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Internal Diameter (internal + diameter)

Distribution by Scientific Domains
Medical Sciences61%
Chemistry25%
Life Sciences7%
2 Other Domains7%
Distribution within Medical Sciences
Cardiovascular Disease24%
Anesthesia & Pain Management8%
11 Other Subdomains60%

Kinds of Internal Diameter

  • ventricular internal diameter
    		•

    Selected Abstracts

    Carvedilol Produces Sustained Long-Term Benefits: Follow-Up at 12 Years

    CONGESTIVE HEART FAILURE, Issue 1 2009
    John F. MacGregor MD
    The authors measured long-term outcomes of patients who initiated carvedilol between 1990 and 1992 to test the hypothesis that carvedilol produces sustained benefits in heart failure patients. The study population consisted of 57 patients who completed a carvedilol placebo-controlled phase II trial. Patients were given open-label carvedilol and were titrated to the maximum dose. Patients were assessed by serial multigated acquisition, echocardiography, and symptom scores. Survival was assessed for all patients and censored as of January 1, 2004. Survival for ischemic vs nonischemic patients was compared using the log-rank test and further compared using Cox regression, controlling for covariates. Etiology of heart failure was ischemic in 15 patients and nonischemic in 42 patients. Median follow-up was 12.9 years. Resting left ventricular ejection fraction (LVEF) and heart failure symptom scores improved at 4 months of treatment and were sustained at 24 months. Left ventricular internal diameter in systole (LVIDS) and left ventricular internal diameter in diastole decreased significantly at 4 and 8 months, respectively, and LVIDS continued to improve at 24 months. Overall mortality was 43% in nonischemic patients and 73% in ischemic patients. In a multivariate analysis, ischemic etiology and baseline LVEF were significant predictors of mortality. Carvedilol produces sustained improvements in left ventricular remodeling and symptoms. Long-term survival is good, particularly in nonischemic patients. [source]

    Echocardiographic Left Ventricular Mass in a Multiethnic Southeast Asian Population: Proposed New Gender and Age-Specific Norms

    ECHOCARDIOGRAPHY, Issue 8 2008
    M.R.C.P., Raymond Ching-Chiew Wong M.B.B.S.
    Background: Left ventricular mass (LVM) is an independent risk factor for cardiovascular outcome. We aimed to define normal reference values of LVM/body surface area (BSA) in a multiethnic Southeast Asian population across ages, and define demographic parameters that predict LVM/BSA. Methods: 198 subjects (44% men, mean age 40 ± 14 years, 82% Chinese, 13% Malay and 5% Indian) with no cardiovascular comorbidity and had normal echo images for age were included in the analysis. Echo LVM was calculated as: 1.04 ×[(left ventricular internal diameter at end-diastole {LVIDd}+ interventricular septal thickness at end-diastole {IVSd}+ left ventricular posterior wall thickness at end-diastole {LVPWd})3, LVIDd3× 0.8]+ 0.61, indexed by BSA (LVM/BSA)* and expressed as g/m2. Results: BSA and blood pressure (BP) were comparable between dichotomous age groups < or , 50 years within the same gender. Women aged , 50 years had larger IVSD, LVPWd, LVM and LVM/BSA compared to younger cohort. (p < 0.01 for all variables). The 95th percentile of LVM in men and women were 189 g and 148 g respectively; corresponding values for LVM/BSA were 106 and 96 g/m2. These values are consistently smaller than published values from the West. Age (r = 0.27, P < 0.001), gender (r =,0.30, P < 0.001), and systolic BP (r = 0.25, P = 0.003) were significant univariate predictors of LVM/BSA. Conclusion: We therefore propose a different cutoff value for the diagnosis of LV hypertrophy among Southeast Asians. [source]

    Relationship between Relative Aerobic Power and Echocardiographic Characteristics in Male Athletes

    ECHOCARDIOGRAPHY, Issue 9 2007
    Zsuzsanna Kneffel M.Ed.
    The relationship between relative aerobic power (rel.VO2max) as a generally accepted indicator of endurance capacity and certain characteristics of the athlete's heart, such as body-size related (relative) left ventricular (LV) diastolic wall thickness (WTd), internal diameter (LVIDd), muscle mass (MM), WTd/IDd, heart rate (HR), fractional shortening (FS) and E/A ratio, were investigated in 346 young males (18,35 years, 291 athletes of various events and 55 nonathletic control subjects). Rel.VO2max was measured by spiroergometry; cardiac characteristics were determined by two-dimensionally guided M-mode and Doppler-echocardiography. When the groups were pooled, correlation of rel.VO2max with the cardiac parameters was significant: LVMM·BSA,1.5= 0.413, LVWTd·BSA,0.5= 0.327, LVIDd·BSA,0.5= 0.292, HR =,0.434, E/A = 0.272 (P < 0.001), but no significant relationship was seen with FS and WTd/IDd. In the endurance trained group, rel. VO2max correlated significantly with LVMM·BSA,1.5, LVWT·BSA,0.5, HR, and E/A, in the ballgame players with LVMM·BSA,1.5, LVWT·BSA,0.5, and E/A, in the power-and-sprint event athletes with HR and E/A. In the control group, no significant relationship was observed. Results indicate that in athletes having higher endurance capacity maximal oxygen consumption depends largely on cardiac condition, while in athletes with a lower endurance capacity it can be limited by peripheral conditions. [source]

    An echocardiographic and auscultation study of right heart responses to training in young National Hunt Thoroughbred horses

    EQUINE VETERINARY JOURNAL, Issue S36 2006
    G. LIGHTFOOT
    Summary Reasons for performing study: There are few data available to determine the effect of training on cardiac valve function. Objectives: To investigate the effect of commercial race training on right ventricular (RV) and tricuspid valve function in an untrained group of National Hunt Thoroughbreds (TB). Material and methods: Cardiac auscultation, guided M-mode echocardiography of the RV, and colour flow Doppler (CFD) tricuspid valve and right atrium were performed in 90 TB horses (age 2,7 years) 1998,2003. Forty horses were examined at least once and 48 horses were examined on at least 2 occasions. Examinations were then classified as: i) before commencement of race training, ii) after cantering exercise had been sustained for a period of 8,12 weeks and iii) at full race fitness. Tricuspid valve regurgitation (TR) murmurs were graded on a 1,6 scale and CFD echocardiography TR signals were graded on a 1,9 scale. Right ventricular internal diameter (RVID) in diastole and systole (RVIDd and RVIDs) was measured by guided M-mode. Associations between continuous RVID and TR measures and explanatory covariates of weight, age, heart rate, yard and stage of training were examined using general linear mixed models with horse-level random effects. Results: On average, RVIDd and RVIDs increased by 0.08 and 0.1 cm, respectively, per year increase in age (P=0.1 and 0.02) and by 0.3 and 0.4 cm, respectively between pre-training and race fitness (P = 0.07 and 0.005). Tricuspid regurgitation score by colour flow Doppler increased by 0.6/year with age (P<0.0001) and by 1.8 between pre-training and race fitness (P< 0.0001). No significant associations were found between any outcomes and weight, heart rate and training yard. Due to the high level of co-linearity between age and training, multivariable models including both terms were not interpretable. Conclusions and clinical relevance: Athletic training of horses exerts independent effects on both severity and prevalence of tricuspid valve incompetence. This effect should therefore be taken into account when examinations are performed. Dimensions of RV increase with age and training in TB horses in a manner that appears to be similar to that of the LV. [source]

    Non-equilibrium water flow characterized by means of upward infiltration experiments

    EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2001

    Summary Upward infiltration experiments under tension were used to demonstrate the presence of non-equilibrium flow in soils, the phenomenon that has important implications for the accelerated movement of fertilizers, pesticides, non-aqueous liquids, and other pollutants. Data obtained from these experiments were analysed using the single-porosity Richards equation, as well as a variably saturated, dual-porosity model and a dual-permeability model for characterizing non-equilibrium water flow. The laboratory experiments were carried out on 0.10-m-long soil cores having an internal diameter of 0.10 m. Constant pressure heads of ,0.10 and ,0.01 m were used as the lower boundary condition. Each infiltration was followed by a single-rate evaporation experiment to re-establish initial conditions, and to obtain the drying soil hydraulic properties. Pressure heads inside the cores were measured using five tensiometers, while evaporative water loss from the top was determined by weighing the soil samples. The data were analysed to estimate parameters using a technique that combined a numerical solution of the governing flow equation (as implemented in a modified version of the Hydrus-1D software) with a Marquardt,Levenberg optimization. The objective function for the parameter estimation was defined in terms of pressure head readings, the cumulative infiltration rate, and the final total water volume in the core during upward infiltration. The final total water volume was used, as well as the pressure head readings during the evaporation part. Analysis of flow responses obtained during the infiltration experiment demonstrated significant non-equilibrium flow. This behaviour could be well characterized using a model of physical non-equilibrium that divides the medium into inter- and intra-aggregate pores with first-order transfer of water between the two systems. The analysis also demonstrated the importance of hysteresis. [source]

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

    EXPERIMENTAL PHYSIOLOGY, Issue 1 2005
    T. A. Lovick
    Neuronal activity-evoked dilatation was investigated in cortical arterioles in brain slices from mature rats maintained in vitro at 31,33°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 ,m) 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 ,m 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 ,m 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 ,m). 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 ,m) 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. [source]

    Fracture strength of bovine incisors after intra-radicular treatment with MTA in an experimental immature tooth model

    INTERNATIONAL ENDODONTIC JOURNAL, Issue 9 2007
    E. A. Bortoluzzi
    Abstract Aim, To evaluate, using an experimental immature tooth model, the fracture resistance of bovine incisors submitted to different reinforcement treatments with mineral trioxide aggregate (MTA). Methodology, An immature tooth model was created by sectioning the coronal and apical portions of 40 bovine incisors 8 mm above and 12 mm below the cementoenamel junction. The root canals were irrigated with 1.0% sodium hypochlorite. They were enlarged both coronally and apically using number 703 carbide burs (ISO: 500,104-168-007-021) and their internal diameter was standardized to 2.1 mm. The specimens were assigned to four groups (n = 10): GI-control (without filling); GII-apical MTA plug + filling with gutta-percha and endodontic sealer; GIII-filling with MTA; GIV-apical MTA plug + filling with MTA + metallic post (Reforpost I). A polyether impression material was used to simulate the periodontal ligament. The specimens were submitted to a compressive load at a crosshead speed of 0.5 mm min,1 in a servo-hydraulic universal testing machine (MTS 810) applied at 45° to the long axis of the tooth until failure. Data were submitted to statistical analysis by the Kruskal,Wallis test at 5% significance level. Results, GIV presented the highest fracture resistance (32.7N) and differed significantly from the other groups (P < 0.05). No statistically difference was found between GII (16.6N) and GIII (23.4N) (P > 0.05). GIII had a significantly higher fracture resistance than GI (P < 0.05). Conclusions, The use of MTA + metallic post as an intra-radicular reinforcement treatment increased the resistance to fracture of weakened bovine teeth in an experimental immature tooth model. [source]

    Extracorporeal photopheresis with permanent subcutaneous right atrial catheters

    JOURNAL DER DEUTSCHEN DERMATOLOGISCHEN GESELLSCHAFT, Issue 12 2007
    Hartmut Ständer
    Summary Background: Adequate peripheral venous access is crucial for successful extracorporeal photopheresis (ECP). As this approach is not always feasible in older patients and patients with graft-versus-host disease, central venous catheters play an increasing role in providing long-term vascular access for ECP.However, not all catheters are able to deliver the minimum flow rate of 7 ml/min for ECP. Patients and Methods: Eight different permanent subcutaneous right atrial catheters were connected in vitro to the UVAR® -XTSÔ photopheresis system and median flow rates were determined. In addition, in vivo flow rates of patients who received ECP, using either peripheral or central venous access, were determined. Results: Hemodialysis catheters with an internal diameter of 2.0 or 1.5 × 3.5 mm and a length up to 48 cm provided in vitro flow rates of 27,28 ml/min, almost identical to a peripheral access needle. Central venous catheters with a length of over 90 cm reached flow rates below 7 ml/min and are impractical for ECP. The analysis of 308 ECP collection cycles with peripheral vascular access revealed an average flow rate of 31.5 ± 6.4 ml/min. Only permanent subcutaneous right atrial catheters made for hemodialysis provided similar flow rates (Quinton PermCath Dual Lumen) (33.7 ± 4.7 ml/min, n = 198). Conclusions: Permanent subcutaneous hemodialysis catheters with a length of maximally 48 cm achieve optimal flow rates for ECP. They represent therefore the central venous access of choice in patients with inadequate peripheral vascular access. [source]

    Light emitting diodes and an infrared bulb as light sources of a fixed-film tubular photobioreactor for conversion of hydrogen sulfide to elemental sulfur

    JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 2 2005
    Murtuza A Syed
    Abstract The effect of light quality on the performance a fixed-film continuous-flow photobioreactor for removal of hydrogen sulfide from synthetic industrial wastewater and conversion of it to elemental sulfur was investigated. Sixteen 150 mm long and 1.6 mm internal diameter (id) Tygon tubes formed the active part of the reactor. At the same light intensity, reactor performance in terms of optimal sulfide loading rates was compared between an infrared bulb and light emitting diodes (LEDs). The LEDs provided light within the peak absorption wavelength range of green sulfur bacteria (GSB) and were used as a light source for the GSB with the goal of reducing the cost of the required light. Though the reactor sustained higher sulfide loading rates using LEDs than when using an infrared bulb at equal light intensities, the infrared bulb has the potential to be more efficient overall. Copyright © 2004 Society of Chemical Industry [source]

    Hardness of Three Resin-Modified Glass-Ionomer Restorative Materials as a Function of Depth and Time

    JOURNAL OF ESTHETIC AND RESTORATIVE DENTISTRY, Issue 4 2009
    HOWARD W. ROBERTS DMD
    ABSTRACT Statement of the Problem:, The polymerization of bulk-placed resin-modified glass-ionomer (RMGI) restoratives is compromised when penetration of the curing light is limited because of the materials' thickness. It is unknown if additional post light-curing resin polymerization and/or glass-ionomer setting occurs over time to ensure adequate polymerization. Purpose:, The primary objective was to evaluate the depth of cure of various thicknesses of RMGI restorative products over 1 year using Knoop hardness (KH) testing. Materials and Methods:, The materials were placed in Delrin molds having an internal diameter of 5.0 mm and heights of 2, 3, 4, and 5 mm and were photopolymerized with a halogen light-curing unit. Five specimens of each depth were prepared for each time period evaluated. Specimens were stored in darkness at 37 ± 2°C and 98 ± 2% humidity until being tested at 24 hours, 1 week, and 1, 3, 6, 9, and 12 months after fabrication. Mean KH values were calculated for the bottom and top surfaces of each thickness group and used to determine bottom/top hardness ratios. Data were compared using two-way analysis of variance (factors of time, thickness) at a 0.05 significance level with Scheffé's post hoc analysis, where required. Results:, The materials had relatively stable top surface KH, which permitted valid assessment of changes in bottom surface KH over time. The bottom surface KH of some RMGIs changed significantly over time (p < 0.001), but degrees of change were material dependent. Certain RMGIs demonstrated a potential for statistically significant post light-activation hardening; however, that too was material dependent. As compared with top surface KH, deeper layers of the thicker RMGI specimens consistently failed to achieve an adequate degree of polymerization. Conclusion:, Although certain RMGI materials demonstrate a potential for post light-activation chemically initiated resin polymerization and/or polyalkenoate acid/base reaction, these reactions may not be sufficient to ensure that the material is adequately polymerized for long-term success. This is particularly true when RMGI materials are placed in thicker layers where curing light penetration may be compromised. CLINICAL SIGNIFICANCE RMGI materials should not be placed in bulk but photopolymerized in layers to ensure adequate light activation. The results of this study suggest that Photac-Fil Quick be placed in layers no thicker than 2 mm while Fuji II LC and Vitremer may be placed in layers up to 3 mm in thickness. [source]

    Band-related leg injuries in an Australian passerine and their possible causes

    JOURNAL OF FIELD ORNITHOLOGY, Issue 2 2006
    Kate Splittgerber
    ABSTRACT We examined the extent and causes of band-related leg injuries in an Australian passerine, the Bell Miner (Manorina melanophrys). Eight percent of banded birds exhibited leg injuries, and most were birds with two plastic color bands on a tarsus. Leg injuries typically followed the accumulation of shed tarsal scales under the color bands. Color bands used on Bell Miners were tighter on the tarsus than the metal band and also tighter than the color bands used on Superb Fairy-wrens (Malurus cyaneus), a commonly banded species with no reported leg injuries. The tendency for scales to accumulate under two plastic color bands appeared to be influenced by the diameter of a band relative to the size of a bird's tarsus (with looser bands less likely to cause accumulation) and the material used to make the band (with smoother surfaces less likely to cause accumulation). Celluloid color bands had rougher internal surfaces than either Darvic or metal bands. In addition, both celluloid and Darvic color bands generated static electricity capable of attracting tarsal scales. Scales that accumulated under bands provided an environment where potentially harmful fungi became established, potentially contributing to the severity of leg injuries. Our results suggest that, when selecting an appropriate band size for a bird, the diameter of the tarsus at its midpoint should occupy only between 60% and 65% of the internal diameter of the band and, when possible, a single, bicolored, anodized aluminum alloy band should be used instead of multiple plastic color bands. SINOPSIS Examinamos la causa y la extensión de lesiones en las patas causadas por anillas en Manorina melanophrys, en Australia. Un 8% de las aves mostraron lesiones en las patas, la mayoría aves con dos anillas plásticas. Las lesiones causaron la acumulación de escamas tarsales mudadas, bajo la anilla. Se encontraron que las anillas plásticas ejercían mas presión o estaban más ajustadas que las anillas de metal y que estaban más apretadas que en Malurus cyaneus, una especie comúnmente anillada y en donde no encontramos lesiones. La tendencia de acumulación de escamas bajo las dos anillas plásticas, parece ser influenciada por el diámetro de la anilla, con respecto al grosor del tarso del ave y del material con que estuvo echo la anilla. Encontramos que las anillas de celuloide tienen una superficie interna más áspera que las anillas de metal. Además, ambos tipos de anillas, generan estática capaz de atraer las escama de la pata. Las partículas de escama que se acumulan bajo una anilla proveen de una buena base para que se crezcan hongos, que contribuyen a la gravedad de la lesión en la pata. Sugerimos que se deben seleccionar anillas apropiadas en tamaño en donde el diámetro del tarso en la parte media de la pata, ocupe entre el 60,65% del diámetro interno de la anilla. También, que cuando sea posible, se utilice una sola anilla de metal pintada con dos colores, en vez de dos anillas plásticas. [source]

    Palliation in cancer of the oesophagus , what passes down an oesophageal stent?

    JOURNAL OF HUMAN NUTRITION & DIETETICS, Issue 5 2003
    A. Holdoway
    Introduction: Self-expanding metal stents are becoming an increasingly popular method of palliation of dysphagia in advanced oesophageal carcinoma. Approximately 10% require intervention post-placement because of blockage (Angorn, 1981). This could be prevented by effective dietary advice. We set out to write evidence-based dietary guidelines for patients undergoing oesophageal stent insertion. A comprehensive literature search failed to identify evidence to support the present guidelines used by manufacturers and dietitians on foods allowed or to avoid and the use of fizzy drinks to ,clean' the stent. Only reference on the ability to consume a semi-solid or solid diet was made (Nedin, 2002). We therefore tested the ability of 50 foods to pass through a stent and the efficacy of fizzy water in unblocking an occluded stent. Method: Normal mouthfuls of raw and cooked, peeled/unpeeled fruit and vegetables, casseroles, griddle or grilled plain meat, poultry or fish, eggs, nuts, dried fruit and bread in various forms were tested. An adult female chewed a ,normal' mouthful of each test food and at the point of swallowing the bolus of food was passed into an expanded Ultraflex metal covered stent (internal diameter 18 mm). If occlusion occurred, water was dribbled through the stent, simulating swallowing fluid, in an attempt to unblock the stent. If the occlusion remained, the stent was agitated to mimic advice given about moving around to unblock a stent in a patient. If it remained occluded, a smaller amount of food, approximately half a mouthful, was chewed for twice as long and re-tested. To test the efficacy of fizzy water to clear an occlusion, we compared the ability of water, warm water and fizzy water to unblock a stent artificially occluded with a bolus of bread. Results: Foods that occluded the stent but passed through if eaten in half mouthfuls and chewed for twice normal chewing time included sandwiches, dry toast, apple, tinned pineapple, fresh orange segments with pith removed, up to six sultanas, chopped dried apricot, boiled egg, muesli, meat and poultry. Dry meat, fruit with pith, skins of capsicum peppers and tomatoes, more than seven sultanas and dried apricots caused occlusion. Nuts and vegetables such as lettuce, which are cited in many diet sheets as items to avoid (Nedin, 2002), passed through the stent when chewed to a normal level. The volumes of fluid required to unblock a stent occluded with bread were 5 l of fizzy water, 3.5 l of cold water or 1 l of warm water. Conclusion: If a patient has good dentition and can chew well and take small mouthfuls and prepare and cook food appropriately, it is likely that they can enjoy a wide variety of solid foods. The use of fizzy drinks to maintain the patency of the stent in patients prone to reflux is questionable, warm fluids may be more efficacious. Based on these initial findings we are updating our dietary guidelines for patients undergoing oesophageal stent insertion and hope to audit stent occlusion following implementation. [source]

    Beckmann rearrangement of cyclohexanone oxime to ,-caprolactam in microreactors

    AICHE JOURNAL, Issue 5 2010
    K. T. Zuidhof
    Abstract Selectivities are presented of the Beckmann rearrangement of cyclohexanone oxime to ,-caprolactam with oleum for various conditions in three microreactors, viz., Y-junction, interdigital, and split and recombine mixers, followed by a 50-cm long microchannel of 250 ,m internal diameter. Cyclohexanone oxime is dissolved in cyclooctane, which is inert for oleum. The selectivity is measured in the temperature range of 80,132°C. The concentration range of caprolactam in the reaction mixture is 31,41 wt %, in oleum. The total volumetric flow rate is 0.4 ml/min, whereas the flow rate ratio of ,-caprolactam/oleum over cyclohexanone oxime/cyclooctane ranges from 0.3 to 3. The selectivities measured with the three microreactors are: 70,99+%, 93,99+%, and 95,99+%, respectively. High ,-caprolactam concentration (41 wt %), high temperature (110,132°C), and a ratio of free H2SO4 to SO3 of unity have a negative effect on the selectivity. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]

    The kinetics of the reduction of iron oxide by carbon monoxide mixed with carbon dioxide

    AICHE JOURNAL, Issue 4 2010
    C. D. Bohn
    Abstract Results are reported for the repeated reduction of iron oxide particles, 300,425 ,m diameter, by a mixture of CO, CO2, and N2 in a fluidized bed of 20 mm internal diameter. The conclusions were as follows: (1) Reduction of either Fe2O3 to Fe3O4 or of Fe3O4 to Fe0.947O is first-order in CO. (2) With the particle sizes used, the rates of the reduction reactions are controlled by intrinsic chemical kinetics. Activation energies and pre-exponential factors are reported. (3) The first cycle gave anomalous results, but (a) the rate of reduction of Fe2O3 to Fe3O4 remained constant over cycles 2,10; (b) the rate of reduction of Fe3O4 to Fe0.947O declined by 60,85% over cycles 2,10. (4) The rates of reduction declined with solids conversion down to zero at 80% conversion. The rates were incorporated into a conventional model of a fixed bed, which was used to predict, satisfactorily, the reduction behavior of iron oxide. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]

    Analysis of aromatic and terpenic constituents of pepper extracts by capillary electrochromatography

    JOURNAL OF SEPARATION SCIENCE, JSS, Issue 4 2007
    Alessandro Musenga
    Abstract An original method based on CEC has been developed for the determination of aromatic and terpenic compounds in extracts of spices obtained from Piper nigrum. The method is based on the use of a fused silica capillary (effective length: 23.5 cm, internal diameter: 100 ,m) packed with a C18 sorbent (packing length: 23 cm, particle size: 5 ,m). The mobile phase is a 50 mM, pH 6.0 ammonium acetate/ACN (10:90 v/v) mixture. Applying a 30 kV voltage, the following 11 compounds were separated and analysed: terpinen-4-ol, caryophyllene oxide, limonene, ,-pinene, 3-carene, ,-pinene, ,-humulene, ,-caryophyllene, ,-phellandrene, eugenol and piperine. Compound determination is carried out using a diode-array detector set at 265 and 338 nm for ,-phellandrene and piperine, respectively, and at 210 nm (reference subtraction at 282 nm) for all the other analytes. The optimised method has been validated with good results in terms of linearity, limits of quantitation, detection and precision. The CEC method was successfully applied to the analysis of essential oils and methanolic extracts of ,black', ,white' and ,green' pepper. [source]

    Tissue Doppler and Strain Imaging in Dogs with Myxomatous Mitral Valve Disease in Different Stages of Congestive Heart Failure

    JOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 6 2009
    A. Tidholm
    Background: Tissue Doppler imaging (TDI) including strain and strain rate (SR) assess systolic and diastolic myocardial function. Hypothesis: TDI, strain, and SR variables of the left ventricle (LV) and the interventricular septum (IVS) differ significantly between dogs with myxomatous mitral valve disease (MMVD) with and without congestive heart failure (CHF). Animals: Sixty-one dogs with MMVD with and without CHF. Ten healthy control dogs. Methods: Prospective observational study. Results: Radial motion: None of the systolic variables were altered and 3 of the diastolic velocities were significantly increased in dogs with CHF compared with dogs without CHF and control dogs. Longitudinal motion: 2 systolic velocities and 3 diastolic velocities were significantly increased in dogs with CHF compared with dogs without CHF and control dogs. Difference in systolic velocity time-to-peak between LV and IVS was significantly increased in dogs with MMVD with and without CHF compared with control dogs. In total, 11 (23%) of 48 TDI and strain variables differed significantly between groups. Left atrial to aortic ratio was positively correlated to early diastolic velocities, percentage increase in left ventricular internal diameter in systole was positively correlated to systolic and diastolic velocities, and mitral E wave to peak early diastolic velocity in the LV basal segment (E/Em) was positively correlated to radial strain and SR. Conclusions and Clinical Importance: Few TDI and strain variables were changed in dogs with MMVD with and without CHF. Intraventricular dyssynchrony may be an early sign of MMVD or may be an age-related finding. [source]

    Effect of Pimobendan or Benazepril Hydrochloride on Survival Times in Dogs with Congestive Heart Failure Caused by Naturally Occurring Myxomatous Mitral Valve Disease: The QUEST Study

    JOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 5 2008
    J. Häggström
    Background: Myxomatous mitral valve disease (MMVD) continues to be an important cause of morbidity and mortality in geriatric dogs despite conventional therapy. Hypothesis: Pimobendan in addition to conventional therapy will extend time to sudden cardiac death, euthanasia for cardiac reasons, or treatment failure when compared with conventional therapy plus benazepril in dogs with congestive heart failure (CHF) attributable to MMVD. Animals: Two hundred and sixty client-owned dogs in CHF caused by MMVD were recruited from 28 centers in Europe, Canada, and Australia. Methods: A prospective single-blinded study with dogs randomized to PO receive pimobendan (0.4,0.6 mg/kg/d) or benazepril hydrochloride (0.25,1.0 mg/kg/d). The primary endpoint was a composite of cardiac death, euthanized for heart failure, or treatment failure. Results: Eight dogs were excluded from analysis. One hundred and twenty-four dogs were randomized to pimobendan and 128 to benazepril. One hundred and ninety dogs reached the primary endpoint; the median time was 188 days (267 days for pimobendan, 140 days for benazepril hazard ratio = 0.688, 95% confidence limits [CL] = 0.516,0.916, P= .0099). The benefit of pimobendan persisted after adjusting for all baseline variables. A longer time to reach the endpoint was also associated with being a Cavalier King Charles Spaniel, requiring a lower furosemide dose, and having a higher creatinine concentration. Increases in several indicators of cardiac enlargement (left atrial to aortic root ratio, vertebral heart scale, and percentage increase in left ventricular internal diameter in systole) were associated with a shorter time to endpoint, as was a worse tolerance for exercise. Conclusions and Clinical Importance: Pimobendan plus conventional therapy prolongs time to sudden death, euthanasia for cardiac reasons, or treatment failure in dogs with CHF caused by MMVD compared with benazepril plus conventional therapy. [source]

    Immediate and Late Outcomes of Transarterial Coil Occlusion of Patent Ductus Arteriosus in Dogs

    JOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 1 2006
    F.E. Campbell
    Records from dogs (n = 125) that underwent attempted transarterial coil occlusion of patent ductus arteriosus (PDA) at the University of California, Davis, between 1998 and 2003, were reviewed, and a subset of these dogs (n = 31) in which the procedure was performed at least 12 months earlier were reexamined to determine long-term outcome. Coil implantation was achieved in 108 dogs (86%). Despite immediate complete ductal closure in only 34% of dogs, the procedure was hemodynamically successful as evidenced by a reduction in indexed left ventricular internal diameter in diastole (LVIDd; P < .0001), fractional shortening (P < .0001), and left atrial to aortic ratio (LA: Ao; P = .022) within 24 hours. Complete ductal closure was documented in 61% of dogs examined 12 to 63 months after coil occlusion. Long-standing residual ductal flow in the other 39% of dogs was not associated with increased indexed LVIDd or LA: Ao and was not hemodynamically relevant. Repeat intervention was deemed advisable in only 4 dogs with persistent (n = 1) or recurrent (n = 3) ductal flow. Complications included aberrant embolization (n = 27), death (n = 3), ductal reopening (n = 3), transient hemoglobinuria (n = 2), hemorrhage (n = 1), aberrant coil placement (n = 1), pulmonary hypertension (n = 1), and skin abscessation (n = 1). Serious infectious complications did not occur despite antibiotic administration to only 40% of these dogs. Transarterial coil occlusion was not possible in 14 dogs (11%) because of coil instability in the PDA and was associated with increased indexed minimum ductal diameter (P= .03), LVIDd (P= .0002), LVIDs (P= 0.001), and congestive left heart failure (P= .03) reflecting a relatively large shunt volume. [source]

    Spontaneous Feline Hypertension: Clinical and Echocardiographic Abnormalities, and Survival Rate

    JOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 1 2003
    Valerie Chetboul
    Systemic hypertension was diagnosed in 58 of 188 untreated cats referred for evaluation of suspected hypertension-associated ocular, neurologic, cardiorespiratory, and urinary disease, or diseases frequently associated with hypertension (hyperthyroidism and chronic renal failure). Hypertensive cats were significantly older than normotensive subjects (13.0 ± 3.5 years versus 9.6 ± 5.0 years; P < .01), and had a greater prevalence of retinal lesions (48 versus 3%; P < .001), gallop rhythm (16 versus 0%; P < .001), and polyuria-polydipsia (53 versus 29%; P < .01). Blood pressure was significantly higher (P < .001) in cats with retinopathies (262 ± 34 mm Hg) than in other hypertensive animals (221 ± 34 mm Hg). Hypertensive cats had a thicker interventricular septum (5.8 ± 1.7 versus 3.7 ± 0.64 mm; P < .001) and left ventricular free wall (6.2 ± 1.6 versus 4.1 ± 0.51 mm; P < .001) and a reduced diastolic left ventricular internal diameter (13.5 ± 3.2 versus 15.8 ± 0.72 mm; P < .001) than control cats. Left ventricular geometry was abnormal in 33 of 39 hypertensive subjects. No significant difference was found in age or blood pressure at the initial visit between cats that died or survived over a 9-month period after initial diagnosis of hypertension. Mean survival times were not significantly different between hypertensive cats with normal and abnormal left ventricular patterns. Further prospective studies are needed to clearly identify the factors involved in survival time in hypertensive cats. [source]

    Rapid Vasodilation in Isolated Skeletal Muscle Arterioles: Impact of Branch Order

    MICROCIRCULATION, Issue 2 2010
    BRUNO T. ROSEGUINI
    Microcirculation (2010) 17, 1,11. doi: 10.1111/j.1549-8719.2009.00005.x Abstract We tested the hypothesis that segmental differences in the responsiveness and time course of vasodilation to metabolic signals putatively involved in rapid onset vasodilation (ROV) at the start of exercise exist within the skeletal muscle vasculature. Cannulated first-order (1As) and third-order arterioles (3As) of the rat gastrocnemius (G) muscle were exposed to cumulative doses of KCl, acetylcholine (Ach), or adenosine (Ado). In addition, time course and magnitude of vasodilation to localized application of these agonists were determined. 1As and 3As dilated similarly to incremental doses of the agonists. Continuous monitoring of internal diameter revealed a fast and transient dilatory response to microinjections of the agonists, with an average time delay (TD) before the onset of vasodilation of 2.8 ± 0.2 seconds (1As: 3.0 ± 0.3 seconds and 3As: 2.6 ± 0.3 seconds) and time-to-peak (TP) of 8.2 ± 0.7 seconds (1As: 10.3 ± 1 seconds and 3As:5.7 ± 0.5 seconds). No significant differences were detected for all parameters between 1As and 3As for KCl or Ado application, while 1As had a significantly longer TP and greater peak dilation than 3As to Ach. These findings demonstrate that 1As and 3As from the rat G muscle appear to have similar responsiveness to vasoactive agonists. Furthermore, the average TD before vasodilation supports a role for metabolic signals as contributors to the ROV. [source]

    Role of Vascular Heme Oxygenase in Reduced Myogenic Reactivity Following Chronic Hypoxia

    MICROCIRCULATION, Issue 2 2006
    JAY S. NAIK
    ABSTRACT Objective: Exposure to chronic hypoxia (CH) results in a persistent endothelium-dependent vascular smooth muscle hyperpolarization that diminishes vasoconstrictor reactivity. Experiments were performed to test the hypothesis that products of both cytochrome P450 epoxygenase (CYP) and heme oxygenase (HO) are required for the persistent diminished myogenic reactivity following CH. Methods: The authors examined myogenic responses of mesenteric arteries isolated from control and CH (48 h; PB = 380 mmHg) rats in the presence of a HO inhibitor (zinc protoporphyrin IX; ZnPPIX) or combined HO and CYP epoxygenase inhibition (sulfaphenazole). Arteries were isolated and cannulated and the vascular smooth muscle was loaded with the Ca2 + indicator Fura-2. Results: Control vessels maintained their internal diameter in response to step increases in intraluminal pressure, whereas arteries from CH animals passively distended. ZnPPIX augmented myogenic reactivity and [Ca2 +] in arteries from CH animals. Combined administration of sulfaphenazole and ZnPPIX did not have an additional effect compared to ZnPPIX alone. Myogenic reactivity in control vessels was not altered by ZnPPIX or ZnPPIX + sulfaphenazole. Conclusions: HO appears to play a role in regulating myogenic reactivity following CH. Furthermore, these data suggest that products of HO and CYP are both required for the observed attenuation in vasoreactivity following CH. [source]

    A New Video Image Analysis System to Study Red Blood Cell Dynamics and Oxygenation in Capillary Networks

    MICROCIRCULATION, Issue 6 2005
    SHRUTI A. JAPEE
    ABSTRACT Objective: The authors present a Measurement and Analysis System for Capillary Oxygen Transport (MASCOT) to study red blood cell (RBC) dynamics and oxygenation in capillary networks. The system enables analysis of capillaries to study geometry and morphology and provides values for capillary parameters such as diameter and segment length. It also serves as an analysis tool for capillary RBC flow characteristics, including RBC velocity, lineal density, and supply rate. Furthermore, the system provides a means of determining the oxygen saturation of hemoglobin contained within RBCs, by analysis of synchronized videotapes containing images at two wavelengths, enabling the quantification of the oxygen content of individual RBCs. Methods: Video recordings of RBC flow at two wavelengths, 420 nm (isosbestic) and 436 nm (oxygen sensitive), are made using a dual camera video microscopy system. The 420-nm recording is used to generate images based on the variance of light intensity fluctuations that help to identify capillaries in a given field of view that are in sharp focus and exhibit flow of individual RBCs separated by plasma gaps. A region of interest enclosing the desired capillary is defined and a fixed number of successive video frames at the two wavelengths are captured. Next a difference image is created, which delineates the RBC column, whose width is used to estimate the internal diameter of the capillary. The 420-nm images are also used to identify the location and centroid of each RBC within the capillary. A space,time image is generated to compute the average RBC velocity. Lineal density is calculated as the number of RBCs per unit length of a capillary segment. The mean optical density (OD) of each RBC is calculated at both wavelengths, and the average SO2 for each cell is determined from OD436/OD420. Results and Conclusions: MASCOT is a robust and flexible system that requires simple hardware, including a SGI workstation fitted with an audio-visual module, a VCR, and an oscilloscope. Since the new system provides information on an individual cell basis from entire capillary segments, the authors believe that results obtained using MASCOT will be more accurate than those obtained from previous systems. Due to its flexibility and ease of extension to other applications, MASCOT has the potential to be applied widely as an analysis tool for capillary oxygen transport measurements. [source]

    Cuff compliance of pediatric and adult cuffed tracheal tubes: an experimental study

    PEDIATRIC ANESTHESIA, Issue 8 2004
    J.-M. Devys MD
    Summary Background :,Tracheal mucosal damage related to tracheal intubation has been widely described in pediatric and adult patients. High volume,low pressure cuffs (HVLPC) are being advertised as safe to avoid this particularly unpleasant complication. Compliances of these supposed pediatric and adult HVLPC are not mentioned by manufacturers and still remain unknown. Methods :,The compliance of HVLPC was measured in vitro and defined as the straight portion of the pressure,volume curve. Cuff pressure was measured after incremental 0.1 ml filling volumes of air for sizes 3.0,8.0 of internal diameter of RüschTM and MallinckrodtTM tracheal tubes. Compliances were assessed in air and in a rigid tube. The filling volume to achieve a 25-mmHg intracuff pressure was also measured. Results :,In air, each 0.1 ml step almost linearly increased cuff pressure by 1 mmHg (size 8.0) to 9 mmHg (size 3). In air, the volume needed to maintain a cuff pressure < 25 mmHg was small for sizes 3,5.5 (0.35,2 ml). The 25 mmHg inflated cuff volume and compliance were decreased within a rigid tube, especially for adult sizes. In a rigid tube simulating a trachea, the compliances of almost every RüschTM tracheal tube were statistically higher than those of the MallinckrodtTM. Conclusion :,We conclude that the tested tracheal tube cuffs have low compliance and cannot be defined as high volume,low pressure. [source]

    Nitrogen Atmospheric Pressure Post Discharges for Surface Biological Decontamination inside Small Diameter Tubes

    PLASMA PROCESSES AND POLYMERS, Issue 6 2008
    Anne-Marie Pointu
    Abstract A nitrogen afterglow at atmospheric pressure has recently been described as able to transport active species over long distances in small diameter tubes, with a biocidal effect. For a discharge gas composed of nitrogen, either of high purity or with some controlled ppm of oxygen, survival curves are presented. The afterglow, flowing at 40 slm in a cylindrical quartz tube with 8 mm internal diameter is studied using emission spectroscopy. Fundamental or excited states of atomic or molecular species of parent gases are detected and evaluated. Their absolute concentration is measured along the tube axis. Correlated to transport equations, results give information on the creation and destruction reactions of these species, especially of the O(1S) metastable state of O, the species that has been shown to boost the biocidal effect. [source]

    Modification of a commercial electrospray nebulizer for operation in a liquid chromatography/mass spectrometry system at flow rates in the low,µL/min range

    RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 18 2001
    Alain Carrier
    A simple and inexpensive approach to convert the electrospray nebulizer of a commercial liquid chromatography/mass spectrometry (LC/MS) system (HP 1100) to accommodate lower flow rates has been proposed and evaluated. This modification consists of simply replacing the nebulizer needle by a commercially available stainless steel needle with a smaller internal diameter. Experiments were conducted in order to optimize operational parameters. Using two different internal diameter needle sizes, flow rates ranging from 1 to 250,µL/min could be accommodated. The modification presented allows an extension of the range of compatible flow rates without major modification of the standard design of the interface. Copyright © 2001 John Wiley & Sons, Ltd. [source]

    Ovum Pick-up in Sheep: a Comparison between Different Aspiration Devices for Optimal Oocyte Retrieval

    REPRODUCTION IN DOMESTIC ANIMALS, Issue 2 2006
    C Rodríguez
    Contents In vivo ovum pick-up (OPU) in sheep may be improved with a proper choice of aspiration elements (needle and tubing) and aspiration vacuum pressure. In the present study, two experiments were carried out. In Expt 1, visible follicles in ovaries of slaughtered ewes (treated separately according to their diameters: small <3 mm, medium 3,5 mm and large >5 mm) were aspirated using different combinations of the three studied factors such as aspiration flow rate (10, 20, 30, 40 and 50 ml water/min), needle gauge (18 and 20 G) and tubing inner diameter (1, 2 or 3 mm internal diameter). In Expt 2, a study with two 18 G needles of different lengths (18 G: 82 mm; 18 GL: 600 mm) was carried out, using ovaries obtained post-mortem, and performing in vivo laparoscopic follicular aspiration on ewes. We considered good quality oocytes as those with both complete compact cumulus and a homogeneous cytoplasm. Recovery rate, proportion of good quality oocytes (good quality oocytes/100 oocytes recovered) and overall efficiency (good quality oocytes/100 follicles aspirated) were noted. In Expt 1, aspiration flow rate affect remarkable proportion of good quality oocytes (69.5%, 50.5%, 44.8%, 36.5% and 28.3% for flows from 10 to 50 ml/min respectively, p < 0.05). Needle gauge did not affect aspiration device efficiency. Thin and intermediate tubings were more effective (overall efficiency rates: 34.9%, 32.3% and 28.1% for 1, 2 and 3 mm respectively, p < 0.05). Follicle size did not affect recovery rate, but proportion of good quality oocytes was higher for large (77.9%) and medium (64.4%) follicles (p < 0.05). Finally, some combinations of the aspiration device showed greater effectiveness. In Expt 2, needle length did not influence recovery rate, but good quality oocytes rate was significantly modified both post-mortem and in vivo (good quality rate for 18 G vs 18 GL needles: 69.5% vs 47.7% and 58.1% vs 25.4%, post-mortem and in vivo respectively, p < 0.05). We conclude that low-aspiration flow rates (10 and 20 ml/min) with thin or intermediate tubings (1 and 2 mm), and any short needle (18 G or 20 G) are the most adequate aspiration factors for OPU in sheep. [source]

    Flow-dependent resistance of nasal masks used for non-invasive positive pressure ventilation

    RESPIROLOGY, Issue 4 2006
    Wolfram WINDISCH
    Objective and background: Endotracheal tube resistance is known to be flow-dependent and this understanding has improved the application of invasive ventilation. However, similar physiological studies on the interface between patients and non-invasive positive pressure ventilation (NPPV) have not been performed. Therefore, this study was aimed at investigating the resistance of nasal masks used for NPPV. Methodology: The flow-dependent pressure drop of the small (S), medium-small (MS) and medium (M) Contour Nasal Mask (Respironics Inc., Murrysville, PA, USA) was measured with and without a connecting tube (length 18 cm, internal diameter 1.5 cm) in a laboratory study. The resistance was calculated by Rohrer's equation using the standard least-squares-fit technique. The present study explicitly differentiated between the resistance of the nasal mask alone when measured against atmosphere and the additional resistance caused by the nasal mask when airtightly fitted to a model head (interaction with the face). Results: Higher flow rates resulted in a non-linearly increasing pressure drop across the interface. This flow-dependent resistance of the S/MS/M mask was comparably low when not interacting with the face, but increased when interacting with the face. This flow-dependent resistance of the mask was several-fold higher when adding the connection tube and tended to be higher during expiration. Conclusion: There is a non-linear flow-dependent pressure drop across the nasal mask which is low and independent of its size, but increases when interacting with the face. The connecting tube is the major determinant of the resistance originating from facial appliances used for NPPV. [source]

    Radioisotope tracer study in trickle bed reactors

    THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2001
    Krishna Deo Prasad Nigam
    Abstract The residence time distribution (RTD) of liquid phase in trickle bed reactors has been measured for air-water system using radioisotope tracer technique. Experiments were carried out in a glass column of internal diameter of 0.152 m packed with glass beads and actual catalyst particles of two different shapes. From the measured RTD curves, mean residence time of liquid was calculated and used to estimate liquid holdup. The axial dispersion model was used to simulate the experimental data and estimate mixing index, ie. Peclet number. The effect of liquid and gas flow rates on total liquid holdup and Peclet number has been investigated. Results of the study indicated that shape of the packing has significant effect on holdup and axial dispersion. Bodenstein number has been correlated to Reynolds number, Galileo number, shape and size of the packing. La distribution de temps de séjour (DTS) de la phase dans des réacteurs a lits ruisselants a été measurée pour le système air-eau à d'une technique par traceurs radio-isotopes. Des expériences ont été menées dans une colonne de verre de 0,152 m de diamètre intérieur garnie de billes de verre et de particules de catalyseur réelles de deux formes différentes. à partir des courbes de DTS mesurées, ie temps de séjour moyen du liquide a été calculé puls utilisé pour l'estimation de la rétention de liquide. On a utilisé. On a utilisé le modèl de dispersion axiale afin de simuler les données expérimentales et d'estimer l'indice de mélange, soit le nombre de Peclet. On a étudié l'effet des débits de liquide et de gaz sur la rétention de liquide totale et le nombre de Peclet. Les résultats de l'étude indiquent que la forme du garnissage a un effet significatif sur la rétention et la dispersion axiale. Le nombre de Bodenstein a été corrélé au nombre de Reynolds, au nombre de Galilée, ainsi qu'à la forme et à la taille du garnissage. [source]

    Leakage of fluid around high-volume, low-pressure cuffs

    ANAESTHESIA, Issue 1 2001
    apparatus
    We studied the ability of high-volume, low-pressure tracheal tube cuffs (Portex Soft Seal®, Portex Profile®, Mallinckrodt Lo-Contour® and Mallinckrodt Hi-Lo® tubes) to prevent leakage of fluid into the airway, in a model trachea and lung. Five tubes (7.0 and 8.0 mm internal diameter) of each type were used. Each tube was inserted into the model trachea and the cuff inflated until the intracuff pressure reached either 20, 30 or 40 cmH2O. The model lung was ventilated with a tidal volume of 700 ml and respiratory rate of 14 breath.min,1 at a compliance of 20 cmH2O. Ten millilitres of 0.01% methylene blue solution were infused over the cuff and the volume of fluid leaking past the cuff over 5 min was measured. The leak volume for the Soft Seal tube was less than that for the Profile or Lo-Contour tubes at all intracuff pressures (all p <,0.05). Compared with the Hi-Lo tube, the volume leaking past the cuff for the Soft Seal tube was greater at an intracuff pressure of 20 cmH2O (p <,0.05), whereas there was no significant difference between these two tubes at an intracuff pressure of 30 or 40 cmH2O. We conclude that the cuff of the Portex Soft Seal tube prevented leakage of fluid significantly more than that of the Portex Profile or Mallinckrodt Lo-Contour tubes, and to a similar degree to that of the Mallinckrodt Hi-Lo tube. [source]

    Engineering of Vascular Grafts With Genetically Modified Bone Marrow Mesenchymal Stem Cells on Poly (Propylene Carbonate) Graft

    ARTIFICIAL ORGANS, Issue 12 2006
    Jun Zhang
    Abstract:, Bone marrow mesenchymal stem cells (MSCs) have demonstrated their pluripotency to differentiate into different cell lineages and may be an alternative cell source for vascular tissue engineering. The objective of this study is to create small diameter vessels by seeding and culture of genetically modified MSCs onto a synthetic polymer scaffold produced by an electrospinning technique. A tubular scaffold (2 mm in diameter) with a microstructure of nonwoven fibers was produced by electrospinning of poly (propylene carbonate) (PPC). Rat MSCs obtained from bone marrow were expanded in culture and modified with vasculoprotective gene endothelial nitric oxide synthase (eNOS) or marker gene green fluorescent protein (GFP). These MSCs were seeded onto the electrospun fibrous grafts (internal diameter = 2 mm), and cultured in 5% CO2 at 37°C. The growth of MSCs in the scaffold was analyzed with scanning electron microscopy (SEM) and hematoxylin and eosin (H&E) staining. The gene transfer and transgenic gene expression were examined with fluorescence-activated cell sorting (FACS), immunochemical staining, reverse transcriptase-polymerase chain reaction (RT-PCR), and western blot. The production of nitric oxide (NO) by the engineered vessels was measured with an NO detection kit. Our data showed that the seeded cells integrated with the microfibers of the scaffold to form a three-dimensional cellular network, indicating a favorable interaction between this synthetic PPC scaffold with MSCs. High transduction efficiency was obtained with the use of concentrated retrovirus in the gene transfection of MSCs. The eNOS gene transcripts and protein were detected in the grafts seeded with eNOS-modified MSCs by RT-PCR and immunochemical staining. The amount of NO produced by grafts seeded with eNOS-modified MSCs was comparable to that produced by native blood vessels, and it was significantly higher than that in the grafts seeded with nonmodified MSCs. In summary, the vascular graft produced by culture of eNOS gene-modified MSCs onto the electrospun tubular scaffolds shows promising results in terms of function. The use of MSCs and therapeutic genes in tissue engineering of blood vessels could be helpful in improving vessel regeneration and patency. [source]