Abstract
Judiciously tuning heart rates is critical for regular cardiovascular function. The fractal pattern of heartbeats — a multiscale regulation in instantaneous fluctuations — is well known for vertebrates. The most primitive heart system of the Drosophila provides a useful model to understand the evolutional origin of such a fractal pattern as well as the alterations of fractal pattern during diseased statuses. We developed a non-invasive visible optical heart rate recording system especially suitable for long-term recording by using principal component analysis (PCA) instead of fluorescence recording system to avoid the confounding effect from intense light irradiation. To deplete intracellular Ca2+ levels, the expression of sarco-endoplasmic reticulum Ca2+-ATPase (SERCA) was tissue-specifically knocked down. The SERCA group shows longer heart beat intervals (Mean ± SD: 1009.7 ± 151.6 ms) as compared to the control group (545.5 ± 45.4 ms, p < 0.001). The multiscale correlation of SERCA group (scaling exponent: 0.77 ± 0.07), on the other hand, is weaker than that of the control Drosophila (scaling exponent: 0.85 ± 0.03) (p = 0.016).
Highlights
The mean number of heart beats throughout mammalian life span is proposed to be a constant
The single pixel M-mode trace corresponding to different positions of heart tube are showed in Fig. 1d, for which the wall of heart is not readily identified as compared to that manifested with green fluorescent protein (GFP) marker
To further minimize the effects of the contaminations to make the quality of reconstructed wall motion with lamplight be as good as that with GFP marker (Fig. 2a), we applied principal component analysis (PCA) to a number of wall motions that were reconstructed from different location of heart tube
Summary
The mean number of heart beats throughout mammalian life span is proposed to be a constant. In addition to numbers of heart beat, this regulation is characterized by fractal structures with properties that remain invariant over a wide range of time scales[7]. These fractal patterns are robust in healthy physiological systems but are significantly disrupted or abolished in degraded systems that are more vulnerable to catastrophic events and less adaptable to perturbations. It is believed that fractal is a hallmark of health physiological systems and that the underlying mechanisms of fractal regulation are of great interests but yet to be elucidated We hypothesized that such fractal patterns of heart beats may be conserved in simple tubular structure of arthropods[14]. To detect Drosophila heart movement in an intact animal but free of thermal stresses, we take the images from the Drosophila under normal lamplight without dissection or exposure to laser radiations in the present study
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