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D Allsop

Publications and source records attributed to D Allsop.

At least 37 records · Page 2Linked to original sources
PubMed1994

Human IMR-32 neuroblastoma cells as a model cell line in Alzheimer's disease research.

The present study investigated expression and processing of amyloid precursor protein by neuronally differentiated IMR-32 neuroblastoma cells. APP mRNA in these cells was found to consist of approximately 58% APP695, 38% APP751, and < 4% APP770. APP-immunoreactive bands detected in western blots of cellular protein extracts were only detected by anti-APP antibodies to peptides with strong homology to APLP2, suggesting that these bands represent APP-like proteins and not APP itself. This result suggests that previous studies claiming immunodetection of cellular forms of APP may have to be re-evaluated. Four main species of C-terminal truncated, secreted APP were detected in blots of protein extracts from medium conditioned by these cells. The immunoreactive profile of these bands suggested a cleavage site N-terminal to the Lys16-Leu17 bond of alpha-secretase. This, together with differences in number and molecular mass of APP-immunoreactive bands between secreted APP from IMR-32 cells and that from the commonly used PC-12 cells, suggests differences in APP processing between these two neuronally differentiated cell lines. In theory, IMR-32 cells being of human neuronal origin may be a more appropriate cell line to study APP-processing in relation to Alzheimer's disease than the rat phaeochromocytoma PC-12 cell line. Therefore, these detected differences warrant further investigation. Additionally IMR-32 cells under certain tissue culture conditions can form intracellular fibrillary material that reacts with anti-PHF specific antibodies. Neuronally differentiated IMR-32 cells could therefore be used as a model system to investigate possible interactions between APP-processing and PHF formation.

Alzheimer Disease↗
PubMed1994

Gerstmann-Sträussler-Scheinker disease showing beta-protein type cerebellar and cerebral amyloid angiopathy.

Cerebral amyloid angiopathy is observed in several brain degenerative disorders, but this pathological condition has received little attention in Gerstmann-Sträussler-Scheinker disease (GSS). We report a 69-year-old man who showed the cardinal features of GSS together with typical and extensive congophilic angiopathy. Immunohistochemical studies revealed that the vast majority of the amyloid plaques present in the brain of this patient were consistently labeled by anti-prion protein (PrP) antibody. Double immunostaining disclosed many additional beta-protein immunoreactive plaque-like lesions, including a special type of "hybrid" plaque with colocalization of PrP and beta-protein (beta-PrP). The vascular amyloid deposits seen in both the cerebellum and cerebrum were immunoreactive only to anti-beta-protein antibody. It seems likely that the extensive deposition of beta-protein amyloid (including brain vascular amyloidosis) seen in this and other similar cases is part of pathology of GSS, although the possibility that this finding is due to ageing or concomitant Alzheimer's disease cannot be completely ruled out.

Aged↗
PubMed1994

Inflammatory mechanisms in Alzheimer's disease.

Alzheimer's disease is aetiologically heterogeneous, but the pathogenesis is often considered to be initiated by the deposition of amyloid fibrils, followed by neuritic tau pathology and neuronal death. A variety of inflammatory proteins has been identified in the brains of patients with Alzheimer's disease post mortem. In this article, Piet Eikelenboom and colleagues review evidence to suggest that the inflammatory processes are intimately involved in several crucial events in the pathological cascade. This suggests possibilities for the treatment of Alzheimer's disease with anti-inflammatory drugs.

Alzheimer Disease↗
PubMed1994

Variability of beta-amyloid protein deposited lesions in Down's syndrome brains.

An immunohistochemical study was carried out on the brains of 7 adult Down's syndrome cases (ages 31 to 62) using antibodies to beta-protein, beta-amyloid protein precursor and tau-protein. Variable forms of beta-protein deposited lesions (including senile plaques and cerebrovascular amyloidosis) were observed in extensive areas of the neocortex of all cases and coexistence of both beta-protein amyloid fibrils and beta-amyloid protein precursors was also seen in some of these lesions. Moreover, 3 cases at an advanced stage showed a few plaque-like lesions with beta-protein immunoreactivity in the white matter. The following temporal morphological change is suggested for the pathogenesis of Alzheimer's disease: senile plaque undergo sequential structural changes and beta-protein amyloid deposits in the form of "early plaque" precede the development of tau-immunoreactive neurofibrillary degeneration.

Adult↗
PubMed1993

Effects of the mutations Glu22 to Gln and Ala21 to Gly on the aggregation of a synthetic fragment of the Alzheimer's amyloid beta/A4 peptide.

We assessed the fibrillogenic properties of synthetic peptides corresponding to residues 13-26 of beta/A4 amyloid, containing either the normal sequence (beta 13 26) or the mutations Glu22 to Gln (beta 13-26Q22) and Ala21 to Gly (beta 13-26G21). The kinetics of aggregation were monitored at 37 degrees C and pH 7.4 by measuring the amount of peptide remaining in solution, using reverse-phase high performance liquid chromatography. Negative stain electron microscopy revealed that all of the peptides formed fibrils. However, beta 13-26Q22 showed greatly accelerated fibril formation compared to the other two. The results suggest that the Q22 mutation confers increased amyloidogenic properties on the beta/A4 peptide, whereas the G21 mutation acts by a different pathogenic mechanism.

Alanine↗
PubMed1993

Endopeptidase 3.4.24.11 converts N-1-(R,S)carboxy-3-phenylpropyl-Ala-Ala-Phe-p-carboxyanilide into a potent inhibitor of angiotensin-converting enzyme.

It was reported recently that N-1-(R,S)carboxy-3-phenylpropyl-Ala-Ala-Phe-p-carboxyanilide (CPP-A-A-F-pAB), an inhibitor of endopeptidase 3.4.24.15 (E-24.15), also inhibits angiotensin-converting enzyme (ACE) from rabbit lung. We have found that this compound is without effect on ACE purified from pig kidney, at a concentration some 1000-fold greater than the Ki reported for inhibition of the enzyme from lung. However, preincubation of CPP-A-A-F-pAB with neutral endopeptidase 3.4.24.11 (E-24.11) does result in potent inhibitory effects on ACE. We have shown this to be due to formation of a fragment, CPP-A-A, the structure of which is closely related to ACE inhibitors such as enalaprilat. CPP-A-A was found to be a potent inhibitor of pig ACE. Under the conditions used it had an IC50 value of 1.6 x 10(-8) M, compared with the value obtained for captopril of 7.5 x 10(-10) M. These results have important implications for studies of E-24.15 when using CPP-A-A-F-pAB in vivo or in crude tissue extracts where E-24.11 might also be present.

Amino Acid Sequence↗
PubMed1993

Secretory form of Alzheimer amyloid precursor protein 695 in human brain lacks beta/A4 amyloid immunoreactivity.

It is not clear how Alzheimer amyloid precursor proteins (APP) are metabolized in the brain itself. Secretory forms of APP in a phosphate buffer-soluble fraction were purified from post-mortem human brain by heparin-affinity and ion-exchange chromatography and analyzed by N-terminal amino acid sequencing and SDS polyacrylamide gel electrophoresis/immunoblotting. We found apparently similar multi-isoforms of secretory APP (at 93-97, 105-112 and 123 KDa) to those that we have described recently in cerebrospinal fluid. Antisera to the initial part of the beta/A4 sequence labelled only those bands that were found to react with antiserum to the Kunitz-type inhibitor insert of APP, suggesting that beta/A4 amyloid may be generated specifically from APP-695.

Adult↗
PubMed1992

Quantification of beta A4 protein deposition in the medial temporal lobe: a comparison of Alzheimer's disease and senile dementia of the Lewy body type.

The distribution of beta-amyloid protein (beta A4) was examined in the medial temporal lobes from cases of Alzheimer's disease (AD) (n = 13), senile dementia of Lewy body type (SDLT) (n = 12) and age matched controls (n = 9). Using a previously described image analysis technique the extent of beta A4 pathology was determined in ten distinct anatomical sites within the medial temporal lobe. AD and SDLT cases contained very similar amounts of beta A4 in the areas sampled and both contained significantly more beta A4 than the age matched controls, particularly in the dentate and parahippocampal gyri. The similarity of the beta A4 load in the two conditions is in contrast to reported differences in the number of neurofibrillary tangles which can be observed. It is suggested that AD and SDLT represent a spectrum of pathology which centres around the aberrant processing of the beta A4 precursor protein.

Aged↗
PubMed1992

Quantitative differences in the deposition of beta A4 protein in the sulci and gyri of frontal and temporal isocortex in Alzheimer's disease.

The distribution of beta-amyloid protein (beta A4) in the frontal and temporal isocortex of 14 Alzheimer's disease brains was examined using a combination of immunohistochemistry and computer image analysis. The area of cortex covered by beta A4 deposits was determined and expressed as a percentage of the total cortical grey matter area in each field of interest. Significantly more beta A4 was found in the grey matter of the sulci as compared to that of the gyral crests in both the frontal and the temporal lobes (P less than 0.05). Furthermore, in each case, greater quantities of beta A4 were observed in the frontal rather than the temporal lobes. This apparent differential vulnerability is likely to reflect underlying anatomical connections or perhaps differences in cell packing density and appears to strengthen the case for an anatomical basis for the spread of the disease pathology.

Alzheimer Disease↗
PubMed1991

Up against a barrier.

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Interprofessional Relations↗
PubMed1991

Alzheimer amyloid beta/A4 peptide binding sites and a possible 'APP-secretase' activity associated with rat brain cortical membranes.

We carried out ligand binding experiments on membranes from rat brain cortical grey matter using radioiodinated beta/A4 8-17, with non-specific binding determined by the addition of 10 microM unlabelled peptide. Specific, reversible binding amounted to 60-75% of total binding and showed a clear dependence on time, temperature, pH and membrane concentration. Kinetic analyses indicated a high-affinity binding site with an apparent KD of 440 pM. However, the ligand was partly degraded with loss of the Ser8, Lys16 and Leu17 residues. Excision of the two C-terminal amino acids was inhibited by EDTA, EGTA, dithiothreitol or Zn2+ but was stimulated by Ca2+ or Mn2+. These studies demonstrate high-affinity binding sites for beta/A4 8-17 (or its derivatives) in rat brain, suggesting that this region may contain a physiologically important amino acid sequence and identify a potential membrane-associated amyloid precursor protein (APP) secretase activity.

Alzheimer Disease↗
PubMed1991

Immunohistochemical and immunoelectron microscopical characterization of cerebrovascular and senile plaque amyloid in aged dogs' brains.

Immunohistochemical and immunoelectron microscopical studies were carried out on 28 aged dogs' brains. Amyloid deposits were seen in the arteries and capillaries in the leptomeninges and in superficial areas of the cortices in 19 (67.9%) of the 28 dogs (10-22 years of age). Immunohistochemically, these amyloid deposits were reactive for anti-beta/A4 antibody. Additionally, a variable number of parenchymal deposits with diffuse beta/A4-immunoreactivity (diffuse plaques) was also noted throughout the cerebral cortex in 24/28 dogs (85.7%). However, these plaque lesions were undetectable in Congo red staining. Electron microscopically, amyloid fibrils, measuring 10 nm in width, were located mainly in the tunica media of the arteries, and in less involved vessels they tended to be present among collagen fibres in the adventitia and smooth muscle cells in the outer layer of the media. The plaque lesions appeared to contain sparse aggregations of amyloid fibrils. In immunoelectron microscopical examinations, all amyloid fibrils in both blood vessels and plaques were selectively labelled by gold particles. These findings indicate that aged dogs can provide a useful experimental model for research into the beta/A4-type of cerebral amyloidosis commonly seen in Alzheimer's disease.

Aging↗
PubMed1991

A monoclonal antibody to common acute lymphoblastic leukemia antigen (neutral endopeptidase) immunostains senile plaques in the brains of patients with Alzheimer's disease.

We immunostained brain tissues of patients with Alzheimer's disease (AD) together with non-demented aged and younger controls with a battery of anti-human hemopoietic cell monoclonal antibodies (OK series, Ortho Diagnostics Co., Ltd. and some others) by the avidin-biotin-peroxidase complex (ABC) method to see if any epitopes are shared with the nervous system or might contribute to the neurodegenerative changes in this disease. One out of 29 monoclonal antibodies, OKBcALLa, which recognizes common acute lymphocytic leukemia antigen (CALLA, CD10), immunostained senile plaques in the brains of patients with AD. The pattern and intensity of this staining, using cryopreserved samples, was almost identical to that obtained with anti beta-protein. Thus, senile plaques in the Alzheimer's brain share an epitope with CALLA.

Aged↗