Mahdi Hasan

Dissolution and removal of neuronal lipofuscin following dimethylaminoethyl p-chlorophenoxyacetate administration to guinea pigs

SummaryDimethylaminoethyl p-chlorophenoxy acetate (80 mg/kg body weight) was administered (i. m.) to guinea pigs for 30 to 56 days. Electron microscopic examination of the hippocampus, mid-brain reticular formation and the area postrema revealed marked diminution in the electron density of the pigment granules and vacuolization. This type of lipofuscin was detected in some phagocytic cells and in the capillary endothelium. Conspicuous vacuolization of the capillary wall was discernible. These changes were not observed in the “control group” of animals.

Fine structural features of the cerebral microvasculature in hydrocephalic human infants: Correlated clinical observations

Four of 30 human cerebral cortex biopsies from infants ranging from four days to about ten years treated for hydrocephalus by shunt operations are described paying special attention to the vascular structures. The biopsy specimens were studied in semi-thin and ultrathin sections. Attention is drawn to the role of pinocytotic vesicles found in capillaries and smaller vessels as a possible transcellular route for the hydrocephalic oedema resolution. No intercellular dehíscences or the so called blisters were observed. With the passage of time, the number of membrane bound vesicles increased and arrays of pinocytotic vesicles were discernible both on the abluminal as well as luminal aspect of the capillary wall. Additionally, larger vacuoles containing electrondense material, apparently undergoing autolysis, were also detected. The basal lamina was of uneven thickness and at places duplicated. Hypertrophic pericytes exhibited remarkable oedamatous changes, increased vesicular or vascular transport, demonstrating pericyte brain-barrier dysfunction. Swelling of the astrocytic end-feet bordering the capillaries was remarkable. These findings indicate that the CSF or oedema fluid is absorbed into the vascular system via a transendothelial pathway.

Ultrastructural features of transneuronal atrophy in monkey geniculate neurones

SummaryElectron microscopical observations on the trans-neuronal atrophy in the lateral geniculate neurones of the monkey are presented. Cytoplasmic shrinkage and folding of nuclear membrane has been observed. In the later stages most of the cell contents disappear leaving empty spaces with irregular boundaries and a large number of vacuoles are seen. The findings have been discussed, elaborating the difference between the loss of Nissl granules in classical chromatolysis and in the present case.ZusammenfassungEs wurde eine elektronenoptische Untersuchung über die Cytologie der transneuronalen Atrophie an CGL-Neuronen des Affen durchgeführt. Eine Schrumpfung des Cytoplasmas und eine Fältelung der Kernmembran zeigt sich in frühen Stadien. In den Spätstadient geht der Hauptteil der Zellorganellen verloren und nur leere, unregelmäßig begrenzte Räume und eine Vielzahl von Vacuolen sind sichtbar. Die cytologischen Unterschiede zwischen der Chromatolyse und transneuronaler (trans-synaptischer) Atrophie werden gegenübergestellt.

Oligodendrocytes in the normal and chronically de-afferented lateral geniculate body of the monkey

SummaryElectron microscopical examination of the norma and de-afferented ‘laterall geniculate body’ of the monkey following paraformaldehyde-glutaraldehyde vascular perfusion revealed distinctive morphological features of different types of oligodendrocyte. These cells were normally situated as perineuronal satellites or in relation to axons and capillaries. A wide range of nuclear and cytoplasmic densities were displayed by both satellite and interfascicular oligodendrocytes. The following distinctive features for the identification of ligodendrocytes were utilised: the presence of large quantities of free ribosomes and ribosomal rosettes, microtubular profiles, dense marginal aggregation of nuclear chromatin together with light patches and numerous nuclear pores; but the absence of broad cytoplasmic processes, glycogen and gliofibrils. Circumferential perinuclear organization of the cytoplasmic organelles was typical of oligodendrocytes. Particular attention was paid to perineuronal satellite cells in view of the known transneuronal atrophy in the de-afferented geniculate body. Some cells having a nuclear pattern of oligodendrocytes but showing hyalinisation of perikaryon were seen in de-afferented laminae. A notable feature was the presence of variegated “osmiophilic bodies” in the perikaryon of oligodendrocytes also situated in the de-afferented laminae. A cell type combining the features of oligodendrocytes and astrocytes was classified as ‘intermediate neuroglia’.

The cytological distribution of ‘Osmiophilic Bodies’ in the normal and degenerating lateral geniculate nucleus of the monkey

SummaryAs a result of an electron-microscopic study of the distribution of ‘osmiophilic bodies’ in the lateral geniculate nucleus obtained from sixteen young monkeys the following conclusion are drawn.1.There are morphologically different types of osmiophilic bodies found in the lateral geniculate nucleus of the monkeys.2.The term ‘osmiophilic body’ seems to be inadequate and confusing in the midst of numerous light and electron-microscopical studies and it is suggested that it may be replaced by a more specific expression—applicable to only electronmicroscopy i.e. ‘electrondense’ bodies. In such cases it is essential to denote the topographical relations, if the exact source or chemical nature is uncertain.3.The possible relationship with the mitochondria has been discussed.4.As osmiophilic bodies within the mitochondria, in the immediate neighbourhood of the blood vessels, and in some of the glia cells have been observed only in the material obtained from the operated animals and not in the normal ‘controls’, a causal association with the pathological alteration is suggested.ZusammenfassungAls Ergebnis einer elektronenmikroskopischen Studie über die Verteilung der “osmiophilen Körperchen” im Corpus geniculatum laterale (Cgl) von 16 jungen Affen wurden folgende Schlüsse gezogen:1.Im Cgl der Affen finden sich verschiedene Arten osmiophiler Körperchen.2.Die Bezeichnung “osmiophile Körperchen” scheint angesichts zahlreicher licht- und elektronenoptischer Untersuchungen unpassend und verwirrend und sollte durch einen präziseren, auf die Elektronenmikroskopie anwendbaren Ausdruck, z. B. “elektronendichte” Körperchen ersetzt werden. Es ist wesentlich, die topographischen Beziehungen zu bezeichnen, wenn die genaue Herkunft oder chemische Natur ungewiß ist.3.Die mögliche Beziehung zu den Mitochondrien wird diskutiert.4.Da osmiophile Körperchen innerhalb der Mitochondrien in der unmittelbaren Nachbarschaft von Blutgefäßen und in einzelnen Gliazellen nur im Untersuchungs-material von operierten Tieren und nicht in normalen Kontrollen angetroffen werden, wird eine Kausalbeziehung mit der pathologischen Veränderung vermutet.

Scanning and Transmission Electron Microscopy of the Ependyma of the Fourth Ventricle in the Monkey Brain

The ependymal structure of the fourth ventricle floor of adult rhesus monkeys was investigated using both scanning and transmission electron microscopy. Each half of the floor exhibited dense ciliation which decreased towards the median sulcus. The area postrema and the facial colliculus lacked cilia and were covered with non-ciliated ependymal cells. Along the entire length of the median sulcus supraependymal globular protrusions were seen. Over the rostral and middle thirds of the sulcus these protrusions exhibited interwoven ridges. At the former situation they were closely approximated but at the latter they were on the surface of non-ciliated nodules which were lying amongst sparsely ciliated cells. In the caudal third these protrusions presented smoother surfaces without any structural details over them. Transmission electron microscopy through the upper two thirds of the median sulcus revealed these surface protrusions to be non-ciliated cells having long and profuse network of interwoven microvilli over their luminal surface. These cell bodies exhibited well-defined supranuclear Golgi complexes, vesiculated rough and smooth surfaced endoplasmic reticulum, free ribosomes and polyribosomes, few electron dense granules, network of microtubules and light and dense multivesiculated bodies. These features suggested a secretory and/or absorptive role, rather that autophagy to these surface specialization.

Surface fine structure of the ependymal lining of the rat fourth ventricle

The floor of the rat brain fourth ventricle has been divided into five zones to study the surface ultrastructure of the ependymal cells. Regional variations in the form of dense ciliation, sparse ciliation, central tufts of cilia, solitary cilia, pores, clavate and filiform microvilli have been observed.