Effect of calcium on locomotor activity of mice.

Intracerebroventricular administration of calcium severely depressed the locomotor activity of unanesthetized mice, producing ataxic gait and motor incoordination. Pretreatment with pentobarbital (30 mg/kg, IP) twice daily for 2 and 6 days partially reversed this effect of calcium, suggesting that calcium and pentobarbital may in part exert their depressant effect by a similar mechanism.

Effect of velocity of distribution on red cell distribution in capillary blood vessels.

Through the use of simulated model experiments, data on blood cell distribution into a bifurcating capillary blood vessel are obtained. The results show that the movement of red blood cells at a bifurcation point is influenced by the difference in velocities of flow in the daughter branches. If the velocity of flow in one branch is slower than that in the other, the hematocrit decreases in the slower branch and increases in the faster branch.

Elasticity of excised dog lung parenchyma.

An experimental procedure was developed to measure the stress-strain relationship on rectangular slabs (5.0 X 5.0 X 0.

Mechanical properties of taenia coli smooth muscle in spontaneous contraction.

The following mechanical tests have been performed on spontaneously contracting taenia coli: isometric step stretch, isotonic step loading, and length-tension. Passive stress-strain tests have also been done. Information on spontaneous contraction was more readily obtained in isometric tests.

Inversion of Fahraeus effect and effect of mainstream flow on capillary hematocrit.

The well known Fahraeus effect (1929) states that if whole blood is allowed to flow from a large reservoir into a small circular cylindrical tube, the hematocrit in the tube is smaller than that in the reservoir, and the smaller the tube, the smaller will be the tube hematocrit. This is interpreted as a feature of particulate flow. We find that this relationship is not monotonic in a model experiment in which gelatin particles (circular disks) are suspended in a silicone fluid to simulate blood.

A noncontact method for three-dimensional analysis of vascular elasticity in vivo and in vitro.

A new method is described to measure the deformation of the blood vessel wall simultaneously in longitudinal and circumferential directions. This information is of paramount importance for further characterization of the elastic properties of the arterial wall. The new method consists of a closed-circuit TV system in conjunction with a video dimension analyzer (VDA).

Determination of vicinal hydroxyl groups in poly(vinyl alcohol) (PVA).

An accurate procedure for the determination of 1,2-diol groups in styrene glycol and poly-(vinyl alcohol) has been demonstrated. The diols are cloven with periodate and the excess of this is determined by means of standard arsenite solution.

A device for testing mechanical properties of biological materials--the "Biodyne".

An electromechanical servo-controlled device has been developed. This device can be used to test the mechanical behavior of a wide variety of biological soft tissues. Control and execution of material testing procedures such as stress-strain, vibration, relaxation, creep etc.

Does the surface tension make the lung inherently unstable?

Many authors regard the human lung as a collection of 300 million bubbles independently connected by cylindrical tubes. Under surface tension such a model is inherently unstable in the sense that the small alveoli would empty into the large ones so that the lung would consist only of collapses and hyperinflated alveoli. It has been demonstrated that this basic model is wrong.

Stress, deformation, and atelectasis of the lung.

The lung parenchyma as a tissue has a rather unusual stress-strain relationship. A theoretical derivation of this relationship is presented which connects the surface tension and the tissue elastic stress in the alveolar septa with the alveolar geometry. The mathematical expression contains a few meaningful physical constants which can be determined by in vitro and in vivo experiments.

Vascular endothelium-leukocyte interaction; sticking shear force in venules.

To determine the shear force acting on a white blood cell sticking to the endothelium of a blood vessel, the flow field about a single white blood cell in a venule was determined by hign-speed motion picture photomicrography. The force acting on the white blood cell was then calculated according to the principles of fluid mechanics. In this paper, the calculation was made using an experimentally determined dimensionless shear force coefficient obtained from a kinematically and dynamically similar model.