Science at Cambridge: Medicine

6D Katy Crooks 1
UniversityPRACTISING THE SCIENCE OF MEDICINE

“There is nothing – nothing at all – that compares with the exhilaration of discovery, of being the first person on the planet to see something new and understand what it means.”
Frances Ashcroft, Professor of Physiology at the University of Oxford

It’s 9am. Having battled my way through the swathes of cyclists coming into Cambridge unscathed (a daily triumph), I make my way into the physiology department, don a lab coat and start the day.

The project I am working on is looking at mouse hearts which beat unusually. The technique is pretty fiddly, it involves inserting a minute glass electrode into one of the cells in the heart. We then measure the changes in potential difference between the inside and outside of the cell – these are the changes in electrical potential that underlie contraction. By understanding their electrical activity, the hope is that the results will further our understanding of the human heart, and what happens when things go wrong.

I head up to the lab and make the electrodes we will use that day. It involves taking a small hollow glass rod, and using an electrode puller to heat and stretch it until it breaks. The result is a tip which is narrower than the wavelength of light, sharp enough to pierce but not disrupt the membrane of a single cell. Using a tapered pipette, I fill each of them with a high concentration of potassium chloride to allow the movement of current through them during the experiments. I work meticulously – one knock of the tip or bubble in the electrode will render my carefully made electrode useless.

It was in my first term at Cambridge that I first studied the physiology of excitable tissues. In the midst of a term full of vast quantities of anatomical terms and complex biochemical pathways, the mathematical rationale and unifying concepts of electrophysiology were refreshingly intuitive. The concepts and techniques baffled me to start with, and still do to some degree. But I loved it because once you understood it, you never lost that understanding – and it changed the way you thought.

While I finish the electrodes, one of the others in our team dissects and cannulates the aorta of the heart we are to use. I load it onto the rig, start perfusing it, and the tissue recovers from the shock of being placed in ice and starts beating again, the different parts contracting in sequence. It’s a strange and miraculous sight. We’re working in a tiny and completely chaotic room – not as glamorous as I once pictured medical research. Forget shiny white surfaces and high tech equipment – the rig I work at is a maze of adjusters and wires patching together an assortment of slightly bizarre looking bits of apparatus and enclosed in a massive wire box to eliminate electrical noise.

We work all day, interrupted only for a lecture on calcium homeostasis and a rushed lunch. The preparation is temperamental, with the heart occasionally moving and dislodging the electrode. Finally however, we get a beautiful train of classic ventricular action potentials. I look at the trace, and see the very same thing I studied in first year – but this time I recorded it myself.

It’s a wonderful feeling, and on my cycle back to Murray Edwards through the dark streets of Cambridge I think over my time here. Medicine at Cambridge has been quite full on. A lot of the time, you feel more like a natural scientist – it is easy for the clinical applications to get lost in the rigorous training in the medical sciences. It has been hard work, and I can count the number of patients I have seen on one hand. Though difficult at times, the firm grounding in science and the opportunities at Cambridge make me so grateful for being here. It’s not just the facts you learn which prepare you for being a doctor, but starting your medical training with the mentality of a scientist teaches you to think analytically and logically. I feel ready to get on the wards next year and apply what I have learnt in this mindset. But for now, I will enjoy seeking discovery as Frances Ashcroft describes. I do not expect this year to reveal anything which will radicalise the way we view the heart – but I do know that what I am seeing, if I do it well, is first hand and real. I could contribute knowledge, and that’s a privilege.

Katy Crooks
Undergraduate

4 responses to “Science at Cambridge: Medicine

    • Sorry about the delay in replying to this!

      So we are actually looking at all ventricular and atrial cells, rather than pacemaker cells specifically. One of the things we are looking at is the conduction velocity at which the depolarisation from the pacemaker cells in the sinoatrial node spread through the tissue as a whole, and we also monitor pacemaker activity by using ECG to measure heart rate. The ECG trace also helps to detect ectopic beats/arrythmias.

      Hope that is helpful!

      • hi Katy, thanks for this. i think pacemaker cells are amazing in that they have ‘intrinsic automaticity’ , hence they really drive the heart rate and related changes . thanks for your post. sabina

      • This is very true, although before working on them we take the heart out of the animal so they are denervated, therefore have lost their autonomic input. And since we perfuse the hearts with a perfusate free of adrenaline or acetylcholine, the heats act independent of any sort of neuro or chemical modulation. If we wish to change the rate of the heart, we use a stimulator to pace it at the desired frequency, which is placed over the heart chamber of interest. This is obviously very useful in some of the protocols we run, particularly when trying to induce an arrhythmia.

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