Spider silk softening by water uptake: an AFM study

We have investigated the mechanical properties of spider dragline fibers of three Nephila species under varied relative humidity. Force maps have been collected by atomic force microscopy. The Young's modulus E was derived from the indentation curves of each pixel by the modified Hertz model. An average decrease in E by an order of magnitude was observed upon immersion of the fiber in water. Single fiber stretching experiments were carried out for comparison, and also showed a strong dependence on relative humidity. However, the absolute values of E are significantly higher than those obtained by indentation. The results of this work thus show that the elastic properties of spider silk are highly anisotropic, and that the silk softens significantly for both tensile and compressional strain (indentation) upon water uptake. In addition, the force maps indicate a surface structure on the sub-micron scale.

Effect of dermatan sulfate glycosaminoglycans on the quasi-static material properties of the human medial collateral ligament

The glycosaminoglycan of decorin, dermatan sulfate (DS), has been suggested to contribute to the mechanical properties of soft connective tissues such as ligaments and tendons. This study investigated the mechanical function of DS in human medial collateral ligaments (MCL) using nondestructive shear and tensile material tests performed before and after targeted removal of DS with chondroitinase B (ChB). The quasi-static elastic material properties of human MCL were unchanged after DS removal. At peak deformation, tensile and shear stresses in ChB treated tissue were within 0.5% (p>0.70) and 2.0% (p>0.30) of pre-treatment values, respectively. From pre- to post-ChB treatment under tensile loading, the tensile tangent modulus went from 242+/-64 to 233+/-57 MPa (p=0.44), and tissue strain at peak deformation went from 4.3+/-0.3% to 4.4+/-0.3% (p=0.54). Tissue hysteresis was unaffected by DS removal for both tensile and shear loading. Biochemical analysis confirmed that 90% of DS was removed by ChB treatment when compared to control samples, and transmission electron microscopy (TEM) imaging further verified the degradation of DS by showing an 88% reduction (p<.001) of sulfated glycosaminoglycans in ChB treated tissue. These results demonstrate that DS in mature knee MCL tissue does not resist tensile or shear deformation under quasi-static loading conditions, challenging the theory that decorin proteoglycans contribute to the elastic material behavior of ligament.

Vascular Elasticity of Systemic Lupus Erythematosus Patients Is Associated with Steroids and Hydroxychloroquine Treatment

We studied the large and small artery elasticity (AE) and systemic vascular resistance (SVR) of systemic lupus erythematosus (SLE) patients according to treatment profile. Forty-one SLE patients (90% female, mean age 48.7 +/- 2.4 years) were compared to 96 healthy controls. The large and small AE and the SVR were derived from radial artery waveforms (model CR-2000, HDI Inc.). Patients were categorized into groups according to treatment: steroid (12), hydroxychloroquine (HCQ) (9), steroid+HCQ (16), and no-steroids-no-HCQ (4). The steroid group had reduced large AE and increased SVR as compared to the HCQ group (8.3 mmHg x mL x 10 and 18.4 dyne x sec x 10(-3) versus 13.7 and 14.4, respectively). Mean large AE and the SVR of the HCQ group was similar to that of the controls (11.8 mmHg x mL x 10 and 14.5 dyne x sec x 10(-3), respectively). Mean large AE and SVR of the steroid+HCQ group were better than the steroid group (10.4 mmHg x mL x 10 and 16.0 dyne x sec x 10(-3)). Patients that received steroids had higher rates of hypertension (36%) and diabetes (1%) compared to rest of the patients (15% and 0%, respectively). Small AE, blood pressure, CRP, and SLEDAI were similar between the groups. Among SLE patients, steroid treatment was associated with the highest degree of vascular damage, and HCQ was associated with the lowest degree of vascular damage. It is possible that the steroids are responsible in part to the increased large-vessel manifestations observed in these patients, and that HCQ might have a protective effect on the vessel wall.

Prenatal programming of skeletal development in the offspring: effects of maternal treatment with beta-hydroxy-beta-methylbutyrate (HMB) on femur properties in pigs at slaughter age

Alteration in fetal growth and development in response to prenatal environmental conditions such as nutrition has long-term or permanent effects during postnatal life. The aim of this study was to investigate effects of beta-hydroxy-beta-methylbutyrate (HMB) treatment of sows during the last 2 weeks of pregnancy on programming of skeletal development in the offspring. The study was performed on 141 pigs born by 12 sows of Polish Landrace breed. Two weeks before delivery, pregnant sows were divided into two groups. The first group consisted of control sows (N=6) that were treated with placebo. Sows that were orally treated with beta-hydroxy-beta-methylbutyrate (N=6) at the dosage of 0.05 g/kg of body weight per day belonged to the second group. Newborn piglets were weighed and subjected to blood collection for determination of serum levels of growth hormone (GH), insulin-like growth factor-1 (IGF-1), insulin, leptin, glucose and bone alkaline phosphatase (BAP) activity and lipid profile. At the age of 6 months, the piglets were slaughtered, their femur was isolated for analysis and assessment of lean meat content of carcasses was performed. The effects of maternal administration with HMB on skeletal properties in the offspring were evaluated in relation to bone mineral density and geometrical and mechanical properties. Maternal treatment with HMB increased serum levels of GH, IGF-1 and BAP activity in the newborns by 38.0%, 20.0% and 26.0%, respectively (P<0.01). HMB administration significantly increased volumetric bone mineral density of the trabecular and cortical bone of femur in the offspring at the age of 6 months (P<0.001). The weight of femur and geometrical parameters such as cross-sectional area, second moment of inertia, mean relative wall thickness and cortical index were significantly increased after HMB treatment (P<0.05). HMB induced higher values of maximum elastic strength and ultimate strength of femur (P<0.01). Furthermore, lean meat content of carcass was significantly increased in the females born by HMB-treated sows (P<0.05). The obtained results showed that maternal administration with HMB has positive long-term effects on bone tissue and improves volumetric bone mineral density, geometrical and mechanical properties of femur in the offspring. These effects were connected with increased level of GH and IGF-1 in the newborns indicating involvement of improved somatotrophic axis function in prenatal programming of skeletal development in pigs.

Docosahexaenoic acid alters bilayer elastic properties

At low micromolar concentrations, polyunsaturated fatty acids (PUFAs) alter the function of many membrane proteins. PUFAs exert their effects on unrelated proteins at similar concentrations, suggesting a common mode of action. Because lipid bilayers serve as the common "solvent" for membrane proteins, the common mechanism could be that PUFAs adsorb to the bilayer/solution interface to promote a negative-going change in lipid intrinsic curvature and, like other reversibly adsorbing amphiphiles, increase bilayer elasticity. PUFA adsorption thus would alter the bilayer deformation energy associated with protein conformational changes involving the protein/bilayer boundary, which would alter protein function. To explore the feasibility of such a mechanism, we used gramicidin (gA) analogues of different lengths together with bilayers of different thicknesses to assess whether docosahexaenoic acid (DHA) could exert its effects through a bilayer-mediated mechanism. Indeed, DHA increases gA channel appearance rates and lifetimes and decreases the free energy of channel formation. The appearance rate and lifetime changes increase with increasing channel-bilayer hydrophobic mismatch and are not related to differing DHA bilayer absorption coefficients. DHA thus alters bilayer elastic properties, not just lipid intrinsic curvature; the elasticity changes are important for DHA's bilayer-modifying actions. Oleic acid (OA), which has little effect on membrane protein function, exerts no such effects despite OA's adsorption coefficient being an order of magnitude greater than DHA's. These results suggest that DHA (and other PUFAs) may modulate membrane protein function by bilayer-mediated mechanisms that do not involve specific protein binding but rather changes in bilayer material properties.

Improving abnormal hemorheological parameters in aging guinea pigs by water-soluble extracts of Salvia miltiorrhiza Bunge

Salvia miltiorrhiza Bunge, known as Danshen in Chinese traditional medicine is effective at promoting blood circulation and removing (or decreasing) blood stasis. In the present study, we selected aging, 24-month-old guinea pigs as the animal experimental models and fed them a diet containing 75, 100 or 150 mg/(kg day) of water-soluble extract components of Salvia miltiorrhiza Bunge (WSm) for 28 days, respectively, in order to evaluate the effects of WSm on their abnormal hemorheological parameters. The results showed that the blood biochemical parameters of the aging guinea pigs remained unaffected by orally given WSm compared to the controls, except that the fibrinogen levels of the group fed the high dose of WSm (150 mg/(kg day)) decreased. Aging guinea pigs fed a low dose of WSm (75 mg/(kg day)) showed no significant difference in hemorheological parameters. However, feeding of WSm at 100 mg/(kg day) (medium dose), significantly reduced erythrocyte membrane MDA levels, which probably increased erythrocyte deformability and decreased erythrocyte flow resistance, though no improvement in erythrocyte aggregation, blood viscosity, and blood viscoelasticity could be observed. Furthermore, when the dose reached 150 mg/(kg day) of WSm (high dose), a significant decrease in whole blood viscosity was observed at high, medium and low shear rates. Blood viscosity and viscoelasticity exhibited significant improvement in oscillatory measurements. Also, we found that the oxygen transport efficiency of whole blood increased.

Differential effects of direct thrombin inhibitors and antithrombin-dependent anticoagulants on the dynamics of clot formation

New anticoagulants, including the direct thrombin inhibitors (DTIs) and fondaparinux, are increasingly replacing unfractionated heparin and enoxaparin. We examined the effects of argatroban (n = 60), bivalirudin (n = 44), heparin (n = 14), enoxaparin (n = 22), and fondaparinux (n = 24) on clot formation utilizing thromboelastography. Blood samples containing anticoagulants at clinically relevant concentrations were prepared ex vivo and analyzed using kaolin or tissue factor activation. Thromboelastography parameters of clot initiation (R), clot propagation (K and angle), clot rigidity (maximum amplitude) and clot elasticity (G) were compared between anticoagulants. Thromboelastography was also performed on blood from eight patients receiving anticoagulants. Each anticoagulant exerted significant concentration-dependent effects on R, K and angle. Only heparin, enoxaparin, and fondaparinux significantly affected maximum amplitude and G. Significant differences existed for all parameters between heparin and each anticoagulant and between fondaparinux and each DTI (P < 0.001), and for angle, maximum amplitude, and G between enoxaparin and each DTI (P < 0.008). Thromboelastography responses in ex-vivo samples and patient samples were comparable. In conclusion, whereas argatroban, bivalirudin, heparin, enoxaparin and fondaparinux each delay clot formation, the DTIs do not alter clot rigidity or elasticity. The reduced bleeding reported with DTIs versus heparin may relate to the fact that clots form with normal rigidity and elasticity.

Viscoelastic measurements of vocal folds using the linear skin rheometer

As the number of interventions for vocal fold scar grows and with the advancement of mathematical modeling, greater accuracy and precision in the measurement of vocal fold pliability will become essential. Although indirect pliability measures have been used successfully, direct measurement of tissue pliability is essential. Indirect measurement with parallel plate technology has limitations; it requires the tissue to be removed from the surrounding framework, allows no site specificity, and offers no future for in vivo use in animals or humans. We tested the linear skin rheometer (LSR) in the evaluation of vocal fold pliability. We measured site-specific rheology of vocal folds thereby creating "pliability maps" in human, dog, and rat cadaveric larynges under conditions of altered stiffness; the canine vocal folds possessed sulci, the rat vocal fold was stiff secondary to controlled biopsy, and the human vocal fold was injected with trichloroacetic acid. Histology was performed to confirm the site and type of canine sulci. We found that the LSR reliably detected stiffness in the vocal folds of all species and created "pliability maps" consistent with previous data and clinical observations. The LSR should prove useful in the evaluation of vocal fold pliability for ex vivo and ultimately for in vivo applications.

Morphological and functional determinants of fluoxetine (Prozac)-induced pulmonary disease in an experimental model

Fluoxetine treatment effects were determined by evaluating respiratory mechanics (elastance/resistance) and exhaled nitric oxide, as well as mononuclear and polymorphonuclear cell recruitment into the lungs, in an experimental guinea pig model. Guinea pigs were divided into four groups: Fl (fluoxetine only, n=7); Fl+Sw (fluoxetine and forced swimming, n=7); Ns+Sw (normal saline and forced swimming, n=8); and Ns (normal saline only, n=8). Treated animals received oral fluoxetine (10 mg/(kg day)) for 30 consecutive days. On day 31, all animals were anesthetized and mechanically ventilated so that respiratory system elastance and resistance, as well exhaled nitric oxide, could be determined. The lungs were then excised en bloc for histological and immunohistochemical evaluation. Forced swimming induced bronchodilation in untreated animals and bronchoconstriction in fluoxetine-treated animals. Fluoxetine treatment was also associated with mononuclear infiltration (predominantly into alveolar walls) and neutrophil recruitment. In addition, levels of exhaled nitric oxide, an inflammatory marker, were higher in fluoxetine-treated animals. Swimming-induced stress also amplified mononuclear cell recruitment to the lungs. These results show that, in this experimental model, fluoxetine treatment reproduces the pathology of chronic interstitial pneumonia in humans.

Effect of topical application of capsaicin and its related compounds on dermal insulin-like growth factor-I levels in mice and on facial skin elasticity in humans

Capsaicin increases calcitonin gene-related peptide (CGRP) release from sensory neurons by stimulating vanilloid receptor-1 (VR-1). Since CGRP increases production of insulin-like growth factor-I (IGF-I) in fetal osteoblasts in vitro, it is possible that sensory neuron activation by capsaicin increases production of IGF-I. In the present study, we attempted to determine whether topical application of capsaicin and related compounds increases dermal IGF-I level in mice and whether it increases facial skin elasticity in humans. Topical application of 0.01% capsaicin significantly increased dermal IGF-I levels from 30 to 180min (p<0.01), but not at 360min, after application in mice. Topical application of 0.01% capsaicinoids (dihydrocapsaicin and nordihydrocapsaicin), 0.01% capsinoids (capsiate, dihydrocapsiate and nordihydrocapsiate), 0.01% anandamide (an endogenous agonist of VR-1), and 0.01% nonylic acid vanillylamide (a synthetic capsaicin) significantly increased dermal IGF-I levels at 30min after topical application in mice (p<0.01). Topical application of 0.01% capsaicin to faces of 17 healthy female volunteers for seven days significantly increased cheek skin elasticity (p<0.01). These observations suggest that topical application of capsaicin and related compounds might be useful in the treatment of detrimental morphological changes of the skin in patients with growth hormone deficiency and those in the elderly by increasing dermal IGF-I levels.

Phimosis and topical steroids: new clinical findings

Phimosis has been defined as unretractable foreskin without adherences and/or a circular band of tight prepuce preventing full retraction. The aim of this study is to evaluate the efficacy (response rate) of topical steroids for the treatment of tight phimosis at different age stages. After using the same medication with different dosage schemes, a retrospective analysis was carried out to assess the efficacy of topical steroids in the treatment of tight phimosis. Patients were divided into three groups: group A (betamethasone scheme A), group B (betamethasone scheme B) and group C (control group). Remission of phimosis, with a complete exposure and without a narrowing behind the glans, was considered a complete response to treatment. The outcomes were then related to dosage scheme and patient's age. The dosage for group A was more effective than the dosage for groups B and C (control group). Phimosis resolved in 90% (group A), 72% (group B) and 56% (group C) of cases. A successful treatment was closely related to the age of patients at the beginning of steroid application. The results showed that treatment with topical steroids, which in general gives good results, proved to be much more successful in patients aged between 4 and 8 years, suggesting the efficacy of an early beginning of the treatment.

Advanced glycation endproduct crosslink breaker (alagebrium) improves endothelial function in patients with isolated systolic hypertension

OBJECTIVES

Arterial stiffening and endothelial dysfunction are hallmarks of aging, and advanced glycation endproducts (AGE) may contribute to these changes. We tested the hypothesis that AGE crosslink breakers enhance endothelial flow-mediated dilation (FMD) in humans and examined the potential mechanisms for this effect.

METHODS

Thirteen adults (nine men, aged 65 +/- 2 years) with isolated systolic hypertension (systolic blood pressure > 140 mmHg, diastolic blood pressure < 90 mmHg or pulse pressure > 60 mmHg) on stable antihypertensive therapy were studied. Subjects received placebo (2 weeks) then oral alagebrium (ALT-711; 210 mg twice a day for 8 weeks). Subjects and data analyses were blinded to treatment. Arterial stiffness was assessed by carotid augmentation index (AI) and brachial artery distensibility (ArtD) using applanation tonometry and Doppler echo, and endothelial function by brachial FMD. Serum markers of collagen metabolism and vascular inflammation were assessed.

RESULTS

Alagebrium reduced carotid AI by 37% (P = 0.007) and augmented pressure (16.4 +/- 10 to 9.6 +/- 9 mmHg; P < 0.001). Heart rate, arterial pressures, and ArtD, were unchanged. FMD increased from 4.6 +/- 1.1 to 7.1 +/- 1.1% with alagebrium (P < 0.05), and was unrelated to altered shear stress or regional arterial distensibility. However, FMD change was inversely related to markers of collagen synthesis, p-selectin and intracellular cell adhesion molecule (all P < 0.05). Alagebrium-associated changes in plasma nitrite plus nitrate was inversely correlated with plasma matrix metalloproteinase 9 and type I collagen (P = 0.007).

CONCLUSIONS

Alagebrium enhances peripheral artery endothelial function and improves overall impedance matching. Improved endothelial function correlates better with reduced vascular fibrosis and inflammation markers than with vessel distensibility. AGE-crosslink breakers may reduce cardiovascular risk in older adults by reduced central arterial stiffness and vascular remodeling.

Dose-dependent endothelial cell growth and stiffening by aldosterone: endothelial protection by eplerenone

BACKGROUND

Aldosterone at high concentrations causes an expansion of apical surface area and volume of cultured endothelial cells. These morphological changes are associated with endothelial cell stiffening. Here, we tested the hypothesis that the aforementioned aldosterone actions are confined to aldosterone concentrations within the pathophysiological range. Moreover, we investigated whether endothelial cells of venous and arterial origin respond similarly to aldosterone and whether the new aldosterone antagonist eplerenone effectively prevents endothelial cell growth and stiffening.

METHODS

We used an endothelial cell line of venous origin (EAHy 926) and primary cultures of human coronary artery endothelial cells (HCAEC). Cells were incubated for 72 h with aldosterone at concentrations of 0.1, 1, 10 and 100 nmol/l. Eplerenone was added at a concentration of 2 micromol/l. Applying atomic force microscopy, we scanned cell layers under fixed and living conditions, allowing measurement of endothelial cell apical surface, volume and cellular stiffness.

RESULTS

Aldosterone had comparable effects on EAHy 926 and HCAEC. In EAHy 926, the apical surface increased dose dependently by up to 72 +/- 5% and cell volume by up to 36 +/- 5%. In HCAEC, the maximum increase of apical surface was 78 +/- 6% and maximum cell volume expansion was 58 +/- 6%. Furthermore, aldosterone increased endothelial cell stiffness from 1.47 +/- 0.08 kPa up to 3.95 +/- 0.15 kPa in EAHy 926, and from 1.64 +/- 0.13 kPa up to 4.31 +/- 0.13 kPa in HCAEC. Physiological aldosterone concentrations had no effect, but starting at 1 nmol/l, corresponding to the low pathophysiological range, substantial cell alterations emerged. Eplerenone, at a therapeutic concentration, prevented the observed actions of aldosterone.

CONCLUSIONS

Aldosterone-induced endothelial cell growth and stiffening in vitro begins with concentrations in the low pathophysiological range. The preventive action of eplerenone indicates that the endothelium could be a major target of this drug in vivo.

The Effect of Bleaching on the Elastic Modulus of Bovine Enamel

The purpose of this study was to determine the elastic modulus of enamel during bleaching procedure with the use of an ultrasonic device. Enamel sections were obtained from freshly extracted bovine incisors. Specimens were exposed to 10% carbamide peroxide for two hours, followed by an application of a fluoride-containing toothpaste for five minutes and stored in artificial saliva (pH 7.0). An ultrasonic device was used to measure the sound velocities of longitudinal and shear waves as well as elastic modulus. The mean elastic modulus of bleached enamel decreased with time, from 15.5 GPa to 10.1 GPa. Conversely, the elastic modulus of bleached enamel followed by application of a fluoride-containing toothpaste increased with time, from 15.2 GPa to 20.2 GPa. Results of this study indicated that a decrease in elastic modulus associated with bleaching occurred, and that fluoride-containing toothpaste reversed this effect.

Modulation of atherosclerosis, blood pressure and arterial elasticity by statins

It is well known that dyslipidemia and hypertension frequently coexist. There is increasing recognition of a mutually facilitative interaction between dyslipidemia and renin- angiotensin system (RAS) activation in the development of atherosclerosis. Both of these systems share many of the same properties in terms of activation of pro-inflammatory, pro-oxidant and pro-atherosclerosis pathways. Statins in particular have been shown to influence the biology of endothelial cells, vascular smooth muscle cells and constituents of the interstitial matrix, particularly fibroblasts. It is no wonder that concurrent therapy of dyslipidemia with statins enhances the effects of RAS inhibitors. Although the effects of statins on the regulation of determinants of vascular stiffness are not well defined, it is quite likely that these regulatory pathways will be influenced by dyslipidemia therapy, especially statins.

Treatment of Hypertension With Thiazides: Benefit or Damage?Effect of Low- and High-Dose Thiazide Diuretics on Arterial Elasticity and Metabolic Parameters in Hypertensive Patients With and Without Glucose Intolerance

Thiazide diuretics may cause multiple metabolic abnormalities. The authors investigated the effects of varying doses of hydrochlorothiazide (HCTZ) on arterial elasticity and metabolic parameters in patients with hypertension (HTN), HTN and impaired fasting glucose (HTN+IFG), and HTN and type 2 diabetes mellitus (HTN+DM). The patients received low and high doses of HCTZ. Systolic and diastolic blood pressures declined significantly during the first 3 months in all patients, but no additional decrease was seen following the increase in HCTZ dose. In HTN, large artery elasticity index and small artery elasticity increased during the study. In HTN+IFG, large artery elasticity index increased without improvement in small artery elasticity index. In HTN+DM, both large artery elasticity index and small artery elasticity index did not improve during follow-up. Low-dose HCTZ improves arterial elasticity in hypertensive patients, but this effect is diminished with concomitant DM or IFG. The HCTZ dose increase worsened parameters of glucose metabolism and did not further decrease blood pressure or improve arterial elasticity.

New insights into the passive force enhancement in skeletal muscles

The steady-state isometric force following active stretching of a muscle is always greater than the steady-state isometric force obtained in a purely isometric contraction at the same length. This phenomenon has been termed "residual force enhancement" and it is associated with an active and a passive component. The origin of these components remains a matter of scientific debate. The purpose of this work was to test the hypothesis that the passive component of the residual force enhancement is caused by a passive structural element. In order to achieve this purpose, single fibers (n=6) from the lumbrical muscles of frog (Rana pipiens) were isolated and attached to a force transducer and a motor that could produce computer-controlled length changes. The passive force enhancement was assessed for three experimental conditions: in a normal Ringer's solution, and after the addition of 5 and 15mM 2,3-butanedione monoxime (BDM) which inhibits force production in a dose-dependent manner. If our hypothesis was correct, one would expect the passive force enhancement to be unaffected following BDM application. However, we found that increasing concentrations of BDM decreased the isometric forces, increased the normalized residual force enhancement, and most importantly for this study, increased the passive force enhancement. Furthermore, BDM decreased the rate of force relaxation after deactivation following active stretching of fibers, passive stretching in the Ringer's and BDM conditions produced the same passive force-sarcomere length relationship, and passive force enhancement required activation and force production. These results led to the conclusion that the passive force enhancement cannot be caused by a structural component exclusively as had been assumed up to date, but must be associated, directly or indirectly, with cross-bridge attachments upon activation and the associated active force.

Preservation of microelastic properties of dentin and tooth enamel in vitro--a scanning acoustic microscopy study

OBJECTIVES

The aim of this study was to examine the influence of storage media on the elastic properties of dentin and tooth enamel with respect to the storage period. Several reports suggest that saline and other aqueous solutions may induce chemical reactions and the dissolution of minerals, which in turn may cause alterations of elastic tissue properties.

METHODS

Three non-erupted human wisdom teeth were extracted and divided in three slices. Sections were stored in three different media for a maximum period of 21 days. During this time all sections were inspected by time-resolved 50-MHz scanning acoustic microscopy.

RESULTS

Storage in saline solution resulted in a progressive decrease of the acoustic impedance up to 70% in dentin but not in enamel tissue. Hank's balanced salts solution and artificial saliva appeared to maintain the elastic properties of dentin and enamel during the entire time of storage. The measurements of surface wave velocities did not show significant differences. High resolution (900 MHz) inspection of sections cut perpendicular to the surface exposed to the storage media for 21 days revealed a progressive increase of impedance in dentin up to the initial values at a depth of approximately 300 microm.

SIGNIFICANCE

These findings suggest that quantitative SAM is a suitable tool for assessing surface and sub-superficial elastic properties of tooth tissue.

Effect of chronic coffee consumption on aortic stiffness and wave reflections in hypertensive patients

OBJECTIVE

Aortic stiffness and wave reflections are important markers and prognosticators of cardiovascular risk. Caffeine increases acutely aortic stiffness and wave reflections. Furthermore, chronic coffee consumption is associated with increased aortic stiffness and wave reflections in normotensive subjects. In the present study, we aimed to assess the association between chronic coffee consumption, and aortic stiffness and wave reflections in hypertensive patients.

DESIGN

Epidemiological survey.

SETTING

Hypertension Unit, University Hospital. SUBJECTS-METHODS: We examined 259 never-treated hypertensives (age 50+/-12 years, 165 males) without diabetes mellitus, who were asked to describe in detail the type and amount of coffee they consumed. Carotid-femoral pulse wave velocity (PWV) and augmentation index (AIx) were measured non-invasively as indices of aortic stiffness and wave reflections, respectively.

RESULTS

When controlled for gender, age, height, smoking status, heart rate, mean pressure, HDL cholesterol and hsCRP, AIx was found to be higher with increasing daily coffee consumption. Post hoc analysis revealed that all groups of coffee consumption had higher AIx compared to no-consumption. PWV did not differ among groups of daily coffee consumption. Each participant had 35% higher relative risk of having high AIx for each cup (150 ml) of coffee per day, and 40% higher relative risk for each 10 cup-years.

CONCLUSIONS

Coffee consumption is associated with increased wave reflections, but not aortic stiffness in never-treated hypertensive patients. This finding may have important clinical implications for cardiovascular health in hypertensive subjects.

Fenofibrate and pioglitazone improve endothelial function and reduce arterial stiffness in obese glucose tolerant men

Obesity is a low grade inflammatory state associated with premature cardiovascular morbidity and mortality. Along with traditional risk factors the measurement of endothelial function, insulin resistance, inflammation and arterial stiffness may contribute to the assessment of cardiovascular risk. We conducted a randomised placebo controlled trial to assess the effects of 12 weeks treatment with a PPAR alpha agonist (fenofibrate) and a PPAR gamma agonist (pioglitazone) on these parameters in obese glucose tolerant men. Arterial stiffness was measured using augmentation index and pulse wave velocity (PWV). E-selectin, VCAM-1 and ICAM-1 were used as markers of endothelial function. Insulin sensitivity improved with pioglitazone treatment (p=0.001) and, in keeping with this, adiponectin increased by 85.2% (p<0.001). Pro-inflammatory cytokine levels (TNFalpha, IL-6 and IL-1 beta) fell with both treatments (p<0.01 for TNFalpha and IL-1 beta, p<0.001 for IL-6). VCAM-1 and ICAM-1 were reduced with both treatments (p<0.001 for VCAM-1, p<0.05 for ICAM-1) and E-selectin improved with pioglitazone treatment (p=0.05). Both treatments resulted in a fall in augmentation index. PWV fell by 17.4% with fenofibrate treatment (p<0.001) and 16.3% with pioglitazone treatment (p<0.001). Pioglitazone and fenofibrate treatment of obese, glucose tolerant men reduces inflammation, improves markers of endothelial function and reduces arterial stiffness. These results suggest that treatment with PPAR agonists has potential to reduce the incidence of premature cardiovascular disease associated with obesity.

Beneficial actions of hyaluronan (HA) on arthritic joints: effects of molecular weight of HA on elasticity of cartilage matrix

Hyaluronan (HA) has viscoelastic, anti-inflammatory and protective actions in joint tissues, and is being widely used for treatment of OA and RA patients. However, the mechanisms underlying the pharmacological action of HA on OA and RA have not been fully understood. In this article, we review the molecular weight-dependent, anti-inflammatory actions of HA preparations - produced in Japan - in joint tissues, and show that the molecular weight of HA, but not its concentration, is crucial for maintenance of cartilage elasticity.

Resistance to pressure-induced dilatation in femoral but not saphenous artery: physiological role of latch?

We recently determined that the ability of the femoral artery (FA) to maintain higher levels of tonic isometric stress compared with the saphenous artery (SA) was due to differential expression of motor proteins permitting latch-bridge formation in FA and not SA. Arteries under pressure in vivo are not constrained to contract isometrically. Thus the significance of latch-bridge formation in arterial physiology remains to be determined. To address this translational question, diameter changes of pressurized FA and SA were compared. The reduction in lumen diameter induced by KCl at 80 mmHg (isobaric active constriction; IAC) was greater at 30 s than 10 min in SA. In FA, the reverse was true, mimicking isometric contractile responses identified in our earlier work. From 80 to 150 mmHg, the %IAC induced by KCl was greater in SA than FA (e.g., ∼80% vs. ∼30% at 120 mmHg). This was not explained by differences in contractile mechanisms but was likely due to differences in absolute artery diameters. In constricted arteries subjected to a ramp increase in pressure from 60 to 120 mmHg, the constricted diameter of FA, but not SA, was greater than the IAC diameter at each pressure. Thus FA but not SA could maintain a smaller diameter on being pressurized when first constricted than it could achieve by isobaric constriction. These data support the hypothesis that latch bridges permit constricted large-diameter elastic arteries such as the FA to temporarily resist dilatation in the face of transient increases in blood pressures.

Assessment by transient elastography of the viscoelastic properties of blood during clotting

Blood clotting is a natural process that can be both beneficial and life-threatening for the human body. It allows the maintenance of hemostasis after vascular injury, but it can also cause deep vein thrombosis and heart stroke. This study aimed better to understand the clotting process from a biomechanical point of view by using an acoustic method. The long-term objective is the staging of the age of clots in deep veins for therapy planning. The transient elastography method using a shear elasticity probe served to evaluate the shear wave velocity (V(S)) and shear wave attenuation (alpha(S)) of porcine whole blood during in vitro clot formation. By solving an inverse problem, it was then possible to provide images of the elasticity (mu(B)) and of the viscosity (eta(B)) from clotting blood. The time-varying elasticity and viscosity were very similar to what has been observed for the sol-gel transition of polymers. The mechanical properties of blood clot, which were modified by varying the hematocrit and by adding heparin or fibrinogen, were clearly assessed by the transient elastography technique. It is concluded that the shear elasticity probe is an appropriate tool to quantify and follow the sol-gel transition of blood during clotting.

Mechanical response to methacholine and deep inspiration in supine men

The effects of supine posture on airway responses to inhaled methacholine and deep inspiration (DI) were studied in seven male volunteers. On a control day, subjects were in a seated position during both methacholine inhalation and lung function measurements. On a second occasion, the whole procedure was repeated with the subjects lying supine for the entire duration of the study. On a third occasion, methacholine was inhaled from the seated position and measurements were taken in a supine position. Finally, on a fourth occasion, methacholine was inhaled from the supine position and measurements were taken in the seated position. Going from sitting to supine position, the functional residual capacity decreased by approximately 1 liter in all subjects. When lung function measurements (pulmonary resistance, dynamic elastance, residual volume, and maximal flows) were taken in supine position, the response to methacholine was greater than at control, and this was associated with a greater dyspnea and a faster recovery of dynamic elastance after DI. By contrast, when methacholine was inhaled in supine position but measurements were taken in sitting position, the response to methacholine was similar to control day. These findings document the potential of the decrease in the operational lung volumes in eliciting or sustaining airflow obstruction in nocturnal asthma. It is speculated that the exaggerated response to methacholine in the supine posture may variably contribute to airway smooth muscle adaptation to short length, airway wall edema, and faster airway renarrowing after a large inflation.

[A new method for examination of human skin vasomotions]

An original method for determination of elasticity of biological tissues from their resonance frequency has been devised. The method can be used for detection and spectral analysis of small oscillations of skin elasticity caused by vasomotions.