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81.
Seeds of cauliflower cv. Hipop and Brussels sprouts cv. Asmer Aries were aged at 20% moisture content for 24 h; all seeds retained a germination of over 70% after ageing although the mean germination time increased. Prolonged aerated hydration for up to 32 h at 20°C followed drying resulted in improved performance of both unaged and aged cauliflower seeds and aged Brussels sprouts. Thus, all seed showed reductions in the mean germination time to the extent that after 32 h hydration the aged cauliflower seeds performed as well as high quality unaged seed. The improvement of aged seeds was also revealed an increase in germination after the controlled deterioration test following up to 24 h (cauliflower) or 32 h (Brussels sprouts) aerated hydration. This increase was indicative of a decrease in the extent of deterioration present after aerated hydration. Deleterious effects of prolonged hydration were observed in Brussels sprouts after 32 h although these may be explained desiccation injury after treatment since radicle emergence had occurred during hydration. The improvements in seed performance may be explained the activation of metabolic repair occurring during the early part of the hydration period therereducing the extent of deterioration that has been sustained during ageing, with further improvements due to the advancement of the germination process. 相似文献
82.
- 1. 1. The thermoregulatory responses to manipulations of photoperiod in wood mice (Apodemus sylvaticus), which were drawn from a population living at a high latitude (57°N) were studied.
- 2. 2. Mice captured in spring were acclimated to two different photoperiod regimes 16L:8D and 8L:16D at a constant ambient temperature of 24°C, for 3 weeks.
- 3. 3. Daily rhythms of body temperature, oxygen consumption and body temperature at various ambient temperatures, nonshivering thermogenesis (the response to a noradrenaline injection) and body mass were measured. Minimal overall thermal conductance was calculated for both groups.
- 4. 4. Acclimation to long photophase increased the thermoregulatory abilities at relatively high ambient temperatures while that of long-scotophase increased thermoregulatory abilities at low ambient temperatures.
- 5. 5. Changes in photoperiod may therefore be used as cues for seasonal acclimatization of thermoregulatory mechanisms in this population of wood mice.
83.
Gottfried J. Feistner 《Biometals》1995,8(4):318-327
Metabolic profiling by capillary liquid chromatography-electrospray mass spectrometry was used to monitor shifts in the proferrioxamine profiles of Erwinia amylovora in response to externally supplied potential proferrioxamine precursors, selected stable-isotope-labeled precursors and atypical precursors. Based on the qualitative and quantitative shifts in the proferrioxamine profiles, lysine and arginine are unambiguous, and agmatine, ornithine, diaminobutyric acid and the corresponding C3–5 diamines are highly likely precursors for proferrioxamine biosynthesis in E. amylovora. 5-Hydroxylysine (Hyl), a recently discovered growth inhibitor for E. amylovora, suppresses proferrioxamine production. The Hyl-induced growth inhibition can be reversed by basic amino acids. The basic amino acids also partly restore proferrioxamine synthesis.Part 12 in the series Metabolites of Erwinia, for Parts 10 and 11 see Feistner (1994d) and Feistner (1995b), respectively. Presented, in part, at ALEX '93. San Francisco. October 5–7. 1993, and at the 42nd ASMS Conference. Chicago. May 29–June 3, 1994. 相似文献
84.
Behm C. A. and Bryant C. 1982. Phosphoenolpyruvate carboxykinase from Fasciola hepatica. International Journal for Parasitology12: 271–278. The kinetic properties of a partially purified preparation of phosphoenolpyruvate carboxykinase (PEPCK) from F. hepatica were examined. The pH optimum for the carboxylation reaction is 5.8–6.2. The enzyme is more active with Mn2+ than Mg2+ and the Mn2+ saturation curve was sigmoid. Apparent Km values for the substrates GDP, IDP, PEP and HCO3? were determined and found to be in the same range as those reported for other helminths except that the enzyme is less sensitive to low PEP concentrations. GTP and ATP at 0.5 and 1.0 mM inhibit the enzyme; the GTP inhibition was greater in the presence of Mg2+ than Mn2+ and was competitive with GDP. It was concluded that the activity of PEPCK from F. hepatica is controlled by the concentration of reactants and the ambient pH, that the accumulation of GTP is a sensitive mechanism for inhibiting the carboxylation reaction and that PEPCK activity in the cytosol is likely to be favoured over that of pyruvate kinase except when pH is high and PEP concentration low. 相似文献
85.
Ann E. Aust Michael R. Antczak Veronica M. Maher J. Justin McCormick 《Journal of cellular biochemistry》1981,16(3):269-279
Human cells that appear capable of metabolizing various classes of carcinogens have been identified using one of two methods: metabolism of tritiated benzo(a)pyrene to aqueous-acetone soluble forms or inhibition of cellular DNA synthesis. Each of the assay systems was optimized and the results on 15 human epithelial cell lines were compared. One or more cell lines were found to activate each of four classes of carcinogens examined: polycyclic hydrocarbons, aromatic amines, heterocyclic hydrocarbons, and nitrosamines. Cells that appeared capable of metabolizing polycyclic hydrocarbons or aromatic amines by these methods were also found to produce metabolites which were cytotoxic to cocultivated human xeroderma pigmentosum fibroblasts after a 48-hr exposure to the carcinogen. 相似文献
86.
A selective chemical photosynthesis inhibitor, DCMU (Dichorophenyl-dimethylurea), dissolved in DMSO (Dimethyl sulfoxide) was substituted for the dark incubation method commonly used to measure the oxygen consumption in metabolic and primary production studies. We compared oxygen fluxes during light incubations with DCMU and dark incubations procedure, on soft bottom benthos. For this purpose, we studied the effects of different DCMU concentrations. A concentration of 5 · 10–5 mol l–1 inside a clear incubation enclosure completely inhibits photosynthesis without affecting the metabolism of soft bottom benthos. 相似文献
87.
Masamitsu Honma Eiko Kataoka Kiyokata Ohnishi Tadao Ohno Masao Takeuchi Nobuo Nomura Hiroshi Mizusawa 《In vitro cellular & developmental biology. Animal》1992,28(1):24-28
Summary Using the polymorphic DNA probes, ChdTC-15, ChdTC-114, pYNH24, and λTM-18, a DNA profiling system was developed that verified
identities of individual cultured cell lines collected in the Japanese cell banks, JCRB, RCB, and IFO. These highly polymorphic
DNA probes include both VNTR (Variable Number of Tandem Repeats) sequences and substantial lengths of unique regions. In the
mixed probe system, several distinct bands from four to eight can be used for cell line identification. These bands were widely
spread in a range of molecular sizes, and were stable and reproducible under stringent conditions of Southern blot hybridization.
Because the DNA profile was specific for each individual human cell line, it is useful not only to authenticate many existing
cultured cell lines but also to monitor their identity during propagation in a laboratory, and to confirm newly established
lines as unique. 相似文献
88.
When varanid lizards, Varanus niloticus, were allowed to select their preferred body temperature (c. 34°C) they exhibited swifter growth, larger food intake and superior efficiency of conversion when compared with animals restricted to a maximum body temperature of 24°C. At the higher temperature the animals also exhibited a higher metabolic rate and increased thyroid activity, while those at the lower temperature lostproportionately more energy via respiration. A complete energy budget over a period of 6 weeks is presented. 相似文献
89.
Paul Jensén 《Physiologia plantarum》1981,52(4):437-441
Uptake of Rb+ from a complete nutrient solution with 2.0 mM Rb+ was studied in roots of spring wheat seedlings ( Triticum aestivum L. cv. Svenno) with different K+ levels. The relationship between Rb+ uptake and concentration of K+ in the roots indicated a negative feedback mechanism operating through allosteric control. The Rb+ uptake process in root cells was divided into two steps: (1) binding of the ion in the free space, and (ii) transmembrane transport into the cytoplasm. Metabolic and non-metabolic components of uptake were separated by addition of the metabolic inhibitor 2,4-dinitrophenol (DNP) to the nutrient solution. It is suggested that metabolic Rb+ uptake requires energy in two uptake steps (for binding to the carrier entity in the free space and for transmembrane transport) or in one step only (for transmembrane transport), dependent on the K+ status of the roots. The change from metabolic to non-metabolic binding in the free space is accomplished by changing the conformational state of the carrier (slow/fast transitions). There may be a hysteretic effect on metabolic Rb+ uptake through a slow transition between carrier states. This is superimposed on the negative cooperativity, strengthening further cooperativity at intermediate K+ levels in the roots. Non-metabolic Rb+ uptake probably consists of two components, a carrier-mediated (facilitated diffusion) and a parallel diffusive component. 相似文献
90.
The uptake of leucine through the tegument of Cotugnia digonopora, a cestode found in the fowl intestine, occurs by a process of active transport. The Kt of transport is 0.87 mM and the Vmax is 0.223 μmol/min/g. Uptake of the amino acid is competitively inhibited by valine (Kt = 1.30 mM). Potassium cyanide and 2,4-dinitrophenol do not completely block the entry of leucine into the parasite. 相似文献