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Biomedical subjects

R S Reneman

Publications and source records attributed to R S Reneman.

At least 37 records · Page 2Linked to original sources
PubMed1999

An in vivo model for studying the dynamics of intracellular free calcium changes in slow- and fast-twitch muscle fibres.

The understanding of the regulation of the free cytosolic [Ca2+] ([Ca2+]i) in skeletal muscle is hampered by the lack of techniques for quantifying free [Ca2+]i in muscle fibres in situ. We describe a model for studying the dynamics of free [Ca2+]i in the fast-twitch extensor digitorum longus (EDL) and the slow-twitch soleus (SOL) muscles of the rat in vivo using caffeine superfusion to induce changes in free [Ca2+]i. We assumed that differences in sensitivity between the two muscle types for this substance reflect differences in intracellular Ca2+ handling in the fibres of which these muscles consist. The Indo-1 ratiometric method, using intravital microscopy with incident light, was adapted to measure free [Ca2+]i in vivo. Fluorescence images were collected by means of a digital camera. Caffeine superfusion at 37 degrees C for 2 min, at concentrations of 1, 2, 5, 10 or 20 mmol/l, induced a concentration-dependent increase in free [Ca2+]i and revealed differences in caffeine sensitivity between the muscle types, with the SOL being more sensitive. In a separate set of experiments the contracture threshold, as assessed by topical application of caffeine, was determined in both muscle types. EDL had a higher threshold for developing contracture than SOL. These finding are in agreement with previous in vitro studies. We may conclude that the dynamics of free [Ca2+]i can be assessed reliably in intact mammalian muscle in vivo.

Animals↗
PubMed1999

Evaluation of off-line automated intima-media thickness detection of the common carotid artery based on M-line signal processing.

Intima-media thickness (IMT) measurements have gained increasing attention, because IMT is assumed to represent the endothelial adaptive response to physiological and pathophysiological processes. The main aim of the present study was to assess the intrasubject intrasession variability of a new off-line automated radio frequency (RF) IMT method in comparison with an already established off-line manual B-mode IMT method. IMT also was assessed by means of an on-line manual B-mode and an on-line manual RF IMT method. We investigated posterior wall IMT 0-1 cm proximal to the bulb in both common carotid arteries of 16 young (20-31 y; mean 25 y) female and male and 13 elderly (51-65 y; mean 56 y) female volunteers. Two commercially available ultrasound devices (Pie Medical Scanner 200 and Ultramark 9) were used to assess the effects of signal processing on the off-line automated RF IMT method. Intrasubject intrasession variability was determined using the standard deviation to evaluate and compare the various methods. Spearman rank correlation coefficients and Bland and Altman bias and limits of agreement were calculated to objectivate the comparability between the various methods. Intrasubject intrasession variation of IMT estimates was not statistically different between any of the methods. We observed a good comparability between the commonly used off-line manual B-mode IMT method and the off-line automated RF IMT method at the level of the common carotid artery.

Adult↗
PubMed1999

Three months use of third-generation oral contraceptives does not affect artery wall properties.

In several studies, artery wall properties have been shown to differ between men and women. It has been hypothesized that these differences may result from hormonal influences but, in a previous study, we were unable to detect any influence of the menstrual cycle on artery wall properties. Therefore, we investigated the differences in artery wall properties, if any, between the menstrual cycle and the use of a third-generation oral contraceptive for 3 months. We investigated the right common carotid (CCA) and femoral (CFA) arteries of normotensive young (18-25-y-old) women volunteers (n = 14). The arterial cross-sectional distensibility and compliance coefficients were determined by means of a specially designed ultrasonic wall-tracking device and automatic brachial artery cuff blood-pressure measurements. The menstrual cycles and the cycles during oral contraceptive use (30 microg ethinylestradiol and 75 microg gestodene) were monitored by ultrasonographic evaluation and the assessment of plasma levels of 17beta-oestradiol and progesterone. The distensibility and cross-sectional compliance coefficients of both the CCA and CFA did not differ significantly between the menstrual cycle and the use of oral contraceptives, despite different ovarian hormone levels. Brachial arterial blood pressure was also not affected. We conclude that 3 months use of a third-generation oral contraceptive does not influence the wall properties of peripheral arteries and cannot explain the observed difference between genders. The absence of a rise in blood pressure and the low androgenic profile of this specific oral contraceptive may have contributed to our findings.

Adolescent↗
PubMed1999

Microcirculatory investigations to determine the effect of spinal cord stimulation for critical leg ischemia: the Dutch multicenter randomized controlled trial.

PURPOSE: Patients with non-reconstructable critical limb ischemia generally undergo medical treatment only to prevent or postpone amputation. There is some evidence that spinal cord stimulation (SCS) stimulates ischemic wound healing. Thus, this could benefit limb survival through improved skin perfusion. We investigated the effect of SCS versus conservative treatment on skin microcirculation in relation to treatment outcome in patients with non-reconstructable critical limb ischemia. METHODS: Standard medical treatment plus SCS was compared with only standard medical treatment in a multicenter randomized controlled trial comprised of 120 patients with surgically non-reconstructable chronic rest pain or ulceration. We investigated skin microcirculation by means of capillary microscopy, laser Doppler perfusion, and transcutaneous oxygen measurements in the foot. The microcirculatory status just before treatment was classified in three categories (poor, intermediate, and good) and was related to limb survival after a minimum follow-up period of 18 months. RESULTS: Clinical parameters, peripheral blood pressures, and limb survival rates showed no significant differences between the SCS and standard groups during the follow-up period. In both treatment groups, amputation frequency after 18 months was high in patients with an initially poor microcirculatory skin perfusion (SCS 80% vs standard treatment 71%; NS) and low in those with a good skin perfusion (29% vs 11 %, respectively; NS). In patients with an intermediate skin microcirculation amputation, frequency was twice as low in patients additionally treated with SCS as in the standard treatment group (48% vs 24%; P =.08). In these patients, microcirculatory reactive hyperemia during the follow-up period reduced in the standard group but not in the SCS group (P <.01). CONCLUSION: Selection on the basis of the initial microcirculatory skin perfusion identifies patients in whom SCS can improve local skin perfusion and limb survival.

Adult↗
PubMed1999

Prediction of imminent amputation in patients with non-reconstructible leg ischemia by means of microcirculatory investigations.

PURPOSE: We investigated the usefulness of skin microcirculatory investigations to predict imminent major amputation in patients with non-reconstructible critical limb ischemia. METHODS: One hundred eleven patients with non-reconstructible chronic rest pain or small ulcers and an ankle blood pressure of 50 mm Hg or less or an ankle-to-brachial pressure index of 0.35 or less were included. Nailfold capillary microscopy (CM; big toe, sitting), transcutaneous oxygen pressure (TcpO2; forefoot, supine; 44 degrees C), and laser Doppler perfusion measurements (LD; pulp of big toe, supine) were performed at rest and during reactive hyperemia. Patients were classified according to their skin microcirculatory status just before the start of the treatment in three groups: those with a "good," "intermediate," or "poor" microcirculation, according to a combination of predefined cutoff values (Poor: capillary density less than 20/mm2, absent reactive hyperemia in CM and LD, TcpO2 less than 10 mm Hg; good: capillary density of 20/mm2 or more, present reactive hyperemia in CM and LD, TcpO 2 of 30 mm Hg or more). Subsequently, patients received maximum conservative therapy from the surgeon, who was unaware of the microcirculatory results. After a follow-up period of as long as 36 months, limb survival and disposing factors were analyzed and compared with the initial microcirculatory status. RESULTS: Cox regression analysis showed a significant prognostic value of the microcirculatory classification (hazard ratio = 0.28, P <.0001), but not of the Fontaine stage, ankle blood pressure, or the presence of diabetes mellitus for the occurrence of an amputation. Positive and negative predictive values were 73% and 67%, respectively. The cumulative limb survival at 6 and 12 months was 42% and 17% in the poor microcirculatory group, 80% and 63% in the intermediate microcirculatory group, and 88% and 88% in the good microcirculatory group ( P <.0001, log-rank). CONCLUSION: Microcirculatory screening and classification is useful in detecting non-reconstructible critical ischemia that requires amputation, which is not detectable by means of the clinical stage or blood pressure parameters. Most of the poor patient group will require amputation. In the intermediate and good groups, nonsurgical treatment appears sufficient for limb salvage.

Aged↗
PubMed1999

An integrated system for the non-invasive assessment of vessel wall and hemodynamic properties of large arteries by means of ultrasound.

OBJECTIVES: To integrate methods for non-invasive assessment of vessel wall properties (diastolic diameter, distension waveform and intima-media thickness) and hemodynamic properties (blood flow velocity and shear rate distribution) of large arteries by means of dedicated ultrasound signal processing. METHODS: we have developed an arterial laboratory (ART-lab) system. ART-lab consists of software running on a standard personal computer, equipped with a data acquisition card for the acquisition of radio frequency (RF) ultrasound signals obtained with a conventional echo scanner. It operates either (1) off-line or (2) in real-time. Real-time operation is restricted to the assessment of vessel wall properties because of limitations in computational power. RESULTS: This paper provides an overview of ART-lab ultrasound radio frequency data acquisition and dedicated RF-signal processing methods. The capabilities of the system are illustrated with some typical applications. CONCLUSIONS: ART-lab in real-time mode is a useful tool for monitoring arterial vessel wall dynamics, while off-line it can be employed to investigate the elastic vessel wall properties in combination with hemodynamics, such as blood flow velocity and shear rate distribution.

Arteries↗
PubMed1999

Kinematic analysis of left ventricular deformation in myocardial infarction using magnetic resonance cardiac tagging.

The Magnetic Resonance (MR) tagging technique provides detailed information about 2D motion in the plane of observation. Interpretation of this information as a reflection of the 3D motion of the entire cardiac wall is a major problem. In finite element models of the mechanics of the infarcted heart, an infarcted region causes motional asymmetry, extending far beyond the infarct boundary. Here we present a method to quantify such asymmetry in amplitude and orientation. For this purpose images of a short-axis cross-section of the ejecting left ventricle were acquired from 9 healthy volunteers and 5 patients with myocardial infarction. MR-tags were applied in a 5 mm grid at end-diastole. The tags were tracked by video-image analysis. Tag motion was fitted to a kinematic model of cardiac motion. For the volunteers and the patients the center of the cavity displaced by about the same amount (p = 0.11) during the ejection phase: 3.8 +/- 1.4 and 3.0 +/- 0.9 mm (mean +/- sd), respectively. Cross-sectional rotation and the decrease in cross-sectional area of the cavity were both greater in the volunteers than in the patients: 6.4 +/- 1.5 vs. 3.0 +/- 0.8 degrees (p < 0.001), and 945 +/- 71 vs. 700 +/- 176 mm2 (p = 0.02), respectively. In the patients, asymmetry of wall motion, as expressed by a sine wave dependency of contraction around the circumference, was significantly enlarged (p = 0.02). The proposed method of kinematic analysis can be used to assess cardiac deformation in humans. We expect that by analyzing images of more cross-sections simultaneously, the 3D location and the degree of infarction can be assessed efficiently.

Biomechanical Phenomena↗
PubMed1999

Effects of venous pressure and posture on skin capillary perfusion.

BACKGROUND: Various vasoconstriction mechanisms after a change in posture are involved in controlling skin blood flow and capillary transmural pressure to maintain adequate transcapillary exchange. The role of venous orthostatic pressure in the regulation of capillary nutritive perfusion, however, is less clear. DESIGN: We investigated capillary perfusion in 30 healthy subjects using intravital capillary microscopy of the big toenail-fold. Measurements were made in the supine and the sitting positions before and after incremental elevation of venous resistance, and thus the pre- to post-capillary pressure difference, by inflating a cuff around the ankle. RESULTS: On dependency, median capillary density rose (P < 0.0001), whereas red blood cell perfusion decreased (P < 0.0001). Cuff inflation of 30-60 mmHg in the supine position induced similar phenomena. Repeatedly, the same capillaries were found to be recruited after an increase in transmural pressure. CONCLUSIONS: We conclude that post-capillary pressure appears to be an important factor in the regulation of capillary perfusion, because an increase in venous resistance mimics the effects of dependency. The findings in this study support the theory of 'minimum perfusion pressure' for each capillary to be perfused with erythrocytes.

Adult↗
PubMed1999

In the femoral artery bifurcation, differences in mean wall shear stress within subjects are associated with different intima-media thicknesses.

In elastic arteries, intima-media thickening is more pronounced in areas with low than with high mean and peak wall shear stress. These findings in elastic arteries are not necessarily representative of the situation in muscular arteries. The former arteries have to store volume energy, whereas the latter are mainly conductive vessels. It was the aim of the present study to investigate noninvasively whether differences in wall shear stress within a muscular artery bifurcation, if any, were associated with different intima-media thicknesses (IMTs). The effect of age on the possible differences was assessed as well. We determined IMT and mean, peak systolic, and the maximum cyclic change in shear stress near the posterior wall in the common (FC) and the superficial (FS) femoral artery 20 to 30 mm from the flow divider in 54 presumed healthy subjects between 21 and 74 years of age. Results were considered in terms of intrasubject differences. Before the study, the reliability of the ultrasonic system to assess wall shear rate and IMT was determined in terms of intrasubject variability. IMT at the posterior wall was significantly larger in the FC than in the FS, probably owing to the significantly lower mean wall shear stress at this site in the FC. The relative differences in IMT and mean wall shear stress between FC and FS were independent of age. The difference in wall shear stress between both arteries can likely be explained by a different influence of reflections. In both the FC and FS, mean, peak systolic, and maximum cyclic change in shear stress near the posterior wall did not change significantly with age, whereas IMT did increase significantly with age.

Adult↗
PubMed1999

Menopausal status and distensibility of the common carotid artery.

Although several studies have shown that exogenous estrogens have beneficial effects on arterial characteristics, the effect of endogenous estrogen on the vascular system is still unknown. In this study, distensibility, an indicator of arterial elasticity, of the common carotid artery was compared in pre- and postmenopausal women. The study comprised 93 premenopausal and 93 postmenopausal women of similar age (range, 43 to 55 years). Women were selected from respondents to a mailed questionnaire about the menopause, which was sent to all women aged 40 to 60 years in the Dutch town of Zoetermeer (n=12 675). Postmenopausal women who were at least 3 years past natural menopause or whose menses had stopped naturally before age 48, were age-matched with premenopausal women with regular menses and without menopausal complaints. The selection aimed at maximizing the contrast in estrogen status between pre- and postmenopausal women of the same age. Distensibility of the carotid artery was measured noninvasively with B-mode ultrasound and a vessel wall movement detector system. Arterial distensibility is expressed as the change in arterial diameter (distension, DeltaD) with the cardiac cycle, adjusted for lumen diameter, pulse pressure, and mean arterial blood pressure. Compared with premenopausal women, postmenopausal women had significantly lower arterial distension (DeltaD 370.5 microm [SE 9.5] versus 397.3 microm [SE 9.6]). These results suggest that the distensibility of the common carotid artery is negatively affected by natural menopause in presumed healthy women.

Adult↗
PubMed1999

Non-invasive measurement of mechanical properties of arteries in health and disease.

Major conduit arteries should, by their elastic nature, be able to store blood volume temporarily during systole and release it during diastole. This reduces the systolic blood pressure required for the flow of a given volume quantity and gradually suppresses the pulsatile flow pattern. The haemodynamic characteristics of arteries have consequences for the load of the heart but also for the mechanical load of the arterial wall. The repetitive stretching of the wall (strains of up to 10 per cent) may cause fragmentation of the elastic fibres in the wall, modifying wall elasticity. To maintain wall stress the elastic arteries respond with a diameter increase in combination with an increase of arterial wall thickness. A larger diameter for a smaller distension (change in artery diameter from diastole to systole) will restrict the reduction in storage capacity. Alternatively, pulse pressure may go up increasing the mechanical load on the wall. In recent years various methods have been developed to assess and monitor the above interaction. Most of these methods are based on ultrasound techniques because of its wide availability and its non-invasive and non-traumatic nature. Presently these techniques enable the assessment of wall thickness, diastolic diameter, distension waveform, i.e., the tie-dependent change in diameter, the relative pulsatile increase in diameter, and pulse wave velocity, for elastic and muscular arteries in humans but also in small animals such as rats and mice. The present paper discusses the techniques in more detail.

Arteries↗
PubMed1998

Asynchronous electrical activation induces asymmetrical hypertrophy of the left ventricular wall.

BACKGROUND: Asynchronous electrical activation, induced by ventricular pacing, causes regional differences in workload, which is lower in early- than in late-activated regions. Because the myocardium usually adapts its mass and structure to altered workload, we investigated whether ventricular pacing leads to inhomogeneous hypertrophy and whether such adaptation, if any, affects global left ventricular (LV) pump function. METHODS AND RESULTS: Eight dogs were paced at physiological heart rate for 6 months (AV sequential, AV interval 25 ms, ventricular electrode at the base of the LV free wall). Five dogs were sham operated and served as controls. Ventricular pacing increased QRS duration from 47.2+/-10.6 to 113+/-16.5 ms acutely and to 133.8+/-25.2 ms after 6 months. Two-dimensional echocardiographic measurements showed that LV cavity and wall volume increased significantly by 27+/-15% and 15+/-17%, respectively. The early-activated LV free wall became significantly (17+/-17%) thinner, whereas the late-activated septum thickened significantly (23+/-12%). Calculated sector volume did not change in the LV free wall but increased significantly in the septum by 39+/-13%. In paced animals, cardiomyocyte diameter was significantly (18+/-7%) larger in septum than in LV free wall, whereas myocardial collagen fraction was unchanged in both areas. LV pressure-volume analysis showed that ventricular pacing reduced LV function to a similar extent after 15 minutes and 6 months of pacing. CONCLUSIONS: Asynchronous activation induces asymmetrical hypertrophy and LV dilatation. Cardiac pump function is not affected by the adaptational processes. These data indicate that local cardiac load regulates local cardiac mass of both myocytes and collagen.

Animals↗
PubMed1998

Biphasic effect of heat stress pretreatment on ischemic tolerance of isolated rat hearts.

Improvement of post-ischemic cardiac function 24 h after heat stress has been attributed to the increased cardiac tissue content of the inducible heat stress protein hsp70. Previous studies indicated that hsp70 is already significantly upregulated a few hours after heat stress. To delineate the relationship between hsp70 tissue content and heat stress-induced cardioprotection in the early time frame after heat stress, if any, post-ischemic functional recovery of isolated, ejecting rat hearts and the actual cardiac hsp70 content were investigated 0.5, 3, 6 and 24 h after heat stress (42 degrees C for 15 min). Recovery (% of pre-ischemic value) of cardiac output, left ventricular developed pressure, and positive and negative left ventricular dP/dtmax was studied during reperfusion after 45 min of global ischemia. Anesthetized non heat-stressed rats served as controls. The recovery of all hemodynamic variables was significantly worse in hearts isolated 30 min after heat stress than in control hearts. When the time interval between heat treatment and the ischemic episode was prolonged, a gradual improvement of post-ischemic functional recovery was observed. Only 24 h after heat treatment functional recovery was significantly better in the heat-stressed than in the control group. Compared to control hearts (0.27+/-0.10 mg/g total protein) cardiac hsp70 content was already significantly increased 0.5 h after heat stress (0.51+/-0.03 mg/g total protein). The cardiac hsp70 content further increased to 0. 70+/-0.11, 0.89+/-0.35 and 1.01+/-0.25 mg/g total protein, at 3, 6 and 24 h after heat stress, respectively. The present findings clearly show that heat stress is associated with a fast rise in the myocardial hsp70 content which, however, is not uniquely correlated with improved ischemia tolerance of the treated hearts, which only occurs 24 h later.

Animals↗
PubMed1998

Transport of long-chain fatty acids across the muscular endothelium.

Both skeletal and cardiac muscle cells rely heavily on the oxidation of long-chain fatty acids to utilize chemically stored energy for contractile work. Under normal conditions fatty acids are continuously supplied from the microvascular compartment to the contracting myocytes. Exogenous fatty acids are transported to muscle tissue via the blood either complexed to albumin or covalently bound in triacylglycerols forming the neutral lipid core of circulating lipoproteins such as chylomicrons or very low-density lipoproteins. The first barrier met by fatty acids on their way from the vascular compartment to the myocytes is the endothelium constituting the capillary wall. After dissociation of the albumin-fatty acid complex or release from the triacylglycerol core of lipoproteins, fatty acids most likely transverse the endothelium by crossing the luminal membrane, the cytosol, and subsequently the abluminal wall of the endothelial cell. Transfer through the interendothelial clefts or lateral diffusion within the phospholipid bilayer of the endothelial plasmalemma should be considered as inconsequential. The mechanism responsible for transmembrane movement of fatty acids is incompletely understood, although recent findings suggest the involvement of a number of membrane-associated proteins. Kinetic studies have revealed that interaction of the albumin-fatty acid complex with the endothelial membrane may accelerate the dissociation of the complex, which facilitates the uptake of fatty acids by the endothelium. Albumin-binding proteins (ABP) might be instrumental in this interaction. Moreover, plasmalemmal fatty acid-binding protein (FABPpm), fatty acid translocase (FAT) and fatty acid-transport protein (FATP) are putatively involved in transmembrane movement of the fatty acid molecules. Diffusion through the endothelial cytosol might be facilitated by a cytoplasmic fatty acid-binding protein, the type of which may be related to the epithelial fatty acid-binding protein (E-FAPBc).

Animals↗
PubMed1998

The role of mast cells and histamine in leukocyte-endothelium interactions in four rat strains.

The objective of the present study was to determine the role of mast cells and histamine in leukocyte-endothelium interactions in mesenteric venules of four rat strains: Brown Norway, Lewis, Sprague-Dawley and Wistar. Intravital microscopy showed that the mast cell stabilizer cromoglycate (5 mg/kg i.v. just before exteriorization of the mesentery) did not affect the baseline level and velocity of leukocyte rolling in any of the four strains. This finding is in agreement with the observation that cromoglycate pretreatment only slightly influenced mast cell degranulation in all strains except the Brown Norway. After mast cell stabilization, only in Sprague-Dawley did topical administration of histamine (10(-4) M) result in a significant increase in the level of leukocyte rolling and a decrease in the rolling velocity compared with the time control. Histamine induced leukocyte adhesion only in the Brown Norway strain. In conclusion, the hypothesis presented in other studies, that degranulation of mast cells, and more specifically the release of histamine, is of major importance for the induction of leukocyte-endothelium interactions in rat mesenteric venules is not generally applicable; the present study shows a clear strain dependency.

Animals↗
PubMed1998

Transcriptional regulation of metabolic processes: implications for cardiac metabolism.

Under normal conditions the oxidation of fatty acids and glucose covers, respectively, approximately 65% and 30% of the energy demand of the beating heart. Evidence is accumulating that various pathophysiological conditions are associated with overt changes in cardiac energy metabolism. For instance, in diabetes cardiac energy conversion relies even more on fatty acid than on glucose oxidation. In contrast, during cardiac hypertrophy the opposite takes place, i. e. the utilization of carbohydrates increases at the expense of lipids. The mechanisms responsible for and the significance of these metabolic adaptations are largely unknown. A growing body of evidence indicates that these metabolic adaptations are brought about, at least in part, through adjustments in the rate of transcription of genes encoding proteins involved in substrate transport and metabolism. There are reasons to believe that the transcriptional regulation of these "metabolic genes" is subject to modulation by metabolites per se, i.e. by oxygen, glucose and fatty acids. In this review the concept of metabolic remodelling as an important facet of cardiac adaptation to chronic pathophysiological conditions is introduced and the putative roles of metabolites in transcriptional regulation in the heart are considered.

Animals↗
PubMed1998

Wall shear stress in the human common carotid artery as function of age and gender.

OBJECTIVES: It has been postulated that in the arterial system mean wall shear stress is maintained at a constant value. The present study was performed to investigate the level of wall shear stress in the common carotid artery (CCA) as function of age and possible interactions between diameter and storage capacity, defined as the absolute area change per heart beat, with mean wall shear stress. METHODS: Wall shear stress (wall shear rate multiplied by whole blood viscosity) was assessed in the right CCA of 111 presumed healthy male (n = 56) and female (n = 55) volunteers, varying in age between 10 and 60 years. Wall shear rate was measured with a high resolution ultrasound system. Simultaneously, arterial diameter and storage capacity were determined. Whole blood viscosity was calculated from haematocrit, plasma viscosity and shear rate. RESULTS: From the second to the sixth age decade peak wall shear stress was significantly higher in males than in females and decreased from 4.3 Pa to 2.6 Pa (r = -0.56, p < 0.001) in males and from 3.3 Pa to 2.5 Pa (r = -0.54, p < 0.001) in females. Mean wall shear stress tended to decrease from 1.5 Pa to 1.2 Pa (r = -0.26, p = 0.057) in males and decreased significantly from 1.3 Pa to 1.1 Pa (r = -0.30, p = 0.021) in females. No significant difference in mean wall shear stress was found between males and females in any age decade. The diameter of the CCA increased significantly in both males (r = 0.26, p < 0.05) and females (r = 0.40, p < 0.003). Storage capacity decreased significantly in both sexes (males: r = -0.63, p < 0.001; females: r = -0.68, p < 0.001). CONCLUSIONS: These observations suggest that the reduction in mean wall shear stress with age results from the concomitant increase in diameter in an attempt of the arterial system to limit the reduction in storage capacity of the arterial system with increasing age.

Adolescent↗