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  • 1980-1984  (6)
  • 1960-1964
  • Crassulacean acid metabolism  (4)
  • Life and Medical Sciences  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Circadian rhythms inKalanchoë: the pathway of14CO2 fixation during prolonged light (1984)
    Springer
    Planta 161 (1984), S. 71-80 
    Details
    ISSN: 1432-2048
    Keywords: Crassulacean acid metabolism ; Carbon dioxide fixation ; Circadian rhythm ; Kalanchoë
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 14CO2 was applied repeatedly at 3- to 6-h intervals toKalanchoë daigremontiana leaves during continuous light of differing irradiances. The circadian rhythm in net CO2 uptake in gasexchange measurements and its disappearance at high irradiances was confirmed by oscillating rates of14CO2 incorporation. At 10–30 W m-2 a markedly circadian oscillation in the14CO2-uptake rate was measured; with increasing energy fluence rate the oscillation levelled off at a constant high uptake rate. The labelling patterns obtained during the 10 min of14CO2 fixation indicated that the rhythm of CO2 exchange is the consequence of a rhythmic behaviour in the C4 pathway of CO2 fixation. During the mininum of14CO2 uptake no C4 products were labelled; however, substantial amounts of label were transferred to C4 products during the peaks of14CO2 uptake. Metabolism of C3 and C4 products was also studied in pulsechase experiments at different points of the circadian cycle. In bright light (100 W m-2), when the14CO2 uptake was constantly high, the transfer of label into C4 products (malic acid) was high in spite of the fact that the malate pool is known to be reduced to a permanently low level under these conditions. This led us to the conclusion that it is not the capacity of the phosphoenolpyruvatecarboxylase-mediated CO2 fixation but rather the storage of malic acid in the vacuole that is disturbed under bright-light conditions when the circadian oscillation levelled off.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00951462
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  • 2
    Electronic Resource
    Electronic Resource
    Circadian rhythms in crassulacean acid metabolism: phase relationships between gas exchange, leaf water relations and malate metabolism in Kalanchoë daigremontiana (1984)
    Springer
    Planta 161 (1984), S. 314-319 
    Details
    ISSN: 1432-2048
    Keywords: Carbon dioxide exchange ; Crassulacean acid metabolism ; Kalanchoë ; Leaf water relations ; Phosphoenolpyruvate carboxylase ; Transpiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Gas exchange, leaf water relations, malate content and phosphoenolpyruvate (PEP) carboxylase activity in crude extracts were examined for circadian rhythmicity in the crassulacean acid metabolism plant Kalanchoë daigremontiana. At low irradiance (20 W m-2) the rhythm in CO2 uptake continued for several days with a period length of approx. 22 h, whereas the transpiration rhythm was no longer apparent after 24 h. This shows that the CO2 rhythm in continuous light (LL) is not under stomatal control. Circadian oscillations in malate content were detectable for up to 72 h in LL but were of much reduced amplitude. This was reflected in the changes in leaf water relations, which quickly damped after transfer to LL. The activity of PEP carboxylase assayed immediately after extraction showed a rhythmicity for at least 18 h, but after 36 h, values from different plants were scattered. We suggest that the CO2-uptake rhythm is primarily the result of endogenous changes in the activity of PEP carboxylase, which competes to varying degrees with ribulose-1,5-bisphosphate carboxylase for CO2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00398721
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  • 3
    Electronic Resource
    Electronic Resource
    Circadian rhythms in Kalanchoë: effects of irradiance and temperature on gas exchange and carbon metabolism (1984)
    Springer
    Planta 160 (1984), S. 264-271 
    Details
    ISSN: 1432-2048
    Keywords: Circadian rhythm ; Crassulacean acid metabolism ; Kalanchoë
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Gas exchange in K. blossfeldiana shows a circadian rhythm in net CO2 uptake and transpiration when measured under low and medium irradiances. The period length varies between 21.4 h at 60 W m-2 and 24.0 h at 10 W m-2. In bright light (≧80 W m-2) or darkness there are no rhythms. High leaf temperatures result in a fast dampening of the CO2-uptake rhythm at moderate irradiances, but low leaf temperatures can not overcome the dampening in bright light. The rhythm in CO2 uptake is accompanied by a less pronounced and more rapidly damped rhythm in transpiration and by oscillations in malate levels with the amplitude being highly reduced. The oscillations in starch content, usually observed to oscillate inversely to the acidification in light-dark cycles, disappear after the first cycle in continuous light. The balance between starch and malate levels depends in continuous light on the irradiance applied. Leaves show high malate and low starch content at low irradiance and high starch and low malate in bright light. During the first 12 h in continuous light replacing the usual dark period, malate synthesis decreases with the increasing irradiance. Up to 50 W m-2 starch content decreases; at higher irradiances it increases above the values usually measured at the end of the light period of the 12:12 h light-dark cycle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00402864
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  • 4
    Electronic Resource
    Electronic Resource
    Crassulacean acid metabolism (CAM) in Kalanchoë daigremontiana: Temperature response of phosphoenolpyruvate (PEP)-carboxylase in relation to allosteric effectors (1981)
    Springer
    Planta 152 (1981), S. 181-188 
    Details
    ISSN: 1432-2048
    Keywords: CO2 dark fixation ; Crassulacean acid metabolism ; Kalanchoë ; PEP-carboxylase ; Temperature (PEP-carboxylase)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Net CO2 dark fixation of Kalanchoë daigremontiana varies with night temperature. We found an optimum of fixation at about 15° C; with increasing night temperature fixation decreased. We studied the temperature dependence of the activity of phosphoenolpyruvate (PEP)-carboxylase, the key enzyme for CO2 dark fixation. We varied the pH, the substrate concentration (PEP), and the L-malate and glucose-6-phosphate (G-6-P) concentration in the assay. Generally, lowering the pH and reducing the amount of substrate resulted in an increase in activation by G-6-P and in an increase in malate inhibition of the enzyme. Furthermore, malate inhibition and G-6-P activation increased with increasing temperature. Activity measurements between 10° C and 45°C at a given concentration of the effectors revealed that the temperature optimum and maximum activities at that optimum varied with the effector applied. Under the influence of 5 mol m-3 L-malate the temperature optimum and maximum activity dropped drastically, especially when the substrate level was low (at 0.5 mol m-3 PEP from 32° C to 20° C). G-6-P raised the temperature optimum and maximum activity when the substrate level was low. If both malate and G-6-P were present, intermediate values were measured. We suggest that changes in metabolite levels in K. daigremontiana leaves can alter the temperature features of PEP-carboxylase so that the observed in vivo CO2 dark fixation can be explained on the basis of PEP-carboxylase activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00385142
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  • 5
    Electronic Resource
    Electronic Resource
    Intracellular accumulation of a fluorescent derivative of paromomycin in human fibroblasts (1982)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 20 (1982), S. 71-80 
    Details
    ISSN: 0730-2312
    Keywords: aminoglycoside ; fluorescent paromomycin ; human fibroblasts ; lysosomes ; endocytosis ; exocytosis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Human fetal lung fibroblasts grown in the presence of dansyl-paromomycin (DNS-Pm), a fluorescent derivative of the aminoglycoside antibiotic, paromomycin, probably accumulate DNS-Pm in the lysosomes. The intracellular concentration of DNS-Pm is proportional to the extracellular concentration and to the length of time cells are exposed to the compound. The accumulation of DNS-Pm by human fibroblasts continued to increase for several days, reaching a saturation after 7 days. The kinetic data are consistent with the establishment of a steady state in the cell between fluid-phase pinocytosis and exocytosis of DNS-Pm. About 80% of the intracellular DNS-Pm was released in 24 hr when fresh medium without the analogue was added. The residual 20% remained within the cells, suggesting that it may be irreversibly bound to the lysosomes, endoplasmic reticulum, or ribosonius. The uptake of paromomycin by cells in culture may be a useful means to study error propagation during growth and lifespan of cells in vitro.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240200108
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  • 6
    Electronic Resource
    Electronic Resource
    Myometrial ultrastructure and innervation in Motis lucifugus, the little brown bat (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 210 (1984), S. 463-475 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Uteri from hibernating bats, Myotis lucifugus, collected periodically from Renfrew County, Ontario, were fixed in 2% glutaraldehyde and processed for electron microscopy or incubated in glyoxylic acid to show adrenergic nerves by fluorescence. The bat uterus is structurally typical of mammalian species; although the right uterine horn is permanently enlarged in parous bats due to hypertrophy of both myometrium and endometrium. Nerves were abundant between both longitudinal and circular layers of muscle cells. Unmyelinated, and some myelinated, axons, ranging from few to many, coursed generally parallel to the uterine long axis. Numerous axonal varicosities containing small dense-cored (adrenergic) vesicles or, less often, small agranular (cholinergic) vesicles, were found forming close nerve-muscle contacts between myometrial cells and blood vessels. Fluorescent microscopy showed a dense network of adrenergic nerves in parous uteri, but a sparse network in nulliparous uteri. A specific adrenergic nerve marker, 5-hydroxydopamine, greatly increased the density and in some instances, the size of granular vesicles, while 6-hydroxydopamine, which depletes adrenergic neutrotransmitter, reduced the number of dense-cored vesicles. Nulliparous uteri appeared unchanged by six daily injections of 0.1 μg estradiol-17β; 0.25 mg progesterone, or both; but parous uteri were greatly enlarged by all regimes. Nerve ultrastructure, however, appeared unaffected by steroid treatment; nor, despite the absolute dextral bias in implantation, were left-right differences observed. Gap junctions were not found between muscle cells in myometria of any bat uteri. Based on this study, we suggest that M. lucifugus may provide a most useful model for examination of neurogenic regulation of the uterus.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092100307
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