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931.
932.
933.
Liat Bahari Yuval Gilad Ilya Borovok Hamutal Kahel-Raifer Bareket Dassa Yakir Nataf Yuval Shoham Raphael Lamed Edward A. Bayer 《Journal of industrial microbiology & biotechnology》2011,38(7):825-832
The composition of the cellulase system in the cellulosome-producing bacterium, Clostridium thermocellum, has been reported to change in response to growth on different carbon sources. Recently, an extensive carbohydrate-sensing
mechanism, purported to regulate the activation of genes coding for polysaccharide-degrading enzymes, was suggested. In this
system, CBM modules, comprising extracellular components of RsgI-like anti-σ factors, were proposed to function as carbohydrate
sensors, through which a set of cellulose utilization genes are activated by the associated σI-like factors. An extracellular module of one of these RsgI-like proteins (Cthe_2119) was annotated as a family 10 glycoside
hydrolase, RsgI6-GH10, and a second putative anti-σ factor (Cthe_1471), related in sequence to Rsi24, was found to contain
a module that resembles a family 5 glycoside hydrolase (termed herein Rsi24C-GH5). The present study examines the relevance
of these two glycoside hydrolases as sensors in this signal-transmission system. The RsgI6-GH10 was found to bind xylan matrices
but exhibited low enzymatic activity on this substrate. In addition, this glycoside hydrolase module was shown to interact
with crystalline cellulose although no hydrolytic activity was detected on cellulosic substrates. Bioinformatic analysis of
the Rsi24C-GH5 showed a glutamate-to-glutamine substitution that would presumably preclude catalytic activity. Indeed, the
recombinant module was shown to bind to cellulose, but showed no hydrolytic activity. These observations suggest that these
two glycoside hydrolases underwent an evolutionary adaptation to function as polysaccharide binding agents rather than enzymatic
components and thus serve in the capacity of extracellular carbohydrate sensors. 相似文献
934.
Baker PJ Costanzo JP Lee RE 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2007,177(8):875-883
Hatchlings of the painted turtle, Chrysemys picta, hibernate terrestrially and can survive subfreezing temperatures by supercooling or by tolerating the freezing of their
tissues. Whether supercooled or frozen, an ischemic hypoxia develops because tissue perfusion is limited by low temperature
and/or freezing. Oxidative stress can occur if hatchlings lack sufficient antioxidant defenses to minimize or prevent damage
by reactive oxygen species. We examined the antioxidant capacity and indices of oxidative damage in hatchling C. picta following survivable, 48 h bouts of supercooling (−6°C), freezing (−2.5°C), or hypoxia (4°C). Samples of plasma, brain, and
liver were collected after a 24 h period of recovery (4°C) and assayed for Trolox-equivalent antioxidant capacity (TEAC),
thiobarbituric acid reactive substances (TBARS), and carbonyl proteins. Antioxidant capacity did not vary among treatments
in any of the tissues studied. We found a significant increase in TBARS in plasma, but not in the brain or liver, of frozen/thawed
hatchlings as compared to untreated controls. No changes were found in the concentration of TBARS or carbonyl proteins in
supercooled or hypoxia-exposed hatchlings. Our results suggest that hatchling C. picta have a well-developed antioxidant defense system that minimizes oxidative damage during hibernation. 相似文献
935.
Thomas M Davis Melanie E Shields Qian Zhang Denise Tombolato-Terzić Jeffrey L Bennetzen Ana C Pontaroli Hao Wang Qin Yao Phillip SanMiguel Kevin M Folta 《BMC plant biology》2010,10(1):81
Background
Strawberry (Fragaria spp.) is the familiar name of a group of economically important crop plants and wild relatives that also represent an emerging system for the study of gene and genome evolution. Its small stature, rapid seed-to-seed cycle, transformability and miniscule basic genome make strawberry an attractive system to study processes related to plant physiology, development and crop production; yet it lacks substantial genomics-level resources. This report addresses this deficiency by characterizing 0.71 Mbp of gene space from a diploid species (F. vesca). The twenty large genomic tracks (30-52 kb) captured as fosmid inserts comprise gene regions with roles in flowering, disease resistance, and metabolism. 相似文献936.
Burbaeva GSh Boksha IS Tereshkina EB Savushkina OK Starodubtseva LI Turishcheva MS Mukaetova-Ladinska E 《Neurochemical research》2007,32(9):1434-1444
We have used a systemic approach to establish a relationship between enzyme measures of glial glutamate and energy metabolism
(glutamine synthetase and glutamine synthetase-like protein, glutamate dehydrogenase isoenzymes, brain isoform creatine phosphokinase)
and two major glial proteins (glial fibrillary acidic protein and myelin basic protein) in autopsied brain samples taken from
patients with schizophrenia (SCH) and mentally healthy subjects (23 and 22 cases, respectively). These biochemical parameters
were measured in tissue extracts in three brain areas (prefrontal cortex, caudate nucleus, and cerebellum). Significant differences
in the level of at least one of the glutamate metabolizing enzymes were observed between two studied groups in all studied
brain areas. Different patterns of correlative links between the biochemical parameters were found in healthy and schizophrenic
brains. These findings give a new perspective to our understanding of the impaired regulation of enzyme levels in the brain
in SCH. 相似文献
937.
Aim
Our objectives were to compare effects of root charge properties on Al adsorption by the roots of rice that differed in Al-tolerance, and to examine effects of different nitrogen forms on charge properties of rice roots and Al adsorption.Methods
Streaming potential and chemical methods were used to measure root zeta potential and investigate Al chemical forms adsorbed on the roots of rice obtained from solution culture experiments.Results
Rice roots of the Al-sensitive variety Yangdao-6 carried greater negative charge than the Al-tolerant variety Wuyunjing-7, which meant the roots of Yangdao-6 adsorbed more exchangeable and complexed Al. When both rice varieties were grown in NH4 +-containing nutrient solutions, there were less functional groups and lower negative surface charge on their roots, which reduced Al adsorption compared to the rice grown in NO3 ? containing nutrient solutions. The decline in nutrient solution pH due to NH4 + uptake by rice roots was responsible for the reduced numbers of functional groups and the lower negative surface charge on the roots compared to the rice grown in NO3 ? containing solutions.Conclusions
Integrated root surface charge, as expressed by zeta potential, played an important role in Al adsorption by the roots of rice with different Al-tolerance.938.
In earlier work, we laid out the foundation for explaining the quantum-like behavior of neural systems in the basic kinematic case of clusters of neuron-like units. Here we extend this approach to networks and begin developing a dynamical theory for them. Our approach provides a novel mathematical foundation for neural dynamics and computation which abstracts away from lower-level biophysical details in favor of information-processing features of neural activity. The theory makes predictions concerning such pathologies as schizophrenia, dementias, and epilepsy, for which some evidence has accrued. It also suggests a model of memory retrieval mechanisms. As further proof of principle, we analyze certain energy-like eigenstates of the 13 three-neuron motif classes according to our theory and argue that their quantum-like superpositional nature has a bearing on their observed structural integrity. 相似文献
939.
Higgins JD Buckling EF Franklin FC Jones GH 《The Plant journal : for cell and molecular biology》2008,54(1):152-162
Meiotic crossovers/chiasmata, that are required to ensure chromosome disjunction, arise via the class I interference-dependent pathway or via the class II interference-free pathway. The proportions of these two classes vary considerably between different organisms. In Arabidopsis, about 85% of chiasmata are eliminated in Atmsh4 mutants, denoting that these are class I events. In budding and fission yeasts Msh4-independent crossovers arise largely or entirely via a Mus81-dependent pathway. To investigate the origins of the 15% residual (AtMSH4-independent) chiasmata in Arabidopsis we conducted a cytological and molecular analysis of AtMUS81 meiotic expression and function. Although AtMUS81 functions in somatic DNA repair and recombination, it is more highly expressed in reproductive tissues. The protein is abundantly present in early prophase I meiocytes, where it co-localizes, in a double-strand break-dependent manner, with the recombination protein AtRAD51. Despite this, an Atmus81 mutant shows normal growth and has no obvious defects in reproductive development that would indicate meiotic impairment. A cytological analysis confirmed that meiosis was apparently normal in this mutant and its mean chiasma frequency was similar to that of wild-type plants. However, an Atmsh4 / Atmus81 double mutant revealed a significantly reduced mean chiasma frequency (0.85 per cell), compared with an Atmsh4 single mutant (1.25 per cell), from which we conclude that AtMUS81 accounts for some, but not all, of the 15% AtMSH4-independent residual crossovers. It is possible that other genes are responsible for these residual chiasmata. Alternatively the AtMUS81 pathway coexists with an alternative parallel pathway that can perform the same functions. 相似文献
940.
Three-dimensional reconstruction of brain surface anatomy based on magnetic resonance imaging diffusion-weighted imaging: A new approach 总被引:1,自引:0,他引:1
Gong X Fang M Wang J Sun J Zhang X Kwong WH Yew DT 《Journal of biomedical science》2004,11(6):711-716
Fifty normal noninfarct patients and 12 cases with infarcts of the cerebrum were examined with routine magnetic resonance imaging and echo-planar diffusion-weighted imaging. The diffusion-weighted three-dimensional images were reconstructed with volume-rendering processing on workstation. Precentral gyrus, post-central gyrus, superior parietal lobule, superior frontal gyrus, precentral sulcus, central sulcus, postcentral sulcus, intraparietal sulcus and superior frontal sulcus were best shown of all structures with an arbitrary score of 2.61–2.77. Supramarginal gyrus, middle frontal gyrus, inferior frontal gyrus and lateral sulcus were clearly shown in the majority of the cerebra with average scores of 2.0–2.49; angular gyrus, inferior frontal sulcus and superior temporal gyrus were not demonstrated satisfactorily and their average scores were 1.67–1.89. Middle temporal gyrus, inferior temporal gyrus, superior temporal sulcus and inferior temporal sulcus were difficult to identify, and thus had average scores of 0.87–1.26. Brain surface structures were better displayed in the older group of individuals than in the younger group. The structures in the 12 cases with acute or chronic cerebrum infarcts were also satisfactorily demonstrated with this new technique. 相似文献