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1.
The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from
nucleotide sequence variation across a 765-bp region in the cytochrome
oxidase I and II genes of the mitochondrial genome. Most parsimonious
relationships of 25 haplotypes from 16 Greya species and two outgroup
genera (Tetragma and Prodoxus) showed substantial congruence with the
species relationships indicated by morphological variation. Differences
between mitochondrial and morphological trees were found primarily in the
positions of two species, G. variabilis and G. pectinifera, and in the
branching order of the three major species groups in the genus. Conflicts
between the data sets were examined by comparing levels of homoplasy in
characters supporting alternative hypotheses. The phylogeny of Greya
species suggests that host-plant association at the family level and larval
feeding mode are conservative characters. Transition/transversion ratios
estimated by reconstruction of nucleotide substitutions on the phylogeny
had a range of 2.0-9.3, when different subsets of the phylogeny were used.
The decline of this ratio with the increase in maximum sequence divergence
among taxa indicates that transitions are masked by transversions along
deeper internodes or long branches of the phylogeny. Among transitions,
substitutions of A-->G and T-->C outnumbered their reciprocal
substitutions by 2-6 times, presumably because of the approximately 4:1
(77%) A+T-bias in nucleotide base composition. Of all transversions,
73%-80% were A<-->T substitutions, 85% of which occurred at third
positions of codons; these estimates did not decrease with an increase in
maximum sequence divergence of taxa included in the analysis. The high
frequency of A<-->T substitutions is either a reflection or an
explanation of the 92% A+T bias at third codon positions.
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2.
Jean‐Noël Octave Nathalie Pierrot Susana Ferao Santos Natalia N. Nalivaeva Anthony J. Turner 《Journal of neurochemistry》2013,126(2):183-190
Despite intensive studies of the secretase‐mediated processing of the amyloid precursor protein (APP) to form the amyloid β‐peptide (Aβ), in relation to Alzheimer's disease (AD), no new therapeutic agents have reached the clinics based on reducing Aβ levels through the use of secretase inhibitors or immunotherapy. Furthermore, the normal neuronal functions of APP and its various metabolites still remain under‐investigated and unclear. Here, we highlight emerging areas of APP function that may provide new insights into synaptic development, cognition, and gene regulation. By modulating expression levels of endogenous APP in primary cortical neurons, the frequency and amplitude of calcium oscillations is modified, implying a key role for APP in maintaining neuronal calcium homeostasis essential for synaptic transmission. Disruption of this homeostatic mechanism predisposes to aging and AD. Synaptic spine loss is a feature of neurogeneration resulting in learning and memory deficits, and emerging evidence indicates a role for APP, probably mediated via one or more of its metabolites, in spine structure and functions. The intracellular domain of APP (AICD) has also emerged as a key epigenetic regulator of gene expression controlling a diverse range of genes, including APP itself, the amyloid‐degrading enzyme neprilysin, and aquaporin‐1. A fuller understanding of the physiological and pathological actions of APP and its metabolic network could provide new opportunities for therapeutic intervention in AD. 相似文献
3.
A wide-ranging examination of plastid (pt)DNA sequence homologies within
higher plant nuclear genomes (promiscuous DNA) was undertaken. Digestion
with methylation-sensitive restriction enzymes and Southern analysis was
used to distinguish plastid and nuclear DNA in order to assess the extent
of variability of promiscuous sequences within and between plant species.
Some species, such as Gossypium hirsutum (cotton), Nicotiana tabacum
(tobacco), and Chenopodium quinoa, showed homogenity of these sequences,
while intraspecific sequence variation was observed among different
cultivars of Pisum sativum (pea), Hordeum vulgare (barley), and Triticum
aestivum (wheat). Hypervariability of plastid sequence homologies was
identified in the nuclear genomes of Spinacea oleracea (spinach) and Beta
vulgaris (beet), in which individual plants were shown to possess a unique
spectrum of nuclear sequences with ptDNA homology. This hypervariability
apparently extended to somatic variation in B. vulgaris. No sequences with
ptDNA homology were identified by this method in the nuclear genome of
Arabidopsis thaliana.
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4.
Fossil fuel reserves are running out, global warming is becoming a reality, waste recycling is becoming ever more costly and problematic, and unrelenting population growth will require more and more energy and consumer products. There is now an alternative to the 100% oil economy; it is a renewable resource based on agroresources by using the whole plant. Production and development of these new products are based on biorefinery concept. Each constituent of the plant can be extracted and functionalized in order to produce non-food and food fractions, intermediate agro-industrial products and synthons. Three major industrial domains can be concerned: molecules, materials and energy. Molecules can be used as solvent surfactants or chemical intermediates in substitution of petrol derivatives. Fibers can be valorized in materials like composites. Sugars and oils are currently used to produce biofuels like bioethanol or biodiesel, but second-generation biofuels will use lignocellulosic biomass as raw material. Lipids can be used to produce a large diversity of products like solvent, lubricants, pastes or surfactants. Industrial biorefinery will be linked to the creation of new processes based on the twelve principles of green chemistry (clean processes, atom economy, renewable feedstocks…). Biotechnology, especially white biotechnology, will take a major part into these new processes with biotransformations (enzymology, micro-organisms…) and fermentation. The substitution of oil products by biobased products will develop a new bioeconomy and new industrial processes respecting the sustainable development concept. Industrial biorefinery can be developed on the principle that any residues of one can then be exploited as raw material by others in an industrial metabolism. 相似文献
5.
6.
An alternatively processed mRNA specific for gamma-glutamyl transpeptidase in human tissues 总被引:4,自引:0,他引:4
A Pawlak E H Cohen J N Octave R Schweickhardt S J Wu F Bulle N Chikhi J H Baik S Siegrist G Guella?n 《The Journal of biological chemistry》1990,265(6):3256-3262
Human gamma-glutamyl transpeptidase (GGT)1 is composed of two subunits derived from a single precursor (Nash, B., and Tate, S.S. (1984) J. Biol. Chem. 259, 678-685; Finidori, J., Laperche, Y., Tsapis, R., Barouki, R., Guella?n, G., and Hanoune, J. (1984) J. Biol. Chem. 259, 4687-4690) consisting of 569 amino acids (Laperche, Y., Bulle, F., Aissani, T., Chobert, M.N., Aggerbeck, M., Hanoune, J., and Guella?n, G. (1986) Proc Natl. Acad. Sci. U.S.A. 83, 937-941). In the present study we report the cloning of an altered form of this precursor from human liver. We have isolated two clones, one 2,632 base pairs (bp) long from a fetal liver cDNA library and one 926 bp long from an adult liver cDNA library, each containing a 22-bp insertion that introduces a premature stop codon and shortens the open reading frame to 1,098 bp when compared with known human cDNA sequences specific for GGT. Sequence analysis of a human genomic GGT clone shows that this insertion of 22 bp is generated by a splicing event involving an alternative 3'-acceptor site. By polymerase chain reaction experiments we demonstrate that the alternatively spliced mRNA is present in polysomes from the microsomal fraction of a human hepatoma cell line (Hep G2) and thus could encode an altered GGT molecule of 39,300 Da (366 amino acids) encompassing most of the heavy subunit which is normally 41,500 Da (380 amino acids). The altered mRNA is detected in various human tissues including liver, kidney, brain, intestine, stomach, placenta, and mammary gland. This report is the first demonstration of an alternative primary sequence in the mRNA coding for GGT, a finding that could be related to the presence of some inactive forms of GGT detected in human tissues. 相似文献
7.
Subcellular localization of transferrin protein and iron in the perfused rat liver. Effect of Triton WR 1339, digitonin and temperature 总被引:1,自引:0,他引:1
J C Sibille J N Octave Y J Schneider A Trouet R Crichton 《European journal of biochemistry》1986,155(1):47-55
The subcellular localization of 3H-labelled 59Fe-loaded transferrin accumulated by the liver has been studied by means of cell fractionation techniques. More than 96% of the 59Fe present in the liver of rats perfused with 59Fe-labelled transferrin is recovered in the parenchymal cells. Rat livers were perfused with 10 micrograms/ml 3H-labelled 59Fe-saturated transferrin, homogenized separated in nuclear (N), mitochondrial (M), light mitochondrial (L), microsomal (P) and supernatant (S) fractions; M, L and P fractions were further analysed by isopycnic centrifugation in sucrose gradients. 3H label distributes essentially around densities of 1.13-1.14 g/ml overlapping to a large extent with the distribution of galactosyltransferase, the marker enzyme of the Golgi complex. However, after treatment with low concentrations of digitonin the 3H label dissociates from galactosyltransferase and is shifted to higher densities, suggesting an association of transferrin with cholesterol-rich endocytic vesicles which could derive from the plasma membrane. 59Fe is mostly found in the supernatant fraction largely in the form of ferritin, as indicated by its reaction with antiferritin antibodies. In the mitochondrial fraction the density distribution of 59Fe suggests an association with lysosomes and/or mitochondria. In contrast to the lysosomal enzyme cathepsin B, the density distribution of 59Fe was only slightly affected by pretreatment of the rats with Triton WR 1339, suggesting its association with the mitochondria. At 15 degrees C, 59Fe and 3H labels are recovered together in low-density endocytic vesicles. On the basis of our results we suggest that, at low extracellular transferrin concentration, iron uptake by the liver involves endocytosis of the transferrin protein. The complex is interiorized in low-density acidic vesicles where iron is released. The iron passes into the cytosol, where it is incorporated into ferritin and into the mitochondria. The iron-depleted transferrin molecule would then be returned to the extracellular medium during the recycling of the plasma membrane. 相似文献
8.
The production of amyloid peptide (Abeta) from its precursor (APP) plays a key role in Alzheimer's disease (AD). However, the link between Abeta production and neuronal death remains elusive. We studied the biological effects associated with human APP expression and metabolism in rat cortical neurons. Human APP expressed in neurons is processed to produce Abeta and soluble APP. Moreover, human APP expression triggers neuronal death. Pepstatin A, an inhibitor of aspartyl proteases that reduces Abeta production, protects neurons from APP-induced neurotoxicity. This suggests that Abeta production is likely to be the critical event in the neurodegenerative process of AD. 相似文献
9.
Aggregates of beta-amyloid peptide (Abeta) are the major component of the amyloid core of the senile plaques observed in Alzheimer's disease (AD). Abeta results from the amyloidogenic processing of its precursor, the amyloid precursor protein (APP), by beta- and gamma-secretase activities. If beta-secretase has recently been identified and termed BACE, the identity of gamma-secretase is still obscure. Studies with knock-out mice showed that presenilin 1 (PS1), of which mutations are known to be the first cause of inherited AD, is mandatory for the gamma-secretase activity. However, the proteolytic activity of PS1 remains a matter of debate. Here we used transfected Sf9 insect cells, a cellular model lacking endogenous beta- and/or gamma-secretase activities, to characterize the role of BACE and PS1 in the amyloidogenic processing of human APP. We show that, in Sf9 cells, BACE performs the expected beta-secretase cleavage of APP, generating C99. We also show that C99, which is a substrate of gamma-secretase, tightly binds to the human PS1. Despite this interaction, Sf9 cells still do not produce Abeta. This strongly argues against a direct proteolytic activity of PS1 in APP processing, and points toward an implication of PS1 in trafficking/presenting its substrate to the gamma-secretase. 相似文献
10.
JN Matthiessen 《Australian Journal of Entomology》1999,38(4):348-353
In field and laboratory studies, mortality of African black beetle, Heteronychus arator, in the winter-rainfall, Mediterranean-type climate region of south-western Australia was higher in the late immature stages during summer than in the early immature stages that occur during spring, a contrast to summer-rainfall climatic regions. Greatest mortality occurred around the pupal stage in contrasting soil types, despite drying differences in summer and supplementary watering in some plots. Sampling of natural populations confirmed experimental results that mortality in late immature stages is the major factor limiting H. arator populations under a Mediterranean-type climate. Inter-generation increase in H. arator abundance was uncommon, explaining the consistent abundance typically observed between years in south-western Australia. Random dispersal of newly emerged adults in autumn was inferred to restore uniformity in adult abundance between areas of varying favourability for immature survival. 相似文献