Origins of techniques in human and animal embryology

Increasingly innovative and imaginative techniques are being developed to investigate the development of animal and human embryos. Among the types of techniques that have been developed are ones that deal with oocyte maturation and culture, the isolation and utilization of stem cells, cryopreservation of reproductive cells and tissues, and various procedures to manipulate early embryos. To appreciate the derivation of these sophisticated techniques, it seems appropriate to consider the very early origins of these current techniques.     

From presence to consciousness through virtual reality

Immersive virtual environments can break the deep, everyday connection between where our senses tell us we are and where we are actually located and whom we are with. The concept of 'presence' refers to the phenomenon of behaving and feeling as if we are in the virtual world created by computer displays. In this article, we argue that presence is worthy of study by neuroscientists, and that it might aid the study of perception and consciousness.     

Introductory class exercises in experimental embryology using Xenopus laevis

Abstract

This paper describes classical experiments of experimental embryology which may be repeated at class level using the early embryos of Xenopus laevis. The experiments demonstrate the effects of lithium on the early development of the nervous system, and the use of hypertonic salt solutions to produce exogastrulation. Both experiments involve the removal of the jelly coats around the embryo, and for this purpose a rapid chemical method using a cysteine hydrochloride/papain solution is described. Both experiments are theoretically important: the effects of lithium are used as evidence for the existence of an anterior-posterior gradient in the early embryo, while exogastrulation provides a convenient system for interfering with the primary inductive effect of the chordo-mesoderm, necessary for ectodermal neuralization.

The procedure for obtaining fertile eggs from mature Xenopus specimens by injection of mammalian chorionic gonadotrophin is described.     

From medical imaging to image-guided therapy

This survey on medical imaging provides a look into three major components. The first one deals with the full steps through which it must be apprehended: from the sensors to the reconstruction, from the image analysis up to its interpretation. The second aspect describes the physical principles used for imaging (magnetic resonance, acoustic, optics, etc.). The last section shows how imaging is involved in therapeutic procedures and in particular the new physical therapies. All along this paper, the research perspectives are sketched.     

Sclerotome development and morphogenesis: when experimental embryology meets genetics

The vertebra develops from the ventral part of the somite, the sclerotome. Sclerotome progenitors are subject to multiple signaling molecules secreted by the adjacent tissues that control their fate. The aim of this article is to discuss the mechanisms of sclerotome induction, chondrogenesis and morphogenesis. By integrating the results from classical studies and recent molecular advances, this will illustrate how the powerful combination of experimental embryology and genetic approaches has recently illuminated the multiple steps of vertebra formation.     

Contribution of late Professor T. C. Tung to the experimental embryology of Amphioxus

Professor T. C. Tung (Fig. 1) was a prominent experimental embryologist in China. He was born in Jin County, Zhejiang Province, China in 1902. After he obtained his Bachelor's degree from the Department of Biology, Fudan University, Shanghai in 1927, he was appointed as a teaching assistant in that department until he moved to Belgium in 1930. He studied as a graduate student in Professors A. Brachet and A. M. Dalcq's laboratory at the Universite Libre de Bruxelles, Belgium and obtained his Doctor of Science degree there in 1934. During that period, he made two short working visits to the Institute of Marine Biology in France and took one training course at Cambridge University (UK). In 1934, he was invited to return to China as a Full Professor to teach at several Chinese universities, (Shandong University in Qingdao, Shandong Province; the National University in Nanjing; and Fudan University in Shanghai). He spent 1 year at Yale University (USA) between 1948 and 1949 as an invited scientist in a joint research project and finally returned to China in 1949. He was Chairman of the Department of Zoology, Shandong University in Qingdao (1949-1952), Vice-President of Shandong University (1952-1960), Director of the Marine Biological Institute, the Chinese Academy of Sciences (CAS) in Qingdao (1949-1958), Director of the Institute of Oceanology (CAS) in Qingdao (1959-1966), Director of the Institute of Zoology (CAS) in Beijing (1960-1962), member of CAS since 1955, Vice-Chairman of the Biological and Geographical Division of CAS (1955-1958), Chairman of the Biological Division of CAS (1959-1979) and Vice-President of CAS in Beijing (1978-1979). In spite of his administrative duties, he spent most of his life conducting bench work in his laboratories at the Institutes of Oceanology and Zoology, CAS, respectively, until he passed away in March 1979. Professor Tung's main research interest was with classic experimental studies on the determination of the egg axis and symmetry planes of fertilized eggs, early differentiation and organizing substances of egg cytoplasm, induction between embryonic cells and cytoplasm in embryogenesis, immunological studies on nuclear transplanted eggs, and cell fusion etc., in several types of animals. He conducted his experiments on a number of invertebrates (ascidians and Amphioxus) and vertebrates (fish and amphibians) by means of very skillful microsurgical operations and the nuclear transplantation method. Among these topics, his studies on the organization and developmental potency of Amphioxus eggs were unique. His important contribution to this research field involved not only establishing a practical method for collecting and using this rare animal for experimental purposes, but also clarifying controversy about the nature and early development of its eggs. He also provided conclusive evidence to determine its evolutionary position between invertebrates and vertebrates. The present article briefly reviews the main results obtained by Professor Tung and his colleagues on Amphioxus. Although their original articles were written both in Chinese and English, many international readers may not even know those original works because they were only published in scientific journals inside China from the 1950s. Comments and discussion on the experimental results of Amphioxus research by Tung's group and those from other earlier authors are also included.     

Homo erectus from the Yunxian and Nankin Chinese sites: Anthropological insights using 3D virtual imaging techniques

Recent applications of 3D virtual imaging techniques in human palaeontology have increased the possibilities and the accuracy of anthropological analysis. Two examples are given for the reconsideration of fossils discovered more than 20 years ago, thanks to this new technology. The Lower and Middle Pleistocene skulls from Yunxian and Nankin in China, which were damaged in the process of fossilization, have been virtually reconstructed. A detailed reinvestigation has been conducted by considering those reconstructed skulls and their unpublished characters (i.e., inner anatomical features inaccessible until now). The results of this analysis provide new information about the early hominids of China and contribute to the discussion of variability in Homo erectus.     

Genetics of hypertension: From experimental animals to humans

Essential hypertension affects 20 to 30% of the population worldwide and contributes significantly to cardiovascular mortality and morbidity. Heridability of blood pressure is around 15 to 40% but there are also substantial environmental factors affecting blood pressure variability. It is assumed that blood pressure is under the control of a large number of genes each of which has only relatively mild effects. It has therefore been difficult to discover the genes that contribute to blood pressure variation using traditional approaches including candidate gene studies and linkage studies. Animal models of hypertension, particularly in the rat, have led to the discovery of quantitative trait loci harbouring one or several hypertension related genes, but translation of these findings into human essential hypertension remains challenging. Recent development of genotyping technology made large scale genome-wide association studies possible. This approach and the study of monogenic forms of hypertension has led to the discovery of novel and robust candidate genes for human essential hypertension, many of which require functional analysis in experimental models.     

Bringing classical embryology to C elegans gastrulation

In a recent paper, Lee and Goldstein develop an explant assay that recapitulates key aspects of gastrulation in C elegans and permits classical embryological manipulations. The resulting detailed analysis of cell behavior will ultimately extend to broader issues, such as, whether morphogenesis can be described as the sum of single-cell events or if unique phenomena emerge at the multicellular level.     

Inside out: modern imaging techniques to reveal animal anatomy

Animal anatomy has traditionally relied on detailed dissections to produce anatomical illustrations, but modern imaging modalities, such as MRI and CT, now represent an enormous resource that allows for fast non-invasive visualizations of animal anatomy in living animals. These modalities also allow for creation of three-dimensional representations that can be of considerable value in the dissemination of anatomical studies. In this methodological review, we present our experiences using MRI, CT and μCT to create advanced representation of animal anatomy, including bones, inner organs and blood vessels in a variety of animals, including fish, amphibians, reptiles, mammals, and spiders. The images have a similar quality to most traditional anatomical drawings and are presented together with interactive movies of the anatomical structures, where the object can be viewed from different angles. Given that clinical scanners found in the majority of larger hospitals are fully suitable for these purposes, we encourage biologists to take advantage of these imaging techniques in creation of three-dimensional graphical representations of internal structures.     

Advanced magnetic resonance imaging techniques to better understand multiple sclerosis

Magnetic resonance imaging (MRI) has considerably improved the diagnosis and monitoring of multiple sclerosis (MS). Conventional MRI such as T₂-weighted and gadolinium-enhanced T₁-weighted sequences detect focal lesions of the white matter, damage of the blood–brain barrier, and tissue loss and inflammatory activity within lesions. However, these conventional MRI metrics lack the specificity required for characterizing the underlying pathophysiology, especially diffuse damage occurring throughout the whole central nervous system. To overcome these limitations, advanced MRI techniques have been developed to get more sensitive and specific parameters of focal and diffuse brain damage. Among these techniques, magnetization transfer imaging, diffusion MRI, functional MRI, and magnetic resonance spectroscopy are the most significant. In this article, we provide an overview of these advanced MRI techniques and their contribution to the better characterization and understanding of MS.