全文获取类型
收费全文 | 112篇 |
免费 | 10篇 |
出版年
2019年 | 2篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2015年 | 8篇 |
2014年 | 2篇 |
2013年 | 10篇 |
2012年 | 7篇 |
2011年 | 4篇 |
2010年 | 5篇 |
2009年 | 5篇 |
2008年 | 4篇 |
2007年 | 3篇 |
2006年 | 5篇 |
2005年 | 2篇 |
2004年 | 1篇 |
2003年 | 1篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 1篇 |
1994年 | 1篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1975年 | 3篇 |
1969年 | 2篇 |
1929年 | 1篇 |
排序方式: 共有122条查询结果,搜索用时 15 毫秒
1.
Andrew W. Saxe Ji-Won Yoon Phillip Gorden Murray F. Brennan 《In vitro cellular & developmental biology. Plant》1982,18(10):884-890
Summary Dispersed cells from both fresh and cryopreserved human insulinoma have been maintained in cell culture. Initial yield of
viable cells was 50% for fresh and 25% for cryopreserved tissue. Viability of cells in culture was documented by increasing
numbers of cells (doubling time approximately 5 d initially and 2 d at the sixth subculture for both fresh and cryopreserved
tissue) and continued release of insulin over time (approximately 100 ng/ml per 105 cells at 10 d and 175 ng/ml per 105 cells at 30 d of culture for both fresh and cryopreserved tissue). Evidence that cells growing in culture were beta cells
was provided by: (a) recovery of intracellular and extracellular immunoreactive insulin (IRI), (b) electron microscopic morphology,
and (c) immunohistochemical staining. Cells from fresh insulinoma incubated with increasing concentrations of extracellular
glucose released increasing amounts of IRI up to approximately 15 mM glucose, which paralleled changes in plasma insulin obtained during a preoperative glucose tolerance test.
Under an Intergovernmental Personnel Act Exchange from the Department of Surgery, University of California, Davis, Sacramento
Medical Center. 相似文献
2.
Structure and expression of the cAMP cell-surface receptor 总被引:3,自引:0,他引:3
Using antibodies specific for the 3',5'-cyclic AMP (cAMP) cell surface receptor of Dictyostelium discoideum, we have screened lambda gtll expression libraries and isolated a series of cDNAs derived from cAMP receptor mRNA during early development. The identity of the cDNA clones was verified by multiple criteria: 1) beta-galactosidase fusion proteins synthesized by isolated cDNA clones stain intensely with cAMP receptor directed antiserum, 2) these fusion proteins affinity purify antibodies specific for the cAMP receptor, 3) the cDNA probes hybridize to a 2 kb mRNA whose change in relative level of abundance during development parallels that of receptor mRNA as assayed by in vitro translation, 4) the 2 kb mRNA size equals that of receptor mRNA as determined by in vitro translation of size fractionated poly (A)+ RNA, and 5) RNA transcribed in vitro from cDNAs containing the entire protein-coding region produces a polypeptide by in vitro translation with an apparent molecular weight in close agreement with that of nascent cAMP receptor protein produced by in vitro translation of cellular RNA. The DNA sequence predicts an open reading frame of 392 amino acids. The deduced amino acid sequence contains seven domains enriched in hydrophobic residues. A model is proposed in which the cAMP cell-surface receptor traverses the lipid bilayer seven times in a pattern similar to that of other receptors, such as rhodopsin, which interact with G-proteins. The structural similarities suggest a gene family of related surface receptors from such evolutionarily diverse species as Dictyostelium, yeast, and mammals. 相似文献
3.
Emile CL. Marnette Harm Houweling Herman Van Dam Jan Willem Erisman 《Biogeochemistry》1993,23(2):119-144
The chemical composition of surface waters of two Dutch moorland pools and of incident precipitation, was monitored from 1982
to 1990. For this period, sulfur and water budgets were calculated using a hydrochemical model developed for well-mixed non-stratifying
lakes. Total atmospheric deposition of S decreased significantly after 1986 at both locations. A model describing the sulfur
budget in terms of input, output and reduction/oxidation processes predicted a fast decrease of pool water SO4
2− concentrations after a decrease of atmospheric input. However, SO4
2− concentrations in the surface water was lowered only slightly or remained constant. Apparently a source within the lake caused
the unexpectedly high SO4
2− concentrations. The possible supply of SO4
2− from the sediment through regulation by (K-)Al-SO4 containing minerals or desorption of SO4
2− from positively charged surfaces in the sediment was evaluated. Solubility calculations of pore water with respect to alunite,
basaluminite and jurbanite indicated that SO4
2− concentration was not regulated by these minerals. It is suggested here (1) that desorption of SO4
2− from peaty sediments may account for the estimated SO4
2− supply provided that the adsorption complex is periodically recharged by partial oxidation of the upper bottom sediments
and (2) that because of exposure of a part of the pool bottom to the atmosphere during dry summers and subsequent oxidation
of reduced S, the amount of SO4
2− may be provided which complements the decreasing depositional SO4
2− input. In future research these two mechanisms need to be investigated. 相似文献
4.
Evidence presented elsewhere (G.B. Williams, E.M. Elder, and M. Sussman 1984, Dev. Biol. 105, 377-388) indicates that NH3 and certain carboxylic acids including propionate, succinate, and acetate modulate the cAMP relay in Dictyostelium discoideum. The former appears to act as a cAMP accumulation inhibitor, the latter as cAMP release inhibitors. The cohesive properties of aggregation competent cells have been assayed quantitatively in the presence of these modulators. The following results were obtained: (1) At pH 7.5, EDTA-resistant cohesivity was greatly inhibited by NH4C within the concentration range tested (30-3.8 mM). Even at the higher concentrations the effect was not immediate but required ca. 10 min for full expression. At the lower concentrations, the inhibitory level was only slightly reduced but the time for full expression progressively increased. At pH 6.5, the level of inhibition was marginal, indicating that NH3 is the active molecular species. By themselves, neither ambient pH nor ionic strength appeared to affect cohesive performance within the ranges employed. The inhibition was immediately and completely reversed upon removal of NH4Cl or a shift of ambient pH from 7.5 to 6.5. The presence of cycloheximide did not affect the recovery of cohesivity after NH4Cl removal. (2) The presence of 15 mM succinate, propionate, or acetate also reduced cell cohesivity. The timing and extent of the inhibition were identical at pH 7.5 and 6.5. The inhibition was expressed immediately and was reversible. Each of the acids acted synergistically with NH4Cl. The relative potencies of these metabolites acting singly or in combination as inhibitors of cohesivity corresponded roughly to their potencies as modulators of the cAMP relay (Williams et al., 1984). (3) The sensitivity to the metabolites was stage specific, being maximal during and shortly after aggregation and disappearing abruptly at 11-12 hr. This corresponds to the time at which this cohesive system, responsible for the end-to-end cell associations evident during aggregation (H. Beug, G. Gerisch, S. Kempff, V. Riedel, and G. Cremer, 1970, Exp. Cell. Res. 63, 147-158) is supplanted by a newly arisen, serologically and genetically distinct system which thereafter maintains the integrity of the aggregate (C. Steinemann and R.W. Parish, 1980, Nature (London) 286, 721-724; D.K. Wilcox and M. Sussman, 1981, Dev. Biol. 82, 102-112, and Proc. Natl. Acad. Sci. USA 78, 358-362; C.L. Saxe III and M. Sussman, 1982, Cell 29, 755-759). The activities of the metabolites, detailed above, are discussed in relation to their previously demonstrated activities as morphogens. 相似文献
5.
Induction of stage-specific cell cohesion in D. discoideum by a plasma-membrane-associated moiety reactive with wheat germ agglutinin 总被引:3,自引:0,他引:3
Dictyostelium discoideum strain JC-5 is a temperature-sensitive, cohesion-defective mutant. At the restrictive temperature, aggregates are formed and develop normally to a specific late stage, but then disperse to a lawn of noncohesive cells. The defect stems from the inability of the mutant at the restrictive temperature to accumulate or retain an adequate level of a newly arisen, plasma-membrane-associated cohesive moiety during the later stages of morphogenesis. We now report that the noncohesive mutant cells can be induced to cohere at a level of greater than 99% by addition of a fraction reactive with wheat germ agglutinin and isolated from the plasma membranes of late-stage, cohesive mutant or wild-type cells. Furthermore, the cohesivities of late-stage, cohesive mutant or wild-type cells can be significantly enhanced by the same preparations but early-stage cohesive cells remain unaffected. The cohesion-inducing activity can be recovered from two regions of a one-dimensional polyacrylamide gel electropherogram following elution and renaturation. The first is associated with a single silver-staining band (apparent molecular weight 95,000). It appears de novo at a postaggregative stage, and accumulates in a thermostable fashion in the wild-type and in a thermosensitive fashion in the mutants, concurrent with the loss of cohesivity. The second is associated with a complex of silver-staining bands (apparent molecular weights 40,000-50,000). The activity of the eluate reactive with wheat germ agglutinate is destroyed within 5 min at 100 degrees C. 相似文献
6.
Vanadate (Na3VO4) selectively and reversibly affects the rhythmic movement of Albizzia julibrissin leaflets. Leaflets floated on 1 millimolar vanadate open at the same rate or more rapidly than controls, but closure is inhibited. After 6 to 24 hours incubation, the inhibition can be reversed by a 24-to 48-hour period on water or control buffer. Recovery is complete in light-dark cycles, and it is almost complete under free-running conditions (prolonged darkness). Leaflets floated on 10 millimolar vanadate do not open in darkness, but they open at a reduced rate in light. Concentrations of 100 micromolar or less are ineffective. 相似文献
7.
Sulfate reduction and S-oxidation in a moorland pool sediment 总被引:3,自引:2,他引:1
In an oligotrophic moorland pool in The Netherlands, S cycling near the sediment/water boundary was investigated by measuring (1) SO4
2– reduction rates in the sediment, (2) depletion of SO4
2– in the overlying water column and (3) release of35S from the sediment into the water column. Two locations differing in sediment type (highly organic and sandy) were compared, with respect to reduction rates and depletion of SO4
2– in the overlying water.Sulfate reduction rates in sediments of an oligotrophic moorland pool were estimated by diagenetic modelling and whole core35SO4
2– injection. Rates of SO4
2– consumption in the overlying water were estimated by changes in SO4
2– concentration over time in in situ enclosures. Reduction rates ranged from 0.27–11.2 mmol m–2 d–1. Rates of SO4
2– uptake from the enclosed water column varied from –0.5, –0.3 mmol m–2 d–1 (November) to 0.43–1.81 mmol m–2 d–1 (July, August and April). Maximum rates of oxidation to SO4
2– in July 1990 estimated by combination of SO4
2– reduction rates and rates of in situ SO4
2– uptake in the enclosed water column were 10.3 and 10.5 mmol m–2 d–1 at an organic rich and at a sandy site respectively.Experiments with35S2– and35SO4
2– tracer suggested (1) a rapid formation of organically bound S from dissimilatory reduced SO4
2– and (2) the presence of mainly non SO4
2–-S derived from reduced S transported from the sediment into the overlying water. A35S2– tracer experiment showed that about 7% of35S2– injected at 1 cm depth in a sediment core was recovered in the overlying water column.Sulfate reduction rates in sediments with higher volumetric mass fraction of organic matter did not significantly differ from those in sediments with a lower mass fraction of organic matter.Corresponding author 相似文献
8.
Effect of vanadate on bean leaf movement, stomatal conductance, barley leaf unrolling, respiration, and phosphatase activity 总被引:3,自引:2,他引:1
下载免费PDF全文
![点击此处可从《Plant physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Vanadate (Na3 VO4) inhibits leaf movement and stomatal conductance of Phaseolus vulgaris L. cv. Carlos Favorit in light-dark cycles as well as photomorphogenetic leaf unrolling of Hordeum vulgare L. cv. Rupal. Inhibition was 50% by 10 to 100 micromolar vanadate and 100% by millimolar vanadate. Leaf unrolling was also inhibited by oligomycin and diethylstilbestrol. 相似文献
9.
L S Saxe 《Biochemistry》1975,14(10):2051-2057
A lambda DNA supercoil system has been developed to study the effects of colicin E2 on DNA in vivo. Colicin E2, a protein antibiotic synthesized by strains of coliform bacteria that carry the Col E2 plasmid, had as its most conspicious effect damage to the DNA of sensitive strains. Colicine E2 attacks the supercoiled molecul formed by labeled lambda DNA in superinfected cells as well as it attacks the bacterial DNA. The rate and extent of acid solubilization of the lambda supercoils and of host bacterial DNA induced by E2 treatment are nearly identical. Treatment of superinfected cells with colicin E2 results in the progressive conversion of lambda DNA supercoils to open circles and/or linear full lenght molecules, and subsequently to fragments less than full lambda in size. The first endonucleolytic reactions are single-strand and or double-strand breaks. The rate of supercoil breakdown as well as the final percent supercoils remaining unconverted, the size of the final lambda fragments, and the extent of solubilization are dependent on the multiplicity of colicin used. Additions of trypsin to E2-treated superinfected cells results in a cessation of further breakdown of the lambda molecules, presumably as a result of digestion of accessible colicin molecules. Energy is essential for an early event in colicin E2 action. The host enzymes, endonuclease I and Rec BC, may be instrumental in the nucleolytic process caused by colicin E2: endonuclease I in reaction preceding cell killing and Rec BC in a secondary degradation of the bacterial DNA. 相似文献
10.
MARTIN CLÉMENT CAROLINE CHAMBERLAND JACQUELINE PÉRODIN RICHARD LEDUC GAÉTAN GUILLEMETTE EMANUEL ESCHER 《Journal of receptor and signal transduction research》2013,33(5-6):417-433
Several models of activation mechanisms were proposed for G protein-coupled receptors (GPCRs), yet no direct methods exist for their elucidation. The availability of constitutively active mutants has given an opportunity to study active receptor conformations within acceptable limits using models such as the angiotensin II type 1 (AT1)1 receptor mutant N111G-hAT1 which displays an important constitutive activity. Recently, by using methionine proximity assay, we showed for the hAT1 receptor that TMD III, VI, and VII form the ligand-binding pocket of the C-terminal amino acid of an antagonistic AngII analogue. In the present contribution, we investigated whether the same residues would also constitute the ligand-binding contacts in constitutively activated mutant (CAM) receptors. For this purpose, the same Met mutagenesis strategy was carried out on the N111G double mutants. Analysis of 43 receptors mutants in the N111G-hAT1 series, photolabeled and CNBr digested, showed that there were only subtle structural changes between the wt-receptor and its constitutively active form. 相似文献