Time Course Of Blood Flow Research Articles

Microvascular blood flow during vascular occlusion tests assessed by diffuse correlation spectroscopy

What is the central question of this study? What are the characteristics of the time courses of blood flow in the brachial artery and microvascular beds of the skin and skeletal muscle following transient ischaemia? What is the main finding and its importance? Skeletal muscle blood flow was significantly slower than the transient increase in the cutaneous tissue, suggesting mechanistic differences between cutaneous and muscular blood flow distribution after transient ischaemia. These results challenge the use of the cutaneous circulation as globally representative of vascular function. Vascular function can be assessed by measuring post-occlusion hyperaemic responses along the arterial tree (vascular occlusion test; VOT). It is currently unclear if responses are similar across vascular beds following cuff release, given potential differences in compliance. To examine this, we compared laser Doppler-derived blood flux in the cutaneous circulation (LDFcut ) and skeletal muscle microvascular blood flux (BFI) using diffuse correlation spectroscopy (DCS), to brachial artery blood flow (BABF) during VOT. We hypothesized that during a VOT following cuff release, (1) BFI response would be delayed compared to the brachial artery response, and (2) time to peak blood flux in the cutaneous vasculature would be slower than both brachial artery and skeletal muscle responses. Seven healthy men (26±4years) performed three trials of a brachial artery VOT protocol with 10min of rest between trials. A combined DCS and near-infrared spectroscopy probe provided BFI and oxygenation characteristics (total-[haem]), respectively, of skeletal muscle. BABF was determined via Doppler ultrasound and microvascular cutaneous blood flux was determined via LDFcut . Following cuff release, time to peak of BFI (32.3±6.0s) was significantly longer than BABF (7.3±2.5s), LDFcut (10.0±6.4s) and total-[haem] (14.2±8.3s) (all P<0.001). However, time to peak of BABF, LDFcut and total-[haem] were not significantly different (P>0.05). These results suggest mechanistic differences in control of cutaneous and muscular blood flow distribution after transient ischaemia.

Blood Flow In The Inferior Vena Cava At The Onset Of Cycling Exercise In Humans

At the onset of exercise, the stroke volume (SV) is typically augmented through the Frank-Starling mechanism by increased venous return (V-Return) from blood storage regions such as the lower limbs and viscera. However, the influence of the respiratory pump in effecting this increased V-Return is not well understood. PURPOSE: We, therefore, aimed to measure blood flow (BF) in the inferior vena cava (IVC) at the onset of cycle ergometry, during modulation of respiratory and muscle pumps. METHODS: Seven healthy females (19-32 yrs) sat at rest in a semi-supine position before the onset of 10 seconds of low-intensity cycling exercise (40 W). BF in the IVC (2-3 cm below the renal vein bifurcation) and the portal vein (PV; as an index of BF of the visceral organs) was measured by echo-Dopplar ultrasonography for 30 s, across the rest (20 s) - exercise (10 s) transition. HR and blood pressure were measured continuously by Finapres. As a control, subjects breathed spontaneously throughout (C condition). To reduce the influence of respiratory pump, the subjects did a 20 s breath-hold (at end-expiration) from 10 s before exercise onset (non-RP condition). In addition, muscle pumped BF was reduced by inflating a cuff (80 mmHg) on the upper thighs from 10 s before exercise onset (non-MP condition). RESULTS: The time course of BF in the IVC was not different (P>0.05) between C and non-RP conditions: an abrupt increase at exercise onset (C; from rest 639 to 2035 at first 2 s after exercise onset, non-RP; 565 to 1848 ml/min, P<0.05) followed by a rapid reduction to a constant level (approx. 1500-1600 ml/min during 5-10 s). BF in the PV was also similar between C and non-RP, decreasing rapidly after exercise onset. The exercise-induced increase BF in IVC was completely ablated in the non-MP condition (averaged 440 ml/min throughout exercise). CONCLUSION: The offsetting of positive and negative effects on BF during inspiration and exhalation appeared to provide no net gain to V-Return, suggesting that the respiratory pump has little influence on the dynamics of cardiac output at exercise onset. In contrast V-Return was determined predominantly by muscle pump - even during low-intensity cycling exercise. (Supported by JSPS #20700526 to MYE, #19650158 to YF and #18207019 to SK)

Slowed convective blood flow delivery speeds the onset of fatigue in highly‐oxidative skeletal muscle

It was the purpose of this study to examine the role of slowed blood flow kinetics at the onset of contractions on fatigue characteristics in highly‐oxidative skeletal muscle. A step change in metabolic rate was elicited by stimulating canine gastrocnemius‐plantaris muscles (n=6) via their sciatic nerves (6‐8 V, 0.2 ms duration, 50 Hz, 200 ms train) at a rate of 1/2 s. With arterial O2 concentration maintained constant, in random order trials, blood flow tau was set at a control transition speed between rest and contractions (determined in pilot work) of 20 s (CT20) or was slowed to tau values of 45 s (EX45) and 70 s (EX70). Resting and steady‐state (4 min of contractions) blood flows were not altered between the transition conditions. Peak force was not significantly different (p&gt;0.05) between conditions (mean±SD; CT20=293±64 N; EX45=265±64 N; EX70=256±56 N). Final normalized force was also not significantly different (p&gt;0.05) between conditions (CT20=87±6; EX45=88±7; EX70=88±11 %). Time from peak force to 50% of final force was significantly faster (p=0.0163) for EX45 (76±25 s) in comparison to CT20 (103±12 s). Time to 50% of final force was also significantly faster (p=0.0195) for EX70 (72±19.391 s) vs. CT20 while EX45 and EX70 were not significantly different. To our knowledge, these are the first experiments to alter only the time course of blood flow at contractions onset without changing the baseline and steady‐state flows, and our data suggest that fatigue occurs more rapidly with slowed blood flow only in the transition period at the onset of contractions in highly‐oxidative skeletal muscle.

Effects of gosha-jinki-gan, a kampo medicine, on peripheral tissue blood flow in streptozotocin-induced diabetic rats.

We examined the effects of Gosha-jinki-gan on peripheral tissue blood flow in streptozotocin-induced diabetic rats and its mechanism. The decrease in peroneal muscular blood flow in diabetic rats was dose-dependently improved by treatment with Gosha-jinki-gan (0.1-1 g/kg/day, p.o.) for 4 weeks. Investigation of the time course of blood flow in the hind paws revealed that single-dose of Gosha-jinki-gan (0.3, 1.5 g/kg, i.d.) increased peripheral blood flow. Peripheral blood flow-increasing effects of Gosha-jinki-gan (1.5 g/kg, i.d.) were reduced in combination with atropine (1 mg/kg, i.v.), and disappeared by pretreatment with NG-nitro-L-arginine methyl ester (10 mg/kg, i.v.). Levels of aortic guanosine 3',5'-cyclic monophosphate were dose-dependently increased by administration of Gosha-jinki-gan (0.3, 1.5 g/kg, p.o). These results suggest that Gosha-jinki-gan has vasodilating effects via increases in nitric oxide production. Gosha-jinki-gan may be useful for treating peripheral circulation disorders in the diabetic state.

Effects of Aconitum alkaloid kobusine and pseudokobusine derivatives on cutaneous blood flow in mice.

Aconitum alkaloids of the C20-diterpenoid type, kobusine (1) and pseudokobusine (2), and their acetyl, benzoyl, propionyl or cinnamoyl derivatives are examined for their peripheral vaso-activities by laser-flowmetrical measurement of the cutaneous blood flow in the hind foot of mice after intravenous administration. A dose-relationship of maximally increased blood flow after the administration of either of the Aconitum alkaloids existed. Kobusine 15-acetate (4), 11-benzoate (6) and 15-benzoate (7) were significantly effective at a low dose of 1 mg/kg, whereas the other kobusine derivatives were all inactive. Alkaloid 2, alone, and the 11-acetate (14), 15-acetate (15), 15-propionate (22) and 15-cinnamoate (25) were all active at 1 mg/kg and the effect of 14 at 5 mg/kg was remarkable. The activity of 2 was abolished by esterification of the hydroxyl group at C-6. Alkaloid 15 at 5 mg/kg showed a pattern of time course of blood flow in which the increase was rapidly replaced with a decrease below the basal flow, probably suggesting the effect of excessive doses. Conclusively, it is considered that the hydroxyl groups of alkaloids, especially a free OH group of 2 at C-6, are important for action on the peripheral vasculature leading to dilatation, and these results indicated that esterification of the hydroxyl group at C-15 with either acetate or benzoate may contribute to enhancement of the activity of the parent alkaloids.

Endogenous prostaglandins and osmotic water flow in the toad bladder.

Endogenous prostaglandins and osmotic water flow in the toad bladder.