Ractopamine-induced changes in the proteome of post-mortem beef longissimus lumborum muscle

Ractopamine is a beta-adrenergic agonist that is approved for use in beef cattle, pigs and turkeys as a repartitioning agent to increase lean muscle deposition and decrease lipogenesis. Although the effects of dietary ractopamine on the proteome profile of post-mortem pork muscles have been examined, its influence on beef muscle proteome has not been studied. Therefore, the objective of this study was to examine the effect of ractopamine on the proteome profile of post-mortem beef longissimus lumborum (LL) muscle. LL muscle samples were obtained from the carcasses of six (n = 6) steers fed ractopamine (RAC; 400 mg ractopamine hydrochloride for 28 days) and six (n = 6) steers fed no ractopamine (CON). The muscle proteome was analysed using two-dimensional gel electrophoresis and tandem mass spectrometry. Five differentially abundant spots were identified, and all the spots were over-abundant in RAC. The identified proteins were involved in muscle structure development (F-actin-capping protein subunit beta-2; PDZ and LIM domain protein-3), chaperone activity (heat shock protein beta-1), oxygen transport (myoglobin), and glycolysis (L-lactate dehydrogenase A chain). These results suggested that dietary ractopamine could influence the abundance of enzymes associated with muscle development and muscle fibre type shift in beef LL muscle.Keywords: growth promotants, meat quality, proteomic

Renal pericytes: regulators of medullary blood flow

Regulation of medullary blood flow (MBF) is essential in maintaining normal kidney function. Blood flow to the medulla is supplied by the descending vasa recta (DVR), which arise from the efferent arterioles of juxtamedullary glomeruli. DVR are composed of a continuous endothelium, intercalated with smooth muscle-like cells called pericytes. Pericytes have been shown to alter the diameter of isolated and in situ DVR in response to vasoactive stimuli that are transmitted via a network of autocrine and paracrine signalling pathways. Vasoactive stimuli can be released by neighbouring tubular epithelial, endothelial, red blood cells and neuronal cells in response to changes in NaCl transport and oxygen tension. The experimentally described sensitivity of pericytes to these stimuli strongly suggests their leading role in the phenomenon of MBF autoregulation. Because the debate on autoregulation of MBF fervently continues, we discuss the evidence favouring a physiological role for pericytes in the regulation of MBF and describe their potential role in tubulo-vascular cross-talk in this region of the kidney. Our review also considers current methods used to explore pericyte activity and function in the renal medulla

Nonautonomous helical motion of magnetization in ferromagnetic nanowire driven by spin-polarized current and magnetic field

We report the nonautonomous domain wall motion in ferromagnetic nanowire driven by spin-polarized current and magnetic field. Our results expatiate the major formation of domain wall velocity which comes from two parts: the longitudinal external field along the easy axis and the coherent domain wall rotation velocity. A critical condition is obtained analytically. Below the critical value, the domain wall rotation stops finally and domain wall velocity is proportional to the longitudinal external field. Above the critical value, the domain wall open out the novel nonautonomous helical motion characterized by the coherent rotation without any distortion. The domain wall velocity can be arbitrarily large for the linear proportion to longitudinal field strength