Synaptic transmission between dorsal root afferents and neurons in the superficial laminae of the spinal dorsal horn (laminae I-III) was examined by intracellular recording in a transverse slice preparation of rat spinal cord. Brief high-frequency electrical stimulation (300 pulses at 100 Hz) of primary afferent fibers produced a long-term potentiation (LTP) or a long-term depression (LTD) of fast (monosynaptic and polysynaptic) EPSPs in a high proportion of dorsal horn neurons. Both the AMPA and the NMDA receptor-mediated components of synaptic transmission at the primary afferent synapses with neurons in the dorsal horn can exhibit LTP and LTD of the synaptic responses. In normal and neonatally capsaicin-treated rats, the induction of LTP requires the activation of NMDA receptor-gated conductances. The induction of LTP or LTD, however, was not abolished in the presence of bicuculline, a GABAA receptor antagonist. The results demonstrate that distinct and long-lasting modulation in synaptic efficiency can be induced at primary afferent synapses with neurons in the superficial laminae of spinal dorsal horn by high-frequency stimulation of dorsal root afferents and that these changes may be physiologically relevant for transmission and integration of sensory information, including pain.

Many clinically relevant congenital malformations arise during mid to late embryonic stages. This period is challenging to image quantitatively in live embryos, necessitating the use of multiple specimens with increased experimental variability. Here we establish X-ray and blood-pool computed tomography (CT) contrast agent toxicity and teratogenesis thresholds for 3D Micro-CT imaging of live avian embryos. Day 4 chick embryos micro-injected with Visipaque™ (VP) developed for an additional 6 days without defect. X-ray radiation up to 798 mGy was nontoxic. Peak average contrast of 1,060 HU occurred within 1 hr of imaging at 50 μm resolution. VP-enhanced contrast persisted past 24 hr with delayed accumulation in the allantois. Regional volumes of VP-injected embryos were statistically identical to those of fixed embryos perfused with osmium tetroxide. We further quantified longitudinal volumetric morphogenesis of the allantois over 30 hr. These results demonstrate the safety and efficacy of contrast enhanced quantitative micro-CT imaging for live embryos.

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Background Three‐dimensional (3D) printing has seen increasing interest in surgery, where it improves the visualization of difficult anatomy in complex cases. This literature review investigates the benefits and limitations of 3D printed models in preoperative planning in the field of orthopaedic surgery. Methods A literature search was performed using the Ovid platform on the Embase and MEDLINE databases using the terms ‘3D printing’, ‘Orthopaedics’ and ‘Surgical Planning’. Studies using 3D printed models as a part of preoperative planning were included. All others were excluded. Data regarding the metrics used to assess the benefit of the use of 3D models, surgical outcome, and surgeon or patient opinion on the technology were extracted. Results A total of 41 studies resulted. Eight (19.5%) were case–control studies, the remainder were case reports or case series. Assessment of benefit was mostly subjective, although the case–control studies included objective metrics such as operation time, intraoperative blood loss and intraoperative fluoroscopy time. The use of 3D printing technology showed subjective benefit for both patient and surgeon as well as indicating clinically significant improvements in intraoperative metrics. Conclusion Despite the current absence of large scale trials, 3D printing has clear benefits in preoperative planning, particularly when utilized in complex cases. A streamlined workflow for case selection, in‐house model creation and preoperative rehearsals is still required to be developed before the process is ready for routine use. Evidence supports an improvement in intraoperative metrics and patient engagement but data to support improved clinical outcome is lacking.