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41.
Nils Empacher Volker Mosbrugger Anita Roth Matthias Wolf Arne Wunderlin 《Journal of biological physics》1995,21(4):241-264
We shall present several qualitative mathematical models to describe the early evolution of water transport systems in plants. To perform this in a systematic way we apply methods which have been developed in phenomenological synergetics. These methods rest on the fact that it becomes possible to describe the macroscopic behavior of a complex system by a set of control and order parameters when they are suitably identified. Our presentation is addressed to community with interdisciplinary interests. 相似文献
42.
Anderberg, A. A. & Karis, P. O. 1995. Psednotrichia , a genus of the tribe Senecioneae hitherto misplaced in the Astereae (Asteraceae). — Nord. J. Bot. 15: 375–379. Copenhagen. ISSN 0107–055X.
The tribal position for the little known genus Psednorrichia , is established. This monotypic genus, hitherto placed in the tribe Astereae, is a congener of Xyridopsis of the tribe Senecioneae (Asteraceae). The two species of Xyridopsis are here transferred to Psednotrichia and the new combinations P. xyridopsis and P. newtonii are made. A brief discussion of the morphology of the genus, and its systematic position within the tribe Senecioneae is provided. 相似文献
The tribal position for the little known genus Psednorrichia , is established. This monotypic genus, hitherto placed in the tribe Astereae, is a congener of Xyridopsis of the tribe Senecioneae (Asteraceae). The two species of Xyridopsis are here transferred to Psednotrichia and the new combinations P. xyridopsis and P. newtonii are made. A brief discussion of the morphology of the genus, and its systematic position within the tribe Senecioneae is provided. 相似文献
43.
Bjørnar Hassel Niels Westergaard Arne Schousboe Frode Fonnum 《Neurochemical research》1995,20(4):413-420
Astrocytes and neurons cultured from mouse cerebellum and cerebral cortex were analyzed with respect to content and synthesis of amino acids as well as export of metabolites to the culture medium and the response to fluorocitrate, an, inhibitor of aconitase. The intracellular levels of amino acids were similar in the two astrocytic populations. The release of citrate, lactate and glutamine, however, was markedly higher from cerebellar than from cortical astrocytes. Neurons contained higher levels of glutamate, aspartate and GABA than astrocytic cultures. Cortical neurons were especially high in GABA and aspartate, and the level of aspartate increased specifically when the extracellular level of glutamine was elevated. Fluorocitrate inhibited the TCA cycle in the astrocytes, but was less effective in cerebellar neurons. Whereas neurons responded to fluorocitrate with an increase in the formation of lactate, reflecting, glycolysis, astrocytes decreased the formation of lactate in the presence of fluorocitrate, indicating that astrocytes to a high degree synthesize pyruvate and hence lactate from TCA cycle intermediates. 相似文献
44.
The synthetic antibody model “M41” was rationally designed with a binding site complementary to chicken egg white cystatin as the prescribed antigen. In order to permit comparison between the computer model and an experimental three-dimensional structure of the artificial protein, its X-ray crystallographic analysis was pursued. For this purpose, M41 was expressed as a recombinant Fab fragment in E. coli by medium cell density fermentation employing the tightly regulated tetracycline promoter. The Fab fragment was efficiently purified via a His-6 tail fused to its heavy chain and immobilized metal affinity chromatography. To raise the chances for the productive formation of crystal packing contacts, three versions of the Fab fragment were generated with differing constant domains. One of these, the variant with murine CK and CH 1γ1 domains, was successfully crystallized by microseeding in a sitting drop. The orthorhombic crystals exhibited symmetry of the space group P212121 with unit cell dimensions a = 104.7 Å, b = 113.9 Å, c = 98.8 Å and diffracted X-rays to a nominal resolution of 2.5 Å. © 1995 Wiley-Liss, Inc. 相似文献
45.
Methods for estimating the absolute polyphenol content of the brown algae Ascophyllum nodosum (L.) Le Jol. and Fucus vesiculosus (L.) have been developed and tested. Polyphenols were extracted almost quantitatively from Ascophyllum nodosum using aqueous acetone, whereas this procedure was somewhat less efficient with Fucus vesiculosus. Colorimetric methods based on the Folin-Denis reagent, Brentamine Fast Red 2G Salt, and vanillin-H2SO4 were applied to acetone-free extracts for determination of polyphenol content relative to suitable reference compounds. Gravimetric methods based on hide powder and on haemoglobin were employed to derive ‘estimation factors’ (EFs) which allow calculation of the absolute polyphenol content from the relative polyphenol content. The values calculated for absolute polyphenol content are considered to be reasonably accurate, despite imprecisions in the methods and despite often large standard deviations, and re-emphasize the potential physiological and ecological significance of brown algal polyphenols. Although the precise EFs calculated here are not valid for other brown algae, the methods are considered to be generally applicable to other Phaeophyceae. 相似文献
46.
ACTIVITY AND ISOENZYME PATTERN OF LACTATE DEHYDROGENASE IN ASTROBLASTS CULTURED FROM BRAINS OF NEWBORN MICE 总被引:3,自引:0,他引:3
Lactate dehydrogenase activity and isoenzyme distribution was determined in primary cultures of astroblasts as a function of the culture period. The specific activity increased during this period with a peak value (1.91 ± 0.18μmol x min-1 x mg-1 cell protein) after 2 weeks in culture. The isoenzyme pattern changed during 3 weeks in culture towards a higher proportion of the H4 (LDH-1) isoenzyme which is analogous to the in vivo pattern. Omission of serum with or without dBcAMP (0.5 mM) in the culture medium during the third week of culture further enhanced this prominence of the H4 isoenzyme. The specific activity (1.58 × 0.06 μmol x min-1 x mg-1 cell protein) of cultures grown in the presence of 0.5 mM-dBcAMP and absence of serum was close to the activity in the adult brain. 相似文献
47.
In a previous experiment, rabbits and goats were immunized with boiled and ethanol precipitated (BE) bovine kidney antigen, and the specificity of the antibodies produced was compared (Andersen 1975). The caprine sera were species specific while the rabbit sera, however, cross-reacted with BE antigens from other ruminant species. Sera from 2 rabbit littermates differed somewhat in that 1 serum seemed to be mainly species specific giving only weak reactions against BE antigens from kidney and spleen from other ruminants, whilst the other serum was more organ specific and reacted equally with homologous and heterologous kidney antigens. 相似文献
48.
M Murby P A Nygren H Rondahl U Hellman S O Enfors M Uhlén 《European journal of biochemistry》1991,199(1):41-46
The degradation in Escherichia coli of the recombinant serum-albumin-binding receptor derived from streptococcal protein G was investigated using a dual-affinity fusion approach. The proteolytic degradation of the receptor was characterized when fused to human proinsulin and human secretin. Several cleavages occurred at sequences not normally regarded as proteolytically sensitive, such as the dipeptide sequences Ile-Gly, Val-Ser and Ser-Ala. Depending on the fusion partner, large differences in the degradation of the albumin-binding domain were observed. Thus, susceptibility to proteolysis of a recombinant protein can be affected by a neighbouring domain. 相似文献
49.
Population structure, density and reproductive potential of perch (Perca fluviatilis L.) from 4 acidified lakes in a river system in Southern Norway were investigated. The upper 3 lakes were most affected by acidification and the number of perch caught per unit effort indicate three-fold increase in density from the upper Gjerstadvann to the lower Brøbørvann. Low density of perch in the upper lakes is explained by; 1) Abnormal mortality occurring in episodes due to acidification, probably caused by aluminium toxicity at pH = 5.2–5.4. 2). Acid water (pH ≤ 5.0) during spawning and development of eggs and larvae, resulting in recruitment failure. Juvenile mortality of perch may depend on the density of the parental stock. In the 3 upper lakes, the density of adult perch probably was too low to produce significant juvenile mortality, and in these lakes the recruitment probably depended more on the May water quality. Improved water quality increases egg hatching and survival and also benefits zooplankton production, the main food for perch during the first summer. Low population density has reduced competition for food and thus improved growth of perch in the 3 upper lakes compared to the lower lake. The perch in Brøbørvann mature at higher age and have lower individual fecundity than perch in Gjerstadvann, an effect of both slower growth and lower length specific fecundity in Brøbørvann. In Gjerstadvann, the perch therefore have a higher reproductive potential relative to the stock density, and may, when the water quality is good enough, give rise to strong year-classes and more frequent year-class fluctuations than perch in the less acid Brøbørvann. 相似文献
50.
The effect of substances proposed to modulate intracellular signal systems on growth and sensitivity to vincristine in the human kidney tumor cell line ACHN was investigated and related to changes in cytoplasmic free Ca2+ concentration ([Ca2+]i) and cytoplasmic pH (pHi). Presence during culture of the protein kinase C (PKC) activator 12-O-tetradecanoyl phorbol 13-acetate (TPA) had no effect on cell growth but significantly increased the EC50 concentration for vincristine inhibited cell growth. There was no indication for endogenous PKC activity being responsible for basal vincristine insensitivity since it was not affected by the PKC inhibitor H-7. The Ca2+ ionophore ionomycin tended to increase cell growth and induced vincristine resistance, whereas the calmodulin inhibitor W-7 had opposite effects. Presence during culture of the adenylate cyclase activator forskolin did not affect basal cell growth but dose-dependently made the cells more sensitive to vincristine. The modulators of vincristine sensitivity had no immediate effect on pHi, whereas after 3 days of incubation ionomycin and forskolin tended to increase pHi. Ionomycin and forskolin induced an immediate increase in [Ca2+]i which remained after 3 days only for ionomycin, whereas TPA decreased [Ca2+]i, a change which tended to remain after 3 days of incubation. It is concluded that perturbation of the intracellular signal system may affect both cell growth and cytotoxic drug sensitivity. However, there is no apparent relationship between immediate or late changes in [Ca2+]i and pHi and vincristine sensitivity. 相似文献