Developmental Fate of Artificially Disordered Somite Cells after Heteroplastic Transplantation

A disordered somite pattern could be produced artificially when the segmental lateral plate of chick embryo was replaced by dissociated cells of quail segmental pate.The artificially disordered somite pattern formed at either place was used in our work as a model to analyze the mechanism of the development and differentiation of somite on chick embryo. Our conclusions include the following: 1.Although the formation of somites from the dissociated segmental plate cells does not require special environment,the development and differentiation of the somltes require a special environment which is related to the neural tube and notochord.The effect of this special environmental factor may decrease gradually with the increase of the distance from neural tube to lateral plate. 2.The somites located on paraxial area at different distances to the axis have different fates in development. 3.The formation of epithelial vesicles is the property of somite cells and the epithelial vesicle is the structural basis of somite differentiation.If and factor interferes with the differentiation of the somite,the epithelial vesicle of the somite will be degenerated within certain period of time. 4.During resegmentation of the somite,the number,size and arrangement of sclerotome in situ do not depend on the somite from which they are derived. 5.Somite cells do not transdifferentiate into kidney tubule directly from their original epithelial vesicles,but are reorganized from the free cells dispersed from the disrupted somites. 6.The establishment of cell commitment may involve several steps.Before commitment is established the of cell commitment is labile. 7.The differentiation of sclerotome starts with the rupture of epithelial wall of somites and the direction of its movement depends not only on the notochord but also on their position with respect to the neural tube and notochord. 8.The disordered somite pattern doesn't influence the segmentation of dorsal root ganglia in situ, but causes the formation of the ectopic dorsal root ganglia.

Somite-specific expression of a novel fibronectin variant FN3 is negatively regulated by SHH

Fibronectins (FNs) are major extracellular proteins in blood plasma and many tissues of vertebrates, and play important roles in adhesion, migration and differentiation of cells. We have identified a novel variant (FN3) of fibronectin in zebrafish. FN3 mRNA is abundant, as detected by whole-mount in situ hybridization, in the presomitic mesoderm and the newly formed somites, but less abundant in mature somites. Ectopic expression of Sonic Hedgehog (SHH) results in a decrease of FN3 expression, whereas the expression level of FN3 increases in the flhi mutants that lack the notochord. Our results suggest that FN3 may be involved in the formation of somites, but during somite differentiation its expression needs to be downregulated by signals derived from the axial tissues.

Mechanism of acupuncture regulating visceral sensation and mobility

Chinese ancient medical scientists have long focused on the internal and external contacts between acupoints on the surface of the body and the viscera.The Miraculous Pivot(it is one of the earliest medical classics in China)stated,“Twelve regular channels belong to the zang-fu organs internally,and connect to the extremities and joints externally.”Traditional Chinese medicine considers acupoints as defined areas where the Qi of viscera and meridians are transfused.These include the reaction points of visceral diseases on the body surface as well as the acupuncture trigger points that promote the flow of Qi and blood,and regulate visceral function.Chinese ancient medical scientists classified the specificity of the main acupoints in the body based on the meridian doctrine,which has been instructing clinical application for about 2000 years.Laws on the domino effect of acupoints have mainly focused on conclusions to clinical experiences.Indications of some acupoints exceed the practical paradigm since the excessive extension occurred during theory derivation.The current research direction on acupuncture focuses on three aspects:the effectiveness of acupuncture and moxibustion;the relevances and associations between meridians and viscera;and the physical and chemical properties and relevant physical basis of acupoints.The relevance between meridians and viscera is the central theory in the meridian doctrine,and acupoints are regarded as an important link in the relationship between meridians and viscera.Specific relationships between acupoints and target organs exist.Stimulating different acupoints on the body surface can help deal with different diseases,especially visceral diseases.In addition,acupoints have a dual function of reflecting and treating visceral diseases.There is no systemic research available on acupoint specificity,despite current knowledge and clinical experiences,which results in a weak foundation for acupuncture theory.This study focuses on the relevance and associations between meridians and viscera.A summary of the mechanisms of acupuncture regulating visceral sensation and mobility and the specific relationships between acupoints and their target organs are presented in this review.

Molecular analyses of Xenopus laevis Mesp-related genes

During vertebrate somitogenesis,somites bud off from the anterior end of the presomitic mesoderm(PSM).Meso-dermal posterior(Mesp)-related genes play essential roles in somitogenesis,particularly in the definition of the somite boundary position.Among vertebrates,two types of Mesp-related genes have been identified:Mesp1 and Mesp2 in the mouse;Meso-1 and Meso-2 in the chicken;Xl-mespa and Xl-mespb(also known as Thylacine1)in the African clawed frog(Xenopus laevis);and mesp-a and mesp-b in the zebrafish.However,the functional differences between two Mesp-related genes remain unknown.In the present study,we carried out comparative analyses of the Xl-mespa and Xl-mespb genes.The amino acid sequences of the Xl-mespa and Xl-mespb proteins showed a high level of similarity.The expression of Xl-mespa started broadly in the ventrolateral mesoderm and gradually shifted to a striped pattern of expression.In contrast,Xl-mespb showed a striped pattern of expression from the start.These expression profiles completely overlapped at the PSM during somitogenesis.To investigate the functional differ-ences between Xl-mespa and Xl-mespb in terms of target gene regulation,we carried out a luciferase assay using the murine Lunatic fringe(L-fng)promoter.Transcription of the L-fng promoter was activated more strongly by Xl-mespb than by Xl-mespa.This same pattern was observed for the murine Mesp-related proteins.These results suggest that the functional differences between the two types of Mesp-related genes are evolutionally conserved in vertebrates.