Nitrite-induced cross-linking alters remodeling and mechanical properties of collagenous engineered tissues

Cumulative damage to long-lived connective tissue proteins play a key role in the development of age-related human diseases such as cardiovascular stiffening and age-related macular degeneration. The processes that result in the accumulation of increasingly insoluble, undigestible damaged collagen are only partially known. Nonenzymatic glycation (NEG) is one such process and has been linked to the development of diabetic-related complications and aging. An additional novel mechanism particularly relevant to smoking- and inflammation-related diseases involves the nonenzymatic nitrite (NEN) modification of connective tissue proteins. The present study was undertaken to examine the effects of NEN of fibrillar type I collagen on cell-mediated remodeling and mechanical properties of collagenous tissues. Using a modification of an in vitro fibroblast-populated collagen gel model system developed in our laboratory, we tested two hypotheses: NEN reduces the ability of primary adult cardiac fibroblasts to remodel type I collagen gels; NEN reduces the deformability of type I collagen gels subjected to mechanical testing. The results show that NEN impairs both cell-mediated remodeling and mechanical deformability in collagenous engineered tissues. Furthermore, these mechanical changes correlate with the degree of cross-linking as determined by SDS-PAGE. Thus, we concluded that NEN reactions may contribute to alterations in the biomechanical properties of collagen-containing tissues consistent with the age-related functional decline observed in human disease.

Long-term effects of hormone therapy on skin rigidity and wrinkles

OBJECTIVE

To evaluate the effects of long-term hormone therapy (HT) on skin rigidity and wrinkling.

DESIGN

Single blinded cross-sectional analysis.

SETTING

Academic medical center.

PATIENT(S)

Sixty-five long-term HT users who underwent menopause at least 5 years before evaluation and who have either consistently used HT or have never used HT.

INTERVENTION(S)

Visual assessment of severity of wrinkles at 11 facial locations using the Lemperle scale by a plastic surgeon blinded to HT use. Measurement of skin rigidity at the cheek and forehead with a durometer.

MAIN OUTCOME MEASURE(S)

Lemperle wrinkle score and skin rigidity.

RESULT(S)

Twenty women met inclusion criteria. Eleven women who had not used HT were compared to nine long-term HT users. Demographics including age, race, sun exposure, sunscreen use, tobacco use, and skin type were similar. Rigidity was significantly decreased in HT users compared to nonusers at both the cheek (1.1 vs. 2.7) and forehead (20 vs. 29). Average wrinkle scores were lower in hormone users than in nonhormone users (1.5 vs. 2.2).

CONCLUSION(S)

Long-term postmenopausal HT users have more elastic skin and less severe wrinkling than women who never used HT, suggesting that hormone therapy may have cosmetic benefits.

Aortic elastic properties in athletes using anabolic-androgenic steroids

The use of anabolic-androgenic steroids (AAS) has been linked to acute cardiovascular events in athletes. The purpose of the present study was to investigate the aortic elastic properties in athletes who had been self-administering AAS compared with a group of athletes not using these drugs. Fourteen male bodybuilders using AAS and 27 male wrestlers (non-users) volunteered to the study. All subjects were placed in a mild recumbent position and the ascending aorta was recorded in the two-dimensional guided M-mode tracings. Although the aortic distensibility was found to be reduced in user athletes (2.1+/-1.1 vs. 3.8+/-1.4 cm(2) dyn(-1) 10(-6), p=0.01; 9.3+/-3.7 vs. 5.9+/-2.5, p=0.003, respectively). The results of this study indicate that aortic stiffness is increasing in athletes using AAS.

Exploring vascular benefits of endothelium-derived nitric oxide

Although the regulation of arterial blood flow has been a subject of intensive medical research, the precise circulatory mechanisms involved are still not fully understood. It has been increasingly recognized that the endothelium plays a vital role in regulating vascular tone, structure, and function. A seminal discovery was made with the identification of endothelium-derived relaxing factor, a key mediator of vasodilation, which was later identified as nitric oxide (NO). Nitric oxide is synthesized from the amino acid L-arginine in the endothelium. Decreased bioavailability of NO is associated with arterial stiffness, hypertension, atherosclerosis, and cardiovascular disease (CVD). Nebivolol is a novel beta-blocker that is highly selective for beta1-adrenergic receptors. Nebivolol also causes vasodilation through a mechanism involving endothelium-derived NO. In clinical studies in hypertensive subjects, nebivolol significantly improves vasodilator responses to endothelium-dependent agonists such as acetylcholine. In addition, nebivolol significantly reduces pulse wave velocity (PWV), a measure of arterial stiffness, whereas the beta-blocker atenolol has no effect on PWV. Because endothelial dysfunction and arterial stiffness play an integral part in the early atherosclerotic process and are associated with poor outcomes and increased mortality, independent of blood pressure, the ability of nebivolol to enhance release of endothelium-derived NO may have significant clinical implications for the use of this agent in the treatment of hypertension and CVD.

Relationships between lung function, smoking and morphology of dermal elastic fibres

OBJECTIVE

To investigate the relationship between lung function and dermal elastic fibres in non-smokers and smokers with and without chronic obstructive pulmonary disease (COPD).

METHOD

A cross-sectional study was performed with lung function as the outcome [forced expiratory volume in the first second (FEV1)%, FEV1/forced vital capacity (FVC)% and residual volume (RV)/total lung capacity (TLC)%] and smoking (pack-years) and morphology of dermal elastic fibres (fibres/mm(2) and percentage histologic field filled with them) as independent variables, with assessment of the associations between these variables by univariate and multivariate testing.

RESULTS

Sixty outpatients reporting chronic cough and/or phle\gm were enrolled (16 non-smokers/44 smokers; COPD: 26, 43.3%). Both lung function and elastic fibres in the reticular dermis (fibres/mm(2)r(s) = 0.36, percentage of the histologic field filled by elastic fibres r(s) = 0.48, P < or = 0.01) correlated with cumulative smoking (Spearman's rank correlation coefficient). Lung function parameters correlated with percentage of the histologic field filled by elastic fibres (FEV1%: r = -0.43; FEV1/FVC%: r = -0.36 and RV/TLC%: r = 0.43; P < or = 0.01, Pearson correlation coefficient), and COPD was significantly related to this morphologic parameter (odds ratio 1.26, 95% confidence interval 1.06-1.48; P = 0.006), associations that depended mainly on cumulative smoking.

CONCLUSION

Lung function impairment with an obstructive pattern is associated with morphologic abnormalities in the reticular dermis appearing in the histologic section as an increase in the percentage of the field filled by elastic fibres. This relationship depends on cumulative smoking and suggests a common effect of smoking on the elastic fibres in both lung and skin.

Elastolytic activity and alveolar epithelial type-1 cell damage after chronic LPS inhalation: effects of dexamethasone and rolipram

This study investigated whether a correlation between leukocyte-derived elastolytic activity, alveolar epithelial type-1 cell damage, and leukocyte infiltration of the airways existed in guinea-pigs chronically exposed to inhaled lipopolysaccharide (LPS). The airway pathology of this model, notably the neutrophilia, resembles chronic obstructive pulmonary disease (COPD). The effect of the corticosteroid, dexamethasone, or the phosphodiesterase-4 (PDE4)-inhibitor, rolipram, on these features was studied. Conscious guinea-pigs were exposed for 1 h to single or repeated (nine) doses of LPS (30 microg ml(-1)). Dexamethasone (20 mg kg(-1), ip) or rolipram (1 mg kg(-1), ip) was administered 24 and 0.5 h before the first exposure and daily thereafter. Bronchoalveolar lavage fluid (BALF) was removed and elastolytic activity determined as the elastase-like release of Congo Red from impregnated elastin. The presence of the specific epithelial cell type-1 protein (40-42 kDa) RT1(40) in BALF was identified by Western blotting using a rat monoclonal antibody and semi-quantified by dot-blot analysis. The antibody was found to identify guinea-pig RT1(40). BALF inflammatory cells, particularly neutrophils and macrophages, and elastolytic activity were increased in chronic LPS-exposed guinea-pigs, the latter by 90%. Chronic LPS exposure also increased (10.5-fold) RT1(40) levels, indicating significant alveolar epithelial type-1 cell damage. Dexamethasone or rolipram treatment reduced the influx of inflammatory cells, the elastolytic activity (by 40% and 38%, respectively), and RT1(40) levels (by 50% and 57%, respectively). In conclusion, chronic LPS-exposed guinea-pigs, like COPD, exhibit elastolytic lung damage. This was prevented by a PDE4 inhibitor and supports their development for suppressing this leukocyte-mediated pathology.

Spironolactone improves carotid artery fibrosis and distensibility in rat post-ischaemic heart failure

Myocardial infarction causes neurohormonal activation involving aldosterone and angiotensin II (AngII). These hormones may increase arterial stiffness, an independent cardiovascular risk factor contributing to progression of congestive heart failure (CHF). This study aimed to determine the effect of aldosterone and AngII blockade on carotid artery distensibility and collagen density in adult Wistar rats with MI-induced CHF. Five groups were studied: Sham-operated, CHF, CHF + spironolactone, CHF + lisinopril, CHF + Spironolactone + Lisinopril. After echocardiography, in vitro isobaric carotid distensibility (echo-tracking technique) and collagen density were measured, and the incremental elastic modulus (Einc) calculated. In the CHF group, intra-ventricular pressure and cardiac weight were increased; carotid distensibility was reduced (CHF: 0.42 +/- 0.30 per mmHg(3) versus sham: 1.75 +/- 0.50 per mmHg(3); P < 0.001), and collagen content increased by 87% when compared to sham. All treatments reduced intra-ventricular pressure, carotid distensibility and fibrosis when compared to CHF but did not change cardiac weight. However, carotid distensibility and intra-ventricular pressure were not completely restored towards sham values and were significantly and inversely related. Spironolactone, which did not decrease significantly blood pressure, was the only drug reducing Einc independently of wall stress (WS). Thus, MI-induced CHF was associated with carotid artery remodeling. This vascular change, which may contribute to maintain cardiac hypertrophy and CHF, is largely prevented by AngII and aldosterone blockade. Only spironolactone reduced the stiffness of carotid wall material independently of blood pressure and WS.

[Effect of vertebral body stiffness before and after vertebroplasty on intradiscal pressure]

Fractures of osteoporotic vertebral bodies are increasingly stabilized with bone cement. The effects of vertebral-body stiffness before and after augmentation with bone cement and of wedge-shaped vertebral body fractures on intradiscal pressure are insufficiently known. In a finite element model of the lumbar spine the elastic modulus of cancellous bone as well as the amount and the elastic modulus of bone cement were varied and the dependency of intradiscal pressure on these parameters was calculated. In addition, a wedge-shaped vertebral-body fracture was simulated. The bulge of the vertebral-body endplate and thus the intradiscal pressure depends strongly on the grade of osteoporosis in the vertebral body. The influence of amount and elastic modulus of bone cement on intradiscal pressure is small. A wedge-shaped vertebral-body fracture causes an anterior shift of upper-body centre of gravity. If this shift is not compensated, it leads to an increased flexion moment that has to be balanced by muscle forces. In addition, this shift leads to a stronger increase of intradiscal pressure than the augmentation of the vertebral body with bone cement.

Nasal wall compliance in vasomotor rhinitis

Nasal compliance is a measure related to the blood volume in the nasal mucosa. The objective of this study was to better understand the vascular response in vasomotor rhinitis by measuring nasal cross-sectional area and nasal compliance before and after mucosal decongestion in 10 patients with vasomotor rhinitis compared with 10 healthy subjects. Nasal compliance was inferred by measuring nasal area by acoustic rhinometry at pressures ranging from atmospheric pressure to a negative pressure of -10 cmH2O. Mucosal decongestion was obtained with one puff per nostril of 0.05% oxymetazoline. At atmospheric pressure, nasal cross-sectional areas were similar in the vasomotor rhinitis group and the healthy subject group. Mucosal decongestion did not induce any decrease of nasal compliance in patients with vasomotor rhinitis in contrast with healthy subjects. Our results support the hypothesis, already proposed, of an autonomic dysfunction based on a paradoxical response of the nasal mucosa in vasomotor rhinitis. Moreover, the clearly different behavior between healthy subjects and vasomotor rhinitis subjects suggests that nasal compliance measurement may therefore represent a potential line of research to develop a diagnostic tool for vasomotor rhinitis, which remains a diagnosis of exclusion.

The relationship between enamel softening and erosion caused by soft drinks at a range of temperatures

OBJECTIVES

Investigations of the erosive potential of soft drinks are usually performed at room or body temperature, but drinks are more frequently served chilled, with ice, or hot. Since the rate of chemical reactions usually increases with temperature, it is predicted that erosion is more severe at high temperatures and reduced at low temperatures. The aim of this study was to investigate the correlation between enamel softening, enamel erosion, and temperature.

METHODS

Atomic force microscopy nanoindentation and non-contact optical profilometry were used to assess changes in enamel nanomechanical properties after 5 min and erosive material loss after 30 min exposure to two different non-carbonated soft drinks at 4, 25, 50 and 75 degrees C.

RESULTS

For one drink (Robinson's Original Juice Drink), there was a statistically significant difference between nanomechanical properties and erosion depth at all temperatures, with softening and erosion increasing with temperature. For another drink (Ribena ToothKind Juice Drink), there was a slight softening and virtually no material loss, and temperature had no statistically significant impact on erosion. There was a good linear correlation (R2 = 0.94) between nanomechanical properties and material loss.

CONCLUSIONS

The difference between the drinks can be explained by their composition. For the erosive drink, material loss increased, and nanohardness decreased, approximately linearly with temperature. The correlation between softening and erosion demonstrated that nanomechanical properties after very short erosion times can be considered a good predictor of bulk material loss after considerably longer erosion times.

Effect of a nifedipine induced reduction in blood pressure on the association between ocular pulse amplitude and ocular fundus pulsation amplitude in systemic hypertension

BACKGROUND

The ocular pressure/volume relation, which is described by the Friedenwald equation, forms the basis of intraocular pressure (IOP) measurement with Schiotz tonometry and measurement of pulsatile ocular blood flow (POBF) with pneumotonometry. Changes in intraocular volume during the cardiac cycle are caused by arterial inflow and venous outflow and are accompanied by changes in IOP. The relation between volume and pressure changes is dependent on the elastic properties of the eye coats as described by the ocular rigidity coefficient. Previous studies indicate that there is a vascular contribution to ocular rigidity and that the volume/pressure relationship may depend on the mean arterial pressure.

METHODS

The effect of a nifedipine induced reduction in systemic blood pressure on pulse amplitude (PA) as assessed with pneumotonometry and fundus pulsation amplitude (FPA), as measured with laser interferometry was investigated in 16 untreated patients with moderate to severe systemic hypertension (mean arterial pressure 123 (SD 12) mm Hg).

RESULTS

The ratio between PA and FPA was taken as a measure of the ocular rigidity coefficient. Nifedipine reduced mean arterial pressure by 17.3% and increased pulse rate by 11.0% (p<0.001 each). Whereas PA was significantly reduced after administration of nifedipine (-15.6%; p<0.001), FPA remained unchanged. Accordingly, the ratio of PA/FPA was reduced from 0.86 mm Hg/mum to 0.73 mm Hg/mum after administration of nifedipine.

CONCLUSION

These data are in keeping with previous animal experiments indicating a blood pressure dependent vascular component to the rigidity of the eye coats in vivo. This needs to be taken into account for measurement of IOP with Schiotz tonometry and POBF with pneumotonometry.

Survival rates of patients with malignant melanoma of the skin

This paper reports on cases of malignant melanoma of the skin diagnosed in Finland between 1963 and 1968. Sufficient data for estimating the survival was obtained in 691 cases. The ten-year relative survival rate for the entire series was 41% for males and 53% for females. This sex difference remained constant throughout the various divisions of the material. The ten-year relative survival rate of males with tumour in stage I was 52% and that of females 59%. The highest survival rate of stage I tumour in males was for the tumours of the lower extremities (77%) and in females for those in the head and neck (79%). The relative survival of patients with tumour of the trunk in stage I was lowest in both sexes (males 49%, females 45%). The ten-year relative survival rate of patients with a local recurrence was 33% in males and 27% in females. The relative ten-year survival rates of patients with superficial melanoma were 130% in males and 92% in females.

High-dose lidocaine reduces airway mucus transport velocity in intubated anesthetized dogs

BACKGROUND

Assessment of mucociliary clearance with displacement of charcoal markers in the central airways needs a bronchoscopic procedure and thus local anesthesia of the upper airways. However, the effects of lidocaine administration on mucus transport in airways are inconclusive. Therefore, detailed information is needed to establish the effects of high- and low-dose lidocaine administration.

OBJECTIVES

To study the dose-dependent effect of instillation of lidocaine on mucus transport velocity (MTV) in intubated, anaesthetized dogs.

METHODS

Displacement of a charcoal spot in time was studied with a bronchoscope in 10 anaesthetized dogs before and after administration of respectively 5 and 10 ml of either 2% lidocaine (n=5) or NaCl 0.9% (n=5). In addition, mucus viscoelastic properties were determined.

RESULTS

No significant differences in MTV were observed after administration of 5 ml of NaCl (8.2+/-3.2 mm/min) or 2% lidocaine (6.7+/-3.8 mm/min) compared to baseline values. By contrast, MTV was reduced after administration of 10 ml of 2% lidocaine (1.9+/-1.0 mm/min; P<0.05 vs. baseline and 5 ml of 2% lidocaine vs. controls, P=0.0035), but not after 10 ml of NaCl (6.2+/-2.1 mm/min). A trend towards an increased mucociliary clearability index was observed for the lidocaine-treated group as compared to the control group (P=0.07). The cough clearability index was not different between groups (P=0.89).

CONCLUSIONS

High-dose lidocaine reduces MTV. Therefore, only low-dose lidocaine administration should be applied in the bronchoscopic procedure for assessment of MTV.

Evaluation of injection augmentation treatment of hyaluronic acid based materials on rabbit vocal folds viscoelasticity

The viscoelastic properties of vocal folds after injection of hyaluronic acid (hyaluronan, HA) based materials have been studied in an animal model (rabbit) six months after injection. The results indicate that the viscoelastic properties of the vocal folds injected with the HA based materials are similar to the healthy vocal folds (non-injected samples) used as control. Histological analysis has been also performed to investigate on the fate of the injected materials after six months from the implant. The HA based materials remain up to six months and they recruited fibroblasts that induce the ingrowth of new connective tissue resulting in an endogenous soft tissue augmentation. The HA based compounds are good candidate for further studies aimed at restoring/preserving the vibratory capacity of the vocal folds with injection treatment in glottal insufficiency.

Chronic coffee consumption has a detrimental effect on aortic stiffness and wave reflections

BACKGROUND

The effect of coffee consumption on the cardiovascular system is still an unresolved issue. Aortic stiffness and wave reflections are important prognosticators of cardiovascular disease risk. We have shown that caffeine acutely increases aortic stiffness and wave reflections.

OBJECTIVE

The objective was to investigate the effect of chronic coffee consumption on aortic stiffness and wave reflections.

DESIGN

This was a cross-sectional study of 228 healthy subjects: 141 men (x +/- SD: 41 +/- 8 y old) and 87 women (41 +/- 9 y old). Aortic stiffness was evaluated with carotid-femoral pulse wave velocity (PWV). Wave reflections were evaluated with augmentation index (AIx) and augmented pressure (AP) of the aortic pressure waveform with the use of high-fidelity pulse wave analysis. Coffee consumption was ascertained over 1 y with a food-frequency questionnaire.

RESULTS

A linear relation between coffee consumption and PWV, AIx, and AP was observed (P for trend < 0.05). Compared with the nonconsumption group, PWV was on average 13% higher, AIx was 2-fold higher, and AP was 2.4-fold higher (P < 0.01 for all) in the high-consumption group (>450 mL/d). The findings remained significant after control for confounders such as age, sex, smoking habits, body mass index, total and LDL cholesterol, triacylglycerols, blood glucose, mean blood pressure, and heart rate. The linear relation (P for trend < 0.05) observed between coffee consumption and arterial pressures was largely explained when the covariates were entered in the model.

CONCLUSIONS

Chronic coffee consumption exerts a detrimental effect on aortic stiffness and wave reflections, which may increase the risk of cardiovascular disease.

Elastic contributions dominate the viscoelastic properties of sputum from cystic fibrosis patients

Sputum samples from cystic fibrosis (CF) patients were investigated by oscillatory, creep and steady shear rheological techniques over a range of time scales from 10(-3) to 10(6) s. The viscoelastic changes obtained by mixing sputa with the actin-filament-severing protein gelsolin and with the thiol-reducing agent dithiothreitol (DTT) were also investigated. At small strains sputum behaves like a viscoelastic solid rather than a liquid. A nearly constant steady shear viscosity at low shear rates is only observed after long shearing times which cause irreversible changes in the samples. Creep-recovery tests confirm that sputa exhibit viscoelastic properties, with a significant elastic recovery. The results suggest that measurements of elastic moduli, rather than viscosities are more closely related to the mechanical properties of sputum in situ. Severing of actin filaments lowers the elastic modulus by 30-40%, but maintains viscoelastic integrity, while reduction of thiols in the glycoproteins nearly completely fluidizes the samples.

Ramipril reduces large-artery stiffness in peripheral arterial disease and promotes elastogenic remodeling in cell culture

Ramipril improves cardiovascular outcome in patients with peripheral arterial disease; however, the precise mechanisms of benefit remain to be elucidated. The effect of ramipril on large-artery stiffness in patients with peripheral arterial disease was examined. In addition, we determined the effect of ramiprilat on extracellular matrix from human aortic smooth muscle cell culture. Forty patients with peripheral arterial disease were randomized to receive ramipril, 10 mg once daily or placebo for 24 weeks. Arterial stiffness was assessed globally via systemic arterial compliance and augmentation index (carotid tonometry and Doppler velocimetry), and regionally via carotid-femoral pulse wave velocity. Angiotensin-converting enzyme inhibition increased arterial compliance by 0.10+/-0.02 mL/mm Hg, (P<0.001, all probability values relative to placebo) and reduced pulse wave velocity by 1.7+/-0.2 m/s (P<0.001), augmentation index by 4.1+/-0.3% (P<0.001), and systolic blood pressure by 5+/-1 mm Hg (P<0.001). Ramipril did not reduce mean arterial pressure significantly compared with placebo (P=0.59). In cell culture, ramiprilat decreased collagen deposition by >50% and increased elastin and fibrillin-1 deposition by >3- and 4-fold respectively (histochemistry and immunohistochemistry). Fibrillin-1 gene expression was increased 5-fold (real-time reverse-transcriptase polymerase chain reaction). Ramiprilat also reduced gene and protein (Western) expression of both matrix metalloproteinase (MMP)-2 and MMP-3. In conclusion, ramipril promoted an elastogenic matrix profile that may contribute to the observed clinical reduction in large-artery stiffness and carotid pressure augmentation, which occurred independently of mean arterial blood pressure reduction in patients with peripheral arterial disease.

Ascorbic acid selectively improves large elastic artery compliance in postmenopausal women

The compliance of large elastic arteries in the cardiothoracic region decreases with advancing age/menopause and plays an important role in the increased prevalence of cardiovascular diseases in postmenopausal women. We determined whether oxidative stress contributes to the reduced large elastic artery compliance of postmenopausal women. Carotid artery compliance was measured during acute intravenous infusions of saline (baseline control) and supraphysiological doses of the potent antioxidant ascorbic acid in premenopausal (n=10; 23+/-1; mean+/-SE) and estrogen-deficient postmenopausal (n=21; 55+/-1 years) healthy sedentary women. Carotid artery compliance was 56% lower in postmenopausal compared with premenopausal women during baseline control (P<0.0001). Ascorbic acid infusion increased carotid artery compliance by 26% in postmenopausal women (1.11+/-0.07 to 1.38+/-0.08 mm2/mm Hgx10(-1); P<0.001) but had no effect in premenopausal women (2.50+/-0.25 versus 2.43+/-0.20 mm2/mm Hgx10(-1)). Carotid artery diameter, blood pressure, and heart rate were unaffected by ascorbic acid. In the pooled population, the change in arterial compliance with ascorbic acid correlated with baseline waist-to-hip ratio (r=0.56; P=0.001), plasma norepinephrine (r=0.58; P=0.001), and LDL cholesterol (r=0.54; P=0.001). These results suggest that oxidative stress may be an important mechanism contributing to the reduced large elastic artery compliance of sedentary, estrogen-deficient postmenopausal women. Increased abdominal fat storage, sympathetic nervous system activity, and LDL cholesterol may be mechanistically involved in oxidative stress-associated suppression of arterial compliance in postmenopausal women.

The effects of hormone replacement on the biomechanical properties of the uterosacral and round ligaments in the monkey model

OBJECTIVE

The purpose of this study was to determine effects of ovariectomy (OVX) and conjugated equine estrogens plus medroxyprogesterone acetate (CEE/MPA), or ethinyl estradiol plus norethindrone acetate (EE/NA) on biomechanics of uterosacral (USL) and round (RL) ligaments in postmenopausal (PMP) monkeys.

STUDY DESIGN

This was a randomized, triple blind, placebo-controlled study. OVX monkeys received 12 months no treatment (Pbo) (n = 19), CEE/MPA (n = 19), or EE/NA (n = 21). USL and RL step strains and stress-relaxation data were curve-fitted, giving strain-dependent tensile modulus (TM) from 0% to 30%.

RESULTS

(1) USL: TM for both treatment groups was greater than Pbo for strains from 0% to 12% (P < .04). (2) RL: TM for both treatment groups was smaller than Pbo for strains from 12% to 30% (P < .05). No differences were found between treatment regimens.

CONCLUSION

CEE/MPA and EE/NA both affect functional biomechanical properties by increasing tensile stiffness in the USL and decreasing it in the RL.

Comparison of Healos/bone marrow to INFUSE(rhBMP-2/ACS) with a collagen-ceramic sponge bulking agent as graft substitutes for lumbar spine fusion

STUDY DESIGN

A rabbit lumbar intertransverse process arthrodesis model was used to evaluate the efficacy of two different bone substitute materials: 1) collagen-hydroxyapatite sponge (Healos bone void filler) combined with heparinized bone marrow; and 2) recombinant human bone morphogenetic protein-2 delivered in a collagen sponge (INFUSE Bone Graft) wrapped around an additional collagen-ceramic sponge (Mastergraft Matrix) as a "bulking agent."

OBJECTIVES

To compare the relative efficacy of two different bone graft substitutes to achieve posterolateral lumbar spine fusion in rabbits.

SUMMARY OF BACKGROUND DATA

Autogenous bone graft is considered the gold standard graft material for spine fusion. Complications with its use, however, may occur in as many as 30% of patients. A variety of bone substitutes have been used for spine fusion, but there are few direct comparison experiments to determine the relative efficacy of any two alternatives.

METHODS

Adult New Zealand white rabbits (n = 24) were divided into two groups and underwent bilateral posterolateral intertransverse process spine arthrodesis at L5-L6. The fusions were augmented by different bone substitute materials as follows: Group 1 (n = 12) received 3 mL of collagen-hydroxyapatite sponge (Healos bone void filler) (10 x 30 x 5 mm, two per side) with 3.0 mL of heparinized bone marrow on each side of the spine. (ratio 1:1); Group 2 (n = 12) received 1.5 mL of rhBMP-2 (0.43 mg/mL solution) on a Type 1 collagen sponge (INFUSE Bone Graft) wrapped around an additional 1.5 mL collagen-ceramic (15%HA/85%TCP) sponge (Mastergraft Matrix) as a bulking agent to provide 3 mL of graft on each side of the spine. Bone marrow was aspirated from posterior iliac crest, and 1 mL of bone marrow was sent to count number of nucleated cells. The rabbits were killed after 8 weeks; the spines were evaluated by manual palpation, radiographs (plain radiograph and CT scan), tensile mechanical testing, and nondecalcified histology.

RESULTS

The bone marrow had average of total nucleated cell count 9 x 10 cells. All rabbits (100%) in Group 2 (INFUSE/Mastergraft Matrix) achieved solid spinal fusions by manual palpation and radiographs, whereas solid spinal fusion was not achieved by manual palpation and radiographs in any of the rabbits treated with Healos combined with heparinized bone marrow (Group 1). The plain radiograph and CT scans of Group 1 showed some minimal new bone formation near the transverse processes, but none of these rabbits formed a continuous fusion mass. In contrast, all of plain radiographs and CT scans in Group 2 showed continuous fusion mass and complete graft incorporation between transverse processes bilaterally. Biomechanically, the relative strength and relative stiffness values of L5-L6 (fusion segment) in Group 2 were statistically significant greater than L5-L6 in Group 1 (P < 0.001). Histologic sections confirmed the palpation and radiographic results.

CONCLUSION

From the manual palpation, radiographic and biomechanical assessment of fusion, the results in this study showed that INFUSE (rhBMP-2/collagen sponge) consistently produced spine fusion when wrapped around a collagen-ceramic sponge bulking agent (Mastergraft Matrix). Meanwhile, Healos was ineffective as a bone graft material when combined with heparinized autogenous bone marrow.

Effect of hydrogen peroxide on intertubular dentine

OBJECTIVES

To evaluate the effect of 30% hydrogen peroxide on the surface changes and nanomechanical properties of intertubular dentine.

METHODS

Five freshly extracted human premolars were sectioned and two specimens were obtained from each tooth. Atomic force microscopy (AFM) images of dentine were taken. Baseline hardness and Young's modulus of intertubular dentine were determined using nanoindentation testing and recorded. The specimens were then treated with either 0.5 ml of Hank's balanced salt solution (control group) or 30% hydrogen peroxide at 24 degrees C for 24 h. AFM imaging and determination of hardness and Young's modulus of intertubular dentine were then repeated. The images were compared and statistical analyses of hardness and Young's modulus were carried out using paired sample t-tests.

RESULTS

The AFM images showed recession of the intertubular dentine surface post-bleaching. For the control group, there was no significant change in hardness (p=0.124) and Young's modulus (p=0.438) of intertubular dentine. However, a significant decrease in hardness (p=0.002) and Young's modulus (p=0.001) of intertubular dentine was observed for the experimental group.

CONCLUSIONS

Exposure to 30% hydrogen peroxide for 24 h caused surface changes to intertubular dentine and significantly decreased the hardness and Young's modulus of intertubular dentine.

Effects of solvents on the early stage stiffening rate of demineralized dentin matrix

OBJECTIVES

To monitor the stiffening rate of demineralized dentin matrix at the early stages after exposure to different neat solvents.

METHODS

Dentin beams approximately 0.8x0.7x8.0 mm were obtained from human third molars. After covering their ends with resin composite, the middle exposed length of 4.0mm (gauge-length) was demineralized in 0.5 M EDTA (pH 7.0) for 7 days. The specimens were gripped by a testing machine, pre-loaded to 10 g and cyclically stressed in tension to 5% strain, for 30 repeated cycles (total 20 min) at 0.6 mm/min while immersed in water (control). Then, water was replaced by either 100% acetone, methanol, ethanol, propanol, HEMA or air and the specimens subjected to the same cyclic protocol. The maximum apparent modulus of elasticity (E(Max)) was calculated for every cycle, plotted as a function of time and subjected to regression analysis. Stiffening rate was calculated as changes in E (min). Regression analysis examined the relationship between E and time for each solvent. Data were analyzed by one-way ANOVA and Student-Newman-Keuls test at alpha=0.05.

RESULTS

Regression analysis showed that E increased significantly with time in all water-free solvents (R2=0.8-0.99). Stiffening rate was higher for acetone (0.9 MPa/min) and ethanol (0.8 MPa/min), intermediate for air (0.7 MPa/min), methanol (0.6 MPa/min) and propanol (0.5 MPa/min), lower for HEMA (0.2 MPa/min) and practically none for water (0.07 MPa/min) with p<0.05.

CONCLUSIONS

The solvent-induced stiffening rate of demineralized dentin matrix is both time and solvent-dependent. The ability of solvents to promptly stiffen the demineralized dentin matrix may be important in maintaining the resin-infiltrated matrix expanded during the solvent evaporation stage of resin bonding.

Influence of indocyanine green staining on the biomechanical properties of porcine anterior lens capsule

PURPOSE

Indocyanine green (ICG) has recently been introduced in cataract surgery to stain the anterior lens capsule for better visualization of the capsulorhexis. The aim of the current in vitro study was to examine the effect of ICG staining on the biomechanical strength of the anterior porcine lens capsule.

METHODS

Two parallel, 8 mm anterior lens capsule strips were prepared from each of 65 porcine postmortem eyes. ICG staining combined with white light exposure of 0.5, 1, 3, and 30 min duration was conducted. Unstained, nonilluminated and 0.1% glutaraldehyde-treated specimens were used as controls. Biomechanical stress-strain measurements were performed using an automated material tester. The absorption spectrum of the 0.5% ICG solution and the emission spectrum of the light source were controlled.

RESULTS

After ICG staining combined with at least 3 min light exposure, a significant increase of stress (31%) at 25% strain and a significant decrease (7%) in ultimate strain was found. Without light exposure, there was no such effect, suggesting a light-dependent process. After 30 min of 0.1% glutaraldehyde treatment, there was a similar increase in stress (322%) at 25% strain and a decrease (47.6%) in ultimate strain.

CONCLUSIONS

ICG staining of the lens capsule causes a significant increase in elastic stiffness and a reduction in ultimate extensibility, thereby facilitating a smooth continuous capsulorhexis. The effect is due to a photosensitizing effect of ICG, leading to collagen cross-linking.

Effects of separate application of three growth factors (TGF-beta1, EGF, and PDGF-BB) on mechanical properties of the in situ frozen-thawed anterior cruciate ligament

OBJECTIVE

To clarify effects of a separate application of TGF-beta1, EGF, and PDGF-BB on the material properties of the in situ frozen-thawed anterior cruciate ligament.

DESIGN

Twenty-eight rabbits were divided into four groups after undergoing the in situ freeze-thaw treatment in the right anterior cruciate ligament. In 3 of the 4 groups, 4 ng TGF-beta1, 20 ng EGF, and 4 microg PDGF-BB was applied to the frozen anterior cruciate ligament, respectively. In the remaining sham treatment group, only fibrin sealant as a vehicle was applied. Each animal was sacrificed at 12 weeks after surgery.

BACKGROUND

If the role of growth factors in ligament healing and remodeling is understood, better therapies can be designed for ligament trauma.

METHODS

The freeze-thaw treatment was performed three times using the originally developed cryo-probe. The cross-sectional area of the anterior cruciate ligament was measured by the optical non-contact method. After preconditioning, each specimen was stretched to failure. The ligament strain was determined with a video dimension analyzer.

RESULTS

The tensile strength and the tangent modulus of the anterior cruciate ligament in the TGF-beta1 group was significantly higher than in the sham group, but significantly lower than in the normal control group. There were no significant differences in the strength and the modulus between the EGF group, the PDGF-BB group, and the sham group.

CONCLUSIONS

In this model, an application of 4 ng TGF-beta1 significantly inhibited some of the material deterioration that occurs in the in situ frozen-thawed anterior cruciate ligament, while an application of 20 ng EGF or 4 microg PDGF-BB did not significantly affect the deterioration.

RELEVANCE

This information will be useful in the future to develop a new biological therapy for ligament reconstruction to prevent the graft deterioration after transplantation.