1,743 research outputs found
Effects of bile salt Sodium glycodeoxycholate on the self-assembly of PEO-PPO-PEO triblock copolymer P123 in aqueous solution
No full textA comprehensive experimental study on the interaction between the PEO-PPO-PEO block copolymer P123 (EO20PO68EO20) and the anionic bile salt sodium glycodeoxycholate (NaGDC) in water has been performed. The work was aimed at investigating the suitability of using P123 as bile salt sequestrant beside the fundamental aspects of PEO-PPO-PEO block copolymer-bile salt interactions. Various experimental techniques including dynamic and static light scattering, small-angle X-ray scattering, and differential scanning calorimetry (DSC) were employed in combination with electrophoretic mobility measurements. The system was investigated at a constant P123 concentration of 1.74 mM and with varying bile salt concentrations up to approximately 250 mM NaGDC (or a molar ratio n(NaGDC)/n(P123) = 144). In the mixed P123-NaGDC solutions, the endothermic process related to the self-assembly of P123 was observed to gradually decrease in enthalpy and shift to higher temperatures upon progressive addition of NaGDC. To explain this effect, the formation of NaGDC micelles carrying partly dehydrated P123 unimers was proposed and translated into a stoichiometric model, which was able to fit the experimental DSC data. In the mixtures at low molar ratios, NaGDC monomers associated with the P123 micelle forming a charged "P123 micelle-NaGDC" complex with a dehydrated PPO core. These complexes disintegrated upon increasing NaGDC concentration to form small "NaGDC-P123" complexes visualized as bile salt micelles including one or a few P123 copolymer chains
Truncated recombinant human SP-D attenuates emphysema and type II cell changes in SP-D deficient mice
No full textBACKGROUND: Surfactant protein D (SP-D) deficient mice develop emphysema-like pathology associated with focal accumulations of foamy alveolar macrophages, an excess of surfactant phospholipids in the alveolar space and both hypertrophy and hyperplasia of alveolar type II cells. These findings are associated with a chronic inflammatory state. Treatment of SP-D deficient mice with a truncated recombinant fragment of human SP-D (rfhSP-D) has been shown to decrease the lipidosis and alveolar macrophage accumulation as well as production of proinflammatory chemokines. The aim of this study was to investigate if rfhSP-D treatment reduces the structural abnormalities in parenchymal architecture and type II cells characteristic of SP-D deficiency. METHODS: SP-D knock-out mice, aged 3 weeks, 6 weeks and 9 weeks were treated with rfhSP-D for 9, 6 and 3 weeks, respectively. All mice were sacrificed at age 12 weeks and compared to both PBS treated SP-D deficient and wild-type groups. Lung structure was quantified by design-based stereology at the light and electron microscopic level. Emphasis was put on quantification of emphysema, type II cell changes and intracellular surfactant. Data were analysed with two sided non-parametric Mann-Whitney U-test. MAIN RESULTS: After 3 weeks of treatment, alveolar number was higher and mean alveolar size was smaller compared to saline-treated SP-D knock-out controls. There was no significant difference concerning these indices of pulmonary emphysema within rfhSP-D treated groups. Type II cell number and size were smaller as a consequence of treatment. The total volume of lamellar bodies per type II cell and per lung was smaller after 6 weeks of treatment. CONCLUSION: Treatment of SP-D deficient mice with rfhSP-D leads to a reduction in the degree of emphysema and a correction of type II cell hyperplasia and hypertrophy. This supports the concept that rfhSP-D might become a therapeutic option in diseases that are characterized by decreased SP-D levels in the lung
Complexes of PEO-PPO-PEO triblock copolymer P123 and bile salt sodium glycodeoxycholate in aqueous solution: A small angle X-ray and neutron scattering investigation
No full textSmall angle X-ray (SAXS) and neutron scattering techniques were combined to study mixed complexesformed between micelles of the nonionic amphiphilic PEO-PPO-PEO copolymer (P123) and the anionicbile salt (NaGDC) in aqueous solution. The purpose was to investigate the structural parameters of thecharged complexes, such as size and internal structure, as well as their interparticle interactions inaqueous solution. The overall aim of this work was to gain understanding of how thermoresponsivePEO-PPO-PEO block copolymers interact with bile salts in order to make predictions as to whether theycan be put forward as a new class of bile salt sequestrants in the treatment of bile-salt related diseases.The system was investigated at a constant P123 concentration of 1.74 mM and bile salt concentrationswere varied up to a molar ratio nNaGDC/nP123(MR) = 5.7. It was found that the NaGDC molecules prefer-entially associated to the PEO corona of the P123 micelle and due to their amphiphilic nature, close tothe core/corona interface. Because of this association the micelles became charged causing their recip-rocal interparticle repulsions in solution to increase. In parallel, the association caused a decrease inthe core radius accompanied by dehydration, which in turn led to a decrease in total radius of the“P123 micelle-NaGDC” complexes. To elucidate the effect of the interactions on their diffusive motion, aninteraction model based on a spherical particle with a hard-core interaction shell was employed using the fitted SAXS data. At higher molar ratios, the interparticle interaction was increasingly screened becauseof nonadsorbed bile salt in the surrounding solution. Meanwhile, a further decrease in total radial sizeof the P123 micelle-NaGDC complexes occurred due to a decrease in the aggregation number of P123as the bile salt finally disintegrated the complexes. However, the micelles were found to be more stableand less prone to disintegration in D2O. This investigation demonstrated the importance of using smallangle scattering techniques for studying intermolecular interactions in order to gain understanding ofhow natural surfactants influence the aggregation behavior of amphiphilic polymers
A recombinant fragment of human surfactant protein D lacking the short collagen-like stalk fails to correct morphological alterations in lungs of SP-D deficient mice
No full textEmphysema-like pathology is a characteristic feature of surfactant protein D (SP-D) knock-out mice. Treatment with a recombinant fragment of human SP-D consisting of a short collagen-like stalk (but not the entire collagen-like domain of native SP-D), neck, and carbohydrate recognizing domain (CRD) inhibits development of emphysema-like pathology in SP-D deficient mice. On the other hand, it has been shown that the entire collagen-like domain is necessary for preventing SP-D knock-out mice from pulmonary emphysema development. Thus, in the present study, we aimed to elucidate the role of the short collagen-like stalk for the function of the recombinant fragment of human SP-D. We treated SP-D knock-out mice with a fragment of human SP-D lacking the short collagen-like stalk and compared the effects on lung morphology with results from untreated wild-type and SP-D knock-out mice and from SP-D knock-out mice treated with a recombinant fragment of human SP-D including the short collagen-like stalk. The fragment of SP-D lacking the short collagen-like stalk failed to correct pulmonary emphysematous alterations demonstrating the importance of the short collagen-like stalk for the biological activity of the recombinant fragment of human SP-
Prenatal care advice to see a dentist: results from a population-based study
No full textMeredith L. Vandermeer (Department of Public Health, Oregon State University), Kenneth D. Rosenberg (Office of Family Health, Oregon Department of Human Services), Alfredo P. Sandoval (Oregon Health & Science University).Title from PDF caption (viewed on August 14, 2020).This archived document is maintained by the State Library of Oregon as part of the Oregon Documents Depository Program. It is for informational purposes and may not be suitable for legal purposes.Mode of access: Internet from the Oregon Government Publications Collection.Text in English
Synthesis and Characterization of a Thermoresponsive Copolymer with an LCST-UCST-like Behavior and Exhibiting Crystallization
No full textIn this work, the diblock copolymer methoxy-poly(ethylene glycol)-block-poly(ϵ-caprolactone) (MPEG-b-PCL) was synthesized with a block composition that allows this polymer in aqueous media to possess both an upper critical solution temperature (UCST) and a lower critical solution temperature (LCST) over a limited temperature interval. The value of the UCST, associated with crystallization of the PCL-block, depended on heating (H) or cooling (C) of the sample and was found to be CPUCSTH = 32 °C and CPUCSTC = 23 °C, respectively. The LCST was not affected by the heating or cooling scans; assumed a value of 52 °C (CPLCSTH = CPLCSTC). At intermediate temperatures (e.g., 45 °C), dynamic light scattering (DLS), small-angle X-ray scattering (SAXS), and cryogenic transmission electron microscopy (cryo-TEM) showed that the solution consisted of a large population of spherical core-shell particles and some self-assembled rodlike objects. At low temperatures (below 32 °C), differential scanning calorimetry (DSC) and wide-angle X-ray scattering (WAXS) in combination with SAXS disclosed the formation of crystals with a cylindrical core-shell structure. Cryo-TEM supported a thread-like appearance of the self-assembled polymer chains. At temperatures above 52 °C, incipient phase separation took place and large aggregation complexes of amorphous morphology were formed. This work provides insight into the intricate interplay between UCST and LCST and the type of structures formed at these conditions in aqueous solutions of MPEG-b-PCL diblock copolymers
Impact of scour on lateral resistance of wind turbine monopiles: An experimental study
No full textThe majority of offshore wind structures are supported on large-diameter, rigid monopile foundations. These piles may be subjected to scour due to the waves and currents that causes a loss of soil support and consequently decreases the pile capacity and system stiffness. The results of numerical models suggest that the shape of the scour hole affects the magnitude of pile capacity loss; however, there is a dearth of experimental test data that quantify this effect. This paper presents a series of centrifuge model tests on an instrumented model pile that investigates the effects of scour-hole geometry on the response of a laterally loaded pile embedded in sand. The pile instrumentation allowed load–displacement and p–y (soil reaction – displacement) curves to be derived. Three scour geometries (global, local wide, and local narrow) and three scour depths (1D, 1.5D, and 2D; where D is pile diameter) were modelled. For all three scour types, pile moment capacity decreased almost linearly with increase of scour depth. Simple empirical relations were proposed to evaluate the detrimental influence of scour on the pile moment capacity. A new method has been developed to allow designers to quantify the effect of scour-hole shape and severity of scour on the pile response.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Geo-engineerin
Interactions in Aqueous Mixtures of Cationic Hydroxyethyl Cellulose and Different Anionic Bile Salts
No full textIt is known that the reduction of blood cholesterol can
be accomplished
through foods containing a large number of dietary fibers; this process
is partially related to the binding of bile salt to fibers. To gain
new insights into the interactions between dietary fibers and bile
salts, this study investigates the interactions between cationic hydroxyethyl
cellulose (catHEC) and sodium deoxycholate (NaDC) or sodium cholate
(NaC), which have a similar structure. Turbidity measurements reveal
strong interactions between catHEC and NaDC, and under some conditions,
macroscopic phase separation occurs. In contrast, the interactions
with NaC are weak. At a catHEC concentration of 2 wt %, incipient
phase separation is approached at concentrations of NaC and NaDC of
32.5 and 19.3 mM, respectively. The rheological results show strong
interactions and a prominent viscosification effect for the catHEC/NaDC
system but only moderate interactions for the catHEC/NaC system. Both
cryogenic transmission electron microscopy and small-angle X-ray scattering
results display fundamental structural differences between the two
systems, which may explain the stronger interactions in the presence
of NaDC. The surmise is that the extended structures formed in the
presence of NaDC can easily form connections and entanglements in
the network
HUMAN CAPITAL ASSESSMENT INDICATORS AS INFLUENTIAL DETERMINANTS PERTAINING TO THE ADMISSION CRITERIA UTILIZED BY PRE-LICENSURE PROGRAMS FOR NURSING EDUCATION
No full textThe attainment of educational credentials contributes to the acquisition of human capital. Academic preparedness is a component therein that allows for the attainment of increased levels of education. Most institutions of higher education utilize measures of academic preparedness, such as grade point averages or standardized tests. Requirements for the levels of academic preparedness are based upon many factors. The requirements most relevant to this study are the selectivity of the institution and the academic preparedness of potential candidates of pre-licensure programs for nursing education.
The pre-licensure education of nurses is enigmatic when compared to other professional disciplines. Pre-licensure education for registered nurses exists in three distinct and differently classified programs: a hospital-based diploma program, an associate degree program, or a baccalaureate program. (There is an additional baccalaureate program, known as accelerated second degree programs, for students possessing a baccalaureate degree in another discipline. These accelerated programs are not included in this discussion.) The National Center for Education Statistics classifies each of the three programs, making clear that the differing program levels of post-secondary education are neither equivalent nor interchangeable.
According to the literature, the academic preparedness of individuals and the level of selectivity of higher education institutions vary greatly depending upon the particular classification of nursing program. What then, is the level of programmatic selectivity, given that all three pre-licensure programs produce candidates for the identical occupational certification while attracting candidates known to have varying levels of academic preparedness? This study aimed to determine the levels of selectivity of the three pre-licensure nursing education programs types so as identify trends and patterns within and across pre-licensure program types. In order to determine these trends and patterns, the author examined the admissions requirements that are transparent to the public on schools’ websites in which these programs are housed, employing the methodology of document analysis. The determination for the level of selectivity was based upon Barron’s Measure of Selectivity (Barron’s Educational Series, 2011)
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