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61.
The abilities of nine genotypes of Amanita muscaria (L.:Fr) Pers. to utilise a range of inorganic and organic nitrogen sources for growth was examined in axenic liquid cultures. Considerable intraspecific variation was observed in biomass yields on all substrates; however biomass yield was highest on glutamine and/or NH4+ for all genotypes. Yields on aspartic acid, glutamic acid and histidine were generally low relative to NH4+, while utilisation of arginine and glycine showed marked variation between genotypes. Eight genotypes produced significantly less biomass on bovine serum albumin than on NH4+, raising questions regarding classification of A. muscaria as a 'protein fungus'. 相似文献
62.
Regulation of PGE(2) and PGI(2) release from human umbilical vein endothelial cells by actin cytoskeleton 总被引:2,自引:0,他引:2
Sawyer SJ Norvell SM Ponik SM Pavalko FM 《American journal of physiology. Cell physiology》2001,281(3):C1038-C1045
Disruption of microfilaments in human umbilical vein endothelialcells (HUVEC) with cytochalasin D (cytD) or latrunculin A (latA)resulted in a 3.3- to 5.7-fold increase in total synthesis ofprostaglandin E2 (PGE2) and a 3.4- to 6.5-foldincrease in prostacyclin (PGI2) compared with controlcells. Disruption of the microtubule network with nocodazole orcolchicine increased synthesis of PGE2 1.7- to 1.9-fold andPGI2 1.9- to 2.0-fold compared with control cells.Interestingly, however, increased release of PGE2 andPGI2 from HUVEC into the media occurred only when microfilaments were disrupted. CytD treatment resulted in 6.7-fold morePGE2 and 3.8-fold more PGI2 released from HUVECcompared with control cells; latA treatment resulted in 17.7-fold more PGE2 and 11.2-fold more PGI2 released comparedwith control cells. Both increased synthesis and release ofprostaglandins in response to all drug treatments were completelyinhibited by NS-398, a specific inhibitor of cyclooxygenase-2 (COX-2).Disruption of either microfilaments using cytD or latA or ofmicrotubules using nocodazole or colchicine resulted in a significantincrease in COX-2 protein levels, suggesting that the increasedsynthesis of prostaglandins in response to drug treatments may resultfrom increased activity of COX-2. These results, together with studies demonstrating a vasoprotective role for prostaglandins, suggest thatthe cytoskeleton plays an important role in maintenance of endothelialbarrier function by regulating prostaglandin synthesis and release from HUVEC. 相似文献
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65.
Taxonomic confusion among closely related and morphologically similar Deprea species has persisted in the literature and in the identification of species. Morphological variation among three closely
related, monophyletic Deprea species was studied to determine if and how they can be distinguished. Their sympatric occurrence in Venezuela afforded an
opportunity to couple field study with analysis of herbarium specimens representing their entire geographic range. An analysis
of 94 morphological characters resulted in five vegetative and 13 reproductive taxonomically informative traits. Canonical
variates analysis clearly separated the three species using six quantitative traits. We conclude that these taxa, although
quite variable and similar morphologically, are taxonomically distinct. Results of character analysis indicated that D. orinocensis is morphologically more similar to D. bitteriana than either are to D. paneroi. In D. paneroi, small, sterile anthers on fruit-bearing plants and the absence of fruits on plants possessing large, plllen-bearing anthers,
suggest cryptic dioecy. Based on these data, D. granulosa is considered to be a synonym of D. orinocensis: Athenaea bitteriana, a misapplied synonym, is the correct basionym and is applicable to many specimens identified as D. granulosa. We submit a new combination, D. bitteriana (Werderm.) Sawyer & Benítez, and designate a lectotype to accommodate these findings. 相似文献
66.
Stanislava Uhrínová Dušan Uhrín Helen Denton Mark Smith Lindsay Sawyer Paul N. Barlow 《Journal of biomolecular NMR》1998,12(1):89-107
Although -lactoglobulin (-LG) has been studied extensively for more than 50 years, its physical properties in solution are not yet understood fully in terms of its three-dimensional (3D) structure. For example, despite a recent high-resolution crystal structure, it is still not clear why the two common variants of bovine -LG which differ by just two residues have different aggregation properties during milk processing. We have conducted solution-state NMR studies on a recombinant form of the A variant of -LG at low pH conditions where the protein is partially unfolded and exists as a monomer rather than a dimer. Using a13 C,15N-labelled sample, expressed in Pichia pastoris, we have employed the standard combination of 3D heteronuclear NMR techniques to obtain near complete assignments of proton, carbon and nitrogen resonances. Using a novel pulse sequence we were able to obtain additional assignments, in particular those of methyl groups in residues preceding proline within the sequence. From chemical shifts and on the basis of inter-residue NOEs, we have inferred the secondary structure and topology of monomeric -LG A. It includes eight antiparallel -strands arranged in a barrel, flanked by an -helix, which is typical of a member of the lipocalin family. A detailed comparison with the crystal structure of the dimeric form (for a mixture of A and B variants) at pH 6.5 reveals a close resemblance in both secondary structure and overall topology. Both forms have a ninth -strand which, at the higher pH, forms part of the dimer interface. These studies represent the first full NMR assignment of -LG and will form the basis for a complete characterisation of the solution structure and dynamics of this protein and its variants. 相似文献
67.
68.
J Drew A Liodakis R Chan H Du M Sadek R Brownlee W H Sawyer 《Biochemistry international》1990,22(6):983-992
Lipid emulsions consisting of a surface monolayer of phospholipid enclosing a core of neutral lipids have been prepared by repeated extrusion through polycarbonate filters of defined pore size. Particle size, as measured by photon correlation spectroscopy, decreases on successive passes through a 100 nm filter, reaching a near constant value (130-150 nm) after 4 passes. A corresponding decrease in the standard deviation of the particle size distribution occurs during this process. The recovery of lipids, especially of cholesterol and cholesterol ester, is improved if the emulsion is sonicated before extrusion through filters. [31P]-NMR and fluorescence techniques are used to confirm that the resulting structures are emulsions rather than lipid bilayers. 相似文献
69.
W H Sawyer K Bankowski A Misicka E Nawrocka M Kruszynski S Stoev W A Klis J P Przybylski M Manning 《Peptides》1988,9(1):157-163
A variety of structural changes were made in the C-terminals of four potent antidiuretic (V2) antagonists. The parent analogs were all derivatives of [1-(beta-mercapto-beta,beta-cyclopentamethylenepropionic acid)]arginine-vasopressin, d(CH2)5AVP, namely d(CH2)5[D-Phe2,Ile4]AVP, d(CH2)5[D-Ile2,Ile4]AVP, d(CH2)5[D-Tyr(Et)2, Val4]AVP and d(CH2)5[D-Tyr(Et)2,Ile4]AVP. A number of amino acid amides were substituted for the C-terminal 9-glycinamide without reducing their V2-antagonistic potencies in rats. Many non-amino acid structures were also tolerated at the C-terminals of these antagonists and this end of these peptides can be prolonged without interfering with antagonistic potencies. Such altered V2-antagonists may be useful for the development of radioactive ligands, affinity labels and in affinity columns for studies on antidiuretic receptors. These C-terminal modifications also provide useful information for the further development of potent and specific V2-antagonists which can be valuable pharmacological tools and also promise to become useful clinically for the treatment of excessive water retention. 相似文献
70.
J A Widness S T Sawyer R L Schmidt D H Chestnut 《Journal of developmental physiology》1991,15(3):139-143
We administered tracer quantities of biologically active 125I-labelled recombinant human erythropoietin by intravenous bolus injection to seven late gestation pregnant ewes. Maternal and fetal blood was sampled over the subsequent six hours and assayed for erythropoietin-specific radioactivity. Despite the expected increase in maternal plasma immunoprecipitable 125I-labelled erythropoietin radioactivity, fetal plasma levels remained unchanged throughout the study. In addition, erythropoietin receptors were not detected in ovine and human placental tissue. We conclude that biologically active 125I-labelled erythropoietin does not cross the placenta from mother to fetus in measurable quantities in sheep, and likely in humans. Thus, these data indicate the levels of erythropoietin measured in fetal plasma are reflective of fetal, and not maternal, erythropoietin production and elimination. 相似文献