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排序方式: 共有436条查询结果,搜索用时 31 毫秒
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2.
Lars Svennerholm Pam Fredman Birgitta Jungbjer Jan-Eric Månsson Britt-Marie Rynmark Kerstin Boström Bengt Hagberg Lars Norén Pirkko Santavuori 《Journal of neurochemistry》1987,49(6):1772-1783
Lipid composition was studied on cerebral tissue from nine children who had died of a progressive encephalopathy called the infantile form of neuronal ceroid lipofuscinosis (INCL) or polyunsaturated fatty acid lipidosis (PFAL). In the terminal stage of the disease, the concentrations of all lipid classes were found to be significantly reduced in the cerebral and cerebellar cortex and white matter. The concentration of gangliosides of the cerebral cortex was 15% and that of cerebrosides (galactosylceramide) in white matter 0.2-5% of the normal values for the children's ages. The reduction of gangliosides mainly affected those of the gangliotetraose series, particularly GD1a. The fatty acids of the linolenic acid series were strongly reduced in ethanolamine and serine phosphoglycerides. A very large increase up to 100-fold of oligoglycosphingolipids of the globo series and two fucose-containing lipids of the neolacto series was found in the forebrain of the three advanced cases examined. The brain tissue also contained very high concentrations of mono-, di-, and trisialogangliosides of the lacto and neolacto series, gangliosides with type 1 chain dominating. The structures of the gangliosides were tentatively identified by gas chromatography-mass spectrometry and monoclonal antibodies with carefully determined epitope specificity. The gangliosides and neutral glycosphingolipids had very similar fatty acid composition, consisting of about 40% stearic acid and 40% C24-acids. 相似文献
3.
Identification of protease 3.4.24.11 as the major atrial natriuretic factor degrading enzyme in the rat kidney 总被引:5,自引:0,他引:5
J L Sonnenberg Y Sakane A Y Jeng J A Koehn J A Ansell L P Wennogle R D Ghai 《Peptides》1988,9(1):173-180
We have identified a metalloendoprotease from rat kidney cortex that cleaves the cysteine-phenylalanine bond (Cys7-Phe8) within the 17 amino acid ring structure of atrial natriuretic factor (ANF). Cleavage at this site represents the major ANF degradative activity in rat kidney, and is inhibited by the known metalloendoprotease inhibitors, thiorphan, phosphoramidon and zincov with IC50 values in the nanomolar range. Since these are specific inhibitors of protease 3.4.24.11, both protease 3.4.24.11 and ANF degrading activities were monitored during purification. Both activities copurified at each chromatographic step. Furthermore, purified protease 3.4.24.11 cleaved ANF specifically at the Cys7-Phe8 bond. It is concluded from this work that the major ANF degrading enzyme in rat kidney is protease 3.4.24.11. 相似文献
4.
Pam Harrison 《CMAJ》1985,132(12):1434-1435
5.
Ring cleavage of atrial natriuretic peptide (ANF) between Cys7 and Phe8 by endoprotease 3.4.24.11 yields X-ANF. Since endoprotease 3.4.24.11 may contribute to ANF metabolism in vivo, the present study determined if X-ANF exhibits reduced biological activity in comparison to the parent molecule. 相似文献
6.
7.
Distinct and overlapping ligand specificities of the alpha 3A beta 1 and alpha 6A beta 1 integrins: recognition of laminin isoforms. 总被引:7,自引:1,他引:6 下载免费PDF全文
G O Delwel A A de Melker F Hogervorst L H Jaspars D L Fles I Kuikman A Lindblom M Paulsson R Timpl A Sonnenberg 《Molecular biology of the cell》1994,5(2):203-215
The ligand specificity of the alpha 3A beta 1 integrin was analyzed using K562 cells transfected with full-length alpha 3A cDNA and was compared with that of alpha 6A beta 1 in similarly transfected K562 cells. Clones were obtained that showed comparable surface expression of either alpha 3A beta 1 or alpha 6A beta 1 integrins. Those expressing alpha 3A beta 1 attached to and spread on immunopurified human kalinin and cellular matrices containing human kalinin, which is a particular isoform of laminin. In addition, alpha 3A transfectants adhered to bovine kidney laminins possessing a novel A chain variant. Binding to kalinin was blocked by a monoclonal antibody against the A chain constituent of kalinin and adhesion to both kalinin and kidney laminins by anti-alpha 3 and beta 1 monoclonal antibodies. The alpha 3A transfected cells bound more strongly to kalinin and bovine kidney laminins after treatment with the beta 1 stimulatory antibody TS2/16. A distinctly weaker and activation-dependent adhesion of alpha 3A transfectants was observed on human placental laminins possessing the Am chain variant (merosin), and no adhesion occurred on bovine heart laminins and murine EHS tumor laminin. Further inactive substrates were fibronectin, nidogen, and collagen types IV and VI, indicating that the alpha 3A beta 1 integrin is a much less promiscuous receptor than thought before. By contrast, alpha 6A transfected cells adhered to all laminin isoforms when stimulated with TS2/16. Adhesion also occurred only on bovine kidney laminins in the absence of TS2/16. These results demonstrate that both alpha 3A beta 1 and alpha 6A beta 1 integrins are typical laminin receptors but that their affinity and activation dependence for binding to various laminin isoforms differ considerably. 相似文献
8.
Robin J. Boyd Martin Harvey David B. Roy Tony Barber Karen A. Haysom Craig R. Macadam Roger K. A. Morris Carolyn Palmer Stephen Palmer Chris D. Preston Pam Taylor Robert Ward Stuart G. Ball Oliver L. Pescott 《Diversity & distributions》2023,29(6):774-784
Aim
To develop a causal understanding of the drivers of Species distribution model (SDM) performance.Location
United Kingdom (UK).Methods
We measured the accuracy and variance of SDMs fitted for 518 species of invertebrate and plant in the UK. Our measure of variance reflects variation among replicate model fits, and taxon experts assessed model accuracy. Using directed acyclic graphs, we developed a causal model depicting plausible effects of explanatory variables (e.g. species' prevalence, sample size) on SDM accuracy and variance and quantified those effects using a multilevel piecewise path model.Results
According to our model, sample size and niche completeness (proportion of a species' niche covered by sampling) directly affect SDM accuracy and variance. Prevalence and range completeness have indirect effects mediated by sample size. Challenging conventional wisdom, we found that the effect of prevalence on SDM accuracy is positive. This reflects the facts that sample size has a positive effect on accuracy and larger sample sizes are possible for widespread species. It is possible, however, that the omission of an unobserved confounder biased this effect. Previous studies, which reported negative correlations between prevalence and SDM accuracy, conditioned on sample size.Main conclusions
Our model explicates the causal basis of previously reported correlations between SDM performance and species/data characteristics. It also suggests that niche completeness has similarly large effects on SDM accuracy and variance as sample size. Analysts should consider niche completeness, or proxies thereof, in addition to sample size when deciding whether modelling is worthwhile. 相似文献9.
Yvonne M. van Houten Pam van Stratum Jan Bruin Alfred Veerman 《Entomologia Experimentalis et Applicata》1995,77(3):289-295
In Europe and North America the western flower thrips,Frankliniella occidentalis, is an important pest in various greenhouse crops, such as sweet pepper and cucumber. Two species of predatory mite are commercially
applied for biological control of this pest:Amblyseius cucumeris andA. barkeri. Thrips control is generally successful from March onwards. During winter, however, thrips control by these predatory mites
is less effective. An important reason for this is that the commercially applied strains of both mite species enter reproductive
diapause under short-day photoperiods, whereas the western flower thrips does not enter diapause. In this paper we report
on selection experiments for non-diapause in strains of both mite species, aimed at obtaining predators that do not enter
diapause under light- and temperature conditions prevailing in winter. Additional experiments were done to estimate the potential
of the selected lines as control agents ofF. occidentalis. Selection for non-diapause proved highly successful in both predatory mite species. In a New Zealand strain ofA. cucumeris diapause incidence decreased from 41% to 0% in about ten generations; in a Dutch strain ofA. barkeri diapause incidence decreased from 67% to 0% in about six generations. Furthermore, selection for non-diapause had no influence
on predator performance, measured as predation rate and oviposition rate on a diet of first instar thirps larvae. Rates of
predation and oviposition were the same for selected and unselected lines in both species; rates of predation and oviposition
were higher forA. cucumeris than forA. barkeri. After 18 months under non-diapause conditions, no less than 92% of a sample of the selected non-diapause line ofA. cucumeris did not enter diapause when tested under diapause-inducing conditions. This indicates that ‘non-diapause’ is a stable trait
in these predatory mites. Finally, a small-scale greenhouse experiment in a sweet pepper crop showed that the selected non-diapause
line ofA. cucumeris established successfully under diapause-inducing short-day conditions. 相似文献
10.
Delayed leaf senescence in ethylene-deficient ACC-oxidase antisense tomato plants: molecular and physiological analysis 总被引:17,自引:3,他引:14
Isaac John Rachel Drake Aldo Farrell Wendy Cooper Pam Lee Peter Horton Don Grierson 《The Plant journal : for cell and molecular biology》1995,7(3):483-490
To determine the role of ethylene during tomato (Lycopersicon esculentum Mill. cv. Alisa Craig) leaf senescence, transgenic ACC oxidase antisense plants were analysed. Northern analysis of wild-type plants indicated that ACC oxidase mRNA accumulation normally begins in pre-senescent green leaves but was severely reduced in the antisense plants. Although the levels of ethylene evolved by wild-type and transgenic leaves increased during the progression of senescence, levels were extremely low in transgenic leaves. Leaf senescence, as assessed by colour change from green to yellow, was clearly delayed by 10–14 days in the antisense plants when compared with wild-type plants. Northern analysis of the photosynthesis-associated genes, cab and rbcS, indicated that levels of the corresponding mRNAs were higher in transgenic leaves which were not yet senescing compared with senescing wild-type leaves of exactly the same age. Northern analysis using probes for tomato fruit ripening-related genes expressed during leaf senescence indicated that once senescence was initiated the expression pattern of these mRNAs was similar in transgenic and wild-type leaves. In the antisense plants chlorophyll levels, photosynthetic capacity and chlorophyll fluorescence were higher when compared with senescing wild-type plants of the same age. Photosynthetic capacity and the quantum efficiency of photosystem II were maintained for longer in the transformed plants at values close to those observed in wild-type leaves prior to the visible onset of senescence. These results indicate that inhibiting ACC oxidase expression and ethylene synthesis results in delayed leaf senescence, rather than inducing a stay-green phenotype. Once senescence begins, it progresses normally. Onset of senescence is not, therefore, related to a critical level of ethylene. The correlation between higher levels prior to senescence and early onset, however, suggests that ethylene experienced by the plant may be a significant contributing factor in the timing of senescence. 相似文献