Home About us Contact
|
Home About us Contact | ||
|
|
||
Knockout Animals (knockout + animals)
Selected AbstractsAltered neuronal responses and regulation of neurotrophic proteins in the medial septum following fimbria-fornix transection in CNTF- and leukaemia inhibitory factor-deficient miceEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2006Thomas Naumann Abstract Degeneration of axotomized GABAergic septohippocampal neurones has been shown to be enhanced in ciliary neurotrophic factor (CNTF)-deficient mice following fimbria-fornix transection (FFT), indicating a neuroprotective function of endogenous CNTF. Paradoxically, however, the cholinergic population of septohippocampal neurones was more resistant to axotomy in these mutants. As leukaemia inhibitory factor (LIF) has been identified as a potential neuroprotective factor for the cholinergic medial septum (MS) neurones, FFT-induced responses were compared in CNTF,/,, LIF,/, and CNTF/LIF double knockout mice. In CNTF,/, mice, FFT-induced cholinergic degeneration was confirmed to be attenuated as compared with wildtype mice. The expression of both LIF and LIF receptor , was increased in the MS providing a possible explanation for the enhanced neuronal resistance to FFT in these animals. However, ablation of the LIF gene also produced paradoxical effects; following FFT in LIF,/, mice no loss of GABAergic or cholinergic MS neurones was detectable during the first postlesional week, suggesting that other efficient neuroprotective mechanisms are activated in these animals. In fact, enhanced activation of astrocytes, a source of neurotrophic proteins, was indicated by increased up-regulation of glial fibrillary acidic protein and vimentin expression. In addition, mRNA levels for neurotrophin signalling components (e.g. nerve growth factor, p75NTR) were differentially regulated. The positive effect on axotomized cholinergic neurones seen in CNTF,/, and LIF,/, mice as well as the increased up-regulation of astrogliose markers was abolished in CNTF/LIF double knockout animals. Our results indicate that endogenous CNTF and LIF are involved in the regulation of neuronal survival following central nervous system lesion and are integrated into a network of neurotrophic signals that mutually influence their expression and function. [source] Activation of the galanin receptor 2 (GalR2) protects the hippocampus from neuronal damageJOURNAL OF NEUROCHEMISTRY, Issue 3 2007Caroline R. Elliott-Hunt Abstract Expression of the neuropeptide galanin is up-regulated in many brain regions following nerve injury and in the basal forebrain of patients with Alzheimer's disease. We have previously demonstrated that galanin modulates hippocampal neuronal survival, although it was unclear which receptor subtype(s) mediates this effect. Here we report that the protective role played by galanin in hippocampal cultures is abolished in animals carrying a loss-of-function mutation in the second galanin receptor subtype (GalR2-MUT). Exogenous galanin stimulates the phosphorylation of the serine/threonine kinase Akt and extracellular signal-regulated kinase (ERK) in wild-type (WT) cultures by 435 ± 5% and 278 ± 2%, respectively. The glutamate-induced activation of Akt was abolished in cultures from galanin knockout animals, and was markedly attenuated in GalR2-MUT animals, compared with WT controls. In contrast, similar levels of glutamate-induced ERK activation were observed in both loss-of-function mutants, but were further increased in galanin over-expressing animals. Using specific inhibitors of either ERK or Akt confirms that a GalR2-dependent modulation in the activation of the Akt and ERK signalling pathways contributes to the protective effects of galanin. These findings imply that the rise in endogenous galanin observed either after brain injury or in various disease states is an adaptive response that reduces apoptosis by the activation of GalR2, and hence Akt and ERK. [source] Increased synthesis but decreased processing of neuronal proCCK in prohormone convertase 2 and 7B2 knockout animalsJOURNAL OF NEUROCHEMISTRY, Issue 6 2002Jens F. Rehfeld Abstract In addition to its role as a gut hormone, cholecystokinin (CCK) is a widespread and potent neurotransmitter. Its biosynthesis requires endoproteolytic cleavage of proCCK at several mono- and dibasic sites by subtilisin-like prohormone convertases (PCs). Of these, PC1 and PC2 are specific for neuroendocrine cells. We have now examined the role of PC2 and its binding protein, 7B2, in the neuronal processing of proCCK by measurement of precursor, processing-intermediates and bioactive end-products in brain extracts from PC2- and 7B2-null mice and from corresponding controls. PC2-null mice displayed a nine-fold increase of cerebral proCCK concentrations, and a two-fold increase in the concentrations of the processing-intermediate, glycine-extended CCK, whereas the concentrations of transmitter-active (i.e. ,-amidated and O -sulfated) CCK peptides were reduced (61%). Chromatography showed that O -sulfated CCK-8 still is the predominant transmitter-active CCK in PC2-null brains, but that the fraction of intermediate-sized CCK-peptides (CCK-58, -33 and -22) was eight-fold increased. 7B2-null brains displayed a similar pattern but with less pronounced precursor accumulation. In contrast with the cerebral changes, PC2 deficiency was without effect on proCCK synthesis and processing in intestinal endocrine cells, whereas 7B2 deficiency halved the concentration of bioactive CCK in the intestine. The results show that PC2 plays a major neuron-specific role in the processing of proCCK. [source] Nicotinic acetylcholine receptor-subunit mRNAs in the mouse superior cervical ganglion are regulated by development but not by deletion of distinct subunit genesJOURNAL OF NEUROSCIENCE RESEARCH, Issue 5 2008G. Putz Abstract Mice with deletions of nicotinic ACh receptor (nAChR) subunit genes are valuable models for studying nAChR functions. We could previously show in the mouse superior cervical ganglion (SCG) that the absence of distinct subunits affects the functional properties of receptors. Here, we have addressed the question of whether deletions of the subunits ,5, ,7, or ,2 are compensated at the mRNA level, monitored by reverse transcription and quantitative real-time polymerase chain reaction. Relative to our reference gene, ,3, which is expressed in all SCG nAChRs, mRNA levels of ,4 showed little change from birth until adult ages in intact ganglia of wild-type mice. In contrast, ,4 declined sharply after birth and was barely detectable in adult animals. ,5, ,7, and ,2 subunit message levels also declined, though more slowly and less completely than ,4. The subunits ,6 and ,3 were detected by conventional polymerase chain reaction at very low levels, if at all, whereas ,2 was never seen in any of our samples. The developmental profile of nAChR mRNA levels in the three knockout strains did not differ markedly from that of wild-type mice. Likewise, message levels of nAChR subunits were similar in cultures prepared from either wild-type or knockout animals. Our observations indicate a developmental regulation of nAChR subunit mRNAs in the SCG of mice after birth that was not affected by the three knockouts under investigation. © 2007 Wiley-Liss, Inc. [source] Protein tyrosine phosphatase ,-deficient mice show aberrant cytoarchitecture and structural abnormalities in the central nervous systemJOURNAL OF NEUROSCIENCE RESEARCH, Issue 1 2002Karen Meathrel Abstract Protein tyrosine phosphatase , (PTP,) is a member of the LAR family of receptor tyrosine phosphatases and is highly expressed in the nervous system during development. PTP, is homologous to the Drosophila DLAR, which plays a key role in the targeting of axonal growth cones in flies. We have previously inactivated the Ptprs gene in mice and demonstrated stunted growth, developmental delays, and neurological and neuroendocrine defects in the PTP, null animals. Here, we mapped the expression of the lac-Z reporter gene included in the knockout cassette and surveyed the development of the CNS in these mice after birth. The strongest expression of ,-galactosidase (PTP,) was observed in the hippocampus, cerebral cortex, olfactory bulbs, and subependymal layer. Our analysis reveals hippocampal dysgenesis, reductions in the thickness of the corpus callosum and the cerebral cortex, and late expression of the growth-associated protein 43 (GAP-43) in the knockout animals. Architectural abnormalities in the brain and spinal cord were confirmed by immunoreactivity to neurofilament and glial fibrillary acidic protein (GFAP) antibodies. Several of these neural abnormalities were corrected with age, suggesting a delay in neurological development related to the knockout of the Ptprs gene. These data suggest that PTP, is likely involved in neurogenesis, axonal growth, and axonal pathfinding in the maturation of the mammalian CNS. © 2002 Wiley-Liss, Inc. [source] Increased collagen and aggrecan degradation with age in the joints of Timp3,/, miceARTHRITIS & RHEUMATISM, Issue 3 2007Solmaz Sahebjam Objective To investigate the in vivo effect of an imbalance between metalloproteinases and their inhibitors, tissue inhibitors of metalloproteinases (TIMPs), in mouse articular cartilage. Methods Hind joints of Timp3,/, and wild-type mice were examined by routine staining and by immunohistochemical analysis using antibodies specific for type X collagen and for the neoepitopes produced on proteolytic cleavage of aggrecan (, VDIPEN and , NVTEGE) and type II collagen. The neoepitope generated on cleavage of type II collagen by collagenases was quantitated in sera by enzyme-linked immunosorbent assay. Results Articular cartilage from Timp3 -knockout animals (ages ,6 months) showed reduced Safranin O staining and an increase in ,VDIPEN content compared with cartilage from heterozygous and wild-type animals. There was also a slight increase in , NVTEGE content in articular cartilage and menisci of Timp3,/, animals. Chondrocytes showed strong pericellular staining for type II collagen cleavage neoepitopes, particularly in the superficial layer, in knockout mice. Also, there was more type X collagen expression in the superficial zone of articular cartilage, especially around clusters of proliferating chondrocytes, in the knockout mice. More type II collagen cleavage product was found in the serum of Timp3,/, mice compared with wild-type animals. This increase was significant in 15-month-old animals. Conclusion These results indicate that TIMP-3 deficiency results in mild cartilage degradation similar to changes seen in patients with osteoarthritis, suggesting that an imbalance between metalloproteinases and TIMP-3 may play a pathophysiologic role in the development of this disease. [source] Knockout of ,1 - and ,2 -adrenoceptors attenuates pressure overload-induced cardiac hypertrophy and fibrosisBRITISH JOURNAL OF PHARMACOLOGY, Issue 4 2008H Kiriazis Background and purpose: The role of ,-adrenoceptors in heart disease remains controversial. Although ,-blockers ameliorate the progression of heart disease, the mechanism remains undefined. We investigated the effect of ,-adrenoceptors on cardiac hypertrophic growth using ,1 - and ,2 -adrenoreceptor knockout and wild-type (WT) mice. Experimental approach: Mice were subjected to aortic banding or sham surgery, and their cardiac function was determined by echocardiography and micromanometry. Key results: At 4 and 12 weeks after aortic banding, the left ventricle:body mass ratio was increased by 80,87% in wild-type mice, but only by 15% in knockouts, relative to sham-operated groups. Despite the blunted hypertrophic growth, ventricular function in knockouts was maintained. WT mice responded to pressure overload with up-regulation of gene expression of inflammatory cytokines and fibrogenic growth factors, and with severe cardiac fibrosis. All these effects were absent in the knockout animals. Conclusion and implications: Our findings of a markedly attenuated cardiac hypertrophy and fibrosis following pressure overload in this knockout model emphasize that ,-adrenoceptor signalling plays a central role in cardiac hypertrophy and maladaptation following pressure overload. British Journal of Pharmacology (2008) 153, 684,692; doi:10.1038/sj.bjp.0707622; published online 14 January 2008 [source] | |||||||||||||