Blood pressures and heart rate during larval development in the anuran amphibian Xenopus laevis

Abstract

Heart rate and blood pressure were measured in lightly anesthetized developing Xenopus laevis from hatching (body mass approximately 3 mg) to the end of metamorphosis (< or = 1 g). Blood pressures in the conus arteriosus, truncus arteriosus, and ventricle were measured by a servo-null micropressure system. Heart rate was determined from blood pressure recordings, and cardiac cycles were videotaped through a dissecting microscope. Heart rate varied from 50 to 150 beats/min and showed a negative correlation with body mass, with a slope less than predicted from allometric equations based on adult vertebrates. Mean truncus pressures showed a positive correlation with body mass, increasing from 4 mmHg in a 25-mg larva to 9 mmHg in a 1-g larva. The pressure waveform during ventricular systole was similar in all developmental stages examined, whereas those in conus and truncus varied with development. Conus pressures differed distinctly from truncus pressure during diastole in all larvae examined, suggesting the existence of functional valves between conus and truncus as early as stage 46 of the Nieuwkoop-Faber larval staging system. Although the developmental patterns of heart rate and blood pressure in X. laevis showed significant correlation with body mass, body mass explained less than one-half of the variation in these variables. Therefore developmental factors other than body mass, such as changes in heart mass and the addition of new resistance vessels, may influence heart rate and blood pressure during development in X. laevis.

A Three‐Dimensional Functional Assessment of Heart and Vessel Development in the Larva of the Zebrafish (Danio rerio)

“…Image Capturing. The imaging techniques developed in this study are based on a standard set of techniques used by Hou and Burggren (1995) in Xenopus laevis and refined by Schwerte and Pelster (2000) for the zebrafish. The imaging system consisted of a trinocular inverted microscope (Nikon Eclipse TS100) equipped with a CCD black and white high-resolution camera.…”

“…Heart rate was then calculated from the time interval required for 30 consecutive heartbeats. The perimeter of the ventricle image during end systole (a single frame selected from the cardiac cycle video) and during end diastole was outlined manually using a computer mouse (Hou and Burggren 1995;Schonweger et al 2000). The perimeter was fitted with an ellipse (using ImagePro imaging software; Media Cybernetics, Silver Springs, MD), and major and minor axes measurements were extracted and exported to an Excel spreadsheet.…”

“…In fact, it does not take its rec- ognizable adult shape of a prolate spheroid until 5 d postfertilization at this temperature (Weinstein and Fishman 1996). Yet, most common previous studies for visual measurement of cardiac output in vertebrate embryos have used the equation for a prolate spheroid for modeling heart shape throughout early development (Burggren and Fritsche 1995;Hou and Burggren 1995;Burggren 2004). The observations of heart shape in this study suggest that the use of a prolate spheroid leads to less accurate stroke volume measurements before day 5 in the zebrafish at 28.5ЊC (day 6 at 25ЊC).…”

“…Consequently, the function of the early heart has long been a source of investigation. In many embryos and larvae, cardiovascular function can be measured optically through video analysis of volume changes of the beating heart (Burggren and Fritsche 1995;Hou and Burggren 1995;Fritsche and Burggren 1996;Mirkovic and Rombough 1998;Burggren 2004). In zebrafish, the relative transparency of the larva allows an even more in-depth optical analysis of the vascular system.…”

Physiological study of larval fishes: challenges and opportunities

“…Cardiac output of larval fishes, for example, can be derived in vivo from heart rate and stroke volume, the latter determined from dimensional changes of the heart during its systolic and diastolic cycling (Hou and Burggren, 1995;Fritsche and Burggren, 1996;Schwerte and Pelster, 2000;Schwerte and Fritsche, 2003;Burggren and Bagatto, 2008). Observations of blood velocity enables the quantitative calculation of blood flow and tissue perfusion, and can be determined in larval fishes and other tiny animals by laser Doppler flow probes (Koyama et al, 1975;Pelster and Bemis, 1991;Schwerte et al, 1997;Pelster and Burggren, 1996), spectroscopic analysis (Altimiras et al, 1995) and digital particle image velocimetry (Hove et al, 2003).…”