Iatrogenic hyperstimulation of the ovary with ascites. Report of a case and considerations and management

Electron microscopic investigations in 7 patients with different dermatoses or skin tumours containing amyloid showed that amyloid is synthesized in the cytoplasm of dermal cells. In 3 cases of localized primary amyloidosis of the skin highly active cells were demonstrated, showing grossly dilated cisternae of rough endoplasmic reticulum, resembling fibroblasts. Their intracellular product seemed amorphous, later filamentous, and was then released into the extracellular space. Extracellular aggregations of typical amyloid filaments were found partially surrounded by thin cytoplasmic remnants of the cells producing them. Subclinical amounts of amyloid found in porokeratosis of Mibelli, in superficial basal-cell carcinoma, in senile skin, and in clinically normal skin of a patient with malignant melanoma showed the same characteristics. Other cell types such as plasma cells and mast cells were well preserved and seemed stimulated; however, no amyloid precursors were found in their cytoplasm and no release was seen. We, therefore, conclude that dermal amyloid is generally produced by falsely programmed fibroblasts.     

Atomic force microscopic imaging of seeded fibril formation and fibril branching by the Alzheimer's disease amyloid-beta protein

BACKGROUND: Amyloid plaques composed of the fibrillar form of the amyloid-beta protein (Abeta) are the defining neuropathological feature of Alzheimer's disease (AD). A detailed understanding of the time course of amyloid formation could define steps in disease progression and provide targets for therapeutic intervention. Amyloid fibrils, indistinguishable from those derived from an AD brain, can be produced in vitro using a seeded polymerization mechanism. In its simplest form, this mechanism involves a cooperative transition from monomeric Abeta to the amyloid fibril without the buildup of intermediates. Recently, however, a transient species, the Abeta amyloid protofibril, has been identified. Here, we report studies of Abeta amyloid protofibril and its seeded transition into amyloid fibrils using atomic force microscopy. RESULTS: Seeding of the protofibril-to-fibril transition was observed. Preformed fibrils, but not protofibrils, effectively seeded this transition. The assembly state of Abeta influenced the rate of seeded growth, indicating that protofibrils are fibril assembly precursors. The handedness of the helical surface morphology of fibrils depended on the chirality of Abeta. Finally, branched and partially wound fibrils were observed. CONCLUSIONS: The temporal evolution of morphologies suggests that the protofibril-to-fibril transition is nucleation-dependent and that protofibril winding is involved in that transition. Fibril unwinding and branching may be essential for the post-nucleation growth process. The protofibrillar assembly intermediate is a potential target for AD therapeutics aimed at inhibiting amyloid formation and AD diagnostics aimed at detecting presymptomatic disease.     

Chicken joint amyloid protein is of the AA-type. I. Characterization of the amyloid protein

Amyloid fibrils were extracted from deposits in joint tissue of heavy breed layers with spontaneous amyloid arthropathy and characterized as being of the AA-type. Amino acid sequencing revealed a pattern quite similar to duck AA. Acute phase sera of chicken experimentally injected with Enterococcus faecalis showed a SAA-protein like band cross reacting with anti-chicken AA in immunoblot.     

Ribosomal DNA internal transcribed spacer sequences do not support the species status of Ampelomyces quisqualis, a hyperparasite of powdery mildew fungi

Amyloid P component (AP) and apolipoprotein E (Apo E), which are known to be minor constituents of amyloid deposits, commonly are associated with almost all types of amyloid deposits. In this study, the distribution of AP-, Apo E- and ubiquitin (Ub)-immunoreactivity (IR) in amyloid deposits in the liver and spleen of human systemic amyloidosis (34 autopsy cases: 17 immunoglobulin light chain derived, 17 amyloid A protein derived) and experimental murine amyloidosis is examined using an immuno-histochemical technique. In human cases, all of the amyloid deposits examined showed colocalization of AP- and Apo E-IR with individual amyloid proteins. In experimental amyloidosis, AP-IR of amyloid deposits in the liver and spleen and Apo E-IR in the liver were seen uniformly throughout this experiment. In contrast, Apo E-IR in the spleen was not uniform at the phase of amyloid deposition. At 4 weeks and at 16 weeks after casein injection, Apo E-IR was unevenly distributed in amyloid deposits in the perifollicular area; however, from 6 to 12 weeks it was seen to be uniform. Ubiquitin-IR of amyloid deposits in human cases was seen in 22 of 34 livers and in 22 of 33 spleens. In experimental amyloidosis, Ub-IR of amyloid deposits was demonstrated in the space of Disse in all mice examined, and there appeared to be a gradual increase in intensity with the amount of amyloid deposition. However, in the spleen, amyloid deposits did not react with anti-Ub antibody in any phase of amyloid induction. These results suggest that Apo E and Ub are not always associated with the process of amyloid deposition and may appear in a deposit after the deposition.     

Hereditary amyloid cardiomyopathy caused by a variant apolipoprotein A1

Autosomal dominant hereditary amyloidosis with a unique cutaneous and cardiac presentation and death from heart failure by the sixth or seventh decade was found to be associated with a previously unreported point mutation (thymine to cytosine, nt 1389) in exon 4 of the apolipoprotein A1 (apoA1) gene. The predicted substitution of proline for leucine at amino acid position 90 was confirmed by structural analysis of amyloid protein isolated from cardiac deposits of amyloid. The subunit protein is composed exclusively of NH2-terminal fragments of the variant apoA1 with the longest ending at residue 94 in the wild-type sequence. Amyloid fibrils derived from four previously described apoA1 variants are composed of similar fragments with carboxyl-terminal heterogeneity, but contrary to those variants, which all carry one extra positive charge, the substitution Leu90Pro does not result in any charge modification. It is unlikely, therefore, that amyloid fibril formation is related to change of charge for a specific residue of the precursor protein. This is in agreement with studies on transthyretin amyloidosis in which no unifying factor such as change of charge for amino acid residues has been noted.     

Amyloidosis: a review of recent diagnostic and therapeutic developments

Amyloid deposition is associated with a diverse range of disorders that includes Alzheimer's disease, type II diabetes mellitus and dialysis arthropathy. Although less common, systemic AA and AL amyloidosis remain important because effective treatments have increasingly become available. The pathology in all forms of amyloidosis involves the extracellular deposition of protein as characteristic fibrillar aggregates which interfere with tissue structure and function. Amyloid fibrils are derived from different unrelated proteins in the different forms of the disease but share many common properties, including the capacity to bind the normal plasma protein serum amyloid P component (SAP). This is the basis for our development of radiolabelled SAP as a nuclear medicine tracer for the diagnosis and quantitative monitoring of amyloid. Serial studies have shown that the deposits are far from inert but are actually turned over quite rapidly in many patients. The treatment of amyloidosis involves supportive measures whilst every effort is made to reduce the supply of the respective fibril precursor protein. Under favourable circumstances further amyloid deposition will be prevented. existing deposits will regress and improvement of organ function will occur. Since this strategy is not always possible or may fail, new approaches to inhibit fibril formation and promote regression of amyloid are being pursued.     

Glycogenolysis stimulation by non-steroidal anti-inflammatories in the perfused rat liver is not accompanied by Ca2+ release

To better understand the characteristics of amyloid deposition in the choroid plexus, we examined autopsied brain by routine histology, immunohistochemistry, and electron microscopy in three group of patients: primary systemic amyloidosis (n = 7), cerebral amyloid angiopathy (CAA, n = 6), and controls (n = 3). Three of the CAA patients had Alzheimer's disease. Congophilic, birefringent amyloid deposits of the choroid plexus were seen in six of the seven cases of systemic light chain amyloidosis. Immunohistochemistry revealed that the deposited amyloids had reactivity for immunoglobulin light chain and amyloid P component. Accumulation of macrophages labeled with monoclonal antibodies against CD 68 and major histocompatibility complex class II antigens were observed around the massive amyloid deposits. The presence of approximately 10 nm amyloid fibrils along the epithelial basement membrane as well as in the vascular walls was ascertained by electron microscopy. In CAA, Congo red-positive amyloid deposits were consistently present in meningeal blood vessels and were often found in senile plaques of the cerebral parenchyma; congophilic amyloid deposits were absent in the choroid plexus. Choroid plexus epithelial cells exhibited immunostaining for beta amyloid precursor protein (APP) with N-terminal- and C-terminal-specific antibodies; in particular, consistent staining was obtained for the latter antibody. Immunoreactivity for amyloid beta protein (A beta) with monoclonal antibodies (6E10, 4G8) was often found in choroid plexus epithelial cells. These findings suggest that amyloid deposition of the choroid plexus depends on the major component protein in amyloidosis, and that the choroid plexus may produce APP and A beta protein although A beta amyloidosis is not evident in the choroid plexus.     

Amyloid and non-amyloid carpal tunnel syndrome in patients receiving chronic renal dialysis

OBJECTIVE: To determine the prevalence of amyloid deposits among patients with carpal tunnel syndrome (CTS) receiving dialysis, and to investigate the factors associated with amyloid and non-amyloid CTS. METHODS: Subjects for this prospective study were dialysis patients who underwent surgery for CTS in the same surgical unit between 1989 and 1997. CTS was diagnosed from clinical and electromyographic (EMG) findings. Systematic standard radiographs and laboratory data were also obtained. Surgical investigations included systematic macroscopic examination and biopsy of the epineurium, flexor retinaculum, synovium, and flexor tendon sheaths. Samples were stained for amyloid and examined by plain and polarized light microscopy, immunohistochemistry, and electron microscopy. RESULTS: Forty-one samples from 30 patients (11 bilateral cases) were examined. Amyloid deposits were found in 26 samples from 18 patients (7 M, 11 F). Fifteen samples from 12 patients (3 M, 9 F) showed no amyloid deposits. Amyloid CTS was statistically significantly associated with arthralgia and longterm dialysis [mean 13.3 (range 5.5-23) vs 7.5 yrs (range 3 mo-14 yrs)] in non-amyloid CTS. Flexor tenosynovitis and carpal bone erosion occurred more frequently in amyloid CTS. There were no statistically significant differences between the 2 groups in clinical, laboratory or EMG findings, type of dialysis membrane, or frequency of ipsilateral fistula. Only amyloid CTS was recurrent. CONCLUSION: Amyloid deposits were confirmed microscopically in 63.4% of patients. The relatively large number of cases of non-amyloid CTS without signs of dialysis associated arthropathy suggests that CTS is not a satisfactory criterion for diagnosis of dialysis arthropathy or beta2-microglobulin amyloidosis unless the presence of amyloid has been confirmed or duration of dialysis treatment has been at least 15 years.     

Analysis of amyloid deposition in a transgenic mouse model of homozygous familial amyloidotic polyneuropathy

Amyloid fibrils derived from the Japanese, Portuguese, and Swedish types of familial amyloidotic polyneuropathy all consist of a variant transthyretin (TTR) with a substitution of methionine for valine at position 30 (TTR Met 30). In an attempt to establish an animal model of TTR Met-30-associated homozygous familial amyloidotic polyneuropathy and to study the structural and functional properties of human TTR Met 30, we generated a mouse line carrying a null mutation at the endogenous ttr locus (ttr-/-) and the human mutant ttr gene (6.0-hMet 30) as a transgene. In these mice, human TTR Met-30-derived amyloid deposits were first observed in the esophagus and stomach when the mice were 11 months of age. With advancing age, amyloid deposits extended to various other tissues. Because no significant difference was detected in the onset, progression, and tissue distribution of amyloid deposition between the ttr-/- and ttr+/+ transgenic mice expressing 6.0-hMet 30, endogenous normal mouse TTR probably does not affect the deposition of human TTR Met-30-derived amyloid in mice. TTR is a tetramer composed of four identical subunits that binds thyroxine (T4) and plasma retinol-binding protein. The introduction of 6.0-hMet 30 into the ttr-/- mice significantly increased their depressed serum levels of T4 and retinol-binding protein, suggesting that human TTR Met 30 binds T4 and retinol-binding protein in vivo. The T4-binding ability of human TTR Met 30 was confirmed by the analysis of T4-binding proteins in the sera of ttr-/- transgenic mice expressing 6.0-hMet 30. The T4-binding studies also demonstrated the presence of hybrid tetramers between mouse and human TTR subunits in the ttr+/+ transgenic mice expressing 6.0-hMet 30.     

Reduction in amyloid A amyloid formation in apolipoprotein-E-deficient mice

Apolipoproteins have been implicated in the formation of amyloid fibrils. Recent studies have demonstrated that apolipoprotein E (apoE), alone or in combination with apolipoprotein J (apoJ), and other lipoproteins appear to enhance deposition of amyloid fibrils both in systemic and cerebral amyloids, especially Alzheimer's disease (AD). ApoE enhanced the ability of the amyloid beta-protein (1-40) fragment (A beta) to form fibrils in vitro, with apoE4 promoting the greatest fibril formation. ApoE was found associated with both human and mouse amyloid A (AA) deposits. To define the role of apoE in vivo, we utilized mice lacking the apoE gene by gene targeting. We used the AA model in mice to characterize the function of the apoE protein in amyloid fibrillogenesis. ApoE-deficient mice exhibited a decrease in deposition of AA when compared with heterozygous mutant or wild-type animals. In addition, apoE-deficient mice that were injected with an adenovirus that expressed the human apoE3 gene had restored AA deposition and the apoE was associated with the AA fibrils. These results are agreement with the in vitro studies using the beta-peptide and suggest that apoE is not essential for amyloid fibrillogenesis but can promote the development of amyloid deposition.     

Brain natriuretic peptide enhances the endothelium-independent cAMP and vasorelaxant responses of calcitonin gene-related peptide in rat aorta

The localization of cathepsin K protein in mouse osteoclasts was examined by immunolight and immunoelectron microscopy using the avidin-biotin-peroxidase complex method with anti-cathepsin K (mouse) antibody. With light microscopy, a strong immunoreaction for cathepsin K was found extracellularly along the bone and cartilage resorption lacunae and detected intracellularly in vesicles, granules, and vacuoles throughout the cytoplasm of multinuclear osteoclasts and chondroclasts attached to the surface of the bone or cartilage. Mononuclear cells, probably preosteoclasts, some distance from the bone also contained a few cathepsin K-positive vesicles and granules. Cathepsin K was sometimes found in the cisternal spaces of the rough endoplasmic reticulum and vesicles of the Golgi apparatus with electron microscopy of the basolateral region of the osteoclasts. Cathepsin K-positive vesicles and granules as lysosomal compartments were present in various stages of fusion with vacuoles as endosomal compartments that contained fragmented cathepsin K-negative fibril-like structures. Some of the vacuoles (endolysosomes), which seemed to be formed by this process of fusion, contained cathepsin K-positive vesicles and fibril-like structures that did not show the regular cross striation of type I collagen fibrils. In the apical region of the osteoclasts, cathepsin K-positive vesicles and pits had already fused with or were in the process of fusing with the ampullar extracellular spaces. There were large deposits of cathepsin K on fragmented fibril-like structures without regular cross striation in the extracellular spaces, as well as on and between the cytoplasmic processes of the ruffled border. There were also extensive deposits of cathepsin K on the type I collagen fibrils with cross striation in the bone resorption lacunae. Osteoblasts and osteocytes were negative for cathepsin K. In the immunocytochemical controls, no immunoreaction was found in the osteoclasts or preosteoclasts, or on the collagen fibrils in the resorption lacunae. The results indicate that cathepsin K is produced in mature osteoclasts attached to the bone and secreted into the bone resorption lacunae. The findings suggest that cathepsin K participates in the extracellular degradation of collagen fibrils in the resorption lacunae and in the subsequent degradation of the fragmented fibrils in the endolysosomes. It is also suggested that cathepsin K degrades the organic cartilage matrix.     

The origin of amyloid in cerebral vessels of aged dogs

Our morphometric study of 30 dogs, mongrels, from 6.5 to 26.5 years of age, shows amyloid angiopathy in cortical and leptomeningeal vessels of all dogs older than 13.2 years of age, and the increase in the numerical density of amyloid-positive vessels correlated with age. Cluster analysis distinguished the group of six dogs (25%) to be relatively less affected, a large group of 13 animals (54%) to have moderate pathology, and five dogs (21%) to have severe amyloid angiopathy. Amyloid accumulation starts in large vessels, particularly in the tunica media of large arteries. Amyloid deposition appears to be associated with smooth muscle cells. Ultrastructural studies of samples from nine dogs are in agreement with in vitro studies suggesting that smooth muscle cells are the source of soluble amyloid beta. beta-protein polymerizes in the basal lamina of the tunica media. Muscle cells in the area of amyloid-beta accumulation degenerate and die. Thioflavin-positivity of only 24% of cortical and 66% of leptomeningeal beta-protein-positive vessels suggests that thioflavin-negative deposits contain soluble, not yet fibrillized protein and/or partially degraded and depolymerized amyloid.     

Serum amyloid P component prevents proteolysis of the amyloid fibrils of Alzheimer disease and systemic amyloidosis

Extracellular deposition of amyloid fibrils is responsible for the pathology in the systemic amyloidoses and probably also in Alzheimer disease [Haass, C. & Selkoe, D. J. (1993) Cell 75, 1039-1042] and type II diabetes mellitus [Lorenzo, A., Razzaboni, B., Weir, G. C. & Yankner, B. A. (1994) Nature (London) 368, 756-760]. The fibrils themselves are relatively resistant to proteolysis in vitro but amyloid deposits do regress in vivo, usually with clinical benefit, if new amyloid fibril formation can be halted. Serum amyloid P component (SAP) binds to all types of amyloid fibrils and is a universal constituent of amyloid deposits, including the plaques, amorphous amyloid beta protein deposits and neurofibrillary tangles of Alzheimer disease [Coria, F., Castano, E., Prelli, F., Larrondo-Lillo, M., van Duinen, S., Shelanski, M. L. & Frangione, B. (1988) Lab. Invest. 58, 454-458; Duong, T., Pommier, E. C. & Scheibel, A. B. (1989) Acta Neuropathol. 78, 429-437]. Here we show that SAP prevents proteolysis of the amyloid fibrils of Alzheimer disease, of systemic amyloid A amyloidosis and of systemic monoclonal light chain amyloidosis and may thereby contribute to their persistence in vivo. SAP is not an enzyme inhibitor and is protective only when bound to the fibrils. Interference with binding of SAP to amyloid fibrils in vivo is thus an attractive therapeutic objective, achievement of which should promote regression of the deposits.     

Synchrotron X-ray studies suggest that the core of the transthyretin amyloid fibril is a continuous beta-sheet helix

BACKGROUND: Amyloid diseases, which include Alzheimer's disease and the transmissible spongiform encephalopathies, are characterized by the extracellular deposition of abnormal protein fibrils derived from soluble precursor proteins. Although different precursors seem to generate similar fibrils, no adequate molecular structure of amyloid fibrils has been produced using modern techniques. Knowledge of the fibril structure is essential to understanding the molecular mechanism of amyloid formation and could lead to the development of agents to inhibit or reverse the process. RESULTS: The structure of amyloid fibrils from patients with familial amyloidotic polyneuropathy (FAP), which are derived from transthyretin (TTR) variants, has been investigated by fibre diffraction methods using synchrotron radiation. For the first time a significant high-angle diffraction pattern has been observed showing meridional reflections out to 2 A resolution. This pattern was fully consistent with the previously reported cross-beta structure for the fibril, but also reveals a new large scale fibre repeat of 115 A. We interpret this pattern as that of a repeating unit of 24 beta strands, which form a complete helical turn of beta sheet about an axis parallel to the fibre axis. This structure has not been observed previously. We have built a model of the protofilament of the FAP amyloid fibril based on this interpretation, composed of four beta sheets related by a single helix axis coincident with the fibre axis, and shown that it is consistent with the observed X-ray data. CONCLUSIONS: This work suggests that amyloid fibrils have a novel molecular structure consisting of beta sheets extended in regular helical twists along the length of the fibre. This implies that the polypeptide chains in the fibres are hydrogen-bonded together along the entire length of the fibres, thereby accounting for their great stability. The proposed structure of the FAP fibril requires a TTR building block that is structurally different from the native tetramer. This is likely to be either a monomer or dimer with reorganized or truncated beta sheets, suggesting that amyloid formation may require significant structural change in precursor proteins.     

Base-sequence dependence of covalent binding of benzo[a]pyrene diol epoxide to guanine in oligodeoxyribonucleotides

We report a solitary nodular form of primary cutaneous amyloidosis due to locally infiltrating plasma cells. An 81-year-old Japanese women presented with a scarlet, dome-shaped 1.5-cm nodule with an irregular surface. Histology showed thick deposits of eosinophilic, oval, and homogeneous bodies in the dermis with mild infiltrates of mononuclear cells. The homogeneous bodies stained positively with periodic acid-Schiff, Congo red, and Yanagihara's Dylon stain, and immunohistochemically with anti-human lambda light-chain antibody. Methylgreen pyronine staining revealed that approximately half of the cellular infiltrates around the vessels were plasma cells. Electron microscopy demonstrated the homogeneous bodies to be amyloid masses, a part of which were in the cytoplasm of the plasma cells. Laboratory examination showed a slight elevation of IgG but no obvious findings suspicious for systemic amyloidosis or gammopathy.     

Pathologic features of spinal disorders in patients treated with long-term hemodialysis

STUDY DESIGN: Pathologic features of hemodialysis-associated spinal disorders were evaluated using preoperative radiographic images and histologic findings of the spinal lesions resected during surgery. OBJECTIVES: To investigate the pathology of hemodialysis-related spinal disorders and to determine the role of amyloidosis in the establishment of severe destruction of the spine. SUMMARY OF BACKGROUND DATA: The pathologic events leading to hemodialysis-associated spinal disorders are poorly understood. The distribution of amyloid deposits in the spine also has not been clarified. METHODS: Twenty patients with hemodialysis-associated spinal disorders were investigated regarding pathologic features of neural compression and spinal destruction. Preoperative radiographic images such as plain radiography, tomography, computed tomography, magnetic resonance imaging, and scintigraphy were assessed for the existence of an intracanal mass, hypertrophy of the ligamentum flavum, and destructive changes of the spinal components. Histologic examination also was conducted by light microscopy and scanning electron microscopy to determine the distribution pattern of amyloid deposits in the spinal components. RESULTS: Six patients with no destructive changes in the spine showed spinal canal stenosis. In the cervical spine, a main factor associated with spinal canal stenosis was the presence of intracanal amyloid deposits in three patients. In the lumbar spine, a main factor associated with spinal canal stenosis was hypertrophied ligamentum flavum in three patients. Destructive changes of the facet joints, intervertebral disc, and vertebral body were seen in the other 14 patients. Amyloid deposits were densely distributed at the enthesis of capsular fibers to the bone and in anular tears in the intervertebral discs. Vertebral end plates were destroyed by penetration of amyloid granulation into the vertebral body. Osteoclast activity in the destroyed vertebral bodies was enhanced, with no evidence of new bone formation. CONCLUSIONS: Amyloid deposits played an important role in the progression of spinal destruction and severe instability.     

Ultrastructural organization of hemodialysis-associated beta 2-microglobulin amyloid fibrils

Fibrils of hemodialysis-associated beta 2-microglobulin amyloid were examined by high resolution electron microscopy and immunohistochemical labeling. The amyloid containing tissues obtained through autopsy were prepared for thin section observations. In contrast to other forms of amyloid, the most conspicuous feature of these fibrils were their curved conformations. The fibril core showed ultrastructural and immunohistochemical features in common with the core of connective tissue microfibrils and of previously observed fibrils of experimental murine AA amyloidosis and familial amyloid polyneuropathy (FAP). The core was wrapped in a layer of 3 nm wide ribbon-like "double tracked" structures identified as chondroitin sulfate proteoglycan (CSPG) with immunogold labeling as well as from the results of previous in vitro experiments. Finally, the outer surface of the fibril was associated with a loose assembly of 1 nm wide filaments immunohistochemically identified as beta 2-microglobulin. This is similar to the manner in which AA protein and transthyretin filaments are associated with their respective fibrils. The results of this study provide an additional example for the concept that amyloid fibrils in general are microfibril-like structures externally associated with amyloid protein filaments. An unusual feature of the fibrils of hemodialysis-associated amyloid, however, is the presence of a peripheral layer composed of CSPG rather than of heparan sulfate proteoglycan (HSPG) as in the case of the other two amyloids above. These chondroitin sulfate chains in the outer CSPG layer may be less effective in providing rigidity to the fibril core, thus allowing for the curved conformations of beta 2-microglobulin amyloid fibrils.     

Turnover of amyloid beta-protein in mouse brain and acute reduction of its level by phorbol ester

Fibrillar amyloid deposits are defining pathological lesions in Alzheimer's disease brain and are thought to mediate neuronal death. Amyloid is composed primarily of a 39-42 amino acid protein fragment of the amyloid precursor protein (APP), called amyloid beta-protein (Abeta). Because deposition of fibrillar amyloid in vitro has been shown to be highly dependent on Abeta concentration, reducing the proteolytic release of Abeta is an attractive, potentially therapeutic target. Here, the turnover rate of brain Abeta has been determined to define treatment intervals over which a change in steady-state concentration of Abeta could be measured. Mice producing elevated levels of human Abeta were used to determine approximate turnover rates for Abeta and two of its precursors, C99 and APP. The t1/2 for brain Abeta was between 1.0 and 2.5 hr, whereas for C99, immature, and fully glycosylated forms of APP695 the approximate t1/2 values were 3, 3, and 7 hr, respectively. Given the rapid Abeta turnover rate, acute studies were designed using phorbol 12-myristate 13-acetate (PMA), which had been demonstrated previously to reduce Abeta secretion from cells in vitro via induction of protein kinase C (PKC) activity. Six hours after intracortical injection of PMA, Abeta levels were significantly reduced, as measured by both Abeta40- and Abeta42-selective ELISAs, returning to normal by 12 hr. An inactive structural analog of PMA, 4alpha-PMA, had no effect on brain Abeta levels. Among the secreted N-terminal APP fragments, APPbeta levels were significantly reduced by PMA treatment, whereas APPalpha levels were unchanged, in contrast to most cell culture studies. These results indicate that Abeta is rapidly turned over under normal conditions and support the therapeutic potential of elevating PKC activity for reduction of brain Abeta.     

Ubiquitin profile in inflammatory leukocytes and binding of ubiquitin to murine AA amyloid: immunocytochemical and immunogold electron microscopic studies

Lysosomes in activated murine monocytoid cells have been implicated in AA amyloid formation. The pathophysiology of this process is not well understood. Previous studies into the nature of the relationship between ubiquitin (UB), possessing intrinsic amyloid enhancing factor (AEF) activity; serum amyloid A (SAA), the precursor protein of AA amyloid; and activated monocytoid cells have indicated a temporal and spatial relationship between these proteins and tissue AA amyloid deposits. To extend these findings, we have examined murine peritoneal leukocytes and splenic tissues during the early amyloid deposition phase by immunocytochemical and immunogold electron microscopic methods using monospecific anti-ubiquitin and anti-mouse AA amyloid antibodies. We show here enrichment of endosome-lysosome-like (EL) vesicles in the activated monocytoid cells with UB and SAA, and the presence of UB-bound AA amyloid fibrils in the EL vesicles, perikarya, and interstitial spaces. The importance of these findings is emphasized by the fact that activated monocytoid cells, containing UB in the EL vesicles, sequester and eventually localize SAA in their EL vesicles, and that UB binds to the EL-contained AA amyloid fibrils. These findings may also have functional consequences for studies on the role of EL and UB in amyloidogenesis.     

Localized amyloid tumour of the duodenum : a case report

Amyloid tumours in the gastrointestinal tract are rare. A case is presented of a localized amyloid tumour in the duodenum, which was removed by loop resection during ERCP.