In response to noxious stimuli, planarians cease their typical ciliary gliding and exhibit an oscillatory type of locomotion called scrunching. We have previously characterized the biomechanics of scrunching and shown that it is induced by specific stimuli, such as amputation, noxious heat, and extreme pH. Because these specific inducers are known to activate Transient Receptor Potential (TRP) channels in other systems, we hypothesized that TRP channels control scrunching. We found that chemicals known to activate TRPA1 (allyl isothiocyanate (AITC) and hydrogen peroxide) and TRPV (capsaicin and anandamide) in other systems induce scrunching in the planarian species Dugesia japonica and, except for anandamide, in Schmidtea mediterranea. To confirm that these responses were specific to either TRPA1 or TRPV, respectively, we tried to block scrunching using selective TRPA1 or TRPV antagonists and RNA interference (RNAi) mediated knockdown. Unexpectedly, co-treatment with a mammalian TRPA1 antagonist, HC-030031, enhanced AITC-induced scrunching by decreasing the latency time, suggesting an agonistic relationship in planarians. We further confirmed that TRPA1 in both planarian species is necessary for AITC-induced scrunching using RNAi. Conversely, while co-treatment of a mammalian TRPV antagonist, SB-366791, also enhanced capsaicin-induced reactions in D. japonica, combined knockdown of two previously identified D. japonica TRPV genes (DjTRPVa and DjTRPVb) did not inhibit capsaicin-induced scrunching. RNAi of DjTRPVa/DjTRPVb attenuated scrunching induced by the endocannabinoid and TRPV agonist, anandamide. Overall, our results show that although scrunching induction can involve different initial pathways for sensing stimuli, this behavior’s signature dynamical features are independent of the inducer, implying that scrunching is a stereotypical planarian escape behavior in response to various noxious stimuli that converge on a single downstream pathway. Understanding which aspects of nociception are conserved or not across different organisms can provide insight into the underlying regulatory mechanisms to better understand pain sensation.

No abstract

We present a multiwavelength study of the massive galaxy cluster Abell 1763 at redshift z = 0.231. Image analysis of a 19.6 ks Chandra archival observation reveals a cluster-wide spiral of enhanced surface brightness in the intracluster medium (ICM). While such spirals are understood to form in clusters with sloshing strong cool cores (SCCs), the gas comprising the spiral's apex is of intermediate entropy (∼ 110 keV cm 2 ) and cooling time (∼ 6.8 Gyr), indicating core disruption is occurring throughout the spiral formation process. Two subclusters dominated by the secondand third-ranked galaxies in the system lie along a line parallel to the elongation axis of the primary cluster's ICM. Both subsystems appear to have fallen in along a previously discovered intercluster filament and are each considered candidates as the perturber responsible for initiating disruptive core sloshing. Dynamical analysis indicates infall is occurring with a relative radial velocity of ∼ 1800 km s −1 . The brightest cluster galaxy of Abell 1763 possesses a high line-of-sight peculiar velocity (v pec ∼ 650 km s −1 ) and hosts a powerful (P 1.4 ∼ 10 26 W Hz −1 ) bent double-lobed radio source, likely shaped by the relative bulk ICM flow induced in the merger. The cluster merger model of SCC destruction invokes low impact parameter infall as the condition required for core transformation. In contrast to this, the high angular momentum event occurring in Abell 1763 suggests that off-axis mergers play a greater role in establishing the non-cool core cluster population than previously assumed.

25In response to noxious stimuli, planarians cease their typical ciliary gliding and exhibit 26 an oscillatory type of locomotion called scrunching. We have previously characterized the 27 biomechanics of scrunching and shown that it is induced by specific stimuli, such as 28 amputation, noxious heat, and extreme pH. Because these specific inducers are known to 29 activate Transient Receptor Potential (TRP) channels in other systems, we hypothesized that 30 TRP channels control scrunching. We found that chemicals known to activate TRPA1 (allyl 31 isothiocyanate (AITC) and hydrogen peroxide) and TRPV (capsaicin and anandamide) in other 32 systems induce scrunching in the planarian species Dugesia japonica and, except for 33 anandamide, in Schmidtea mediterranea. To confirm that these responses were specific to 34 either TRPA1 or TRPV, respectively, we tried to block scrunching using selective TRPA1 or 35 TRPV antagonists and RNA interference (RNAi) mediated knockdown. Unexpectedly, co-36 treatment with a mammalian TRPA1 antagonist, HC-030031, enhanced AITC-induced 37 scrunching by decreasing the latency time, suggesting an agonistic relationship in planarians. 38 We further confirmed that TRPA1 in both species is necessary for AITC-induced scrunching 39 using RNAi. Conversely, while co-treatment of a mammalian TRPV antagonist, SB-366791, 40 also enhanced capsaicin-induced reactions in D. japonica, combined knockdown of two 41 previously identified D. japonica TRPV genes (DjTRPVa and DjTRPVb) did not inhibit 42 capsaicin-induced scrunching. Surprisingly, RNAi of either DjTRPAa or DjTRPVa/DjTRPVb 43 disrupted scrunching induced by the endocannabinoid and TRPV agonist, anandamide. 44 Overall, our results show that although scrunching induction can involve different initial 45 pathways for sensing stimuli, this behavior's signature dynamical features are independent of 46 the inducer, implying that scrunching is a stereotypical planarian escape behavior in response 47 to various noxious stimuli that converge on a single downstream pathway. Understanding 48 which aspects of nociception are conserved or not across different organisms can provide 49 3 insight into the underlying regulatory mechanisms to better understand pain sensation. 50 51 52Normal locomotion of freshwater planarians, termed gliding, is achieved through 53 synchronous beating of cilia in a layer of secreted mucus (1-3). Gliding planarians display a 54 smooth motion without major body shape changes, except for turning movements of the 55 anterior end. However, when exposed to certain noxious stimuli (e.g. low pH, high temperature, 56 or amputation), planarians switch to a muscular-based escape gait that is characterized by 57 oscillatory body length changes (4). We termed this gait scrunching and showed that it has a 58 characteristic set of 4 quantifiable parameters: 1. frequency of body length oscillations, 2. 59 relative speed, 3. maximum amplitude, and 4. asymmetry of body elongation and contraction 60 (4). Moreover, scrunching is conserve...