The template activity of nuclear chromatin of pyramids and stellate neurons of rat sensorimotor cortex during postnatal differentiation is studied in intact brains and after transplantation. In none of the examined periods after homotopic transplantation does the mean level of template activity of the extranucleolar chromatin in different populations of neurons reach the maximum level observed in normal ceils. By contrast, at almost at all times after heterotopic transplantation the mean level of transcription is significantly higher than in the control.
Key Words: chromatin; transplantation; transcription; neuron; sensorimotor cortexThe transplantation of embryonal nervous tissue in the brain of humans and animals has become an increasingly important research and clinical tool. A large body of experimental evidence has been accumulated on the development and function of nerve cells in a graft [2]. However, numerous aspects of this problem have not been investigated. The use of modem methods is vital for the evaluation of the major parameters of neuronal vitality and their specific features after transplantation.Our aim was to study the transcriptional activity of chromatin in the neurons of the rat sensofimotor cortex (SMC) after homo-and heterotopic transplantation in different periods of postnatal ontogenesis corresponding to the differentiated and nondifferentiated states.
MATERIALS AND METHODSLarge and medium pyramidal and stellate neurons of the 3rd, 5th, and 4th layers of SMC were studied on days 14, 45, and 90 of postnatal ontogenesis Russian State Medical University, Moscow in intact outbred albino rats and after transplantation in the SMC of the cerebral hemispheres or in the cerebellar cortex. Brain cortex of 19-day-old embryos served as grafts. Transplantation was performed by the standard method. The recipient rats were sacrificed 17, 48, and 93 days after the operation.The transcriptional activity of chromatin was evaluated using the radioautography technique, which reveals the activity of endogenous RNA polyrnerases in fixed cells on histological preparations [3]. Sections (8 g thick) of the brain cortex or cerebellum with grafted tissue were cut on a histocryotome at20oC, air dried, and fixed with an ethanol-acetone mixture (1:1) (4~ 5 man). Then the sections were incubated at 37~ for 30 rain with 0.02 ml of a mixture containing (in mM): Tris-HC1 (pH 7.9) 100, sucrose 150, ammoniurn sulfate 80, 2-mercaptoethanol 12, sH-UTP 0.02, unlabeled triphosphates 0.6 each; MgC12 8, and MnCl: 2. The reaction was stopped by a thorough washing of the preparations in distilled water, which was followed by a 30-rnin postfLxation with ethanolacetic acid (3:1). Unincorporated phosphates were removed by treatment with 5% trichloroacetic acid (4~ 15 rain); the sections
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