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排序方式: 共有119条查询结果,搜索用时 15 毫秒
91.
Alycia G. Berman Creasy A. Clauser Caitlin Wunderlin Max A. Hammond Joseph M. Wallace 《PloS one》2015,10(6)
Strain-induced adaption of bone has been well-studied in an axial loading model of the mouse tibia. However, most outcomes of these studies are restricted to changes in bone architecture and do not explore the mechanical implications of those changes. Herein, we studied both the mechanical and morphological adaptions of bone to three strain levels using a targeted tibial loading mouse model. We hypothesized that loading would increase bone architecture and improve cortical mechanical properties in a dose-dependent fashion. The right tibiae of female C57BL/6 mice (8 week old) were compressively loaded for 2 weeks to a maximum compressive force of 8.8N, 10.6N, or 12.4N (generating periosteal strains on the anteromedial region of the mid-diaphysis of 1700 με, 2050 με, or 2400 με as determined by a strain calibration), while the left limb served as an non-loaded control. Following loading, ex vivo analyses of bone architecture and cortical mechanical integrity were assessed by micro-computed tomography and 4-point bending. Results indicated that loading improved bone architecture in a dose-dependent manner and improved mechanical outcomes at 2050 με. Loading to 2050 με resulted in a strong and compelling formation response in both cortical and cancellous regions. In addition, both structural and tissue level strength and energy dissipation were positively impacted in the diaphysis. Loading to the highest strain level also resulted in rapid and robust formation of bone in both cortical and cancellous regions. However, these improvements came at the cost of a woven bone response in half of the animals. Loading to the lowest strain level had little effect on bone architecture and failed to impact structural- or tissue-level mechanical properties. Potential systemic effects were identified for trabecular bone volume fraction, and in the pre-yield region of the force-displacement and stress-strain curves. Future studies will focus on a moderate load level which was largely beneficial in terms of cortical/cancellous structure and cortical mechanical function. 相似文献
92.
Richoux J. P. Cordonnier J. L. Bouhnik J. Clauser E. Corvol P. Menard J. Grignon G. 《Cell and tissue research》1983,233(2):439-451
Cell and Tissue Research - The renin substrate, angiotensinogen, was localized by immunocytochemistry in liver and kidney of normal rats by the use of an antiserum directed against pure rat... 相似文献
93.
S J Gardell C S Craik E Clauser E J Goldsmith C B Stewart M Graf W J Rutter 《The Journal of biological chemistry》1988,263(33):17828-17836
A new member of the carboxypeptidase gene family, carboxypeptidase A2 (CPA2), has been identified from the predicted amino acid sequence of a rat pancreatic cDNA clone. In vivo recombination and in situ hybridization techniques employing the CPA2 cDNA resulted in the isolation of two genomic clones spanning the 25-kilobase pair rat CPA2 gene. Evolutionary trees built from the amino acid sequences of the known pancreatic carboxypeptidases show that CPA2 and carboxypeptidase A1 (CPA1) are the products of genes which duplicated before the mammalian radiation, and that bovine CPA is of the A1 type. The substrate specificities of CPA1 and CPA2 isolated from rat pancreas are similar to bovine CPA in that carboxyl-terminal amino acids with aromatic or branched aliphatic side chains are preferred. However, the substrate preference of rat CPA1 is skewed toward smaller amino acids, while that of rat CPA2 is skewed toward bulkier amino acids as compared to bovine CPA. The differences in the substrate specificities of these three carboxypeptidases are compatible with the nature of the amino acid replacements in their binding pockets for the carboxylterminal amino acid of the substrate. 相似文献
94.
N-linked oligosaccharide chains of the insulin receptor beta subunit are essential for transmembrane signaling. 总被引:3,自引:0,他引:3
I Leconte C Auzan A Debant B Rossi E Clauser 《The Journal of biological chemistry》1992,267(24):17415-17423
Insulin receptor (IR) is a glycoprotein possessing N-linked oligosaccharide side chains on both alpha and beta subunits. The present study focuses for the first time on the potential contribution of N-linked oligosaccharides of the beta subunit in the processing, structure, and function of the insulin receptor. To investigate this point, a receptor mutant (IR beta N1234) was obtained by stable transfection into Chinese hamster ovary cells of an IR cDNA modified by site-directed mutagenesis on the four potential N-glycosylation sites (Asn-X-Ser/Thr) of the beta subunit. The mutated receptor presents an alpha subunit of 135 kDa, indistinguishable from the wild type alpha subunit, but the beta subunit has a reduced molecular mass (80 kDa instead of 95 kDa) most likely due to the absence of N-glycosylation. Metabolic labeling experiments indicate a normal processing and maturation of this mutated receptor which is normally expressed at the surface of the cells as demonstrated by indirect immunofluorescence. The affinity of the mutant for insulin (Kd = 0.12 nM) is similar to that of the wild type receptor (Kd = 0.12 nM). However, a major defect of the mutated IR tyrosine kinase was assessed both in vitro and in vivo by (i) the absence of insulin-stimulated phosphorylation of the poly(Glu-Tyr) substrate in vitro; (ii) the reduction of the insulin maximal stimulation of the mutated IR autophosphorylation in vitro (2-fold stimulation for the mutant receptor as compared to a 7-fold stimulation for the wild type); and (iii) a more complex alteration of the mutated receptor tyrosine autophosphorylation in vivo (3-fold increase of the basal phosphorylation and a 4-fold simulation of this phosphorylation as compared to the wild type receptor, the phosphorylation of which is stimulated 14-fold by insulin). The physiological consequences of this defect were tested on three classical insulin cellular actions; in Chinese hamster ovary IR beta N1234, glucose transport, glycogen synthesis, and DNA synthesis were all unable to be stimulated by insulin indicating the absence of insulin transduction through this mutated receptor. These data provide the first direct evidence for a critical role of oligosaccharide side chains of the beta subunit in the molecular events responsible for the IR enzymatic activation and signal transduction. 相似文献
95.
L Wei F Alhenc-Gelas F Soubrier A Michaud P Corvol E Clauser 《The Journal of biological chemistry》1991,266(9):5540-5546
Chinese hamster ovary (CHO) cells have been transfected with either a full-length cDNA encoding human angiotensin I-converting enzyme (kininase II; EC 3.4.15.1) (ACE) or a mutated cDNA, in which the last C-terminal 47 amino acids, including the putative transmembrane domain, are not translated. Cell lines expressing high levels of the wild-type ACE or the mutant were established. The cells transfected with the wild-type cDNA (CHO-ACE) express a membrane-bound ectoenzyme with an intracellular C terminus, as shown by indirect immunofluorescence using an antiserum (28A7) raised against a synthetic peptide corresponding to the deduced C terminus of ACE. This enzyme is structurally, immunologically, and enzymatically identical to human kidney ACE. In addition, CHO-ACE cells also produce a secreted form of the enzyme. Neither this secreted form nor the enzyme purified from human plasma is recognized by the antiserum 28A7, indicating that they undergo a truncation in the C-terminal region. On the other hand, the transfected cells expressing the C-terminally truncated mutant (CHO-ACE delta COOH) do not retain ACE in the plasma membrane, but secrete it into the medium. These results indicate that ACE is anchored to the plasma membrane by the predicted C-terminal transmembrane domain, and the secreted form is derived from the membrane-bound form by a post-translational proteolytic cleavage of the C-terminal region. 相似文献
96.
Facile labeling of oligosaccharides (acidic and neutral) in a nonselective
manner was achieved with highly fluorescent anthranilic acid (AA,
2-aminobenzoic acid) (more than twice the intensity of 2- aminobenzamide,
AB) for specific detection at very high sensitivity. Quantitative labeling
in acetate-borate buffered methanol (approximately pH 5.0) at 80 degreesC
for 60 min resulted in negligible or no desialylation of the
oligosaccharides. A high resolution high performance liquid chromatographic
method was developed for quantitative oligosaccharide mapping on a
polymeric-NH2bonded (Astec) column operating under normal phase and anion
exchange (NP-HPAEC) conditions. For isolation of oligosaccharides from the
map by simple evaporation, the chromatographic conditions developed use
volatile acetic acid-triethylamine buffer (approximately pH 4.0) systems.
The mapping and characterization technology was developed using well
characterized standard glycoproteins. The fluorescent oligosaccharide maps
were similar to the maps obtained by the high pH anion-exchange
chromatography with pulsed amperometric detection (HPAEC-PAD), except that
the fluorescent maps contained more defined peaks. In the map, the
oligosaccharides separated into groups based on charge, size, linkage, and
overall structure in a manner similar to HPAEC-PAD with contribution of
-COOH function from the label, anthranilic acid. However, selectivity of
the column for sialic acid linkages was different. A second dimension
normal phase HPLC (NP-HPLC) method was developed on an amide column (TSK
Gel amide-80) for separation of the AA labeled neutral complex type and
isomeric structures of high mannose type oligosaccharides. The
oligosaccharides labeled with AA are compatible with biochemical and
biophysical techniques, and use of matrix assisted laser desorption mass
spectrometry for rapid determination of oligosaccharide mass map of
glycoproteins is demonstrated. High resolution of NP-HPAEC and NP-HPLC
methods combined with mass spectrometry (MALDI-TOF) can provide an
effective technology for analyzing a wide repertoire of oligosaccharide
structures and for determining the action of both transferases and
glycosidases.
相似文献
97.
MOTIVATION: Molecular biology databases hold a large number of empirical
facts about many different aspects of biological entities. That data is
static in the sense that one cannot ask a database 'What effect has protein
A on gene B?' or 'Do gene A and gene B interact, and if so, how?'. Those
questions require an explicit model of the target organism. Traditionally,
biochemical systems are modelled using kinetics and differential equations
in a quantitative simulator. For many biological processes however,
detailed quantitative information is not available, only qualitative or
fuzzy statements about the nature of interactions. RESULTS: We designed and
implemented a qualitative simulation model of lambda phage growth control
in Escherichia coli based on the existing simulation environment QSim.
Qualitative reasoning can serve as the basis for automatic transformation
of contents of genomic databases into interactive modelling systems that
can reason about the relations and interactions of biological entities.
相似文献
98.
The inhibitory effect of 23N-alkyl-4-piperidylesters (alkyl = ethyl-butyl) (APEA) and 8N-ethyl-2-pyrrolidinylmethylesters (EPMEA) of 2- and 3-substituted alkoxyphenylcarbamic acids (alkoxy = butoxy-heptyloxy-) on photosynthetic Hill reaction activity of spinach chloroplasts and on chlorophyll (Chl) synthesis in green algaeChlorella vulgaris was investigated. Inhibitory activities of these compounds were strongly connected with the lipophilicity of the whole molecule. A lower inhibitory activity of 2-alkoxy-substituted derivatives in relation to the corresponding 3-substituted ones was confirmed. Electron spin resonance (ESR) spectra of spinach chloroplasts demonstrated that the studied compounds affected the structure of photosystem (PS) 2 with the release of Mn2+ ions into interior of thylakoid membranes. 相似文献
99.
LARA MODOLO ROBERT D. MARTIN CAREL P. VAN SCHAIK MARIA A. VAN NOORDWIJK MICHAEL KRÜTZEN 《Molecular ecology》2008,17(18):4027-4038
Barbary macaques (Macaca sylvanus), now restricted in the wild to a few isolated forested areas of Morocco and Algeria, are present in a free‐ranging colony on Gibraltar. For many decades, the Gibraltar colony was exposed to multiple bottlenecks due to highly nonrandom removal of animals, followed by repeated introductions of animals from North Africa. Moreover, because of complete isolation, Gibraltar's several social groups of macaques provide an ideal system to study the genetic consequences of dispersal in cercopithecines in situ. Predictions of genetic consequences due to male‐biased dispersal in cercopithecines will be different for autosomal and maternally inherited genetic markers, such as the control region of the mitochondrial DNA. We used a panel of 14 highly polymorphic microsatellite loci and part of the hypervariable region I of the mitochondrial control region to estimate genetic structure between five social groups in Gibraltar. Surprisingly, for autosomal markers, both classical summary statistics and an individual‐based method using a Bayesian framework detected significant genetic structure between social groups in Gibraltar, despite much closer proximity than wild Algerian and Moroccan populations. Mitochondrial data support this finding, as a very substantial portion of the total genetic variation (70.2%) was found between social groups. Using two Bayesian approaches, we likewise identified not only a small number of male first‐generation immigrants (albeit less than expected for cercopithecines) but also unexpectedly a few females. We hypothesize that the culling of males that are more likely to disperse might slow down genetic homogenization among neighbouring groups, but may also and more perversely produce selection on certain behavioural traits. This may have important repercussions for conservation, as it could lead to evolutionary changes that are not due to inbreeding or genetic drift. 相似文献