Endocrine cells do not exist in rat brunner''s glands. An electron microscopic study

It was revealed by light microscopic experiments that in Brunner's glands and the epithelium of the human and mammalian duodenum, cells were present, with basally lying granulations. These granules could be identified at the ultrastructural level as accumulations of pleomorphe electron-dense granules ('argentaffin', 'chromaffin' and 'osmiophilic' granules). Depending on the light and electron microscopic staining techniques used, these cells were classified as 'mucous', 'serous', or 'endocrine' ('enteroendocrine', 'paracrine' and 'enterochromaffin') cells. In the present study, the following ultrastructural morphological criteria of Brunner's gland cells were correlated: size, shape and electron density of their nuclei and nucleoli with morphological changes of their cytoplasmic and intranuclear organelles, which serve the synthesis of mucopeptides. This proved that the synthesis of mucopeptides occurred in 3 phases. The first phase served the intranuclear synthesis of organelles, which latterly were used for the cytoplasmic mucopeptide synthesis. This phase was characterized by the appearance of an electron-lucent and euchromatic nucleus, which also contained an euchromatic and electron-lucent nucleolus, and a thin electron-dense nucleus membrane (euchromatic phase). Only a few freely lying ribosomes, membrane-bound ribosomes (rough endoplasmic reticulum, RER) and mitochondria were dispersed throughout the cytoplasm. Therefore, the cytoplasm appeared electron-lucent and nearly empty. The second phase was characterized by a round but heterochromatical nucleus containing also a heterochromatic nucleolus, and the appearance of receptosome- (endosome, endocytotic vesicle) and lysosome-like structures near to the cytoplasmic membrane of the basal cell portion, as well as in the basal and lateral perinuclear region (early heterochromatic phase). The receptosome-like structures were round-oval and contained a single electron-lucent inclusion vesicle, which had an empty space or an electron-opaque granule. Both inclusion structures were located eccentrically on the inner surface of the membrane of the receptosome-like structure. Here and there, it was possible to visualize great receptosome-like structures (multivesicular bodies) containing numerous membranous electron-lucent and electron-opaque inclusion vesicles. Electron-dense pleomorphe lysosome-like structures, bearing 1-4 electron-lucent inclusion vesicles with faint grains in their spaces, were also recognized in the basal cell portion, as well as in the basal and lateral perinuclear region.(ABSTRACT TRUNCATED AT 400 WORDS)     

Experimental germinaium dioxide-induced neuropathy in rats

We report and experimental model of germanium dioxide (GeO₂)-induced neuropathy in rats. More than 6 months administration of GeO₂ to young rats produced neuropathy characterized by segmental demyelination/remyelination and nerve edema. Electron microscopic studies demonstrated that changes in Schwann cells, such as an increased cytoplasmic volume or disintegration of the cytoplasm, were the earliest pathological findings. Schwann cell mitochondria contained high electron-dense materials. Subsequent removal of necrotic Schwann cell debris and myelin by invading macrophages was evident. These findings suggested that the Schwann cells themselves are the primary target of the toxin. The deposition of electron-dense granules in the intra-axonal vesicles, which was suggestive of glycogen granules in mitochondria, was observed in the advanced stage of the neuropathy. The findings of endoneurial edema with splitting of myelin lamellae were noted at the early stage of demyelination. Nerve edema may be the result of GeO₂-induced endothelial cell injury.Supported by a grant from the National Center of Neurology and Psychiatry of the Ministry of Health and Welfare, Japan     

An electron microscopic study of cerebral vasospasm with resultant myonecrosis in cases of subarachnoid haemorrhage,meningitis and trans-sylvian surgery

Summary Electron microscopic data on the development of myonecrosis following cerebral vasospasm associated with subarachnoid haemorrhage, meningitis and trans-sylvian surgery are presented. The basic feature of myonecrosis was dissolution of myofilaments with resultant fine granular or filamentous material. The disintegrating cytoplasm often contained numerous glycogen granules, dense bodies, autophagic vacuoles and myelin-like membranous bodies. A well-developed sarcoplasmic reticulum was preserved despite myofilament dissolution, while mitochondria showed marked sweling. The nuclei showed either dilution of chromatin or pyknotic change. The basal lamina was remarkably thickened and maintained an irregular outline of the necrotic smooth muscle cells. Enlarged intercellular space contained abundant cellular debris, vesicular structures and connective tissue fibres. The pathogenesis of these changes is discussed.     

Ultrastructure of a composite glioma-sarcoma of the brain

Summary The ultrastructural features of a composite glioma-sarcoma of the brain are described. Glial cells had short cytoplasmic processes, a highly developed rough endoplasmic reticulum and bundles of intracytoplasmic filaments 80–90 Å thick. The nucleus contained evenly distributed chromatin and spheroidal bodies up to 5000 Å in diameter. Mesenchymal cells had elongated cytoplasm, a rough endoplasmic reticulum with short cisternae, numerous lysosomes and groups of vesicles associated with the plasma membrane. Nuclei were elongated and contained spheroidal bodies similar to those observed in glial cells. The interstitial space contained abundant collagen fibers. The endothelial cells exhibited rows of pinocytotic vesicles and a well developed Golgi complex. The ultrastructural observations are considered confirmatory of the composite nature of these tumors. It is believed that the sarcomatous component originates in the hyperplastic endothelial cells.Supported in part by Public Health Service Grant FR 5360-08.     

Ultrastructural findings in pigs experimentally infected with bovine spongiform encephalopathy agent

We report here an electron microscopic study of selected nervous system tissues from pigs infected experimentally with the agent of bovine spongiform encephalopathy (BSE). Generally, the ultrastructural neuropathology of BSE-affected pig brain resembled that of BSE-affected cattle brain. Spongiform change, in the form of membrane-bound vacuoles separated by septae into secondary chambers, dominated the pathology. Numerous astrocytic processes were visible in close conjunction with elongated microglial cells. Neuronal degeneration presented as either dystrophic neurites or by the formation of autophagic vacuoles. Altered subcellular organelles: mitochondria, electron-dense bodies, autophagic vacuoles, neurofilaments and "branching-cisterns" accumulated in abnormal neurites. Autophagic vacuoles appeared as neuronal cytoplasm of increased electron-density sequestrated by intracytoplasmic membranes. Tubulovesicular structures were numerous, particularly in the cerebellum. Unusual crystalloids were observed in the white matter. In conclusion, experimental BSE in pigs demonstrated ultrastructural pathology in keeping with that observed in other spongiform encephalopathies.     

Neuronal degeneration in the brain of the bindled mouse

Summary Two types of intra-cytoplasmic inclusions were observed in many cortical neurons of hemizygous brindled mutant mice (MO^br/Y) which survived for more than 1 month.One type is an electron-lucent vacuole containing numerous vesicles and membrane fragments, some arranged concentrically, and the other consisted of electron-dense matrix with myelin figures. These inclusions were, as a rule, found near the axonal hillock where abnormally enlarged mitochondria were often present.In view of the presence of many features suggestive of autophagic vacuoles and absence of such inclusions in the oldest mice (91 days old), we hypothesize that these inclusions probably represent a focal repairing process of neurons from the sublethal injury.     

Ultrastructural Relationships Between GABAergic Terminals and Cardiac Vagal Preganglionic Motoneurons and Vagal Afferents in the Cat: A Combined HRP Tracing and Immunogold Labelling Study

The ultrastructural relationships between gamma-aminobutyric acid-immunoreactive (GABA-ir) neurons and other neurons of the nucleus tractus solitarius (NTS) and motoneurons of the nucleus ambiguus (NA) and dorsal motor vagal nucleus (DMVN), were examined by electron microscopic (EM) immunogold labelling with an anti-GABA antiserum on brain stem sections in which vagal motoneurons and vagal afferent fibres were labelled with horseradish peroxidase (HRP). HRP was applied to the cervical vagus or the cardiac vagal branch of anaesthetized cats. After 24 - 48 h survival, brains were glutaraldehyde-fixed and a stable HRP-tetramethylbenzidine reaction product compatible with EM processing was revealed on 250 microm vibratome sections. Following osmium postfixation, dehydration and resin embedding, GABA-ir was localized on ultrathin sections by an immunogold technique. GABA-ir axon terminals, heavily and specifically labelled with gold particles, were very numerous within NTS, DMVN and NA. All terminals contained small, clear, pleomorphic vesicles and a few also contained larger dense cored vesicles. The density of gold particles over clear vesicles, dense cored vesicles and mitochondria was significantly greater than over the cytoplasm of these terminals. GABA-ir synapses were found on the soma and dendrites of neurons, but rarely on other axon terminals within NTS, where GABA-ir cell bodies and dendrites were also seen. These received synaptic contacts from both GABA-ir terminals and from HRP-labelled vagal afferents. In both the DMVN and NA, similar GABA-ir synapses were present on both the soma and dendrites of HRP-labelled motoneurons. GABA synapses were also present on other cell types in DMVN. These observations provide an anatomical basis for a GABAergic inhibition of neurons forming the central pathways of cardiovascular and other autonomic reflexes.     

NEURONAL CHANGES IN EXPERIMENTAL GLIOMAS

Gliomas were induced transplancentally by the administration of ethylnitrosourea to pregnant rats on the 15th day of gestation. The fine structure of neurones involved in these tumours was studied in order to assess the changes caused by neoplasia. The severity of the neuronal damage depended on their location, Those within the tumours being more affected than those in the neighbouring brain. The histological type and grade of malignancy also influenced the changes: periventricular pleomorphic gliomas and ependymomas of high-grade malignancy caused the most severe alterations. Neurones displayed a spectrum of appearances from apparent normality to complete necrosis. Both nucleus and cytoplasm were affected: of the cytoplasmic organelles the rough-surfaced endoplasmic reticulum and mitochondria showed the most striking changes. There were many lipofuscin granules and autophagic vacuoles. Axons underwent advanced degeneration: swollen mitochondria, disrupted vesicles and vacuoles, disintegrated microtubules, irregular filaments and unidentified debris were sometimes seen. Disintegration of myelin sheaths frequently occurred with consequent engulfing of their debris by macrophages and reacting astrocytes. The neuronal satellites--mainly oligodendrocytes--were often replaced by neoplastic glial cells. Hydrolytic 'marker' enzymes were demonstrated in neurones at various stages of degeneration. In all cases neurones displayed low acid phosphatase activity, while thiamine pyrophosphatase activity decreased with increasing neuronal degeneration.     

An electron microscopic study of the choroid plexuses of Necturus maculosus

The choroid plexuses of the neotenous salamander, Necturus maculosus, were examined by light and electron microscopy. Their epithelium was found to consist of a single layer of flattened to cuboidal cells resting upon a well-developed, continuous basement membrane. The cytoplasm of a typical epithelial cell contained, besides a large, centrally-placed nucleus, numerous mitochondria, an extensive agranular endoplasinic reticulum, prominent Golgi complexes and a variety of dense bodies. In addition, occasional clusters of ribosomes, lipid droplets, fascicles of fine filaments and numerous glycogen granules were present within the cytoplasm. Specializations of the apical (ventricular) surfaces of the epithelial cells included an irregular brush border, cilia, and minute, possibly micropinocytotic, invaginations of the plasma membrane. Surfaces of contacts between epithelial cells were specialized by “tight junctions” desmosomes, and complex inter dictations of the apposed plasma membranes. The interstitial space separating the epithelial layer from the thin-walled, non-fenestrated plexus blood vessels contained a mesh-work of collagen fibrils and a variety of connective tissue cell types. Electron dense Thorotrast particles were found to traverse the endothelial walls of the blood vessels and accumulate within the interstitial spaces within 30 minutes after being injected into the blood stream. The epithelial basement membrane, however, apparently prevented the tracer particles from reaching the epithelial cells, and the ventricular spaces beyond, as long as five hours after injection.     

A suspected new canine storage disease

Summary This paper describes three cases of what is probably a new form of storage disorder. The affected animals were English Springer Spaniels and they had developed progressive neurological signs when 2–3 years old. They had gross enlargement of the vagi and of the spinal nerves supplying the brachial plexus. By light microscopy in these nerves there were massive amounts of endoneurial loose fibrous tissue with dispersion of nerve fibres and many foamy phagocyte-like cells. In the central nervous system there was very severe cytoplasmic vacuolation of most neurones and neuroglia, perivascular phagocyte-like cells, loss of myclin, loss of Purkinje cells, numerous spheroids, hypertrophic astrocytes and fibrous astrocytosis. There was also foamy cytoplasmic vacuolation of renal convoluted tubules and pancreatic exocrine parenchyma and numerous foamy phagocyte-like cells in lymph node and lung. On ultrastructural examination membrane bound vacuoles wee present in the cytoplasm of affected neurones and phagocyte-like cells. Most of the vacuoles were empty, some contained amorphous materials and some, in neurones, contained stacks of curved or straight lamellae. It is suggested that the stored material could be an oligosaccharide.     

Ultrastructural Characterization of Adrenocorticotrope Hormone (ACTH) Immunoreactive Fibres in the Mesencephalic Central Grey Substance of the Rat

The fine structural localization of fibres immunoreactive for the adrenocorticotrope hormone (ACTH) was studied in the mesencephalic central grey substance (MCG) of the male Wistar rat. Light microscopically, varicose ACTH-immunoreactive fibres were found throughout the MCG in a dorsal, lateral and ventral, periventricular position. Electron microscopically, the immunoreactivity was most prominent in the direct vicinity of electron-dense secretory granules in axonal varicosities, and, although to a lower degree, around other cytoplasmic organelles such as electron-lucent synaptic vesicles, mitochondria and microtubules. With serial section analysis two types of ACTH-immunoreactive varicosity were discerned. The first type is large, contains many, small electron-lucent synaptic vesicles, that are located in the vicinity of a morphologically well-defined synaptic contact. In this type of varicosity, large dense-core secretory granules are scarce. Immunoreactivity is low or absent, particularly near the active zone. The second type is strongly immunoreactive. It always contains many large, dense-core secretory granules; electron-lucent vesicles are rare. The smaller varicosities of this type never make synaptic contacts, but a few of the larger varicosities have synaptic contacts with dendrites of MCG cells.     

Some observations on the fine structure of the sensory cells in the neuromasts (ordinary lateral line) of the teleost Gambusia affinis.

The structural and ultrastructural features of the sensory cells in the neuromasts of G. affinis were studied. These pear-shaped cels present a tuft of sensory hairs rising from the apex and a highly dense cytoplasm with multivesicular bodies, dyctiosomes, granular and smooth endoplasmic reticulum and numerous mitochondria. Large round granular dense bodies of an unknown nature can be observed inside and outside the nucleus. A great number of vesicles are present at the base of the cells, some of them associated with an afferent synapse, which also presents a presynaptic dense body. An efferent synapse with a nerve ending full of vesicles and a postsynaptic subsurface cisterna is also present at the base of these cells.     

Ultrastructural evidence for peptidergic innervation of the apical region of frog olfactory epithelium

Ultrastructural examination of the region near the olfactory epithelial surface of leopard frogs revealed the presence of nerve terminals just proximal to the zonula adherens between adjacent sustentacular cells, and between sustentacular cells and olfactory receptor neurons. Terminal varicosities, located about 20 nm from sustentacular cell membranes, contained numerous large-diameter dense-cored vesicles, small-diameter agranular vesicles, and mitochondria. On the basis of ultrastructural characteristics, they are identified as peptidergic sensory terminals.     

Synaptic organization of the interstitial subdivision of the nucleus tractus solitarii and of its laryngeal afferents in the rat

The nucleus tractus solitarii, the first central relay for gustatory and a variety of visceral afferents, is also an integrative center for numerous functions. Its interstitial subdivision is involved in swallowing and respiratory reflexes. The ultrastructural characteristics of this subdivision and of its laryngeal afferents were investigated in adult rat by a serial-section study and by application of wheat germ agglutinin-horseradish peroxidase conjugate to the peripheral afferent fibers. The interstitial subnucleus contained scattered small neuronal cell bodies with such ultrastructural features as a large nucleus with deep indentations and an organellepoor cytoplasm. On the basis of their size and vesicular content, the axon terminals were classified into three categories. Group I and group II terminals were small or large, respectively, and contained mainly small, round, and clear synaptic vesicles. Group III terminals were also small but contained small, pleomorphic, and clear vesicles. Axodendritic synapses were the most numerous. They were either asymmetrical, comprised of group I and II terminals, or symmetrical, comprised of group III terminals. More than 50% were part of complex synaptic arrangements in the form of rosettes or glomeruli. Axosomatic contacts involved both group I and group III terminals and were always symmetrical. A high frequency of axoaxonic synapses was found. They were symmetrical, comprised of group III terminals on group I or II terminals. Different types of symmetrical synaptic contacts made by dendrites were also found. This study indicates also that the ipsilateral interstitial subdivision constitutes the preferential site of termination for superior laryngeal afferents. The labeled axon terminals belonged exclusively to groups I and II and were involved in both axodendritic and axodxonic synapses. Some of the axodendritic synapses were part of rosettes or glomeruli. All these synaptic arrangements may be considered a morphological substrate for important processing of afferent information in the nucleus tractus solitarii. They may account for some of the integrative functions of the interstitial subnucleus such as physiological processes triggered from the superior laryngeal nerve.     

Distribution of calcitonin-gene-related peptide, neuropeptide-Y, vasoactive intestinal polypeptide, cholecystokinin-8, substance P and islet peptides in the pancreas of normal and diabetic rats

Neuropeptides and peptides are particularly important in the co-ordination of pancreatic exocrine and endocrine secretions. In diabetes mellitus, pancreatic endocrine secretion is particularly impaired. This study investigates whether there is a change in the pattern of distribution of neuropeptides including calcitonin-gene-related peptide (CGRP), neuropeptide-Y (NPY), vasoactive intestinal polypeptide (VIP), cholecystokinin-octapeptide (CCK-8), substance P (SP), and islet peptides including insulin (INS), glucagon (GLU), somatostatin (SOM) and pancreatic polypeptide (PP) in the pancreas of streptozotocin (STZ)-diabetic rats. After the onset of diabetes, the pattern of distribution of INS, GLU, SOM and PP cells was deranged. CGRP was demonstrated in ganglion cells of both normal and diabetic pancreas. CGRP was also localized in nerve fibres innervating the blood vessels of both normal and diabetic pancreas. The pancreata of both normal and diabetic rats contained numerous NPY-immunopositive varicose nerve fibres in the wall of blood vessels. In normal pancreatic tissue, VIP-immunopositive nerve fibres were observed in all areas of the pancreas. After the onset of diabetes, VIP-positive nerve fibres were still discernible in the interacinar regions of the pancreas. CCK-8 was identified in nerve fibres innervating both the normal and diabetic rat pancreata. These CCK-8-immunopositive nerves were varicose in nature and distributed in the wall of blood vessels. SP was demonstrated in neurons located in the interlobular areas of normal tissue and in fine varicose nerve fibres of the interacinar region of STZ-induced diabetic pancreas. In conclusion, CGRP, NPY, VIP, CCK-8 and SP are well distributed in both normal and diabetic pancreas.     

A light- and electron-microscopic study of a temporal-lobe ganglioglioma

A temporal-lobe ganglioglioma was surgically removed from a 13-year-old boy who had psychomotor seizures for 4 years. By light microscopy, the ganglion cells were encompassed in a rich network of fibrous connective tissue. They merged with areas composed of sparser neuronal cells and numerous fibrillary astrocytes. The ganglionic and astrocytic areas contained many tiny eosinophilic granules, and proteinaceous globules which measured from 1 to 10 μ and often formed circular aggregates measuring up to 60 μ. By electron microscopy, three main cell types were seen:

1.

(1) Ganglion cells, whose cytoplasm and processes frequently contained dense-core vesicles measuring from 1250 to 1800 Å. These cells were sometimes found in synaptic contact with adjacent processes. The dilated nerve cell processes often contained concentrically laminated bodies resembling those reported in experimental axonal reaction and degeneration. Some of these bodies may represent degenerative changes in the dense-core vesicles. Larger autophagic vacuoles, occasionally containing a dense-core vesicle, were also found.     

Neuronal and glial characteristics of central neurocytoma: electron microscopical analysis of two cases

We have identified two central neurocytomas which contained cells co-expressing glial fibrillary acidic protein and synaptophysin defined by double-label immunostaining. Dual-positive cells were mostly polygonal in shape and with a morphological appearence similar to that of reactive astrocytes. This distinct morphology could be used to distinguish cells expressing glial fibrillary acidic protein from cells with round and clear cytoplasm which did not express glial fibrillary acidic protein and which composed the majority of the tumor. Samples containing polygonal cells were selected for electron microscopy from toluidine blue-stained semithin sections. Ultrastructural findings were similar in both neurocytomas, with both being composed predominantly of round cells with clear cytoplasm corresponding to the clear cells identified by light microscopy. Dense-core vesicles and clear vesicles were frequently observed in the cell processes. Apart from these clear cells, polygonal cells with electron-dense cytoplasm were noted. Paralleling the results of double immunostaining, these polygonal cells contained both dense-core vesicles and intermediate, presumably glial filaments. Microtubules and lipofuscin granules were also observed. These results suggest that cells expressing glial fibrillary acidic protein in central neurocytoma include tumor cells with both neuronal and glial characteristics. Received: 25 January 1995 / Revised: 9 June 1995 / Revised, accepted: 1 December 1995     

Ultrastructural pathology of prion diseases revisited: brain biopsy studies

We report here a detailed ultrastructural comparison of brain biopsies from 13 cases of Creutzfeldt-Jakob disease (CJD) and from one case of fatal familial insomnia (FFI). The latter disease has not heretofore benefited from ultrastructural study. In particular, we searched for tubulovesicular structures (TVS), 35-nm particles regarded as the only disease-specific structures at the level of thin-section electron microscopy. Our material consisted of brain biopsies obtained by open surgery from one FFI case from a new French family, one case of variant CJD (vCJD), nine cases of sporadic CJD (sCJD), two cases of iatrogenic (human growth hormone) CJD and one case of hereditary CJD (Val203Iso). The ultrastructural picture of the cerebral cortex of the FFI patient was virtually indistinguishable from that of CJD. TVS were found, albeit only after prolonged search. Typical spongiform change was observed, consisting of intracellular membrane-bound vacuoles containing secondary chambers (vacuoles within vacuoles) and amorphous material. Neuronal degeneration was widespread: some processes contained degenerating mitochondria and lysosomal electron-dense bodies and these met the criteria for neuroaxonal dystrophy. Other processes contained branching cisterns; still others were filled with electron-dense masses and amorphous vesicles. The overall ultrastructural appearance of variant CJD was similar to that of FFI cerebral cortex, except for a much higher number of cellular processes containing TVS. We detected TVS in the majority of sCJD cases that, in addition to typical spongiform change and robust astrocytic reaction, showed widespread neuritic and synaptic degeneration and autophagic vacuoles. We conclude that TVS are readily found in FFI, vCJD and sCJD and that widespread neuritic degeneration is a part of ultrastructural pathology in prion diseases.     

Ultrastructural changes in muscle and motor end-plate of the dystrophic mouse

A comparative study of dystrophic mice (C57BL/6J-dy2J) and normal littermates, 6 to 9 months old, has revealed numerous ultrastructural changes in the dystrophic soleus. Vacuoles, swollen mitochondria, vesicular aggregates, membranous bodies, Z-line degradation, localized hypercontraction, myofibrillar disorientation, and focal necrosis were common. We report here new observations. Discontinuous, dense bands (240 A wide) were observed rarely between inner and outer membranes in some nuclei. Closely associated with infoldings of nuclear membrane were paracrystalline, vesicular structures, actin-like filaments, and autophagic vacuoles. With the degeneration of the nuclear membrane, actin-like filaments were observed within the nucleus. The primary synaptic clefts were widened and contained osmophilic-dense granules (diameter 0.2 to 0.7 micrometer). There was loss of secondary synaptic folds. Discontinuity of pre- and postsynaptic membranes could be observed, though rarely. Lysosome-like dense bodies were present among myofilaments. The myeloid bodies and autophagic vacuoles that were associated with nuclei, sarcoplasmic reticulum, and mitochondria gave a positive acid phosphatase reaction. Such degeneration changes were not observed in the normal soleus.