bluuebunny/crossref_metadata_2025 huggingface dataset:
Methysergide delays the decompensatory responses to severe hemorrhage by activating 5-HT1Areceptors
Authors: Scrogin Karie E. , Johnson Alan Kim , Brooks Virginia L.
Published: December 2017

Central administration of the serotonin receptor ligand methysergide delays the decompensatory response to hypotensive hemorrhage. This study was performed to determine the receptor subtype that mediates this effect. Lateral ventricular (LV) injection of methysergide (40 μg) delayed the hypotensive, bradycardic, and sympathoinhibitory responses to blood withdrawal (1.26 ml/min) in conscious rats. The response was quantified, in part, as the blood volume withdrawal that produced a 40-mmHg fall in blood pressure. The delayed hypotensive response produced by methysergide (8.2 ± 0.2 vs. 5.6 ± 0.2 ml, P < 0.01) was reversed by the 5-hydroxytryptamine (HT)1Aantagonist WAY-100635 (30 μg iv: 6.7 ± 0.4 ml, P < 0.01; 100 μg iv: 5.6 ± 0.1 ml, P < 0.01). LV injection of the 5-HT1Aagonist (+)-8-hydroxy-2-(di- n-propylamino)tetralin (8-OH-DPAT) also delayed the hypotensive (10 μg: 8.6 ± 0.3, P < 0.01; 20 μg: 9.2 ± 0.3 ml, P < 0.01), bradycardic, and sympathoinhibitory responses to hemorrhage. WAY-100635 (10 μg iv) completely reversed the effects of 8-OH-DPAT (20 μg: 5.4 ± 0.3 ml). Neither selective blockade of 5-HT2receptors nor stimulation of 5-HT1B/1Dreceptors had any effect on hemorrhage responses. These data indicate that methysergide stimulates 5-HT1Areceptors to delay the decompensatory responses to hemorrhage.
Evolution of structure, ontogeny of gene expression, and function ofXenopus laevistransthyretin
Authors: Prapunpoj Porntip , Yamauchi Kiyoshi , Nishiyama Norihito , Richardson Samantha J. , Schreiber Gerhard
Published: December 2017

Xenopus laevis transthyretin (xTTR) cDNA was cloned and sequenced. The derived amino acid sequence was very similar to those of other vertebrate transthyretins (TTR). TTR gene expression was observed during metamorphosis in X. laevis tadpole liver but not in tadpole brain nor adult liver. Recombinant xTTR was synthesized in Pichia pastoris and identified by amino acid sequence, subunit molecular mass, tetramer formation, and binding to retinol-binding protein. Contrary to mammalian xTTRs, the affinity of xTTR was higher for l-triiodothyronine than forl-thyroxine. The regions of the TTR genes coding for the NH2-terminal sections of the polypeptide chains of TTR seem to have evolved by stepwise shifts of mRNA splicing sites between exons 1 and 2, resulting in shorter and more hydrophilic NH2termini. This may be one molecular mechanism of positive Darwinian evolution. Open reading frames with xTTR-like sequences in the genomes of C. elegans and several microorganisms suggested evolution of the TTR gene from ancestor TTR gene-like “DNA modules.” Increasing preference for binding of l-thyroxine overl-triiodothyronine may be associated with evolving tissue-specific regulation of thyroid hormone action by deiodination.
Nitric oxide and vascular reactivity in developing zebrafish,Danio rerio
Authors: Fritsche Regina , Schwerte Thorsten , Pelster Bernd
Published: December 2017

We used a newly developed digital motion analysis video technique to study the effects of nitric oxide (NO) and epinephrine on the early larval arterial and venous vasculature of zebrafish. Application of the NO donor sodium nitroprusside resulted in a significant increase in both the venous and arterial vessel diameters, whereas NG-nitro-l-arginine methyl ester caused a significant decrease in the same diameters. Thus our results show that both the venous and arterial vasculature of the 5- and 6-day-old zebrafish larvae are influenced by endogenously produced NO. By use of immunohistochemistry, NO synthase immunoreactivity was demonstrated in endothelial cells of the dorsal vein. Local application of epinephrine onto the dorsal artery had no effect on vessel diameter. However, if the embryos were preincubated with Nω-nitro-l-arginine methyl ester, addition of epinephrine resulted in a significant reduction in both arterial and venous vessel diameters. Thus this study provides increasing evidence that before a functional autonomic innervation of the peripheral vascular system, vascular tone in larval tissue is regulated by a complex interaction of vasoactive substances that are produced locally by vascular endothelial cells.
Oxidative stress and antioxidant defenses in goldfishCarassius auratusduring anoxia and reoxygenation
Authors: Lushchak Volodymyr I. , Lushchak Ludmyla P. , Mota Alice A. , Hermes-Lima Marcelo
Published: December 2017

The purpose of this work was to evaluate the response of the antioxidant system of goldfish Carassius auratus during anoxia and reoxygenation. The exposure of goldfish to 8 h of anoxia induced a 14% decrease in total glutathione levels in the kidney, although the liver, brain, and muscle were unaffected. Anoxia also resulted in increases in the activities of liver catalase, brain glucose-6-phosphate dehydrogenase, and brain glutathione peroxidase (by 38, 26, and 79%, respectively) and a decrease in kidney catalase activity (by 17.5%). After 14 h of reoxygenation, liver catalase and brain glutathione peroxidase activities remained higher than controls and several other tissue-specific changes occurred in enzyme activities. Superoxide dismutase activity was unaffected by anoxia and reoxygenation. The levels of conjugated dienes, as indicators of lipid peroxidation, increased by 114% in liver after 1 h of reoxygenation and by 75% in brain after 14 h of reoxygenation. Lipid peroxidation was unaffected in kidney and depressed during anoxia and reoxygenation (by 44–61%) in muscle. Regulation of the goldfish antioxidant system during anoxia may constitute a biochemical mechanism that minimizes oxidative stress following reoxygenation.
Feeding inhibition by urocortin in the rat hypothalamic paraventricular nucleus
Authors: Wang Chuanfeng , Mullet Mary A. , Glass Michael J. , Billington Charles J. , Levine Allen S. , Kotz Catherine M.
Published: December 2017

Ventricular administration of urocortin (UCN) inhibits feeding, but specific site(s) of UCN action are unknown. In the current studies we examined the effect of UCN in the hypothalamic paraventricular nucleus (PVN) on feeding. We tested UCN administered into the PVN in several paradigms: deprivation-induced, nocturnal, and neuropeptide Y (NPY)-induced feeding. We compared the effect of equimolar doses of UCN and corticotrophin releasing hormone (CRH) on NPY-induced and nocturnal feeding, determined whether UCN in the PVN produced a conditioned taste aversion (CTA) and induced changes in c-Fos immunoreactivity (c-Fos-ir) after UCN and NPY administration in the PVN. UCN in the PVN significantly decreased NPY and nocturnal and deprivation-induced feeding at doses of 1, 10, and 100 pmol, respectively. UCN anorectic effects lasted longer than those attributed to CRH. Ten and thirty picomoles UCN did not induce a CTA, whereas 100 pmol UCN produced a CTA. UCN (100 pmol) in the PVN neither increased c-Fos-ir in any brain region assayed nor altered c-Fos-ir patterns resulting from PVN NPY administration. These data suggest the hypothalamic PVN as a site of UCN action.
Comparative effects of amylin and cholecystokinin on food intake and gastric emptying in rats
Authors: Reidelberger Roger D. , Arnelo Urban , Granqvist Lars , Permert Johan
Published: December 2017

CCK is a physiological inhibitor of gastric emptying and food intake. The pancreatic peptide amylin exerts similar actions, yet its physiological importance is uncertain. Objectives were to compare the dose-dependent effects of intravenous infusion of amylin and CCK-8 on gastric emptying and food intake in rats, and to assess whether physiological doses of amylin are effective. Amylin and CCK-8 inhibited gastric emptying with mean effective doses (ED50s) of 3 and 35 pmol · kg−1 · min−1 and maximal inhibitions of 60 and 65%, respectively. Amylin and CCK-8 inhibited food intake with ED50s of 8 and 14 pmol · kg−1 · min−1 and maximal inhibitions of 78 and 69%, respectively. The minimal effective amylin dose for each effect was 1 pmol · kg−1 · min−1. Our previous work suggests that this dose increases plasma amylin by an amount comparable to that produced by a meal. These results support the hypothesis that amylin acts as a hormonal signal to the brain to inhibit gastric emptying and food intake and that amylin produces satiety in part through inhibition of gastric emptying.
Microinjection of glutamate into the pedunculopontine tegmentum induces REM sleep and wakefulness in the rat
Authors: Datta Subimal , Spoley Eric E. , Patterson Elissa H.
Published: December 2017

The aim of this study was to test the hypothesis that the cells in the brain stem pedunculopontine tegmentum (PPT) are critically involved in the normal regulation of wakefulness and rapid eye movement (REM) sleep. To test this hypothesis, one of four different doses of the excitatory amino acid l-glutamate (15, 30, 60, and 90 ng) or saline (control vehicle) was microinjected unilaterally into the PPT while the effects on wakefulness and sleep were quantified in freely moving chronically instrumented rats. All microinjections were made during wakefulness and were followed by 6 h of polygraphic recording. Microinjection of 15- ng (0.08 nmol) and 30-ng (0.16 nmol) doses ofl-glutamate into the PPT increased the total amount of REM sleep. Both doses of l-glutamate increased REM sleep at the expense of slow-wave sleep (SWS) but not wakefulness. Interestingly, the 60-ng (0.32 nmol) dose of l-glutamate increased both REM sleep and wakefulness. The total increase in REM sleep after the 60-ng dose of l-glutamate was significantly less than the increase from the 30-ng dose. The 90-ng (0.48 nmol) dose ofl-glutamate kept animals awake for 2–3 h by eliminating both SWS and REM sleep. These results show that thel-glutamate microinjection into the PPT can increase wakefulness and/or REM sleep depending on the dosage. These findings support the hypothesis that excitation of the PPT cells is causal to the generation of wakefulness and REM sleep in the rat. In addition, the results of this study led to the identification of the PPT dosage of l-glutamate that optimally induces wakefulness and REM sleep. The knowledge of this optimal dose will be useful in future studies investigating the second messenger systems involved in the regulation of wakefulness and REM sleep.
Glucocorticoids modulate baroreflex control of renal sympathetic nerve activity
Authors: Scheuer Deborah A. , Mifflin Steven W.
Published: December 2017

Experiments were performed to determine the effects of glucocorticoids on arterial baroreceptor reflex control of renal sympathetic nerve activity (RSNA). Intravenous infusions of phenylephrine and nitroprusside were used to produce graded changes in arterial pressure (AP) in Inactin-anesthetized male Sprague-Dawley rats. Baroreflex control of RSNA was determined during a baseline period and 2 and 3 h after administration of the glucocorticoid type II receptor antagonist Mifepristone (30 mg/kg sc) or vehicle (oil). Corticosterone (cort) treatment (100 mg cort pellet sc for 2–3 wk) increased baseline AP from 115 ± 2 to 128 ± 1 mmHg. Cort treatment also decreased the gain coefficient and increased the midpoint of the baroreflex curve. Treatment of cort rats with Mifepristone decreased AP within 2 h and increased the gain coefficient and decreased the midpoint of the baroreflex function curve back toward values measured in control rats. Mifepristone altered the baroreflex function curve even when AP was maintained at baseline levels. Therefore, these data demonstrate for the first time that glucocorticoids can modulate baroreflex control of RSNA by a mechanism that is, in part, independent of changes in AP.
Endogenous angiotensin II in the NTS contributes to sympathetic activation in rats with aortocaval shunt
Authors: Shigematsu Hideaki , Hirooka Yoshitaka , Eshima Kenichi , Shihara Miwako , Tagawa Tatsuya , Takeshita Akira
Published: December 2017

Recent studies have suggested that the central nervous system is responsible for activation of sympathetic nerve activity (SNA) and the renin-angiotensin system in heart failure (HF). The aim of this study was to determine whether activation of the renin-angiotensin system within the nucleus of the solitary tract (NTS) plays a role in enhanced SNA in HF. High-output HF was induced by an aortocaval (A-V) shunt with some modifications in the rat. These rats exhibited a left ventricular dilatation and hemodynamic signs of high-output HF. Urinary catecholamine excretion and maximal renal SNA (RSNA) were greater in the A-V shunted rats than in the control rats. Microinjection of an angiotensin II type 1-receptor antagonist, CV11974, into the NTS was performed. The arterial pressure and RSNA were reduced by CV11974 to a greater degree in the A-V shunted rats than in the control rats. The expression of angiotensin-converting enzyme mRNA in the medulla was greater in the A-V shunted rats than in the control rats. These results suggest that activation of the renin-angiotensin system within the NTS contributes to an enhanced SNA in this model.
Hemodynamic effects of lipids in humans
Authors: Stojiljkovic Milos P. , Zhang Da , Lopes Heno F. , Lee Christine G. , Goodfriend Theodore L. , Egan Brent M.
Published: December 2017

Evidence suggests lipid abnormalities may contribute to elevated blood pressure, increased vascular resistance, and reduced arterial compliance among insulin-resistant subjects. In a study of 11 normal volunteers undergoing 4-h-long infusions of Intralipid and heparin to raise plasma nonesterified fatty acids (NEFAs), we observed increases of blood pressure. In contrast, blood pressure did not change in these same volunteers during a 4-h infusion of saline and heparin. To better characterize the hemodynamic responses to Intralipid and heparin, another group of 21 individuals, including both lean and obese volunteers, was studied after 3 wk on a controlled diet with 180 mmol sodium/day. Two and four hours after starting the infusions, plasma NEFAs increased by 134 and 111% in those receiving Intralipid and heparin, P < 0.01, whereas plasma NEFAs did not change in the first group of normal volunteers who received saline and heparin. The hemodynamic changes in lean and obese subjects in the second study were similar, and the results were combined. The infusion of Intralipid and heparin induced a significant increase in systolic (13.5 ± 2.1 mmHg) and diastolic (8.0 ± 1.5 mmHg) blood pressure as well as heart rate (9.4 ± 1.4 beats/min). Small and large artery compliance decreased, and systemic vascular resistance rose. These data raise the possibility that lipid abnormalities associated with insulin resistance contribute to the elevated blood pressure and heart rate as well as the reduced vascular compliance observed in subjects with the cardiovascular risk factor cluster.
Influence of barometric pressure on interleukin-1β secretion
Authors: Becker William J. , Cannon Joseph G.
Published: December 2017

Monocytes and macrophages are activated by various environmental challenges, including microorganisms, radiation, and pollutants. These cells release cytokines, such as interleukin (IL)-1β, that mediate physiological adaptations to stress. This study sought to define further the role of IL-1β in general adaptation to environmental stress by testing the hypothesis that high altitude (20,000 ft, 6,096 m) would stimulate IL-1β secretion from isolated human blood mononuclear cells. Cells from six young men (aged 22–26 yr) were divided into separate cultures incubated in either standard ambient conditions or in one of three test conditions, hypobaric hypoxia (simulating 20,000 ft), hypobaric normoxia (20,000 ft, O2supplemented), and normobaric hypoxia (10% O2). This design allowed differentiation between pressure-related vs. oxygen-related effects. Each subject made multiple blood donations in order that cells from all subjects were tested in all conditions. Contrary to the hypothesis, IL-1β secretion was not induced at simulated altitude in basal cell cultures. In lipopolysaccharide-stimulated cell cultures, exposure to altitude inhibited IL-1β secretion by ∼40%, and the inhibition was due to the change in pressure ( P = 0.039) rather than the change in oxygen. Secretion of other factors (IL-1 receptor antagonist and soluble IL-1 receptor type II) was not inhibited. Although these results are in opposition to the original hypothesis, they provide insight regarding adaptations necessary for hematopoiesis in response to high altitude and also provide a cellular rationale for the mountain sanatoriums of the 19th and early 20th centuries.
Analysis of the calcium paradox of renin secretion
Authors: Steppan D. , Pan L. , Gross K. W. , Kurtz A.
Published: December 2017

The secretion of the protease renin from renal juxtaglomerular cells is enhanced by subnormal extracellular calcium concentrations. The mechanisms underlying this atypical effect of calcium have not yet been unraveled. We therefore aimed to characterize the effect of extracellular calcium concentration on calcium handling of juxtaglomerular cells and on renin secretion in more detail. For this purpose, we used a combination of experiments with isolated perfused mouse kidneys and direct calcium measurements in renin-secreting cells in situ. We found that lowering of the extracellular calcium concentration led to a sustained elevation of renin secretion. Electron-microscopical analysis of renin-secreting cells exposed to subnormal extracellular calcium concentrations revealed big omega-shaped structures resulting from the intracellular fusion and subsequent emptying of renin storage vesicles. The calcium concentration dependencies as well as the kinetics of changes were rather similar for renin secretion and for renovascular resistance. Since vascular resistance is fundamentally influenced by myosin light chain kinase (MLCK), myosin light chain phosphatase (MLCP), and Rho-associated protein kinase (Rho-K) activities, we examined the effects of MLCK-, MLCP-, and Rho-K inhibitors on renin secretion. Only MLCK inhibition stimulated renin secretion. Conversely, inhibition of MCLP activity lowered perfusate flow and strongly inhibited renin secretion, which could not be reversed by lowering of the extracellular calcium concentration. Renin-secreting cells and smooth muscle cells of afferent arterioles showed immunoreactivity of MLCK. These findings suggest that the inhibitory effect of calcium on renin secretion could be explained by phosphorylation-dependent processes under control of the MLCK.
Modification of respiratory center output in the unanesthetized fetal sheep "in utero"
Authors: Maloney J. E. , Adamson T. M. , Brodecky V. , Dowling M. H. , Ritchie B. C.
Published: December 2017

Diaphragmatic electromyographic activity, tracheal and amniotic fluid pressures, lung liquid flow, and carotid and jugular venous pressures were measured on eight fetal lambs who survived for periods of 9–43 days postoperatively. The fetal gestational age ranged from 98 to 113 days at operation. Respiratory center output of the fetus as indicated by electromyographic activity was modified by the following stimuli. It was suppressed by anesthesia and fetal hypoxia (Pao2 = 12 mmHg), tonically reduced by lung inflation, and stimulated by cyanide injections (150–600 mug) into the fetal jugular vein. Neuromuscular transmission to the diaphragm was blocked with d-tubocurarine (0.2–0.6 mg). These experiments indicate that central and motor pathways to the diaphragm are sufficiently mature by 101 days in the fetal sheep to permit their output to be modified by chemical and mechanical stimuli.
Insulative power of body fat on deep muscle temperatures and isometric endurance
Authors: Petrofsky J. S. , Lind A. R.
Published: December 2017

Four male subjects were examined to assess the relationship of body fat content to deep muscle temperature and the endurance of a fatiguing isometric handgrip contraction at a tension set at 40% MVC. Muscle temperature was altered by the immersion of the forearm in water at temperatures varying from 7.5 to 40 degrees C. In all subjects, there was a water bath temperature above and below which isometric endurance decreased markedly; the difference among individuals was solely accounted for by the individual's body fat content. Thus, subjects with higher body fat content required lower bath temperatures to cool the forearm musculature to its optimum temperature, which we found to always be approximately 27 degrees C measured 2 cm perpendicularly to the skin in the belly of the brachioradialis muscle. Further, in one subject, we found that a reduction in this subject's body fat content resulted in a corresponding increase in the water bath temperature necessary to cool his muscles to their optimum isometric performance. The data demonstrate the striking insulative power of the thin layer of fat around the forearm in man in protecting shell tissues from cold exposure.
Correlation of blood rheology with vascular resistance in critically ill patients
Authors: Scholz P. M. , Karis J. H. , Gump F. E. , Kinney J. M. , Chien S.
Published: December 2017

Blood rheologic measurements together with peripheral resistance determinations in vivo were made in 27 critically ill patients. Eighteen of these patients (group I) suffered from violent trauma or operative injury and the other 9 (group II) were patients with generalized sepsis. As a result of fluid therapy all patients underwent hemodilution, resulting in a decrease in blood viscosity. This drop in blood viscosity was counteracted to some extent by an increased plasma viscosity due to elevated fibrinogen levels and a decreased red cell deformability associated with massive transfusions of stored blood. The correlation of vivo hemodynamics with blood rheological data made it possible to separate the relative roles of vascular dimensions and blood viscosity in affecting the total peripheral resistance. This approach permitted us to distinguish varying degrees of vasoconstriction in nonseptic patients in low flow states (group I) and varying degrees of vasodilation in septic patients (group II). This type of analysis serves to elucidate the pathophysiology of hemodynamic alterations in disease and provides a rational basis for devising an effective therapeutic program.
Prediction of body density in young and middle-aged men
Authors: Pollock M. L. , Hickman T. , Kendrick Z. , Jackson A. , Linnerud A. C. , Dawson G.
Published: December 2017

The purpose of this investigation was to predict body density of young (18–22 yr) and middle-aged (40–55 yr) men and to determine if generalized equations were appropriate to both populations. The dependent variable, body density, was determined by the hydrostatic technique. Independent variables included 7 skinfold fat, 11 girth, and 7 diameter measures; age; height; and weight. Mean body density for young men was 1.068 g/ml (SD +/- 0.014) and percent fat, 13.4 (SD +/- 6.0); the values for middle-aged subjects were 1.043 g/ml (SD +/- 0.0130) and 24.7% (SD +/- 5.9). Incomplete principal components analysis was used to examine the dimensions measured by the independent variables, and these analyses revealed differences between samples. Using multiple regression analysis, with the exception of girth measurements, the slopes of the regression lines were equal. For all analyses, however, the intercepts were different. These results confirmed the need for different regression equations for these populations. The most accurate prediction for young men was with two skinfold, four girth, and two diameter measures (R = 0.88; SE = 0.0069 g/ml); two skinfold and three girth measures accurately predicted body density for middle-aged men (R = 0.84; SE = 0.0074 g/ml).
Elastic constants of inflated lobes of dog lungs
Authors: Lai-Fook S. J. , Wilson T. A. , Hyatt R. E. , Rodarte J. R.
Published: December 2017

The elastic constants of dog lungs were determined at various degrees of inflation. In one set of experiments, the lobes were subjected to deformations that approximated the conditions of uniaxial loading. These data, together with the bulk modulus data obtained from the local slope of the pressure-volume curve, were used to determine the two elastic moduli that are needed to describe small nonuniform deformations about an initial state of uniform inflation. The bulk modulus was approximately 4 times the inflation pressure, and Young's modulus was approximately 1.5 times the inflation pressure. In a second set of experiments, lobes were subjected to indentation tests using cylindric punches 1–3 cm in diameter. The value for Young's modulus obtained from these data was slightly higher, approximately twice the inflation pressure. These experiments indicate that the lung is much more easily deformable in shear than in dilatation and that the Poisson ratio for the lung is high, approximately 0.43.
Influence of lung volume and electrode position on electromyography of the diaphragm
Authors: Grassino A. E. , Whitelaw W. A. , Milic-Emili J.
Published: December 2017

In cats anesthetized with Nembutal, electromyograms of the diaphragm (Edi) were recorded from an anchored esophageal electrode, a pair of silver hooks inserted in the paratendinous region, and a pair of silver hooks and a pair of clips of small surface inserted in the costal region of the diaphragm facing the rib cage at FRC but covered with lung tissue at FRC + 80 ml. When single supramaximal electrical stimuli were applied to an isolated phrenic nerve, changes in lung volume from RV to near TLC had a negligible effect on muscle potentials from esophageal or paratendinous hooks, but increased the amplitude of potentials recorded from peripheral hooks and clips. In addition, it was found that small displacements of the esophageal electrode caused substantial changes in the amplitude of the recorded muscle potentials. The integration of the Edi spontaneously generated during occluded inspirations, recorded from paratendinous hooks and the esophageal electrode was linearly related to transdiaphragmatic pressure up to 50 cmH2O at all lung volumes. Above that level, esophageal electrode recordings showed a curvilinear Edi/Pdi relationship, while hook recordings showed a rectilinear relationship.
Effect of adrenergic agents and their mode of action on mucociliary clearance in man
Authors: Foster W. M. , Bergofsky E. H. , Bohning D. E. , Lippmann M. , Albert R. E.
Published: December 2017

The aerosolized adrenergic (ADR) agent, isoproterenol (ISO), was found markedly to accelerate mucus clearance within the human tracheobronchial tree. Mucus transport was measured by external gamma counting of aerosolized Fe2O3 particles deposited on the mucous membrane during inhalation. Aerosolized epinephrine (EPI), despite its alpha-ADR bronchial vasoconstrictor activity, increased mucus clearance to the same degree as did aerosolized ISO, with its beta-ADR bronchial vasodilator activity. The vehicle used for delivery of the ADR agents, i.e., a H2O aerosol by intermittent positive-pressure breathing (IPPB), itself increased mucus clearance slightly, but did notelicit the enormous increases produced by the ADR agents. Parenteral ISO caused increases in clearances similar to aerosolized ISO and EPI (consistentwith different tissue drug levels achieved). Oral atropine delayed clearance, but atropine prior to an ADR aerosol did not alter the mucus transporteffect of the ADR agent. ISO and atropine, despite opposite effects on mucus clearance, caused equal bronchodilation. Thus, increased clearance following aerosolized ISO was not dependent on bronchial vasodilation, aqueous aerosol droplets, reflex parasympathetic activation, or bronchodilation, and seems best attributable to increased ciliary beat rate.
Cardiorespiratory responses of sedentary college women as a function of training intensity
Authors: Kearney J. T. , Stull G. A. , Ewing J. L. , Strein J. W.
Published: December 2017

Twenty-seven sedentary college women trained on a treadmill 3 times weekly over a 9-wk experimental period. Subjects exercised at a heart rate (HR)of either 50 or 65% of the HR reserve added to the resting HR with the duration of each session limited to the time required to elicit 1,000 beats above the resting value. Treadmill speed was adjusted automatically to maintain the prescribed exercise heart rate (EHR) within +/- 5 beats-min(-1). A comparison of the pretraining and posttraining results revealed that both training intensities caused significant increases in VO2max (1-min(-1) and ml-kg(-1)-min(-1)), V at VO2max, and O2 pulse at VO2max, and a significant decrease in VEO2 at VO2max. There was no alteration in EHR at VO2max for either intensity. For every dependent variable in which training effects were noted, the absolute gain made by the subjects training at the 65% intensity was greater than for those exercising at 50%. In no instance, however, was the difference between groups statistically significant. It was concluded that training at an EHR of either 50 or 65% of the HR reserve plus resting HR is sufficient to elicit a training response.
Effects of age, sex, and physical fitness on responses to local cooling
Authors: LeBlanc J. , Cote J. , Dulac S. , Dulong-Turcot F.
Published: December 2017

The response to local cooling was estimated by the cold hand test (5 degrees C for 2 min) and the cold face test (0 degrees C with 66 km.h-1 wind for 2 min). Heart rate, blood pressure, and skin temperature were measured before, during, and after the tests. The increase in blood pressure (cold hand test) and the fall in Tsk (cold face test) were reduced in trained subjects. Similarly older subjects (53–60 yr of age) responded less to a cold hand test than younger subjects aged 20–40. However, the bradycardia caused by the cold face test was more pronounced in the older subjects. The responses to the cold hand and cold face tests were the same for male and female subjects. During the 2 min after the test, blood pressure and heart rate fell below initial values in the female group but not in the male. It is concluded that, besides adaptation to cold, individual factors such as age, sex, and physical fitness also have a relative importance in the responses to local cooling.
Cardiovascular response to acute aquatic and treadmill exercise in the untrained rat
Authors: Flaim S. F. , Minteer W. J. , Clark D. P. , Zelis R.
Published: December 2017

The cardiovascular effects of acute aquatic (AE) and treadmill (TE) exercise were determined in untrained adult male Sprague-Dawley rats. Animals were exercised to exhaustion or for a maximum of 5 min with either exercise mode and data collected during the last minute of exercise were compared to preexercise rest data. Heart rate and cardiac output increased only with TE; arterial pressure remained stable during both protocols. Regional blood flow was determined by the radioactive microsphere technique. Coronary flow increased only with TE. Skeletal muscle flow, determined in six muscle groups, increased more with TE (97 to 587%) than with AE (-44 to 260%) (flow in the quadriceps group decreased during AE). Flow to the skin and splanchnic regions decreased; cerebral flow increased in both groups. Blood gas data suggest lactic acidosis and hyperventilation only with TE. These data indicate that 1) the cardiovascular effects of acute, exhaustive bouts of AE and TE in the rat are not comparable, and 2) the hemodynamic changes occurring with exhaustive TE in rat, as in man, involve a shunting of blood to the regions of demand and away from the nonessential circulations.
Arousal, ventilatory, and airway responses to bronchopulmonary stimulation in sleeping dogs
Authors: Sullivan C. E. , Kozar L. F. , Murphy E. , Phillipson E. A.
Published: December 2017

We studied waking, ventilatory, and reflex tracheal smooth muscle (TSM) responses to tracheobronchial irritation or lung inflation in three sleeping dogs. The dogs breathed through a cuffed endotracheal tube, and airflow was measured with a pneumotachograph. TSM tone was monitored directly by measuring pressure in the water-filled cuff of the endotracheal tube. Mild degrees of tracheobronchia irritation, produced by squirting 0.1--1.0 ml of water into the lower trachea, or by having the dogs inhale one breath of acetic acid vapor (concentration 17 ppm), generally caused arousal from slow-wave sleep (SWS), but not from rapid-eye-movement (REM) sleep. During wakefulness the irritant stimuli caused coughing and TSM constriction; during SWS or REM sleep, these responses occurred only if the stimulus first produced arousal. In contrast, stimulation of pulmonary stretch receptors by lung inflation did not cause arousal, but readily produced apnea and TSM relaxation during SWS. The results indicate that cough and airway smooth muscle constriction in response to bronchopulmonary irritant stimuli do not occur in the absence of arousal, and that arousal responses to such stimuli are depressed in REM sleep.
Improved measurements of shear modulus and pleural membrane tension of the lung
Authors: Hajji M. A. , Wilson T. A. , Lai-Fook S. J.
Published: December 2017

The continuum solution for the deformation of an elastic half space covered by a membrane is used to interpret measurements of the indentation of lung lobes under a column of fluid. The shear modulus mu of the underlying parenchyma is found to be approximately 0.7 times transpulmonary pressure, independent of species size. The tension in the pleural membrane T increases rapidly with increasing membrane area. For dog lungs, the value of T is 10(3) to 10(4) dyn/cm. For the larger species tested, pigs and horses, T is larger. The continuum solution shows that a concentrated force applied to the pleural surface is distributed over a distance T/mu as it is transmitted across the pleural membrane. The membrane is important in determining the displacement produced by forces that act within a region that is small compared to this distance, approximately 2 cm for dog lungs. By comparing the tension-area curve of the pleural membrane with the pressure-volume curve of the lobe, it is found that the pleural membrane contributes about 20% of the work done by the lung during deflation.
Lipid metabolism in skeletal muscle of endurance-trained males and females
Authors: Costill D. L. , Fink W. J. , Getchell L. H. , Ivy J. L. , Witzmann F. A.
Published: December 2017

Bipsies were obtained from the gastrocnemius muscle of 13 male and 12 female distance runners and analyzed for [14C]palmitoyl-CoA oxidation, fiber composition, and the activities of selected enzymes. The male and female runners were similar in terms of maximal oxygen uptake (VO2max), training mileage, fiber compositions, and data collected during a 60-min treadmill run at 70% VO2max. Muscle succinate dehydrogenase and carnitine palmitoyl transferase activities were, however, significantly greater (P less than 0.05) in the male than in female runners. In addition, the male runners' muscle also showed a greater capacity to oxidize palmitoyl CoA. Little relationship, however, was found between muscle lipid metabolism, enzyme activities, and the calculated (respiratory exchange) fraction of energy derived from fat during 60 min of running at 70% VO2max. Although these data support the concept that endurance training (80–115 km/wk) markedly enhances the capacity of muscles to metabolize fats, the factors that regulate the usage of lipids during prolonged exercise do not appear to be limited by the capacity of the fibers to oxidize fatty acids, as determined by in vitro measurements.
Early change in skeletal muscle protein synthesis after limb immobilization of rats
Authors: Booth F. W. , Seider M. J.
Published: December 2017

The atrophy of skeletal muscle accruing from disuse, or limb immobilization, is caused by a decreased rate of protein synthesis and an increased rate of protein degradation. Currently, little information is available regarding the initial time of the decline in the rate of protein synthesis in skeletal muscle. The purpose of the present study was to determine, as precisely as possible, the time at which the protein synthesis rate first begins to decline in skeletal muscle, utilizing immobilized limbs of rats for a model. A constant-infusion technique employing [14C]tyrosine was used to estimate protein synthesis rates. During the first 6 h of immobilization, a significant decline of 37% in the fractional rate of protein synthesis from the control level of 5.7%/day was observed. These results suggest that very early changes are occurring in molecular events that regulate protein synthesis in disused or immobilized skeletal muscle.
Maximum oxygen consumption of rats and its changes with various experimental procedures
Authors: Bedford T. G. , Tipton C. M. , Wilson N. C. , Oppliger R. A. , Gisolfi C. V.
Published: December 2017

A ten-stage treadmill test was developed and standardized to secure the VO2max of male and female rats assigned to various cross-sectional and longitudinal experimental groups. Repeated measurements indicated that the test procedure was reliable and could be used for research purposes. When the test was used with different strains, the untrained Sprague-Dawley rats had significantly higher VO2max values than animals of the Wistar-Kyoto (WKY) or the Okamoto-Aoki (SHR) strains. Exercise schedules were evaluated that were similar to those previously used by various investigators and it was found that most were exercising their rats at levels exceeding 75% VO2max. After 6--10 wk of chronic exercise, significant increases in VO2max occurred that ranged between 12 and 26%. Longitudinal studies (1 yr) with hypertensive (SHR) rats revealed that it was more desirable to logarithmically evaluate the relationship between VO2max and body mass than by the conventional method of ml . kg-1 . min-1. When this approach was used with SHR animals, the VO2max differences between the sexes were not apparent until the animals were 1 yr of age. On the other hand, training by male SHR rats caused significant increases in VO2max regardless of the method used to express the results. It is recommended that future studies designed to elucidate exercise mechanisms in rats should include a standardized VO2max test.
Differential permeability of endothelial and epithelial barriers to albumin flux
Authors: Gorin A. B. , Stewart P. A.
Published: December 2017

We measured the flux of albumin between the vascular space and the pulmonary interstitial and luminal lining fluids in 20 adult sheep with chronic lung lymph fistulas. We sampled the bronchoalveolar lining layer by episodic fiberbronchoscopic lavage. A total of 62 alveolar lavages were performed at times ranging between 30 min and 60 h after intra-arterial injection of 100 microCi of 125I-labeled albumin. Samples of lymph and plasma were obtained simultaneously with lavage fluid, and the radioactivity and albumin content of all samples were measured and expressed as specific activity (counts/min . g albumin). We found that alveolar lavage fluid collected by our technique is not significantly contaminated by plasma or interstitial fluid proteins. Proteins present in alveolar lavage fluid and also present in plasma reach the alveolar space by a normal diffusive process, and not as a result of epithelial membrane damage occurring at the time of lavage. Lung epithelial permeability to albumin in small, but finite (4.3--5.8 x 10(-10) cm/s). Virtually all (greater than 92%) of resistance to albumin flux across the alveolocapillary membrane lies in the epithelial barrier. Increases in permeability of the respiratory epithelium, even minor, would have a marked effect on water and solute balance in the lung. Epithelial injury will potentiate pulmonary edema formation even in the presence of normal pulmonary microvascular pressure, plasma oncotic pressure, and endothelial permeability.
Exercise training-induced hypervolemia: role of plasma albumin, renin, and vasopressin
Authors: Convertino V. A. , Brock P. J. , Keil L. C. , Bernauer E. M. , Greenleaf J. E.
Published: December 2017

To investigate the time course and mechanism of the increase in blood volume (BV) during isotonic exercise training, blood hemoglobin, hematocrit, and plasma volume (PV), osmotic, electrolyte, renin activity (PRA), vasopressin (AVP), and protein fractions were measured periodically in eight trained men 20-22 yr (Vo2max = 57 ml . min-1 . kg-1) before, during, and after ergometer exercise training (approximately 160 W, 65% Vo2max) for 2 h/day for 8 days. During training, plasma total osmolar and albumin contents increased to maintain a constant plasma osmolality and protein concentration during PV expansion. After training, BV increased by 457 ml (+8.1% P less than 0.05), due to an increase in PV of 427 ml (+12.1%, P less than 0.05); red cell volume was essentially constant (delta = +30 ml, NS). Plasma hypervolemia during training was associated with two major factors: 1) a ninefold elevation in PRA and AVP during exercise that facilitated Na+ and H2O retention, and 2) a progressive, chronic increase in plasma albumin content that provided increased H2O-binding capacity for the blood. Thus an efficient procedure for increasing PV is the daily performance of high-intensity isotonic leg exercise (65% Vo2max) for 2 h/day.
Effect of a precooling maneuver on body temperature and exercise performance
Authors: Schmidt V. , Bruck K.
Published: December 2017

Twelve subjects exercised to exhaustion at an ambient temperature of 18 degrees C on a bicycle ergometer with the load being stepwise increased. On one day, exercise was preceded by a precooling maneuver. In the precooling tests, deep body temperature attained values of about 1 degree C lower than in the control tests. There was no indication of metabolic cold defense reactions being evoked throughout the exercise period. In the precooling tests, heart rate was significantly lower than in the controls, but the mean maximum work rate, peak oxygen uptake (VO2), time to exhaustion, and total work were not reduced, i.e., work rate and VO2 were increased for a given heart rate. In the three subjects with the lowest maximum work rates, total work and exhaustion time and, in two cases, maximum work rate were increased after precooling. The onset of sweating occurred at higher work rates but at lower core, mean skin, and mean body temperature after precooling. However, the accumulated sweat secretion was considerably smaller after precooling, indicating less thermoregulatory effort.
Coordination of breathing and swallowing in human infants
Authors: Wilson S. L. , Thach B. T. , Brouillette R. T. , Abu-Osba Y. K.
Published: December 2017

Spontaneous nonfeeding swallows taken during wakefulness and sleep were identified in nine preterm infants by characteristic patterns in pharyngeal pressure, submental electromyogram, and respiratory airflow. Two hundred and seventeen swallows during ongoing respiration interrupted either inspiratory or expiratory airflow with airway closure for approximately 1 s. The duration of airway closure was independent of respiratory rate. A brief "swallow-breath" was associated with swallow onset in most instances. The respiratory nature of this movement was confirmed by simultaneous recording of a fall in pharyngeal or esophageal pressure and outward movement of the abdomen. Prolongation of the respiratory cycle was generally observed when a swallow interrupted ventilation at higher lung volumes, i.e., in late inspiration or early expiration. When the swallow interrupted ventilation at lower lung volume, i.e, in late expiration or early inspiration, the subsequent inspiratory effort was usually obstructed as it preceded airway opening at the end of the swallow synergism.
Muscular endurance and surface electromyogram in isometric and dynamic exercise
Authors: Hagberg M.
Published: December 2017

In nine male volunteers, the endurance time for sustained isometric exercise (right-angle elbow flexion) and dynamic exercise (continuous concentric and eccentric elbow flexions) was measured at different contraction levels. Intermittent isometric exercises were also performed by four of the subjects in whom surface electromyographic elbow flexor recordings were obtained during the three types of exercise. A rapid decrease of the endurance time was seen at contraction levels above 15–20% of the maximum voluntary contraction for both the sustained isometric and dynamic exercise. There were no significant difference between the regression of the endurance time vs. the contraction level for the sustained isometric exercise and that of the dynamic exercise. However, the endurance time was enhanced in the intermittent isometric exercise compared with the sustained isometric exercise. The development of muscle fatigue was well correlated to change of the myoelectric rootmean-square amplitude and the mean power frequency. Differences in exercise did not significantly affect the relation between the time constant of the mean power frequency decrease and the endurance time.
Effect of PEEP on left ventricular function in right-heart-bypassed dogs
Authors: Wise R. A. , Robotham J. L. , Bromberger-Barnea B. , Permutt S.
Published: December 2017

Positive-pressure ventilation with positive end-expiratory pressure (PEEP) has been associated with elevation of left ventricular filling pressure for a stable or reduced cardiac output. To exclude the possibility that right ventricular distension due to increased pulmonary vascular resistance decreases left ventricular compliance (ventricular interdependence), we studied the effect of PEEP on left ventricular function in open-chest right-heart-bypassed dogs. A rightward shift of the left ventricular function curve was caused by 15 cmH2O PEEP without a change in the aortic pressure-flow relationship. The pericardial pressure, however, was found to exceed atmospheric pressure on 15 cmH2O even with the chest widely opened. This increase in the pressure surrounding the heart accounted for the increase in left ventricular filling pressure. We postulate, therefore, that the elevation in left ventricular filling pressure found with PEEP is due in part, if not entirely, to mechanical interaction of the heart and lungs by direct compression or pericardial traction.
Changes in ventilation and chest wall mechanics during sleep in normal adolescents
Authors: Tabachnik E. , Muller N. L. , Bryan A. C. , Levison H.
Published: December 2017

The effect of sleep state on ventilation and the mechanics of breathing was studied in nine normal adolescents by use of a respiratory inductive plethysmograph and surface electromyogram electrodes. Minute ventilation was state dependent (P less than 0.01), decreasing by a mean of 8% from wakefulness to nonrapid-eye-movement (NREM) sleep and increasing 4% from NREM to rapid-eye-movement (REM) sleep. These changes were caused by changes in respiratory rate. Tidal volume (VT) was not affected by sleep state (P greater than 0.10). The pattern of breathing during wakefulness was similar to that of REM sleep. During NREM sleep intercostal and diaphragmatic muscle activity increased by a mean of 34% and 11%, respectively, as compared with wakefulness, indicating an increase in the respiratory work load. This was accompanied by a substantial increase in rib cage contribution to VT. REM sleep was associated with a marked decrease in intercostal muscle activity (P less than 0.05) and a diminished rib cage contribution; VT was maintained due to a mean increase of 34% in diaphragmatic muscle activity (P less than 0.05).