Examination of a new arthrodesis technique for equine cervical vertebrae

Objectives – To investigate a new technique for fusion of equine cervical vertebrae: 1. Report the findings from a single case. 2. Examine the biomechanical properties of the construct in cadaver specimens and compare the biomechanical properties with the currently used arthrodesis technique. Study design – Case report, followed by two in vitro biomechanical investigations. Sample population – Single case for the case report then cadaveric adult equine cervical vertebral columns for biomechanical testing. Methods –A three month old foal with cervical stenotic myelopathy was deemed too small for treatment with a kerf cut cylinder, so arthrodesis was performed using a ventrally placed locking compression plate. The case was followed and reported. A test modulus was developed to allow biomechanical testing of a single cervical vertebral articulation and the biomechanical properties of different implants were investigated. The investigation was followed by further investigation in different loading directions. Results –The foal responded well to treatment and had improved 2.5 neurological grades by 30 months post-operatively. Results of the two biomechanical studies demonstrated that the biomechanical properties of the LCP construct were comparable to superior to the KCC constructs in flexion, extension and lateral flexion. Conclusions –The LCP technique has potential as an arthrodesis technique for equine cervical vertebrae. Evaluation of the technique in live adult cases is warranted

Aerospace Medicine and Biology: A continuing bibliography with indexes, supplement 136, January 1975

This special bibliography lists 238 reports, articles, and other documents introduced into the NASA scientific and technical information system in December 1974

Towards a Systematic Understanding of the Neural Circuits of the Periaqueductal Grey (PAG)

The midbrain periaqueductal grey (PAG) is commonly recognised as the exit relay for the coordination and execution of a wide range of instinctive behaviours, such as defense, reproduction and predation. In line with its functional diversity, are the range of inputs it receives from higher cortical and subcortical areas as well as ascending spinal pathways, and the various neurotransmitter and neuromodulatory mechanisms active in its different subregions. However, the lack of a comprehensive cell-type classification of the PAG hinders systematic investigations into the intricacies of its many behavioural roles. Here, we applied high-throughput single neuronal nucleus RNA-sequencing to profile transcriptomes of adult mouse PAG neurons. Our data revealed at least 9 distinct PAG neuronal subpopulations, marked by differential expressions of neurotransmitter, neuromodulator and ion channel genes. In addition, using a combination of optogenetic manipulations and a carefully designed defense test battery, we identified separate functions of dPAG vGlut2+, PACAP+ and Tac2+ neurons in triggering and modulating defensive behaviour. We showed that dlPAG vGlut2+ neurons project to the Cuneiform nucleus, and this projection is an output pathway for PAG elicited escape behaviour. Our work supports the existence of molecularly distinct, functionally divergent pathways in the PAG underlying defensive behaviour, and demonstrates a framework towards a systematic dissection of cell-type specific functions of complex brain regions

Brainstem circuits involved in skilled forelimb movements

Movement is the main output of the nervous system as well as the fundamental form of interaction animals have with their environment. Due to its function and scope, movement has to be characterized by both stability and flexibility. Such apparently conflicting attributes are reflected in the complex organization of the motor system, composed of a vast network of widely distributed circuits interacting with each other to generate an appropriate motor output. Different neuronal structures, located throughout the brain, are responsible for producing a broad spectrum of actions, ranging from simple locomotion to complex goal directed movements such as reaching for food or playing a musical instrument. The brainstem is one of such structures, holding considerable importance in the generation of the motor output, but also largely unexplored, due to its less-than-accessible anatomic location, functional intricacies and the lack of appropriate techniques to investigate its complexity. Despite recent advances, a deeper understanding of the role of brainstem neuronal circuits in skilled movements is still missing. In this dissertation, we investigated the involvement of the lateral rostral medulla (LatRM) in the construction of skilled forelimb behaviors. The focus of my work was centered on elucidating the anatomical and functional relationships between LatRM and the caudal brainstem, and specifically on the interactions with the medullary reticular formation, considering both its ventral (MdV) and dorsal subdivisions (MdD). In summary, we reveal the existence of anatomically segregated subpopulations of neurons in the lower brainstem which encode different aspects of skilled forelimb movements. Moreover, we show that LatRM neurons are necessary for the correct execution of skilled motor programs and their activation produces complex coordinated actions. All this evidence suggests that LatRM may be a key orchestrator for skilled movements by functioning as integration center for upstream signals as well as coordinator by selecting the appropriate effectors in the lower medulla and the spinal cord