Pit bull-type breeds with dilated cardiomyopathy eating nontraditional diets improve after diet change (2015-2022).

OBJECTIVE: To compare signalment, clinical signs, diet, echocardiographic findings, and outcome for pit bull-type breeds diagnosed between 2015 and 2022 with dilated cardiomyopathy (DCM) or with DCM diagnosed by a cardiologist but that did not meet all study echocardiographic criteria (DCM-C). ANIMALS: 91 dogs with DCM and 11 dogs with DCM-C. PROCEDURES: Data were collected on clinical findings, echocardiographic measurements, and diet at the time of diagnosis (for 76/91 dogs); echocardiographic changes; and survival. RESULTS: For dogs with diet information available for time of diagnosis, 64/76 (84%) dogs were eating nontraditional commercial diets, while 12/76 (16%) were eating traditional commercial diets. There were few differences between diet groups at baseline, with congestive heart failure and arrhythmias common in both groups. Thirty-four dogs with known baseline diet and diet change status had follow-up echocardiograms between 60 and 1,076 days later (traditional diet, n = 7; nontraditional diet that changed diets, 27; and nontraditional diet group without diet change, 0). Dogs in the nontraditional diet group that changed diets had a significantly greater decrease in normalized left ventricular diameter (diastolic, P = .02; systolic, P = .048) and the left atrium-to-aorta ratio (P = .002) and a significantly greater increase in fractional shortening (P = .02) compared to dogs eating traditional diets. Dogs eating nontraditional diets with diet change (n = 45; P < .001) and dogs eating traditional diets (12; P < .001) had a significantly longer survival time compared to dogs eating nontraditional diets without diet change (4). Dogs with DCM-C also had significant echocardiographic improvements after diet change. CLINICAL RELEVANCE: Congestive heart failure and arrhythmias were common in pit bull-type breeds with DCM. Those eating nontraditional diets that changed diets had significant improvements in echocardiographic measurements after diet change.

Hyper-swivel head domain motions are required for complete mRNA-tRNA translocation and ribosome resetting.

Translocation of messenger RNA (mRNA) and transfer RNA (tRNA) substrates through the ribosome during protein synthesis, an exemplar of directional molecular movement in biology, entails a complex interplay of conformational, compositional, and chemical changes. The molecular determinants of early translocation steps have been investigated rigorously. However, the elements enabling the ribosome to complete translocation and reset for subsequent protein synthesis reactions remain poorly understood. Here, we have combined molecular simulations with single-molecule fluorescence resonance energy transfer imaging to gain insights into the rate-limiting events of the translocation mechanism. We find that diffusive motions of the ribosomal small subunit head domain to hyper-swivelled positions, governed by universally conserved rRNA, can maneuver the mRNA and tRNAs to their fully translocated positions. Subsequent engagement of peptidyl-tRNA and disengagement of deacyl-tRNA from mRNA, within their respective small subunit binding sites, facilitate the ribosome resetting mechanism after translocation has occurred to enable protein synthesis to resume.