Muscle bioenergetics of speeding fish: In vivo ³¹P‐NMR studies in a 4.7 T MR scanner with an integrated swim tunnel

Abstract

Energetic studies on exercising animals are usually limited to oxygen consumption measurements in respirometers followed by invasive tissue sampling and analysis of metabolites. Noninvasive studies of exercising animals like through the use of 31 P NMR are typically restricted to ''stop and go'' measurements. Furthermore, magnetic resonance studies of marine animals are hampered by sea water, a highly electric conductive and dielectric medium, resulting in heavy loading and strong RF loss. In this work, we present a set-up for online determination of muscle bioenergetics in swimming marine fish, Atlantic cod (Gadus morhua), using in vivo 31 P NMR spectroscopy, which overcome these limitations. Special hardware and RF coils were developed for this purpose.

Effects of Phosphates and Salt in Ground Raw and Cooked Farmed Cod (Gadus morhua) Muscle Studied by the Water Holding Capacity (WHC), and Supported by 31P‐NMR Measurements

“…A fraction of an additional peak at approximately 3.0 to 4.5 ppm was observed in all muscle samples during the experimental period as well at a relatively constant level (approximately 0.43 ± 0.04 g s‐P/100 g sample, n = 6; uncorrected values); most probably sugar phosphates (s‐P) (Burt and others 1976; Belton and others 1987) already present as a breakdown products from muscular ATP hydrolysis in the original raw material before freezing 2 d postmortem. No other peaks of phosphate compounds were identified in the control samples, except a minor signal at approximately 0.5 ppm which might be traces of phosphor‐creatine (Bock and others 2008) which normally decline during ATP breakdown and following Pi increase during postmortem metabolism (Bertram and others 2001). …”

“…Recovery of added tripolyphosphate varied from 88% to 100% and the individual phosphate components could be identified. Only in vivo studies on muscular phosphate in fish using 31 P NMR metabolites are available (Van Waarde and others 1990; Sartoris and others 2003; Bock and others 2008). Although these are not directly comparable, the signal profile of metabolites in cod (and other species) illustrates the natural phosphorous content present.…”

CO2 induced pHi changes in the brain of polar fish: a TauCEST application

“…The pH i can be determined by the pH dependent chemical shift of intracellular inorganic phosphate, relative to an endogenous reference signal, using an adequate calibration . In vivo 31 P NMR spectroscopy has already been applied to aquatic animals (for a review see the work of Van der Linden et al), including polar and marine fish species . Nevertheless, the determination of pH i using 31 P NMR spectroscopy has some shortcomings: e.g., the inherently low sensitivity of the 31 P nucleus for NMR spectroscopy limits the temporal and spatial resolution.…”

“…including polar and marine fish species. 37,38 Nevertheless, the determination of pH i using 31 P NMR spectroscopy has some shortcomings: e.g., the inherently low sensitivity of the 31 P nucleus for NMR spectroscopy limits the temporal and spatial resolution. Surface coils are frequently used in 31 P NMR spectroscopy, applied close to the tissue, with the shortcoming of an inhomogeneous B 1 field excitation and a limited spatial resolution.…”

Thermal acclimation to 4 or 10°C imparts minimal benefit on swimming performance in Atlantic cod (Gadus morhua L.)

“…The swim tunnel set-up has previously been described elsewhere (Lurman et al 2007;Bock et al 2008). Briefly, it consisted of three major parts.…”