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排序方式: 共有822条查询结果,搜索用时 62 毫秒
1.
Piet J. van den Hout Theunis Piersma Anne Dekinga Suzanne K. Lubbe G. Henk Visser 《Journal of avian biology》2006,37(5):425-430
To cope with changes in the environment, organisms not only show behavioural but also phenotypic adjustments. This is well established for the digestive tract. Here we present a first case of birds adjusting their flight machinery in response to predation risk. In an indoor experiment, ruddy turnstones Arenaria interpres were subjected to an unpredictable daily appearance of either a raptor or a small gull (as a control). Ruddy turnstones experiencing threat induced by a flying raptor model, longer than after similar passage by the gull model, refrained from feeding after this disturbance. Pectoral muscle mass, but not lean mass, responded in a course of a few days to changes in the perceived threat of predation. Pectoral muscle mass increased after raptor scares. Taking the small increases in body mass into account, pectoral muscle mass was 3.6% higher than aerodynamically predicted for constant flight performance. This demonstrates that perceived risk factors may directly affect organ size. 相似文献
2.
The histone H1°/H5 variant and terminal differentiation of cells during development of Xenopus laevis 总被引:1,自引:0,他引:1
Antoon F.M. Moorman Piet A.J. de Boer Rob Charles Wouter H. Lamers 《Differentiation; research in biological diversity》1987,35(2):100-107
The maintenance of the differentiated condition is supposed to be associated with the presence of a histone of the H1(0)/H5 subclass. If the H1(0)/H5 variant has an important role in differentiation distinct from that of H1, it should display differential expression in time and position during development. Here we report that this prediction is verified during Xenopus laevis development, in which tadpoles exhibit a very characteristic, developmentally regulated pattern of histone H1(0)/H5 expression that is different for the derivatives of each embryonic germ layer. However, the pattern of appearance of this variant during development does not reflect a simple correlation between its presence and the state of differentiation. Therefore, these results are pertinent to current ideas on differentiation and the involvement of lysine-rich histones in the repression of eukaryotic genes. 相似文献
3.
Hugues Puissant Martine Azoulay Jean-Louis Serre LucLarget Piet Claudine Junien 《Human genetics》1988,79(3):280-282
Summary Most patients with the complex association aniridia — predisposition to Wilms' tumor (WAGR syndrome) present with a de novo constitutional deletion of band 11p13. We report a patient with WAGR syndrome and a reciprocal translocation between chromosomes 5 and 11 t(5;11)(q11;p13). High resolution banding cytogenetic analysis and molecular characterization using 11p13 DNA markers showed a tiny deletion encompassing the gene for CAT but sparing the gene for FSHB. This suggests that syndromes associated with apparently balanced translocations may be due to undetectable loss of material at the breakpoint(s) rather than to breakage in the gene itself. 相似文献
4.
Jeanine Brederoo Piet de Wildt Corrie Popp-Snijders Robin F. Irvine Alan Musgrave Herman van den Ende 《Planta》1991,184(2):175-181
InChlamydomonas eugametos gametes, phosphatidylinositol 4-phosphate (PtdInsP) and phosphatidylinositol 4,5-bisphosphate (PtdInsP2) comprised 0.4 and 0.3% of the whole-cell phospholipids. They were concentrated in the plasma membrane around the cell body and were present in low concentrations in the flagellar membrane. When gametes were fed32PO
4
-
, the label was rapidly incorporated into PtdInsP and PtdInsP2 and only slowly incorporated into structural lipids such as phosphatidylethanolamine and phosphatidylglycerol. Similarly, when a pulse of32PO
4
-
was chased with PO
4
-
, the label was rapidly lost from the polyphosphoinositol lipids but not from the structural lipids. The major fatty acids in the polyphosphoinositides were C-22 carbon polyenoic acids (70%). The significance of these results in relationship to intracellular signalling via inositol phosphates and Ca2+ is discussed.Abbreviations InsP3
inositol 1,4,5-trisphosphate
- mt–/mt+
mating-type plus or minus
- PtdA
phosphatidic acid
- PtdEtn
phosphatidylethanolamine
- PtdGro
phosphatidylglycerol
- PtdIns
phosphatidylinositol
- PtdInsP
phosphatidylinositol 4-phosphate;
- PtdInsP2
phosphatidylinositol 4,5-bisphosphate
- TCA
trichloroacetic acid
We thank Frank Schuring for Fig. 5A and Susan Kenter, Hans Kruisselbrink, Saskia Bijvank and Nelleke Corbett for their enthousiastic assistance. 相似文献
5.
The distribution of aquatic oligochaetes in the fenland area of N.W. Overijssel (The Netherlands) 总被引:5,自引:5,他引:0
Piet F. M. Verdonschot 《Hydrobiologia》1984,115(1):215-222
A synoptic study of the aquatic ecosystems in the Dutch province of Overijssel revealed the presence of 33 oligochaete taxa in the fendland area of N.W. Overijssel. The material was collected at 101 sampling sites in 1981. Oligochaetes were grouped by means of a normal and inverse cluster analysis. Although most oligochaetes are quite biquitous, differences in occurrence and abundance were observed and related to minor differences in environmental parameters. 相似文献
6.
Huub J. M. Op den Camp Claudius K. Stumm Gerben Straatsma Piet J. L. Derikx Leo J. L. D. van Griensven 《Microbial ecology》1990,19(3):303-309
The interaction betweenAgaricus bisporus andScytalidium thermophilum on agar media was studied by differential interference contrast and phase contrast microscopy.A. bisporus combatively replacesS. thermophilum in culture on agar media. The antagonistic effect ofA. bisporus is transmissible through a cellophane membrane and causes irreversible disintegration ofS. thermophilum protoplasm, resulting in a total loss of viability after prolonged interaction between the two fungi. On compost extract agar, but not on other media, the growth rate ofA. bisporus increased from 2.7 to 5.3 mm·d–1 following contact withS. thermophilum mycelium. 相似文献
7.
Piet F.M. Verdonschot 《Hydrobiologia》1996,334(1-3):169-183
Eight experimental ditch mesocosms were used to study the effect of eutrophication over four years. The experimental ditches had a sand or clay bottom. The ditches were treated with additions of phosphorus, phosphorus and nitrogen, or without additions (controls). Oligochaetes were sampled by deploying trays with substratum for colonization over twenty weeks. Both the important variables phosphorus, nitrogen and oxygen as well as the oligochaete species and numbers are presented. The effects of nutrient additions on phosphorus, nitrogen and oxygen concentrations were described together with changes in oligochaete species composition and numbers. The results were further analyzed by redundancy analysis (RDA). In the clay-lined ditches nutrient addition coincided with fluctuation in oxygen concentration. The higher the nutrient addition levels the longer the period of oxygen depletion became. During oxygen depletion the number of oligochaetes was strongly reduced or even became zero. The low nutrient status of the sandy bed in the sand-lined ditches slowed down the rate of colonization. Only a few tubificids were collected. Eutrophication effects were only observed at the highest nutrient addition level. Considerable variation is attributed to stochastic factors in the sand-lined ditches. Whether oligochaete species were present was related to the length of the colonization period. The substratum composition and food together with oxygen regime decided whether they become more or less abundant in ditches. Large-scale mesocosm experiments require time to develop. Only after the first colonization period variables of species presences and abundances can be employed to detect changes associated with eutrophication. Oligochaetes can be used to measure colonization as well as eutrophication processes. 相似文献
8.
Uulke A. van der Heide Olaf E. Rem Hans C. Gerritsen Evert L. de Beer Piet Schiereck Ian P. Trayer Yehudi K. Levine 《European biophysics journal : EBJ》1994,23(5):369-378
A fluorescence depolarization study of the orientational distribution of crossbridges in dye-labelled muscle fibres is presented. The characterization of this distribution is important since the rotation of crossbridges is a key element in the theory of muscle contraction. In this study we exploited the advantages of angle-resolved experiments to characterize the principal features of the orientational distribution of the crossbridges in the muscle fibre. The directions of the transition dipole moments in the frame of the dye and the orientation and motion of the dye relative to the crossbridge determined previously were explicitly incorporated into the analysis of the experimental data. This afforded the unequivocal determination of all the second and fourth rank order parameters. Moreover, this additional information provided discrimination between different models for the orientational behaviour of the crossbridges. Our results indicate that no change of orientation takes place upon a transition from rigor to relaxation. The experiments, however, do no rule out a conformational change of the myosin S 1 during the transition.
Correspondence to: Y. K. Levine 相似文献
9.
Jeffrey P. Woessner Arthur J. Molendijk Piet van Egmond Frans M. Klis Ursula W. Goodenough Michel A. Haring 《Plant molecular biology》1994,26(3):947-960
Based on our previous work demonstrating that (SerPro)x epitopes are common to extensin-like cell wall proteins in Chlamydomonas reinhardtii, we looked for similar proteins in the distantly related species C. eugametos. Using a polyclonal antiserum against a (SerPro)10 oligopeptide, we found distinct sets of stage-specific polypeptides immunoprecipitated from in vitro translations of C. eugametos RNA. Screening of a C. eugametos cDNA expression library with the antiserum led to the isolation of a cDNA (WP6) encoding a (SerPro)x-rich multidomain wall protein. Analysis of a similarly selected cDNA (VSP-3) from a C. reinhardtii cDNA expression library revealed that it also coded for a (SerPro)x-rich multidomain wall protein. The C-terminal rod domains of VSP-3 and WP6 are highly homologous, while the N-terminal domains are dissimilar; however, the N-terminal domain of VSP-3 is homologous to the globular domain of a cell wall protein from Volvox carteri. Exon shuffling might be responsible for this example of domain conservation over 350 million years of volvocalean cell wall protein evolution. 相似文献
10.
Habitat occupation and habitat overlap of the introduced tilapia Oreochromis mossambicus and co-occurring indigenous fish species were studied in a shallow lowland reservoir in Sri Lanka. Results were used to discuss the possible existence of empty habitats in reservoirs and the position of the introduced O. mossambicus in the fish community. Predictions were made of the effects of a subsidiary small-meshed gillnet fishery for indigenous minor cyprinids on the yield of tilapia. The zooplanktivorous halfbeak Hyporamphus gaimardi, an indigenous invader from brackish water estuaries and lagoons, has successfully colonized the pelagic habitat in this reservoir. The habitat of the introduced O. mossambicus overlapped significantly with those of the indigenous minor cyprinids. Only the smallest size classes of O. mossambicus (below 45 mm) arc spatially segregated from these cyprinids. Spatial distribution patterns are influenced by the rainy seasons which trigger an inshore movement of O. mossambicus and several other species around November and May. Barbus spp, (Cyprinidae) need riverine habitats for spawning, but for all other species the available habitats within the reservoir are suitable to complete their full life cycle. Exploitation of Barbus spp. with gillnets with a mesh size of 30-mm stretched mesh is predicted to have considerable detrimental effects on the existing fishery for O. mossambicus. However, a gillnet fishery with 15-mm stretched mesh to exploit Amblypharyngodon melettinus, Rasbora daniconius and H. gaimardi in the open water zone is expected to be successful without harming the existing fishery for O, mossambicus or the populations of Barbus spp. 相似文献