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Carbon dioxide (CO2) is one of the most commonly used gas euthanasia agents in mice, despite reports of aversion and nociception. Inert gases such as nitrogen (N2) may be a viable alternative to carbon dioxide. Here we compared behavioural and electrophysiological reactions to CO2 or N2 at either slow fill or rapid fill in C57Bl/6 mice undergoing gas euthanasia. We found that mice euthanised with CO2 increased locomotor activity compared to baseline, whereas mice exposed to N2 decreased locomotion. Furthermore, mice exposed to CO2 showed significantly more vertical jumps and freezing episodes than mice exposed to N2. We further found that CO2 exposure resulted in increased theta:delta of the EEG, a measure of excitation, whereas the N2 decreased theta:delta. Differences in responses were not oxygen-concentration dependent. Taken together, these results demonstrate that CO2 increases both behavioural and electrophysiological excitation as well as producing a fear response, whereas N2 reduces behavioural activity and central neurological depression and may be less aversive although still produces a fear response. Further studies are required to evaluate N2 as a suitable euthanasia agent for mice.

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An analysis of the MR-images of 75 patients with calcifying tendinitis of the shoulder was performed. The aim of the study was to recognize characteristic findings of the calcific deposits and their relation to the involved tendons as well as the coincidence with additional degenerative alterations of the rotator cuff. The calcifications can be demonstrated with high accuracy (> 95%) in T1-weighted images as areas of decreased signal intensity. It is possible to characterize the calcifications similar to Gärtner's radiologic classification differentiating form and density of the calcific deposits as well as their delimitation to the tendon structure. In T2-images there frequently is a perifocal band of increased signal intensity which can be identified as an oedema around the calcification. Analysing two perpendicular planes the calcifications can be assigned to the corresponding anatomical structure. 83 percent were located in the supraspinatus tendon above the humeral head or in the superior part of the subscapularis tendon. Degenerative areas of the rotator cuff are demonstrated as small zones of increased signal intensity, abnormal morphology or discontinuity of the tendon. Only in one patient a partial tear could be found; 11 percent showed variable signs of degenerative alteration of the involved tendon.

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