全文获取类型
收费全文 | 70篇 |
免费 | 1篇 |
出版年
2021年 | 2篇 |
2019年 | 3篇 |
2016年 | 2篇 |
2013年 | 7篇 |
2012年 | 4篇 |
2011年 | 4篇 |
2009年 | 1篇 |
2008年 | 4篇 |
2007年 | 2篇 |
2006年 | 5篇 |
2003年 | 1篇 |
2002年 | 2篇 |
2001年 | 3篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1994年 | 2篇 |
1992年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1978年 | 4篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 3篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1970年 | 2篇 |
1969年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有71条查询结果,搜索用时 15 毫秒
1.
M. A. Blight A. L. Pimenta J. -C. Lazzaroni C. Dando L. Kotelevets S. J. Séror I. B. Holland 《Molecular & general genetics : MGG》1994,245(4):431-440
We have carried out a genetic analysis of Escherichia coli HlyB using in vitro(hydroxylamine) mutagenesis and regionally directed mutagenesis. From random mutagenesis, three mutants, temperature sensitive (Ts) for secretion, were isolated and the DNA sequenced: Glyl0Arg close to the N-terminus, Gly408Asp in a highly conserved small periplasmic loop region PIV, and Pro624Leu in another highly conserved region, within the ATP-binding region. Despite the Ts character of the Gly10 substitution, a derivative of HlyB, in which the first 25 amino acids were replaced by 21 amino acids of the Cro protein, was still active in secretion of HlyA. This indicates that this region of HlyB is dispensable for function. Interestingly, the Gly408Asp substitution was toxic at high temperature and this is the first reported example of a conditional lethal mutation in HlyB. We have isolated 4 additional mutations in PIV by directed mutagenesis, giving a total of 5 out of 12 residues substituted in this region, with 4 mutations rendering HlyB defective in secretion. The Pro624 mutation, close to the Walker B-site for ATP binding in the cytoplasmic domain is identical to a mutation in HisP that leads to uncoupling of ATP hydrolysis from the transport of histidine. The expression of a fully functional haemolysin translocation system comprising HlyC,A,B and D increases the sensitivity of E. coli to vancomycin 2.5-fold, compared with cells expressing HlyB and HlyD alone. Thus, active translocation of HlyA renders the cells hyperpermeable to the drug. Mutations in hlyB affecting secretion could be assigned to two classes: those that restore the level of vancomycin resistance to that of E. coli not secreting HlyA and those that still confer hypersensitivity to the drug in the presence of HlyA. We propose that mutations that promote vancomycin resistance will include mutations affecting initial recognition of the secretion signal and therefore activation of a functional transport channel. Mutations that do not alter HlyA-dependent vancomycin sensitivity may, in contrast, affect later steps in the transport process. 相似文献
2.
Nóra M. Márkus Philip Hasel Jing Qiu Karen F. S. Bell Samuel Heron Peter C. Kind Owen Dando T. Ian Simpson Giles E. Hardingham 《PloS one》2016,11(2)
Uptake of Ca2+ into the mitochondrial matrix controls cellular metabolism and survival-death pathways. Several genes are implicated in controlling mitochondrial Ca2+ uptake (mitochondrial calcium regulatory genes, MCRGs), however, less is known about the factors which influence their expression level. Here we have compared MCRG mRNA expression, in neural cells of differing type (cortical neurons vs. astrocytes), differing neuronal subtype (CA3 vs. CA1 hippocampus) and in response to Ca2+ influx, using a combination of qPCR and RNA-seq analysis. Of note, we find that the Mcu-regulating Micu gene family profile differs substantially between neurons and astrocytes, while expression of Mcu itself is markedly different between CA3 and CA1 regions in the adult hippocampus. Moreover, dynamic control of MCRG mRNA expression in response to membrane depolarization-induced Ca2+ influx is also apparent, resulting in repression of Letm1, as well as Mcu. Thus, the mRNA expression profile of MCRGs is not fixed, which may cause differences in the coupling between cytoplasmic and mitochondrial Ca2+, as well as diversity of mitochondrial Ca2+ uptake mechanisms. 相似文献
3.
We purified forms of legumain from a plant source (seeds of kidney bean, Phaseolus vulgaris) and a mammal (kidney of pig, Sus scropha) for comparison of their properties. Both forms were found to be stable only under moderately acidic pH conditions, and were maximally active at about pH 6; the plant enzyme was somewhat less stable and had a slightly higher pH optimum. With benzyloxycarbonyl-Xaa-Ala-Asn-aminomethylcoumarylamide substrates, the two forms of legumain showed distinctly different specificities for the P3 residue, the plant legumain preferring amino acids with bulky hydrophobic side chains because of lower Km values. Both forms of legumain were highly specific for hydrolysis of asparaginyl bonds in the arylamide substrates and in neurotensin. Aspartyl bonds were hydrolysed about 100-fold more slowly with lower pH optima. Potential substrates containing other amino acids structurally similar to asparagine were not hydrolysed. There were clear differences in specificity of hydrolysis of protein substrates. The plant legumain differed from pig legumain in its action on tetanus toxoid C-fragment, cleaving at Asn97 but not at Asn337, and produced more extensive digestion of phaseolin. The plant form of legumain was much more weakly inhibited by egg-white cystatin than was the mammalian form. 相似文献
4.
Lo?c Nazaries Kevin R Tate Des J Ross Jagrati Singh John Dando Surinder Saggar Elizabeth M Baggs Peter Millard J Colin Murrell Brajesh K Singh 《The ISME journal》2011,5(11):1832-1836
Methanotrophs use methane (CH4) as a carbon source. They are particularly active in temperate forest soils. However, the rate of change of CH4 oxidation in soil with afforestation or reforestation is poorly understood. Here, soil CH4 oxidation was examined in New Zealand volcanic soils under regenerating native forests following burning, and in a mature native forest. Results were compared with data for pasture to pine land-use change at nearby sites. We show that following soil disturbance, as little as 47 years may be needed for development of a stable methanotrophic community similar to that in the undisturbed native forest soil. Corresponding soil CH4-oxidation rates in the regenerating forest soil have the potential to reach those of the mature forest, but climo-edaphic fators appear limiting. The observed changes in CH4-oxidation rate were directly linked to a prior shift in methanotrophic communities, which suggests microbial control of the terrestrial CH4 flux and identifies the need to account for this response to afforestation and reforestation in global prediction of CH4 emission. 相似文献
5.
Watt MS Moore JR Façon JP Downes GM Clinton PW Coker G Davis MR Simcock R Parfitt RL Dando J Mason EG Bown HE 《Annals of botany》2006,98(4):765-775
Background and Aims Although density-specific stiffness,E/, (where E is Young's modulus and is wood density) is oftenassumed constant by the elastic similarity model, and in determinationof critical buckling height (Hcrit), few studies have testedthis assumption within species. Here this assumption is testedfor Pinus radiata growing across an environmental gradient,and theory is combined with data to develop a model of Young'smodulus. Methods Analyses use an extensive series of environmentalplots covering the range of climatic and edaphic conditionsover which P. radiata is grown in New Zealand. Reduced majoraxis regression was used to determine scaling exponents betweenloglog plots of Hcrit vs. groundline diameter (D), andE/ vs. D. Path analysis was used to identify significant directand indirect (through stem slenderness) edaphic and climaticinfluences on E. Key Results Density-specific stiffness exhibited 3-foldvariation. As E/ scaled positively with D, the exponent of 0·95between Hcrit and D exceeded the assumed value of 0·67under constant E/. The final path analysis model included meanair temperature in early autumn (Taut) and slenderness as significant(P < 0·05) positive direct influences on E. Tree leafarea index and Taut were indirectly associated with E throughtheir significant (P < 0·05) positive direct relationshipwith stem slenderness. Young's modulus was most sensitive toTaut, followed by stem slenderness then leaf area index, andthe final model explained 76 % of the variance in E. Conclusions The findings suggest that within speciesE/ variation may influence Hcrit and the scaling exponent betweenD and Hcrit so important in assumptions regarding allometricrelationships. The model presented may provide a useful meansof determining variation in E, E/ and Hcrit across environmentalgradients. 相似文献
6.
In previously reported work, we developed a new technique, synchronization modulation, to electrically activate Na/K pump
molecules. The fundamental mechanism involved in this technique is a dynamic entrainment procedure of the pump molecules,
carried out in a stepwise pattern. The entrainment procedure consists of two steps: synchronization and modulation. We theoretically
predicted that the pump functions can be activated exponentially as a function of the membrane potential. We have experimentally
demonstrated synchronization of the Na/K pump molecules and acceleration of their pumping rates by many fold through use of
voltage-clamp techniques, directly monitoring the pump currents. We further applied this technique to intact skeletal muscle
fibers from amphibians and found significant effects on the membrane resting potential. Here, we extend our study to intact
mammalian cardiomyocytes. We employed a noninvasive confocal microscopic fluorescent imaging technique to monitor electric
field–induced changes in ionic concentration gradient and membrane resting potential. Our results further confirm that the
well-designed synchronization modulation electric field can effectively accelerate the Na/K pumping rate, increasing the ionic
concentration gradient across the cell membrane and hyperpolarizing the membrane resting potential. 相似文献
7.
W. Wales Dr. F. Clarac Dr. M. R. Dando M. S. Laverack 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1970,68(4):345-384
Summary This paper gives a full account of the number and structure of the chordotonal organs present at all joints between the coxopodite and dactylopodite of the pereiopods and 3rd maxilliped of the macruran Homarus gammarus L. (H. vulgaris M. Ed.). Some comparative data is supplied for other macruran decapods. As the form of the receptors depends to some degree upon the structure of the joint we have included details of musculature, planes of movement and degrees of freedom at each of the joints.The third maxilliped has a smaller number of chordotonal organs than the pereiopod, in particular at the mero-carpopodite and carpopodite-propodite joints where only one organ is present. In some species the propodite-dactylopodite organ is absent from this limb.The electrical activity recordable from the receptors in the 3rd maxilliped shows considerable differences from the corresponding receptors in the pereiopod.The structure of the carpopodite-propodite joint of both limbs is discussed in detail as this joint differs greatly from that of the Brachyura. In the 3rd maxilliped and 2nd pereiopod three muscles are present. In the latter the joint is capable of rotation about the longitudinal axis but the third muscle does not appear to produce this rotation. A small number of units in the CP2 receptor respond to rotation.A receptor is described in the basipodite of the pereiopod and 3rd maxilliped situated just proximal to the plane through which the limb breaks at autotomy or autospasy. This receptor does not monitor joint movement and may detect cuticular strain, thus preventing accidental autotomy of limbs. A similar receptor has been observed in Carcinus.Cuticular receptor structures (CAP organs) are described as present at the M-C and C-P joints in both limbs, and at the I-M joint of the pereiopod. 相似文献
8.
Bettencourt R Dando P Rosa D Riou V Colaço A Sarrazin J Sarradin PM Santos RS 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2008,150(1):1-7
The deep-sea hydrothermal vent mussel Bathymodiolus azoricus has been the subject of several studies aimed at understanding the physiological adaptations that vent animals have developed in order to cope with the particular physical and chemical conditions of hydrothermal environments. In spite of reports describing successful procedures to maintain vent mussels under laboratory conditions at atmospheric pressure, few studies have described the mussel's physiological state after a long period in aquaria. In the present study, we investigate changes in mucocytes and hemocytes in B. azoricus over the course of several months after deep-sea retrieval. The visualization of granules of mucopolysaccharide or glycoprotein was made possible through their inherent auto-fluorescent property and the Alcian blue-Periodic Acid Schiff staining method. The density and distribution of droplets of mucus-like granules was observed at the ventral end of lamellae during acclimatization period. The mucus-like granules were greatly reduced after 3 months and nearly absent after 6 months of aquarium conditions. Additionally, we examined the depletion of endosymbiont bacteria from gill tissues, which typically occurs within a few weeks in sea water under laboratory conditions. The physiological state of B. azoricus after 6 months of acclimatization was also examined by means of phagocytosis assays using hemocytes. Hemocytes from mussels held in aquaria up to 6 months were still capable of phagocytosis but to a lesser extent when compared to the number of ingested yeast particles per phagocytic hemocytes from freshly collected vent mussels. We suggest that the changes in gill mucopolysaccharides and hemocyte glycoproteins, the endosymbiont abundance in gill tissues and phagocytosis are useful health criteria to assess long term maintenance of B. azoricus in aquaria. Furthermore, the laboratory set up to which vent mussels were acclimatized is an applicable system to study physiological reactions such as hemocyte immunocompetence even in the absence of the high hydrostatic pressure found at deep-sea vent sites. 相似文献
9.
The biogeography and ecology of the species of Chthamalus present on the west coast of America are described, using data from 51 localities from Alaska to Panama, together with their zonation on the shore with respect to that of other barnacles. The species present were C. dalli, Pilsbry 1916, C. fissus, Darwin, 1854, C. anisopoma Pilsbry 1916 and four species in the C. panamensis complex. The latter are C. panamensis Pilsbry, 1916, C. hedgecocki, Pitombo & Burton, 2007, C. alani nom. nov. (formerly C. southwardorum Pitombo & Burton, 2007) and C. newmani sp. nov.). These four species were initially separated by enzyme electrophoresis. They could only be partially separated by DNA bar coding but may be separated using morphological characters. 相似文献
10.