Airway responses in healthy and asthmatic subjects following exposure to low ambient air temperature

Agonist-activated Ca2+ entry is important in many biological responses such as secretion and cell growth(1,2). In nonexcitable cells which have no voltage-operated Ca2+ channels (VOCC), agonist-receptor interaction can trigger Ca2+ entry across the plasmalemma via several entry pathways(1-3) (Fig 1): (A) channels which are intrinsic structures of the receptor (receptor-operated channels), (B) channels which are coupled to receptors via a G-protein (G-protein-operated channels), (C) channels which are activated by some second messengers (second-messenger-operated channels), and (D) channels which open upon intracellular nonmitochondrial Ca2+ store depletion (Ca2+ release-activated channels) resulting from inositol 1, 4, 5-trisphosphate-induced Ca2+ release or inhibition of Ca2+ re-uptake (see next section). Ca2+ entry via the 4th type of channel, also known as "capacitative Ca2+ entry" (CCE)[4], has aroused much interest in the past decade because of its intriguing nature as retrograde signalling. In this brief review, we present the evidence for and the possible biochemical processes involved in CCE. We also discuss the use of 2 novel Ca2+ entry blockers: tetrandrine and SK&F 96365. Emphasis will be put on the human leukemic HL-60 cell line, a popular cell system for intracellular Ca2+ homeostasis studies and also a model the signal transduction of which we have been investigating during the past few years.     

Leaching kinetics of digenite concentrate in oxygenated chloride media at ambient pressure

The leaching of digenite concentrate in CuCl₂-HCl-NaCl oxygenated solutions is very rapid. From the effect of variables on the leaching rate and measurements of the concentrations of cuprous and cupric species in the solution as a function of time, it was concluded that the leaching in O₂ atmosphere proceeds by the attack of cupric ions on the copper sulfides to produce cuprous ions which are subsequently oxidized to cupric by the O₂ present in the system. The kinetic study showed that the leaching proceeds in two sequential stages. In the first stage, the digenite is transformed to covellite, and in the second stage, the covellite is dissolved to copper and elemental sulfur. In the first stage, the fraction of copper extracted varied linearly with time according to α=k _l t, whereas in the second stage, the dissolution of covellite was well represented by a shrinking core model controlled by diffusion through a porous product layer kinetic equation: 1−2/3α _cv−(1−α _cv)^2/3=k _cv t. The calculated activation energies were 15.8 and 80.0 kJ/mol for the first and second stages, respectively. These results were explained by an electrochemical mechanism of digenite dissolution.     

Metabolic responses of White Pekin ducks to ambient temperature

Metabolic responses of unrestrained White Pekin ducks, Anas platyrhynchos, were determined at ambient temperatures of -5 degrees, 1 degrees, 10 degrees, 20 degrees, and 30 degrees C. Temperatures from the pectoralis and the subcutaneous back were monitored. Unrestrained ducks exhibited two metabolic states, a high response (540 cc. O2/kg/hr. at 20 degrees C.) and a low response (427 cc. O2/kg./hr. at 20 degrees C). Pectoralis muscle temperature did not vary greatly over the range of ambient temperatures tested and was considered to be a good representative of body temperature.     

Hemodynamic and regional blood flow responses to nicotine at rest and during exercise

We hypothesized that nicotine compromises cardiovascular responses to dynamic exercise. Hemodynamic variables were measured in conscious miniswine before and at 2 min of nicotine infusion (20 micrograms.kg-1.min-1; i.a.; N = 6) during resting conditions. Mean arterial pressure elevations (MAP; 14%) and plasma nicotine concentrations (49 +/- 7 ng.ml-1) were similar to those elicited by cigarette smoking in humans. In addition, nicotine increased systemic vascular resistance (SVR; 56%), the heart rate x systolic blood pressure product (RPP; 11%), and regional vascular resistance in the left-ventricular, renal, and splanchnic circulations, while cardiac output decreased (CO; 23%) and skeletal muscle blood flow and vascular resistance were unaffected. Plasma norepinephrine and epinephrine increased by approximately 30% and 90%, respectively. On separate days, the same hemodynamic responses were measured before and at 20 min of treadmill running during vehicle or nicotine infusion for the last 2 min of exercise (N = 10). Nicotine increased MAP (6%), SVR (14%), and RPP (3%), and elevated vascular resistance in the proximal colon and pancreas. Moreover, compared to exercise + vehicle, norepinephrine and epinephrine increased by approximately 13% and 24%, respectively, during exercise + nicotine infusion. These findings suggest that the detrimental effects of nicotine observed at rest are minimized during exercise. Nicotine's effects may be reduced during exercise by competition from local vasodilators in the heart and active musculature, and/or by differing activation of sympathetic nerve activity.     

Renal hemodynamic responses to dynamic exercise in rabbits

Cardiovascular hemodynamics, including renal blood flow, were measured in rabbits with one intact and one denervated kidney during various intensities of treadmill exercise. Within the first 10 s of exercise, there was rapid vasoconstriction in the innervated kidney associated with decreases in renal blood flow (range -10 to -17%). The vasoconstriction in the innervated kidney was evident at all workloads and was intensity dependent. There was no significant vasoconstriction or change in renal blood flow (range 0.5 to -3.1%) in the denervated kidney at the onset of exercise. However, a slowly developing vasoconstriction occurred in the denervated kidney as exercise progressed to 2 min at all workloads. Examination of responses to exercise performed under alpha-adrenergic blockade with phentolamine (5 mg/kg iv) revealed that the vasoconstriction in the innervated kidney at the onset of exercise and the delayed vasoconstriction in the denervated kidney were due primarily to activation of alpha-adrenergic receptors. In addition, a residual vasoconstriction was also present in the innervated kidney after alpha-adrenergic blockade, suggesting that, during exercise, activation of other renal vasoconstrictor mechanisms occurs which is dependent on the presence of renal nerves.     

Cardiovascular responses to treadmill exercise testing in anemia

Gunshot wounds are rare in Japan because of few regulatory laws against the possession of guns. Nevertheless such wounds are increasing in prevalence these days. Reports on the microscopic findings concerning these intracerebral lesions are fewer than those on the macroscopic findings in the scalp, the skull and the intracranial cavity. In this study we evaluated computed tomographical and histopathological findings in craniocerebral gunshot injuries. CASES: Nine patients with gunshot wounds to the head were presented. All were male and the age ranged from 17 to 66 years. Four were suicides and four were attempted murders and the last one was of unknown etiology. Morphological examination was performed on 5 autopsy cases. The distance of the bullet from the cranial cavity was as follows: long distance, 4 cases; close contiguity, 5 cases. The calibers of the weapons were as follows: 38 mm in 6 cases, 45 mm in 1 case and unknown in 2 cases. RESULTS: CT scans were examined in six cases, which revealed a missile track, hemorrhagic contusion, traumatic subarachnoid hemorrhage and marked tension pneumocephalus. In some cases, CT scan also revealed bony and metallic fragments, some deep within the cranial cavity. In the histopathological study, we found marked swollen brain (brain weight over 1500 mg) and hemorrhagic contusion in the vicinity of the missile track and interhemispheric fissure, and widespread traumatic subarachnoid hemorrhage and intraventricular hematoma. We would like to emphasize especially the remote contusion seen in the distant part of the missile track as well as massive exsudation and hemorrhage around the nerve fiber bundles. Remote contusion was observed in the inferior surface of the fronto-temporal lobes, and bilateral hemorrhagic contusion was seen in the vicinity of the superior longitudinal fissure on CT scans and autopsy findings. In one case, the bullet rotated within the intracranial cavity. In conclusion, nine cases of craniocerebral gunshot injuries were examined, while we also reviewed the medical literature concerning the shearing injury produced by gunshot brain wounds. The head injuries were further delineated by the correlation between autopsy and computerized tomography findings.     

Respiratory responses to repeated prolonged exposure to 0.12 ppm ozone

Repeated exposure to high concentrations of ozone results first in augmentation (typically on the second day) and then attenuation of pulmonary response in humans. To determine the effects of repeated prolonged low-concentration ozone exposure, we exposed 17 healthy nonsmoking male subjects to 0.12 ppm ozone for 6.6 h on 5 consecutive days. Subjects were also exposed once to filtered air. Volunteers exercised at a ventilation of approximately 39 L/min for 50 min of each hour during the exposure. Spirometry, plethysmography, and symptom responses were obtained before, during, and after each exposure. Nasal lavage and aerosol bolus dispersion were obtained before and after exposure. Spirometry decreased and symptoms increased on the first day. Responses were less on the second day compared with those on the first day, and they were absent compared with control values on the subsequent 3 days of ozone exposure. Percent change in FEV1 after ozone exposure compared with that after air exposure averaged -12.79, -8.73, -2.54, -0.6, +0.18% for Days 1 to 5 of ozone exposure, respectively. FEV1 responses ranged from a zero to 34% decrease on Days 1 and 2. After each exposure, we determined the ratio of SRaw after inhaling a fixed dose of methacholine to SRaw after inhaling saline aerosol, as an index of airway responsiveness. Airway responsiveness was significantly increased after each ozone exposure. The mean ratios were 2.22, 3.67, 4.55, 3.99, 3.24, and 3.74 for filtered air and ozone Days 1 to 5, respectively. Symptoms of cough and pain on deep inspiration increased significantly on ozone Day 1 only.(ABSTRACT TRUNCATED AT 250 WORDS)     

Respiratory responses to unsupported arm lifts paced during expiration

Unsupported arm exercise endurance is reduced in both normal subjects and patients with chronic obstructive pulmonary disease in association with an increase in dyspnea and alterations in the pattern of respiratory muscle recruitment. Some report greater difficulty carrying out arm activity paced during the expiratory phase of respiration rather than during inspiration. The purpose of this study was to determine the effect of unsupported arm exercise lifts paced in phase with expiration (EUAL) on (a) diaphragm recruitment measured as the electromyographic amplitude (EMG-DI), (b) the pattern of thoracoabdominal motion measured with inductive plethysmography, and (c) the sensation of dyspnea measured with a 100 mm visual analog scale. Data were collected from 18 normal adult subjects at baseline and during EUAL. When compared with rest, EUAL resulted in significant increases in mean inspiratory and expiratory diaphragm EMG amplitudes, dyssynchronous thoracoabdominal motion, and dyspnea intensity. These changes in diaphragm recruitment and thoracoabdominal motion may in part explain reports of increased dyspnea intensity with unsupported arm exercise.     

MgO solubility in BOF slag equilibrated with ambient air

The MgO solubility in the CaO‐MgO‐Fe₂O₃‐FeO‐SiO₂‐(MnO)‐(Al₂O₃) slag was measured under the condition of equilibrium with the ambient air at 1873 K as a fundamental study for precise slag coating control in BOF operation. The CaO/SiO₂ mass ratios of the main slag were 1, 1.5, 2, 3 and 4, and total iron content was in the range of 10 to 35 %. Moreover, 1 to 13 % of MnO and 2 to 12 % of Al₂O₃ were added to the melt to evaluate their effects on the MgO solubility. The effect of slag composition on the MgO solubility was discussed and quantified by means of a newly developed formula. As the basicity in slag increases, the MgO solubility decreases. The effect of iron oxide content is observed to be dependent on the basicity of slag. An increase in iron oxide content makes the MgO solubility higher for basic slag but lower for acidic slag. It is revealed that the MgO solubility in steelmaking slag is controlled by the complex anion formation reaction of iron oxide. Both Al₂O₃ and P₂O₅ increase the MgO solubility by diluting the basic oxides as SiO₂ does, while manganese oxide affects the MgO solubility in a similar manner as iron oxide. The MgO solubility can be described as a function of slag composition, X = (%CaO) + 0.45(%Fe₂O₃+ %FeO) + 0.55(%MnO), in the equation of (%MgO) = 0.00816X^2‐1.404X + 62.31. Based on the results, the guidance for addition of MgO‐containing material could be suggested for best slag coating practice.     

Physiological responses to maximal treadmill and handweighted exercise

The purpose of this investigation was to compare the peak physiological responses among four protocols that employed different amounts of handweighted exercise in 16 males (aged 26.3 +/- 4.1 years). The four protocols were (a) uphill treadmill running (UR; 3.36 m.s-1, 2.5% grade increase-3 min-1); (b) uphill treadmill walking while pumping 1.36-kg handweights (HW) (UWHW; 1.79 m.s-1, 5.0% grade increase x 3 min-1; (c) treadmill walking while pumping .91-kg HW (WHW; 1.79 m.s-1, 0% grade, .91-kg HW increase x 3 min-1); and (d) standing in place and pumping HW (SHW; arm work as described in WHW). It was hypothesized that the peak responses would be inversely proportional to the estimated muscle mass activated (i.e., UR = UWHW > WHW > SHW). Dependent variables included peak oxygen uptake (VO2 peak), peak heart rate (HRpeak), peak ventilation (Ve peak), and peak respiratory exchange ratio (RERpeak). No differences were noted between UR and UWHW with respect to any of the dependent variables. All variables (except RERpeak) were greater (p < .01) in UR and UWHW than either WHW or SHW. RERpeak was greater (p < .01) in UR and UWHW than in WHW. VO2 peak and HRpeak were greater (p < .01) in WHW when compared to SHW. Mean VO2 peak was 97.5, 69.7, and 60% of UR for UWHW, WHW, and SHW, respectively. Therefore, walking and pumping handweights provides a maximal stimulus to the oxygen transport system.     

Catecholamine responses to short-term high-intensity resistance exercise overtraining

Seventeen weight-trained males were divided into an overtraining group [OT; n = 11; age = 22.0 +/- 0.9 (SE) yr] that weight trained their legs daily for 2 wk with 100% 1 repetition maximum relative intensity on a squat machine and a control group (n = 6; age = 23.7 +/- 2.4 yr) that exercised 1 day/wk with low relative intensity (50% 1 repetition maximum). Test batteries including strength assessments and resting and exercise-induced concentrations of epinephrine and norepinephrine were conducted at the beginning, middle, and end (tests 1-3, respectively) of the study. Strength capabilities decreased by test 3 for the OT group (P < 0.05). Resting catecholamine concentrations did not change for either group during the study, whereas exercise-induced concentrations of both epinephrine (test 1 = 3,407.9 +/- 666.6 pmol/l, test 2 = 7,563.7 +/- 1,210.6 pmol/l, test 3 = 6,931.6 +/- 919.3 pmol/l) and norepinephrine (test 1 = 42.9 +/- 7.4 nmol/l, test 2 = 70.0 +/- 8.8 nmol/l, test 3 = 85.2 +/- 14.5 nmol/l) significantly increased by tests 2 and 3 for only the OT group. Correlation coefficients suggested decreased responsitivity of skeletal muscle to sympathetic nervous system activity. It appears that altered exercise-induced sympathetic nervous system activity accompanies high relative intensity resistance exercise overtraining and may be among the initial responses to the onset of the previously theoretical sympathetic overtraining syndrome.     

Effects of ambient temperature on the capacity to perform prolonged cycle exercise in man

Eight healthy males performed four rides to exhaustion at approximately 70% of their VO2max obtained in a neutral environment. Subjects cycled at ambient temperatures (Ta) of 3.6 +/- 0.3 (SD), 10.5 +/- 0.5, 20.6 +/- 0.2, and 30.5 +/- 0.2 degrees C with a relative humidity of 70 +/- 2% and an air velocity of approximately 0.7 m.s-1. Weighted mean skin temperature (Tsk), rectal temperature (Tre), and heart rate (HR) were recorded at rest, during exercise and at exhaustion. Venous samples were drawn before and during exercise and at exhaustion for determination of hemoglobin, hematocrit, blood metabolites, and serum electrolytes and osmolality. Expired air was collected for calculation of VO2 and R which were used to estimate rates of fuel oxidation. Ratings of perceived exertion (RPE) were also obtained. Time to exhaustion was significantly influenced by Ta (P = 0.001): exercise duration was shortest at 30.5 degrees C (51.6 +/- 3.7 min) and longest at 10.5 degrees C (93.5 +/- 6.2 min). Significant effects of Ta were also observed on VE, VO2, R, estimated fuel oxidation, HR, Tre, Tsk, sweat rate, and RPE. This study demonstrates that there is a clear effect of temperature on exercise capacity which appears to follow an inverted U relationship.     

Cardiovascular responses at the onset of static exercise in patients with dual-chamber pacemakers

Cardiac output (CO) responses to exercise can be altered by ventricular pacing in pacemaker-dependent patients. The relative contributions of CO and peripheral vascular resistance (PVR) toward the initial increase in blood pressure with the initiation of static exercise were investigated in eight otherwise healthy pacemaker-dependent subjects [age 24 +/- 2 yr (range 17-37 yr)]. Beat-by-beat measures of heart rate (HR; electrocardiography), mean arterial pressure (MAP), and CO derived from stroke volume (SV) (CO = HR.SV; 2-D echocardiography) were determined during the first 20 s of a one-legged static knee extension performed at 20% maximal voluntary effort by using three pacing modalities: dual pacing and sensing mode (DDD, i.e., normal physiological HR response), fixed at resting HR (DOO-R), and fixed at peak exercise HR (DOO-E), as previously achieved during 5 min of sustained contraction in the DDD mode. There were no differences in MAP, CO, or PVR (PVR = MAP/CO) between modes at rest (P > 0.05). With DOO-E pacing, SV was lower at rest compared with the other modes and increased with exercise (P < 0.05). Although there were no significant increase in MAP or CO during DOO-R pacing, both variables were elevated by leg contraction during DDD and DOO-E pacing (P < 0.05), with no significant change in PVR. Additionally, the CO and MAP increases were significantly greater with DOO-E pacing (P < 0.05). Thus the magnitude of the initial increase in arterial pressure at the onset of mild one-legged static exercise was dictated by the changes in CO as PVR remained unchanged.     

Operation of gas pipe at working pressures up to 11.8 MPa

Full-scale hydraulic and pneumatic tests of spiral- and straight-seam gas pipe (diameter 1420 mm) produced by OAO Volzhskii Trubnyi Zavod are described. Satisfactory and equivalent resistance of different types of pipe to ductile failure is established. In terms of its operational characteristics, the pipe may be used in pipelines of working pressure up to 11.8 MPa in any Russian climatic zones, including the Far North.     

Unaltered oxygen uptake kinetics at exercise onset with lower-body positive pressure in humans

The purpose of this study was to determine the influence of a reduced skeletal muscle blood flow on oxygen uptake (VO2) kinetics at the onset of cycle ergometer exercise. Seven healthy subjects performed rest-to-exercise transitions with a lower-body positive pressure (LBPP) of 45 Torr. Two work rates were selected for each subject: a moderate intensity (VO2, approximately 1.9 l min-1; delta[lactate], approximately 1 mequiv l-1) below the estimated lactate threshold and a heavy intensity (VO2, approximately 2.6 l min-1; delta[lactate], approximately 3 mequiv l-1) above this threshold. Pulmonary gas exchange variables and ventilatory (VE) responses were computed breath-by-breath from mass spectrometer and turbine volume meter signals, respectively, and mean response times (MRT) calculated. Samples of 'arterialized' venous blood were used for the determination of [lactate], pH and [K+]. While the application of 45 Torr LBPP had no effects on VO2 kinetics during moderate exercise (MRT: 33.5 +/- 1.2 s at 45 Torr vs. 32.8 +/- 1.3 s at 0 Torr; P > 0.05) or on [lactate], pH or [K+], breathing frequency (f) was increased (P < 0.05) and tidal volume (VT) reduced (P < 0.05). The addition of LBPP during heavy exercise did not alter VO2 kinetics (MRT: 35.2 +/- 1.5 s at 45 Torr vs. 34.8 +/- 1.5 s at 0 Torr; P > 0.05), or [lactate], pH or [K+]. Although both the VE (via an increased f) and CO2 output (VCO2) were significantly greater with LBPP by approximately 30 l min-1 and approximately 500 ml min-1, respectively, end-tidal CO2 partial pressure was decreasing, suggesting an additional ventilatory stimulus. These data can be interpreted to suggest that oxygen delivery is not critically dependent upon blood flow to the working muscle at exercise onset, while LBPP-induced increases in VE during suprathreshold exercise may be related to an accumulation of metabolites at the working muscle or the effects of pressure per se.