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Biomedical subjects

J Wegiel

Publications and source records attributed to J Wegiel.

At least 73 records · Page 4Linked to original sources
PubMed1992

Ultrastructure of the microglia that phagocytose amyloid and the microglia that produce beta-amyloid fibrils.

The function of microglia associated with beta-amyloid deposits still remains a controversial issue. On the basis of recent ultrastructural data, microglia were postulated to be cells that form amyloid fibrils, not phagocytes that remove amyloid deposits. In this electron microscopic study, we examined the ability of microglia to ingest and digest exogenous amyloid fibrils in vitro. We demonstrate that amyloid fibrils are ingested by cultured microglial cells and collected and stored in phagosomes. The ingested, nondegraded amyloid remains within phagosomes for up to 20 days, suggesting a very limited effectiveness of microglia in degrading beta-amyloid fibrils. On the other hand, we showed that in microglial cells of classical plaques in brain cortex of patients with Alzheimer's disease, amyloid fibrils appear first in altered endoplasmic reticulum and deep infoldings of cell membranes. These differences in intracellular distribution of amyloid fibrils in microglial cells support our observations that microglial cells associated with amyloid plaques are engaged in production of amyloid, but not in phagocytosis.

Amyloid↗
PubMed1992

Tubuloreticular structures in microglial cells, pericytes and endothelial cells in Alzheimer's disease.

In two of six brain biopsies of patients with Alzheimer's disease (AD), tubuloreticular structures (TRS) were observed in the distended endoplasmic reticulum of microglial cells, endothelial cells of vessels, and pericytes. In the microglial cells that produce amyloid fibrils, TRS were found in the cytoplasmic channels, which were filled with newly formed amyloid fibrils. Co-localization of TRS and newly formed amyloid fibrils in the same cellular compartment strengthens the hypothesis that amyloid fibrils are formed in the endoplasmic reticulum of microglial cells. Formation of TRS in microglial cells, pericytes, and endothelial cells of vessels probably reflects local or systemic alpha-interferon production. In some cells, this pathological process coexists with the second type of pathological changes: formation of amyloid fibrils.

Aged↗
PubMed1992

Ultrastructural studies of the cells forming amyloid in the cortical vessel wall in Alzheimer's disease.

Ultrastructural studies of serial sections of the vessels with amyloid deposits in the brain cortex of patients with Alzheimer's disease showed that cells in the position of pericytes--perivascular cells--and perivascular microglial cells are producers of amyloid fibrils in the vascular wall. Three types of changes from normal are distinguishable in the vessel wall: (1) semicircular or circular thickening of vascular wall containing a large amount of amorphous material and various number of amyloid fibrils, (2) tuberous amyloid deposits containing both amorphous material and amyloid fibrils, some of the fibrils being arranged in strata and others arranged radially, and (3) amyloid star composed of a predominantly radial arrangement of bundles of amyloid fibrils and a less prominent amorphous component. A mixture of amorphous material and amyloid fibrils is present in cell membrane invaginations of perivascular cells, and occasionally perivascular microglial cells. Bundles of amyloid fibrils are found in altered cisternae of the endoplasmic reticulum and in the channels confluent with the infoldings of the plasma membrane of perivascular microglial cells. The amyloid deposition in the wall of the vessel causes degeneration of endothelial cells and the reduction of, and in some vessels obliteration of, the vessel lumen. In areas affected by amyloid angiopathy, extensive degeneration both of the neuropil and of neurons was observed. These changes were accompanied by astrogliosis. This study demonstrates similarities in amyloid formation in amyloid angiopathy and in beta-amyloid plaques in the neuropil and suggests that cells of the mononuclear phagocyte system of the brain (perivascular cells and perivascular microglia) are engaged in amyloid fibril formation.

Aged↗
PubMed1992

Polysaccharides from fruitbodies and mycelial culture of the fungus Trametes hirsuta (Wulf. ex Fr.) Lloyd.

The fruitbodies and mycelial culture of the wood destroying fungus Trametes hirsuta (Wulf. ex Fr.) Lloyd were investigated as a source of polysaccharides. Four different polysaccharide fractions were isolated from these sources with the good yield 4.76% (PfA) and 1.18% (PfB)--(fruitbodies) and 2.33% (PmcA), 3.25% (PmcB)--(mycelium) respectively. Some chemical differences were found in the composition of isolated polysaccharides. Some of them contained aminoacids as the structural components, especially those isolated from mycelial culture of the fungus. In all polysaccharide fractions glucose was present as a main monosugar.

Basidiomycota↗
PubMed1990

Ultrastructure of the cells forming amyloid fibers in Alzheimer disease and scrapie.

Ultrastructural, three-dimensional reconstruction of cells surrounding the amyloid star in classical plaques in Alzheimer disease (AD) and histochemical studies of the cells associated with the deposits of amyloid fibers in scrapie were carried out. These studies showed that in both diseases, the fibers appear within the smooth endoplasmic reticulum (ER) and infoldings of cytoplasmic membranes of microglia/macrophages. Additional information about the site of formation of the amyloid fibers derives from histochemical studies of the localization of nucleoside diphosphatase (NDPase) activity. In normal microglia, this enzyme is associated with smooth ER and cell membranes. In the cells that form amyloid fibers, the NDPase activity is associated with the newly formed amyloid fibers within the distended cisternae of ER and the finger-like cytoplasmic projections. In the center of the amyloid star, the NDPase activity disappears. The presence of NDPase-positive amyloid fibers in the same location, where the enzyme is found in non-amyloid-forming cells, further supports our conclusion that the microglia/macrophages are the source of amyloid deposits. These studies also show that in spite of the differences in the proteins that produce the amyloid fibers in AD and scrapie, in both diseases, the microglia/macrophages play a key role in amyloid formation.

Acid Anhydride Hydrolases↗
PubMed1990

The complex of microglial cells and amyloid star in three-dimensional reconstruction.

Ultrastructural, three-dimensional reconstruction and morphometric studies of classical plaques from the cortex of a patient with Alzheimer's disease showed five or six microglial cells, which form, together with the amyloid star, the central complex of the classical plaque. Microglial cells associated with the amyloid star show marked polymorphism, but all forms possess an amyloid making pole. The surface of the cell membrane at this pole is extended by apparent connection with membranes of cytoplasmic channels filled with amyloid fibers. The amyloid pole also shows other features of local activation with nuclei translocation, expansion of Golgi apparatus and endoplasmic reticulum, and multiplication of vacuoles and coated vesicles that are in close proximity to channels filled with new polymerized amyloid fibers. On the basis of ultrastructural studies, three forms of microglial cells can be distinguished: macrophage-like, cap-like, and octopus-like cells. The most effective in production of amyloid fibers seem to be cap-like microglial cells, which have the greatest interface with the amyloid star. Octopus-like cells have the least contact with the amyloid star. The size of the surface of the interface with the amyloid star appears to be an indicator of the extent of cell engagement in amyloid fiber formation.

Aged↗
PubMed1989

Ultrastructural studies of the cells forming amyloid fibers in classical plaques.

Three-dimensional reconstruction and ultrastructural studies of classical plaques from the cortex of patients with Alzheimer's disease showed that microglial cells of the plaques are the amyloid-forming cells. The amyloid star of the single plaque represents the product of five or six microglial cells covering about 80% of the amyloid star surface. The amyloid fibers appear to be formed within altered cisterns of the endoplasmic reticulum. Distended cisterns form channels filled with amyloid fibers. Numerous vesicles derived from the Golgi apparatus appear to be attached to or fused with the amyloid-filled channels. Reconstruction of the amyloid star and the microglia cell pole that forms the amyloid star reveals three different zones of distribution of cytoplasmic organelles and amyloid deposits. The peripheral zone comprises channels filled with loosely packed amyloid fibers arranged in a parallel manner. The transient zone consists of a mixture of fusing amyloid channels and products of disintegration of cytoplasmic pockets, dense bodies and fragments of cellular membranes. The core of the amyloid star is composed of condensed, densely packed amyloid fibers that are free of cellular debris. Formation of the three zones supports the idea that the microglia/macrophages are not phagocytes but instead are the cells manufacturing the amyloid fibers.

Aged↗
PubMed1989

[Morphological evaluation of tissue and cellular components of the corpus striatum, globus pallidus and substantia nigra in 7-day-old rats].

The aim of the study was the morphometric evaluation of tissue and cell composition of brain structures which are involved into transplantation in experimental model of parkinsonism in the rat-substantia nigra as the implanted structure and caudate-putamen as the host structure into which the graft is placed. Three parts of caudate-putamen (anterior, medial and posterior), three parts of substantia nigra (compact, reticular and lateral) as well as pallidum were investigated in 7-day-old rat. It was found that the density of nerve cells is highest in medial part (2236/l mm2), lower in anterior part (2129/1 mm2) and the lowest in posterior one (1842/1 mm2). The number of giant neurons in relation to the rest of neurons in anterior, medial and posterior parts of caudate-putamen was 1:268, 1:147 and 1:545 respectively. This indicates that the numbers of complexes formed by giant neurons with other neurons vary depending on the area of this brain structure. The zonal differences in distribution and size of neurons in caudate-putamen should be taken in account in qualitative and quantitative studies.

Age Factors↗
PubMed1989

[Effect of histological technics on the volume and weight of various brain structures of rats at the early stages of life].

The aim of the studies was to elaborate technical procedure of material preparation for quantitative studies and determination of correction coefficients of morphometric parameters in dependence on histological procedures. Moreover, volume changes of the rat substantia nigra and striatum (structures degenerating in Parkinson's disease) during the first half year of life were estimated. As fixatives 4 and 8% formaldehyde in 4 and 20 degrees C were used. Irrespective of applied variant of fixation formaldehyde produced during first 48 hrs rapid increase of the brain weight and volume up to 52% of that of the fresh brain, which was followed by slow decrease of brain weight of about 1-3%/24 hrs. The most pronounced changes caused 4% formaldehyde in 20 degrees C. The best conditions for morphometric studies were obtained with the use of 8% formaldehyde in 20 degrees C. Dehydration in ethyl alcohol produced violent decrease of brain volume and weight (from 32% up to 39% of the fresh brain weight). Clearing in methyl bensoesane increases again the brain weight by a few percentage. The obtained results make possible to estimate error size in morphometric studies conducted on the formaldehyde-fixed material. It was stated also that the above histological procedure causes more pronounced changes in fetal rat brain and in brain of 1-2-day-old rats. Stabilization of changes caused by histological procedure is achieved between first and sixth months of rat life.

Age Factors↗
PubMed1984

Morphology and function of liver after intravenous and intraportal injections of the immunomodulating agent Propionibacterium granulosum.

An immunomodulator, cell walls from Propionibacterium granulosum strain KP-45 (PG), has been applied in rabbits to test its influence on morphology and function of liver cells. For investigation of distribution in internal organs, the PG preparation was 51Cr-labelled and injected i.v. into mice. Functional liver tests were performed in rabbits injected intravenously or intraportally with PG. Morphologic studies (light and electron microscopy) of liver sections were performed in mice and rats injected intravenously with PG, 1-60 d prior to liver examination. Intravenous or intraportal application of PG did not cause detectable clinical symptoms during the whole observation period (1-60 d). During the first 3-7 d, elevation of serum globulins and transaminases (SGOT, SGPT) were noted with reappearance of normal values after 14-20 d. 131I-labelled Bengal Rose injected into PG-treated rabbits was trapped mostly in the spleen, and to a smaller extent in liver, where radioactivity was significantly lower than in saline-injected control animals. 51Cr-labelled PG injected i.v. into mice were after 60-90 min localized preferentially in lungs and liver, where the radioactivity was much higher than in the spleen. Morphological studies revealed that 6 h following i.v. injection of PG, there appeared partial clearing of the hepatocyte cytoplasm and lowering of their basophilic content with enhancement of pinocytic activity of the hepatocytes. This was accompanied by enlargement of RES cells in liver with enhanced intracellular digestion, higher number of lysosomes and appearance of phagocytic vacuoles.(ABSTRACT TRUNCATED AT 250 WORDS)

Alanine Transaminase↗