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1.
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.
Nucleotide sequence of the intron of the germline human kappa immunoglobulin gene connecting the J and C regions reveals a matrix association region (MAR) next to the enhancer.
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C Whitehurst H R Henney E E Max H W Schroeder Jr F Stüber K A Siminovitch W T Garrard 《Nucleic acids research》1992,20(18):4929-4930
4.
Pam Harrison 《CMAJ》1985,132(12):1434-1435
5.
Sucrose accumulated in the cytoplasm of mesophyll, parenchyma cells when maize scutella (whole or sliced) were put in concentrated (e.g. 1·0 M) fructose solutions. This accumulated cytoplasmic sucrose leaked from the tissue when the fructose solution was replaced with water or with a more dilute hexitol solution. The amount of leakage was proportional to the concentration difference between the fructose solution bathing the scutellum slices during the sucrose accumulation period and the hexitol solution bathing the slices during the leakage period. Only small amounts of cytoplasmic sucrose leaked from the whole scutellum into water until the root-shoot axis was removed. Other substances also leaked, with sucrose, from the scutellum. Sucrose, nitrogenous compounds, K+ and phosphorous compounds leaked in greatest amounts. The results presented are consistent with the ideas of the mass flow hypothesis. In the scutellum system a pressure flow of solution originates in the mesophyll cells, flows from cell to cell through plasmodesmata, into and through the phloem sieve tubes, and, finally, into the bathing solution. 相似文献
6.
Two genes encode the major membrane-associated protein of methanol-induced peroxisomes from Candida boidinii 总被引:7,自引:0,他引:7
A massive proliferation of peroxisomes occurs in the yeast Candida boidinii when methanol is utilized as the sole carbon source; these peroxisomes contain the enzymes which catalyze the initial steps of methanol utilization. The most abundant peroxisomal membrane-associated protein has an apparent molecular mass of 20 kDa and is termed PMP20. We report the isolation of two genes that encode very similar forms of PMP20; this is the first report of genes that encode proteins associated with peroxisomal membranes. Southern analysis demonstrates that the two genes are on different loci, although there are several homologous regions of both 5'- and 3'-untranslated sequence. One of the areas of 5' homology is within the untranslated region of the mRNA. Within the coding region there are 35 base differences between the two genes that are reflected in only five amino acid differences. The mRNAs representing both genes of PMP20 are induced in cells grown in methanol-containing medium and are below detection in cells grown in glucose. S1 nuclease protection analysis indicates that there is a 2.5-fold difference in mRNA expression between the two genes when induced. The predicted sequences of both PMP20 genes show the absence of a cleaved amino-terminal leader sequence and the presence of only 1 cysteine residue. In agreement with previous biochemical data suggesting a peripheral association of this protein with the membrane (Goodman, J. M., Maher, J., Silver, P. A., Pacifico, A., and Sanders, D. (1986) J. Biol. Chem. 261, 3464-3468), there are no obvious membrane spanning regions predicted in the sequences. Both PMP20 gene products contain the carboxyl-terminal sequence AKL, similar to the putative SKL peroxisomal sorting sequence (Gould, S. J., Keller, G.-A., and Subramani, S. (1988) J. Cell Biol. 107, 897-905). 相似文献
7.
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8.
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
9.
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
10.
Two-dimensional electrophoretic analysis of polynucleosomes 总被引:22,自引:0,他引:22