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Arteriolar Diameter (arteriolar + diameter)
Selected AbstractsFrequency of Fish Consumption, Retinal Microvascular Signs and Vascular MortalityMICROCIRCULATION, Issue 1 2008Shweta Kaushik BMed (Hons) ABSTRACT Objective: Fish consumption has established cardiovascular and cerebrovascular benefits, but its effects on microvascular structure have not been examined in population-based studies. We investigated this association, in relation to vascular mortality in an Australian cohort (1992,2004). Methods: Of 3654 participants aged 49+ years, 2683 (73%) with available data were included. Retinal arteriolar and venular diameters were measured, and signs of arterio-venous nicking and retinopathy were assessed from digital retinal images. Fish consumption was evaluated using a food frequency questionnaire. Results: Both wider mean arteriolar diameter (p = 0.002) and narrower venular diameter (p = 0.02) were associated with increasing frequency of consuming any or oily fish, after adjusting for cardiovascular risk factors, diet, inflammatory factors and socioeconomic status. This association was mainly present in persons with hypertension. Greater frequency of fish consumption was associated with a reduced prevalence of arterio-venous nicking and a borderline significant trend for reduced retinopathy prevalence. Ten year stroke-related mortality was significantly lower in persons consuming fish at least once per week compared to less frequent consumption (hazard ratio 0.57, 95% CI: 0.35 to 0.93). Conclusions: Recent evidence shows that narrower arterioles and wider venules may predict vascular events. Our new findings suggest that the vascular protective effects of consuming fish could act, in part, by preventing pathological microvasculature change. [source] Blunting of rapid onset vasodilatation and blood flow restriction in arterioles of exercising skeletal muscle with ageing in male miceTHE JOURNAL OF PHYSIOLOGY, Issue 12 2010Dwayne N. Jackson Exercise capacity and skeletal muscle blood flow are diminished with ageing but little is known of underlying changes in microvascular haemodynamics. Further, it is not clear how the sympathetic nervous system affects the microcirculation of skeletal muscle with ageing or whether sex differences prevail in the regulation of arteriolar diameter in response to muscle contractions. In the gluteus maximus muscle of C57BL/6 mice, we tested the hypothesis that ageing would impair ,rapid onset vasodilatation' (ROV) in distributing arterioles (second-order, 2A) of old (20-month) males (OM) and females (OF) relative to young (3-month) males (YM) and females (YF). Neither resting (,17 ,m) nor maximum (,30 ,m) 2A diameters differed between groups. In response to single tetanic contractions at 100 Hz (duration, 100,1000 ms), ROV responses were blunted by half in OM relative to OF, YM or YF. With no effect in YM, blockade of ,-adrenoreceptors with phentolamine (1 ,m) restored ROV in OM. Topical noradrenaline (1 nm) blunted ROV in YM and YF to levels seen in OM and further suppressed ROV in OM (P < 0.05). To evaluate arteriolar blood flow, red blood cell velocity was measured in 2A of OM and YM; respective heart rates (353 ± 22 vs. 378 ± 15 beats min,1) and carotid arterial blood pressures (76 ± 3 vs. 76 ± 1 mmHg) were not different. Blood flows at rest (0.6 ± 0.1 vs. 1.6 ± 0.2 nl s,1) and during maximum dilatation (2.0 ± 0.8 vs. 5.4 ± 0.8 nl s,1) with sodium nitroprusside (10 ,m) were attenuated >60% (P < 0.05) in OM. Blood flow at peak ROV was blunted by 75,80% in OM vs. YM (P < 0.05). In response to 30 s of rhythmic contractions at 2, 4 and 8 Hz, progressive dilatations did not differ with age or sex. Nevertheless, resting and peak blood flows in YM were 2- to 3-fold greater (P < 0.05) than OM. We suggest that ageing blunts ROV and restricts blood flow to skeletal muscle of OM through subtle activation of ,-adrenoreceptors in microvascular resistance networks. [source] Arteriolar network architecture and vasomotor function with ageing in mouse gluteus maximus muscleTHE JOURNAL OF PHYSIOLOGY, Issue 2 2004Shawn E. Bearden Physical diminishes with ageing, but little is known of how the microvascular supply to skeletal muscle fibres is affected. To test the hypothesis that ageing alters blood flow control, we investigated network architecture and vasomotor responses of arterioles in the gluteus maximus muscle of young (2,3 months), adult (12,14 months) and old (18,20 months) C57BL6 male mice (n= 83) (Young, Adult and Old, respectively). Microvascular casts revealed that the total number, length and surface area of arteriolar segments (diameter, 10,50 ,m) were not significantly different across age-groups. However, for arterioles with diameter of 30 ,m, tortuosity and branch angles increased with age (P < 0.05). In anaesthetized mice, second-order (2A) distributing arterioles had similar resting (17 ± 1 ,m) and maximal (37 ± 1 ,m) diameters and similar responsiveness to cumulative (10,10,10,4m) superfusion of acetylcholine or phenylephrine. With superfusate oxygen level raised from 0 to 21%, 2A arteriolar constriction in Young (11 ± 1 ,m) was greater (P < 0.05) than Adult and Old (5 ± 1 ,m). Observed 1 mm upstream from microiontophoresis of ACh (1 ,A, 1 s), conducted vasodilatation was 10 ± 1 ,m in Young, 17 ± 1 ,m in Adult and 6 ± 1 ,m in Old (P < 0.05). With muscle contractions (2, 4 and 8 Hz; 30 s) arteriolar diameter increased similarly across age-groups (6 ± 1, 11 ± 1 and 18 ± 1 ,m, respectively). Muscle mass and active tension were similar across age-groups yet postcontraction vasodilatation recovered more rapidly in Old versus Adult and Young (P < 0.05). With arteriolar network architecture maintained during ageing, the impairment in conducted vasodilatation and attenuation of postcontraction vasodilatation may compromise exercise tolerance. [source] Anandamide mediates hyperdynamic circulation in cirrhotic rats via CB1 and VR1 receptorsBRITISH JOURNAL OF PHARMACOLOGY, Issue 7 2006L Moezi Background and purpose: Hyperdynamic circulation and mesenteric hyperaemia are found in cirrhosis. To delineate the role of endocannabinoids in these changes, we examined the cardiovascular effects of anandamide, AM251 (CB1 antagonist), AM630 (CB2 antagonist) and capsazepine (VR1 antagonist), in a rat model of cirrhosis. Experimental approach: Cirrhosis was induced by bile duct ligation. Controls underwent sham operation. Four weeks later, diameters of mesenteric arteriole and venule (intravital microscopy), arterial pressure, cardiac output, systemic vascular resistance and superior mesenteric artery (SMA) flow were measured after anandamide, AM251 (with or without anandamide), AM630 and capsazepine administration. CB1, CB2 and VR1 receptor expression in SMA was assessed by western blot and RT-PCR. Key results: Anandamide increased mesenteric vessel diameter and flow, and cardiac output in cirrhotic rats, but did not affect controls. Anandamide induced a triphasic arterial pressure response in controls, but this pattern differed markedly in cirrhotic rats. Pre-administration of AM251 blocked the effects of anandamide. AM251 (without anandamide) increased arterial pressure and systemic vascular resistance, constricted mesenteric arterioles, decreased SMA flow and changed cardiac output in a time-dependent fashion in cirrhotic rats. Capsazepine decreased cardiac output and mesenteric arteriolar diameter and flow, and increased systemic vascular resistance in cirrhotic rats, but lacked effect in controls. Expression of CB1 and VR1 receptor proteins were increased in cirrhotic rats. AM630 did not affect any cardiovascular parameter in either group. Conclusions and implications: These data suggest that endocannabinoids contribute to hyperdynamic circulation and mesenteric hyperaemia in cirrhosis, via CB1 - and VR1-mediated mechanisms. British Journal of Pharmacology (2006) 149, 898,908. doi:10.1038/sj.bjp.0706928 [source] Losartan and Ozagrel Reverse Retinal Arteriolar Constriction in Non-Obese Diabetic MiceMICROCIRCULATION, Issue 5 2008Seungjun Lee ABSTRACT Objective: Reductions in retinal blood flow are observed early in diabetes. Venules may influence arteriolar constriction and flow; therefore, we hypothesized that diabetes would induce the constriction of arterioles that are in close proximity to venules, with the constriction mediated by thromboxane and angiotensin II. Methods: Using nonobese diabetic (NOD) mice, retinal measurements were performed three weeks following the age at which glucose levels exceeded 200 mg/dL, with accompanying experiments on age-matched normoglycemic NOD mice. The measurements included retinal arteriolar diameters and red blood cell velocities and were repeated following an injection of the thromboxane synthase inhibitor, ozagrel. Mice were subdivided into equal groups and given drinking water with or without the angiotensin II receptor antagonist, losartan. Results: Retinal arterioles were constricted in hyperglycemic mice, with a significant reduction in flow. However, not all arterioles were equally affected; the vasoconstriction was limited to arterioles that were in closer proximity to venules. The arteriolar vasoconstriction (mean arteriolar diameters = 51 ± 1 vs. 61 ± 1 , m in controls; p < 0.01) was eliminated by both ozagrel (61 ± 2 , m) and losartan (63 ± 2 , m). Conclusions: Venule-dependent arteriolar vasoconstriction in NOD mice is mediated by thromboxane and/or angiotensin II. [source] Static Magnetic Fields Affect Capillary Flow of Red Blood Cells in Striated Skin MuscleMICROCIRCULATION, Issue 1 2008Gunnar Brix ABSTRACT Blood flowing in microvessels is one possible site of action of static magnetic fields (SMFs). We evaluated SMF effects on capillary flow of red blood cells (RBCs) in unanesthetized hamsters, using a skinfold chamber technique for intravital fluorescence microscopy. By this approach, capillary RBC velocities (vRBC), capillary diameters (D), arteriolar diameters (Dart), and functional vessel densities (FVD) were measured in striated skin muscle at different magnetic flux densities. Exposure above a threshold level of about 500 mT resulted in a significant (P < 0.001) reduction of vRBC in capillaries as compared to the baseline value. At the maximum field strength of 587 mT, vRBC was reduced by more than 40%. Flow reduction was reversible when the field strength was decreased below the threshold level. In contrast, mean values determined at different exposure levels for the parameters D, Dart, and FVD did not vary by more than 5%. Blood flow through capillary networks is affected by strong SMFs directed perpendicular to the vessels. Since the influence of SMFs on blood flow in microvessels directed parallel to the field as well as on collateral blood supply could not be studied, our findings should be carefully interpreted with respect to the setting of safety guidelines. [source] | ||||||||||