Patterns of Spontaneous Hemostasis in the Blood Vessels of the Rabbit's Ear
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Abstract1. A technique has been developed for the continuous recording of the amount of blood flowing from single vessels following their transection.2. the blood is washed away by a stream of saline flowing at constant rate. the mixture of blood and saline crosses a beam of blue light directed to a phototube. the output of the associated circuit is fed into an ink writer which records the changes in the concentration of erythrocytes suspended in the saline.3. Experiments performed with this technique on the small vessels of the rabbit's ear have revealed two basic patterns of hemostasis.4. the “arterial pattern” is characterized by a sudden outburst of blood when the vessel is cut, followed within a few seconds by a marked decrease in the rate of blood outflow. Therefore, the record begins with a sharp initial peak. Rhythmic fluctuations in the rate of blood outflow which might be due to vasomotion, are often seen in this type of patterns.5. the “venous pattern” lacks the initial peak, looking roughly trapezoidal with a hump or plateau.6. A mixed “peak and hump” pattern is also often found; its significance is discussed.7. in a small group of experiments, the influence of mechanical pressure, infiltration of the perivascular tissue with local anesthetics, and the injection of heparine and antiplatelet serum on the patterns of hemostasis were studied.Keywords:
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A major heterogeneous distribution of blood flow has been described on a non‐microvascular level within single skeletal muscles at rest and during exercise hyperaemia both in the dog and in the rabbit. Thde heterogeneity in blood flow distribution could bhd composed of both a steady‐state region‐to‐region variability (spatial) and a time‐dependent variability (temporal) in blood flow to each region. In the present study we estimated their relative contributions to the variations in blood flow within the muscles. Furthermore, we determined whether sympathetic nerve activity contributed to and whether pharmacologically induced vasodilation affected the heterogeneous blood flow pattern. Regional blood flow measurements were based on microsphere infusions into anaesthetized rabbits. Blood flow was determined under both resting conditions and during exercise hyperaemia in regions weighing 0.25 g each within hind leg muscles. Thde coefficient of variation for the spatial variability wahd twice that of the temporal one: 0.32 and 0.16 (mean) respectively. Neither stimulation of the sympathetic nerves, sympathectomy nor vasodilation affected the heterogeneity in blood flow. When exercise hyperaemia was induced, blood flow increased in all regions so that a positive ( P l 0.05) correlation was present between resting and exercising blood flow values in the individual regions. Although regional variation in vascularization could explain the observations during exercise hyperaemia, we have at present no fully satisfying explanation for the observed regional heterogeneity in blood flow.
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SIGNAL (programming language)
Doppler ultrasound
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The spontaneous and rhythmic constriction of peripheral arterioles, which is not associated with the cardiac or respiratory cycles, is called vasomotion. Vasomotion is observed in various tissues of various species, but the physiological role of vasomotion has not been clarified because of the difficulty in controlling the appearance of vasomotion in in vivo preparations. We developed a method of controlling vasomotion in in vivo experiments. The electrical stimulation of the cervical sympathetic nerve could reproducibly evoke vasomotion in rabbit ear skin. The frequencies of the evoked vasomotion were 0.04-0.07 Hz, which corresponded to spontaneously occurring vasomotion that has been reported before. Vasomotion was always evoked between 25 and 35 degrees C. At lower than 17 degrees C or higher than 37 degrees C, vasomotion was not evoked. With the use of this method of evoking vasomotion in vivo, the role of vasomotion in tissue perfusion was examined. A tracer (Cr-EDTA) was injected into the ear tissue, and tracer fading was then measured by using a camera. The rates of fading (clearance) of the tracer with vasomotion were significantly greater (1.7 to 8.1 times) than those without vasomotion. These results provided evidence that vasomotion enhanced tissue perfusion.
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Blood flow in microcirculation has found vital role in maintenance of body temperature. Its measurement is vital in the field of skin-vessel reactivity, ageing of skin, micro vascular repair of the ulnar artery and wound healing in association with total elbow replacement. The existing techniques for blood flow measurements like Electromagnetic blood flow measurement, Thermal convection method, Dual radiographie method, Ultrasonic Blood flow measurement and NMR method are not found suitable for measurement of blood flow in microcirculation due to their large size, complexity, invasive nature of measuring element and possibility of radiation exposure to the patient. Hence, a new technology is developed for micro vascular blood flow or velocity measurement using He-Ne laser of wavelength 632.8nm.
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Rhythmical variations in human skin blood flow have been studied with laser Doppler flowmetry. In healthy adults the appearance of the rhythmical activity and its magnitude were found to differ widely between subjects, while the individual frequencies of the oscillations studied on forehead skin were close to the group average (8.6 +/- 0.7 cycles/min, mean +/- S.D.). Intraindividual variations in frequency of the blood flow rhythmicity were found in different skin regions, indicating the local nature of its control mechanism. Application of anaesthetic paste on forearm skin completely blocked the rhythmical variations in blood flow that were recorded before the experiment. Increasing frequency of the rhythmical variations in blood flow with skin temperature was demonstrated on the forehead, upper arm and forearm skin. Neither oxygen breathing nor anaesthetic block of the nerves innervating the skin region examined influenced the rhythmical variations in skin blood flow. On the basis of the results obtained, it was concluded that the oscillatory variations in skin blood flow are intimately associated with the rhythmical active vasomotion (small vessel rhythmical diameter changes) reported previously in the literature.
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Skin Temperature
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