RESUMO
A novel developmental mutant in the Mexican axolotl is described. Designated redneck (rn), the mutant gene is inherited as a simple Mendelian recessive. In homozygotes, rn causes massive haemorrhage in the posterior head, rostrocaudal compression of the craniovisceral skeleton, abnormal differentiation of vertebral cartilage, micrognathia, aglossia, microphthalmia and abnormal hepatic development. Affected larvae become evident at the onset of feeding, and eventually die of starvation. Based on the tissues affected, we propose that rn affects later developmental events in the differentiation and morphogenesis of a subset of cranial neural crest cells. Thus, rn may prove a valuable model system for examining the role of neural crest cells in the development of cranial and endodermal derivatives.
Assuntos
Regulação da Expressão Gênica no Desenvolvimento , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/fisiologia , Crista Neural/embriologia , Ambystoma , Animais , Diferenciação Celular , Feminino , Homozigoto , Hibridização In Situ , Masculino , Mutação , Neovascularização Fisiológica , LinhagemRESUMO
To establish whether a region of the cranial neural crest contributes cells to the developing heart of Ambystoma mexicanum (axolotl), as it does in many other vertebrates, we constructed a fate map for the neural crest in late neurula stage (stage 19-20) embryos. The fluorescent vital dye, Dil, was used as the lineage label. The various regions of the cranial neural folds were identified in relation to such landmarks as the developing forebrain, midbrain and hindbrain, and the appearance and extent of emerging somites. Labelled cells originating in the rhombencephalic region were found in the aortic arches and in the truncus arteriosus, and occasionally in the walls of the conus arteriosus. Cells were also found in the third and fourth branchial arches. Labelled neural crest from the adjacent anterior trunk region appeared neither in the heart nor the visceral skeleton, whereas those from the mesencephalic region contributed to the first hypobranchial cartilage and to the first three branchial arches, but not to the heart. No labelled cells from any of the regions were seen in the ventricle or auricle.
Assuntos
Ambystoma mexicanum/embriologia , Movimento Celular , Coração/embriologia , Crista Neural/embriologia , Animais , Diferenciação Celular , Miocárdio/citologia , Crista Neural/citologiaRESUMO
UNLABELLED: In older children with cystic fibrosis (CF), well-documented improvements in lung function occur during hospitalization for treatment of pulmonary exacerbations. OBJECTIVES: (1) To test the hypothesis that improvement in lung function occurs in infants and toddlers hospitalized because of CF pulmonary exacerbations. (2) To compare changes in lung function measured during forced expiratory flow and tidal breathing. STUDY DESIGN: Seventeen infants and toddlers with CF were evaluated at the beginning and end of hospitalization by the rapid thoracic compression technique to yield maximal flow at forced residual capacity. Tidal mechanics were measured by the esophageal balloon technique to yield lung conductance and compliance. RESULTS: Lung function improved during the course of hospitalization. The greatest change was observed in measurements of maximal flow at functional residual capacity (.VmaxFRC), increasing from 38.5% +/- 6% predicted (mean +/- SEM) to 59.8% +/- 6% at the end (p < 0.005). Lung conductance (GL) increased from 60% +/- 6% to 78% +/- 8% (p < 0.02); lung compliance (CL) increased from 66% +/- 5% to 75% +/- 5% (p < 0.03). The degree of improvement of .VmaxFRC, GL, and CL was related to baseline measurements; those with poorer pulmonary function at baseline had the greatest degree of improvement during hospitalization. CONCLUSION: Assessments of airflow obstruction from measurements of .VmaxFRC and GL do not necessarily demonstrate similar findings in a given infant with CF, perhaps because these two techniques measure different physiologic properties. Changes in .VmaxFRC may best reflect the predominant pathophysiology of lung disease in infants and toddlers with CF.