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Science and Discovery: Novel Molecular Biology Discovery in Sea slugs

The domain Science and technology is one of discoveries and mind-boggling innovations with the sole purpose of bettering human life. Every year, hundreds of new discoveries and serendipity are being recorded that are changing life sciences as we know it. 2019 has been a special year where several such inspiring discoveries were made. This blog addresses one of them.

Using a tiny thermometer, researchers record fluctuations of more than 7 Kelvin in sea slug neurons when a heat-generating mitochondrial process is switched on.

The speed at which mouse neurons release calcium, for example, is lower in tissue sections kept at 25 °C than in those at physiological temperature.

A few years ago, neurosurgeon Huan “John” Wang, then at Carle Hospital in Urbana, Illinois, approached Sanjiv Sinha, a mechanical engineer at the nearby flagship campus of the University of Illinois, about working together to answer that question. To do so, Sinha’s team would first need to figure out how to take a cell’s temperature. Some techniques for this already existed, but the researchers thought there was room for improvement. For example, one popular technique involving fluorescent molecules had a high margin of error and could be influenced by changes in factors other than temperature, such as ion concentrations and pH.

Temperature measurement via fluorescence had also yielded results Sinha considered questionable. “In the last ten years or so, there have been numerous publications that report temperature rises in cells that are a few degrees centigrade,” he says. “This doesn’t make physical sense. Where would all this heat be coming from?”

So Manjunath Rajagopal, a graduate student in Sinha’s lab, set out to devise a new, more accurate type of cellular thermometer. He and Sinha used atomic force microscopy (AFM), which delivers very precise measurements of the forces at work between a probe and a sample. Adapting the technology for use inside a living cell took years. “We redesigned to make sure the probe is sufficiently long and thin . . . which makes it less damaging to the cell when it’s entering the cell,” Rajagopal says. Calibrating the instrument posed another challenge; rather than using hot and cold water—the usual approach for calibrating temperature-measuring instruments—they aimed for higher accuracy with techniques taken from the semiconductor industry, where AFM is used to measure the smoothness of surfaces.

For the device’s trial run, Sinha and Rajagopal worked with neuroscientist Rhanor Gillette, also at the University of Illinois at Urbana-Champaign (UIUC), to measure the temperature of some unusually large neurons—those found in the abdomen of a sea slug known as the California sea hare (Aplysia californica). The team placed cultured neurons under a microscope and inserted the custom thermometer into one of them, as well as a voltage-measuring device to monitor the cell’s health.