Increase In Internal Diameter Research Articles

Placental Macrovascular Pattern from Pregnancies with Maternal Hypertensive and Fetal Growth Capacity Complications.

The research included placentas from singleton pregnancies complicated by preeclampsia and/or fetal growth restriction, women delivered in medical institutions in Karaganda city (Kazakhstan). Placentas were divided into three groups: PE (n = 59), isolated FGR (n = 24), and PE with FGR (n = 41). The control group consisted of normotensive pregnancies, compared by gestation period. Placental examination and selection of placental tissue fragments were carried out in accordance with the consensus recommendations of the Amsterdam Placental Workshop Group. The sections were stained with hematoxylin and eosin and Masson trichrome. Morphometric measurements were performed using ImageJ software version 1.52p. Our data showed that, in the PE group, there was a significant decrease in the wall thickness of the proximal and distal vessels with an increase in internal diameter compared with the control group (p < 0.01). In the PE + FGR group, there was a thickening of the wall of the proximal part of the vessels with a decrease in their lumen and a decrease in the wall thickness of the vessels with an increase in the lumen in the distal part compared with the control group (p < 0.01). Two histopatterns of placental macrovessels in preeclampsia were revealed: the histophenotype of diffuse (proximal and distal) ectatic macroangiopathy with a thin vascular wall with a decrease in the thickness of the muscle layer and the histophenotype of proximal fibromuscular sclerosis with vascular obliteration/spasm and distal ectatic macroangiopathy. We believe that significant structural differences in vascular remodeling may reflect the different temporal and spatial nature of the pathological factor. Future research is needed to investigate the associations between histopatterns of placental vascular remodeling in preeclampsia and long-term perinatal/maternal outcomes.

Relationship between internal diameter and vasoconstriction in human varicose veins.

Varicose veins are common lower extremity venous disorders characterized by dilated veins and incompetent valves. Although maintaining the required vein wall tone for adaptive responses depends on a proper contractile function of the human saphenous smooth muscle, the contractile properties of varicose veins are mostly unknown. We investigated the relationship between contractile responses and the internal diameter of human saphenous varicose veins. The absolute contractile forces induced by potassium chloride (KCl, 60 mmol/l), serotonin (5-hydroxytryptamine [5-HT], 10 µmol/l), and noradrenaline (NAd, 10 µmol/l) were similar between normal saphenous veins (control) and varicose veins. When the contractile forces were normalized to the internal diameter in each preparation, the contractile responses to these stimuli were significantly lower in varicose veins than in the control veins. Furthermore, varicose veins were divided into three groups according to their internal diameter (group 1, 3-4.5 mm; group 2, 4.5-6 mm; group 3, >6 mm). The contractile responses induced by KCl, 5-HT, and NAd did not differ between groups 1 and 2 and the control group, while the contractile responses in group 3 were significantly lower than those in the control group. Moreover, the contractions induced by KCl and NAd in Group 3 were smaller than those in group 1 or group 2. This trend was also observed in 5-HT-induced contractions, although the results were not statistically significant. In conclusion, contractile responses in varicose veins may be altered by an increase in internal diameter, although adequate contractile responses are preserved in some diameters.

Effect of local warming for arterial catheterization in adult cardiac surgery: a randomized controlled trial.

The increase in internal diameter (ID) and cross-sectional area (CSA) may facilitate better arterial catheterization. Since an increase in body temperature can cause peripheral vasodilation, we aimed to determine if local warming of the radial artery (RA) catheterization site could improve the success rate of catheterization. This randomized, controlled study enrolled 160 patients aged >18 years who were scheduled for heart surgery. They were randomized into non-warming palpation (NP), non-warming ultrasonography-guided (NU), warming palpation (WP), and warming ultrasonography-guided (WU) groups. After induction, the baseline RA ultrasonography images were collected. In the warming groups (WP, WU), local warming was applied on the catheterization site. Before catheterization, the RA ultrasonography images were collected. The primary outcome was the first-attempt success rate. The secondary outcomes included the ID and CSA of the RA and overall complications. Totally 152 adults were included in the analysis. The first-attempt success rates in each of the four groups were not significantly different (P=0.985). The rates in the non-warming (NP + NU) and warming (WP + WU) groups were also not different (P=0.827). Unlike non-warming group, the warming group had increased ID (3.34±0.78 vs. 3.02±0.73 mm; P<0.001) and CSA (6.9±2.8 vs. 5.8±2.4 mm2; P<0.001) compared with baseline. Local warming for peripheral artery catheterization does not increase the first-attempt success rate in adults undergoing cardiac surgery; however, it can increase the ID and CSA of the RA and prevent vasospasm. ClinicalTrials.gov NCT04969692.

Using APRIS for QA/QC of Newly Fabricated Heat Exchangers

Acoustic Pulse Reflectometry (APR) has been applied extensively to tubular systems in research laboratories, for purposes of measuring input impedance, bore reconstruction, and fault detection. Industrial applications have been mentioned in the literature, though they have not been widely implemented. Academic APR systems are extremely bulky, often employing sophisticated set up, which limits their industrial use severely. Furthermore, leak detection methods described in the literature are based on indirect methods, by carrying out bore reconstruction and finding discrepancies between the expected and reconstructed bore. Here, we describe an APR system which is named APRIS designed specifically for detecting faults commonly found in industrial tube systems such as heat exchangers, condensers and boilers leaks, increase in internal diameter caused by wall thinning, and constrictions by blockages or deposits or scales. The system employs extremely hardware setup, making it extremely portable, but creating a large degree of overlap between forward and backward propagating waves in the system. A series of patented algorithmic innovations enable the system to perform the wave separation mathematically, and then identify the above faults automatically, with a measurement time on the order of 10 seconds per tube.

Flow-Mediated Dilatation of the Brachial Artery for Assessing Endothelial Dysfunction in Children with Moyamoya Disease

Background: Moyamoya disease is a progressive, steno-occlusive arteriopathy involving the internal carotid artery and its branches and causing recurrent stroke episodes in children. Patients with moyamoya disease may be more susceptible to influences that cause endothelial dysfunction. We evaluated whether flow-mediated dilatation (FMD) of the brachial artery is useful for assessing endothelial dysfunction in children with moyamoya disease. Methods: This prospective observational study included 30 children with moyamoya disease and 30 controls. After anesthesia induction, a blood pressure cuff was applied to the forearm and inflated to a pressure that was 50 mm Hg above the baseline systolic blood pressure for 5 min. From 30 s before to 2 min after deflation, the brachial artery diameter was recorded on ultrasound. The increase in internal diameter was expressed as the percentage of the baseline diameter. Results: Fifty-nine patients were analyzed. Baseline brachial artery diameters in the moyamoya and control groups were 3.00 and 3.37 mm, respectively (p = 0.004; difference, 0.38; 95% CI 0.12–0.63), while those after deflation were 3.06 and 3.48 mm, respectively (p = 0.003; difference, 0.42; 95% CI 0.15–0.68). The percent change of the baseline diameter value was 4.0% in the disease group and 8.3% in the control group (p = 0.10). There was a group and time interaction for brachial artery diameter (p = 0.01; main effect of group, p = 0.009; main effect of time, p = 0.007). Conclusion: FMD of the brachial artery may not be enough for determining endothelial dysfunction under general anesthesia in children with moyamoya disease.

Characteristic chest CT findings for progressive cavities in Mycobacterium avium complex pulmonary disease: a retrospective cohort study

BackgroundAlthough cavities are an important finding in Mycobacterium avium complex pulmonary disease (MAC-PD), there is little information regarding the types of cavities that indicate disease progression. This study was performed to identify cavity characteristics that were associated with disease progression in patients with MAC-PD.MethodsThis retrospective cohort study included 97 patients presenting with MAC-PD with cavities between December 2006 and June 2016. We compared initial and final computed tomography (CT) findings, classified 52 and 45 patients in the progressive and non-progressive cavity groups, respectively, and examined the progression-related imaging features in initial CT images. A progressive cavity was defined by more than two-fold increase in internal diameter or emergence of a new cavity around the initial cavity.ResultsPatients in the progressive group were older (p < 0.001), had a lower body mass index (p = 0.043), and showed higher diabetes complication rates (p = 0.005). The initial CT in the progressive group showed a longer maximum internal diameter of the cavity (p < 0.001) and higher rates of cavities close to the chest wall (p < 0.001), multiple cavities (p = 0.023), consolidation around the cavity (p < 0.001), atelectasis (p = 0.011), and pleural thickening (p < 0.001). Multivariable logistic regression analysis revealed that the maximum internal diameter of the cavity (odds ratio [OR]: 1.11, 95% confidence interval [CI]: 1.02–1.21; p=0.012) and consolidation around the cavity (OR: 16.15, 95% CI: 4.05–64.46; p < 0.001) were significantly associated with progressive cavities. In cavities with a maximum internal diameter of ≥10 mm and simultaneous consolidation, the probability of progression was as high as 96.2%. The 10-year mortality rates in the progressive and non-progressive cavity groups were 46.7 and 9.8% (p < 0.001), respectively, while the 10-year respiratory failure rates were 28.1 and 0%, respectively (p < 0.001).ConclusionsLarge cavity size and consolidation on CT showed strong relationships with disease progression, which led to respiratory failure and high mortality rate.

Abstract 038: The Arg16 / Gln27 Diplotype of the Beta-2 Adrenergic Receptor: Cardiovascular Insights from a Novel Transgenic Mouse Model

The beta-2 adrenergic receptor (B2AR) is an established regulator of vascular tone and cardiac contractility. Two polymorphisms of the B2AR (Gly16Arg and Glu27Gln) have been associated with cardiovascular phenotypes, including hypertension, salt sensitivity of BP, cardiovascular disease and responses to antihypertensives. These same variants are associated with changes in receptor downregulation and desensitization in pulmonary tissues; however, there is no information on the effect of these polymorphisms on B2AR expression/function in cardiovascular tissues. To investigate the effect of these variants on cardiovascular function, we used the CRISPR/Cas9 approach to generate transgenic mice that carry the diplotype Arg16/Gln27 on 2, 1 or 0 alleles, i. e. mutant (Mut), heterozygous (Het) and wild-type (WT). Both male and female mice displayed significantly higher body weights with the increase in number of mutated alleles (P&lt;0.05). Systolic and diastolic BP showed a similar positive dose-response relationship with the number of mutated alleles, irrespective of the gender (P(trend) &lt; 0.001). In contrast, pulse pressure and heart rates were not significantly affected by the diplotype. Urine and plasma aldosterone levels (but not plasma renin activity) were progressively downregulated in the male but not female carriers of the diplotype (P&lt;0.01). Cardiac ultrasound measurements revealed that male diplotype carriers displayed a decrease in left ventricular wall thickness, especially during systole (P&lt;0.05), with a corresponding increase in internal diameter and volume, decreased stroke volume and fractional shortening (P&lt;0.05); however, there were no significant effects of diplotype in the females. Cardiac B2AR transcript levels were significantly decreased in male but not female diplotype carriers versus WT. Our study provides strong support for a direct sex-dependent effect of the Arg16/Gln27 diplotype on cardiovascular function and supports the translational value of our novel animal model.

Numerical simulation of rock failure under static and dynamic loading by splitting test of circular ring

The fracture propagation and failure process in rock are subjects of great interest in rock mechanics. In the present study, an approach combining the finite element method (FEM) and the discrete element method (DEM), named ELFEN, is adopted to simulate and investigate the failure process of a typical hard rock (Carrara marble) under static and dynamic splitting ring tests. The FDEM software is firstly validated by simulating the test of a Brazilian disk under static loading. Then, the failure of circular ring specimens is numerically studied under static and dynamic loading, with the ratio of internal to external diameter (represented by λ) of the specimen groups varying from 0.1 to 0.6, with increments of 0.1. Under static loading, with the increase in internal diameter, the failure mode is transformed from diametrical splitting to four-fan-shaped failure (when λ≥0.4). Under dynamic loading, four-fan-shaped failure occurs from geometric axial symmetry to axial asymmetry, which means that, with increasing internal diameter, the tensile cracks along the horizontal diametrical direction gradually deviate toward the top loading platen. The peak load of the circular ring has a descending trend with the increase in internal diameter under both loading conditions. A rational load value (peak load or crack initiation load) is suggested to calculate the tensile strength of circular rock ring specimens under the splitting ring test. Finally, the numerical results are compared with previous experimental results. The good agreement between the two sets of results, in terms of the failure modes and variation trend of the indirect tensile strength with increasing internal diameters, verify the accuracy and applicability of the FDEM approach.

Novel RAGE Antagonist, FPS‐ZM1, Reverses Mesenteric Arteriolar Remodeling in Type 2 Diabetic db/db Mice.

Type II diabetes (T2D) is a major risk factor for cardiovascular diseases. Recently, our laboratory established a differential effect of T2D on vascular remodeling that was dependent upon vessel size and location. In addition, our preliminary data showed an increase in circulating levels of advanced glycation end products (AGE) in T2D mice. Activation of AGE receptors (RAGE) was shown to be associated with vascular dysfunction and vascular smooth muscle proliferation, which may result in vascular remodeling. In the present study, we hypothesized that pharmacological RAGE blockade using a novel antagonist would reverse microvascular remodeling observed in T2D. Using a pressure myograph system, passive vascular mechanics were assessed in aortae and mesenteric arterioles (MA) isolated from 16 week‐old lean control mice (Db/db), obese T2D mice (db/db) and T2D mice (db/db+FPS) treated with RAGE antagonist (FPS‐ZM1, 1mg/Kg/day ip, 28 days). Body weight (BW) and fasting blood glucose (BG) were significantly increased in diabetic db/db compared to control Db/db mice (BW: 29.8±0.5 in Db/db vs. 47.3± 1.5 g db/db, p&lt;0.05 and BG: 185 Db/db ± 13 vs 687 ± 20 mg/dL in db/db, p&lt;0.05). FPS‐ZM‐1 treatment did not affect BW (46.3±1.5g) nor BG (679±17 mg/dL) in T2D mice. In aorta, neither diabetes nor RAGE antagonism in diabetic mice affected the macrovascular mechanical properties. In contrast, MAs isolated from T2D mice exhibited a significant increase in internal diameter (158±2 in Db/db vs. 208±13 μm in db/db at 100mmHg, p&lt;0.05), external diameter (180±3 in Db/db vs. 233±14 μm in db/db at 100mmHg, p&lt;0.05) and cross‐sectional area (CSA) (6066±597 in Db/db vs. 8753±881 μm2 in db/db at 100mmHg, p&lt;0.05). RAGE antagonism in T2D significantly reduced MAs internal diameter (178±5 in db/db+FPS vs. 208±13 μm in db/db at 100mmHg, p&lt;0.05), external diameter (200±5 in db/db+FPS vs. 233±14 μm in db/db at 100mmHg, p&lt;0.05) and CSA (6453±400 in db/db+FPS vs. 8753±881 μm2 in db/db at 100mmHg, p&lt;0.05). Together, our data showed a variation in macrovascular vs. microvascular remodeling in T2D as we have previously shown. Furthermore, our data suggest that AGE/RAGE signaling contributes to the microvascular remodeling observed in T2D and that RAGE blockade using a novel antagonist may present a potential therapeutic target to reduce or reverse diabetes‐mediated vascular complications.Support or Funding InformationR00 HL116769 and Nationwide Children's Hospital

Enhancement of thermoelectric performance in InAs nanotubes by tuning quantum confinement effect

By using the nonequilibrium Green's function method, we study the thermoelectric properties of InAs nanotubes. The results show that InAs nanotube with a certain internal diameter has much higher ZT value than nanowire due to the enhancement of quantum confinement effect leading to the increase of the power factor S2G. The ZT value of InAs nanotube can reach 1.74, which is about three times greater than that of nanowires. Moreover, it is found that the ZT values of InAs nanotubes decrease rapidly with the increase of internal diameter, which results from the rapid increase of phonons thermal conductance due to the “red shift” of low-frequency optical phonon modes.

Сharacteristics of flexible elastic properties of the carotid arteries in women with arterial hypertension.

The article presents the results of study of the features of the carotid wall structure using ultrasound scanning with differential measurement of intima and media thickness, as well as characteristics of arterial elasticity in women with hypertension without comorbidities. It is shown that in women with hypertension vascular remodeling occurs mainly in the form of thickening of the intima-media due to increase in the media layer and is associated with remodeling of the left heart. Carotid remodeling in women with hypertension is associated with worsening of vascular elasticity - increased vascular stiffness and decreased distension, wherein correlation analysis has shown that mentioned parameters are mostly associated with thickening of the medial layer of the artery wall and increase of internal diameter of the artery, as well as with increase in left ventricular mass. Ultrasound method of estimating elastic characteristics of arterial vessels is informative, relatively inexpensive and safe.

Mechanical properties intermaxillary latex and latex-free elastics

BackgroundHypersensitivity to latex is frequently observed in patients undergoing orthodontic treatment. In the search for new alternatives to meet the needs of these patients, latex-free intermaxillary elastics were developed in the 1920s. Although the use of latex-free elastics in dentistry is not new, studies evaluating the mechanical properties of these devices in the literature are scarce. ObjectiveThe aim of this study was to evaluate the mechanical properties of latex and synthetic latex-free intermaxillary elastics. MethodsLatex and latex-free orthodontic elastics, both of 5/16 diameter, were preselected with regard to uniformity of diameter and thickness and were evaluated (n = 17 per group). Initially, the elastics were weighed, and their external diameters at rest were measured. After this, they were taken to a digital dynamometer mounted on a device suitable for measuring initial force. The elastics were kept distended (10 cm) and were immersed into artificial saliva at 37°C. A series of evaluations of force were performed at 2, 6, 8, 12, and 24 hours, and weight and diameter evaluations were repeated at 24 hours. The values for the amount of force released and weight and diameter were analyzed using ANOVA and the Tukey test. ResultsThe latex elastics released statistically greater force than did the latex-free elastics at each time point (all, P < 0.05). The weight of the latex-free elastics did not increase from 0 to 24 hours, whereas the weight of the latex elastics presented a statistical difference (P < 0.05). All of the elastics evaluated had an increase in internal diameter showing permanent deformation (P < 0.05). ConclusionThe intermaxillary latex elastics released greater force and underwent greater degradation than did the latex-free type.

Long-Term Arterial Adaptation to High Blood Flow in the Feeding Artery of Vascular Access for Hemodialysis

Arteries continuously respond to changing tissue demands and to hemodynamic conditions by altering their diameter and wall structure. The relatively slow dilatation of the feeding artery of vascular accesses continues at least two years after access creation with a continuous decrease in wall shear rate (WSR), which however, remains highly supra-physiological. The aim of this study was to test the hypothesis that after a longer time period the WSR returns to its baseline value. In a cross-sectional study patients with arteriovenous fistulae were classified into four groups according to the access vintage (from new access to accesses older than six years). The WSR, cross-sectional area, and mean circumferential wall stress were measured and compared between groups. WSR decreased from group 1 (fistula < ninety days old) to group 4 (fistulae > six years old) with a concomitant increase in internal diameter. Patients with the oldest access had normal WSR values (compared to the contralateral brachial artery) and the largest internal diameter of the feeding artery. In diabetic patients the absolute values of WSR were higher and internal diameter was lower compared to nondiabetic patients. Brachial artery WSR is normal in accesses older than six years with an increased internal diameter and wall cross-sectional area as compared to "younger" accesses. This suggests a process of vascular remodeling with an increase in vascular wall mass and normalization of WSR to physiologic values at the price of increased mean cross-sectional wall stress.

Experimental investigation of dryout of propane in uniformly heated single vertical mini-channels

This article presents dryout results of propane in single vertical circular minichannels made of stainless steel with internal diameters of 1.70 mm and 1.224 mm. The heat flux is increased in steps up to occurrence of dryout. The effects of different parameters such as mass flux, saturation temperature, vapour quality and internal diameter on the dryout are investigated. The results show that the dryout heat flux increases with the increase in mass velocity, with the decrease of vapour quality and with the increase of internal diameter. Almost no effect of saturation temperature on dryout heat flux is observed. Generalised CHF correlations developed for macro and micro scale from the literature are also compared with the experimental results.

Post irradiation examination of reactor operated pressure tube S-07 of KAPS-2

An irradiated Zr–2.5% Nb pressure tube removed from Kakrapar Atomic Power Station unit #2 (KAPS-2) after eight effective full power years was subjected to post irradiation examination in BARC hot cells facility. The examination included visual examination of outer and inner surface, gamma scanning, measurement of internal diameter, measurement of oxide thickness on the inner surface and analysis of hydrogen content in the tube. Examination revealed satisfactory performance of the pressure tube in the reactor. The maximum oxide thickness on the inside surface was found to be less than 15 μm at 4 m from the inlet end and maximum hydrogen pick up at the peak location was 6 ppm. The maximum increase in internal diameter was 0.82 mm at 3.2 m from the inlet end.

Neuronal activity-related coupling in cortical arterioles: involvement of astrocyte-derived factors.

Neuronal activity-evoked dilatation was investigated in cortical arterioles in brain slices from mature rats maintained in vitro at 31-33 degrees C. In the presence of the thromboxane A2 agonist U46619 (75 nM) to preconstrict vessels, internal diameter decreased by 14.2% and rhythmic contractile activity (vasomotion) developed. Addition of the epoxygenase inhibitor miconazole (20 microm) produced a further decrease in diameter and increase in the frequency of vasomotion, suggesting that tonic release of epoxygenase products maintains a level of cerebrovascular dilator tone. Addition of 1 mum AMPA for 5 min evoked a 15.4 +/- 3.7% increase in diameter and the frequency of vasomotion decreased by -6.7 +/- 1.4 contractions min(-1). The response persisted in the presence of 1 mum TTX, indicating that it was independent of neuronal activity and thus likely to have been evoked by activation of AMPA receptors on astrocytes rather than neurones. The response to the brief (5 min) application of AMPA remained unchanged in the presence of miconazole (20 microm). Prolonged (30 min) application of AMPA produced a +12.1 +/- 1.5% increase in internal diameter and reduction in vasomotion (-8.4 +/- 1.7 contractions min(-1)) that were sustained throughout the stimulation period. However, when AMPA was applied in the presence of miconazole (20 microm) it evoked only a transient increase in diameter (+9.8 +/- 3.1%) and decrease in vasomotion (-6.6 +/- 1.5 contractions min(-1)) that lasted for less than 10 min despite continued application of AMPA. The results suggest that products of epoxygenase activity, probably epoxyeicosatrienoic acids (EETs) are involved in activity-related dilatation in cortical arterioles. Whilst epoxygenase activity is not required to initiate dilatation, it appears to be involved in sustaining the response. Thus EETs released from membrane stores could contribute to the initial stages, but once these have been depleted de novo synthesis of EETs is required to maintain the effect.

Native arteriovenous fistula: Preoperative evaluation

Duplex sonography recently has been recognized as an objective and noninvasive method to assess morphological and functional parameters of vessels that could predict arteriovenous fistula (AVF) patency and time of adequate maturation. To prospectively study prognostic indicators of native AVFs, forearm arteries and veins of patients with end-stage renal disease were examined by duplex sonography before AVF construction. Several anatomic parameters, including feeding artery internal diameter (IDA), resistance index (RI), and arterial blood flow (QA) before and at reactive hyperemia (RH) and internal diameter of the vein (IDV) before and after proximal vein compression (PVC), were measured. Measurements of the feeding artery were repeated at different periods after native AVF construction. One hundred sixteen patients were included on the study. The primary patency rate (successful constructed AVF) of native AVFs was 80.2%. In this group, mean values for IDA were 0.264 cm; RI at RH, 0.50; and QA, 54.5 mL/min. IDV increased after PVC for 59.3%. In the group with failed AVFs (19.8%), mean IDA was 0.162 cm; RI at RH, 0.70; and QA, 24.1 mL/min. IDV increased after PVC for only 12.4%. Patency rates after surgery in a group with IDAs greater than 0.16 cm was 93%, and with IDAs of 0.16 cm or less, 32%. In a group with RIs at RH less than 0.7, the patency rate was 95.3%, and with RIs of 0.7 or greater, 38.7%. An AVF feeding artery QA of 300 mL/min was achieved in the group with IDAs greater than 0.16 cm, those with RIs at RH less than 0.7 after 1 week, those with IDAs of 0.16 cm or less between 3 and 8 weeks, and those with RIs of 0.7 or greater between 8 and 12 weeks. This study shows that duplex sonography may provide useful data on preoperative morphological and functional characteristics of vessels used for AVF construction. Increase in IDA, QA, RI at RH, and IDV after PVC are important to predict AVF primary patency rate. Based on these measurements, the most adequate location for AVF construction, as well as time of optimal AVF development, can be determined, particularly for patients at greater risk for primary failure, such as the elderly and patients with diabetes. © 2002 by the National Kidney Foundation, Inc.

Aminoguanidine and aortic wall mechanics, structure, and composition in aged rats.

With aging, the aortic wall becomes stiffer. This could be because of changes in wall stress or composition. We investigated whether a specific change in wall composition, ie, accumulation of advanced glycation end products (AGEs) on the extracellular matrix, is a major factor. We measured aortic mechanics, geometry, and composition in 3-, 10-, 15-, 20-, and 30-month-old inbred normotensive Wistar-Glaxo/Rijswick rats and in a group of 30-month-old rats treated from 20 months onward with aminoguanidine (AG, 42 mg/kg per day), an inhibitor of AGE formation. Thoracoabdominal aortic (pressure) pulse-wave velocity (PWV) increased progressively with age (44% from 3 to 30 months). This age-related increase in aortic PWV was not related to changes in wall stress. For all ages, central (and peripheral) aortic mean blood pressures were not statistically different. Dilatation occurred (18% increase in internal diameter from 3 to 30 months), but this was accompanied by outward hypertrophic remodeling, with an increase in the medial cross-sectional area of 95% and in the ratio of medial thickness to internal diameter of 29%. Wall stress decreased with age (-34%). There was an increase in the ratio of elastic modulus (calculated from the Moens-Korteweg equation) to wall stress (calculated from the Lamé equation, 117% from 3 to 30 months), suggesting that a change in the composition of the wall is responsible for the age-linked increase in wall stiffness. Dry weight decreased slightly but significantly (-14%) with age. Total protein, elastin, collagen, and nonscleroprotein protein [total-(elastin+collagen)] contents did not change with age, but calculated densities of all 4 were halved (as the medial cross-sectional area doubled). The elastin/collagen ratio was statistically similar at all ages. The only significant effect of AG treatment was a fall in PWV (-20%), leading to a fall in the elastic modulus/wall stress ratio (-27% at 10 months of AG treatment versus 30 months of no treatment). In conclusion, the age-related increase in aortic wall stiffness is prevented by 10 months of treatment with AG, which has no effect on wall stress or composition, suggesting that AG may improve aortic wall stiffness by lowering the degree of AGE-induced cross-linking of the extracellular matrix scleroproteins, such as collagen.

Aortic wall mechanics and composition in a transgenic mouse model of Marfan syndrome.

In Marfan syndrome, mutations of the fibrillin gene (FBN1) lead to aneurysm of the thoracic aorta, making the aortic wall more susceptible to dissection, but the precise sequence of events underlying aneurysm formation is unknown. We used a rodent model of Marfan syndrome, the mgR/mgR mouse (with mgR: hypomorphic FBN1 mutation), which underexpresses FBN1, to distinguish between a defect in the early formation of elastic fibers and the later disruption of elastic fibers. The content of desmosine plus isodesmosine was used as an index of early elastogenesis; disruption of elastic fibers was analyzed by histomorphometry. Because disruption of the medial elastic fibers may produce aortic stiffening, so amplifying the aneurysmal process, we measured thoracoabdominal pulse wave velocity as an indicator of aortic wall stiffness. Both mgR/mgR and wild-type (C57BL/6J-129SV) strains were normotensive, and wall stress was not significantly modified because the increase in internal diameter (0.80+/-0.06 vs 0.63+/-0.03 mm in wild type, P<0.05) was accompanied by increased medial cross-sectional area. The aortic wall stiffened (4-fold increase in the elastic modulus-to-wall stress ratio). Desmosine content was not modified (mgR/mgR 432+/-31 vs wild type 492+/-42 microg/mg wet weight, P>0.05). Elastic fibers showed severe fragmentation: the percentage of the media occupied by elastic fibers was 18+/-3% in mgR/mgR mice vs 30+/-1% in wild-type mice, with the number of elastic segments being 1.9+/-0.2 vs 1.4+/-0.1x10(-6)/mm(2) in the wild type (both P<0.05). In conclusion, underexpression of FBN1 in mice leads to severe elastic network fragmentation but no change in cross-linking, together with aortic dilatation. This result suggests that fragmentation of the medial elastic network and not a defect in early elastogenesis is 1 of the determinants of aortic dilatation in Marfan syndrome.

Compensatory increase in common carotid artery diameter. Relation to blood pressure and artery intima-media thickness in older adults. Cardiovascular Health Study.

Common carotid artery (CCA) diameter is thought to increase as a consequence of hypertension and may increase as the thickness of the arterial wall increases. The purpose of this study was to determine CCA dimensions and correlate them with clinical features. We performed a cross-sectional, community-based study of adults 65 years of age and older, measuring inner and outer diameter of the CCA in vivo with carotid sonography. Findings were correlated against risk factors for atherosclerosis, CCA intima-media thickness (IMT), and echocardiographically determined left ventricular (LV) mass. Independent variables showing strong positive associations with outer and inner CCA diameter included age, male sex, height, weight, and systolic blood pressure. As an independent variable, LV mass (r = .40 and r = .37, respectively; P < .00001) had a strong positive relation to inner and outer CCA diameters. The relationship between diameter and IMT was different. In a model that controlled for age, sex, and estimated LV mass, an increase of 1 mm in CCA IMT corresponded to a 1.9 mm increase in the outer diameter of the artery (P < .00001) but was not significantly related to the inner diameter (slope = +0.07 mm; P = .26). Increase in the outer diameter of the CCA is associated with subject size, sex, age, echocardiographically estimated LV mass, and CCA IMT. Increases in internal diameter of the CCA have similar relationships but are not related to IMT. This supports the hypothesis that the human CCA dilates as the thickness of the artery wall increases.