| 1. |
- Larsson, Marcus, et al.
(författare)
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A solid state transition in the tetragonal lipid bilayer structure at the lung alveolar surface
- 2003
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Ingår i: Solid State Sciences. - 1873-3085. ; 5:1, s. 109-114
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Tidskriftsartikel (refereegranskat)abstract
- According to our recent results the alveolar surface is formed by a coherent phase, not a monolayer as has been assumed earlier. This surface phase is a tetragonal organization of the lipid bilayer which seems to follow the CLP minimal surface structure. As lipid bilayers at cooling will undergo a transition from the liquid-crystalline type of structure into a solid state structure, we have followed the changes in the X-ray scattering curves versus temperature of a sample of lung lavage from rabbit. There are significant changes in the range 15-25 degreesC indicating a solid/liquid bilayer transition. The size of the X-ray scattering changes indicate that only parts of the bilayers are involved. As indicated by similar studies of lung surfactant extracts, there are cholesterol-rich regions that remain in the liquid-like disordered conformation at cooling through this transition. The bilayer-embedded proteins in the alveolar CLP; structure are proposed to be located in the "corners" of the CLP-structure. This surface-phase structure was also examined by conventional electron microscopy with fixation at room temperature, and it was found to exhibit quite planar bilayer regions. On the other side, the same-sample seen in cryo-transmission electron microscopy vitrified from 40 degreesC was more disordered. These observations are consistent with a partial solid state transition of the bilayer on cooling, with segregation of lipids within the bilayers into cholesterol-rich regions remaining in a liquid-like disordered state and cholesterol-poor regions crystallizing in the range 25-15 degreesC. Physiological consequences-of such a partial solidification are finally discussed.
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| 2. |
- Larsson, Marcus, et al.
(författare)
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Enhanced efficacy of porcine lung surfactant extract by utilization of its aqueous swelling dynamics.
- 2002
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Ingår i: Clinical Physiology and Functional Imaging. - 1475-0961. ; 22:1, s. 39-48
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates the interactions between a porcine lung surfactant (PLS) extract and distilled water, saline solution or Ringer solution. The phases which coexist in equilibrium with water or electrolyte solutions were analysed by X-ray diffraction and cryo transmission electron microscopy (cryo-TEM). A lamellar phase with a structure unit consisting of double bilayers was observed in water, whereas lamellar phases with the usual bilayer structure unit were formed in saline and in Ringer solutions. At 25 degrees C the presence of a 4.2-A peak in the X-ray diffraction wide-angle region of these three maximally swollen phases showed that most of the hydrocarbon chains were organized in a crystalline packing. At 42 degrees C the chains in all three phases were melted which, in combination with the low-angle diffraction, shows that they were liquid-crystalline. Polyhedral-like vesicles and spherically shaped multilamellar vesicles were observed in cryo-TEM. The bilayer unit structures were consistent with the periodicity seen by X-ray diffraction. The dynamic swelling behaviour was followed in the polarizing microscope. A remarkable growth of birefringent networks was seen at the air interface of samples swollen in Ringer solution and saline solution. No such interfacial growth phenomena were observed during swelling in water without electrolytes. Then, these dynamics were analysed in relation to time-dependent pulmonary administration of the surfactant extract in rats. Variation in the time of administration (20 and 60 min) after mixing the extract with saline or Ringer solution showed clear differences in physiological effects. At pulmonary administration when the swelling behaviour in vitro showed a maximum in dynamics, the arterial oxygenation was superior to that of administration at a time after a steady-state had been reached. This means that the clinical performance of mammalian lung surfactant extracts can be significantly improved by taking the time-dependent aqueous swelling of the extract into account.
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| 3. |
- Larsson, Marcus, et al.
(författare)
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Periodic minimal surface organizations of the lipid bilayer at the lung surface and in cubic cytomembrane assemblies.
- 2013
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Ingår i: Advances in Colloid and Interface Science. - : Elsevier BV. - 1873-3727 .- 0001-8686.
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Tidskriftsartikel (refereegranskat)abstract
- The existence of infinite periodic lipid bilayer structures in biological systems was first demonstrated in cell membrane assemblies. Such periodicity is only possible in symmetric bilayers, and their occurrence is discussed here in relation to the asymmetry of cell membranes in vivo. A periodic membrane conformation in the prolamellar body of plants corresponds to a dormant state without photosynthesis. A similar reversible formation of a dormant state has also been observed in the mitochondria of the amoeba Chaos. In these cases the energy production has become insufficient to maintain the membrane asymmetry. Formation of membranes that are symmetric over the bilayer is proposed to be a principal mechanism behind formation of cubic membrane systems. Another type of bicontinuous minimal surface structure is considered to form the alveolar lining of mammals at normal breathing conditions. The CLP surface corresponds to such a tetragonal surface phase. It is also a symmetric bilayer and in a state of zero energy expenditure. Structural alternatives of the bilayer conformation in this latter system are also discussed here.
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| 4. |
- Larsson, Marcus, et al.
(författare)
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The bilayer melting transition in lung surfactant bilayers: the role of cholesterol.
- 2003
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Ingår i: European Biophysics Journal. - : Springer Science and Business Media LLC. - 0175-7571 .- 1432-1017. ; 31:8, s. 633-636
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Tidskriftsartikel (refereegranskat)abstract
- Aqueous di persions of a porcine lung surfactant (PLS) extract with and without cholesterol supplementation were analyzed by X-ray scattering. Lamellar liquid-crystalline and gel-type bilayer phases are formed, as in pure phosphatidylcholine (PC)-cholesterol systems. This PLS extract, developed for clinical applications, has a cholesterol content of less than 1% (w/w). Above the limit of swelling, the bilayer structure shows a melting (main) transition during heating at about 34 degreesC. When 13 mol% cholesterol was added to PLS, so that the cholesterol content of natural lung surfactant was reached, the X-ray scattering pattern showed pronounced changes. The main transition temperature was reduced to the range 20-25 degreesC, whereas according to earlier studies of disaturated PC-cholesterol bilayers in water the main transition remains almost constant when the amount of solubilized cholesterol is increased. Furthermore, the changes in scattering pattern at passing this transition in PLS-cholesterol samples were muc smaller than at the same transition in PLS samples. These effects of cholesterol solubilization can be related to phase segregation within the bilayers, known from pure PC-cholesterol systems. One phase, solubilizing about 8 mol% cholesterol, exhibits a melting transition, whereas the other bilayer phase, with a liquid-crystalline disordered conformation, has a cholesterol content in the range 20-30 mol% and this phase shows no thermal transition. The relative amount of bilayer lipids that is transformed at the main transition in the PLS-cholesterol sample is therefore only half compared to that in PLS samples. The reduction in transition temperature in the segregated bilayer of lung surfactant lipids is probably an effect of enrichment of disaturated PC species in the phase, which is poor in cholesterol. This work indicates that cholesterol in lung surfactant regulates the crystallization behavior.
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| 5. |
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| 6. |
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| 7. |
- Eriksson, Kåre, et al.
(författare)
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Dermal exposure to terpenic resin acids in Swedish carpentry workshops and sawmills
- 2004
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Ingår i: Annals of Occupational Hygiene. - : Oxford University Press. - 0003-4878 .- 1475-3162. ; 48:3, s. 267-275
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: The aim of this study was to evaluate dermal exposure to the resin acids abietic acid, dehydroabietic acid and 7-oxodehydroabietic acid during collecting in sawmills and during sawing in carpentry workshops, respectively. METHODS: Sampling was performed by fastening patches at 12 different areas on a sampling overall, one patch on the front of a cap, one patch on the chest inside the clothing and one patch on the inner lower right leg. Exposure of the hands was assessed by fastening patches on cotton gloves representing the dorsal sides and the palms of the left and right hands. Sampling was performed on 30 different occasions in the sawmills and in the carpentry workshops with mean sampling times of 120 and 59 min, respectively. The acids were solvent desorbed from the patches. Identification and quantification of the resin acids was performed by gas chromatography-mass spectrometry. RESULTS: The geometric means (GMs) of the potential body exposures to abietic acid, dehydroabietic acid and 7-oxodehydroabietic acid during sawing and collecting of wood from pine and spruce were 3346 and 17 247 micro g/h, respectively. The GM of the potential exposure on the hands was 3020 micro g/h in the carpentry workshops and 4365 micro g/h in the sawmills. Resin acids were detected on the inner chest and inner lower front right leg, respectively. CONCLUSIONS: There is a potential dermal exposure to terpenic resin acids in carpentry workshops as well as in sawmills. The hands have the highest exposure during sawing as well as during collecting. There is a spatial distribution of contaminants, with the outer chest, arms and legs showing the highest exposures. Resin acids also contaminated the inner chest and inner lower leg. It is necessary to take action to reduce dermal exposure to these allergenic substances.
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| 8. |
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| 9. |
- Grape, Sophie, 1982-, et al.
(författare)
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Partial defect verification using the DCVD : a capability evaluation approach
- 2011
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Digital Cherenkov Viewing Device (DCVD) is a non-intrusive instrument available to theInternational Atomic Energy Agency (IAEA) for verifying spent nuclear fuel in storage pools. It iscurrently used for gross-defect evaluations, i.e. to verify that an item in a storage pool is anirradiated fuel assembly and not a fresh assembly or a dummy. This is done by recording images ofthe Cherenkov light emitted in the water surrounding the fuel. Currently, the instrument’s ability toalso detect partial defects at the 50% level or even lower is under study. Here, experimental work iscomplimented by modeling and simulations due to the limited availability of assemblies with partialdefects.Ideally, an IAEA inspector should be able to use the DCVD at e.g. a fuel storage site andimmediately after scanning obtain information on (1) whether an item is an irradiated fuel assemblyor not, and (2) whether the assembly is intact or suffers from a partial defect. This paper discusses adecision-making methodology intended for the latter purpose with the objective to implement it inthe DCVD software in order to facilitate smooth inspection procedures. Inspectors will thus not berequired to possess any expertise in the decision-making methodology.The paper also describes measurements performed during spring 2011 at the CLAB interim spentfuel storage in Sweden. The measurements were carried out with the objective to optimize theequipment handling and work flow during this type of measurement campaigns and to form a basisfor the evaluation of the DCVD’s ability to detect partial defects.
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| 10. |
- Gustafsson, Jonas, et al.
(författare)
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Cubic lipid-water phase dispersed into submicron particles
- 1996
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Ingår i: Langmuir. ; 12:20, s. 4611-4613
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Tidskriftsartikel (refereegranskat)abstract
- The formation of dispersed colloidal particles of a bilayer cubic phase is demonstrated and discussed in relation to the phase behavior of the components used. Examination by means of cryotransmission electron microscopy reveals submicron particles of fac
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