Suzanne S. Stensaas

Astrocytic neuroglial cells, oligodendrocytes and microgliacytes in the spinal cord of the toad

SummaryThree types of glial cells corresponding to astrocytes, oligodendrocytes, and microgliacytes were found in the toad spinal cord stained with a modification of the Golgi-Río Hortega technique. Each can be correlated with a characteristic type of nucleus stained with toluidine blue.Astrocytic neuroglial cells are common near the central canal and have large nuclei with lightly stained nucleoplasm and finely granular chromatin. In silver impregnations, astrocytic neuroglial cells are characterized by many fine, spinose or lamellate excrescences which arise from cell somata and from the long peripherally directed processes that extend to the pia. No cells having the stellate form of mammalian astrocytes were seen, and large end-feet have only been seen near the surface of the brain suggesting that the primary relation of this cell is with the pia rather than with the capillaries.Oligodendrocytes are common in the white matter and near capillaries, but do not occur as neuronal satellites. Nuclei are characterized by large aggregates of chromatin and deep membrane invaginations. A spectrum of oligodendrocytes has been seen with the Golgi technique similar to the four types described in mammals by del Río Hortega. Small stellate cells of type I and II are most common and are seen in both white and gray matter. Tubular reticulate structures typical of type IV oligodendrocytes are identical to Golgi impregnated Schwann cells of peripheral nerves and are most abundant in the white matter. The absence of an identifiable soma raises the question of whether the reticulum is located on the outer or the inner surface of myelin.Microgliacytes are most common in areas of dense neuropile and do not form satellites. Nuclei are small, dark, and elongate often with irregular protuberances. In Golgi impregnations two or more long processes arise from a small, irregularly shaped soma. They are covered by spinous or thorn-like processes similar to those of the primitive mammalian pseudopodial variety.

Histopathological evaluation of materials implanted in the cerebral cortex.

SummaryHistopathological changes of the cerebral cortex in response to small, penetrating metal and non-metal implants were analyzed by means of light and electron microscopy. The needle-shaped implants were left in place during all stages of histological preparation and embedded in plastic together with the cortex. Changes of the brain-implant boundary were classified as non-reactive, reactive, or toxic, according to the reactive cellular constituents. Among the non-reactive materials were several plastics and metals such as aluminum, gold, platinum, and tungsten. The boundary of these implants displayed little or no gliosis and normal neuropile with synapses within 5 μm of the implants surface. The boundary of reactive materials such as tantalum or silicon dioxide was marked by multinucleate giant cells and a thin layer (10 μm) of connective tissue. Toxic materials such as iron and copper were separated from the cortical neuropile by a capsule of cellular connective tissue and a zone of astrocytosis. Cobalt, a highly toxic material, produced more extensive changes in the zones of connective tissue and astrocytes. These results indicate that a variety of materials are well tolerated by the brain and could be used in the fabrication of neuroprosthetic devices.

An electron microscope study of cells in the matrix and intermediate laminae of the cerebral hemisphere of the 45 mm rabbit embryo

SummaryThe morphology and intercellular relations of cells in the matrix, lower intermediate, and upper intermediate laminae of the cerebral hemisphere of rabbit embryos was studied with the electron microscope. Models of cells reconstructed from serial sections confirm previous observations made with the Golgi technique. Most cells in the matrix lamina appear to be spongioblasts; there are relatively few neuroblasts and columnar epithelial cells. Neuroblasts predominate in the intermediate lamina. Their short processes are intercalated among axons and spongioblast processes in the lower part. A large process, the preapex, distinguishes nerve cells in the upper part of the intermediate lamina, and its orientation in the direction of movement suggests that it may actively participate in the migration of neuroblasts.Serial section analysis confirms the fact that mitotic cells in the matrix lamina are spherical and have no processes. Assuming that neuroblasts are incapable of further division, it seems probable that intermitotic germinal cells have the form of spongioblasts and columnar epithelial cells and that they give rise to neuroblasts and other spongioblasts.

Light and electron microscopy of motoneurons and neuropile in the amphibian spinal cord

Summary Neuropile of the amphibian spinal cord was studied by light and electron microscopy to determine whether there are intercellular relations involving dendrites which would provide support for electrical interaction between montoneuron dendrites. Golgi studies show dendrites of monotoneurons to extend for long distances in a rostro-caudal direction, and electron micrographs reveal dendrodendritic contacts to be common in the vicinity of motoneuron somata. However, no membrane specializations were seen, and the percentage of the dendrite surface apposed to other dendrites is quite small except in small, circumscribed areas referred to as dendrodendritic ‘thickets’ where approximately 15% of the surface of large dendrites involves such contacts. Measurements were also made showing appositional relations of axons, astrocytes, and other elements to neuron somata and dendrites.

Light microscopy of glial cells in turtles and birds

SummaryFour classes of glial cells can be recognized in the central nervous system of turtles and birds on the basis of nuclear characteristics (methylene blue) and external morphology (Golgi technique). It seems likely that astrocytes and ependymal cells have a similar origin and function, but no evidence has been seen to indicate that transitional forms exist between astrocytes and oligodendrocytes or microgliacytes. Ependymal cells in the tectum and forebrain are covered by lamellate excrescences which are absent on cells in the spinal cord. Protoplasmic astrocytes are restricted to the gray matter. In the turtle they have an elongate shape characteristic of primitive elements, but stellate forms typical of mammals predominate in the bird. Fibrous astrocytes are abundant in the white matter. Endfeet are lacking in the turtle except on cells located near the pia; they are common for all elements in the bird and can sometimes be observed to outline the course of capillaries. Oligodendrocytes are identical to mammalian and amphibian forms. Small, round somata and long, thin processes are typical of types I and II while a tubular reticulum or membranous sheath characterizes type IV. The lack of a well defined somata and absence of transitional forms (type III) are compatible with the possibility that type IV is not a true cell type but corresponds to the inner cytoplasmic tongue of myelin. Microgliacytes are present in gray and white matter; they have a smaller overall size in the turtle and young chicken than in adult birds.

An experimental study of hyperchromic nerve cells in the cerebral cortex.

Abstract An attempt was made to study the cytology and synaptic relations of dark or hyperchromic cells in a primary and secondary epileptogenic lesion. Epileptogenic agents (alumina cream—penicillin, dry ice and ethyl chloride) were used to produce lesions in rabbits. Hyperchromic cells which had been reported to develop as a consequence of high levels of synaptic activation and to be restricted to the site of the lesion were found in large numbers in all cortical areas of brains which were removed immediately after perfusion. Further experiments with abrasion or cut-type lesions at various times before and after perfusion indicated that hyperchromic cells can be produced by mechanical trauma to the cortex after short periods of fixation, or while the animal is still alive. No evidence was seen to indicate that hyperchromic cells specifically develop as a consequence of procedures known to produce epileptic lesions.

Some morphological aspects of the visual system of Hermissenda crassicornis (Mollusca: Nudibranchia).

The eye of Hermissenda consists primarily of a lens and five photoreceptor cells. Earlier studies show that the photoreceptor cells have position sensitivity and that each sends nerve impulses to the brain along an axon. There is strong reciprocal inhibitory synaptic interaction between the photoreceptors which might serve to increase visual acuity, and a weak excitatory interaction tending to synchronize their discharge. This study analyses serial sections to determine the anatomical basis for the position sensitivity and the inhibitory and excitatory interaction. The asymmetrical arrangement of the photoreceptors could account for position sensitivity if the lens is an effective diopteric apparatus. Absence of well defined membrane densifications between neuron processes in the eye, optic ganglion, and brain suggests the possibility that they are not essential features of synapses in this animal. Areas of complex infolding containing vesicles are probably sites of reciprocal inhibitory connections and occur along axons in the eye and optic ganglion. Excitatory interaction seems to be possible wherever axons are apposed.

Autoradiographic evidence of [3H]SCH 23390 binding sites in human prefrontal cortex (Brodmann's area 9)

Abstract: The distribution of dopamine D‐1 receptors has been determined in human prefrontal cortex (Brodmanns area 9) by an in vitro light microscopic autoradiographic method. Dopamine D‐l receptors were localized by using [3H]SCH 23390 as a ligand. Our results indicated that [3H]‐SCH 23390 binding to slide‐mounted tissue sections of human brain is specific, saturable, and of high affinity. Lamina Va contained the highest density of D‐l receptors, with a Bmax value of 11.2 × 1.3 fmol/mg tissue. The KD values for [3H]SCH 23390 in all laminae ranged from 2.6 to 3.2 nM. Competition studies performed with [3H]SCH 23390 indicated a pharmacologic profile consistent with labeling of the D‐l receptor.

Brain abscess of odontogenic origin: report of case

Advanced dental infection rarely causes brain abscess resulting in death. Good dental hygiene and removing abscessed teeth are advised for prevention of any such occurrence. An intercranial infection is described in a 29-year-old male who also had a dental phobia.