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Biomedical subjects

M R Fedde

Publications and source records attributed to M R Fedde.

At least 37 records · Page 2Linked to original sources
PubMed1996

Blood viscosity in broilers: influence on pulmonary hypertension syndrome.

Elevation in apparent blood viscosity may enhance the pulmonary hypertension that leads to pulmonary hypertension syndrome (PHS) and ascites in fast-growing broilers. We investigated the importance of packed cell volume (PCV) and shear rate in modifying apparent viscosity of the blood from broilers assigned to normal, preascites, and ascites groups. Apparent viscosity of broiler blood increased at all shear rates as PCV increased; the increase in apparent viscosity became greater as the shear rate decreased at PCV above 0.30. At the PCV of normal broilers (0.30 or below), apparent viscosity was nearly shear rate independent, at least down to 11.25 per second, the lowest shear rate studied. Apparent viscosity, at any given PCV and shear rate, was significantly lower in the blood of birds with ascites than in normal birds; however, the relative viscosity was not different between those groups, indicating that lower plasma viscosity in the birds with PHS was responsible for the finding. The results show that the principal factor responsible for increased apparent viscosity of blood in birds with PHS is the increase in PCV. The increased resistance to flow of blood as the result of higher blood viscosity may contribute to the pulmonary hypertension.

Animals↗
PubMed1995

Extreme derangements of acid-base balance in exercise: advantages and limitations of the Stewart analysis.

The acid-base analysis method described by Stewart (1981) was applied to the greyhound, an animal that undergoes large changes in intra- and extracellular hydrogen ion concentrations during a race. Increases in plasma [H+] especially during the first 15 min of recovery, induced by increases in lactate concentration in the plasma, were reduced by lowering of PCO2 (hyperventilation) and removal of Cl- from the plasma. [H+] calculated by the Stewart method is similar to that measured directly with a pH electrode when the strong ion difference is within 10 meq/L of resting values (approximately 40 meq/L); thus the measured independent variables were sufficient to account for the [H+] using the Stewart analysis. When the strong ion difference became lower than 30 meq/L, increased variability between measured and calculated [H+] occurred. An error analysis demonstrated the importance of minimizing measurement error of all independent variables, including as many strong and weak electrolytes as possible in the analyses, using the most accurate dissociation constants possible, and understanding the dissociation behavior of the weak electrolytes, especially the plasma proteins, when using the Stewart analysis. The Stewart method of analyzing acid-base balance can contribute to improved training methods for obtaining maximum exercise performance.

Acid-Base Equilibrium↗
PubMed1995

Effects of restraint and isolation stress and epidural blockade on endocrine and blood metabolite status, muscle glycogen metabolism, and incidence of dark-cutting longissimus muscle of sheep.

Crossbred lambs (47.3 kg BW) were used to study the effects of restraint and isolation stress on endocrine status and blood metabolites, antemortem glycogenolysis, and incidence of the dark-cutting condition (DCC) in the longissimus muscle (LM) and to determine the role of muscle contraction in the formation of the DCC in sheep. Lambs were assigned randomly to three treatments: unstressed controls (C); a single 6-h period of restraint and isolation stress (RIS); and a single 6-h period of RIS following epidural blockade (RISEB) with lidocaine. Blood was collected immediately before lambs were subjected to RIS and RISEB and at 12-min intervals during the 6-h period. Serum concentrations of glucose, lactate, and insulin were higher (P < .01) in RIS and RISEB lambs than in C lambs. Serum free fatty acid concentrations were higher (P < .01) in stressed lambs only during the first 4 h of stress. Plasma epinephrine and cortisol concentrations also were higher (P < .01) in RIS and RISEB lambs than in C lambs. Lambs were slaughtered within 30 min after completion of stress. Immediately after stunning and at .75, 3, 6, 12, and 24 h postmortem, samples were removed from the LM in the hindsaddle and foresaddle for glycogen, lactate, and pH determinations. Muscle pH was elevated (P < .01) by RIS and RISEB; ultimate pH exceeded 6.0. The LM from carcasses of RIS and RISEB lambs had lower (P < .01) glycogen and lactate concentrations in both regions than the LM of C lambs. Subjecting sheep to a single 6-h period of RIS was an effective animal model to induce the DCC. Failure of the epidural blockade to inhibit antemortem glycogen metabolism and formation of the DCC indicates that muscle contraction was not requisite to those processes in sheep.

Anesthesia, Epidural↗
PubMed1995

Fluid, electrolyte, and packed cell volume shifts in racing greyhounds.

Arterial blood samples were obtained at rest, just before, and 5 minutes after a 704-m race, to quantify changes in hematologic variables, plasma electrolyte and protein concentrations, osmolality, and acid/base variables. Changes in plasma volume were estimated from the change in plasma protein concentration. Immediately prior to the race, plasma volume decreased by 10% from rest and total circulating RBC volume increased by 60%, attributable to increased RBC number rather than size. Increases in blood volume (VB) by 24% and PCV by 29% also were detected before the race. Five minutes after the race, plasma volume was 21% below the resting value and total circulating RBC volume had increased 73% above the resting value, resulting in a 40% increase in PCV. Contraction of the spleen appeared responsible for increased PCV and VB before the race and maintenance of VB after the race. Plasma chloride concentration was the same before and after the race; the chloride content of the plasma decreased by the same fraction (22%) as did the plasma volume, indicating Cl- loss from the plasma. Plasma Na+ content decreased by a smaller fraction (13%), causing Na+ concentration to increase from 151 mEq/L at rest to 167 mEq/L after the race. Assuming that Na+ concentration was the same throughout the extracellular fluid, H2O likely moved into the intracellular compartment. As a consequence of these changes, the inorganic strong ion difference in plasma increased by about 16 mEq/L, tending to minimize the acid/base disturbance induced by the 33 mEq/L increase in lactate concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid-Base Equilibrium↗
PubMed1994

Exercise performance of birds.

Birds are excellent endurance athletes. Not only do many birds undertake long migratory flights, but many do so under extreme environmental conditions: excessive heat, extreme cold, and the hypoxic conditions of high altitude. We are just now starting to understand the physiological adaptations these animals possess for surviving and thriving in these environments. Still, relatively few studies have actually been performed on exercising birds, particularly on birds flying under the conditions mentioned here. Furthermore, not all birds are capable of sustained exercise in hypoxia, heat, and cold. More work is needed to increase our understanding of the differences in the physiological systems that allow some birds to be better able to exercise under such conditions.

Adaptation, Physiological↗
PubMed1994

Influence of different preamplifier bandpass cutoff frequencies on the basic pattern of sympathetic nerve discharge.

Autospectral analysis reveals that most of the power in sympathetic nerve discharge (SND) is contained between 1 and 10 Hz in anesthetized animals. The synchronized discharge bursts of the fibers comprising sympathetic nerves are usually recorded after capacity-coupled preamplification with a bandpass of 1-1000 Hz. However, cardiac- and respiratory-related movement artifacts can adversely affect the signal when this wide bandpass (1-1000 Hz) is used. To eliminate the influence of movement artifacts on the basic pattern of SND, we have routed the output of a preamplifier (bandpass 30-1000 Hz) through a frequency analyzer which measures the frequency of spike discharges exceeding a threshold voltage. After the impulses are rectified and integrated a smooth envelope of the synchronized sympathetic nerve discharge bursts is produced. The following observations have been made: 1) The autospectra of SND constructed after either wide-band preamplification or 30-1000 Hz using the frequency analyzer are similar and 2) Narrow-band preamplification (30-1000 Hz) eliminates movement-related artifacts which adversely influence the sympathetic nerve signal. These results indicate that the basic pattern of SND can be faithfully recorded after narrow-band preamplification which eliminates potential movement-related artifacts.

Action Potentials↗
PubMed1993

Rheological characteristics of horse blood: significance during exercise.

When horses maximally exercise, splenic contraction and fluid movement out of the vascular compartment greatly increase the hematocrit (up to 0.70). We studied the in vitro rheological characteristics of blood from Thoroughbreds and Quarter Horses to determine the interaction of hematocrit and shear rate on apparent viscosity. We also compared the rheological characteristics of the blood before and after horses received furosemide, a drug commonly used to prevent exercise-induced pulmonary hemorrhage. Although the apparent viscosity of blood with a high hematocrit was high at low shear rates, it rapidly decreased as the shear rate increased and appeared to continue to decrease at shear rates above 450 sec-1, which was the limit of our measurement capability. Furosemide had no detectable influence on the measured in vitro rheological characteristics of the blood at any hematocrit or shear rate studied. We postulate that during exercise, when shear rates in the circulation are high, apparent viscosity at high hematocrit may approach values similar to those that occur during rest when both hematocrit and shear rates are lower. Consequently, the shear-dependent properties of blood may create a homeostasis of viscosity in vivo during exercise so that high viscosity is not a major factor contributing to vascular resistance.

Animals↗
PubMed1992

Changes in haemorheology in the racing greyhound as related to oxygen delivery.

Arterial blood samples were obtained from six greyhounds during rest, immediately before, and after a 704-m (7/16th mile) race. Measurements were made of various haematological (red cell count, haemoglobin, packed cell volume, white cell count, plasma proteins) and haemorheological variables. Blood and plasma viscosity were determined at high wall shear stresses (67-200 dynes.cm-2, 670-2000 microN.cm-2) in a 20-microns glass capillary device which was designed to take the diameter dependence of blood viscosity (Fahraeus-Lindqvist effect) into account. Compared to values at rest, substantial haemoconcentration occurred before the race, mainly due to splenic discharge of red cells. Additional haemoconcentration was found after the race. The increase of effective blood viscosity caused by elevation of packed cell volume was greater than the increase in O2 binding capacity resulting from the elevated haemoglobin concentration, suggesting that the haemoconcentration observed in the exercising greyhound does not enhance O2 delivery to skeletal muscle. The main physiological effect of red cell discharge from the contracting spleen appeared to be a consequence of the volume rather than the composition of the circulating blood.

Animals↗
PubMed1992

Microcontroller-based system for collecting anaerobic blood samples from a running greyhound.

Many physiological variables change rapidly in the blood during sprint exercise. To characterize the dynamics and extent of these changes, blood samples must be obtained during exercise. We describe herein a portable, microcontroller-based system used to automatically obtain repeated, anaerobic, arterial blood samples from greyhounds before, during, and following a race on a track. In addition, the system also records the blood temperature in the pulmonary artery each time a blood sample is taken. The system has been tested for more than 2 years and has proven to be reliable and effective.

Anaerobiosis↗
PubMed1992

Acid-base changes in the running greyhound: contributing variables.

To determine the factors responsible for changes in [H+] during and after sprint exercise in the racing greyhound, Stewart's quantitative acid-base analysis was applied to arterial blood plasma samples taken at rest, at 8-s intervals during exercise, and at various intervals up to 30 min after a 402-m spring (approximately 30 s) on the track. [Na+], [K+], [Cl-], [total Ca], [lactate], [albumin], [Pi], PCO2, and pH were measured, and the [H+] was calculated from Stewart's equations. This short sprint caused all measured variables to change significantly. Maximal changes were strong ion difference decreased from 36.7 meq/l at rest to 16.1 meq/l; [albumin] increased from 3.1 g/dl at rest to 3.7 g/dl; PCO2, after decreasing from 39.6 Torr at rest to 27.9 Torr immediately prerace, increased during exercise to 42.8 Torr and then again decreased to near 20 Torr during most of recovery; and [H+] rose from 36.6 neq/l at rest to a peak of 76.6 neq/l. The [H+] calculated using Stewart's analysis was not significantly different from that directly measured. In addition to the increase in lactate and the change in PCO2, changes in [albumin], [Na+], and [Cl-] also influenced [H+] during and after sprint exercise in the running greyhound.

Acid-Base Equilibrium↗
PubMed1991

Physiological changes in the running greyhound (Canis domesticus): influence of race length.

1. Racing greyhounds were allowed to run 402 m, 503 m, and 704 m to determine the influence of increased race length on physiological changes during and after exercise. 2. Plasma and whole blood variables that changed significantly with increased race length were [K+], [total protein], [lactate], hematocrit, and arterial pH. 3. Those variables that changed with increased race distance showed no indication of reaching a plateau; thus, the maximum changes that these variables might undergo with longer exercise duration remains unknown.

Animals↗
PubMed1991

Blood gas analyses on equine blood: required correction factors [see comment].

Correction factors have been determined to obtain the best estimates of PO2, PCO2 and pH in equine blood with standard blood gas and pH electrodes. There was a significant difference between the PO2 readings for tonometred blood of most horses and the equilibrating gas. Thus, if the PO2 electrode is calibrated with a gas, an electrode correction factor should be obtained by tonometring a blood sample from each horse. This factor was not dependent on packed cell volume. No such correction is required for the PCO2 electrode. If the animal's temperature differs from that of the analyser, the PO2, PCO2 and pH values must be corrected to the animal's body temperature. Temperature correction factors determined for equine blood were similar to those for human blood. Failure to make temperature corrections can result in errors for PO2 and PCO2 of 6 to 7 per cent per degree of temperature difference.

Animals↗
PubMed1990

Effect of exercise conditioning on red blood cell volume and erythropoietin concentration in the beagle dog.

To determine if endurance conditioning has a stimulating effect on red blood cell and erythropoietin production, we exercised five beagle dogs on a motor-driven treadmill for 1 hour per day, 5 days per week, for 6 weeks at a speed near their maximal capability. Three additional beagles were kept in cages and served as nonconditioned controls. Endurance conditioning in these dogs produced no increase in red blood cell mass, serum erythropoietin concentration, or any other blood cell index measured. We conclude that this type of exercise conditioning does not produce the necessary stimulus for an increase in erythropoiesis.

Animals↗
PubMed1989

Cardiopulmonary function in exercising bar-headed geese during normoxia and hypoxia.

To investigate possible physiologic mechanisms that allow the bar-headed goose to perform strenuous physical activity when flying at high altitude (e.g., above 9,000 m), we measured cardiopulmonary variables during running exercise (treadmill; 0.6 m.sec-1; 2 degrees incline) while the bird breathed either normoxic (21% O2) or hypoxic (7% O2) gases via a face mask. 1. During normoxic exercise, O2 uptake rate doubled and both ventilation and cardiac output increased. Blood gases and pH in arterial, mixed venous and blood from the leg, however, remained virtually unaltered. 2. Hypoxia at rest stimulated ventilation to rise but not cardiac output. The birds reached a steady state with virtually unaltered O2 uptake. 3. Exercise during hypoxia further stimulated ventilation, resulting in elevated arterial PO2 and O2 content compared to hypoxia at rest. However, O2 uptake increased only slightly, and cardiac output did not rise over the resting hypoxic value. The hyperventilation resulted in respiratory alkalosis and increased CO2 output, with R values being as high as 2.0. 4. It is concluded that neither ventilation nor pulmonary gas transfer were the limiting step in supplying O2 to the working muscles during hypoxic exercise in our experiments. It is more likely that muscle blood flow or diffusion from muscle capillaries to mitochondria, or both, determined the aerobic capacity under these conditions.

Animals↗
PubMed1989

Mechanism of exercise-induced hypoxemia in horses.

Arterial hypoxemia has been reported in horses during heavy exercise, but its mechanism has not been determined. With the use of the multiple inert gas elimination technique, we studied five horses, each on two separate occasions, to determine the physiological basis of the hypoxemia that developed during horizontal treadmill exercise at speeds of 4, 10, 12, and 13-14 m/s. Mean, blood temperature-corrected, arterial PO2 fell from 89.4 Torr at rest to 80.7 and 72.1 Torr at 12 and 13-14 m/s, respectively, whereas corresponding PaCO2 values were 40.3, 40.3, and 39.2 Torr. Alveolar-arterial PO2 differences (AaDO2) thus increased from 11.4 Torr at rest to 24.9 and 30.7 Torr at 12 and 13-14 m/s. In 8 of the 10 studies there was no change in ventilation-perfusion (VA/Q) relationships with exercise (despite bronchoscopic evidence of airway bleeding in 3) and total shunt was always less than 1% of the cardiac output. Below 10 m/s, the AaDO2 was due only to VA/Q mismatch, but at higher speeds, diffusion limitation of O2 uptake was increasingly evident, accounting for 76% of the AaDO2 at 13-14 m/s. Most of the exercise-induced hypoxemia is thus the result of diffusion limitation with a smaller contribution from VA/Q inequality and essentially none from shunting.

Animals↗
PubMed1988

O2 transport in the horse during rest and exercise.

We studied mechanisms of O2 transport in 6 adult (2-5 year old) horses at rest and during steady-state exercise on a treadmill (0% slope) at 12 m/s (a submaximal gallop). Oxygen consumption was measured using an open-flow system. Arterial and mixed venous blood samples were simultaneously obtained for measurement of O2 content and hemoglobin concentration. VO2 increased from 1.5 +/- 0.2 L/min at rest to 46.2 +/- 4.8 L/min during exercise. HR increased from a resting value of 36.9 +/- 2.5 bpm to 196.5 +/- 10.9 bpm and the arterio-venous O2 content difference (a-v O2) increased from 4.2 +/- 0.8 ml O2/100 ml blood to 20.3 +/- 1.6 ml O2/100 ml blood. The 30.4-fold increase in oxygen consumption in the horse at submaximal VO2 versus only a 10-fold increase in man at VO2 max demonstrates the marked ability of the horse to transfer O2 at each step in the O2 transport pathway.

Animals↗