Buy essay on Xenopus and Avian as Model Organisms for Developmental Neurobiology

Xenopus
Life cycle and nervous system
Xenopus is a genus, highly aquatic frog native to Sub-Saharan Africa. Basically, Xenopus are widely-spread and often they are used for experiments, mainly related to cell researches and genetics. Xenopus have flattened, egg-shaped and streamlined bodies and very slippery skin due to a protective mucus which serves as a protection from predators that can threaten to the life of Xenopus. Xenopus are excellent swimmers and they have haptoglobin in their blood (). The life cycle of Xenophus is presented on the following graph and in the table 1:

Table 1. Life Cycle of Xenophus
Species X. laevis X. tropicalis
ploidy allotetraploid diploid
N 18 chromosomes 10 chromosomes
genome size 3.1 x 10 9 bp 1.7 x 10 9 bp
temp. optima 16-22o C 25-30o C
adult size 10 cm 4-5 cm
egg size 1-1.3 mm 0.7-0.8 mm
eggs/spawn 300-1000 1000-3000
generation time 1-2 years 4 months

The nervous system of Xenopus is well-developed and allows to study the basic reactions and functions of the nervous system. At the same time, the current researches are concerned not only with the study of the nervous system of Xenopus but also and mainly cells and genetics experiments involving Xenopus are widely-spread.
Benefits of Xenopus and experiments involving Xenopus
Traditionally, Xenopus was a subject to numerous experiments in the field of medicine and biology. Xenopus was always interesting for researchers due to the relative simplicity of its structure and basic characteristics which were common not only for Xenopus and other frogs but also for other animals and species. In such a way, researchers were traditionally concerned with the study of Xenopus because they can conduct various experiments without any significant ethical effects. In this regard, it is worth mentioning the fact that Xenopus are widely-spread in their natural environment and they can be breed for scientific experiments specifically. It is very simple to obtain samples as models for experiments and conduct in-depth researches at different level from mere study of the structure and functioning of the vitally important systems to profound and sophisticated experiments in the field of genetics.

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Today, Xenopus are mainly used for gene and protein expression and knockdown studies. In this respect, the main advantage of Xenopus which makes it useful for experiments is its oocytes which are very large cells. They are easy for scientists to culture and use in their experiments. For instance, RNA from other organisms can be injected into the large oocytes and the resulting expression studied via molecular biology techniques and electrophysiology experimentation. In such a way, it is quite natural that today Xenopus are very popular subjects to scientific experiments because the rapid development of genetics and the limitations concerning the study of genetics, especially stem cells, force scientists to look for reliable alternatives. In such a context, Xenopus can become a perfection option that can help researchers to study cells and conduct genetic experiments successfully. In addition, Xenopus are often used as low-tech pregnancy test.
Limitations of Xenopus and experiments involving Xenopus
At first glance, Xenopus are very good subjects to experiments but, in actuality, Xenopus have certain limitations concerning experiments involving these frogs. As the matter of fact Xenopus is widely-used in genetics and experiment related to this science. However, the use of Xenopus cannot always lead to reliable because, even though Xenopus is the most commonly used species for developmental biology studies and genetic experiments, the latter can be complicated by their pseudotetraploid genome. In such a way, researches in the field of genetics can be complicated and have misleading outcomes in some cases when Xenopus are involve in experiments. However, this problem arises when researchers conduct complicated experiments which naturally imply the high level of the development of the subject to the experiment. As the matter of fact, Xenopus still can be used successfully in experiments which do not involve very complex studies. Xenopus provides a simple model for genetic studies, having a relatively simple structure and large oocytes.
In fact, the limitations of experiments involving Xenopus are relatively insignificant and problems arise only when complex and very specific experiments are used. Instaed, Xenopus are widely applied for various experiments throughout long time and researchers working in different fields of science use Xenopus in their studies en masse.
The contribution of Xenopus made to neuroscience researches
In actuality, Xenopus made a significant contribution to the development of neuroscience researches. In this respect, it is possible to refer to numerous studies conducted by different scientists involving Xenopus as subjects to experiments. For instance, the study conducted by Y. Kato and others “Neuralization of the Xenobus by Inhibition of p/300 Creb-Binding Protein Function” is particularly noteworthy. The researchers have found out that the inhibition of protein p300/CBP function in the Xenobus embryo abolishes non-neural tissue formation and, strikingly, initiates neural induction and primary neurogenesis in the entire embryo. The observed neutralization was achieved in the absence of anterior or posterior gene expression. As the result, the researchers concluded that neural fate activation and anterior pattering may represent distinct molecular events. In addition, the researchers have found out that the neurolizing and anteriorizing activities of chrodin and noggin are separable properties of this cellar inducer. In such a way, the researchers concluded that all embryonic cells possess intrinsic neutralizing capability and that p300/CBP function is essential for embryonic germ layer function and neural fate suppression during vertebrate embryogenesis.
Another research involving Xenopus was conducted by J.E. Lee and others, “Conversion of Xenopus Ecoderm into Neurons by NeuroD, a Basic Helix-Loop-Helix Protein”. In actuality, the researchers stood on the ground that basic Helix-Loop-Helix Proteins are instrumental in determining cell type during development. A basic Helix-Lool-Helix protein, named NeuroD, for neurogenic differentiation, has been identified as a differentiation factor because it is expressed transiently in a subset of neurons in the central and peripheral nervous systems at the time of their terminal differentiation into mature neurons; and ectopic expression of NeuroD in Xenopus embryos causes premature differentiation or neuronal precursors. Furthermore, the researchers have found out that neuroD can convert presumptive epidermal cells into neurons and also act as a neuronal determination gene. However, unlike other previously identified proneural genes, NeuroD seems competent to bypass the normal inhibitory influences that usually prevent neurogenesis in ventral and lateral ectoderm and is capable of converting most of the embryonic ectoderm into neurons. The researchers suggest that NeuroD may participate into the terminal differentiation step during vertebrate neuronal development.