Little is known about the characteristics of hemolymph (blood) flow in animals with open circulatory systems. We measured cardiac output and blood flow to specific tissues in the black abalone, Haliotis cracherodii, a gastropod mollusk. The use of thermodilution allowed us to make repeated measurements of cardiac output and cardiac stroke volume over relatively short time intervals (5-10 heart beats) in resting, unrestrained abalone while disturbing the animals minimally. Anatomical studies of the abalone circulation showed that the arterial system terminated in small diameter (approaching 10-20 micron in some cases) lacunar tissue spaces. Because of this, we used radioactive microspheres (which must be trapped in the tissue vasculature) to measure blood flow rates to selected tissues. The major findings of our study were that 1) cardiac output in the black abalone ranged from about 100 to 150 ml X kg-1 X min-1, and was highly correlated with body size; 2) weight-specific cardiac stroke volume was about 5 ml X kg-1, considerably larger than that of a mammal; 3) tissue blood flow rates ranged from 10 ml X 100 g-1 X min-1 (foot muscle) to 80 ml X 100 g-1 X min-1 (nephridial tissue), similar to typical tissue blood flow rates in mammals. Our data suggest that the blood in the abalone is directed to the tissues not in proportion to percent total body weight the tissues represent (as might be expected in an open vascular system), but apparently in proportion to tissue metabolic rate.
The study purpose was to determine if menstrual cycle (mc) phase impacts the cutaneous vascular response to exercise in young women. Thirteen healthy women ages 20‐28 yrs were studied (mean 23.3 years). None of the women were taking oral contraceptives and all reported having had regular menstrual cycles for the past year. The exercise consisted of 20 min of brisk treadmill walking at a room temp of 32 C and 45% relative humidity. Skin blood flow (SBF) at the forearm and back was recorded before and throughout the exercise. A dual‐channel laser Doppler flowmeter was used to measure SBFs, and the values were stored in computer and later analyzed by commercial software. Using ANOVA mean SBFs for both skin locations were compared before and at 2 min intervals during exercise. One set of SBFs was taken at the mid‐follicular phase (F) of the mc. Another set was recorded at the mid‐luteal phase (L). The order in which the mc phases were studied was randomized. The vascular responses at the two phases were then compared to determine if mc phase altered the thermoregulatory response. Results showed vasodilation at each skin location during both mc phases. When the two phases were compared, it was found that the response was most pronounced during the L phase (12% greater SBF at forearm, P = 0.08; 23% greater SBF at back, P = 0.03). The different vascular responses to exercise are likely accounted for by the different hormonal conditions present.
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