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1.
P. MOLLOY, L. BRYDON, A.J, PORTER AND W.J. HARRIS. 1995. New methods to quantitatively remove bacteria from food and water samples are required to meet modern safety standards. The recent development of techniques to make Fab/Fv/scFv fragments in bacteria has provided the opportunity to exploit antibodies as specialized chemicals for affinity removal technologies. Single-chain fragments against Pseudomonas aeruginosa have been expressed in Escherichia coli , purified via a fused poly-histidine tail and immobilized upon polystyrene beads. The resulting immunoaffinity columns have been shown to effectively remove greater than 90% of an applied 10 million bacteria after a single passage through the column. Column material in the absence of single-chain retained less than 10% of the bacteria. Pseudomonas were also removed from milk, mixed bacterial cultures and when present at low cell densities.  相似文献   
2.
The opportunistic pathogen Pseudomonas aeruginosa is among the main colonizers of the lungs of cystic fibrosis (CF) patients. We have isolated and sequenced several P. aeruginosa isolates from the sputum of CF patients and compared them with each other and with the model strain PAO1. Phenotypic analysis of CF isolates showed significant variability in colonization and virulence-related traits suggesting different strategies for adaptation to the CF lung. Genomic analysis indicated these strains shared a large set of core genes with the standard laboratory strain PAO1, and identified the genetic basis for some of the observed phenotypic differences. Proteomics revealed that in a conventional laboratory medium PAO1 expressed 827 proteins that were absent in the CF isolates while the CF isolates shared a distinctive signature set of 703 proteins not detected in PAO1. PAO1 expressed many transporters for the uptake of organic nutrients and relatively few biosynthetic pathways. Conversely, the CF isolates expressed a narrower range of transporters and a broader set of metabolic pathways for the biosynthesis of amino acids, carbohydrates, nucleotides and polyamines. The proteomic data suggests that in a common laboratory medium PAO1 may transport a diverse set of “ready-made” nutrients from the rich medium, whereas the CF isolates may only utilize a limited number of nutrients from the medium relying mainly on their own metabolism for synthesis of essential nutrients. These variations indicate significant differences between the metabolism and physiology of P. aeruginosa CF isolates and PAO1 that cannot be detected at the genome level alone. The widening gap between the increasing genomic data and the lack of phenotypic data means that researchers are increasingly reliant on extrapolating from genomic comparisons using experimentally characterized model organisms such as PAO1. While comparative genomics can provide valuable information, our data suggests that such extrapolations may be fraught with peril.  相似文献   
3.
Previous studies have suggested that negative feedback is more effective in driving learning than positive feedback. We investigated the effect on learning of providing varying amounts of negative and positive feedback while listeners attempted to discriminate between three identical tones; an impossible task that nevertheless produces robust learning. Four feedback conditions were compared during training: 90% positive feedback or 10% negative feedback informed the participants that they were doing equally well, while 10% positive or 90% negative feedback informed them they were doing equally badly. In all conditions the feedback was random in relation to the listeners’ responses (because the task was to discriminate three identical tones), yet both the valence (negative vs. positive) and the probability of feedback (10% vs. 90%) affected learning. Feedback that informed listeners they were doing badly resulted in better post-training performance than feedback that informed them they were doing well, independent of valence. In addition, positive feedback during training resulted in better post-training performance than negative feedback, but only positive feedback indicating listeners were doing badly on the task resulted in learning. As we have previously speculated, feedback that better reflected the difficulty of the task was more effective in driving learning than feedback that suggested performance was better than it should have been given perceived task difficulty. But contrary to expectations, positive feedback was more effective than negative feedback in driving learning. Feedback thus had two separable effects on learning: feedback valence affected motivation on a subjectively difficult task, and learning occurred only when feedback probability reflected the subjective difficulty. To optimize learning, training programs need to take into consideration both feedback valence and probability.  相似文献   
4.
Human furin is a calcium-dependent serine endoprotease that can efficiently cleave many precursor proteins on the carboxyl side of the consensus cleavage sequence, -Arg-X-Lys/Arg-Arg-, both in vivo and in vitro. Analysis of furin proteins in extracts of cells infected with a vaccinia recombinant expressing human furin show that the enzyme is present as two prominent forms of 90 and 96 kDa. Because the structurally related bacterial subtilisins require endoproteolytic removal of the NH2-terminal pro-region by an autocatalytic intramolecular cleavage, we speculated that the size heterogeneity in the furin doublet similarly may result from a proteolytic removal of an NH2-terminal pro-region. Here we report identification of the 90-kDa furin NH2 terminus and, based on the reported sequence of the furin cDNA, demonstrate that this furin protein is derived from a larger precursor by an endoproteolytic cleavage on the COOH-terminal side of a consensus furin cleavage site, -Arg-Thr-Lys-Arg107-. Expression of mutant furin molecules containing an altered cleavage site (Arg104----Ala or Arg107----Gly) resulted in the production of only the 96-kDa furin protein. Assays of furin-dependent cleavage of a protein substrate in vitro showed that proteolytic activity was associated with the 90-kDa and not the 96-kDa furin protein, demonstrating that removal of the NH2-terminal pro-region is required for furin activity. Expression of a third furin construct containing a mutation of the active site aspartate (Asp153----Asn) similarly resulted in the expression of only the 96-kDa protein, suggesting that furin activation occurs by an autoproteolytic cleavage. Finally, the production of 90-kDa furin from either site-directed furin mutant could not be potentiated by overexpressing active furin, suggesting that the autoproteolytic activation was an intramolecular event.  相似文献   
5.
6.
We investigated the efficacy of Ocimum basilicum (OB) essential oils for treating depression related behavioral, biochemical and histopathological changes caused by exposure to chronic unpredictable mild stress (CUMS) in mice and to explore the mechanism underlying the pathology. Male albino mice were divided into four groups: controls; CUMS; CUMS plus fluoxetine, the antidepressant administered for pharmacological validation of OB; and CUMS plus OB. Behavioral tests included the forced swim test (FST), elevated plus-maze (EPM) and the open ?eld test (OFT); these tests were performed at the end of the experiment. We assessed serum corticosterone level, protein, gene and immunoexpression of brain-derived neurotropic factor (BDNF) and glucocorticoid receptors (GRs) as well as immunoexpression of glial fibrillary acidic protein (GFAP), Ki67, caspase-3 in the hippocampus. CUMS caused depression in the mice as evidenced by prolonged immobility in the FST, prolonged time spent in the open arms during the EPM test and reduction of open field activity in the OFT. OB ameliorated the CUMS induced depressive status. OB significantly reduced the corticosterone level and up-regulated protein and gene expressions of BDNF and GR. OB reduced CUMS induced hippocampal neuron atrophy and apoptosis, and increased the number of the astrocytes and new nerve cells. OB significantly increased GFAP-positive cells as well as BDNF and GR immunoexpression in the hippocampus.  相似文献   
7.
D W Molloy  G H Guyatt  D B Wilson  R Duke  L Rees  J Singer 《CMAJ》1991,144(1):29-34
OBJECTIVE: To determine the efficacy of tetrahydroaminoacridine (THA) in Alzheimer''s disease. DESIGN: Randomized, double-blind, multiple crossover trial with three treatment periods, each consisting of 3 weeks of active drug therapy and 3 weeks of placebo administration. SETTING: Referral-based geriatric practice in a community hospital. PATIENTS: Thirty-four patients with moderate to severe Alzheimer''s disease. Subjects were included if they had stage 3 to 6 disease (as determined by the Reisberg scale) and had not been taking psychotropic drugs for at least 1 month and if informed consent had been obtained from the patients and their next of kin. INTERVENTIONS: Fifty to 100 mg of THA daily and matched placebo. RESULTS: Of the initial 34 patients 14 experienced liver toxicity and 3 gastrointestinal side effects during the study; however, all 22 who completed the study were able to tolerate at least the minimum dose. For the 22 patients there was no clinically or statistically significant effect of THA on cognition, functional status or behaviour. The results for individual patients showed no subgroup of THA-responsive patients. CONCLUSION: THA has no clinically important benefits in Alzheimer''s disease and is associated with appreciable toxic effects.  相似文献   
8.
The bulk alignment of actin filament sliding movement, powered by randomly oriented myosin molecules, has been observed and studied using an in vitro motility assay. The well established, actin filament gliding assay is a minimal experimental system for studying actomyosin motility. Here, we show that when the assay is performed at densities of actin filaments approaching those found in living cells, filament gliding takes up a preferred orientation. The oriented patterns of movement that we have observed extend over a length scale of 10–100 μm, similar to the size of a mammalian cell. We studied the process of filament alignment and found that it depends critically upon filament length and density. We developed a simple quantitative measure of filament sliding orientation and this enabled us to follow the time course of alignment and the formation and disappearance of oriented domains. Domains of oriented filaments formed spontaneously and were separated by distinct boundaries. The pattern of the domain structures changed on the time scale of several seconds and the collision of neighboring domains led to emergence of new patterns. Our results indicate that actin filament crowding may play an important role in structuring the leading edge of migrating cells. Filament alignment due to near-neighbor mechanical interactions can propagate over a length scale of several microns; much greater than the size of individual filaments and analogous to a log drive. Self-alignment of actin filaments may make an important contribution to cell polarity and provide a mechanism by which cell migration direction responds to chemical cues.  相似文献   
9.
The reaction between nickel(II) nitrate and potassium phosphorus-1,1-dithiolates (di-sec-butyl and di-iso-butyl) in methanol yields 2:1 complexes which were characterized by FT-IR and NMR spectroscopy. 2:1 pyrazole adducts of both compounds were also obtained.The X-ray diffraction analysis of the compounds reveals square planar, four-coordination geometry for the homoleptic compounds and a six-coordinated distorted octahedral geometry for the adducts. In Ni[S2P(OBus)2]2 the molecules are associated through C-H?O hydrogen bonds (2.652 Å), and in Ni[S2P(OBui)2]2 the molecules are associated through C-H?S hydrogen bonds (2.948 Å). The pyrazole adducts are associated through N-H?O bonds and N-H?S bonds from the pyrazole nitrogen atoms, to form supramolecular assemblies. Thus, Ni[S2P(OBus)2(Pz)2]2 (Pz = pyrazole) forms bi-dimensional layers through N-H?O and N-H?S bonds (2.502 and 2.965 Å, respectively), whereas Ni[S2P(OBui)2(Pz)2]2 forms linear chains with N-H?S bonds 2.728 Å. The dithiophosphato groups behave as isobidentate chelating ligands.  相似文献   
10.
Mesomermis camdenensis n. sp. is described from larvae of Simulium tuberosum (lundstroem) collected in Camden Valley Creek, Washington County, New York. This species possesses a barrel-shaped vagina, vulval flap. two short separate spicules, terminal mouth, six longitudinal chords, six cephalic papillae, large sexually dimorpbic anaphids, an esophagns of uniform width which extends for less than one-third of the body length, and a cone-shaped tail directed ventrally without appendage. Juveniles also are described and illustrated.A detailed morphological comparison with the mermithid M. flumenalis Welch is presented. The most pronounced morphological differences between these species are in the shape of the vulva, juvenile tail, and infective stage. Cross-mating trials support the integrity of the new species.The life cycle of M. camdenensis is closely synchronized with that of its primary host, S. tuberosum larvae. Infected S. tuberosum larvae were first collected in May. Emergence of postparasites from late instars took place from mid-June through mid-October. Sampling data indicate a lower susceptibility to infection among S. venuslum Say larvae.  相似文献   
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