The pharynx is a heart-like neuromuscular organ involved in nematodes’ feeding behavior. During a pharyngeal muscle contraction, the ion exchange underlying the pharyngeal action potential generates a change of voltage in the worm’s direct environment. The ScreenChip platform detects such voltage change using external electrodes placed onto the glass floor of the microfluidic chips (Lockery et el., 2012) and directs it to the acquisition software. The design of the chips ensures a snug fit of the worm to create a sufficiently large electrical resistance to record the electrical activity with a high signal-to-noise ratio.
You will need to connect the outlet of your ScreenChip system to a vacuum source (portable vacuum pump or house vacuum tap). The worms are moved from the epitube and through the chips by the negative pressure generated by the vacuum source. Each worm is carried by the flowing fluid until it reaches the constriction part of the main channel (“trap”). Worms are then mechanically held in position throughout an experiment.
Using the ScreenChip system does not require intensive training and users usually get usable data on the first day of use. We stay in touch with our customers to help you with your experimental design or with the platform set-up if needed.
In order to record feeding behavior, pharyngeal activity must be induced. This can be achieved by including either the neuromodulator serotonin or fresh bacteria in the saline medium. Inducing pharyngeal pumping allows you to study the effect of various environmental components such as bacterial strains and drugs. Simply incubate or cultivate your worms into the desired environmental conditions and load the worm.
Each worm can be recorded, one at a time, for several minutes up to 24 hours. At the end of each recording, vacuum each worm out of the chip while loading the next worm by using the vacuum source.
On average, we have observed that it takes 30-60 seconds to load 50 worms into the first loading chamber within the chip. Once all the worms are loaded in the chamber, it takes on average less than 10 seconds to move a worm into the recording channel.
The ScreenChip platform is composed of two key elements: a custom dock with electrical components and a mini amplifier. When you purchase the ScreenChip starter kit, you will receive all of the elements that you will need to start your experiments right away. Just install our free data acquisition software to start recording your data.
We designed the ScreenChip platform to fit entirely on the stage of a dissection microscope.
Please note that in order to load worms within the ScreenChip, you will need a vacuum source, which is not included in the starter kit as many labs already own one. However, we are happy to provide you with a vacuum pump if needed (link to product page).
The ScreenChips are composed of polydimethylsiloxane (PDMS), a completely optically clear and gas permeable material, bonded on a glass slide. Another distinct characteristic of PDMS is its ability to absorb hydrophobic small molecules. Re-using chips beyond the recommended time of 8 hours could result in an overall change in solution concentrations and could potentially alter experimental outcomes.
As in the vertebrate heart, the pattern of rhythmic contractions of the nematode pharynx is primarily generated by the pharyngeal muscles themselves. Each contraction is associated with an action potential, a large voltage transient that can be recorded by electrodes placed on the surface of the body. By analogy to an electrocardiogram, such a recording in nematodes is called an electropharyngeogram (EPG)(Lockery et al., 2012). In addition to registering action potentials in the pharyngeal muscles, the EPG also registers the activity of neurons that regulate the rate of pharyngeal pumping in much the same way as the autonomic nervous system regulates the vertebrate heart. Thus, the EPG can be used to investigate the effects of drugs that act on neurons as well as muscles.
The ScreenChips are completely optically clear and allow you to perform imaging experiments up to 20X with an inverted microscope or with a dissecting microscope.
We do offer an imaging solution with our imaging chip, which allows you to take high resolution images of your worms using brightfield or fluorescence. The imaging chip does not contain electrodes, and therefore does not let you records EPGs.
On average, ScreenChip user record 50-70 worms with one chip. We recommend changing the chips after about 8 hours of use.
The data acquisition process is rapid and simple as presented here. Both data acquisition and analysis are automated through our free, open source softwares: NemAcquire and NemAnalaysis. NemAcquire allows you to monitor each worm’s feeding behavior in real time, while recording 500 data points per second. Data from each worm is recorded in a .txt file that can be read by multiple free softwares, including NemAnalysis.
NemAnalysis is designed to help you get the most information out of your data, while allowing you to control how your data is analyzed. NemAnalysis automatically extracts the data from NemAcquire files to identify and measure pharyngeal pumping events and quantify various aspects of the feeding pattern of your worms (changes of pumping frequency over time, consistency of feeding, duration of pharyngeal contractions etc…).
NemAnalysis lets you extract raw and analyzed data from your worms into an Excel sheet, so you can perform the statistical analyses of your choice.
Using the ScreenChip phenotyping platform, you will be able to extract:
– the pumping pattern of your worms,
– the interpump interval duration (pauses),
– pump duration,
– pumping frequency (rate),
– frequency changes throughout your recording
– export your data into an Excel sheet.
We have recorded feeding activity for multiple nematode parasitic and free-living species such as C. elegans, and various species of hookworms larvae, Panagrellus redivivus or Pristionchus pacificus.
We offer 4 sizes of chips that allow you to phenotype worms at various developmental stages such as L1, L4, young adult and older adults (link to product page – chips).