Figure 4.

P. regalis venom induces weight loss and damage in the tibialis anterior muscle in mice. (A) Graphical representation of the protocol used for the in vivo muscle damage experiment in mice. (B) The percentage of weight change for the venom-injected TA muscles of C57BL/6 mice compared to their contralateral TA muscles at day 5, 10, and 20 following venom administration. The muscle weights were measured in milligrams, and they were normalised by taking contralateral control muscles as 100%. (C) H and E staining of the muscle sections of the undamaged contralateral control and the venom-injected muscles at different time points [green arrows indicate the peripheral nuclei in the undamaged contralateral muscle and the centrally located nuclei (CLN) in the regenerating fibres on days 5, 10, and 20. The black arrows on day 5 indicate the infiltration of immune cells]. (D) Picrosirius red staining for fibrosis (indicated by purple arrows) and quantification of the percentage of staining compared to the contralateral controls. (E) Intra-fibre IgG localisation (arrows indicate the infiltration of IgG) and quantification of the area of infiltrated necrotic fibres that were fully or partially affected in selected 200 µm² areas. Data represent the mean ± SEM (n = 5 mice in each cohort). p values (** p < 0.01 and *** p < 0.001) shown were calculated by one-way ANOVA followed by the Bonferroni post-test except for (B) in which student’s t-test was used. The scale bar represents 50 µm and is applicable to all images.