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排序方式: 共有76条查询结果,搜索用时 9 毫秒
1.
Olga S. Ostroumova Svetlana S. Efimova Ludmila V. Schagina 《The Journal of membrane biology》2013,246(12):985-991
The phloretin-induced reduction in the dipole potential of planar lipid bilayers containing cholesterol, ergosterol, stigmasterol, 7-dehydrocholesterol and 5α-androstan-3β-ol was investigated. It is shown that effects depend on the type and concentration of membrane sterol. It is supposed that the effectiveness of phloretin in reducing the dipole potential of the bilayers that contain cholesterol, ergosterol and 7-dehydrocholesterol correlates with the ordering and condensing effects. The role of the concentration-dependent ability of different sterols to promote lateral heterogeneity in membranes is also discussed. 相似文献
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To probe the size of the ion channel formed by Pseudomonas syringae lipodepsipeptide syringomycin E, we use the partial blockage of ion current by penetrating poly(ethylene glycol)s. Earlier experiments with symmetric application of these polymers yielded a radius estimate of approximately 1 nm. Now, motivated by the asymmetric non-ohmic current-voltage curves reported for this channel, we explore its structural asymmetry. We gauge this asymmetry by studying the channel conductance after one-sided addition of differently sized poly(ethylene glycol)s. We find that small polymers added to the cis-side of the membrane (the side of lipodepsipeptide addition) reduce channel conductance much less than do the same polymers added to the trans-side. We interpret our results to suggest that the water-filled pore of the channel is conical with cis- and trans-radii differing by a factor of 2-3 and that the smaller cis-radius is in the 0.25-0.35 nm range. In symmetric, two-sided addition, polymers entering the pore from the larger opening dominate blockage. 相似文献
4.
Ostroumova TV Markova LN 《Rossi?skii fiziologicheski? zhurnal imeni I.M. Sechenova / Rossi?skaia akademiia nauk》2000,86(10):1246-1254
Obvious inhibition of the hydra regeneration with no subsequent morphological abnormalities, was shown to occur when using alpha-methylthyrosine and 3 Jthyrosine. alpha-Methyldopa induced a slight inhibition but a considerable morphological change: ectopic tentacles, projections, bipolar forms in the gastric fragment. The apical and basal fragments did not suffer. The role of neurotransmitters in the hydra morphogenesis is discussed. 相似文献
5.
Hatch M Furukawa K Brenner A Olinjyk V Ron E Zablotska L Terekhova G McConnell R Markov V Shpak V Ostroumova E Bouville A Tronko M 《Radiation research》2010,174(6):763-772
Relatively few data are available on the prevalence of hyperthyroidism (TSH concentrations of <0.3 mIU/liter, with normal or elevated concentrations of free T4) in individuals exposed to radioiodines at low levels. The accident at the Chornobyl (Chernobyl) nuclear plant in Ukraine on April 26, 1986 exposed large numbers of residents to radioactive fallout, principally to iodine-131 ((131)I) (mean and median doses = 0.6 Gy and 0.2 Gy). We investigated the relationship between (131)I and prevalent hyperthyroidism among 11,853 individuals exposed as children or adolescents in Ukraine who underwent an in-depth, standardized thyroid gland screening examination 12-14 years later. Radioactivity measurements taken shortly after the accident were available for all subjects and were used to estimate individual thyroid doses. We identified 76 cases of hyperthyroidism (11 overt, 65 subclinical). Using logistic regression, we tested a variety of continuous risk models and conducted categorical analyses for all subjects combined and for females (53 cases, n = 5,767) and males (23 cases, n = 6,086) separately but found no convincing evidence of a dose-response relationship between (131)I and hyperthyroidism. There was some suggestion of elevated risk among females in an analysis based on a dichotomous dose model with a threshold of 0.5 Gy chosen empirically (OR = 1.86, P = 0.06), but the statistical significance level was reduced (P = 0.13) in a formal analysis with an estimated threshold. In summary, after a thorough exploration of the data, we found no statistically significant dose-response relationship between individual (131)I thyroid doses and prevalent hyperthyroidism. 相似文献
6.
S. S. Efimova O. S. Ostroumova V. V. Malev L. V. Schagina 《Cell and Tissue Biology》2011,5(4):397-405
The effect of the membrane dipole potential (φ
d
) on conductance and the steady-state number of functioning channels formed by cyclic lipodepsipeptide syringomycin E (SRE)
in bilayer lipid membranes made from phosphocholine and bathed in 0.4 M solution of sodium salts of aspartate, gluconate,
and chloride was shown. The φ
d
value varied with the introduction of phloretin to membrane bathing solutions, which reduces φ
d
and RH 421, which increases φ
d
. It was established that, in all studied systems, an increase in the membrane dipole potential caused a decrease in the steady-state
number of open channels. In systems containing sodium salts of aspartate (Asp) or gluconate (Glc), changes in the number of
functioning channels are one order lower than those of systems that contain sodium chloride. At the same time, the conductance
(g) of single SRE channels in the membranes bathed in NaCl solution increases with increase in φ
d
and in the systems containing NaAsp or NaGlc the conductance of single channels does not depend on the φ
d
. The latter is due to the lack of cation/anion selectivity of the SRE channels in these systems. The different channel-forming
activity of SRE in the experimental systems is determined by the gating charge of the channel and the partition coefficient
of the dipole modifiers between the lipid and aqueous phases. 相似文献
7.
Ostroumova EA Ostroumov VA Sumina ON Misharin SI Antipina AI Grabelnych OI Zykova VV Pobezhimova TP Kolesnichenko AV 《Journal of thermal biology》2001,26(3):209-214
The search for proteins with immunochemical affinity to plant stress proteins in endemic Baikal fishes shows the presence of proteins, immunochemically related to plant heat-stabile proteins and plant uncoupling protein CSP 310. Western blotting showed that among the native cytoplasmic proteins of endemic Baikal fishes there are proteins immunochemically related to heat-stabile plant proteins with molecular weights about 480, 200-290, 150, 140 and about 90-100kD. SDS-electrophoresis showed the presence of polypeptides with molecular weights 23, 17 and 14kD in all species investigated and an additional 35kD polypeptide in Cottocomephorus grewingki. The search for polypeptides with immunochemical affinity to plant stress uncoupling protein CSP 310 in endemic Baikal fishes shows the presence of a 14kD polypeptide, immunochemically related to it. 相似文献
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10.
O. S. Ostroumova L. V. Schagina 《Biochemistry (Moscow) Supplemental Series A: Membrane and Cell Biology》2009,3(3):281-285
The effects of dipole modifier phloretin on the activity of syringomycin (SRE) channels in the lipid bilayers containing different
sphingolipids, N-stearoyl-phytosphingosine (PSP) and N-stearoyl-D-erythrosphingosine (DSP), have been compared. It is shown
that the addition of phloretin up to a concentration of 10 μM into solutions bathing the bilayers containing 20 mol.% PSP
causes a 170-fold increase in the SRE channel-forming activity. In the case of DSP-containing membranes, a more significant
(5200-fold) increase of the equilibrium number of open SRE channels is observed. The enhancement of SRE activity is accompanied
by about 2-fold increase of the gating charge of SRE channels in the membranes with PSP, while in the bilayers with DSP the
gating charge increases about 4-fold. The revealed differences in the parameters of SRE channels in the membranes including
phloretin and PSP or DSP are accounted for by different partition coefficients of the toxin and dipole modifier between the
lipid and water phases. The data suggest heterogeneity of dipole potential of the PSP-containing membranes in the presence
of phloretin. This heterogeneity is due to the possibility of formation in these membranes of rafts with the dipole potential
not affected by modifier. 相似文献