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51.
Livia R. Tanjung Gabrielle Whittle Bruce E. Shaw Garry A. Bloomfield Margaret E. Katz Brian F. Cheetham 《Anaerobe》2009,15(5):219-224
The Gram-negative anaerobic pathogen Dichelobacter nodosus is the principal causative agent of footrot in sheep. The intA, intB and intC elements are mobile genetic elements which integrate into two tRNA genes downstream from csrA (formerly glpA) and pnpA in the D. nodosus chromosome. CsrA homologues act as global repressors of virulence in several bacterial pathogens, as does polynucleotide phosphorylase, the product of pnpA. We have proposed a model in which virulence in D. nodosus is controlled in part by the integration of genetic elements downstream from csrA and pnpA, altering the expression of these putative global regulators of virulence. We describe here a novel integrated genetic element, the intD element, which is 32 kb in size and contains an integrase gene, intD, several genes related to genes on other integrated elements of D. nodosus, a type IV secretion system and a putative mobilisation region, suggesting that the intD element has a role in the transfer of other genetic elements. Most of the D. nodosus strains examined which contained the intD gene were benign, with intD integrated next to pnpA, supporting our previous observation that virulent strains of D. nodosus have the intA element next to pnpA. 相似文献
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Intensity Coding in the Frog Retina : Quantitative relations between impulse and graded activity 总被引:3,自引:2,他引:1 下载免费PDF全文
The impulse discharge of single on-off neurons and a graded field potential, the proximal negative response (PNR), were simultaneously recorded with an extracellular microelectrode in the inner frog retina. Normalized amplitude-intensity functions for the on-response of the PNR and the neuron's post-stimulus time histogram (PSTH) were nearly coincident and typically showed a dynamic range spanning approximately 2 log units of intensity. Thus a nearly linear relation is found between the amplitude of the PNR and the neuron's PSTH. A neuron's PSTH amplitude and maximum instantaneous frequency of discharge were usually highly correlated, but occasional marked disparities indicate that temporal jitter of the first spike latency is an additional, relatively independent variable influencing PSTH amplitude. It typically changes by a factor of 20–30 over the intensity range. These and other findings have implications for the functional significance of the PNR and the PSTH, for a possible linear link between amacrine and on-off ganglion cells, and for a mechanism of intensity coding in which temporal jitter of latency exerts a major role. 相似文献
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Antigen-Specific Expansion of Cytotoxic T Lymphocytes in Acute Measles Virus Infection 总被引:6,自引:3,他引:3 下载免费PDF全文
Juthathip Mongkolsapaya Assan Jaye Margaret F. C. Callan Albert F. Magnusen Andrew J. McMichael Hilton C. Whittle 《Journal of virology》1999,73(1):67-71
Skewing of the T-cell receptor repertoire of CD8+ T cells has been shown in some persistent infections with viruses, such as human immunodeficiency virus, simian immunodeficiency virus, and Epstein-Barr virus. We have demonstrated that similar distortions also occur in nonpersistent measles virus infection. In addition, two of four children immunized with live, attenuated measles virus showed larger and more persistent CD8+ T-cell expansions than their naturally infected counterparts. The expanded lymphocyte populations were monoclonal or oligoclonal and lysed target cells infected with recombinant vaccinia virus expressing measles virus protein. These results demonstrate that the expansions of CD8+ T lymphocytes are antigen driven. 相似文献
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A relationship between zinc (Zn)-deficiency and mood disorders has been suspected. Here we examined for the first time whether
experimentally-induced Zn-deficiency in mice would alter depression- and anxiety-related behaviour assessed in established
tests and whether these alterations would be sensitive to antidepressant treatment. Mice receiving a Zn-deficient diet (40%
of daily requirement) had similar homecage and open field activity compared to normally fed mice, but displayed enhanced depression-like
behaviour in both the forced swim and tail suspension tests which was reversed by chronic desipramine treatment. An anxiogenic
effect of Zn-deficiency prevented by chronic desipramine and Hypericum perforatum treatment was observed in the novelty suppressed feeding test, but not in other anxiety tests performed. Zn-deficient mice
showed exaggerated stress-evoked immediate-early gene expression in the amygdala which was normalised following DMI treatment.
Taken together these data support the link between low Zn levels and depression-like behaviour and suggest experimentally-induced
Zn deficiency as a putative model of depression in mice. 相似文献
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