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91.
92.
With a unique corporate culture based on ancient Ch in ese wisdom being implemented at workplace for more than 10 years, we have been e ncountering various issue of managing conflicts, in particular at organization r estructure period, although we perceive that conflict does not necessarily have dysfunctional effect on our group performance. However, conflicts between and am ong various levels of the organization hierarchy are inevitably creating certain impact on our organization cohesiveness, performa...  相似文献   
93.
R A Silver  S F Traynelis  S G Cull-Candy 《Nature》1992,355(6356):163-166
Neurotransmission from mossy fibre terminals onto cerebellar granule cells is almost certainly mediated by L-glutamate. By taking advantage of the small soma size, limited number of processes and short dendrite length of granule cells, we have obtained high-resolution recordings of spontaneous miniature excitatory postsynaptic currents (m.e.p.s.cs) and evoked currents in thin cerebellar slices. Miniature currents have a similar time-course and pharmacology to evoked currents and consist of an exceptionally fast non-NMDA (N-methyl-D-aspartate) component (measured rise-time, 200 microseconds; estimated pre-filtered rise-time less than 100 microseconds; decay time constant, tau = 1.0 ms), followed by 50 pS NMDA channel openings that are directly resolvable. We could find no evidence for the recent proposal that miniature currents in granule cells are mediated solely by NMDA channels with a novel time course. The non-NMDA receptor component of m.e.p.s.cs has a skewed amplitude distribution, which suggests potential complications for quantal analysis. The difference in time course between the m.e.p.s.cs reported here and other synaptic currents in the brain could reflect differences in synaptic function or electrotonic filtering; the relative contribution of these possibilities has yet to be established.  相似文献   
94.
The inherited osteolyses or 'vanishing bone' syndromes are a group of rare disorders of unknown etiology characterized by destruction and resorption of affected bones. The multicentric osteolyses are notable for interphalangeal joint erosions that mimic severe juvenile rheumatoid arthritis (OMIMs 166300, 259600, 259610 and 277950). We recently described an autosomal recessive form of multicentric osteolysis with carpal and tarsal resorption, crippling arthritic changes, marked osteoporosis, palmar and plantar subcutaneous nodules and distinctive facies in a number of consanguineous Saudi Arabian families. We localized the disease gene to 16q12-21 by using members of these families for a genome-wide search for homozygous-by-descent microsatellite markers. Haplotype analysis narrowed the critical region to a 1.2-cM region that spans the gene encoding MMP-2 (gelatinase A, collagenase type IV; (ref. 3). We detected no MMP2 enzymatic activity in the serum or fibroblasts of affected family members. We identified two family-specific homoallelic MMP2 mutations: R101H and Y244X. The nonsense mutation effects a deletion of the substrate-binding and catalytic sites and the fibronectin type II-like and hemopexin/TIMP2 binding domains. Based on molecular modeling, the missense mutation disrupts hydrogen bond formation within the highly conserved prodomain adjacent to the catalytic zinc ion.  相似文献   
95.
量子力学是当前物理学及其相关科学的重要科学分支,也是当前许多新科学技术中的重要应用的基础。本书包含了现代新科学技术工程师所需要的量子力学方面的新材料,如研究和了解原子核、原子、分子和固体材料,以及激光器和其他量子光学器件所需要的科学资料等。  相似文献   
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97.
Summary During the spontaneous differentiation (day 5 to day 15 of the culture) of Caco-2 cells, the sulfation of cell layer glycosaminoglycans increased, whereas protein kinase C activity was concomitantly redistributed from the membrane to the cytosol. The protein kinase C activators, 4-phorbol 12-myristate, 13-acetate and 1,2-dioctanoyl-glycerol inhibited glycosaminoglycan sulfation. By contrast, 4-phorbol 12, 13 didecanoate was ineffective.These results suggest that membrane-bound PKC may exert a modulatory effect on glycosaminoglycan sulfation, and this effect is gradually attenuated as Caco-2 cell differentiation progresses.  相似文献   
98.
Chemical ecology of oviposition in phytophagous insects   总被引:3,自引:0,他引:3  
Summary Selection of a suitable site for oviposition by phytophagous insects is critical for successful development of the offspring. The behavioral events leading to oviposition are mediated to a large extent by chemical cues associated with potential host plants. Orientation and landing are primarily guided by volatile constituents of a plant, whereas assessment of a leaf surface depends on contact stimuli. Chemical mechanisms that ensure adequate spacing of progeny on limited resources include the production of oviposition-deterring pheromones as well as recognition of plant constituents released as a result of previous damage. Perception of chemical cues that affects oviposition involves receptors on antennae, tarsi, mouthparts or the ovipositor. Complex behavior such as tarsal drumming or stem runs may serve to provide increased receptor contact with chemical stimuli. Abiotic and biotic environmental factors often influence the production or release of behavior-modifying chemicals by a plant, and therefore affect oviposition preferences. Plant chemistry may be involved in associative learning, but may also lead to mistakes. Thus a clear correlation between oviposition preference and offspring success does not always exist.  相似文献   
99.
Summary The opioid agonists morphine (selective for -receptors) and ethylketocyclazocine (selective for kappa-receptors), at concentrations evoking strong effects in neuronal structures, did not significantly affect the configuration of the intracellularly recorded action potential and the force of contraction in ventricular heart muscle isolated from guinea pigs, rabbits and man. These results suggest that any changes of heart functions in vivo in response to opioid-like drugs are probably not mediated postsynaptically at the myocardial cell membrane but rather presynaptically, influencing the release of noradrenaline and/or acetylcholine from the nerve terminals.  相似文献   
100.
Summary Using brine shrimp lethality for activity-directed fractionation, goniothalamicin (I), a new tetrahydroxy-mono-tetrahydrofuran fatty acid -lactone (acetogenin), has been isolated from ethanolic extracts of the stem bark ofGoniothalamus giganteus Hook. f., Thomas (Annonaceae). This novel compound was found to be cytotoxic and insecticidal and inhibited the formation of crown gall tumors on potato discs. Annonacin (II), the only other reported mono-tetrahydrofuran acetogenin, was also isolated; the previously reported 9ASK (astrocytoma reversal) activity ofII was confirmed, andII is now also found to be weakly active against 3PS murine leukemia.  相似文献   
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