H. M. Zimmerman

FINE STRUCTURE OBSERVATIONS OF THE UPTAKE OF INTRAVENOUSLY INJECTED PEROXIDASE BY THE RAT CHOROID PLEXUS

The uptake by the choroid plexus of adult rats of intravenously injected horseradish peroxidase has been investigated by electron microscopy. Within 4 min, the injected protein passes the capillary and is rapidly distributed through extracellular space and choroidal cells. Peroxidase enters the choroidal cells within coated vesicles which act as pinocytotic vesicles. At 15 min, peroxidase activity is present in numerous membrane-bound vesicles, multivesicular bodies, dense bodies and what appear to be segments of smooth endoplasmic reticulum. None of the peroxidase-containing organelles is seen to empty to the ventricular surface. Egress of the extracellular peroxidase into the cerebrospinal fluid is apparently blocked by apical zonulae occludentes between the choroidal cells.

An epithelial cyst of the spinal cord. An electron microscopic study.

SummaryThe fine structure of an intradural and extramedullary cyst compressing the spinal cord was examined. The cyst was lined by a single epithelial layer of both ciliated and non-ciliated cells. The non-ciliated cells differ from the former by the presence of secretory granules and a surface coating as well as other characteristics. The epithelial layer was bordered by a basement membrane and prominent interdigitation was found along the lateral borders. The origin of these cells is unknown but the similarity between them and the epithelium of the respiratory tract is noted.

Experimental cyanide encephalopathy: electron microscopic observations of early lesions in white matter.

Cyanide holds great interest for neuropathologists because of its strong tendency to damage cerebral white matter selectively, both in experimental (1–7) and in accidental (8) poisoning. In fact, the lesions of cyanide encephalopathy have been compared to those of Schilders disease and Marchiafava-Bignami disease. Experimental cyanide encephalopathy has been studied for many years by light microscopy, and recent publications have described observations made by metallic impregnation and enzyme histochemistry (6, 7). Neuronal changes have been studied by electron microscopy (9). Nevertheless, certain problems arc unresolved. These include the nature and precise localization of the tissue spaces that give cyanide lesions in white matter a fenestrated appearance, the state of the axons, the role of the oligodendrocytes, the question of selectivity for myelin, and the time needed for lesion formation. The present study utilized the electron microscope to answer some of these questions. For this study, the older technics of repeated injections of potassium or sodium cyanide were inadequate because of the variable yield of lesions and the inability to time the onset of lesion formation. On the other hand, the administration of hydrogen cyanide by the respiratory route for a single short period yielded lesions of exactly timed onset, in a predetermined location (corpus callosum), in nearly all of the animals (5). There is no basic difference in neurotoxic effect between hydrogen cyanide and cyanide salts, inasmuch as the lesions produced by a single hydrogen cyanide exposure have been duplicated exactly by a single treatment with a cyanide salt under appropriate conditions (10).

Fine Structure of Cerebral Fluid Accumulation

Although cerebral edema has been studied for many years, conclusive evidence as to the precise origin, location and morphological nature of the edema fluid had to await both the advent of the electron microscope and improved techniques of preservation. The development of better techniques has permitted us to carry out a series of studies which, we feel, provide some information clarifying the edema process. Edema is a condition which affects primarily white matter. Therefore, in our experiments we studied several different types of white matter injury. One type of injury followed implantation into the brain of the relatively bland polysaccharide isolated from Cryptococcus neoformans. Another type of injury followed implantation of the powerfully necrotizing chemical agent, silver nitrate. A third type of injury was of systemic, auto-immune origin, that is, experimental allergic encephalomyelitis (EAE).

Electron microscopic study of neurofibrillary tangles in Steele-Richardson-Olszewski syndrome

SummaryThe neurofibrillary tangles found in the neurons of a case of Steele-Richardson-Olszewski syndrome were studied by electron microscopy. Both the flame-shaped and globose type of tangles were present. The neurofibrillary tangles were composed of bundles of straight tubules measuring approximately 150 Å in diameter. This ultrastructural appearance of the tangles in Steele-Richardson-Olszewski syndrome is different from the appearance of tangles found in other neurological disorders and is probably indicative of intraneuronal accumulation of a new type of fibrous protein.

Electron microscopic observations of peripheral myelin in a central nervous system lesion

SummaryAfter cyanide intoxication and after triethyltin implantation in the brain, cystic spaces were found in the forebrains, of two rats. Within these spaces, many examples of remyelinating axons were observed. Most of them displayed typical mature or developing “central type” myelin sheaths. Some, however, showed all the morphological features characteristic of mature or developing peripheral myelin. In both rats, the cavities of the cysts were open to the overlying subarachnoid spaces due to partial disruption of the subpial astrocytic layer. It was concluded that the myelin-forming cells responsible for the formation of the “peripheral type” myelin within the cyst were probably Schwann cells derived from peripheral nervous elements accompanying some subarachnoid blood vessels. It could not be determined whether the axons within the “peripheral type” sheaths were part of the central or peripheral nervous systems. These data might be relevant to the origin of central neurinomas.ZusammenfassungNach Cyanidvergiftung und Implantation von Triäthylzinn in das Gehirn wurden im Vorderhirn von zwei Ratten cystische Hohlräume gefunden. In diesen Höhlen fanden sich zahlreiche remyelinisierte Axone. Die meisten wiesen typische reife oder in Entwicklung begriffene Markscheiden vom “zentralen Typ” auf. Einzelne hingegen boten alle morphologischen Merkmale reifen oder in Bildung begriffenen peripheren Myelins. Bei beiden Ratten zeigten die cystischen Hohlräume offene Kommunikation mit dem darüberliegenden Subarachnoidalraum infolge teilweiser Durchbrechung der subpialen Astrogliaschicht. Es wird geschlossen, daß die für die Bildung des Myelins vom “peripheren Typ” innerhalb der Cysten verantwortlichen myelinbildenden Zellen vermutlich Schwann.-Zellen aus peripher-nervösen Elementen darstellen, welche einige subarachnoidale Gefäße begleiten. Es war nicht festzustellen, ob die Axone innerhalb der Markscheiden vom “peripheren Typ” dem zentralen oder peripheren Nervensystem angehören. Diese Befunde erscheinen von Bedeutung für die Genese zentraler Neurinome.

A comparison of the fine structure of small blood vessels in intracranial and retroperitoneal malignant lymphomas

SummaryThe fine structure of the blood vessels of an apparently primary intracerebral malignant lymphoma was compared with those in another malignant lymphoma in a retroperitoneal lymph node. The essential features of the blood vessels in both cases were the same. They resembled the blood vessels found in normal lymph nodes and were both distinctly different from those seen in normal brain. It was concluded that the direction of differentiation of the blood vessels which arise to nourish the neoplastic tissue is determined by the nature of the tumor rather than the vessels from which they originate.The fine structure of the blood vessels of an apparently primary intracerebral malignant lymphoma was compared with those in another malignant lymphoma in a retroperitoneal lymph node. The essential features of the blood vessels in both cases were the same. They resembled the blood vessels found in normal lymph nodes and were both distinctly different from those seen in normal brain. It was concluded that the direction of differentiation of the blood vessels which arise to nourish the neoplastic tissue is determined by the nature of the tumor rather than the vessels from which they originate.

The fine structure of blood vessels in chromophobe adenoma

SummaryThe fine structure of the small blood vessels in chromophobe adenoma was compared to normal pituitary. The most striking difference was the relative paucity of endothelial fenestrae in the tumor accompanied by a widened perivascular space. The origin of these changes and their possible functional significance are discussed.

A histochemical and fine structure study of the developing rat choroid plexus

Summary1.A histochemical and fine structural study of the developing rat choroid plexus was made from 1–3 days before birth to the adult stage.2.The maturation of the choroidal epithelium is associated with a loss of cytoplasmic glycogen, increasing surface area of the plasma membrane associated with the development of an apparent adenosine triphosphatase activity, and increasing numbers of mitochondria and prominence of the rough endoplasmic reticulum associated with increasing diaphorase and dehydrogenase activity. Following birth, thiamine pyrophosphatase and adenosine mono- and diphosphatase activity appear in the blood vessels. Structures associated with pinocytotic activity are most numerous in young rats.3.It is suggested that the increased susceptibility of young rats to experimentally produced hydrocephalus is related to the potential of their choroid plexus for active transport.Zusammenfassung1.Die Entwicklung des Plexus choroideus in der Ratte vom 1.–3. Tag vor der Geburt bis zur Reife wurde mit histochemischen Methoden und mit dem Elektronen-Mikroskop untersucht.2.Die Reifung des Plexus-Epithels ist verbunden mit dem Schwund des Glykogens im Cytoplasma, mit eine Zunahme der Oberfläche der Zellmembrane zusammen mit dem Erscheinen von Adenosine-Triphosphatase-Aktivität sowie mit einer Zunahme von Mitochondrien und von endoplasmischem Reticulum zusammen mit einer Zunahme der Diaphorase- und Dehydrogenase-Aktivität. Nach der Geburt kann die Aktivität von Thiamine-Pyrophosphatase und von Adenosine-Mono- und Di-Phosphatase in den Blutgefäßen nachgewiesen werden. Zellstrukturen, die pinocytotische Aktivität besitzen, sind in größter Anzahl in jungen Ratten vorhanden.3.Es wird angenommen, daß die erhöhte Empfänglichkeit von jungen Ratten für experimentell erzeugten Hydrocephalus auf die besondere Fähigkeit von deren Plexus choroideus zu aktivem Transport zurückzuführen ist.

The Fine Structure of Ependymoblastoma

An ependymoblastoma in the vermis of the cerebellum of a three-year-old girl has been examined in the light and electron microscopes. The densely packed cells were arranged in masses, in cords around blood vessels and in rare rosettes around clear lumens. In the electron microscope, the cells are characterized by a poorly differentiated cytology except for the presence of rather prominent junctional devices and, in some rosette formations, of basal bodies. From a morphological viewpoint, the tumor cells appear remarkably similar to the cells which line the normal, embryonic neural tube.