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161.
Intravenously administered endotoxin inhibits the polymorphonuclear leukocyte (PMN)-dependent airway edema produced in guinea pigs exposed to toluene diisocyanate (TDI). Tumor necrosis factor (TNF) is produced in vivo by peripheral blood monocytes and tissue macrophages stimulated with endotoxin and has been shown to activate PMN's and vascular endothelial cells. To determine whether the inhibition of airway edema is mediated by TNF, guinea pigs were treated with intravenous saline or 75,000 U/kg recombinant human TNF 1.5 h before exposure to air or 3 ppm TDI for 1 h. Animals were then injected intravenously with 50 mg/kg Evans blue dye as a marker of protein extravasation. Saline-treated animals exposed to TDI had a significant increase in tracheal Evans blue dye extravasation (85 +/- 6.5 micrograms dye/g trachea, mean +/- SE) compared with saline-treated animals exposed to air (31.3 +/- 2.5, P less than 0.001). The tracheal extravasation of Evans blue dye was significantly inhibited (P less than 0.05) in TDI-exposed animals treated with TNF (64.7 +/- 7.5). Neither heat-inactivated TNF (104.9 +/- 9.5) nor TNF neutralized with a monoclonal antibody against TNF (99.7 +/- 17.9) inhibited TDI-induced airway edema. In addition, treatment with 15,000 U/kg (99.9 +/- 21.3) or 150,000 U/kg (103.2 +/- 17.6) interleukin 1, a monokine also produced in response to endotoxin, did not prevent airway edema. These results suggest that TNF released in response to endotoxin mediates endotoxin's inhibition of a PMN-dependent airway edema. 相似文献
162.
Surfactin is a lipopeptide produced by certain strains of Bacillus subtilis and has potent surface activity. Here, we present the first results showing that ion-conducting pores can be formed by surfactin in artificial lipid membranes. With a low aqueous concentration of surfactin (1 microM) and a restricted membrane area (5.10(-5) cm2) we observed conductance jumps that indicate the formation of individual ionic channels in the presence of K+, Rb+, Cs+, Na+ or Li+ chlorides. Although for every salt concentration (Ci), the distribution in amplitude of the conductance steps (lambda i) may be rather broad, there is always a step amplitude which is more frequent than the others. In addition, the channels corresponding to this most frequent step amplitude are the longest in duration. For Ci = 1 M, the cationic selectivity sequence deduced from these most frequent events is K+ greater than Rb+ greater than Na+ greater than Cs+ = Li+ with respective values for lambda Mi: 130, 110, 80 and 30 pS. In KCl solutions lambda MKCl increases as a function of Ci for low Ci, and shows a plateau for Ci greater than 0.5 M. When measured on larger area membranes (10(-2)cm2) with 1 M solutions of the monovalent salts KCl, NaCl, RbCl and CsCl or the divalent salt CaCl2, the macroscopic low voltage conductance (G0) increases with a slope of 2 on a log-log plot as a function of surfactin concentration. These results demonstrate that surfactin produces selective cationic channels in lipid bilayer membranes and suggest that at higher salt concentration, a dimer is involved in this functional channel-forming process. 相似文献
163.
164.
Electron cryotomography of Mycoplasma pneumoniae mutants correlates terminal organelle architectural features and function
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Duncan C. Krause Songye Chen Jian Shi Ashley J. Jensen Edward S. Sheppard Grant J. Jensen 《Molecular microbiology》2018,108(3):306-318
The Mycoplasma pneumoniae terminal organelle functions in adherence and gliding motility and is comprised of at least eleven substructures. We used electron cryotomography to correlate impaired gliding and adherence function with changes in architecture in diverse terminal organelle mutants. All eleven substructures were accounted for in the prkC, prpC and P200 mutants, and variably so for the HMW3 mutant. Conversely, no terminal organelle substructures were evident in HMW1 and HMW2 mutants. The P41 mutant exhibits a terminal organelle detachment phenotype and lacked the bowl element normally present at the terminal organelle base. Complementation restored this substructure, establishing P41 as either a component of the bowl element or required for its assembly or stability, and that this bowl element is essential to anchor the terminal organelle but not for leverage in gliding. Mutants II‐3, III‐4 and topJ exhibited a visibly lower density of protein knobs on the terminal organelle surface. Mutants II‐3 and III‐4 lack accessory proteins required for a functional adhesin complex, while the topJ mutant lacks a DnaJ‐like co‐chaperone essential for its assembly. Taken together, these observations expand our understanding of the roles of certain terminal organelle proteins in the architecture and function of this complex structure. 相似文献
165.
166.
A. M. L. Azeredo-Espin R. F. W. Schroder G. K. Roderick W. S. Sheppard 《Biochemical genetics》1996,34(7-8):253-268
Restriction endonuclease analyses of mitochondrial DNA (mtDNA) were used to examine genetic variability and population structure
inLeptinotarsa decemlineata (Say). A group of three enzymes, EcoRI, HpaI, and PstI, was used to reveal polymorphism both within and among some of the 10 populations tested, yielding 16 haplotypes in combination.
The frequencies of these 16 haplotypes differed significantly across geographic regions, indicating some partitioning of mtDNA
haplotypes. Estimates of mtDNA sequence divergence (δ) between haplotypes ranged from 0.016 to 0.135%, suggesting local differentiation
of mtDNA in some populations. Analysis of these data suggests that Texas was colonized by more than one mtDNA lineage, most
likely originating in Mexico. We hypothesize that a larger founder size for the initial introductions or high levels of variability
in the parent population at the edge of the CPB expanding range led to the initial partitioning of haplotypes observed in
samples from Texas. 相似文献
167.
Christopher L. Sheppard Santokh S. Tandon Laurence K. Thompson John N. Bridson David O. Miller Makoto Handa Francesc Lloret 《Inorganica chimica acta》1996,250(1-2):227-239
Two novel, weakly antiferromagnetically coupled, tetranuclear copper(II) complexes [Cu4(PAP)2(μ2-1,1-N3)2(μ2-1,3-N3)2(μ2-CH3OH)2(N3)4 (1) (PAP = 1,4-bis-(2′-pyridylamino)phthalazine) and [Cu4(PAP3Me)2 (μ2-1,1-N3)2(μ2-1,3-N3)2(H2O)2(NO2)2]- (NO3)2 (2) (PAP3Me = 1,4-bis-(3′-methyl-2′-pyridyl)aminophthalazine) contain a unique structural with two μ2-1,1-azide intramolecular bridges, and two μ2-1,3-azide intermolecular bridges linking pairs of copper(II) centers. Four terminal azide groups complete the five-coordinate structures in 1, while two terminal waters and two nitrates complete the coordination spheres in 2. The dinuclear complexes [Cu2(PPD)(μ2-1,1-N3)(N3)2(CF3SO3)]CH3OH) (3) and [Cu2(PPD)(μ2-1,1-N3)(N3)2(H2O)(ClO4)] (4) (PPD = 3,6-bis-(1′-pyrazolyl)pyridazine) contain pairs of copper centers with intramolecular μ2-1,1-azid and pyridazine bridges, and exhibit strong antiferromagnetic coupling. A one-dimensional chain structure in 3 occurs through intermolecular μ2-1,1-azide bridging interactions. Intramolecular Cu-N3-Cu bridge angles in 1 and 2 are small (107.9 and 109.4°, respectively), but very large in 3 and 4 (122.5 and 123.2°, respectively), in keeping with the magnetic properties. 2 crystallizes in the monoclinic system, space group C2/c with a = 26.71(1), b = 13.51(3), c = 16.84(1) Å, β = 117.35(3)° and R = 0.070, Rw = 0.050. 3 crystallizes in the monoclinic system, space group P21/c with a = 8.42(1), b = 20.808(9), c = 12.615(4) Å, β = 102.95(5)° and R = 0.045, Rw = 0.039. 4crystallizes in the triclinic system, space group P1, with a = 10.253(3), b = 12.338(5), c = 8.072(4) Å, = 100.65(4), β = 101.93(3), γ = 87.82(3)° and R = 0.038, Rw = 0.036 . The magnetic properties of 1 and 2 indicate the presence of weak net antiferromagnetic exchange, as indicated by the presence of a low temperature maximum in χm (80 K (1), 65 K (2)), but the data do not fit the Bleaney-Bowers equation unless the exchange integral is treated as a temperature dependent term. A similar situation has been observed for other related compounds, and various approaches to the problem will be discussed. Magnetically 3 and 4 are well described by the Bleaney-Bowers equation, exhibiting very strong antiferromagnetic exchange (− 2J = 768(24) cm−1 (3); − 2J = 829(11) cm−1 (4)). 相似文献
168.
A single gene encoding the fiber is responsible for variations in virulence in the fowl adenoviruses. 总被引:1,自引:0,他引:1
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Intertypic recombinant fowl adenoviruses (FAVs) were generated to determine regions of the viral genome involved in virulence. Recombinants were produced with two serotype 8 FAVs, mildly virulent CFA 3 and hypervirulent CFA 40. Restriction endonuclease fragments from the genomes of the two FAVs were used to transfect primary chicken kidney cells. Virulence testing of these recombinants located the region responsible for differences in virulence to an 8.4-kb fragment of the genome located between kb 26.6 and 35.0. According to data available for a serotype 10 FAV that had been partially characterized in the laboratory, this segment of the genome contained three genes of known identity (100K, 33K, and pVIII) and a region between kb 31 and 35 with unknown coding potential (although this information subsequently became available for a serotype 1 FAV, CELO). Therefore, the region between kb 30.5 and 34.5 was sequenced. The results revealed that the unknown region encoded a fiber gene on the right strand and several small open reading frames of unknown identity on the left strand. Further recombinant viruses containing defined exchanges within the 4-kb fragment were constructed, and virulence testing of these viruses indicated that the fiber was responsible for differences in virulence for CFA 40 and CFA 3. 相似文献
169.
D. Mears N. F. Sheppard Jr. I. Atwater E. Rojas 《The Journal of membrane biology》1995,146(2):163-176
The parallel gap junction electrical conductance between a -cell and its nearest neighbors was measured by using an intracellular microelectrode to clamp the voltage of a -cell within a bursting islet of Langerhans. The holding current records consisted of bursts of inward current due to the synchronized oscillations in membrane potential of the surrounding cells. The membrane potential record of the impaled cell, obtained in current clamp mode, was used to estimate the behavior of the surrounding cells during voltage clamp, and the coupling conductance was calculated by dividing the magnitude of the current bursts by that of the voltage bursts. The histogram of coupling conductance magnitude from 26 cells was bimodal with peaks at 2.5 and 3.5 nS, indicating heterogeneity in extent of electrical communication within the islet of Langerhans. Gap junction conductance reversibly decreased when the temperature was lowered from 37 to 30°C and when the extracellular calcium concentration was raised from 2.56 to 7.56 mm. The coupling conductance decreased slightly during the active phase of the burst. Activation of adenylate cyclase with forskolin (10 m) resulted in an increase in cell-to-cell electrical coupling. We conclude that -cell gap junction conductance can be measured in situ under near physiological conditions. Furthermore, the magnitude and physiological regulation of -cell gap junction conductance suggest that intercellular electrical communication plays an important role in the function of the endocrine pancreas.The authors thank Dr. Arthur Sherman for sharing his insights on in situ coupling measurements, and for helpful discussions throughout the work. DM acknowledges partial support by a National Institutes of Health training grant to the Johns Hopkins University, Department of Biomedical Engineering (5 T32 GM7057). This work was supported in part by a National Science Foundation PYI award (ECS-9058419) to NFS. 相似文献
170.
The production of poly-beta-hydroxybutyrate (PHB) by Alcaligenes eutrophus DSM 545 in a cyclone bioreactor was compared using various culture methods: batch, fed-batch, and self-cycling fermentation (SCF) with and without extended periods of nutrient deprivation. SCF is a semi-continuous method that results in a nutrient limitation for every successive generation of cells and, therefore, may have advantages for products whose formation follow secondary metabolite kinetics. Use of the SCF technique without extended nutrient deprivation produced a PHB concentration of 1.2 g L(-1) as 40% of the biomass dry weight. With nitrogen deprivation for 4 or 6 h, the concentration of PHB decreased when compared to the standard SCF technique. However, nitrogen deprivation periods of 8 h resulted in an increase in PHB concentration to 2.7 g L(-1) or 59% of the biomass dry weight. The nutrient cycling may act to repress PHB accumulation during periods of nitrogen deprivation, unless a time threshold has been reached, after which PHB accumulation occurs as in normal batch culture. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 815-820, 1997. 相似文献