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1.
Gerd Reuter Roland Schauer Claudia Szeiki Johannis P Kamerling Johannes FG Vliegenthart 《Glycoconjugate journal》1989,6(1):35-44
Periodate oxidation of terminalN-acetyl- andN-glycoloylneuraminic acid residues in the mucins from edible bird nest substance and pig submandibular gland, respectively, can be carried out under conditions which exclusively give rise to the formation of the C-7 analogues of these sialic acids. In contrast, the C-8 compounds can be obtained in a maximum yield of about 40%. Under identical conditions,N-glycoloylneuraminic acid is oxidized about 1.5 times faster than theN-acetylated derivative. After release of the sialic acids by acid hydrolysis, the characterization of the oxidation products was carried out by TLC, by GLC and GLC-MS of the corresponding pertrimethylsilyl derivatives, and by 500-MHz1H-NMR spectroscopy. In addition, molar response factors for GLC analysis and extinction coefficients in the orcinol/Fe3+/HCl assay were determined. 相似文献
2.
alpha 1-Proteinase inhibitor (alpha 1-PI), a member of the serine
proteinase inhibitor superfamily, has a primary role in controlling
neutrophil elastase activity within the mammalian circulation. Several
studies have indicated that the reactive center region of alpha 1-PI, the
amino acid sequence of which is critical to recognition of and binding to
target proteinases, is highly divergent within and among species. This
appears to be a consequence of accelerated rates of evolution that may have
been driven by positive Darwinian selection. In order to examine this and
other features of alpha 1-PI evolution in more detail, we have isolated and
sequenced cDNAs representing alpha 1- PI mRNAs of the mouse species Mus
saxicola and Mus minutoides and have compared these with a number of other
mammalian alpha 1-PI mRNAs. Relative to other mammalian mRNAs, the extent
of nonsynonymous substitution is generally high throughout the alpha 1-PI
mRNA molecule, indicating greater overall rates of amino acid substitution.
Within and among mouse species, the 5'-half of the mRNA, but not the
3'-half, has been homogenized by concerted evolution. Finally, the reactive
center is under diversifying or positive Darwinian selection in murid
rodents (rats, mice) and guinea pigs yet is under purifying selection in
primates and artiodactyls. The significance of these findings to alpha 1-PI
function and the possible selective forces driving evolution of serpins in
general are discussed.
相似文献
3.
Nicholas M. Wragg Diogo Mosqueira Lia Blokpeol‐Ferreras Andrew Capel Darren J. Player Neil R. W. Martin Yang Liu Mark P. Lewis 《Biotechnology journal》2020,15(1)
In vitro 3D tissue‐engineered (TE) structures have been shown to better represent in vivo tissue morphology and biochemical pathways than monolayer culture, and are less ethically questionable than animal models. However, to create systems with even greater relevance, multiple integrated tissue systems should be recreated in vitro. In the present study, the effects and conditions most suitable for the co‐culture of TE skeletal muscle and bone are investigated. High‐glucose Dulbecco's modified Eagle medium (HG‐DMEM) supplemented with 20% fetal bovine serum followed by HG‐DMEM with 2% horse serum is found to enable proliferation of both C2C12 muscle precursor cells and TE85 human osteosarcoma cells, fusion of C2C12s into myotubes, as well as an upregulation of RUNX2/CBFa1 in TE85s. Myotube formation is also evident within indirect contact monolayer cultures. Finally, in 3D co‐cultures, TE85 collagen/hydroxyapatite constructs have significantly greater expression of RUNX2/CBFa1 and osteocalcin/BGLAP in the presence of collagen‐based C2C12 skeletal muscle constructs; however, fusion within these constructs appears reduced. This work demonstrates the first report of the simultaneous co‐culture and differentiation of 3D TE skeletal muscle and bone, and represents a significant step toward a full in vitro 3D musculoskeletal junction model. 相似文献
4.
We delve into the study of a Markov chain formalism applied to the thermal prebiotic oligomerization of amino acids. We find for the case of only two types of electromagnetic interactions, that the steady state attainment by the Markov chain is a built in mechanism limiting the expected variability in sequences in a population of polymers. Such result may be of importance as it makes more accessible the replication of a minimal chemical machinery compatible with life. 相似文献
5.
Duchenne Muscular Dystrophy (DMD) is caused by mutations in the DMD gene resulting in an absence of dystrophin in neurons and muscle. Respiratory failure is the most common cause of mortality and previous studies have largely concentrated on diaphragmatic muscle necrosis and respiratory failure component. Here, we investigated the integrity of respiratory control mechanisms in the mdx mouse model of DMD. Whole body plethysmograph in parallel with phrenic nerve activity recordings revealed a lower respiratory rate and minute ventilation during normoxia and a blunting of the hypoxic ventilatory reflex in response to mild levels of hypoxia together with a poor performance on a hypoxic stress test in mdx mice. Arterial blood gas analysis revealed low PaO2 and pH and high PaCO2 in mdx mice. To investigate chemosensory respiratory drive, we analyzed the carotid body by molecular and functional means. Dystrophin mRNA and protein was expressed in normal mice carotid bodies however, they are absent in mdx mice. Functional analysis revealed abnormalities in Dejours test and the early component of the hypercapnic ventilatory reflex in mdx mice. Together, these results demonstrate a malfunction in the peripheral chemosensory drive that would be predicted to contribute to the respiratory failure in mdx mice. These data suggest that investigating and monitoring peripheral chemosensory drive function may be useful for improving the management of DMD patients with respiratory failure. 相似文献
6.
Dual effects of nitric oxide on cat carotid body chemoreception. 总被引:2,自引:0,他引:2
We studied the effects of nitric oxide (NO) released by NO donors on cat carotid body (CB) chemosensory activity during normoxia and hypoxia. CBs excised from pentobarbital sodium-anaesthetized cats were perfused with Tyrode at 38 degrees C and pH 7.40. The frequency of chemosensory discharges (f(x)) was recorded from the carotid sinus nerve, and changes of NO concentration were measured by a chronoamperometric technique, with NO-selective carbon-fiber microelectrodes inserted in the CB. During steady chemosensory excitation induced by hypoxia, bolus injections of NO (DeltaNO = 0. 5-12 microM), released by S-nitroso-N-acetylpenicillamine (SNAP) and 6-(2-hydroxy-1-methyl-nitrosohydrazino)-N-methyl-1-hexanamine++ + (NOC-9), transiently reduced f(x) in a dose-dependent manner. However, during normoxia, the same concentration of NO (DeltaNO = 0. 5-13 microM) released by the NO donors increased f(x) in a dose-dependent manner. The present results show a dual effect of NO on CB chemoreception that is dependent on the PO(2) levels. During hypoxia, NO is predominantly an inhibitor of chemoreception, whereas, in normoxia, NO increased f(x). The mechanisms by which NO produces chemosensory excitation during normoxia remain to be determined. 相似文献
7.
F. G. Mosqueira 《Origins of life and evolution of the biosphere》1988,18(1-2):143-156
On the assumption of a uniform sample space probability hypothesis it is estimated a maximum number of polypeptides (or other kind of polymers) that could be synthesized in the prebiotic Earth. Besides, on the basis of five premises that are postulated as indispensable requirements for the origin of a living system, under the constraints of a protein-nucleic acid chemistry, it is concluded categorically that the origin of life event could not be the result of unbiased polymerization phenomena. On the contrary, biased and specific patterns of polymerization had to be an essential component in this fundamental event.Finally, several theories on the origin of life and complementary concepts like hypercyclic organization and self-organization phenomena in dissipative structures are discussed in the light of the conclusions arrived at in this work. 相似文献
8.
Tyrosine phosphorylation of Munc18‐1 inhibits synaptic transmission by preventing SNARE assembly 下载免费PDF全文
Marieke Meijer Bernhard Dörr Hanna CA Lammertse Chrysanthi Blithikioti Jan RT van Weering Ruud FG Toonen Thomas H Söllner Matthijs Verhage 《The EMBO journal》2018,37(2):300-320
Tyrosine kinases are important regulators of synaptic strength. Here, we describe a key component of the synaptic vesicle release machinery, Munc18‐1, as a phosphorylation target for neuronal Src family kinases (SFKs). Phosphomimetic Y473D mutation of a SFK phosphorylation site previously identified by brain phospho‐proteomics abolished the stimulatory effect of Munc18‐1 on SNARE complex formation (“SNARE‐templating”) and membrane fusion in vitro. Furthermore, priming but not docking of synaptic vesicles was disrupted in hippocampal munc18‐1‐null neurons expressing Munc18‐1Y473D. Synaptic transmission was temporarily restored by high‐frequency stimulation, as well as by a Munc18‐1 mutation that results in helix 12 extension, a critical conformational step in vesicle priming. On the other hand, expression of non‐phosphorylatable Munc18‐1 supported normal synaptic transmission. We propose that SFK‐dependent Munc18‐1 phosphorylation may constitute a potent, previously unknown mechanism to shut down synaptic transmission, via direct occlusion of a Synaptobrevin/VAMP2 binding groove and subsequent hindrance of conformational changes in domain 3a responsible for vesicle priming. This would strongly interfere with the essential post‐docking SNARE‐templating role of Munc18‐1, resulting in a largely abolished pool of releasable synaptic vesicles. 相似文献
9.
10.
Martin Read Ingrid B Müller Sarah L Mitchell Paul FG Sims John E Hyde 《Malaria journal》2010,9(1):1-19