We evaluated the extent to which the myogenic autoregulatory response was affected by sympathetic vasoconstriction in humans. The stimulus used to produce sympathetic vasoconstriction was the cold water immersion of a contralateral finger. The stimulus used to elicit myogenic response was gravitational potential energy change (GPEC), that is, arm position change, i.e., the raising and lowering of the upper extremity 40 cm above and below the heart level. The response was observed in terms of the changes in amplitude on a differential digital photoplethysmogram (delta DPG) during this maneuver with and without cold stimulation. The subjects were seven healthy males. During non-immersion, the delta DPG amplitude increased to 55.7 +/- 7.6% (SE) at the elevated position and decreased to -56.3 +/- 4.0% at the lowered position. Mean finger arterial blood pressure (MBP) decreased by 34.0 +/- 1.8% at the elevated position and increased by 39.9 +/- 3.3% at the lowered position. During immersion, the delta DPG amplitude was significantly (p < 0.05) decreased by 25-40, 33-57, and 33-38% at the heart, elevated, and lowered position, respectively. MBP increased by 5-9%, but heart rate was unchanged throughout immersion. These results indicate that the myogenic response of arterioles is not entirely abolished by the present sympathetic vasoconstrictor effect. Thus interactions between these two effects may maintain both systemic and local circulatory homeostasis.
The purpose of this study was to clarify whether peripheral vascular response to alteration of transmural pressure is changed by endurance exercise training. The healthy male subjects (training group; n = 6) performed endurance exercise training that consisted of cycle ergometer exercise 5 d.week-1 and 30 min.d-1 for a period of 8 weeks. Changes in the peripheral vascular response to alteration of transmural pressure in the human finger were measured by a differential digital photoplethysmogram (DeltaDPG) and blood pressure during passive movement of the arm to different vertical hand positions relative to heart level. Following 8 weeks of endurance training, percent changes in DeltaDPG from heart level in the training group increased significantly (mean +/- SD, -48.1 +/- 7. 3 to -58.7 +/- 9.3% at the lowered position, 46.1 +/- 13.4 to 84.6 +/- 8.8% at the elevated position, p<0.05). Similarly, the arterial compliance index, which was calculated from DeltaDPG-P wave amplitude and arterial pulse pressure, also significantly changed in the training group over the 8 weeks (5.6 +/- 1.3 to 2.7 +/- 1.6 mV. V-1.s-1.mmHg-1 at the lowered position, 30.0 +/- 12.4 to 54.4 +/- 18. 9 mV.V-1.s-1.mmHg-1 at the elevated position ). Maximal oxygen uptake (V.O2 max) was significantly increased in the training group. On the other hand, the control group (n = 6) showed no significant changes in all parameters for 8 weeks. Therefore these results suggest that endurance exercise training induces an increase in peripheral vascular response to alteration of transmural pressure in the human finger.
A case of Noonan's syndrome with cervical syringomyelia is presented here representing the second reported instance of such association. A CT of metrizamide myelography revealed a high density in the middle subintradural space in the cervical region below C2. Sensory dissociation was minimal and localized in the left C4. It could not be determined whether this association between syringomyelia and Noonan's syndrome is related or represents a chance.
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