Some morphometric methods for the central nervous system

Friedreich Ataxia: Hypoplasia of Spinal Cord and Dorsal Root Ganglia

After Friedreich's description in 1877, depletion of myelinated fibers in the dorsal columns, dorsal spinocerebellar and lateral corticospinal tracts, and neuronal loss in the dorsal nuclei of Clarke columns were considered unique and essential neuropathological features of Friedreich ataxia (FA). Lack of large neurons in dorsal root ganglia (DRG), thinning of dorsal roots (DR), and poor myelination in sensory nerves are now recognized as key components of FA. Here, we measured cross-sectional areas of the mid-thoracic spinal cord (SC) and neuronal sizes in lumbosacral DRG of 24 genetically confirmed FA cases. Mean thoracic SC areas in FA (24.17 mm2) were significantly smaller than those in 12 normal controls (37.5 mm2); DRG neuron perikarya in FA (1362 µm2) were also significantly smaller than normal (2004 µm2). DRG neuron sizes were not correlated with SC areas. The FA patients included a wide range of disease onset and duration suggesting that the SC undergoes growth arrest early and remains abnormally small throughout life. Immunohistochemistry for phosphorylated neurofilament protein, peripheral myelin protein 22, and myelin proteolipid protein confirmed chaotic transition of axons into the SC in DR entry zones. We conclude that smaller SC areas and lack of large DRG neurons indicate hypoplasia rather than atrophy in FA.

Cortical dysplasia resembling human type 2 lissencephaly in mice lacking all three APP family members

The Alzheimer's disease beta-amyloid precursor protein (APP) is a member of a larger gene family that includes the amyloid precursor-like proteins, termed APLP1 and APLP2. We previously documented that APLP2-/-APLP1-/- and APLP2-/-APP-/- mice die postnatally, while APLP1-/-APP-/- mice and single mutants were viable. We now report that mice lacking all three APP/APLP family members survive through embryonic development, and die shortly after birth. In contrast to double-mutant animals with perinatal lethality, 81% of triple mutants showed cranial abnormalities. In 68% of triple mutants, we observed cortical dysplasias characterized by focal ectopic neuroblasts that had migrated through the basal lamina and pial membrane, a phenotype that resembles human type II lissencephaly. Moreover, at E18.5 triple mutants showed a partial loss of cortical Cajal Retzius (CR) cells, suggesting that APP/APLPs play a crucial role in the survival of CR cells and neuronal adhesion. Collectively, our data reveal an essential role for APP family members in normal brain development and early postnatal survival.

Diffuse thalamic degeneration in fatal familial insomnia. A morphometric study

A morphometric investigation disclosed most thalamic nuclei severely degenerated in two patients with fatal familial insomnia. Associative and motor nuclei lost 90% neurons, and limbic-paralimbic, intralaminar and reticular nuclei lost 60%. These findings point to the disorganization of most thalamic circuits as a condition necessary for the sleep-wake rhythm being affected.

A method to quantitate axonal injury

The quantitation of diffuse axonal injury provides a more objective approach to the assessment of tissue damage in head injuries. The method designed in this study takes into account the anisotropy and structural inhomogeneity of the brain, and the distribution of lesions in diffuse axonal injury. The number of counts required for the statistical analysis is inversely proportional to the square of the desired accuracy, specified as the percentage of the mean value of the axonal balloons since the true mean is unknown from the outset. The number of fields are examined using an indexed-squares graticule in 10 different areas of the brain. Silver-stained sections from the brains of head injured patients that survived longer than 12 h must be used with this method. Difficulties may arise when patients of different survival times are compared since it takes some time for the axonal balloons to develop. A correlation with the survival time can be established with the quantitative data collected. The morphometric principles and the statistical rationale on which this methodology is based are briefly presented.

Morphometric study of cervical anterior horn cells and pyramidal tracts in medulla oblongata and the spinal cord in patients with cerebrovascular diseases

To clarify the effect of damage to the upper motor neurons on lower motor neurons, quantitative studies were made regarding the cross-sectional area and the number of the individual anterior horn cells in the lateral nuclear cell groups of the 5th segment of the cervical spinal cord (C5), and regarding the cross-sectional areas of the pyramidal tract in the medulla, and in the spinal cord at the C5 and L2 levels. The subjects included 45 patients with cerebrovascular disease (CVD), and 50 age-matched controls without neurological disease. The medullary pyramid (MP) and the ventral funiculus (VF), ipsilateral to the hemispheric lesion, were compared with the MP and VF of the other, unaffected, side. The ventro-lateral funiculus (VLF), anterior horn (AH) and C5 anterior horn cell (AHC), contralateral to the lesion, were also compared with the VLF, AH, and AHC of the other, unaffected, side. The AHC area (mean cross-sectional area of anterior horn cells) and the MP area, VF area, VLF area, AH area (mean cross-sectional areas of MP, VF, VLF and AH) associated with the hemispheric lesional side were significantly decreased, compared with those of the unaffected sides and the controls. However, there was no significant difference in AHC number between the affected and unaffected sides in patients with CVD, nor between the affected side and the controls. In order to examine the relationship between a decrease in AHC area and degree of paralysis, CVD patients were divided into two groups according to degree of muscle strength: the severe and mild paralysis groups.(ABSTRACT TRUNCATED AT 250 WORDS)

All peroneal motoneurons of the rat survive crush injury but some fail to reinnervate their original targets

This is a quantitative study of the motoneuronal population of the rat's common peroneal nerve following severe crush injury of the sciatic nerve or its component branches. The crush was performed unilaterally under anesthesia for 60 seconds with hemostat jaws covered with tubing to form a smooth, 2 mm long, injured zone. Recovery from injury was allowed for 14 to 188 days. It was measured behaviorally using the sciatic functional index (SFI) and electrophysiologically by comparing the conduction velocity and amplitudes of evoked muscle action potentials prior to injury, and again after injury just before the nerve was labeled with horseradish peroxidase (HRP), and/or its wheat germ agglutinin conjugate (WGA-HRP), 48-72 hours before sacrifice. The motoneurons were retrogradely labeled on both sides so that the uninjured side might serve as a control. On the injured side the nerves were labeled either distal or proximal to the crush site. The tibialis anterior muscles on both sides were removed and weighted. Spinal segments L2 to L6 were cut in serial, frozen cross-sections. HRP reaction products were formed using TMB as the chromogen. The normal peroneal nerve was found to contain 634 +/- 26 motoneurons (22 cases). The number of motoneurons labeled 5-15 mm distal to the injury site (22 cases) was 535 +/- 69 or 84.4% of normal. In 12 cases in which the nerve was labeled 5 mm proximal to the injury normal population numbers (648 +/- 30) were found. These counts demonstrated that the unlabeled 15.6% in the distal labeled cases had not vanished as a result of cell death. Instead, the unlabeled group was composed mainly of small motoneurons whose axons probably had not regenerated distal to the crushed zone. Mean soma size of injured neurons increased to maximum 3-6 weeks after injury and then gradually decreased in size over the following weeks to nearly normal values. This transient increase in size was due to two factors: 1) soma swelling in response to axonal injury, and 2) absence of many small motoneurons, presumably gamma-motoneurons, which were either incapable of, or prevented from, regenerating beyond the injury zone long after larger motoneurons had reinnervated their targets. SFI scores, muscle weights, and amplitude ratios of evoked potentials recovered to control values by 70-80 days post-injury. Conduction velocities remained 20-25% below normal at the end of 80 days.(ABSTRACT TRUNCATED AT 400 WORDS)

On the number of Purkinje cells in the human cerebellum: unbiased estimates obtained by using the "fractionator"

Stereological estimates of the numbers of Purkinje cell nucleoli in human cerebellar cortex have been obtained from systematic random samples of tissue by using the fractionator. The estimates are unbiased by fixation, section thickness, or sampling errors and are independent of any assumptions about cell shape, size, or spatial orientation. Twelve brains from aged subjects of both sexes were examined. The average complement of nucleoli in four female brains (age range 71-93 years) amounted to 14.8 millions (with an observed coefficient of variation between subjects of 29%). For three male brains (76-91 years), the corresponding estimates were 15.7 millions (10%). No significant sex differences were found for these small samples. Five brains of unknown sex and age yielded values of 15.8 millions (18%). For the twelve brains examined, the total number of Purkinje cell nucleoli per cerebellum was found to be 15.4 millions (19%). Estimated numbers showed a significant positive correlation with cerebellar weights. The number of nucleoli in an individual cerebellum was obtained with high precision in as short a time as 4 hours.

The nucleus pontis centralis caudalis in Huntington's disease

Slow saccadic eye movements occur in some patients with Huntington's disease (HD), and minor defects of supranuclear eye movement control can be demonstrated in the majority by neuroophthalmological laboratory methods. In the pathogenesis of slowed saccades, a lesion of the paramedian pontine reticular formation and specifically the nucleus pontis centralis caudalis was considered likely due to similar eye movement disturbances in well documented degenerative and vascular lesions of the lower pontine tegmentum. A systematic morphometric study was performed on the nucleus pontis centralis caudalis in 9 patients with HD. Two of them had grossly defective saccades during life, and 7 had normal eye movements on routine examination. In 8 patients, the nucleus was reduced in size, revealed a higher than normal neuronal density, and a striking loss of large neurons. One patient with HD and normal morphometric results had died 2 years after the onset of chorea from an unrelated illness. It is proposed that the nucleus pontis centralis caudalis is regularly affected in HD and that progressive loss of large neurons is the cause of saccadic slowing.

A quantitative method for the estimation of the degree of uniformity and isotropy of the structures of the central nervous system in cytoarchitectonic preparations

The statistical method for the estimation of the degree of uniformity and isotropy of structures in brain sections proposed in this paper allows integral estimates to be made of the character of the distribution of nerve cells during the formation of the central nervous system. The method is convenient to work with in photomicrographs. Automatic computerized counting of cell elements takes little time and involves a minimum of images.

Quantitative morphological studies of neuropathological changes. Part 1

Quantitation of morphological changes in the nervous system is valuable for demonstrating different regions and cell types involved in a pathological process. Quantitative anatomical studies are numerous, whereas quantitations of pathological conditions are relatively few. This seems to be due partly to technical difficulties arising when comparing normal with pathological brain tissue. Shrinkage of the whole brain or of substructures is important but difficult to determine, and earlier studies are often inaccurate due to lack of precise measurement of this parameter. This review deals with three different technical aspects: (1) measurements at the macroscopical level, (2) the light microscopical morphometry, and (3) the stereological principles which are used primarily in electron microscopical quantitation. The most used techniques and formulas are reviewed in order to give an impression of the possibilities and requirements in quantitative neuropathology. After each of the major areas, macroscopical measurements, determination of nuclear and cell size and nuclear number, vascular network, and stereology, a few practical comments are given as well as references for further information on the topic. The quickly developing electronic image analysis is dealt with in the section on capillary network measurements and in the last, concluding section.

The intermediolateral gray columns in the spinal cord of Macaca mulatta

The mean length of spinal segments in Macaca mulatta varied from 0.55 to 1.4 cm. Upper thoracic and lumbar segments were shorter; middle and distal thoracic segments are longer. The intermediolateral gray column extended from the middle of the eighth cervical to the fourth lumbar spinal segments. This column as observed in the serially cut cross-sections varied in shape and in position in different regions of the spinal cord. The mean counts of intermediolateral neurons in the males were significantly higher than females (P less than 0.001) and varied from segment to segment. Their number was slightly higher on the right side and funicular cells were more numerous in male spinal cords than in females. The neurons were of varied shapes from fusiform to multipolar and measured from 7.5 to 25 micrometers in size.

The density of neurons in the human hippocampus

The aim of this study was to determine the density and pattern of distribution of the neurons in the human hippocampus, and twenty-nine brains of healthy individuals were examined. The cells counted in each unit area were the pyramidal cells in the H-fields and the granule cells. Difference in density was found between all H-fields. The neuronal density was highest in the H2-fields. The density decreased through the transitional area H1-2 and H1, with the lowest density in H3. The neuronal density increased in all H-fields in the antero-posterior direction, while the granule cells decreased in density. In the individual brain there was a positive correlation found respectively between high and low cell density in the different H-fields. The pyramidal cell density decreased in persons more than 68 years old. No difference was found between neruonal cell density in the two sides of the brain. Sex did not influence the neuronal cell density.

The estimation of neuronal population density by a robust distance method

A new "nearest-neighbour" or "distance" method of estimating neurone population density is introduced. The method was originally developed for ecological studies but can be imported into histology without significant modification; changes in population density can be estimated by inverting the measure of area per unit cell (the so-called mean area). Its advantages include tests of randomness for the spatial distribution of the cells at issue and a robustness which can tolerate some departure from a random distribution pattern. To illustrate how the method is applied estimates of neurone density, in terms of "mean area" per cell-point, are made on a montage tracing of the human cerebellar dentate nucleus.

Light and electron microscopic observations on the relationship between Hirano bodies, neuron and glial perikarya in the human hippocampus

Hippocampi from two intellectually normal and four demented subjects were examined in autopsy material. Large Hirano bodies seen by light and electron microscopy were thought to be glial in origin and not to be produced by the perikarya of neurons as has been suggested in the literature. Myelination of two Hirano bodies found in the stratum lacunosum-granulosum where neuron perikarya are rare suggests that these bodies are produced by oligodendroglia. Hirano bodies were found to be associated with neurons showing granulovaculoar degeneration. With electron microscope they were frequently seen to be divided by clefts filled with amorphous material which possibly consisted of free ribosomes.