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101.
Julian Di Stefano 《Ecological Management & Restoration》2004,5(1):61-67
Summary Ecosystem management often proceeds within the context of sub‐optimal relationships between ecologists and ecosystem managers, and management outcomes could be improved with greater collaboration between members of these disciplines. This paper identifies an ecosystem management problem resulting from the interaction between timber harvesting and browsing wallabies, and this case study is used to exemplify how ecological data and expertise can contribute to the process of ecosystem management. It is argued that appropriate use of existing ecological data, establishment of strategic new research and the implementation of management actions as experimental hypothesis tests can facilitate achievement of management objectives, but greater collaboration between ecologists and managers is required before this can occur. Reasons for sub‐optimal relationships are outlined, and the potential for structural change within large State‐run ecosystem management agencies to improve interactions between managers and ecologists is discussed. 相似文献
102.
Reproductive performance varies with age in a wide range of organisms, and increasingly such patterns are interpreted in terms of state-dependent models. We sought to characterise 'state' with regards to age-related variation in clutch size, egg mass and timing of breeding in captive zebra finches Taeniopygia guttata , focusing on the roles of diet quality, age and breeding experience. Females on a high-quality diet laid larger clutches of larger eggs than did females on a low-quality diet. The effect of age on reproductive performance was examined by comparing females breeding (i.e. paired) for the first time at either 3- and/or 6-months of age. Clutch size increased with age but on the low-quality diet only, not on the high-quality diet. Furthermore, clutch size decreased between 3- and 6-months of age in birds bred first on the high-quality diet and then on the low-quality diet. Age did not affect egg mass but older birds had shorter laying intervals. Reproductive performance did not differ between females breeding at 6-months of age for the first or second time: the effects of age were not due to 'training' effects or experience specific to breeding (e.g. undergoing the physiological process of egg formation). In conclusion, nutritional condition (diet) emerged as a central component of state that could strongly influence, and even reverse, any age-dependent increase in primary reproductive performance. 相似文献
103.
M E de la Torre A Diaz B Ruiz A Farres C Aramburo S Sanchez 《Journal of industrial microbiology & biotechnology》1996,17(2):73-76
Penicillium candidum grew and produced lipase in a culture medium supplemented with 0.2% olive oil. Significant enzyme production required the presence of olive, oil and was prevented by cycloheximide. Polyacrylamide gel electrophoresis of filtrates from olive oil fermentations gave a single band of lipase activity (MW 80 KDa). Among the olive oil components only oleate allowed significant lipase production. Other carboxylic and saturated fatty acids containing similar or lower numbers of carbon atoms, did not cause derepression of lipase formation. 相似文献
104.
Protein folding in vivo and renaturation of recombinant proteins from inclusion bodies 总被引:13,自引:0,他引:13
Eukaryotic proteins expressed inEscherichia coli often accumulate within the cell as insoluble protein aggregates or inclusion bodies. The recovery of structure and activity
from inclusion bodies is a complex process, there are no general rules for efficient renaturation. Research into understanding
how proteins fold in vivo is giving rise to potentially new refolding methods, for example, using molecular chaperones. In
this article we review what is understood about the main three classes of chaperone: the Stress 60, Stress 70, and Stress
90 proteins. We also give an overview of current process strategies for renaturing inclusion bodies, and report the use of
novel developments that have enhanced refolding yields. 相似文献
105.
Julian Chela-Flores 《Journal of biological physics》1995,20(1-4):315-330
A review is presented within the framework of the theory of evolution, after it has been extrapolated from the population level to the cellular and molecular levels. From Darwin's seminal and persuasive insight - the theory of common descent - we assume, with him, that probably all the organic beings which have ever lived on this earth have descended from some one primordial form, into which life was first breathed [1]. We are now aware that this primordial cell may have been a protocyanobacterium, but it has often been called a last universal ancestor, a breakthrough organism, or a progenote, a term introduced by Woese [2] which has gained wide acceptance. Strictly speaking, in the intermediate period, ranging from the first living cell to the progenote, life may have evolved in the absence of significant diversity, effectively as a single phylum, incorporating organisms whose genetic systems were already based on DNA. Earlier still, prior to the encapsulation of nucleic acids in microspheres, evolution may already have been at work on RNA molecules (the RNA world). This takes our discussion into the period of chemical evolution, a concept first put forward by Oparin [3], whose principal merit is to have formulated the underlying problem in clear scientific terms. This review does not attempt to be comprehensive. It is mainly devoted to the discussion of certain concepts that may have played a relevant role in the pathway that led to the origin and evolution of the progenote. We do not dwell on the main events of the intermediate period. The topics that we have chosen to include are: the origin of chirality of protein amino acids, the origin of translation, and the origin of the genome. We conclude with some comments on one further aspect of the evolutionary process - the development of biodiversity - by considering the origin of the first eukaryotic cell, an event which, according to the fossil record, may have preceded the evolutionary radiation in the early Cambrian by over a billion years. 相似文献
106.
Verónica Alvarez Maubecin Viviana N. Sanchez Marcelo D. Rosato Siri Bruce D. Cherksey Mutzuyuki Sugimori Rodolfo Llinás Osvaldo D. Uchitel 《Journal of neurochemistry》1995,64(6):2544-2551
Abstract: The voltage-dependent calcium channels present in mammalian and chicken brain synaptosomes were characterized pharmacologically using specific blockers of L-type channels (1,4-dihydropyridines), N-type channels (ω-conotoxin GVIA), and P-type channels [funnel web toxin (FTX) and ω-agatoxin IVA]. K+-induced Ca2+ uptake by chicken synaptosomes was blocked by ω-conotoxin GVIA (IC50 = 250 nM). This toxin at 5 µM did not block Ca2+ entry into rat frontal cortex synaptosomes. FTX and ω-agatoxin IVA blocked Ca2+ uptake by rat synaptosomes (IC50 = 0.17 µl/ml and 40 nM, respectively). Likewise, in chicken synaptosomes, FTX and ω-agatoxin IVA affected Ca2+ uptake. FTX (3 µl/ml) exerted a maximal inhibition of 40% with an IC50 similar to the one obtained in rat preparations, whereas with ω-agatoxin IVA saturation was not reached even at 5 µM. In chicken preparations, the combined effect of saturating concentrations of FTX (1 µl/ml) and different concentrations of ω-conotoxin GVIA showed no additive effects. However, the effect of saturating concentrations of FTX and ω-conotoxin GVIA was never greater than the one observed with ω-conotoxin GVIA. We also found that 60% of the Ca2+ uptake by rat and chicken synaptosomes was inhibited by ω-conotoxin MVIID (1 µM), a toxin that has a high index of discrimination against N-type channels. Conversely, nitrendipine (10 µM) had no significant effect on Ca2+ uptake in either the rat or the chicken. In conclusion, Ca2+ uptake by rat synaptosomes is potently inhibited by different P-type Ca2+ channel blockers, thus indicating that P-type channels are predominant in this preparation. In contrast, Ca2+ uptake by chicken synaptosomes is sensitive to ω-conotoxin GVIA, FTX, ω-agatoxin IVA, and ω-conotoxin MVIID. This suggests that a channel subtype with a mixed pharmacology is present in chicken synaptosomes. 相似文献
107.
108.
Benech-Arnold R.L.; Kristof Graciela; S. Steinbach Hayde; Sanchez R.A. 《Journal of experimental botany》1995,46(6):711-717
The effect of fluctuating temperatures on the germination ofimmature caryopses of two Sorghum varieties presenting contrastingsusceptibility to pre-harvest sprouting was investigated. Fluctuatingtemperatures were able to stimulate germination of immaturecaryopses of both varieties from early stages of development(i.e. 15 d after pollination). Isolated embryos from both varietiesgerminated well in water irrespective of the thermal regimeof incubation. However, the ability of ABA to block germinationin Redland B2 (sproutingsusceptible) isolated embryos was significantlyreduced when embryos were incubated under fluctuating temperaturesfrom 23 DAP onwards. No such effect was found in IS 9530 (sprouting-resistant)embryos. No differences in the pattern with which embryonicABA content decreased during whole grain incubation were foundin 25 and 35 DAP grains from both varieties incubated underconstant or fluctuating temperatures. Therefore, these resultsindicate that alternating temperatures can promote germinationthrough different mechanisms. One of them is the decrease inembryo sensitivity to ABA inhibition which appears to be actingin Redland B2 caryopses from 23 DAP onwards; the other one seemsto be independent of ABA level and sensitivity and is activeat very early stages of development in one variety (RedlandB2) and throughout seed development in the other (IS 9530). Key words: Germination, dormancy, fluctuating temperatures, abscisic acid, seed development, Sorghum bicolor 相似文献
109.
Toxicology of vanadium compounds in diabetic rats: The action of chelating agents on vanadium accumulation 总被引:1,自引:0,他引:1
Jose L. Domingo Mercedes Gomez Domenec J. Sanchez Juan M. Llobet Carl L. Keen 《Molecular and cellular biochemistry》1995,153(1-2):233-240
The possible use of vanadium compounds in the treatment of diabetic patients is now being evaluated. However, previously to establish the optimal maximum dose for diabetes therapy, it should be taken into account that vanadium is a highly toxic element to man and animals. The toxic effects of vanadium are here reviewed. The tissue vanadium accumulation, which would mean an additional risk of toxicity following prolonged vanadium administration is also discussed. Recently, it has been shown that coadministration of vanadate and TIRON, an effective chelator in the treatment of vanadium intoxication, reduced the tissue accumulation of this element, decreasing the possibility of toxic side effects derived from chronic vanadium administration without diminishing the hypoglycemic effect of vanadium. However, previously to assess the effectiveness of this treatment in diabetic patients, a critical reevaluation of the antidiabetic action of vanadium and its potential toxicity is clearly needed. 相似文献
110.
Lack of Correlation between Activation of Jun–NH2-terminal Kinase and Induction of Apoptosis after Detachment of Epithelial Cells
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Detachment of epithelial cells from the extracellular matrix leads to induction of programmed cell death, a process that has been termed “anoikis.” It has been reported recently that detachment of MDCK cells from matrix results in activation of Jun–NH2-terminal kinases (JNKs) and speculated that these stress activated protein kinases play a causal role in the induction of anoikis (Frisch, S.M., K. Vuori, D. Kelaita, and S. Sicks. 1996. J. Cell Biol. 135:1377–1382). We report here that although JNK is activated by detachment of normal MDCK cells, study of cell lines expressing activated signaling proteins usually controlled by Ras shows that stimulation of JNK fails to correlate with induction of anoikis. Activated phosphoinositide 3-OH kinase and activated PKB/Akt protect MDCK cells from detachment-induced apoptosis without suppressing JNK activation. Conversely, activated Raf and dominant negative SEK1, a JNK kinase, attenuate detachment-induced JNK activation without protecting from apoptosis. zVAD-fmk, a peptide inhibitor of caspases, prevents MDCK cell anoikis without affecting JNK activation. p38, a related stress-activated kinase, is also stimulated by detachment from matrix, but inhibition of this kinase with SB 203580 does not protect from anoikis. It is therefore unlikely that either JNK or p38 play a direct role in detachment-induced programmed cell death in epithelial cells. 相似文献