Histological and magnetic resonance imaging assessment of Liqoseal in a spinal in vivo pig model

Background:Liqoseal (Polyganics,B.V.) is a dural sealant patch for preventing postoperative cerebrospinal fluid (CSF) leakage.It has been extensively tested preclinically and CE (Conformite Européenne) approved for human use after a first cranial in-human study.However,the safety of Liqoseal for spinal application is still unknown.The aim of this study was to assess the safety of spinal Liqoseal application compared with cranial application using histology and magnetic resonance imaging characteristics.Methods:Eight female Dutch Landrace pigs underwent laminectomy,durotomy with standard suturing and Liqoseal application.Three control animals underwent the same procedure without sealant application.The histological characteristics and imaging characteristics of animals with similar survival times were compared to data from a previous cranial porcine model.Results:Similar foreign body reactions were observed in spinal and cranial dura.The foreign body reaction consisted of neutrophils and reactive fibroblasts in the first3 days,changing to a chronic granulomatous inflammatory reaction with an increasing number of macrophages and lymphocytes and the formation of a fibroblast layer on the dura by day 7.Mean Liqoseal plus dura thickness reached a maximum of 1.2mm(range 0.7-2.0mm) at day 7.Conclusion:The spinal dural histological reaction to Liqoseal during the first 7days was similar to the cranial dural reaction.Liqoseal did not swell significantly in both application areas over time.Given the current lack of a safe and effective dural sealant for spinal application,we propose that an in-human safety study of Liqoseal is the logical next step.

Spinal fixation after laminectomy in pigs prevents postoperative spinal cord injury

Background:A safe,effective,and ethically sound animal model is essential for preclinical research to investigate spinal medical devices.We report the initial failure of a porcine spinal survival model and a potential solution by fixating the spine.Methods:Eleven female Dutch Landrace pigs underwent a spinal lumbar interlaminar decompression with durotomy and were randomized for implantation of a medical device or control group.Magnetic resonance imaging(MRI)was performed before termination.Results:Neurological deficits were observed in 6 out of the first 8 animals.Three of these animals were terminated prematurely because they reached the predefined humane endpoint.Spinal cord compression and myelopathy was observed on postoperative MRI imaging.We hypothesized postoperative spinal instability with epidural hematoma,inherent to the biology of the model,and subsequent spinal cord injury as a potential cause.In the subsequent 3 animals,we fixated the spine with Lubra plates.All these animals recovered without neurological deficits.The extent of spinal cord compression on MRI was variable across animals and did not seem to correspond well with neurological outcome.Conclusion:This study shows that in a porcine in vivo model of interlaminar decompression and durotomy,fixation of the spine after lumbar interlaminar decompression is feasible and may improve neurological outcomes.Additional research is necessary to evaluate this hypothesis.

Ontogeny of vocal rhythms in harbor seal pups: an exploratory study

Puppyhood is a very active social and vocal period in a harbor seal's life Ph oca vitulina. An important feature of vocalizations is their temporal and rhythmic structure, and understanding vocal timing and rhythms in harbor seals is critical to a cross-species hypothesis in evolutionary neuroscience that links vocal learning, rhythm perception, and synchronization. This study utilized analytical techniques that may best capture rhythmic structure in pup vocalizations with the goal of examining whether (1) harbor seal pups show rhythmic structure in their calls and (2) rhythms evolve over time. Calls of 3 wild-born seal pups were recorded daily over the course of 1-3 weeks;3 temporal features were analyzed using 3 complementary techniques. We identified temporal and rhythmic structure in pup calls across different time windows. The calls of harbor seal pups exhibit some degree of temporal and rhythmic organization, which evolves over puppyhood and resembles that of other species' in teractive comm un icati on. We suggest n ext steps for investigating call structure in harbor seal pups and propose comparative hypotheses to test in other pinniped species.