A light microscopic investigation of the anulus fibrosus in cervical intervertebral discs of the dog was conducted to ascertain the arrangement and distribution of elastic fibers. Elastic fibers were observed in all lamellae of the anulus fibrosus. However, collagenous fibers were the predominant type of connective tissue fiber, and elastic fibers were randomly dispersed among them. Intralamellar (collagenous and elastic) fibers were vertically and obliquely oriented in both superficial and deep lamellae of the anulus fibrosus. All intralamellar fibers were densely and regularly arranged in superficial lamellae, but they were more loosely organized in deep lamellae. A narrow border of interlamellar, elastic fibers was observed between broader, contiguous lamellae in the superficial zone of the anulus fibrosus. Interlamellar elastic fibers were vertically and obliquely arranged in superficial lamellae; however, they were radially oriented in deep lamellae. The deepest lamella of the anulus fibrosus consisted of a loose, three-dimensional network of intermeshing collagenous and elastic fibers. These observations suggest that elastic fibers are integral components of the articular and shock absorption mechanisms of the anulus fibrosus, and the cervical intervertebral disc of the dog is a suitable model for experimental investigation of the role of elastic fibers in intervertebral disc herniation.

A light microscopical study was conducted to ascertain the type of cells in the nucleus pulposus of theadult human intervertrebral disc. Three lumbar intervertebral discs were removed from each of 15 male and femaleadults at autopsy (ages ranged from 19 to 62 years). The tissue was fixed in formalin, decalcified in formic acid, dehydrated in a graded series of ethanol, embedded in paraffin, and serially sectioned at 7–10 µm. Tissue sectionswere affixed to albuminized glass slides and stained either by hematoxylin and eosin or hematoxylin and VanGieson’s stain. The cells of the bulk of the nucleus pulposus consisted of chondrocytes and a few fibroblasts;however, the subchondral matrix of the nucleus pulposos contained numerous stellate cells with (from 1 to 8)unusually long (up to 80 µm) primary cytoplasmic porcesses that often branch into secondary processes. The cellprocesses contained cytoplasmic varicosities at various intervals along their lengths; and their endings oftenexpanded into bulbous, vesicle-filled process terminals. The surrounding extracellular matrix usually containednumerous, vesicle-filled, eosinophil matrix bodies. Morphological similarities of cytoplasmic varicosities, processterminals, and matrix bodies, as well as the apparent budding of process terminals, suggest that these previouslyunidentified cells are secreting an unknown matrix component into the subchondral matrix of the nucleus pulposusof the adult human. *

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Abstract:The organization of the primary somatosensory cortex innervated by the ulnar nerve was studied before and immediately after ulnar nerve transection in 11 cats electrophysiologically mapped under Nembutal or Ketamine anesthesia. The cortex was reexamined a second time beginning 42 hr after nerve transection in four cats anesthetized with Nembutal. One additional sham-operated control was also mapped. The region of cortex formerly served by the ulnar nerve remained largely unresponsive to somatic stimulation independent of the type of anesthetic used during recording. Nonetheless, animals anesthetized with Ketamine had more new responsive sites in deafferented cortex following nerve cut than cats anesthetized with Nembutal. New responses, when observed, were evoked by stimulation of a region of skin adjacent to the region served by the ulnar nerve. These findings suggest that the immediate response to deafferentation of somatosensory cortex is a limited acquisition of novel responses restricted to a region immediately adjacent to cortex containing normal afferent input.Resume: Zones et endues de non-reponse apparaissant dans le cortex somesthesique du chat immediatement apres la section du nerf cubital. Nous avons Studie l'organisation du cortex somesthesique primaire innerve par le nerf cubital avant et immediatement apres la section du nerf cubital chez 11 chats cartographies au point de vue 61ectrophysiologique sous anesth6sie au Nembutal ou a la ketamine. Le cortex a tt& reaxamine une seconde fois 42 heures apres la section nerveuse chez 4 chats anesthesies au Nembutal. Un chat controle ayant subi une operation factice a aussi ete cartographie. La region du cortex desservie anterieurement par le nerf cubital est demeuree en grande partie insensible a la stimulation somatique, quel qu'ait ete le type d'anesthesie utilise pendant l'enregistrement. Cependant, les animaux anesthesies a la ketamine avaient plus de sites sensibles nouveaux dans le cortex desafferentie suite a la section nerveuse que les chats anesthesies au Nembutal. Quand de nouvelles reponses etaient observees, elles etaient provoquees par la stimulation d'une region de la peau adjacente a la region innervee par le nerf cubital. Ces observations suggerent que la reponse immediate a la desafferentiation du cortex somesthesique est une acquisition limitee de reponses nouvelles, restreintes a la region immediatement adjacente au cortex contenant l'infux afferent normal.

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