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71.
Andrea Villarino Marie-No?lle Rager Patrick A D Grimont Odile M M Bouvet 《European journal of biochemistry》2003,270(12):2689-2695
Cells that have lost the ability to grow in culture could be defined operationally as either alive or dead depending on the method used to determine cell viability. As a consequence, the interpretation of the state of 'nonculturable' cells is often ambiguous. Escherichia coli K12 cells inactivated by UV-irradiation with a low (UV1) and a high (UV2) dose were used as a model of nonculturable cells. Cells inactivated by the UV1 dose lost 'culturability' but they were not lysed and maintained the capacity to respond to nutrient addition by protein synthesis and cell wall synthesis. The cells also retained both a high level of glucose transport and the capacity for metabolizing glucose. Moreover, during glucose incorporation, UV1-treated cells showed the capacity to respond to aeration conditions modifying their metabolic flux through the Embden-Meyerhof and pentose-phosphate pathways. However, nonculturable cells obtained by irradiation with the high UV2 dose showed several levels of metabolic imbalance and retained only residual metabolic activities. Nonculturable cells obtained by irradiation with UV1 and UV2 doses were diagnosed as active and inactive (dying) cells, respectively. 相似文献
72.
Alessandro Viggiano Davide Viggiano Andrea Viggiano Bruno De Luca 《The journal of histochemistry and cytochemistry》2003,51(7):865-871
Superoxide anions are highly reactive radicals overproduced in many pathological situations such as inflammation and ischemia. One of the major factors in the protection from superoxide anions is the enzyme superoxide dismutase (SOD), which catalyzes the dismutation of superoxide to hydrogen peroxide. This study presents a quantitative histochemical method to estimate SOD activity in rat brain tissue sections. This method is based on the cerium capture method and 3,3'-diaminobenzidine amplification of transition cerium compounds. Substrate for SOD was provided by reduction of oxygen during the autoxidation of riboflavin in the presence of UV light. This histochemical method reveals the overall activity of the three different forms of SOD described in mammalian tissues: cytosolic copper-zinc SOD, mitochondrial manganese SOD, and the high molecular weight extracellular SOD. Eventually, this method can be used to quantify SOD activity in tissue sections by image analysis. 相似文献
73.
74.
SPONTANEOUS AND STIMULATED BIOLUMINESCENCE OF THE DINOFLAGELLATE CERATOCORYS HORRZDA (PERIDINIALES)1
This is the first report of spontaneous bioluminescence in the autotrophic dinoflagellate Ceratocorys horrida von Stein. Bioluminescence was measured, using an automated data acquisition system, in a strain of cultured cells isolated from the Sargasso Sea. Ceratocorys horrida is only the second dinoflagellate species to exhibit rhythmicity in the rate of spontaneous flashing, flash quantum flux (intensity), and level of spontaneous glowing. The rate of spontaneous flashing was maximal during hours 2–4 of the dark phase [i.e. circadian time (CT)16–18 for a 14:10 h LD cycle (LD14:10)], with approximately 2% of the population flashing-min?1, a rate approximately one order of magnitude greater than that of the dinoflagellate Gonyaulax polyedra. Flash quantum flux was also maximal during this period. Spontaneous flashes were 134 ms in duration with a maximum flux (intensity) of 3.1×109 quanta-s?1. Light emission presumably originated from blue fluorescent microsources distributed in the cell periphery and not from the spines. Values of both spontaneous flash rate and maximum flux were independent of cell concentration. Isolated cells also produced spontaneous flashes. Spontaneous glowing was dim except for a peak of 6.4× 104quanta-s?1 cell?1, which occurred at CT22.9 for LD14:10 and at CT22.8 for LD12:12. The total integrated emission of spontaneous flashing and glowing during the dark phase was 4×109 quantacell?1, equivalent to the total stimulable luminescence. The rhythms for C. horrida flash and glow behavior were similar to those of Gonyaulax polyedra, although flash rate and quantum flux were greater. Spontaneous bioluminescence in C. horrida may be a circadian rhythm because it persisted for at least three cycles in constant dark conditions. This is also the first detailed study of the stimulated bioluminescence of C. horrida, which also displayed a diurnal rhythm. Cultures exhibited >200 times more mechanically stimulated bioluminescence during the dark phase than during the light phase. Mechanical stimulation during the dark phase resulted in 6.7 flashes. cell?1; flashes were brighter and longer in duration than spontaneous flashes. Cruise-collected cells exhibited variability in quantum flux with few differences in flash kinetics. The role of dinoflagellate spontaneous bioluminescence in the dynamics of near-surface oceanic communities is unknown, but it may be an important source of natural in situ bioluminescence. 相似文献
75.
Kroniger Werner; Rennenberg Heinz; Tadros Monier H.; Polle Andrea 《Plant & cell physiology》1995,36(1):191-196
A manganese-containing superoxide dismutase (SOD; EC 1.15.1.1
[EC]
)was purified to electrophoretic homogeneity from seeds of Norwayspruce (Picea abies L.). The apparent molecular mass of thepurified enzyme was 86 kDa, as determined by gel filtration.The subunit molecular mass, estimated by SDS-polyacrylamidegel electrophoresis, was 22 kDa both in the presence and inthe absence of 2-mercaptoethanol. Thus, the native enzyme isa homotetramer with subunits that were not linked by disulfidebonds. The isoelectric point of this Mn-SOD was 5.5. The specificactivity of the Mn-SOD was strongly pH-dependent and was 400units per nmol SOD at pH 7.8 and 30 units per nmol SOD at pH10.4. The first 25 amino acid residues in the amino terminalregion of spruce Mn-SOD exhibited a high degree of sequencehomology to those of Mn-SODs from other organisms. In Mn-deficientneedles the activity of Mn-SOD was only half of that in non-deficientneedles, whereas the activity of CuZn-SOD was doubled. (Received May 20, 1994; Accepted October 31, 1994) 相似文献
76.
Ivana Gribaudo M. Asuncion Morte Andrea Schubert 《Plant Cell, Tissue and Organ Culture》1995,42(3):303-303
Corrigendum
Use of gentian violet to differentiate in vitro and ex vitro- formed roots during acclimatization of grapevine 相似文献77.
Andrea Peitsch 《Hydrobiologia》1995,311(1-3):127-137
Production rates of the calanoid copepod Eurytemora affinis were estimated from field studies in the Elbe estuary and from an enclosure experiment. As one basic parameter of production rates, the body length, was compared between both investigations. Most of the copepodid stages in the enclosure experiment reached a significant greater length than the copepodids in the estuary. The differences in length between copepods from the field and the experiment could mainly be explained by a four times higher chlorophyll-a level in the enclosure experiment. The better food supply also results in a higher individual growth rate for all instars in the enclosure experiment. Therefore the population of Eurytemora affinis in the Elbe estuary was regarded as food limited during certain times of the year, especially in late spring and summer.Maximum daily production rate in the enclosure experiment (40 µg dw l–1 d–1) was four times higher than in the estuary (12 µg dw l–1 d–1). The mean daily P:B ratio in the enclosure was 0.301 d–1 compared to 0.11 d–1 in the estuary. 相似文献
78.
Andrea Manni Rita Wechter Lisa Wei Daniel Heitjan Laurence Demers 《Journal of cellular physiology》1995,163(1):129-136
Polyamines (PA) have been shown to be critical mediators of estradiol-induced breast cancer cell proliferation. This finding suggests that constitutive activation of the PA pathway may promote tumor progression, possibly leading to hormone independence. To test this hypothesis, we transfected hormone-responsive MCF-7 breast cancer cells with a complementary DNA coding for ornithine-decarboxylase (ODC), the first rate-limiting enzyme in PA biosynthesis. Marked ODC over-expression observed in stably transfected clones was associated with a selective increase in cellular putrescine content, while spermidine and spermine levels were not altered. ODC-overexpressing MCF-7 cells were resistant to the antiproliferative effects of low but not high concentrations of the enzyme inhibitor, α-difluoromethylornithine. In agreement with our hypothesis, sensitivity to the growth-promoting action of estradiol was reduced by approximately one third (P < 0.001) in ODC-overexpressing MCF-7 cells compared with vector-only transfected clones. Basal growth under anchorage-dependent conditions was only marginally increased by ODC overexpression (P = 0.048), while clonogenicity in soft agar was actually reduced. These data suggest that activation of PA biosynthesis may contribute in part to the acquisition of estrogen independence by breast cancer cells. Since only putrescine content was increased as a result of ODC overexpression, these data may underestimate the overall influence of the PA pathway on breast cancer phenotype. © 1995 Wiley-Liss, Inc. 相似文献
79.
80.
Susanne Metzger Andrea Erxleben B. Lippert 《Journal of biological inorganic chemistry》1997,2(2):256-264
The analogy between H-bonded nucleobase pairs and their metalated analogues is extended to the hemiprotonated pair of 7,9-dimethylguanine
(7,9-DimeG) and the Watson-Crick and reversed Watson-Crick pair between 7,9-dimethylguaninium (7,9-DimeGH+) and 1-methylcytosine (1-MeC). The crystal structure analyses of two model compounds, trans–[Pt(CH3NH2)2(7,9-DimeG-N1)2](NO3)2 (1) and trans–[Pt(NH3)2(1-MeC-N3)(7, 9-DimeG-N1)](PF6)2· 2.5 H2O (3a) are reported. Pt binding is through N1 of 7,9-DimeG and N3 of 1-MeC. In solution, 3a exists in a mixture with Watson-Crick and reversed Watson-Crick arrangements of the two bases, depending on solvent, concentration
and anions.
Received: 16 October 1996 / Accepted: 27 January 1997 相似文献