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At least 973 records · Page 54Linked to original sources
PubMed1990

Leukotoxic activity of Clostridium perfringens of equine origin.

Leukotoxic activity of equine isolates of Clostridium perfringens type A was examined. Thirty-seven isolates (94.9%) of 39 isolates demonstrated leukotoxic effects on mouse peritoneal macrophages. Phase contrast microscopy revealed that the toxic preparations induced rounded protoplasmic extrusion and sometimes destruction of the cells, leaving some membrane fragments. These findings suggest that the leukotoxic activity could be considered to be a virulence factor of C. perfringens.

Animals↗
PubMed2006

Ultrastructural characteristics of tau filaments in tauopathies: immuno-electron microscopic demonstration of tau filaments in tauopathies.

The microtubule-associated protein tau aggregates into filaments in the form of neurofibrillary tangles, neuropil threads and argyrophilic grains in neurons, in the form of variable astrocytic tangles in astrocytes and in the form of coiled bodies and argyrophilic threads in oligodendrocytes. These tau filaments may be classified into two types, straight filaments or tubules with 9-18 nm diameters and "twisted ribbons" composed of two parallel aligned components. In the same disease, the fine structure of tau filaments in glial cells roughly resembles that in neurons. In sporadic tauopathies, individual tau filaments show characteristic sizes, shapes and arrangements, and therefore contribute to neuropathologic differential diagnosis. In frontotemporal dementias caused by tau gene mutations, variable filamentous profiles were observed in association with mutation sites and insoluble tau isoforms, including straight filaments or tubules, paired helical filament-like filaments, and twisted ribbons. Pre-embedding immunoelectron microscopic studies were carried out using anti-3-repeat tau and anti-4-repeat tau specific antibodies, RD3 and RD4. Straight tubules in neuronal and astrocytic Pick bodies were immunolabeled by the anti-3-repeat tau antibody. The anti-4-repeat tau antibody recognized abnormal tubules comprising neurofibrillary tangles, coiled bodies and argyrophilic threads in progressive supranuclear palsy (PSP) and corticobasal degeneration. In the pre-embedding immunoelectron microscopic study using the phosphorylated tau AT8 antibody, tuft-shaped astrocytes of PSP were found to be composed of bundles of abnormal tubules in processes and perikarya of protoplasmic astrocytes. In this study, the 3-repeat tau or 4-repeat tau epitope was detected in situ at the ultrastructural level in abnormal tubules in representative pathological lesions in Pick's disease, PSP and corticobasal degeneration.

Astrocytes↗
PubMed1980

An autopsy case of Tay-Sachs disease--with special reference to axonal swellings of the central nervous system and freeze-fracture replication studies of the membranous cytoplasmic bodies.

The following is a report of the light and electron microscopic findings of the axonal swellings of the central nervous system and the freeze-fracture replication studies of the membranous cytoplasmic bodies in Tay-Sachs disease. The axonal swellings were observed mainly in the subthalamic nucleus, thalamus, globus pallidus, red nucleus, dentate nucleus, inferior olivary nucleus, nucleus gracilis, spinal anterior nucleus and so on. They contained many electron dense bodies and neurofilaments. Typical membranous cytoplasmic bodies were not seen in these axonal swellings. The freeze-fracture replication studies demonstrated that the membranous cytoplasmic bodies were composed of parallel stacks or concentric whorls of lamellae at an interval of 5 to 6 nm, with membrane-associated particles of 8 to 10 nm diameters on their protoplasmic face. It was postulated that the membranous cytoplasmic bodies constituted various compound lipids including the GM2-ganglioside and some proteins.

Axons↗
PubMed1984

So-called nasal glioma.

Nasal glioma is heterotopic brain tissue which usually presents as a tumor around the nose of children and infants. We have encountered two cases of nasal glioma during the past nine years at Hokkaido University Hospital. One showed a tumor in the subcutis of the nasal bridge and the other a polypoid mass arising in the soft palate. Both consisted of proliferation of fibrillary spindle cells consistent with fibrillary astrocytes divided by fibrovascular septa. This was reminiscent of "gliosis" of the central nervous system. Occasional protoplasmic astrocytes were present in both and, in addition, one case showed neuronal cells and choroid plexus. The glial nature of the lesion was confirmed by the presence of glial fibrillary acidic protein demonstrated by the immunoperoxidase method. Nasal glioma is not neoplastic contrary to its name and is considered heterotopic brain tissue which was displaced during fetal development by similar pathogenetic mechanisms of sincipital and basal encephalocele, although its communication to the brain was lost.

Astrocytes↗
PubMed1992

Light and Electron Microscopic Localization of the Neutral Metalloendopeptidase EC 3.4.24.16 in the Mesencephalon of the Rat.

The topographic and cellular distribution of the neurotensin-hydrolysing neutral metalloendopeptidase 24.16 (EC 3.4.24.16) was examined by light and electron microscopic immunohistochemistry in adult rat mesencephalon. Light microscopic immunoradioautography revealed a ubiquitous distribution of the enzyme throughout the midbrain with a relative enrichment of grey matter areas including the substantia nigra, ventral tegmental area, interfascicular nucleus, interpeduncular nucleus, rostral and caudal linear raphe nuclei, central grey and superficial grey of the superior colliculus. Peroxidase - antiperoxidase immunocytochemistry revealed two distinct cellular patterns of immunostaining: (1) weakly labelled neuronal perikarya more or less uniformly distributed throughout the grey matter, and (2) intensely immunoreactive glial cells heterogeneously distributed across the mesencephalon. Areas exhibiting dense concentrations of endopeptidase 24.16-containing glial cells corresponded to those displaying enhanced immunoreactivity in immunoradioautographs, suggesting that a major proportion of brain endopeptidase 24.16 is associated with glia. Electron microscopic examination of the substantia nigra and ventral tegmental area confirmed the association of the enzyme with a subpopulation of neurons and allowed identification of labelled glial cells as protoplasmic astrocytes. In neurons, endopeptidase 24.16 immunoreactivity was distributed heterogeneously within the cytoplasm of perikarya, dendrites and axons. Reaction product was also characteristically associated with restricted zones of the plasma membrane and underlying neuroplasm. In astrocytes, endopeptidase 24.16 immunostaining was densely and uniformly distributed throughout the cytoplasm of cell bodies and processes. Many of these processes were in direct contact with endopeptidase 24.16-immunopositive neuronal elements. The present results demonstrate that within the midbrain, endopeptidase 24.16 is both intracytoplasmic and membrane-associated in neurons and predominantly intracytoplasmic in glia. The presence of a large number of immunostained elements within areas of the midbrain known to display high levels of neurotensin and/or neurotensin receptors, together with the demonstrated catabolic activity of the enzyme on neurotensin in vitro, is consistent with a role of endopeptidase 24.16 in the functional inactivation of endogenous neurotensin in this region of the brain.

Journal Article↗
PubMed1987

Free amino acid content of astroglial cell clones derived from 8-day postnatal mouse cerebella.

We have measured the free amino acid content of three distinct astroglial cell clones derived from permanent lines obtained after "spontaneous immortalization" of 8-day postnatal mouse cerebellar cultures; these clones show characteristics similar to the Golgi Bergmann glia cells, the fibrous astrocytes, and the velate protoplasmic astrocytes, i.e., the three main types of cerebellar astrocytes. The relative concentrations of amino acids that are thought to act as neurotransmitters were compared in confluent cultures of the different astroglial clones. The most striking result was a high concentration of glycine (20% of free amino acids), even in astroglial cells cultured in a glycine-free medium, a finding suggesting that glycine is synthesized by the astroglial clones. Furthermore, no gamma-aminobutyric acid (GABA) was detected. In contrast, a "neuron-like" clone derived from the same cerebellar culture contained GABA, whereas its glycine content was much lower than that of the astroglial clones. The present results, together with our previous finding of glycine synthesis in an astrocytic clone derived from 14-day postnatal mouse cerebella transformed by simian virus 40, indicate that a high glycine content may be characteristic of many cerebellar astroglial types.

Amino Acids↗
PubMed1988

Glutamate dehydrogenase activity is markedly higher in a "Golgi-Bergmann"-like glial clone than in other astroglial cell lines.

Glutamate appears to be the neurotransmitter of granule cells, the major neuronal population of the cerebellar cortex. To determine the role of astroglial cells in the synthesis of glutamate, we have measured the specific activity of glutamate dehydrogenase (GDH) in clonal cell lines that might be the in vitro equivalents of the different cerebellum astroglial cell types. In conditions where GDH operates in the direction of glutamate synthesis, the specific activity of GDH measured in the "Golgi-Bergmann"-like clone was 4-6 times higher than in the "velate protoplasmic"- or "fibrous-like" astrocytic clones. These data correlate well with the intense immunoreactivity to GDH in Golgi-Bergmann astrocytes in vivo that has been recently reported.

Animals↗
PubMed1991

Isolation of a novel cDNA corresponding to a transcript expressed in the choroid plexus and leptomeninges.

The CNS is composed of neurons and glial cells (i.e., astrocytes, oligodendrocytes, and microglia). The brain communicates with the blood circulation through choroid plexus and meninges as well as through the blood-brain barrier. To identify transcripts specifically expressed in a distinct brain cell type, we have previously constructed a subtracted cDNA library from the poly(A)+ RNAs of a velate protoplasmic-like astrocytic cell line, designated D19. This library was screened in order to isolate transcripts over-expressed in this astroglial cell line versus another astroglial cell line. Of the six recombinants which have been isolated, three sequences have not been described. Their sizes ranged from 100 to 200 bp and they hybridized to mRNAs expressed in vivo inside and outside the CNS. We have constructed a size-selected D19 cDNA library in order to obtain the full length cDNAs corresponding to the three undescribed sequences. We report here the isolation of a 1.6 kb cDNA corresponding to one of these recombinants, named p14. Its sequence has not yet been described and its deduced amino acid sequence codes for a 43 kDa protein with a putative signal peptide. In situ hybridization shows that this transcript is expressed at a high level in choroid plexus and leptomeninges and also in perivascular cells in the adult mouse brain. It is also expressed in cell subsets of kidney and gonads as well as in perivascular cells in skeletal and cardiac muscles. These localizations suggest that the encoded protein might be involved in transport processes and hormonally controlled.

Animals↗
PubMed1991

Ultrastructural changes induced by 12-O-tetradecanoylphorbol 13-acetate in pure cholinergic synaptosomes of Torpedo electric organ.

We have studied the morphological changes induced by the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) treatment on pure cholinergic synaptosomes from Torpedo electric organ. These changes were studied by both ultrathin sections and freeze-fracture techniques. We found that after a treatment with TPA, a redistribution of synaptic vesicles inside the nerve endings and exocytotic images could be observed. Also, TPA, under conditions that induced the acetylcholine release, did not change the density of intramembrane particles at the synaptosomal protoplasmic hemimembrane leaflet. Similar results were found when calcium was not present in the extrasynaptosomal medium, and our results suggest that acetylcholine release induced by phorbol ester is probably mediated by exocytosis of synaptic vesicles.

Acetylcholine↗
PubMed1984

A freeze-fracture electron microscope study of Trichomonas vaginalis Donné and Tritrichomonas foetus (Riedmüller).

Two strains of Trichomonas vaginalis, JH162A , with low pathogenicity, and Balt 44, with high pathogenicity, as well as one highly pathogenic strain, KV-1, of Tritrichomonas foetus were studied by freeze-fracture electron microscopy. The protoplasmic faces ( PFs ) of the cell membranes of all three strains of both species had similar numbers of intramembranous particles (IMPs); however, the particles in the external faces (EFs) of these membranes were least abundant in Trichomonas vaginalis strain Balt 44 and most numerous in those of strain JH162A of this species. In Tritrichomonas foetus strain KV-1 the number of IMPs in the EF was close to but somewhat lower than that in the mild strain of the human urogenital trichomonad . In both species, the anterior, but not the recurrent, flagella had rosette-like formations, consisting of approximately 9 to 12 IMPs on both the PFs and EFs. The numbers and distribution of the rosettes appeared to vary among different flagella and in different areas of individual flagella of a single organism belonging to either species. The freeze-fracture electron micrographs provided a more complete understanding of the fine structure of undulating membranes of Trichomonadinae , as represented by Trichomonas vaginalis, and of Tritrichomonadinae (the Tritrichomonas augusta -type), as exemplified by Tritrichomonas foetus, than was gained from previous transmission and scanning electron microscope studies. Typically three longitudinal rows of IMPs on the PF of the recurrent flagellum of Trichomonas vaginalis were noted in the area of attachment of this flagellum to the undulating membrane. The functional aspects of the various structures and differences between certain organelles revealed in the two trichomonad species by the freeze-fracture method are discussed.

Animals↗
PubMed1988

Freeze-fracture study of Blastocystis hominis.

The ultrastructure of Blastocystis hominis was investigated by the freeze-fracture method. Freeze-fracture replicas of the membranes of B. hominis and its organelles were studied with special regard to the density and distribution of the intramembranous particles (IMP's). On all membrane replicas, the concentration of IMP's on the protoplasmic face (P face) invariably was greater than on the exoplasmic face (E face). On the P face, IMP's were heterogeneously distributed in dense aggregates, alternating with particle-free, smooth surface areas. Occasionally, small depressions and protrusions were observed in these areas. On the membrane of the central vacuole, invaginations into the vacuole were frequently observed within the smooth surface regions. Since most of the granules in the central vacuoles had no IMP's, it seems likely that the intervacuolar granules were formed from these invaginations of the vacuole membrane. The width of the intermembrane space between the inner and outer membranes of the nuclear envelope was uneven, with regions of relative narrowness interspersed with regions of expansion. Nuclear pores were localized within the narrow portions of this space. A nucleus, apparently in the process of dividing, was observed enclosed within an intact outer membrane. Division of the outer membrane would then result in the formation of two discrete nuclei.

Animals↗
PubMedDate not supplied

Freeze-fracture study of the bloodstream form of Trypanosoma brucei gambiense.

The ultrastructure of Trypanosoma brucei gambiense was investigated by the freeze-fracture method. Three different regions of the continuous plasma membrane; cell body proper, flagellar pocket, and flagellum were compared in density and distribution of the intramembranous particles (IMP's). The IMP-density was highest in the flagellar pocket membrane and lowest in flagellum. Intra membranous particles of the cell body membrane were distributed uniformly on both the protoplasmic (P) and exoplasmic (E) faces. On the P face of the flagellar membrane, a single row of IMP-clusters was seen along the juncture of the flagellum to the cell body. Since the spacing of the IMP-clusters was almost equal to the spacing of the paired rivet structures observed in thin section, these clusters likely are related to the junction of flagellum and cell body. At the neck of the flagellar pocket, several linear arrays of IMP's were found on the P face of the flagellar membrane, while on the E face rows of depressions were seen. At the flagellar base, the clusters of IMP's were only seen on the P face. On the flagellar pocket membrane, particle-rich depressions and linear particle arrays were also found on the P face, while on the E face such special particle arrangements were not recognized. These particle-rich depressions may correspond to the sites of pinocytosis of the bloodstream forms which have been demonstrated in thin sections.

Animals↗
PubMedDate not supplied

Structural alteration of the plasma membrane in spores of the microsporidium Nosema algerae on germination.

The fine structure of the plasma membrane in spores of the microsporidium Nosema algerae, a pathogen of mosquitoes, was examined in the resting condition and after the spores were stimulated to germinate in vitro. Slow penetration of resin caused collapse of the germinated spores. Thin sections of germinated spores showed peculiar membrane infoldings that were never found in ungerminated samples. Analogous germination-dependent configurations of the plasma membrane were observed in freeze-fractured preparations of spores either fixed and impregnated with glycerol prior to freezing, or rapidly frozen with liquid propane while in the process of germination. In every case, the replicas presented germinated spores with indentations in the protoplasmic face of the plasma membrane, and apparently complementary blunt spines on the external face, that were absent in ungerminated spores. It suggests that these alterations of the plasma membrane result from a structural adjustment to a spontaneous contraction of the spore case after germination. We discuss this interpretation with regard to conflicting views on the nature of such morphological features.

Animals↗
PubMedDate not supplied

Surface domains in the pathogenic protozoan Tritrichomonas foetus.

The quick-freezing and freeze-etching techniques were used to analyze surface domains of Tritrichomonas foetus. The surface of the protozoan body was not smooth, presenting surface projections, except on the flagellar surface. Images of the actual surface of the anterior flagella revealed the presence of intramembranous particles that form rosettes, as observed on the protoplasmic fracture face. They may represent integral transmembrane proteins exposed at the cell surface. Surface specializations were also observed at the flagella base and where the recurrent flagellum attaches to the cell body.

Animals↗
PubMedDate not supplied

Brachiola vesicularum, n. g., n. sp., a new microsporidium associated with AIDS and myositis.

Brachiola vesicularum, n. g., n. sp., is a new microsporidum associated with AIDS and myositis. Biopsied muscle tissue, examined by light and electron microscopy, revealed the presence of organisms developing in direct contact with muscle cell cytoplasm and fibers. No other tissue types were infected. All parasite stages contain diplokaryotic nuclei and all cell division is by binary fission. Sporogony is disporoblastic, producing 2.9 x 2 microns diplokaryotic spores containing 8-10 coils of the polar filament arranged in one to three rows, usually two. Additionally, this microsporidium produces electron-dense extracellular secretions and vesiculotubular appendages similar to Nosema algerae. However, the production of protoplasmic extensions which may branch and terminate in extensive vesiculotubular structures is unique to this parasite. Additionally, unlike Nosema algerae, its development occurred at warm blooded host temperature (37-38 degrees C) and unlike Nosema connori, which disseminates to all tissue types, B. vesicularum infected only muscle cells. Thus, a new genus and species is proposed. Because of the similarities with the genus Nosema, this new genus is placed in the family Nosematidae. Successful clearing of this infection (both clinically and histologically) resulted from treatment with albendazole and itraconozole.

AIDS-Related Opportunistic Infections↗
PubMedDate not supplied

An analysis of the microsporidian genus Brachiola, with comparisons of human and insect isolates of Brachiola algerae.

The genus Brachiola is the newest microsporidian genus established for a human infection with the type species being B. vesicularum in skeletal muscle. Subsequently, the microsporidium, Nosema algerae, identified from mosquitoes, was added to this genus because of morphological and physiological similarities. The present report illustrates a confirmed case of Brachiola algerae infecting skeletal muscle in a 56-year-old woman who was being treated for rheumatoid arthritis with immunosuppressive drugs. In the following study, these two human-infecting microsporidian species are ultrastructurally compared from human biopsy tissue. Additionally, Brachiola algerae from mosquitoes as reference B. algerae, was grown in athymic mice and compared to the human isolate in vivo, and in culture. B. algerae is morphologically identical in the host situations presented and different from B. vesicularum in human skeletal muscle. B. algerae has a consistently, slightly longer spore that typically contains one row of polar filament coils, while B. vesicularum typically contains two rows of polar filament coils and occasionally, one or three rows. In proliferative development, B. vesicularum forms protoplasmic extensions which do not occur on B. algerae, nor have they been reported on any other microsporidium. This report demonstrates that B. vesicularum and B. algerae are two different species of Brachiola that infect human skeletal muscle.

Animals↗
PubMedDate not supplied

Neuronal-glial networks as substrate for CNS integration.

Astrocytes have been considered, for a long time, as the support and house-keeping cells of the nervous system. Indeed, the astrocytes play very important metabolic roles in the brain, but the catalogue of nervous system functions or activities that involve directly glial participation has extended dramatically in the last decade. In addition to the further refining of the signalling capacity of the neuroglial networks and the detailed reassessment of the interactions between glia and vascular bed in the brain, one of the important salient features of the increased glioscience activity in the last few years was the morphological and functional demonstration that protoplasmic astrocytes occupy well defined spatial territories, with only limited areas of morphological overlapping, but still able to communicate with adjacent neighbours through intercellular junctions. All these features form the basis for a possible reassessment of the nature of integration of activity in the central nervous system that could raise glia to a role of central integrator.

Animals↗
PubMed1988

Glial fibrillary acidic protein immunohistochemical study of Alzheimer I & II astrogliosis in Wilson's disease.

This study compared the relationships of the development of both Alzheimer I & II cells to reactive astrogliosis and also their distributional patterns in the demyelinated and non-demyelinated lesions in 6 cases of Wilson's disease by the use of PAP immunohistochemical technique for glial fibrillary acidic protein (GFAP). The development of GFAP positive Alzheimer I (A-I) cells was found to be directly proportional to the capability of reactive astrogliosis, and inversely proportional to the severity of Alzheimer II (A-II) change. The GFAP negative A-II cells could be identified morphologically into 2 subtypes: one with well-developed nuclei, the other with "shrunken" nuclei. They were believed to stand for the "compensatory" and "decompensatory" stages of this dynamic astrogliotic process respectively. The distribution patterns of these 2 types of astrogliosis were different: A-I cells were found only in the regions of demyelination with intensive reactive astrogliosis, while A-II cells were found diffusely in both the grey and white matter, affecting both the protoplasmic and fibrous astrocytes without special predilection.

Adult↗