To investigate the morphologic basis of blood flow-dependent adaptive vascular enlargement, we quantitated endothelial cell density, dimensions, and structure in canine carotid arteries that were flow-loaded for 4 weeks, i.e., just before the development of significant adaptive enlargement. Increased flow was produced in the right common carotid artery of seven adult beagle dogs by an arteriovenous shunt to the right external jugular vein. The left common carotid artery was used to produce sham-operated controls. Five additional animals were used to produce sham-shunted controls, and two dogs were used as nonoperated controls. The blood flow rate (BFR) and wall shear rate (WSR) were markedly increased immediately after anastomosis in the proximal segment of the shunted artery (BFR = 719 +/- 142 ml/min, WSR greater than 4127 +/- 1002/sec) and after 4 weeks (BFR = 628 +/- 157 ml/min, WSR greater than 2919 +/- 388/sec) compared to the same artery before anastomosis (BFR = 154 +/- 50 ml/min, WSR = 904 +/- 314/sec, p less than 0.01 x 10(-3) for both comparisons) and to the contralateral control artery after 4 weeks (BFR = 365 +/- 110 ml/min, WSR = 2136 +/- 876/sec, p less than 0.01 and p less than 0.05, respectively, compared to the shunted side). In the shunted artery, endothelial cell density was markedly increased (6.15 +/- 0.68 x 10(3) cells/mm2 compared to 3.33 +/- 0.70 x 10(3) cells/mm2 for the controls, p less than 0.001). Endothelial cells on the high flow side were markedly narrowed in both axial and circumferential directions, but were radially thickened; nuclei became prolate-spheroid in shape. On the control side, cells were relatively flat and thin. We conclude that elevated wall shear stress induces an early increase in endothelial cell number and that this increase precedes the development of significant blood flow-dependent vascular enlargement.

Animals↗

PubMedDate not supplied

An experimental evaluation of isometric placement for extraarticular reconstructions of the anterior cruciate ligament.

We measured the changes in distance between the tibial and femoral attachment points of the extraarticular ACL substitute during knee motion. To measure the changes in distance continuously and directly, a computer-assisted experimental system was developed using an electrolyte-in-rubber transducer. We used 6 cadaveric knees to measure changes in distance of 15 combinations during a simple flexion and extension knee motion. The distance became longer with flexion in each pair of attachment locations. Although the smallest change in distance was obtained between the posterolateral site of the femoral distal metaphysis and a point posterior to the Gerdy tubercle (percent average of the maximum strain was about 12%), it was concluded that the extraarticular ACL reconstruction is not recommended from a standpoint of isometry of the substitute.

Aged↗

PubMedDate not supplied

Intracellular calcium response to directly applied mechanical shearing force in cultured vascular endothelial cells.

We studied the responses of cultured endothelial cells to mechanical shearing force directly applied to those cells in vitro to determine changes in the concentration of intracellular calcium ion (Ca++), one of the factors that transfers information within the cell. Cultured bovine fetal aortic endothelial cells containing the Ca++ fluorescence indicator, Fura-2, were rubbed with a latex balloon in a specially designed system, and changes in the fluorescence of Fura-2 caused by this shear stimulation were determined by photometric fluorescence microscopy. Immediately after shear stimulation, the concentration of Ca++ in the cells was increased and reached a peak (511 +/- 165 nM, n = 12) within 15 seconds after stimulation. After the peak, the concentration was gradually restored to the resting level (55 +/- 17 nM, n = 12). The magnitude of the Ca++ response was dependent on the intensity of the shear force applied. Analysis of fluorescence images of Fura-2 revealed that the cells showed this Ca++ reaction without being injured or desquamated, although there were slight differences in the degree and duration of reaction among cells. This reaction appeared even when the cells were placed in the air with no contact with the fluid. This result suggests that neither the fluid flow associated with the balloon movement nor chemical substances in the fluid are involved in the reaction, but that pure physical force alone is responsible for the Ca++ reaction. Further, it suggests that endothelial cells have the ability to perceive such physical stimulation as shear force and to transfer this information to the interior of the cell via changes in the intracellular Ca++ concentration.

Animals↗

PubMedDate not supplied

Disorder of phase-related modulation of soleus H-reflex during hip movement in stroke patients.

PURPOSE: The soleus H-reflex during passive hip movement was measured to clarify the modulation of excitability of the soleus monosynaptic reflex during locomotion-like movement in spastic stroke patients. METHOD: The experiment was performed in five patients with spastic hemiparesis. The hip joint was moved passively ranging from 0 to 40 degrees. The knee joint was fixed at full extension and the ankle joint was fixed at the mid-position. During the movement, the soleus M-wave and soleus H-reflex were measured. RESULTS: Flexion caused a decrease in the soleus H-reflex, whereas extension caused an increase symmetrically for both the static and dynamic conditions. In addition, the lowest value was observed at the end of the flexion phase during fast movement. CONCLUSION: These findings indicate that the phase-related modulation of soleus H-reflex during hip movement is partially disordered in stroke patients.

Adaptation, Physiological↗