The effects of arm crank training on the physiological responses to silbmaximal wheelchair ergometry

Summary The purpose of this investigation was to examine the cardiovascular and metabolic effects of a 5 wk arm crank (AC) training program on submaximal wheelchair (WC) ergometry in ablebodied women. The 6 subjects in the training group (TG) and 4 in the control group (CG) performed a 10 min WC exercise prior to and following the training period at a power output (PO) that elicited 70% of the pre-training peak oxygen uptake ( ). Steady state , heart rate (HR), cardiac output and stroke volume (V _s) were measured. Resting and post-exercise blood lactate concentrations (LA) were measured, the difference was recorded as net LA. The TG exercised on the AC 3 d · wk^–1 at a PO that elicited 85% of each subject's recorded peak HR. Each session consisted of four 4 min exercise bouts preceded by a 2 min warm-up and interspersed with 2 min rest periods. After training, the TG had a significantly (p<0.05) lower HR, largerV _s and lower LA in response to the WC exercise. and were not significantly altered. The results demonstrate that the AC exercise program used in this study produced a physiological training effect which was observed during submaximal WC exercise of an intensity frequently encountered during daily WC ambulation. It appears that short-term, moderate intensity AC training offers an adequate stimulus to reduce the stress imposed by wheelchair locomotion.     

周期性牵张力对成骨细胞细胞骨架影响的实验研究

目的 对大鼠成骨细胞施加单轴向周期性牵张应力,观察单轴向周期性牵张应力对大鼠成骨细胞细胞骨架的影响.方法 无菌环境下,组织分离法培养SD大鼠颅骨成骨细胞,体外培养,应用DioDynamic细胞应力加载系统分别对2组第3代大鼠成骨细胞加载0%和2%的单轴向周期性牵张应力,使用免疫荧光法检测细胞骨架蛋白表达,使用激光共聚焦显微镜观察细胞骨架的变化,随即抽取视野并测量各组细胞骨架蛋白表达的荧光强度,进行统计学分析.结果 经统计学计算,施加单轴向周期性牵张应力实验组与空白对照组相比,实验组大鼠成骨细胞骨架蛋白的荧光表达减弱;应力纤维变细,明显沿受力方向分布.结论 DioDynamic细胞应力加载系统可以很好地模拟生物体内成骨细胞所受单向周期牵张应力;大鼠成骨细胞细胞骨架感知单轴向周期性牵张应力,参与细胞的力学信号转导和细胞形态重构.     

Effects of the transition time between muscle-tendon stretch and shortening on mechanical efficiency

The net mechanical efficiency of positive work (η_pos) has been shown to increase if it is immediately preceded by negative work. This phenomenon is explained by the storage of elastic energy during the negative phase and its release during the subsequent positive phase. If a transition time (T) takes place, the elastic energy is dissipated into heat. The aim of the present study was to investigate the relationship between η_pos and T, and to determine the minimal T required so that η_pos reached its minimal value. Seven healthy male subjects were tested during four series of lowering–raising of the body mass. In the first series (S ₀), the negative and positive phases were executed without any transition time. In the three other series, T was varied by a timer (0.12, 0.24 and 0.56 s for series S ₁, S ₂ and S ₃, respectively). These exercises were performed on a force platform sensitive to vertical forces to measure the mechanical work and a gas analyser was used to determine the energy expenditure. The results indicated that η_pos was the highest (31.1%) for the series without any transition time (S ₀). The efficiencies observed with transition times (S ₁, S ₂ and S ₃) were 27.7, 26.0 and 23.8%, respectively, demonstrating that T plays an important role for mechanical efficiency. The investigation of the relationship between η_pos and T revealed that the minimal T required so that η_pos reached its minimal value is 0.59 s.     

The effect of hyperhydration on physiological and perceived strain during treadmill exercise in personal protective equipment

Work in personal protective equipment (PPE) impairs thermoregulation causing cardiovascular stress, increased core body temperature, and hypohydration. We examined the effect of pretreating first responders performing treadmill exercise in PPE with an infusion of normal saline on physiological and perceptual strain. Ten (eight males, two females) euhydrated subjects performed treadmill exercise on two occasions wearing a chemical resistant coverall, air purifying respirator, butyl gloves, and heavy boots. During the hyperhydration session, normal saline was rapidly infused through an arm vein prior to donning PPE. Exercise duration and maximum core temperature did not differ between euhydrated and hyperhydrated conditions. Perceptual strain index (PeSI) was higher than physiological strain index (PhSI) in the euhydrated condition (P = 0.002) but neither index differed between the control and experimental conditions. Intravenous hyperhydration did not reduce physiological stress, increase exercise, or influence perceptual strain time when compared to the euhydrated condition in moderately fit individuals. This work has been presented at the American College of Sports Medicine Annual Meeting (2008) and the Mid-Atlantic Chapter of the American College of Sports Medicine Annual Meeting (2007).     

Energy cost and mechanical efficiency of riding a four-wheeled, human-powered, recumbent vehicle

Oxygen consumption at steady state (V˙O ₂, l · min⁻¹) and mechanical power (W˙, W) were measured in five subjects riding a human-powered vehicle (HPV, the Karbyk, a four-wheeled recumbent cycle) on a flat concrete road at constant sub-maximal speeds. The external mechanical work spent per unit of distance (W, J · m⁻¹), as calculated from the ratio of W˙ to the speed (v, m · s⁻¹), was found to increase with the square of v: W˙=8.12+(0.262 ·v ²) (r=0.986, n=31), where the first term represents the mechanical energy wasted, over a unit of distance, against frictional forces (rolling resistance, R_r), and the second term (k · v ²) is the work performed, per unit distance, to overcome the air drag. The rolling coefficient (C_r, obtained dividing R_r by m · g, where m is the overall mass and g is the acceleration of gravity) amounted to [mean (SD)] 0.0084 (0.0008), that is about 60% higher than that of a racing bicycle. The drag coefficient was calculated from the measured values of k, air density (ρ) and frontal area (A) [C_x=k · (0.5 · A · ρ)⁻¹], and amounted to 1.067 (0.029), that is about 20% higher than that of a racing bicycle. The energy cost of riding the HPV (C_k, J · m⁻¹) was measured from the ratio of metabolic power above rest (net V˙O ₂, expressed in J · s⁻¹) to the speed (v, m · s⁻¹); the value of this parameter increased with the square of v, as described by: C_k=61.45 + (0.675 · v ²) (r=0.711, n=23). The net mechanical efficiency (η) was calculated from the ratio of W to C_k: over the investigated speed range this turned out to be 0.22 (0.021). Best performance times (BPTs) of a “typical”élite athlete riding the Karbyk were calculated over the distances of 1, 5 and 10 km: these were about 8% longer than the BPTs calculated, on the same subjects, when riding a conventional racing bicycle. Accepted: 7 August 2000     

The mechanical efficiency of locomotion in men and women with special emphasis on stretch-shortening cycle exercises

Summary The mechanical efficiency of the leg extensor musculature of men and women was examined with a special sledge ergometer. The subjects (ten males and ten females) performed (a) pure positive work, (b) pure negative work and (c) a combination of negative and positive work (strech-shortening cycle). The mechanical efficiency of pure positive work was on average 19.8±1.2% for female subjects and 17.4±1.2% for male subjects (t=4.12, P<0.001), although the work intensity was equal in both groups. The mechanical efficiency of pure negative work was slightly lower in women than in men (59.3±14.4% vs 75.6±29.3%). The mechanical efficiency of positive work (₊) in a stretch-shortening cycle exercise was 38.1±6.8% in men and 35.5±6.9% in women. The utilization of prestretch was better for female subjects at low prestretch levels, whereas males showed greater potentiation of elastic energy at higher prestretch levels. Regarding absolute W _el (work due to elasticity) values, male subjects showed greater (P<0.001) values than females (189±44 J vs 115±36 J, respectively). Fundamental differences in neuromuscular functions in men and women might cause the differences in the results obtained.     

Differential effects of extracellular matrix and mechanical strain on airway smooth muscle cells from ovalbumin- vs. saline-challenged Brown Norway rats

The asthmatic airway is characterized by alterations in decorin and biglycan and increased airway smooth muscle (ASM). Further, the asthmatic airway may be subjected to abnormal mechanical strain. We hypothesized that ASM cells obtained from ovalbumin (OVA)--and saline (SAL)--challenged rats would respond differently to matrix and mechanical strain. ASMC were seeded on plastic, decorin or biglycan. Additional cells were grown on decorin, biglycan or collagen type 1, and then subjected to mechanical strain (Flexercell). The number of OVA ASMC was significantly greater than SAL ASM when seeded on plastic. A significant decrease was observed for both OVA and SAL ASMC seeded on decorin compared to plastic; the reduction in ASMC number was more modest for OVA. Biglycan decreased SAL ASMC number only. Strain reduced cell number for SAL and OVA ASMC grown on all matrices. Strain affected expression of β1-integrin differently in OVA vs. SAL ASMC. These data suggest that matrix and mechanical strain modulate ASMC number; these effects are differentially observed in OVA ASMC.     

Effects of shortening velocity and of oxygen consumption on efficiency of contraction in dog gastrocnemius

Previous observations have shown that, in isolated perfused dog gastrocnemii in situ, stimulated to aerobic rhythmic isotonic tetanic contractions (at about 40% of maximal isometric force), only about 20% of the overall metabolic power (proportional to the rate of O₂ consumption, O₂) was converted into mechanical power (Ẇ). Here we report that, in the same preparation, the maximal velocity during the shortening phase of each tetanus (v, mm s^–1) increased with the rate of energy dissipation, as given by the difference between O₂ and Ẇ (W kg^–1). The relationship between these variables was described by: v=2.85(O₂–Ẇ)^1.24 (R ²=0.85; n=17). A mathematical analysis of this equation shows that the overall mechanical efficiency (=ẆO₂ ^–1) decreased with increasing v (at constant O₂), whereas it increased with increasing O₂ (at constant v). The net effect of this state of affairs was that the decrease of over the entire range of work intensities was relatively minor (from 0.22 to 0.15), in spite of a large increase of v, (from 40 to 120 mm s^–1), thanks to the concomitant increase of O₂ (from 10 to 25 W kg^–1). So, under these experimental conditions, the energetics of work performance seems to be governed by two conflicting needs. The need for a sufficiently high shortening speed (and hence power output), itself requiring a sufficiently large energy dissipation rate, which, however, brings about a fall in . This is counteracted by the increased O₂, which in turn leads to an increased efficiency at the expense of a fall in shortening speed.This article was published in Human Muscular Function during Dynamic Exercise, Marconnet P, Saltin B, Komi P, Poortmans J (eds) Med Sport Sci 41 (series editors: M. Hebbelink, R.J. Shephard) pp. 1–9, Karger, Basel, 1996. It is reproduced with minor editorial modifications. Permission from Karger is gratefully acknowledged.     

Effects on efficiency in repetitive lifting of load and frequency combinations at a constant total power output

Sumary Boxes were lifted and lowered repetitively at three different combinations of load and frequency. These combinations were chosen such that the total mechanical power generated was constant. Effects of the varying load or frequency conditions (but constant total mechanical power) on the rate of energy expenditure (M) and on the mechanical efficiency (ME) were measured. Mechanical power was determined from film analysis and separated into external power (generated to lift the load) and internal power (to raise the lifter's body mass). The M was determined from oxygen consumption measurements. The ME was calculated in two ways, depending on the definition of mechanical power, including either the external power only (ME_ext) or the total power output (ME_tot). Despite a constant total mechanical power, M increased at higher loads and lower frequencies. This might be explained by the increasing isometric force required in postural and load control. The M increase resulted in a decrease of ME_tot. However, at higher loads and lower frequencies ME_ext increased, indicating that more external work can be done at the same energy costs at higher loads or lower frequencies, which could be of interest from the point of view of occupational physiology. It would seem that at higher loads or lower frequencies the increased costs for isometric muscle action do not outweigh the benefit of raising the body less frequently. Furthermore, it was found that the ME,, in lifting was much lower than the values reported for other kinds of activity. This was due to the large proportion of total power output that was internal power in repetitive lifting [e.g. 83.1% (at a load of 6 kg) in the present study].     

Effects of strain rate, mixing ratio, and stress–strain definition on the mechanical behavior of the polydimethylsiloxane (PDMS) material as related to its biological applications

Tensile tests on Polydimethylsiloxane (PDMS) materials were conducted to illustrate the effects of mixing ratio, definition of the stress-strain curve, and the strain rate on the elastic modulus and stress-strain curve. PDMS specimens were prepared according to the ASTM standards for elastic materials. Our results indicate that the physiological elastic modulus depends strongly on the definition of the stress-strain curve, mixing ratio, and the strain rate. For various mixing ratios and strain rates, true stress-strain definition results in higher stress and elastic modulus compared with engineering stress-strain and true stress-engineering strain definitions. The elastic modulus increases as the mixing ratio increases up-to 9:1 ratio after which the elastic modulus begins to decrease even as the mixing ratio continues to increase. The results presented in this study will be helpful to assist the design of in vitro experiments to mimic blood flow in arteries and to understand the complex interaction between blood flow and the walls of arteries using PDMS elastomer.     

Effects of competitive pressure on expert performance: underlying psychological, physiological, and kinematic mechanisms

Although it is well established that performance is influenced by competitive pressure, our understanding of the mechanisms which underlie the pressure-performance relationship is limited. The current experiment examined mediators of the relationship between competitive pressure and motor skill performance of experts. Psychological, physiological, and kinematic responses to three levels of competitive pressure were measured in 50 expert golfers, during a golf putting task. Elevated competitive pressure increased putting accuracy, anxiety, effort, and heart rate, but decreased grip force. Quadratic effects of pressure were noted for self-reported conscious processing and impact velocity. Mediation analyses revealed that effort and heart rate partially mediated improved performance. The findings indicate that competitive pressure elicits effects on expert performance through both psychological and physiological pathways.     

Effects of crosslinking on the mechanical properties,drug release and cytocompatibility of protein polymers

Recombinant elastin-like protein polymers are increasingly being investigated as component materials of a variety of implantable medical devices. This is chiefly a result of their favorable biological properties and the ability to tailor their physical and mechanical properties. In this report, we explore the potential of modulating the water content, mechanical properties, and drug release profiles of protein films through the selection of different crosslinking schemes and processing strategies. We find that the selection of crosslinking scheme and processing strategy has a significant influence on all aspects of protein polymer films. Significantly, utilization of a confined, fixed volume, as well as vapor-phase crosslinking strategies, decreased protein polymer equilibrium water content. Specifically, as compared to uncrosslinked protein gels, water content was reduced for genipin (15.5%), glutaraldehyde (GTA, 24.5%), GTA vapor crosslinking (31.6%), disulfide (SS, 18.2%) and SS vapor crosslinking (25.5%) (P < 0.05). Distinct crosslinking strategies modulated protein polymer stiffness, strain at failure and ultimate tensile strength (UTS). In all cases, vapor-phase crosslinking produced the stiffest films with the highest UTS. Moreover, both confined, fixed volume and vapor-phase approaches influenced drug delivery rates, resulting in decreased initial drug burst and release rates as compared to solution phase crosslinking. Tailored crosslinking strategies provide an important option for modulating the physical, mechanical and drug delivery properties of protein polymers.     

力学刺激和成骨化学诱导剂对大鼠骨髓间充质干细胞成骨分化能力的影响

目的 探讨力学刺激与成骨化学诱导剂对大鼠骨髓间充质干细胞（rat bone mesenchymal stem cells,rBMSCs）碱性磷酸酶（alkaline phosphatase, ALP）、I 型胶原(collagen type I, COL I）和骨钙素 (osteocalcin, OCN) 基因表达与钙化结节形成的影响。方法 体外分离培养rBMSCs,分别在成骨诱导和非成骨诱导条件下应用双轴力学应变加载系统对rBMSCs施加周期性的机械张应变（应变2%,频率1 Hz,每次2 h,间隔2 h,每天加载3 次）。力学刺激作用3 d和6 d,采用实时荧光定量RT-PCR检测ALP、COL I和OCN的mRNA表达,同时采用茜素红染色法观察钙化结节的形成情况。结果 力学刺激作用后,成骨诱导6 d组出现明显的钙化结节,其余各组均无明显钙化结节形成。与相应非诱导组比较,成骨诱导3 d组ALP、COL I和OCN的mRNA表达量分别增加0.6、3和11.8倍;成骨诱导6 d组ALP、COL I和OCN的mRNA表达量分别增加2.7、3.2和10倍。结论 成骨化学诱导剂和力学刺激均能促进rBMSCs的骨向分化,且二者之间具有协同作用。     

不同压力及时间机械通气对大鼠血清白细胞介素8、白细胞介素10水平和肺组织形态学的影响

目的 探讨不同压力及时间机械通气对大鼠血清白细胞介素8(IL-8)、IL-10水平及肺组织形态学的影响.方法 成年雄性SD大鼠30只,随机分为空白对照组(C组)、低气道压力2 h组[L2组,压力为15 cm H2O(1 cm H2O=0.098 kPa),通气时间为2 h]、低气道压力4 h组(L4组,压力为15 cmH2O,通气时间为4 h)和高气道压力2 h组(H2组,压力为25 cm H2O,通气时间为2 h)、高气道压力4 h组(H4组,压力为25 cm H2O,通气时间为4 h),每组6只.连接呼吸机,设定呼吸频率为40次/min,按既定压力及时间进行机械通气,分别于机械通气2、4 h后血处死大鼠,检测血清中IL-8、IL-10的含量,并取肺组织,光镜及电镜下观察组织损伤的病理改变.结果 与C组相比,L2、L4、H2、H4组血清中IL-8、IL-10的含量均明显增加,且随通气时间的延长而升高,L4组高于L2组[IL-8:(71.5±7.6)ng/L比(38.4±6.3)ng,L,IL-10:(364.5±18.6)ng/L比(271.6±21.3)ng/L,P<0.05],H4组高于H2组[IL-8:(140.7±23.5)ng/L比(76.4±9.2)ng/L,IL-10:(472.8±22.5)ng/L比(357.6±20.4)ng/L,P<0.05];相同通气时间下,高气道压力组血清中IL-8、IL-10的含量较低气道压力组明显增多,H2组高于L2组,H4组高于L4组(P<0.05).光镜及电镜下组织学检查显示与C组比较,其余各组肺组织均出现不同程度的炎性细胞浸润、肺气肿、线粒体肿胀、内质网扩张、细胞核质间隙增宽等炎性反应改变,且随时问及气道压力的增加而加重.结论 通气压力及时间的增加能够刺激大鼠血清中炎性反应因子IL-8、IL-10水平的升高,加重肺组织的损伤.有效控制通气的压力及时间可以减轻肺组织炎性反应和损伤.     

生理水平流体剪应力对三维多孔支架中成骨细胞力学敏感性及黏附、分化的影响

目的 构建可以达到生理剪应力水平的三维流动模型,研究流体剪应力对成骨细胞黏附、分化及力学敏感性的影响。方法 利用灌注式流动腔对生长在β-磷酸三钙（β-TCP）多孔支架内的MC3T3-E1成骨样细胞施加不同强度的流体剪应力6 h,比较加载组和静态组的细胞活性表征细胞黏附;一氧化氮（NO）和碱性磷酸酶（ALP）表征力学敏感性和细胞分化。采用流固非线性耦合的数值计算,获得支架内各流量下的剪应力分布。结果 平均剪应力小于0.4 Pa,细胞的黏附率为74% ~ 81%;0.41 Pa时,黏附率为60.22%。NO的产生率在加载后5 min达到最大,15 min显著降低,30 min后产生率趋近于0。在0.232 ~ 0.304 Pa平均剪应力强度范围,ALP水平随着剪应力的升高显著增强（P<0.01）;而在0.304 ~ 0.412 Pa范围,剪应力增加对ALP水平的改变无显著影响（P>0.05）。结论 生理水平剪应力条件下,支架内大部分细胞可以维持正常黏附。三维条件下细胞力学敏感性与剪应力变化率成正比,与二维条件的规律相同。支架内平均剪应力小于0.304 Pa,剪应力显著促进细胞分化;大于这一剪应力,细胞分化水平不再明显变化。该研究有望加快骨组织工程的实现。     

Effects of caspase-1 knockout on chronic neural recording quality and longevity: Insight into cellular and molecular mechanisms of the reactive tissue response

Chronic implantation of microelectrodes into the cortex has been shown to lead to inflammatory gliosis and neuronal loss in the microenvironment immediately surrounding the probe, a hypothesized cause of neural recording failure. Caspase-1 (aka Interleukin 1β converting enzyme) is known to play a key role in both inflammation and programmed cell death, particularly in stroke and neurodegenerative diseases. Caspase-1 knockout (KO) mice are resistant to apoptosis and these mice have preserved neurologic function by reducing ischemia-induced brain injury in stroke models. Local ischemic injury can occur following neural probe insertion and thus in this study we investigated the hypothesis that caspase-1 KO mice would have less ischemic injury surrounding the neural probe. In this study, caspase-1 KO mice were implanted with chronic single shank 3 mm Michigan probes into V1m cortex. Electrophysiology recording showed significantly improved single-unit recording performance (yield and signal to noise ratio) of caspase-1 KO mice compared to wild type C57B6 (WT) mice over the course of up to 6 months for the majority of the depth. The higher yield is supported by the improved neuronal survival in the caspase-1 KO mice. Impedance fluctuates over time but appears to be steadier in the caspase-1 KO especially at longer time points, suggesting milder glia scarring. These findings show that caspase-1 is a promising target for pharmacologic interventions.     

Effects of fentanyl on procedural pain and discomfort associated with central venous catheter insertion: A prospective,randomized, double-blind,placebo controlled trial

Context:

Central venous catheter (CVC) insertion induces pain and discomfort to a conscious patient despite application of a local anesthetic (LA) field block and this pain can be greatly lessened by using additional analgesics.

Aim:

The aim of this study is to evaluate the efficacy of fentanyl along with LA field infiltration in controlling pain and discomfort associated with CVC insertion.

Settings and Design:

A prospective, randomized, double-blind, placebo-controlled trial was conducted at tertiary referral center.

Materials and Methods:

Fifty-four patients scheduled for planned CVC were randomly assigned to receive either fentanyl (2 μg/kg) or 0.9% normal saline. Pain and discomfort using a verbal numeric rating pain scale at 5 times points during CVC insertion were assessed and analyzed.

Results:

The median interquartile range pain score is worst for placebo group after LAI (5 [3-6]) and in the immediate postprocedure period (5 [4-5]) which was significantly attenuated by addition of fentanyl (3.5 [2-5] and 3 [2-4]) (P = 0.009 and 0.001 respectively). Overall, fentanyl and placebo group were not statistically different with median discomfort score except at T10 (P = 0.047).

Conclusions:

Preprocedural bolus fentanyl infusion provides adequate analgesia and can be safely used for alleviating pain during CVC insertion in conscious patients.     

Effects of strain rate and temperature on mechanical behaviour of Ti–15Mo–5Zr–3Al alloy

This study uses the compressive split-Hopkinson pressure bar to investigate the mechanical behaviour of Ti–15Mo–5Zr–3Al alloy deformed at strain rates ranging from 8×10² to 8×10³ s⁻¹ and temperatures between 298 and 1173 K. The results indicate that the mechanical behaviour of the alloy is highly sensitive to both the strain rate and the temperature. The flow stress curves are found to include a work hardening region and a work softening region. The strain rate sensitivity parameter, m, increases with increasing strain and strain rate, but decreases with increasing temperature. The activation energy varies inversely with the flow stress, and has a low value at high deformation strain rates or low temperatures. Correlating the mechanical properties of the Ti alloy with the transmission electron microscope (TEM) observations, it is concluded that the precipitation of α phase dominates the fracture strain. TEM observations reveal that the amount of α phase increases with increasing temperature below the β transus temperature. The maximum amount of α phase is formed at a temperature of 973 K and results in the minimum fracture strain observed under the current loading conditions.     

Effects of inotropic drugs on mechanical function and oxygen balance in postischemic canine myocardium: comparison of dobutamine, epinephrine, amrinone, and calcium chloride

Brief ischemic episodes that induce myocardial and coronary endothelial dysfunction may alter the responses to inotropic drugs. To determine the effects of inotropic drugs in stunned myocardium, the coronary blood flow (CBF), myocardial oxygen consumption (MVO2), and regional mechanical function in response to intracoronary dobutamine, epinephrine, amrinone, and calcium chloride (CaCl2) were measured before (normal) and 30 min after a 15-min-period occlusion of the left anterior descending artery (stunned) in an open-chest canine model. Percent segment shortening (%SS) and post-systolic shortening (%PSS) were determined. Myocardial extraction of oxygen (EO2) and lactate (E(lac)) was calculated. The inotropic drugs increased %SS, CBF, and MVO2 in normal myocardium. Epinephrine and amrinone decreased, while dobutamine and CaCl2 did not affect EO2. The ischemia and reperfusion itself significantly reduced %SS and E(lac), and increased %PSS. In stunned myocardium, the responses to inotropic drugs were not significantly altered, except that they progressively reduced %PSS and epinephrine did not affect EO2. These findings indicate that a brief episode of ischemia does not affect the mechanical and metabolic coronary flow responses to inotropic drugs, although it abolishes direct vasodilator responses to epinephrine.