Quantitative studies on the postnatal growth of the spinal cord and the vertebral column of the albino mouse

Abstract

The rate of growth of the various regions of the spinal cord and the vertebral column of the albino mouse aged, 1, 10, 20, 30 and 120 days was studied. It was found that:(1) There is more rapid growth in the length of the vertebral column than that of the spinal cord. The lower regions of the vertebral column grow more rapidly than the upper regions but the reverse was found in the spinal cord resulting in regression of the spinal cord. The cord ends at one day opposite the fifth sacral vertebra and then receded to the fifth lumbar vertebra till 120 days.( 2 ) The white matter has a more rapid rate of growth in volume than the gray matter. So the process of myelination and the growth of the fibers in diameter exceed the rate of growth of the neurons and their dendrites.( 3 ) The packing density of the neurons is nearly the same in all regions of the cord with the exception of the cervical region which showed less packing density due to more branching of their dendrites.( 4 ) The total number of neurons at each region is fixed from birth till maturity. The thoracic region contains the highest number of neurons followed by the cervical then the lumbar and the least number is i n the sacral region.The purpose of this paper is to study: ( 1) the postnatal growth of the spinal cord and its regions compared to the growth of the vertebral column in length; ( 2 ) the postnatal growth in surface area and in volume of the various regions of the spinal cord; and ( 3 ) to study the postnatal growth of the neurons and their packing density at the various regions of the spinal cord and calculating the total number of neurons at each region. MATERIAL AND METHODSThe mice used in this study were bred in the department. These were descendants of Rockefeller strain albino mice, kindly given to us by the U. S. Naval Medical Research Unit 3 at Cairo. Several adult males and females were left together and the pregnant females were subsequently isolated. The offspring were taken at the following ages: 1, 10, 20, 30 and 120 days. Six mice of each stage were sacrificed with ether and perfused with saline followed by Bouin's fixative. Fixation was complete in Bouin. The spinal cord was preserved inside the vertebral column which was decalcified in a mixture of equal parts of J. COMP. NEUR., 136: 237-252.20% sodium citrate and 50% formic acid before being washed. Three mice of each age group were dehydrated and embedded in paraffin in the usual manner then were cut longitudinally in serial sections at 15 1-1 and stained with gallocyanin. In the other three mice of each age group the cervical, the thoracic, the lumbar and the sacral regions were separated with the vertebral column then were dehydrated and embedded in paraffin. Transverse serial sections of each region were cut at 15 I.I and were stained with gallocyanin and cresyl violet. Measurement of length of the various regions of the vertebral column and t h e spinal cordThe length of each region of the vertebral column and of the spinal cord was measured in the nearest longit...

Changes in the Termination of Spinal Cord at Vertebral Levels during Pre- and Postnatal Development of Sheep

“…Our observations on the termination of spinal cord in 83.4% of newly born lambs and adults at the levels of S-3 and S-2 vertebrae, respectively, indicated that there is a marked change in the situation of the termination of this organ even after birth and the regression process continues during adult life of the animal also. The results are, therefore, more or less comparable with those of human subjects as reported by Needles (1935), Lassek and Rusmussen (1938), Reimann and Anson (194.4) and also in albino mouse by Sakla (1969). The latter reported the regression of the spinal cord inside the vertebral column causing the conus medullaris to recede cranially from the lower border of the 5-5 vertebra at the age of one day.…”

A study of the length of the spinal cord in pre- and postnatal life in Mehraban sheep (Ovis Aries)

“…However, in the albino mouse, the cervical region was the most rapidly lengthening region of the spinal cord, followed by the sacral and lumbar regions (Sakla, 1969).…”

Mammals

“…In primates, the entire formatio hippocampi occupies a postcommissural position in the wall of the inferior horn of the lateral ventricle. In adult mammals, it is shorter, due to the continued growth of the vertebral column (Sakla 1969). It is relatively large in small brains.…”