrane.
Independent secretion of different digestive enzymes by the pancreas
Authors: Rothman SS
Published: December 2017

Pancreatic secretion was collected from the cannulated duct of anesthetized rabbits during the perfusion of the upper duodenum with a balanced salt solution with or without 5 mM glucose. The secretion of amylase, chymotrypsinogen, trypsinogen, and total protein was measured. While glucose did not increase overall digestive enzyme secretion, it did change the proportions of the enzymes in secretion. In addition, the following was observed: 1) non-0,0 intercepts when the output of one enzyme was plotted against that of another (an enzyme-pair plot), 2) changes in the variance of the slope and intercept of enzyme-pair plots, and 3) an increase in the variance around the slope of an enzyme-pair plot, concurrent with a decrease in the variance around the slope of a plot for another enzyme pair that contained a common member. These observations suggest that different digestive enzymes can be secreted independently of each other.
Hemorrhage activates NF-kappa B in murine lung mononuclear cells in vivo
Authors: Shenkar R. , Schwartz M. D. , Terada L. S. , Repine J. E. , McCord J. , Abraham E.
Published: December 2017

Hemorrhage rapidly increases the expression of proinflammatory and immunoregulatory cytokines in the lungs. Binding elements for the nuclear transcriptional regulatory factors (NF)-kappa B and NF-IL6 (C/EBP beta) are present in the promoter regions of multiple cytokine genes, including those whose expression is increased after blood loss. In the present experiments, we found increased activation in vivo of NF-kappa B in lung mononuclear cells, but not in splenocytes, taken from mice 1 h after hemorrhage. In contrast, hemorrhage did not activate NF-IL6 in lung cells or splenocytes. Inhibition of xanthine oxidase by prior feeding of a tungsten-enriched diet prevented hemorrhage-induced activation in lung cells of NF-kappa B. Incubating splenocytes in vitro with xanthine oxidase activated NF-kappa B but not NF-IL6. Xanthine oxidase-induced activation of NF-kappa B was inhibited by manganese superoxide dismutase, but not by catalase. These results suggest that xanthine oxidase-mediated superoxide anion-dependent activation of NF-kappa B occurs in vivo and in vitro. This mechanism may contribute to increased lung cytokine responses after hemorrhage.
Asthma and endotoxin: lipopolysaccharide-binding protein and soluble CD14 in bronchoalveolar compartment
Authors: Dubin W. , Martin T. R. , Swoveland P. , Leturcq D. J. , Moriarty A. M. , Tobias P. S. , Bleecker E. R. , Goldblum S. E. , Hasday J. D.
Published: December 2017

In allergic asthma, inhalation of antigen provokes an early increase in microvascular permeability with protein extravasation and a delayed recruitment of inflammatory cells. We showed that similar concentrations of lipopolysaccharide (LPS) are present in bronchoalveolar lavage fluid (BALF) in 12 subjects without asthma (86.5 +/- 53.8 pg/ml) and 12 subjects with mild asthma (111 +/- 37.0 pg/ml). These LPS levels are insufficient to stimulate cytokine release without accessory molecules. BALF obtained 24 h after segmental ragweed antigen challenge in 11 asthmatics allergic to ragweed contained increased levels of two LPS accessory molecules compared with preantigen BALF, 158-fold more LPS-binding protein (LBP) 4.83 +/- 2.02 vs. 742 +/- 387 ng/ml; P < 0.03) and 31.6-fold more soluble CD14 (sCD14) (3.45 +/- 1.04 vs. 110 +/- 51.6 ng/ml; P < 0.02). Postantigen BALF enhanced binding of fluorescein-conjugated LPS to CD14-bearing THP-1 cells and supported LPS-induced non-CD14-bearing endothelial cell expression of intercellular adhesion molecule-1 and interleukin-6, indicating functional LBP and sCD14. We suggest that extravasation of LBP and sCD14 into the bronchoalveolar compartment after antigen inhalation may enhance the capacity of inhaled or aspirated LPS to activate an inflammatory cascade that may amplify the inflammatory response to inhaled antigen in some asthmatics.
Mast cell tryptase stimulates human lung fibroblast proliferation via protease-activated receptor-2
Authors: Akers Ian A. , Parsons Maddy , Hill Michael R. , Hollenberg Morley D. , Sanjar Shahin , Laurent Geoffrey J. , McAnulty Robin J.
Published: December 2017

Mast cells play a potentially important role in fibroproliferative diseases, releasing mediators including tryptase that are capable of stimulating fibroblast proliferation and procollagen synthesis. The mechanism by which tryptase stimulates fibroblast proliferation is unclear, although recent studies suggest it can activate protease-activated receptor (PAR)-2. We therefore investigated the role of PAR-2 in tryptase-induced proliferation of human fetal lung and adult lung parenchymal and airway fibroblasts and, for comparative purposes, adult dermal fibroblasts. Tryptase (0.7–70 mU/ml) induced concentration-dependent increases in proliferation of all fibroblasts studied. Antipain, bis(5-amidino-2-benzimidazolyl)methane, and benzamidine inhibited tryptase-induced fibroblast proliferation, demonstrating that proteolytic activity is required for the proliferative effects of tryptase. RT-PCR demonstrated the presence of PAR-2 mRNA, and immunohistochemical staining localized PAR-2 to the cell surface of lung fibroblasts. In addition , specific PAR-2 activating peptides, SLIGKV and SLIGRL, mimicked the proliferative effects of tryptase. In contrast, human dermal fibroblasts only weakly stained with the PAR-2 antibody, PAR-2 mRNA was almost undetectable, and fibroblasts did not respond to PAR-2 activating peptides. These results suggest that tryptase induces lung, but not dermal, fibroblast proliferation via activation of PAR-2 and are consistent with the hypothesis that the release of tryptase from activated mast cells may play an important role in the fibroproliferative response observed in asthma, chronic obstructive pulmonary disease, and patients with pulmonary fibrosis.
Airway fibrosis in rats induced by vanadium pentoxide
Authors: Bonner James C. , Rice Annette B. , Moomaw Cindy R. , Morgan Daniel L.
Published: December 2017

Vanadium pentoxide (V2O5) is a cause of occupational asthma and bronchitis. We previously reported that intratracheal instillation of rats with V2O5causes fibrosis of the lung parenchyma (J. C. Bonner, P. M. Lindroos, A. B. Rice, C. R. Moomaw, and D. L. Morgan. Am. J. Physiol. Lung Cell. Mol. Physiol. 274: L72–L80, 1998). In this report, we show that intratracheal instillation of V2O5induces airway remodeling similar to that observed in individuals with asthma. These changes include airway smooth muscle cell thickening, mucous cell metaplasia, and airway fibrosis. The transient appearance of peribronchiolar myofibroblasts, which were desmin and vimentin positive, coincided with a twofold increase in the thickness of the airway smooth muscle layer at day 6after instillation and preceded the development of airway fibrosis by day 15. The number of nuclear profiles within the smooth muscle layer also increased twofold after V2O5instillation, suggesting that hyperplasia accounted for thickening of the smooth muscle layer. The majority of cells incorporating bromodeoxyuridine at day 3 were located in the connective tissue surrounding the airway smooth muscle wall that was positive for vimentin and desmin. These data suggest that myofibroblasts are the principal proliferating cell type that contributes to the progression of airway fibrosis after V2O5injury.
Retinoic acid-induced proliferation of lung alveolar epithelial cells is linked to p21CIP1downregulation
Authors: Nabeyrat Elodie , Corroyer Sophie , Epaud Ralph , Besnard Valérie , Cazals Véronique , Clement Annick
Published: December 2017

Retinoids, including retinol and retinoic acid (RA) derivatives, have been shown to be involved in the processes of lung development as well as of lung repair after injury. Recently, we have provided evidence that RA could stimulate proliferation of lung alveolar type 2 epithelial cells (E. Nabeyrat, V. Besnard, S. Corroyer, V. Cazals, and A. Clement. Am. J. Physiol. Lung Cell. Mol. Physiol. 275: L71–L79, 1998). To gain some insight into the mechanisms involved in the mitogenic action of RA, we focused in the present study on the effects of RA on the expression of G1phase cyclins and their cell cycle-dependent kinases (Cdks). Experiments were performed with serum-deprived cells cultured in the absence and presence of RA. The results showed no effects of RA on the expression of either cyclins or Cdks. In contrast, RA treatment was found to prevent the decrease in cyclin E-Cdk2 activity observed when cells were growth arrested by serum deprivation. The observation that changes in cyclin E-Cdk2 activity were not associated with modifications in the amount of complexes formed led to the suggestion that the Cdk inhibitory protein (CKI) was involved. Study of the CKI p21CIP1revealed marked differences in its expression in the absence and presence of RA, with a dramatic downregulation observed in RA-treated cells. Interestingly, immunoprecipitation experiments provided evidence that the decreased levels of p21CIP1were associated with a reduced interaction of this CKI with cyclin E-Cdk2 complexes. These data together with previous results obtained in various situations of type 2 cell growth arrest emphasize the role of p21CIP1in the control of lung alveolar epithelial cell proliferation.
IL-4 increases surfactant and regulates metabolism in vivo
Authors: Ikegami Machiko , Whitsett Jeffrey A. , Chroneos Zissis C. , Ross Gary F. , Reed Jacquelyn A. , Bachurski Cindy J. , Jobe Alan H.
Published: December 2017

Mice that express interleukin (IL)-4 in Clara cells (CCSP-IL-4) develop chronic airway inflammation and an alveolar proteinosis-like syndrome. To identify the role of IL-4 in surfactant homeostasis, we measured lipid and protein metabolism in the lungs of CCSP-IL-4 mice in vivo. Alveolar saturated phosphatidylcholine (Sat PC) pools were increased 6.5-fold and lung tissue Sat PC pools were increased 4.8-fold in the IL-4 transgenic mice. Whereas surfactant protein (SP) A was increased proportionately to Sat PC, SP-D was increased approximately 90-fold in the IL-4 mice compared with wild-type mice and was associated with 2.8-fold increase in SP-D mRNA. The incorporation of palmitate and choline into Sat PC was increased about twofold in CCSP-IL-4 mice. Although trace doses of radiolabeled Sat PC were cleared from the air spaces and lungs of CCSP-IL-4 mice more slowly than in wild-type mice, net clearance of Sat PC from the lungs of CCSP-IL-4 mice was sixfold higher in the IL-4 mice than in wild-type mice because of the larger Sat PC pool sizes. Expression of IL-4 in Clara cells increased surfactant lipid synthesis and clearance, establishing a new equilibrium with increased surfactant pools and an alveolar proteinosis associated with a selective increase in SP-D protein, demonstrating a previously unexpected effect of IL-4 in pulmonary surfactant homeostasis.
Heme oxygenase-1 inhibits TNF-α-induced apoptosis in cultured fibroblasts
Authors: Petrache Irina , Otterbein Leo E. , Alam Jawed , Wiegand Gordon W. , Choi Augustine M. K.
Published: December 2017

Heme oxygenase (HO)-1 catalyzes the oxidative cleavage of heme to yield equimolar amounts of biliverdin, iron, and carbon monoxide. HO-1 is a stress response protein, the induction of which is associated with protection against oxidative stress. The mechanism(s) of protection is not completely elucidated, although it is suggested that one or more of the catalytic by-products provide antioxidant functions either directly or indirectly. The involvement of reactive oxygen species in apoptosis raised the question of a possible role for HO-1 in programmed cell death. Using the tetracycline-regulated expression system, we show here that conditional overexpression of HO-1 prevents tumor necrosis factor-α-induced apoptosis in murine L929 fibroblasts. Inhibition of apoptosis was not observed in the presence of tin protoporphyrin, a specific inhibitor of HO activity, and in cells overexpressing antisense HO-1. Interestingly, exogenous administration of a low concentration of carbon monoxide also prevented tumor necrosis factor-α-induced apoptosis in L929 fibroblasts. Inhibition of tumor necrosis factor-α-induced apoptosis by HO-1 overexpression was reversed by 1 H-(1,2,4)oxadiazolo(4,3- a)quinoxalin-1-one, an inhibitor of guanylate cyclase, which is a target enzyme for carbon monoxide. Taken together, our data suggest that the antiapoptotic effect of HO-1 may be mediated via carbon monoxide.
Polyamines in the lung: polyamine uptake and polyamine-linked pathological or toxicological conditions
Authors: Hoet Peter H. M. , Nemery Benoit
Published: December 2017

The natural polyamines putrescine, cadaverine, spermidine, and spermine are found in all cells. These (poly)cations exert interactions with anions, e.g., DNA and RNA. This feature represents their best-known direct physiological role in cellular functions: cell growth, division, and differentiation. The lung and, more specifically, alveolar epithelial cells appear to be endowed with a much higher polyamine uptake system than any other major organ. In the lung, the active accumulation of natural polyamines in the epithelium has been studied in various mammalian species including rat, hamster, rabbit, and human. The kinetic parameters (Michaelis-Menten constant and maximal uptake) of the uptake system are the same order of magnitude regardless of the polyamine or species studied and the in vitro system used. Also, other pulmonary cells accumulate polyamines but never to the same extent as the epithelium. Although different uptake systems exist for putrescine, spermidine, and spermine in the lung, neither the nature of the carrier protein nor the reason for its existence is known. Some pulmonary toxicological and/or pathological conditions have been related to polyamine metabolism and/or polyamine content in the lung. Polyamines possess an important intrinsic toxicity. From in vitro studies with nonpulmonary cells, it has been shown that spermidine and spermine can be metabolized to hydrogen peroxide, ammonium, and acrolein, which can all cause cellular toxicity. In hyperoxia or after ozone exposure, the increased polyamine synthesis and polyamine content of the rat lung is correlated with survival of the animals. Pulmonary hypertension induced by monocrotaline or hypoxia has also been linked to the increased polyamine metabolism and polyamine content of the lung. In a small number of studies, it has been shown that polyamines can contribute to the suppression of immunologic reactions in the lung.
O2-evoked regulation of HIF-1α and NF-κB in perinatal lung epithelium requires glutathione biosynthesis
Authors: Haddad John J. E. , Land Stephen C.
Published: December 2017

To test the genetic capacity of the perinatal lung to respond to O2shifts that coincide with the first respiratory movements, rat fetal alveolar type II (fATII) epithelial cells were cultured at fetal distal lung[Formula: see text] (23 Torr) and then exposed to postnatal (23 → 76 Torr; mild hyperoxic shift), moderate (23 → 152 Torr; moderate hyperoxic shift), or severe (23 → 722 Torr; severe hyperoxic shift) oxygenation. Nuclear abundance and consensus binding characteristics of hypoxia-inducible factor (HIF)-1α and nuclear factor (NF)-κB (Rel A/p65) plus glutathione biosynthetic capacity were determined. Maximal HIF-1α activation at 23 Torr was sustained over the postnatal shift in (Δ)[Formula: see text] and was elevated in vivo throughout late gestation. NF-κB was activated by the acute postnatal[Formula: see text] in fATII cells, becoming maximal with moderate and severe oxygenation in vitro and within 6 h of birth in vivo, declining thereafter. fATII cell and whole lung glutathione and GSH-to-GSSG ratio increased fourfold with a postnatal[Formula: see text] and were matched by threefold activity increases in γ-glutamylcysteine synthetase and glutathione synthase. GSH concentration depletion byl-buthionine-( S,R)-sulfoximine abrogated both HIF-1α and NF-κB activation, with HIF-1α showing a heightened sensitivity to GSH concentration. We conclude that O2-linked genetic regulation in perinatal lung epithelium is responsive to developmental changes in glutathione biosynthetic capacity.
Dexamethasone potentiates high-affinity β-agonist binding and Gsα protein expression in airway smooth muscle
Authors: Kalavantavanich Karl , Schramm Craig M.
Published: December 2017

Corticosteroids enhance β-adrenergic responses by actions at both β-adrenoceptor (β-AR) and post-β-AR sites. The present study investigated the effects of dexamethasone on β-AR density, high-affinity β-agonist binding, Gsα and Giα protein expression, and cAMP responses in bovine tracheal smooth muscle (bTSM). Dexamethasone treatment of cultured bTSM cells increased total β-AR density 1.6- to 1.9-fold as assessed by the saturation binding of [3H]CGP-12177 and by displacement of radioligand binding with isoproterenol. Isoproterenol bound to the β-AR at two sites, a high-affinity site with a density of 5.9 ± 1.2 fmol/mg protein and a low-affinity site with a density of 16.9 ± 1.0 fmol/mg protein. Dexamethasone increased both high- and low-affinity isoproterenol binding sites to 11.1 ± 2.2 and 25.9 ± 2.1 fmol/mg protein, respectively, without influencing agonist binding affinities. Dexamethasone also selectively increased Gsα protein levels from 0.99 ± 0.14 to 1.46 ± 0.17 μg/mg protein without affecting Giα levels. The net effect of these changes was a 1.8-fold increase in maximal isoproterenol-induced cAMP generation in dexamethasone-treated bTSM cells. These findings provide new insights into the corticosteroid regulation of β-adrenergic signaling pathways in airway smooth muscle.