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41.
42.
Wolfgang Rössler 《Cell and tissue research》1992,269(3):505-514
Summary The postembryonic development of the morphology and anatomy of the complex tibial organ in the foreleg of the bushcricket Ephippiger ephippiger is described. All the receptor cells are present in the subgenual organ, the intermediate organ and the crista acustica in the 1st larval instar. Generally, even in the 1st instar, the arrangement of the scolopidia in the three organs resembles the adult structure. The acoustic trachea, the tympana, the tympanal covers and the acoustic spiracle develop step by step in subsequent instars. The acoustic trachea resembles the adult structure for the first time in the 4th instar, although its volume is still small. The auditory threshold curves recorded from the tympanal nerve in instars 4, 5 and 6 show the same frequency maxima as those in the adult. The overall sensitivity significantly increases after the final moult. The dimensions of structures that lie within the crista acustica and that are probably involved in stimulus transduction and in frequency tuning have been analysed. The dorsal wall of the anterior trachea, the tectorial membrane and the cap cells have similar dimensions, especially in the last three instars and in adults. 相似文献
43.
Of the five human alcohol dehydrogenase (ADH) genes located in the region q21–25 of chromosome 4, genetic markers have been reported previously only for class I enzymes, ADH1-3. Here, new restriction fragment length polymorphisms (RFLPs) are described for the genes of two other classes, ADH4 () and ADH5 ( or formaldehyde dehydrogenase, FDH). The frequencies and modes of inheritance of these RFLPs were determined with DNA both from unrelated individuals and from families. A polymorphic PstI site is assigned to the fourth intron of the ADH4 gene. Pairwise linkage disequilibrium calculations for these new RFLPs and already known RFLPs at the ADH2 and ADH3 loci establish strong linkage disequilibria between polymorphic MspI and BstXI sites in the ADH5 gene as well as between XbaI and MspI sites in the ADH3 gene. Furthermore, linkage disequilibria were detected between RFLPs of the ADH2 and ADH3 genes as well as between those of the ADH4 and ADH5 genes. The latter disequilibrium implies a hitherto unknown physical proximity of two genes belonging to different ADH classes. The RFLPs were used to construct chromosomal haplotypes that include three ADH classes. Of the 16 possible haplotypes for four RFLP markers used here, 10 were experimentally detected. The potential application of the ADH RFLPs and haplotypes in linkage or association studies of inherited diseases such as familial alcoholism is discussed. 相似文献
44.
Ecophysiology of Aufwuchs-eating cichlids in Lake Tanganyika: niche separation by trophic specialization 总被引:1,自引:0,他引:1
Christian Sturmbauer Wolfgang Mark Reinhard Dallinger 《Environmental Biology of Fishes》1992,35(3):283-290
Synopsis The Aufwuchs-eating cichlids of Lake Tanganyika show clear trophic differences that are correlated to their morphology, physiology and foraging behaviour. The species are grouped into three categories of relative intestinal length according to their feeding habits. A correlation between the intestinal length and the diet could be demonstrated, ranging from around 2.5 for species ingesting more animal food, to 7.8 for detritivorous and microalgivorous species. The relative intestinal length of domesticTropheus moorii, raised in aquaria was significantly lower than that of wild individuals by a factor of 1.7, demonstrating a wide range of phenotypic adaptability. The activities of trypsin and amylase were at an equal level in four Aufwuchseating species, but the activity of laminarinase of a detritivorous-microalgivorous species (Petrochromis orthognathus) was 2.6 times higher than that of an algivorous species (Tropheus moorii). The laminarinase seems to be an excellent marker enzyme for detritivorous or microalgivorous feeding. 相似文献
45.
Iris Maldener Wolfgang Lockau Yuping Cai C. Peter Wolk 《Molecular & general genetics : MGG》1991,225(1):113-120
Summary It has been suggested that a calcium-dependent intracellular protease of the cyanobacterium, Anabaena sp., participates in the differentiation of heterocysts, cells that are specialized for fixation of N2. Clones of the structural gene (designated prcA) for this protease from Anabaena variabilis strain ATCC 29413 and Anabaena sp. strain PCC 7120 were identified via their expression in Escherichia coli. The prcA gene from A. variabilis was sequenced. The genes of both strains, mutated by insertion of a drug resistance cassette, were returned to these same strains of Anabaena on suicide plasmids. The method of sacB-mediated positive selection for double recombinants was used to achieve replacement of the wild-type prcA genes by the mutated forms. The resulting mutants, which lacked Ca2+-dependent protease activity, were not impaired in heterocyst formation and grew on N2 as sole nitrogen source. 相似文献
46.
47.
Contribution of organic acids to the acidification of the rhizosphere of maize seedlings 总被引:3,自引:0,他引:3
The participation of organic acids in the process of soil acidification was related to other H+ pumping processes. The ratio between efflux of organic acids and proton secretion of maize roots was determined with the
use of a pH-stat combined with a collecting system for organic acids. Changes in the composition of carboxylic acids influenced
by nitrogen supply were monitored by HPLC and via enzymatic conversion. The following substances were found to be secreted
by maize roots: glycolate, glyoxylate, fumarate, 2-oxoglutarate and oxalate. Malate, however, could not be detected.
There is no organic acid dominantly secreted by the roots, but changes are observed during aging which might result from deficiencies
of nutrients e.g. P.
Fertilization of N-deficient plants with urea leads to a significant change in the composition of acids secreted. In this
case, oxalate was additionally detected with a concomitant increase in glyoxylate, indicating important changes in metabolism.
Acidification of the rhizosphere is predominantly maintained by secretion of protons, not by efflux of organic acids, which
contributed 0.2 to 0.3% to this process only. The role of organic acids in nutrient uptake is discussed. 相似文献
48.
49.
Hans-Jürgen Peter Christiane Krüger-Alef Wolfgang Knogge Klaus Brinkmann Gottfried Weissenböck 《Planta》1991,183(3):409-415
Chalcone-synthase (CHS) activity was followed during the development of primary leaves of oat (Avena sativa L.) seedlings grown under different illumination conditions. Continuous darkness and continuous light resulted in similar time courses of enzyme activity. The maximum of CHS activity in etiolated leaves was delayed by 1 d and reached about half the level of that of light-grown leaves. In seedlings grown under defined light-dark cycles a diurnal rhythm of CHS activity and its protein level was observed which followed the rhythm of CHS-mRNA translational activity (Knogge et al. 1986). This rhythm persisted in continuous light after a short-term pre-exposure to the light-dark cycle but not in continuous darkness.Abbreviations CHS
chalcone synthase
- PAL
phenylalanine ammonio lyase
Financial support by the Deutsche Forschungsgemeinschaft is gratefully acknowledged (G.W., We 630/9-7; We 630/10-1). Thanks are given to Dr. St. Kellam (Department of Plant Microbiological Sciences, University of Canterbury, New Zealand) for correcting the English. 相似文献
50.
Peter Bramley Chantal Teulieres Ian Blain Colin Bird Wolfgang Schuch 《The Plant journal : for cell and molecular biology》1992,2(3):343-349
Transgenic tomato plants expressing antisense RNA to a ripening-related cDNA clone (pTOM5) had yellow ripening fruit and pale coloured flowers. Carotenoid levels in fruit of these plants were reduced by up to 97%. In order to determine the step of carotenoid biosynthesis which was blocked, a cell-free system active in the synthesis of carotenoid intermediates was prepared. Incubations with radiolabelled carotenoid precursors led to the identification of the block between GGDP and phytoene. Analysis of carotenoids in different tissues of transgenic and control plants indicated that although ripe fruit and flower carotenoid levels were reduced in the modified plants, leaf carotenoid levels were not decreased. This implies that the pTOM5 gene product is not involved in carotenoid synthesis in the leaf. 相似文献