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Biomedical subjects

C Hildebrand

Publications and source records attributed to C Hildebrand.

At least 127 records · Page 7Linked to original sources
PubMed1981

Abnormally high content of unmyelinated axon profiles in the ventral root L7 of a cat with an abdominal neoplasm.

The ventral roots of L7 of a cat with an intestinal neoplasm were examined electron-microscopically at different proximo-distal levels. The proportion of unmyelinated axon profiles was 50-55% at mid-root and distal levels as compared to 30% in normal adult cats. In the juxtamedullary root fascicles the proportion was normal (average 20%), and few unmyelinated axons seemed to penetrate into the CNS through the ventral root. The number of myelinated axons was within the normal range.

Animals↗
PubMed1978

Relation between myelin sheath thickness and axon size in spinal cord white matter of some vertebrate species.

The relation between number of myelin lamellae and axon size in the CNS was examined by electron microscopy of spinal cord white matter fibres in different vertebrate species (cat, rabbit, guinea pig, rat, mouse, frog and perch). The results show that the number of myelin lamellae increases with increasing axon size in a non-linear fashion. Below an axon size of 4--5 micron the relation follows a fairly straight line but above this size rectilinearity is lost. The mouse and the frog differ from the pattern shared by the other animals. In the mouse the lamellar number increases more slowly with axon size and the relation is close to linear. In the frog the number of lamellae increases very slowly with axon size and the relation is markedly curvilinear. Measurements of the myelin repeating period show that in the mammals and the frog the average period of thick sheaths is about 85% of that in thin sheaths, in accordance with previous findings in the cat. In the perch a clearcut difference in this respect between thick and thin sheaths is not found. Calculations of the g-ratio on the basis of the findings indicate that it increases with increasing fibre size. This is most pronounced in the perch and the frog in which the g-ratio for the largest fibres far exceeds the functionally optimal value defined in theoretical analyses on impulse propagation.

Animals↗
PubMed1977

Age-related changes in occurrence of Marchi-positive granules and Marchi-positive myelinoid bodies in postnatally developing feline white matter.

The occurrence of clusters of Marchi-positive granules and of Marchi-positive myelinoid bodies at different postnatal developmental stages was examined lightmicroscopically in Vibratome sections from the cervical lateral funiculus of the cat, after perfusion-fixation with glutaraldehyde. The findings show that clusters of Marchi-positive granules are most common at birth and rapidly decrease in number with development, being largely absent in animals older than 1 month. The pattern of change resembles the postnatal changes in content of esterified cholesterol in the cervical lateral funiculus and is compatible with the view that the clusters of Marchi-positive granules may result from spontaneous myelin sheath disintegration occurring early postnatally. The incidence of Marchi-positive myelinoid bodies increases 7 times during the first 4 months after birth to a peak and declines about 40% during late maturation. The size spectrum of the Marchi-positve bodies shifts markedly towards larger sizes with development and presents a close to mature picture from 120 days on. Comparisons between the Marchi-positive myelinoid bodies and the myelin sheaths in the same region, with respect to postnatal change in occurrence and size spectrum, suggest that the Marchi-positive bodies are related to myelin sheaths of large fibres or fibres destined to become large.

Age Factors↗
PubMed1976

Electron-microscopic identification of Marchi-positive bodies and argyrophilic granules in the spinal cord white matter of the guinea pig.

Sections from spinal cord white matter of normal and rhizotomized guinea pigs fixed by glutaraldehyde perfusion were stained with Marchi fluid or according to a suppressive silver technique. With the aid of the section-embedding method thin sections, cut from light-microscopically identified areas containing Marchi-positive bodies or argyrophilic granules, were examined in the electron microscope. The results show that the Marchi-positive bodies and argyrophilic granules, which are present in normal white matter, represent different histochemical expressions of the same entity--the myelinoid body. In view of the similarities between myelinoid bodies and myelin fragments formed during Wallerian degeneration it is suggested that this type of so called artifact staining of normal white matter inherent to both methods should instead be considered as an expression of a specificity of the two methods for degenerating nervous elements.

Animals↗
PubMed1975

Postnatal growth of nerve fibres in the pyramidal tract of the rabbit.

The postnatal growth in diameter of corticospinal nerve fibres was studied in the medullary pyramid of the rabbit in order to make comparisons with the development of functional properties, which has been demonstrated by previous workers. During the first postnatal days the as yet unmyelinated fibres underwent a distinct increase in size. The first signs of myelin ensheathment were seen in 5-day-old animals, the ensheathed fibres varying between 0.4 and 0.7 mu in diameter. The growth in size of the largest myelinated fibres was more rapid during the second week and thereafter continued at a slower rate to a final size of 4--5 mu. The number of myelinated pyramidal fibres increased most rapidly during the first postnatal month and reached around 90,000 (unilaterally) in the adult. The vascular density initially increased, reaching a peak at 3 weeks and thereafter decreased. Comparison with physiological data showed that the initiation of myelination does not coincide in time with any striking decrease in response latency but rather seems to allow for a continued steady decrease. At a size of 3.5-4 mu the fibres appear to have attained the capability to follow rapid rates of stimulation.

Age Factors↗