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PubMed1976

Lack of amyloidosis and renal disease in A strain mice.

Amyloid deposition in two sublines of the A strain mouse, a reputedly reliable murine model of spontaneous amyloidosis, was reevaluated using combined green polarization birefringence after Congo red staining and a fibrillar ultrastructure for amyloid identification. Both sublines were found to be devoid of amyloid at an age when the A strain mouse had been reported to have a high incidence of papillonephritis, amyloidosis, and death. This finding indicates a need for reassessment of this and other traditional models of spontaneous amyloidosis.

Adrenal Glands↗
PubMed2003

Role of the C-terminal 28 residues of beta2-microglobulin in amyloid fibril formation.

Beta2microglobulin (beta2m) is the major protein component of the fibrillar amyloid deposits isolated from patients diagnosed with dialysis-related amyloidosis (DRA). While investigating the molecular mechanism of amyloid fibril formation by beta2m, we found that the beta2m C-terminal peptide of 28 residues (cbeta2m) itself forms amyloid fibrils. When viewed by electron microscopy, cbeta2m aggregates appear as elongated unbranched fibers, the morphology typical for amyloids. Cbeta2m fibers stain with Congo red and show apple-green birefringence in polarized light, characteristic of amyloids. The observation that the beta2m C-terminal fragment readily forms amyloid fibrils implies that beta2m amyloid fibril formation proceeds via interactions of amyloid forming segments, which become exposed when the beta2m subunit is partially unfolded.

Amino Acid Sequence↗
PubMed2004

Aggregation of mycobacteria caused by disruption of fibronectin-attachment protein-encoding gene.

The fibronectin-attachment protein (FAP) is conserved among several species of mycobacteria. Although this protein is associated with attachment and internalization of bacteria to host cells via fibronectin, the physiological role of the protein still remains unclear. To investigate this point, we generated FAP gene disruptant in Mycobacterium smegmatis. The gene disruption, verified by Southern blot and PCR analysis, induced changes on the bacteria, which are associated with strong aggregation and alteration of cell surface properties. Increased hydrophobicity and Congo red accumulation was observed in the FAP gene disruptant. In addition, the complementation experiment demonstrated that the corresponding gene restored wild type morphology in the disruptant. These results indicate that the FAP affects the cell surface properties, and its deletion lead to enhanced aggregation of the M. smegmatis.

Adhesins, Bacterial↗
PubMed2003

The neuroprotective peptide NAP inhibits the aggregation of the beta-amyloid peptide.

Alzheimer's disease (AD) is characterized by brain plaques containing the beta-amyloid peptide (Abeta). One approach for treating AD is by blocking Abeta aggregation. Activity-dependent neuroprotective protein contains a peptide, NAP that protects neurons in culture against Abeta toxicity. Here, NAP was shown to inhibit Abeta aggregation using: (1) fluorimetry; (2) electron microscopy; (3) high-throughput screening of Abeta deposition onto a synthetic template (synthaloid); and (4) Congo Red staining of neurons. Further assays showed biotin-NAP binding to Abeta. These results suggest that part of the neuroprotective mechanism exerted by NAP is through modulation of toxic protein folding in the extracellular milieu.

Alzheimer Disease↗
PubMed1997

Molten globule as an intermediate on the human prostatic phosphatase folding pathway.

Human prostatic acid phosphatase (hPAP, EC.3.1.3.2), a secretory homodimeric protein was denatured in 6 M urea, pH 2.5, and refolded by dilution at pH 7.2 with recovery of the enzymatic activity and dimeric structure. Circular dichroism, intrinsic fluorescence and chromatographic analysis of renaturating protein suggested that the kinetic intermediate of the hPAP folding is a monomer which displays a molten globule state (R. Kuciel, A. Mazurkiewicz & W.S. Ostrowski, 1996, Int. J. Biol. Macromol. 18, 167-175). To confirm these data experiments were performed to estimate the interaction of the renaturating protein with dyes and amphipathic lipid structures. Increased binding of the hydrophobic probe 1-anilinonaphthalene-8-sulfonate and Congo Red to the refolding enzyme supported the existence of molten globule state with the relaxed beta-structure in the renaturating protein. Presence of liposomes, included in the renaturation mixture as a model of acid phospholipid, resulted in perturbations of the human PAP refolding process. Some folding intermediates were bound to phosphatidylserine liposomes or, alternatively, water soluble, inactive aggregates were formed.

Acid Phosphatase↗
PubMedDate not supplied

Abdominal fat tissue aspirate in amyloidosis of familial Mediterranean fever.

Abdominal fat tissue aspirates from 20 patients with biopsy-proved amyloidosis were investigated by polarized microscopy after staining with Congo-red. Positive results were obtained in 4 of 5 patients with primary amyloidosis (AL) and in none of 15 with amyloidosis (AA) of Familial Mediterranean Fever (FMF). We suggest that although this technique is simple, safe and effective in other forms of amyloidosis, it cannot be used as a diagnostic tool in FMF patients suffering from amyloidosis.

Abdomen↗
PubMed2005

Polarimetric imaging of amyloid.

New developments in optical microscopy are discussed with relevance to the imaging of amyloid plaques that are pathognomonic of a variety of degenerative disorders. We present the results of linear birefringence, linear dichroism, and circular dichroism imaging of Congo red stained plaques ex vivo and in vitro. A new technique for measuring rapid changes in linear anisotropies is introduced. The application of polarimetric imaging as demonstrated here can be extended to broader pathological practice since polarimetric measurements are sensitive to transformations in tissues that are specific disease signatures.

Amyloid↗
PubMed1998

[Isolated and primary palpebro-conjunctival amylosis. Apropos of 2 cases].

Ocular amyloidosis a an uncommon condition and conjunctival involvement rarely occurs, representing 15% of all ocular localizations. Clinical manifestations show a polymorphism requiring a histological diagnosis. Based on two cases of primary isolated conjunctivo-palpebral amyloidosis, we discuss the different ocular sites. The first case involved false ptosis, a conjunctival infiltration and a lower eyelid tumefaction; all located in the left eye. The second case had ptosis, a right lower eyelid tumefaction with ectropion and esthetic damage. Amyloidosis was confirmed at histologic examination of the conjunctival mucous after a special congo red coloration. In order to affirm the isolated conjunctival localization, it is necessary to eliminate another amyloidis site. The treatment was surgical with excision and cure of ptosis. Ocular amyloidosis is a rare condition with polymorphism manifestations. Confirmation is histological. The greatest difficulty is management due to disease recurrence.

Adult↗
PubMed2005

Interactions of charged ligands with beta(2)-microglobulin conformers in affinity capillary electrophoresis.

Alternative conformations of beta(2)-microglobulin (beta(2)m) are involved in its transformation from soluble monomeric precursor molecules to the insoluble polymeric material that constitutes beta(2)m amyloid. Accordingly, non-native conditions such as low pH or high ionic strength promote beta(2)m amyloid formation in vitro. The early events in these processes are not well known, partly because of the paucity of techniques available for the characterization of transient folding intermediates in proteins. We have used high-resolution separations in capillaries (capillary electrophoresis, CE) to resolve putative conformer fractions in native and structurally modified beta(2)m and to show the induction of alternatively folded beta(2)m under different experimental conditions. The conformer fractions are observed as distinct peaks in the separation profiles and thus it is possible to probe for the reactivity of these individual beta(2)m species with specific ligands that, upon binding, alter analyte mobility in affinity capillary electrophoresis experiments. Interactions were shown in this way for the negatively charged substances heparin, Congo red, and suramin, as well as for Cu(2+) ions. Marked differences in the binding behavior of the beta(2)m conformational variants compared with native beta(2)m could be demonstrated. This approach for conformer separation and binding characterization is a valuable starting point for the assessment of various ligand molecules, or analogues thereof, as agents capable of perturbing the mechanisms of fibril formation.

Amyloid↗
PubMedDate not supplied

[Barrett esophagus following peptic and alkaline esophagitis].

Eight cases of Barrett's esophagus are presented, six as a result of long-term reflux esophagitis, three of them with ulcer in gastric-like mucosa, two with stenosis. The Congo-Red test in three patients showed non-secretory pattern. They could twice confirm the epithelial change in previous normal esophageal mucosa, once after alkaline reflux esophagitis in a patient with total gastrectomy and esophagus-jejunostomy. Both surgical and medical treatment of reflux could afford relief of the symptoms but they produce no change in the ectopic mucosa.

Adult↗
PubMed2005

Thermostable direct hemolysin of Vibrio parahaemolyticus is a bacterial reversible amyloid toxin.

Thermostable direct hemolysin (TDH), a major virulence factor of Vibrio parahaemolyticus, is detoxified by heating at approximately 60-70 degrees C but is reactivated by additional heating above 80 degrees C. This paradoxical phenomenon, known as the Arrhenius effect, has remained unexplained for approximately 100 years. We now demonstrate that the effect is related to structural changes in the protein that produce fibrils. The native TDH (TDHn) is transformed into nontoxic fibrils rich in beta-strands by incubation at 60 degrees C (TDHi). The TDHi fibrils are dissociated into unfolded states by further heating above 80 degrees C (TDHu). Rapid cooling of TDHu results in refolding of the protein into toxic TDHn, whereas the protein is trapped in the TDHi structure by slow cooling of TDHu. Transmission electron microscopy indicates the fibrillar structures of TDHi. The fibrils show both the property of the nucleation-dependent elongation and the increase in its thioflavin T fluorescence. Formation of beta-rich structures of TDH was also observed in the presence of lipid vesicles containing ganglioside G(T1b), a putative TDH receptor. Congo red was found to inhibit the hemolytic activity of TDH in a dose-dependent manner. These data reveal that the mechanism of the Arrhenius effect which is tightly related to the fibrillogenicity of TDH.

Amyloid↗
PubMed1992

Stromal amyloid in pheochromocytomas.

Amyloid has been documented in the stroma of a number of neuroendocrine tumors. It is usually associated with elaboration of a polypeptide hormone product. Twenty-three adrenal pheochromocytomas occurring in 18 patients were graded for the extent of amyloid deposits on the hematoxylin-eosin-stained slides, confirmed to be amyloid by Congo red stain and polarization microscopy. Fourteen of 20 cases (70%) showed evidence of stromal amyloid; in two thirds of these cases, it was considered abundant. The awareness of amyloid deposits in approximately 70% of pheochromocytomas is important for surgical pathologists, as this occurrence has not been thought to be common in these tumors and might be a source of diagnostic difficulty.

Adrenal Gland Neoplasms↗
PubMed2004

High pressure induces scrapie-like prion protein misfolding and amyloid fibril formation.

Our understanding of conformational conversion of proteins in diseases is essential for any diagnostic and therapeutic approach. Although not fully understood, misfolding of the prion protein (PrP) is implicated in the pathogenesis of prion diseases. Despite several efforts to produce the pathologically misfolded conformation in vitro from a recombinant PrP, no positive result has yet been obtained. Within the "protein-only hypothesis", the reason for this hindrance may be that the experimental conditions used did not allow selection of the pathway adopted in vivo resulting in conversion into the infectious form. Here, using a pressure perturbation approach, we show that recombinant PrP is converted to a novel misfolded conformer, which is prone to aggregate and ultimately form amyloid fibrils. A short incubation at high pressure (600 MPa) of the truncated form of hamster prion protein (SHaPrP(90-231)) resulted in the formation of pre-amyloid structures. The mostly globular aggregates were characterized by ThT and ANS binding, and by a beta-sheet-rich secondary structure. After overnight incubation at 600 MPa, amyloid fibrils were formed. In contrast to pre-amyloid structures, they showed birefringency of polarized light after Congo red staining and a strongly decreased ANS binding capacity, but enhanced ThT binding. Both aggregate types were resistant to digestion by PK, and can be considered as potential scrapie-like forms or precursors. These results may be useful for the search for compounds preventing pathogenic PrP misfolding and aggregation.

Amyloid↗
PubMed2005

Multiple ligand binding sites on A beta(1-40) fibrils.

Although the structures of Thioflavin T and another benzothiazole, BTA-1, are similar, they bind to A beta non-competitively, probably to different sites on the A beta(1-40) fibrils. The amyloid fibril-induced fluorescence of ThT that corresponds to a fraction of total ThT binding is not displaced by high concentrations of (S)-naproxen or (R)-ibuprofen, which are reported to potently block high affinity binding of the radiolabeled malononitrile FDDNP and derivatives. The binding of the benzothiazole ligands is significantly substoichiometric with respect to A beta(1-40) monomer peptide, unlike Congo Red, which binds to A beta(1-40) fibrils on a 1:1 basis with monomer peptide. These results indicate that there are multiple domains for ligand binding to amyloid fibrils and suggest that it may be possible to design ligands that bind selectively to particular forms of fibrils that are connected with the pathogenesis of Alzheimer's disease and potentially other protein misfolding diseases.

Alzheimer Disease↗
PubMed2001

Spectroscopic evidence for amyloid-like interfacial self-assembly of hydrophobin Sc3.

Amphipathic fungal proteins called hydrophobins are able to self-assemble into insoluble supramolecular structures at hydrophobic/hydrophilic interfaces, but the molecular mechanism and underlying protein conformation changes are not known. Secondary-structure prediction indicated that hydrophobin Sc3 is an all-beta protein. Many amyloidogenic proteins self-assemble into insoluble amyloid fibrils while undergoing a change to an all-beta conformation. In this study we show that two dyes, thioflavin T, and Congo red, which are widely used for specific detection of stacked beta sheets, interact with Sc3 assemblies in the same way as with the amyloid beta-sheet fibrils. We conclude that Sc3, and probably other hydrophobins too, self-assemble at interfaces in the same manner as amyloidogenic proteins, i.e., through beta-sheet stacking.

Amyloid beta-Peptides↗
PubMed2004

Human amylin oligomer growth and fibril elongation define two distinct phases in amyloid formation.

Human amylin (hA), a 37-amino-acid polypeptide, is one of a number of peptides with the ability to form amyloid fibrils and cause disease. It is the main constituent of the pancreatic amyloid deposits associated with type 2 diabetes. Increasing interest in early assembly intermediates rather than the mature fibrils as the cytotoxic agent has led to this study in which the smallest hA oligomers have been captured by atomic force microscopy. These are 2.3 +/- 1.9 nm in height, 23 +/- 14 nm in length, and consist of an estimated 16 hA molecules. Oligomers first grow to a height of about 6 nm before they begin to significantly elongate into fibrils. Congo red inhibits elongation but not the growth in height of hA oligomers. Two distinct phases have thus been identified in hA fibrillogenesis: lateral growth of oligomers followed by longitudinal growth into mature fibrils. These observations suggest that mature fibrils are assembled directly via longitudinal growth of full-width oligomers, making assembly by lateral association of protofibrils appear less likely.

Adsorption↗
PubMed2005

Transformation of diffuse beta-amyloid precursor protein and beta-amyloid deposits to plaques in the thalamus after transient occlusion of the middle cerebral artery in rats.

BACKGROUND AND PURPOSE: The present study examined the long-term presence of beta-amyloid precursor protein (APP) and beta-amyloid (Abeta) accumulation in the rat thalamus after focal cerebral ischemia. METHODS: Male Wistar rats were subjected to transient middle cerebral artery occlusion (MCAO) for 2 hours. Sensorimotor outcome was assessed using a tapered/ledged beam-walking task after operation. The distribution of APP and Abeta was examined immunohistochemically at 1 week, 1 month, and 9 months after MCAO. RESULTS: MCAO caused a long-lasting deficit in forelimb and hind limb function assessed using the beam-walking test. Histologic examination revealed a transient increase in APP and Abeta staining in axons in the corpus callosum and in neurons at the border of the ischemic region. APP and Abeta deposits persisted in the thalamic nuclei (ventroposterior lateral and ventroposterior medial nuclei), eventually leading to dense plaque-like deposits by the end of the 9-month follow-up. The deposits were surrounded by an astroglial scar. The deposits were positive for Abeta and N-terminal APP, but not for C-terminal APP. Antibodies against the C-terminal of Abeta, ie, Abeta42 and Abeta40, showed a preferential staining for Abeta42. Congo red or thioflavine S did not stain the deposits. CONCLUSIONS: The present results demonstrated the persistent presence and aggregation of APP and Abeta, or their fragments, to dense plaque-like deposits in the ventroposterior lateral and ventroposterior medial nuclei of rats subjected to focal cerebral ischemia.

Amyloid beta-Peptides↗
PubMed2002

Cytogical features of calcifying epithelial odontogenic tumor (Pindborg tumor) with abundant cementum-like material.

Calcifying epithelial odontogenic tumor (CEOT) is a rare tumor, most frequently occurring in the mandible and composed of large sheets of epithelial cells, sometimes showing nuclear pleomorphism. This paper was aimed at reporting of the cytological features of an unusual case of CEOT, affecting a 14-year-old female, with abundant deposition of intercellular calcified material. The cytological preparations were characterized by large clusters of scarcely cohesive, large polyhedral cells and abundant calcified material. The latter consisted of intensely basophilic substance either in large clusters or discrete concretions and, at high-power view, occasional tumor cells also contained calcified material. Histologically, the uncalcified stroma displayed focal Congo Red positivity with the typical birefringence under polarized light. The neoplastic cells were consistently immunoreactive for epithelial membrane antigen, vimentin and, to a lesser extent, for wide spectrum cytokeratins (AE1 AE3) and cytokeratins 8-18 and 19. The cytological features of CEOT are rather characteristic, and the detection of intra- and extracellular calcifications may help to differentiate this neoplasm from others that most commonly arise in this area.

Adolescent↗