Effect of extreme elevations in venous pressure on reflection coefficient in the lung.
Animals; Blood Pressure/*physiology; Blood Proteins/analysis; Capillary Permeability/*physiology; Dogs; Endothelium; Female; Forelimb/physiology; Hematocrit; In Vitro Techniques; Lung/*drug effects/physiology; Male; Perfusion; Pulmonary Veins/*physiology; Solvents/*chemistry; Vascular/*drug effects
We determined whether the solvent drag reflection coefficient (sigma f) for total proteins of a canine perfused left lower lung lobe (LLL) preparation decreases at elevated venous pressures (Pv). We found that sigma f (estimated using the hematocrit-protein technique) remained constant at all Pv's (30-95 mm Hg) evaluated. These results were unanticipated, since previous studies reported increases in protein permeability at Pv's within this range. We conducted two additional studies to better understand the basis for these observations. In the first, we evaluated the effect of high Pv (85 mm Hg) on sigma f of a canine perfused forelimb preparation and found sigma f to be reduced. This difference in response suggests that the normal sigma f's observed in the LLL were not due to high Pv per se, but rather that there is some intrinsic difference between the pulmonary and the systemic circulations that accounts for the difference. The second study was designed to determine whether the normal sigma f's observed in the LLL at high Pv's provide meaningful information about pulmonary vascular endothelial permeability. We damaged LLL's with alloxan, oleic acid, or HCl and obtained near normal estimates of sigma f at high Pv. These results indicated that it is not possible to easily distinguish between a normal and a damaged pulmonary vasculature when sigma f is measured at high Pv. We suggest that the normal estimates of sigma f obtained at high Pv in the LLL results from an increased fraction of the transvascular flow occurring through pathways that exclude macromolecules.
Maron M B; Lang S A
Microvascular research
1992
1992-01
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1016/0026-2862(92)90006-b" target="_blank" rel="noreferrer noopener">10.1016/0026-2862(92)90006-b</a>
Effects of support diameter and compliance on common marmoset (Callithrix jacchus) gait kinematics.
Male; Animals; Callithrix/*physiology; Gait/*physiology; *Balance; *Branch stiffness; *Fine branch niche; *Locomotion; *Stability; Biomechanical Phenomena; Compliance; Forelimb/physiology; Hindlimb/physiology; Video Recording; Computer-Assisted; Image Processing
Locomotion is precarious in an arboreal habitat, where supports can vary in both diameter and level of compliance. Several previous studies have evaluated the influence of substrate diameter on the locomotor performance of arboreal quadrupeds. The influence of substrate compliance, however, has been mostly unexamined. Here, we used a multifactorial experimental design to investigate how perturbations in both diameter and compliance affect the gait kinematics of marmosets (Callithrix jacchus; N=2) moving over simulated arboreal substrates. We used 3D-calibrated video to quantify marmoset locomotion over a horizontal trackway consisting of variably sized poles (5, 2.5 and 1.25 cm in diameter), analyzing a total of 120 strides. The central portion of the trackway was either immobile or mounted on compliant foam blocks, depending on condition. We found that narrowing diameter and increasing compliance were both associated with relatively longer substrate contact durations, though adjustments to diameter were often inconsistent relative to compliance-related adjustments. Marmosets also responded to narrowing diameter by reducing speed, flattening center of mass (CoM) movements and dampening support displacement on the compliant substrate. For the subset of strides on the compliant support, we found that speed, contact duration and CoM amplitude explained \textgreater60% of the variation in substrate displacement over a stride, suggesting a direct performance advantage to these kinematic adjustments. Overall, our results show that compliant substrates can exert a significant influence on gait kinematics. Substrate compliance, and not just support diameter, should be considered a critical environmental variable when evaluating locomotor performance in arboreal quadrupeds.
Young Jesse W; Stricklen Bethany M; Chadwell Brad A
The Journal of experimental biology
2016
2016-09
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1242/jeb.140939" target="_blank" rel="noreferrer noopener">10.1242/jeb.140939</a>