Construction and use of a miniaturized rabbit ear chamber

Microscopic Observation of Leukocyte Kinesis in the Vascular Bed during Hemodialysis Using the Rabbit Ear Chamber Technique

Leukocyte kinesis in the capillary vascular bed during hemodialysis (HD) was investigated to elucidate the mechanism of transient leukopenia. Leukocyte movement was observed microscopically during HD using the rabbit ear chamber (REC) technique, which permits visualization of the movement of blood corpuscles in capillaries. Blood was drawn from the femoral artery and returned into the auricular and/or carotid artery so that the blood passing through the hollow fiber artificial kidney (HFAK) flowed into capillaries in the REC. Leukocyte counts of blood samples taken from the afferent and efferent limbs of the HD circuit, the right jugular vein and the right atrium were determined consecutively during HD. The difference in the leukocyte count was observed between the afferent and efferent limbs for the first 15 minutes and thereafter between the efferent limb and the jugular vein. The “transpulmonary” difference in the leukocyte count was not noticed throughout HD. Between 15 and 90 minutes after the start of HD, scarcely any circulating leukocytes were found in capillaries in the REC and some leukocytes were attached to the endothelial surface. Thereafter circulating leukocytes were seen again and detachment of leukocytes from the endothelial surface was observed. No leukocyte aggregation or embolization of aggregating leukocytes was noticed. This evidence suggests that leukopenia may be attributed to the transient shift of leukocytes to the marginal pool of the vessel lumen and this process may not be specific for the pulmonary vasculature, but may occur in the first capillary bed into which the blood passing through the HFAK flows. The attachment of leukocytes to the surface membrane of the HFAK may contribute to the transient leukopenia especially during the initial period of the HD.

In vivo microscopy of a rat abdominal skin flap: a new model

This study describes a rat abdominal skin flap model of in vivo microscopy which provides a reliable, easy to perform system in which to examine the microcirculation of flaps. The island flap, which is based on the superficial inferior epigastric vessels caudally, and drained proximally by the lateral thoracic vein, can be mounted directly on a Perspex microscope stage. In vivo microscopy of the subdermal plexus of the flap allows detailed study of blood flow pattern, capillary flow, microvessel diameter, and margination of leucocytes, in a skin flap with versatile blood supply and innervation.

Microvascular response in the rabbit ear to total body cooling: a model for study of human digits

Conditions such as Raynaud's disease, cold intolerance following digit replantation, and reflex sympathetic dystrophy are all exacerbated by diminished blood flow in the digits. The rabbit ear, being similar to the human digit, is an excellent model for studying microvascular responses during thermoregulation and was used in this study of microcirculatory changes during total-body cold stress. In eight rabbits a window was placed in one ear each, and the underlying vascular beds were photographed with the unanesthetized animal at room temperature (23 degrees C) and in a cold room (6 degrees C). Luminal arterial diameters constricted more than venular diameters during cold stress (39.6% vs. 16.5%, respectively, of the control diameters; P = 0.014). All responses were linear; the slopes of the regression lines were significantly different between arterioles and venules (P < 0.0001). This study suggests that decreased circulation in response to cold is due to decreases in the diameter and number of vessels available for perfusion, as predicted by the Poiseuille equation.

Response of rabbit ear microvasculature to total body cooling as observed through a new implantable window

A new implantable window was developed in order to study the native microcirculation of the rabbit ear. The responses of the ear microvasculature to total body cooling were studied before and after implantation of the window. No differences were found between arteriolar and venular vasoconstriction with cooling before and after implantation of the window. Arteriolar constriction was significantly greater than the venular response both before and after placement of the window (P = 0.014). Surface skin temperature of the instrumented and control ears was similar at room temperature (35.2 +/- 2.6 versus 36.1 +/- 1.0 degrees, respectively; P = 0.280); however, the instrumented ear was slightly warmer during cooling (17.9 +/- 1.9 versus 15.2 +/- 3.1 degrees; P = 0.024), suggesting increased blood flow in the instrumented ear. Details of construction and implantation of the window are described.

Laser-irradiation-induced relaxation of blood vessels in vivo

The response of blood vessels to laser irradiation in vivo was studied in the dorsal skin flap glass window chamber model of hamsters. The vasodilatory response of venules was critically dependent on the wavelength of irradiating laser. Relaxation was not produced in arterioles, although it was tried repeatedly. Vessels were irradiated with the 514.5 nm single line argon laser with irradiances from 1 to 10 W/cm2 on a 1.2 mm-diameter spot. Irradiation of venules with 2.2 W/cm2 and 4.25 W/cm2 produced reversible relaxation. Venules relaxed initially and after the interruption of irradiation returned to their original diameter. At higher irradiances (8.5 W/cm2) an irreversible relaxation was observed. At irradiances of 10 W/cm2 and above initial relaxation was accompanied with constriction, focal coaguli, and hemostasis. Irradiation with the argon-pumped dye laser at 595 nm did not produce any significant relaxation.