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41.
Gravity-independent inequality in pulmonary blood flow in humans 总被引:3,自引:0,他引:3
Single-photon emission computerized tomography of the lung with 99mTc-labeled human albumin macroaggregates (99mTc-MAA) was used in six healthy subjects to study the three-dimensional distribution of pulmonary blood flow. 99mTc-MAA was injected while the subjects were resting in the supine position and holding their lung volume at normal end expiration. Tomography was performed on each subject from 120 projections of radioactivity in the lungs acquired with a rotating gamma camera. To minimize lung motion artifacts, the subjects were asked to hold their breath at end expiration during the 10-s duration of data acquisition in each projectional angle. Perfusion images of lung slices (11 mm thick) were reconstructed, and the radioactivity within each slice was expressed per unit lung volume of 3.7 X 3.7 X 11 mm. Perfusion images of a midcoronal slice from each subject manifested a concentric pattern of radioactivity that decreased significantly from the center to the periphery, suggesting that blood flow rate per unit lung volume was up to 10 times larger near the central region. This gradient in activity between the center and the periphery of the coronary slices was gravity independent as the subjects were supine. Images of sagittal slices from the middle of the right lung also manifested a similar pattern of concentric gradient in activity, with the vertical distribution (gravity related) almost comparable with the horizontal distribution (gravity independent). These results indicate that pulmonary blood flow in resting supine humans is spatially stratified with a marked central-to-peripheral gradient in all directions. It appears that zone 4 (reduced blood flow) is not a phenomenon limited to the dependent region of the lung as commonly thought but rather is a manifestation of this spatial distribution whereby blood flow is lowest in all peripheral regions of the lung. 相似文献
42.
The selection of antibody fragments from libraries using in vitro screening technologies has proven to be a very good alternative to the classical hybridoma technology, and has overcome the laborious process of antibody humanization. However, the complexity of the library is critical in the probability of being able to directly isolate a high affinity antibody specific to a target. We report a method to make hyperdiversified antibody fragment libraries, based on human immunoglobulin variable genes mimicking the somatic hypermutation process. This mutagenesis technology, MutaGen, was used for the first time on the entire variable domain (frameworks and CDRs) of large repertoires of human variable antibody domains. Our MutaGen process uses low-fidelity human polymerases, known as mutases, suggested to be involved in the somatic hypermutation process of immunoglobulin genes. Depending on the mutases used, we generated complementary mutation patterns with randomly distributed mutations. The libraries were generated with an average of 1.8 mutations per 100 amino acids. The hyperdiversified antibody fragment libraries constructed with our process should enable the selection of antibody fragments specific to virtually any target. 相似文献
43.
44.
Gana ML Kebbouche-Gana S Touzi A Zorgani MA Pauss A Lounici H Mameri N 《Journal of industrial microbiology & biotechnology》2011,38(3):391-404
The present study enlightens the role of the antagonistic potential of nonpathogenic strain B21 against sulfate-reducing bacteria
(SRB) consortium. The inhibitor effects of strain B21 were compared with those of the chemical biocide tetrakishydroxymethylphosphonium
sulfate (THPS), generally used in the petroleum industry. The biological inhibitor exhibited much better and effective performance.
Growth of SRB in coculture with bacteria strain B21 antagonist exhibited decline in SRB growth, reduction in production of
sulfides, with consumption of sulfate. The observed effect seems more important in comparison with the effect caused by the
tested biocide (THPS). Strain B21, a dominant facultative aerobic species, has salt growth requirement always above 5% (w/v)
salts with optimal concentration of 10–15%. Phylogenetic analysis based on partial 16S rRNA gene sequences showed that strain B21
is a member of the genus Bacillus, being most closely related to Bacillus qingdaonensis DQ115802 (94.0% sequence similarity), Bacillus aidingensis DQ504377 (94.0%), and Bacillus salarius AY667494 (92.2%). Comparative analysis of partial 16S rRNA gene sequence data plus physiological, biochemical, and phenotypic
features of the novel isolate and related species of Bacillus indicated that strain B21 may represent a novel species within the genus Bacillus, named Bacillus sp. (EMBL, FR671419). The results of this study indicate the application potential of Bacillus strain B21 as a biocontrol agent to fight corrosion in the oil industry. 相似文献
45.
Srdjan Ostojic Nicolas Brunel Vincent Hakim 《Journal of computational neuroscience》2009,26(3):369-392
We investigate how synchrony can be generated or induced in networks of electrically coupled integrate-and-fire neurons subject
to noisy and heterogeneous inputs. Using analytical tools, we find that in a network under constant external inputs, synchrony
can appear via a Hopf bifurcation from the asynchronous state to an oscillatory state. In a homogeneous net work, in the oscillatory
state all neurons fire in synchrony, while in a heterogeneous network synchrony is looser, many neurons skipping cycles of
the oscillation. If the transmission of action potentials via the electrical synapses is effectively excitatory, the Hopf
bifurcation is supercritical, while effectively inhibitory transmission due to pronounced hyperpolarization leads to a subcritical
bifurcation. In the latter case, the network exhibits bistability between an asynchronous state and an oscillatory state where
all the neurons fire in synchrony. Finally we show that for time-varying external inputs, electrical coupling enhances the
synchronization in an asynchronous network via a resonance at the firing-rate frequency.
相似文献
Srdjan OstojicEmail: |
46.
As more information becomes available regarding the role of inflammation following stroke, it is apparent that some inflammatory
mediators are detrimental and others are beneficial to the progression of ischemic injury. Cortical spreading depression (CSD)
is known to impart some degree of ischemic tolerance to the brain and to influence the expression of many genes. Many of the
genes whose expression is altered by CSD are associated with inflammation, and it appears likely that modulation of the inflammatory
response to ischemia by CSD contributes to ischemic tolerance. Understanding which inflammatory processes are influenced by
CSD may lead to the identification of novel targets in the effort to develop an acute treatment for stroke. 相似文献
47.
Tan-Trung Nguyen Noelya Planchard Jennifer Dahan Nadge Arnal Sandrine Balzergue Abdelilah Benamar Pierre Bertin Vronique Brunaud Cline Dargel-Graffin David Macherel Marie-Laure Martin-Magniette Martine Quadrado Olivier Namy Hakim Mireau 《Molecular biology and evolution》2021,38(8):3445
The high mutational load of mitochondrial genomes combined with their uniparental inheritance and high polyploidy favors the maintenance of deleterious mutations within populations. How cells compose and adapt to the accumulation of disadvantageous mitochondrial alleles remains unclear. Most harmful changes are likely corrected by purifying selection, however, the intimate collaboration between mitochondria- and nuclear-encoded gene products offers theoretical potential for compensatory adaptive changes. In plants, cytoplasmic male sterilities are known examples of nucleo-mitochondrial coadaptation situations in which nuclear-encoded restorer of fertility (Rf) genes evolve to counteract the effect of mitochondria-encoded cytoplasmic male sterility (CMS) genes and restore fertility. Most cloned Rfs belong to a small monophyletic group, comprising 26 pentatricopeptide repeat genes in Arabidopsis, called Rf-like (RFL). In this analysis, we explored the functional diversity of RFL genes in Arabidopsis and found that the RFL8 gene is not related to CMS suppression but essential for plant embryo development. In vitro-rescued rfl8 plantlets are deficient in the production of the mitochondrial heme–lyase complex. A complete ensemble of molecular and genetic analyses allowed us to demonstrate that the RFL8 gene has been selected to permit the translation of the mitochondrial ccmFN2 gene encoding a heme–lyase complex subunit which derives from the split of the ccmFN gene, specifically in Brassicaceae plants. This study represents thus a clear case of nuclear compensation to a lineage-specific mitochondrial genomic rearrangement in plants and demonstrates that RFL genes can be selected in response to other mitochondrial deviancies than CMS suppression. 相似文献
48.
Emond S André I Jaziri K Potocki-Véronèse G Mondon P Bouayadi K Kharrat H Monsan P Remaud-Simeon M 《Protein science : a publication of the Protein Society》2008,17(6):967-976
Amylosucrase is a transglucosidase that catalyzes amylose-like polymer synthesis from sucrose substrate. About 60,000 amylosucrase variants from two libraries generated by the MutaGen random mutagenesis method were submitted to an in vivo selection procedure leading to the isolation of more than 7000 active variants. These clones were then screened for increased thermostability using an automated screening process. This experiment yielded three improved variants (two double mutants and one single mutant) showing 3.5- to 10-fold increased half-lives at 50 degrees C compared to the wild-type enzyme. Structural analysis revealed that the main differences between wild-type amylosucrase and the most improved variant (R20C/A451T) might reside in the reorganization of salt bridges involving the surface residue R20 and the introduction of a hydrogen-bonding interaction between T451 of the B' domain and D488 of flexible loop 8. This double mutant is the most thermostable amylosucrase known to date and the only one usable at 50 degrees C. At this temperature, amylose synthesis by this variant using high sucrose concentration (600 mM) led to the production of amylose chains twice as long as those obtained by the wild-type enzyme at 30 degrees C. 相似文献
49.
50.
Various factor affecting NADPH-oxidation by resting human leucocyte granules (LG) at acid pH, have been investigated. It was found that: 1) oxidation of NADPH by LG was increasingly inhibited by increased cyanide concentrations in the medium and was abolished by 4 mM cyanide. 2) with or without cyanide in the incubation medium, LG omitted, Mn++ in the presence of NADPH induced superoxide anion (O- WITH 2) production, as evidenced by oxygen consumption and H2O2 production, which were abolished (in the absence of cyanide) by cytochrome C (a potent O- with 2 scavenger). 3) Both NADPH oxidation in the presence of 2 mM cyanide (cyanide-resistant) and in its absence (cyanide-sensitive) by LG occurred only in the presence of Mn++, and both were inhibited by superoxide dismutase. 4) Cyanide-resistant NADPH oxidation by LG generated H2O2, was inhibited by H2O2 and was not modified by "active" catalase. The ratio of cyanide-resistant NADPH oxidation/O2 uptake was 1 up to 1.25 mM NADPH, and increased above this concentration. 5) Cyanide-sensitive NADPH oxidation was inhibited by catalase and increased upon addition of H2O2. The ratio of cyanide-sensitive NADPH oxidation/O2 uptake was 2. It was concluded that after initiation by O - with 2, produced independently of LG, two sequential types of LG dependent NADPH oxidations occur. First, an O - with 2-dependent protein mediated NADPH oxidation (cyanide-resistant) which generates H2O2 and O - with 2 occurs. Second, NADPH peroxidation (cyanide-sensitive) which utilizes H2O2 takes place. 相似文献