bluuebunny/crossref_metadata_2025 huggingface dataset:
Antenatal betamethasone therapy augments nitric oxide-mediated relaxation of preterm ovine pulmonary veins
Authors: Zhou H. , Gao Y. , Raj J. U.
Published: December 2017

Antenatal glucocorticoid therapy improves pulmonary function in preterm newborns. We have determined the effect of antenatal glucocorticoid therapy on nitric oxide-mediated relaxation in pulmonary vessels of preterm lambs. Ovine fetuses (126 days gestation; full term = 150 days) were injected with betamethasone (0.5 mg/kg body wt) or saline. After 48 h, lambs were delivered, ventilated for 3 h, and killed. Isolated fourth-generation pulmonary arteries (2-3 mm diameter) and veins (1.5-2 mm diameter) were suspended in organ chambers filled with modified Krebs-Ringer solution (95% O2-5% CO2) at 37 degrees C, and their isometric tension was recorded. During contractions to endothelin-1 or U-46619 (in the presence of indomethacin), acetylcholine and bradykinin induced endothelium-dependent nitro-L-arginine-inhibitable relaxation in arteries and veins. The relaxation was greater in veins of betamethasone-treated than in those of control lambs. Veins from lambs without endothelium treated with betamethasone were more sensitive to sodium nitroprusside than veins from controls. For arteries, there was no significant difference in relaxation between different groups. Relaxation induced by 8-bromoguanosine 3′,5′-cyclic monophosphate was similar in arteries and veins of different groups. Radioimmunoassay showed that nitric oxide caused a greater increase in guanosine 3′,5′-cyclic monophosphate in betamethasone-treated veins than in controls. These data suggest that antenatal betamethasone therapy augments nitric oxide-mediated relaxation of pulmonary veins of preterm lambs, probably by increasing soluble guanylate cyclase activity of vascular smooth muscle.
Skeletal muscle GLUT-4 and postexercise muscle glycogen storage in humans
Authors: McCoy M. , Proietto J. , Hargreaves M.
Published: December 2017

The purpose of this study was to examine the relationship between skeletal muscle GLUT-4 protein and postexercise glycogen storage in human subjects fed adequate carbohydrate. Eleven men completed 2 h of cycling, and a biopsy of the vastus lateralis was performed immediately after exercise cessation for the determination of muscle GLUT-4 protein and glycogen concentrations, glycogen synthase activity, and citrate synthase activity. The subjects ingested meals providing 2.0 g carbohydrate/kg body weight at 0, 2, and 4 h postexercise, and a second biopsy was performed 6 h postexercise. Muscle glycogen concentration increased significantly during the 6-h recovery period (glycogen immediately postexercise, 27.2 +/- 5.4 mmol/kg wet weight; glycogen storage, 52.4 +/- 2.9 mmol x kg wet weight-1 x 6 h-1; P<0.05). Glycogen storage during recovery was directly related to GLUT-4 protein (2.20 +/- 0.33 arbitrary standard units; r = 0.63; P<0.05) and inversely related to glycogen immediately postexercise (r = -0.70; P < 0.05). A direct correlation existed between glycogen storage during recovery and the activity of the I form of glycogen synthase (r = 0.60; P < 0.05). These results suggest that muscle GLUT-4 protein concentration, as well as factors relating to glucose disposal, may affect postexercise glycogen storage in humans fed adequate carbohydrate.
Lactate uptake by skeletal muscle sarcolemmal vesicles decreases after 4 wk of hindlimb unweighting in rats
Authors: Dubouchaud H. , Granier P. , Mercier J. , Le Peuch C. , Prefaut C.
Published: December 2017

We investigated the effects of 4 wk of hypodynamia on the rate of lactate transport in skeletal muscle sarcolemmal vesicles from control and hindlimb-suspended rats. Characterization of the sarcolemmal preparations was achieved with a marker enzyme (K+-p-nitrophenylphosphatase) and measurement of 1 mM [U-14C]lactate transport activity under zero-trans conditions with or without a pH gradient or the transport inhibitor alpha-hydroxycinnamate. Preparations from the two groups were not significantly different concerning yield and purification. Based on these results, we used this model to analyze the lactate transport activity after hypodynamia by tail suspension. Hindlimb suspension caused a shift from slow to fast myosin heavy chain isoforms in soleus muscles with a 40% decrease in the citrate synthase activity (from 35.3 +/- 3.7 to 21.4 +/- 2.1 mu mol x g-1 x min-1; P < 0.05). Lactate (1 mM) uptake in vesicles from the two groups was a function of time, and the rate after hindlimb suspension was significantly decreased in the suspended compared with the control group (2.25 +/- 0.44 and 3.50 +/- 0.26 nmol x min-1 x mg protein-1, respectively; P < 0.05). These differences were not observed for a higher lactate concentration (50 mM). These results suggest that the level of physical activity plays a role in the regulation of sarcolemmal lactate transport activity implicated in the exchanges of lactate between producing and utilizing cells, organs, and tissues, which are major ways of carbohydrate energy distribution in humans and others species.
Eucapnic hypoxia lowers human cold thermoregulatory response thresholds and accelerates core cooling
Authors: Johnston C. E. , White M. D. , Wu M. , Bristow G. K. , Giesbrecht G. G.
Published: December 2017

Hypoxia lowers the basic thermoregulatory responses of animals and humans. In cold-exposed animals, hypoxia increases core temperature (Tco) cooling rate and suppresses shivering thermogenesis. In humans, the experimental effects of hypoxia on thermoregulation are equivocal. Also, the effect of hypoxia has not been separated from that of hypocapnia consequent to hypoxic hyperventilation. To determine the isolated effects of hypoxia on warm and cold thermoregulatory responses and core cooling during mild cold stress, we examined the Tco thresholds for sweating, vasoconstriction, and shivering as well as the core cooling rates of eight subjects immersed in 28 degrees C water under eucapnic conditions. On 2 separate days, subjects exercised on an underwater cycle ergometer to elevate Tco above the sweating threshold. They then rested and cooled until they shivered vigorously. Subjects inspired humidified room air during the control trial. For the eucapnic hypoxia trial, they inspired 12% O2-balance N2 with CO2 added to maintain eucapnia. Eucapnic hypoxia lowered the Tco thresholds for vasoconstriction and shivering by 0.14 and 0.19 degrees C, respectively, and increased core cooling rate by 33% (1.83 vs. 1.38 degrees C/h). These results demonstrate that eucapnic hypoxia enhances the core cooling rate in humans during mild cold stress. This may be attributed in part to a delay in the onset of vasoconstriction and shivering as well as increased respiratory heat loss during hypoxic hyperventilation.
Distribution of pulmonary and bronchial blood supply to airways measured by fluorescent microspheres
Authors: Bernard S. L. , Glenny R. W. , Polissar N. L. , Luchtel D. L. , Lakshminarayan S.
Published: December 2017

This study determined the relative contributions of systemic (bronchial) and pulmonary blood flow to the intraparenchymal airways =1 mm in diameter by using 15-mu m fluorescent microspheres and fluorescence microscopy in four dogs. Fluorescent microspheres of one color were injected into the inferior vena cava as a pulmonary blood flow marker, and fluorescent microspheres of another color were injected into the left ventricle as a systemic blood flow marker. After the second injection, the animals were killed and the lungs were excised and air dried at total lung capacity. The left lung was sliced into transverse planes and then sectioned into smaller blocks containing airways down to 1 mm in diameter. The blocks were then sectioned using a Vibratome and examined with a fluorescence microscope. Pulmonary and systemic blood flow markers were counted in airway walls, and the diameter of each airway was measured to determine the bronchial tissue volume. After a correction for the number of blood flow markers injected into each circulation, the average ratio of pulmonary to systemic blood flow markers seen in airway walls was 1:37, indicating that 97% of the blood supply to the intraparenchymal airways down to 1 mm in diameter was from the bronchial circulation. Furthermore, on the basis of a weighted least squares regression analysis, systemic (bronchial) blood flow per unit tissue volume increased as airway diameter decreased (P = 0.03).
Effects of upper airway stimulation on swallowing, gasping, and autoresuscitation in hypoxic mice
Authors: Khurana A. , Thach B. T.
Published: December 2017

Severe hypoxia produces a state of neural depression known as hypoxic coma in which reflex activity is believed to be absent but from which spontaneous recovery (“autoresuscitation”) still can occur. We evaluated the swallowing reflex during hypoxic coma by employing mechanical and chemosensory stimuli. BALB/c mice were given 97% N2-3% CO2 to breathe. At onset of coma, a 0.05-ml bolus of saline or water was infused into the pharynx. Unlike mechanical stimulation (sham infusion), fluid infusion usually was followed by rapid swallowing, more so with water than with saline. This model allowed examination of interactions among swallowing, hypoxic gasping, airway fluid removal, and autoresuscitation. Compared with sham infusion, saline and water reduced gasping rate equally. Saline, however, prolonged the process of autoresuscitation more than did water, an effect possibly related to an observed increased retention of saline in the airway. Occasionally, mice failed to swallow after infusions, in which case airway obstruction during gasping and autoresuscitation failure was repeatedly observed. These studies suggest that the swallowing component of the laryngeal chemoreflex is present during hypoxic coma and that swallowing facilitates autoresuscitation when upper airway fluid is present.
Effect of measurement error on calculated variables of oxygen transport
Authors: Woda R. P. , Dzwonczyk R. D. , Orlowski J. P. , Van Lente F. , Lynn L. A.
Published: December 2017

The effect of measurement error in pH, PCO2, and PO2 on mathematically derived variables of oxygen transport in patients was delineated by comparing calculated oxygen saturations from a blood-gas machine with measured saturations from a CO-oximeter and further by modeling the error in a computer simulation. Twenty-one critically ill patients aged 30-84 yr were studied. A total of 80 arterial and 80 mixed venous blood gas samples were collected. The intraclass correlation results between measured and calculated arterial (SaO2) and mixed venous (Sv-O2) oxygen saturations were 0.59 and 0.68, respectively. The product-moment correlation for SaO2 was 0.75 and for Sv-O2 was 0.77. The percent error in calculating and measuring oxygen saturation was found to be greater at low PO2 values, whereas percent error of calculating oxygen consumption increased as the PO2 increased. Measurement repeatability at high PO2 is better than at low PO2 for both measured and calculated methods. We conclude from this comparison that measured and calculated SaO2 and Sv-O2 values are not interchangeable. Each can introduce substantial error in calculating oxygen consumption through error propagation and error amplification.
Prevention of ischemia-reperfusion lung injury by inhaled nitric oxide in neonatal piglets
Authors: Barbotin-Larrieu F. , Mazmanian M. , Baudet B. , Detruit H. , Chapelier A. , Libert J. M. , Dartevelle P. , Herve P.
Published: December 2017

Lung ischemia-reperfusion results in a decrease in the release of nitric oxide (NO) by the pulmonary endothelium. NO may have lung-protective effects by decreasing neutrophil accumulation in the lung. We tested whether NO inhalation would attenuate reperfusion-induced endothelial dysfunction and increases in microvascular permeability and total pulmonary vascular resistance (RT) by preventing neutrophil lung accumulation. After baseline determinations of RT, coefficient of filtration (Kfc), and circulating neutrophil counts, isolated neonatal piglet lungs were subjected to a 1-h period of ischemia followed by a 1-h period of blood reperfusion and reventilation with or without addition of NO (10 ppm). NO prevented reperfusion-induced increases in RT and Kfc, as well as the decrease in circulating neutrophils. After reperfusion, increases in Kfc were correlated with decreases in circulating neutrophils. NO prevented reperfusion-induced decrease in endothelium-dependent relaxation in precontracted pulmonary arterial rings. This demonstrates that inhaled NO prevents microvascular injury, endothelial dysfunction, and pulmonary neutrophil accumulation in a neonatal piglet model of lung ischemia-reperfusion.
Interaction between hypoxia and hypercapnia in regulating canine diaphragm arteriolar diameter
Authors: Ward M. E.
Published: December 2017

In alpha-chloralose-anesthetized mongrel dogs, the microvascular responses to hypoxia and hypercapnia were studied in the vascularly isolated ex vivo left hemidiaphragm. The diaphragm was perfused with arterial blood diverted from the femoral artery by a pump. A series of membrane oxygenators was used to adjust the blood gas composition of the blood perfusing the diaphragm. Arteriolar diameters were measured by intravital microscopy during an infusion of sodium nitroprusside, moderate hypoxia (phrenic venous PO2 25 Torr), severe hypoxia (phrenic venous PO2 13 Torr), hypercapnia (phrenic venous PCO2 100 Torr), and a simultaneous presentation of hypoxia and hypercapnia. Recordings were made after 15 min under each condition when a steady state had been established for vessel diameter and flow. Pump speed was adjusted manually under each condition to ensure that the steady-state perfusion pressure was the same as that under the control condition. Moderate hypoxia generally resulted in dilation; however, vasoconstriction was seen in some arterioles. Severe hypoxia caused vasodilation that was inversely related to baseline vessel diameter and paralleled the response to sodium nitroprusside. Hypercapnia resulted in vasodilation of the diaphragmatic circulation at values of phrenic venous PCO2 = 80 Torr. The arteriolar response to hypercapnia was also inversely related to baseline vessel diameter. Hypoxia and hypercapnia in combination exerted an additive effect on arteriolar diameter but produced a greater than additive effect on blood flow. Both PO2 and PCO2 may contribute to the local regulation of diaphragmatic blood flow. The vasodilator effects of both hypoxia and hypercapnia are greater in smaller than in larger arterioles. The interaction between PO2 and PCO2 on arteriolar diameter is additive. An apparent synergistic effect on blood flow results from the power function relating diameter to flow.
Exercise-induced stimulation of murine macrophage phagocytosis may be mediated by thyroxine
Authors: Forner M. A. , Barriga C. , Ortega E.
Published: December 2017

The present study was designed to test the hypothesis that changes in plasma concentrations of hormones may be responsible for the exercise-induced macrophage phagocytic stimulation. The effect of 30-min incubation of macrophages with plasma from mice previously exposed to swimming until exhaustion (with or without previous training) was studied, and the results showed a similar stimulation of the phagocytic capacity (attachment and ingestion) of these cells to that found in previous studies after exercise. Also, changes in plasma concentration of both thyroxine (T4) and 3,3′,5-triiodo-L-thyronine (T3) after exercise were measured, and their effect on phagocytic capacity after in vitro incubation with peritoneal macrophages was investigated. Results indicated that, after exercise, plasma concentrations of T3 and T4 increased. Incubation of peritoneal macrophages for 30 min with a concentration of T3 similar to that observed in the plasma immediately after exercise (1.5 ng/ml) induced no modifications in the phagocytic capacity. However, a physiological concentration of T4 after exercise (75 ng/ml) stimulated the phagocytic capacity of peritoneal macrophages. In addition, a 10,000-fold greater concentration of these thyroid hormones did not modify the macrophage function. It is concluded that physiological concentration of T4 may be a mediator of the stimulation of the phagocytic function in macrophages induced by exercise.
Capillary-to-fiber surface ratio in rat fast-twitch hindlimb muscles after chronic electrical stimulation
Authors: Mathieu-Costello O. , Agey P. J. , Wu L. , Hang J. , Adair T. H.
Published: December 2017

We examined the relative plasticity of capillaries and fiber mitochondria in rat fast-twitch hindlimb muscles in response to chronic electrical stimulation. Specifically we addressed whether the size of the capillary-fiber interface increases in proportion to fiber mitochondrial volume, inasmuch as fiber aerobic capacity increases severalfold with chronic stimulation. Tibialis anterior and extensor digitorum longus muscles of six rats [367 +/- 17 (SD) g body wt] were stimulated (10 Hz, 8 h/day, 7 days/wk) for 28 consecutive days. Subsequently they were perfusion fixed in situ and stimulated, and contralateral control samples from the midbelly were processed for electron microscopy and morphometry. Capillary length density, capillary-to-fiber ratio, and fiber mitochondrial volume density increased two- to threefold in stimulated muscles, with no change in fiber or capillary diameter. Capillary-to-fiber surface area ratio per fiber unit mitochondrial volume was unchanged in stimulated muscles compared with contralateral controls, indicating a proportional increase in the size of the capillary-fiber interface and fiber mitochondrial volume in the muscles after chronic electrical stimulation.
Effect of drink flavor and NaCL on voluntary drinking and hydration in boys exercising in the heat
Authors: Wilk B. , Bar-Or O.
Published: December 2017

This study was intended to assess the influence of drink flavor and composition on voluntary drinking and hydration status in children exercising intermittently at 35 +/- 1 degrees C and 45-50% relative humidity. Twelve boys (9-12 yr) performed three 3-h identical sessions (four 20-min cycling bouts at 50% maximal O2 uptake followed by 25-min rest). One of three beverages (chilled to 8-10 degrees C) was assigned to each session in a Latin-square sequence: unflavored water (W), grape-flavored water (FW), and grape-flavored water plus 6% carbohydrate and 18 mmol/l NaCl (CNa). Drinking was ad libitum. Body weight, heart rate, rectal and skin temperatures, and thirst and stomach fullness perceptions were monitored periodically. Total intake was 610, 882, and 1,157 g in W, FW, and CNa, respectively (CNa-W and CNa-FW; P < 0.05). Hypohydration was observed with W (-0.65% body wt) and FW (-0.32% body wt), but drinking CNa resulted in slight overhydration (+0.47% body wt, CNa-W, CNa-FW; P < 0.05). Other physiological and all perceptual variables were insignificantly different among trails. In conclusion, while flavoring of water reduces children's voluntary dehydration, further addition of 6% carbohydrates and 18 mmol/l NaCl prevents it altogether.
Water turnover and body composition during long-term exposure to high altitude (4,900-7,600 m)
Authors: Fusch C. , Gfrorer W. , Koch C. , Thomas A. , Grunert A. , Moeller H.
Published: December 2017

Thirteen healthy subjects (11 men and 2 women; 30.2 +/- 5.4 yr; 73.5 +/- 10.3 kg; 178.9 +/- 10.4 cm; body mass index, 22.9 +/- 1.6 kg/m2) participated at the 62-day expedition to the Broad Peak (8,047 m), Pakistan. Weight, body water, and water turnover (deuterium dilution and elimination) were measured eight times to assess long-term changes. Body weight fell during the ascent to the base camp [from 73.2 +/- 9.8 (baseline) to 71.7 +/- 9.7 kg; P < 0.05] and decreased until the end of the base camp stay (66.7 +/- 7.2 kg; P < 0.0001). Body compartments changed at different rates. Total body water decreased during the ascent (from 43.1 +/- 7.3 to 41.0 +/- 7.7 liters; P < 0.05) and remained unchanged until the base camp was reached (41.2 +/- 6.9 liters; P < 0.01) but decreased further during the base camp stay (40.6 +/- 5.2 liters). Water content of the body (total body water-to-body weight ratio) fell during the ascent (from 58.6 +/- 3.4 to 55.8 +/- 4.4%; P < 0.01), approached the baseline value during the base camp (57.4 +/- 4.0 and 58.3 +/- 5.1%), and increased again until the end of the base camp (60.6 +/- 3.4 and 60.9 +/- 4.3%). The compartment of the solids increased during the ascent (from 30.2 +/- 3.4 to 32.2 +/- 4.9 kg; P < 0.01) and approached the baseline value on arrival at the base camp (30.5 +/- 4.7 kg). Until the end of the base camp, the compartment of the solids fell (26.9 +/- 2.6 and 26.1 +/- 4.0 kg), indicating that weight loss was due to a loss of body solids, presumably mostly fat mass. Water turnover during the pretest period (sea level) was 45 +/- 7 ml.kg-1.day-1; it increased during the ascent (56 +/- 11 and 60 +/- 10 ml.kg-1.day-1) but remained constant during the base camp stay (63 +/- 12, 58 +/- 9, and 56 +/- 10 ml.kg-1.day-1). It increased during the ascent to Broad Peak (73 +/- 20 ml.kg-1.day-1; P < 0.05) and even more during the descent to civilization (83 +/- 17 ml.kg-1.day-1; P < 0.05).
Body-mass dependence of age-related deterioration in human muscular function
Authors: Meltzer D. E.
Published: December 2017

Maximal anaerobic power of human muscles declines with increasing chronological age and is correlated with body mass. This study investigated whether the rate of deterioration in human muscular function among trained weight lifters is also correlated with body mass. Cross-sectional analysis of performance data of over 1,100 Masters competitors in Olympic-style weight lifting was carried out; eight body-weight classes and six age groups were represented. Two-lift total data (sum of snatch and clean and jerk lifts) were analyzed. Mean deterioration rates in the performance of athletes of widely diverse body masses were compared over the following age ranges: 42-57, 42-62, and 42-67 yr. No statistically significant correlation (P < 0.05) was found between rate of performance decline and body mass. The relationship between body mass and the magnitude of age-related variation of deterioration rate was also studied; no significant correlation was found. Previous studies have demonstrated that performance in Olympic-style weight lifting is correlated with maximal anaerobic muscular power. This leads us to suggest that the age-related deterioration rate of anaerobic power in trained subjects may not be correlated with the body mass of the individual.
Hypoxic pulmonary vasoconstriction and gas exchange in acute canine pulmonary embolism
Authors: Delcroix M. , Melot C. , Vermeulen F. , Naeije R.
Published: December 2017

Hypoxic pulmonary vasoconstriction (HPV) is inhibited in several models of acute lung injury. Whether HPV is preserved in pulmonary embolism is unknown. We investigated the effects of a reduction in the fraction of inspired O2 (FIO2) on pulmonary hemodynamics and gas exchange in anesthetized dogs before and after autologous blood clot pulmonary embolism. In a first group of 14 dogs, stimulus-response curves for HPV were constructed as pulmonary arterial pressure (Ppa) vs. FIO2 varied between 1.0 and 0.06 at a cardiac output (Q) kept constant at 3.5 l.min-1.m-2. Gas exchange was evaluated by using the multiple inert-gas elimination technique at FIO2 of 1.0, 0.4, and 0.1. Embolism decreased the relative magnitude of HPV, expressed as the gradient between Ppa and pulmonary arterial occluded pressure in hypoxia divided by (Ppa-pulmonary arterial occluded pressure) at FIO2 of 1.0, from 1.8 to 1.2 (P < 0.05). Retention minus excretion gradients for sulfur hexafluoride and ethane were increased by decreased FIO2 (P < 0.005 and P < 0.05, respectively) before but not after embolism. Hypoxia-induced deterioration in gas exchange before embolism was related to the amount of baseline very low ventilation-perfusion (VA/Q) ratios. Similar results were obtained in a second group of seven dogs with Q decreased to maintain Ppa at the same average value as before embolism. However, gas exchange was not affected by inspiratory hypoxia before as well as after embolism in this group, which presented with a lesser amount of baseline very low VA/Q. In both groups of dogs, increase in the FIO2 from 0.4 to 1.0 did not affect gas exchange. We conclude that 1) pulmonary embolism is associated with a partial inhibition of HPV, 2) HPV does not contribute to preserve gas exchange in pulmonary embolism, and 3) a strong HPV may deteriorate gas exchange in severe hypoxia in the presence of minor very low VA/Q inequality.
Control of skin blood flow in the neutral zone of human body temperature regulation
Authors: Savage M. V. , Brengelmann G. L.
Published: December 2017

In humans, matching of heat loss and heat production in the “neutral” zone, defined operationally in terms of a range of skin temperatures (Tsk), is accomplished by regulation of skin blood flow (SkBF). Our studies were designed to reveal the characteristics of control of SkBF [from measurements of forearm blood flow (FBF)] in this zone. We controlled the temperature of water sprayed on most of the body of supine men and women at 33 or 35 degrees C in a square-wave pattern (15 min at each temperature) or a step pattern (60 min at 33 degrees C separated by short periods at 35 degrees C). FBF followed Tsk (0.5 ml.min-1.degrees C-1). Esophageal temperature changed approximately 0.11 degrees C with each 2 degrees C change in Tsk, falling with Tsk increase and vice versa. Little influence on FBF, < 0.1 ml.min-1.100 ml-1. degrees C-1, was observed when only the forearm was sprayed with 33 and 35 degrees C water. We conclude that SkBF control in the 33-35 degree C range of Tsk is dominated by the feedforward reflex influence of Tsk on SkBF. The reflex response overcompensates for the effect of Tsk on thermal balance in the neutral zone, so that equilibrium core temperature has an inverse relationship to Tsk.
Effects on muscle of dieting with or without exercise in overweight postmenopausal women
Authors: Svendsen O. L. , Krotkiewski M. , Hassager C. , Christiansen C.
Published: December 2017

The main aim of this study was to investigate the effect of an energy-restrictive, high-protein diet with or without exercise on muscle morphology and biochemistry. Moderately overweight postmenopausal women (49-58 yr, body mass index: 25-42 kg/m2) were randomly assigned to three groups for 12 wk of intervention; namely, a control group, a group on a 4.2 MJ/day diet, and a group on 4.2 MJ/day diet combined with aerobic and anaerobic exercise. Muscle morphology and biochemistry analysis were performed in 69 and 58 women, respectively. In contrast to the diet-only group, the die-plus- exercise group significantly increased the muscle fiber areas by 20-25%, the number of capillaries per muscle fiber type I by approximately 20%, and the activities of citrate synthase by approximately 35% and hexokinase by approximately 20% (P < 0.05). There were no statistically significant changes in any other muscle variable (P < 0.05). The respiratory exchange ratio decreased in both intervention groups by 2-4% (P < 0.01). It is concluded that 12-wk period of an energy-restrictive high-protein diet was not associated with major changes in muscle morphology or biochemistry. The addition of exercise to the die led to an adaptive increase in muscle fiber areas and in the oxidative capacity of the muscles.
Effects of genioglossal response to negative airway pressure on upper airway collapsibility during sleep
Authors: Philip-Joet F. , Marc I. , Series F.
Published: December 2017

Continuous negative airway pressure (CNAP) trials can be used to measure upper airway (UA) collapsibility. This procedure can be accompanied by an increase in UA muscle activity. The purpose of this study was to evaluate the influence of CNAP-induced increase in genioglossal (GG) activity on UA collapsibility in 10 healthy sleeping men. UA collapsibility was measured on two occasions; each recording was preceded by the administration of a placebo or diazepam (0.15 mg/kg) in a randomized double-blind crossover design. In seven subjects, the decrease in mask pressure (Pmask) was associated with an increase in mean GG electromyographic (EMG) activity during the placebo trial, with a significant negative relationship between these two variables. This relationship was still observed with diazepam. In six subjects, the slope of the relationship between mean EMG and Pmask was less negative with diazepam. This was associated with an increase in critical pressure (Pcrit). With the placebo, a positive relationship was found between Pcrit and the slope of the mean EMG/Pmask relationship. We conclude that Pcrit is influenced by the GG response to the decrease in Pmask during CNAP.
Influence of mechanical loading on myosin heavy-chain protein and mRNA isoform expression
Authors: Caiozzo V. J. , Haddad F. , Baker M. J. , Baldwin K. M.
Published: December 2017

The overall objective of the studies reported herein was to examine the effects of high-resistance training on myosin heavy-chain (MHC) protein and mRNA isoform expression. The findings from these studies can be summarized as follows: 1) there was a substantial increase in the fast type IIX MHC protein isoform content of the trained red and white medial gastrocnemius muscles, but this did not occur until after the eighth training session (i.e., 16 days); 2) single-fiber analyses demonstrated that many so-called fast type IIB fibers contained small amounts of the fast type IIX MHC protein isoform and that the high-resistance training program altered the bias of fast type IIB-type IIX MHC protein isoform distribution in these fibers but did not increase the number of fibers that could be categorized as exclusively fast type IIX fibers; 3) the high-resistance training program produced a rapid (i.e., after two training sessions) elevation in the fast type IIX MHC mRNA isoform and a corresponding repression of the fast type IIB MHC mRNA isoform; and 4) the dose-response study revealed that as few as 10 contractions (40 s) per training session were capable of elevating the expression of the fast type IIX MHC mRNA isoform by approximately 250%. These collective findings demonstrate that high-resistance training is a powerful modulator of MHC protein isoforms and that pretranslational mechanisms are very sensitive to even small amounts of high-resistance training.
In vitro human masseter muscle hypersensitivity: a possible explanation for increase in masseter tone
Authors: Adnet P. J. , Reyford H. , Tavernier B. M. , Etchrivi T. , Krivosic I. , Krivosic-Horber R. , Haudecoeur G.
Published: December 2017

To determine whether a difference in fiber-type caffeine and Ca2+ sensitivities exists between human masseter and vastus lateralis skeletal muscle, we compared the fiber-type caffeine sensitivities in chemically skinned muscle fibers from 13 masseter and 18 vastus lateralis muscles. Caffeine sensitivity was defined as the threshold concentration inducing > 10% of the maximal tension obtained after the fiber was loaded with a 1.6 x 10(-2) mM Ca2+ solution for 30 s. Significant difference in the mean caffeine sensitivity was found between type I masseter fibers [2.57 +/- 1.32 (SD) mM] vs. type I (6.02 +/- 1.74 mM) and type II vastus lateralis fibers (11.25 +/- 3.13 mM). Maximal Ca(2+)-activated force per cross-sectional area was significantly different between masseter and vastus lateralis fibers. However, the Ca2+ concentration corresponding to half-maximal tension (pCa50) was not significantly different between type I masseter (pCa50 5.9 +/- 0.02) and type I vastus lateralis muscle (pCa50 6.01 +/- 0.08). These results suggest that the increase in caffeine sensitivity of masseter muscle reflects the presence of a low reactivity threshold of the sarcoplasmic reticulum.
Inspiratory coactivation of the genioglossus enlarges retroglossal space in laryngectomized humans
Authors: Kobayashi I. , Perry A. , Rhymer J. , Wuyam B. , Hughes P. , Murphy K. , Innes J. A. , McIvor J. , Cheesman A. D. , Guz A.
Published: December 2017

To investigate the relationship between the electrical activity of the genioglossus (GG-EMG) and associated tongue movement, seven laryngectomized subjects breathing through a tracheal stoma (without pressure or flow change in the upper airway) were studied in the supine position. Tongue movement, with the use of lateral fluoroscopy, and GG-EMG expressed as a percentage of maximum voluntary genioglossal activation were monitored simultaneously during 1) spontaneous inspiration (SI), 2) resistive loaded inspiration (LI), and 3) rapid inspiration (RI). Tongue position during each maneuver was compared with its position during spontaneous expiration. Peak GG-EMG during the three maneuvers was significantly different from each other (SI: 5.4 +/- 1.6, LI: 11.9 +/- 1.8, and RI: 51.6 +/- 9.4 (SE) %, respectively). Associated forward movement of the posterior aspect of the tongue was minimum during SI; however, significant movement was observed during LI, and this was increased during RI. Significant covariance existed between peak GG-EMG and this movement. Genioglossal coactivation with inspiration enlarges the glossopharyngeal airway, particularly in its caudal part. In subjects with intact upper airways, this activation may protect or enhance upper airway patency in an effort-dependent manner.
Postnatal lung responses and surfactant function after fetal or maternal corticosteroid treatment
Authors: Rebello C. M. , Ikegami M. , Polk D. H. , Jobe A. H.
Published: December 2017

To evaluate the effect of dose and route of administration of betamethasone on subsequent postnatal lung function, pregnant ewes were randomized at 127 days gestation to receive maternal or fetal intramuscular doses of 0.2 or 0.5 mg/kg body wt betamethasone or saline. At delivery 24 h later, preterm lambs were treated with surfactant and ventilated for 4 h. The lambs exposed to 0.5 mg/kg betamethasone by either the maternal or fetal route had higher Po2 values, lung volumes, dynamic compliances, and ventilatory efficiency indexes, as well as lower ventilatory pressure requirements, than did control animals (P < 0.05). There were no consistent improvements in postnatal lung function for the 0.2 mg/kg dose given to the fetus or ewe. However, measurements of radiolabeled protein in the total lung were decreased in all treatment groups (P < 0.01). Surfactant that was recovered from all groups of lambs and fractionated to isolate the large-aggregate fraction improved lung volumes in preterm rabbits to a greater degree than the surfactant used to treat the lambs (P < 0.05). Surfactant recovered from both groups treated with 0.5 mg/kg betamethasone was less sensitive to inactivation by plasma than was surfactant from the 0.2 mg/kg groups or the controls (P < 0.01). Fetal or maternal treatment with 0.5 mg/kg betamethasone improved postnatal lung function and increased the resistance of surfactant to inactivation.
Determinants of basal fat oxidation in healthy Caucasians
Authors: Nagy T. R. , Goran M. I. , Weinsier R. L. , Toth M. J. , Schutz Y. , Poehlman E. T.
Published: December 2017

In a retrospective study, we examined several determinants of basal fat oxidation in 720 healthy Caucasian volunteers. Adult men (n = 427) and women (n = 293) were characterized for resting energy expenditure and substrate oxidation by indirect calorimetry (after a 12-h overnight fast), peak O2 consumption by a treadmill test to exhaustion, body composition by hydrodensitometry, food intake from a 3-day food diary, and hormonal status by fasting hormone concentrations. Fat oxidation was negatively correlated with fat mass in men (r = -0.11; P < 0.05), but no statistical relationship was found in women. In a stepwise multiple regression analysis, fat oxidation was best predicted by peak O2 consumption and fat-free mass in men (model R2 = 0.142) and by free thyroxine, fat-free mass, and fasting insulin in women (model R2 = 0.153). Relative rates of fat oxidation (fat oxidation adjusted for differences in resting energy expenditure) were not correlated with fat mass in either gender. Women showed a lower rate of basal fat oxidation (both absolute and adjusted) than did men. Our results show that fat oxidation is not greater in individuals with a greater fat mass. Furthermore, our results support a sexual dimorphism in basal rates of fat oxidation.
Ozone toxicity in the rat. II. Modeling changes due to ambient temperatures and duration
Authors: Highfill J. W. , Watkinson W. P.
Published: December 2017

Previous studies involving exposures to xenobiotic agents have demonstrated decreases in physiological parameters such as heart rate (HR) and core body temperature (Tco) and have shown that these toxic responses are modulated by changes in ambient temperature (Ta). We recently published the results of a study in which male Fischer 344 rats were implanted with radiotelemetry transmitters that permitted continuous monitoring of HR, Tco, and motor activity. These animals were divided into nine treatment groups (n = 4-5/group) composed of combinations of one of three O3-exposure regimens [0.0 parts/million (ppm) O3 x 24 h/day x 5 days; 0.5 ppm O3 x 6 h/day x 5 days; or 0.5 ppm O3 x 23 h/day x 5 days] at one of three Ta values (10,22, or 34 degrees C). We now report on statistical approaches for the modeling and analyses of these data. The models utilized were dependent on the treatment combinations. Circadian rhythms of Tco during air control periods were fit by cosine models. Overall effects of O3 in the 6- and 23-h exposure groups were best modeled by modified damped-sine and one-compartment models, respectively, for both HR and Tco. These results demonstrate improved methods for the evaluation of biorhythmicity.
In-flight and postflight changes in skeletal muscles of SLS-1 and SLS-2 spaceflown rats
Authors: Riley D. A. , Ellis S. , Slocum G. R. , Sedlak F. R. , Bain J. L. , Krippendorf B. B. , Lehman C. T. , Macias M. Y. , Thompson J. L. , Vijayan K. , De Bruin J. A.
Published: December 2017

Spacelab Life Sciences-1 and -2 provided skeletal muscles from rats dissected in flight for the first time and 2 h to 14 days postflight. The muscles permitted the distinguishing of primary adaptations to microgravity from secondary reloading-induced alterations. In microgravity, rats adopted bipedal forelimb locomotion with the hindlimbs relegated to grasping activities. On landing day, body posture was abnormally low and walking was stilted at a rate one-third of normal. The adductor longus (AL) and soleus muscles exhibited decreased myofiber areas that did not recover 14 days postflight. Doubling of the nonmyofiber area indicated interstitial edema in AL muscles 2.3 h postflight. Solei did not manifest edema postflight, and neither muscle showed edema in flight. Sarcomere eccentric contraction-like lesions were detected in 2.6% of AL myofibers 4.5 h postflight; lesions were absent earlier postflight and in flight. At 9 days postflight, these lesions were repaired but regenerating AL myofibers were present, which suggests that myofiber necrosis occurred 1-2 days postflight. These studies demonstrate that muscle atrophy occurs in microgravity, whereas interstitial edema and sarcomere lesions are postflight phenomena.
Spaceflight effects on beta-adrenoceptor and metabolic properties in rat plantaris
Authors: Ohira Y. , Yasui W. , Kariya F. , Tanaka T. , Kitajima I. , Maruyama I. , Nagaoka S. , Sekiguchi C. , Hinds W. E.
Published: December 2017

Effects of 14 days of spaceflight on beta-adrenoceptor (beta-AR), mitochondrial enzyme activities, and fiber type composition were studied in plantaris muscles of male adult Sprague-Dawley rats. The beta-AR was analyzed in cross sections by quantitative autoradiography. The maximum binding capacity (Bmax) of beta-AR was significantly lowered (approximately 29%) after flight, but the recovery was not completed within 9 days in 1-G environment. Because the dissociation constant remained unchanged, it is suggested that the changes in the Bmax were caused by the alteration of receptor number. The activities of succinate dehydrogenase (SDH) measured in whole homogenates were subnormal (approximately -24%) in muscles sampled approximately 5 h after flight but they were normalized during 9 days of recovery. The percent composition of fiber types and beta-hydroxyacyl CoA dehydrogenase (HAD) activity did not change significantly due to spaceflight. It is suggested that the spaceflight-induced decrease of the Bmax of beta-AR in plantaris was accompanied by a lowered activity of a mitochondrial inner-membrane enzyme SDH but not a matrix enzyme HAD.
Cosmos 2229 mission. Overview
Authors: Korolkov V. , Helwig D. , Viso M. , Connolly J.
Published: December 2017

The Cosmos 2229 unmanned biosatellite was launched from the Plesetsk Cosmodrome in northern Russia on December 29, 1992. This was the 10th Russia-sponsored international mission dedicated to space biology and marked the 8th mission with United States participation. The payload, which orbited the Earth for 11 days 16 h, included two rhesus monkeys; the papers that follow report studies on these monkeys.
Energy expenditure in rhesus monkeys (Macaca mulatta) during spaceflight using doubly labeled water (2H2(18)O)
Authors: Stein T. P. , Dotsenko M. A. , Korolkov V. I. , Griffin D. W. , Fuller C. A.
Published: December 2017

The mean daily energy expenditure rates of three rhesus monkeys (Macaca mulatta) were determined during spaceflight on the joint US-Russian Cosmos 2044 and 2229 missions by the doubly labeled water (2H2(18)O) method. In-flight values were compared with ground data obtained from seven measurements taken from six chair-adapted control monkeys. The mean energy expenditure for the ground control determinations was 94.5 +/- 6.4 kcal.kg-1.day-1 (n = 6). The mean in-flight energy expenditure, 55.1 +/- 8.0 kcal.kg-1.day-1 (n = 3), was significantly less than the mean ground control value (P < 0.05). These data suggest that energy expenditure in restrained rhesus monkeys is significantly reduced during spaceflight.
Forced expirations and maximum expiratory flow-volume curves during sustained microgravity on SLS-1
Authors: Elliott A. R. , Prisk G. K. , Guy H. J. , Kosonen J. M. , West J. B.
Published: December 2017

Gravity is known to influence the mechanical behavior of the lung and chest wall. However, the effect of sustained microgravity (microG) on forced expirations has not previously been reported. Tests were carried out by four subjects in both the standing and supine postures during each of seven preflight and four postflight data-collection sessions and four times during the 9 days of microG exposure on Spacelab Life Sciences-1. Compared with preflight standing values, peak expiratory flow rate (PEFR) was significantly reduced by 12.5% on flight day 2 (FD2), 11.6% on FD4, and 5.0% on FD5 but returned to standing values by FD9. The supine posture caused a 9% reduction in PEFR. Forced vital capacity and forced expired volume in 1 s were slightly reduced (approximately 3-4%) on FD2 but returned to preflight standing values on FD4 and FD5, and by FD9 both values were slightly but significantly greater than standing values. Forced vital capacity and forced expiratory volume in 1 s were both reduced in the supine posture (approximately 8-10%). Forced expiratory flows at 50% and between 25 and 75% of vital capacity did not change during microG but were reduced in the supine posture. Analysis of the maximum expiratory flow-volume curve showed that microG caused no consistent change in the curve configuration when individual in-flight days were compared with preflight standing curves, although two subjects did show a slight reduction in flows at low lung volumes from FD2 to FD9. The interpretation of the lack of change in curve configuration must be made cautiously because the lung volumes varied from day to day in flight. Therefore, the flows at absolute lung volumes in microG and preflight standing are not being compared. The supine curves showed a subtle but consistent reduction in flows at low lung volumes. The mechanism responsible for the reduction in PEFR is not clear. It could be due to a lack of physical stabilization when performing the maneuver in the absence of gravity or a transient reduction in respiratory muscle strength.
Diet and nitrogen metabolism during spaceflight on the shuttle
Authors: Stein T. P. , Leskiw M. J. , Schluter M. D.
Published: December 2017

Human spaceflight is associated with a loss of body protein. To investigate this problem, dietary intake, nitrogen balance, the whole body protein, and fibrinogen protein synthesis rates were measured on the crews of two Spacelab Life Sciences (SLS) shuttle missions before, during, and after spaceflight. The first mission, SLS-1, lasted 9.5 days, and the second, SLS-2, lasted 15 days. The 15N-glycine method was used for the protein synthesis measurements. The following results were obtained. 1) There was a rapid decline in weight for the first 5 days and then the body weight appeared to stabilize. 2) The mean energy intake preflight was 39.0 +/- 2.5 kcal x kg-1 x day-1 (n = 10). There was a sharp drop in dietary intake on flight day 1, with recovery by the second day, and then energy intake was constant at 30.4 +/- 1.5 kcal x kg-1 x day-1 (n = 12) for the remainder of the flight period (P < 0.05). 3) Nitrogen retention was decreased during flight, with the magnitude of the decrease lessening toward the end of the mission. The daily mean nitrogen balance changed from 58 +/- 9 mg x kg-1 x day-1 (n = 9) preflight to 16 +/- 3 mg N x kg-1 x day-1; P < 0.05; n = 11) in flight, corresponding to a loss of approximately 1 kg of lean body mass over 14 days. 4) Whole body protein synthesis was increased early in flight and on recovery, as was fibrinogen synthesis. We conclude that 1) the rapid readjustment and stabilization of energy intake and the improved nitrogen retention with increasing flight duration are consistent with a rapid metabolic accommodation to the novel environment; and that 2) the increased protein turnover indicates that a metabolic stress response is an important factor in this adjustment process.
Body plethysmographic measurement of thoracic gas volume without panting against a shutter
Authors: Agrawal A. , Agrawal K. P.
Published: December 2017

When a subject breathes through a pneumotachograph in a body box, the measured value of specific airway resistance (sRaw1) is equal to the product of thoracic gas volume (TGV) and the sum of the airway resistance (Raw) and the instrument resistance (Rins). If an additional resistance (Radd) is put in the breathing path, the measured specific, airway resistance (sRaw2) exceeds sRaw1 by the product of TGV and Radd and can be used for determining TGV. With the use of a device increasing Rins by a known amount (Radd) during normal breathing, sRaw1 and sRaw2 were measured in 3 normal subjects, 16 asthmatic patients, 2 patients with chronic obstructive pulmonary disease, and 1 patient with restrictive lung disease from the slopes of the x-y plots of airflow vs. box signals obtained before and after adding Radd. TGV was calculated by dividing (sRaw2-sRaw1) bu Radd. We also determined subjects' TGV by the panting method of A. B. DuBois, S. Y. Botelho, G. N. Bedell, and J. H. Comroe, Jr. (J. Clin. Invest. 35: 322–326, 1956) and functional residual capacity by the helium-dilution method. The results of the new method were quite reproducible (coefficient of variation = 5.6) and equivalent to those obtained by the other two methods.