Bone Blood Flow in Conscious Dogs at Rest and During Exercise

Using the microsphere technique bone blood flow was measured in different anatomical and functional regions in long bones in conscious dogs. The measurements were performed during physical exercise upon a treadmill, and the bone blood flow values were obtained as prework resting values after 1 and 2 hours of exercise and after I hour of rest.

The perfusion rates increased 50 per cent from 1.6 to 2.5 ml 100 g tissue^-1 min^-1 in the femoral and tibial cortical bones during work. In the cancellous bone of the femoral head an increase from 12.6 to 20.6 ml 100 g tissue^-1 min^-1 was found. Equal flow responses were determined in the fat-filled tibia-condylar and femoral supracondylar bone. The increase took place after 2 hours' exercise, but nonstatisti-cally verified increased perfusion was found after 1 hour's work. The alternation in bone blood flow suggests that bone has a capability of physical vasodilatation during muscular work but the flow response is slow and therefore the vasodilatation seems mediated by a metabolically induced stimulus.     

Effect of Caffeine on Oxidative Stress During Maximum Incremental Exercise

Caffeine (1,3,7-trimethylxanthine) is an habitual substance present in a wide variety of beverages and in chocolate-based foods and it is also used as adjuvant in some drugs. The antioxidant ability of caffeine has been reported in contrast with its pro- oxidant effects derived from its action mechanism such as the systemic release of catecholamines. The aim of this work was to evaluate the effect of caffeine on exercise oxidative stress, measuring plasma vitamins A, E, C and malonaldehyde (MDA) as markers of non enzymatic antioxidant status and lipid peroxidation respectively. Twenty young males participated in a double blind (caffeine 5mg·kg- 1 body weight or placebo) cycling test until exhaustion. In the exercise test, where caffeine was ingested prior to the test, exercise time to exhaustion, maximum heart rate, and oxygen uptake significantly increased, whereas respiratory exchange ratio (RER) decreased. Vitamins A and E decreased with exercise and vitamin C and MDA increased after both the caffeine and placebo tests but, regarding these particular variables, there were no significant differences between the two test conditions. The results obtained support the conclusion that this dose of caffeine enhances the ergospirometric response to cycling and has no effect on lipid peroxidation or on the antioxidant vitamins A, E and C.

Key Points

• Caffeine ingestion may improve maximal aerobic performance in non trained men.
• Cellular oxidative damage is not altered by caffeine ingestion in maximal aerobic exercises.
• Antioxidant response to exercise, vitamins A, E and C, is not modified by caffeine action in maximal aerobic efforts.

Key words: Trimethylxanthine, malonaldehyde, vitamins, catecholamines, VO₂ max     

Changes in Pain Perception in Women During and Following an Exhaustive Incremental Cycling Exercise

Exercise has been found to alter pain sensitivity with a hypoalgesic response (i.e., diminished sensitivity to pain) typically reported during and/or following high intensity exercise. Most of this research, however, has involved the testing of men. Thus, the purpose of the following investigation was to examine changes in pain perception in women during and following exercise. Seventeen healthy female subjects (age 20.47±.87; VO₂ peak 36.77± 4.95) volunteered to undergo pain assessment prior to, during, and after a graded exhaustive VO₂ peak cycling challenge. Heart Rate (HR) and Oxygen Uptake (VO₂) were monitored along with electro-diagnostic assessments of Pain Threshold (PT) and Pain Tolerance (PTOL) at: 1) baseline (B), 2) during exercise (i.e., 120 Watts), 3) at exhaustive intensity (VO₂ peak), and 4) 10 minutes into recovery (R). Data were analyzed using repeated measures ANOVA to determine differences across trials. Significant differences in PT and PTOL were found across trials (PT, p = 0.0043; PTOL p = 0.0001). Post hoc analyses revealed that PT were significantly elevated at VO₂ peak in comparison to B (p = 0.007), 120 Watts (p = 0.0178) and R (p = 0.0072). PTOL were found to be significantly elevated at 120 Watts (p = 0.0247), VO₂ peak (p < 0.001), and R (p = 0.0001) in comparison to B. In addition, PTOL were found to be significantly elevated at VO₂ peak in comparison to 120 Watts (p = 0.0045). It is concluded that exercise-induced hypoalgesia occurs in women during and following exercise, with the hypoalgesic response being most pronounced following exhaustive exercise.

Key Points

• Exercise-induced hypoalgesia (i.e., elevated PT and PTOL) was found to occur in women during and following exercise, with the hypoalgesic response being most pronounced during exhaustive exercise.

Key Words: Nociception, cycling, hypoalgesia, pain tolerance threshold     

Chaotic Hemodynamics During Oscillated Blood Flow

Abstract: A vibrating flow pump (VFP), which can generate oscillated blood flow (10–50 Hz/min), has been developed by our team for the artificial heart system. However, the flow pattern of this pump was different from that of the natural heart; therefore, it is important to analyze the effect of this oscillated blood flow on the circulatory regulatory system. To analyze the hemodynamics of high frequency oscillated blood flow as an entity, (not decomposed), nonlinear mathematical techniques were utilized. VFPs were implanted between the left atrium in animal experiments using adult goats. After the implantation procedure, the ascending aorta was clamped to constitute the complete left heart circulation with VFP. Using a nonlinear mathematical technique, an arterial blood pressure waveform was embedded into four–dimensional phase space and projected into three–dimensional phase space. The Lyapunov numerical method was used as an adjunct to graphic analysis of the state space. Phase portrait of the attractor showed a high dimension complex structure, suggesting deterministic chaos during natural circulation. However, phase portrait of the hemodynamics during oscillated blood flow showed a single circle with banding and a forbidden zone, similar to a limit–cycle attractor, suggesting a lower dimensional dynamic system. Positive Lyapunov exponent during oscillated blood flow suggests the existence of lower dimensional chaotic dynamics. These results suggest that the circulatory regulatory system during oscillated blood flow may be a lower dimensional homeochaotic state; thus, hemodynamic parameters must be carefully regulated when unexpected external stimuli are present.     

Carotid Arterial Impedance During Oscillated Blood Flow

Abstract: Blood perfusion of systemic circulation is influenced by the physical characteristics of artery. Several investigations proposed that the physical parameters of vessels are determined by neurological factors, hormonal factors, and physical properties of arteries among others. In this study, arterial impedance was estimated because it may express the condition of vessels. To examine the change of arterial impedance according to the blood flow pattern, the typical sine wave blood flow (oscillated flow) was used during total cardiopulmonary bypass (CPB) because it is considered the most simple pulsatile flow. CPB using oscillated blood flow was performed in acute experiments on adult goats. Total systemic flow was controlled to remain at approximately 80 ml/min. Carotid arterial flow, aortic pressure, central venous pressure, and systemic flow were measured. Total peripheral resistance, carotid arterial resistance, systemic impedance, and carotid arterial impedance were calculated to evaluate blood flow distribution during CPB. This study suggested that the parameters of carotid arterial blood flow changed according to the change of flow frequency during oscillated blood flow. This change may occur because arterial impedance was influenced by flow frequency; therefore, the blood flow of the carotid artery was significantly changed according to the change of the frequency component of blood flow.     

Rotary Blood Pump Flow Spontaneously Increases During Exercise Under Constant Pump Speed: Results of a Chronic Study

Many types of rotary blood pumps and pump control methods have recently been developed with the goal of clinical use. From experiments, we know that pump flow spontaneously increases during exercise without changing pump control parameters. The purpose of this study was to determine the hemodynamics associated with the long-term observation of calves implanted with centrifugal blood pumps (EVAHEART, Sun Medical Technology Research Corporation, Nagano, Japan). Two healthy female Jersey calves were implanted with devices in the left thoracic cavity. A total of 22 treadmill exercise tests were performed after the 50th postoperative day. During exercise, the following parameters were compared with conditions at rest: heart rate, blood pressure, central venous oxygen saturation (SvO2), pump speed, and pump flow. The pump flow in a cardiac cycle was analyzed by separating the systole and diastole. Compared to the base data, statistically significant differences were found in the following interrelated parameters: the heart rate (66.8 +/- 5.2 vs. 106 +/- 9.7 bpm), mean pump flow (4.8 +/- 0.2 vs. 7.0 +/- 0.3 L/min), and volume of pump flow in diastole (26.0 +/- 1.8 vs. 13.5 +/- 2.5 ml). During exercise, the volume of pump flow in systole was 3 times larger than that measured in diastole. Blood pressure, SvO2, and pump speed did not change significantly from rest to exercise. These results suggested that the mean pump flow depends on the systolic pump flow. Therefore, the increase in the mean pump flow during exercise under constant pump speed was caused by an increase in the heart rate.     

An Enjoyable Distraction During Exercise Augments the Positive Effects of Exercise on Mood

The hypothesis that an enjoyable distraction during exercise will augment the intensity of positive mood post-exercise was tested. A sample of 84 undergraduate students rated their mood and arousal before and after a standardized exercise, which consisted of walking on a treadmill at a pace of 3.6 mph for 10 minutes. During the work out session, participants watched the same television show, which they previously rated as enjoyable, or not enjoyable. As added controls, a third group exercised with no distraction (the TV was turned off); a fourth group did not exercise, but watched the television show. The results showed that exercise alone was sufficient to increase pleasant mood (95% CI 0.61, 1.46) and that including an enjoyable distraction during exercise significantly augmented pleasant mood compared to all other groups (95% CI 1.58, 2.99; R² = 0.29). These results show that the enjoyment of a distraction is a key factor that can augment the intensity of positive mood following exercise.

Key points

• The hypothesis that an enjoyable distraction during exercise will augment the intensity of positive mood post-exercise was tested.
• The results support this hypothesis by showing for the first time that while exercise alone was sufficient to increase the intensity of positive mood; combining exercise with an enjoyable distraction resulted in significantly greater increases in pleasant mood compared to exercise alone.
• Accounting for the enjoyment of a distraction type in future studies can increase the sensitivity of research designs used to detect changes in positive mood post-exercise.

Key words: Distraction, exercise, aerobic, mood, enjoyment     

Effects on Cerebral Blood Flow of Infusion of Hyperosmolar Saline During Cerebral Vasodilation in the Dog

In six anaesthetized dogs, cerebrovascular reaction to experimental hyperosmolality (plasma osmolality in the range of 350–400 mosm kg water^-1) induced by intravenous infusion of 0.6 M saline was studied. In order to provoke and reinforce any effects from saline passage over the blood-brain barrier, pre-experimental submaximal vasodilation was induced by means of hypercapnia and in some cases haemodilution. Cerebral blood flow (CBF) was measured by the radioactive gas elimination method. CBF was unaffected by progressive hyperosmolality during a 2-h observation period.     

Influence of Anaesthesia on Blood Flow to the Calves During Surgery

The blood flow to the calves during abdominal surgery under different kinds of general anaesthesia was measured by strain gauge plethysmography in 12 patients. The volume flow increased 100% during surgery in both light and deep anaesthesia, caused by a decrease in peripheral resistance. The increase in volume flow could partly be explained by the anaesthesia itself, possibly induced by the use of a nitrous oxide-oxygen gas mixture. The surgical procedure caused a further increase in volume flow. Possible underlying mechanisms are discussed.     

Effects of Endothelin-1 on Hepatic Blood Flow

Endothelin-1 belongs to a family of potent vasoconstrictors, recently isolated from endothelial cells. Endothelin-1 has a variety of hepatic effects and hepatic clearance from the circulation is important. Elevated plasma concentrations of Endothelin-1 are found after orthotopic liver transplantation and in cirrhosis with ascites.This study in piglets on hepatic bloodflow was designed to compare differences in effects between central venous and intraportal injection of endothelin-1, and to evaluate effects of repeated injections. Central venous injection of endothelin-1 caused a larger reduction in portal vein flow, while intraportal injection caused a larger increase in portal vein pressure. Repeated injections resulted in a reduction in portal vein flow and an increase in portal vein vascular resistance.     

Blood Flow After Peripheral Arterial Reconstruction:V. Effect of Body Position on Leg Blood Flow at Rest and during Exercise

Common iliac arterial blood flow was measured with implanted electromagnetic flow probes in 6 patients after reconstruction of the aorto-iliac-femoral region. On the 3rd, 4th or 5th day after operation heart rate, oxygen uptake and local leg blood flow were studied at rest and during exercise on a bicycle ergometer in supine and sitting position. Heart rate at rest was 10 beats/min higher in sitting than in supine position. During exercise there was no significant difference in heart rate between the two postures. Oxygen uptake was 8% higher in sitting than in supine position at rest. During exercise oxygen uptake did not differ significantly between the two postures. Local leg blood flow was significantly lower in sitting position both at rest and during exercise.