Neurodevelopmental Effects of Chronic Exposure, Research Paper Example

Introduction

In this study, the authors have used the Xenopus laevis tadpole visual system in an effort to establish a relationship between abnormal cytokine levels and their effects on neural development in order to affirm that they might be having some role in human neurodevelopmental disorders (Lee et al, 2010). The authors highlighted the suitability and recognition of this model for developmental studies on microneuronal circuitry. The authors have cited evidence for a peculiar signaling role of cytokines in the central nervous system, independent of their primary role of immune signaling during inflammatory condition as a basis for their hypothesis. The pro-inflammatory cytokines shortlisted by the authors for this study included (IL)-1?, IL-6 and tumor necrosis factor (TNF)-?.

Methodology

The methodology employed by the authors included measurement and evaluation of developmental changes at the levels of synaptic transmission, intrinsic excitability, retinotectal circuit refinement and visually guided behavior, within the 44^th and 49^th stages of larval development in Xenopus laevis tadpoles by rearing them in cytokine rich media of the respective kinds being tested (Lee et al, 2010). Neuroanatomical abnormalities in visual projection and deficiencies in visually guided behavior after the respective rearing with each cytokine were tested. On the basis of these tests specific groups were identified for subjecting to electrophysiological evaluations.

Behavioral screening of tadpoles was tested by employing a visual avoidance test which is considered as standard for evaluating developmental deficits in tectal circuits. Tadpoles were placed in rectangular clear bottomed tanks filled with rearing media at room temperature and the sides and top were blackened to obliterate light. Custom written MATLAB using Psychophysics Toolbox Extensions were used to generate stimulus patterns in the form of alternate black and white bars drifting across the tank, as well as presentation of white dots with 2 mm radius for a total span of 30 seconds to check for avoidance behavior. In the latter experiment a stimulus pattern was generated which made one half of the tank stationary while the other half drifted. Control tadpoles were expected to stay in the stationary half according to the test protocol.

Neuroanatomy of the retinotectal projection was studied by obtaining Isl2b:GFP transgenic tadpoles which are known for primarily driving expression in retinal ganglion cells (Lee et al, 2010). After 10 days of treatment with the respective cytokines, the tadpoles were euthanized and after immunostaining, fluorescent microscopy was used to take pictures.

Electrophysiological responses were measured for whole-brain recordings by preparing and isolating tadpole brains in HEPESbuffered extracellular saline (Lee et al, 2010). The brains were opened along the dorsal midline and pinned to a submerged block of Sylgard in a recording chamber maintained at room temperature with continuous perfusion of external saline. A bipolar stimulating electrode was placed on the optic chiasm to stimulate retinal ganglion cell axons and visualized wholecell voltage-clamp recordings were made.An Axopatch 200B amplifier was used for recording electrophysiological responses and appropriate software used for analysis. AMPA/NMDA ratios were calculated.

Besides above, single cell electroporation, imaging and reconstruction studies were done by artificially stimulating the superficial tectum. Seizures were induced by Pentylenetetrazole and evaluated using Apple Computer’s quicktime movie software. Mann-Whitney test was employed for statistical analysis (Lee et al, 2010).

Conclusion

The authors have used well established techniques taking precautions for intricate details for the comprehensive behavioral, neuroanatomical and electrophysiological studies on a recognized animal model to detect neuronal changes due to proinflammatory cytokines. Their results suggest observation of significant differences encountered in control and treated tadpoles thereby suggesting this methodology as a comprehensive model for further studies of this kind.

In my opinion, the study is comprehensive in nature, uses precise methodology and warrants publication.