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排序方式: 共有168条查询结果,搜索用时 31 毫秒
1.
Interactions between plasma proteins and pulmonary surfactant: pulsating bubble studies 总被引:2,自引:0,他引:2
K M Keough C S Parsons M G Tweeddale 《Canadian journal of physiology and pharmacology》1989,67(6):663-668
The influence of human albumin, alpha-globulin, and fibrinogen on the actions of porcine pulmonary surfactant in a pulsating bubble surfactometer has been investigated. All three proteins detracted from the ability of the surfactant to adsorb to the air-water interface. The proteins also reduced the ability of surfactant to lower the opening pressures of bubbles cycling between different sizes in suspensions of surfactant. This was equivalent to restricting the ability of the surfactant to achieve low surface tension during compression of the surface. Of the three proteins, globulin competed most effectively with surfactant during the adsorption process, and albumin competed the least effectively. The proteins also may have interfered with the processes of surface refinement, which usually yields a monolayer enriched enough in dipalmitoyl phosphatidylcholine to achieve very low surface tension (very low opening pressures in the bubbles). Of the three proteins tested, albumin was least deleterious to surface refining whereas globulin and fibrinogen appeared to be about equally detrimental to the process. 相似文献
2.
Hydrophobic pulmonary surfactant protein enriched in SP-C has been mixed in amounts up to 10% by weight with various phospholipids. The lipids used were dipalmitoyl phosphatidylcholine (DPPC), or DPPC plus unsaturated phosphatidylglycerol (PG), or phosphatidylinositol (PI) in molar ratios of 9:1 and 7:3. The protein enhanced the rate and extent of adsorption of each lipid preparation into the air-water interface, and its respreading after compression on a surface balance. Maximum surface pressures attained on compression of monolayers of mixtures of lipids were slightly higher in the presence of protein. The effects on rate and extent of adsorption were proportional to the amount of protein present. Mixtures containing 30 mol% PG or PI adsorbed more readily into the interface than those containing 10% acidic lipid or DPPC alone. Mixtures containing 30% PI were slightly more rapidly adsorbed than those containing 30% PG. The results suggest that mixtures of DPPC with either acidic lipid in the presence of surfactant protein could be effective in artificial surfactants. 相似文献
3.
Isotherms have been obtained near 37 degrees C for a series of repetitive compressions and expansions of monolayers that contain major components of lung surfactant. The minimum surface tension or maximum surface pressure which could be achieved under conditions of dynamic compression, and the rate of return of lipid from excluded phase to the monolayers were measured. Monolayers of pure 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), or of DPPC plus 10 or 30 mol% of the calcium salt of 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-rac-glycerol (POPG) (POPG-Ca) achieved very high surface pressures or low surface tensions (near 0 mN m-1), but they showed no return of material from the collapse phases under the test conditions. Monolayers of POPG-Ca alone collapsed at relatively low surface pressures (high surface tensions), but showed good return of material from the collapse phase into the monolayer. Monolayers containing more complex mixtures of lipids (DPPC, phosphatidylglycerol (PG), unsaturated phosphatidylcholine (PC), cholesterol (chol] in ratios similar to those found in surfactant achieved minimum surface tensions intermediate between those of monolayers with less complex compositions. These more complex mixtures showed a better rate of return of lipids from the collapse phases to the monolayer than did simple DPPC-POPG mixtures. 31P-NMR and differential scanning calorimetric investigations of the mixture DPPC/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine(POPC)/POP G/DPPG/chol (10:4:2:1:3) showed that in the bulk phase at 37 degrees C, it was in bilayers in the liquid-crystalline state. 相似文献
4.
Chain Arrangements in the Gel State and the Transition Temperatures of Phosphatidylcholines 总被引:3,自引:3,他引:0
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Measures of chain length, inequivalence of chain length, and chain position have been incorporated into a parameter, D, which we call the “relative chain inequivalence.” D has been calculated for a number of saturated phosphatidylcholines (PC) containing one type of chain (homoacid PC), saturated PC containing two different acyl chains (heteroacid PC), and heteroacid PC containing one saturated and one unsaturated chain. The gel to liquid-crystalline transition temperatures and D are related in a regular pattern, which suggests similarity of chain packing in the gel. This pattern may have useful predictive value. 相似文献
5.
Some properties of monolayers of (POPG) alone or of POPG in mixtures with (DPPC) have been measured near 35°C during dynamic compression and expansion at 3.6 cm2·s?1. (2) The mean values of minimum surface tension (corresponding to maximum surface pressure) which could be obtained with pure POPG monolayers at high compression ranged from 15 to 18 mN·m?1 in the presence of Na+, Ca2+ or low pH (2.0) in the subphase. (3) The presence of Ca2+ or low pH in the subphase increased the collapse plateau ratios obtained on cyclic compression. This might represent enhanced respreading into the monolayer of pure POPG from a collapsed form during reexpansion of the surface. (4) Monolayers containing 10% or 30% POPG and 90% or 70% DPPC could be compressed to surface tensions approaching zero. (5) In such mixed monolayers, 10% or 30% POPG did not appear to enhance respreading, as measured by collapse plateau ratios, in the presence of Na+ or Ca2+ in the subphase. 相似文献
6.
Direct sequencing of the mitochondrial displacement loop (D-loop) of shrews
(genus Sorex) for the region between the tRNA(Pro) and the conserved
sequence block-F revealed variable numbers of 79-bp tandem repeats. These
repeats were found in all 19 individuals sequenced, representing three
subspecies and one closely related species of the masked shrew group (Sorex
cinereus cinereus, S. c. miscix, S. c. acadicus, and S. haydeni) and an
outgroup, the pygmy shrew (S. hoyi). Each specimen also possessed an
adjacent 76-bp imperfect copy of the tandem repeats. One individual was
heteroplasmic for length variants consisting of five and seven copies of
the 79-bp tandem repeat. The sequence of the repeats is conducive to the
formation of secondary structure. A termination-associated sequence is
present in each of the repeats and in a unique sequence region 5' to the
tandem array as well. Mean genetic distance between the masked shrew taxa
and the pygmy shrew was calculated separately for the unique sequence
region, one of the tandem repeats, the imperfect repeat, and these three
regions combined. The unique sequence region evolved more rapidly than the
tandem repeats or the imperfect repeat. The small genetic distance between
pairs of tandem repeats within an individual is consistent with a model of
concerted evolution. Repeats are apparently duplicated and lost at a high
rate, which tends to homogenize the tandem array. The rate of D- loop
sequence divergence between the masked and pygmy shrews is estimated to be
15%-20%/Myr, the highest rate observed in D-loops of mammals. Rapid
sequence evolution in shrews may be due either to their high metabolic rate
and short generation time or to the presence of variable numbers of tandem
repeats.
相似文献
7.
Hugh D. Campbell David A. Dionysius Dianne T. Keough Bruce E. Wilson John de Jersey Burt Zerner 《Biochemical and biophysical research communications》1978,85(2):615-622
The iron-containing violet acid phosphatases from beef spleen and pig allantoic fluid have been purified to homogeneity. Molecular weight determinations by zonal gel filtration, SDS-gel electrophoresis, and ultracentrifugation support values close to 40,000 for both enzymes, necessitating reappraisal of literature values. Similarly, the equivalent weight for iron is close to 20,000 for both enzymes, indicating the presence of two iron atoms per molecule of enzyme. The enzymes also have very similar ultraviolet and visible spectra, with λmax values close to 550 nm, and ?550 values(in terms of iron) of 2.04 × 103 and 2.00 × 103 for the beef spleen and pig allantoic fluid enzymes respectively. 相似文献
8.
High voltage-activated (HVA) Cav channels form complexes with KCa1.1 channels, allowing reliable activation of KCa1.1 current through a nanodomain interaction. We recently found that low voltage-activated Cav3 calcium channels also create KCa1.1-Cav3 complexes. While coimmunoprecipitation studies again supported a nanodomain interaction, the sensitivity to calcium chelating agents was instead consistent with a microdomain interaction. A computational model of the KCa1.1-Cav3 complex suggested that multiple Cav3 channels were necessary to activate KCa1.1 channels, potentially causing the KCa1.1-Cav3 complex to be more susceptible to calcium chelators. Here, we expanded the model and compared it to a KCa1.1-Cav2.2 model to examine the role of Cav channel conductance and kinetics on KCa1.1 activation. As found for direct recordings, the voltage-dependent and kinetic properties of Cav3 channels were reflected in the activation of KCa1.1 current, including transient activation from lower voltages than other KCa1.1-Cav complexes. Substantial activation of KCa1.1 channels required the concerted activity of several Cav3.2 channels. Combined with the effect of EGTA, these results suggest that the Ca2+ domains of several KCa1.1-Cav3 complexes need to cooperate to generate sufficient [Ca2+]i, despite the physical association between KCa1.1 and Cav3 channels. By comparison, Cav2.2 channels were twice as effective at activating KCa1.1 channels and a single KCa1.1-Cav2.2 complex would be self-sufficient. However, even though Cav3 channels generate small, transient currents, the regulation of KCa1.1 activity by Cav3 channels is possible if multiple complexes cooperate through microdomain interactions. 相似文献
9.
Perturbation of DPPC bilayers by high concentrations of pulmonary surfactant protein SP-B 总被引:3,自引:0,他引:3
Deuterium (2H) NMR has been used to observe perturbation of dipalmitoylphosphatidylcholine (DPPC) bilayers by the pulmonary surfactant protein B (SP-B) at concentrations up to 17% (w/w). Previous 2H NMR studies of DPPC/dipalmitoylphosphatidylglycerol (DPPG) (7:3) bilayers containing up to 11% (w/w) SP-B and DPPC bilayers containing up to 11% (w/w) synthetic SP-B indicated a slight effect on bilayer chain order and a more substantial effect on motions that contribute to decay of quadrupole echoes obtained from bilayers of deuterated DPPC. This is consistent with the perturbation of headgroup-deuterated DPPC reported here for bilayers containing 6 and 9% (w/w) SP-B. For the higher concentrations of SP-B investigated in the present work, 2H NMR spectra of DPPC deuterated in both the headgroup and chain display a prominent narrow component consistent with fast, large amplitude reorientation of some labeled lipid. Similar spectral perturbations have been reported for bilayers in the presence of the antibiotic polypeptide nisin. The observation of large amplitude lipid reorientation at high SP-B concentration could indicate that SP-B can induce regions of high bilayer curvature and thus provides some insight into local interaction of SP-B with DPPC. Such local interactions may be relevant to the formation, in vitro and in vivo, of tubular myelin, a unique structure found in extracellular pulmonary surfactant, and to the delivery of surfactant material to films at the air–water interface.Abbreviations DPPC 1,2-dipalmitoyl-sn-glycero-3-phosphocholine - DPPG 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol - DPPC-d62 1,2-perdeuterodipalmitoyl-sn-glycero-3-phosphocholine - DPPC-d4 1,2-dipalmitoyl-sn-glycero-3-phospho-(, perdeutero)-choline 相似文献
10.
Aravinthan DT Samuel Venkatesh N Murthy Michael O Hengartner 《BMC developmental biology》2001,1(1):8-6