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71.
Uta Kühne Branka Filjak Hans Kröger 《Biochimica et Biophysica Acta (BBA)/General Subjects》1975,399(1):42-49
An injection of cortisone acetate at a dose of 5 mg/100 g body weight concomitant with dibutryl cyclic AMP prevents the increase in the activity of rat liver cytosol serine aminotransferase (L-serine: pyruvate aminotransferase, EC 2.6.1.51) elicited by the nucleotide with a lag of about 2 h. If the glucocorticoid is given 2 h prior to the nucleotide inducer, the lag disappears. The inhibitory effect of cortisone acetate gradually decays and is no longer detectable 12 h following its administration. Theophylline, insulin and glucose at doses which affect significantly the level of tyrosine aminotransferase, have no effect on the level of serine aminotransferase and on the cortisone inhibition. The inhibitory effect of the glucocorticoid on the dibutyryl cyclic AMP-mediated increase in serine aminotransferase diminishes with the age of animals. Increase in the enzyme activity by a single dose of glucagon can also be inhibited by cortisone acetate and actinomycin D as in the case with dibutyrl cyclic AMP as an inducer. The possibility of the existence of a specific inhibitory factor which is formed in response to cortisone acetate is discussed. 相似文献
72.
Andrea Schrödel 《当今生物学》2007,37(5):289-289
73.
The influence of moulded hay (Alternaria alternata, Epicoccum nigrum, Mucor racemosus, Ulocladium chartarum) and the efficiency of Vitamin B1 substitution to cope these effects on rumen protozoa was investigated using the longterm rumen simulation technique (RUSITEC) for about 25 days. Moulded hay affected medium-sized protozoa to a different extent (Alternaria alternata: ?16 %, Epicoccum nigrum: ?27 %, Mucor racemosus: ?9 %, Ulocladium chartarum: +2 %). The vitamin B1 substitution had positive effects during the feeding of Mucor racemosus and Ulocladium chartarum. 相似文献
74.
T. Cichocki B. Gonsior J. Glazur M. Höfert L. Jarczyk E. Rokita A. Strzałkowski M. Sych 《Biological trace element research》1987,13(1):167-177
The elemental composition of rabbit liver was determined by the PIXE and micro-PIXE methods. The mean concentrations of P,
S, Cl, K, Fe, Cu, Zn, and Rb measured by both methods were similar. The latter method also allowed for localization of elements
within lobule territory. It has been found that some elements are more prevalent in the veins (Cl, Fe) and others in the liver
parenchyma (P, Cu, Zn). Moreover, Zn showed the characteristic intralobular distribution. Some methodological aspects of microbeam
application to biological materials were also discussed. 相似文献
75.
The protolytic reactions of PSII membrane fragments were analyzed by measurements of absorption changes of the water soluble indicator dye bromocresol purple induced by a train of 10 s flashes in dark-adapted samples. It was found that: a) in the first flash a rapid H+-release takes place followed by a slower H+-uptake. The deprotonation is insensitive to DCMU but is completely eliminated by linolenic acid treatment of the samples; b) the extent of the H+-uptake in the first flash depends on the redox potential of the suspension. In this time domain no H+-uptake is observed in the subsequent flashes; c) the extent of the H+-release as a function of the flash number in the sequence exhibits a characteristic oscillation pattern. Multiphasic release kinetics are observed. The oscillation pattern can be satisfactorily described by a 1, 0, 1, 2 stoichiometry for the redox transitions Si Si+1 (i=0, 1, 2, 3) in the water oxidizing enzyme system Y. The H+-uptake after the first flash is assumed to be a consequence of the very fast reduction of oxidized Q400(Fe3+) formed due to dark incubation with K3[Fe(CN)6]. The possible participation of component Z in the deprotonation reactions at the PSII donor side is discussed.Abbreviations A
protonizable group at the PSII acceptor side
- BCP
Bromocresol Purple
- DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- FWHM
Full Width at Half Maximum
- QA, QB
primary and secondary plastoquinone at PSII acceptor side
- Q400
redox group at PSII-acceptor side (high spin Fe2+)
- P680
Photoactive chlorophyll of PSII reaction center
- Si
redox states of the catalytic site of water oxidation
- Z
redox component connecting the catalytic site of water oxidation with the reaction center 相似文献
76.
Ursula Niesert 《Origins of life and evolution of the biosphere》1987,17(2):155-169
A geneticist's view on the origin of life would focus on individual nucleic acid molecules rather than on their concentrations, on stochastics rather than on differential equations.The package model envisages primordial compartments that contain ensembles of primordial genes. These are replicated independently from each other. During package fission they are distributed to two daughter packages. Packages with a complete ensemble of genes can continue to propagate. However, mutations as well as the stochastic nature of replication and package fission occasionally cause arising packages to miss genes from the ensemble, thus resulting in the death of those packages.A computer simulation, considering the complementarity of RNA as well as abortive termination of replication, yielded results that are similar to those of a preliminary simulation irrespective of these parameters: the results suggest that life could not have started with more than 3 genes, or else the primordial replicase would have to achieve at least a reduction of the replicational error rate by a factor of 13 and a reduction of undue chain termination by a factor of 10 to 25. 相似文献
77.
We estimate the active part of cytochrome P-450, which is involved in a special substrate transformation, by measuring the initial change of the production rate as a function of the relaxation transitions between two different steady states of the reaction cycle of cytochrome P-450 using the light-reversibility of the carbon monoxide inhibition. The kinetic data of such relaxations are interpreted within a model cycle, which reduces the reaction cycle to three steps. The estimation of the rate constant of the first reduction step, derived from model simulation of the production rate, is confirmed by independent experimental study of the reduction kinetics.An application of our model to the O-deethylation of 7-ethoxycoumarin reveals that — in a time average — 10%–15% of the spectroscopically detectable cytochrome P-450 is involved in that transformation.Abbreviations Cyt. P-450
microsomal cytochrome P-450
- 7-EC
7-ethoxycoumarin 相似文献
78.
Summary Phenylalanine production from E. coli KA 197/pJN6 (plasmid harboring genes for aro F, phe AFBR, AmpR and TcR) was studied under varying nutritional conditions in batch and continuous cultures. In batch culture experiments where growth was deliberately interrupted by limiting concentrations of sulphate and phosphate the phenylalanine production continued from the non-growing cells. However, the depletion of phosphate resulted in an immediate cessation of phenylalanine production but thereafter a low specific rate of phenylalanine formation resumed, while the decrease in specific rate of product formation was less after sulphate depletion. In the chemostat experiments, however, phosphate limitation was the only case where the specific rate of phenylalanine formation remained constant, while at the corresponding time in sulphate and glucose limited chemostats it was declining respectively had ceased. 相似文献
79.
Summary The yield of cell mass and the morphology of Armillaria mellea, strain ATCC 11114, was studied using a variety of cultivation methods: solid media, standing liquid culture, shake flasks, tower reactors and impeller-stirred reactors. Two different media, malt extract broth and a glucose/asparagine/peptone-medium, and the corresponding agar media, were used. Yields were higher in the malt extract media than in the glucose media. Generally the highest yields were obtained on solid media while agitated cultures gave the lowest yields. Morphological characteristics such as pellet formation, adhesion to surfaces and pigment production were significantly affected by culture conditions. 相似文献
80.
K. Hövemeyer 《Oecologia》1987,73(4):537-542
Summary A population of Cheilosia fasciata Schin. & Egg., 1853 was studied in a beech forest (Melico-Fagetum allietosum) near Göttingen (FRG). This syrphid species is closely associated with ramson (Allium ursinum L.), as the larvae mine the plant's leaves. Adult abundance was determined using emergence traps (1981–1986); egg and larval abundance was determined by examining ramson leaves: puparia were extracted from soil samples (1984 and 1986). Cheilosia fasciata is a univoltine species; the imagines emerge in late April/early May. Larval development took five (1986) to six (1984) weeks. In late June/early July the larvae enter the soil for pupariation. A linear relationship was found between the area of the mines and larval biomass (dry wt.). It was concluded that one larva had to mine 51.90 cm2 of leaf area in order to gain the mean maximum dry weight (11.15 mg). Furthermore, it was shown that ovipositing females, laying just one egg per leaf, tended to select large leaves providing this minimum amount of food. It is hypothesized that females probably follow straight-lined routes on their oviposition flights, rather than ovipositing on leaves chosen at random. By applying such a strategy, females can almost completely avoid competition for food among their own offspring. Furthermore, competition among the progeny of the whole population is also reduced, particularly in years when adult abundance is very low. The significance of certain factors influencing the population dynamics of Cheilosia fasciata was evaluated by applying a rank correlation analysis. It was shown that high precipitation rates in April reduced the time available for mating and oviposition resulting in low emergence abundance in the next spring. Larval survivorship was enhanced by high precipitation rates in May and June, indicating that drought may be unfavourable to larvae and reduce food availability. Predation by a parasitoid Phygadeuon ursini Horstmann, 1986 (Hymenoptera, Ichneumonidae), appears to be just an imperfect (Milne 1984) density-dependent control mechanism; in fact, it was shown that food limitation is the only significant mechanism of density-dependent population control. 相似文献