Analysis of Variance of Microspheres Blood Flow Measurements in Rabbits

Iris Blood Flow Response to Acute Decreases in Ocular Perfusion Pressure: A Laser Doppler Flowmetry Study in Humans

“…2) is in agreement with the findings of Duijm et al, (1996Duijm et al, ( , 1997 and Tomidokoro et al, (1998) in rabbits. However, it is in sharp contrast with the findings of Bill (1972, 1973), who reported that IBF autoregulates in cats and monkeys (Macaca irus).…”

“…These studies demonstrated a vast range of behavior of IBF m vs PP m,norm . Duijm et al (1997) have attempted to explain the considerable variation in the IBF vs PP m observed in the experiments with the microspheres method by invoking the presence of hyperemia in response to the decrease in PP m . This hyperemia could be provoked by the release of vasoactive substances like prostaglandin, due to contact of the needles used to elevate and measure the IOP with the iris or the combination of trauma due to the insertion of these needles and general anesthesia with pentobarbital and mydriasis.…”

“…Our findings in human and those in cats and monkeys could be at variance due to either a species or methodological difference. The studies of Duijm et al (1996Duijm et al ( , 1997 and Bill (1972, 1973) were performed with the microspheres method. These studies demonstrated a vast range of behavior of IBF m vs PP m,norm .…”

“…Blood flow has been measured by means of radioactive labeled microspheres Bill, 1972, 1973 ;Duijm et al, 1996), radio-opaque dyes (Heymann et al, 1985) and the laser speckle phenomenon (Tomidokoro et al, 1998). Studies have documented perfusion changes in response to neurological (Beausang-Linder, 1982) and pharmacological interventions (Morgan, Green and Bowmann, 1981), as well as changes in ocular perfusion pressure Bill, 1972, 1973 ;Duijm et al, 1997 pendence of IBF upon mean ocular perfusion pressure (PP m ), when this pressure was decreased by increasing the intraocular pressure (IOP ; Bill, 1972, 1973). In contrast, in rabbits, IBF was found to decrease linearly as a function of PP m (Duijm et al, 1997 ;Tomidokoro et al, 1998).…”

Acute hemodynamic responses in the head during microgravity induced by free drop in anesthetized rats

“…It is well known that in some organs (e.g., the brain and retina), a change in perfusion pressure within a certain range does not cause change in blood flow due to the automatic regulation of vascular resistance, i.e., autoregulation, in humans and animals. However, in others, e.g., the iris (animal results) and head skin (human results), autoregulation of blood flow is weak (1,4,6,23). In the second group, an increase in perfusion pressure elicits an increase in blood flow, as shown in the present study.…”