Zebrafish cardiovascular system - heartbeat monitoring

Studies on new drugs are often discontinued due to negative side effects on the cardiovascular system; therefore many studies in toxicology and pharmacology focus on heart function. Heart rate is an important variable of interest: specifically, how this parameter responds to genetic, physiological, and pharmacological interventions is investigated in many studies. 

The cardiovascular system in zebrafish

Zebrafish, particularly embryos and larvae, are often the animal of choice in this type of research [1,2,3,4,5]. The heart is the first organ to develop in zebrafish, and development is similar to the human heart. Also, unlike rodent models, fish do not depend on the cardiovascular system for survival during embryogenesis. Therefore, defects in its development are less likely to result in early mortality and other problems. Add to that the fact that zebrafish larvae are transparent, and you can understand why zebrafish are useful in the study of cardiac or cardiovascular development.  

Traditional research methods

The zebrafish cardiac system is often assessed by measuring the heart rate or inter-beat interval. Traditional methods include counting this manually (using a stopwatch), a micro pressure system, Laser Doppler microscopy, or electrocardiograms. These methods are labor-intensive and time-consuming, and on top of that, require specific training to perform. [2] 

Imaging method using video analysis

Video image analysis can be used as a method to accurately and efficiently, assess the heart rate of zebrafish larvae. DanioScope provides you with a way to analyze your video images and accurately extract the heartbeat. 

DanioScope

DanioScope detects activity, meaning it detects active pixel changes from one frame to the next. To monitor the heartbeat, you simply define the heart area (as an arena), and DanioScope will detect the the activity, and subsequently the heartbeat within this frame, during your video.  You can detect the heartbeat of multiple larvae in the same video simultaneoulsy.  

Straight-forward

With this technique, all you need is a video of your larvae and DanioScope. There is no need for fluorescence labeling of specific training for your lab staff. 

In practice

In practice, larvae are usually immobilized (for instance, in agarose) and positioned laterally for an optimal view of the heart area. Then a video is made of one or more individuals simultaneously, in most cases using digital video microscopy. DanioScope supports MPEG1, MPEG2 and MPEG4 video formats, but works with most standard video formats as well (MOV, AVI). 

References 

  1. Barros, T.P.; Alderton, W.K.; Reynolds, H.M.; Roach, A.G.; Berghmans, S. (2008). Zebrafish: an emerging technology for in vivo pharmacological assessment to identify potential safety liabilities in early drug developmentBritish Journal of Pharmacology, 154, 1400-1413.
  2. Chan, P.K.; Lin, C.C.; Cheng, S.H. (2009). Noninvasive technique for measurement of heartbeat regularity in zebrafish (Danio rerio) embryos. BMC Biotechnology, 9, 11.
  3. Denvir, M.A.; Tucker, C.S.; Mullins, J.J. (2008). Systolic and diastolic ventricular function in zebrafish embryos: influence of norepinephrine, MS-222 and temperatureBMC Biotechnology8, 21. 
  4. Fink, M.; Callol-Massot, C.; Chu, A.; Ruiz-Lozano, P.; Izpisua Belmonte, J.C.; Giles, W.; Bodmer, R.; Ocorr, K. (2009) A new method for detection and quantification of heart-beat parameters in Drosophila, zebrafish, and embryonic mouse hearts. Bio Techniques46, 101-113.
  5. Jacob, E.; Drexel, M.; Schwerte, T.; Pelster, B. (2002). Influence of hypoxia and of hypoxemia on the development of cardiac activity in zebrafish larvae. American Journal of Physiology - Regulatory, Integrative and Comparative Physiology, 283, R911-R917.

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