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31.
Starvation-Induced Stress Resistance in Lactococcus lactis subsp. lactis IL1403 总被引:2,自引:1,他引:1 下载免费PDF全文
Axel Hartke Sandrine Bouche Xavier Gansel Philippe Boutibonnes Yanick Auffray 《Applied microbiology》1994,60(9):3474-3478
Carbohydrate-starved cultures of Lactococcus lactis subsp. lactis IL1403 showed enhanced resistance to heat, ethanol, acid, osmotic, and oxidative stresses. This cross-protection seems to be established progressively during the transitional growth phase, with maximum resistance occurring when cells enter the stationary phase. Chloramphenicol or rifamycin treatment does not abolish the development of a tolerant cell state but, on the contrary, seems to provoke this response in L. lactis subsp. lactis. 相似文献
32.
33.
Xavier Roig Isabel S. Novella Ernest Giralt David Andreu 《Letters in Peptide Science》1994,1(1):39-49
Summary The conformation of a peptide that represents antigenic site A of foot-and-mouth disease virus strain C-S8c1 (residues 136–156 of VP1; YTASARGDLAHLTTTHARHLP) has been studied by circular dichroism and compared with three analogs that reproduce amino acid substitutions at position 146 (HisArg, Gln or Asp) which affect antibody recognition. Four other peptides, incorporating replacements at position 147 predicted to maintain (LeuIle, Nle and Ala) or disrupt (LeuGly) helical structure at this site, have also been studied. In aqueous solution or in 4 M urea, the spectra of all eight peptides were typical of aperiodic conformation and independent of concentration or pH. However, upon addition of solvents such as methanol or hexafluoroisopropanol, spectral patterns evidenced significant levels (ca. 50%) of helical structure. The single residue substitutions at positions 146 and 147 caused minor to significant variations in the calculated amount of -helix of the peptides. An attempt to relate these changes in helical content to the antigenic behaviour of the peptides towards five monoclonal antibodies elicited with virus and mapping at site A could not find any straightforward correspondence between the two sets of results. The parent peptide and its His146Arg analog were also analyzed by circular dichroism in the presence of the Fab fragment of SD6, a monoclonal antibody mapping at site A and much less reactive with viruses carrying the referred mutation. Although a peptide-antibody interaction was evident from spectral changes, careful inspection of the difference spectra (peptide-Fab minus Fab) of both peptides failed to detect any significant distinction between them that could be attributed to their different immunoreactivity. While these findings do not necessarily conflict with previous reports that the interaction of antigenic site A with antibodies is mediated to some extent by the adoption of a helix structure, they suggest that, at least for C-serotype viruses, other structural features in addition to a helical conformation are critically involved in antigenic recognition. 相似文献
34.
Carles Campmajó Jordi Joan Cairó Anna Sanfeliu Esteve Martínez Salvador Alegret Francesc Gòdia 《Cytotechnology》1994,14(3):177-182
A flow injection anlytical system based on a gas diffusion membrane module for ammonia and an ammonium flow-through potentiometric detector has been set up for measurement of L-glutamine and ammonium ions in hybridoma cell cultures. The main feature of the system is that the same basic analytical concept and equipment is used in both measurements, the only difference being for the determination of L-glutamine, in which the sample flows through an immobilized glutaminase cartridge. The conditions to enable the performance of both analysis consecutively, avoiding potential interferences by unwanted deamination of other compounds in the samples, have been determined. Finally, the proposed system has been compared with reference analytical methods for batch hybridoma cell culture experiments. 相似文献
35.
Longitudinal patterns of dissolved organic carbon concentration and suspended bacterial density along a blackwater river 总被引:2,自引:0,他引:2
Dissolved organic carbon (DOC) is the dominant form of carbon in transport in blackwater rivers, and bacteria are the major
biological agents of its utilization. This study describes longitudinal patterns in DOC concentration and relates them to
suspended bacterial populations in the channel. Concentrations of total DOC, three molecular weight fractions, and bacterial
numbers were determined at 12 sites along the Ogeechee River in 1985–1986 and 1989 during periods of low and high discharge.
Suspended bacterial populations were compared with DOC concentrations to determine if differences in bacterial abundance were
related to longitudinal patterns of DOC concentration. Three distinct longitudinal patterns were observed: (1) The longitudinal
pattern followed by both total and intermediate molecular weight DOC concentrations was a linear function of the geographic
distance along the river. (2) During low flow conditions, there was a high degree of correspondence between patterns of bacterial
numbers and low MW DOC (< 1000 apparent MW). (3) During periods of high discharge, the proportion of high (> 10,000) and intermediate
(1000–10,000) MW fractions increased, and there was no longer a clear relationship between bacterial cells and low MW DOC. 相似文献
36.
Xavier Pasteur Philippe Mtzeau Ivan Maubon Odile Sabido Hlagne Kiefer 《Molecular reproduction and development》1994,38(3):303-309
Flow cytometric studies of human sperm from fertile men display a constant and characteristic bimodal nonartifactual DNA pattern confirming the existence of two distinct populations. The main population is represented by a peak followed by a shoulder (“marginal population”). The appearance of this marginal population fluctuates with either freezing and thawing or with Percoll gradient centrifugation. We have analyzed both the main and marginal sperm populations by flow cytometry after cell sorting, laser scanning cytometry, light microscopic evaluation, and their sensitivity to DNase digestion. We have observed that the marginal population detected in fertile men represents a sperm group altered in the nuclear condensation, yielding unstable chromatin which appears more stainable with propidium iodide. © 1994 Wiley-Liss, Inc. 相似文献
37.
Carles Ibáñez Nuno Caiola José Barquín Oscar Belmar Xavier Benito-Granell Frederic Casals Siobhan Fennessy Jocelyne Hughes Margaret Palmer Josep Peñuelas Estela Romero Jordi Sardans Michael Williams 《Global Change Biology》2023,29(5):1248-1266
Trends and ecological consequences of phosphorus (P) decline and increasing nitrogen (N) to phosphorus (N:P) ratios in rivers and estuaries are reviewed and discussed. Results suggest that re-oligotrophication is a dominant trend in rivers and estuaries of high-income countries in the last two–three decades, while in low-income countries widespread eutrophication occurs. The decline in P is well documented in hundreds of rivers of United States and the European Union, but the biotic response of rivers and estuaries besides phytoplankton decline such as trends in phytoplankton composition, changes in primary production, ecosystem shifts, cascading effects, changes in ecosystem metabolism, etc., have not been sufficiently monitored and investigated, neither the effects of N:P imbalance. N:P imbalance has significant ecological effects that need to be further investigated. There is a growing number of cases in which phytoplankton biomass have been shown to decrease due to re-oligotrophication, but the potential regime shift from phytoplankton to macrophyte dominance described in shallow lakes has been documented only in a few rivers and estuaries yet. The main reasons why regime shifts are rarely described in rivers and estuaries are, from one hand the scarcity of data on macrophyte cover trends, and from the other hand physical factors such as peak flows or high turbidity that could prevent a general spread of submerged macrophytes as observed in shallow lakes. Moreover, re-oligotrophication effects on rivers may be different compared to lakes (e.g., lower dominance of macrophytes) or estuaries (e.g., limitation of primary production by N instead of P) or may be dependent on river/estuary type. We conclude that river and estuary re-oligotrophication effects are complex, diverse and still little known, and in some cases are equivalent to those described in shallow lakes, but the regime shift is more likely to occur in mid to high-order rivers and shallow estuaries. 相似文献
38.
We have studied the role of second messenger and protein phosphorylation pathways in mediating changes in neuronal function associated with opiate addiction in the rat locus coeruleus. We have found that chronic opiates increase levels of the G-protein subunits Gi and Go, adenylate cyclase, cyclic AMP-dependent protein kinase, and a number of phosphoproteins (including tyrosine hydroxylase) in this brain region. Electrophysiological data have provided direct support for the view that this up-regulation of the cyclic AMP system contributes to opiate tolerance, dependence, and withdrawal exhibited by these neurons. As the adaptations in G-proteins and the cyclic AMP system appear to occur at least in part at the level of gene expression, current efforts are aimed at identifying the mechanisms, at the molecular level, by which opiates regulate the expression of these intracellular messenger proteins in the locus coeruleus. These studies will lead to an improved understanding of the biochemical basis of opiate addiction.Special issue dedicated to Dr. Paul Greengard 相似文献
39.
This paper describes a computational algorithm (STADEERS-STAtisticalDesign of Exeriments in Enzyme ReactorS) for the statisticaldesign of biochemical engineering experiments. The type of experimentthat qualifies for this package involves a batch reaction catalyzedby a soluble enzyme where the activity of the enzyme decayswith time. Assuming that both the catalytic action and the deactivationof the enzyme obey known rate expressions, the present codeis helpful in the process of obtaining estimates of the kineticparameters by providing as output the times at which samplesshould be withdrawn from the reacting mixture. Starting D-optimaldesign is used as a basis for the statistical approach. ThisBASIC code is a powerful tool when fitting a rate expressionto data because it increases the effectiveness of experimentationby helping the biochemical kineticist obtain data points withthe largest possible informa tional content. 相似文献
40.
Bo Damgaard Anna Sanfeliu Jordi Joan Cairó Carles Casas Carles Solà Francesc Gòdia 《Cytotechnology》1993,11(2):133-141
KB-26.5, a murine hybridoma cell line producing an IgG3 monoclonal antibody used in blood type determination, primarily adapted to grow at 5% foetal calf serum (FCS) concentration has been adapted to grow at 0.5% FCS, maintaining its ability to produce antibodies at the same level. In the final step of adaptation, the addition of insulin, transferrin, ethanolamine and selenium to the media formulation was studied, using factorial assay techniques to check the effect of the different compounds and to optimize their required level for satisfactory growth and antibody secretion. KB-26.5 cells required only 20 g/ml of transferrin to adapt to 0.5% FCS medium. Furthermore, transferrin could be substituted by FeCl3, at a relatively low level of 2 g/ml. Maximum cell density decreased by 31.5% in spinner flask test, but the antibody titer was maintained, thus the specific productivity increased. However, inoculum size had to be increased three-fold with 0.5% FCS medium in order to assure cell growth. 相似文献