Time of Origin of the Neurons in the Caudal Brain Stem of RatNornes, Howard O.; Morita, Michio
doi: 10.1159/000112444pmid: N/A
This study was designed to determine the time of origin of neurons in the caudal brain stem of rat. A single injection of [<sup>3</sup>H]-thymidine was given to a pregnant animal for each of the days of gestation from 11 to 20. By analyzing the location of the heavily labeled neurons in the offspring of these animals, it was determined that the neurons in this part of the brain of rat originated on days 11–16 of gestation. The motor neurons were heavily labeled on days 11–13 of gestation, with the majority labeled on day 12 in all motor nuclei except in the facial nucleus where they peaked on day 13. The somatic and visceral sensory neurons were heavily labeled on days 12–15 of gestation with the peak on days 13 and 14. The neurons derived from the rhombic lip were heavily labeled on days 12–16.
Development of Rat Spinal Cordde Sousa, Byron N.; Horrocks, Lloyd A.
doi: 10.1159/000112445pmid: N/A
At birth, the rat spinal cord has 5% of the adult weight and 21% of the adult length. The ratio of weight to length, the 'thickness', more than doubled between 7 and 20 days of age and doubled again between 20 days and adulthood. The intact spinal cord can be removed from rats of any age within 1 min. After decapitation and partial dissection of the vertebral column at the sacral level, the spinal cord is ejected by means of hydraulic pressure from a syringe. Use of this method avoids prolonged dissection of the vertebral column with associated anoxia and trauma.
Development of Rat Spinal Cordde Sousa, Byron N.; Horrocks, Lloyd A.
doi: 10.1159/000112446pmid: N/A
Protein concentration increases in cerebrum and spinal cord during maturation of the rat were rather similar, but at all ages the spinal cord contained a higher protein concentration than cerebrum. Concentrations of cholesterol, galactolipids and phospholipids were higher in spinal cord than in cerebrum at all ages. Marked changes in the phospholipid composition in both tissues were also observed during development. The proportion of ethanolamine plasmalogens increased from 9 to 19% in cerebrum and from 18 to 29% in spinal cord. Choline phosphoglyceride proportions decreased from 58 to 33% in cerebrum and 54 to 25 % in spinal cord, while the proportion of sphingomyelin increased moderately throughout maturation in both tissues. The marked increase in concentrations of protein, cholesterol and galactolipids took place earlier in spinal cord than in cerebrum. The results suggest an earlier maturation of the myelin lipid composition in spinal cord than in brain, which is consistent with an earlier development of a phylogenetically older organ.
Developmental Changes in Ganglioside Composition of Hippocampus, Retina, and Optic TectumIrwin, L.N.; Irwin, C.C.
doi: 10.1159/000112447pmid: N/A
Ganglioside content and pattern were analyzed in the rat hippocampus and in the retina and optic tectum of the chick embryo during periods of maximum neural differentiation. Allometric plots of ganglioside sialic acid against tissue dry weight were linear on a log-log scale, in either one (hippocampus and retina) or two (optic tectum) phases and at unique rates for each tissue. Ganglioside patterns changed consistently during development with decreases in D3 and increases in M1 and D1a. The ratio of D3 to M1 + D1a was found to be a simple quantitative predictor of the extent of differentiation (particularly synaptogenesis) in each tissue. However, a full complement of gangliosides was found prior to the onset of significant synapse formation.
Membrane Enzyme Development in Nerve Ending Mitochondria during Neonatal HypothyroidismBattie, C.A.; Verity, M.A.
doi: 10.1159/000112448pmid: N/A
The effect of propylthiouracil-induced neonatal hypothyroidism on the development of synaptosome fraction mitochondrial membrane enzymes has been determined. Total and specific activities of two mitochondrial inner membrane (cytochrome c oxidase and succinate cytochrome c reductase) and two outer membrane enzymes (monoamine oxidase and rotenone-insensitive NADH cytochrome c reductase) were determined. The inner mitochondrial membrane enzymes developed in synchrony in euthyroid animals, but a decrease in fractional and specific activities of both inner membrane enzymes occurred in hypothyroidism. The outer membrane enzymes developed asynchronously; monoamine oxidase revealed a 9-fold increase while NADH cytochrome c reductase increased 4-fold. Hypothyroidism caused no change in total fractional activity or K<sub>m</sub> and an increased specific activity of outer membrane enzymes.