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71.
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
72.
蓝藻型富营养湖泊藻量的昼夜变化节律 总被引:3,自引:0,他引:3
杭州西湖为蓝藻型富营养湖泊,根据1980年9月及11月二次昼夜分层采样调查,该湖浮游藻在一昼夜中有二次上下垂直移位,使近表层藻量形成规则或不规则的双峰型昼夜变化曲线,双峰分别出现在日照开始与日落后2h左右,认为昼夜光暗交替与其昼夜变化有一定相关关系,同时,双峰的形成与蓝藻门优势藻种对光照强度的适应性能相关。文中对其优势藻种的浮沉与日照关系作了讨论。 相似文献
73.
W. Dörr J. Kummermehr 《Virchows Archiv. B, Cell pathology including molecular pathology》1991,60(1):287-294
Epithelial proliferation in the ventral surface of mouse tongue follows a pronounced circadian rhythm with a peak in mitotic
activity at 10.00 a.m., preceded by a wave of DNA synthesis 8 h earlier. Nearly all cells (85%) pass through G2 and mitosis
immediately after the S-phase; they subsequently divide again, usually after 2 or 3 days, indicating cohorts of cells with
different G1-duration. The fraction of all nucleated cells comprised in one daily proliferation wave is about 20%, indicating
a turnover time of the nucleated cell compartment of about 5 days. Cytotoxic injury by a single radiation dose of 20 Gy causes
a steep decrease in cell counts, leading to complete denudation after 9–13 days. The difference between the latent period
before ulceration and the tissue turnover time is explained by a marked proliferative activity of the doomed cells. The mitotic
index increases steeply after day 1 to three times the control level, but most mitotic figures display gross abnormalities
such as multipolar spindles or chromosome clumping. As a consequence cells with abnormal or multiple nuclei appear in the
basal layers 3 days post irradiation and subsequently migrate to the upper layers. After denudation the epithelium rapidly
becomes restored, with a phase of transient hyperplasia on days 13–14. Normal architecture is regained by day 15. Over the
whole healing period the mitotic index remains at a high level, with most of the mitoses appearing histologically normal. 相似文献
74.
W. Puchalski G. R. Lynch 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1991,169(2):185-189
Summary Djungarian hamsters (Phodopus sungorus), were exposed to constant light with increasing intensities (20, 60, 350 lux), and wheel running activity was recorded. With increasing light intensity the percentage of hamsters showing a split in their daily activity pattern increased and the free running period was lengthened for both the unsplit and the split state. The fact that the free running period of both states depended on the light intensity together with the observation that the highest incidence of acircadian activity occurred under 350 lux, provoked the idea that the emergence of splitting or acircadian rhythmicity is a direct consequence of the light induced lengthening of the free running period. However, analysis of the data failed to support the idea that emergence of a split or acircadian activity is a threshold phenomenon with respect to the free running period.Due to differences in circadian function some Djungarian hamsters do not exhibit photoinduction following short day exposure. In these individuals splitting also occurred but required exposure to a higher light intensity than in photo-responsive hamsters. This observation is in accordance with the idea that the two phenotypes differ in the interaction of the two component oscillators underlying circadian rhythmicity.Abbreviations
LD
long day photoperiod
-
LL
constant light
-
SD
short day photoperiod
-
free running period 相似文献
75.
Kenji Tomioka Kenji Yamada Shinya Yokoyama Yoshihiko Chiba 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1991,169(3):291-298
The coupling mechanism between the bilaterally paired optic lobe circadian pacemakers in the cricket Gryllus bimaculatus was investigated by recording locomotor activity, under constant light or constant red light, after the optic nerve was unilaterally severed.
These results suggest that the 2 optic lobe pacemakers weakly couple to one another and that the cricket maintains a stable temporal structure in its behavior through the phase-dependent mututal inhibition of activity and the phase-dependent freerunning period modulation. 相似文献
1. | The majority (about 70%) of the animals showed a locomotor rhythm with 2 rhythmic components; one freerunning with a period of 25.33 ± 0.41 (SD) h and the other with 24.36 ± 0.37 (SD) h under constant light (Fig. 3A). |
2. | Removal of the intact side optic lobe abolished the longer period component (Fig. 4A), while the operation on the operated side caused a reverse effect (Fig. 4B), indicating that the longer and the shorter period components are driven by the pacemaker on the intact and the operated side, respectively. |
3. | The activity driven by a pacemaker was inhibited during the subjective day of the contralateral pacemaker (circadian time 0–10, Fig. 5). |
4. | The freerunning periods of the two components were not constant but varied as a function of the mutual phase angle relationship (Figs. 3A, 7, 8). |
76.
W. Junger 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1991,169(5):633-639
Waterstriders on ponds and creeks compensate for displacement caused by wind or water current with periodical jumps against the direction of drift. This behavior is mediated by visual stimuli.
相似文献
1. | Waterstriders are able to detect the direction and extent of their displacement on an artificial canal when visual cues are reduced to a single point-like light source above the upstream end of the canal. They adjust the frequency and direction of the compensatory jumps to keep their mean position on the canal constant. The mean amplitude of the jumps is constant and independent of the stream velocity. |
2. | During drift compensation the light spot is kept in the frontal visual field at a fixed angle of elevation. This set angle differs among individuals and can be changed with time. |
3. | The station-keeping ability can hardly be explained by a velocity servo system since there is no accumulating position error. The average compensatory movements are governed by a discontinuously working position servo. |
4. | When the light spot is switched off, a few jumps are still performed. Jumps, therefore, are not triggered individually by visual cues. Waterstriders must possess an endogenous jump-generator. |
77.
Andrew Sillen 《American journal of physical anthropology》1988,76(1):49-60
Elemental analyses of mammalian bone (e.g., strontium-calcium ratios, or Sr/Ca) distinguish between herbivores and carnivores; however, the relationships among herbivores are unclear. To study this question, a modern faunal sample from the Nagupande Tsetse Control Area (Zambezi drainage, Northwestern Zimbabwe) was used. This collection has the advantage of well-established geographical controls in addition to a varied fauna, which includes both bovids and suids. The grazing/browsing dietary status of each species was ascertained by means of isotopic analysis of carbon. Clear differences were seen in the δ13C of grazing and browsing animals; a specialized grazer was found to have significantly lower Sr/Ca than less specialized grazers and browsers. In this study it was also possible to examine differences in Sr/Ca by sex; female warthogs were found to have significantly lower Sr/Ca than males. The variation in certain animal groups was found to be abnormal. Implications for reconstruction of prehistoric human diets using trace-element techniques are discussed. 相似文献
78.
Consumption of leaf detritus by a stream shredder: Influence of tree species and nutrient status 总被引:8,自引:3,他引:5
Four species of riparian vegetation (alder, birch, willow and poplar) were fertilized with nitrogen, phosphorus, nitrogen
+ phosphorus, or no fertilizer (control). The resulting leaf detritus (leached but not microbially colonized) was offered
to a stream shredder, Hydatophylax variabilis (Trichoptera: Limnephilidae). In one experiment, shredder consumption of leaf detritus from different nutrient treatments
(within tree species) was compared, and in a second experiment, consumption of different tree species (within nutrient treatments)
was compared. Larvae preferred leaf detritus from nitrogen + phosphorus treatments (except in poplar where nitrogen treatment
was preferred). Alder was preferred over other tree species for all treatments. Chemical and physical analyses of leaf litter
showed differences between tree species and nutrient treatments in nutrient content, tannins and leaf toughness. Leaf consumption
by larvae was positively associated with nitrogen content and negatively associated with condensed tannin content. Species
composition and nutrient status of riparian vegetation may strongly influence detrital food webs in streams. 相似文献
79.
Spatial patterns and feeding of meiobenthic harpacticoid copepods in relation to resident microbial flora 总被引:2,自引:2,他引:0
Distributional and feeding relationships of harpacticoid copepods and their microbial prey were examined in a tidal channel at Great Sippewissett Marsh. A horizontal zonation of photosynthetic microorganisms was composed of: 1) a diatom area; 2) a purple sulfur bacterial (Thiocapsa sp.) area; and 3) a clear area. Four species of harpacticoid copepods were associated with given areas. Leptocaris brevicornis occurred in very high densities in the diatom area but in relatively low densities in other areas. Mesochra lilljeborgi occurred in significantly higher densities in the purple and clear areas.Feeding experiments, using resident microbial flora labelled with NaH14CO3 and 3H-thymidine, were conducted to determine which foods are 1) ingested but simply pass through the gut and 2) ingested, and retained. These experiments indicated that L. brevicornis ingested diatoms and the heterotrophs associated with the diatoms, but only retained the heterotrophic portion. Microscopic examination indicated that diatoms were passed out intact in feces. Oscillatoria sp. (cyanobacterium) was not ingested. Mesochra lilljeborgi ingested Spirulina sp. (cyanobacterium), Thiocapsa sp., and the heterotrophs associated with Thiocapsa but only retained the Thiocapsa label.These data for harpacticoids suggest that spatial distributions of meiofauna may be closely coupled with microbial food organisms which they consume. Also, that while several microbial foods may be ingested, only certain microbes are digested and assimilated as a food resource, further indicating the complexity of feeding relationships among the meiofauna. 相似文献
80.
Noritsugu Yabe Yutaka Matsuya Isao Yamane Mitsuru Takada 《In vitro cellular & developmental biology. Plant》1986,22(7):363-368
Summary A newly developed, serum-free medium (NYSF-404) selects for antibody-producing hybridomas after fusion of antigen-sensitized
mouse spleen cells with myeloma cell lines P3-X63-Ag8-U1 (P3-U1), P3-X63-Ag8-6.5.3 (Ag8.653), or P3-NSI/1-Ag4-1 (NS-1). Without
the need for hypoxanthine-aminopterinthymidine (HAT) selection of hybrid cells, frequency of hybridoma formation in medium
NYSF-404 is higher (twice) than that in serum- and HAT-containing medium. Colonies developed upon limiting dilution in the
presence of the mortal parent myeloma cells in medium NYSF-404 and pure culture of antibody-secreting cells could be subsequently
established. The results suggest that fusions can be done in serum-free medium and that the clonal growth of hybridomas is
dependent on factors produced by parent myeloma cells under serum-free culture conditions. Such factors seem deficient in
serum- and HAT-containing medium or are masked by serum. 相似文献