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21.
J. G. Salway J. L. Harwood M. Kai G. L. White J. N. Hawthorne 《Journal of neurochemistry》1968,15(3):221-226
—The activities of four enzymes concerned with inositol lipid metabolism have been determined in homogenates of rat brains of different ages. The enzymes are CDP-diglyceride inositol phosphatidate transferase, phosphatidylinositol kinase, diphosphoinositide kinase and triphosphoinositide phosphomonoesterase. The activities of all the enzymes increased with age. Phosphatidylinositol kinase activity rose most sharply well before myelination, reaching a maximum at about 6 days of age. Diphosphoinositide kinase and triphosphoinositide phosphomonoesterase activities increased most rapidly during myelination. The increase in CDP-diglyceride inositol phosphatidate transferase showed no definite association with any period of development. It is concluded that triphosphoinositide metabolism is associated with myelin or a closely related structure. 相似文献
22.
Consequences of herbivory in the mountain birch (Betula pubescens ssp tortuosa): importance of the functional organization of the tree 总被引:3,自引:0,他引:3
Summary Three types of experiments indicate that the functional organization of the mountain birch may influence the ways in which the tree responds to simulated or natural herbivory. The first experiment showed that herbivory to both short and long shoot leaves affects plant development but, because growth largely proceeds by resources of the previous year, is manifested only in the year following the damage. The second experiment showed that even partial damage to a single long shoot leaf caused the axillary bud of that leaf to produce a shorter shoot the next year. Therefore, the value of a leaf depends also on the organ which it is subtending. In the third experiment we manipulated the apical dominance of shoots in ramets and caused improvement to leaf quality in extant shoots. Ramets within a tree responded individually, probably mediated by disturbance of the hormonal control because removal of apical buds elicited the response although removal of the same number of basal buds did not. Induced amelioration is a different response to induced resistance. The two responses are triggered by different cues and may occur in the same plant. By altering hormonal balance of shoots it is potentially possible for herbivores to induce amelioration of food quality. The ways in which herbivory is simulated may explain variability of results obtained when herbivory-induced responses in plants have been studied. 相似文献
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25.
Kai Larsen 《Nordic Journal of Botany》1996,16(6):636-636
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By means of an in vivo brain microdialysis, the effect of different concentrations of physostigmine on the acetylcholine level in the dialysate of rat frontal cortex was studied. Perfusion of the various degrees of physostigmine (eserine) concentration (10 nM−10 μM) into the cortex through the dialysis membrane increased the basal acetylcholine level in a dose-dependent manner. In the presence of 10 nM, 0.1 μM and 10 μM physostigmine in the perfusate, systemic treatment with scopolamine (0.5 mg/kg, i.p.) increased 200, 270 and 510%, respectively, the relative acetylcholine level in the dialysates in comparison with the corresponding basal levels, while in the absence of physostigmine the treatment increased it only 40%. From these results, it appears that perfusion of physostigmine at a variety of concentrations, changes not only the basal level of acetylcholine induced by the inhibition of acetylcholinesterase but also the relative acetylcholine output induced by systemic treatment with scopolamine. 相似文献
28.
Akira Kai Takaaki Arashida
Kenichi Hatanaka
Toshihiro AkaikeKei Matsuzaki
Tohru Mimura
Yutaro Kaneko 《Carbohydrate polymers》1994,23(4):235-239In order to elucidate the biosynthetic process of cellulose and curdlan, 13C-labeled polysaccharides were biosynthesized by Acetobacter xylinum (IFO 13693) and Agrobacterium sp. (ATCC 31749), from culture media containing
-(1-13C)glucose,
-(2-13C)glucose,
-(4-13C)glucose, or
-(6-13C)glucose as the carbon source, and their structures were determined by 13C NMR spectroscopy. The labeling was mainly found in the original position, indicating direct polymerization of introduced glucoses. In addition, the transfer of labeling from C-2 to C-1, C-3 and C-5, from C-4 to C-1, C-2 and C-3, and from C-6 to C-1 was found in celluloses. In curdlan, the transfer of labeling from C-1 to C-3, from C-2 to C-1 and C-3, from C-4 to C-1, C-2 and C-3, and from C-6 to C-1 and C-3 was observed. From analysis of this labeling, the biosynthetic process of cellulose and curdlan was explained as involving six routes. The percentages of each route via which cellulose or curdlan is biosynthesized were estimated for upper (C-1 to C-3) and lower portions (C-4 to C-6) of glucosidic units in the polysaccharides. It is noted that very few polysaccharides are formed via the Embden-Meyerhof pathway. The lower half (C-4 to C-6) structure of introduced glucoses is well preserved in the polysaccharides. 相似文献
29.
Repeated polyketide synthase modules involved in the biosynthesis of a heptaene macrolide by Streptomyces sp. FR-008 总被引:4,自引:2,他引:2
Zhihao Hu Kai Bao Xiufen Zhou Qi Zhou David A. Hopwood Tobias Kieser Zixln Deng 《Molecular microbiology》1994,14(1):163-172
Genes for biosynthesis of a Streptomyces sp. FR-008 heptaene macrolide antibiotic with antifungal and mosquito larvicidal activity were cloned in Escherichia coli using heterologous DNA probes. The cloned genes were implicated in heptaene biosynthiesis by gene replacement. The FR-008 antibiotic contains a 38-membered, poiyketide-derived macrolide ring. Southern hybridization using probes encoding domains of the type i modular erythromycin polyketide synthase (PKS) showed that the Streptomyces sp. FR-008 PKS gene cluster contains repeated sequences spanning c. 105 kb of contiguous DNA; assuming c. 5 kb for each PKS module, this is in striking agreement with the expectation for the 21-step condensation process required for synthesis of the FR-008 carbon chain. The methods developed for transformation and gene replacement in Streptomyces sp. FR-008 make it possible to genetically manipulate polyene macrolide production, and may later lead to the biosynthesis of novel polyene macrolides. 相似文献
30.
S. Takai M. Kasama K. Yamada N. Kai N. Hirayama H. Namiki T. Taniyama 《Human genetics》1994,93(1):13-15
The human FcRI gene encodes for a highaffinity Fc receptor that plays pivotal roles in the immune response. We have used fluorescence in situ hybridization analysis to localize the FcRI gene to human chromosome 1. The human FcRI (CD64) gene has been assigned to human chromosome 1q21.2-q21.3 using R-banded human (pro)metaphase chromosomes. 相似文献