Adenosine deaminase was determined in 28 different areas of the human neuraxis
in 5 adult male cadavers, with no known disease of the nervous system, using a very
sensitive colorimetric method. The enzyme was highest in the frontal lobe white matter, and
lowest in the medulla and all levels of the spinal cord. Enzyme content was about twice as
great in the white matter of the frontal and temporal lobes and cerebellum as it was in the
cortical gray matter of these areas, but only slightly higher in the white matter of the parietal
and occipital lobes as compared to gray. Average values of the enzyme were found in the
remaining areas of the brain, with the exception of the pons and cerebellar white matter,
where a higher than average value was noted.
This investigation was undertaken to examine the observations of Becker ('72) pertaining to the electrical facilitation of partial limb regenerative responses by means of Ag-Pt wire couples applied to the limb stumps of young, forelimb-amputated white rats. Additionally, in order to examine the possible role of mechanical effects of such device implantations, we have employed uncoupled devices delivering no current or potential difference. In the present experiments, in response to coupled device implantation, cartilage and bone were actively formed in the vicinity of the Pt electrode tip. These tissues contributed to the lengthwise extension of the limb and to the partial restoration of the distal humeral extremity. In limbs bearing the uncoupled electrical devices, qualitatively similar responses were noted, but osteogenesis was diminished in extent compared to that seen in limbs bearing the active or coupled devices. It is therefore necessary to consider the role of mechanical factors in the elicitation of the observed regenerative responses. Myogenesis was enhanced in electrically stimulated limbs, but not in those rats bearing uncoupled devices.
A simple program of handling and care of pregnant rats before delivery makes it possible to carry out surgical procedures on newborn pups without resultant cannibalism or rejection of the operated animals by their mothers.
It has long been appreciated that the neonatal rat can regenerate the distal femoral growth-plate. Earlier descriptions of this process pointed to the age of the rodent and level and angle of amputation as significant modifiers of the regeneration process; but none identified the origin of the chondrocytes forming the growth-plate regenerate, nor described the time course and significant milestones of the process. Examination of these issues constitutes the objective of the present report. Fifty-four male, outbred albino rats sustained low femoral (48 rats) or midtibiofibular (six rats) hind-limb amputations when ten to eleven days old. They were killed after 0, 1, 2, 4, 7, 14, 22 or 29 postoperative days; and their amputation stumps were sectioned longitudinally. Twenty-four hr after amputation, the distal femoral periosteum was thickened and metachromatic regions were observed forming within it. Intraperiosteal cartilage was observed by the end of the second postoperative day in four of six limb stumps and, during the following week, expanded considerably in volume. Regenerated growth-plate cell architecture was recognized within the enlarging cartilage mass by the end of the second week; and, by the end of the fourth postoperative week, the regenerating growth-plate region had achieved considerable architectural maturity.
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