Biomedical subjects

S L Schaefer

Publications and source records attributed to S L Schaefer.

6 recordsLinked to original sources

PubMed1998

Kinematic gait analysis of hind limb symmetry in dogs at the trot.

OBJECTIVE: To describe intratrial differences in hind limb symmetry in healthy dogs at the trot, using noninvasive, computer-assisted, three-dimensional kinematic gait analysis. ANIMALS: 8 clinically normal large-breed adult dogs. PROCEDURE: Dynamic flexion and extension angles and angular velocities were calculated for the coxofemoral, femorotibial, and tarsal joints of dogs at the trot. Temporal and distance variables were computed. Essential Fourier coefficients were used to determine mean flexion and extension curves for all joints and to compare differences in movement between right and left hind limbs. Variances attributable to limb, dog, and trial were determined. RESULTS: Each joint had a characteristic pattern of flexion and extension movement that was used to compare intratrial symmetry of hind limb gait. Significant differences were not detected in temporal or distance variables between the right and left hind limbs. Significant differences were not noted in essential Fourier coefficients used to characterize coxofemoral, femorotibial, and tarsal joint angles and angular velocities, with the exception of the cosine-0 coefficient for coxofemoral angular velocity. Variation in joint angle and angular velocity measurements were attributable to individual dog and trial. Variation attributable to limb was negligible. CONCLUSIONS: Intratrial evaluation of right-left hind limb symmetry, using kinematic gait analysis, indicated objectively that hind limb movement is symmetrical at the trot in healthy large-breed dogs. CLINICAL RELEVANCE: Documentation of hind limb symmetry at the trot will help provide a basis for direct comparison of both hind limbs in future studies evaluating gait and treatment of dogs with musculoskeletal disease.

Animals↗

PubMed1996

Effects of acid aspiration-induced lung injury on left ventricular function.

BACKGROUND: Acid aspiration-induced acute lung injury (AALI) leads to myocardial leukosequestration and edema in rats and hemodynamic depression in dogs, but the effects of AALI on left ventricular (LV) function have not been carefully studied. METHODS: We examined the effects of 0.1 N HCl administration into the lung on LV function, leukosequestration, and edema in pentobarbital-anesthetized, atropinized (n = 8), or autonomically blocked (n = 7) dogs. Saline solution was administered into the lungs of a control group of autonomically blocked dogs (n = 6). LV contractility was assessed by end-systolic elastance (EES) and preload recruitable stroke work (PRSW). Active relaxation was assessed by the time constant of LV pressure decline (tau). RESULTS: AALI resulted in significant (p < 0.05) decreases in mean arterial pressure and cardiac output and increases in pulmonary artery pressure and systemic vascular resistance in atropinized and autonomically blocked dogs but not in saline control group. In atropinized dogs tau did not change after injury, but EES and PRSW were increased significantly at 2 and 3 hours after injury, despite significant myeloperoxidase activity and extravascular fluid wet-dry weight ratios. EES, PRSW, and tau did not change in the autonomically blocked dogs in response to AALI or in the saline control group. CONCLUSIONS: We concluded that AALI results in a baroreflex mediated enhancement of LV contractility in dogs, despite mild myocardial leukosequestration and edema formation.

Acid-Base Equilibrium↗

PubMed1996

Acute transient coronary sinus hypertension impairs left ventricular function and induces myocardial edema.

This study was performed to evaluate the direct and indirect effects of acute coronary sinus hypertension (CSH) on systolic and diastolic left ventricular (LV) function. Coronary sinus pressure was elevated to 25 mmHg for 3 h in eight pentobarbital-anesthetized dogs and then relieved. LV contractility was assessed by preload recruitable stroke work (PRSW) and end-systolic elastance (Ees). Diastolic function was assessed by the time constant of isovolumic relaxation (tau) and the end-diastolic pressure volume relationship (EDPVR). PRSW and Ees decreased progressively, and tau and the slope of the EDPVR increased progressively with CSH. These changes persisted after relief of CSH. beta-Adrenergic and cholinergic receptor blockade, performed in six dogs, did not alter the effects of CSH on systolic or diastolic function. The LV wet-to-dry weight ratios of the groups with CSH were significantly greater than those of a control group without CSH. We conclude that CSH results in changes in the left ventricle that depress contractility, prolong active relaxation, and increase diastolic stiffness. The dysfunction was not the direct effect of CSH or autonomic reflex activation, but may have been induced by fluid accumulation within the interstitium.

Animals↗

PubMed1989

Ventilatory control during exercise with peripheral chemoreceptor stimulation: hypoxia vs. domperidone.

Hypoxia potentiates the ventilatory response to exercise, eliciting a greater decrease in arterial PCO2 (PaCO2) from rest to exercise than in normoxia. The mechanism of this hypoxia-exercise interaction requires intact carotid chemoreceptors. To determine whether carotid chemoreceptor stimulation alone is sufficient to elicit the mechanism without whole body hypoxia, ventilatory responses to treadmill exercise were compared in goats during hyperoxic control conditions, moderate hypoxia (PaO2 = 38-44 Torr), and peripheral chemoreceptor stimulation with the peripheral dopamine D2-receptor antagonist, domperidone (Dom; 0.5 mg/kg iv). Measurements with Dom were made in both hyperoxia (Dom) and hypoxia (Dom/hypoxia). Finally, ventilatory responses to inspired CO2 at rest were compared in each experimental condition because enhanced CO2 chemoreception might be expected to blunt the PaCO2 decrease during exercise. At rest, PaCO2 decreased from control with Dom (-5.0 +/- 0.9 Torr), hypoxia (-4.1 +/- 0.5 Torr), and Dom/hypoxia (-11.1 +/- 1.2 Torr). The PaCO2 decrease from rest to exercise was not significantly different between control (-1.7 +/- 0.6 Torr) and Dom (-1.4 +/- 0.8 Torr) but was significantly greater in hypoxia (-4.3 +/- 0.7 Torr) and Dom/hypoxia (-3.5 +/- 0.9 Torr). The slope of the ventilation vs. CO2 production relationship in exercise increased with Dom (16%), hypoxia (18%), and Dom/hypoxia (68%). Ventilatory responses to inspired CO2 at rest increased from control to Dom (236%) and Dom/hypoxia (295%) and increased in four of five goats in hypoxia (mean 317%).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1988

Minimum anesthetic dose and cardiopulmonary dose response for halothane in chickens.

The minimum anesthetic dose (MAD) and the cardiopulmonary dose-response for halothane were determined in male chickens. The MAD for halothane was 0.85 +/- 0.09% (mean +/- SD), with a range of 0.75% to 0.98%. There was a significant (P less than 0.002) positive correlation between increasing concentrations of halothane and PaCO2, and significant negative correlations of halothane concentration with respiratory rate (P less than 0.04), arterial blood pH (P less than 0.008), and mean arterial blood pressure P less than 0.008). A significant correlation was not found between halothane concentration and heart rate or arterial blood bicarbonate concentration. It was concluded that the MAD for halothane in chickens is similar to values for minimum alveolar concentrations of halothane in mammalian species, and that there is substantial dose-dependent depression of cardiopulmonary function in chickens.

Anesthesia, General↗

PubMedDate not supplied

Tissue shrinkage with the holmium:yttrium aluminum garnet laser. A postoperative assessment of tissue length, stiffness, and structure.

The effect of laser energy on the length, stiffness, and structure of connective tissue was examined in a rabbit patellar tendon model. A holmium:yttrium-aluminum-garnet laser was used to deliver a calculated dose of laser energy (300 J/cm2) to one randomly selected patellar tendon in each of 13 adult New Zealand White rabbits. The contralateral patellar tendon was used as a control. Radiopaque markers were placed in the patella and tibial tuberosity to allow for patellar tendon length measurements (via standard lateral radiographs) before and after laser application and at 4 and 8 weeks. Limbs were not immobilized during the postoperative period. The tendons were harvested at 0 weeks (N = 7) and 8 weeks (N = 6) and evaluated for tensile, stiffness, cross-sectional area, histologic changes, and electron microscopic appearance. The results demonstrated significant tendon shrinkage (6.6% +/- 1.4%) after application of the calculated laser energy dose. However, tendon length had increased significantly beyond the immediate postlaser length at 4 weeks and beyond its original length by 8 weeks. At 8 weeks, the lased tendons were significantly less stiff with significantly greater cross-sectional areas than contralateral controls. There was generalized fibroblastic response throughout the entire lased tendon characterized by a marked increase in cellularity. There was also a change from the normal bimodal pattern of large- and small-diameter collagen fibers to a unimodal pattern with predominantly small-diameter fibers in the lased tendons. The tissue alterations seen in this study suggest that the biologic response of connective tissue to laser energy causes a further compromise in tissue integrity, beyond that attributed to the initial physical effects of the laser. These alterations must be taken into consideration when determining postoperative rehabilitation of laser-modified tissues.

Adult↗