6 research outputs found
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Changes in myofibrils and cytoskeleton of neonatal hamster myocardial cells in culture: An immunofluorescence study
Myocardial cells in culture offer many possibilities for studying cellular and molecular biology of cardiac muscles. However, it is important to know how long these cells can be maintained in vitro without significant structural and biochemical changes. In this study, we have investigated the morphological changes of myofibril proteins and cytoskeletons by using immunofluorescent techniques in cultured neonatal hamster myocardial cells at different culture durations. Our results have demonstrated that these cultured cells still contain intact myofibrils and cytoskeletal proteins after 6 days in vitro incubation, however, the organization of some of these proteins is altered. The proteins most sensitive to these in vitro conditions are: myosin heavy chain, actin and desmin. The data indicate that the duration of the culture and the contractile activity of the myocardial cells in culture can influence organization of their contractile apparatus and cytoskeleton
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Downregulation of N1 gene expression inhibits the initial heartbeating and heart development in axolotls
Recessive mutant gene
c in the axolotl results in a failure of affected embryos to develop contracting hearts. This abnormality can be corrected by treating the mutant heart with RNA isolated from normal anterior endoderm or from endoderm conditioned medium. A cDNA library was constructed from the total conditioned medium RNA using a random priming technique in a pcDNAII vector. We have previously identified a clone (designated as N1) from the constructed axolotl cDNA library, which has a unique nucleotide sequence. We have also discovered that the N1 gene product is related to heart development in the Mexican axolotl [Cell Mol. Biol. Res. 41 (1995) 117]. In the present studies, we further investigate the role of N1 on heartbeating and heart development in axolotls. N1 mRNA expression has been determined by using semi-quantitative RT–PCR with specifically designed primers. Normal embryonic hearts (at stages 30–31) have been transfected with anti-sense oligonucleotides against N1 to determine if downregulation of N1 gene expression has any effect on normal heart development. Our results show that cardiac N1 mRNA expression is partially blocked in the hearts transfected with anti-sense nucleotides and the downregulation of N1 gene expression results in a decrease of heartbeating in normal embryos, although the hearts remain alive as indicated by calcium spike movement throughout the hearts. Confocal microscopy data indicate some myofibril disorganization in the hearts transfected with the anti-sense N1 oligonucleotides. Interestingly, we also find that N1 gene expression is significantly decreased in the mutant axolotl hearts. Our results suggest that N1 is a novel gene in Mexican axolotls and it probably plays an important role in myofibrillogenesis and in the initiation of heartbeating during heart development
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Molecular and immunohistochemical analyses of cardiac troponin T during cardiac development in the Mexican axolotl, Ambystoma mexicanum
Supplementary Material for: Loss of Maspardin Attenuates the Growth and Maturation of Mouse Cortical Neurons
<br><strong><em>Background:</em></strong> Mast syndrome, an autosomal recessive, progressive form of hereditary spastic paraplegia, is associated with mutations in SPG21 loci that encode maspardin protein. Although SPG21<sup>-/-</sup> mice exhibit lower limb dysfunction, the role of maspardin loss in mast syndrome is unclear. <b><i>Objective:</i></b> To test the hypothesis that loss of maspardin attenuates the growth and maturation of cortical neurons in SPG21<sup>-/-</sup> mice. <b><i>Methods and Results:</i></b> In a randomized experimental design SPG21<sup>-/-</sup> mice demonstrated significantly less agility and coordination compared to wild-type mice in beam walk, ledge, and hind limb clasp tests for assessing neuronal dysfunction (p ≤ 0.05). The SPG21<sup>-/-</sup> mice exhibited symptoms of mast syndrome at 6 months which worsened in 12-month-old cohort, suggesting progressive dysfunction of motor neurons. Ex vivo, wild-type cortical neurons formed synapses, ganglia and aggregates at 96 h, whereas SPG21<sup>-/-</sup> neurons exhibited attenuated growth with markedly less axonal branches. Additionally, epidermal growth factor markedly promoted the growth and maturation of SPG21<sup>+/+</sup> cortical neurons but not SPG21<sup>-/-</sup> neurons. Consequently, quantitative RT-PCR identified a significant reduction in the expression of a subset of EGF-EGFR signaling targets. <b><i>Conclusions:</i></b> Our current study uncovered a direct role for maspardin in normal and EGF-induced growth and maturation of primary cortical neurons. The loss of maspardin resulted in attenuated growth, axonal branching, and attenuation of EGF signaling. Reinstating the functions of maspardin may reverse hind limb impairment associated with neuronal dysfunction in mast syndrome patients