Gomori's trichrome stain. Its use with myelin sheaths

We report the use of Gomori's one-step trichrome stain as a method for staining myelin sheaths of peripheral nerves. The stain is simple to perform and allows myelin sheaths to be easily detected and evaluated.

Effects of undernutrition on glial maturation

Rats of Wistar strain were conceived and breast-fed until the 25th day by mothers maintained on a low protein (5%) and low caloric (21 calories/day) diet, producing a severe deficiency in weight body growth (more than 50% at the 10th day) and of the weight of the central nervous system (40% on the 15th day) both in the cerebral hemispheres and the spinal cord. Histological and biochemical analysis of the central nervous system shows: (1) Glial proliferation is insufficient and delayed, the number of glial cells is reduced by 50% on the 10th day in the cuneatus and gracilis tracts and the density of the glial cells is reduced by 50% in the corpus callosum at the 19th day. (2) Maturation of the glial cells is greatly retarded, especially in the corpus callosum a structure which matures late. On the 19th day, the majority of the cells in this structure still have a glioblastic appearence, whereas in the normal rat, at this age the majority of the glial cells are oligodendrocytes. (3) These abnormalities of glial maturation agree well with the delay of the increase of DNA, RNA and protein measured in the spinal cord and cerebral hemispheres. (4) There is a defect in myelination assessed by estimation of the density of the myelin fibres, and a definitive reduction in the caliber of the spinal tracts.

A simple stain for myelin in frozen sections: a modification of Mahon's method

A simple and rapid method for demonstrating myelinated nerve fibers in frozen sections of the central and peripheral nervous system is described. Material fixed by perfusion with mixed aldehydes gives the best results but the method also works on specimens fixed by immersion in formaldehyde. Frozen sections varying in thickness from 15-50 micron are mounted on slides subbed with chrome alum-gelatin. After hydration (60-120 min), sections are mordanted (20-40 min) in 2.5% iron alum and rinsed briefly in three changes of distilled H2O (total 2 min). Staining is for 60-180 min in 20 cc freshly made 10% alcoholic hematoxylin diluted with 165 cc distilled H2O to which 15 cc saturated Li2CO3 is added. The sections are washed in distilled H2O (5-15 min) and dehydrated in graded alcohols without differentiation in mordant, and covered. Myelin stains a dark blue-purple against a light grey background. Fiber tracts, as well as individual myelinated fibers, are clearly demonstrated.

[The jimpy mouse]

Ultrastructural study of the Jimpy mice shows lack of myelin in the central nervous system: low density of glial cells, defect of maturation of oligodendrocytes and deficiency in axonal growth. The lack of myelin is more proeminent in late myelinating structures: corpus callosum and corticospinal fasciculus. Failure in myelin is rather the consequence of an early interruption of myelination as that of demyelination (a destruction of the sheats).

Myelinated nerve cell bodies in the dorsal horn of the monkey (Saimiri sciureus)

While observing electronmicroscopic preparations of laminae I-III of Rexed ('52), taken from the lumbosacral region of squirrel monkey spinal cord, several small neuronal cell bodies were found which were partially or completely encircled by compact myelin sheaths of varying thickness. Though found in all three laminae, the occurrence of these perikaryal sheaths was less frequent in the "inner zone" of lamina II where there were few myelinated fibers. Perikaryal profiles which were completely surrounded by myelin exhibited meither internal mesaxons nor external tongue processes and the origin of their myelin is obscure. In cases of partially enveloped cells the myelin was often clearly derived from extensions of myelin sheaths surrounding small-diameter axons. These overgrowths of myelin extended away from their axons at a pole near their internal mesaxon and spread out across the surface of neighboring nerve cells. In some cases the extensions were derived from the entire axonal sheath while in others only the external lamellae were included. The external tongue process, when observed, was located at the distal end of the axonal myelin extension. Overgrowths of axonal myelin which were unrelated to neuronal cell bodies were also found but these formations were less extensive.

Luxol Fast Blue MBSN-Levafix Red Violet E-2BL. A combined stain for myelin sheaths and glia fibers

During investigations of reactive dyes, Levafix Red Violet E-2BL was found suitable for staining of glia fibers. Experiments were carried out on 37% formaldehyde-fixed human autopsy material. Paraffin sections were treated with Luxol Fast Blue MBSN as usual, differentiated until glia fibers were decolorized, and counter-stained in a 0.25% solution of Levafix Red Violet E-2BL in 0.25% acetic acid. Myelin sheaths were colored blue. Gila fibers, smooth muscle cells, and nuclei were stained red violet. Axons and connective tissue remained unstained; occasionally, coarse bundles of collagen showed patchy coloration. Polarization microscopic studies proved that Levafix Red Violet E-2BL is bound to well-oriented fibrous proteins in glia fibers. The similar staining and polarization microscopic properties of glia fibers and smooth muscle support previous findings that glia fibers contain a myosin-like protein.

Synaptic contacts within the intraganglionic spiral bundle and other recent ultrastructural findings in relation to concepts of efferent cochlear innervation

Synaptic contacts which show many characteristic features of chemically transmitting axodendritic synapses have been demonstrated in guinea pigs, in the unmyelinated component of the so-called olivocochlear bundle (OCB) within the intraganglionic spiral bundle. Morphologically the synaptic contacts appear to form part of a cholinergic innervation. Previous reports by the author have described termination of the myelin sheath of OCB fibers and demonstrated branching of unmyelinated axons in this region. Denervation studies at an ultrastructural level following excision of the superior cervical ganglion support light microscopy fluorescent histochemical evidence for an adrenergic innervation, which distributes in part within the intraganglionic spiral bundle and the osseous spiral lamina. Although it has not been possible to demonstrate anatomical continuity between these separate findings, the pathways in which they may be involved are discussed.

A quantitative study of anterior root fibres during early myelination. II. Longitudinal variation in sheath thickness and axon circumference

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Sensitivity in electron microscope autoradiography. II. Effect of heavy metal staining

In quantitative electron microscopic autoradiography test specimens for sensitivity usually consist of plastic or protein films 500-1000 Å in thickness. For tritium, the applicability of sensitivity values derived from such specimens to biologic sections which had been stained with heavy metals was determined. It was found that, within the range of section thickness used for electron microscopic autoradiography, fixation with OsO4 followed by uranyl acetate staining increases self-absorption by less than 7% over that seen in Epon sections of the same thickness. A somewhat larger effect is seen in sections used for light microscopic autoradiography. The effect on electron microscopic autoradiographic resolution is estimated to be within 10%.

A time-sequence autoradiographic study of the in vivo incorporation of (1,2-3H)cholesterol into peripheral nerve myelin

A time-sequence study of the incorporation and distribution of cholesterol in peripheral nerve myelin was carried out by electron microscope autoradiography. [1,2-(3)H]Cholesterol was injected into 10-day old mice and the sciatic nerves were dissected out at 10, 20, 40, 60, 90, 120, and 180 min after the injection. 20 min after injection the higher densities of grains due to the presence of [(3)H]cholesterol were confined to the outer and inner edges of the myelin sheath. Practically no cholesterol was detected in the midzone of the myelin sheath. 1 (1/2) h after injection, cholesterol showed a wider distribution within the myelin sheath, the higher densities of grains occurring over the two peripheral myelin bands, each approximately 3,100 A wide. Cholesterol was also present in the center of the myelin sheath but to a considerably lesser extent. 3 h after injection cholesterol appeared homogeneously distributed within the myelin sheath. Schwann cell and axon compartments were also labeled at each time interval studied beginning 20 min postinjection. These observations indicate that preformed cholesterol enters myelin first and almost simultaneously through the inner and outer edges of the sheath; only after 90 min does the density of labeled cholesterol in the central zone of myelin reach the same density as that in the outer and inner zones. These findings suggest that cholesterol used by the nerve fibers in the formation and maintenance of the myelin sheath enters the lamellae from the Schwann cell cytoplasm and from the axon. The possibility of a bidirectional movement of molecules, i.e. from the Schwann cell to the axon and from the axon to the Schwann cell through the myelin sheath, is noted. The results are discussed in the light of recent observations on the exchange, reutilization, and transaxonal movement of cholesterol.