Indirect effect of sciatic nerve injury on the epidermal thickness of plantar glabrous skin in rats.

In patients with nerve injuries, the skin over the denervated part tends to atrophy. Few experimental studies have dealt with this issue. In this paper we examine the effects of nerve injury on the epidermis in plantar glabrous skin in rats. Analysis of paraffin sections showed that the epidermis becomes abnormally thin after sciatic neurotomy and suture or neurectomy, but not after nerve crush. Autoradiographic analysis showed a subnormal number of thymidine-labelled epidermal cells in plantar skin of rats subjected to sciatic neurectomy. However, after selective division of the sciatic foot branches, with preserved function of thigh and leg muscles, the number of labelled epidermal cells did not differ significantly between the side operated on and the control side. We conclude that the effect of sciatic nerve division on plantar skin in rats is caused by the motor deficiency in the foot rather than by deficient innervation of the skin.

The attachments of the rabbit medial meniscus. A morphological investigation using image analysis and immunohistochemistry.

In the search for a suitable experimental model the rabbit has increasingly been used for investigations on the meniscus. The present study focused on the morphology and innervation of the anterior and posterior medial meniscal attachments in adolescent and adult rabbits in comparison with man. Grossly, the posterior attachment has a similar anatomical position as in man, but the anterior is inserted more anteriorly and more laterally, with a long ligament-like structure between the osseous insertion and the meniscal horn. As in man, the attachment resembles a ligamentous insertion and contains zones of uncalcified and calcified fibrocartilage and subchondral bone. The proportion of the calcified cartilaginous zone in the attachment increases during maturation as in articular cartilage. Nerve fibres were found not only at the horns but also in the uncalcified and calcified fibrocartilaginous zones and the underlying bone. The differences between rabbit and human menisci should be borne in mind when interpreting data from animal experiments.

Anatomy of the rat knee joint and fibre composition of a major articular nerve.

Several recent reports discuss the role of joint nerves in arthritis. Many of these are based on studies in the rat. The aim of this study is to examine the anatomy of the rat knee joint, in search for a primary articular nerve, and to analyze the fibre composition of that nerve. The results show that the structure of the joint differs in some respects from the human knee. At the upper end of the bony patella a cartilaginous patella extends proximally, forming the anterior wall of the suprapatellar bursa. Distinct collateral ligaments are integrated in the joint capsule. The extensor digitorum longus muscle bridges the knee joint, originating from the lateral femoral epicondyle. The well-developed menisci contain pyramid-shaped ossicles. The cruciate ligaments are arranged like in the human knee. A large posterior (PAN) and a small medial (MAN) articular nerve can be identified. The PAN is composed of some 400 axons, about 80% of which are unmyelinated. All myelinated fibres are sensory. They present a unimodal size spectrum with a size range of 1-8 microns, and a predominance of small fibres. Specific denervations indicate that about 1/3 of the unmyelinated axons represent afferents, and some 2/3 are sympathetic efferents. Interestingly, neonatal capsaicin treatment did not influence the number of unmyelinated PAN axons. The functional significance of the numerous unmyelinated sympathetic and sensory PAN axons in the normal knee joint remains to be elucidated.