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981.
Development of the mammalian inner ear requires coordination of cell proliferation, cell fate determination and morphogenetic movements. While significant progress has been made in identifying developmental signals required for inner ear formation, less is known about how distinct signals are coordinated by their downstream mediators. Members of the Rac family of small GTPases are known regulators of cytoskeletal remodeling and numerous other cellular processes. However, the function of Rac GTPases in otic development is largely unexplored. Here, we show that Rac1 and Rac3 redundantly regulate many aspects of inner ear morphogenesis. While no morphological defects were observed in Rac3(-/-) mice, Rac1(CKO); Rac3(-/-) double mutants displayed enhanced vestibular and cochlear malformations compared to Rac1(CKO) single mutants. Moreover, in Rac1(CKO); Rac3(-/-) mutants, we observed compromised E-cadherin-mediated cell adhesion, reduced cell proliferation and increased cell death in the early developing otocyst, leading to a decreased size and malformation of the membranous labyrinth. Finally, cochlear extension was severely disrupted in Rac1(CKO); Rac3(-/-) mutants, accompanied by a loss of epithelial cohesion and formation of ectopic sensory patches underneath the cochlear duct. The compartmentalized expression of otic patterning genes within the Rac1(CKO); Rac3(-/-) mutant otocyst was largely normal, however, indicating that Rac proteins regulate inner ear morphogenesis without affecting cell fate specification. Taken together, our results reveal an essential role for Rac GTPases in coordinating cell adhesion, cell proliferation, cell death and cell movements during otic development. 相似文献
982.
Elizabeth?A. Booth-Gauthier Turi?A. Alcoser Ge Yang Kris?N. Dahl 《Biophysical journal》2012,103(12):2423-2431
Extracellular mechanical forces result in changes in gene expression, but it is unclear how cells are able to permanently adapt to new mechanical environments because chemical signaling pathways are short-lived. We visualize force-induced changes in nuclear rheology to examine short- and long-time genome organization and movements. Punctate labels in the nuclear interior of HeLa, human umbilical vein endothelial, and osteosarcoma (Saos-2) cells allow tracking of nuclear movements in cells under varying levels of shear and compressive force. Under adequate shear stress two distinct regimes develop in cells under mechanical stimulation: an initial event of increased intranuclear movement followed by a regime of intranuclear movements that reflect the dose of applied force. At early times there is a nondirectionally oriented response with a small increase in nuclear translocations. After 30 min, there is a significant increase in nuclear movements, which scales with the amount of shear or compressive stress. The similarities in the nuclear response to shear and compressive stress suggest that the nucleus is a mechanosensitive element within the cell. Thus, applied extracellular forces stimulate intranuclear movements, resulting in repositioning of nuclear bodies and the associated chromatin within the nucleus. 相似文献
983.
AtPTR4 and AtPTR6 are differentially expressed,tonoplast-localized members of the peptide transporter/nitrate transporter 1 (PTR/NRT1) family 总被引:1,自引:0,他引:1
Weichert A Brinkmann C Komarova NY Dietrich D Thor K Meier S Suter Grotemeyer M Rentsch D 《Planta》2012,235(2):311-323
Members of the peptide transporter/nitrate transporter 1 (PTR/NRT1) family in plants transport a variety of substrates like
nitrate, di- and tripepetides, auxin and carboxylates. We isolated two members of this family from Arabidopsis, AtPTR4 and AtPTR6, which are highly homologous to the characterized di- and tripeptide transporters AtPTR1, AtPTR2 and AtPTR5.
All known substrates of members of the PTR/NRT1 family were tested using heterologous expression in Saccharomyces cerevisiae mutants and oocytes of Xenopus laevis, but none could be identified as substrate of AtPTR4 or AtPTR6. AtPTR4 and AtPTR6 show distinct expression patterns, while AtPTR4 is expressed in the vasculature of the plants, AtPTR6 is highly expressed in pollen and during senescence. Phylogenetic analyses revealed that AtPTR2, 4 and 6 belong to one clade
of subgoup II, whereas AtPTR1 and 5 are found in a second clade. Like AtPTR2, AtPTR4-GFP and AtPTR6-GFP fusion proteins are
localized at the tonoplast. Vacuolar localization was corroborated by co-localization of AtPTR2-YFP with the tonoplast marker
protein GFP-AtTIP2;1 and AtTIP1;1-GFP. This indicates that the two clades reflect different intracellular localization at
the tonoplast (AtPTR2, 4, 6) and plasma membrane (AtPTR1, 5), respectively. 相似文献
984.
985.
Neutrophils are among the first cells to arrive at the site of injury. Chemokines secreted by neutrophils affect the migration of both neutrophils and other inflammatory cells, such as monocytes. It has been reported that LPS-induced release of IL-8 (CXCL-8) by neutrophils is amplified by neutrophil-derived TNF-α. We hypothesize that chemokine release by neutrophils is altered in chronic obstructive pulmonary disease (COPD) compared with healthy controls and that TNF-α may be involved in this alteration. Peripheral blood neutrophils isolated from smokers with COPD (n?=?12), smokers without COPD (n?=?12) and healthy, non-smokers (n?=?12) were stimulated with LPS, TNF-α or organic dust. Anti-TNF-α Ab (infliximab) was used to study the effect of neutrophil-derived TNF-α. Release of CXCL-8, macrophage inflammatory protein-1 α (MIP-1α, CCL-3), monocyte chemotactic protein-1 (MCP-1, CCL-2) and TNF-α was measured. Neutrophils spontaneously released CXCL-8, CCL-2 and CCL-3. Inhibition of TNF-α reduced the spontaneous release of CXCL-8 and CCL-3. Stimulation with LPS and organic dust increased the release of CXCL-8 and CCL-3 (but not CCL-2) which was reduced by inhibition of TNF-α. In the COPD group, inhibition of TNF-α failed to inhibit the release of LPS-induced CXCL-8. The role of neutrophils as cytokine and chemokine producers was confirmed. Neutrophil-derived TNF-α contributed to the release of chemokines after stimulation with LPS and organic dust, as the response was inhibited by infliximab. In the COPD group, infliximab did not significantly inhibit the release of CXCL-8, suggesting that the role of TNF-α is altered in COPD. 相似文献
986.
Jansen JJ Szymańska E Hoefsloot HC Jacobs DM Strassburg K Smilde AK 《Metabolomics : Official journal of the Metabolomic Society》2012,8(3):422-432
Not only the levels of individual metabolites, but also the relations between the levels of different metabolites may indicate (experimentally induced) changes in a biological system. Component analysis methods in current 'standard' use for metabolomics, such as Principal Component Analysis (PCA), do not focus on changes in these relations. We therefore propose the concept of 'Between Metabolite Relationships' (BMRs): common changes in the covariance (or correlation) between all metabolites in an organism. Such structural changes may indicate metabolic change brought about by experimental manipulation but which are lost with standard data analysis methods. These BMRs can be analysed by the INdividual Differences SCALing (INDSCAL) method. First the BMR quantification is described and subsequently the INDSCAL method. Finally, two studies illustrate the power and the applicability of BMRs in metabolomics. The first study is about the induced plant response of cabbage to herbivory, of which BMRs are a considerable part. In the second study-a human nutritional intervention study of green tea extract-standard data analysis tools did not reveal any metabolic change, although the BMRs were considerably affected. The presented results show that BMRs can be easily implemented in a wide variety of metabolomic studies. They provide a new source of information to describe biological systems in a way that fits flawlessly into the next generation of systems biology questions, dealing with personalized responses. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11306-011-0316-1) contains supplementary material, which is available to authorized users. 相似文献
987.
Christin Büchner Susann Thomas Doris Jaros Harald Rohm 《Engineering in Life Science》2012,12(1):109-112
The knowledge of thermal inactivation kinetics, usually expressed in terms of D‐ and z‐values, is of crucial importance for the design of sanitation and sterilization processes. In this study, we designed a simple, fast‐responding, and mechanically stable aluminum tube for inactivation measurements and compared these experiments with the successive‐sampling method at different temperatures. Up to 65°C, we determined a come‐up time of approximately 15 s for the tubes, which is lower than the corresponding values of other devices, presumably because of lower wall thickness, material properties, and a higher surface to volume ratio. D‐values of Escherichia coli calculated from tube inactivation experiments by first‐order kinetics were 370 s (56°C), 126 s (58°C), 53.2 s (60°C), 33.8 s (62°C), and 3.22 s (65°C), and the corresponding values determined with the successive‐sampling flask method were insignificantly different (417, 138, 48.6, and 29.1 s for 56, 58, 60, and 62°C, respectively). These data as well as those measured for Enterobacter cloacae, Pseudomonas putida, Serratia odorifera, and Yersinia rhodei were in close accordance with literature values. 相似文献
988.
Background
Subjects with Attention-Deficit Hyperactivity Disorder (ADHD) are overdistractible by stimuli out of the intended focus of attention. This control deficit could be due to primarily reduced attentional capacities or, e. g., to overshooting orienting to unexpected events. Here, we aimed at identifying disease-related abnormalities of novelty processing and, therefore, studied event-related potentials (ERP) to respective stimuli in adult ADHD patients compared to healthy subjects.Methods
Fifteen unmedicated subjects with ADHD and fifteen matched controls engaged in a visual oddball task (OT) under simultaneous EEG recordings. A target stimulus, upon which a motor response was required, and non-target stimuli, which did not demand a specific reaction, were presented in random order. Target and most non-target stimuli were presented repeatedly, but some non-target stimuli occurred only once (‘novels’). These unique stimuli were either ‘relative novels’ with which a meaning could be associated, or ‘complete novels’, if no association was available.Results
In frontal recordings, a positive component with a peak latency of some 400 ms became maximal after novels. In healthy subjects, this novelty-P3 (or ‘orienting response’) was of higher magnitude after complete than after relative novels, in contrast to the patients with an undifferentially high frontal responsivity. Instead, ADHD patients tended to smaller centro-parietal P3 responses after target signals and, on a behavioural level, responded slower than controls.Conclusion
The results demonstrate abnormal novelty processing in adult subjects with ADHD. In controls, the ERP pattern indicates that allocation of meaning modulates the processing of new stimuli. However, in ADHD such a modulation was not prevalent. Instead, also familiar, only context-wise new stimuli were treated as complete novels. We propose that disturbed semantic processing of new stimuli resembles a mechanism for excessive orienting to commonly negligible stimuli in ADHD. 相似文献989.
Demonstration of Allelic Exchange in the Slow-Growing Bacterium Mycobacterium avium subsp. paratuberculosis, and Generation of Mutants with Deletions at the pknG, relA, and lsr2 Loci 下载免费PDF全文
Kun Taek Park John L. Dahl John P. Bannantine Raúl G. Barletta Jongsam Ahn Andrew J. Allen Mary Jo Hamilton William C. Davis 《Applied microbiology》2008,74(6):1687-1695
Mycobacterium avium subsp. paratuberculosis is the causative pathogen of Johne's disease, a chronic inflammatory wasting disease in ruminants. This disease has been difficult to control because of the lack of an effective vaccine. To address this need, we adapted a specialized transduction system originally developed for M. tuberculosis and modified it to improve the efficiency of allelic exchange in order to generate site-directed mutations in preselected M. avium subsp. paratuberculosis genes. With our novel optimized method, the allelic exchange frequency was 78 to 100% and the transduction frequency was 1.1 × 10−7 to 2.9 × 10−7. Three genes were selected for mutagenesis: pknG and relA, which are genes that are known to be important virulence factors in M. tuberculosis and M. bovis, and lsr2, a gene regulating lipid biosynthesis and antibiotic resistance. Mutants were successfully generated with a virulent strain of M. avium subsp. paratuberculosis (M. avium subsp. paratuberculosis K10) and with a recombinant K10 strain expressing the green fluorescent protein gene, gfp. The improved efficiency of disruption of selected genes in M. avium subsp. paratuberculosis should accelerate development of additional mutants for vaccine testing and functional studies. 相似文献
990.
Engineering of a Glycerol Utilization Pathway for Amino Acid Production by Corynebacterium glutamicum 下载免费PDF全文
The amino acid-producing organism Corynebacterium glutamicum cannot utilize glycerol, a stoichiometric by-product of biodiesel production. By heterologous expression of Escherichia coli glycerol utilization genes, C. glutamicum was engineered to grow on glycerol. While expression of the E. coli genes for glycerol kinase (glpK) and glycerol 3-phosphate dehydrogenase (glpD) was sufficient for growth on glycerol as the sole carbon and energy source, additional expression of the aquaglyceroporin gene glpF from E. coli increased growth rate and biomass formation. Glutamate production from glycerol was enabled by plasmid-borne expression of E. coli glpF, glpK, and glpD in C. glutamicum wild type. In addition, a lysine-producing C. glutamicum strain expressing E. coli glpF, glpK, and glpD was able to produce lysine from glycerol as the sole carbon substrate as well as from glycerol-glucose mixtures. 相似文献