Comparative morphological study of homo- and heterotopic neural transplants

Abstract

Neural transplantation provides an approach to problems in the practice of medicine, as well as to basic questions relating to mechanism of histogenetic processes, synaptogenesis, and the pathogenesis of a number of neuropsychic illnesses. An adequate, and in many respects unique, model for studies of the mechanisms of nerve tissue histogenesis is provided by transplantation of embryonic rudiments of the nervous system into ectopic sites in adult animals, which allows studies of the roles of the microenvironment and innervation in the fulfillment of histoblastic potential. Transplantation of embryonic neocortex rudiments into different parts of the brain [4,5,13], spinal cord [8,12,14], peripheral nerves [10,11,19], anterior chamber of the eye [7,17], testicle [2], and salivary glands [9] has been shown to result in realization of the histoblastic potential of the transplanted tissue; the cellular elements differentiate into mature neurons and glial cells. However, comparative analysis of the development of cellular elements transplanted into different parts of the body has not yet been performed, and the characteristics of histogenesis in homo-and heterotopic transplants have not been determined.The aim of the present work was to compare the dynamics of the development of autotransplants of rat embryo neocortex into the brain and peripheral nerves of adult animals. MATERIALS AND METHODSStudies were carried out on 40 male Wistar rats (200-250 g). Embryonic material was transplanted into the brain (experiment I) and sciatic nerve (experiment II) under anesthesia (Calypsol 200 mg/kg i.p.). Donors were Wistar rat embryos of 15 days of development. The dorsolateral wall of the anterior cerebral ventricle, containing deposits of neocortex, was collected, and was placed for no more than 2 h in medium 199 (Moscow) containing streptomycin sulfate (0.01 g per 10 mg of medium); prior to transplantation, embryonic material was cut into pieces of 0.5 x 1 mm. In experiment I, the head was shaved over the projection of the right cerebral hemisphere and the skin was incised, and an opening was made in the skull using a dental drill in the region of the tuberosity over the right ventricle. Embryonic material was transplanted using a glass eannula passed through the dura mater. In experiment II, hair was removed over the upper third of the thigh, the skin and underlying muscles were incised, the nerve was freed from loose connective tissue, and was clamped for 30 see. Fibers from one of the nerve stems were cut, and a glass cannula was used to introduce embryonic material under the perineurium. Animals were kept in standard animal-house cor, ditions, and were sacrificed by overdosage with ether vapors at 1, 3, 7, 10, and 30 days after surgery. For histological studies, brains were fixed in Bouin's fluid, and paraffin sections of thickness 5/~m were stained with hematoxylin and eosin and Nissrs toluidine blue. The ratio of neurons to the total number of transplant cells was measured, using 4000-5000 cells. Results were analyzed st...

The kinetics of neurite structure after isolation from the Mollusk brain

“…However, it should be emphasized that the data indicating that after retraction of all processes, even neurons which have rounded up, i.e., cells which have lost all signs of differentiation, still have the ability to regenerate [4,5]. Most studies on the regeneration of isolated neurons and on their cultivation and transplantation have been carried out using neurons from embryos or neonates [7,16,19,22]. It has been suggested that poorly differentiated neuronal cells have greater regenerative potential than neurons from adults.…”