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131.
132.
The gastrointestinal tract is a highly complex organ in which multiple dynamic physiological processes are tightly coordinated while interacting with a dense and extremely diverse microbial population. From establishment in early life, through to host‐microbe symbiosis in adulthood, the gut microbiota plays a vital role in our development and health. The effect of the microbiota on gut development and physiology is highlighted by anatomical and functional changes in germ‐free mice, affecting the gut epithelium, immune system and enteric nervous system. Microbial colonisation promotes competent innate and acquired mucosal immune systems, epithelial renewal, barrier integrity, and mucosal vascularisation and innervation. Interacting or shared signalling pathways across different physiological systems of the gut could explain how all these changes are coordinated during postnatal colonisation, or after the introduction of microbiota into germ‐free models. The application of cell‐based in‐vitro experimental systems and mathematical modelling can shed light on the molecular and signalling pathways which regulate the development and maintenance of homeostasis in the gut and beyond. 相似文献
133.
Flavonol-deficient petunia pollen [conditionally male fertile (CMF) pollen] is unable to germinate but application of nanomolar
concentrations of flavonol aglycones completely restores function (Mo et al. 1992). In this study a chemically synthesized
radioactive flavonol, [4′-O-14C]kaempferide, was used as a model compound to study the metabolism of flavonols during the first few hours of pollen germination.
[4′-O-14C] Kaempferide was as efficient at inducing CMF pollen germination as kaempferol and quercetin, the aglycone form of the endogenous
flavonols in petunia pollen. Analysis by high-performance liquid chromatography (HPLC) of extracts from both in-vitro-germinated
pollen and the germination medium showed that more than 95% of the applied radioactivity was recovered as three kaempferide
3-O-glycosides and unmetabolized kaempferide; no flavonol catabolites were detected. Only HPLC fractions that contained the aglycone, or produced
it upon acid hydrolysis, could induce CMF pollen germination in vitro. Structurally diverse flavonols could be classified
according to how efficiently the aglycone was internalized and glycosylated during pollen germination. The ability of an individual
flavonol to restore germination correlated with the total uptake of flavonols but not with the amount of glycoside formed
in the pollen. Thus this study reinforces the conclusion that flavonol aglycones are the active compound for inducing pollen
germination.
Received: 4 November 1996/Accepted: 4 December 1996 相似文献
134.
Camille Loupiac Marco Bonetti Serge Pin Patrick Calmettes 《European journal of biochemistry》2002,269(19):4731-4737
Small-angle neutron scattering experiments were performed on horse azidometmyoglobin (MbN3) at pressures up to 300 MPa. Other spectroscopic techniques have shown that a reorganization of the secondary structure and of the active site occur in this pressure range. The present measurements, performed using various concentrations of MbN3, show that the compactness of the protein is not altered as the value of its radius of gyration remains constant up to 300 MPa. The value of the second virial coefficient of the protein solution indicates that the interactions between the molecules are always strongly repulsive even if their magnitude decreases with increasing pressure. Taking advantage of the pressure-induced contrast variation, these experiments allow the partial specific volume of MbN3 to be determined as a function of pressure. Its value decreases by 5.4% between atmospheric pressure and 300 MPa. In this pressure range the isothermal compressibility of hydrated MbN3 is found to be almost constant. Its value is (1.6 +/- 0.1) 10-4 MPa-1. 相似文献
135.
J. Gautron F. Rieger B. Blondet M. Pinçon-Raymond 《Biology of the cell / under the auspices of the European Cell Biology Organization》1984,49(1):55-67
Denervated neonatal rat sternocleidomastoid muscle has decreased levels of total AChE when compared to control muscle. Denervated versus control values of total muscle AChE present a three-phase curve in function of time after denervation. There is a rapid initial fall 0-3 days after denervation, an increase during about 2 weeks, then again a decrease in total AChE. Thus, there is a transitory net accumulation of AChE after the initial fall of activity in denervated developing muscle. Extrasynaptic areas of high AChE activity develop between 1 and 2 weeks after denervation and remain visible up to 1 month after denervation before vanishing. An electron microscope study shows that these accumulations are internal to the muscle fiber, close to a limited number of muscle nuclei and associated to the sarcoplasmic reticulum and nuclear envelope, but not to the T-tubule system. As found in adult rat muscle, the initial fall in AChE affects first the 16 S AChE form, and soon after, the 4 S and 10 S AChE forms. A main difference with adult muscle is the sudden increase and predominance over other forms of 10 S AChE 2 weeks after denervation at birth. Later, the decrease in AChE affects 16 S and 4 S AChE before 10 S AChE. The regions rich in extrasynaptic sites of AChE accumulation possess a very high proportion of 10 S AChE. Thus, the mechanisms of biosynthesis, intracellular transport and/or secretion of AChE may be very different in young, developing muscle compared to adult muscle. 相似文献
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139.
Methylation‐associated DOK1 and DOK2 down‐regulation: Potential biomarkers for predicting adverse prognosis in acute myeloid leukemia
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140.
Phylogeny and species delineation in the marine diatom Pseudo‐nitzschia (Bacillariophyta) using cox1, LSU,and ITS2 rRNA genes: A perspective in character evolution
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Hong Chang Lim Suh Nih Tan Sing Tung Teng Nina Lundholm Emma Orive Helena David Sonia Quijano‐Scheggia Sandric Chee Yew Leong Matthias Wolf Stephen S. Bates Po Teen Lim Chui Pin Leaw 《Journal of phycology》2018,54(2):234-248
Analyses of the mitochondrial cox1, the nuclear‐encoded large subunit (LSU), and the internal transcribed spacer 2 (ITS2) RNA coding region of Pseudo‐nitzschia revealed that the P. pseudodelicatissima complex can be phylogenetically grouped into three distinct clades (Groups I–III), while the P. delicatissima complex forms another distinct clade (Group IV) in both the LSU and ITS2 phylogenetic trees. It was elucidated that comprehensive taxon sampling (sampling of sequences), selection of appropriate target genes and outgroup, and alignment strategies influenced the phylogenetic accuracy. Based on the genetic divergence, ITS2 resulted in the most resolved trees, followed by cox1 and LSU. The morphological characters available for Pseudo‐nitzschia, although limited in number, were overall in agreement with the phylogenies when mapped onto the ITS2 tree. Information on the presence/absence of a central nodule, number of rows of poroids in each stria, and of sectors dividing the poroids mapped onto the ITS2 tree revealed the evolution of the recently diverged species. The morphologically based species complexes showed evolutionary relevance in agreement with molecular phylogeny inferred from ITS2 sequence–structure data. The data set of the hypervariable region of ITS2 improved the phylogenetic inference compared to the cox1 and LSU data sets. The taxonomic status of P. cuspidata and P. pseudodelicatissima requires further elucidation. 相似文献