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1.
Maria Luisa Dalla Chiara 《Foundations of Science》2002,7(1-2):1-9
In recent times, a particular attention has been devoted to thesignificance of Quantum Theory for other disciplines. The articlescollected in this issue discuss some interesting cases,characterized by an interaction between Quantum Theory andother fields. Some basic notrons of the mathematical formalismof the theory are here summarized. 相似文献
2.
This paper stresses the restrictive nature of the standard unit root/cointegration assumptions and examines a more general type of time heterogeneity, which might characterize a number of economic variables, and which results in parameter time dependence and misleading statistical inference. We show that in such cases ‘operational’ models cannot be obtained, and the estimation of time‐varying parameter models becomes necessary. For instance, economic processes subject to endemic change can only be adequately modelled in a state space form. This is a very important point, because unstable models will break down when used for forecasting purposes. We also discuss a new test for the null of cointegration developed by Quintos and Phillips (1993), which is based on parameter constancy in cointegrating regressions. Finally, we point out that, if it is possible to condition on a subset of superexogenous variables, parameter instability can be handled by estimating a restricted system. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
3.
P. J. Müller P. Masner Maria Kälin W. S. Bowers 《Cellular and molecular life sciences : CMLS》1979,35(5):704-705
Summary Corpora allata fromOncopeltus fasciatus incubated in vitro in medium containing 10–5.35 M (1 g/ml) of precocene II lose their ability to secrete juvenile hormone when reimplanted into last instar larvae.Acknowledgments. We thank Mr K. Dorn, Mrs L. Dolezal, Mrs V. Nötzli-Graf, Mr K.H. Trautmann and Mr A. Schuler for technical help, Dr W. Vogel and Dr A. Dübendorfer for valuable discussions. 相似文献
4.
5.
Novel neurotrophic factor CDNF protects and rescues midbrain dopamine neurons in vivo 总被引:1,自引:0,他引:1
Lindholm P Voutilainen MH Laurén J Peränen J Leppänen VM Andressoo JO Lindahl M Janhunen S Kalkkinen N Timmusk T Tuominen RK Saarma M 《Nature》2007,448(7149):73-77
In Parkinson's disease, brain dopamine neurons degenerate most prominently in the substantia nigra. Neurotrophic factors promote survival, differentiation and maintenance of neurons in developing and adult vertebrate nervous system. The most potent neurotrophic factor for dopamine neurons described so far is the glial-cell-line-derived neurotrophic factor (GDNF). Here we have identified a conserved dopamine neurotrophic factor (CDNF) as a trophic factor for dopamine neurons. CDNF, together with its previously described vertebrate and invertebrate homologue the mesencephalic-astrocyte-derived neurotrophic factor, is a secreted protein with eight conserved cysteine residues, predicting a unique protein fold and defining a new, evolutionarily conserved protein family. CDNF (Armetl1) is expressed in several tissues of mouse and human, including the mouse embryonic and postnatal brain. In vivo, CDNF prevented the 6-hydroxydopamine (6-OHDA)-induced degeneration of dopaminergic neurons in a rat experimental model of Parkinson's disease. A single injection of CDNF before 6-OHDA delivery into the striatum significantly reduced amphetamine-induced ipsilateral turning behaviour and almost completely rescued dopaminergic tyrosine-hydroxylase-positive cells in the substantia nigra. When administered four weeks after 6-OHDA, intrastriatal injection of CDNF was able to restore the dopaminergic function and prevent the degeneration of dopaminergic neurons in substantia nigra. Thus, CDNF was at least as efficient as GDNF in both experimental settings. Our results suggest that CDNF might be beneficial for the treatment of Parkinson's disease. 相似文献
6.
7.
FADD prevents RIP3-mediated epithelial cell necrosis and chronic intestinal inflammation 总被引:2,自引:0,他引:2
Welz PS Wullaert A Vlantis K Kondylis V Fernández-Majada V Ermolaeva M Kirsch P Sterner-Kock A van Loo G Pasparakis M 《Nature》2011,477(7364):330-334
Intestinal immune homeostasis depends on a tightly regulated cross talk between commensal bacteria, mucosal immune cells and intestinal epithelial cells (IECs). Epithelial barrier disruption is considered to be a potential cause of inflammatory bowel disease; however, the mechanisms regulating intestinal epithelial integrity are poorly understood. Here we show that mice with IEC-specific knockout of FADD (FADD(IEC-KO)), an adaptor protein required for death-receptor-induced apoptosis, spontaneously developed epithelial cell necrosis, loss of Paneth cells, enteritis and severe erosive colitis. Genetic deficiency in RIP3, a critical regulator of programmed necrosis, prevented the development of spontaneous pathology in both the small intestine and colon of FADD(IEC-KO) mice, demonstrating that intestinal inflammation is triggered by RIP3-dependent death of FADD-deficient IECs. Epithelial-specific inhibition of CYLD, a deubiquitinase that regulates cellular necrosis, prevented colitis development in FADD(IEC-KO) but not in NEMO(IEC-KO) mice, showing that different mechanisms mediated death of colonic epithelial cells in these two models. In FADD(IEC-KO) mice, TNF deficiency ameliorated colon inflammation, whereas MYD88 deficiency and also elimination of the microbiota prevented colon inflammation, indicating that bacteria-mediated Toll-like-receptor signalling drives colitis by inducing the expression of TNF and other cytokines. However, neither CYLD, TNF or MYD88 deficiency nor elimination of the microbiota could prevent Paneth cell loss and enteritis in FADD(IEC-KO) mice, showing that different mechanisms drive RIP3-dependent necrosis of FADD-deficient IECs in the small and large bowel. Therefore, by inhibiting RIP3-mediated IEC necrosis, FADD preserves epithelial barrier integrity and antibacterial defence, maintains homeostasis and prevents chronic intestinal inflammation. Collectively, these results show that mechanisms preventing RIP3-mediated epithelial cell death are critical for the maintenance of intestinal homeostasis and indicate that programmed necrosis of IECs might be implicated in the pathogenesis of inflammatory bowel disease, in which Paneth cell and barrier defects are thought to contribute to intestinal inflammation. 相似文献
8.
Bedding TR Mosser B Huber D Montalbán J Beck P Christensen-Dalsgaard J Elsworth YP García RA Miglio A Stello D White TR De Ridder J Hekker S Aerts C Barban C Belkacem K Broomhall AM Brown TM Buzasi DL Carrier F Chaplin WJ Di Mauro MP Dupret MA Frandsen S Gilliland RL Goupil MJ Jenkins JM Kallinger T Kawaler S Kjeldsen H Mathur S Noels A Aguirre VS Ventura P 《Nature》2011,471(7340):608-611
Red giants are evolved stars that have exhausted the supply of hydrogen in their cores and instead burn hydrogen in a surrounding shell. Once a red giant is sufficiently evolved, the helium in the core also undergoes fusion. Outstanding issues in our understanding of red giants include uncertainties in the amount of mass lost at the surface before helium ignition and the amount of internal mixing from rotation and other processes. Progress is hampered by our inability to distinguish between red giants burning helium in the core and those still only burning hydrogen in a shell. Asteroseismology offers a way forward, being a powerful tool for probing the internal structures of stars using their natural oscillation frequencies. Here we report observations of gravity-mode period spacings in red giants that permit a distinction between evolutionary stages to be made. We use high-precision photometry obtained by the Kepler spacecraft over more than a year to measure oscillations in several hundred red giants. We find many stars whose dipole modes show sequences with approximately regular period spacings. These stars fall into two clear groups, allowing us to distinguish unambiguously between hydrogen-shell-burning stars (period spacing mostly ~ 50 seconds) and those that are also burning helium (period spacing ~ 100 to 300 seconds). 相似文献
9.
Sensory information is transmitted to the brain where it must be processed to translate stimulus features into appropriate behavioural output. In the olfactory system, distributed neural activity in the nose is converted into a segregated map in the olfactory bulb. Here we investigate how this ordered representation is transformed in higher olfactory centres in mice. We have developed a tracing strategy to define the neural circuits that convey information from individual glomeruli in the olfactory bulb to the piriform cortex and the cortical amygdala. The spatial order in the bulb is discarded in the piriform cortex; axons from individual glomeruli project diffusely to the piriform without apparent spatial preference. In the cortical amygdala, we observe broad patches of projections that are spatially stereotyped for individual glomeruli. These projections to the amygdala are overlapping and afford the opportunity for spatially localized integration of information from multiple glomeruli. The identification of a distributive pattern of projections to the piriform and stereotyped projections to the amygdala provides an anatomical context for the generation of learned and innate behaviours. 相似文献
10.
Metabolic priming by a secreted fungal effector 总被引:1,自引:0,他引:1
Djamei A Schipper K Rabe F Ghosh A Vincon V Kahnt J Osorio S Tohge T Fernie AR Feussner I Feussner K Meinicke P Stierhof YD Schwarz H Macek B Mann M Kahmann R 《Nature》2011,478(7369):395-398
Maize smut caused by the fungus Ustilago maydis is a widespread disease characterized by the development of large plant tumours. U. maydis is a biotrophic pathogen that requires living plant tissue for its development and establishes an intimate interaction zone between fungal hyphae and the plant plasma membrane. U. maydis actively suppresses plant defence responses by secreted protein effectors. Its effector repertoire comprises at least 386 genes mostly encoding proteins of unknown function and expressed exclusively during the biotrophic stage. The U. maydis secretome also contains about 150 proteins with probable roles in fungal nutrition, fungal cell wall modification and host penetration as well as proteins unlikely to act in the fungal-host interface like a chorismate mutase. Chorismate mutases are key enzymes of the shikimate pathway and catalyse the conversion of chorismate to prephenate, the precursor for tyrosine and phenylalanine synthesis. Root-knot nematodes inject a secreted chorismate mutase into plant cells likely to affect development. Here we show that the chorismate mutase Cmu1 secreted by U. maydis is a virulence factor. The enzyme is taken up by plant cells, can spread to neighbouring cells and changes the metabolic status of these cells through metabolic priming. Secreted chorismate mutases are found in many plant-associated microbes and might serve as general tools for host manipulation. 相似文献