Reversing the Outcome of Synapse Elimination at Developing Neuromuscular Junctions In Vivo: Evidence

Reversing the Outcome of Synapse Elimination at Developing Neuromuscular Junctions In Vivo: Evidence

Objectives of the study

The main reasons for this study include:

Objectives

1. To assess how in vivo imaging is used to analyze the connections between the target muscle cells and neuron axons (motor). In explanation, the study is based at the neuromuscular junction (NMJ) while in the developmental stage the time when every NMJ has various connections
2. To investigate how synapse loss develops.
3. To identify the functional neurons and connections with issues.
4. To analyze competitive mechanism and how it increases the strength and size of inputs related to shrinking and weakening, thus affect other axons.

 

Summary of experiments and findings

The experiment requirements were mice expressing cytoplasmic GFP1; another was YFP line 16. Both could also be used or CFP-23 and do a cross-breeding with YFP-16. GFP is not meant for imaging. In the experiment, the procedures done were photobleaching and multicolor axon labeling, laser ablation, imaging, and modelling (Turney & Lichtman, 2012). The experiment begins with the classification of the synapses, and the neuromuscular synapse is the major point of focus. The experiment involves tests about if or if not, the elimination of synapse is due to interactional competition. During the experiment, different images of axons and NMJ were analyzed to find about competition among two axons, which may be vying for a similar postsynaptic site. This causes one to be eliminated. In the procedure, the axon was ablated, especially the one which could maintain within the neuromuscular junction. The aim was to see if a weaker input could cause a reversal in fate and also if it can be maintained. Another issue to be determined was on deciding if an eliminated axon becomes irreversible finally. The synapses can be measured in number through dyes revealing synaptic vesicle release, electrophysiological recording, and analysis through electron microscopy.

The axons could compete in a program of motion of elimination, which is typically irreversible even after an axonal loss has occurred. In this case, the events of synaptic reorganization are may or may not ne played out, especially with little lag around the consequences and competitive actions on retraction or growth of axons (Turney & Lichtman, 2012).

An example is when the input is pushed off another synaptic site. The withdrawal from the axon is coordinated temporarily, remembering the simultaneous near axonal takeover. From some of the results, it has revealed that a synaptic territory can be decreased or increased dynamically. The laser-based technique was developed to remove the few axons that were closely spaced and also innervated a similar neuromuscular junction. The axons, therefore, grow occupying the vacant sites no matter their appearance while withdrawing when the sites become vacated. This entails a combination of axonal takeover and synaptic vacancy and also allows for an explanation concerning the synapse elimination phenomenon (Turney & Lichtman, 2012).  In the experiment, to remove an axonal branch selectively minus damaging the neighboring axons (in vivo) diode-pumped locked mode Ti: sapphire oscillator was used to cause phototoxicity in protein fluorescent axons (motor) in mice that are alive. The focus should be laser spot placed over a branch of an axon and after the adjacent axons are unscathed.

 

The most important finding? What it means and the relevance

The crucial finding from the experiment is that synapse loss is found to be driven by nerve cell competition, especially those vying to remain in touch with a similar target cell. The axons that may be eliminated can always be spared by the application of the removal, especially with laser microsurgery. This is another axon that converges on a similar synaptic site. The other axons, therefore, do not only survive but also grow rapidly, occupying the synaptic sites which were originally vacated the axon removed. The significance and meaning are that it leads to the provision of a framework used in understanding the rearrangements in the synapse, especially for the nervous system development (Turney & Lichtman, 2012).  The neurons can produce various synaptic connections, especially with their target cells. With time the connections might disappear and leave a fraction of original connections. For axons to be damaged, time consumed is 30-45 minutes, but removing axon needs several hours. During irradiation, a segment of the axon may be irradiated. When the axon is damaged, the signs are swelling in the distal of the axon to a laser focus site as well as the progressive widening of non-fluorescence for the proximal and distal site of irradiation. Protein leakages from the cytoplasm can damage the site.

 

How does the finding relate to classwork?

The finding is quite significant in analyzing the competition for the site by various nerve cells. There are various mechanisms proposed to help improve the process. One of the ideas for the situation is random removal within a motor unit and is also related to an intrinsic requirement (Turney & Lichtman, 2012).  This is true in that these neurons scale back to their original exuberantarbors. These axons are fated to be predetermined by position or even other molecular cues specifying the axon, which can best match every muscle fiber. In relation to classwork about reversal and neuron functions, the removal of axons that compete for an active site, most of which are less in number. Typically, we identified that laser surgery could help achieve the expectation. Sooner than later, according to the laboratory report and results, elimination is through revers-fate. The vacant sites are taken by axons when the input is less strong. The axons typically face reversal; fate an also grow occupying most of the vacant sites. This occurs at the neuromuscular junction. In the normal development with regards to the results, a takeover follows any withdrawal, therefore, producing their stimulus for the growth of the axon. According to the results and conclusion can be made depending on the work and activities undertaken as well as understanding the form of spastic synaptic plasticity. The classwork was about an experiment related to axons and neurons in terms of competition for the target cells.

 

What you like most about the study

What I liked most about this study is how axons behave with regards to the active sites in which they can bind to the target cells. The whole idea is about the mechanism of competition among the axons to bind to the target cells. After some weeks of study, all innervated multiple junctions may lose input for the next days. Laser irradiation could remove the axons successfully from the NMJ. A re-anesthetized mouse in a later day was used, and it returned to the same fibers (muscles). For every case, a remaining axon changed in a manner that is striking like the axons have extended branches for the postsynaptic area to fully take the space, which was formerly overlain for axon irradiated by laser. The irradiation offered assistance in terms of competition, which is vital for the experiment. Neuromuscular junction formation is interesting, and the muscle fiber is targeted, and on contact, the pre- and postsynaptic cells of the muscles undergo changes (Turney & Lichtman, 2012). The neurotransmitter receptors in the membrane are also observed upregulation of the receptor and neurotransmitter expression. The synapses are multiple, for example, those with electrical or chemical signals and interneural synapses between the neurons. Neuromuscular synapses for studying the post and pre-synaptic interactions. The synapses are points of communication between the neurons.

What you did not like about the study

What I did not like in this study how single and multiple transitions in terms of innervation occurs in the skeletal muscle. I’m not too fond of the fact that it occurs in the axon when a takeover happens in the synaptic sites originally, which were occupied by different axons. The case is not clear; for example, some questions remain unanswered. The first one is which particular thing drives the exchanging of territories like one loses access, the other takes over due to competition (Turney & Lichtman, 2012). Another unanswered issue is what investigates the identity and eventual input survival when an axon loses territory at a point that will access it again. The third unanswered issue is why contracts with an axon in NMJ cluster over time occupying the segregated territory.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

References

Turney, S. G., & Lichtman, J. W. (2012). Reversing the outcome of synapse elimination at developing neuromuscular junctions in vivo: evidence for synaptic competition and its mechanism. PLoS biology, 10(6).

 

 

There are multiple types of synapses