China
Africa
Explore chapters and articles related to this topic
Comparative Immunology
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
Xenopus has a well-characterized MHC with Class I, II and III regions called XLA. The Class II region contains genes for both α and β chains. About twenty Class I and thirty Class II alleles are believed to exist. The Class III region contains a gene for C4. It is possible that Xenopus may also possess Class TV products related to those seen in birds. It is interesting to note that while MHC Class II molecules are expressed early in larval development on B cells and tadpole epithelia, MHC Class I molecules are not expressed on the surface of cells prior to larval metamorphosis.
Evolution of Histone Genes
Published in S. K. Dutta, DNA Systematics, 2019
The organization in the frog Xenopus, another primitive vertebrate which has been extensively studied, is more complex. The repeat structure in Xenopus is a relatively rapid evolving structure. In Xenopus laevis, there are at least three types of repeat, with different gene orders.38–42 There are substantial differences in repeat length and restriction maps between individuals.39,40 In contrast, in a closely related species, Xenopus borealis, there is a single major repeat which is found in all individuals.39 The repeat unit is large (>16 kb) and contains 1 copy each of the 5 histone genes. Interestingly, the gene order is not the same in the newt36 and the frog (Figure 1). In addition to the major repeat there are other genes which are separate from the repeat, probably in dispersed clusters similar to that found in the late sea urchin histone gene and mammalian histone genes.39 Because of the size of the repeat it is not yet known whether these are tandemly repeated units.
Genotoxicity of Ni2+ in Xenopus: Search for the Molecular Mechanisms
Published in Maryce M. Jacobs, Vitamins and Minerals in the Prevention and Treatment of Cancer, 2018
F. William Sunderman, Gregory S. Makowski, Marilyn C. Plowman, Sidney M. Hopfer
This chapter describes the initial steps in our search for the molecular mechanisms whereby Ni2+ causes genotoxicity, using embryos of the South African clawed toad, Xenopus laevis, as the experimental system. Xenopus embryos seem ideally suited for this investigation, since they are available in large numbers, are fertilized externally, develop rapidly, and are amenable to experimental interventions, such as microinjection. Xenopus embryos have been used in embryological research for over a century and have recently come under close scrutiny at the molecular level, stemming from the discovery that growth factors related to mammalian oncogenes are involved in cell-signalling processes that specify cell fate during Xenopus embryogenesis. Since the genotoxicity of nickel compounds has not previously been studied in Xenopus, several basic investigations were necessary in order to initiate this avenue of research.
Using Xenopus oocytes in neurological disease drug discovery
Published in Expert Opinion on Drug Discovery, 2020
Steven L. Zeng, Leland C. Sudlow, Mikhail Y. Berezin
An oocyte is a female germ cell in the process of development. Compared to other cells, Xenopus oocytes have striking physical characteristics with visually polarized dark and light hemispheres. This separation goes deeper than just the plasma membrane as intracellular components such as the germinal vesicle, distribution of yolk platelets, maternal mRNA, membrane receptors, and any endogenous ion channels have polarized localizations [40]. This uneven distribution is typically considered when performing microinjection or membrane transporter detection. Xenopus oocytes are also incredibly large cells with an average diameter of 1.3 mm [41]. In terms of sheer volume, they greatly exceed other cells used for drug discovery. In addition to providing greater source material for biochemical assays, this size advantage gives researchers ease of access and convenience when performing delicate procedures such as microinjection or voltage clamping. This includes using two recording electrodes during two-electrode voltage clamp (TEVC). Xenopus oocytes can even accommodate a third electrode, which can be used for intracellular injection during recordings or to collect additional data [42].
Evolutionary Underpinnings of Innate-Like T Cell Interactions with Cancer
Published in Immunological Investigations, 2019
Maureen Banach, Jacques Robert
Before describing recent developments in iT/MHC class I-like axis in Xenopus tumor immunity, we will first give a brief overview of the general knowledge on Xenopus tumors and immune system. Xenopus is a model of choice for developmental, evolutionary, and biomedical research, including cancer (Tandon et al., 2017). As other amphibians, Xenopus has 2 life stages: tadpole and adult. Both stages are characterized by distinct morphological as well as immunological features (Robert and Ohta, 2009). A small body size, great fecundity, and fast development make Xenopus a favorable experimental platform. Furthermore, owing to the external development of Xenopus embryos, all developmental stages are easily accessible for manipulations. In addition, the transparent skin renders Xenopus tadpoles convenient for real-time intravital microscopy (Haynes-Gimore et al., 2015).
Thematic 2019 Letter from the Editor
Published in Immunological Investigations, 2019
Xenopus research resource for Immunobiology, which is the world’s most comprehensive facility specializing in the use of this species for immunological research. Dr Robert and his team are interested in developmental and evolutionary aspects of immune surveillance, tumor, and viral immunity using the amphibian Xenopusas animal model. In addition to comparative studies on T cell and macrophage development, immunomodulation and anti-tumor immunity elicited by heat shock proteins, molecular evolution of immunologically relevant genes, and immunity to emerging infectious diseases in aquatic vertebrates caused by ranaviruses, Dr Robert’s team has recently unveiled the importance of MHC class I-like-and innate-like T cells outside mammals, particularly during early development and in antimicrobial immunity.