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201.
Klaus Zuberbühler Lorenz Gygax Nerida Harley Hans Kummer 《Primates; journal of primatology》1996,37(1):1-12
In a captive group of long-tailed macaques, tool-using behavior by a single competent individual had a significant effect on the synchronous manipulative behavior of naïve animals. Group members engaged in manipulations on the same object class more frequently during times when the model was working than when it was not. The form of their behavior, however, in no way resembled the technique used by the model. All three animals that later became successful tool users were among the few subjects that exhibited a significant increase in manipulations on the same object class while the model was working. Possible causal relationships between this stimulus enhancement and the transmission of the new behavior to other group members are analyzed and discussed. 相似文献
202.
203.
Oxygen-dependent electron transport and protection from photoinhibition in leaves of tropical tree species 总被引:7,自引:0,他引:7
The roles of photorespiration and the Mehlerperoxidase pathway in sustaining electron transport and protection from photoinhibition were studied in outer canopy leaves of two species of tropical trees: the drought-deciduous Pseudobombax septenatum (Jacq.) Dug. and the evergreen Ficus insipida Willd. Ficus had a higher photosynthetic capacity than Pseudobombax and also a greater capacity for light-dependent electron transport under photorespiratory conditions (in the absence of CO2). As a consequence, in the absence of CO2, Ficus was able to maintain a largely oxidized electron-transport chain at higher photon flux densities than Pseudobombax. Under the same light conditions, photoinhibition (reduction in Fv/Fm) was always greater in Pseudobombax than Ficus, was increased when leaves were exposed to 2% O2 in nitrogen compared to 21% O2 in CO2-free air, but was not increased by the absence of CO2. Rates of electron transport due to the Mehler-peroxidase pathway (assessed in 2% O2 in nitrogen) ranged between 16–40 mol · m–2·s–1 in both species. As the dry season approached and Pseudobombax neared leaf senescence there was a decline in the capacity for photorespiratory flux to maintain electron transport in Pseudobombax, but not in Ficus. Ratios of light-dependent electron transport to net CO2 fixation for Pseudobombax, Ficus and two other species in the field, Luehea seemannii Tr. & Planch, and Didymopanax morototoni (Aubl.) Dec. & Planch., ranged from 6.2 (Ficus) to 16.7 (Pseudobombax). High in-situ rates of photorespiration combined with the decreased capacity of Pseudobombax for photorespiratory flux as the dry season approached indicates a decreased capacity to protect against photooxidative damage. This may contribute to the promotion of leaf senescence in Pseudobombax during the transition from wet to dry season.Abbreviations Fv/Fm
ratio of variable to maximum chlorophyll a fluorescence
- NPQ
nonphotochemical fluorescence quenching
- PFD
photon flux density
- QA
primary electron acceptor of PSII
This research was supported by a grant from the Mellon Foundation. We thank Monica Mejia and Juan Posada for assisting with the fluorescence measurements and Aurelio Virgo for assisting with the field CO2-exchange measurements. 相似文献
204.
205.
206.
Hector M. Alvarez Frank Mayer Dirk Fabritius A. Steinbüchel 《Archives of microbiology》1996,165(6):377-386
An oleaginous hydrocarbon-degrading Rhodococcus opacus strain (PD630) was isolated from a soil sample. The cells were able to grow on a variety of substrates and to produce large
amounts of three different types of intracellular inclusions during growth on alkanes, phenylalkanes, or non-hydrocarbon substrates.
Electron microscopy revealed large numbers of electron-transparent inclusions with a sphere-like structure. In addition, electron-dense
inclusions representing polyphosphate and electron-transparent inclusions with an elongated disc-shaped morphology occurred
in small amounts. The electron-transparent inclusions of alkane- or gluconate-grown cells were composed of neutral lipids
(98%, w/w), phospholipids (1.2%, w/w), and protein (0.8%, w/w). The major component of the cellular inclusions was triacylglycerols;
minor amounts of diacylglycerols and probably also some free fatty acids were also present. Free fatty acids and/or fatty
acids in acylglycerols in cells of R. opacus amounted up to 76 or 87% of the cellular dry weight in gluconate- or olive-oil-grown cells, respectively. The fatty acid composition
of the inclusions depended on the substrate used for cultivation. In cells cultivated on n-alkanes, the composition of the
fatty acids was related to the substrate, and intermediates of the β-oxidation pathway, such as hexadecanoic or pentadecanoic
acid, were among the acylglycerols. Hexadecanoic acid was also the major fatty acid (up 36% of total fatty acids) occurring
in the lipid inclusions of gluconate-grown cells. This indicated that strain PD630 utilized β-oxidation and de novo fatty
acid biosynthesis for the synthesis of storage lipids. Inclusions isolated from phenyldecane-grown cells contained mainly
the non-modified substrate and phenylalkanoic acids derived from the hydrocarbon oxidation, such as phenyldecanoic acid, phenyloctanoic
acid, and phenylhexanoic acid, and approximately 5% (w/w) of diacylglycerols. The lipid inclusions seemed to have definite
structures, probably with membranes at their surfaces, which allow them to maintain their shape, and with some associated
proteins, probably involved in the inclusion formation.
Received: 22 December 1995 / Accepted: 12 March 1996 相似文献
207.
Seong-Lyul Rhim Hwa-Jin Cho Byung-Dong Kim Wolfgang Schnetter Klaus Geider 《Molecular breeding : new strategies in plant improvement》1995,1(3):229-236
A crystal -endotoxin gene ofBacillus thuringiensis subsp.tenebrionis (B.t.t.) encoding a coleopteran insect-specific toxin was used to construct a chimeric gene which expressed the toxin in plant cells. Via anAgrobacterium tumefaciens binary vector system, the toxin gene was transferred into tomato cells. From leaf disks recombinant plants were regenerated. Hybridization experiments demonstrated that these plants synthesized toxin-specific mRNA of the expected size. Transgenic tomato plants with the chimericB.t.t. toxin gene contained a 74 kDa protein which cross-reacted with toxin antibodies. The expression caused a significant insecticidal activity of the transgenic tomato plants against Colorado potato beetle larvae. 相似文献
208.
209.
Gerhard Bringmann Klaus-Peter Gulden Daniel Vitt Klaus Birken Clemens Helf 《Journal of molecular modeling》1995,1(3):161-175
AdaptivSearch is the first adaptive strategy based algorithm for the rational and economical construction of n-dimensional hypersurfaces. AdaptivSearch works iteratively: At each step it parcels out the definition range into several triangles, evaluates the worst according to a built-in error criterion, and refines the approximation to the unknown function by choosing the barycenter of this partial area as the node to be calculated next. Based upon the error criterion, AdaptivSearch selectively approaches those parts of the hypersurface in which the curvature exhibits the strongest changes. Some examples of AdaptivSearch applications for both analytical functions and chemical model surfaces are given in order to demonstrate the behavior of the algorithm. These show its broad applicability and the usefulness, especially for chemical problems. 相似文献
210.
Nitric oxide synthase in the rat carotid body and carotid sinus 总被引:5,自引:0,他引:5
The participation of nitric oxide synthase (NOS) in the innervation of the rat carotid body and carotid sinus was investigated by means of NADPH-diaphorase histochemistry and NOS immunohistochemistry using antisera raised against purified neuronal NOS and a synthetic tridecapeptide. NOS was detected in 23% of neurons at the periphery of the carotid bodies. Some negative neurons were surrounded by NOS-positive terminals. NOS-containing varicose nerve fibres innervated the arterial vascular bed and, to a lesser extent, the islands of glomus cells. These fibres persisted after transection of the carotid sinus nerve and are probably derived from intrinsic neurons. Large NOS-positive axonal swellings in the wall of the carotid sinus were absent after transection of the sinus nerve, indicating their sensory origin. The results suggest a neuronal nitrergic control of blood flow, neuronal activity and chemoreception in the carotid body, and an intrinsic role of NO in the process of arterial baroreception. 相似文献