Retinal Strip Culture for Studying Ganglion Cell Axon Growth

Integrin-mediated electric axon guidance underlying optic nerve formation in the embryonic chick retina

Retinal ganglion cell (RGC) axons converge on the optic disc to form an optic nerve. However, the mechanism of RGC axon convergence remains elusive. In the embryonic retina, an electric field (EF) exists and this EF converges on the future optic disc. EFs have been demonstrated in vitro to orient axons toward the cathode. Here, I show that the EF directs RGC axons through integrin in an extracellular Ca2+-dependent manner. The cathodal growth of embryonic chick RGC axons, which express integrin α6β1, was enhanced by monoclonal anti-chicken integrin β1 antibodies. Mn2+ abolished these EF effects, as Mn2+ occupies the Ca2+-dependent negative regulatory site in the β1 subunit to eliminate Ca2+ inhibition. The present study proposes an integrin-mediated electric axon steering model, which involves directional Ca2+ movements and asymmetric microtubule stabilization. Since neuroepithelial cells generate EFs during neurogenesis, electric axon guidance may primarily be used in central nervous system development.

Electrical Circuits That Supply Constant Electric Fields In Vitro

Background: To study the molecular mechanism of galvanotropism in vitro, the strength of an electric field (EF) must be controlled precisely. In this study, I present a culture system that supplies an EF of constant strength by regulating the amount of current supplied to the culture medium.

Materials and Methods: Voltage of the medium was recorded at two fixed points along the current flow throughout the culture period. The voltage drop between the two points was maintained at the desired value by a negative feedback circuit and an operational amplifier.

Results: The field strength was defined by the voltage drop and the distance between the two points, and in this system, the EF can range from 0.0005 to 15 mV/mm.

Conclusions: This culture system may be a useful tool to determine the nature of galvanotropism.

[Aerobic exercise combined with huwentoxin-I upregulates phase-Ⅱ detoxification enzymes to alleviate obstructive jaundice-induced central nervous system injury in mice]

OBJECTIVE

To explore the effects of aerobic exercise combined with huwentoxin-I (HWTX-I)-mediated Keap1-Nrf2-ARE pathway on phase II detoxification enzymes HO-1 and NQO1 and their protective effects against obstructive jaundice (OJ)-induced central nervous system injury in mice.

METHODS

50 male KM mice were randomly divided into blank group (GO), model group (M), aerobic exercise group (T), HWTX-I group (H), and aerobic exercise combined with HWTX-I group (TH). Mouse models of OJ were established with surgical suture for 72 h in the mice in all the groups except for the blank control group. The mice received interventions by aerobic exercise and tail vein injection of HWTX-I (0.05 μg/g) and were assessed by behavioral observation, Clark's neurological function scores, enzyme-linked immunosorbent assay (ELISA), brain tissue Nissl staining, hippocampal tissue Western blotting, and liver tissue mRNA expression profiling and sequencing.

RESULTS

The mice in group M had obvious jaundice symptoms after the operation with significantly increased Clark's neurological score (P < 0.01). Compared with those in group M, the mice in group T, group H, and group TH showed significantly decreased serum levels of ALT, AST, TBIL, and TBA (P < 0.01) with increased contents of 5-HT and BDNF and decreased contents of S100B and NSE in the hippocampus (P < 0.01). Synergistic effects between aerobic exercise and HWTX-I were noted on the above parameters except for the liver function indicators. Interventions with aerobic exercise and HWTX-I, alone or in combination, obviously lessened pathologies in the brain tissue induced by OJ, and the combined treatment produced the strongest effect. The treatment also increased the expression levels of Nrf2, HO-1, and NQO1 mRNA and protein in brain tissues (P < 0.01 or 0.05) with a synergistic effect between aerobic exercise and HWTX-I. Illumina high-throughput sequencing showed that the differentially expressed factors participated mainly in such neural regulatory pathways as neuroactive ligand-receptor interaction, GABAergic synapses, dopaminergic synapses, synaptic vesicle circulation, and axon guidance, involving tissue cell neuronal signal transduction, apoptosis inhibition, immune response, and toxicity. Aerobic exercise and HWTX-I synergistically increased the accumulation of the signal pathways related with neuron damage repair and proliferation.

CONCLUSIONS

Aerobic exercise combined with HWTX-I can up-regulate the expression of phase Ⅱ detoxification enzymes HO-1 and NQO1 through the Keap1-Nrf2-ARE pathway to protect the central nervous system against OJ-induced damage in mice.

An integrated 3D fluidic device with bubble guidance mechanism for long-term primary and secondary cell recordings on multi-electrode array platform

A 3D fluidic device (3D-FD) is designed and developed with the capability of auto bubble guidance via a helical pathway in a 3D geometry. This assembly is integrated to a multi-electrode array (MEA) to maintain secondary cell lines, primary cells and primary retinal tissue explants of chick embryos for continuous monitoring of the growth and electrophysiology recording. The ability to maintain the retinal tissue explant, extracted from day 14 (E-14) and day 21 (E-21) chick embryos in an integrated 3D-FD MEA for long duration (>100 h) and study the development is demonstrated. The enhanced duration of monitoring offered by this device is due to the controlled laminar flow and the maintenance of a stable microenvironment. The spontaneous electrical activity of the retina, including the spike recordings from the retinal ganglion layer, was monitored over a long duration. Specifically, the spiking activity in embryonic chick retinas of different days (E-14 to 21) is studied, and the presence of light-stimulated firings along with a distinct electroretinogram for E-21 mature retina provides the evidence of a stable microenvironment over a sustained period.